Carbon-silicon alloy fibers: Optimizing tensile properties by control of the stabilization stage

The stabilization stage in the processing of carbon-silicon alloy (CSA) pre cursor fibers is investigated in this study. The critical stabilization par ameters are identified and shown to control the mechanical properties of fi bers both at the stabilization stage and, after further pyrolysis and contr olled oxidation, to produce oxidation-resistant fibers. The attainment of i nfusibility in the stabilized fibers, necessary for the production of CSA f ibers, determines the lowest stabilization degree, whereas the highest stab ilization degree can be identified from the relationship between stabilizat ion temperature and tensile properties of CSA fibers, thus enabling the opt imum stabilization conditions to be determined. The CSA fibers produced by proper control of stabilization conditions significantly enhance mechanical properties, which are more than double those of CSA fibers obtained previo usly. Fourier transform infrared spectroscopy and nuclear magnetic resonanc e studies show that at stabilization temperatures above the optimum there i s significant formation of silica in the stabilized fibers. This leads to a higher modulus but lower tensile strength and elongation.