Preparation of oxynitride glasses from woody biofuel ashes

Oxynitride glasses have been prepared by melting woody biofuel ash from a power plant in south Sweden with addition of calcium metal as an extra modifier in a nitrogen atmosphere at 1350-1500 C The glasses were characterized by X-ray powder diffraction differential thermal analysis and scanning electron microscopy Cation and anion glass compositions were determined by energy dispersive X-ray analysis and combustion analysis respectively The glasses were found to be homogenous translucent gray to black and to contain up to 23 e/o of calcium and 5 e/o of nitrogen The glass formation depends on the ratio of calcium metal introduction to the ash precursors A strong exothermic reaction was observed at 650-850 C leading to the formation of amorphous and crystalline oxynitride phases that melt at high temperatures upon further heating The glass densities vary between 2 76 g/cm(3) and 292 g/cm(3) The glass transition temperature was found to vary from 670 C to 749 C and increase linearly with the nitrogen content (C) 2010 Elsevier BV All rights reserved