Modified zirconium silicate whisker reinforced alumina ceramic and its preparation method and application

Abstract

The application provides a modified zirconium silicate whisker reinforced alumina ceramic and a preparation method and application thereof, and belongs to the technical field of new materials. After the surface of alumina powder is modified by a silane coupling agent with a mercapto group, zirconium silicate is generated in situ, and then the zirconium silicate is uniformly mixed with zirconium silicate whiskers treated by hydrogen peroxide, phytic acid and tannic acid, and a CeO2-Y2O3-MgO-SiO2 compound, so as to prepare the modified zirconium silicate whisker reinforced alumina ceramic through discharge plasma sintering. The modified zirconium silicate whisker reinforced alumina ceramic prepared by the application has good interface bonding force, good mechanical properties and good wear resistance, realizes ceramic densification, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, specifically to a modified zirconium silicate whisker-reinforced alumina ceramic, its preparation method, and its application. Background Technology

[0002] Ceramics, in terms of their materials, are divided into earthenware, stoneware, and porcelain, commonly known as pottery, stoneware, and porcelain. Alumina ceramic materials possess properties such as low density, high strength, high wear resistance, high chemical stability, and a stable coefficient of friction at high temperatures, making them extremely promising for applications in the field of friction materials. However, given increasingly stringent usage requirements, the wear resistance of single-phase alumina ceramics needs improvement. Furthermore, the inherent brittleness of ceramics significantly limits their application in harsher environments.

[0003] Zirconium silicate, as an important high-temperature inorganic non-metallic material, not only possesses a high melting point, excellent chemical and phase stability, and low thermal conductivity, but also exhibits high high-temperature strength, strong oxidation resistance, and a low coefficient of thermal expansion. Furthermore, zirconium silicate exhibits significantly better thermal shock resistance than mullite and alumina, with a critical thermal shock temperature difference ΔTc of 280℃, compared to 200℃ for mullite and 150℃ for alumina. Whiskers typically refer to fibrous single-crystal materials with a specific aspect ratio and small diameter, preferentially grown along a one-dimensional direction under artificially controlled conditions. Due to the highly ordered atomic arrangement and few internal defects, the strength of whiskers approaches the theoretical value of a perfect crystal. Zirconium silicate whiskers combine the advantages of both zirconium silicate and whisker materials, making them an excellent reinforcing agent for composite materials. They hold promise as reinforcements for ceramics, metals, and polymers, significantly improving the overall mechanical properties of composite materials. However, they suffer from insufficient interfacial bonding with alumina ceramics. Summary of the Invention

[0004] The purpose of this invention is to propose a modified zirconium silicate whisker-reinforced alumina ceramic, its preparation method, and its application. It has good interfacial bonding, excellent mechanical properties, good wear resistance, and achieves ceramic densification, thus having broad application prospects.

[0005] The technical solution of this invention is implemented as follows:

[0006] This invention provides a method for preparing modified zirconium silicate whisker-reinforced alumina ceramics. The method involves modifying the surface of alumina powder with a silane coupling agent containing mercapto groups to generate zirconium silicate in situ. The zirconium silicate is then mixed uniformly with zirconium silicate whiskers that have been treated with hydrogen peroxide, modified with phytic acid and tannic acid, and a CeO2-Y2O3-MgO-SiO2 composite. Finally, the modified zirconium silicate whisker-reinforced alumina ceramics are obtained by discharge plasma sintering.

[0007] As a further improvement to the present invention, the following steps are included:

[0008] S1. Preparation of modified alumina powder: Add a silane coupling agent with mercapto groups and alumina powder to ethanol, heat and stir to react, centrifuge, wash, and dry to obtain modified alumina powder;

[0009] S2. Preparation of alumina powder with in-situ zirconium silicate: Modified alumina powder and tetraethyl orthosilicate were mixed, added to ethanol, zirconium chloride was added, the mixture was heated and stirred under reflux, the solvent was removed under reduced pressure, dried, mixed with sodium molybdate, calcined, washed with water and HF aqueous solution, and dried to obtain alumina powder with in-situ zirconium silicate.

[0010] S3. Preparation of zirconium silicate whiskers: Tetraethyl orthosilicate was added to ethanol, zirconium chloride and lithium fluoride were added, the mixture was heated to reflux and stirred to react, the solvent was removed under reduced pressure, dried, mixed with sodium molybdate, calcined, washed with water and HF aqueous solution, and dried to obtain zirconium silicate whiskers;

[0011] S4. Preparation of modified zirconium silicate whiskers: After heating the zirconium silicate whiskers in hydrogen peroxide, filter, dry, add them to Tris-HCl solution, add phytic acid and tannic acid, heat and stir to react, filter, wash, and dry to obtain modified zirconium silicate whiskers.

[0012] S5. Preparation of sintering aid: Lanthanum chloride and yttrium chloride are added to ethanol, along with tetraethyl orthosilicate and magnesium chloride. Water is added to adjust the pH of the solution. The mixture is heated and stirred to react, then filtered, washed, dried, and calcined to obtain the sintering aid.

[0013] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramics: Alumina powder with in-situ zirconium silicate, modified zirconium silicate whiskers, and sintering aids are mixed evenly, and modified zirconium silicate whisker-reinforced alumina ceramics are obtained by discharge plasma sintering.

[0014] As a further improvement of the present invention, the silane coupling agent with mercapto group in step S1 is at least one of KH580 and KH590, the mass ratio of the silane coupling agent with mercapto group to alumina powder is 2-3:10, and the heating and stirring reaction temperature is 45-55℃ and the time is 2-4h.

[0015] As a further improvement of the present invention, the mass ratio of modified alumina powder, tetraethyl orthosilicate, zirconium chloride, and sodium molybdate in step S2 is 50:6-7:7-7.3:8-15, the heating, reflux, and stirring reaction time is 20-24 h, the concentration of the HF aqueous solution is 5-15 wt%, and the calcination temperature is 1550-1600 °C for 2-4 h.

[0016] As a further improvement of the present invention, the mass ratio of tetraethyl orthosilicate, zirconium chloride, lithium fluoride and sodium molybdate in step S3 is 6-7:7-7.2:7-15:2-4, the heating and reflux stirring reaction time is 22-26 h, the calcination temperature is 900-1000℃ and the time is 2-4 h, and the concentration of the HF aqueous solution is 5-15 wt%.

[0017] As a further improvement of the present invention, the concentration of hydrogen peroxide in step S4 is 20-30 wt%, the temperature of the heating treatment is 30-40℃, the time is 0.5-1.5 h, the mass ratio of zirconium silicate whiskers, phytic acid, and tannic acid is 10:2-3:1-2, the temperature of the heating and stirring reaction is 45-55℃, the time is 4-6 h, and the pH value of the Tris-HCl solution is 8.5-9.5.

[0018] As a further improvement of the present invention, the mass ratio of lanthanum chloride, yttrium chloride, tetraethyl orthosilicate and magnesium chloride in step S5 is 1-2:1-2:8-12:2-3, the pH value of the solution is adjusted to 5-6, the temperature of the heating and stirring reaction is 45-55℃ and the time is 5-7h, and the calcination temperature is 600-700℃ and the time is 2-4h.

[0019] As a further improvement of the present invention, the mass ratio of alumina powder for in-situ generation of zirconium silicate, modified zirconium silicate whiskers, and sintering aid in step S6 is 100:5-10:1-2, the pulse sequence of the discharge plasma sintering is set to 12:2, the sintering is carried out in a dynamic vacuum of 5-7 Pa, the sintering temperature range is 1200-1300℃, and the holding time is 5-10 min.

[0020] The present invention further protects a modified zirconium silicate whisker-reinforced alumina ceramic prepared by the above-described preparation method.

[0021] This invention further protects the application of the above-mentioned modified zirconium silicate whisker-reinforced alumina ceramic in the preparation of wear-resistant materials.

[0022] The present invention has the following beneficial effects:

[0023] This invention modifies the surface of alumina powder with a silane coupling agent containing mercapto groups. Thiol reacts with alumina to form Al-S bonds, while siloxane condenses to form Si-O-Al covalent bonds, thus modifying the alumina. The siloxane portion can also be hydrolyzed and react with zirconium chloride to obtain Si-Zr structural bonds, thereby promoting the in-situ generation of zirconium silicate to obtain alumina powder with in-situ zirconium silicate. This avoids the agglomeration problem of externally added whiskers. The fine zirconium silicate formed can also improve the wear resistance of alumina ceramics. At the same time, it can also improve the compatibility and interfacial bonding force of the two after subsequent mixing with modified zirconium silicate whiskers. In addition, zirconium silicate and alumina can react at high temperatures: ZrSiO4 + Al2O3 → Al2ZrO5 + SiO2. The generated Al2ZrO5 has a high lattice matching degree with Al2O3 (both are orthorhombic crystals with similar lattice constants), and SiO2 can further react with Al2O3 to form mullite, forming a gradient transition of "Al2O3-Al2ZrO5-mullite-ZrSiO4", which significantly reduces interfacial stress and improves the wear resistance of the material.

[0024] This invention prepares modified zirconium silicate whiskers. The surface of the zirconium silicate whiskers, prepared by a non-hydrolytic sol-gel method combined with a molten salt process, is treated with hydrogen peroxide to expose a large number of hydroxyl groups. After modification with phytic acid and tannic acid, the content of hydroxyl, carboxyl, and phosphate groups on the surface is further increased. Through hydroxyl coordination, carboxyl coordination, and Al-P coordination with Al, the bonding force between the whiskers and alumina is significantly improved, and the agglomeration of the whiskers is reduced, thereby improving the wear resistance and mechanical strength properties of the ceramic.

[0025] This invention prepares a low-eutectic sintering aid (La2O3-Y2O3-MgO-SiO2 composite system), which inhibits high-temperature whisker decomposition while lowering the sintering temperature (<1300℃), thus balancing density and toughening effects. During high-temperature sintering, the sintering aid forms a low-melting-point liquid phase (such as a eutectic), which can fill interfacial voids and promote Al... 3+ Zr 4+ Si 4+ Diffusion at the interface forms a solid solution or a compound transition phase, thereby achieving densification and ceramization at a lower calcination temperature, and enhancing the interfacial bonding force, resulting in a more mechanically robust ceramic material.

[0026] This invention improves the microstructure, enhances strength, hardness, and fracture toughness to a certain extent through advanced spark plasma sintering, thereby achieving ceramic densification and strengthening the mechanical properties of ceramics.

[0027] The modified zirconium silicate whisker-reinforced alumina ceramic prepared by this invention is a composite modification using in-situ generated small-particle zirconium silicate and large-particle zirconium silicate whiskers. During the sintering process, the small particles precipitate in situ through a solid-phase reaction of ZrO2 + SiO2, uniformly pinning them to the Al2O3 grain boundaries to form nano-pinning bands, which passivate cracks and refine grains. The large whiskers form a three-dimensional network that penetrates the matrix, bridging and pulling out, and dissipating energy, forming a hierarchical framework of "nano-pinning + micro-bridging". This inhibits grain growth, reduces porosity, and forms an Al-O-Si-O-Zr gradient transition layer at the interface, reducing thermal mismatch and enhancing shear transfer. This synergistically improves mechanical properties, resulting in good interfacial bonding, excellent mechanical properties, good wear resistance, and ceramic densification, with broad application prospects. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Alumina powder: purity > 99.99%, particle size 0.3-0.5μm. Example 1

[0030] This embodiment provides a method for preparing modified zirconium silicate whisker-reinforced alumina ceramics, including the following steps:

[0031] S1. Preparation of modified alumina powder: 2g of silane coupling agent KH580, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 45℃, stirred and reacted for 2h, centrifuged, washed and dried to obtain modified alumina powder.

[0032] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7g of zirconium chloride was added and the mixture was heated under reflux and stirred for 20h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 8g of sodium molybdate and calcined at 1550℃ for 2h. After washing with water and 5wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0033] S3. Preparation of zirconium silicate whiskers: 6g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7g of zirconium chloride and 7g of lithium fluoride. The mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 2g of sodium molybdate and calcined at 900℃ for 2h. After washing with water and 5wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0034] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 20wt% hydrogen peroxide and heated to 30℃. After stirring for 0.5h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 8.5. 2g of phytic acid and 1g of tannic acid were added, and the mixture was heated to 45℃ and stirred for 4h. After filtration, washing, and drying, modified zirconium silicate whiskers were obtained.

[0035] S5. Preparation of sintering aid: 1g lanthanum chloride and 1g yttrium chloride were added to 100mL ethanol, 8g tetraethyl orthosilicate and 2g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5, heated to 45℃, stirred for 5h, filtered, washed, dried, and calcined at 600℃ for 2h to obtain the sintering aid.

[0036] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate generation, 5g of modified zirconium silicate whiskers, and 1g of sintering aid are mixed evenly and sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0037] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 5 Pa. The sintering temperature range was 1200℃, and the holding time was 5 min. Example 2

[0038] This embodiment provides a method for preparing modified zirconium silicate whisker-reinforced alumina ceramics, including the following steps:

[0039] S1. Preparation of modified alumina powder: 3g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 55℃, stirred and reacted for 4h, centrifuged, washed and dried to obtain modified alumina powder.

[0040] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 7g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.3g of zirconium chloride was added and the mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 15g of sodium molybdate and calcined at 1600℃ for 4h. After washing with water and 15wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0041] S3. Preparation of zirconium silicate whiskers: 7g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.2g of zirconium chloride and 15g of lithium fluoride. The mixture was heated under reflux and stirred for 26h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 4g of sodium molybdate and calcined at 1000℃ for 4h. After washing with water and a 15wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0042] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 30wt% hydrogen peroxide and heated to 40℃. After stirring for 1.5h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9.5. 3g of phytic acid and 2g of tannic acid were added, and the mixture was heated to 55℃ and stirred for 6h. After filtration, washing, and drying, modified zirconium silicate whiskers were obtained.

[0043] S5. Preparation of sintering aid: Add 2g lanthanum chloride and 2g yttrium chloride to 100mL ethanol, add 12g tetraethyl orthosilicate and 3g magnesium chloride, add 50mL water, adjust the pH of the solution to 6, heat to 55℃, stir and react for 7h, filter, wash, dry, calcine at 700℃ for 4h to obtain sintering aid.

[0044] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate generation, 10g of modified zirconium silicate whiskers, and 2g of sintering aid are mixed evenly and sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0045] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 7 Pa. The sintering temperature range was 1300℃, and the holding time was 10 min. Example 3

[0046] This embodiment provides a method for preparing modified zirconium silicate whisker-reinforced alumina ceramics, including the following steps:

[0047] S1. Preparation of modified alumina powder: 2.5g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 50℃, stirred for 3h, centrifuged, washed and dried to obtain modified alumina powder.

[0048] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6.4g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.1g of zirconium chloride was added, and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g of sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0049] S3. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0050] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9. 2.5g of phytic acid and 1.5g of tannic acid were added, and the mixture was heated to 50℃ and stirred for 5h. After filtering, washing, and drying, modified zirconium silicate whiskers were obtained.

[0051] S5. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0052] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate, 7g of modified zirconium silicate whiskers, and 1.5g of sintering aid were mixed evenly and then sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0053] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0054] Comparative Example 1

[0055] The difference from Example 3 is that step S1 was not performed.

[0056] Specifically as follows:

[0057] S1. Preparation of alumina powder with in-situ zirconium silicate: 50g alumina powder and 6.4g tetraethyl orthosilicate were mixed and added to 300mL ethanol. 7.1g zirconium chloride was added and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0058] S2. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0059] S3. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9. 2.5g of phytic acid and 1.5g of tannic acid were added, and the mixture was heated to 50℃ and stirred for 5h. After filtering, washing, and drying, modified zirconium silicate whiskers were obtained.

[0060] S4. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0061] S5. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate generation, 7g of modified zirconium silicate whiskers, and 1.5g of sintering aid were mixed evenly and then sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0062] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0063] Comparative Example 2

[0064] The difference from Example 3 is that steps S1 and S2 were not performed.

[0065] Specifically as follows:

[0066] S1. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0067] S2. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9. 2.5g of phytic acid and 1.5g of tannic acid were added, and the mixture was heated to 50℃ and stirred for 5h. After filtering, washing, and drying, modified zirconium silicate whiskers were obtained.

[0068] S3. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0069] S4. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g alumina powder, 7g modified zirconium silicate whiskers and 1.5g sintering aid are mixed evenly and sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0070] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0071] Comparative Example 3

[0072] The difference from Example 3 is that phytic acid was not added in step S4.

[0073] Specifically as follows:

[0074] S1. Preparation of modified alumina powder: 2.5g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 50℃, stirred for 3h, centrifuged, washed and dried to obtain modified alumina powder.

[0075] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6.4g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.1g of zirconium chloride was added, and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g of sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0076] S3. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0077] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9. 4g of tannic acid was added, and the mixture was heated to 50℃ and stirred for 5h. After filtering, washing, and drying, modified zirconium silicate whiskers were obtained.

[0078] S5. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0079] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate, 7g of modified zirconium silicate whiskers, and 1.5g of sintering aid were mixed evenly and then sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0080] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0081] Comparative Example 4

[0082] The difference from Example 3 is that tannic acid was not added in step S4.

[0083] Specifically as follows:

[0084] S1. Preparation of modified alumina powder: 2.5g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 50℃, stirred for 3h, centrifuged, washed and dried to obtain modified alumina powder.

[0085] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6.4g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.1g of zirconium chloride was added, and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g of sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0086] S3. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0087] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, added to 200mL of Tris-HCl solution with pH 9, 4g of phytic acid was added, heated to 50℃, stirred for 5h, filtered, washed, and dried to obtain modified zirconium silicate whiskers.

[0088] S5. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0089] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate, 7g of modified zirconium silicate whiskers, and 1.5g of sintering aid were mixed evenly and then sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0090] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0091] Comparative Example 5

[0092] The difference from Example 3 is that step S4 was not performed.

[0093] Specifically as follows:

[0094] S1. Preparation of modified alumina powder: 2.5g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 50℃, stirred for 3h, centrifuged, washed and dried to obtain modified alumina powder.

[0095] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6.4g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.1g of zirconium chloride was added, and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g of sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0096] S3. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0097] S4. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0098] S5. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate generation, 7g of zirconium silicate whiskers, and 1.5g of sintering aid were mixed evenly and then sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0099] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0100] Comparative Example 6

[0101] The difference from Example 3 is that no sintering aid was added in step S6.

[0102] Specifically as follows:

[0103] S1. Preparation of modified alumina powder: 2.5g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 50℃, stirred for 3h, centrifuged, washed and dried to obtain modified alumina powder.

[0104] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6.4g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.1g of zirconium chloride was added, and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g of sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0105] S3. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0106] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9. 2.5g of phytic acid and 1.5g of tannic acid were added, and the mixture was heated to 50℃ and stirred for 5h. After filtering, washing, and drying, modified zirconium silicate whiskers were obtained.

[0107] S5. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate formation and 7g of modified zirconium silicate whiskers were mixed evenly and sintered by discharge plasma to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0108] The pulse sequence for the discharge plasma sintering was set to 12:2, and it was carried out in a dynamic vacuum of 6 Pa. The sintering temperature range was 1250℃, and the holding time was 8 min.

[0109] Comparative Example 7

[0110] The difference from Example 3 is that discharge plasma sintering was not performed in step S6.

[0111] Specifically as follows:

[0112] S1. Preparation of modified alumina powder: 2.5g of silane coupling agent KH590, 10g of alumina powder and 1g of triethylamine were added to 150mL of ethanol, heated to 50℃, stirred for 3h, centrifuged, washed and dried to obtain modified alumina powder.

[0113] S2. Preparation of alumina powder with in-situ zirconium silicate: 50g of modified alumina powder and 6.4g of tetraethyl orthosilicate were mixed and added to 300mL of ethanol. 7.1g of zirconium chloride was added, and the mixture was heated under reflux and stirred for 22h. The solvent was removed under reduced pressure, and the mixture was dried. It was then mixed with 12g of sodium molybdate and calcined at 1570℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain alumina powder with in-situ zirconium silicate.

[0114] S3. Preparation of zirconium silicate whiskers: 6.5g of tetraethyl orthosilicate was added to 150mL of ethanol, along with 7.1g of zirconium chloride and 12g of lithium fluoride. The mixture was heated under reflux and stirred for 24h. The solvent was removed under reduced pressure, and the mixture was dried. The mixture was then mixed with 3g of sodium molybdate and calcined at 950℃ for 3h. After washing with water and 10wt% HF aqueous solution, the mixture was dried to obtain zirconium silicate whiskers.

[0115] S4. Preparation of modified zirconium silicate whiskers: 10g of zirconium silicate whiskers were added to 25wt% hydrogen peroxide and heated to 35℃. After stirring for 1h, the mixture was filtered, dried, and added to 200mL of Tris-HCl solution with pH 9. 2.5g of phytic acid and 1.5g of tannic acid were added, and the mixture was heated to 50℃ and stirred for 5h. After filtering, washing, and drying, modified zirconium silicate whiskers were obtained.

[0116] S5. Preparation of sintering aid: 1.5g lanthanum chloride and 1.5g yttrium chloride were added to 100mL ethanol, 10g tetraethyl orthosilicate and 2.5g magnesium chloride were added, 50mL water was added, the pH of the solution was adjusted to 5.5, heated to 50℃, stirred for 6h, filtered, washed, dried, and calcined at 650℃ for 3h to obtain the sintering aid;

[0117] S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramic: 100g of alumina powder with in-situ zirconium silicate formation, 7g of modified zirconium silicate whiskers, and 1.5g of sintering aid are mixed evenly, heated to 1500℃, and calcined for 3h to obtain modified zirconium silicate whisker-reinforced alumina ceramic.

[0118] Test Example 1

[0119] The modified zirconium silicate whisker-reinforced alumina ceramics obtained in Examples 1-3 and Comparative Examples 1-7 were prepared into samples with dimensions of 35 mm × 35 mm × 2.5 mm.

[0120] The bending strength of the material was tested using the three-point bending method with a span of 20 mm and a pressing head rate of 0.5 mm / min.

[0121] The thermal shock resistance of the specimens was tested using the cyclic thermal shock method. The specimens were placed in an electric furnace at 1380℃ and held for 14 minutes, then removed and air-cooled. After 30 minutes, the specimens were placed back in the electric furnace for heating, holding, and cooling. This process was repeated multiple times until cracks or fractures appeared in the specimens. The number of thermal shocks before specimen failure was recorded.

[0122] The abrasion resistance of the samples was tested according to GB / T3810-2016 "Test Methods for Ceramic Tiles". The abrasion resistance grades are shown in Table 1.

[0123] Table 1

[0124]

[0125] The results are shown in Table 2.

[0126] Table 2

[0127]

[0128] As can be seen from the table above, the modified zirconium silicate whisker-reinforced alumina ceramics prepared in Examples 1-3 of the present invention have good comprehensive properties.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing modified zirconium silicate whisker-reinforced alumina ceramic, characterized in that, Zirconium silicate was generated in situ by modifying the surface of alumina powder with a silane coupling agent containing mercapto groups. After being uniformly mixed with zirconium silicate whiskers that had been treated with hydrogen peroxide, modified with phytic acid and tannic acid, and a La2O3-Y2O3-MgO-SiO2 composite, modified zirconium silicate whisker-reinforced alumina ceramic was obtained by discharge plasma sintering. The specific preparation method for in-situ generation of zirconium silicate after surface modification of alumina powder with a thiol-containing silane coupling agent is as follows: S1. Preparation of modified alumina powder: Add a silane coupling agent with mercapto groups and alumina powder to ethanol, heat and stir to react, centrifuge, wash, and dry to obtain modified alumina powder; S2. Preparation of alumina powder with in-situ zirconium silicate: Modified alumina powder and tetraethyl orthosilicate were mixed, added to ethanol, zirconium chloride was added, the mixture was heated and stirred under reflux, the solvent was removed under reduced pressure, dried, mixed with sodium molybdate, calcined, washed with water and HF aqueous solution, and dried to obtain alumina powder with in-situ zirconium silicate.

2. The preparation method according to claim 1, characterized in that, Includes the following steps: S1. Preparation of modified alumina powder: Add a silane coupling agent with mercapto groups and alumina powder to ethanol, heat and stir to react, centrifuge, wash, and dry to obtain modified alumina powder; S2. Preparation of alumina powder with in-situ zirconium silicate: Modified alumina powder and tetraethyl orthosilicate were mixed, added to ethanol, zirconium chloride was added, the mixture was heated and stirred under reflux, the solvent was removed under reduced pressure, dried, mixed with sodium molybdate, calcined, washed with water and HF aqueous solution, and dried to obtain alumina powder with in-situ zirconium silicate. S3. Preparation of zirconium silicate whiskers: Tetraethyl orthosilicate was added to ethanol, zirconium chloride and lithium fluoride were added, the mixture was heated to reflux and stirred to react, the solvent was removed under reduced pressure, dried, mixed with sodium molybdate, calcined, washed with water and HF aqueous solution, and dried to obtain zirconium silicate whiskers; S4. Preparation of modified zirconium silicate whiskers: After heating the zirconium silicate whiskers in hydrogen peroxide, filter, dry, add them to Tris-HCl solution, add phytic acid and tannic acid, heat and stir to react, filter, wash, and dry to obtain modified zirconium silicate whiskers. S5. Preparation of sintering aid: Lanthanum chloride and yttrium chloride are added to ethanol, along with tetraethyl orthosilicate and magnesium chloride. Water is added to adjust the pH of the solution. The mixture is heated and stirred to react, then filtered, washed, dried, and calcined to obtain the sintering aid. S6. Preparation of modified zirconium silicate whisker-reinforced alumina ceramics: Alumina powder with in-situ zirconium silicate, modified zirconium silicate whiskers, and sintering aids are mixed evenly, and modified zirconium silicate whisker-reinforced alumina ceramics are obtained by discharge plasma sintering.

3. The preparation method according to claim 2, characterized in that, The silane coupling agent with mercapto group mentioned in step S1 is at least one of KH580 and KH590, the mass ratio of the silane coupling agent with mercapto group to alumina powder is 2-3:10, the heating and stirring reaction temperature is 45-55℃, and the time is 2-4h.

4. The preparation method according to claim 2, characterized in that, In step S2, the mass ratio of modified alumina powder, tetraethyl orthosilicate, zirconium chloride, and sodium molybdate is 50:6-7:7-7.3:8-15. The heating, reflux, and stirring reaction time is 20-24 hours. The concentration of the HF aqueous solution is 5-15 wt%. The calcination temperature is 1550-1600℃, and the time is 2-4 hours.

5. The preparation method according to claim 2, characterized in that, In step S3, the mass ratio of tetraethyl orthosilicate, zirconium chloride, lithium fluoride, and sodium molybdate is 6-7:7-7.2:7-15:2-4. The heating, reflux, and stirring reaction time is 22-26 h. The calcination temperature is 900-1000 °C and the time is 2-4 h. The concentration of the HF aqueous solution is 5-15 wt%.

6. The preparation method according to claim 2, characterized in that, In step S4, the concentration of hydrogen peroxide is 20-30 wt%, the heating treatment temperature is 30-40℃, the time is 0.5-1.5 h, the mass ratio of zirconium silicate whiskers, phytic acid, and tannic acid is 10:2-3:1-2, the heating and stirring reaction temperature is 45-55℃, the time is 4-6 h, and the pH value of the Tris-HCl solution is 8.5-9.

5.

7. The preparation method according to claim 2, characterized in that, In step S5, the mass ratio of lanthanum chloride, yttrium chloride, tetraethyl orthosilicate, and magnesium chloride is 1-2:1-2:8-12:2-3. The pH of the solution is adjusted to 5-6. The heating and stirring reaction is carried out at a temperature of 45-55°C for 5-7 hours. The calcination is carried out at a temperature of 600-700°C for 2-4 hours.

8. The preparation method according to claim 2, characterized in that, In step S6, the mass ratio of alumina powder for in-situ generation of zirconium silicate, modified zirconium silicate whiskers, and sintering aid is 100:5-10:1-2. The pulse sequence for the discharge plasma sintering is set to 12:

2. The sintering is carried out in a dynamic vacuum of 5-7 Pa, with a sintering temperature range of 1200-1300℃ and a holding time of 5-10 min.

9. A modified zirconium silicate whisker-reinforced alumina ceramic prepared by the preparation method according to any one of claims 1-8.

10. The application of the modified zirconium silicate whisker-reinforced alumina ceramic as described in claim 9 in the preparation of wear-resistant materials.

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