Porous ceramic and method of making same, aerosol generation device

Abstract

The application relates to a porous ceramic and a preparation method thereof, and an aerosol generating device. The preparation method of the porous ceramic material comprises the following steps: mixing a ceramic preliminary material, a gel mixture, a dispersing agent and an initiator to obtain a precursor, the mass of the initiator is 0.1 wt% to 3 wt% of the total mass of the gel mixture, and the mass of the dispersing agent is 0.1 wt% to 2.0 wt% of the total mass of the ceramic preliminary material; performing a forming treatment on the precursor to obtain a green body; and performing a segmented temperature rising treatment and a sintering treatment on the green body to obtain the porous ceramic material. The porous ceramic material prepared by the application has a pore size gradient distribution which increases from an atomization surface to an oil guiding surface. The large pore size near the oil guiding surface is beneficial to oil guiding, and the small pore size near the atomization surface is beneficial to oil locking, effectively avoiding oil leakage. Meanwhile, the method effectively avoids the situation that the pore size near an oil reservoir is too small to cause oil leakage and poor oil guiding, thereby avoiding the situation of "paste core".

Description

Technical Field

[0001] This application belongs to the field of aerosol technology, and particularly relates to a porous ceramic and its preparation method, as well as an aerosol generating device. Background Technology

[0002] The atomizer is the core component of e-cigarettes. Currently, the mainstream structure uses a porous ceramic atomizer core. Furthermore, porous ceramic atomizer cores can also be applied to other atomization fields such as medical atomization. Addressing the increasingly stringent technical requirements of e-cigarette atomizer cores and medical atomization, existing porous ceramics include an oil guide end and an atomizing end, both with porous structures. During operation, the atomized liquid is transported from the oil guide end to the atomizing end via these pores. The atomized liquid is then heated and atomized by a heating element near the atomizing end, producing atomized vapor. The pore size within existing porous ceramics is uniformly distributed. If the pore size is too small, the atomized liquid cannot move quickly within the porous ceramic, leading to dry burning of the heating element and a burnt taste when inhaled. If the pore size is too large, the atomized liquid moves rapidly from the oil guide end to the atomizing end, resulting in a large accumulation of liquid and a tendency for "spitting" (or "oil splattering"). Additionally, larger pore sizes increase the risk of "oil leakage" from the ceramic core. Therefore, existing porous ceramics are insufficient to meet people's needs. Summary of the Invention

[0003] To overcome the above-mentioned defects, this application provides a porous ceramic and its preparation method, as well as an aerosol generating device. The porous ceramic prepared by this application has the advantage of a gradient distribution of pore size.

[0004] In a first aspect, this application provides a method for preparing porous ceramics, comprising the following steps:

[0005] A precursor is obtained by mixing ceramic preparative material, gel mixture, dispersant and initiator, wherein the mass of the initiator is 0.1 wt% to 3 wt% of the total mass of the gel mixture, and the mass of the dispersant is 0.1 wt% to 2.0 wt% of the total mass of the ceramic preparative material.

[0006] The precursor is shaped to obtain a blank;

[0007] The green body is subjected to segmented heating and sintering treatment to obtain porous ceramic material.

[0008] In conjunction with the first aspect, the ceramic preparatory material comprises ceramic powders in at least two particle size ranges.

[0009] In conjunction with the first aspect, the ceramic preparatory material comprises ceramic powders in at least three particle size ranges.

[0010] In conjunction with the first aspect, the ceramic preparatory material includes ceramic powders with median particle sizes of 30μm~35μm, 60μm~65μm, and 80μm~95μm.

[0011] In conjunction with the first aspect, the method of mixing the ceramic preparator, the gel mixture, and the initiator to obtain the precursor includes: first mixing the ceramic preparator, the dispersant, and the gel mixture, and then adding the initiator and stirring to mix, wherein the ceramic preparator accounts for 45 wt% to 55 wt% of the mass of the precursor.

[0012] In conjunction with the first aspect, the ceramic preparatory material comprises the following components by mass percentage: 55 wt% to 70 wt% ceramic powder, 10 wt% to 20 wt% sintering aid, and 5 wt% to 20 wt% pore-forming agent;

[0013] In conjunction with the first aspect, the ceramic powder includes at least one of diatomaceous earth, quartz sand, montmorillonite, kerosene, and feldspar.

[0014] In conjunction with the first aspect, the sintering aid is glass powder and silicate, and the melting temperature of the sintering aid is 500℃~800℃.

[0015] In conjunction with the first aspect, the median particle size of the sintering aid is 2 μm to 10 μm.

[0016] In conjunction with the first aspect, the pore-forming agent includes at least one of resin balls, polystyrene, starch, carbon black, graphite powder, ammonium bicarbonate, and wood chips.

[0017] In conjunction with the first aspect, the median particle size of the pore-forming agent is 10 μm to 50 μm.

[0018] In conjunction with the first aspect, the dispersant includes at least one selected from ammonium polyacrylate, ammonium citrate, sodium hexametaphosphate, polyethylene, polyvinyl chloride, polystyrene, polyethylene glycol, and glycerol esters.

[0019] In conjunction with the first aspect, the initiator includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate, and diisopropyl peroxide.

[0020] In conjunction with the first aspect, the gel mixture comprises the following components by mass percentage: 75 wt% to 80 wt% solvent, 15 wt% to 25 wt% binder, and 0.5 wt% to 5 wt% crosslinking agent.

[0021] In conjunction with the first aspect, the solvent includes at least one of phthalates, diesters, gasoline with a boiling point of 50°C to 85°C, dodecanol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, dodecyl alcohol, and deionized water.

[0022] In conjunction with the first aspect, the adhesive includes at least one of trimethylolpropane triacrylate, ethylene glycol diacrylate, acrylamide, methacrylamide, and epoxy resin.

[0023] In conjunction with the first aspect, the crosslinking agent includes at least one of N,N-methylenebisacrylamide and 3,3'-diaminopropylamine.

[0024] In conjunction with the first aspect, the ceramic preparative, dispersant, and gel mix are mixed by ball milling.

[0025] In conjunction with the first aspect, the ceramic preparative, dispersant, and gel mixture are mixed by ball milling for a period of 2 to 12 hours.

[0026] In conjunction with the first aspect, the ceramic preparator, dispersant, and gel mix are mixed by ball milling, and the resulting material is further subjected to vacuum filtration.

[0027] In conjunction with the first aspect, the stirring and mixing rate is 10 rpm / min to 20 rpm / min.

[0028] In conjunction with the first aspect, the segmented heating process of the billet includes: heating the billet to 80℃~200℃ at a rate of 0.2℃ / min~1℃ / min and holding it at that temperature for 1h~3h; then heating it to 300℃~400℃ at a rate of 0.5℃ / min~5℃ / min and holding it at that temperature for 2h~6h.

[0029] In conjunction with the first aspect, the sintering temperature is 500℃~800℃.

[0030] In conjunction with the first aspect, the holding time for the sintering treatment is 30 min to 60 min.

[0031] In conjunction with the first aspect, the atmosphere for the sintering process is at least one of a mixture of air, N2, and H2.

[0032] Secondly, this application provides a porous ceramic, which is obtained according to the preparation method described in the first aspect. The porous ceramic includes an atomizing surface and an oil guiding surface arranged opposite to each other. The porous ceramic has pores, and the pore diameter increases sequentially from the atomizing surface to the oil guiding surface.

[0033] In conjunction with the second aspect, the porosity of the porous ceramic is 45% to 62%.

[0034] In conjunction with the second aspect, the average pore size of the pores near the atomizing surface is 8 μm to 18 μm.

[0035] In conjunction with the second aspect, the average pore size of the pores near the oil guiding surface is 22 μm to 44 μm.

[0036] Thirdly, this application provides an aerosol generating device, the aerosol generating device comprising the porous ceramic material prepared by the method described in the first aspect or the porous ceramic material described in the second aspect.

[0037] Compared with the prior art, this technical solution has at least the following technical advantages:

[0038] This application prepares a precursor by adding a dispersant, a gelling agent, and an initiator to a ceramic pre-material. By controlling the amount of dispersant added, larger particles in the ceramic pre-material sink to the bottom, while smaller particles remain suspended at the top. The gelation reaction time is controlled by adjusting the amount of initiator added, resulting in a longer gelation reaction time. This further ensures that larger ceramic particles are distributed at the bottom layer and smaller ceramic particles at the top layer, achieving a gradient distribution of ceramic particles—that is, the particle size gradually decreases from the bottom to the top. After molding, segmented heating, and sintering, the larger ceramic particles in the bottom layer form larger pores, while the smaller ceramic particles in the top layer form smaller pores, thus forming a porous ceramic with a gradient pore size distribution. The preparation method of this application uses gel casting technology to achieve the preparation of porous ceramics with a gradient pore size distribution, and the prepared porous ceramic material has high strength.

[0039] The porous ceramic of this application features a gradient distribution of pore size. Larger pores near the oil-guiding surface facilitate oil flow, while smaller pores near the atomizing heating surface help retain oil, effectively preventing oil leakage. This continuous gradient effectively balances oil flow and retention performance. It also effectively prevents oil leakage near the atomizing heating surface due to excessively large pores, while simultaneously preventing poor oil flow caused by excessively small pores near the oil reservoir. Both oil leakage and poor oil flow can easily lead to "wick clogging," and this invention effectively avoids this problem.

[0040] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a flowchart illustrating the preparation process of the porous ceramic material described in this application.

[0043] Figure 2 This is a schematic diagram of the structure of the porous ceramic material prepared in this application;

[0044] Figure 3 This is a schematic diagram of the aerosol generating device of this application;

[0045] Figure 4 This is a SEM image of the porous ceramic material from Example 1.

[0046] In the picture:

[0047] 1-Aerosol generating device;

[0048] 2-Mouthpiece;

[0049] 3-Atomizer;

[0050] 31 - Receiving cavity;

[0051] 32-Atomizer Core;

[0052] 4-Fluid channels;

[0053] 5-Power supply;

[0054] 100-Porous ceramics;

[0055] 101 - Oil guiding surface;

[0056] 102-Atomizing surface;

[0057] 103-Porosity. Detailed Implementation

[0058] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0059] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0060] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0061] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0062] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0063] In existing technologies, porous ceramics with uniform pore size distribution are insufficient to meet production requirements. Researchers have begun to explore methods for preparing porous ceramics with gradient pore size distributions. Current techniques involve stacking several ceramic green bodies with different pore structures using dry pressing or tape casting processes, followed by co-firing into a single ceramic block. However, this method is difficult to implement, expensive, and results in uneven pore gradients between layers. Furthermore, existing technologies employ hot-pressing casting, which requires large amounts of paraffin wax. This leads to long dewaxing times and significant energy loss during sintering. Additionally, excessive paraffin wax can cause significant shrinkage after sintering, potentially resulting in severe deformation or even cracking.

[0064] In order to overcome the shortcomings of existing technologies, there is an urgent need for a porous ceramic material with high strength and gradient pore size.

[0065] Specifically, such as Figure 1 The diagram shown is a flowchart of the preparation method of the porous ceramic material of this application, which includes the following steps:

[0066] Step 100: Mix the ceramic preparator, gel mixture, dispersant and initiator to obtain the precursor. The mass of the initiator is 0.1 wt% to 3 wt% of the total mass of the gel mixture, and the mass of the dispersant is 0.1 wt% to 2.0 wt% of the total mass of the ceramic preparator.

[0067] Step 200: The precursor obtained in step 100 is subjected to molding treatment to obtain a blank;

[0068] Step 300: The green body obtained in step 200 is subjected to segmented heating treatment to obtain porous ceramic material.

[0069] In the above-mentioned scheme, this application prepares a precursor by adding a dispersant, a gelling agent, and an initiator to the ceramic pre-material. By controlling the amount of dispersant added, larger particles in the ceramic pre-material sink to the bottom, while smaller particles remain suspended at the top. Furthermore, by controlling the amount of initiator added, the gelation reaction time is controlled, resulting in a longer gelation reaction time. This further ensures that larger ceramic particles are distributed at the bottom layer and smaller ceramic particles at the top layer, thus achieving a gradient distribution of ceramic particles—that is, the particle size gradually decreases from the bottom to the top layer. After molding, segmented heating, and sintering, the larger ceramic particles in the bottom layer form larger pores, while the smaller ceramic particles in the top layer form smaller pores, thereby forming a porous ceramic with a gradient pore size distribution. The preparation method of this application uses gel casting technology to achieve the preparation of porous ceramics with a gradient pore size distribution, and the prepared porous ceramic material has high strength.

[0070] The preparation method of this application will be further described below according to specific embodiments.

[0071] Step 100: Mix the ceramic preparator, gel mixture, dispersant and initiator to obtain a precursor. The mass of the initiator is 0.1 wt% to 3 wt% of the total mass of the gel mixture, and the mass of the dispersant is 0.1 wt% to 2.0 wt% of the total mass of the ceramic preparator.

[0072] Step 101: Mix the ceramic preparative, dispersant and gel mix to obtain gel casting slurry.

[0073] In the above steps, the ceramic preparatory material is composed of the following components by mass percentage: 55 wt% to 70 wt% ceramic powder, 10 wt% to 20 wt% sintering aid, and 5 wt% to 20 wt% pore-forming agent.

[0074] In some embodiments, the ceramic powder includes at least one of diatomaceous earth, quartz sand, montmorillonite, kerosene, and feldspar, and is used to provide a skeletal structure for porous ceramics.

[0075] In some embodiments, the ceramic powder includes ceramic powder with at least two particle size ranges. Exemplarily, the ceramic powder can be a mixture of two particle size ranges, or a mixture of three, four, or five different particle size ranges. This application selects a mixture of powders with multiple particle size ranges as raw materials, which is beneficial for forming a gradient distribution of porous ceramics. Preferably, the ceramic powder includes a mixture of three different particle size ranges, wherein the fine particles have a particle size D50 of 30μm~35μm, the medium-sized particles have a D50 of 60μm~65μm, and the coarse-sized particles have a D50 of 80μm~95μm. Of course, the particle size of each particle size distribution is not limited to the above values; only the median particle size D50 is as described above.

[0076] In some embodiments, the sintering aid is glass powder or silicate, and the melting temperature of the sintering aid is 500°C to 800°C. For example, the silicate may be sodium silicate.

[0077] In some embodiments, the proportion of the sintering aid in the ceramic preparatory material is 10 wt% to 20 wt%. Specifically, the proportion of the sintering aid in the ceramic preparatory material can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, and 20 wt%, etc. Of course, it can also be other values ​​within the above range. This application does not limit it here. The addition of the above-mentioned mass ratio of sintering aid is beneficial to the bonding of ceramic powder and the reduction of the sintering temperature of ceramic.

[0078] In some embodiments, the median particle size of the sintering aid is 2μm to 10μm. Specifically, the median particle size of the sintering aid can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm and 10μm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0079] In some embodiments, the proportion of the pore-forming agent in the ceramic preparatory material can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, and 20 wt%, etc., and of course, other values ​​within the above range are also possible. This application does not impose any limitations on this. The addition of the pore-forming agent at the above mass ratio can improve the porosity and increase the connectivity of pores in the ceramic material.

[0080] In some embodiments, the pore-forming agent includes at least one of resin balls-PMMA, polystyrene, starch, carbon black, graphite powder, ammonium bicarbonate, and wood chips.

[0081] In some embodiments, the median particle size of the pore-forming agent is 10 μm to 50 μm. Specifically, the median particle size of the pore-forming agent can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm and 50 μm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0082] In some embodiments, the dispersant includes at least one selected from ammonium polyacrylate, ammonium citrate, sodium hexametaphosphate, polyethylene, polyvinyl chloride, polystyrene, polyethylene glycol, and glycerol esters. Ammonium polyacrylate, ammonium citrate, and sodium hexametaphosphate have relatively small molecular weights and high ionic charge, while polyethylene, polyvinyl chloride, polystyrene, polyethylene glycol, and glycerol esters have high molecular weights. The above-mentioned dispersants are selected in this application to disperse inorganic powders in the gel mixture, separating the inorganic powder particles from each other through steric hindrance or electrostatic repulsion of the double layer, thus preventing particle agglomeration.

[0083] In some embodiments, the mass of the dispersant is 0.1 wt% to 2.0 wt% of the total mass of the ceramic preparator. The mass of the dispersant can be 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, and 2.0 wt% of the total mass of the ceramic preparator, or other values ​​within the above range. This application does not impose any limitations on these values. This application alters the suspension characteristics of the ceramic powder by adding a dispersant, and controls the degree of dispersion of the ceramic powder by controlling the amount of dispersant added. By limiting the amount of dispersant added, this application causes the ceramic powder to stratify along the gravity direction of the gel slurry. If the mass of the dispersant is less than 0.1 wt% of the total mass of the ceramic preparator, the ceramic particles are prone to agglomeration, which is detrimental to slurry dispersion and subsequent gel casting processes. If the mass of the dispersant is greater than 2.0 wt% of the total mass of the ceramic preparator, the slurry viscosity is too high, making the slurry too sticky and hindering mold filling.

[0084] In some embodiments, the gel mixture comprises the following components by weight percentage: 75 wt% to 80 wt% solvent, 15 wt% to 25 wt% binder, and 0.5 wt% to 5 wt% crosslinking agent.

[0085] In some embodiments, the solvent includes organic solvents or inorganic solvents, wherein the organic solvent includes at least one of phthalates, diesters, gasoline with a boiling point of 50°C to 85°C, dodecanol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, and dodecyl alcohol having low viscosity and saturated vapor pressure; and the inorganic solvent includes deionized water.

[0086] In some embodiments, the mass percentage of the solvent in the gel mixture can be 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, and 80 wt%, etc., and of course, it can be other values ​​within the above range, which are not limited herein.

[0087] In some embodiments, the adhesive includes at least one selected from trimethylolpropane triacrylate, ethylene glycol diacrylate, acrylamide, methacrylamide, and epoxy resin. When an organic solvent is used, the adhesive is selected from at least one selected from trifunctional trimethylolpropane triacrylate and bifunctional ethylene glycol diacrylate; when deionized water is used as the solvent, the adhesive is selected from at least one selected from acrylamide, methacrylamide, and epoxy resin.

[0088] In some embodiments, the mass percentage of the adhesive in the gel mixture can be 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, and 25 wt%, etc., and of course, it can be other values ​​within the above range, which are not limited herein.

[0089] In some embodiments, the crosslinking agent includes at least one of N,N-methylenebisacrylamide and 3,3'-diaminopropylamine.

[0090] In some embodiments, the mass percentage of the crosslinking agent in the gel mixture can be 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%, etc., and of course, it can be other values ​​within the above range, which are not limited herein.

[0091] Step 102: Ball mill the gel casting slurry and then vacuum filter the resulting material.

[0092] In some embodiments, the ball milling mixing apparatus includes a ball mill jar, such as a polytetrafluoroethylene ball mill jar.

[0093] In some embodiments, the ball milling time is 2h to 12h. The ball milling time can be, for example, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h and 12h, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0094] In some implementations, the resulting material is vacuum filtered to remove air bubbles.

[0095] Step 103: Under stirring conditions, an initiator is added to the material obtained in step 102 to obtain a precursor.

[0096] In some embodiments, the initiator includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate, and diisopropyl peroxide.

[0097] In some embodiments, the initiator mass is 0.1 wt% to 3 wt% of the total mass of the gel mixture. The initiator mass can be 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, or 3 wt% of the total mass of the gel mixture, or other values ​​within the above range; this application does not impose any limitations on these values. The aforementioned amount of initiator is used to control the gel reaction time. By adjusting the amount of initiator added, the free radical polymerization reaction time of the gel is prolonged, resulting in coarse particles being distributed in the lower layer and fine particles in the upper layer of the gel slurry, thereby achieving a gradient distribution of ceramic particles.

[0098] In some implementations, the initiator is added dropwise in small amounts multiple times.

[0099] In some embodiments, the initiator is added under stirring conditions at a stirring rate of 1 rpm / min to 20 rpm / min, specifically 1 rpm / min, 3 rpm / min, 5 rpm / min, 7 rpm / min, 10 rpm / min, 12 rpm / min, 15 rpm / min, 18 rpm / min, and 20 rpm / min, etc., or other values ​​within the above range, which are not limited herein. Controlling the stirring rate within the above range ensures that the initiator is uniformly distributed in the material.

[0100] This application involves adding a crosslinking agent, a binder, and an initiator to the system. The initiator provides free radicals to initiate the formation of long chains in the binder, and the crosslinking agent can network the long chains of the binder, enabling the binder to form a three-dimensional spatial network structure. Finally, it is combined with ceramic powder and solvent for in-situ curing and molding.

[0101] Step 200: The precursor obtained in step 100 is shaped to obtain a blank.

[0102] In some implementations, a precursor (wet blank) is transferred into a silicone mold of a pre-set size, and the silicone mold is dried to obtain a blank.

[0103] In some embodiments, the humidity of the drying process is 93% to 99%, specifically 93%, 94%, 95%, 96%, 97%, 98%, and 99%, etc., and of course, other values ​​within the above range are also possible, which are not limited herein.

[0104] In some embodiments, the drying temperature is 25°C to 60°C, specifically 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C and 60°C, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0105] In some embodiments, the drying time is 2 h to 48 h. The specific drying time can be 2 h, 4 h, 8 h, 10 h, 12 h, 16 h, 24 h, 36 h and 48 h, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0106] This application uses the above-mentioned drying process to dehydrate and solidify the precursor (wet blank) to generate a porous ceramic green blank.

[0107] Step 300: The green body obtained in step 200 is subjected to segmented heating treatment to obtain porous ceramic material.

[0108] Step 301: Perform pre-sintering treatment on the blank obtained in step 200.

[0109] The billet is heated to 80℃~200℃ at a rate of 0.2℃ / min~1℃ / min and held for 1h~3h.

[0110] Then raise the temperature to 300℃~400℃ at a rate of 0.5℃ / min~5℃ / min and hold for 2h~6h.

[0111] This application uses the above-mentioned pre-sintering treatment to degrease and remove pore-forming agents, so that the pore-forming agent and solvent decompose at the temperature of the pre-sintering treatment, leaving holes in the corresponding positions of the ceramic green body after decomposition, thus obtaining a degreased green body.

[0112] Step 302: Sinter the degreased blank obtained in step 301 to obtain porous ceramic.

[0113] In some embodiments, the gas atmosphere for the sintering process includes at least one of a mixture of air, N2, and H2.

[0114] In some embodiments, the sintering temperature is 500℃~800℃. The specific sintering temperature can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ and 800℃, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0115] In some embodiments, the sintering time is 30 min to 60 min. The specific sintering time can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min and 60 min, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0116] The preparation method of this application uses ceramic powders with at least two particle size ranges and gel mixtures as raw materials to prepare gradient porous ceramic materials through gel casting technology. Specifically, by limiting the ratio of ceramic powders to dispersants, ceramic powders with different particle size distributions are layered along the gravity direction of the gel slurry. Then, by adding gel mixtures and initiators, the initiators are used to control the free radical polymerization reaction time of the gel. By adjusting the amount of initiator added, the free radical polymerization reaction time of the gel is extended, so that coarse particles are distributed in the lower layer and fine particles are distributed in the upper layer in the gel slurry, thereby achieving a gradient distribution of ceramic particles. After molding treatment to form a green body, pre-sintering for degreasing and removal of pore-forming agents, and sintering treatment, porous ceramics with gradient pore size distribution are obtained, with the pore size gradually decreasing from the oil guiding surface to the atomizing heating surface.

[0117] This application also provides porous ceramics prepared by the above-described method, such as... Figure 2 The diagram shown is a structural schematic of the porous ceramic of this application. The porous ceramic 100 includes an atomizing surface 102 and an oil guiding surface 101 arranged opposite to each other. The porous ceramic 100 is provided with pores 103, and the pore size of the pores 103 increases sequentially from the atomizing surface 102 to the oil guiding surface 101.

[0118] In the above design, the large aperture near the wicking surface 101 facilitates wicking, while the small aperture near the atomizing surface 102 facilitates wicking retention, effectively preventing wicking leakage. The continuous gradient change effectively balances wicking and wicking performance. It also effectively prevents wicking leakage near the atomizing surface 102 due to excessively large apertures, while simultaneously preventing poor wicking due to excessively small apertures near the oil reservoir. Both wicking leakage and poor wicking can easily lead to "burnt coils," and this invention effectively avoids "burnt coils."

[0119] In some embodiments, the porosity of the porous ceramic is 45% to 62%, specifically 45%, 47%, 50%, 52%, 54%, 58%, 60%, and 62%, etc., and of course, other values ​​within the above range are also possible, which are not limited herein.

[0120] In some embodiments, the average pore size of the pores near the atomizing surface is 8μm to 18μm, specifically 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm and 18μm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0121] In some embodiments, the average pore size of the pores near the oil guiding surface is 22μm to 44μm, specifically 22μm, 25μm, 27μm, 30μm, 32μm, 35μm, 38μm, 40μm, 42μm and 44μm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0122] This application also provides an aerosol generating device 1, which may be, for example, an electronic cigarette.

[0123] like Figure 3 The diagram shown is a structural schematic of the aerosol generating device 1 of this application, including a mouthpiece 2, an atomizer 3, an airflow channel 4, and other necessary or existing components or structures. The atomizer 3 includes a receiving cavity 31 for accommodating a substrate capable of generating aerosols and an atomizing core 32 for heating the substrate capable of generating aerosols and generating aerosols. The airflow channel 4 is connected to the mouthpiece 2 and the outlet of the atomizer 3, respectively, for delivering aerosols to the user.

[0124] In some embodiments, the outer shell of the aerosol generating device 1 can be cylindrical or designed in other shapes. When the aerosol generating device 1 is cylindrical, the atomizer 3 can be designed as a tube, and its sidewall can overlap with the outer shell, or there can be a gap between the two. The receiving cavity 31 of the atomizer 3 can be an annular space surrounded by the inner side of the outer shell and the outer side of the airflow channel 4. The upper end of the airflow channel 4 is connected to the mouthpiece part 2, and the lower end can pass through the bottom of the receiving cavity 31 and enter the atomizing core of the atomizer 3. The porous ceramic material of this application is disposed inside the atomizing core.

[0125] In some embodiments, the aerosol generating device 1 uses a battery 5 as a power source, and the power source 5 is connected to the electrical contact of the atomizing core 32 via a connecting wire.

[0126] Those skilled in the art will understand that the methods for preparing porous ceramic materials described above are merely examples. Other methods commonly used in the art can be employed without departing from the disclosure of this application.

[0127] The embodiments of this application will be further described below with reference to several examples. However, the embodiments of this application are not limited to the specific embodiments described below. Appropriate modifications can be made within the scope of the main claims.

[0128] Example 1

[0129] (1) Weigh 62 wt% ceramic powder (including two particle size ranges: D50=30μm~35μm and D50=60μm~65μm), 20% glass powder (D50=6μm), and 18% pore-forming agent (PMMA, D50=20μm) according to the mass ratio, and add the above raw materials into a drum-type ball mill jar to obtain mixed powder.

[0130] (2) Add gel mix (solvent-water, binder-acrylamide, crosslinking agent-N,N-methylenebisacrylamide and dispersant-ammonium methacrylate) to the mixed powder and continue ball milling for 12 hours. The added mass of water, acrylamide, N,N-methylenebisacrylamide and ammonium methacrylate is 25 wt%, 5 wt%, 0.7 wt% and 0.1 wt% of the mass of the mixed powder, respectively. After ball milling, the obtained material is vacuum filtered to remove bubbles until no bubbles emerge from the slurry, and then the filtration is stopped.

[0131] (3) Add 0.2% by mass of initiator ammonium persulfate to the slurry in small amounts and multiple times, while stirring at a stirring rate of 15 rpm / min, until the ammonium persulfate is completely dissolved to obtain the precursor.

[0132] (4) Transfer the precursor to a silicone mold of a specific shape and size, and place the gel preform in the silicone mold together with the mold in a vacuum drying oven at a temperature of 25-60℃ and a humidity of 93-99% for 10 hours to allow the gel preform to solidify and form a gel preform with a certain strength. During the drying process, the gel preform is dehydrated, and the binder monomer and crosslinking agent undergo monomer polymerization reaction under the action of the initiator, which solidifies the ceramic powder, sintering aid particles and pore-forming agent particles in the three-dimensional network structure formed by the monomer, so that the ceramic green body has a certain strength.

[0133] (5) The gel preform is heated to 100℃ at a rate of 0.5℃ / min and held for 2h. Then it is heated to 300℃ at a rate of 3℃ / min and held for 4h. Finally, it is sintered at 700℃ and held for 45min to obtain porous ceramic.

[0134] The microstructure of the porous ceramic prepared in this embodiment is shown in the figure below. Figure 4 As shown, Figure 4 As shown, the pore size in the porous ceramic decreases from bottom to top, indicating that this application has successfully prepared a porous material with a gradient pore size distribution.

[0135] Example 2

[0136] Unlike Example 1, the amount of dispersant added in step (2) is 0.6 wt% of the mass of the mixed powder.

[0137] Example 3

[0138] Unlike Example 1, in step (2), the amount of dispersant added is 1 wt% of the mixed powder.

[0139] Example 4

[0140] Unlike Example 1, the amount of dispersant added in step (2) is 2 wt% of the ceramic powder.

[0141] Example 5

[0142] Unlike Example 1, the amount of initiator added in step (3) is 0.5 wt% of the gel mixture.

[0143] Example 6

[0144] Unlike Example 1, the amount of initiator added in step (3) is 1 wt% of the gel mixture.

[0145] Example 7

[0146] Unlike Example 1, the amount of initiator added in step (3) is 2 wt% of the gel mixture.

[0147] Example 8

[0148] Unlike Example 1, the amount of initiator added in step (3) is 3 wt% of the gel mixture.

[0149] Example 9

[0150] Unlike Example 1, the ceramic powder in step (1) includes three different particle size ranges: D50=30μm~35μm, D50=60μm~65μm and D50=80μm~95μm.

[0151] Comparative Example 1

[0152] Unlike Example 1, the amount of dispersant added in step (2) is 0.05 wt% of the ceramic powder.

[0153] Comparative Example 2

[0154] Unlike Example 1, the amount of dispersant added in step (2) is 2.4 wt% of the ceramic powder.

[0155] Comparative Example 3

[0156] Unlike Example 1, the amount of initiator added in step (3) is 0.05 wt% of the gel mixture.

[0157] Comparative Example 4

[0158] Unlike Example 1, the amount of initiator added in step (3) is 3.5 wt% of the gel mixture.

[0159] Comparative Example 5

[0160] Unlike Example 1, the amount of dispersant added in step (2) is 0.05 wt% of ceramic powder, and the amount of initiator added in step (3) is 0.07 wt% of gel mixture.

[0161] Performance testing

[0162] (1) Oil conduction rate test method: The e-liquid was used for internal standard test. The titration method was adopted to measure the time taken for a unit volume of e-liquid to pass through the ceramic. By volume, the e-liquid used for the test was composed of 50% propylene glycol and 50% glycerol. Three samples were tested for each example formulation, and the average value was used as the oil conduction rate of the example sample, in μL / s.

[0163] (2) Leakage rate test method: The sample was stored under low pressure under the following conditions: -30kPa for 6 hours; then the e-liquid was used for internal standard testing. By volume, the e-liquid used for testing consisted of 50% propylene glycol and 50% glycerol. A total of 8 samples were tested in each example. Leakage rate = (number of leaking samples / total number of test samples) 100%.

[0164] (4) The porosity test method refers to GB / T1966-1996 Test Method for Apparent Porosity and Bulk Density of Porous Ceramics, and the specific test method is Archimedes' drainage method.

[0165] (5) The aperture testing method is as follows: the aperture in the electron microscope image is analyzed using image recognition software. The performance test data of each embodiment and Comparative Example 1 are shown in Table 1.

[0166] Table 1. Performance tests of each embodiment and comparative example

[0167]

[0168] As shown in Table 1, this application prepares a precursor by adding a dispersant, a gelling agent, and an initiator to the ceramic preparatory material. By controlling the amount of dispersant added, larger particles in the ceramic preparatory material sink to the bottom, while smaller particles remain suspended at the top. By controlling the amount of initiator added, the gelation reaction time is controlled, resulting in a longer gelation reaction time. This further leads to larger ceramic particles being distributed at the bottom layer and smaller ceramic particles at the top layer, thus achieving a gradient distribution of ceramic particles. That is, the particle size of the ceramic particles gradually decreases from the bottom layer to the top layer. After molding, segmented heating, and sintering, the larger ceramic particles in the bottom layer form larger pores, while the smaller ceramic particles in the top layer form smaller pores, thereby forming a porous ceramic with a gradient distribution of pore size.

[0169] When the amount of dispersant or initiator added in Comparative Examples 1 to 5 is not within the range specified in this application, the porous ceramics prepared by them have partial oil leakage problems, resulting in a decrease in oil conduction rate.

Claims

1. A method for preparing porous ceramics, characterized in that, Includes the following steps: First, ceramic preparative, dispersant, and gel mix are mixed, and then an initiator is added and stirred to obtain a precursor. This causes larger particles in the ceramic preparative to sink to the bottom, while smaller particles are suspended at the top. The mass of the initiator is 0.1 wt% to 3 wt% of the total mass of the gel mix, and the mass of the dispersant is 0.1 wt% to 2.0 wt% of the total mass of the ceramic preparative. The ceramic preparative includes ceramic powders with at least two particle size ranges. The precursor is shaped to obtain a blank; The green body is subjected to segmented heating and sintering treatment to obtain porous ceramics; The porous ceramic includes an atomizing surface and an oil guiding surface arranged opposite each other. The porous ceramic has pores, and the pore diameter increases sequentially from the atomizing surface to the oil guiding surface. The porosity of the porous ceramic is 45% to 62%. The average pore diameter of the pores near the atomizing surface is 8 μm to 18 μm, and the average pore diameter of the pores near the oil guiding surface is 22 μm to 44 μm.

2. The preparation method according to claim 1, characterized in that, The ceramic preparatory material includes ceramic powders in at least three particle size ranges.

3. The preparation method according to claim 2, characterized in that, The ceramic preparatory material includes ceramic powders with median particle sizes of 30μm~35μm, 60μm~65μm, and 80μm~95μm.

4. The preparation method according to claim 1, characterized in that, The ceramic pre-material accounts for 45 wt% to 55 wt% of the mass of the precursor.

5. The preparation method according to claim 1 or 4, characterized in that, The method includes at least one of the following features (1) to (13): (1) The ceramic preparatory material comprises the following components by mass percentage: 55 wt% to 70 wt% ceramic powder, 10 wt% to 20 wt% sintering aid and 5 wt% to 20 wt% pore-forming agent, wherein the ceramic powder comprises at least one of diatomaceous earth, quartz sand, montmorillonite, kerosene and feldspar; (2) The ceramic preparatory material comprises the following components by mass percentage: 55 wt%~70 wt% ceramic powder, 10 wt%~20 wt% sintering aid and 5 wt%~20 wt% pore-forming agent, wherein the sintering aid includes glass powder or silicate, and the melting temperature of the sintering aid is 500℃~800℃; (3) The ceramic preparatory material comprises the following components by mass percentage: 55 wt%~70 wt% ceramic powder, 10 wt%~20 wt% sintering aid and 5 wt%~20 wt% pore-forming agent, wherein the median particle size of the sintering aid is 2 μm~10 μm; (4) The ceramic preparatory material comprises the following components by mass percentage: 55 wt% to 70 wt% ceramic powder, 10 wt% to 20 wt% sintering aid and 5 wt% to 20 wt% pore-forming agent, wherein the pore-forming agent comprises at least one of resin balls, polystyrene, starch, carbon black, graphite powder, ammonium bicarbonate and sawdust; (5) The ceramic preparatory material comprises the following components by mass percentage: 55 wt%~70 wt% ceramic powder, 10 wt%~20 wt% sintering aid and 5 wt%~20 wt% pore-forming agent, wherein the median particle size of the pore-forming agent is 10 μm~50 μm; (6) The dispersant includes at least one of ammonium polyacrylate, ammonium citrate, sodium hexametaphosphate, polyethylene, polyvinyl chloride, polystyrene, polyethylene glycol and glycerol ester; (7) The initiator includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate and diisopropyl peroxide; (8) The gel mixture comprises the following components by mass percentage: 75 wt% to 80 wt% solvent, 15 wt% to 25 wt% binder and 0.5 wt% to 5 wt% crosslinking agent, wherein the solvent includes at least one of phthalate, diester, gasoline with a boiling point of 50°C to 85°C, dodecanol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, dodecyl alcohol and deionized water; (9) The gel mixture comprises the following components by mass percentage: 75 wt% to 80 wt% solvent, 15 wt% to 25 wt% adhesive and 0.5 wt% to 5 wt% crosslinking agent, wherein the adhesive comprises at least one of trimethylolpropane triacrylate, ethylene glycol diacrylate, acrylamide, methacrylamide and epoxy resin; (10) The gel mixture comprises the following components by mass percentage: 75 wt% to 80 wt% solvent, 15 wt% to 25 wt% binder and 0.5 wt% to 5 wt% crosslinking agent, wherein the crosslinking agent comprises N,N-methylenebisacrylamide; (11) The ceramic preparative, dispersant and gel mixture are mixed by ball milling for 2h to 12h; (12) The ceramic preparative, dispersant and gel mixture are mixed by ball milling, and the mixture is further subjected to vacuum filtration after mixing; (13) The stirring and mixing rate is 10 rpm / min to 20 rpm / min.

6. The preparation method according to claim 1, characterized in that, The method includes at least one of the following features (1) to (4): (1) The segmented heating process of the billet includes: heating the billet to 80℃~200℃ at a rate of 0.2℃ / min~1℃ / min and holding it for 1h~3h; then heating it to 300℃~400℃ at a rate of 0.5℃ / min~5℃ / min and holding it for 2h~6h; (2) The sintering temperature is 500℃~800℃; (3) The holding time for the sintering treatment is 30 min to 60 min; (4) The atmosphere of the sintering process is at least one of the mixed gas of air, N2 and H2.

7. A porous ceramic, characterized in that, The porous ceramic is prepared by the method according to any one of claims 1 to 6, wherein the porous ceramic includes an atomizing surface and an oil guiding surface arranged opposite to each other, the porous ceramic has pores, and the pore diameter of the pores increases sequentially from the atomizing surface to the oil guiding surface.

8. The porous ceramic according to claim 7, characterized in that, The porous ceramic includes at least one of the following features (1) to (3): (1) The porosity of the porous ceramic is 45%~62%; (2) The average pore size of the pores near the atomizing surface is 8 μm ~ 18 μm; (3) The average pore size of the pores near the oil guiding surface is 22μm ~ 44μm.

9. An aerosol generating device, characterized in that, The aerosol generating device comprises porous ceramic prepared by the method according to any one of claims 1 to 6 or porous ceramic according to any one of claims 7 to 8.

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