Abstract
It is considered that the emissivity, one of thermal properties, is an important charcteristic to be measured as well as electrical and mechanical properties in exploring and developing MoSi2 as a heating element.
We measured the spectral emissivity of MoSi2 in the temperature range between 800°C and 1700°C for the wave length of 0.65μ.
The method of the measurement is as follows.
A cylinderical sample of MoSi2 is placed horizontally in a vacuum vessel and heated radially by a Mo heating element that is placed at the center of the sample.
The temperature of the sample is measured at the bottom of several pores of different depths, previously drilled on the wall of the cylindrical sample.
Since the thermal conductivity is approximately constant throughout the sample, the true temperature at the outer surface of the sample, T, can easily be obtained from measurements of Ta and Tb, the temperature at the distance γa and γb from the center of the cylinder respectively, by extrapolation.
Using the true temperature T and the apparant temperature TB, the emissivity, Eλ, can be calcurated by the equation; log Eλ=9.62×10(1/T-1/TB).
The result obtained is as follows. The emissivity is 0.83 at 800°C, takes the minimum value of 0.75 at 1150°C and increases herefrom with temperature to reach 0.87 at 1700°C.
