bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nano-Size Silicon Whiskers Produced by Chemical Vapor Deposition
Authors: Shen Lu , Xiao Youming , Ma Ying , Galasso Francis S. , Suib Steven L. , Freihaut James D. 
Published: April 2011

ABSTRACTSponge type deposits composed of nanometer sized Si whiskers were formed on Davisil (porous SiO2) gel substrates by chemical vapor deposition (CVD) using methyltrichlorosilane (MTS) as a precursor and H2 as carrier gas. The diameters of the fine whiskers are estimated to be 100 nm or smaller from SEM observations. XRD analyses revealed that the coatings formed at 800 and 900°C contained microcrystalline Si and the Auger analysis indicated the existence of free carbon. The surface area of the coated Davisil was approximately 189 ± 5 m2/g, as obtained from BET measurements. The coatings were also applied on several other substrates, such as AIN and low surface area (< 224 m2/g) silica gel, with the same coating conditions. On these substrates, highly porous Si has also been observed on AIN substrates, and nonporous, half sphere shaped coatings were observed on low surface area silica gel substrates.
Barium Titanium Alkoxides for Barium Titanates: Synthesis, Characterization, and Applications
Authors: Day Victor W. , Eberspacher Todd A. , Klemperer Walter G. , Liang Shurong 
Published: April 2011

ABSTRACTSeveral new crystalline bimetallic alkoxide precursors for barium titanates processing have been prepared: {[Ba(Solv)2]2[Ti(OAr)6]2} (1) (Solv = coordinated solvent molecule, Ar = aryl group), [Ba(CH2OHCH2OH)4(H20)][Ti(OCH2CH2O)3] (2), Ba[Ti2(OR)9]2 (3) (R = methyl, ethyl, and n-propyl), and [Ba(BzOH)Ti2O(OBz)8]2 (4) (Bz = benzyl). These precursors have been characterized by elemental analysis, IR, NMR, and single-crystal X-ray diffraction techniques. Compound 1 is well-suited for sol-gel processing of BaTiO3 powders and thin films under a variety of conditions. The facile preparation of 2 using relatively inexpensive starting materials makes it a viable alternative for the synthesis of BaTiO3 fine powders. Both compounds 3 and 4 are fairly moisture-sensitive; hydrolysis of these precursors under acidic conditions affords the formation of gels instead of precipitates. The reactivity of 3 toward hydrolysis can be tailored by varying the alkyl group.
Characterization of the Interaction of Hydrogen with Iridium Clusters in Zeolites by Inelastic Neutron Scattering Spectroscopy
Authors: Nicol J.M. , Udovic T.J. , Cavanagh R.R. , Xu Z. , Kawi S. , Mure T. , Gates B.C. 
Published: April 2011

ABSTRACTIncoherent inelastic neutron scattering (IINS) measurements of hydrogen bound to Ir6 clusters in the nanoscale pores of zeolite NaY and similar clusters in KL zeolite are reported. On the basis of hydrogen uptake measurements and the observation of peaks in the IINS spectra, we infer that hydrogen is bound to the metal nanoclusters in the zeolite pores. The HINS data for both zeolites are similar and consistent with the presence of IrH2 species.
Sonochemical Synthesis and Catalytic Properties of Nanostructured Molybdenum Carbide
Authors: Suslick Kenneth S. , Hyeon Taeghwan , Fang Mingming , Cichowlas Andrzej A. 
Published: April 2011

ABSTRACTMolybdenum hexacarbonyl in hexadecane was irradiated with high intensity ultrasound under argon at 90°C to yield face centered cubic molybdenum carbide, Mo2C. After thermal treatment, oxygen and excess carbon were removed to give stoichiometric Mo2C. SEM micrographs showed that the surface was extremely porous. TEM micrographs showed that the solid was an aggregate of particles with diameters of ≈ 2 nm. This material has a very high surface area, 188 m2/g as determined by BET gas adsorption. Catalytic studies have been conducted on the dehydrogenation of cyclohexane and the hydrogenolysis of ethane. The sonochemically prepared Mo2C shows good catalytic activity for the dehydrogenation of cyclohexane with 100% selectivity for formation of benzene without hydrogenolysis to methane. The material revealed poor catalytic activity for the hydrogenolysis of ethane.
Application of Fractals and Kinetic Equation in Modelling Cluster and Ultrafine Particle Size Distributions
Authors: Chaiken J. , Goodisman Jerry 
Published: April 2011

ABSTRACTWe briefly describe a model which seems to be applicable to a variety of coalescence growth systems. Spanning cluster growth, particle growth and hillock formation in thin metal films, this model is based on the Smoluchowski kinetic equations and fractals. We describe how this model has been able to suggest the effect of translational to internal energy conversion in coalescing systems in determining the shape of particle size distributions. We also suggest how this model can be employed to account for the behavior of hillocks in supersaturated alloy films under thermal annealing conditions.
Grain-Size Stability and Microhardness of Copper-Fullerene Nanocomposites
Authors: Holtz R.L. , Barrera E.V. , Milliken J. , Provenzano V. 
Published: April 2011

ABSTRACTNanocomposites of copper with low concentrations of dispersed fullerenes were synthesized by simultaneous sputtering of copper and sublimation of fullerenes. Postdeposition heat treatments at 400 and 800 °C were performed to assess the thermal stability of the microstructure and the effect on the Vicker's microhardness. The as-deposited copperfullerene composite has submicron-scale granularity, in contrast to pure copper which has conventional columnar growth. Grain growth in the heat-treated fullerene-containing specimens is suppressed and the microhardness enhanced relative to pure copper.
Structural Characterization of Ordered Phases in Hydrocarbon Dendrimers
Authors: Buchko Christopher J. , Sioshansi Atisa , Xu Zhifu , Moore Jeffrey S. , Martin David C. 
Published: April 2011

ABSTRACTStructural characterization of phenylacetylene dendrimers (PADs) makes it possible to explore the relationship between molecular architecture and condensed phase organization. The size and geometry of the PAD series is precisely controlled, with phenylacetylene units emanating from a central phenylene in the manner of a tridendron. The branched molecule rapidly increases in size with each synthetic generation. The “shape-persistent” nature of the phenylacetylene molecule makes it ideal for use in the construction of self-assembling supramolecular systems.Transmission electron microscopy (TEM) has been used to identify the crystal structure of lower generation PADs, and wide-angle X-ray studies confirm the decrease in crystallinity with size. Hot stage optical microscopy studies of thermal transitions reveal melting points for lower generation PADs, and an apparent glass transition for the amorphous higher generations. This type of structural information is essential to the rational design of self-assembling materials.
Nanostructured Fe-Co Catalysts Generated by Ultrasound
Authors: Suslick Kenneth S. , Fang Mingming , Hyeon Taeghwan , Cichowlas Andrzej A. 
Published: April 2011

ABSTRACTBimetallic catalysts have been studied intensively because of their unique activity and selectivity. Unsupported alloy catalysts, however, are usually of limited value due to their very small surface areas. We have now developed a sonochemical synthesis of bimetallic alloys that provides both high surface areas and high catalytic activity. We have produced Fe-Co alloys by ultrasonic irradiation of mixed solutions of Fe(CO)5 and Co(CO)3(NO) in hydrocarbon solvents. The alloy composition can be controlled simply by changing the ratio of precursor concentrations. After treatment at 673K under H2 flow for 2 hours, we obtain nearly pure alloys. BET results show that the surface areas of these alloys are large (10-30 m2/g). TEM and SEM show that the alloy particles are porous agglomerates of particles with diameters of 10-20 nm. Sonochemically prepared Fe, Co, and Fe-Co powders have very high catalytic activity for dehydrogenation and hydrogenolysis of cyclohexane. Furthermore, sonochemically prepared Fe-Co alloys show high catalytic selectivity for dehydrogenation of cyclohexane to benzene; the 1:1 ratio alloy has much higher selectivity for dehydrogenation over hydrogenolysis than either pure metal.
Development and Characterization of Artificial Microstructures in Long Lengths of Superconducting Wire
Authors: Jablonski P. D. , Lee P. J. , Larbalestier D. C. 
Published: April 2011

ABSTRACTConventional Nb-Ti superconductors are optimized by thermal and mechanical treatments which ultimately produce a nanostructure consisting of 1-2nm thick ribbons of α-Ti dispersed in a matrix of β-Nb-Ti. Several groups are now investigating artificial dispersions of second phase in Nb-Ti which may develop stronger flux pinning nanostructures. However, these new methods generally require true strains of 30 or more. We avoid these large strains (and their associated problems) by forming our composites from a mixture ∼ -50¼m size Nb and Nb-Ti powders, thus permitting the desired nanostructure to be produced with strains of order 12. Nb pinning particles were found to develop an irregular shape, tending to nanometer thick ribbons at large strains. The final size nanostructure resembles conventional Nb-Ti, except that the “second” phase is Nb rather than α-Ti. The critical current density (Jc) was found to increase by over two orders of magnitude to peak values of 5490 and 1980A/mm2 at 2 and 5T as the particle thickness was reduced.
Migration of Radioactive 85Sr, 134Cs and 60Co Through a Loess Soil Layer
Authors: Li Zhentang , Wang Hui , Takebe Shinichi , Tanaka Tadao 
Published: April 2011

AbstractColumn experiments have been completed on the migration of 85Sr, 134Cs and 60Co through a loess layer in order to examine the migration behavior of radionuclides in an aerated soil layer. Radionuclide concentration distributions between the effluent and the soil layer were measured after the solution containing the radionuclides was introduced into the column from the top of the soil layer and Fifty liters of the underground water were introduced at a constant flow. Results indicate most of the 85Sr, 134Cs and 60Co remained attached to the soil layer, and only a small amount of radionuclide was released from the soil layer. Within the soil layer, the migration depths of three radionuclides are 85Sr > l34Cs = 60Co.
Alteration Minerals in Granitic Rock at Ashio as Radionuclide Adsorption Materials
Authors: Hamasaki S. , Tsukimura K. , Fujimoto K. , Omura K. , Ikeda R. 
Published: April 2011

AbstractAlteration minerals from a drill-core (maximum depth 2002 m) in the granitic rock at Ashio, central Japan, were studied by optical microscopy, X-ray diffractometry and analytical scanning electron microscopy. In the host rock, biotite is altered to chlorite and plagioclase to illite. Calcite has precipitated in veinlets and grain boundaries. The host rock close to fractures is strongly altered, whereas the rocks distant from fractures are less altered. Quartz, illite, chlorite, laumontite and calcite have precipitated on fracture walls. The alteration minerals are estimated to have formed in the range 140–200°C, higher than the present temperature (13°96°C). The chemical composition of the ground water in the granitic rock at Ashio was estimated thermodynamically from the mineral assemblage. The alteration reaction of palgioclase and the precipitation of calcite may occur simultaneously. The alteration minerals formed in the host rock and in the fractures may adsorb radionuclides effectively, and thus may inhibit radionuclide transport to biosphere.
Use of Natural Analog and Modeling Studies to Constrain the Effects of Magmatic Activity on Long-Term Geologic Repositories
Authors: Valentine Greg A. , Rosenberg N. D. , Crowe B. M. , Perry F. V. 
Published: April 2011

AbstractExamples of the application of natural-analog studies to the estimation of the consequences of a volcanic eruption penetrating a radioactive waste repository are given, including the criteria for analog selection and new data from ongoing studies. Examples of early modeling results focusing on the spatial and temporal scale of subsurface processes are also provided. All of these examples are taken from studies of the potential Yucca Mountain repository, Nevada, but similar approaches could be applied in other areas. In addition, studies of subsurface processes initiated by magmatic events serve as useful analogs for repository thermal loading studies.
Photochemical Valence Adjustment of Pu and Np in Nitric Acid Solution for Separation and Co-Extraction
Authors: Wada Y. , Morimoto K. , Goibuchi T. , Tomiyasu H. 
Published: April 2011

AbstractPhotochemical redox reaction tests were corried out where the experimental variables were irradiation rate using a Hg lamp light and molarity of nitric acid containing different reductant reagents such as hydroxylamine(HAN), hydrazine(HDZ) and urea. Based on these tests, we confirmed that the valences of Pu and Np were easily photochemically adjusted to two conditions of Pu(IV,VI)-Np(V) and Pu(IV,VI)-Np(VI), indicating that photochemical valence adjustment for the separation and co-extraction of Pu and Np has excellent potential as an advanced process technology.
The Swiss Strategy for HLW Siting; Parallel Investigation of two Alternative Host Rocks
Authors: McCombie C. , McKinley I.G. , Lambert A. , Thury M. , Birkhäuser P. 
Published: April 2011

AbstractRegional characterisation studies of two potential host rocks for a HLW repository - the crystalline basement and the Opalinus clay of Northern Switzerland - have now been completed and documented. Application is now proceeding for the legally required federal, cantonal and communal drilling permits to initiate parallel local investigations in both these formations. The decision to continue with work in both formations is a departure from previously published plans which is intended to maximise the probability that the next major milestone in the HLW programme - demonstrating the feasibility of siting for a deep geological repository in Switzerland - can be reached by the year 2000. This paper reviews the current status of the Swiss HLW programme and outlines the planned “Phase II” site characterisation of the two chosen sites.
Geological Characteristics of “Mayak” Enterprise Area Regarding Underground Nuclear Waste Disposal and Rehabilitation of Territory (Southern Urals, Russia)
Authors: Velichkin V. I. , Tarasov N. N. , Poluektov V. V. , Asadulin A. A. 
Published: April 2011

AbstractThe geological investigations necessary for the HLW underground disposal site selection were udertaken on the contaminated territory mostly covered by vegetation and water-bodies. For lack of availiable outcrops, special attention was given to detailed petrological and geochemical studies for more reliable extrapolations. As a result, models of structure, geochemical background, and rock basement origin scenario provided general criteria for selection of geological blocks suitable for HLW deep burial.
Microbial Considerations and Studies in the Canadian Nuclear Fuel Waste Management Program
Authors: Stroes-Gascoyne S. , West J.M. 
Published: April 2011

AbstractAECL Research is developing a concept for the permanent disposal of nuclear fuel waste. A program to address the potential effects of microbial action on the integrity of the multiple barrier system, on which the disposal concept is based has been initiated. This microbial program focusses on answering specific questions in areas such as the survival and growth of microbes in compacted clay buffer materials and the potential consequences for container corrosion and microbial gas production; microbial effects on transport of radionuclides through the buffer into the geosphere; the presence and activity of microbes in deep granitic groundwaters; and the effects of biofilms on radionuclide migration in the geosphere.
Effect of Crystallochemistry of Starting Materials on the Rate of Smectite to Illite Reaction
Authors: Sato Tsutomu , Murakami Takashi , Isobe Hiroshi , Ohnuki Toshihiko 
Published: April 2011

AbstractA series of hydrothermal experiments was performed to determine the effect of layer charge of starting materials on the smectite to illite reaction rate that might be applied to nuclear-waste repository design. The experiments were conducted on K-saturated <2μm fractions of Wyoming smectite (SWy-1) and Tsukinuno smectite (SKu-F, commercially, Kunipia-F) in a closed system at temperatures of 95, 150, 200, 250, 300°C for run durations of up to 477 days with a 1:20 mass ratio of solid to deionized water. The mean layer charge and tetrahedral charge of SKu-F are larger than those of SWy-1. The proportion of smectite layers in illite/smectite interstratified minerals rapidly decreases, and then slowly decreases with increase in reaction time; a plot of In (100/% smectite) vs. time produces two distinct straight lines in all experiments. These lines are suggestive of two first-order kinetic processes with different rates for this reaction; the first process has a greater rate than the second one. An Arrhenius plot of the reaction rates for each process produces a folding and straight lines for the first and second processes, respectively, suggesting that there are at least two parallel processes in the first process, and a dominant process is different between high- and low-temperature reactions. The activation energies of the first and second processes determined from the plots are the same for the two starting materials, meaning that the reaction mechanisms for the two starting materials are the same. However, the rate of the first process is different between the two starting materials, although that of the second process is similar. The difference in the rate of the first process results possibly from the difference in the amount of layer charge between the two starting smectites.
Method of Designing Bentonite/Sand Mixture to Achieve the Target Permeability
Authors: Nakashima Hitoshi , Ishii Takashi , Nagasawa Tatsuro , Ogata Nobuhide , Komine Hideo 
Published: April 2011

AbstractBentonite/sand mixture is expected to be an effective component of barriers for radioactive waste disposal facility. Impermeable mixture can be obtained through enrichment of the bentonite content,but it is difficult to estimate a permeability of bentonite/sand mixture before permeability test. At designing of bentonite/sand mixture, we have to decide which sand to be used, and what bentonite content is. But.this means that designing will be a time-consuming task.
In this report, we made many kinds of bentonite/sand mixtures using some kinds of sand with different bentonite content, and permeability tests were conducted for these mixtures. After examination of the permeability tests results, the effective void ratio of bentonite/sand mixture which was obtained by compaction test, is an efficient parameter for estimation of the permeability.
Last of all, we propose the method of designing bentonite/sand mixture using the effective void ratio.
Diffusion Behavior for Se and Zr in Sodium-Bentonite
Authors: Sato Haruo , Yui Mikazu , Yoshikawa Hideki 
Published: April 2011

AbstractApparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite. KunigelVl® * containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400–1800kg/m3. Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N2 atmospheric condition (O2: 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted SeO32-, Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted Zr(OH)5- or HZrO3-. Distribution coefficient measured for Zr on the bentonite was about 1.0m3/kg from batch experiment. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modelling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement.
Thermodynamic Properties of Water in Compacted Bentonite Under External Pressure-free Conditions
Authors: Torikai Yuji , Sato Seichi , Ohashi Hiroshi 
Published: April 2011

AbstractIn an attempt to determine the thermodynamic properties of water in bentonite, the vapor pressure of water in compacted bentonite was measured as functions of water content and temperature, under external pressure-free conditions. The relative partial molar Gibbs free energy ΔGH2O, enthalpy ΔHH2Oand entropy ΔSH2O of tne waler in bentonite were determined at temperature of 298.15K. The interlayer distance of montmorillonite in bentonite was also measured by X-ray diffraction.It is probable that one fourth of the total water included in the bentonite at water content of 20.3wt% and dry density of 1.76 × 103kg/m3 is nearly free water; the water is not regarded as dilute electrolytic solution but the solution with higher ionic strength. Another one fourth of the water in the bentonite at the water content is bound water; the partial molar entropy of the bound water referred to pure water is from a half to whole of solidification entropy of pure water. The remainder is regarded as intermediately bound water.
Corrosion of Iron and Migration of Corrosion Products in Compacted Bentonite
Authors: Kozaki T. , Imamura Y. , Takada J. , Sato S. , Ohashi H. 
Published: April 2011

AbstractFor safety assessment of the geological disposal of the high level radioactive waste, it is necessary to study corrosion of the overpack materials and migration of the corrosion products in the compacted bentonite. In the present study, average corrosion rates of iron foil and apparent diffusion coefficients of the corrosion products were determined using a neutron- activated iron foil. The average corrosion rates were on the order of 10-6m/y, while apparent diffusion coefficients were in the range from 10-12 to 10-14m2/s. No tendency to decrease in the corrosion rates with increasing corrosion time was observed. This suggests that the iron foil corrodes under reducing condition. Asymmetric concentration profiles of iron corrosion products were obtained in some experiments. It can be considered that either cathodic or anodic reaction would dominantly occur on one side of the iron foil surfaces and that each reaction would change the pH in pore water of bentonite specimens adjacent to the iron foil surfaces.