Synthesis of nanostructured chromium nitrides through mechanical activation process

Abstract

High energy milling prior to nitriding chromium metals has led to the formation of nanostructured CrN. Furthermore, high energy milling has substantially enhanced the chromium nitridation process. Under the same nitridation condition, nearly 100% CrN is formed for Cr powder milled in NH 3 for 24 hours prior to nitridation, whereas little CrN is produced for Cr powder without milling. More nitrides are formed as milling time increases. The enhanced nitridation process is believed to be primarily related to the enhanced reaction kinetic of the milled powder due to the presence of the sorbed nitrogen (when milled in NH 3), the reduced crystallite size, large grain boundary areas associated with ultrafine grains, the reduced correlation length of ordered stacking, and possibly the increased defect concentration induced by high energy milling.