Preparation method of alumina slurry and alumina ceramic

Abstract

The invention discloses aluminum oxide slurry and a preparation method thereof, and a preparation method of aluminum oxide ceramic. The alumina slurry comprises a solvent, a dispersant, an auxiliary dispersant and alumina; the solvent comprises water, and the particle size of alumina is less than or equal to 150nm. Mixing a solvent, a dispersing agent, an auxiliary dispersing agent and aluminum oxide, and carrying out ball milling treatment to obtain aluminum oxide slurry; and carrying out curing treatment and sintering treatment on the aluminum oxide slurry to obtain the aluminum oxide ceramic disclosed by the invention. The preparation process of the alumina slurry and the alumina ceramic is simple, the cost is easy to control, the prepared alumina slurry has low viscosity and good dispersibility, and the alumina ceramic has excellent mechanical properties and thermal conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of structural ceramic preparation, and particularly relates to an alumina slurry with a relatively small particle size and a relatively high solid content, and a preparation method of high-strength alumina ceramics. Background Art

[0002] As one of the most common and widely used oxide ceramics, alumina plays an important role in industries such as aerospace, electronics, machinery, petrochemical industry, etc. due to its excellent properties such as high strength, high hardness, wear resistance, and corrosion resistance. The forming method has always been one of the most important steps in ceramic preparation, which determines whether the microstructure of the ceramic green body is uniform, whether macro and micro defects are generated, and ultimately directly affects the performance of the ceramic product. Among them, colloidal forming, as an advanced wet forming process, has received extensive attention and research from domestic and foreign research institutions and enterprises due to the advantages of uniform microstructure of the green body prepared by it, high green body density, simple preparation method, and suitability for preparing complex-shaped parts.

[0003] Colloidal forming can be divided into many systems according to different gel or curing mechanisms. Among them, the acrylamide gel system has been widely used in the preparation of ceramic products since it was invented by the Oak Ridge National Laboratory in the United States. It uses acrylamide as a monomer and N,N'-methylenebisacrylamide as a cross-linking agent. Under the action of an initiator (APS) and a catalyst (TEMED), the monomers and cross-linking agents in the ceramic slurry undergo a free radical polymerization reaction to form a three-dimensional network structure, thereby in-situ curing the ceramic particles. However, acrylamide used in this system has certain neurotoxins and is not conducive to human health; at the same time, its preparation process is cumbersome and not conducive to industrial production. For other types of colloidal forming processes, due to the need to add a certain amount of organic additives during use, the solid content of the slurry is relatively low, resulting in a decrease in the density and strength of the green body.

[0004] In addition to the forming method, in the preparation of high-performance structural ceramics, people often pursue ceramic raw materials with smaller particle sizes and stronger sintering activities to reduce the size defects generated during the preparation process and lower the sintering temperature. However, in colloidal forming, as the particle size of the ceramic powder decreases, the rapidly increasing specific surface area causes the dispersibility of the ceramic slurry to decrease sharply, making it difficult to prepare an alumina slurry with a relatively small particle size, a relatively high solid content, and good dispersibility. Therefore, there is an urgent need in the related field to develop a technology that can prepare an alumina slurry with a relatively small particle size and good dispersibility in colloidal forming, and further improve the strength and thermal conductivity of alumina ceramics. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides an alumina slurry and a preparation method thereof, as well as a preparation method of alumina ceramics. The average particle size of alumina in the alumina slurry of the present invention is small, the viscosity of the slurry is low, and the dispersion performance is good. The alumina ceramics prepared therefrom have excellent mechanical properties and thermal conductivity, thereby further enhancing the strength of the alumina ceramics.

[0006] Therefore, in the first aspect of the present invention, the present invention proposes an alumina slurry, which includes a solvent, a dispersant, an auxiliary dispersant, and alumina; the solvent includes water, and the particle size of the alumina is ≤150 nm.

[0007] The average particle size of alumina in the alumina slurry of the present invention is small. To prevent particle aggregation caused by the small particle size, the slurry of the present invention includes a dispersant and an auxiliary dispersant, which can effectively prevent the deposition or aggregation of alumina, avoid the agglomeration phenomenon. At the same time, the dispersant can reduce the viscosity of the alumina slurry and maintain good fluidity, further improving the dispersion performance of the slurry. Thus, the alumina slurry of the present invention has excellent dispersion performance, which is beneficial to subsequent injection molding. The alumina ceramics prepared therefrom will have excellent mechanical properties and thermal conductivity, thereby further enhancing the strength of the alumina ceramics.

[0008] In some embodiments, the particle size of the alumina in the alumina slurry is 80 - 150 nm.

[0009] In some embodiments, the solid content of the alumina slurry is 50 - 56 vol%.

[0010] In some embodiments, the alumina slurry satisfies at least one of the following:

[0011] (1) The dispersant includes at least one of Isobam 600AF, Isobam 104, Isobam 04, and Isobam 06;

[0012] (2) The auxiliary dispersant includes at least one of ammonium citrate, 1,2,3 - propane tricarboxylic acid, and 1,2,3,4 - butane tetracarboxylic acid;

[0013] (3) The addition amount of the dispersant is 0.1 - 0.5% of the mass of the alumina;

[0014] (4) The addition amount of the auxiliary dispersant is 0.1 - 0.3% of the mass of the alumina.

[0015] In the second aspect of the present invention, the present invention proposes a method for preparing the alumina slurry of the first aspect, including:

[0016] Mix a solvent, alumina, a dispersant, and an auxiliary dispersant, and perform ball milling to obtain an alumina slurry.

[0017] The preparation process of the alumina slurry of the present invention is simple, the production efficiency is relatively high, and the cost is controllable.

[0018] In some embodiments, in the step of mixing the solvent, alumina, the dispersant, and the auxiliary dispersant, it includes: adding the alumina to the solvent in multiple portions.

[0019] In the third aspect of the present invention, a method for preparing an alumina ceramic is provided, including:

[0020] Subject the alumina slurry to solidification treatment and sintering treatment in sequence to obtain an alumina ceramic; the alumina slurry is the alumina slurry of the first aspect or the alumina slurry obtained by the preparation method of the second aspect.

[0021] The method for preparing an alumina ceramic of the present invention is simple and the production efficiency is relatively high. By subjecting the alumina slurry to solidification treatment and sintering treatment in sequence, an alumina ceramic with excellent performance can be obtained. It has a dense structure and excellent mechanical properties and thermal conductivity.

[0022] In some embodiments, the relative humidity of the solidification treatment is 70-90RH%, and the temperature is 25-40°C.

[0023] In some embodiments, the temperature of the sintering treatment is 1300-1450°C, and the time is 2 h.

[0024] In some embodiments, after the solidification treatment is completed, a drying treatment is further included; the temperature of the drying treatment is 50°C, and the time is 24 h.

[0025] Compared with the prior art, the beneficial technical effects achieved by the present invention are:

[0026] (1) The alumina slurry of the present invention has a smaller particle size, a higher solid content, better fluidity and dispersibility, and when the shear rate is 100 s -1 , the viscosity is lower than 1 Pa·s, which is beneficial to subsequent injection molding.

[0027] (2) The preparation process of the alumina ceramic of the present invention is simple, the cost is controllable, and the obtained alumina ceramic has a high density, strength and thermal conductivity. Its overall performance is excellent, and it has great application value in the development field of high-performance structural ceramics.

[0028] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, where:

[0030] Figure 1 It is a graph of the slurry rheological behavior of Embodiment 1 of the present invention;

[0031] Figure 2 It is a SEM image of the alumina ceramic of Embodiment 1 of the present invention; wherein, Figure (a) is a cross-sectional view of the green body after curing treatment; Figure (b) is a cross-sectional view of the sintered body after polishing and thermal etching after sintering treatment. Detailed Embodiments

[0032] The embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0033] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise stated, the meaning of "plurality" is two or more.

[0034] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0035] In this article, the term "comprising" or "including" is an open expression, that is, it includes the content specified by the present invention, but does not exclude other aspects of the content.

[0036] In the first aspect of the embodiments of the present invention, the present invention provides an alumina slurry, which includes a solvent, a dispersant, an auxiliary dispersant, and alumina; the solvent includes water, and the particle size of the alumina ≤ 150 nm.

[0037] The average particle size of the alumina in the alumina slurry of the present invention is relatively small, and the slurry powder is delicate, which can reduce the defect size generated during the preparation process and further improve the density of the alumina ceramic. According to the embodiments of the present invention, at a shear rate of 100 s -1When the viscosity of the slurry is < 1 Pa·s, its viscosity is relatively low, indicating that the slurry has good fluidity and dispersibility, which is beneficial to increasing the solid content of the slurry to obtain a slurry with a high solid content. Since the average particle size of the alumina in the present invention is relatively small, in order to prevent particle aggregation, the slurry of the present invention includes a dispersant and a co-dispersant, which can effectively prevent the deposition or aggregation of alumina, avoid agglomeration, and at the same time the dispersant can reduce the viscosity of the alumina slurry and maintain good fluidity, further improving the dispersion performance of the slurry. The co-dispersant plays a role in assisting the dispersion of the slurry, further improving the dispersion performance of the dispersant. Thus, the alumina slurry of the present invention has excellent dispersion performance, which is beneficial to subsequent injection molding. The alumina ceramic prepared thereby will have excellent mechanical properties and thermal conductivity, thereby further enhancing the strength of the alumina ceramic.

[0038] In some embodiments of the present invention, the particle size of the alumina in the alumina slurry is 80 - 150 nm.

[0039] As an example, the particle size is 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, etc.

[0040] In some embodiments of the present invention, the solid content of the alumina slurry is 50 - 56 vol%.

[0041] According to the embodiments of the present invention, when the solid content of the alumina slurry is 50 - 56 vol%, it has excellent dispersion performance, and at the same time can make the alumina ceramic obtained after sintering treatment have excellent density, thereby improving its performance. Thus, the alumina slurry of the present invention has a small particle size and a high solid content, making it have excellent dispersibility.

[0042] As an example, the solid content is 50 vol%, 51 vol%, 52 vol%, 53 vol%, 54 vol%, 55 vol%, 56 vol%, etc.

[0043] In some embodiments of the present invention, the alumina slurry satisfies at least one of the following:

[0044] (1) The dispersant includes at least one of Isobam 600AF, Isobam 104, Isobam 04, and Isobam 06;

[0045] (2) The co-dispersant includes at least one of ammonium citrate, 1,2,3-propane tricarboxylic acid, and 1,2,3,4-butane tetracarboxylic acid;

[0046] (3) The addition amount of the dispersant is 0.1 - 0.5% of the mass of the alumina;

[0047] (4) The addition amount of the auxiliary dispersant is 0.1 - 0.3% of the mass of alumina.

[0048] According to the embodiments of the present invention, Isobam series substances are selected as the dispersant, which can have excellent dispersion performance for alumina, with less dosage and being non-toxic. After Isobam adsorbs on the surface of alumina particles, a large number of carboxylate groups in the molecule increase the negative charge density on the surface of alumina particles, increasing the absolute value of the particle Zeta potential, thereby achieving a good dispersion effect; selecting organic substances such as ammonium citrate as the auxiliary dispersant will further enhance the negative charge density on the surface of alumina particles, contributing to further improving the dispersion performance of the alumina slurry. Thus, the alumina slurry of the present invention can further improve the dispersion performance.

[0049] As an example, the addition amounts of the dispersant are 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc. of the mass of alumina.

[0050] As an example, the addition amounts of the auxiliary dispersant are 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc. of the mass of alumina.

[0051] In the second aspect of the embodiments of the present invention, the present invention provides a method for preparing the alumina slurry of the first aspect, including:

[0052] Mix the solvent, alumina, dispersant and auxiliary dispersant, and perform ball milling to obtain the alumina slurry.

[0053] The preparation process of the alumina slurry of the present invention is simple, with high production efficiency and controllable cost.

[0054] In some embodiments of the present invention, the rotation speed of the ball milling is 300 rpm / min and the time is 4 h.

[0055] In some embodiments of the present invention, in the step of mixing the solvent, alumina, dispersant and auxiliary dispersant, it includes: adding alumina to the solvent in multiple times.

[0056] According to the embodiments of the present invention, alumina is added to the solvent three times for ball milling. First, one-third of the total required amount of alumina is added to the whole mixture for ball milling, and then the remaining alumina is added to the mixture in two times to continue to complete the ball milling. Because the particle size of alumina is small and the particles are delicate, adding it in three times helps to disperse alumina more evenly, prevent powder agglomeration, and better control the viscosity of the slurry, avoiding a sharp increase in the viscosity of the slurry caused by adding too much alumina powder at one time. Therefore, adding alumina powder in portions can gradually adjust the dispersibility and viscosity of the slurry. Thus, the preparation method of the alumina slurry of the present invention is simple to operate, the slurry particles are delicate, and it has excellent dispersibility and viscosity.

[0057] In a third aspect of the embodiments of the present invention, a method for preparing alumina ceramics is provided, which includes:

[0058] Subjecting the alumina slurry to solidification treatment and sintering treatment in sequence to obtain alumina ceramics; the alumina slurry is the alumina slurry of the first aspect or the alumina slurry obtained by the preparation method of the second aspect.

[0059] The method for preparing alumina ceramics of the present invention is simple and has a relatively high production efficiency. According to the embodiments of the present invention, after the alumina slurry is solidified, it is fixed and formed to obtain a ceramic green body. Then, a pressureless sintering treatment is further carried out to make its structure more dense, improve its mechanical properties and thermal conductivity, thereby obtaining alumina ceramics with excellent properties. Thus, the alumina ceramics of the present invention have excellent mechanical properties and thermal conductivity.

[0060] In some embodiments of the present invention, the relative humidity for the solidification treatment is 70 - 90RH%, and the temperature is 25 - 40°C.

[0061] Subjecting the alumina slurry to solidification treatment at a certain temperature and humidity helps the moisture in the slurry to slowly evaporate, improves its stability, reduces shrinkage during drying and sintering, and avoids deformation and cracking. The solidified ceramic green body has a uniform and dense structure and high strength. Thus, alumina ceramics with excellent properties can be obtained.

[0062] As an example, the relative humidity is 70RH%, 72RH%, 75RH%, 77RH%, 80RH%, 82RH%, 85RH%, 87RH%, 90RH%, etc.

[0063] As an example, the temperature is 25°C, 28°C, 30°C, 33°C, 35°C, 37°C, 40°C, etc.

[0064] In some embodiments of the present invention, after the solidification treatment is completed, a drying treatment is further included; the temperature of the drying treatment is 50°C and the time is 24h.

[0065] The drying treatment further completely evaporates the moisture in the ceramic green body, makes its microstructure uniform and has good density, avoids the generation of pores or cracking during the subsequent sintering treatment, and improves its mechanical properties.

[0066] In some embodiments of the present invention, the temperature of the sintering treatment is 1300 - 1450°C and the time is 2h.

[0067] Subjecting the solidified and formed ceramic green body to pressureless sintering to obtain dense alumina ceramics. Thus, the alumina ceramics of the present invention have excellent thermal and mechanical properties.

[0068] As an example, the temperatures for sintering treatment are 1300°C, 1325°C, 1350°C, 1375°C, 1400°C, 1425°C, 1450°C, etc.

[0069] In some embodiments of the present invention, the heating rate for sintering treatment is 5°C / min.

[0070] In some embodiments of the present invention, a preheating treatment is further included before the sintering treatment. During the preheating treatment, the heating rate is 1°C / min and the temperature is 500°C.

[0071] According to the embodiments of the present invention, first, the temperature is raised to 500°C at a heating rate of 1°C / min. At a temperature of 500°C, it is beneficial to release and decompose organic substances such as dispersants in the ceramic green body, avoiding carbonization of organic substances during subsequent sintering, which may cause pores or defects inside the ceramic. Thus, the structure of the alumina ceramic becomes more dense, further improving its mechanical properties and thermal conductivity.

[0072] In some embodiments of the present invention, the temperature for sintering treatment is 1300 - 1450°C and the time is 2 h.

[0073] The following will explain the solution of the present invention in combination with embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product instructions. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0074] Example 1

[0075] (1) Slurry preparation: Add 0.124 g of Isobam600AF and 0.041 g of ammonium citrate to 9.6 mL of deionized water, and vibrate and stir to completely dissolve the dispersant in the deionized water to form a premixed solution. Then, adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496 g (solid content 52 vol%) of ultrafine alumina powder with a particle size of 120 nm into a nylon ball milling tank, and ball mill at a speed of 300 rpm / min for 4 h on a planetary ball mill. Divide the 41.496 g of powder into three parts, and gradually add the powder in the way of adding one-third of the powder at one-hour intervals. After the ball milling is completed, take out the slurry and remove bubbles through vacuum to obtain a uniform and bubble-free slurry. Use a Kinexus Pro+ rheometer to measure the shear rate-viscosity curve, the test temperature is room temperature, the test shear rate range is from 0.1 to 1000 s -1 , and the test time is 4 min. Measure that the viscosity of the slurry at a shear rate of 100 s -1 is 0.24 Pa·s ( Figure 1as shown

[0076] (2) Curing treatment: Inject the slurry into a plastic mold with a diameter of Φ35mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 90RH%. After curing and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry it for 24h.

[0077] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1350°C at a heating rate of 5°C / min and hold for 2h to obtain alumina ceramics. The SEM image of the alumina ceramics is as Figure 2 shown

[0078] Example 2

[0079] (1) Slurry preparation: Add 0.134g of Isobam600AF and 0.045g of ammonium citrate to 8.8mL of deionized water, vibrate and stir to completely dissolve the dispersant in the deionized water to form a premixed solution. Then adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 44.688g (solid content 56vol%) of ultra-fine alumina powder with a particle size of 150nm into a nylon ball mill tank, and ball mill at a speed of 300rpm / min for 4h on a planetary ball mill. Divide the 44.688g of powder into three parts and add the powder step by step at intervals of one hour, adding one-third of the powder each time. After the ball milling is completed, take out the slurry and remove the bubbles through vacuum to obtain a uniform and bubble-free slurry. Use a Kinexus Pro+ rheometer to measure the shear rate-viscosity curve, the test temperature is room temperature, the test shear rate range is from 0.1 to 1000s -1 and the test time is 4min. Measure that the viscosity of the slurry at a shear rate of 100s -1 is 0.74Pa·s.

[0080] (2) Curing treatment: Inject the slurry into a plastic mold with a diameter of Φ35mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 90RH%. After curing and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry it for 24h.

[0081] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1400°C at a heating rate of 5°C / min and hold for 2h to obtain alumina ceramics.

[0082] Example 3

[0083] (1) Slurry preparation: Add 0.124 g of Isobam 06 and 0.041 g of 1,2,3-propanetricarboxylic acid to 9.6 mL of deionized water. Vibrationally stir to completely dissolve the dispersant in the deionized water to form a premixed solution. Then, adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496 g (solid content 52 vol%) of ultrafine alumina powder with a particle size of 120 nm into a nylon ball milling jar. Ball mill at a speed of 300 rpm / min for 4 h on a planetary ball mill. Divide the 41.496 g of powder into three parts and gradually add the powder in a way of adding one-third of the powder at one-hour intervals. After the ball milling is completed, take out the slurry and remove the bubbles through vacuum to obtain a uniform and bubble-free slurry. Measure the shear rate-viscosity curve with a Kinexus Pro+ rheometer. The test temperature is room temperature, and the test shear rate range is from 0.1 to 1000 s -1 , and the test time is 4 min. Measure that the viscosity of the slurry at a shear rate of 100 s -1 is 0.46 Pa·s.

[0084] (2) Curing treatment: Inject the slurry into a plastic mold with a diameter of Φ35 mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 90 RH%. After curing and demolding, place the green body in a constant temperature drying oven at 50°C and dry for 24 h.

[0085] (3) Sintering treatment: Place the dried green body in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1350°C at a heating rate of 5°C / min and hold for 2 h to obtain alumina ceramics.

[0086] Example 4

[0087] (1) Slurry preparation: Add 0.124 g of Isobam 600AF and 0.041 g of ammonium citrate to 9.6 mL of deionized water. Vibrationally stir to completely dissolve the dispersant in the deionized water to form a premixed solution. Then, adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496 g (solid content 52 vol%) of ultrafine alumina powder with a particle size of 120 nm into a nylon ball milling jar. Ball mill at a speed of 300 rpm / min for 4 h on a planetary ball mill. Divide the 41.496 g of powder into three parts and gradually add the powder in a way of adding one-third of the powder at one-hour intervals. After the ball milling is completed, take out the slurry and remove the bubbles through vacuum to obtain a uniform and bubble-free slurry. Measure the shear rate-viscosity curve with a Kinexus Pro+ rheometer. The test temperature is room temperature, and the test shear rate range is from 0.1 to 1000 s -1 , and the test time is 4 min. Measure that the viscosity of the slurry at a shear rate of 100 s -1 is 0.24 Pa·s.

[0088] (2) Solidification treatment: Inject the slurry into a plastic mold with a diameter of Φ35mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 40°C and a humidity of 80RH%. After solidification and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry for 24h.

[0089] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1450°C at a heating rate of 5°C / min and hold for 2h to obtain alumina ceramics.

[0090] Example 5

[0091] (1) Slurry preparation: Add 0.041g of Isobam600AF and 0.041g of ammonium citrate to 9.6mL of deionized water, vibrate and stir to completely dissolve the dispersant in deionized water to form a premixed solution. Then adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496g (solid content 52vol%) of ultrafine alumina powder with a particle size of 120nm into a nylon ball mill tank, and ball mill at a speed of 300rpm / min for 4h on a planetary ball mill. Divide the 41.496g of powder into three parts and add the powder step by step at intervals of one hour with one-third of the powder added each time. After the ball milling is completed, take out the slurry and remove the bubbles through vacuum to obtain a uniform and bubble-free slurry. Use a Kinexus Pro+ rheometer to measure the shear rate-viscosity curve, the test temperature is room temperature, the test shear rate range is from 0.1 to 1000s -1 , and the test time is 4min. Measure that the viscosity of the slurry at a shear rate of 100s -1 is 0.42Pa·s.

[0092] (2) Solidification treatment: Inject the slurry into a plastic mold with a diameter of Φ35mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 70RH%. After solidification and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry for 24h.

[0093] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1350°C at a heating rate of 5°C / min and hold for 2h to obtain alumina ceramics.

[0094] Example 6

[0095] (1) Slurry preparation: Add 0.207 g of Isobam600AF and 0.041 g of ammonium citrate to 9.6 mL of deionized water, and vibrate and stir to completely dissolve the dispersant in the deionized water to form a premixed solution. Then, adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496 g (solid content 52 vol%) of ultrafine alumina powder with a particle size of 120 nm into a nylon ball mill tank, and ball mill at a speed of 300 rpm / min for 4 h on a planetary ball mill. Divide 41.496 g of the powder into three parts, and gradually add the powder in the way of adding one-third of the powder at one-hour intervals. After the ball milling is completed, take out the slurry and remove the bubbles under vacuum to obtain a uniform and bubble-free slurry. Measure the shear rate-viscosity curve with a Kinexus Pro+ rheometer, the test temperature is room temperature, and the test shear rate range is from 0.1 to 1000 s -1 , and the test time is 4 min. It is measured that the viscosity of the slurry at a shear rate of 100 s -1 is 0.78 Pa·s.

[0096] (2) Curing treatment: Inject the slurry into a plastic mold with a diameter of Φ35 mm, seal it with plastic wrap, and put it into a constant temperature and humidity drying oven at a temperature of 25 °C and a humidity of 90 RH%. After curing and demolding, place the green body in a constant temperature drying oven at 50 °C and dry for 24 h.

[0097] (3) Sintering treatment: Place the dried green body in a box furnace and heat it to 500 °C at a heating rate of 1 °C / min, and then heat it to 1300 °C at a heating rate of 5 °C / min and hold for 2 h to obtain alumina ceramics.

[0098] Example 7

[0099] (1) Slurry preparation: Add 0.124 g of Isobam600AF and 0.124 g of ammonium citrate to 9.6 mL of deionized water, and vibrate and stir to completely dissolve the dispersant in the deionized water to form a premixed solution. Then, adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496 g (solid content 52 vol%) of ultrafine alumina powder with a particle size of 120 nm into a nylon ball mill tank, and ball mill at a speed of 300 rpm / min for 4 h on a planetary ball mill. Divide 41.496 g of the powder into three parts, and gradually add the powder in the way of adding one-third of the powder at one-hour intervals. After the ball milling is completed, take out the slurry and remove the bubbles under vacuum to obtain a uniform and bubble-free slurry. Measure the shear rate-viscosity curve with a Kinexus Pro+ rheometer, the test temperature is room temperature, and the test shear rate range is from 0.1 to 1000 s -1 , and the test time is 4 min. It is measured that the viscosity of the slurry at a shear rate of 100 s -1 is 0.45 Pa·s.

[0100] (2) Solidification treatment: Inject the slurry into a plastic mold with a diameter of Φ35mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 90RH%. After solidification and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry it for 24h.

[0101] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1350°C at a heating rate of 5°C / min and hold for 2h to obtain alumina ceramics.

[0102] Example 8

[0103] (1) Slurry preparation: Add 0.120g of Isobam600AF and 0.040g of ammonium citrate to 10mL of deionized water, vibrate and stir to completely dissolve the dispersant in deionized water to form a premixed solution. Then adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 39.9g (solid content 50vol%) of ultra-fine alumina powder with a particle size of 120nm into a nylon ball mill tank, and ball mill at a speed of 300rpm / min for 4h on a planetary ball mill. Divide the 39.9g powder into three parts and add the powder step by step at intervals of one hour. After the ball milling is completed, take out the slurry and remove the bubbles through vacuum to obtain a uniform and bubble-free slurry. Use a Kinexus Pro+ rheometer to measure the shear rate-viscosity curve, the test temperature is room temperature, the test shear rate range is from 0.1 to 1000s -1 , and the test time is 4min. Measure that the viscosity of the slurry at a shear rate of 100s -1 is 0.27Pa·s.

[0104] (2) Solidification treatment: Inject the slurry into a plastic mold with a diameter of Φ35mm, seal it with plastic wrap, and place it in a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 90RH%. After solidification and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry it for 24h.

[0105] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, then heat it to 1350°C at a heating rate of 5°C / min and hold for 2h to obtain alumina ceramics.

[0106] Example 9

[0107] (1) Slurry preparation: Add 0.124 g of Isobam600AF and 0.041 g of ammonium citrate to 9.6 mL of deionized water. Vibration stir to completely dissolve the dispersant in deionized water to form a premixed solution. Then adjust the pH value of the premixed solution to 9 with ammonia water. After stirring the premixed solution evenly, add it together with 41.496 g (solid content 52 vol%) of ultrafine alumina powder with a particle size of 80 nm into a nylon ball mill tank, and ball mill at a speed of 300 rpm / min for 4 h on a planetary ball mill. Divide the 41.496 g of powder into three parts and gradually add the powder in the way of adding one-third of the powder at one-hour intervals. After the ball milling is completed, take out the slurry and remove the bubbles through vacuum to obtain a uniform and bubble-free slurry. Use a Kinexus Pro+ rheometer to measure the shear rate-viscosity curve, the test temperature is room temperature, the test shear rate range is from 0.1 to 1000 s -1 , and the test time is 4 min. It is measured that the viscosity of the slurry at a shear rate of 100 s -1 is 0.89 Pa·s.

[0108] (2) Curing treatment: Inject the slurry into a plastic mold with a diameter of Φ35 mm, seal it with plastic wrap and put it into a constant temperature and humidity drying oven at a temperature of 25°C and a humidity of 90RH%. After curing and demolding, place the wet blank in a constant temperature drying oven at 50°C and dry it for 24 h.

[0109] (3) Sintering treatment: Place the dried blank in a box furnace and heat it to 500°C at a heating rate of 1°C / min, and then heat it to 1350°C at a heating rate of 5°C / min and hold for 2 h to obtain alumina ceramics.

[0110] Performance testing of alumina ceramics

[0111] I. Testing methods

[0112] 1. Relative density

[0113] Test the density of alumina ceramics according to GB / T 25995-2010 "Test methods for density and apparent porosity of fine ceramics" and calculate the relative density of alumina ceramics based on the theoretical density of 3.99 g / cm 3 .

[0114] 2. Linear shrinkage rate

[0115] Test the linear shrinkage rate of alumina ceramics according to QB / T 1548-2015 "Determination method for linear shrinkage rate of ceramic blank and body".

[0116] 3. Flexural strength

[0117] Test the three-point flexural strength of alumina ceramics according to GB / T 4741-1999 "Test method for flexural strength of ceramic materials".

[0118] 4. Room temperature thermal conductivity

[0119] The room temperature thermal conductivity of alumina ceramics was tested in accordance with GB / T 14335-2008 "Test Method for Thermal Conductivity of Ceramics".

[0120] II. Test results

[0121] The performance test results of the alumina ceramics of the above embodiments are shown in Table 1.

[0122] Table 1 Performance test results of the alumina ceramics of the embodiments

[0123]

[0124] As can be seen from Table 1, the viscosity of the alumina slurry of the present invention is less than 1 Pa·s at a shear rate of 100 s -1 -1, indicating that the slurry has good dispersibility. The performance test results of the prepared alumina ceramics are excellent, and they all have good mechanical properties and thermal conductivity. In addition, from Figure 1 it can be seen that the alumina slurry prepared in Example 1 shows that the viscosity decreases with the increase of the shear rate in the shear rate-viscosity curve, indicating that the slurry has good stability; from Figure 2 (a) it can be seen that the ceramic green body has a uniform microstructure and no obvious agglomeration, and from Figure 2 (b) it can be seen that the grain size of the alumina ceramics is small and the particle size distribution is uniform. Therefore, the alumina ceramics prepared by the present invention have excellent properties.

[0125] In the description of this specification, the description of reference terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0126] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. An alumina slurry, characterized in that: The alumina slurry comprises a solvent, a dispersant, an auxiliary dispersant and alumina; the solvent comprises water, and the particle size of the alumina is ≤150nm.

2. The alumina slurry according to claim 1, characterized in that: The particle size of the aluminum oxide in the aluminum oxide slurry is 80 to 150 nm.

3. The alumina slurry according to claim 1, characterized in that: The solid phase content of the alumina slurry is 50-56 vol%.

4. The alumina slurry according to any one of claims 1 to 3, characterized in that: The alumina slurry satisfies at least one of the following: (1) The dispersant comprises at least one of Isobam 600AF, Isobam 104, Isobam 04 and Isobam 06; (2) The auxiliary dispersant includes at least one of ammonium citrate, 1,2,3-propanetricarboxylic acid, and 1,2,3,4-butanetetracarboxylic acid; (3) The amount of the dispersant added is 0.1 to 0.5% of the mass of the alumina; (4) The amount of the auxiliary dispersant added is 0.1 to 0.3% of the mass of the alumina.

5. A method for preparing the alumina slurry according to any one of claims 1 to 4, characterized in that: include: The solvent, alumina, a dispersant and an auxiliary dispersant are mixed and ball-milled to obtain an alumina slurry.

6. The preparation method according to claim 5, characterized in that: The step of mixing the solvent, aluminum oxide, dispersant and auxiliary dispersant includes: adding aluminum oxide into the solvent in multiple times.

7. A method for preparing alumina ceramics, characterized in that: include: The alumina slurry is sequentially subjected to a curing treatment and a sintering treatment to obtain an alumina ceramic; The alumina slurry is the alumina slurry according to any one of claims 1 to 4, or the alumina slurry obtained by the method according to claim 5 or 6.

8. The preparation method according to claim 7, characterized in that: The relative humidity of the curing treatment is 70-90 RH%, and the temperature is 25-40°C.

9. The preparation method according to claim 7, characterized in that: The sintering process is carried out at a temperature of 1300-1450° C. and for a time of 2 hours.

10. The preparation method according to claim 7, characterized in that: After the curing process is completed, a drying process is also included; the drying process temperature is 50° C. and the time is 24 hours.

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