Synthesis and structural characterization of SiBOC ceramic fibers derived from single-source polyborosiloxane

SiBOC ceramic fibers have been successfully prepared from single-source polyborosiloxanes which are synthesized from polymethylethoxysiloxane and B(OH)₃ via a sol-gel route. The morphological change, structural evolution and crystallization behavior of fibers as a function of thermal treatment are studied by several techniques. Polyborosiloxane sols exhibit remarkable spinnability, in which B atoms are homogenously incorporated into the linear Si-O-Si skeleton via Si-O-B bridges. SiBOC ceramic fibers with diameters of about 10μm are prepared with high ceramic yield ranging from 80.5 to 86%. Although a continuous structural evolution occurs with increasing pyrolysis temperature, the SiBOC ceramic fiber with B/Si atom ratio of 0.14 is thermal stable at 1500°C. The thermolysis and crystallization behaviors are closely related to the boron content. The tendency toward crystallization of SiC and graphitization of free carbon is strengthened with the increase of boron content and pyrolysis temperature.