Aluminum–silicon alloys are an important class of commercial casting materials having wide applications in automotive and aerospace industries. Etching the Al–Si eutectic leads to selective dissolution of Al, resulting in novel morphology – macroporous Si spheres with a three-dimensional nano network. Up to 5% Al is dissolved in Si, leading to an expansion of the crystal lattice. The resulting porous Si is electrochemically active with lithium and thus can be used as a high capacity anode for lithium-ion batteries. The etching of Al–Si provides a simple and low-cost method of producing nano-structured Si materials.

We demonstrate that alternating the oxygen partial pressure gradient across a yttria-stabilized zirconia (YSZ) electrolyte membrane prior to solid oxide fuel cell (SOFC) testing with nanoporous Pt electrodes greatly increases (e.g. by >70-fold at 350 °C) peak power density compared with devices without pretreatment. Transiently altering the oxygen activity at the cathode–YSZ interface appears to change the wetting characteristics of the nanoporous Pt, significantly affecting the stability and low-temperature performance of the SOFCs. Image analysis and impedance spectroscopy results suggest that an increase in triple-phase boundary area fraction at the cathode–YSZ interface contributes to the observed effect.

Tetrahedrite-structure compounds, of general composition Cu12−xZnxSb4S13, are an earth-abundant alternative to PbTe for thermoelectric power generation applications in the intermediate high-temperature range (300–400°C). Tetrahedrites can be synthesized in the laboratory using a multi-step process involving long annealing times. However, this compound also exists in natural mineral form, and, in fact, is one of the most abundant copper-bearing minerals in the world. We show here that by simply mixing natural mineral tetrahedrite with pure elements through high-energy ball milling without any further heat treatment, we can successfully obtain material with figure of merit near unity at 723 K.

We report the synthesis of a direct gap semiconductor, ZnSnN2, by a plasma-assisted vapor–liquid–solid technique. Powder X-ray diffraction measurements of polycrystalline material yielded lattice parameters in good agreement with predicted values. Photoluminescence efficiency at room temperature was observed to be independent of excitation intensity between 103 and 108 W/cm2. The band gap was measured by photoluminescence excitation spectroscopy to be 1.7 ± 0.1 eV. The range of direct band gaps for the Zn(Si,Ge,Sn)N2 alloys is now predicted to extend from 4.5 to 1.7 eV, opening up this little-studied family of materials to a host of important applications.

Electrical fields can be used to heat selectively dislocations and grain boundaries to a much higher temperature compared with the bulk. This selective joule heating, if uncontrolled by limiting the current flow, can lead to melting of grain boundaries and sintering of poly- and nanocrystalline materials close to the theoretical density in a much shorter time due to fast diffusivities of the order of 10−4 to 10−5 cm2/s in the liquid. I refer to this sintering mode as selective-melt sintering, which can occur at lower overall temperatures with much lower energy consumption compared with conventional sintering involving solid-state diffusion.

Mn-doped bismuth oxide bromide microspheres have been prepared by the hydrothermal method. The resultant composite microspheres exhibited higher photocatalytic activity under visible light irradiation, attributing to the improvement of the photo-absorption property and the separation efficiency of photogenerated electrons and holes. The holes and O2•− are the main active species in aqueous solution under visible light irradiation, rather than •OH.

We report that an electron beam focused for high-resolution imaging rapidly initiates observable crystallization of amorphous Me–Si–C films. For 200-keV electron irradiation of Nb–Si–C and Zr–Si–C films, crystallization is observed at doses of ~2.8 × 109 and ~4.7 × 109 e−/nm2, respectively. The crystallization process is driven by atomic displacement events, rather than heating from the electron beam as in situ annealing (400–600 °C) retains the amorphous state. Our findings demand a critical analysis of alleged amorphous and nanocrystalline ceramics including reassessing previous reports on nanocrystalline Me–Si–C films for possible electron-beam-induced crystallization effects.

We employed ab initio global structural prediction algorithms to obtain the ground-state structure of CuBO2 This is a very promising p-type transparent conductive oxide that was synthesized recently, and thought to belong to the delafossite family. We proved that the true ground state is certainly not the delafossite structure, and that the most promising candidate is a low symmetry monoclinic phase. This is still a layered structure, but with boron and copper having a different coordination with respect to the delafossite phase.

Solid oxide fuel cells (SOFCs) are attractive for clean and efficient electricity generation, but high operating temperatures (Top > 800 °C) limit their widespread usage. Oxygen ion conducting cathode materials (mixed ion-electron conductors, MIECs), such as La1−xSrxCo1−yFeyO3 (LSCF), enable lower Top by reducing cathode polarization losses. Understanding how composition affects oxygen diffusion in LaFeO3 is vitally important for designing high-performance LSCF cathodes. To do this, we employ first-principles density functional theory plus U (DFT+U) calculations to show how lanthanum vacancies in LaFeO3 dramatically change the oxygen diffusion coefficient. Our ab initio results show that A-site substoichiometry is a viable route to increased oxygen diffusion and higher SOFC performance.

It is widely believed that switching to the conductive state in memristive materials is triggered by the external field that drives defect dynamics. In polycrystalline materials, grain boundaries are further believed to cause switching by enabling faster defect motion. Here, we report a first-principle study of oxygen vacancy dynamics at a grain boundary (GB) in polycrystalline ZnO and show that switching to the conductive state is triggered by a recombination-enhanced motion of vacancies perpendicular to the GB. We call this mechanism the “breathing” trigger of memristive switching.

We present a comparative ab initio study of surface diffusion of Li and Na on planar and curved graphene. The barrier for diffusion is ~0.1 eV lower for Na than for Li, and is changed significantly by curvature. The maximum change is similar for Li for Na, of the order of ±0.1 eV on the convex and concave sides. The difference in barrier for metal atoms adsorbed on the concave and convex sides can reach 0.2 eV. This modulation of the diffusion barrier by curvature is therefore expected to affect significantly the rate capability of graphene-based anodes.

The fabrication of bimetallic magnetic nanoparticles (NPs) smaller than the size of single magnetic domain is very challenging because of the agglomeration, non-uniform size, and possible complex chemistry at nanoscale. In this paper, we present an alloyed ferromagnetic 4 ± 1 nm thiolated Au/Co magnetic NPs with decahedral and icosahedral shape. The NPs were characterized by Cs-corrected scanning transmission electron microscopy (STEM) and weretheoretically studied by Grand Canonical Monte Carlo simulations. Comparison of Z-contrast imaging and energy dispersive x-ray spectroscopy used jointly with STEM simulated images from theoretical models uniquely showed an inhomogeneous alloying with minor segregation. The magnetic measurements obtained from superconducting quantum interference device magnetometer exhibited ferromagnetic behavior. This magnetic nanoalloy in the range of single domain is fully magnetized and carries significance as a promising candidate for magnetic data recording, permanent magnetization, and biomedical applications.

Spider dragline silk is a self-assembling protein that rivals many engineering fibers in strength, extensibility, and toughness, making it a versatile biocompatible material. Here, atomistic-level structures of wildtype MaSp1 protein from the Nephila clavipes spider dragline silk sequences, obtained using an in silico approach based on replica exchange molecular dynamics and explicit water, are subjected to nanomechanical testing and released preceding failure. We approximate the relaxation time from an exponential decay function, and identify permanent changes in secondary structure. Our work provides fundamental insights into the time-dependent properties of silk and possibly other protein materials.