Preparation method of micron-sized aluminum oxide

Abstract

The invention provides a preparation method of micron-sized aluminum oxide. The preparation method comprises three steps of melt preparation, ultrasonic oxidation and finished product collection. According to the method, ultrasonic vibration treatment is conducted on the pure aluminum melt, in-situ oxidation of the surface of the pure aluminum melt is promoted, by setting ultrasonic vibration parameters, the conditions of particle aggregation, uneven particle size and overlarge crystal grains can be effectively avoided, meanwhile, the in-situ oxidation rate of the aluminum melt can be increased, and the uniformity degree and dispersity of aluminum oxide particles are improved. The method does not need multi-step reaction, solvent addition and high-temperature calcination, and is short in process and simple and convenient to operate; pure aluminum and air are used as raw materials, an exogenous precursor is not needed, and the cost is remarkably reduced; ultrasonic cavitation and disturbance effects reduce particle aggregation and improve product dispersity; no harmful substance is used and no harmful by-product is generated, so that the method is green and environment-friendly; the method has the advantages of high feasibility, simple preparation process, low implementation cost and convenience in popularization and implementation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal oxide production, and particularly relates to a preparation method of micron-grade aluminum oxide. BACKGROUND

[0002] In the prior art, micron-grade aluminum oxide particles play a crucial role in industrial production and scientific research. Due to excellent thermal stability, mechanical strength and chemical inertness, they can improve the mechanical properties of ceramic materials, optimize the reaction efficiency of catalyst carriers, provide reliable insulation protection for electronic devices, and enhance the comprehensive performance of composite materials, and are widely used in ceramics, chemical industry, electronics, new materials and other fields, promoting the technological upgrading and product innovation of related industries. However, there are some deficiencies in the preparation process of micron-grade aluminum oxide on the market at present.

[0003] In the prior art, although the traditional wet chemical method (such as sol-gel method and precipitation method) is relatively simple to operate and can be synthesized at room temperature or lower temperature, particle agglomeration easily occurs during the preparation process, resulting in an increase in the particle size of the generated micron-grade aluminum oxide and uneven distribution, which seriously affects the use performance and application range of the product. High-temperature calcination method for preparing aluminum oxide usually involves heating aluminum hydroxide and other high-aluminum compounds at high temperature and removing the crystal water therein, so that they are converted into aluminum oxide. Although this method can realize crystal transformation and impurity removal, and ensure the purity of micron-grade aluminum oxide, it is easy to cause grain growth during high-temperature treatment, and it is difficult to stably maintain the micron size of the particles, which cannot meet the use requirements in high-precision fields. In addition, some preparation methods also rely on organic solvents or complex reaction conditions, which not only make the process flow cumbersome and prolong the production cycle, but also increase the environmental burden and production cost, which is not conducive to large-scale industrial promotion.

[0004] In the prior art, the process of generating aluminum oxide particles in situ in high-temperature melt starting from pure aluminum has attracted much attention due to its industrial adaptability and cost advantage, but this preparation method also has difficulties: the reaction kinetics of aluminum melt and oxygen is slow, and an oxide film is usually formed on the surface instead of the target oxide; the rate and morphology control of the oxidation reaction are difficult, which easily causes uneven particles, large particle size and serious agglomeration; and stable dispersion of particles in high-temperature melt environment is difficult to achieve, and the particle size control precision is limited, making it difficult to mass-produce high-quality micron-grade aluminum oxide products.

[0005] Therefore, in order to comprehensively improve the preparation efficiency, product quality, environmental friendliness and cost advantage of micron-grade aluminum oxide, it is now necessary to improve the existing preparation process. SUMMARY

[0006] The application aims to solve the technical problems of particle agglomeration, uneven particle size distribution of nano-alumina, difficulty in maintaining micron scale due to alumina grain growth caused by high-temperature calcination process, slow reaction, uneven particles, difficulty in dispersion, and poor particle size controllability in in-situ aluminum melt generation process in the prior art, and proposes a preparation method of micron alumina.

[0007] The application adopts the following scheme, a preparation method of micron alumina, comprising the following steps:

[0008] Step 101. Melt preparation:

[0009] A predetermined amount of pure aluminum is put into an alumina crucible, and the pure aluminum is heated to a predetermined temperature by a vacuum arc furnace and is kept for 2-3 hours, and then a melt to be oxidized is obtained;

[0010] Step 102. Ultrasonic oxidation:

[0011] After the melt to be oxidized is cooled to a predetermined temperature, an ultrasonic vibration probe is inserted into the melt to be oxidized, and the melt to be oxidized is subjected to ultrasonic vibration treatment, so that the oxygen in the air oxidizes the surface of the melt to be oxidized, and alumina is generated on the surface of the melt to be oxidized;

[0012] Step 103. Product collection:

[0013] After the melt to be oxidized is subjected to ultrasonic vibration treatment for a predetermined time, the ultrasonic vibration treatment is stopped, the oxides on the surface of the melt to be oxidized are collected, and the collected oxides are sequentially cooled, solidified, separated and impurities removed, and then micron alumina products are obtained. Repeat steps 102 to 103 until the melt to be oxidized is completely oxidized;

[0014] In step 102, the vibration frequency of the ultrasonic vibration probe is 19-25 kHz, and the vibration power is 1500-2000 W;

[0015] In step 103, the median particle size of the micron alumina product prepared is 7.9-8.2 μm.

[0016] In the actual implementation process, in step 102, ultrasonic vibration can break through the oxidation kinetics limit and effectively improve the oxidation rate of pure aluminum; and by adjusting the ultrasonic frequency and power, the product particle size can be accurately controlled.

[0017] In some feasible embodiments, in step 101, the content of aluminum element in the pure aluminum is higher than 99.8wt.%, and the content of unavoidable impurities in the pure aluminum is lower than 0.2wt.%;

[0018] A predetermined amount of pure aluminum is put into an alumina crucible, and the pure aluminum is heated to 850℃ by a vacuum arc furnace and is kept for 2-3 hours, and then a melt to be oxidized is obtained.

[0019] In some possible embodiments, in step 102, after the to-be-oxidized melt is cooled to 800℃, the ultrasonic vibration probe is vertically inserted into the to-be-oxidized melt and the to-be-oxidized melt is subjected to ultrasonic oscillation treatment.

[0020] The depth of the ultrasonic vibration probe inserted into the to-be-oxidized melt is defined as H, and the H satisfies the following relationship: 3.2 cm≤H≤5.8 cm.

[0021] In some possible embodiments, in steps 101 and 102, the width of the ultrasonic vibration probe is defined as w, and the width of the alumina crucible is defined as W, and the w and the W satisfy the following relationship: 2.8≤W / w≤4.6.

[0022] In some possible embodiments, in steps 101 and 102, the length of the ultrasonic vibration probe is defined as l, and the cross-sectional width of the alumina crucible is defined as L, and the l and the L satisfy the following relationship: 3.2≤L / l≤5.2.

[0023] In some possible embodiments, in step 103, the ultrasonic vibration treatment time is 0.5 h-2 h.

[0024] In actual implementation, when the ultrasonic vibration propagates in the melt, the vibration will attenuate with the increase of the depth. When the probe is inserted too shallowly, the energy is concentrated in the region of 0 cm-2 cm on the surface of the melt, which easily leads to too fast surface oxidation and insufficient disturbance of the internal melt, and the generated alumina particles are easily agglomerated due to local overheating. When the probe is inserted too deeply, the vibration generated by the ultrasonic vibration probe will attenuate, and the vibration intensity of the deep layer of the melt is insufficient, which cannot effectively break the surface oxidation film, and thus the surface oxidation rate of the to-be-oxidized melt is reduced, and it is difficult to generate alumina particles on the surface.

[0025] In actual implementation, by controlling the insertion depth of the ultrasonic vibration probe, the fresh aluminum layer on the surface can be continuously exposed, and the generated alumina particles can be “pushed” to the surface for easy collection, avoiding that the particles sink to the bottom and are wrapped by the unoxidized melt.

[0026] In actual implementation, when the ultrasonic vibration propagates in the melt, the crucible wall will reflect part of the energy to form an “edge interference zone”. By simultaneously designing the size of the crucible and the size of the ultrasonic vibration probe, the probe energy can cover the entire surface of the to-be-oxidized melt, and the oxidation of the central region of the to-be-oxidized melt is ensured.

[0027] In some possible embodiments, in step 102, the vibration frequency of the ultrasonic vibration probe is 19 kHz-21 kHz, and the vibration power is 1800 W-2000 W.

[0028] In some possible embodiments, in step 102, the ultrasonic vibration probe is preheated to a temperature of 820 DEG C before being inserted into the molten melt to be oxidized.

[0029] In some possible embodiments, in step 103, a high-temperature-resistant K-type thermocouple is used to connect a high-speed data acquisition device to monitor the temperature of the molten melt to be oxidized during the ultrasonic vibration treatment, so as to maintain the temperature of the molten melt to be oxidized at 800 DEG C.

[0030] In some possible embodiments, in step 103, the phase composition of the micron-sized aluminum oxide product is alpha-Al2O3 and gamma-Al2O3.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] The present application provides a preparation method of micron-sized aluminum oxide, which comprises the steps of melt preparation, ultrasonic oxidation, and product collection. In the ultrasonic oxidation step, an ultrasonic vibration probe with a specific frequency and power is used to treat the molten melt to be oxidized, which effectively solves the technical problems of uneven particle size distribution caused by particle agglomeration in the process of preparing micron-sized aluminum oxide by traditional wet chemical method, difficulty in maintaining micron-sized scale due to grain growth of aluminum oxide caused by high-temperature calcination process, and slow reaction, uneven particles, difficulty in dispersion, and poor controllability of particle size in the process of in-situ generation of aluminum melt.

[0033] The present preparation method directly uses ultrasonic waves on the industrial pure aluminum melt to realize the in-situ generation of aluminum oxide particles, avoids the complex processes such as multi-step reaction, solvent addition, and high-temperature calcination involved in the traditional wet chemical method, and is more simple in operation and significantly simplifies the process flow. At the same time, the present method uses industrial pure aluminum as the only raw material and combines oxygen in the air as the reaction atmosphere, and does not rely on aluminum oxide precursors (such as aluminum salt and organic aluminum), which greatly reduces the material cost and is suitable for large-scale industrialization. Due to the strong cavitation and disturbance effect of ultrasonic waves in the high-temperature melt, the agglomeration problem in the generation process of aluminum oxide particles can be effectively inhibited, and the prepared particles have good dispersibility and stability. The entire preparation process does not use harmful substances such as acid, alkali, and organic solvent, and does not produce wastewater, waste gas, or solid waste, which conforms to the green manufacturing concept and has high environmental friendliness. The present method has the advantages of high feasibility, low implementation cost, and easy popularization and implementation. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the XRD pattern of the micron-sized aluminum oxide prepared in Example 4 of the present application;

[0035] Figure 2 is the particle size distribution graph of the micron-sized aluminum oxide prepared in Examples 1 to 4 of the present application;

[0036] Figure 3is a schematic diagram of the principle of a method for preparing micron-sized aluminum oxide according to the present application;

[0037] Figure 4 is a schematic diagram of the surface state of the melt to be oxidized in a method for preparing micron-sized aluminum oxide according to the present application. DETAILED DESCRIPTION

[0038] In combination Figures 1 to 4 The content shown further illustrates the technical solutions proposed in the present application.

[0039] Example 1: A method for preparing micron-sized aluminum oxide

[0040] Step 101: Melt preparation

[0041] A predetermined mass of pure aluminum is placed in an aluminum oxide crucible, and the pure aluminum is heated to 850℃ using a vacuum arc furnace and maintained for 2h to obtain a melt to be oxidized;

[0042] Step 102: Ultrasonic oxidation

[0043] After the melt to be oxidized is cooled to 800℃, an ultrasonic vibration probe preheated to 820℃ is vertically inserted into the melt to be oxidized and ultrasonic vibration treatment is performed on the melt to be oxidized, so that the oxygen in the air oxidizes the surface of the melt to be oxidized, and aluminum oxide is generated on the surface of the melt to be oxidized;

[0044] The vibration frequency of the ultrasonic vibration probe is 19kHz, and the vibration power is 1800W;

[0045] The insertion depth of the ultrasonic vibration probe is 3.2cm;

[0046] The width of the ultrasonic vibration probe is w, and the width of the aluminum oxide crucible is W, and w and W satisfy the following relationship: W / w=2.8;

[0047] The length of the ultrasonic vibration probe is l, and the cross-sectional width of the aluminum oxide crucible is L, and l and L satisfy the following relationship: L / l=3.2;

[0048] Step 103: Product collection

[0049] After the melt to be oxidized is ultrasonically vibrated for 0.5h, the ultrasonic vibration treatment is stopped, the oxides on the surface of the melt to be oxidized are collected, and the collected oxides are sequentially cooled, solidified, separated and impurities removed to obtain micron-sized aluminum oxide products. Repeat the above steps 102 to 103 until the melt to be oxidized is completely oxidized. During the ultrasonic vibration treatment, a high-temperature-resistant K-type thermocouple is used to connect a high-speed data acquisition device to monitor the temperature of the melt to be oxidized, so as to maintain the temperature of the melt to be oxidized at 800℃.

[0050] Example 2 A preparation method of micron-sized aluminum oxide

[0051] Step 101. Melt preparation:

[0052] A predetermined mass of pure aluminum is put into the aluminum oxide crucible, and the pure aluminum is heated to 850 DEG C by the vacuum arc furnace and kept for 3h, and then the melt to be oxidized is obtained;

[0053] Step 102. Ultrasonic oxidation:

[0054] After the melt to be oxidized is cooled to 800 DEG C, the ultrasonic vibration probe preheated to 820 DEG C is vertically inserted into the melt to be oxidized, and the melt to be oxidized is ultrasonically vibrated to oxidize the surface of the melt to be oxidized by oxygen in the air, and generate aluminum oxide on the surface of the melt to be oxidized;

[0055] The vibration frequency of the ultrasonic vibration probe is 20 kHz, and the vibration power is 1850 W;

[0056] The insertion depth of the ultrasonic vibration probe is 4.5 cm;

[0057] The width of the ultrasonic vibration probe is w, and the width of the aluminum oxide crucible is W, and w and W satisfy the following relationship: W / w = 3.3;

[0058] The length of the ultrasonic vibration probe is l, and the cross-sectional width of the aluminum oxide crucible is L, and l and L satisfy the following relationship: L / l = 3.8;

[0059] Step 103. Product collection:

[0060] After the melt to be oxidized is ultrasonically vibrated for 1h, the ultrasonic vibration treatment is stopped, the oxide on the surface of the melt to be oxidized is collected, and the collected oxide is sequentially cooled, solidified, separated and impurity-removed, and then micron-sized aluminum oxide products are obtained. Repeat steps 102 to 103, until the melt to be oxidized is completely oxidized. During the ultrasonic vibration treatment, a high-temperature-resistant K-type thermocouple is used to connect a high-speed data acquisition device to monitor the temperature of the melt to be oxidized, so that the temperature of the melt to be oxidized is maintained at 800 DEG C.

[0061] Example 3 A preparation method of micron-sized aluminum oxide

[0062] Step 101. Melt preparation:

[0063] A predetermined mass of pure aluminum is put into the aluminum oxide crucible, and the pure aluminum is heated to 850 DEG C by the vacuum arc furnace and kept for 3h, and then the melt to be oxidized is obtained;

[0064] Step 102. Ultrasonic oxidation:

[0065] After the to-be-oxidized melt is cooled to 800°C, an ultrasonic vibration probe preheated to 820°C is vertically inserted into the to-be-oxidized melt and ultrasonic vibration treatment is performed on the to-be-oxidized melt, so that oxygen in the air oxidizes the surface of the to-be-oxidized melt, and aluminum oxide is generated on the surface of the to-be-oxidized melt;

[0066] The vibration frequency of the ultrasonic vibration probe is 20 kHz, and the vibration power is 1900 W.

[0067] The insertion depth of the ultrasonic vibration probe is 4.8 cm.

[0068] The width of the ultrasonic vibration probe is w, and the width of the aluminum oxide crucible is W, and w and W satisfy the following relationship: W / w = 4.

[0069] The length of the ultrasonic vibration probe is l, and the cross-sectional width of the aluminum oxide crucible is L, and l and L satisfy the following relationship: L / l = 4.

[0070] Step 103. Finished product collection:

[0071] After the to-be-oxidized melt is ultrasonically vibrated for 1.5 h, the ultrasonic vibration treatment is stopped, the oxides on the surface of the to-be-oxidized melt are collected, and the collected oxides are sequentially cooled, solidified, and separated and impurities are removed to obtain micron-sized aluminum oxide finished products. Repeat steps 102 to 103 above until the to-be-oxidized melt is completely oxidized. During the ultrasonic vibration treatment, a high-temperature-resistant K-type thermocouple is used to connect a high-speed data acquisition device to monitor the temperature of the to-be-oxidized melt, so as to maintain the temperature of the to-be-oxidized melt at 800°C.

[0072] Example 4: A method for preparing micron-sized aluminum oxide

[0073] Step 101. Melt preparation:

[0074] A predetermined mass of pure aluminum is put into the aluminum oxide crucible, and the pure aluminum is heated to 850°C by the vacuum arc furnace and is kept for 2 h to obtain the to-be-oxidized melt.

[0075] Step 102. Ultrasonic oxidation:

[0076] After the to-be-oxidized melt is cooled to 800°C, an ultrasonic vibration probe preheated to 820°C is vertically inserted into the to-be-oxidized melt and ultrasonic vibration treatment is performed on the to-be-oxidized melt, so that oxygen in the air oxidizes the surface of the to-be-oxidized melt, and aluminum oxide is generated on the surface of the to-be-oxidized melt;

[0077] The vibration frequency of the ultrasonic vibration probe is 21 kHz, and the vibration power is 2000 W.

[0078] The insertion depth of the ultrasonic vibration probe is 5.8 cm.

[0079] The width of the ultrasonic vibration probe is w, and the width of the alumina crucible is W, and w and W satisfy the following relationship: W / w=4.6.

[0080] The length of the ultrasonic vibration probe is l, and the cross-sectional width of the alumina crucible is L, and l and L satisfy the following relationship: L / l=5.2.

[0081] Step 103. Finished product collection:

[0082] After the ultrasonic vibration treatment of the melt to be oxidized for 2h, the ultrasonic vibration treatment is stopped, the oxides on the surface of the melt to be oxidized are collected, and the collected oxides are sequentially cooled, solidified, separated and impurities removed to obtain the micron alumina finished product. Repeat the above steps 102 to 103 until the melt to be oxidized is completely oxidized. During the ultrasonic vibration treatment, a high-temperature-resistant K-type thermocouple is used to connect a high-speed data acquisition device to monitor the temperature of the melt to be oxidized, so as to maintain the temperature of the melt to be oxidized at 800℃.

[0083] The micron alumina prepared in Examples 1 to 4 is subjected to the following detection:

[0084] (1) The micron alumina prepared in Example 4 is transferred to an XRD device (SmartLab 9kw, Rigaku) to detect the crystal phase of the micron alumina;

[0085] (2) The micron alumina prepared in Examples 1 to 4 is respectively transferred to a particle size analyzer (Seishin, LMS-2000e, Japan), and the particle size distribution of the micron alumina prepared in Examples 1-4 is respectively detected. The test results are shown in Figures 2-3

[0086] As shown in Figure 1 , the micron alumina prepared in Example 4 is mainly composed of alumina and a small amount of aluminum, and the alumina is composed of α-Al2O3 and γ-Al2O3. For α-Al2O3, multiple small diffraction peaks are detected; for γ-Al2O3, two diffraction peaks of γ-Al2O3 are observed, and it is speculated that other peaks may overlap with the diffraction peaks of α-Al2O3. The diffraction peak of aluminum exists, and the possible reason is that a small amount of aluminum enters the sample during the collection of the micron alumina finished product; in addition, during the cooling of the micron alumina, part of the residual aluminum is coated on the outer periphery of the micron alumina to form an aluminum shell.

[0087] As shown in Figure 2 (a), when the ultrasonic vibration treatment time in Example 1 is 0.5h, the median particle size of the micron alumina particles is 8.117μm;

[0088] As shown in Figure 2 ​(b) shows that the median size of the micron alumina particles is 8.014 μm when the ultrasonic vibration treatment time is 1 h in Example 2;

[0089] As Figure 2 (c) shows that the median size of the micron alumina particles is 7.979 μm when the ultrasonic vibration treatment time is 1.5 h in Example 3;

[0090] As Figure 2 (d) shows that the median size of the micron alumina particles is 8.036 μm when the ultrasonic vibration treatment time is 2 h in Example 4;

[0091] It can be seen that the particle size distribution of the micron alumina particles prepared in Examples 1 to 4 is relatively concentrated, and the median particle size fluctuates little, i.e. the ultrasonic treatment process adopted in the present application can stably obtain alumina particles with uniform particle size.

[0092] As Figure 3 (a) and Figure 4 As shown in (a) and (b), during the process of treating the melt to be oxidized by the ultrasonic vibration probe, the surface of the melt to be oxidized is in full contact with air, and micron alumina is generated {as shown in the red circles in (a) and (b)}. Figure 3 (a) and Figure 4 (b) shows that the median size of the micron alumina particles is 8.014 μm when the ultrasonic vibration treatment time is 1 h in Example 2;

[0093] Further, as shown in (b), Figure 3 (b), Figure 3 (c) and Figure 4 (c) shows that after the ultrasonic vibration probe is inserted into the melt to be oxidized, cavitation bubbles are generated inside the melt and float to the surface of the melt to be oxidized covered by the oxidation film. When these bubbles collapse or break at the free surface, local disturbance or even liquid droplets can be caused. In addition, microjets can also be generated towards the free surface during the bubble collapse process. These microjets can form bumps on the surface of the melt to be oxidized. Furthermore, the high pressure generated by the bubble collapse can exert shear force, thereby inducing shear deformation of the oxidation film, and further allowing the oxidation film to be broken into small particles. That is, the ultrasonic vibration not only causes the fragmentation of the oxidation film on the surface of the melt to be oxidized, but also intensifies the oxidation reaction of aluminum due to the continuous renewal of the surface of the melt to be oxidized in contact with oxygen, thereby stably generating a large amount of micron alumina particles.

[0094] In summary, the application provides a preparation method of micron-sized aluminum oxide, which comprises three steps of melt preparation, ultrasonic oxidation and product collection. The method promotes in-situ oxidation of a pure aluminum melt surface by ultrasonic vibration treatment of the pure aluminum melt, and by setting the ultrasonic vibration parameters, particle agglomeration, uneven particle size, and large grain size can be effectively avoided, and the in-situ oxidation rate of the aluminum melt, the uniformity and dispersibility of the aluminum oxide particles can be improved. The method does not require multi-step reactions, solvent addition and high-temperature calcination, and has a short process and simple operation; it uses pure aluminum and air as raw materials, without the need for external precursors, significantly reducing costs; ultrasonic cavitation and disturbance effect reduce particle agglomeration and improve product dispersibility; no harmful substances are used and no harmful by-products are generated, which is green and environmentally friendly; and the method has the advantages of high feasibility, simple preparation process, low implementation cost, and easy popularization and implementation.

[0095] The above has described the embodiments provided by the application in detail. The principles and implementation modes of the application are described by applying specific examples, and the above description of the embodiments is only used to help understand the method of the application and its core idea. It should be noted that, for those skilled in the art, without departing from the principles of the application, the application can be improved and modified in several ways, and these improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A method for producing micrometer-sized aluminum oxide, characterized by, The method comprises the following steps: Step 101. Melt preparation: A preset mass of pure aluminum is put into an alumina crucible, and the pure aluminum is heated to a preset temperature by a vacuum arc furnace and kept for 2-3 hours to obtain a melt to be oxidized; Step 102. Ultrasonic oxidation: After the melt to be oxidized is cooled to a preset temperature, an ultrasonic vibration probe is inserted into the melt to be oxidized and ultrasonic vibration treatment is performed on the melt to be oxidized, so that the oxygen in the air oxidizes the surface of the melt to be oxidized, and alumina is generated on the surface of the melt to be oxidized; Step 103. Product collection: After the melt to be oxidized is ultrasonically vibrated for a preset time, the ultrasonic vibration treatment is stopped, the oxide on the surface of the melt to be oxidized is collected, and the collected oxide is sequentially cooled, solidified, separated and impurities removed to obtain micron alumina products, and the steps 102-103 are repeated until the melt to be oxidized is completely oxidized; In step 102, the vibration frequency of the ultrasonic vibration probe is 19-25 kHz, and the vibration power is 1500-2000 W; In step 103, the median particle size of the micron alumina products prepared is 7.9-8.2 μm.

2. The method for preparing micron-sized alumina according to claim 1, characterized in that, In step 101, the content of aluminum in the pure aluminum is higher than 99.8 wt.%, and the content of unavoidable impurities in the pure aluminum is lower than 0.2 wt.%. A preset mass of pure aluminum is put into an alumina crucible, and the pure aluminum is heated to 850°C by a vacuum arc furnace and kept for 2-3 hours to obtain a melt to be oxidized.

3. The method of claim 1, wherein the micro-sized alumina is prepared by the steps of: preparing a mixture of alumina and a dispersant; and mixing the mixture to prepare the micro-sized alumina. In step 102, after the melt to be oxidized is cooled to 800°C, an ultrasonic vibration probe is vertically inserted into the melt to be oxidized and ultrasonic vibration treatment is performed on the melt to be oxidized. The depth of the ultrasonic vibration probe inserted into the melt to be oxidized is defined as H, and the H satisfies the following relationship: 3.2 cm≤H≤5.8 cm.

4. The method of claim 1, wherein the micro-sized alumina is prepared by the steps of: preparing a mixture of alumina and a dispersant; and mixing the mixture to prepare the micro-sized alumina. In steps 101 and 102, the width of the ultrasonic vibration probe is defined as w, and the width of the alumina crucible is defined as W, and the w and the W satisfy the following relationship: 2.8≤W / w≤4.

6.

5. The method for preparing micron-sized alumina according to claim 1, characterized in that, In steps 101 and 102, the length of the ultrasonic vibration probe is defined as l, and the cross-sectional width of the alumina crucible is defined as L, and the l and the L satisfy the following relationship: 3.2≤L / l≤5.

2.

6. The method for preparing micron-sized alumina according to claim 1, characterized in that, In step 102, the vibration frequency of the ultrasonic vibration probe is 19-21 kHz, and the vibration power is 1800-2000 W.

7. The method for preparing micron-sized alumina according to claim 1, characterized in that, In step 102, the ultrasonic vibration probe is preheated to a temperature of 820°C before being inserted into the melt to be oxidized.

8. The method for preparing micron-sized alumina according to claim 1, characterized in that, In step 103, during the ultrasonic vibration treatment, a high-temperature-resistant K-type thermocouple is used to connect a high-speed data acquisition device to monitor the temperature of the melt to be oxidized, so that the temperature of the melt to be oxidized is maintained at 800°C.

9. The method for preparing micron-sized alumina according to claim 1, characterized in that, In step 103, the ultrasonic vibration treatment time is 0.5-2 hours.

10. The method for preparing micron-sized alumina according to claim 1, characterized in that, In step 103, the phase composition of the micron alumina products is α-Al2O3 and γ-Al2O3.

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