1997 年 44 巻 6 号 p. 547-553
Nanocrystalline titanium nitride (Ti56N44) powder with an average grain size of 5 nm has been synthesized by ball-milling elemental Ti powder under flow of nitrogen gas at room temperature. During the first stage of the reactive ball milling time (0 ks-3.6 ks), the metallic Ti particles agglomerate to form powder particles with larger diameter. At the second stage (3.6 ks-22 ks), these agglomerated particles are disintegrated to form smaller particles. The disintegrated particles which have fresh surfaces begin to react with nitrogen (milling atmosphere) during the third stage of milling (22 ks-86 ks) to form TiN powder coexisting with unreacted metallic Ti powder. Towards the end of milling (86 ks-173 ks), a single phase of nanocrystalline TiN with NaCI-structure was obtained. The powder of this end product has spherical like morphology with an average particle size of about 0.4 μm in diameter. A consolidation procedure using a plasma activated sintering method has been employed to consolidate the powder particles at the several stages of the reactive ball milling. The density measurements of the consolidated samples show that after 86 ks to 173 ks of the reactive ball milling time, the compacted samples are fully dense. The results have shown also that the consolidated TiN compacts still maintain their unique nanocrystalline properties with an average grain size of about 65 run. The hardness and some mechanical properties of the consolidated TiN compacts have been determined as a function of the reactive ball milling time.
