ABSTRACT
Noncontacting, laser-based resonant ultrasound spectroscopy (RUS) was applied to characterize the microstructure of a polycrystalline sample of high purity copper. The frequencies and shapes of 40 of the first 50 resonant vibrational modes were determined. The sample's elastic constants, used for theoretical prediction, were estimated using electron backscatter diffraction data to form a polycrystalline average. The difference in mode frequency between theory and experiment averages 0.7% per mode. The close agreement demonstrates that, using standard metallurgical imaging as a guide, laser-based RUS is a promising approach to characterizing material microstructure. In addition to peak location, the Q of the resonant peaks was also examined. The average Q of the lasergenerated and laser-detected resonant ultrasound spectrum was 30% higher than a spectrum produced employing a piezoelectric transducer pair for excitation and detection.
Subject(s)
Lasers , Materials Testing/instrumentation , Refractometry/instrumentation , Spectrum Analysis/instrumentation , Ultrasonography/instrumentation , Equipment Design , Equipment Failure Analysis , Materials Testing/methods , Refractometry/methods , Sensitivity and Specificity , Spectrum Analysis/methods , Ultrasonography/methodsABSTRACT
The effect of surface acoustic waves, generated on a silver catalyst using a comb transducer, on the catalytic decomposition of ethanol is examined. The comb transducer employs purely mechanical means for surface acoustic wave (SAW) transduction. Unlike interdigital SAW transducers on piezoelectric substrates, the complicating effects of heat generation due to electromechanical coupling, high electric fields between adjacent electrodes, and acoustoelectric currents are avoided. The ethanol decomposition reactions are carried out at 473 K. The rates of acetaldehyde and ethylene production are retarded when acoustic waves are applied. The rates recover to varying degrees when acoustic excitation ceases.
