It was demonstrated that the principles of ion pairing could be used to predict the effect of a quaternary ammonium salt on the rate of electrodeposition of several metals. In agreement with prediction the cationic surfactant, in general, appreciably increased the limiting current, the current efficiency, and the percentage composition in alloys of metals deposited from negative ions in solution while decreasing slightly the same factors for metals deposited from positive ions in solution. It was also shown that there are predictable situations in which the ion paired acceleration would not be observed when expected. Those situations are: (1) processes not limited by the rate of adsorption; (2) processes in which the rate is limited by reaction with a species different from the predominant negatively charged species; and (3) processes in which a film is formed on the electrode.
completely oxidized, thereby rendering the collection efficiency higher and less dependent on the generation current. However, the variation of N with I2 (and hence 11) is reproducible, which is the principal requirement for using this technique to delineate the anodic (aluminum oxidation) and cathodic (hydrogen evolution) currents on corroding aluminum.Aluminum electrodissolution.--Using the techniques described above, we have delineated the partial anodic and cathodic processes that occur on aluminum and various aluminum alloys in 4M K:OH at temperatures of 25 ~ 50 ~ and 80 ~ (Fig. 6~8). A detailed analysis of these data is reported in Part III(6) of this series, so that only a brief discussion will be presented here.The total current vs. voltage curves for aluminum in 4M KOH are characteristic of a metal undergoing active dissolution coupled to hydrogen evolution. However, the anodic partial current observed at 25~ and possibly also at 50~ demonstrates that aluminum is a passive metal in concentrated alkali, with an active-to-passive transition being clearly evident at -1.9V and a passive range extending from this voltage to about -1.6V. At higher voltages, aluminum dissolves in a transpassive mode, most likely via cation conduction through a porous corrosion product film. The existence of such a film on aluminum in sodium hydroxide solution (0.1-4M) has been reported by Heusler and Allgaier (3) and more recently by Greef and Norman (4) and Brown and Whitley (5). At the highest temperature (80~ the greatly increased rate of hydrogen evolution prevented the voltage being made more negative than -1.8V (vs. Hg/HgO), so that the passive state (if it exists) could not be detected. In this case, aluminum is found to dissolve in the transpassive mode over the entire range of potential that is accessible.
It was demonstrated that the formation of insoluble films of compounds containing the metal to be deposited furnished a method of controlling the relative rates of competing electroreduction processes. It was shown that additives, such as halide and thiocyanate ions, that caused the precipitation of insoluble copper(I) films in the electrodeposition of copper would cause an increase in the current efficiency and would increase the relative amount of copper deposited in binary alloys. It was also shown that an insoluble adherent film [Pb6Os(NO3)2] was formed on the cathode during the deposition of lead from alkaline solutions. The formation of this film was aided by the introduction of a protective cationic surfactant. Therefore, addition of the surfactant caused increases in current efficiency and increases in the lead concentration in electrodeposited lead alloys. Deposition of thallium in the presence of oxygen leads to the formation of insoluble thallium (III) oxide at the cathode by the reaction of the metal with hydrogen peroxide formed by reduction of oxygen. However, this insoluble oxide did not adhere to the cathode, therefore the addition of oxygen did not cause increases in the relative concentration of thallium in binary electrodeposited alloys. Instead, since a corrosion process was involved, the current efficiency and relative amount of thallium in the alloy decreased upon addition of oxygen. Thus, in oxygen containing solutions, addition of sulfite ions which react with hydrogen peroxide cause increases in the current efficiency and increases in the relative amount of thallium in electrodeposited binary alloys. ABSTRACTWe examine the first three moments and the peak depths of implanted depth profiles measured using secondary ion mass spectrometry and, in a few cases, using Polaron C-V, for H, He, rare earths, and the more common dopants, Be, Mg, Zn, C, St, Ge, S, Se, and Te in GaP, GaAs, and InP, determined from a Pearson IV computer fitting routine. These experimental values are compared with those of Lindhard-Scharff-SchiOtt (LSS) calculation tables, an implant profile code, and a TRIM program. Implant energies vary between 0.1 and 6.0 MeV.
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