Thermal Degradation of a Black Chrome Solar Selective Absorber Coating: Short Term

摘要

Both the energy absorption properties and chemical microstructure of CHROM-ONYX were investigated using electron microscopy and X-ray diffraction techniques. Different temperatures for short annealing times were used to evaluate this coating's temperature resistance limitations along with possible degradation mechanisms for various stagnation situations. Samples were tested in both air and vacuum. As a result, each sample regardless of atmosphere was characteristically similar, with air acting to mildly accelerate optical degradation at higher temperatures. Below 300 to 400 exp 0 C black chrome exhibited a structural transformation precipitating Cr sub 2 O sub 3 . Above 500 exp 0 C this phase grew considerably, while chromium was depleted. At 600 exp 0 C and above, a new dominant phase developed corresponding to NiCr sub 2 O sub 4 , a cubic spinel. However, for all practical purposes black chrome optically degraded between 500 to 600 exp 0 C during short exposure times. (ERA citation 04:046225)