Effects of microstructure on the oxidation behavior of A3 matrix-grade graphite

The oxidation behavior of matrix-grade graphite in air- or steam-ingress accident scenarios is of great interest for high-temperature gas reactors (HTGRs). In this study, the microstructures of two variants of matrix-grade graphite based on the German A3-3 and A3-27 formulations were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and correlated to oxidation behavior observed through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Through TEM imaging and selected area electron diffraction (SAED), a higher volume fraction of partially graphitized carbon was identified in the A3-3 type graphite than in the A3-27 type. This structure is believed to have contributed to the accelerated oxidation exhibited by A3-3 in the chemical reaction-controlled oxidation regime.

Automated summary

This study characterized the microstructures of two variants of matrix-grade graphite and correlated them to oxidation behavior. It was found that the A3-3 type graphite contained a higher volume fraction of partially graphitized carbon, contributing to its accelerated oxidation in the chemical reaction-controlled regime.