Percolation channels: a universal idea to describe the atomic structure and dynamics of glasses and melts

Charles Le Losq,Charles Le Losq,Charles Le Losq,Dominique Massiot,Dominique Massiot,Dominique Massiot,Daniel R Neuville,Daniel R Neuville,Wenlin Chen,Pierre Florian,Pierre Florian,Pierre Florian,George N Greaves,George N Greaves,George N Greaves,Zhongfu Zhou

doi:10.1038/s41598-017-16741-3

Abstract

Understanding the links between chemical composition, nano-structure and the dynamic properties of silicate melts and glasses is fundamental to both Earth and Materials Sciences. Central to this is whether the distribution of mobile metallic ions is random or not. In silicate systems, such as window glass, it is well-established that the short-range structure is not random but metal ions cluster, forming percolation channels through a partly broken network of corner-sharing SiO4 tetrahedra. In alumino-silicate glasses and melts, extensively used in industry and representing most of the Earth magmas, metal ions compensate the electrical charge deficit of AlO4− tetrahedra, but until now clustering has not been confirmed. Here we report how major changes in melt viscosity, together with glass Raman and Nuclear Magnetic Resonance measurements and Molecular Dynamics simulations, demonstrate that metal ions nano-segregate into percolation channels, making this a universal phenomenon of oxide glasses and melts. Furthermore, we can explain how, in both single and mixed alkali compositions, metal ion clustering and percolation radically affect melt mobility, central to understanding industrial and geological processes.

Highlights

Alumino-silicate melts represent the majority of the Earth’s molten rocks, and are fundamental starting materials from which technical glasses are manufactured in industry
Part of the metal cations that are present in the melt compensate this electrical charge deficit as they do in the crystalline state
The Compensated Continuous Random Network (CCRN) model[11] accounts for these effects in the glassy state by locating compensating metallic ions in the vicinity of AlO4−. Both the Modified Random Network (MRN) and CCRN models are based on the fact that metal cations occupy well-defined sites, similar to those in crystalline structures, as observed from neutron scattering and X-ray spectroscopy for example

Summary

Introduction

Alumino-silicate melts represent the majority of the Earth’s molten rocks, and are fundamental starting materials from which technical glasses are manufactured in industry. Melt and glass properties are determined by how their chemical composition controls their molecular structure Such interplay and its importance in defining key geoscience and industrial properties explains why the first model of glass structure, the Continuous Random Network (CRN) model, dates back from 19321. The Compensated Continuous Random Network (CCRN) model[11] accounts for these effects in the glassy state by locating compensating metallic ions in the vicinity of AlO4− Both the MRN and CCRN models are based on the fact that metal cations occupy well-defined sites, similar to those in crystalline structures, as observed from neutron scattering and X-ray spectroscopy for example. Rich in metallic ions, would influence ionic diffusion pathways and molecular configurations, and their presence may have important consequences for the thermo-physical properties of alumino-silicate glasses and their corresponding melts

Methods

Results

Conclusion