Maria E. Pozo de Fernandez

Results of a hydrogen sensor based on light scattering from a porous silicon surface coated with a thin palladium film are discussed. Reflected light scattered from the rough surface of porous silicon surface with a thin palladium film is compared before and after exposure to hydrogen gas. After exposure to hydrogen gas the sensor's optical reflectance is decreased indicating the presence of hydrogen.

In this paper we excite the surface of porous silicon with incoherent, broad band white light and observe the spectrum of colors reflected from the surface. Using an atomic force microscope images from red and green porous silicon samples are collected. In this paper we relate the optical color of the surface to the size of scattering features on the textured surface. From image segmentation using the watershed transform the height distributions of the optical scattering features are determined. The heights of these surface features are then used as input variables to a computer simulation of a reflective grating. The computer predicted color is compared to the measured color. In this manner, by inspection of the reflected color from the textured porous silicon surface the physical size of the surface features can be estimated.

Injecting aqueous solutions of hydrogen peroxide (H2O2) into hot flue gases can convert nitric oxide (NO) to higher oxidation states (NO2, HNO2, and HNO3), which can then be removed in a wet scrubber. The optimum temperature for such conversion is 500°C (930°F), at which H2O2 is thermally “activated” (split into free radicals). At lower temperatures ultraviolet (UV) light can be used to activate the peroxide molecules. In this pilot plant study at Kennedy Space Center, experiments were done with none, one, or two UV lamps on, with and without SO2 present in the flue gases, at various temperatures, and with various injection rates of peroxide. Temperatures ranged from 117 to 350°C (243 to 660°F), and the molar ratios (peroxide to NOx) ranged from 0.68 to 5.02. Conversions of NO varied from below 10 to above 70%, with the highest conversions occurring with higher temperatures, higher dosages of hydrogen peroxide, and with both UV lamps turned on. Conversions of NOx (NO+NO2) varied from below 5 to above 40%....