J.M. Okoh’s scientific contributions

The work presented in this report is part of an ongoing effort in the microgravimetric evaluation of the intrinsic reaction parameters for air reactions with graphite over the temperature range of 450 to 750°C. Earlier work in this laboratory addressed the oxidation/etching of H-451 graphite by oxygen and steam. This report addresses the air oxidation of the Japanese formulated material, IG-110. Fractal analysis showed that each cylinder was remarkably smooth, with an average value, D, the fractal dimension of 0.895. The activation energy, Ea, was determined to be 187.89 kJ/mol indicative of reactions occurring in the zone II kinetic regime and as a result of the porous nature of the cylinders. IG-110 is a microporous solid. The low initial reaction rate of 9.8 × 10-5 at 0% burn-off and the high value (764.9) of Φ, the structural parameter confirm this. The maximum rate, 1.35 × 10-3 g/m2s, was measured at 34% burn-off. Reactions appeared to proceed in three stages and transition between them was smooth over the temperature range investigated. Both Ea and 1n A did not vary with burn-off. The value of ΔS, the entropy of activation, was - 41.4 eu, suggesting oxygen adsorption through an immobile transition state complex. Additional work is recommended to validate the predictions that will be made in relation to accident scenarios for reactors such as the modular high temperature gas-cooled reactor where fine grained graphites such as IG-110 could be used in structural applications.