Production and characterization of hollow glass microspheres with high diffusivity for hydrogen storage

A process is developed to produce high diffusivity hollow glass microspheres (HGMs) with high concentration of silica for applications in hydrogen storage by volatilizing alkali and boron oxides in shell-forming process. We investigate the effects of the initial glass compositions of gel particles, the pressure and composition of furnace atmosphere, the temperature and length of refining zone on the diffusivity, quality and yield of the resulting HGMs. The results show that with the preferred total contents of alkali oxides and the ratios of potassium to sodium in the initial glass compositions, the ultimate concentrations of SiO₂ in the resulting HGMs can be up to 95%, with most alkali and boron oxides being volatilized in the refining process. The quality and yield of the high silica HGMs change significantly with the initial glass compositions of the gel particles. The total alkali oxide concentrations ranging from 15% to 20% in the initial glass compositions are preferred to obtain high silica HGMs with high quality and yield. The permeability coefficients of the resulting HGMs can be improved remarkably by increasing the temperature and length of the refining zone. The permeability coefficients of the high silica HGMs to hydrogen gas at ambient temperature are between 3 and 4 × 10⁻²⁰ (mol·m)/(m²·s·Pa).