Atomic-level structure and structure–property relationship in metallic glasses

The elastic properties, elastic models and elastic perspectives of metallic glasses

The atomic-level structure of a representative ternary Cu-Zr-Al bulk metallic glass (BMG) has been resolved. Cu- (and Al-) centered icosahedral clusters are identified as the basic local structural motifs. Compared with the Cu-Zr base binary, a small percentage of Al in the ternary BMG leads to dramatically increased population of full icosahedra and their spatial connectivity. The stabilizing effect of Al is not merely topological, but also has its origin in the electronic interactions and bond shortening.

Atomic level structure in multicomponent bulk metallic glass.

Undesired ice accumulation leads to severe economic issues and, in some cases, loss of lives. Although research on anti-icing has been carried out for decades, environmentally harmless, economical, and efficient strategies for anti-icing remain to be developed. Recent researches have provided new insights into the icing phenomenon and shed light on some promising bio-inspired anti-icing strategies. The present review critically categorizes and discusses recent developments. Effectively trapping air in surface textures of superhydrophobic surfaces weakens the interaction of the surfaces with liquid water, which enables timely removal of impacting and condensed water droplets before freezing occurs. When ice already forms, ice adhesion can be significantly reduced if liquid is trapped in surface textures as a lubricating layer. As such, ice could be shed off by an action of wind or its gravity. In addition, bio-inspired anti-icing strategies via trapping or introducing other media, such as phase change mate...

Bio-inspired strategies for anti-icing.

The atomic configuration of metallic glasses is a long-standing issue important to the understanding of their properties Nanobeam electron diffraction experiments now enable a direct determination of the local atomic order in a metallic glass The determination of the atomic configuration of metallic glasses is a long-standing problem in materials science and solid-state physics1,2 So far, only average structural information derived from diffraction and spectroscopic methods has been obtained Although various atomic models have been proposed in the past fifty years3,4,5,6,7,8, a direct observation of the local atomic structure in disordered materials has not been achieved Here we report local atomic configurations of a metallic glass investigated by nanobeam electron diffraction combined with ab initio molecular dynamics simulation Distinct diffraction patterns from individual atomic clusters and their assemblies, which have been theoretically predicted as short- and medium-range order6,7,8, can be experimentally observed This study provides compelling evidence of the local atomic order in the disordered material and has important implications in understanding the atomic mechanisms of metallic-glass formation and properties

Direct observation of local atomic order in a metallic glass

The properties of nanoconfined and interfacial water in the proximity of hydrophobic surfaces play a pivotal role in a variety of important phenomena such as protein folding. Water inside single-walled carbon nanotubes (SWNTs) can provide an ideal system for investigating such nanoconfined interfacial water on hydrophobic surfaces, provided that the nanotubes can be opened without introducing excess defects. Here, we report a hydrophobic-hydrophilic transition upon cooling from 22°C to 8°C via the observation of water adsorption isotherms in SWNTs measured by nuclear magnetic resonance. A considerable slowdown in molecular reorientation of such adsorbed water was also detected. The observed transition demonstrates that the structure of interfacial water could depend sensitively on temperature, which could lead to intriguing temperature dependences involving interfacial water on hydrophobic surfaces.

https://science.sciencemag.org/content/sci/322/5898/80.full.pdf

Temperature-induced hydrophobic-hydrophilic transition observed by water adsorption.

Out-of-plane, nanoscale periodic corrugations are observed in the dynamic fracture surface of brittle bulk metallic glasses with fracture toughness approaching that of silica glasses. A model based on the meniscus instability and plastic zone theory is used to explain such dynamic crack instability. The results indicate that the local softening mechanism in the fracture is an essential ingredient for controlling the formation of the unique corrugations, and might provide a new insight into the origin of fracture surface roughening in brittle materials.

Nanoscale periodic morphologies on the fracture surface of brittle metallic glasses

Local structures play a crucial role in glass formation and properties. In addition to topological short-range order, the geometric property of site symmetry is another important but less known characteristic of local structures. It is shown that the observed sharp increase of glass forming ability of Ce70-xAl10Cu20Cox upon Co addition is correlated with a dramatic increase of Al site symmetry, as reflected by decreasing quadrupole frequency measured by 27Al NMR. The result is consistent with the structure model of Al-centered icosahedral clusters as the predominant structural building blocks.

Correlation of Atomic Cluster Symmetry and Glass-Forming Ability of Metallic Glass

Aluminum-rich bulk metallic glasses

http://mmp.iphy.ac.cn/UpLoadFile/2010012010332773499.pdf

Xue Kui Xi

Papers

Temperature-induced hydrophobic-hydrophilic transition observed by water adsorption.

Nanoscale periodic morphologies on the fracture surface of brittle metallic glasses

Correlation of Atomic Cluster Symmetry and Glass-Forming Ability of Metallic Glass

Aluminum-rich bulk metallic glasses

Structural changes induced by microalloying in Cu46Zr47−xAl7Gdx metallic glasses