A study of evolved gas control and its effect on carbon yield during the activation of carbon fibres by controlled rate methods

The rate of evolution of CO2 or CO was used to control the low temperature activation of carbon fibres in O2 mixtures via a feedback loop operated by a PC and in-house software. The CO2 or CO concentration was monitored by a mass spectrometer and its level kept constant by varying the O2 concentration using mass flow controllers. Experiments were carried out at the same evolution rates for identical times at temperatures of 500–800 °C. It was found that the rate of carbon burn off was not constant and varied with the temperature, especially where the rate of CO2 evolution was controlled. The proposed reason for this was the high temperature gas phase oxidation of CO. However, surface areas of up to 1500 m2 g−1 were produced by these methods and thermal runaway was avoided