Hydroxyapatite (HA) Modified Nanocoating Enhancement on AZ31 Mg Alloy by Combined Surface Mechanical Attrition Treatment and Electrochemical Deposition Approach.

Hydroxyapatite (HA) nanocoating was electrodeposited on the surface mechanical attrition treated (SMATed) AZ31 magnesium alloy. Phases, morphologies and the adhesion of coating were characterized by X-ray diffraction, scanning electron microscopy (SEM) and 3D optical profiler. The corrosion resistance of the HA coating was tested by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the HA coating on SMATed sample had a better crystallization than that on original one. The thickness of HA coating increased from 25 to 40 µm. The bonding strength between HA coating and SMATed substrate was higher than that between the coating and untreated counterpart. Potentiodynamic polarization and EIS demonstrated that the corrosion current density of HA coating on SMATed substrate decreased by 30.84% than that on original. The corrosion potential shifted 80.3 mV to the positive direction. The corrosion resistance of coatings on SMATed sample was significantly enhanced. The immersion experiments showed that the HA coatings on SMATed sample exhibited a better biological activity.

Carbon Nanomaterials in Direct Liquid Fuel Cells.

Fuel cells have attracted more attentions due to many advantages they can provide, including high energy efficiency and low environmental burden. To form a stable, low cost and efficient catalyst, we presented here the state of the art of electrocatalyst fabrication approaches, involving carbon nanotubes and their multifunctional nanocomposites incorporated with noble metals, such as Pt, Pd, Au, their binary and ternary systems. Both fuel oxidation reactions and oxygen reduction reactions were emphasized with comprehensive examples and future prospects.

Ultrathin Solid Polymer Electrolyte Design for High-Performance Li Metal Batteries: A Perspective of Synthetic Chemistry.

Li metal batteries (LMBs) have attracted widespread attention in recent years because of their high energy densities. But traditional LMBs using liquid electrolyte have potential safety hazards, such as: leakage and flammability. Replacing liquid electrolyte with solid polymer electrolyte (SPE) can not only significantly improve the safety, but also improve the energy density of LMBs. However, till now, there is only limited success in improving the various physical and chemical properties of SPE, especially in thickness, posing great obstacles to further promoting its fundamental and applied studies. In this review, the authors mainly focus on evaluating the merits of ultrathin SPE and summarizing its existing challenges as well as fundamental requirements for designing and manufacturing advanced ultrathin SPE in the future. Meanwhile, the authors outline existing cases related to this field as much as possible and summarize them from the perspective of synthetic chemistry, hoping to provide a comprehensive understanding and serve as a strategic guidance for designing and fabricating high-performance ultrathin SPE. Challenges and opportunities regarding this burgeoning field are also critically evaluated at the end of this review.

A New Explanation for the Effect of Dynamic Strain Aging on Negative Strain Rate Sensitivity in Fe-30Mn-9Al-1C Steel.

In this study, the evolution of the mechanical properties of Fe-30Mn-9Al-1C steel has been determined in tensile tests at strain rates of 10-4 to 102 s-1. The results show that the strain rate sensitivity becomes a negative value when the strain rate exceeds 100 s-1 and this abnormal evolution is attributed to the occurrence of dynamic strain aging. Due to the presence of intergranular κ-carbides, the fracture modes of steel include ductile fracture and intergranular fracture. The values of dislocation arrangement parameter M were obtained using a modified Williamson-Hall plot. It has been found that once the strain rate sensitivity becomes negative, the interaction of dislocations in the steel is weakened and the free movement of dislocation is enhanced. Adiabatic heating promotes the dynamic recovery of steel at a high strain rate.

Corrosion Behavior of the As-Cast and As-Solid Solution Mg-Al-Ge Alloy.

The corrosion behavior of Mg-3Al-xGe (x = 1, 3, 5) alloy in as-cast and as-solid was investigated by virtue of microstructure, corrosion morphology observation, and electrochemical measurement. Among the as-cast alloys, the corrosion rate of Mg-3Al-1Ge with a discontinuous bar-morphology was the highest, which was 101.7 mm·a-1; the corrosion rate of Mg-3Al-3Ge with a continuous network distribution was the lowest, which was 23.1 mm·a-1; and the corrosion rate of Mg-3Al-5Ge of Ge-enriched phase with sporadic distribution was in-between, which was 63.9 mm·a-1. It is suggested that the morphology of the Mg2Ge phase changes with a change in Ge content, which affects the corrosion performance of the alloy. After solid solution treatment, the corrosion rate of the corresponding solid solution alloy increased-Mg-3Al-1Ge to 140.5 mm·a-1, Mg-3Al-3Ge to 52.9 mm·a-1, and Mg-3Al-5Ge to 87.3 mm·a-1, respectively. After investigation of the microstructure, it can be suggested that solid solution treatment dissolves the Mg17Al12 phase, which changes the phase composition of the alloy and also affects its microstructure, thus affecting its corrosion performance.

Structural characteristics of nanocrystalline copper after carbon ion implantation.

A gradient structure was produced in a pure copper plate by means of surface mechanical attrition treatment (SMAT). The microstructure of the surface layer was reduced to nanoscale and the grain size increased gradually along the depth of the treated sample. In situ transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) observation was performed on the nanocrystalline copper after implantation of carbon. Carbon atoms first precipitated along the edges of the copper substrate or at the surface, then formed amorphous carbon layers. Subsequently, onion-like fullerenes were formed under electron-beam irradiation. The effects of ion implantation, electron beam irradiation, nanostructure of the substrate and interaction of C and Cu atoms on the formation of the onion-like fullerenes are discussed.