Nobuyuki Koura

Preparation of Various Oxide Films by an Electrophoretic Deposition Method: A Study of the Mechanism.

The electrification mechanism of an oxide particle in a bath was analyzed. The zeta-potentials of various oxide particles in an acetone bath were found to be positive. The data suggested that H+ ions are generated in an acetone bath containing a small amount of added I2 and H2O by the keto-enol equilibrium reaction and then adsorbed on the oxide resulting in positively charged particles. The adsorption of H+ ions was assumed to be of the type of mono-molecular adsorption. Moreover, the electrodeposition flocculation mechanism for the particle was also investigated. On the basis of a relation of electrophoretic current with depositing time well described by the Cottrell equation, it was suggested that the electrochemical reaction proceeds on the cathode substrate surface and that the rate-determining step arises from the diffusion of H+ ions in the deposited film.

Microbial conversion of n-alkanes into glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma (Candida antarctica)

Abstractn-Alkanes ranging from C12 to C18 were converted into glycolipid biosurfactants, mannosylerythritol lipids (MEL), by resting cells of Pseudozyma (Candida) antarctica T-34. The highest yield (0.87 g g−1 substrate) was obtained from 6% (v/v) of n-octadecane after 7 days reaction. The amount of MEL reached 140 g l−1 by intermittent feeding of the substrate.

Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating

In order to improve the pervaporation performance of silicalite membrane, two types of silicone rubber, KE45 and KE108, were coated on the membrane surface. The initial molecular weight of KE108 is high and vulcanizing starts when it comes into contact with moisture in air, whereas the initial molecular weight of KE45 is low and vulcanizing starts when it is mixed with a catalyst. KE108 was found to be more effective than KE45 in enhancing the ethanol selectivity of silicalite membranes. A membrane coated using a 3 wt.% KE108 hexane solution showed separation factor of α=125 with a total flux of 0.14 kg/m2 h.

Polyaniline Secondary Cells with Ambient Temperature Molten Salt Electrolytes

An Al/polyaniline (PAn) powder secondary cell with an AlCl[sub 3]-1-butylpyridinium chloride (BPC) or an AlCl[sub 3]-1-ethyl-3-methylimidazolium chloride (EMIC) electrolyte has been investigated. The configuration of the Al/PAn secondary cell with an acidic AlCl[sub 3]-EMIC electrolyte was: open-circuit voltage (OCV) = 1.7 V, discharge capacity = 42 Ah, charge/discharge efficiency = 90%. A 24% increase in the discharge capacity over a BPC system electrolyte is obtained. The difference was attributed to the electrolyte properties, i.e., conductivity and viscosity. In the basic EMIC system bath of 44.4 m/o AlCl[sub 3], the redox potential of PAn was less noble and the reaction current was large. A PAn/PAn secondary cell with the acidic AlCl[sub 3]-EMIC catholyte and the basic anolyte was proposed. The OCV showed 1.0 V and the PAn/PAn secondary cell was promising. A PAn prepared from a nonaqueous BPC system bath was more electrochemically active than that prepared from an aqueous bath. The optimum OCV, discharge capacity, and charge/discharge efficiency of the Al/PAn (from the BPC bath) were 1.6 V, 68 Ah/kg-PAn, and 99%, respectively.

Electrochemical oxidation of glucose at Hg adatom-modified Au electrode in alkaline aqueous solution

Electrochemical oxidation of glucose at Hg adatom-modified Au polycrystalline electrode was examined in alkaline aqueous solutions using cyclic voltammetry. Two oxidation current peaks for glucose were observed on Hg adatom-modified Au electrode at almost the same potentials as those observed on a bare Au electrode. The oxidation peak currents were much larger than those on a bare Au electrode in the concentration range from 0.5 to 20 mM. The observed enhancement of the glucose oxidation was considered to be due to the increase in the amount of the adsorbed OH− on the Hg adatom-modified Au electrode. The reaction was catalyzed through the pairing of glucose and the intermediate in the oxidation to the large amount of the adsorbed OH− on the Hg adatom-modified Au electrode.

Production of highly concentrated ethanol in a coupled fermentation/pervaporation process using silicalite membranes

The fermentation performance of a coupled fermentation/pervaporation process using silicalite membranes, which are ethanol permselective for an ethanol/water solution, was studied. The process exhibited about a 20% increase in an average glucose consumption rate as compared with that without the pervaporation unit. A strong correlation was observed between the membrane flux and the consumption rate. Ethanol concentrations in the permeates reached a maximum of 85% (v/v).

Fabrication of Ferroelectric BaTiO3 Films by Electrophoretic Deposition

BaTiO3 thick films on Pt substrates were fabricated by the electrophoretic deposition method. The suspension was prepared with fine powder (0.1 µm in diameter) of BaTiO3, acetone and iodine. Dense and strong films were formed in an applied DC field of 500 V/cm. The films sintered at 1200°C were crystallized into the tetragonal phase at room temperature. The coercive field Ec and the remanent polarization Pr were estimated to be 1.6 kV/cm and 2.1 µC/cm2, respectively, from the P-E hysteresis loop observation.

Effects of preparation condition of photoinduced graft filling-polymerized membranes on pervaporation performance

Abstract Modification of poly(acrylonitrile) membrane was carried out by heterogeneous photoinduced graft polymerization of methyl acrylate from the vapor phase. The technique of transmembrane monomer flow has proved to be effective for filling pores. The effect of preparation conditions like initiator concentration, reaction time and monomer concentration on the membrane separation was investigated. These graft modified membranes showed benzene permselectivity for benzene/cyclohexane mixture (50/50, v/v) on pervaporation.

Preparation of polyacrylonitrile ultrafiltration membranes for wastewater treatment

Abstract The preparation conditions of a polyacrylonitrile (PAN) ultrafiltration membrane for wastewater treatment was investigated. The PAN membranes were prepared by the phase-inversion process in a water gelation bath using casting solutions of varying compositions of PAN/polyvinylpyrolidone (PVP)/N,N-dimethylacetamide (DMAc) and showed a molecular weight cut-off of 50,000–500,000. Especially, the membrane prepared from casting solutions with PVP and annealed at 80°C in water showed high water flux with a molecular weight cut-off of 500,000. Furthermore, the composite membranes of PAN-acrylic acid, prepared by the photo-induced graft polymerization technique, improved high performance.

Technological and scientific issues of room-temperature molten salts

A comprehensive review of the physico-chemical properties of room-temperature molten salts composed of binary solutions of metal halides with either alkylpyridinium halides or di-alkylimidazolium halides is given. A special emphasis is given to the applications of these materials. The most important applications so far are in high-energy batteries and in electrodeposition of selected metals, which is only possible in these media.