Behavior of Oxygen and Carbon in Ball-Milled Si3N4 Powders during Heat Treatment and Sintering

Three kinds of Si3N4 powders, DW, TX and E10, with and without sintering additives were ball-milled using ethanol as medium. Oxygen and carbon contents in the mixed powders increased due to the mechanochemical reaction between the powders and ethanol. The increases of oxygen and carbon were almost the same for the three powders. After heat treatment at 800-1200°C in vacuum or nitrogen gas, most of the carbon was desorbed. On the other hand, the increment of oxygen remained in the ceramic body even after sintering at 1750°C.