Nondestructive acoustic microcharacterisation of heteropolysiloxane thin films

Heteroplysiloxanes (HPS) thin films, recognised as a new class of materials that can be used as very versatile coating systems, are nondestructively characterised by means of a scanning acoustic microscope. The acoustic material signatures were first measured, from which the characteristic surface velocities were determined. The influence of film thicknesses as well as operating frequencies on such velocities are reported. The results are then compared with theoretical velocity dispersion curves, giving good agreements. Rayleigh velocities were found to be 3080 m/s and 3420 m/s for HPS films and glass substrates respectively. Finally using an approximation method we were able to deduce Young modulus (E = 51 GPa) and shear modulus (G = 22 GPa) for HPS films; these constants were also determined for glass substrates: E = 86 GPa and 35 GPa. (C) 1997 Elsevier Science S.A.