Preparation method and application of spherical alpha alumina powder

Abstract

The invention discloses a preparation method and application of spherical alpha alumina powder. The preparation method comprises the following steps: obtaining alumina; pretreating the aluminum oxide to obtain first aluminum oxide powder; carrying out grinding treatment on the first aluminum oxide powder to obtain second aluminum oxide powder; and firing the second alumina powder to obtain the spherical alpha alumina powder. According to the scheme, the stacking density, porosity and interface morphology of the alumina powder can be improved, the high-thermal-conductivity spheroid alpha alumina powder is prepared, and the manufacturing cost can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic non-metallic micropowders, and in particular to a preparation method of spherical alpha alumina powder and application thereof. Background Art

[0002] Domestic alumina powder mainly uses industrial-grade γ-alumina (alumina with a crystal form of γ-Al2O3) to sinter α-alumina (alumina with a crystal form of α-Al2O3) with different original grain sizes at different temperature ranges. High-purity alumina mainly uses industrial-grade γ-alumina to extract impurities in alumina using hydrochloric acid, nitric acid, sulfuric acid, etc., and the extracted materials are calcined;

[0003] The morphology of α-alumina prepared by γ-alumina in existing production technology is mainly flaky and angular, and the thermal conductivity of flaky and angular α-alumina is lower than that of spherical α-alumina. At the same time, the existing spherical α-alumina powder can only be prepared by secondary flame melting, which has high manufacturing cost. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing spherical α-alumina powder and its application, which can improve the packing density, porosity and interface morphology of alumina powder, prepare high thermal conductivity spherical α-alumina powder, and help reduce manufacturing costs.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following solutions:

[0006] The first aspect of the present invention provides a method for preparing spherical α-alumina powder, comprising:

[0007] Obtaining aluminum oxide;

[0008] Pre-treating the aluminum oxide to obtain a first aluminum oxide powder;

[0009] Grinding the first alumina powder to obtain a second alumina powder;

[0010] The second alumina powder is fired to obtain spherical α-alumina powder.

[0011] Optionally, the alumina obtained is nano alumina having a γ-Al2O3 crystal form.

[0012] Optionally, pre-treating the aluminum oxide to obtain a first aluminum oxide powder comprises:

[0013] Pour the aluminum oxide into a mixed solution of water and alcohol and stir;

[0014] After the stirring process is completed, nitric acid is added to the mixed solution, and heating and stirring are performed;

[0015] After the reaction is completed, the solid matter in the mixed solution is filtered and washed to obtain the first alumina powder.

[0016] Optionally, the volume ratio of alumina, water and alcohol is 2:2:0.05;

[0017] The stirring time is 5 minutes.

[0018] Optionally, the concentration of the nitric acid is 65%;

[0019] The mass ratio of aluminum oxide to 65% nitric acid is 100:(0.7-1.5);

[0020] The heating temperature for heating and stirring was 60° C., and the heating and stirring time was 1 hour.

[0021] Optionally, grinding the first alumina powder to obtain the second alumina powder comprises:

[0022] The first alumina powder, boric acid and mixing balls are wet mixed to obtain a second alumina powder.

[0023] Optionally, the mass ratio of alumina, boric acid and mixing balls is 100:(0.5-1.0):50;

[0024] The wet mixing time is 20-40 minutes.

[0025] Optionally, a rotary kiln is used for firing;

[0026] Material temperature is 1500-1600℃;

[0027] The flame temperature is 1800-2000℃;

[0028] The material comes into direct contact with the flame.

[0029] The second aspect of the present invention provides a thermally conductive material, comprising spherical α-alumina powder prepared according to the preparation method of the first aspect.

[0030] A third aspect of the present invention provides a power battery, comprising the thermally conductive material of the second aspect.

[0031] The above solution of the present invention includes at least the following beneficial effects:

[0032] The above scheme of the present invention obtains alumina; pre-treats the alumina to obtain alumina powder; grinds the alumina powder to obtain alumina micropowder; and sinters the alumina micropowder to obtain spherical α alumina powder. This can improve the packing density, porosity and interface morphology of the alumina powder, prepare high thermal conductivity spherical α alumina powder, and help reduce manufacturing costs. DETAILED DESCRIPTION

[0033] The exemplary embodiments of the present invention will be described in more detail below. The exemplary embodiments of the present invention should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0034] The present invention provides a method for preparing spherical alpha alumina powder, comprising:

[0035] Step 11, obtaining aluminum oxide;

[0036] Step 12, pretreating the alumina to obtain a first alumina powder;

[0037] Step 13, grinding the first alumina powder to obtain a second alumina powder;

[0038] Step 14: sinter the second alumina powder to obtain spherical α-alumina powder.

[0039] In this embodiment, by obtaining aluminum oxide; pre-treating the aluminum oxide to obtain aluminum oxide powder; grinding the aluminum oxide powder to obtain aluminum oxide micropowder; sintering the aluminum oxide micropowder to obtain spherical α-alumina powder; the packing density, porosity and interface morphology of the aluminum oxide powder can be improved to prepare high thermal conductivity spherical α-alumina powder, which helps to reduce manufacturing costs;

[0040] Wherein, the aluminum oxide obtained is nano aluminum oxide with a crystal form of γ-Al2O3.

[0041] In an optional embodiment of the present invention, step 12 includes:

[0042] Step 121, pouring the aluminum oxide into a mixed solution of water and alcohol and stirring;

[0043] Step 122, after the stirring process is completed, nitric acid is added to the mixed solution, and heating and stirring are performed;

[0044] Step 123, after the reaction is completed, filter the solid matter in the mixed solution, rinse the solid matter, and obtain the first alumina powder.

[0045] Further, the volume ratio of alumina, water and alcohol is 2:2:0.05;

[0046] The stirring time is 5 min;

[0047] The concentration of the nitric acid is 65%;

[0048] The mass ratio of aluminum oxide to 65% nitric acid is 100:(0.7-1.5);

[0049] The heating temperature for heating and stirring was 60° C., and the heating and stirring time was 1 hour.

[0050] In this embodiment, 100g of γ-alumina is placed in a 500ml stirred reactor, 200ml of water and 100ml of alcohol solution are added and stirred for 5min; then 0.7-1.5g of 65% nitric acid is added dropwise, the reaction stirrer is heated to 60°C, and stirred for 1 hour; after the reaction is complete, 2000ml of clean water is used to rinse and filter the alumina powder as the first alumina powder;

[0051] The existing preparation method is to stir the solution of alumina and acid, without considering the oxidation characteristics and Na ion distribution. The microstructure of γ alumina is generally cracked, and some impurities will remain in the cracks of γ alumina. Due to the surface tension of the solution, it is difficult to extract the impurities in the crack structure, which affects the extraction purity. At the same time, the remaining sodium ions promote the formation of β alumina during the reaction, thereby affecting the crystal structure of alumina.

[0052] The preparation method of the present application is different from the existing preparation method in that the gamma alumina is placed in a solution of water and alcohol and stirred, which can reduce the surface tension of the solution on the surface of the alumina and allow the liquid to completely penetrate into the tiny gaps of the alumina, thereby removing impurities in the tiny gaps of the alumina, which helps to improve the extraction purity of the alumina; it can effectively remove impurities in the gaps of the alumina, thereby reducing the retention of sodium ions and reducing the influence of sodium ions on the formation of the alumina crystal structure.

[0053] In an optional embodiment of the present invention, step 13 includes:

[0054] Step 131, wet-mixing the mixture of the first alumina powder, boric acid and mixing balls to obtain a second alumina powder.

[0055] Further, the mass ratio of alumina, boric acid and mixing balls is 100:(0.5-1.0):50;

[0056] The wet mixing time is 20-40 minutes.

[0057] In this embodiment, the first alumina powder (γ alumina) with a certain amount of water after pre-treatment and washing is placed in a mixing tank, and 50g of mixing balls and 0.5-1.0g of boric acid are added, and wet mixing is performed for 20-40min;

[0058] The existing preparation method is to dry the material washed in step 123 and then mix it with boric acid;

[0059] The preparation method of the present application is different from the existing preparation method in that a wet mixing method is adopted and mixing balls are added to mix the first alumina powder and boric acid. The boric acid is ground into fine powder by adding mixing balls for wet co-grinding, thereby increasing the contact area between the boric acid and the first alumina powder, improving the adsorption performance of the boric acid, and allowing the boric acid to fully and evenly act on the surface of the first alumina powder and its gaps. In the subsequent firing process, the generation of pores can be effectively reduced. At the same time, the liquid phase can be evenly generated, which is conducive to the better development of the crystal morphology and improves the density and thermal conductivity of the alumina powder itself.

[0060] In an optional embodiment of the present invention, a rotary kiln is used for firing;

[0061] Material temperature is 1500-1600℃;

[0062] The flame temperature is 1800-2000℃;

[0063] The material comes into direct contact with the flame.

[0064] In this embodiment, the second alumina powder is fired in a rotary kiln, the material temperature is 1500-1600°C, the flame temperature is 1800-2000°C, and the high-temperature fired material of the rotary kiln is directly in contact with the high-temperature flame, which makes it easier to form spherical α-alumina powder;

[0065] The existing preparation method uses a tunnel kiln or a muffle furnace for firing, which easily forms a lamellar hexagonal crystal structure during the long-term heat preservation process;

[0066] The preparation method of the present application is different from the existing preparation method in that a rotary kiln is used for firing, and the flame is in direct contact with the material, which can cause the surface of the alumina to melt quickly to form liquid crystals, thereby preventing the formation of a flaky hexagonal crystal structure during long-term heat preservation. The high temperature firing and rapid cooling of the rotary kiln are more conducive to the formation of spherical α-alumina powder.

[0067] The present invention also provides a thermally conductive material, comprising spherical α-alumina powder prepared according to the above preparation method.

[0068] The present invention also provides a power battery, comprising the above-mentioned thermal conductive material.

[0069] The following is a specific embodiment of the above method:

[0070] Embodiment 1:

[0071] (1) 100 g of γ-alumina was placed in a 500 ml beaker, 200 ml of water and 100 ml of alcohol solution were added and stirred for 5 min, then 1.3 g of 65% nitric acid was added dropwise, and the mixture was heated to 60° C. and stirred for 1 hour; wherein the stirring blade speed was 750 r / min; after the reaction was complete, the reacted alumina powder was rinsed with 2000 ml of pure water in a Buchner funnel;

[0072] (2) Put the gamma alumina with a certain amount of water obtained in step (1) into a mixing tank, add 50 g of mixing balls, add 0.5 g of boric acid, and wet mix for 20 min;

[0073] (3) The alumina powder obtained in step (2) is fired in a rotary kiln, the material temperature is 1550°C, the flame temperature is 1800-2000°C, and the material is in direct contact with the flame for firing; the material is rapidly cooled after leaving the kiln to obtain spherical α-alumina powder.

[0074] Embodiment 2:

[0075] Example 2 Referring to the method of Example 1, the difference between Example 2 and Example 1 is that the amount of nitric acid with a concentration of 65% is 1.0 g, as shown in Table 1;

[0076] Embodiment 3:

[0077] Example 3 Referring to the method of Example 1, the difference between Example 3 and Example 1 is that the amount of nitric acid with a concentration of 65% is 0.7 g, as shown in Table 1;

[0078] Embodiment 4:

[0079] Example 4 Referring to the method of Example 1, Example 4 differs from Example 1 in that the amount of boric acid added is 0.75 g, as shown in Table 1;

[0080] Implementation 5:

[0081] Example 5 Referring to the method of Example 1, Example 5 differs from Example 1 in that the amount of boric acid added is 1.0 g, as shown in Table 1;

[0082] Implementation 6:

[0083] Example 6 Referring to the method of Example 2, the difference between Example 6 and Example 2 is that the amount of boric acid added is 0.75 g, as shown in Table 1;

[0084] Implementation column 7:

[0085] Example 7 refers to the method of Example 2. The difference between Example 7 and Example 2 is that the amount of boric acid added is 1.0 g, as shown in Table 1;

[0086] Implementation 8:

[0087] Example 8 refers to the method of Example 3. The difference between Example 8 and Example 3 is that the amount of boric acid added is 0.75 g, as shown in Table 1;

[0088] Implementation column 9:

[0089] Example 9 refers to the method of Example 3. The difference between Example 9 and Example 3 is that the amount of boric acid added is 1.0 g, as shown in Table 1;

[0090] Comparative Example 1:

[0091] (1) 100 g of γ-alumina was placed in a 500 ml beaker, 200 ml of water was added, and then 1.3 g of 65% nitric acid was dropped into the beaker, and stirred for 1 hour, wherein the stirring speed of the stirring blade was 750 r / min; after the reaction was complete, the reacted alumina powder was rinsed with 2000 ml of pure water in a Buchner funnel;

[0092] (2) drying the rinsed material, and then mixing it with 0.5 g of boric acid in a mixing cup for 20 min;

[0093] (3) The mixed materials are fired at a temperature of 1550°C, fired and cooled.

[0094] Table 1 Data of various embodiments and comparative examples

[0095]

[0096]

[0097] The α-alumina powders prepared in the examples and comparative examples were tested, and the test results are shown in Table 2.

[0098] Table 2 Experimental results

[0099]

[0100] It can be seen from the data in the above table that the α alumina powder prepared by the method for preparing spherical α alumina powder provided by the present invention has good thermal conductivity, which solves the shortcomings of the prior art. The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing spherical α-alumina powder, characterized in that: include: Obtaining aluminum oxide; Pre-treating the aluminum oxide to obtain a first aluminum oxide powder; Grinding the first alumina powder to obtain a second alumina powder; The second alumina powder is fired to obtain spherical α-alumina powder.

2. The method for preparing spherical α-alumina powder according to claim 1, characterized in that: The alumina obtained is nano alumina with a γ-Al2O3 crystal form.

3. The method for preparing spherical α-alumina powder according to claim 2, characterized in that: Pre-treating the alumina to obtain a first alumina powder comprises: Pour the aluminum oxide into a mixed solution of water and alcohol and stir; After the stirring process is completed, nitric acid is added to the mixed solution, and heating and stirring are performed; After the reaction is completed, the solid matter in the mixed solution is filtered and washed to obtain the first alumina powder.

4. The method for preparing spherical α-alumina powder according to claim 3, characterized in that: The volume ratio of alumina, water and alcohol is 2:2:0.05; The stirring time is 5 minutes.

5. The method for preparing spherical α-alumina powder according to claim 3, characterized in that: The concentration of the nitric acid is 65%; The mass ratio of aluminum oxide to 65% nitric acid is 100:(0.7-1.5); The heating temperature for heating and stirring was 60° C., and the heating and stirring time was 1 hour.

6. The method for preparing spherical α-alumina powder according to claim 2, characterized in that: Grinding the first alumina powder to obtain a second alumina powder comprises: The first alumina powder, boric acid and mixing balls are wet mixed to obtain a second alumina powder.

7. The method for preparing spherical α-alumina powder according to claim 6, characterized in that: The mass ratio of alumina, boric acid and mixing balls is 100:(0.5-1.0):50; The wet mixing time is 20-40 minutes.

8. The method for preparing spherical α-alumina powder according to claim 2, characterized in that: The firing is carried out using a rotary kiln; Material temperature is 1500-1600℃; The flame temperature is 1800-2000℃; The material comes into direct contact with the flame.

9. A thermally conductive material, characterized in that: The invention comprises spherical alpha alumina powder prepared by the preparation method according to any one of claims 1 to 8.

10. A power battery, characterized in that: Comprising the thermally conductive material as claimed in claim 9.

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