Hachiro Imai

The formation of nanoporous membranes from anodically oxidized aluminium and their application to Li rechargeable batteries

Abstract A method for the preparation of nanoporous dielectric membranes from anodically oxidized aluminium is described. Pores of an initially formed free anodic alumina film were protected with gelatin gel, and the oxide barrier layer was chemically dissolved from bottom side of the film. The method is advantageous in that it permits complete removal of the barrier layer and fabrication of large-area fine-porous membranes without introducing discontinuities in the pore network across the membrane surface. The membranes produced here were investigated by scanning electron microscopy and preliminarily examined as an electrolyte carrier/separator for Li rechargeable batteries by impedance measurements and charge–discharge cycle experiments. Repeated electrodeposition–dissolution of Li metal on Ni and Al substrates in LiPF6/propylene carbonate electrolyte was performed through the alumina membrane or through a commercially available polymeric separator, and charge–discharge coulombic efficiencies were then calculated.

Effect of pH on the interaction between zwitterions and titanium oxide

The isoelectric points (IEPs) of two zwitterions, glycine and both-terminals-terminated poly(ethylene glycol) (NH(2)-PEG-COOH), were determined from the titration curves, and the thicknesses of zwitterion layers immobilized on titanium (Ti) with immersion and electrodeposition at various pH based on IEPs were evaluated with ellipsometry to investigate the effect of pH and the immobilization technique on the interactions between the zwitterions and the Ti surface. From the titration curves, pK(1), pK(2), and the IEP of glycine were determined as 2.8, 8.9, and 5.9, respectively, and pK(1), pK(2), and the IEP of NH(2)-PEG-COOH were determined as 2.1, 11.7, and 6.9, respectively. At a certain specific pH, (+)H(3)N-CH(2)-COO(-) or (+)H(3)N-PEG-COO(-) was formed by hydrolysis of glycine or NH(2)-PEG-COOH. In addition, the Ti surface was negatively charged at this pH. As a result, for immersion, the electrostatic reactivity between terminal groups of zwitterions and hydroxyl groups on the Ti surface was the highest and the thickness of the immobilized layer was significantly the largest at pH 12. For electrodeposition, glycine, with its lower molecular weight, was more easily attracted to the Ti surface than NH(2)-PEG-COOH, which has a higher molecular weight, while the thickness of the immobilized layer was the greatest at pH 12 in both zwitterions.

Effect of free carbon dioxide on corrosion behavior of copper in simulated water

Abstract The effect of free carbon dioxide on the copper corrosion-behavior has been investigated by the immersion tests with electrochemical impedance spectroscopy. The copper corrosion-rate increased with the concentration of the free carbon dioxide. The free carbon dioxide continuously provides water with H+ ions if the CO2 gas existed in the atmosphere. The production of H+ might assist the reduction of the dissolved oxygen to start the oxidation of copper. This might be the reason why the free carbon dioxide promotes the oxidation of copper.

Biofunctionalization of Metal Surface by Immobilization of Poly(Ethylene Glycol) Terminated Amine

In many biomedical devices such as catheters and diagnostic sensors, blood compatibility is required. The best way to control this property is to prevent or drastically reduce the adsorption of proteins. Poly(ethylene glycol) terminated amine at both terminals, NH2-PEG-NH2, is immobilized on a commercially pure titanium, a 316L austenitic stainless steel, and a cobalt-chromium-molybdenum alloy with immersion or electrodeposition. Chemical bonding states at the interface and orientation of PEG molecules were characterized using X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, and Fourie-transformed infrared spectrometer with a reflection absorption spectrometer. As a result, NH2-PEG-NH2 was immobilized onto metal surface as a U-shape mainly with stable NHO bonding in electrodeposition. In the case of electrodepostion, the concentration of active surface hydroxyl groups on surface oxide film played an important role in the immobilization.