Micro-Raman Study on Structure Evolution of Graphite Exposed to Intense Thermal Shock Load

Abstract

A small area of a fine grain graphite block was exposed to intense thermal shock load at 9.6 GW/m2 and investigated by micro-Raman spectroscopy. Raman spectra of the loaded area show a reduction of the intensity ratio of D and G peaks in comparison with the one of unloaded graphite, indicating the ordering of graphitic structure even for as short as 5 ms. Raman spectra of the surrounding area, on the other hand, exhibited broad features of amorphous carbon, indicating a carbon deposits from the loaded area. The broad spectra showed a strong positional dependence, reflecting the temperature gradient of the block induced by the shock load. Fitting analysis of the Raman spectra clearly shows two linear relationships between the G-peak width (FWHMG) and the peak intensity ratio (ID / IG), corresponding to two steps of ordering process of the amorphous carbon deposits.