High-temperature measurement of ultrasonic wave velocity in refractory materials

A pulse-echo technique, based on ultrasonic long bar' mode (LBM) velocity measurements, working up to 1700 °C, is described. Magnetostrictive transducers and ultrasonic lines used in a 40-350 kHz frequency range are detailed. The conditions of choice of fundamental parameters (frequency, line geometry, sample size) are discussed in relation to the nature and the microstructure of the materials under test. This technique can be used to study the variations of elastic moduli of materials at high temperature. Examples are reported concerning a wide range of refractory materials: oxynitride glasses, fibrous ceramic-ceramic composites, refractory bricks used in the steel-making industry.