Correlation between microstructure and electrical properties of SiC-based fibres derived from organosilicon precursors

The chemical, structural and electrical properties of various SiC-based fibres prepared from the pyrolysis of organosilicon precursors were studied as a function of their maximum (post) processing temperature T-p. The magnitude of the electrical conductivity (sigma) and its thermal dependence (the apparent activation energy E-a) are mainly controlled by the carbon excess present in the fibres. The free carbon phase is observed by TEM analysis as turbostratic stacks of aromatic carbon layers. The extent of those carbon domains (in length. L-a and thickness. N) increases with T-p. The amount of free carbon but above all its microstructure (i.e. the size of the carbon domains and their residual hydrogen content) and its microtexture (isolated domains or interconnected network) govern the electrical properties of the fibres through a percolation effect. (C) 1998 Elsevier Science Limited. All rights reserved.