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

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.