M. H. Fawzy

Effect of Some Operating Variables on the Characteristics of Electrodeposited Ni-α-Al2O3 and Ni-TiO2 Composites

Copper--Al 2 O 3 and Copper-TiO 2 composites were electrodeposited from acidic baths containing 150 CuSO 4 .5H 2 O, 50 Na 2 SO 4 .10H 2 O, 25 H 3 BO 3 and either 1-20 gl -1 -Al 2 O 3 or TiO 2 particles suspended in the bath. The effects were studied of particle size, particle concentration and plating conditions on the cathodic polarization, current efficiency, inert particle content in the composite deposit and on the surface morphology and microhardness of the as-received plate. A mechanism of coelectrodeposition of the inert particles with copper could be suggested from measurements of the cathodic polarization. The efficiency of copper electrodepostion from the selected bath was relatively high (98.5%) and was increased further by increasing the current density and by raising the pH of the bath. The inert particle content reached 1.7% for -Al 2 O 3 and 2.3% for TiO 2 . At a current density of 0.66A dm -2 , the microhardness of the copper plate approached 100 kgf mm -2 and the inclusion of the inert particles in copper composites led to an increase of about 25% in the microhardness. A further increase in the microhardness of copper--Al 2 O 3 was achieved by raising of the deposition current density, where it reached 165 kgf mm -2 at 1.66 A dm -2 . Scanning electron microscopy examination showed a direct correlation between both the inert particles content, their morphological shape and the microhardness of the copper composites.

Cyclic voltammetric behaviour and some surface characteristics of the lead electrode in aqueous NaCl solutions

The positive linear sweep voltammograms of lead were investigated in 0.01-2.00 M aqueous HCl solutions. The results revealed the occurrence of one anodic current peak as the result of formation of a thin PbCl2 surface layer. Intensive study of the electrochemical behaviour of the lead electrode in 1.00 M HCl solution was carried out by cyclic voltammetry. The results indicated that the formation of PbCl2 is a reversible process controlled by diffusion of Cl- ions to the electrode surface. Controlling the voltammetric conditions enabled the building up of a relatively thick and porous PbCl2 layer that could resist rupture or breakdown. In addition, the electrode surface products were examined by scanning electron microscopy and X-ray diffractometry. The morphology of the as-formed PbCl2 layers showed a primitive dependence on the voltammetric conditions. X-ray diffraction analysis proved that only PbCl2 was formed on the electrode surface and no other products could be detected.

Influence of Bath Compositions and Some Operating Conditions on the Electroplating of Cobalt from Aqueous Sulphate Baths

SUMMARYA systematic study has been made of the influence of aqueous sulphate bath constituents on the cathodic polarization curves during cobalt electrodeposition. The optimum bath composition has been established and it contains: 0.30 mol l−1 CoSO4.7 H30, 0.30 mol−1 H3BO3. 0.05 mol l−1 (NH4)2SO4 and 0.10 mole l−1 Na2SO4.10 H2o. Cobalt electroplating from the optimized bath has been performed under a variety of conditions viz: pH, 1.5 to 5.3; current density, 0.2 to 2.0 A dm−2 and temperature 25 to 53°C. Under the most suitable conditions, the optimum bath is characterized by a high cathodic efficiency (~ 99%), moderate throwing power (21.6%) and throwing index (1.47). The bath produced smooth, adherent and semibright plates characterized by a high microhardness (411.4 kgf mm−2) and their morphologies, as revealed by scanning electron microscopy, showed a dependence on the plating variables.

Performance characteristics of a pilot sea-water activated battery with Pb/PbCl2 cathodes, prepared by cyclic voltammetry

Abstract Cyclic voltammetry was utilized in preparation of PbCl 2 -active material on the surfaces of lead electrodes in 1.0 M HCl solutions. X-ray diffraction analysis proved that only PbCl 2 was formed and no other products could be detected. The morphology of the Pb/PbCl 2 surface layer, as revealed by scanning electron microscopy, showed a primitive dependence on the employed voltammetric conditions. The Pb/PbCl 2 electrodes prepared by cyclic voltammetry were employed as cathodes in a pilot sea-water activated cell using Mg-alloy anodes. The voltage-time and current-time discharge curves of the pilot cell were examined as a function of the Mg% in the anode material, magnitude of the load resistance and salinity of the electrolyte. The discharge characteristics of a pilot 5-cell battery were also tested. Under the optimum conditions, the voltage of a unit cell attained 1.2 V which agrees well with the voltage of the corresponding conventional cells. In addition to the easy method of preparation, the present cathodes are characterized by many advantages over those prepared by the traditional techniques.

Use of iodide and silver/sulfide ion-selective electrodes for the determination of some tertiary amines and alkaloids

SummarySome tertiary amines and alkaloides were determined by reaction with methyl iodide at 43 °C. The produced quaternary ammonium iodide salts were potentiometrically titrated with standard silver nitrate solution using either the iodide or silver/sulfide ion-selective electrode. The effects of solvent, temperature and time of reaction were examined. An average recovery of 99.0% and 98.9% with standard deviations of 0.73 and 0.52 were obtained for the studied amines and alkaloides, respectively.

Effect of Superimposed Sinusoidal a.c. on the Characteristics of Electrodeposited Ni, Cu and Cu-Ni Alloy Composites with α-Al2O3 and TiO2

Nickel, copper and copper-nickel alloy composites were electrodeposited without and with inclusions of inert α-Al 2 O 3 and TiO 2 particles from closely similar selected baths. It was found that during electrodeposition a superimposed sinusoidal a.c. exerted a decrease in the cathodic polarization for the individual metals and the alloy composites. The higher the superimposed a.c. density and the lower its frequency the greater was the depolarizing effect. The combined effect of superimposed a.c. and inclusion of the inert particles in the bath on the cathodic polarization proved to be additive. Superimposed a.c. induced negligible changes in the cathodic current efficiency of nickel and copper metal composites deposition, whereas it caused a marked decrease (about 20%) in that of the copper-nickel alloy composites. The inert (α-Al 2 O 3 and TiO 2 ) particles content in the individual metal and alloy composites as well as the alloy composition were influenced by the superimposed a.c. and correlated with its depolarizing effect. The above-mentioned changes exerted by superimposed a.c. controlled the growth morphology, as revealed by SEM, and the microhardness of the as-deposited metal and alloy composites. A correlation could be detected between superimposed a.c. and dispersion of α-Al 2 O 3 or TiO 2 particles in an individual metal or alloy matrix, the grain refinement, and an improvement of its microhardness could be detected.

Effect of Some Operating Variables on the Characteristics of Electrodeposited Cu-Ni Alloys with and without α-Al2O3 and TiO2 Inert Particles

A study was carried out on the electrodeposition of Cu-Ni alloys containing inert (α-Al 2 O 3 and TiO 2 ) particles from a selected citrate bath. The cathodic polarization curves show that alloy deposition occurs at more noble potentials relative to either of the two parent metals and this indicated the formation of a solid solution. The addition of the inert particles into the selected bath led to a polarization-increasing effect and this increased with increases in the size and concentration of the particles in the bath. An explanation of the mechanism of codeposition of the inert particles with the alloy has been presented. On controlling the bath composition, Cu-Ni alloys containing 11-40% of nickel could be deposited. The effect of the operating variables such as the concentration of the metal ions in the bath, pH and current density on the alloy composition indicated that the formation of the Cu-Ni alloy belongs to the regular alloy deposition system. The current efficiency of the alloy deposition is relatively lower than for either of the two parent metals, from similar baths, and ranges between 76 and 84%. The microhardness of the deposited Cu-Ni alloy improved from 170 to 248 kfg mm -2 as a result of codeposition of 1-2% of the inert particles. A direct correlation between the surface morphology of the deposited Cu-Ni alloy, as revealed by SEM, and its microhardness could be detected. X-ray diffraction studies confirmed the dispersion of the α-Al 2 O 3 and TiO 2 phases in the Cu-Ni alloy phase.

Electroplating of Co-Fe alloys from Aqueous Sulphate Baths

SUMMARYEarlier work on the electroplating of cobalt and iron individually has been extended to the electroplating of Co-Fe alloys from sulphate—based baths containing in: 0.10–0.20 CoSO4.7H2O, 0.20–0.10 FeSO4.7H2O, 0.10 H3BO3 and 0.10 mol l−1 Na2SO4.10H2O in addition to 3 g/l-1 sodium potassium tartrate, at pH 3.4. The alloy deposition was attended by a lower polarization than either of the parent metals from baths of similar composition, except for the absence of the other depositable metal ion, indicating the formation of Co-Fe solid solution. Moreover, the less noble metal (Fe) deposits in the alloy preferentially, pointing to alloy plating of the anomalous type. A comparison between the experimental and the actual (calculated) polarization curves during codeposition was utilized to provide an explanation of the anomalous phenomenon. Under identical conditions of current density (1 Adm−2), duration (20 min) and temperature (25 °C), the current efficiency (f) of the alloy plating (44%) and the percentag...

Application of silver/sulfide ion-selective electrode for the determination of aliphatic primary and secondary amines

Aliphatic primary and secondary amines were determined utilizing their reaction with carbon disulfide. A potentiometric titration of the formed dithiocarbamates (I) with silver nitrate using a silver/sulfide ion-selective electrode was carried out. The effects of solvent, base, temperature and reaction time were investigated. The optimum conditions for a quantitative formation of (I) requires a minimal amount of 1,4-dioxane, 2 drops of 0.2% sodium hydroxide solution, excess carbon disulfide to stand at room temperature for 15 min. The titration requires prior evaporation of the unreacted carbon disulfide at 46 ° C. An average recovery of 98.5% with a standard deviation of 0.69 was obtained for the analyzed amines.

Application of rhodanine, fluorene and semicarbazide hydrochloride as new spectrophotometric reagents for quinones

New selective and sensitive Spectrophotometric methods for quinone determination are described. Quinone samples are treated with either methanolic solution of rhodanine, fluorene in ammoniacal media or aqueous semicarbazide hydrochloride solution. Semicarbazide is the most sensitive reagent for the determination of 1,4-benzoquinone, 1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone. Quinones substituted with electron withdrawing groups are better determined using rhodanine. The average recovery is 99.1%, 98.7% and 99.2% using rhodanine, fluorene and semicarbazide as reagents, respectively.