CN117208910A - Preparation method of superfine high-purity silicon carbide powder - Google Patents
Preparation method of superfine high-purity silicon carbide powder Download PDFInfo
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 96
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 239000007789 gas Substances 0.000 claims abstract description 82
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 73
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 69
- 239000010703 silicon Substances 0.000 claims abstract description 69
- 239000002245 particle Substances 0.000 claims abstract description 62
- 239000002994 raw material Substances 0.000 claims abstract description 61
- 238000000034 method Methods 0.000 claims abstract description 27
- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 27
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 15
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 15
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 15
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000001301 oxygen Substances 0.000 claims abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 8
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 26
- 238000012546 transfer Methods 0.000 claims description 20
- 238000001878 scanning electron micrograph Methods 0.000 claims description 18
- 229910052786 argon Inorganic materials 0.000 claims description 13
- 239000001257 hydrogen Substances 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 11
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 10
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 10
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 7
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 7
- 239000011863 silicon-based powder Substances 0.000 claims description 6
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 5
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 5
- 239000005977 Ethylene Substances 0.000 claims description 5
- 239000001294 propane Substances 0.000 claims description 5
- 239000001307 helium Substances 0.000 claims description 4
- 229910052734 helium Inorganic materials 0.000 claims description 4
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000002210 silicon-based material Substances 0.000 claims 1
- 230000015572 biosynthetic process Effects 0.000 abstract description 14
- 238000003786 synthesis reaction Methods 0.000 abstract description 12
- 238000009776 industrial production Methods 0.000 abstract description 10
- 239000006227 byproduct Substances 0.000 abstract description 3
- 238000011161 development Methods 0.000 abstract description 3
- 238000009826 distribution Methods 0.000 abstract description 3
- 210000002381 plasma Anatomy 0.000 description 97
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 27
- 229910052799 carbon Inorganic materials 0.000 description 22
- 238000006243 chemical reaction Methods 0.000 description 13
- 239000000463 material Substances 0.000 description 13
- 230000008020 evaporation Effects 0.000 description 11
- 238000001704 evaporation Methods 0.000 description 11
- 238000012360 testing method Methods 0.000 description 10
- 239000000843 powder Substances 0.000 description 8
- 239000000047 product Substances 0.000 description 6
- 238000004438 BET method Methods 0.000 description 5
- 238000010924 continuous production Methods 0.000 description 5
- 238000001000 micrograph Methods 0.000 description 5
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 4
- 230000005495 cold plasma Effects 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 238000012423 maintenance Methods 0.000 description 4
- 229910000077 silane Inorganic materials 0.000 description 4
- 238000001308 synthesis method Methods 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 150000003254 radicals Chemical class 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 230000002194 synthesizing effect Effects 0.000 description 3
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 229930195735 unsaturated hydrocarbon Natural products 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- 238000002679 ablation Methods 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
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- 150000002431 hydrogen Chemical class 0.000 description 1
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- 238000003701 mechanical milling Methods 0.000 description 1
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Abstract
The preparation method of the superfine high-purity silicon carbide powder comprises the following preparation steps: (1) After the gas in the reactor is replaced by the circulating working gas, introducing plasma working gas into the plasma arc torch and maintaining the stability of the plasma arc; (2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with the ionized plasma working gas to generate silicon carbide particles; (3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder, wherein the circulating working gas is non-oxygen-containing element gas, and the oxygen content is less than 1wt%; the plasma working gas comprises at least a hydrocarbon gas. The invention uses the plasma thermal synthesis process, the obtained silicon carbide powder has concentrated particle size distribution, regular shape and high purity, and the emission of the three wastes as byproducts is extremely small, thereby providing a feasible development direction for the industrial production of superfine silicon carbide powder.
Description
Technical Field
The invention relates to the technical field of superfine powder production, in particular to a preparation method of superfine high-purity silicon carbide powder.
Background
Silicon carbide is the most widely used non-oxide ceramic material in many industrial environments due to its high mechanical strength, hardness, thermal conductivity, and excellent corrosion resistance, thermal shock resistance, semiconductor properties, etc., its application includes independent assembly components, and as a filler material in thin layer depositions and composites. Given the unique properties of nanomaterials and the superior physical properties of nanocomposites over conventional materials, those skilled in the art have begun to attempt to synthesize nanosized silicon carbide powders over the last decades.
The conventional method for preparing silicon carbide is to carry out carbothermic reduction on silicon dioxide by coke at 2200-2500 ℃ to obtain a silicon carbide product; because of the high reaction temperature and long reaction time of the process, the particle size of the product tends to be large with an accompanying difficult-to-control oxygen content. As for the preparation of nano silicon carbide powder, many process routes have been developed in the prior art, among which the most studied include mechanical milling method, carbothermic synthesis method, self-propagating high temperature synthesis method, microwave synthesis method, polymer coking method, sol-gel method, vapor deposition method, laser synthesis method, and the like. All the above processes have respective advantages such as lower precursor cost, lower reaction temperature, higher purity of the product, etc., but various advantages are often not compatible, and there are limitations. The plasma thermal synthesis process in the vapor deposition method has the advantages of low cost and easy continuous production during the synthesis of the nano-sized silicon carbide powder, and has wide industrial prospect.
In the Chinese patent application publication No. CN1445164A, a method is disclosed in which a DC arc plasma is used as a heat source, and N 2 -H 2 Ar is a working gas, CH 3 SiCl 3 A preparation process for rapidly decomposing and synthesizing silicon carbide powder by arc heating as a raw material, wherein the grain diameter of the silicon carbide powder obtained in the process is between 0.08 and 0.5 mu m; but due to N in the working gas 2 The existence of the silicon nitride impurity is unavoidable, and a large amount of HCl gas is generated by the decomposition of the silicon source material, so that the balance of the internal pressure and the gas quantity in the reaction section is difficult to control, the contact time of the plasma and the raw material is further influenced, and the comprehensive energy utilization rate and the silicon carbide are realizedThe yield cannot meet the requirements of economic production.
In the chinese patent application with publication number CN102689903a, a method for synthesizing silicon carbide nanoparticles by using direct current arc plasma is disclosed, wherein micron-sized silicon powder and carbon powder are used as raw materials and made into an anode, a graphite rod is used as a cathode, a mixed atmosphere of inert gas and hydrogen is introduced. The silicon carbide powder obtained by the method has high purity, the heat transfer and atmosphere conditions of the reaction section are relatively stable, but the biggest problem is that the consumed plasma anode structure is unfavorable for the feasibility of industrial continuous production, and the production efficiency is greatly influenced.
In addition, chinese patent application publication No. CN112978731a discloses a method of synthesizing high purity silicon carbide particles in an inert atmosphere by introducing high purity silane and acetylene as gas raw materials into a combination apparatus of a cold plasma generator and medium frequency induction heating. However, it is known that cold plasma has poor stability and is easily disturbed by external air intake, especially the external air intake, to lose balance state; on the premise of adopting silane and acetylene as gas raw materials, the stability of the reaction working condition of the catalyst under the industrial production condition cannot be ensured, and the maintenance cost is high.
Disclosure of Invention
The invention aims to solve the problems of difficult continuous production, low comprehensive yield, high impurity content of products, high operating condition maintenance cost and the like in the industrial production of superfine high-purity silicon carbide powder in the prior art, and provides a preparation method of superfine high-purity silicon carbide powder based on a plasma thermal synthesis process.
The invention provides a preparation method of superfine high-purity silicon carbide powder, which comprises the following steps:
(1) After the gas in the reactor is replaced by the circulating working gas, introducing plasma working gas into the plasma arc torch and maintaining the stability of the plasma arc;
(2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with the ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein the circulating working gas is a non-oxygen-containing element gas with an oxygen content of <1wt%; the plasma working gas comprises at least a hydrocarbon gas.
The invention adopts hydrocarbon gas as plasma working gas, while the hydrocarbon gas is used as carbon source, the hydrocarbon gas is ionized to form charged plasma, hydrocarbon molecules are activated to break C-H bonds and form a large amount of CH in gas phase x The free radical is more favorable for the reaction of carbon and silicon to synthesize silicon carbide at the high temperature generated by the plasma, and the reaction is more sufficient.
Another reason for using hydrocarbon gas as the plasma working gas is that if hydrocarbon gas is directly added into the reactor or directly fed into the plasma arc region, because of the high-speed thermal fluid nature of the plasma arc, the volume of the plasma arc rapidly expands due to the high temperature, so that a larger part of hydrocarbon gas fed into the plasma thermal fluid from the outside can be flicked by the thermal fluid, or only a part of hydrocarbon gas enters the plasma arc region, so that hydrocarbon gas is only cracked in a high-temperature state, elemental carbon is easily generated, and the hydrocarbon gas cannot react with silicon.
In theory, silane can be used as the plasma working gas, and the solid phase feeding correspondingly adopts conventional carbon source materials such as graphite, carbon black (powder) and the like, so that the preparation method and the principle are kept unchanged; however, since the boiling point (4827 ℃) of carbon is doubled and more than that of silicon (2355 ℃) and in order to ensure the evaporation of carbon raw materials, the requirements on the heat preservation performance of a plasma arc high-temperature area, the restraint degree of plasma arcs, the granularity and dispersion degree of powder fed in and other technological parameters are raised, the equipment and production cost are greatly increased, or the production capacity per unit time is greatly limited on the premise of controlling the same cost, and the method is difficult to popularize in actual industrial production.
The invention is not particularly limited to the type of the adopted plasmas, and low-temperature plasmas (including hot plasmas and cold plasmas) which are easy to obtain and maintain in industrial production can be obtained only by meeting the condition that the carbon source materials and the silicon source materials can be evaporated or ionized into substances which are easy to react; for example, direct current arc plasmas (including transferred arcs, non-transferred arcs, combined arcs, etc.), high frequency discharge plasmas, microwave discharge plasmas, and the like.
Further, in the step (1), the circulating working gas is at least one of helium, nitrogen and argon, or other gases which are inert to the silicon carbide preparation environment of the invention.
Further, in step (1), the plasma working gas includes at least one of methane, ethane, propane, ethylene, and acetylene.
Further, in the step (1), the plasma working gas further includes at least one of hydrogen and argon; when the plasma working gas contains unsaturated hydrocarbon, the addition of hydrogen is more beneficial to CH x The formation of free radicals promotes the carbo-silicon reaction.
Further, in the step (2), the silicon raw material is silicon powder, and the D50 particle size of the silicon powder calculated by SEM image is 0.3-30 mu m; the silicon raw material can be easily evaporated by controlling the particle size of the silicon raw material, so that the reaction phases are more fully mixed, and the reaction is facilitated.
Further, in the step (2), the mass power ratio between the unit time feeding amount of the silicon raw material and the power of the plasma arc is 0.001-0.5kg/kW.
Furthermore, the plasma arc is a non-transferred arc generated by a non-transferred arc torch, and the non-transferred arc plasma torch (namely the non-transferred arc torch) can form stable, high-temperature and high-energy density plasma jet, so that the energy requirement of raw material evaporation is fully met, phenomena such as ablation or raw material back flow sintering and the like at a nozzle can be prevented to a certain extent, consumable materials such as a crucible and a graphite electrode are not needed to be additionally arranged besides the plasma gun, and the plasma arc torch is a preferable choice for industrial production; when the number of the non-transfer torches is greater than 1, each adjacent non-transfer torches form the same included angle with the axis of the reactor and are converged at an intersection point, the included angle is 15-90 degrees, and each non-transfer torch is uniformly distributed on the cross section of the reactor in an equal radian manner.
Still further, the silicon feedstock is fed to the flame core region of the non-transferred arc torch at an angle of 15-90 °; when the number of non-transferred torches is greater than 1, the silicon feedstock is fed 0-20cm above the intersection of a plurality of the non-transferred torches.
Another technical problem to be solved by the invention is to provide the superfine high-purity silicon carbide powder.
Another technical solution of the present invention is to provide an ultrafine high-purity silicon carbide powder obtained by the production method according to any one of claims 1 to 8, which has an average particle diameter of 10 to 250nm in terms of BET specific surface area.
On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the invention.
The invention has the positive progress effects that: the invention uses the plasma thermal synthesis process, solves the problems of difficult continuous production, low comprehensive yield, high impurity content of products, high operating condition maintenance cost and the like of the nanoscale silicon carbide powder in the prior art by selecting hydrocarbon plasma working gas and a silicon source and optimizing a preparation method, and the obtained silicon carbide powder has concentrated particle size distribution, regular morphology, high purity and extremely few discharge of three wastes as byproducts, thereby providing a feasible development direction for the industrial production of the superfine silicon carbide powder.
Drawings
Fig. 1 is an SEM electron microscope image of the silicon carbide powder of example 1.
Fig. 2 is an SEM electron microscope image of the silicon carbide powder of example 2.
Fig. 3 is an SEM electron microscope image of the silicon carbide powder of example 3.
Fig. 4 is an SEM electron microscope image of the silicon carbide powder of example 4.
Fig. 5 is an SEM electron microscope image of the silicon carbide powder of example 5.
Detailed Description
The following describes the embodiments of the present invention further with reference to the drawings. It should be noted that the description of these embodiments is for aiding in understanding the present invention, but is not to be construed as limiting the invention. In addition, the technical features described in the following embodiments of the present invention may be combined with each other as long as they do not collide with each other.
The invention relates to a method for preparing superfine high-purity silicon carbide powder based on a plasma thermal synthesis process, which basically adopts the prior art, and comprises a plasma generator, a powdery silicon raw material feeding device, an evaporation synthesis cavity (i.e. a reactor), a particle forming cavity (i.e. a particle forming controller), a gas-solid separation collecting device (i.e. a collector) and the like.
For example, the particle forming chamber, or the particle forming controller, or the particle grower can be the particle grower 2 in the rapid gas cooling device (hereinafter referred to as patent one) of low-melting metal and alloy with the patent number of 202023112892.4, or the growth and solidification temperature control tube in the preparation device of the superfine powder of conductive material with the patent number of 202122770104.9. The collector may be the collector 4 of the above-mentioned first patent. The evaporation synthesis cavity is also called a reactor, and the reactor 1 in the first patent can be adopted; or a conductive crucible high-temperature evaporator which is heated by a plasma transfer arc and has the patent number of 202120045905.6; or adopts a physical vapor phase method to prepare the metal vapor nucleation device for the superfine powder material with the patent number of 202122514416.3.
The preparation method of the superfine high-purity silicon carbide powder comprises the following steps:
(1) After the gas in the reactor is replaced by the circulating working gas, introducing plasma working gas into the plasma arc torch and maintaining the stability of the plasma arc;
(2) Feeding the powdered silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with the ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein the circulating working gas comprises at least one of helium, nitrogen, argon, the oxygen content of the circulating working gas being <1wt%; the plasma working gas includes at least one of methane, ethane, propane, ethylene, and acetylene.
Theoretically, silane can also be used as the plasma working gas in the embodiment of the invention, and the solid phase feeding correspondingly adopts conventional carbon source materials such as graphite, carbon black (powder) and the like, so that the preparation method and principle are kept unchanged; however, since the boiling point (4827 ℃) of carbon is doubled and more than that of silicon (2355 ℃) and in order to ensure the evaporation of carbon raw materials, the requirements on the heat preservation performance of a plasma arc high-temperature area, the restraint degree of plasma arcs, the granularity and dispersion degree of powder fed in and other technological parameters are raised, the equipment and production cost are greatly increased, or the production capacity per unit time is greatly limited on the premise of controlling the same cost, and the method is difficult to popularize in actual industrial production.
The embodiment of the invention is not particularly limited to the type of the adopted plasmas, and low-temperature plasmas (including hot plasmas and cold plasmas) which are easy to obtain and maintain in industrial production can be obtained only by meeting the condition that the carbon source materials and the silicon source materials can be evaporated or ionized into substances which are easy to react; for example, direct current arc plasmas (including transferred arcs, non-transferred arcs, combined arcs, etc.), high frequency discharge plasmas, microwave discharge plasmas, and the like.
In the step (1), the plasma working gas further comprises at least one of hydrogen and argon. When the plasma working gas contains unsaturated hydrocarbon, the addition of hydrogen is more beneficial to CH x The formation of free radicals promotes the carbo-silicon reaction.
In the step (2), the silicon raw material is silicon powder, and the D50 particle size of the silicon powder calculated by SEM image is 0.3-30 mu m; the silicon raw material can be easily evaporated by controlling the particle size of the silicon raw material, so that the reaction phases are more fully mixed, and the reaction is facilitated.
In the step (2), the mass power ratio between the feeding amount of the silicon raw material per unit time and the power of the plasma arc is 0.001-0.5kg/kW.
In the embodiment of the invention, when the adopted plasma arcs are non-transferred arcs generated by non-transferred arcs, and the number of the non-transferred arcs is larger than 1, each adjacent non-transferred arc forms the same included angle with the axis of the reactor and is converged at an intersection point, the included angle is 15-90 degrees, each non-transferred arc is uniformly distributed on the cross section of the reactor, and the silicon raw material is sent to the position 0-20cm above the intersection point of a plurality of non-transferred arcs.
The present invention also provides an ultrafine high-purity silicon carbide powder obtained by the production method as described above, the silicon carbide powder having an average particle diameter of 10 to 250nm in terms of BET specific surface area.
Example 1
The preparation method of the superfine high-purity silicon carbide powder comprises the following steps:
(1) After the gas in the reactor is replaced by the mixed gas of argon and nitrogen, arcing and maintaining the stability of a plasma arc;
(2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein the plasma working gas is methane, and the D50 particle size of the silicon raw material calculated by SEM image is 0.3 mu m; a mass-to-power ratio between a unit time feed amount of the silicon raw material and a power of the plasma arc is 0.001kg/kW; the plasma arc is a non-transferred arc generated by a non-transferred arc torch, and the number of the non-transferred arc torches is 1; the silicon feedstock is fed into the flame core region of the non-transferred arc torch at an included angle of 90 °.
Fig. 1 is an SEM image of the silicon carbide powder prepared in this example, and it can be seen from fig. 1 that the obtained silicon carbide powder particles were spheroid, the average particle diameter calculated from the SEM image was 22nm, the average particle diameter converted by the BET method test was 18 nm, d50=100 nm by the laser particle sizer, and the carbon content in the silicon carbide powder was 30.2wt% by the carbon content test.
Example 2
The preparation method of the superfine high-purity silicon carbide powder comprises the following steps:
(1) After the helium gas is used for replacing the gas in the reactor, arcing and maintaining the stability of a plasma arc;
(2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein the plasma working gas is ethylene, hydrogen and argon, and the flow ratio of ethylene to hydrogen is not more than 1:1, the flow ratio of argon to hydrogen is not more than 19:1, wherein argon accounts for not more than 90% of the total flow of the plasma working gas; the D50 particle diameter of the silicon raw material calculated by SEM image is 30 μm; the mass-to-power ratio between the unit-time feeding amount of the silicon raw material and the power of the plasma arc is 0.05kg/kW; the plasma arc is a non-transfer arc generated by non-transfer arc torches, the number of the non-transfer arc torches is 4, each adjacent non-transfer arc torches form the same included angle with the axis of the reactor and are converged at an intersection point, the included angle is 90 degrees, each non-transfer arc torch is uniformly distributed on the cross section of the reactor, and the silicon raw material is sent to the position 5cm above the intersection point of a plurality of non-transfer arc torches.
Fig. 2 is an SEM image of the silicon carbide powder prepared in this example, and it can be seen from fig. 2 that the obtained silicon carbide powder particles were spheroid, the average particle diameter calculated from the SEM image was 70nm, the average particle diameter converted by the BET method test was 53nm, d50=180 nm by the laser particle sizer, and the carbon content in the silicon carbide powder was 29.9wt% by the carbon content test.
Example 3
The preparation method of the superfine high-purity silicon carbide powder comprises the following steps:
(1) After replacing the gas in the reactor with argon, arcing and maintaining the stability of the plasma arc;
(2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with the ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein, the plasma working gas is ethane and propane, and the flow ratio of the ethane to the propane is 2:1, a step of; the D50 particle diameter of the silicon raw material calculated by SEM image is 10 μm; the mass-to-power ratio between the unit time feed amount of the silicon raw material and the power of the plasma arc is 0.5kg/kW; the plasma arc is a non-transferred arc generated by non-transferred arc torches, the number of the non-transferred arc torches is 3, each adjacent non-transferred arc torches form the same included angle with the axis of the reactor and are converged at an intersection point, the included angle is 60 degrees, each non-transferred arc torch is uniformly distributed on the cross section of the reactor, and the silicon raw material is sent to the intersection point of a plurality of non-transferred arc torches.
Fig. 3 is an SEM image of the silicon carbide powder prepared in this example, and it can be seen from fig. 3 that the obtained silicon carbide powder particles were spheroid, the average particle diameter calculated from the SEM image was 163nm, the average particle diameter converted by the BET method test was 142 nm, d50=245 nm by the laser particle sizer, and the carbon content in the silicon carbide powder was 29.5wt% by the carbon content test.
Example 4
The preparation method of the superfine high-purity silicon carbide powder comprises the following steps:
(1) After replacing the gas in the reactor with argon, arcing and maintaining the stability of the plasma arc;
(2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with the ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein the plasma working gas is acetylene and hydrogen, and the flow ratio of the acetylene to the hydrogen is not more than 1:2; the D50 particle diameter of the silicon raw material calculated by SEM image is 20 μm; the mass-to-power ratio between the unit-time feeding amount of the silicon raw material and the power of the plasma arc is 0.1kg/kW; the plasma arc is a non-transfer arc generated by non-transfer arc torches, the number of the non-transfer arc torches is 3, each adjacent non-transfer arc torches form the same included angle with the axis of the reactor and are converged at an intersection point, the included angle is 15 degrees, each non-transfer arc torch is uniformly distributed on the cross section of the reactor, and the silicon raw material is sent to the position 20cm above the intersection point of a plurality of non-transfer arc torches.
Fig. 4 is an SEM image of the silicon carbide powder prepared in this example, and it can be seen from fig. 4 that the obtained silicon carbide powder particles were spheroid, the average particle diameter calculated from the SEM image was 279nm, the average particle diameter converted by the BET method test was 242nm, d50=355 nm by the laser particle sizer, and the carbon content in the silicon carbide powder was 30.1wt% by the carbon content test.
Example 5
The reactor of the embodiment is provided with an evaporation synthesis cavity formed by combining a crucible and a crucible cover, and the evaporation synthesis cavity is divided into a lower evaporation cavity and an upper synthesis cavity;
this example prepares ultra-fine high purity silicon carbide powder by transferred arc comprising the steps of:
(1) Paving a silicon raw material in an evaporation cavity of the reactor in advance, and replacing gas in the reactor with argon;
(2) Striking an arc and maintaining the stability of a plasma arc, heating the silicon raw material in the evaporation cavity, gasifying the silicon raw material and reacting with ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
the container used for containing the silicon raw material in the evaporation cavity is a quartz crucible with a silicon nitride coating or other high-temperature resistant crucibles with the same performance; the plasma working gas is methane, the D50 particle size of the silicon raw material calculated by SEM image is 20 mu m, and the mass power ratio between the unit time feeding amount of the silicon raw material and the power of the plasma arc is 0.02kg/kW; the plasma arc is a transferred arc created between a transferred arc plasma torch and silicon feedstock.
Fig. 5 is an SEM image of the silicon carbide powder prepared in this example, and it can be seen from fig. 5 that the obtained silicon carbide powder particles were spheroid, the average particle diameter calculated from the SEM image was 154nm, the average particle diameter converted by the BET method test was 98nm, d50=217 nm by the laser particle sizer, and the carbon content in the silicon carbide powder was 29.8wt% by the carbon content test.
It can be seen from example 5 that the present invention can be applied to different types of plasmas as long as different engineering means are used to ensure that the carbon source material and the silicon source material can be evaporated or ionized into a state of a substance that is easy to react.
The invention uses the plasma thermal synthesis process, solves the problems of difficult continuous production, low comprehensive yield, high impurity content of products, high operating condition maintenance cost and the like of the nanoscale silicon carbide powder in the prior art by selecting hydrocarbon plasma working gas and a silicon source and optimizing a preparation method, and the obtained silicon carbide powder has concentrated particle size distribution, regular morphology, high purity and extremely few discharge of three wastes as byproducts, thereby providing a feasible development direction for the industrial production of the superfine silicon carbide powder.
Claims (9)
1. The preparation method of the superfine high-purity silicon carbide powder is characterized by comprising the following preparation steps:
(1) After the gas in the reactor is replaced by the circulating working gas, introducing plasma working gas into the plasma arc torch and maintaining the stability of the plasma arc;
(2) Feeding a silicon raw material into a plasma arc, gasifying the silicon raw material and reacting the silicon raw material with the ionized plasma working gas to generate silicon carbide particles;
(3) The generated silicon carbide particles are grown, formed, cooled and collected to obtain silicon carbide powder;
wherein the circulating working gas is a non-oxygen-containing element gas with an oxygen content of <1wt%; the plasma working gas comprises at least a hydrocarbon gas.
2. The method of claim 1, wherein in the step (1), the circulating working gas is at least one of helium, nitrogen and argon.
3. The method of producing ultra-fine high purity silicon carbide powder according to claim 1, wherein in step (1), said plasma working gas comprises at least one of methane, ethane, propane, ethylene and acetylene.
4. The method of producing ultra-fine high purity silicon carbide powder according to claim 1, wherein in step (1), said plasma working gas further comprises at least one of hydrogen and argon.
5. The method of producing ultrafine high purity silicon carbide powder according to claim 1, wherein in the step (2), the silicon material is silicon powder having a D50 particle diameter of 0.3 to 30. Mu.m, as calculated from SEM images.
6. The method of producing an ultrafine high purity silicon carbide powder according to claim 1, wherein in the step (2), the mass/power ratio between the amount of the silicon raw material fed per unit time and the power of the plasma arc is 0.001 to 0.5kg/kW.
7. The method of producing ultra-fine high purity silicon carbide powder according to claim 1, wherein the plasma arc is a non-transferred arc generated by a non-transferred arc torch; when the number of the non-transfer torches is greater than 1, each adjacent non-transfer torches form the same included angle with the axis of the reactor and are converged at an intersection point, the included angle is 15-90 degrees, and each non-transfer torch is uniformly distributed on the cross section of the reactor in an equal radian manner.
8. A process for preparing ultra-fine high purity silicon carbide powder according to claim 1, wherein said silicon feedstock is piped to a location 0-20cm above the intersection of a plurality of said non-transferred arc torches.
9. An ultrafine high-purity silicon carbide powder, which is characterized in that: obtained by the production method according to any one of claims 1 to 8, wherein the silicon carbide powder has an average particle diameter of 10 to 250nm in terms of BET specific surface area.
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