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 (II) 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.

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.

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.

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。

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 .

Ni-P-SiC复合镀工艺的优化

为进一步提高镍磷镀层的耐磨性 ,在普通镍磷化学镀的基础上 ,进行了 Ni P Si C复合镀及磨损试验。用正交设计法对影响复合镀工艺的主要因素 ,活性剂、Si C、温度、p H值和稳定剂进行了优化 ,同时就各因素对镀层耐磨性的影响进行了分析 ,得出了一组最佳 Ni P Si C施镀工艺参数 :活性剂 0 .15 g.L-1,Si C12 .5g.L-1,施镀温度 90℃ ,p H值 4 .6 ,稳定剂 0 .5 5 mg.L-1。试验验证结果表明 ,该工艺稳定 ,获得的镀层光亮、致密、耐磨性好。

高温热处理对高磷Ni-P化学镀层耐蚀性的影响

对高磷 ( 12 .8%P)化学镀Ni -P合金镀层进行了 75 0℃高温热处理 ,研究了经高温热处理后镀层的耐蚀性。结果表明 ,高温热处理后 ,镀层耐蚀性大大优于镀态。晶粒长大、晶界面积减少以及镀层表面生成较厚的。

Ni-P合金化学镀非晶态合金的耐蚀性研究

研究了化学镀非晶态Ni P合金的耐蚀性及耐蚀机理 ,证明了非晶态Ni

十六烷基三甲基溴化铵对化学镀Co-Ni-P的影响

通过正交试验得到化学镀Co-Ni-P的优化基础配方(g.L-1)和施镀条件:CoSO4.7H2O为16、NiSO4.6H2O为9、NaH2PO2.H2O为30、Na3C6H5O7.2H2O为60、(NH4)2SO4为70,于pH=10、80℃施镀1 h;研究了阳离子表面活性剂十六烷基三甲基溴化铵对Co-Ni-P镀层成分以及镀层与基体结合力的影响。实验结果表明,在优化的基础配方中加入30 mg.L-1的十六烷基三甲基溴化铵,镀液稳定性好,沉积速率加快,镀层表面光亮,镀层与基体的结合力增强,镀层中钴含量增加,镍、磷含量降低,镀层的性能得到了很大的改善。

温度对Ni-P化学镀层结合力影响的研究

用弯曲法、划痕法研究了镀后加热温度对Ni-P化学镀层结合力的影响,结果表明:镀后退火温度越高,镀层结合力越好,但温度过高时,镀层硬度将下降。用金相观察及电子探针分析,探讨了镀后退火温度影响结合力的机理。结果指出:退火时将在镀层和基体界面上发生Ni与Fe的互扩散,形成Ni-Fe合金扩散层,从而提高了结合力。为了能在保证镀层硬度的前提下提高结合力,本文提出了二次镀覆的设想,获得较好试验结果。

化学镀Ni-P-(CF)_n复合镀层的研究

对化学镀Ni—P— (CF) n 复合镀层工艺进行了较全面的研究 ,详细测定和评述了氟化石墨浓度与镀层中(CF) n 粒子含量及镀速的关系 ,以及基础镀液性质和操作条件 (如温度、pH值、搅拌方式等 )对复合镀的影响。提出了一种具有实用价值的化学镀Ni—P— (CF) n 复合镀层工艺技术。与电镀相比 ,该复合镀层无应力、难以从机体上剥离、硬度高、无磁性、耐热性好。

复合化学镀Ni-P-石墨工艺对镀速的影响

研究了用化学复合镀方法在A3碳钢基体上镀覆Ni-P-石墨复合镀层,不同的施镀工艺条件对镀层中石墨粒子的分布密度及镀速的影响.结果表明:温度、pH值升高,镀速会迅速增加;石墨的体积分数大小对镀速的影响不大;络合剂柠檬酸钠的质量浓度对镀速影响较大.确定了实现高镀速的工艺条件:镀液中含NiSO4为25 g/L,NaH2PO2为30 g/L,络合剂为5 g/L,石墨为4 g/L,稳定剂的质量分数为5×10-6~10-5,施镀温度为90℃,镀液的pH值为5.0;在此工艺条件下镀速可大于8.5μm/h,镀层中石墨的体积分数达到22%.

化学镀Ni-P合金工艺

研究了化学镀镍磷合金溶液的组成对镀层沉积速度及耐蚀性的影响 ,确定了Ni-P合金的化学镀工艺 .该工艺沉积速度较快 ,平均沉积速度约为 1 1 μm/h ,且在HCl,H2 SO4 等酸性介质中 ,表现出良好的耐蚀性能 .