CN1449994A

CN1449994A - Industrial preparation method for silica carbide crystal whisker and micropowder

Info

Publication number: CN1449994A
Application number: CN 03114672
Authority: CN
Inventors: 王晓刚; 李晓池
Original assignee: XI'AN SCIENCE AND TECHNOLOGY COLLEGE
Current assignee: Xi'an Boer New Material Co ltd
Priority date: 2003-05-09
Filing date: 2003-05-09
Publication date: 2003-10-22
Anticipated expiration: 2023-05-09
Also published as: CN100415644C

Abstract

The industrial preparation method of silicon carbide whiskers and micrpowder is characterized by that the graphite and other industrial carbon and silicon raw materials are mixed, and placed into industrial SiC smelting furnace to make synthesis reaction, the graphite is used as conductive heating body to prepare silicon carbide whiskers and micropowder. Said preparation method is simple, the diameter of whiskers produced by said invented method is uniform, and length-diameter ratio is large and the heteromorphous crystal is less, and product quality is high.

Description

Industrial preparation method of silicon carbide crystal whisker and micro powder

Technical Field

The invention relates to a preparation method of silicon carbide whiskers and micro powder, in particular to a method for industrially preparing the silicon carbide whiskers and the micro powder.

Background

The silicon carbide whisker and the silicon carbide micropowder have excellent performances of high melting point, high strength, high modulus, low thermal expansion rate, corrosion resistance, wear resistance and the like, are used as reinforcing flexibilizers of composite materials such as metal bases and ceramic bases and high-grade raw materials of structural ceramics, high-grade refractory materials and coating materials, and are widely applied to the fields of machinery, electronics, aerospace, energy sources and the like. However, in the existing preparation method, the carbonized rice hulls are treated by acid and SiO is added in addition₂Adjusting raw materials, adding a composite catalyst, loading the mixture into a graphite crucible, placing the graphite crucible into a high-temperature furnace, introducing protective gas Ar gas, and carrying out carbothermic reduction reaction at high temperature to prepare silicon carbide whiskers; the invention patent of a preparation method of nanometer silicon carbide whiskers (application number 99110846.9) adopts another method: preparing carbon and silicon clean raw materials into sol, fully mixing and drying the sol according to a proportion to prepare binary xerogel, placing the xerogel into a graphite crucible, placing the xerogel into a high-temperature furnace, introducing argon, and carrying out carbothermic reduction reaction at 1300-1600 ℃ to prepareObtaining the silicon carbide crystal whisker. Both of the above methods have the following drawbacks: 1. the purity and the cost of raw materials are high; 2. the high-temperature furnace used in the production has complex structure and high manufacturing cost; 3. the production process is complex and the synthesis difficulty is high; 4. the high-temperature heating process belongs to external heating of raw materials, so that the raw materials are heated unevenly, the heating time is short, and more special-shaped crystals are generated; 5. due to the reasons, the production cost is high, the yield is small, and the mass industrial production is difficult.

Disclosure of Invention

In order to overcome the defects, the invention aims to provide a preparation method which has low production cost and simple production process and can be used for industrially producing silicon carbide whiskers and micro powder on a large scale. The crystal whisker produced by the method has uniform diameter, large length-diameter ratio and good product quality.

The invention is realized by the following method for realizing the aim: (1) the graphite and other industrial carbonaceous and siliceous raw materials are crushed and fully mixed, and the ratio of the total weight of the carbonaceous raw materials to the total weight of the siliceous raw materials is as follows: 1: 1.1-2.5; (2) the mixed reaction materials are put into an industrial SiC smelting furnace for synthetic reaction, the smelting furnace adopts variable power or constant power for power supply, graphite is used as a conductive heating body at the moment until the flame of the furnace body is extinguished, and the furnace is closed after the synthetic reaction is finished; (3) and (3) taking the prepared silicon carbide whiskers and the micro powder out of the furnace and purifying.

The industrial carbonaceous raw material used in the preparation process comprises one or a mixture of more of anthracite, bituminous coal, graphite, carbon black or petroleum coke; the industrial siliceous raw material comprises one or a mixture of quartz sand, metallic silicon or organic silicon. The mixed reaction materials can be added with or without catalyst during the synthesis in the furnace, and the catalyst can be one or the combination of more than two of sodium salt, sulfate, silicate and metal oxide during the addition, and is fully and uniformly mixed with the reaction materials.

The carbon monoxide gas generated in the synthesis reaction in the step (2) can be used as protective gas without adding argon, the synthesis temperature is 1400 ℃ and 2000 ℃, the reaction time is 2-60 hours, and the synthesis reaction equationThe formula is as follows: 。

after the synthesis reaction in the furnace is finished, the prepared silicon carbide whisker product can be purified by adopting chemical treatment methods of decarburization, silica removal and iron removal.

Compared with the prior art, the invention adopts industrial raw materials and the SIC industrial smelting furnace for production, the raw materials are rich and cheap, the structure of the synthesis furnace is simple, and the industrialized mass production can be realized; the CO gas generated in the synthesis process can replace argon gas to be used as protective gas, meanwhile, graphite is used as a heat conduction heating body in the production process, an infinite micro heat source in the raw materials in the furnace uniformly heats, the synthesis time is long, and therefore the product is uniform in diameter, few in special-shaped crystals and large in length-diameter ratio. Therefore, the invention has the characteristics of simple preparation process, small equipment investment, low production cost, high product diameter rate and good quality.

Detailed Description

Example 1: (1) mixing the mixture of fixed carbon 90%, ash 0.2% and volatile matter 8.7%Crushing petroleum coke and 98% carbon-containing graphite into powder with particle size within 1MM, and pulverizing SIO₂Crushing quartz sand with the content of 99.3% into powder within 1.5 MM; according to the ratio of C to SiO₂The two kinds of powder are mixed in the ratio of 0.56 to 1 and then fully mixed to form the reaction material. (2) Sodium chloride accounting for 0.15 percent of the amount of the reactants and cobalt chloride accounting for 0.05 percent of the amount of the reactants are added into the reactants as catalysts and are fully and uniformly mixed. (3) And (3) loading the prepared reaction material into an industrial SIC smelting furnace, and adopting constant power to supply power for smelting, wherein the synthesis reaction temperature is 1400 ℃, the reaction time is about 2 hours, CO generated in the synthesis can play a role of protecting gas, and the furnace is closed after the flame of the furnace body is extinguished. (4) And (3) discharging the prepared silicon carbide whiskers and the differentiated mixture primary product and purifying.

Example 2: (1) anthracite with fixed carbon content of 88 percent, ash content of 3 percent and volatile matter content of 6 percent and graphite with carbon content of 98 percent are crushed into 0-1.5MM particles, and SiO₂Crushing 99.3% of silica into 0-2.0MM fine particlesThe raw materials are mixed according to the proportion of C to SiO₂The ingredients were dosed at a ratio of 0.6: 1 and mixed thoroughly. (2) Adding milling quartz sand 0.1% of the mixture amount and salt 0.2% of the mixture amount as catalysts into the mixture amount, and fully and uniformly mixing. (3) And (3) filling the prepared reaction material into a combined electrode multi-core SIC smelting furnace, supplying power by constant power, conducting graphite in the furnace to generate heat, reacting at the temperature of 1800 ℃ for about 30 hours, generating CO in the synthesis to play a role of protecting gas, and closing the furnace after the flame of the furnace body is extinguished. (4) The prepared product is primary silicon carbide whisker and micro powder with the content of 40-50%, and the primary product is taken out of the furnace for purification.

Example 3: crushing bituminous coal coke with the fixed carbon content of 89 percent, the ash content of 4.6 percent and the volatile matter content of 5 percent and industrial graphite with the carbon content of 99 percent into 0-0.5MM particles, and crushing SiO₂Crushing 99% silica sandinto 0-0.5MM fine particles, mixing the two raw materials according to the ratio of C to SiO₂The materials are mixed according to the proportion of 0.7: 1.0 and fully mixed. (2) And (3) putting the prepared reaction material into a combined electrode multi-core SIC smelting furnace, supplying power by adopting constant power, conducting graphite in the furnace to generate heat, reacting at the temperature of 2000 ℃, and synthesizing for about 60 hours, wherein CO generated in the synthesizing process can play a role of protecting gas until the flame in the furnace is extinguished and the furnace is closed. (3) The prepared product is primary silicon carbide whisker with the content of about 50 percent and differential, and the primary product is taken out of the furnace for purification.

Claims

1. An industrial preparation method of silicon carbide crystal whiskers and micro powder is characterized by comprising the following specific steps: (1) the graphite and other industrial carbonaceous and siliceous raw materials are crushed and fully mixed, and the ratio of the total weight of the carbonaceous raw materials to the total weight of the siliceous raw materials is as follows: 1: 1.1-2.5; (2) the mixed reaction materials are put into an industrial SiC smelting furnace for synthetic reaction, the smelting furnace adopts variable power or constant power for power supply, graphite is used as a conductive heating body at the moment until the flame of the furnace body is extinguished, and the furnace is closed after the synthetic reaction is finished; (3) and (3) taking the prepared silicon carbide whiskers and the micro powder out of the furnace and purifying.

2. The industrial preparation method of silicon carbide whiskers and micropowder according to claim 1, wherein the industrial carbonaceous raw material used in step (1) comprises anthracite, bituminous coal, graphite, carbon black or petroleum coke; the industrial siliceous raw material comprises quartz sand, metallic silicon or organic silicon.

3. The industrial preparation method of silicon carbide whiskers and micropowder according to claim 1, wherein a single or combined catalyst of sodium salt, sulfate, silicate and metal oxide can be added to the reaction material and mixed well.

4. The industrial preparation method of silicon carbide whiskers and micropowder according to claim 1, characterized in that the synthesis reaction temperature in the industrial SiC smelting furnace in step (2) is 1400-2000 ℃ and the reaction time is 2-60 hours.

5. The method for industrially producing silicon carbide whiskers and micropowder according to claim 1, wherein carbon monoxide gas generated in the synthesis reaction in the step (2) is used as a substitute for other inert shielding gas.