Tatsuhiko Yajima

Oxidation of aromatic hydrocarbons with oxygen in a radiofrequency plasma

The reactions of three aromatic hydrocarbons, benzene, toluene, and styrene, with oxygen in a radiofrequency (r∫) plasma were investigated. Benzene was oxidized to yield phenol as a single volatile organic product. Similarly, toluene gave the ring oxidation products, cresols, as well as considerable amounts of methyl oxidation products, consisting mainly of benzaldehyde and benzyl alcohol. In contrast, the oxidation of styrene took place predominantly on the olefinic double bond to produce styrene oxide On basis of the products and effects of reaction variables, r∫ power and flow rates of hydrocarbons and oxygen, on the reaction rate, the oxidation mechanism was discussed, particularly focusing on the intermediate species responsible for the formation of major products.

Vanadium Pentoxide-Based Composite Synthesized Using Microwave Water Plasma for Cathode Material in Rechargeable Magnesium Batteries

Multivalent cation rechargeable batteries are expected to perform well as high-capacity storage devices. Rechargeable magnesium batteries have an advantage in terms of resource utilization and safety. Here, we report on sulfur-doped vanadium pentoxide (S-V2O5) as a potential material for the cathodes of such a battery; S-V2O5 showed a specific capacity of 300 mAh·g−1. S-V2O5 was prepared by a method using a low-temperature plasma generated by carbon felt and a 2.45 GHz microwave generator. This study investigates the ability of S-V2O5 to achieve high capacity when added to metal oxide. The highest recorded capacity (420 mAh·g−1) was reached with MnO2 added to composite SMn-V2O5, which has a higher proportion of included sulfur than found in S-V2O5. Results from transmission electron microscopy, energy-dispersive X-ray spectroscopy, Micro-Raman spectroscopy, and X-ray photoelectron spectroscopy show that the bulk of the SMn-V2O5 was the orthorhombic V2O5 structure; the surface was a xerogel-like V2O5 and a solid solution of MnO2 and sulfur.

Electrochemical characteristics of platinum surface treated by RF plasma

Abstract On the basis of the Nernstian pH–potential response, E = E 0 ′−2.303( RT / F )pH, according to the reaction Pt+H 2 O→PtOH+H + +e − at the platinum surface, in this work the electric potentials of platinum wires treated by radio-frequency plasmas of oxygen, hydrogen and helium were measured. The potential was related theoretically to the surface coverage ( θ ) of the oxide layer at the platinum surface by means of the equation: E 0 ′=E 0 ″+2.303(RT/F) log [θ/(1−θ)] . By using this relationship, the effect of the plasma treatments was successfully explained: (1) an oxygen plasma oxidized the platinum surface to enlarge the oxide layer, (2) a hydrogen plasma reduced the oxide layer to diminish it and (3) the helium plasma, since it has no reducing power, might etch the oxide layer to remove it from the surface.

Surface characterization of titanium dioxide powder treated by the CH4-H2 plasma CVD method

Abstract Anatase is a naturally occurring crystalline form of titanium dioxide (TiO 2 ) powder was treated by microwave-induced low temperature plasma of methane–hydrogen mixed gas. The light grayish sample was observed by the hydrogen-rich plasma treatment. Since the superior photocatalytic activity of TiO 2 under ultraviolet irradiation is well known, we examined the photocatalytic characterization of the samples. On the gas-phase decomposition of acetaldehyde a good evaluation of the plasma-treated sample was obtained under ultraviolet irradiation. Moreover, the light grayish sample showed photocatalytic activity under visible light irradiation. Plasma-treated samples were characterized by XRD, FT–IR, FT-Raman and XPS measurements.

Decomposition of poly(amide-imide) film enameled on solid copper wire using atmospheric pressure non-equilibrium plasma.

The decomposition of a poly(amide-imide) thin film coated on a solid copper wire was attempted using atmospheric pressure non-equilibrium plasma. The plasma was produced by applying microwave power to an electrically conductive material in a gas mixture of argon, oxygen, and hydrogen. The poly(amide-imide) thin film was easily decomposed by argon-oxygen mixed gas plasma and an oxidized copper surface was obtained. The reduction of the oxidized surface with argon-hydrogen mixed gas plasma rapidly yielded a metallic copper surface. A continuous plasma heat-treatment process using a combination of both the argon-oxygen plasma and argon-hydrogen plasma was found to be suitable for the decomposition of the poly(amide-imide) thin film coated on the solid copper wire.

Transposition of the cyano group on a benzene ring in a gaseous plasma

Transposition of the cyano group in dicyanobenzene in a radiofrequency plasma occurred predominantly via the prismane-type structure.

Development of an environmentally acceptable volatile organic compounds recovery and reuse system based on vacuum spray flash with dibasic acid esters as absorbents.

We used dibasic acid esters as the absorbent for a volatile organic compounds (VOC) recovery and reuse system geared mainly toward VOCs from painting and presswork. The system consists of three elements: absorption using dibasic acid esters, separation by vacuum spray flash method, and recovery by condensation. The concentration of both ethyl acetate (EtAc) and isopropyl alcohol (IPA) decreased around 90% at room temperature. Vacuum spray flash was found as a useful process for cost-effective and energy-effective VOC removal system. The difference in the dissolubility parameters (Hansen constant) between dibasic acid esters and VOCs and the boiling point of VOCs was the main contributor to the separation behavior.

Chemical Characterization of Odortypes in Mice

The odors of individual mice are specified by the genes of the major histocompatibility complex (MHC), which are the same genes that help regulate the immune response. Specifically, mice can discriminate urine samples obtained from strains of inbred mice that are genetically identical except for genes of the MHC [1]. The odors specified by the MHC genes have been called odortypes. These odors are involved in mate selection, which is strongly biased toward preference for a mate of a histocompatibility type different from that of the individual’s parents. This tendency for outbreeding appears to be important to maintain the genetic diversity of MHC alleles and serves to help avoid inbreeding.

Formation of dialkylaminoacetonitrile from N,N-dialkylamides in an RF plasma

Abstract An unprecedented transformation of N,N-dimethylamides into dimethylaminoacetonitrile ( 1 ) by passing through a 13.56 MHz gaseous discharge was found. Diethylaminoacetonitrile ( 2 ) was similarly given from N,N-diethylformamide.