Preparation method for high-purity quasi‑single‑crystal alumina, and high-purity quasi‑single‑crystal alumina

Abstract

A preparation method for high-purity quasi‑single‑crystal alumina comprises: mixing submicron high-purity alumina, a wetting dispersant and a solvent to obtain a first mixture, and grinding the first mixture to obtain an ultrahigh-activity alumina initiator having a set particle size; mixing the ultrahigh-activity alumina initiator with high-purity alumina to obtain mixed slurry; and drying the mixed slurry to obtain a second mixture, and calcining the second mixture in an inert atmosphere to obtain the high-purity quasi‑single‑crystal alumina.

Description

A method for preparing high-purity single-crystal alumina and the high-purity single-crystal alumina Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411220522.2, filed on September 2, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of alumina refining technology, and in particular to a method for preparing high-purity single-crystal alumina and the high-purity single-crystal alumina. Background Technology

[0003] High-purity single-crystal alumina is a polyhedral single-crystal α-alumina with characteristics such as high purity, narrow particle size distribution, regular morphology, small specific surface area, and extremely low oil absorption value. It is widely used in semiconductor thermal conductive materials, aero-engine thermal conductive composite materials, plasma spraying, and low-shrinkage high-purity ceramic materials.

[0004] However, existing methods for preparing high-purity single-crystal alumina suffer from the following problems: some existing processes require calcination in the presence of highly toxic chlorine gas, placing stringent demands on equipment and resulting in complex processes; furthermore, some existing processes require calcination in the presence of metallic compounds such as molybdenum and vanadium, resulting in α-alumina particles containing less than 10 wt.% molybdenum oxide and / or vanadium oxide, which fails to meet the requirements for high purity (above 99.99%) and also exhibits uneven particle size distribution. Therefore, how to simplify the preparation methods of high-purity single-crystal alumina while improving its overall performance is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] This disclosure provides a method for preparing high-purity single-crystal alumina and high-purity single-crystal alumina through one or more embodiments, in order to solve the following technical problem: how to improve the overall performance of high-purity single-crystal alumina while simplifying the preparation method.

[0006] In a first aspect, a method for preparing high-purity monocrystalline alumina according to some embodiments of the present disclosure includes: mixing submicron high-purity alumina, a wetting and dispersing agent, and a solvent to obtain a first mixture; grinding the first mixture to obtain an ultra-high activity alumina initiator with a set particle size; mixing the ultra-high activity alumina initiator with high-purity alumina to obtain a mixed slurry; drying the mixed slurry to obtain a second mixture; and calcining the second mixture in an inert atmosphere to obtain high-purity monocrystalline alumina.

[0007] Secondly, a high-purity near-single-crystal alumina prepared by the method described in any one of the embodiments of the first aspect according to some embodiments of this disclosure satisfies at least one of the following properties: morphology is near-single-crystal morphology, purity ≥99.99%, and particle size D50 is 0.5μm~3μm. Attached Figure Description

[0008] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0009] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0010] Figure 1 shows a flowchart of a method for preparing high-purity single-crystal alumina according to some embodiments of the present disclosure;

[0011] Figure 2 shows a schematic diagram of a method for preparing high-purity single-crystal alumina according to some embodiments of the present disclosure;

[0012] Figure 3 shows a scanning electron microscope image of high-purity single-crystal alumina prepared according to the preparation method of high-purity single-crystal alumina provided in Embodiment 1 of this disclosure;

[0013] Figure 4 shows a scanning electron microscope image of high-purity single-crystal alumina prepared according to the preparation method of high-purity single-crystal alumina provided in Embodiment 2 of this disclosure. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0015] Various embodiments of this disclosure may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this disclosure; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0016] Furthermore, in the description of this disclosure, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0017] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this disclosure are available on the market or can be prepared by existing methods.

[0018] Figure 1 shows a flowchart of a method for preparing high-purity single-crystal alumina according to some embodiments of the present disclosure; Figure 2 shows a schematic diagram of a method for preparing high-purity single-crystal alumina according to some embodiments of the present disclosure.

[0019]

[0020] Please refer to Figures 1 and 2. A method for preparing high-purity single-crystal alumina according to some embodiments of this disclosure includes:

[0021] S1. Mix submicron high-purity alumina, wetting and dispersing agent and solvent to obtain a first mixture, and grind the first mixture to obtain an ultra-high activity alumina initiator with a set particle size;

[0022] S2. The ultra-high activity alumina initiator is mixed with high-purity alumina to obtain a mixed slurry; and

[0023] S3. The mixed slurry is dried to obtain a second mixture, and the second mixture is calcined in an inert atmosphere to obtain high-purity single-crystal alumina.

[0024] In some embodiments, the submicron high-purity alumina meets the following properties: purity > 99.99%, particle size D50 of 0.1 μm to 0.5 μm, and particle size D99 < 2 μm.

[0025] In the above embodiments, the submicron high-purity alumina is submicron in size, with uniform particle size, narrow distribution, good activity, purity >99.99%, and few impurities. In some embodiments of this disclosure, submicron high-purity alumina is used as a seed to induce the conversion of high-purity alumina, thereby obtaining high-purity near-single-crystal alumina with uniform size and regular morphology. Chinese Patent CN112758968A discloses alumina precursors and their preparation methods, as well as submicron alumina and their preparation methods. In some embodiments of this disclosure, the submicron high-purity alumina prepared by the preparation method disclosed in the above-mentioned Chinese patent can be used as a seed. For example, the purity of submicron high-purity alumina can be 99.991%, 99.992%, 99.993%, 99.995%, 99.997%, 99.999%, etc., the particle size D50 can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, etc., and the particle size D99 can be 1.0μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 1.9μm, etc.

[0026] In some embodiments, the wetting and dispersing agent comprises one or more of an ammonium salt solution of an acrylate copolymer and a polar acidic ester of a long-chain alkanol, wherein the amount of the wetting and dispersing agent added is 0.05% to 0.2% of the mass of the submicron high-purity alumina.

[0027] Wetting and dispersing agents are commonly used chemicals with wide applications in various fields. They possess wetting and dispersing properties, which can improve the distribution of substances in different media and enhance their solubility and stability. This disclosure does not impose any particular limitation on the type of wetting and dispersing agent; any organic compound with wetting and dispersing properties will meet the application requirements.

[0028] In the above embodiments, on the one hand, the wetting and dispersing agent can improve the dispersibility of submicron high-purity alumina in the solvent. On the other hand, since the wetting and dispersing agent is an organic component, it can be completely decomposed during calcination, ensuring the stability of the purity of the high-purity single-crystal alumina. Simultaneously, by controlling the amount of wetting and dispersing agent added to 0.05% to 0.2% of the mass of the ultra-high activity alumina initiator, this disclosure ensures effective dispersion of the ultrafine seed particles. If the amount of dispersing agent added is too low, the ultrafine seed particles cannot be effectively dispersed, and the subsequent mixing stage cannot uniformly mix with the high-purity alumina, thus affecting the morphology of the final product and making it impossible to control the particle size of the final product; if the amount of wetting and dispersing agent added is too high, on the one hand, it will lead to poor economic efficiency, and on the other hand, it will be detrimental to subsequent freeze-drying, increasing the drying time. For example, the amount of wetting and dispersing agent added can be 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2% of the mass of the submicron high-purity alumina.

[0029] In some implementations, the grinding is performed using a grinding method in a sand mill.

[0030] In some embodiments, the ultra-high activity alumina initiator has a set particle size D50 ≤ 0.1 μm and a solid content of 5% to 20%.

[0031] In the above embodiments, controlling the particle size of the ultra-high activity alumina initiator to ≤0.1μm ensures that the ultra-high activity alumina initiator has high surface activity, thereby better initiating the formation of single-crystal alumina. For example, the set particle size D50 of the ultra-high activity alumina initiator can be 0.05μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm, 0.10μm, etc.

[0032] It should be noted that the solid content of ultra-high activity alumina initiator, also known as solid content, refers to the percentage by mass of the remaining solid portion after drying under specified conditions relative to the total mass of the ultra-high activity alumina initiator.

[0033] In the above embodiments, controlling the solid content of the ultra-high activity alumina initiator to be 5% to 20% ensures that the ultra-high activity alumina initiator has a high initiation effect. If the solid content of the ultra-high activity initiator is too low, it will not have an initiation effect, and subsequent calcination will not form alumina with a near-single-crystal morphology. If the solid content of the ultra-high activity alumina initiator is too high, on the one hand, it will increase costs and reduce economic efficiency; on the other hand, it will result in fine and abundant small particles in the ultra-high activity alumina initiator, leading to high reactivity of the ultra-high activity alumina initiator and making the particle size of the obtained near-single-crystal alumina uncontrollable. For example, the solid content of the ultra-high activity alumina initiator can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.

[0034] In some embodiments, the high-purity alumina meets the following properties: purity ≥ 99.995%, and particle size D50 of 0.3 μm to 1.5 μm.

[0035] It should be noted that in some embodiments of this disclosure, the purity and particle size of high-purity alumina are subject to the above-mentioned performance requirements, but there are no special provisions for the production method of high-purity alumina. High-purity alumina can be prepared by production methods such as the ammonium aluminum sulfate method, the ammonium aluminum carbonate method, the organoaluminum method, and the modified Bayer process.

[0036] In the above embodiments, high-purity alumina is used as raw material, and the purity and particle size of the high-purity alumina are controlled to ensure that the purity and particle size of the obtained high-purity single-crystal alumina meet the corresponding performance requirements. For example, the purity of the high-purity alumina can be 99.995%, 99.996%, 99.997%, 99.998%, 99.999%, etc., and the particle size D50 can be 0.3μm, 0.5μm, 0.7μm, 0.9μm, 1.0μm, 1.2μm, 1.4μm, 1.5μm, etc.

[0037] In some embodiments, the amount of the ultra-high activity alumina initiator added is 0.5% to 2% of the mass of the high-purity alumina.

[0038] In the above embodiments, controlling the amount of ultra-high activity alumina initiator added to be 0.5% to 2% of the mass of the high-purity alumina ensures that the ultra-high activity alumina initiator has a high initiation effect. If the amount of ultra-high activity initiator added is too low, it will not achieve a good initiation effect, and alumina with a near-single-crystal morphology cannot be obtained; if the amount of ultra-high activity initiator added is too high, on the one hand, it will increase costs and reduce economic efficiency, and on the other hand, it will result in finer particle size of the initiator particles, higher reactivity, and uncontrollable particle size of the obtained near-single-crystal alumina. For example, the amount of ultra-high activity alumina initiator added can be 0.5%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2% of the mass of the high-purity alumina, etc.

[0039] In some embodiments, the solids content of the mixed slurry is 20% to 40%.

[0040] In the above embodiments, controlling the solid content of the mixed slurry to be 20%–40% ensures a good mixing effect between the ultra-high activity alumina initiator and high-purity alumina, reduces drying time, and increases calcination yield. If the solid content of the mixed slurry is too low, under the same conditions, the amount of mixed product to be calcined will be less, resulting in poor economic efficiency; if the solid content of the mixed slurry is too high, the mixing effect will be poor, and the high-purity alumina and ultra-high activity initiator cannot be mixed uniformly and effectively, making the morphology and particle size of the subsequent calcination product uncontrollable. For example, the solid content of the mixed slurry can be 20%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0041] In some embodiments, the ball milling is performed using a ball milling jar, and the mixing time in the ball milling jar is 10 min to 30 min.

[0042] In the above embodiments, the mixing time in the ball mill jar is controlled to be 10 min to 30 min, thereby ensuring that the ultra-high activity alumina initiator and high-purity alumina can be mixed uniformly. For example, the mixing time in the ball mill jar can be 10 min, 15 min, 20 min, 25 min, 30 min, etc.

[0043] In some embodiments, the calcination temperature is 1200℃~1450℃, and the calcination time is 120min~360min; the inert atmosphere includes one or more of nitrogen and argon.

[0044] In the above embodiments, if the calcination temperature is too low or the calcination time is too short, alumina with a near-single-crystal morphology cannot be formed and will not develop into a near-single-crystal morphology. If the calcination temperature is too high or the time is too long, on the one hand, energy consumption will be high, increasing costs; on the other hand, the near-single-crystal high-purity alumina will sinter together, resulting in larger particle sizes, inhomogeneity, and the presence of large particles. For example, the calcination temperature can be 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, etc., and the calcination time can be 120min, 150min, 180min, 200min, 250min, 300min, 320min, 360min, etc.

[0045] In some embodiments, the drying is performed using a freeze dryer.

[0046] Based on a general inventive concept, a high-purity near-single-crystal alumina prepared by the method described in any of the above embodiments according to some embodiments of the present disclosure satisfies at least one of the following properties: morphology is near-single-crystal morphology, purity ≥99.99%, and particle size D50 is 0.5μm~3μm.

[0047] In some embodiments of this disclosure, submicron high-purity alumina is used as the seed material, and high-purity alumina is used as the raw material. The dispersant added during the grinding process is an organic component, thus ensuring complete decomposition of the dispersant during calcination and guaranteeing the stability of the purity of the obtained high-purity single-crystal alumina. Furthermore, this disclosure achieves particle size control of the high-purity single-crystal alumina by controlling the particle size of the high-purity alumina raw material and the calcination temperature; and it obtains high-purity single-crystal alumina with uniform size and regular morphology through induction with an ultra-highly active alumina initiator. The high-purity single-crystal alumina prepared by this disclosure can be used in high-tech fields such as semiconductor thermal conductive materials, aero-engine thermal conductive composite materials, plasma spraying, and low-shrinkage high-purity ceramic materials.

[0048] This high-purity single-crystal alumina is achieved based on the preparation method of the high-purity single-crystal alumina described above. The specific steps of the preparation method of this high-purity single-crystal alumina can be referred to in the above embodiments. Since this high-purity single-crystal alumina adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0049] The present disclosure is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0050] Example 1

[0051] This embodiment provides a method for preparing high-purity single-crystal alumina, the specific steps of which are as follows:

[0052] (1) Preparation of ultra-high activity alumina initiator: Using submicron high-purity alumina prepared by the method disclosed in CN112758968A as seed, 100g of seed was added to 900g of high-purity water, and then 0.1g of ammonium salt solution of acrylate copolymer (BYK-LP C 22092 wetting and dispersing agent) was added to obtain the first mixture. The first mixture was ground in a sand mill to a particle size D50 = 0.085μm to obtain ultra-high activity alumina initiator.

[0053] (2) Preparation of mixed slurry: 3g of ultra-high activity alumina initiator, 300g of high-purity alumina with a purity of 99.995% and a particle size of D50 = 0.3μm and 700g of high-purity water were put into a ball mill jar and mixed for 20min to obtain a mixed slurry.

[0054] (3) Drying: The ball-milled slurry is placed in a freeze dryer for drying to obtain a second mixture.

[0055] (4) Calcination: The dried second mixture is placed in an argon atmosphere furnace and calcined at a temperature of 1200℃ to obtain high-purity single-crystal alumina.

[0056] Example 2

[0057] This embodiment provides a method for preparing high-purity single-crystal alumina, the specific steps of which are as follows:

[0058] (1) Preparation of ultra-high activity alumina initiator: Using submicron high-purity alumina prepared by the method disclosed in CN112758968A as seed, 200g of seed was added to 800g of high-purity water, and then 0.16g of ammonium salt solution of acrylate copolymer (BYK-LP C 22092 wetting and dispersing agent) was added to obtain the first mixture. The first mixture was ground in a sand mill to a particle size D50 = 0.092μm to obtain ultra-high activity alumina initiator.

[0059] (2) Preparation of mixed slurry: 2.4g of ultra-high activity alumina initiator, 300g of high-purity alumina with a purity of 99.995% and a particle size of D50 = 1.5μm and 700g of high-purity water were put into a ball mill jar and mixed for 20min to obtain a mixed slurry.

[0060] (3) Drying: The ball-milled slurry is placed in a freeze dryer for drying to obtain a second mixture.

[0061] (4) Calcination: The dried second mixture is placed in an argon atmosphere furnace and calcined at a temperature of 1450℃ to obtain high-purity single-crystal alumina.

[0062] Example 3

[0063] This embodiment provides a method for preparing high-purity single-crystal alumina, the specific steps of which are as follows:

[0064] (1) Preparation of ultra-high activity alumina initiator: Using submicron high-purity alumina prepared by the method disclosed in CN112758968A as seed, 100g of seed was added to 900g of high-purity water, and then 0.15g of polar acid ester of long-chain alkanol (BYK-LP C22141 wetting and dispersing agent) was added to obtain the first mixture. The first mixture was ground in a sand mill to a particle size D50 = 0.088μm to obtain ultra-high activity alumina initiator.

[0065] (2) Preparation of mixed slurry: 3g of ultra-high activity alumina initiator, 200g of high-purity alumina with a purity of 99.995% and a particle size of D50 = 0.5μm and 800g of high-purity water were put into a ball mill jar and mixed for 20min to obtain a mixed slurry.

[0066] (3) Drying: The ball-milled slurry is placed in a freeze dryer for drying to obtain a second mixture.

[0067] (4) Calcination: The dried second mixture is placed in a nitrogen atmosphere furnace and calcined at a temperature of 1200℃ to obtain high-purity single-crystal alumina.

[0068] Example 4

[0069] This embodiment provides a method for preparing high-purity single-crystal alumina, the specific steps of which are as follows:

[0070] (1) Preparation of ultra-high activity alumina initiator: Using submicron high-purity alumina prepared by the method disclosed in CN112758968A as seed, 200g of seed was added to 800g of high-purity water, and then 0.4g of polar acid ester of long-chain alkanol (BYK-LP C22141 wetting and dispersing agent) was added to obtain the first mixture. The first mixture was ground in a sand mill to a particle size D50 = 0.097μm to obtain ultra-high activity alumina initiator.

[0071] (2) Preparation of mixed slurry: 8g of ultra-high activity alumina initiator, 400g of high-purity alumina with a purity of 99.995% and a particle size of D50 = 1.2μm and 600g of high-purity water were put into a ball mill jar and mixed for 20min to obtain a mixed slurry.

[0072] (3) Drying: The ball-milled slurry is placed in a freeze dryer for drying to obtain a second mixture.

[0073] (4) Calcination: The dried second mixture is placed in a nitrogen atmosphere furnace and calcined at a temperature of 1350°C to obtain high-purity single-crystal alumina.

[0074] Comparative Example 1

[0075] Comparative Example 1 is based on Example 1. The difference between Comparative Example 1 and Example 1 is that in step (1), the particles are ground to a particle size of D50 = 0.150 μm, and the rest is the same as in Example 1.

[0076] Comparative Example 2

[0077] Comparative Example 2 is based on Example 1. The difference between Comparative Example 2 and Example 1 is that in step (2), the amount of ultra-high activity initiator added is 0.9g, and the rest is the same as in Example 1.

[0078] Comparative Example 3

[0079] Comparative Example 3 is based on Example 1. The difference between Comparative Example 3 and Example 1 is that in step (4), the calcination temperature is 1100℃, and the rest is the same as in Example 1.

[0080] Comparative Example 4

[0081] Comparative Example 4 is based on Example 1. The difference between Comparative Example 4 and Example 1 is that in step (4), the calcination temperature is 1550°C, and the rest is the same as in Example 1.

[0082] The morphology, particle size, and purity of the high-purity single-crystal alumina prepared in Examples 1-4 and Comparative Examples 1-4 were determined, and the results are shown in Table 1. The impurity content of the high-purity single-crystal alumina prepared in Examples 1-4 and Comparative Examples 1-4 was also determined, and the results are shown in Table 2.

[0083] Table 1. Morphology, particle size, and purity of the high-purity single-crystal alumina prepared in Examples 1-4 and Comparative Examples 1-4.

[0084] Table 2. Impurity content of high-purity near-single-crystal alumina prepared in Examples 1-4 and Comparative Examples 1-4

[0085] Figure 3 shows a scanning electron microscope (SEM) image of high-purity single-crystal alumina prepared according to the method for preparing high-purity single-crystal alumina provided in Embodiment 1 of this disclosure. Figure 4 shows a scanning electron microscope (SEM) image of high-purity single-crystal alumina prepared according to the method for preparing high-purity single-crystal alumina provided in Embodiment 2 of this disclosure. As can be seen from Figures 3 and 4, the high-purity single-crystal alumina prepared in the embodiments of this disclosure has uniform size, regular morphology, and a single-crystal morphology.

[0086] Compared with related technologies, the technical solutions provided in this disclosure have the following advantages:

[0087] This disclosure provides a method for preparing high-purity single-crystal alumina, comprising: mixing submicron high-purity alumina, a wetting and dispersing agent, and a solvent to obtain a first mixture; grinding the first mixture to obtain an ultra-highly active alumina initiator with a set particle size; mixing the ultra-highly active alumina initiator with high-purity alumina to obtain a mixed slurry; drying the mixed slurry to obtain a second mixture; and calcining the second mixture in an inert atmosphere to obtain high-purity single-crystal alumina. By using submicron high-purity alumina as a seed and high-purity alumina as the raw material, and by adding an organic dispersant during the grinding process, the dispersant can be completely decomposed during calcination, ensuring the stability of the purity of the high-purity single-crystal alumina. By controlling the particle size of the high-purity alumina raw material and calcination, the particle size of the high-purity single-crystal alumina can be controlled, and by induction with the ultra-highly active alumina initiator, high-purity single-crystal alumina with uniform size and regular morphology can be obtained. Furthermore, the preparation method provided in this disclosure only includes four steps: grinding, mixing, drying, and calcination, making the process flow simple. This simplifies the preparation method of high-purity single-crystal alumina while improving its overall performance.

[0088] Furthermore, according to some embodiments of this disclosure, a method for preparing high-purity single-crystal alumina has at least the following technical effects or advantages:

[0089] In the above embodiments of this disclosure, the process flow is simple and does not require a chlorine-containing atmosphere. The preparation method of high-purity single-crystal alumina disclosed in this disclosure includes only four steps: grinding, mixing, drying, and calcination. The process flow is simple, and the calcination atmosphere is an inert gas, which does not require a chlorine-containing atmosphere and has no demanding equipment requirements.

[0090] In the above embodiments of this disclosure, submicron high-purity alumina is used as seed, and commercially available high-purity alumina with a purity ≥99.995% is used as raw material. The dispersant added during the grinding process is an organic component, and the calcination process can completely decompose it, thus ensuring the stability of the purity of high-purity single-crystal alumina.

[0091] In the above embodiments of this disclosure, the particle size of high-purity alumina-like material can be controlled by controlling the particle size and calcination temperature. High-purity alumina-like material with uniform size and regular morphology can be obtained by induction with ultra-high activity alumina initiator.

[0092] In the above embodiments of this disclosure, a high-purity, near-single-crystal alumina product with high purity, narrow particle size distribution, and regular morphology was prepared. The high-purity near-single-crystal alumina meets the following properties: morphology is near-single-crystal, purity ≥99.99%, and particle size D50 is 0.5μm~3μm.

[0093] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-purity single-crystal alumina, comprising: Submicron high-purity alumina, wetting and dispersing agent and solvent are mixed to obtain a first mixture. The first mixture is then ground to obtain an ultra-high activity alumina initiator with a set particle size. The ultra-high activity alumina initiator was mixed with high-purity alumina to obtain a mixed slurry; as well as The mixed slurry is dried to obtain a second mixture, which is then calcined in an inert atmosphere to obtain high-purity single-crystal alumina.

2. The method according to claim 1, wherein, The submicron high-purity alumina meets the following properties: purity > 99.99%, particle size D50 of 0.1 μm to 0.5 μm, and particle size D99 < 2 μm.

3. The method according to claim 1, wherein, The wetting and dispersing agent comprises one or more of an ammonium salt solution of an acrylate copolymer and a polar acidic ester of a long-chain alkanol, and the amount of the wetting and dispersing agent added is 0.05% to 0.2% of the mass of the submicron high-purity alumina.

4. The method according to claim 1, wherein, The ultra-high activity alumina initiator has a set particle size D50 ≤ 0.1 μm and a solid content of 5% to 20%.

5. The method according to claim 1, wherein, The high-purity alumina meets the following properties: purity ≥ 99.995%, particle size D50 is 0.3μm~1.5μm.

6. The method according to claim 1, wherein, The amount of the ultra-high activity alumina initiator added is 0.5% to 2% of the mass of the high-purity alumina.

7. The method according to claim 1, wherein, The solids content of the mixed slurry is 20% to 40%.

8. The method according to claim 1, wherein, The ball milling process employs a ball milling jar mixing method, with the mixing time in the ball milling jar ranging from 10 to 30 minutes.

9. The method according to claim 1, wherein, The calcination temperature is 1200℃~1450℃, and the calcination time is 120min~360min; the inert atmosphere includes one or more of nitrogen and argon.

10. A high-purity quasi-single-crystal alumina prepared by the method according to any one of claims 1 to 9, satisfying at least one of the following properties: morphology is quasi-single-crystal morphology, purity ≥99.99%, and particle size D50 is 0.5μm to 3μm.

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