Cerium Oxide Film Prepared from Molten Salts

Cerium oxide film is used in many fields,such as corrosion and protection, cell, high-temperature condition, superconductor, catalyst,electronic equipmeflt and meter indication. Nonaqueous oxide film is needed under many actualsituations. Oxide film prepared by electrochemical deposition in aqueous solution, however, isat least partly hydrated. Though dehydration canbe realized by heat tramment, the quality of thefilm will be apparently abased because of the afresh arrangement of atom/molecula…     

Electrochemical fabrication of a porous nanostructured nickel hydroxide film electrode with superior pseudocapacitive performance

A porous nickel film is prepared by selectively anodic dissolution of copper from an electrodeposited Ni-Cu alloy film. A porous nanostructured nickel hydroxide film electrode is further fabricated by the cathodic electrodeposition of Ni(OH)₂ film on the obtained porous nickel film. The specific capacitances of the as-prepared porous nanostructured Ni(OH)₂ film electrode at current densities of 2, 5 and 10 A/g are 1634, 1563 and 1512 F/g, respectively. The nanoporous Ni substrate significantly improves the electrochemically cyclic stability of the electrodeposited nickel hydroxide film in 1.0 M KOH solution. The superior pseudocapacitive properties such as large specific capacitance, excellent rate capability and improved electrochemically cyclic stability of the as-prepared nickel hydroxide electrode suggest its potential application in electrochemical capacitors.     

Electrochemical behavior of nickel in HNO<Subscript>3</Subscript> and the effect of chloride ions

The electrochemical behavior of nickel in HNO₃ solutions of varying concentrations was examined using the cyclic voltammetry and potentiodynamic anodic polarization techniques. The anodic branch of the cyclic voltammogram is characterized by one anodic dissolution peak and a passivation region before oxygen evolution. The cathodic branch shows only one cathodic reduction peak corresponding to the reduction of HNO₃. Analysis of the anodic polarization data shows features of both reversible and irreversible reactions pointing to the complexity of the system. CT⁻ ions enhance the active dissolution of nickel in HNO₃ due to the adsorption on the bare metal surface and cause destruction of the passive film and initiation of pitting corrosion.     

强碱性介质铝阳极析氢影响因素研究

结合恒电流集气试验和表面分析手段研究了强碱性介质中影响铝阳极析氢作用的因素,分析了铝阳极的合金化、电解液浓度、工作温度和抑氢物质对材料析氢性能的影响.结果表明:4 mol/L KOH是综合性能较好的强碱性介质,并且选择稀土铝阳极,引入邻胺基苯酚抑氢剂,能够显著抑制铝阳极表面的析氢速率.     

稀土铈对Ni-GO镀层的组织形貌和性能的影响研究

采用电沉积方法在Q235钢上制备Ni-Go复合镀层,研究添加稀土铈对复合镀层形貌、性能的影响。结果表明,当铈浓度为0.8 g.L_-1^时,得到的复合镀层沉积速率增加到7.142 g.dm_-2^.h_^-1,^,硬度达到608.8 HV,磨损量最小,摩擦系数最低为0.387,自腐蚀电位E_corr(-0.3993 V)更正,同时腐蚀电流I_corr(3.258.10_-6 ^A.cm_-2⁾最小,腐蚀速率最低,复合镀层的耐腐蚀性能最优。研究发现,加入稀土铈后,Ni-1.0GO复合镀层的类似珊瑚状的微大尺寸的凸聚体变成了尺寸较小的珊瑚珠状的小凸聚体,镀层组织得到明显细化。在铈浓度为0.8 g.L_-1^时,Ni-1.0GO-0.8RE复合镀层的组织致密性最好,各种性能达到最佳,主要在于稀土铈提高镀液中微粒的分散能力和阴极极化率的效果,提高氢离子在阴极的析出电位,从而抑制析氢反应的发生,使得复合镀层的性能得到进一步提高。     

An investigation into the mechanisms of protection afforded by a cathodic current and the implications for advances in the field of cathodic protection

The influence of a cathodic current on the corrosion behaviour of mild steel exposed to both dilute sodium nitrate solutions and chloride contaminated concrete has been examined. In both cases the formation of passive films was promoted by stimulating a cathodic reaction on the metal surface, the cathodic kinetics being under activation control in the near passive region. The sodium nitrate solution was not capable of supporting a passive film on its own and it is suggested that, in this environment, film formation is promoted by the production of inhibitors (hydroxyl ions, free radical intermediates and metal oxide intermediates) resulting from the cathodic reduction reaction. In chloride-contaminated concrete an additional effect is the removal of aggressive anions via the flow of negative ionic current away from the metal surface. These passivating effects of the cathodic current provide persistent protection and may be harnessed to develop intermittent cathodic protection for use in areas such as the tidal zone where an electrolyte is not always present. The improvement in the local environment at the steel surface may facilitate a reduction in the protection current density, a factor which may be used to reduce the risk of overprotection when cathodic protection is applied to prestressing steel. The use of potential depolarisation and current density related criteria may be more appropriate than the achievement of a predetermined absolute potential in cases where the purpose of the cathodic protection system is to induce passivation.     

硫酸铈对三价铬钝化膜耐腐蚀性的影响研究

目的研究硫酸铈对三价铬钝化膜耐蚀性能的影响。方法通过在三价铬镀铬盐溶液中分别添加0.3、0.5、0.8、1.0、1.5 g/L的硫酸铈,然后通过极化曲线测试,对比不同硫酸铈添加量的钝化膜的腐蚀电流密度,确定硫酸铈在三价铬镀铬盐溶液中的最佳添加量,然后分别制备未添加硫酸铈和添加最佳添加量硫酸铈的三价铬钝化膜,通过电化学工作站CHI660E测量Tafel极化曲线和电化学阻抗谱。分析钝化膜的电化学性能,研究不同钝化膜的耐腐蚀性。观察试样表面的微观形貌,对比添加硫酸铈和未添加硫酸铈的钝化膜的微观形貌。结果通过极化曲线测试发现,当硫酸铈的添加量为1.0 g/L时,钝化膜的腐蚀电流密度小于其余添加量的钝化膜,添加硫酸铈和未添加硫酸铈的钝化膜的耐蚀性能不同,添加硫酸铈后的钝化膜性能得到改善,且钝化膜膜层的微观形貌发生改变。结论添加硫酸铈后,三价铬钝化膜的耐腐蚀性能增强。当硫酸铈的添加量为1.0 g/L时,腐蚀电流密度最小,为3.835×10~(-6) A/cm~2,耐腐蚀性能优于其余钝化膜。     

Kinetics of Contact Plating of Nickel on Aluminum from Alkaline Ammonia Solutions

Kinetics of the contact deposition of nickel on aluminum from alkaline ammonia solutions of different composition is studied by methods of voltammetry, gravimetry, and x-ray fluorescent analysis. It is shown that conventional voltammetric diagrams cannot be applied for determining the contact-exchange, current because they represent the net curve reflecting the conjugate processes of metal dissolution and cathodic hydrogen evolution. In connection with this, we propose determining the contact-exchange and aluminum dissolution rates from a cathodic voltammogram of a nickel electrode in the working solution.     

Thin-layer electrolytic nickel hydroxide Ni(OH)2 in an electrochemical capacitor

Thin-layer electrolytic nickel hydroxide Ni(OH)₂ has been obtained from an aqueous solution of nickel sulfate and nickel nitrate. The capacitor characteristics of Ni(OH)₂ depending on the synthesis and technology parameters, the thermal treatment and storage conditions of the deposits, the KOH concentration, the potential sweep rates, and the relation with the adverse process of oxygen isolation in an electrochemical capacitor were investigated by cyclic voltammetry. It was established that the optimal KOH concentration in the solution of an electrochemical capacitor is 0.1 M, and it allows one to attain an active material discharge capacitance of 427?C457 F/g. The additional anode polarization of cathode deposited Ni(OH)₂ stabilizes the discharge characteristics of the obtained Ni(OH)₂ + NiO mixture in storage processes. It was established that the mass transport process in the solid state phase is the limiting stage of the Ni(OH)₂/NiOOH system??s electrode process in a KOH medium.     

重稀土元素对氢氧化镍电极高温性能的影响

研究了在覆钴球镍中低量添加重稀土元素对镍电极性能的影响。结果表明,60℃时添加1%(原子分数)重稀土的镍电极的1C充放电效率比无添加剂的镍电极有所提高;重稀土氧化物的添加对镍电极的常温高倍率放电性能有一定的负面影响;在常温时,重稀土氧化物的加入增大镍电极氧化-还原反应的电位差,从而增大电极反应的不可逆性,其中添加氧化铥与氧化镥的电极最为明显;在60℃时,添加重稀土氧化物的镍电极的氧化峰与析氧峰区别明显,且镍电极的氧化峰电位与析氧电位普遍负移,还原峰电位普遍正移,显著提高镍电极在高温下的析氧过电位以及可逆性。     

Electrochemical oxidation of pyrrhotute in aqueous solution

The anodic surface oxidation of natural pyrrhotite in 0.3 mol/L KCI and HCI solution （pH 4.0） and 0.1 mol/L Na2B4O7 solution （pH 9.18） respectively was investigated by using cyclic voltammetry, Tafel plot, and chronoamperometry. In 0.3 mol/L KCl and HCl solution （pH 4.0）, at potential less than 0.5 V（vs SHE）, the production of anodic oxidation on pyrrhotite surface can not maintain a stable phase to form a passive film. In 0.1 mol/L Na2B4O7 solution （pH 9.18）, when the electrode potential increases to more than 0.5 V （vs SHE）, part of S is oxidized to sulfate, making the passive film somewhat porous, but elemental S and metal oxidates Fe（OH）3 still remain on the electrode surface, and the passive film can not be broken down totally. According to PARCalc Tafel analysis, the corresponding corrosion current density （J0） is 5.34 μA/cm^2 , which is also the exchange current density of the oxidation reaction on pyrrhotite electrode surface in 0. 1 mol/L Na2B4O7 solution （pH 9. 18）. The electrochemical dynamics equation of the oxidation was determined.     

表面处理对储氢合金电化学性能的影响研究

通过电化学方法,研究了储氢合金碱化处理及碱液中加入KBH4对合金电极的电催化活性和高倍率放电性能的影响.结果表明:处理后合金颗粒分布均匀,表面变得粗糙.两种处理方法均增加了合金表面的电催化活性,降低了合金电极的极化电阻,从而提高了高倍率放电能力.尤其在900mA/g放电时,处理前合金电极不能放电,单一碱处理合金电极和加入还原剂碱处理合金电极仍具有较高的高倍率放电能力,分别为69.2%和83.4%.在单一碱溶液中加入还原剂KBH4处理后,合金电极的电化学性能明显高于单一碱处理合金电极.     

氨络合物体系中杂质Zn~(2+)对电沉积镍的影响

通过霍尔槽试验研究氨络合物体系中杂质Zn~(2+)对镍电沉积的影响,采用电化学工作站测试不同Zn~(2+)浓度时的循环伏安曲线、稳态极化曲线及电流时间暂态曲线.结果表明:杂质Zn~(2+)的含量为0.1 g/L时,在小于2.78 A/dm的电流密度范围内可正常沉积出金属镍;杂质Zn~(2+)含量大于0.5 g/L时,在较大的电流密度范围内均无法正常沉积出金属镍;过电位小于640 mV时,Zn~(2+)的存在不影响阴极反应的传递系数,且不改变阴极反应机理;当过电位大于640 mV,且杂质Zn~(2+)的浓度大于0.5 g/L时,阴极反应的传递系数减小,阴极反应机理发生改变;杂质Zn~(2+)浓度大于0.5 g/L时,严重影响镍电结晶过程的成核速率,这是其抑制金属镍电沉积的主要原因.因此,采用镍氨络合物体系电积金属镍,应控制杂质Zn~(2+)的含量小于0.1 g/L.     

铝合金稀土转化膜碱性成膜工艺T3/T7的研究

采用正交实验方法得出了最佳成膜工艺T3/T7,利用线性极化、极化曲线测试、中性盐雾实验等对该工艺形成的膜层耐蚀性进行了研究,并对表面膜层的性能进行了一系列测试.结果表明:在NaCl水溶液中的全面腐蚀速度可降低10～20倍,可通过504h的中性盐雾试验;经该工艺处理后铝合金腐蚀的阴阳极过程都受到明显阻滞,且自然腐蚀电位负移,点蚀电位相对于自然腐蚀电位明显正移,T3/T7处理明显的改善了铝合金在氯化物介质中的耐点蚀性能     

镀锌钢板铈盐钝化的电化学性能研究

采用稀土铈盐钝化工艺对镀锌钢板进行了钝化处理.比较了镀锌钢板在0.5mol/L的NaCl溶液中钝化前后的极化曲线、电化学交流阻抗谱.研究了铈盐钝化膜的耐蚀性能,并根据阻抗谱特征建立了腐蚀等效电路.结果表明:经铈盐钝化处理后的镀锌钢板,其腐蚀电流密度下降、极化电阻升高,稀土铈盐钝化膜抑制了镀锌钢板的腐蚀过程,经铈盐钝化处理后,镀锌钢板的耐蚀性能优于空白试样,接近低铬钝化处理样品的耐蚀性.同时,简要分析了稀土铈盐对镀锌钢板的钝化机理.     

Elaboration and microstructural characterization of calcareous/ceria based composite on zinc substrate

Cerium conversion coatings were prepared by cathodic electrodeposition from a low concentrated aqueous solution of Ce(NO₃)₃ with KNO₃ addition to insure the conductivity of the electrolyte. The cerium oxide film was characterized by Scanning Electronic Microscopy (SEM). Although the deposit is uniform with current density of 2 mA/cm², it shows cauliflower morphology with a crack network, giving rise to bad mechanical and electrochemical behaviour. Elaboration of a calcareous deposit inside crack network of the cerium coating by cathodic polarization from artificial seawater is investigated at different applied potential, in order to increase the quality of the cerium coating formed. For cathodic potentials lower than–1.5 V/SCE, zinc corrosion products (gordaite) were observed inside the cerium oxide film instead of calcareous deposit although the current density decrease during the deposition suggesting a partially blocked surface. A pure calcareous compound was observed at–1.5 and–1.6 V/SCE. SEM and EDX cartography of the cross section revealed that open cracks in the cerium oxide structure are filled by calcium. Calcium was also detected inside the CeO₂ film not only all around the cracks but also in all the porosity of the CeO₂ film. It has precipitated as CaCO₃ (aragonite form) as revealed by micro-Raman spectroscopy and XRD.     

Direct Electrodeposition of Fe-Ni Alloy Films on Silicon Substrate

在n-型Si片(100)面上直接电沉积Fe-Ni合金薄膜,并对电沉积过程特征及薄膜的结构和性能进行了研究。当阴极电流密度高于1.0 A/dm2时,可获得连续致密的合金薄膜,且电沉积表现为异常共沉积过程。在1.0~4.0 A/dm2范围内改变电流密度可调控合金薄膜的Ni质量分数从45%到78%之间改变,对应的电流效率在60%到66%之间变动。从XRD和TEM结果来看,合金薄膜由尺寸为10~30nm的纳米晶粒组成,且表现为Fe-Ni面心立方固溶体结构。合金薄膜的磁滞回线表现出较高的饱和磁化强度和接近于零的矫顽力,表明该种纳米合金薄膜具有很好的软磁性能。     

Q235钢表面铈盐掺杂乙烯基三乙氧基硅烷膜制备及耐蚀性能

在Q235钢表面制备铈盐掺杂乙烯基三乙氧基硅烷膜。利用电化学阻抗谱(EIS)确定了最佳铈盐添加量,利用EIS和动电位极化法研究了涂覆掺杂硅烷膜的Q235钢在3.5% NaCl水溶液中的耐蚀性能,利用扫描电镜(SEM)观察了掺杂硅烷膜的表面形貌。结果表明,铈盐最佳添加量为1×10^-3 mol/L,经涂镀掺杂硅烷的Q235钢在腐蚀过程中的阳极反应和阴极反应受到抑制,与空白Q235钢相比其腐蚀电流密度减小近3个数量级,极化电阻提高3个数量级,低频阻抗值提高至少4个数量级。     

RuTiSnMn/Ti阳极的电化学性能

热分解制备了RuTiSnMn／Ti阳极，在4mA／cm^2的电流密度下进行了恒电流试验。通过循环伏安法和交流阻抗谱研究了阳极在35g／LNaCl溶液、20g／LNaOH溶液和模拟孔隙液中的电化学行为．利用EsEM对阳极失效前后的微观形貌进行了观察,结果表明：阳极具有优良的耐析氯、氧反应能力；钛基体逐渐形成TiO2的钝化膜使阳极的氧化物膜电阻增大，活性组元的消耗使法拉第电荷传递电阻增加，这两者最终导致阳极失效。     

Study of Cerium and Lanthanum Conversion Coatings on AZ63 Magnesium Alloy Surface

采用扫描电子显微镜,X射线能谱,Tafel极化曲线和电化学阻抗谱法研究了铈镧转化膜对AZ63镁合金耐蚀性能的影响。结果表明,铈和镧的复合转化膜比单一稀土膜的表面更加均匀致密,对镁合金的耐蚀性有明显改善。双稀土转化膜的缓蚀效果随着浸泡成膜时间的增长而增加。延长时效时间有助于铈和镧的进一步氧化,耐蚀性能先增后减,时效48 h膜层的耐蚀效果最好。