The adiabatic elastic constants c44, ½(c11−c12), and ½(c11+c12+2c44) have been measured for copper, silver, and gold over the temperature range from 300° to about 800°K using the conventional ultrasonic pulse-echo technique. The room-temperature values of the stiffness coefficients are shown to be in acceptable agreement with previously published data for the noble metals. Over the entire range from 300° to 800°K, it is found that, to a remarkably good approximation, the elastic constants for all three metals decrease linearly with temperature. Additional evidence is presented to show that the linear temperature dependence of the elastic constants for silver extends to at least 1000°K, i.e., to within 80% of the absolute melting temperature. The isothermal compressibilities calculated from the elastic constant data are used to evaluate the dilational term in the specific heat, Cdil=Cp−Cv, and it is established that the approximate Nernst-Lindemann relation for estimating Cdil is valid for Cu, Ag, and Au at least up to 800°K.

No abstract

Using Channeltron-type detectors and magnetic discrimination techniques, it has been shown that electrons, positive and negative ions, and photons are all emitted spontaneously while oxide-covered metals such as AI and Ni are being deformed in a tensile mode in a vacuum of approximately 10-10 Torr in total darkness. For dense anodically grown Al z 0 3 films of a given thickness on high-purity AI substrates, the emission yields of all charged particles and photons are found to exhibit identically the same strain dependence. The same applies to compact thermally grown NiO films on Ni. It is concluded from these and other observations that the entire emission spectrum is generated simultaneously as a result of the formation and propagation of cracks in the oxide film during the deformation process. The shortcomings of previously proposed models for this type of triboinduced emission are pointed out, and some alternative suggestions regarding the emission mechanism are offered.

No abstract