An electrochemical method of preparing a high surface area nickel electrode by NiZn alloy formation and subsequent dealloying in ZnCl 2 -NaCl ͑60-40 mol %͒ at 450°C was studied. A nickel electrode was kept at 0.22 V vs. Zn in ZnCl 2 -NaCl͑sat͒ where ␥-NiZn alloy was formed, and then at 0.5 V where partial dealloying occurred to yield ␣-NiZn alloy. Scanning electron microscope observation showed that the microporous structure was formed on the surface. The roughness factor of a sample was determined to be 240 from the double layer capacitance obtained in the ac impedance measurement. Thickness, porosity, and pore size of the surface layer were estimated.
The electrodeposition of tungsten has been investigated in the molten salt systems ZnBr2-NaBr-WBr5 and ZnCI2-NaC1-WC16 at 450~ Voltammetric results showed that the reduction of tungsten species is an irreversible process. Electrodeposits were mixtures of a-and ~-tungstens, the former being the thermodynamically stable phase, a-Tungsten exhibited the shape of cubic crystallites which tended to grow larger, whereas 13-tungsten always had a crystal size smaller than 1 ixm. The 13-tungsten was formed during the initial stage of electrodeposition, irrespective of the substrata material, and remained predominant at high current densities or in pulsed electrolysis. It is likely that the phase transition of 13-tungsten to a-tungsten occurs when the size of the [3-tungsten crystallites becomes larger than a critical value.
NzN2
ABSTRACT:The intrinsic viscosity, [11], was measured for the betaine-type polyampholyte, poly(2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate), in aqueous solution at various pH and ionic strengths, I. The linear relationship between 1/JT and [11] for ordinary polyelectrolytes was also observed for the polyampholyte at low I near isoionic pH and over a wide range of I at other pH. By comparing I dependence of the electrostatic expansion factor of the polyampholyte with that of poly(sodium acrylate), it is suggested that there is a pronounced intramolecular attraction between the segments due to the oppositely-charged groups even when pH deviates from the isoionic pH.
An electrochemical method of preparing a porous nickel electrode by NiZn alloy formation and subsequent dealloying in zinc chloride-alkali chloride ͑60-40 mol %͒ melts at 350-450°C was studied. X-ray diffraction measurements at different stages of dealloying suggested that two step transformation from ␥to  1 -and from  1 -to ␣-NiZn alloy occurred. Dealloyed material exhibited well-developed porous structure of hundreds of nanometers in size. Electron probe microanalysis of a partially dealloyed layer showed that the dissolution of zinc occurred relatively uniformly throughout the alloy layer. Scanning electron microscopy of samples obtained at different temperatures showed that the size of porous structure ͑crevices and pores͒ was smaller at lower temperatures. The porous nickel electrode showed relatively low overvoltages in the hydrogen evolution reaction in 1 M KOH aqueous solution.
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