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. Carbon powder, silicon powder and a metal compound are mixed to obtain a mixture, and the ratio of the total mass of the carbon powder and the silicon powder to the mass of the metal compound is 1: (15-30); heating the mixture in a protective gas atmosphere to enable the carbon powder and the silicon powder to react, so as to prepare a silicon carbide crude body; the melting point of the metal compound is higher than the reaction temperature of the carbon powder and the silicon powder; and removing the metal compound in the silicon carbide coarse body to prepare the silicon carbide powder. The silicon carbide prepared by the preparation method of the silicon carbide powder is relatively high in looseness, relatively high in purity and relatively low in carbon coating content.

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] Silicon carbide (SiC) powder, as an important inorganic non-metallic material, is widely used in many fields such as semiconductors, abrasives, and refractory materials. However, in the preparation process of silicon carbide powder, powder agglomeration often occurs, resulting in poor looseness. This not only affects the fluidity and dispersibility of silicon carbide powder in subsequent processing, increasing the difficulty of processing, but also may reduce its reinforcing effect in composite materials, thereby limiting the application of silicon carbide powder in high-end fields.

[0003] At present, common solutions include adding dispersants and improving the crushing process. However, adding dispersants may introduce impurities, affecting the purity of silicon carbide powder, and is not suitable for applications with extremely high purity requirements; and simply improving the crushing process has limited effect on improving looseness and may lead to uneven distribution of powder particle size. Therefore, it is of great practical significance to develop a production method that can effectively improve the looseness of silicon carbide powder without affecting its purity. Summary of the invention

[0004] Based on this, the present application provides a silicon carbide powder with higher looseness, higher purity and lower carbon encapsulation content, and a preparation method and application thereof.

[0005] The specific technical solutions are as follows:

[0006] The first aspect of the present application provides a method for preparing silicon carbide powder, comprising the following steps:

[0007] Mixing carbon powder, silicon powder and a metal compound to obtain a mixture, wherein the mass ratio of the total mass of the carbon powder and the silicon powder to the mass ratio of the metal compound is 1:15-30;

[0008] The mixed material is subjected to a temperature-raising treatment in a protective gas atmosphere to allow the carbon powder and the silicon powder to react to prepare a rough body of silicon carbide; the melting point of the metal compound is higher than the reaction temperature of the carbon powder and the silicon powder;

[0009] The metal compounds in the crude silicon carbide are removed to prepare silicon carbide powder.

[0010] In the preparation method of the above-mentioned silicon carbide powder of the present application, a specific carbon powder, silicon powder and metal compound having a specific ratio are mixed, and then the mixture is subjected to a temperature treatment in a protective gas atmosphere to react with the carbon powder and the silicon powder to prepare a silicon carbide crude; then the impurities in the tantalum carbide crude are removed to prepare the silicon carbide powder. In the traditional preparation process, there is a problem of incomplete reaction of the raw materials, that is, the carbon powder is wrapped in the silicon carbide, and the silicon carbide on the outer skin prevents the reaction of the silicon powder and the carbon. Compared with the traditional process, in the preparation method of the present application, during the temperature treatment process, the carbon powder and the silicon powder fully react to generate silicon carbide, wherein the metal compound exists in a stable form during the temperature treatment process of the silicon carbide synthesis, and can adsorb the carbon powder, which will reduce the formation of carbon encapsulation and increase the looseness, while not affecting the synthesis reaction of the SiC powder.

[0011] In some embodiments, the metal compound includes one or more of tantalum carbide, tantalum phosphide, cerium dioxide, cerium oxide, lanthanum oxide, gallium oxide, erbium oxide, samarium oxide, yttrium oxide, europium oxide, and gadolinium oxide;

[0012] and / or, the molar ratio of the carbon powder to the silicon powder is 1:1.01-1.05;

[0013] And / or, the particle size of the silicon carbide powder is less than or equal to 4 mm;

[0014] And / or, the particle size of the metal compound is 0.6 cm to 0.8 cm;

[0015] And / or, the mass ratio of the total mass of the carbon powder and the silicon powder to the mass ratio of the metal compound is 1:15-20.

[0016] In some embodiments, the temperature treatment step includes: subjecting the mixture to a first temperature treatment under a protective gas atmosphere to react the carbon powder and the silicon powder to obtain β-SiC; subjecting the β-SiC to a second temperature treatment to transform the β-SiC into α-SiC to obtain α-SiC; subjecting the α-SiC to a third temperature treatment to obtain silicon carbide rough body after cooling.

[0017] In some embodiments, the conditions of the first temperature treatment include: in a protective gas atmosphere and a pressure of 200Pa to 80000Pa, heating to 1300°C to 1500°C at a heating rate of 0.1°C to 20°C per minute for a first heat preservation treatment for 2h to 4h;

[0018] And / or, the conditions of the second temperature-raising treatment include: in a protective gas atmosphere and a pressure of 200Pa~80000Pa, heating to 1500℃~2150℃ at a heating rate of 0.1℃~20℃ per minute for 1h~15h, the temperature of the second temperature-raising treatment is higher than that of the first temperature-raising treatment, and the temperature difference between the temperature of the second temperature-raising treatment and the temperature of the first temperature-raising treatment is 550℃~650℃;

[0019] And / or, the conditions of the third temperature treatment include: in a protective gas atmosphere and a pressure of 50Pa~80000Pa, heating the temperature to 2150℃~2580℃ at a heating rate of 0.1℃~20℃ per minute for 1h~5h, the temperature of the third temperature treatment is higher than that of the second temperature treatment, and the temperature difference between the temperature of the third temperature treatment and the temperature of the second temperature treatment is 100℃~300℃.

[0020] In some embodiments, the cooling step comprises the following steps:

[0021] The product after the third heating treatment is subjected to a first cooling treatment, so that the temperature of the product is reduced to 2100°C~2150°C at a cooling rate of 0.1°C~10°C per minute, and a first heat preservation treatment is performed; then a first heating treatment is performed, so that the temperature of the product is increased to 2280°C~2580°C at a heating rate of 0.1°C~20°C per minute, and a second heat preservation treatment is performed; the steps of the first cooling treatment and the first heating treatment are repeated n times, n≥3, to obtain a silicon carbide intermediate;

[0022] The silicon carbide intermediate is subjected to a cooling treatment so as to reduce the temperature of the silicon carbide intermediate to room temperature at a cooling rate of 0.1° C. to 20° C. per minute.

[0023] In some embodiments, the first heat preservation treatment lasts for 1 h to 5 h;

[0024] And / or, the second heat preservation treatment time is 1h~5h.

[0025] In some embodiments, the step of removing impurities from the silicon carbide bulk comprises the steps of screening and removing impurities from the silicon carbide bulk in sequence.

[0026] In some of the embodiments, the impurity removal step includes placing the screened silicon carbide crude in an oxidation furnace and oxidizing it at 600° C. to 1000° C. for 1 h to 10 h.

[0027] A second aspect of the present application provides a silicon carbide powder, which is prepared by the above-mentioned method for preparing silicon carbide powder.

[0028] 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

[0029] Figure 1 This is a schematic diagram of the silicon carbide powder prepared in Example 1;

[0030] Figure 2 Schematic diagram of the silicon carbide powder prepared in Comparative Example 1.

[0031] Description of reference numerals:

[0032] 10. Silicon carbide powder; 11. Unreacted carbon powder. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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).

[0044] As shown in the background technology, in the traditional technology, the most used is the self-propagating method to synthesize silicon carbide powder. The self-propagating method generally provides the activation energy required for the reaction by adding an activator, but the introduction of the activator inevitably brings impurities, which is unfavorable for semiconductor preparation. Therefore, the later improvement is to maintain the energy required for the normal reaction by continuous heating, without the need to introduce an activator. This method is called the improved self-propagating synthesis method. However, this method is not completely synthetic. Carbon powder is wrapped in silicon carbide, commonly known as carbon encapsulation, which is difficult to remove in subsequent processes. Carbon encapsulation has a great impact on the quality of crystal growth, that is, the outermost layer of silicon carbide will expose carbon powder after sublimation, and carbon powder will adhere to the surface of the seed crystal due to Brownian motion, thereby causing the crystal grown by the PVT method to have an inclusion, making the crystal scrapped. Moreover, the hardness of silicon carbide is second only to diamond and is very hard, and it is difficult to break. Forced violent breaking will inevitably introduce impurities. The raw material crushing process is the process that is most likely to introduce impurities in the synthesis process of high-purity SiC powder. Subsequently, multiple processes such as acid washing, alkali washing and water washing are arranged to remove impurities, which can easily pollute the environment and increase the secondary pollution of silicon carbide powder.

[0045] Based on this, an embodiment of the present application provides a method for preparing silicon carbide powder, including steps S10 to S30.

[0046] Step S10: Mix carbon powder, silicon powder and a metal compound to obtain a mixture, wherein the mass ratio of the total mass of the carbon powder and silicon powder to the metal compound is 1:15-30, for example, it can be: 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29 or 1:30. In some examples, it can be within the range formed by any two of these point values ​​as end values, the same below.

[0047] Step S20: heating the mixture in a protective gas atmosphere to allow the carbon powder and the silicon powder to react to prepare silicon carbide crude, wherein the melting point of the metal compound is higher than the reaction temperature of the carbon powder and the silicon powder.

[0048] Step S30: removing impurities from the silicon carbide crude to prepare silicon carbide powder.

[0049] In the preparation method of the above-mentioned silicon carbide powder of the present application, a specific carbon powder, silicon powder and metal compound having a specific ratio are mixed, and then the mixture is subjected to a temperature treatment in a protective gas atmosphere to react with the carbon powder and the silicon powder to prepare a silicon carbide crude; then the impurities in the tantalum carbide crude are removed to prepare the silicon carbide powder. In the traditional preparation process, there is a problem of incomplete reaction of the raw materials, that is, the carbon powder is wrapped in the silicon carbide, and the silicon carbide on the outer skin prevents the reaction of the silicon powder and the carbon. Compared with the traditional process, in the preparation method of the present application, during the temperature treatment process, the carbon powder and the silicon powder fully react to generate silicon carbide, wherein the metal compound exists in a stable form during the temperature treatment process of the silicon carbide synthesis, and can adsorb the carbon powder, which will reduce the formation of carbon encapsulation and increase the looseness, while not affecting the synthesis reaction of the SiC powder.

[0050] The technical personnel of this application have found that the metal compound adsorbs carbon, which will reduce the formation of carbon encapsulation, increase the looseness, and do not affect the synthesis reaction of SiC powder. It is further speculated that the possible reason is that the powder near the crucible wall preferentially decomposes and sublimates, causing graphitization at the edge, and the graphitized part hinders the heat transfer between the crucible and the powder (the graphitized part has a loose structure and low effective thermal conductivity), resulting in a further increase in the temperature difference between the middle and edge of the powder, which may further reduce the temperature in the middle of the powder, so that it cannot be fully decomposed and sublimated, resulting in a certain strength of the powder. In the high-temperature stage of SiC raw material synthesis, the main heat conduction mechanism is heat conduction and heat radiation, and the metal compound has good thermal conductivity, so it is conducive to improving the uniformity of the thermal field, thereby avoiding the hardening of the raw material. At the same time, the metal compound acts as a nucleation site in the formation process of silicon carbide embryos, and more nucleation sites ensure that the raw material reaction is more sufficient, thereby reducing the formation of carbon encapsulation. The metal compound has a high chemical stability. At a temperature of 3880°C, it can still exist stably and does not react chemically with carbon powder, silicon powder and silicon carbide powder.

[0051] In some embodiments, the metal compound includes one or more of tantalum carbide, tantalum phosphide, cerium dioxide, cerium oxide, lanthanum oxide, gallium oxide, erbium oxide, samarium oxide, yttrium oxide, europium oxide and gadolinium oxide.

[0052] In some embodiments, the molar ratio of the carbon powder to the silicon powder is 1:1.01-1.05, for example, it can be 1:1.01, 1:1.02, 1:1.03, 1:1.04 or 1:1.05.

[0053] In some embodiments, the particle size of the silicon carbide powder is less than or equal to 4 mm.

[0054] In some embodiments, the particle size of the metal compound is 0.6 cm to 0.8 cm.

[0055] In some embodiments, the mass ratio of the total mass of the carbon powder and the silicon powder to the mass of the metal compound is 1:15-20.

[0056] Furthermore, by controlling the mass ratio of the total mass of the carbon powder and the silicon powder to the mass of the metal compound within the above preferred range, the looseness and purity of the silicon carbide powder are higher, and the carbon encapsulation content is lower.

[0057] In some embodiments, the mixing speed is 200 rpm to 350 rpm, and the mixing time is 3 h to 6 h.

[0058] It can be understood that the above mixing treatment is intended to ensure that the three raw materials are fully contacted and evenly dispersed. Uniform mixing is conducive to the smooth progress of subsequent reactions and can ensure that during the heating reaction, the carbon powder and silicon powder can fully react to form silicon carbide, and the metal compound can also be evenly distributed in the system to play its specific role.

[0059] In some embodiments, the temperature treatment step includes: subjecting the mixture to a first temperature treatment under a protective gas atmosphere so that the carbon powder and the silicon powder react to obtain β-SiC; subjecting the β-SiC to a second temperature treatment so that the β-SiC is transformed into α-SiC to obtain α-SiC; and continuing to subject the α-SiC to a third temperature treatment to obtain a rough silicon carbide body after cooling.

[0060] In some of the embodiments, the conditions for the first temperature treatment are: in a protective gas atmosphere and a pressure of 200Pa~80000Pa, the temperature is increased to 1300℃~1500℃ at a heating rate of 0.1℃~20℃ per minute for a first insulation treatment for 2h~4h.

[0061] In some embodiments, the protective gas includes at least one of argon and hydrogen.

[0062] It can be understood that in this stage, the argon pressure and heating rate are controlled to create suitable conditions for the self-propagating reaction. The argon pressure affects the gas phase environment of the reaction system. If the pressure is too high, the material obtained by the reaction will appear black. If the pressure is too low, the corrosion of the graphite crucible will be aggravated. The heating rate affects the start and progress of the reaction. The appropriate heating rate helps to initiate and control the self-propagating reaction and make the reaction proceed stably.

[0063] In some of the embodiments, the conditions of the second temperature rising treatment are: in a protective gas atmosphere and a pressure of 200Pa~80000Pa, the temperature is raised to 1500℃~2150℃ at a heating rate of 0.1℃~20℃ per minute for a second insulation treatment for 1h~15h, the temperature of the second insulation treatment is higher than the first insulation treatment, and the temperature difference between the second insulation treatment and the first insulation treatment is 550℃~650℃.

[0064] It can be understood that within the above temperature range, silicon carbide undergoes a phase transition process from β-SiC to α-SiC. Controlling the argon pressure and heating rate helps guide and control the phase transition process, allowing silicon carbide to form the expected crystal structure and avoid crystal defects or structural abnormalities caused by improper conditions.

[0065] In some of the embodiments, the conditions of the third temperature treatment are: in a protective gas atmosphere and a pressure of 50Pa~80000Pa, the temperature is increased to 2150℃~2580℃ at a heating rate of 0.1℃~20℃ per minute for a third insulation treatment for 1h~5h, the temperature of the third insulation treatment is higher than that of the second insulation treatment, and the temperature difference between the temperature of the third insulation treatment and the temperature of the second insulation treatment is 100℃~300℃.

[0066] It can be understood that the third heating treatment stage promotes the growth of silicon carbide grains by precisely controlling the temperature, pressure and holding time. Appropriate conditions help the migration and arrangement of atoms in the crystal structure, causing the grains to grow gradually, thereby improving the properties of the silicon carbide material, such as improving strength and electrical properties.

[0067] In some of the embodiments, an acrylic spatula is used to transfer the mixed material into a graphite crucible, and the loaded graphite crucible is then loaded into a graphite resistance furnace.

[0068] It is understandable that this is mainly to prevent the introduction of impurities during the transfer process. The acrylic material is relatively pure and will not introduce metal impurities into the raw materials during operation like some metal tools. At the same time, the high-purity graphite crucible can provide a stable container environment for subsequent high-temperature reactions.

[0069] In some embodiments, the cooling process comprises steps a and b.

[0070] Step a: performing a first cooling treatment on the product after the third heating treatment, so that the temperature of the above product is reduced to 2100°C~2150°C at a cooling rate of 0.1°C~10°C per minute, and performing a first heat preservation treatment; then performing a first heating treatment, so that the temperature of the above silicon carbide crude is increased to 2280°C~2580°C at a heating rate of 0.1°C~20°C per minute, and then performing a second heat preservation treatment; repeating the above first cooling treatment and the above first heating treatment steps n times, n≥3, to obtain a silicon carbide intermediate.

[0071] It can be understood that through multiple heating and cooling cycles, the crystal structure is further optimized, the grain size is made more uniform, and crystal defects are reduced. During each heating and cooling process, the atoms inside the crystal have the opportunity to rearrange to achieve a more stable state, thereby improving the quality of the silicon carbide material.

[0072] Step b: subjecting the silicon carbide intermediate to a cooling treatment so as to cool the silicon carbide intermediate to room temperature at a cooling rate of 0.1° C. to 20° C. per minute.

[0073] It can be understood that the above-mentioned cooling process can adjust the crystal structure to a certain extent, and heat preservation helps to eliminate the internal stress of the crystal and make the crystal structure more stable.

[0074] In some embodiments, the above-mentioned cooling process adopts a uniform cooling process.

[0075] It is understandable that the purpose of cooling at a constant cooling rate during the cooling stage is to avoid the formation of dendrites. The growth of dendrites will lead to an uneven crystal structure and reduce the performance of the material. A constant cooling rate helps control the crystal growth process, allowing atoms to be arranged in an orderly manner in the lattice to form a uniform and dense crystal structure, thereby improving the quality and performance of silicon carbide materials.

[0076] In some embodiments, the first heat preservation treatment lasts for 1 hour to 5 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0077] In some embodiments, the second heat preservation treatment time is 1 hour to 5 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours or 5 hours.

[0078] In some embodiments, the step of removing impurities from the silicon carbide bulk comprises the steps of screening and removing impurities from the silicon carbide bulk in sequence.

[0079] In some embodiments, the step of screening further includes rotating the silicon carbide crude body at a rotation speed of 60 rpm to 350 rpm for 1 hour to 5 hours.

[0080] It can be understood that the above stirring is performed to break up the raw materials of the clusters into fine blocks, so as to prepare for the subsequent screening of metal compounds and improve the purity and performance of the silicon carbide powder.

[0081] In some of the embodiments, the method further comprises screening the ground product to screen out the metal compounds.

[0082] In some embodiments, the above-mentioned screening is specifically to distinguish metal particles larger than 5 mesh from raw materials with 5 mesh to 20 mesh, 20 mesh to 60 mesh, 60 mesh to 80 mesh and less than 80 mesh by large difference in particle size.

[0083] It can be understood that the metal compound does not participate in the chemical reaction of generating silicon carbide during the reaction process, and can be separated from the silicon carbide powder by screening to improve the purity of the silicon carbide powder.

[0084] In some of the embodiments, the impurity removal step includes placing the screened silicon carbide crude in an oxidation furnace and oxidizing it at 600° C. to 1000° C. for 1 h to 10 h.

[0085] It can be understood that at the above temperature, the oxygen in the air can react with the free carbon powder and other possible impurities to produce an oxidation reaction, and the generated gas will evaporate, thereby further improving the purity of the silicon carbide powder, and finally obtaining silicon carbide powder with a purity of 99.9999% and a low carbon inclusion content.

[0086] In some of the embodiments, treated air is introduced during the oxidation process.

[0087] It can be understood that the purpose of the above treatment is to use the oxygen in the air to remove the free carbon in the silicon carbide powder. The free carbon is different from carbon encapsulation. Carbon encapsulated in SiC is called carbon encapsulation, and carbon outside SiC is free carbon. Therefore, the purpose of oxidation is to remove free carbon. The reason for pre-treatment of air is to prevent impurities in the air from contaminating SiC raw materials.

[0088] One 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.

[0089] The silicon carbide prepared by the above-mentioned method for preparing silicon carbide powder has high looseness, high purity and low carbon encapsulation content.

[0090] 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.

[0091] 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.

[0092] In order to better illustrate the present application, the contents of the present application are further described below in conjunction with embodiments.

[0093] Example 1

[0094] (1) High-purity carbon powder, high-purity silicon powder and tantalum carbide were mixed and placed in a pot mill barrel and mixed at 200 rpm for 1 hour to obtain a mixture; wherein the molar ratio of the carbon powder to the silicon powder was 1:1.02, and the mass ratio of the total mass of the carbon powder and the silicon powder to the mass of the tantalum carbide was 1:20.

[0095] (2) Use an acrylic shovel to gently transfer the mixture obtained in step (1) into a high-purity graphite crucible, place the loaded graphite crucible into a graphite resistance furnace, purge the furnace four times, exhaust the air in the furnace, and ensure that the gas in the furnace is argon.

[0096] (3) The mixture is subjected to a first temperature-raising treatment, wherein the mixture is heated to 1500° C. at a heating rate of 0.5° C. per minute under an argon atmosphere at a pressure of 28,000 Pa, and the mixture is kept at this temperature for 5 hours to allow the carbon powder and the silicon powder to react to obtain β-SiC.

[0097] (4) The β-SiC is subjected to a second temperature-raising treatment, wherein the temperature is raised to 2100°C at a rate of 0.5°C per minute under an argon atmosphere at a pressure of 15000 Pa, and the temperature is maintained for 15 hours to transform the β-SiC into α-SiC to obtain α-SiC.

[0098] (5) The α-SiC is subjected to a third temperature increase treatment by heating the α-SiC to 2380°C at a heating rate of 0.5°C per minute under an argon atmosphere at a pressure of 50 Pa and then maintaining the temperature for 2 hours.

[0099] (6) Reduce the furnace temperature to 2150°C at a cooling rate of 1°C / min, adjust the argon pressure to 20,000 Pa, and keep it at this temperature for 2 h.

[0100] (7) Raise the furnace temperature to 2380°C at a heating rate of 0.5°C / min, adjust the argon pressure to 50 Pa, and keep warm for 1 h; repeat steps (6) and (7) 5 times.

[0101] (8) During the cooling stage, the temperature is cooled at a constant cooling rate (1°C / min).

[0102] (9) After the graphite crucible has cooled to room temperature, use a sickle made of silicon dioxide to cut the raw materials.

[0103] (10) Place the raw materials in a jar mill and rotate at a speed of 60 rpm to 200 rpm for 1 h to 5 h.

[0104] (11) The raw material obtained in step (10) is screened to screen out the metal compound and obtain silicon carbide powder.

[0105] (12) The silicon carbide powder is placed in an oxidation furnace, and treated air is introduced into the furnace for oxidation at 850° C. for 8 h to obtain silicon carbide powder.

[0106] Example 2

[0107] The preparation methods of silicon carbide powder in Example 2 and Example 1 are basically the same, the only difference is that the total mass ratio of carbon powder and silicon powder to tantalum carbide is different, specifically 1:15.

[0108] The other steps and conditions are the same as those in Example 1.

[0109] Example 3

[0110] The preparation method of silicon carbide powder in Example 3 is basically the same as that in Example 1, the only difference is that the mass ratio of the total mass of carbon powder and silicon powder to the mass ratio of tantalum carbide is different, specifically 1:30.

[0111] The other steps and conditions are the same as those in Example 1.

[0112] Example 4

[0113] The preparation method of silicon carbide powder in Example 4 is basically the same as that in Example 1, except that the type of metal compound is different, specifically yttrium oxide, and the mass ratio of the total mass of carbon powder and silicon powder to yttrium oxide is 1:20.

[0114] The other steps and conditions are the same as those in Example 1.

[0115] Example 5

[0116] The preparation method of silicon carbide powder in Example 5 is basically the same as that in Example 1, except that the cooling process in step (8) is different, specifically, the cooling rate is 5°C / min.

[0117] The other steps and conditions are the same as those in Example 1.

[0118] Comparative Example 1

[0119] The preparation methods of silicon carbide powder in Comparative Example 1 and Example 1 are basically the same, except that tantalum carbide is not added.

[0120] The other steps and conditions are the same as those in Example 1.

[0121] Comparative Example 2

[0122] The preparation methods of silicon carbide powder in Comparative Example 2 and Example 1 are basically the same, the only difference being the type of metal compound, specifically copper oxide.

[0123] The other steps and conditions are the same as those in Example 1.

[0124] Comparative Example 3

[0125] The preparation methods of silicon carbide powder in Comparative Example 3 and Example 1 are basically the same, the only difference being that the mass ratio of the total mass of carbon powder and silicon powder to the mass ratio of tantalum carbide is different, specifically 1:5.

[0126] The other steps and conditions are the same as those in Example 1.

[0127] Comparative Example 4

[0128] The preparation methods of silicon carbide powder in Comparative Example 4 and Example 1 are basically the same, the only difference being that the mass ratio of the total mass of carbon powder and silicon powder to the mass ratio of tantalum carbide is different, specifically 1:40.

[0129] The other steps and conditions are the same as those in Example 1.

[0130] Performance Testing

[0131] 1. The looseness of the silicon carbide powder obtained in the embodiment and the comparative example was tested. Specifically, a certain mass of SiC crystal blocks were placed in the tank mill barrel, the rotation speed was set to 280 rpm, and the particles were crushed to a size of 2 mm to 2.8 mm. By comparing different crushing times, it took a longer time for the material to harden, and a relatively short time was needed for the material to be loose.

[0132] 2. The purity of the silicon carbide powder obtained in the embodiment and the comparative example was tested, and specifically analyzed by inductively coupled plasma mass spectrometry.

[0133] 3. The carbon coating content of the silicon carbide powder obtained in the embodiment and the comparative example was tested by randomly sampling 5 cubic centimeters of raw material ten times and calculating the raw material with carbon coated particles / the sum of the raw material particles. The results are shown in Table 1.

[0134] Table 1

[0135]

[0136] Compared with Example 1, in Comparative Example 1, no metal compound was added, the crushing time was longer, the carbon coating amount of the prepared silicon carbide increased, and the purity decreased; Figure 1 This is a schematic diagram of the silicon carbide powder prepared in Example 1; Figure 2 Schematic diagram of the silicon carbide powder prepared in Comparative Example 1.

[0137] In Comparative Example 2, the melting point of copper oxide is relatively low, which is lower than the reaction temperature of carbon powder and silicon powder, resulting in a serious decrease in the purity of the prepared silicon carbide.

[0138] The mass ratio of the total mass of the carbon powder and the silicon powder used in Comparative Examples 3 to 4 to the mass ratio of the metal compound is not appropriate. The mass ratio is too low, the crushing time is long, the looseness is low, and the carbon encapsulation content of the prepared silicon carbide powder is increased; while the mass ratio is too high, the production capacity is seriously affected.

[0139] Compared with the silicon carbide powder prepared in the comparative example, the silicon carbide powder prepared in the embodiment of the present application has higher looseness and purity and lower carbon encapsulation content, which can meet the practical application of semiconductor materials.

[0140] 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.

[0141] 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 carbon powder, silicon powder and a metal compound to obtain a mixture, wherein the mass ratio of the total mass of the carbon powder and the silicon powder to the mass ratio of the metal compound is 1:15-30; The mixed material is subjected to a temperature-raising treatment in a protective gas atmosphere to allow the carbon powder and the silicon powder to react to prepare a rough body of silicon carbide; the melting point of the metal compound is higher than the reaction temperature of the carbon powder and the silicon powder; The metal compounds in the crude silicon carbide are removed to prepare silicon carbide powder.

2. The method for preparing silicon carbide powder according to claim 1, characterized in that: The metal compound includes one or more of tantalum carbide, tantalum phosphide, cerium dioxide, cerium oxide, lanthanum oxide, gallium oxide, erbium oxide, samarium oxide, yttrium oxide, europium oxide and gadolinium oxide; And / or, the molar ratio of the carbon powder to the silicon powder is 1:1.01-1.05; And / or, the particle size of the silicon carbide powder is less than or equal to 4 mm; And / or, the particle size of the metal compound is 0.6 cm to 0.8 cm; And / or, the mass ratio of the total mass of the carbon powder and the silicon powder to the mass ratio of the metal compound is 1:15-20.

3. The method for preparing silicon carbide powder according to any one of claims 1 to 2, characterized in that: The step of temperature treatment comprises: subjecting the mixture to a first temperature treatment under a protective gas atmosphere to react the carbon powder and the silicon powder to obtain β-SiC; subjecting the β-SiC to a second temperature treatment to transform the β-SiC into α-SiC to obtain α-SiC; subjecting the α-SiC to a third temperature treatment to obtain a rough silicon carbide after cooling.

4. The method for preparing silicon carbide powder according to claim 3, characterized in that: The conditions of the first temperature treatment include: in a protective gas atmosphere and a pressure of 200Pa~80000Pa, heating to 1300℃~1500℃ at a heating rate of 0.1℃~20℃ per minute for a first heat preservation treatment for 2h~4h; And / or, the conditions of the second temperature-raising treatment include: in a protective gas atmosphere and a pressure of 200Pa~80000Pa, heating to 1500℃~2150℃ at a heating rate of 0.1℃~20℃ per minute for 1h~15h, the temperature of the second temperature-raising treatment is higher than that of the first temperature-raising treatment, and the temperature difference between the temperature of the second temperature-raising treatment and the temperature of the first temperature-raising treatment is 550℃~650℃; And / or, the conditions of the third temperature treatment include: in a protective gas atmosphere and a pressure of 50Pa~80000Pa, heating the temperature to 2150℃~2580℃ at a heating rate of 0.1℃~20℃ per minute for 1h~5h, the temperature of the third temperature treatment is higher than that of the second temperature treatment, and the temperature difference between the temperature of the third temperature treatment and the temperature of the second temperature treatment is 100℃~300℃.

5. The method for preparing silicon carbide powder according to claim 3, characterized in that: The cooling process comprises the following steps: The product after the third heating treatment is subjected to a first cooling treatment, so that the temperature of the product is reduced to 2100° C. to 2150° C. at a cooling rate of 0.1° C. to 10° C. per minute, and a first heat preservation treatment is performed; Then, a first heating treatment is performed to raise the temperature of the product to 2280°C to 2580°C at a heating rate of 0.1°C to 20°C per minute, and then a second heat preservation treatment is performed; Repeating the first temperature reduction treatment and the first temperature increase treatment steps n times, where n≥3, to obtain a silicon carbide intermediate; The silicon carbide intermediate is subjected to a cooling treatment so as to reduce the temperature of the silicon carbide intermediate to room temperature at a cooling rate of 0.1° C. to 20° C. per minute.

6. The method for preparing silicon carbide powder according to claim 5, characterized in that: The first heat preservation treatment time is 1h~5h; And / or, the second heat preservation treatment time is 1h~5h.

7. The method for preparing silicon carbide powder according to any one of claims 1 to 2 and 4 to 6, characterized in that: The step of removing impurities from the silicon carbide rough body includes the steps of screening and removing impurities from the silicon carbide rough body in sequence.

8. The method for preparing silicon carbide powder according to claim 7, characterized in that: The impurity removal step includes placing the screened silicon carbide crude body in an oxidation furnace and oxidizing it at 600° C. to 1000° C. for 1 hour to 10 hours.

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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