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The structure analysis of amorphous materials still leaves much room for improvement. Owing to the lack of translational or rotational symmetry of amorphous materials, it is important to develop a different approach from that used for crystals for the structure analysis of amorphous materials. Here, the angstrom-beam electron diffraction method was used to obtain the local structure information of amorphous materials at a sub-nanometre scale. In addition, we discussed the relationship between the global and local diffraction intensities of amorphous structures, and verified the effectiveness of the proposed method through basic diffraction simulations. Finally, some applications of the proposed method to structural and functional amorphous materials are summarized.

A crystallographically heterogeneous interface was fabricated by growing hexagonal graphene (Gr) using chemical vapor deposition (CVD) on a tetragonal FePd epitaxial film grown by magnetron sputtering. FePd was alternately arranged with Fe and Pd in the vertical direction, and the outermost surface atom was identified primarily as Fe rather than Pd. This means that FePd has a high degree of

Glass forming ability (GFA) is critically important for large-scale applications of bulk metallic glasses with maximized functionalities at low costs in materials and processing. Traditionally, excellent glass formers usually have compositions in eutectic regions where liquid phases have high stability and low liquid temperatures while GFA of off-eutectic alloys is largely limited by primary crystallization. In this study we reported that the GFA of Ni-based off-eutectic alloys can be dramatically improved by manipulating the primary crystallization reaction through minor alloying. As a result, a novel Ni60Pd20P14Si2B4 metallic glass with excellent GFA is developed by substituting P in Ni60Pd20P20 using 2 at.% Si and 4 at.% B. The minor alloying leads to the transition of the primary crystallization from a tetragonal (Ni, Pd)3P phase to a chemically modulated complex monoclinic phase. The enhanced GFA results in the largest achievable processing diameter (25 mm) of Ni-based bulk metallic glasses, which is more than four times larger than that of Ni60Pd20P20. The complex crystal structure of the primary crystalline phase with chemical modulation and a large unit cell leads to slow crystal growth, and hence the improved stability of supercooled liquid for better GFA.

Understanding the formation and evolution of bicontinuous nanoporous structure during dealloying has been one of the most challenging subjects of dealloying research. However, previous in situ investigations either suffer from insufficient spatial resolution (e.g., X-ray tomography) or lack morphology visualization and mass information (e.g., scanning tunneling microscopy). In this work, we report the kinetics of the whole course of dealloying by utilizing liquid-cell aberration-corrected scanning transmission electron microscopy. With Z-contrast imaging analysis, the in situ sub-nanoscale characterization reveals two new phenomena, an initial period of dealloying indicative of an initial length scale for bulk dealloying and a large volume shrinkage in a nanoscale alloy precursor. We explain the particle-size-dependent volume shrinkage with the formation of a dense shell and quantify the dependence with a simple geometric model. These insights into the mechanisms of dealloying will enable deliberate designs of nanoporous structures.

All-solid-state batteries using sodium are promising candidates for next-generation rechargeable batteries due to the limited lithium resources. A practical sodium battery requires an electrolyte with high conductivity. Cubic Na$_3$PS$_4$ exhibiting high conductivity of over 10$^{-4}$ S cm$^{-1}$ is obtained by crystallizing amorphous Na$_3$PS$_4$ synthesized by ball milling. Amorphous Na$_3$PS$_4$ crystallizes in a cubic structure and then is transformed into a tetragonal phase upon heating. In this study, in situ observation by transmission electron microscopy demonstrates that the crystallite size drastically increases during the transition from the cubic phase to the tetragonal phase. Moreover, an electron diffraction analysis reveals that amorphous domains and nano-sized crystallites coexist in the cubic Na$_3$PS$_4$ specimen, while the tetragonal phase contains micro-sized crystallites. The nano-sized crystallites and the composite formed by crystallites and amorphous domains are most likely responsible for the increase in conductivity in the cubic Na$_3$PS$_4$ specimens.

Developing highly active electrocatalysts with low costs and long durability for oxygen evolution reactions (OERs) is crucial towards the practical implementations of electrocatalytic water-splitting and rechargeable metal–air batteries. Anodized nanostructured 3d transition metals and alloys with the formation of OER-active oxides/hydroxides are known to have high catalytic activity towards OERs but suffer from poor electrical conductivity and electrochemical stability in harsh oxidation environments. Here we report that high OER activity can be achieved from the metallic state of Ni which is passivated by atomically thick graphene in a three-dimensional nanoporous architecture. As a free-standing catalytic anode, the non-oxide transition metal catalyst shows a low OER overpotential, high OER current density and long cycling lifetime in alkaline solutions, benefiting from the high electrical conductivity and low impedance resistance for charge transfer and transport. This study may pave a new way to develop high efficiency transition metal OER catalysts for a wide range of applications in renewable energy.

The coarsening of crystalline nanoparticles, driven by reduction of surface energy, is the main factor behind the degeneration of their physical and chemical properties. The kinetic phenomenon has been well described by various models, such as Ostwald ripening and coalescence. However, the coarsening mechanisms of metallic glass nanoparticles (MGNs) remains largely unknown. Here we report atomic-scale observations on the coarsening kinetics of MGNs at high temperatures by in situ heating high-resolution transmission electron microscopy. The coarsening of the amorphous nanoparticles takes place by fast coalescence which is dominated by facet-free surface diffusion at a lower onset temperature. Atomic-scale observations and kinetic Monte Carlo simulations suggest that the high surface mobility and the structural isotropy of MGNs, originating from the disordered structure and unique supercooled liquid state, promote the fast coalescence of the amorphous nanoparticles at relatively lower temperatures., The coarsening of amorphous metallic nanoparticles remains poorly understood. Here, the authors combine high resolution microscopy and atomistic simulations to show the disordered structure of amorphous nanoparticles makes them coarsen faster than crystalline ones.

Since their discovery in 19601, metallic glasses based on a wide range of elements have been developed2. However, the theoretical prediction of glass-forming compositions is challenging and the discovery of alloys with specific properties has so far largely been the result of trial and error3–8. Bulk metallic glasses can exhibit strength and elasticity surpassing those of conventional structural alloys9–11, but the mechanical properties of these glasses are critically dependent on the glass transition temperature. At temperatures approaching the glass transition, bulk metallic glasses undergo plastic flow, resulting in a substantial decrease in quasi-static strength. Bulk metallic glasses with glass transition temperatures greater than 1,000 kelvin have been developed, but the supercooled liquid region (between the glass transition and the crystallization temperature) is narrow, resulting in very little thermoplastic formability, which limits their practical applicability. Here we report the design of iridium/nickel/tantalum metallic glasses (and others also containing boron) with a glass transition temperature of up to 1,162 kelvin and a supercooled liquid region of 136 kelvin that is wider than that of most existing metallic glasses12. Our Ir–Ni–Ta–(B) glasses exhibit high strength at high temperatures compared to existing alloys: 3.7 gigapascals at 1,000 kelvin9,13. Their glass-forming ability is characterized by a critical casting thickness of three millimetres, suggesting that small-scale components for applications at high temperatures or in harsh environments can readily be obtained by thermoplastic forming14. To identify alloys of interest, we used a simplified combinatorial approach6–8 harnessing a previously reported correlation between glass-forming ability and electrical resistivity15–17. This method is non-destructive, allowing subsequent testing of a range of physical properties on the same library of samples. The practicality of our design and discovery approach, exemplified by the identification of high-strength, high-temperature bulk metallic glasses, bodes well for enabling the discovery of other glassy alloys with exciting properties. Bulk metallic glasses made from alloys of iridium, nickel, tantalum and boron are developed by combinatorial methods, with higher strength at high temperature than those previously produced.

It has been known for decades that nanopores produced by selective leaching during galvanic corrosion can lead to dramatic loss of materials ductility and strength under tension. However, the underlying atomic mechanisms of the nanopore induced embrittlement remain to be poorly known. Here we report in situ observations of the deformation and failure of dealloyed nanoporous gold by utilizing the state-of-the art aberration-corrected transmission electron microscopy and fast direct electron detection camera. Our time-resolved atomic observations reveal that the brittle failure of the nanoporous gold originates from plastic instability of individual gold ligaments by the interplay between dislocation plasticity and stress-driving surface diffusion.

Localized surface plasmon resonance (LSPR) excitation enhanced chemical and electrochemical reactions represent a promising pathway for solar-to-chemical energy conversion. However, plasmonic catalysts usually suffer from low collection efficiency of hot charge carries generated by LSPR excitation due to short lifetime of hot carriers and fast electron-hole recombination. Schottky barriers between plasmonic catalysts and semiconducting supports have been utilized to prevent the electron-hole recombination. However, the interfacial barriers also hinder low-energy hot charge collection and thus affect solar-to-chemical energy conversion efficiency. Here we report that bicontinuous nanoporous gold as a Schottky barriers-free direct plasmonic catalyst can significantly enhance electro-oxidation of alcohol molecules. A high energetic hole yield of 0.486% is achieved, which is 4 times higher than that of discrete plasmonic AuAg nanoparticles. The direct plasmonic catalyst offers the highest methanol oxidation current density of 531 µA cm−2 among all known Au catalysts. This work provides compelling evidence that higher hot carrier collection efficiency can be achieved from direct plasmonic electrocatalysis without the assistance of Schottky junctions and has important implications in developing high efficiency plasmonic catalysts for photo-enhanced electrochemical reactions.

A single-phase Al0.1CoCrFeNi high-entropy alloy (HEA) with face-centered cubic structure was subjected to cryo-rolling at the liquid N2 temperature and subsequent annealing. Microstructural characterization of post-annealed samples by electron backscattered diffraction and transmission electron microscopy revealed that, the dominant grain boundaries (GBs) are of Σ3 type low energy twin boundaries owing to the low stacking fault energy of the HEA. The resulting ultrafine-grained single-phase HEA with abundant Σ3 twin boundaries shows a high strength above 1.0 GPa and a tensile strain larger than 20%. The quantitative analysis on the grain size dependence of strength suggests that a high lattice friction stress and a high GB strengthening via low energy Σ3 twin boundaries are two major contributions for the excellent strength-ductility balance of the ultra-fine grained HEA.

The network topology in disordered materials is an important structural descriptor for understanding the nature of disorder that is usually hidden in pairwise correlations. Here, we compare the covalent network topology of liquid and solidified silicon (Si) with that of silica (SiO2) on the basis of the analyses of the ring size and cavity distributions and tetrahedral order. We discover that the ring size distributions in amorphous (a)-Si are narrower and the cavity volume ratio is smaller than those in a-SiO2, which is a signature of poor amorphous-forming ability in a-Si. Moreover, a significant difference is found between the liquid topology of Si and that of SiO2. These topological features, which are reflected in diffraction patterns, explain why silica is an amorphous former, whereas it is impossible to prepare bulk a-Si. We conclude that the tetrahedral corner-sharing network of AX2, in which A is a fourfold cation and X is a twofold anion, as indicated by the first sharp diffraction peak, is an important motif for the amorphous-forming ability that can rule out a-Si as an amorphous former. This concept is consistent with the fact that an elemental material cannot form a bulk amorphous phase using melt quenching technique., Scientific Reports, 11, ISSN:2045-2322

We investigated 120-GHz-band sheet LAN that enables the connection to LAN simply by placing portable devices on the sheet and can achieve 10-Gbit/s data transmission. We designed dielectric sheets and waveguide-to-dielectric sheet transition, and evaluated their transmission losses. The transmission loss over 100-mm-long dielectric sheet was about -6 dB at the 120 GHz band. We have succeeded in 10-Gbit/s data transmission over the dielectric sheet using 120-GHz wireless signal.

This paper proposes an algorithm for automatic planning of 300-GHz-band wireless backhaul link deployment. The algorithm consists of two steps; Selecting the pair of adjacent cells that can get a line of sight, and Deployment of base stations. We succeeded in the automatic planning of 300-GHz-band backhaul link in Shinjuku, Japan by using this algorithm. We conducted radio wave propagation simulation of the wireless backhaul links, and showed that SNR of 99.5 % of the wireless backhaul links deployed by using this algorithm exceeds the standard demand SNR for 100-Gbit/s data transmission even when the rain rate is 100 mm/hr.

In 6G mobile communication, 300-GHz-band terahertz (THz) system is a promising candidate for achieving ultra-high-speed wireless communication. However, the experimental data on the reflectance and transmittance of building materials at 300GHz were insufficient. In this paper, we employed terahertz time-domain spectroscopy (THz-TDS) spectroscopy to obtain the complex permittivity of building materials, glass, concrete, and granite at 200-500 GHz in order to calculate the reflectance and transmittance of building materials. In THz-TDS spectroscopy, the effect of multiple reflections was removed by time-gating the acquired waveform. We conducted 300-GHz-band indoor propagation simulation by using the calculated complex permittivity of building materials.