Processing and characterization of polymer precursor derived silicon oxycarbide ceramic foams and compacts

摘要

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°Cin argon atmosphere with a ceramic yield of approximately 85%.Increased resistance to phase separation and crystallization up to 1400°Cwas attributed to the presence of large volume fraction of free carbon in the material which was confirmed by Raman spectroscopy.