Lithium-free high-heat-resistant ceramic paste and preparation method thereof

Abstract

The application discloses a lithium-free high-heat-resistant ceramic mud and a preparation method thereof, and relates to the technical field of ceramic materials. In the preparation of the lithium-free high-heat-resistant ceramic mud, alumina is reacted with 3-(2,3-epoxypropoxy) propyl trimethoxysilane to obtain pre-modified alumina; the pre-modified alumina is reacted with starch to obtain modified alumina; ethyl acetoacetate, isopropyl alcohol, zirconium oxychloride, aluminum sec-butoxide, polyvinylpyrrolidone and N-N dimethylformamide are mixed to form a spinning solution, the spinning solution is electrospun, and then immersed in yttrium oxide sol to obtain alumina-zirconia-yttria composite fibers; the modified alumina, talc, alumina-zirconia-yttria fibers, hydroxypropyl methyl cellulose, glycerol, oleic acid, polyethylene glycol and water are stirred and mixed, and vacuum pugging is carried out to obtain the lithium-free high-heat-resistant ceramic mud. The lithium-free high-heat-resistant ceramic mud prepared by the application has good thermal shock resistance and bending strength after sintering.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a lithium-free high-heat-resistant ceramic clay and its preparation method. Background Technology

[0002] Traditional heat-resistant ceramics (such as spodumene ceramics and lithium feldspar ceramics) typically use lithium compounds as a key component, as lithium can lower the sintering temperature and increase density. However, mineral resources such as spodumene and lithium feldspar are not abundant in China and are mainly imported. With the explosive growth in demand for new energy vehicles and energy storage batteries in recent years, lithium prices have fluctuated dramatically. Therefore, developing a lithium-free high-heat-resistant ceramic is particularly important.

[0003] Cordierite has a low bulk density, with large gaps in its crystal structure, low symmetry, and a loose structure. Due to the ample space available for molecular vibrations during heating, it exhibits a low coefficient of thermal expansion and good thermal shock resistance. Therefore, it has broad application prospects in metallurgy, electronics, automotive, chemical, and environmental protection fields.

[0004] In alumina ceramics, aluminum and oxygen have a strong bond, resulting in excellent properties such as high melting point, high strength, high hardness, and good insulation. However, the material is relatively brittle and cannot withstand severe mechanical and thermal shock, exhibiting poor thermal shock resistance. Therefore, this invention uses alumina as a matrix and adds components that can reduce the coefficient of thermal expansion to prepare lithium-free high-heat-resistant ceramic clay. After sintering, the lithium-free high-heat-resistant ceramic clay exhibits good thermal shock resistance and flexural strength. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium-free high-heat-resistant ceramic clay and its preparation method, so as to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a lithium-free high heat-resistant ceramic clay, wherein the lithium-free high heat-resistant ceramic clay is prepared by mixing modified alumina, talc, alumina-zirconia-yttrium oxide fiber, hydroxypropyl methylcellulose, glycerol, oleic acid, polyethylene glycol and water, and then vacuum kneading the clay.

[0007] As an optimization, the alumina-zirconia-yttrium oxide fiber is prepared by mixing ethyl acetoacetate, isopropanol, zirconium oxychloride, aluminum sec-butoxide, polyvinylpyrrolidone, and N,N dimethylformamide to form a spinning solution, electrospinning the solution, and then immersing it in yttrium oxide sol.

[0008] As an optimization, the modified alumina is prepared by reacting alumina sequentially with 3-(2,3-epoxypropoxy)propyltrimethoxysilane and starch.

[0009] A method for preparing lithium-free, high-heat-resistant ceramic clay includes the following preparation steps:

[0010] (1) Mix pre-modified alumina, starch and N,N-dimethylformamide at a mass ratio of 1:(0.05~0.07):(10~12) until uniform, stir at 70~80℃ and 200~300r / min for 10~12h, centrifuge at 3000~4000r / min for 10~12min, wash the precipitate with anhydrous ethanol 3~5 times, and vacuum dry at 60~70℃ for 10~12h to obtain modified alumina;

[0011] (2) Mix ethyl acetoacetate and isopropanol at a mass ratio of 1:(5.5~6.5) until homogeneous. Stir at 500~700 r / min for 10~20 min at room temperature. Add zirconium oxychloride at 0.06~0.07 times the mass of ethyl acetoacetate. Stir at 500~700 r / min for 15~25 min at room temperature. Add aluminum sec-butoxide at 0.9~0.95 times the mass of ethyl acetoacetate and N,N dimethylformamide at 0.6~0.7 times the mass of ethyl acetoacetate. Stir at 500~700 r / min for 20~30 min at room temperature. Add ethyl... Polyvinylpyrrolidone (PVP) in 1-1.02 times the mass of ethyl acetylacetonate was stirred at 500-700 r / min for 5-6 h at room temperature to prepare a spinning solution. The spinning solution was added to an electrospinning machine for electrospinning. After being collected from the collecting roller, the solution was immersed in 15 wt% yttrium oxide sol and vacuum impregnated for 10 min. It was then placed in a vacuum oven and vacuum dried at 90℃ for 2 h. The solution was then transferred to a muffle furnace and heated to 800℃ at a heating rate of 2℃ / min and held for 2 h. After naturally cooling to room temperature, the solution was dispersed in a high-speed stirrer and cut to a length of 1-3 mm to obtain alumina-zirconia-yttrium oxide composite fibers.

[0012] (3) Modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose are added to a mixer in a mass ratio of 1:(0.13~0.14):(0.1~0.15):(0.06~0.08) and stirred for 2~3 hours. Then, 0.02~0.04 times the mass of modified alumina, 0.04~0.06 times the mass of modified alumina, 0.018~0.022 times the mass of modified alumina, and 0.2~0.3 times the mass of modified alumina are added and stirred for 20~40 minutes. The mixture is then vacuum-kneaded 3 times to obtain lithium-free high heat-resistant ceramic clay.

[0013] As an optimization, the preparation steps of the pre-modified alumina in step (1) are as follows: 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 95wt% ethanol aqueous solution are mixed evenly at a mass ratio of 1:(15~20), 10wt% citric acid aqueous solution is added to adjust the pH to 4, and the mixture is allowed to stand for hydrolysis for 50~60 min at room temperature. 0.4~0.5 times the mass of 3-(2,3-epoxypropoxy)propyltrimethoxysilane alumina is added, and the mixture is stirred at 500~600 r / min for 5~6 h at 40~50 °C. The mixture is then centrifuged at 10000~12000 r / min for 10~12 min, and the resulting precipitate is washed 3~5 times with anhydrous ethanol and dried under vacuum at 50~60 °C for 20~24 h to obtain the pre-modified alumina.

[0014] As an optimization, the starch in step (1) is soluble starch, purchased from Tianjin Yongda Chemical Reagent Co., Ltd.

[0015] As an optimization, the vacuum impregnation process parameters in step (2) are: vacuum pressure of 600 Pa and external pressure of 0.3 MPa.

[0016] As an optimization, the electrospinning technical parameters in step (2) are: electrospinning voltage of 12kV, feeding rate of 0.5mL / h, and spinning distance of 12cm.

[0017] As an optimization, the polyvinylpyrrolidone in step (2) is polyvinylpyrrolidone K30, which was purchased from Nantong Runfeng Petrochemical Co., Ltd.

[0018] As an optimization, the talc in step (3) is 325 mesh talc powder, purchased from Nanjing Chemical Reagent Co., Ltd.

[0019] As an optimization, the polyethylene glycol in step (3) has a weight-average molecular weight of 4000 and was purchased from Shanghai Yuanye Biotechnology Co., Ltd.

[0020] As an optimization, the alumina has an average particle size of 500 nm and was purchased from Shanghai Xiaohuang Nanotechnology Co., Ltd.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: In preparing lithium-free high heat-resistant ceramic clay, the present invention reacts alumina with 3-(2,3-epoxypropoxy)propyltrimethoxysilane to obtain pre-modified alumina; reacts the pre-modified alumina with starch to obtain modified alumina; mixes ethyl acetoacetate, isopropanol, zirconium oxychloride, aluminum sec-butoxide, polyvinylpyrrolidone, and N,N dimethylformamide to prepare a spinning solution, electrospins it, and then immerses it in yttrium oxide sol to obtain alumina-zirconia-yttrium oxide composite fibers; and mixes modified alumina, talc, alumina-zirconia-yttrium oxide fibers, hydroxypropyl methylcellulose, glycerol, oleic acid, polyethylene glycol, and water, and then vacuum kneads the clay to obtain lithium-free high heat-resistant ceramic clay.

[0022] First, alumina is reacted with 3-(2,3-epoxypropoxy)propyltrimethoxysilane to introduce epoxy groups onto the alumina surface, thus preparing pre-modified alumina. The pre-modified alumina is then reacted with starch to prepare modified alumina. The epoxy groups on the pre-modified alumina react with the hydroxyl groups on the starch surface, grafting starch onto the alumina surface. During subsequent sintering, the starch decomposes, forming uniform pores, avoiding localized macropores or defects, thereby improving the flexural strength of the lithium-free high-heat-resistant ceramic. Simultaneously, the porous structure effectively resists surface-generated thermal stress. When the ceramic is subjected to significant thermal stress, the internal molecules undergo vigorous movement; the loose structure provides more displacement space for the molecules, more effectively resisting thermal stress and thus improving the ceramic's thermal shock resistance.

[0023] Secondly, ethyl acetoacetate, isopropanol, zirconium oxychloride, aluminum sec-butoxide, polyvinylpyrrolidone, and N,N-dimethylformamide were mixed to prepare a spinning solution. After electrospinning, the solution was immersed in yttrium oxide sol to obtain alumina-zirconia-yttrium oxide composite fibers. These composite fibers, acting as a ceramic reinforcing phase, can improve the flexural strength of alumina ceramics when added to them. Simultaneously, during the sintering process, under the influence of yttrium oxide, when the porous ceramic sample is subjected to external force, the high-stress region at the microcracks and gas-solid interface within the ceramic induces the transformation of zirconia from a tetragonal phase to a monoclinic phase. This reduces the stress at the crack tip, alters the crack propagation path, increases crack propagation resistance, and enhances the fracture toughness of the ceramic, further improving the flexural strength and thermal shock resistance of the porous ceramic.

[0024] Finally, modified alumina, talc, alumina-zirconia-yttrium oxide fiber, hydroxypropyl methylcellulose, glycerol, oleic acid, polyethylene glycol, and water are stirred and mixed, and then vacuum-kneaded to obtain lithium-free high-heat-resistant ceramic clay. During the sintering process, the lithium-free high-heat-resistant ceramic clay can generate cordierite with a low coefficient of expansion, thus obtaining ceramic materials with a low coefficient of linear expansion, thereby improving the thermal shock resistance of ceramics. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] A method for preparing lithium-free, high-heat-resistant ceramic clay includes the following preparation steps:

[0028] (1) Mix 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 95wt% ethanol aqueous solution at a mass ratio of 1:15, adjust the pH to 4 with 10wt% citric acid aqueous solution, let stand for hydrolysis for 50 min at room temperature, add 0.4 times the mass of 3-(2,3-epoxypropoxy)propyltrimethoxysilane alumina, stir at 500 r / min for 5 h at 40 °C, centrifuge at 10000 r / min for 10 min, wash the precipitate three times with anhydrous ethanol, and vacuum dry at 50 °C for 20 h to obtain pre-modified alumina; mix pre-modified alumina, starch and N,N-dimethylformamide at a mass ratio of 1:0.05:10, stir at 200 r / min for 10 h at 70 °C, centrifuge at 3000 r / min for 10 min, wash the precipitate three times with anhydrous ethanol, and vacuum dry at 60 °C for 10 h to obtain modified alumina;

[0029] (2) Ethyl acetoacetate and isopropanol were mixed evenly at a mass ratio of 1:5.5. The mixture was stirred at 500 r / min for 10 min at room temperature. Zirconium oxychloride was added at 0.06 times the mass of ethyl acetoacetate. The mixture was stirred at 500 r / min for 15 min at room temperature. Aluminum sec-butoxide and N,N dimethylformamide were added at 0.9 times the mass of ethyl acetoacetate and 0.6 times the mass of ethyl acetoacetate. The mixture was stirred at 500 r / min for 20 min at room temperature. Polyvinylpyrrolidone was added at 1 times the mass of ethyl acetoacetate. The mixture was stirred at 500 r / min for 5 h at room temperature to obtain the spinning solution. The spinning solution was added to the electrospinning machine. Electrospinning was performed on a spinning machine. After collection from the collecting roller, the fibers were immersed in 15wt% yttrium oxide sol under vacuum for 10 minutes, then placed in a vacuum oven and dried at 90℃ for 2 hours. The fibers were then transferred to a muffle furnace and heated to 800℃ at a rate of 2℃ / min, held for 2 hours, and allowed to cool naturally to room temperature. The fibers were then dispersed in a high-speed stirrer and cut to a length of 1 mm to obtain alumina-zirconia-yttrium oxide composite fibers. The impregnation process parameters were: vacuum pressure of 600 Pa and applied pressure of 0.3 MPa; the spinning technical parameters were: electrospinning voltage of 12 kV, feed rate of 0.5 mL / h, and spinning distance of 12 cm.

[0030] (3) Modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose were added to a mixer in a mass ratio of 1:0.13:0.1:0.06 and stirred for 2 hours. Then, 0.02 times the mass of modified alumina, 0.04 times the mass of modified alumina, 0.018 times the mass of modified alumina, and 0.2 times the mass of modified alumina were added and stirred for 20 minutes. The mixture was then vacuum-kneaded three times to obtain lithium-free high heat-resistant ceramic clay.

[0031] (4) The lithium-free high-heat-resistant ceramic clay was aged for 24 hours at 18℃ and 98% humidity, and then extruded to obtain lithium-free high-heat-resistant ceramic green bodies. The lithium-free high-heat-resistant ceramic green bodies were dried in a 30℃ forced-air drying oven for 12 hours, then heated to 100℃ for 4 hours, and then heated to 120℃ for 2 hours. The green bodies were then placed in a debinding furnace under a nitrogen atmosphere for debinding. The debinded samples were then placed in a sintering furnace for sintering to obtain lithium-free high-heat-resistant ceramics. The debinding process is as follows: heat to 250℃ at a heating rate of 0.5℃ / min, hold for 20 min, heat to 400℃ at a heating rate of 0.3℃ / min, hold for 1 h, heat to 600℃ at a heating rate of 0.5℃ / min, hold for 2 h; the sintering process is as follows: heat to 600℃ at a heating rate of 5℃ / min, hold for 1 h, heat to 1600℃ at a heating rate of 5℃ / min, hold for 2 h.

[0032] Example 2

[0033] A method for preparing lithium-free, high-heat-resistant ceramic clay includes the following preparation steps:

[0034] (1) Mix 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 95wt% ethanol aqueous solution at a mass ratio of 1:18. Adjust the pH to 4 with 10wt% citric acid aqueous solution. Let it stand for hydrolysis for 55 min at room temperature. Add 0.45 times the mass of alumina of 3-(2,3-epoxypropoxy)propyltrimethoxysilane. Stir the reaction at 550 r / min for 5.5 h at 45 °C. Centrifuge at 11000 r / min. The precipitate was washed four times with anhydrous ethanol and dried under vacuum at 55°C for 22 hours to obtain pre-modified alumina. The pre-modified alumina, starch, and N,N-dimethylformamide were mixed evenly at a mass ratio of 1:0.06:11 and stirred at 75°C and 250 r / min for 11 hours. The mixture was then centrifuged at 3500 r / min for 11 minutes, and the precipitate was washed four times with anhydrous ethanol and dried under vacuum at 65°C for 11 hours to obtain modified alumina.

[0035] (2) Ethyl acetoacetate and isopropanol were mixed evenly at a mass ratio of 1:6. The mixture was stirred at 600 r / min for 15 min at room temperature. Zirconium oxychloride was added at 0.065 times the mass of ethyl acetoacetate. The mixture was stirred at 600 r / min for 20 min at room temperature. Aluminum sec-butoxide and N,N dimethylformamide were added at 0.925 times the mass of ethyl acetoacetate and 0.65 times the mass of ethyl acetoacetate. The mixture was stirred at 600 r / min for 25 min at room temperature. Polyvinylpyrrolidone was added at 1.01 times the mass of ethyl acetoacetate. The mixture was stirred at 600 r / min for 5.5 h at room temperature to obtain the spinning solution. The spinning solution was then added to... Electrospinning was performed in an electrospinning machine. After collection from the collecting roller, the fibers were immersed in 15wt% yttrium oxide sol under vacuum for 10 minutes. They were then placed in a vacuum oven and dried at 90℃ for 2 hours. The fibers were then transferred to a muffle furnace and heated to 800℃ at a rate of 2℃ / min, held for 2 hours, and allowed to cool naturally to room temperature. The fibers were then dispersed in a high-speed stirrer and cut to a length of 2 mm to obtain alumina-zirconia-yttrium oxide composite fibers. The impregnation process parameters were: vacuum pressure of 600 Pa and applied pressure of 0.3 MPa; the spinning technology parameters were: electrospinning voltage of 12 kV, feed rate of 0.5 mL / h, and spinning distance of 12 cm.

[0036] (3) Modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose were added to a mixer in a mass ratio of 1:0.135:0.125:0.07 and stirred for 2.5 hours. Then, 0.03 times the mass of modified alumina, 0.05 times the mass of modified alumina, 0.02 times the mass of modified alumina, polyethylene glycol, and 0.25 times the mass of modified alumina were added and stirred for 30 minutes. The mixture was then vacuum-kneaded three times to obtain lithium-free high heat-resistant ceramic clay.

[0037] (4) The lithium-free high-heat-resistant ceramic clay was aged for 24 hours at 18℃ and 98% humidity, and then extruded to obtain lithium-free high-heat-resistant ceramic green bodies. The lithium-free high-heat-resistant ceramic green bodies were dried in a 30℃ forced-air drying oven for 12 hours, then heated to 100℃ for 4 hours, and then heated to 120℃ for 2 hours. The green bodies were then placed in a debinding furnace under a nitrogen atmosphere for debinding. The debinded samples were then placed in a sintering furnace for sintering to obtain lithium-free high-heat-resistant ceramics. The debinding process is as follows: heat to 250℃ at a heating rate of 0.5℃ / min, hold for 20 min, heat to 400℃ at a heating rate of 0.3℃ / min, hold for 1 h, heat to 600℃ at a heating rate of 0.5℃ / min, hold for 2 h; the sintering process is as follows: heat to 600℃ at a heating rate of 5℃ / min, hold for 1 h, heat to 1600℃ at a heating rate of 5℃ / min, hold for 2 h.

[0038] Example 3

[0039] A method for preparing lithium-free, high-heat-resistant ceramic clay includes the following preparation steps:

[0040] (1) Mix 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 95wt% ethanol aqueous solution at a mass ratio of 1:20. Add 10wt% citric acid aqueous solution to adjust the pH to 4. Let stand for hydrolysis for 60 min at room temperature. Add 0.5 times the mass of 3-(2,3-epoxypropoxy)propyltrimethoxysilane alumina. Stir at 50℃ and 600 r / min for 6 h. Centrifuge at 12000 r / min for 12 min. Wash the precipitate with anhydrous ethanol 5 times. Dry under vacuum at 60℃ for 24 h to obtain pre-modified alumina. Mix pre-modified alumina, starch and N,N-dimethylformamide at a mass ratio of 1:0.07:12. Stir at 80℃ and 300 r / min for 12 h. Centrifuge at 4000 r / min for 12 min. Wash the precipitate with anhydrous ethanol 5 times. Dry under vacuum at 70℃ for 12 h to obtain modified alumina.

[0041] (2) Ethyl acetoacetate and isopropanol were mixed evenly at a mass ratio of 1:6.5. The mixture was stirred at 700 r / min for 20 min at room temperature. Zirconium oxychloride was added at 0.07 times the mass of ethyl acetoacetate. The mixture was stirred at 700 r / min for 25 min at room temperature. Aluminum sec-butoxide and N,N dimethylformamide were added at 0.95 times the mass of ethyl acetoacetate and 0.7 times the mass of ethyl acetoacetate. The mixture was stirred at 700 r / min for 30 min at room temperature. Polyvinylpyrrolidone was added at 1.02 times the mass of ethyl acetoacetate. The mixture was stirred at 700 r / min for 6 h at room temperature to obtain the spinning solution. The spinning solution was added to the static... Electrospinning was performed on an electrospinning machine. After collection from the collecting roller, the fibers were immersed in 15wt% yttrium oxide sol under vacuum for 10 minutes, then placed in a vacuum oven and dried at 90℃ for 2 hours. The fibers were then transferred to a muffle furnace and heated to 800℃ at a rate of 2℃ / min, held for 2 hours, and allowed to cool naturally to room temperature. The fibers were then dispersed in a high-speed stirrer and chopped to a length of 3 mm to obtain alumina-zirconia-yttrium oxide composite fibers. The impregnation process parameters were: vacuum pressure of 600 Pa and applied pressure of 0.3 MPa; the spinning technical parameters were: electrospinning voltage of 12 kV, feed rate of 0.5 mL / h, and spinning distance of 12 cm.

[0042] (3) Modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose were added to a mixer in a mass ratio of 1:0.14:0.15:0.08 and stirred for 3 hours. Then, 0.04 times the mass of modified alumina, 0.06 times the mass of modified alumina, 0.022 times the mass of modified alumina, and 0.3 times the mass of modified alumina were added and stirred for 40 minutes. The mixture was then vacuum-kneaded three times to obtain lithium-free high heat-resistant ceramic clay.

[0043] (4) The lithium-free high-heat-resistant ceramic clay was aged for 24 hours at 18℃ and 98% humidity, and then extruded to obtain lithium-free high-heat-resistant ceramic green bodies. The lithium-free high-heat-resistant ceramic green bodies were dried in a 30℃ forced-air drying oven for 12 hours, then heated to 100℃ for 4 hours, and then heated to 120℃ for 2 hours. The green bodies were then placed in a debinding furnace under a nitrogen atmosphere for debinding. The debinded samples were then placed in a sintering furnace for sintering to obtain lithium-free high-heat-resistant ceramics. The debinding process is as follows: heat to 250℃ at a heating rate of 0.5℃ / min, hold for 20 min, heat to 400℃ at a heating rate of 0.3℃ / min, hold for 1 h, heat to 600℃ at a heating rate of 0.5℃ / min, hold for 2 h; the sintering process is as follows: heat to 600℃ at a heating rate of 5℃ / min, hold for 1 h, heat to 1600℃ at a heating rate of 5℃ / min, hold for 2 h.

[0044] Comparative Example 1

[0045] The difference between the preparation method of lithium-free high-heat-resistant ceramic clay in Comparative Example 1 and Example 2 lies in step (1). Step (1) is modified as follows: alumina, starch, and N,N-dimethylformamide are mixed evenly at a mass ratio of 1:0.06:11, stirred at 75°C and 250 r / min for 11 h, centrifuged at 3500 r / min for 11 min, the resulting precipitate is washed four times with anhydrous ethanol, and vacuum dried at 65°C for 11 h to obtain modified alumina. The remaining steps are the same as in Example 2.

[0046] Comparative Example 2

[0047] The preparation method of lithium-free high-heat-resistant ceramic clay in Comparative Example 2 differs from that in Example 2 in that step (1) is omitted, and step (3) is modified as follows: Alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose are added to a mixer in a mass ratio of 1:0.135:0.125:0.07 and stirred for 2.5 hours. Then, 0.03 times the mass of modified alumina, 0.05 times the mass of modified alumina, 0.02 times the mass of modified alumina, and 0.25 times the mass of modified alumina, are added and stirred for 30 minutes. The mixture is then vacuum-kneaded three times to obtain lithium-free high-heat-resistant ceramic clay. The remaining steps are the same as in Example 2.

[0048] Comparative Example 3

[0049] The difference between the preparation method of lithium-free high heat-resistant ceramic clay in Comparative Example 3 and Example 2 lies in the difference in steps (2) and (3). Step (2) is modified as follows: Ethyl acetoacetate and isopropanol are mixed evenly at a mass ratio of 1:6. The mixture is stirred at 600 r / min for 15 min at room temperature. Zirconium oxychloride with a mass of 0.065 times that of ethyl acetoacetate is added. The mixture is stirred at 600 r / min for 20 min at room temperature. Aluminum sec-butoxide with a mass of 0.925 times that of ethyl acetoacetate and N,N-dimethylformamide with a mass of 0.65 times that of ethyl acetoacetate are added. The mixture is stirred at 600 r / min for 25 min at room temperature. Polyvinylpyrrolidone with a mass of 1.01 times that of ethyl acetoacetate is added. The mixture is stirred at 600 r / min for 5.5 h at room temperature to obtain the spinning solution. The spinning solution is added to an electrospinning machine for electrospinning. After being collected from the collecting roller, it is placed in a vacuum oven at 90°C for vacuum spinning. After drying for 2 hours, the product was transferred to a muffle furnace and heated to 800℃ at a heating rate of 2℃ / min. It was then kept at this temperature for 2 hours and allowed to cool naturally to room temperature. The product was then dispersed in a high-speed stirrer and cut to a length of 2 mm to obtain alumina-zirconia composite fiber. The spinning parameters were: electrospinning voltage of 12kV, feeding rate of 0.5mL / h, and spinning distance of 12cm. Step (3) was modified as follows: modified alumina, talc, alumina-zirconia composite fiber, and hydroxypropyl methylcellulose were added to a stirrer in a mass ratio of 1:0.135:0.125:0.07 and stirred for 2.5 hours. Then, 0.03 times the mass of modified alumina, 0.05 times the mass of modified alumina, 0.02 times the mass of modified alumina, polyethylene glycol, and 0.25 times the mass of modified alumina were added and stirred for 30 minutes. The mixture was then vacuum-kneaded 3 times to obtain lithium-free high-heat-resistant ceramic clay. The remaining steps are the same as in Example 2.

[0050] Comparative Example 4

[0051] The preparation method of lithium-free high-heat-resistant ceramic clay in Comparative Example 4 differs from that in Example 2 in that step (2) is omitted, and step (3) is modified as follows: Modified alumina, talc, and hydroxypropyl methylcellulose are added to a mixer in a mass ratio of 1:0.135:0.07 and stirred for 2.5 hours. Then, 0.03 times the mass of modified alumina, 0.05 times the mass of modified alumina, 0.02 times the mass of modified alumina, polyethylene glycol, and 0.25 times the mass of modified alumina are added and stirred for 30 minutes. The mixture is then vacuum-kneaded three times to obtain lithium-free high-heat-resistant ceramic clay. The remaining steps are the same as in Example 2.

[0052] Comparative Example 5

[0053] The difference between the preparation method of lithium-free high-heat-resistant ceramic clay in Comparative Example 5 and Example 2 lies in step (3). Step (3) is modified as follows: Modified alumina, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose are added to a mixer in a mass ratio of 1:0.125:0.07 and stirred for 2.5 hours. Then, 0.03 times the mass of modified alumina, 0.05 times the mass of modified alumina, 0.02 times the mass of modified alumina, polyethylene glycol, and 0.25 times the mass of modified alumina are added and stirred for 30 minutes. The mixture is then vacuum-kneaded three times to obtain lithium-free high-heat-resistant ceramic clay. The remaining steps are the same as in Example 2.

[0054] Test Example 1

[0055] Thermal shock resistance test: The lithium-free high heat-resistant ceramics prepared in each example and comparative example were placed in an electric furnace preheated to 1400℃ and held for 15 minutes. Then they were quickly removed and cooled in air for 30 minutes. The above steps were repeated until the lithium-free high heat-resistant ceramics showed obvious cracks or broke directly. The number of thermal shocks before the sample was damaged was recorded. Ten samples were tested in parallel in each group, and the lowest number of thermal shocks was recorded.

[0056] The results are shown in Table 1.

[0057]

[0058] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 1 reveals that the lithium-free high heat-resistant ceramic clay prepared by the present invention exhibits good thermal shock resistance after sintering.

[0059] By comparison, the number of thermal shocks in Examples 1-3 was greater than that in Comparative Example 2, indicating that reacting alumina with 3-(2,3-epoxypropoxy)propyltrimethoxysilane introduces epoxy groups onto the alumina surface to prepare pre-modified alumina; reacting the pre-modified alumina with starch to prepare modified alumina, the epoxy groups on the pre-modified alumina react with the hydroxyl groups on the starch surface to graft starch onto the alumina surface. During subsequent sintering, the starch decomposes to form uniform pores. The porous structure can effectively resist the thermal stress generated on the surface. When ceramics are subjected to large thermal stress, the internal molecules will undergo violent movement. The loose structure provides more displacement space for molecules, which can more effectively resist thermal stress, thereby improving the thermal shock resistance of ceramics.

[0060] By comparison, the number of thermal shocks in Examples 1-3 was greater than that in Comparative Examples 3-4, indicating that during the sintering process of zirconia, under the action of yttrium oxide, when the porous ceramic sample is subjected to external force, the high stress region at the gas-solid interface and the microcracks inside the ceramic induces the zirconia to transform from the tetragonal phase to the monoclinic phase. This reduces the stress at the crack tip, changes the crack propagation path, and increases the crack propagation resistance, thereby improving the thermal shock resistance of the ceramic.

[0061] By comparison, the number of thermal shocks in Examples 1-3 was greater than that in Comparative Example 5, indicating that lithium-free high-heat-resistant ceramic clay can generate cordierite with a low coefficient of expansion during the sintering process, thereby obtaining ceramic materials with a lower coefficient of linear expansion and improving the thermal shock resistance of ceramics.

[0062] Test Example 2

[0063] Bending strength test: The lithium-free high-heat-resistant ceramics prepared in each embodiment and comparative example were made into specimens of 25mm × 5mm × 2.5mm. Using an electronic universal testing machine, the displacement rate of the indenter was 0.5mm / min; the span was 20mm, and the bending strength was calculated using the three-point bending method. Where σ (MPa) represents the bending strength (MPa), P (N) represents the maximum load, L (mm) represents the span, h (mm) represents the specimen thickness, and b (mm) represents the specimen width.

[0064] The results are shown in Table 2.

[0065]

[0066] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 2 reveals that the lithium-free high heat-resistant ceramic clay prepared by the present invention exhibits good flexural strength after sintering.

[0067] By comparison, the bending strength of Examples 1-3 is greater than that of Comparative Example 1, indicating that the reaction of alumina with 3-(2,3-epoxypropoxy)propyltrimethoxysilane introduces epoxy groups on the surface of alumina to prepare pre-modified alumina. The pre-modified alumina is then reacted with starch to prepare modified alumina. The epoxy groups on the pre-modified alumina react with the hydroxyl groups on the surface of starch to graft starch onto the surface of alumina. During the subsequent sintering process, the starch decomposes to form uniform pores, avoiding local macropores or defects, thereby improving the bending strength of lithium-free high heat-resistant ceramics.

[0068] By comparison, the bending strength of Examples 1-3 is greater than that of Comparative Example 3, indicating that during the sintering process of zirconia, under the action of yttrium oxide, when the porous ceramic sample is subjected to external force, the high stress region at the gas-solid interface and the microcracks inside the ceramic induces the zirconia to transform from the tetragonal phase to the monoclinic phase. This reduces the stress at the crack tip, changes the crack propagation path, increases the crack propagation resistance, increases the fracture toughness of the ceramic, and further improves the bending strength of the porous ceramic.

[0069] By comparison, the bending strength of Examples 1-3 is greater than that of Comparative Example 4, indicating that the alumina-zirconia-yttrium oxide composite fiber, as a ceramic reinforcing phase, can improve the bending strength of alumina ceramics. At the same time, during the sintering process, under the action of yttrium oxide, when the porous ceramic sample is subjected to external force, the high stress region at the gas-solid interface and the microcracks inside the ceramic induces the zirconia to transform from a tetragonal phase to a monoclinic phase. This reduces the stress at the crack tip, changes the crack propagation path, increases the crack propagation resistance, increases the fracture toughness of the ceramic, and further improves the bending strength of the porous ceramic.

[0070] By comparison, the bending strength of Examples 1-3 is less than that of Comparative Examples 2 and 5, indicating that the epoxy groups on the pre-modified alumina react with the hydroxyl groups on the starch surface, grafting starch onto the alumina surface. During subsequent sintering, the starch decomposes, forming uniform pores. The porous structure improves the thermal shock resistance of the ceramic, but at the same time, it reduces the bending strength. During the sintering process, lithium-free high-heat-resistant ceramic clay can generate cordierite with a low coefficient of expansion. Cordierite has slightly poor mechanical properties, which improves the thermal shock resistance of the ceramic, but reduces the bending strength.

[0071] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium-free, high-heat-resistant ceramic clay, characterized in that, The lithium-free, high-heat-resistant ceramic clay is prepared by mixing modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, hydroxypropyl methylcellulose, glycerol, oleic acid, polyethylene glycol, and water, followed by vacuum kneading. The alumina-zirconia-yttrium oxide composite fiber is prepared by mixing ethyl acetoacetate, isopropanol, zirconium oxychloride, aluminum sec-butoxide, polyvinylpyrrolidone, and N,N-dimethylformamide to form a spinning solution, followed by electrospinning and immersion in yttrium oxide sol. The modified alumina is prepared by reacting alumina sequentially with 3-(2,3-epoxypropoxy)propyltrimethoxysilane and starch. The preparation steps of the lithium-free, high-heat-resistant ceramic clay are as follows: (1) Mix 3-(2,3-epoxypropoxy)propyltrimethoxysilane and 95wt% ethanol aqueous solution at a mass ratio of 1:(15~20), add 10wt% citric acid aqueous solution to adjust the pH to 4, let stand for hydrolysis for 50~60 min at room temperature, add 0.4~0.5 times the mass of 3-(2,3-epoxypropoxy)propyltrimethoxysilane alumina, stir and react at 40~50℃ for 5~6 h, centrifuge, wash and dry to obtain pre-modified alumina; Pre-modified alumina, starch, and N,N-dimethylformamide were mixed evenly at a mass ratio of 1:(0.05~0.07):(10~12), and stirred at 70~80℃ for 10~12 h. The mixture was then centrifuged, washed, and dried to obtain modified alumina. (2) Ethyl acetoacetate, isopropanol, zirconium oxychloride, aluminum sec-butoxide, N,N-dimethylformamide and polyvinylpyrrolidone are mixed evenly and stirred at room temperature for 5-6 hours to obtain a spinning solution; the spinning solution is added to an electrospinning machine for electrospinning, and after being collected from the collecting roller, it is immersed in 15wt% yttrium oxide sol for vacuum impregnation for 10 minutes, placed in a vacuum oven and vacuum dried at 90℃ for 2 hours, transferred to a muffle furnace, heated to 800℃ at a heating rate of 2℃ / min and held for 2 hours, naturally cooled to room temperature, dispersed in a high-speed stirrer, and the length is cut to 1-3 mm to obtain alumina-zirconia-yttrium oxide composite fiber; (3) Modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose are added to a mixer in a mass ratio of 1:(0.13~0.14):(0.1~0.15):(0.06~0.08) and stirred for 2~3 hours. Then, glycerol, oleic acid, polyethylene glycol, and water are added and stirred for 20~40 minutes. The mixture is then vacuum-kneaded three times to obtain lithium-free high heat-resistant ceramic clay.

2. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The starch mentioned in step (1) is soluble starch.

3. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The preparation steps of the alumina-zirconia-yttrium oxide composite fiber in step (2) are as follows: Ethyl acetoacetate and isopropanol are mixed evenly at a mass ratio of 1:(5.5~6.5), and stirred for 10~20 min at room temperature. Zirconium oxychloride is added at 0.06~0.07 times the mass of ethyl acetoacetate, and stirred for 15~25 min at room temperature. Aluminum sec-butoxide at 0.9~0.95 times the mass of ethyl acetoacetate and N,N-dimethylformamide at 0.6~0.7 times the mass of ethyl acetoacetate are added. The mixture is stirred for 20~30 min at room temperature. Polyvinylpyrrolidone (PVP) was added in 1-1.02 times the mass of ethyl acetoacetate and stirred at room temperature for 5-6 hours to prepare a spinning solution. The spinning solution was then added to an electrospinning machine for electrospinning. After being collected from the collecting roller, the solution was immersed in 15 wt% yttrium oxide sol and vacuum impregnated for 10 minutes. It was then placed in a vacuum oven and vacuum dried at 90°C for 2 hours. The solution was then transferred to a muffle furnace and heated to 800°C at a heating rate of 2°C / min and held for 2 hours. After naturally cooling to room temperature, the solution was dispersed in a high-speed stirrer and cut to a length of 1-3 mm to obtain alumina-zirconia-yttrium oxide composite fibers.

4. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The vacuum impregnation process parameters in step (2) are: vacuum pressure of 600 Pa and external pressure of 0.3 MPa; the electrospinning technology parameters are: electrospinning voltage of 12 kV, feeding rate of 0.5 mL / h and spinning distance of 12 cm.

5. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The polyvinylpyrrolidone mentioned in step (2) is polyvinylpyrrolidone K30.

6. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The preparation steps of the lithium-free high heat-resistant ceramic clay in step (3) are as follows: Modified alumina, talc, alumina-zirconia-yttrium oxide composite fiber, and hydroxypropyl methylcellulose are added to a mixer in a mass ratio of 1:(0.13~0.14):(0.1~0.15):(0.06~0.08) and stirred for 2~3 hours. Then, 0.02~0.04 times the mass of modified alumina, 0.04~0.06 times the mass of modified alumina, 0.018~0.022 times the mass of modified alumina, and 0.2~0.3 times the mass of modified alumina are added and stirred for 20~40 minutes. The mixture is then vacuum-kneaded 3 times to obtain the lithium-free high heat-resistant ceramic clay.

7. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The talc in step (3) is 325 mesh talc powder; the weight average molecular weight of the polyethylene glycol is 4000.

8. The lithium-free high-heat-resistant ceramic clay according to claim 1, characterized in that, The alumina has an average particle size of 500 nm.

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