bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Forces Generated by Chemomechanical Protein Aggregates Using Polymer BioMEMS
Authors: Ferrell Nicholas , Schwan Stefan , Spohn Uwe , Heilmann Andreas , Hansford Derek
Published: April 2011

P-protein bodies (forisomes), in phloem cells of legumes, transform the chemical free energy of their reaction with alkaline earth metal ions into mechanical energy. In addition to using the bending of glass fibers, micromechanical forces generated by the switching of forisomes in aqueous solutions were measured by monitoring the bending of microscale polymer cantilever beams. The forisomes were fixed by chemisorption to the tips of four orthogonal beams of a BioMEMS microsystem designed and manufactured using the process of sacrificial layer micromolding. The sensor layout allows force measurements in the longitudinal and radial direction of the forisomes. For different forisomes a longitudinal force in the range from 84-136 nN and a radial force of 22-61 nN were measured.
Electrically Switchable Liquid Crystal Polymer Rod Actuators
Authors: Shafran Matthew , Sierros Konstantinos , Huebsch Wade , Cairns Darran
Published: April 2011

Stimulus responsive liquid crystal nanorods, 60 μm in length and 200 nm in diameter, were fabricated by a template synthesis technique. The liquid crystal, RM 257, is a reactive monomer which polymerizes with the application of UV light. After polymerization the liquid crystal's orientational order is permanently “frozen”. Therefore, the subsequent structures are temperature independent after curing. In this study the liquid crystal was confined in the pores of Anopore membranes before curing, which results in rod structures after photo-polymerization. After fabrication, the rods were observed under the application of both AC and DC electric fields. DC fields were noted by either up and down or translational movement of the rods. Application of AC fields resulted in random movement of the rods.
Nanoindentation of Histological Specimens using an Extension of the Oliver and Pharr Method
Authors: Akhtar Riaz , Sherratt Michael J , Bierwisch Nick , Derby Brian , Mummery Paul M , Watson Rachel E.B , Schwarzer Norbert
Published: April 2011

The micro-mechanical properties of 5 μm thick histological sections of ferret aorta and vena cava were mapped as a function of distance from the outer adventitial layer using nanoindentation. In order to decouple the effect of the glass substrate on the elastic modulus of these thin sections, the nanoindentation data were analyzed using the extended Oliver and Pharr method which is readily accessible for coatings and layered materials with the software package, FilmDoctor®. In the aorta, the elastic modulus was found to decrease progressively from 35 MPa at the adventitia (outermost layer) to 8 MPa at the intima (innermost layer). This decrease in modulus was inversely correlated with elastic fibre density. In contrast, in the vena cava, the stiffest regions were found to be the adventitial (outer) and intimal (innermost) sections of the vessel cross-section. Both these regions were enriched in ECM components. The central region, thought to be largely cellular, had a relatively constant modulus of around 20 MPa. This study demonstrates that with this methodology it is possible to distinguish micro-mechanically between large arteries and veins, and therefore the same approach should allow age or disease related changes in the mechanical properties within a tissue to be quantified.
Design of a Dielectrophoretic Mechanical Testing Device
Authors: Manomohan Greeshma , Rajendran Kavitha , Morss Clyne Alisa
Published: April 2011

Mechanics play a critical role in cell function in health and disease. While a variety of techniques exist to measure cell mechanics, no single device or testing method can answer all biomechanics questions. We have designed a novel dielectrophoretic cell mechanics device to apply piconewton forces to single, asymmetric attached cells without physical contact. This device uses negative dielectrophoresis to trap individual cells, after which cells attach to the device substrate. Negative dielectrophoresis is then used to apply compressive force to attached cells, and cell displacement is measured via microscopy.

COMSOL software was used to model the two-dimensional electric and force fields. Based on modeling results, a quadrupole electrode configuration was designed in AutoCad,fabricated using microfabrication techniques, and tested with endothelial cells. A modeled quadrupole electrode with a 50 μm center diameter operating at 1 volt and 1 MHz generated 100's piconewtons of compressive force. This force was sufficient to trap both polystyrene beads and cells. While trapped cells did attach to the glass substrate, further refinement of the device is needed to maintain the cells in a healthy state.

This dielectrophoretic mechanics testing device expands the existing biomechanics toolbox by providing a non-contact method to test mechanics of attached cells under diverse conditions. Future dielectrophoretic systems could allow tensile as well compressive forces, and when coupled with microfluidic systems, could test cell mechanics under fluid flow or a chemotactic gradient. This device will improve our understanding of cell mechanics in healthy cell function and how perturbation of the mechanical environment contributes to disease.
Micromechanical Simulations on Hygro-Mechanical Properties of Bio-fiber Plastic Composites
Authors: Xue Yibin , Wang Kunpeng
Published: April 2011

The hygro-mechanical properties of bio-fiber composites comprise two aspects: the coupling between moisture diffusion and mechanical deformations and the coupling of moisture contents and the constitutive behaviors. Bio-fiber is hydrophilic, which absorbs water promptly when environmental moisture content increases; as the moisture content in the fiber increases, its mechanical properties decrease. This paper presents a series of micromechanical simulations to predict the hygro-mechanical behaviors of woodfiber-reinforced plastic composites considering the effects of fiber arrangements on the stress-strain relations and moisture-expansions on three progressively constructed constitutive configurations: 1) the fiber is elastic orthotropic and expandable under moisture variations; the plastic matrix is elastic isotropic and insensitive to environmental moisture variations, and the interface between fiber and matrix is perfectly bounded; 2) the plastic matrix is hyperelastic and expresses a certain degree of damage as deformation progresses; and 3) the interface has a pseudo adhesive layer that obeys Smith and Ferrante's universal binding law implemented as a cohesive zone model in the micromechanical simulation. In configuration II, micromechanical simulations demonstrate significant reductions in the nominal elastic modulus of composites when a nonlinear elastic model for the polymer matrix is assumed. The prediction for stress-strain relationship is found to be comparable to the experimental measurements. A cohesive model in configuration III is introduced to evaluate the possible moisture degradation to the fiber-matrix interface, which results in a reduction in elastic modulus and failure strength of the composite s, as observed in experiments. The cohesive zone model parameters as a function of moisture content in the composites requires more attention in model correlation and guarantee more direct experimental observations.
Study of the Crystal Structure and Phase Transition of Li2NH System
Authors: Yang Jinbo , Lamsal J. , Cai Q , Yelon W B , James W J
Published: April 2011

Neutron diffraction at different temperatures has been used to study the crystal structure and possible phase transitions of Li2NH. It was found that the crystal structure and phase transition are related to the synthesis methods. A phase transition from the low temperature phase 16-350 K to the high temperature phase above 370 K has been confirmed for the ケ-Li2NH sample prepared by reacting Li3N with LiNH2. The Li2NH (β-Li2NH) prepared by decomposition of LiNH2 shows only the high temperature phase. The reaction of LiH+LiNH2 at 300°C for 12 h under vacuum produces some Li2NH (γ-Li2NH) with partially unreacted LiNH2 and LiH as impurities. There is no phase transition in the temperature range from 16 K to 400 K for the - and β-Li2NH phases.ケ-Li2NH exhibits a higher reversible hydrogen storage capacity and faster kinetics. The structural differences among the lithium imides may lead to different reaction mechanisms for hydrogen absorption/desorption in the Li-N-H system.
Oxide ion conduction of yttria-stabilized zirconia films deposited by atomic layer deposition
Authors: Chao Cheng-Chieh , Huang Hong , Park Joon Seok , Prinz Fritz B.
Published: April 2011

Yttria-stabilized zirconia (YSZ) is one of the most common electrolytes in high temperature solid oxide fuel cell (SOFCs). We utilize atomic layer deposition (ALD) to fabricate the electrolyte of SOFC, which may potentially improve several fundamental characteristics of SOFC. Recently, our group demonstrated that ultra-thin ALD YSZ SOFSs can deliver high power density at low temperatures [1]. These SOFCs demonstrated not only reduction of Ohmic loss, but also enhancement of surface kinetics.

The focus of this work is to investigate the surface and bulk conduction characteristics of YSZ films produced by ALD. In plane conductivity was measured as a function of film thickness and temperature dependence. YSZ thin films were deposited on standard 4 ” quartz substrates with thicknesses ranging from 8 nanometers to 55 nanometers. Micro-electrodes were patterned on top of the ALD YSZ layer by standard photolithography process. The impedances of the YSZ thin films with different thicknesses were measured. We have observed higher conductivities for thinner films which were attributed to higher oxide ion conductivity in the vicinity of the surface, and similar phenomenon was observed with YSZ films produced by electron beam evaporation [2].
Hydrogenation Of The Titanium Aluminides
Authors: Kazantseva Nataiya , Mushnikov Nikolai V , Popov Alexandr G , Sasonova Valentina A , Teren'ev Pavel B
Published: April 2011

The hydrogen absorption properties of the Ti-Al-Nb system intermetallics subjected by ball milling were studied. It was found that the hydrogenation of the titanium aluminides during ball milling in hydrogen atmosphere could occur at room temperature without any special requirements to the quality of hydrogen. The crystal structure of the hydrides and phase transformations were also studied.
Mechanism of Hydrogen Storage on Reduced Carbon Single-Walled Nanotubes
Authors: Curtis Calvin J , Gennett Thomas , Engtrakul Chaiwat , O'Neill Kevin , Ellis Jamie E. , Heben Michael J.
Published: April 2011

Carbon single-walled nanotubes (SWNTs) have been studied extensively as hydrogen storage materials. Herein, a novel hydrogen sorbtion behavior was observed for alkali metal reduced SWNTs and the mechanism of hydrogen binding in these materials has now been elucidated. SWNTs prepared by laser vaporization and purified by oxidation were reduced with Na in combination with naphthalene in tetrahydrofuran (THF) solution. The product, initially formulated as (Na+)xSWNTx-, was dark colored and insoluble in all common solvents examined. Temperature programmed desorption studies showed that hydrogen amounting to 3.5-4.2% w/w was released between 200 and 500°C from the Na-reduced material. This is consistent with hydrogenation of the reduced nanotubes to form C-H bonds with a C2H empirical formula. It appears that SWNT radical anions produced by reaction with sodium deprotonate THF to form hydrogenated nanotubes and the THF cleavage products ethylene and sodium enolate, as confirmed by isotope labeling. A structure consisting of pairs of lines of C-H units that spiral about the long tube axis with a coverage of 50% of the tube carbons is proposed.
RECENT PROGRESS IN SECOND-GENERATION HTS WIRE TECHNOLOGY AT SUPERPOWER
Authors: Chen Yimin , Xiong Xuming , Xie Yiyuan , Qiao Yunfei , Zhang Xun , Rar Andrei , Martchevskii Maxim , Schmidt Robert , Lenseth Kenneth , Herrin John , Hazelton Drew , Selvamanickam Venkat
Published: April 2011

We report recent progress in 2G-HTS wire technology at Superpower Inc. The throughputs of 4mm-wide tape have reached 750m/h for sputtering AlO3+Y2O3 base layer, 360m/h for IBAD MgO template, 345m/h for sputtering Homo-epi MgO+LMO buffer, 180m/h for MOCVD REBCO. Critical current (Ic) of 813A/cm-width at 77K and self-field has been achieved on 1 meter length of 12mm-wide tape in which the thickness of GdYBCO film is 3.3 microns. Ic in a magnetic field has been significantly improved through composition modification, doping and MOCVD condition optimization. Ic of 185.6A/cm-width at 77K and 1Tesla has been obtained. For Ic on long lengths, 314A/cm-width on 202m, 221A/cm-width on 610m and 170A/cm-width on 935m have been achieved. A coil of 19.1mm diameter we made with our 2G wires generated 26.8T magnetic field in the magnet. A 30m-long cable made with nearly 10,000 meters of Superpower 2G wires showed excellent overall performance and has been installed and energized in the power grid.
Microporous Carbon-halide Nanocomposites Electrodes for Symmetric and Asymmetric Capacitor
Authors: Barpanda Prabeer , Fanchini Giovanni , Amatucci Glenn G
Published: April 2011

Microporous carbon containing little mesoporosity was chemically modified through a vapor phase iodation treatment in an effort to improve the electrochemical performance of activated carbon system commonly utilized in symmetric and asymmetric capacitors. This new carbon system has been studied with respect to their structural, morphological and electrochemical properties and contrasted to the mesoporous carbon based nanocomposites.
Record Conductivity for P-Type Transparent Conductors in Polycrystalline Thin Films of a Sulfide-Fluoride
Authors: Frantz Jesse , Sanghera Jasbinder S. , Qadri Syed B. , Aggarwal Ishwar D.
Published: April 2011

Barium copper sulfur fluoride thin films with a face-centered cubic phase in the Fm3m space group were synthesized via RF magnetron sputtering. The results of a detailed optical and electronic characterization of the films are presented. As-deposited, they exhibit degenerate p-type conductivity at room temperature of approximately 260 S/cm – higher than that of any previously reported p-TC. Their conductivity after post-deposition processing increases to as high as 800 S/cm. The films exhibit bandgaps ranging from 1.45-1.75 eV. They are typically deposited with a substrate temperature between room temperature and 100°C, making them suitable for deposition on plastic as well as glass or crystalline substrates. It was found that a silica protective layer reduces degradation in film transparency that is caused by exposure to air.
Nano-scale Investigation of Light Scattering at Randomly Textured Light Trapping Structures for Thin-film Silicon Solar Cells
Authors: Bittkau Karsten , Beckers Thomas , Rockstuhl Carsten , Fahr Stephan , Lederer Falk , Carius Reinhard
Published: April 2011

We report on nano-scale optical effects of amorphous silicon layer conformally deposited on randomly textured zinc oxide layers on glass substrates investigated by near-field scanning microscopy. Such textured layers are used in thin-film photovoltaic devices to enhance light trapping. Experimental results are compared to theoretical data, obtained from large scale finite-difference time-domain simulations. Light localization on the surface of the textured interface and a focusing of light by the structure further away are observed. The measurements are compared with simulations, which provide additional insight into the light intensity distribution inside the solar cell on a nm-scale. It will be shown how this information can be used to optimize light trapping in thin-film solar cells using an amorphous silicon solar cell as an example.
Optical developments for silicon thin film solar cells in the substrate configuration
Authors: Soderstrom Thomas , Haug Franz-Joseph , Niquille Xavier , Cubero Oscar , Perregaux Stéphanie , Ballif Christophe
Published: April 2011

In the nip or substrate configuration thin film silicon solar cells, the choice of front TCO contact is critical because there is a trade off between its transparency which influences the current in the solar cell and its conductivity which influences the series resistance. Here, we investigate the optical behavior of two different TCO front contacts, either a 70 nm thick, nominally flat ITO or a 2 μm thick rough LPCVD ZnO. The back contact consists of LP-CVD ZnO with random texture. First we investigate the influence of the rough and flat front TCOs in μc-Si:H and a-Si:H solar cells. With the back contact geometries used in this work, the antireflection properties of ITO are effective at providing as much light trapping as the rough LP-CVD ZnO. In the second part, we demonstrate that total of 25 to 26 mA/cm2is achievable in nip micromorph tandem cells and show short circuit current up to 11.7 mA/cm2 using an SIO based intermediate reflector.
Shape-Controllable Surface Texturization for Crystalline Silicon Solar Cells
Authors: Im Jong-San , Jeon Jin-Wan , Lim Koeng Su
Published: April 2011

This paper describes a new method to make surface textures for photovoltaic application. Using this method, we can make textures having various shapes. The first step is to make photo-resist (PR) molds using the polymer dispersed liquid crystal (PDLC) film. The second step is to transfer the PR molds to silicon by inductively coupled plasma etching process. The final step is a solar cell fabrication process. The structure of the solar cell is simple Al Grid/c-Si/Al back contact. The solar cells show the increase of the short circuit current (Jsc) comparing to the planar cells. By this texturing method, we can get solar cells having various textures which we want to make.
Microscopic Theory of Coupled Quantum Well Structures in Photovoltaics
Authors: Aeberhard Urs , Morf Rudolf
Published: April 2011

We use our recently developed microscopic approach to a quantum theory of photovoltaic processes in nanostructures [1]to investigate geometry effects in quantum well photovoltaics, focussing on the role of asymmetry and inter-well coupling in double quantum well (DQW) systems. For that purpose, the IV and power characteristics for DQW systems with different asymmetry and degree of coupling are calculated numerically in the vicinity of the maximum power point. In order to assess the transport properties of a specific QW structure, we isolate these from the effects of absorption by normalizing to the absorptivity. The results obtained from this procedure reveal the escape regime dominating at room temperature and confirm previous experimental observations.
Loss Mechanisms in Photovoltaic Fluorescent Collectors
Authors: Proenneke Liv , Rau Uwe
Published: April 2011

Monte-Carlo simulations calculate the photon collection of fluorescent collectors in photovoltaic systems. We focus on two collector geometries: solar cells mounted at the collector sides, and solar cells covering the back of the collector. A mirror covers the bare back sides of both systems. On top lies optionally a photonic structure, which acts as an energy selective filter. Ideal systems in their radiative limits are compared to systems where loss mechanisms in the dye, at the mirror, or the filter are included. The examination of loss mechanisms in photovoltaic systems with fluorescent collectors enables us to estimate quality limitations of the used materials and components.
MeV Si Ions Bombardment Effects on SiO2/SiO2-ZrNiSn Nano-layered Thermoelectric Generator
Authors: Budak S. , Guner S. , Muntele C. , ILA D.
Published: April 2011

We have deposited 50 nano-layers of 710 nm of SiO2/SiO2+ZrNiSn with a periodic structure consisting of alternating layers where each layer is about 14 nm thick. The purpose of this research is to generate nanolayers of nanostructures of ZrNiSn with SiO2 as host and as buffer layer using a combination of co-deposition and MeV ion bombardment taking advantage of the energy deposited in the MeV ions track to nucleate nanostructures. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/ĸ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and ĸ is the thermal conductivity. ZT can be increased by increasing S, increasing σ, or decreasing ĸ. The electrical and thermal properties of the layered structures were studied before and after bombardment by 5 MeV Si ions at seven different fluences ranging from 1014 to 1015 ions/cm2 in order to form nanostructures in layers of SiO2 containing few percent of ZrNiSn. Rutherford Backscattering Spectrometry (RBS) was used to monitor elemental analysis of the film.
Chemical Modification on Hierarchically Structured ZnO Films for Energy Conversion Efficiency Enhancement of Dye-Sensitized Solar Cells
Authors: Zhang Qifeng , Jenekhe Samson A , Cao Guozhong
Published: April 2011

We report the synthesis of ZnO aggregates in the presence of lithium salt and the enhancement on the energy conversion efficiency of dye sensitized solar cells when the photoelectrode films consist of as-synthesized ZnO aggregates. The conversion efficiency for ZnO film consisting of aggregates synthesized with lithium involvement is significantly improved up to 5.8%, which is 32% higher than that of 4.4% obtained for pure ZnO film. Such an enhancement can be attributed to the effect of lithium-induced changes on the morphology and crystallinity of aggregates, the optical absorption of films, and the surface chemistry of ZnO, which provides the film with decreased electron trapping and increased refractive index, and enhances the electronic coupling between the dye molecules and ZnO.
Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in Aqueous Surfactant Systems
Authors: Deshpande Aniruddha Subhash , Khomane Ramdas B. , Vaidya Bhalchandra K. , Joshi Renuka M. , Harle Arti S. , Kulkarni Bhaskar D.
Published: April 2011

Sulfur nanoparticles were synthesized from hazardous H2S gas by desulfurization based on liquid redox process [1]. The use of novel biodegradable iron chelates, in particular, FeCl3-malic acid chelate system has been extensively studied in various aqueous surfactant systems of Tween 80, SDS, CTAB for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure and neutral pH. The structural features of sulfur nanoparticles have been characterized by XRD, TEM, and DLS measurements. XRD analysis indicates the presence of Metal-sulfur (JCPDS-08247). TEM analysis shows that the morphology of sulfur nanoparticles synthesized in aqueous surfactant system of Tween 80 is nearly uniform in size of 12nm average particle size, in SDS surfactant system shows 15nm average particle size, where as sulfur nanoparticles synthesized in CTAB shows average particle size of 7nm. The DLS result shows the mono-dispersity of the sulfur nanoparticles in the aqueous surfactant systems. The described process serves mainly two objectives; (a) waste utilization for preparation of commercially important nano-sulfur product and (b) reduction in environmental pollution. 1. G. Nagal, Chem. Eng. 104, 125 (1997).
Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. % Ga
Authors: Jeffries Jason R , Blobaum Kerri J. M. , Wall Mark A. , Schwartz Adam J.
Published: April 2011

The gallium-stabilized Pu-2.0 at. % Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable δ phase to the gallium-containing, monoclinic α′ phase near -100 °C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation (TTT) diagram, where two nose temperatures anchoring an upper- and lower-C describe minima in the time for the initiation of transformation. The underlying mechanisms responsible for the double-C behavior are currently unresolved, although recent experiments suggest that a conditioning treatment—wherein, following an anneal at 375 °C, the sample is held at a sub-anneal temperature for a period of time—significantly influences the upper-C of the TTT diagram. As such, elucidating the effects of the conditioning treatment upon the δ⟶α′ transformation can provide valuable insights into the fundamental mechanisms governing the double-C kinetics of the transition. Following a high-temperature anneal, a differential scanning calorimeter (DSC) was used to establish an optimal conditioning curve that depicts the amount of α′ formed during the transformation as a function of conditioning temperature for a specified time. With the optimal conditioning curve as a baseline, the DSC was used to explore the circumstances under which the effects of the conditioning treatment were destroyed, resulting in little or no transformation.
Enabling the Double-C Curve in Pu-Ga Alloy Time-Temperature-Transformation Diagrams
Authors: Jeffries Jason R. , Blobaum Kerri J. M. , Wall Mark A. , Schwartz Adam J.
Published: April 2011

Under ambient conditions, a Pu-2.0 at.% Ga alloy is retained in the metastable δ phase. Upon cooling to approximately -120 °C, the face-centered-cubic δ phase partially transforms to the metastable monoclinic α′ phase via a martensitic transformation. The kinetics of the δ⟶α′ transformation are reported to have double-C curve kinetics in a time-temperature-transformation (TTT) diagram, but the mechanisms responsible for this unusual behavior are not understood. Our work focuses on determining the underlying cause of the two noses. Optical microscopy has been used to investigate the role of “conditioning”—an isothermal hold at sub-anneal temperatures—on the δ⟶α′ transformation and to illuminate any disparities in transformation products. Conditioning was found to affect substantially the amount of transformation that occurs at particular points corresponding to both the upper- and lower-C of the TTT diagram.
Comparison of Aromatic Dithiophosphinic and Phosphinic Acid Derivatives for Minor Actinide Extraction
Authors: Harrup Mason K. , Peterman Dean R. , Greenhalgh Mitchell R. , Luther Thomas A. , Klaehn John
Published: April 2011

A new extractant for the separation of actinide(III) and lanthanide(III), bis(o-trifluoromethylphenyl)phosphinic acid (O-PA) was synthesized. The synthetic route employed mirrors one that was employed to produce the sulfur containing analog bis(o-trifluoromethylphenyl)dithiophosphinic acid (S-PA). Multinuclear NMR spectroscopy was used for elementary characterization of the new O-PA derivative. This new O-PA extractant was used to perform Am(III)/Eu(III) separations and the results were directly compared to those obtained in identical separation experiments using S-PA, an extractant that is known to exhibit separation factors of ∼100,000 at low pH. The separations data are presented and discussed in terms comparing the nature of the oxygen atom as a donor to that of the sulfur atom in extractants that are otherwise identical.
Preliminary Study of Corrosion Mechanisms of Actinides Alloys: Calibration of FT-IR Spectroscopy
Authors: Magnien Véronique , Cadignan Marx , Faivret Olivier , Rosa Gaelle
Published: April 2011

In situ analyzes of gaseous atmospheres could be performed by FT-IR spectroscopy in order to study the corrosion reactions of actinides. Nevertheless experimental conditions and the nature of studied species have a strong effect on IR absorption laws. Thus a prior calibration of our set-up is required to obtain an accurate estimation of gas concentration. For this purpose, the behavior of several air pure gases has been investigated according to their concentration from IR spectra. Reproducible results revealed subsequent increases of the most significant peak areas with gas pressure and small deviations from Beer Lambert's law. This preliminary work allowed to determine precise absorption laws for each studied pure gas in our in situ experimental conditions. Besides our FT-IR set-up was well suitable to quantitative analysis of gaseous atmosphere during corrosion reactions. Finally the effect of foreign gas will be investigated through more complex air mixtures to obtain a complete calibration network.
A Model for the Study of Molecules Radiochemical Decomposition by Actinides Materials
Authors: Berlu Lilian , Rosa Gaëlle
Published: April 2011

The radiochemical decomposition of molecules in storage environment which could lead to the corrosion of container or the formation of dangerous gas mixtures is a critical problem for radioactive materials. The complexity of the chemical system makes numerical models suitable for the reproduction mechanisms and the prediction of phenomena. In this study, a mathematical model for the dose rate distribution in external medium surrounding an α emitter actinide material has been proposed. The model has been implemented in a Monte Carlo scheme. An evaluation of the dose rate in the surrounding medium as a function of the sample size was shown and a discussion of the expected reactivity was made.
Signatures of Non-integer 5f Occupancy in Pu Systems: Magnetic Properties and Photoelectron Spectroscopy Studies
Authors: Havela Ladislav , Shick Alexander , Gouder Thomas , Wastin Franck , Rebizant Jean
Published: April 2011

Very diverse Pu compounds exhibit strikingly universal features in their valence-band photoemission (PES) spectra. The conjecture that such features represent the 5f5 final state multiplet has been corroborated by LDA+Hubbard I calculations, meaning that the ground state has a mixed 5f5-5f6 character. Later on, more elaborated DMFT techniques (one crossing approximation, QMC) led to similar conclusions, providing quantitative explanation of such intermeate-valent situation in more details. Analogies in PES spectra of δ-Pu and other Pu systems suggest that the situation envisaged for δ-Pu is relevant for a large group of Pu compounds. Here we show that the around mean field LDA+U in conjunction with the Hubbard I approximation, which describes well the non-magnetic ground state for δ-Pu, captures in reality properties of a large group of Pu (as well as e.g. Am) compounds, reproducing correctly the onset of magnetism and size of magnetic moments.
Thermodynamic Simulation and Experimental Study of Irradiated Reactor Graphite Waste Processing with REE Oxides
Authors: Karlina Olga K. , Klimov Vsevolod L. , Pavlova Galina Yu. , Ojovan Michael I.
Published: April 2011

Thermochemical processing of reactor graphite waste is based on self-sustaining reaction 4Al + 3TiO2 + 3C = 3TiC + 2Al2O3 which chemically binds 14C from the irradiated graphite in the titanium carbide. Thermochemical processing was investigated to analyse the behaviour of rare earth elements (REE), where REE = Y, La, Ce, Nd, Sm, Eu and Gd. Both thermodynamic simulations and laboratory scale experiments were used. The REEs in the irradiated reactor graphite are formed as activation products of impurities and spread over the graphite bricks surfaces as well as arise from fission of nuclear fuel. REEs can be used also to substitute for waste actinides as well as to increase the durability of carbide-corundum ceramics relative to waste actinides.

Thermodynamic calculations and X-ray diffraction analysis of ceramic specimens synthesized revealed that durable REE's aluminates with perovskite, β-alumina and garnet structures are formed by interaction of REE oxides with the Al2O3 melt during the selfpropagating reaction of ceramic formation.

The porous carbide-corundum ceramics synthesized have a high hydrolytic durability, e.g. the normalised leaching rates of 137Cs, 90Sr and Nd are of the order of 10–7 – 10–8 g/(cm2·day).
Opportunities for Research in the UK for Decommissioning and Disposal
Authors: Smart Neil
Published: April 2011

The NDA remit as set out within the Energy Act includes – “promote, and where necessary fund, research relevant to nuclear clean up”. The NDA need to underpin delivery and / or accelerate programmes to fulfil the overall mission and technical underpinning of these activities is critical. In this paper we will present consideration of the investment required in nuclear waste Research and Development.

Firstly, NDA set the requirement for nuclear sites to write down within the Life Time Plans (LTP), at a high level, the proposed technical baseline underpinning the LTP activities; furthermore we required technology gaps / opportunities in the technical baselines to be outlined in a R&D requirements section to the LTP. Criteria were established to categorise the R&D in three areas:

“needs” - those development activities needed to underpin the proposed technical solutions

“risks” – those activities required to reduce / eliminate key risks to the proposed technical solutions

“opportunities” – innovations / changes to the technical baselines

The purpose of production of the technical baselines and underpinning R&D requirements is to establish an auditable trail through the LTP from programme components into how the programme will be delivered.

NDA believes the production of the technical baselines and R&D requirements will be of benefit to the Site License Companies (SLC) in terms of ensuring a focus on overall programme delivery and not just short term activities. Furthermore, we can ensure that investment in technology is targeted at priority areas, with common issues and requirements identified and solutions on a broader scale will be achievable.
Cement Based Encapsulation Trials for Low-Level Radioactive Effluent Containing Nitrate Salts
Authors: Sugaya Atsushi , Horiguchi Kenichi , Tanaka Kenji , Kobayashi Kentaro
Published: April 2011

The operation of nuclear fuel reprocessing plants generates a radioactive effluent containing nitrate salts as the major constituent. This waste must be disposed of safely and economically, and to achieve this aim the Japan Atomic Energy Agency (JAEA) is developing a cement based encapsulation method to immobilise this waste. Non-radioactive development work has been performed at both small and large-scale (up to 200 litres) to investigate the optimum cement formulation. The results from these studies demonstrate that nitrate waste that has been concentrated by evaporation of the water to a predetermined level can be successfully encapsulated up to a waste loading corresponding to 50 wt% sodium nitrate. It has been identified that high concentrations of bicarbonate ions in the effluent can have a detrimental effect on the strength of the cement encapsulated waste; however, provided this concentration is controlled, successful encapsulation of the effluent is still achieved.
Electron Irradiation and Electron Tomography Studies of Glasses and Glass Nanocomposites
Authors: Möbus G. , Yang G. , Saghi Z. , Xu X. , Hand R.J. , Pankov A. , Ojovan M.I.
Published: April 2011

Characterization of glasses and glass nanocomposites using modern transmission electron microscopy techniques is demonstrated. Techniques used include: (i) high-angle-annular dark field STEM for imaging of nanocomposites, (ii) electron tomography for 3D reconstruction and quantification of nanoparticle volume fractions, and (iii) fine structure electron energy loss spectroscopy for evaluation of boron coordination. Precipitation of CeO2nanoparticles in borosilicate glasses is examined as a function of glass composition and redox partner elements. A large increase in the solubility of Ce is found for compositions where Ce retains +IV valence in the glass. Irradiation experiments with electrons and λ-rays are summarized and the degree of damage is compared by using changes in the boron K-edge fine structure, which allows the gradual transition from BO4to BO3coordination to be followed.
Glass Composite Materials for Nuclear and Hazardous Waste Immobilisation
Authors: Ojovan Michael I. , Juoi Jariah M. , Boccaccini Aldo R. , Lee William E.
Published: April 2011

Glass composite materials (GCM) are versatile wasteforms for immobilising various types of both radioactive and hazardous wastes. We review current research on the utilisation of GCMs for hazardous and radioactive waste immobilisation. Compared to homogeneous glassy materials GCMs can incorporate larger amounts of waste elements and, in the case of glass matrix composites, they can be produced using lower processing temperatures (by viscous flow sintering) than those of conventional melting.
Waste Loading of Actinide Chloride Surrogates in an Iron Phosphate Glass
Authors: Schofield James M. , Bingham Paul A. , Hand Russell J.
Published: April 2011

Pyrochemical and aqueous processing of impure Pu metal and Pu oxide results in a waste stream that contains calcium, plutonium and americium chlorides (CaCl2, PuCl3 and AmCll3) that tend to form insoluble salt layers on top of melts during vitrification. By adding chlorides to ammonium dihydrogen phosphate, ammonium chloride is evolved during vitrification, leaving behind the Ca, Pu and Am cations as oxides. HfO2 and Sm2O3 were used as surrogates for PuO2 and Am2O3 respectively. The effects of waste loading and melt duration on some basic physical properties for different melt durations were investigated. Synthetic batches containing CaO, HfO2 and Sm2O3 in molar ratios 93.34 : 5.91 : 0.74 respectively, reflecting the waste composition, were mixed with a fixed glass composition of P2O5 (75 mol%) and Fe2O3 (25 mol%). NH4H2PO4 was used as a precursor material. The solubility of calcium, hafnium and samarium oxides into phosphate glasses is reported and elemental analysis of the glasses is compared with expected glass compositions.
Mechanistic Investigation of Internal Corrosion in Nuclear Waste Containers Over Extended Time Periods
Authors: Onumonu Elsie , Stevens Dr Nicholas P.C.
Published: April 2011

Storage of the UK's Intermediate Level Wastes (ILW), which comprises Magnox fuel cladding, uranium and small items of equipment exposed to radiation, is currently achieved via encapsulation within cementitious grout housed in 500 litre 316L stainless steel drums. The cements used display a high pH; in such an environment many metals form surface hydroxides or oxides. Magnox reacts with free water at high pH with the liberation of hydrogen whilst undergoing corrosion to form hydroxide species.

Corrosion of Magnox cladding has previously been monitored by measuring the rate of hydrogen evolution and/or weight loss. Recent work by our group has shown impedance techniques may also be useful in monitoring early corrosion behaviour. In this project electrochemical polarisation techniques will be employed to examine the corrosion behaviour of Magnox fuel in situations where it is in electrical contact with other metals, including uranium, and hence determine how galvanic effects influence corrosion behaviour. In this paper we describe the background to such experiments along with some preliminary results.
Effect of Gallium Oxide on Phase Assemblage in Apatite and Whitlockite Hosts for Waste Immobilization
Authors: Gerrard Lee. A. , Fong Shirley. K. , Metcalfe Brian. L. , Donald Ian. W.
Published: April 2011

To immobilize halide and actinide ions present in specific ILW waste a process has been developed that uses mineral phases as the host material. The mechanism of substitution of gallium into these phases will have a large effect on the phase assemblage. This will inevitably affect the total amount of halide that can be immobilized in to total phase mixture.

The full simulated waste stream composition containing varying concentrations (1–40 wt.%) of gallium oxide was studied. Also nominal compositions for gallium doped fluorapatites (Ca10-1.5xGax)F2(PO4)6 (x = 0, 0.25, 0.5, 0.75, 1.0) and gallium doped whitlockites Ca9Gay(PO4)6+y (x = 0.2, 0.4, 0.6, 0.8, 1.0) were prepared at 750–1050 °C.

These were studied by powder x-ray diffraction (XRD) to determine the phase assemblage and solid solution limits of gallium in the apatite and whitlockite phases. It was found that a complete solid solution was formed between whitlockite, Ca3(PO4)2, and Ca9Gay(PO4)6+y. In the nominal apatite compositions it was found that gallium did not substitute into the apatite structure but was instead partitioned over Ca9Gay(PO4)6+y, gallium phosphate, and unreacted gallium oxide. At higher temperatures gallium suppressed the formation of the apatite phase and was largely partitioned into the Ca9Gay(PO4)6+y phase whereas at lower temperature the majority was present as unreacted Ga2O3. In the full DCHP compositions it was found that gallium is likely to be partitioned over a number of phases including apatite, cationdoped whitlockite and gallium phosphate.
Alpha-Decay Damage in Murataite-Based Ceramics
Authors: Stefanovsky S.V. , Lukinykh A.N. , Tomilin S.V. , Lizin A.A. , Yudintsev S.V.
Published: April 2011

Samples of murataite ceramics with the composition (wt.%) 3.8 Al2O3, 10.5 CaO, 54.0 TiO2, 10.6 MnO, 6.0 Fe2O3, 4.6 ZrO2, 8.1 ThO2, 2.4 Cm2O3 (1.8 244Cm) and a specific activity of 5.5×1010 Bq/g were prepared by cold pressing and sintering at 1250 °C for 24 hrs or by melting and recrystallisation in a resistive furnace at 1325 °C and 1350 °C for 1 hr. In the sintered ceramics murataite polytypes with five-fold (5C) or three-fold (3C) repeats of the fluorite unit cell and crichtonite were found to be the major phases. Perovskite, pseudobrookite, and pyrochlore were observed as minor phases. The 5C polytype was rendered X-ray amorphous at a cumulative dose of 2.73×1018 μ–decays/g (0.21 dpa) whilst the 3C polytype, which contained only traces of Cm, remains crystalline at this dose. In the melted ceramics the 5C and 8C murataite polytypes were found to be the major phases (80–90 % of the bulk) and minor amounts of rutile, crichtonite and perovskite were also observed. Complete amorphization of the murataite polytypes in the ceramics melted at 1325 and 1350 °C was achieved at doses of 2.46×1018 μ-decays/g (0.19 dpa) and 2.53×1018 μ-decays/g (0.20 dpa), respectively.
The Use of Surrogates in Waste Immobilization Studies: A Case Study of Plutonium
Authors: Bingham Paul A. , Hand Russell J. , Stennett Martin C. , Hyatt Neil C. , Harrison Mike T.
Published: April 2011

Surrogates are widely used in the research and development of nuclear wasteforms, providing detailed insight into the chemical and physical behaviour of the wasteform whilst avoiding the widespread (restricted and costly) use of radiotoxic elements in the laboratory. However, caution must be exercised when dealing with surrogates since no single element or compound perfectly mimics all aspects of the behaviour of another. In this paper we present a broad discussion of the use of surrogates in waste immobilization, drawing upon and highlighting our research into glass and ceramic wasteforms for the immobilization of bulk PuO2.
Durability of Borosilicate Glass Compositions for the Immobilisation of the UK's Separated Plutonium Stocks
Authors: Harrison Mike T. , Scales Charlie R.
Published: April 2011

Several glass compositions are currently under investigation for immobilisation of the separated PuO2 that has been produced as a result of civil nuclear fuel reprocessing in the UK. Whilst a final decision on the fate of what ultimately will be over 100 tonnes of plutonium has yet to be made, all options for the disposition of this material are currently being investigated by Nexia Solutions Ltd on behalf of the Nuclear Decommissioning Authority (NDA).

As one of the immobilisation options, vitrification in borosilicate glass could potentially provide a criticality-safe and stable waste form with durability suitable for long term storage and subsequent repository disposal. From an initial experimental survey of potential candidates, three borosilicate compositions were selected for a more detailed study of the waste loading and chemical durability: lanthanide borosilicate (LaBS), alkali tin silicate (ATS) and high-lanthanide alkali borosilicate (modified-MW). In these inactive tests, hafnium was used as the surrogate for plutonium. This paper describes a range of static leach tests that were undertaken in order to understand the overall durability of the waste forms, as well as the release rates of the Pusurrogate when compared to any neutrons poisons present in the glass. For the LaBS compositions it was found that the release rate of gadolinium was potentially slightly higher than that of hafnium, although both were as low as 10-5 to 10-6 g m2 day-1. The potential implications for long-term repository behaviour are discussed.
Waste Package Corrosion Studies Using Small Mockup Experiments
Authors: Anderson B.E. , Helean K.B. , Bryan C.R. , Brady P.V. , Ewing R.C.
Published: April 2011

Understanding the corrosion of spent nuclear fuel (SNF) and the subsequent mobilization of released radionuclides, particularly under oxidizing conditions, is one of the key issues in evaluating the long-term performance of a nuclear waste repository. However, the large amounts of iron in the metal waste package may create locally reducing conditions that would lower corrosion rates for the SNF, as well as reduce the solubility of some key radionuclides, e.g., Tc and Np. In order to investigate the interactions among SNF-waste package-fluids, four smallscale (∼1:40 by length) waste package mockups were constructed using metals similar to those proposed for use in waste packages at the proposed repository at Yucca Mountain. Each mockup experiment differed with respect to water input, exposure to the atmosphere, and temperature. Simulated Yucca Mountain process water (YMPW) was injected into three of the mockups at a rate of 200 μL per day for five days a week using a calibrated needle syringe. The YMPW was prepared by equilibrating 50 mg/L silica as sodium metasilicate with air, and adding enough HCl to lower the pH to 7.6 in contact with an excess of powdered calcite.

X-ray powder diffraction and scanning electron microscopy confirm that, where corrosion occurred, the dominant corrosion product in all cases was magnetite. In the high temperature (60°C) experiment, hematite and a fibrous, Fe-O-Cl phase were also identified. The Fe(II)/Fe(III) ratios measured in the corrosion products using a wet chemistry technique indicate extremely low oxygen fugacities (10-36 bar). Experiments are in progress in which 0.1g powdered UO2 was included in the mock-up in order to investigate the relative kinetics of Fe and U oxidation and to identify the U corrosion products formed under these conditions.
A New Method for Real-Time Monitoring of Grout Spread Through Fractured Rocks
Authors: Henderson Alasdair E. , Robertson Iain A. , Whitfield John M , Garrard Graham F.G. , Swannell Nicholas G. , Fisch Hansruedi
Published: April 2011

Reducing water ingress into the Shaft at Dounreay is essential for the success of future intermediate level waste (ILW) recovery using the dry retrieval method. The reduction is being realised by forming an engineered barrier of ultrafine cementitious grout injected into the fractured rock surrounding the Shaft. Grout penetration of 6m in <50μm fractures is being reliably achieved, with a pattern of repeated injections ultimately reducing rock mass permeability by up to three orders of magnitude.

An extensive field trials period, involving over 200 grout mix designs and the construction of a full scale demonstration barrier, has yielded several new field techniques that improve the quality and reliability of cementitious grout injection for engineered barriers.

In particular, a new method has been developed for tracking in real-time the spread of ultrafine cementitious grout through fractured rock and relating the injection characteristics to barrier design. Fieldwork by the multi-disciplinary international team included developing the injection and real-time monitoring techniques, pre- and post injection hydro-geological testing to quantify the magnitude and extent of changes in rock mass permeability, and correlation of grout spread with injection parameters to inform the main works grouting programme.