High-temperature, normal spectral emittance of silicon carbide based materials

An emissometer was designed and constructed to measure the normal, spectral emittance of opaque solids over the spectral range from 1 to 8 μm for temperatures ranging from 500 to 1500°C using an integral blackbody technique. The emissometer is gas-tight so that the gas environments surrounding the sample can be controlled and emittance data can be collected as a function of exposure time to a specific environment at a particular temperature. An FT-IR spectrometer collects the blackbody and sample infrared signals, which are ratioed to calculate the material's emittance. A computer code was developed to check the validity of the assumptions associated with the measurement technique. The emittance of silicon carbide in the form of α-SiC (Hexoloy SA) and TiB₂-toughened SiC (Hexoloy ST) was collected over the spectral and temperature ranges given above. The emittance for Hexoloy SA was measured in the as-received condition and after sample exposure at 1300°C to carburizing, oxidizing, and low-pressure nitrogen environments. Emittance data for Hexoloy ST were collected for samples in the as-received condition and for samples exposed to oxidizing environments. The surface morphology and composition of the samples were characterized using SEM, EDX, and X-ray diffraction techniques.