bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanocomposites Containing Nanoclusters of Metals or Semiconductors
Authors: Burnam Kimberly J. , Carpenter Joseph P. , Lukehart Charles M. , Milne Stephen B. , Stock S. R. , Glosser R. , Jones Bobby D. 
Published: April 2011

ABSTRACTNeutral, low-valent complexes of transition metals or an organometallic compound of Ge are prepared containing ancillary ligands which bear silicate ester or (alkoxy)silicon functional groups. Inclusion of these molecules as dopant species in a conventional sol-gel synthesis of silica xerogels affords silica xerogels in which dopant molecules have presumably been covalently incorporated into the xerogel matrix with uniform and high dispersion. Subsequent thermal treatment of these molecularly doped xerogels under reducing or oxidizing/reducing conditions gives nanocomposites containing nanoclusters of metals or semiconductor substances. By this procedure, nanocomposites containing nanoclusters of Ag, Cu, Pt, Os, CCo3, Fe2P, Ni2P, or Ge have been prepared. Preliminary evidence for the formation of a nanocomposite containing Pt-Sn nanoclusters derived from a bimetallic molecular precursor is also presented. Characterization data for the nanocomposite materials include TEM, electron diffraction, EDS, XRD, and selected use of micro-Raman spectroscopy. These results support the hypothesis that covalent incorporation of molecular precursors containing low-valent metals into a silica xerogel can afford nanocluster phases with high dispersion, relatively small particle size, and unusual elemental composition.
Synthesis of Low Density Microcellular Activated Carbon Supported Nanophase Pt and Pd Particles and Study of Its Catalytic Properties
Authors: Lin Hong-Ming , Huang Ching-Shung , Hsu Chi-Ming 
Published: April 2011

ABSTRACTThe use of activated low density microcellular carbon (LDMC) as a catalysis supporter for nanophase Pt or Pd particles has been successfully developed in this study. The good dispersion and interfacial properties of nanophase Pt or Pd particles on activated LDMC are formed by using an impregnation and sintering process. The interfacial structures are examined by TEM, HRTEM and an image analyst system. No preferred orientation of interfacial bonding has been found between nanophase Pt and activated LDMC. The activated LDMC supported Pt or Pd catalysts have the high reactivity which can complete hydrogenation and oxidation of CO gas at low temperatures (<453 K). The catalytic activity of CO hydrogenation is increased as the size of the nanophase Pt and Pd particles decreases.
Catalytic Properties of Nanocrystalline WO3−X, Pt/WO3−X and Pd/WO3−X Particles
Authors: Tung Chiun-Yen , Lin Hong-Ming , Hsu Chi-Ming , Yang Chao-Cheng 
Published: April 2011

ABSTRACTThe gas-condensation technique is used to produce the nanocrystalline WO3−C, Pt/WO3−X and Pd/WO3−X powders under different atmospheres and pressures. High resolution electron microscope shows there exists well bonded interface between Pt or Pd and WO3−X The WO3−X, Pt/WO3−X and Pd/WO3−x nanocrystals grow into needle shape with plate inside when these asevaporated powders are compacted and sintered at 900 °C for two hours. The plate grows preferentially in {220) plane along < 001 > direction. However, the mean particle size of nanophase Pt and Pd only increases from less than 10 nm to 30 nm and 50 nm, respectively. The gas chromatography results show that nanophase Pt/VO3−X powders have better catalytic effects in converting CO to CO2 than nanophase WO3−X and Pd/WO3−X powders.
Subwavelength Localization of Optical Modes in Fractals
Authors: Shalaev Vladimir , Botet R. , Moskovits M. 
Published: April 2011

ABSTRACTResonant optical excitation of fractal clusters generates dipolar eigenmodes which are extremely localized within areas much smaller than the wavelength. The localization occurs due to the fractal morphology and accounts for the very high local fields leading to the huge enhancement of various optical effects. In particular, Rayleigh and Raman light scattering and, especially, nonlinear optical processes, such as 2-photon photoemission and degenerate four-wave mixing, are strongly enhanced in fractal clusters. The spatial distribution of the modes shows the frequency and polarization selectivity.
Aluminophosphate Glasses with High Sulfate Content
Authors: Stefanovsky Sergey V. , Ivanov Igor A. , Gulin Anatolii N. 
Published: April 2011

AbstractTo immobilize a high sulfate radioactive wastes a system Na2O-A12O3-P2O5-SO3 has been chosen as one where glasses have a relatively low melting points and good chemical durability. Glasses within partial system 44 Na2O, 20 A12O3 (36-x) P2O5 x SO3 have been prepared at 1000 °C. A possibility of assimilation up to 12 mole % of SO3 has been established. The basic properties of sulfate-containing glasses as density, microhardness, thermal expansion coefficient, transformation and deformation temperatures, viscosity, electric resistivity, leach rate of ions and diffusion coefficients of 22Na, 35S, 90Sr and 137Cs have been measured. Glass structure by infrared and EPR spectroscopies has been investigated.
Sorption of60Co,85Sr,137Cs,237Np and241Am on Soil Under Coexistence of Humic Acid: Effects of Molecular Size of Humic Acid
Authors: Tanaka Tadao , Senoo Muneaki 
Published: April 2011

AbstractSorption experiments have been performed by a batch method, to study the effects of humic acid of different molecular size on the complexing stability with60Co,85Sr,137Cs,237Np and241Am, and on the sorption behavior of these radionuclides on a sandy soil.Equilibrium constantsKin the sorption of137Cs and237Np onto the soil were not changed at different concentrations of humic acid since137Cs and237Np do not interact with humic acid, while those of60Co and241Am decreased with increasing humic acid concentration due to forming humic complexes. However, theKof85Sr was not changed at different humic acid concentrations, despite85Sr interacts with humic acid. This contradiction was probably caused from that a main binding of85Sr with humic acid is not based on coordination bond but electrostatic force, due to relatively high concentration of non–radioactive strontium. The theoretical sorption model taking account of the interaction of60Co and241Am with humic acid could well reproduce the values ofKfor each radionuclide at different concentrations of humic acid.Concentration profiles of the radionuclides in each size fraction of the solution before and after the sorption experiments were examined by ultrafiltration technique. The reduction of concentration of60Co in the fraction less than 300,000 of cutoff molecular weight (MW) and that of concentration of241Am in the fraction larger than 100,000MW, respectively, by the sorption onto the soil decreased with increasing humic acid concentration. This decrease resulted in the decrease in theKof60Co and241Am with increasing humic acid concentration.
Modeling of Yb(III) Sorption on Kaolinite by Using Single Oxide Surface Complexation Models
Authors: Marmier Nicolas , Dumonceau Jacques , Chupeau Joël , Fromage Francine 
Published: April 2011

AbstractSurface complexation model was used to describe ytterbium sorption on kaolinite using surface acidity constants and surface complexation constants determined on alumina and silica.
Uranium(IV) Solubility and Hydrolysis Constants Under Reduced Conditions
Authors: Yajima Tatsuya , Kawamura Yuji , Ueta Shinzo 
Published: April 2011

AbstractThe solubility of UO2 (s) was examined in dilute NaCl solutions at room temperature and in the pH range from 2 to 12. Dissolution equilibrium showed good agreements between the data obtained by oversaturation and undersaturation experiments.The dissolution reactions that control the solubility of U[IV] are estimated as UO2 (s) + 4H+ → U4+ + 2H2O and UO2 (s) + 2H2O → U(OH)4°. The log K at zero ionic strength are yielded 0.34 ± 0.4 and −8.7 ± 0. 4, respectively. The hydrolysis constant (log β14) is calculated −9.0 ± 0.5 for the hydrolysis reaction of U4+ + 4H2) → U(OH)4° + 4H+. Contribution of the other uranium species to the solubility are of minor importance.The crystallization of the precipitations of U02 (s) progressed gradually in the oversaturation experiments. Nevertheless the progress of crystallization had little effect on the solubility.
The Identification and Degradation of Isosaccharinic Acid, a Cellulose Degradation Product
Authors: Greenfield B. F. , Holtom G. J. , Hurdus M. H. , O’Kelly N. , Pilkington N.J. , Rosevear A. , Spindler M. W. , Williams S. J. 
Published: April 2011

AbstractNirex is seeking to develop a deep underground repository for the disposal of solid intermediate-level and low-level radioactive wastes (ILW and LLW) in the UK. One possible influence on the behaviour of radionuclides is the formation of water-soluble complexants by the degradation of the solid organic polymers that will be present in the wastes. The degradation products of cellulose have been shown to increase the solubility of plutonium and other radionuclides and to reduce sorption onto near-field and far-field materials. Degradation of cellulose under anaerobic alkaline conditions produces a range of organic acids. In this paper 2-C-(hydroxymethyl)-3-deoxy-D-pentonic acid (isosaccharinic acid, ISA) is identified by High Performance Liquid Chromatography as a significant component of cellulose leachates. A combination of fractionation of cellulose leachates and plutonium solubility determinations shows that ISA is responsible for the majority of the enhancement of plutonium solubility observed in such leachates. Further degradation of ISA by chemical or microbial action may lessen the effect of degraded cellulose leachates. Experimental studies on the chemical degradation of this compound under alkaline conditions suggest that the presence of oxygen is required. Microbial degradation studies show that the plutonium solubility in solutions of ISA is reduced by their exposure to microbial action.
Corrosion Behavior of a Powdered Simulated Nuclear Waste Glass Under Anoxic Condition
Authors: Inagaki Y. , Furuya H. , Idemitsu K. , Maeda T. , Sakai A. , Banba T. , Muraoka S. 
Published: April 2011

AbstractStatic corrosion tests were carried out with a powdered simulated waste glass in deionized water at 90 °C under oxic and anoxic conditions, respectively. The corrosion tests under anoxic condition were performed in a globe box purged with mixed gas (N2+5%H2), where the pH and Eh of deionized water were maintained at 6.9 and −0.35 V vs.S.H.E. at 25 °C, respectively.It was observed that there is a little difference between NL values under oxic and anoxic conditions. For soluble elements (Li, B, Na, Mo) and Ca, NL values under anoxic condition were slightly smaller than those under oxic condition. For Fe and Al, NL values under anoxic condition were slightly larger than those under oxic condition. For Si, Ce, La and Nd, there was no difference between NL values under oxic and anoxic conditions. The experimental results were analyzed on the basis of a corrosion model (Diffusion-combined Model), in which the solution concentration of elements associated with solution pH and Eh can be derived thermodynamically by use of PHREEQE. The analysis suggests that precipitating minerals controlling the solution concentrations of Fe and Ca under anoxic condition are different from those under oxic condition.
Modeling of Solution Renewal with the Kindis Code: Example of R7T7 Glass Dissolution at 90°C
Authors: Advocat T. , Crovisier J. L. , Clement A. , Gerard F. , Vernaz E. 
Published: April 2011

AbstractThe deep underground environment that would correspond to a geological repository is a system open to fluid flow. It is therefore necessary to investigate the effects of solution renewal on the long-term behavior of glass in contact with water. These effects can now be simulated using the new version of the geochemical Kindis model (thermodynamic and kinetic model).We tested the model at 90°C with an SAIV ratio of 400 m−1 at twelve renewal rates of pure water ranging from 200 to 0 vol% per day. With renewal rates between 200 and 0.065 vol% per day, steady-state conditions were obtained in the reaction system: i.e. the glass corrosion rate remained constant as did the concentrations of the dissolved species in solution (although at different values depending on the renewal rate). The ionic strength never exceeded 1 (the validity limit for the Debye-Huckel law) and long term predictions of the dissolved glass mass, the solution composition and the potential secondary mineral sequence are possible. For simulated renewal rates of less than 0.065 vol% per day (27 vol% per year), the ionic strength rose above 1 (as in a closed system) before steady-state conditions were reached, making it critical to calculate long-term rates; A constant and empirical long-term rate, derived from laboratory measurement, have to be extrapolated. These calculations were based on a first order equation to describe the glass dissolution kinetics. The results obtained with the KINDIS code show discrepancies with some major experimental kinetic data (the long term rate must decrease with the « glass-water » reaction progress, under silica saturation conditions). This clearly indicates that a more refine kinetic relation is needed for the glass matrix.
Preliminary Test on Gas Migration Through Bentonite-Sand Mixture
Authors: Hokari T. , Ishii T. , Nagasawa T. , Tomita R. , Nakajima M. 
Published: April 2011

AbstractThe Low-Level Radioactive Disposal facility [1] is planned to cover the vaults with impermeable bentonite-sand mixture in order to minimize groundwater flux through the facility. In case that metal wastes are to be disposed of in the burial facility in the future, it is essential to confirm that bentonite mixture should have gas permeability enough for the gas volume which would be expected to be generated due to an aerobic corrosion of metals[2].
This report performed a preliminary test with a bentonite-sand mixture whose aggregate was Japanese Standard sand. Results are the followings;(l)Gas breakthrough pressure of the mixture was less than the overburden pressure. The gas permeability was estimated to be of order of 10-2 md. (2)The mixture did not deteriorate in hydraulic conductivity after gas breakthrough.
Radionuclide Retardation in Crystalline Rock Fractures.
Authors: HÖlttÄ P. , Hakanen M. , Siitari-Kauppi M. , HautojÄrvi A. 
Published: April 2011

AbstractTransport and retardation of slightly sorbing sodium was studied in Syyry area SY-KR7 mica gneiss and in altered porous tonalite. Experiments were performed using dynamic fracture and crushed rock column methods and the static batch method. Flow conditions in the columns were determined using tritiated water and chloride as non-sorbing tracers. 14C-PMMA method was used to study the pore structure of matrices and the surface areas were determined by B.E.T. method. Sodium was retarded strongly in altered tonalite owing to homogeneously porous matrix structure and the composition of alteration minerals. An agreement between retardation values in batch and crushed rock column experiments as well as in fracture column experiments was good.
Mechanism of Unirradiated UO2 (S) Dissolution in Nacl and Mgcl2 Brines at 25°C
Authors: de Pablo Joan , Giménez J. , Torrero M. E. , Casas I. 
Published: April 2011

AbstractThe dissolution of unirradiated UO2 (s) has been studied in NaCl and MgCl2 brines under both reducing and oxidizing conditions.The initial uranium release under reducing conditions has been attributed to the dissolution of an initial oxidized layer. The final uranium concentrations have been modeled by using the PHRQPITZ computer program giving the solubility of the solid phase UO2 (s).Under oxidizing conditions, the initial release is the sum of the oxidized layer dissolution and the oxidation/dissolution of the UO2. The release rates calculated are 1.4·10−5 mol d−1 m−2 in NaCl2-brine and 3.6·10−5 mol d−1 m−2 in MgCl2-brine. After the initial release, uranium concentration in the NaCI-brine reaches a constant value, which has been attributed to the formation of a secondary solid phase. In MgCl2-brine, the uranium concentration increases slowly indicating, in this case, no control by secondary phase formation.
Simulation of The State of Carbon Steel n Years After Disposal with n Years of Corrosion Product on its Surface in a Bentonite Environment
Authors: Kojima Yoichi , Hioki Toshinobu , Tsujikawa Shigeo 
Published: April 2011

AbstractThe use of bentonite as buffer and carbon steel as overpack material for the geological disposal of nuclear waste is under investigation. To better assess the long term integrity of the carbon steel overpack, a quantitative analysis of the corrosion behavior on the steel surface for time frames beyond that of feasible empirical determination is required. The state n years after disposal, consisting of Carbon Steel / Corrosion Products + Bentonite / Water, was simulated and the corrosion behavior of the carbon steel in this state investigated. The following facts became apparent. Both the corrosion rate and the non-uniformity of it increased with increase in the corrosion product content in the compacted bentonite. When the corrosion product layer was formed between the carbon steel and the bentonite, it ennobled the corrosion potential and increased the corrosion rate.
Zirconolite-Rich Ceramics for Actinide Wastes
Authors: Vance Eric R , Begg B. D. , Day R. A. , Ball C. J. 
Published: April 2011

AbstractNew X-ray diffraction and scanning electron microscopy data are given for the incorporation of Np and Pu in zirconolite, at levels of tens of percent. The actinide valences and the cations they replace are deduced from the microanalysis of the zirconolite compositions, and X-ray absorption data are used to obtain more direct information on the valences of Ce and Nd, which are used as simulants of Pu and trivalent actinides respectively. Trivalent rare earths and actinides have extensive solid solubility in zirconolite, mainly but not exclusively in the Ca site. Tetravalent rare earths and actinides have considerable solid solubility in the Zr site of zirconolite, and some solubility in the Ca site, but the strong tendency of zirconolite with ions substituted in the Zr site to undergo phase separation complicates structural interpretation. In zirconolite-rich Synroc-type ceramics designed to immobilise waste actinides, the target actinide waste loading has been set at 20 wt% and early leach results indicate the durability is at least as good as that of Synroc-C.
Synroc for Immobilising Excess Weapons Plutonium
Authors: Jostsons A. , Vance E. R. , Mercer D. J. , Oversby V. M. 
Published: April 2011

AbstractThe immobilisation of excess weapons plutonium into Synroc can meet all of the important criteria discussed by the U.S. National Academy of Sciences (NAS)(1)for disposal, if the disposal option is pursued rather than options that exploit the energy value of plutonium. This paper summarises the relevant background of Pu incorporation into Synroc, the durability of Pu-containing Synroc and outlines a process flowsheet based on the experience with the 10 kg/hr Synroc Demonstration Plant at ANSTO. The extensive solid solubility of Pu in Synroc, coupled with a very high degree of chemical durability under hydrothermal conditions, makes Synroc ideal as a waste matrix for Pu disposal in deep boreholes to minimise diversion and proliferation risks.
Hydrothermal Synthesis of Hydroxyapatite and Pollucite from Calcium Phosphate
Authors: Kaneko Masaaki , Shoji Yuichi , Matsuura Hiroyuki , Yamasaki Nakamichi 
Published: April 2011

AbstractHydroxyapatite (HAP : Ca10(PO4 ) 6 (OH) 2 ) and aluminosili-cate were easily synthesized using a hydrothermal process with mixing ratios of Ca/P=1.67 (Ca(PO3)2 and Ca(OH)2) and Si/Al=4 (SiO2 and Al(OH)3). The temperature was kept constant at 573 K for 60 minutes. .Cesium (Cs) and Cerium (Ce) contained in Ca(PO3)2 , were found to take on a stable form in the pollucite (CsAlSi2O6) structure and the monazite (CePO4) structure.
Integrated Approach to Modeling Long-Term Durability of Concrete Engineered Barriers in Llrw Disposal Facility
Authors: Lee J. H. , Roy D. M. , Mann B. , Stahl D. 
Published: April 2011

AbstractThis paper describes an integrated approach to developing a predictive computer model for long-term performance of concrete engineered barriers utilized in LLRW and ILRW disposal facilities. The model development concept consists of three major modeling schemes: hydration modeling of the binder phase, pore solution speciation, and transport modeling in the concrete barrier and service environment. Although still in its inception, the model development approach demonstrated that the chemical and physical properties of complex cementitious materials and their interactions with service environments can be described quantitatively.Applying the integrated model development approach to modeling alkali (Na and K) leaching from a concrete pad barrier in an above-grade tumulus disposal unit, it is predicted that, in a near-surface land disposal facility where water infiltration through the facility is normally minimal, the alkalis control the pore solution pH of the concrete barriers for much longer than most previous concrete barrier degradation studies assumed. The results also imply that a highly alkaline condition created by the alkali leaching will result in alteration of the soil mineralogy in the vicinity of the disposal facility.
Gas Transportation in Saturated Cementitious Materials
Authors: Iriya K. , Hironaga M. , Kawanishi M. 
Published: April 2011

AbstractRadioactive waste repositories are constructed underground below ground water level. Main engineered barrier of the repository consists of structural walls, backfill mortar, and consolidated wastes. Cementitious materials are mainly adopted for the engineered barrier. Gas (hydrogen or methane) generation due to corrosion and microbial degradation is predicted, since the waste consists of metals like steel and organic material. It is important issue to define gas transport mechanism in cementitious materials in order to assess the gas release influence on the engineered barrier and pressure rise in the repository. Although cementitious materials have enough permeability to transport gas in dry condition, it is expected to be impermeable or so in saturated condition, in which repository is placed. In this paper, water and gas permeability both in dry and saturated conditions are investigated. The pressure in the vault, and gas transport mechanism is predicted. Certain threshold pressure exists, and it can be recognized that gas permeability is dependent on water saturation degree at a pressure greater than the threshold pressure. Loading pressure of 0.7 MN / m2 is needed for the flow of gas in saturated concrete. Intrinsic gas permeability of 6.5 × 10−19 m2 is obtained, which is very small value to keep the low pressure inside the vault. Consequently, it is predicted that gas cannot be transported through the intact concrete, however, it can be transported through defective zone which is developed during construction, and so on.