Effect of Substrate Emissivity on the Spectral Emission of a Hot-Gas Overlayer.

摘要

Fourier transform infrared (FTIR) emission spectroscopy, recently implemented for in operando testing of solid oxide fuel cell (SOFC) anodes by Pomfret and coworkers, has become a novel means to directly measure the radiative emission of hot gases within the volume over an anode surface. Ideally, the FTIR detector will only see the infrared emission of the hot anode surface and any gases in the anode head space, though in reality broad-band, non-molecular (and frequency-dependent) emission sources (e.g., furnace walls) can contribute to the signal reaching the detector via geometric form factors. These contributions must be removed from each spectrum collected during an experiment to leave behind the difference that shows only molecular contributions. This report describes the effect of background surface emissivity on the gas emission spectrum. An analytic model, which is confirmed by numerical analysis, is developed and demonstrates that the emitted background radiation is indeed coupled to gas-phase molecular emissions in a nonlinear way and cannot be completely removed from the molecular gas spectrum by subtraction of the background spectrum.