Alpha-aluminum oxide with sphere-like polyhedron structure and preparation method of alpha-aluminum oxide

Abstract

According to the preparation method, monodisperse high-purity alpha-aluminum oxide with a sphere-like polyhedral structure is obtained through two times of calcination, in the process of first-time calcination, a proper amount of an inducing phase change growth auxiliary agent is added, so that the alpha-aluminum oxide is fully developed in a fluxing agent liquid phase, sphere-like single crystals can be obtained through one-time calcination, and the sphere-like single crystals are narrow in particle size distribution and good in dispersity; in the second calcination process, the ball-like single crystal aluminum oxide is secondarily developed in the high-temperature calcination process under the action of the sintering aid, the ball-like morphology is further improved, and finally the alpha-aluminum oxide with a ball-like polyhedral structure, which is high in dispersity, high in sphericity degree, narrow in particle size distribution range and good in fluidity, is formed. The method can be widely applied to various industries such as integrated circuits, semiconductors and heat-conducting fillers.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, and specifically relates to a kind of α-aluminum oxide with a spherical polyhedron structure and a preparation method thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to increase the understanding of the overall background of the present invention, and it is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Spherical alumina powder is a new type of electronic material, which has the advantages of high purity, high filling property, high thermal conductivity, high insulation property, high fluidity, low thermal expansion rate, low abrasion and high sphericity, etc. It is widely used as a thermal conductive interface material, a thermal conductive engineering plastic and a thermal conductive filler for aluminum-based copper clad laminates. In recent years, it has been applied in key fields such as new energy vehicle batteries and 5G base stations, and the demand for high-purity spherical alumina powder at home and abroad is increasing.

[0004] At present, the production processes of α-aluminum oxide powder mainly include: sol-emulsification-gel method, melt spraying method, high-temperature calcination method, homogeneous precipitation method, template method, drop ball method, etc. Among them, the sol-emulsification-gel method, melt spraying method and high-temperature calcination method can prepare spherical / spherical-like α-aluminum oxide powder with a single crystal particle size in the micron range. The sol-emulsion-gel method uses auxiliary materials such as organic solvents and surfactants, which increases the difficulty of powder separation and drying, and the product is prone to agglomeration, making it difficult to achieve large-scale production; the melt spraying method directly melts and spheroidizes solid aluminum powder or alumina powder by using a plasma flame, and can obtain α-aluminum oxide particles with a high sphericity and a large particle size, but pores will be formed inside the particles, reducing the density and thermal conductivity of the particles; the high-temperature calcination method requires calcination at a temperature above 1300°C for more than 10 hours and the addition of specific mineralizing agents to produce spherical-like α-aluminum oxide powder, which consumes a high amount of energy and has a high production cost. In the existing production processes of spherical / spherical-like α-aluminum oxide powder, there are still problems such as difficult control of powder morphology, wide particle size distribution, inability to regulate particle size, easy agglomeration, poor dispersibility, time-consuming and energy-consuming, and high production cost. Summary of the Invention

[0005] In order to overcome the above problems, the present invention provides a kind of α-aluminum oxide with a spherical polyhedron structure and a preparation method thereof.

[0006] To achieve the above technical purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect of the present invention, a preparation method of α-aluminum oxide with a spherical polyhedron structure is provided, including the following steps:

[0008] (1) Mix the alumina precursor, the induced phase transition growth promoter, and the flux, and conduct the first calcination to form an intermediate;

[0009] (2) Mix the intermediate with the sintering aid and conduct the second calcination to obtain α-alumina with a spherical polyhedron structure.

[0010] In one or more embodiments, the alumina precursor is selected from one or more of pseudoboehmite, aluminum sulfate octadecahydrate, aluminum nitrate, aluminum hydroxide, γ-alumina, and boehmite.

[0011] In one or more embodiments, the induced phase transition growth promoter is selected from one or more of titanium oxysulfate, silicon dioxide, magnesium chloride, calcium chloride, boron oxide, and sodium tungstate.

[0012] In one or more embodiments, the flux includes solvent A, solvent B, and solvent C, where solvent A is one of sodium chloride, potassium chloride, and calcium chloride, solvent B is potassium sulfate, and solvent C is sodium sulfate;

[0013] Preferably, the mass ratio of solvent A, solvent B, and solvent C is (5-30):(20-90):(20-70).

[0014] In one or more embodiments, the sintering aid includes at least two compounds, and the compounds are composed of at least one element selected from fluorine, boron, chlorine, sulfur, silicon, aluminum, calcium, magnesium, and iron.

[0015] Preferably, the sintering aid may include one or more of silicon oxide, aluminum fluoride, magnesium oxide, aluminum oxide, boron oxide, calcium oxide, and iron.

[0016] In one or more embodiments, the mass ratio of the alumina precursor, the induced phase transition growth promoter, and the flux is (10-65):(0.5-10):(35-90);

[0017] The mass percentage of the intermediate to the sintering aid is 100:(0.25-20).

[0018] In one or more embodiments, in step (1), the method of mixing the alumina precursor, the induced phase transition growth promoter, and the flux and conducting the first calcination to form an intermediate includes:

[0019] Disperse the alumina precursor, the induced phase transition growth promoter, and the flux in a dispersant, and mix to obtain a precursor suspension;

[0020] After the precursor suspension is dried, it is pulverized to obtain a composite powder, and the composite powder is calcined to form an intermediate.

[0021] Preferably, the dispersant is selected from one of deionized water and ethanol.

[0022] Preferably, the temperature for drying the precursor suspension is 60°C to 140°C, and the drying time is 12 to 48 h.

[0023] Preferably, the pulverization is carried out by ball milling, the ball milling speed is 200 to 400 r / min, and the ball milling time is 1 to 5 h.

[0024] Preferably, the temperature for calcining the composite powder to form the intermediate is 900°C to 1300°C, and the heat preservation time is 1 to 4 h.

[0025] In one or more embodiments, after calcining to form the intermediate, it is washed and dried, and then mixed with a sintering aid.

[0026] Preferably, the solvent used for washing is deionized water or ethanol, the washing temperature is 40°C to 100°C, the drying temperature is 60°C to 140°C, and the drying time is 3 to 24 h.

[0027] In one or more embodiments, the second calcination temperature is 1100°C to 1500°C, and the heat preservation time is 2 to 6 h.

[0028] In a second aspect of the present invention, there is provided α-aluminum oxide having a spherical polyhedron structure prepared by the above preparation method.

[0029] In one or more embodiments, the main particle size of the α-aluminum oxide having a spherical polyhedron structure is 1 to 60 μm, specifically including 1 to 10 μm, 8 to 20 μm, and 12 to 60 μm.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) In the present invention, α-aluminum oxide having a monodisperse and high-purity spherical polyhedron structure is obtained through two calcinations. During the first calcination, by adding an appropriate amount of an induced phase transformation growth aid, it is fully developed in the flux liquid phase, and spherical single crystals can be obtained in one calcination, and the particle size distribution is narrow and the dispersibility is good; during the second calcination, the spherical single crystal alumina is secondarily developed during high-temperature calcination under the action of a sintering aid, and the spherical morphology is further improved, and finally α-aluminum oxide having a spherical polyhedron structure with high dispersibility, high sphericity, narrow particle size distribution range, and good fluidity is formed, which can be widely applied to many industries such as integrated circuits, semiconductors, and thermal conductive fillers.

[0032] (2) In the present invention, α-aluminum oxide having a spherical polyhedron structure with various particle sizes such as 1 to 10 μm, 8 to 20 μm, and 12 to 60 μm is obtained by regulating raw materials, process parameters, etc., realizing the regulation of size and meeting the applicable requirements of different particle sizes.

[0033] (3) The preparation method of the α-aluminum oxide with a spherical polyhedron structure provided by the present invention controls the maximum temperature of the secondary calcination within 1500 °C and the maximum holding time within 6 hours, reducing energy consumption and equipment loss, and being energy-saving and environmentally friendly.

[0034] (4) The raw materials of the present invention have a wide source, are not limited to a single raw material, are cheap and easy to obtain, and are convenient for storage. The process is simple, the cost is low, the repeatability is high, it is green and environmentally friendly, and it is easy to industrialize production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The attached drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0036] Figure 1 It is the scanning electron microscope image of the α-aluminum oxide with a spherical polyhedron structure prepared in Example 1;

[0037] Figure 2 It is the scanning electron microscope image of the α-aluminum oxide with a spherical polyhedron structure prepared in Example 2;

[0038] Figure 3 It is the scanning electron microscope image of the α-aluminum oxide with a spherical polyhedron structure prepared in Example 3;

[0039] Figure 4 It is the scanning electron microscope image of the single-crystal alumina powder with a polyhedron structure prepared in Comparative Example 1;

[0040] Figure 5 It is the scanning electron microscope image of the single-crystal alumina powder with a polyhedron structure prepared in Comparative Example 2;

[0041] Figure 6 It is the scanning electron microscope image of the single-crystal alumina powder with a polyhedron structure prepared in Comparative Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0045] Example 1

[0046] Preparation of α-aluminum oxide with a spherical polyhedron structure:

[0047] Take 5 g of boehmite, 5 g of γ-aluminum oxide, 0.1 g of titanium dioxide, 0.15 g of boron oxide, 1 g of sodium chloride, 4.5 g of potassium sulfate, and 4.5 g of sodium sulfate, add them to 350 mL of deionized water, stir magnetically for 30 min, mix evenly, and obtain a precursor suspension;

[0048] Place the obtained precursor suspension in a blast drying oven and dry it at 80 °C for 24 h;

[0049] After drying, carry out ball milling and pulverization. The rotation speed of the ball milling is 300 r / min, and the ball milling time is 2 h;

[0050] Load the fully crushed powder into a crucible, seal it with a sealing cover, and place it in a muffle furnace for calcination;

[0051] Raise the temperature to 500 °C at a heating rate of 3 °C / min, then raise the temperature to 1050 °C at a heating rate of 4 °C / min, hold for 3 h, wash the obtained solid with deionized water, filter by suction, and dry at 100 °C for 5 h to obtain single crystal alumina powder with a polyhedron structure, namely the intermediate;

[0052] Mix all the obtained intermediates (about 10 g) with 0.02 g of aluminum fluoride and 0.05 g of magnesium oxide evenly, and then carry out calcination again. The calcination temperature is 1350 °C, and hold for 4 h to obtain α-aluminum oxide with a spherical polyhedron structure.

[0053] The scanning electron microscope image of the α-aluminum oxide with a spherical polyhedron structure obtained in this example is as Figure 1 shown. In this example, α-aluminum oxide with a spherical polyhedron structure with a main particle size of about 1 - 10 μm can be obtained.

[0054] Example 2

[0055] Preparation of α-aluminum oxide with a spherical polyhedron structure:

[0056] Take 5 g of industrial aluminum hydroxide, 5 g of γ-aluminum oxide, 0.15 g of titanium dioxide, 0.1 g of boron oxide, 1 g of sodium chloride, 4.5 g of potassium sulfate, and 4.5 g of sodium sulfate, add them to 350 mL of deionized water, stir magnetically for 30 min, mix evenly, and obtain a precursor suspension;

[0057] The obtained precursor suspension was placed in a forced-air drying oven and dried at 80 °C for 24 h;

[0058] After drying, it was ball-milled and pulverized. The rotation speed of the ball mill was 300 r / min and the ball-milling time was 2 h;

[0059] The fully crushed powder was loaded into a crucible, sealed with a sealing cover, and placed in a muffle furnace for calcination;

[0060] It was heated to 500 °C at a heating rate of 3 °C / min, then heated to 1050 °C at a heating rate of 4 °C / min, and held for 3 h. The obtained solid was washed with deionized water, filtered by suction, and dried at 100 °C for 5 h to obtain single-crystalline alumina powder with a polyhedral structure, i.e., the intermediate;

[0061] All the obtained intermediates (about 10 g) were mixed evenly with 0.02 g of aluminum fluoride and 0.05 g of magnesium oxide, and then calcined again. The calcination temperature was 1350 °C and the holding time was 4 h to obtain α-alumina with a spherical polyhedral structure.

[0062] The scanning electron microscope image of the α-alumina with a spherical polyhedral structure obtained in this example is as Figure 2 shown. In this example, α-alumina with a spherical polyhedral structure and a main particle size of about 8 - 20 μm was obtained.

[0063] Example 3

[0064] Preparation of α-alumina with a spherical polyhedral structure:

[0065] 5 g of pseudoboehmite, 5 g of γ-alumina, 0.15 g of titanium dioxide, 0.1 g of boron oxide, 1 g of sodium chloride, 4.5 g of potassium sulfate, and 4.5 g of sodium sulfate were added to 350 mL of deionized water, and magnetically stirred for 30 min to mix evenly, obtaining a precursor suspension;

[0066] The obtained precursor suspension was placed in a forced-air drying oven and dried at 80 °C for 24 h;

[0067] After drying, it was ball-milled and pulverized. The rotation speed of the ball mill was 300 r / min and the ball-milling time was 2 h;

[0068] The fully crushed powder was loaded into a crucible, sealed with a sealing cover, and placed in a muffle furnace for calcination;

[0069] It was heated to 500 °C at a heating rate of 3 °C / min, then heated to 1050 °C at a heating rate of 4 °C / min, and held for 3 h. The obtained solid was washed with deionized water, filtered by suction, and dried at 100 °C for 5 h to obtain single-crystalline alumina powder with a polyhedral structure, i.e., the intermediate;

[0070] Mix all the obtained intermediates (about 10 g) evenly with 0.02 g of aluminum fluoride and 0.05 g of magnesium oxide, and then calcine again. The calcination temperature is 1350 °C, and keep the temperature for 4 h to obtain α-aluminum oxide with a spherical polyhedron structure.

[0071] The scanning electron microscope image of the α-aluminum oxide with a spherical polyhedron structure obtained in this example is as Figure 3 shown. This example can obtain α-aluminum oxide with a spherical polyhedron structure with a main particle size of about 12 - 60 μm.

[0072] Through the comparison of Examples 1 - 3, it is found that the particle size of α-aluminum oxide with a spherical polyhedron structure has a great relationship with the activity of the alumina precursor. Under the same experimental conditions, the higher the activity of the alumina precursor, the larger the particle size of the obtained alumina powder. Therefore, in this invention, alumina precursors with different activities are used as raw materials, and at the same time, the coupling effects of various factors such as the type and addition amount of the optimal induced phase transition growth aid, the flux ratio, the type and addition amount of the sintering aid, and the temperature parameter setting are explored to realize the regulation of the particle size and morphology of the alumina powder.

[0073] Comparative Example 1

[0074] Take 5 g of boehmite, 0.1 g of titanium dioxide, 0.15 g of boron oxide, 1 g of sodium chloride, 4.5 g of potassium sulfate, and 4.5 g of sodium sulfate, add them to 350 mL of deionized water, stir magnetically for 30 min to mix evenly, and obtain a precursor suspension;

[0075] Place the obtained precursor suspension in a forced-air drying oven and dry it at 80 °C for 24 h;

[0076] After drying, carry out ball milling and crushing. The rotation speed of the ball milling is 300 r / min, and the ball milling time is 2 h;

[0077] Put the fully crushed powder into a crucible, seal it with a sealing cover, and place it in a muffle furnace for calcination;

[0078] Raise the temperature to 500 °C at a heating rate of 3 °C / min, then raise the temperature to 1000 °C at a heating rate of 4 °C / min, and keep the temperature for 3 h. After washing the obtained solid with deionized water, filtering by suction, and drying at 100 °C for 5 h, obtain single-crystal alumina powder with a polyhedron structure.

[0079] The scanning electron microscope image of the single-crystal alumina powder with a polyhedron structure prepared in this comparative example is as Figure 4 shown. This comparative example can obtain α-aluminum oxide with a polyhedron structure with a main particle size of about 1 - 10 μm. Compared with this comparative example, in Example 1, through secondary calcination, under the action of the sintering aid, the polyhedron structure α-aluminum oxide develops secondarily, and finally obtains α-aluminum oxide with a spherical polyhedron structure with better sphericity and more uniform particle size distribution.

[0080] Comparative Example 2

[0081] Take 5 g of industrial aluminum hydroxide, 0.51 g of titanium dioxide, 0.1 g of boron oxide, 1 g of sodium chloride, 4.5 g of potassium sulfate, and 4.5 g of sodium sulfate, add them to 350 mL of deionized water, stir magnetically for 30 min to mix evenly, and obtain a precursor suspension;

[0082] Place the obtained precursor suspension in a forced-air drying oven and dry it at 80 °C for 24 h;

[0083] After drying, perform ball milling and pulverization. The rotation speed of the ball milling is 300 r / min, and the ball milling time is 2 h;

[0084] Load the fully crushed powder into a crucible, seal it with a sealing lid, and place it in a muffle furnace for calcination;

[0085] Raise the temperature to 500 °C at a heating rate of 3 °C / min, then raise the temperature to 1000 °C at a heating rate of 4 °C / min, hold for 3 h, wash the obtained solid with deionized water, filter by suction, and dry at 100 °C for 5 h to obtain single-crystal alumina powder with a polyhedral structure.

[0086] The scanning electron microscope image of the single-crystal alumina powder with a polyhedral structure prepared in this comparative example is as Figure 5 shown. Through this comparative example, α-alumina with a polyhedral structure and a main particle size of about 8 - 20 μm can be obtained. Compared with this comparative example, in Example 2, through secondary calcination, under the action of a sintering aid, the polyhedral structure α-alumina undergoes secondary growth, and finally α-alumina with a better sphericity and a more uniform particle size distribution, a spherical polyhedral structure, is obtained.

[0087] Comparative Example 3

[0088] Take 5 g of pseudo-boehmite, 0.15 g of titanium dioxide, 0.1 g of boron oxide, 1 g of sodium chloride, 4.5 g of potassium sulfate, and 4.5 g of sodium sulfate, add them to 350 mL of deionized water, stir magnetically for 30 min to mix evenly, and obtain a precursor suspension;

[0089] Place the obtained precursor suspension in a forced-air drying oven and dry it at 80 °C for 24 h;

[0090] After drying, perform ball milling and pulverization. The rotation speed of the ball milling is 300 r / min, and the ball milling time is 2 h;

[0091] Load the fully crushed powder into a crucible, seal it with a sealing lid, and place it in a muffle furnace for calcination;

[0092] It is heated to 500 °C at a heating rate of 3 °C / min, then heated to 1000 °C at a heating rate of 4 °C / min, and held for 3 h. The obtained solid is washed with deionized water, filtered by suction, and dried at 100 °C for 5 h to obtain single-crystalline alumina powder with a polyhedral structure.

[0093] The scanning electron microscope image of the single-crystalline alumina powder with a polyhedral structure prepared in this comparative example is as Figure 6 shown. Through this comparative example, α-alumina with a polyhedral structure and a main particle size of about 12 - 60 μm can be obtained. Compared with this comparative example, in Example 3, through secondary calcination, the polyhedral structure α-alumina is secondarily developed under the action of a sintering aid, and finally α-alumina with a better sphericity and a more uniform particle size distribution, namely a spherical polyhedral structure, is obtained.

[0094] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of α-aluminum oxide with a truncated icosahedron structure, characterized in that, It includes the following steps: (1) Mix an alumina precursor, an induced phase transition growth aid, and a flux, and conduct the first calcination to form an intermediate; (2) Mix the intermediate with a sintering aid and conduct the second calcination to obtain α-alumina with a spherical polyhedron structure.

2. The preparation method according to claim 1, characterized in that, The alumina precursor is selected from one or more of pseudoboehmite, aluminum sulfate octadecahydrate, aluminum nitrate, aluminum hydroxide, γ-alumina, and boehmite; Or, the induced phase transition growth aid is selected from one or more of titanium oxysulfate, silicon dioxide, magnesium chloride, calcium chloride, boron oxide, and sodium tungstate.

3. The preparation method according to claim 1, characterized in that, The flux includes solvent A, solvent B, and solvent C, where solvent A is one of sodium chloride, potassium chloride, and calcium chloride, solvent B is potassium sulfate, and solvent C is sodium sulfate; preferably, the mass ratio of solvent A, solvent B, and solvent C is (5 - 30):(20 - 90):(20 - 70); Or, the sintering aid includes at least two compounds, and the compounds are composed of at least one element among fluorine, boron, chlorine, sulfur, silicon, aluminum, calcium, magnesium, and iron. The sintering aid may include one or more of silicon oxide, aluminum fluoride, magnesium oxide, aluminum oxide, boron oxide, calcium oxide, and iron.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the alumina precursor, the induced phase transition growth aid, and the flux is (10 - 65):(0.5 - 10):(35 - 90); The mass percentage of the intermediate to the sintering aid is 100:(0.25 - 20).

5. The preparation method according to claim 1, characterized in that, In step (1), the method of mixing the alumina precursor, the induced phase transition growth aid, and the flux and conducting the first calcination to form an intermediate includes: Disperse the alumina precursor, the induced phase transition growth aid, and the flux in a dispersant, and mix to obtain a precursor suspension; After the precursor suspension is dried and pulverized, a composite powder is obtained, and the composite powder is calcined to form an intermediate.

6. The preparation method according to claim 5, characterized in that, The dispersant is selected from one of deionized water and ethanol; Or, the drying temperature of the precursor suspension is 60°C - 140°C, and the drying time is 12 - 48 h. The pulverization is carried out by ball milling, the ball milling speed is 200 - 400 r / min, and the ball milling time is 1 - 5 h; Or, the temperature for calcining the composite powder to form an intermediate is 900°C - 1300°C, and the heat preservation time is 1 - 4 h.

7. The preparation method according to claim 5, characterized in that, The pulverization is carried out by ball milling, the ball milling speed is 200 - 400 r / min, and the ball milling time is 1 - 5 h; Or, the temperature for calcining the composite powder to form an intermediate is 900°C - 1300°C, and the heat preservation time is 1 - 4 h.

8. The preparation method according to claim 1, characterized in that, After the intermediate is formed by calcination, it is washed and dried, and then mixed with the sintering aid; Preferably, the solvent used for washing is deionized water or ethanol, the washing temperature is 40°C - 100°C, the drying temperature is 60°C - 140°C, and the drying time is 3 - 24 h; Or, the second calcination temperature is 1100°C - 1500°C, and the heat preservation time is 2 - 6 h.

9. α-alumina with a spherical polyhedron structure prepared by the preparation method according to any one of claims 1 - 8.

10. The α-aluminum oxide with a spherical polyhedron structure according to claim 8, wherein, The main particle size of the α-alumina with a spherical polyhedron structure is 1 - 60 μm.

Images