CN102689903B - Method for preparing silicon carbide nanometer particle and composite material thereof by evaporating solid raw materials - Google Patents

Abstract

The invention relates to a method for preparing silicon carbide nano-particles and composite materials thereof by evaporating solid raw materials, and belongs to the field of nano-material preparation technology and application. It is characterized in that it uses automatic control DC arc plasma equipment to uniformly mix solid raw materials, namely micron-sized silicon powder and carbon powder, and press them into blocks in a certain proportion. This is used as the anode, and the graphite rod is used as the cathode. In a certain proportion of inert gas Evaporate raw materials in a mixed atmosphere of hydrogen and hydrogen to obtain single-phase silicon carbide nanoparticles or multi-phase composite materials. The invention has the advantages of simple preparation process, low cost, large-scale preparation, and can realize the control of phase composition, particle size and shape in the product.

Description

A method for preparing silicon carbide nanoparticles and composite materials thereof by evaporating solid raw materials

technical field

The invention belongs to the technical field of nanomaterial preparation, and relates to a method for preparing silicon carbide nanoparticles and composite materials thereof by evaporating solid raw materials.

Background technique

Silicon carbide has high hardness, mechanical strength, thermal conductivity, high temperature strength, creep resistance, oxidation resistance and acid and alkali corrosion resistance. Its high temperature strength and creep resistance are better than metals and intermetallic compounds, thermal conductivity and thermal shock resistance are better than oxide ceramics, and its hardness is second only to diamond, and its wear resistance is 5-20 times that of cast iron and rubber. , is the main material for making grinding and cutting supplies, and can also be used as a high-temperature indirect heating material in the non-ferrous metal smelting industry. In addition, silicon carbide has the advantages of wide band gap, high working temperature (up to 600°C), good thermal stability, small on-state resistance, good thermal conductivity, extremely small leakage current, and high withstand voltage of PN junction. It is one of the earliest semiconductor materials discovered. First, it can become a new type of power semiconductor device material.

The smaller the particle size of silicon carbide powder, the fewer structural defects it has, and it has unique properties such as small size effect and surface effect, and is expected to achieve important applications in electromagnetic wave absorption, photoluminescence and other fields. At present, the methods for synthesizing nano-silicon carbide particles can be divided into three categories: solid-phase method, liquid-phase method, and gas-phase method. Solid-phase methods include carbothermal reduction (S.Ohsaki, D.H.Cho, H.Sano, Y.Uchiyama, K.Kobayashi, Synthesis of β-SiC by the Reaction of Gaseous SiO with Activated Carbon, Key Eng. Mater., 1999 , 159:89-94.), direct reaction of carbon and silicon (Wang Tiejun, Wang Shenghong. Study on the mechanism of preheating self-propagating synthesis of nano-SiC powder. Acta Silicate, 1998, 26(2): 237-242); liquid phase Methods include sol-gel method, polymer thermal decomposition method; gas phase method includes gas phase reaction deposition method (Yang Xiuchun, Han Gaorong, Du Piyi, Ding Zishang, Zhou Guozhi. Research on the preparation of nano silicon carbide powder by thermochemical gas phase reaction. Function Materials, 1998, 29:523-526), plasma method (N.Rao, B.Micheel, D.Hansen, C.Fandrey, M.Bench, S.Girshick, J.Heberlein and P.McMurry.Synthesis of nanophase silicon, carbon, and silicon carbide powders using a plasma expansion process. J. Mater. Res., 1995, 10 (8): 2073-2084), laser-induced gas phase method (Y. Zhang, K. Suenaga, C. Colliex, S. Iijima. Science, 1998, 281, 973-975) and the like. The DC arc plasma method is used to prepare SiC nano powder (Dai Xuegang, Zheng Guoliang. Research on the preparation of silicon carbide ultrafine powder by plasma method. Chemical Metallurgy, 1996, 17(4): 310-315). The organic raw material used is methyl trichloride Silane is highly toxic and dangerous, and is also harmful to the environment and equipment, and it is easy to introduce external impurities into the produced product.

The above-mentioned preparation method of nano-silicon carbide has some disadvantages such as complex process, high cost, low output, low purity, and large environmental pollution to a certain extent. The invention adopts DC arc plasma evaporation technology (Chinese Patent No.: 200410021190.1), and uses solid micron-level silicon powder and carbon powder as raw materials to prepare silicon carbide nanopowder and its composite material. This method integrates the advantages of carbon-silicon direct reaction in the solid-phase method and the plasma technology in the gas-phase method, and has the advantages of short reaction time, simple process, uniform particle size distribution, high purity, and large-scale production. Silicon and carbon micron-level single-phase solid raw materials are used, and no other impurities are introduced during the reaction process to achieve high purity of the product and controllability of particle characteristics. The nano-silicon carbide powder material prepared by the invention can be applied to the fields of abrasives, modifiers, refractory and corrosion-resistant materials, electrochemical electrodes, light-emitting devices, semiconductor devices and the like.

China authorized patent: automatic control DC arc metal nano powder production equipment (ZL200410021190.1), the equipment consists of sequentially connected powder generation chamber, powder particle size classification chamber, powder collection chamber, powder processing chamber, vacuum system , gas circulation pump, hydraulic transmission system, water cooling system, and programming control system; the anode and cathode are installed in the powder generation chamber, and are connected to the external hydraulic transmission and programming control system through the wall of the powder generation chamber; the powder particle size classification chamber It is composed of a double-walled water-cooled shell and a liquid nitrogen cooling tank; the hydraulic transmission system is composed of a hydraulic tank and a transmission rod that control the movement of the cathode dimension and the anode dimension. The equipment loads the material into the anode and becomes a part of the anode, forming a gap of 10-30mm with the cathode, the whole equipment is vacuumed, and cooling water is passed through. After the active gas and condensed gas are introduced, the arc starter and power supply are started to form an arc between the cathode and anode electrodes, and the material begins to evaporate and form nano-powder particles. The equipment can realize mass production of silicon carbide nanopowder.

Contents of the invention

The invention provides a method and process for preparing silicon carbide nanoparticles and their composite materials, which realizes the preparation of large-scale and high-purity silicon carbide nanopowders, and the preparation of composite powder materials with controllable phase composition and particle characteristics. .

The invention uses automatic control DC arc plasma equipment, uses micron-sized silicon powder and carbon powder as raw materials, uniformly mixes and presses them into blocks as anodes, graphite rods as cathodes, and introduces a mixed atmosphere of inert gas and hydrogen to evaporate the raw materials and obtain Silicon carbide nanoparticles and their composites. Specific steps are as follows:

(1) Mix and grind micron carbon powder raw materials and silicon powder raw materials evenly, press them into blocks under a pressure of 20MPa-30MPa, put them in a graphite crucible as an anode, and a graphite rod as a cathode, and adjust the distance between the two electrodes at 10-30mm; The molar ratio of carbon powder raw material and silicon powder raw material is 10:1～1:10;

(2) The reaction chamber is evacuated, filled with hydrogen and inert gas; the pressure ratio of inert gas to hydrogen is 0:1～5:1;

(3) Connect the automatic control DC arc metal nano powder production equipment with the cooling water system, turn on the power supply and start the arc, adjust the current and the distance between the poles to form a stable arc;

(4) Under the action of the hydrogen plasma heat source, the anode evaporates into gas-phase silicon and carbon atomic states, forming atomic clusters and condensing into nanoparticles, which are deposited on the inner wall of the water-cooled reaction chamber, or transported to the trapping chamber with the circulating airflow. After the nano-powder is completely deposited, the powder is collected after the passivation process and preliminarily sieved.

in:

The carbon powder raw material in the step (1) is a mixture of one or both of micron graphite and carbon black;

The inert gas described in step (2) is one or its combination in argon, helium, neon;

The beneficial effects of the present invention are:

1. The preparation process is simple, the cost of solid raw materials is low, no harmful substances are produced, and industrial production can be realized.

2. By adjusting the ratio of carbon and silicon in the solid raw material, single-phase silicon carbide nanoparticles can be obtained.

3. By adjusting the ratio of carbon and silicon in the solid raw material, a two-phase silicon carbide/carbon nanocomposite material can be obtained, that is, the mass ratio of the two phases can be changed by the composition of the raw material.

4. Control the size, distribution, and shape of nanoparticles through current, voltage, atmosphere type and its air pressure ratio, passivation, sieving and other processes.

Description of drawings

FIG. 1 is an SEM image of the single-phase silicon carbide nanoparticles synthesized in Example 1.

2 is the XRD spectrum of the single-phase silicon carbide nanoparticles synthesized in Example 1.

3 is an SEM image of the composite material of silicon carbide and carbon synthesized in Example 2.

Fig. 4 is the XRD spectrum of the silicon carbide and carbon material composite material synthesized in Example 2.

Detailed ways

The technical solution of the present invention will be further described below in combination with specific embodiments.

Example 1:

Take micron-sized carbon powder and silicon powder with a molar ratio of 1:0.9, mix them evenly and grind them, press them into a block under a pressure of 25MPa, put them in a graphite crucible as an anode, and a graphite rod as a cathode, adjust the distance between the two electrodes to 30mm . The reaction chamber was evacuated to about 10 ^-2 Pa, and filled with argon and hydrogen at a ratio of 2:1 to reach 5×10 ⁴ Pa and 2.5×10 ⁴ Pa respectively. Turn on the cooling water system, turn on the power and start the arc, adjust the current and the distance between the electrodes and stabilize the arc, evaporate the bulk target, form atomic clusters and gather them into nanoparticles and deposit them on the wall of the reaction chamber, and collect the powder through passivation process.

The SEM image of silicon carbide nanoparticles obtained in Example 1 is shown in FIG. 1 , showing spherical particles.

The XRD spectrum of silicon carbide nanoparticles obtained in Example 1 is shown in FIG. 2 , which shows that it is single-phase silicon carbide.

Example 2:

Take micron-sized carbon powder and silicon powder with a molar ratio of 4.3:1, mix them evenly and grind them, press them into a block under a pressure of 25 MPa, put them in a graphite crucible as an anode, and a graphite rod as a cathode, adjust the distance between the two electrodes to 30mm . The reaction chamber was evacuated to about 10 ^-2 Pa, and filled with argon and hydrogen at a ratio of 11:1 to reach 5.5×10 ⁴ Pa and 5×10 ³ Pa, respectively. Turn on the cooling water system, turn on the power and start the arc, adjust the current and the distance between the electrodes and stabilize the arc, evaporate the bulk target, form atomic clusters and gather them into nanoparticles and deposit them on the wall of the reaction chamber, and collect the powder through passivation process.

The SEM image of the silicon carbide and carbon material composite material obtained in Example 2 is shown in FIG. 3 , and the particle appearance is diverse, including flake, spherical and rod-like shapes.

The XRD spectrum of the composite material of silicon carbide and carbon material obtained in Example 2 is shown in FIG. 4 , and there are two phases, ie, a silicon carbide phase and a graphite phase.

Claims (3)

1. A method for evaporating solid raw materials to prepare silicon carbide nanoparticles, using automatic control DC arc plasma equipment, the solid raw materials, namely micron-sized silicon powder and carbon powder, are uniformly mixed and pressed into blocks in a certain proportion, and this is used as an anode , the graphite rod is used as the cathode, and the raw material is evaporated in the mixed atmosphere of inert gas and hydrogen to obtain single-phase silicon carbide nanoparticles and multi-phase composite materials thereof; its characteristics include the following steps, (1) Mix and grind micron-sized carbon powder raw materials and silicon powder raw materials evenly, press them into blocks under a pressure of 20MPa-30MPa, put them into graphite crucibles as anodes, and graphite rods as cathodes, and adjust the distance between the two electrodes at 10-30mm; The molar ratio of carbon powder raw material and silicon powder raw material is 10:1～1:10; (2) Vacuumize the reaction chamber and fill it with hydrogen and inert gas; the pressure ratio of inert gas to hydrogen is 0:1~5:1; (3) Connect the automatic control DC arc metal nano powder production equipment with the cooling water system, turn on the power and start the arc, adjust the current and the distance between the two poles to form a stable arc; (4) Under the action of the hydrogen plasma heat source, the anode evaporates into gas-phase silicon and carbon atomic states, forming atomic clusters and condensing into nanoparticles, which are deposited on the inner wall of the water-cooled reaction chamber, or transported to the trapping chamber with the circulating airflow; After the powder is completely deposited, the powder is collected after the passivation process and subjected to preliminary screening. 2. The method according to claim 1, characterized in that: the carbon powder raw material is one or a mixture of micron graphite and carbon black. 3. The method according to claim 1, wherein the inert gas is one of argon, helium, neon and a mixture thereof.

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