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A Consistent Rationale for the Superior Strength and Ultra-Hardness of Ceramic Nano-Composite Coatings

Published online by Cambridge University Press:  17 March 2011

A. S. Argon  and
S. Veprek
A. S. Argon
Affiliation:
Massachusetts Institute of Technology, Cambridge, MA 02139, USA
S. Veprek
Affiliation:
Institute for Chemistry of Inorganic Materials, Technical University of Munich, D-85747 Munich, Germany
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Abstract

Nano-structured composite ceramic coatings such as TiN with Si3N4 orT iSi2 prepared by variousforms 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. Preliminary considerations indicate that such ultra-hardness, uninfluenced by the usual artifacts of nano-indentations are not governed by processes of crystal plasticity in the crystalline component but by the characteristic flow mechanisms of the often topologically continuous amorphous component exhibiting “liquid-like” behavior in the constrained spaces between the crystalline components.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 697: Symposium P – Surface Engineering 2001--Fundamentals and Applications , January 2001 , P1.2
Copyright
Copyright © Materials Research Society 2002

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