A kind of method that prepares silicon carbide fiber by high softening point polycarbosilane

Abstract

The invention provides a method for preparing silicon carbide fiber through high-softening-point polycarbosilane. The method includes the following steps that 1. low-molecular-weight polycarbosilane is mixed with organosilane containing vinyl or silazane compound containing the vinyl, the polymerization reaction is catalyzed through hydrosilylation or spinning-class polycarbosilane is precipitated or classified, and high-softening-point polycarbosilane is obtained; 2. melt spinning is conducted on the high-softening-point polycarbosilane, and continuous polycarbosilane fiber is obtained; 3. the continuous polycarbosilane is placed in the non-oxidative activity atmosphere to be subjected to non-melting treatment, and polycarbosilane non-melting fiber is obtained; 4. the polycarbosilane non-melting fiber is subjected to hard fire again after being subjected to hard fire or pyrolysis decarburization, and the low-oxygen-content silicon carbide fiber or near-stoichiometric silicon carbide fiber is obtained. The method is simple in process, low in investment and preparation cost and suitable for industrialization batch preparation; the oxygen content of the obtained low-oxygen-content silicon carbide fiber is smaller than or equal to 1.2 wt%, the near-stoichiometric silicon carbide fiber C/Si ranges from 1 to 1.07, and the mechanical property is excellent.

Description

technical field [0001] The invention relates to a method for preparing silicon carbide fibers, in particular to a method for preparing silicon carbide fibers from polycarbosilane with a high softening point. Background technique [0002] Silicon carbide (SiC) ceramic fiber has important application value in high-tech fields such as aviation, aerospace, nuclear industry, and weaponry due to its high strength, high modulus, high temperature resistance, oxidation resistance, and corrosion resistance. [0003] At present, the industrial production of continuous SiC fibers has been realized by the conversion method of organosilicon polymer-polycarbosilane (PCS) precursor. Its typical preparation process is as follows: polycarbosilane PCS obtained by high-temperature cracking, rearrangement and polycondensation of organosilicon polymers is used as a precursor, and continuous PCS fibers are prepared by melt spinning, and the continuous PCS fibers are placed in air for oxidation rea...

AI Technical Summary

Problems solved by technology

[0009] CN102634867B discloses a method for preparing silicon carbide fibers with a near-stoichiometric ratio, using catalysts containing Pt, Rh or Ru to synthesize high Softening point polycarbosilane, and after melt spinning, non-melting treatment in active atmosphere, decarburization treatment in hydrogen or hydrogen-containing mixed atmosphere, high-temperature firing to prepare silicon carbide fibers with a near-stoichiometric ratio, but when this method is used, due to the introduction of Catalyzed polymerization requires a higher synthesis temperature (380-460°C). Catalyzed polymerization reaction is severe at high temperature, and excessive polymerization is prone to occur, which rapidly broadens the molecular weight distribution. Obtain high softening point polycarbosilane with uniform molecular weight distribution and good spinnability

In addition, due to the residual catalyst in the product polycarbosilane with high softening point, there is a phenomenon of continuous polymerization during the high-temperature defoaming after heating in the spinning tube and the subsequent melt spinning process, resulting in an increase in the viscosity of the polycarbosilane melt with time. Large, spinnability becomes poor or even lost