Nano‐structured composite ceramic coatings such as TiN with Si3N4 or TiSi2 prepared by various forms of plasma assisted CVD composed of crystalline components of equiaxed TiN of several nm diameter, surrounded by amorphous Si3N4 intercrystalline layers of roughly 0.2 volume fraction have exhibited hardnesses in the range of 70–100 GPa—quite commensurate with polycrystalline diamond layers—and thermal stability up to 1000C. Best present considerations indicate that such ultra‐hardness is not governed by processes of crystal plasticity in the crystalline component but by the characteristics of flow mechanisms of the often topologically continuous amorphous component exhibiting “liquid‐like” behavior in the constrained spaces between the crystalline components.

Topics
Diamond, Materials properties, Plasticity, Ceramics
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© 2004 American Institute of Physics.
2004
American Institute of Physics
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