SYNTHESIS OF ZRC AND ZRN IN AIR FROM MECHANICALLY ACTIVATED ZR-C POWDER MIXTURES

Mixtures of zirconium and carbon powders in various atomic fractions ( 5-75 at.% of C) were ground in a planetary ball mill. When the mixture s thus activated mechanically were transferred into a graphite crucibl e and exposed to air, they ignited spontaneously and the self-propagat ing high-temperature synthesis (SHS) took place in two successive step s, Zirconium carbide and zirconium nitride were formed, depending on t he initial C concentration. The almost stoichiometric ZrC was formed i n air from the Zr-C powder mixtures with C = 50-60 at.%. From the meas urement of the lattice constant and X-ray photoelectron spectroscopy ( XPS) spectra, the formation of solid solutions between ZrC and ZrN was also estimated. A possible reaction mechanism for the formation of th e zirconium carbide and nitride is discussed.