Oxidation mechanism of zirconium carbide single crystals with formation of carbon

The isothermal oxidation of ZrC single crystals was carried out at 500 to 600 degrees C at an oxygen pressure of 2.6 kPa. The oxide scale was observed to consist of two subscales, zones 1 and 2; zone I is adjacent to the ZrC. It was found that carbon is retained in both zones, zone 1 containing carbon (about 20 at.%) two times greater than zone 2. The oxidation mechanism of ZrC with formation of carbon is discussed in terms of growth kinetics of zones 1 and 2, observation by backscattered electron imaging (BEI) in scanning electron microscope (SEM), interfacial observation by transmission electron microscopy (TEM) equipped with energy dispersive X-ray analyis (EDX), quantitative analysis of Zr, O and C by wave-length-dispersive (WDS) X-ray microanalysis (XMA), and Raman spectra.