Chemical formation of ceramics

Abstract

Technical non-oxide ceramic materials are fabricated according to conventional powder processing methods, which involves heat-treatment at temperatures up to 1700–2100 °C and addition of metal oxides for the purpose of enhanced densification. Since the investigations of Verbeek et al. and Yajima et al. in the mid-1970s, a new method has been available to produce advanced ceramics at significantly lower temperatures (800–1500 °C) by the polymer pyrolysis of appropriate organometallic precursors. The work presented in this paper focuses on the synthesis and characterization of advanced ceramic fibres, bulk materials and powders based on the binary, ternary and quaternary systems SiN, SiCN and Si ECN. Herein E refers to B, Al, Ti, P or Zr. In particular, the cross-linking and pyrolysis behaviour of polysilazanes, polysilanes and polysilylcarbodiimides has been analysed by chemical analysis, FTIR, TGA, XRD, analytical TEM and mass spectrometry. Additionally, the crystallization behaviour of the pyrolysed amorphous intermediates into multiphase ceramic materials has been characterized. Since the partitioning of boron containing ternary and quaternary systems has been shifted to extraordinarily high temperatures (1700 °C), a novel class of metastable, amorphous high-temperature materials could be generated, which is not available using conventional techniques. The study of the oxidation behaviour of dense polysilazane derived SiCN bulk materials revealed corrosion resistance in pure oxygen up to 1600 °C.