Cathodic phosphate coating containing nano zinc particles on magnesium alloy

A technology for preparation of a cathodic phosphate coating mainly containing nano metallic zinc particles and phosphate compounds on magnesium alloy was developed.The influence of cathodic current density on the microstructure of the cathodic phosphate coating was investigated.The results show that the crystals of the coating are finer and the microstructures of the outer surface of the coatings are zigzag at the cathodic density of 0.2-0.5 A/dm^2.The content of nano metallic zinc particles in the coating decreases with the increase of the thickness of the coatings and tends to be zero when the coating thickness is 4.14μm.The cathodic phosphate coating was applied to be a transition coating for improving the adhesion between the paints and the magnesium alloys. The formation mechanism of the cathodic phosphate coating was investigated as well.

Microstructure and mechanical properties of GTA weldments of titanium matrix composites prepared with or without current pulsing

The effects of current pulsing on the microstructure, hardness and tensile properties at different temperatures of gas tungsten arc （GTA） weldments of titanium matrix composites were studied. Full-penetration butt joints were made with or without current pulsing. Optical microscopy, hardness test and scanning electron microscopy were employed to evaluate the metallurgical characteristics of welded joints. Tensile properties of weldments at different temperatures were studied and correlated with the microstructure. The results exhibit that current pulsing leads to the refinement of the weld microstrucmre and TiB whisker and the redistribution of reinforcements resulting in higher hardness, tensile strength and ductility of weldments in the as-welded condition.

Effects of polyaniline on electrochemical properties of composite inert anodes used in zinc electrowinning

In order to search for a suitable anode material used in zinc electrowinning in place of Pb-Ag alloy,Al/Pb-PANI（polyaniline）-WC（tungsten carbide） composite inert anodes were prepared on aluminum alloy substrate by double pulse electrodeposition（DPE） of PANI and WC particles with Pb2＋ from an original plating bath.Thereafter,anodic polarization curves,cyclic voltammetry curves and Tafel polarization curves for the composite inert anodes obtained under different PANI concentrations in the original plating bath were measured,and the microstructural features were also investigated by scanning electron microscopy（SEM）.The results show that Al/Pb-PANI-WC composite inert anode obtained under PANI concentration of 20 g/L in the original plating bath possesses uniform microstructures and composition distributions,higher electrocatalytic activity,better reversibility of electrode reaction and corrosion resistance in a synthetic zinc electrowinning electrolyte of 50 g/L Zn2＋,150 g/L H2SO4 at 35 °C.Compared with Pb-1%Ag alloy,the overpotential of oxygen evolutions for the composite inert anode are decreased by 185 mV and 166 mV,respectively,under 500 A/m2 and 1000 A/m2.

Electroanalytical studies on electrically conductive polyaniline： Nylon-6,6 composite film

Electrically conductive composite films ofpolyaniline and nylon-6.6 are prepared by diffusing aniline followed by oxidative polymerization of aniline into nylon-6.6 matrix. In order to determine the diffusion coefficient for the chloride ion diffusion into the composite matrix electrochemically, galvanostatic pulse method is used and the diffusion coefficient is estimated to be -6.48× 10^-17 cm^2s^-1. The results are discussed in view of them being potential replacement materials for battery. electrodes and sensors devices.

Influence of SiO_2 nano-particles on microstructures and properties of Ni-W-P/CeO_2-SiO_2 composites prepared by pulse electrodeposition

Ni-W-P base composites containing CeO2 and SiO2 nano-particles were prepared on common carbon steel surface by pulse co-deposition of Ni,W,P,CeO2 and SiO2 nano-particles.The influence of SiO2 concentrations in bath on microstructures and properties of Ni-W-P/CeO2-SiO2 composites was studied,and the characteristics were assessed by chemical compositions,element distribution,surface morphologies,deposition rate and microhardness.The results indicate that when SiO2 concentration in bath is controlled at 20 g/L,the composites possess the fastest deposition rate,the highest microhardness,compact microstructures,smaller crystallite sizes and uniform distribution of W,P,Ce and Si within Ni-W-P matrix metal.Increasing SiO2 concentration in bath from 10 to 20 g/L leads to the refinement in grain size and the inhomogeneity of microstructures.While when SiO2 concentration is increased to 30 g/L,the crystallite sizes increase again and some bosses with nodulation shape appear on the surface of composites.

Nanopore-based sensing and analysis: beyond the resistive-pulse method

Solid-state nanopores are generally considered as an indispensable element in the research field of fundamental ion transport and molecular sensing. The im- provement in fabrication and chemical modification of the solid-state nanopores remains increasingly updated. During the last decades, numerous works have been reported on the nanopore-based sensing applications. More and more new analytical methods using nanopore-based devices are emerging. In this review, we highlight the recent progress on the analytical methods for the interdisciplinary and fast- growing area of nanopore research. According to the dif- ferent types of the electrical readout, whether it is steady- state ionic current or transient current fluctuation, the nanopore-based sensing and analysis can be generally di- vided into two categories. For the first type, the electrical readout shows a stable blockade or reopening of the nanopore conductance in the presence of target analytes, termed steady-state analysis, including the conductance change, electrochemical analysis, and two-dimensional scanning and imaging. The other type is based on the transient fluctuation in the transmembrane ionic current, termed transient-state analysis, including the noise analysis, transient ion transport, and transverse tunneling current. The investigation of solid-state nanopores for chemical sensing is just in its infancy. For further research work, not only new nanopore materials and chemical modifications are needed, but also other non-electric-based sensing techniques should be developed. We will focus our future research in the framework of bio-inspired, smart, multiscale interfacial materials and extend the spirit of binary cooperative complementary nanomaterials.