Manganese dioxide is a low-cost catalyst for oxygen reduction reaction (ORR) in alkaline media. In this paper, the amorphous MnO ₂ (AMO) was prepared, its characteristics and the effects of mixed with carbon nanotubes (CNTs), doped with silver nanoparticles on catalytic performance were investigated. The experimental results show that the performance of the AMO is slightly worse than that of the β -MnO ₂ , which is possibly caused by the absence of the high catalytic activity (110) surface in the amorphous state. However, the addition of carbon nanotubes significantly improves the catalytic properties of AMO. Furthermore, the nanoscale silver particles doped AMO was prepared and characterized, and it is shown that the AMO/CNTs catalyst with 10 wt% Ag nanoparticles owns the best catalytic performance. Quantum chemical calculation on the ligand effect by electron structure shows that the interaction between Ag and Mn can shift the d-band center of Ag and lower the activation barrier of the O–O bond fracture, while Ag can low the adsorption of O ₂ for Mn. However, when the Ag content in MnO ₂ up to 20%, the adsorption will be weakened and the break kinetics of O–O bond will be reduced, which leads to the catalytic effect reduced.

Aluminum Foam Sandwich panels were fabricated via liquid diffusion welding and glue adhesive methods. The Microstructure of the Aluminum Foam Sandwich joints were analyzed by Optical Microscopy, Scanning Electron Microscopy, and Energy Dispersive Spectroscopy. The metallurgical joints of Aluminum Foam Sandwich panels are compact, uniform and the chemical compositions in the diffusion transitional zone are continuous, so well metallurgy bonding between Aluminum face sheet and foam core was obtained. The joining strength of an Aluminum Foam Sandwich was evaluated by standard peel strength test and the metallurgical joint Aluminum Foam Sandwich panels had a higher peel strength. Moreover, a three-point bending fatigue test was conducted to study the flexural fatigue behavior of Aluminum Foam Sandwich panels. The metallurgical joint panels have a higher fatigue limit than the adhesive joining sandwich. Their fatigue fracture mode are completely different, the failure mode of the metallurgical joint is faced fatigue; the failure mode for the adhesive joint is debonding. Therefore, the higher joining strength leads to a longer fatigue life.

In this paper, an equiatomic NiTi (55NiTi) alloy powder was mixed with pure Ni powder to prepare laser cladding coatings on a 316L stainless steel substrate to study the effect of Ni addition on the microstructure and corrosion resistance of the coatings. The microstructure and phase composition of the coatings were analyzed using a scanning electron microscope (SEM) with configured energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD). OCP (open-circuit potential), PD (potentiodynamic polarization) and EIS (electrochemical impedance spectroscopy) experiments were conducted by a Gamry electrochemical workstation, and corresponding eroded morphologies were observed to evaluate the coating’s anti-corrosion performance. The addition of Ni led to fine and uniform dendrites and dense microstructure under the metallurgical microscope, which were beneficial for the formation of the passive film mainly consisting of titanium dioxide (TiO₂). The results show that the pitting potential of the 55NiTi + 5Ni coating was 0.11 V nobler than that of the 55NiTi coating, and the corrosion current density was less than half that of the 55NiTi coating. The corrosion initiated preferentially at the interfaces of dendrites and inter-dendritic areas, then spread first to dendrites rather than in the inter-dendritic areas.