Preparation and Properties of SiC Fiber with a Stable Excess Carbon Layer on the Surface

Abstract

<FONT face=Verdana>A new SiC fiber was prepared by the pyrolysis of polycarbosilane (PCS) fiber cured with unsaturated hydrocarbons. The fiber with oxygen content of 4wt%-6wt%, has high tensile strength of 2.5-2.8GPa. The specific resistance of the fiber is only about 0.5¦¸¡¤cm, which is much lower than general SiC fiber obtained from traditional air curing process. Results show that the fiber has an excess carbon layer with a thickness of about 50nm in the circular outer part, and the layer changes little after thermal exposure in argon. Compared with the ceramic grade fiber Nicalon NL202, thermal resistance to degradation of the fiber¡¯s mechanical property is improved by 200-300¡䬠The low specific resistance of the fiber also exhibits excellent thermal stability, which almost remains at 0.4-0.8¦¸¡¤cm after thermal exposure test from the room temperature to 1600¡䟩n argon.</FONT

Microstructure and Mechanical Properties of Compact SiC/SiC Composite Fabricated with an Infiltrative Liquid Precursor

“…When the heat‐treatment temperature increases, decomposition reactions and carbothermic reductions occur while the crystallization of SiC takes place, leading to the degradation of the fibers and the matrix, hence the overall mechanical properties. Moreover, the oxygen content of the as‐received SiC/SiC composite is rather high, 10.8 wt% for the SiC matrix and 18.3% for the fibers, which accelerated the damage of the composites. The following reactions occur when the temperature exceeded 1500°C:…”

“…KD‐I SiC fiber bundles were woven into 3D (three‐dimensional, four‐directional) preform as the reinforcement. General characteristics of the fiber provided by National University of Defense Technology were described elsewhere . The fiber preform was coated with a 0.5‐μm‐thick pyrolytic carbon (PyC) layer as the interface to adjust bonding between the matrix and fibers.…”

Studying SiC/SiC Composites by X-Ray Tomography

“…KD-I SiC fiber bundles (provided by National University of Defense Technology, NUDT, China) were used as the reinforcement. General characteristics of the fiber are described elsewhere [13,14]. Two types of polymer precursors were used, the conventional, commonly used polycarbosilane (PCS) and the newly invented LPVCS.…”