Electrochemical behavior of Cu-Zn-Al shape memory alloy after surface modification by electroless plated Ni-P

The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.

Preparation and Properties of Conductive Polyester Fabric Based on Ni-P Chemical Plating with Pd-Chitosan Activation

In this study, an effective deposition of Ni-P alloy on polyester （PET） was proposed by a chemical plating method with PdCl2 solution and a chelating agent chitosan （CTS）. As a critical step in chemical plating of making electromagnetic shielding fabric, the optimized processing of textile chemical plating is the fabrics padded with 3 % acetic acid （HAc） solution containing 10 g/L CTS and 5.5 mL/L formaldehyde （HCHO） as cross-linking agent for 20 min at room temperature. The highest weight gain and the lowest surface resistance of the treated fabric were achieved by the optimum pretreatment method. The CTS-Pd PET fabrics were characterized by scanning electron microscopy （SEM）, scanning probe microscope （SPM）, and the glancing incident angle X-ray diffraction （XRD） pattern. The results showed that CTS acting as a chelating had effectively fixed Pd （H） ions. A uniform and continuous structure of Ni-P plating layer was obtained using the CTS pretreatment.

Magneto-Impedance Effect of Composite Wires Prepared by Chemical Plating under DC Current

CuBe composite wires of 100 μm in diameter coated with a layer of NiCoP were prepared by a chemical plating method under DC current(CPUDC). The influences of DC current on coating morphology,deposition rate, composition, giant magneto-impedance(GMI) effect and magnetic properties were investigated.It was shown that the circumferential domain structure of coating layer was induced by the DC current going through the wires. A maximum GMI ratio of 870% was obtained in the composite wire prepared under 150 m A and tested at 180 k Hz. It is 30 times higher than that of the composite wire plated in the same condition by conventional chemical plating method, indicating that CPUDC is an easy and effective approach to obtain composite wires and its applications will be further extended on magnetic sensors.

Thermal Diffusion Effect on MHD Heat and Mass Transfer Flow past a Semi Infinite Moving Vertical Porous Plate with Heat Generation and Chemical Reaction

The objective of present work is to study the thermo diffusion effect on an unsteady simultaneous convective heat and mass transfer flow of an incompressible, electrically conducting, heat generating/absorbing fluid along a semi-infinite moving porous plate embedded in a porous medium with the presence of pressure gradient, thermal radiation field and chemical reaction. It is assumed that the permeable plate is embedded in a uniform porous medium and moves with a constant velocity in the flow direction in the presence of a transverse magnetic field. It is also assumed that the free stream consists of a mean velocity, temperature and concentration over which are super imposed an exponentially varying with time. The equations of continuity, momentum, energy and diffusion, which govern the flow field, are solved by using a regular perturbation method. The behavior of the velocity, temperature, concentration, Skin-friction, rate of heat transfer and rate of mass transfer has been discussed for variations in the physical parameters. An increase in both Pr and R results a decrease in thermal boundary layer thickness. However, concentration decreases as Kr, Sc increase but it increases with an increase in both So and δ.

Visco-elastic fluid flow past an infinite vertical porous plate in the presence of first-order chemical reaction

An analysis has been developed to study the unsteady free convection flow of an incompressible visco-elastic fluid on a continuously moving vertical porous plate in the presence of a first-order chemical reaction. The governing equations are solved numerically using an implicit finite difference technique. The obtained numerical solutions are compared with the analytical solutions. The velocity profiles are presented. A parametric analysis is performed to illustrate the influences of the visco-elastic parameter, the dimensionless chemical reaction parameter, and the plate moving velocity on the steady state velocity profiles, the time dependent friction coefficient, the Nusselt number, and the Sherwood number.

Chemical Reaction and Thermal Diffusion Effects on Mass Transfer Flow through an Inclined Plate

A numerical investigation of boundary layer mass transfer flow through an inclined plate with the effect of chemical reaction and thermal diffusion is presented in this study. The governing partial differential equations (PDE) are transformed to a system of dimensionless non-similar coupled PDEs. The transformed, non-similar conservations equations (momentum balance equation, energy balance equation and concentration balance equation) are then solved using a numerical approach known as explicit finite difference method (EFDM). Basically EFDM introduced for the unsteadiness in the momentum, temperature, and concentration fluid fields is based on the time dependent fluid velocity, temperature and concentration of the boundary surface. During the course of discussion, it is found that the various parameters related to the problem influence the calculated resultant expressions. The computed numerical solution results for the velocity, temperature, and concentration distribution with the effect of various important dimensionless parameters (Grashof number, Modified Grashof number, Prandtl number, Schmidt number, Soret number, Dufour number, chemical reaction parameter and inclination parameter) entering into the problems are critically analyzed and discussed graphically. It can be seen that two physical phenomena chemical reaction and thermal diffusion can greatly effect on the boundary layer fluid flows through an inclined plate.

Electroless Ni-P plating on Mg-Li alloy by two-step method

Pretreated Mg-Li alloy sheets were pre-plated in a NiCO3？2Ni（OH）2？4H2O solution to form a thin Ni-P alloy film and then plating in a NiSO4？6H2O solution was carried out to obtain a protective coating.The surface morphology,structure and corrosion resistance of the coating were studied.The results showed that a flat,bright and compact plating layer,which was integrated into the matrix metal,was obtained.The P content of the Ni-P coating reached 13.56%（mass fraction）.The hardness value of the Ni-P coating was about HV 549.The polarization curve showed that the corrosion potential of the Ni-P coating reached ？0.249 V（vs SCE）.A long passivation region was found on the polarization curve,and this phenomenon indicated that the coating has an excellent anti-corrosion property.

Electroless plating and growth kinetics of Ni-P alloy film on SiC_p/Al composite with high SiC volume fraction

After Sn/Pd activating, the SiCp/Al composite with 65% SiC (volume fraction) was coated by electroless Ni?P alloy plating. Surface morphology of the composite and its effect on the Ni?P alloy depositing process and bonding action of Ni and P atoms in the Ni?P alloy were studied. The results show that inhomogeneous distribution of the Sn/Pd activating points results in preferential deposition of the Ni?P alloy particles on the Al alloy and rough SiC particle surfaces and in the etched caves. The Ni?P alloy film has an amorphous structure where chemical bonding between Ni and P atoms exists. After a continuous Ni?P alloy film formed, electroless Ni?P alloy plating is not affected by surface morphology and characteristics of the SiCp/Al composite any longer, but by the electroless plating process itself. The Ni?P alloy film follows linear growth kinetics with an activation energy of 68.44 kJ/mol.

Study of Electroless Ni-P-CNTs Composite Plating

The electroless Ni-P-carbon nanotubes composite plating was studied on the copper substrate. Metallurgical microscope, scanning electronic microscope, X-ray diffractometer and micro hardness tester were used to study the structure, constitution and performance of the electroless Ni-P-carbon nanotubes composite deposit. Experiential results show that, with the increment of carbon nanotubes content in electroless plating solution, the grain size on the sample surface decreases whereas the density of grains and the hardness for composite deposit increases. Moreover, adding carbon nanotubes not only improves the degree of crystallization for the composite deposit but also helps their transformation from the amorphous state to the nanocrystal state.

High-temperature tribological properties of Ni-P alloy coatings deposited by electro-brush plating

High-temperature tribological properties of Ni-P alloy coatings processed by electro-brush plating on 20CrMo steel have been investigated. A baU-on-disc configuration was employed and 4 mm diameter Si3N4 balls were used as static counterpart. All the wear tests were carried out at 450℃ for 180 rain without lubricants. The electro-brush plating Ni-P coating is amorphous in as-deposited condition, and it becomes polycrystalline with the formation of Ni and Ni3P after heat treatment at 450℃for 1 h. The friction coefficient of the Ni-P coating is just 50% of that of the 20CrMo steel at the friction temperature of 450℃. A mild adhesive wear mechanism was found for the electro-brush plating Ni-P coating tested at 450℃, whereas for the 20CrMo steel at the same temperature a mixed adhesive and abrasive wear mechanism was observed.

Pretreatment-free Ni-P plating on magnesium alloy at low temperatures

Electrochemically promoted electroless plating(EPEP)was used for the application of pretreatment-free Ni-P coating on AM60B magnesium alloy at low temperatures and the obtained coating was characterized by SEM,AFM,EDS and XRD techniques.Compact,uniform,and medium-phosphorus Ni-P coating with mixed crystalline-amorphous microstructure was obtained by applying a cathodic current density of4mA/cm^2at50℃.Also,island-like nickel clusters were deposited on the alloy surface under the same plating condition but without applying the cathodic current.In addition,the durability of the magnesium alloy against corrosion was strongly improved after plating via EPEP technique which was revealed by electrochemical examinations in3.5%NaCl(mass fraction)corrosive electrolyte.The results of the electrochemical examinations were confirmed by microscopic observations.Thickness,microhardness,porosity and adhesive strength of the deposits were also qualified.

Evaluation of residual stress and corrosion behaviour of electroless plated Ni-P/Ni-Mo-P coatings

Single Ni-P and Ni-Mo-P coatings as well as duplex Ni-P/Ni-Mo-P coatings with the same compositions were prepared by electroless plating.The residual stresses of the coatings on the surface and cross sections were measured by nanoindentation and AFM analysis,and the corrosion behaviour of the coatings in10%HCl solution was evaluated by electrochemical methods,to establish the correlation between the residual stresses and corrosion behaviour of the coatings.The results showed that the single Ni-P and duplex Ni-P/Ni-Mo-P coatings presented residual compressive stresses of241and206MPa respectively,while the single Ni-Mo-P coating exhibited a residual tensile stress of257MPa.The residual compressive stress impeded the growth of the pre-existing porosity in the coatings,protecting the integrity of the coating.The duplex Ni-P/Ni-Mo-P coatings had better corrosion resistance than their respective single coating.In addition,the stress states affect the corrosive form of coatings.

Wear and Corrosion Resistance of Electroless Plating Ni-P Coating on P110 Steel

In order to improve the surface performance and increase the lifetime of P 110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/element distribution and phase constitution of the Ni-P coating were analyzed using scanning electron microscope （SEM） equipped with energy dispersive spectrometry （EDS） and X-ray diffraction （XRD）. Tribological and electrochemical measurement tests were applied to investigate the wear and corrosion resistance of P110 steel and the Ni-P coating. The results showed that a uniform and compact, high phosphorous Ni-P coating was formed. The obtained Ni-P coating indicated certain friction-reduction effect and lower mass loss during friction-wear tests. The Ni-P coating also exhibited higher corrosion resistance in comparison with bared P 110 steel. The obtained N i-P coating has significantly improved the surface performance of P110 steel.

Investigation on a Non-cyanide Plating Process of Ni-P Coating on Magnesium Alloy AZ91D

In this research we presented a non-cyanide plating process of Ni-P alloy coating on Mg alloy AZ91D. By applying a new process flow of electroless nickel plating in which zinc coating is used as transition of Ni-P coating on Mg alloy AZ91D, the process of copper transition coating plated in the cyanides bath can be replaced. A new bath composed of NiSO4 was established by orthogonal test. The results show that zinc transition coating can increase the adhesion and protect the Mg alloy substrate from the bath corrosion. The optimal plating bath composition is NiSO4·6H2O 20 g/L, NaH2PO2·H2O20g/L and C6H8O7·H2O 2.5 g/L, and optimal bath acidity and optimal plating temperature are pH 4.0 and 95℃, respectively. The present process flow is composed of ultrasonic cleaning→alkaline cleaning→acid pickling→activation→double immersing zinc→electroplating zinc→electroless nickel plating→passivation treatment. The present non-cyanide process of electroless nickel plating is harmless to our surroundings and Ni-P coating on Mg alloy AZ91D produced by present process possesses good adhesion and corrosion resistance.

桥梁支座球冠衬板化学镀镍磷工艺研究

主要研究了桥梁支座球冠衬板不同的化学镀镍磷工艺路线,结果表明当基材粗糙度Ra≤0.12μm、磷含量12%、施镀4h后进行钝化处理为球冠衬板最优的工艺路线,同时发现不同热处理工艺和基材粗糙度对化学镀镍磷镀层硬度、耐蚀性都有影响,当热处理温度为200℃时,镀层硬度有少许增加,耐蚀性能无变化;当热处理温度为360℃时,镀层硬度明显增加,耐蚀性能下降明显,基材粗糙度Ra≥1.6时,镀层耐蚀性能下降明显。

线锯用金刚石微粉表面化学镀镍工艺及性能研究

金刚石微粉性能是提升金刚石线锯性能的关键因素。用化学镀方法在线锯用金刚石微粉表面镀镍,通过正交试验研究金刚石粒度、次亚磷酸钠浓度、镀液pH值和镀液温度对化学镀镀层沉积速率、镀层密度、镀层耐腐蚀性能、镀层致密度等性能的影响。结果表明:M1/2、M6/12、M20/30三种不同粒度金刚石微粉,在次亚磷酸钠浓度为25~35g/L、化学镀液pH值为3~11、化学镀温度为30℃~90℃时,针对镀层沉积速率、镀层密度和镀层耐腐蚀性的最佳工艺参数不同;不同粒度的金刚石微粉在相同工艺条件下化学镀镍,金刚石微粉粒度越大,镀层越均匀致密;金刚石微粉化学镀镍各工艺参数之间相互作用,共同影响镀层性能。对于不同粒度的金刚石微粉,各因素对镀层性能的影响权重不同,因此针对不同粒度、不同镀层性能需求的金刚石微粉应采取不同的镀覆工艺参数。

镁合金建筑模板的表面化学镀与耐蚀性能

采用化学镀的方法在镁合金建筑模板表面分别制备了单一Sn膜、单一Zn膜和复合Sn-Zn膜,对比分析了pH、温度和膜层数对镁合金表面膜层显微形貌和电化学性能的影响。结果表明:对于单一膜,在pH值为6.0、温度为75℃时制备的单一Sn膜和在pH值为9.5、温度为75℃时制备的单一Zn膜都具有较好成膜质量;当膜层数为9时,复合Sn-Zn膜完全覆盖镁合金基体且膜层成膜质量较好。相较于镁合金基体,单一Sn膜、单一Zn膜、复合Sn-Zn膜的腐蚀电位都发生正向移动,腐蚀电流密度发生不同程度减小,复合Sn-Zn膜的腐蚀电位最正、腐蚀电流密度最小。在镁合金基体表面化学镀单一Sn膜、单一Zn膜、复合Sn-Zn膜都有助于提升镁合金的耐蚀性能,且复合Sn-Zn膜对基体的保护作用要优于单一Sn膜、单一Zn膜。

Preparation and tribological performances of Ni-P-multi-walled carbon nanotubes composite coatings

Multi-walled carbon nanotubes （MWNTs） were wet-milled in the presence of ammonia and cationic surfactant and then used as reinforcements to prepare Ni-P-MWNTs composite coatings by electroless plating. The tribological performances of the composite coatings under dry condition were investigated in comparison with 45 steel and conventional Ni-P coating, Micrographs show that short MWNTs with uniform length and open tips were obtained through the wet-milling process. The results of wear test reveal that the Ni-P-MWNTs composite coatings posses much better friction reduction and anti-wear performances when compared with 45 steel and Ni-P coating. Within the MWNTs content range of 0.74%-1.97%, the friction coefficient and the volume wear rate of the composite coatings decrease gradually and reach the minimum values of 0.08 and 6.22x10-15 m3/（N.m）, respectively. The excellent tribological performances of the composite coatings can be attributed to the introduction of MWNTs, which play both roles of reinforcements and solid lubricant during the wear process.

激光处理在化学镀Ni-P合金镀层上的应用

研究了不同的激光工艺参数对化学镀Ni-P合金镀层表面形貌、结构和硬度的影响。结果表明,激光处理也可使镀层发生晶化转变,析出弥散分布的金属间化合物Ni3P,从而提高了镀层的硬度。同时在镀层硬度达到最大值时,其对基材也不产生影响。

化学复合镀Ni-P-PTFE镀层耐蚀性研究

化学复合镀Ni-P -PTFE镀层具有低的摩擦系数和自润滑性能 .运用电化学方法进一步探讨其耐蚀性 ,以拓宽其应用场所 ,进一步推动Ni-P -PTFE复合镀层进入工业领域 .