A continuous silicon carbide fiber with wide-range controllable electrical properties and its preparation method

Abstract

The invention discloses a continuous silicon carbide fiber with wide-range controllable electrical properties and a preparation method thereof. Carbosilane precursor; the precursor is melt-spun to obtain polycarbosilane fibers; polycarbosilane fibers are sequentially oxidized and pre-crosslinked, vacuum heat treated, and fired at a high temperature in a hydrogen / nitrogen atmosphere to obtain silicon carbide with wide-range controllable electrical properties fiber. Compared with the prior art, the preparation method provided by the invention has low cost of raw materials, simple preparation process and equipment, and the resistivity of the prepared silicon carbide fiber is between 10 ‑2 ~10 7 It is controllable in the range of Ω·cm, the tensile strength of single filament can reach 3.0GPa, the fiber strength retention rate after treatment at 1000°C in air is more than 90%, and the change of electrical properties is less than 15%. It has a good application in high-temperature wave-absorbing materials prospect.

Description

technical field [0001] The invention relates to the technical field of functional ceramic fibers, in particular to a continuous silicon carbide fiber with wide-range controllable electrical properties and a preparation method thereof. Background technique [0002] Continuous SiC fiber has excellent properties such as high strength, low density, high temperature oxidation resistance, chemical corrosion resistance, thermal shock resistance, high tensile strength, good creep resistance and good compatibility with ceramic matrix. It is an advanced composite fiber. The structural reinforcement commonly used in materials has been widely used in aerospace, aviation and high-performance weaponry. With the new requirements of technological progress and equipment development, there is an urgent demand for structural / functional integrated composite materials, which require that the reinforced fiber not only have excellent mechanical properties and high temperature resistance, but also ...

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Problems solved by technology

[0005] The invention provides a continuous silicon carbide fiber preparation method with wide-range controllable electrical properties, which is used to overcome the low content of free carbon in the silicon carbide fiber prepared by polycarbosilane without melting in the prior art, which cannot be produced. Low-resistivity fibers are obtained; the free carbon content in silicon carbide fibers prepared by anaerobic non-melting combined with hydrogen firing is high, and SiC x o y The content of amorphous phase is small, and high resistivity fibers cannot be prepared. However, silicon carbide fibers prepared by anaerobic non-melting combined with ammonia nitriding firing have low strength, poor oxidation resistance, and high cost. , polyphenylmethylsilane as raw materials, synthesized phenyl-containing polycarbosilane precursors with excellent molding properties under high temperature and high pressure in xylene solvent and hydrogen atmosphere, using the introduced phenyl groups to control the carbon-silicon ratio of the precursors, and then control The content of free carbon in silicon carbide fibers; at the same time, air pre-oxidation combined with vacuum thermal crosslinking is used to achieve the non-melting of the fibers, and the oxygen content in the fibers, that is, SiC, is achieved under the premise of ensuring that the fibers do not melt. x o y Large-scale control of the amorphous phase, and further precise control of the free carbon content in the fiber by firing under a hydrogen / nitrogen atmosphere, through the free carbon low-resistance phase and SiC x o y Coordination of high-resistance phases realizes wide-area regulation and achieves silicon carbide fiber resistivity of 10 -2 ~10 7 Controllable preparation in the range of Ω·cm, the tensile strength of the prepared silicon carbide fiber monofilament can reach 3.0GPa, the strength retention rate after treatment at 1000°C in air is greater than 90%, and the resistivity change is less than 15%

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