A high-strength alumina ceramic and its processing technology

Abstract

The present invention relates to the technical field of alumina ceramics, and specifically relates to a high-strength alumina ceramic and its processing technology, including the following processes: Step 1, take a dispersant and dissolve it in deionized water to obtain a mixed solution; place the mixed solution and graphene in a ball mill, add grinding media and start the stirring mill, slowly add alumina to the stirring mill, and ball mill for 1 to 4 hours to obtain a slurry; Step 2, place the slurry obtained in Step 1 under constant temperature and humidity conditions for dehydration for 1 to 6 days, filter press to obtain a green body; place it in a muffle furnace, heat it to 800 to 1000 °C, and keep it warm for 2 to 6 hours to remove the binder; heat it up to 1850 °C at one time, then cool it down to 1400 to 1500 °C, keep it warm for 2 to 3 hours, and then heat it up to 1850 °C again and keep it warm for 6 hours. Through the adjustment of the process and the components required for the preparation of the alumina ceramic, the present invention combines the dispersant with inorganic salts and the process to promote the gel curing of the slurry and the improvement of the density of the green body, thereby obtaining an alumina ceramic with high strength.

Description

Technical Field

[0001] The present invention relates to the technical field of alumina ceramics, and particularly to a high-strength alumina ceramic and its processing technology. Background Art

[0002] With the progress of technology and the development of techniques, the research on ceramic materials has advanced by leaps and bounds. Due to its high mechanical strength and excellent high-temperature resistance, wear resistance, corrosion resistance, chemical stability and other characteristics, alumina ceramics are widely used in the fields of electrician electronics, automobiles, biology, medicine, aerospace and so on. The existing alumina ceramics are usually prepared by pressing forming and tape casting forming processes. Gelcasting, on the other hand, has received wide attention for its ability to prepare ceramics with large sizes, complex shapes, low shrinkage, low cost and high precision. The basic forming principle is to use organic substances to in-situ fix micro-nano alumina particles and bond and solidify them into a green body, and then sinter them into alumina ceramics. However, agglomeration is likely to occur between micro-nano alumina particles, and heterogeneous deposition will also occur between some added reinforcing particles, which has a negative impact on the gel curing of the slurry and the density of the green body. Therefore, we propose a high-strength alumina ceramic and its processing technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a high-strength alumina ceramic and its processing technology to solve the problems raised in the above background art.

[0004] To solve the above technical problems, the present invention provides the following technical solution: A high-strength alumina ceramic and its processing technology, including the following processes:

[0005] Step 1: Take a dispersant and dissolve it in deionized water to obtain a mixed solution; place the mixed solution and graphene in a ball mill, add a grinding medium and start the stirring mill, slowly add alumina to the stirring mill, and ball mill for 1 - 4 h to obtain a slurry;

[0006] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions for dehydration for 1 - 6 d, seal it in a pressure filtration mold and perform pressure filtration to obtain a green body;

[0007] Place it in a muffle furnace, and carry out debinding at a temperature of 800 - 1000 °C for 2 - 6 h;

[0008] Raise the temperature to 1850 °C at one time, then cool down to 1400 - 1500 °C, keep it warm for 2 - 3 h, and then raise the temperature to 1850 °C again and keep it warm for 6 h.

[0009] Further, in Step 1, the rotation speed of the stirring mill is 200 - 300 r / min;

[0010] The grinding medium is zirconia, and the addition amount of the grinding medium is 1.1 - 1.2 times the mass of alumina.

[0011] Further, in Step 2, the constant temperature and humidity conditions are: temperature 25°C, relative humidity 85%;

[0012] The pressure applied in the pressure filtration process is 0.37 - 0.45 MPa;

[0013] The heating rate in the debinding process is 1 - 2 °C / min;

[0014] The first heating rate in the sintering process is 10 °C / min, and the second heating rate is 2 °C / min.

[0015] Further, the slurry comprises the following mass components: 100 parts of alumina, 0.6 - 1.0 part of graphene, 0.2 - 0.4 part of dispersant.

[0016] Further, the slurry further comprises the following mass components: 13.0 - 13.4 parts of aluminum nitride, 0.34 - 0.40 part of yttrium oxide, 0.026 - 0.030 part of lanthanum oxide.

[0017] Further, the solid content of the slurry is 40 - 55 vol%.

[0018] Alumina: α - Al2O3 powder, with a particle size of 0.4 - 0.6 μm, sourced from Beijing Decode Island Gold Technology Co., Ltd.;

[0019] Graphene: flaky, with a particle size of 0.8 - 1.2 μm, sourced from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.;

[0020] Aluminum nitride: with an average particle size of 0.6 μm, sourced from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.;

[0021] Yttrium oxide: with a particle size of 0.8 - 1.5 μm, sourced from Ganzhou Guangli High - tech Materials Co., Ltd.;

[0022] Lanthanum oxide: with a particle size of 0.8 - 1.5 μm, sourced from Ganzhou Guangli High - tech Materials Co., Ltd.

[0023] Further, the dispersant is one or more of Isobam104, Isobam600AF, ammonium polyacrylate PAA - NH2, and branched polyamide;

[0024] After the ball - milling process in Step 1 is completed, an inorganic salt is added, and ball - milling is continued for 50 - 75 min;

[0025] The inorganic salt is one of cesium chloride and magnesium chloride, and its concentration in the slurry is 120 - 180 ppm.

[0026] Isobam104: average molecular weight 55,000 - 65,000; Isobam600AF: average molecular weight 5,500 - 6,500, both from Kuraray of Japan; ammonium polyacrylate: from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0027] Furthermore, the branched polyamide is prepared by the following process:

[0028] (1) Take trimesic acid, pyridine, and N-methylpyrrolidone, mix and dissolve them, add triphenyl phosphite, heat up to 100 - 110 °C, slowly add 1,8-octanediamine, and finish adding it within 2 h, react for 1 - 3 h to obtain an amide product;

[0029] (2) Take the amide product and sodium 2-carboxymethoxy-5-methylbenzenesulfonate and place them in a reactor, add N-methylpyrrolidone, pyrrole, triphenyl phosphite, calcium chloride, and lithium chloride, mix them evenly, under the protection of a nitrogen atmosphere, heat up to 105 - 115 °C, stir and react for 24 h; cool to room temperature, precipitate in acetone, filter, wash, and dry to obtain the branched polyamide.

[0030] Furthermore, in the step (1), the molar ratio of trimesic acid to 1,8-octanediamine is 1:(3.1 - 3.3);

[0031] The molar ratio of 1,8-octanediamine to pyridine is 1:1;

[0032] The molar ratio of trimesic acid to triphenyl phosphite is 1:3;

[0033] The ratio of trimesic acid to N-methylpyrrolidone is 0.20 - 0.22 mol / L.

[0034] Furthermore, in the step (2), the molar ratio of the amide product to sodium 2-carboxymethoxy-5-methylbenzenesulfonate is 1:(1.0 - 1.1);

[0035] The ratio of the amide product to N-methylpyrrolidone is (20 - 25) g:100 mL;

[0036] The mass ratio of the amide product, pyrrole, triphenyl phosphite, calcium chloride, and lithium chloride is 10:(23.0 - 23.2):(2.23 - 2.25):(0.74 - 0.76).

[0037] In the above technical solution, when the dispersant is a mixture of Isobam104 and Isobam600AF, it has amide, carboxylate ions and carboxylic anhydrides, and can be used as a gelling system for ceramic slurries to disperse and gel alumina particles, realizing the injection molding of alumina. In the slurry material system, the carboxylic anhydride in Isobam hydrolyzes. Since the Zeta potential of nano-alumina in neutral aqueous solution is positive, it can be considered to carry a positive charge, and the carboxylate ions can adsorb onto the positive charges on the surface of alumina, making the alumina surface carry a negative charge, increasing the electrostatic repulsion potential energy between alumina particles, so that the slurry has good fluidity; and because Isobam has a large molecular weight, the polymer chains fully stretch during grafting, forming an adsorption layer with a thickness of several nanometers to dozens of nanometers, generating a steric hindrance effect, and cooperating with the above electrostatic repulsion, it can effectively prevent the aggregation of alumina particles, thus providing electrostatic and steric stability for alumina, achieving a dispersion effect and obtaining a suspension with low viscosity. As the ball milling time prolongs, the repulsion between alumina particles disappears. At this time, there is only an attractive force between the particles. The unadsorbed carboxylate anions bond with the amide in the system to form hydrogen bonds, and the alumina particles are bridged and solidified, and the viscosity of the slurry increases, and gel solidification occurs, thus realizing the injection molding of alumina. When the dispersant is ammonium polyacrylate, it has the same technical effect as above. And the branched polyamide dispersant in this application has amide and sodium sulfonate groups, and has the same or similar technical effects as above.

[0038] The slurry composition of the present application further adds a non-metallic compound, graphene, as the second phase in alumina ceramics, which can inhibit the growth of alumina grain structure, play a role in refining grains, enhance and toughen the prepared alumina ceramics, and improve their mechanical properties. The amino group in the above dispersant component will modify graphene, enabling the amino group to adsorb on the surface of graphene, promoting the dispersion of graphene in the slurry, while the carboxylate ion exhibits electrostatic repulsion during grafting and does not produce gel curing; and in the slurry system, graphene and aluminum nitride will attract alumina, causing graphene and aluminum nitride to adsorb on the surface of alumina, resulting in heterogeneous deposition and hindering the gel curing of the slurry; and graphene and aluminum nitride repel each other, which will also cause uneven distribution of the two in the slurry. Therefore, after the dispersant and the powder materials (alumina, graphene, aluminum nitride, etc.) are ball-milled and mixed, the present application adds a water-soluble metal inorganic salt, introducing metal ions into the slurry system, which acts through ionic bonds with negatively charged groups such as carboxylate ions and sulfonate ions in the dispersant; among them, as alkali metal elements, magnesium and cesium, through the adsorption with carboxylate ions and sulfonate bonds, form a self-assembled structure with the dispersant, form a hexagonal phase with branched polyamide, increase the cross-linking between dispersant molecules, can enhance the anisotropy of the above dispersant on the surface of alumina particles, promote the gel curing of the slurry, form a gel three-dimensional network, improve the gel strength, and contribute to the improvement of the mechanical properties of the prepared alumina ceramics. And the introduction of metal element magnesium / replacing metal sodium element with metal element cesium helps the diffusion of the alumina ceramic grain boundary, promotes the discharge of pores, and improves the density and strength of the prepared alumina ceramics.

[0039] Through the reaction among trimesic acid, 1,8-octanediamine, and sodium 2-carboxymethoxy-5-methylbenzenesulfonate, a small molecule polyamide with a symmetric structure, branched polyamide, with trimesic acid as the center and sulfonate as the end group, was prepared. After reacting with the inorganic salt, it changes the surface charge amount in the above self-assembled structure, enabling alumina to aggregate around the self-assembled structure, promoting the dispersion and aggregation among powder particles such as alumina in the green body, improving the dispersibility of the slurry system while increasing the density of the green body and the prepared alumina ceramics; at the same time, the molecular weight of branched polyamide is small, the steric hindrance effect is weakened, and the debinding difficulty is reduced, which helps to further improve the mechanical properties of the alumina ceramics.

[0040] Then, pressure filtration and dehydration shrinkage are carried out. The grading effect among powder particles makes the slurry have a certain compressibility, enabling the free water in the slurry to be discharged, and the solid content of the slurry increases to a certain extent, thereby obtaining a green body with higher density, which helps to improve the mechanical properties of alumina ceramics.

[0041] Finally, sintering is carried out. Yttrium oxide and lanthanum oxide are compounded as sintering aids and distributed on the surface of alumina particles. A low-melting-point liquid phase is formed, and through the capillary action between powder particles, the pores between powder particles are filled, thereby reducing the porosity of the prepared alumina ceramic, increasing the density, and lowering the sintering temperature. During the sintering process, first, the sintering temperature is raised to 1850 °C to make the green body reach above the critical density, and then it is kept warm at a lower temperature. At this time, the pores in the green body gradually shrink through grain boundary diffusion, making it gradually densify; since the activation energy of grain boundary diffusion is lower than that of grain boundary migration, the grains mainly grow through grain boundary migration and are pinned by pores, and the grain structure remains unchanged in its original size. The temperature is raised again and kept warm, so that the residual pores in the green body are further removed, the pinning effect of pores is weakened, grain boundary migration promotes the growth of grains, pores are further removed, and the relative density of the ceramic is increased. Graphene is deposited between alumina grains, which can inhibit the growth of alumina grains, refine the grains, enhance and toughen the alumina ceramic, thereby improving the mechanical properties of the alumina ceramic.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] The high-strength alumina ceramic and its processing technology of the present invention, through the adjustment of the process and the components required for the preparation of the alumina ceramic, cooperate the dispersant with inorganic salts and the process, promoting the gel curing of the slurry and the improvement of the density of the green body, thereby obtaining an alumina ceramic with high strength. Specific embodiments

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0045] In the following specific embodiments, alumina: α-Al2O3 powder, with a particle size of 0.4 - 0.6 μm, is sourced from Beijing DeKeDaoJin Technology Co., Ltd.;

[0046] Graphene: flaky, with a particle size of 0.8 - 1.2 μm, is sourced from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.;

[0047] Aluminum nitride: with an average particle size of 0.6 μm, is sourced from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.;

[0048] Yttrium oxide: with a particle size of 0.8 - 1.5 μm, is sourced from Ganzhou Guangli High-tech Materials Co., Ltd.;

[0049] Lanthanum oxide: with a particle size of 0.8 - 1.5 μm, sourced from Ganzhou Guangli High-tech Materials Co., Ltd.;

[0050] Isobam104: average molecular weight 55000 - 65000; Isobam600AF: average molecular weight 5500 - 6500, both sourced from Kuraray Co., Ltd. of Japan;

[0051] Ammonium polyacrylate: sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0052] Among them, the "parts" number, one part is 10 grams.

[0053] Example 1: A high-strength alumina ceramic and its processing technology, including the following processes:

[0054] Step 1: Take 0.1 part of Isobam104 and 0.2 part of Isobam600AF and dissolve them in deionized water to obtain a mixed solution; place the mixed solution and 0.6 part of graphene in a ball mill, add 110 parts of zirconia as the grinding medium, and start the stirring mill. The rotation speed of the stirring mill is 200 r / min. Slowly add 100 parts of alumina, 13.0 parts of aluminum nitride, 0.34 part of yttrium oxide, and 0.026 part of lanthanum oxide to the stirring mill, and ball mill for 1 h; add inorganic salt magnesium chloride and continue to ball mill for 50 min; obtain a slurry with a solid content of 40 vol%; the concentration of magnesium chloride in the slurry is 120 ppm;

[0055] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions of 25 °C and 85% relative humidity for dehydration for 1 d, seal it in a pressure filtration mold and apply a pressure of 0.37 MPa to obtain a green body; place it in a muffle furnace, heat it at a heating rate of 1 °C / min to a temperature of 1000 °C, and keep it warm for 6 h to remove binder; heat it at a heating rate of 10 °C / min to 1850 °C, then cool it to 1500 °C, keep it warm for 2 h, and heat it at a heating rate of 2 °C / min to 1850 °C and keep it warm for 6 h.

[0056] Example 2: A high-strength alumina ceramic and its processing technology, including the following processes:

[0057] Step 1: Take 0.35 part of ammonium polyacrylate and dissolve it in deionized water to obtain a mixed solution; place the mixed solution and 0.8 part of graphene in a ball mill, add 110 parts of zirconia as the grinding medium, and start the stirring mill. The rotation speed of the stirring mill is 250 r / min. Slowly add 100 parts of alumina, 13.2 parts of aluminum nitride, 0.37 part of yttrium oxide, and 0.028 part of lanthanum oxide to the stirring mill, and ball mill for 2.5 h; add inorganic salt magnesium chloride and continue to ball mill for 60 min; obtain a slurry with a solid content of 47 vol%; the concentration of magnesium chloride in the slurry is 180 ppm;

[0058] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions of 25°C and 85% relative humidity for dehydration for 3 days. Seal it in a pressure filtration mold and apply a pressure of 0.40 MPa to obtain a green body. Place it in a muffle furnace and heat it at a heating rate of 2°C / min to a temperature of 900°C, and keep it warm for 4 hours to remove the binder. Heat it at a heating rate of 10°C / min to 1850°C, then cool it to 1450°C, keep it warm for 3 hours, heat it at a heating rate of 2°C / min to 1850°C, and keep it warm for 6 hours.

[0059] Example 3: A high-strength alumina ceramic and its processing technology, including the following processes:

[0060] Preparation of branched polyamide:

[0061] Take 2.5 g of benzene-1,3,5-tricarboxylic acid, 0.8 g of pyridine, and 50 mL of N-methylpyrrolidone and mix and dissolve them. Add 9.3 g of triphenyl phosphite, heat up to 100°C, and slowly add 4.4 g of 1,8-octanediamine within 2 hours, and react for 1 hour to obtain an amide product;

[0062] Take 10 g of the amide product and 7.8 g of 2-carboxymethoxy-5-methylbenzenesulfonate and place them in a reactor. Add 50 mL of N-methylpyrrolidone, 8.3 mL of pyrrole, 23.0 g of triphenyl phosphite, 2.23 g of calcium chloride, and 0.74 g of lithium chloride, mix them evenly, heat up to 105°C under the protection of a nitrogen atmosphere, and stir and react for 24 hours; cool to room temperature, precipitate in acetone, filter, wash, and dry to obtain branched polyamide;

[0063] Step 1: Dissolve 0.30 part of branched polyamide in deionized water to obtain a mixed solution; place the mixed solution and 1.0 part of graphene in a ball mill, add 120 parts of grinding medium zirconia, and start the stirring mill. The rotation speed of the stirring mill is 250 r / min. Slowly add 100 parts of alumina, 13.4 parts of aluminum nitride, 0.4 part of yttrium oxide, and 0.03 part of lanthanum oxide to the stirring mill, and ball mill for 4 hours; add inorganic salt cesium chloride and continue ball milling for 75 minutes; obtain a slurry with a solid content of 55 vol%; the concentration of magnesium chloride in the slurry is 150 ppm;

[0064] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions of 25°C and 85% relative humidity for dehydration for 3 days. Seal it in a pressure filtration mold and apply a pressure of 0.45 MPa to obtain a green body. Place it in a muffle furnace and heat it at a heating rate of 2°C / min to a temperature of 800°C, and keep it warm for 6 hours to remove the binder. Heat it at a heating rate of 10°C / min to 1850°C, then cool it to 1400°C, keep it warm for 3 hours, heat it at a heating rate of 2°C / min to 1850°C, and keep it warm for 6 hours.

[0065] Example 4: A high-strength alumina ceramic and its processing technology, including the following processes:

[0066] Preparation of branched polyamide:

[0067] Take 2.5 g of benzene-1,3,5-tricarboxylic acid, 0.8 g of pyridine, and 50 mL of N-methylpyrrolidone and mix them for dissolution. Add 9.3 g of triphenyl phosphite, heat up to 105 °C, and slowly add 4.5 g of 1,8-octanediamine, adding it all within 2 h. React for 2 h to obtain an amide product;

[0068] Take 10 g of the amide product and 8.2 g of 2-carboxymethoxy-5-methylbenzenesulfonate and place them in a reactor. Add 50 mL of N-methylpyrrolidone, 8.3 mL of pyrrole, 23.1 g of triphenyl phosphite, 2.24 g of calcium chloride, and 0.75 g of lithium chloride. Mix them evenly. Under the protection of a nitrogen atmosphere, heat up to 110 °C and stir and react for 24 h; cool to room temperature, precipitate in acetone, filter, wash, and dry to obtain branched polyamide;

[0069] Step 1: Take 0.35 part of branched polyamide and dissolve it in deionized water to obtain a mixed solution; place the mixed solution and 1.0 part of graphene in a ball mill, add 120 parts of grinding medium zirconia, and start the stirring mill. The rotation speed of the stirring mill is 250 r / min. Slowly add 100 parts of alumina, 13.4 parts of aluminum nitride, 0.4 part of yttrium oxide, and 0.03 part of lanthanum oxide to the stirring mill and ball mill for 4 h; add inorganic salt cesium chloride and continue ball milling for 75 min; obtain a slurry with a solid content of 55 vol%; the concentration of magnesium chloride in the slurry is 150 ppm;

[0070] Step 2: Place the slurry obtained in Step 1 under the constant temperature and humidity conditions of 25 °C and 85% relative humidity for dehydration for 3 d, seal it in a pressure filtration mold and apply a pressure of 0.45 MPa to obtain a green body; place it in a muffle furnace, heat it up to 800 °C at a heating rate of 2 °C / min, and keep it warm for 6 h to remove the binder; heat it up to 1850 °C at a heating rate of 10 °C / min, then cool it down to 1400 °C, keep it warm for 3 h, and heat it up to 1850 °C at a heating rate of 2 °C / min and keep it warm for 6 h.

[0071] Example 5: A high-strength alumina ceramic and its processing technology, including the following processes:

[0072] Preparation of branched polyamide:

[0073] Take 2.5 g of benzene-1,3,5-tricarboxylic acid, 0.8 g of pyridine, and 50 mL of N-methylpyrrolidone and mix them for dissolution. Add 9.3 g of triphenyl phosphite, heat up to 110 °C, and slowly add 4.7 g of 1,8-octanediamine, adding it all within 2 h. React for 3 h to obtain an amide product;

[0074] Take 10 g of the amide product and 8.6 g of sodium 2 - carboxymethoxy - 5 - methylbenzenesulfonate and place them in a reactor. Add 50 mL of N - methylpyrrolidone, 8.3 mL of pyrrole, 23.2 g of triphenyl phosphite, 2.25 g of calcium chloride, and 0.76 g of lithium chloride. Mix them evenly. Under the protection of a nitrogen atmosphere, heat up to 105 - 115 °C and stir - react for 24 h; cool to room temperature, precipitate in acetone, filter, wash, and dry to obtain the branched polyamide;

[0075] Step 1: Take 0.40 part of the branched polyamide and dissolve it in deionized water to obtain a mixed solution; place the mixed solution and 1.0 part of graphene in a ball mill, add 120 parts of zirconia as the grinding medium, and start the stirring mill. The rotation speed of the stirring mill is 250 r / min. Slowly add 100 parts of alumina, 13.4 parts of aluminum nitride, 0.4 part of yttrium oxide, and 0.03 part of lanthanum oxide to the stirring mill and ball - mill for 4 h; add cesium chloride as an inorganic salt and continue ball - milling for 75 min; obtain a slurry with a solid content of 55 vol%; the concentration of magnesium chloride in the slurry is 150 ppm;

[0076] Step 2: Place the slurry obtained in Step 1 under the constant - temperature and constant - humidity conditions of 25 °C and 85% relative humidity for dehydration for 3 d, seal it in a pressure - filtration mold and apply a pressure of 0.45 MPa to obtain a green body; place it in a muffle furnace, heat it up to 800 °C at a heating rate of 2 °C / min, and keep it at this temperature for 6 h to remove the binder; heat it up to 1850 °C at a heating rate of 10 °C / min, then cool it to 1400 °C, keep it at this temperature for 3 h, heat it up to 1850 °C at a heating rate of 2 °C / min, and keep it at this temperature for 6 h.

[0077] Comparative Example 1: A high - strength alumina ceramic and its processing technology, including the following processes:

[0078] Step 1: Take 0.1 part of Isobam104 and 0.2 part of Isobam600AF and dissolve them in deionized water to obtain a mixed solution; place the mixed solution and 0.6 part of graphene in a ball mill, add 110 parts of zirconia as the grinding medium, and start the stirring mill. The rotation speed of the stirring mill is 200 r / min. Slowly add 100 parts of alumina, 13.0 parts of aluminum nitride, 0.34 part of yttrium oxide, and 0.026 part of lanthanum oxide to the stirring mill and ball - mill for 1 h to obtain a slurry with a solid content of 40 vol%;

[0079] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions of 25°C and 85% relative humidity for dehydration for 1 day, seal it in a filter press mold and apply a pressure of 0.37 MPa to obtain a green body; place it in a muffle furnace, heat it to a temperature of 1000°C at a heating rate of 1°C / min, and keep it at this temperature for 6 hours to remove binder; heat it to 1850°C at a heating rate of 10°C / min, then cool it to 1500°C, keep it at this temperature for 2 hours, and then heat it to 1850°C at a heating rate of 2°C / min and keep it at this temperature for 6 hours.

[0080] Comparative Example 2: A high-strength alumina ceramic and its processing technology, including the following processes:

[0081] Step 1: Dissolve 0.1 part of Isobam104 and 0.2 part of Isobam600AF in deionized water to obtain a mixed solution; place the mixed solution in a ball mill, add 110 parts of zirconia as grinding medium, start the stirring mill, the rotation speed of the stirring mill is 200 r / min, slowly add 100 parts of alumina, 13.0 parts of aluminum nitride, 0.34 part of yttrium oxide, and 0.026 part of lanthanum oxide to the stirring mill, and ball mill for 1 hour to obtain a slurry with a solid content of 40 vol%.

[0082] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions of 25°C and 85% relative humidity for dehydration for 1 day, seal it in a filter press mold and apply a pressure of 0.37 MPa to obtain a green body; place it in a muffle furnace, heat it to a temperature of 1000°C at a heating rate of 1°C / min, and keep it at this temperature for 6 hours to remove binder; heat it to 1850°C at a heating rate of 10°C / min, then cool it to 1500°C, keep it at this temperature for 2 hours, and then heat it to 1850°C at a heating rate of 2°C / min and keep it at this temperature for 6 hours.

[0083] Comparative Example 3: A high-strength alumina ceramic and its processing technology, including the following processes:

[0084] Step 1: Dissolve 0.1 part of Isobam104 and 0.2 part of Isobam600AF in deionized water to obtain a mixed solution; place the mixed solution in a ball mill, add 110 parts of zirconia as grinding medium, start the stirring mill, the rotation speed of the stirring mill is 200 r / min, slowly add 113 parts of alumina, 0.34 part of yttrium oxide, and 0.026 part of lanthanum oxide to the stirring mill, and ball mill for 1 hour to obtain a slurry with a solid content of 40 vol%.

[0085] Step 2: Place the slurry obtained in Step 1 under constant temperature and humidity conditions of 25°C and 85% relative humidity for dehydration for 1 day to obtain a green body; place it in a muffle furnace, heat it at a heating rate of 1°C / min to a temperature of 1000°C, and hold for 6 hours to remove the binder; heat it at a heating rate of 10°C / min to 1850°C, then cool it to 1500°C, hold for 2 hours, heat it at a heating rate of 2°C / min to 1850°C, and hold for 6 hours.

[0086] Experiment

[0087] Take the alumina ceramics obtained in Examples 1-5 and Comparative Examples 1-3, prepare specimens, and detect their properties respectively and record the test results:

[0088] Adopt the three-point bending method, and use a bending strength tester to detect the bending strength of the specimen. The specimen size is 3mm×4mm×35mm;

[0089] Adopt the single-edge notched beam method to detect the fracture toughness of the specimen. The specimen size is 3mm×4mm×35mm, and the notch size is 2mm;

[0090] Detect the density of the specimen by the Archimedes drainage method, and obtain the relative density of the specimen according to theoretical conversion.

[0091]

[0092]

[0093] According to the data in the above table, the following conclusions can be clearly obtained:

[0094] The alumina ceramics obtained in Examples 1-5 are compared with the alumina ceramics obtained in Comparative Examples 1-3. From the test results, it can be seen that

[0095] Compared with the comparative examples, the alumina ceramics obtained in Examples 1-5 have higher bending strength, fracture toughness and relative density data, which fully shows that the present invention has achieved the improvement of the density and mechanical properties of the prepared alumina ceramics.

[0096] Compared with Example 1, magnesium chloride was not added in Comparative Example 1; magnesium chloride and graphene were not added in Comparative Example 2; magnesium chloride, graphene and aluminum nitride were not added in Comparative Example 3; for the alumina ceramics obtained in Comparative Examples 1-3, the bending strength, fracture toughness and relative density data decreased. It can be seen that the setting of the preparation process and its required components in the present invention can promote the improvement of the density and mechanical properties of the prepared alumina ceramics.

[0097] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0098] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A processing technology for high-strength alumina ceramics, characterized in that: It includes the following processes: Step 1: Dissolve a dispersant in deionized water to obtain a mixed solution; place the mixed solution and graphene in a ball mill, add grinding media and start the stirring mill, slowly add alumina to the stirring mill, and ball mill for 1 - 4 h to obtain a slurry. Step 2: Place the slurry obtained in Step 1 under the conditions of a temperature of 25°C and a relative humidity of 85% for dehydration for 1 - 6 d, seal and filter press it in a filter press mold to obtain a green body. Place it in a muffle furnace, and degum at a temperature of 800 - 1000°C for 2 - 6 h. Raise the temperature to 1850°C at one time, then cool down to 1400 - 1500°C, hold for 2 - 3 h, and then raise the temperature to 1850°C again and hold for 6 h. The dispersant is one or more of Isobam104, Isobam600AF, ammonium polyacrylate, and branched polyamide. The branched polyamide is prepared by the following process: Take trimesic acid, pyridine, and N-methylpyrrolidone and dissolve them, add triphenyl phosphite, raise the temperature to 100 - 110°C, slowly add 1,8-octanediamine, and add it within 2 h, and react for 1 - 3 h to obtain an amide product. Take the amide product and sodium 2-carboxymethoxy-5-methylbenzenesulfonate and place them in a reactor, add N-methylpyrrolidone, pyrrole, triphenyl phosphite, calcium chloride, and lithium chloride, mix evenly, under the protection of a nitrogen atmosphere, heat and raise the temperature to 105 - 115°C, stir and react for 24 h; cool to room temperature, precipitate in acetone, filter, wash, and dry to obtain the branched polyamide. After the ball milling process in Step 1 is completed, add an inorganic salt and continue ball milling for 50 - 75 min; the inorganic salt is one of cesium chloride and magnesium chloride, and its concentration in the slurry is 120 - 180 ppm.

2. The processing technology for high-strength alumina ceramics according to claim 1, characterized in that: The slurry also includes the following mass components: 13.0 - 13.4 parts of aluminum nitride, 0.34 - 0.40 parts of yttrium oxide, and 0.026 - 0.030 parts of lanthanum oxide.

3. The processing technology for high-strength alumina ceramics according to claim 1, characterized in that: The solid content of the slurry is 40 - 55 vol%.

4. The processing technology for high-strength alumina ceramics according to claim 1, characterized in that: The molar ratio of trimesic acid to 1,8-octanediamine is 1:(3.1 - 3.3).

5. The processing technology for high-strength alumina ceramics according to claim 1, characterized in that: The molar ratio of the amide product to sodium 2-carboxymethoxy-5-methylbenzenesulfonate is 1:(1.0 - 1.1).

6. A high-strength alumina ceramic prepared by the processing technology according to any one of claims 1-5.

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