We have investigated the crystallization kinetics of Cu 50 Zr 50 metallic glass thin films using nanocalorimetry. The crystallization process is growth-controlled during heating and nucleation-controlled during cooling, resulting in different critical heating and cooling rates to suppress crystallization. Measurements over a wide range of scanning rates (13 K/s to 24,000 K/s) reveal that crystallization does not follow Arrhenius kinetics upon heating. Instead, the behavior on heating is well described by a fragilitybased model of growth-controlled kinetics that takes into account breakdown of the Stokes-Einstein relationship. Upon cooling, the quench rate required to suppress crystallization of the melt is much higher than for bulk samples. This reduced asymmetry in critical heating and cooling rates compared to bulk materials suggests that crystallization of the thin-film metallic glass is controlled by heterogeneous nucleation.

Nanostructured transition metal oxides have been investigated extensively for supercapacitor electrodes due to their high theoretical specific capacitance, low-cost, environment benignity and abundance.However, pristine transition metal oxides suffer from difficulty of synthesis, poor electronic conductivity and mechanical flexibility. In this work, we report a facile, low-cost and high-throughput synthesis of hierarchical structure which consists of cuprous oxide (Cu 2 O) microsphere-nanosheets on the surface of flexible Cu foil (namely Cu 2 O@Cu) via a two-step electrochemical method (anodization and electrooxidation). The influence of the anodization parameters on surface roughness of Cu foil has been investigated, and the optimum anodization procedure was determined to be 50 V for 4 cycles. This Cu 2 O@Cu electrode exhibits excellent capacitance properties, such as up to 390.9 mF cm À2 at 2 mA cm À2 in areal capacitance, and high flexibility, as observed by cyclic voltammetry measurement under various deformation (bending and folding) situations. Furthermore, the Cu 2 O@Cu electrode presents superior long-term cycling stability over 100 000 cycles, with the capacitance retention of over 80%.The present binder-free Cu 2 O@Cu microsphere-nanosheets electrode is highly promising for future applications in flexible supercapacitors.

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In this paper, the amorphous CeAlCuCo (atom %) alloy was in situ prepared by nanocalorimetry. The high cooling and heating rates accessible with this technique facilitate the suppression of crystallization on cooling and the identification of homogeneous nucleation. Different from the generally accepted notion that metallic glasses form just by avoiding crystallization, the role of nucleation and growth in the crystallization behavior of amorphous alloys is specified, allowing an access to the ideal metallic glass free of nuclei. Local atomic configurations are fundamentally significant to unravel the glass forming ability (GFA) and phase transitions in metallic glasses. For this reason, isothermal annealing near T from 0.001 s to 25,000 s following quenching becomes the strategy to tune local atomic configurations and facilitate an amorphous alloy, a mixed glassy-nanocrystalline state, and a crystalline sample successively. On the basis of the evolution of crystallization enthalpy and overall latent heat on reheating, we quantify the underlying mechanism for the isothermal nucleation and crystallization of amorphous alloys. With Johnson-Mehl-Avrami method, it is demonstrated that the coexistence of homogeneous and heterogeneous nucleation contributes to the isothermal crystallization of glass. Heterogeneous rather than homogeneous nucleation dominates the isothermal crystallization of the undercooled liquid. For the mixed glassy-nanocrystalline structure, an extraordinary kinetic stability of the residual glass is validated, which is ascribed to the denser packed interface between amorphous phase and ordered nanocrystals. Tailoring the amorphous structure by nanocalorimetry permits new insights into unraveling GFA and the mechanism that correlates local atomic configurations and phase transitions in metallic glasses.