As shown in Table 3, after calcination and decarburization, the light grey AlN sample is stable in composition with low O and C contents and high N content, indicating that the synthesis reaction for the AlN products is complete in the CRN process, and the decarburization effect is satisfactory. In comparison, the dark grey sample has low N content and significantly higher O content than the former. Also, the C content of the dark grey sample is about two times higher than that of the light grey sample. It is obvious that there are impurities containing C and O in the dark grey AlN products.