bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Molecular Dynamics Study of Short Nanoparticle Chains under Mechanical Strain: Linear and Kinked Configurations
Authors: Dalis Adamos , Friedlander Sheldon K. 
Published: April 2011

AbstractPrevious studies in our laboratory have shown that individual nanoparticle chain aggregates (NCA) exhibit remarkable mechanical behavior when under strain inside the transmission electron microscope. NCA made of various materials (e.g. carbon, metal oxides, metals, etc.) were strained by as much as 100% when tension was applied to them. After breaking, the NCA rapidly contracted to form more compact structures. In this study, molecular dynamics (MD) computer simulations are employed to investigate, at the atomic scale, the behavior of short nanoparticle chains under strain and to obtain quantitative information of the forces involved in chain straining and fracturing. The interaction potential used is that of copper obtained with the embedded atom method (EAM). Although the methodology is generally applicable, copper was selected as a test material because reliable interatomic potentials are available. Seven single- crystal nanoparticles, each 2.452 nm in diameter, are placed in contact in two chain configurations, linear and kinked. The structures are initially relaxed adiabatically with MD steps for 225 ps, at a starting temperature of 300 K. The bonding energy between any two nanoparticles in contact ranges from about 20 eV to 30 eV at 0 K. The two relaxed chain configurations are strained along their longest dimension, to the breaking point, at strain rates spanning from 0.3 m/s to 10 m/s. We identify mechanisms of stress accommodation that lead to plastic deformation and eventually fracture for both chain configurations, linear and kinked, and we construct the corresponding stress-strain curves. The two chain configurations exhibit different mechanical behavior. Applications of our experimental and simulation studies on NCA are to the behavior of nanocomposite materials, including carbon black reinforced rubber, sampling of aggregates by high speed impactors and the formation of flexible coatings of nanoparticles.
Nanoscale Structure and High Velocity Sliding at Cu/Ag Interfaces
Authors: Hammerberg James E. , Germann Timothy C. , Holian Brad Lee , Ravelo Ramon 
Published: April 2011

AbstractWe present the results of large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations for Cu/Ag interfaces sliding in the velocity regime 0≤v≤1Km/sec. System sizes of 2.8 × 106 atoms are considered using Embedded Atom Method (EAM) potentials. Single crystals with 010 interfaces sliding along the <100> direction are considered. We discuss the observed velocity weakening in the tangential force at high velocities, and its connection with the observed dislocation structure and nanostructure that are nucleated during dry sliding.
Improved Fracture Toughness in Advanced Nanocrystalline Ceramic Composites
Authors: Kuntz Joshua D. , Zhan Guo-Dong , Mukherjee Amiya K. 
Published: April 2011

AbstractNanocrystalline materials have demonstrated very interesting changes in physical, chemical and mechanical properties at severely diminished length scales. This article focuses on the topic of nanocrystalline ceramic composites specifically designed for applications requiring improved fracture toughness. The difficulty in producing fully consolidated ceramic composites that retain a nanocrystalline structure is the main hurdle for thorough investigations in this area. This obstacle has been overcome in the current investigation through the use of a fast, comparably lower temperature, sintering technique e.g., Spark Plasma Sintering. Alumina based nanocomposites incorporating carbon nanotubes and additionally incorporating nanocrystalline niobium have yielded fracture toughness values that have exceeded that for pure nanocrystalline alumina by more that 300%. This introduces the question of whether this improvement is merely additive or evidence of a synergistic toughening mechanism involving ductile phase and fiber toughening.
Analysis of Residual Stress and Damage Durability with Thermal Fatigue Behavior in Thermal Barrier Coatings
Authors: Park Dong-Ho , Jang Hyung-Jun , Jung Yeon-Gil , Chang Jung-Chel , Paik Ungyu 
Published: April 2011

AbstractStatic thermal fatigue tests for thermal barrier coatings (TBCs) were conducted to observe effects of temperature and holding time on its mechanical properties, hardness and modulus, and damage durability. For which three TBCs samples with different thickness in bonding layer (0.08, 0.14, and 0.28 mm) were prepared using an air plasma spraying (APS) method. Temperature of 950 and 1100°C and holding time of 10 and 100 hr were selected for the thermal fatigue tests. The TBCs with thin bonding layer (0.08 mm) maintain sound condition for all the thermal fatigue tests, even showing an evidence of cracking at the interface between coating and bonding layers. However, the TBCs with intermediate (0.14 mm) and thick (0.28 mm) bonding layers show delamination at interface and fracture of coating layer after the thermal fatigue tests at 1100°C for 100 hr. Thermal growth oxide (TGO) layer is created at the interface between coating and bonding layers in all the TBCs after the thermal fatigue tests, and the TGO layer thickness is mainly affected by temperature. Modulus and hardness of coating layer are increased with an increase of temperature in the thermal fatigue tests, due to the re-sintering of coating layer during the thermal fatigue tests. Effects of bonding layer thickness and thermal fatigue condition on mechanical properties, residual stresses, damage durability of the TBCs are discussed extensively.
Analysis of a one-billion atom simulation of work-hardening in ductile materials
Authors: Buehler Markus J. , Hartmaier Alexander , Duchaineau Mark , Abraham Farid F. , Gao Huajian 
Published: April 2011

AbstractWe analyze a large-scale molecular dynamics simulation of work hardening in a ductile model material comprising of 500 million atoms interacting with a Lennard-Jones pair potential within a classical molecular dynamics scheme. With tensile loading, we observe emission of thousands of dislocations from two sharp cracks. The dislocations interact in a complex way, revealing three fundamental mechanisms of work-hardening. These are (1) dislocation cutting processes, jog formation and generation of point defects; (2) activation of secondary slip systems by cross-slip; and (3) formation of sessile Lomer-Cottrell locks. The dislocations self-organize into a complex sessile defect topology. Our analysis illustrates mechanisms formerly only known from textbooks and observed indirectly in experiment. It is the first time that such a rich set of fundamental phenomena has been seen in a single computer simulation.
Application of Composite Technology for SOFCs
Authors: Petrovsky Vladimir , Anderson Harlan U. , Petrovsky Tatiana 
Published: April 2011

AbstractComposite technology is a new approach to solid oxide fuel cell (SOFC) fabrication. It is based on the net shape processing, which uses a combination of colloidal suspension and polymer precursor techniques. Different elements of SOFC can be prepared and optimized using this approach and the flexibility of the net shape processing. The goal of this research was to develop net shape procedures for different elements of SOFC, to show the real possibility preparing all these elements of SOFC and to investigate the advantages of composite technology. A nickel-YSZ composite was prepared and investigated as the prospective anode material. High electronic conductivity and stability in REDOX cycles were shown for this material. Different cathode compositions were prepared using composite technology and tested. It was shown, that these materials ensure low overpotentials and are time stable at operation temperature up to 800°C. All three SOFC designs were tested: anode, cathode and electrolyte supported SOFCs. It was possible to achieve low resistance of SOFC structure for all designs, but electrode supported SOFCs had limitation in the current connected with the gas diffusion through thick electrode substrates. The best performance was achieved on an electrolyte supported system with 100 [.proportional]m YSZ electrolyte and composite anode and cathode: 0.75W/cm2 power density at 0.6 V at 800°C.
Directed Osteoblast Adhesion at Particle Boundaries: Promises for Nanophase Metals
Authors: Perla Venu , Ejiofor Jeremiah U. , Webster Thomas J. 
Published: April 2011

AbstractIn spite of under performance, metals and metal alloys are currently being used in orthopedic implantable devices. Poor osseointegration, severe stress shielding, bone cell death and eventual necrotic bone resulting from the generation of wear debris are known to be some of the reasons responsible for their under performance. In addition, metallic corrosion products may also initiate cancer. Steady growth in the use of metals in orthopedic applications inspired researchers to deal with these problems in an integrated way. When conventional Ti, Ti6Al4V, and CoCrMo surfaces were modified to the nano-range, this study showed increased percentages of osteoblast (bone forming cell) adhesion on nanophase metals. Moreover, larger amounts of osteoblast adhesion was related to quantitative increases in the total length of particle boundaries per unit area and the total number of pores between surface particles per unit area, and the surface particle boundary index (SPBI) of nanophase metals. Additionally, we have developed a novel anticarcinogenic orthopedic metalloid, selenium (Se). When micron range surface particles of Se compacts were modified to the nano-range by chemical etching, we found positive relationships between directed osteoblast adhesion and various particle boundary parameters mentioned above under in vitro conditions. These results provided the first evidence to utilize nanosurface Se as an anticarcinogenic and bio-inspiring material for future applications in orthopedic metallic devices.
Block Copolymer-Based Biomembranes Functionalized with Energy Transduction Proteins
Authors: Ho Dean , Chu Benjamin , Lee Hyeseung , Kuo Karen , Montemagno Carlo D. 
Published: April 2011

AbstractBlock copolymer-based membranes can be functionalized with energy transducing proteins to reveal a versatile family of nanoscale materials. Our work has demonstrated the fabrication of protein-functionalized ABA triblock copolymer nanovesicles that possess a broad applicability towards areas like biosensing and energy production. ABA triblock copolymers possess certain advantages over lipid systems. For example, they can mimic biomembrane environments necessary for membrane protein refolding in a single chain (hydrophilic(A)- hydrophobic(B)-hydrophilic(A)), enabling large-area membrane fabrication using methods like Langmuir-Blodgett (LB) deposition. Furthermore, the robustness of the polymer molecules/structure result in spontaneous and rapid protein-functionalized nano-vesicle formation that retains structure as well as protein functionality for up to several months, compared to one to two weeks for the lipid systems (e.g. POPC). The membrane protein, Bacteriorhodopsin (BR), found in Halobacterium Halobium, is a light-actuated proton pump that develops gradients towards the demonstration of coupled functionality with other membrane proteins, such as the production of electricity through Bacteriorhodopsin activity-dependent reversal of Cytochrome C Oxidase (COX), found in Rhodobacter Sphaeroides. Protein-functionalized materials have the exciting potential of serving as the core technology behind a series of fieldable devices that are driven completely by biomolecules.
Stable, Nanoscale Glycosphingolipid Films for Use in Sensing Applications
Authors: Stine Rory , Schengrund Cara-Lynne , Pishko Michael V. 
Published: April 2011

AbstractWe have developed a means of producing thin, oriented lipid monolayers which are stable under repeated washing and which may be useful in biosensing or surface- coating applications. Phosphotidylcholine (PC) and the glycosphingolipid (GSL) GM1 were used as representative lipids for this process. Initially, a mixed self-assembled monolayer of octanethiol and hexadecanethiol was constructed on a clean gold surface. This hydrophobic surface was then brought into contact with a thin lipid layer that had been deposited at the air/liquid interface of a solution by evaporating a mixture of lipid in hexane on top of a layer of water. The lipid layer, now deposited on the gold surface, was then heated to cause intercalation of the fatty acid and alkanethiol chains, and cooled to form a highly stable film which withstood repeated rinsing and solution exposure. Presence and stability of the film was confirmed via ellipsometry, FTIR, and QCM, with an average overall thickness of ∼3.5 nm. These films may be potentially useful in biotoxin detection or as a protein resistant layer for the prevention of biofouling.
In Vitro and In Vivo Tests Of Hydroxyapatite-Gleatin Nanocomposites For Bone Regeneration: A Preliminary Report.
Authors: Cc Ko , Y-L Wu , Wh Douglas , R Narayanan , W-S Hu 
Published: April 2011

AbstractA biomimetic process has been developed to fabricate hydroxyapatite-gelatin (HAP-GEL) nanocomposites for bone regeneration (Chang and Ko et al. 2003). We hypothesize that this newly developed HAP-GEL is osteoconductive and is suitable for tissue engineered scaffolds. This preliminary study is aimed to characterize cell affinity and osseous regeneration of the HAP-GEL. The HAP-GEL was synthesized according to the procedures described in the previous publication. The attachment and proliferation of human fetal osteoblasts on HAP-GEL discs were evaluated using three different gelatin contents (2g, 3g, and 4g). The cells were seeded onto each disc and incubated at 34 degrees Celsius in 5% CO2 air atmosphere. At different time points of cultivation, cells were stained with fluorescein diacetate (FDA) and ethidium bromide (EB) to determine their viability and morphology. To assess the cell proliferation, cells were detached at Days 1, 4, and 7 by trypsinzation and counted. For in vivo tests, HAP-GEL rods were implanted into the proximal femur of Sprague-Dawley rats. One month after the implantation, the femurs were harvested and the undecalcified HAP-GEL-bone sections were stained for histopathology. Four hours after attachment, most cells appeared round in all discs; cell spreading was observed after 24 hours. The highest gelatin content supported a significantly higher cell growth than the others at 7 days. Thus all compositions support satisfactory attachment, spreading and growth. In vivo results showed excellent interfacial bone regeneration. No necrotic tissues were found. In conclusion, the HAP-GEL not only mimics the biochemistry and nanostructures of bone but also supports the attachment, proliferation and differentiation (bone formation) of osteoblasts. The HAP-GEL we developed provides a suitable surface for regeneration.
In Situ Polypeptide Directed Silica Biomineralization
Authors: Glawe Diana D. , RodrÍguez Francisco , Stone Morley O. , Naik Rajesh R. 
Published: April 2011

AbstractSilica-precipitating polypeptides were deposited onto an indium tin oxide (ITO) surface from bulk solution with and without the assistance of an externally applied electrostatic field. Exposure of the peptide-coated surface to an alkoxide precursor produced biosilica structures that were securely attached to the electrode surface. The silica morphologies resulting from the test cases using an externally applied electrostatic field during peptide deposition were distinct from the morphologies resulting from cases without an applied field. The silica morphologies observed on the ITO surface were different from the usual silica morphology resulting from static conditions. Peptide size was also shown to influence resulting biosilica morphology. The experimental results presented herein demonstrate the feasibility of creating biosilica nanostructures with controlled morphologies using polypeptides in vitro.
Microtubule Templated Synthesis of Inorganic Nanomaterials
Authors: Boal Andrew K. , Headley Thomas J. , Tissot Ralph G. , Bunker Bruce C. 
Published: April 2011

AbstractProtein microtubules (MTs) have been used as templates for the biomimetic synthesis of metal oxide, metal sulfide, and metallic nanomaterials. These materials were coated onto MTs via three distinct synthetic pathways: metal ion hydrolysis which yielded iron oxide or zinc oxide-coated microtubules, metal ion/sulfide co-precipitation which yielded zinc sulfide coated MTs, and metal ion reduction which yielded gold-coated MTs. The growth process of metal oxide coating involves heterogeneous nucleation on the MT surface and produces even, microcrystalline films. Metal sulfide and metal coating initially involves the formation of nanoparticle arrays that decorate the MT surface and can eventually lead to either semi- or fully continuous coatings.
Cyclodextrins Stabilize TOPO-(CdSe)ZnS Quantum Dots In Water
Authors: Feng Jun , Kim Yong-Hyun , Zhang S. B. , Ding Shi-You , Tucker Melvin P. , Rumbles Garry , Himmel Michael E. 
Published: April 2011

AbstractChemical action between cyclodextrins (CDs) and TOPO-(CdSe)ZnS quantum dots (QDs) generates a water-soluble solution of CD-QDs. Hydrophobic TOPO molecules on surface of the QDs are compatible to thread through the pockets of CDs and make the hydroxyl group on end of CDs to approach the ZnS surface, and then cause the interaction between ZnS and the hydroxyls. In this paper, Photoluminescence of the γ-CD-QD solution appeared about 15 nm of red movement compared with that of the QDs in hexane; 58% replacement of the crystal coordinate bond of Zn-S with that of Zn-O in the ZnS shell was demonstrated by using first-principles density functional theory and the red shift of the photoluminescence of CD-QDs; and –0.11eV of the energy gain of the exchange model was calculated by using an effective mass (EM) model. CD-QDs will provide water-soluble QDs with conjugational group for biology and molecule-device applications.
Impact of Hydrogen Overpressure on Spent Fuel Alteration Behavior in Salt Brine During a Three-Year Long Corrosion Test
Authors: Loida Andreas , Metz Volker , Kienzler Bernhard , Geckeis Horst 
Published: April 2011

AbstractThe corrosion of the Fe-based spent fuel containing canister produces large amounts of hydrogen, which dominate the composition of the gas phase. To quantify to what extent the hydrogen over- pressure may counteract radiolysis enhanced matrix dissolution, related experimental work has been performed. High burnup spent fuel was corroded in 5 M NaCl solution in different tests: (1) Fe ab-sence (<0.16 bar H2 overpressure), (2) Fe presence (2.8 bar H2 overpressure), (3) Fe absence, external applied H2 overpressure of 3.2 bar. In the absence of Fe, after the application of H2 overpressure the UO2 matrix dissolution rate decreased by a factor of about 10. The concentrations of U, Np, Tc in so- lution were found to be decreasing at least two orders, and ranging within the same level as in the presence of Fe powder. However, Pu and Am concentrations were less affected, due to the absence of Fe powder and the associated high sorption capacity for these radioelements.
Site Decommissioning of AECL Whiteshell Laboratories
Authors: Koroll Grant W. 
Published: April 2011

AbstractAECL Whiteshell Laboratories (WL), near Winnipeg, Canada has been in operation since the early 1960s. R&D programs carried out at WL include a 60 MW organic-cooled research reactor, which operated from 1965 to 1985, reactor safety research, small reactor development, materials science, post irradiation examinations, chemistry, biophysics and radiation applications. The Canadian Nuclear Fuel Waste Management Program was conducted and continues to operate at WL and also at the nearby Underground Research Laboratory.In the late-1990s, AECL began to consolidate research and development activities at its Chalk River Laboratories (CRL) and began preparations for decommissioning WL. Preparations for decommissioning included a staged shutdown of operations, planning documentation and licensing for decommissioning. As a prerequisite to AECL's application for a decommissioning licence, an environmental assessment (EA) was carried out according to Canadian environmental assessment legislation. The EA concluded in 2002 April when the Federal Environment Minister published his decision that WL decommissioning was not likely to cause significant adverse environmental effects and that no further assessment by a review panel or mediation would be requiredIn 2002 December, the Canadian Nuclear Safety Commission issued a decommissioning licence for WL, valid until December 31, 2008. The licence authorized the first planned phase of site decommissioning as well as the continuation of selected research programs. The six-year licence for Whiteshell Laboratories was the first overall decommissioning license issued for a Canadian Nuclear Research and Test Establishment and was the longest licence term ever granted for a nuclear installation of this complexity in Canada.The first phase of decommissioning is now underway and focuses on decontamination and modifications to nuclear facilities, such as the shielded facilities, the main R&D laboratories and the associated service systems, to achieve a safe state of storage-with-surveillance. Later phases have planned waste management improvements for selected wastes already in storage, eventually followed by final decommissioning of facilities and infrastructure and removal of most wastes from the site.This paper provides an overview of the planning, environmental assessment, licensing, and organizational processes for decommissioning and selected descriptions of decommissioning activities currently underway at AECL Whiteshell Laboratories.
In-Situ Diffusion Experiment In Sparsely Fractured Granite
Authors: Vilks Peter , Miller Neil H. , Jensen Mark 
Published: April 2011

AbstractThe in-situ diffusion experiment was conducted at AECL's Underground Research Laboratory (URL) to improve the understanding of diffusive solute transport in sparsely fractured or intact granitic rock (SFR). The experimental program used a comparative series of laboratory and in-situ field experiments to evaluate the ability of laboratory measurements to estimate in-situ rock properties and to explore issues surrounding the influence of stress relaxation, rock texture, porosity, pore geometry, and anisotropy on derived effective diffusion coefficients (De). In-situ experiments yielded iodide Debetween 1.4 × 10−13 and 1.1 × 10−12 m2/s. Unlike laboratory results, the in-situ De estimates did not exhibit correlation with sample depth or varied stress regime. Laboratory-derived measurements of De, porosity and permeability were found to systematically increase for samples removed from greater depths and higher stress regimes. Laboratory-derived iodide De values consistently trended higher than in-situ values by a factor of 1 to 15, except on the shallowest 240-m Level (σ1 ≍ 30 MPa) where differences were negligible. Laboratory-derived estimates of permeability were consistently higher than in-situ derived values by a factor of 2 to 100. This experimental program provides evidence that laboratory steady-state diffusion experiments are most likely to yield conservative values of De for simulation of diffusive mass transport in SFR.