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Your search keyword '"Wai, Chien M."' showing total 449 results
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449 results on '"Wai, Chien M."'

52. Supercritical fluid extraction of uranium and thorium from nitric acid solutions with organophosphorus reagents

Author

Lin, Yuehe, Smart, Neil G., and Wai, Chien M.

Subjects
Supercritical fluid extraction -- Methods, Organophosphorus compounds -- Analysis, Environmental issues, Science and technology
Abstract

A method for extracting uranium and thorium from nitric acid solutions with organophosphorus reagents is examined. Organophosphorus reagents are first dissolved in supercritical carbon dioxide by passing the fluid through a reagent vessel placed upstream of the sample vessel in the extractor. When the extraction is complete, the sample is removed from the extraction cell and analyzed by neuron activation analysis. The amount of uranium and thorium ions remaining in the solution after extraction provides a measure of the reagents' extraction efficiency.

Published
1995

55. Characterization of uranyl(VI) nitrate complexes in a room temperature ionic liquid using attenuated total reflection-Fourier transform infrared spectrometry

Author

Quach, Donna L., Wai, Chien M., and Pasilis, Sofie P.

Subjects
Ammonium chloride -- Chemical properties, Ammonium compounds -- Chemical properties, Ammonium paratungstate -- Chemical properties, Fourier transform infrared spectroscopy -- Usage, Ionic solutions -- Chemical properties, Nitrates -- Chemical properties, Chemistry
Published
2010

56. Application of green chemistry techniques to prepare electrocatalysts for direct methanol fuel cells

Author

Shimizu, Kenichi, Wang, Joanna S., and Wai, Chien M.

Subjects
Fuel cells -- Research, Green chemistry -- Usage, Methanol -- Chemical properties, Methanol -- Electric properties, Organometallic compounds -- Chemical properties, Organometallic compounds -- Electric properties, Organometallic compounds -- Environmental aspects, Platinum -- Chemical properties, Platinum -- Electric properties, Chemicals, plastics and rubber industries
Published
2010

57. Influence of the characteristics of a water-in-CO2 microemulsion on separation of metal species

Author

Wang, Joanna S., Wai, Chien M., Hwa-Kwang Yak, and KongHwa Chiu

Abstract

In this study, AOT [sodium bis(2-ethylhexyl) sulfosuccinate] combined with fluorinated cosurfactant or alcohol was used to form a water-in-CO2 (W/C) microemulsion. The amount of water uptake in the microemulsion was closely related to the PFPE-PO4/AOT (P/A) ratio. The stability of the microemulsion decreased with the amount of water. Lower temperature and higher pressure stabilize W/C microemulsions. The extraction efficiencies of metals (Cd, Co, Cu, Pb, Zn), when this W/C microemulsion method was used, exceeded 90% (AOT + octanol). The efficiencies for the extraction of Eu, La, and Sr could exceed 94% (AOT + PFPE-PO4) in sc-CO2.

Published
2016
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61. Investigations into the Reusability of Amidoxime-Based Polymeric Adsorbents for Seawater Uranium Extraction

Author

Kuo, Li-Jung, primary, Pan, Horng-Bin, additional, Wai, Chien M., additional, Byers, Margaret F., additional, Schneider, Erich, additional, Strivens, Jonathan E., additional, Janke, Christopher J., additional, Das, Sadananda, additional, Mayes, Richard T., additional, Wood, Jordana R., additional, Schlafer, Nicholas, additional, and Gill, Gary A., additional

Published
2017
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64. An FT-IR study of crown ether-water complexation in supercritical CO2D

Author

Rustenholtz, Anne, Fulton, John L., and Wai, Chien M.

Subjects
Ether -- Research, Ether -- Chemical properties, Fourier transform infrared spectroscopy -- Usage, Chemistry, Physical and theoretical -- Research, Chemicals, plastics and rubber industries
Abstract

D2O forms a 1:1 complex with the macrocyclic molecule in supercritical fluid CO2 with two different configurations in the presence of 18-crown-6. Formation of a 1:2 complex in SF-CO2 that involves one D2O molecule hydrogen bonded to two crown ether molecules becomes possible at high 18-crown-6 to D2O ratios.

Published
2003

65. On-Line Speciation of Uranyl Chelates in Supercritical [CO.sub.2] by Time-Resolved Laser-Induced Fluorescence Spectroscopy

Author

Addleman, R. Shane, Carrott, Mike, Wai, Chien M., Carleson, Tom E., and Wenclawiak, B. W.

Subjects
Chemistry, Analytic -- Research, Carbon dioxide -- Analysis, Chelates -- Analysis, Chemistry
Abstract

The dynamic emission characteristics of selected uranyl complexes in supercritical (ScF) [CO.sub.2] have been quantified with time-resolved laser-induced fluorescence (TRLIF). A variety of factors were found to affect the emission from uranyl complexes in ScF including ligand, adduct, pressure, and temperature. TRLIF was shown to allow on-line speciation and quantitative analysis of uranyl complexes with different primary ligands in ScF [CO.sub.2]. The method was applied to real-time analysis of multiligand uranium extractions from aqueous solutions with ScF [CO.sub.2].

Published
2001

66. Voltammetric Measurement in Supercritical [CO.sub.2] Utilizing a Water-in-[CO.sub.2] Microemulsion

Author

Ohde, Hiroyuki, Hunt, Fred, Kihara, Sorin, and Wai, Chien M.

Subjects
Voltammetry -- Methods, Emulsions -- Testing, Supercooled liquids -- Analysis, Carbon dioxide -- Thermal properties, Chemistry
Abstract

A novel method for voltammetric measurement in supercritical [CO.sub.2] is described. In this method a water-in-supercritical [CO.sub.2] microemulsion is utilized to raise the conductivity of the fluid phase. Well-defined voltammograms for the redox reactions of ferrocene and tetramethyl-p-phenylenediamine were obtained in supercritical [CO.sub.2] in the presence of the microemulsion. The electrolysis product is stabilized in the water core of the microemulsion. This implies a wide range of electrochemical synthesis involving ionic or radical species in supercritical [CO.sub.2] may be possible utilizing the microemulsion. The electrochemical results obtained from the water-in-supercritical [CO.sub.2] microemulsion system are different from that obtained from a supercritical [CO.sub.2]-ethanol mixture system.

Published
2000

74. Elution of Uranium and Transition Metals from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

Author

Pan, Horng-Bin, primary, Kuo, Li-Jung, additional, Wai, Chien M., additional, Miyamoto, Naomi, additional, Joshi, Ruma, additional, Wood, Jordana R., additional, Strivens, Jonathan E., additional, Janke, Christopher J., additional, Oyola, Yatsandra, additional, Das, Sadananda, additional, Mayes, Richard T., additional, and Gill, Gary A., additional

Published
2015
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82. Hydrogenation of olefins in supercritical CO (sub)2 catalyzed by palladium nanoparticles in a water-in-CO (sub)2 microemulsion

Author

Ohde, Hiroyuki, Wai, Chien M., Kim, Hakwon, Kim, Jeongryul, and Ohde, Mariko

Subjects
Chemical research -- Analysis, Carbon dioxide -- Physiological aspects, Water -- Physiological aspects, Solvation -- Physiological aspects, Silver -- Physiological aspects, Copper -- Physiological aspects, Olefins -- Physiological aspects, Palladium -- Physiological aspects, Nanotechnology -- Research, Chemistry
Abstract

Research has been conducted on the water-in-CO (sub)2 microemulsions. Results indicate that this microemulsion system can dissolve ionic species and hydrophilic organic compounds in water core.

Published
2002

89. Synthesizing and dispersing silver nanoparticles in a water-in-supercritical carbon dioxide microemulsion

Author

Ji, Min, Chen, Xiaoyuan, Wai, Chien M., and Fulton, John L.

Subjects
Emulsions -- Research, Silver compounds -- Research, Carbon dioxide -- Research, Chemistry
Abstract

The synthesis and dispersion of silver nanoparticles in a water-in-supercritical carbon dioxide microemulsion were investigated. To this end, the size of the particles in the microemulsion was calculated from the height and width of the surface plasmon resonance band in the ultraviolet-visible absorption spectra. Results revealed a stable suspension of nanometer-sized metallic particles in carbon dioxide and represents the first step to formation and stabilization of a variety of metallic particles in carbon dioxide.

Published
1999

91. Advanced Materials Deposition for Semiconductor Nanostructures Using Supercritical Fluids

Author

IDAHO UNIV MOSCOW, Wai, Chien M., IDAHO UNIV MOSCOW, and Wai, Chien M.

Abstract

Supercritical fluid carbon dioxide provides an attractive medium for depositing materials in small structures with high aspect ratios and poorly wettable substrates due to the fact that it is able to dissolve solutes like a liquid and transport dissolved materials like a gas. Metal and metal sulfide nanoparticles of controllable size can be synthesized in supercritical fluid carbon dioxide using water-in-CO2 microemulsion as template. Continuous tuning the size of metallic nanoparticles and metal sulfide nanoparticles with diameters from less than 2 nm to over 10 nm can be achieved by varying the density of the fluid phase in the synthetic process. The synthesized nanoparticles are stabilized in the fluid phase using an alkylthiol compound. Deposition of the stabilized metal nanoparticles in the fluid phase forming self-assembled arrays has been demonstrated. Supercritical fluid deposition of metals on surfaces of carbon nanotubes has also been studied. Metal nanoparticles of narrow size distributions can be uniformly attached to carbon nanotube surfaces using this method. The carbon nanotube-supported platinum group metal nanoparticles show remarkably high activities for catalyzing chemical and electrochemical reactions. Examples of utilizing the carbon nanotube-nanoparticle composite materials as catalysts for chemical reactions, fuel cells and sensor applications are given.

Published
2007

92. Influence of the characteristics of a water-in-CO2 microemulsion on the separation of metal species.

Author

Wang, Joanna S., Wai, Chien M., Hwa-Kwang Yak, and Kong-Hwa Chiu

Subjects
*MICROEMULSIONS, *SEPARATION (Technology), *METAL absorption & adsorption, *SURFACE active agents, *SUPERCRITICAL fluids, *ALCOHOL, *EXTRACTION (Chemistry)
Abstract

In this study, AOT [sodium bis(2-ethylhexyl) sulfosuccinate] combined with fluorinated cosurfactant or alcohol was used to form a water-in-CO2 (W/C) microemulsion. The amount of water uptake in the microemulsion was closely related to the PFPE-PO4/AOT (P/A) ratio. The stability of the microemulsion decreased with the amount of water. Lower temperature and higher pressure stabilize W/C microemulsions. The extraction efficiencies of metals (Cd, Co, Cu, Pb, Zn), when this W/C microemulsion method was used, exceeded 90% (AOT + octanol). The efficiencies for the extraction of Eu, La, and Sr could exceed 94% (AOT + PFPE-PO4) in sc-CO2. [ABSTRACT FROM AUTHOR]

Published
2016
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93. Two-Dimensional Nanoparticle Cluster Formation in Supercritical Fluid CO2.

Author

Wang, Joanna S., Wai, Chien M., Brown, Gail J., and Apt, Scott D.

Subjects
*SUPERCRITICAL carbon dioxide, *GOLD nanoparticles, *BIOCHEMICAL substrates, *SOLVATION, *MICROCLUSTERS
Abstract

Supercritical fluid carbon dioxide (sc-CO2) is capable of depositing nanoparticles in small structures of silicon substrates because of its gas-like penetration, liquid-like solvation abilities, and near-zero surface tension. In nanometer-sized shallow wells on silicon surface, formation of two-dimensional (2D) monolayer metal nanoparticle (NP) clusters can be achieved using the sc-CO2 deposition method. Nanoparticles tend to fill nanostructured holes first, and then, if sufficient nanoparticles are available, they will continue to cover the flat areas nearby, unless defects or other surface imperfections are available. In addition, SEM images of two-dimensional gold (Au) nanoparticle clusters formed on a flat silicon surface with two to a dozen or more of the nanoparticles are provided to illustrate the patterns of nanoparticle cluster formation in sc-CO2. [ABSTRACT FROM AUTHOR]

Published
2016
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