Molecular structure of amorphous slags: An experimental and numerical approach

This study presents a description of the structure of amorphous slags, with particular attention to the Ca local environment and the medium range arrangement of Ca-sites. Using Ca K-edge X -ray absorption spectroscopy (XANES and EXAFS) and pair distribution function (PDF) as well as numerical modeling combining Molecular Dynamics and Reverse Monte-Carlo, we demonstrate that Ca occurs in a complex environment with a distribution between 6- and 7-coordinated sites. Ca atoms are not distributed randomly within the glass structure: the Ca sites are linked by edges and form a complex percolating sub-network of network-modifying cations. The aluminosilicate network in slags is highly depolymerized with, on average, Q2.06 arrangements for Si, indicating the predominance of chain-like structural units and Q2.67 arrangements for Al in more polymerized units cross-linking the Ca-domains. The Ca percolating sub-network forms clusters that may enhance the early dissolution rate of slags in water.