Production and characterization of hierarchically porous transparent glasses

Ertuş, Emre Burak
A sodium borosilicate glass (SBG) with nominal composition of 55.7SiO2-33.6B2O3-9.2Na2O-1.5Al2O3 (wt %) was produced by the conventional melt-quenching method. The as cast SBG was heat treated at various temperatures to induce phase separation. The phase separated glass was then acid (HCl) leached using three different HCl molarities to dissolve alkali-borate phase hence, to obtain a porous glass (PG). In order to control the pore structure and to find out a correlation between the pore architecture and the resulting properties, PG was subsequently alkali (NaOH) leached or heat treated at 800 °C for 1 h. The effects of the applied heat treatment temperature and acid concentration of leach solution on pore architecture were investigated. Results revealed that the heat treatment temperature influences the width of liquation channels whereas, the primary pores associated with silica precipitates were more affected by the molarity of the acid leaching solution. The total pore volume of PG increased by alkali leaching but decreased by additional heat treatment. The microhardness and tribological properties of parent SBG and PGs were evaluated. The microhardness was lower but, wear rate was higher than that of the parent SBG for all PGs. TiO2 crystals were grown within the pores of PG and the results were evaluated in terms of the appropriateness of this system for wastewater treatment. Methylene Blue (MB) degradation tests revealed that the TiO2 embedded PG (TiPG) has photocatalytic activity under UV illumination and could be utilized as a promising material in wastewater treatment.