CN117003244B - High-purity silicon carbide powder and preparation method thereof - Google Patents
High-purity silicon carbide powder and preparation method thereof Download PDFInfo
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 103
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- 239000000203 mixture Substances 0.000 claims abstract description 123
- FLJPGEWQYJVDPF-UHFFFAOYSA-L caesium sulfate Chemical compound [Cs+].[Cs+].[O-]S([O-])(=O)=O FLJPGEWQYJVDPF-UHFFFAOYSA-L 0.000 claims abstract description 86
- 238000010438 heat treatment Methods 0.000 claims abstract description 41
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 38
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 38
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000003756 stirring Methods 0.000 claims abstract description 35
- 239000007789 gas Substances 0.000 claims abstract description 32
- 239000000243 solution Substances 0.000 claims abstract description 30
- 238000001816 cooling Methods 0.000 claims abstract description 29
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000011863 silicon-based powder Substances 0.000 claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 23
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 21
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052786 argon Inorganic materials 0.000 claims abstract description 19
- 239000011259 mixed solution Substances 0.000 claims abstract description 19
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 19
- 239000001301 oxygen Substances 0.000 claims abstract description 19
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000002048 multi walled nanotube Substances 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000008367 deionised water Substances 0.000 claims abstract description 15
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 15
- 239000012298 atmosphere Substances 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 9
- 238000004140 cleaning Methods 0.000 claims abstract description 8
- 238000007789 sealing Methods 0.000 claims abstract description 8
- 230000009467 reduction Effects 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 58
- 230000008569 process Effects 0.000 claims description 37
- 238000009826 distribution Methods 0.000 claims description 14
- 239000002245 particle Substances 0.000 claims description 11
- 238000005868 electrolysis reaction Methods 0.000 claims description 9
- 238000011049 filling Methods 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 229910010271 silicon carbide Inorganic materials 0.000 description 33
- 239000012300 argon atmosphere Substances 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 10
- 239000013078 crystal Substances 0.000 description 10
- 238000009835 boiling Methods 0.000 description 8
- 229910052792 caesium Inorganic materials 0.000 description 8
- -1 cesium ions Chemical class 0.000 description 8
- 239000000843 powder Substances 0.000 description 8
- 238000001308 synthesis method Methods 0.000 description 8
- 230000002194 synthesizing effect Effects 0.000 description 8
- 239000012535 impurity Substances 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000003980 solgel method Methods 0.000 description 5
- 238000003786 synthesis reaction Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 235000012431 wafers Nutrition 0.000 description 5
- 239000002041 carbon nanotube Substances 0.000 description 4
- 229910021393 carbon nanotube Inorganic materials 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000005229 chemical vapour deposition Methods 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000010532 solid phase synthesis reaction Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- PFRUBEOIWWEFOL-UHFFFAOYSA-N [N].[S] Chemical compound [N].[S] PFRUBEOIWWEFOL-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 229910007159 Si(CH3)4 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000012190 activator Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- NCMHKCKGHRPLCM-UHFFFAOYSA-N caesium(1+) Chemical compound [Cs+] NCMHKCKGHRPLCM-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000002848 electrochemical method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- CZDYPVPMEAXLPK-UHFFFAOYSA-N tetramethylsilane Chemical compound C[Si](C)(C)C CZDYPVPMEAXLPK-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
- C01B32/963—Preparation from compounds containing silicon
- C01B32/984—Preparation from elemental silicon
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Inorganic Chemistry (AREA)
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Abstract
The invention provides high-purity silicon carbide powder and a preparation method thereof, wherein the preparation method comprises the following steps: dissolving cesium sulfate in deionized water to obtain cesium sulfate solution; adding absolute ethyl alcohol, absolute n-propanol and absolute glutaraldehyde into cesium sulfate solution to obtain a mixed solution I; adding silicon powder and carbon powder into the first mixed solution, and stirring to obtain a first mixture; adding carboxylated multiwall carbon nanotubes into the mixture I and stirring to obtain a mixture II; electrolyzing the mixture II to obtain a mixture III; placing the mixture III into a high-pressure heating device, sealing, and sequentially performing pressurization, temperature rise, temperature reduction and depressurization to normal temperature and normal pressure to obtain a mixture IV; cleaning and drying the mixture IV in an inert atmosphere to obtain a mixture V; and sequentially heating, preserving heat and cooling the mixture five in an argon/oxygen mixed gas atmosphere at a preset vacuum degree to obtain the high-purity silicon carbide powder. The invention can realize the efficient preparation of the high-purity low-nitrogen silicon carbide powder.
Description
Technical Field
The invention relates to the technical field of silicon carbide materials, in particular to high-purity silicon carbide powder and a preparation method thereof.
Background
Silicon carbide wafers are one of the third generation semiconductor materials, and have the characteristics of high temperature, high frequency, high voltage, high radiation, and the like, so that the silicon carbide wafers have wide application in the fields of high power, high frequency, high temperature, and the like. The application fields of silicon carbide wafers include: new energy automobiles, photovoltaic power generation, rail transit, power electronics, military aviation and the like. Among them, the use of silicon carbide wafers as substrate materials is gradually maturing and entering the industrialization stage. The prior mature technology is to take high-purity silicon powder and high-purity carbon powder as raw materials, grow silicon carbide crystals by a physical vapor transport method (PVT), and then process the silicon carbide crystals into silicon carbide wafers. Wherein, the process of producing silicon carbide single crystal by physical vapor transmission method requires high quality silicon carbide seed crystal and high purity silicon carbide micro powder raw material.
Silicon carbide powder for growing silicon carbide single crystals is required to have a high purity, and the impurity content should be at least less than 0.001%. Among the silicon carbide powder synthesis methods, the gas phase method can obtain silicon carbide powder with higher purity by controlling the impurity content in a gas source; only sol-gel method can synthesize silicon carbide powder with purity meeting the requirement of single crystal growth in liquid phase method; the improved self-propagating high-temperature synthesis method in the solid phase method is a preparation method of silicon carbide powder with the widest application range and the most mature synthesis process at present.
The gas phase method includes CVD method and plasma method. The CVD method is to obtain superfine and high-purity silicon carbide powder through high-temperature reaction of gases, wherein Si sources are generally SiH 4, siC l4 and the like, C sources are generally CH 4、C2H2, CCl 4 and the like, and (the gases such as CH 3)2SiCl2、Si(CH3)4 and the like can simultaneously provide Si sources and C sources, the purities of the gases are both over 99.9999 percent.
In the liquid phase method, only a sol-gel method can synthesize high-purity silicon carbide powder at present, and the preparation process comprises the steps of dissolving inorganic salt or alkoxide in a solvent (water or alcohol) to form a uniform solution, obtaining uniform sol, drying or dehydrating and converting the uniform sol into gel, and then carrying out heat treatment to obtain the required superfine powder. Silicon carbide powder synthesized by a sol-gel method is firstly used for sintering silicon carbide ceramics, the purity of the synthesized powder is continuously improved along with the continuous improvement of the process, and the silicon carbide powder prepared by the sol-gel method can be used for the growth of single crystals at present. The sol-gel method can prepare high-purity superfine SiC powder, but has higher preparation cost and complex synthesis process, and is not suitable for industrial production.
The solid phase method is mainly a self-propagating high-temperature synthesis method, and the method is characterized in that the chemical reaction of reactants is spontaneously and continuously carried out by adding an activating agent under the condition of an external heat source. However, the addition of the activator tends to introduce other impurities, and in order to ensure the purity of the product, researchers choose to increase the reaction temperature and keep the reaction running by continuous heating, which is called an improved self-propagating high-temperature synthesis method. The improved self-propagating high-temperature synthesis method has simple preparation process and high synthesis efficiency, and is widely used for producing high-purity silicon carbide powder in industry. The method takes solid Si source and C source as raw materials to continuously react at the high temperature of 1400-2000 ℃ to finally obtain the high-purity silicon carbide powder. Currently, in the modified self-propagating synthesis method, researchers can control most of impurities such as B, fe, al, cu, P and the like to be 1×10 -6 or less by controlling the impurity contents in the starting Si source and the C source and purifying the synthesized SiC powder. However, in order to prepare the semi-insulating silicon carbide single crystal substrate, the content of N element in the silicon carbide powder must be reduced as much as possible, and no matter the silicon carbide powder or the C powder, a large amount of N element in the air is easily adsorbed, so that the content of N element in the synthesized SiC powder is higher, and the use requirement of the semi-insulating single crystal substrate cannot be met. Therefore, the current research on the preparation of silicon carbide powder by an improved self-propagating synthesis method focuses on how to reduce the content of N element in the silicon carbide powder.
In a word, the current method for synthesizing high-purity silicon carbide powder for single crystal growth is not more, mainly comprises a CVD method and an improved self-propagating synthesis method, wherein the powder synthesized by a gas phase method is mostly nano-scale, has low production efficiency and cannot meet industrial requirements; meanwhile, the content of N element in a plurality of impurities in the preparation process of the solid phase method is always high. Therefore, a preparation method of high-purity low-nitrogen silicon carbide powder suitable for industrial mass production is needed at present.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide high-purity silicon carbide powder and a preparation method thereof.
According to one aspect of the present invention, there is provided a method for preparing high purity silicon carbide powder, the method comprising:
dissolving cesium sulfate in deionized water to obtain cesium sulfate solution;
Absolute ethyl alcohol, absolute n-propanol and absolute glutaraldehyde are added into the cesium sulfate solution according to a preset proportion to obtain a mixed solution I;
adding silicon powder and carbon powder into the first mixed solution, and stirring to obtain a first mixture;
adding carboxylated multiwall carbon nanotubes into the mixture I and stirring to obtain a mixture II;
adding the mixture II into an electrolytic cell for electrolysis to obtain a mixture III;
Placing the mixture III into a high-pressure heating device, sealing, and sequentially performing pressurization, temperature rise, temperature reduction and depressurization to normal temperature and normal pressure to obtain a mixture IV;
cleaning and drying the mixture IV in an inert atmosphere to obtain a mixture V;
and sequentially heating, preserving heat and cooling the mixture five in an argon/oxygen mixed gas atmosphere at a preset vacuum degree to obtain the high-purity silicon carbide powder.
Optionally, the dissolving cesium sulfate in deionized water, wherein: the purity of cesium sulfate is 99.99%; the concentration of cesium sulfate solution was 2mol/L.
Optionally, the anhydrous ethanol, anhydrous n-propanol and anhydrous glutaraldehyde are added into the cesium sulfate solution according to preset proportions, wherein: the mass ratio of the absolute ethyl alcohol to the absolute n-propyl alcohol to the absolute glutaraldehyde to the cesium sulfate solution is 1:1.5:1.2:6.3.
Optionally, the silicon powder and the carbon powder are added into the mixed solution one and stirred, wherein: the purity of the silicon powder is 99.99 percent, and the grain size distribution is 100-200 microns; the purity of the carbon powder is 99.99 percent, and the particle size distribution is 100-200 microns; the mol ratio of the silicon powder to the carbon powder is 1-1.05:1; the stirring speed is 1000rpm, and the stirring time is 3-5 hours.
Optionally, carboxylated multiwall carbon nanotubes are added to the mixture one and stirred, wherein: the mass ratio of the carboxylated multi-wall carbon nano tube to the silicon powder in the first mixture is 0.1:1; the stirring speed is 1000rpm, and the stirring time is 2-4 hours.
Optionally, the mixture II is added into an electrolytic cell for electrolysis, wherein: applying a direct current voltage of 20-40V to two ends of the electrolytic cell, and electrolyzing for 10-20 minutes; stirring was continued during electrolysis.
Optionally, the pressurizing, heating, cooling and decompressing processes are sequentially performed to normal temperature and normal pressure to obtain a mixture four, wherein the pressurizing and heating processes comprise: firstly, the pressure is increased to 160-180 GPa, then the temperature is gradually increased to 321-440 ℃, and the pressure is kept for 0.5-1 hour; stirring is continuously carried out in the processes of pressurizing, heating, cooling and decompressing to normal temperature and normal pressure.
Optionally, the fifth mixture is subjected to heating, heat preservation and cooling processes in sequence in an argon/oxygen mixed gas atmosphere under a preset vacuum degree, and the fifth mixture comprises the following steps: filling the mixture five into a vacuum furnace, introducing argon/oxygen mixed gas with the volume ratio of 1:1 into the vacuum furnace at the flow rate of 0.01cc/min, reducing the vacuum degree to be less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing the mixed gas, then heating to 1976-2387 ℃ at the heating rate of 3-5 ℃/min, preserving heat for 2.4-3.6 hours, and cooling to room temperature to obtain high-purity silicon carbide powder with the nitrogen content of less than or equal to 12ppm; the whole process was kept with an argon/oxygen mixture gas at a flow rate of 0.01 cc/min.
According to another aspect of the invention, a high purity silicon carbide powder is provided, and the high purity silicon carbide powder is prepared by the preparation method.
Compared with the prior art, the invention has at least one of the following beneficial effects:
The invention adopts cesium ions in combination with the carbon nano tube to assist the electrochemical process, so as to realize the full premixing of the precursor for synthesizing the silicon carbide and greatly improve the synthesizing efficiency of the high-purity silicon carbide; and through the mutual coordination among the steps, in the reaction of synthesizing silicon carbide at the subsequent temperature rise of trace (about 10 ppm) cesium ions remained in the earlier process, the combination of nitrogen element and silicon carbide can be effectively inhibited, and the silicon carbide is fully volatilized under the continuous high-temperature and high-vacuum environment, so that the high-efficiency preparation of the high-purity low-nitrogen silicon carbide powder can be realized.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a schematic flow chart of a method for preparing high purity silicon carbide powder according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
The embodiment of the invention provides a preparation method of high-purity silicon carbide powder, and referring to FIG. 1, the method comprises the following steps:
S1, dissolving cesium sulfate in deionized water to obtain cesium sulfate solution;
S2, adding absolute ethyl alcohol, absolute n-propanol and absolute glutaraldehyde into cesium sulfate solution according to a preset proportion to obtain a mixed solution I;
s3, adding silicon powder and carbon powder into the first mixed solution, and stirring to obtain a first mixture;
s4, adding carboxylated multiwall carbon nanotubes into the mixture I, and stirring to obtain a mixture II;
s5, adding the mixture II into an electrolytic cell for electrolysis to obtain a mixture III;
S6, placing the mixture III into a high-pressure heating device, sealing, and sequentially performing pressurization, temperature rise, temperature reduction and depressurization to normal temperature and normal pressure to obtain a mixture IV;
s7, cleaning and drying the mixture IV in an inert atmosphere to obtain a mixture V;
And S8, sequentially heating, preserving heat and cooling the mixture five in an argon/oxygen mixed gas atmosphere at a preset vacuum degree to obtain the high-purity silicon carbide powder.
In some embodiments, cesium sulfate is dissolved in deionized water, wherein: the purity of cesium sulfate is 99.99%; the concentration of the cesium sulfate solution is 2mol/L, so that the high-purity silicon carbide powder can be obtained later.
In some embodiments, anhydrous ethanol, anhydrous n-propanol, and anhydrous glutaraldehyde are added in a predetermined ratio to cesium sulfate solution, wherein: the mass ratio of the absolute ethyl alcohol to the absolute n-propyl alcohol to the absolute glutaraldehyde to the cesium sulfate solution is 1:1.5:1.2:6.3. The three solvents are mixed to obtain a mixed liquid with proper dielectric constant, thereby facilitating the subsequent electrolytic process.
In some embodiments, silicon powder and carbon powder are added to the first mixed solution and stirred, wherein: the purity of the silicon powder is 99.99 percent, and the grain size distribution is 100-200 microns; the purity of the carbon powder is 99.99 percent, and the particle size distribution is 100-200 microns; the mol ratio of the silicon powder to the carbon powder is 1-1.05:1; the stirring speed is 1000rpm and the stirring time is 3-5 hours, thereby being beneficial to improving the purity of the final product silicon carbide.
In some embodiments, carboxylated multi-walled carbon nanotubes are added to mixture one and stirred, wherein: the mass ratio of the carboxylated multi-wall carbon nano tube to the silicon powder in the first mixture is 0.1:1; the stirring speed is 1000rpm, and the stirring time is 2-4 hours, so that the subsequent obtaining of the high-purity silicon carbide powder is facilitated.
In some embodiments, the second mixture is added to an electrolytic cell for electrolysis, wherein: applying a direct current voltage of 20-40V to two ends of the electrolytic cell, and electrolyzing for 10-20 minutes; stirring is continuously carried out in the electrolytic process so as to ensure the uniformity of the reaction system in the treatment process.
In some embodiments, the mixture four is obtained by sequentially performing the processes of pressurizing, heating, cooling and depressurizing to normal temperature and normal pressure, wherein the pressurizing and heating processes comprise: firstly, the pressure is increased to 160-180 GPa, then the temperature is gradually increased to 321-440 ℃, and the pressure is kept for 0.5-1 hour; continuously stirring in the processes of pressurizing, heating, cooling and decompressing to normal temperature and normal pressure so as to ensure the uniformity of a reaction system in the treatment process.
In some embodiments, subjecting mixture five to sequential heating, maintaining and cooling processes in an argon/oxygen mixed gas atmosphere at a preset vacuum level comprises: filling the mixture five into a vacuum furnace, introducing argon/oxygen mixed gas with the volume ratio of 1:1 into the vacuum furnace at the flow rate of 0.01cc/min, reducing the vacuum degree to be less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing the mixed gas, then heating to 1976-2387 ℃ at the heating rate of 3-5 ℃/min, preserving heat for 2.4-3.6 hours, and cooling to room temperature to obtain high-purity silicon carbide powder with the nitrogen content of less than or equal to 12ppm; the whole process was kept with an argon/oxygen mixture gas at a flow rate of 0.01 cc/min. Trace amounts (about 10 ppm) of cesium ions remaining in the earlier process are fully volatilized under continuous high temperature and high vacuum environments. The high-purity silicon oxide can be better obtained through the processes of temperature rising, heat preservation, temperature reduction and the like.
The cesium ions have large ionic radius and strong electron donating property, so that the adhesion and reaction of nitrogen elements on the surface of the material can be reduced in the preparation process of the material, the nitrogen content of the high-purity silicon carbide can be effectively reduced, and further, the carbon nanotubes have strong electron conducting property, so that the combination of the nitrogen elements can be further reduced by being matched with the cesium ions. The embodiment of the invention adopts cesium ions in combination with the carbon nano tube to assist the electrochemical process, so that the full premixing of the precursor for synthesizing the silicon carbide is realized, and the synthesizing efficiency of the high-purity silicon carbide is greatly improved; and through the interaction among the steps, trace (about 10 ppm) cesium ions remained in the previous process (all processes before sintering in a furnace) can effectively inhibit the combination of nitrogen element and silicon carbide in the subsequent process of synthesizing the silicon carbide through the reaction of silicon and carbon at high temperature, and can fully volatilize in a continuous high-temperature and high-vacuum environment, so that the high-efficiency preparation of the high-purity low-nitrogen silicon carbide powder can be realized.
In the above embodiment, the silicon carbide powder with high purity is finally obtained through strict control and mutual matching of the process parameters in each step. If the parameters are changed, the silicon carbide powder may be influenced, which is unfavorable for preparing the high-purity silicon carbide powder.
The invention also provides high-purity silicon carbide powder, which is prepared by adopting the preparation method of the high-purity silicon carbide powder.
The technical scheme of the application is described in more detail below by using more specific examples.
Example 1
The preparation method of the high-purity silicon carbide powder provided by the embodiment comprises the following steps:
s1, boiling deionized water in an argon atmosphere, cooling to room temperature, and repeatedly boiling and cooling for 4 times for standby;
Dissolving cesium sulfate with the purity of 99.99% into deionized water obtained by the treatment to obtain cesium sulfate solution with the concentration of 2mol/L for standby;
S2, adding absolute ethyl alcohol, absolute n-propyl alcohol and absolute glutaraldehyde into cesium sulfate solution to obtain a mixed solution I; wherein, the mass ratio of the anhydrous ethanol, the anhydrous n-propanol, the anhydrous glutaraldehyde and the cesium sulfate solution is 1:1.5:1.2:6.3;
S3, mixing silicon powder (purity 99.99%, particle size distribution 100-150 microns) with carbon powder (purity 99.99%, particle size distribution 100-150 microns) according to a mole ratio of 1:1, adding the mixture into the first mixed solution, and continuously stirring at 1000rpm for 3 hours to obtain a first mixture;
S4, adding carboxylated multiwall carbon nanotubes into the mixture I, wherein the mass ratio of the carboxylated multiwall carbon nanotubes to silicon powder in the mixture I is 0.1:1, stirring continuously at 1000rpm for 2 hours to obtain a mixture II;
S5, adding the second mixture into a strip-type electrolytic cell with the length of 1000mm and the width of 10mm, and adding the second mixture into the strip-type electrolytic cell with the height of 20 mm; applying a direct current voltage of 20V to two ends of the electrolytic cell, and electrolyzing for 10 minutes to obtain a mixture III;
S6, placing the mixture III into a high-pressure heating device, and sealing; firstly, the pressure is increased to 160GPa, then the temperature is gradually increased to 321 ℃, the temperature is kept for 0.5 hour, and the temperature is reduced and the pressure is reduced to normal temperature and normal pressure, so that a mixture IV is obtained;
S7, cleaning the mixture IV in an argon atmosphere for 5 times by using absolute ethyl alcohol, and then drying the mixture IV in the argon atmosphere at 60 ℃ for 6 hours to obtain a mixture V;
S8, filling the mixture five into a vacuum furnace, and introducing the mixture into the vacuum furnace at a flow rate of 0.01cc/min with a volume ratio of 1:1, and reducing the vacuum degree to less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing the mixed gas, then heating to 1976 ℃ at the heating rate of 3 ℃/min, preserving the heat for 2.4 hours, and then cooling to room temperature to obtain the high-purity silicon carbide powder. The whole process needs to keep the argon/oxygen mixed gas at the flow rate of 0.01 cc/min.
And (3) testing the nitrogen content by adopting a CHN628 type hydrocarbon nitrogen-sulfur element analyzer, wherein the nitrogen content of the obtained high-purity silicon carbide powder is 12ppm.
Example 2
The preparation method of the high-purity silicon carbide powder provided by the embodiment comprises the following steps:
s1, boiling deionized water in an argon atmosphere, cooling to room temperature, and repeatedly boiling and cooling for 4 times for standby;
Dissolving cesium sulfate with the purity of 99.99% into deionized water obtained by the treatment to obtain cesium sulfate solution with the concentration of 2mol/L for standby;
S2, adding absolute ethyl alcohol, absolute n-propyl alcohol and absolute glutaraldehyde into cesium sulfate solution to obtain a mixed solution I; wherein, the mass ratio of the anhydrous ethanol, the anhydrous n-propanol, the anhydrous glutaraldehyde and the cesium sulfate solution is 1:1.5:1.2:6.3;
S3, mixing silicon powder (purity 99.99%, particle size distribution 150-200 microns) with carbon powder (purity 99.99%, particle size distribution 150-200 microns) according to a mole ratio of 1.05:1, adding the mixture into the first mixed solution, and continuously stirring at 1000rpm for 5 hours to obtain a first mixture;
s4, adding carboxylated multiwall carbon nanotubes into the mixture I, wherein the mass ratio of the carboxylated multiwall carbon nanotubes to silicon powder in the mixture I is 0.1:1, stirring continuously at 1000rpm for 4 hours to obtain a mixture II;
s5, adding the second mixture into a strip-type electrolytic cell with the length of 1000mm and the width of 10mm, and adding the second mixture into the strip-type electrolytic cell with the height of 20 mm; adding 40V direct current voltage at two ends of the electrolytic cell, and electrolyzing for 20 minutes to obtain a mixture III;
S6, placing the mixture III into a high-pressure heating device, and sealing; firstly, the pressure is increased to 180GPa, then the temperature is gradually increased to 440 ℃, the temperature is kept for 1 hour, and the temperature is reduced and the pressure is reduced to normal temperature and normal pressure to obtain a mixture IV;
S7, cleaning the mixture IV with absolute ethyl alcohol for 7 times in an argon atmosphere, and then drying the mixture IV in the argon atmosphere at 80 ℃ for 8 hours to obtain a mixture V;
S8, filling the mixture five into a vacuum furnace, and introducing the mixture into the vacuum furnace at a flow rate of 0.01cc/min with a volume ratio of 1:1, and reducing the vacuum degree to less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing the mixed gas, then heating to 2387 ℃ at a heating rate of 5 ℃/min, preserving heat for 3.6 hours, and then cooling to room temperature to obtain the high-purity silicon carbide powder. The whole process needs to keep the argon/oxygen mixed gas at the flow rate of 0.01 cc/min.
The test shows that the nitrogen content of the obtained high-purity silicon carbide powder is 7ppm.
Example 3
The preparation method of the high-purity silicon carbide powder provided by the embodiment comprises the following steps:
s1, boiling deionized water in an argon atmosphere, cooling to room temperature, and repeatedly boiling and cooling for 4 times for standby;
Dissolving cesium sulfate with the purity of 99.99% into deionized water obtained by the treatment to obtain cesium sulfate solution with the concentration of 2mol/L for standby;
S2, adding absolute ethyl alcohol, absolute n-propyl alcohol and absolute glutaraldehyde into cesium sulfate solution to obtain a mixed solution I; wherein, the mass ratio of the anhydrous ethanol, the anhydrous n-propanol, the anhydrous glutaraldehyde and the cesium sulfate solution is 1:1.5:1.2:6.3;
S3, mixing silicon powder (purity 99.99%, particle size distribution 100-200 microns) with carbon powder (purity 99.99%, particle size distribution 100-200 microns) according to a molar ratio of 1-1.05: 1, adding the mixture into the first mixed solution, and continuously stirring at 1000rpm for 3-5 hours to obtain a first mixture;
s4, adding carboxylated multiwall carbon nanotubes into the mixture I, wherein the mass ratio of the carboxylated multiwall carbon nanotubes to silicon powder in the mixture I is 0.1:1, stirring continuously at 1000rpm for 2-4 hours to obtain a mixture II;
s5, adding the second mixture into a strip-type electrolytic cell with the length of 1000mm and the width of 10mm, and adding the second mixture into the strip-type electrolytic cell with the height of 20 mm; d, adding 20-40V direct current voltage at two ends of the electrolytic cell, and electrolyzing for 10-20 minutes to obtain a mixture III;
S6, placing the mixture III into a high-pressure heating device, and sealing; firstly, the pressure is increased to 160-180 GPa, then the temperature is gradually increased to 321-440 ℃, the temperature is kept for 0.5-1 hour, and the temperature is reduced and the pressure is reduced to normal temperature and normal pressure to obtain a mixture IV;
S7, cleaning the mixture IV in an argon atmosphere for 5-7 times by using absolute ethyl alcohol, and then drying the mixture IV in the argon atmosphere at 60-80 ℃ for 6-8 hours to obtain a mixture V;
S8, filling the mixture five into a vacuum furnace, and introducing the mixture into the vacuum furnace at a flow rate of 0.01cc/min with a volume ratio of 1:1, and reducing the vacuum degree to less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing the mixed gas, then heating to 1976-2387 ℃ at the heating rate of 3-5 ℃/min, preserving heat for 2.4-3.6 hours, and cooling to room temperature to obtain the high-purity silicon carbide powder. The whole process needs to keep the argon/oxygen mixed gas at the flow rate of 0.01 cc/min.
The test shows that the nitrogen content of the obtained high-purity silicon carbide powder is 9ppm.
Comparative example 1
The nitrogen content test (using CHN628 hydrocarbon nitrogen sulfur analyzer) was conducted with the same nitrogen content test method as in the above example, with the commercial high purity silicon carbide powder (constant-current metallurgy) as a comparison, and the nitrogen content was 17ppm. It can be seen that the silicon carbide powder in the above examples of the present invention has a nitrogen content lower than that of commercially available high purity silicon carbide powder and has a higher purity.
Comparative example 2
S1, boiling deionized water in an argon atmosphere, cooling to room temperature, and repeatedly boiling and cooling for 4 times for standby;
Dissolving cesium sulfate with the purity of 99.99% into deionized water obtained by the treatment to obtain cesium sulfate solution with the concentration of 0.5mol/L for standby;
S2, adding absolute ethyl alcohol, absolute n-propanol and absolute glutaraldehyde into cesium sulfate solution to obtain a mixed solution I; wherein, the mass ratio of the absolute ethyl alcohol, the absolute n-propyl alcohol, the absolute glutaraldehyde and the cesium sulfate solution is 1:0.8:1.75:6.3;
S3, mixing silicon powder (purity 99.99%, particle size distribution 100-150 microns) with carbon powder (purity 99.99%, particle size distribution 100-150 microns) according to a mole ratio of 1:1, adding the mixture into the first mixed solution, and continuously stirring at 1000rpm for 1 hour to obtain a first mixture;
S4, adding carboxylated multiwall carbon nanotubes into the mixture I, wherein the mass ratio of the carboxylated multiwall carbon nanotubes to silicon powder in the mixture I is 0.3:1, stirring continuously at 1000rpm for 1 hour to obtain a mixture II;
S5, adding the second mixture into a strip-type electrolytic cell with the length of 1000mm and the width of 10mm, and adding the second mixture into the strip-type electrolytic cell with the height of 20 mm; 10V direct current voltage is added at two ends of the electrolytic cell, and electrolysis is carried out for 7 minutes to obtain a mixture III;
S6, placing the mixture III into a high-pressure heating device, and sealing; firstly, the pressure is increased to 110GPa, then the temperature is gradually increased to 275 ℃, the temperature is kept for 1 hour, and the temperature is reduced and the pressure is reduced to normal temperature and normal pressure to obtain a mixture IV;
S7, cleaning the mixture IV in an argon atmosphere for 5 times by using absolute ethyl alcohol, and then drying the mixture IV in the argon atmosphere at 60 ℃ for 6 hours to obtain a mixture V;
S8, filling the mixture five into a vacuum furnace, and introducing the mixture into the vacuum furnace at a flow rate of 0.01cc/min with a volume ratio of 1:1, and reducing the vacuum degree to less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing the mixed gas, then heating to 1976 ℃ at the heating rate of 3 ℃/min, preserving the heat for 2.4 hours, and then cooling to room temperature to obtain the high-purity silicon carbide powder. The whole process needs to keep the argon/oxygen mixed gas at the flow rate of 0.01 cc/min.
The test shows that the nitrogen content of the obtained high-purity silicon carbide powder is 51ppm. It can be seen that the control and the mutual coordination of the steps and the technological parameters play an important role in preparing the high-purity silicon carbide powder. Other process parameters are adopted, so that the purity of the silicon carbide powder is influenced, and the preparation of the high-purity silicon carbide powder is not facilitated.
According to the embodiment of the invention, the silicon carbide is prepared by adopting a high-voltage electrochemical method, and through strict control and mutual coordination of each process parameter in each step and adopting an original cesium ion and carbon nano tube assisted electrochemical process, the full premixing of the silicon carbide synthesis precursor is realized, and the high-purity silicon carbide synthesis efficiency is greatly improved. Meanwhile, trace cesium ions (about 10 ppm) remained in the earlier process can be effectively combined with the silicon carbide at all times in the subsequent reaction of synthesizing the silicon carbide at a high temperature, and are fully volatilized under a continuous high-temperature and high-vacuum environment, so that the silicon carbide powder with high purity is finally obtained.
The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the claims without affecting the spirit of the invention. The above-described preferred features may be used in any combination without collision.
Claims (8)
1. The preparation method of the high-purity silicon carbide powder is characterized by comprising the following steps of:
dissolving cesium sulfate in deionized water to obtain cesium sulfate solution;
Absolute ethyl alcohol, absolute n-propanol and absolute glutaraldehyde are added into the cesium sulfate solution according to a preset proportion to obtain a mixed solution I;
adding silicon powder and carbon powder into the first mixed solution, and stirring to obtain a first mixture;
adding carboxylated multiwall carbon nanotubes into the mixture I and stirring to obtain a mixture II;
adding the mixture II into an electrolytic cell for electrolysis to obtain a mixture III;
Placing the mixture III into a high-pressure heating device, sealing, and sequentially performing pressurization, temperature rise, temperature reduction and depressurization to normal temperature and normal pressure to obtain a mixture IV; wherein the pressurizing and heating process comprises the following steps: firstly, the pressure is increased to 160-180 GPa, then the temperature is gradually increased to 321-440 o ℃ and the pressure is kept for 0.5-1 hour;
cleaning and drying the mixture IV in an inert atmosphere to obtain a mixture V;
Sequentially heating, preserving heat and cooling the mixture five in an argon/oxygen mixed gas atmosphere at a preset vacuum degree to obtain high-purity silicon carbide powder, wherein the mixture five sequentially heating, preserving heat and cooling the mixture five in the argon/oxygen mixed gas atmosphere at the preset vacuum degree comprises the following steps: and fifthly, filling the mixture into a vacuum furnace, reducing the vacuum degree to be less than or equal to 1 x 10 -3 Pa under the condition of continuously introducing argon/oxygen mixed gas, then heating to 1976-2387 o ℃ at the heating rate of 3-5 o C/min, preserving heat for 2.4-3.6 hours, and then cooling to room temperature to obtain the high-purity silicon carbide powder with the nitrogen content of less than or equal to 12ppm.
2. A method of preparing high purity silicon carbide powder as claimed in claim 1 wherein cesium sulfate is dissolved in deionized water, wherein: the purity of cesium sulfate is 99.99%; the concentration of cesium sulfate solution was 2mol/L.
3. The method for preparing high purity silicon carbide powder as claimed in claim 1, wherein the anhydrous ethanol, anhydrous n-propanol and anhydrous glutaraldehyde are added to the cesium sulfate solution in a predetermined ratio, wherein: the mass ratio of the absolute ethyl alcohol to the absolute n-propyl alcohol to the absolute glutaraldehyde to the cesium sulfate solution is 1:1.5:1.2:6.3.
4. A method for producing high purity silicon carbide powder according to claim 1 wherein said adding silicon powder and carbon powder to said first mixed solution is performed with stirring, wherein: the purity of the silicon powder is 99.99 percent, and the grain size distribution is 100-200 microns; the purity of the carbon powder is 99.99 percent, and the particle size distribution is 100-200 microns; the mol ratio of the silicon powder to the carbon powder is 1-1.05:1; the stirring speed is 1000rpm, and the stirring time is 3-5 hours.
5. A method of preparing high purity silicon carbide powder as claimed in claim 1 wherein carboxylated multiwall carbon nanotubes are added to the mixture one and stirred, wherein: the mass ratio of the carboxylated multi-wall carbon nano tube to the silicon powder in the first mixture is 0.1:1; the stirring speed is 1000rpm, and the stirring time is 2-4 hours.
6. A method of producing high purity silicon carbide powder as claimed in claim 1, wherein the second mixture is added to an electrolytic cell for electrolysis, wherein: applying a direct current voltage of 20-40V to two ends of the electrolytic cell, and electrolyzing for 10-20 minutes; stirring was continued during electrolysis.
7. The method for preparing high purity silicon carbide powder according to claim 1, wherein the mixture four is obtained by sequentially performing the processes of pressurizing, heating up, cooling down and decompressing to normal temperature and normal pressure, wherein: stirring is continuously carried out in the processes of pressurizing, heating, cooling and decompressing to normal temperature and normal pressure.
8. The method for preparing high purity silicon carbide powder according to claim 1, wherein the step of sequentially heating, maintaining and cooling the mixture five in an argon/oxygen mixed gas atmosphere at a predetermined vacuum level comprises: argon/oxygen mixed gas with the volume ratio of 1:1 is introduced into the vacuum furnace at the flow rate of 0.01cc/min, and the argon/oxygen mixed gas is introduced at the flow rate of 0.01cc/min in the whole process.
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| KR101678624B1 (en) * | 2015-09-14 | 2016-11-23 | 한국과학기술연구원 | A method for preparing silicon carbide powder of ultra-high purity |
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