Alumina for thermally conductive fillers and method for its preparation

Abstract

The application discloses an alumina for heat-conducting filler and a preparation method thereof. The preparation method comprises the following steps: S1, purifying industrial crystallized aluminum chloride to obtain a purified aluminum chloride solution; S2, adding urea and a surfactant into the purified aluminum chloride solution to perform a reaction, and then adding ammonia water to adjust the pH of the reaction solution to be alkaline; S3, heating the solution of S2 to perform a reaction, and then washing, drying and calcining the product to obtain an alumina powder; and S4, treating the alumina powder of S3 by a surface treatment agent to obtain the alumina for heat-conducting filler. The method for purifying the industrial crystallized aluminum chloride in S1 comprises the following steps: S11, calcining the industrial crystallized aluminum chloride, and then adding hydrochloric acid to perform a reaction; and S12, drying and calcining the product after the reaction, and then adding hydrochloric acid to dissolve the product to obtain the purified aluminum chloride solution. The application improves the heat-conducting performance of the alumina, and the prepared alumina has a smaller particle size and a more uniform distribution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting fillers, in particular to an alumina for heat-conducting fillers and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electronic components, the demand for heat-conducting materials is also increasing. Materials with good heat-conducting performance can efficiently transfer heat to the heat dissipation unit, thereby ensuring the normal use of electronic components and prolonging the service life of electronic components.

[0003] At present, the commonly used heat-conducting materials mainly add heat-conducting fillers to the materials, and alumina is the mainstream heat-conducting filler. In the existing patents, different particle sizes of alumina are compounded and added to the materials to improve the heat-conducting performance. The alumina is in the shape of a sphere or a sphere-like shape. Although the alumina has high strength and electrical insulation, the thermal conductivity of the alumina is low. How to process the alumina to improve the heat-conducting performance of the alumina is a problem to be solved in the field. SUMMARY

[0004] Based on the technical problems existing in the background technology, the present application provides an alumina for heat-conducting fillers and a preparation method thereof, which improves the heat-conducting performance of the alumina and the particle size of the prepared alumina is smaller and more uniform.

[0005] The preparation method of the alumina for heat-conducting fillers provided by the present application has the following steps:

[0006] S1: purifying industrial crystalline aluminum chloride to obtain a purified aluminum chloride solution;

[0007] S2: adding urea and a surfactant to the purified aluminum chloride solution of S1 for reaction, and then adding ammonia water to adjust the pH of the reaction solution to alkaline;

[0008] S3: heating the solution of S2 for reaction, and then washing, drying and calcining the product to obtain alumina powder;

[0009] S4: treating the alumina powder of S3 with a surface treatment agent to obtain the alumina for heat-conducting fillers.

[0010] Preferably, the method steps of purifying the industrial crystalline aluminum chloride in S1 are as follows:

[0011] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid for dissolution;

[0012] S12: drying and calcining the dissolved product, and then adding hydrochloric acid for dissolution to obtain the purified aluminum chloride solution.

[0013] Preferably, the calcination temperature in S11 is 450-550 DEG C, the time is 3-5h; the mass ratio of hydrochloric acid to industrial crystalline aluminum chloride is 1:2-4; the reaction temperature is 180-220 DEG C, and the time is 6-12h.

[0014] Preferably, the calcination temperature in S12 is 700-800 DEG C, the time is 1-2h; the mass-volume ratio of hydrochloric acid to the product after calcination is 1g:10-15mL; and the dissolving temperature is 180-220 DEG C.

[0015] Preferably, the mass ratio of aluminum chloride, urea and surfactant in S2 is 1:5-10:0.05-0.15; and the surfactant is composed of tetradecyl methyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphate betaine with a mass ratio of 3:1-10.

[0016] Preferably, the reaction temperature in S2 is 80-100 DEG C, the time is 10-20min, and the adjusted pH is 9-10.

[0017] Preferably, the reaction temperature in S3 is 150-170 DEG C, the time is 5-10h; the calcination temperature is 800-1000 DEG C, and the time is 1-2h.

[0018] Preferably, the amount of surface treatment agent used in S4 is 1-5% of the mass of the alumina powder; and the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate with a mass ratio of 1:0.5-2.

[0019] The above method prepares the heat-conducting filler alumina.

[0020] The application of the heat-conducting filler alumina in heat-conducting materials.

[0021] The beneficial technical effects of the application are as follows:

[0022] (1) The heat-conducting filler alumina prepared by the application has smaller particle size and more uniform distribution because the treatment of the aluminum chloride solution by the surfactant can form steric hindrance on the particle surface, thereby reducing the agglomeration between particles, and the surfactant is composed of tetradecyl methyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphate betaine, which has a synergistic effect on improving the purity and reducing the particle size of the alumina.

[0023] (2) The application further processes the calcined alumina powder through a surface treatment agent, thereby improving the thermal conductivity of the alumina powder, because the alumina powder treated through the surface treatment agent has more heat conduction channels, thereby being capable of more efficiently transferring heat, and the surface treatment agent of the application is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate, and also has a synergistic effect on improving the heat conduction performance of the alumina powder. DETAILED DESCRIPTION

[0024] The hydrochloric acid has a concentration of 18% and is commercially available; the polyisobutylene succinic anhydride triethanolamine is purchased from Jinzhou Shengda Chemical Co., Ltd.; the dehydrated xylitol monooleate is purchased from Jiangsu Maoheng Chemical Co., Ltd.; the tetradecyl methyl dihydroxyethyl ammonium bromide is purchased from Shanghai Yiji Industry Co., Ltd.; and the dodecyl hydroxypropyl phosphatidyl betaine is purchased from Hangzhou Tuomo Technology Co., Ltd.

[0025] Example 1

[0026] The preparation method of the alumina for heat-conducting fillers provided by the application has the following steps:

[0027] S1: purifying industrial crystalline aluminum chloride to obtain a purified aluminum chloride solution, and the specific steps are as follows:

[0028] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid to dissolve the calcined product;

[0029] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve the calcined product, thereby obtaining the purified aluminum chloride solution.

[0030] S2: adding urea and a surfactant to the purified aluminum chloride solution obtained in S1 to react, and then adding ammonia water to adjust the pH of the reaction solution to alkaline;

[0031] S3: heating the solution obtained in S2 to react, and then washing, drying and calcining the product after the reaction, thereby obtaining an alumina powder;

[0032] S4: treating the alumina powder obtained in S3 through a surface treatment agent, thereby obtaining the alumina for heat-conducting fillers.

[0033] In S11, the calcining temperature is 500 DEG C, and the time is 4 h; the mass ratio of hydrochloric acid to industrial crystalline aluminum chloride is 1:3; and the dissolution temperature is 200 DEG C, and the time is 9 h.

[0034] In S12, the calcining temperature is 750 DEG C, and the time is 2 h; the mass-volume ratio of hydrochloric acid to the calcined product is 1 g:12 ml; and the reaction temperature is 200 DEG C.

[0035] The mass ratio of aluminum chloride, urea and surfactant in S2 is 1:8:0.1; the surfactant is composed of tetradecylmethyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphate betaine according to a mass ratio of 1:1; the reaction temperature in S2 is 85 DEG C, the reaction time is 18 min, and the adjusted pH is 9.

[0036] The reaction temperature in S3 is 160 DEG C, and the reaction time is 8 h; the calcination temperature is 900 DEG C, and the calcination time is 1.5 h.

[0037] The amount of the surface treatment agent used in S4 is 3% of the mass of the aluminum oxide powder; the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate according to a mass ratio of 1:1.

[0038] Example 2

[0039] The preparation method of the aluminum oxide for heat-conducting filler provided by the application comprises the following steps:

[0040] S1: purifying the industrial crystalline aluminum chloride to obtain a purified aluminum chloride solution, and the specific steps are as follows:

[0041] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid to dissolve the product;

[0042] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve the product, thereby obtaining the purified aluminum chloride solution.

[0043] S2: adding urea and a surfactant to the purified aluminum chloride solution obtained in S1 to react, and then adding ammonia water to adjust the pH of the reaction solution to alkaline;

[0044] S3: heating and reacting the solution obtained in S2, and then washing, drying and calcining the product, thereby obtaining the aluminum oxide powder;

[0045] S4: treating the aluminum oxide powder obtained in S3 by using a surface treatment agent, thereby obtaining the aluminum oxide for heat-conducting filler.

[0046] The calcination temperature in S11 is 450 DEG C, and the calcination time is 3 h; the mass ratio of hydrochloric acid to the industrial crystalline aluminum chloride is 1:2; the dissolution temperature is 180 DEG C, and the dissolution time is 6 h.

[0047] The calcination temperature in S12 is 700 DEG C, and the calcination time is 1 h; the mass ratio of hydrochloric acid to the calcined product is 1 g:10 ml; and the dissolution temperature is 180 DEG C.

[0048] The mass ratio of aluminum chloride, urea and surfactant in S2 is 1:5:0.05; the surfactant is composed of tetradecylmethyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphate betaine according to a mass ratio of 3:1; the reaction temperature in S2 is 80 DEG C, the reaction time is 10 min, and the adjusted pH is 9.

[0049] The temperature of the reaction in S3 is 150 DEG C, and the time is 5h; the temperature of the calcination is 800 DEG C, and the time is 1h.

[0050] The amount of the surface treatment agent used in S4 is 1% of the mass of the alumina powder; the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate in a mass ratio of 2:1.

[0051] Example 3

[0052] The preparation method of the alumina for heat-conducting fillers provided by the application comprises the following steps:

[0053] S1: purifying industrial crystalline aluminum chloride to obtain a purified aluminum chloride solution, and the specific steps are as follows:

[0054] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid to dissolve the product;

[0055] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve the product, thereby obtaining the purified aluminum chloride solution.

[0056] S2: adding urea and a surfactant to the purified aluminum chloride solution obtained in S1 to react, and then adding ammonia water to adjust the pH of the reaction solution to be alkaline;

[0057] S3: heating the solution obtained in S2 to react, and then washing, drying and calcining the product to obtain an alumina powder;

[0058] S4: treating the alumina powder obtained in S3 by using a surface treatment agent, thereby obtaining the alumina for heat-conducting fillers.

[0059] The temperature of the calcination in S11 is 550 DEG C, and the time is 5h; the mass ratio of hydrochloric acid to the industrial crystalline aluminum chloride is 1:4; the dissolution temperature is 220 DEG C, and the time is 12h.

[0060] The temperature of the calcination in S12 is 800 DEG C, and the time is 2h; the mass ratio of hydrochloric acid to the calcined product is 1g:15ml; the dissolution temperature is 220 DEG C.

[0061] The mass ratio of the aluminum chloride, urea and the surfactant in S2 is 1:10:0.15; the surfactant is composed of tetradecylmethyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphobetaine in a mass ratio of 1:3; the temperature of the reaction in S2 is 100 DEG C, and the time is 20min; and the adjusted pH is 10.

[0062] The temperature of the reaction in S3 is 170 DEG C, and the time is 10h; the temperature of the calcination is 1000 DEG C, and the time is 2h.

[0063] The amount of surface treatment agent in S4 is 5% of the mass of the aluminum oxide powder; the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate at a mass ratio of 1:2.

[0064] Comparative Example 1

[0065] The preparation method of the aluminum oxide for heat-conducting fillers provided in the present application has the following steps:

[0066] S1: purifying industrial crystalline aluminum chloride to obtain a purified aluminum chloride solution, and the specific steps are as follows:

[0067] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid to dissolve the product;

[0068] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve the product, thereby obtaining the purified aluminum chloride solution.

[0069] S2: adding urea and a surfactant to the purified aluminum chloride solution obtained in S1 to react, and then adding ammonia water to adjust the pH of the reaction solution to alkaline;

[0070] S3: heating the solution obtained in S2 to react, and then washing, drying and calcining the product to obtain aluminum oxide powder;

[0071] S4: treating the aluminum oxide powder obtained in S3 with a surface treatment agent, thereby obtaining the aluminum oxide for heat-conducting fillers.

[0072] In S11, the calcination temperature is 500℃, and the time is 4h; the mass ratio of hydrochloric acid to industrial crystalline aluminum chloride is 1:3; the dissolution temperature is 200℃, and the time is 9h.

[0073] In S12, the calcination temperature is 750℃, and the time is 2h; the mass ratio of hydrochloric acid to the calcined product is 1g:12ml; the dissolution temperature is 200℃.

[0074] In S2, the mass ratio of aluminum chloride, urea and the surfactant is 1:8:0.1; the surfactant is tetradecylmethyl dihydroxyethyl ammonium bromide; the reaction temperature in S2 is 85℃, the time is 18min, and the adjusted pH is 9.

[0075] In S3, the reaction temperature is 160℃, and the time is 8h; the calcination temperature is 900℃, and the time is 1.5h.

[0076] In S4, the amount of the surface treatment agent is 3% of the mass of the aluminum oxide powder; the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate at a mass ratio of 1:1.

[0077] Comparative Example 2

[0078] The application discloses a preparation method of aluminum oxide for heat-conducting fillers.

[0079] S1: purifying industrial crystallized aluminum chloride to obtain a purified aluminum chloride solution, and the specific steps are as follows:

[0080] S11: calcining the industrial crystallized aluminum chloride, and then adding hydrochloric acid to dissolve the calcined product;

[0081] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve the calcined product, so that the purified aluminum chloride solution is obtained.

[0082] S2: adding urea and a surfactant into the purified aluminum chloride solution obtained in S1 to react, and then adding ammonia water to adjust the pH of the reaction solution to be alkaline;

[0083] S3: heating the solution obtained in S2 to react, and then washing, drying and calcining the product, so that the aluminum oxide powder is obtained;

[0084] S4: treating the aluminum oxide powder obtained in S3 by using a surface treatment agent, so that the aluminum oxide for heat-conducting fillers is obtained.

[0085] In S11, the calcining temperature is 500 DEG C, and the time is 4h; the mass ratio of hydrochloric acid to the industrial crystallized aluminum chloride is 1:3; the dissolving temperature is 200 DEG C, and the time is 9h.

[0086] In S12, the calcining temperature is 750 DEG C, and the time is 2h; the mass ratio of hydrochloric acid to the calcined product is 1g:12ml; and the dissolving temperature is 200 DEG C.

[0087] In S2, the mass ratio of aluminum chloride, urea and the surfactant is 1:8:0.1; the surfactant is dodecyl hydroxypropyl phosphatidyl betaine; the reaction temperature in S2 is 85 DEG C, the time is 18min, and the adjusted pH is 9.

[0088] In S3, the reaction temperature is 160 DEG C, and the time is 8h; the calcining temperature is 900 DEG C, and the time is 1.5h.

[0089] In S4, the surface treatment agent is used in an amount of 3% of the mass of the aluminum oxide powder; and the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate in a mass ratio of 1:1.

[0090] Comparative Example 3

[0091] The application discloses a preparation method of aluminum oxide for heat-conducting fillers.

[0092] S1: purifying industrial crystallized aluminum chloride to obtain a purified aluminum chloride solution, and the specific steps are as follows:

[0093] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid to dissolve;

[0094] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve, to obtain the purified aluminum chloride solution.

[0095] S2: adding urea and a surfactant to the purified aluminum chloride solution obtained in S1 to react, and then adding ammonia water to adjust the pH of the reaction solution to be alkaline;

[0096] S3: heating the solution obtained in S2 to react, and then washing, drying and calcining the product to obtain the aluminum oxide powder;

[0097] S4: treating the aluminum oxide powder obtained in S3 by a surface treatment agent, to obtain the aluminum oxide for the heat-conducting filler.

[0098] In S11, the calcining temperature is 500 DEG C, and the time is 4 h; the mass ratio of hydrochloric acid to the industrial crystalline aluminum chloride is 1:3; the dissolving temperature is 200 DEG C, and the time is 9 h.

[0099] In S12, the calcining temperature is 750 DEG C, and the time is 2 h; the mass ratio of hydrochloric acid to the calcined product is 1 g:12 ml; the dissolving temperature is 200 DEG C.

[0100] In S2, the mass ratio of aluminum chloride, urea and the surfactant is 1:8:0.1; the surfactant is composed of tetradecylmethyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphatidyl betaine at a mass ratio of 1:1; the reaction temperature in S2 is 85 DEG C, the time is 18 min, and the adjusted pH is 9.

[0101] In S3, the reaction temperature is 160 DEG C, and the time is 8 h; the calcining temperature is 900 DEG C, and the time is 1.5 h.

[0102] In S4, the amount of the surface treatment agent used is 3% of the mass of the aluminum oxide powder; and the surface treatment agent is polyisobutylene succinic anhydride triethanolamine.

[0103] Comparative Example 4

[0104] The preparation method of the aluminum oxide for the heat-conducting filler provided by the application comprises the following steps:

[0105] S1: purifying the industrial crystalline aluminum chloride to obtain the purified aluminum chloride solution, and the specific steps are as follows:

[0106] S11: calcining the industrial crystalline aluminum chloride, and then adding hydrochloric acid to dissolve;

[0107] S12: drying and calcining the dissolved product, and then adding hydrochloric acid to dissolve, to obtain the purified aluminum chloride solution.

[0108] S2: urea and surfactant are added into the purified aluminum chloride solution in S1 to react, and then ammonia is added to adjust the pH of the reaction solution to alkaline;

[0109] S3: the solution in S2 is heated to react, and the product is washed, dried and calcined to obtain aluminum oxide powder;

[0110] S4: the aluminum oxide powder in S3 is treated by a surface treatment agent to obtain the aluminum oxide for heat-conducting filler.

[0111] In S11, the calcination temperature is 500℃, and the time is 4h; the mass ratio of hydrochloric acid to industrial crystalline aluminum chloride is 1:3; the dissolution temperature is 200℃, and the time is 9h.

[0112] In S12, the calcination temperature is 750℃, and the time is 2h; the mass ratio of hydrochloric acid to the product after calcination is 1g:12ml; the dissolution temperature is 200℃.

[0113] In S2, the mass ratio of aluminum chloride, urea and surfactant is 1:8:0.1; the surfactant is composed of tetradecylmethyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphate betaine in a mass ratio of 1:1; the reaction temperature in S2 is 85℃, the time is 18min, and the adjusted pH is 9.

[0114] In S3, the reaction temperature is 160℃, and the time is 8h; the calcination temperature is 900℃, and the time is 1.5h.

[0115] In S4, the amount of the surface treatment agent used is 3% of the mass of the aluminum oxide powder; the surface treatment agent is anhydrous xylitol monooleate.

[0116] The particle size of the aluminum oxide for heat-conducting filler prepared in Example 1 and Comparative Examples 1-4 and the thermal conductivity of the composite material are determined, and the results are shown in Table 1. The composite material is the aluminum oxide prepared in Example 1 and Comparative Examples 1-4 filled into the epoxy resin at a filling amount of 50%, and the rest of the test conditions are the same.

[0117] Table 1: Test of particle size of aluminum oxide and thermal conductivity of composite material

[0118] Group Alumina particle size D 50 (μm) Thermal conductivity of composite (W / m·K) Example 1 4 1.18 Comparative Example 1 8 1.12 Comparative Example 2 11 1.09 Comparative Example 3 4 0.83 Comparative Example 4 5 0.75

[0119] As can be seen from the test data of Example 1 in Table 1, the alumina used for preparing the heat-conductive filler prepared by the present application has a smaller particle size, and the composite material prepared by using the filler has a larger thermal conductivity, because the surfactant added in the present application can form steric hindrance on the surface of the particles, thereby reducing the agglomeration between the particles, and the heat-conductive filler with smaller particle size is beneficial to be filled in the epoxy resin, and can form a close heat-conductive circuit in the epoxy resin, thereby being able to more efficiently transfer heat. In addition, as can be seen from the test results of Example 1 and Comparative Examples 1 and 2, the alumina used for preparing the heat-conductive filler in the present application has such a small particle size mainly because the surfactant in the present application is composed of tetradecylmethyl dihydroxyethyl ammonium bromide and dodecyl hydroxypropyl phosphobetaine, which have a synergistic effect on improving the purity of alumina and reducing the particle size of alumina. As can be seen from the test results of Example 1 and Comparative Examples 3 and 4, the surface treatment agent polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate in the present application have a synergistic effect on improving the heat-conductive performance of alumina powder, and the prepared alumina powder has good compatibility with the resin, reduces the interfacial thermal resistance, and improves the heat-conductive effect, so that the composite material prepared by using the alumina used for preparing the heat-conductive filler as the filler has a larger thermal conductivity.

[0120] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing alumina as a thermally conductive filler, characterized in that, The steps are as follows: S1: Purify industrial crystalline aluminum chloride to obtain a purified aluminum chloride solution; S2: Urea and surfactant are added to the aluminum chloride solution purified in S1 to react, and then ammonia is added to adjust the pH of the reaction solution to alkaline. S3: The solution of S2 is heated to react, and the product after the reaction is washed, dried and calcined to obtain alumina powder; S4: Alumina powder of S3 is treated with a surface treatment agent to obtain alumina for thermally conductive filler; In S2, the mass ratio of aluminum chloride, urea, and surfactant is 1:5-10:0.05-0.15; the surfactant is composed of tetradecylmethyldihydroxyethylammonium bromide and dodecyl hydroxypropyl phosphate betaine in a mass ratio of 3:1-10. The surface treatment agent used in S4 is 1-5% of the mass of alumina powder; the surface treatment agent is composed of polyisobutylene succinic anhydride triethanolamine and dehydrated xylitol monooleate in a mass ratio of 1:0.5-2.

2. The method for preparing alumina for thermally conductive filler according to claim 1, characterized in that, The purification steps for industrial crystalline aluminum chloride in S1 are as follows: S11: Industrial crystalline aluminum chloride is calcined and then dissolved in hydrochloric acid; S12: The dissolved product is dried and calcined, and then dissolved in hydrochloric acid to obtain a purified aluminum chloride solution.

3. The method for preparing alumina for thermally conductive filler according to claim 2, characterized in that, The calcination temperature of S11 is 450-550℃, and the time is 3-5h; the mass ratio of hydrochloric acid to industrial crystalline aluminum chloride in S11 is 1:2-4; the dissolution temperature of S11 is 180-220℃, and the time is 6-12h.

4. The method for preparing alumina for thermally conductive filler according to claim 2, characterized in that, The calcination temperature of S12 is 700-800℃, and the time is 1-2h; the mass-volume ratio of hydrochloric acid in S12 to the calcined product is 1g:10-15mL; the dissolution temperature of S12 is 180-220℃.

5. The method for preparing alumina for thermally conductive filler according to claim 1, characterized in that, The reaction temperature in S2 is 80-100℃, the time is 10-20 min, and the adjusted pH is 9-10.

6. The method for preparing alumina for thermally conductive filler according to claim 1, characterized in that, The reaction temperature in S3 is 150-170℃, and the time is 5-10h; the calcination temperature is 800-1000℃, and the time is 1-2h.

7. Alumina for thermally conductive filler prepared by the method according to any one of claims 1-6.

8. The application of alumina as described in claim 7 in thermally conductive materials.