NONDESTRUCTIVE ACOUSTIC MICROCHARACTERISATION OF HETEROPOLYSILOXANE THIN-FILMS

Heteroplysiloxanes (HPS) thin films, recognised as a new class of mate rials that can be used as very versatile coating systems, are nondestr uctively characterised by means of a scanning acoustic microscope. The acoustic material signatures were first measured, from which the char acteristic surface velocities were determined. The influence of film t hicknesses as well as operating frequencies on such velocities are rep orted. The results are then compared with theoretical velocity dispers ion curves, giving good agreements. Rayleigh velocities were found to be 3080 m/s and 3420 m/s for HPS films and glass substrates respective ly. Finally using an approximation method we were able to deduce Young modulus (E = 51 GPa) and shear modulus (G = 22 GPa) for HPS films; th ese constants were also determined for glass substrates: E = 86 GPa an d 35 GPa. (C) 1997 Elsevier Science S.A.