Electrodeposition of Ni-B and Ni-Co-B Alloys by Using Boric Acid as Boron Source

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Processing of enriched elemental boron (B-10 similar to 65 at. %)

Procedures were developed for purification and processing of electrodeposited enriched boron powder for control rod application in India's first commercial Proto Type Fast Breeder Reactor (PFBR). Methodology for removal of anionic (F-, Cl-, BF4-) and cationic (Fe2+, Fe3+, Ni2+) impurities was developed. Parameters for grinding boron flakes obtained after electrodeposition were optimized to obtain the boron powder having particle size less than 100 gm. The rate of removal of impurities was studied with respect to time and concentration of the reagents used for purification. Process parameters for grinding and removal of impurities were optimized. A flowsheet was proposed which helps in minimizing the purification time and concentration of the reagent used for the effective removal of impurities. The purification methodology developed in this work could produce boron that meets the technical specifications for control rod application in a fast reactor.

Cu(In,Al)Se-2 thin films by one-step electrodeposition for photovoltaics

Chalcopyrite Cu(In,Al)Se-2 (CIAS) thin films are grown on stainless steel substrate through one-step electrodeposition at room temperature. Indium is partially replaced with aluminum to increase the band gap of CuInSe2 without creating significant change in the original structure. The deposition potential is optimized at -0.8 V (vs. SCE) and annealing of the films is performed in vacuum to remove binary phases present in the as-deposited films. In/Al ratio is varied from 1/9 to 8/2, to find the suitability for solar cell fabrication. For In/Al ratio of less than 8/2, CuAlSe2 phase is formed in the film in addition to the CIAS phase. Depth profile X-ray photoelectron spectroscopy analysis of the CIAS sample prepared with In/Al ratio of 8/2 in the precursor solution confirmed the existence of single phase CIAS throughout the film. This film showed p-type conductivity while the rest of the samples with In/Al ratio less than 8/2 showed n-type conductivity. The band gap of the film varied from 1.06 to 1.45 eV, with variation in deposition potential. Structural, optical, morphological, compositional and electrical characterizations are carried out to establish the suitability of this film for solar cell fabrication. (C) 2013 Elsevier B.V. All rights reserved.

Polyamidoamine dendrimers-assisted electrodeposition of gold-platinum bimetallic nanoflowers

Novel Au-Pt bimetallic flower nanostructures fabricated on a polyamidoamine dendrimers-modified surface by electrodeposition are reported. These polyamidoamine dendrimers were stable, and they assisted the formation of Au-Pt bimetallic nanoflowers during the electrodeposition process. These nanoflowers were characterized by field-emitted scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and electrochemical methods. FE-SEM images showed that the bimetallic nanoflower included two parts: the "light" and the "pale" part. The two parts consisted of many small bimetallic nanoparticles, which was attributed to the progressive nucleation process. Moreover, the "light" part contained more bimetallic nanoparticles. The morphologies of bimetallic nanoflowers depended on the electrodeposition time and potential and the layer number of assembled dendrimers. The average size of nanoflowers increased with the increase in electrodeposition time. The layer number of assembled dendrimers obviously affected the size and morphologies of the "pale" parts of deposited nanoflowers.

PHOTOELECTROCHEMISTRY OF ELECTRODEPOSITED POLYCRYSTALLINE CUINSE2 THIN-FILMS .1. ELECTRODEPOSITION OF CUINSE2 FILMS

Electrodeposition of CuInSe2 was investigated in acidic solutions containing Cu2+, In3+ and HSeO2+ ions. The electrodeposition condition was optimized with the aim of obtaining uniform thin films on titanium substrate. The mechanism of the electrodeposition process is discussed. Structure analysis of the deposited film shows a typical polycrystalline chalcopyrite structure, good crystallinity and homogeneous dispersion. The photoelectrochemical cells made of these kinds of deposited films in polysulfide redox solution give distinct photoresponse.

ELECTRODEPOSITION OF POLYCRYSTALLINE CD-RICH HG1-XCDXTE AND PHOTOELECTRO-CHEMICAL BEHAVIOR OF HG0.09CD0.91TE THIN-FILM

Electrodeposition process of polycrystalline Cd-rich Hg_(1-z)Cd_xTe (x>0.5) in acidic bath of CdSO_4+HTeO_2~+HgCl_2 was investigated. The simultaneous electrodeposition technique of three kinds of ions at the same potential has been achieved. The XRD, SEM and EDAX analysis of the thin film electrodeposited on titanium substrate showed a typical cubic zinc blende polycrystalline structure and homogeneous dispersion. The photoelectrochemical behavior of (1-x)=0.09 polycrystalline thin film in a polysulfide re...

Influence of the anion on the electrodeposition of cobalt from imidazolium ionic liquids

Cyclic voltammetry and absorption spectrophotometry were used to examine the complex formation of cobalt (II) in the ionic liquids 1-butyl-3-methylimidazolium chloride ([C(4)mim] Cl) and 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([C(4)mim][Tf2N]). In [C(4)mim]Cl, cobalt(II) is complexed as [CoCl4](2-) at CoCl2 concentrations less than 33 mol %. Cyclic voltammograms show that cobalt cannot be electrodeposited at these concentrations. However, cobalt metal can be electrodeposited at CoCl2 concentrations above the threshold concentration of 33 mol %. In the ionic liquid [C(4)mim][Tf2N] there is no threshold CoCl2 concentration for electrodeposition due to the absence of [CoCl4](2-). (C) 2007 The Electrochemical Society.

Organic addittives in zinc electrowinning and electrodeposition of Fe-Mo-P alloys as cathodes for chlorate production

Ce projet de travail est divisé en deux études principales: (a) l’influence des certains additifs organiques sur la consommation d’énergie et la pureté du métal de zinc déposé dans le processus d’extraction électrolytique, et (b) l’électrodéposition des alliages binaires et ternaires de Fe-Mo et Fe-Mo-P sur des substrats d’acier doux afin d’agir comme cathodes pour la production de chlorate. (a) Parmi les sept différents additifs organiques examinés, les sels des liquides ioniques ont réussi à augmenter le rendement du courant jusqu’à 95,1% comparé à 88,7% qui a obtenu à partir de l’électrolyte standard en présence des ions de Sb3+. La réduction maximale de la consommation d’énergie de ~173 kWh tonne-1 a été obtenue en ajoutant de 3 mg dm-3 du chlorure de 1-butyl-3-méthylimidazolium dans le même électrolyte. La teneur en plomb dans le dépôt de zinc est réduite de 26,5 ppm à 5,1-5,6 ppm en utilisant les sels des liquides ioniques. (b) Des différents binaires Fe-Mo et ternaires Fe-Mo-P alliages ont été électrodéposés sur des substrats d’acier doux. Les alliages préparés ont une tenure en Mo entre 21-47 at.% et une tenure en P de 0 à 16 at.%. L’activité électrocatalytique de ces alliages vers la réaction de dégagement d’hydrogène (RDH) a été étudiée dans des solutions de chlorure de sodium. La réduction maximale de la surtension de RDH de ~313 mV a été obtenue par l’alliage ternaire préparé Fe54Mo30P16 par rapport à celle obtenue pour l’acier doux. La rugosité de surface et l’activité intrinsèque des revêtements de Fe-Mo-P peuvent être l’origine du comportement prometteur de ces électrocatalyseurs vers la RDH.

Synthesis of L1(0) Fe-Pd films by electrodeposition and thermal annealing

Fe-Pd alloy films have been prepared by electrochemical deposition from an alkaline electrolyte containing Fe sulfate, Pd chloride and 5-sulfosalicylic acid onto polycrystalline titanium substrates. The as-deposited films were nanocrystalline and magnetically soft (coercivity similar to 25 Oe). L1(0) Fe-Pd films with a (111) preferred orientation were obtained by post-deposition thermal annealing of films with composition about 37 at% Fe in an (Ar + 5% H-2) gas flow at 500 degrees C. Such films exhibit hard magnetic properties, with a coercivity up to 1880 Oe, and a slightly anisotropic magnetic response, with a larger in-plane remanence. Preliminary magnetic investigations support magnetization switching through pinning of domain walls. (c) 2008 Elsevier B.V. All rights reserved.

Electrodeposition and characterization of thin selenium films modified with lead ad-atoms

The deposition and characterization of Se films doped with Pb underpotentially deposited (UPD) ad-atoms was studied in this work. The employed experimental techniques were cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, UV-vis spectroscopy and atomic force microscopy. The initial deposition of Se film by chronoamperometry yielded a thin film composed of approximately 700 layers. The Pb UPD on Se was achieved by chronoamperometry in a potential value previously determined in voltammetric experiments. This deposition yielded a deposition charge of approximately 7.5% of the total one. The film resistance altered from 320 Omega cm(2) for Se to 65 Omega cm(2) for the Se/Pb one. Flat band potential values and number of acceptors and donors were also calculated for both films and the values obtained were + 0.95 and -0.51 V for Se and Se/Pb, respectively. The Se coating presented 1.2 x 10(17) cm(3) acceptors while the Se/Pb one presented 3.2 x 10(17) cm(3) donors. The band gap values for both films were 2.4 eV and 1.9 eV, correspondingly. (C) 2008 Elsevier B.V. All rights reserved.

The processes involved in the Se electrodeposition and dissolution on Au electrode: the H2Se formation

The processes involved in the Se electrodeposition, mainly the one related to the formation of H2Se species on Au electrode in perchloric acid solutions, have been investigated through cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), rotating ring-disc electrode (RRDE), and atomic force microscopy (AFM) techniques. In the experiments performed with the EQCM, with the potential sweep in the negative direction, the responses for the mass variation were divided in three well-defined potential regions: A (from 1.55 to 0.35 V), B (from 0.35 to -0.37 V), and C (from -0.37 to -0.49 V). It was verified that the following processes can occur, respectively: the species (AuO)(2)H2SeO3 was desorbed during the AuO reduction, the reduction of Se(IV) to Se(0), and the formation of H2Se. When the potential was swept in the positive direction, the responses for the mass variation were divided in four well-defined potential regions: D (from -0.49 to 0.66 V), E (from 0.66 to 0.99 V), F (from 0.99 to 1.26 V), and G (from 1.26 to 1.55 V), and the described processes in these regions were, respectively: the Se deposition and adsorption of water molecules and/or perchlorate ions, the Se dissolution, the Se incorporating mass in the form of HO-Se, and the Au oxidation (all potentials are referred to the Ag/AgCl electrode). Making use of the RRDE, using the collection technique, the formation of H2Se species during the Se electrodeposition was investigated. Therefore, it was confirmed that this species is formed on the disc electrode between -0.3 and -0.55 V vs the Ag/AgCl potential range (collecting the oxidized compound onto the ring electrode). AFM images also indicated that the surface topography of the Se-massive deposit on Au is different from the images registered after the formation of H2Se species, confirming the cathodic stripping of Se.

Electrodeposition and characterization of undoped and nitrogen-doped ZnSe films

Semiconducting films of (n-type) ZnSe and (p-type) nitrogen-doped ZnSe were electrodeposited by a linear-sweep voltammetric technique on to a substrate of fluorine-tin oxide (FM) glass ceramics. The films were characterized by scanning electron microscopy, energy-dispersive X-ray analysis and grazing-incidence X-ray diffraction. The results indicated that the material was deposited uniformly over the substrate, forming clusters when the Zn content of the bath was 0.1 mol L(-1) and a film when it was 0.2 or 0.3 mol L(-1). The effectiveness of doping the films with nitrogen by adding ammonium sulfate to the deposition solution was assessed by measuring the film-electrolyte interface capacitance (C) at various applied potentials (E(ap)) and plotting Mott-Schottky curves (C(-2) vs E(ap)), whose slope sign was used to identify p-type ZnSe. (C) 2009 Elsevier B.V. All rights reserved.