实践逼出来的点滴创新第五部分——光亮酸性镀锡液中铜杂质的去除

传统的黄血盐沉淀过滤法除铜效果不好,不能用于实际的镀锡生产。根据难溶物的溶度积常数,最终找出了一种去除酸性光亮镀锡液中铜杂质的方法:在强烈搅拌下,缓慢加入理论量110%的稀Na2S溶液(现配现用),然后滤除所生成的沉淀。该法在生产中应用3年多,效果均良好,消除了因铜杂质所引起的硫酸盐镀锡层低电流密度区无光、发黄、发黑等故障。     

硫酸盐三价铬镀铬工艺中杂质的影响及去除

研究了硫酸盐三价铬镀铬工艺中铜、锌、铁、镍离子(含量均为50mg/kg)对镀层外观和厚度、镀液极化的影响,比较了不同除杂方法的除杂效果。结果发现,金属离子杂质对镀液的污染使镀层外观发生变化,使镀层厚度减少、镀液极化增大;金属离子的去除可以采用加入除杂剂和电解相结合的方法。指出六价铬、镀镍光亮剂等杂质对三价铬镀铬工艺影响较大,加入双氧水可以去除六价铬;往循环过滤泵中加入活性炭,可以去除镀镍光亮剂。     

铜线材防变色光亮锡电镀工艺

铜线材经光亮镀锡后易产生腐蚀变色。讨论了镀锡层产生变色的原因并提出了防变色措施。在酸性光亮镀锡液中加入3-5g/L硫酸铋，控制电流密度为2-5A/dm^2范围内，铜线材上可得到光亮不变色的锡镀层。     

Fe~(2+)对硫酸盐三价铬镀液镀铬的影响

研究了硫酸盐三价铬镀铬液中Fe2+对镀液和镀层性能的影响.赫尔槽试验发现适量的Fe2+可增加光亮阴极电流密度范围;阴极极化曲线显示Fe2+的加入有去极化作用;镀层在3.5% NaCl溶液中极化曲线、电化学阻抗谱测量以及浸泡试验表明:随着溶液中ρ(Fe2+)含量的增加,沉积速率增加镀层的耐蚀性略有降低,镀层逐渐发暗.     

酸性硫酸盐镀锡工艺(二)

介绍了酸性镀锡液的维护与调整,杂质对镀锡液的影响,常见故障及其排除方法,不同基材上镀锡层的去除方法,镀锡层表面防氧化方法,以及从镀锡泥渣与回收槽液中回收锡的工艺。     

高压接线鼻镀锡-铈-锑合金工艺

将化学镀锡和电镀锡工艺有机结合,完成了采用单一电镀方式难以镀覆的高压接线鼻深孔电镀。给出了工艺流程,并分别介绍了各步骤的工艺规范及化学镀锡和电镀锡-铈-锑合金的镀液维护方法。对锡-铈-锑合金形成的机理、镀液的稳定性和镀层的可焊性能进行了研究,结果表明,酸性镀液中加入铈和锑可以提高镀液的稳定性,以及镀层的可焊性和抗氧化性。     

酸性光亮镀锡

酸性光亮镀锡常用于电器开关的生产以提高其零件的导电性 和耐蚀性,介绍了酸性光亮镀锡的工艺,镀液中各成分的作用以及镀液的维护,讨论了杂质的影响及去除。     

酸性镀锡液的稳定性与镀层的可焊性

酸性镀锡液的稳定性对镀层的可焊性产生影响,而影响镀液稳定性的因素包括有稳定剂的选择、操作条件、Sn~(2+)的氧化以及各种杂质等.要提高锭层可焊性,必须注意基体表面状态、镀液性能、操作条件、镀层质量等问题     

电镀锡及晶花化工艺的研究

介绍了电镀锡的镀液配方和工艺条件,分析了酸性镀锡液的性能,并对锡镀层的晶花化热处理工艺进行了研究,阐述了产生晶花的机理.结果表明,酸性镀锡工艺在表面装饰应用中更为经济实用;同时发现锡镀层在250～350℃下进行热处理,会产生美丽的锡晶花,扩大了锡镀层在表面装饰中的应用.     

稀土催化剂抗酸性镀锡液氧化变质的研究

酸性镀锡液稳定性差,易氧化变质。探讨了酸性镀锡液产生氧化变质的机理。在镀锡液中加入0．05－0．1g/L稀土催化剂,通过加速氧化试验和空气暴露试验研究镀锡液的稳定性。结果表明：镀液稳定性显著提高。     

PCB电镀中极化曲线的应用

通过对PCB镀铜液的阴极极化曲线的测量,研究了添加剂的作用及其影响规律;分析了极化曲线与镀层质量的关系.通过极化曲线,可以分析镀液是否受污染,若已被污染,则可以确认污染源;确定适宜的工作电流密度,从而保证镀层质量.     

Application of fringe field capacitance sensor for the study of water permeation in organic coatings

Water permeation in organic coatings can be monitored by measuring the capacitance change in coatings. A new method of measuring water content in organic coatings using a miniature fringe field capacitance (FFC) sensor is described in this paper. The FFC sensor comprises two planar interdigitated electrodes on a dielectric substrate which is connected to a measuring circuit. Coating capacitance is measured by measuring the sensor capacitance when it is in contact with the surface of the coating. Sensor capacitance is theoretically calculated based on IDC capacitor theory for various sensor geometrical parameters at different water ingression levels in the coating. The computed sensor capacitance is validated with experimental values of five miniature sensors which are fabricated by lithography. The calibrated FFC sensor is used to monitor the water permeation profile in the coating, and the results are compared with that of electrochemical impedance spectroscopy technique. The technique provides scope for developing a portable, hand-held, and noninvasive technique to measure water permeation in organic coatings in the field.     

Effects of hydrogen on the corrosion of pure magnesium

Electrochemical measurements and capacitance measurements were performed for better understanding of the effects of hydrogen on the corrosion of pure magnesium. Anodic polarization curves, activation energy (E_a), pitting initiation time and electrochemical noise (EN) were carried out, which showed that hydrogen had a strong influence on the corrosion of magnesium. There existed a highest corrosion resistance of magnesium, when a series of cathodic charging current density were applied to the specimens due to the optimum hydrogen concentration in the hydride coating (MgH₂) on the surface. Mott-Schottky results confirmed that there was a hydride coating on the charged magnesium. Hydrogen ionized as H⁻ and depleted donor/electron, which induced the inversion of semi-conductivity from N-type to P-type.     

海工混凝土结构养护龄期控制对涂层防腐质量的影响初探

主要探讨海工混凝土结构养护龄期对其防腐蚀涂层防腐效果及涂层质量的影响,试验结果表明,在一定的条件下,混凝土龄期控制可以突破现行规范28d的要求,龄期控制在18d时涂装,涂层防腐效果能满足现行规范的相关要求。     

Nanodevices that explore the synergies between PDCs and carbon nanotubes

There is now good evidence that carbon nanotubes can be coated uniformly with a very thin, perhaps even a monolayer, of a polymer-derived ceramic (SiCN) by a simple process of soaking the nanotube surfaces with the liquid precursor followed by pyrolysis. The ceramic coating bonds the nanotubes to one another, which suppresses time-dependent creep that is present without the ceramic bonding. In this article we address the influence of the ceramic coating on two functional properties of carbon nanotube structures—the electrolytic supercapacitance and electrochemico-mechanical actuation. The results, when expressed as the equivalent surface capacitance of carbon sheets, are quite unexpected. The ceramic coating appears to increase the surface capacitance of the nanotube structure. The actuation induced by capacitive charging is also shown to be somewhat enhanced, although the principal influence of the coating is to suppress the drift of the actuation seen in unbonded carbon nanotube structures. It is inferred that the thickness of the SiCN coating amounts to approximately one monolayer of coverage of the nanotubes.     

Novel capacitance sensor design for measuring coating debonding: the effects of thermal-hygroscopic cycling

The effects of combined thermal and hygroscopic cycling on the adhesion performance of an epoxy coating were measured using a novel electrode sensor. The sensor is uniquely designed, consisting of a series of independent interdigitated electrode traces which are arranged parallel to the sensor edges. Coupled with single-frequency capacitance measurements, the sensor detects changes in capacitance in the adhered coating–sensor interfacial region as a function of the distance from the edge of the sensor, x. Recently, this sensor was utilized by O'Brien and co-workers to measure interfacial diffusion and the concentration profile of fluid in an adhesive joint (Int. J. Adhesion Adhesives 23, 335–338 (2003)). In the present work, large capacitance changes due to debonding and displacement of the coating by fluids at the sensor surface were used to monitor coating delamination. The apparent debond growth rate and number of cycles until failure were determined as a function of coating thickness, fluid environment and sensor surface chemistry. The results show that the coating becomes more durable as the thickness is reduced; and also that thermal and hygroscopic cycling of coatings produces different results than conventional continuous adhesion tests. This study suggests that this novel sensor or a similar design is applicable for the study of adhesion loss and interfacial diffusion processes, and could be extended to other coatings or adhesives in a variety of environments. General trends about coating durability are also discussed.     

微量元素对热浸镀铝层的影响

通过向热浸镀铝液中添加微量的混合稀土（ＲＥ）元素，研究了ＲＥ对热浸镀铝层的影响。结果表明，适量的ＲＥ可以提高镀层的质量和镀件的抗氧化性。     

铁基电弧喷涂铝层的高频感应重熔工艺

利用高频感应重熔工艺对铁基电弧喷涂铝层进行处理。分析了工作电流、感应时间对涂层组织的影响,并做出了感应重熔过程中平均功率和温度的分布情况。结果表明,铁基电弧喷涂铝层的重熔先从界面开始,然后向表层推进,处理后的喷涂层与基体之间形成了铁铝金属间化合物,达到了冶金结合,当感应电流为300A,感应时间为35s时,所获得的重熔涂层质量最好。     

Evaluation of the elastic-plastic properties of SiCN coating system by finite element simulations

The elastic properties of SiCN coating on substrates can be evaluated by nano-indentation test, however, it is challenging for experiments to evaluate the plastic performance of SiCN coating. Finite element (FE) is a numerical method for investigating in-depth mechanical behavior of various structures. In this paper, a contact model between Berkovich indenter and SiCN/Si system is established by FE method. The stress-strain behavior of SiCN coating is obtained by comparing the calculated P-h curves with experimental results. The indentation depth dependent elastic modulus and hardness of the SiCN coating are calculated from the P-h curves and are close to the experimental data. When the indentation depth is in excess of 10% of the coating thickness, the mechanical properties of SiCN coating tend to be influenced by the Si substrate, which also consists with experiments. The proposed approach provides an efficient tool to predict the mechanical properties of SiCN coating.     

Hydrogen evolution on RuxTi1−xO2 in 0.5 M H2SO4

Hydrogen evolution from 0.5 M H₂SO₄ on Ti electrodes coated with a Ru_xTi_1−xO₂ (x=0.04-0.5) layer has been studied by potentiostatic polarisation, cyclic voltammetry and ac-impedance spectroscopy. The results indicate that after a certain activation period the performance of such an electrode coating is comparable to platinum. The addition of small amounts of sodium molybdate increased the capacitance of the electrode and a reduction of the performance was observed. Increasing the temperature of the pure electrolyte from 20 to 75 °C caused an increase in the rate of the hydrogen evolution and in addition an increase of the electrode capacitance. The electrodes have been found to be rather tolerant to chloride and Fe²⁺ ions, and could hence be promising candidates as catalyst materials for solid polymer water electrolysis systems. From steady state measurements the Tafel slopes were found to change from −105 mV/decade for pure titanium to about −40 mV/decade for the (RuTi)O₂ coated electrodes. The exchange current densities were calculated from the steady state curves, as well as from impedance data, to be about 10⁻⁴ A cm⁻² after activation.