Abstract
In this study, the effects of calcination on the structural properties and surface morphology of black volcanic ash were investigated. The chemical composition, texture properties, and thermal behavior of raw black volcanic ash were studied using x-ray fluorescence spectrometry, micromeritics surface area, porosity analyzer, and thermogravimetric and differential scanning calorimetry analysis, respectively. According to the thermogravimetric results, the powder of raw volcanic ash was calcined at 800, 1000, and 1100 °C. X-ray diffraction (XRD), Raman spectroscopy, and electron microscopy were employed to study the crystalline phase, mineralogical composition, and morphology of the calcinated volcanic ash. Based on the characterization of the XRD and Raman spectra, we observed that phase transformation started at 800 °C along with a change in color of volcanic ash from black to poor red. Moreover, the degree of crystallinity and peak intensity increased as the calcination temperature increased, without a significant change in the surface morphology. These findings can help in understanding the surface and bulk characteristics of black volcanic ash at high temperatures and serve to enhance their technological and economical applications.