Raman, Infrared, and Chemical Characterization of Fly Ash-Generated Spherules
Abstract
The majority of studies on silicate glass spherules containing fly ash deal only with the determination of their chemical composition. Nearly 70 vol.% of fly ash is comprised of silicate glass spherules. Here, we report spectroscopic properties of silicate glass spherules using the laser micro-Raman and Fourier transform infrared techniques coupled with refractive index measurements, X-ray diffraction, and electron probe micro-analysis to better ascertain their physical and chemical properties. Glass spherules show similar refractive indices (1.499-1.510) and a bell-shaped diffraction pattern with 5-10 vol.% of crystallites observed on microscopic and submicroscopic scales. The bulk chemical composition of fly ash spherules is predominantly silica-rich (SiO2: 70.96-74.13 wt.%) with a subordinate amount of Al2O3 (0.11-0.69 wt.%), FeO(Total) + MgO (3.6-4.94 wt.%), and CaO + Na2O + K2O (20.83-22.62 wt.%). The infrared spectra suggest the presence of a dissolved -OH- bearing fluid phase in the studied fly ash spherules. The spectra also show symmetric stretching peaks of C-O-C due to the atmospheric CO2 adsorption at 2350 cm-1. The Raman spectra show broad amorphous and/or short-ordered phases.
- Publication:
-
Journal of Applied Spectroscopy
- Pub Date:
- November 2018
- DOI:
- 10.1007/s10812-018-0729-y
- Bibcode:
- 2018JApSp..85..856N
- Keywords:
-
- Raman and infrared spectroscopy;
- silicate glass spherules;
- fly ash;
- micro-chemical analysis