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Disordered systems

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Diagram of lab results

Glasses are thermodynamically metastable and thus prefer to devitrify when provided with enough energy to overcome the kinetic barrier to crystallization. In addition to stability concerns for material applications, research on devitrification can elucidate underlying correlations between disordered glasses and ordered crystals. Due to the absence of the well-defined dislocation defects in crystalline alloys, metallic glasses exhibit very high compressive strength, good corrosion resistance, and large elasticity. With a close-packed Bernal structure, they also represent a model system for understanding structure-property relationships in glasses. For example high pressure X-ray measurements have proven critical in demonstrating that metallic glasses display fractal packing relationship where the nearest neighbor distance (measured by XRD) scales with volume (measured by nanoTXM) via power law of 2.5 (Zeng et al., 2014, Zeng et al., 2016). Probing different regions in momentum space may lead to changes in the power law exponent, resulting in a crossover in the power law exponent from fractal values to homogeneous values past the correlation length. Coupling high pressure nanoTXM with other X-ray techniques could also shed light onto the structure of other glass systems which would provide key information for understanding the nature of glasses and the glass transition.