A method for preparing silicon carbide material using silicon slag as raw material and its application

Abstract

The present invention discloses a method and application for preparing silicon carbide material using silicon slag as raw material, and belongs to the field of silicon carbide preparation. The specific preparation method is as follows: the silicon slag is crushed and wet-ground, and the wet-ground material is added into a flotation tank for flotation to obtain a flotation concentrate, and then the flotation concentrate is acid-leached and then graphite is added for ultrasonic treatment, and constant temperature drying is performed for rapid Joule thermal shock, and the powder produced after the thermal shock is ultrasonically treated, and filtered and dried to obtain silicon carbide powder. The present invention is applied to the preparation of silicon carbide, and belongs to a rapid Joule thermal shock synthetic material process, which provides a feasible development direction for the industrial production of silicon carbide powder prepared by recycling silicon slag, and the operation process of the present invention is simple, the process cost is low, and it is pollution-free to the environment.

Description

Technical Field

[0001] The invention relates to a method for preparing silicon carbide material by taking silicon slag as raw material and application thereof, belonging to the technical field of silicon slag recovery and preparation. Background Art

[0002] As one of the third-generation semiconductors, silicon carbide (SiC) has good electrical and optical properties such as large band gap width, high electron mobility, critical breakdown electric field strength and adjustable luminescence performance. At the same time, SiC has excellent mechanical properties such as high mechanical strength and high hardness, and good thermal properties such as high thermal conductivity and low thermal expansion coefficient. The excellent electrical, optical, thermal and mechanical properties make SiC promising for use in high-temperature and high-frequency devices. However, due to the presence of Si-C covalent bonds with high bond energy in SiC, on the one hand, it has extremely high hardness and is difficult to process; on the other hand, it has a high melting point and is difficult to achieve dense sintering. Therefore, as a typical difficult-to-process material, silicon carbide greatly limits its application in its respective fields. Finding a method to easily prepare silicon carbide is an urgent problem to be solved.

[0003] At present, the preparation of silicon carbide powder is mainly achieved by high-temperature self-propagating synthesis. This method uses high temperature to give the reactants initial heat to start a chemical reaction. As the reaction proceeds, the unreacted substances continue to complete the chemical reaction under the condition of reaction exotherm. However, the silicon powder used in this method usually contains a high content of impurity elements, which will participate in the reaction during the subsequent synthesis process, resulting in a high concentration of impurities in the powder. The low melting point of silicon powder limits the high-temperature purification treatment before the synthesis reaction, resulting in the inability to remove impurities in the growth environment. In addition, the self-propagating method usually requires the addition of additional auxiliary reactants to maintain the process, which inevitably causes contamination by foreign impurities. The above factors will lead to the presence of higher concentrations of impurity elements in the synthesized silicon carbide powder, thereby affecting the subsequent preparation of semi-insulating silicon carbide single crystals.

[0004] In summary, it is necessary to develop a new technology for preparing silicon carbide, which uses silicon slag as the source of raw materials to reduce impurity elements, and through simple pretreatment to form a small amount of silicon carbide as a doping material for rapid synthesis in a short time, so as to prepare silicon carbide powder material. Summary of the invention

[0005] In order to solve the problem that silicon carbide is difficult to prepare, one of the purposes of the present invention is to provide a method for preparing silicon carbide material using silicon slag as raw material, the method comprising the following steps:

[0006] (1) The silicon slag is crushed and classified to screen the fine silicon slag.

[0007] (2) The fine silicon slag screened in step (1) is wet-ground, and the silicon slag solution after wet-ground is added to a flotation tank, and an inhibitor and a collector are added to perform interface modification flotation, and the flotation concentrate is acid-leached with an acid leaching solution and dried at a constant temperature to obtain silicon slag fine powder.

[0008] (3) The silicon slag fine powder and graphite obtained in step (2) are added to a dispersant solution (there is no special requirement for the amount of the dispersant solution, as long as the silicon slag fine powder and graphite are evenly dispersed) and ultrasonically mixed to obtain a uniform slurry.

[0009] (4) Drying the uniform slurry obtained in step (3), placing it in a Joule thermal shock mold, extruding the powder to obtain a thin film powder bed with porosity, further treating it by rapid thermal shock flash method, thermal shock treatment in a vacuum atmosphere, and preparing silicon carbide powder by direct silicon-carbon reaction.

[0010] Preferably, the silicon slag in step (1) is waste silicon slag produced by bulk industrial refined silicon.

[0011] Preferably, the crusher used in the crushing in step (1) is one of a jaw crusher, a cone crusher, an impact crusher, a gyratory crusher and a roll crusher.

[0012] Preferably, the fine silicon slag screened in step (1) has a particle size of 1 mm to 100 μm.

[0013] Preferably, the wet grinding method in step (2) is one of rod milling, ball milling, sand milling and stirred milling.

[0014] Preferably, the amount of the inhibitor added in step (2) is 50-1000 g / t, and the inhibitor is one or more of water glass, PAM, SHMP, -PEG, sodium carboxymethyl cellulose, starch, sodium metaphosphate and thioacid salt mixed in any proportion.

[0015] Preferably, the amount of collector added in step (2) is 100-1000 g / t, and the collector is one or more of No. 2 oil, oleic acid, kerosene, xanthate, OP-10, fatty amine, etc. mixed in any proportion.

[0016] Preferably, the amount of the acid leaching solution in step (2) is 1-50 ml / g, the concentration of the acid leaching solution is 1-6 mol / L, and the acid leaching solution is one or more of hydrochloric acid, nitric acid, hypochlorous acid, perchloric acid, and hydrofluoric acid mixed in any proportion.

[0017] Preferably, the mass of graphite added in step (3) is 5% to 50% of the mass of graphite and silicon slag powder.

[0018] Preferably, the graphite in step (3) is one or more of spherical graphite, flake graphite, artificial graphite, and natural graphite mixed in any proportion.

[0019] Preferably, the concentration of the dispersant solution in step (3) is 5-50%, and the dispersant is one or more of glucose, sucrose, asphalt, citric acid mixed in any proportion with deionized water to form the dispersant solution.

[0020] Preferably, in step (4), a flash thermal shock method is used, the resistance of the mixed powder in the thermal shock mold is adjusted to 0.5-2Ω, the Joule thermal shock voltage is set to 50-220V, the shock temperature is set to 650-2500°C, the heating rate is set to 1000-4000°C / s, and the number of Joule thermal shocks is set to 1-10 times.

[0021] Beneficial Effects of the Invention

[0022] (1) The invention has a simple operation process. The first step of the treatment can simply and effectively obtain the flotation concentrate powder of silicon and silicon carbide. The subsequent carbon doping and thermal shock can effectively reduce the resistance and better realize the preparation of silicon carbide. The flotation concentrate containing a small amount of silicon carbide can effectively induce the growth of silicon and carbon after ultrasonic mixing on the original silicon carbide, so that the prepared silicon carbide powder has a regular morphology, uniform particle size, and concentrated particle distribution. The specific surface area of ​​the prepared silicon carbide is 20 to 28 m 2 / g, and the dielectric constant is 9.72~9.86.

[0023] (2) The present invention provides a method and application for preparing silicon carbide material using silicon slag as raw material. Silicon carbide prepared using cheap silicon slag realizes the value-added utilization of waste materials and provides an application for the subsequent preparation of single-crystal silicon carbide.

[0024] (3) The silicon carbide prepared by the present invention is hexagonal α-SiC, and the prepared silicon carbide has a relatively high specific surface area of ​​20 to 28 m 2 / g, and the dielectric constant is 9.74-9.86. The measured specific surface area and dielectric constant can meet the needs of semiconductor applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of preparing silicon carbide in the present invention.

[0026] Figure 2 This is the XRD pattern of silicon carbide prepared in Example 1.

[0027] Figure 3 This is the SEM image of the silicon carbide prepared in Example 1. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following embodiments are merely simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0029] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0030] Example 1

[0031] A method for preparing silicon carbide material using silicon slag as raw material, the preparation process is as follows Figure 1 As shown, the specific steps include:

[0032] (1) The silicon slag produced by refining the raw material block industrial silicon is crushed and classified by a jaw crusher to screen the fine silicon slag with a particle size of 1 mm.

[0033] (2) The fine silicon slag is wet-grinded by a rod mill, and the silicon slag solution after wet grinding is added to a flotation tank, and 300 g / t of an inhibitor sodium silicate and 200 g / t of a collector No. 2 oil are added to perform interface modification flotation. The flotation concentrate is acid-leached with 3 mol / L hydrochloric acid, and then dried at 60° C. for 120 minutes to obtain silicon slag fine powder.

[0034] (3) The dried silicon slag fine powder and artificial graphite are added to a dispersion solution containing 10% asphalt and ultrasonically mixed to obtain a uniform slurry, wherein the amount of artificial graphite is 10% of the total mass of the silicon slag fine powder and the artificial graphite.

[0035] (4) The uniform slurry is dried and placed in a Joule thermal shock mold. The powder is extruded to obtain a thin film powder bed with porosity. The powder is further treated by a rapid thermal shock flash method, with the flash resistance set to 1.5Ω, the heating temperature to 1650°C in a vacuum atmosphere, and the impact is performed twice to prepare silicon carbide powder.

[0036] The XRD pattern of silicon carbide prepared in this example is as follows: Figure 2 As shown in the figure, it can be seen that the XRD graph mainly shows characteristic peaks of silicon carbide. Silicon carbide was prepared by thermal shock. Through detection, it was found that the prepared silicon carbide was hexagonal α-SiC, and the relative crystallinity of silicon carbide was good.

[0037] The SEM image of silicon carbide prepared in this embodiment is as follows: Figure 3 As shown, it can be seen from the figure that the prepared silicon carbide is in the form of stacked layers, which can effectively increase the specific surface area of ​​the prepared silicon carbide.

[0038] The specific surface area of ​​the silicon carbide prepared in this example is 25.7 m 2 / g, and the dielectric constant is 9.86.

[0039] Example 2

[0040] A method for preparing silicon carbide material using silicon slag as raw material, the preparation process is as follows Figure 1 As shown, the specific steps include:

[0041] (1) The silicon slag produced by refining the raw material block industrial silicon is crushed and classified by a jaw crusher to screen the fine silicon slag with a particle size of 1 mm.

[0042] (2) The fine silicon slag is wet-grinded by a rod mill, and the silicon slag solution after wet grinding is added to a flotation tank, and 300 g / kg of an inhibitor sodium silicate and 200 g / kg of a collector PEG are added to perform interface modification flotation. The flotation concentrate is acid-leached with 4 mol / L hydrochloric acid, dried at 60° C., and the silicon slag fine powder is obtained for 120 minutes.

[0043] (3) The dried silicon slag fine powder and artificial graphite are added to a dispersant solution containing 10% glucose and ultrasonically mixed to obtain a uniform slurry, wherein the amount of artificial graphite is 10% of the total mass of the silicon slag fine powder and the artificial graphite.

[0044] (4) The uniform slurry is dried and placed in a Joule thermal shock mold. The powder is extruded to obtain a thin film powder bed with porosity. The powder is further treated by a rapid thermal shock flash method, with the flash resistance set to 1.5Ω, the heating temperature to 1650°C in a vacuum atmosphere, and the impact is performed twice to prepare silicon carbide powder.

[0045] The specific surface area of ​​the silicon carbide prepared in this example is 24.5 m 2 / g, and the dielectric constant is 9.76.

[0046] Example 3

[0047] A method for preparing silicon carbide material using silicon slag as raw material, the preparation process is as follows Figure 1 As shown, the specific steps include:

[0048] (1) The silicon slag produced by refining the raw material block industrial silicon is crushed and classified by a jaw crusher to screen the fine silicon slag with a particle size of 1 mm.

[0049] (2) The fine silicon slag is wet-grinded by a rod mill, and the silicon slag solution after wet grinding is added to a flotation tank, and 200 g / kg of an inhibitor sodium silicate and 200 g / kg of a collector PEG are added to perform interface modification flotation. The flotation concentrate is acid-leached with 3 mol / L hydrochloric acid, dried at 80° C., and the silicon slag fine powder is obtained for 120 minutes.

[0050] (3) The dried silicon slag fine powder and artificial graphite are added to a dispersant solution containing 10% sucrose and ultrasonically mixed to obtain a uniform slurry, wherein the amount of artificial graphite is 20% of the total mass of the silicon slag fine powder and the artificial graphite.

[0051] (4) The uniform slurry is dried and placed in a Joule thermal shock mold. The powder is extruded to obtain a thin film powder bed with porosity. The powder is further treated by a rapid thermal shock flash method, with the flash resistance set to 2Ω, the heating temperature to 1650°C in a vacuum atmosphere, and the impact is performed twice to prepare silicon carbide powder.

[0052] The specific surface area of ​​the silicon carbide prepared in this example is 27.2 m 2 / g, and the dielectric constant is 9.76.

[0053] Example 4

[0054] A method for preparing silicon carbide material using silicon slag as raw material, the preparation process is as follows Figure 1 As shown, the specific steps include:

[0055] (1) The silicon slag produced by refining the raw material block industrial silicon is crushed and classified by a jaw crusher to screen the fine silicon slag with a particle size of 1 mm.

[0056] (2) The fine silicon slag is wet-grinded by a rod mill, and the silicon slag solution after wet grinding is added to a flotation tank, and 100 g / kg of an inhibitor sodium silicate and 200 g / kg of a collector PEG are added to perform interface modification flotation. The flotation concentrate is acid-leached with 2 mol / L hydrochloric acid, dried at 80° C., and the silicon slag fine powder is obtained for 180 minutes.

[0057] (3) The dried silicon slag fine powder and spherical graphite are added to a dispersant solution containing 10% glucose and ultrasonically mixed to obtain a uniform slurry, wherein the amount of artificial graphite is 10% of the total mass of the silicon slag fine powder and the spherical graphite.

[0058] (4) The uniform slurry is dried and placed in a Joule thermal shock mold. The powder is extruded to obtain a thin film powder bed with porosity. The silicon carbide material is prepared by further rapid thermal shock treatment, heating to 1350°C in a vacuum atmosphere and impacting twice.

[0059] The specific surface area of ​​the silicon carbide prepared in this example is 23.2 m 2 / g, and the dielectric constant is 9.89.

[0060] Example 5

[0061] A method for preparing silicon carbide material using silicon slag as raw material, the preparation process is as follows Figure 1 As shown, the specific steps include:

[0062] (1) The silicon slag produced by refining the raw material block industrial silicon is crushed and classified by a jaw crusher to screen the fine silicon slag with a particle size of 1 mm.

[0063] (2) The fine silicon slag is wet-grinded by a rod mill, and the silicon slag solution after wet grinding is added to a flotation tank, and 300 g / kg of an inhibitor sodium silicate and 200 g / kg of a collector PEG are added to perform interface modification flotation. The flotation concentrate is acid-leached with 3 mol / L hydrochloric acid, and then dried at 60° C. for 120 minutes to obtain silicon slag fine powder.

[0064] (3) The dried silicon slag fine powder and 20% natural graphite are added to a dispersant solution containing 50% asphalt and ultrasonically mixed to obtain a uniform slurry, wherein the amount of natural graphite is 20% of the total mass of the silicon slag fine powder and the spherical graphite.

[0065] (4) The uniform slurry is dried and placed in a Joule thermal shock mold. The powder is extruded to obtain a thin film powder bed with porosity. The powder is further treated by a rapid thermal shock flash method, with the flash resistance set to 1.5Ω, the heating temperature to 1650°C in a vacuum atmosphere, and the impact is performed 4 times to prepare silicon carbide powder.

[0066] The specific surface area of ​​the silicon carbide prepared in this example is 22.4 m 2 / g, and the dielectric constant is 9.96.

[0067] Example 6

[0068] A method for preparing silicon carbide material using silicon slag as raw material, the preparation process is as follows Figure 1 As shown, the specific steps include:

[0069] (1) The silicon slag produced by refining the raw material block industrial silicon is crushed and classified by a jaw crusher to screen the fine silicon slag with a particle size of 1 mm.

[0070] (2) The fine silicon slag is wet-grinded by a rod mill, and the silicon slag solution after wet grinding is added to a flotation tank, and 300 g / kg of an inhibitor sodium silicate and 200 g / kg of a collector PEG are added to perform interface modification flotation. The flotation concentrate is acid-leached with 3 mol / L hydrochloric acid, dried at 80° C., and the silicon slag fine powder is obtained for 180 minutes.

[0071] (3) The dried silicon slag fine powder and 20% artificial graphite are added to a dispersant solution containing 20% ​​sucrose and ultrasonically mixed to obtain a uniform slurry, wherein the amount of artificial graphite is 20% of the total mass of the silicon slag fine powder and the spherical graphite.

[0072] (4) The uniform slurry is dried and placed in a Joule thermal shock mold. The powder is extruded to obtain a thin film powder bed with porosity. The powder is further treated by a rapid thermal shock flash method, with the flash resistance set to 1.5Ω, the heating temperature to 1650°C in a vacuum atmosphere, and the impact is performed twice to prepare silicon carbide powder.

[0073] The specific surface area of ​​the silicon carbide prepared in this example is 23.7 m 2 / g, and the dielectric constant is 9.91.

Claims

1. A method for preparing silicon carbide material from silicon slag, characterized in that: The method comprises the following steps: (1) Crushing and classifying the silicon slag to screen out fine silicon slag; (2) wet-grinding the fine silicon slag screened in step (1), adding the wet-grinded silicon slag into a flotation tank, adding an inhibitor and a collector to perform interface modification flotation, and acid-leaching the flotation concentrate with an acid leaching solution and drying at a constant temperature to obtain silicon slag fine powder; (3) adding the silicon slag fine powder obtained in step (2) and graphite to a dispersant solution and performing ultrasonic mixing to obtain a uniform slurry; The mass of graphite is 10%~20% of the total mass of graphite and silicon slag fine powder; (4) drying the uniform slurry obtained in step (3), placing it in a Joule thermal shock mold, extruding the powder to obtain a thin film powder bed with porosity, further treating it by a rapid thermal shock flash method, thermal shock treatment in a vacuum atmosphere, and preparing silicon carbide powder by direct silicon-carbon reaction; The parameters of the flash thermal shock method are as follows: the resistance of the mixed powder in the thermal shock mold is adjusted to 1.5~2Ω, the shock temperature is 1350~1650℃, and the number of Joule thermal shocks is 2~4 times.

2. The method for preparing silicon carbide material from silicon slag according to claim 1, characterized in that: The silicon slag described in step (1) is waste silicon slag produced by blocky industrial refined silicon. The crusher used for crushing is one of a jaw crusher, a cone crusher, an impact crusher, a gyratory crusher and a roller crusher. The particle size of the screened fine silicon slag is 100 μm~1 mm.

3. The method for preparing silicon carbide material from silicon slag according to claim 1, characterized in that: In step (2), the wet grinding method is one of rod milling, ball milling, sand milling and stirred milling, and the constant temperature drying temperature is 25~100℃.

4. The method for preparing silicon carbide material from silicon slag according to claim 1, characterized in that: In step (2), the amount of the inhibitor added is 50-1000 g / t, and the amount of the collector added is 100-1000 g / t. The inhibitor is one or more of water glass, PAM, SHMP, PEG, sodium carboxymethyl cellulose, starch, sodium metaphosphate and thioacid salts mixed in any proportion, and the collector is one or more of No. 2 oil, oleic acid, kerosene, xanthate, OP-10 and fatty amines mixed in any proportion.

5. The method for preparing silicon carbide material from silicon slag according to claim 1, characterized in that: In step (2), the amount of the acid leaching solution used is 1-50 ml / g, the concentration of the acid leaching solution is 1-6 mol / L, and the acid leaching solution is one or more of hydrochloric acid, nitric acid, hypochlorous acid, perchloric acid, and hydrofluoric acid mixed in any proportion.

6. The method for preparing silicon carbide material from silicon slag according to claim 1, characterized in that: The graphite in step (3) is one or more of spherical graphite, flake graphite, artificial graphite, and natural graphite mixed in any proportion.

7. The method for preparing silicon carbide material from silicon slag according to claim 1, characterized in that: The concentration of the dispersant solution in step (3) is 5-50%, and the dispersant is one or more of glucose, sucrose, asphalt, and citric acid mixed in any proportion with deionized water to form the dispersant solution.

8. Use of silicon carbide prepared by the method of any one of claims 1 to 7 in the preparation of semiconductor materials.

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