Preparation method of alpha-alumina powder with controllable particle size for electronic ceramics

Abstract

The invention discloses a preparation method of alpha-alumina powder with controllable particle size for electronic ceramics, which comprises the following steps: carrying out impurity removal pretreatment on an aluminum source to obtain a pretreated aluminum source; preparing core-shell structure intermediate powder from the pretreated aluminum source and the sintering aid; carrying out shell layer mechanical shell breaking on the core-shell structure intermediate powder to obtain pre-sintered powder; the powder to be sintered is subjected to segmented sintering, and sintered powder is obtained; grinding and grading the sintered powder to obtain alpha-aluminum oxide powder for electronic ceramics; the grinding and grading process comprises the following steps: adding the sintered powder, a dispersing agent and a ball-milling auxiliary agent into ball-milling equipment for intermittent dry-milling to obtain ball-milled powder; the dispersing agent is one of polycarboxylate; the powder obtained after ball milling is graded through airflow or centrifugal force; the alpha-aluminum oxide powder for preparing the electronic ceramics is low in sodium impurity content, large in grain size, uniform in grain size and uniform in grain size distribution.

Description

Technical Field

[0001] The present invention relates to the field of alpha-alumina powder, and in particular to the technical field of a method for preparing alpha-alumina powder with controllable particle size for electronic ceramics. Background Art

[0002] α-Al2O3 powder has the advantages of high melting point, corrosion resistance, good chemical stability and excellent insulation properties. It is widely used in the manufacture of high-performance ceramic products such as structural ceramics and electronic ceramics. Among them, high-purity α-Al2O3 powder with a purity of more than 99% can meet the material purity requirements of different high-end application fields, such as semiconductors, optics and other fields, and has broad application prospects and large market potential.

[0003] Currently, α-Al2O3 powder with high purity and uniform particle size can be prepared by sol-gel method, precipitation method, hydrothermal method and vapor deposition method. However, these methods are expensive and complex, making them unsuitable for large-scale industrial production.

[0004] In industry, calcination is often used to prepare α-Al2O3 powder. Appropriate calcination temperature and time are used to fully convert the precursor into α-Al2O3. However, α-Al2O3 powder prepared by calcination is prone to particle growth or agglomeration, thereby reducing powder uniformity.

[0005] Traditionally, surface treatment methods are used to treat α-Al2O3 powder, such as adding surfactants and coupling agents, to improve the surface properties of the powder and reduce the agglomeration force between particles. However, surface treatment methods are complex, introduce many impurities, are costly, and are not suitable for large-scale production.

[0006] The agglomerated α-Al2O3 powder is crushed by grinding, but there is a problem that the large grains in the α-Al2O3 powder are reduced after crushing;

[0007] Electronic ceramic applications have strict requirements for α-alumina powder. They need high strength and high thermal conductivity. Therefore, it is necessary to increase the grain size of α-alumina powder and make the grain distribution uniform. Specifically, the sodium ion content (Na + <100ppm), grain D50 ≥ 6.5μm, and uniform particle size distribution (D90 / D10 < 3), and the α-alumina powder particle size distribution is required to be uniform.

[0008] Therefore, how to prepare α-alumina powder for electronic ceramics, achieve low sodium impurity content in α-alumina powder, large α-alumina grain size, uniform grain size, and uniform α-alumina powder particle size distribution has become a difficult problem that needs to be solved urgently in this field. Summary of the Invention

[0009] In order to solve the above technical problems, a method for preparing α-alumina powder for electronic ceramics with controllable particle size is provided, so that the prepared α-alumina powder has low sodium impurity content, large α-alumina grain size, uniform grain size, and uniform particle size distribution of the α-alumina powder.

[0010] According to the present invention, a method for preparing α-alumina powder for electronic ceramics with controllable particle size is provided, comprising the following steps: pre-treating an aluminum source to remove impurities to obtain a pre-treated aluminum source;

[0011] A core-shell structure intermediate powder is prepared by pre-treating an aluminum source and a sintering aid;

[0012] Mechanically breaking the shell of the core-shell structure intermediate powder to obtain a pre-sintered powder;

[0013] Sintering the prepared sintered powder in sections to obtain sintered powder;

[0014] Grinding and classifying the sintered powder to obtain α-alumina powder for electronic ceramics;

[0015] The grinding and grading process includes adding the sintered powder, dispersant, and ball milling aid into a ball mill and performing intermittent dry grinding to obtain ball milled powder;

[0016] The dispersant is one of polycarboxylates, and the grinding aid includes one of ethylene glycol, glycerol, and oleic acid;

[0017] The ball-milled powder is classified by airflow or centrifugal force to obtain α-alumina powder for electronic ceramics.

[0018] Compared with the prior art, the present invention has the following beneficial effects: by pre-treating the aluminum source to remove impurities, the pre-treated aluminum source is obtained, thereby removing sodium ions in the aluminum source, which is conducive to obtaining α-alumina powder with low sodium residue;

[0019] A core-shell structure intermediate powder is prepared by pre-treating an aluminum source and a sintering aid, wherein the core-shell structure intermediate powder includes an Al2O3 shell layer and a sintering aid nanocore coated with the Al2O3 shell layer, thereby achieving uniform distribution of Al2O3 and the sintering aid in the prepared sintered powder, thereby avoiding the problem of abnormal growth of some particles due to uneven distribution of Al2O3 and the sintering aid during the sintering process, achieving uniform grain size in the prepared α-alumina powder, and at the same time, the sintering aid reduces the grain boundary energy, which is conducive to achieving large grain size in the prepared α-alumina powder;

[0020] By mechanically breaking the shell of the core-shell structure intermediate powder, the alumina shell of the core-shell structure intermediate powder is partially broken, and the sintering aid crystal core is partially exposed, thereby avoiding the problem of the sintering aid being coated inside the core-shell structure and causing the sintering aid to have a slow heating rate during the sintering process, thereby avoiding the problem of the sintering temperature being too high due to the high temperature at which the sintering aid forms a liquid phase; avoiding the problem of the sintering aid forming a liquid phase at a high temperature and causing the grain boundary energy of the externally coated alumina to decrease rapidly and too much, thereby avoiding the phenomenon of some alumina grains merging with each other to produce some abnormally grown grains, and achieving uniform grain size in the α-alumina powder;

[0021] By sintering the prepared sintered powder in stages, the alumina shell of the core-shell structure intermediate powder is first broken during the sintering process, and then the alumina shell is completely dehydrated to generate crystal nuclei. Subsequently, the grains gradually grow, resulting in large grains with a D50 of ≥6.5μm and uniform particle size.

[0022] The grinding and grading process includes adding the sintered powder, dispersant, and ball milling aid into a ball mill for intermittent dry grinding to obtain ball milled powder, thereby achieving uniform particle size dispersion in the ball milled powder and avoiding the problem of severe grain wear of the powder particles during the ball milling process, resulting in a significant reduction in grain size.

[0023] Thus, the prepared α-alumina powder has low sodium impurity content, large α-alumina grain size, uniform grain size, and uniform α-alumina powder particle size distribution.

[0024] Furthermore, the powder preparation process after ball milling includes the following steps:

[0025] Mix the sintered powder, dispersant and ball milling aid in a mass ratio of 1: (0.1-0.3):

[0026] (0.2-0.5) Add ball milling equipment and perform ball milling in an anhydrous environment;

[0027] The ball mill speed is 300-400 rpm, and the ball milling time is 5-8 hours. During the ball milling process, stop the ball milling for 10-15 minutes every 1-1.5 hours, and then change the ball mill rotation direction and continue the ball milling.

[0028] After ball milling, the mass of the powder with a grain size of (6-8) μm accounts for more than 85% of the total powder mass, and the mass of the powder with a grain size of less than 1 μm accounts for less than 3% of the total powder mass.

[0029] The beneficial effect of adopting the above step is that it is conducive to improving the grinding efficiency and avoiding or reducing environmental pollution. At the same time, the ball mill speed is 300-400 rpm. The low ball mill speed avoids the problem of severe grain wear of the powder particles during the ball milling process; by stopping the ball milling for 10-15 minutes every 1-1.5 hours during the ball milling process, and then changing the ball mill rotation direction to continue the ball milling, the damage to the grains is further reduced without significantly reducing the dispersion efficiency.

[0030] After ball milling, the mass of powder with a grain size of (6-8) μm accounts for more than 85% of the total powder mass, and the mass of powder with a grain size of less than 1 μm accounts for less than 3% of the total powder mass, so that the obtained α-alumina powder for electronic ceramics has uniform particle size and a larger grain size.

[0031] Furthermore, the ball-to-material ratio during ball milling is: (3-5):1;

[0032] The grinding balls include zirconia balls and corundum balls in a mass ratio of (50-60): (40-50);

[0033] The diameter of the zirconia ball is 10-8 mm; the diameter of the corundum ball is 3-5 mm.

[0034] The beneficial effect of adopting the above step is that it further facilitates achieving uniform dispersion while avoiding the problem of severe damage to the grain size of the α-alumina powder and the problem of a significant reduction in the grain size.

[0035] Furthermore, the aluminum source includes industrial alumina powder;

[0036] The aluminum source is subjected to impurity removal pretreatment and comprises the following steps:

[0037] Mix the aluminum source and deionized water in a double-helix staggered layer washing tank, add polyethylene glycol-400 for washing, the washing temperature is 60±2℃, and the washing time is 15-25min;

[0038] The washed aluminum source is then mixed with an organic acid for cleaning and pickled at a temperature of 45±2° C. for 8-12 minutes. Preferably, the organic acid for cleaning comprises two or more of acetic acid, lactic acid, oxalic acid, malic acid, tartaric acid, and citric acid.

[0039] The aluminum source after pickling is mixed with deionized water again and heated for cleaning at a heating temperature of 80±2°C. When the conductivity of the mixed solution of aluminum source and water is less than 50μS / cm and the redox potential is greater than 200mV, the heating and cleaning is stopped, and the aluminum source impurity removal pretreatment is completed.

[0040] The beneficial effect of the above step is that it is conducive to achieving a low sodium content in the α-alumina powder; by adding polyethylene glycol-400 for water washing, the water washing temperature is 60±2°C, and the water washing time is 15-25 minutes, the sodium on the surface of the aluminum source is removed by more than 92%; the lattice sodium removal rate in the aluminum source is achieved by the acid washing process to reach more than 98%; after the final heating and cleaning stage, the acid radical residue is achieved to be less than 5ppm;

[0041] When the conductivity of the mixed solution of aluminum source and water is less than 50μS / cm and the redox potential is greater than 200mV, the segmented pretreatment of the aluminum source is completed, thereby achieving a high sodium removal rate while effectively avoiding a high aluminum loss rate, achieving an aluminum loss rate of less than 0.8%.

[0042] Furthermore, the double-helix staggered water washing tank includes a main helix and a secondary helix; the main helix rotates in the opposite direction to the secondary helix;

[0043] The pitch ratio of the main screw and the auxiliary screw is (1.6-2.0):1;

[0044] The difference between the inclination angle of the main screw and the horizontal direction and the inclination angle of the auxiliary screw and the horizontal direction is 11-20°;

[0045] During the aluminum source segmented pretreatment process, the liquid in the double-helix staggered water washing tank forms a turbulent flow zone, and the Reynolds number in the flow zone is greater than 2200;

[0046] Preferably, the pitch of the main screw is 145-155 mm, and the inclination angle of the main screw to the horizontal direction is 43-48°; the pitch of the auxiliary screw is 75-85 mm, and the inclination angle of the auxiliary screw to the horizontal direction is 28-32°.

[0047] The beneficial effect of the above step is that the main screw rotates in the opposite direction to the auxiliary screw, thereby forming a turbulent zone in the solution, strengthening the penetration of the acid radical into the aluminum source, and improving the sodium removal rate.

[0048] Furthermore, the preparation of the core-shell structure intermediate powder comprises the following steps:

[0049] preparing aluminum hydroxide sol by pretreating an aluminum source;

[0050] A TiO2-ZrO2 precursor solution was prepared by using tetrabutyl titanate and zirconium oxychloride;

[0051] The core-shell structure intermediate powder is prepared by TiO2-ZrO2 precursor solution and aluminum hydroxide sol.

[0052] Furthermore, the aluminum hydroxide sol preparation process comprises the following steps:

[0053] The pretreated aluminum source is added to deionized water, and then an organic acid is added for reaction, and the reaction is carried out at 100-120° C. for 5-10 hours to obtain aluminum hydroxide sol;

[0054] The molar ratio of the aluminum element in the aluminum source after the pretreatment to the carboxylate radical of the organic acid for the reaction is 1:(3.5-4);

[0055] The organic acid used in the reaction includes two or more of formic acid, acetic acid, lactic acid, and oxalic acid;

[0056] and / or

[0057] The TiO2-ZrO2 precursor solution preparation process comprises the following steps:

[0058] adding tetrabutyl titanate and zirconium oxychloride into deionized water to obtain a first mixed solution;

[0059] Then adjust the pH of the first mixed solution to 3.0-4.0;

[0060] Then, the mixture is aged at 55-65°C for 0.8-1.2h to obtain a TiO2-ZrO2 precursor solution;

[0061] The molar ratio of tetrabutyl titanate and zirconium oxychloride is (2.5-6.5):1.

[0062] Furthermore, the process of preparing the core-shell structure intermediate powder by using TiO2-ZrO2 precursor solution and aluminum hydroxide sol includes the following steps:

[0063] adding Al(OH)3 sol to the TiO2-ZrO2 precursor to obtain a second mixed solution;

[0064] Adjusting the pH of the second mixed solution to 2.2-2.8, and then stirring at 75-85° C. for 2-4 hours to obtain a third mixed solution;

[0065] Adjusting the pH of the third mixed solution to 4.0-5.0, and then spray drying to obtain a core-shell structure intermediate powder;

[0066] The third mixed solution includes TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores; the diameter of the TiO2-ZrO2 nanocores is 5-8nm, and the diameter of the TiO2-ZrO2-SiO2 nanocores is 5-8nm;

[0067] The core-shell structure intermediate powder includes an Al2O3 shell layer, and a TiO2-ZrO2 nanocore or a TiO2-ZrO2-SiO2 nanocore coated with the Al2O3 shell layer;

[0068] The Al2O3 shell layer has a thickness of 10-100 nm;

[0069] The mass ratio of the Al2O3 shell to the TiO2-ZrO2 nanocore is (0.5-0.7):

[0070] (99.3-99.5).

[0071] The beneficial effect of the above step is that by adding Al(OH)3 sol to the TiO2-ZrO2 precursor and adjusting the pH of the second mixed solution to 2.2-2.8, TiO2-ZrO2 nanocores are generated in the second mixed solution, and at the same time, silicon impurities in the Al(OH)3 sol and the TiO2-ZrO2 precursor are combined to form TiO2-ZrO2-SiO2 nanocores.

[0072] By adjusting the pH of the third mixed solution to 4.0-5.0, an aluminum hydroxide shell layer is coated on the outside of the nanocore;

[0073] The core-shell structure intermediate powder is obtained by spray drying to achieve dehydration.

[0074] The third mixed solution includes TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores, thereby reducing the silicon content in the lattice of the α-alumina powder;

[0075] The core-shell structure intermediate powder includes an Al2O3 shell layer, and TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores coated with the Al2O3 shell layer, so that the outer shell layer of the core-shell structure intermediate powder is an Al2O3 shell layer, and the nanocore is a sintering aid nanocore, which is conducive to achieving uniform grain size in the prepared α-alumina powder. At the same time, the sintering aid lowers the grain boundary energy, which is conducive to achieving large grain size in the prepared α-alumina powder.

[0076] Furthermore, the preparation process of the pre-sintered powder includes the following steps: adding the core-shell intermediate powder to a differential stirring device and stirring at room temperature, the speed of the device is 80-120 rpm, and the stirring time is 12-18 minutes to obtain the pre-sintered powder.

[0077] The beneficial effect of adopting the above step is that the alumina shell of the core-shell intermediate powder is partially broken.

[0078] Furthermore, the process of sintering the prepared sintered powder in stages includes:

[0079] The prepared sintered powder is subjected to the first stage sintering, heating from room temperature to 600-800°C at a heating rate of 8-10°C / min, the sintering atmosphere is air, and the heating time at 600-800°C is 12-18 minutes;

[0080] Then the second stage of sintering is carried out, heating from 600-800℃ to 1000-1200℃, with a heating rate of 4-6℃ / min, sintering atmosphere is air, and heating time at 1000-1200℃ is 18-22min;

[0081] Then the third stage of sintering is carried out, heating from 1000-1200℃ to 1650±10℃, with a heating rate of 1-3℃ / min, in an oxygen-rich atmosphere, and heating time at 1650±10℃ for 40-50min;

[0082] Rapid cooling stage: from 750-850℃ to 180-220℃, the cooling rate is 8-15℃ / min, and the cooling atmosphere is air;

[0083] Preferably, the oxygen-rich atmosphere has an O2 mass fraction of 28%.

[0084] The beneficial effect of the above step is that rapid dehydration is achieved through the first stage of sintering, which is conducive to the continued crushing of the alumina shell of the core-shell intermediate powder;

[0085] The alumina shell is dehydrated and a crystal nucleus is generated through the second stage of sintering;

[0086] The third stage of sintering achieves directional grain growth, resulting in large grains and uniform grain size;

[0087] The rapid cooling stage is helpful to avoid secondary agglomeration of the generated α-alumina powder.

[0088] It is further beneficial to achieve the prepared α-alumina powder for electronic ceramics with controllable particle size, the grain D50 of which is ≥6.0 μm, D90 / D10 is <3; the residual sodium in the α-alumina powder is <100 ppm, and the residual silicon is <100 ppm. DETAILED DESCRIPTION

[0089] In order to better understand the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments.

[0090] Example 1:

[0091] This embodiment provides a method for preparing α-alumina powder for electronic ceramics with controllable particle size, comprising the following steps: pre-treating an aluminum source to remove impurities to obtain a pre-treated aluminum source; the aluminum source comprises industrial alumina powder;

[0092] The aluminum source is subjected to impurity removal pretreatment and comprises the following steps:

[0093] The aluminum source was mixed with deionized water in a double-helix staggered layer washing tank, and polyethylene glycol-400 was added for washing at a temperature of 60°C for 20 minutes.

[0094] Then, the aluminum source after water washing is mixed with an organic acid for cleaning and pickled at a temperature of 45° C. for 10 minutes; the organic acid for cleaning includes acetic acid and lactic acid;

[0095] The aluminum source after pickling is mixed with deionized water again and heated for cleaning at a heating temperature of 80°C. When the conductivity of the mixed solution of aluminum source and water is less than 50μS / cm and the redox potential is greater than 200mV, the heating and cleaning is stopped, and the aluminum source impurity removal pretreatment is completed.

[0096] The double-helix staggered water washing tank comprises a main helix and a secondary helix; the main helix rotates in the opposite direction to the secondary helix;

[0097] During the aluminum source segmented pretreatment process, the liquid in the double-helix staggered water washing tank forms a turbulent flow zone, and the Reynolds number in the flow zone is greater than 2200;

[0098] The pitch of the main screw rod is 150 mm, and the inclination angle of the main screw rod to the horizontal direction is 45°; the pitch of the auxiliary screw rod is 80 mm, and the inclination angle of the auxiliary screw rod to the horizontal direction is 30°.

[0099] A core-shell structure intermediate powder is prepared by pre-treating an aluminum source and a sintering aid. The preparation of the core-shell structure intermediate powder comprises the following steps:

[0100] Aluminum hydroxide sol is prepared by pre-treating an aluminum source; the aluminum hydroxide sol preparation process comprises the following steps:

[0101] The pretreated aluminum source was added to deionized water, and then an organic acid for reaction was added, and the reaction was carried out at 110°C for 7.5 hours to obtain aluminum hydroxide sol;

[0102] The molar ratio of the aluminum element in the aluminum source after the pretreatment to the carboxylate radical of the organic acid for the reaction is 1:3.8;

[0103] The organic acid used in the reaction includes formic acid and acetic acid;

[0104] A TiO2-ZrO2 precursor solution is prepared by tetrabutyl titanate and zirconium oxychloride; the TiO2-ZrO2 precursor solution preparation process comprises the following steps:

[0105] adding tetrabutyl titanate and zirconium oxychloride into deionized water to obtain a first mixed solution;

[0106] Then adjust the pH of the first mixed solution to 3.5;

[0107] Then, the mixture was aged at 60 °C for 1 h to obtain a TiO2-ZrO2 precursor solution;

[0108] The molar ratio of tetrabutyl titanate to zirconium oxychloride is 4.5:1.

[0109] The core-shell structure intermediate powder is prepared by using TiO2-ZrO2 precursor solution and aluminum hydroxide sol, which specifically includes the following steps:

[0110] adding Al(OH)3 sol to the TiO2-ZrO2 precursor to obtain a second mixed solution;

[0111] The pH of the second mixed solution was adjusted to 2.5, and then stirred at 80° C. for 3 h to obtain a third mixed solution;

[0112] Adjusting the pH of the third mixed solution to 4.5, and then spray drying to obtain a core-shell structure intermediate powder;

[0113] The third mixed solution includes TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores; the diameter of the TiO2-ZrO2 nanocores is 6.5 nm, and the diameter of the TiO2-ZrO2-SiO2 nanocores is 6.5 nm;

[0114] The core-shell structure intermediate powder includes an Al2O3 shell layer, and a TiO2-ZrO2 nanocore or a TiO2-ZrO2-SiO2 nanocore coated with the Al2O3 shell layer;

[0115] The Al2O3 shell layer has a thickness of 55 nm;

[0116] The mass ratio of the Al2O3 shell to the TiO2-ZrO2 nanocore is 0.6:99.38.

[0117] The core-shell structure intermediate powder is subjected to mechanical shell breaking to obtain a pre-sintered powder, which specifically includes the following steps:

[0118] The preparation process of the pre-sintered powder includes the following steps: adding the core-shell intermediate powder to a differential stirring device and stirring at room temperature at a speed of 100 rpm for 15 minutes to obtain the pre-sintered powder.

[0119] The prepared sintered powder is sintered in stages to obtain sintered powder. The staged sintering process includes:

[0120] The prepared sintered powder was subjected to the first stage sintering, heating from room temperature to 700°C at a heating rate of 9°C / min, in air atmosphere, and heating at 700°C for 15 min.

[0121] Then the second sintering was carried out, heating from 700℃ to 1100℃ at a heating rate of 5℃ / min, the sintering atmosphere was air, and the heating time at 1100℃ was 20min;

[0122] Then the third sintering was carried out, heating from 1100℃ to 1650℃ at a heating rate of 2℃ / min, in an oxygen-rich atmosphere, with a heating time of 45min at 1650℃; the mass fraction of O2 in the oxygen-rich atmosphere was 28%;

[0123] In the rapid cooling stage, the temperature was cooled from 800°C to 200°C at a cooling rate of 13°C / min, and the cooling atmosphere was air.

[0124] Grinding and classifying the sintered powder to obtain α-alumina powder for electronic ceramics;

[0125] The grinding and grading process includes adding the sintered powder, dispersant, and ball milling aid into a ball mill and performing intermittent dry grinding to obtain ball milled powder;

[0126] The dispersant is one of the polycarboxylates, and the grinding aid includes ethylene glycol;

[0127] The ball-milled powder preparation process comprises the following steps:

[0128] The sintered powder, dispersant and ball milling aid were added into the ball mill at a mass ratio of 1:0.2:0.35 and ball milled in an anhydrous environment;

[0129] The ball milling speed was 350 rpm and the ball milling time was 6.5 h. During the ball milling process, the ball milling was stopped for 13 min after every 1.2 h of ball milling, and then the ball milling direction was changed and the ball milling was continued.

[0130] The ball-to-material ratio during ball milling is 4:1; the grinding balls include zirconia balls and corundum balls with a mass ratio of 55:45;

[0131] The diameter of the zirconia ball is 9 mm; the diameter of the corundum ball is 4 mm.

[0132] After ball milling, the mass of the powder with a grain size of (6-8) μm accounts for 88% of the total powder mass, and the mass of the powder with a grain size of less than 1 μm accounts for 2.5 of the total powder mass.

[0133] The ball-milled powder is classified by airflow or centrifugal force to obtain α-alumina powder for electronic ceramics;

[0134] The α-alumina powder for electronic ceramics with controllable particle size prepared by the method has a grain size of 6.8 μm and a D90 / D10 of 2.6. The residual sodium and silicon contents in the α-alumina powder are 75 ppm and 70 ppm, respectively.

[0135] Example 2:

[0136] The same contents as those in Example 1 will not be repeated here. The differences between this embodiment and Example 1 are as follows: This embodiment provides a method for preparing α-alumina powder for electronic ceramics with controllable particle size, further comprising the following steps:

[0137] Organic acids used for cleaning include oxalic acid and malic acid.

[0138] The aluminum hydroxide sol preparation process comprises the following steps:

[0139] The pretreated aluminum source was added to deionized water, and then an organic acid was added for reaction, and the reaction was carried out at 118°C for 6 hours to obtain aluminum hydroxide sol;

[0140] The molar ratio of aluminum element in the aluminum source after pretreatment to carboxylate radical of the organic acid for reaction is 1:3.9; the organic acid for reaction includes lactic acid and oxalic acid;

[0141] The TiO2-ZrO2 precursor solution preparation process comprises the following steps:

[0142] Adjusting the pH of the first mixed solution to 3.8;

[0143] Then, the mixture was aged at 63 °C for 0.85 h to obtain a TiO2-ZrO2 precursor solution;

[0144] The molar ratio of tetrabutyl titanate to zirconium oxychloride is 5.5:1.

[0145] The core-shell structure intermediate powder is prepared by using TiO2-ZrO2 precursor solution and aluminum hydroxide sol, which specifically includes the following steps:

[0146] The second mixed solution was adjusted to pH = 2.7, and then stirred at 83° C. for 2.5 h to obtain a third mixed solution;

[0147] The pH of the third mixed solution was adjusted to 4.8, and then spray-dried to obtain a core-shell structure intermediate powder;

[0148] The third mixed solution includes TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores; the diameter of the TiO2-ZrO2 nanocores is 7.5 nm, and the diameter of the TiO2-ZrO2-SiO2 nanocores is 7.5 nm;

[0149] The Al2O3 shell layer has a thickness of 90 nm;

[0150] The mass ratio of the Al2O3 shell to the TiO2-ZrO2 nanocore is 0.68:99.315.

[0151] The core-shell intermediate powder was added to a differential stirring device and stirred at room temperature at a speed of 118 rpm for 17 min to obtain a pre-sintered powder.

[0152] The staged sintering process includes: performing the first stage sintering of the prepared sintering powder from room temperature to 780°C at a heating rate of 9.5°C / min in an air atmosphere and heating at 780°C for 13 minutes;

[0153] Then the second stage of sintering was carried out, heating from 780℃ to 1180℃ at a heating rate of 5.8℃ / min, the sintering atmosphere was air, and the heating time at 1180℃ was 19min;

[0154] Then the third sintering was carried out, heating from 1180℃ to 1656℃ at a heating rate of 2.8℃ / min, in an oxygen-rich atmosphere, and heating time at 1656℃ for 41min.

[0155] In the rapid cooling stage, the temperature was cooled from 830°C to 210°C at a cooling rate of 14°C / min, and the cooling atmosphere was air.

[0156] The grinding aid includes glycerol;

[0157] The ball-milled powder preparation process comprises the following steps:

[0158] Add the sintered powder, dispersant and ball milling aid into the ball mill at a mass ratio of 1:0.28:0.46;

[0159] The ball milling speed was 380 rpm and the ball milling time was 7 h. During the ball milling process, the ball milling was stopped for 14 min after every 1.1 h of ball milling, and then the ball milling direction was changed and the ball milling was continued.

[0160] The ball-to-material ratio during ball milling was 4.8:1;

[0161] The grinding balls include zirconia balls and corundum balls in a mass ratio of 58:42.

[0162] After ball milling, the mass of the powder with a grain size of (6-8) μm accounts for 90% of the total powder mass, and the mass of the powder with a grain size of less than 1 μm accounts for 1.9% of the total powder mass. The α-alumina powder for electronic ceramics with controllable particle size prepared by the method has a grain size D50 of 7.8 μm and a D90 / D10 ratio of 2.6. The α-alumina powder contains 78 ppm of residual sodium and 65 ppm of residual silicon.

[0163] Example 3:

[0164] The same contents as those in Example 1 will not be repeated here. The differences between this embodiment and Example 1 are as follows: This embodiment provides a method for preparing α-alumina powder for electronic ceramics with controllable particle size, further comprising the following steps:

[0165] Organic acids used for cleaning include acetic acid, tartaric acid, and citric acid.

[0166] The aluminum hydroxide sol preparation process comprises the following steps:

[0167] The pretreated aluminum source was added to deionized water, and then an organic acid was added for reaction, and the reaction was carried out at 105°C for 9 hours to obtain aluminum hydroxide sol;

[0168] The molar ratio of the aluminum element in the aluminum source after the pretreatment to the carboxylate radical of the organic acid for the reaction is 1:3.6;

[0169] The organic acid used in the reaction includes two or more of formic acid, acetic acid, lactic acid, and oxalic acid;

[0170] The TiO2-ZrO2 precursor solution preparation process comprises the following steps:

[0171] Adjusting the pH of the first mixed solution to 3.2;

[0172] Then, the mixture was aged at 58 °C for 1.1 h to obtain a TiO2-ZrO2 precursor solution;

[0173] The molar ratio of tetrabutyl titanate to zirconium oxychloride is 3:1.

[0174] The core-shell structure intermediate powder is prepared by using TiO2-ZrO2 precursor solution and aluminum hydroxide sol, which specifically includes the following steps:

[0175] The pH of the second mixed solution was adjusted to 2.3, and then stirred at 78° C. for 3.8 hours to obtain a third mixed solution;

[0176] The third mixed solution was adjusted to pH 4.2, and then spray-dried to obtain a core-shell structure intermediate powder;

[0177] The third mixed solution includes TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores; the diameter of the TiO2-ZrO2 nanocores is 5.6 nm, and the diameter of the TiO2-ZrO2-SiO2 nanocores is 5.6 nm;

[0178] The Al2O3 shell layer has a thickness of 40 nm;

[0179] The mass ratio of the Al2O3 shell to the TiO2-ZrO2 nanocore is 0.55:99.435.

[0180] The core-shell intermediate powder was added to a differential stirring device and stirred at room temperature at a speed of 88 rpm for 13 min to obtain a pre-sintered powder.

[0181] The staged sintering process includes: performing the first stage sintering of the prepared sintering powder from room temperature to 620°C at a heating rate of 8.5°C / min in an air atmosphere and heating at 620°C for 17 minutes;

[0182] Then the second sintering was carried out, heating from 620℃ to 1050℃ at a heating rate of 4.3℃ / min, the sintering atmosphere was air, and the heating time at 1050℃ was 19min;

[0183] Then the third sintering was carried out, heating from 1050℃ to 1645℃ at a heating rate of 1.2℃ / min, in an oxygen-rich atmosphere, and heating time at 1645℃ for 48min.

[0184] In the rapid cooling stage, the temperature was cooled from 760°C to 185°C at a cooling rate of 9°C / min, and the cooling atmosphere was air.

[0185] The grinding aid includes oleic acid;

[0186] The ball-milled powder preparation process comprises the following steps:

[0187] Add the sintered powder, dispersant and ball milling aid into the ball mill at a mass ratio of 1:0.18:0.22;

[0188] The ball milling speed was 320 rpm and the ball milling time was 5.5 h. During the ball milling process, the ball milling was stopped for 11 min after every 1.4 h of ball milling, and then the ball milling direction was changed and the ball milling was continued.

[0189] The ball-to-material ratio during ball milling was 3.5:1;

[0190] The grinding balls include zirconia balls and corundum balls in a mass ratio of 52:48.

[0191] After ball milling, the mass of the powder with a grain size of (6-8) μm accounts for 88% of the total powder mass, and the mass of the powder with a grain size of less than 1 μm accounts for 2.5% of the total powder mass.

[0192] The α-alumina powder for electronic ceramics with controllable particle size prepared by the method has a grain size of 7.3 μm and a D90 / D10 ratio of 2.3. The α-alumina powder contains 70 ppm of residual sodium and 63 ppm of residual silicon.

[0193] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A method for preparing α-alumina powder for electronic ceramics with controllable particle size, characterized in that: The following steps are involved: performing impurity removal pretreatment on the aluminum source to obtain a pretreated aluminum source; A core-shell structure intermediate powder is prepared by pre-treating an aluminum source and a sintering aid; Mechanically breaking the shell of the core-shell structure intermediate powder to obtain a pre-sintered powder; Sintering the prepared sintered powder in sections to obtain sintered powder; Grinding and classifying the sintered powder to obtain α-alumina powder for electronic ceramics; The grinding and grading process includes adding the sintered powder, dispersant, and ball milling aid into a ball mill and performing intermittent dry grinding to obtain ball milled powder; The dispersant is one of polycarboxylates, and the grinding aid includes one of ethylene glycol, glycerol, and oleic acid; The ball-milled powder is classified by airflow or centrifugal force to obtain α-alumina powder for electronic ceramics.

2. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 1, characterized in that: The ball-milled powder preparation process comprises the following steps: Add the sintered powder, dispersant and ball milling aid into the ball mill at a mass ratio of 1: (0.1-0.3): (0.2-0.5) and perform ball milling in an anhydrous environment; The ball mill speed is 300-400 rpm, and the ball milling time is 5-8 hours. During the ball milling process, stop the ball milling for 10-15 minutes every 1-1.5 hours, and then change the ball mill rotation direction and continue the ball milling. After ball milling, the mass of the powder with a grain size of (6-8) μm accounts for more than 85% of the total powder mass, and the mass of the powder with a grain size of less than 1 μm accounts for less than 3% of the total powder mass.

3. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 1, characterized in that: The ball-to-material ratio during ball milling is (3-5):1; The grinding balls include zirconia balls and corundum balls in a mass ratio of (50-60): (40-50); The diameter of the zirconia ball is 10-8 mm; the diameter of the corundum ball is 3-5 mm.

4. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 1, characterized in that: The aluminum source includes industrial alumina powder; The aluminum source is subjected to impurity removal pretreatment and comprises the following steps: Mix the aluminum source and deionized water in a double-helix staggered layer washing tank, add polyethylene glycol-400 for washing, the washing temperature is 60±2℃, and the washing time is 15-25min; Then the washed aluminum source is mixed with an organic acid for cleaning and pickled at a temperature of 45±2°C for 8-12 minutes. The aluminum source after pickling is mixed with deionized water again and heated for cleaning at a heating temperature of 80±2°C. When the conductivity of the mixed solution of aluminum source and water is less than 50μS / cm and the redox potential is greater than 200mV, the heating and cleaning is stopped, and the aluminum source impurity removal pretreatment is completed.

5. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 4, characterized in that: The double-helix staggered water washing tank comprises a main helix and a secondary helix; the main helix rotates in the opposite direction to the secondary helix; The pitch ratio of the main screw and the auxiliary screw is (1.6-2.0):1; The difference between the inclination angle of the main screw and the horizontal direction and the inclination angle of the auxiliary screw and the horizontal direction is 11-20°; During the segmented pretreatment of aluminum source, the liquid in the double-helix staggered water washing tank forms a turbulent zone, and the Reynolds number in the turbulent zone is greater than 2200.

6. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 1, characterized in that: The preparation of the core-shell structure intermediate powder comprises the following steps: preparing aluminum hydroxide sol by pretreating an aluminum source; A TiO2-ZrO2 precursor solution was prepared by using tetrabutyl titanate and zirconium oxychloride; A core-shell structure intermediate powder is prepared by using TiO2-ZrO2 precursor solution and aluminum hydroxide sol.

7. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 6, characterized in that: The aluminum hydroxide sol preparation process comprises the following steps: Add the pretreated aluminum source to deionized water, then add an organic acid for reaction, and react at 100-120° C. for 5-10 hours to obtain aluminum hydroxide sol; The molar ratio of the aluminum element in the aluminum source after the pretreatment to the carboxylate radical of the organic acid for the reaction is 1:(3.5-4); The organic acid used in the reaction includes two or more of formic acid, acetic acid, lactic acid, and oxalic acid; and / or The TiO2-ZrO2 precursor solution preparation process comprises the following steps: adding tetrabutyl titanate and zirconium oxychloride into deionized water to obtain a first mixed solution; Then adjust the pH of the first mixed solution to 3.0-4.0; Then, the mixture is aged at 55-65°C for 0.8-1.2h to obtain a TiO2-ZrO2 precursor solution; The molar ratio of tetrabutyl titanate and zirconium oxychloride is (2.5-6.5):

1.

8. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 6, characterized in that: The process of preparing a core-shell structure intermediate powder by using a TiO2-ZrO2 precursor solution and an aluminum hydroxide sol includes the following steps: adding Al(OH)3 sol to the TiO2-ZrO2 precursor to obtain a second mixed solution; Adjusting the pH of the second mixed solution to 2.2-2.8, and then stirring at 75-85° C. for 2-4 hours to obtain a third mixed solution; Adjusting the pH of the third mixed solution to 4.0-5.0, and then spray drying to obtain a core-shell structure intermediate powder; The third mixed solution includes TiO2-ZrO2 nanocores and TiO2-ZrO2-SiO2 nanocores; the diameter of the TiO2-ZrO2 nanocores is 5-8nm, and the diameter of the TiO2-ZrO2-SiO2 nanocores is 5-8nm; The core-shell structure intermediate powder includes an Al2O3 shell layer, and a TiO2-ZrO2 nanocore or a TiO2-ZrO2-SiO2 nanocore coated with the Al2O3 shell layer; The Al2O3 shell layer has a thickness of 10-100 nm; The mass ratio of the Al2O3 shell to the TiO2-ZrO2 nanocore is (0.5-0.7): (99.3-99.5)。 9. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 1, characterized in that: The preparation process of the pre-sintered powder comprises the following steps: adding the core-shell intermediate powder into a differential stirring device and stirring at room temperature at a speed of 80-120 rpm for 12-18 minutes to obtain the pre-sintered powder.

10. The method for preparing α-alumina powder for electronic ceramics with controllable particle size according to claim 1, characterized in that: The process of sintering the prepared sintered powder in stages includes: The prepared sintered powder is subjected to the first stage sintering, heating from room temperature to 600-800°C at a heating rate of 8-10°C / min, the sintering atmosphere is air, and the heating time at 600-800°C is 12-18 minutes; Then the second stage of sintering is carried out, heating from 600-800℃ to 1000-1200℃, with a heating rate of 4-6℃ / min, sintering atmosphere is air, and heating time at 1000-1200℃ is 18-22min; Then the third stage of sintering is carried out, heating from 1000-1200℃ to 1650±10℃, with a heating rate of 1-3℃ / min, in an oxygen-rich atmosphere, and heating time at 1650±10℃ for 40-50min; In the rapid cooling stage, the temperature is lowered from 750-850°C to 180-220°C at a cooling rate of 8-15°C / min, and the cooling atmosphere is air.