This work focused on the fabrication of silicon oxycarbide ceramic (SiOC) foams as well as dense compacts using poly(hydridomethylsiloxane) (PHMS) as a polymer precursor. The room-temperature cross-linking of PHMS was achieved by the addition of 1,4-diazabicyclo [2.2.2] octane (DABCO) with the release of hydrogen gas as a by-product. This resulted in self-blowing of the polymer precursor at room temperature and thereby offered the possibility of producing SiOC foams without the need of any external blowing agents. We also reported the fabrication of crack-free silicon oxycarbide compacts by cold compaction and pyrolysis route using polyvinyl alcohol (PVA) as a processing additive. Cylindrical-shaped pellets were pyrolysed at 1300 ℃ in argon atmosphere with a ceramic yield of approximately 85%. Increased resistance to phase separation and crystallization up to 1400 ℃ was attributed to the presence of large volume fraction of free carbon in the material which was confirmed by Raman spectroscopy.

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The deformation behavior of pulsed electric current sintered silicon oxycarbide ceramics produced by the solid-state thermolysis of polyhydridomethylsiloxane at small-scale is investigated. The ceramics remained X-ray amorphous after sintering at 1300°C in vacuum and a high density of %2.35 g cm À3 is achieved. The elastic constants of these ceramics are determined using non-destructive ultrasonic testing method. The elasto-plastic deformation under contact loading is determined using depth sensing nanoindentation technique. An indentation hardness of %11 GPa and reduced elastic modulus of %105 GPa is observed. The load-displacement curves display significant elastic recovery with an elastic work ratio of %0.71. The evolution of Hertzian cone cracks upon microindentation indicates an anomalous deformation behavior.

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