Silicon nitride porous ceramic with stable chemical performance and high strength as well as method and application of silicon nitride porous ceramic
The high-purity silicon nitride porous ceramics prepared through casting molding process solve the problems of unstable chemical properties and insufficient strength of existing ceramics, and achieve higher chemical stability and mechanical strength. They are suitable for electronic atomizers and other high-tech fields.
Patent Information
- Application Number
- CN202510178862.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-18
- Publication Date
- 2025-05-27
AI Technical Summary
The existing porous silicon nitride ceramics have insufficient chemical stability and low strength during the preparation process, which affects their application in electronic atomizers and other high-tech fields.
The casting molding process is adopted, by mixing high-purity silicon powder, pore-forming agent, solvent and dispersant, the viscosity is adjusted after ball milling, casting molding is performed, followed by drying, laminate pressing, degreasing sintering and reaction sintering to produce silicon nitride porous ceramics with stable chemical properties and high strength.
The chemical stability and mechanical strength of silicon nitride porous ceramics are improved, and their performance retention capabilities in complex environments are enhanced, process flow is simplified and production costs are reduced.
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Figure CN120040190A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electronic atomization, and in particular to a silicon nitride porous ceramic with stable chemical properties and high strength, a method and an application thereof. Background Art
[0002] The core working principle of the electronic atomizer is to convert the liquid atomized substance into aerosol through a specific heating device for the user to inhale. In this conversion process, the porous ceramic matrix becomes an indispensable key component. The porous ceramic matrix achieves efficient and uniform heating evaporation through precise coordination with the heating component, ensuring the stability and durability of the atomization effect.
[0003] Porous silicon nitride ceramics, with their excellent physical and chemical properties, have become the first choice for the atomizer core matrix material of electronic atomizers. Silicon nitride materials have high hardness, high wear resistance, good chemical stability and thermal stability. These characteristics make porous silicon nitride ceramics not easy to deform when subjected to high temperature heating, and can effectively prevent the chemical substances in the atomizing liquid from corroding the matrix material. Therefore, using porous silicon nitride ceramics as the atomizer core matrix material can not only significantly improve the atomization efficiency and extend the service life of the electronic atomizer, but also ensure the safety and stability of the product, providing users with a purer and healthier smoking experience.
[0004] However, although porous silicon nitride ceramics have shown great application potential in the field of electronic atomizers, their preparation process faces many challenges. At present, the common methods for preparing porous silicon nitride ceramics mainly include adding pore-forming agents, templates, foams, gel injection molding and freeze-drying. However, these methods often have some problems in the preparation process, resulting in insufficient chemical stability of the porous ceramics. For example, although the addition of pore-forming agents can achieve the introduction of pores, the distribution of pore-forming agents in ceramic slurry is difficult to be uniform, which easily leads to problems such as irregular pore shape and uneven size distribution, thereby affecting the mechanical properties and thermal conductivity of the material. The template method and the foam method have the problems of difficult template removal and poor pore connectivity, which limits the application scope of porous ceramics. The gel injection molding method and the freeze-drying method require complex process equipment and a long preparation cycle, and the porosity and pore size distribution of the porous ceramics obtained are difficult to accurately control. In addition, if the purity of the silicon powder in the early stage is not high, it will also affect the purity of silicon nitride, resulting in unsatisfactory material strength. These problems not only affect the application effect of porous silicon nitride ceramics in the field of electronic atomizers, but also limit its wide application in other high-tech fields.
[0005] In summary, how to prepare porous silicon nitride ceramics with stable chemical properties and high strength has become a key technical problem that needs to be solved urgently. Summary of the invention
[0006] In the prior art, there are problems of unstable chemical properties and low strength of porous ceramics. Therefore, in order to solve the above problems, the present invention provides a silicon nitride porous ceramic with stable chemical properties and high strength, as well as a method and application thereof.
[0007] To achieve the above object, the present invention provides the following technical solution: A preparation method of a silicon nitride porous ceramic with stable chemical properties and high strength, the specific steps are as follows: Mix silicon powder, pore former, solvent, and dispersant, and ball mill to obtain slurry 1; Adjust the viscosity of slurry 1 to 50000 pa.s - 200000 pa.s to obtain slurry 2; Cast and form slurry 2 to obtain a green body, and dry, stack and press, degrease and sinter, and reaction sinter the green body to obtain a silicon nitride porous ceramic.
[0008] Further, in the step of mixing silicon powder, pore former, solvent, and dispersant, and ball milling to obtain slurry 1, specifically: By weight percentage, it includes 40% - 70% of silicon powder, 3% - 31% of pore former, 0.5% - 2% of dispersant, and 20% - 50% of solvent; The silicon powder uses SiO powder with a purity of 99.9%; 2 The pore former is polymethyl methacrylate, cross-linked polystyrene, starch, carbon powder, sawdust or PP; the solvent is alcohol; the dispersant is n-butanol, sec-octanol or stearic acid.
[0009] Further, in the step of mixing silicon powder, pore former, solvent, and dispersant, and ball milling to obtain slurry 1, specifically: The ball milling uses a planetary ball mill or a sand mill, the ball milling time is 0.5 h - 6 h, the rotation speed is 800 r / min - 2000 r / min, and the median particle size D50 of the particles in the obtained slurry 1 is 0.8 μm - 5 μm, and D90 is 1 μm - 15 μm.
[0010] Further, in the step of adjusting the viscosity of slurry 1 to 50000 pa.s - 200000 pa.s to obtain slurry 2, specifically: By weight percentage, add 0.1% - 2% of defoamer and 0.1% - 3% of binder to slurry 1, and adjust the viscosity of slurry 1 to 50000 pa.s - 200000 pa.s; The defoamer is AFE0400 defoamer or AFE1410 defoamer; the binder is phenolic resin, carboxymethyl cellulose, PVB, phenolic resin or PVC glue solution.
[0011] Further, in the steps of casting the slurry 2 into a green body, drying the green body, laminating and pressing, debinding and sintering, and reaction sintering to obtain the silicon nitride porous ceramic, specifically: When performing the casting, the casting temperature is 10°C to 40°C, and the casting speed is 0.1 cm / s to 3 cm / s.
[0012] Further, in the steps of casting the slurry 2 into a green body, drying the green body, laminating and pressing, debinding and sintering, and reaction sintering to obtain the silicon nitride porous ceramic, specifically: The drying is as follows: heating the green body to 50°C to 80°C at a rate of 0.1°C / min to 10°C / min and drying for 2 h to 8 h; The laminating and pressing is as follows: laminating and pressing the dried green body at 1 MPa to 10 MPa; The debinding and sintering is as follows: heating to 300°C to 380°C at a rate of 1°C to 10°C, performing debinding and sintering for 3 h to 12 h, and naturally cooling.
[0013] Further, in the steps of casting the slurry 2 into a green body, drying the green body, laminating and pressing, debinding and sintering, and reaction sintering to obtain the silicon nitride porous ceramic, specifically: The reaction sintering is as follows: in a protective atmosphere, heating to 1350°C to 1500°C at a rate of 1°C / min to 20°C / min and holding for 3 h to 13 h; starting to introduce hydrogen at a flow rate of 0.1 ml / s to 10 ml / s at 1200°C and maintaining for 1 to 3 h; switching to nitrogen and maintaining at 0.1 ml / s to 10 ml / s for 2 h to 12 h; heating to 1750°C to 1900°C at a rate of 1°C / min to 5°C / min, holding for 2 h to 8 h for sintering and crystallization, and naturally cooling to obtain the silicon nitride porous ceramic.
[0014] The present invention also provides a silicon nitride porous ceramic with stable chemical properties and high strength, which is prepared by the above preparation method.
[0015] The present invention also provides an atomizing core, which includes a heating component and the above silicon nitride porous ceramic with stable chemical properties and high strength.
[0016] The present invention also provides an electronic atomizer, which includes the above atomizing core.
[0017] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength. Through the tape casting process, the silicon nitride porous ceramic prepared by the present invention has a flat structure. This structural feature enables nitrogen and silicon source to fully contact and react completely during the reaction process, thereby effectively reducing the impurity content and improving the chemical stability of the material. This stability allows the silicon nitride porous ceramic to maintain its excellent properties in a complex and variable usage environment. Further, the previous independent debinding and sintering steps effectively improve the purity of the silicon powder, resulting in a higher purity of the silicon nitride generated in the subsequent reaction. High-purity silicon nitride has stronger mechanical strength. Therefore, the silicon nitride porous ceramic prepared by the present invention has excellent mechanical properties and can withstand large external forces without being easily damaged.
[0018] Compared with the prior art, the preparation method of the present invention does not require the use of complex templates or gel additives, thereby simplifying the process flow and reducing the production cost. During the preparation process, the present invention selects environmentally friendly raw materials such as solvents, dispersants, defoamers, and binders. These raw materials do not produce harmful substances during the production process and have less impact on the environment. In addition, both the debinding and sintering steps and the reaction sintering steps are carried out in a protective atmosphere, effectively avoiding the emission of harmful gases and further enhancing the environmental friendliness of the preparation process. At the same time, the carefully designed slurry formula and sintering process result in an ideal pore structure and distribution of the porous ceramic, with a uniform pore size distribution and a reasonable porosity, which further enhances the mechanical strength and toughness of the material.
[0019] The silicon nitride porous ceramic prepared by the present invention can be used as a key material for the atomizing core. Its excellent chemical stability and high strength enable the atomizing core to maintain stable performance during use and extend its service life. At the same time, the porous structure is conducive to the uniform distribution and full atomization of the e-liquid, improving the taste and quality of the electronic cigarette. Applying the silicon nitride porous ceramic prepared by the present invention to the electronic atomizer can significantly improve the overall performance of the electronic atomizer. Its high strength and stability make the electronic atomizer safer and more reliable during use, while improving the atomization efficiency and smoke quality, meeting the higher requirements of users for electronic cigarette products. In addition to the field of electronic cigarettes, the silicon nitride porous ceramic prepared by the present invention can also be applied to other fields that require high-performance porous ceramic materials, such as catalyst carriers, gas separation membranes, biomedical materials, etc. Its excellent performance and preparation process make these application fields have broad market prospects and development potential. Brief Description of the Drawings
[0020] Figure 1 It is a flow chart for the preparation of the silicon nitride porous ceramic of the present invention.
[0021] Figure 2 It is a SEM picture of the side of the silicon nitride porous ceramic. Detailed Embodiments
[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.
[0023] As Figure 1 shown, the present invention provides a method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength. High-purity silicon powder is selected, and the silicon powder is mixed with a solvent pore former and ball milled to prepare a suitable slurry. Using the tape casting process, after completion, it is dried. The dried film tapes are stacked and pressed to obtain a film sheet. During the process, the thickness is controlled within a certain range. The pressed sample is degreased and sintered to obtain a sample with a porous structure. Then the sample is transferred to a vacuum high-temperature reaction furnace, and hydrogen is introduced for purification at a certain temperature and atmosphere. Then hydrogen is turned off, and a mixed gas of nitrogen and argon is introduced. Nitrogen reacts with silicon to form a silicon nitride porous ceramic. The specific steps are as follows: including: Step 1: Mix silicon powder, pore former, solvent, and dispersant in a certain proportion and ball mill to obtain a uniform slurry; Step 2: Add auxiliaries such as defoamer and binder to the slurry. After adjusting the viscosity of the slurry, tape cast the slurry to obtain a green body. Dry, stack and press, degrease and sinter, and react sinter the tape cast green body to form a silicon nitride porous ceramic; Step 3: Surface polish and laser cut the sintered silicon nitride porous ceramic to obtain the required shape.
[0024] Preferably, step 1 includes: Step 101: The chemical formula of the silicon powder is SiO 2 , with a purity of 99.9%; the preferred pore formers are polymethyl methacrylate (PMMA) and cross-linked polystyrene, and the secondary choices are organic flammable substances such as starch, carbon powder, sawdust, and PP; the solvent is alcohol; the dispersants are n-butanol, sec-octanol, or stearic acid; Step 102: By weight percentage, it includes 40% - 70% of silicon powder, 3% - 31% of pore former, 0.5% - 2% of dispersant, and 20% - 50% of solvent; Step 103: Mix the ingredients evenly and put them into a planetary ball mill or sand mill for ball milling. The ball milling time is 0.5h - 6h, and the rotation speed is 800r / min - 2000r / min. Laser particle size detection is used to measure the particle size of the particles in the slurry. Among them, the median particle size D50 is controlled within 0.8μm - 5μm, and D90 is controlled within 1μm - 15μm; Preferably, step 2 includes: Step 201: Add 0.1% - 2% of defoamer and 0.1% - 3% of binder to the ball milled slurry, and adjust the viscosity of the slurry to 50000 - 200000 pa.s; Preferably, the defoamer is AFE0400 defoamer or AFE1410 defoamer; Preferably, the adhesive is phenolic resin, carboxymethyl cellulose, PVB, phenolic resin or PVC glue solution; Further preferably, the adhesive is phenolic resin or carboxymethyl cellulose; Step 202, tape-casting the slurry to obtain a green body, the tape-casting temperature is controlled at 10-40°C; the tape-casting speed is controlled at 0.1 cm / s-3 cm / s.
[0025] Step 203, heating the green body formed by tape casting to 50-80°C at a rate of 0.1-10°C / min for 2-8h, laminating and pressing the green body at 1MPa-10MPa, heating the green body to 300-380°C at a rate of 1-10°C for degreasing and sintering for 3-12h, and cooling naturally; Step 204, reaction sintering is specifically as follows: first, with argon protection, heat up to 1350-1500°C at 1-20°C / min, and keep warm for 3-13 hours; at 1200°C, start passing hydrogen at a flow rate of 0.1ml / s-10ml / s to purify silicon powder, and keep it for 1-3 hours; switch to nitrogen at 0.1ml / s-10ml / s for 2-12 hours to make the silicon powder react with nitrogen to form silicon nitride; heat up to 1750-1900°C at 1-5°C / min, keep warm for 2-8 hours to sinter and crystallize, and cool naturally to obtain silicon nitride porous ceramics.
[0026] Preferably, step 3 includes: Step 301, using a machine tool (CNC) to polish and grind the surface of the sintered silicon nitride porous ceramic; Step 302: Use laser cutting to cut the porous ceramic into a desired shape, generally a square.
[0027] Embodiment 1: A method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength, comprising the following steps: Step 1: Ingredients: Mix 45% silicon powder, 18% polymethyl methacrylate (PMMA), 36.5% alcohol and 0.5% n-butanol in proportion. The chemical formula of silicon powder is SiO 2 , purity is 99.9%; Step 2, ball milling: the mixture in step 1 is placed in a planetary ball mill for ball milling for 3 hours at a rotation speed of 1200 r / min; Step 3, slurry preparation: add 1% of defoamer AFE0400 and 1.5% of adhesive phenolic resin to the slurry after ball milling in step 2, stir evenly, and adjust the slurry viscosity to 100000 Pa.s; Step 4, tape casting: tape casting the slurry in step 3 at a temperature of 25° C. and a tape casting speed of 1 cm / s; Step 5, Drying: Heat the cast green body in Step 4 to 70°C at a heating rate of 5°C / min and keep it warm for 4 hours for drying; Step 6, Laminating and Pressing: Laminate the dried film strips in Step 5, with a pressing pressure of 5 MPa, and press them into the required thickness of 2 mm; Step 7, Debinding and Sintering: Heat the pressed film in Step 6 to 350°C at a heating rate of 5°C / hour, keep it warm for 6 hours for debinding and sintering, and then cool it naturally; Step 8, Reaction Sintering: First, under argon protection, heat the debound and sintered film in Step 7 to 1400°C at a heating rate of 10°C / min and keep it warm for 8 hours; start introducing hydrogen at a flow rate of 5 ml / s at 1200°C and keep it for 2 hours for silicon powder purification; then switch to nitrogen and introduce it at a flow rate of 5 ml / s and keep it for 6 hours to react silicon powder with nitrogen to form silicon nitride; then heat it to 1800°C at a heating rate of 3°C / min, keep it warm for 4 hours for sintering and crystallization, and finally cool it naturally; Step 9, Surface Treatment: Use a numerical control machine tool to polish and flatten the surface of the sintered porous ceramic in Step 8, and then use laser cutting to cut the porous ceramic into a square of 20 mm × 20 mm × 1.5 mm, and a silicon nitride porous ceramic with stable chemical properties and high strength can be obtained, as Figure 2 shown. Specifically, it is a SEM picture of the side of the silicon nitride porous ceramic. It can be seen from the figure that the porosity distribution of the ceramic is uniform and the porosity is high, which is the key to the stable material properties.
[0028] Example 2: A preparation method of a silicon nitride porous ceramic with stable chemical properties and high strength, comprising the following steps: Step 1, Batching: Mix 60% silicon powder, 15% cross-linked polystyrene, 24% alcohol, and 2% dispersant n-butanol evenly by proportion. The chemical formula of the silicon powder is SiO 2 , and the purity is 99.9%; Step 2, Ball Milling: Put the mixture in Step 1 into a sand mill for ball milling. The ball milling time is 4 hours and the rotation speed is 1500 r / min; Step 3, Pulp Making: Add 0.5% defoamer AFE1410 and 2% binder carboxymethyl cellulose to the milled slurry in Step 2, stir evenly, and adjust the slurry viscosity to 150000 pa.s; Step 4, Casting: Cast the slurry in Step 3 under the conditions of a temperature of 30°C and a casting speed of 2 cm / s; Step 5, Drying: Heat the cast green body in Step 4 to 60°C at a heating rate of 2°C / min and keep it warm for 6 hours for drying; Step 6. Laminating and pressing: Stack the dried film tapes in Step 5, with a pressing pressure of 8 MPa, and press them into the required thickness of 2 mm; Step 7. Debinding and sintering: Heat the pressed film sheets in Step 6 to 370 °C at a heating rate of 8 °C / hour, hold for 10 hours for debinding and sintering, and then cool naturally; Step 8. Reaction sintering: First, under argon protection, heat the film sheets after debinding and sintering in Step 7 to 1450 °C at a heating rate of 15 °C / min, and hold for 10 hours; Start passing hydrogen at a flow rate of 2 ml / s at 1200 °C and keep for 2.5 hours for silicon powder purification; Then switch to nitrogen and pass it in at a flow rate of 2 ml / s and keep for 8 hours to react silicon powder with nitrogen to form silicon nitride; Then heat to 1850 °C at a heating rate of 2 °C / min, hold for 6 hours for sintering crystallization, and finally cool naturally; Step 9. Surface treatment: Use a numerical control machine tool to polish and flatten the surface of the sintered porous ceramic in Step 8, and then use laser cutting to cut the porous ceramic into a square of 20 mm × 20 mm × 1.5 mm, and a silicon nitride porous ceramic with stable chemical properties and high strength can be obtained.
[0029] Example 3: A preparation method of a silicon nitride porous ceramic with stable chemical properties and high strength includes the following steps: Step 1. Batching: Mix 70% silicon powder, 3% starch, 26.2% alcohol, and 0.8% dispersant sec-octanol evenly by proportion, where the chemical formula of the silicon powder is SiO 2 , and the purity is 99.9%; Step 2. Ball milling: Put the mixture in Step 1 into a sand mill for ball milling, with a ball milling time of 6 hours and a rotation speed of 1500 r / min; Step 3. Pulp making: Add 2% defoamer AFE0400 and 3% binder phenolic resin to the slurry after ball milling in Step 2, stir evenly, and adjust the slurry viscosity to 200000 pa.s; Step 4. Tape casting: Carry out tape casting on the slurry in Step 3 under the conditions of a temperature of 10 °C and a tape casting speed of 0.1 cm / s; Step 5. Drying: Heat the tape-cast green body in Step 4 to 50 °C at a heating rate of 0.1 °C / min, and hold for 8 hours for drying; Step 6. Laminating and pressing: Stack the dried film tapes in Step 5, with a pressing pressure of 1 MPa, and press them into the required thickness of 2 mm; Step 7. Debinding and sintering: Heat the pressed film sheets in Step 6 to 380 °C at a heating rate of 10 °C / hour, hold for 3 hours for debinding and sintering, and then cool naturally; Step 8, reaction sintering: First, under argon protection, heat the debound and sintered diaphragm in Step 7 to 1500 °C at a heating rate of 20 °C / min and hold for 3 hours; start introducing hydrogen at a flow rate of 10 ml / s at 1200 °C and hold for 3 hours for silicon powder purification; then switch to nitrogen and introduce it at a flow rate of 10 ml / s and hold for 2 hours to react silicon powder with nitrogen to form silicon nitride; then heat it to 1900 °C at a heating rate of 5 °C / min and hold for 2 hours for sintering and crystallization, and finally cool it naturally; Step 9, surface treatment: Use a numerical control machine tool to polish and flatten the surface of the sintered porous ceramic in Step 8, and then use laser cutting to cut the porous ceramic into a square with dimensions of 20 mm × 20 mm × 1.5 mm, and a silicon nitride porous ceramic with stable chemical properties and high strength can be obtained.
[0030] Example 4: A preparation method of a silicon nitride porous ceramic with stable chemical properties and high strength, comprising the following steps: Step 1, batching: Mix 40% silicon powder, 31% carbon powder, 28.4% alcohol, and 0.6% dispersant n-butanol evenly by proportion, where the chemical formula of the silicon powder is SiO 2 , and the purity is 99.9%; Step 2, ball milling: Put the mixture in Step 1 into a sand mill for ball milling, the ball milling time is 0.5 hours, and the rotation speed is 2000 r / min; Step 3, pulping: Add 0.1% defoamer AFE0400 and 1% binder PVB to the slurry after ball milling in Step 2, stir evenly, and adjust the slurry viscosity to 80000 pa.s; Step 4, tape casting: Carry out tape casting on the slurry in Step 3 under the conditions of a temperature of 20 °C and a tape casting speed of 0.8 cm / s; Step 5, drying: Heat the tape-cast green body in Step 4 to 80 °C at a heating rate of 10 °C / min and hold for 2 hours for drying; Step 6, lamination pressing: Stack the dried film tapes in Step 5, the pressing pressure is 3 MPa, and press them into the required thickness of 2 mm; Step 7, debinding and sintering: Heat the pressed diaphragm in Step 6 to 300 °C at a heating rate of 1 °C / hour and hold for 12 hours for debinding and sintering, and then cool it naturally; Step 8, reactive sintering: First, under argon protection, heat the degreased and sintered diaphragm in Step 7 to 1350 °C at a heating rate of 1 °C / min and hold for 13 hours; start introducing hydrogen at a flow rate of 0.1 ml / s at 1200 °C and maintain for 1 hour for silicon powder purification; then switch to nitrogen and introduce it at a flow rate of 0.1 ml / s and maintain for 12 hours to react silicon powder with nitrogen to form silicon nitride; then heat it to 1750 °C at a heating rate of 1 °C / min, hold for 8 hours for sintering crystallization, and finally cool it naturally; Step 9, surface treatment: Use a numerical control machine tool to polish and flatten the surface of the sintered porous ceramic in Step 8, and then use laser cutting to cut the porous ceramic into a square with a size of 20 mm × 20 mm × 1.5 mm, and then a silicon nitride porous ceramic with stable chemical properties and high strength can be obtained.
[0031] Example 5: A preparation method of a silicon nitride porous ceramic with stable chemical properties and high strength, comprising the following steps: Step 1, batching: Mix 60% silicon powder, 19.5% sawdust, 20% alcohol and 0.5% dispersant stearic acid evenly, wherein the chemical formula of the silicon powder is SiO 2 , and the purity is 99.9%; Step 2, ball milling: Put the mixture in Step 1 into a sand mill for ball milling, the ball milling time is 6 hours, and the rotation speed is 800 r / min; Step 3, pulping: Add 1.5% defoamer AFE0400 and 2.5% binder PVC glue solution to the slurry after ball milling in Step 2, stir evenly, and adjust the slurry viscosity to 180000 pa.s; Step 4, tape casting: Carry out tape casting on the slurry in Step 3 under the conditions of a temperature of 35 °C and a tape casting speed of 2.5 cm / s; Step 5, drying: Heat the tape-cast green body in Step 4 to 60 °C at a heating rate of 2 °C / min and hold for 6 hours for drying; Step 6, lamination pressing: Stack the dried film tapes in Step 5, the pressing pressure is 9 MPa, and press them into the required thickness of 2 mm; Step 7, degreasing sintering: Heat the pressed diaphragm in Step 6 to 320 °C at a heating rate of 8 °C / hour, hold for 10 hours for degreasing sintering, and then cool it naturally; Step 8, reaction sintering: First, under argon protection, heat the debound and sintered diaphragm in Step 7 to 1450 °C at a heating rate of 8 °C / min and hold for 10 hours; start introducing hydrogen at a flow rate of 7 ml / s at 1200 °C and keep for 2.5 hours for silicon powder purification; then switch to nitrogen and introduce it at a flow rate of 8 ml / s and keep for 10 hours to react silicon powder with nitrogen to form silicon nitride; then heat to 1750 °C at a heating rate of 2 °C / min and hold for 2 hours for sintering and crystallization, and finally cool naturally; Step 9, surface treatment: Use a numerical control machine tool to polish and flatten the surface of the sintered porous ceramic in Step 8, and then use laser cutting to cut the porous ceramic into a square of 20 mm × 20 mm × 1.5 mm, and a silicon nitride porous ceramic with stable chemical properties and high strength can be obtained.
[0032] Example 6: A preparation method of a silicon nitride porous ceramic with stable chemical properties and high strength, comprising the following steps: Step 1, batching: Mix 40% silicon powder, 9.5% PP, 50% alcohol and 0.5% dispersant stearic acid evenly by proportion, where the chemical formula of the silicon powder is SiO 2 , and the purity is 99.9%; Step 2, ball milling: Put the mixture in Step 1 into a sand mill for ball milling, the ball milling time is 6 hours, and the rotation speed is 1500 r / min; Step 3, pulping: Add 1% defoamer AFE1410 and 0.1% binder carboxymethyl cellulose to the slurry after ball milling in Step 2, stir evenly, and adjust the slurry viscosity to 50000 pa.s; Step 4, tape casting: Carry out tape casting on the slurry in Step 3 under the conditions of a temperature of 40 °C and a tape casting speed of 3 cm / s; Step 5, drying: Heat the tape-cast green body in Step 4 to 60 °C at a heating rate of 2 °C / min and hold for 6 hours for drying; Step 6, lamination pressing: Laminate the dried film belt in Step 5, the pressing pressure is 10 MPa, and press it to the required thickness of 2 mm; Step 7, debinding and sintering: Heat the pressed diaphragm in Step 6 to 370 °C at a heating rate of 8 °C / hour, hold for 10 hours for debinding and sintering, and then cool naturally; Step 8, reactive sintering: First, under argon protection, heat the debound and sintered diaphragm in Step 7 to 1450 °C at a heating rate of 15 °C / min and hold for 10 hours; start introducing hydrogen at a flow rate of 2 ml / s at 1200 °C and hold for 2.5 hours for silicon powder purification; then switch to nitrogen and introduce it at a flow rate of 2 ml / s and hold for 8 hours to react silicon powder with nitrogen to form silicon nitride; then heat it to 1850 °C at a heating rate of 3 °C / min and hold for 6 hours for sintering and crystallization, and finally cool it naturally; Step 9, surface treatment: Use a numerical control machine tool to polish and flatten the surface of the sintered porous ceramic in Step 8, and then use laser cutting to cut the porous ceramic into a square with a size of 20 mm × 20 mm × 1.5 mm, and then a silicon nitride porous ceramic with stable chemical properties and high strength can be obtained.
[0033] Perform performance tests on the silicon nitride porous ceramics prepared in Examples 1 to 6, and the test results are shown in the following table:
[0034] It can be seen from the table that as the proportion of silicon powder increases (from 40% to 70%), the porosity gradually decreases. This indicates that the increase in the silicon powder content makes the ceramic matrix more dense and the pore space decreases. In Examples 4 and 6, although the proportion of the pore-forming agent is different (31% and 9.5%), due to the low basic proportion of silicon powder (40%), the porosity is still relatively high (77% and 78%). This further confirms the dominant role of the silicon powder proportion in the porosity.
[0035] The plane compressive strength gradually increases as the proportion of silicon powder increases. In Example 3, the proportion of silicon powder is the highest (70%), and the plane compressive strength also reaches the maximum value (17 mpa). This indicates that a high proportion of silicon powder is beneficial to obtaining a high-strength silicon nitride porous ceramic. The porosity of all examples is greater than 53%, and the highest can reach 78%. This indicates that this preparation method can prepare a silicon nitride porous ceramic with a high porosity to meet specific application requirements. The plane compressive strength is at least 6.5 mpa and at most 17 mpa. These strength values indicate that this preparation method can prepare a silicon nitride ceramic material with both a porous structure and relatively high strength, which is suitable for a variety of application scenarios.
Claims
1. A method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength, characterized in that: The specific steps are as follows: The silicon powder, pore-forming agent, solvent and dispersant are mixed and ball-milled to obtain slurry 1; The viscosity of slurry 1 is adjusted to 50000 pa.s to 200000 pa.s to obtain slurry 2; The slurry 2 is tape-cast to obtain a green body, and the green body is dried, laminated, pressed, degreased, sintered, and reaction-sintered to obtain a silicon nitride porous ceramic.
2. The method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength according to claim 1, characterized in that: In the step of mixing silicon powder, pore-forming agent, solvent and dispersant, and ball milling to obtain slurry 1, specifically: In terms of weight percentage, it includes 40% to 70% of silicon powder, 3% to 31% of pore-forming agent, 0.5% to 2% of dispersant, and 20% to 50% of solvent; The silicon powder is SiO2 powder with a purity of 99.9%; the pore-forming agent is polymethyl methacrylate, cross-linked polystyrene, starch, carbon powder, sawdust or PP; the solvent is alcohol; and the dispersant is n-butanol, 2-octanol or stearic acid.
3. The method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength according to claim 1, characterized in that: In the step of mixing silicon powder, pore-forming agent, solvent and dispersant, and ball milling to obtain slurry 1, specifically: The ball milling adopts a planetary ball mill or a sand mill, the ball milling time is 0.5h to 6h, the rotation speed is 800r / min to 2000r / min, and the median particle size D50 of the particles in the obtained slurry 1 is 0.8μm to 5μm, and D90 is 1μm to 15μm.
4. The method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength according to claim 1, characterized in that: The viscosity of slurry 1 is adjusted to 50000 pa.s to 200000 pa.s to obtain slurry 2. Specifically: In terms of weight percentage, 0.1% to 2% of a defoamer and 0.1% to 3% of a binder are added to the slurry 1 to adjust the viscosity of the slurry 1 to 50000 pa.s to 200000 pa.s; The defoaming agent is AFE0400 defoaming agent or AFE1410 defoaming agent; the adhesive is phenolic resin, carboxymethyl cellulose, PVB, phenolic resin or PVC adhesive solution.
5. The method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength according to claim 1, characterized in that: The steps of tape-casting the slurry 2 to obtain a green body, drying the green body, laminating and pressing, degreasing and sintering, and reaction sintering to obtain a silicon nitride porous ceramic include: When the tape casting is performed, the tape casting temperature is 10° C. to 40° C., and the tape casting speed is 0.1 cm / s to 3 cm / s.
6. The method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength according to claim 1, characterized in that: The steps of tape-casting the slurry 2 to obtain a green body, drying the green body, laminating and pressing, degreasing and sintering, and reaction sintering to obtain a silicon nitride porous ceramic include: The drying comprises: heating the green body to 50°C to 80°C at a temperature of 0.1°C / min to 10°C / min for 2h to 8h; The lamination pressing comprises: lamination pressing of the dried green body at 1MPa to 10MPa; The debinding and sintering is as follows: heating the temperature from 1°C to 10°C to 300°C to 380°C, debinding and sintering for 3h to 12h, and then cooling naturally.
7. The method for preparing a silicon nitride porous ceramic with stable chemical properties and high strength according to claim 1, characterized in that: The steps of tape-casting the slurry 2 to obtain a green body, drying the green body, laminating and pressing, degreasing and sintering, and reaction sintering to obtain a silicon nitride porous ceramic include: The reaction sintering is as follows: in a protective atmosphere, heating to 1350°C-1500°C at 1°C / min-20°C / min, and keeping the temperature for 3h-13h; at 1200°C, hydrogen is introduced at a flow rate of 0.1ml / s-10ml / s, and the temperature is maintained for 1-3h; nitrogen is switched at a flow rate of 0.1ml / s-10ml / s and the temperature is maintained for 2h-12h; heating to 1750°C-1900°C at 1°C / min-5°C / min, and the temperature is maintained for 2h-8h for sintering and crystallization, and the silicon nitride porous ceramic is obtained by naturally cooling the temperature.
8. A silicon nitride porous ceramic with stable chemical properties and high strength, characterized in that: The method according to any one of claims 1 to 7.
9. An atomizer core, characterized in that: It comprises a heating component and a silicon nitride porous ceramic with stable chemical properties and high strength as described in claim 8.
10. An electronic atomizer, characterized in that: Comprising the atomizer core as described in claim 9.