JP6172048B2 - Silicon carbide fine powder and method for producing the same - Google Patents

Description

  The present invention relates to a silicon carbide fine powder and a method for producing the same, and more particularly to a silicon carbide fine powder containing more β-type crystals than α-type crystals and having a very small particle size and a method for producing the same.

  Conventionally, it is known that exhaust gas from a diesel engine contains a large amount of combustible fine particles that may affect the atmosphere and the human body. In particular, in Europe where the ratio of diesel engine vehicles to automobiles is large, exhaust gas standards for diesel engines are tightened, and further purification of exhaust gas is required. Various methods for purifying exhaust gas from diesel engines have been proposed. For example, a diesel particulate filter (hereinafter referred to as “DPF”) having a honeycomb structure is one of them. Yes (Patent Documents 1 to 3).

  The honeycomb structure DPF disclosed in Patent Document 3 is characterized in that the constituent material is silicon carbide. A DPF made of silicon carbide is formed, for example, by adding and mixing a binder, a sintering aid or the like to a material containing silicon carbide powder to form a predetermined shape, and firing the resulting molded body, It is produced as a ligation. Silicon carbide sintered body has high silicon carbide properties, ie, hardness and thermal conductivity, mechanical properties such as mechanical strength, heat resistance, thermal shock resistance, wear resistance, and slidability, oxidation resistance, and chemical resistance. It retains the properties such as excellent chemical properties and has a relatively high porosity, so it effectively collects combustible particles in the exhaust gas of diesel engines and is effective in purifying the exhaust gas. . However, since the conventional silicon carbide sintered body has room for further improvement in terms of compactness, the mechanical strength decreases when exposed to high-temperature exhaust gas for a long period of time, and the collection of combustible particulates. There is a problem that the efficiency decreases with time.

  In addition to DPF, silicon carbide uses mechanical properties, bearings, sliding parts such as shafts and bearings of chemical pumps, semiconductor manufacturing equipment parts such as wafer forks, wafer chucks and push-up pins, banners, etc. It is used for various applications such as heat-resistant parts such as nozzles and heat exchangers, wear-resistant parts such as blast nozzles and pulverizer liners, grinding parts, and abrasives. These various parts are also mainly composed of a silicon carbide sintered body, but the denseness of the silicon carbide sintered body also affects its long-term durability and the like.

  On the other hand, various techniques for reusing silicon chips generated as a by-product when cutting a silicon plate from a silicon ingot by cutting have been proposed (Patent Documents 4 and 5).

  Patent Document 4 discloses that a waste liquid produced as a by-product when a silicon plate is cut out from a silicon ingot using silicon carbide abrasive grains having a particle size of 10 to 20 μm and water-soluble or water-insoluble coolant (cutting fluid) is centrifuged or filtered. By solid-liquid separation with a vessel, a solid material mainly composed of silicon chips having a particle size of about 2 to 6 μm, silicon carbide abrasive grains having a particle size of 10 to 20 μm, and iron having a particle size of about 1.5 to 4 μm is obtained. The use of this solid material as a raw material for a silicon carbide sintered body is disclosed. However, Patent Document 4 is intended to collect and reuse expensive silicon carbide abrasive grains, and discloses a method for obtaining fine silicon carbide powder from silicon chips contained in the solid matter. Not what you want.

  In Patent Document 5, silicon chips produced as a by-product when cutting a silicon plate from a silicon ingot are subjected to degreasing treatment and dehydration treatment with acid, alkali or alcohol and then mixed with carbon powder, and the resulting mixed powder is non-oxidizing. The manufacturing method of the silicon carbide powder characterized by baking for 6 to 24 hours at the temperature of 1000-1400 degreeC in atmosphere is disclosed. However, since the silicon carbide powder obtained by the method disclosed in Patent Document 5 has a relatively large particle size of about 7 to 13 μm, the silicon carbide sintered body produced from this silicon carbide powder is There is still room for improvement in terms of denseness.

  Silicon carbide is often obtained as a mixed crystal of hexagonal α-type crystals and cubic β-type crystals. It is customary that the content ratio of α-type crystals and β-type crystals in silicon carbide is determined by the temperature and time when the mixture of the Si source compound and the C source compound is fired. It is also considered that other factors such as the type and particle size of the C source compound, the presence of compounds other than the Si source compound and the C source compound are also involved.

JP-A-7-19026 Japanese Patent Application Laid-Open No. 8-283636 Japanese Patent Laid-Open No. 09-071466 JP 2006-256894 A JP 2010-173916 A

  An object of the present invention is to provide a silicon carbide sintered body having a fine grain size and a crystal structure containing more β-type crystals than α-type crystals, and having higher density and mechanical strength than conventional silicon carbide sintered bodies. It is to provide a silicon carbide fine powder and a method for producing the same.

  As a result of intensive research to solve the above problems, the present inventors have conventionally used silicon chips produced as a by-product from the cutting of a silicon ingot as a raw material for silicon carbide synthesis (Si source compound). Whereas only silicon chips were separated and washed from sludge containing silicon chips and coolant such as cutting fluid, the silicon chips with the coolant component adhering to the sludge as it is or as the surface should be used as the Si source compound. Thus, a silicon carbide fine powder having a very fine particle diameter and containing more β-type crystals than α-type crystals can be obtained. By using the silicon carbide fine powder, the fineness, hardness, mechanical strength, etc. The inventors have found that a high silicon carbide sintered body can be obtained, and have completed the present invention.

  That is, the present invention provides the following (1) to (6) silicon carbide fine powder and the following (7) to (12) silicon carbide fine powder.

(1) A β-type crystal obtained by firing a mixture of a silicon powder and a sludge containing silicon chips and coolant having fine irregularities on the surface, obtained by cutting a silicon ingot, and a carbon powder rather than an α-type crystal Silicon carbide fine powder characterized by containing a large amount.
(2) The silicon carbide fine powder according to (1) above, wherein the silicon chips have an average particle size of 1 μm or less.
(3) The above (1) or (2), wherein the sludge is a by-product in a step of cutting a silicon plate from a silicon ingot using a fixed abrasive tool having a strand diameter of 120 μm or less and an abrasive grain size of 30 μm or less and a coolant. Silicon carbide fine powder.
(4) The silicon carbide fine powder according to any one of (1) to (3), wherein the firing is performed at a temperature of 1100 to 1450 ° C. in a non-oxidizing atmosphere.
(5) The silicon carbide fine powder according to any one of (1) to (4), wherein the mixture is dried and then fired.
(6) The silicon carbide fine powder according to any one of the above (1) to (5), which substantially does not contain α-type crystals and consists only of β-type crystals.

(7) β-type characterized by mixing sludge containing silicon chips and coolant having fine irregularities on the surface obtained by cutting a silicon ingot and carbon powder, and firing the obtained mixture A method for producing fine silicon carbide powder containing more crystals than α-type crystals.
(8) The method for producing a silicon carbide fine powder according to (7), wherein the silicon chips have an average particle size of 1 μm or less.
(9) The above (7) or (8), wherein the sludge is a by-product in the step of cutting a silicon plate from a silicon ingot using a fixed abrasive tool having a strand diameter of 120 μm or less and an abrasive grain size of 30 μm or less and a coolant. Of manufacturing silicon carbide fine powder.
(10) The method for producing a silicon carbide fine powder according to any one of (7) to (9), wherein the firing is performed at a temperature of 1100 to 1450 ° C. in a non-oxidizing atmosphere.
(11) The method for producing a silicon carbide fine powder according to any one of (7) to (10), wherein the mixture is dried and then fired.
(12) The method for producing a silicon carbide fine powder according to any one of (7) to (11), wherein at least one treatment selected from a decarburization treatment and a pulverization treatment is further performed after firing.

  ADVANTAGE OF THE INVENTION According to this invention, the silicon carbide fine powder which can provide the silicon carbide sintered compact with high density and high mechanical strength, and its manufacturing method are provided.

It is process drawing which outlines and shows one Embodiment of the manufacturing method of the silicon carbide fine powder of this invention.

  The silicon carbide fine powder of the present invention comprises silicon chips (Si source compound) having a coolant component adhering to sludge or a surface containing silicon chips and coolant, and carbon powder (C source). It is obtained by firing a mixture with (compound) and is characterized by its particle size and crystal structure as shown below.

  The silicon carbide fine powder of the present invention has an average particle diameter substantially equal to that of silicon chips used as the Si source compound, and the average particle diameter is preferably 1 μm or less. By having such a fine average particle diameter, a silicon carbide sintered body having a high density and a predetermined porosity can be obtained. Therefore, the DPF made of the sintered body has a very high collection effect of combustible fine particles in the exhaust gas of the diesel engine. In the present specification, the average particle diameter means a volume average particle diameter, and is measured using a laser diffraction / scattering particle size distribution measuring apparatus or a flow image analysis method. Laser diffraction / scattering type particle size distribution measuring devices are commercially available, and examples include LA-920 (trade name, manufactured by Horiba, Ltd.), Microtrack MT3000 (trade name, manufactured by Nikkiso Co., Ltd.), and the like. Various types of flow image analysis apparatuses are also commercially available.

  Moreover, the silicon carbide fine powder of the present invention has a crystal structure containing more β-type crystals than α-type crystals. Since the β-type crystal of silicon carbide is the same cubic crystal as diamond, the silicon carbide fine powder of the present invention containing a large amount of β-type crystal has characteristics such as extremely high hardness and mechanical strength. The silicon carbide sintered body produced using the silicon carbide fine powder of the present invention has high properties such as hardness and thermal conductivity of the silicon carbide fine powder of the present invention, mechanical strength, heat resistance, thermal shock resistance, wear resistance. Reflecting properties such as excellent mechanical properties such as resistance and slidability, and chemical properties such as oxidation resistance and chemical resistance, the hardness and mechanical strength are remarkably high, and heat resistance and the like are also excellent. Due to its high density and mechanical strength, the DPF made of the sintered body has little deterioration even when exposed to high-temperature exhaust gas from a diesel engine for a long period of time. Can fully demonstrate.

  The content ratio of β-type crystal and α-type crystal in the fine powder of silicon carbide of the present invention is such that β-type crystal: α-type crystal (weight ratio) is 50 or more: less than 50 to 100: 0, preferably 90:10 to 100 : 0, more preferably 95: 5 to 100: 0, still more preferably 99: 1 to 100: 0. The silicon carbide fine powder of the present invention is generally composed of β-type crystals and may contain a trace amount of α-type crystals. To do. The silicon carbide fine powder of the present invention preferably contains more β-type crystals from the viewpoint of higher hardness and mechanical strength. In the present invention, the presence of β-type crystals and α-type crystals can be confirmed by an X-ray diffraction method, and each content ratio of β-type crystals and α-type crystals can be quantified by an X-ray diffraction powder method.

  Next, the manufacturing method of the silicon carbide fine powder of this invention is demonstrated. The silicon carbide fine powder of the present invention can be obtained, for example, by the production method shown in FIG. FIG. 1 is a process diagram schematically showing an embodiment of a method for producing a silicon carbide fine powder of the present invention. The manufacturing method shown in FIG. 1 includes steps (S1) to (S6).

  Step (S1) is a Si source preparation step of preparing silicon chips having a coolant component adhering to the sludge or surface to be the Si source compound in the present invention. In the step (S1), sludge is obtained as a waste liquid by cutting a silicon ingot using a coolant.

  From the viewpoint of efficiently synthesizing the silicon carbide fine powder of the present invention, the sludge contains silicon chips and coolant, and preferably contains silicon chips and coolant and does not contain silicon carbide abrasive grains. Since the silicon carbide abrasive grains are usually about 10 to 20 μm in average particle size, the particle growth is promoted during firing and the like, and the average particle size of the silicon carbide fine powder as a target product may be increased. There is. The silicon ingot used here is made of silicon single crystal or polycrystal, and is a high-purity product having a silicon purity of preferably 99% or more, more preferably 99.9% or more, and further preferably 99.99% or more. It is desirable.

  The cutting method of the silicon ingot is not particularly limited as long as it is a cutting method that cuts the silicon plate that is the base of the silicon substrate from the silicon ingot using the coolant, but the silicon chips and the average particle of the silicon carbide fine powder that is the target product are not limited. From the viewpoint of making the diameter smaller, a fixed abrasive method is preferable, and a fixed abrasive method using a fixed abrasive tool having a wire diameter of 120 μm or less and an abrasive particle size of 30 μm or less (preferably 4 to 30 μm). The cutting method is more preferable. Examples of the fixed abrasive tool include a diamond saw wire in which the wire diameter and the abrasive particle diameter are in the above ranges, and the abrasive grains are diamond abrasive grains.

  The silicon chips produced as a by-product when cutting a silicon ingot have an average particle size of several tens of μm or less, preferably several μm or less, more preferably 1 μm or less, fine irregularities on the surface, and a specific surface area. Large silicon particles. As described above, the average particle size of the silicon chips has an influence on the average particle size of the silicon carbide fine powder that is the object. Moreover, the average particle diameter and specific surface area of silicon chips may affect the crystal structure of the target silicon carbide fine powder. In particular, although not sufficiently clear at present, it is presumed that the content ratio of β-type crystals may be increased due to the large specific surface area of silicon chips.

  Among silicon chips, from the viewpoint of further increasing the specific surface area and further reducing the average particle size, a fixed abrasive type cutting method using a fixed abrasive tool having a wire diameter of 120 μm or less and an abrasive particle size of 30 μm or less Silicon chips generated as a by-product in are preferable. The silicon chips are silicon particles having an average particle size as fine as usually 1 μm or less, having fine irregularities on the surface, and a very large specific surface area. In addition, since the fixed abrasive type cutting method using a fixed abrasive tool having an element wire diameter of 120 μm or less and an abrasive particle size of 30 μm or less can be carried out without using silicon carbide abrasive grains, the by-product sludge is silicon chips and Since only the coolant is included and no silicon carbide abrasive grains are included, the cutting method is preferable also in this respect.

  Moreover, as a coolant, a coolant (or cutting fluid) used for cutting a silicon ingot can be used without any particular limitation, and includes, for example, a solvent as an essential component, and a lubricant, anticorrosive, antifoaming agent, thickener, etc. An aqueous coolant containing as an optional component.

Examples of the solvent contained in the aqueous coolant include a water-soluble solvent and a water-miscible solvent.
The water-soluble solvent is not particularly limited. For example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, glycerin, polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol Polymer, hexylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, pentaerythritol, sorbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Lower alcohols such as methanol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, methanol, ethanol and isopropyl alcohol And the like. Among these, from the viewpoint of reducing the average particle size of the target silicon carbide fine powder, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, glycerin, Polyoxyalkylene glycols such as polyethylene glycol and polypropylene glycol are preferred, and diethylene glycol is more preferred. The water-miscible solvent is not particularly limited, and examples thereof include acetone, tetrahydrofuran, and kerosene. Each of the water-soluble solvent and the water-miscible solvent can be used alone or in combination of two or more, and a water-soluble solvent and a water-miscible solvent may be used in combination. The content of the solvent in the aqueous coolant is not particularly limited, but is preferably 0.05 to 98% by weight of the total amount of the aqueous coolant, and more preferably 0.2 to 70% by weight of the total amount of the aqueous coolant.

  Examples of the lubricant include polyoxyalkylene alkyl aryl ether, polyoxyethylene polyoxypropylene polyol, polyoxyalkylene alkyl ether, polyoxyalkylene polyhydric alcohol fatty acid ester, polyoxyalkylene styrenated aryl ether, polyoxyalkylene fatty acid ester. , Polyoxyalkylene alkylamines, polyoxyalkyl mercaptans and polyhydric alcohol fatty acid esters, ethylene oxide adducts of hydroxycarboxylic acid and diglycerin esters, ethylene oxide adducts of hydroxycarboxylic acid and triglycerin esters Surfactants, anionic surfactants, fatty acids, fatty acid polycondensates and the like can be mentioned. Examples of the anticorrosive include benzotriazoles such as benzotriazole, and amines such as monoethanolamine and diethanolamine. Examples of the antifoaming agent include silicone compounds, acetylenic diol compounds, polyglycol compounds, and lower alcohols exemplified as water-soluble solvents. Examples of the thickener include water-soluble polymer compounds such as methylcellulose, polyacrylic acid, and polyvinylpyrrolidone.

  In the present invention, the sludge can be used as it is as a Si source compound, but from the viewpoint of improving work efficiency, etc., the sludge is solid-liquid separated by a separation means such as filtration, and the coolant component is attached to the surface. Silicon chips may be used as the Si source compound.

  Step (S2) is a mixing step in which silicon sludge having a coolant component attached to the sludge or surface obtained in step (S1) and carbon powder are mixed.

  The average particle size of the carbon powder used here is not particularly limited, but the reactivity with the silicon chips contained in the sludge, the dispersibility of the carbon powder in the sludge, the silicon chips with the coolant component adhering to the surface and the carbon powder In consideration of the uniform mixing property, the thickness is preferably 1 μm or less, and more preferably 0.2 μm or less. When the sludge and carbon powder are mixed, a general dispersant for dispersing the inorganic powder in the liquid may be added in order to improve the dispersibility of the carbon powder in the sludge.

  The mixing ratio of silicon chips with coolant components attached to the sludge or the surface and the carbon powder is appropriately selected according to the amount of silicon chips, etc., but if the amount of carbon powder is too large, the unreacted carbon afterwards is removed. Since the cost required for the decarburizing step to be performed becomes high and the time becomes long, it is preferable to mix carbon in a ratio of 1 to 1.5 mol with respect to 1 mol of silicon. If the mixing amount of the carbon powder is less than 1 mol, a large amount of unreacted silicon and silicon compounds other than silicon carbide may be formed after firing. On the other hand, if it exceeds 1.5 mol, the decarburization process requires more cost and time than necessary. There is a fear.

  Further, the content of solids in the mixture of sludge and carbon powder (mainly the total content of silicon chips and carbon powder) may be appropriately selected within a range in which operability and the like do not deteriorate, preferably It is 10% by weight or more, preferably 15% by weight or more of the total amount of the mixture. When the solid content is less than 10% by weight, the operability and the like are lowered, and the solid and the liquid component of the coolant are easily separated, which may reduce the effect of coexisting the coolant.

Step (S3) is a drying step of drying the mixture of silicon chips and carbon powder having the coolant component attached to the sludge or surface obtained in step (S2).
In the step (S4), which will be described later, since the drying of the mixture proceeds even while the mixture is put into a firing furnace and raised to a predetermined firing temperature, the step (S3) is an essential step in the production method of the present invention. is not. However, depending on the particle size and specific surface area of silicon chips, the positional relationship between silicon chips and carbon powder in the mixture may affect the particle size and crystal structure of the silicon carbide fine powder obtained. Therefore, although the step (S3) is an optional step, it is preferably performed. The drying temperature of the mixture is appropriately selected in consideration of the type and cost of the firing furnace as long as the reaction between silicon and carbon does not occur. Moreover, you may dry, after shape | molding the mixture obtained at the process (S2) in the predetermined shape.

  In step (S4), silicon carbide is obtained by firing the sludge obtained in step (S2) or a mixture of silicon chips and carbon powder having a coolant component attached to the surface or the dried product obtained in step (S3). This is a firing step for obtaining fine powder or a sintered body thereof.

  Although the firing temperature in the step (S4) is not particularly limited, reducing the average particle size of the obtained silicon carbide fine powder, making the fine powder a crystal structure containing more β-type crystals than α-type crystals, Furthermore, in view of facilitating crushing of the sintered body, the temperature is preferably 1100 to 1450 ° C, more preferably 1200 to 1450 ° C. When the firing temperature is less than 1100 ° C., the reaction between silicon chips and carbon powder becomes insufficient, and a large amount of unreacted silicon or carbon may remain. If the firing temperature exceeds 1450 ° C., the particle size of the resulting silicon carbide fine powder may increase, and the content ratio of β-type crystals in the fine powder may decrease. The firing time can be appropriately selected according to the firing temperature. For example, when the firing temperature is 1200 to 1450 ° C., it is 1 to 2 hours, and when the firing temperature is 1100 ° C. or more and less than 1200 ° C., fine powder crystals A slightly longer baking time may be set while checking the structure.

  In addition, even if the calcination temperature and / or the calcination time in the step (S4) are out of the above range, the silicon carbide fine powder of the present invention can be obtained by adjusting the particle size and specific surface area of silicon chips, for example. Is possible. Moreover, the adjustment of the particle size and specific surface area of the silicon chips can be performed, for example, by changing cutting conditions of the silicon ingot.

  In the step (S4), silicon carbide fine powder or a sintered body thereof is obtained. When the silicon carbide fine powder is obtained, the production may be finished as it is, and the step (S5) may be performed as necessary. Further, when a sintered body of silicon carbide fine powder is obtained, the sintered body is not sintered and can be pulverized by applying a light load. The silicon carbide fine powder may be used to complete the production, and the step (S5) may be performed as necessary.

  Step (S5) is a crushing step for pulverizing the sintered body of the silicon carbide fine powder obtained in step (S4). Step (S5) is an optional step. As described above, since the sintered body has not been sintered and has low mechanical strength, it is not necessary to perform pulverization using a pulverizer such as a ball mill or a jet mill. It can be easily pulverized by a method of applying a light load such as a method of lightly grinding with a method of applying a light load such as a method of applying vibration to the container. If necessary, a further pulverization treatment may be performed to further refine the silicon carbide fine powder obtained by crushing. In the present invention, the production may be terminated in step (S5), and step (S6) may be performed as necessary.

In step (S6), decarburization is performed to remove unreacted carbon and the like from the silicon carbide fine powder of the present invention obtained in step (S4) or step (S5), and to further increase the silicon carbide purity of the fine powder. It is a process. Step (S6) is an optional step. The step (S6) can be performed according to a known method, for example, by heating the silicon carbide fine powder of the present invention to 500 to 700 ° C. in an oxidizing atmosphere.
In addition, in this embodiment, although it performs in order of a crushing process (S5) and a decarburizing process (S6), it is not limited to this, In order of a decarburizing process (S6) and a crushing process (S5). You may do it.

  By using the silicon carbide fine powder of the present invention obtained by the above-described production method, a silicon carbide sintered body having high density and high mechanical strength can be obtained.

  A known method can be used to obtain a silicon carbide sintered body from the silicon carbide fine powder of the present invention. For example, a binder, a sintering aid, and the like are added to and mixed with the fine powder of silicon carbide of the present invention, and the resulting mixture is degreased and / or dried as necessary, and then fired to obtain denseness and mechanical strength. High silicon carbide sintered body can be obtained. Alternatively, a silicon carbide sintered body may be manufactured by preparing an aqueous slurry containing the silicon carbide fine powder of the present invention, forming the slurry into a predetermined shape, and firing the slurry.

  Examples of the binder used above include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, and epoxy resin. At this time, a dispersant or a dispersion medium may be added together with the binder. Examples of the dispersant include phosphoric acid ester compounds such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris (2-chloroethyl) phosphate, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, and the like. Examples of the dispersion medium liquid include organic solvents such as benzene and cyclohexane, lower alcohols such as methanol, water, and the like. Examples of the sintering aid include C, B, Al, Y, and Ca. Moreover, although the baking temperature of the said molded object is not specifically limited, For example, it is 400-650 degreeC.

  The silicon carbide sintered body produced using the silicon carbide fine powder of the present invention can be used for various applications similar to conventional silicon carbide sintered bodies, but is particularly preferably used for DPF. That is, the silicon carbide fine powder of the present invention is preferably used as a raw material for a DPF silicon carbide sintered body.

  The present invention will be specifically described with reference to examples.

Example 1
A silicon ingot (purity 99.9999% or more) is cooled with an aqueous coolant containing 70% by weight of diethylene glycol using a saw wire (diamond abrasive grains, average particle size of about 10 to 20 μm) prepared by a fixed abrasive method. Then, a sludge containing 1% by weight of silicon chips, which is silicon powder having an average particle diameter of about 1 μm, was obtained. Next, the sludge was filtered to obtain silicon chips with a coolant component attached to the surface.

  100 parts by weight of silicon chips having a coolant component adhered to the surface obtained above are mixed with 100 parts by weight of carbon black (average particle size: about 0.04 μm) as a carbon powder so that the molar ratio of silicon to carbon is 1. : Adjusted to 1.4 and kneaded. The obtained mixture (kneaded product) was dried by heating in air at a temperature of 250 ° C. for 2 hours, and then calcined in an argon atmosphere at a temperature of 1250 ° C. for 2 hours to cause silicon and carbon to react. A sintered body was obtained.

  The sintered body obtained above was decarburized by heating in air at 550 ° C. for 2 hours, and further pulverized to obtain a fine powder having an average particle size of 1 μm or less. When the crystal structure of this fine powder was confirmed by X-ray diffraction, it was a silicon carbide fine powder consisting essentially of β-type crystals. Further, the oxygen content of this silicon carbide fine powder was 0.75% by weight, and metal impurities were most detected in Fe, Ni and Zr, but all were 0.1% by weight or less.

Claims (6)

Silicon carbide fine powder substantially free of α-type crystals and consisting only of β-type crystals . Obtained by cutting the silicon ingot, the surface looking containing silicon chips and coolant having fine irregularities, and silicon chips coolant component is attached to the sludge or the surface not containing silicon carbide abrasive grains, and carbon powder were mixed And the obtained mixture is fired at a temperature of 1200 to 1450 ° C. in a non-oxidizing atmosphere, and the production of silicon carbide fine powder substantially free of α-type crystals and consisting only of β-type crystals Method. The method for producing a silicon carbide fine powder according to claim 2 , wherein the silicon chips have an average particle size of 1 μm or less. The silicon carbide according to claim 2 or 3 , wherein the sludge is a by-product in a step of cutting a silicon plate from a silicon ingot using a fixed abrasive tool having a strand diameter of 120 µm or less and an abrasive grain size of 30 µm or less and a coolant. Manufacturing method of fine powder. The method for producing fine silicon carbide powder according to any one of claims 2 to 4 , wherein the mixture is dried and then fired. The method for producing silicon carbide fine powder according to any one of claims 2 to 5 , wherein at least one treatment selected from a decarburization treatment and a pulverization treatment is further performed after the firing.

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