Thermal insulation pressure-resistant ceramic material and method for manufacturing the same

Abstract

This invention discloses a thermally insulating and pressure-resistant ceramic material and its preparation method, belonging to the field of ceramic materials technology. The process involves mixing and stirring phosphoric acid, urea, and hollow alumina microspheres to obtain acidified and activated microspheres; mixing and stirring the acidified and activated microspheres, L-dopamine, and tannic acid to obtain cross-linked coated microspheres; mixing and stirring cerium nitrate hexahydrate and cross-linked coated microspheres to obtain modified alumina microspheres; mixing and stirring alumina ceramic powder, modified alumina microspheres, and modified silicon carbide to obtain a pre-dispersion system; mixing and stirring polyvinyl alcohol and polyethylene glycol 400 to obtain a molding agent; mixing the molding agent and the pre-dispersion system to obtain a paste-like mixture; sequentially kneading and aging the paste-like mixture to obtain aged clay; pressing the aged clay to obtain a green body; and sequentially drying and sintering the green body to obtain the thermally insulating and pressure-resistant ceramic material. Through a synergistic reinforcement mechanism, the compressive strength and high-temperature stability are significantly improved while maintaining a low thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a heat-insulating and pressure-resistant ceramic material and its preparation method. Background Technology

[0002] While traditional ceramic materials possess excellent high-temperature resistance, they often exhibit brittleness and insufficient thermal shock resistance in practical applications. To improve thermal insulation performance, existing technologies often introduce lightweight insulating phases such as aerogels, hollow microspheres, or porous structures. However, these strategies typically lead to a decrease in the overall density of the material, thereby weakening its mechanical strength and compressive strength. Furthermore, most composite ceramics use physical blending to bond the insulating phase to the matrix, resulting in weak interfacial bonding. Under high-temperature or dynamic load conditions, problems such as debonding and cracking easily occur, limiting the application of materials in scenarios requiring both high thermal insulation and high compressive strength.

[0003] Patent application CN112897885A discloses a high-purity silica glass-ceramic material and its preparation method. This material is produced by mixing three silica powders with different particle size distributions and then casting them into a slurry, resulting in a product with excellent thermal shock resistance and insulation properties. This approach balances thermal insulation and structural stability to some extent, but it primarily relies on a single silica system and does not introduce an effective reinforcing phase or interface control mechanism. Therefore, there is room for improvement in compressive strength and structural load-bearing capacity.

[0004] Patent application CN115521071A discloses a dry granule and ceramic composite high-temperature wear-resistant material, which strengthens the glaze surface by combining high-temperature wear-resistant particles with a frit and utilizing the "mixed but not melted" property of the wear-resistant particles. Although this technology improves surface hardness and wear resistance, its design focuses on optimizing the glaze performance and does not systematically construct the overall material's thermal insulation-compression resistance synergy. Furthermore, the frit system used has strong fluidity at high temperatures, which is not conducive to forming a stable porous thermal insulation structure.

[0005] Existing technologies still have limitations in synergistically improving thermal insulation and compressive strength: on the one hand, while simply introducing porous or lightweight phases can improve thermal insulation, it negatively impacts compressive strength; on the other hand, existing composite strategies lack sufficient control over interfacial bonding, failing to effectively construct a microstructure that combines a high-strength framework with an efficient thermal insulation network. Therefore, there is an urgent need to develop a novel ceramic material system and its preparation method to achieve simultaneous optimization of thermal insulation and compressive strength through component design and process control. Summary of the Invention

[0006] This invention provides a thermally insulating and compressive-resistant ceramic material and its preparation method. The ceramic material is prepared by introducing hollow alumina microspheres and silicon carbide nanowires with multi-level interface functionalization treatment into an alumina matrix. Through surface chemical modification, coordination crosslinking and high-temperature in-situ ceramic phase transformation mechanism, a three-dimensional interlocking network structure with high porosity and strong interface is formed in the alumina matrix. While maintaining ultra-low thermal conductivity, the compressive strength and structural reliability are improved, solving the problem of significant decrease in mechanical properties of traditional ceramics after the introduction of the thermally insulating phase. Specifically, the technical solution of the present invention includes the following: a method for preparing a heat-insulating and pressure-resistant ceramic material, the preparation method comprising the following steps: mixing and stirring phosphoric acid, urea and hollow alumina microspheres to obtain acidified and activated microspheres; mixing and stirring the acidified and activated microspheres, L-dopaamine and tannic acid to obtain cross-linked coated microspheres; mixing and stirring cerium nitrate hexahydrate and cross-linked coated microspheres to obtain modified alumina microspheres; mixing and stirring alumina ceramic powder, modified alumina microspheres and modified silicon carbide to obtain a pre-dispersion system; mixing and stirring polyvinyl alcohol and polyethylene glycol 400 to obtain a molding agent; mixing and stirring the molding agent and the pre-dispersion system to obtain a paste mixture; subjecting the paste mixture to kneading and aging to obtain aged clay; pressing the aged clay to obtain a green body; and subjecting the green body to drying and sintering to obtain a heat-insulating and pressure-resistant ceramic material.

[0007] Furthermore, the phosphoric acid is a 5 wt% phosphoric acid solution.

[0008] Furthermore, the hollow alumina microspheres have a particle size of 0.2~0.4 mm and a wall thickness of 10~20 μm.

[0009] Furthermore, the weight ratio of phosphoric acid, urea and hollow alumina microspheres is (50~80):(1~3):10.

[0010] Furthermore, the conditions for the mixing and stirring reaction of phosphoric acid, urea and hollow alumina microspheres include a reaction temperature of 120~130℃ and a reaction time of 1.5~2.5h; the hydroxyl groups on the surface of the hollow alumina microspheres react with phosphoric acid to form surface phosphate ester bonds, while the weak acidity of phosphoric acid etches the surface of the microspheres to form a micron-scale rough structure.

[0011] Furthermore, the weight ratio of the acidified activated microspheres, L-dopamine, and tannic acid is 10:(0.2~0.3):(0.1~0.15).

[0012] Furthermore, the conditions for the acidified activated microspheres, L-dopamine, and tannic acid mixed and stirred include a reaction temperature of 25°C and a reaction time of 10-14 h; dopamine undergoes a self-polymerization reaction under weakly alkaline conditions to form a polydopamine film, and the phenolic hydroxyl groups in tannic acid and the amino groups in polydopamine form a cross-linked network coating through Schiff base reaction and hydrogen bonding.

[0013] Furthermore, the weight ratio of cerium nitrate hexahydrate to cross-linked coated microspheres is (7~9):10.

[0014] Furthermore, the conditions for the mixing and stirring reaction of the cerium nitrate hexahydrate and the cross-linked coated microspheres include a reaction temperature of 50-70°C and a reaction time of 3-5 hours; the Ce dissociated from the cerium nitrate... 3+ Modified alumina microspheres were obtained by coordination with the tannic acid phenolic hydroxyl groups and oxygen atoms in the phosphate ester bonds of the cross-linked coated microsphere surface coating. Subsequent high-temperature sintering carbonized the organic matter, resulting in Ce... 3+ It will also oxidize into a CeO2 ceramic phase, which will firmly lock the interface and prevent it from failing.

[0015] Furthermore, the preparation method of the modified silicon carbide includes the following steps: mixing hydrofluoric acid and nitric acid to obtain an acidification solution; mixing silicon carbide nanowires and the acidification solution and stirring to react to obtain roughened silicon carbide; mixing roughened silicon carbide, L-dopamine and phytic acid and stirring to react to obtain composite layer grafted silicon carbide; mixing lanthanum nitrate hexahydrate and composite layer grafted silicon carbide and stirring to react to obtain modified silicon carbide.

[0016] Furthermore, the hydrofluoric acid is a 40wt% hydrofluoric acid solution.

[0017] Furthermore, the nitric acid is a 65wt% nitric acid solution.

[0018] Furthermore, the volume ratio of hydrofluoric acid to nitric acid is 3:1.

[0019] Furthermore, the silicon carbide nanowires have a diameter of 100~200nm and a length of 50~100μm.

[0020] Furthermore, the weight ratio of the silicon carbide nanowires to the acidification solution is (9~11):50.

[0021] Furthermore, the conditions for the mixing and stirring reaction of the silicon carbide nanowires and the acidification solution include a reaction temperature of 80~100℃ and a reaction time of 30~50min; hydrofluoric acid selectively etches the oxide layer on the surface of the silicon carbide nanowires, forming a trench structure after etching.

[0022] Furthermore, the weight ratio of the roughened silicon carbide, L-dopamine, and phytic acid is 10:(0.3~0.4):(0.2~0.3).

[0023] Furthermore, the conditions for the mixed stirring reaction of roughened silicon carbide, L-dopamine, and phytic acid include a reaction temperature of 60-70°C and a reaction time of 12-18 hours. L-dopamine first self-polymerizes on the surface of roughened silicon carbide to form a polydopamine film. The phosphate groups in phytic acid combine with the amino groups in polydopamine through neutralization reaction and electrostatic interaction to construct a polydopamine-phytic acid composite graft layer on the surface of roughened silicon carbide. This composite layer retains the adhesiveness of polydopamine and enhances its coordination ability with subsequent rare earth ions by means of the polyphosphate groups of phytic acid.

[0024] Furthermore, the weight ratio of lanthanum nitrate hexahydrate to composite layer grafted silicon carbide is (4~6):10.

[0025] Furthermore, the conditions for the mixed and stirred reaction of lanthanum nitrate hexahydrate and composite layer grafted silicon carbide include a reaction temperature of 50-60°C and a reaction time of 4-6 hours.

[0026] Furthermore, the weight ratio of the alumina ceramic powder, modified alumina microspheres, and modified silicon carbide is (55~65):(20~30):(10~15).

[0027] Furthermore, the mixing conditions for the alumina ceramic powder, modified alumina microspheres, and modified silicon carbide include a stirring speed of 450 r / min and a stirring time of 40-60 min.

[0028] Furthermore, the weight ratio of polyvinyl alcohol to polyethylene glycol 400 is (3~5):(0.5~1).

[0029] Furthermore, the conditions for mixing and stirring the polyvinyl alcohol and polyethylene glycol 400 include a stirring speed of 200 r / min, a stirring temperature of 80°C, and a stirring time of 30 min.

[0030] Furthermore, the weight ratio of the molding agent to the pre-dispersed system is (80~100):100.

[0031] Furthermore, the mixing conditions for the molding agent and the pre-dispersed system include a mixing time of 2.5 to 3.5 hours.

[0032] Furthermore, the conditions for kneading the mud include a vacuum of 8-10 Pa, a time of 10 min, and a temperature of 50-60 °C.

[0033] Furthermore, the aging conditions include an aging temperature of 25°C and an aging time of 36 hours.

[0034] Furthermore, the pressing conditions include a pressure of 60-80 MPa and a holding time of 10-15 min.

[0035] Furthermore, the drying conditions include drying at 40°C for 12 hours, then raising the temperature to 60°C for 12 hours, and then raising the temperature to 80°C for 24 hours.

[0036] Furthermore, the sintering conditions include heating to 600°C at a rate of 5°C / min and holding for 2 hours, then heating to 1200°C at a rate of 5°C / min and holding for 1 to 1.5 hours, and then heating to 1500 to 1580°C at a rate of 3°C / min and holding for 2 to 3 hours.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, the modified alumina microspheres are modified through a multi-step process of activation, coating, and coordination to solve the problems of weak interfacial bonding and mutual repulsion between thermal insulation and strength in traditional ceramic materials. Active functional groups and a rough surface are constructed through acidification activation, and interfacial compatibility is enhanced through dopamine-tannic acid crosslinking coating. Cerium nitrate is then used for coordination curing, and sintering forms a high-temperature resistant ceramic phase, locking the interfacial bonding sites. Its hollow structure retains its high-efficiency thermal insulation function. Through a gradient modification of "phosphoric acid etching for pore formation - biomass polyphenol crosslinking - cerium ion coordination," the organic coordination layer on the surface is transformed in situ into a nano-ceramic pinning layer mainly composed of cerium dioxide and cerium aluminate during sintering. This pinning layer not only physically fills the micro-rough structure on the surface of the microspheres but also chemically locks the interface through Al-O-Ce-O-Al bonding, effectively solving the problems of easy collapse and interface debonding under pressure in hollow structures. However, the hollow nature of these microspheres has inherent mechanical shortcomings; they are prone to structural collapse under stress, limiting the improvement of the overall mechanical properties of the material. Modified silicon carbide nanowires were constructed using an acid etching-phytic acid / dopamine grafting-lanthanum ion coordination process to create a lanthanum phosphate-rich interfacial transition layer. Utilizing the high-temperature stability and chemical compatibility of rare-earth phosphates, the wettability between silicon carbide and alumina substrates was significantly improved, preventing oxidation damage to the nanowires at high temperatures. The modified silicon carbide nanowires were further modified through etching, grafting, and coordination to form a three-dimensional reinforcing framework. Etching broke up agglomerates, composite layer grafting created interfacial bridging sites, and lanthanum nitrate coordination strengthened the framework before sintering to form a high-temperature resistant ceramic phase. This structural support specifically compensated for the mechanical defects of the modified alumina microspheres and achieved interfacial fusion with the microspheres and ceramic matrix. (2) In this invention, the hollow heat insulation unit of the modified alumina microspheres and the three-dimensional reinforcing skeleton of the modified silicon carbide nanowires interpenetrate to form a heat insulation-support complementary structure; the composite ceramic phase generated at the interface eliminates gaps and achieves chemical bonding, thus solving the problem of interface debonding in traditional blending systems; in terms of function, the heat insulation properties and the reinforcement effect complement each other, and the heat insulation and pressure resistance ceramic material is ultimately enhanced by the interface effect between components and the synergy of structural functions through raw material modification optimization, precise dispersion molding and gradient sintering process. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0040] Preparation Example 1 The preparation method of modified silicon carbide includes the following steps: 40 wt% hydrofluoric acid solution and 65 wt% nitric acid solution are mixed at a volume ratio of 3:1 to obtain an acidification solution. Nine parts by weight of silicon carbide nanowires (100 nm in diameter and 50 μm in length) are dispersed in 50 parts by weight of the acidification solution. The mixture is heated to 80 °C and stirred at 150 r / min for 30 min. After the reaction, 500 parts by weight of deionized water are added to dilute the reaction solution and terminate the etching reaction. The precipitate is then collected by centrifugation at 10000 r / min for 15 min, washed six times with deionized water, and vacuum dried at 60 °C for 8 h to obtain roughened silicon carbide. Ten parts by weight of the roughened silicon carbide are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 500 W for 15 min. After stirring, 0.3 parts by weight of L-dopamine were added, and the mixture was stirred at 400 r / min for 2 h. Then, 0.2 parts by weight of phytic acid were added, and the temperature was raised to 60 °C and the reaction was stirred for another 12 h. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 min, washed 4 times with deionized water, and dried under vacuum at 80 °C for 8 h to obtain composite layer grafted silicon carbide. 4 parts by weight of lanthanum nitrate hexahydrate and 10 parts by weight of composite layer grafted silicon carbide were dispersed in 50 parts by weight of deionized water, sonicated at 300 W for 10 min, and then the temperature was raised to 50 °C and stirred at 300 r / min for 4 h. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 min, washed 4 times with deionized water, and dried under vacuum at 100 °C for 7 h to obtain modified silicon carbide.

[0041] Preparation Example 2 The preparation method of modified silicon carbide includes the following steps: 40 wt% hydrofluoric acid solution and 65 wt% nitric acid solution are mixed at a volume ratio of 3:1 to obtain an acidification solution. 9.5 parts by weight of silicon carbide nanowires (100 nm in diameter and 50 μm in length) are dispersed in 50 parts by weight of the acidification solution. The mixture is heated to 85 °C and stirred at 150 r / min for 35 min. After the reaction, 500 parts by weight of deionized water are added to dilute the reaction solution and terminate the etching reaction. The precipitate is then collected by centrifugation at 10000 r / min for 15 min, washed 6 times with deionized water, and vacuum dried at 60 °C for 8 h to obtain roughened silicon carbide. 10 parts by weight of the roughened silicon carbide are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 500 W for 15 min. Add 0.32 parts by weight of L-dopamine, stir at 400 r / min for 2.5 h, then add 0.22 parts by weight of phytic acid, heat to 62 °C and continue stirring for 13 h. After the reaction is complete, centrifuge at 10000 r / min for 20 min to collect the precipitate, wash with deionized water 4 times, and vacuum dry at 80 °C for 8 h to obtain composite layer grafted silicon carbide; disperse 4.5 parts by weight of lanthanum nitrate hexahydrate and 10 parts by weight of composite layer grafted silicon carbide in 50 parts by weight of deionized water, sonicate at 300 W for 10 min, heat to 52 °C, stir at 300 r / min for 4.5 h, after the reaction is complete, centrifuge at 10000 r / min for 20 min to collect the precipitate, wash with deionized water 4 times, and vacuum dry at 100 °C for 7 h to obtain modified silicon carbide.

[0042] Preparation Example 3 The preparation method of modified silicon carbide includes the following steps: 40 wt% hydrofluoric acid solution and 65 wt% nitric acid solution are mixed at a volume ratio of 3:1 to obtain an acidification solution. 10 parts by weight of silicon carbide nanowires (100 nm in diameter and 50 μm in length) are dispersed in 50 parts by weight of the acidification solution. The mixture is heated to 90 °C and stirred at 150 r / min for 40 min. After the reaction, 500 parts by weight of deionized water are added to dilute the reaction solution and terminate the etching reaction. The precipitate is then collected by centrifugation at 10000 r / min for 15 min, washed 6 times with deionized water, and vacuum dried at 60 °C for 8 h to obtain roughened silicon carbide. 10 parts by weight of the roughened silicon carbide are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 500 W for 15 min. After stirring for 3 hours, 0.35 parts by weight of L-dopamine were added, and the mixture was stirred at 400 r / min for 3 hours. Then, 0.25 parts by weight of phytic acid were added, and the temperature was raised to 65℃ and the reaction was stirred for another 16 hours. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 minutes, washed four times with deionized water, and dried under vacuum at 80℃ for 8 hours to obtain composite-layer grafted silicon carbide. 5 parts by weight of lanthanum nitrate hexahydrate and 10 parts by weight of composite-layer grafted silicon carbide were dispersed in 50 parts by weight of deionized water, sonicated at 300 W for 10 minutes, and then the temperature was raised to 55℃ and stirred at 300 r / min for 5 hours. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 minutes, washed four times with deionized water, and dried under vacuum at 100℃ for 7 hours to obtain modified silicon carbide.

[0043] Preparation Example 4 The preparation method of modified silicon carbide includes the following steps: 40 wt% hydrofluoric acid solution and 65 wt% nitric acid solution are mixed at a volume ratio of 3:1 to obtain an acidification solution. 10.5 parts by weight of silicon carbide nanowires (100 nm in diameter and 50 μm in length) are dispersed in 50 parts by weight of the acidification solution. The mixture is heated to 95 °C and stirred at 150 r / min for 45 min. After the reaction, 500 parts by weight of deionized water are added to dilute the reaction solution and terminate the etching reaction. The precipitate is then collected by centrifugation at 10000 r / min for 15 min, washed 6 times with deionized water, and dried under vacuum at 60 °C for 8 h to obtain roughened silicon carbide. 10 parts by weight of the roughened silicon carbide are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 500 W for 15 min. Then, 0.38 parts by weight of L-dopamine were added, and the mixture was stirred at 400 r / min for 3.5 h. Then, 0.28 parts by weight of phytic acid were added, and the temperature was raised to 68 °C and the reaction was stirred for another 17 h. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 min, washed four times with deionized water, and dried under vacuum at 80 °C for 8 h to obtain composite-layer grafted silicon carbide. 5.5 parts by weight of lanthanum nitrate hexahydrate and 10 parts by weight of composite-layer grafted silicon carbide were dispersed in 50 parts by weight of deionized water, sonicated at 300 W for 10 min, and then the temperature was raised to 58 °C and stirred at 300 r / min for 5.5 h. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 min, washed four times with deionized water, and dried under vacuum at 100 °C for 7 h to obtain modified silicon carbide.

[0044] Preparation Example 5 The preparation method of modified silicon carbide includes the following steps: 40 wt% hydrofluoric acid solution and 65 wt% nitric acid solution are mixed at a volume ratio of 3:1 to obtain an acidification solution. 11 parts by weight of silicon carbide nanowires (100 nm in diameter and 50 μm in length) are dispersed in 50 parts by weight of the acidification solution. The mixture is heated to 100 °C and stirred at 150 r / min for 50 min. After the reaction, 500 parts by weight of deionized water are added to dilute the reaction solution and terminate the etching reaction. The precipitate is then collected by centrifugation at 10000 r / min for 15 min, washed 6 times with deionized water, and vacuum dried at 60 °C for 8 h to obtain roughened silicon carbide. 10 parts by weight of the roughened silicon carbide are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 500 W for 15 minutes. After 1 minute, 0.4 parts by weight of L-dopamine were added, and the mixture was stirred at 400 r / min for 4 hours. Then, 0.3 parts by weight of phytic acid were added, and the temperature was raised to 70℃ and the reaction was stirred for another 18 hours. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 minutes, washed 4 times with deionized water, and dried under vacuum at 80℃ for 8 hours to obtain composite layer grafted silicon carbide. 6 parts by weight of lanthanum nitrate hexahydrate and 10 parts by weight of composite layer grafted silicon carbide were dispersed in 50 parts by weight of deionized water, sonicated at 300 W for 10 minutes, and then the temperature was raised to 60℃ and stirred at 300 r / min for 6 hours. After the reaction was completed, the precipitate was collected by centrifugation at 10000 r / min for 20 minutes, washed 4 times with deionized water, and dried under vacuum at 100℃ for 7 hours to obtain modified silicon carbide.

[0045] Preparation Example 6 The method for preparing modified silicon carbide includes the following steps: replacing 6 parts by weight of lanthanum nitrate hexahydrate in Preparation Example 5 with 6 parts by weight of yttrium nitrate hexahydrate, and keeping other operations consistent with Preparation Example 5.

[0046] Example 1 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: 50 parts by weight of 5 wt% phosphoric acid solution and 1 part by weight of urea are placed in a reaction vessel, heated to 70°C, and 10 parts by weight of hollow alumina microspheres (particle size 0.2 mm, wall thickness 10 μm) are added. The mixture is heated to 120°C and stirred at 200 r / min for 1.5 h. After the reaction, the microspheres are washed four times with deionized water and dried under vacuum at 80°C for 6 h to obtain acidified and activated microspheres. 10 parts by weight of the acidified and activated microspheres are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 300 W for 10 min. 0.2 parts by weight of L-dopamine and 0.1 parts by weight of tannic acid are added and the mixture is stirred at 300 r / min. The reaction mixture was stirred at 25℃ for 10 h. After the reaction, it was centrifuged at 8000 r / min for 15 min, the solid was collected, washed three times with deionized water, and dried under vacuum at 70℃ for 8 h to obtain cross-linked coated microspheres. 7 parts by weight of cerium nitrate hexahydrate and 10 parts by weight of cross-linked coated microspheres were placed in 50 parts by weight of deionized water and ultrasonically dispersed at 300 W for 15 min. The mixture was then heated to 50℃ and stirred at 300 r / min for 3 h. After the reaction, it was centrifuged at 10000 r / min for 10 min, the solid was collected, washed three times with deionized water, and dried under vacuum at 100℃ for 10 h to obtain modified alumina microspheres. 55 parts by weight of alumina ceramic powder were dried at 120℃ for 10 h. Then, place it in a planetary mixer, stir at 300 r / min and disperse with ultrasonic assistance at 500 W. After stirring for 10 min, add 20 parts by weight of modified alumina microspheres, continue stirring and mixing for 25 min, then add 10 parts by weight of modified silicon carbide prepared in Preparation Example 1, and stir and mix at 450 r / min for 40 min to obtain a pre-dispersion system; disperse 3 parts by weight of polyvinyl alcohol (molecular weight 9000) and 0.5 parts by weight of polyethylene glycol 400 in 100 parts by weight of deionized water, heat to 80℃ and stir at 200 r / min for 30 min to obtain a molding agent. Add 80 parts by weight of the molding agent to 100 parts by weight of the pre-dispersion system in 3 portions, and stir and mix for 2.5 h to obtain a paste. The paste-like mixture was transferred to a vacuum ply mill and ply-plied four times for 10 minutes each time under a vacuum of 10 Pa and a temperature of 60°C. The resulting paste was then placed in a sealed bag and aged at 25°C for 36 hours to obtain aged ply material. The aged ply material was then filled into a mold and placed in a hydraulic molding machine. A pressure of 70 MPa was applied at 26°C and held for 15 minutes to obtain a green body. The green body was then placed in a ventilated drying oven and dried at 40°C for 12 hours, followed by drying at 60°C for another 12 hours, and then at 80°C for another 24 hours to obtain a dried green body. The dried green body was then placed in a dry sintering furnace and heated to 600°C at a rate of 5°C / min and held for 2 hours under argon protection. The temperature was then increased to 1200°C at a rate of 5°C / min and held for 1 hour.After 5 hours, the temperature is increased to 1580℃ at a rate of 3℃ / min and held for 3 hours, then cooled to 26℃ to obtain a heat-insulating and pressure-resistant ceramic material.

[0047] Example 2 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: 55 parts by weight of 5 wt% phosphoric acid solution and 1.5 parts by weight of urea are placed in a reaction vessel, heated to 75°C, and 10 parts by weight of hollow alumina microspheres (particle size 0.2 mm, wall thickness 10 μm) are added. The mixture is heated to 122°C and stirred at 220 r / min for 1.7 h. After the reaction, the microspheres are washed four times with deionized water and dried under vacuum at 80°C for 6 h to obtain acidified and activated microspheres. 10 parts by weight of the acidified and activated microspheres are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 300 W for 10 min. 0.22 parts by weight of L-dopamine and 0.11 parts by weight of tannic acid are added and the mixture is stirred at 300 r / min. The reaction mixture was stirred at 25°C for 11 hours. After the reaction, it was centrifuged at 8000 r / min for 15 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 70°C for 8 hours to obtain cross-linked coated microspheres. 7.5 parts by weight of cerium nitrate hexahydrate and 10 parts by weight of cross-linked coated microspheres were placed in 50 parts by weight of deionized water and ultrasonically dispersed at 300 W for 15 minutes. The mixture was then heated to 55°C and stirred at 300 r / min for 3.5 hours. After the reaction, it was centrifuged at 10000 r / min for 10 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 100°C for 10 hours to obtain modified alumina microspheres. 57 parts by weight of alumina ceramic powder were dried at 120°C. After 10 hours, the mixture was placed in a planetary mixer and stirred at 300 rpm with ultrasonic dispersion at 500 W. After stirring for 10 minutes, 22 parts by weight of modified alumina microspheres were added, and stirring was continued for 30 minutes. Then, 12 parts by weight of modified silicon carbide prepared in Preparation Example 2 were added, and the mixture was stirred at 450 rpm for 45 minutes to obtain a pre-dispersion system. 3.5 parts by weight of polyvinyl alcohol (molecular weight 9000) and 0.6 parts by weight of polyethylene glycol 400 were dispersed in 100 parts by weight of deionized water, heated to 80°C, and stirred at 200 rpm for 30 minutes to obtain a molding agent. 85 parts by weight of the molding agent were added to 100 parts by weight of the pre-dispersion system in three portions, and the mixture was stirred for 2.7 hours to obtain the desired product. The paste-like mixture was transferred to a vacuum ply mill and ply-plied four times for 10 minutes each time under a vacuum of 10 Pa and a temperature of 60 °C. The resulting paste was then placed in a sealed bag and aged at 25 °C for 36 hours to obtain aged ply material. The aged ply material was then filled into a mold and placed in a hydraulic molding machine. A pressure of 70 MPa was applied at 26 °C and held for 15 minutes to obtain a green body. The green body was placed in a ventilated drying oven and dried at 40 °C for 12 hours, then heated to 60 °C and dried for another 12 hours, followed by further heating to 80 °C and drying for 24 hours to obtain a dried green body. The dried green body was then placed in a dry sintering furnace and heated to 600 °C at a rate of 5 °C / min and held for 2 hours under argon protection, followed by further heating to 1200 °C at a rate of 5 °C / min and holding for 1 hour.After 5 hours, the temperature is increased to 1580℃ at a rate of 3℃ / min and held for 3 hours, then cooled to 26℃ to obtain a heat-insulating and pressure-resistant ceramic material.

[0048] Example 3 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: 60 parts by weight of 5 wt% phosphoric acid solution and 1 part by weight of urea are placed in a reaction vessel, heated to 80°C, and 10 parts by weight of hollow alumina microspheres (particle size 0.2 mm, wall thickness 10 μm) are added. The mixture is heated to 125°C and stirred at 250 r / min for 2.0 h. After the reaction, the microspheres are washed four times with deionized water and vacuum dried at 80°C for 6 h to obtain acidified and activated microspheres. 10 parts by weight of the acidified and activated microspheres are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 300 W for 10 min. 0.25 parts by weight of L-dopamine and 0.13 parts by weight of tannic acid are added and the mixture is ultrasonically dispersed at 300 r / min. The reaction mixture was stirred at 25°C for 12 hours. After the reaction, it was centrifuged at 8000 r / min for 15 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 70°C for 8 hours to obtain cross-linked coated microspheres. Eight parts by weight of cerium nitrate hexahydrate and ten parts by weight of cross-linked coated microspheres were placed in 50 parts by weight of deionized water and ultrasonically dispersed at 300 W for 15 minutes. The mixture was then heated to 60°C and stirred at 300 r / min for 4 hours. After the reaction, the solid was collected by centrifugation at 10000 r / min for 10 minutes, washed three times with deionized water, and dried under vacuum at 100°C for 10 hours to obtain modified alumina microspheres. Sixty parts by weight of alumina ceramic powder were dried at 120°C for 10 hours. After h, place it in a planetary mixer, stir at 300 r / min and disperse with ultrasonic assistance of 500 W. After stirring for 10 min, add 25 parts by weight of modified alumina microspheres, continue stirring and mixing for 35 min, then add 13 parts by weight of modified silicon carbide prepared in Preparation Example 3, stir and mix at 450 r / min for 50 min to obtain a pre-dispersion system; 4 parts by weight of polyvinyl alcohol (molecular weight 9000) and 0.8 parts by weight of polyethylene glycol 400 are dispersed in 100 parts by weight of deionized water, heated to 80℃ and stirred at 200 r / min for 30 min to obtain a molding agent. Add 90 parts by weight of the molding agent to 100 parts by weight of the pre-dispersion system in 3 portions, stir and mix for 3.0 h to obtain a paste. The mixture was transferred to a vacuum ply mill and ply four times for 10 minutes each time under a vacuum of 10 Pa and a temperature of 60°C. The mixture was then placed in a sealed bag and aged at 25°C for 36 hours to obtain aged ply material. The aged ply material was then filled into a mold and placed in a hydraulic molding machine. A pressure of 70 MPa was applied at 26°C and held for 15 minutes to obtain a green body. The green body was placed in a ventilated drying oven and dried at 40°C for 12 hours, then heated to 60°C and dried for another 12 hours, followed by further heating to 80°C and drying for 24 hours to obtain a dried green body. The dried green body was then placed in a dry sintering furnace and heated to 600°C at a rate of 5°C / min and held for 2 hours under argon protection, followed by further heating to 1200°C at a rate of 5°C / min and holding for 1 hour.After 5 hours, the temperature is increased to 1580℃ at a rate of 3℃ / min and held for 3 hours, then cooled to 26℃ to obtain a heat-insulating and pressure-resistant ceramic material.

[0049] Example 4 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: 70 parts by weight of 5 wt% phosphoric acid solution and 2.5 parts by weight of urea are placed in a reaction vessel, heated to 85°C, and 10 parts by weight of hollow alumina microspheres (particle size 0.2 mm, wall thickness 10 μm) are added. The mixture is heated to 128°C and stirred at 280 r / min for 2.2 h. After the reaction, the microspheres are washed four times with deionized water and dried under vacuum at 80°C for 6 h to obtain acidified and activated microspheres. 10 parts by weight of the acidified and activated microspheres are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 300 W for 10 min. 0.28 parts by weight of L-dopamine and 0.14 parts by weight of tannic acid are added and the mixture is stirred at 300 r / min. The reaction mixture was stirred at 25°C for 13 hours. After the reaction, it was centrifuged at 8000 r / min for 15 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 70°C for 8 hours to obtain cross-linked coated microspheres. 8.5 parts by weight of cerium nitrate hexahydrate and 10 parts by weight of cross-linked coated microspheres were placed in 50 parts by weight of deionized water and ultrasonically dispersed at 300 W for 15 minutes. The mixture was then heated to 65°C and stirred at 300 r / min for 4.5 hours. After the reaction, it was centrifuged at 10000 r / min for 10 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 100°C for 10 hours to obtain modified alumina microspheres. 62 parts by weight of alumina ceramic powder were dried at 120°C. After 10 hours, the mixture was placed in a planetary mixer and stirred at 300 rpm with ultrasonic dispersion at 500 W. After stirring for 10 minutes, 28 parts by weight of modified alumina microspheres were added, and stirring was continued for 42 minutes. Then, 14 parts by weight of modified silicon carbide prepared in Preparation Example 4 were added, and the mixture was stirred at 450 rpm for 55 minutes to obtain a pre-dispersion system. 4.5 parts by weight of polyvinyl alcohol (molecular weight 9000) and 0.9 parts by weight of polyethylene glycol 400 were dispersed in 100 parts by weight of deionized water, heated to 80°C, and stirred at 200 rpm for 30 minutes to obtain a molding agent. 95 parts by weight of the molding agent were added to 100 parts by weight of the pre-dispersion system in three portions, and the mixture was stirred for 3.2 hours to obtain the desired product. The paste-like mixture was transferred to a vacuum ply mill and ply-plied four times for 10 minutes each time under a vacuum of 10 Pa and a temperature of 60 °C. The resulting paste was then placed in a sealed bag and aged at 25 °C for 36 hours to obtain aged ply material. The aged ply material was then filled into a mold and placed in a hydraulic molding machine. A pressure of 70 MPa was applied at 26 °C and held for 15 minutes to obtain a green body. The green body was placed in a ventilated drying oven and dried at 40 °C for 12 hours, then heated to 60 °C and dried for another 12 hours, followed by further heating to 80 °C and drying for 24 hours to obtain a dried green body. The dried green body was then placed in a dry sintering furnace and heated to 600 °C at a rate of 5 °C / min and held for 2 hours under argon protection, followed by further heating to 1200 °C at a rate of 5 °C / min and holding for 1 hour.After 5 hours, the temperature is increased to 1580℃ at a rate of 3℃ / min and held for 3 hours, then cooled to 26℃ to obtain a heat-insulating and pressure-resistant ceramic material.

[0050] Example 5 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: 80 parts by weight of 5 wt% phosphoric acid solution and 3 parts by weight of urea are placed in a reaction vessel, heated to 90°C, and 10 parts by weight of hollow alumina microspheres (particle size 0.2 mm, wall thickness 10 μm) are added. The mixture is heated to 130°C and stirred at 300 r / min for 2.5 h. After the reaction, the microspheres are washed four times with deionized water and dried under vacuum at 80°C for 6 h to obtain acidified and activated microspheres. 10 parts by weight of the acidified and activated microspheres are dispersed in 100 parts by weight of pH 8.0 Tris-HCl buffer solution and ultrasonically dispersed at 300 W for 10 min. 0.3 parts by weight of L-dopamine and 0.15 parts by weight of tannic acid are added and the mixture is ultrasonically dispersed at 300 r / min. The reaction mixture was stirred at 25°C for 14 hours. After the reaction, it was centrifuged at 8000 r / min for 15 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 70°C for 8 hours to obtain cross-linked coated microspheres. Nine parts by weight of cerium nitrate hexahydrate and ten parts by weight of cross-linked coated microspheres were placed in 50 parts by weight of deionized water and ultrasonically dispersed at 300 W for 15 minutes. The mixture was then heated to 70°C and stirred at 300 r / min for 5 hours. After the reaction, it was centrifuged at 10000 r / min for 10 minutes, the solid was collected, washed three times with deionized water, and dried under vacuum at 100°C for 10 hours to obtain modified alumina microspheres. Sixty-five parts by weight of alumina ceramic powder were dried at 120°C for 10 hours. After h, place it in a planetary mixer, stir at 300 r / min and disperse with ultrasonic assistance of 500 W. After stirring for 10 min, add 30 parts by weight of modified alumina microspheres, continue stirring and mixing for 45 min, then add 15 parts by weight of modified silicon carbide prepared in Preparation Example 5, stir and mix at 450 r / min for 60 min to obtain a pre-dispersion system; disperse 5 parts by weight of polyvinyl alcohol (molecular weight 9000) and 1 part by weight of polyethylene glycol 400 in 100 parts by weight of deionized water, heat to 80℃ and stir at 200 r / min for 30 min to obtain a molding agent. Add 100 parts by weight of the molding agent to 100 parts by weight of the pre-dispersion system in 3 portions, stir and mix for 3.5 h to obtain a paste mixture. The paste-like mixture was transferred to a vacuum ply mill and ply-plied four times for 10 minutes each time under a vacuum of 10 Pa and a temperature of 60°C. The resulting paste was then placed in a sealed bag and aged at 25°C for 36 hours to obtain aged ply material. The aged ply material was then filled into a mold and placed in a hydraulic molding machine. A pressure of 70 MPa was applied at 26°C and held for 15 minutes to obtain a green body. The green body was then placed in a ventilated drying oven and dried at 40°C for 12 hours, followed by drying at 60°C for another 12 hours, and then at 80°C for another 24 hours to obtain a dried green body. The dried green body was then placed in a dry sintering furnace and heated to 600°C at a rate of 5°C / min and held for 2 hours under argon protection. The temperature was then increased to 1200°C at a rate of 5°C / min and held for 1 hour.After 5 hours, the temperature is increased to 1580℃ at a rate of 3℃ / min and held for 3 hours, then cooled to 26℃ to obtain a heat-insulating and pressure-resistant ceramic material.

[0051] Comparative Example 1 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: removing the modification step of hollow alumina microspheres in Example 5, replacing the modified alumina microspheres with original hollow alumina microspheres without any surface treatment, and keeping other operations consistent with Example 5.

[0052] Comparative Example 2 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: 80 parts by weight of 5 wt% phosphoric acid solution and 3 parts by weight of urea are placed in a reaction vessel, heated to 90°C, and 10 parts by weight of hollow alumina microspheres (particle size 0.2 mm, wall thickness 10 μm) are added. The temperature is raised to 130°C and the mixture is stirred at 300 r / min for 2.5 h. After the reaction, the microspheres are washed four times with deionized water and dried under vacuum at 80°C for 6 h to obtain acidified and activated microspheres. 10 parts by weight of acidified and activated microspheres and 0.2 parts by weight of silane coupling agent are dispersed in 100 parts by weight of 85 wt% ethanol solution, and the mixture is heated to 60°C and stirred at 300 r / min for 14 h. After the reaction was completed, the solid was centrifuged at 8000 r / min for 15 min, washed three times with deionized water, and dried under vacuum at 70 °C for 8 h to obtain cross-linked coated microspheres. Nine parts by weight of cerium nitrate hexahydrate and ten parts by weight of cross-linked coated microspheres were placed in 50 parts by weight of deionized water, ultrasonically dispersed at 300 W for 15 min, heated to 70 °C, and stirred at 300 r / min for 5 h. After the reaction was completed, the solid was centrifuged at 10000 r / min for 10 min, washed three times with deionized water, and dried under vacuum at 100 °C for 10 h to obtain modified alumina microspheres. Other operations were the same as in Example 5.

[0053] Comparative Example 3 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: replacing 9 parts by weight of cerium nitrate hexahydrate in Example 5 with 9 parts by weight of scandium nitrate hexahydrate, and keeping other operations consistent with Example 5.

[0054] Comparative Example 4 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: replacing 15 parts by weight of the modified silicon carbide prepared in Example 5 with 15 parts by weight of the roughened silicon carbide in Example 5, and keeping other operations consistent with Example 5.

[0055] Comparative Example 5 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: replacing the modified silicon carbide prepared in Preparation Example 6 with the modified silicon carbide prepared in Preparation Example 5, and keeping other operations consistent with those in Example 5.

[0056] Comparative Example 6 A method for preparing a heat-insulating and pressure-resistant ceramic material includes the following steps: removing the modified silicon carbide obtained in Example 5, while keeping other operations consistent with Example 5.

[0057] Performance Testing: The thermal insulation and compressive strength ceramic materials prepared in Examples 1-5 and Comparative Examples 1-6 were tested for various properties. The test methods are as follows: Compressive strength: A universal testing machine was used, with sample size of 10 mm × 10 mm × 10 mm and loading rate of 0.5 mm / min; Thermal conductivity: Thermal conductivity was tested using a Hot Disk TPS 2500S thermal constant analyzer (25℃); Number of thermal shock cycles: After holding the sample at 1000℃ for 10 min, it was quickly quenched in room temperature water (25℃), and the number of cycles when through cracks appeared or the strength decreased by more than 30% was recorded; Fracture toughness: According to GB / T 23806-2009 standard, the single-sided notched beam method was used for determination, with sample size of 2 mm × 4 mm × 20 mm, notch depth of 2 mm, span of 40 mm, and loading rate of 0.05 mm / min; The test results are shown in Table 1.

[0058]

[0059] (1) The test results in Table 1 show that the thermal insulation and compressive strength ceramic materials prepared in Examples 1-5 of the present invention have good performance, while the thermal insulation and compressive strength ceramic materials prepared in Comparative Examples 1-6 have lower performance than those prepared in Examples 1-5. (2) The reason for the decrease in Comparative Example 1 may be that the original hollow alumina microspheres used have not undergone multi-step modification treatment of acidification activation, cross-linking coating and rare earth ion coordination. The surface lacks micro-rough structure and hydroxyl active sites, and cannot form an effective chemical bond and physical anchoring effect with the ceramic matrix. The interfacial bonding strength is weak and it is easy to debond and separate during stress or thermal cycling. At the same time, the original microspheres do not have the protection and reinforcement of a dense composite coating layer, and their mechanical properties are insufficient. They are difficult to cooperate with the matrix to bear the load, and gaps and channels are easily formed between the interfaces, which destroys the integrity of the thermal insulation system. Ultimately, this leads to a decrease in compressive strength, fracture toughness and thermal shock stability. The thermal insulation performance is also damaged due to the increase in the interfacial heat conduction path. (3) The reason for the decrease in Comparative Example 2 may be that the commercially available silane coupling agent KH-550 coating was used to replace the L-dopamine-tannic acid crosslinking layer. This coating is a single chemical modification system, and its crosslinking density and interfacial force are far inferior to the composite coating layer formed by L-dopamine and tannic acid. Silane coupling agents can only achieve surface modification through simple chemical bonding and cannot construct a dense interfacial transition layer that is both elastic and adhesive. It is difficult to effectively alleviate the difference in thermal expansion coefficients between microspheres and the matrix, and it cannot provide sufficient interfacial bonding force. During stress or thermal cycling, the coating is prone to detach from the microspheres or the matrix, resulting in interfacial bonding failure, which in turn reduces the mechanical properties and thermal shock stability of the material, and the thermal insulation performance is also affected by the destruction of interfacial integrity. (4) The reason for the decrease in Comparative Example 3 may be that the coordination ability and interface regulation effect of rare earth ions changed significantly after replacing cerium nitrate hexahydrate with scandium nitrate hexahydrate. When cerium ions coordinate with the active groups of the cross-linked coating layer, they can form more stable metal-organic coordination bonds and regulate the electronic structure of the interface, thereby improving the compatibility and thermal stability of the microspheres and the matrix. However, the ionic radius, charge distribution and coordination characteristics of scandium ions are not suitable for this modified system, and the coordination bond strength formed is low. It cannot effectively enhance the structural stability of the cross-linked coating layer, nor can it optimize the interface bonding state between the microspheres and the matrix. This leads to a decrease in the mechanical strength and interfacial bonding force of the modified microspheres, and the overall compressive strength, fracture toughness and thermal shock stability of the material decrease accordingly. The thermal insulation performance is also affected by the unstable interface structure. (5) The reason for the decrease in Comparative Example 4 may be that the unmodified silicon carbide nanowires used only underwent roughening treatment, lacking polydopamine-phytic acid composite grafting layer and rare earth ion coordination modification, resulting in insufficient interfacial compatibility and structural stability. Roughening treatment can only provide limited physical adhesion points and cannot build an interfacial "bridge" through chemical action, resulting in weak bonding between nanowires and alumina matrix and modified alumina microspheres, making it difficult to form a continuous three-dimensional reinforcing network. Under stress, nanowires cannot effectively play the role of stress sharing and crack deflection, and may even become stress concentration points due to interfacial debonding; during thermal cycling, gaps are easily generated between interfaces, destroying structural integrity, ultimately leading to a significant decrease in the compressive strength, fracture toughness and thermal shock stability of the material, and the thermal insulation performance is also impaired due to the increase in interfacial heat conduction paths; (6) The reason for the decrease in Comparative Example 5 may be that after replacing lanthanum nitrate hexahydrate with yttrium nitrate hexahydrate, the modification effect of rare earth ions on silicon carbide nanowires was significantly weakened. Lanthanum ions have good coordination compatibility with the phosphate groups and phenolic hydroxyl groups of the polydopamine-phytic acid composite graft layer, which can form a dense protective layer and optimize the matching of the interfacial thermal expansion coefficients between the nanowires and the matrix; while the coordination characteristics of yttrium ions have poor compatibility with the active sites of the composite graft layer, and the stability of the resulting coordination complex is insufficient, which cannot effectively enhance the structural stability and interfacial bonding of the nanowires. This leads to a decrease in the continuity and durability of the enhanced network formed by the modified silicon carbide nanowires, a weakening of stress sharing and crack deflection effects, and a decrease in the compressive strength, fracture toughness and thermal shock stability of the material. The destruction of interfacial integrity also has a certain negative impact on the thermal insulation performance. (7) The reason for the decrease in Comparative Example 6 may be the absence of modified silicon carbide nanowires, which resulted in the material losing its continuous three-dimensional mechanical reinforcement network and failing to compensate for the inherent limitations of modified alumina microspheres in improving toughness. As a particulate modifier, modified alumina microspheres can improve their own strength and interfacial bonding force through modification, but they are difficult to form a continuous stress transmission path in the matrix, and their inhibitory effect on crack propagation is limited. Without the "bridging" and crack deflection effect of modified silicon carbide nanowires, the material is prone to rapid crack propagation under stress, and the fracture toughness is significantly insufficient; during thermal cycling, it is impossible to disperse interfacial stress through the reinforcement network, resulting in a decrease in thermal shock stability. Although the hollow structure of modified alumina microspheres can still maintain a certain thermal insulation performance, the overall mechanical properties and comprehensive stability are significantly inferior to those of Example 5 due to the lack of key reinforcing components.

[0060] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a heat-insulating and pressure-resistant ceramic material, characterized in that, The preparation method includes the following steps: Acidified and activated microspheres are obtained by mixing and stirring phosphoric acid, urea, and hollow alumina microspheres; cross-linked coated microspheres are obtained by mixing and stirring the acidified and activated microspheres, L-dopamine, and tannic acid; modified alumina microspheres are obtained by mixing and stirring cerium nitrate hexahydrate and cross-linked coated microspheres; a pre-dispersion system is obtained by mixing and stirring alumina ceramic powder, modified alumina microspheres, and modified silicon carbide; a molding agent is obtained by mixing and stirring polyvinyl alcohol and polyethylene glycol 400; the molding agent and the pre-dispersion system are mixed and stirred to obtain a paste mixture; the paste mixture is successively kneaded and aged to obtain aged clay; the aged clay is pressed and molded to obtain a green body; the green body is successively dried and sintered to obtain a heat-insulating and pressure-resistant ceramic material.

2. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 1, characterized in that, The weight ratio of phosphoric acid, urea, and hollow alumina microspheres is (50~80):(1~3):10; the weight ratio of acidified activated microspheres, L-dopamine, and tannic acid is 10:(0.2~0.3):(0.1~0.15); the weight ratio of cerium nitrate hexahydrate and cross-linked coated microspheres is (7~9):10; the particle size of the hollow alumina microspheres is 0.2~0.4 mm, and the wall thickness of the microspheres is 10~20 μm.

3. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 1, characterized in that, The method for preparing the modified silicon carbide includes the following steps: mixing hydrofluoric acid and nitric acid to obtain an acidification solution; mixing silicon carbide nanowires and the acidification solution and stirring to obtain roughened silicon carbide; mixing and stirring the roughened silicon carbide, L-dopamine and phytic acid to obtain composite layer grafted silicon carbide; and mixing and stirring the lanthanum nitrate hexahydrate and composite layer grafted silicon carbide to obtain modified silicon carbide.

4. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 3, characterized in that, The volume ratio of hydrofluoric acid to nitric acid is 3:1; the diameter of the silicon carbide nanowire is 100~200nm and the length is 50~100μm.

5. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 3, characterized in that, The weight ratio of the silicon carbide nanowires to the acidification solution is (9~11):

50.

6. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 3, characterized in that, The weight ratio of the roughened silicon carbide, L-dopamine, and phytic acid is 10:(0.3~0.4):(0.2~0.3).

7. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 3, characterized in that, The weight ratio of lanthanum nitrate hexahydrate to composite layer grafted silicon carbide is (4~6):10; the conditions for the mixing and stirring reaction of lanthanum nitrate hexahydrate and composite layer grafted silicon carbide include a reaction temperature of 50~60℃ and a reaction time of 4~6h.

8. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 1, characterized in that, The weight ratio of the alumina ceramic powder, modified alumina microspheres, and modified silicon carbide is (55~65):(20~30):(10~15); the weight ratio of the polyvinyl alcohol and polyethylene glycol 400 is (3~5):(0.5~1); and the weight ratio of the molding agent and the pre-dispersion system is (80~100):

100.

9. The method for preparing a heat-insulating and pressure-resistant ceramic material as described in claim 1, characterized in that, The sintering conditions include heating to 600°C at a rate of 5°C / min and holding for 2 hours, then heating to 1200°C at a rate of 5°C / min and holding for 1 to 1.5 hours, and then heating to 1500 to 1580°C at a rate of 3°C / min and holding for 2 to 3 hours.

10. A heat-insulating and pressure-resistant ceramic material, characterized in that, It is prepared by the preparation method of the heat-insulating and pressure-resistant ceramic material according to any one of claims 1 to 9.

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