The Effect of Polymer Char on Nitridation Kinetics of Silicon

Abstract : Effects of polymer char on nitridation kinetics of attrition milled silicon powder have been investigated from 1200 to 1350 deg C. Results indicate that at and above 1250 deg C, the silicon compacts containing 3.5 wt% polymer char were fully converted to Si3N4 after 24 hr exposure in nitrogen. In contrast, the silicon compacts without polymer char could not be fully converted to Si3N4 at 1350 deg C under similar exposure conditions. At 1250 and 1350 deg C, the silicon compacts with polymer char showed faster nitridation kinetics than those without the polymer char. As the polymer char content is increased, the amount of SiC in the nitrided material is also increased. By adding small amounts (approx. 2.5 wt%) of NiO, the silicon compacts containing polymer char can be completely nitrided at 1200 deg C. The probable mechanism for the accelerated nitridation of silicon containing polymer char is discussed. jg