A method for preparing high-sphericity silicon nitride powder

Abstract

The present invention provides a method for preparing silicon nitride powder with high sphericity, belonging to the field of inorganic non-metallic material preparation. The present invention utilizes countless nano-scale oil-in-water microemulsion systems in a W / O type microemulsion as independent "microreactors" to allow the hydrolysis of chlorosilane to proceed in tiny water cores, thereby obtaining silicon dioxide with small particle size and high sphericity; then, a water-soluble carbon source is uniformly coated on the surface of the spherical silicon dioxide, carbonized to form amorphous carbon-coated silicon dioxide, and subjected to in-situ carbon thermal reduction so that the morphology of the generated spherical silicon nitride is controlled by the morphology of the silicon dioxide, thereby improving the sphericity of the silicon nitride; by performing carbon thermal reduction under high-pressure nitrogen, the solubility of the raw material is increased, so that the silicon nitride grows uniformly on the spherical surface instead of growing into a columnar shape along a fixed direction, thereby improving the sphericity of the silicon nitride. Experimental results show that the sphericity of the silicon nitride powder prepared by the preparation method provided by the present invention is above 0.85.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic material preparation, in particular to a method for preparing high-sphericity silicon nitride powder. Background Art

[0002] With the miniaturization of integrated circuits and the increase in operating frequency, heat dissipation has become a major issue restricting their development. Ceramic particle-reinforced polymer-based composites are currently commonly used materials for electronic packaging and thermal interfaces. This is because polymers themselves have low thermal conductivity and are often filled with thermally conductive ceramic particles to improve their thermal conductivity. Among the many ceramic materials, silicon nitride is increasingly used as a filler ceramic particle to improve the thermal conductivity of polymers due to its excellent thermal conductivity and electrical insulation properties.

[0003] Silicon nitride exists in two phases, α and β, under normal conditions. β-Silicon nitride tends to grow into a rod-like structure along the c-axis. However, this rod-like structure results in insufficient filling density when silicon nitride particles are used as fillers, leading to low thermal conductivity in polymer-based composites. Spherical filler particles, on the other hand, can increase the filling density while maintaining a low viscosity, thereby improving the thermal conductivity of polymer-based composites.

[0004] Therefore, how to improve the sphericity of silicon nitride powder has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for preparing silicon nitride powder with high sphericity. The silicon nitride powder prepared by the preparation method provided by the present invention has high sphericity.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing high-sphericity silicon nitride powder, comprising the following steps:

[0008] (1) mixing oil, emulsifier and water for emulsification to obtain a W / O type microemulsion;

[0009] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) to carry out a hydrolysis reaction to obtain spherical silica;

[0010] (3) mixing the spherical silica obtained in step (2) with a water-soluble carbon source and water, and then drying and carbonizing the mixture to obtain amorphous carbon-coated silica;

[0011] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbon thermal reduction reaction in high-pressure nitrogen to obtain a powder;

[0012] (5) Decarburizing the powder obtained in step (4) to obtain silicon nitride powder with high sphericity.

[0013] Preferably, the molar ratio of water to emulsifier in step (1) is (5-7):1.

[0014] Preferably, the mass ratio of oil to emulsifier in step (1) is (6-10):1.

[0015] Preferably, the amount ratio of water in step (1) to the amount of chlorosilane in step (2) is (1-4):1.

[0016] Preferably, the addition rate of chlorosilane in step (2) is 15 to 25 g / min.

[0017] Preferably, the hydrolysis reaction time in step (2) is 1 to 5 hours.

[0018] Preferably, in step (3), the molar ratio of the spherical silica to the water-soluble carbon source is 1:(0.5-2).

[0019] Preferably, the carbonization temperature in step (3) is 450-500° C., and the carbonization time is 2-8 hours.

[0020] Preferably, the pressure of the high-pressure nitrogen in step (4) is 1 to 3 MPa.

[0021] Preferably, the temperature of the carbothermal reduction reaction in step (4) is 1200-1500° C., and the time of the carbothermal reduction reaction is 1-8 hours.

[0022] The present invention provides a method for preparing high-sphericity silicon nitride powder, comprising: (1) mixing oil, an emulsifier and water for emulsification to obtain a W / O type microemulsion; (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) for hydrolysis reaction to obtain spherical silicon dioxide; (3) mixing the spherical silicon dioxide obtained in step (2) with a water-soluble carbon source and water, and then drying and carbonizing the mixture in sequence to obtain amorphous carbon-coated silicon dioxide; (4) subjecting the amorphous carbon-coated silicon dioxide obtained in step (3) to a carbon thermal reduction reaction in high-pressure nitrogen to obtain powder; and (5) decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder. The present invention utilizes numerous nanoscale water-in-oil microemulsion systems in a W / O microemulsion as independent "microreactors" to allow the hydrolysis of chlorosilane to proceed in tiny water cores, thereby obtaining silicon dioxide with small particle size and high sphericity; a water-soluble carbon source is then uniformly coated on the surface of the spherical silicon dioxide, carbonized to form amorphous carbon-coated silicon dioxide, and subjected to in-situ carbon thermal reduction so that the morphology of the generated spherical silicon nitride is controlled by the morphology of the silicon dioxide, thereby improving the sphericity of the silicon nitride; by performing carbon thermal reduction under high-pressure nitrogen, the solubility of the raw material is increased, so that the silicon nitride grows uniformly on the spherical surface rather than growing into a columnar shape along a fixed direction, thereby improving the sphericity of the silicon nitride. The experimental results of the embodiment show that the sphericity of the silicon nitride powder prepared by the preparation method provided by the present invention is above 0.85. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing high-sphericity silicon nitride powder, comprising the following steps:

[0024] (1) mixing oil, emulsifier and water for emulsification to obtain a W / O type microemulsion;

[0025] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) to carry out a hydrolysis reaction to obtain spherical silica;

[0026] (3) mixing the spherical silica obtained in step (2) with a water-soluble carbon source and water, and then drying and carbonizing the mixture to obtain amorphous carbon-coated silica;

[0027] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbon thermal reduction reaction in high-pressure nitrogen to obtain a powder;

[0028] (5) Decarburizing the powder obtained in step (4) to obtain silicon nitride powder with high sphericity.

[0029] Unless otherwise specified, the present invention has no particular limitation on the sources of the raw materials used, and commercially available products known to those skilled in the art may be used.

[0030] The present invention emulsifies oil, an emulsifier, and water to produce a W / O microemulsion. The present invention utilizes an emulsifier to emulsify the oil and water, allowing the emulsifier to surround the water phase and disperse within the continuous oil phase, resulting in a water-in-oil microemulsion. This microemulsion contains numerous water-in-oil microemulsion systems. The enclosed water cores within the microemulsions act as independent "microreactors," allowing controlled reactions within the water cores. The resulting silica is uniformly dispersed, has a small particle size, and is highly spherical.

[0031] In the present invention, the mass ratio of the oil to the emulsifier is preferably (6-10):1, more preferably (7-9):1, and even more preferably 8:1. By controlling the ratio of the oil to the emulsifier, the present invention can promote sufficient emulsification of the oil phase and water to obtain a water-in-oil microemulsion.

[0032] In the present invention, the oil preferably includes one or more of n-hexane, cyclohexane and n-heptane.

[0033] In the present invention, the emulsifier preferably includes one or more of SPAN emulsifiers, OP-10, TWEEN emulsifiers and polyoxyethylene ether emulsifiers.

[0034] In the present invention, the molar ratio of water to emulsifier is preferably (5-7):1, more preferably 6:1. In the present invention, the particle size of the silica particles increases with the increase in the ratio of water to emulsifier. By controlling the ratio of the two within the above range, the water core of the microemulsion can be of an appropriate size to accommodate an appropriate amount of chlorosilane for hydrolysis reaction, while further improving the sphericity of the silica particles.

[0035] In the present invention, the oil, emulsifier, and water are preferably mixed by first mixing the oil and emulsifier and then stirring, and then adding water dropwise under stirring. In the present invention, the stirring time after mixing the oil and emulsifier is preferably 10 to 30 minutes, more preferably 15 to 25 minutes.

[0036] In the present invention, the water drop rate is preferably 15 to 25 g / min, more preferably 20 g / min. By controlling the water drop rate, the present invention can promote emulsification and obtain a uniform microemulsion.

[0037] In the present invention, the emulsification is preferably carried out under ultrasonic conditions. The present invention has no particular limitation on the operation of the ultrasound, and any ultrasound parameters well known to those skilled in the art can be used to obtain a microemulsion.

[0038] After obtaining a W / O microemulsion, the present invention adds chlorosilane to the W / O microemulsion to carry out a hydrolysis reaction, thereby obtaining spherical silica. The present invention adds chlorosilane to the W / O microemulsion, allowing the chlorosilane to enter the microemulsion system for hydrolysis, and controls the morphology of the silica through the microemulsion system, thereby obtaining silica with high sphericity.

[0039] In the present invention, the molar ratio of water to chlorosilane is preferably (1-4):1, more preferably (2-3):1. In the present invention, the particle size of the silica particles increases as the ratio of water to chlorosilane increases. By controlling the ratio of the water to chlorosilane, the present invention can keep the ratio of water to chlorosilane in a single microreactor within an appropriate range, thereby promoting the hydrolysis of chlorosilane, obtaining silica particles with a suitable particle size, and further improving the sphericity of the silica particles.

[0040] In the present invention, the addition rate of the chlorosilane is preferably 15 to 25 g / min, more preferably 20 g / min. By controlling the addition rate of the chlorosilane, the hydrolysis rate of the chlorosilane is adjusted, which facilitates the entry of the chlorosilane into the microemulsion system for hydrolysis, thereby further improving the sphericity of the silica particles.

[0041] In the present invention, the hydrolysis reaction time is preferably 1 to 5 hours, more preferably 2 to 4 hours, and most preferably 3 hours. In the present invention, the hydrolysis reaction is preferably carried out at room temperature. In the present invention, the hydrolysis reaction begins when the chlorosilane is added to the W / O microemulsion.

[0042] After the hydrolysis reaction is completed, the present invention preferably separates, washes, and dries the product of the hydrolysis reaction in sequence to obtain spherical silica. The present invention is not particularly limited to the separation, washing, and drying operations, as long as the solid product can be separated from the liquid to obtain dry spherical silica.

[0043] After obtaining the spherical silica, the present invention mixes the spherical silica with a water-soluble carbon source and water, and then sequentially performs drying and carbonization to obtain amorphous carbon-coated silica.

[0044] In the present invention, the molar ratio of the spherical silica to the water-soluble carbon source is preferably 1:(0.5-2), more preferably 1:(0.8-1.8), and most preferably 1:(1-1.5). By controlling the ratio of silica to carbon source, the present invention can improve the efficiency of the carbothermal reduction reaction, promote the in-situ reduction of silica to silicon nitride, and further improve the sphericity of the silicon nitride.

[0045] In the present invention, the water-soluble carbon source preferably includes one or more of glucose, maltose, water-soluble starch and sucrose.

[0046] In the present invention, the mass ratio of the water-soluble carbon source to water is preferably (3-5):(4-6). The present invention can fully dissolve the water-soluble carbon source by controlling the amount of water, thereby uniformly coating the spherical silica.

[0047] In the present invention, the mixing of the spherical silica with the water-soluble carbon source and water is preferably carried out under stirring conditions; the stirring is preferably carried out by first stirring at room temperature for 30 to 40 minutes, then heating to 70 to 90°C and stirring for 20 to 30 minutes. The present invention does not particularly limit the stirring rate, and technical solutions familiar to those skilled in the art can be used. By controlling the stirring mode, the present invention further promotes thorough mixing of the various materials and ensures that the water-soluble carbon source is evenly coated on the surface of the spherical silica.

[0048] In the present invention, the drying temperature is preferably 100-110°C, more preferably 105°C; the drying time is preferably 12-24 hours, more preferably 16-20 hours. By controlling the drying temperature and time, the present invention can remove water from the mixed system while ensuring that the carbon source is uniformly coated on the silica surface.

[0049] In the present invention, the carbonization temperature is preferably 450-500°C, more preferably 460-480°C; the carbonization time is preferably 2-8h, more preferably 4-6h. In the present invention, the heating rate for heating to the carbonization temperature is preferably 10-20°C / min, more preferably 15°C / min. In the present invention, the carbonization is preferably carried out in a nitrogen atmosphere. The present invention can carbonize the water-soluble carbon source in situ on the surface of silica by controlling the carbonization method, and obtain amorphous carbon-coated silica without changing the structure.

[0050] After obtaining the amorphous carbon-coated silica, the present invention performs a carbothermal reduction reaction on the amorphous carbon-coated silica in high-pressure nitrogen to obtain a powder. The present invention utilizes high-pressure nitrogen to increase the solubility of the raw materials and silicon nitride in the liquid phase, allowing for in-situ carbothermal reduction of the silica to produce silicon nitride particles with high sphericity.

[0051] In the present invention, the pressure of the high-pressure nitrogen is preferably 1-3 MPa, more preferably 2 MPa. The present invention controls the rate of the nitridation reaction by controlling the nitrogen pressure, so that the silicon nitride grows uniformly on the spherical surface, avoids growing into rods along a fixed direction, and further improves the sphericity of the product.

[0052] In the present invention, the temperature of the carbothermal reduction reaction is preferably 1200-1500°C, more preferably 1250-1450°C, and most preferably 1300-1400°C; the time of the carbothermal reduction reaction is preferably 1-8 hours, more preferably 2-7 hours, and most preferably 3-6 hours. In the present invention, during the carbothermal reduction reaction, silicon dioxide reacts with carbon and nitrogen to produce silicon nitride and carbon dioxide / carbon monoxide. By controlling the temperature and time of the carbothermal reduction reaction, the morphology of the silicon nitride can be precisely controlled, thereby improving the sphericity.

[0053] In the present invention, the carbothermal reduction reaction is preferably carried out in a high-pressure tube furnace.

[0054] After obtaining the powder, the present invention decarburizes the powder to obtain silicon nitride powder with high sphericity.

[0055] In the present invention, the decarburization temperature is preferably 700-800°C, more preferably 750°C; the decarburization time is preferably 1-3 hours, more preferably 2 hours. By controlling the decarburization temperature and time, the present invention can fully remove unreacted carbon and improve product purity.

[0056] The present invention utilizes numerous nano-scale water-in-oil microemulsion systems in a W / O type microemulsion as independent "microreactors" to allow the hydrolysis of chlorosilane to proceed in tiny water cores, thereby obtaining silicon dioxide with small particle size and high sphericity. A water-soluble carbon source is then uniformly coated on the surface of the spherical silicon dioxide, carbonized to form amorphous carbon-coated silicon dioxide, and subjected to in-situ carbothermal reduction so that the morphology of the generated spherical silicon nitride is controlled by the morphology of the silicon dioxide, thereby improving the sphericity of the silicon nitride. Carbothermal reduction is performed under high-pressure nitrogen to increase the solubility of the raw material, so that the silicon nitride grows uniformly on the spherical surface instead of growing into columns along a fixed direction, thereby improving the sphericity of the silicon nitride.

[0057] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. The embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0058] Example 1

[0059] A method for preparing high-sphericity silicon nitride powder comprises the following steps:

[0060] (1) Cyclohexane and OP-10 were first mixed and ultrasonically stirred for 30 minutes, and then water was added dropwise at a rate of 20 g / min under ultrasonic stirring to obtain a W / O type microemulsion; the mass ratio of the cyclohexane to the OP-10 was 10:1; and the molar ratio of the water to the OP-10 was 7:1;

[0061] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) at a rate of 20 g / min to carry out a hydrolysis reaction for 3 hours, and then separating, washing and drying in sequence to obtain spherical silica; the molar ratio of water to chlorosilane is 4:1;

[0062] (3) The spherical silica obtained in step (2) was stirred and mixed with glucose and water at room temperature for 30 minutes, then heated to 90° C. and stirred and mixed for 20 minutes, and the obtained mixture was dried at 105° C. for 12 hours to obtain water-soluble carbon-coated silica; under a nitrogen atmosphere, the water-soluble carbon-coated silica was heated to 450° C. at a heating rate of 15° C. / min and carbonized for 5 hours to obtain amorphous carbon-coated silica;

[0063] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbothermal reduction reaction in high-pressure nitrogen to obtain a powder; the pressure of the high-pressure nitrogen is 3 MPa; the temperature of the carbothermal reduction reaction is 1300° C., and the time of the carbothermal reduction reaction is 3 hours;

[0064] (5) Decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder; the decarburization temperature is 750° C., and the decarburization time is 2 h.

[0065] The high-sphericity silicon nitride powder prepared in this example was tested and found to have a particle size of 90-100 nm and a sphericity of 9.

[0066] Example 2

[0067] A method for preparing high-sphericity silicon nitride powder comprises the following steps:

[0068] (1) Cyclohexane and OP-10 were first mixed and ultrasonically stirred for 30 minutes, and then water was added dropwise at a rate of 20 g / min under ultrasonic stirring to obtain a W / O type microemulsion; the mass ratio of the cyclohexane to the OP-10 was 8:1; and the molar ratio of the water to the OP-10 was 6:1;

[0069] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) at a rate of 20 g / min to carry out a hydrolysis reaction for 3 hours, and then separating, washing and drying in sequence to obtain spherical silica; the molar ratio of water to chlorosilane is 4:1;

[0070] (3) The spherical silica obtained in step (2) was stirred and mixed with glucose and water at room temperature for 30 minutes, then heated to 90° C. and stirred and mixed for 20 minutes, and the obtained mixture was dried at 105° C. for 12 hours to obtain water-soluble carbon-coated silica; under a nitrogen atmosphere, the water-soluble carbon-coated silica was heated to 450° C. at a heating rate of 15° C. / min and carbonized for 5 hours to obtain amorphous carbon-coated silica;

[0071] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbothermal reduction reaction in high-pressure nitrogen to obtain a powder; the pressure of the high-pressure nitrogen is 3 MPa; the temperature of the carbothermal reduction reaction is 1300° C., and the time of the carbothermal reduction reaction is 3 hours;

[0072] (5) Decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder; the decarburization temperature is 750° C., and the decarburization time is 2 h.

[0073] The high-sphericity silicon nitride powder prepared in this example was tested and found to have a particle size of 80-90 nm and a sphericity of 9.2.

[0074] Example 3

[0075] A method for preparing high-sphericity silicon nitride powder comprises the following steps:

[0076] (1) Cyclohexane and OP-10 were first mixed and ultrasonically stirred for 30 minutes, and then water was added dropwise at a rate of 20 g / min under ultrasonic stirring to obtain a W / O type microemulsion; the mass ratio of the cyclohexane to the OP-10 was 8:1; and the molar ratio of the water to the OP-10 was 5:1;

[0077] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) at a rate of 20 g / min to carry out a hydrolysis reaction for 3 hours, and then separating, washing and drying in sequence to obtain spherical silica; the molar ratio of water to chlorosilane is 3:1;

[0078] (3) The spherical silica obtained in step (2) was stirred and mixed with glucose and water at room temperature for 30 minutes, then heated to 90° C. and stirred and mixed for 20 minutes, and the obtained mixture was dried at 105° C. for 12 hours to obtain water-soluble carbon-coated silica; under a nitrogen atmosphere, the water-soluble carbon-coated silica was heated to 450° C. at a heating rate of 15° C. / min and carbonized for 5 hours to obtain amorphous carbon-coated silica;

[0079] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbothermal reduction reaction in high-pressure nitrogen to obtain a powder; the pressure of the high-pressure nitrogen is 3 MPa; the temperature of the carbothermal reduction reaction is 1300° C., and the time of the carbothermal reduction reaction is 3 hours;

[0080] (5) Decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder; the decarburization temperature is 750° C., and the decarburization time is 2 h.

[0081] The high-sphericity silicon nitride powder prepared in this example was tested and found to have a particle size of 60 to 80 nm and a sphericity of 9.3.

[0082] Example 4

[0083] A method for preparing high-sphericity silicon nitride powder comprises the following steps:

[0084] (1) Cyclohexane and OP-10 were first mixed and ultrasonically stirred for 30 minutes, and then water was added dropwise at a rate of 20 g / min under ultrasonic stirring to obtain a W / O type microemulsion; the mass ratio of the cyclohexane to the OP-10 was 7:1; and the molar ratio of the water to the OP-10 was 5:1;

[0085] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) at a rate of 20 g / min to carry out a hydrolysis reaction for 3 hours, and then separating, washing and drying in sequence to obtain spherical silica; the molar ratio of water to chlorosilane is 2:1;

[0086] (3) The spherical silica obtained in step (2) was stirred and mixed with glucose and water at room temperature for 30 minutes, then heated to 90° C. and stirred and mixed for 20 minutes, and the obtained mixture was dried at 105° C. for 12 hours to obtain water-soluble carbon-coated silica; under a nitrogen atmosphere, the water-soluble carbon-coated silica was heated to 450° C. at a heating rate of 15° C. / min and carbonized for 5 hours to obtain amorphous carbon-coated silica;

[0087] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbothermal reduction reaction in high-pressure nitrogen to obtain a powder; the pressure of the high-pressure nitrogen is 3 MPa; the temperature of the carbothermal reduction reaction is 1300° C., and the time of the carbothermal reduction reaction is 3 hours;

[0088] (5) Decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder; the decarburization temperature is 750° C., and the decarburization time is 2 h.

[0089] The high-sphericity silicon nitride powder prepared in this example was tested and found to have a particle size of 40 to 60 nm and a sphericity of 9.5.

[0090] Example 5

[0091] (1) Cyclohexane and OP-10 were first mixed and ultrasonically stirred for 30 minutes, and then water was added dropwise at a rate of 20 g / min under ultrasonic stirring to obtain a W / O type microemulsion; the mass ratio of the cyclohexane to the OP-10 was 8:1; and the molar ratio of the water to the OP-10 was 5:1;

[0092] (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) at a rate of 20 g / min to carry out a hydrolysis reaction for 3 hours, and then separating, washing and drying in sequence to obtain spherical silica; the molar ratio of water to chlorosilane is 3:1;

[0093] (3) The spherical silica obtained in step (2) was stirred and mixed with glucose and water at room temperature for 30 minutes, then heated to 90° C. and stirred and mixed for 20 minutes, and the obtained mixture was dried at 105° C. for 12 hours to obtain water-soluble carbon-coated silica; under a nitrogen atmosphere, the water-soluble carbon-coated silica was heated to 450° C. at a heating rate of 15° C. / min and carbonized for 5 hours to obtain amorphous carbon-coated silica;

[0094] (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbothermal reduction reaction in high-pressure nitrogen to obtain a powder; the pressure of the high-pressure nitrogen is 2 MPa; the temperature of the carbothermal reduction reaction is 1400° C., and the time of the carbothermal reduction reaction is 4 hours;

[0095] (5) Decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder; the decarburization temperature is 750° C., and the decarburization time is 2 h.

[0096] The high-sphericity silicon nitride powder prepared in this example was tested and found to have a particle size of 30 to 50 nm and a sphericity of 8.8.

[0097] It can be seen from the above examples that the silicon nitride prepared by the carbothermal reduction nitridation method provided by the present invention has a very high sphericity.

[0098] The above is only 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. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing high-sphericity silicon nitride powder, characterized in that: The steps are: (1) Cyclohexane and OP-10 were first mixed and ultrasonically stirred for 30 minutes, and then water was added dropwise at a rate of 20 g / min under ultrasonic stirring to obtain a W / O type microemulsion; the mass ratio of the cyclohexane to the OP-10 was 7:1; and the molar ratio of the water to the OP-10 was 5:1; (2) adding chlorosilane to the W / O type microemulsion obtained in step (1) at a rate of 20 g / min to carry out a hydrolysis reaction for 3 hours, and then separating, washing and drying in sequence to obtain spherical silica; the molar ratio of water to chlorosilane is 2:1; (3) The spherical silica obtained in step (2) was stirred and mixed with glucose and water at room temperature for 30 minutes, then heated to 90° C. and stirred and mixed for 20 minutes, and the obtained mixture was dried at 105° C. for 12 hours to obtain water-soluble carbon-coated silica; under a nitrogen atmosphere, the water-soluble carbon-coated silica was heated to 450° C. at a heating rate of 15° C. / min and carbonized for 5 hours to obtain amorphous carbon-coated silica; (4) subjecting the amorphous carbon-coated silica obtained in step (3) to a carbothermal reduction reaction in high-pressure nitrogen to obtain a powder; the pressure of the high-pressure nitrogen is 3 MPa; the temperature of the carbothermal reduction reaction is 1300° C., and the time of the carbothermal reduction reaction is 3 hours; (5) Decarburizing the powder obtained in step (4) to obtain high-sphericity silicon nitride powder; the decarburization temperature is 750° C., and the decarburization time is 2 h.