Nanometre pyroxenic glass-ceramics prepared by crystallization of Saudi basalt glass

Abstract Glass from the melting of basaltic rocks has many technological applications. Crystallization of basaltic glass from the northern Harrat area in the temperature range of 800–1000 °C gave augitic pyroxene as the major phase with small amounts of olivine, haematite and magnetite. Differential thermal analysis (DTA) indicated that the crystallization occurred within 810–900 °C, and partial melting occurred near 1150 °C. The microcrystalline structure shows nanospheres 10–100 nm in diameter from the augitic phase in all the crystalline samples, and the nanospheres may include small amounts of olivine, haematite and magnetite. The dilatometer showed that the glass-transition temperature is 650 °C. The coefficient of thermal expansion (CTE) of the glass-ceramic was between 70.84 and 79.91 × 10−7 °C−1. Additionally, the Vickers microhardness and density values of the basaltic glass-ceramic were within 718–800 kg/mm2 and 2.88–2.98 g/cc, respectively. Generally, the samples resistance to acidic solutions is lower than in alkaline solutions. A thin metallic film on the glass-ceramic surface was obtained after heat treatment at 1000 °C due to the oxidation of iron on the surface. However, the present basaltic glass can be used in solid oxide fuel cells (SOFCs) as a sealant between connectors and fuel cells and as coatings for some metals.