Gap absorption spectrum analysis cuvette - has rhodium coating alone or on backing gold and diffusion barrier layers

摘要

For identifying specific gases or their concn. in a mixt., the gases undergo photometric adsorption measurement inside an apertured cylindrical cuvette. To improve reflectivity and increase resistance to aggressive gases, the interior face of the cuvette, pref. made of high grade steel, is coated with a dense layer (2) of bright rhodium. The layer may be applied galvanically, sputtering or plasma-enhanced chemical vapour deposition, and is 1-2 microns thick. In a variation a thinner rhodium layer (5) about 0.2 microns, is applied to an inner gold layer (4) about 5 microns thick, with these two layers sepd. by a diffusion barrier layer (3) from the main cuvette surface. ADVANTAGE - Despite rhodium being rather less reflective than gold, compensatory benefits (high chemical resistance, service life, sensitivity, etc.) make total effect beneficial.