Three-dimensional micro-actuators consisting of a polypyrrole (PPy)/Au bi-layer, were fabricated by Al anodizing, laser irradiation, and electrochemical techniques. Aluminum specimens covered with porous type oxide films were irradiated with a pulsed Nd-YAG laser to remove the oxide films locally. Then an Au layer and a PPy layer were deposited at the area where the film had been removed. Finally, the specimens were immersed in a NaOH solution after connection with or without a Pt plate to separate PPy/Au actuators from the Al substrate and anodic oxide film. The PPy layer did not lose its electroconductivity when the specimen was immersed in NaOH solution after connection with a Pt plate, although the conductivity was lost after immersion of the specimen alone. Immersion with the Pt connection suppressed the PPy reduction and enabled the fabrication of PPy/Au actuators. Three-dimensional PPy/Au bi-layer micro-actuators were fabricated using column Al specimens. They are much more flexible than PPy/Au/resin three-layer actuators described in a previous paper.
Electrochemical migration processes on two screen-printed silver wiring electrodes were investigated using electrochemical impedance spectroscopy. The impedance measured immediately after initial growth of silver dendrites on the cathode shows three capacitive loops. A loop in the low frequency range was dependent on the electric double layer capacitance and reaction resistance of electrodeposition of silver and oxygen reduction on the cathode. The capacitive loop diameter in the low frequency range decreased with dendrite growth. A capacitive loop in the middle frequency range was attributed to the dissolution reaction of silver on the anode. Results showed that a capacitive loop in the high-frequency range was related to the interelectrode capacitance between the silver wiring electrodes and the water film’s solution resistance. Curve fitting was performed for the impedance spectra by assuming an equivalent circuit. The calculated impedance spectra showed good agreement with experimental results: the reaction resistances and double layer capacitances varied remarkably with dendrite generation, suggesting that the present silver wiring electrode is applicable to an electrochemical migration monitoring sensor.
As described in this paper, we report the first successful trial of a facile carbon nanotube synthesis method yielding high-quality multi-walled carbon nanotubes (MWNTs) using low current arc discharge in water. The low current arc (10 A, 20 V) discharge system obviated nearly all complex and expensive machinery that is usually required. Using this method, the low current underwater arc discharge process produced carbon nanotubes simply, easily, and inexpensively.
Carbon nanotubes, synthesized in water using arc discharge method, were purified using ultraviolet (UV) radiation. Raman spectra showed that contamination was reduced concomitantly with the irradiation time. After seven hours’ irradiation, the IG/ID ratios of samples were up to 2.3 times as high as that of the original products. This treatment readily removes amorphous carbon at room temperature without damaging the nanotubes.