Preparation method of high-temperature-resistant composite ceramic material

Abstract

The application discloses a preparation method of a high-temperature-resistant composite ceramic material and relates to the field of composite ceramic materials. In the preparation of the high-temperature-resistant composite ceramic material, boron nitride nanosheets are dispersed, then are subjected to electronegative treatment by using metal lithium particles, and then are reacted with oxygen to obtain hydroxylated nanometer boron nitride; mullite whiskers are reacted with hydroxymethyl triethoxysilane to obtain modified mullite whiskers; chloromethyl trichlorosilane is coupled by magnesium powder initiation to prepare polycarbosilane; the polycarbosilane is reacted with maleic anhydride to prepare modified polycarbosilane; and the modified polycarbosilane, polystyrene porogen, hydroxylated nanometer boron nitride and modified mullite whiskers are uniformly mixed and calcined to obtain the high-temperature-resistant composite ceramic material. The high-temperature-resistant composite ceramic material prepared by the application has excellent high-temperature resistance, heat preservation and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of composite ceramic materials, specifically a method for preparing a high-temperature resistant composite ceramic material. Background Technology

[0002] Porous ceramic matrix composites are considered an ideal alternative to porous media for sweating and cooling due to their excellent properties, including low density, low coefficient of thermal expansion, excellent thermal shock resistance, and high-temperature oxidation resistance. Among them, silicon carbide-based porous ceramics have attracted widespread attention from researchers in this field due to their excellent mechanical properties, thermal shock resistance, and corrosion resistance. Silicon carbide ceramics, also known as carborundum, are covalently bonded inorganic materials. Their composition consists of equal amounts of silicon and carbon forming a tetrahedral crystal structure similar to diamond, and this unique structure endows silicon carbide ceramics with excellent properties. Silicon carbide ceramics are widely used in extreme environments such as aerospace engines, thermal protection material systems, hypersonic propulsion systems, and nuclear engineering due to their excellent high-temperature resistance, oxidation resistance, wear resistance, thermal stability, and chemical corrosion resistance. However, due to the inherent chemical bonding characteristics of ceramic materials, dislocation movement is difficult in their internal microstructure, resulting in inherent brittleness. Therefore, this invention prepares a high-temperature resistant composite ceramic material with excellent mechanical properties. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing high-temperature resistant composite ceramic materials to solve the problems existing in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A method for preparing a high-temperature resistant composite ceramic material, wherein the high-temperature resistant composite ceramic material is obtained by calcining a mixture of modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano-boron nitride, and modified mullite whiskers.

[0006] As an optimization, the polystyrene pore-forming agent is sourced from Dongguan Baolimei Plastic Raw Materials Co., Ltd.

[0007] As an optimization, the modified polycarbosilane is prepared by reacting chloromethyltrichlorosilane with maleic anhydride after initiation coupling with magnesium powder.

[0008] As an optimization, the nickel acetylacetone dihydrate was sourced from Wuhan Chengtian Fine Chemical Co., Ltd.

[0009] As an optimization, the hydroxylated boron nitride nanoparticles are obtained by dispersing boron nitride nanosheets, electronegating them with lithium metal particles, and then reacting them with oxygen.

[0010] As an optimization, the boron nitride nanosheets are sourced from Hubei Xinyuhong Biomedical Technology Co., Ltd.

[0011] As an optimization, the modified mullite whiskers are obtained by reacting mullite whiskers with hydroxymethyltriethoxysilane.

[0012] As an optimization, the mullite whiskers are of 800 mesh and are sourced from Shijiazhuang Supermicro New Materials Technology Co., Ltd.

[0013] As an optimization, the preparation method of the high-temperature resistant composite ceramic material includes the following preparation steps:

[0014] (1) Mix boron nitride nanosheets and N-methylpyrrolidone at a mass ratio of 1:(900~1100), sonicate for 47~49h, centrifuge, collect the supernatant and let it settle, filter with a 0.05~0.15μm filter membrane, wash 3~5 times with anhydrous ethanol, and dry at 75~85℃ for 23~25h to obtain dispersed boron nitride nanosheets; mix dispersed boron nitride nanosheets and tetrahydrofuran at a mass ratio of 1:(350~450), sonicate for 55~65min, and add to anhydrous and oxygen-free environment at -79~-77℃. Liquid nitrogen was used to stir the mixture at 400-600 r / min for 55-65 min. Then, lithium metal particles with a mass of 1.3-1.5 times that of dispersed boron nitride nanoparticles were added and stirred for 1-2 h. Oxygen was introduced and stirring was continued for 5-7 h. Deionized water with a mass of 2-4 times that of dispersed boron nitride nanoparticles was added at a uniform rate over 1-3 h and stirring was continued for 55-65 min. The mixture was filtered through a filter membrane and washed 3-5 times with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water, respectively. The mixture was then dried at 75-85℃ for 23-25 ​​h to obtain hydroxylated boron nitride nanoparticles.

[0015] (2) Mix mullite whiskers, hydroxymethyltriethoxysilane and ethanol solution at a mass ratio of 1:(0.04~0.06):(35~45), add acetic acid to adjust the pH to 3~4, stir at 20~30℃ and 100~200rpm for 5~7h, filter, wash with anhydrous ethanol and deionized water 3~5 times respectively, and dry at 75~85℃ for 23~25h to obtain modified mullite whiskers;

[0016] (3) Mix chloromethyltrichlorosilane, magnesium powder and tetrahydrofuran at a mass ratio of 1:(0.4~0.6):(10~20), stir for 1~2 hours at 35~45℃ and 100~200 rpm in a nitrogen atmosphere, heat to 55~65℃ and keep at that temperature for 11~13 hours, cool to -1~1℃, add 0.02~0.04 times the mass of chloromethyltrichlorosilane of lithium aluminum hydride, heat to 55~65℃ and keep at that temperature for 11~13 hours, quench with hydrochloric acid solution, add n-hexane and deionized water, let stand and separate into layers, and then filter. The lower layer was washed 3-5 times with 4-6 mol / L hydrochloric acid solution, dried with anhydrous sodium sulfate, and then rotary evaporated to obtain polycarbosilane. Polycarbosilane, maleic anhydride, chloroplatinic acid and xylene were mixed in a mass ratio of 1:(0.04-0.06):(0.2-0.3):(15-25), stirred in an argon atmosphere at 75-85℃ and 300-400 rpm for 2-4 hours, cooled naturally to room temperature, and then rotary evaporated under negative pressure. The mixture was ground and sieved, and kept at 95-105℃ for 2-4 hours to obtain modified polycarbosilane.

[0017] (4) Modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, modified mullite whiskers and anhydrous ethanol are mixed in a mass ratio of 1:(0.07~0.09):(0.02~0.03):(0.01~0.03):(1~2), ultrasonicated for 25~35 min, ball-milled at 250~350 r / min for 5~7 h, stirred in a water bath at 85~95℃ until viscous, dried at 75~85℃ for 11~13 h, ground and sieved through a 35~45 mesh, loaded into a grinding mold, heated to 1400~1600℃ at 1~3℃ / min and held at 35~45MPa for 55~65 min in a nitrogen atmosphere, cooled to room temperature with the furnace, taken out and polished to obtain high-temperature resistant composite ceramic material.

[0018] As an optimization, the ultrasonic fragmentation conditions in step (1) are 450~460W.

[0019] As an optimization, the settling time in step (1) is 23~25h.

[0020] As an optimization, the amount of liquid nitrogen added in step (1) is 900 to 1000 times the mass of the dispersed nano boron nitride.

[0021] As an optimization, the filter membrane size in step (1) is 0.05~0.15μm.

[0022] As an optimization, the ethanol solution in step (2) has a mass fraction of 90% to 100%.

[0023] As an optimization, the concentration of the hydrochloric acid solution used for quenching in step (3) is 2~4 mol / L.

[0024] As an optimization, the grinding and sieving particle size in step (3) is 40~60 mesh.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0026] In preparing high-temperature resistant composite ceramic materials, the present invention disperses boron nitride nanosheets, electronegates them with lithium metal particles, and then reacts them with oxygen to obtain hydroxylated boron nitride nanosheets; mullite whiskers are reacted with hydroxymethyltriethoxysilane to obtain modified mullite whiskers; chloromethyltrichlorosilane is coupled with magnesium powder to obtain polycarbosilane; the polycarbosilane is then reacted with maleic anhydride to obtain modified polycarbosilane; the modified polycarbosilane, polystyrene porogen, hydroxylated boron nitride nanosheets, and modified mullite whiskers are mixed and calcined to obtain the high-temperature resistant composite ceramic material.

[0027] First, boron nitride nanosheets are dispersed, electronegated with lithium metal particles, and then reacted with oxygen to obtain hydroxylated boron nitride nanosheets. Mullite whiskers are reacted with hydroxymethyltriethoxysilane to obtain modified mullite whiskers. The thermal expansion coefficients of boron nitride nanosheets and mullite whiskers are close to those of silicon carbide ceramics, and as reinforcing phases, they can avoid thermal stress caused by the mismatch in thermal expansion coefficients. The layered structure of boron nitride nanosheets can prevent or deflect cracks, while mullite whiskers can act as a "bridging" agent when the material is under stress, further increasing the difficulty of crack propagation and improving the mechanical properties of the high-temperature resistant composite ceramic material. Finally, boron nitride nanosheets and mullite whiskers are hydroxylated and then subjected to transesterification with maleic anhydride to form ester groups, promoting dispersion and cross-linking, further improving the mechanical properties of the high-temperature resistant composite ceramic material.

[0028] Secondly, polycarbosilane is prepared by coupling chloromethyltrichlorosilane with magnesium powder; then, modified polycarbosilane is prepared by reacting polycarbosilane with maleic anhydride; the modified polycarbosilane, polystyrene porogen, hydroxylated nano-boron nitride, and modified mullite whiskers are mixed and calcined to obtain a high-temperature resistant composite ceramic material; maleic anhydride is grafted onto polycarbosilane by hydrosilylation, and transesterification reaction is carried out with hydroxylated nano-boron nitride and modified mullite whiskers. The ester groups formed are converted into small molecule gases during calcination and escape, enriching the pore structure and improving the heat insulation performance of the high-temperature resistant composite ceramic material; at the same time, polystyrene is doped as a porogen, which decomposes into low molecular weight organic gases during sintering and escapes, further improving the heat insulation performance of the high-temperature resistant composite ceramic material; the presence of pores usually reduces the mechanical properties of ceramics. This invention enriches the pore structure while retaining high bonding strength, thereby improving the comprehensive performance of the high-temperature resistant composite ceramic material. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0030] A method for preparing a high-temperature resistant composite ceramic material, the method comprising the following preparation steps:

[0031] (1) Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:900, ultrasonically broken at 450W for 49h, centrifuged, and the supernatant was allowed to settle for 25h. The mixture was filtered through a 0.05μm filter membrane, washed three times with anhydrous ethanol, and dried at 75℃ for 25h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:350, ultrasonicated for 55min, and then the mixture was added at -79℃ in an anhydrous and oxygen-free environment. 900 times the volume of liquid nitrogen was added, and the mixture was stirred at 400 r / min for 65 min. Then, 1.3 times the mass of dispersed boron nitride nanoparticles of metallic lithium were added, and the mixture was stirred for another 2 h. Oxygen was introduced and the mixture was stirred for another 7 h. Deionized water with a mass of 2 times the mass of dispersed boron nitride nanoparticles was added at a uniform rate over 1 h, and the mixture was stirred for another 65 min. The mixture was filtered through a 0.05 μm filter membrane, washed three times each with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water, and dried at 75 °C for 25 h to obtain hydroxylated boron nitride nanoparticles.

[0032] (2) Mullite whiskers, hydroxymethyltriethoxysilane and 90% ethanol solution were mixed at a mass ratio of 1:0.04:35. Acetic acid was added to adjust the pH to 3. The mixture was stirred at 20℃ and 100 rpm for 7 h and then filtered. The mixture was washed three times with anhydrous ethanol and deionized water respectively and dried at 75℃ for 25 h to obtain modified mullite whiskers.

[0033] (3) Mix chloromethyltrichlorosilane, magnesium powder and tetrahydrofuran at a mass ratio of 1:0.4:10, stir at 35°C and 100 rpm for 2 h in a nitrogen atmosphere, heat to 55°C and keep warm for 13 h, cool to -1°C, add 0.02 times the mass of chloromethyltrichlorosilane lithium aluminum hydride, heat to 55°C and keep warm for 13 h, add 2 mol / L hydrochloric acid solution to quench, add n-hexane and deionized water, let stand for layering and filter, wash the lower layer with 4 mol / L hydrochloric acid solution 3 times, dry with anhydrous sodium sulfate and then rotary evaporate to obtain polycarbosilane; mix polycarbosilane, maleic anhydride, chloroplatinic acid and xylene at a mass ratio of 1:0.04:0.2:15, stir at 75°C and 300 rpm for 4 h in an argon atmosphere, cool naturally to room temperature and then rotary evaporate under negative pressure, grind and sieve through 40 mesh, keep warm at 95°C for 4 h to obtain modified polycarbosilane;

[0034] (4) Modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, modified mullite whiskers and anhydrous ethanol were mixed in a mass ratio of 1:0.07:0.02:0.01:1, ultrasonicated for 25 min, ball-milled at 250 r / min for 7 h, stirred in a water bath at 85 °C until viscous, dried at 75 °C for 13 h, ground and sieved through a 35 mesh, loaded into a grinding mold, heated to 1400 °C at 1 °C / min and held at 35 MPa for 65 min in a nitrogen atmosphere, cooled to room temperature with the furnace, removed and polished to obtain a high-temperature resistant composite ceramic material. Example 2:

[0035] A method for preparing a high-temperature resistant composite ceramic material, the method comprising the following preparation steps:

[0036] (1) Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:950, ultrasonically broken at 455W for 48h, centrifuged, and the supernatant was allowed to settle for 24h. The mixture was filtered through a 0.1μm filter membrane, washed four times with anhydrous ethanol, and dried at 80℃ for 24h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:400, ultrasonicated for 60min, and then added at -78℃ in an anhydrous and oxygen-free environment. 50 times the amount of liquid nitrogen was added and stirred at 500 r / min for 60 min. Then, 1.4 times the mass of dispersed boron nitride nanoparticles of metallic lithium were added and stirred for another 1.5 h. Oxygen was introduced and stirring was continued for another 6 h. Over 2 h, 3 times the mass of dispersed boron nitride nanoparticles of deionized water were added at a uniform rate and stirring was continued for another 60 min. The mixture was filtered through a 0.1 μm filter membrane and washed four times each with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water. The mixture was then dried at 80 °C for 24 h to obtain hydroxylated boron nitride nanoparticles.

[0037] (2) Mullite whiskers, hydroxymethyltriethoxysilane and 95% ethanol solution were mixed at a mass ratio of 1:0.05:40. Acetic acid was added to adjust the pH to 3.5. The mixture was stirred at 25°C and 150 rpm for 6 h and then filtered. The mixture was washed 4 times with anhydrous ethanol and deionized water respectively and dried at 80°C for 24 h to obtain modified mullite whiskers.

[0038] (3) Mix chloromethyltrichlorosilane, magnesium powder, and tetrahydrofuran at a mass ratio of 1:0.5:15. Stir at 40°C and 150 rpm for 1.5 h in a nitrogen atmosphere. Heat to 60°C and hold for 12 h. Cool to 0°C. Add 0.03 times the mass of lithium aluminum hydride of chloromethyltrichlorosilane. Heat to 60°C and hold for 12 h. Quench with 3 mol / L hydrochloric acid solution. Add n-hexane and deionized water. Let stand for separation and then filter. The mixture was filtered, and the lower layer was washed four times with 5 mol / L hydrochloric acid solution. After drying with anhydrous sodium sulfate, it was rotary evaporated to obtain polycarbosilane. Polycarbosilane, maleic anhydride, chloroplatinic acid and xylene were mixed in a mass ratio of 1:0.05:0.25:20 and stirred at 80℃ and 350 rpm for 3 h in an argon atmosphere. After naturally cooling to room temperature, it was rotary evaporated under negative pressure, ground and sieved through a 50-mesh sieve, and kept at 100℃ for 3 h to obtain modified polycarbosilane.

[0039] (4) Modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, modified mullite whiskers and anhydrous ethanol were mixed in a mass ratio of 1:0.08:0.025:0.02:1.5, ultrasonicated for 30 min, ball-milled at 300 r / min for 6 h, stirred in a water bath at 90 °C until viscous, dried at 80 °C for 12 h, ground and sieved through a 40 mesh, loaded into a grinding mold, heated to 1500 °C at 2 °C / min and held at 40 MPa for 60 min in a nitrogen atmosphere, cooled to room temperature with the furnace, removed and polished to obtain a high-temperature resistant composite ceramic material. Example 3:

[0040] A method for preparing a high-temperature resistant composite ceramic material, the method comprising the following preparation steps:

[0041] (1) Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:1100, ultrasonically crushed at 460W for 47h, centrifuged, and the supernatant was allowed to settle for 23h. The mixture was filtered through a 0.15μm filter membrane, washed 5 times with anhydrous ethanol, and dried at 85℃ for 23h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:450, ultrasonicated for 65min, and then the mixture was added at -77℃ in an anhydrous and oxygen-free environment. 1000 times the amount of liquid nitrogen was added and stirred at 600 r / min for 55 min. Then, 1.5 times the mass of dispersed boron nitride nanoparticles of metallic lithium were added and stirred for 1 h. Oxygen was introduced and stirring was continued for 5 h. Deionized water with 4 times the mass of dispersed boron nitride nanoparticles was added at a uniform rate over 3 h and stirred for 55 min. The mixture was filtered through a 0.15 μm filter membrane and washed 5 times each with tetrahydrofuran, chloroform, anhydrous ethanol and deionized water. The mixture was dried at 85 °C for 23 h to obtain hydroxylated boron nitride nanoparticles.

[0042] (2) Mullite whiskers, hydroxymethyltriethoxysilane and 100% ethanol solution were mixed at a mass ratio of 1:0.06:45. Acetic acid was added to adjust the pH to 4. The mixture was stirred at 30℃ and 200rpm for 5h and then filtered. The mixture was washed 5 times with anhydrous ethanol and deionized water respectively and dried at 85℃ for 23h to obtain modified mullite whiskers.

[0043] (3) Mix chloromethyltrichlorosilane, magnesium powder and tetrahydrofuran at a mass ratio of 1:0.6:20, stir at 45°C and 200 rpm for 1 h in a nitrogen atmosphere, heat to 65°C and hold for 11 h, cool to 1°C, add 0.04 times the mass of chloromethyltrichlorosilane lithium aluminum hydride, heat to 65°C and hold for 11 h, add 4 mol / L hydrochloric acid solution to quench, add n-hexane and deionized water, let stand for separation and filter, wash the lower layer with 6 mol / L hydrochloric acid solution 5 times, dry with anhydrous sodium sulfate and then rotary evaporate to obtain polycarbosilane; mix polycarbosilane, maleic anhydride, chloroplatinic acid and xylene at a mass ratio of 1:0.06:0.3:25, stir at 85°C and 400 rpm for 2 h in an argon atmosphere, cool naturally to room temperature and then rotary evaporate under negative pressure, grind and sieve through 60 mesh, heat at 105°C for 2 h to obtain modified polycarbosilane;

[0044] (4) Modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, modified mullite whiskers and anhydrous ethanol were mixed in a mass ratio of 1:0.09:0.03:0.03:2, ultrasonicated for 35 min, ball-milled at 350 r / min for 5 h, stirred in a water bath at 95 °C until viscous, dried at 85 °C for 11 h, ground and sieved through a 45 mesh, loaded into a grinding mold, heated to 1600 °C at 3 °C / min and held at 45 MPa for 55 min in a nitrogen atmosphere, cooled to room temperature with the furnace, removed and polished to obtain a high-temperature resistant composite ceramic material.

[0045] Comparative Example 1:

[0046] A method for preparing a high-temperature resistant composite ceramic material, the method comprising the following preparation steps:

[0047] (1) Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:950, ultrasonically broken at 455W for 48h, centrifuged, and the supernatant was allowed to settle for 24h. The mixture was filtered through a 0.1μm filter membrane, washed four times with anhydrous ethanol, and dried at 80℃ for 24h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:400, ultrasonicated for 60min, and then added at -78℃ in an anhydrous and oxygen-free environment. 50 times the amount of liquid nitrogen was added and stirred at 500 r / min for 60 min. Then, 1.4 times the mass of dispersed boron nitride nanoparticles of metallic lithium were added and stirred for another 1.5 h. Oxygen was introduced and stirring was continued for another 6 h. Over 2 h, 3 times the mass of dispersed boron nitride nanoparticles of deionized water were added at a uniform rate and stirring was continued for another 60 min. The mixture was filtered through a 0.1 μm filter membrane and washed four times each with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water. The mixture was then dried at 80 °C for 24 h to obtain hydroxylated boron nitride nanoparticles.

[0048] (2) Mix chloromethyltrichlorosilane, magnesium powder, and tetrahydrofuran at a mass ratio of 1:0.5:15. Stir at 40°C and 150 rpm for 1.5 h in a nitrogen atmosphere. Heat to 60°C and hold for 12 h. Cool to 0°C. Add lithium aluminum hydride at 0.03 times the mass of chloromethyltrichlorosilane. Heat to 60°C and hold for 12 h. Quench with 3 mol / L hydrochloric acid solution. Add n-hexane and deionized water. Let stand for separation and then filter. The mixture was filtered, and the lower layer was washed four times with 5 mol / L hydrochloric acid solution. After drying with anhydrous sodium sulfate, it was rotary evaporated to obtain polycarbosilane. Polycarbosilane, maleic anhydride, chloroplatinic acid and xylene were mixed in a mass ratio of 1:0.05:0.25:20 and stirred at 80℃ and 350 rpm for 3 h in an argon atmosphere. After naturally cooling to room temperature, it was rotary evaporated under negative pressure, ground and sieved through a 50-mesh sieve, and kept at 100℃ for 3 h to obtain modified polycarbosilane.

[0049] (3) Modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, mullite whiskers and anhydrous ethanol were mixed in a mass ratio of 1:0.08:0.025:0.02:1.5, sonicated for 30 min, ball-milled at 300 r / min for 6 h, stirred in a water bath at 90 °C until viscous, dried at 80 °C for 12 h, ground and sieved through a 40 mesh, loaded into a grinding mold, heated to 1500 °C at 2 °C / min and held at 40 MPa for 60 min in a nitrogen atmosphere, cooled to room temperature with the furnace, removed and polished to obtain a high-temperature resistant composite ceramic material.

[0050] Comparative Example 2:

[0051] A method for preparing a high-temperature resistant composite ceramic material, the method comprising the following preparation steps:

[0052] (1) Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:950, ultrasonically broken at 455W for 48h, centrifuged, and the supernatant was allowed to settle for 24h. The mixture was filtered through a 0.1μm filter membrane, washed four times with anhydrous ethanol, and dried at 80℃ for 24h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:400, ultrasonicated for 60min, and then added at -78℃ in an anhydrous and oxygen-free environment. 50 times the amount of liquid nitrogen was added and stirred at 500 r / min for 60 min. Then, 1.4 times the mass of dispersed boron nitride nanoparticles of metallic lithium were added and stirred for another 1.5 h. Oxygen was introduced and stirring was continued for another 6 h. Over 2 h, 3 times the mass of dispersed boron nitride nanoparticles of deionized water were added at a uniform rate and stirring was continued for another 60 min. The mixture was filtered through a 0.1 μm filter membrane and washed four times each with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water. The mixture was then dried at 80 °C for 24 h to obtain hydroxylated boron nitride nanoparticles.

[0053] (2) Mullite whiskers, hydroxymethyltriethoxysilane and 95% ethanol solution were mixed at a mass ratio of 1:0.05:40. Acetic acid was added to adjust the pH to 3.5. The mixture was stirred at 25°C and 150 rpm for 6 h and then filtered. The mixture was washed 4 times with anhydrous ethanol and deionized water respectively and dried at 80°C for 24 h to obtain modified mullite whiskers.

[0054] (3) Mix chloromethyltrichlorosilane, magnesium powder and tetrahydrofuran at a mass ratio of 1:0.5:15, stir at 40°C and 150 rpm for 1.5 h in a nitrogen atmosphere, heat to 60°C and keep warm for 12 h, cool down to 0°C, add 0.03 times the mass of chloromethyltrichlorosilane of lithium aluminum hydride, heat to 60°C and keep warm for 12 h, add 3 mol / L hydrochloric acid solution to quench, add n-hexane and deionized water, let stand and separate into layers, filter, wash the lower layer with 5 mol / L hydrochloric acid solution 4 times, dry with anhydrous sodium sulfate and evaporate by rotary evaporation to obtain polycarbosilane;

[0055] (4) Polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, modified mullite whiskers and anhydrous ethanol were mixed in a mass ratio of 1:0.08:0.025:0.02:1.5, ultrasonicated for 30 min, ball-milled at 300 r / min for 6 h, stirred in a water bath at 90 °C until viscous, dried at 80 °C for 12 h, ground and sieved through a 40 mesh, loaded into a grinding mold, heated to 1500 °C at 2 °C / min and held at 40 MPa for 60 min in a nitrogen atmosphere, cooled to room temperature with the furnace, removed and polished to obtain a high-temperature resistant composite ceramic material.

[0056] Comparative Example 3:

[0057] A method for preparing a high-temperature resistant composite ceramic material, the method comprising the following preparation steps:

[0058] (1) Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:950, ultrasonically broken at 455W for 48h, centrifuged, and the supernatant was allowed to settle for 24h. The mixture was filtered through a 0.1μm filter membrane, washed four times with anhydrous ethanol, and dried at 80℃ for 24h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:400, ultrasonicated for 60min, and then added at -78℃ in an anhydrous and oxygen-free environment. 50 times the amount of liquid nitrogen was added and stirred at 500 r / min for 60 min. Then, 1.4 times the mass of dispersed boron nitride nanoparticles of metallic lithium were added and stirred for another 1.5 h. Oxygen was introduced and stirring was continued for another 6 h. Over 2 h, 3 times the mass of dispersed boron nitride nanoparticles of deionized water were added at a uniform rate and stirring was continued for another 60 min. The mixture was filtered through a 0.1 μm filter membrane and washed four times each with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water. The mixture was then dried at 80 °C for 24 h to obtain hydroxylated boron nitride nanoparticles.

[0059] (2) Mix chloromethyltrichlorosilane, magnesium powder and tetrahydrofuran at a mass ratio of 1:0.5:15, stir at 40°C and 150 rpm for 1.5 h in a nitrogen atmosphere, heat to 60°C and keep warm for 12 h, cool to 0°C, add 0.03 times the mass of chloromethyltrichlorosilane of lithium aluminum hydride, heat to 60°C and keep warm for 12 h, add 3 mol / L hydrochloric acid solution to quench, add n-hexane and deionized water, let stand and separate into layers, filter, wash the lower layer with 5 mol / L hydrochloric acid solution 4 times, dry with anhydrous sodium sulfate and evaporate by rotary evaporation to obtain polycarbosilane;

[0060] (4) Mix polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, mullite whiskers and anhydrous ethanol in a mass ratio of 1:0.08:0.025:0.02:1.5, sonicate for 30 min, ball mill at 300 r / min for 6 h, stir in a 90℃ water bath until viscous, dry at 80℃ for 12 h, grind and sieve through 40 mesh, load into a grinding mold, heat to 1500℃ at 2℃ / min and hold at 40MPa for 60 min in a nitrogen atmosphere, cool to room temperature with the furnace, take out and grind and polish to obtain high temperature resistant composite ceramic material.

[0061] Test case

[0062] 1. High temperature resistance

[0063] Test method: 10mg samples of the high-temperature resistant composite ceramic materials obtained in each example and the comparative example were weighed and measured using a TGA / DSC thermogravimetric analyzer manufactured by Mettler Toledo, Switzerland. The weight loss rate was measured after heating to 1200℃ for 1h in an argon atmosphere at a heating rate of 5℃ / min.

[0064] 2. Mechanical properties

[0065] Test method: The high-temperature resistant composite ceramic materials obtained in each embodiment and the comparative example were tested according to GB / T1964 using a HY-0380 universal mechanical testing instrument from Shanghai Hengyi Precision Instrument Co., Ltd. The compressive strength was calculated as the failure load / the area under stress.

[0066] 3. Thermal insulation

[0067] Test method: The high-temperature resistant composite ceramic materials obtained in each embodiment and the comparative example were measured according to GB / T25995 using an AuY120 electronic analytical balance manufactured by Shimadzu Corporation of Japan. The porosity was calculated as (wet weight - dry weight) / (wet weight - buoyant weight) * 100%.

[0068] Table 1 below shows the analysis results of the high temperature resistance, heat insulation and mechanical properties of the high temperature resistant composite ceramic materials of Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0069] Table 1

[0070] weight loss % Flexural strength MPa Porosity % Example 1 0.63 38.8 45.6 Example 2 0.61 39.4 45.8 Example 3 0.69 38.2 45.5 Comparative Example 1 0.71 39.6 39.3 Comparative Example 2 0.69 41.2 21.7 Comparative Example 3 0.72 40.9 18.4

[0071] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-3 in Table 1 reveals that the high-temperature resistant composite ceramic material prepared by the present invention has good high-temperature resistance, heat insulation and mechanical properties.

[0072] By comparing the thermal weight loss rates of Examples 1, 2, and 3 with those of Comparative Examples 1, 2, and 3, it is demonstrated that the high-temperature resistant composite ceramic material prepared in this invention has good high-temperature resistance.

[0073] By comparison, Examples 1, 2, and 3 showed lower flexural strength and higher porosity compared to Comparative Example 1, indicating that mullite whiskers have good grain boundary bonding ability. Using mullite whiskers as a reinforcing phase, they play a "bridging" role when the material is under stress, increasing the difficulty of crack propagation and improving the mechanical properties of high-temperature resistant composite ceramic materials. At the same time, maleic anhydride was grafted onto polycarbosilane through hydrosilylation, and then transesterified with modified mullite whiskers. During calcination, the ester groups were converted into small molecule gases that escaped, forming a porous structure and improving the thermal insulation performance of high-temperature resistant composite ceramic materials.

[0074] By comparison, Examples 1, 2, and 3 showed lower flexural strength and higher porosity compared to Comparative Example 2, indicating that the grafting of maleic anhydride onto polycarbosilane via hydrosilylation, followed by transesterification with hydroxylated boron nitride nanoparticles and modified mullite whiskers, resulted in the formation of ester groups that were converted into small molecule gases during calcination, enriching the pore structure and improving the thermal insulation performance of the high-temperature resistant composite ceramic material.

[0075] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant composite ceramic material, characterized in that, The high-temperature resistant composite ceramic material is obtained by calcining a mixture of modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, and modified mullite whiskers. The specific preparation process of the modified polycarbosilane is as follows: Chloromethyltrichlorosilane, magnesium powder, and tetrahydrofuran were mixed at a mass ratio of 1:(0.4~0.6):(10~20). The mixture was stirred for 1~2 hours at 35~45℃ and 100~200 rpm under a nitrogen atmosphere. The temperature was then raised to 55~65℃ and held for 11~13 hours. The mixture was then cooled to -1~1℃, and 0.02~0.04 times the mass of lithium aluminum hydride (by weight of chloromethyltrichlorosilane) was added. The temperature was raised to 55~65℃ and held for 11~13 hours. The mixture was quenched with hydrochloric acid solution, and then hexane and deionized water were added. After standing and separating into layers, the mixture was filtered. The lower layer was washed 3-5 times with 4-6 mol / L hydrochloric acid solution, dried with anhydrous sodium sulfate, and then rotary evaporated to obtain polycarbosilane. Polycarbosilane, maleic anhydride, chloroplatinic acid and xylene were mixed in a mass ratio of 1:(0.04-0.06):(0.2-0.3):(15-25), stirred in an argon atmosphere at 75-85℃ and 300-400 rpm for 2-4 hours, cooled naturally to room temperature, and then rotary evaporated under negative pressure. The mixture was ground and sieved, and kept at 95-105℃ for 2-4 hours to obtain modified polycarbosilane. The specific preparation process of the hydroxylated boron nitride nanoparticles is as follows: Boron nitride nanosheets and N-methylpyrrolidone were mixed at a mass ratio of 1:(900~1100), ultrasonically disrupted for 47~49 h, centrifuged, and the supernatant was allowed to settle. The mixture was filtered through a 0.05~0.15 μm filter membrane, washed 3~5 times with anhydrous ethanol, and dried at 75~85℃ for 23~25 h to obtain dispersed boron nitride nanosheets. The dispersed boron nitride nanosheets and tetrahydrofuran were mixed at a mass ratio of 1:(350~450), ultrasonicated for 55~65 min, and then, under anhydrous and oxygen-free conditions at -79~-77℃, liquid... Nitrogen was stirred at 400-600 r / min for 55-65 min, and lithium metal particles with a mass of 1.3-1.5 times that of dispersed boron nitride nanoparticles were added. Stirring was continued for 1-2 h, oxygen was introduced and stirring was continued for 5-7 h, and deionized water with a mass of 2-4 times that of dispersed boron nitride nanoparticles was added at a uniform rate over 1-3 h. Stirring was continued for 55-65 min, filtered through a filter membrane, and washed 3-5 times with tetrahydrofuran, chloroform, anhydrous ethanol and deionized water respectively. The mixture was dried at 75-85℃ for 23-25 ​​h to obtain hydroxylated boron nitride nanoparticles. The modified mullite whiskers are obtained by reacting mullite whiskers with hydroxymethyltriethoxysilane.

2. The method for preparing a high-temperature resistant composite ceramic material according to claim 1, characterized in that, The preparation steps include the following: (1) Mix boron nitride nanosheets and N-methylpyrrolidone at a mass ratio of 1:(900~1100), sonicate for 47~49h, centrifuge, collect the supernatant and let it settle, filter with a 0.05~0.15μm filter membrane, wash 3~5 times with anhydrous ethanol, and dry at 75~85℃ for 23~25h to obtain dispersed boron nitride nanosheets; mix dispersed boron nitride nanosheets and tetrahydrofuran at a mass ratio of 1:(350~450), sonicate for 55~65min, and add to anhydrous and oxygen-free environment at -79~-77℃. Liquid nitrogen was used to stir the mixture at 400-600 r / min for 55-65 min. Then, lithium metal particles with a mass of 1.3-1.5 times that of dispersed boron nitride nanoparticles were added and stirred for 1-2 h. Oxygen was introduced and stirring was continued for 5-7 h. Deionized water with a mass of 2-4 times that of dispersed boron nitride nanoparticles was added at a uniform rate over 1-3 h and stirring was continued for 55-65 min. The mixture was filtered through a filter membrane and washed 3-5 times with tetrahydrofuran, chloroform, anhydrous ethanol, and deionized water, respectively. The mixture was then dried at 75-85℃ for 23-25 ​​h to obtain hydroxylated boron nitride nanoparticles. (2) Mix mullite whiskers, hydroxymethyltriethoxysilane and ethanol solution at a mass ratio of 1:(0.04~0.06):(35~45), add acetic acid to adjust the pH to 3~4, stir at 20~30℃ and 100~200rpm for 5~7h, filter, wash with anhydrous ethanol and deionized water 3~5 times respectively, and dry at 75~85℃ for 23~25h to obtain modified mullite whiskers; (3) Mix chloromethyltrichlorosilane, magnesium powder and tetrahydrofuran at a mass ratio of 1:(0.4~0.6):(10~20), stir for 1~2 hours at 35~45℃ and 100~200 rpm in a nitrogen atmosphere, heat to 55~65℃ and keep at that temperature for 11~13 hours, cool to -1~1℃, add 0.02~0.04 times the mass of chloromethyltrichlorosilane of lithium aluminum hydride, heat to 55~65℃ and keep at that temperature for 11~13 hours, quench with hydrochloric acid solution, add n-hexane and deionized water, let stand and separate into layers, and then filter. The lower layer was washed 3-5 times with 4-6 mol / L hydrochloric acid solution, dried with anhydrous sodium sulfate, and then rotary evaporated to obtain polycarbosilane. Polycarbosilane, maleic anhydride, chloroplatinic acid and xylene were mixed in a mass ratio of 1:(0.04-0.06):(0.2-0.3):(15-25), stirred in an argon atmosphere at 75-85℃ and 300-400 rpm for 2-4 hours, cooled naturally to room temperature, and then rotary evaporated under negative pressure. The mixture was ground and sieved, and kept at 95-105℃ for 2-4 hours to obtain modified polycarbosilane. (4) Modified polycarbosilane, polystyrene pore-forming agent, hydroxylated nano boron nitride, modified mullite whiskers and anhydrous ethanol are mixed in a mass ratio of 1:(0.07~0.09):(0.02~0.03):(0.01~0.03):(1~2), ultrasonicated for 25~35 min, ball-milled at 250~350 r / min for 5~7 h, stirred in a water bath at 85~95℃ until viscous, dried at 75~85℃ for 11~13 h, ground and sieved through a 35~45 mesh, loaded into a grinding mold, heated to 1400~1600℃ at 1~3℃ / min and held at 35~45MPa for 55~65 min in a nitrogen atmosphere, cooled to room temperature with the furnace, taken out and polished to obtain high-temperature resistant composite ceramic material.

3. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The ultrasonic fragmentation conditions in step (1) are 450~460W.

4. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The settling time in step (1) is 23~25h.

5. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The amount of liquid nitrogen added in step (1) is 900 to 1000 times the mass of the dispersed nano boron nitride.

6. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The filter membrane size in step (1) is 0.05~0.15μm.

7. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The ethanol solution in step (2) has a mass fraction of 90% to 100%.

8. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The concentration of the hydrochloric acid solution used for quenching in step (3) is 2~4 mol / L.

9. The method for preparing a high-temperature resistant composite ceramic material according to claim 2, characterized in that, The grinding and sieving particle size in step (3) is 40~60 mesh.