TITANIUM CARBIDE, NITRIDE AND CARBONITRIDES - A C-13, N-14, N-15 AND TI-47,TI-49 SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE STUDY

The first Ti-47,Ti-49, C-13, N-14 and N-15 solid-state nuclear magneti c resonance (NMR) spectra of titanium carbide, nitride and a series of cubic carbonitrides have been obtained under both static and magic-an gle spinning (MAS) conditions. The N-15 samples were isotopically enri ched by gas-solid exchange at 1000 degrees C C in a closed system. The Ti spectra of the carbide and nitride are sharp, reflecting the well defined cubic symmetry of these compounds, but become considerably bro adened in the carbonitride series, with the spectra being approximatel y the sum of TiC and TiN together with some small electric field gradi ent (EFG) effects. The resonance positions and widths of all the NMR s pectra change as carbon is progressively replaced by nitrogen. A relat ionship is observed between the C-13 chemical shift and the nitrogen c ontent of the carbonitrides, suggesting a possible NMR method for esti mating the composition of these compounds. Although electron paramagne tic resonance (EPR) spectra of all these compounds show typically meta llic behaviour, the NMR spectra show few effects attributable to condu ction electrons, probably due to the lack of s-orbital contributions t o the conduction band.