Superhard nanocomposite coatings

Superhard materials implies the materials with Vickers hardness larger than 40 GPa. There are two kinds of super-hard materials one is the intrinsic superhard materials, another is nanostructured superhard coatings. Diamond is considered to be the hardest intrinsic material with a hardness of 70-100 GPa. Synthetic c-BN is another intrinsic superhard material with a hardness of about 48 GPa. As introduced in Section 2, ta-C coatings with the sp fraction of larger than 90 % show a superhardness of 60-70 GPa. A typical nanostructured superhard coating is the heterostructures or superlattices as introduced in Section 4. For example, TiN/VN superlattice coating can achieve a super-hardnessof56 GPa as the lattice period is 5.2 nm[101]. 

Unlike the heterostructures whose periodic structure must be accurately controlled, the formation of nanocomposite structure is self-organized based upon thermodynamically driven spinodal phase segregation [118-121]. For the CVD 

In addition, the impurities, especially the oxygen, can strongly decrease the hardness of nanocomposite coatings. That should be the primary reason for the lower hardness 

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Holubar, P., Jilek, M., and Sima, M., "Present and Possible Future Applications of Superhard Nanocomposite Coatings, Surf. Coat. Technol,Vol. 133/134,2000,pp. 145-151. 

I should like to thank the coworkers from my institute for their enthusiastic collaborations, my colleagues and friends Profs. Li Shizhi, H. Warlimont, V. Vitek, and many others for illuminating discussions, and my wife Dr. Maritza Vepfek-Heijman for her valuable comments on the manuscript. I am very much indebted to Drs. M. Jilek, M. Sima, and P. Holubar from the SHM Company for a very fruitful collaboration towards the industrialization of our superhard nanocomposite coatings. Partial financial support of our work by the German Science Foundation (DFG) and the Bavarian Ministry for Education and Science is thankfully acknowledged. 

Yang D (2011) Nanocomposite films for gas sensing. In Reddy B (ed) Advances in nanocomposites—synthesis, characterization and industrial applications. InTech, Ch. 37, pp 857-882. http //www.intechopen.com Zhang S, Yongqing DS, Du FH (2003a) Recent advances of superhard nanocomposite coatings a review. Surf Coat Technol 167 13-119... 

Zhang S, Yongqing DS, Du FH (2003a) Recent advances of superhard nanocomposite coatings a review. Surf Coat Technol 167 13-119... 

Veprek et al. [120,121,144] present the explanation of the superhardness for the nanocomposite coating on the basis of the absence of dislocation activity in a few-nanometre-... 

Nanocomposite coatings, which require thermo-dynamically driven phase segregation. The superhardness of nanocomposites lies in the nanostructured condition of the coatings, whose structural stability could result from a spinodal... 

Veprek, S., Veprek-Heijman, M. 2007. The formation and role of interfaces in superhard nc-Me N/a-Si3N4 nanocomposites. Surf. Coat. Technol. 201. iss.l3 6064—6070. 

J. Musil, P. Zeman, H. Hruby, P.H. Mayrhofer, ZrN/Cu Nanocomposite Film - A novel Superhard material. Surface Coatings Technology, 120-121, 179-183 (1999)... 

S. Veprek, M.G.J. Veprek-Heijman, P. Karvankova, J. Prochazka, Different approaches to superhard coatings and nanocomposites. Thin Solid Films 476(1), 1-29 (2005)... 

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