Effects of air oxidation on the evolution of surface area within nuclear graphite and the contribution of macropores

Reactive surface area and its evolution play an important role in the oxidation behavior of porous carbon materials. Here, the evolution of reactive surface area within nuclear graphite grades NBG-18, IG-110, and PCEA were examined using chronic oxidation experiments interrupted with short thermal gravimetric analyses. To help interpret the observed changes in reactive surface area, the contribution of macropore total surface area was estimated using X-ray computed tomography with repeated morphological dilations of the digitally isolated pore structure. For these nuclear graphites, the reactive surface area changes by more than an order of magnitude between 0 and 70% conversion. Surface roughening, macropore opening and evolution, as well as late exposure of filler material likely contribute to the observed behavior of reactive surface area in these nuclear graphites.