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Shear bands generally initiate strain softening and result in low ductility of metallic glasses. In this Letter, we report high-resolution electron microscope observations of shear bands in a ductile metallic glass. Strain softening caused by localized shearing was found to be effectively prevented by nanocrystallization that is in situ produced by plastic flow within the shear bands, leading to large plasticity and strain hardening. These atomic-scale observations not only well explain the extraordinary plasticity that was recently observed in some bulk metallic glasses, but also reveal a novel deformation mechanism that can effectively improve the ductility of monolithic metallic glasses.

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Water oxidation is significant in both natural and artificial photosynthesis. In nature, water oxidation occurs at the oxygen-evolving center of photosystem II, and leads to the generation of oxygen, protons, and electrons. The last two are used for fixation of carbon dioxide to give carbohydrates. In artificial processes, the coupling of water oxidation to evolve O2 and water reduction to evolve H2 is known as water splitting, which is an attractive method for solar energy conversion and storage. Because water oxidation is a thermodynamically uphill reaction and is kinetically slow, this reaction causes a bottleneck in large-scale water splitting. As a consequence, the development of new and efficient water oxidation catalysts (WOCs) has attracted extensive attention. Recent efforts have identified a variety of mononuclear earth-abundant transition-metal complexes as active and stable molecular WOCs. This review article summarizes recent progress in research on mononuclear catalysts that are based on first-row transition-metal elements, namely manganese, iron, cobalt, nickel, and copper. Particular attention is paid to catalytic mechanisms and the key O−O bond formation steps. This information is critical for designing new catalysts that are highly efficient and stable.

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This article introduces the uses of transparent synthetic soil for geotechnical problems using optical system, including transparent materials, sample preparation, geotechnical properties, experimental methods, and applications in physical modeling. Four typical kinds of transparent synthetic soil are shown and compared. For amorphous silica powder, normally the consolidated amorphous silica has a higher normalized strength but a lower modulus than the natural clays. For amorphous silica gels, the stressstrain behaviors are consistent with the typical stress-strain behaviors of sand for both dense and loose conditions. For fused silica, it has a higher shearing strength and higher modulus than the natural sand does; the deviatoric stress increases with the confining pressure, but the stress-strain curves of fused silica and the natural sand are particularly similar. For glass sand, with increasing of the relative density, the strainstress relationship varies from strain hardening to stress softening, while its failure form is essentially the same as that of standard sand. According to the geotechnical properties of four typical materials of transparent synthetic soil grain, they are used to simulate different conditions and analyze practical engineering problems in different physical model tests. The process included the generation of a speckle pattern created by the interaction of laser light with transparent particles. Using digital image processing technology, speckle patterns can be obtained and used to calculate the displacement field. By utilizing this optical system, transparent synthetic soil can be used to nonintrusively investigate internal soil deformation, flow problems, and ground movement in physical model tests. Finally, both the advantages and disadvantages of the transparent soil experimental technique are analyzed.