Glass-Transition-Like Behavior of Grain Boundaries in Nanocrystalline Gold

Abstract

Characteristic property changes were observed for high density and high purity nanocrystalline (n-) Au prepared by the gas deposition method. The increase in internal friction with a modulus defect started at 180 K and became steep above 200 K. An increase in endothermic heat ow began at 170 K. The electrical resistivity showed a deviation from a linear increase with the temperature at 130 K. All the characteristic changes were reproduced by the repetition of the thermal cycle below 300 K, but the amounts diminished after the grain growth. These characteristic temperature changes indicate a glass-transition-like behavior of the grain boundaries in n-Au.

Low-Temperature Anelastic Property of Nanocrystalline Ag Fabricated by Gas Deposition Method

“…Since the nanoparticles are directly deposited on the substrate by He gas jet-flow in the gas deposition method, n-metals with non-equilibrium grain boundaries can be prepared like the severe plastic deformation methods 19,20 . Recently, we reported characteristic low temperature properties of n-Au prepared by the gas deposition method 21 . From the thermal analysis of n-Au, an endothermic tendency above 150 K was observed for the repetition of the cool-down and warm-up below 350 K. The deviation to slightly lower values from the linear increase with temperature was also observed for the resistivity of n-Au above ~150 K. As well as the rapid increase in the internal friction, these observations suggested that the reversible state change in the grain boundaries is thermally induced at 150~200 K. These behaviors at low temperatures indicate that a glass-transition-like change of the grain boundaries in n-Au is thermally activated above 150 K and characteristic for the non-equilibrium grain boundaries.…”

Inhibition of Electropulsing Nanocrystallization in Amorphous ZrCu under Helium Atmosphere

“…The enhancement in plastic deformation by applying high power current (electromagnetic pulsing deformation) is attracting more attention as a powerful technique for hard and brittle metallic materials. 3437) The glass transition-like behavior of the grain boundaries was suggested from the experimental 38) and simulation 39,40) studies on nanocrystalline metals. The results of this study also contribute to further enhancement of these electromagnetic pulsing deformation techniques for amorphous alloys and provide a deep insight into the characteristics of the grain boundaries in nanocrystalline metals.…”