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Seiichi Takami Teruyuki Sato Tahereh Mousavand Satoshi Ohara Mitsuo Umetsu Tadafumi Adschiri 《Materials Letters》2007,61(26):4769-4772
We synthesized surface-modified iron oxide nanoparticles in aqueous phase by heating an aqueous solution of iron sulfate (FeSO4) at 473 K with a small amount of either n-decanoic acid (C9H19COOH) or n-decylamine (C10H21NH2), which is not miscible with water at room temperature. Transmission electron microscopy showed that the addition of n-decanoic acid or decylamine changed the shape of the obtained nanoparticles. X-ray diffraction spectra revealed that the synthesized nanoparticles were in α-Fe2O3 or Fe3O4 phase while Fourier transform infrared spectroscopy and thermogravimetry indicated the existence of an organic layer on the surface of the nanoparticles. In the synthetic condition, decreased dielectric constant of water at higher temperature increased the solubility of n-decanoic acid or n-decylamine in water to promote the reaction between the surface of iron oxide nanoparticles and the organic reagents. After the synthesis, the used organic modifiers separated from the aqueous phase at room temperature, which may help the environmentally benign synthesis of surface-modified metal oxide nanoparticles. 相似文献
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Toshihiko AritaHidetsugu Hitaka Kimitaka MinamiTakashi Naka Tadafumi Adschiri 《The Journal of Supercritical Fluids》2011,57(2):183-189
Supercritical hydrothermal syntheses of metal nanoparticles were investigated. Organic metal salt and hydrogen gas produced by water catalyzed decomposition of formic acid was employed as metal sources and reduction agent, respectively. The formation of iron was verified by measuring the magnetic property of the products by superconducting quantum interference device (SQUID) magnetometer as well as crystallographic analysis by X-ray diffraction (XRD). As predicted by the free energy calculation of reduction of metal oxides by hydrogen molecule, silver, palladium, copper, nickel and cobalt nanoparticles were synthesized without using surface modifier, whereas, iron could be synthesized at small yield. The main product was iron oxides (mainly magnetite). In order to increase the yield of iron, hexanoic acid was employed as an in situ surface modifier of the synthesis. The surface modification lessened the size of the synthesized nanoparticles and increased the yield of iron. The optimum condition for iron synthesis was also investigated, as a result, 7.6% yield of iron was achieved. 相似文献
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Yoshiharu Hatakeyama Mitsuo Umetsu Masahiro Minami Satoshi Ohara Seiichi Takami Tadafumi Adschiri 《Journal of Materials Science》2008,43(7):2426-2430
The DNA, which forms a double helical conformation by the highly selective base-pairing rule with the width of 2 nm, is one
of the polymers utilized as a template for nanoparticle assembly. Then, holiday junction structure, where two different DNA
double strands intersect and replace each complement strand, is an important artificial motif for forming two-dimensional
mesh-like DNA morphology. In this study, the two-dimensional sheet with the mesh-like conformation is formed and the growth
of the DNA morphology is controlled by changing the temperature in the formation process. The influence of the cooling procedure
on the formation process of the two-dimensional DNA sheet is observed by atomic force microscope, and the formation of double
strands in the process is traced by absorption spectra. The spectroscopic results demonstrate that the two-dimensional DNA
sheet is strongly dependent on the correlation between the applied cooling process and the melting temperature of double helical
conformation, and that the growth of the two-dimensional DNA sheet can be manipulated by the cooling procedure. Further, we
will show the size control of the DNA sheet by mixing the designed DNA which inhibits the growth of the DNA sheet. 相似文献
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Rapid and Continuous Hydrothermal Synthesis of Boehmite Particles in Subcritical and Supercritical Water 总被引:2,自引:0,他引:2
Tadafumi Adschiri Katsuhito Kanazawa Kunio Arai 《Journal of the American Ceramic Society》1992,75(9):2615-2618
Hydrothermal synthesis of AlOOH particles from an Al(NO3 )3 aqueous solution was examined in subcritical and supercritical water. Continuous and rapid production of AlOOH fine particles was achieved by mixing a metal salt aqueous solution with preheated water fed from another line. The effects of temperature, pressure, and initial concentration of solution on the particle size, morphology, and crystal structure of the metal (hydrous) oxides were examined. These properties are strongly affected by slight changes in pressure and temperature. This strong effect is attributed to the large changes in the properties of water near its critical point resulting from the slight changes in pressure and temperature. The results suggest the simultaneous control of size, crystal structure, and morphology of the particles by hydrothermal synthesis in supercritical water. 相似文献
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Kenta Inagaki Takatoshi Hijikata Takeshi Tsukada Tadafumi Koyama Keiji Ishikawa Shoichi Ono 《Journal of Nuclear Science and Technology》2014,51(7-8):906-915
A simulation code was developed to evaluate the performance of the cesium adsorption instrument operating in Fukushima Daiichi Nuclear Power Station. Since contaminated water contains seawater whose salinity is not constant, a new model was introduced to the conventional zeolite column simulation code to deal with the variable salinity of the seawater. Another feature of the cesium adsorption instrument is that it consists of several columns arranged in both series and parallel. The spent columns are replaced in a unique manner using a merry-go-round system. The code is designed by taking those factors into account. Consequently, it enables the evaluation of the performance characteristics of the cesium adsorption instrument, such as the time history of the decontamination factor, the cesium adsorption amount in each column, and the axial distribution of the adsorbed cesium in the spent columns. The simulation is conducted for different operation patterns and its results are given to Tokyo Electric Power Company (TEPCO) to support the optimization of the operation schedule. The code is also used to investigate the cause of some events that actually occurred in the operation of the cesium adsorption instrument. 相似文献
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Kato M Kinoshita H Enokita M Hori Y Hashimoto T Iwatsubo T Toyo'oka T 《Analytical chemistry》2007,79(13):4887-4891
More than 20 million people are suffering from Alzheimer's disease, and the number of patients will dramatically increase with the arrival of an aging society unless preventive or curative medications are discovered. A fast and sensitive analytical method for beta-amyloid (Abeta) aggregates was developed by the combination of CE-laser induced fluorescence and the fluorescence reagent, thioflavine T. The developed method separates two different fibrils within 5 min. The first peak, which migrated at approximately 4 min, was supposed to be derived from a precursor of a fibril that migrated at approximately 3.5 min. The developed method was also applicable to the high-throughput screening of the Abeta aggregation inhibitors, which was expected to be an effective therapeutic agent candidate of Alzheimer's disease. Three compounds (daunomycin, 3-indolepropionic acid (3-IPA), melatonin) were used for the assay. The order of the antiaggregation activity of these compounds was daunomycin > 3-IPA > melatonin, which was the same as that of the reported one. These results suggest that this analytical method may be used to analyze the Abeta fibrils and identify potential therapeutic agents for the treatment of Alzheimer's disease. 相似文献
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Polymer films consisting of nematic liquid crystal (LC) droplets and polymer networks were prepared by using a low-energy electron beam to irradiate a homogeneous mixture of nematic LC and bifunctional methacrylate monomer. Influences of such polymerization conditions as polymerization temperature, monomer concentration, and radiation energy on electrooptical properties of the compound films were examined. The polymer yield, affecting to a large extent the film properties, depended on the monomer concentration and the radiation energy. Compound films, which have a switching function from the scattering state to transparency by applying approximately 20–30 V between the two sides of the film, were obtained. In addition, it was found that a compound film with excellent electrooptical properties was prepared by changing impure LC in the droplets into pure LC. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1675–1681, 1997 相似文献
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Lu J Minami K Takami S Shibata M Kaneko Y Adschiri T 《ACS applied materials & interfaces》2012,4(1):351-354
ITO nanoparticles were synthesized hydrothermally and surface modified in supercritical water using a continuous flow reaction system. The organic modification of the nanoparticles converted the surface from hydrophilic to hydrophobic, making the modified nanoparticles easily dispersible in organic solvent. The addition of a surface modifier into the reaction system impacted the crystal growth and particle size as well as dispersion. The particle size was 18 nm. Highly crystalline cubic ITO with a narrow particle size distribution was obtained. The advantages of short reaction time and the use of a continuous reaction system make this method suitable for industrial scale synthesis. 相似文献