bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fibers and Fiber Coatings for IMCs
Authors: Misra Ajay K. 
Published: April 2011

AbstractThis paper presents a review of the current status of fibers and fiber coatings for intermetallic matrix composites (IMCs). The properties of commercial and developmental fibers are reviewed and their potential as reinforcements for various intermetallics discussed. The potential fibers for near-term IMC applications are SiC (both monofilament and tow), single crystal Al2O3 and YAG/Al2O3 eutectic monofilaments, and sol-gel derived Al2O3- mullite nanocomposite tow fiber. The chemical compatibility of these fibers with various intermetallic matrices is reviewed. The issues related to the coefficient of thermal expansion (CTE) mismatch between the fiber and the matrix, attaining optimum interfacial bond strength, and fiber damage during composite processing are addressed. The effectiveness and limitations of fiber coatings in accommodating various fiber-matrix incompabilities, both chemical and mechanical, are discussed.
Microstructure and High Temperature Properties of 85% Al2O3-15% SiO2 Fibers
Authors: Wilson D. M. , Lieder S. L. , Lueneburg D. C. 
Published: April 2011

AbstractA new sol/gel fiber which exhibits exceptional high temperature properties was recently developed at 3M. This fiber has the composition 85% Al2O3-15% SiO2 (85A-15S). High temperature tensile strength and creep properties were measured in the temperature range 1000°C – 1300°C. The creep rate for the 85A-15S fibers was three orders of magnitude less than single phase polycrystalline alumina fibers such as Nextel 610, and 90% of room tensile strength was retained at 1250°C. These exceptional high temperature properties were attributed to a unique, two-phase microstructure consisting of globular and elongated grains of a-Al2O3 and mullite (3Al2O3-2SiO2). The room temperature single filament strength of the 85% Al2O3-15% SiO2 fibers was 2130 MPa, and the elastic modulus was 260 GPa.
Layered Silicate/ATBN Nanocomposite
Authors: Moet A. , Akelah A. , Salahuddin N. , Hiltner A. , Baer E. 
Published: April 2011

ABSTRACTComposites of amine terminated butadieneacrylonitrile (ATBN) and montmorillonite (MMT) were prepared by ion exchange between the onium salt of the polymer and the interlamellar cation of the mineral following two different preparation approaches. The first carried out the ion exchange in situ and used dioxane, a better solvent for the polymer, and the second administered the onium salt to MMT using dimethylsulfoxide (DMSO). Elemental analysis and IR spectroscopy indicated that all the ionic sites of the mineral have been occupied by polymer end groups. The d (001) spacing and the span between the internal lamelar surface were only expanded to about 14 Å and 5 Å, respectively, suggesting horizontal packing of the polymer molecules. TEM of microtome sections prepared from compression molded composites revealed that the lamellae, laminated with polymers assembled into multiplets of about 5 nm for both preparations. The multiplets clustered into mineral rich domains whose average size was 250 nm for the DMSO preparation. Finer clusters (70 nm) were obtained by the first method. This three fold decrease in the average domain size was attributed to the strong solvation power of dioxane in the binary solvent and to the locale of ion exchange.
Self-Assembly of Cobalt/Bipyridine Multilayers Modeled After Hofmann Clathrate Compounds
Authors: Ansell Michael A. , Zeppenfeld Astrid C. , Ham William K. , Page Catherine J. 
Published: April 2011

ABSTRACTProgress has been made towards the development of inorganic-organic multilayered films modeled after Hofmann clathrate compounds. Cobalt-bipyridine multilayers were grown layer by layer on a silicon substrate. The resulting films were characterized using ellipsometry, grazing angle X-ray diffraction, Auger electron spectroscopy and EPMA (Electron Probe Micro- Analysis). Results indicate that moderately well ordered layers have been synthesized, but cross-linking with M(CN)42(M = Ni, Pd, or Pt) to simulate the model structure does not significantly occur.
Processing of Nanostructured Zirconia Ceramics
Authors: Skandan G. , Hahn H. , Kear B. H. , Roddy M. , Cannon W. R. 
Published: April 2011

ABSTRACTThe inert gas condensation (IGC) technique was employed to synthesize non-agglomerated nanoparticles of ZrO2 and Y2O3 with different average particle sizes ranging from 4 to 14 run. The sintering behaviors (in air and vacuum) of single phase n-ZrO2 (monoclinic crystal structure) and Y2O3-ZrO2 mixture (Y-TZP) were studied in terms of densification rate and final sintering temperature. There was a strong correlation between densification characteristics and properties of the starting powder compacts such as average particle size, particle and pore size distributions. n-ZrO2 was sintered to full density in air at temperatures as low as 1125°C (0.47 Tm) and in vacuum at 975 °C (0.42 Tm). Although the grain sizes in the fully sintered samples were well below 100 nm, the grains had grown by a factor of 10 as compared to the initial particle size. Therefore, a pressureassisted sintering technique was employed to further reduce the densification temperature and final grain size. Threshold effects in this process are also discussed.
Surface Chemistry of Nanocrystalline Cerium Oxide
Authors: Tschöpe Andreas , Ying J.Y. , Amonlirdviman K. , Trudeau M. L. 
Published: April 2011

ABSTRACTNanocrystalline cerium oxide was synthesized by magnetron sputtering of a metallic target, followed by controlled post-oxidation. The resulting cerium oxide clusters were <10 nm in size, and highly non-stoichiometric in nature. The oxygen deficiency of such materials was associated with the unusual catalytic activity in oxidation and redox reactions. This paper compares the surface chemistry of nanocrystalline CeO2−x with stoichiometric CeO2. It further explores the promoting effect of Cu-doping on surface reduction and oxidation.The oxidation states of metal cations were examined with X-ray photoelectron spectroscopy after various oxidizing and reducing heat treatments in a connected reaction chamber. Isothermal pulsed reduction and oxidation of the samples were investigated by thermogravimetric analysis. Reduction properties of the different materials are discussed in terms of their microstructure, oxygen deficiency and chemical composition. These studies will help to understand the importance of bulk defects and synergistic effects in multicomponent and multiphase materials for high surface reactivity.
Organic/Inorganic Superlattices: Structural and Optical Properties
Authors: Tokito Shizuo , Sakata J. , Taga Y. 
Published: April 2011

ABSTRACTA new class of superlattices consisting of alternating layers of organic and inorganic materials has been prepared from 8-hydroxyquinoline aluminium (Alq), copper phthalocyanine (CuPc), 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) and MgF2 by molecular beam deposition. Small-angle x-ray diffraction data and cross-sectional transmission electron micrograph of the superlattices reveal that the superlattices have layered structure throughout the entire stack. From comparison of the x-ray diffraction patterns, it is found that the interface roughness between organic and MgF2 layers depends on the materials for organic layers. High-angle x-ray diffraction data indicate that there is a structural ordering in the CuPc and PTCDI layers. From the optical absorption and photoluminescence measurements, it is found that the exciton energy of Alq shifts to higher energy with decreasing Alq layer thickness.
Formation and Properties of Silane Monolayers on Iron and Aluminum Surfaces
Authors: Petrunin Maxim A. , Nazarov Andrey P. 
Published: April 2011

ABSTRACTThe adsorption of ethoxysilanes RSi(OEt)3 on the Fe and Al surfaces from the vapor phase, water and toluene solutions was studied by the piezoquartz nanobalance and ellypsometry. The values of the “landing sites” and the energy of the interaction for different silanes were calculated. The self-assembling silane monolayers with good adhesion to the Al surface (due to the covalent bonds Al–O–Si) was shown to format during adsorption from dilute water solution. The influence of silane monolayers on the H2O adsorption and wetting of the surface was studied. The silane layers have considerably hydrophobic effect and prevent the growth of hydroxide film on the Al. The synthesis of charged silane nanophases was carried out by the addition of the acid (sulfo-, imididiaoetate-) and the basic (amino-) groups into the epoxysilane molecule. The effect of the charge density and the surface potential on the ion adsorption at the interface metal/electrolyte was investigated.
Small Angle Neutron Scattering from Nanocrystalline Pd and Cu Compacted at Elevated Temperatures
Authors: Sanders P.G. , Weertman J.R. , Barker J.G. , Siegel R.W. 
Published: April 2011

ABSTRACTNanocrystalline (n-) Cu and Pd, prepared by inert gas condensation (IGC) and in situ room temperature (RT) and elevated temperature (warm) compactions, have been studied by small angle neutron scattering (SANS). Previous work [1] on room temperature compacted and subsequently annealed n-Pd seemed to show that all the scattering could be accounted for by a distribution of pores. Analysis of more extensive SANS measurements, together with the results of prompt gamma activation analysis (PGAA), indicates that the SANS can be explained by the presence of pores and hydrogen. Warm compaction reduces the hydrogen impurity level, while increasing the bulk density and decreasing the pore size. This can lead to a dramatic hardness increase in these materials.
Atomistic Simulation of Vapor-Phase Nanoparticle Formation
Authors: Zachariah Michael R. , Carrier Michael J. , Blaisten-Barojas Estela 
Published: April 2011

ABSTRACTIn order to understand from a fundamental view how nanoparticles form and grow, classical molecular dynamics simulations of cluster growth and energy accommodation processes have been conducted for clusters of silicon (< 1000 atoms), over a wide temperature range. Simulations involved solution of the classical equations of motion constrained with the three body Stillinger-Weber potential. The results show the large heat release and resulting cluster heating during a cluster-cluster collision event, and the corresponding time evolution of the internal energy to a more stable state. Dynamic effects associated with the temperature of the cluster and the impact parameter are also clearly evident. In particular, clusters show a large sensitivity to temperature in the rate of coalescence, particularly at low temperature. Calculated diffusion coefficients are significantly larger than surface diffusion constants stated in the literature. Phonon density of states spectra do not seem to show size effects.
A New Process for Preparing Nanosize Ceramic Powders
Authors: Zhen Yong S. , Hrdina Kenneth E. , Remick Robert J. 
Published: April 2011

ABSTRACTWe have developed a new poly-foam process for the cost effective preparation of ceramic nanoparticles. The process utilizes the chemistry of polyurethane reactions and is proven to be effective for forming nanometer size ceramic powders of a great variety of single metal oxides and mixed metal oxides. In general, ceramic powders can be prepared by this process having a range of average particle size between 3 to 50 nm, with very narrow particle size distribution. They are free of hard agglomerates, are chemically pure and uniform, and are essentially spherical in shape.
Physical Properties of Diamond-Like Nanocomposite Films
Authors: Dorfman B. , Abraizov M. , Pypkin B. , Strongin M. , Yangn X.-Q. , Yan D. , Pollak Fred H. , Grow J. , Levy R. 
Published: April 2011

ABSTRACTDiamond-like nanocomposite (DLN) and metal containing DLN (Me-DLN) films, synthesized in a combined process of deposition of carbon-silicon precursor and magnetron sputtering of a metal target, have been examined by Auger electron spectroscopy, Raman and IR spectroscopy, nanoindentation and internal stress measurements. The stability of the films under ion and electron irradiation and thermal annealing has been tested.
Thermal Conductivity Reductions in Sige via Addition of Nanophase Particles
Authors: Scoville Nancy , Bajger Clara , Rolfe Jon , Vandersande Jan 
Published: April 2011

ABSTRACTTransport models have predicted that the thermal conductivity of SiGe alloys could be appreciably reduced by incorporating a discrete 40Å particles with the SiGe grains. Such a thermal conductivity reduction would lead to substantial improvements in the figure-of-merit of thermoelectric materials. This paper reports on recent results on adding 40Å particles to SiGe via a spark erosion process. Thermal conductivity reductions consistent with the transport models have been achieved, however, the improvement in figure-of-merit has not been as large as predicted.
Polymerizable Self-Organized Membranes: A Novel Class of Organic Compounds
Authors: Singh Alok , Markowitz Michael , Chow Gan Moog 
Published: April 2011

ABSTRACTMolecular Self-assembly of amphiphilic phospholipid molecules (containing a hydrophobic acyl chain and a hydrophilic phosphate group attached to glycerol backbone) and other amphiphiles offers a versatile approach to form ordered structures. Stabilization of lipid microstructures by polymerization renders them useful for practical applications in the areas ranging from controlled release technology to template mediated synthesis of metals. Our efforts are focussed on the development and use of polymerizable diacetylenic phospholipids and their microstructures as template for chemical synthesis. The surface of vesicles and lipid microcylinders (0.5 μm dia.) is made reactive by chemically modifying the hydrophilic region of phospholipids. Lipids with chemically reactive sites were incorporated into lipid membranes predominantly formed from charge neutral lipids and used for binding metal ions and growing fine metal particles.
Preparation of Nanocomposites Containing Poly(Ethylene Oxide) and MoS2, TiS2, or MoO3
Authors: Lemmon John P. , Wu Jinghe , Lerner Michael M. 
Published: April 2011

ABSTRACTSingle-phase nanocomposites containing montmorillonite, MoS2, MoO3or TiS2with poly(ethylene oxide) are obtained by the exfoliation of the layered solid, adsorption of polymer, and subsequent precipitation of solid product. Aqueous solutions can be employed for all syntheses except PEO/TiS2, which is prepared from lithiated TiS2in an N-methyl formamide (NMF) solution. X-ray diffraction indicates that the resulting solids increase in basal-plane repeat by approximately 4 or 8 Å, consistent with the incorporation of a single or double layer of polymer between the inorganic layers. Reaction stoichiometries and elemental analyses provide compositions for the single-phase products.
Absorption Study of the Tc(IV) on Rocks and Minerals Under Simulated Geological Conditions
Authors: Amaya Takayuki , Kobayashi Wataru , Suzuki Kazunori 
Published: April 2011

AbstractThe absorption of the technetium on rocks and minerals have been studied by using freshly quarried rocks to provide reducing conditions, without the addition of reductive reagents. The initial99Tc concentration in this study was about 1x10-8mol/1 (0.62 Bq/ml). Technetium was not absorbed on tuff or granite under oxidizing conditions, but higher Kd values of Tc were obtained for granite under reducing conditions. The Tc absorbed on granite was not desorbed under reducing condition. This indicates the absorption reaction is irreversible.
Reversibility of Strontium Sorption on Fracture Fillings
Authors: Cui Daqing , Eriksen Trygve E. 
Published: April 2011

AbstractWe have carried out a comparative study of sorption and desorption of strontium in groundwater on separated size and magnetic fractions of fracture fillings from deep granite. Complete reversibility of the sorption process was demonstrated by identical Freundlich isotherms, isotopic exchangeability and pH dependence of the distribution coefficient Rd.
Studies of the Liquid-Solid Ratio Effect on the Distribution Ratio Rd, in Sorption
Authors: Bors J. , Erten H. N. , Assemi S. 
Published: April 2011

AbstractThe variation of the distribution ratio Rdas a function of aqueous volume to solid mass ratio (V/M) for several sorption systems involving the cations Zn2+, Co2+, Ba2+, the anion I−and different solid matrices has been extensively examined. Empirical relationships for the concentrations of the sorbed species in the aqueous and solid phases as well as for the distribution ratio Rdare proposed. Generally Rdis found to increase with increasing V/M for tracer concentrations. A gradual increase in the initial concentration of the sorbed species eventually leads to a decrease in Rdwith V/M.
The Use of Some Ion-Exchange Sorbing Tracer Cations in Insitu Experiments in High Saline Groundwaters
Authors: Byegård J. , Skarnemark G. , Skålberg M. 
Published: April 2011

AbstractThe possibility to use alkali metals and alkaline earth metals as slightly sorbing tracers in in-situ sorption experiments in high saline groundwaters has been investigated. The cation exchange characteristics of granite and some fracture minerals (chlorite and calcite) have been studied using the proposed cations as tracers. The results show low Kd’s for Na, Ca and Sr (∽0.1 ml/g), while the sorption is higher for the more electropositive cations (Rb, Cs and Ba). A higher contribution of irreversible sorption can also be observed for the latter group of cations. For calcite the sorption of all the tracers, except Ca, is lower compared to the corresponding sorption to granite and chlorite. Differences in selectivity coefficients and cation exchange capacity are obtained when using different size fractions of crushed granite. The difference is even more pronounced when comparing crushed granite to intact granite.
Analysis of Radionuclide Migration Behavior in Loess Medium
Authors: Zhiming Wang , Shushen Li , Zede Guo , Yingjie Zhao , Zhentang Li , Shengfang Li , Yamamoto Tadatoshi , Takebe Shinichi , Ogawa Hiromichi , Tanaka Tadao , Mukai Masayumi 
Published: April 2011

AbstractA five-year cooperative research program has been carried out by China Institute for Radiation Protection and Japan Atomic Energy Research Institute to develop safety assessment methodology for disposal of low level radioactive waste. Migration behavior of radionuclides 3H and 85Sr through field tests, simulation tests in the laboratory and determination of distribution coefficients is discussed and analyzed in this paper. The results show that the retardation coefficients, Rd, from field tests are about 0.08−3.3 times those from simulation tests and Rd from batch tests are 1.1−44 times those from field tests for 85Sr and loess medium. It was observed from field tests that radionuclides moved mainly downward under artificial sprinkling and a part of them moved up besides downward under natural rain condition. In addition, it was discovered that the retardation coefficient, Rd , increases with velocity of unsaturated water flow, u, in the analysis.
Some Evidence of Radiolysis in a Uranium ore Body - Quantification and Interpretation
Authors: Liu Jinsong , Neretnieks Ivars 
Published: April 2011

AbstractLocally oxidising conditions in the near-field of the Cigar Lake uranium deposit was observed. Ongoing processes of water radiolysis has also been predicted previously by our mass transport model. In the ore there was an enhanced concentration of helium, hydrogen and sulphate. Sulphate is the only oxidising species of substantial amount in the groundwater samples, and is possibly indirectly produced by water radiolysis and oxidation of sulphides. The ongoing oxidant production rate has been calculated by the mass transport model.In this paper, the issue of water radiolysis is addressed from a more fundamental angle of approach. The maximum oxidant production rate is calculated based on the assumptions of geometric dispersion of the ore constituents, the estimate of the total radiation energy, the fraction of energy deposited into the pore water, and the G-values of water. The results show that only a few percent of the total radiation energy is deposited into the pore water to cause water radiolysis. If the recombination factor projected by other researchers are accounted for, the oxidant production rate thus calculated agrees with the present-day ongoing oxidant production rate predicted by the mass transport model.
Precipitation of Uraninite in Chlorite-Bearing Veins of the Hydrothermal Alteration Zone (Argile De Pile) of the Natural Nuclear Reactor at Bangombé, Republic of Gabon
Authors: Eberly P. , Janeczek J. , Ewing R. 
Published: April 2011

AbstractThis paper describes the mineralogy of a phyllosilicate/uraninite/galena-bearing vein located within the hydrothermal alteration halo associated with the Bangombé reactor. Phyllosilicates within the vein include a trioctahedral Al-Mg-Fe chlorite (ripidolite), Al-rich clay (kaolinite and/or donbassite) and illite. Textural relations obtained by backscattered-electron imaging suggest that ripidolite crystallized first among the sheet silicates. Uraninite is spatially associated with ripidolite and probably precipitated at a later time. While energy-dispersive x-ray analyses suggest that the uranium phase is predominantly uraninite, coffinite or other phases may also be present.
Uranium Redistribution Under Oxidizing Conditions in Oklo Natural Reactor Zone 2, Gabon
Authors: Isobe H. , Ohnuki T. , Murakami T. , Gauthier-Lafaye F. 
Published: April 2011

AbstractThis mineralogical study was completed to elucidate the relationships between uranium distribution and alteration products of the host rock of natural reactor zone 2 at Oklo. The samples used were from the reactor core and reactor zone clays just below the reactor core. Uraninite is preserved without any alteration in the reactor core. Uranium minerals found to be present in the fractures in the reactor zone clays associated with iron-mineral veins, galena and Ti-bearing minerals. Uranium, for which the phases could not be identified, occurs in iron-mineral veins and the iron-mineral rim of pyrite grains in the reactor zone clays. Uranium is not associated with granular iron minerals occurring in the illite matrix of the reactor zone clays. The degree of crystallinity and uranium content of the three iron-bearing alteration products suggest that they formed under different conditions; the granular iron minerals, under alteration conditions where uranium was not mobilized while the iron-mineral veins and the iron-mineral rim of pyrite, under conditions in which uranium is mobilized after the formation of the granular iron minerals.
Measurement of Uranium Series Radionuclides in Rock and Groundwater at the Koongarra ore Deposit, Australia, by Gamma Spectrometry
Authors: Yanase Nobuyuki , Sekine Keiichi 
Published: April 2011

AbstractGamma spectrometry without any self-absorption correction was developed to measure low energy gamma rays emitted by uranium and actinium series radionuclides in rock samples and groundwater residues collected at the Koongarra ore deposit, Australia. Thin samples were prepared to minimize the self-absorption by uranium in the samples. The present method gave standard deviations of 0.9 to 18% for the measurements of concentrations of uranium and actinium series radionuclides. The concentrations of238U,230Th and235U measured by gamma spectrometry were compared with those by alpha spectrometry that requires a complicated chemical separation procedure. The results obtained by both methods were in fairly good agreement, and it was found that the gamma spectrometry is applicable to rock and groundwater samples having uranium contents up to 8.1% (103Bq/g) and 3 Bq/1 of238U, respectively. The detection limits were calculated to be of the order of 10−2Bq/g for rock samples and 10−2Bq/1 for groundwater samples. The concentrations of uranium and actinium series radionuclides can be determined precisely in these samples using gamma spectrometry without any self-absorption correction.