Preparation method of near-stoichiometric silicon carbide fiber

Abstract

The invention relates to a preparation method of a near-stoichiometric silicon carbide fiber, which comprises the following steps: (1) catalytically synthesizing HPCS: synthesizing high-molecular-weight polycarbosilane HPCS under the catalysis of metal by using liquid polycarbosilane or liquid polysilane as the material; (2) preparing a continuous HPCS fiber through melt spinning; (3) preparing an infusible fiber; (4) decarburizing: removing redundant carbon in the infusible fiber in a reducing atmosphere, thus forming a near-stoichiometric fiber; and (5) firing: carrying out high-temperature firing densification on the decarburized fiber under the protection of an inert atmosphere, thus obtaining a near-stoichiometric continuous SiC fiber. The preparation method can improve the performance of the composite material; the equipment and the process are simple; and the preparation method can be implemented by conventional fiber production equipment, can be easily industrialized and can promote the application of the SiC fiber.

Description

technical field [0001] The invention relates to a silicon carbide fiber, in particular to a method for preparing a silicon carbide fiber with a nearly stoichiometric ratio. Background technique [0002] Silicon carbide (SiC) fibers have excellent properties such as high strength, high modulus, high temperature resistance, oxidation resistance, and corrosion resistance, and have important application prospects in high-tech fields such as aviation, aerospace, nuclear industry, and weaponry. Research institutions at home and abroad have realized the industrial production of continuous SiC fibers by adopting the polycarbosilane (PCS) conversion method. The commonly used preparation process is: using polycarbosilane with a suitable softening point as a precursor, continuous PCS fibers are obtained by melt spinning, and then placed in air for oxidative cross-linking to form infusible fibers (called non-melting treatment) ), and finally fired at high temperature under the protecti...

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Problems solved by technology

At present, foreign preparation strategies can be divided into three categories: (1) Synthesis of high-molecular-weight PCS precursors, skipping the non-melting process and direct high-temperature firing to produce SiC fibers with low oxygen content, but this method requires high control of the synthesis process , spinning is difficult and there is environmental pollution, it is difficult to obtain fine diameter SiC fibers; (2) use electron beam or γ-ray irradiation instead of air oxidation for non-melting treatment (such as US patents US4220600, US4283367 and US4342712); Japan Carbon Corporation adopts This technology produces SiC fibers with low oxygen content - the trade name is Hi-Nicalon (oxygen content <0.5wt%), and after further decarburization treatment, a near-stoichiometric SiC fiber (Hi-Nicalon S) is obtained

With the reduction of impurity oxygen and carbon content in the fiber, the temperature resistance of continuous SiC fiber is significantly improved, but the non-melting treatment method of electron beam or γ-ray irradiation requires an expensive electron accelerator, and requires much higher than usual The high-dose irradiation of chemical fiber irradiation also needs to consume a large amount of high-purity argon for heat dissipation and oxygen isolation. The process is extremely complicated, which leads to a significant increase in the manufacturing cost of SiC fibers. Take Hi-Nicalon as an example. The price is 7~8 times that of general-purpose Nicalon fiber

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