Nanostructure analysis of pyrolyzing conversion from organic polymer precursors to Si–C–(Ti)–O inorganic fibers

Abstract

The Si–C–(Ti)–O inorganic fibers prepared by pyrolyzing poly(titano) carbosilane organic polymer precursors are well known to keep a very high tensile strength of about 250 kg mm^-2 at high temperatures above 1000°C in air for several hours. The structural evolution during the organic-to-inorganic conversion was measured by small angle X-ray scattering (SAXS) using a point-collimated Cu Kα X-ray beam and a two-dimensional imaging plate detector. The SAXS profile for the fibers generally comprises two components; an anisotropic scattering observed in the lower q region (<0.07 Å^-1) and an isotropic one in the higher q region (>0.1 Å^-1), where $\text{q=4π}\text{sin}\text{θ/λ}$ is the scattering vector. The isotropic SAXS profiles, which sensitively depend on the pyrolyzing temperature, are contributed from the β-SiC nanoparticles embedded in the amorphous matrix of the fibers. The very high mechanical strength of the Si–C–(Ti)–O inorganic fibers originates from the formation of a carbon-rich shell-like interface boundary surrounding the β-SiC nanoparticles which is sharply separated from the amorphous matrix.