bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multifunctional Ceramic Materials–Review and Projections
Authors: Mackenzie John D. 
Published: March 2011

AbstractMultifunctional engineering systems made up of different material components each providing primarily a single function are well known. Frequently, even for a monofunctional application, the material component must already have an optimum set of secondary properties to fulfill that function. It would be desirable to have multifunctional material components. In this paper some known multifunctional ceramic materials, mainly crystalline and glassy oxide systems, are reviewed. These are conveniently divided into molecular, ultrastructural and integrated materials systems. Projections are made regarding the future developments of multifunctional ceramics as well as nanocomposites with both inorganic and organic components based on the sol-gel technique.
Multi-Layers Thin Films of Acetalized Poly(Vinyl Alcohol) Derivatives Obtained by the LB Method and Their Opto-Electronic Properties
Authors: Oguchi Kiyoshi , Yokoh Yasuhiko , Sanui Kohei , Ogata Naoya 
Published: March 2011

AbstractThe formation of surface films of acetalized poly(vinyl alcohol)s at the air/water interface has been investigated in terms of the structure of the transferred films, after transfer of these surface films to solid substrates by means of the Langmuir-Blodgett technique. Furthermore, their electron beam exposure characteristics and non-linear optical properties were measured. It was found that the monolayers of acetalized poly(vinyl alcohol)s having aliphatic side chaines gave stable surface films with a limiting area of ca. 0.3nm2/average repeat unit, irrespective of the side-chain length and the degree of polymerization of the starting poly(vinyl alcohol). The surface films could be deposited onto various substrates with deposition ratios of 1.0. The resulting multilayers were Y type. The thickness of the multilayers was proportional to the number of layers, and the single-layer thickness increased with increasing sidechain length. The surface wettability of the multilayers changed alternatingly, depending on whether the number of layers was even or odd. These results indicated that the surface films were monolayers of polymers, with hydrophilic main chains spread over the air/water interface and hydrophobic side chains directed approximately normal to the interface. The transferred films maintained the oriented structure of the monolayers at the interface. The acetalized poly(vinyl alcohol)s prepared by the LB technique is adaptable as a high resolution negative-type EB resist. And the second harmonic generation (SHG) of some acetalized poly(vinyl alcohol)s was observed by LB method and by electric field poling method.
Dielectric, TSC and Electromechanical Measurements on some Prospective NLO Polymers
Authors: Carr Paul L. , Davies Geoff R. , Ward Ian M. 
Published: March 2011

AbstractThe pyroelectric coefficients of a range of polymers with a methacrylate backbone and nitrostilbene or nitrobipheny mesogens attached by a 3 or 6 carbon spacer have been measured in order to assess the efficiency of the poling process. It is found that the response is much lower than the guest-host system MNA in PMMA, suggesting that the polar mesogens pack anti-parallel and that this alignment is not broken by the applied field.These strong interactions also provide an explanation for the absence of the β relaxation process in the experimental polymers and therefore the brittle nature of the films. They may also explain the stability of the polarisation achieved.
Vicrostructure and Electrical Properties of Kevlar/Polypyrrole Composite Fibers
Authors: Rector L. P. , DeGroot D. , Marks T. J. , Carr S. H. 
Published: March 2011

AbstractElectrically conducting composite polypyrrole/poly(p-phenyleneterephthalamide) (PPTA or KEVLAR) fibers have been prepared by chemical polymerization of pyrrole within the interstices of the hydrogen-bonded gel structure of never-dried PPTA fibers. The resultant fibers contain a uniform dispersion of polypyrrole, as evidenced by scanning electron microscopy. The temperature dependence of the electrical conductivity of these hybrid fibers is presented. The conductivity is well described by the fluctuation-induced charge transport model over the entire temperature range of interest. However, the low temperature electrical conductivity also exhibits a hoppinglike temperature dependence, and an Arrhenius-like temperature dependence is observed in the high temperature limit. Measurements of the temperaturedependent tbermopower are indicative of a p-type carrier.
Photoactive Liquid Crystalline Polymers as Multifunctional Materials
Authors: Creed David , Griffin Anselm C. , Hoyle Charles E. , Venkataram Krishnan 
Published: March 2011

AbstractUV-VIS spectral comparison with model compounds and isolation of the major product from preparative photolysis of one of the models has been used to show that the predominant photochemical reactions in the solid state of an aryl cinnamate polymer are 2+2 cycloaddition and photo-Fries rearrangement.
Enhancement of Third Order Nonlinearity on Phthalocyanine Compounds
Authors: Hosoda Masahiro , Wada Tatsuo , Yamada Akira , Garitoa Anthony F. , Sasabe Hiroyuki 
Published: March 2011

AbstractThe third order optical susceptibilities (−3ω; ω, ω ω,) for soluble metallophthalocyanine derivatives were determined by optical third harmonic generation measurements of molecularly doped polymer films at a wavelength of 1907nm. The X(3) value of tetra-tert-butylvanadylphthalocyanine is larger than that of metal-free derivative. We demonstrate experiment on modes of propagating light wave in molecularly doped films which exhibit excellent optical quality. The enhancement of third order optical nonlinear susceptibilities in phthalocyanine compounds are discussed in terms of molecular structure and molecular packing.
Thermochemistry and Structure of Model Waste Glass Compositions
Authors: Ellison Adam J. G. , Navrotsky Alexandra 
Published: March 2011

ABSTRACTEnthalpies of mixing of major oxide and waste components of proposed DWPF glasses are estimated. Several proposed glass compositions have very similar molar proportions of major structure-related components. Heats of mixing of major components are predicted to be small (glassy reference states), but may be endothermic or exothermic. Lanthanides are likely to form regions in the glasses rich in R-O-Si bonds but relatively depleted in Si-O-Si bonds. Measured enthalpies of solution of simple lanthanide-bearing glasses resemble those of mechanical mixtures of these end-members, with near-zero enthalpies of mixing for fairly large variations in lanthanide concentrations. DWPF glasses have alkalis in excess of those needed to charge-balance all T3+ cations in tetrahedral coordination. Electropositive +4, +5, and +6 cations are expected to use these excess alkalis to stabilize their own coordination polyhedra, forming complexes with effectively constant macroscopic stoichiometric ratios which contribute to enthalpies of solution in direct proportion to their concentration. Therefore, variations in the concentrations of high-valence cations in DWPF waste containment glasses are also predicted to result in near-zero enthalpies of mixing.
Effect of Curing Temperature on the Properties of Cementitious Waste Forms
Authors: Lokken Ryan O. , Shade John W. , Martin Paul F. C. 
Published: March 2011

ABSTRACTCurrent plans for disposing various low-level radioactive and/or hazardous liquid wastes include solidification of the waste using cementitious materials. One process, known as grouting, involves mixing liquid wastes with a blend of cementitious materials and pumping the resultant slurry to lined, underground concrete vaults. As the grout slurry begins to solidify and harden, the temperature within the grout increases due to exothermic hydration reactions. Depending on the the particular grout composition and on the disposal conditions, the grout may be exposed to temperatures of around 90°C for extended time periods. Studies are being conducted to determine the effects of high-temperature curing on selected properties of grouts prepared with a simulated low-level liquid waste. Grout samples cured at temperatures up to 950C in the laboratory absorbed water during curing. The resultant leach resistance and compressive strength of these grouts decreased with increases in curing temperature and curing time.
Thermokinetic Model of Borosilicate Glass Dissolution: Contextual Affinity
Authors: Advocat T. , Crovisier J.L. , Fritz B. , Vernaz E. 
Published: March 2011

ABSTRACTShort and long-term geochemical interactions of R7T7 nuclear glass with water at 100°C were simulated with the DISSOL thermokinetic computer code. Both the dissolved glass quantity and the resulting water composition, saturation states and mineral quantities produced were calculated as a function of time. The rate equation used in the simulation was first proposed by Aagaard and Hegelson: v = k+.S.a(H+)-n(l - e-(A/RT)). It simulates a gradually diminishing dissolution rate as the reaction affinity diminishes. The best agreement with 1-year experimental data was obtained with a reaction affinity calculated from silica activity (Grambow's hypothesis) rather than taking into account the activity of all the glass components as proposed by Jantzen and Plodinec. The concept of residual affinity was introduced by Grambow to express the fact that the glass dissolution rate does not cease. We prefer to replace the term “residual affinity” by “contextual affinity”, which expresses the influence on the dissolution rate of three factors: the solution chemistry, the metastability of SiO2(m), and the possible precipitation of certain aluminosilicates such as zeolites.
Effect of γ-Radiation on the Microstructure and Microchemistry of ggbfs/OPC Cemet Blends
Authors: Richardson I.G. , Groves G.W. , Wilding C.R. 
Published: March 2011

ABSTRACTGround granulated blast-furnace slag (ggbfs)/OPC blends are among the materials being considered as possible encapsulating matrices for low and intermediate level radioactive wastes. It is therefore desirable to identify any microstructural modifications which may result in these systems frmn exposure to ionizing radiations. In order to investigate this, ggbfs/COC blends were γ-irradiated to >80M3y at 50°C over a period of 2 years. These were examined by electron optical, X-ray and thermal analysis techniques and the results ccmpared with controls subjected to a similar hydration regime. The morphological and ccmpositional similarities and differences revealed between the irradiated and control samples are presented and discussed.
Parametric Effects of Glass Reaction Under Unsaturated Conditions
Authors: Bates John K. , Gerding Thomas J. , Woodland Alan B. 
Published: March 2011

ABSTRACTEventual liquid water contact of high-level waste glass stored under the unsaturated conditions anticipated at the Yucca Mountain site will be by slow intrusion of water into a breached container/canister assembly. The water flow patterns under these unsaturated conditions will vary, and the Unsaturated Test method has been developed by the YMP to study glass reaction. The results from seven different sets of tests done to investigate the effect of systematically varying parameters such as composition and degree of sensitization of 304L stainless steel, water input volume, and the interval of water contact are discussed. Glass reaction has been monitored over a period of five years, and the parametric effects can result in up to a ten-fold variance in the degree of glass reaction.
Behavior of Concrete as a Barrier Material for Nuclear Waste Disposal
Authors: James R. J. , Rashid Y. R. 
Published: March 2011

SummaryThe foundation necessary for a constitutive model to simulate the response of concrete at elevated temperature has been presented. A model including temperature dependent creep, material property degradation, and cracking is needed to evaluate the long term functional requirements of concrete as a barrier material for nuclear waste disposal. Since the stress due to thermal load is proportional to the modulus, the degradation of the modulus with time even at constant elevated temperatures requires continual redistribution of load. Furthermore, since this degradation is not recoverable, the response of the material at elevated temperatures exhibits a complex dependence not only on the temperature distribution, but on the prior thermal history of the structure.This constitutive model for the response of concrete at elevated temperatures has been implemented into an implicit, finite element program called ANACAP [8]. Because of the direct coupling with temperature, both through thermal loads and material property dependency, ANACAP also contains a heat transfer module that includes thermal effects due to fluid flow and moving material boundaries. This program has been applied to problems involving underground waste storage tanks and grout vaults at the DOE Hanford site in Richland, Washington.
Constraints by Experimental Data for Modeling of Radionuclide Release from Spent Fuel
Authors: Grambow Bernd , Werme L.O. , Forsyth R.S. , Bruno J. 
Published: March 2011

ABSTRACTComparison of spent fuel corrosion data from nuclear waste management projects in Canada, Sweden and the USA strongly suggests that the release of 90Sr to the leachant can be used as a measure of the degradation (oxidation/dissolution) of the fuel matrix. A surprisingly quantitative similarity in the 90 Sr release data for fuel of various types (BWR, PWR, Candu), linear power ratings and burnups leached under oxic conditions was observed in the comparison. After 1000 days of leachant contact, static or sequential, the fractional release rates for 90Sr (and for cesium nuclides) were of the order of 10−7/d.The rate of spent fuel degradation (alteration) under oxic conditions can be considered to be controlled either by the growth rates of secondary alteration products, by oxygen diffusion through a product layer, by the rate of formation of radiolytic oxidants or by solubility-controlled dissolution of the matrix. These processes are discussed. Methods for determining upper limits for long-term 90Sr release, and hence fuel degradation, have been derived from the experimental data and consideration of radiolytic oxidant production.
Speciation of Pu(Vi) in Near-Neutral to Basic Solutions via Spectroscopy
Authors: Okajima Shigeo , Reed Donald T. , Mazer James J. , Sabau Carmen A. 
Published: March 2011

ABSTRACTThe high sensitivity technique of laser photoacoustic spectroscopy and optical absorption spectroscopy were utilized to investigate the hydrolysis of Pu(VI) in perchlorate media. Absorption bands attributed to the hydrolysis of Pu(VI) were characterized in the pH = 6–8 regime which is of most interest to the proposed repository site at Yucca Mountain. Evidence was presented that supported the assignment of the polynuclear species (640 nm species) reported previously \1] as (PuO2)3(OH)5+1. Some temperature-dependent LPAS spectra are reported. The results obtained were compared to the predicted speciation of the geochemical code EQ3NR using the associated data base.
In-Situ Observation of the Alpha/beta Cristobalite Transition Using High Voltage Electron Microscopy
Authors: Meike A. , Glassley W. E. 
Published: March 2011

ABSTRACTA high temperature water vapor phase is expected to persist in the vicinity of high level radioactive waste packages for several hundreds of years. We have begun an investigation of the structural and chemical effects of water on cristobalite because of its abundance in the near field environment. A high voltage transmission electron microscope (HVEM) investigation of bulk synthesized α-cristobalite to be used in single phase dissolution and precipitation kinetics experiments revealed the presence β cristobalite, quartz and amorphous silica, in addition to α-cristobalite. Consequently, this apparent metastable persistence of β-cristobalite and amorphous silica during the synthesis of α-cristobalite was investigated using a heating stage and an environmental cell installed in the HVEM that allowed the introduction of either dry CO2or a CO2+ H2O vapor. Preliminary electron diffraction evidence suggests that the presence of water vapor affected the α-β transition temperature. Water vapor may also be responsible for the development of an amorphous silica phase at the transition that may persist over an interval of several tens of degrees. The amorphous phase was not documented during the dry heating experiments.
A Lagrangian Reactive Transport Simulator with Successive Paths and Stationary-States: Concepts, Implementation and Verification
Authors: Knapp R. B. 
Published: March 2011

ABSTRACTA geochemical software package which models static, single-path kinetic water-rock interactions, EQ3/6, has been modified to incorporate successive-paths and stationary states under high Peclet number transport conditions in a Lagrangian reference frame. These modifications permit calculation of reactive transport with reasonable computational requirements. Results from the new option in EQ3/6 have been compared with analytical results for the simple HC1 - SiO2 system; excellent agreements were achieved. Results have also been compared with published results for a portion of the A12O3 - HCI - K2O - SiO2 system. The results are in good qualitative and, in some cases, good quantitative agreement. However, the values of some variables differ substantially; these differences can be attributed to use of a different set of Al and Si aqueous species.
Modelling the in Situ Performance of Bentonite-Sand Buffer
Authors: Radhakrishna H.S. , Lau K.-C , Kjartanson B.H. , Cheung S.C.H. 
Published: March 2011

ABSTRACTIn the Canadian nuclear fuel waste management concept, a number of engineered barriers, such as the bentonite-sand buffer which surrounds the waste container in the emplacement boreholes, are used to inhibit the transport of radionuclides. The buffer material is also required to effectively conduct heat from the fuel-waste containers to the surrounding rock. To a large extent, in situ buffer performance will depend on the degree of moisture within the buffer. The moisture content will in turn depend on temperature, temperature gradients, and buffer initial and moisture flux boundary conditions. Modelling of coupled heat and moisture transport in the buffer before resaturation is necessary to assess in situ buffer performance. This paper describes the results of a parametric study using the Philip and de Vries coupled heat and moisture transport model to assess the effects of variations in the moisture diffusivity parameters and the boundary conditions on buffer performance.The results show that the thermal performance of the buffer is affected by heat-induced moisture movement. In particular, the thermal vapour diffusivity, DTvap, has the most significant effect on thermal drying in a closed system. Work is currently underway to improve our capability to model coupled heat and moisture transport in buffer. Laboratory experiments are in progress to more accurately define the moisture diffusivity parameters and the model is being modified to include the effects of boundary moisture fluxes and pressure potentials so that the resaturation process may be modelled. A full scale buffer/container experiment is currently being planned for conduct in AECL's Underground Research Laboratory to assess further the effects of scale and in situ boundary conditions on buffer performance and to qualify the model.
The Effect of Cracks on Diffusive Mass Transport through a Clay Barrier
Authors: Garisto Nava C. , Garisto Frank 
Published: March 2011

AbsractClay-based buffers are often proposed as engineered barriers for underground disposal vaults of used nuclear fuel. Thus, in the Canadian conceptual vault design, each used-fuel container is emplaced in a vertical borehole in rock and surrounded by a compacted buffer material, made up of a mixture of sodium bentonite and sand. There is some evidence, however, that the buffer may be susceptible to cracking due to, for example, cementation or moisture depletion.In this paper we estimate numerically the consequences of cracking on the diffusion of uranium through a finite buffer layer. In particular, we study how the effects of cracks depend on the rock conditions at the edge of the vault.For swept-away boundary conditions at the rock/buffer interface (e.g., representing a major fracture zone in granite), the total flux through the cracked buffer system is greater than through the corresponding uncracked buffer, particularly for buffers with a very small effective diffusion coefficient. On the other hand, for the case in which the rock at the rock/buffer interface is intact and, thus, the mass transport of material from the buffer into the rock is small, the effect of the cracks on the total release flux is negligible.
The Effects of Temperature on the Leaching Behavior of Cement Waste Forms - The Cement/Sodium Sulfate System
Authors: Fuhrmann Mark , Pietrzak Richard , Heiser John , Franz Eena-Mai , Colombo Peter 
Published: March 2011

ABSTRACTThe leaching mechanisms of simulated low-level radioactive waste forms are being determined as support for development of an accelerated leach test. Two approaches are being used: (1) comparison of leaching data with results of a model that describes diffusion from a finite cylinder, and (2) observation of the leaching process at temperatures between 20°C and 65°C. To provide results that can be used for modeling, leaching at elevated temperatures must change neither the leaching mechanism nor the structural controls of leaching such as the porosity. Releases of 137Cs, 85Sr, calcium, sodium and potassium from portland cement containing sodium sulfate, as a simulated evaporator sludge, have been determined under a variety of experimental conditions. Data from the leach tests were compared to model results for diffusion from the finite cylinder. While most leaching appears to be diffusion controlled, notable exceptions occur. For all samples, activation energies ranging between 6 and 11 Kcal/mole have been calculated from the relationship of the effective diffusion coefficient to increasing temperature, close to the expected value of 5 Kcal/mole for diffusion.
Dynamic Rigidity Percolation in AOT Micelles and Microemulsions
Authors: Ye L. , Weitz D. A. , Sheng Ping , Huang J. S. 
Published: March 2011

ABSTRACTWe study the acoustic properties of AOT micelles and microemulsions by measuring the velocity of sound as a function of droplet volume fraction and of frequency, using Brillouin scattering and ultrasonic techniques. These weakly attractive interparticle interactions lead to the formation of short–lived networks of droplets, which can support shear and result in a pronounced increase in the speed of sound at high frequencies. These networks do not persist for sufficiently long times to affect the sound velocity at lower frequencies. The increased rigidity due to the networks exhibits a percolation behavior with volume fraction, while the frequency dependence of the interactions depends on hydrocarbon chain length of the solvent. Increasing the water concentration results in an increase in interaction energy, but a decrease in the intrinsic droplet rigidity, which affects the magnitude and frequency dependence of the contribution of the microemulsion networks to the elastic constant of the suspension. A consistent picture of the viscoelastic behavior of these suspensions is obtained.