Carbon Mobility in SiOC/HfO2 Ceramic Nanocomposites

Silicon oxycarbide/hafnia (SiOC/HfO2) ceramic nanocomposites were studied by transmission electron microscopy (TEM) upon isothermal annealing at 1300 degrees C for 1-200h. TEM investigations in conjunction with energy-dispersive X-ray spectroscopy (EDS) analysis revealed a pronounced reduction in the local carbon content in close proximity to internal surfaces. Such small microcracks are a consequence of the polymer-to-ceramic transition and, hence, are commonly formed upon thermal annealing. The profiles of the carbon content between surface and bulk were analyzed employing error functions to yield carbon diffusivities.