Influence of titanium doping on the shell-forming process and geometrical properties of hollow glass microspheres

• Titanium doped hollow glass microspheres are potential hydrogen and deuterium-tritium containers.
• A mathematical model is constructed to quantify the shell-forming process.
• The multiple-step decomposition mode and loss of acetate ions reduce the blowing efficiencies of gels.
• The wall thickness and aspect ratio of spheres could be controlled by changing the types and contents of blowing agent.

As hydrogen storage containers, titanium-doped hollow glass microspheres (HGMs) have been fabricated using the dried-gel method. A mathematical model was constructed to quantify the shell-forming process and make predictions on the wall thickness and aspect ratio of HGMs. Geometrical parameters of the HGMs were measured. The results showed that titanium doping would significantly change the compositions of gel precursor and glass melt. The multiple-step decomposition mode and loss of blowing agent in gels with more than 6.5 mol% titania reduced the blowing efficiency, thus producing greater wall thickness and smaller aspect ratio of HGMs. The measured aspect ratio decreased with increasing gel particle size, which was contrary to the predicted result. This was attributed to the poor blowing ability of large gel particles due to the limited residual time in the furnace. Moreover, the surface tension and viscosity of the glass melt were changed by titanium doping as well, which resulted in inadequate refining for heavily doped glass and consequently reduced the sphericity and surface finish of HGMs.