Influence of temperature on ultrasound absorption in waveguides made out of refractory materials.

We studied the influence of temperature increase to 1500 °C on ultrasound absorption at frequencies from 0.1 to 1.0 MHz in tungsten, molybdenum, vanadium, graphite, and fused silica. The ultrasound absorption coefficient in these materials was calculated. It was shown that the fused silica has the smallest ultrasound absorption coefficient for temperatures up to 1000 °C. Vanadium and graphite also have small values of this coefficient for the considered temperature. The ultrasound absorption was investigated experimentally in graphite and fused silica waveguides. We demonstrated that the ultrasound absorption did not change in graphite with the temperature increase, but it increased in fused silica by a factor 2 for the temperature above 1000 °C. We show that different acoustical and mechanical properties of vanadium, graphite, and fused silica allow using them for waveguide applications and buffer rods in crystal growth at temperatures below 1500 °C and ultrasound frequency below 1.0 MHz. [ABSTRACT FROM AUTHOR]