Method for preparing submicron spherical α-phase alumina powder using boehmite

Abstract

The present invention discloses a method for preparing submicron spherical α-phase alumina powder using boehmite, which relates to the technical field of inorganic materials. The D of the submicron spherical α-phase alumina powder in the present invention 50 ranges from 0.4 to 0.8 μm, the sphericity is greater than 70%, and the α-phase content is greater than 98%; and the content of sodium oxide in the submicron spherical α-phase alumina powder is less than 40 ppm, and the contents of potassium, silicon, calcium, iron, and copper elements are all less than 10 ppm. The alumina powder prepared by the present invention has low harmful impurity content, high spheroidization, high α-phase content, narrow particle size distribution, and good dispersibility; and its preparation process is simple, does not require grinding, has low production cost, and can be mass-produced industrially.

Description

Technical Field:

[0001] The present invention relates to the technical field of inorganic powder materials, and specifically relates to a method for preparing submicron spherical α-phase alumina powder using boehmite. Background Art:

[0002] α-Al2O3, also known as calcined alumina, has good optical and mechanical properties. It has a large lattice energy, a compact structure, and characteristics such as high melting point, high hardness, strong corrosion resistance, small friction coefficient, high resistivity, and good thermal conductivity. With the rise of high-precision and advanced technology fields such as lithium battery ceramic separator coating, thermal interface materials, and fine polishing materials, higher requirements are placed on the properties of alumina, such as small size, narrow particle size distribution, high purity, and high crystallinity. Compared with ordinary alumina, spherical α-Al2O3 has advantages such as good fluidity, high hardness, and strong acid and alkali resistance, which can increase the fluidity and thermal conductivity of thermal conductive fillers, etc.

[0003] Conventional large-sized spherical alumina is mainly obtained by crushing alumina and flash spheroidizing. Due to the high hardness of alumina, although the particle size can be reduced by grinding and ball milling, it is always impossible to reach the submicron level (0.1 - 1 μm) or the nanometer level, which has become a difficulty in the industry. Moreover, when grinding spherical alumina, the particle morphology is damaged, the sphericity of alumina decreases, the particle size distribution range expands, and the uniformity will decline. At the same time, trace amounts of nanoscale particles generated during the grinding process will adsorb on the surface of large particles, resulting in an increase in the specific surface area of alumina, an increase in the viscosity of thermal conductive systems such as epoxy resin, and a decrease in the filling amount.

[0004] Patent CN 113184886 A discloses a method for preparing high-thermal-conductivity spherical alumina. The particle size of the product alumina is large (D 50 is about 100 μm), the thermal conductivity is high (greater than 6 W / (m·K)), at the same time, the calcination temperature is high (1250 - 1600 °C), the time is long (8 - 22 h), and rare earth oxides are used as additives, which are expensive.

[0005] Patent CN 111392752 A discloses a submicron spherical alumina and its preparation method. Industrial aluminum hydroxide, a surfactant, and water are mixed and then subjected to hydrothermal reaction, calcination, and grinding to obtain submicron spherical α-Al2O3, with the particle size ranging from 0.1 - 1 μm and the sphericity ranging from 0.42 - 0.49. Since there is hard agglomeration during the calcination process in this method and grinding is required, the sphericity of the product is lower than 50%.

[0006] The definitions of soft agglomeration and hard agglomeration are as follows:

[0007] Soft agglomeration: The agglomeration formed between inorganic powder particles through electrostatic force and van der Waals force. This kind of agglomerate will open under a weak force, such as being dispersed. Compared with the morphology before agglomeration, the morphology remains unchanged after opening.

[0008] Hard agglomeration: The agglomeration formed between inorganic powder particles through chemical bonds. This kind of agglomerate requires a large force to open, such as mechanical crushing, grinding, etc. Compared with the morphology before agglomeration, the morphology changes after opening. Summary of the Invention:

[0009] The technical problem to be solved by the present invention is to provide a method for preparing submicron spherical α-phase alumina powder using boehmite. This method can effectively control the melting and bonding between alumina grains at high temperature to form large particles. The obtained product, α-phase alumina powder, has a low content of harmful impurities, high sphericity of particles, narrow particle size distribution, and good dispersibility. Moreover, this method has a simple process and low production cost, and is suitable for large-scale production.

[0010] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0011] One of the purposes of the present invention is to provide a submicron spherical α-phase alumina powder, and the D 50 of the submicron spherical α-phase alumina powder ranges from 0.4 to 0.8 μm, the sphericity is greater than 70%, and the α-phase content is greater than 98%.

[0012] Preferably, the content of sodium oxide in the submicron spherical α-phase alumina powder is less than 40 ppm, and the contents of potassium, silicon, calcium, iron, and copper elements are all less than 10 ppm.

[0013] Another purpose of the present invention is to provide a method for preparing submicron spherical α-phase alumina powder using boehmite, comprising the following steps:

[0014] (1) Using boehmite as the aluminum source, soaking it with acid to obtain material A;

[0015] (2) Drying material A, then adding deionized water, a morphology control agent, and a grain growth inhibitor, and mixing evenly to obtain material B;

[0016] (3) Calcining, pickling, washing with water, drying, and dispersing material B to obtain submicron spherical α-phase alumina powder.

[0017] Another purpose of the present invention is to provide a submicron spherical α-phase alumina powder prepared according to the aforementioned method.

[0018] A fourth object of the present invention is to provide the application of the aforementioned sub-micron spherical α-phase alumina powder in lithium battery ceramic diaphragm coatings, thermal interface materials, thermally conductive engineering plastics, high thermally conductive aluminum-based copper clad laminates, and polishing materials.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. In the present invention, boehmite is soaked and modified with an acid solution, washed, dried, and then mixed evenly with a morphology control agent and a grain growth inhibitor, and calcined at a high temperature. The morphology control agent reacts with alumina to generate a gaseous compound, increasing the vapor pressure of the system. At this time, solid-state mass transfer is transformed into gas-phase mass transfer, overcoming the nucleation barrier. The grain growth inhibitor adsorbs on the surface of alumina, reducing the surface energy of alumina, thereby reducing the dissolution rate of alumina at high temperatures and inhibiting further growth. The calcined powder is washed with dilute nitric acid to remove sodium, and finally, after washing with deionized water and drying, sub-micron, high-purity spherical α-Al2O3 is obtained.

[0021] 2. The sub-micron spherical α-Al2O3 powder prepared by the present invention can be used in fields such as fine polishing of chips and electronic ceramics. The product contains low levels of harmful impurities, has a high degree of sphericity, a high α-phase content, a narrow particle size distribution, and good dispersibility. It solves the problem that it is difficult to obtain sub-micron spherical α-Al2O3 with high sphericity and high crystallinity in the prior art, and effectively controls the growth of alumina grains by fusion between grains at high temperatures. Moreover, the preparation process of the present invention is simple, does not require grinding, has low production costs, and can be mass-produced industrially. Description of the Drawings:

[0022] Figure 1 SEM image of α-Al2O3 obtained in Example 1 of the present invention;

[0023] Figure 2 SEM image of α-Al2O3 obtained in Example 2 of the present invention;

[0024] Figure 3 SEM image of α-Al2O3 obtained in Example 3 of the present invention;

[0025] Figure 4 SEM image of alumina obtained in Comparative Example 1 of the present invention;

[0026] Figure 5 SEM image of alumina obtained in Comparative Example 2 of the present invention;

[0027] Figure 6 SEM image of alumina obtained in Comparative Example 3 of the present invention;

[0028] Figure 7 SEM image of alumina obtained in Comparative Example 4 of the present invention;

[0029] Figure 8 SEM image of alumina obtained in Comparative Example 5 of the present invention;

[0030] Figure 9 SEM image of alumina obtained in Comparative Example 6 of the present invention;

[0031] Figure 10 SEM image of alumina obtained in Comparative Example 7 of the present invention;

[0032] Figure 11 SEM image of alumina obtained in Comparative Example 8 of the present invention;

[0033] Figure 12 SEM image of alumina obtained in Comparative Example 9 of the present invention;

[0034] Figure 13 SEM image of alumina obtained in Comparative Example 10 of the present invention;

[0035] Figure 14 XRD pattern of α-Al2O3 obtained in Examples 1-3 of the present invention;

[0036] Figure 15 Particle size distribution diagram of α-Al2O3 obtained in Example 1 of the present invention;

[0037] Figure 16 Particle size distribution diagram of α-Al2O3 obtained in Example 2 of the present invention;

[0038] Figure 17 Particle size distribution diagram of α-Al2O3 obtained in Example 3 of the present invention. Detailed implementation method:

[0039] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific examples and illustrations.

[0040] One of the purposes of the present invention is to provide a submicron spherical α-phase alumina powder, and the D of the submicron spherical α-phase alumina powder 50 is in the range of 0.4-0.8 μm, the sphericity is greater than 70%, and the α-phase content is greater than 98%.

[0041] Preferably, the content of sodium oxide in the submicron spherical α-phase alumina powder is less than 40 ppm, and the contents of potassium, silicon, calcium, iron, and copper elements are all less than 10 ppm.

[0042] Another purpose of the present invention is to provide a method for preparing submicron spherical α-phase alumina powder using boehmite, which includes the following steps:

[0043] (1) Using boehmite as the aluminum source, soak it with acid to obtain material A;

[0044] (2) Dry material A, then add deionized water, a morphology control agent, and a grain growth inhibitor, and mix evenly to obtain material B;

[0045] (3) Calcinate material B, perform acid washing, water washing, drying, and dispersion to obtain sub-micron spherical α-phase alumina powder.

[0046] Preferably, the boehmite in step (1) is massive boehmite.

[0047] Preferably, the D 50 value of the boehmite in step (1) is 0.2 - 0.5 μm, and the sodium oxide content is less than 80 ppm.

[0048] Preferably, the acid in step (1) is any one of dilute nitric acid and acetic acid, the pH value is 3 - 5, and the soaking time is 8 - 10 h.

[0049] Preferably, the solid content of material A in step (2) is 30 - 50%.

[0050] Preferably, the morphology control agent in step (2) is any one of NH4F and AlF3; the grain growth inhibitor is any one of NaCl, KCl, Na2SO4, and K2SO4.

[0051] Preferably, the mass ratio of material A, water, the morphology control agent, and the grain growth inhibitor in step (2) is (3 - 8):(10 - 15):(0.1 - 0.5):(0.01 - 0.1), and material A is calculated based on the mass after drying.

[0052] Preferably, the calcination temperature of material B in step (3) is 1100 - 1250 °C, and the calcination time is 1.5 - 2.5 h.

[0053] Preferably, the acid used for acid washing in step (3) is any one of dilute nitric acid and acetic acid.

[0054] Preferably, the dispersion in step (3) is air flow dispersion.

[0055] The third object of the present invention is to provide a sub-micron spherical α-phase alumina powder prepared according to the foregoing method. The D 50 range of the sub-micron spherical α-phase alumina powder is 0.4 - 0.8 μm, the sphericity is greater than 70%, the α-phase content is greater than 98%, the sodium oxide content is less than 40 ppm, and the contents of potassium, silicon, calcium, iron, and copper elements are all less than 10 ppm.

[0056] A fourth object of the present invention is to provide the application of the aforementioned submicron spherical α-phase alumina powder in lithium battery ceramic diaphragm coatings, thermal interface materials, thermally conductive engineering plastics, high-thermal-conductivity aluminum-based copper clad laminates, and polishing materials.

[0057] The technical solutions of the present invention are described in detail below through examples:

[0058] Example 1

[0059] Take block boehmite with a D 50 value of 0.25 μm and a Na2O content of 76 ppm, soak it in dilute nitric acid with a pH of 4 for 8 h and then dry it; add the dried material, deionized water, AlF3, and NaCl to a stirring tank according to a mass ratio of 3:10:0.25:0.02 and mix for 3 h. The obtained slurry is dried, dispersed, and then placed in a high-temperature furnace, heated to 1150 °C, and kept warm for 2 h to end the calcination. The calcined material is washed successively with dilute nitric acid and deionized water, and finally dried and dispersed to obtain spherical α-Al2O3 with a D 50 value of 0.5 μm.

[0060] Example 2

[0061] Take block boehmite with a D 50 value of 0.40 μm and a Na2O content of 70 ppm, soak it in dilute nitric acid with a pH of 4.5 for 10 h and then dry it; add the dried material, deionized water, NH4F, and K2SO4 to a stirring tank according to a mass ratio of 4:13:0.1:0.08 and mix for 3 h. The obtained slurry is dried, dispersed, and then placed in a high-temperature furnace, heated to 1250 °C, and kept warm for 1.5 h to end the calcination. The calcined material is washed successively with dilute nitric acid and deionized water, and finally dried and dispersed to obtain spherical α-Al2O3 with a D 50 value of 0.7 μm.

[0062] Example 3

[0063] Take block boehmite with a D 50 value of 0.5 μm and a Na2O content of 73 ppm, soak it in dilute nitric acid with a pH of 4 for 9 h and then dry it; add the dried material, deionized water, AlF3, and Na2SO4 to a stirring tank according to a mass ratio of 6:15:0.4:0.1 and mix for 5 h. The obtained slurry is dried, dispersed, and then placed in a high-temperature furnace, heated to 1200 °C, and kept warm for 2 h to end the calcination. The calcined material is washed successively with dilute nitric acid and deionized water, and finally dried and dispersed to obtain spherical α-Al2O3 with a D 50 value of 0.6 μm.

[0064] It can be seen from Figure 1-3 Examples 1-3 that the alumina prepared is spherical with uniform particle size.

[0065] It can be seen fromFigure 14 It can be seen that the alumina crystal form prepared in Examples 1-3 is the α phase.

[0066] From Figure 15 、 Figure 16 and Figure 17 it can be seen that the particle size distribution range of the alumina prepared in Examples 1-3 is narrow, and D 50 is between 0.4 and 0.8 μm.

[0067] The impurity content, sphericity and α-phase content of the alumina prepared in Examples 1-3 are shown in Table 1.

[0068] Table 1

[0069] <![CDATA[Na2O]]> Fe Mg Ca Si K Sphericity rate α-phase content Example 1 28 ND ND 9 4 5 78 98.9％ Example 2 32 ND ND 5 10 6 73 98.6％ Example 3 30 ND ND 8 6 2 72 99.1％

[0070] As can be seen from Table 1, the alumina prepared in Examples 1-3 has high purity, high α-phase content and good sphericity.

[0071] Comparative Example 1

[0072] The preparation method of Comparative Example 1 is the same as that of Example 1, except that the morphology control agent and the grain growth inhibitor are not added, and irregularly shaped alumina with a D 50 value of 5.32 μm is obtained, as shown in Figure 4 shown.

[0073] Comparative Example 2

[0074] The preparation method of Comparative Example 2 is the same as that of Example 1, except that irregular aluminum hydroxide is used as the aluminum source, and irregularly shaped alumina with a D 50 value of 0.76 μm is obtained, as shown in Figure 5 shown.

[0075] Comparative Example 3

[0076] The preparation method of Comparative Example 3 is the same as that of Example 1, except that the pH is adjusted to 2.5, and irregularly shaped alumina with a D 50 value of 1.1 μm is obtained, as shown in Figure 6 shown.

[0077] Comparative Example 4

[0078] The preparation method of Comparative Example 4 is the same as that of Example 1, except that the calcined material is not pickled with acid, and vermicular alumina with a D 50 value of 0.67 μm is obtained, as shown in Figure 7 shown, and the Na2O content is 62 ppm.

[0079] Comparative Example 5

[0080] The preparation method of Comparative Example 5 is the same as that of Example 1, except that the calcined material is pickled with dilute hydrochloric acid, and D50 Worm-like alumina with a value of 0.93 μm, such as Figure 8 shown, the Na2O content is 54 ppm.

[0081] Comparative Example 6

[0082] The preparation method of Comparative Example 6 is the same as that of Example 1, except that the raw materials are replaced with D 50 Boehmite with an irregular morphology and a value of 0.75 μm is obtained to get D 50 Alumina with an irregular morphology and a value of 0.99 μm, such as Figure 9 shown.

[0083] Comparative Example 7

[0084] The preparation method of Comparative Example 7 is the same as that of Example 1, except that the raw materials are replaced with D 50 Massive pseudo-boehmite with a value of 0.75 μm is obtained to get D 50 Alumina with different sizes and irregular morphologies and a value of 0.9 μm, such as Figure 10 shown.

[0085] Comparative Example 8

[0086] The preparation method of Comparative Example 8 is the same as that of Example 1, except that no grain growth inhibitor is added to get D 50 Alumina with an irregular morphology and a value of 1.6 μm, such as Figure 11 shown.

[0087] Comparative Example 9

[0088] The preparation method of Comparative Example 9 is the same as that of Example 1, except that no morphology control agent is added to get D 50 Alumina with a worm-aggregated morphology and a value of 6.8 μm, such as Figure 12 shown.

[0089] Comparative Example 10

[0090] The preparation method of Comparative Example 10 is the same as that of Example 1, except that boehmite is not soaked in acid to get D 50 Alumina with an irregular morphology and a value of 1.6 μm, such as Figure 13 shown.

[0091] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing sub-micron spherical α-phase alumina powder using boehmite, characterized in that, It includes the following steps: (1) Using boehmite as the aluminum source, soaking it with acid to obtain material A; (2) Drying material A, then adding deionized water, a morphology control agent, and a grain growth inhibitor, and mixing evenly to obtain material B; (3) Calcining, pickling, washing with water, drying, and dispersing material B to obtain sub-micron spherical α-phase alumina powder; The D of the sub-micron spherical α-phase alumina powder 50 is in the range of 0.4 - 0.8 μm, the sphericity is greater than 70%, and the α-phase content is greater than 98%; The boehmite described in step (1) is massive boehmite, and the D 50 value is 0.2 to 0.5 μm; In step (1), the pH value of the acid is 3 - 5; In step (2), the morphology control agent is any one of NH4F and AlF3; the grain growth inhibitor is any one of NaCl, KCl, Na2SO4, and K2SO4; In step (3), the acid used for pickling is any one of dilute nitric acid and acetic acid.

2. The method according to claim 1, wherein: The sodium oxide content in the sub-micron spherical α-phase alumina powder is less than 40 ppm, and the contents of potassium, silicon, calcium, iron, and copper elements are all less than 10 ppm.

3. The method according to claim 1, wherein: In step (1), the sodium oxide content of the boehmite is less than 80 ppm.

4. The method according to claim 1, characterized in that: In step (1), the acid is any one of dilute nitric acid and acetic acid, and the soaking time is 8 - 10 h.

5. The method according to claim 1, characterized in that: In step (2), the solid content of material A is 30 - 50%; the mass ratio of material A, water, the morphology control agent, and the grain growth inhibitor is (3 - 8) : (10 - 15) : (0.1 - 0.5) : (0.01 - 0.1), and material A is calculated based on the mass after drying.

6. The method according to claim 1, characterized in that: In step (3), the calcination temperature of material B is 1100 - 1250 °C, and the calcination time is 1.5 - 2.5 h; the dispersing is air flow dispersion.

7. The sub-micron spherical α-phase alumina powder prepared by the method according to any one of claims 1 - 6.

8. The application of the sub-micron spherical α-phase alumina powder according to claim 7 in lithium battery ceramic separator coatings, thermal interface materials, thermally conductive engineering plastics, high thermally conductive aluminum-based copper clad laminates, and polishing materials.

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