Enhancement of corrosion resistance of electrocodeposited Ni–SiC composites by magnetic field

The corrosion behavior and surface morphology of Ni–SiC composite coatings produced by electrodeposition with the aid of magnetic field were studied. The results of the electrochemical analysis including polarization resistance and potentiodynamic polarization curves showed that a magnetic field of 0.1 T could significantly improve the corrosion resistance of the composite. The electrochemical impedance spectra revealed that a passive layer was formed on the surface of the Ni–SiC coating with the magnetic field. The microstructures of electrodeposited Ni–SiC composite coatings were also examined. More SiC particles were found to be incorporated into the coating with the presence of magnetic field, which was considered to be one of the reasons for the enhancement of corrosion resistance as SiC particles were reported to be corrosion inhibitors. Contribution to special issue “Magnetic field effects in Electrochemistry”     

双金属在掺硼金刚石表面电化学共沉积-共溶出模型

采用微分脉冲阳极溶出伏安法, 研究了Ag+、Cu2+、Pb2+、Sn2+、Cd2+等多种共存金属离子在掺硼金刚石(BDD)表面双金属共沉积-共溶出电化学行为. 结果表明, 双金属在掺硼金刚石膜表面的共沉积-共溶出模型是由金属本身的析出电位, 金属之间的相互作用, 金属离子和溶液间的相互作用等多种因素决定的. 微分阳极溶出法的研究结果表明, 双金属在掺硼金刚石电极上的共沉积-共溶出过程表现出金属1溶出-金属2溶出、金属1溶出-析氢-金属2溶出、金属1溶出-金属合金溶出-金属2溶出、金属1溶出-析氢-金属2络合物形成-金属2溶出等四种模型.     

Ni/ZrO2复合电沉积机理的研究

研究了在Ｗａｔｔｓ镀镍液中ＺｒＯ２颗粒与镍复合电沉积的阴极电流密度以及颗粒在镀液中分散量对颗粒共析量的影响，探讨了复合电沉积的过程与模型。研究表明，在小的颗粒分散量下，复合电沉积为颗粒向阴极的传输所控制，导致共析量随电流密度增大而减少。在大的颗粒分散量，小电流密度时复合电沉积为颗粒的强吸附过程所控制，致使共析量随电流密度增大而增加；大电流密度时，复合电沉积为颗粒向阴极的传输所控制，造成共析量随电流     

Effect of magnetic field on electrocodeposition behavior of Ni–SiC composites

In this paper, an external magnetic field was applied in the electrodeposition of Ni–SiC composites, and its effects on surface morphology, SiC content, and crystal orientation were examined. It was found that the magnetic field modified the surface morphology and the orientation of the composites and significantly increased the SiC content. The phenomenon can be attributed to the change of charge transfer reactions and the mass transport process through the micromagnetohydrodynamic effect.     

现场表面拉曼光谱研究Ni-P合金电沉积机理

由于Ｎｉ Ｐ合金具有许多优越的物理和化学性能 ,如高的耐蚀性［１］、好的电催化特性［２,３］以及好的非磁特性［４,５］,人们对这种合金的沉积方法进行了大量的研究．磷是一种不能从水溶液中单独进行电沉积的元素 ,但它很容易和铁组元素共沉积．为了解释这一现象 ,Ｂｒｅｎｎｅｒ曾提出直接机理［６］．认为镀液中磷的含氧酸 (根 )直接在电极上还原成合金中的磷．然而 ,磷不能用电化学方法以纯态沉积出来,所以直接机理没有被广泛接受．第二种是由Ｆｅｄｏｔ′ｅｖ等提出的间接机理［７］,认为磷的含氧酸（根）首先还原成磷化氢（ＰＨ…     

CaB3—A new calcium boride stabilized by thin film epitaxy

Codeposition of Ca and B on various single crystal substrates was carried out by MBE technique. A new calcium boride CaB₃ was epitaxially grown on Al₂O₃(0001) with substrate temperature . Structural characterization by RHEED and X-ray diffraction indicated that CaB₃ has a hexagonal cell with lattice parameters and . No evidence for superconductivity was found down to 2 K.     

Synthesis and characterization of Cu3Se2 nanofilms by an underpotential deposition based electrochemical codeposition technique

The Cu₃Se₂ nanofilms were synthesized with underpotential deposition based electrochemical codeposition technique for the first time in the literature. The electrochemical behaviors of copper and selenium were investigated in 0.1 M H₂SO₄ on Au electrode. The effects of concentration and scan rate on the electrochemical behavior of selenium were studied. The electrochemical behaviors in underpotential deposition and bulk regions of the Cu-Se system were investigated in acidic solution by cyclic voltammetry and electrolysis techniques. X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy, and ultraviolet and visible absorption spectroscopy techniques were used for characterization of synthesized films. According to the X-ray photoelectron spectroscopy spectrum, Cu/Se ratio was determined to be approximately 3/2. Copper selenide nanofilms are two phases and polycrystalline according to X-ray diffraction. The films mainly formed tetragonal Cu₃Se₂ (umangite mineral structure) structure and the particle size was approximately 45.95 nm. Scanning electron microscopy images showed that Cu₃Se₂ nanofilms consisted of uniform, nano-sizes and two-dimensional. It was found through AFM that the surface roughness of the film was 6.173 nm, with a mean particle size of around 50 nm. Depending on the deposition time, the band gaps of the Cu₃Se₂ films were in the range of 2.86–3.20 eV. Three characteristic vibrational modes belonging to Cu₃Se₂ nanofilms were recorded in the Raman spectrum.     

镍-碳化钨微粒复合电沉积机理的研究

研究了在普通镀镍溶液中导电性微粒碳化钨与基质金属镍形成复合镀层的电沉积过程，实验结果表明，导电性的ＷＣ微粒在与Ｎｉ共沉积形成Ｎｉ－ＷＣ复合镀层的过程中，也遵循Ｇｕｇｌｉｅｌｍｉ的两步吸附机理，只是在电极表面，ＷＣ微粒的弱吸附覆盖度与强吸附覆盖度的比值，较非导电性微粒的复合共沉积体系的要小得多。     

Matrix isolation infrared spectroscopic investigation of the coordination chemistry and reactivity of OVF3

The matrix isolation technique has been combined with infrared spectroscopy to identify and characterize the product of the codeposition of OVF₃ with NH₃ and with a series of nitrogen and oxygen donor bases into argon matrices at 14 K. This codeposition led to the formation of the isolated 1:1 complexes between OVF₃ and these bases. Each complex was characterized spectroscopically, including strong shifts to the V–F stretching modes, and a lesser shift to the V=O stretching mode. Numerous perturbed vibrational modes of the base subunits were noted, including a strong, 230 cm⁻¹ blue shift to the symmetric bending mode of NH₃. The magnitudes of these shifts indicate that OVF₃ is a moderate strength Lewis acid. However, in contrast to analogous reactions with OVCl₃, no further thermal or photochemical transformations of the complex occurred. Theoretical calculations were also carried out in support of the experimental work.     

Electrochemical Formation of Al-Li Alloys by Codeposition of Al and Li from LiCl-KCl-AlF3 Melts at 853 K

The electrochemical behavior of Al(III) ions was studied in molten LiCl-KCl melts on a molybdenum electrode. Cyclic voltammetry, chronopotentiometry and chronoamperometry were used to explore the deposition mechanism of Al and Li. Cyclic voltammetry expriment indicates that under potential deposition(UPD) of lithium on pre-deposited aluminium led to the formation of liquid Al-Li alloys at 853 K. The diffusion coefficient of Al(III) ions at 853 K in LiCl-KCl-AlF₃(1%, mass fraction) melts was determined to be (2.79±0.05)×10^?5 cm²/s. Chronopotentiograms and chronoamperograms demonstrate that the codeposition of Al(III) and Li(I) ions formed Al-Li alloys at cathodic current densities higher than ?0.28 A/cm² or cathodic potentials more negative than ?2.20 V. X-Ray diffraction(XRD) pattern indicates that Al-Li alloys with different phases formed via galvanostatic electrolysis. Inductively coupled plasma(ICP) analyses of the samples obtained by electrolysis show that lithium and aluminium contents of Al-Li alloys could be controlled by AlF₃ concentration and current intensity.