Sachio Yoshihara

Oxygen reduction on Au nanoparticle deposited boron-doped diamond films

Nanoparticle Au was deposited on as grown boron-doped diamond (BDD). The coverage and the morphology of the deposited Au particles were investigated by means of the linear sweep voltammeter and scanning electron microscopy (SEM). From SEM, the gold electrodeposited randomly as small spherical particles with an average diameter of 60nm. The applications of the as grown BDD film deposited by Au for electrocatalytic reduction of the oxygen in acidic solution were investigated. The catalytic efficiency of the Au deposited as grown BDD with the coverage of 0.06 is near 20 times larger than that of polycrystalline gold. The mechanism of the highly electrocatalytic active was investigated by ac impedance and hydrodynamic voltammetric methods.

Photocatalytic ZnO films prepared by anodizing

Photoactive zinc oxide films were prepared by anodizing a zinc plate. Thus, prepared films could decompose acetaldehyde gas with the aid of black lights. The photocatalytic activity was correlated to the XRD peak intensity ratio (1010):(0002).

Anodic oxidation of ketoprofen—An anti-inflammatory drug using boron doped diamond and platinum electrodes

The mineralization of ketoprofen (KP) by anodic oxidation was studied by employing boron doped diamond (BDD) and Pt electrodes. The redox behavior of KP molecule, fouling of electrodes, generation of oxygen and active chlorine species were studied by cyclic voltammetry. The effect of electrolyte, pH of aqueous medium and applied current density on the mineralization behavior of KP was also investigated. The degradation and mineralization were monitored by UV-vis spectrophotometer and total organic carbon analyzer, respectively. The results were explained in terms of in situ generation of hydroxyl radical (OH), peroxodisulfate (S(2)O(8)(2-)), and active chlorine species (Cl(2), HOCl, OCl(-)). The physisorbed OH on BDD was observed to trigger the combustion of KP in to CO(2) and H(2)O. The poor mineralization at both BDD and Pt anodes in the presence of NaCl as supporting electrolyte was ascribed to the formation of chlorinated organic compounds which are refractory. Complete mineralization of KP molecule was achieved using Na(2)SO(4) as supporting electrolyte.

Preferred orientation and morphology of electrodeposited iron from iron(II) chloride solution

Abstract The effects of each electrolytic condition on current efficiency, Vickers hardness, crystal structure and crystal morphology were studied with respect to the electrodeposited iron films obtained from iron(II) chloride solution. The temperature of the solution was varied from 20 to 60°C, the pH value of the solution varied from 0 to 2, and the applied current density varied from 5 to 100 mAcm −2 . Higher current efficiency was obtained at a higher solution temperature, higher pH value of the solution and lower applied current density. The films thus obtained showed a lower Vickers hardness and a preferred orientation of the (110) plane. Lower current efficiency was obtained at a lower solution temperature, lower pH-value of the solution showed a higher Vickers hardness, and a preferred orientation of the (211) plane. It is thought that these tendencies are related to the contribution of the hydrogen evolution reaction as a side reaction.

The effects of magnetic fields on the corrosion of aluminum foil in sodium chloride solutions

Abstract The corrosion of aluminum foil was inhibited in 0.1–10 wt% NaCl aqueous solutions in the presence of an external magnetic field. The inhibition increased as the magnetic flux density was increased. The amount of aluminum oxide film on the foil surface was increased by magnetic field effects.

Electrochemical degradation of PNP at boron-doped diamond and platinum electrodes.

The electrochemical degradation of p-nitrophenol (PNP) at boron-doped diamond (BDD) and platinum (Pt) anodes was studied by varying the parameters such as Cl(-) concentration, pH of aqueous medium and applied current density. The results obtained were explained in terms of in situ concomitant generation of hydroxyl radicals and chloride based oxidant species. The degradation of PNP was highly promoted in low concentration of NaCl electrolyte (less than 0.10 M), on contrary, the mineralization efficiency was poor at both BDD and Pt anodes with the NaCl concentration up to 0.20 M, which was ascribed to the formation of refractory chlorinated organic compounds. A maximum of 100% and 70% of COD removal was achieved in 5h of electrolysis period using both BDD and Pt anodes under similar experimental conditions. Kinetic study indicated that the degradation of PNP at BDD and Pt anodes followed pseudo-first-order reactions, and the reaction rate constant (k(s)) of the former was observed to be higher than that of the latter. Besides COD, conversion of PNP into various intermediate compounds and their degradations were also monitored. The mechanisms for PNP degradation at BDD and Pt anodes were proposed separately by considering the nature of respective intermediate species and their concentrations.

STM study of photoelectrochemical plating on p-type silicon electrodes

Abstract We succeeded in observing surface changes in p-type silicon in aqueous chloroplatinic acid solution under illumination or in the dark. The scanning tunneling microscope (STM) image obtained after cathodic polarization in the dark implies that the crystal growth of deposited platinum predominates over nucleation. However, the STM image obtained after cathodic polarization under illumination implies that nucleation predominates in the initial deposition. The explanation for this behavior is that electron transfer occurs at a relatively high overpotential under illumination, i.e. the charge transfer potential of the electron under illumination is higher than that in dark.

Magnetic Finishing Abrasive with Nickel-Plated Active Carbon

A novel magnetic abrasive particle (MAP) was developed by using electroless nickel or nickel-diamond composite plating on active carbon (AC) powder. The chelating compound of picolinic acid with nickel anion was used in the activated process instead of the conventional PdCl 2 and SnCl 2 . X-ray diffraction and scanning electron microscopy images showed the completely coated nickel or nickel-diamond electroless deposits on the AC particles. A mirror finish of Cu plate was obtained by using the newly developed MAP in practice in the process of magnetic-field-assisted finishing.

Electrochemical behavior of 3,6-dihydroxyphenanthrene on boron-doped diamonds

Abstract The electrochemical behaviors of 3,6-dihydroxyphenanthrene in non-aqueous or aqueous solutions were investigated using boron-doped diamond electrodes. 3,6-Dihydroxyphenanthrene exhibited different cyclic voltammetric behaviors in organic and aqueous solutions. Cyclic voltammetry, hydrodynamic voltammetry and flow injection analysis (FIA) with amperometric detection were used to study the oxidation reactions. Experiments were concurrently performed using glassy carbon electrodes as comparison. The detection limit of 5 μM for 3,6-dihydroxyphenanthrene in organic medium was obtained by the use of the FIA technique with the diamond electrode. The peak current at +1.2 V vs. Ag/AgCl due to the oxidation of 3,6-dihydroxyphenanthrene is proportional to its bulk concentration in the range of 10–100 μM with R =0.99. The FIA response was highly reproducible, and the response variation was below 6% from film to film in detectable range.

Microhardness and crystal structure of iron films electrodeposited from iron (II) chloride solution

The relationship between microhardness and crystal structure was studied with respect to electrodeposited iron films obtained from iron(II) chloride solution under various electrolytic conditions. The deposits with a lower microhardness showed a preferred orientation of the (110) plane, and the microhardness and the orientation index of the (110) plane were represented by an approximately linear relationship. In order to obtain the deposits with a lower microhardness, it is necessary to electrolyze under a lower current density, at a higher temperature and in the solution with higher pH. The deposits obtained showed large crystal grains having a preferred orientation of the (110) plane. A dependence was revealed betweenb microhardness and crystal structure of the deposits