Laser ultrasonic monitoring of ceramic sintering

Abstract

Noncontacting laser-ultrasonic measurements of the sintering of ceramics in real-time are described. Lasers are used for both generation and detection of ultrasonic waves propagating through the material. A pulsed laser generates the ultrasonic wave from thermoelastic absorption at the material surface. Detection is accomplished by a confocal Fabry–Perot interferometer, which is insensitive to the speckle nature of the scattered light from the sample surface and can obtain measurements from samples with rough or diffusely reflecting surfaces. The densification of the ceramic sample is determined by changes in the bulk longitudinal wave velocity and the sample shrinkage.