Nanotech 2011

Pseudoplastic Deformation of Thin Nanostructured Porous Ceramic Films

H. Hofmann
Ecole Polytechnique Federal de Lausanne, EPFL, CH

Keywords: nanoporous ceramic, pseudo plastic

Abstract:

The understanding of the properties of porous thin ceramic layers is still insufficient and therefore applications are limited. Nanosized ceramic particles enable the formation of nanosized pore structures and therefore a crack development which is total different from bulk material. In the sample with a stochastic distribution of pores, the first damage usually appears far from the loading surfaces, at the weakest sites characterized by the maximum local porosity. The formation of the main crack in this case requires additional energy, since the paths of crack propagation from the weak sites are not rectilinear and exhibit a random character. Therefore a quasi-viscous fracture of such brittle materials could be observed. In this presentation we present our experimental results regarding the deformation behaviour of nanosized porous titania coatings on a metal wire. Deformation of more than 20 % without formation of macroscopic cracks could be achieved. Also a new method for the characterisation of crack formation based on a statistical treatment will be presented. The combination of high porosity, different pore sizes with high adhesion and surprisingly good mechanical properties as well as the structuring of the surface enables the use of such type of coatings for novel applications.
 

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