High-strength special ceramic and preparation method thereof

Abstract

The invention belongs to the technical field of special ceramic preparation, and particularly relates to high-strength special ceramic and a preparation method thereof. The high-strength special ceramic is prepared from the following raw materials: alumina powder, quartz powder, serpentine, phosphorus slag, eucryptite, barium borate, nano yttrium trifluoride, nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and polyborosilazane. According to the high-strength special ceramic disclosed by the invention, the aluminum oxide powder, the quartz powder, the serpentine and the phosphorus slag are taken as matrix raw materials, eucryptite, barium borate and yttrium trifluoride are taken as fluxing agents, and nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and polyborosilazane are taken as fillers, so that the prepared special ceramic has excellent bending strength and fracture toughness.

Description

Technical Field

[0001] This invention belongs to the field of special ceramics preparation technology, specifically relating to a high-strength special ceramic and its preparation method. Background Technology

[0002] Specialty ceramic products are mainly used in various modern industries and cutting-edge technologies, such as aerospace, nuclear industry, new energy, and national defense. These fields urgently require a large amount of new materials, and specialty ceramics, due to their excellent heat resistance, dielectric properties, wear resistance, thermal insulation, piezoelectric properties, and light transmittance, have received widespread attention from various countries. Specialty ceramic materials include many types such as high-alumina ceramics, magnesia ceramics, titania-magnesia ceramics, zircon ceramics, lithium ceramics, magnetic ceramics, and cermets.

[0003] In terms of raw materials, special ceramics break through the traditional ceramics' limitation of using clay as the main raw material, generally using oxides, nitrides, silicides, borides, carbides, etc., as the main raw materials. In terms of processing, the chemical composition, particle size distribution, and particle morphology of special ceramics require strict control, necessitating precise stoichiometry and new equipment technologies to achieve certain special performance requirements. However, existing special ceramics still suffer from the drawback of difficulty in simultaneously improving mechanical strength and toughness, significantly limiting their application range. Therefore, it is necessary to develop a new type of high-strength special ceramic. Summary of the Invention

[0004] The purpose of this invention is to provide a special ceramic with excellent flexural strength and fracture toughness; in addition, this invention also provides a method for its preparation.

[0005] The high-strength special ceramic of the present invention is composed of the following raw materials in parts by weight: 70-71 parts alumina powder, 1.2-1.5 parts quartz powder, 3.5-4.0 parts serpentine, 1.4-1.5 parts phosphorus slag, 1.2-1.5 parts nepheline, 0.8-1.0 parts barium borate, 0.2-0.3 parts nano yttrium trifluoride, 3.5-4.0 parts nano hafnium boride, 2.0-2.1 parts nano strontium zirconate, 2.5-2.8 parts nano lanthanum titanate, and 1.8-2.0 parts polyborosilicate.

[0006] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0007] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0008] The method for preparing high-strength special ceramics according to the present invention comprises the following steps: (1) Place nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and nano yttrium trifluoride into a ball mill jar, add anhydrous ethanol and polyacrylamide for ball milling, and then perform ultrasonic dispersion after ball milling to prepare nano powder slurry. (2) Alumina powder, quartz powder, serpentine, phosphorus slag, nepheline and barium borate are added to the nano powder slurry and ball milled for 6-6.5 hours. Then anhydrous ethanol-polyborosilicate mixture is added and stirred evenly. Finally, the mixture is dried and sieved to prepare ceramic powder. (3) The ceramic powder is mixed with deionized water to form a slurry, then granulated by spray drying, and finally cold isostatic pressing is performed to prepare the green body; (4) The green blank obtained in step (3) is sintered under a nitrogen atmosphere and then cooled to room temperature to prepare high-strength special ceramics.

[0009] In step (1), the mass ratio of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride to anhydrous ethanol is 1:1.

[0010] In step (1), the mass of polyacrylamide accounts for 0.2% of the total mass of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride.

[0011] In step (1), the ball milling speed is 300 r / min and the ball milling time is 15-17 h; the ultrasonic dispersion power is 300 W and the ultrasonic dispersion time is 40-50 min.

[0012] In step (2), the ball mill is run at a speed of 300 r / min for 6-6.5 h.

[0013] The anhydrous ethanol-polyborosilicate mixture mentioned in step (2) is made by mixing anhydrous ethanol and polyborosilicate at a mass ratio of 2:1.

[0014] In step (2), the stirring speed when adding the anhydrous ethanol-polyborosilicate mixture is 250 r / min and the stirring time is 25-30 min.

[0015] In step (2), the drying temperature is 70℃, the drying time is 12h, the drying vacuum degree is -0.08MPa, and it passes through a 100-mesh sieve.

[0016] In step (3), the mass ratio of ceramic powder to deionized water is 1:0.3.

[0017] In step (3), the inlet temperature during granulation is 180℃ and the outlet temperature is 80℃.

[0018] In step (3), the pressure for cold isostatic pressing is 210 MPa, and the holding time is 8-10 min.

[0019] The sintering process in step (4) involves heating from room temperature to 120-125℃ at a rate of 2℃ / min and holding for 20-25 min, then heating to 400-405℃ at a rate of 1℃ / min and holding for 45-50 min, heating to 800-805℃ at a rate of 3℃ / min and holding for 20-25 min, heating to 1450-1455℃ at a rate of 3℃ / min and holding for 43-45 min, and finally heating to 1605-1610℃ at a rate of 2℃ / min and holding for 1.8 h.

[0020] The final cooling to room temperature mentioned in step (4) is to first cool down to 1000°C at a rate of 5°C / min, and then cool down to room temperature with the furnace.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The high-strength special ceramics of the present invention use alumina powder, quartz powder, serpentine and phosphorus slag as matrix raw materials, lithium nepheline, barium borate and yttrium trifluoride as fluxes, and nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and polyborosilicate as fillers to ensure that the prepared special ceramics have excellent bending strength and fracture toughness.

[0022] (2) The high-strength special ceramic of the present invention uses alumina powder, quartz powder, serpentine and phosphorus slag as matrix raw materials. Alumina powder is the main raw material. After sintering, it forms a continuous and dense corundum skeleton, which provides core strength and hardness support for the special ceramic and is the main bearing phase for mechanical properties. Quartz powder provides active SiO2, which on the one hand generates mullite phase in situ with alumina, and improves the toughness of the matrix through fine grain strengthening. On the other hand, it undergoes a eutectic reaction with phosphorus slag, which effectively reduces the viscosity of the sintering liquid phase and promotes mass transfer and densification between powder particles. Serpentine provides MgO, which generates aluminum-magnesium spinel in situ with alumina at high temperature. The aluminum-magnesium spinel phase effectively inhibits the coarsening of corundum grains by pinning grain boundaries. At the same time, the SiO2 released by the decomposition of serpentine can supplement the silicon source required for the formation of mullite phase. 2+ The infiltration of the sintered glassy phase network optimizes the thermal expansion matching between the matrix and the secondary phase, reducing interfacial thermal stress cracks. The CaO introduced by the phosphorus slag and the MgO provided by serpentine synergistically regulate the sintering liquid phase characteristics, broaden the liquid phase stability temperature range (i.e., the sintering window), and improve the uniformity of ceramic density. P2O5 in the phosphorus slag forms a liquid phase at high temperature, dissolving impurities and purifying grain boundaries. CaF2 in the phosphorus slag forms gun crystal microcrystals during sintering, which further enhances the fracture toughness of the ceramic by inducing microcrack deflection and branching effects.

[0023] (3) The high-strength special ceramic of the present invention uses nepheline, barium borate and yttrium trifluoride as fluxes. Nepheline melts first in the medium and low temperature range, wetting the surface of powder particles such as alumina and nanofillers, eliminating interparticle interfacial tension, and building a substrate for subsequent liquid phase diffusion. Barium borate gradually dissolves in the initial liquid phase formed by nepheline in the medium temperature range, synergistically forming a low-viscosity Ba-B-Li-Si quaternary composite liquid phase, significantly reducing interparticle mass transfer resistance and accelerating the densification process of the ceramic body. Yttrium trifluoride has a dual role in the high temperature range: on the one hand, it releases F - On the one hand, the density is further improved by disconnecting the network and reducing viscosity; on the other hand, Y is dissociated. 3+ Its ionic radius is similar to that of Al 3+ Significant differences exist; the material preferentially adsorbs at the grain boundaries of corundum, mullite, and spinel phases, hindering the migration of grain growth units through grain boundary pinning. Thus, the synergistic effect of these three factors significantly reduces the sintering temperature and, through the dual effects of accelerating densification and inhibiting grain growth, lays the foundation for the high strength and high toughness of the ceramic matrix.

[0024] (4) The high-strength special ceramic of the present invention uses nano-hafnium boride, nano-strontium zirconate, nano-lanthanum titanate, and polyborosilicate as fillers, which work synergistically to improve the mechanical strength of the prepared ceramic. Among them, nano-hafnium boride forms a rigid skeleton and induces crack deflection; nano-strontium zirconate has a higher coefficient of thermal expansion than corundum matrix, and induces tensile stress microcracks at grain boundaries during cooling, accompanied by crack deflection / bridging, thereby improving fracture toughness; nano-lanthanum titanate serves as a heterogeneous nucleation site to refine the main phase grains, while La 3+ Enriching at grain boundaries purifies impurities and strengthens grain boundary bonding, achieving fine grain control and grain boundary strengthening. Polyborosilazane can cross-link and solidify at low temperatures. Its excellent adhesion to ceramic powder helps improve the density and drying strength of the green body, reducing defects in the green body after cold isostatic pressing. As the temperature rises, it gradually undergoes pyrolysis, releasing small molecule byproducts and forming an amorphous ceramic precursor structure. With further temperature increases, final ceramization is completed at high temperatures. Combined with a nitrogen inert atmosphere, the product is a SiC and Si3N4 composite ceramic phase. This ceramization product can fill the micropores and grain boundary gaps within the matrix, improving both the overall density of the ceramic and strengthening grain boundary bonding, thus enhancing the mechanical stability of the ceramic. Therefore, these four components construct a four-fold synergistic system of "hard strengthening - microcrack toughening - fine grain control - dense reinforcement," ultimately endowing special ceramics with excellent flexural strength and fracture toughness.

[0025] (5) The preparation method of the high-strength special ceramics described in this invention has easy-to-control process parameters, is easy to realize industrial production, and the prepared special ceramics have stable performance. Detailed Implementation

[0026] Example 1 The high-strength special ceramic described in Example 1 is composed of the following raw materials by weight: 70.5 parts alumina powder, 1.3 parts quartz powder, 3.7 parts serpentine, 1.45 parts phosphorus slag, 1.4 parts nepheline, 0.9 parts barium borate, 0.25 parts nano yttrium trifluoride, 3.8 parts nano hafnium borate, 2.05 parts nano strontium zirconate, 2.6 parts nano lanthanum titanate, and 1.9 parts polyborosilicate.

[0027] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0028] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0029] The preparation method of the high-strength special ceramics described in Example 1 consists of the following steps: (1) Place nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and nano yttrium trifluoride into a ball mill jar, add anhydrous ethanol and polyacrylamide for ball milling, and then perform ultrasonic dispersion after ball milling to prepare nano powder slurry. (2) Alumina powder, quartz powder, serpentine, phosphorus slag, nepheline and barium borate were added to the nano powder slurry and ball milled for 6.3 h. Then anhydrous ethanol-polyborosilicate mixture was added and stirred evenly. Finally, the mixture was dried and sieved to prepare ceramic powder. (3) The ceramic powder is mixed with deionized water to form a slurry, then granulated by spray drying, and finally cold isostatic pressing is performed to prepare the green body; (4) The green blank obtained in step (3) is sintered under a nitrogen atmosphere and then cooled to room temperature in the furnace to prepare high-strength special ceramics.

[0030] In step (1), the mass ratio of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride to anhydrous ethanol is 1:1.

[0031] In step (1), the mass of polyacrylamide accounts for 0.2% of the total mass of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride.

[0032] In step (1), the ball milling speed is 300 r / min and the ball milling time is 16 h; the ultrasonic dispersion power is 300 W and the ultrasonic dispersion time is 45 min.

[0033] In step (2), the ball milling is performed at a speed of 300 r / min for 6.3 h.

[0034] The anhydrous ethanol-polyborosilicate mixture mentioned in step (2) is made by mixing anhydrous ethanol and polyborosilicate at a mass ratio of 2:1.

[0035] In step (2), the stirring speed when adding the anhydrous ethanol-polyborosilicate mixture is 250 r / min and the stirring time is 27 min.

[0036] In step (2), the drying temperature is 70℃, the drying time is 12h, the drying vacuum degree is -0.08MPa, and it passes through a 100-mesh sieve.

[0037] In step (3), the mass ratio of ceramic powder to deionized water is 1:0.3.

[0038] In step (3), the inlet temperature during granulation is 180℃ and the outlet temperature is 80℃.

[0039] In step (3), the pressure for cold isostatic pressing is 210 MPa, and the holding time is 9 min.

[0040] The sintering process in step (4) involves heating from room temperature to 123°C at a rate of 2°C / min and holding for 23 min, then heating to 403°C at a rate of 1°C / min and holding for 47 min, heating to 803°C at a rate of 3°C / min and holding for 23 min, heating to 1453°C at a rate of 3°C / min and holding for 44 min, and finally heating to 1607°C at a rate of 2°C / min and holding for 1.8 h.

[0041] The final cooling to room temperature mentioned in step (4) is to first cool down to 1000°C at a rate of 5°C / min, and then cool down to room temperature with the furnace.

[0042] Example 2 The high-strength special ceramic described in Example 2 is composed of the following raw materials by weight: 71 parts alumina powder, 1.5 parts quartz powder, 3.5 parts serpentine, 1.5 parts phosphorus slag, 1.5 parts nepheline, 0.8 parts barium borate, 0.3 parts nano yttrium trifluoride, 3.5 parts nano hafnium borate, 2.1 parts nano strontium zirconate, 2.5 parts nano lanthanum titanate, and 2.0 parts polyborosilicate.

[0043] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0044] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0045] The preparation method of the high-strength special ceramics described in Example 2 consists of the following steps: (1) Place nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and nano yttrium trifluoride into a ball mill jar, add anhydrous ethanol and polyacrylamide for ball milling, and then perform ultrasonic dispersion after ball milling to prepare nano powder slurry. (2) Alumina powder, quartz powder, serpentine, phosphorus slag, nepheline and barium borate were added to the nano powder slurry and ball milled for 6.5 h. Then anhydrous ethanol-polyborosilicate mixture was added and stirred evenly. Finally, the mixture was dried and sieved to prepare ceramic powder. (3) The ceramic powder is mixed with deionized water to form a slurry, then granulated by spray drying, and finally cold isostatic pressing is performed to prepare the green body; (4) The green blank obtained in step (3) is sintered under a nitrogen atmosphere and then cooled to room temperature in the furnace to prepare high-strength special ceramics.

[0046] In step (1), the mass ratio of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride to anhydrous ethanol is 1:1.

[0047] In step (1), the mass of polyacrylamide accounts for 0.2% of the total mass of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride.

[0048] In step (1), the ball milling speed is 300 r / min and the ball milling time is 15 h; the ultrasonic dispersion power is 300 W and the ultrasonic dispersion time is 40 min.

[0049] In step (2), the ball milling is performed at a speed of 300 r / min for 6.5 h.

[0050] The anhydrous ethanol-polyborosilicate mixture mentioned in step (2) is made by mixing anhydrous ethanol and polyborosilicate at a mass ratio of 2:1.

[0051] In step (2), the stirring speed when adding the anhydrous ethanol-polyborosilicate mixture is 250 r / min and the stirring time is 30 min.

[0052] In step (2), the drying temperature is 70℃, the drying time is 12h, the drying vacuum degree is -0.08MPa, and it passes through a 100-mesh sieve.

[0053] In step (3), the mass ratio of ceramic powder to deionized water is 1:0.3.

[0054] In step (3), the inlet temperature during granulation is 180℃ and the outlet temperature is 80℃.

[0055] In step (3), the pressure for cold isostatic pressing is 210 MPa, and the holding time is 8 min.

[0056] The sintering process in step (4) involves heating from room temperature to 120°C at a rate of 2°C / min and holding for 25 min, then heating to 400°C at a rate of 1°C / min and holding for 45 min, heating to 800°C at a rate of 3°C / min and holding for 20 min, heating to 1450°C at a rate of 3°C / min and holding for 43 min, and finally heating to 1605°C at a rate of 2°C / min and holding for 1.8 h.

[0057] The final cooling to room temperature mentioned in step (4) is to first cool down to 1000°C at a rate of 5°C / min, and then cool down to room temperature with the furnace.

[0058] Example 3 The high-strength special ceramic described in Example 3 is composed of the following raw materials by weight: 70 parts alumina powder, 1.2 parts quartz powder, 4.0 parts serpentine, 1.4 parts phosphorus slag, 1.2 parts nepheline, 1.0 part barium borate, 0.2 parts nano yttrium trifluoride, 4.0 parts nano hafnium borate, 2.0 parts nano strontium zirconate, 2.8 parts nano lanthanum titanate, and 1.8 parts polyborosilicate.

[0059] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0060] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0061] The preparation method of the high-strength special ceramics described in Example 3 consists of the following steps: (1) Place nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and nano yttrium trifluoride into a ball mill jar, add anhydrous ethanol and polyacrylamide for ball milling, and then perform ultrasonic dispersion after ball milling to prepare nano powder slurry. (2) Alumina powder, quartz powder, serpentine, phosphorus slag, nepheline and barium borate were added to the nano powder slurry and ball milled for 6 hours. Then anhydrous ethanol-polyborosilicate mixture was added and stirred evenly. Finally, the mixture was dried and sieved to prepare ceramic powder. (3) The ceramic powder is mixed with deionized water to form a slurry, then granulated by spray drying, and finally cold isostatic pressing is performed to prepare the green body; (4) The green blank obtained in step (3) is sintered under a nitrogen atmosphere and then cooled to room temperature in the furnace to prepare high-strength special ceramics.

[0062] In step (1), the mass ratio of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride to anhydrous ethanol is 1:1.

[0063] In step (1), the mass of polyacrylamide accounts for 0.2% of the total mass of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride.

[0064] In step (1), the ball milling speed is 300 r / min and the ball milling time is 17 h; the ultrasonic dispersion power is 300 W and the ultrasonic dispersion time is 50 min.

[0065] In step (2), the ball mill is run at a speed of 300 r / min for 6 hours.

[0066] The anhydrous ethanol-polyborosilicate mixture mentioned in step (2) is made by mixing anhydrous ethanol and polyborosilicate at a mass ratio of 2:1.

[0067] In step (2), the stirring speed when adding the anhydrous ethanol-polyborosilicate mixture is 250 r / min and the stirring time is 25 min.

[0068] In step (2), the drying temperature is 70℃, the drying time is 12h, the drying vacuum degree is -0.08MPa, and it passes through a 100-mesh sieve.

[0069] In step (3), the mass ratio of ceramic powder to deionized water is 1:0.3.

[0070] In step (3), the inlet temperature during granulation is 180℃ and the outlet temperature is 80℃.

[0071] In step (3), the pressure for cold isostatic pressing is 210 MPa, and the holding time is 10 min.

[0072] The sintering process in step (4) involves heating from room temperature to 125°C at a rate of 2°C / min and holding for 20 min, then heating to 405°C at a rate of 1°C / min and holding for 50 min, heating to 800°C at a rate of 3°C / min and holding for 25 min, heating to 1455°C at a rate of 3°C / min and holding for 45 min, and finally heating to 1610°C at a rate of 2°C / min and holding for 1.8 h.

[0073] The final cooling to room temperature mentioned in step (4) is to first cool down to 1000°C at a rate of 5°C / min, and then cool down to room temperature with the furnace.

[0074] Comparative Example 1 The preparation method of the high-strength special ceramic described in Comparative Example 1 is the same as that in Example 1, the only difference being the composition of the raw materials. The high-strength special ceramic described in Comparative Example 1, by weight, consists of the following raw materials: 70.5 parts alumina powder, 1.3 parts quartz powder, 3.7 parts serpentine, 1.45 parts phosphorus slag, 1.4 parts nepheline, 0.9 parts barium borate, 0.25 parts nano-yttrium trifluoride, 2.05 parts nano-strontium zirconate, 2.6 parts nano-lanthanum titanate, and 1.9 parts polyborosilicate.

[0075] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0076] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0077] Comparative Example 2 The preparation method of the high-strength special ceramic described in Comparative Example 2 is the same as that in Example 1, except that the raw material composition is different. The high-strength special ceramic described in Comparative Example 2, by weight, is composed of the following raw materials: 70.5 parts alumina powder, 1.3 parts quartz powder, 3.7 parts serpentine, 1.45 parts phosphorus slag, 1.4 parts nepheline, 0.9 parts barium borate, 0.25 parts nano yttrium trifluoride, 3.8 parts nano hafnium boride, 2.6 parts nano lanthanum titanate, and 1.9 parts polyborosilicate.

[0078] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0079] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0080] Comparative Example 3 The preparation method of the high-strength special ceramic described in Comparative Example 3 is the same as that in Example 1, except that the raw material composition is different. The high-strength special ceramic described in Comparative Example 3, by weight, is composed of the following raw materials: 70.5 parts alumina powder, 1.3 parts quartz powder, 3.7 parts serpentine, 1.45 parts phosphorus slag, 1.4 parts nepheline, 0.9 parts barium borate, 0.25 parts nano yttrium trifluoride, 3.8 parts nano hafnium boride, 2.05 parts nano strontium zirconate, and 1.9 parts polyborosilicate.

[0081] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0082] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0083] Comparative Example 4 The preparation method of the high-strength special ceramic described in Comparative Example 4 is the same as that in Example 1, except that the raw material composition is different. The high-strength special ceramic described in Comparative Example 4, by weight, is composed of the following raw materials: 70.5 parts alumina powder, 1.3 parts quartz powder, 3.7 parts serpentine, 1.45 parts phosphorus slag, 1.4 parts nepheline, 0.9 parts barium borate, 0.25 parts nano yttrium trifluoride, 3.8 parts nano hafnium boride, 2.05 parts nano strontium zirconate, and 2.6 parts nano lanthanum titanate.

[0084] The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

[0085] The manufacturer of polyborosilazane is Anhui Aiyota Silicon Oil Co., Ltd., and the model number is IOTA-9120.

[0086] The high-strength special ceramics prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance testing. Fracture toughness was tested according to ASTM C1421, and flexural strength was tested according to ASTM C1161. The results are shown in Table 1 below. Table 1 Test Results of High-Strength Special Ceramics

[0087] As shown in Table 1, the flexural strength and fracture toughness of the special ceramics prepared in Examples 1-3 are significantly better than those in Comparative Examples 1-4. The performance of the special ceramics prepared in Comparative Examples 1-4 is greatly reduced due to the absence of any one of nano hafnium boride, nano lanthanum titanate, nano strontium zirconate, and polyborosilicate.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-strength special ceramic, characterized in that: By weight, it is composed of the following raw materials: 70-71 parts alumina powder, 1.2-1.5 parts quartz powder, 3.5-4.0 parts serpentine, 1.4-1.5 parts phosphorus slag, 1.2-1.5 parts nepheline, 0.8-1.0 parts barium borate, 0.2-0.3 parts nano yttrium trifluoride, 3.5-4.0 parts nano hafnium boride, 2.0-2.1 parts nano strontium zirconate, 2.5-2.8 parts nano lanthanum titanate, and 1.8-2.0 parts polyborosilicate.

2. The high-strength special ceramic according to claim 1, characterized in that: The phosphorus slag, by mass percentage, has the following chemical composition: CaO 43.07%, SiO2 36.12%, Al2O3 3.28%, Fe2O3 1.36%, MgO 4.87%, SO3 4.55%, CaF2 3.09%, P2O5 2.00%, and loss on ignition 1.66%.

3. A method for preparing the high-strength special ceramic according to claim 1, characterized in that: It consists of the following steps: (1) Place nano hafnium boride, nano strontium zirconate, nano lanthanum titanate and nano yttrium trifluoride into a ball mill jar, add anhydrous ethanol and polyacrylamide for ball milling, and then perform ultrasonic dispersion after ball milling to prepare nano powder slurry. (2) Alumina powder, quartz powder, serpentine, phosphorus slag, nepheline and barium borate are added to the nano powder slurry and ball milled for 6-6.5 hours. Then anhydrous ethanol-polyborosilicate mixture is added and stirred evenly. Finally, the mixture is dried and sieved to prepare ceramic powder. (3) The ceramic powder is mixed with deionized water to form a slurry, then granulated by spray drying, and finally cold isostatic pressing is performed to prepare the green body; (4) The green blank obtained in step (3) is sintered under a nitrogen atmosphere and then cooled to room temperature in the furnace to prepare high-strength special ceramics.

4. The method for preparing high-strength special ceramics according to claim 3, characterized in that: In step (1), the mass ratio of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride to anhydrous ethanol is 1:

1. In step (1), the mass of polyacrylamide accounts for 0.2% of the total mass of nano hafnium boride, nano strontium zirconate, nano lanthanum titanate, and nano yttrium trifluoride.

5. The method for preparing high-strength special ceramics according to claim 3, characterized in that: In step (1), the ball milling speed is 300 r / min and the ball milling time is 15-17 h; the ultrasonic dispersion power is 300 W and the ultrasonic dispersion time is 40-50 min.

6. The method for preparing high-strength special ceramics according to claim 3, characterized in that: In step (2), ball milling is performed at a speed of 300 r / min for 6-6.5 h; The anhydrous ethanol-polyborosilicate mixture mentioned in step (2) is made by mixing anhydrous ethanol and polyborosilicate at a mass ratio of 2:

1.

7. The method for preparing high-strength special ceramics according to claim 3, characterized in that: In step (2), the stirring speed when adding the anhydrous ethanol-polyborosilicate mixture is 250 r / min and the stirring time is 25-30 min. In step (2), the drying temperature is 70℃, the drying time is 12h, the drying vacuum degree is -0.08MPa, and it passes through a 100-mesh sieve.

8. The method for preparing high-strength special ceramics according to claim 3, characterized in that: In step (3), the mass ratio of ceramic powder to deionized water is 1:0.

3.

9. The method for preparing high-strength special ceramics according to claim 3, characterized in that: In step (3), the inlet temperature during granulation is 180℃ and the outlet temperature is 80℃. In step (3), the pressure for cold isostatic pressing is 210 MPa, and the holding time is 8-10 min.

10. The method for preparing high-strength special ceramics according to claim 3, characterized in that: The sintering process described in step (4) involves heating from room temperature to 120-125℃ at a heating rate of 2℃ / min and holding for 20-25 min, then heating to 400-405℃ at a heating rate of 1℃ / min and holding for 45-50 min, heating to 800-805℃ at a heating rate of 3℃ / min and holding for 20-25 min, heating to 1450-1455℃ at a heating rate of 3℃ / min and holding for 43-45 min, and finally heating to 1605-1610℃ at a heating rate of 2℃ / min and holding for 1.8 h. The final cooling to room temperature mentioned in step (4) is to first cool down to 1000 ℃ at a rate of 5 ℃ / min, and then cool down to room temperature with the furnace.

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