Improved aerosol-forming substrate

Abstract

An aerosol-forming substrate is provided comprising, on a dry weight basis, 10-90 wt% carbon particles, 7-60 wt% aerosol formers, 2-20 wt% fibres and 2-10 wt% binder. Each of the carbon particles comprises one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal and diamond. An aerosol-generating article including the aerosol-forming substrate and a method of forming the aerosol-forming substrate are also provided.

Description

[Technical field]

[0001] The present disclosure relates to an aerosol-forming substrate. The present disclosure also relates to a method of making the aerosol-forming substrate, an aerosol-generating article, and an aerosol-generating system. [Background technology]

[0002] A typical aerosol generating system comprises an aerosol generating device and an aerosol-generating article that includes an aerosol-forming substrate. In use, the aerosol generating device interacts with the aerosol-generating article to heat the aerosol-forming substrate, causing the aerosol-forming substrate to release volatile compounds. These compounds then cool to form an aerosol, which is inhaled by the user.

[0003] Known aerosol-forming substrates typically have a relatively low thermal conductivity. This may be particularly undesirable in aerosol generating systems where a blade is inserted into the aerosol-forming substrate and heated to heat the aerosol-forming substrate. This is because the low thermal conductivity of the aerosol-forming substrate may cause a relatively large temperature gradient in the aerosol-forming substrate during use. This may mean that the part of the aerosol-forming substrate located farthest from the blade does not reach high temperatures and therefore does not release as many volatile compounds as if the aerosol-forming substrate had a higher thermal conductivity. In other words, aerosol-forming substrates with low thermal conductivity may undesirably lead to a low usage efficiency of the aerosol-forming substrate.

[0004] Furthermore, known aerosol-forming substrates are typically not inductively heatable to operating temperatures. This means that a separate susceptor element is typically required for inductive heating, which can increase costs. Furthermore, this can result in the same problems as described above. For example, if an inductively heated susceptor element is placed in a central position on the substrate, the part of the aerosol-forming substrate that is located furthest from the susceptor element may not reach high temperatures and therefore not emit many volatile compounds.

[0005] Attempts have been made to increase the thermal conductivity of aerosol-forming substrates, but so far these attempts have been inadequate in one or more respects. Summary of the Invention

[0006] It is an object of the present invention to provide an improved aerosol-forming substrate, for example an aerosol-forming substrate having increased thermal conductivity.

[0007] According to the present disclosure, there is provided an aerosol-forming substrate. The aerosol-forming substrate may comprise 10 to 90 weight percent [wt%] of thermally conductive particles on a dry weight basis. The aerosol-forming substrate may comprise 7 to 60 wt% of aerosol formers on a dry weight basis. The aerosol-forming substrate may comprise 2 to 20 wt% of fibres on a dry weight basis. The aerosol-forming substrate may comprise 2 to 10 wt% of a binder on a dry weight basis. Each of the thermally conductive particles may comprise one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal and diamond.

[0008] Thus, according to a first aspect of the present disclosure, there is provided an aerosol-forming substrate comprising, on a dry weight basis, 10-90 wt % thermally conductive particles, 7-60 wt % aerosol former, 2-20 wt % fibres and 2-10 wt % binder, each of the thermally conductive particles being comprised of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal and diamond.

[0009] When the term "thermally conductive particles" is used to refer to particles that include carbon, such as particles that include or consist of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, the thermally conductive particles may be referred to as carbon particles or carbon-containing particles.

[0010] Advantageously, the thermally conductive particles can increase the thermal conductivity of the aerosol-forming substrate. The increased thermal conductivity of the substrate can provide a more uniform temperature distribution throughout the substrate during use. This can allow a greater proportion of the aerosol-forming substrate to reach a temperature high enough to release the volatile compound, and therefore a more efficient use of the aerosol-forming substrate. Furthermore, the increased thermal conductivity of the substrate can allow the heater, e.g., a heating blade configured to heat the substrate, to operate at a lower temperature and therefore require less power. Furthermore, the increased thermal conductivity of the substrate can allow the heater to heat the substrate to a temperature at which the volatile compound is released in a shorter time. Thus, the increased thermal conductivity can reduce the time required to form an aerosol that can be inhaled by a user.

[0011] Advantageously, one or both of the fibers and the binder may increase the tensile strength of the aerosol-forming substrate. The increased tensile strength may allow for the production of sheets of the aerosol-forming substrate that do not tear easily. The increased tensile strength may allow for the production of sheets of the aerosol-forming substrate using existing manufacturing machinery.

[0012] The aerosol-forming substrate may have a thermal conductivity in at least one direction, or in all directions, of at least 0.05, 0.1, 0.15, 0.2, 0.22, 0.3, 0.4, or 0.5 W / (mK) at 25 degrees Celsius. This thermal conductivity may be measured when the moisture content of the substrate is 0-20%, or 5-15%, for example about 10%. This thermal conductivity may be measured when the substrate contains 0-20wt%, or 5-15wt%, for example about 10wt% water. The moisture or moisture content of the substrate may be measured using a titration method. The moisture or moisture content of the substrate may be measured using the Karl Fisher method.

[0013] Optionally, some or all of the thermally conductive particles comprise at least 10, 30, 50, 70, 90, 95, 98, or 99 wt% carbon.

[0014] Optionally, some or all of the thermally conductive particles are graphite particles. Optionally, some or all of the thermally conductive particles are expanded graphite particles. Optionally, some or all of the thermally conductive particles are graphene particles. Optionally, some or all of the thermally conductive particles are carbon nanotubes or carbon nanotube particles. Optionally, some or all of the thermally conductive particles are charcoal particles. Optionally, some or all of the thermally conductive particles are diamond particles, e.g., synthetic diamond particles. Advantageously, such materials have a relatively high thermal conductivity.

[0015] Expanded graphite has a density of 2, 1.8, 1.5, 1.2, 1, 0.8, 0.5, 0.2, 0.1, 0.05, or 0.02 grams per cubic centimeter (g / cm 3 The expanded graphite may have a density of less than 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, or 1.8 grams per cubic centimeter (g / cm 3 The expanded graphite may have a density greater than 0.01 to 3, 0.01 to 2, 0.01 to 1.8, 0.01 to 1.5, 0.01 to 1.2, 0.01 to 1, 0.01 to 0.8, 0.01 to 0.5, 0.02 to 3, 0.02 to 2, 0.02 to 1.8, 0.02 to 1.5, 0.02 to 1.2, 0.02 to 1, 0.02 to 0.8, 0.02 to 0.5, 0.01 to 3, 0.05 to 2, 0.05 to 1.8, 0.05 to 1.5, 0.05 to 1.2, 0.05 to 1, 0.05 to 0.8, 0.05 to 0.5 g / cm 3、 0.1~3, 0.1~2, 0.1~1.8, 0.1~1.5, 0.1~1.2, 0.1~1, 0.1~0.8, 0.1~0.5, 0.2~3, 0.2~2, 0.2~1.8, 0.2~1.5, 0.2~1.2, 0.2~1, 0.2~0.8, 0.2~0.5, 0.5~3, 0.5~2, 0.5~1.8, 0.5~1.5, 0.5~1.2, 0.5~1, 0.5~0.8, 0.8~3, 0.8~2, 0.8~1.8, 0.8~1.5, 0.8~1.2, 0.8~1 grams per cubic centimeter (g / cm 3 )

[0016] Optionally, according to an embodiment in which each of the thermally conductive particles is not necessarily comprised of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, some or all of the thermally conductive particles include a metal. Alternatively, or in addition, some or all of the thermally conductive particles include an alloy. Alternatively, or in addition, some or all of the thermally conductive particles include an intermetallic compound. Advantageously, such materials have relatively high thermal conductivity.

[0017] Optionally, according to alternative aspects, where each of the thermally conductive particles is not necessarily comprised of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, some or all of the thermally conductive particles include one or more of silicon carbide, silver, copper, gold, aluminum nitride, aluminum, tungsten, and boron nitride. Optionally, some or all of the thermally conductive particles are silicon carbide particles. Optionally, some or all of the thermally conductive particles are silver particles. Optionally, some or all of the thermally conductive particles are copper particles. Optionally, some or all of the thermally conductive particles are gold particles. Optionally, some or all of the thermally conductive particles are aluminum nitride particles. Optionally, some or all of the thermally conductive particles are aluminum particles. Optionally, some or all of the thermally conductive particles are tungsten particles. Optionally, some or all of the thermally conductive particles are boron nitride particles. Advantageously, such materials have relatively high thermal conductivity.

[0018] The thermally conductive particles may each have a “particle size.” The meaning of the term “particle size” and methods for measuring particle size are explained below.

[0019] Thermally conductive particles can be characterized by particle size distribution. The particle size distribution can have a number D10, D50, and D90 particle size. The number D10 particle size is defined such that 10% of the particles have a particle size equal to or less than the number D10 particle size. Similarly, the number D50 particle size is defined such that 50% of the particles have a particle size equal to or less than the number D50 particle size. Thus, the number D50 particle size can also be called the median particle size. The number D90 particle size is defined such that 90% of the particles have a particle size equal to or less than the number D90 particle size. Thus, if there are 1,000 particles in a distribution and the particles are ordered in ascending order by particle size, the number D10 particle size is expected to be approximately equal to the 100th particle size, the number D50 particle size is expected to be approximately equal to the 500th particle size, and the number D90 particle size is expected to be approximately equal to the 900th particle size.

[0020] The particle size distribution may have volume D10, D50, and D90 particle sizes. The volume D10 particle size is defined such that 10% of the total volume of all particles is occupied by the total volume of particles having a particle size equal to or less than the volume D10 particle size. Similarly, the volume D50 particle size is defined such that 50% of the total volume of all particles is occupied by the total volume of particles having a particle size equal to or less than the volume D50 particle size. Also, the volume D90 particle size is defined such that 90% of the total volume of all particles is occupied by the total volume of particles having a particle size equal to or less than the volume D90 particle size.

[0021] Optionally, the thermally conductive particles have a particle size distribution with a number D10 particle size, the number D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0022] Optionally, the thermally conductive particles have a particle size distribution with a number D10 particle size, the number D10 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0023] A compromise must be made in determining the size of the particles: larger thermally conductive particles can advantageously increase the thermal conductivity of the aerosol-forming substrate more than smaller thermally conductive particles, however, large thermally conductive particles can reduce the space within the substrate available to the aerosol-forming material.

[0024] Optionally, the thermally conductive particles have a particle size distribution with a number D50 particle size, the number D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0025] Optionally, the thermally conductive particles have a particle size distribution with a number D50 particle size, the number D50 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0026] Optionally, the thermally conductive particles have a particle size distribution with a number D90 particle size, the number D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0027] Optionally, the thermally conductive particles have a particle size distribution with a number D90 particle size, the number D90 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0028] Optionally, the thermally conductive particles have a particle size distribution having a number D10 particle size and a number D90 particle size, the number D90 particle size being no greater than 50, 40, 30, 20, 10, or 5 times the number D10 particle size.

[0029] Optionally, the thermally conductive particles have a particle size distribution having a number D10 particle size and a number D90 particle size, the number D90 particle size being at least 1.5, 2, 3, 5, 10, or 20 times the number D10 particle size.

[0030] A compromise must be made regarding particle size distribution. For example, a tighter particle size distribution, characterized by a smaller ratio between D90 and D10 particle sizes, may advantageously provide a more uniform thermal conductivity throughout the aerosol-forming substrate. This is because there is less variation in particle size at different locations within the substrate. This may advantageously allow for more efficient use of the aerosol-forming material throughout the aerosol-forming substrate. However, a tight particle size distribution may be disadvantageously more difficult and expensive to achieve. The inventors have found that the particle size distribution described above may provide an optimal compromise between these two factors.

[0031] Optionally, the thermally conductive particles have a particle size distribution with a volume D10 particle size, the volume D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0032] Optionally, the thermally conductive particles have a particle size distribution with a volume D10 particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0033] Optionally, the thermally conductive particles have a particle size distribution with a volume D50 particle size, the volume D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0034] Optionally, the thermally conductive particles have a particle size distribution with a volume D50 particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0035] Optionally, the thermally conductive particles have a particle size distribution with a volume D90 particle size, the volume D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0036] Optionally, the thermally conductive particles have a particle size distribution with a volume D90 particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

[0037] It may be particularly preferred that the thermally conductive particles have a particle size distribution with a volume D10 particle size of 1 to 20 microns. Alternatively, or additionally, it may be particularly preferred that the thermally conductive particles have a particle size distribution with a volume D90 particle size of 50 to 300 microns, or 50 to 200 microns.

[0038] Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, the volume D90 particle size being no greater than 50, 40, 30, 20, 10, or 5 times the volume D10 particle size.

[0039] Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, where the volume D90 particle size is at least 1.5, 2, 3, 5, 10, or 20 times the volume D10 particle size.

[0040] As explained above, a compromise has to be made with respect to particle size distribution and the inventors have found that the particle size distribution described above may provide an optimal compromise.

[0041] Optionally, each of the thermally conductive particles has a particle size of at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Optionally, each of the thermally conductive particles has a particle size of 1,000, 500, 300, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less. It may be particularly preferred that each of the thermally conductive particles has a particle size of at least 1 micron. Alternatively, or additionally, it may be particularly preferred that each of the thermally conductive particles has a particle size of 300 microns or less. Particles less than 1 micron may be difficult to handle during manufacturing. In addition, particles less than 1 micron may be more likely to pass through filters in aerosol-generating articles that include the aerosol-forming substrate. Particles larger than 300 microns may occupy a significant amount of space within a substrate that may be used for aerosol-forming materials. Therefore, it may be particularly advantageous for each of the thermally conductive particles to have a particle size of at least 1 micron, or a particle size of 300 microns or less, or both.

[0042] Optionally, each of the thermally conductive particles has three mutually orthogonal dimensions, and the largest of the three dimensions is 10, 8, 5, 3, or 2 times or less than the smallest of the three dimensions. Optionally, each of the thermally conductive particles has three mutually orthogonal dimensions, and the largest of the three dimensions is 10, 8, 5, 3, or 2 times or less than the second largest of the three dimensions. Optionally, each of the thermally conductive particles is substantially spherical. Advantageously, the orientation of substantially spherical particles may not affect the thermal conductivity of the substrate as much as the orientation of non-spherical particles. Thus, the use of more spherical particles may result in reduced variation between different substrates, and the orientation of the particles is not controlled. Additionally, substantially spherical particles may be easier to characterize.

[0043] Optionally, the thermally conductive particles include at least 10, 20, 50, 100, 200, 500, or 1000 particles. Advantageously, a greater number of particles in the aerosol-forming substrate may allow for a more uniform thermal conductivity of the substrate.

[0044] Optionally, the substrate comprises at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 wt% of thermally conductive particles on a dry weight basis. Optionally, the substrate comprises 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt% of thermally conductive particles on a dry weight basis. Optionally, the substrate is, on a dry weight basis, 10-90 wt%, 20-90 wt%, 30-90 wt%, 40-90 wt%, 50-90 wt%, 60-90 wt%, 70-90 wt%, 80-90 wt%, 10-80 wt%, 20-80 wt%, 30-80 wt%, 40-80 wt%, 50-80 wt%, 60-80 wt%, 70-80 wt%, 10-70 wt%, 20-70 wt%, 30-70 wt%, %, 40-70wt%, 50-70wt%, 60-70wt%, 10-60wt%, 20-60wt%, 30-60wt%, 40-60wt%, 50-60wt%, 10-50wt%, 20-50wt%, 30-50wt%, 40-50wt%, 10-40wt%, 20-40wt%, 30-40wt%, 10-30wt%, 20-30wt%, or 10-20wt% of thermally conductive particles. It may be particularly preferred that the substrate comprises 50-90wt%, or more preferably 60-90wt%, or even more preferably 65-85wt% of thermally conductive particles on a dry weight basis.

[0045] A compromise may need to be made regarding the weight percentage of thermally conductive particles in the substrate. Increasing the weight percentage of particles in the aerosol-forming substrate may advantageously increase the thermal conductivity of the substrate. However, increasing the weight percentage of particles in the aerosol-forming substrate may also reduce the space available to one or more of the aerosol formers, binders, and fibers, which may result in a substrate that forms less aerosol or has less tensile strength.

[0046] Optionally, the substrate comprises at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 wt% of the aerosol former on a dry weight basis. Optionally, the substrate comprises no more than 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt% of the aerosol former on a dry weight basis. Optionally, the substrate comprises 7-60 wt%, 10-60 wt%, 20-60 wt%, 30-60 wt%, 40-60 wt%, 50-60 wt%, 7-50 wt%, 10-50 wt%, 20-50 wt%, 30-50 wt%, 40-50 wt%, 7-40 wt%, 10-40 wt%, 20-40 wt%, 30-40 wt%, 7-30 wt%, 10-30 wt%, 20-30 wt%, 7-20 wt%, 10-20 wt%, or 7-10 wt% of the aerosol former on a dry weight basis. It may be particularly preferred for the substrate to comprise 15-25 wt% of the aerosol former on a dry weight basis.

[0047] Optionally, the aerosol former comprises or consists of one or more of polyhydric alcohols (such as propylene glycol, polyethylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol), mono-, di-, or tri-acetates, and aliphatic esters or mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Optionally, the aerosol-forming substrate comprises one or both of glycerin and glycerol.

[0048] Optionally, the substrate comprises at least 2, 4, 6, 8, 10, 12, 14, 16, or 18 wt% fibers on a dry weight basis. Optionally, the substrate comprises no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt% fibers on a dry weight basis. Optionally, the substrate is, on a dry weight basis, 4-20 wt%, 6-20 wt%, 8-20 wt%, 10-20 wt%, 12-20 wt%, 14-20 wt%, 16-20 wt%, 18-20 wt%, 2-18 wt%, 4-18 wt%, 6-18 wt%, 8-18 wt%, 10-18 wt%, 12-18 wt%, 14-18 wt%, 16-18 wt%, 2-16 wt%, 4-16 wt%, 6-16 wt%, 8-16 wt%, 10-16 wt%, t%, 12-16wt%, 14-16wt%, 2-14wt%, 4-14wt%, 6-14wt%, 8-14wt%, 10-14wt%, 12-14wt%, 2-12wt%, 4-12wt%, 6-12wt%, 8-12wt%, 10-12wt%, 2-10wt%, 4-10wt%, 6-10wt%, 8-10wt%, 2-8wt%, 4-8wt%, 6-8wt%, 2-6wt%, 4-6wt%, or 2-4wt% of fibers. It may be particularly preferred that the substrate comprises 2-10wt% of fibers on a dry weight basis.

[0049] Optionally, the fibers are cellulose fibers. Advantageously, cellulose fibers are not overly expensive and can increase the tensile strength of the substrate.

[0050] Optionally, each of the fibers has three mutually orthogonal dimensions, the largest of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times greater than the smallest of the three dimensions. Optionally, each of the fibers has three mutually orthogonal dimensions, the largest of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times greater than a second largest of the three dimensions.

[0051] Optionally, the substrate comprises at least 4, 6, or 8 wt% binder on a dry weight basis. Optionally, the substrate comprises no more than 8, 6, or 4 wt% binder on a dry weight basis. Optionally, the substrate comprises 4-10 wt%, 6-10 wt%, 8-10 wt%, 2-8 wt%, 4-8 wt%, 6-8 wt%, 2-6 wt%, 4-6 wt%, 2-4 wt% binder on a dry weight basis. It may be particularly preferred that the substrate comprises 2-10 wt% binder on a dry weight basis.

[0052] Suitable binders are known in the art and include, but are not limited to, natural pectins (such as fruit pectins, citrus pectins, or tobacco pectins), guar gums (such as hydroxyethyl guar, hydroxypropyl guar), locust bean gums (such as hydroxyethyl locust bean gum, hydroxypropyl locust bean gum), alginates, starches (such as modified or derivatized starches), celluloses (such as methylcellulose, ethylcellulose, ethylhydroxymethylcellulose, carboxymethylcellulose), tamarind gum, dextran, pralon, konjac flour, xanthan gum, and the like. It may be particularly preferred that the binder is or comprises guar. It may be particularly preferred that the binder comprises or consists of one or more of carboxymethylcellulose or hydroxypropylcellulose, or a gum such as guar gum.

[0053] Optionally, the thermally conductive particles are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the aerosol formers are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the fibers are substantially homogeneously distributed throughout the aerosol-forming substrate. Optionally, the binder is substantially homogeneously distributed throughout the aerosol-forming substrate. Advantageously, homogeneous distribution of the substrate components may result in the substrate having more spatially uniform properties. For example, substantially homogeneously distributed thermally conductive particles may result in a substrate having a substantially uniform thermal conductivity. As another example, substantially homogeneously distributed binders or fibers may result in a substrate having a substantially uniform tensile strength.

[0054] Optionally, the substrate comprises nicotine. Optionally, the substrate comprises at least 0.01, 1, 2, 3, or 4 wt% nicotine on a dry weight basis. Optionally, the substrate comprises no more than 5, 4, 3, 2, or 1 wt% nicotine on a dry weight basis. Optionally, the substrate comprises 0.01-5 wt%, 1-5 wt%, 2-5 wt%, 3-5 wt%, 4-5 wt%, 0.01-4 wt%, 1-4 wt%, 2-4 wt%, 3-4 wt%, 0.01-3 wt%, 1-3 wt%, 2-3 wt%, 0.01-2 wt%, 1-2 wt%, 0.01-1 wt% nicotine on a dry weight basis. It may be particularly preferred that the substrate comprises 0.5-4 wt% nicotine on a dry weight basis.

[0055] Optionally, the nicotine is distributed substantially homogeneously throughout the aerosol-forming substrate.

[0056] Optionally, the substrate comprises an acid. Optionally, the substrate comprises at least 0.01, 1, 2, 3, or 4 wt% acid on a dry weight basis. Optionally, the substrate comprises no more than 5, 4, 3, 2, or 1 wt% acid on a dry weight basis. Optionally, the substrate comprises 0.01-5 wt%, 1-5 wt%, 2-5 wt%, 3-5 wt%, 4-5 wt%, 0.01-4 wt%, 1-4 wt%, 2-4 wt%, 3-4 wt%, 0.01-3 wt%, 1-3 wt%, 2-3 wt%, 0.01-2 wt%, 1-2 wt%, 0.01-1 wt% acid on a dry weight basis. It may be particularly preferred that the substrate comprises 0.5-5 wt% acid on a dry weight basis.

[0057] Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

[0058] Optionally, the acid is distributed substantially homogeneously throughout the aerosol-forming substrate.

[0059] Optionally, the substrate comprises at least one plant. Optionally, the substrate comprises at least 0.01, 1, 2, 5, 10, or 15 wt% of at least one plant on a dry weight basis. Optionally, the substrate comprises no more than 20, 15, 10, 5, 2, or 1 wt% of at least one plant on a dry weight basis. Optionally, the substrate comprises, on a dry weight basis, 0.01-20 wt%, 1-20 wt%, 2-20 wt%, 5-20 wt%, 10-20 wt%, 15-20 wt%, 0.01-15 wt%, 1-15 wt%, 2-15 wt%, 5-15 wt%, 10-15 wt%, 0.01-10 wt%, 1-10 wt%, 2-10 wt%, 5-10 wt%, 0.01-5 wt%, 1-5 wt%, 2-5 wt%, 0.01-2 wt%, 1-2 wt%, 0.01-1 wt% of at least one plant. It may be particularly preferred that the substrate comprises, on a dry weight basis, 1-15 wt% of at least one plant.

[0060] Optionally, the at least one plant includes or consists of one or both of clove and rosmarinus.

[0061] Optionally, the at least one plant is substantially homogeneously distributed throughout the aerosol-forming substrate.

[0062] Optionally, the substrate comprises at least one flavorant. Optionally, the substrate comprises at least 0.1, 1, 2, or 5 wt% of at least one flavorant on a dry weight basis. Optionally, the substrate comprises no more than 10, 5, 2, or 1 wt% of at least one flavorant on a dry weight basis. Optionally, the substrate comprises 0.1-10 wt%, 1-10 wt%, 2-10 wt%, 5-10 wt%, 0.1-5 wt%, 1-5 wt%, 2-5 wt%, 0.1-2 wt%, 1-2 wt%, 0.1-1 wt% of at least one flavorant on a dry weight basis. It may be particularly preferred that the substrate comprises 0.1-5 wt% of at least one flavorant on a dry weight basis.

[0063] Optionally, the at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-forming substrate. Alternatively, or additionally, the at least one flavourant is substantially homogeneously distributed throughout the aerosol-forming substrate.

[0064] Optionally, the aerosol-forming substrate comprises at least one organic material, such as tobacco. The at least one organic material comprises one or more of herb leaves, tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Optionally, the at least one organic material is substantially homogeneously distributed throughout the aerosol-forming substrate.

[0065] The substrate may comprise less than 10, 5, 3, 2 or 1 wt% tobacco on a dry weight basis.Optionally, the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

[0066] The aerosol-forming substrate may be in the form of a rod, so that a rod of the aerosol-forming substrate may be provided.

[0067] The susceptor element may be located within the rod of the aerosol-forming substrate. The susceptor element may be an elongated susceptor element. The susceptor element may extend longitudinally within the rod of the aerosol-forming substrate. The rod may be substantially cylindrical, for example, right cylindrical. The susceptor element may be located at a radially central position within the rod of the aerosol-forming substrate. The susceptor element may extend along a central longitudinal axis of the rod of the aerosol-forming substrate. The susceptor element may extend all the way to the downstream end of the rod of the aerosol-forming substrate. The susceptor element may extend all the way to the upstream end of the rod of the aerosol-forming substrate. The susceptor element may have substantially the same length as the rod of the aerosol-forming substrate. The susceptor element may extend from the upstream end to the downstream end of the rod of the aerosol-forming substrate. The susceptor element may be in the form of a pin, rod, strip, or blade. The susceptor element may have a length of 5 to 15 millimeters, 6 to 12 millimeters, or 8 to 10 millimeters. The susceptor element may have a width of 1 to 5 millimeters. The susceptor element may have a thickness of 0.01 to 2 millimeters, 0.5 to 2 millimeters, or 0.5 to 1 millimeter.

[0068] Alternatively, there may be no susceptor material within the aerosol-forming substrate or within the rod of the aerosol-forming substrate.

[0069] Optionally, some or each of the thermally conductive particles may be inductively heatable, for example to a temperature of at least 100 degrees Celsius, 150 degrees Celsius, or 200 degrees Celsius. Optionally, some or each of the thermally conductive particles may comprise or consist of one or more susceptor materials. Advantageously, this may allow the thermally conductive particles to be inductively heated. The thermally conductive particles may comprise or be the only susceptor material(s) present within the aerosol-forming substrate or within the rod of the aerosol-forming substrate. That is, there may be cases where there are no susceptor elements present within the aerosol-forming substrate or within the rod of the aerosol-forming substrate, except for the thermally conductive particles or the carbon particles.

[0070] Suitable susceptor materials include, but are not limited to, carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, nickel, nickel-containing compounds, titanium, and composites of metal materials. Suitable susceptor materials may include ferromagnetic materials, such as ferritic iron, ferromagnetic alloys such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrites. Suitable susceptor materials may be or include aluminum. The susceptor material preferably includes more than 5% ferromagnetic or paramagnetic material, preferably more than 20% ferromagnetic or paramagnetic material, and more preferably more than 50% or more than 90% ferromagnetic or paramagnetic material. Preferred susceptor materials may include metals, metal alloys, or carbon.

[0071] Particularly preferred susceptor materials may be or include carbon, carbon-based materials, graphene, graphite, or expanded graphite. Advantageously, such materials have relatively high thermal conductivity, relatively low density, and may be inductively heated.

[0072] Optionally, the aerosol-forming substrate has a thermal conductivity in at least one direction greater than 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.25, 1.5, 2, 5, 10, 20, 50, 100, 200, or 500 W / (mK) at 25 degrees Celsius.

[0073] Optionally, the aerosol-forming substrate has a viscosity of 1500, 1450, 1400, 1350, 1300, 1250, 1200, 1100, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, 650, or 600 kg / m 3 Optionally, the aerosol-forming substrate has a density of from 600 to 1400 kg / m 3 , 800~1200kg / m 3 , or 900-1100kg / m 3Advantageously, by reducing the density of the substrate, the cost of shipping the substrate may be reduced.

[0074] Optionally, the aerosol-forming substrate has a moisture content of 1-20 wt%, or 3-15 wt%. The moisture content may be measured after 48 hours of equilibration at 50% relative humidity and 20 degrees Celsius. Optionally, the aerosol-forming substrate comprises 1-20 wt%, or 3-15 wt% water. The moisture or moisture content of the substrate may be measured using a titration method. The moisture or moisture content of the substrate may be measured using the Karl Fisher method.

[0075] Optionally, the aerosol-forming substrate comprises or is in the form of one or more of cut filler, powder particles, granules, pellets, pieces, spaghetti, strips, threads, ribbons, or sheets. Optionally, the aerosol-forming substrate comprises or is in the form of one or more sheets or strips.

[0076] Optionally, the aerosol-forming substrate comprises or is in the form of one or more sheets, e.g. an assembly of sheets. Optionally, the aerosol-forming substrate comprises or is in the form of a plurality of strips.

[0077] Optionally, the or each sheet or strip has a thickness of at least 5, 10, 20, 50, 100, 150, or 200 microns. Optionally, the or each sheet or strip has a thickness of no more than 2000, 1000, 500, 400, 300, or 250 microns. Optionally, the or each sheet or strip has a thickness of 100-350 microns, or 150-300 microns.

[0078] Optionally, the or each sheet or strip has a width of at least 100, 200, 500, or 1000 microns. Optionally, the or each sheet or strip has a width of no more than 2000, 1000, 500, 400, 300, 250, or 200 microns. Optionally, the or each sheet or strip has a width of 100-2000 microns, or 500-1000 microns, or 600-1000 microns.

[0079] Optionally, the sheets or strips, or each of them, have a length of at least 100, 200, 500, 1000, 2000, or 3000 microns. Optionally, the sheets or strips, or each of them, have a length of no more than 6000, 5000, 3000, 2000, 1000, 500, or 200 microns. Optionally, the sheets or strips, or each of them, have a length of 100-6000 microns, or 500-5000 microns, or 1000-4000 microns.

[0080] Optionally, the sheet or strip, or each, has a density of at least 20, 50, or 100 g / m 2 Optionally, the sheet or strip, or each, has a basis weight of 300 g / m 2 Optionally, the sheet or strip, or each, has a basis weight of from 20 to 300 g / m 2 , 50~250g / m 2 , or 100~250g / m 2 The sheet has a basis weight of 1.0 g.

[0081] Optionally, the sheet or strip, or each, has a density of at least 0.1, 0.2, 0.3, or 0.5 g / m 3 Optionally, the sheet or strip, or each, has a density of 2, 1.5, 1.2, or 1 g / m 3 Optionally, the sheet or strip, or each, has a density of from 0.1 to 2 g / m 3 , 0.2~2g / m 3 , 0.3~2g / m 3, 0.3~1.5g / m 3 , or 0.3 to 1.2 g / m 3 has a density of

[0082] When the substrate comprises one or more collections of sheets, the or each collection of sheets may have a width of at least about 1, 2, 5, 10, 25, 50, or 100 mm.

[0083] According to the present disclosure, a combined aerosol-forming substrate is also provided. The combined aerosol-forming substrate may include a first material and a second material, the first material being included as a first plurality of individual elements within the combined aerosol-forming substrate, and the second material being included as a second plurality of individual elements within the combined aerosol-forming substrate. The first material may include an aerosol former. The first material may have a first thermal conductivity. The second material may have a second thermal conductivity that is greater than the first thermal conductivity.

[0084] Thus, according to a second aspect of the present disclosure,

[0085] a first material and a second material, the first material being contained within a combined aerosol-forming substrate as a first plurality of individual elements and the second material being contained within a combined aerosol-forming substrate as a second plurality of individual elements;

[0086] a first material comprising an aerosol former and having a first thermal conductivity;

[0087] An associated aerosol-forming substrate is provided in which the second material has a second thermal conductivity greater than the first thermal conductivity.

[0088] Advantageously, the second material may increase the thermal conductivity of the substrate, which, as discussed above in relation to the first embodiment, may provide one or more of the following advantages: smaller temperature gradients exist in the substrate during use, more efficient use of the substrate, the heater of the aerosol generating device may operate at lower temperatures, and the time taken to generate an aerosol is reduced.

[0089] The first material may be described as having a different material composition than the second material. Optionally, the second material is or comprises an aerosol-forming substrate as described above, such as the aerosol-forming substrate of the first aspect.

[0090] Optionally, the second thermal conductivity is at least 5% greater than the first thermal conductivity, e.g., at least 7, 10, 12, 15, 30, 50, 100, 200, or 500% greater. Optionally, the thermal conductivity of the second material is at least 10% greater than the thermal conductivity of the first material, e.g., at least 12, 15, 20, 30, 50, 100, 200, or 500% greater.

[0091] Optionally, the first plurality of individual elements, or the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are elongated elements, each having a length dimension greater than its width and thickness dimensions.

[0092] Optionally, the elongate elements are in the form of strips, pieces, threads, or ribbons.

[0093] Optionally, the first plurality of individual elements, or the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are formed by a casting process, for example, by a casting process followed by a cutting process.

[0094] Optionally, the first plurality of individual elements, or the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are formed by an extrusion process.

[0095] Optionally, at least a portion of the first plurality of individual elements, or at least a portion of the second plurality of individual elements, or at least a portion of both the first plurality of individual elements and the second plurality of individual elements are crimped elements, e.g., each crimped element may have one or more twists or changes in direction defined in the length dimension of the crimped element.

[0096] Optionally, one or both of the first material and the second material are included within the combined aerosol-forming substrate in the form of a cut filler.

[0097] Optionally, the first plurality of individual elements, or the second plurality of individual elements, or the individual elements of both the first and second plurality of individual elements, have an average thickness of from 5 microns to 2000 microns, such as from 50 microns to 500 microns, for example from 150 microns to 300 microns.

[0098] Optionally, the first plurality of individual elements, or the second plurality of individual elements, or the individual elements of both the first and second plurality of individual elements, have an average width between 100 microns and 2000 microns, such as between 500 microns and 1500 microns, for example between 600 microns and 1000 microns.

[0099] Optionally, the individual elements of the first plurality, or the individual elements of the second plurality, or the individual elements of both the first and second plurality, have an average length of between 100 microns and 60 millimeters, such as between 500 microns and 30 millimeters, e.g., between 1000 microns and 10000 microns.

[0100] Advantageously, the above-mentioned thicknesses, widths and lengths have been found to facilitate the production of an appropriate amount of aerosol having desirable properties upon heating by a heating element of an aerosol generating device.

[0101] Optionally, the second material includes thermally conductive particles. Optionally, the second material includes at least 1, 2, 5, 10, 20, 30, 40, 50, 60, 70, or 80 wt % thermally conductive particles. Optionally, the second material includes no more than 90, 80, 70, 60, 50, 40, 30, 20, 10, or 5 wt % thermally conductive particles. Optionally, the second material is, on a dry weight basis, 1-90 wt%, 2-90 wt%, 5-90 wt%, 10-90 wt%, 20-90 wt%, 30-90 wt%, 40-90 wt%, 50-90 wt%, 60-90 wt%, 70-90 wt%, 80-90 wt%, 10-80 wt%, 20-80 wt%, 30-80 wt%, 40-80 wt%, 50-80 wt%, 60-80 wt%, 70-80 wt%, 10-70 wt%, 2 and containing 0-70wt%, 30-70wt%, 40-70wt%, 50-70wt%, 60-70wt%, 10-60wt%, 20-60wt%, 30-60wt%, 40-60wt%, 50-60wt%, 10-50wt%, 20-50wt%, 30-50wt%, 40-50wt%, 10-40wt%, 20-40wt%, 30-40wt%, 10-30wt%, 20-30wt%, or 10-20wt% thermally conductive particles.

[0102] Optionally, the second material includes thermally conductive particles formed from a thermally conductive material selected from the list consisting of carbon, graphite, expanded graphite, graphene, and metal. Optionally, the second material is a thermally conductive material selected from the list consisting of carbon, graphite, expanded graphite, graphene, and metal, for example, each individual element of the second material is a strip of metal or carbon foil, such as copper foil, or aluminum foil, or stainless steel foil, or graphite foil. Such materials advantageously have a relatively high thermal conductivity.

[0103] Optionally, the first material has a thermal conductivity in at least one direction of less than 10, 5, 2, 1, 0.5, or 0.2 W / (mK) at 25 degrees Celsius. Optionally, the second material has a thermal conductivity in at least one direction of greater than 0.1, 0.22, 0.3, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 1500, or 1700 W / (mK) at 25 degrees Celsius.

[0104] Optionally, the first material is configured to generate an aerosol upon heating, e.g., when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius, and the second material is not configured to generate an aerosol upon heating, e.g., when heated to a temperature between 120 degrees Celsius and 350 degrees Celsius. Optionally, both the first material and the second material are configured to generate an aerosol upon heating, e.g., when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius.

[0105] Optionally, the first material includes tobacco, for example, the first material is formed from homogenized tobacco. Optionally, the first material includes tobacco and an aerosol former, and is configured to generate an aerosol when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius. Optionally, the first material is a homogenized tobacco material, and further includes one or both of a fiber and a binder.

[0106] Optionally, the second material includes an aerosol former and thermally conductive particles constituting between 3 wt% and 90 wt% of the second material on a dry weight basis, the second material configured to generate an aerosol when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius. Optionally, the second material includes tobacco, an aerosol former and conductive particles constituting between 3 wt% and 90 wt% of the second material on a dry weight basis, the second material configured to generate an aerosol when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius. Optionally, the second material is a thermally conductive homogenized tobacco material, further comprising fibers and a binder.

[0107] Optionally, the second material is tobacco-free, for example, the second material is a thermally conductive tobacco-free material, further comprising fibers and a binder.

[0108] Optionally, individual elements of the first material and individual elements of the second material are formed separately and mixed together in a predetermined ratio to form a combined aerosol-forming substrate.

[0109] Optionally, the ratio of the first material to the second material in the combined aerosol-forming substrate is from 1:10 to 10:1, such as from 1:5 to 8:1, such as from 1:1 to 5:1.

[0110] Optionally, the second material comprises, on a dry weight basis, 40-80 wt. % particulate carbon material, 10-40 wt. % aerosol former, 4-20 wt. % fibers, and 2-10 wt. % binder, wherein the particulate carbon material is one or more of graphite, expanded graphite, graphene, carbon nanotubes, and charcoal.

[0111] Optionally, the first material comprises, on a dry weight basis, 40-80 wt.% particulate carbon material, 10-40 wt.% aerosol former, 4-20 wt.% fibers, and 2-10 wt.% binder, wherein the particulate carbon material is one or more of graphite, expanded graphite, graphene, carbon nanotubes, and charcoal, and wherein the first material has a lower thermal conductivity than the second material.

[0112] Optionally, the particulate carbon material comprises graphite.

[0113] Optionally, the second material and the first material are homogeneously distributed within the combined aerosol-forming substrate.

[0114] According to the present disclosure, there is provided a method of forming a combined aerosol-forming substrate, for example the combined aerosol-forming substrate described above, such as the combined aerosol-forming substrate of the second aspect. The method may include forming a first plurality of individual elements from a first material. The method may include forming a second plurality of individual elements from a second material. The method may include combining the first plurality of individual elements with the second plurality of individual elements to form, for example, the combined aerosol-forming substrate. The second material may have a greater thermal conductivity than the first material.

[0115] Thus, according to a third aspect of the present disclosure, there is provided a method of forming a combined aerosol-forming substrate, such as the combined aerosol-forming substrate of the second aspect described above, comprising forming a first plurality of individual elements from a first material, forming a second plurality of individual elements from a second material, and combining the first plurality of individual elements and the second plurality of individual elements to form a combined aerosol-forming substrate, wherein the second material has a greater thermal conductivity than the first material.

[0116] Optionally, the method includes providing a first plurality of individual elements from a first material, providing a second plurality of individual elements from a second material, and combining the first plurality of individual elements with the second plurality of individual elements to form a combined aerosol-forming substrate, wherein the second material has a greater thermal conductivity than the first material.

[0117] Optionally, the first plurality of discrete elements are formed by cutting a sheet of a first material into strips, and the second plurality of discrete elements are formed by cutting a sheet of a second material into strips.

[0118] Optionally, the first plurality of discrete elements and the second plurality of discrete elements are cut to substantially the same size.

[0119] Optionally, forming at least one of the first plurality of individual elements and the second plurality of individual elements involves crimping, e.g., such that the first plurality of individual elements, the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are crimped elements.

[0120] Optionally, the method includes forming a first material, forming a second material, or forming both the first and second materials.

[0121] Optionally, the combined aerosol-forming substrate is an combined aerosol-forming substrate according to the second embodiment.

[0122] According to a fourth aspect of the present disclosure, there is also provided an aerosol-generating article.

[0123] The article may comprise an aerosol-forming substrate as described above, for example an aerosol-forming substrate according to the first aspect.

[0124] The article may comprise an associated aerosol-forming substrate as described above, for example an associated aerosol-forming substrate according to the second aspect.

[0125] The article may be manufactured by any of the methods described above.

[0126] Optionally, the article is in the form of a rod and comprises an aerosol-forming substrate assembled within a wrapper or casing or multiple components including combined aerosol-forming substrates.

[0127] Optionally, the aerosol-generating article comprises a front plug. Optionally, the aerosol-generating article comprises a first hollow tube, e.g., a first hollow acetate tube. Optionally, the aerosol-generating article comprises a second hollow tube, e.g., a second hollow acetate tube. Optionally, the second hollow tube comprises one or more vent holes. Optionally, the aerosol-generating article comprises a mouth-side plug filter. Optionally, the aerosol-generating article comprises a wrapper, e.g., a paper wrapper.

[0128] Optionally, the front plug is disposed at the most upstream end of the article. Optionally, the aerosol-forming substrate is disposed downstream of the front plug. Optionally, the first hollow tube is disposed downstream of the aerosol-forming substrate. Optionally, the second hollow tube is disposed downstream of the first hollow tube. Optionally, the mouth plug filter is disposed downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouth plug filter is disposed at the most downstream end of the article. Optionally, the most downstream end of the article, which may be referred to as the mouth end of the article, may be configured to be inserted into the mouth of a user. The user may, for example, be able to directly inhale the mouth end of the article.

[0129] Optionally, the front plug, the aerosol-forming substrate, one or both of the first and second hollow tubes, and the oral plug filter are surrounded by a wrapper, for example a paper wrapper.

[0130] Optionally, the front plug has a length of 2-10 mm, 3-8 mm, or 4-6 mm, for example about 5 mm. Optionally, the aerosol-forming substrate has a length of 5-20 mm, 8-15 mm, or 10-15 mm, for example about 12 mm. Optionally, the first hollow tube has a length of 2-20 mm, 5-15 mm, or 5-10 mm, for example about 8 mm. Optionally, the second hollow tube has a length of 2-20 mm, 5-15 mm, or 5-10 mm, for example about 8 mm. Optionally, the mouth plug filter has a length of 5-20 mm, 8-15 mm, or 10-15 mm, for example about 12 mm. The length of one or more of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth plug filter may extend longitudinally.

[0131] One or more of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the oral plug filter may be substantially cylindrical in shape, for example a right cylinder.

[0132] According to a fourth aspect of the present disclosure, an aerosol generation system is provided.

[0133] The system may comprise an aerosol generating article and an electrical aerosol generating device. The article may be as described above, for example an article according to the third aspect.

[0134] Optionally, the electrical aerosol generating device is configured to resistively heat the aerosol-generating article in use.

[0135] Optionally, the electrical aerosol generating device is configured, in use, to inductively heat the aerosol-generating article, for example an aerosol-forming substrate of the aerosol-generating article.

[0136] According to the present disclosure, there is provided a method of forming an aerosol-forming substrate, such as a substrate as described above, such as a substrate according to the first aspect. The method may comprise forming a slurry including one or more or all of thermally conductive particles, an aerosol former, fibres and a binder. The method may comprise casting and drying the slurry to form the aerosol-forming substrate or a precursor for forming into an aerosol-forming substrate.

[0137] Thus, according to a fifth aspect of the present disclosure, there is provided a method of forming an aerosol-forming substrate, for example a substrate as described above, such as a substrate according to the first aspect, the method comprising:

[0138] forming a slurry including thermally conductive particles, an aerosol former, fibers, and a binder;

[0139] Casting and drying the slurry to form an aerosol-forming substrate or a precursor for forming into an aerosol-forming substrate.

[0140] Optionally, the slurry comprises water. Optionally, the slurry comprises 20-90 wt%, 30-90 wt%, 40-90 wt%, 40-85 wt%, 50-80 wt%, 60-80 wt%, or 60-75 wt% water.

[0141] Optionally, the slurry comprises an acid. Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

[0142] Optionally, the slurry includes nicotine.

[0143] Optionally, forming the slurry includes forming a first mixture. The first mixture may include an aerosol former. The first mixture may include fibers. The first mixture may include water. The first mixture may include an acid. The first mixture may include nicotine. Forming the slurry may include forming a second mixture. The second mixture may include thermally conductive particles. The second mixture may include a binder. Forming the slurry may include adding the second mixture to the first mixture to form a combined mixture.

[0144] Thus, forming a slurry includes:

[0145] forming a first mixture including an aerosol former, fibers, water, optionally an acid, and optionally nicotine;

[0146] forming a second mixture comprising thermally conductive particles and a binder;

[0147] adding the second mixture to the first mixture to form a combined mixture.

[0148] The combined mixture may then be formed into a slurry, for example by mixing.

[0149] Optionally, forming the first mixture includes providing an aerosol former, or a solution including an aerosol former and nicotine.

[0150] Optionally, forming the first mixture includes adding an acid to an aerosol former, or a solution including an aerosol former and nicotine, to form a first pre-mixture.

[0151] Optionally, forming the first mixture includes adding water to the aerosol former, or to a solution comprising the aerosol former and nicotine, or to the first pre-mixture to form a second pre-mixture.

[0152] Optionally, forming the first mixture includes adding fibers to the second pre-mixture.

[0153] Optionally, forming the second mixture includes mixing thermally conductive particles with a binder.

[0154] Optionally, the method, e.g., forming a slurry, includes a first mixing of the combined mixture. Optionally, the first mixing is performed under a first pressure of less than or equal to 500, 400, 300, 250, or 200 mbar. Optionally, the first mixing is performed for 1-10 minutes, 2-8 minutes, or 3-6 minutes, e.g., about 4 minutes.

[0155] Optionally, the method, e.g., forming a slurry, includes a second mixing after the first mixing. Optionally, the second mixing is performed under a second pressure less than the first pressure. Optionally, the second pressure is less than or equal to 500, 400, 300, 200, 150, or 100 mbar. Optionally, the second mixing is performed for 5-120 seconds, 5-80 seconds, 5-40 seconds, or 10-30 seconds, e.g., about 20 seconds.

[0156] Optionally, casting the slurry includes casting the slurry onto a flat support, such as a flat steel support.

[0157] Optionally, after casting the slurry and before drying the slurry, the method includes setting a thickness of the slurry, for example setting a thickness of the slurry between 100 and 1200 microns, between 200 and 1000 microns, between 300 and 900 microns, between 500 and 700 microns, for example about 600 microns.

[0158] Optionally, drying the slurry includes providing a flow of gas, such as air, over or through the slurry. Optionally, the flow of gas is heated. Optionally, the flow of gas is heated to a temperature of 100-160 degrees Celsius, or 120-140 degrees Celsius. Optionally, the flow of gas is provided for 1-10 minutes, or 2-5 minutes. Optionally, drying the slurry includes drying the slurry until the slurry has a moisture content of 1-20 wt%, 2-15 wt%, 2-10 wt%, or 3-7 wt%.

[0159] Optionally, the slurry is dried to form a precursor for forming into an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Optionally, the method includes cutting the sheet of aerosol-forming material.

[0160] As will be understood by those of skill in the art upon reading this disclosure, features described herein in relation to one embodiment may be applicable to any other embodiment, for example features described in relation to the combined aerosol-forming substrate of the second embodiment, or in relation to the first and second materials of the combined aerosol-forming substrate of the second embodiment, may be applicable to the aerosol-forming substrate of the first embodiment, and vice versa.

[0161] As used herein, the term "aerosol-forming substrate" may refer to a substrate capable of emitting an aerosol or volatile compound capable of forming an aerosol. Such a volatile compound may be emitted by heating the aerosol-forming substrate. The aerosol-forming substrate may comprise an aerosol-forming material. The aerosol-forming substrate may be adsorbed, coated, impregnated, or otherwise loaded onto a carrier or support. The aerosol-forming substrate may conveniently be part of an aerosol-generating article or a smoking article.

[0162] As used herein, the term "thermally conductive particles" may refer to particles having a thermal conductivity of greater than 0.3, preferably 0.5, or more preferably 1 W / (mK) in at least one direction at 25 degrees Celsius, such as in all directions at 25 degrees Celsius. The particles may exhibit anisotropic or isotropic thermal conductivity.

[0163] As used herein, the term "expanded graphite" may refer to a graphite-based material or a material having a graphite-like structure. Expanded graphite may have carbon layers (e.g., similar to graphite) where the spacing between the carbon layers is greater than the spacing found between the carbon layers of regular graphite. Expanded graphite may have carbon layers with elements or compounds interposed within the spaces between the carbon layers.

[0164] As used herein, the term "particle size" may refer to a single dimension and may be used to characterize the size of a given particle. The dimension may be the diameter of a spherical particle that occupies the same volume as the given particle. All particle sizes and particle size distributions herein may be obtained using standard laser diffraction techniques. The particle sizes and particle size distributions described herein may be obtained using commercially available sensors, such as Sympatec's HELOS laser diffraction sensor.

[0165] As used herein, unless otherwise specified, the term "density" may be used to refer to true density. Thus, unless otherwise specified, the density of a powder or particles may refer to the true density of the powder or particles (rather than the bulk density of the powder or particles, which may vary greatly depending on how the powder or particles are handled). Measurement of true density can be performed using many standard methods, which are often based on Archimedes' principle. The most widely used method used to measure the true density of a powder involves the powder being placed and weighed inside a container of known volume (pycnometer). The pycnometer is then filled with a fluid of known density in which the powder is not volatile. The volume of the powder is determined by the difference between the volume indicated by the pycnometer and the volume to which the liquid is added (i.e., the volume of air displaced).

[0166] As used herein, the term "aerosol-generating article" may refer to an article that is capable of generating or releasing an aerosol, for example, upon heating.

[0167] As used herein, the term "longitudinal" may refer to the direction extending between a downstream or proximal end and an upstream or distal end of a component, such as an aerosol-forming substrate or an aerosol-generating article.

[0168] As noted above, the term "transverse" may refer to a direction perpendicular to the longitudinal axis.

[0169] As used herein, the term "aerosol-generating device" may refer to a device used in conjunction with an aerosol-generating article to enable the generation or emission of an aerosol.

[0170] As used herein, the term "assembly of a sheet" may refer to an aerosol-forming substrate, or a sheet of an aerosol-generating article that is spiralled, folded, or otherwise compressed or contracted in a direction substantially transverse to the longitudinal axis of the aerosol-forming substrate, or the aerosol-generating article.

[0171] As used herein, the term "sheet" can refer to a generally planar, laminar element having a width and length substantially greater than, for example, at least 2, 3, 5, 10, 20, or 50 times its thickness.

[0172] As used herein, the term "strip" may refer to a generally planar, laminar element having a width and length substantially greater than its thickness. The width of a strip may be greater than its thickness, e.g., at least 2, 3, 5, or 10 times its thickness. The length of a strip may be greater than its width, e.g., at least 2, 3, 5, or 10 times its width.

[0173] As used herein, the term "aerosol former" may refer to any suitable known compound or mixture of compounds that facilitates the formation of an aerosol upon use. The aerosol may be a dense and stable aerosol. The aerosol may be substantially resistant to thermal decomposition at the operating temperature of the aerosol-forming substrate or aerosol-generating article.

[0174] As used herein, the term "aerosol cooling element" may refer to a component of an aerosol-generating article that is located downstream of an aerosol-forming substrate such that, in use, an aerosol formed by the substrate or by volatile compounds released from the aerosol-forming substrate passes through and is cooled by the aerosol cooling element before being inhaled by a user.

[0175] As used herein, the term "rod" may refer to a generally cylindrical element, for example a right cylindrical element of substantially circular, oval, or elliptical cross-section.

[0176] As used herein, the term "crimped" may refer to a sheet having one or more ridges or corrugations. The ridges or corrugations may be substantially parallel. When present in a component of an aerosol-generating article, the ridges or corrugations may extend longitudinally relative to the aerosol-generating article.

[0177] As used herein, the term "aeration level" can refer to the volume ratio of the airflow entering the aerosol-generating article via the ventilation zone (ventilation airflow) to the sum of the aerosol airflow and the ventilation airflow. The higher the aeration level, the higher the dilution of the aerosol stream delivered to the consumer.

[0178] The present invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0179] Example 1. On a dry weight basis, 10 to 90 wt % of thermally conductive particles; 7 to 60 wt % of an aerosol former; 2-20wt% fiber; 2 to 10 wt % of a binder; 1. An aerosol-forming substrate, wherein each of the thermally conductive particles comprises one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond. Example 2. An aerosol-forming substrate according to any of the preceding embodiments, wherein each of the thermally conductive particles has a thermal conductivity in at least one direction of at least 0.3, 0.5, 1, 2, 5, or 10 W / (mK) at 25 degrees Celsius. Example 3. An aerosol-forming substrate according to either Example 1 or 2, wherein some or all of the thermally conductive particles comprise carbon, for example at least 10, 30, 50, 70, 90, 95, 98, or 99 wt% carbon. Example 4. An aerosol-forming substrate according to any one of Examples 1 to 3, wherein some or all of the thermally conductive particles are graphite particles, or some or all of the thermally conductive particles are expanded graphite particles, or some of the thermally conductive particles are graphite particles and some of the thermally conductive particles are expanded graphite particles. Example 5. An aerosol-forming substrate according to any one of Examples 1 to 4, wherein some or all of the thermally conductive particles are diamond particles, for example artificial diamond particles. Example 6. 6. An aerosol-forming substrate according to any of Examples 1 to 5, wherein some or all of the thermally conductive particles are graphene particles. Example 7. An aerosol-forming substrate according to any of Examples 1 to 6, wherein some or all of the thermally conductive particles are carbon nanotubes. Example 8. An aerosol-forming substrate according to any of Examples 1 to 7, wherein some or all of the thermally conductive particles are charcoal particles. Example 9. An aerosol-forming substrate according to any of Examples 1 to 8, wherein some or all of the thermally conductive particles comprise a metal. Example 10. An aerosol-forming substrate according to any of Examples 1-9, wherein some or all of the thermally conductive particles comprise one or both of copper and aluminium. Example 11. An aerosol-forming substrate according to any of Examples 1 to 10, wherein some or all of the thermally conductive particles comprise an alloy. Example 12. An aerosol-forming substrate according to any of Examples 1 to 11, wherein some or all of the thermally conductive particles comprise an intermetallic compound. Example 13. 13. An aerosol-forming substrate according to any of Examples 1-12, wherein the thermally conductive particles have a particle size distribution with a number D10 particle size, the number D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 14. 14. An aerosol-forming substrate according to any of Examples 1-13, wherein the thermally conductive particles have a particle size distribution with a number D10 particle size, the number D10 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 15. 15. An aerosol-forming substrate according to any of Examples 1-14, wherein the thermally conductive particles have a particle size distribution with a number D50 particle size, the number D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 16. 16. An aerosol-forming substrate according to any of Examples 1-15, wherein the thermally conductive particles have a particle size distribution with a number D50 particle size, the number D50 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 17. 17. An aerosol-forming substrate according to any of Examples 1-16, wherein the thermally conductive particles have a particle size distribution with a number D90 particle size, the number D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 18. 18. An aerosol-forming substrate according to any of Examples 1-17, wherein the thermally conductive particles have a particle size distribution with a number D90 particle size, the number D90 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 19. 19. An aerosol-forming substrate according to any of Examples 1-18, wherein the thermally conductive particles have a particle size distribution with a volume D10 particle size, the volume D10 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 20. 20. An aerosol-forming substrate according to any of Examples 1-19, wherein the thermally conductive particles have a particle size distribution with a volume D10 particle size, the volume D10 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 21. 21. An aerosol-forming substrate according to any of Examples 1-20, wherein the thermally conductive particles have a particle size distribution with a volume D50 particle size, the volume D50 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 22. 22. An aerosol-forming substrate according to any of Examples 1-21, wherein the thermally conductive particles have a particle size distribution with a volume D50 particle size, the volume D50 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 23. 23. An aerosol-forming substrate according to any of Examples 1-22, wherein the thermally conductive particles have a particle size distribution with a volume D90 particle size, the volume D90 particle size being at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 24. 24. An aerosol-forming substrate according to any of Examples 1-23, wherein the thermally conductive particles have a particle size distribution with a volume D90 particle size, the volume D90 particle size being less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 25. the thermally conductive particles have a particle size distribution having a number D10 particle size, a number D90 particle size, a volume D10 particle size, and a volume D90 particle size; The number D90 particle size is 50, 40, 30, 20, 10, or 5 times less than the number D10 particle size; or the volume D10 particle size is less than or equal to 50, 40, 30, 20, 10, or 5 times the volume D10 particle size; Or an aerosol-forming substrate according to any of Examples 1 to 24, wherein both the number D90 particle size is 50, 40, 30, 20, 10, or 5 times the number D10 particle size and the volume D10 particle size is 50, 40, 30, 20, 10, or 5 times the volume D10 particle size. Example 26. An aerosol-forming substrate according to any of Examples 1-25, wherein the thermally conductive particles have a particle size distribution, and one or both of the number D10 particle size and the volume D10 particle size is from 1 to 20 microns. Example 27. An aerosol-forming substrate according to any of Examples 1 to 26, wherein the thermally conductive particles have a particle size distribution, and one or both of the number D90 particle size and the volume D90 particle size are from 50 to 300 microns, or from 50 to 200 microns. Example 28. An aerosol-forming substrate according to any of Examples 1-27, wherein each of the thermally conductive particles has a particle size of at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Example 29. An aerosol-forming substrate according to any of Examples 1-28, wherein each of the thermally conductive particles has a particle size of less than or equal to 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. Example 30. An aerosol-forming substrate according to any of Examples 1 to 29, wherein each of the thermally conductive particles has three mutually perpendicular dimensions, and the largest dimension of the three dimensions is no more than 10, 8, 5, 3, or 2 times greater than one or both of the smallest dimension of the three dimensions and a second largest dimension of the three dimensions. Example 31. An aerosol-forming substrate according to any of Examples 1 to 30, wherein each of the thermally conductive particles is substantially spherical. Example 32. An aerosol-forming substrate according to any of Examples 1-31, wherein the thermally conductive particles comprise at least 10, 20, 50, 100, 200, 500, or 1000 particles. Example 33. 33. An aerosol-forming substrate according to any of Examples 1-32, wherein the substrate comprises at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 wt % of thermally conductive particles on a dry weight basis. Example 34. 34. The aerosol-forming substrate according to any of Examples 1-33, wherein the substrate comprises, on a dry weight basis, no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt % of thermally conductive particles. Example 35. The substrate is, on a dry weight basis, 10-90wt%, 20-90wt%, 30-90wt%, 40-90wt%, 50-90wt%, 60-90wt%, 70-90wt%, 80-90wt%, 10-80wt%, 20-80wt%, 30-80wt%, 40-80wt%, 50-80wt%, 60-80wt%, 70-80wt%, 10-70wt%, 20-70wt%, 30-70wt%, 40-70wt%, 50-7 35. An aerosol-forming substrate according to any of Examples 1 to 34 comprising 0 wt%, 60-70 wt%, 10-60 wt%, 20-60 wt%, 30-60 wt%, 40-60 wt%, 50-60 wt%, 10-50 wt%, 20-50 wt%, 30-50 wt%, 40-50 wt%, 10-40 wt%, 20-40 wt%, 30-40 wt%, 10-30 wt%, 20-30 wt%, or 10-20 wt% of thermally conductive particles. Example 36. The aerosol-forming substrate according to any of Examples 1-35, wherein the substrate comprises at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 wt % of the aerosol former on a dry weight basis. Example 37. The aerosol-forming substrate according to any of Examples 1-36, wherein the substrate comprises, on a dry weight basis, 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt % or less of the aerosol former. Example 38. 38. The aerosol-forming substrate according to any of Examples 1 to 37, wherein the substrate comprises, on a dry weight basis, 7 to 60 wt%, 10 to 60 wt%, 20 to 60 wt%, 30 to 60 wt%, 40 to 60 wt%, 50 to 60 wt%, 7 to 50 wt%, 10 to 50 wt%, 20 to 50 wt%, 30 to 50 wt%, 40 to 50 wt%, 7 to 40 wt%, 10 to 40 wt%, 20 to 40 wt%, 30 to 40 wt%, 7 to 30 wt%, 10 to 30 wt%, 20 to 30 wt%, 7 to 20 wt%, 10 to 20 wt%, or 7 to 10 wt% of the aerosol former, particularly preferably 15 to 25 wt% of the aerosol former. Example 39. The aerosol-forming substrate according to any of Examples 1-38, wherein the aerosol former comprises or consists of one or more of polyhydric alcohols (such as propylene glycol, polyethylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol), mono-, di-, or tri-acetates, and aliphatic esters or mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Example 40. An aerosol-forming substrate according to any of Examples 1-39, wherein the aerosol-forming substrate comprises one or both of glycerin and glycerol. Example 41. An aerosol-forming substrate according to any of Examples 1-40, wherein the substrate comprises at least 2, 4, 6, 8, 10, 12, 14, 16, or 18 wt% of fibers on a dry weight basis. Example 42. 42. An aerosol-forming substrate according to any of Examples 1-41, wherein the substrate comprises, on a dry weight basis, no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt. % of fibers. Example 43. The substrate is, on a dry weight basis, 4-20wt%, 6-20wt%, 8-20wt%, 10-20wt%, 12-20wt%, 14-20wt%, 16-20wt%, 18-20wt%, 2-18wt%, 4-18wt%, 6-18wt%, 8-18wt%, 10-18wt%, 12-18wt%, 14-18wt%, 16-18wt%, 2-16wt%, 4-16wt%, 6-16wt%, 8-16wt%, 10-16wt%, 12-16wt%, 14-16wt%, 2-1 45. An aerosol-forming substrate according to any of Examples 1 to 42 comprising 4wt%, 4-14wt%, 6-14wt%, 8-14wt%, 10-14wt%, 12-14wt%, 2-12wt%, 4-12wt%, 6-12wt%, 8-12wt%, 10-12wt%, 2-10wt%, 4-10wt%, 6-10wt%, 8-10wt%, 2-8wt%, 4-8wt%, 6-8wt%, 2-6w%, 4-6wt%, or 2-4wt% of fibres, preferably 2-10wt% of fibres. Example 44. An aerosol-forming substrate according to any one of Examples 1 to 43, wherein the fibres are cellulose fibres. Example 45. An aerosol-forming substrate according to any of Examples 1-44, wherein each of the fibers has three mutually perpendicular dimensions, the largest of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times greater than the smallest of the three dimensions. Example 46. An aerosol-forming substrate according to any of Examples 1-45, wherein each of the fibers has three mutually perpendicular dimensions, and the largest of the three dimensions is at least 1.5, 2, 3, 5, 10, or 20 times greater than the second largest of the three dimensions. Example 47. An aerosol-forming substrate according to any of Examples 1-46, wherein the substrate comprises at least 4, 6, or 8 wt% binder, on a dry weight basis. Example 48. An aerosol-forming substrate according to any of Examples 1-47, wherein the substrate comprises no more than 8, 6, or 4 wt % binder, on a dry weight basis. Example 49. An aerosol-forming substrate according to any of Examples 1 to 48, wherein the substrate comprises, on a dry weight basis, 4 to 10 wt%, 6 to 10 wt%, 8 to 10 wt%, 2 to 8 wt%, 4 to 8 wt%, 6 to 8 wt%, 2 to 6 wt%, 4 to 6 wt%, 2 to 4 wt% of binder, particularly preferably 2 to 10 wt% of binder. Example 50. An aerosol-forming substrate according to any of Examples 1-49, wherein the binder comprises or consists of one or both of carboxymethylcellulose or hydroxypropylcellulose. Example 51. An aerosol-forming substrate according to any of Examples 1-50, wherein the binder comprises or consists of one or more gums, such as guar gum. Example 52. An aerosol-forming substrate according to any of Examples 1 to 51, wherein the thermally conductive particles are substantially homogeneously distributed throughout the aerosol-forming substrate. Example 53. An aerosol-forming substrate according to any of Examples 1 to 52, wherein the aerosol formers are substantially homogeneously distributed throughout the aerosol-forming substrate. Example 54. An aerosol-forming substrate according to any of Examples 1 to 53, wherein the fibers are substantially homogeneously distributed throughout the aerosol-forming substrate. Example 55. An aerosol-forming substrate according to any of Examples 1 to 54, wherein the binder is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 56. An aerosol-forming substrate according to any of Examples 1-55, wherein the substrate comprises nicotine. Example 57. An aerosol-forming substrate according to Example 56, wherein the substrate comprises at least 0.01, 1, 2, 3, or 4 wt% nicotine on a dry weight basis. Example 58. 58. An aerosol-forming substrate according to any of Examples 56-57, wherein the substrate comprises, on a dry weight basis, no more than 5, 4, 3, 2, or 1 wt% nicotine. Example 59. An aerosol-forming substrate according to any of Examples 1-58, wherein the substrate comprises, on a dry weight basis, 0.01-5, 1-5, 2-5, 3-5, 4-5, 0.01-4, 1-4, 2-4, 3-4, 0.01-3, 1-3, 2-3, 0.01-2, 1-2, 0.01-1 wt% of nicotine, particularly preferably 0.5-4 wt% of nicotine. Example 60. An aerosol-forming substrate according to any of Examples 56 to 58, wherein the nicotine is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 61. An aerosol-forming substrate according to any of Examples 1 to 60, wherein the substrate comprises an acid. Example 62. 62. The aerosol-forming substrate according to example 61, wherein the substrate comprises at least 0.01, 1, or 2 wt % acid on a dry weight basis. Example 63. The aerosol-forming substrate according to any of Examples 61-62, wherein the substrate comprises no more than 3, 2, or 1 wt % acid on a dry weight basis. Example 64. 64. The aerosol-forming substrate according to any of Examples 61 to 63, wherein the substrate comprises, on a dry weight basis, 0.01 to 3 wt%, 1 to 3 wt%, 2 to 3 wt%, 0.01 to 2 wt%, 1 to 2 wt%, 0.01 to 1 wt% of acid, particularly preferably 0.5 to 5 wt% of acid. Example 65. An aerosol-forming substrate according to any of Examples 61-64, wherein the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid. Example 66. An aerosol-forming substrate according to any of Examples 61 to 65, wherein the acid is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 67. An aerosol-forming substrate according to any of Examples 1-66, wherein the substrate comprises at least one plant. Example 68. 68. An aerosol-forming substrate according to example 67, wherein the substrate comprises at least 0.01, 1, 2, 5, 10, or 15 wt % of at least one plant, on a dry weight basis. Example 69. 69. The aerosol-forming substrate according to any of Examples 67-68, wherein the substrate comprises, on a dry weight basis, no more than 20, 15, 10, 5, 2, or 1 wt% of at least one plant. Example 70. 70. The aerosol-forming substrate according to any of Examples 67 to 69, wherein the substrate comprises, on a dry weight basis, 0.01 to 20 wt%, 1 to 20 wt%, 2 to 20 wt%, 5 to 20 wt%, 10 to 20 wt%, 15 to 20 wt%, 0.01 to 15 wt%, 1 to 15 wt%, 2 to 15 wt%, 5 to 15 wt%, 10 to 15 wt%, 0.01 to 10 wt%, 1 to 10 wt%, 2 to 10 wt%, 5 to 10 wt%, 0.01 to 5 wt%, 1 to 5 wt%, 2 to 5 wt%, 0.01 to 2 wt%, 1 to 2 wt%, 0.01 to 1 wt% of at least one plant, particularly preferably 1 to 15 wt% of at least one plant. Example 71. An aerosol-forming substrate according to any of Examples 67-70, wherein the at least one plant comprises or consists of one or both of clove and rosmanus. Example 72. An aerosol-forming substrate according to any of Examples 67 to 71, wherein the at least one plant is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 73. An aerosol-forming substrate according to any of Examples 1 to 72, wherein the substrate comprises at least one flavourant. Example 74. An aerosol-forming substrate according to Example 73, wherein the substrate comprises at least 0.1, 1, 2, or 5 wt % of at least one flavorant, on a dry weight basis. Example 75. An aerosol-forming substrate according to any of Examples 73-74, wherein the substrate comprises no more than 10, 5, 2, or 1% by weight, on a dry weight basis, of at least one flavorant. Example 76. 76. An aerosol-forming substrate according to any of Examples 73 to 75, wherein the substrate comprises, on a dry weight basis, 0.1 to 10 wt%, 1 to 10 wt%, 2 to 10 wt%, 5 to 10 wt%, 0.1 to 5 wt%, 1 to 5 wt%, 2 to 5 wt%, 0.1 to 2 wt%, 1 to 2 wt%, 0.1 to 1 wt% of at least one flavourant, particularly preferably 0.1 to 5 wt% of at least one flavourant. Example 77. An aerosol-forming substrate according to any of Examples 73-76, wherein at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-forming substrate. Example 78. An aerosol-forming substrate according to any of Examples 73 to 77, wherein the at least one flavourant is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 79. An aerosol-forming substrate according to any of Examples 1-78, wherein the aerosol-forming substrate comprises one or more organic materials, such as tobacco. Example 80. The aerosol-forming substrate according to any of Examples 1-79, wherein the organic material comprises one or more of herb leaves, tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Example 81. An aerosol-forming substrate according to any of Examples 1 to 80, wherein the organic material is substantially homogeneously distributed throughout the aerosol-forming substrate. Example 82. The aerosol-forming substrate according to any one of Examples 1 to 81, wherein the aerosol-forming substrate is an aerosol-forming substrate that does not contain tobacco. Example 83. An aerosol-forming substrate according to any of Examples 1-82, wherein some or each of the thermally conductive particles comprises a susceptor material. Example 84. An aerosol-forming substrate according to any of Examples 1 to 83, wherein the aerosol-forming substrate has a thermal conductivity in at least one direction, or in all directions, of at least 0.15, 0.2, 0.22, 0.3, 0.4, 0.5, 0.75, 1, 1.25, or 1.5 W / (mK) at 25 degrees Celsius. Example 85. The aerosol-forming substrate may have a viscosity of 1500, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, or 650 kg / m 3 An aerosol-forming substrate according to any of Examples 1 to 84 having a density of less than 100 nm. Example 86. The aerosol-forming substrate is 500 to 900 kg / m 3 , or 600-800kg / m 3 An aerosol-forming substrate according to any of Examples 1 to 85, having a density of Example 87. An aerosol-forming substrate according to any of Examples 1 to 86, wherein the aerosol-forming substrate has a water content of from 1 to 20 wt %, or from 3 to 15 wt %. Example 88. 88. An aerosol-forming substrate according to any of Examples 1 to 87, wherein the aerosol-forming substrate comprises 1 to 20 wt %, or 3 to 15 wt % water. Example 89. An aerosol-forming substrate according to any of Examples 1-88, wherein the aerosol-forming substrate comprises or is in the form of one or more of cut filler, powder particles, granules, pellets, pieces, spaghetti, strips, or sheets. Example 90. An aerosol-forming substrate according to any of Examples 1-89, wherein the aerosol-forming substrate comprises or is in the form of one or more sheets or strips. Example 91. An aerosol-forming substrate according to any of Examples 1 to 90, wherein the aerosol-forming substrate comprises or is in the form of an assembly of one or more sheets. Example 92. An aerosol-forming substrate according to Example 91, wherein the, or each, of the collection of sheets has a width of at least about 5, 10, 25, 50, or 100 mm. Example 93. An aerosol-forming substrate according to any of Examples 1 to 92, wherein the aerosol-forming substrate comprises or is in the form of a plurality of strips. Example 94. An aerosol-forming substrate according to any of Examples 93, wherein each of the plurality of strips has a length of at least about 3, 5, or 10 mm. Example 95. An aerosol-forming substrate according to any of Examples 93-94, wherein each of the plurality of strips has a width of less than about 3, 2, or 1 mm. Example 96. An aerosol-forming substrate according to any of Examples 90-95, wherein the sheet or strip, or each thereof, has a thickness of at least 100, 150, or 200 microns. Example 97. An aerosol-forming substrate according to any of Examples 90-96, wherein the sheet or strip, or each thereof, has a thickness of 300, or 250 microns or less. Example 98. An aerosol-forming substrate according to any of Examples 90 to 97, wherein the sheet or strip, or each thereof, has a thickness of from 100 to 300 microns, or from 150 to 250 microns, or from 200 to 250 microns. Example 99. The sheets or strips, or each of them, have a mass of at least 20, 50, or 100 g / m 2 97. An aerosol-forming substrate according to any one of Examples 90 to 98, having a basis weight of Example 100. The sheets or strips, or each of them, are 300 g / m 2 An aerosol-forming substrate according to any of Examples 90 to 99, having the following basis weight: Example 101. The sheets or strips, or each of them, are 20 to 300 g / m 2 , 50~250g / m 2 , or 100~250g / m2 An aerosol-forming substrate according to any one of Examples 90 to 100, having a basis weight of Example 102. The sheets or strips, or each of them, have a density of at least 0.1, 0.2, 0.3, or 0.5 g / m 3 2. An aerosol-forming substrate according to any of Examples 90 to 101, having a density of Example 103. The sheets or strips, or each of them, have a density of 2, 1.5, 1.2, or 1 g / m 3 An aerosol-forming substrate according to any of Examples 90 to 102, having the following density: Example 104. The sheets or strips, or each of them, are 0.1 to 2 g / m 2 , 0.2~2g / m 2 , 0.3~2g / m 2 , 0.3~1.5g / m 2 , or 0.3 to 1.2 g / m 3 An aerosol-forming substrate according to any of Examples 90 to 103, having a density of Example 105. a first material and a second material, the first material being contained within a combined aerosol-forming substrate as a first plurality of individual elements and the second material being contained within a combined aerosol-forming substrate as a second plurality of individual elements; a first material comprising an aerosol former and having a first thermal conductivity; The associated aerosol-forming substrate, wherein the second material has a second thermal conductivity greater than the first thermal conductivity. Example 106. The combined aerosol-forming substrate according to Example 105, wherein the second material is or comprises an aerosol-forming substrate according to any of Examples 1-104. Example 107. The combined aerosol-forming substrate according to example 105 or 106, wherein the second thermal conductivity is at least 5% greater than the first thermal conductivity, e.g., at least 7% greater, or at least 10% greater, or at least 12% greater, or at least 15% greater. Example 108. The combined aerosol-forming substrate according to any of Examples 105-107, wherein the thermal conductivity of the second material is at least 10% greater than the thermal conductivity of the first material, e.g., at least 12% greater, or at least 15% greater, or at least 20% greater. Example 109. The combined aerosol-forming substrate according to any of Examples 105-108, wherein the first plurality of individual elements, or the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are elongated elements, each having a length dimension greater than its width and thickness dimensions. Example 110. The combined aerosol-forming substrate according to example 109, wherein the elongate elements are in the form of strips, pieces, threads, or ribbons. Example 111. The combined aerosol-forming substrate according to any of Examples 105-110, wherein the first plurality of individual elements, or the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are formed by a casting process, e.g., by a casting process followed by a cutting process. Example 112. The combined aerosol-forming substrate according to any of Examples 105-111, wherein the first plurality of individual elements, or the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are formed by an extrusion process. Example 113. The combined aerosol-forming substrate according to any of Examples 105-112, wherein at least a portion of the first plurality of individual elements, or at least a portion of the second plurality of individual elements, or at least a portion of both the first plurality of individual elements and the second plurality of individual elements are crimped elements, e.g., each crimped element has one or more twists or changes in direction defined in a length dimension of the crimped element. Example 114. The combined aerosol-forming substrate according to any of Examples 105-113, wherein one or both of the first material and the second material are included in the combined aerosol-forming substrate in the form of a cut filler. Example 115. The combined aerosol-forming substrate according to any of Examples 105-114, wherein the individual elements of the first plurality of individual elements, or the second plurality of individual elements, or the individual elements of both the first plurality of individual elements and the second plurality of individual elements have an average thickness of from 5 microns to 2000 microns, such as from 50 microns to 500 microns, for example from 150 microns to 300 microns. Example 116. The combined aerosol-forming substrate according to any of Examples 105-115, wherein the individual elements of the first plurality of individual elements, or the second plurality of individual elements, or the individual elements of both the first and second plurality of individual elements, have an average width of from 100 microns to 2000 microns, such as from 500 microns to 1500 microns, for example from 600 microns to 1000 microns. Example 117. The combined aerosol-forming substrate according to any of Examples 105-116, wherein the individual elements of the first plurality of individual elements, or the second plurality of individual elements, or the individual elements of both the first plurality of individual elements and the second plurality of individual elements, have an average length of from 100 microns to 60 millimeters, such as from 500 microns to 30 millimeter-microns, for example from 1000 microns to 10000 microns. Example 118. The combined aerosol-forming substrate according to any of Examples 105-117, wherein the second material comprises thermally conductive particles. Example 119. The combined aerosol-forming substrate according to any of Examples 105-118, wherein the second material comprises, on a dry weight basis, 1% to 50% thermally conductive particles. Example 120. The combined aerosol-forming substrate according to any of Examples 105-119, wherein the second material comprises thermally conductive particles formed from a thermally conductive material selected from the list consisting of carbon, graphite, expanded graphite, graphene, and metal. Example 121. The combined aerosol-forming substrate according to any of Examples 105-120, wherein the second material is a thermally conductive material selected from the list consisting of carbon, graphite, expanded graphite, graphene, and metal, e.g., each individual piece of the second material is a strip of metal or carbon foil, e.g., copper foil, or aluminum foil, or stainless steel foil, or graphite foil. Example 122. A combined aerosol-forming substrate according to any of Examples 105-121, wherein the first material has a thermal conductivity of less than 0.2 W / (mK) at 25 degrees Celsius and the second material has a thermal conductivity of greater than 0.1, 0.22, 0.3, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 1500, or 1700 W / (mK) at 25 degrees Celsius. Example 123. A combined aerosol-forming substrate according to any of Examples 105-122, wherein the first material is configured to generate an aerosol upon heating, e.g., when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius, and the second material is not configured to generate an aerosol upon heating, e.g., when heated to a temperature between 120 degrees Celsius and 350 degrees Celsius. Example 124. The combined aerosol-forming substrate according to any of Examples 105-123, wherein both the first material and the second material are configured to generate an aerosol upon heating, for example, upon heating to a temperature between 120 degrees Celsius and 395 degrees Celsius. Example 125. The combined aerosol-forming substrate according to any of Examples 105-124, wherein the first material comprises tobacco, e.g., the first material is formed from homogenized tobacco. Example 126. The combined aerosol-forming substrate according to any of Examples 105-125, wherein the first material comprises tobacco and an aerosol former and is configured to generate an aerosol when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius. Example 127. The combined aerosol-forming substrate according to Example 126, wherein the first material is a homogenized tobacco material and further comprises fibers and a binder. Example 128. The combined aerosol-forming substrate according to any of Examples 105-127, wherein the second material comprises an aerosol former and conductive particles constituting between 3 wt% and 90 wt% of the second material on a dry weight basis, and the second material is configured to generate an aerosol when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius. Example 129. The combined aerosol-forming substrate according to any of Examples 105-128, wherein the second material comprises tobacco, an aerosol former, and conductive particles constituting between 3 wt% and 90 wt% of the second material on a dry weight basis, and the second material is configured to generate an aerosol when heated to a temperature between 120 degrees Celsius and 395 degrees Celsius. Example 130. The combined aerosol-forming substrate according to Example 129, wherein the second material is a thermally conductive homogenized tobacco material and further comprises fibers and a binder. Example 131. The combined aerosol-forming substrate according to example 128, wherein the second material is tobacco-free, e.g., the second material is a thermally conductive tobacco-free material, further comprising fibers and a binder. Example 132. The combined aerosol-forming substrate according to any of Examples 105-131, wherein the individual elements of the first material and the individual elements of the second material are formed separately and mixed together in a predetermined ratio to form the combined aerosol-forming material. Example 133. The combined aerosol-forming substrate according to any of Examples 105 to 132, wherein the ratio of the first material to the second material in the combined aerosol-forming substrate is from 1:10 to 10:1, such as from 1:5 to 8:1, for example from 1:1 to 5:1. Example 134. The combined aerosol-forming substrate according to any of Examples 105-133, wherein the second material comprises, on a dry weight basis, 40-80 wt.% of a particulate carbon material, 10-40 wt.% of an aerosol former, 4-20 wt.% of fibers, and 2-10 wt.% of a binder, and the particulate carbon material comprises one or more of graphite, expanded graphite, graphene, carbon nanotubes, and charcoal. Example 135. 5. The combined aerosol-forming substrate according to any of Examples 105-134, wherein the first material comprises, on a dry weight basis, 40-80 wt.% particulate carbon material, 10-40 wt.% aerosol former, 4-20 wt.% fibers, and 2-10 wt.% binder, the particulate carbon material consisting of one or more of graphite, expanded graphite, graphene, carbon nanotubes, and charcoal, and the first material has a lower thermal conductivity than the second material. Example 136. The combined aerosol-forming substrate according to example 135, wherein the particulate carbon material comprises graphite. Example 137. The combined aerosol-forming substrate according to any of Examples 105-136, wherein the second material and the first material are homogeneously distributed within the combined aerosol-forming substrate. Example 138. A method of forming a combined aerosol-forming substrate, comprising: forming a first plurality of individual elements from a first material; forming a second plurality of individual elements from a second material; and combining the first plurality of individual elements with the second plurality of individual elements to form a combined aerosol-forming substrate, wherein the second material has a greater thermal conductivity than the first material, e.g., a combined aerosol-forming substrate according to any of Examples 105-137. Example 139. A method of forming a combined aerosol-forming substrate, comprising the steps of providing a first plurality of individual elements from a first material, providing a second plurality of individual elements from a second material, and combining the first plurality of individual elements with the second plurality of individual elements to form a combined aerosol-forming substrate, wherein the second material has a greater thermal conductivity than the first material, e.g., a combined aerosol-forming substrate according to any of Examples 105-137. Example 140. The method according to example 138 or 139, wherein the first plurality of discrete elements are formed by cutting a sheet of a first material into strips and the second plurality of discrete elements are formed by cutting a sheet of a second material into strips. Example 141. The method according to example 140, wherein the first plurality of individual elements and the second plurality of individual elements are cut to substantially the same size. Example 142. The method according to any of Examples 138-141, wherein forming at least one of the first plurality of individual elements and the second plurality of individual elements includes crimping, e.g., such that the first plurality of individual elements, the second plurality of individual elements, or both the first plurality of individual elements and the second plurality of individual elements are crimped elements. Example 143. The method according to any of Examples 138-142, further comprising forming a first material, forming a second material, or forming both the first material and the second material. Example 144. The method according to any of Examples 138 to 143, wherein the combined aerosol-forming substrate is a combined aerosol-forming substrate as described in relation to any of Examples 105 to 137. Example 145. An aerosol-generating article comprising an associated aerosol-forming substrate as defined in any of Examples 105-137 or produced by the method as defined in any of Examples 138-144. Example 146. The aerosol-generating article according to example 145, wherein the article is in the form of a rod and comprises multiple components including combined aerosol-forming substrates assembled within a wrapper or casing. Example 147. An aerosol-generating article comprising an aerosol-forming substrate or an aerosol-forming substrate combined according to any of Examples 1-146. Example 148. The aerosol-generating article according to Example 147, wherein the aerosol-generating article comprises a front plug. Example 149. The aerosol-generating article according to any of Examples 147-148, wherein the aerosol-generating article comprises a first hollow tube, such as a first hollow acetate tube. Example 150. The aerosol-generating article according to any of Examples 147-148, wherein the aerosol-generating article comprises a second hollow tube, such as a second hollow acetate tube. Example 151. The aerosol-generating article according to example 150, wherein the second hollow tube comprises one or more vent holes. Example 152. An aerosol-generating article according to any one of Examples 147 to 151, wherein the aerosol-generating article is provided with a mouth-side plug filter. Example 153. The aerosol-generating article according to any of Examples 147-152, wherein the aerosol-generating article comprises a wrapper, such as a paper wrapper. Example 154. An aerosol-generating article according to any of Examples 147 to 153, comprising a front plug, an aerosol-forming substrate disposed downstream of the front plug, a first hollow tube disposed downstream of the aerosol-forming substrate, a second hollow tube disposed downstream of the first hollow tube, and an oral plug filter disposed downstream of the second hollow tube. Example 155. The aerosol-generating article according to example 154, wherein the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the oral plug filter are surrounded by a wrapper, such as a paper wrapper. Example 156. The aerosol-generating article according to any of Examples 148 or 149-155 when dependent on Example 148, wherein the front plug has a length of 2-10 mm, 3-8 mm, or 4-6 mm, for example about 5 mm. Example 157. The aerosol-generating article according to any of Examples 147 to 156, wherein the aerosol-forming substrate has a length of 5 to 20 mm, 8 to 15 mm, or 10 to 15 mm, for example about 12 mm. Example 158. The aerosol-generating article according to any of Examples 149 or 150-157 when dependent on Example 149, wherein the first hollow tube has a length of 2-20 mm, 5-15 mm, or 5-10 mm, e.g., about 8 mm. Example 159. The aerosol-generating article according to any of Examples 150 or 151-158 when dependent on Example 150, wherein the second hollow tube has a length of 2-20 mm, 5-15 mm, or 5-10 mm, e.g., about 8 mm. Example 160. The aerosol-generating article according to any of Examples 152 or 153-159 when dependent on Example 152, wherein the mouth plug filter has a length of 5-20 mm, 8-15 mm, or 10-15 mm, e.g., about 12 mm. Example 161. An aerosol generating system comprising an aerosol generating article according to any one of Examples 145 to 160 and an electrical aerosol generating device. Example 162. An aerosol generating system according to Example 161, wherein the electrical aerosol generating device is configured to resistively heat the aerosol generating article during use. Example 163. An aerosol generating system according to any of Examples 161-162, wherein the electrical aerosol generating device is configured, in use, to inductively heat an aerosol-generating article, such as an aerosol-forming substrate of the aerosol-generating article. Example 164. A method of forming an aerosol-forming substrate according to any one of Examples 1 to 163, for example, any one of Examples 1 to 104, comprising the steps of: forming a slurry including thermally conductive particles, an aerosol former, fibers, and a binder; casting and drying the slurry to form an aerosol-forming substrate or a precursor for forming into an aerosol-forming substrate. Example 165. The process according to example 164, wherein the slurry comprises water. Example 166. The process according to any of embodiments 164-165, wherein the slurry comprises 40-90 wt%, 40-85 wt%, 50-80 wt%, 60-80 wt%, or 60-75 wt% water. Example 167. The process according to any of examples 164-166, wherein the slurry comprises an acid, such as fumaric acid. Example 168. The method according to any of Examples 164-167, wherein the slurry comprises nicotine. Example 169. forming a slurry an aerosol former; Fibers and Water, Optionally, an acid, forming a first mixture, optionally including nicotine; Thermally conductive particles; forming a second mixture comprising a binder; The method according to any of Examples 164-168, comprising adding the second mixture to the first mixture to form a combined mixture. Example 170. The method according to example 170, wherein forming the first mixture includes providing an aerosol former, or a solution including an aerosol former and nicotine. Example 171. The method according to example 171, wherein forming the first mixture comprises adding an acid to an aerosol former, or a solution comprising an aerosol former and nicotine, to form a first premixture. Example 172. The method according to any of Examples 170-171, wherein forming the first mixture comprises adding water to the aerosol former, or to a solution comprising the aerosol former and nicotine, or to the first pre-mixture to form a second pre-mixture. Example 173. The method according to any of Examples 169-172, wherein forming the first mixture includes adding fibers to the second pre-mixture. Example 174. The method according to any of Examples 169-173, wherein forming the second mixture includes mixing thermally conductive particles and a binder. Example 175. The method according to any of Examples 169-174, wherein the method comprises first mixing the combined mixture. Example 176. The process according to example 175, wherein the first mixing is carried out under a first pressure of not more than 500, 400, 300, 250, or 200 mbar. Example 177. The method according to example 175 or 176, wherein the first mixing is carried out for 1 to 10 minutes, 2 to 8 minutes, or 3 to 6 minutes, e.g., about 4 minutes. Example 178. The method according to any of examples 175-177, wherein the method includes, after the first mixing, a second mixing. Example 179. The process according to example 178, wherein the second mixing is conducted under a second pressure less than the first pressure. Example 180. The method according to example 179, wherein the second pressure is less than or equal to 500, 400, 300, 200, 150, or 100 mbar. Example 181. The method according to example 178 or 179 or 180, wherein the second mixing is carried out for 5 to 120 seconds, 5 to 80 seconds, 5 to 40 seconds, or 10 to 30 seconds, for example, about 20 seconds. Example 182. The method according to any of Examples 164-181, wherein casting the slurry includes casting the slurry onto a flat support, such as a flat steel support. Example 183. The method according to any of Examples 164-182, wherein after casting the slurry and before drying the slurry, the method comprises setting a thickness of the slurry, e.g., setting a thickness of the slurry to between 100 and 1,000 microns, between 200 and 900 microns, between 300 and 800, between 500 and 700 microns, e.g., about 600 microns. Example 184. The method according to any of Examples 164-183, wherein drying the slurry comprises providing a flow of gas, such as air, over or through the slurry. Example 185. The method according to embodiment 184, wherein the gas stream is heated. Example 186. The method according to example 185, wherein the gas stream is heated to a temperature of 100 to 160 degrees Celsius, or 120 to 140 degrees Celsius. Example 187. The method according to any of Examples 184-186, wherein the flow of gas is provided for 1 to 10 minutes or 2 to 5 minutes. Example 188. The method according to any of Examples 164-187, wherein drying the slurry comprises drying the slurry until the slurry has a moisture content of 1-20 wt%, 2-15 wt%, 2-10 wt%, or 3-7 wt%. Example 189. The method according to any of Examples 164-188, wherein drying the slurry forms a precursor for formation into an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Example 190. The method according to example 189, wherein the method includes cutting a sheet of aerosol-forming material.

[0180] The embodiments will now be further described with reference to the following figures: [Brief description of the drawings]

[0181] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article. [Diagram 2] FIG. 2 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating article. [Diagram 3] FIG. 3 shows a schematic cross-sectional view of a first embodiment of an aerosol generation system. [Figure 4] FIG. 4 shows a schematic cross-sectional view of a second embodiment of an aerosol generation system. [Diagram 5] FIG. 5 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating article. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0182] 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article 10. The aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or proximal or mouth end 20 and has an overall length of about 45 millimeters.

[0183] The aerosol-generating article 10 comprises a rod of aerosol-forming substrate 12 and a downstream section 14 located downstream of the rod of aerosol-forming substrate 12. Additionally, the aerosol-generating article 10 comprises an upstream section 16 located upstream of the rod of aerosol-forming substrate 12.

[0184] The downstream section 14 includes a support element 22 located immediately downstream of the rod 12 of the aerosol-forming substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1, the upstream end of the support element 22 abuts the downstream end of the rod 12 of the aerosol-generating substrate. In addition, the downstream section 14 includes an aerosol cooling element 24 located immediately downstream of the support element 22, the aerosol cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of Figure 1, the upstream end of the aerosol cooling element 24 abuts the downstream end of the support element 22.

[0185] As will become apparent from the following description, the support element 22 and the aerosol cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 10. Taken as a whole, the intermediate hollow section 50 does not contribute substantially to the overall RTD of the aerosol-generating article. The RTD of the intermediate hollow section 26 as a whole is substantially 0 millimeters HO.

[0186] The support element 22 may include a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an interior cavity 28 extending entirely from an upstream end 30 of the first hollow tubular segment 26 to a downstream end 32 of the first hollow tubular segment 26. The interior cavity 28 is substantially empty, thereby allowing substantially unrestricted airflow along the interior cavity 28. As such, the first hollow tubular segment 26, and, consequently, the support element 22, does not substantially contribute to the overall RTD of the aerosol-generating article 10. More specifically, the RTD of the first hollow tubular segment 26 (which is substantially the RTD of the support element 22) is substantially 0 millimeters H2O.

[0187] The first hollow tubular segment 26 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D FTS ), the peripheral wall thickness of the first hollow tubular segment 26 is therefore approximately 2.67 millimeters.

[0188] The aerosol cooling element 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an interior cavity 36 extending entirely from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The interior cavity 36 is substantially empty, thereby allowing substantially unrestricted airflow therealong. The second hollow tubular segment 28, and consequently the aerosol cooling element 24, does not substantially contribute to the overall RTD of the aerosol-generating article 10. More specifically, the RTD of the second hollow tubular segment 34 (which is essentially the RTD of the aerosol cooling element 24) is substantially 0 millimeters H2O.

[0189] The second hollow tubular segment 34 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D STS ) of the peripheral wall of the second hollow tubular segment 34 is approximately 2 millimeters. FTS ) and the inner diameter (D STS ) is about 0.75.

[0190] The aerosol-generating article 10 includes a ventilation zone 60 provided at a location along the second hollow tubular segment 34. More specifically, the ventilation zone is provided approximately 2 millimeters from the upstream end of the second hollow tubular segment 34. In this embodiment, the ventilation zone 60 includes a circumferential row of perforations through the paper wrapper 70, and the ventilation level of the aerosol-generating article 10 is approximately 25 percent.

[0191] 1, the downstream section 14 further includes a mouthpiece element 42, also referred to as an oral plug filter, at a location downstream of the intermediate hollow section 50. More specifically, the mouthpiece element 42 is positioned immediately downstream of the aerosol cooling element 24. As shown in the drawing of FIG.

[0192] Mouthpiece element 42 is provided in the form of a cylindrical plug of low density cellulose acetate.

[0193] Mouthpiece element 42 has a length of about 12 millimeters and an outer diameter of about 7.25 millimeters. The RTD of mouthpiece element 42 is about 12 millimeters H2O. The ratio of the length of mouthpiece element 42 to the length of intermediate hollow section 50 is about 0.6.

[0194] The rod 12 of the aerosol-forming substrate has an outer diameter of about 7.25 millimeters, and a length of about 12 millimeters.

[0195] The upstream section 16 includes an upstream element 46, also called a forward plug, located immediately upstream of the rod 12 of the aerosol-forming substrate, with the upstream element 46 being longitudinally aligned with the rod 12. In the embodiment of FIG. 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of the aerosol-forming substrate. The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate. The upstream element 46 has a length of about 5 millimeters. The RTD of the upstream element 46 is about 30 millimeters HO.

[0196] The upstream element 46 , the rod of aerosol-forming substrate 12 , the support element 22 , the aerosol cooling element 24 , and the mouthpiece element 42 are surrounded by a paper wrapper 70 .

[0197] The aerosol-forming substrate rod 12 comprises, on a dry weight basis, about 76.1 wt% of thermally conductive particles 44. In this embodiment, the thermally conductive particles 44 are graphite particles, in particular FP 99.5 (>99.5% purity) graphite particles from Graphit Kropfmul GmbH, AMG Graphite GK, although other particles or mixtures of particles may be used. The thermally conductive particles each have a thermal conductivity in at least one direction of about 6 W / (mK) at 25 degrees Celsius.

[0198] The aerosol-forming substrate rod 12 comprises, on a dry weight basis, about 17.7 wt% aerosol former, in this embodiment, the aerosol former is glycerol, particularly ICOF Europe fodd grade (>99.5% purity) glycerol.

[0199] The aerosol-forming substrate rod 12 comprises, on a dry weight basis, about 3.9 wt% fibres, in this embodiment the fibres are cellulose fibres, in particular birch cellulose fibres from Stora Enso OYJ.

[0200] The aerosol-forming substrate rod 12 comprises, on a dry weight basis, about 2.3 wt% of a binder. In this embodiment, the binder is guar gum, specifically Gumix International Inc's guar gum.

[0201] The aerosol-forming substrate rod 12 contains approximately 10 wt % water when measured at 25 degrees Celsius.

[0202] In other embodiments, the rod 12 of aerosol-forming substrate further comprises one or more of nicotine, an acid such as fumaric acid, a botanical such as clove or rosmarinus, and a flavouring agent.

[0203] The aerosol-forming substrate has a thermal conductivity in at least one direction of at least 0.1 W / (mK) at 25 degrees Celsius. The aerosol-forming substrate may have a thermal conductivity in at least one direction of 0.2, 0.5, 1, 1.5 or more W / (mK) at 25 degrees Celsius.

[0204] Each of the thermally conductive particles 44 is substantially spherical in shape. The thermally conductive particles 44 are substantially homogeneously distributed throughout the aerosol-forming substrate. The particle size distribution has a volume D10 particle size of about 6 microns, a volume D50 particle size of about 20 microns, and a volume D90 particle size of about 56 microns. Each of the thermally conductive particles 44 has a particle size greater than about 1 micron and less than about 300 microns.

[0205] The thermally conductive particles 44 have a density of about 2200 kilograms per cubic meter. The aerosol-forming substrate has a density of about 800 kilograms per cubic meter.

[0206] The aerosol-forming substrate rod 12 is formed by the process described below.

[0207] The slurry is formed using a laboratory spasser, which has the ability to mix viscous liquids, disperse powders through liquids, and remove gas from the mixture (e.g., by applying a vacuum or other suitably low pressure). In this embodiment, a laboratory spasser commercially available from PC Laborsystem was used.

[0208] To form the slurry, a first mixture is formed by adding about 7.11 grams of aerosol former, then about 157.5 grams of water, then about 1.57 grams of fiber to a lab dispenser. These first components are then mixed at 600-700 rpm for 5 minutes at 25 degrees Celsius to ensure a homogenous mixture and to hydrate the fiber. A second mixture is then formed by manually mixing about 32.95 grams of thermally conductive particles and about 0.92 grams of binder. This mixing of the second mixture avoids the formation of lumps in the lab dispersion. The second mixture is then added to the first mixture to form a combined mixture. The combined mixture is then mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of about 200 mbar. The reduced pressure can help ensure that the thermally conductive particles are homogenously dispersed in the mixture and that there is little trapped air and few lumps in the combined mixture. The combined mixture is then mixed at 5000 rpm for 20 seconds at 25 degrees Celsius and a second reduced pressure of about 100 mbar. This second reduced pressure may help remove any remaining air bubbles. This forms a slurry for casting.

[0209] The slurry is then cast and dried using a suitable device. In this embodiment, a commercially available Labcoater Mathis device is used. The device includes a stainless steel, flat support, and a castor blade to control the thickness of the slurry cast onto the flat support.

[0210] The slurry is cast onto a flat support and the gap between the caster blade and the flat support is set at 0.6 millimeters, ensuring that the thickness of the slurry at any given point is no more than 0.6 millimeters.

[0211] The slurry is then dried with hot air at 120-140 degrees Celsius for 2-5 minutes. After this drying, a sheet of aerosol-forming substrate is formed. The sheet has a thickness of about 159 microns, a basis weight of about 125.7 grams per square meter, and a density of about 0.79 kilograms per cubic meter.

[0212] The sheets are then collected and cut to form rods of aerosol-forming substrate 12. In another embodiment, the sheets are also crimped.

[0213] After forming the rod 12 of aerosol-forming substrate, the aerosol-generating article 10 is assembled by positioning the various components of the article 10 and packaging the components within a wrapper 70.

[0214] Figure 2 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating article 11. This second embodiment is identical to the first embodiment of Figure 1, except that the rod of aerosol-forming substrate 12 is replaced by an alternative rod of associated aerosol-forming substrate 13. The same reference numbers have been used for identical components in the embodiments of Figures 1 and 2.

[0215] In the second embodiment of the rod 13, the combined aerosol-forming substrate comprises a first material and a second material. The first material is included as a first plurality of individual elements in the combined aerosol-forming substrate, and the second material is included as a second plurality of individual elements in the combined aerosol-forming substrate. In this embodiment, the first material and the second material are equally weighted in the combined aerosol-forming substrate. However, in other embodiments, there may be more or less of the first material than the second material in the combined aerosol-forming substrate.

[0216] In this embodiment, the elements of both the first and second pluralities of discrete elements have an average thickness between 150 microns and 300 microns, an average width between 600 microns and 1000 microns, and an average length between 1000 microns and 10000 microns.

[0217] The first material may be a conventional tobacco cut filler. As such, the first material may be formed by a conventional tobacco cut filler manufacturing process and may include an aerosol former, fibers, and binder, but does not include thermally conductive particles. As an example, the first material may be made using a method similar to that described above for the rod 12 of the aerosol-forming substrate of the first embodiment of FIG. 1, except that the thermally conductive particles are not included, and the sheet is shredded to form the reconstituted cut filler, rather than being assembled and cut to form the rod 12.

[0218] The second material is formed from an aerosol-forming substrate similar to that of rod 12 in the first embodiment of Figure 1. The second material includes, on a dry weight basis, about 76.1 wt% thermally conductive particles 45, about 17.7 wt% aerosol former, about 3.9 wt% fiber, and about 2.3 wt% binder. In the second material, all of the thermally conductive particles are either graphite particles or expanded graphite particles, although other particles or mixtures of particles may be used.

[0219] The first material has a first thermal conductivity and the second material has a second thermal conductivity that is at least 10% greater than the first thermal conductivity, such that the second material serves to increase the thermal conductivity of the associated aerosol-forming substrate.

[0220] The rod 13 of assembled aerosol-forming substrate is formed by the process described below.

[0221] The slurry is formed using a laboratory spasser, which has the ability to mix viscous liquids, disperse powders through liquids, and remove gas from the mixture (e.g., by applying a vacuum or other suitably low pressure). In this embodiment, a laboratory spasser commercially available from PC Laborsystem was used.

[0222] To form the slurry, a first mixture is formed by adding about 7.11 grams of aerosol former, then about 157.5 grams of water, then about 1.57 grams of fiber to a lab dispenser. These first components are then mixed at 600-700 rpm for 5 minutes at 25 degrees Celsius to ensure a homogenous mixture and to hydrate the fiber. A second mixture is then formed by manually mixing about 32.95 grams of thermally conductive particles and about 0.92 grams of binder. This mixing of the second mixture avoids the formation of lumps in the lab dispersion. The second mixture is then added to the first mixture to form a combined mixture. The combined mixture is then mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of about 200 mbar. The reduced pressure can help ensure that the thermally conductive particles are homogenously dispersed in the mixture and that there is little trapped air and few lumps in the combined mixture. The combined mixture is then mixed at 5000 rpm for 20 seconds at 25 degrees Celsius and a second reduced pressure of about 100 mbar. This second reduced pressure may help remove any remaining air bubbles. This forms a slurry for casting.

[0223] The slurry is then cast and dried using a suitable device. In this embodiment, a commercially available Labcoater Mathis device is used. The device includes a stainless steel, flat support, and a castor blade to control the thickness of the slurry cast onto the flat support.

[0224] The slurry is cast onto a flat support and the gap between the caster blade and the flat support is set at 0.6 millimeters, ensuring that the thickness of the slurry at any given point is no more than 0.6 millimeters.

[0225] The slurry is then dried with hot air at 120-140 degrees Celsius for 2-5 minutes. After this drying, a sheet of aerosol-forming substrate is formed. The sheet has a thickness of about 159 microns, a basis weight of about 125.7 grams per square meter, and a density of about 0.79 kilograms per cubic meter.

[0226] The sheet is then chopped to form a plurality of individual elements of the aerosol-forming substrate, in other words, the sheet is then cut to form the second material present in the combined aerosol-forming substrate into a second plurality of individual elements.

[0227] This second material is then mixed with the first material, which is the first plurality of individual elements. As mentioned above, the first material may be formed using conventional tobacco cut filler manufacturing processes, which will not be described in detail herein.

[0228] The mixed first and second materials, present as a plurality of individual elements, are then formed into a combined aerosol-forming substrate rod 13, for example by enclosing it in a wrapper.

[0229] After forming the rod 13 of assembled aerosol-forming substrates, the aerosol-generating article 11 is then assembled by positioning the various components of the article 11 and packaging the components within a wrapper 70.

[0230] 3 shows a schematic cross-sectional view of a first embodiment of an aerosol generating system 100. The system 100 comprises an aerosol generating device 102 and the aerosol-generating article 10 of FIG. 1, although the device 102 can equally be used with the aerosol-generating article 11 of FIG.

[0231] The aerosol generating device 102 comprises a battery 104, a controller 106, a heating blade 108 coupled to the battery, and a puff detection mechanism (not shown). The controller 106 is coupled to the battery 104, the heating blade 108, and the puff detection mechanism.

[0232] The aerosol generating device 102 further comprises a housing 110 defining a substantially cylindrical cavity for receiving a portion of the article 10. The heating blade 108 is centrally positioned within the cavity and extends longitudinally from the base of the cavity.

[0233] In this embodiment, the heating blade 108 includes a substrate and an electrically resistive track located on the substrate. The battery 104 is coupled to the heating blade 108 such that a current can be passed through the electrically resistive track to heat the electrically resistive track and the heating blade 108 to an operating temperature.

[0234] In use, a user inserts the article 10 into the cavity and causes the heating blade 108 to penetrate the upstream element 46 and rod 12 of the aerosol-forming substrate of the article 10. FIG.

[0235] The user then takes a puff at the downstream end of the article 10. This causes air to flow through an air inlet (not shown) of the device 102, then through the article 10, from the upstream end 18 to the downstream end 20, and into the user's mouth.

[0236] When a user puffs on the article 10, air flows through the air inlet of the device. The puff detection mechanism detects when the airflow rate through the air inlet increases above a non-zero threshold flow rate. The puff detection mechanism sends a signal to the controller 106 in response. The controller 106 then controls the battery 104 to apply a current to the electrically resistive track, heating the heating blade 108. This heats the rod 12 of the aerosol-forming substrate, which is in contact with the heating blade 108.

[0237] The thermally conductive particles 44 have a significantly higher thermal conductivity than the surrounding aerosol-forming material. As such, these particles can act as localized hot spots and provide a more uniform temperature across the aerosol-forming substrate, particularly in the radial direction from the heating blade 108, whereas in prior art substrates there can be significant temperature gradients. This can allow a greater proportion of the aerosol-forming substrate to reach a temperature high enough to release volatile compounds, and therefore a more efficient use of the aerosol-forming substrate.

[0238] Heating of the aerosol-forming substrate causes it to release volatile compounds. These compounds are entrained in air flowing from the upstream end 18 of the article 10 toward the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as they pass through the interior cavities 28, 36 of the support element 22 and the aerosol cooling element 24. The aerosol then passes through the mouthpiece element 42, which may remove undesirable particles that may be entrained in the airflow and enter the user's mouth.

[0239] When the user stops inhaling on the article 10, the airflow rate through the air inlet of the device decreases below a non-zero threshold flow rate. This is detected by the puff detection mechanism, which in response sends a signal to the controller 106. The controller 106 then controls the battery 104 to reduce the current passing through the electrically resistive track to zero.

[0240] After taking a number of puffs on the article 10, the user may choose to replace the article 10 with a new article.

[0241] 4 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system 200. System 200 comprises an aerosol-generating device 202 and the aerosol-generating article 11 of FIG. 2, although device 202 can equally be used with aerosol-generating article 10 of FIG.

[0242] The aerosol generating device 202 includes a battery 204, a controller 206, an inductor coil 208, and a puff detection mechanism (not shown). The controller 206 is coupled to the battery 204, the inductor coil 208, and the puff detection mechanism.

[0243] The aerosol generating device 202 further comprises a housing 210 defining a substantially cylindrical cavity for receiving a portion of the article 11. An inductor coil 208 spirals around the cavity.

[0244] The battery 204 is coupled to the inductor coil 208 such that an alternating current can be applied to the inductor coil 208 .

[0245] In use, a user inserts an item 11 into the cavity. Figure 4 shows an item 11 inserted into the cavity of the device 202.

[0246] The user then takes a puff on the downstream end of article 11. This causes air to flow through an air inlet (not shown) of device 202, then through article 11, from upstream end 18 to downstream end 20, and into the user's mouth.

[0247] When a user puffs on the article 11, air flows through the air inlet of the device. The puff detection mechanism detects that the airflow rate through the air inlet has increased above a non-zero threshold flow rate. The puff detection mechanism accordingly sends a signal to the controller 206. The controller 206 then controls the battery 204 to apply an alternating current to the inductor coil 208. This causes the inductor coil 208 to generate a varying electromagnetic field. The rod 13 of the combined aerosol-forming substrate is located within this varying electromagnetic field. The material of the particles 45, graphite and expanded graphite, is a susceptor material. The varying electromagnetic field thus induces eddy currents in the particles 45. This causes the particles 45 to heat, which in turn heats the nearby aerosol-forming material.

[0248] Heating of the aerosol-forming material causes it to release volatile compounds. These compounds are entrained in air flowing from the upstream end 18 of the article 11 toward the downstream end 20 of the article 11. The compounds cool and condense to form an aerosol as they pass through the internal cavities 28, 36 of the support element and the aerosol cooling element. The aerosol then passes through the mouthpiece element 42, which may remove undesirable particles that may be entrained in the airflow and enter the user's mouth.

[0249] When the user stops inhaling on the article 11, the airflow rate through the air inlet of the device decreases below a non-zero threshold flow rate. This is detected by the puff detection mechanism, which in response sends a signal to the controller 206. The controller 206 then controls the battery 204 to reduce the current passing through the electrically resistive track to zero.

[0250] After taking a number of puffs on the article 11, the user may choose to replace the article 11 with a new article.

[0251] Figure 5 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating article 510. This third embodiment is identical to the first embodiment of Figure 1, except that the rod of aerosol-forming substrate 12 is replaced by an alternative rod of aerosol-forming substrate 512. The same reference numbers have been used for identical components in the embodiments of Figures 1 and 5.

[0252] The rod 512 of the aerosol-forming substrate of the third embodiment of FIG.

[0253] The susceptor element 580 is disposed substantially longitudinally within the aerosol-forming substrate rod 512 such that it is approximately parallel to the longitudinal axis of the aerosol-forming substrate rod 512. As shown in the drawing in Figure 5, the susceptor element 580 is located at a radially central position within the rod and extends along the longitudinal axis of the rod 12.

[0254] The susceptor element 580 extends completely from the upstream end to the downstream end of the aerosol-forming substrate rod 512. Thus, the susceptor element 580 has substantially the same length as the aerosol-forming substrate rod 512.

[0255] In the embodiment of FIG. 5, the susceptor element 580 is provided in the form of a strip of ferromagnetic steel and has a length of about 12 millimeters, a thickness of about 60 micrometers, and a width of about 4 millimeters.

[0256] The aerosol-generating article 510 of Figure 5 may be used with the aerosol-generating device 202 of Figure 4 in the same manner as the aerosol-generating article 11 of Figure 2. Notably, the inclusion of the susceptor element 580 means that the article 510 may be inductively heated regardless of whether the thermally conductive particles include a suitable susceptor material for inductive heating.

[0257] The aerosol-forming substrate rod 512 comprises, on a dry weight basis, about 66 wt% of thermally conductive particles 44. In this embodiment, the thermally conductive particles 44 are graphite particles, specifically FP 99.5 (>99.5% purity) graphite particles available from Graphit Kropfmul GmbH, AMG Graphite GK, although other particles or mixtures of particles may be used. The thermally conductive particles each have a thermal conductivity in at least one direction of about 6 W / (mK) at 25 degrees Celsius.

[0258] The rod of aerosol-forming substrate 512 comprises, on a dry weight basis, about 20 wt% of the aerosol former, in this embodiment, the aerosol former is glycerol, specifically food grade (>99.5% purity) glycerol available from ICOF Europe.

[0259] The aerosol-forming substrate rod 512 comprises, on a dry weight basis, about 7 wt% fibres, in this embodiment the fibres are cellulose fibres, in particular birch cellulose fibres available from Stora Enso OYJ.

[0260] The aerosol-forming substrate rod 512 comprises, on a dry weight basis, about 4 wt % binder. In this embodiment, the binder is sodium carboxymethylcellulose, specifically carboxymethylcellulose (CMC) Type K-700 available from Gumix International Inc.

[0261] The aerosol-forming substrate rod 512 contains, on a dry weight basis, about 1 wt% nicotine.

[0262] The aerosol-forming substrate rod 512 comprises, on a dry weight basis, about 2 wt % acid, in this embodiment, fumaric acid, specifically fumaric acid commercially available from Sigma-Aldrich (>99% purity).

[0263] In other embodiments, the substrate further comprises at least one plant, such as clove or rosmarinus.

[0264] The aerosol-forming substrate rod 12 contains approximately 10 wt % water when measured at 25 degrees Celsius.

[0265] The aerosol-forming substrate has a thermal conductivity in at least one direction of at least 0.1 W / (mK) at 25 degrees Celsius. The aerosol-forming substrate may have a thermal conductivity in at least one direction of 0.2, 0.5, 1, 1.5 or more W / (mK) at 25 degrees Celsius.

[0266] The thermally conductive particles 44 are identical to those in the rod 12 of the first embodiment of FIG.

[0267] The aerosol-forming substrate rod 512 is formed by the process described below.

[0268] The slurry is formed using a laboratory spasser, which has the ability to mix viscous liquids, disperse powders through liquids, and remove gas from the mixture (e.g., by applying a vacuum or other suitably low pressure). In this embodiment, a laboratory spasser commercially available from PC Laborsystem was used.

[0269] To form the slurry, a first mixture is formed by adding about 12 grams of nicotine solution in glycerin at 10% concentration (aerosol former), about 13.2 grams of glycerin, about 2.4 grams of fumaric acid, about 280 grams of water, and about 8.4 grams of fiber to a lab dispenser. These first ingredients are then mixed at 600-700 rpm for 5 minutes at 25 degrees Celsius to ensure a homogenous mixture and to hydrate the fiber. A second mixture is then formed by manually mixing about 79.2 grams of thermally conductive particles and about 4.8 grams of binder. This mixing of the second mixture avoids the formation of lumps in the lab dispersion. The second mixture is then added to the first mixture to form a combined mixture. The combined mixture is then mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of about 200 mbar. The reduced pressure can help ensure that the thermally conductive particles are homogenously dispersed in the mixture and that there is little air trapped in the combined mixture and few lumps. The combined mixture is then mixed at 5000 rpm for 20 seconds at a second reduced pressure of 25 degrees Celsius and about 100 mbar. This second reduced pressure can help remove any remaining air bubbles. This forms a slurry for casting.

[0270] The slurry is then cast and dried using a suitable device. In this embodiment, a commercially available Labcoater Mathis device is used. The device includes a stainless steel, flat support, and a castor blade to control the thickness of the slurry cast onto the flat support.

[0271] The slurry is cast onto a flat support and the gap between the caster blade and the flat support is set at 0.6 millimeters, ensuring that the thickness of the slurry at any given point is no more than 0.6 millimeters.

[0272] The slurry is then dried with hot air at 120-140 degrees Celsius for 2-5 minutes. After this drying, a sheet of aerosol-forming substrate is formed. The sheet has a thickness of about 230 microns and a basis weight of about 200 grams per square meter.

[0273] The sheets are then assembled and cut to form a substantially rod-shaped precursor. A susceptor element is then inserted into the precursor to form a rod 512 of the aerosol-forming substrate.

[0274] After forming the rod 512 of aerosol-forming substrate, the aerosol-generating article 510 is assembled by positioning the various components of the article 510 and packaging the components within the wrapper 70.

[0275] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all cases as being modified by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A ± 10% of A. Within this context, the number A may be considered to include numerical values ​​that are within the general standard error for the measurement of the property that the number A modifies. The number A may, in some instances used in the appended claims, deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel properties of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. On a dry weight basis, 70 to 90 wt% of carbon particles, 7 to 26 wt% of an aerosol former, 2 to 20 wt% of fibers, 2 to 10 wt% of a binder, and comprising each of the carbon particles consisting of one or more of graphite, exfoliated graphite, graphene, carbon nanotubes, charcoal, and diamond, an aerosol-forming substrate.

2. The aerosol-forming substrate according to claim 1, wherein the carbon particles have a particle size distribution having a volume D10 particle size of 1 to 20 microns.

3. The aerosol-forming substrate according to claim 1, wherein the carbon particles have a particle size distribution having a volume D90 particle size of 50 to 300 microns.

4. The aerosol-forming substrate according to claim 1, wherein the carbon particles have a particle size distribution having a volume D10 particle size and a number D90 particle size, and the volume D90 particle size is 50 times or less of the number D10 particle size.

5. The aerosol-forming substrate according to claim 1, wherein some or all of the carbon particles are substantially spherical.

6. The aerosol-forming substrate according to claim 1, wherein each of the carbon particles consists of one or more of exfoliated graphite, graphene, and diamond.

7. The aerosol-forming substrate according to claim 1, wherein the substrate contains at least 75 wt% of the carbon particles on a dry weight basis.

8. The aerosol-forming substrate according to claim 1, wherein the substrate contains at least 80 wt% of the carbon particles on a dry weight basis.

9. The aerosol-forming substrate according to claim 1, wherein the carbon particles are substantially homogeneously distributed throughout the aerosol-forming substrate.

10. The aerosol-forming substrate according to claim 1, which is a tobacco-free aerosol-forming substrate.

11. The aerosol-forming substrate according to claim 1, wherein the aerosol-forming substrate contains 1 to 20 wt% of water.

12. A first material and a second material, wherein the first material is included as a first plurality of individual elements in the combined aerosol-forming substrate, and the second material is included as a second plurality of individual elements in the combined aerosol-forming substrate, the first material and the second material, wherein the first material includes an aerosol former and has a first thermal conductivity, The combined aerosol-forming substrate, wherein the second material is, or comprises, the aerosol-forming substrate according to claim 1 and has a second thermal conductivity greater than the first thermal conductivity.

13. An aerosol-generating article comprising the aerosol-forming substrate according to claim 1 or the combined aerosol-forming substrate according to claim 12.

14. An aerosol-generating system comprising the aerosol-generating article according to claim 13 and an electric aerosol-generating device for heating the aerosol-forming substrate or the combined aerosol-forming substrate of the aerosol-generating article.

15. A method of forming the aerosol-forming substrate according to claim 1 or the combined aerosol-forming substrate according to claim 12, the method comprising: forming a slurry comprising the carbon particles, the aerosol-forming body, the fibers, and the binder; casting and drying the slurry to form the aerosol-forming substrate or a precursor for forming on the aerosol-forming substrate.

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