Accession Number : AD0707786

Title :   DAMPING OF DISLOCATIONS IN NIOBIUM BY PHONON VISCOSITY.

Descriptive Note : Technical rept.,

Corporate Author : GEORGE WASHINGTON UNIV WASHINGTON D C INST FOR THE STUDY OF FATIGUE FRACTURE AND STRUCTURAL RELIABILITY

Personal Author(s) : Mason,Warren P. ; MacDonald,Douglas E.

Report Date : JUN 1970

Pagination or Media Count : 30

Abstract : Attenuation measurements have been made of the body centered crystal niobium for three waves along the <110> direction. The room temperature measurements are consistent with dislocations lying in the (110) planes with glide directions along the <100> axes. The fast shear has the largest attenuation and it has been measured over a temperature range from 30K to 300K with frequencies from 10 MHz to 150 MHz. The attenuation can be divided into a square-law attenuation and a dislocation component. The dislocation component can be used to evaluate a drag coefficient which is nearly constant down to 78K. It rises at low temperatures indicating an electron drag effect. The constant region is consistent with a phonon viscosity damping with a crystal having a peak in the thermal conductivity. The electron drag confirms a theoretical calculation giving a drag inversely proportional to the electrical resistivity. (Author)

Descriptors :   (*NIOBIUM, FRACTURE(MECHANICS)), (*DISLOCATIONS, MOTION), FATIGUE(MECHANICS), PHONONS, DAMPING, CRYOGENICS

Subject Categories : Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE