Silicon carbide powder as well as preparation method and application thereof

Abstract

The invention relates to silicon carbide powder as well as a preparation method and application thereof. Comprising the following steps: mixing silicon powder with negative charges and graphite powder with positive charges to obtain a mixture; and heating the mixture to enable the silicon powder with the negative charges and the graphite powder with the positive charges to react, so as to prepare the silicon carbide powder. The relatively compact and uniform structure formed by electrostatic self-assembly of the positively charged silicon powder and the negatively charged graphite powder is beneficial to self-propagating reaction synthesis of silicon carbide, so that the reaction is more sufficient, the carbon wrapping of the silicon carbide powder is reduced, and a foundation is laid for subsequent preparation of high-quality SiC substrate wafers or SiC-based devices.

Description

Technical Field

[0001] The present application relates to the field of semiconductor material technology, and in particular to a silicon carbide powder and a preparation method and application thereof. Background Art

[0002] As an important third-generation semiconductor material, silicon carbide (SiC) exhibits excellent performance in high temperature, high frequency, high power, radiation resistance, etc. SiC substrate wafers are at the foundation of the SiC industry chain, and high-quality and low-carbon coated silicon carbide powder is essential for the preparation of good substrate wafers.

[0003] At present, the industry mainly uses the self-propagating high-temperature solid-phase synthesis method to produce silicon carbide powder. However, unlike the liquid phase method, it is difficult to avoid the carbon inclusion phenomenon in silicon carbide powder synthesized by the solid phase method. On the one hand, the relative atomic mass of carbon is less than that of silicon, and the silicon particles are larger than the carbon powder, which makes it very easy for carbon powder and silicon powder to be separated during the crucible loading process. The carbon powder is light in weight and small in particle size, and is greatly affected by air resistance, resulting in an imbalance in the carbon-silicon stoichiometric ratio, which in turn leads to serious carbon inclusion in the generated silicon carbide powder. On the other hand, when the PVT method is used to prepare silicon carbide single crystals, carbon inclusion is extremely harmful to crystal growth. After the outermost layer of silicon carbide decomposes and sublimates, the carbon powder exposed inside diffuses to the surface of the SiC crystal due to Brownian motion, causing carbon inclusion in the crystal and producing more defects.

[0004] Therefore, the traditional technology still needs to be improved. Summary of the invention

[0005] Based on this, the present application provides a silicon carbide powder with a low carbon encapsulation amount and a preparation method and application thereof.

[0006] The specific technical solutions are as follows:

[0007] The first aspect of the present application provides a method for preparing silicon carbide powder, comprising the following steps:

[0008] Mixing negatively charged silicon powder and positively charged graphite powder to obtain a mixture;

[0009] The mixed material is subjected to a temperature-raising treatment to allow the negatively charged silicon powder and the positively charged graphite powder to react to prepare silicon carbide powder.

[0010] The method for preparing silicon carbide powder of the present application has the following beneficial effects:

[0011] In the preparation method of the silicon carbide powder of the present application, firstly, negatively charged silicon powder and positively charged graphite powder are mixed to obtain a mixture, and the electrostatic self-assembly effect can effectively promote the uniform mixing of negatively charged silicon powder and positively charged graphite powder, and reduce the stratification phenomenon caused by differences in density and particle size. Then the mixture is heated to make the negatively charged silicon powder and the positively charged graphite powder react to prepare silicon carbide powder, because the relatively tight and uniform structure formed by the electrostatic self-assembly of the positively charged silicon powder and the negatively charged graphite powder is conducive to the self-propagating reaction to synthesize silicon carbide, so that the reaction is more sufficient, the carbon encapsulation of the silicon carbide powder is reduced, and the foundation is laid for the subsequent preparation of high-quality SiC substrate wafers or SiC-based devices.

[0012] In some embodiments, the negatively charged silicon powder includes protonated silicon powder.

[0013] In some embodiments, the surface charge of the negatively charged silicon powder has a zeta potential of -7mV to -10mV, and the surface charge of the positively charged graphite powder has a zeta potential of 12mV to 16mV;

[0014] And / or, the molar ratio of the positively charged graphite powder to the negatively charged silicon powder is 1:1-1.04.

[0015] In some of the embodiments, a step of preparing negatively charged silicon powder is further included, which comprises the following steps: protonating the silicon powder with an acid solution to obtain negatively charged silicon powder;

[0016] And / or, the method further comprises the step of preparing graphite powder with positive charge, which comprises the following steps: subjecting the graphite powder to radiation treatment to obtain graphite powder with positive charge.

[0017] In some embodiments, the acid in the acid solution includes one or more of nitric acid, sulfuric acid and hydrochloric acid;

[0018] And / or, based on the total mass of the acid solution and the silicon powder, the mass fraction of the acid solution is 20% to 40%;

[0019] And / or, the protonation treatment time is 1h~5h;

[0020] And / or, the radiation treatment includes at least one of thermal radiation and light radiation.

[0021] In some embodiments, the temperature of the thermal radiation is 80°C to 260°C, the time of the thermal radiation is 2h to 6h, and the pressure of the thermal radiation is 50Pa to 600Pa;

[0022] The wavelength of the light radiation is 100nm~400nm;

[0023] And / or, the light source of the light radiation includes any one of UVA, UVB, UVC and UVD.

[0024] In some embodiments, the step of irradiating the graphite powder to obtain the graphite powder with positive charge comprises:

[0025] Mixing a fluorine-containing reagent and the graphite powder to obtain an intermediate mixture, wherein the fluorine-containing reagent includes at least one of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, fluorinated ethylene-propylene copolymer and polyvinylidene fluoride;

[0026] The intermediate mixture is subjected to radiation treatment to prepare positively charged graphite powder.

[0027] In some embodiments, the temperature treatment conditions include: in a protective gas atmosphere at a pressure of 5000Pa to 20000Pa, heating to 2000°C to 2400°C at a heating rate of 1°C to 10°C per minute for 15h to 20h;

[0028] And / or, after the step of heating the mixed material and before the step of preparing the silicon carbide powder, the method further includes the steps of successively cooling, crushing, oxidizing and screening the product after the heating treatment.

[0029] A second aspect of the present application provides a silicon carbide powder, which is prepared by the method for preparing the silicon carbide powder as described above.

[0030] The third aspect of the present application provides a use of the above-mentioned silicon carbide powder in the preparation of SiC crystals or ceramic refractory materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the Zeta potential diagram of the carbon powder and silicon powder in Example 1. DETAILED DESCRIPTION

[0032] For ease of understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application are provided. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0033] The implementation of this application is described in detail below in combination with some implementation methods and examples. This example is implemented based on the technical solution of this application, and provides a detailed implementation method and specific operation process, but the protection scope of this application is not limited to the following examples.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0035] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0036] In the present application, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0037] In the present application, the terms "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0038] In the present application, "room temperature" generally refers to 4°C to 35°C, preferably 20°C ± 5°C. In some embodiments of the present application, room temperature refers to 20°C to 30°C.

[0039] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0040] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0041] In this application, unless otherwise specified, the temperature parameter is allowed to be either a constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0042] In this application, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 2~5h means that the units of the left endpoint "2" and the right endpoint "5" are both h (hours).

[0043] In this application, in this system, due to the charge characteristics of the negatively charged silicon powder surface and the positively charged graphite powder surface, the zeta potential refers to the potential difference generated at the shear plane between the graphite powder or silicon powder surface and the surrounding dispersion medium (gas dispersion medium). The sign and magnitude of the zeta potential directly reflect the nature (positive or negative) and intensity of the particle surface charge. The absolute value of the zeta potential is related to the amount of charge on the particle surface. The larger the absolute value, the higher the surface charge density of the particle and the more charge it carries; conversely, the smaller the absolute value, the lower the surface charge density and the less charge it carries.

[0044] An embodiment of the present application provides a method for preparing silicon carbide powder, including steps S100 to S200.

[0045] Step S100: mixing negatively charged silicon powder and positively charged graphite powder to obtain a mixture.

[0046] Step S200: heating the mixed material to allow the negatively charged silicon powder and the positively charged graphite powder to react to prepare silicon carbide powder.

[0047] In the preparation method of the silicon carbide powder of the present application, firstly, negatively charged silicon powder and positively charged graphite powder are mixed to obtain a mixture, and the electrostatic self-assembly effect can effectively promote the uniform mixing of negatively charged silicon powder and positively charged graphite powder, and reduce the stratification phenomenon caused by differences in density and particle size. Then the mixture is heated to make the negatively charged silicon powder and the positively charged graphite powder react to prepare silicon carbide powder, because the relatively tight and uniform structure formed by the electrostatic self-assembly of the positively charged silicon powder and the negatively charged graphite powder is conducive to the self-propagating reaction to synthesize silicon carbide, so that the reaction is more sufficient, the carbon encapsulation of the silicon carbide powder is reduced, and the foundation is laid for the subsequent preparation of high-quality SiC substrate wafers or SiC-based devices.

[0048] In some embodiments, the negatively charged silicon powder includes protonated silicon powder.

[0049] In some embodiments, the surface charge of the negatively charged silicon powder has a zeta potential of -7mV to -10mV, for example, -7mV, -7.1mV, -7.2mV, -7.3mV, -7.4mV, -7.5mV, -7.6mV, -7.7mV, -7.8mV, -7.9mV, -8.0mV, -8.1mV, -8.2mV, -8.3mV, - 8.4mV, -8.5mV, -8.6mV, -8.7mV, -8.8mV, -8.9mV, -9.0mV, -9.1mV, -9.2mV, -9.3mV, -9.4mV, -9.5mV, -9.6mV, -9.7mV, -9.8mV, -9.9mV, -10mV. In some examples, any two of these point values ​​can be within the range formed by the end values, the same below.

[0050] In some embodiments, the surface charge of the positively charged graphite powder has a zeta potential of 12 mV to 16 mV, for example, 12 mV, 12.1 mV, 12.2 mV, 12.3 mV, 12.4 mV, 12.5 mV, 12.6 mV, 12.7 mV, 12.8 mV, 12.9 mV, 13 mV, 13.1 mV, 13.2 mV, 13.3 mV, 13.4 mV, 13.5 mV, 13.6 mV. V, 13.7mV, 13.8mV, 13.9mV, 14mV, 14.1mV, 14.2mV, 14.3mV, 14.4mV, 14.5mV, 14.6mV, 14.7mV, 14.8m V, 14.9mV, 15mV, 15.1mV, 15.2mV, 15.3mV, 15.4mV, 15.5mV, 15.6mV, 15.7mV, 15.8mV, 15.9mV or 16mV.

[0051] In a specific example, the surface charge of the negatively charged silicon powder has a zeta potential of -8.98 mV, and the surface charge of the positively charged graphite powder has a zeta potential of 15.8 mV.

[0052] In some of the embodiments, the molar ratio of the positively charged graphite powder to the negatively charged silicon powder is 1:1-1.04, for example, 1:1.01, 1:1.02, 1:1.03 or 1:1.04.

[0053] Some of the embodiments further include a step of preparing negatively charged silicon powder, which includes the following steps: protonating the silicon powder with an acid solution to obtain negatively charged silicon powder.

[0054] In some embodiments, the acid in the acid solution includes one or more of nitric acid, sulfuric acid and hydrochloric acid.

[0055] In some embodiments, based on the total mass of the acid solution, the mass fraction of the acid solution (i.e., the working concentration of the acid in the acid solution) is 20% to 40%, for example, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%.

[0056] In some embodiments, the protonation treatment time is 1 h to 5 h, for example, 1 h, 2 h, 3 h, 4 h or 5 h.

[0057] It can be understood that the surface of silicon powder is mainly composed of silicon-oxygen bonds and silicon-hydrogen bonds, among which silicon-oxygen bonds are one of the most abundant functional groups on the surface. The ability of oxygen atoms to attract electrons is greater than that of silicon atoms. The electron cloud density in silicon-oxygen bonds is biased toward the oxygen atom side, so the natural surface Zeta potential of silicon powder is negative. The above-mentioned acid protonation treatment of silicon powder can enhance the negative Zeta potential of the silicon powder surface.

[0058] In some of the embodiments, a step of preparing positively charged graphite powder is further included, which includes the following steps: irradiating the graphite powder to obtain positively charged graphite powder.

[0059] In some embodiments, the radiation treatment includes at least one of thermal radiation and optical radiation.

[0060] In some embodiments, the temperature of the thermal radiation is 80°C~260°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or 260°C.

[0061] In some embodiments, the thermal radiation time is 2 hours to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0062] In some embodiments, the pressure of the thermal radiation is 50Pa~600Pa, for example, it can be 50Pa, 100Pa, 150Pa, 200Pa, 250Pa, 300Pa, 350Pa, 400Pa, 450Pa, 500Pa, 550Pa, 600Pa.

[0063] In some embodiments, the wavelength of the light radiation is 100 nm to 400 nm.

[0064] In some embodiments, the light source of the light radiation includes any one of UVA, UVB, UVC and UVD.

[0065] In some embodiments, the step of irradiating the graphite powder to obtain graphite powder with positive charge includes step a to step b.

[0066] Step a: Mixing a fluorine-containing reagent and the above-mentioned graphite powder to obtain an intermediate mixture.

[0067] Step b: subjecting the intermediate mixture to radiation treatment to prepare graphite powder with positive charge.

[0068] It can be understood that the zeta potential of the graphite surface is positive by utilizing the photoionization and charge accumulation effects through thermal radiation and light radiation. This is because there is an unpaired electron in the pz orbit of the graphite surface. This electron is highly active and can easily break free from the constraints of the graphite surface and escape under the stimulation of external physical factors, thus making the zeta potential of the graphite surface positive.

[0069] In some embodiments, the fluorine-containing reagent includes at least one of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, fluorinated ethylene-propylene copolymer, and polyvinylidene fluoride.

[0070] It can be understood that there are a large number of F atoms on the surface of the fluorine-containing reagent. The F atoms have strong electronegativity and are easy to attract electrons, so that their surface is negatively charged and the graphite surface is positively charged, which has a stabilizing effect on the positive potential of the graphite surface Zeta potential. Preferably, polytetrafluoroethylene can be decomposed into gas when heated, and the decomposition temperature is lower than the synthesis temperature of SiC, and the decomposition will not cause pollution to the raw materials.

[0071] In some of the embodiments, the above-mentioned temperature treatment conditions include: in a protective gas atmosphere and a pressure of 5000Pa~20000Pa, heating the temperature to 2000℃~2400℃ at a heating rate of 1℃~10℃ per minute and maintaining the temperature for 15h~20h.

[0072] In some embodiments, the protective gas includes at least one of argon and hydrogen.

[0073] It can be understood that a specific heating rate can make the raw materials gradually reach the activation state required for the reaction; argon as a protective gas can prevent the raw materials and products from being oxidized at high temperatures; appropriate gas pressure and insulation time can ensure that the self-propagating reaction is fully carried out, so that the silicon powder and graphite powder can fully react to generate silicon carbide powder.

[0074] In some of the embodiments, after the step of heating the mixture and before the step of preparing silicon carbide powder, the steps of successively cooling, crushing, oxidizing and screening the product after the heating treatment are also included.

[0075] It can be understood that after the temperature of the resistance furnace drops to room temperature, the above-mentioned crushing is to break the large pieces of product into smaller particles; the oxidation treatment is to remove free carbon; the screening is to screen out the silicon carbide powder that meets the particle size requirements, and finally obtain low-carbon-encapsulated silicon carbide powder to meet specific quality and performance requirements, so as to be suitable for subsequent applications, such as abrasives, semiconductor materials, etc. The above-mentioned preparation method is conducive to the synthesis of silicon carbide by self-propagating reaction, making the reaction more complete and reducing the carbon encapsulation of silicon carbide powder.

[0076] An embodiment of the present application further provides a silicon carbide powder, which is prepared by the above-mentioned method for preparing the silicon carbide powder.

[0077] The silicon carbide powder prepared by the above-mentioned method for preparing silicon carbide powder has a low carbon encapsulation content.

[0078] One embodiment of the present application also provides a use of the above-mentioned silicon carbide powder in the preparation of SiC crystals or ceramic refractory materials.

[0079] In order to make the purpose, technical solutions and advantages of the present application more concise and clear, the present application is described with the following specific embodiments, but the present application is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present application and can be used to describe the present application, and cannot be understood as limiting the scope of the present application. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

[0080] In order to better illustrate the present application, the contents of the present application are further described below in conjunction with embodiments.

[0081] Example 1

[0082] (1) Polytetrafluoroethylene particles and graphite powder were mixed in a jar mill at a mass ratio of 1:15 for 2 h at a jar mill speed of 200 rpm to obtain graphite powder with a positive charge on the surface. The mixture of graphite powder and polytetrafluoroethylene particles was recorded as the intermediate mixture.

[0083] (2) The intermediate mixture is placed in an oven and dried and heated at 180°C for 5 h. The pressure is controlled to 80,000 Pa, and irradiated with UVC waves (short-wave ultraviolet rays) with a wavelength of 200 to 275 nm. The intermediate mixture treated with light radiation and heat radiation is recorded as positively charged graphite powder.

[0084] (3) Immerse the silicon powder in dilute hydrochloric acid and stir for 2 hours for protonation treatment. The mass fraction of the dilute hydrochloric acid is 20%. The protonated silicon powder is recorded as negatively charged silicon powder.

[0085] (4) The negatively charged silicon powder and the positively charged graphite powder are placed in a jar mill and mixed for 2 hours to ensure that the molar ratio of the graphite powder with positive charge on the surface to the negatively charged silicon powder is 1:1.01 to obtain a mixture.

[0086] (5) In the crucible loading process, the mixture is loaded into a graphite crucible with an acrylic shovel, and the temperature is raised to 2100°C in a resistance furnace at a heating rate of 1°C per minute. Argon gas is introduced, and the gas pressure is maintained at 5000 Pa. The mixture is kept warm for 20 hours to allow a self-propagating reaction to occur to synthesize silicon carbide.

[0087] (6) After the temperature of the resistance furnace drops to room temperature, silicon carbide powder can be obtained through the processes of opening the crucible, crushing, oxidation and screening.

[0088] (7) The prepared silicon carbide powder is subjected to performance testing.

[0089] Example 2

[0090] The preparation methods of silicon carbide powder in Example 2 and Example 1 are basically the same, the only difference is that the treatment method for modifying the graphite surface is different, specifically, in step (2), the intermediate mixture is only subjected to light radiation treatment.

[0091] The other steps and conditions are the same as those in Example 1.

[0092] Example 3

[0093] The preparation methods of silicon carbide powder in Example 3 and Example 1 are basically the same, the only difference is that the treatment method for modifying the graphite surface is different, specifically, in step (2), the intermediate mixture is only subjected to thermal radiation treatment.

[0094] The other steps and conditions are the same as those in Example 1.

[0095] Example 4

[0096] The preparation method of silicon carbide powder in Example 4 is basically the same as that in Example 1, except that the conditions for protonation treatment of silicon powder in step (3) are different, specifically: the type of acid in the acid solution is sulfuric acid, the mass fraction of the acid in the acid solution is 20%, and the acid solution treatment time is 2 h.

[0097] The other steps and conditions are the same as those in Example 1.

[0098] Comparative Example 1

[0099] The preparation method of silicon carbide powder in Comparative Example 1 is basically the same as that in Example 1, except that no modification treatment is performed on the surface of silicon powder and graphite powder, specifically:

[0100] (1) Graphite powder and silicon powder are uniformly mixed at a molar ratio of 1:1.01 to obtain a mixture.

[0101] (2) In the crucible loading process, the above-mentioned mixture is loaded into a graphite crucible with an acrylic shovel, and the temperature is raised to 2100°C in a resistance furnace at a heating rate of 1°C per minute. Argon gas is introduced and the gas pressure is maintained at 5000 Pa. The mixture is kept warm for 20 hours to allow a self-propagating reaction to occur to synthesize silicon carbide.

[0102] (3) After the temperature of the resistance furnace drops to room temperature, silicon carbide powder can be obtained through the processes of opening the crucible, crushing, oxidation and screening.

[0103] (4) Performing performance tests on the prepared silicon carbide powder.

[0104] The other steps and conditions are the same as those in Example 1.

[0105] Comparative Example 2

[0106] (1) Graphite powder and silicon powder are uniformly mixed at a molar ratio of 1:1.01 to obtain a first mixture.

[0107] (2) Polytetrafluoroethylene and the first mixed material are mixed at a mass ratio of 1:15 to obtain a second mixed material.

[0108] (3) In the crucible loading process, the second mixed material is loaded into a graphite crucible with an acrylic shovel, and the temperature is raised to 2100°C in a resistance furnace at a heating rate of 1°C per minute. Argon gas is introduced and the gas pressure is maintained at 5000 Pa. The mixture is kept warm for 20 hours to allow a self-propagating reaction to occur to synthesize silicon carbide.

[0109] (4) After the temperature of the resistance furnace drops to room temperature, silicon carbide powder can be obtained through the processes of opening the crucible, crushing, oxidation and screening.

[0110] (5) Performing performance tests on the prepared silicon carbide powder.

[0111] Comparative Example 3

[0112] The preparation method of silicon carbide powder in Comparative Example 3 is basically the same as that in Example 1, except that the intermediate mixture is not subjected to heat radiation and light radiation, specifically:

[0113] (1) Polytetrafluoroethylene particles and graphite powder were mixed in a jar mill at a mass ratio of 1:15 for 2 h at a jar mill speed of 200 rpm to obtain graphite powder with a positive charge on the surface. The mixture of graphite powder and polytetrafluoroethylene particles was recorded as the intermediate mixture.

[0114] (2) The silicon powder is placed in a dilute acid and stirred for 2 hours for protonation treatment. The acid used for protonation is dilute hydrochloric acid. The mass concentration of the acid during pickling is 20%. The silicon powder that has been protonated is recorded as negatively charged silicon powder.

[0115] (3) The negatively charged silicon powder and the positively charged graphite powder are placed in a jar mill and mixed for 2 hours to ensure that the molar ratio of the graphite powder with positive charge on the surface to the negatively charged silicon powder is 1:1.01 to obtain a mixture.

[0116] (4) In the crucible loading process, the mixture is loaded into a graphite crucible with an acrylic shovel, and the temperature is raised to 2100°C in a resistance furnace at a heating rate of 1°C per minute. Argon gas is introduced, and the gas pressure is maintained at 5000 Pa. The mixture is kept warm for 20 hours to allow a self-propagating reaction to occur to synthesize silicon carbide.

[0117] (5) After the temperature of the resistance furnace drops to room temperature, silicon carbide powder can be obtained through the processes of opening the crucible, crushing, oxidation and screening.

[0118] (6) The prepared silicon carbide powder is subjected to performance testing.

[0119] The other steps and conditions are the same as those in Example 1.

[0120] Performance Testing

[0121] 1. The carbon coating content of the silicon carbide powder obtained in the examples and comparative examples was tested by randomly sampling 5 cubic centimeters of raw materials ten times and calculating the raw materials with carbon coated particles / the sum of the raw material particles. The results are shown in Table 1.

[0122] Table 1

[0123]

[0124] Figure 1 The Zeta potential diagram of carbon powder and silicon powder in Example 1. Compared with Example 1, in Example 1, no modification treatment is performed on the surface of silicon powder and graphite powder, and the carbon encapsulation amount of the prepared silicon carbide increases; in Example 2, graphite powder and silicon powder are first mixed, and then polytetrafluoroethylene is added, and graphite powder and silicon powder with opposite charges cannot be obtained, resulting in that the graphite powder and silicon powder are easily separated, because the graphite powder is too light and has a small particle size, and is easily affected by air resistance, which leads to an imbalance in the carbon-silicon stoichiometric ratio in the crucible loading process, and then leads to serious carbon encapsulation of the generated silicon carbide powder; in Example 3, the intermediate mixture is not subjected to heat radiation and light radiation treatment, which also leads to an increase in the carbon encapsulation amount of the prepared silicon carbide. The purity of the silicon carbide prepared in the embodiment of the present application is greater than 99.999%, which can be used normally in the SiC industry.

[0125] In summary, it is shown that the silicon carbide powder prepared in the embodiment of the present application has higher purity and lower carbon encapsulation content than the silicon carbide powder prepared in the comparative example, and can meet the practical application of semiconductor materials.

[0126] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A method for preparing silicon carbide powder, characterized in that: The steps include: Mixing negatively charged silicon powder and positively charged graphite powder to obtain a mixture; The mixed material is subjected to a temperature-raising treatment to allow the negatively charged silicon powder and the positively charged graphite powder to react to prepare silicon carbide powder.

2. The method for preparing silicon carbide powder according to claim 1, characterized in that: The negatively charged silicon powder includes protonated silicon powder.

3. The method for preparing silicon carbide powder according to claim 1, characterized in that: The surface charge of the negatively charged silicon powder has a zeta potential of -7mV to -10mV, and the surface charge of the positively charged graphite powder has a zeta potential of 12mV to 16mV; And / or, the molar ratio of the positively charged graphite powder to the negatively charged silicon powder is 1:1-1.

04.

4. The method for preparing silicon carbide powder according to any one of claims 1 to 3, characterized in that: The method also includes the step of preparing negatively charged silicon powder, which includes the following steps: protonating the silicon powder with an acid solution to obtain negatively charged silicon powder; And / or, the method further comprises the step of preparing graphite powder with positive charge, which comprises the following steps: subjecting the graphite powder to radiation treatment to obtain graphite powder with positive charge.

5. The method for preparing silicon carbide powder according to claim 4, characterized in that: The acid in the acid solution includes one or more of nitric acid, sulfuric acid and hydrochloric acid; And / or, based on the total mass of the acid solution, the mass fraction of the acid solution is 20% to 40%; And / or, the protonation treatment time is 1h~5h; And / or, the radiation treatment includes at least one of thermal radiation and light radiation.

6. The method for preparing silicon carbide powder according to claim 5, characterized in that: The temperature of the thermal radiation is 80°C to 260°C, the time of the thermal radiation is 2h to 6h, and the pressure of the thermal radiation is 50Pa to 600Pa; The wavelength of the light radiation is 100nm~400nm; And / or, the light source of the light radiation includes any one of UVA, UVB, UVC and UVD.

7. The method for preparing silicon carbide powder according to claim 4, characterized in that: The step of subjecting the graphite powder to radiation treatment to obtain graphite powder with positive charge comprises: Mixing a fluorine-containing reagent and the graphite powder to obtain an intermediate mixture, wherein the fluorine-containing reagent includes at least one of polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, fluorinated ethylene-propylene copolymer and polyvinylidene fluoride; The intermediate mixture is subjected to radiation treatment to prepare positively charged graphite powder.

8. The method for preparing silicon carbide powder according to any one of claims 1 to 3 and claims 5 to 7, characterized in that: The conditions of the temperature treatment include: in a protective gas atmosphere and a pressure of 5000Pa~20000Pa, heating to 2000℃~2400℃ at a heating rate of 1℃~10℃ per minute and heat preservation for 15h~20h; And / or, after the step of heating the mixed material and before the step of preparing the silicon carbide powder, the method further includes the steps of successively cooling, crushing, oxidizing and screening the product after the heating treatment.

9. A silicon carbide powder, characterized in that: The silicon carbide powder is prepared by the method for preparing the silicon carbide powder according to any one of claims 1 to 8.

10. Use of the silicon carbide powder according to claim 9 in preparing SiC crystals or ceramic refractory materials.

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