EDTA体系无氰碱性镀铜的电化学成核机理

采用循环伏安法和计时电流暂态曲线研究了EDTA(乙二胺四乙酸)体系无氰碱性镀铜的电化学成核机理。结果表明,铜在玻碳电极上的沉积遵循3D"成核/生长"机制;计时电流暂态曲线分析表明,在高负电位下铜离子的结晶成核方式遵循瞬时成核机制,低负电位下则趋向遵循连续成核机制,且过电位增加会促进铜离子结晶形核,随最大电流Im增大,电结晶成核数增多。     

镍铁钨合金的电沉积行为研究

应用电化学方法研究了Ni-Fe-W合金的电沉积机理,并对Ni-Fe-W合金镀层的微观形貌和组成成分进行了表征.循环伏安测试表明,Ni-Fe-W合金电沉积是不可逆电极过程,且WO42-浓度的变化不改变电沉积机理;计时电流法研究表明,Ni-Fe-W合金在铜电极上的电结晶过程符合三维瞬时成核的生长机理;SEM和EDS结果表明,Ni-Fe-W合金镀层由纳米级的小颗粒组成,合金的组成为Ni 58.76%,Fe 32.72%,W 8.52%(原子数分数,后同).     

占空比对高频脉冲电沉积( Ni-Co) / 纳米 Al2O3复合镀层的影响

采用高频脉冲电沉积法制备(Ni-Co)/纳米Al2O3复合镀层,研究了占空比对复合镀层沉积速率、成分、形貌及表面显微硬度的影响。结果表明:随着占空比由0.3提高至0.5,复合镀层的沉积速率增加,晶粒尺寸变大,表面变粗糙,并且Co含量降低,Ni含量增加,纳米Al2O3颗粒含量变化不明显,Co含量的降低导致硬度降低。     

海工机械Ni-Co/SiC纳米复合镀层微观结构及耐蚀性能研究

采用扫描电子显微镜（SEM）、能谱分析（EDS）和X射线衍射（XRD）研究了纳米SiC颗粒对Ni-Co镀层结构和形貌的影响规律,通过EIS, Tafel电化学方法探究了Ni-Co/SiC电沉积过程及镀层的电化学腐蚀性能。结果表明,Co的加入使Ni镀层晶粒细化,孔隙率降低,并使部分结构非晶化,耐蚀性提高。纳米SiC颗粒具有促进Ni-Co合金形核长大和提高其硬度的双重作用,使Ni-Co/SiC耐磨性增强,与Ni-Co合金相比其Ecorr更正,icorr更小,Rc更大,具有优异的耐蚀性和耐磨性。Ni-Co/SiC具有更好的服役稳定性,而Ni-Co合金服役中耐蚀性降低较快。在服役过程中,镀层腐蚀过程经历了三个阶段,即浸润阶段,电解液在涂层中传输的扩散控制阶段,电解液到达基材表面后扩散速率已大于电化学速率的电化学控制阶段。Ni-Co/SiC合金具有良好的耐磨耐蚀性能,在海水多重因素交互作用下能够对海工机械提供长效防护,在海工防护领域具有良好的应用前景。     

纳米SiO2粒子/镍基复合镀层腐蚀行为

将纳米SiO2粒子通过超声分散引入到化学镀Ni-P合金镀液中,在碳钢基体表面共沉积得到纳米SiO2粒子/镍基复合镀层。通过X射线衍射(XRD)、扫描电镜(SEM)对Ni-P镀层和纳米SiO2粒子/镍基镀层的微观结构形貌进行了分析;采用失重法和电化学方法研究了纳米SiO2粒子/镍基复合镀层在3.5%NaCl溶液中的腐蚀行为。结果表明,纳米SiO2粒子/镍基复合镀层仍是非晶态,纳米SiO2粒子的加入提高了镀层的致密性,提高了镀层的耐腐蚀性能。     

海工机械Ni-Co/SiC纳米复合镀层微观结构及耐蚀性能

采用扫描电子显微镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)研究了纳米SiC颗粒对Ni-Co镀层结构和形貌的影响,通过EIS,Tafel电化学方法探究了Ni-Co/SiC电沉积过程及镀层的电化学腐蚀性能。结果表明,Co的加入使Ni镀层晶粒细化,孔隙率降低,并使部分结构非晶化,耐蚀性提高。纳米SiC颗粒具有促进Ni-Co合金形核长大和提高其硬度的双重作用,使Ni-Co/SiC耐磨性增强,与Ni-Co合金相比其E_(corr)更正,i_(corr)更小,R_c更大,具有优异的耐蚀性和耐磨性。Ni-Co/SiC具有更好的服役稳定性,而Ni-Co合金服役中耐蚀性降低较快。在服役过程中,镀层腐蚀过程经历了3个阶段:即浸润阶段;电解液在涂层中传输的扩散控制阶段;电解液到达基材表面后扩散速率已大于电化学速率的电化学控制阶段。Ni-Co/SiC合金具有良好的耐磨耐蚀性能,在海水多重因素交互作用下能够对海工机械提供长效防护,在海工防护领域具有良好的应用前景。     

三价铬超声-脉冲电沉积Ni-Cr/SiC纳米复合镀层

利用超声-脉冲复合电沉积法,在三价铬镀液体系中,添加羧酸盐-尿素配合剂和SiC纳米颗粒,制备了Ni-Cr/SiC纳米复合镀层。研究了超声-脉冲工艺参数对SiC纳米粒子复合量、铬含量以及镀层厚度的影响;利用电化学法分析了超声波对基质金属电沉积行为的影响。结果表明,超声-脉冲作用均有利于基质金属铬-镍的电沉积,从而提高镀层厚度及SiC与Cr的含量。利用SEM、XRD、和EDS分别对Ni-Cr/SiC纳米复合镀层的表面形貌、微观结构和相组成等进行表征。结果表明,采用该技术可制备厚度为21.2μm、SiC和Cr含量分别为3.8%和24.68%(质量分数)的Ni-Cr/SiC纳米复合镀层。磨损量和腐蚀曲线测试结果表明,SiC含量高的复合镀层,其耐磨性和耐蚀性更好。     

Zn-Co-TiO2纳米复合镀层的光生阴极保护特性

用纳米复合电沉积技术在低碳钢表面制备了Zn-Co-TiO₂纳米复合镀层。用SEM、EDS和XRD等技术手段对样品进行了分析与表征。结果表明,镀层中TiO₂的含量约为12.63%,并均匀分散在镀层中,可以起到细化Zn-Co合金镀层晶粒的作用,并使Zn-Co合金镀层的耐蚀性能得到提高。用紫外光辅助照射电极电位监测方法研究Zn-Co-TiO₂纳米复合镀层光生阴极保护特性。结果表明,在紫外光照射下,镀层的电极电位负移,说明镀层具有光生阴极保护性能;关闭紫外光灯后,其电极电位正移,但仍低于镀层未光照前的电极电位。在400℃下氧化6 h后镀层表面生成了ZnO薄膜,其与TiO₂的协同作用可进一步提高镀层的光生阴极保护性能。     

石墨烯颗粒对Ni-Co-石墨烯复合镀层的表面性能影响

为了得到性能更加优异全面的复合镀层,使用复合电沉积技术制备不同石墨烯颗粒大小的Ni-Co-石墨烯复合镀层,并制备了Ni-Co合金镀层。测试镀层的表面形貌,相结构,显微硬度,耐磨性和耐蚀性能。结果显示,石墨烯在电沉积中很好的嵌入到了镀层基质中,而且石墨烯的存在并没有改变镀层基质的晶体结构;石墨烯的填加增加了复合镀层的显微硬度,最高可达805HV;降低了复合镀层的摩擦系数,在一定程度上减少了粘着磨损的面积;复合镀层的自腐蚀电流密度可以降低到1.0905×10-5A/cm2,低于Ni-Co合金镀层的自腐蚀电流密度。说明了石墨烯的添加增强了复合镀层的硬度,耐磨性和耐蚀性。     

脉冲电沉积纳米晶Ni-Co合金镀层腐蚀特性研究

采用X射线衍射(XRD)、扫描电镜(SEM)、能谱分析(EDS)等方法研究了脉冲电沉积法制各纳米晶Ni和纳米晶Ni-Co合金镀层的组织结构、表面形貌和成分.用浸泡法和电化学极化法研究了纳米晶Ni和不同Co含量的纳米晶Ni-C0合金镀层在3.5%NaCl(质量分数,下同)和5%HCl溶液中的腐蚀行为.结果表明:通过脉冲电沉积法制各的Ni和Ni-Co合金镀层具有典型的纳米晶结构; 随着含Co量的增加,镀层的晶粒尺寸减小,硬度增加;所制备的纳米晶Ni-Co合金镀层组织结构均匀致密,其在3.5%NaCl溶液和5%HCl溶液中的耐蚀性均优于纳米晶Ni镀层;纳米晶Ni-Co合金镀层在3.5%NaCl溶液的浸泡腐蚀中腐蚀极少,表现出优异的耐腐蚀性能,而在5%HCl溶液中的腐蚀形态则为均匀腐蚀.     

Electrodeposition and characterization of Ni-Co/SiC nanocomposite coatings

Ni-Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni-Co alloy and Ni-Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.% SiC in the Ni-Co matrix increased hardness more than 60%. The average depth of scratch in the mentioned composite coating was about 15% less than that of the Ni-Co alloy coating. The corrosion penetration rate (CPR) of the Ni-Co alloy coating in a 3.5 wt.% NaCl solution was more than 17 times greater than that of the Ni-Co/SiC coating with 30.5 vol.% SiC.     

Ni-Co/纳米金刚石复合镀层抗磨损性能的研究

采用电沉积法在45#钢样品表面制备了含有纳米金刚石的镍-钴合金基复合镀层。对复合镀层的显微硬度和微观结构进行了测试。并考察了阴极电流密度、镀液pH值等主要工艺参数对纳米复合镀层耐磨性的影响。结果表明：纳米金刚石的弥散强化作用，可以有效地提高镀层的硬度。在干摩擦条件下，纳米复合镀层的耐磨性是镍-钴合金镀层的3倍；     

Beneficial effects of Co2＋ on co-electrodeposited Ni-SiC nanocomposite coating

Ni-SiC nanocomposites were fabricated by co-electrodeposition of nickel with silicon carbide nanoparticles on the pure nickel substrates from a nickel sulfate bath with and without the addition of Co2+. The presence of Co2+ in the electrolyte modifies the Ni matrix to Ni-Co solid solution matrix. It helps to refine the grain size of the nanocomposite coating and improves the content of SiC dispersed in the matrix, and consequently results in higher microhardness. The cathodic polarization curves and electrochemical impedance spectroscopy (EIS) at cathodic potential were investigated in the electrolyte with and without Co2+. A modified cathodic polarization curve with a positive shift in reduction potential and a smaller capacitive loop of EIS are observed. These are attributed to the strong adsorption of Co2+ on the SiC nanoparticles. Consequently, it increases the forces of electrostatic attraction between the SiC nanoparticles and the cathode, which promotes the codeposition of SiC nanoparticles in the matrix.     

Synthesis and Characterization of Functionally Gradient Ni-ZrO<Subscript>2</Subscript> Composite Coating

For the first time, functionally ZrO₂ content graded Ni-ZrO₂ composite coating has been successfully co-electrodeposited from a bath with gradually increasing stirring rate. For this, different composite coatings were electroplated in the same bath with different stirring rates to find the optimum stirring rate in which the maximum content with uniform distribution of ZrO₂ particles in the coating can be achieved. To produce ZrO₂ content graded Ni-ZrO₂ composite coating, the stirring rate was continuously increased from 0 to optimum value. By increasing of ZrO₂ particles content, the microhardness increases from interface towards the surface of the coating. The results of wear resistance measurements, Electrochemical impedance spectroscopy and potentiodynamic polarization test revealed that wear and corrosion resistances of functionally graded Ni-ZrO₂ (FGNZ) is higher than that of ordinary Ni-ZrO₂ (ONZ) composite coating. This result has been attributed to lower mechanical mismatch between coating and substrate in the functionally graded composite coating with respect to the uniformly distributed one.     

Study on the characteristics of Ni-W-P composite coatings containing nano-SiO2 and nano-CeO2 particles

The aim of this research work was to co-deposit nano-SiO₂ and nano-CeO₂ particles into the Ni-W-P alloy coating in order to improve the surface properties further. Ni-W-P-SiO₂-CeO₂ composite coatings were prepared by co-deposition of nickel, tungsten, phosphorus, nano-SiO₂ and nano-CeO₂ particles on the surface of 15 steel from the electroplating bath which nano-SiO₂ and nano-CeO₂ particles were suspended by high speed mechanical stirring. The characteristics of the composite coatings were assessed by micro hardness test, Taber Abrader test, scanning electron microscopy and X-ray diffraction. The results obtained in this study indicate that the nano-SiO₂ and nano-CeO₂ particles were dispersed evenly within the Ni-W-P alloy coating and the bonding between the matrix metal and nano-SiO₂ and nano-CeO₂ particles is compact. That the co-deposition of nickel, tungsten, phosphorus, nano-SiO₂ and nano-CeO₂ particles leads to uniform Ni-W-P-SiO₂-CeO₂ composite coatings possessing better micro hardness and abrasion resistance properties when heat-treated at 400 °C for 3 h. In addition, that nano-CeO₂ and nano-SiO₂ particles can increase the thermal stability of Ni-W-P alloy coating at high temperature.     

Comparative study on corrosion protection properties of electroless Ni‐P‐ZrO2 and Ni‐P coatings on AZ91D magnesium alloy

Electroless Ni‐P‐ZrO₂ and Ni‐P coatings on AZ91D magnesium alloy were prepared, and their corrosion protection properties were compared in this paper. The potentiodynamic curves and electrochemical impedance spectroscopy (EIS) of the coated magnesium alloy in 3.5% NaCl solution showed that the corrosion performance of Ni‐P‐ZrO₂ composite coating was superior to that of Ni‐P coating. The same conclusion was obtained with salt spray and immersion tests. The corrosion morphologies of two kinds of coatings with various immersion time intervals in 3.5% NaCl solution indicated that most corrosion products concentrated on the nodules boundaries of Ni‐P coating and blocked corrosion pit was the main corrosion form. For the Ni‐P‐ZrO₂ coating, tortuous nodules boundaries were not the weak sites of the coating and corrosion initiated from the nickel phosphor alloy around the nanometer powders. Open corrosion pits occurred on the composite coating surface, and the coating was corroded gradually. Thus, the Ni‐P‐ZrO₂ coating exhibited better corrosion protection property to magnesium alloy substrate than Ni‐P coating.     

An Investigation into the Corrosion Behavior of MgO/ZrO<Subscript>2</Subscript> Nanocomposite Coatings Prepared by Plasma Electrolytic Oxidation on the AZ91 Magnesium Alloy

Plasma electrolytic oxidation (PEO) of AZ91 Mg alloys was performed in ZrO₂ nanoparticles containing Na₂SiO₃-based electrolytes. The phase composition and the microstructure of PEO coatings were analyzed by x-ray diffraction and scanning electron microscopy followed by energy dispersive spectroscopy. Pitting corrosion properties of the coatings were investigated using cyclic polarization and electrochemical impedance spectroscopy tests in a Ringer solution. The results showed the better pitting corrosion resistance of the composite coating, as compared to the oxide one, due to the thickened inner layer and the decrease in the surface defects of the composite coating. Also, the PEO process decreased the corrosion current density from 25.06 µA/cm² in the Mg alloy to 2.7 µA/cm² in the oxide coating and 0.47 µA/cm² in the composite coating.     

Al2O3-ZrO2 mixed oxide composite incorporated aluminium rich zinc coatings for high wear resistance

Corrosion resistance and wear resistance are the two important parameters for high performance of zinc galvanic coating. In the present work, the improvement of these two characteristics was achieved by the incorporation of Al₂O₃-ZrO₂ mixed oxide composite in the coating. Al₂O₃-ZrO₂ mixed oxide composite was synthesized from ZrOCl₂·8H₂O. Aluminium rich zinc coatings with high sliding wear resistance was developed from a galvanic bath containing the mixed oxide. Based on the performance of the coating during physicochemical and electrochemical characterization, the concentration of mixed oxide composite in the bath was optimized as 0.50 wt% Al₂O₃-0.50 wt% ZrO₂. While rich in Al-metal content in the coating caused high corrosion resistance, the incorporation of the mixed oxide improved structural characteristics of the coating resulting in high wear resistance also. The coating was nonporous in nature and even the interior layers had high stability. The coatings have potential scope for high industrial utility.     

Corrosion performance of epoxy coatings containing silane treated ZrO2 nanoparticles on mild steel in 3.5% NaCl solution

Clear epoxy coatings were modified by adding various levels of ZrO₂ nanoparticles. In order to achieve proper dispersion of nanoparticles in the epoxy-based coating and making possible chemical interactions between nanoparticles and polymeric coating, the surface of the nanoparticles was treated with amino propyl trimethoxy silane (APS). Corrosion performance of mild steel coated specimens was investigated employing EIS, electrochemical noise (ECN) techniques and salt spray test. Coatings with 2–3 wt% ZrO₂ nanoparticles possessed the best corrosion performance among the coating specimens. Possible chemical interactions between polymeric matrix and treated nanoparticles in nanocomposites cause high barrier properties and ionic resistances.