Electrodeposition various samples

Mishra et al. [198] discussed in an exemplary way the dark and photocorrosion behavior of their SnS-electrodeposited polycrystalline films on the basis of Pourbaix diagrams, by performing photoelectrochemical studies in aqueous electrolytes with various redox couples. Polarization curves for the SnS samples in a Fe(CN) redox electrolyte revealed partial rectification for cathodic current flow in the dark, establishing the SnS as p-type. The incomplete rectification was... 

Various methods ofachieving preconcentration have been applied, including Hquid -hquid extraction, precipitation, immobihzation and electrodeposition. Most of these have been adapted to a flow-injection format for which retention on an immobihzed reagent appears attractive. Sohd, sihca-based preconcentration media are easily handled [30-37], whereas resin-based materials tend to swell and may break up. Resins can be modified [38] by adsorption of a chelating agent to prevent this. Sohds are easily incorporated into flow-injection manifolds as small columns [33, 34, 36, 39, 40] 8-quinolinol immobilized on porous glass has often been used [33, 34, 36]. The flow-injection technique provides reproducible and easy sample handhng, and the manifolds are easily interfaced with flame atomic absorption spectrometers. 

To study in detail the process of the nickel electrodeposition into porous silicon, the electrodeposition was stopped at various process stages, namely, after 10, 20, and 30 min, and the cross-sections of the samples formed were examined by the scanning electron microscopy. The A, B, and C points in the potential curve (Fig. 1) correspond to these stages. 

Most metals except the alkalis and alkaline earths can be electroplated at the cathode with suitable applied voltage from acid solutions. Relatively early experience with electrodeposition of various metals is summarized in Fig. 3.9. The process typically is applied for carrier-free or low-concentration samples to prepare sources for alpha-particle spectral analysis. It is also useful for depositing thin sources for counting radionuclides that emit beta-particles with low maximum energy. 

Methods used for concentrating plutonium in a sample by a carrier are often specific to one oxidation state of the plutonium. For example, the classical bismuth phosphate-lanthanum fluoride method of concentrating plutonium from urine samples is specific to plutonium in the tri- and tetravalent states and will leave plutonium(VI) in solution. The fate of the various oxidation states of plutonium in man is not well understood and analysis procedures must insure reduction or oxidation of plutonium into appropriate oxidation states. Liver and kidney samples may contain metals (e.g., iron) which may greatly reduce chemical yields during the final electrodeposition step (Bernhardt 1976). 

XRD was used to evaluate the structural differences between the samples with various compositional ratios of Ni and Sn. Electrodeposited Sn-Ni film forms metastable phases that do not appear in the equilibrium phase diagram. Watanabe et ah carried out a detailed study of the structure of Sn-Ni films. The peak assignments made for the samples shown in Fig. 3.1 are based on the result of their work. The metastable phase Ml is a Ni-Sn phase with a composition ratio of almost 50 50, and the metastable phase M2 is a phase where Ni is melted into Sn ciystals. Samples with higher Sn contents were confirmed to have a structure similar to that of Sn. It is assumed that these electrodes with a high Sn content may show electrode properties similar to those of pure Sn electrodes, which means a high initial capacity, but a poor cyclability resulting from electrode degradation. 

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