Accession Number : AD0248935

Title :   INTERNAL FRICTION IN ALUMINUM OXIDE SINGLE CRYSTALS

Corporate Author : UTAH UNIV SALT LAKE CITY INST FOR THE STUDY OF RATE PROCESSES

Personal Author(s) : HUBER, R.J. ; BAKER, G.S. ; GIBBS, P.

Report Date : 01 NOV 1960

Pagination or Media Count : 1

Abstract : INTERNAL FRICTION MEASUREMENTS WERE MADE ON Al2O3 single crystals in longitudinal oscillation at a frequency of 50 kc and at strain amplitudes up to 10 to the -5th power, by the composite oscillator technique as a function of temperature between 25 and 1850 degrees C, and as a function of plastic deformation of the samples. Dislocation densities (over) range from about 5 x 10 to the 6th power dislocations sq cm. in the undeformed crystals to near 5 x 10 to the 7th power dislocations sq cm. in the heavily deformed samples. Undeformed crystals showed no observable change in internal friction below 1800 degrees C. Samples deformed near 1300 C showed a thermally activated change in internal friction which was observable above a background logarithmic decrement of 4 x 10 to the -5th power at temperatures greater than 1450 C. The logarithmic decrement at the maximum temperature of 1850 was 4 x 10 the -3rd power. Activation energies ranged between 80 and 140 kilocalories/mole. A few minutes exposure of these samples to temperatures above 1900 C resulted in a decrease of a factor of 5 in the internal friction vs. temperature curve. Crystals deformed in tension in an oxygen-natural gas flame near 1900 C showed a similar form, but smaller increase in internal friction than the samples deformed at the lower temperature. No amplitude dependence was observed at strains of 10 to the -5th power or less. (Author)

Descriptors :   *CORUNDUM, *INTERNAL FRICTION, *SAPPHIRE, *SINGLE CRYSTALS, ALUMINUM COMPOUNDS, CRYSTAL STRUCTURE, DEFORMATION, MEASUREMENT, OXIDES.

Distribution Statement : APPROVED FOR PUBLIC RELEASE