Manipulating the Water Dissociation Electrocatalytic Sites of Bimetallic Nickel-Based Alloys for Highly Efficient Alkaline Hydrogen Evolution.

Transition-metal alloys are currently drawing increasing attention as promising electrocatalysts for the alkaline hydrogen evolution reaction (HER). However, traditional density-functional-theory-derived d-band theory fails to describe the hydrogen adsorption energy (ΔGH ) on hollow sites. Herein, by studying the ΔGH for a series of Ni-M (M=Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, W) bimetallic alloys, an improved d-band center was provided and a potential NiCu electrocatalyst with a near-optimal ΔGH was discovered. Moreover, oxygen atoms were introduced into Ni-M (O-NiM) to balance the adsorption/desorption of hydroxyl species. The tailored electrocatalytic sites for water dissociation can synergistically accelerate the multi-step alkaline HER. The prepared O-NiCu shows the optimum HER activity with a low overpotential of 23 mV at 10 mA cm-2 . This work not only broadens the applicability of d-band theory, but also provides crucial understanding for designing efficient HER electrocatalysts.

A Study of Silver Decoration on Carbon Nanotubes via Ultrasonic Chemical Synthesis and Their Reinforced Copper Matrix Composites.

The homogeneous distribution of carbon nanotubes (CNTs) in the Cu matrix and good interfacial bonding are the key factors to obtain excellent properties of carbon nanotube-reinforced Cu-based composites (CNT/Cu). In this work, silver-modified carbon nanotubes (Ag-CNTs) were prepared by a simple, efficient and reducer-free method (ultrasonic chemical synthesis), and Ag-CNTs-reinforced copper matrix composites (Ag-CNTs/Cu) were fabricated by powder metallurgy. The dispersion and interfacial bonding of CNTs were effectively improved by Ag modification. Compared to CNTs/Cu counterparts, the properties of Ag-CNTs/Cu samples were significantly improved, with the electrical conductivity of 94.9% IACS (International Annealed Copper Standard), thermal conductivity of 416 W/m·k and tensile strength (315 MPa). The strengthening mechanisms are also discussed.

Interfacial Bonding Improvement through Nickel Decoration on Carbon Nanotubes in Carbon Nanotubes/Cu Composite Foams Reinforced Copper Matrix Composites.

Inhomogeneous structures with carbon nanotubes (CNTs), reinforced with Cu composite foams as the reinforcing skeletons (CNTs/Cuf®Cu), have been designed to overcome the paradox between strength and ductility or conductivity in copper matrix composites. The interface between CNTs and the copper matrix is usually weak, due to poor wettability and interaction. In this study, nickel nanoparticles are decorated onto CNTs to improve interfacial bonding. The broader interface transition area between CNTs and copper with Ni3C interfacial products formed, and a combination of improved electrical conductivity (95.6% IACS), tensile strength (364.9 MPa), and elongation (40.6%) was achieved for the Ni-decorated CNTs/Cuf®Cu (Ni-CNTs/Cuf®Cu). In addition, the strengthening mechanisms are discussed in this study.

Influence of stacking fault energy on defect structures and microhardness of Cu and Cu alloys.

Nano-structured Cu, Cu-10 wt%Zn and Cu-2 wt%Al with stacking fault energies (SFE) of 78, 35 and 37 mJ/m2, respectively, were preprared through high energy ball milling. X-ray diffraction and Vickers microharness test were used to investigate the microstructure and microhardness of all the samples after ball milling. X-ray diffraction measurements indicate that lower SFEs lead both to decrease in grain size and increase in microstrain, dislocation and twin densities for Cu-10 wt%Zn and Cu-2 wt%Al after 5 h of ball milling. The microhardnesses of Cu-10 wt%Zn and Cu-2 wt%Al reach to nearly the same values of 2.5 GPa after 5 h of ball milling, which is higher than that of Cu of 2.0 GPa. Two factors are considered to contribute to the finer grian size and higher microhardness of Cu-10 wt%Zn and Cu-2 wt%Al: (1) the effect of solid solution strengthening, which result in the interaction of solute atoms with screw dislocations; (2) the introduction of deformation twins during ball milling process by the decreasing of SFE, which results in the grain refinement.

Effect of Cu Content on Performance of Sn-Zn-Cu Lead-Free Solder Alloys Designed by Cluster-Plus-Glue-Atom Model.

The mechanical properties of solder alloys are a performance that cannot be ignored in the field of electronic packaging. In the present study, novel Sn-Zn solder alloys were designed by the cluster-plus-glue-atom (CPGA) model. The effect of copper (Cu) addition on the microstructure, tensile properties, wettability, interfacial characterization and melting behavior of the Sn-Zn-Cu solder alloys were investigated. The Sn29Zn4.6Cu0.4 solder alloy exhibited a fine microstructure, but the excessive substitution of the Cu atoms in the CPGA model resulted in extremely coarse intermetallic compound (IMC). The tensile tests revealed that with the increase in Cu content, the tensile strength of the solder alloy first increased and then slightly decreased, while its elongation increased slightly first and then decreased slightly. The tensile strength of the Sn29Zn4.6Cu0.4 solder alloy reached 95.3 MPa, which was 57% higher than the plain Sn-Zn solder alloy, which is attributed to the fine microstructure and second phase strengthening. The spreadability property analysis indicated that the wettability of the Sn-Zn-Cu solder alloys firstly increased and then decreased with the increase in Cu content. The spreading area of the Sn29Zn0.6Cu0.4 solder alloy was increased by 27.8% compared to that of the plain Sn-Zn solder due to Cu consuming excessive free state Zn. With the increase in Cu content, the thickness of the IMC layer decreased owing to Cu diminishing the diffusion force of Zn element to the interface.