1999 Volume 85 Issue 3 Pages 221-228
Concerning about the thermal radiation, either theoretically or practically, the basis is the blackbody (full-radiator). The blackbody is an ideal body, and practically, an artificial blackbody i.e. blackbody furnace is made and used. Graphite used in the existing blackbody is oxidized, exhausted, and deformed on heated in the atmosphere, and it was necessary to heat up in the controlled atmosphere like nitrogen.
In recent years, silicon carbide (SiC), silicon nitride (Si3N4), inconel, nickel, stainless steel etc. are used as blackbody materials which can be heated in the atmosphere. But a blackbody whose spectral emissivity is a little less than 1 is large in scale.
This study is carried to develop a simple and small sized blackbody which can be heated in the atmosphere and has the traceability of the thermal radiation pyrometer or can be used as the thermal radiation pyrometer traceability. The blackbody is spherical and made of SiC, and the diameter of their aperture should be more than 20 mm. Spectral emissivity of the blackbody depends on the ratio of the diameter of the sphere D to the radius of the aperture r, i.e. the aperture ratio D/r. Thus three types of blackbody whose aperture ratio D/r is 150 mm/15 mm (=10), 90 mm/ 10 mm (=9), and 60 mm/10 mm (=6), respectively, are manufactured.
Then we compare the characteristics of spectral radiation of this three types under the condition that the temperature range is 1000-1200°C and the wavelength region is 0.38-0.76 μm.