Ultrasonic diffraction grating spectroscopy and characterization of fluids and slurries

Abstract

The ultrasonic diffraction grating is formed by machining triangular grooves, 300 microns apart, on a stainless steel surface. The grating surface is in contact with the liquid or slurry. The ultrasonic beam, traveling in the solid, strikes the back of the grating and produces a transmitted m = 1 beam in the liquid. The angle of this beam in the liquid increases with decreasing frequency and the critical frequency FCR occurs when the angle is 90°. At frequencies below FCR, this m = 1 wave does not exist and its energy is shared with other types of waves. The signal of the reflected m = 0 wave is observed and an increase is observed at FCR. This information yields the velocity of sound in the liquid and particle size. © 2004 Elsevier B.V. All rights reserved.