170,220 research outputs found
Electrodeposition of stoichiometric polycrystalline ZnTe on n+-GaAs and Ni-P
No full textAn acid aqueous sulphate electrolyte is proposed for the low temperature direct electrochemical growth of single-phase polycrystalline ZnTe. Single-crystal n+-GaAs and amorphous electroless Ni-P were used as substrates. The relationship between electrochemical growth conditions and the crystalline structure of as-deposited ZnTe were disclosed and correlated to the cathode chemistry during the growth process. Under suitable plating conditions the removal of tellurium (Te) excess from the deposit can be achieved, resulting in stoichiometric ZnTe. The nucleation of ZnTe was assessed through morphology observations by scanning electron microscopy: an instantaneous type prevails on GaAs and a progressive one on amorphous Ni-P. Chemical depth profiles of Zn and Te were investigated by X-ray photoelectron spectrometry measurements
Electrochemical fabrication of nano- and micrometric Cu particles: in situ investigation by electroreflectance and optical second harmonic generation
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Spectroelectrochemical investigation of the anodic and cathodic behaviour of zinc in 5.3 M KOH
No full textA corrosion and electrodeposition study of a Zn
electrode in 5.3 M KOH, used as a model system for the
anode of a secondary Zn–air battery, was performed by
means of electrochemical and spectroelectrochemical
techniques. The formation of a zinc oxide passive film and
its cathodic removal were monitored by electroreflectance
spectroscopy, spectroellipsometry and optical second harmonic
generation. A dynamic optical model of the growth
pathway, morphology and failure modes of the interfacial
Zn oxide films was proposed to rationalise the electrokinetics
of the secondary battery anode. Some experiments
were performed in the absence and in the presence of
polyethylene glycol. In situ spectroscopy confirmed and
placed on a molecular basis the well-known formation of
more compact and uniform electrodeposits crucial for
secondary batteries.
Keywords Zn–air batter
Electrochemical fabrication of nanoporous gold decorated with manganese oxide nanowires from eutectic urea/choline chloride ionic liquid. Part III − Electrodeposition of Au–Mn: a study based on in situ Sum-Frequency Generation and Raman spectroscopies
No full textIn two previous papers (C. Mele, M. Catalano, A. Taurino, B. Bozzini. Electrochim. Acta 87 (2013) 918; B. Bozzini, A. Gianoncelli, C. Mele, M. Kiskinova. Electrochim. Acta 114 (2013) 889), we have: (i) fabricated high-capacitance materials consisting of nanoporous gold (NPG)-supported MnO2 nanowires (NW), by electrochemical etching of single-phase Au-Mn alloys electrodeposited from a deep eutectic solvent (DES) electrolyte and (ii) investigated some aspects of the precursor Au-Mn alloy electrodeposition process by following it in situ with space-resolved soft X-ray fluorescence (XRF) and absorption (XAS) microspectroscopies: this study has allowed to single-out the peculiarities of elemental and chemical-state distribution that contribute to the nanostructure fabrication. The present paper completes the electrodeposition study by investigating the potential-dependent interfacial composition of the growing Au-Mn alloys by complementary in situ linear (Raman) and non-linear (Sum-Frequency Generation - SFG) vibrational spectroscopies. The results regarding alloy electrodeposition are compared to those obtained with a pure Au bath. In situ spectroscopy during electrodeposition reveals that both choline cation and urea are present at the growing metal/DES interface, coadsorbed with CN resulting from the decomposition of the Au complex. Electrostatic adsorption controls the surface coverage scenario at the Au/DES interface, while Mn favours the relative surface coverage with urea. Moreover, the interaction of urea with the metal film is modified by the addition of Mn, switching from solid-like to liquid-like at the Mn-alloying potential threshold. Also the CN adsorption scenario is sensitive to surface alloying: the Mn-containing interface shows two adsorption sites with lower degree of metal-adsorbate charge transfer. Finally, the degree of surface enhancement correlates well on the one hand with the applied potential and the interfacial chemistry, and on the other hand with the crystallite morphology induced by alloying Au with Mn. The correlation among the spectroelectrochemical scenario, the potential-dependent alloy composition and the crystallite shape expressed by this investigation fits within the framework set by recent modelling of dynamic electrodeposition morphochemistry and opens up novel opportunities for improving the control over the functional properties of net-shape electrodeposited material
Electrochemical and X-ray photoelectron spectroscopy investigation into anodic behaviour of electroless Ni–9·5 wt-%P in acidic chloride environment
No full textThis paper reports on the anodic behaviour of as plated (X-ray amorphous) and heat treated (crystalline) high P electroless Ni-P deposits investigated by potentiodynamic and potentiostatic methods in acidic aqueous chloride solutions. Potentiodynamic measurements show all active-passive behaviour for both structures. The valence of P dissolution was assessed by the weight loss v. charge technique; dissolution valences do not correlate clearly with potentiodynamic behaviour. This call nevertheless he clearly interpreted ill terms of ex situ X-ray photoelectron spectroscopy analyses of attacked layer composition: the layers formed at lower anodic potential within the passive range consist of NiO, the ones obtained at high anodic polarisation contain phosphate. Differences ill anodic behaviour of as plated and heat treated specimens can he explained in terms of the defectiveness of protective NiO layers as a function of grain boundaries emerging at the surface
Feedback control of morphology evolution in metal electrodeposition by optical means
No full textControl of morphology and in particular of roughness, is critical in metal electrodeposition. Morphology control is traditionally achieved by indirect chemical methods implying addition agents whose mechanisms of action are often rather poorly known, thus rendering the stability of processes questionable. In this paper we mean to tackle some basic problems paving the way to direct closed-loop control of morphology. The single components of a possible control loop are developed conceptually and implemented in actual devices and routines. Proper closed-loop operation of the system is on its way and will be reported in a subsequent paper. An optical method meant to directly quantify surface-roughness is devised. IR radiation scattering by reflecting surfaces is sensitive to roughness in the range typically relevant to electroplating. Reflected IR intensity at suitable frequencies is used to transduce in-situ time-dependent electrode roughness. Quantitative correlations are proposed and checked against samples of calibrated roughness both ex-situ and in-situ. A simple analytical model of roughness evolution during galvanostatic electroplating is proposed for control purposes. A suitable algorithm for automatic galvanostatic control is developed
Electrodeposition of copper from triethanolamine as a complexing agent in alkaline solution
Get PDFThe use of triethanolamine (TEA) as a cyanide-free electrolyte for copper electrodeposition was studied. The effect of TEA concentration on electrodeposition rate and cathodic adsorption during 3D copper growth was investigated. Linear sweep voltammetry (LSV), electrochemical quartz crystal microbalance (EQCM), scanning electron microscope (SEM), chronoamperometry and in situ surface-enhanced Raman scattering (SERS) were used to achieve a kinetic, thermodynamic, and mechanistic understanding. TEA forms stable complexes with copper, the most stable being Cu(TEA)(OH)3?. Also, it acts as a surface modifier, promoting instantaneous nucleation and lower reduction rates to metallic copper. Thus, three-dimensional growth is controlled and, consequently, a smooth and homogeneous copper deposit is achieved
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