Enhanced Catalytic Activity of PdNi Dilute Nanoalloy for Selective Phenylacetylene Hydrogenation

Coordination of identical metals has significant impact on catalytic activity and selectivity of heterogeneous catalyst. Here, we show that the selectivity for hydrogenation of Pd can be manipulated by altering the coordinate environment. PdNi/SiO2 dilute alloy nanocatalysts have been synthesized at room temperature, which show effectively the unparalleled catalytic performance (about 100% selectivity to styrene) for phenylacetylene hydrogenation at 30 °C with full conversion. Structural and surface analyses show that the improvement in dispersion of the Pd active sites and the changed electronic structure of Pd contribute the catalytic performance significantly. This work is an important step towards developing highly active hydrogenation catalysts by forming dilute alloys.

Lattice Dynamics of CrW Dilute Alloy Using Modified Embedded Atom Method Potential

A modified embedded atom method (MEAM) has been used to study the lattice dynamics and vibrational properties of CrW alloy. Using the MEAM potential the force-constants up to second neighbours for pure Cr and its dilute alloy with small concentration of W as substitutional impurity are calculated. The Phonon dispersions for dilute CrW alloy at 0.3%, 0.8% and 1.6 % concentration of W substitutional impurity have been computed and the obtained results are compared with the available experimental data. We have obtained a very good agreement with the experimentally measured results of phonon dispersions. With the application of obtained force-constants from MEAM potential, the local vibrational density of states in ideal crystal and its alloys using Green’s function method has been calculated. On the basis of the results of local vibrational density of states, the condition of resonance modes has been investigated. Using the calculated vibrational local density of states, the mean square thermal displacements of impurity atoms in CrW alloys are also calculated.

Rare-earth- and aluminum-free, high strength dilute magnesium alloy for Biomedical Applications

Lightweight, recyclable, and plentiful Mg alloys are receiving increased attention due to an exceptional combination of strength and ductility not possible from pure Mg. Yet, due to their alloying elements, such as rare-earths or aluminum, they are either not economical or biocompatible. Here we present a new rare-earth and aluminum-free magnesium-based alloy, with trace amounts of Zn, Ca, and Mn (≈ 2% by wt.). We show that the dilute alloy exhibits outstanding high strength and high ductility compared to other dilute Mg alloys. By direct comparison with annealed material of the same chemistry and using transmission electron microscopy (TEM), high-resolution TEM (HR-TEM) and atom probe tomography analyses, we show that the high strength can be attributed to a number of very fine, Zn/Ca-containing nanoscale precipitates, along with ultra-fine grains. These findings show that forming a hierarchy of nanometer precipitates from just miniscule amounts of solute can invoke simultaneous high strength and ductility, producing an affordable, biocompatible Mg alloy.

On the behaviour of structure-sensitive reactions on single atom and dilute alloy surfaces

Typically structure sensitive dissociation reactions exhibit reduced structure-sensitivity when taking place over low-index single atom alloy surfaces.

Stabilization of a nanoporous NiCu dilute alloy catalyst for non-oxidative ethanol dehydrogenation

In situ and ex situ X-ray photoelectron spectroscopy and electron-microscopy reveal that the stability of nanoporous NiCu alloy catalysts for non-oxidative ethanol dehydrogenation improves by generating kinetically trapped Ni2+ subsurface states.