The effect of thermal treatment on the properties and structure of carbon-s
ilicon alloy fibres produced from a novel silicon-containing carbon precurs
or is reported. The precursor, containing about 22 wt % Si, was melt spun i
nto fibres and then oxidatively stabilized under different conditions to re
nder the fibres infusible. The fibres were pyrolysed and heat treated to 16
00 degrees C in inert atmosphere. The extent of stabilization was found to
be critical to the development of mechanical strength of the fibres which v
aried with heat treatment temperature, showing a maximum at 1200 degrees C
when the strength was 1.2-1.4 GPa. Moduli were low because of the lack of o
rientation of the carbon layer planes along the fibre axis. The maximum str
ength and the thermal stability at high temperatures is considerably reduce
d if the fibres are excessively oxidized at the stabilization stage. Optima
lly stabilized fibres show a drop in strength at 1300 degrees C but this st
abilizes at about 600 MPa over the range 1300-1600 degrees C. These strengt
hs are remarkably good considering the low modulus which is due to the quit
e high failure strains. The fibres can show excellent resistance to oxidati
on if given an initial short exposure to oxygen at high temperature. This i
s considered to be due to an imperceptible layer of silica. (C) 1999 Kluwer
Academic Publishers.