Article with tubular aerosol-forming substrate

Abstract

To provide an aerosol-generating article having an aerosol generating substrate that is adapted to provide more efficient aerosolization of the aerosol generating substrate and that reduces waste of the substrate materials, such as tobacco.SOLUTION: An aerosol-generating article for producing inhalable aerosol upon heating comprises a plurality of components including an aerosol-forming substrate. The aerosol-forming substrate is in a form of a hollow tubular segment defining a substrate cavity extending between an upstream end of the aerosol-forming substrate and a downstream end of the aerosol-forming substrate. The aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-former. Combination of tubular geometry and thermally conductive particles allows swifter time to first puff, improved efficiency of aerosol extraction, and lighter weight of the aerosol-generating article.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an aerosol-generating article comprising a tubular aerosol-forming substrate. The present disclosure also relates to a method of making an aerosol-forming substrate for such an article and an aerosol-generating system.

Background Art

[0002] Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than burned are known in the art. Typically, in such heated smoking articles, an aerosol is generated by transferring heat from a heat source to a physically separated aerosol-generating substrate or material, which may be located in contact with, within, around or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in the air drawn through the aerosol-generating article. The released compounds condense as they cool to form an aerosol.

[0003] In many prior art documents, aerosol generating devices for consuming aerosol generating articles are disclosed. Such devices include, for example, electrically heated aerosol generating devices in which aerosol is generated by heat transfer from one or more electrical heater elements of the aerosol generating device to an aerosol generating substrate of a heatable aerosol generating article. For example, electrically heated aerosol generating devices have been proposed that include an internal heater blade adapted to be inserted into an aerosol generating substrate. It is also well known to use aerosol generating articles in combination with an external heating system. For example, International Application Publication No. 2020 / 115151 describes the provision of an external heating body disposed around the periphery of an aerosol generating article when the aerosol generating article is received within a cavity of the aerosol generating device. Alternatively, inductively heatable aerosol generating articles including an aerosol generating substrate and a susceptor disposed within the aerosol generating substrate have been proposed by International Application Publication No. 2015 / 176898. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Generally, it can be difficult to provide efficient heating of an aerosol generating substrate across the entire length of the substrate rod. While the portion of the substrate closest to the heating element is necessarily heated most effectively, if heat transfer through the substrate is incomplete, it means that the portion of the substrate furthest from the heating element may not be effectively heated. Thus, aerosol generation from these portions of the substrate that are not effectively heated is not optimal, and in some cases, portions of the substrate may not reach a sufficiently high temperature to generate aerosol during use. For example, as described above, when an external heating body is used to heat the rod of an aerosol generating substrate, the central portion of the rod of the aerosol generating substrate is less likely to generate as much aerosol as the outer portion of the rod, and in some cases, may not generate any aerosol. Thus, overall, aerosol generation from the aerosol generating rod can be inefficient and a portion of the aerosol generating substrate may potentially be wasted.

[0005] In addition, the aerosol is generally not generated immediately by the aerosol generating substrate when the heating element is operating. This is because there is a preheating time after the heating element is activated, during which the aerosol generating substrate is heated to the temperature required for aerosol generation. Therefore, there can be a relatively long duration between the activation of the heating element and the generation of a sensibly acceptable aerosol for inhalation by the user.

[0006] Accordingly, it is desirable to provide an aerosol generating article having an aerosol generating substrate that is adapted to provide more efficient aerosolization of the aerosol generating substrate and that reduces waste of substrate material such as tobacco. It is also desirable to provide such an aerosol generating article that can achieve a relatively short preheating time, such that a sensibly acceptable aerosol can be delivered to the user immediately after the start of heating of the aerosol generating substrate. It would be desirable to provide such an aerosol generating article that can provide optimized delivery of the aerosol from the aerosol generating substrate. It would be particularly desirable to provide such an aerosol generating article in a relatively simple design that can be manufactured in a cost-effective manner and incorporated into existing product designs. It would be even more desirable to provide such an article that can be easily adapted to be heated by various types of heating devices, including induction heating devices and resistive heating devices.

[0007] Well-known aerosol-forming substrates typically have a relatively low thermal conductivity. Due to the low thermal conductivity of the aerosol-forming substrate, a relatively large temperature gradient can be imposed on the aerosol-forming substrate during use. This can mean that the portion of the aerosol-forming substrate located furthest from the heater element does not reach as high a temperature and thus does not release as much of the volatile compound as the aerosol-forming substrate could if it had a higher thermal conductivity. In other words, the low thermal conductivity of the aerosol-forming substrate can undesirably result in inefficient use of the aerosol-forming substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0009] According to the present disclosure, upon heating, an aerosol-generating article for generating an inhalable aerosol is provided. The heated aerosol-generating article may comprise a plurality of components including an aerosol-forming substrate. The aerosol-forming substrate may be in the form of a hollow tubular segment and preferably defines a substrate recess extending between an upstream end of the aerosol-forming substrate and a downstream end of the aerosol-forming substrate. The aerosol-forming substrate preferably comprises a plurality of thermally conductive particles and an aerosol-forming body.

[0010] For example, upon heating, an aerosol-generating article for generating an inhalable aerosol may be provided, the aerosol-generating article comprising a plurality of components including an aerosol-forming substrate, the aerosol-forming substrate being in the form of a hollow tubular segment defining a substrate recess extending between an upstream end of the aerosol-forming substrate and a downstream end of the aerosol-forming substrate, and the aerosol-forming substrate comprising a plurality of thermally conductive particles and an aerosol-forming body.

[0011] Using a tubular shape for the aerosol-forming substrate can help avoid the thermal gradient effect on heating of the substrate. With the tubular shape, the substrate has no core, and the aerosol-forming material is concentrated in the region of the substrate that is heated either internally or externally. This can significantly increase the extraction efficiency, which in turn can reduce the total amount of substrate required for the user experience. The reduction in the mass of the substrate reduces the heating inertia, and thus the time required to heat to a sufficient temperature is shortened, thereby shortening the time to the first puff. By using a thermally conductive substrate, the advantages obtained by adopting the tubular substrate shape can be significantly increased. The increase in the thermal conductivity of the substrate resulting from the presence of thermally conductive particles can further reduce the heating inertia of the substrate, further shorten the time to the first puff, and increase the overall extraction efficiency. By selecting certain thermally conductive particles, such as graphite or expanded graphite, the weight of the substrate can be further reduced. Reducing the overall mass of the aerosol-forming substrate required for a proper user experience has many advantages, including reducing the overall heating inertia and the weight of the aerosol-generating article including the substrate. The reduction in the weight of the article can provide cost savings in shipping and energy associated with shipping, and in certain jurisdictions, tax benefits can be provided.

[0012] The aerosol-generating article according to the present invention can be particularly advantageously used in an aerosol-generating system that utilizes progressive heating or zonal heating. The aerosol-generating article according to the present invention can also be particularly advantageously used in an aerosol-generating system that utilizes heating in response to a desire to smoke.

[0013] The aerosol-forming substrate may contain, on a dry weight basis, 5 to 95 wt% of heat-conductive particles, for example, 10 to 90 wt% of heat-conductive particles. The aerosol-forming substrate may contain, on a dry weight basis, 7 to 60 wt% of an aerosol-forming agent. The aerosol-forming substrate may contain, on a dry weight basis, 2 to 20 wt% of fibers. The aerosol-forming substrate may contain, on a dry weight basis, 2 to 10 wt% of a binder. Each of the heat-conductive particles may consist of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

[0014] Accordingly, there is provided an aerosol-forming substrate containing, on a dry weight basis, 10 to 90 wt% of heat-conductive particles, 7 to 60 wt% of an aerosol-forming agent, 2 to 20 wt% of fibers, and 2 to 10 wt% of a binder, and each of the heat-conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

[0015] The aerosol-generating article may contain, on a dry weight basis, 5 to 95 wt%, for example 10 to 90 wt% of heat-conductive particles, and each of the heat-conductive particles has a thermal conductivity of at least 1 W / (mK). The thermal conductivity may be measured in at least one direction of the particle. The thermal conductivity may be measured at a temperature of 25 degrees Celsius.

[0016] When the term "heat-conductive particle" is used to refer to a particle containing carbon, for example, one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, or consisting of them, the heat-conductive particle may be referred to as a carbon particle or a carbon-containing particle.

[0017] Advantageously, the thermally conductive particles can increase the thermal conductivity of the aerosol-forming substrate. An increase in the thermal conductivity of the substrate can provide a more uniform temperature distribution across the substrate during use. Thereby, the proportion of the aerosol-forming substrate that reaches a temperature high enough to release the volatile compound can increase, and thus the efficiency of use of the aerosol-forming substrate can be increased. Further, an increase in the thermal conductivity of the substrate can enable a heater, for example, a heating blade configured to heat the substrate, to operate at a lower temperature, and thus the power required can be reduced. Further, an increase in the thermal conductivity of the substrate can enable the heater to heat the substrate to a temperature at which the volatile compound is released in a shorter time. Therefore, an increase in the thermal conductivity can shorten the time required for the user to form an inhalable aerosol.

[0018] Advantageously, one or both of the fiber and the binder can increase the tensile strength of the material forming the aerosol-forming substrate. An increase in the tensile strength can enable, for example, a sheet of the aerosol-forming material to be manufactured using existing manufacturing machinery, and the sheet can be formed in a tube to form the aerosol-forming substrate.

[0019] The aerosol-forming substrate can have a thermal conductivity 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 in at least one direction, or in all directions. This thermal conductivity can be measured when the moisture content of the substrate is 0 - 20%, or 5 - 15%, for example, about 10%. This thermal conductivity can be measured when the substrate contains 0 - 20 wt%, or 5 - 15 wt%, for example, about 10 wt% water. The moisture content or water content of the substrate can be measured using a titration method. The moisture content or water content of the substrate can be measured using the Karl Fisher method.

[0020] Optionally, some or all of the thermally conductive particles contain at least 10, 30, 50, 70, 90, 95, 98, or 99 wt% carbon.

[0021] 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, for example, artificial diamond particles. Advantageously, such materials can have a relatively high thermal conductivity.

[0022] Expanded graphite may have a density of less than 2, 1.8, 1.5, 1.2, 1, 0.8, or 0.5, 0.2, 0.1, 0.05, 0.02 grams per cubic centimeter (g / cm 3 )). Expanded graphite may have a density of more 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 )). Expanded graphite may have a density of 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 to 3, 0.1 to 2, 0.1 to 1.8, 0.1 to 1.5, 0.1 to 1.2, 0.1 to 1, 0.1 to 0.8, 0.1 to 0.5, 0.2 to 3, 0.2 to 2, 0.2 to 1.8, 0.2 to 1.5, 0.2 to 1.2, 0.2 to 1, 0.2 to 0.8, 0.2 to 0.5, 0.5 to 3, 0.5 to 2, 0.5 to 1.8, 0.5 to 1.5, 0.5 to 1.2, 0.5 to 1, 0.5 to 0.8, 0.8 to 3, 0.8 to 2, 0.8 to 1.8, 0.8 to 1.5, 0.8 to 1.2, 0.8 to 1 grams per cubic centimeter (g / cm 3 ).

[0023] Optionally, according to an embodiment in which each of the thermally conductive particles is not necessarily from one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, some or all of the thermally conductive particles include a metal. As another method, or additionally, some or all of the thermally conductive particles include an alloy. As another method, or additionally, some or all of the thermally conductive particles include an intermetallic compound. Advantageously, such materials can have a relatively high thermal conductivity.

[0024] Optionally, according to an alternative embodiment in which each of the thermally conductive particles is not necessarily from 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 can have a relatively high thermal conductivity.

[0025] The thermally conductive particles can each have a "particle diameter". The meaning of the term "particle diameter" and the method for measuring the particle diameter will be described later.

[0026] The thermally conductive particles can be characterized by a particle size distribution. The particle size distribution can have particle sizes of number D10, D50, and D90. The particle size of number D10 is defined such that 10% of the particles have a particle size less than or equal to the particle size of number D10. Similarly, the particle size of number D50 is defined such that 50% of the particles have a particle size less than or equal to the particle size of number D50. Thus, the particle size of number D50 can also be referred to as the median particle size. The particle size of number D90 is defined such that 90% of the particles have a particle size less than or equal to the particle size of number D90. Thus, if there are 1,000 particles in the distribution and the particles are arranged in ascending order of particle size, the particle size of number D10 is expected to be approximately equal to the particle size of the 100th particle, the particle size of number D50 is expected to be approximately equal to the particle size of the 500th particle, and the particle size of number D90 is expected to be approximately equal to the particle size of the 900th particle.

[0027] The particle size distribution can have particle sizes of volume D10, D50, and D90. The particle size of volume D10 is defined such that 10% of the total volume of all the particles is occupied by the total volume of the particles having a particle size less than or equal to the particle size of volume D10. Similarly, the particle size of volume D50 is defined such that 50% of the total volume of all the particles is occupied by the total volume of the particles having a particle size less than or equal to the particle size of volume D50. Also, the particle size of volume D90 is defined such that 90% of the total volume of all the particles is occupied by the total volume of the particles having a particle size less than or equal to the particle size of volume D90.

[0028] Optionally, the thermally conductive particles have a particle size distribution having a particle size of number D10, and the particle size of number D10 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0029] Optionally, the thermally conductive particles have a particle size distribution having a particle size of number D10, and the particle size of number D10 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less.

[0030] When determining the particle size, a compromise is necessary. Advantageously, the larger the thermally conductive particles, the more significantly the thermal conductivity of the aerosol-forming substrate can increase compared to when the thermally conductive particles are smaller. However, the larger the thermally conductive particles, the more the available space for the aerosol-forming material within the substrate can be reduced.

[0031] Optionally, the thermally conductive particles have a particle size distribution with a particle size of number D50, and the particle size of number D50 is 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 particle size of number D50, and the particle size of number D50 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less.

[0033] Optionally, the thermally conductive particles have a particle size distribution with a particle size of number D90, and the particle size of number D90 is 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 particle size of number D90, and the particle size of number D90 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less.

[0035] Optionally, the thermally conductive particles have a particle size distribution with a particle size of number D10 and a particle size of number D90, and the particle size of number D90 is 50, 40, 30, 20, 10, or 5 times or less the particle size of number D10.

[0036] Optionally, the thermally conductive particles have a particle size distribution with a particle size of number D10 and a particle size of number D90, and the particle size of number D90 is at least 1.5, 2, 3, 5, 10, or 20 times the particle size of number D10.

[0037] Regarding the particle size distribution, compromises may be necessary. For example, a more narrow particle size distribution, characterized by a smaller ratio between the D90 particle size and the D10 particle size, can advantageously provide a more uniform thermal conductivity across the aerosol-forming substrate. This is because there is less variation in particle size at different positions within the substrate. This can advantageously enable more efficient use of the aerosol-forming material throughout the aerosol-forming substrate. However, if the particle size distribution is more narrow, it can disadvantageously be more difficult and expensive to achieve. The inventors have found that the above-described particle size distribution can provide an optimal compromise between these two factors.

[0038] Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size, and the volume D10 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0039] Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size, and the volume D10 particle size is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less.

[0040] Optionally, the thermally conductive particles have a particle size distribution having a volume D50 particle size, and the volume D50 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0041] Optionally, the thermally conductive particles have a particle size distribution having a volume D50 particle size, and the volume D50 particle size is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less.

[0042] Optionally, the thermally conductive particles have a particle size distribution having a volume D90 particle size, and the volume D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

[0043] Optionally, the thermally conductive particles have a particle size distribution having a particle size of volume D90, and the particle size of volume D90 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less.

[0044] It may be particularly preferred that the thermally conductive particles have a particle size distribution having a particle size of volume D10 of 1 to 20 microns. As another method, or additionally, it may be particularly preferred that the thermally conductive particles have a particle size distribution having a particle size of volume D90 of 50 to 300 microns, or 50 to 200 microns.

[0045] Optionally, the thermally conductive particles have a particle size distribution having a particle size of volume D10 and a particle size of volume D90, and the particle size of volume D90 is 50, 40, 30, 20, 10, or 5 times or less the particle size of volume D10.

[0046] Optionally, the thermally conductive particles have a particle size distribution having a particle size of volume D10 and a particle size of volume D90, and the particle size of volume D90 is at least 1.5, 2, 3, 5, 10, or 20 times the particle size of volume D10.

[0047] As described above, it is necessary to compromise regarding the particle size distribution, and the inventors have found that the above particle size distribution can provide an optimal compromise.

[0048] 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 for each of the thermally conductive particles to have a particle size of at least 1 micron. As another method, or additionally, it may be particularly preferred for each of the thermally conductive particles to have a particle size of 300 microns or less. Particles less than 1 micron may be difficult to handle during manufacture. In addition, particles less than 1 micron may be more likely to pass through filters in aerosol-generating articles comprising an aerosol-forming substrate. Particles greater than 300 microns may occupy a relatively large space within the substrate that can be used in the aerosol-forming material. Thus, it may be particularly advantageous for each of the thermally conductive particles to have a particle size of at least 1 micron, or 300 microns or less, or both.

[0049] Optionally, each of the thermally conductive particles has three mutually orthogonal dimensions, and the largest dimension of the three dimensions is 10, 8, 5, 3, or 2 times or less the smallest dimension of the three dimensions. Optionally, each of the thermally conductive particles has three mutually orthogonal dimensions, and the largest dimension of the three dimensions is 10, 8, 5, 3, or 2 times or less the second largest dimension 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, by using more spherical particles, variations between different substrates where the orientation of the particles is not controlled can be reduced as a result. Additionally, substantially spherical particles may be easier to characterize.

[0050] Optionally, the thermally conductive particles comprise at least 10, 20, 50, 100, 200, 500, or 1,000 particles. Advantageously, the greater the number of particles in the aerosol-forming substrate, the more possible it may be to make the thermal conductivity of the substrate more uniform.

[0051] Optionally, the substrate contains, on a dry weight basis, at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 wt% of thermally conductive particles. Optionally, the substrate contains, on a dry weight basis, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20 or 15 wt% or less of thermally conductive particles. Optionally, the substrate contains, on a dry weight basis, 10-90, 20-90, 30-90, 40-90, 50-90, 60-90, 70-90, 80-90, 10-80, 20-80, 30-80, 40-80, 50-80, 60-80, 70-80, 10-70, 20-70, 30-70, 40-70, 50-70, 60-70, 10-60, 20-60, 30-60, 40-60, 50-60, 10-50, 20-50, 30-50, 40-50, 10-40, 20-40, 30-40, 10-30, 20-30, or 10-20 wt% of thermally conductive particles. It may be particularly preferred for the substrate to contain, on a dry weight basis, 50-90, or more preferably 60-90, or even more preferably 65-85 wt% of thermally conductive particles.

[0052] Regarding the wt% of thermally conductive particles in the substrate, a compromise may be necessary. By increasing the wt% of particles in the aerosol-forming substrate, advantageously, the thermal conductivity of the substrate can be increased. However, increasing the wt% of particles in the aerosol-forming substrate may also reduce the available space for one or more of the aerosol-forming body, binder, and fibers, and thus may result in a substrate that forms less aerosol or has a lower tensile strength.

[0053] Optionally, the substrate contains, on a dry weight basis, at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 wt% of an aerosol former. Optionally, the substrate contains, on a dry weight basis, 55, 50, 45, 40, 35, 30, 25, 20, or 15 wt% or less of an aerosol former. Optionally, the substrate contains, on a dry weight basis, 7 - 60, 10 - 60, 20 - 60, 30 - 60, 40 - 60, 50 - 60, 7 - 50, 10 - 50, 20 - 50, 30 - 50, 40 - 50, 7 - 40, 10 - 40, 20 - 40, 30 - 40, 7 - 30, 10 - 30, 20 - 30, 7 - 20, 10 - 20, or 7 - 10 wt% of an aerosol former. It may be particularly preferred that the substrate contains, on a dry weight basis, 15 - 25 wt% of an aerosol former.

[0054] Optionally, the aerosol former contains 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 monotriacetate, glycerol diacetate, or glycerol triacetate), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (such as dimethyl dodecanedioic acid and dimethyl tetradecanedioic acid). Optionally, the aerosol - forming substrate contains one or both of glycerin and glycerol.

[0055] Optionally, the substrate contains at least 2, 4, 6, 8, 10, 12, 14, 16, or 18 wt% of fibers on a dry weight basis. Optionally, the substrate contains 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt% or less of fibers on a dry weight basis. Optionally, the substrate contains 4-20, 6-20, 8-20, 10-20, 12-20, 14-20, 16-20, 18-20, 2-18, 4-18, 6-18, 8-18, 10-18, 12-18, 14-18, 16-18, 2-16, 4-16, 6-16, 8-16, 10-16, 12-16, 14-16, 2-14, 4-14, 6-14, 8-14, 10-14, 12-14, 2-12, 4-12, 6-12, 8-12, 10-12, 2-10, 4-10, 6-10, 8-10, 2-8, 4-8, 6-8, 2-6, 4-6, or 2-4 wt% of fibers on a dry weight basis. It may be particularly preferred that the substrate contains 2-10 wt% of fibers on a dry weight basis.

[0056] Optionally, the fibers are cellulose fibers. Advantageously, the cellulose fibers are not overly expensive and can increase the tensile strength of the substrate.

[0057] Optionally, each of the fibers has three mutually orthogonal dimensions, and the largest dimension among the three dimensions is at least 1.5, 2, 3, 5, 10, or 20 times larger than the smallest dimension among the three dimensions. Optionally, each of the fibers has three mutually orthogonal dimensions, and the largest dimension among the three dimensions is at least 1.5, 2, 3, 5, 10, or 20 times larger than the second largest dimension among the three dimensions.

[0058] Optionally, the substrate contains at least 4, 6, or 8 wt% of a binder on a dry weight basis. Optionally, the substrate contains 8, 6, or 4 wt% or less of a binder on a dry weight basis. Optionally, the substrate contains 4-10, 6-10, 8-10, 2-8, 4-8, 6-8, 2-6, 4-6, 2-4 wt% of a binder on a dry weight basis. It may be particularly preferred that the substrate contains 2-10 wt% of a binder on a dry weight basis.

[0059] Suitable binders are known in the art and include, but are not limited to, natural pectins (such as fruit pectin, citrus pectin, or tobacco pectin), guar gum (such as hydroxyethyl guar, hydroxypropyl guar, etc.), locust bean gum (such as hydroxyethyl locust bean gum, hydroxypropyl locust bean gum, etc.), alginate, starch (such as modified starch or derivatized starch, etc.), cellulose (such as methyl cellulose, ethyl cellulose, ethyl hydroxy methyl cellulose, carboxymethyl cellulose, etc.), tamarind gum, dextran, pullulan, konjac flour, xanthan gum, and the like. It may be particularly preferred that the binder is guar or contains guar. It may be particularly preferred that the binder comprises or consists of one or more of gums such as carboxymethyl cellulose or hydroxypropyl cellulose, or guar gum.

[0060] Optionally, the heat conductive particles are distributed substantially homogeneously throughout the aerosol-forming substrate. Optionally, the aerosol former is distributed substantially homogeneously throughout the aerosol-forming substrate. Optionally, the fibers are distributed substantially homogeneously throughout the aerosol-forming substrate. Optionally, the binder is distributed substantially homogeneously throughout the aerosol-forming substrate. Advantageously, the homogeneous distribution of the components of the substrate can result in the substrate having more spatially uniform properties. For example, the substantially homogeneous distribution of heat conductive particles can result in the substrate having a substantially uniform thermal conductivity. As another example, the substantially homogeneous distribution of the binder or fibers can result in the substrate having a substantially uniform tensile strength.

[0061] Optionally, the substrate contains nicotine. Optionally, the substrate contains at least 0.01, 1, 2, 3, or 4 wt% nicotine on a dry weight basis. Optionally, the substrate contains 5, 4, 3, 2, or 1 wt% or less nicotine on a dry weight basis. Optionally, the substrate contains 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% nicotine on a dry weight basis. It may be particularly preferred that the substrate contains 0.5 - 4 wt% nicotine on a dry weight basis.

[0062] Optionally, the nicotine is distributed substantially homogeneously throughout the aerosol-forming substrate.

[0063] Optionally, the substrate contains an acid. Optionally, the substrate contains at least 0.01, 1, 2, 3, or 4 wt% acid on a dry weight basis. Optionally, the substrate contains 5, 4, 3, 2, or 1 wt% or less acid on a dry weight basis. Optionally, the substrate contains 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% acid on a dry weight basis. It may be particularly preferred that the substrate contains 0.5 - 5 wt% acid on a dry weight basis.

[0064] Optionally, the acid contains or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

[0065] Optionally, the acid is distributed substantially homogeneously throughout the aerosol-forming substrate.

[0066] Optionally, the substrate comprises at least one plant. Optionally, the substrate comprises at least one plant in an amount of at least 0.01, 1, 2, 5, 10, or 15 wt% on a dry weight basis. Optionally, the substrate comprises at least one plant in an amount of 20, 15, 10, 5, 2, or 1 wt% or less on a dry weight basis. Optionally, the substrate comprises at least one plant in an amount of 0.01 - 20, 1 - 20, 2 - 20, 5 - 20, 10 - 20, 15 - 20, 0.01 - 15, 1 - 15, 2 - 15, 5 - 15, 10 - 15, 0.01 - 10, 1 - 10, 2 - 10, 5 - 10, 0.01 - 5, 1 - 5, 2 - 5, 0.01 - 2, 1 - 2, 0.01 - 1 wt% on a dry weight basis. It may be particularly preferred that the substrate comprises at least one plant in an amount of 1 - 15 wt% on a dry weight basis.

[0067] Optionally, at least one plant comprises or consists of one or both of clove and rosmarinus.

[0068] Optionally, at least one plant is distributed substantially homogeneously throughout the aerosol - forming substrate.

[0069] Optionally, the substrate comprises at least one flavorant. Optionally, the substrate comprises at least one flavorant in an amount of at least 0.1, 1, 2, or 5 wt% on a dry weight basis. Optionally, the substrate comprises at least one flavorant in an amount of 10, 5, 2, or 1 wt% or less on a dry weight basis. Optionally, the substrate comprises at least one flavorant in an amount of 0.1 - 10, 1 - 10, 2 - 10, 5 - 10, 0.1 - 5, 1 - 5, 2 - 5, 0.1 - 2, 1 - 2, 0.1 - 1 wt% on a dry weight basis. It may be particularly preferred that the substrate comprises at least one flavorant in an amount of 0.1 - 5 wt% on a dry weight basis.

[0070] Optionally, at least one flavorant is present as a coating, for example on one or more other components of the aerosol - forming substrate. Alternatively, or in addition, at least one flavorant is distributed substantially homogeneously throughout the aerosol - forming substrate.

[0071] Optionally, the aerosol-forming substrate contains at least one organic material such as tobacco. Optionally, the at least one organic material includes one or more of herb leaves, tobacco leaves, fragments of tobacco stems, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Optionally, the at least one organic material is homogeneously distributed substantially throughout the aerosol-forming substrate.

[0072] The substrate may contain less than 10, 5, 3, 2, or 1 wt% of tobacco on a dry weight basis. Optionally, the aerosol-forming substrate is an aerosol-forming substrate that does not contain tobacco.

[0073] The tubular segment of the aerosol-forming substrate may be described as a rod. Accordingly, a rod of the aerosol-forming substrate may be provided.

[0074] The aerosol-forming substrate is preferably in the form of a tube having an outer diameter, an inner diameter, and a length, the length of the tube being 5 mm to 100 mm, the outer diameter being 3 mm to 20 mm, and the inner diameter being 2.5 mm to 19.5 mm. The length of the tube may be 8 mm to 25 mm, the outer diameter of the tube may be 6 mm to 8 mm, and the inner diameter of the tube may be 5 mm to 7.9 mm.

[0075] The susceptor element can be located within the rod of the aerosol-forming substrate. The susceptor element may be an elongated susceptor element. The susceptor element may, for example, contact the inner surface of the tubular aerosol-generating substrate and extend in the longitudinal direction within the rod of the aerosol-forming substrate. The rod may be substantially cylindrical in shape, for example, a straight cylindrical shape. The susceptor element may extend over the entire length to the downstream end of the rod of the aerosol-forming substrate. The susceptor element may extend over the entire length 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.

[0076] Alternatively, there may be no susceptor material within the aerosol-forming substrate or within the rod of the aerosol-forming substrate.

[0077] Optionally, some or each of the thermally conductive particles may be inductively heatable to a temperature of, for example, at least 100 degrees Celsius, 150 degrees Celsius, or 200 degrees Celsius. Optionally, some or each of the thermally conductive particles comprises or consists of one or more susceptor materials. Advantageously, this may enable the thermally conductive particles to be inductively heated. The thermally conductive particles may comprise the only susceptor material present within the aerosol-forming substrate or within the rod of the aerosol-forming substrate, or may be the only susceptor material. That is, there may be no susceptor element within the aerosol-forming substrate or within the rod of the aerosol-forming substrate, except for the thermally conductive particles or carbon particles.

[0078] 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 metallic materials. Suitable susceptor materials may include ferromagnetic materials such as ferromagnetic iron, ferromagnetic alloys such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. Suitable susceptor materials may be aluminum or may contain aluminum. The susceptor material preferably contains more than 5% ferromagnetic or paramagnetic material, more preferably contains more than 20% ferromagnetic or paramagnetic material, and even more preferably contains more than 50% or more than 90% ferromagnetic or paramagnetic material. Preferred susceptor materials may contain metals, metal alloys or carbon.

[0079] Particularly preferred susceptor materials may be or may contain carbon, carbon-based materials, graphene, graphite, or expanded graphite. Advantageously, such materials have relatively high thermal conductivity, relatively low density, and can be induction heated.

[0080] Optionally, the aerosol-forming substrate has a thermal conductivity of more 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) in at least one direction at 25 degrees Celsius.

[0081] Optionally, the aerosol-forming substrate has a density 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 as follows. Optionally, the aerosol-forming substrate has a density of 600 - 1400 kg / m 3 , 800 - 1200 kg / m 3 , or 900 - 1100 kg / m 3 . Advantageously, reducing the density of the substrate can reduce the transportation cost of the substrate.

[0082] Optionally, the aerosol-forming substrate has a moisture content of from 1 to 20, or from 3 to 15% by weight. This moisture content can be measured after equilibration at 20 °C and 50% relative humidity for 48 hours. Optionally, the aerosol-forming substrate contains from 1 to 20, or from 3 to 15% by weight of water. The moisture content or water content of the substrate can be measured using a titration method. The moisture content or water content of the substrate can be measured using the Karl Fisher method.

[0083] Optionally, the aerosol-forming substrate is formed from a sheet of aerosol-forming material that is wound to form a tubular segment. Thus, the hollow tubular segment can be a wound sheet of aerosol-forming material, for example, a wound sheet of homogenized tobacco material, or for example, a wound sheet of a tobacco-free aerosol-forming material.

[0084] The aerosol-forming substrate may have a thickness equivalent to that of a single layer of aerosol-forming material sheet. The aerosol-forming substrate may have a thickness equivalent to that of two or more layers of sheets. The sheet of aerosol-forming material may have a thickness of at least 5, 10, 20, 50, 100, 150, or 200 microns. Optionally, the sheet or strip may have a thickness of 2000, 1000, 500, 400, 300, or 250 microns or less. Optionally, the sheet may have a thickness of 100 - 350 microns, or 150 - 300 microns.

[0085] Optionally, the sheet of aerosol-forming material has a basis weight of at least 20, 50, or 100 g / m 2 . Optionally, the sheet or strip has a basis weight of 300 g / m 2 or less. Optionally, the sheet has a basis weight of 20 - 300 g / m 2 , 50 - 250 g / m 2 , or 100 - 250 g / m 2 .

[0086] Optionally, the sheet has a density of at least 0.1, 0.2, 0.3, or 0.5 g / m 3 . Optionally, the sheet has a density of 2, 1.5, 1.2, or 1 g / m 3 or less. Optionally, the sheet has a density of 0.1 - 2 g / m 3 , 0.2 - 2 g / m 3 , 0.3 - 2 g / m 3 , 0.3 - 1.5 g / m 3 , or 0.3 - 1.2 g / m 3 .

[0087] The hollow tubular segment may be an extruded tube of aerosol - forming material, for example, an extruded tube of homogenized tobacco material, or for example, an extruded tube of tobacco - free aerosol - forming material.

[0088] The aerosol - generating article can be in the form of a rod and can comprise a plurality of components including an aerosol - forming substrate assembled within a wrapper or casing.

[0089] Optionally, the aerosol - generating article comprises a front plug. Optionally, the aerosol - generating article comprises a first hollow tube, for example, a first hollow acetate tube. Optionally, the aerosol - generating article comprises a second hollow tube, for example, a second hollow acetate tube. Optionally, the second hollow tube includes one or more ventilation holes. Optionally, the aerosol - generating article comprises a mouth - side plug filter. Optionally, the aerosol - generating article comprises a wrapper, for example, a paper wrapper.

[0090] 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 mouthpiece plug filter is disposed downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouthpiece plug filter is disposed at the most downstream end of the article. Optionally, the most downstream end of the article, which may also be referred to as the mouthpiece end of the article, may be configured to be inserted into the user's mouth. The user may, for example, directly inhale the mouthpiece end of the article.

[0091] Optionally, the front plug, the tubular aerosol-forming substrate, one or both of the first and second hollow tubes, and the mouthpiece plug filter are surrounded by a wrapper, such as a paper wrapper.

[0092] Optionally, the front plug has a length of 2 to 10 mm, 3 to 8 mm, or 4 to 6 mm, for example, about 5 mm. Optionally, 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. Optionally, the first hollow tube has a length of 2 to 20 mm, 5 to 15 mm, or 5 to 10 mm, for example, about 8 mm. Optionally, the second hollow tube has a length of 2 to 20 mm, 5 to 15 mm, or 5 to 10 mm, for example, about 8 mm. Optionally, the mouthpiece plug filter has a length of 5 to 20 mm, 8 to 15 mm, or 10 to 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 mouthpiece plug filter may extend in the longitudinal direction.

[0093] One or more of the front plug, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouthpiece plug filter may be substantially cylindrical in shape, such as a right circular cylinder.

[0094] According to an aspect of the present disclosure, an aerosol generating system is provided.

[0095] The system may include an aerosol-generating article and an electric aerosol-generating device. The article may be the article described above, for example, the article according to the third aspect.

[0096] Optionally, the electric aerosol-generating device is configured to resistively heat the aerosol-generating article during use.

[0097] Optionally, the electric aerosol-generating device is configured to inductively heat the aerosol-generating article, for example, the aerosol-forming substrate of the aerosol-generating article, during use.

[0098] According to the present disclosure, a method of forming a hollow tubular aerosol-forming substrate, for example, the substrate for the aerosol-generating article described above, is provided. The method may include forming a slurry comprising one or more or all of thermally conductive particles, an aerosol former, fibers, and a binder. The method may include molding and drying the slurry to form the aerosol-forming substrate, or extruding the slurry to form the aerosol-forming substrate, or molding and drying the slurry to form a precursor such as a sheet of the aerosol-forming substrate and then forming the precursor into the aerosol-forming substrate.

[0099] Optionally, the slurry contains water. Optionally, the slurry contains 20-90, 30-90, 40-90, 40-85, 50-80, 60-80, or 60-7 wt% water.

[0100] Optionally, the slurry contains an acid. Optionally, the acid contains or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

[0101] Optionally, the slurry contains nicotine.

[0102] 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.

[0103] Thus, forming the slurry includes forming a first mixture that includes an aerosol former, fibers, water, optionally an acid, and optionally nicotine, forming a second mixture that includes thermally conductive particles and a binder, and adding the second mixture to the first mixture to form a combined mixture, may be included.

[0104] Subsequently, the combined mixture can be formed into a slurry, for example, by mixing.

[0105] Optionally, forming the first mixture includes providing an aerosol former or a solution comprising an aerosol former and nicotine.

[0106] Optionally, forming the first mixture includes adding an acid to an aerosol former or a solution comprising an aerosol former and nicotine to form a first premix.

[0107] Optionally, forming the first mixture includes adding water to an aerosol former or a solution comprising an aerosol former and nicotine or to the first premix to form a second premix.

[0108] Optionally, forming the first mixture includes adding fibers to a second premix.

[0109] Optionally, forming the second mixture includes mixing thermally conductive particles and a binder.

[0110] Optionally, the step of forming a method, e.g., a slurry, includes a first mixing of the combined mixtures. Optionally, the first mixing is performed under a first pressure of 500, 400, 300, 250, or 200 mbar or less. Optionally, the first mixing is performed for 1 to 10 minutes, 2 to 8 minutes, or 3 to 6 minutes, e.g., for about 4 minutes.

[0111] Optionally, the step of forming a method, e.g., a slurry, includes a second mixing after the first mixing. Optionally, the second mixing is performed under a second pressure that is less than the first pressure. Optionally, the second pressure is 500, 400, 300, 200, 150, or 100 mbar or less. Optionally, the second mixing is performed for 5 to 120 seconds, 5 to 80 seconds, 5 to 40 seconds, or 10 to 30 seconds, e.g., for about 20 seconds.

[0112] Optionally, shaping the slurry includes shaping the slurry onto a flat support, e.g., a flat steel support.

[0113] Optionally, after shaping the slurry and before drying the slurry, the method includes setting the thickness of the slurry, e.g., setting the thickness of the slurry to 100 to 1200 microns, 200 to 1000 microns, 300 to 900 microns, 500 to 700 microns, e.g., to about 600 microns.

[0114] Optionally, drying the slurry involves providing a flow of gas, such as air, over or through the slurry. Optionally, the gas flow is heated. Optionally, the gas flow is heated to a temperature of from 100 to 160 °C, or from 120 to 140 °C. Optionally, the gas flow is provided for from 1 to 10 minutes, or from 2 to 5 minutes. Optionally, drying the slurry involves drying the slurry until it has a moisture content of from 1 to 20, 2 to 15, 2 to 10, or 3 to 7 wt%.

[0115] Optionally, drying the slurry forms a precursor for forming on an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Optionally, the method involves cutting the sheet of aerosol-forming material.

[0116] The sheet of aerosol-forming material can be formed on the aerosol-forming substrate by winding the sheet of aerosol-forming substrate around a tube. Thus, the wall of the tube is formed from the sheet of aerosol-forming material. The tubular shape can be maintained by overlapping a portion of the wound sheet and attaching the overlapping portion with an adhesive such as gum. The wall of the tube formed by winding the sheet of aerosol-forming material can have a thickness equal to the thickness of the sheet of aerosol-forming material, i.e., the tube can be formed from a single layer of the sheet of aerosol-forming material. However, the wall of the tube can be formed from a plurality of layers of sheet wound in the form of a tube. Once wound and fixed, the tube of aerosol-forming material can be cut to a certain length to form a tubular segment of the aerosol-forming substrate.

[0117] As will be understood by those skilled in the art upon reading this disclosure, the features described herein in relation to one aspect may be applicable to any other aspect.

[0118] As used herein, the term "aerosol-forming substrate" can refer to a substrate having the ability to emit an aerosol or a volatile compound capable of forming an aerosol. Such volatile compounds can be released by heating the aerosol-forming substrate. The aerosol-forming substrate may contain an aerosol-forming material. The aerosol-forming substrate may be adsorbed, coated, impregnated, or otherwise loaded onto a carrier or a support. For convenience, the aerosol-forming substrate can be part of an aerosol-generating article or a smoking article.

[0119] As used herein, the term "thermally conductive particle" can refer to a particle having a thermal conductivity of at least 0.3, preferably 0.5, or more preferably greater than 1 W / (mK) in at least one direction at 25 degrees Celsius, for example, in all directions at 25 degrees Celsius. The particles can exhibit anisotropic or isotropic thermal conductivity.

[0120] As used herein, the term "expanded graphite" can refer to a graphite-based material or a material having a graphite-like structure. Expanded graphite can have carbon layers (e.g., similar to graphite) with an interlayer spacing greater than that found between the carbon layers of normal graphite. Expanded graphite may have carbon layers with elements or compounds interposed within the interlayer space.

[0121] As used herein, the term "particle size" may refer to a single dimension and can be used to characterize a given particle size. The dimension may be the diameter of a spherical particle that occupies the same volume as a given particle. All particle sizes and particle size distributions herein can be obtained using standard laser diffraction techniques. The particle sizes and particle size distributions described herein can be obtained using commercially available sensors, such as the Sympatec HELOS laser diffraction sensor.

[0122] As used herein, the term "density", unless otherwise specified, can be used to refer to true density. Thus, unless otherwise specified, the density of a powder or a plurality of particles can refer to the true density of the powder or the plurality of particles (not the bulk density of the powder or the plurality of particles, which can vary significantly depending on how the powder or the plurality of particles are handled). The measurement of true density can be performed using many standard methods, and these methods are often based on Archimedes' principle. When used to measure the true density of a powder, the most widely used method involves placing the powder inside a container of known volume (a pycnometer) and weighing it. Thereafter, the pycnometer is filled with a fluid of known density in which the powder is insoluble. The volume of the powder is determined by the difference between the volume indicated by the pycnometer and the volume of the added liquid (i.e., the volume of the displaced air).

[0123] As used herein, the term "aerosol-generating article" can refer to an article that can generate or emit an aerosol when heated, for example.

[0124] As used herein, the term "longitudinal direction" can refer to the direction extending between the downstream or proximal end and the upstream or distal end of a component such as an aerosol-forming substrate or an aerosol-generating article.

[0125] As used above, the term "transverse direction" can refer to the direction perpendicular to the longitudinal direction.

[0126] As used herein, the term "aerosol-generating device" can refer to a device for use with an aerosol-generating article to enable the generation or emission of an aerosol.

[0127] As used herein, the term "sheet" can refer to a substantially planar, thin-layered element having a width and a length that are, for example, at least 2, 3, 5, 10, 20, or 50 times greater than its thickness.

[0128] 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 during use. The aerosol may be a high-density 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.

[0129] As used herein, the term "aerosol cooling element" may refer to a component of an aerosol-generating article that is located downstream of the aerosol-forming substrate such that an aerosol formed by the substrate or by a volatile compound released from the aerosol-forming substrate passes through and is cooled by the aerosol cooling element before being inhaled by the user.

[0130] As used herein, the term "rod" may refer to an element having a generally cylindrical shape, such as a straight cylindrical shape with a substantially circular, oval, or elliptical cross-section.

[0131] As used herein, the term "ventilation level" may refer to the volume ratio of the airflow entering the aerosol-generating article through the ventilation zone (ventilation airflow) to the sum of the aerosol airflow and the ventilation airflow. The higher the ventilation level, the greater the dilution of the aerosol stream delivered to the consumer.

[0132] [Examples] The present invention is defined in the claims. However, a non-exhaustive list of non-limiting examples is provided below. Any one or more of the features of these examples may be combined with any one or more of the features of another example, embodiment, or aspect described herein.

[0133] Example i. An aerosol-generating article for generating an inhalable aerosol comprising a hollow tubular aerosol-forming substrate, the aerosol-forming substrate comprising a plurality of thermally conductive particles and an aerosol former. Example 1. An aerosol-generating article for generating an inhalable aerosol upon heating, comprising a plurality of components including an aerosol-forming substrate, the aerosol-forming substrate being in the form of a hollow tubular segment defining a substrate recess extending between an upstream end of the aerosol-forming substrate and a downstream end of the aerosol-forming substrate, the aerosol-forming substrate comprising a plurality of thermally conductive particles and an aerosol-forming agent, the aerosol-generating article. Example 2. Each of the plurality of thermally conductive particles has a thermal conductivity of more than 1, 2, 5, 10, 20, 50, 100, 200, 500, or 1000 W / mK, the aerosol-generating article according to Example i or 1. Example 3. The aerosol-forming substrate contains 5 to 95% by weight, for example, 10 to 90% by weight of thermally conductive particles on a dry weight basis, and each of the thermally conductive particles has a thermal conductivity of at least 1 W / (mK) in at least one direction at 25 degrees Celsius, the aerosol-generating article according to any one of Examples 1 and 2. Example 4. The aerosol-forming substrate further contains 7 to 60% by weight of an aerosol-forming agent, 2 to 20% by weight of fibers, and 2 to 10% by weight of a binder, the aerosol-generating article according to Example 3. Example 5. The aerosol-forming substrate has a thermal conductivity of at least 0.12 W / (mK), for example, at least 0.14 W / (mK), for example, at least 0.22 W / (mK) in at least one direction at 25 degrees Celsius, the aerosol-generating article according to Example 3 or 4. Example 6. The aerosol-forming substrate contains, on a dry weight basis, 10 to 90% by weight of thermally conductive particles, 7 to 60% by weight of an aerosol-forming agent, 2 to 20% by weight of fibers, and 2 to 10% by weight of a binder, and each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, the aerosol-generating article according to any one of Examples 1 to 5. Example 7. Each of the plurality of thermally conductive particles has a thermal conductivity of at least 0.3, 0.5, 1, 2, 5, or 10 W / (mK) in at least one direction, for example, when measured at 25 degrees Celsius, and is an aerosol generating article according to any one of Examples 1 to 6. Example 8. Some or all of the thermally conductive particles contain carbon, for example, at least 10, 30, 50, 70, 90, 95, 98, or 99% by weight of carbon, and is an aerosol generating article according to any one of Examples 1 to 7. Example 9. 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, and is an aerosol generating article according to any one of Examples 1 to 8. Example 10. Some or all of the thermally conductive particles are diamond particles, for example, artificial diamond particles, and is an aerosol generating article according to any one of Examples 1 to 9. Example 11. Some or all of the thermally conductive particles are graphene particles, and is an aerosol generating article according to any one of Examples 1 to 10. Example 12. Some or all of the thermally conductive particles are carbon nanotubes, and is an aerosol generating article according to any one of Examples 1 to 11. Example 13. Some or all of the thermally conductive particles are charcoal particles, and is an aerosol generating article according to any one of Examples 1 to 12. Example 14. Some or all of the thermally conductive particles contain a metal, and is an aerosol generating article according to any one of Examples 1 to 13. Example 15. Some or all of the thermally conductive particles contain one or both of copper and aluminum, and is an aerosol generating article according to any one of Examples 1 to 14. Example 16. Some or all of the heat-conductive particles are the aerosol generating articles according to any one of Examples 1 to 15, which contain an alloy. Example 17. Some or all of the heat-conductive particles are the aerosol generating articles according to any one of Examples 1 to 16, which contain an intermetallic compound. Example 18. The heat-conductive particles have a particle size distribution having a particle size of number D10, and the particle size of number D10 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns, which are the aerosol generating articles according to any one of Examples 1 to 17. Example 19. The heat-conductive particles have a particle size distribution having a particle size of number D10, and the particle size of number D10 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, which are the aerosol generating articles according to any one of Examples 1 to 18. Example 20. The heat-conductive particles have a particle size distribution having a particle size of number D50, and the particle size of number D50 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns, which are the aerosol generating articles according to any one of Examples 1 to 19. Example 21. The heat-conductive particles have a particle size distribution having a particle size of number D50, and the particle size of number D50 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, which are the aerosol generating articles according to any one of Examples 1 to 20. Example 22. The heat-conductive particles have a particle size distribution having a particle size of number D90, and the particle size of number D90 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns, which are the aerosol generating articles according to any one of Examples 1 to 21. Example 23. The heat-conductive particles have a particle size distribution having a particle size of number D90, and the particle size of number D90 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, and are aerosol generating articles according to any one of Examples 1 to 22. Example 24. The heat-conductive particles have a particle size distribution having a particle size of volume D10, and the particle size of volume D10 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns, and are aerosol generating articles according to any one of Examples 1 to 23. Example 25. The heat-conductive particles have a particle size distribution having a particle size of volume D10, and the particle size of volume D10 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, and are aerosol generating articles according to any one of Examples 1 to 24. Example 26. The heat-conductive particles have a particle size distribution having a particle size of volume D50, and the particle size of volume D50 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns, and are aerosol generating articles according to any one of Examples 1 to 25. Example 27. The heat-conductive particles have a particle size distribution having a particle size of volume D50, and the particle size of volume D50 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, and are aerosol generating articles according to any one of Examples 1 to 26. Example 28. The heat-conductive particles have a particle size distribution having a particle size of volume D90, and the particle size of volume D90 is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns, and are aerosol generating articles according to any one of Examples 1 to 27. Example 29. The heat-conductive particles have a particle size distribution having a particle size of volume D90, and the particle size of volume D90 is 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, and are aerosol generating articles according to any one of Examples 1 to 28. Example 30. The heat-conductive particles have a particle size distribution having a particle size of number D10, a particle size of number D90, a particle size of volume D10, and a particle size of volume D90, and the particle size of number D90 is 50, 40, 30, 20, 10, or 5 times or less the particle size of number D10, or the particle size of volume D10 is 50, 40, 30, 20, 10, or 5 times or less the particle size of number D10, or both particle sizes of number D90 are 50, 40, 30, 20, 10, or 5 times or less the particle size of number D10, and the particle size of volume D10 is 50, 40, 30, 20, 10, or 5 times or less the particle size of number D10, and are aerosol generating articles according to any one of Examples 1 to 29. Example 31. The heat-conductive particles have a particle size distribution, and one or both of the particle size of number D10 and the particle size of volume D10 are 1 to 20 microns, and are aerosol generating articles according to any one of Examples 1 to 30. Example 32. The heat-conductive particles have a particle size distribution, and one or both of the particle size of number D90 and the particle size of volume D90 are 50 to 300 microns, or 50 to 200 microns, and are aerosol generating articles according to any one of Examples 1 to 31. Example 33. Each of the heat-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, and are aerosol generating articles according to any one of Examples 1 to 32. Example 34. Each of the heat-conductive particles has a particle size of 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns or less, and are aerosol generating articles according to any one of Examples 1 to 33. Example 35. Each of the heat conductive particles has three mutually orthogonal dimensions, and the maximum dimension among the three dimensions is 10, 8, 5, 3, or 2 times or less greater than one or both of the minimum dimension among the three dimensions and the second largest dimension among the three dimensions. The aerosol generating article according to any one of Examples 1 to 34. Example 36. Each of the heat conductive particles is substantially spherical. The aerosol generating article according to any one of Examples 1 to 35. Example 37. The heat conductive particles include at least 10, 20, 50, 100, 200, 500, or 1000 particles. The aerosol generating article according to any one of Examples 1 to 36. Example 38. The substrate contains at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85% by weight of heat conductive particles based on the dry weight. The aerosol generating article according to any one of Examples 1 to 37. Example 39. The substrate contains 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15% by weight or less of heat conductive particles based on the dry weight. The aerosol generating article according to any one of Examples 1 to 38. Example 40. The substrate contains 10 to 90, 20 to 90, 30 to 90, 40 to 90, 50 to 90, 60 to 90, 70 to 90, 80 to 90, 10 to 80, 20 to 80, 30 to 80, 40 to 80, 50 to 80, 60 to 80, 70 to 80, 10 to 70, 20 to 70, 30 to 70, 40 to 70, 50 to 70, 60 to 70, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 10 to 40, 20 to 40, 30 to 40, 10 to 30, 20 to 30, or 10 to 20% by weight of heat conductive particles based on the dry weight. The aerosol generating article according to any one of Examples 1 to 39. Example 41. The substrate contains at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55% by weight of an aerosol former on a dry weight basis, and is an aerosol generating article according to any one of Examples 1 to 40. Example 42. The substrate contains 55, 50, 45, 40, 35, 30, 25, 20, or 15% by weight or less of an aerosol former on a dry weight basis, and is an aerosol generating article according to any one of Examples 1 to 41. Example 43. The substrate contains 7 to 60, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 7 to 50, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 7 to 40, 10 to 40, 20 to 40, 30 to 40, 7 to 30, 10 to 30, 20 to 30, 7 to 20, 10 to 20, or 7 to 10% by weight of an aerosol former, particularly preferably 15 to 25% by weight of an aerosol former, and is an aerosol generating article according to any one of Examples 1 to 42. Example 44. The aerosol former contains one or more of, or consists of, polyhydric alcohols (such as propylene glycol, polyethylene glycol, triethylene glycol, 1,3 - butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol monotriacetate, glycerol diacetate, or glycerol triacetate), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (such as dimethyl dodecanedioic acid and dimethyl tetradecanedioic acid), and is an aerosol generating article according to any one of Examples 1 to 43. Example 45. The aerosol - forming substrate contains one or both of glycerin and glycerol, and is an aerosol generating article according to any one of Examples 1 to 44. Example 46. The substrate contains at least 2, 4, 6, 8, 10, 12, 14, 16, or 18% by weight of fibers on a dry weight basis, and is an aerosol generating article according to any one of Examples 1 to 45. Example 47. The substrate contains fibers at 20, 18, 16, 14, 12, 10, 8, 6, or 4 wt% or less on a dry weight basis, and is an aerosol generating article according to any one of Examples 1 to 46. Example 48. The substrate contains fibers at 4 to 20, 6 to 20, 8 to 20, 10 to 20, 12 to 20, 14 to 20, 16 to 20, 18 to 20, 2 to 18, 4 to 18, 6 to 18, 8 to 18, 10 to 18, 12 to 18, 14 to 18, 16 to 18, 2 to 16, 4 to 16, 6 to 16, 8 to 16, 10 to 16, 12 to 16, 14 to 16, 2 to 14, 4 to 14, 6 to 14, 8 to 14, 10 to 14, 12 to 14, 2 to 12, 4 to 12, 6 to 12, 8 to 12, 10 to 12, 2 to 10, 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4 to 8, 6 to 8, 2 to 6, 4 to 6, or 2 to 4 wt%, preferably 2 to 10 wt% of fibers, and is an aerosol generating article according to any one of Examples 1 to 47. Example 49. The fibers are cellulose fibers, and is an aerosol generating article according to any one of Examples 1 to 48. Example 50. Each of the fibers has three mutually orthogonal dimensions, and the maximum dimension among the three dimensions is at least 1.5, 2, 3, 5, 10, or 20 times larger than the minimum dimension among the three dimensions, and is an aerosol generating article according to any one of Examples 1 to 49. Example 51. Each of the fibers has three mutually orthogonal dimensions, and the maximum dimension among the three dimensions is at least 1.5, 2, 3, 5, 10, or 20 times larger than the second largest dimension among the three dimensions, and is an aerosol generating article according to any one of Examples 1 to 50. Example 52. The substrate contains at least 4, 6, or 8 wt% of a binder on a dry weight basis, and is an aerosol generating article according to any one of Examples 1 to 51. Example 53. The substrate contains 8, 6, or 4 wt% or less of a binder on a dry weight basis, and is an aerosol generating article according to any one of Examples 1 to 52. Example 54. The substrate contains, on a dry weight basis, 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4 to 8, 6 to 8, 2 to 6, 4 to 6, 2 to 4% by weight of a binder, particularly preferably 2 to 10% by weight of a binder, and is an aerosol-generating article according to any one of Examples 1 to 53. Example 55. The binder contains, or consists of, one or both of carboxymethyl cellulose or hydroxypropyl cellulose, and is an aerosol-generating article according to any one of Examples 1 to 54. Example 56. The binder contains, or consists of, one or more gums such as guar gum, and is an aerosol-generating article according to any one of Examples 1 to 55. Example 57. The thermally conductive particles are distributed substantially homogeneously throughout the aerosol-forming substrate, and is an aerosol-generating article according to any one of Examples 1 to 56. Example 58. The aerosol former is distributed substantially homogeneously throughout the aerosol-forming substrate, and is an aerosol-generating article according to any one of Examples 1 to 57. Example 59. The fibers are distributed substantially homogeneously throughout the aerosol-forming substrate, and is an aerosol-generating article according to any one of Examples 1 to 58. Example 60. The binder is distributed substantially homogeneously throughout the aerosol-forming substrate, and is an aerosol-generating article according to any one of Examples 1 to 59. Example 61. The substrate contains nicotine, and is an aerosol-generating article according to any one of Examples 1 to 60. Example 62. The substrate contains, on a dry weight basis, at least 0.01, 1, 2, 3, or 4% by weight of nicotine, and is an aerosol-generating article according to Example 61. Example 63. The substrate contains, on a dry weight basis, 5, 4, 3, 2, or 1% by weight or less of nicotine, and is an aerosol-generating article according to any one of Examples 61 to 62. Example 64. The substrate contains nicotine in an amount of 0.01 to 5, 1 to 5, 2 to 5, 3 to 5, 4 to 5, 0.01 to 4, 1 to 4, 2 to 4, 3 to 4, 0.01 to 3, 1 to 3, 2 to 3, 0.01 to 2, 1 to 2, 0.01 to 1% by weight based on dry weight, particularly preferably 0.5 to 4% by weight of nicotine, and is an aerosol generating article according to any one of Examples 1 to 63. Example 65. Nicotine is substantially homogeneously distributed throughout the aerosol-forming substrate, and is an aerosol generating article according to any one of Examples 61 to 63. Example 66. The substrate contains an acid, and is an aerosol generating article according to any one of Examples 1 to 65. Example 67. The substrate contains at least 0.01, 1, or 2% by weight of an acid based on dry weight, and is an aerosol generating article according to Example 66. Example 68. The substrate contains 3, 2, or 1% by weight or less of an acid based on dry weight, and is an aerosol generating article according to any one of Examples 66 to 67. Example 69. The substrate contains an acid in an amount of 0.01 to 3, 1 to 3, 2 to 3, 0.01 to 2, 1 to 2, 0.01 to 1% by weight based on dry weight, particularly preferably 0.5 to 5% by weight of an acid, and is an aerosol generating article according to any one of Examples 66 to 68. Example 70. The acid contains or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid, and is an aerosol generating article according to any one of Examples 66 to 69. Example 71. The acid is substantially homogeneously distributed throughout the aerosol-forming substrate, and is an aerosol generating article according to any one of Examples 66 to 70. Example 72. The substrate contains at least one plant, and is an aerosol generating article according to any one of Examples 1 to 71. Example 73. The substrate contains at least one plant in an amount of at least 0.01, 1, 2, 5, 10, or 15% by weight based on dry weight, and is an aerosol generating article according to Example 72. Example 74. The substrate contains at least one plant at 20, 15, 10, 5, 2, or 1 wt% or less on a dry weight basis, and is an aerosol generating article according to any one of Examples 72 to 73. Example 75. The substrate contains at least one plant at 0.01 to 20, 1 to 20, 2 to 20, 5 to 20, 10 to 20, 15 to 20, 0.01 to 15, 1 to 15, 2 to 15, 5 to 15, 10 to 15, 0.01 to 10, 1 to 10, 2 to 10, 5 to 10, 0.01 to 5, 1 to 5, 2 to 5, 0.01 to 2, 1 to 2, or 0.01 to 1 wt%, particularly preferably at least one plant at 1 to 15 wt%, and is an aerosol generating article according to any one of Examples 72 to 74. Example 76. The at least one plant contains or consists of one or both of clove and rosemary, and is an aerosol generating article according to any one of Examples 72 to 75. Example 77. The at least one plant is substantially homogeneously distributed throughout the aerosol forming substrate, and is an aerosol generating article according to any one of Examples 72 to 76. Example 78. The substrate contains at least one flavorant, and is an aerosol generating article according to any one of Examples 1 to 77. Example 79. The substrate contains at least one flavorant at at least 0.1, 1, 2, or 5 wt% on a dry weight basis, and is an aerosol generating article according to Example 78. Example 80. The substrate contains at least one flavorant at 10, 5, 2, or 1 wt% or less on a dry weight basis, and is an aerosol generating article according to any one of Examples 78 to 79. Example 81. The substrate contains at least one flavorant at 0.1 to 10, 1 to 10, 2 to 10, 5 to 10, 0.1 to 5, 1 to 5, 2 to 5, 0.1 to 2, 1 to 2, or 0.1 to 1 wt%, particularly preferably at least one flavorant at 0.1 to 5 wt%, and is an aerosol generating article according to any one of Examples 78 to 80. Example 82. The aerosol generating article according to any one of Examples 78 to 81, wherein at least one flavoring agent is present as a coating on one or more other components of a coating, for example, an aerosol-forming substrate. Example 83. The aerosol generating article according to any one of Examples 78 to 82, wherein at least one flavoring agent is distributed substantially homogeneously throughout the aerosol-forming substrate. Example 84. The aerosol generating article according to any one of Examples 1 to 83, wherein the aerosol-forming substrate comprises one or more organic materials such as tobacco. Example 85. The aerosol generating article according to any one of Examples 1 to 84, wherein the organic material comprises one or more of herb leaves, tobacco leaves, fragments of tobacco stems, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Example 86. The aerosol generating article according to any one of Examples 1 to 85, wherein the organic material is distributed substantially homogeneously throughout the aerosol-forming substrate. Example 87. The aerosol generating article according to any one of Examples 1 to 86, wherein the aerosol-forming substrate is a tobacco-free aerosol-forming substrate, for example, the aerosol-forming substrate does not contain tobacco. Example 88. The aerosol generating article according to any one of Examples 1 to 87, wherein some or each of the thermally conductive particles comprises a susceptor material and / or is formed from a susceptor material, for example, a carbon susceptor material. Example 89. The aerosol generating article according to any one of Examples 1 to 88, wherein the aerosol-forming substrate has a thermal conductivity 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) in at least one direction or in all directions at 25 degrees Celsius. Example 90. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 89, having a density of less than 1500, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, or 650 kg / m3. Example 91. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 90, having a density of 500 - 900 kg / m 3 or 600 - 800 kg / m 3 . Example 92. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 91, having a moisture content of 1 - 20 or 3 - 15 wt%. Example 93. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 92, containing 1 - 20 or 3 - 15 wt% water. Example 94. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 93, having a density of at least 0.1, 0.2, 0.3, or 0.5 g / m 3 . Example 95. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 94, having a density of at least 2, 1.5, 1.2, or 1 g / m 3 . Example 96. The aerosol-forming substrate is an aerosol-generating article according to any one of Examples 1 to 95, having a density of 0.1 - 2 g / m 2 , 0.2 - 2 g / m 2 , 0.3 - 2 g / m 2 , 0.3 - 1.5 g / m 2 , or 0.3 - 1.2 g / m 3 . Example 97. 97. The aerosol-generating article of any of Examples 1 to 96, wherein the substrate is in the form of a tube having a width in the radial dimension and a length in the longitudinal dimension, the length being 5 mm to 100 mm, for example, 6 mm to 80 mm, for example, 7 mm to 60 mm, for example, 8 mm to 55 mm, for example, 9 mm to 50 mm, for example, 10 mm to 45 mm, for example, 11 mm to 35 mm, for example, 12 mm to 25 mm. Example 98. An aerosol-generating article according to any of Examples 1 to 97, wherein the substrate is in the form of a tube having a width in the radial dimension and a length in the longitudinal dimension, the width being defined by the outer diameter of the tube, the outer diameter being from 3mm to 20mm, for example, from 4mm to 12mm, such as from 4.5mm to 10mm, for example, from 5mm to 9mm, such as from 6mm to 8mm, for example, from 6.5mm to 7.5mm, for example, about 7mm. Example 99. 99. The aerosol-generating article of any of Examples 1 to 98, wherein the substrate is in the form of a tube having an outer diameter and an inner diameter, the inner diameter being from 2.5 mm to 19 mm, for example, from 3.5 mm to 11.5 mm, for example, from 4 mm to 9 mm, for example, from 4.5 mm to 8.5 mm, for example, from 5.5 mm to 7.5 mm, for example, from 6.9 mm to 7.3 mm, for example, about 7 mm. Example 100. 99. An aerosol-generating article according to any of Examples 1 to 99, wherein the substrate is in the form of a tube having a length, an outer diameter and an inner diameter, a wall thickness of the tube defined by the difference between the outer and inner diameters, and the wall thickness is from 100 microns to 5 mm, such as from 150 microns to 3 mm, for example from 200 microns to 2 mm, for example from 250 microns to 1.5 mm, such as from 300 microns to 1 mm, for example from 350 microns to 500 microns. Example 101. The aerosol-generating article of any of Examples 1-100, wherein the substrate is in the form of a tube, and the tube is a rolled sheet of aerosol-forming material, e.g., a rolled sheet of homogenized tobacco material, e.g., a rolled sheet of cast leaf tobacco, or, e.g., a rolled sheet of tobacco-free aerosol-forming material. Example 102. The substrate is in the form of a tube, and the tube is an aerosol-generating article according to any one of Examples i to 100, which is an extruded tube of an aerosol-forming material, for example, an extruded tube of a homogenized tobacco material, or an extruded tube of an aerosol-forming material that does not contain tobacco, for example. Example 103. The aerosol-generating article comprises a front plug, for example, the front plug has a length of 2 mm to 10 mm, 3 mm to 8 mm, or 4 mm to 6 mm, for example, about 5 mm, and is an aerosol-generating article according to any one of Examples 1 to 102. Example 104. The aerosol-generating article comprises a first hollow support tube, for example, a first hollow acetate tube, and for example, the first hollow support tube is located downstream of the aerosol-forming substrate within the aerosol-generating article, and is an aerosol-generating article according to any one of Examples 1 to 103. Example 105. The aerosol-generating article comprises a second hollow support tube, for example, a second hollow acetate tube, and for example, the second hollow support tube is located downstream of the aerosol-forming substrate within the aerosol-generating article, and is an aerosol-generating article according to any one of Examples 1 to 104. Example 106. The second hollow support tube comprises one or more ventilation holes, and is an aerosol-generating article according to Example 105. Example 107. The aerosol-generating article comprises a mouthpiece-side plug filter, and is an aerosol-generating article according to any one of Examples 1 to 106. Example 108. The aerosol-generating article comprises a wrapper, for example, a paper wrapper, and for example, the components of the aerosol-generating article including the aerosol-forming substrate are assembled within the wrapper, and is an aerosol-generating article according to any one of Examples 1 to 107. Example 109. The aerosol-generating article is a front plug, and an aerosol-forming substrate is disposed downstream of the front plug. It includes the front plug, a first hollow support tube disposed downstream of the aerosol-forming substrate, a second hollow support tube disposed downstream of the first hollow support tube, and a mouth-side plug filter disposed downstream of the second hollow support tube. Preferably, the front plug, the aerosol-forming substrate, the first hollow support tube, the second hollow support tube, and the mouth-side plug filter are surrounded by a wrapper, such as a paper wrapper. The aerosol-generating article according to any one of Examples 1 to 108. Example 110. The aerosol-forming substrate has a length of 5 millimeters to 30 millimeters. The aerosol-generating article according to any one of Examples 1 to 109. Example 111. The aerosol-forming substrate has a length of 5 millimeters to 16 millimeters. The aerosol-generating article according to any one of Examples 1 to 110. Example 112. The wall thickness of the aerosol-forming substrate is 5 percent to 40 percent of the outer diameter of the aerosol-forming substrate. The aerosol-generating article according to any one of Examples 1 to 111. Example 113. A method for forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, such as the aerosol-generating article defined by any one of Examples i to 112, forming a slurry comprising thermally conductive particles, an aerosol-forming agent, fibers, and a binder; The method includes molding the slurry into the shape of a hollow tubular aerosol-forming substrate and drying the molded slurry to form a hollow tubular aerosol-forming substrate. Example 114. A method for forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, such as the aerosol-generating article defined by any one of Examples i to 112, forming a slurry comprising thermally conductive particles, an aerosol-forming agent, fibers, and a binder; A method comprising extruding a slurry into the shape of a hollow tubular aerosol-forming substrate and drying the slurry extruded into the hollow tube. Example 115. The method according to Example 114, further comprising the step of cutting a hollow tube to form a hollow tubular aerosol-forming substrate. Example 116. A method of forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, for example, an aerosol-generating article defined by any of Examples i to 112, comprising: forming a slurry comprising thermally conductive particles, an aerosol former, fibers, and a binder; A method comprising molding and drying the slurry to form a sheet of aerosol-forming material and forming the sheet into a hollow tube. Example 117. The method according to Example 116, further comprising the step of cutting a hollow tube to form a hollow tubular aerosol-forming substrate. Example 118. The step of forming the sheet into a hollow tube comprises winding the sheet into a tubular shape and applying an adhesive to the overlapping ports of the wound sheet to maintain the wound sheet in a tubular shape, according to the method described in Example 116 or 117. Example 119. The slurry contains water, according to the method described in any of Examples 113 to 118. Example 120. The slurry contains 40 to 90% by weight, 40 to 85% by weight, 50 to 80% by weight, 60 to 80% by weight, 60 to 75% by weight of water, according to the method described in any of Examples 113 to 119. Example 121. The slurry contains an acid such as fumaric acid, according to the method described in any of Examples 113 to 120. Example 122. The slurry contains nicotine, according to the method described in any of Examples 113 to 121. Example 123. Forming the slurry comprises: an aerosol former; a fiber, water, optionally, an acid, optionally, nicotine, and forming a first mixture comprising the same, forming a second mixture comprising a heat conductive particle and a binder, and adding the second mixture to the first mixture to form a combined mixture, a method according to any of Examples 113 to 122. Example 124. Example 124. Forming the first mixture comprises providing an aerosol former, or a solution comprising an aerosol former and nicotine, a method according to Example 123. Example 125. 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 premix, a method according to Example 124. Example 126. Forming the first mixture comprises adding water to an aerosol former, or a solution comprising an aerosol former and nicotine, or to the first premix to form a second premix, a method according to any of Examples 123 to 125. Example 127. Forming the first mixture comprises adding a fiber to the second premix, a method according to Example 126. Example 128. Forming the second mixture comprises mixing a heat conductive particle and a binder, a method according to any of Examples 126 to 127. Example 129. The method comprises a first mixing of the combined mixture, a method according to any of Examples 126 to 128. Example 130. The first mixing is carried out under a first pressure of 500, 400, 300, 250, or 200 mbar or less, a method according to Example 129. Example 131. The first mixing is carried out for 1 to 10 minutes, 2 to 8 minutes, or 3 to 6 minutes, for example, about 4 minutes, by the method described in Example 129 or 130. Example 132. The method includes a second mixing after the first mixing, by the method described in any of Examples 129 to 131. Example 133. The second mixing is carried out under a second pressure that is lower than the first pressure, by the method described in Example 132. Example 134. The second pressure is 500, 400, 300, 200, 150, or 100 mbar or less, by the method described in Example 133. Example 135. 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, by the method described in Example 132 or 133 or 134. Example 136. Molding the slurry includes molding the slurry on a flat support, for example, a flat steel support, by the method described in any of Examples 116 to 135. Example 137. After molding the slurry and before drying the slurry, the method includes setting the thickness of the slurry, for example, setting the thickness of the slurry to 100 to 1,000 microns, 200 to 900 microns, 300 to 800, 500 to 700 microns, for example, about 600 microns, by the method described in any of Examples 113 to 136. Example 138. Drying the slurry includes providing a flow of gas, such as air, over or through the slurry, by the method described in any of Examples 113 to 137. Example 139. The flow of gas is heated, by the method described in Example 138. Example 140. The flow of gas is heated to a temperature of 100 to 160 °C or 120 to 140 °C, by the method described in Example 139. Example 141. The gas flow is the method according to any one of Examples 138 to 140, provided for 1 to 10 minutes or 2 to 5 minutes. Example 142. Drying the slurry includes drying the slurry until the slurry has a moisture content of 1 to 20, 2 to 15, 2 to 10, or 3 to 7% by weight, and is the method according to any one of Examples 113 to 141. Example 143. Drying the slurry is the method according to any one of Examples 113 to 142, which includes forming a precursor for forming on an aerosol-forming substrate, and the precursor is a sheet of aerosol-forming material. Example 144. An aerosol generation system comprising an aerosol-generating article according to any one of Examples i to 112 and an electric aerosol-generating device. Example 145. The electric aerosol-generating device is configured to resistively heat the aerosol-generating article during use, and is the aerosol generation system according to Example 144. Example 146. The electric aerosol-generating device is configured to inductively heat the aerosol-generating article, for example, the aerosol-forming substrate of the aerosol-generating article, during use, and is the aerosol generation system according to any one of Examples 144 to 145.

[0134] Here, the examples will be further described with reference to the following figures.

[0135] FIG. 1 shows a schematic cross-sectional view of an exemplary aerosol-generating article 10 according to an embodiment of the present invention. The aerosol-generating article 10 extends from an upstream end or distal end 18 to a downstream end or proximal end or mouth-side end 20 and has an overall length of about 45 millimeters and a diameter of about 7.2 mm.

[0136] The aerosol-generating article 10 comprises a plurality of elements arranged coaxially and assembled within a wrapper 70. The plurality of elements forming the article are, from the distal end to the proximal end, a front plug 46, a tubular segment of a thermally enhanced aerosol-forming substrate 12, a flow filter 34 without a cardboard tube, and a mouthpiece filter 42. The wrapper 70 may be a cigarette paper.

[0137] The front plug 46, also referred to as the upstream element, is located immediately upstream of the tubular aerosol-forming substrate 12. The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate. The front plug 46 has a diameter of about 7.2 mm and a length of about 5 millimeters. The RTD of the front plug 46 is about 30 millimeters H2O.

[0138] The tubular segment of the aerosol-forming substrate 12 has an outer diameter of about 7.2 millimeters, an inner diameter of about 6.8 millimeters, and a length of about 12 millimeters. The aerosol-forming substrate 12 is formed from a wound sheet of aerosol-forming material that includes thermally conductive particles 44. The tubular aerosol-forming substrate 12 is configured to form an aerosol when heated to a temperature between 150 degrees Celsius and 350 degrees Celsius. Some specific examples of suitable aerosol-forming substrate compositions are provided below.

[0139] The cardboard tube 34 has a length of 16 mm and provides a free space within the article 10 in which the volatile components generated by heating of the aerosol-forming substrate can be cooled and form an aerosol.

[0140] The mouthpiece element 42 is provided in the form of a cylindrical plug of low-density cellulose acetate. The mouthpiece element 42 has a length of about 12 millimeters and an outer diameter of about 7.2 mm. The RTD of the mouthpiece element 42 is about 12 millimeters H2O.

[0141] It is clear that the configuration of the aerosol generating article 10 of FIG. 1 is intended to function only as an example. The thermally enhanced tubular aerosol forming substrate 12 can be used, for example, in aerosol generating articles that are longer, for example 80 mm in length, and thinner, for example 4.5 mm in diameter.

[0142] In a particular embodiment of the aerosol generating article shown in FIG. 1, the tubular segment 12 of the aerosol forming substrate contains, on a dry weight basis, approximately 76.1 wt% of thermally conductive particles 44. In this embodiment, the thermally conductive particles 44 are graphite particles, in particular AMG Graphite GK of FP 99.5 (>99.5% purity) graphite particles manufactured by Graphit Kropfmul GmbH, although other particles or mixtures of particles can also be used. Each thermally conductive particle has a thermal conductivity of at least about 6 W / (mK) in at least one direction at 25 degrees Celsius.

[0143] The tubular aerosol forming substrate 12 contains, on a dry weight basis, approximately 17.7 wt% of an aerosol former. In this embodiment, the aerosol former is glycerol, in particular ICOF European food grade (>99.5% purity) glycerol.

[0144] The tubular aerosol forming substrate 12 contains, on a dry weight basis, approximately 3.9 wt% of fibers. In this embodiment, the fibers are cellulose fibers, in particular Kib cellulose fibers manufactured by Stora Enso OYJ.

[0145] The tubular aerosol forming substrate 12 contains, on a dry weight basis, approximately 2.3 wt% of a binder. In this embodiment, the binder is guar gum, in particular guar gum manufactured by Gumix International Inc.

[0146] The tubular aerosol forming substrate contains approximately 10 wt% water when measured at 25 degrees Celsius.

[0147] In other embodiments, the tubular aerosol-forming substrate 12 further comprises one or more of nicotine, an acid such as fumaric acid, a plant such as clove or rosmarinus, and a flavorant.

[0148] The tubular aerosol-forming substrate 12 has a thermal conductivity of at least 0.1 W / (mK) in at least one direction at 25 degrees Celsius. The aerosol-forming substrate 12 may have a thermal conductivity of 0.2, 0.5, 1, 1.5 or more W / (mK) in at least one direction at 25 degrees Celsius.

[0149] Each of the thermally conductive particles 44 is substantially spherical in shape. The thermally conductive particles 44 are distributed substantially homogeneously 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.

[0150] 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.

[0151] The aerosol-forming substrate is formed by the process described below.

[0152] The slurry is formed using a laboratory disperser having the ability to mix viscous liquids, disperse powders through liquids, and remove gases from the mixture (e.g., by applying a vacuum or other suitably low pressure). In this embodiment, a laboratory disperser commercially available from PC Laborsystem was used.

[0153] To form the slurry, a first mixture is formed by adding approximately 7.11 grams of aerosol former, then approximately 157.5 grams of water, and then approximately 1.57 grams of fibers to a lab disperser. These first components are then mixed at 25 degrees Celsius for 5 minutes at 600 - 700 rpm to ensure a homogeneous mixture and to hydrate the fibers. A second mixture is then formed by manually mixing approximately 32.95 grams of thermally conductive particles and approximately 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 the combined mixture. The combined mixture is then mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of approximately 200 mbar. The reduced pressure can help ensure that the thermally conductive particles are homogeneously 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 25 degrees Celsius and a second reduced pressure of approximately 100 mbar. This second reduced pressure can help remove any remaining bubbles. Thereby, a slurry for molding is formed.

[0154] The slurry is then molded and dried using a suitable apparatus. In this embodiment, a commercially available Labcoater Mathis apparatus is used. This apparatus includes stainless steel, a flat support, and a comma blade for adjusting the thickness of the slurry molded on the flat support.

[0155] The slurry is molded onto the flat support, and the gap between the comma blade and the flat support is set to 0.6 millimeters. This ensures that the thickness of the slurry is 0.6 millimeters or less at any given point.

[0156] The slurry is then dried with hot air at a temperature of 120 to 140 degrees Celsius for 2 to 5 minutes. After this drying, a sheet of the aerosol-forming substrate is formed. This sheet has a thickness of about 300 microns, a basis weight of about 250 grams per square meter, and a density of about 0.79 kilograms per cubic meter.

[0157] Thereafter, the sheet is wound to form a tube. An adhesive is applied to the overlapping portions of the wound sheet to attach the sheet in the form of a tube, and then the tube is cut to a length of 12 mm for the tubular aerosol-forming substrate 12.

[0158] After forming the tubular aerosol-forming substrate 12, the aerosol-generating article 10 is assembled by positioning the various components of the article 10 and packaging the components within the wrapper 70.

[0159] Other embodiments may have the same structure as those described above, but may have an aerosol-forming substrate of a different composition. For example, in a further embodiment, the aerosol-forming material comprises a thermally enhanced homogenized tobacco tube containing the thermally conductive particles 44. The thermally conductive particles 44 are carbon particles, specifically, expanded graphite particles, and have a particle size distribution with a D10 particle size of 6.6 micrometers, a D50 particle size of 20 micrometers, and a D90 particle size of 56 micrometers. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume average particle size of about 35 micrometers. Each of the expanded graphite particles has a substantially spherical shape. The expanded graphite particles have a density of less than 1000 kilograms per cubic meter. The aerosol-forming substrate comprising the aerosol-forming material and the thermally conductive particles 44 has a composite density of about 760 kilograms per cubic meter. The expanded graphite particles constitute approximately 5% by weight of the aerosol-forming substrate.

[0160] The tube 12 of the aerosol-forming substrate is formed by a process comprising the following steps: · To form a first premix, pre-mix guar gum, which is a binder, with glycerin, which is an aerosol former. · To form a second premix, pre-mix a fine cut tobacco material with a powder consisting of expanded graphite particles 44 and having a bulk density of about 0.065 grams per cubic centimeter. · To form a slurry, mix the first and second premixes with water. · Using a high-shear mixer, homogenize the slurry. · Mold the slurry onto a conveyor belt. · To form a sheet of the aerosol-forming substrate, control the thickness of the slurry, dry the slurry, and · To form a tubular segment of the aerosol-forming substrate, wind the sheet of the aerosol-forming substrate around a tube and cut the tube.

[0161] The aerosol-forming substrate formed of the composition containing conductive particles according to the present invention showed improved aerosol delivery as compared with a reference substrate not containing thermally conductive particles.

[0162] FIG. 2 shows a schematic cross-sectional view of a first embodiment of an aerosol generating system 100. The system 100 includes an aerosol generating device 102 and the aerosol article 10 of FIG. 1.

[0163] The aerosol generating device 102 includes a battery 104, a control device 106, a heating blade 108 coupled to the battery, and a smoking detection mechanism (not shown). The control device 106 is coupled to the battery 104, the heating blade 108, and the smoking detection mechanism.

[0164] The aerosol generating device 102 further includes a housing 110 that defines a substantially cylindrical cavity for receiving a portion of the article 10. The heating blade 108 is positioned in the center of the cavity and extends in the longitudinal direction from the base of the cavity.

[0165] 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 it can pass current through the electrically resistive track and heat the electrically resistive track and the heating blade 108 to an operating temperature.

[0166] In use, the user inserts the article 10 into the cavity, passes the upstream element 46 through the heating blade 108, and extends it into the internal bore or cavity of the tubular aerosol-forming substrate 12 of the article 10. FIG. 3 shows the article 10 inserted into the cavity of the device 102 and the heating blade extending into the internal bore of the tubular aerosol-forming substrate.

[0167] Thereafter, the user smokes 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.

[0168] When the user smokes the article 10, air flows through the air inlet of the device. The smoking detection mechanism detects that the air flow rate through the air inlet has increased above a non-zero threshold flow rate. The smoking detection mechanism then sends a signal to the control device 106. Thereafter, the control device 106 controls the battery 104 to pass current through the electrically resistive track and heat the heating blade 108. Thereby, the tubular aerosol-forming substrate is heated.

[0169] The heat-conductive particles 44 have a significantly higher thermal conductivity than the surrounding aerosol-forming material. Therefore, these particles act as local hot spots and can provide a more uniform temperature across the aerosol-forming substrate, particularly radially from the heating blade 108, whereas in prior art substrates, significant temperature gradients can exist. Further, since the aerosol-forming substrate is in the form of a tube, the temperature equalizes relatively quickly between the inner and outer surfaces of the tube. By combining the tubular structure for the aerosol-forming substrate with the presence of heat-conductive particles in the aerosol-forming substrate, a larger proportion of the aerosol-forming substrate can reach a temperature high enough to release the volatile compounds quickly, and thus a higher utilization efficiency of the aerosol-forming substrate becomes possible.

[0170] Upon heating of the aerosol-forming substrate, the aerosol-forming substrate releases volatile compounds. These compounds are entrained in the air flowing from the upstream end 18 of the article 10 towards the downstream end 20 of the article 10. The compounds are cooled and condensed to form an aerosol as they pass through the cardboard tube 34. The aerosol then passes through the mouthpiece element 42, whereby undesirable particles that can be entrained in the airflow and enter the user's mouth can be removed.

[0171] When the user stops inhaling on the article 10, the airflow rate through the air intake of the device decreases to less than a non-zero threshold flow rate. This is detected by the smoking detection mechanism. The smoking detection mechanism accordingly transmits a signal to the control device 106. The control device 106 then controls the battery 104 to reduce the current passing through the electrically resistive track to zero.

[0172] After smoking several times on the article 10, the user may choose to replace the article 10 with a new article.

[0173] Figure 3 shows a schematic cross-sectional view of a second embodiment of the aerosol generation system 300. The system 300 comprises an aerosol generating device 302 and the aerosol generating article 10 of FIG. 1.

[0174] The aerosol generating device 302 includes a battery 304, a control device 306, an external resistance heater 308, and a smoking detection mechanism (not shown). The control device 306 is coupled to the battery 304, the resistance heater 308, and the smoking detection mechanism.

[0175] The aerosol generating device 302 further includes a housing 310 that defines a substantially cylindrical cavity for receiving a portion of the article 10. The external heater 208 is located on the inner surface of the cavity.

[0176] The use of the system is similar to that described above in connection with the system of FIG. 2, with the difference that the tubular aerosol-forming substrate 12 is heated from the outside rather than by a heater located within an internal portion of the aerosol-forming substrate.

[0177] FIG. 4 shows a schematic cross-sectional view of a third embodiment of an aerosol generating system 400. The system 400 includes an aerosol generating device 402 and the aerosol generating article 10 of FIG. 1.

[0178] The aerosol generating device 402 includes a battery 404, a control device 406, an inductor coil 408, and a smoking detection mechanism (not shown). The control device 406 is coupled to the battery 404, the inductor coil 408, and the smoking detection mechanism.

[0179] The aerosol generating device 402 further includes a housing 410 that defines a substantially cylindrical cavity for receiving a portion of the article 10. The inductor coil 408 is spiral around the cavity.

[0180] The battery 404 is coupled to the inductor coil 408 such that an alternating current can flow through the inductor coil 408.

[0181] In use, the user inserts article 10 into the cavity. FIG. 4 shows article 10 inserted into the cavity of device 402. An air flow is detected and the device operates as described above in connection with the system of FIG. 1. If smoking is detected, control device 406 controls battery 404 to pass an alternating current through inductor coil 408. Thereby, inductor coil 408 generates a varying electromagnetic field. The aerosol-forming substrate 12 is positioned within this varying electromagnetic field. Particles 44, for example, made of graphite or expanded graphite, are susceptor materials. Thus, the varying electromagnetic field induces eddy currents in particles 44. Thereby, particles 44 are heated, and thereby the aerosol-forming material of the aerosol-forming substrate is also heated.

[0182] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, etc. are to be understood as being modified in all instances by the term "about." Also, all ranges include the disclosed maximum and minimum points, and any intermediate ranges therebetween, whether or not specifically enumerated herein. Thus, in this context, number A is understood as A ± 10% of A. Within this context, number A can be considered to include numerical values within the general standard error of the measured value of the property being modified by number A. Number A can deviate from the percentages listed above in some instances used in the appended claims, provided that the amount by which A deviates does not substantially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and any intermediate ranges therebetween, whether or not specifically enumerated herein.

Claims

**Claim 1** An aerosol generating article for generating an inhalable aerosol upon heating, comprising a plurality of components including an aerosol-forming substrate, wherein the aerosol-forming substrate is in the form of a hollow tubular segment defining a substrate recess extending between an upstream end and a downstream end of the aerosol-forming substrate, and the aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol former, the aerosol generating article. **Claim 2** The aerosol-forming substrate contains, on a dry weight basis, 5 to 95% by weight, for example, 10 to 90% by weight of thermally conductive particles, and each of the thermally conductive particles has a thermal conductivity of at least 1 W / (mK) in at least one direction at 25 degrees Celsius. The aerosol generating article according to claim 1. **Claim 3** The aerosol-forming substrate has a thermal conductivity of at least 0.12 W / (mK) in at least one direction at 25 degrees Celsius. The aerosol generating article according to claim 1 or 2. **Claim 4** Each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond. The aerosol generating article according to any one of claims 1 to 3. **Claim 5** The aerosol-forming substrate contains, on a dry weight basis, 10 to 90% by weight of thermally conductive particles, 7 to 60% by weight of an aerosol former, 2 to 20% by weight of fibers, and 2 to 10% by weight of a binder, and each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond. The aerosol generating article according to any one of claims 1 to 4. **Claim 6** The thermally conductive particles are substantially homogeneously distributed throughout the aerosol-forming substrate. The aerosol generating article according to any one of claims 1 to 5. **Claim 7** The aerosol-forming substrate contains one or more organic materials such as tobacco. The aerosol generating article according to any one of claims 1 to 6. **Claim 8** The aerosol-forming substrate is an aerosol-forming substrate that does not contain tobacco. The aerosol generating article according to any one of claims 1 to 6. **Claim 9** 9. The aerosol-generating article of claim 1, wherein the aerosol-forming substrate is in the form of a tube having an outer diameter, an inner diameter and a length, the length of the tube being between 5 mm and 100 mm, the outer diameter being between 3 mm and 20 mm and the inner diameter being between 2.5 mm and 19.5 mm.

10. 10. The aerosol-generating article of claim 9, wherein the length of the tube is between 8 mm and 25 mm, the outer diameter of the tube is between 6 mm and 8 mm, and the inner diameter of the tube is between 5 mm and 7.9 mm.

11. 11. An aerosol-generating article according to any of claims 1 to 10, wherein the hollow tubular segment is a rolled sheet of aerosol-forming material, such as a rolled sheet of homogenized tobacco material, or such as a rolled sheet of tobacco-free aerosol-forming material.

12. 11. An aerosol-generating article according to any of claims 1 to 10, wherein the hollow tubular segment is an extruded tube of aerosol-forming material, such as an extruded tube of homogenized tobacco material, or, for example, an extruded tube of tobacco-free aerosol-forming material.

13. A method for forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, for example an aerosol-generating article as defined by any of claims 1 to 12, 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 a sheet of aerosol-forming material; and forming the sheet into a hollow tube.

14. Forming the slurry comprises: The aerosol former; The fibers, Water, Optionally, an acid, forming a first mixture comprising, optionally, nicotine; The thermally conductive particles; forming a second mixture comprising the binder; and 14. The method of claim 13 comprising adding the second mixture to the first mixture to form a combined mixture.

15. An aerosol generating system comprising the aerosol generating article according to any one of claims 1 to 12 and an electric aerosol generator, preferably, the electric aerosol generator is configured to resistively heat the aerosol generating article during use, or the electric aerosol generator is configured to inductively heat the aerosol generating article, for example, the aerosol forming substrate of the aerosol generating article, during use.

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