Elastic Moduli of Diarnond.--An ultrasonic technique for accurately measuring the elastic moduli of small specimens of a wide variety of materials has been developed by H. J. Mc-Skimin and W. L. Bond of Bell Telephone Laboratories. With suitable auxiliary equipment, the method can be applied to specimens under widely varying conditions of temperature and pressure.
Precise information on the elastic constants of materials is of importance in many fundamental studies of the solid state. Of particular interest is the diamond, since there are very few recorded measurements of its elastic moduli.
The ultrasonic technique developed at Bell Laboratories consists essentially of transmitting short trains of high-frequency mechanical waves into the specimen and determining their velocity of propagation. From these data and the known density of the specimen, the elastic moduli can be calculated. In the work with diamond, both longitudinal and shear waves were used, giving data for determining its three elastic moduli.
Flat and parallel surfaces were ground on opposite sides of the diamond, and its thickness measured very precisely. The specimen was then fastened to one end of a fused silica "buffer" rod by means of a thin film of viscous liquid. A suitable quartz transducer was attached to the opposite end of the buffer.