Core-skin structure micropore silicon carbide fiber and method for producing the same

Abstract

The invention relates to skin-core structure micro-pore silicon carbide fiber and the preparation method, the fiber is characterized in that both the skin layer and the core part contain the micro-pore with pore diameter less than 2 nm, and the micro-pore volume content of the skin is higher than the core part; the ratio between the skin layer thickness and the radius is 0.1 to 0.9; according to the differences of the skin thickness, the specific surface area of the fiber is 400m<2> / g to 1400m<2> / g, and the average pore diameter is 1.30 to 1.60 nm; the C content of the skin layer is more than 90 wt percent, the residual is Si, or Si and O; the C content of the core part is 27 to 35 wt percent, the O content is 10 to 20 wt percent, and the residual is Si. The preparation method is characterized in that the Si element of the skin layer is etched through the KOH activation method and the skin-core structure is formed, simultaneously, the micro-pore with higher proportion is formed, the specific surface area and the conducting property of the fiber can be adjusted through the method. The skin-core structure micro-pore silicon carbide fiber of the invention can be used in the physico chemical adsorption field, catalyst carrier field, and wave-absorbed stealth field.

Description

technical field [0001] The invention relates to a silicon carbide fiber and a preparation method thereof, in particular to a microporous silicon carbide fiber with a skin-core structure and a preparation method thereof. Background technique [0002] Silicon carbide (SiC) fibers have the advantages of high strength, high temperature resistance, oxidation resistance, chemical corrosion resistance and high temperature creep resistance. Continuous SiC fibers are mainly used as reinforcements of high temperature resistant ceramic matrix composites (CMC) to improve strength and toughness, and are key raw materials in the fields of aerospace, defense weapons and ceramic engines. In addition, due to its outstanding chemical inertness and semiconductor characteristics, continuous SiC fibers have outstanding application prospects in the fields of nuclear radiation components, chemical and chemical devices, and radar stealth structures. [0003] In addition, if the porous SiC fiber fo...

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Problems solved by technology

[0004] The current methods for preparing SiC fibers include chemical vapor deposition (CVD) method (US Patent 3433725), powder sintering method (US Patent 4908340, 1990), precursor transformation method (Chemical Letters, 1975: 931), chemical vapor phase reaction method (CVR ) (JP Patent 58 / 91823, 1983; JP Patent 55 / 085472, 1980), etc., wherein the fiber prepared by CVD is a skin-core composite fiber with C fiber or W wire as the core and SiC as the skin, with good mechanical properties and diameter Coarse, dense structure without pores; SiC fibers prepared by powder sintering method have high porosity, in the range of mesopores (~10-100nm), and poor mechanical properties; SiC fibers prepared by precursor conversion method have good mechanical properties and fiber diameter Thin, good weavability, there are a small amount of micropores (Journal of Material Science, 1990: 2118), but these micropores are closed cells, and the specific surface area of ​​the fiber is very low (2 / g), mainly the external specific surface area, and does not have a skin-core structure; the chemical vapor phase reaction method is obtained from the Si of active C fibers, which has similar pore characteristics to active C fibers, but does not have a skin-core structure

[0005] Chinese patent No. ZL02140433.X discloses a fiber with a skin-core structure with a skin layer of C and a core of SiC prepared by a two-component spinning method, but the purpose of this method is to finally oxidize and remove the surface layer C to obtain continuously sintered SiC Fibers, similar to the powder sintering method (US Patent 4908340, 1990), cannot obtain microporous fibers

[0006] In addition, the Si element on the surface of the SiC fiber is etched and removed by chlorine gas, and a SiC fiber with a skin-core structure (Nature Material, 1994: 628; Ceramic Engineering and Science Proceedings, 1998: 87), but this method is very inefficient, it is difficult to obtain a thicker skin layer, and it is only suitable for fibers with pure SiC on the surface, and is not suitable for SiC fibers with rich C on the surface

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