Photo-induced hydrogen outgassing of glass

Hollow glass microspheres have long been proposed as a hydrogen storage solution. Further development has been limited as conventional heating of the microspheres fails to produce sufficient hydrogen release rates. The recent discovery of photo-enhanced diffusion achieved by exposing iron oxide doped glasses to high intensity light has suggested that the microsphere storage methodology is more viable than previously concluded.; A saturation-outgassing technique is used to study the photo-induced outgassing phenomenon. Bulk glass samples are saturated by heat treating in a hydrogen atmosphere. Saturated samples are outgassed in a high vacuum environment by exposure from a high intensity incandescent lamp or by using a furnace. The release of hydrogen is monitored via mass spectrometry. An extensive evaluation of the experimental variables affecting the photo-induced outgassing response is presented, from which an optimized experimental approach is derived for studying this unique phenomenon. A novel dilatometric method is developed to estimate the photo-induced sample temperature. The spectral energy distribution of the lamp was found to be composed primarily of near-infrared light. Increased light intensity results in an increased amount of hydrogen released from samples. The effects of host glass and dopant chemistry, in addition to the effects of using filtered light on the photo-induced hydrogen outgassing response are reported. The photo-induced outgassing response is strongly dependent on glass chemistry. Phase separated borosilicate glasses doped with Fe 3O4, CoO and NiO exhibit superior photo-induced outgassing response, due to the absorption of light from 1400 to 1600 nm, with lesser contributions from wavelengths ranging from 800 to 1150 nm, and those exceeding 1700 nm. Hydrogen reactions with transition metal oxide dopants result in improved hydrogen release. The effect of hydrogen reactions on the spectroscopic properties of selected glasses is presented and used to calculate hydrogen permeability from the tarnishing model. A glass was discovered which exhibits macroscopic magnetic properties due to metallic Ni colloids. Experimental results are compared to literature data and discussed from a mechanistic viewpoint and within the context of the hollow glass microsphere application.