Keiichi Furuya

SEASONAL VARIATION AND THEIR CHARACTERIZATION OF SUSPENDED PARTICULATE MATTER IN THE AIR OF SUBWAY STATIONS

In order to accumulate fundamental data on the atmospheric environments in subway, the mass concentration, particle size distribution and elemental constitution of suspended particulate matter (SPM), and the concentration and constitution of polycyclic aromatic hydrocarbon (PAH), were measured and analyzed at three subway stations with different air supply systems on the same line. The mass concentration of SPM in the subway stations showed seasonal variations, and was higher in December and October than in March and June. It was also higher at the subway stations than in the aboveground throughout the seasons. The concentrations of SPM in the size range of 0.5–5.0 μm were higher in the subway stations than aboveground, suggesting this size of SPM was generated by the operation of trains. The elements that were observed at high concentrations in the subway SPM were Fe, Ba, Cu and Ca. On the other hand, the elements of which concentrations were relatively higher in the aboveground air were Cl, Na and K. Polycylic aromatic hydrocarbons collected at the subway stations showed similar concentrations and characteristics to those observed in the urban atmosphere.

Thermal degradation and combustion process of liquid crystalline polyesters studied by directly coupled thermal analysis-mass spectrometry

Thermal degradation and combustion processes of commercial liquid crystalline polyesters (LCPs) were studied by directly coupled thermal analysis-mass spectrometry (TA-MS) under inert and quasi-air atmosphere. The first major degradation step of LCPs was the ester linkage rupture reaction. In the case of fully aromatic LCPs, this process was little influenced by 20% oxygen atmosphere. The main evolved gaseous products at this step were CO, CO2, H2O and phenol for fully aromatic LCP samples, in addition, aliphatic products for a semi-aromatic LCP sample. Evolution of CO2 was followed by that of flammable organic products for fully aromatic LCPs, while flammable organic products evolved prior to CO2 for semi-aromatic LCP. The flame resistant and self-extinguishing mechanisms of LCPs are discussed on the basis of their thermal degradation behavior.

Some considerations of the SERS effect of L‐phenylalanine in the near‐infrared region using silver colloid solution

The surface-enhanced Raman scattering (SERS) spectra of L-phenylalanine were examined in the near-infrared region using silver colloid solutions. It was shown that near-infrared SERS (NIR-SERS) was not detected for L-phenylalanine in a normal silver colloid solution, whereas in the visible region a distinct SERS intensity enhancement was realized for such sample systems. In the present study, this situation was considered from the viewpoint that the degree of aggregation of colloid particles necessary to cause the SERS effect is different between visible and near-infrared radiation. In this work, silver colloid solution containing dissolved L-phenylalanine was dropped on to a filter-paper and this filter-paper sample was then dried. It was confirmed by SEM (scanning electron microscopy) that as a result of this sample preparation, the degree of aggregation of colloid particles increased considerably. It was shown that the near-infrared SERS was detected with high sensitivity for L-phenylalanine adsorbed on silver particles condensed on filter-paper. From consideration of the magnitudes of the SERS intensity enhancement in this case, it is suggested that the mechanism of NIR-SERS for the present sample system is the electromagnetic effect, related to the excitation of surface plasmons (the surface plasmon polariton mechanism).

Depth profiling of surface oxidized TiAlN film by synchrotron radiation excited X-ray photoelectron spectroscopy

Abstract Depth profiling analysis of the surface oxide layer of Ti 0.55 Al 0.45 N film was performed by means of synchrotron radiation excited X-ray photoelectron spectroscopy (SR-XPS). The results indicated that the oxidation of nitride and segregation into TiO 2 and Al 2 O 3 occur simultaneously and that the Al 2 O 3 layer is formed at the upper surface layer of the film. The depth profile of nitrogen species indicated that molecular N 2 which was formed by the oxidation of the nitride occurred only in the TiO 2 matrix. This implied that the surface Al 2 O 3 layer functions as a surface protective layer for not only the inward diffusion of oxygen but also the outward diffusion of molecular N 2 .

X-ray absorption and X-ray photoelectron spectroscopic studies of air-oxidized chromium nitride thin films

Abstract The surface oxidation of CrN thin films prepared by the cathode are ion plating method was studied by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) using soft X-rays from synchrotron radiation. The results indicate that molecular nitrogen is formed in the interstitial position of the chromium oxide matrix at the initial stage of oxidation. On further oxidation, at a higher temperature, molecular nitrogen is gradually released from the surface, with part of the displaced nitrogen remaining in the interstitial position.

A static-sims study on preferential sputtering on copper-nickel alloy surface

Abstract Preferential sputtering on homogeneous copper-nickel alloy surface has been studied with static-SIMS, and the overall ionization probability ratio of sputtered atoms has been estimated. The measurement of preferential sputtering was made on a range of all alloy compositions with Ar + ion impacts of 700 eV. Sample alloy surfaces were prepared by abrasion in running water in order to avoid surface segregation. After 10 min bombardment of Ar + ions in each measurement, the static-SIMS peak ratio of copper and nickel comes to a steady state. The nickel surface concentration derived from the peak ratio, was compared with AES results previously reported, and found to be higher than those in the range of lower nickel concentrations. The difference can be explained with the measurement mechanism of SIMS and AES concerning the “altered layer”. It is reasonable to consider that AES investigates the “altered layer”, while static-SIMS investigation after establishment of steady state is independent of the “altered layer” and gives information just below the “altered layer”.

Composition dependence of the initial oxidation behaviour of Ti1−xAlxN (x = 0.20, 0.45, 0.65) films studied by XAS and XPS

The difference in the initial oxidation behaviours of Ti 1-x Al x N (x = 0.20, 0.45, 0.65) films was studied by x-ray absorption (XAS) and by x-ray photoelectron spectroscopy (XPS) using synchrotron radiation (SR-XPS). The N K-edge XAS results indicated rapid decreases in the relative ratio of Al-N relative to the total nitride with surface oxidation for all the Ti 1-x Al x N films. The SR-XPS analysis of O, Ti and Al species with different photon energies disclosed the formation of Al 2 O 3 at an upper layer and TiO 2 at a lower layer in oxidized Ti 1-x Al x N films with x = 0.20 and 0.45. In contrast, a mixed Al 2 O 3 and TiO 2 surface layer was formed in the oxidized Ti 1-x Al x N film with high aluminium content (x = 0.65). In addition, N 2 molecules, which were formed as an intermediate species during the oxidation, were concentrated in the interface of Al 2 O 3 and TiO 2 in the oxidized Ti 0.55 Al 0.45 N and Ti 0.80 Al 0.20 N films, whereas they occurred near the surface in the oxidized Ti 0.35 Al 0.65 N film. From these results, it was concluded that the high surface oxidation-resistant properties of Ti 1-x Al x N film with low aluminium content originated from the rapid formation of a surface Al 2 O 3 layer that prevented inward diffusion of oxygen as well as outward diffusion of molecular nitrogen.

Hydrogen Desorption Behaviors of HF-Treated Silicon Wafer

Hydrogen desorption behaviors of HF-treated silicon wafer and decomposition reaction of water vapor on an HF-treated silicon surface under UHV were investigated by means of thermal desorption spectroscopy (TDS). When an HF-treated silicon surface was annealed in high vacuum, silicon trihydride species (SiH3) desorbed from the HF-treated silicon surface at 580°C, and SiH2F species which had probably the same structure as SiH3 on an HF-treated silicon surface desorbed and then recombined to form volatile SiH3-F with adjacent hydrogen at 580°C in addition to H2 desorption at about 400, 500 and 600°C. The decomposition reaction of water vapor was found to proceed in two steps at 500 and 750°C on a dehydrogenated silicon surface. The reaction made background hydrogen increase at 500 and 750°C in H2+ spectra from HF-treated silicon wafer.

Solubility of Nickel Oxide Particles in Various Solutions and Rat Alveolar Macrophages

The solubility of five types of commercial nickel oxide particles was determined in different types of solutions, including distilled water, physiological saline, buffered saline, and tissue-culture medium, in order to estimate their solubility in the human respiratory tract. In addition, we examined the solubility of the two types of particles that were the most and least soluble particles of the above five types of nickel oxide, in rat alveolar macrophages cultured in vitro. The solubility of the nickel oxide particles in these solutions varied remarkably with their types, suggesting that, even though they are called as “nickel oxide,” their solubilities are different among the manufacturer and the product lot. Their solubilities were also influenced by the types of solution and the existence of carbon dioxide in the atmosphere. The solubility of nickel oxide particles in the alveolar macrophages was significantly larger than that observed in the culture medium without macrophages, but smaller than that observed in the distilled water. These results suggest that the actual solubility of nickel oxide particles in the respiratory tract may be difficult to estimate by the conventional solubility analysis method using distilled water, and that the enhancement of particle dissolution by the alveolar macrophages and the depression of particle solubility by the coexisting salt and carbon dioxide should be taken into consideration for the accurate estimation.

Geometric and electronic structures of NO adsorbed on Ni, Rh and Pt studied by using near edge X-ray absorption fine structure (NEXAFS) and resonant photoemission spectroscopy

Abstract The geometric and electronic structures of NO adsorbed on three metals (Ni, Rh, and Pt) from 130 to 600 K were investigated by using near edge X-ray absorption fine structure (NEXAFS) and resonant photoemission spectroscopy (RPS). NEXAFS revealed that NO was molecularly adsorbed on all three metals at 130 K with its molecular axis normal to the surface. The elongation of the NO intramolecular bond on metal was in the order Ni>Rh>Pt, and was related to the electron-back donation from metal-d band to 2π of NO. This order was the same for the electron donation from 5σ of NO to metal-d band estimated by using RPS. With heating, NO was desorbed from Pt without dissociation, whereas NO on Ni and Rh dissociated. Both NEXAFS and RPS showed that the electronic interaction between NO and Pt was increased by heating, but desorption preceded dissociation. The above results were finally related to the catalytic properties of the three metals for the reaction of NO.