Development of a technique to prepare porous materials from glasses

A new technique to prepare porous materials has been developed for recycling of used glasses. Porous materials were produced from used glass powders by hydrothermal reaction of glass powders with water at low temperatures followed by calcination at high temperatures for expansion. The new technique does not require additional vesicants such as calcium carbonate, silicon carbide, and organic polymers that have been used in the ordinary method. In this process, the water incorporated into the glass structure by hydrothermal treatment acts as a vesicant. When the hydrothermally treated glass was heated at high temperatures around 700 °C, water was released as vapor from the softened glass to form pores. The obtained porous materials had different pore structures that were determined by the sizes of raw glass particles. Crystallization occurred during the calcination of the hydrothermally treated glass powder.