C. Vahlas et al., THERMAL-DEGRADATION MECHANISMS OF NICALON FIBER - A THERMODYNAMIC SIMULATION, Journal of Materials Science, 29(22), 1994, pp. 5839-5846
Thermodynamic calculations for the thermal degradation of the Nicalon
fibre in inert gas flow at atmospheric pressure have been performed, b
ased on minimization of the Gibbs energy of the Si-C-O-H chemical syst
em. The calculations are based on a critically selected thermodynamic
database of the participating compounds, The results are presented by
means of diagrams illustrating the quantities of condensed and gaseous
species obtained as a function of treatment temperature. These are co
mpared with recently reported TEM studies of as-received and heat-trea
ted material, which illustrate the sequential morphologies of its stru
cture and nanotexture as a function of treatment temperature. The main
step of the observed degradation mechanism is successfully simulated
in terms of the temperature, the oxygen content and the weight loss of
the material. An endogenous oxidation mechanism is proposed for degra
dation of the fibre.