Goal
A systematic study of ceramic matrix graphene composites, including processing and microstructural, mechanical and electrical characterization is proposed in this project, with the aim of improving the comprehension of mechanisms controlling these properties when adding graphene nanostructures to a ceramic matrix.
Both alumina and yttria tetragonal zirconia (3YTZP) graphene composites will be processed by means of colloidal techniques. Special attention will be devoted to the dispersion of graphene in the ceramic matrix which is not a straightforward aspect, but is key to improve mechanical and functional properties. Sintering will be carried out by spark plasma sintering, SPS. Conditions will be optimized in order to obtain fully dense composites with nanometric grain size. Microstructural analysis will be performed by X ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM). The present crystallographic phases, grain size and distribution of graphene nanostructures will be evaluated. In order to design advanced materials, it is necessary to study the relationship between microstructure and mechanical or electrical properties. Room temperature mechanical properties (hardness, fracture toughness and flexural resistance) will be characterized by indentation and bending tests at macro and microscopic scales. At high temperature, the plastic behavior of these ceramic-graphene composites will be assessed by creep tests under controlled atmosphere. Tribological behavior of the composites will also be studied to evaluate their resistance to wear. The electrical response will be assessed in a wide range of temperatures by means of complex impedance spectroscopy or by direct current conductivity measurements in the composites with lower resistivity. This is a most interesting property since it can be strongly increased when incorporating graphene to these ceramic systems.