Electrocatalytic activity and electrochemical hydrogen storage of Ni-La alloy prepared by electrodeposition from aqueous electrolyte

Ni-La alloy coating was prepared by electrodeposition. The effect of cathodic current density on the La content of the alloy coatings was discussed. It is found that the content of La in the alloy increases with increasing the cathodic current density. The microstructures and codeposition mechanism of Ni-La alloy coatings were investigated by means of X-ray diffraction (XRD) and cyclic voltammetry (CV). The results demonstrate that the Ni-La alloy is FCC and codeposited by the induced mechanism. The hydrogen evolution reaction (HER) on the electrodeposited Ni-La alloy electrodes in alkaline solution was evaluated by Tafel polarization curves. It is found that La-Ni alloy coating exhibites much higher exchange current density for HER than pure Ni electrode, and that the exchange current density increases with increasing the La content of alloys. The good electrocatalytic activity for HER of this Ni-La alloy is attributed to the synergism of the electronic structure of La and Ni. The electrodeposited La-Ni alloys have a certain dectrochemical hydrogen storage capacity of 34- 143 mAh/g, which increases with increasing the La content of alloys.     

Supercapacitor characteristic of La-doped Ni(OH)_2 prepared by electrodeposition

Samples of lanthanum-doped nickel hydroxide were prepared by electrodeposition method. The structure and electrochemical properties of the samples were studied by X-ray diffraction and a home-made open three-electrode cell system,respectively. The results show that the deposition process of Ni(OH)2 and La(OH)3 is mainly controlled by electrochemical polarization,which makes it easy to form uniform fine crystals. In addition,La(OH)3 is not a separate phase and lanthanum ions are doped into Ni(OH)2 crystal la...     

Amorphization of Fe38Ni30Si16B14V2 surface layers by laser cladding

Fe38Ni30Si16B14V2 amorphous composite coatings were fabricated by laser cladding on AISI 1045 steel in order to increase the wear resistance. The phase and microstructure of the coatings were analyzed by X-ray diffractometry and transmission electron microscopy. The wear properties of the coatings were also investigated by means of sliding wear test. The results show that the coating consists of amorphous phase in majority and nanocrystalline phase in minority. The amorphous coatings can be obtained while the scanning speed is 3 500 mm/min and the laser power is 4.8 kW. With increase of the laser power, the amorphous phase in the coating increases when it is lower than 4.8 kW. A gradient distribution of the microhardness ranges from Hv0.2 1 208 to Hv0.2 891 in the coating from top surface of the coating to the substrate. The amorphous coating is found to possess better property of wear than AISI 1045 steel substrate.     

Synthesis and properties of electrodeposited Ni-CeO_2 nano-composite coatings

Current machinery requires metallic materials to have better surface properties. Based on an orthogonal experimental design and analysis method, the CeO_2-reinforced nickel nano-composite coatings were prepared by direct current electrodeposition in a nickel sulfate bath containing CeO_2 nanoparticles. Statistical results indicate that current density is the most significant variable in the electrodeposition processing, while temperature is the least important factor. The microstructure of Ni and Ni-CeO_2 nano-composite coatings was characterized by scanning electron microscopy(SEM) equipped with energy-dispersive spectroscopy(EDS), and X-ray diffraction(XRD).The microhardness of the Ni coating is enhanced by the incorporation of CeO_2 nanoparticles. Potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) were used to characterize the corrosion behavior of Ni and Ni-CeO_2 coatings. These studies show that NiCeO_2 coating has better corrosion resistance compared to Ni coating.     

ELECTRODEPOSITED NiSCo ALLOY USED AS HYDROGEN EVOLUTION REACTION CATHODE IN WATER ELECTROLYSIS

NiSCo catalytic cathodes were obtained by electrodeposition in a typical Watt cell with addition of NH2CSNH2 and CoCl2 Using CoCl2 concentration, current density, temperature and pH value as main factors, an orthogonal experiment was designed to determine the optimum technological conditions according to HER overpotentials. The optimum technological conditions were obtained from the minimum HER overpoten-tial-70mV. The corresponding electrochemical parameters (Tafel slope b, exchange current density io) were determined by steady-state polarization curves. The content of S, Co and its microstructure were measured by EPMA and XRD.     

Improving tribological and corrosion resistance of Ti6Al4V alloy by hybrid microarc oxidation/enameling treatments

A promising duplex coating was prepared by microarc oxidation(MAO) and enameling processes onto polished Ti6A14V alloy. The TiO_2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6A14V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6A14V alloy were evaluated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and Vickers microhardness tester, respectively.The tribological performance was investigated using a ballon-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization.Wear tests show that the enamel coating on the MAOcoated surface causes a reduction in the friction coefficient.Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6A14V than the MAO coating especially at high temperature(80 ℃). Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6A14V.     

Compound Ceramic Coatings on Ti-6AI-4V by Micro-Plasma Oxidation in NaAlO2 Solution

Micro-plasma oxidation (MPO) technique is a new technique by which compound ceramic coating can be grown in situ on AI, Ti, Mg and many other valve-metals. Compound ceramic coatings on Ti-6Al-4V alloy were prepared for different time by pulsed bi-polar MPO in NaAlO2 solution. The phase composition, morphology and the element distribution of the coatings were studied by XRD, SEM and JEOL SUPERPROBE 733 electric probe, respectively. Electrochemical Impedance Spectra (EIS) of the coatings were measured to study the structure character of the coatings. Through the proper EIS interpreting software, the “equivalent circuit“ of the coatings was established, and the fitting values of equivalent element were calculated. The coating is mainly composed of Al2TiO5, α-Al2O3 and futile TiO2. The content of Ti element in the coating is less than that of substrate; its distribution is relatively uniform, and Ti in the outer layer is less than that in the inner layer. The content of A1 in the coating is more than that of substrate, and its distribution is not even: Al in the middle part is more than that on both sides of the coating; And the EIS analysis has illustrated the double-layer structure of the coatings, and the outside layer is loosen and the inner layer compact; with the increase of the oxidizing time, the surface roughness of the coatings, and the porosity of the outer layer of the coating are increased while the compactness of the inner layer of the coatings are improved.     

Electroless plating Ni-P matrix composite coating reinforced by carbon nanotubes

Ni-P matrix composite coating reinforced by carbon nanotubes (CNTs) was deposited by electroless plating. The most important factors that influence the content of carbon nanotubes in deposits, such as agitation, surfactant and carbon nanotubes concentration in the plating bath were investigated. The surface morphology, structure and properties of the Ni-P-CNTs coating were examined. It is found that the maximum content of carbon nanotubes in the deposits is independent of carbon nanotubes concentration in the plating bath when it is up to 5 mg/L. The test results show that the carbon nanotubes co-deposited do not change the structure of the Ni-P matrix of the composite coating, but greatly increase the hardness and wear resistance and decrease the friction coefficient of the Ni-PCNTs composite coating with increasing content of carbon nanotubes in deposits.     

Microstructure and Electrochemical Properties of CoCrCuFeNiNb High-Entropy Alloys Coatings

The CoCrCuFeNiNb high-entropy alloys coatings were prepared by using plasma-transferred arc cladding process. The microstructure and electrochemical behaviors of the coating were investigated in detail. The experimental results indicated that the coating consists of a simple fcc solid solution phase and an order（Co Cr）Nb-type Laves phase. The polarization curves, obtained in 1 and 6 mol/L hydrochloric acid solutions, clearly indicated that the general corrosion resistance of the coating at ambient temperature was better than that of 304 stainless steel. The coating displayed a lower corrosion current and lower corrosion rate. Electrochemical impedance spectroscopy demonstrated that the impedance of the coating was significantly higher than that of the 304 stainless steel.     

Study on Phosphating by Ultrasonic Wave at Room Temperature for Sintered NdFeB Magnet

The corrosion behavior of a NdFeB magnet obtained at room temperature,with and without ultrasonic were investigated.The corrosion resistance was investigated by corrosion immersion tests in 3 wt%neutral NaCl solutions,potentiodynamic polarization tests and electrochemical impedance spectroscopy(EIS).The morphology of the conversion coatings on NdFeB surface were analyzed by scanning electron microscopy(SEM).And the forming mechanism of coatings was studied by potential-time curves.The tests of corrosion resistances show that the combination of phosphating treatment with ultrasonic will further improve the corrosion resistance of the NdFeB.The SEM also confirms that phosphating coating under ultrasonic is more homogeneous and compact.     

镍硫钴析氢电极的制备及性能研究

采用电沉积方法制备Ni-S-Co合金电极,通过正交实验和极化曲线测试研究了CoSO4·7H2O浓度、电流密度、电镀液温度、电沉积时间和电解液温度对Ni-S-Co电极析氢性能的影响.采用SEM,XRD和EDXA对镀层的形貌、结构和组成进行观察和分析.实验结果表明:制备具有最佳析氢活性的Ni-S-Co电极的工艺条件是25 ...     

La3+离子在EMIMBF4离子液体中的电化学行为研究

采用三电极体系对La3+离子在0.01mol/LLaCl3-0.1mol/LLiCl-EMIMBF4离子液体电化学还原制备金属镧的电极过程进行了研究。循环伏安法结合恒电位电解法研究结果表明:La3+离子的电化学还原是不可逆过程,还原步骤为一次完成La3++3e-→La。计时电流法结合恒电位电解法研究表明:La3+离子的还原过程受到扩散控制,传递系数和扩散系数分别为0.0492和(1.07～1.19)×10-6cm2/s。     

钛基钌镧氧化物涂层结构对电化学活性的影响

以RuCl33H2O和LaCl37H2O为前驱物,通过热分解方法制备Ti基Ru-La氧化物涂层,用循环伏安法(CV)、热分析(DSC-TG)法、X射线衍射(XRD)仪及原子力显微镜(AFM)等测试手段对涂层电化学活性、结构和形貌进行表征。结果表明,加入La使钌基氧化物涂层晶粒细化,扩大了活性表面积,从而使电化学活性得到提高。另外,La提高了RuCl3热分解温度,并抑制了RuO2和RuOx(x>2)结晶和长大,其混合氧化物主要以非晶态形式存在。当La含量达到30%(摩尔分数)时,晶粒尺寸达到最小值,其电化学活性最好。     

Comparative study of protective magnesium deposit behaviour obtained by continuous and pulsed currents from methylmagnesium chloride solution

Pulsed and continuous (or direct) currents were used for the electrodeposition of magnesium from methylmagnesium chloride solution. The analytical characterization of the magnesium coating was performed by scanning electron spectroscopy (SEM) and the X-ray diffraction (XRD). The electrochemical behaviour of the steel substrate coated by magnesium was assessed by electrochemical impedance spectroscopy and potentiodynamic polarization curves. The deposits morphology was quite different; it changed from smooth and irregular with cracks for the deposit obtained by continuous current (cc), to granulate with an average grain diameter of about 3 µm for the deposit obtained by pulsed current (pc). The electrochemical results showed that the protection of the steel substrate against corrosion was better with the magnesium deposit obtained by pulsed electrodeposition process.     

Sn含量对镁合金电镀Sn-Ni合金镀层性能的影响

采用阴极电沉积法在AZ3lB镁合金表面上制备了不同Sn含量的Sn-Ni合金镀层.利用x射线荧光光谱仪(XRF)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、动电位极化曲线(Tafel)、电化学阻抗谱(EIS)和硬度仪研究了不同Sn含量时镀层的结构、表面形貌、耐蚀性及硬度.结果表明,镀层中Sn含量对镀层各种性能的影...     

Comparison of a cold-sprayed and plasma-sprayed Fe25Cr20Mo1Si amorphous alloy coatings on 40Cr substrates

The purpose of this paper is to examine whether cold spraying is capable of manufacturing high-quality ferrous-based amorphous alloy coatings by comparing the performance of a cold-sprayed with a plasma-sprayed Fe25Cr20Mo1Si amorphous coating on a 40Cr substrate. The hardness, microstructure, wear resistance, and corrosion resistance of the two coatings were determined with potentiodynamic polarization curves, neutral salt spray tests, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction and their performance differences were examined. The results show that the cold-sprayed Fe25Cr20Mo1Si coating has an amorphous content of 97.63%, which is slightly higher than that for the raw powder (97.24%) and plasma-sprayed coating (96.55%). The coating hardness ranges from 720 HV to 1,030 HV, which is higher than plasma-sprayed coating (590–610 HV) and decreases the wear rate to about 2/3. The average porosity is 2.97 ± 0.59%, which is lower than that of the plasma-sprayed coating (4.95 ± 0.13%). The cold-sprayed Fe25Cr20Mo1Si coating can pass the 3,000 hr neutral salt spraying test, while the plasma-sprayed coating fails within 120 hr. The corrosion current in 3.5% NaCl solution reached to its stable value about 1.66 A/cm², which is about 1/4 of the plasma-sprayed coating (5.81 A/cm²). Upon analyzing the properties and the anticorrosion performance, it was found that there are no through-thickness pores in the cold-sprayed coating that impact its long-term anticorrosion performance. Cold spraying can be used to fabricate ferrous-based amorphous coatings instead of traditional thermal spraying technologies to obtain high-quality ferrous-based amorphous coatings.     

大气等离子喷涂制备Fe基非晶涂层及微观结构表征

选用Fe-10W-4Cr-3Ni-2Mo-4B-4Si-1C(质量比)合金粉末作为喷涂原料,采用大气等离子喷涂工艺在1Cr18Ni9Ti不锈钢基底上制备了Fe基涂层。利用扫描电镜、透射电镜和X射线衍射仪表征了粉末和涂层的相组成和微观形貌;用Olycia m3分析软件对涂层的孔隙率进行测定;用热分析系统对喷涂粉末和涂层从室温到1 173K范围的DSC曲线进行记录;同时,测定了涂层的显微硬度和结合强度。结果表明:大气等离子喷涂制备的Fe基涂层与基底的结合良好,涂层较为致密并且存在灰色氧化带组织,表现出典型的层状组织结构;涂层不但具有低的表面粗糙度和孔隙率,而且具有高的显微硬度和结合强度;所制备涂层中的非晶含量约为89.2%(质量分数),涂层中形成的晶相组织为纳米晶结构。     

Wear and Corrosion Behaviors of FeCrBSiNbW Amorphous/Nanocrystalline Coating Prepared by Arc Spraying Process

FeCrBSiNbW coatings were synthesized using robotically manipulating twin wires arc spraying system. The microstructure and mechanical properties of the coating were characterized. The coating has a laminated structure, and its porosity is 2.8%. The microstructure of the coating consists of amorphous and α-(Fe,Cr) nanocrystalline. The nanocrystalline grains with a scale of 20-75 nm are homogenously dispersed in amorphous matrix. The results show that FeCrBSiNbW coating has excellent wear and corrosion resistance. The wear resistance of the coating is about 4.6 times higher than that of 3Cr13 coating under the same testing condition. In 3.5% NaCl aqueous solution, the amorphous/nanocrystalline coating presents lower I _corr values in polarization curves and higher fitted R _t values in EIS plots than that of the 0Cr18Ni9 coating (chemical composition by EDAX analysis: C1.07-O12.38-Si0.49-Cr15.18-Mn0.89-Ni7.09-Fe62.24 at.%).     

等离子喷涂工艺对锅炉管束用Fe 基非晶涂层组织结构和耐蚀性能的影响

目的研究等离子喷涂功率和喷涂时间对锅炉管束用Fe基非晶涂层的相组成、微观组织结构及涂层耐蚀性能的影响。方法通过X射线衍射、扫描电子显微镜和三电极电化学研究进行分析。结果涂层主要由非晶相组成,表面较为平整致密;随着喷涂功率和喷涂时间的增加,涂层非晶相含量降低,孔隙率降低,致密性升高。非晶涂层在0.5mol/L H2SO4溶液和在3.5%(质量分数)NaCl溶液中均表现出良好的钝化作用,在0.5mol/L H2SO4溶液中钝化区较宽,在3.5%NaCl溶液中自腐蚀电流密度较低。随喷涂功率和时间的增加,阳极极化曲线钝化区加宽,电流密度降低。结论喷涂功率升高会导致涂层孔隙率下降,喷涂时间增加则致使涂层厚度增加,腐蚀介质渗透到基体的表面路径和阻力增加,从而可以进一步改善Fe基非晶涂层的耐蚀性能。