Okio Nishimura

Properties of copper-aluminum oxide films prepared by solution methods

Abstract Conducting copper–aluminum oxide films have been prepared by employing the dip-coating method. Metal alkoxides and nitrates were examined as metal sources in the precursor solutions for the preparation of CuAlO 2 samples based on the procedures of sol–gel and nitrate processes, respectively. Fired samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis and electrical measurements. Properties of the samples depended on the calcination temperature and the composition of the precursor solution. Electrical conductance of the samples corresponds well with the delafossite CuAlO 2 content, which was determined by the intensity of corresponding lines in the XRD patterns. The lowest sheet resistance (≈45 Ω/□) was obtained for a film sample prepared by the nitrate process followed by a calcination at 1100 °C for 4 h in air.

X-ray photoelectron spectroscopy studies of high-dose nitrogen ion implanted-chromium: a possibility of a standard material for chemical state analysis

Abstract To examine the possibility of utilizing an ion-implanted material for a standard sample of XPS chemical state analysis, a chromium metal ion implanted with nitrogen in a high dose was studied by XPS. In the implanted layer, the nitrogen density distribution ranged from zero to the maximum density of 40at.%, and different chemical states of chromium existed depending on nitrogen density. The binding energy of the XPS lines shifted in a simple relationship to the N : Cr atomic ratio. Good agreement in the binding energy data between the ion-implanted chromium and stoichiometric nitrides indicated that there is a good possibility of ion-implanted materials being used as standard samples.

Surface characterization of Ti-implanted iron by XPS and AES*

A study has been made of the surface analyses of Ti- and C-implanted irons by means of AES and XPS combined with At sputtering. The Ti- and C-implantations were performed with a dose of 1017 ions/cm2 at energies of 20, 75 and 150 keV at nearly room temperature. The Ti implantation causes a carbon invasion of iron surface layers to form a diffusion-like distribution dependent on the acceleration energy of the Ti ions. The Auger spectra of C (KLL) point to a carbide-like structure in the interior, whereas the XPS spectra related to Ti2p3/2 show a metallic state of the Ti atoms. The binding energy of C1s in the interior where AES spectra reveal a carbide-like structure is approximately 238.3 eV, which is different from that of hydrocarbon, graphite and TiC. Its energy is identified with that of C1s in C-implanted irons and in Fe3C particles.

Morphological and Compositional Characterization of Self-Preserved Gas Hydrates by Low-Vacuum Scanning Electron Microscopy

Gas hydrates (also called clathrate hydrates) are non-stoichiometric solid compounds that form when small guest molecules of suitable size and shape are enclathrated by host cage structures comprising hydrogen-bonded water molecules under appropriate conditions (pressure, temperature, and concentration). The decomposition rates of gas hydrates are known to be suppressed considerably at temperatures below the ice melting point: this is the so-called self-preservation effect. Selfpreservation is not only scientifically interesting; it is also important for the application of gas hydrates as energy-storage materials. For instance, a project for the large-scale transport of natural gas using self-preserved hydrates is underway. A general explanation for self-preservation is that coating of dissociating hydrates by ice products prevents further decomposition either by maintaining internal gas pressure at or near the equilibrium pressure or by limiting gas diffusion through the reaction boundary 8, 9] (note that ice formation is not necessary for decomposition of certain double hydrates; for example, CO2 in the small cages of dimethyl ether-CO2 hydrates can be released without disruption of the basic hydrate structure). However, this simple idea is insufficient to account for the observed complexity of preservation effect. Preservation behaviors are known to vary nonlinearly with temperature and pressure. They also depend strongly on the guest-gas composition. Although the detailed mechanism remains unclear, previous studies have indicated that the texture of ice from hydrate dissociation can be modified according to P-T conditions and according to the type of guest species, engendering different degrees of ice-shielding effects. 11, 14] Scanning electron microscopy (SEM) has been used to investigate microstructures of gas hydrates and hydrate–ice mixtures. 16] Stern et al. conducted SEM observations of partly dissociated methane hydrate particles. They reported a lack of evidence for development of ice-coating around individual hydrate grains. In contrast, SEM studies by Kuhs and co-workers, from their observations of both natural and synthetic specimens, have revealed the evolution of ice films on decaying hydrates. 17] Nevertheless, details of the microstructure of selfpreserved gas hydrates remain unclear because of methodological limitations of previous SEM experiments, such as specimen sublimation in a high-vacuum atmosphere necessary for normal SEM observations, and charging artifacts (abnormal image contrast unrelated to actual surface topology) incurred by negative charge of insulating samples. The most severe problem is how to differentiate hydrate and ice phases. For phase identification, earlier studies 12, 16, 17] relied mainly on surface appearances because a conventional secondary-electron image fundamentally does not contain compositional information, but the difference in textures between the two components is often unclear. Although X-ray analyses are useful for this purpose in some cases, they require a considerable amount of samples for detection (e.g. submicron hydrate inclusions shown in Figures 2 f, 2 h, 3 f and 3 h are too small to analyze with energy-dispersive spectra). Additionally, X-ray scans often give rise to beam damage of the analyzed surfaces. To overcome these difficulties, we use low-vacuum SEM (LVSEM). At a low vacuum, the sample sublimation is negligible (see Figure S1 of the Supporting Information). Interaction between ionized atmospheric gases and sample surfaces neutralizes the negative specimen charge. More importantly, for LVSEM, micrographs are imaged from backscattered electrons, which provide compositional image contrasts because atomic composition dominantly influences the intensity of backscattered electrons (see Supporting Information and Figure S2). Ar and Kr hydrates were investigated in this work for comparison with our latest report : we have reported that different modes of hydrate dissociation to ice were observed between the two systems using microfocus X-ray computed tomography (MFXCT). Figure 1 portrays LVSEM images of as-grown samples. Synthesized hydrates were pure crystals of clathrate structure II, as described in a previous report. Ar hydrates exhibited dimpled surfaces with scattered hollows up to a few tens of micrometers (Figures 1 a and 1 b). Observations of inner surfaces that had been exposed accidentally during sample preparation indicated that crystals were dense, although some voids were included (Figures 1 c and 1 d). Kr hydrates presented a similar pitted surface topology (Figure 1 e), but magnified images [a] Dr. H. Ohno , Dr. J. Nagao Production Technology Team, National Institute of Advanced Industrial Science and Technology 2-17-2-1 Tsukisamu-Higashi Toyohiraku, Sapporo 062-8517 (Japan) Fax: (+ 81) 11-857-8985 E-mail : hiroshi-ohno@aist.go.jp jiro.nagao@aist.go.jp [b] Dr. O. Nishimura , Dr. K. Suzuki Reservoir Characterization Team, National Institute of Advanced Industrial Science and Technology 2-17-2-1 Tsukisamu-Higashi Toyohiraku, Sapporo 062-8517 (Japan) [c] Dr. H. Ohno , Dr. O. Nishimura , Dr. K. Suzuki , Dr. H. Narita, Dr. J. Nagao Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology 2-17-2-1 Tsukisamu-Higashi Toyohiraku, Sapporo 062-8517 (Japan) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cphc.201100079.

Analysis of blood pulse wave measured by reflective optical sensor

Spectrum analysis of a blood pulse wave (BPW) has been carried out by a novel optical measurement system. The BPW is detected at the second finger of a left hand by a photoelectric plethysmography. Spectrum analysis of the BPW reveals two independent signals, which are at about 1 Hz and 0.1 Hz. The higher-frequency signal is due to heart beats, and the lower signal is the result of breath. The BPW spectrum has been investigated in terms of frequency stability of heart rate (HR). The correlation coefficient between HR and standard deviation of HR in the amplitude spectrum is -0.90. The standard deviation of BPW in amplitude spectrum is presented as a parameter of the cardiovascular system.<<ETX>>