The challenge of ceramic/metal microcomposites and nanocomposites

It is increasingly being recognized that new applications for materials require functions and properties that are not achievable with monolithic materials. The combination of dissimilar materials for these new applications creates interfaces whose properties and processing need to be understood before they can be applied commercially. In the present review paper we try to emphasize the important role and challenges of ceramic/metal micro/nanocomposites in the new technologies. In this respect we will study and review the exotic effects of metal particles embedded into matrix ceramics due to the dissimilar properties of the components, percolation laws, and the nature of the interfaces. From an electromagnetic point of view we have underlined the enormous enhancement of permittivity in the proximity of the percolation threshold, associated with an induced soft mode similar to para-ferroelectric transition. From a mechanical standpoint, the synergic effect of nanometer size, clustering addressed by the percolation theory and ceramic/metal interface features produces an unexpected enhancement in the hardness of the composite giving rise to superhard materials. (c) 2007 Elsevier Ltd. All rights reserved.