Electrochemical Properties Of Alloys Research Articles

Preparation of porous polyaniline/RGO composite and its application in improving the electrochemical properties of Co9S8 hydrogen storage alloy

The sea urchin-like porous polyaniline (PPANI) is prepared by a facile saturated solution synthetic route. The porous polyaniline/reduced graphene oxide composite (PPANI/RGO) is synthesized via a solution-assisted self-assembly method. Mechanical alloying is used to obtain the Co9S8 alloy. Composites of Co9S8 mixed with PPANI and PPANI/RGO are fabricated through ball-milling to improve the electrochemical performance of Co9S8 alloy. The structures and morphologies of the composite alloys are studied by XRD, SEM and BET. The electrochemical properties of alloys are tested as negative electrodes of Ni-MH batteries by the LAND CT2001A tester and three-electrode system. For comparison, Co9S8 alloys doped with conventional polyaniline (CPANI) and RGO are also prepared. Ultimately, the Co9S8 + PPANI composite shows preferable discharge capacity compared with CPANI modified Co9S8 and matrix alloy. In addition, the PPANI/RGO composite modified Co9S8 electrode exhibits superior discharge capacity than separate PPANI and RGO coated alloys. A maximum discharge capacity (701.4 mAh/g) is achieved for Co9S8 + PPANI/RGO electrode. Furthermore, the Co9S8 + PPANI/RGO composite materials exhibit preferable high-rate dischargeability, improved corrosion and oxidation resistance and excellent kinetics properties. The PPANI material with special porous structure and unique morphology displays better performance than CPANI. Moreover, a synergistic effect between PPANI and RGO species in the PPANI/RGO material may provide a rapid passageway for charge transfer and accelerate the hydrogen transmission. Accordingly, the electrochemical activity and kinetic properties are improved for Co9S8 + PPANI/RGO composite electrode.

Effect of Cu and Ti electrodes on surface and electrochemical properties of Electro Discharge Machined (EDMed) structures made of Co-Cr and Ti dental alloys

ObjectivesPrevious studies have shown that the use of Cu electrodes compromises the electrochemical properties of Co-Cr and Ti alloys used for the fabrication of implant retained superstructures by Electro Discharge Machining (EDM). A possible solution is the use of Ti instead of Cu electrodes and thus the aim of this study was to evaluate the effect of Cu and Ti electrodes on surface and electrochemical properties of two types of dental alloys used for fabrication of implant retained superstructures after EDM. MethodsThree full arch frameworks were prepared from a Co–Cr and three from Ti6Al7Nb alloy. One framework from each alloy was used as control, one was subjected to EDM with Cu electrodes and the last one with Ti electrodes. Morphological and elemental characterization was studied by SEM/EDX. The electrochemical properties of the alloys were evaluated by Open Circuit Potential (OCP) and Linear Sweep Voltammetry (LSV) in Ringer’s solution. Electrochemical data were analyzed statistically by one way ANOVA and SNK multiple comparison tests at a = 0.05 ResultsAll groups demonstrate the typical surface after EDM treatment with almost circular valleys and an increase in C and O content compared to control groups. Both alloys demonstrated an uptake of C and Cu by Cu electrodes and C and Ti after treatment with Ti electrodes. The use of Cu electrodes had a detrimental effect on corrosion resistance of Ti alloy. SignificanceThe use of Ti electrodes mitigates the degradation of electrochemical properties compared to Cu electrodes and from this standpoint is safer for the EDM of implant retained superstructures made of Co-Cr and Ti alloys.

Correlation between electrochemical properties of the CNTs/AB5 composite hydrogen storage alloys and their catalytic properties for KBH4

Searching for non-precious metal anode catalysts with high catalytic activity and capable of inhibiting hydrolysis side reactions is very important for direct borohydride fuel cell (DBFC). In this work, the as-cast AB5 alloy powders are firstly mixed with CNTs in a ratio of 1:9. Then the mixture of AB5 alloy and CNTs is ball milled in different milling time. Finally, the CNTs/AB5 composite alloys are obtained. Not only the catalytic properties of the CNTs/AB5 composite alloys used as anode catalysts in DBFC, but also the electrochemical properties of the alloys have been investigated in detail. The research results indicate that, as the ball milling time is extended, the electrochemical properties and catalytic properties on ΒΗ4− of the CNTs/AB5 composite alloys become better first and then worsen. The CNTs/AB5 alloy milled 2 h exhibits the best electrochemical properties and catalytic properties. Furthermore, we predict that the electrochemical properties of the composite alloy are positively correlated with the catalytic properties as anode catalyst for DBFC.

Phase Structure and Electrochemical Properties of Melt-Spun La4MgNi17.5Mn1.5 Hydrogen Storage Alloys

The (La4MgNi17.5Mn1.5) alloys at different melt-spun speeds were prepared by using a vacuum melt-spun furnace, and the phase structure and electrochemical properties of alloys were studied. X-ray diffraction analysis results show that melt-spun La4MgNi17.5Mn1.5 alloys are composed of CeCu5-type, Pr5Co19-type and CeNi2-type phase. As the melt-spun speed increased, the phase abundance of CeCu5-type increased, but that of Pr5Co19-type decreased. Scanning electron microscopy–energy-dispersive spectroscopy analysis results show that melt-spun treatment can refine grain and make the alloys homogenization. Electrochemical tests show that all alloys have good activation performance within four cycles. With the increase in melt-spun speed, the cycle stability (S) of the alloys was improved obviously. After 100 cycles, the retention rate (S 100) of the alloy increased from 54.82% (as-cast) to 82.29% (25 m/s). Nevertheless, the maximum discharge capacity (C max) and high-rate dischargeability gradually decreased.

Electrochemical behavior of Mg-Al-Pb alloy in 3.5% NaCl solution

An investigation on electrochemical behavior of Mg-5%Pb alloy, Mg-6%Al alloy and Mg-6%Al-5%Pb alloy (mass fraction) in 3.5% NaCl (mass fraction) solution was conducted using electrochemical measurements and corroded morphology observation, in which solid solution and the as-aged state of each alloy were compared to discuss the influence mechanism of lead and aluminium on the electrochemical properties of alloys. The X-ray diffraction (XRD) analysis was performed to make microstructure characterization. The electrochemical results indicate that the corrosion of Mg-5%Pb alloy is predominated by homogeneous pitting and dissolution of PbCl2 film due to Cl ions attack, while corrosion crevice propagates along grain boundaries in solid solution of Mg-6%Al alloy and the micro galvanic corrosion also plays vital role in Mg17Al12 phase containing experimental alloys. The co-existence of lead and aluminium in magnesium alloy increases corrosion current density and electrochemical activity as well. The comparison between solid solution and the as-aged state demonstrates that Mg2Pb and Mg17Al12 somewhat increase corrosion resistance but lighten anodic polarization by facilitating corrosion product flaking off.

Effects of Lanthanum and Cerium Mixed Rare Earth Metal on Abrasion and Corrosion Resistance of AM60 Magnesium Alloy

Abstract The effects of lanthanum and cerium mixed rare earth metal on the abrasion and corrosion resistance of AM60 magnesium alloy were analyzed by the hydrogen evolution method, mass gain test, electrochemical test, as well as friction and wear characteristics test. It can be found that after adding lanthanum and cerium mixed rare earth metal, AM60 magnesium alloy's electrochemical properties, friction and wear performance are all improved in 0.35%NaCl solution. For example, hydrogen evolution corrosion current density, polarization current density and capacitance all decrease while its corrosion potential and polarization resistance increase. Moreover, its friction coefficient and specific wear rate decrease. This is because adding of lanthanum and cerium results in refining of the grains of α phase and Mg17Al12 phase of AM60 magnesium alloy and forming of new Al2Ce and Al11La3 phases, which inhibit the progress of cathodic depolarization, whilst the added Ce and La form a composite anodic film on the surface of the alloy, which block the dissolution and improve the corrosion resistance.

Improvement in −40 °C electrochemical properties of AB2 metal hydride alloy by silicon incorporation

The ultra-low temperature (−40°C) charge transferred resistance of a Laves phase based-AB2 metal hydride alloy was reduced by a factor of 5 by a partial substitution of Ni with Si in Ti12Zr21.5V10Cr7.5Mn8.1Co8.0Ni32.2−xSixSn0.3Al0.4, where x=0–4. This improvement was due to the increases in surface area from the higher leaching-rate of the oxidation product of Si and to the surface catalytic effect with the incorporation of Si. The microstructure, gaseous phase hydrogen storage, and electrochemical properties of these alloys were investigated and reported. With the addition of Si in the formula, the abundances of both C15 and TiNi minor phases increased, which resulted in decreases in both maximum gaseous phase hydrogen storage and electrochemical capacities. Some changes on the chemical compositions of the minor phases from the Si-incorporation were observed but cannot be correlated to the improvement in low-temperature performance. These changes are the transition from Zr to ZrO2, the decrease in Ti/Zr ratio in the TiNi phase, and the higher Sn-content in the TiNi phase. An amount of 1at.% of Si is recommended from the balance among capacity, bulk diffusion, surface area, and catalytic properties of the alloys. In addition, a special sample preparation method for using inductively coupled plasma analysis to determine the Si-content in the sample was developed and presented.

Effects of Cerium on the Microstructures and Electrochemical Properties of Al-Zn-Sn Sacrificial Anodes

To improve the current efficient of Al-Zn-Sn alloy, the influence of different contents Ce on the microstructures and electrochemical properties of alloy was investigated. The results show that the appropriate amount of Ce was effective on improving the electrochemical properties of Al-Zn-Sn alloy. The corrosion potential shifted negatively and the current efficiency increased with the increasing of Ce contents. The optimal microstructure and electrochemical properties were obtained when the Ce content in the alloy was 0.5 wt.%. The good electrochemical properties of Al-7Zn-0.1Sn- 0.5Ce (wt.%) alloy is mainly attributed to the fine grains and the less segregation phases at grain boundary.

Recent progress in hydrogen storage alloys for nickel/metal hydride secondary batteries

This paper reviews the development of hydrogen storage alloys prepared by an effective method of mechanical alloying and milling. It emphasizes alloys based on Mg or that contain Mg due to their low cost, low weight and high hydrogen storage capacity. Hydrogen absorption/desorption and electrochemical measurements are briefly discussed. The electrochemical properties of the alloys that contain Mg are covered in detail, emphasizing the effects of changes in alloy composition. The system of Ti–Ni-based alloys is also introduced. At present, composite hydrogen storage alloys may be the most effective materials for practical application in new nickel/metal hydride secondary batteries. The steps of hydrogen absorption/desorption such as charge-transfer and hydrogen diffusion for evaluating the electrochemical properties of hydrogen storage alloys are discussed. The relationship between alloy composition and electrochemical properties is noted and evaluated.

Electrochemical properties of Mg-based hydrogen storage alloys prepared by hydriding combustion synthesis and subsequent mechanical milling (HCS+MM)

In this paper, a novel method, namely hydriding combustion synthesis (HCS) and subsequent mechanical milling (MM) was used to prepare Mg-based hydrogen storage electrode alloy. The phase structures and electrochemical properties of the alloys before and after MM were characterized by X-ray diffraction (XRD) analysis and galvanotactic charge–discharge cycle test, respectively. The XRD results showed that the structure of the as-milled alloys was nanocrystallite or amorphous-like state. Electrochemical measurements showed that the discharge capacity was improved greatly for the products of HCS+MM. The HCS product with only 5h MM showed markedly increased discharge capacity up to 481.5mAh/g for the first cycle, which was 10 times higher than the HCS product (39.4mAh/g). The discharge capacity was further increased to 628.3mAh/g for the HCS product after milling with nickel powder. Besides, the addition of nickel also led to an improved cycling stability of the alloy electrode during cycling in KOH electrolyte. It was indicated that the HCS+MM was promising for preparing Mg-based hydrogen storage electrode alloys.

Effects of chemical coating with Ni on electrochemical properties of Mg 2Ni hydrogen storage alloys

The effects of nickel coating on the electrochemical properties of Mg 2Ni hydrogen storage alloys are presented in this paper. X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques were employed to examine the crystal structure and surface morphologies of the bare and Ni-coated Mg 2Ni alloys. The electrochemical properties of alloys were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that Ni coating not only decreased the charge transfer resistance, but also decreased the H atom diffusion resistance for Mg 2Ni alloys. It was also found that Ni coating effectively improved the discharge capacity, but decreased the cycling performance of the as-synthesized Ni-coated Mg 2Ni alloys. The discharge current has a great impact on the cycling performance of the as-synthesized Ni-coated Mg 2Ni alloys.

Hydrogen sorption and electrochemical properties of alloys: Systems Zr-Ti-Ni-V-Mn with laves phase structures

Using scanning electron microscopy and x-ray phase analysis techniques, it is shown that the C14-type Laves phase with a wide homogeneity reaching the AB2.3 stoichiometry is the main phase in the Zr0.5Ti0.5NiyV0.5Mnx alloys, where y = 0.8–1.4 and x = 0.1–1.7. With the increase in the nickel and manganese contents and in the stoichiometric ratio B/A, the hydrogen capacity decreases from 2 to 1.6 wt %, the equilibrium pressure of hydride phases increases, and the hydrides become less stable. The highest discharge capacity is reached for stoichiometric ratios AB1.7–2.3, where the maximum discharge capacity at a discharge current density of 100 mA/g is 300 (mA h)/g. Alloys that contain ferrovanadium in place of vanadium are also considered.

Crystal structure and electrochemical properties of rare earth non-stoichiometric AB5-type alloy as negative electrode material in Ni-MH battery

The La 0.85Mg x Ni 4.5Co 0.35Al 0.15 (0.05⩽ x⩽0.35) system compounds have been prepared by arc melting method under Ar atmosphere. X-ray diffraction (XRD) analysis reveals that the as-prepared alloys have different lattice parameters and cell volumes. The electrochemical properties of these alloys have been studied through the charge–discharge recycle testing at different temperatures and discharge currents. It is found that the La 0.85Mg 0.25Ni 4.5Co 0.35Al 0.15 alloy electrode is capable of performing high-rate discharge. Moreover, it has very excellent electrochemical properties as negative electrode materials in Ni-MH battery at low temperature, even at −40°C.

Study on the Electrode Characteristics of Hypostoichiometric Zr‐Ti‐V‐Mn‐Ni Hydrogen Storage Alloys

The hydrogen storage performance and electrochemical properties of alloys are investigated. All of these alloys have mainly a C14‐type Laves phase structure according to X‐ray diffraction analysis. As the mole fraction of Ti in the alloy increases, the reversible hydrogen storage capacity decreases, while the equilibrium hydrogen pressure increases. Furthermore, the discharge capacity shows a maximum and the rate capability is increased, but the cycling durability is rapidly degraded with increasing Ti content in the alloy. The analysis of surface composition shows that the rapid degradation of Ti‐substituted Zr‐based alloy electrodes is due to the growth of an oxygen penetration layer. After comparing the radii of atoms and ions in the electrolyte, it is clear that the electrode surface becomes more porous, which is the source of growth of the oxygen penetration layer and causes accelerating the dissolution of alloy constituting elements with increasing Ti content. Consequently, the rapid degradation (fast growth of the oxygen‐penetrated layer) with increasing Ti substitution in Zr‐based alloy is ascribed to the formation of a porous surface oxide through which the oxygen atom and hydroxyl ion, with relatively large radii can easily transport into the alloy surface. © 2000 The Electrochemical Society. All rights reserved.

Effects of Lead Oxide Addition on the Electrochemical Properties of Alloy 600 in Aqueous 1 M Sodium Hydroxide Solution

Abstract Effects of lead oxide (PbO) addition on the electrochemical properties of alloy 600 (UNS N06600) have been studied in aqueous 1 M sodium hydroxide (NaOH) solution at room temperature using...

Effect of microstructure, composition and non-stoichiometry on electrochemical properties of low-Co rare-earth nickel hydrogen storage alloys

A series of low-Co stoichiometric and non-stoichiometric rare-earth nickel hydrogen storage alloys were examined for the possible application as negative electrodes in NiMH batteries. Partial substitution of Co by one transitional metal such as Cu, Fe, Cr or Zn did not effectively improve the electrochemical cycling stability, while a combined replacement of Co by Cr, Cu and Si was very effective in improving the cycling durability though the initial capacity was slightly low as compared with the parent alloy. In this work, the low-Co non-stoichiometric alloys did not appear superior in the capacity, rate capability and the charge–discharge cycling stability. The discharge capacity seems to be determined by the alloying components and compositional homogeneity. The cycling durability was dominated by the microstructure of alloys. The microstructure and chemical composition of alloys were examined and analyzed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The relationship between the microstructure and electrochemical properties of alloys was discussed.

Studies of Electrochemical Properties of Ti0.35Zr0.65Nix V 2 − x − yMny Alloys with C14 Laves Phase for Nickel/Metal Hydride Batteries

Electrochemical properties of alloys used as metal hydride electrode material have been investigated. In the cathodic charging process, alloy B has the largest reduction current followed by alloy C and alloy D . On the other hand, hydrogen evolution reaction occurs when the electrode potentials of alloy B to D reach −0.946, −0.941, and −0.932 V vs. Hg/HgO, respectively. In the anodic process, the discharge capacities were measured. The activation overpotential and concentration overpotential of electrode can be separately calculated from the anodic polarization data. At low discharge current density, the charge‐transfer process is the dominant electrode reaction, whereas at high discharge current density, hydrogen diffusion within the bulk of alloy is the rate‐determining step. Finally, some electrochemical parameters concerning the electrode kinetics of hydrogen‐absorbing alloy such as exchange current density, limiting current density, and transfer coefficient are estimated.

合金の電気化学的性質に関する研究（第8報）Fe-Cr, Fe-Ni及びFe-Cr-Ni合金の陽極的挙動に及ぼすMo添加の影響

合金の電気化学的性質に関する研究（第8報）Fe-Cr, Fe-Ni及びFe-Cr-Ni合金の陽極的挙動に及ぼすMo添加の影響

合金の電気化学的性質に関する研究（第7報）Fe-Cr-Ni三元合金の硫酸水溶液中における陽極的挙動

合金の電気化学的性質に関する研究（第7報）Fe-Cr-Ni三元合金の硫酸水溶液中における陽極的挙動

第3報 第4報 正誤表

第3報 第4報 正誤表