Improved thermomechanical stability of polymer-derived silicon carbide fibers by decaborane incorporation

Abstract

Decaborane was investigated as a precursor for boron-based densification aid to polymer-derived SiC fibers. By means of acid-base interaction, the infusibility of polycarbosilane-based polymers upon pyrolysis was enhanced significantly. The beneficial effect of decaborane toward improved thermomechanical stability took place when decaborane-doped SiC fibers were treated at 1800 degrees C. With the decaborane content at 2-4 wt%, the strength retention after the 1800 degrees C treatment was enhanced as high as 80%. Elastic modulus was improved as well, partly due to increased density and crystallinity. Improved densification by decaborane resulted in the fiber density as high as 2840 kg/m(3), which corresponds to 89% densification. Decaborane also increased the Weibull modulus after the 1800 degrees C treatment, indicating an enhancement in fiber reliability. (C) 2000 Kluwer Academic Publishers.