The formation and growth of pure zinc films on iron substrates was investigated. The film formation process used was rf-magnetron sputtering, and the variable parameter that was used to affect film formation was sputtering power. At higher sputtering power the films oriented to the (002) plane in the vicinity of the interface, but (101) plane orientation increased with film thickness. Films consisted of a layer of fine particles several micrometers thick formed on the substrate, with columnar crystals on top of it. At lower sputtering power the films oriented to the (101) plane regardless of the film thickness and the columnar crystals could not be seen, but the sponge-like crystals were formed. These phenomena will be explained from the viewpoint of the adsorption inhibition.
Heavy electrodeposition of silver from highly concentrated cyanide baths was studied in terms of bath composition, cathodic polarization curves and the range of appropriate current densities. The structure of silver cyanide complex in the bath was also studied. It was found that highly concentrated potassium hydroxide effected a remarkable improvement in the characteristics of cyanide baths for heavy electrodeposition of silver. The range of appropriate potassium carbonate concentration was increased by the addition of potassium hydroxide into the baths. Cathodic polarization was increased by increases in the concentration of potassium carbonate, but was changed little by the addition of potassium hydroxide. The structure of silver cyanide complex was estimated to be Ag(CN)32-. The following conditions for heavy electrodeposition of silver in cyanide solutions can be recommended: AgCN: 120-134g/L, KCN: 176-195g/L, KOH: 20-40g/L, K2CO3: 140-170g/L and current densities of 1-3A/dm2.
The morphologies of zinc leaves electrodeposited at the interface between several acetic esters and ZnSO4 aqueous solution were investigated. At electrolysis voltages of 1 to 3V, two types of deposits were obtained: mainly film-like at 1V and spoke-like at higher voltages. With the increased presence of branched chains in butyl acetate isomer, spoke-like deposits formed preferentially. With the increased number of methylenes in straight-chain acetic ester, film-like deposits were favored, but current flow decreased, resulting in the slow growth and irregular shape of the deposit.
A study has been made of electrochemical techniques for the measurement of ferric chloride spray etching. Since, in spray etching, the limiting current is very high due to the violent agitation caused by the strong impingment of spray. The solution resistance of ferric chloride etchant was first determined by AC impedance technique to compensate for IR drop. Measurements of cathodic limiting current for the reduction of ferric ion at platinum ring-disk electrode on the impinged surface, were then made at spraying pressures of 25-98kPa and temperatures of 30-60°C. The spray etch rate of copper was proportional to the cathodic limiting current obtained in this study. The results indicate that the use of this technique makes possible the electrochemical monitoring of ferric chloride spray etching.
DC etching of aluminum is used in the fabrication of electrodes to enlarge the surface area of the aluminum base plate, thereby increasing its capacitance. To clarify the basic mechanism of this etching process, in situ monitoring was attempted using a photoacoustic (PA) technique. The base plate was 99.99% aluminum foil, the electrolyte was an aqueous solution 2mol/dm3 HCl, 0.2mol/dm3 AlCl3. Etching was done under galvanostatic conditions at 80°C. The light source for the PA technique was an Ar ion laser beam that was chopped mechanically. A PA signal from a piezoelectric transducer attached to the rear surface of the working electrode (Al) was detected by a lock-in amplifier. Changes in the PA signal over time suggests information about the initial roughness of the surface, the growth of etching pits and the penetration of the pits through the foil. The current density at which etching was carried out changed the behavior of the PA signal. The process of etching was confirmed ex situ by SEM and optical microscopy. The above data yielded in situ information about the DC etching process.
The influence of chloride and chlorate ions on the anodizing of aluminum in sodium hydroxide solutions was studied. The baths used were composed of sodium hydroxide (0.1M) and chloride and chlorate (NaCl, NaClO, NaClO3, NaClO4) ions and bath volume was 1L. Anodizing was carried out for 30min at a current density of 3A/dm2 and a bath temperature of 10°C. The concentration of additives at which no pitting occurred was 0.005M. The thickest film (5.5μm) was formed in an NaOH-NaClO bath. It is suggested that Cl- is changed to ClO- by electrolysis in NaOH solution and promotes anodizing as an oxygen supplier.