Thermo-oxidative resistance of C-rich SiCN(O) nonwovens influenced by the pretreatment of the silazane

Abstract

C-rich SiCN(O) ceramic nonwovens with thermo-oxidation resistance up to 600 °C were developed from electrospinning of polyacrylonitrile in combination with different ratios of an oligomeric or polymeric silazane and subsequent pyrolysis. The influence of the selective pre-polymerization of the oligosilazane and the respective amount on the electrospinning, pyrolysis, phase formation and the properties of the resulting C-rich ceramic nonwovens was evaluated. The fiber diameter after pyrolysis at 1000 °C ranges from 0.26 to 0.63 µm. The oligosilazane/PAN-derived ceramic nonwovens contain high oxygen and carbon content because of high reactivity leading to a high ceramic yield due to additional crosslinking. A higher initial oxidation temperature compared to pure carbon was confirmed for all samples. However, the best result was achieved with a sample based on a high proportion of polysilazane in combination with PAN, as a dense passivating layer to protect the free carbon regions was obviously better able to form.