Structural, Electronic, and Dynamic Properties of Metallic Supercooled Liquid and Glasses Studied by NMR
Final rept. 1 Aug 1999-31 Jan 2003
NORTH CAROLINA UNIV AT CHAPEL HILL
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Metallic glasses possess unique mechanical and magnetic properties such as extremely high hardness and have novel applications in many areas including national defense. What prevents the widespread use of metallic glasses is the difficulty in achieving the glassy form due to the low glass forming ability GFA of most metallic alloys. The search of new BMCs requires an understanding of GFA on the atomic level and over a wide range of timescales. In this study we used nuclear magnetic resonance NMR, along with other techniques, to study both structures and atomic motions in Zr-based and Pd-based BMO systems over the entire temperature range from the liquid state down to the glassy state. We observed a clear evidence of a dynamic crossover at temperature Tc above the glass transition temperature Tg. This observation shows that below Tc atomic raffling within cages formed by neighboring atoms freezes rapidly. It demonstrates that such dynamic crossover plays a crucial role in glass transition. Comprehensive studies using NMR, x-ray diffraction, and differential scanning calorimetry revealed the details of nucleation and growth processes in such BMGs and 14.
- Ceramics, Refractories and Glass
- Properties of Metals and Alloys