Correlation between supercooled liquid relaxation and glass Poisson's ratio.

We report on a correlation between the supercooled liquid (SL) relaxation and glass Poisson's ratio (v) by comparing the activation energy ratio (r) of the α and the slow ß relaxations and the v values for both metallic and nonmetallic glasses. Poisson's ratio v generally increases with an increase in the ratio r and this relation can be described by the empirical function v = 0.5 - A*exp(-B*r), where A and B are constants. This correlation might imply that glass plasticity is associated with the competition between the α and the slow ß relaxations in SLs. The underlying physics of this correlation lies in the heredity of the structural heterogeneity from liquid to glass. This work gives insights into both the microscopic mechanism of glass deformation through the SL dynamics and the complex structural evolution during liquid-glass transition.

Structural evolution during fragile-to-strong transition in CuZr(Al) glass-forming liquids.

In the present work, we show experimental evidence for the dynamic fragile-to-strong (F-S) transition in a series of CuZr(Al) glass-forming liquids (GFLs). A detailed analysis of the dynamics of 98 glass-forming liquids indicates that the F-S transition occurs around Tf-s ≈ 1.36 Tg. Using the hyperquenching-annealing-x-ray scattering approach, we have observed a three-stage evolution pattern of medium-range ordering (MRO) structures during the F-S transition, indicating a dramatic change of the MRO clusters around Tf-s upon cooling. The F-S transition in CuZr(Al) GFLs is attributed to the competition among the MRO clusters composed of different locally ordering configurations. A phenomenological scenario has been proposed to explain the structural evolution from the fragile to the strong phase in the CuZr(Al) GFLs.

Sub-T(g) relaxation patterns in Cu-based metallic glasses far from equilibrium.

We investigate the sub-T(g) relaxation patterns (RPs) in binary and quaternary Cu-based glass ribbons (GRs) by using the hyperquenching-sub-T(g) annealing-calorimetric approach. This study contributes to revealing the structural or dynamic evolution in liquids related to the observed three-stage sub-T(g) relaxation processes in GRs. In this work, we have achieved the following three findings. First, the abnormal three-stage relaxation behavior is not a general phenomenon for Cu-based metallic glasses and could not be simply predicted by the large difference in the enthalpy of mixing between different elements in alloys. Second, the abnormal three-stage RP is associated with the non-monotonic change of cluster size with medium range order in supercooled liquids. Third, the existence of the liquid-liquid phase transition depicted by anomalous viscosity drop during cooling in superheated liquids could be a signature of the unusual structural change causing the abnormal three-step sub-T(g) RP in the GRs. This work helps to better understand the complex structural evolution from superheated to supercooled liquids approaching T(g).

Stable superhydrophobic coating on Zr-based bulk metallic glass exhibiting excellent antibacterial property and cytocompatibility.

A central challenge in the study of clinical medicine is to reduce the infection rate of implants without affecting cell adhesion and reproduction. For the first time, we prepared a robust and stable superhydrophobic Zn/pDop/SA coating on Zr56Al16Co28 bulk metallic glass by electrodeposition that exhibits a maximum water contact angle of 158° and a sliding angle less than 1°. The growth of the coating micro-nano structure was controlled by changing the electrodeposition process parameters. The coating showed excellent antimicrobial adhesion properties in the environment to avoid bacteria adhesion and can transform from superhydrophobic to hydrophilic in body fluids to promote cell adhesion. The biodegradation of the Zn crystal structure was responsible for the hydrophobic transformation of the coating and the rough surface after biodegradation provided a point of adhesion for the cells. By designing a uniform crater structure on the substrate as an "armour" and co-depositing dopamine into the coating, the coating's wear resistance was greatly improved. The superhydrophobic coating can maintain stable superhydrophobicity in high temperature environment, air and UV irradiation. This study opens new horizons for the surface modification of bulk metallic glass and promotes its application in the medical field.

ZrO2 Superhydrophobic Coating with an Excellent Corrosion Resistance and Stable Degradation Performance on Zr-Based Bulk Metallic Glass.

Photocatalysis is an energy-saving and high-efficiency green environmental technology. Because of its wide band gap and low light utilization, few studies have been conducted on ZrO2 used as a photocatalytic material. In this paper, a corrosion-resistant superhydrophobic ZrO2 coating was prepared on the surface of Zr-based bulk metallic glass by electrochemical etching. This coating not only showed a better corrosion resistance and easier collection, but also presented a stable degradation performance when combined with H2O2; these characteristics are necessary for photocatalysts to survive under harsh environments. This study provides a new direction for designing superhydrophobic surfaces on bulk metallic glass that possess a functional performance.

A Direct Link between the Fragile-to-Strong Transition and Relaxation in Supercooled Liquids.

It is known that both the fragile-to-strong (F-S) transition and relaxation processes occur in numerous supercooled liquids upon cooling toward the glass transition temperature. The key question is whether and how these two dynamic processes are correlated. Here, we show a direct link between the two processes for both metallic glass-forming liquids (MGFLs) with different fragilities and also for nonmetallic glass-forming liquids. By comparing the F-S transition extent parameter f with the parameter r that characterizes the competition between the α and the slow ß relaxations, we have discovered a negative exponential connection between the two parameters of supercooled liquids. The finding indicates that the slow ß relaxation plays a dominant role in the F-S transition. This work provides new insight into the microscopic mechanism of the F-S transition and creates a strong basis for predicting whether and to what extent the F-S transition occurs in supercooled liquids.

Anomalous crystallization as a signature of the fragile-to-strong transition in metallic glass-forming liquids.

We study the fragile-to-strong (F-S) transition of metallic glass-forming liquids (MGFLs) by measuring the thermal response during annealing and dynamic heating of La55Al25Ni5Cu15 glass ribbons fabricated at different cooling rates. We find that the glasses fabricated in the intermediate regime of cooling rates (15-25 m/s) exhibit an anomalous crystallization behavior upon reheating as compared to the glasses formed at other cooling rates. This anomalous crystallization behavior implies the existence of a thermodynamic F-S transition, could be used as an alternative method for detecting the F-S transition in MGFLs, and sheds light on the structure origin of the F-S transition. This work also contributes to obtaining a general thermodynamic picture of the F-S transition in supercooled liquids.