Monte Carlo simulation of metal deposition on foreign substrates

The deposition of a metal on a foreign substrate is studied by means of grand canonical Monte Carlo simulations and a lattice-gas model with pair potential interactions between nearest neighbors. The influence of temperature and surface defects on adsorption isotherms and differential heat of adsorption is considered. The general trends can be explained in terms of the relative interactions between adsorbate atoms and substrate atoms. The systems Ag/Au(100), Ag/Pt(100), Au/Ag(100) and Pt/Ag(100) are analyzed as examples.Comment: 26 pages, 9 figure

Characterisation of MEAs for Electrochemical Energy Conversion Using an Easy Test Technique

The paper describes an EasyTest cell developed for simple, safe and inexpensive to run testing and optimisation of the active materials (catalysts, catalytic supports, polymer membrane electrolytes) and electrode structures utilized in PEM Fuel cells and Electrolysers. The main advantages of the new EasyTest technique are demonstrated by a comparative study on the performance of two types of membrane electrode assemblies for electrochemical energy conversion. Nafion and PBI-based polymer electrolyte membranes covered with catalytic layers containing 20 % Pt dispersed on carbon black (E-TEK, De Nora) are tested as hydrogen electrodes working in a fuel cell and an electrolyser mode at two characteristic temperatures, varying the total partial pressure in the cell. The PBI-based membrane electrode assembly (MEA) gives lower current densities compared to that containing Nafion, while its performance remains stable in a much broader potential range. At overpotentials of about = 300–350 mV the Nafion MEA reaches a limiting current density, while in the case of PBI-based MEA such an effect is not registered in the whole potential range tested

Room Temperature Electrochemical Synthesis of Hg-1212 Superconducting Thin Films

In the present investigation, the novel two-step electrochemical process of room temperature synthesis of Hg-1212 superconducting films has been developed and reported first time. Electrochemical parameters were optimized by studying cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) for the deposition of Hg-Ba-Ca-Cu alloy at room temperature. Current time transient showed progressive growth with hemispheriodal granules, which were then revealed by scanning electron microscopy (SEM). Stoichiometric electrocrystallization to get Hg1Ba2Ca1Cu2O6+x (Hg-1212) was completed by electrochemically intercalating oxygen species into Hg-Ba-Ca-Cu alloy at room temperature. The oxygen content in the samples was varied by varying the electrochemical oxidation period and the changes in the crystal structure, microstructure, and superconducting transition temperature (Tc) and critical current density (Jc) were recorded. The films oxidized for 28 min showed Tc = 104.7 K with Jc = 1.437 x 103 A/cm2. The dependence of superconducting parameters on oxygen content is correlated with structure property relations and reported in this paper.Comment: 39 pages, 17 figures. Submitted to Physica

Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte

A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm−2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially

Characterization and microhardness of Co-W coatings electrodeposited at different pH using gluconate bath: A comparative study

Electrodeposition of Co–W alloy coatings has been carried out with DC and PC using gluconate bath at different pH. These coatings are characterized for their structure, morphology and chemical composition by XRD, FESEM, DSC and XPS. Alloy coatings plated at pH8 are crystalline, whereas coatings electrodeposited at pH5 are nanocrystalline in nature. XPS studies have demonstrated that as-deposited alloy plated at pH8 with DC contain only Co2+ and W6+ species, whereas that alloy plated at pH5 has significant amount of Co0 and W0 along with Co2+ and W6+ species. Again, Co2+ and W6+ are main species in all as-deposited PC plated alloys in both pH. Co0 concentration increases upon successive sputtering of all alloy coatings. In contrast, mainly W6+ species is detected in the following layers of all alloys plated with PC. Alloys plated at pH5 shows higher microhardness compared to their pH8 counterparts