Synthesis of biomorphic SiC ceramics from coir fibreboard preform

Abstract

Coir fibre, an agricultural waste material of immense economic importance in Indian subcontinent, was used as a precursor to biomorphic SiC ceramics. Fibreboards made of coir fibres were converted to carbon templates by controlled thermal processing. Plant material precursors were characterised by analysis of molecular composition, by determination of bulk density and by scanning electron microscopy. Carbon templates were characterised by measurement of dimensional shrinkages, mass loss and bulk density and by scanning electron microscopy and XRD. The carbon templates were further subjected to infiltration with liquid Si at 1550°C under vacuum, when spontaneous infiltration and reaction yielded composite ceramics preserving the morphology of native coir fibre derived precursors on macro and micro scale. The resulting material had a density of 2.59gcm−3 and, on a microstructural scale, contained SiC and Si in addition to carbon (trace) and porosity (2vol%). The end ceramics offered room temperature flexural strength of 116MPa and elastic modulus of 167GPa. Fractographic examination indicated brittle failure. The biomorphic SiC material derived from coir fibreboard precursor is likely to be suitable for use in advanced engineering applications as structural ceramics.