Résumé
Clay membranes containing various percentages of coal before sintering have been manufactured in order to obtain various volume fractions of porosity. Using echographic techniques, the longitudinal ultrasonic velocity and damping have been measured between 0 and 20% of coal. These results, compared to porosity measurements show that there is a simple linkage between porosity and ultrasonic parameters. Furthermore, the anomalous behaviour of one batch of membranes has been detected with ultrasonic waves and confirmed using classical porosity measurements (triple weight method). A linear behaviour of the ultrasonic velocity versus porosity has been obtained from 38 to 60% of porosity