化学镀Ni-Co-W-P及其析氢性能的研究

用化学镀方法制备出Ni-Co-W-P合金电极,测量了其在1 mol/L NaOH溶液中的阴极极化曲线并研究了其析氢电催化活性.试验表明,在相同的电流密度下,Ni-Co-P,Ni-W-P和Ni-Co-W-P合金电极的析氢过电位较Fe电极降低,其中Ni-Co-W-P的析氢过电位降低约230 mV,XRD试验显示其镀层为非晶态.并进一步测试了其在7 mol/L KOH中的连续电解曲线.结果表明:Ni-Co-W-P合金电极比Ni-Co-P,Ni-W-P合金电极具有更好的析氢电催化活性和电化学稳定性,有利于降低槽压,减少能耗.     

Electrochemical properties of amorphous Ni-S-Co alloy in alkaline medium

用电沉积方法制备非晶态Ni-S-Co合金镀层, 研究了镀层的电化学性能. 结果表明,与非晶态Ni--S合金相比, Co的引入可提高镀层中S的含量.在析氢反应中非晶态Ni--S--Co合金电极具有很高的电化学活性,电流密度为150 mA×cm-2时其析氢过电位仅为70 mV,比非晶态Ni-S合金低20 mV.在长时间电解过程中S发生溶出反应有助于提高电极的表面粗糙程度, 是提高电极析氢活性的重要原因之一. 在析氢过程中,非晶态Ni--S--Co合金电极吸附大量的H原子, 使反应的活化能降低,这是其析氢活性高的主要原因. 非晶态Ni--S--Co合金镀层的析氢机理为电化学脱附机理,即一快速的Volmer反应(电化学步骤)和一较慢的Heyrovsky反应(电化学脱附步骤).     

非晶态Ni-S-Co合金的制备和电化学性能

用电沉积方法制备非晶态Ni-S-Co合金镀层,研究了镀层的电化学性能.结果表明,与非晶态Ni-S合金相比,Co的引入可提高镀层中S的含量.在析氢反应中非晶态Ni-S-Co合金电极具有很高的电化学活性,电流密度为150 mA·cm-2时其析氢过电位仅为70 mV,比非晶态Ni-S合金低20 mV.在长时间电解过程中S发生溶出反应有助于提高电极的表面粗糙程度,是提高电极析氢活性的重要原因之一.在析氢过程中,非晶态Ni-S-Co合金电极吸附大量的H原子,使反应的活化能降低,这是其析氢活性高的主要原因.非晶态Ni-S-Co合金镀层的析氢机理为电化学脱附机理,即-快速的Volmer反应(电化学步骤)和一较慢的Heyrovsky反应(电化学脱附步骤).     

非晶态Ni—Mo—Fe合金作电解水析氢反应电极

用电沉积法制备非晶态Ｎｉ４１．５Ｍｏ５．５Ｆｅ２３．０合金电极。该合金电极在３０ｗｔ％ＫＯＨ溶液，７０℃作析氢反应阴极，实验研究结果表明，合金电极对氢的析出反应具有优良的电催化性能。在２００ｍＡ／ｃｍ＾２电流密度下析氢反应过电位约９０ｍＶ，在连续电解和间歇电解条件下有良好的电化学稳定性。     

碱液中镍电极的析氢机理

研究镍电极在碱液中的析氢机理对开发二次清洁能源有指导意义,过去对其研究不够.通过Tafel曲线和电化学阻抗谱对镍电极在KOH溶液中的析氢机理进行了研究.结果表明,过电位低于600 mV时,析氢服从复合脱附机理,反应历程为电化学步骤+复合脱附步骤;过电位高于600 mV时,析氢服从迟缓放电机理或电化学脱附机理,反应历程为电化学步骤+电化学脱附步骤.     

泡沫镍基镍硫合金涂层形貌、结构和析氢性能研究

在含有柠檬酸、硫脲和少许糖精的Watt镀液中,用电沉积的方法在镍泡沫基体上制备了镍硫合金涂层.各层涂层的形貌用SEM分析,各层硫量的分布用EDX测量.第1层涂层的结构用XRD测定.对各种电极包括镍泡沫基、镍网基上镍硫涂层电极,空白镍泡沫、镍网电极等的极氢电位进行了测量,研究了不同温度下镍泡沫基镍硫涂层电极的析氢活性.结果表明,镍泡沫基Ni-S涂层电极的析氢活性比镍网基Ni-S涂层电极活性高得多.镍泡沫各层硫量呈梯度的分布规律,由表及里硫含量逐步降低,中心层硫含量最低.各层表面微细颗粒大小及其均一性不相同,第1层的颗粒尺寸大于其它层的颗粒,其大小均一性也较其它层差.镍硫涂层是镍和Ni3S2组成的非晶态,使涂层具有丰富的表面积和氢气析出反应的活性中心.在加热的电解液中,在60℃以下和60℃以上的温区内电极析氢反应的机制不完全一样,受温度影响的程度也不一样.4000A/m2、90℃时,这种电极的析氢电位比15℃时析氢电位低180mV.     

非晶态Ni－Mo－Fe合金作电解水析氢反应电极

用电沉积法制备非晶态Ｎｉ＿（４１．５）Ｍｏ＿（３５．５）Ｆｅ＿（２３．０）合金电极。该合金电极在３０ｗｔ％ＫＯＨ溶液，７０℃作析氢反应阴极，实验研究结果表明，合金电极对氢的析出反应具有优良的电催化性能。在２００ｍＡ／ｃｍ￣２电流密度下析氢反应过电位约９０ｍＶ，在连续电解和间歇电解条件下有良好的电化学稳定性。     

聚苯并咪唑膜用于膜法酸碱两性电解水制氢研究

针对电解水制氢过程能耗过高的问题,提出膜法酸碱两性电解水过程。用隔膜将高浓度的酸碱电解液分隔,在酸性溶液中发生析氢反应,提高电化学反应活性,降低析氢过电位。该过程核心问题是阻止酸碱中和,限制对离子跨膜渗透.本文选择对离子体积较大的季铵碱作为碱溶液,分析酸碱种类、对离子体积与离子渗透的关系,探讨电解电流与酸碱种类、浓度、温度的关系.为了阻隔高浓度酸碱中和,使用聚苯并咪唑膜作为电解槽隔膜,经过酸或碱掺杂形成传导离子能力.初步验证了聚苯并咪唑膜在酸碱溶液中的稳定性,为发展膜法酸碱两性电解水制氢技术提供依据.     

稀土铈对镍-钴-磷合金电极的析氢催化性能的影响

采用自行研制的复合配合剂,用化学沉积法在酸性体系中制备了Ni-Co-P和Ni-Co-P稀土合金电极.研究了稀土元素铈对Ni-Co-P合金电极的析氢电催化活性和电化学稳定性的影响.通过电化学方法测定合金电极在7 mol/L KOH溶液中的阴极极化曲线、Tafel曲线和电化学稳定性曲线,结果表明,与Ni-Co-P合金电极相比,Ni-Co-P(RE)合金电极的析氢电位正移约90 mV,Ni-Co-P(RE)合金电极具有较优的析氢电催化活性和电化学稳定性.此外,还通过X射线衍射、扫描电镜和合金镀层成分分析,结果表明,稀土元素铈的加入使非晶态Ni-Co-P合金镀层晶粒细化,但稀土元素铈不与合金共沉积,只是起到改变镀层组织结构的作用.     

Ni-W-TiO2复合镀工艺及其镀层性能研究

为了进一步提高Ni-W合金镀层的析氢电催化活性,用电沉积方法制备了Ni-W-TiO2复合镀层,通过阴极极化曲线和交流阻抗等电化学技术研究了其在碱性溶液中的析氢电催化活性,并用扫描电镜观察了电极的表面形貌.结果表明,在Ni-W合金中掺入TiO2微粒可增大电极的比表面积,并改变Ni-W合金在碱性介质中的析氢反应机理.Ni-W-TiO2复合镀层有较高的析氢电催化活性,可用作电解水反应的活性电极.     

锌-镍合金电镀中氢的共沉积

用电化学渗透测试方法研究了电镀锌－镍合金时渗氢量的变化规律，能够监控和评价镀层的氢脆性能，初步筛选出两种呆用于高强度钢抗氢脆电镀用槽液组成。在氯化物－硫酸盐槽液体系和含有添加剂B的氯化物糟液中，常温下可获得耐氢脆性能良好的Zn－Ni镀层。此外，缺口拉伸试验结果与电化学渗透测试结果相吻合。     

Hydrogen diffusivity and solubility in crystalline and amorphous alloys

The hydrogen permeation behaviour of iron- and nickel-based amorphous alloys was characterized using electrochemical methodology and compared with the properties of crystalline metals and alloys. The materials studied were amorphous Fe40Ni38Mo4B18, Fe74Ni4Mo3B17, Fe78B13Si9 and Ni81P19, as well as a crystalline low-carbon steel, pure nickel and pure palladium. The double potentiostatic electrochemical hydrogen permeation tests were performed at 40°C using a 0.1 N NaOH solution as electrolyte. It was found that the hydrogen diffusivity in the iron-based amorphous alloys is a few orders of magnitude lower than in carbon steel and iron, while a much smaller difference exists between Ni81P19 and pure nickel. Furthermore, the amorphous alloys showed a strikingly greater capacity to dissolve hydrogen in solid solution compared with their crystalline counterparts. In some cases, their apparent hydrogen solubility was even greater than that for the liquid metal of the main element present in their chemical composition. This revised version was published online in November 2006 with corrections to the Cover Date.     

SURFACE ALLOYING OF MILD STEEL BY LASER MELTING OF AN ELECTROLESS NICKEL DEPOSIT CONTAINING CHROMIUM CARBIDES

It is possible to realize surface alloys by laser melting an electroless nickel layer containing chromium carbide particles predeposited on a mild steel substrate. By this way the surface alloy is expected to have not only a high nickel content but also an important chromium content in order to improve the corrosion resistance. The presence of chromium in solid solution results from the dissolution or melting of the carbide particles. Typical laser solidification microstructures are obtained. Dendrites consist of an austenitic Fe-Ni-Cr solid solution and interdendritic regions are constituted by an eutectic mixture containing the same austenitic solid solution and complex Fe, Ni, Cr carbides and phosphides. In comparison with a surface alloy obtained by laser melting of an electroless nickel layer without carbide particles, the corrosion resistance was slightly improved in saline aqueous solutions. The limited effect was due to the fact that the final chromium content in the present experimental conditions was not as high as that initially expected.     

Suppression of moisture-induced embrittlement of Ni3(Si, Ti) alloys by a surface nickel alloying layer

The effect of a surface nickel alloying layer on moisture-induced embrittlement of Ni3(Si, Ti) alloys has been investigated by tensile tests at room temperature, using nickel-deposited materials. Undeposited Ni3(Si, Ti) alloy became remarkably embrittled in air. However, nickel-deposited Ni3(Si, Ti) alloy showed a high elongation value, indicating the suppression of embrittlement caused by hydrogen decomposed from moisture in the air. When the surface nickel alloying layer consists of f c c(γ) solid solution with a high nickel concentration and good adhesion to the substrate, improvement of tensile elongation is the greatest. The results have been discussed from the chemical and structural viewpoints of the surface nickel alloying layer. This revised version was published online in November 2006 with corrections to the Cover Date.     

化学修饰对NiTi形状记忆合金氧化膜的影响

用X光电子能谱（XPS）研究了NiTi形状记忆合金经酸、碱处理后表面氧化膜成分和结构的变化。结果表明，未经处理的NiTi合金表面最外层氧化膜主要由TiO2、TiO和少量的Ni组成，酸、碱处理后，最外层氧化膜由TiO2、Ni2O3组成，但经碱处理后，氧化膜的厚度大大增加。     

粘结剂对储氢合金电极电化学容量的影响

采用夹片式电极测试系统,研究了铜粉,镍粉及聚乙烯醇等粘结剂对ＡＢ５型储氢合金电极电化学容量的影响。结果表明,用镍粉做粘结剂的电极活化容易,容量高。随着镍粉比例的增加,电极容量增大。镍粉的电催化作用强,镍粉比例的增加抑制了电极在充放电过程中的疏松,改善了电极的导电性。     

Sulfide stress cracking resistance of API-X100 high strength low alloy steel

Sulfide Stress Cracking (SSC) of API-X100 high strength low alloy steel was evaluated in NACE solution “A” at room temperature. The corrosion rate, utilizing electrochemical polarization techniques, in the solution was 97 mpy. Proof ring testing, per NACE TM-0177, generated an SSC threshold stress value of 46% of yield strength. SSC susceptibility was caused by the high corrosion rate which formed corrosion pits that acted as crack initiation sites on the metal surface and provided more hydrogen to migrate into the steel. In addition, the X100 inhomogeneous microstructure provided a high density of hydrogen traps which promoted hydrogen embrittlement.     

Microstructure and corrosion behaviour of FeCoNiCuSnx high entropy alloys

Abstract

The FeCoNiCuSn_x alloys with different Sn contents are prepared, the microstructure and the corrosion behaviour of the alloys are investigated. When Sn content is lower than 0.09, FeCoNiCuSn_x alloys consist of a single FCC phase. While Sn content of the alloy is 0.09, a small quantity of BCC structure is present. The FeCoNiCuSn_x alloys have a wider passive region in the NaOH solution. FeCoNiCuSn_x alloys exhibit a better corrosion resistance in NaCl solution than 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.04 alloy is best among all the alloys. The corrosion resistance of FeCoNiCuSn_x alloys in NaOH solution is lower than that of 304 stainless steel, the corrosion resistance of FeCoNiCuSn_0.03 alloy is best among all FeCoNiCuSn_x alloys.     

Formation of nickel aluminide/nickel hybrid coatings on alloy steels by two step process of nickel plating and low temperature pack aluminisation

Abstract

The present study investigates the conditions required for forming a hybrid coating consisting of an outer nickel aluminide layer and an inner nickel layer on alloy steels. A commercial alloy steel of 9Cr–1Mo was used as a substrate. Electroless and electronickel plating processes were used to form an initial nickel layer on the steel. The AlCl₃ activated packs containing pure Al as a depositing source were then used to aluminise the nickel deposit at temperatures ≤650°C. The effect of phosphorus or boron content in the initial nickel layer deposited with the electroless nickel plating solutions using hypophosphite or boron–hydrogen compound as reducing agent was investigated in relation to the spallation tendency of the coating either immediately after the aluminising process or during the thermal annealing post-aluminising process. Under the aluminising conditions used, the outer nickel aluminide layer formed was Ni₂Al₃. For the electroplated nickel deposit, the growth kinetics of the outer Ni₂Al₃ layer during the pack aluminising process was found to obey the parabolic rate law with a parabolic rate constant being 12·67 μm at 650°C for 2 wt-%AlCl₃ activated pack containing 4 wt-% pure Al as a deposition source.