Porous carbon heating element and preparation method thereof, electric heating atomization core and electronic cigarette

Abstract

The present application relates to a porous carbon heating element and a preparation method thereof, an electric heating atomization core and an electronic cigarette, and belongs to the technical field of electronic cigarettes. The porous carbon heating element has a plurality of through holes inside, and a plurality of blind holes are arranged on the hole wall of each through hole, and the aperture of the through hole is larger than the aperture of the blind hole. The aperture of the through hole is not larger than the micron level, and the aperture of the blind hole is nanometer level. By matching the through hole with an aperture not larger than the micron level with the blind hole with an aperture of nanometer level, the heating element can still have a certain liquid locking ability, which can prevent oil leakage and prevent dry burning due to insufficient infiltration of the smoke oil. At the same time, the material of the heating element is porous carbon, and the overall homogeneous heating of the heating element improves the temperature uniformity, avoids local overheating and material cracking caused by thermal shock; and the carbon material has a high infrared emissivity (>90%), high penetration of radiated heat, and high electrothermal conversion efficiency (>90%), which is more energy-saving and efficient, and is conducive to the miniaturization of the equipment.

Description

Technical Field

[0001] The present application relates to the technical field of electronic cigarettes, and in particular to a porous carbon heating element and a preparation method thereof, an electrically heated atomizing core and an electronic cigarette. Background Art

[0002] With the universalization of the global trend of tobacco control, new tobacco products have gradually become an important development direction of the tobacco industry due to their advantage of reducing harmful ingredients. Among them, e-cigarettes have become one of the hot spots of new tobacco products in the world.

[0003] The core component of electronic cigarettes is the atomizer core. After more than ten years of development, the atomizer core has undergone three generations of technological evolution. The first generation of technology is a glass fiber rope wrapped with a heating wire. It has been eliminated due to the problems of easy floccules, easy powder loss, and uneven heating. The second generation of technology is a resistance wire cotton core, which has the advantages of large oil storage capacity, good oil conductivity, and dense smoke, but it also has obvious disadvantages, such as the cotton core is not resistant to high temperature and easy to dry burn, the resistance wire heats the smoke oil unevenly, and it is easy to produce a burnt smell, the cotton core structure is loose, the liquid locking ability is poor, it is easy to leak oil, and the atomized molecular particles are large. The third generation of technology is a ceramic atomizer core, which has the advantages of small atomized particles, delicate taste, good consistency, and not easy to leak oil and burn.

[0004] At present, ceramic atomizer cores have shown a trend of gradually replacing resistor wire cotton cores, but ceramic atomizer cores still have defects. Their preparation method is usually to embed alloy heating wires, heating sheets, and metal meshes inside or on the surface of porous ceramics, or to print heating circuits on the surface of porous ceramics. The alloy wires or metal printed circuits usually account for a very small volume. The ceramic material as the main part of the atomizer core does not generate heat itself, but relies on the heat conduction of the resistor to heat the e-liquid. Therefore, there is obvious temperature unevenness. When the suction volume is large and the e-liquid is insufficiently infiltrated, the metal wire will be locally overheated to produce a burnt smell, while the temperature of the ceramic matrix will be low and the atomization effect will be insufficient. Moreover, due to the inconsistent thermal expansion coefficients of metal and ceramic, cracks will occur under long-term thermal shock. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the embodiments of the present application includes providing a porous carbon heating element, an electrically heated atomizer core and an electronic cigarette, using carbon material as the heating element of the electrically heated atomizer core in the electronic cigarette, and having a good heating effect.

[0006] In the first aspect, the embodiment of the present application provides a porous carbon heating element, wherein the porous carbon heating element has a plurality of through holes inside, and a plurality of blind holes are arranged on the hole wall of each through hole, and the aperture of the through hole is larger than the aperture of the blind hole. The aperture of the through hole is not larger than the micron level, and the aperture of the blind hole is nanometer level.

[0007] In the present application, the arrangement of multiple through holes with apertures no larger than micrometers can make the oil absorption effect of the heating element better, and the through holes cooperate with the blind holes with apertures of nanometers, so that the heating element has a certain liquid locking ability, which can prevent oil leakage and prevent dry burning due to insufficient oil infiltration. At the same time, the material of the heating element is porous carbon, and the overall homogeneous heating of the heating element improves the temperature uniformity, avoids local overheating and material cracking caused by thermal shock; and the carbon material has a high infrared emissivity (>90%), high penetration of radiated heat, and high electrothermal conversion efficiency (>90%), which is more energy-saving and efficient, and is conducive to the miniaturization of the equipment.

[0008] In some embodiments of the present application, the pore size of the through hole is 200-1000nm, the pore size of the blind hole is 10-100nm, the pore depth of the blind hole is 10-100nm, and the porosity of the porous carbon heating element is 60%-90%. The porous carbon heating element can have a stronger oil absorption capacity and better liquid locking ability. The porous carbon heating element has a high porosity, a large specific surface area, a large oil absorption capacity, and small atomized particles, ensuring a delicate taste while ensuring a dense smoke volume.

[0009] In some embodiments of the present application, the through hole includes a zigzag through hole, and a plurality of zigzag through holes are connected. The zigzag through hole cooperates with the blind hole to form a zigzag porous structure and a multi-level pore structure with alternating large and small pores, which enhances the capillary force of the material to absorb oil, improves the oil absorption speed and liquid locking ability.

[0010] In a second aspect, an embodiment of the present application provides a method for preparing a porous carbon heating element, comprising: forming a porous carbon substrate having a plurality of through holes inside, and forming a plurality of blind holes on the hole walls of the through holes.

[0011] Multiple through holes and blind holes can be formed, so that the heating element has better oil absorption and liquid locking capabilities, preventing oil leakage and preventing dry burning due to insufficient oil infiltration. At the same time, the material of the heating element is porous carbon, and the overall homogeneous heating of the heating element improves temperature uniformity and avoids local overheating and material cracking caused by thermal shock; and the carbon material has a high infrared emissivity (>90%), high penetration of radiated heat, and high electrothermal conversion efficiency (>90%), which is more energy-saving and efficient, and is conducive to the miniaturization of equipment.

[0012] In some embodiments of the present application, the method for forming a porous carbon matrix having multiple through holes inside is selected from: any one of: carbon fiber needle punching molding method, polymer pore-forming carbonization molding method, carbon fiber and polymer mixed pore-forming carbonization molding method and porous template vapor deposition molding method.

[0013] In some embodiments of the present application, the method for forming a plurality of blind holes on the hole wall of the through hole may be a chemical vapor deposition method or a gas activation method. The chemical vapor deposition method is a method of preparing blind holes by adding materials, and the gas activation method is a method of preparing blind holes by subtracting materials, both of which can prepare nanoscale blind holes to achieve a good oil locking effect and avoid the occurrence of oil leakage to a certain extent.

[0014] In some embodiments of the present application, the carbon fiber needle punching method includes: immersing the carbon fiber in a polymer solution, filtering and placing it in a needle punching device for needle punching, or first needle punching the carbon fiber and then immersing it in a polymer solution, draining and then heating it; wherein the conditions for the heating treatment are: inert gas protection, the temperature is 500-1500°C; wherein the polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin, and asphalt.

[0015] In some embodiments of the present application, the polymer pore-forming carbonization molding method includes: drying and solidifying a solution containing a polymer and a pore-forming agent and then performing a heat treatment; wherein the conditions for the heat treatment are: inert gas protection, a temperature of 500-1500°C, and a mass ratio of the polymer to the pore-forming agent of (95:5)-(60:40); wherein the polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin, and asphalt; and the pore-forming agent is one or more of ammonium bicarbonate, ammonium nitrate, starch, glucose, polyvinyl pyrrolidone, and polyvinyl butyral.

[0016] In some embodiments of the present application, the carbon fiber and polymer mixed pore-forming carbonization molding method includes: dispersing the carbon fiber, polymer and pore-forming agent in the same solution, and performing heat treatment after molding; wherein the conditions for the heat treatment are: inert gas protection, the temperature is 500-1500°C, and the mass ratios of the carbon fiber, polymer and pore-forming agent are (80-40):(80-40):(20-5) respectively; wherein the polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin, and asphalt; the pore-forming agent is one or more of ammonium bicarbonate, ammonium nitrate, starch, glucose, polyvinyl pyrrolidone, and polyvinyl butyral.

[0017] In some embodiments of the present application, the porous template vapor deposition molding method includes: using porous metal as a template and hydrocarbon gas as a carbon source to perform vapor deposition, and then removing the porous metal template by acid washing; wherein the vapor deposition temperature is 800-1500°C and the time is 1-8h.

[0018] In some embodiments of the present application, the chemical vapor deposition method includes: placing a porous carbon matrix in a heating furnace, introducing an inert gas as a protective gas, raising the temperature to 1000-1500°C, introducing hydrogen and methane, and treating for 1-8 hours to grow graphene nanosheets on the pore walls of the porous carbon matrix, and the graphene nanosheets are overlapped to form blind holes.

[0019] Graphene nanosheets are uniformly grown on the pore wall surface of the porous carbon matrix by the chemical vapor deposition method, and the graphene nanosheets overlap each other to form a blind hole structure for oil locking.

[0020] In some embodiments of the present application, the gas activation method includes: placing the porous carbon matrix in a heating furnace, introducing an inert gas as a protective gas, raising the temperature to 1000-1500°C, introducing water vapor and / or carbon dioxide, and treating for 1-3 hours to form blind holes on the pore walls of the porous carbon matrix.

[0021] The gas activation method can be used to convert part of the carbon on the pore wall surface of the porous carbon matrix into gas by reacting with water vapor or carbon dioxide, thereby forming blind holes on the surface of the porous carbon matrix.

[0022] In a third aspect, an embodiment of the present application provides an electrically heated atomizing core, comprising two electrodes and the above-mentioned porous carbon heating element, wherein the two electrodes are respectively fixed at two ends of the porous carbon heating element.

[0023] The above-mentioned porous carbon heating element is used in the electric heating atomizer core. Through the through holes and blind holes with different apertures, the oil absorption effect of the heating element can be better. The through holes are matched with the blind holes with nanometer apertures, so that the heating element has a certain liquid locking ability, which can prevent oil leakage and prevent dry burning due to insufficient infiltration of smoke oil. At the same time, the porous carbon homogeneous heating atomizer core is an overall homogeneous heating. The entire atomizer core can be used as an oil absorption part and an atomization part. The temperature is highly uniform and there is no local overheating. The material can achieve synchronous heating and atomization while absorbing oil. The atomization speed is fast, the smoke volume is large, and the suction is controllable. At the same time, the porous carbon homogeneous heating atomizer core has good stability and good heat shock resistance, and is not prone to failure behaviors such as cracking.

[0024] In some embodiments of the present application, the electrode and the porous carbon heating element are fixed by welding, riveting, conductive paste layer, elastic clamping or pressure clamping, which can make the fixing effect between the electrode and the porous carbon heating element better.

[0025] In some embodiments of the present application, the electrode is one of a graphite electrode, a nickel electrode, a copper electrode, an iron electrode, an aluminum electrode, a silver electrode and a gold electrode.

[0026] In some embodiments of the present application, the electrode is a porous metal electrode. The electrode will not block the porous carbon heating element from absorbing oil at the electrode connection, and the atomized smoke particles can escape from the electrode connection, which not only increases the liquid absorption and liquid conduction part of the porous carbon heating element but also increases the atomization surface, thereby improving the overall material utilization.

[0027] In some embodiments of the present application, the electrode is one of porous nickel, porous copper, porous iron, porous aluminum, and porous silver.

[0028] In some embodiments of the present application, the porous carbon heating element is in the shape of a cuboid, a polygonal column, or a prism.

[0029] In some embodiments of the present application, at least one surface of the porous carbon heating element is a liquid absorbing and guiding portion. By penetrating the surface of the porous carbon heating element, the liquid absorbing effect of the electrically heated atomizing core can be improved.

[0030] In some embodiments of the present application, the porous carbon heating element includes a heating atomization part and a liquid suction and liquid guiding part connected to each other, and the electrode is fixed at the connection between the heating atomization part and the liquid suction and liquid guiding part. Both the liquid suction part and the atomization part are made of porous carbon materials, which can make the oil suction and oil guiding effect of the atomization core better and can be atomized well.

[0031] In some embodiments of the present application, the outer dimensions of the porous carbon heating element are 3-15 mm in length, 1-5 mm in width, and 0.5-2 mm in height; the distance between the two electrodes is 3-15 mm, which can make the atomizer core heat evenly and avoid excessive or insufficient resistance.

[0032] In some embodiments of the present application, the electrically heated atomizer core further includes two current-carrying conductors, one current-carrying conductor being connected to one electrode, so that the atomizer core can be conveniently connected to an external power source.

[0033] In a fourth aspect, an embodiment of the present application provides an electronic cigarette, comprising the above-mentioned electrically heated atomizing core. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 A schematic diagram of the structure of the electrically heated atomizer core provided in an embodiment of the present application;

[0036] Figure 2 A partial cross-sectional view of the electrically heated atomizer core provided in an embodiment of the present application;

[0037] Figure 3 This is a 10K-fold scanning electron microscope photo of the porous carbon heating element provided in Example 1 of the present application;

[0038] Figure 4 This is a 40K-magnification scanning electron microscope photograph of the porous carbon heating element provided in Example 1 of the present application.

[0039] Icon: 110 - electrode; 120 - current-carrying conductor; 130 - porous carbon heating element; 131 - liquid aspiration and guiding part; 132 - heating atomization part. DETAILED DESCRIPTION

[0040] In the prior art, the ceramic in the ceramic atomizer core does not generate heat itself, but the metal resistor in the ceramic atomizer core generates heat to heat the e-liquid, so there is obvious temperature non-uniformity. When the amount of suction is large and the e-liquid is not sufficiently soaked, the metal wire will be partially overheated to produce a burnt smell, while the temperature of the ceramic matrix is ​​low and the atomization effect is insufficient. In addition, due to the inconsistency of the thermal expansion coefficients of metal and ceramic, cracks will occur under long-term thermal shock.

[0041] The embodiment of the present application provides a new electrically heated atomizer core, which uses a new heating element and can improve some problems of the ceramic atomizer core. In order to make the purpose, technical solution and advantages of the embodiment of the present application clearer, the technical solution of the present application is described clearly and completely below.

[0042] Figure 1 A schematic diagram of the structure of the electrically heated atomizer core provided in an embodiment of the present application; Figure 2 This is a partial cross-sectional view of the electrically heated atomizer core provided in the embodiment of the present application. Figure 1 and Figure 2 The electric heating atomization core includes two electrodes 110 and a porous carbon heating element 130. The two electrodes 110 are respectively fixed at both ends of the porous carbon heating element 130. The porous carbon heating element 130 has a plurality of through holes inside, and a plurality of blind holes are arranged on the hole wall of each through hole. The aperture of the through hole is larger than that of the blind hole. The aperture of the through hole is not larger than the micron level, and the aperture of the blind hole is nanometer level.

[0043] The arrangement of multiple through holes with apertures no larger than micrometers can make the heating element absorb oil better, and the through holes cooperate with the blind holes with apertures of nanometers, so that the heating element has a certain ability to lock liquid, which can prevent oil leakage and prevent dry burning due to insufficient oil infiltration. At the same time, the material of the heating element is porous carbon, and the heating element generates heat uniformly as a whole, which improves the temperature uniformity and avoids local overheating and material cracking caused by thermal shock; and the carbon material has a high infrared emissivity (>90%), high penetration of radiated heat, and high electrothermal conversion efficiency (>90%), which is more energy-saving and efficient, and is conducive to the miniaturization of the equipment.

[0044] In order to make the porous carbon heating element 130 have better oil absorption and oil conduction effects, and to better lock oil and avoid oil leakage, the aperture of the through hole is 200-1000nm, the aperture of the blind hole is 10-100nm, and the depth of the blind hole is 10-100nm.

[0045] It should be noted that: there are multiple through holes, and the apertures of the multiple through holes do not need to be limited to be the same. The apertures of the through holes can be the same or different, and the aperture of the blind hole does not need to be larger than the micron level; and the apertures at different positions of the same through hole may also be different, which is not limited in this application.

[0046] There are multiple blind holes, and the apertures of the multiple blind holes do not need to be limited to be the same. The apertures of the blind holes can be the same or different, as long as the apertures of the blind holes reach the nanometer level; the depths of the multiple blind holes do not need to be limited to be the same. The depths of the blind holes can be the same or different, as long as the depths of the blind holes reach the nanometer level.

[0047] Optionally, the through hole includes a zigzag through hole, and a plurality of zigzag through holes are connected. The zigzag through hole cooperates with the blind hole to form a zigzag porous structure and a multi-level pore structure with alternating large and small pores, which enhances the capillary force of the material to absorb oil, improves the oil absorption speed and liquid locking ability.

[0048] Among them, all through holes may be zigzag through holes, or some of the through holes may be zigzag through holes; all through holes may be interconnected, or some of the through holes may be interconnected, and this application does not limit this.

[0049] Optionally, the porosity of the porous carbon heating element 130 is 60%-90%. The porous carbon heating element 130 has high porosity, large specific surface area, large oil absorption, and small atomized particles, ensuring a delicate taste while ensuring dense smoke.

[0050] In the present application, the porous carbon heating element 130 is one of a rectangular parallelepiped, a polygonal prism, and a prism. The heating element can also be in other shapes. After the porous carbon heating element 130 is matched with the two electrodes 110, the obtained electric heating atomization core can also be one of a rectangular parallelepiped, a polygonal prism, and a prism.

[0051] Optionally, the outer dimensions of the porous carbon heating element are 3-15 mm in length, 1-5 mm in width, and 0.5-2 mm in height; the distance between the two electrodes is 3-15 mm. This allows the atomizer core to heat evenly and avoids resistance that is too large or too small. It should be noted that although the length, width, and height are recorded here, it does not limit the porous carbon heating element to a rectangular structure, but is only a rough description of its outer dimensions.

[0052] Please continue reading Figure 1 and Figure 2The electrode 110 is a block structure, and the two electrodes 110 are respectively arranged at the two ends of the porous carbon heating element 130, and are in basic surface contact with the porous carbon heating element 130. The electrode 110 is a porous metal electrode 110. The electrode 110 will not block the porous carbon heating element 130 from absorbing oil at the connection of the electrode 110, and the atomized smoke particles can escape from the connection of the electrode 110, which increases both the oil absorption surface of the porous carbon heating element 130 and the atomization surface, thereby improving the overall material utilization.

[0053] In the present application, the electrode can be one of a graphite electrode, a nickel electrode, a copper electrode, an iron electrode, an aluminum electrode, a silver electrode and a gold electrode. Optionally, the electrode is a porous metal electrode 110, and the porous metal electrode is one of porous nickel, porous copper, porous iron, porous aluminum and porous silver.

[0054] In the present application, in order to achieve a better fixing effect between the electrode 110 and the porous carbon heating element 130, the electrode 110 and the porous carbon heating element 130 are fixed by a conductive paste layer. In other embodiments, the two ends of the porous carbon heating element 130 can also be fixed by welding, riveting, elastic clamping or pressure clamping.

[0055] In the present application, a power conductor 120 (e.g., a power wire) may be connected to the electrode 110 to be powered by an external power source. Optionally, the power conductor 120 is one of metals silver, copper, iron, aluminum, nickel, and zinc. The power conductor 120 is fixed to the electrode 110 by welding. In other embodiments, the electrode 110 and the power conductor 120 may be connected by riveting or pressure connection.

[0056] The porous carbon heating element 130 provided in the present application includes a liquid absorption and liquid guiding part 131 and a heating and atomization part 132 which are interconnected. The electrode 110 is fixed at the connection between the liquid absorption and liquid guiding part 131 and the heating and atomization part 132, so as to realize overall homogeneous heating. The entire atomization core can be used as an oil absorption part and an atomization part. The temperature is highly uniform, and there is no local overheating phenomenon. The material can realize synchronous heating and atomization while absorbing oil. The atomization speed is fast, the amount of smoke is large, and the suction is controllable. At the same time, the porous carbon homogeneous heating atomization core has good stability, good heat shock resistance, and is not prone to failure behaviors such as cracking.

[0057] Optionally, at least one surface of the porous carbon heating element 130 is an oil absorbing surface, and the liquid absorbing effect of the electric heating atomization core can be improved by penetrating the surface of the porous carbon heating element.

[0058] In other embodiments, the heating atomization part 132 may be a porous carbon heating element, the liquid suction and liquid guiding part 131 may be a porous ceramic material, and the porous ceramic and the porous carbon may be connected by bonding or inlaying.

[0059] The above-mentioned electric heating atomizer core is used to prepare electronic cigarettes. The heating method of the electric heating atomizer core is carbon material infrared radiation heating. The infrared radiation has high penetrability, high efficiency and uniformity in heating the e-liquid, more energy-saving and efficient, and is conducive to the miniaturization of the atomization equipment.

[0060] After introducing the electric heating atomizer core, the preparation method of the electric heating atomizer core is introduced below. The preparation method includes:

[0061] S110, preparing porous carbon heating element 130

[0062] S111, forming a porous carbon matrix having a plurality of through holes therein, wherein the forming method may be any one of a carbon fiber needle punching forming method, a polymer pore forming carbonization forming method, a carbon fiber and polymer mixed pore forming carbonization forming method, and a porous template vapor deposition forming method.

[0063] Optionally, the carbon fiber needle punching method includes: immersing the carbon fiber in a polymer solution, filtering and placing it in a needle punching device for needle punching, or first needle punching the carbon fiber and then immersing it in a polymer solution, draining and then heating it; wherein the conditions for the heating treatment are: inert gas protection, and a temperature of 500-1500°C.

[0064] The carbon fiber is one or both of chopped carbon fiber and continuous carbon fiber. The polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin and asphalt.

[0065] For example: the carbon fiber is immersed in a polyvinyl alcohol aqueous solution and stirred to be evenly dispersed, filtered and placed in a needle-punching device for needle-punching to obtain a carbon fiber block solid (or the carbon fiber is placed in a needle-punching device for needle-punching, then immersed in a polyvinyl alcohol aqueous solution, and drained to obtain a carbon fiber block solid), placed in an oven to dry, after removing the solvent, the obtained solid is placed in a heating furnace, nitrogen is introduced as a protective gas, the temperature is raised to 1200-1400°C for heat treatment, and the insulation time is 60-120 minutes to obtain a porous carbon matrix with a tortuous through-pore structure.

[0066] Optionally, the polymer pore-forming carbonization molding method includes: drying and curing a solution containing a polymer and a pore-forming agent and then performing a heat treatment; wherein the conditions for the heat treatment are: inert gas protection, a temperature of 500-1500°C, and a mass ratio of polymer to pore-forming agent of (95:5)-(60:40).

[0067] Among them, the polymer in the polymer pore-forming carbonization molding method is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin, and asphalt; the pore-forming agent is one or more of ammonium bicarbonate, ammonium nitrate, starch, glucose, polyvinyl pyrrolidone, and polyvinyl butyral.

[0068] For example: dissolve the polymer in a solvent, add a pore-forming agent and mix them, and after uniform mixing, obtain a mixed solution (disperse the polymer and the pore-forming agent in the same solution at the same time to obtain a mixed solution), place the mixed solution in a mold, and then put it into an oven, treat it at a temperature of 300-400°C, and keep it for more than 30 minutes (for example: 60-120 minutes). During the insulation process, the solvent in the mold evaporates, the pore-forming agent decomposes, and a polymer solid with a porous structure is formed. The polymer solid is placed in a heating furnace, nitrogen is introduced as a protective gas, and the temperature is raised to 1200-1400°C for carbonization, and the insulation time is 60-120 minutes to obtain a porous carbon matrix.

[0069] Optionally, the carbon fiber and polymer mixed pore-forming carbonization molding method includes: dispersing the carbon fiber, polymer and pore-forming agent in the same solution, and performing heat treatment after molding; wherein the heating treatment conditions are: inert gas protection, temperature of 500-1500°C, and the mass ratio of carbon fiber, polymer and pore-forming agent is (80-40):(80-40):(20-5) respectively.

[0070] The carbon fiber in the carbon fiber and polymer mixed pore-forming carbonization molding method is one or two of chopped carbon fiber and continuous carbon fiber. The polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin, and asphalt; the pore-forming agent is one or more of ammonium bicarbonate, ammonium nitrate, starch, glucose, polyvinyl pyrrolidone, and polyvinyl butyral.

[0071] For example, carbon fibers are dispersed in a solvent, polymer powder is added, and the mixture is stirred and dissolved at 80-100°C to obtain a mixed solution A. A pore-forming agent is dissolved in the solvent, and the mixture is stirred and dissolved at room temperature to obtain a solution B. Liquids A and B are mixed and stirred evenly, and then poured into a rectangular mold and placed in an oven to dry. After removing the solvent, the obtained solid is placed in a heating furnace, nitrogen is introduced as a protective gas, and the temperature is raised to 1200-1400°C for heat treatment. The heat preservation time is 60-120 minutes to obtain a porous carbon matrix with a tortuous through-hole structure.

[0072] Optionally, the porous template vapor deposition molding method includes: using porous metal as a template and hydrocarbon gas as a carbon source to perform vapor deposition, and then removing the porous metal template by pickling; wherein the vapor deposition temperature is 800-1500°C and the time is 1-8 hours. The porous metal is porous nickel or porous copper, and the hydrocarbon gas is methane or acetylene.

[0073] For example: using nickel foam as a template, placing the nickel foam in a chemical vapor deposition furnace, heating to 1000-1200°C, introducing acetylene for carbon deposition, cooling after 60-120 minutes, and immersing the obtained solid in hydrochloric acid after cooling to room temperature, removing the nickel foam template, and obtaining a porous carbon matrix with a tortuous through-pore structure.

[0074] S112, forming a plurality of blind holes on the hole wall of the through hole. The forming method may be: chemical vapor deposition method or gas activation method. Chemical vapor deposition method is to prepare blind holes by additive method, and gas activation method is to prepare blind holes by subtractive method, both of which can prepare nano-scale blind holes to achieve good oil locking effect and avoid oil leakage to a certain extent.

[0075] In one embodiment, the chemical vapor deposition method includes: placing a porous carbon matrix in a heating furnace, introducing an inert gas (e.g., argon) as a protective gas, heating to 1000-1500°C, introducing hydrogen and methane, and treating for 1-8 hours, so that graphene nanosheets grow on the pore walls of the porous carbon matrix, and the graphene nanosheets overlap to form blind holes. Graphene nanosheets are uniformly grown on the pore wall surface of the porous carbon matrix, and the graphene nanosheets overlap each other, thereby forming a blind hole structure for oil locking.

[0076] In another embodiment, the gas activation method includes: placing the porous carbon matrix in a heating furnace, introducing an inert gas (for example, argon) as a protective gas, raising the temperature to 1000-1500°C, introducing water vapor and / or carbon dioxide, and treating for 1-3 hours, so that part of the carbon on the pore wall surface of the porous carbon matrix reacts with water vapor or carbon dioxide to be converted into gas, thereby forming blind holes on the surface of the porous carbon matrix.

[0077] S120, preparation of electric heating atomizer core

[0078] S121, fix the electrode 110 on the porous carbon heating element 130. Optionally, the porous metal electrode 110 is fixed on both sides of the porous carbon heating element 130 by conductive paste, the conductive paste is coated on both ends of the porous carbon heating element 130, and then the electrode 110 is fixed. The conductive paste is a high temperature resistant conductive silver paste, such as a sintered silver paste, gold paste, platinum paste, and graphene paste.

[0079] Both sides of the porous carbon heating element 130 can be metallized to be connected with the wire. The porous metal electrode 110 is used to increase the liquid absorption and liquid conduction part 131 and the atomization surface of the porous carbon heating element 130, thereby improving the overall material utilization.

[0080] S122, fix the current-carrying conductor 120 on the electrode 110. The current-carrying conductor 120 is fixed on the porous metal electrode 110 by welding. The welding solder can be selected from high-temperature resistant solders, such as silver solder, zinc-aluminum-silver-copper alloy solder. The purpose of this step is to extend the metal electrode 110 so as to connect with the positive and negative electrodes of the battery to realize battery power supply.

[0081] The effects of the electrically heated atomizer core provided in this application are as follows:

[0082] (1) The arrangement of multiple through holes with a pore size no larger than micrometers can make the porous carbon heating element 130 have a better oil absorption effect. In addition, the through holes cooperate with the blind holes with a pore size of nanometers, so that the porous carbon heating element 130 has a certain liquid locking ability, which can prevent oil leakage and prevent dry burning due to insufficient oil infiltration.

[0083] (2) The tortuous porous structure and the multi-level pore structure with alternating large and small pores (larger through holes and smaller blind holes) enhance the capillary force of the material to absorb oil, thereby improving the oil absorption speed and liquid locking ability.

[0084] (3) The porous metal electrode 110 is connected to the porous carbon heating element 130, which will not block the porous carbon heating element 130 from absorbing oil at the connection between the electrode 110, and the atomized smoke particles can escape from the connection between the electrode 110, which increases both the oil absorption surface of the porous carbon heating element 130 and the atomization surface, thereby improving the overall material utilization.

[0085] (4) The porous carbon heating body is heated uniformly as a whole. The entire heating body can be used as an oil absorption part and an atomization part. The temperature is highly uniform and there is no local overheating. The material can be heated and atomized simultaneously while absorbing oil. The atomization speed is fast, the amount of smoke is large, and the suction is controllable. At the same time, the porous carbon heating body 130 has good stability and good heat shock resistance, and is not prone to failure behaviors such as cracking.

[0086] (5) The material of the heating element is porous carbon, and the overall heat generation of the heating element is homogeneous, which improves the temperature uniformity and avoids local overheating and material cracking caused by thermal shock. In addition, the carbon material has a high infrared emissivity (>90%), high penetration of radiated heat, and high electrothermal conversion efficiency (>90%). It has high efficiency and uniformity in heating the e-liquid, is more energy-saving and efficient, and is conducive to the miniaturization of atomization equipment.

[0087] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0088] Example 1

[0089] This embodiment provides a method for preparing an electrically heated atomizer core, comprising the following steps:

[0090] (1) Short chopped carbon fibers with a length of about 5 cm and a diameter of about 5 um are dispersed in a dimethylformamide solvent, polyacrylonitrile powder is added, and the mixture is stirred and dissolved at 80°C to obtain a mixed solution A. Starch is then dissolved in a dimethyl sulfoxide solvent, and the mixture is stirred and dissolved at room temperature to obtain a solution B, wherein the mass ratio of carbon fiber, polyacrylonitrile and starch is 50:30:20. Liquids A and B are mixed and stirred evenly, and then poured into a rectangular mold, and the mixture is placed in an oven to dry. After removing the solvent, the obtained solid is placed in a heating furnace, nitrogen is introduced as a protective gas, and the temperature is raised to 1200°C for heat treatment. The temperature is kept for 60 minutes to obtain a porous carbon matrix with a tortuous through-pore structure.

[0091] (2) Continue to introduce hydrogen and methane into the heating furnace for chemical vapor deposition, wherein the flow ratio of hydrogen to methane is 10:1 and the insulation time is 6 hours, so that vertical graphene nanosheets are evenly distributed on the surface of the porous carbon matrix. The graphene nanosheets overlap each other to form a tiny blind hole structure, thereby obtaining a porous carbon heating element.

[0092] (3) Cut the porous carbon heating element into a rectangular block of 8 cm × 6 cm × 5 cm, adhere two porous nickel electrode sheets of 6 cm × 5 cm on the two surfaces of the porous carbon heating element using a sintered conductive silver paste, and sinter at 500°C; finally, use silver solder to weld the current-carrying conductor to the porous nickel electrode to obtain an electrically heated atomizing core.

[0093] Figure 3 This is a 10K-fold scanning electron microscope photo of the porous carbon heating element provided in the embodiment of the present application; Figure 4 This is a 40K scanning electron microscope photo of the porous carbon heating element provided in the embodiment of the present application. Figure 3 and Figure 4 It can be seen that vertical graphene nanosheets are evenly distributed on the surface of the porous carbon matrix. The graphene nanosheets overlap each other to form a tiny blind hole structure. The pore size of the blind holes on the surface of the carbon fiber is about 50nm.

[0094] Through the nitrogen isothermal adsorption-desorption curve test, the specific surface area of ​​the porous carbon heating element provided in this embodiment is 226 m2 / g, and the porosity is 87%.

[0095] Example 2

[0096] Example 2 is an improvement on Example 1. The difference between Example 2 and Example 1 is that in step (1), short chopped carbon fibers with a length of about 5 cm and a diameter of about 5 um are immersed in a polyvinyl alcohol aqueous solution and stirred and dispersed evenly. After filtering, they are placed in a needle-punching device for needle-punching treatment to obtain carbon fiber block solids, which are placed in an oven for drying. After removing the solvent, the obtained solids are placed in a heating furnace, nitrogen is introduced as a protective gas, the temperature is raised to 1200°C for heat treatment, and the heat preservation time is 60 minutes to obtain a porous carbon matrix with a tortuous through-pore structure.

[0097] Through the nitrogen isothermal adsorption-desorption curve test, the specific surface area of ​​the porous carbon heating element provided in this embodiment is 180m 2 / g, and the porosity is 90%.

[0098] Example 3

[0099] Example 3 is an improvement on Example 1. The difference between Example 3 and Example 1 is that: in step (1), polyamic acid is dissolved in dimethylacetamide solvent, stirred until the solution is clarified, and then ammonium bicarbonate is added and stirred at high speed to mix evenly. The resulting mixed solution is poured into a rectangular mold, placed in an oven, and subjected to imidization reaction at 350°C for 60 minutes. The reaction process is accompanied by solvent volatilization and ammonium bicarbonate decomposition to obtain a porous structure polyimide solid, wherein the mass ratio of polyamic acid to ammonium bicarbonate is 90:10; the polyimide solid is further placed in a heating furnace, nitrogen is introduced as a protective gas, the temperature is raised to 1200°C for carbonization, and the insulation time is 60 minutes to obtain a porous carbon matrix.

[0100] Through the nitrogen isothermal adsorption-desorption curve test, the specific surface area of ​​the porous carbon heating element provided in this embodiment is 215m 2 / g, and the porosity is 78%.

[0101] Example 4

[0102] Example 4 is an improvement on Example 1. The difference between Example 4 and Example 1 is that in step (1), nickel foam is used as a template, the nickel foam is placed in a chemical vapor deposition furnace, the temperature is raised to 1000°C, acetylene is introduced for carbon deposition, the temperature is lowered after 60 minutes, and after cooling to room temperature, the obtained solid is immersed in hydrochloric acid, the nickel foam template is removed, and a porous carbon matrix with a tortuous through-pore structure is obtained.

[0103] Through the nitrogen isothermal adsorption-desorption curve test, the specific surface area of ​​the porous carbon heating element provided in this embodiment is 160m 2 / g, and the porosity is 70%.

[0104] Example 5

[0105] Example 5 is an improvement on Example 1. The difference between Example 5 and Example 1 is that in step (2), water vapor and carbon dioxide gas are continuously introduced into the heating furnace for gas activation for 2 hours, so that part of the carbon on the pore wall surface of the porous carbon matrix can react with water vapor or carbon dioxide to be converted into gas, thereby forming blind holes on the surface of the porous carbon matrix to obtain a porous carbon heating element.

[0106] Through the nitrogen isothermal adsorption-desorption curve test, the specific surface area of ​​the porous carbon heating element provided in this embodiment is 198m 2 / g, and the porosity is 75%.

[0107] Comparative Example 1

[0108] A method for preparing an electrically heated atomizing core comprises the following steps:

[0109] (1) Short chopped carbon fibers with a length of about 5 cm and a diameter of about 5 um are dispersed in a dimethylformamide solvent, polyacrylonitrile powder is added, and the mixture is stirred and dissolved at 80°C to obtain a mixed solution A. Starch is then dissolved in a dimethyl sulfoxide solvent, and the mixture is stirred and dissolved at room temperature to obtain a solution B, wherein the mass ratio of carbon fiber, polyacrylonitrile and starch is 50:30:20. Liquids A and B are mixed and stirred evenly, and then poured into a rectangular mold, and the mixture is placed in an oven to dry. After removing the solvent, the obtained solid is placed in a heating furnace, nitrogen is introduced as a protective gas, and the temperature is raised to 1200°C for heat treatment. The temperature is kept for 60 minutes to obtain a porous carbon matrix with a tortuous through-pore structure.

[0110] (2) Cut the porous carbon substrate into a rectangular block of 8 cm × 6 cm × 5 cm, and use sintered conductive silver paste to adhere two porous nickel electrode sheets of 6 cm × 5 cm on the two surfaces of the porous carbon heating element, and sinter them at 500 ° C; finally, use silver solder to weld the current-carrying conductor to the porous nickel electrode to obtain an electrically heated atomizing core.

[0111] Through the nitrogen isothermal adsorption-desorption curve test, the specific surface area of ​​the porous carbon heating element provided in the comparative example is 50m 2 / g, and the porosity is 63%.

[0112] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A porous carbon heating element, characterized in that: The porous carbon heating element has a plurality of through holes inside, and a plurality of blind holes are arranged on the pore wall of each through hole, and the pore diameter of the through hole is larger than the pore diameter of the blind hole; the pore diameter of the through hole is 200-1000 nm, the pore diameter of the blind hole is 10-100 nm, the pore depth of the blind hole is 10-100 nm, and the porosity of the porous carbon heating element is 60%-90%.

2. The porous carbon heating element according to claim 1, characterized in that: The through holes include zigzag through holes, and a plurality of the zigzag through holes are connected.

3. A method for preparing a porous carbon heating element according to any one of claims 1 to 2, characterized in that: include: forming a porous carbon matrix having a plurality of through holes therein; A plurality of blind holes are formed on the hole wall of the through hole.

4. The method for preparing a porous carbon heating element according to claim 3, characterized in that: The method for forming the porous carbon matrix having a plurality of through holes inside is selected from any one of: a carbon fiber needle punching molding method, a polymer pore-forming carbonization molding method, a carbon fiber and polymer mixed pore-forming carbonization molding method, and a porous template vapor deposition molding method; Or / and, the method of forming the plurality of blind holes on the hole wall of the through hole is chemical vapor deposition or gas activation.

5. The method for preparing a porous carbon heating element according to claim 4, characterized in that: The carbon fiber needle punching method comprises: immersing the carbon fiber in a polymer solution, filtering and placing in a needle punching device for needle punching, or first immersing the carbon fiber in a polymer solution after needle punching, and then heating after draining; wherein the heating treatment conditions are: inert gas protection, the temperature is 500-1500° C.; wherein the polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin; Or, the polymer pore-forming carbonization molding method comprises: drying and curing a solution containing a polymer and a pore-forming agent and then performing a heat treatment; wherein the conditions for the heat treatment are: inert gas protection, a temperature of 500-1500° C., and a mass ratio of the polymer to the pore-forming agent of (95:5)-(60:40); wherein the polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, and epoxy resin; and the pore-forming agent is one or more of ammonium bicarbonate, ammonium nitrate, starch, glucose, polyvinyl pyrrolidone, and polyvinyl butyral; Or, the carbon fiber and polymer mixed pore-forming carbonization molding method comprises: dispersing the carbon fiber, polymer and pore-forming agent in the same solution, and performing heat treatment after molding; wherein the conditions of the heat treatment are: inert gas protection, temperature of 500-1500°C, and the mass ratios of the carbon fiber, the polymer and the pore-forming agent are (80-40):(80-40):(20-5) in sequence; wherein the polymer is one or more of polyacrylonitrile, polyimide, polycarbonate, polyarylacetylene, phenolic resin, epoxy resin; the pore-forming agent is one or more of ammonium bicarbonate, ammonium nitrate, starch, glucose, polyvinyl pyrrolidone, polyvinyl butyral; Alternatively, the porous template vapor deposition molding method includes: using porous metal as a template and hydrocarbon gas as a carbon source to perform vapor deposition, and then removing the porous metal template by acid washing; wherein the vapor deposition temperature is 800-1500°C and the time is 1-8h.

6. The method for preparing a porous carbon heating element according to claim 4, characterized in that: The chemical vapor deposition method comprises: placing the porous carbon substrate in a heating furnace, introducing an inert gas as a protective gas, heating to 1000-1500° C., introducing hydrogen and methane, and treating for 1-8 hours, so that graphene nanosheets grow on the pore walls of the porous carbon substrate, and the graphene nanosheets overlap to form the blind holes; Alternatively, the gas activation method comprises: placing the porous carbon substrate in a heating furnace, introducing an inert gas as a protective gas, heating to 1000-1500° C., introducing water vapor and / or carbon dioxide, and treating for 1-3 h to form the blind holes on the pore walls of the porous carbon substrate.

7. An electrically heated atomizing core, characterized in that: It comprises two electrodes and the porous carbon heating element according to any one of claims 1 to 3, wherein the two electrodes are respectively fixed at two ends of the porous carbon heating element.

8. The electrically heated atomizing core according to claim 7, characterized in that: The electrically heated atomizing core satisfies at least one of the following conditions ag: a. The electrode and the porous carbon heating element are fixed by welding, riveting, conductive paste layer, elastic clamping or pressure clamping; b, the electrode is one of a graphite electrode, a nickel electrode, a copper electrode, an iron electrode, an aluminum electrode, a silver electrode and a gold electrode; c. The porous carbon heating element is one of a polygonal column and a prism; d. at least one surface of the porous carbon heating element is an oil absorbing surface; e. The porous carbon heating element comprises a heating atomization part and a liquid suction and liquid guiding part which are connected to each other, and the electrode is fixed at the connection between the heating atomization part and the liquid suction and liquid guiding part; f, the outer dimensions of the porous carbon heating element are 3-15 mm in length, 1-5 mm in width, and 0.5-2 mm in height; the distance between the two electrodes is 3-15 mm; g. The electrically heated atomizing core further comprises two current-carrying conductors, one of the current-carrying conductors being connected to one of the electrodes.

9. The electrically heated atomizing core according to claim 8, characterized in that: The porous carbon heating element is a rectangular parallelepiped.

10. An electronic cigarette, characterized in that: Comprising the electrically heated atomizing core as described in any one of claims 7 to 9.

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