The corrosion behavior of pure aluminum in inhibited and uninhibited 4 M KOH was investigated by means of hydrogen collection, polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion of pure aluminum was greatly inhibited by the addition of ZnO and dimethyl amine epoxy propane (designated as DE). EIS and EDAX analyses revealed that ZnO produces its effect by depositing on the aluminum surface, which increases the overpotential of hydrogen evolution. It was also found that the addition of DE could greatly improve the deposition of zinc layers.

The effects of zinc oxide and/or polyethylene glycol (PEG) as electrolyte additives on the corrosion and electrochemical performances of pure aluminum in 4.0 M KOH solutions were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, scanning electron microscopy (SEM), and energy dispersive analysis of X-ray (EDAX). The addition of ZnO markedly inhibited the corrosion of aluminum in 4.0 M KOH solutions, resulting from the deposition of zinc with high hydrogen evolution overpotential in aluminum surfaces. The introduction of PEG in the alkaline zincate solution obviously improved the deposition of zinc by increase in the overpotential of zinc deposition, thus the corrosion rate of aluminum in the alkaline zincate solutions with PEG was further decreased. The enhancement effect of PEG on the inhibition of zinc oxide first increased and then decreased with increasing the content of PEG in the electrolyte. The electrolyte system with 0.2 M ZnO and 2.0 mM PEG presented the highest inhibition efficiency (98.8%) for the corrosion of aluminum. The results of galvanostatic discharge indicated that the aluminum anode shows excellent discharge performances in the 4.0 M KOH solution with 0.2 M ZnO and 2.0 mM PEG.

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We studied the propagation of extensional waves in a thin piezoelectric semiconductor rod of ZnO whose c-axis is along the axis of the rod. The macroscopic theory of piezoelectric semiconductors was used which consists of the coupled equations of piezoelectricity and the conservation of charge. The problem is nonlinear because the drift current is the product of the unknown electric field and the unknown carrier density. A perturbation procedure was used which resulted in two one-way coupled linear problems of piezoelectricity and the conservation of charge, respectively. The acoustic wave and the accompanying electric field were obtained from the equations of piezoelectricity. The motion of carriers was then determined from the conservation of charge using a trigonometric series. It was found that while the acoustic wave was approximated by a sinusoidal wave, the motion of carriers deviates from a sinusoidal wave qualitatively because of the contributions of higher harmonics arising from the originally nonlinear terms. The wave crests become higher and sharper while the troughs are shallower and wider. This deviation is more pronounced for acoustic waves with larger amplitudes. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license