The purpose of the research is to develop and establish a technique for characterising the subsurface quality of materials that have been prepared to have a high quality surface finish to nanometre standards. Subsurface damage is present in an engineering component whenever residual elastic or plastic strain near the surface adversely affects its intended function, this includes the whole range of damage from cracks to small atomic displacements. This project will use a new instrument, the SBS, unique in the world to measure the subsurface damage in nanocomposites ceramics. I shall start to measure changes in SBS measurements due to subsurface damage in single crystals of ceramics such as alumina and sapphire before move to polycrystalline materials and nanocomposites. It has been demonstrated that the signal-to-noise ratio obtained from SBS measurements from transparent materials can be improved by evaporating a very thin aluminium layer, less than 10 nm, on these surfaces. I shall evaluate the thickness of the layer which gives the best results and use this for SBS measurements of nanocomposites. I shall study the effect that the grain size has in the propagation of the surface acoustic waves. I shall aim to develop a model for interpreting measurements and properties that are important for the functional use of the materials.
The experience obtained during the calibration and alignment of the new urface Brillouin spectrometer, using single and polyinstalline materials the use of alternative techniques and the theoretical model put us in a strong position to the characterization of the nanocomposites ceramics.