A novel carborane-containing ceramic precursor: Synthesis, characterization, and ceramic conversion mechanism

Abstract

Linear carborane-carbosilane-phenylacetylene polymers have been synthesized as precursors for ceramic and characterized by Fourier transform infrared (FT-IR), proton nuclear magnetic resonance (1H-NMR), and carbon-nuclear magnetic resonance (13C-NMR). Novel linear polymers have the advantage of being extremely easy to process and convert into ceramics, since they are either viscous liquids or low melting solids at room temperature and are soluble in most organic solvents. Ceramic conversion reaction of the polymers was studied, and the conversion mechanism using thermogravimetric analyzer, FT-IR, and pyrolysis-gas chromatography-mass spectrometry was proposed. During the early heating period in the mechanism, the precursor polymer is cured and oligomer is formed. Then the degradation of oligomer takes place at higher temperatures with the weak bond cleaved and cross-linked simultaneously. Ceramic yield of the polymer after heating up to 1000°C in nitrogen (N2) was 77.6%. The derived ceramics exhibit excellent thermal and thermo-oxidative stability, whose 5% mass loss temperature was identified to be 650°C in N2 and 665°C in air, respectively. Boron appears to be the key element to achieve the outstanding thermo-oxidative stability. The relevant kinetic data were obtained by two kinds of model-free-kinetic algorithms, differential Friedman and integral Kissinger–Akahira–Sunose. These two methods were combined to give the energy profile, which has been identified to be a function of the transformation degree ( α), since the energy demand at each degradation stage is different depending on α.