ELECTRICAL-RESISTIVITY OF SI-TI-C-O FIBERS AFTER RAPID HEAT-TREATMENT

Two types of Si-Ti-C-O fibres were heat treated in a preheated graphit e furnace at temperatures between 1273 and 1973 K, and the change in t he electrical resistivity was measured after removing the fibres from the furnace. The resistivity of the fibres decreased monotonically wit h increasing heat-treatment temperature, but showed a significant incr ease of the order of 10(1)-10(2) in the temperature range of gas evolu tion from the fibres. The resistivity of the fibre which has an amorph ous character began to increase at a lower temperature than that of th e fibre with a crystalline character. This increase in resistivity did not occur during heat treatment in a pure oxygen atmosphere, because the oxide layer formed on the fibre surface suppressed gas evolution f rom the fibres. The X-ray diffraction patterns of heat-treated fibres in nitrogen or oxygen atmospheres revealed that beta-SiC crystals bega n to precipitate from the amorphous state as the heat-treatment temper ature increased. The beta-SiC crystal growth, however, did not always correspond with the decrease in the fibre resistivity.