Using piezoelectric film and ultrasound resonance to measure the elastic moduli of spherical ceramic particles

Abstract

The search for alternate sources of energy has prompted interest in small ceramic beads, called “proppants,” which were developed as a means of “propping” open cracks during the hydraulic fracturing of bedrock in the vicinity of oil wells; recently, they have been considered as possible thermal transfer media for use in solar receivers [J. R. Hellmann et al., “Evaluation of Spherical Ceramic Particles for Solar Thermal Transfer Media,” SAND86-0981, Sandia National Laboratories, January 1987]. To monitor the effects of repeated thermal stresses on the proppants, one would like to have a reliable measure of their elastic constants; however, their spherical shape and small size (≃ 500 μm) make conventional techniques, such as pulse-echo, inapplicable. Using a special piezoelectric film transducer and a small-sample resonance technique [J. D. Maynard, J. Acoust. Soc. Am. Suppl. 1 85, S20 (1989)], the authors have been able to determine the elastic constants and their variation as a function of heat treatment. [Work supported by the Office of Naval Research and NSF Grant DMR 9000549.]