Synergistic inhibition effect of poly(ethylene glycol) and cetyltrimethylammonium bromide on corrosion of Zn and Zn-Ni alloys for alkaline batteries

The synergistic inhibition effect of poly(ethylene glycol)-400(PEG-400)and cetyltrimethylammonium bromide(CTMAB)on the corrosion of Zn and Zn-Ni alloys in 8 mol/L KOH solution saturated with Zn O was observed by potentiodynamic anodic/cathodic polarization(PDP),and electrochemical impedance spectroscopy(EIS)measurements.The electrochemical studies confirmed that there was a synergism between PEG-400 and CTMAB on corrosion inhibition of Zn and its alloys.Corrosion inhibition efficiency of the mixed inhibitors,250 mg/L CTMAB+250 mg/L PEG-400,was found to be much higher than that of the single inhibitor,500 mg/L PEG-400 or 500 mg/L CTMAB.Scanning electron microscopic(SEM)investigations before and after the corrosion inhibition process emphasize the synergistic effect of the mixed inhibitors.Accordingly,it was found that the addition of the investigated inhibitors to the alkaline solution enhanced the discharge and capacity of the alkaline battery anodes.The obtained electrochemical data exhibited a good correlation with the computational one.

Improved hydrogen oxidation reaction under alkaline conditions by Au–Pt alloy nanoparticles

This work demonstrates the outstanding performance of alloyed Au1 Pt1 nanoparticles on hydrogen oxidation reaction(HOR)in alkaline solution.Due to the weakened hydrogen binding energy caused by uniform incorporation of Au,the alloyed Au1Pt1/C nanoparticles exhibit superior HOR activity than commercial PtRu/C.On the contrary,the catalytic performance of the phase-segregated Au2Pt1/C and Au1Pt1/C bimetallic nanoparticles in HOR is significantly worse.Moreover,Au1Pt1/C shows a remarkable durability with activity dropping only 4% after 3000 CV cycles,while performance attenuation of commercial PtRu/C is high up to 15% under the same condition.Our results indicate that the alloyed Au1Pt1/C is a promising candidate to substitute commercial PtRu/C for hydrogen oxidation reaction in alkaline electrolyte.

Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Potentiodynamic polarization tests and slow strain rate test（SSRT） in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking（SCC） behavior of 7003 aluminum alloy（AA7003） in acid and alkaline chloride solutions under various applied potentials（Ea）. The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution（AD） at open-circuit potential（OCP） and is highly susceptible to hydrogen embrittlement（HE） at high negative Ea in the solutions with p H levels of 4 and 11. The susceptibility increases with negative shift in the potential when Ea is less than-1000 m V vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when Ea is equal to-1000 m V vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.

THERMODYNAMICAL CALCULATION OF FORMATION ENTHALPIES FOR ALKALINE METAL ALLOYS

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Effects of alternating current imposition and alkaline earth elements on modification of primary Mg_2Si crystals in hypereutectic Mg-Si alloy

The effects of alternating current imposition and/or alkaline earth elements on modification of the primary Mg2Si crystals in the hypereutectic Mg-Si alloy were investigated.An alternating current of 60 A with frequency of 1 kHz was applied into the hypereutectic Mg-Si melt which was alloyed with alkaline earth elements or not in the fixed temperature range from 700 to 630℃. The results show that the primary Mg2Si crystals could be refined by imposing alternating current or adding alkaline elements. Compared with the samples treated by adding 0.4%Ca or 0.4%Sr,higher modification efficiency could be obtained for the samples treated by imposing alternating current.No further modification efficiency could be obtained for the samples treated by imposing alternating current combined with 0.4%Ca or 0.4%Sr addition.

Corrosion-wear behavior of nanocrystalline Fe88Si12 alloy in acid and alkaline solutions

The corrosion-wear behavior of a nanocrystalline Fe_（88）Si_（12） alloy disc coupled with a Si_3N_4 ball was investigated in acid（pH 3） and alkaline（pH 9） aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe_（88）Si_（12） alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe_（88）Si_（12） alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe_（88）Si_（12） alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si_3N_4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe_（88）Si_（12） alloy in the pH 9 aqueous solution.

Effect of magnesium on the aluminothermic reduction rate of zinc oxide obtained from spent alkaline battery anodes for the preparation of Al–Zn–Mg alloys

The aluminothermic reduction of zinc oxide（ZnO） from alkaline battery anodes using molten Al may be a good option for the elaboration of secondary 7000-series alloys. This process is affected by the initial content of Mg within molten Al, which decreases the surface tension of the molten metal and conversely increases the wettability of ZnO particles. The effect of initial Mg concentration on the aluminothermic reduction rate of ZnO was analyzed at the following values： 0.90wt%, 1.20wt%, 4.00t%, 4.25wt%, and 4.40wt%. The ZnO particles were incorporated by mechanical agitation using a graphite paddle inside a bath of molten Al maintained at a constant temperature of 1123 K and at a constant agitation speed of 250 r/min, the treatment time was 240 min and the ZnO particle size was 450？500 mesh. The results show an increase in Zn concentration in the prepared alloys up to 5.43wt% for the highest initial concentration of Mg. The reaction products obtained were characterized by scanning electron microscopy and X-ray diffraction, and the efficiency of the reaction was measured on the basis of the different concentrations of Mg studied.

THIN FILM ELECTRODES OF AMORPHOUS Ml－Ni ALLOY AS HYDROGEN CATHODES IN ALKALINE SOLUTION

Thin film electrodes of amorphous Ml-Ni (Ml-Mischmetal) alloy prepared by ion beam sputtering were investigated as cathodes for hydrogen evolutionreaction in alkaline solution. The results show that the film cathodes of amorp-hous Ml-Ni alloy have good catalytic activity and excellent resistance to hydro-gen embrittlement.

Surface Modification With Zinc and Zn-Ni Alloy Compositionally Modulated Multilayer Coatings

Zinc and Zn-Ni alloy compositionally modulated multilayer （CMM） coatings were electrodeposited on to a steel substrate by the successive deposition of zinc and Zn-Ni alloy sublayers from dual baths. The coated samples were evaluated in terms of the surface appearance, surface and cross-sectional morphologies, as well as corrosion resistance. The microstructural characteristics that were examined using the field emission gun scanning electron microscopy （FEGSEM） confirmed the layered structure, grain refinement of the zinc and Zn-Ni alloy CMM coatings, and revealed the existence of microcracks caused by the internal stress in the thick Zn-Ni alloy sublayers. The corrosion resistance that was evaluated by means of the salt spray test shows that the zinc and Zn-Ni alloy CMM coatings were more corrosion-resistant than the monolithic coatings of zinc or Zn-Ni alloy of the same thickness. The possible reasons for the better protective performance of Zn-Ni/Zn CMM coatings were given on the basis of the analysis on the micrographic features of zinc and Zn-Ni alloy CMM eoatings after the corrosion test. A probable corrosion mechanism of zinc and Zn-Ni alloy CMM coatings was also proposed.

Role of Ni content in improvement of corrosion resistance of Zn-Ni alloy in 3.5% Na Cl solution. Part I: Polarization and impedance studies

Zn plays an important role in the protection of iron and steel from corrosion in sea water, and the alloying of Zn and Ni can improve its corrosion resistance. The corrosion behavior of Zn？Ni alloys in synthetic sea water （3.5% NaCl, mass fraction） was studied using Tafel plot and electrochemical impedance spectroscopy （EIS） techniques. The corrosion resistance of the investigated alloys with various Ni contents （0.5%？10%, mass fraction） was compared with that of Zn. The results show that the corrosion resistance of Zn？Ni alloys （except 0.5% Ni） is superior to that of Zn. The 10% Ni gives the highest corrosion resistance due to the formation ofγ-Zn3Ni withγ-ZnNi phases in the alloy. In the case of alloy I （0.5% Ni）, it exhibits a higher corrosion rate （less corrosion resistance） than Zn.

Corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding in alkaline solution

This study was done to evaluate the nugget zone(NZ)corrosion behavior of dissimilar copper/brass joints welded by friction stir lap welding(FSLW)in a solution of 0.015 mol/L borax(pH 9.3).To this end,dissimilar copper/brass plates were welded with two dissimilar heat inputs(low and high)during the welding procedure.The high and low heat inputs were conducted with 710 r/min,16 mm/min and 450 r/min,25 mm/min,respectively.Using open circuit potential(OCP)measurements,electrochemical impedance spectroscopy(EIS)and Tafel polarization tests,the electrochemical behavior of the specimens in borate buffer solution was assessed.With the help of scanning electron microscope(SEM),the morphology of welded specimen surfaces was examined after immersion in the test solution.According to the results,the NZ grain size and resistance improvement reduced due to the nugget zone corrosion with a decreased heat input.The results obtained from Tafel polarization and EIS indicated the improved corrosion behavior of the welded specimen NZ with a decrease in the heat input during the welding process unlike the copper and brass metals.Furthermore,an increased heat input during the welding process shows a reduction in the conditions for forming the passive films with higher protection behavior.

In situ Hydrothermal Oxidation of Ternary FeCoNi Alloy Electrode for Overall Water Splitting

Exploring noble metal-free catalyst materials for high efficient electrochemical water splitting to produce hydrogen is strongly desired for renewable energy development.In this article,a novel bifunctional catalytic electrode of insitu-grown type for alkaline water splitting based on FeCoNi alloy substrate has been successfully prepared via a facile one-step hydrothermal oxidation route in an alkaline hydrogen peroxide medium.It shows that the matrix alloy with the atom ratio 4∶3∶3 of Fe∶Co∶Ni can obtain the best catalytic performance when hydrothermally treated at 180℃for 18 h in the solution containing 1.8 M hydrogen peroxide and 3.6 M sodium hydroxide.The as-prepared Fe_(0.4)Co_(0.3)Ni_(0.3)-1.8 electrode exhibits small overpotentials of only 184 and 175 mV at electrolysis current density of 10 mA cm^(-2)for alkaline OER and HER processes,respectively.The overall water splitting at electrolysis current density of 10 mA cm^(-2)can be stably delivered at a low cell voltage of 1.62 V.These characteristics including the large specific surface area,the high surface nickel content,the abundant catalyst species,the balanced distribution between bivalent and trivalent metal ions,and the strong binding of in-situ naturally growed catalytic layer to matrix are responsible for the prominent catalytic performance of the Fe_(0.4)Co_(0.3)Ni_(0.3)-1.8 electrode,which can act as a possible replacement for expensive noble metal-based materials.

Corrosion behaviors of zinc and Zn-Ni alloy compositionally modulated multilayer coatings

Zinc and Zn-Ni alloy compositionally modulated multilayer （CMM） coatings were electrodeposited from dual baths. The coated samples were evaluated in terms of surface appearance, surface and cross-sectional morphologies, as well as corrosion resistance. The results obtained from the salt spray test show that the zinc and Zn-Ni alloy CMM coatings are more corrosion-resistant than the monolithic coatings of zinc or Zn-Ni alloy alone with a similar thickness. The corrosion potential measurement and anodic polarisation tests were undertaken to examine the probable corrosion mechanisms of zinc and Zn-Ni alloy CMM coatings. Analysis on the micrographic features of zinc and Zn-Ni alloy CMM coatings after the corrosion test explains the probable reasons why the Zn-Ni/Zn CMM coatings have a better protective performance. Surface morphologies and compositional analysis of the remaining coating material of Zn-Ni alloy deposit after the corrosion test confirms the dezincification mechanism of the Zn-Ni alloy deposit during the corrosion process.

Synergetic effect of stannate with o-aminophenol on inhibiting H2 evolution of A1 anode in strong alkaline media

The performance of Al-alloy anode in 4 mol/L KOH with and without stannate and o-aminophenol at 25℃ and 55℃ was studied by hydrogen collection, potentiodynamic polarization and electrochemical impedance spectrum, o-aminophenol acts as a perfect inhibitor because of its adsorbability and forming chelate complex at its optimum concentration of 0.4 mol/L. Stannate enhances the inhibition of o-aminophenol and improves the activity of Al-alloy because of its reduction to tin. There is synergetic effect of stannate with o-aminophenol on the behavior of Al-alloy, and the inhibitive efficiency at 55℃ is better than that at 25 ℃.

Zn-Ni合金电镀、钝化工艺及镀层性能

为了简化碱性体系Zn-Ni合金电镀,进一步提高镀层质量,对自制、多功能镀锌添加剂SD-1采用多乙烯多胺、香草醛等改性后,进行Zn-Ni合金电镀。以控制变量法通过霍尔槽和小槽试验获得了光亮、平整、细致的Zn-Ni合金镀层。通过扫描电子显微镜(SEM)、能量弥散X射线(EDAX)、X射线衍射(XRD)能谱仪分别对Zn-Ni合金镀层的微观结构及镍含量进行了表征;讨论了改性SD-1、镍离子、三乙醇胺(TEA)、电流密度等对Zn-Ni合金镀层性能的影响。结果表明:改性SD-1能使镀液透明稳定,可获得含镍量13%左右、结构致密、均匀平整、单一相的Zn-Ni合金镀层;Zn-Ni合金镀层的结合力较大,经彩色钝化之后,耐盐雾腐蚀高达1200 h以上。

光亮碱性Zn-Ni合金电镀工艺研究

采用碱性锌酸盐镀液为基础,加入适当的络合剂、镍盐和自制添加剂与光亮剂,研究成功了一种新的光亮碱性Zn-Ni合金电镀工艺,采用霍尔槽试验探讨了添加剂、光亮剂、主盐的影响,检测了镀液、镀层性能.结果表明:该镀液成分简单、操作方便,镀液分散能力和复盖能力好,所得锌镍合金镀层结晶细致、光亮平整,其耐蚀性明显优于锌镀层,适用于钢铁件高耐蚀性电镀.

镀液组成对碱性体系Zn-Ni合金镀层性能的影响

目的发现最优工艺条件,了解Zn-Ni电沉积机理。方法通过场发射电镜分析、能谱分析以及电化学分析等方法,研究以一种胺羧多官能团配体为Ni2+络合剂的碱性锌酸盐电解液体系中,锌/镍离子物质的量之比与锌镍离子总浓度对镀层的光泽度、镍含量、耐蚀性、表观质量和微观结构的影响。结果锌/镍离子物质的量之比增加会使得镀层镍含量降低,最后稳定在15%~19%,镀层微观结构由晶粒细致平滑型转化为粗大疏松型。物质的量之比为1.9时,镀层的腐蚀电流最小。锌镍离子总浓度增加会使得镀层镍含量缓慢减小,镀层微观结构由晶粒细致疏松型转化为细致紧密型,最后又转变为粗大疏松型,镀层的腐蚀电流先减小后急剧增大,即镀层的耐蚀性先增加后急剧降低。结论在锌/镍离子物质的量之比为1.9、锌镍离子总浓度为0.12 mol/L时,所得镀层的综合性能最好。镀层锌/镍含量变化趋势符合Brenner吸附膜理论。

Porous Nickel-Molybdenum Phosphide Alloy Electrodes for Alkaline Hydrogen Evolution Reaction at the High-Current Density

Alkaline water electrolysis is a practical route for large-scale green hydrogen production to assist decarbonization,whereby carbon dioxide emissions are limited.However,the use of this process in hydrogen evolution reaction(HER)is hampered by the alkaline solution,which leads to slow H_(2)O dissociation kinetics,especially when nickel–molybdenum(NiMo)alloy catalysts are utilized;thus,an improvement of this approach for effective HER activity is desirable.In this work,a porous phosphide NiMo-based(NiMoP)alloy electrode catalyst was engineered using a multistep electrodeposition method.Various experiments,combined with theoretical calculations,confirmed that the phosphide incorporation in the NiMo alloys promoted alkaline HER performance at a high current density of 1000 mA cm^(−2)with the potential−0.191 V.The evaluation of the effect of electrodeposition current density on HER performance revealed that the P content indeed positively impacted the accompanying alkaline HER performance,attributable to phosphide contribution in the electron reconstruction.Density functional theory(DFT)calculations demonstrated that the P atom promoted the loss of Mo electrons and hindered Ni from gaining electrons.This charge reconstruction allowed the optimization of the H^(*)adsorption,contributing to a stronger H_(2)O adsorption and encouraging H-OH^(*)bond breakage.Our current approach may provide the possibility of designing high-performance alkaline HER electrodes at high current density.

Effect of Surface Pretreatment on Adhesive Properties of Aluminum Alloys

The lap-shear strength and durability of adhesive bonded AI alloy joints with different pretreatments were studied by the lap-shear test and wedge test. The results indicate that the maximum lap-shear strength and durability of the bonding joints pretreated by different processes are influenced by the grade of abrasive papers and can be obviously improved by phosphoric acid anodizing. Alkali etching can obviously improve the durability of bonding joints although it slightly influences the maximum lap-shear strength. The process which is composed of grit-finishing, acetone degreasing, alkali etching and phosphoric acid anodizing, provides a better adhesive bonding property of Al alloy.

Role of nickel alloying on anodic dissolution behavior of zinc in 3.5% NaCl solution.Part II:Potentiodynamic,potentiostatic and galvanostatic studies

Zinc is common metal used for steel protection from corrosion.The addition of further element,such as Ni,can modify the corrosion rate and maintain sacrificial protection.The anodic dissolution behavior of Zn,Ni and Zn-Ni alloys with different Ni contents（from 0.5% to 10%,mass fraction） in 3.5% Na Cl solution was investigated using potentiodynamic,potentiostatic and galvanostatic techniques.The composition and microstructure of the corrosion layer on Zn,Ni and Zn-Ni alloys were characterized by energy-dispersive X-ray spectroscopy analysis（EDX） and scanning electron microscopy（SEM）.The galvanostatic curves show that the anodic behavior of all investigated electrodes exhibits active/passive transition and the tendency of the alloys to passivity decreases with the increase in Ni content,except for 99.5Zn-0.5Ni alloy.While the potentiodynamic curves exhibit active passive transition only for pure Zn.Surface analysis reveals the presence of oxides,chlorides and metal hydroxide chloride in corrosion products,and very small cracks are observed for 90Zn-10 Ni alloy compared with that of Zn.