Structure of glasses and melts contains atomic channels, influencing their properties.

What is it about?

We address the longstanding problem of the structure of glasses. In contrast to crystals, glasses are materials quenched from melts that do not present an organised molecular structure but can be cast in any shape or size. In this study, we are interested in a particular type of glasses: alumino-silicates. They represent most of the industrial and geological glasses on Earth. They are mostly composed of aluminium and silicon oxides, and can further contain various elements such as Na, K, Ca or Mg, increasing their flexibility and chemical resistance. Research has shown that, in the microscopic range of a few atoms, such glasses may be quite ordered. However, further out, the structure of these glasses is considered increasingly random. What we have done is to “deconstruct” this idea, using many new experiments and computer simulation. We discovered that the structure of oxide glasses is not so mixed up after all. It is quite ordered over many nanometres distance and that it is this that makes its applications so brilliant. The picture, then, is that there is a network made up oxygen linked to silicon and aluminium atom. Interlaced through this are atoms like sodium and potassium that percolate in channels, rather like freeways through city centres. These microscopic “veins” can become exaggerated resulting in dramatic changes in the way molten glass flows, whether in an industrial furnace or in an erupting volcano.

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Why is it important?

Glasses are used to build, for instance, cellphone screens, car windshields, windows or optical fibers for fast internet communications. They further are quenched relics of hot magmas in volcanic environments. As such, glasses have a fundamental importance in our understanding of our planet and in our everyday life. This study bring new insights that will allow to fine tune the glass composition to build resistant cellphone screens or nuclear waste containers. The new knowledge further helps understanding how alumino-silicate liquids flow, and, as such, it will help our understanding of volcanic phenomena.

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