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Nanostructured composite coatings: thin films and applications

Nanocomposite coatings: composed of crystalline/amorphous phases mixture are synthesized (PVD and lasers) with unique physical-chemical properties that cannot be attained in bulk materials. By controlling the size and volume fraction of nanocrystalline phases in an amorphous matrix and consequently the separation width of amorphous matrix among the nanocrystallites, the properties of the nanocomposite coatings can be tailored, e.g. to make a balance between hardness and elastic modulus to permit close match to the elastic modulus of substrates, and particularly to obtain high toughness that is crucial for applications under high loading contact and surface fatigue.

nano_compEspecially, we combine PVD with the deposition of mass-selected clusters to design novel cluster-based thin films. The nano-composite films will be grown by deposition of pre-formed clusters on a substrate in conjunction with a beam of atoms from a conventional magnetron sputtering deposition process, producing embedded cluster assemblies in a matrix.

Friction coefficients as low as 0.01- 0.001 have been attained. For details see: Nanostructured Coatings, Springer, New York, pp. 1-648, 2006, and Nanoprecipitates and nanocavities in functional materials, Encycl. of Nanoscience and nanotechnology, Vol. 7, 297-349 (2004).

Applied Physics Letters, in press 2010

ACTA MATERIALIA Volume: 57 Issue: 17 Pages: 5156-5164 Published: OCT 2009 and APPLIED PHYSICS LETTERS Volume: 95 Issue: 22 Article Number: 223102 Published: NOV 30 2009

nano_comp_2This paper reports several new findings on the breakdown of dynamic roughening in thin film growth. With increasing energy flux of concurrent ion impingement during pulsed DC sputtering, a transition from dynamic roughening to dynamic smoothening is observed in the growth behavior of TiC/a-C nanocomposite films. The nanocomposite films show a negative growth exponent and ultra-smoothness (RMS roughness similar to 0.2 nm at a film thickness of 1.5 μm). Based on high-resolution cross-sectional transmission electron microscopy observations we conclude that during growth an amorphous front layer of 2 nm covers the nanocomposite film and suppresses the influence of nanocrystallites on the roughness evolution of the nanocomposite films. In addition we were able to control growth and microstructural evolution of self-assembled nanocomposite multilayers that are induced by surface ion-impingement.

JOURNAL OF APPLIED PHYSICS Volume: 105 Issue: 11 Article Number: 114314 Published: JUN 1 2009
International Journal of Solids and Structures 43 (24) 7371-7377 (2006)