Scientists Visualize Transformation of Powder Mixtures Into Molten Glass

Posted on April 16, 2012

Scientists have visualized the transformation of powder mixtures into molten glass for the first time. Glass is produced by the fusion of crystalline powder mixtures heated to high temperatures. The ingredients include quartz sand, sodium and calcium carbonates and some additional minor additives. Scientists are setting up an experiment at beamline ID15 at the European Synchrotron Radiation Facility (ESRF) in Grenoble in the above photo.

In industrial foundries, the powder mixture is heated to about 1500�C and kept at this elevated temperature for many days to eliminate bubbles and unmolten grains. This consumes a lot of energy and one of the current industrial challenges is obtaining glass of good quality at lower temperatures. A better understanding of the transformation of powder mixtures into molten glass could help reduce the costs associated with creating it.

To make visible chemical reactions between individual grains, the scientists used X-ray microtomography, a technique that enables visualizing of changes in shape and positions of all grains in a given volume in real time. These changes are probed by a fine, intense beam of X-rays sent through the sample.

Marco Di Michiel at the ESRF says, "At the ESRF, we can take a microtomography image with a spatial resolution of 1.6 micrometres every few seconds. Observing fast changes with a high spatial resolution deep inside an oven held at close to 1000�C is impossible without X-rays."

A granular packing of sand, sodium carbonate and calcium carbonate was heated at high temperatures and observed using in-situ tomography while the grains reacted together and glassy melts were produced. The movie starts by showing the different types of grains and the granular packing at room temperature. Then images at different temperatures are shown for the same vertical cut. Take a look:

The scientists were led by Emmanuelle Gouillart from the joint research unit between CNRS and Saint Gobain, a global glass manufacturer, and included scientists from the Universities of Toulouse and Grenoble, INRIA Saclay and the European Synchrotron Radiation Facility (ESRF) in Grenoble.

Emmanuelle Gouillart says, "I have been working on these processes for many years, and it was absolutely fascinating to see like in a movie what happens at the onset of the powder/glass transition."

The results are published in the Journal of the American Ceramic Society.

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