Surface and subsurface structure of solids by laser photoacoustic spectroscopy

Abstract

The new technique of photoacoustic spectroscopy is applied to studies of surface and subsurface structures of solids. In the present case, special attention is focused on silicon-nitride ceramic material, which is used for the manufacturing of turbine blades. Good correlation is obtained between the observed photoacoustic signal and surface microstructure. In addition, the photoacoustic signal shows inhomogeneities that are not visually detected under a microscope.