Study of Crystallization and Composition on Silicon Oxycarbide (SiOC) and Silicon Boron Oxycarbide (SiBOC) Ceramics Obtained from Alkoxysilanes Precursors

This work deals on the preparation of silicon oxycarbide (SiOC) and boron (SiBOC) ceramics from pyrolysis involving alkoxysilanes with different organic groups. Boron content, substituent annealing time were evaluated crystallization composition resulting ceramics. B-free precursors composed methyltriethoxysilane (MTES), phenyltriethoxysilane (PTES) vinyltrimethoxysilane (VTMS) obtained by sol-gel method, whilst B-containing prepared adding to each alkoxysilane a proper amount boric acid in B/Si atomic ratios 0.1 0.5. Precursors pyrolyzed at 1500 °C for 1 3 h produce respective SiOC SiBOC X-ray diffraction (XRD) patterns revealed enhanced SiC phase PTES-derived ceramics, followed those containing vinyl methyl groups, which was also confirmed photoelectron spectroscopy (XPS) percentages Si-C Si-O bonds. Csp2 Csp3 amounts varied among indicating direct influence conductive carbon development. addition induced growth crystallites, having more evident effect matrices higher proportions amorphous fraction lower residual amounts. Organic group nature, content played an important role production evolution C phases into