Particulate nanostructured silicon nitride and titanium nitride

In recent years nanostructured (nanocrystalline, nanophase, or ultra-grained) materials (NM), which are commonly characterized by a grain size less than 100 nm have attracted the most attention because of the hope of realizing the unique physical, mechanical and chemical properties in the nanocrystalline state. In this connection the advanced ceramics as a whole, and silicon and titanium nitrides in particular because of their promising properties, are of great interest. Such properties of TiN and Si3N4 particulate NM as gas evolution at high-vacuum treatment and behavior during compaction, sintering, and high pressure sintering are described. The hardness values of these materials in the near dense state are discussed in detail. The necessity of further investigations is stressed.