Synthesis and Characterization of Porous Silica Structures based on Phase Separation of Borosilicate Glasses Containing ZrO2, TiO2, MoO3

In this study, researchers prepared porous glasses through the phase separation of a borosilicate-based glass composition. Subsequently, the team employed a conventional melting method to synthesize the glasses. Heat treatment of alkali borosilicate glass samples caused phase separation, resulting in two distinct phases: a silicon-rich phase and a boron-rich phase. This study examined phase-separated glassy samples under leaching conditions. In the subsequent stage of the study, the team investigated and compared the phase separation process, as well as the size and morphology of the resulting pores, in the presence of TiO₂, ZrO₂, and MoO₃ additives. The analysis of the glass samples utilized X-ray diffractometry (XRD), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), and Brunauer-Emmett-Teller (BET) techniques. The results indicated that the highest porosity occurred in the samples containing 1.5% mol of ZrO₂ and 2.5% mol of MoO₃, with three and two acid-leaching steps, respectively. The highest and lowest specific surface areas were related to 1.5%mol ZrO₂ (three and two steps acid-leached). This low specific surface is attributed to the deposition of colloidal particles within the structure and the formation of cracks during the acid-leaching process. The porous glass containing ZrO₂ with an average pore diameter in the range of 4 nm, acid-leached in three controlled steps with the highest specific surface area reported among the rest of the samples, was considered sufficiently high and practical.