Spherical powder with high filling rate and high thermal conductivity and preparation method thereof

Abstract

The invention provides high-filling-rate and high-thermal-conductivity spherical powder and a preparation method thereof, and belongs to the technical field of high-thermal-conductivity spherical powder. The preparation method comprises the steps of magnesium oxide slurry preparation, magnesium salt solution preparation, spray granulation and calcination. The step of preparing the magnesium oxide slurry comprises the following steps: mixing light magnesium oxide powder, dead burned magnesium oxide powder, deionized water, nano aluminum oxide, carbon nanotubes and an additive I, and carrying out vacuum stirring to obtain the magnesium oxide slurry; the additive I is prepared from a PVA (Polyvinyl Alcohol) solution, magnesium stearate, glycerol and gamma-methacryloxy propyl trimethoxy silane; the high-filling-rate high-thermal-conductivity spherical powder prepared by the preparation method disclosed by the invention is controllable in particle size of 1-100 microns, high in sphericity degree, good in mechanical strength and stable in temperature resistance and chemical resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of high thermal conductivity spherical powders, and particularly relates to a high filling rate and high thermal conductivity spherical powder and a preparation method thereof. Background Art

[0002] With the rapid development of modern technology, numerous industries have put forward more stringent requirements for material properties. High filling rate and high thermal conductivity spherical powders have emerged as the times require, and they play an irreplaceable and important role in many key fields; in the fields of electronic devices, energy storage, and aerospace, efficient heat dissipation is always a key factor to ensure the stable operation of equipment.

[0003] For a long time, alumina thermal conductive powders, boron nitride thermal conductive powders, etc. have been widely used, but the following problems generally exist: First, the morphology of the thermal conductive powder is irregular, resulting in insufficient packing density of the powder in the substrate, and the filling amount is usually less than 50wt%, which limits the formation of the heat conduction path; second, the hydrophilicity and hydrophobicity of the surface of the thermal conductive powder do not match the substrate, and the interfacial bonding force is poor, resulting in an increase in the interfacial thermal resistance; third, the brittleness of the thermal conductive powder is high, it is easy to crack under thermal cycling, and the mechanical strength is low, thus reducing the long-term stability performance.

[0004] Magnesium oxide has a relatively high thermal conductivity, and its thermal conductivity coefficient is better than that of alumina, and it can transfer heat more quickly and effectively. Moreover, the raw materials for preparing magnesium oxide powder are widely sourced, and the preparation process is relatively simple, and it has greater potential for large-scale popularization and application.

[0005] For the existing preparation methods of magnesium oxide thermal conductive powders, the sol-gel method, hydrothermal method, precipitation method, and traditional spray drying method are usually adopted; The sol-gel method forms a sol by hydrolysis of the precursor, and then obtains spherical powders through gelation and calcination. However, it is difficult to control the particle size uniformity and the yield is low; the hydrothermal method synthesizes spherical particles in a high-temperature and high-pressure aqueous solution, which has high requirements for equipment, a long reaction time, and it is difficult to achieve a wide range of particle size regulation; the precipitation method generates a precipitate by reacting magnesium nitrate and other salt substances with an alkaline solution, and then obtains magnesium oxide through calcination. However, the product is prone to agglomeration, the sphericity is low, and the filler is limited by the single particle size; the traditional spray drying method sprays and dries the precursor solution and then calcines it. The obtained powder has a rough surface, insufficient sphericity, low filling rate, and it is difficult to achieve a dense structure.

[0006] Therefore, providing a magnesium oxide thermal conductive powder with a dense and smooth surface, high sphericity and filling rate, excellent thermal conductivity, controllable particle size in the range of 1-100μm, high mechanical strength, and stable temperature resistance and chemical resistance is a technical problem that the existing technology urgently needs to solve. Summary of the Invention

[0007] To solve the technical problems existing in the prior art, the present invention provides a high-fill-ratio and high-thermal-conductivity spherical powder and its preparation method. The particle size is controllable within 1 - 100 μm, the sphericity is high, and the mechanical strength is good, and the temperature resistance and chemical resistance are stable.

[0008] In view of the above technical problems, the present invention adopts the following technical solutions: A preparation method of a high-fill-ratio and high-thermal-conductivity spherical powder, comprising the steps of preparing a magnesium oxide slurry, preparing a magnesium salt solution, spray granulation, and calcination. The specific operations are as follows: 1. Preparation of magnesium oxide slurry Mix light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, carbon nanotubes, and additive 1, put them into a vacuum stirring tank, stir at a speed of 760 - 830 r / min at 78 - 82 °C for 5.8 - 6.5 hours, and control the vacuum degree to be -0.09~-0.05 MPa to obtain a magnesium oxide slurry; The light magnesium oxide powder has a purity of 98.0 - 99.0% and a particle size of 0.1 - 1 μm; The dead-burned magnesium oxide powder has a purity of 96.5 - 97.0% and a particle size of 5 - 10 μm; The nano-aluminum oxide has a particle size of 1 - 100 nm; The carbon nanotubes have a particle size of 1 - 50 nm; The mass ratio of the light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, and carbon nanotubes is 10 - 28:20 - 25:50 - 60:1.5 - 3.0:0.5 - 2.0; The addition amount of additive 1 in the magnesium oxide slurry is 1.0 - 3.0 wt%; Additive 1 is composed of a PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane. The mass ratio of the PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane is 0.6 - 1.0:0.4 - 0.6:0.3 - 0.7:0.2 - 0.4.

[0009] 2. Preparation of magnesium salt solution Mix deionized water, magnesium chloride, magnesium sulfate, magnesium nitrate, and additive 2, stir at a speed of 290 - 310 r / min for 27 - 35 minutes, then place it in a sealed tank and keep it warm in an oven at 98 - 105 °C for 11 - 13 hours to obtain a magnesium salt solution with a viscosity of 50 - 80 mPa·S; The mass ratio of the deionized water, magnesium chloride, magnesium sulfate, and magnesium nitrate is 20 - 70:20 - 40:5 - 25:5 - 15; The addition amount of the second additive in the magnesium salt solution is 3.0 - 5.0 wt%; The second additive is composed of OP emulsifier, polyvinylpyrrolidone, and oxalic acid, and the mass ratio of the OP emulsifier, polyvinylpyrrolidone, and oxalic acid is 4.8 - 5.2:0.1:1.3 - 1.7.

[0010] 3. Spray granulation Mix the magnesium oxide slurry and the magnesium salt solution, and stir at a normal temperature of 780 - 820 r / min for 0.8 - 1.3 hours to obtain the slurry to be spray granulated; perform spray granulation on the slurry to be spray granulated, control the inlet temperature to be 195 - 205 °C, the outlet temperature to be 85 - 95 °C, the nozzle aperture to be 0.4 - 0.6 mm, and the centrifugal rotation speed to be 14000 - 16000 r / min to obtain spherical powder; The mass ratio of the magnesium oxide slurry to the magnesium salt solution is 1:1.0 - 1.4.

[0011] 4. Calcination Calcine the spherical magnesium oxide powder in a nitrogen atmosphere, heat it up to 1350 - 1450 °C at a rate of 4.5 - 5.5 °C / min, and keep it warm for 1.8 - 2.3 h to obtain high - filling - rate and high - thermal - conductivity spherical powder.

[0012] A high - filling - rate and high - thermal - conductivity spherical powder is prepared by the foregoing preparation method.

[0013] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. In the magnesium oxide slurry of the present invention, under the action of nano - alumina and carbon nanotubes, the interior of the spherical magnesium oxide obtains a toughening effect, improving the toughness and thermal shock resistance of the spherical magnesium oxide. For the first additive such as magnesium stearate, glycerol, γ - methacryloxypropyltrimethoxysilane, etc., their organic functional groups react with the surface of the magnesium oxide powder to form stable chemical bonds. This chemical bond not only enhances the strength of the magnesium oxide powder, but also, under the action of the silyl group, makes the magnesium oxide powder have a certain hydrophobicity, making the surface of the spherical magnesium oxide in a mirror state, enhancing the interfacial bonding force between the powder and the substrate, and improving the overall thermal conductivity; in the magnesium salt solution, under the action of additives such as oxalic acid, nano - magnesium salt particles with a certain proportion are formed in the magnesium salt solution, and the magnesium salt solution has a certain viscosity under the action of the OP emulsifier; in the preparation method of the spherical powder, when the magnesium oxide slurry is mixed with the magnesium salt solution, the nano - magnesium salt particles fill the gaps on the surface of the magnesium oxide powder, and the magnesium salt solution with a certain viscosity coats the surface of the magnesium oxide, forming a dense and smooth surface. After spray granulation and firing, magnesium oxide powder with a mirror state, high sphericity, high filling amount, and high thermal conductivity is formed; 2. The high - filling - rate and high - thermal - conductivity spherical powder of the present invention has a particle size of 1 - 100 μm; 3. The high-fill-ratio and high-thermal-conductivity spherical powder of the present invention has a sphericity > 98%, a fill ratio reaching 76 - 85%, a thermal conductivity of 37 - 50 W / (m·K), and a compressive strength of 41.5 - 50.6 MPa; 4. The high-fill-ratio and high-thermal-conductivity spherical powder of the present invention, when heat-insulated at 1300 °C for 20 h in an air atmosphere, has a compressive strength of 39.4 - 48.4 MPa; when immersed in a 15 wt% hydrochloric acid solution with a mass three times that of the powder for 48 h, the mass loss rate is 0.42 - 0.58%. Brief Description of the Drawings

[0014] Figure 1 SEM image of the high-fill-ratio and high-thermal-conductivity spherical powder prepared in Example 2 at 1400 times magnification; Figure 2 SEM image of the high-fill-ratio and high-thermal-conductivity spherical powder prepared in Example 2 at 300 times magnification; Figure 3 SEM image of the high-fill-ratio and high-thermal-conductivity spherical powder prepared in the comparative example at 1700 times magnification. Detailed Description of the Invention

[0015] To better understand the technical features, objectives, and effects of the present invention, the specific implementation manners of the present invention are described below.

[0016] Example 1 1. Preparation of magnesium oxide slurry Mix light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, carbon nanotubes, and additive 1, and place them in a vacuum stirring tank. Stir at 78 °C at a speed of 760 r / min for 6.5 hours, and control the vacuum degree to -0.09 MPa to obtain magnesium oxide slurry; The light magnesium oxide powder has a purity of 98.0% and a particle size of 0.1 um; The dead-burned magnesium oxide powder has a purity of 96.5% and a particle size of 5 um; The nano-aluminum oxide has a particle size of 100 nm; The carbon nanotubes have a particle size of 1 nm; The mass ratio of the light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, and carbon nanotubes is 10:20:50:1.5:0.5; The addition amount of additive 1 in the magnesium oxide slurry is 1.0 wt%; Additive 1 is composed of a PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane, and the mass ratio of the PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane is 0.6:0.4:0.3:0.2.

[0017] 2. Preparation of magnesium salt solution Mix deionized water, magnesium chloride, magnesium sulfate, magnesium nitrate and additive II, stir at a speed of 290 r / min for 35 minutes, then place it in a sealed tank and keep it warm in an oven at 98 °C for 13 hours to obtain a magnesium salt solution with a viscosity of 50 mPa·S; The mass ratio of the deionized water, magnesium chloride, magnesium sulfate, and magnesium nitrate is 20:20:5:5; The addition amount of additive II in the magnesium salt solution is 3.0 wt%; The additive II is composed of OP emulsifier, polyvinylpyrrolidone, and oxalic acid, and the mass ratio of the OP emulsifier, polyvinylpyrrolidone, and oxalic acid is 4.8:0.1:1.3.

[0018] 3. Spray granulation Mix the magnesium oxide slurry and the magnesium salt solution, stir at room temperature at a speed of 780 r / min for 1.3 hours to obtain the slurry to be spray granulated; perform spray granulation on the slurry to be spray granulated, control the inlet temperature at 195 °C, the outlet temperature at 85 °C, the nozzle aperture at 0.4 mm, and the centrifugal rotation speed at 14000 r / min to obtain spherical powder; The mass ratio of the magnesium oxide slurry and the magnesium salt solution is 1:1.0.

[0019] 4. Calcination Calcine the spherical magnesium oxide powder in a nitrogen atmosphere, heat it up to 1350 °C at a rate of 4.5 °C / min, and keep it warm for 1.8 h to obtain a spherical powder with high filling rate and high thermal conductivity.

[0020] The spherical powder with high filling rate and high thermal conductivity prepared by the method of Example 1 has a sphericity of 98.3%, a filling rate of 76%, a thermal conductivity of 37 W / (m·K), and a compressive strength of 41.5 MPa; in an air atmosphere, after heat preservation treatment at 1300 °C for 20 h, the compressive strength is 39.4 MPa; after soaking in a 15 wt% hydrochloric acid solution with 3 times the mass for 48 h, the mass loss rate is 0.58%.

[0021] Example 2 1. Preparation of magnesium oxide slurry Mix light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, carbon nanotubes and additive I, put them into a vacuum stirring tank, stir at 800 r / min at 80 °C for 6.0 hours, and control the vacuum degree at -0.07 MPa to obtain a magnesium oxide slurry; The light magnesium oxide powder has a purity of 99.0% and a particle size of 0.5 um; The dead-burned magnesium oxide powder has a purity of 97.0% and a particle size of 8 um; The particle size of the nano-aluminum oxide is 40 nm; The particle size of the carbon nanotubes is 20 nm; The mass ratio of the light magnesium oxide powder, dead-burned magnesia powder, deionized water, nano-aluminum oxide, and carbon nanotubes is 20:22:54:2.2:1.5; The addition amount of the first additive in the magnesia slurry is 2.0 wt%; The first additive is composed of a PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane, and the mass ratio of the PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane is 0.8:0.5:0.5:0.3.

[0022] 2. Preparation of magnesium salt solution Mix deionized water, magnesium chloride, magnesium sulfate, magnesium nitrate, and the second additive, stir at a speed of 300 r / min for 30 minutes, then place it in a sealed tank, and keep it warm in an oven at 100 °C for 12 hours to obtain a magnesium salt solution with a viscosity of 60 mPa·S; The mass ratio of the deionized water, magnesium chloride, magnesium sulfate, and magnesium nitrate is 50:30:16:10; The addition amount of the second additive in the magnesium salt solution is 4.0 wt%; The second additive is composed of an OP emulsifier, polyvinylpyrrolidone, and oxalic acid, and the mass ratio of the OP emulsifier, polyvinylpyrrolidone, and oxalic acid is 5:0.1:1.5.

[0023] 3. Spray granulation Mix the magnesia slurry and the magnesium salt solution, stir at room temperature at a speed of 800 r / min for 1.0 hour to obtain a slurry to be spray-granulated; perform spray granulation on the slurry to be spray-granulated, control the inlet temperature to be 200 °C, the outlet temperature to be 90 °C, the nozzle aperture to be 0.5 mm, and the centrifugal rotation speed to be 15000 r / min to obtain spherical powder; The mass ratio of the magnesia slurry and the magnesium salt solution is 1:1.2.

[0024] 4. Calcination Calcine the spherical magnesium oxide powder in a nitrogen atmosphere, heat it up to 1400 °C at a rate of 5.0 °C / min, and keep it warm for 2.0 h to obtain a spherical powder with high filling rate and high thermal conductivity.

[0025] The spherical powder with high filling rate and high thermal conductivity prepared by the method of Example 2 has a sphericity of 99.6%, a filling rate of 85%, a thermal conductivity of 50 W / (m·K), and a compressive strength of 50.6 MPa; in an air atmosphere, after heat preservation treatment at 1300 °C for 20 h, the compressive strength is 48.4 MPa; after soaking in 3 times the mass of 15 wt% hydrochloric acid solution for 48 h, the mass loss rate is 0.42%.

[0026] Example 3 1. Preparation of magnesium oxide slurry Mix light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, carbon nanotubes and additive 1, put them into a vacuum stirring tank, stir at a speed of 830 r / min at 82 °C for 5.8 hours, and control the vacuum degree to be -0.05 MPa to obtain magnesium oxide slurry; The light magnesium oxide powder has a purity of 98.5% and a particle size of 1 μm; The dead-burned magnesium oxide powder has a purity of 96.8% and a particle size of 10 μm; The nano-aluminum oxide has a particle size of 1 nm; The carbon nanotubes have a particle size of 50 nm; The mass ratio of the light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-aluminum oxide, and carbon nanotubes is 28:25:60:3.0:2.0; The addition amount of additive 1 in the magnesium oxide slurry is 3.0 wt%; Additive 1 is composed of PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane. The mass ratio of the PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane is 1.0:0.6:0.7:0.4.

[0027] 2. Preparation of magnesium salt solution Mix deionized water, magnesium chloride, magnesium sulfate, magnesium nitrate and additive 2, stir at a speed of 310 r / min for 27 minutes, then place it in a sealed tank and keep it warm in an oven at 105 °C for 11 hours to obtain a magnesium salt solution with a viscosity of 80 mPa·S; The mass ratio of the deionized water, magnesium chloride, magnesium sulfate, and magnesium nitrate is 70:40:25:15; The addition amount of additive 2 in the magnesium salt solution is 5.0 wt%; Additive 2 is composed of OP emulsifier, polyvinylpyrrolidone, and oxalic acid. The mass ratio of the OP emulsifier, polyvinylpyrrolidone, and oxalic acid is 5.2:0.1:1.7.

[0028] 3. Spray granulation Mix the magnesium oxide slurry and the magnesium salt solution, stir at room temperature at a speed of 820 r / min for 0.8 hours to obtain the slurry to be sprayed; perform spray granulation on the slurry to be sprayed, control the inlet temperature to be 205 °C, the outlet temperature to be 95 °C, the nozzle aperture to be 0.6 mm, and the centrifugal rotation speed to be 16,000 r / min to obtain spherical powder; The mass ratio of the magnesium oxide slurry and the magnesium salt solution is 1:1.4.

[0029] 4. Calcination The spherical magnesium oxide powder is calcined under a nitrogen atmosphere. It is heated to 1450 °C at a rate of 5.5 °C / min and held for 2.3 h to obtain a spherical powder with high filling rate and high thermal conductivity.

[0030] The spherical powder with high filling rate and high thermal conductivity prepared by the method of Example 3 has a sphericity of 99.2%, a filling rate of 80%, a thermal conductivity of 45 W / (m·K), and a compressive strength of 47.3 MPa; in an air atmosphere, after heat preservation treatment at 1300 °C for 20 h, the compressive strength is 45.1 MPa; when immersed in a 15 wt% hydrochloric acid solution with 3 times the mass for 48 h, the mass loss rate is 0.46%.

[0031] Comparative Example Based on Example 2, the following changes are made: 1. In the step of preparing the magnesium oxide slurry, the carbon nanotube component is equally replaced with light magnesium oxide powder, and the first additive is equally replaced with dead-burned magnesium oxide powder; the light magnesium oxide powder has a purity of 99.0% and a particle size of 0.5 μm; the dead-burned magnesium oxide powder has a purity of 97.0% and a particle size of 8 μm; the rest of the operations remain unchanged; 2. In the step of preparing the magnesium salt, the second additive is equally replaced with deionized water, and the rest of the operations remain unchanged; 3. The spray granulation step and the calcination step are exactly the same as those in Example 2.

[0032] The product obtained in the comparative example has a sphericity of 82.5%, a filling rate of 64%, a thermal conductivity of 30 W / (m·K), and a compressive strength of 35.2 MPa; in an air atmosphere, after heat preservation treatment at 1300 °C for 20 h, the compressive strength is 28.3 MPa; when immersed in a 15 wt% hydrochloric acid solution with 3 times the mass for 48 h, the mass loss rate is 2.4%.

[0033] Unless otherwise specified, the ratios described in the present invention are all mass ratios, and the percentages are all mass percentages.

[0034] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a spherical powder with high filling rate and high thermal conductivity, characterized in that: The method comprises the steps of preparing magnesium oxide slurry, preparing magnesium salt solution, spray granulation and calcination; The step of preparing the magnesium oxide slurry is to mix light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-alumina, carbon nanotubes and an additive, and perform vacuum stirring to obtain magnesium oxide slurry; The additive 1 is composed of PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane; The step of preparing the magnesium salt solution is to mix deionized water, magnesium chloride, magnesium sulfate, magnesium nitrate and the second additive, stir them evenly, place them in a sealed tank, and keep them warm at 98-105° C. to obtain a magnesium salt solution with a viscosity of 50-80 mPa·S; The second additive is composed of OP emulsifier, polyvinyl pyrrolidone and oxalic acid.

2. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: In the step of preparing magnesium oxide slurry, the vacuum stirring is performed at a stirring temperature of 78-82° C., a stirring speed of 760-830 r / min, a stirring time of 5.8-6.5 hours, and a vacuum degree of -0.09 to -0.05 MPa.

3. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: In the step of preparing magnesium oxide slurry, the light magnesium oxide powder has a purity of 98.0-99.0% and a particle size of 0.1-1um; The dead-burned magnesium oxide powder has a purity of 96.5-97.0% and a particle size of 5-10 um; The particle size of the nano-alumina is 1-100 nm; The particle size of the carbon nanotubes is 1-50 nm; The mass ratio of the light magnesium oxide powder, dead-burned magnesium oxide powder, deionized water, nano-alumina and carbon nanotubes is 10-28:20-25:50-60:1.5-3.0:0.5-2.0; The amount of the additive 1 added to the magnesium oxide slurry is 1.0-3.0wt%.

4. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: In the additive 1, the mass ratio of the PVA solution, magnesium stearate, glycerol, and γ-methacryloxypropyltrimethoxysilane is 0.6-1.0:0.4-0.6:0.3-0.7:0.2-0.

4.

5. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: In the step of preparing magnesium salt, the mass ratio of deionized water, magnesium chloride, magnesium sulfate and magnesium nitrate is 20-70:20-40:5-25:5-15; The amount of the second additive added to the magnesium salt solution is 3.0-5.0wt%.

6. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: In the second admixture, the mass ratio of the OP emulsifier, polyvinyl pyrrolidone and oxalic acid is 4.8-5.2:0.1:1.3-1.

7.

7. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: The spray granulation step comprises: mixing magnesium oxide slurry and magnesium salt solution, stirring at room temperature for 0.8-1.3 hours at a speed of 780-820 r / min to obtain slurry to be sprayed; spraying granulating the slurry to be sprayed, controlling the inlet temperature to be 195-205° C., the outlet temperature to be 85-95° C., the nozzle aperture to be 0.4-0.6 mm, and the centrifugal speed to be 14000-16000 r / min to obtain spherical powder; The mass ratio of the magnesium oxide slurry to the magnesium salt solution is 1:1.0-1.

4.

8. The method for preparing a spherical powder with high filling rate and high thermal conductivity according to claim 1, characterized in that: The calcination step comprises calcining the spherical magnesium oxide powder in a nitrogen atmosphere, heating the temperature to 1350-1450° C. at a rate of 4.5-5.5° C. / min, and keeping the temperature for 1.8-2.3 hours to obtain a spherical powder with a high filling rate and high thermal conductivity.

9. A spherical powder with high filling rate and high thermal conductivity, prepared by the preparation method according to any one of claims 1 to 8.

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