Minoru Mizuhata

Water Uptake of Perfluorosulfonic Acid Membranes from Liquid Water and Water Vapor

The water uptake of several perfluorosulfonic acid membranes from liquid water over the temperature range 25 to 130 C and from water vapor at 80 C was determined. For water uptake from liquid water, the water uptake depended on the immersion temperature, the ion exchange capacity of the membrane, and the pretreatment of the membrane. The effects of pretreatment were not significant at immersion temperatures higher than 100 to 110 C. For water uptake from water vapor at 80 C, the sorption isotherms were similar in shape of those reported by previous investigators for 18.5 to 30 C, although the water uptake at 80 C was less than that reported for the lower temperatures. The water uptake from water vapor of some membranes that have been found to give relatively good performance when used in polymer electrolyte fuel cells was higher then that observed with, e.g., Nafion[reg sign] 117.

Preparation and characterization of polymer thin films containing silver and silver sulfide nanoparticles

Abstract Composite thin films consisting of nano-sized Ag particles dispersed in nylon 11 thin films have been prepared by using a thermal relaxation technique. The films obtained were characterized by transmission electron microscopy (TEM), electron diffraction (ED), energy-dispersive X-ray (EDX) microanalysis, and optical absorption spectroscopy. The Ag nanoparticles with 4.5–9.1 nm in diameter were found to be isolated individually and dispersed uniformly in the nylon 11 matrix. The volume fraction and the mean size of Ag nanoparticles in the film could be controlled by varying the initial amount of Ag deposition. Optical absorption peak due to the surface plasmon resonance of the Ag particles were observed around 430 nm and shifted to a longer wavelength with increasing the mean size of Ag nanoparticles, and absorbance increased simultaneously. We have also prepared Ag 2 S nanoparticles with 4.7–11.2 nm in diameter in nylon 11 films from exposing the Ag/nylon 11 films to H 2 S/O 2 mixed gas. ED patterns of the particles formed after the reaction with H 2 S were completely indexed as those of β -Ag 2 S with a monoclinic structure. The onset of the optical absorption spectra is similar to that of bulk β -Ag 2 S, suggesting that Ag 2 S nanoparticles with diameter of ca. 5nm preserve the band structure of bulk Ag 2 S.

Preparation and characterization of iron oxyhydroxide and iron oxide thin films by liquid-phase deposition

Iron oxyhydroxide thin films have been prepared from the aqueous solution system of FeOOH–NH 4 F·HF (aq.) with added boric acid by a novel liquid-phase deposition (LPD) method and is the first attempt to preparate iron oxide thin films by this method. A crystalline β-FeOOH thin film was formed directly on the substrate upon immersion into a mixed solution of FeOOH–NH 4 F·HF and H 3 BO 3 . The orientation of the deposited film differed according to the concentration of H 3 BO 3 in the solution. When the concentration of H 3 BO 3 was >0.30 mol dm -3 , the β-FeOOH thin film was preferentially oriented in the [211] direction. The β-FeOOH thin film formed was transformed into α-Fe 2 O 3 upon heat treatment in air flow. The α-Fe 2 O 3 thin films obtained were oriented in the [110] direction. The F content of the as-deposited β-FeOOH film was ca. 15% F/Fe and was reduced to 0.19% upon heat treatment.

Preparation and characterization of copper(I) oxide nanoparticles dispersed in a polymer matrix

Nano-sized copper(i) oxide particles dispersed in nylon 11 thin films have been prepared by a thermal relaxation technique. The obtained composite films were characterized by XRD, HRTEM, XPS, AES and UV-VIS absorption spectroscopy. Upon heat treatment under air, metallic copper initially deposited on the nylon 11 surface penetrates into the bulk phase of the nylon 11 as Cu2O particles. The mean size of the Cu2O particles increased from 3.2 to 6.3nm in diameter upon increasing the amount of Cu deposition. UV-VIS spectroscopy revealed that the absorption increased from as low as 600nm with increasing the size and the concentration of the dispersed Cu2O particles.

Versatile Supramolecular Gelators That Can Harden Water, Organic Solvents and Ionic Liquids

We developed novel supramolecular gelators with simple molecular structures that could harden a broad range of solvents: aqueous solutions of a wide pH range, organic solvents, edible oil, biodiesel, and ionic liquids at gelation concentrations of 0.1-2 wt %. The supramolecular gelators were composed of a long hydrophobic tail, amino acids and gluconic acid, which were prepared by liquid-phase synthesis. Among seven types of the gelators synthesized, the gelators containing L-Val, L-Leu, and L-Ile exhibited high gelation ability to various solvents. These gelators were soluble in aqueous and organic solvents, and also in ionic liquids at high temperature. The gelation of these solvents was thermally reversible. The microscopic observations (TEM, SEM, and CLSM) and small-angle X-ray scattering (SAXS) measurements suggested that the gelator molecules self-assembled to form entangled nanofibers in a large variety of solvents, resulting in the gelation of these solvents. Molecular mechanics and density functional theory (DFT) calculations indicated the possible molecular packing of the gelator in the nanofibers. Interestingly, the gelation of an ionic liquid by our gelator did not affect the ionic conductivity of the ionic liquid, which would provide an advantage to electrochemical applications.

Studies on PVdF-based gel polymer electrolytes

Abstract A complex of polymer, plasticizer and lithium salts can be used as a solid gel polymer electrolyte in lightweight and rechargeable lithium batteries. Considerable research has been directed towards the development of a gel polymer with high conductivity at room temperature. In this work, a gel polymer electrolyte using polyvinylidene fluoride (PVdF)-1000 (KF), a plasticizer of 1:1 ethylene carbonate (EC) and propylene carbonate (PC), and LiBF 4 salt is optimized. Gel electrolytes have high ionic conductivity, good mechanical stability, a wide electrochemical stable window, and a stable lithium interface. The results of preliminary charge–discharge of cells are discussed in detail.

Preparation and characterization of Au-dispersed TiO2 thin films by a liquid-phase deposition method

Au-dispersed TiO2(anatase) thin films have been prepared by a novel method, liquid-phase deposition (LPD). The deposited films were characterized by XRD, XPS, TEM and UV–VIS absorption spectroscopy. The results showed that the titanium oxide thin film containing AuIII ions was formed from a mixed solution of ammonium hexafluorotitanate, boric acid and tetrachloroauric acid. Heat treatment above 200 °C of the deposited film under flowing air produced dispersed Au metal particles, accompanied by the crystallization of titanium oxide as a matrix. The mean particle size of the dispersed Au particles was ca. 15 nm. The optical absorption band due to the surface plasmon resonance of the dispersed Au particles shifted toward longer wavelengths with increasing heat-treatment temperature.

Growth of metal oxide thin films from aqueous solution by liquid phase deposition method

Abstract The deposition process of iron oxyhydroxide (β-FeOOH) from aqueous solution system of FeOOH–NH 4 F·HF (aq.) with H 3 BO 3 by the liquid phase deposition (LPD) method has been investigated. The effect of initial concentration in the treatment solution and reaction time on microstructure and orientation of the deposited films were studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) observation. The films deposited were constructed by small particles having a crown-like and columnar structure, depending on the concentration range in the treatment solution. XRD measurements revealed that the deposited film preferred the specific direction normal to (211) plane and the dimension of the crystallites varied with the initial concentration of the solution. The deposition process and structure of the films appeared to be strongly affected by the hydrolysis reaction of Fe 3+ ions coordinated by F − and/or partial OH − ions by adding boric acid.

Synthesis and characterization of nano-sized gold-palladium bimetallic particles dispersed in polymer thin film matrix

We have prepared nano-sized Au/Pd bimetallic particles with various compositions dispersed in nylon 11 thin films by thermal relaxation technique. The films obtained were characterized by TEM, EDX, XPS and visible absorption spectroscopy. The Au/Pd molar ratio in the bimetallic particles could be varied over the entire composition range by controlling the initial deposition amount of constituent metals. It was found that the mean size of the dispersed particles decreased from 5.3 to 3.2 nm in diameter with increasing the Pd content in the bimetallic particles. Optical absorption due to surface plasmon resonance absorption of the Au particles decreased with decreasing the Au/Pd ratio, which can be caused by the changes in the band structure of the Au particles due to alloying with Pd.

Monitoring the growth of titanium oxide thin films by the liquid-phase deposition method with a quartz crystal microbalance

The quartz crystal microbalance (QCM) technique has been applied to investigate the formation of titanium oxide thin films by the liquid-phase deposition (LPD) method. A linear relationship was observed between the thickness measured by the QCM technique and that measured by direct observation with a scanning electron microscope, indicating that it is possible to monitor the growth of thin films from aqueous solution systems by the LPD method with the QCM technique. The concentration effects of free F - , H 3 BO 3 and (NH 4 ) 2 TiF 6 on the film deposition rate are discussed.