Properties of CMAS glass from desert sand

X-ray diffraction analysis of as-received desert sand from a Middle East country showed the presence of quartz (SiO2), calcite (CaCO3), gypsum (CaSO4.2H(2)O), NaAlSi3O8, Mg-2(Al3.9Si5.1O18) and Mg3Al2(SiO4)(3) phases. A batch of as-received desert sand was melted into calcium magnesium aluminosilicate (CMAS) glass at similar to 1500 degrees C. From inductively coupled plasma-atomic emission spectrometry, chemical composition of the CMAS glass was analyzed to be 27.8CaO-4MgO-5Al(2)O(3)-61.6SiO(2)-0.6Fe(2)O(3)-1K(2)O (mole %). Various physical, thermal, and mechanical properties of the glass have been evaluated. Bulk density of CMAS glass was 2.69 g/cm(3), Young's modulus 92 GPa, Shear modulus 36 GPa, Poisson's ratio 0.28, dilatometric glass transition temperature (;) 706 degrees C, softening point (T-d) 764 degrees C, Vickers microhardness 6.3 +/- 0.4 GPa, indentation fracture toughness 0.75 +/- 0.15 MPa.m(1/2), and coefficient of thermal expansion (CTE) 9.8 x 10(-6)/degrees C in the temperature range 25 to 700 degrees C. Temperature dependence of viscosity has also been estimated from various reference points of the CMAS glass using the Vogel-FulcherTamman (VFT) equation as well as from the glass composition. The glass remained amorphous after heat treating at 850 degrees C for 10 h but crystallized into CaSiO3 and Ca2Mg0.5AlSi1.5O7 phases at 900 degrees C or higher temperatures. Crystallization kinetics of the CMAS glass has also been investigated by differential thermal analysis (DTA). Published by Elsevier Ltd and Techna Group S.r.l.