High-temperature fcc phase of Pr:  Negative thermal expansion and intermediate valence state

NASA Astrophysics Data System (ADS)

Kuznetsov, A. Yu.; Dmitriev, V. P.; Bandilet, O. I.; Weber, H.-P.

2003-08-01

A high-temperature angle-dispersive synchrotron radiation diffraction study has revealed the double hexagonal-close-packed-to-face-centered-cubic (dhcp-to-fcc) transformation in the Pr metal occurring martensitically between 575 and 1035 K. The high-temperature fcc phase shows a negative thermal expansion in the range 600 800 K, attributed to the 4f-electron delocalization. A phenomenological theory is developed, which explains consistently the observed effect in terms of the mean valence variation of the metal as a function of temperature; it also predicts the existence of an isostructural phase transition and of a critical end point of a gas-liquid type in compressed Pr. The analysis of published data on P-T variation of conductivity of Pr supports this prediction.

Analysis of fcc metals fracture behaviour: Fracture behaviour of fcc metals: brittle/ductile behaviour criteria : with ab-initio, embedded atom and pseudopotential parameterization for Au, Ir and Al. analysis for Au, Ir and Al.

NASA Astrophysics Data System (ADS)

Gornostyrev, Yu. N.; Katsnelson, M. I.; Mryasov, Oleg N.; Freeman, A. J.; Trefilov, M. V.

1998-03-01

Theoretical analysis of the fracture behaviour of fcc Au, Ir and Al have been performed within various brittle/ductile criteria (BDC) with ab-initio, embedded atom (EAM), and pseudopotential parameterizations. We systematically examined several important aspects of the fracture behaviour: (i) dislocation structure, (ii) energetics of the cleavage decohesion and (iii) character of the interatomic interactions. Unit dislocation structures were analyzed within a two dimensional generalization of the Peierls-Nabarro model with restoring forces determined from ab-initio total energy calculations and found to be split with well defined highly mobile partials for all considered metals. We find from ab-initio and pseudopotential that in contrast with most of fcc metals, cleavage decohesion curve for Al appreciably differs from UBER relation. Finally, using ab-initio, EAM and pseudopotential parameterizations, we demonstrate that (i) Au (as a typical example of a ductile metal) is well described within existing BDC's, (ii) anomalous cleavage-like crack propagation of Ir is driven predominantly by it's high elastic modulus and (iii) Al is not described within BDC due to it's long-range interatomic interactions (and hence requires adjustments of the brittle/ductile criteria).

Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

PubMed

Lee, Stephen; Hoffmann, Roald

2002-05-01

Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.

FCC-HCP coexistence in dense thermo-responsive microgel crystals

NASA Astrophysics Data System (ADS)

Karthickeyan, D.; Joshi, R. G.; Tata, B. V. R.

2017-06-01

Analogous to hard-sphere suspensions, monodisperse thermo-responsive poly (N-isopropyl acrylamide) (PNIPAM) microgel particles beyond a volume fraction (ϕ) of 0.5 freeze into face centered cubic (FCC)-hexagonal close packed (HCP) coexistence under as prepared conditions and into an FCC structure upon annealing. We report here FCC-HCP coexistence to be stable in dense PNIPAM microgel crystals (ϕ > 0.74) with particles in their deswollen state (referred to as osmotically compressed microgel crystals) and the FCC structure with particles in their swollen state by performing annealing studies with different cooling rates. The structure of PNIPAM microgel crystals is characterized using static light scattering technique and UV-Visible spectroscopy and dynamics by dynamic light scattering (DLS). DLS studies reveal that the particle motion is diffusive at short times in crystals with ϕ < 0.74 and sub-diffusive at short times in PNIPAM crystals with ϕ > 0.74. The observed sub-diffusive behavior at short times is due to the overlap (interpenetration) of the dangling polymer chains between the shells of neighbouring PNIPAM microgel particles. Overlap is found to disappear upon heating the crystals well above their melting temperature, Tm due to reduction in the particle size. Annealing studies confirm that the overlap of dangling polymer chains between the shells of neighbouring PNIPAM spheres is responsible for the stability of FCC-HCP coexistence observed in osmotically compressed PNIPAM microgel crystals. Results are discussed in the light of recent reports of stabilizing the HCP structure in hard sphere crystals by adding interacting polymer chains.

Current advances in precious metal core-shell catalyst design.

PubMed

Wang, Xiaohong; He, Beibei; Hu, Zhiyu; Zeng, Zhigang; Han, Sheng

2014-08-01

Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core-shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core-shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core-shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core-shell nanoparticles in this paper. The current research trends of these core-shell catalysts are also highlighted.

Floating stacking faults on the (111) surface of FCC metals: a finite-temperature first-principles study

NASA Astrophysics Data System (ADS)

Rechtsman, Mikael; de Gironcoli, Stefano; Ceder, Gerbrand; Marzari, Nicola

2003-03-01

The (111) surfaces of FCC metals can develop anomalous thermal expansion properties at high temperatures (e.g. for the case of Ag(111)), and display floating stacking faults during homoepitaxial growth in the presence of surfactants. Inspired by the results of high-temperature ensemble-DFT molecular dynamics simulations, we investigate here the relative stability of FCC and HCP stacking in simple and transition metals (Al, Ag, Zn), searching for a structural phase transition taking place at the surface layer in the high-temperature regime. We use a combination of total-energy structural relaxations and linear-response perturbation theory to determine the surface phonon dispersions, and then the relative free energies in the quasi-harmonic approximation. Our results in Al show that the vibrational entropy strongly favors HCP stacking, substantially offsetting the energetic cost of the stacking fault that becomes favored close to the melting temperature. Besides its fundamental interest, HCP phonon softening is relevant in determining the relative stability of small islands during homoeptiaxial growth.

Dislocation creation and void nucleation in FCC ductile metals under tensile loading: a general microscopic picture.

PubMed

Pang, Wei-Wei; Zhang, Ping; Zhang, Guang-Cai; Xu, Ai-Guo; Zhao, Xian-Geng

2014-11-10

Numerous theoretical and experimental efforts have been paid to describe and understand the dislocation and void nucleation processes that are fundamental for dynamic fracture modeling of strained metals. To date an essential physical picture on the self-organized atomic collective motions during dislocation creation, as well as the essential mechanisms for the void nucleation obscured by the extreme diversity in structural configurations around the void nucleation core, is still severely lacking in literature. Here, we depict the origin of dislocation creation and void nucleation during uniaxial high strain rate tensile processes in face-centered-cubic (FCC) ductile metals. We find that the dislocations are created through three distinguished stages: (i) Flattened octahedral structures (FOSs) are randomly activated by thermal fluctuations; (ii) The double-layer defect clusters are formed by self-organized stacking of FOSs on the close-packed plane; (iii) The stacking faults are formed and the Shockley partial dislocations are created from the double-layer defect clusters. Whereas, the void nucleation is shown to follow a two-stage description. We demonstrate that our findings on the origin of dislocation creation and void nucleation are universal for a variety of FCC ductile metals with low stacking fault energies.

Adsorption of metal ions by pecan shell-based granular activated carbons.

PubMed

Bansode, R R; Losso, J N; Marshall, W E; Rao, R M; Portier, R J

2003-09-01

The present investigation was undertaken to evaluate the adsorption effectiveness of pecan shell-based granular activated carbons (GACs) in removing metal ions (Cu(2+), Pb(2+), Zn(2+)) commonly found in municipal and industrial wastewater. Pecan shells were activated by phosphoric acid, steam or carbon dioxide activation methods. Metal ion adsorption of shell-based GACs was compared to the metal ion adsorption of a commercial carbon, namely, Calgon's Filtrasorb 200. Adsorption experiments were conducted using solutions containing all three metal ions in order to investigate the competitive effects of the metal ions as would occur in contaminated wastewater. The results obtained from this study showed that acid-activated pecan shell carbon adsorbed more lead ion and zinc ion than any of the other carbons, especially at carbon doses of 0.2-1.0%. However, steam-activated pecan shell carbon adsorbed more copper ion than the other carbons, particularly using carbon doses above 0.2%. In general, Filtrasorb 200 and carbon dioxide-activated pecan shell carbons were poor metal ion adsorbents. The results indicate that acid- and steam-activated pecan shell-based GACs are effective metal ion adsorbents and can potentially replace typical coal-based GACs in treatment of metal contaminated wastewater.

Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation.

PubMed

Zhang, Peili; Li, Lin; Nordlund, Dennis; Chen, Hong; Fan, Lizhou; Zhang, Biaobiao; Sheng, Xia; Daniel, Quentin; Sun, Licheng

2018-01-26

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm -2 . The core-shell NiFeCu electrode exhibits pH-dependent oxygen evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.

Dislocation creation and void nucleation in FCC ductile metals under tensile loading: A general microscopic picture

PubMed Central

Pang, Wei-Wei; Zhang, Ping; Zhang, Guang-Cai; Xu, Ai-Guo; Zhao, Xian-Geng

2014-01-01

Numerous theoretical and experimental efforts have been paid to describe and understand the dislocation and void nucleation processes that are fundamental for dynamic fracture modeling of strained metals. To date an essential physical picture on the self-organized atomic collective motions during dislocation creation, as well as the essential mechanisms for the void nucleation obscured by the extreme diversity in structural configurations around the void nucleation core, is still severely lacking in literature. Here, we depict the origin of dislocation creation and void nucleation during uniaxial high strain rate tensile processes in face-centered-cubic (FCC) ductile metals. We find that the dislocations are created through three distinguished stages: (i) Flattened octahedral structures (FOSs) are randomly activated by thermal fluctuations; (ii) The double-layer defect clusters are formed by self-organized stacking of FOSs on the close-packed plane; (iii) The stacking faults are formed and the Shockley partial dislocations are created from the double-layer defect clusters. Whereas, the void nucleation is shown to follow a two-stage description. We demonstrate that our findings on the origin of dislocation creation and void nucleation are universal for a variety of FCC ductile metals with low stacking fault energies. PMID:25382029

Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Peili; Li, Lin; Nordlund, Dennis

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here in this paper, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm -2. The core-shell NiFeCu electrode exhibits pH-dependent oxygenmore » evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.« less

Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation

DOE PAGES

Zhang, Peili; Li, Lin; Nordlund, Dennis; ...

2018-01-26

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here in this paper, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm -2. The core-shell NiFeCu electrode exhibits pH-dependent oxygenmore » evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.« less

Possible origin of the discrepancy in Peierls stresses of fcc metals: First-principles simulations of dislocation mobility in aluminum

NASA Astrophysics Data System (ADS)

Shin, Ilgyou; Carter, Emily A.

2013-08-01

Dislocation motion governs the strength and ductility of metals, and the Peierls stress (σp) quantifies dislocation mobility. σp measurements carry substantial uncertainty in face-centered cubic (fcc) metals, and σp values can differ by up to two orders of magnitude. We perform first-principles simulations based on orbital-free density functional theory (OFDFT) to calculate the most accurate currently possible σp for the motion of (1)/(2)<110>111 dislocations in fcc Al. We predict the σps of screw and edge dislocations (dissociated in their equilibrium state) to be 1.9×10-4G and 4.9×10-5G, respectively (G is the shear modulus). These values fall within the range of measurements from mechanical deformation tests (10-4-10-5G). OFDFT also finds a new metastable structure for a screw dislocation not seen in earlier simulations, in which a dislocation core on the glide plane does not dissociate into partials. The corresponding σp for this undissociated dislocation is predicted to be 1.1×10-2G, which agrees with typical Bordoni peak measurements (10-2-10-3G). The calculated σps for dissociated and undissociated screw dislocations differ by two orders of magnitude. The presence of undissociated, as well as dissociated, screw dislocations may resolve the decades-long mystery in fcc metals regarding the two orders of magnitude discrepancy in σp measurements.

Formation of fivefold axes in the FCC-metal nanoclusters

NASA Astrophysics Data System (ADS)

Myasnichenko, Vladimir S.; Starostenkov, Mikhail D.

2012-11-01

Formation of atomistic structures of metallic Cu, Au, Ag clusters and bimetallic Cu-Au clusters was studied with the help of molecular dynamics using the many-body tight-binding interatomic potential. The simulation of the crystallization process of clusters with the number of atoms ranging from 300 to 1092 was carried out. The most stable configurations of atoms in the system, corresponding to the minimum of potential energy, was found during super-fast cooling from 1000 K. Atoms corresponding to fcc, hcp, and Ih phases were identified by the method of common neighbor analysis. Incomplete icosahedral core can be discovered at the intersection of one of the Ih axes with the surface of monometallic cluster. The decahedron-shaped structure of bimetallic Cu-Au cluster with seven completed icosahedral cores was obtained. The principles of the construction of small bimetallic clusters with icosahedral symmetry and increased fractal dimensionality were offered.

Temperature dependence of dynamic deformation in FCC metals, aluminum and invar

DOE PAGES

Chen, Laura; Swift, D. C.; Austin, R. A.; ...

2017-01-01

Laser-driven shock experiments were performed on fcc metals, aluminum and invar, at a range of initial temperatures from approximately 120-800 K to explore the effect of initial temperature on dynamic strength properties at strain rates reaching up to 10 7 s -1. In aluminum, velocimetry data demonstrated an increase of peak stress of the elastic wave, σ E, with initial temperature. Alternatively, for invar, σ E exhibits little-to-no decrease over the same initial temperature range. Aluminum’s unusual deformation behavior is found to primarily be due to anharmonic vibrational effects. Differences in the magnetic structure of aluminum and invar can accountmore » for discrepancies in high rate deformation behavior.« less

Synthesis of Multicolor Core/Shell NaLuF4:Yb3+/Ln3+@CaF2 Upconversion Nanocrystals

PubMed Central

Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

2017-01-01

The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF4:Yb3+/Ln3+@CaF2 (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF4). We exploited the liquid-solid-solution method to synthesize the NaLuF4 core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF2) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals. PMID:28336867

A thermally activated dislocation-based constitutive flow model of nanostructured FCC metals involving microstructural evolution

NASA Astrophysics Data System (ADS)

Zhang, J. Y.; Li, J.; Wu, K.; Liu, G.; Sun, J.

2017-03-01

Due to their interface and nanoscale effects associated with structural peculiarities of nanostructured, face-centered-cubic (FCC) ultrafine-grained/nanocrystalline (UFG/NC) metals, in particular nanotwinned (NT) metals exhibit unexpected deformation behaviours fundamentally different from their coarse-grained (CG) counterparts. These internal boundaries, including grain boundaries and twin boundaries in UFG/NC metals, strongly interact with dislocations as deformation barriers to enhance the strength and strain rate sensitivity (SRS) of materials on the one hand, and play critical roles in their microstructural evolution as dislocation sources/sinks to sustain plastic deformation on the other. In this work, building on the findings of twin softening and (de)twinning-mediated grain growth/refinement in stretched free-standing NT-Ni foils, a constitutive model based on the thermally activated depinning process of dislocations residing in boundaries has been proposed to predict the steady-state grain size and simulate the plastic flow of NT-Ni, by considering the blocking effects of nanotwins on the absorption of dislocations emitted from boundaries. It is uncovered that the stress ratio (ηstress) of effective-to-internal stress can be taken as a signature to estimate the stability of microstructures during plastic deformation. This model not only reproduces well the plastic flow of the stretched NT-Ni foils as well as reported NT-Cu and the steady-state grain size, but also sheds light on the size-dependent SRS and failure of FCC UFG/NC metals. This theoretical framework offers the opportunity to tune the microstructures in the polycrystalline materials to synthesise high performance engineering materials with high strength and great ductility.

Tight-binding study of stacking fault energies and the Rice criterion of ductility in the fcc metals

NASA Astrophysics Data System (ADS)

Mehl, Michael J.; Papaconstantopoulos, Dimitrios A.; Kioussis, Nicholas; Herbranson, M.

2000-02-01

We have used the Naval Research Laboratory (NRL) tight-binding (TB) method to calculate the generalized stacking fault energy and the Rice ductility criterion in the fcc metals Al, Cu, Rh, Pd, Ag, Ir, Pt, Au, and Pb. The method works well for all classes of metals, i.e., simple metals, noble metals, and transition metals. We compared our results with full potential linear-muffin-tin orbital and embedded atom method (EAM) calculations, as well as experiment, and found good agreement. This is impressive, since the NRL-TB approach only fits to first-principles full-potential linearized augmented plane-wave equations of state and band structures for cubic systems. Comparable accuracy with EAM potentials can be achieved only by fitting to the stacking fault energy.

Deformation and erosion of f.c.c. metals and alloys under cavitation attack

NASA Technical Reports Server (NTRS)

Rao, B. C. S.; Buckley, D. H.

1984-01-01

Experimental investigations have been conducted to determine the early stages of cavitation attack on 6061-T6 aluminum alloy, electrolytic tough pitch copper, brass, and bronze, all having polycrystalline fcc matrices. The surface profiles and scanning electron micrographs show that the pits are initially formed at the grain boundaries, while the grain surfaces are progressively roughened by multiple slip and twinning. The initial erosion is noted to have occurred from the material in the grain boundaries, as well as by fragmentation of part of the grains. Further erosion occurred by shearing and necking of the surface undulations caused by plastic deformation. The mean penetration depth, computed on the basis of mass loss, was lowest on the bronze and greatest on the copper. Attention is given to the relation of cavitation attack to grain size, glide stress and stacking fault energy.

High-quality metal oxide core/shell nanowire arrays on conductive substrates for electrochemical energy storage.

PubMed

Xia, Xinhui; Tu, Jiangping; Zhang, Yongqi; Wang, Xiuli; Gu, Changdong; Zhao, Xin-Bing; Fan, Hong Jin

2012-06-26

The high performance of a pseudocapacitor electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. We present a powerful two-step solution-based method for the fabrication of transition metal oxide core/shell nanostructure arrays on various conductive substrates. Demonstrated examples include Co(3)O(4) or ZnO nanowire core and NiO nanoflake shells with a hierarchical and porous morphology. The "oriented attachment" and "self-assembly" crystal growth mechanisms are proposed to explain the formation of the NiO nanoflake shell. Supercapacitor electrodes based on the Co(3)O(4)/NiO nanowire arrays on 3D macroporous nickel foam are thoroughly characterized. The electrodes exhibit a high specific capacitance of 853 F/g at 2 A/g after 6000 cycles and an excellent cycling stability, owing to the unique porous core/shell nanowire array architecture, and a rational combination of two electrochemically active materials. Our growth approach offers a new technique for the design and synthesis of transition metal oxide or hydroxide hierarchical nanoarrays that are promising for electrochemical energy storage, catalysis, and gas sensing applications.

Does the 4f-shell contribute to bonding in tetravalent lanthanide halides?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Wen-Xin; School of Chemistry and Chemical Engineering, Ningxia University, 750015 Yinchuan; Xu, Wei

2014-12-28

Lanthanide tetrahalide molecules LnX{sub 4} (Ln = Ce, Pr, Tb; X = F, Cl, Br, I) have been investigated by density functional theory at the levels of the relativistic Zero Order Regular Approximation and the relativistic energy-consistent pseudopotentials, using frozen small- and medium-cores. The calculated bond lengths and vibrational frequencies are close to the experimental data. Our calculations indicate 4f shell contributions to bonding in LnX{sub 4}, in particular for the early lanthanides, which show significant overlap between the Ln 4f-shell and the halogen np-shells. The 4f shells contribute to Ln-X bonding in LnX{sub 4} about one third more thanmore » in LnX{sub 3}.« less

Mussel Shell Evaluation as Bioindicator For Heavy Metals

NASA Astrophysics Data System (ADS)

Andrello, Avacir Casanova; Lopes, Fábio; Galvão, Tiago Dutra

2010-05-01

Recently, in Brazil, it has appeared a new and unusual "plague" in lazer and commercial fishing. It is caused by the parasitic larval phase of certain native bivalve mollusks of fresh water known as "Naiades" and its involves the presence of big bivalve of fresh water, mainly Anodontites trapesialis, in the tanks and dams of the fish creation. These bivalve mollusks belong to the Unionoida Order, Mycetopodidae Family. The objective of the present work was to analyze the shells of these mollusks to verify the possibility of use as bioindicators for heavy metals in freshwater. The mollusks shells were collected in a commercial fishing at Londrina-PR. A qualitative analysis was made to determine the chemical composition of the shells and verify a possible correlation with existent heavy metals in the aquatic environment. In the inner part of the shells were identified the elements Ca, P, Fe, Mn and Sr and in the outer part were identified Ca, P, Fe, Mn, Sr and Cu. The Ca ratio of the outer part by inner part of the analyzed shells is around of 1, as expected, because Ca is the main compound of mollusks shells. The ratio of P, Fe, Mn, and Sr to the Ca were constant in all analyzed shells, being close to 0.015. The ratio Cu/Ca varied among the shells, showing that this mollusk is sensitive to concentration of this element in the aquatic environment.

New mechanisms of cluster diffusion on metal fcc(100) surfaces

NASA Astrophysics Data System (ADS)

Trushin, Oleg; Salo, Petri; Alatalo, Matti; Ala-Nissila, Tapio

2001-03-01

We have studied atomic mechanisms of the diffusion of small clusters on the fcc(100) metal surfaces using semi-empirical and ab-initio molecular static calculations. Primary goal of these studies was to investigate possible many-body mechanisms of cluster motion which can contribute to low temperature crystal growth. We used embedded atom and Glue potentials in semi-empirical simulations of Cu and Al. Combination of the Nudged Elastic Band and Eigenvector Following methods allowed us to find all the possible transition paths for cluster movements on flat terrace. In case of Cu(001) we have found several new mechanisms for diffusion of clusters, including mechanisms called row-shearing and dimer-rotating in which a whole row inside an island moves according to a concerted jump and a dimer rotates at the periphery of an island, respectively. In some cases these mechanisms yield a lower energy barrier than the standard mechanisms.

Glass shell manufacturing in space. [residual gases in spherical shells made from metal-organic gels

NASA Technical Reports Server (NTRS)

Nolen, R. J.; Ebner, M. A.; Downs, R. L.

1980-01-01

Residual gases always found in glass shells are CO2, O2 and N2. In those cases where high water vapor pressure is maintained in the furnace, water is also found in the shells. Other evidence for the existence of water in shells is the presence of water-induced surface weathering of the interior shell surface. Water and CO2 are the predominant volatiles generated by the pyrolysis of both inorganic and hydrolyzed metal-organic gels. The pyrolysates of unhydrolyzed metal-organic gels also contain, in addition to water and CO2, significant levels of organic volatiles, such as ethanol and some hydrocarbons; on complete oxidation, these produce CO2 and water as well. Water is most likely the initial blowing agent, it is produced copiously during the initial stages of heating. In the later stages, CO2 becomes the dominant gas as H2O is lost at increasing rates. Water in the shell arises mainly from gel dehydration, CO2 by sodium bicarbonate/carbonate decomposition and carbon oxidation, and O2 and N2 by permeation of the ambient furnace air through the molten shell wall.

Bioaccumulation of metals in the soft tissue of Patella aspera: Application of metal/shell weight indices

NASA Astrophysics Data System (ADS)

Cravo, A.; Bebianno, M. J.

2005-11-01

Patella aspera limpets were taken from a marine clean site (MCS) and an estuarine contaminated site (ECS). The concentrations of Fe, Mn, Zn, Cu, Cd, Ni and Co were determined individually over the available size range. Since there were significant differences in the soft tissue weight between populations, but shell characteristics were similar (length and weight), metal/shell weight indices (MSI) were calculated in order to compare populations. For both populations iron, zinc and manganese/shell weight indices were consistently higher, in the order Fe ≫ Zn ≫ Mn than those of Cu, Ni, Co and Cd. The results exhibited a marked intra- and inter-population variability. The highest intra-variability was observed at ECS, particularly where a strong effect of shell weight upon the metal accumulation in the soft tissue was evident. Due to this effect, the comparison of populations was carried out between three selected shell weight ranges representative of light shells (0.45-1.95 g), intermediate shells (2.95-4.45 g) and heavy shells (5.45-7.33 g). The results indicate that, in general, MSI at ECS (a sewage contaminated site), except for Cd, was higher than at MCS possibly reflecting a higher environmental bioavailability of these metals. The resolution between populations was higher when the smallest range of limpets was considered and it decreased with the increase of shell weight. The highest discrimination amongst populations was found for zinc/shell weight index that showed much higher values than those of Mn, Cu, Cd, Ni and Co/shell weight indices, and spatial differentiation between populations persisted amongst the selected shell weight ranges.

Metal and transuranic records in mussel shells, byssal threads and tissues

NASA Astrophysics Data System (ADS)

Koide, Minoru; Lee, Dong Soo; Goldberg, Edward D.

1982-12-01

Bivalve shells offer several advantages over tissues for the monitoring of heavy metal pollutants in the marine environment. They are easier to handle and to store. The problem of whether to depurate the animals before analyses is avoided. The shells appear to be more sensitive to environmental heavy metals levels over the long term than do the soft parts. Of the substances examined (Cd, Cu, Zn, Pb, Ag, Ni, 238Pu and 239 + 240Pu) only Pb and Pu displayed a strong covariance between soft tissue and shell concentrations. There were strong correlations between metals in the shell but not in the soft tissues in general. The byssal threads, because of their enrichment of transuranic elements and of their ease in handling, may be useful in monitoring these metals. A very weak discharge of 238Pu to marine waters adjacent to a nuclear reactor was detected in the byssal threads of mussels.

Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

DOE PAGES

Garg, Aaron; Milina, Maria; Ball, Madelyn; ...

2017-05-25

Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. In conclusion, the ability to control shell coveragemore » and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.« less

Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garg, Aaron; Milina, Maria; Ball, Madelyn

Core–shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. In conclusion, the ability to control shell coveragemore » and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.« less

Full f-p Shell Calculation of {sup 51}Ca and {sup 51}Sc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novoselsky, A.; Vallieres, M.; Laadan, O.

The spectra and the electromagnetic transitions of the nuclei {sup 51}Ca and {sup 51}Sc with 11 nucleons in the {ital f-p} shell are described in the nuclear shell-model approach by using two different two-body effective interactions. The full {ital f-p} shell basis functions are used with no truncation. The new parallel shell-model computer code DUPSM (Drexel University parallel shell model), that we recently developed, has been used. The calculations have been done on the MOSIX parallel machine at the Hebrew University of Jerusalem. {copyright} {ital 1997} {ital The American Physical Society}

Equation of state and electron localisation in fcc lithium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frost, Mungo; Levitan, Abraham L.; Sun, Peihao

We present an improved equation of state for the high-pressure fcc phase of lithium with ambient temperature experimental data, extending the pressure range of previous studies to 36 GPa. Accompanying density functional theory calculations, which reproduce the experimental equation of state, show that with increasing density the phase diverges from a nearly free electron metal. At the high pressure limit of its stability fcc lithium exhibits enhanced electron density on the octahedral interstices with a high degree of localisation.

Equation of state and electron localisation in fcc lithium

DOE PAGES

Frost, Mungo; Levitan, Abraham L.; Sun, Peihao; ...

2018-02-14

We present an improved equation of state for the high-pressure fcc phase of lithium with ambient temperature experimental data, extending the pressure range of previous studies to 36 GPa. Accompanying density functional theory calculations, which reproduce the experimental equation of state, show that with increasing density the phase diverges from a nearly free electron metal. At the high pressure limit of its stability fcc lithium exhibits enhanced electron density on the octahedral interstices with a high degree of localisation.

Recombination of open-f-shell tungsten ions

NASA Astrophysics Data System (ADS)

Krantz, C.; Badnell, N. R.; Müller, A.; Schippers, S.; Wolf, A.

2017-03-01

We review experimental and theoretical efforts aimed at a detailed understanding of the recombination of electrons with highly charged tungsten ions characterised by an open 4f sub-shell. Highly charged tungsten occurs as a plasma contaminant in ITER-like tokamak experiments, where it acts as an unwanted cooling agent. Modelling of the charge state populations in a plasma requires reliable thermal rate coefficients for charge-changing electron collisions. The electron recombination of medium-charged tungsten species with open 4f sub-shells is especially challenging to compute reliably. Storage-ring experiments have been conducted that yielded recombination rate coefficients at high energy resolution and well-understood systematics. Significant deviations compared to simplified, but prevalent, computational models have been found. A new class of ab initio numerical calculations has been developed that provides reliable predictions of the total plasma recombination rate coefficients for these ions.

Mobile application MDDCS for modeling the expansion dynamics of a dislocation loop in FCC metals

NASA Astrophysics Data System (ADS)

Kirilyuk, Vasiliy; Petelin, Alexander; Eliseev, Andrey

2017-11-01

A mobile version of the software package Dynamic Dislocation of Crystallographic Slip (MDDCS) designed for modeling the expansion dynamics of dislocation loops and formation of a crystallographic slip zone in FCC-metals is examined. The paper describes the possibilities for using MDDCS, the application interface, and the database scheme. The software has a simple and intuitive interface and does not require special training. The user can set the initial parameters of the experiment, carry out computational experiments, export parameters and results of the experiment into separate text files, and display the experiment results on the device screen.

Cross-shell excitations from the f p shell: Lifetime measurements in 61Zn

NASA Astrophysics Data System (ADS)

Queiser, M.; Vogt, A.; Seidlitz, M.; Reiter, P.; Togashi, T.; Shimizu, N.; Utsuno, Y.; Otsuka, T.; Honma, M.; Petkov, P.; Arnswald, K.; Altenkirch, R.; Birkenbach, B.; Blazhev, A.; Braunroth, T.; Dewald, A.; Eberth, J.; Fransen, C.; Fu, B.; Hess, H.; Hetzenegger, R.; Hirsch, R.; Jolie, J.; Karayonchev, V.; Kaya, L.; Lewandowski, L.; Müller-Gatermann, C.; Régis, J.-M.; Rosiak, D.; Schneiders, D.; Siebeck, B.; Steinbach, T.; Wolf, K.; Zell, K.-O.

2017-10-01

Lifetimes of excited states in the neutron-deficient nucleus 61Zn were measured employing the recoil-distance Doppler-shift (RDDS) and the electronic fast-timing methods at the University of Cologne. The nucleus of interest was populated as an evaporation residue in 40Ca(24Mg,n 2 p )61Zn and 58Ni(α ,n )61Zn reactions at 67 and 19 MeV, respectively. Five lifetimes were measured for the first time, including the lifetime of the 5 /21- isomer at 124 keV. Short lifetimes from the RDDS analysis are corrected for Doppler-shift attenuation (DSA) in the target and stopper foils. Ambiguous observations in previous measurements were resolved. The obtained lifetimes are compared to predictions from different sets of shell-model calculations in the f p , f5 /2p g9 /2 , and multishell f p -g9 /2d5 /2 model spaces. The band built on the 9 /21+ state exhibits a prolate deformation with β ≈0.24 . Especially, the inclusion of cross-shell excitation into the 1 d5 /2 orbital is found to be decisive for the description of collectivity in the first excited positive-parity band.

NaF-loaded core-shell PAN-PMMA nanofibers as reinforcements for Bis-GMA/TEGDMA restorative resins.

PubMed

Cheng, Liyuan; Zhou, Xuegang; Zhong, Hong; Deng, Xuliang; Cai, Qing; Yang, Xiaoping

2014-01-01

A kind of core-shell nanofibers containing sodium fluoride (NaF) was produced and used as reinforcing materials for dimethacrylate-based dental restorative resins in this study. The core-shell nanofibers were prepared by coaxial-electrospinning with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) solutions as core and shell fluids, respectively. The produced PAN-PMMA nanofibers varied in fiber diameter and the thickness of PMMA shell depending on electrospinning parameters. NaF-loaded nanofibers were obtained by incorporating NaF nanocrystals into the core fluid at two loadings (0.8 or 1.0wt.%). Embedment of NaF nanocrystals into the PAN core did not damage the core-shell structure. The addition of PAN-PMMA nanofibers into Bis-GMA/TEGDMA clearly showed the reinforcement due to the good interfacial adhesion between fibers and resin. The flexural strength (Fs) and flexural modulus (Ey) of the composites decreased slightly as the thickness of PMMA shell increasing. Sustained fluoride releases with minor initial burst release were achieved from NaF-loaded core-shell nanofibers and the corresponding composites, which was quite different from the case of embedding NaF nanocrystals into the dental resin directly. The study demonstrated that NaF-loaded PAN-PMMA core-shell nanofibers were not only able to improve the mechanical properties of restorative resin, but also able to provide sustained fluoride release to help in preventing secondary caries. © 2013.

Metal-metal bonds in f-element chemistry.

PubMed

Liddle, Stephen T; Mills, David P

2009-08-07

The molecular chemistry of the f-elements is traditionally dominated by the use of carbon-, nitrogen-, oxygen-, or halide-ligands. However, the use of metal-based fragments as ligands is underdeveloped, which contrasts to the fields of d- and p-block metal-metal complexes that have developed extensively over the last fifty years. This perspective outlines the development of compounds, which possess polarised covalent or donor-acceptor f-element-metal bonds. For this review, the f-element is defined as (i) a group 3 or lanthanide metal: scandium, yttrium, lanthanum to lutetium, or (ii) an actinide metal: thorium, or uranium, and the metal is defined as a d-block transition metal, or a group 13 (aluminium or gallium), a group 14 (silicon, germanium, or tin), or a group 15 (antimony, or bismuth) metal. Silicon, germanium, and antimony are traditionally classified as metalloids but they are included for completeness. This review focuses mainly on complexes that have been structurally authenticated by single-crystal X-ray diffraction studies and we highlight novel aspects of their syntheses, properties, and reactivities.

First-second shell interactions in metal binding sites in proteins: a PDB survey and DFT/CDM calculations.

PubMed

Dudev, Todor; Lin, Yen-lin; Dudev, Minko; Lim, Carmay

2003-03-12

The role of the second shell in the process of metal binding and selectivity in metalloproteins has been elucidated by combining Protein Data Bank (PDB) surveys of Mg, Mn, Ca, and Zn binding sites with density functional theory/continuum dielectric methods (DFT/CDM). Peptide backbone groups were found to be the most common second-shell ligand in Mg, Mn, Ca, and Zn binding sites, followed (in decreasing order) by Asp/Glu, Lys/Arg, Asn/Gln, and Ser/Thr side chains. Aromatic oxygen- or nitrogen-containing side chains (Tyr, His, and Trp) and sulfur-containing side chains (Cys and Met) are seldom found in the second coordination layer. The backbone and Asn/Gln side chain are ubiquitous in the metal second coordination layer as their carbonyl oxygen and amide hydrogen can act as a hydrogen-bond acceptor and donor, respectively, and can therefore partner practically every first-shell ligand. The second most common outer-shell ligand, Asp/Glu, predominantly hydrogen bonds to a metal-bound water or Zn-bound histidine and polarizes the H-O or H-N bond. In certain cases, a second-shell Asp/Glu could affect the protonation state of the metal ligand. It could also energetically stabilize a positively charged metal complex more than a neutral ligand such as the backbone and Asn/Gln side chain. As for the first shell, the second shell is predicted to contribute to the metal selectivity of the binding site by discriminating between metal cations of different ionic radii and coordination geometries. The first-shell-second-shell interaction energies decay rapidly with increasing solvent exposure of the metal binding site. They are less favorable but are of the same order of magnitude as compared to the respective metal-first-shell interaction energies. Altogether, the results indicate that the structure and properties of the second shell are dictated by those of the first layer. The outer shell is apparently designed to stabilize/protect the inner-shell and complement/enhance its

Metal shell technology based upon hollow jet instability. [for inertial confinement fusion

NASA Technical Reports Server (NTRS)

Kendall, J. M.; Lee, M. C.; Wang, T. G.

1982-01-01

Spherical shells of submillimeter size are sought as ICF targets. Such shells must be dimensionally precise, smooth, of high strength, and composed of a high atomic number material. A technology for the production of shells based upon the hydrodynamic instability of an annular jet of molten metal is described. Shells in the 0.7-2.0 mm size range have been produced using tin as a test material. Specimens exhibit good sphericity, fair concentricity, and excellent finish over most of the surface. Work involving a gold-lead-antimony alloy is in progress. Droplets of this are amorphous and possess superior surface finish. The flow of tin models that of the alloy well; experiments on both metals show that the technique holds considerable promise.

Effect of vacancy defects on generalized stacking fault energy of fcc metals.

PubMed

Asadi, Ebrahim; Zaeem, Mohsen Asle; Moitra, Amitava; Tschopp, Mark A

2014-03-19

Molecular dynamics (MD) and density functional theory (DFT) studies were performed to investigate the influence of vacancy defects on generalized stacking fault (GSF) energy of fcc metals. MEAM and EAM potentials were used for MD simulations, and DFT calculations were performed to test the accuracy of different common parameter sets for MEAM and EAM potentials in predicting GSF with different fractions of vacancy defects. Vacancy defects were placed at the stacking fault plane or at nearby atomic layers. The effect of vacancy defects at the stacking fault plane and the plane directly underneath of it was dominant compared to the effect of vacancies at other adjacent planes. The effects of vacancy fraction, the distance between vacancies, and lateral relaxation of atoms on the GSF curves with vacancy defects were investigated. A very similar variation of normalized SFEs with respect to vacancy fractions were observed for Ni and Cu. MEAM potentials qualitatively captured the effect of vacancies on GSF.

Core–Shell Au@Metal-Oxide Nanoparticle Electrocatalysts for Enhanced Oxygen Evolution

DOE PAGES

Strickler, Alaina L.; Escudero-Escribano, Marı́a; Jaramillo, Thomas F.

2017-09-25

Enhanced catalysis for electrochemical oxygen evolution is essential for the efficacy of many renewable energy technologies, including water electrolyzers and metal–air batteries. Recently, Au supports have been shown to enhance the activity of many 3d transition metal-oxide thin films for the oxygen evolution reaction (OER) in alkaline media. In this paper, we translate the beneficial impact of Au supports to high surface area, device-ready core–shell nanoparticles consisting of a Au-core and a metal-oxide shell (Au@M xO y where M = Ni, Co, Fe, and CoFe). Through a systematic evaluation, we establish trends in performance and illustrate the universal activity enhancementmore » when employing the Au-core in the 3d transition metal-oxide nanoparticles. Finally, the highest activity particles, Au@CoFeO x, demonstrate an overpotential of 328 ± 3 mV over a 2 h stability test at 10 mA cm –2, illustrating that strategically coupling Au support and mixed metal-oxide effects in a core–shell nanoparticle morphology is a promising avenue to achieve device-ready, high-performance OER catalysts.« less

Core–Shell Au@Metal-Oxide Nanoparticle Electrocatalysts for Enhanced Oxygen Evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strickler, Alaina L.; Escudero-Escribano, Marı́a; Jaramillo, Thomas F.

Enhanced catalysis for electrochemical oxygen evolution is essential for the efficacy of many renewable energy technologies, including water electrolyzers and metal–air batteries. Recently, Au supports have been shown to enhance the activity of many 3d transition metal-oxide thin films for the oxygen evolution reaction (OER) in alkaline media. In this paper, we translate the beneficial impact of Au supports to high surface area, device-ready core–shell nanoparticles consisting of a Au-core and a metal-oxide shell (Au@M xO y where M = Ni, Co, Fe, and CoFe). Through a systematic evaluation, we establish trends in performance and illustrate the universal activity enhancementmore » when employing the Au-core in the 3d transition metal-oxide nanoparticles. Finally, the highest activity particles, Au@CoFeO x, demonstrate an overpotential of 328 ± 3 mV over a 2 h stability test at 10 mA cm –2, illustrating that strategically coupling Au support and mixed metal-oxide effects in a core–shell nanoparticle morphology is a promising avenue to achieve device-ready, high-performance OER catalysts.« less

Progress Toward Fabrication of Machined Metal Shells for the First Double-Shell Implosions at the National Ignition Facility

DOE PAGES

Cardenas, Tana; Schmidt, Derek W.; Loomis, Eric N.; ...

2018-01-25

The double-shell platform fielded at the National Ignition Facility requires developments in new machining techniques and robotic assembly stations to meet the experimental specifications. Current double-shell target designs use a dense high-Z inner shell, a foam cushion, and a low-Z outer shell. The design requires that the inner shell be gas filled using a fill tube. This tube impacts the entire machining and assembly design. Other intermediate physics designs have to be fielded to answer physics questions and advance the technology to be able to fabricate the full point design in the near future. One of these intermediate designs ismore » a mid-Z imaging design. The methods of designing, fabricating, and characterizing each of the major components of an imaging double shell are discussed with an emphasis on the fabrication of the machined outer metal shell.« less

Progress Toward Fabrication of Machined Metal Shells for the First Double-Shell Implosions at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardenas, Tana; Schmidt, Derek W.; Loomis, Eric N.

The double-shell platform fielded at the National Ignition Facility requires developments in new machining techniques and robotic assembly stations to meet the experimental specifications. Current double-shell target designs use a dense high-Z inner shell, a foam cushion, and a low-Z outer shell. The design requires that the inner shell be gas filled using a fill tube. This tube impacts the entire machining and assembly design. Other intermediate physics designs have to be fielded to answer physics questions and advance the technology to be able to fabricate the full point design in the near future. One of these intermediate designs ismore » a mid-Z imaging design. The methods of designing, fabricating, and characterizing each of the major components of an imaging double shell are discussed with an emphasis on the fabrication of the machined outer metal shell.« less

Controlled Formation of Radial Core-Shell Si/Metal Silicide Crystalline Heterostructures.

PubMed

Kosloff, Alon; Granot, Eran; Barkay, Zahava; Patolsky, Fernando

2018-01-10

The highly controlled formation of "radial" silicon/NiSi  core-shell nanowire heterostructures has been demonstrated for the first time. Here, we investigated the "radial" diffusion of nickel atoms into crystalline nanoscale silicon pillar 11 cores, followed by nickel silicide phase formation and the creation of a well-defined shell structure. The described approach is based on a two-step thermal process, which involves metal diffusion at low temperatures in the range of 200-400 °C, followed by a thermal curing step at a higher temperature of 400 °C. In-depth crystallographic analysis was performed by nanosectioning the resulting silicide-shelled silicon nanopillar heterostructures, giving us the ability to study in detail the newly formed silicide shells. Remarkably, it was observed that the resulting silicide shell thickness has a self-limiting behavior, and can be tightly controlled by the modulation of the initial diffusion-step temperature. In addition, electrical measurements of the core-shell structures revealed that the resulting shells can serve as an embedded conductive layer in future optoelectronic applications. This research provides a broad insight into the Ni silicide "radial" diffusion process at the nanoscale regime, and offers a simple approach to form thickness-controlled metal silicide shells in the range of 5-100 nm around semiconductor nanowire core structures, regardless the diameter of the nanowire cores. These high quality Si/NiSi core-shell nanowire structures will be applied in the near future as building blocks for the creation of utrathin highly conductive optically transparent top electrodes, over vertical nanopillars-based solar cell devices, which may subsequently lead to significant performance improvements of these devices in terms of charge collection and reduced recombination.

Facile, general and template-free construction of monodisperse yolk-shell metal@carbon nanospheres.

PubMed

Xu, Fei; Lu, Yuheng; Ma, Junhao; Huang, Zhike; Su, Quanfei; Fu, Ruowen; Wu, Dingcai

2017-11-07

Herein, we report a general and template-free protocol to construct novel yolk-shell metal@carbon nanospheres based on confined interfacial copolymerization, which greatly simplifies the synthetic route, yields uniform nanospheres with controllable diameters, and results in highly porous carbon shells. The yolk-shell Au@carbon shows improved adsorption capacity and high catalytic ability due to the synergistic effect of Au and the porous carbon shell.

Coulomb excitations for a short linear chain of metallic shells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhemchuzhna, Liubov, E-mail: lzhemchuzhna@unm.edu; Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87106; Gumbs, Godfrey

2015-03-15

A self-consistent-field theory is given for the electronic collective modes of a chain containing a finite number, N, of Coulomb-coupled spherical two-dimensional electron gases arranged with their centers along a straight line, for simulating electromagnetic response of a narrow-ribbon of metallic shells. The separation between nearest-neighbor shells is arbitrary and because of the quantization of the electron energy levels due to their confinement to the spherical surface, all angular momenta L of the Coulomb excitations, as well as their projections M on the quantization axis, are coupled. However, for incoming light with a given polarization, only one angular momentum quantummore » number is usually required. Therefore, the electromagnetic response of the narrow-ribbon of metallic shells is expected to be controlled externally by selecting different polarizations for incident light. We show that, when N = 3, the next-nearest-neighbor Coulomb coupling is larger than its value if they are located at opposite ends of a right-angle triangle forming the triad. Additionally, the frequencies of the plasma excitations are found to depend on the orientation of the line joining them with respect to the axis of quantization since the magnetic field generated from the induced oscillating electric dipole moment on one sphere can couple to the induced magnetic dipole moment on another. Although the transverse inter-shell electromagnetic coupling can be modeled by an effective dynamic medium, the longitudinal inter-shell Coulomb coupling, on the other hand, can still significantly modify the electromagnetic property of this effective medium between shells.« less

Recrystallization as a controlling process in the wear of some f.c.c. metals

NASA Technical Reports Server (NTRS)

Bill, R. C.; Wisander, D.

1977-01-01

Detailed examination of copper specimens after sliding against 440 C steel in liquid methane at speeds up to 25 m/s and loads of up to 2 kg showed the metal comprising the wear surface to possess a fine cell recrystallized structure. Wear proceeded by the plastic shearing of metal in this near surface region without the occurrence of visible metal transfer. A dynamic balance between the intense shear process at the surface and the nucleation of recrystallized grains was proposed to account for the behavior of the metal at the wear surface. Sliding wear experiments were also conducted on Ag, Cu-10% Al, Cu-10% Sn, Ni and Al. It was found that low wear and the absence of heavy metal transfer were associated with those metals observed to undergo recrystallization nucleation without prior recovery.

Status and availability of FCC hardware

NASA Technical Reports Server (NTRS)

Romriell, G. K.

1973-01-01

The source availability of FCC and/or FCC connectors was surveyed. The results for the following areas are presented: (1) cost of FCC versus standard round cable, (2) qualification status, (3) size of wire available in FCC, (4) availability of hermetic connectors for FCC, (5) conversion from flat cable to round cable and visa versa, (6) availability of shielded flat cable for RF usage, (7) termination techniques, and (8) repair techniques.

Deformation-mechanism map for nanocrystalline metals by molecular-dynamics simulation.

PubMed

Yamakov, V; Wolf, D; Phillpot, S R; Mukherjee, A K; Gleiter, H

2004-01-01

Molecular-dynamics simulations have recently been used to elucidate the transition with decreasing grain size from a dislocation-based to a grain-boundary-based deformation mechanism in nanocrystalline f.c.c. metals. This transition in the deformation mechanism results in a maximum yield strength at a grain size (the 'strongest size') that depends strongly on the stacking-fault energy, the elastic properties of the metal, and the magnitude of the applied stress. Here, by exploring the role of the stacking-fault energy in this crossover, we elucidate how the size of the extended dislocations nucleated from the grain boundaries affects the mechanical behaviour. Building on the fundamental physics of deformation as exposed by these simulations, we propose a two-dimensional stress-grain size deformation-mechanism map for the mechanical behaviour of nanocrystalline f.c.c. metals at low temperature. The map captures this transition in both the deformation mechanism and the related mechanical behaviour with decreasing grain size, as well as its dependence on the stacking-fault energy, the elastic properties of the material, and the applied stress level.

Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering.

PubMed

Çınar, Simge; Tevis, Ian D; Chen, Jiahao; Thuo, Martin

2016-02-23

Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.

Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

PubMed Central

Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

2016-01-01

Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

17 CFR 240.15d-19 - Reports by shell companies on Form 20-F.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Reports by shell companies on... Under the Securities Exchange Act of 1934 Other Reports § 240.15d-19 Reports by shell companies on Form 20-F. Every foreign private issuer that was a shell company, other than a business combination...

17 CFR 240.13a-19 - Reports by shell companies on Form 20-F.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Reports by shell companies on... Under the Securities Exchange Act of 1934 Other Reports § 240.13a-19 Reports by shell companies on Form 20-F. Every foreign private issuer that was a shell company, other than a business combination...

17 CFR 240.15d-19 - Reports by shell companies on Form 20-F.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Reports by shell companies on... Under the Securities Exchange Act of 1934 Other Reports § 240.15d-19 Reports by shell companies on Form 20-F. Every foreign private issuer that was a shell company, other than a business combination...

17 CFR 240.13a-19 - Reports by shell companies on Form 20-F.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 3 2010-04-01 2010-04-01 false Reports by shell companies on... Under the Securities Exchange Act of 1934 Other Reports § 240.13a-19 Reports by shell companies on Form 20-F. Every foreign private issuer that was a shell company, other than a business combination...

Investigation on the preparation and luminescence emission of LaF{sub 3}:Eu{sup 3+}@LaF{sub 3}/SiO{sub 2} core-shell nanostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Jun, E-mail: jun-shao@snnu.edu.cn; Wang, Zhaojin; Wang, Ruibo

LaF{sub 3}:Eu{sup 3+}, LaF{sub 3}:Eu{sup 3+}@LaF{sub 3}, LaF{sub 3}:Eu{sup 3+}@CeF{sub 3} and LaF{sub 3}:Eu{sup 3+}@SiO{sub 2} nanoparticles were successfully synthesized via hydrothermal route and modified Stöber method. The surface property of LaF{sub 3}:Eu{sup 3+} particle was successfully modified by coating LaF{sub 3} and SiO{sub 2} shell onto the particle, which resulted in the change of the surface property and luminescence emission of LaF{sub 3}:Eu{sup 3+}. It was found that the surface quenchers were decreased and thus the nonradiative pathways were reduced with core/shell structure, which not only enhanced the yellow emission of the sample, but also changed the intensity ratiomore » of the yellow to orange emission. The dependence of the shell property and shell thickness on the luminescence emission spectra were investigated systematically. The current investigation can provide useful information for developing applications in biological imaging, detection, and sensing and other aspects.« less

The FCC in Fiscal 1971.

ERIC Educational Resources Information Center

Federal Communications Commission, Washington, DC.

Fiscal 1971 saw major actions by the Federal Communications Commission (FCC) in all areas of its jurisdiction. In broadcasting, the FCC proposed new renewal rules and policies and issued a number of significant rulings on Fairness Doctrine matters. A policy statement outlining FCC cable television plans was submitted to the Congress. In the common…

New theory for crack-tip twinning in fcc metals

NASA Astrophysics Data System (ADS)

Andric, Predrag; Curtin, W. A.

2018-04-01

Dislocation emission from a crack tip is a necessary mechanism for crack tip blunting and toughening. In fcc metals under Mode I loading, a first partial dislocation is emitted, followed either by a trailing partial dislocation ("ductile" behaviour) or a twinning partial dislocation ("quasi-brittle"). The twinning tendency is usually estimated using the Tadmor and Hai extension of the Rice theory. Extensive molecular statics simulations reveal that the predictions of the critical stress intensity factor for crack tip twinning are always systematically lower (20-35%) than observed. Analyses of the energy change during nucleation reveal that twin partial emission is not accompanied by creation of a surface step while emission of the trailing partial creates a step. The absence of the step during twinning motivates a modified model for twinning nucleation that accounts for the fact that nucleation does not occur directly at the crack tip. Predictions of the modified theory are in excellent agreement with all simulations that show twinning. Emission of the trailing partial dislocation, including the step creation, is predicted using a model recently introduced to accurately predict the first partial emission and shows why twinning is preferred. A second mode of twinning is found wherein the crack first advances by cleavage and then emits the twinning partial at the new crack tip; this mode dominates for emission beyond the first twinning partial. These new theories resolve all the discrepancies between the Tadmor twinning analysis and simulations, and have various implications for fracture behaviour and transitions.

Core-Shell Structuring of Pure Metallic Aerogels towards Highly Efficient Platinum Utilization for the Oxygen Reduction Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Bin; Hübner, René; Sasaki, Kotaro

The development of core–shell structures remains a fundamental challenge for pure metallic aerogels. Here we report the synthesis of Pd xAu-Pt core–shell aerogels composed of an ultrathin Pt shell and a composition-tunable Pd xAu alloy core. The universality of this strategy ensures the extension of core compositions to Pd transition-metal alloys. The core–shell aerogels exhibited largely improved Pt utilization efficiencies for the oxygen reduction reaction and their activities show a volcano-type relationship as a function of the lattice parameter of the core substrate. The maximum mass and specific activities are 5.25 A mg Pt -1 and 2.53 mA cm -2,more » which are 18.7 and 4.1 times higher than those of Pt/C, respectively, demonstrating the superiority of the core–shell metallic aerogels. The proposed core-based activity descriptor provides a new possible strategy for the design of future core–shell electrocatalysts.« less

Core-Shell Structuring of Pure Metallic Aerogels towards Highly Efficient Platinum Utilization for the Oxygen Reduction Reaction

DOE PAGES

Cai, Bin; Hübner, René; Sasaki, Kotaro; ...

2018-02-08

The development of core–shell structures remains a fundamental challenge for pure metallic aerogels. Here we report the synthesis of Pd xAu-Pt core–shell aerogels composed of an ultrathin Pt shell and a composition-tunable Pd xAu alloy core. The universality of this strategy ensures the extension of core compositions to Pd transition-metal alloys. The core–shell aerogels exhibited largely improved Pt utilization efficiencies for the oxygen reduction reaction and their activities show a volcano-type relationship as a function of the lattice parameter of the core substrate. The maximum mass and specific activities are 5.25 A mg Pt -1 and 2.53 mA cm -2,more » which are 18.7 and 4.1 times higher than those of Pt/C, respectively, demonstrating the superiority of the core–shell metallic aerogels. The proposed core-based activity descriptor provides a new possible strategy for the design of future core–shell electrocatalysts.« less

Predicted trends of core-shell preferences for 132 late transition-metal binary-alloy nanoparticles.

PubMed

Wang, Lin-Lin; Johnson, Duane D

2009-10-07

Transition-metal alloyed nanoparticles with core-shell features (shell enrichment by one of the metals) are becoming ubiquitous, from (electro-)catalysis to biomedical applications, due to their size control, performance, biocompatibility, and cost. We investigate 132 binary-alloyed nanoparticle systems (groups 8 to 11 in the Periodic Table) using density functional theory (DFT) and systematically explore their segregation energies to determine core-shell preferences. We find that core-shell preferences are generally described by two independent factors: (1) cohesive energy (related to vapor pressure) and (2) atomic size (quantified by the Wigner-Seitz radius), and the interplay between them. These independent factors are shown to provide general trends for the surface segregation preference for atoms in nanoparticles, as well as semi-infinite surfaces, and give a simple correlation (a "design map") for the alloying and catalytic behavior. Finally, we provide a universal description of core-shell preference via tight-binding theory (band-energy differences) that (i) quantitatively reproduces the DFT segregation energies and (ii) confirms the electronic origins and correlations for core-shell behavior.

Computer Modeling of the Dynamic Strength of Metal-Plastic Cylindrical Shells Under Explosive Loading

NASA Astrophysics Data System (ADS)

Abrosimov, N. A.; Novosel'tseva, N. A.

2017-05-01

A technique for numerically analyzing the dynamic strength of two-layer metal-plastic cylindrical shells under an axisymmetric internal explosive loading is developed. The kinematic deformation model of the layered package is based on a nonclassical theory of shells. The geometric relations are constructed using relations of the simplest quadratic version of the nonlinear elasticity theory. The stress and strain tensors in the composite macrolayer are related by Hooke's law for an orthotropic body with account of degradation of the stiffness characteristics of the multilayer package due to local failure of some its elementary layers. The physical relations in the metal layer are formulated in terms of a differential theory of plasticity. An energy-correlated resolving system of dynamic equations for the metal-plastic cylindrical shells is derived by minimizing the functional of total energy of the shells as three-dimensional bodies. The numerical method for solving the initial boundary-value problem formulated is based on an explicit variational-difference scheme. The reliability of the technique considered is verified by comparing numerical results with experimental data. An analysis of the ultimate strains and strength of one-layer basalt-and glass-fiber-reinforced plastic and two-layer metalplastic cylindrical shells is carried out.

Fretting and Corrosion Between a Metal Shell and Metal Liner May Explain the High Rate of Failure of R3 Modular Metal-on-Metal Hips.

PubMed

Ilo, Kevin C; Derby, Emma J; Whittaker, Robert K; Blunn, Gordon W; Skinner, John A; Hart, Alister J

2017-05-01

The R3 acetabular system used with its metal liner has higher revision rates when compared to its ceramic and polyethylene liner. In June 2012, the medical and healthcare products regulatory agency issued an alert regarding the metal liner of the R3 acetabular system. Six retrieved R3 acetabular systems with metal liners underwent detailed visual analysis using macroscopic and microscopic techniques. Visual analysis discovered corrosion on the backside of the metal liners. There was a distinct border to the areas of corrosion that conformed to antirotation tab insertions on the inner surface of the acetabular shell, which are for the polyethylene liner. Scanning electron microscopy indicated evidence of crevice corrosion, and energy-dispersive X-ray analysis confirmed corrosion debris rich in titanium. The high failure rate of the metal liner option of the R3 acetabular system may be attributed to corrosion on the backside of the liner which appear to result from geometry and design characteristics of the acetabular shell. Copyright © 2016 Elsevier Inc. All rights reserved.

Stability of cylindrical thin shell wormholes supported by MGCG in f(R) gravity

NASA Astrophysics Data System (ADS)

Eid, A.

2018-02-01

In the framework of f(R) modified theory of gravity, the dynamical equations of motion of a cylindrical thin shell wormholes supported by a modified generalized Chaplygin gas are constructed, using the cut and paste scheme (Darmois Israel formalism). The mechanical stability analysis of a cylindrical thin shell wormhole is discussed using a linearized radial perturbation around static solutions at the wormhole throat. The presence of stable static solutions depends on the suitable values of some parameters of dynamical shell.

Nanoscale semiconductor-insulator-metal core/shell heterostructures: facile synthesis and light emission

NASA Astrophysics Data System (ADS)

Li, Gong Ping; Chen, Rui; Guo, Dong Lai; Wong, Lai Mun; Wang, Shi Jie; Sun, Han Dong; Wu, Tom

2011-08-01

Controllably constructing hierarchical nanostructures with distinct components and designed architectures is an important theme of research in nanoscience, entailing novel but reliable approaches of bottom-up synthesis. Here, we report a facile method to reproducibly create semiconductor-insulator-metal core/shell nanostructures, which involves first coating uniform MgO shells onto metal oxide nanostructures in solution and then decorating them with Au nanoparticles. The semiconductor nanowire core can be almost any material and, herein, ZnO, SnO2 and In2O3 are used as examples. We also show that linear chains of short ZnO nanorods embedded in MgO nanotubes and porous MgO nanotubes can be obtained by taking advantage of the reduced thermal stability of the ZnO core. Furthermore, after MgO shell-coating and the appropriate annealing treatment, the intensity of the ZnO near-band-edge UV emission becomes much stronger, showing a 25-fold enhancement. The intensity ratio of the UV/visible emission can be increased further by decorating the surface of the ZnO/MgO nanowires with high-density plasmonic Au nanoparticles. These heterostructured semiconductor-insulator-metal nanowires with tailored morphologies and enhanced functionalities have great potential for use as nanoscale building blocks in photonic and electronic applications.Controllably constructing hierarchical nanostructures with distinct components and designed architectures is an important theme of research in nanoscience, entailing novel but reliable approaches of bottom-up synthesis. Here, we report a facile method to reproducibly create semiconductor-insulator-metal core/shell nanostructures, which involves first coating uniform MgO shells onto metal oxide nanostructures in solution and then decorating them with Au nanoparticles. The semiconductor nanowire core can be almost any material and, herein, ZnO, SnO2 and In2O3 are used as examples. We also show that linear chains of short ZnO nanorods embedded in

Core-Shell Structuring of Pure Metallic Aerogels towards Highly Efficient Platinum Utilization for the Oxygen Reduction Reaction.

PubMed

Cai, Bin; Hübner, René; Sasaki, Kotaro; Zhang, Yuanzhe; Su, Dong; Ziegler, Christoph; Vukmirovic, Miomir B; Rellinghaus, Bernd; Adzic, Radoslav R; Eychmüller, Alexander

2018-03-05

The development of core-shell structures remains a fundamental challenge for pure metallic aerogels. Here we report the synthesis of Pd x Au-Pt core-shell aerogels composed of an ultrathin Pt shell and a composition-tunable Pd x Au alloy core. The universality of this strategy ensures the extension of core compositions to Pd transition-metal alloys. The core-shell aerogels exhibited largely improved Pt utilization efficiencies for the oxygen reduction reaction and their activities show a volcano-type relationship as a function of the lattice parameter of the core substrate. The maximum mass and specific activities are 5.25 A mg Pt -1 and 2.53 mA cm -2 , which are 18.7 and 4.1 times higher than those of Pt/C, respectively, demonstrating the superiority of the core-shell metallic aerogels. The proposed core-based activity descriptor provides a new possible strategy for the design of future core-shell electrocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ru nanoframes with an fcc structure and enhanced catalytic properties

DOE PAGES

Ye, Haihang; Wang, Qingxiao; Catalano, Massimo; ...

2016-03-21

Noble-metal nanoframes are of great interest to many applications due to their unique open structures. Among various noble metals, Ru has never been made into nanoframes. In this study, we report for the first time an effective method based on seeded growth and chemical etching for the facile synthesis of Ru nanoframes with high purity. The essence of this approach is to induce the preferential growth of Ru on the corners and edges of Pd truncated octahedra as the seeds by kinetic control. The resultant Pd–Ru core–frame octahedra could be easily converted to Ru octahedral nanoframes of ~2 nm inmore » thickness by selectively removing the Pd cores through chemical etching. Most importantly, in this approach the face-centered cubic (fcc) crystal structure of Pd seeds was faithfully replicated by Ru that usually takes an hcp structure. Furthermore, the fcc Ru nanoframes showed higher catalytic activities toward the reduction of p-nitrophenol by NaBH 4 and the dehydrogenation of ammonia borane compared with hcp Ru nanowires with roughly the same thickness.« less

High-pressure phase transitions in rare earth metal thulium to 195 GPa.

PubMed

Montgomery, Jeffrey M; Samudrala, Gopi K; Tsoi, Georgiy M; Vohra, Yogesh K

2011-04-20

We have performed image plate x-ray diffraction studies on a heavy rare earth metal, thulium (Tm), in a diamond anvil cell to a pressure of 195 GPa and volume compression V/V₀ = 0.38 at room temperature. The rare earth crystal structure sequence, hcp →Sm-type→ dhcp →fcc → distorted fcc, is observed in Tm below 70 GPa with the exception of a pure fcc phase. The focus of our study is on the ultrahigh-pressure phase transition and Rietveld refinement of crystal structures in the pressure range between 70 and 195 GPa. The hexagonal hR-24 phase is seen to describe the distorted fcc phase between 70 and 124 GPa. Above 124 ± 4 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of -1.5%. The equation of state data shows rapid stiffening above the phase transition at 124 GPa and is indicative of participation of f-electrons in bonding. We compare the behavior of Tm to other heavy rare-earths and heavy actinide metals under extreme conditions of pressure.

High-pressure phase transitions in rare earth metal thulium to 195 GPa

NASA Astrophysics Data System (ADS)

Montgomery, Jeffrey M.; Samudrala, Gopi K.; Tsoi, Georgiy M.; Vohra, Yogesh K.

2011-04-01

We have performed image plate x-ray diffraction studies on a heavy rare earth metal, thulium (Tm), in a diamond anvil cell to a pressure of 195 GPa and volume compression V/Vo = 0.38 at room temperature. The rare earth crystal structure sequence, {hcp}\\to {Sm {-}type} \\to {dhcp} \\to {fcc} \\to distorted fcc, is observed in Tm below 70 GPa with the exception of a pure fcc phase. The focus of our study is on the ultrahigh-pressure phase transition and Rietveld refinement of crystal structures in the pressure range between 70 and 195 GPa. The hexagonal hR- 24 phase is seen to describe the distorted fcc phase between 70 and 124 GPa. Above 124 ± 4 GPa, a structural transformation from hR 24 phase to a monoclinic C 2/m phase is observed with a volume change of - 1.5%. The equation of state data shows rapid stiffening above the phase transition at 124 GPa and is indicative of participation of f-electrons in bonding. We compare the behavior of Tm to other heavy rare-earths and heavy actinide metals under extreme conditions of pressure.

Molecular dynamics (MD) studies on phase transformation and deformation behaviors in FCC metals and alloys

NASA Astrophysics Data System (ADS)

Qi, Yue

This thesis focused on the phase transformation and deformation behaviors in face center cubic (FCC) metals and alloys. These studies used the new quantum modified Sutton-Chen (QMSC) many-body potentials for Cu, Ni, Ag, and Au and for their alloys through simple combination rules. Various systems and processes are simulated by standard equilibrium molecular dynamics (MD), quasi-static equilibrium MD and non-equilibrium MD (NEMD), cooperated with different periodic boundary conditions. The main topics include: (1) Melting, glass formation, and crystallization processes in bulk alloys. In our simulation CuNi and pure Cu always form an FCC crystal, while Cu4Ag6 always forms glass (with Tg decreasing as the quench rate increases) due to the large atomic size difference. (2) Size effects in melting and crystallization in Ni nano clusters. There is a transition from cluster or molecular regime (where the icosahedral is the stable structure) below ˜500 atoms to a mesoscale regime (with well-defined bulk and surface properties and surface melting processes, which leads to Tm,N = Tm,B - alpha N-1/3) above ˜750 atoms. (3) The deformation behavior of metallic nanowires of pure Ni, NiCu and NiAu alloys, under high rates of uniaxial tensile strain, ranging from 5*108/s to 5*1010/s. We find that deformation proceeds through twinning and coherent slipping at low strain rate and amorphization at high strain rate. This research provides a new method, fast straining, to induce amorphization except fast cooling and disordering. (4) The calculation of the ½ <110> screw dislocation in nickel (Ni). We calculated the core energy of screw dislocation after dissociation is 0.5 eV/b, the annihilation process of opposite signed dislocations depends dramatically on the configurations of dissociation planes and the cross-slip energy barrier is 0.1eV/b. (5) Friction anisotropy on clean Ni(100)/(100) interface. We found that static friction coefficient on flat and incommensurate interface is

Single-step generation of metal-plasma polymer multicore@shell nanoparticles from the gas phase.

PubMed

Solař, Pavel; Polonskyi, Oleksandr; Olbricht, Ansgar; Hinz, Alexander; Shelemin, Artem; Kylián, Ondřej; Choukourov, Andrei; Faupel, Franz; Biederman, Hynek

2017-08-17

Nanoparticles composed of multiple silver cores and a plasma polymer shell (multicore@shell) were prepared in a single step with a gas aggregation cluster source operating with Ar/hexamethyldisiloxane mixtures and optionally oxygen. The size distribution of the metal inclusions as well as the chemical composition and the thickness of the shells were found to be controlled by the composition of the working gas mixture. Shell matrices ranging from organosilicon plasma polymer to nearly stoichiometric SiO 2 were obtained. The method allows facile fabrication of multicore@shell nanoparticles with tailored functional properties, as demonstrated here with the optical response.

Inner-shell photodetachment of transition metal negative ions

NASA Astrophysics Data System (ADS)

Dumitriu, Ileana

This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe- and Ru- . Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy. Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons is interesting but difficult to analyze in detail because the angular momentum coupling generates a large number of possible terms resulting from the open d shell. Our work reports on the first inner-shell photodetachment studies and absolute cross section measurements for Fe- and Ru -. In the case of Fe-, an important astrophysical abundant element, the inner-shell photodetachment cross section was obtained by measuring the Fe+ and Fe2+ ion production over the photon energy range of 48--72 eV. The absolute cross sections for the production of Fe+ and Fe2+ were measured at four photon energies. Strong shape resonances due to the 3p→3d photoexcitation were measured above the 3p detachment threshold. The production of Ru+, Ru2+, and Ru3+ from Ru- was measured over 30--90 eV photon energy range The absolute photodetachment cross sections of Ru - ([Kr] 4d75s 2) leading to Ru+, Ru2+, and Ru 3+ ion production were measured at three photon energies. Resonance effects were observed due to interference between transitions of the 4 p-electrons to the quasi-bound 4p54d85s 2 states and the 4d→epsilonf continuum. The role of many-particle effects, intershell interaction, and polarization seems much more significant in Ru- than in Fe- photodetachment.

The elastic properties and stability of fcc-Fe and fcc-FeNi alloys at inner-core conditions

NASA Astrophysics Data System (ADS)

Martorell, Benjamí; Brodholt, John; Wood, Ian G.; Vočadlo, Lidunka

2015-07-01

The agreement between shear wave velocities for the Earth's inner core observed from seismology with those derived from mineral physics is considerably worse than for any other region of the Earth. Furthermore, there is still debate as to the phase of iron present in the inner core, particularly when alloying with nickel and light elements is taken into account. To investigate the extent to which the mismatch between seismology and mineral physics is a function of either crystal structure and/or the amount of nickel present, we have used ab initio molecular dynamics simulations to calculate the elastic constants and seismic velocities (Vp and Vs) of face centred cubic (fcc) iron at Earth's inner core pressures (360 GPa) and at temperatures up to ˜7000 K. We find that Vp for fcc iron (fcc-Fe) is very similar to that for hexagonal close packed (hcp) iron at all temperatures. In contrast, Vs for fcc-Fe is significantly higher than in hcp-Fe, with the difference increasing with increasing temperature; the difference between Vs for the core (from seismology) and Vs for fcc-Fe exceeds 40 per cent. These results are consistent with previous work at lower temperatures. We have also investigated the effect of 6.5 and 13 atm% Ni in fcc-Fe. We find that Ni only slightly reduces Vp and Vs (e.g. by 2 per cent in Vs for 13 atm% Ni at 5500 K), and cannot account for the difference between the velocities observed in the core and those of pure fcc-Fe. We also tried to examine pre-melting behaviour in fcc-Fe, as reported in hcp-Fe by extending the study to very high temperatures (at which superheating may occur). However, we find that fcc-Fe spontaneously transforms to other hcp-like structures before melting; two hcp-like structures were found, both of hexagonal symmetry, which may most easily be regarded as being derived from an hcp crystal with stacking faults. That the structure did not transform to a true hcp phase is likely as a consequence of the limited size of the

78 FR 66357 - Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-05

... 499-A, FCC Form 499-Q, and Accompanying Instructions AGENCY: Federal Communications Commission. ACTION..., FCC Form 499-Q (Form 499-Q) and accompanying instructions (Form 499-Q Instructions) to be used in 2014... Worksheet, FCC Form 499-Q (Form 499-Q) and accompanying instructions (Form 499-Q Instructions) to be used in...

76 FR 35934 - In the Matter of: SHC Corp. (f/k/a Victormaxx Technologies, Inc.), Shells Seafood Restaurants...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-20

... SECURITIES AND EXCHANGE COMMISSION [File No. 500-1] In the Matter of: SHC Corp. (f/k/a Victormaxx Technologies, Inc.), Shells Seafood Restaurants, Inc., SI Restructuring, Inc. (f/k/a Schlotzsky's, Inc.), SLS... a lack of current and accurate information concerning the securities of Shells Seafood Restaurants...

Switching Plasmons: Gold Nanorod-Copper Chalcogenide Core-Shell Nanoparticle Clusters with Selectable Metal/Semiconductor NIR Plasmon Resonances.

PubMed

Muhammed, Madathumpady Abubaker Habeeb; Döblinger, Markus; Rodríguez-Fernández, Jessica

2015-09-16

Exerting control over the near-infrared (NIR) plasmonic response of nanosized metals and semiconductors can facilitate access to unexplored phenomena and applications. Here we combine electrostatic self-assembly and Cd(2+)/Cu(+) cation exchange to obtain an anisotropic core-shell nanoparticle cluster (NPC) whose optical properties stem from two dissimilar plasmonic materials: a gold nanorod (AuNR) core and a copper selenide (Cu(2-x)Se, x ≥ 0) supraparticle shell. The spectral response of the AuNR@Cu2Se NPCs is governed by the transverse and longitudinal plasmon bands (LPB) of the anisotropic metallic core, since the Cu2Se shell is nonplasmonic. Under aerobic conditions the shell undergoes vacancy doping (x > 0), leading to the plasmon-rich NIR spectrum of the AuNR@Cu(2-x)Se NPCs. For low vacancy doping levels the NIR optical properties of the dually plasmonic NPCs are determined by the LPBs of the semiconductor shell (along its major longitudinal axis) and of the metal core. Conversely, for high vacancy doping levels their NIR optical response is dominated by the two most intense plasmon modes from the shell: the transverse (along the shortest transversal axis) and longitudinal (along the major longitudinal axis) modes. The optical properties of the NPCs can be reversibly switched back to a purely metallic plasmonic character upon reversible conversion of AuNR@Cu(2-x)Se into AuNR@Cu2Se. Such well-defined nanosized colloidal assemblies feature the unique ability of holding an all-metallic, a metallic/semiconductor, or an all-semiconductor plasmonic response in the NIR. Therefore, they can serve as an ideal platform to evaluate the crosstalk between plasmonic metals and plasmonic semiconductors at the nanoscale. Furthermore, their versatility to display plasmon modes in the first, second, or both NIR windows is particularly advantageous for bioapplications, especially considering their strong absorbing and near-field enhancing properties.

The use of waste mussel shells for the adsorption of dyes and heavy metals

NASA Astrophysics Data System (ADS)

Papadimitriou, Chrysi A.; Krey, Grigorios; Stamatis, Nikolaos; Kallaniotis, Argyris

2016-04-01

Mussel culture is very important sector of the Greek agricultural economy. The majority of mussel culture activities take place in the area of Central Macedonia, Greece, 60% of total mussel production in Greece producing almost 12 tons of waste mussels shells on a daily basis. Currently there is no legislation concerning the disposal of mussel shells. In the present study the waste shells were used for the removal of dyes and heavy metals from aqueous solutions while powdered mussel shells were added in activated sludge processes for the removal of hexavalent chromium. Mussel shells were cleaned, dried and then crushed in order to form a powder. Powdered mussels shells were used in standard adsorption experiments for the removal of methylene blue and methyl red as well as for the removal of Cr (VI), Cd and Cu. Moreover the powdered mussel shells were added in laboratory scale activated sludge reactors treating synthetic wastewater with hexavalent chromium, in order investigate the effects in activated sludge processes and their potential attribution to the removal of hexavalent chromium. Adsorption experiments indicated almost 100% color removal, while adsorption was directly proportional to the amount of powdered mussel shells added in each case. The isotherms calculated for the case of methylene blue indicated similar adsorption capacity and properties to those of the commercially available activated carbon SAE 2, Norit. High removal efficiencies were observed for the metals, especially in the case of chromium and copper. The addition of powdered mussel shells in the activated sludge processes enhanced the removal of chromium and phosphorus, while enabled the formation of heavier activated sludge flocs and thus enhanced the settling properties of the activated sludge.

The FCC: A Research Tool.

ERIC Educational Resources Information Center

Wilson, Paul

The numerous forms filed with the Federal Communications Commission (FCC) provide information about a variety of topics. Basic licensing information that is available concerns engineering, ownership, and equal employment opportunity. The FCC's broadcast bureau collects information about programing, the ascertainment of community needs, public…

Nanoscale semiconductor-insulator-metal core/shell heterostructures: facile synthesis and light emission.

PubMed

Li, Gong Ping; Chen, Rui; Guo, Dong Lai; Wong, Lai Mun; Wang, Shi Jie; Sun, Han Dong; Wu, Tom

2011-08-01

Controllably constructing hierarchical nanostructures with distinct components and designed architectures is an important theme of research in nanoscience, entailing novel but reliable approaches of bottom-up synthesis. Here, we report a facile method to reproducibly create semiconductor-insulator-metal core/shell nanostructures, which involves first coating uniform MgO shells onto metal oxide nanostructures in solution and then decorating them with Au nanoparticles. The semiconductor nanowire core can be almost any material and, herein, ZnO, SnO(2) and In(2)O(3) are used as examples. We also show that linear chains of short ZnO nanorods embedded in MgO nanotubes and porous MgO nanotubes can be obtained by taking advantage of the reduced thermal stability of the ZnO core. Furthermore, after MgO shell-coating and the appropriate annealing treatment, the intensity of the ZnO near-band-edge UV emission becomes much stronger, showing a 25-fold enhancement. The intensity ratio of the UV/visible emission can be increased further by decorating the surface of the ZnO/MgO nanowires with high-density plasmonic Au nanoparticles. These heterostructured semiconductor-insulator-metal nanowires with tailored morphologies and enhanced functionalities have great potential for use as nanoscale building blocks in photonic and electronic applications. This journal is © The Royal Society of Chemistry 2011

Electrostatically assisted fabrication of silver-dielectric core/shell nanoparticles thin film capacitor with uniform metal nanoparticle distribution and controlled spacing.

PubMed

Li, Xue; Niitsoo, Olivia; Couzis, Alexander

2016-03-01

An electrostatically-assisted strategy for fabrication of thin film composite capacitors with controllable dielectric constant (k) has been developed. The capacitor is composed of metal-dielectric core/shell nanoparticle (silver/silica, Ag@SiO2) multilayer films, and a backfilling polymer. Compared with the simple metal particle-polymer mixtures where the metal nanoparticles (NP) are randomly dispersed in the polymer matrix, the metal volume fraction in our capacitor was significantly increased, owing to the densely packed NP multilayers formed by the electrostatically assisted assembly process. Moreover, the insulating layer of silica shell provides a potential barrier that reduces the tunneling current between neighboring Ag cores, endowing the core/shell nanocomposites with a stable and relatively high dielectric constant (k) and low dielectric loss (D). Our work also shows that the thickness of the SiO2 shell plays a dominant role in controlling the dielectric properties of the nanocomposites. Control over metal NP separation distance was realized not only by variation the shell thickness of the core/shell NPs but also by introducing a high k nanoparticle, barium strontium titanate (BST) of relatively smaller size (∼8nm) compared to 80-160nm of the core/shell Ag@SiO2 NPs. The BST assemble between the Ag@SiO2 and fill the void space between the closely packed core/shell NPs leading to significant enhancement of the dielectric constant. This electrostatically assisted assembly method is promising for generating multilayer films of a large variety of NPs over large areas at low cost. Copyright © 2015 Elsevier Inc. All rights reserved.

A Facile Method for Synthesizing Dendritic Core–Shell Structured Ternary Metallic Aerogels and Their Enhanced Electrochemical Performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Qiurong; Zhu, Chengzhou; Li, Yijing

2016-11-08

Currently, three dimensional self-supported metallic structures are attractive for their unique properties of high porosity, low density, excellent conductivity etc. that promote their wide application in fuel cells. Here, for the first time, we report a facile synthesis of dendritic core-shell structured Au/Pt3Pd ternary metallic aerogels via a one-pot self-assembly gelation strategy. The as-prepared Au/Pt3Pd ternary metallic aerogels demonstrated superior electrochemical performances toward oxygen reduction reaction compared to commercial Pt/C. The unique dendritic core-shell structures, Pt3Pd alloyed shells and the cross-linked network structures are beneficial for the electrochemical oxygen reduction reaction performances of the Pt-based materials via the electronic effect,more » geometric effect and synergistic effect. This strategy of fabrication of metallic hydrogels and aerogels as well as their exceptional properties hold great promise in a variety of applications.« less

Synthesis of ligand-stabilized metal oxide nanocrystals and epitaxial core/shell nanocrystals via a lower-temperature esterification process.

PubMed

Ito, Daisuke; Yokoyama, Shun; Zaikova, Tatiana; Masuko, Keiichiro; Hutchison, James E

2014-01-28

The properties of metal oxide nanocrystals can be tuned by incorporating mixtures of matrix metal elements, adding metal ion dopants, or constructing core/shell structures. However, high-temperature conditions required to synthesize these nanocrystals make it difficult to achieve the desired compositions, doping levels, and structural control. We present a lower temperature synthesis of ligand-stabilized metal oxide nanocrystals that produces crystalline, monodisperse nanocrystals at temperatures well below the thermal decomposition point of the precursors. Slow injection (0.2 mL/min) of an oleic acid solution of the metal oleate complex into an oleyl alcohol solvent at 230 °C results in a rapid esterification reaction and the production of metal oxide nanocrystals. The approach produces high yields of crystalline, monodisperse metal oxide nanoparticles containing manganese, iron, cobalt, zinc, and indium within 20 min. Synthesis of tin-doped indium oxide (ITO) can be accomplished with good control of the tin doping levels. Finally, the method makes it possible to perform epitaxial growth of shells onto nanocrystal cores to produce core/shell nanocrystals.

Ionic bonding of lanthanides, as influenced by d- and f-atomic orbitals, by core-shells and by relativity.

PubMed

Ji, Wen-Xin; Xu, Wei; Schwarz, W H Eugen; Wang, Shu-Guang

2015-03-15

Lanthanide trihalide molecules LnX3 (X = F, Cl, Br, I) were quantum chemically investigated, in particular detail for Ln = Lu (lutetium). We applied density functional theory (DFT) at the nonrelativistic and scalar and SO-coupled relativistic levels, and also the ab initio coupled cluster approach. The chemically active electron shells of the lanthanide atoms comprise the 5d and 6s (and 6p) valence atomic orbitals (AO) and also the filled inner 4f semivalence and outer 5p semicore shells. Four different frozen-core approximations for Lu were compared: the (1s(2) -4d(10) ) [Pd] medium core, the [Pd+5s(2) 5p(6) = Xe] and [Pd+4f(14) ] large cores, and the [Pd+4f(14) +5s(2) 5p(6) ] very large core. The errors of LuX bonding are more serious on freezing the 5p(6) shell than the 4f(14) shell, more serious upon core-freezing than on the effective-core-potential approximation. The LnX distances correlate linearly with the AO radii of the ionic outer shells, Ln(3+) -5p(6) and X(-) -np(6) , characteristic for dominantly ionic Ln(3+) -X(-) binding. The heavier halogen atoms also bind covalently with the Ln-5d shell. Scalar relativistic effects contract and destabilize the LuX bonds, spin orbit coupling hardly affects the geometries but the bond energies, owing to SO effects in the free atoms. The relativistic changes of bond energy BE, bond length Re , bond force k, and bond stretching frequency vs do not follow the simple rules of Badger and Gordy (Re ∼BE∼k∼vs ). The so-called degeneracy-driven covalence, meaning strong mixing of accidentally near-degenerate, nearly nonoverlapping AOs without BE contribution is critically discussed. © 2015 Wiley Periodicals, Inc.

Analysis of the heat capacity of nanoclusters of FCC metals on the example of Al, Ni, Cu, Pd, and Au

NASA Astrophysics Data System (ADS)

Gafner, Yu. Ya.; Gafner, S. L.; Zamulin, I. S.; Redel, L. V.; Baidyshev, V. S.

2015-06-01

The heat capacity of ideal nickel, copper, gold, aluminum, and palladium fcc clusters with diameter of up to 6 nm has been studied in the temperature range of 150-800 K in terms of the molecular-dynamics theory using a tight-binding potential. The heat capacity of individual metallic nanoclusters has been found to exceed that characteristic of the bulk state, but by no more than 16-20%, even in the case of very small clusters. To explain the discrepancy between the simulated data and the experimental results on the compacted metals, aluminum and palladium samples with 80% theoretical density have also been investigated. Based on the simulation results and analysis of the experimental data, it has been established that the increased heat capacity of the compacted nanomaterials does not depend on the enhanced heat capacity of the individual clusters but rather, can be due to either the disordered state of the nanomaterial or a significant content of impurities (mainly, hydrogen).

Ultrafast Three-Dimensional Integrated Imaging of Strain in Core/Shell Semiconductor/Metal Nanostructures.

PubMed

Cherukara, Mathew J; Sasikumar, Kiran; DiChiara, Anthony; Leake, Steven J; Cha, Wonsuk; Dufresne, Eric M; Peterka, Tom; McNulty, Ian; Walko, Donald A; Wen, Haidan; Sankaranarayanan, Subramanian K R S; Harder, Ross J

2017-12-13

Visualizing the dynamical response of material heterointerfaces is increasingly important for the design of hybrid materials and structures with tailored properties for use in functional devices. In situ characterization of nanoscale heterointerfaces such as metal-semiconductor interfaces, which exhibit a complex interplay between lattice strain, electric potential, and heat transport at subnanosecond time scales, is particularly challenging. In this work, we use a laser pump/X-ray probe form of Bragg coherent diffraction imaging (BCDI) to visualize in three-dimension the deformation of the core of a model core/shell semiconductor-metal (ZnO/Ni) nanorod following laser heating of the shell. We observe a rich interplay of radial, axial, and shear deformation modes acting at different time scales that are induced by the strain from the Ni shell. We construct experimentally informed models by directly importing the reconstructed crystal from the ultrafast experiment into a thermo-electromechanical continuum model. The model elucidates the origin of the deformation modes observed experimentally. Our integrated imaging approach represents an invaluable tool to probe strain dynamics across mixed interfaces under operando conditions.

47 CFR 95.117 - Where to contact the FCC.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES General Mobile Radio Service (GMRS) § 95.117 Where to contact the FCC. Additional GMRS information...) FCC World Wide Web homepage: http://www.fcc.gov/wtb/prs. (c) In writing, to the FCC, Attention: GMRS...

Facile fabrication of core-in-shell particles by the slow removal of the core and its use in the encapsulation of metal nanoparticles.

PubMed

Choi, Won San; Koo, Hye Young; Kim, Dong-Yu

2008-05-06

Core-in-shell particles with controllable core size have been fabricated from core-shell particles by means of the controlled core-dissolution method. These cores in inorganic shells were employed as scaffolds for the synthesis of metal nanoparticles. After dissolution of the cores, metal nanoparticles embedded in cores were encapsulated into the interior of shell, without any damage or change. This article describes a very simple method for deriving core-in-shell particles with controllable core size and encapsulation of nanoparticles into the interior of shell.

Lattice dynamics and metastability of fcc metals in the hcp structure and the crucial role of spin-orbit coupling in platinum

NASA Astrophysics Data System (ADS)

Schönecker, Stephan; Li, Xiaoqing; Richter, Manuel; Vitos, Levente

2018-06-01

We investigate the lattice dynamical properties of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au in the nonequilibrium hcp structure by means of density-functional simulations, wherein spin-orbit coupling (SOC) was considered for Ir, Pt, and Au. The determined dynamical properties reveal that all eight elements possess a metastable hcp phase at zero temperature and pressure. The hcp Ni, Cu, Rh, Pd, and Au previously observed in nanostructures support this finding. We make evident that the inclusion of SOC is mandatory for an accurate description of the phonon dispersion relations and dynamical stability of hcp Pt. The underlying sensitivity of the interatomic force constants is ascribed to a SOC-induced splitting of degenerate band states accompanied by a pronounced reduction of electronic density of states at the Fermi level. To give further insight into the importance of SOC in Pt, we (i) focus on phase stability and examine a lattice transformation related to optical phonons in the hcp phase and (ii) focus on the generalized stacking fault energy (GSFE) of the fcc phase pertinent to crystal plasticity. We show that the intrinsic stable and unstable fault energies of the GSFE scale as in other common fcc metals, provided that the spin-orbit interaction is taken into account.

LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

NASA Astrophysics Data System (ADS)

Ximendes, Erving Clayton; Rocha, Uéslen; Kumar, Kagola Upendra; Jacinto, Carlos; Jaque, Daniel

2016-06-01

We report on Ytterbium and Neodymium codoped LaF3 core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd3+ → Yb3+ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.

Synthesis of Various Metal/TiO2 Core/shell Nanorod Arrays

NASA Astrophysics Data System (ADS)

Zhu, Wei; Wang, Guan-zhong; Hong, Xun; Shen, Xiao-shuang

2011-02-01

We present a general approach to fabricate metal/TiO2 core/shell nanorod structures by two-step electrodeposition. Firstly, TiO2 nanotubes with uniform wall thickness are prepared in anodic aluminum oxide (AAO) membranes by electrodeposition. The wall thickness of the nanotubes could be easily controlled by modulating the deposition time, and their outer diameter and length are only limited by the channel diameter and the thickness of the AAO membranes, respectively. The nanotubes' tops prepared by this method are open, while the bottoms are connected directly with the Au film at the back of the AAO membranes. Secondly, Pd, Cu, and Fe elements are filled into the TiO2 nanotubes to form core/shell structures. The core/shell nanorods prepared by this two-step process are high density and free-standing, and their length is dependent on the deposition time.

78 FR 69415 - Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions.

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-19

... FEDERAL COMMUNICATIONS COMMISSION [WC Docket No. 06-122; DA 13-2090] Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions. AGENCY: Federal Communications Commission. ACTION: Notice; correction. SUMMARY: The Federal Communications Commission published a document in the...

True Upward Adatom Diffusion and Faceting in fcc metal (110) homoepitaxy

NASA Astrophysics Data System (ADS)

Buatier de Mongeot, Francesco

2004-03-01

Recent studies of Ge heteroepitaxial growth on Si(100) have led to the discovery of an intriguing bimodal growth mode, characterised by the coexistence of smaller hut islands and much larger domes. Efforts aimed to understand the microscopic mechanisms involved have so far been focused predominantly on the role of the thermodynamic driving force associated with stress. Here we report on the observation of bimodal growth in an entirely unexpected system, homoepitaxial growth of Al on Al(110), characterised by the coexistence of smaller mound islands and tenfold taller nanocrystals with well-defined facets (the huts). Whereas the formation of the mounds results from kinetic roughening due to slow downward adatom diffusion at step edges, the formation of the huts demands atom extraction from the mounds and true upward diffusion of such atoms through the (110) terraces onto the facets serving as kinetic traps. A critical role in the faceting instability, is found to be played by the surprisingly low activation barriers for adatom ascent at step edges and island corners(F.Buatier de Mongeot, W.Zhu, A.Molle, R.Buzio, C.Boragno, U. Valbusa, E.G.Wang, Z.Zhang, Physical Review Letters 91, 016102 (2003)),(Physics News Update, AIP, Number 643,2003 Mountain climbing atoms (http://www.aip.org/enews/physnews/2003/split/643-2.html)). Extensions of the results to other related systems will be presented, in particular for the fcc(110) class of substrates Cu, Pb, Ag as well as for heteroepitaxyal systems like Co/Cu(110).

77 FR 74010 - Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-12

... 499-A, FCC Form 499-Q, and Accompanying Instructions AGENCY: Federal Communications Commission. ACTION... revenues, and the quarterly Telecommunications Reporting Worksheet, FCC Form 499-Q (Form 499-Q) and accompanying instructions (Form 499-Q Instructions) to be used in 2013 to report projected collected revenues...

Manipulation of metal-dielectric core-shell particles in optical fields

NASA Astrophysics Data System (ADS)

Chvátal, Lukáš; Šiler, Martin; Zemánek, Pavel

2014-12-01

Metal-dielectric core-shell particles represent promising tools in nanoplasmonics. In combination with optical tweezers they can be manipulated in a contactless way through fluid and their plasmonic properties can be used to probe or modify the local environment. We perform a numerical parametric study to find the particle geometry and material parameters under which such particle can be stably confined in optical tweezers. We use the theory based on Mie scattering in the focal field of an ideal water immersion objective of numerical aperture NA=1.2. For very thin metal layers we find that strong trapping on the optical axis can be achieved.

The fcc - bcc structural transition: I. A band theoretical study for Li, K, Rb, Ca, Sr, and the transition metals Ti and V

NASA Astrophysics Data System (ADS)

Sliwko, V. L.; Mohn, P.; Schwarz, K.; Blaha, P.

1996-02-01

Employing a high-precision band structure method (FP LAPW - full potential linearized augmented plane wave) we calculate the total energy variation along the tetragonal distortion path connecting the body centred cubic (bcc) and the face centred cubic (fcc) structures. The total energy along this Bain transformation is calculated, varying c/a and volume, providing a first-principles energy surface which has two minima as a function of c/a. These are shallow and occur for the sp metals at the two cubic structures, while Ti (V) has a minimum at fcc (bcc) but a saddle point (i.e. a minimum in volume and a maximum with respect to c/a) at the other cubic structure. These features can be analysed in terms of an interplay between the Madelung contribution and the band energies. Our total energy results allow us to calculate the elastic constants 0953-8984/8/7/006/img1 and 0953-8984/8/7/006/img2 and to study the influence of pressure on the phase stability. These energy surfaces will be used in part II of this paper to investigate finite-temperature effects by mapping them to a Landau - Ginzburg expansion.

Ultrafast Three-Dimensional Integrated Imaging of Strain in Core/Shell Semiconductor/Metal Nanostructures

DOE PAGES

Cherukara, Mathew J.; Sasikumar, Kiran; DiChiara, Anthony; ...

2017-11-07

Visualizing the dynamical response of material heterointerfaces is increasingly important for the design of hybrid materials and structures with tailored properties for use in functional devices. In situ characterization of nanoscale heterointerfaces such as metal-semiconductor interfaces, which exhibit a complex interplay between lattice strain, electric potential, and heat transport at subnanosecond time scales, is particularly challenging. Here in this work, we use a laser pump/X-ray probe form of Bragg coherent diffraction imaging (BCDI) to visualize in three-dimension the deformation of the core of a model core/shell semiconductor-metal (ZnO/Ni) nanorod following laser heating of the shell. We observe a rich interplaymore » of radial, axial, and shear deformation modes acting at different time scales that are induced by the strain from the Ni shell. We construct experimentally informed models by directly importing the reconstructed crystal from the ultrafast experiment into a thermo-electromechanical continuum model. The model elucidates the origin of the deformation modes observed experimentally. Our integrated imaging approach represents an invaluable tool to probe strain dynamics across mixed interfaces under operando conditions.« less

Ultrafast Three-Dimensional Integrated Imaging of Strain in Core/Shell Semiconductor/Metal Nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cherukara, Mathew J.; Sasikumar, Kiran; DiChiara, Anthony

Visualizing the dynamical response of material heterointerfaces is increasingly important for the design of hybrid materials and structures with tailored properties for use in functional devices. In situ characterization of nanoscale heterointerfaces such as metal-semiconductor interfaces, which exhibit a complex interplay between lattice strain, electric potential, and heat transport at subnanosecond time scales, is particularly challenging. Here in this work, we use a laser pump/X-ray probe form of Bragg coherent diffraction imaging (BCDI) to visualize in three-dimension the deformation of the core of a model core/shell semiconductor-metal (ZnO/Ni) nanorod following laser heating of the shell. We observe a rich interplaymore » of radial, axial, and shear deformation modes acting at different time scales that are induced by the strain from the Ni shell. We construct experimentally informed models by directly importing the reconstructed crystal from the ultrafast experiment into a thermo-electromechanical continuum model. The model elucidates the origin of the deformation modes observed experimentally. Our integrated imaging approach represents an invaluable tool to probe strain dynamics across mixed interfaces under operando conditions.« less

Computational study of dislocation based mechanisms in FCC materials

NASA Astrophysics Data System (ADS)

Yellakara, Ranga Nikhil

Understanding the relationships between microstructures and properties of materials is a key to developing new materials with more suitable qualities or employing the appropriate materials in special uses. In the present world of material research, the main focus is on microstructural control to cost-effectively enhance properties and meet performance specifications. This present work is directed towards improving the fundamental understanding of the microscale deformation mechanisms and mechanical behavior of metallic alloys, particularly focusing on face centered cubic (FCC) structured metals through a unique computational methodology called three-dimensional dislocation dynamics (3D-DD). In these simulations, the equations of motion for dislocations are mathematically solved to determine the evolution and interaction of dislocations. Microstructure details and stress-strain curves are a direct observation in the simulation and can be used to validate experimental results. The effect of initial dislocation microstructure on the yield strength has been studied. It has been shown that dislocation density based crystal plasticity formulations only work when dislocation densities/numbers are sufficiently large so that a statistically accurate description of the microstructure can be obtainable. The evolution of the flow stress for grain sizes ranging from 0.5 to 10 mum under uniaxial tension was simulated using an improvised model by integrating dislocation pile-up mechanism at grain boundaries has been performed. This study showed that for a same initial dislocation density, the Hall--Petch relationship holds well at small grain sizes (0.5--2 mum), beyond which the yield strength remains constant as the grain size increases. Various dislocation-particle interaction mechanisms have been introduced and investigations were made on their effect on the uniaxial tensile properties. These studies suggested that increase in particle volume fraction and decrease in particle

Improved open-circuit voltage in polymer/oxide-nanoarray hybrid solar cells by formation of homogeneous metal oxide core/shell structures.

PubMed

Wu, Fan; Cui, Qi; Qiu, Zeliang; Liu, Changwen; Zhang, Hui; Shen, Wei; Wang, Mingtai

2013-04-24

Incorporation of vertically aligned nanorod/nanowire arrays of metal oxide (oxide-NAs) with a polymer can produce efficient hybrid solar cells with an ideal bulk-heterojunction architecture. However, polymer/oxide-NAs solar cells still suffer from a rather low (normally, < 0.4 V) open-circuit voltage (Voc). Here we demonstrate, for the first time, a novel strategy to improve the Voc in polymer/oxide-NAs solar cells by formation of homogeneous core/shell structures and reveal the intrinsic principles involved therein. A feasible hydrothermal-solvothermal combined method is developed for preparing homogeneous core/shell nanoarrays of metal oxides with a single-crystalline nanorod as core and the aggregation layer of corresponding metal oxide quantum dots (QDs) as shell, and the shell thickness (L) is easily controlled by the solvothermal reaction time for growing QDs on the nanorod. The core/shell formation dramatically improves the device Voc up to ca. 0.7-0.8 V depending on L. Based on steady-state and dynamic measurements, as well as modeling by space-charge-limited current method, it is found that the improved Voc originates from the up-shifted conduction band edge in the core by the interfacial dipole field resulting from the decreased mobility difference between photogenerated electrons and holes after the shell growth, which increases the energy difference between the quasi-Fermi levels of photogenerated electrons in the core and holes in the polymer for a higher Voc. Our results indicate that increasing Voc by the core/shell strategy seems not to be dependent on the kinds of metal oxides.

Hydrogen vibrations in austenitic fcc Fe-Cr-Mn-Ni steels

NASA Astrophysics Data System (ADS)

Danilkin, S. A.; Fuess, H.; Wipf, H.; Ivanov, A.; Gavriljuk, V. G.; Delafosse, D.; Magnin, T.

2003-07-01

By neutron spectroscopy, we studied vibrations of H interstitials in two austenitic fcc steels (Fe0.55Cr0.20Mn0.10Ni0.15 and Fe0.54Cr0.27Ni0.19) doped with 0.37 and 0.33 at% H. The band modes, in which H vibrates with its metal neighbours, cause a weak intensity in the energy range of the acoustic vibrations of the H-free steels. The energies of the fundamental and the twofold local-mode excitations, in which H vibrates against its metal neighbours, were ~ 130 and ~ 260 meV, respectively. The respective peaks in the spectra were broadened because the metal neighbours of H, and thus its vibrational energies, vary from interstitial site to interstitial site. The above energy values support an H occupation of octahedral interstitial sites.

From Mixed-Metal MOFs to Carbon-Coated Core-Shell Metal Alloy@Metal Oxide Solid Solutions: Transformation of Co/Ni-MOF-74 to CoxNi1-x@CoyNi1-yO@C for the Oxygen Evolution Reaction.

PubMed

Sun, Dengrong; Ye, Lin; Sun, Fangxiang; García, Hermenegildo; Li, Zhaohui

2017-05-01

Calcination of the mixed-metal species Co/Ni-MOF-74 leads to the formation of carbon-coated Co x Ni 1-x @Co y Ni 1-y O with a metal core diameter of ∼3.2 nm and a metal oxide shell thickness of ∼2.4 nm embedded uniformly in the ligand-derived carbon matrix. The close proximity of Co and Ni in the mixed-metal Co/Ni-MOF-74 promotes the metal alloying and the formation of a solid solution of metal oxide during the calcination process. The presence of the tightly coated carbon shell prohibits particle agglomeration and stabilizes the Co x Ni 1-x @Co y Ni 1-y O nanoparticles in small size. The Co x Ni 1-x @Co y Ni 1-y O@C derived from Co/Ni-MOF-74 nanocomposites show superior performance for the oxygen evolution reaction (OER). The use of mixed-metal MOFs as precursors represents a powerful strategy for the fabrication of metal alloy@metal oxide solid solution nanoparticles in small size. This method also holds great promise in the development of multifunctional carbon-coated complex core-shell metal/metal oxides owing to the diversified MOF structures and their flexible chemistry.

Tracking the Magnetization Evolution in γ-Fe2O3 / Metallic Fe Core-Shell Nanoparticle Variants

NASA Astrophysics Data System (ADS)

Kons, C.; Nemati, Z.; Srikanth, H.; Phan, M.-H.; Krycka, K.; Borchers, J.; Keavney, D.; Arena, D. A.

Iron-core magnetic nanoparticles (MNPs) with oxide shells exhibit varying magnetic properties due to the different ordering temperatures of the core and shell spins, as well as the coupling across the metal/oxide interface. While spin coupling across two dimensional interfaces has been well explored, less is known about three dimensional interfaces such as those presented in the MNPs. In this work, MNPs were synthesized with a bcc Fe core and γ-Fe2O3 shell and placed in an oxygen rich environment to encourage the transition from cores shell (CS) to core void shell (CVS) to hollow (H) structures. Static magnetic measurements (MvT) and AC magnetometry were performed to explore the magnetic behavior of the various synthesized structures. To further understand the nature of the spin coupling in the MNPs, TEM and conventional magnetometry as well as variable-temperature small angle neutron scattering (SANS), x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) spectroscopy were performed. Modeling of the x-ray spectra and SANS data will enable us to develop a cohesive picture of spin coupling, freezing and frustration along the three-dimensional metal / oxide interface. Supported by Department of Energy award #DE-FG02-07ER46438; NSF Award #DMR-1508249.

Metal-core/semiconductor-shell nanocones for broadband solar absorption enhancement.

PubMed

Zhou, Lin; Yu, Xiaoqiang; Zhu, Jia

2014-02-12

Nanostructure-based photovoltaic devices have exhibited several advantages, such as reduced reflection, extraordinary light trapping, and so forth. In particular, semiconductor nanostructures provide optical modes that have strong dependence on the size and geometry. Metallic nanostructures also attract a lot of attention because of the appealing plasmonic effect on the near-field enhancement. In this study, we propose a novel design, the metal-core/semiconductor-shell nanocones with the core radius varying in a linearly gradient style. With a thin layer of semiconductor absorber coated on a metallic cone, such a design can lead to significant and broadband absorption enhancement across the entire visible and near-infrared solar spectrum. As an example of demonstration, a layer of 16 nm thick crystalline silicon (c-Si) coated on a silver nanocone can absorb 27% of standard solar radiation across a broad spectral range of 300-1100 nm, which is equivalent to a 700 nm thick flat c-Si film. Therefore, the absorption enhancement factor approaching the Yablonovitch limit is achieved with this design. The significant absorption enhancement can be ascribed to three types of optical modes, that is, Fabry-Perot modes, plasmonic modes, and hybrid modes that combine the features of the previous two. In addition, the unique nanocone geometry enables the linearly gradient radius of the semiconductor shell, which can support multiple optical resonances, critical for the broadband absorption. Our design may find general usage as elements for the low cost, high efficiency solar conversion and water-splitting devices.

Graphitic carbon nitride nanosheet@metal-organic framework core-shell nanoparticles for photo-chemo combination therapy

NASA Astrophysics Data System (ADS)

Chen, Rui; Zhang, Jinfeng; Wang, Yu; Chen, Xianfeng; Zapien, J. Antonio; Lee, Chun-Sing

2015-10-01

Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX and the PDT effect of g-C3N4 nanosheets can lead to considerably enhanced efficacy. Furthermore, the red fluorescence of DOX and the blue fluorescence of g-C3N4 nanosheets provide the additional function of dual-color imaging for monitoring the drug release process.Recently, nanoscale metal-organic frameworks (NMOFs) have started to be developed as a promising platform for bioimaging and drug delivery. On the other hand, combination therapies using multiple approaches are demonstrated to achieve much enhanced efficacy. Herein, we report, for the first time, core-shell nanoparticles consisting of a photodynamic therapeutic (PDT) agent and a MOF shell while simultaneously carrying a chemotherapeutic drug for effective combination therapy. In this work, core-shell nanoparticles of zeolitic-imadazolate framework-8 (ZIF-8) as shell embedded with graphitic carbon nitride (g-C3N4) nanosheets as core are fabricated by growing ZIF-8 in the presence of g-C3N4 nanosheets. Doxorubicin hydrochloride (DOX) is then loaded into the ZIF-8 shell of the core-shell nanoparticles. The combination of the chemotherapeutic effects of DOX

Three-Dimensional Solution of the Free Vibration Problem for Metal-Ceramic Shells Using the Method of Sampling Surfaces

NASA Astrophysics Data System (ADS)

Kulikov, G. M.; Plotnikova, S. V.

2017-03-01

The possibility of using the method of sampling surfaces (SaS) for solving the free vibration problem of threedimensional elasticity for metal-ceramic shells is studied. According to this method, in the shell body, an arbitrary number of SaS parallel to its middle surface are selected in order to take displacements of these surfaces as unknowns. The SaS pass through the nodes of a Chebyshev polynomial, which improves the convergence of the SaS method significantly. As a result, the SaS method can be used to obtain analytical solutions of the vibration problem for metal-ceramic plates and cylindrical shells that asymptotically approach the exact solutions of elasticity as the number of SaS tends to infinity.

Variational finite-difference methods in linear and nonlinear problems of the deformation of metallic and composite shells (review)

NASA Astrophysics Data System (ADS)

Maksimyuk, V. A.; Storozhuk, E. A.; Chernyshenko, I. S.

2012-11-01

Variational finite-difference methods of solving linear and nonlinear problems for thin and nonthin shells (plates) made of homogeneous isotropic (metallic) and orthotropic (composite) materials are analyzed and their classification principles and structure are discussed. Scalar and vector variational finite-difference methods that implement the Kirchhoff-Love hypotheses analytically or algorithmically using Lagrange multipliers are outlined. The Timoshenko hypotheses are implemented in a traditional way, i.e., analytically. The stress-strain state of metallic and composite shells of complex geometry is analyzed numerically. The numerical results are presented in the form of graphs and tables and used to assess the efficiency of using the variational finite-difference methods to solve linear and nonlinear problems of the statics of shells (plates)

Ab Initio Study of Chemical Reactions of Cold SrF and CaF Molecules with Alkali-Metal and Alkaline-Earth-Metal Atoms: The Implications for Sympathetic Cooling.

PubMed

Kosicki, Maciej Bartosz; Kędziera, Dariusz; Żuchowski, Piotr Szymon

2017-06-01

We investigate the energetics of the atom exchange reaction in the SrF + alkali-metal atom and CaF + alkali-metal atom systems. Such reactions are possible only for collisions of SrF and CaF with the lithium atoms, while they are energetically forbidden for other alkali-metal atoms. Specifically, we focus on SrF interacting with Li, Rb, and Sr atoms and use ab initio methods to demonstrate that the SrF + Li and SrF + Sr reactions are barrierless. We present potential energy surfaces for the interaction of the SrF molecule with the Li, Rb, and Sr atoms in their energetically lowest-lying electronic spin states. The obtained potential energy surfaces are deep and exhibit profound interaction anisotropies. We predict that the collisions of SrF molecules in the rotational or Zeeman excited states most likely have a strong inelastic character. We discuss the prospects for the sympathetic cooling of SrF and CaF molecules using ultracold alkali-metal atoms.

Metal Oxide Assisted Preparation of Core-Shell Beads with Dense Metal-Organic Framework Coatings for the Enhanced Extraction of Organic Pollutants.

PubMed

Del Rio, Mateo; Palomino Cabello, Carlos; Gonzalez, Veronica; Maya, Fernando; Parra, Jose B; Cerdà, Victor; Turnes Palomino, Gemma

2016-08-08

Dense and homogeneous metal-organic framework (MOF) coatings on functional bead surfaces are easily prepared by using intermediate sacrificial metal oxide coatings containing the metal precursor of the MOF. Polystyrene (PS) beads are coated with a ZnO layer to give ZnO@PS core-shell beads. The ZnO@PS beads are reactive in the presence of 2-methylimidazole to transform part of the ZnO coating into a porous zeolitic imidazolate framework-8 (ZIF-8) external shell positioned above the internal ZnO precursor shell. The obtained ZIF-8@ZnO@PS beads can be easily packed in column format for flow-through applications, such as the solid-phase extraction of trace priority-listed environmental pollutants. The prepared material shows an excellent permeance to flow when packed as a column to give high enrichment factors, facile regeneration, and excellent reusability for the extraction of the pollutant bisphenol A. It also shows an outstanding performance for the simultaneous enrichment of mixtures of endocrine disrupting chemicals (bisphenol A, 4-tert-octylphenol and 4-n-nonylphenol), facilitating their analysis when present at very low levels (<1 μg L(-1) ) in drinking waters. For the extraction of the pollutant bisphenol A, the prepared ZIF-8@ZnO@PS beads also show a superior extraction and preconcentration capacity to that of the PS beads used as precursors and the composite materials obtained by the direct growth of ZIF-8 on the surface of the PS beads in the absence of metal oxide intermediate coatings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A GREEN CHEMISTRY APPROACH TO PREPARATION OF CORE (FE OR CU)-SHELL (NOBLE METALS) NANOCOMPOSITES USING AQUEOUS ASCORBIC ACID

EPA Science Inventory

A greener method to fabricate novel core (Fe or Cu)-shell (noble metals) nanocomposites of transition metals such as Fe and Cu and noble metals such as Au, Pt, Pd, and Ag using aqueous ascorbic acid is described. Transition metal salts such as Cu and Fe were reduced using ascor...

Synthesis and functionalization of NaGdF4:Yb,Er@NaGdF4 core-shell nanoparticles for possible application as multimodal contrast agents.

PubMed

Baziulyte-Paulaviciene, Dovile; Karabanovas, Vitalijus; Stasys, Marius; Jarockyte, Greta; Poderys, Vilius; Sakirzanovas, Simas; Rotomskis, Ricardas

2017-01-01

Upconverting nanoparticles (UCNPs) are promising, new imaging probes capable of serving as multimodal contrast agents. In this study, monodisperse and ultrasmall core and core-shell UCNPs were synthesized via a thermal decomposition method. Furthermore, it was shown that the epitaxial growth of a NaGdF 4 optical inert layer covering the NaGdF 4 :Yb,Er core effectively minimizes surface quenching due to the spatial isolation of the core from the surroundings. The mean diameter of the synthesized core and core-shell nanoparticles was ≈8 and ≈16 nm, respectively. Hydrophobic UCNPs were converted into hydrophilic ones using a nonionic surfactant Tween 80. The successful coating of the UCNPs by Tween 80 has been confirmed by Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), photoluminescence (PL) spectra and magnetic resonance (MR) T1 relaxation measurements were used to characterize the size, crystal structure, optical and magnetic properties of the core and core-shell nanoparticles. Moreover, Tween 80-coated core-shell nanoparticles presented enhanced optical and MR signal intensity, good colloidal stability, low cytotoxicity and nonspecific internalization into two different breast cancer cell lines, which indicates that these nanoparticles could be applied as an efficient, dual-modal contrast probe for in vivo bioimaging.

Synthesis and microstructure of electrodeposited and sputtered nanotwinned face-centered-cubic metals

DOE PAGES

Bufford, Daniel C.; Wang, Morris; Liu, Yue; ...

2016-04-01

The remarkable properties of nanotwinned (NT) face-centered-cubic (fcc) metals arise directly from twin boundaries, the structures of which can be initially determined by growth twinning during the deposition process. When we understand the synthesis process and its relation to the resulting microstructure, and ultimately to material properties, we realize how key it is to understanding and utilizing these materials. Furthermore, our article presents recent studies on electrodeposition and sputtering methods that produce a high density of nanoscale growth twins in fcc metals. Nanoscale growth twins tend to form spontaneously in monolithic and alloyed fcc metals with lower stacking-fault energies, whilemore » engineered approaches are necessary for fcc metals with higher stacking-fault energies. Finally, growth defects and other microstructural features that influence nanotwin behavior and stability are introduced here, and future challenges in fabricating NT materials are highlighted.« less

Synthesis and microstructure of electrodeposited and sputtered nanotwinned face-centered-cubic metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bufford, Daniel C.; Wang, Morris; Liu, Yue

The remarkable properties of nanotwinned (NT) face-centered-cubic (fcc) metals arise directly from twin boundaries, the structures of which can be initially determined by growth twinning during the deposition process. When we understand the synthesis process and its relation to the resulting microstructure, and ultimately to material properties, we realize how key it is to understanding and utilizing these materials. Furthermore, our article presents recent studies on electrodeposition and sputtering methods that produce a high density of nanoscale growth twins in fcc metals. Nanoscale growth twins tend to form spontaneously in monolithic and alloyed fcc metals with lower stacking-fault energies, whilemore » engineered approaches are necessary for fcc metals with higher stacking-fault energies. Finally, growth defects and other microstructural features that influence nanotwin behavior and stability are introduced here, and future challenges in fabricating NT materials are highlighted.« less

Universal liquid-phase laser fabrication of various nano-metals encapsulated by ultrathin carbon shells for deep-UV plasmonics.

PubMed

Yu, Miao; Yang, Chao; Li, Xiao-Ming; Lei, Tian-Yu; Sun, Hao-Xuan; Dai, Li-Ping; Gu, Yu; Ning, Xue; Zhou, Ting; Wang, Chao; Zeng, Hai-Bo; Xiong, Jie

2017-06-29

The exploration of localized surface plasmon resonance (LSPR) beyond the usual visible waveband, for example within the ultraviolet (UV) or deep-ultraviolet (D-UV) regions, is of great significance due to its unique applications in secret communications and optics. However, it is still challenging to universally synthesize the corresponding metal nanostructures due to their high activity. Herein, we report a universal, eco-friendly, facile and rapid synthesis of various nano-metals encapsulated by ultrathin carbon shells, significantly with a remarkable deep-UV LSPR characteristic, via a liquid-phase laser fabrication method. Firstly, a new generation of the laser ablation in liquid (LAL) method has been developed with an emphasis on the elaborate selection of solvents to generate ultrathin carbon shells, and hence to stabilize the formed metal nanocrystals. As a result, a series of metal@carbon nanoparticles (NPs), including Cr@C, Ti@C, Fe@C, V@C, Al@C, Sn@C, Mn@C and Pd@C, can be fabricated by this modified LAL method. Interestingly, these NPs exhibit LSPR peaks in the range of 200-330 nm, which are very rare for localized surface plasmon resonance. Consequently, the UV plasmonic effects of these metal@carbon NPs were demonstrated both by the observed enhancement in UV photoluminescence (PL) from the carbon nanoshells and by the improvement of the photo-responsivity of UV GaN photodetectors. This work could provide a universal method for carbon shelled metal NPs and expand plasmonics into the D-UV waveband.

Hybrid core shell nanoparticles entrapping Gd-DTPA and 18F-FDG for simultaneous PET/MRI acquisitions.

PubMed

Vecchione, Donatella; Aiello, Marco; Cavaliere, Carlo; Nicolai, Emanuele; Netti, Paolo Antonio; Torino, Enza

2017-09-01

Although there has been an improvement in the hardware and software of the PET/MRI system, the development of the nanoprobes exploiting the simultaneous acquisition of the bimodal data is still under investigation. Moreover, few studies on biocompatible and clinically relevant probes are available. This work presents a core-shell polymeric nanocarrier with improved relaxometric properties for simultaneous PET/MRI acquisitions. Core-shell nanoparticles entrapping the Gd-DTPA and 18 F-FDG are obtained by a complex coacervation. The boosting of r 1 of the entrapped Gd-DTPA up to five-times compared with 'free Gd-DTPA', is confirmed by the PET/MRI scan. The sorption of 18 F-FDG into the nanoparticles is studied and designed to be integrated downstream for the production of the tracer.

A triangular prism solid and shell interactive mapping element for electromagnetic sheet metal forming process

NASA Astrophysics Data System (ADS)

Cui, Xiangyang; Li, She; Feng, Hui; Li, Guangyao

2017-05-01

In this paper, a novel triangular prism solid and shell interactive mapping element is proposed to solve the coupled magnetic-mechanical formulation in electromagnetic sheet metal forming process. A linear six-node "Triprism" element is firstly proposed for transient eddy current analysis in electromagnetic field. In present "Triprism" element, shape functions are given explicitly, and a cell-wise gradient smoothing operation is used to obtain the gradient matrices without evaluating derivatives of shape functions. In mechanical field analysis, a shear locking free triangular shell element is employed in internal force computation, and a data mapping method is developed to transfer the Lorentz force on solid into the external forces suffered by shell structure for dynamic elasto-plasticity deformation analysis. Based on the deformed triangular shell structure, a "Triprism" element generation rule is established for updated electromagnetic analysis, which means inter-transformation of meshes between the coupled fields can be performed automatically. In addition, the dynamic moving mesh is adopted for air mesh updating based on the deformation of sheet metal. A benchmark problem is carried out for confirming the accuracy of the proposed "Triprism" element in predicting flux density in electromagnetic field. Solutions of several EMF problems obtained by present work are compared with experiment results and those of traditional method, which are showing excellent performances of present interactive mapping element.

Prospects for detecting light bosons at the FCC-ee and CEPC

NASA Astrophysics Data System (ADS)

Chang, We-Fu; Ng, John N.; White, Graham

2018-06-01

We look at the prospects for detecting light bosons, X , at proposed Z factories assuming a production of 1 012 Z bosons. Such a large yield is within the design goals of future FCC-ee and CEPC colliders. Specifically, we look at the cases where X is either a singlet scalar that mixes with the standard model Higgs or a vector boson with mass 1 ≲MX≲80 GeV . We find that several channels are particularly promising for discovery prospects. In particular, Z →f f ¯X and Z →VQX give a promising signal above a very clean standard model background. We also discuss several channels that have too large a background to be useful.

Incredible antibacterial activity of noble metal functionalized magnetic core-zeolitic shell nanostructures.

PubMed

Padervand, M; Janatrostami, S; Karanji, A Kiani; Gholami, M R

2014-02-01

Functionalized magnetic core-zeolitic shell nanostructures were prepared by hydrothermal and coprecipitation methods. The products were characterized by Vibrating Sample Magnetometer (VSM), X-ray powder diffraction (XRD), Fourier Transform Infrared (FTIR) spectra, nitrogen adsorption-desorption isotherms, and Transmission Electron Microscopy (TEM). The growth of mordenite nanoparticles on the surface of silica coated nickel ferrite nanoparticles in the presence of organic templates was also confirmed. Antibacterial activity of the prepared nanostructures was investigated by the inactivation of Escherichia coli as a gram negative bacterium. A new mechanism was proposed for inactivation of E. coli over the prepared samples. In addition, the Minimum Inhibitory Concentration (MIC) and reuse ability were studied. TEM images of the destroyed cell wall after the treatment time were performed to illustrate the inactivation mechanism. According to the experimental results, the core-shell nanostructures which were modified by organic agents and then functionalized with noble metal nanoparticles were the most active. The interaction of the noble metals with the organic components on the surface of nanostructures was studied theoretically and the obtained results were used to interpret the experimental results. © 2013. Published by Elsevier B.V. All rights reserved.

Green Synthesis of InP/ZnS Core/Shell Quantum Dots for Application in Heavy-Metal-Free Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Kuo, Tsung-Rong; Hung, Shih-Ting; Lin, Yen-Ting; Chou, Tzu-Lin; Kuo, Ming-Cheng; Kuo, Ya-Pei; Chen, Chia-Chun

2017-09-01

Quantum dot light-emitting diodes (QD-LEDs) have been considered as potential display technologies with the characterizations of high color purity, flexibility, transparency, and cost efficiency. For the practical applications, the development of heavy-metal-free QD-LEDs from environment-friendly materials is the most important issue to reduce the impacts on human health and environmental pollution. In this work, heavy-metal-free InP/ZnS core/shell QDs with different fluorescence were prepared by green synthesis method with low cost, safe, and environment-friendly precursors. The InP/ZnS core/shell QDs with maximum fluorescence peak at 530 nm, superior fluorescence quantum yield of 60.1%, and full width at half maximum of 55 nm were applied as an emission layer to fabricate multilayered QD-LEDs. The multilayered InP/ZnS core/shell QD-LEDs showed the turn-on voltage at 5 V, the highest luminance (160 cd/m2) at 12 V, and the external quantum efficiency of 0.223% at 6.7 V. Overall, the multilayered InP/ZnS core/shell QD-LEDs reveal potential to be the heavy-metal-free QD-LEDs for future display applications.

Nitride stabilized core/shell nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuttiyiel, Kurian Abraham; Sasaki, Kotaro; Adzic, Radoslav R.

Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

47 CFR 1.8001 - FCC Registration Number (FRN).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC Registration Number (FRN). 1.8001 Section 1.8001 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE FCC... unique identifying number that is assigned to entities doing business with the Commission. (b) The FRN is...

Inner-shell chemistry under high pressure

NASA Astrophysics Data System (ADS)

Miao, Maosheng; Botana, Jorge; Pravica, Michael; Sneed, Daniel; Park, Changyong

2017-05-01

Chemistry at ambient conditions has implicit boundaries rooted in the atomic shell structure: the inner-shell electrons and the unoccupied outer-shell orbitals do not contribute as the major component to chemical reactions and in chemical bonds. These general rules govern our understanding of chemical structures and reactions. We review the recent progresses in high-pressure chemistry demonstrating that the above rules can be violated under extreme conditions. Using a first principles computation method and crystal structure search algorithm, we demonstrate that stable compounds involving inner shell electrons such as CsF3, CsF5, HgF3, and HgF4 can form under high external pressure and may present exotic properties. We also discuss experimental studies that have sought to confirm these predictions. Employing our recently developed hard X-ray photochemistry methods in a diamond anvil cell, we show promising early results toward realizing inner shell chemistry experimentally.

Wooden shell of M2-F1 being assembled at El Mirage

NASA Technical Reports Server (NTRS)

1962-01-01

Wooden shell of the M2-F1 being assembled at El Mirage, CA. While Flight Research Center technicians built the internal steel structure of the M2-F1, sailplane builder Gus Briegleb built the vehicle's outer wooden shell. Its skin was 3/32-inch mahogany plywood, with 1/8-inch mahogany rib sections reinforced with spruce. The wingless, lifting body aircraft design was initially conceived as a means of landing an aircraft horizontally after atmospheric reentry. The absence of wings would make the extreme heat of re-entry less damaging to the vehicle. In 1962, Dryden management approved a program to build a lightweight, unpowered lifting body as a prototype to flight test the wingless concept. It would look like a 'flying bathtub,' and was designated the M2-F1, the 'M' referring to 'manned' and 'F' referring to 'flight' version. It featured a plywood shell placed over a tubular steel frame crafted at Dryden. Construction was completed in 1963. The first flight tests of the M2-F1 were over Rogers Dry Lake at the end of a tow rope attached to a hopped-up Pontiac convertible driven at speeds up to about 120 mph. This vehicle needed to be able to tow the M2-F1 on the Rogers Dry Lakebed adjacent to NASA's Flight Research Center (FRC) at a minimum speed of 100 miles per hour. To do that, it had to handle the 400-pound pull of the M2-F1. Walter 'Whitey' Whiteside, who was a retired Air Force maintenance officer working in the FRC's Flight Operations Division, was a dirt-bike rider and hot-rodder. Together with Boyden 'Bud' Bearce in the Procurement and Supply Branch of the FRC, Whitey acquired a Pontiac Catalina convertible with the largest engine available. He took the car to Bill Straup's renowned hot-rod shop near Long Beach for modification. With a special gearbox and racing slicks, the Pontiac could tow the 1,000-pound M2-F1 110 miles per hour in 30 seconds. It proved adequate for the roughly 400 car tows that got the M2-F1 airborne to prove it could fly safely and to

The Origin of the s, p, d, f Orbital Labels

ERIC Educational Resources Information Center

Jensen, William B.

2007-01-01

The theory of s, p, d and f dealing with the line spectra of the alkali metals during the period 1881 based on analogies with the harmonic ratios of sound is described. Friedrich Hund followed Bohr's practice of labelling the various shells and subshells by replacing the secondary quantum number with the series notations (s, p, d, and f), which…

Nanostructured core-shell electrode materials for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Jiang, Long-bo; Yuan, Xing-zhong; Liang, Jie; Zhang, Jin; Wang, Hou; Zeng, Guang-ming

2016-11-01

Core-shell nanostructure represents a unique system for applications in electrochemical energy storage devices. Owing to the unique characteristics featuring high power delivery and long-term cycling stability, electrochemical capacitors (ECs) have emerged as one of the most attractive electrochemical storage systems since they can complement or even replace batteries in the energy storage field, especially when high power delivery or uptake is needed. This review aims to summarize recent progress on core-shell nanostructures for advanced supercapacitor applications in view of their hierarchical architecture which not only create the desired hierarchical porous channels, but also possess higher electrical conductivity and better structural mechanical stability. The core-shell nanostructures include carbon/carbon, carbon/metal oxide, carbon/conducting polymer, metal oxide/metal oxide, metal oxide/conducting polymer, conducting polymer/conducting polymer, and even more complex ternary core-shell nanoparticles. The preparation strategies, electrochemical performances, and structural stabilities of core-shell materials for ECs are summarized. The relationship between core-shell nanostructure and electrochemical performance is discussed in detail. In addition, the challenges and new trends in core-shell nanomaterials development have also been proposed.

Green Synthesis of InP/ZnS Core/Shell Quantum Dots for Application in Heavy-Metal-Free Light-Emitting Diodes.

PubMed

Kuo, Tsung-Rong; Hung, Shih-Ting; Lin, Yen-Ting; Chou, Tzu-Lin; Kuo, Ming-Cheng; Kuo, Ya-Pei; Chen, Chia-Chun

2017-09-19

Quantum dot light-emitting diodes (QD-LEDs) have been considered as potential display technologies with the characterizations of high color purity, flexibility, transparency, and cost efficiency. For the practical applications, the development of heavy-metal-free QD-LEDs from environment-friendly materials is the most important issue to reduce the impacts on human health and environmental pollution. In this work, heavy-metal-free InP/ZnS core/shell QDs with different fluorescence were prepared by green synthesis method with low cost, safe, and environment-friendly precursors. The InP/ZnS core/shell QDs with maximum fluorescence peak at ~ 530 nm, superior fluorescence quantum yield of 60.1%, and full width at half maximum of 55 nm were applied as an emission layer to fabricate multilayered QD-LEDs. The multilayered InP/ZnS core/shell QD-LEDs showed the turn-on voltage at ~ 5 V, the highest luminance (160 cd/m 2 ) at 12 V, and the external quantum efficiency of 0.223% at 6.7 V. Overall, the multilayered InP/ZnS core/shell QD-LEDs reveal potential to be the heavy-metal-free QD-LEDs for future display applications.

Facile preparation of magnetic metal organic frameworks core-shell nanoparticles for stimuli-responsive drug carrier

NASA Astrophysics Data System (ADS)

Li, Sheng; Bi, Ke; Xiao, Ling; Shi, Xiaowen

2017-12-01

Facile synthesis of core-shell magnetic MOFs for drug delivery is of significance due to the advantages of high drug load and easy separation. In this work, magnetic metal organic frameworks (MOFs, Fe3O4-NH2@MIL101-NH2) core-shell nanoparticles were synthesized rapidly in water phase by microwave irradiation using Fe3+ and 2-amino-1,4-benzenedicarboxylate (BDC-NH2) as metal ions and ligands respectively. The resulting magnetic MOFs exhibit large surface areas (96.04 m2 g-1), excellent magnetic response (20.47 emu g-1) and large mesopore volume (22.07 cm3 g-1) along with spherical morphologies with the diameters ranging from 140-330 nm. Using doxorubicin (DOX) as a model drug, the drug loading capacity of Fe3O4-NH2@MIL101-NH2 could reach 36.02%, substantially higher than pristine MIL101-NH2. Importantly, the release of DOX could be controlled by pH as well as the meso pore size of MOFs. The cytotoxicity assay showed that the magnetic MOFs have low cytotoxicity and good biocompatibility. The results suggest great potential of the magnetic MOFs core-shell nanoparticles fabricated in this study on controlled drug release of DOX.

Facile preparation of magnetic metal organic frameworks core-shell nanoparticles for stimuli-responsive drug carrier.

PubMed

Li, Sheng; Bi, Ke; Xiao, Ling; Shi, Xiaowen

2017-12-08

Facile synthesis of core-shell magnetic MOFs for drug delivery is of significance due to the advantages of high drug load and easy separation. In this work, magnetic metal organic frameworks (MOFs, Fe 3 O 4 -NH 2 @MIL101-NH 2 ) core-shell nanoparticles were synthesized rapidly in water phase by microwave irradiation using Fe 3+ and 2-amino-1,4-benzenedicarboxylate (BDC-NH 2 ) as metal ions and ligands respectively. The resulting magnetic MOFs exhibit large surface areas (96.04 m 2 g -1 ), excellent magnetic response (20.47 emu g -1 ) and large mesopore volume (22.07 cm 3 g -1 ) along with spherical morphologies with the diameters ranging from 140-330 nm. Using doxorubicin (DOX) as a model drug, the drug loading capacity of Fe 3 O 4 -NH 2 @MIL101-NH 2 could reach 36.02%, substantially higher than pristine MIL101-NH 2 . Importantly, the release of DOX could be controlled by pH as well as the meso pore size of MOFs. The cytotoxicity assay showed that the magnetic MOFs have low cytotoxicity and good biocompatibility. The results suggest great potential of the magnetic MOFs core-shell nanoparticles fabricated in this study on controlled drug release of DOX.

Symmetry-guaranteed nodal-line semimetals in an fcc lattice

NASA Astrophysics Data System (ADS)

Kawakami, Takuto; Hu, Xiao

2017-12-01

We demonstrate theoretically that nodal-line semimetals (NLSs) can be realized in an fcc lattice with orbitals belonging to the same irreducible representation, such as {px,py,pz} or {dx y,dy z,dz x} orbitals on every lattice site. The three orbitals are divided into two subgroups in terms of the parity with respect to the mirror reflections on high-symmetry planes of the fcc lattice, which, with rotation symmetry, endows symmetry-guaranteed NL passing through W points in the Brillouin zone. Depending on the parameters, there also appears an accidental NL around the Γ point. We notice that the symmetry-guaranteed NL addressed in the present work can be found in band structures of elemental solids taking the fcc structure, such as Cu, Ag, Au, In, Ga, etc., as well as opal, which is an fcc photonic crystal of SiO2 spheres. Furthermore, we clarify that the fcc lattice of Si spheres exhibits a NL in a frequency band where no other photonic band exists, which provides a unique platform to realize topological NLSs under intensive search, and can be explored for achieving slow light.

Facet-Dependent Deposition of Highly Strained Alloyed Shells on Intermetallic Nanoparticles for Enhanced Electrocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chenyu; Sang, Xiahan; Gamler, Jocelyn T. L.

Compressive surface strains can enhance the performance of platinum-based core@shell electrocatalysts for the oxygen reduction reaction (ORR). Bimetallic core@shell nanoparticles (NPs) are widely studied nanocatalysts but often have limited lattice mismatch and surface compositions; investigations of core@shell NPs with greater compositional complexity and lattice misfit are in their infancy. Here, a new class of multimetallic NPs composed of intermetallic cores and random alloy shells is reported. Specifically, face-centered cubic (fcc) Pt- Cu random alloy shells were deposited non-epitaxially on PdCu B2 intermetallic seeds, giving rise to faceted core@shell NPs with highly strained surfaces. In fact, high resolution transmission electron microscopymore » (HRTEM) revealed orientation-dependent surface strains, where the compressive strains were minimal on Pt-Cu {111} facets but greater on {200} facets. These core@shell NPs provide higher specific and mass activities for the ORR when compared to conventional Pt-Cu NPs. Moreover, these intermetallic@random alloy NPs displayed high endurance, undergoing 10,000 cycles with only a slight decay in activity and no apparent structural changes.« less

Facet-Dependent Deposition of Highly Strained Alloyed Shells on Intermetallic Nanoparticles for Enhanced Electrocatalysis

DOE PAGES

Wang, Chenyu; Sang, Xiahan; Gamler, Jocelyn T. L.; ...

2017-08-25

Compressive surface strains can enhance the performance of platinum-based core@shell electrocatalysts for the oxygen reduction reaction (ORR). Bimetallic core@shell nanoparticles (NPs) are widely studied nanocatalysts but often have limited lattice mismatch and surface compositions; investigations of core@shell NPs with greater compositional complexity and lattice misfit are in their infancy. Here, a new class of multimetallic NPs composed of intermetallic cores and random alloy shells is reported. Specifically, face-centered cubic (fcc) Pt- Cu random alloy shells were deposited non-epitaxially on PdCu B2 intermetallic seeds, giving rise to faceted core@shell NPs with highly strained surfaces. In fact, high resolution transmission electron microscopymore » (HRTEM) revealed orientation-dependent surface strains, where the compressive strains were minimal on Pt-Cu {111} facets but greater on {200} facets. These core@shell NPs provide higher specific and mass activities for the ORR when compared to conventional Pt-Cu NPs. Moreover, these intermetallic@random alloy NPs displayed high endurance, undergoing 10,000 cycles with only a slight decay in activity and no apparent structural changes.« less

Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes

DOE PAGES

Liu, Wei; Li, Weiyang; Zhuo, Denys; ...

2017-02-08

Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO 2@PMMA) core–shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Lastly, enhanced Coulombic efficiencies during lithium charge/discharge cycles have been achieved at various current densities andmore » areal capacities.« less

Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Li, Weiyang; Zhuo, Denys

Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO 2@PMMA) core–shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Lastly, enhanced Coulombic efficiencies during lithium charge/discharge cycles have been achieved at various current densities andmore » areal capacities.« less

Carboxyl-functionalized nanoparticles with magnetic core and mesopore carbon shell as adsorbents for the removal of heavy metal ions from aqueous solution.

PubMed

Wang, Hui; Yu, Yi-Fei; Chen, Qian-Wang; Cheng, Kai

2011-01-21

This communication demonstrates superparamagnetic nanosized particles with a magnetic core and a porous carbon shell (thickness of 11 nm), which can remove 97% of Pb(2+) ions from an acidic aqueous solution at a Pb(2+) ion concentration of 100 mg L(-1). It is suggested that a weak electrostatic force of attraction between the heavy metal ions and the nanoparticles and the heavy metal ions adsorption on the mesopore carbon shell contribute most to the superior removal property.

An Enzyme-Coated Metal-Organic Framework Shell for Synthetically Adaptive Cell Survival.

PubMed

Liang, Kang; Richardson, Joseph J; Doonan, Christian J; Mulet, Xavier; Ju, Yi; Cui, Jiwei; Caruso, Frank; Falcaro, Paolo

2017-07-10

A bioactive synthetic porous shell was engineered to enable cells to survive in an oligotrophic environment. Eukaryotic cells (yeast) were firstly coated with a β-galactosidase (β-gal), before crystallization of a metal-organic framework (MOF) film on the enzyme coating; thereby producing a bioactive porous synthetic shell. The β-gal was an essential component of the bioactive shell as it generated nutrients (that is, glucose and galactose) required for cell viability in nutrient-deficient media (lactose-based). Additionally, the porous MOF coating carried out other vital functions, such as 1) shielding the cells from cytotoxic compounds and radiation, 2) protecting the non-native enzymes (β-gal in this instance) from degradation and internalization, and 3) allowing for the diffusion of molecules essential for the survival of the cells. Indeed, this bioactive porous shell enabled the survival of cells in simulated extreme oligotrophic environments for more than 7 days, leading to a decrease in cell viability less than 30 %, versus a 99 % decrease for naked yeast. When returned to optimal growth conditions the bioactive porous exoskeleton could be removed and the cells regained full growth immediately. The construction of bioactive coatings represents a conceptually new and promising approach for the next-generation of cell-based research and application, and is an alternative to synthetic biology or genetic modification. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Principles and Methods for the Rational Design of Core-Shell Nanoparticle Catalysts with Ultralow Noble Metal Loadings.

PubMed

Hunt, Sean T; Román-Leshkov, Yuriy

2018-05-15

Conspecuts Commercial and emerging renewable energy technologies are underpinned by precious metal catalysts, which enable the transformation of reactants into useful products. However, the noble metals (NMs) comprise the least abundant elements in the lithosphere, making them prohibitively scarce and expensive for future global-scale technologies. As such, intense research efforts have been devoted to eliminating or substantially reducing the loadings of NMs in various catalytic applications. These efforts have resulted in a plethora of heterogeneous NM catalyst morphologies beyond the traditional supported spherical nanoparticle. In many of these new architectures, such as shaped, high index, and bimetallic particles, less than 20% of the loaded NMs are available to perform catalytic turnovers. The majority of NM atoms are subsurface, providing only a secondary catalytic role through geometric and ligand effects with the active surface NM atoms. A handful of architectures can approach 100% NM utilization, but severe drawbacks limit general applicability. For example, in addition to problems with stability and leaching, single atom and ultrasmall cluster catalysts have extreme metal-support interactions, discretized d-bands, and a lack of adjacent NM surface sites. While monolayer thin films do not possess these features, they exhibit such low surface areas that they are not commercially relevant, serving predominantly as model catalysts. This Account champions core-shell nanoparticles (CS NPs) as a vehicle to design highly active, stable, and low-cost materials with high NM utilization for both thermo- and electrocatalysis. The unique benefits of the many emerging NM architectures could be preserved while their fundamental limitations could be overcome through reformulation via a core-shell morphology. However, the commercial realization of CS NPs remains challenging, requiring concerted advances in theory and manufacturing. We begin by formulating seven

Non-empirical Prediction of the Photophysical and Magnetic Properties of Systems with Open d- and f-Shells Based on Combined Ligand Field and Density Functional Theory (LFDFT).

PubMed

Daul, Claude

2014-09-01

Despite the important growth of ab initio and computational techniques, ligand field theory in molecular science or crystal field theory in condensed matter offers the most intuitive way to calculate multiplet energy levels arising from systems with open shells d and/or f electrons. Over the past decade we have developed a ligand field treatment of inorganic molecular modelling taking advantage of the dominant localization of the frontier orbitals within the metal-sphere. This feature, which is observed in any inorganic coordination compound, especially if treated by Density Functional Theory calculation, allows the determination of the electronic structure and properties with a surprising good accuracy. In ligand field theory, the theoretical concepts consider only a single atom center; and treat its interaction with the chemical environment essentially as a perturbation. Therefore success in the simple ligand field theory is no longer questionable, while the more accurate molecular orbital theory does in general over-estimate the metal-ligand covalence, thus yields wave functions that are too delocalized. Although LF theory has always been popular as a semi-empirical method when dealing with molecules of high symmetry e.g. cubic symmetry where the number of parameters needed is reasonably small (3 or 5), this is no more the case for molecules without symmetry and involving both an open d- and f-shell (# parameters ∼90). However, the combination of LF theory and Density Functional (DF) theory that we introduced twenty years ago can easily deal with complex molecules of any symmetry with two and more open shells. The accuracy of these predictions from 1(st) principles achieves quite a high accuracy (<5%) in terms of states energies. Hence, this approach is well suited to predict the magnetic and photo-physical properties arbitrary molecules and materials prior to their synthesis, which is the ultimate goal of each computational chemist. We will illustrate the

Disorders of metal metabolism

PubMed Central

Ferreira, Carlos R.; Gahl, William A.

2017-01-01

Trace elements are chemical elements needed in minute amounts for normal physiology. Some of the physiologically relevant trace elements include iodine, copper, iron, manganese, zinc, selenium, cobalt and molybdenum. Of these, some are metals, and in particular, transition metals. The different electron shells of an atom carry different energy levels, with those closest to the nucleus being lowest in energy. The number of electrons in the outermost shell determines the reactivity of such an atom. The electron shells are divided in sub-shells, and in particular the third shell has s, p and d sub-shells. Transition metals are strictly defined as elements whose atom has an incomplete d sub-shell. This incomplete d sub-shell makes them prone to chemical reactions, particularly redox reactions. Transition metals of biologic importance include copper, iron, manganese, cobalt and molybdenum. Zinc is not a transition metal, since it has a complete d sub-shell. Selenium, on the other hand, is strictly speaking a nonmetal, although given its chemical properties between those of metals and nonmetals, it is sometimes considered a metalloid. In this review, we summarize the current knowledge on the inborn errors of metal and metalloid metabolism. PMID:29354481

Promising half-metallicity in ductile NbF3: a first-principles prediction.

PubMed

Yang, Bo; Wang, Junru; Liu, Xiaobiao; Zhao, Mingwen

2018-02-14

Materials with half-metallicity are long desired in spintronics. Using first-principles calculations, we predicted that the already-synthesized NbF 3 crystal is a promising half-metal with a large exchange splitting and stable ferromagnetism. The mechanical stability, ductility and softness of the NbF 3 crystal were confirmed by its elastic constants and moduli. The Curie temperature (T C = 120 K) estimated from the Monte Carlo simulations based on the 3D Ising model is above the liquid nitrogen temperature (78 K). The ferromagnetism and half-metallicity can be preserved on the surfaces of NbF 3 . The NbOF 2 formed by substituting F with O atoms, however, has an antiferromagnetic ground state and a normal metallic band structure. This work opens an avenue for half-metallic materials and may find applications in spintronic devices.

First Determination of the Level Structure of an s d -Shell Hypernucleus, F19Λ

NASA Astrophysics Data System (ADS)

Yang, S. B.; Ahn, J. K.; Akazawa, Y.; Aoki, K.; Chiga, N.; Ekawa, H.; Evtoukhovitch, P.; Feliciello, A.; Fujita, M.; Hasegawa, S.; Hayakawa, S.; Hayakawa, T.; Honda, R.; Hosomi, K.; Hwang, S. H.; Ichige, N.; Ichikawa, Y.; Ikeda, M.; Imai, K.; Ishimoto, S.; Kanatsuki, S.; Kim, S. H.; Kinbara, S.; Kobayashi, K.; Koike, T.; Lee, J. Y.; Miwa, K.; Moon, T. J.; Nagae, T.; Nakada, Y.; Nakagawa, M.; Ogura, Y.; Sakaguchi, A.; Sako, H.; Sasaki, Y.; Sato, S.; Shirotori, K.; Sugimura, H.; Suto, S.; Suzuki, S.; Takahashi, T.; Tamura, H.; Tanida, K.; Togawa, Y.; Tsamalaidze, Z.; Ukai, M.; Wang, T. F.; Yamamoto, T. O.; J-PARC E13 Collaboration

2018-03-01

We report on the first observation of γ rays emitted from an s d -shell hypernucleus, F19Λ . The energy spacing between the ground state doublet, 1 /2+ and 3 /2+ states, of F19Λ is determined to be 315.5 ±0.4 (stat )-0.5+0.6(syst ) keV by measuring the γ -ray energy of the M 1 (3 /2+→1 /2+) transition. In addition, three γ -ray peaks are observed and assigned as E 2 (5 /2+→1 /2+), E 1 (1 /2-→1 /2+), and E 1 (1 /2-→3 /2+) transitions. The excitation energies of the 5 /2+ and 1 /2- states are determined to be 895.2 ±0.3 (stat )±0.5 (syst ) and 1265.6 ±1.2 (stat )-0.5+0.7(syst ) keV , respectively. It is found that the ground state doublet spacing is well described by theoretical models based on existing s - and p -shell hypernuclear data.

On the Highest Oxidation States of Metal Elements in MO4 Molecules (M = Fe, Ru, Os, Hs, Sm, and Pu).

PubMed

Huang, Wei; Xu, Wen-Hua; Schwarz, W H E; Li, Jun

2016-05-02

Metal tetraoxygen molecules (MO4, M = Fe, Ru, Os, Hs, Sm, Pu) of all metal atoms M with eight valence electrons are theoretically studied using density functional and correlated wave function approaches. The heavier d-block elements Ru, Os, Hs are confirmed to form stable tetraoxides of Td symmetry in (1)A1 electronic states with empty metal d(0) valence shell and closed-shell O(2-) ligands, while the 3d-, 4f-, and 5f-elements Fe, Sm, and Pu prefer partial occupation of their valence shells and peroxide or superoxide ligands at lower symmetry structures with various spin couplings. The different geometric and electronic structures and chemical bonding types of the six iso-stoichiometric species are explained in terms of atomic orbital energies and orbital radii. The variations found here contribute to our general understanding of the periodic trends of oxidation states across the periodic table.

Core/Shell NaGdF4:Nd3+/NaGdF4 Nanocrystals with Efficient Near-Infrared to Near-Infrared Downconversion Photoluminescence for Bioimaging Applications

PubMed Central

Chen, Guanying; Ohulchanskyy, Tymish Y.; Liu, Sha; Law, Wing-Cheung; Wu, Fang; Swihart, Mark T.; Ågren, Hans; Prasad, Paras N.

2012-01-01

We have synthesized core/shell NaGdF4:Nd3+/NaGdF4 nanocrystals with an average size of 15 nm and exceptionally high photoluminescence (PL) quantum yield. When excited at 740 nm, the nanocrystals manifest spectrally distinguished, near infrared to near infrared (NIR-to-NIR) downconversion PL peaked at ~900, ~1050, and ~1300 nm. The absolute quantum yield of NIR-to-NIR PL reached 40% for core-shell nanoparticles dispersed in hexane. Time-resolved PL measurements revealed that this high quantum yield was achieved through suppression of nonradiative recombination originating from surface states and cross relaxations between dopants. NaGdF4:Nd3+/NaGdF4 nanocrystals, synthesized in organic media, were further converted to be water-dispersible by eliminating the capping ligand of oleic acid. NIR-to-NIR PL bioimaging was demonstrated both in vitro and in vivo through visualization of the NIR-to-NIR PL at ~900 nm under incoherent lamp light excitation. The fact that both excitation and the PL of these nanocrystals are in the biological window of optical transparency, combined with their high quantum efficiency, spectral sharpness and photostability, makes these nanocrystals extremely promising as optical biomaging probes. PMID:22401578

Assessment of heavy metal contamination in intertidal gastropod and bivalve shells from central Arabian Gulf coastline, Saudi Arabia

NASA Astrophysics Data System (ADS)

El-Sorogy, Abdelbaset S.; Youssef, Mohamed

2015-11-01

In order to assess pollutants and impact of environmental changes along the Saudi Arabian Gulf coast, forty specimens of gastropod and bivalve shells belonging to Diodora funiculata, Lunella coronata, Cerithium caeruleum, Barbatia parva, Pinctada margaritifera, Amiantis umbonella, Acrosterigma assimile and Asaphis violascens from five localities are selected for Fe, Cu, Pb, Mn, Cd, Se, As, Co, B, Cr, Hg, Mo analysis. The analysis indicated that heavy metal values (except Fe) were less than those recorded in molluscan shells from Gulf of Oman, Red Sea and Indian Ocean. D. funiculate, L. coronata, B. parva and P. margaritifera are good accumulators of Cu, As, Cr. The other species gave a nearly constant concentration in all the studied areas. Al Jubail coast recorded the highest heavy metal concentrations (except Mn at Ras Al-Ghar and Se at Al Jubail industrial city). Heavy metal contamination is mostly attributed to anthropogenic sources, especially effluents from petrochemical industries, sewage and desalination plants.

Pb(core)/ZnO(shell) nanowires obtained by microwave-assisted method

PubMed Central

2011-01-01

In this study, Pb-filled ZnO nanowires [Pb(core)/ZnO(shell)] were synthesized by a simple and novel one-step vapor transport and condensation method by microwave-assisted decomposition of zinc ferrite. The synthesis was performed using a conventional oven at 1000 W and 5 min of treatment. After synthesis, a spongy white cotton-like material was obtained in the condensation zone of the reaction system. HRTEM analysis revealed that product consists of a Pb-(core) with (fcc) cubic structure that preferentially grows in the [111] direction and a hexagonal wurtzite ZnO-(Shell) that grows in the [001] direction. Nanowire length was more than 5 μm and a statistical analysis determined that the shell and core diameters were 21.00 ± 3.00 and 4.00 ± 1.00 nm, respectively. Experimental, structural details, and synthesis mechanism are discussed in this study. PMID:21985637

47 CFR 0.409 - Commission policy on private printing of FCC forms.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Commission policy on private printing of FCC... ORGANIZATION General Information General § 0.409 Commission policy on private printing of FCC forms. The Commission has established a policy regarding the printing of blank FCC forms by private companies if they...

Stacking fault density and bond orientational order of fcc ruthenium nanoparticles

NASA Astrophysics Data System (ADS)

Seo, Okkyun; Sakata, Osami; Kim, Jae Myung; Hiroi, Satoshi; Song, Chulho; Kumara, Loku Singgappulige Rosantha; Ohara, Koji; Dekura, Shun; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi

2017-12-01

We investigated crystal structure deviations of catalytic nanoparticles (NPs) using synchrotron powder X-ray diffraction. The samples were fcc ruthenium (Ru) NPs with diameters of 2.4, 3.5, 3.9, and 5.4 nm. We analyzed average crystal structures by applying the line profile method to a stacking fault model and local crystal structures using bond orientational order (BOO) parameters. The reflection peaks shifted depending on rules that apply to each stacking fault. We evaluated the quantitative stacking faults densities for fcc Ru NPs, and the stacking fault per number of layers was 2-4, which is quite large. Our analysis shows that the fcc Ru 2.4 nm-diameter NPs have a considerably high stacking fault density. The B factor tends to increase with the increasing stacking fault density. A structural parameter that we define from the BOO parameters exhibits a significant difference from the ideal value of the fcc structure. This indicates that the fcc Ru NPs are highly disordered.

In situ TEM observation of FCC Ti formation at elevated temperatures

DOE PAGES

Yu, Qian; Kacher, Josh; Gammer, Christoph; ...

2017-07-04

Pure Ti traditionally exhibits the hexagonal closed packed (HCP) crystallographic structure under ambient conditions and the body centered cubic (BCC) structure at elevated temperatures. In addition to these typical structures for Ti alloys, the presence of a face centered cubic (FCC) phase associated with thin films, interfaces, or high levels of plastic deformation has occasionally been reported. Here in this paper we show that small FCC precipitates form in freestanding thin foils during in situ transmission electron microscope (TEM) heating and we discuss the potential origins of the FCC phase in light of the in situ observations. This FCC phasemore » was found to be stable upon cooling and under ambient conditions, which allowed us to explore its mechanical properties and stability via nanomechanical in situ TEM testing. It was found that FCC platelets within the HCP matrix phase were stable under mechanical deformation and exhibited similar mechanical deformation behavior as the parent HCP phase.« less

In situ TEM observation of FCC Ti formation at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Qian; Kacher, Josh; Gammer, Christoph

Pure Ti traditionally exhibits the hexagonal closed packed (HCP) crystallographic structure under ambient conditions and the body centered cubic (BCC) structure at elevated temperatures. In addition to these typical structures for Ti alloys, the presence of a face centered cubic (FCC) phase associated with thin films, interfaces, or high levels of plastic deformation has occasionally been reported. Here in this paper we show that small FCC precipitates form in freestanding thin foils during in situ transmission electron microscope (TEM) heating and we discuss the potential origins of the FCC phase in light of the in situ observations. This FCC phasemore » was found to be stable upon cooling and under ambient conditions, which allowed us to explore its mechanical properties and stability via nanomechanical in situ TEM testing. It was found that FCC platelets within the HCP matrix phase were stable under mechanical deformation and exhibited similar mechanical deformation behavior as the parent HCP phase.« less

The relative energy of fcc and hcp foams

NASA Astrophysics Data System (ADS)

Whyte, D.; Weaire, D.; Drenckhan, W.; Hutzler, S.

2015-06-01

The energies of face-centred cubic (fcc) and hexagonal close-packed (hcp) monodisperse foams, associated with their total surface area, are equal in the wet and dry limits, in the usual model. We prove that for all intermediate values of liquid fraction, hcp has lower energy. Energy considerations are thus not sufficient to explain the observed preference for crystallization into fcc over hcp in experiments using monodisperse bubbles.

Quantitative investigation on the critical thickness of the dielectric shell for metallic nanoparticles determined by the plasmon decay length.

PubMed

Li, Anran; Lim, Xinyi; Guo, Lin; Li, Shuzhou

2018-04-20

Inert dielectric shells coating the surface of metallic nanoparticles (NPs) are important for enhancing the NPs' stability, biocompatibility, and realizing targeting detection, but they impair NPs' sensing ability due to the electric fields damping. The dielectric shell not only determines the distance of the analyte from the NP surface, but also affects the field decay. From a practical point of view, it is extremely important to investigate the critical thickness of the shell, beyond which the NPs are no longer able to effectively detect the analytes. The plasmon decay length of the shell-coated NPs determines the critical thickness of the coating layer. Extracting from the exponential fitting results, we quantitatively demonstrate that the critical thickness of the shell exhibits a linear dependence on the NP volume and the dielectric constants of the shell and the surrounding medium, but only with a small variation influenced by the NP shape where the dipole resonance is dominated. We show the critical thickness increases with enlarging the NP sizes, or increasing the dielectric constant differences between the shell and surrounding medium. The findings are essential for applications of shell-coated NPs in plasmonic sensing.

Quantitative investigation on the critical thickness of the dielectric shell for metallic nanoparticles determined by the plasmon decay length

NASA Astrophysics Data System (ADS)

Li, Anran; Lim, Xinyi; Guo, Lin; Li, Shuzhou

2018-04-01

Inert dielectric shells coating the surface of metallic nanoparticles (NPs) are important for enhancing the NPs’ stability, biocompatibility, and realizing targeting detection, but they impair NPs’ sensing ability due to the electric fields damping. The dielectric shell not only determines the distance of the analyte from the NP surface, but also affects the field decay. From a practical point of view, it is extremely important to investigate the critical thickness of the shell, beyond which the NPs are no longer able to effectively detect the analytes. The plasmon decay length of the shell-coated NPs determines the critical thickness of the coating layer. Extracting from the exponential fitting results, we quantitatively demonstrate that the critical thickness of the shell exhibits a linear dependence on the NP volume and the dielectric constants of the shell and the surrounding medium, but only with a small variation influenced by the NP shape where the dipole resonance is dominated. We show the critical thickness increases with enlarging the NP sizes, or increasing the dielectric constant differences between the shell and surrounding medium. The findings are essential for applications of shell-coated NPs in plasmonic sensing.

THE KINEMATICS OF THE NEBULAR SHELLS AROUND LOW MASS PROGENITORS OF PNe WITH LOW METALLICITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pereyra, Margarita; López, José Alberto; Richer, Michael G., E-mail: mally@astrosen.unam.mx, E-mail: jal@astrosen.unam.mx, E-mail: richer@astrosen.unam.mx

2016-03-15

We analyze the internal kinematics of 26 planetary nebulae (PNe) with low metallicity that appear to derive from progenitor stars of the lowest masses, including the halo PN population. Based upon spatially resolved, long-slit, echelle spectroscopy drawn from the San Pedro Mártir Kinematic Catalog of PNe, we characterize the kinematics of these PNe measuring their global expansion velocities based upon the largest sample used to date for this purpose. We find kinematics that follow the trends observed and predicted in other studies, but also find that most of the PNe studied here tend to have expansion velocities less than 20more » km s{sup −1} in all of the emission lines considered. The low expansion velocities that we observe in this sample of low metallicity PNe with low mass progenitors are most likely a consequence of a weak central star (CS) wind driving the kinematics of the nebular shell. This study complements previous results that link the expansion velocities of the PN shells with the characteristics of the CS.« less

Determination and Quantification of metals in the shells of Crassostrea virginica after the Deepwater Horizon oil spill utilizing Atomic Absorption Spectrometry.

NASA Astrophysics Data System (ADS)

Roopnarine, D.; Patel, S.; Roopnarine, P.; Giarikos, D.; Anderson, L. C.

2017-12-01

The Deepwater Horizon (DWH) oil rig explosion on April 20, 2010 resulted in the release of 685,000 tons of crude oil into the Gulf of Mexico (GOM) over a period of three months. There were obvious immediate effects, but the long-term ramifications are still being studied. The primary constituent of crude oil is hydrocarbons with other organic compounds containing nitrogen, oxygen and sulfur. There are also a number of trace metals with the most abundant frequently being iron, nickel, copper and vanadium. These do not degrade like organic materials. However, the exact composition varies among the production sites. The oil from the DWH rig was classified as light crude which is moderately volatile. Natural oil seeps occur in the environment, but the DWH spill represented an acute impact. Trace amounts of heavy metals are a normal part of the composition of marine organisms, but can be toxic in high concentrations. Bivalved molluscs bioaccumulate heavy metals in their tissues and shells, and are therefore often useful as monitors of environmental pollution. We thus used the Eastern oyster Crassostrea virginica to determine the impact of the spill by measuring the concentrations of metals in the shells utilizing flame emission atomic absorption spectrometry. We focused on the hypothesis that DWH spill exposure resulted in an increase in metal uptake into the shells. Specimens spanned the years 2010 to 2014 and ranged from Grand Isle, LA to Apalachicola Bay, Fl. Vanadium had the greatest concentration in the shells, and along with copper, cadmium, zinc and iron displayed an upward trend of increase from 2010 to 2013, with a decline in 2014. However there was unexpected variability, as the specimens from Apalachicola Bay, Fl had higher levels of vanadium when compared to those from Grand Isle, LA. Ongoing work includes an increase of sample sizes from the same geographic localities and time period.

Analysis of reversed torsion of FCC metals using polycrystal plasticity models

DOE PAGES

Guo, Xiao Qian; Wang, Huamiao; Wu, Pei Dong; ...

2015-06-19

Large strain behavior of FCC polycrystals during reversed torsion are investigated through the special purpose finite element based on the classical Taylor model and the elastic-viscoplastic self-consistent (EVPSC) model with various Self-Consistent Schemes (SCSs). It is found that the response of both the fixed-end and free-end torsion is very sensitive to the constitutive models. The models are assessed through comparing their predictions to the corresponding experiments in terms of the stress and strain curves, the Swift effect and texture evolution. It is demonstrated that none of the models examined can precisely predict all the experimental results. However, more careful observationmore » reveals that, among the models considered, the tangent model gives the worst overall performance. As a result, it is also demonstrated that the intensity of residual texture during reverse twisting is dependent on the amounts of pre-shear strain during forward twisting and the model used.« less

Shell Filling and Magnetic Anisotropy In A Few Hole Silicon Metal-Oxide-Semiconductor Quantum Dot

NASA Astrophysics Data System (ADS)

Hamilton, Alex; Li., R.; Liles, S. D.; Yang, C. H.; Hudson, F. E.; Veldhorst, M. E.; Dzurak, A. S.

There is growing interest in hole spin states in group IV materials for quantum information applications. The near-absence of nuclear spins in group IV crystals promises long spin coherence times, while the strong spin-orbit interaction of the hole states provides fast electrical spin manipulation methods. However, the level-mixing and magnetic field dependence of the p-orbital hole states is non-trivial in nanostructures, and is not as well understood as for electron systems. In this work, we study the hole states in a gate-defined silicon metal-oxide-semiconductor quantum dot. Using an adjacent charge sensor, we monitor quantum dot orbital level spacing down to the very last hole, and find the standard two-dimensional (2D) circular dot shell filling structure. We can change the shell filling sequence by applying an out-of-plane magnetic field. However, when the field is applied in-plane, the shell filling is not changed. This magnetic field anisotropy suggests that the confined hole states are Ising-like.

On the Structure Sensitivity of Dimethyl Ether Electro-oxidation on Eight FCC Metals: A First-Principles Study

DOE PAGES

Herron, Jeffrey A.; Ferrin, Peter; Mavrikakis, Manos

2015-09-24

The electro-oxidation of dimethyl ether (DME) was investigated using periodic, self-consistent density functional theory (DFT) calculations on the (111) and (100) facets of eight fcc metals: Au, Ag, Cu, Pt, Pd, Ni, Ir, and Rh. The goal of this study is to understand the experimentally observed structure sensitivity of this reaction on Pt, and to predict trends in structure sensitivity of this reaction across the other seven metals studied. The main conclusion is that the enhanced activity of Pt(100) originates from more facile C–O bond breaking and removal of surface poisoning species, including CO and CH. When comparing C–O bondmore » breaking energetics, we do not find a universal trend where these elementary steps are always more exergonic on the (100) facet. However, we find that, at a given potential, DME can be dehydrogenated (prior to breaking the C–O bond) to a greater extent on the (100) facet. Additionally, we find that the reaction energy for C–O bond breaking in CHxOCHy-type species becomes increasingly exergonic as the species becomes increasingly dehydrogenated. Together, the more facile dehydrogenation on the (100) facets provides more favorable routes to C–O bond activation. Though we calculate a lower onset potential on Au(100), Ag(100), Cu(100), Pt(100), and Pd(100) than their respective (111) facets, the calculated onset potential for Ni(100), Ir(100), and Rh(100) are actually higher than for their respective (111) facets. Lastly, by constructing theoretical volcano plots, we conclude that Au(100), Ag(100), Cu(100), Pt(100), and Pd(100) should be more active than their respective (111) facets, while Ni(100), Rh(100), and Ir(100) will show the opposite trend.« less

78 FR 49126 - Modernizing the FCC Form 477 Data Program

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-13

... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Parts 0, 1, and 43 [WC Docket No. 11-10; FCC 13-87] Modernizing the FCC Form 477 Data Program AGENCY: Federal Communications Commission. ACTION: Final rule. SUMMARY: The Report and Order revises the Federal Communications Commission's Form 477 collection to...

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE PAGES

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.; ...

2016-11-11

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

The role of interfacial metal silicates on the magnetism in FeCo/SiO 2 and Fe 49% Co 49% V 2% /SiO 2 core/shell nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desautels, R. D.; Freeland, J. W.; Rowe, M. P.

2015-05-07

We have investigated the role of spontaneously formed interfacial metal silicates on the magnetism of FeCo/SiO2 and Fe49%Co49%V2%/SiO2 core/shell nanoparticles. Element specific x-ray absorption and photoelectron spectroscopy experiments have identified the characteristic spectral features of metallic iron and cobalt from within the nanoparticle core. In addition, metal silicates of iron, cobalt, and vanadium were found to have formed spontaneously at the interface between the nanoparticle core and silica shell. X-ray magnetic circular dichroism experiments indicated that the elemental magnetism was a result of metallic iron and cobalt with small components from the iron, cobalt, and vanadium silicates. Magnetometry experiments havemore » shown that there was no exchange bias loop shift in the FeCo nanoparticles; however, exchange bias from antiferromagnetic vanadium oxide was measured in the V-doped nanoparticles. These results showed clearly that the interfacial metal silicates played a significant role in the magnetism of these core/shell nanoparticles, and that the vanadium percolated from the FeCo-cores into the SiO2-based interfacial shell.« less

Trace Metals in Noah's Ark Shells (Arca noae Linnaeus, 1758): Impact of Tourist Season and Human Health Risk.

PubMed

Ivanković, Dušica; Erk, Marijana; Župan, Ivan; Čulin, Jelena; Dragun, Zrinka; Bačić, Niko; Cindrić, Ana-Marija

2016-10-01

Commercially important bivalve Noah's Ark shell (Arca noae Linnaeus, 1758) represents a high-quality seafood product, but the data on levels of metal contaminants that could pose a human health risk and also on some essential elements that are important for health protection are lacking. This study examined the concentrations of Cd, Pb, Cr, Ni, Cu, Co, and Zn in the soft tissue of A. noae from harvesting area in the central Adriatic Sea, to survey whether heavy metals are within the acceptable limits for public health and whether tourism could have an impact on them. The concentrations of analysed metals varied for Cd: 0.15-0.74, Pb: 0.06-0.26, Cr: 0.11-0.34, Ni: 0.09-0.22, Cu: 0.65-1.95, Co: 0.04-0.09, and Zn: 18.3-74.7 mg/kg wet weight. These levels were lower than the permissible limits for safe consummation of seafood, and only for Cd, some precautions should be taken into account if older shellfish were consumed. Increase of Cd, Cr, and Cu in shell tissue was observed during the tourist season at the site closest to the marine traffic routes, indicating that metal levels in shellfish tissue should be monitored especially carefully during the peak tourist season to prevent eventual toxic effects due to increased intake of metals, specifically of Cd.

1/f noise in metallic and semiconducting carbon nanotubes

NASA Astrophysics Data System (ADS)

Reza, Shahed; Huynh, Quyen T.; Bosman, Gijs; Sippel-Oakley, Jennifer; Rinzler, Andrew G.

2006-11-01

The charge transport and noise properties of three terminal, gated devices containing multiple single-wall metallic and semiconducting carbon nanotubes were measured at room temperature. Applying a high voltage pulsed bias at the drain terminal the metallic tubes were ablated sequentially, enabling the separation of measured conductance and 1/f noise into metallic and semiconducting nanotube contributions. The relative low frequency excess noise of the metallic tubes was observed to be two orders of magnitude lower than that of the semiconductor tubes.

The Microstructural Evolution of Fatigue Cracks in FCC Metals

NASA Astrophysics Data System (ADS)

Gross, David William

The microstructural evolution during fatigue crack propagation was investigated in a variety of planar and wavy slip FCC metals. The planar materials included Haynes 230, Nitronic 40, and 316 stainless steel, and the wavy materials included pure nickel and pure copper. Three different sets of experiments were performed to fully characterize the microstructural evolution. The first, performed on Haynes 230, mapped the strain field ahead a crack tip using digital image correlation and electron backscatter diffraction techniques. Focused ion beam (FIB) lift-out techniques were then utilized to extract transmission electron microscopy (TEM) samples at specific distances from the crack tip. TEM investigations compared the measured strain to the microstructure. Overall, the strain measured via DIC and EBSD was only weakly correlated to the density of planar slip bands in the microstructure. The second set of experiments concerned the dislocation structure around crack tips. This set of experiments was performed on all the materials. The microstructure at arrested fatigue cracks on the free surface was compared to the microstructure found beneath striations on the fracture surfaces by utilizing FIB micromachining to create site-specific TEM samples. The evolved microstructure depended on the slip type. Strong agreement was found between the crack tip microstructure at the free surface and the fracture surface. In the planar materials, the microstructure in the plastic zone consisted of bands of dislocations or deformation twins, before transitioning to a refined sub-grain microstructure near the crack flank. The sub-grain structure extended 300-500 nm away from the crack flank in all the planar slip materials studied. In contrast, the bulk structure in the wavy slip material consisted of dislocation cells and did not transition to a different microstructure as the crack tip was approached. The strain in wavy slip was highest near the crack tip, as the misorientations

On the shock response of cubic metals

NASA Astrophysics Data System (ADS)

Bourne, N. K.; Gray, G. T.; Millett, J. C. F.

2009-11-01

The response of four cubic metals to shock loading is reviewed in order to understand the effects of microstructure on continuum response. Experiments are described that link defect generation and storage mechanisms at the mesoscale to observations in the bulk. Four materials were reviewed; these were fcc nickel, the ordered fcc intermetallic Ni3Al, the bcc metal tantalum, and two alloys based on the intermetallic phase TiAl; Ti-46.5Al-2Cr-2Nb and Ti-48Al-2Cr-2Nb-1B. The experiments described are in two groups: first, equation of state and shear strength measurements using Manganin stress gauges and, second, postshock microstructural examinations and measurement of changes in mechanical properties. The behaviors described are linked through the description of time dependent plasticity mechanisms to the final states achieved. Recovered targets displayed dislocation microstructures illustrating processes active during the shock-loading process. Reloading of previously shock-prestrained samples illustrated shock strengthening for the fcc metals Ni and Ni3Al while showing no such effect for bcc Ta and for the intermetallic TiAl. This difference in effective shock hardening has been related, on the one hand, to the fact that bcc metals have fewer available slip systems that can operate than fcc crystals and to the observation that the lower symmetry materials (Ta and TiAl) both possess high Peierls stress and thus have higher resistances to defect motion in the lattice under shock-loading conditions. These behaviors, compared between these four materials, illustrate the role of defect generation, transport, storage, and interaction in determining the response of materials to shock prestraining.

Metals anomalies in foraminiferal shells as indicators for industrial pollution: a case study from the Mediterranean coast of Israel

NASA Astrophysics Data System (ADS)

Titelboim, Danna; Sadekov, Aleksey; Almogi-Labin, Ahuva; Herut, Barak; Kucera, Michal; Abramovich, Sigal

2017-04-01

In recent years we have been witnessing a considerable growth of industrial facilities along coastal areas. Some of these have major economical and national importance yet their operation can introduce a wide range of chemicals that might contaminate the coastal area and impact local ecosystems and our health. Among some of these harmful chemicals are metals that are introduced to the coastal environment by some of these facilities. Here we present a novel approach for monitoring low-level industrial pollution in coastal environments based on anomalies in metal concentration within foraminiferal shells. Living foraminifera are used as bio-indicators of the environmental status of any marine habitat. As unicellular organisms with short life and reproductive cycles, they are extremely sensitive to long and short-term changes. The majority of foraminifera precipitate CaCO3 (low-Mg-calcite, high-Mg calcite or rarely aragonite tests). Their calcareous shells are precipitated by a mechanism that involves direct seawater vacuolization which reflects the chemical composition of the ambient water. For this reason the geochemical composition of their shells is particularly applicable as a tool for marine environmental monitoring. Material for this study was obtained during the monthly campaigns of a biomonitoring project (2012-2015) of a heat polluted area and of a nearby natural clean station off the northern Mediterranean coast of Israel. Essentially, monitoring of water chemistry in both habitats showed no indications of presence of heavy metal contamination. Yet, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of two common local foraminifera the hyaline species Pararotalia calcariformata and the miliolid species Lachlanella sp. 1 that were collected alive from both areas, recorded presence of various metals (Mn, Cu, Zn, Ba, Pb) within their shells. Metal concentrations within the miliolid species were significantly higher than those of

Bi-metallic nanoparticles as cathode electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Jun; Amine, Khalil; Wang, Xiaoping

A lithium-air battery cathode catalyst includes core-shell nanoparticles on a carbon support, wherein: a core of the core-shell nanoparticles is platinum metal; and a shell of the core-shell nanoparticles is copper metal; wherein: the core-shell nanoparticles have a weight ratio of the copper metal to the platinum metal from about 4% to about 6% copper to from about 2% to about 12% platinum, with a remaining percentage being the carbon support.

The Electronic Structure of Transition Metal Coated Fullerenes

NASA Astrophysics Data System (ADS)

Patton, David C.; Pederson, Mark R.; Kaxiras, Efthimios

1998-03-01

Clusters composed of fullerene molecules with an outer shell of transition metal atoms in the composition C_60M_62 (M being a transition metal) have been produced with laser vaporisation techniques(F. Tast, N. Malinowski, S. Frank, M. Heinebrodt, I.M.L. Billas, and T. P. Martin, Z. Phys D 40), 351 (1997).. We have studied several of these very large systems with a parallel version of the all-electron NRLMOL cluster code. Optimized geometries of the metal encased fullerenes C_60Ti_62 and C_60V_62 are presented along with their HOMO-LUMO gaps, electron affinities, ionization energies, and cohesive energies. We compare the stability of these clusters to relaxed met-car structures (e.g. Ti_8C_12) and to relaxed rocksalt metal-carbide fragments (TiC)n with n=8 and 32. In addition to metal-coated fullerenes we consider the possibility of a trilayered structure consisting of a small shell of metal atoms enclosed by a metal coated fullerene. The nature of bonding in these systems is analyzed by studying the electronic charge distributions.

Fracture of coherent interfaces between an fcc metal matrix and the Cr23C6 carbide precipitate from first principles

NASA Astrophysics Data System (ADS)

Barbé, Elric; Fu, Chu-Chun; Sauzay, Maxime

2018-02-01

It is known that microcrack initiation in metallic alloys containing second-phase particles may be caused by either an interfacial or an intraprecipitate fracture. So far, the dependence of these features on properties of the precipitate and the interface is not clearly known. The present study aims to determine the key properties of carbide-metal interfaces controlling the energy and critical stress of fracture, based on density functional theory (DFT) calculations. We address coherent interfaces between a fcc iron or nickel matrix and a frequently observed carbide, the M23C6 , for which a simplified chemical composition Cr23C6 is assumed. The interfacial properties such as the formation and Griffith energies, and the effective Young's modulus are analyzed as functions of the magnetic state of the metal lattice, including the paramagnetic phase of iron. Interestingly, a simpler antiferromagnetic phase is found to exhibit similar interfacial mechanical behavior to the paramagnetic phase. A linear dependence is determined between the surface (and interface) energy and the variation of the number of chemical bonds weighted by the respective bond strength, which can be used to predict the relative formation energy for the surface and interface with various chemical terminations. Finally, the critical stresses of both intraprecipitate and interfacial fractures due to a tensile loading are estimated via the universal binding energy relation (UBER) model, parametrized on the DFT data. The validity of this model is verified in the case of intraprecipitate fracture, against results from DFT tensile test simulations. In agreement with experimental evidences, we predict a much stronger tendency for an interfacial fracture for this carbide. In addition, the calculated interfacial critical stresses are fully compatible with available experimental data in steels, where the interfacial carbide-matrix fracture is only observed at incoherent interfaces.

Metal-Organic-Framework-Derived Yolk-Shell-Structured Cobalt-Based Bimetallic Oxide Polyhedron with High Activity for Electrocatalytic Oxygen Evolution.

PubMed

Yu, Zhou; Bai, Yu; Liu, Yuxuan; Zhang, Shimin; Chen, Dandan; Zhang, Naiqing; Sun, Kening

2017-09-20

The development of inexpensive, efficient, and environmentally friendly catalysts for oxygen evolution reaction (OER) is of great significant for green energy utilization. Herein, binary metal oxides (M x Co 3-x O 4 , M = Zn, Ni, and Cu) with yolk-shell polyhedron (YSP) structure were fabricated by facile pyrolysis of bimetallic zeolitic imidazolate frameworks (MCo-ZIFs). Benefiting from the synergistic effects of metal ions and the unique yolk-shell structure, M x Co 3-x O 4 YSP displays good OER catalytic activity in alkaline media. Impressively, Zn x Co 3-x O 4 YSP shows a comparable overpotential of 337 mV at 10 mA cm -2 to commercial RuO 2 and exhibits superior long-term durability. The high activity and good stability reveals its promising application.

Transition Metal-Mediated and -Catalyzed C-F Bond Activation via Fluorine Elimination.

PubMed

Fujita, Takeshi; Fuchibe, Kohei; Ichikawa, Junji

2018-06-28

Activation of carbon-fluorine (C-F) bonds is an important topic in synthetic organic chemistry recently. Among the methods for C-F bond cleavage, metal mediated and catalyzed β- or α-fluorine elimination proceeds under mild conditions compared with oxidative addition of C-F bond. The β- or α-fluorine elimination is initiated from organometallic intermediates having fluorine substituents on carbon atoms β or α to metal centers, respectively. Transformations via these elimination processes (C-F bond cleavage), which are typically preceded by carbon-carbon (or carbon-heteroatom) bond formation, have been remarkably developed as C-F bond activation methods in the past five years. In this minireview, we summarize the applications of transition metal-mediated and -catalyzed fluorine elimination to synthetic organic chemistry from a historical perspective for early studies and from a systematic perspective for recent studies. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effectiveness of Rotation-free Triangular and Quadrilateral Shell Elements in Sheet-metal Forming Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunet, M.; Sabourin, F.

2005-08-05

This paper is concerned with the effectiveness of triangular 3-node shell element without rotational d.o.f. and the extension to a new 4-node quadrilateral shell element called S4 with only 3 translational degrees of freedom per node and one-point integration. The curvatures are computed resorting to the surrounding elements. Extension from rotation-free triangular element to a quadrilateral element requires internal curvatures in order to avoid singular bending stiffness. Two numerical examples with regular and irregular meshes are performed to show the convergence and accuracy. Deep-drawing of a box, spring-back analysis of a U-shape strip sheet and the crash simulation of amore » beam-box complete the demonstration of the bending capabilities of the proposed rotation-free triangular and quadrilateral elements.« less

Radionuclides, Trace Metals, and Organic Compounds in Shells of Native Freshwater Mussels Along the Hanford Reach of the Columbia River: 6000 Years Before Present to Current Times

DOE Office of Scientific and Technical Information (OSTI.GOV)

B. L. Tiller; T. E. Marceau

2006-01-25

This report documents concentrations of radionuclides, trace metals, and semivolatile organic compounds measured in shell samples of the western pearl shell mussel collected along the Hanford Reach of the Columbia River.

Nucleation of fcc Ta when heating thin films

DOE PAGES

Janish, Matthew T.; Mook, William M.; Carter, C. Barry

2014-10-25

Thin tantalum films have been studied during in-situ heating in a transmission electron microscope. Diffraction patterns from the as-deposited films were typical of amorphous materials. Crystalline grains were observed to form when the specimen was annealed in-situ at 450°C. Particular attention was addressed to the formation and growth of grains with the face-centered cubic (fcc) crystal structure. As a result, these observations are discussed in relation to prior work on the formation of fcc Ta by deformation and during thin film deposition.

PCDD/F catalysis by metal chlorides and oxides.

PubMed

Zhang, Mengmei; Yang, Jie; Buekens, Alfons; Olie, Kees; Li, Xiaodong

2016-09-01

Model fly ash (MFA) samples were composed of silica, sodium chloride, and activated carbon, and doped with metal (0.1 wt% Cu, Cr, Ni, Zn and Cd) chloride or oxide. Each sample was de novo tested at 350 °C for 1 h, in a flow of gas (N2, N2 + 10% O2, +21% O2 or +10% H2) to investigate the effect of metal catalyst and gas composition on PCDD/F formation. Total PCDD/F yield rises rapidly with oxygen content, while the addition of hydrogen inhibits the formation and chlorination of PCDD/F. The amount of PCDD on average rises linearly with the oxygen concentration, while that of PCDF follows a reaction order of about 1/2; thus the PCDF to PCDD ratio drops when more oxygen becomes available. Some samples do not follow this trend. Chlorides are much more active than oxides, yet there are marked differences between individual metals. Principal component analysis (PCA) was applied to study the signatures from all samples, showing their unique specificity and diversity. Each catalyst shows a different signature within its individual homologue groups, demonstrating that these signatures are not thermodynamically controlled. Average congener patterns do not vary considerably with oxygen content changing from oxidising (air) to reducing (nitrogen, hydrogen). Copyright © 2016 Elsevier Ltd. All rights reserved.

Yolk@Shell Nanoarchitectures with Bimetallic Nanocores-Synthesis and Electrocatalytic Applications.

PubMed

Guiet, Amandine; Unmüssig, Tobias; Göbel, Caren; Vainio, Ulla; Wollgarten, Markus; Driess, Matthias; Schlaad, Helmut; Polte, Jörg; Fischer, Anna

2016-10-10

In the present paper, we demonstrate a versatile approach for the one-pot synthesis of metal oxide yolk@shell nanostructures filled with bimetallic nanocores. This novel approach is based on the principles of hydrophobic nanoreactor soft-templating and is exemplified for the synthesis of various AgAu NP @tin-rich ITO (AgAu@ITO TR ) yolk@shell nanomaterials. Hydrophobic nanoreactor soft-templating thereby takes advantage of polystyrene-block-poly(4-vinylpiridine) inverse micelles as two-compartment nanoreactor template, in which the core and the shell of the micelles serve as metal and metal oxide precursor reservoir, respectively. The composition, size and number of AuAg bimetallic nanoparticles incorporated within the ITO TR yolk@shell can easily be tuned. The conductivity of the ITO TR shell and the bimetallic composition of the AuAg nanoparticles, the as-synthesized AuAg NP @ITO TR yolk@shell materials could be used as efficient electrocatalysts for electrochemical glucose oxidation with improved onset potential when compared to their gold counterpart.

MicroED Structure of Au146(p-MBA)57 at Subatomic Resolution Reveals a Twinned FCC Cluster.

PubMed

Vergara, Sandra; Lukes, Dylan A; Martynowycz, Michael W; Santiago, Ulises; Plascencia-Villa, Germán; Weiss, Simon C; de la Cruz, M Jason; Black, David M; Alvarez, Marcos M; López-Lozano, Xochitl; Barnes, Christopher O; Lin, Guowu; Weissker, Hans-Christian; Whetten, Robert L; Gonen, Tamir; Yacaman, Miguel Jose; Calero, Guillermo

2017-11-16

Solving the atomic structure of metallic clusters is fundamental to understanding their optical, electronic, and chemical properties. Herein we present the structure of the largest aqueous gold cluster, Au 146 (p-MBA) 57 (p-MBA: para-mercaptobenzoic acid), solved by electron micro-diffraction (MicroED) to subatomic resolution (0.85 Å) and by X-ray diffraction at atomic resolution (1.3 Å). The 146 gold atoms may be decomposed into two constituent sets consisting of 119 core and 27 peripheral atoms. The core atoms are organized in a twinned FCC structure, whereas the surface gold atoms follow a C 2 rotational symmetry about an axis bisecting the twinning plane. The protective layer of 57 p-MBAs fully encloses the cluster and comprises bridging, monomeric, and dimeric staple motifs. Au 146 (p-MBA) 57 is the largest cluster observed exhibiting a bulk-like FCC structure as well as the smallest gold particle exhibiting a stacking fault.

MicroED structure of Au146(p-MBA)57 at subatomic resolution reveals a twinned FCC cluster

PubMed Central

Vergara, Sandra; Lukes, Dylan A.; Martynowycz, Michael W.; Santiago, Ulises; Plascencia-Villa, German; Weiss, Simon C.; de la Cruz, M. Jason; Black, David M.; Alvarez, Marcos M.; Lopez-Lozano, Xochitl; Barnes, Christopher O.; Lin, Guowu; Weissker, Hans-Christian; Whetten, Robert L.; Gonen, Tamir; Jose-Yacaman, Miguel; Calero, Guillermo

2018-01-01

Solving the atomic structure of metallic clusters is fundamental to understanding their optical, electronic, and chemical properties. Herein we present the structure of the largest aqueous gold cluster, Au146(p-MBA)57 (p-MBA: para-mercaptobenzoic acid), solved by electron diffraction (MicroED) to subatomic resolution (0.85 Å) and by X-ray diffraction at atomic resolution (1.3 Å). The 146 gold atoms may be decomposed into two constituent sets consisting of 119 core and 27 peripheral atoms. The core atoms are organized in a twinned FCC structure whereas the surface gold atoms follow a C2 rotational symmetry about an axis bisecting the twinning plane. The protective layer of 57 p-MBAs fully encloses the cluster and comprises bridging, monomeric, and dimeric staple motifs. Au146(p-MBA)57 is the largest cluster observed exhibiting a bulk-like FCC structure as well as the smallest gold particle exhibiting a stacking fault. PMID:29072840

47 CFR 2.936 - FCC inspection.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC inspection. 2.936 Section 2.936 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL... manufacturing plant and facilities. [62 FR 10471, Mar. 7, 1997] ...

47 CFR 2.936 - FCC inspection.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false FCC inspection. 2.936 Section 2.936 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL... manufacturing plant and facilities. [62 FR 10471, Mar. 7, 1997] ...

Optical temperature sensing of NaYbF4: Tm3+@SiO2 core-shell micro-particles induced by infrared excitation.

PubMed

Wang, Xiangfu; Zheng, Jin; Xuan, Yan; Yan, Xiaohong

2013-09-09

NaYbF(4):Tm3+@SiO(2) core-shell micro-particles were synthesized by a hydrothermal method and subsequent ultrasonic coating process. Optical temperature sensing has been observed in NaYbF4: Tm(3+)@SiO(2)core-shell micro-particles with a 980 nm infrared laser as excitation source.The fluorescence intensity ratios, optical temperature sensitivity, and temperature dependent population re-distribution ability from the thermally coupled (1)D(2)/(1)G(4) and (3)F(2) /(3)H(4) levels of the Tm(3+) ion have been analyzed as a function of temperature in the range of 100~700 K in order to check its availability as a optical temperature sensor. A better behavior as a lowtemperature sensor has been obtained with a minimum sensitivity of 5.4 × 10(-4) K(-1) at 430 K. It exhibits temperature induced population re-distribution from (1)D(2) /(1)G(4) thermally coupled levels at higher temperature range.

Characterization of an Aluminum Alloy Hemispherical Shell Fabricated via Direct Metal Laser Melting

NASA Astrophysics Data System (ADS)

Holesinger, T. G.; Carpenter, J. S.; Lienert, T. J.; Patterson, B. M.; Papin, P. A.; Swenson, H.; Cordes, N. L.

2016-03-01

The ability of additive manufacturing to directly fabricate complex shapes provides characterization challenges for part qualification. The orientation of the microstructures produced by these processes will change relative to the surface normal of a complex part. In this work, the microscopy and x-ray tomography of an AlSi10Mg alloy hemispherical shell fabricated using powder bed metal additive manufacturing are used to illustrate some of these challenges. The shell was manufactured using an EOS M280 system in combination with EOS-specified powder and process parameters. The layer-by-layer process of building the shell with the powder bed additive manufacturing approach results in a position-dependent microstructure that continuously changes its orientation relative to the shell surface normal. X-ray tomography was utilized to examine the position-dependent size and distribution of porosity and surface roughness in the 98.6% dense part. Optical and electron microscopy were used to identify global and local position-dependent structures, grain morphologies, chemistry, and precipitate sizes and distributions. The rapid solidification processes within the fusion zone (FZ) after the laser transit results in a small dendrite size. Cell spacings taken from the structure in the middle of the FZ were used with published relationships to estimate a cooling rate of ~9 × 105 K/s. Uniformly-distributed, nanoscale Si precipitates were found within the primary α-Al grains. A thin, distinct boundary layer containing larger α-Al grains and extended regions of the nanocrystalline divorced eutectic material surrounds the FZ. Subtle differences in the composition between the latter layer and the interior of the FZ were noted with scanning transmission electron microscopy (STEM) spectral imaging.

Regulation of Fumonisin B1 Biosynthesis and Conidiation in Fusarium verticillioides by a Cyclin-Like (C-Type) Gene, FCC1†

PubMed Central

Shim, Won-Bo; Woloshuk, Charles P.

2001-01-01

Fumonisins are a group of mycotoxins produced in corn kernels by the plant-pathogenic fungus Fusarium verticillioides. A mutant of the fungus, FT536, carrying a disrupted gene named FCC1 (for Fusarium cyclin C1) resulting in altered fumonisin B1 biosynthesis was generated. FCC1 contains an open reading frame of 1,018 bp, with one intron, and encodes a putative 319-amino-acid polypeptide. This protein is similar to UME3 (also called SRB11 or SSN8), a cyclin C of Saccharomyces cerevisiae, and contains three conserved motifs: a cyclin box, a PEST-rich region, and a destruction box. Also similar to the case for C-type cyclins, FCC1 was constitutively expressed during growth. When strain FT536 was grown on corn kernels or on defined minimal medium at pH 6, conidiation was reduced and FUM5, the polyketide synthase gene involved in fumonisin B1 biosynthesis, was not expressed. However, when the mutant was grown on a defined minimal medium at pH 3, conidiation was restored, and the blocks in expression of FUM5 and fumonisin B1 production were suppressed. Our data suggest that FCC1 plays an important role in signal transduction regulating secondary metabolism (fumonisin biosynthesis) and fungal development (conidiation) in F. verticillioides. PMID:11282612

Effect of stacking fault energy on mechanism of plastic deformation in nanotwinned FCC metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borovikov, Valery; Mendelev, Mikhail I.; King, Alexander H.

Starting from a semi-empirical potential designed for Cu, we have developed a series of potentials that provide essentially constant values of all significant (calculated) materials properties except for the intrinsic stacking fault energy, which varies over a range that encompasses the lowest and highest values observed in nature. In addition, these potentials were employed in molecular dynamics (MD) simulations to investigate how stacking fault energy affects the mechanical behavior of nanotwinned face-centered cubic (FCC) materials. The results indicate that properties such as yield strength and microstructural stability do not vary systematically with stacking fault energy, but rather fall into twomore » distinct regimes corresponding to 'low' and 'high' stacking fault energies.« less

Effect of stacking fault energy on mechanism of plastic deformation in nanotwinned FCC metals

DOE PAGES

Borovikov, Valery; Mendelev, Mikhail I.; King, Alexander H.; ...

2015-05-15

Starting from a semi-empirical potential designed for Cu, we have developed a series of potentials that provide essentially constant values of all significant (calculated) materials properties except for the intrinsic stacking fault energy, which varies over a range that encompasses the lowest and highest values observed in nature. In addition, these potentials were employed in molecular dynamics (MD) simulations to investigate how stacking fault energy affects the mechanical behavior of nanotwinned face-centered cubic (FCC) materials. The results indicate that properties such as yield strength and microstructural stability do not vary systematically with stacking fault energy, but rather fall into twomore » distinct regimes corresponding to 'low' and 'high' stacking fault energies.« less

FCC and the Sunshine Act.

ERIC Educational Resources Information Center

Weiss, Kenneth

The Sunshine Act, designed to encourage open meetings to increase public understanding of the governmental decision-making process, went into effect in March 1977. A total of 50 agencies, including the Federal Communications Commission (FCC), are subject to the provisions of the Sunshine Act. The act lists 10 exemptions, any of which can result in…

FCC, CATV, ETV, and ITFS.

ERIC Educational Resources Information Center

Schwartz, Louis; Woods, Robert A.

Actions taken in 1970 by the Federal Communications Commission (FCC) are reviewed and discussed in this paper. These actions include amendment of educational broadcast rules for the first time in 17 years, decisions in the area of educational programing, a decision regarding the ultra high frequency (UHF)-land mobile dilemma, and a promise to…

Shell tile thermal protection system

NASA Technical Reports Server (NTRS)

Macconochie, I. O.; Lawson, A. G.; Kelly, H. N. (Inventor)

1984-01-01

A reusable, externally applied thermal protection system for use on aerospace vehicles subject to high thermal and mechanical stresses utilizes a shell tile structure which effectively separates its primary functions as an insulator and load absorber. The tile consists of structurally strong upper and lower metallic shells manufactured from materials meeting the thermal and structural requirements incident to tile placement on the spacecraft. A lightweight, high temperature package of insulation is utilized in the upper shell while a lightweight, low temperature insulation is utilized in the lower shell. Assembly of the tile which is facilitated by a self-locking mechanism, may occur subsequent to installation of the lower shell on the spacecraft structural skin.

Structural, spectroscopic and cytotoxicity studies of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals.

PubMed

Grzyb, Tomasz; Runowski, Marcin; Dąbrowska, Krystyna; Giersig, Michael; Lis, Stefan

2013-01-01

Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. Their complex structure was formed spontaneously during the synthesis. The surface of these core/shell nanocrystals was additionally modified by silica. The properties of TbF 3 @CeF 3 and TbF 3 @CeF 3 @SiO 2 nanocrystals, formed in this way, were investigated. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO 2 shell. X-ray diffraction patterns confirmed the trigonal crystal structure of TbF 3 @CeF 3 nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. Crystallized as small discs, 'the products', with an average diameter around 10 nm, showed an increase in the concentration of Tb 3+ ions from surface to the core of nanocrystals. In addition to photo-physical analyses, cytotoxicity studies were performed on HSkMEC (Human Skin Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The cytotoxicity of the nanomaterials was neutral for the investigated cells with no toxic or antiproliferative effect in the cell cultures, either for normal or for cancer cells. This fact makes the obtained nanocrystals good candidates for biological applications and further modifications of the SiO 2 shell. .

Structural, spectroscopic and cytotoxicity studies of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Grzyb, Tomasz; Runowski, Marcin; Dąbrowska, Krystyna; Giersig, Michael; Lis, Stefan

2013-10-01

Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. Their complex structure was formed spontaneously during the synthesis. The surface of these core/shell nanocrystals was additionally modified by silica. The properties of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals, formed in this way, were investigated. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO2 shell. X-ray diffraction patterns confirmed the trigonal crystal structure of TbF3@CeF3 nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. Crystallized as small discs, `the products', with an average diameter around 10 nm, showed an increase in the concentration of Tb3+ ions from surface to the core of nanocrystals. In addition to photo-physical analyses, cytotoxicity studies were performed on HSkMEC (Human Skin Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The cytotoxicity of the nanomaterials was neutral for the investigated cells with no toxic or antiproliferative effect in the cell cultures, either for normal or for cancer cells. This fact makes the obtained nanocrystals good candidates for biological applications and further modifications of the SiO2 shell.

In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts

DOE PAGES

Ishige, Ryohei; Williams, Gregory A.; Higaki, Yuji; ...

2016-04-19

A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated byin situultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis ofin situUSAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction inmore » proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishige, Ryohei; Williams, Gregory A.; Higaki, Yuji

A molded film of single-component polymer-grafted nanoparticles (SPNP), consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated byin situultra-small-angle X-ray scattering (USAXS) measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c.) lattice structure with the [11-1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis ofin situUSAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction inmore » proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.« less

Protein-assisted synthesis of double-shelled CaCO3 microcapsules and their mineralization with heavy metal ions.

PubMed

Li, Xuan Qi; Feng, Zhiwei; Xia, Yinyan; Zeng, Hua Chun

2012-02-13

Calcium carbonate (CaCO(3)) is one of the most abundant and important biominerals in nature. Due to its biocompatibility, biodegradability and nontoxicity, CaCO(3) has been investigated extensively in recent years for various fundamental properties and technological applications. Inspired by basic wall structures of cells, we report a protein-assisted approach to synthesize CaCO(3) into a double-shelled structural configuration. Due to varying reactivities of outer and inner shells, the CaCO(3) microcapsules exhibit different sorption capacities and various resultant structures toward different kinds of heavy metal ions, analogical to biologically controlled mineralization (BCM) processes. Surprisingly, three mineralization modes resembling those found in BCM were found with these bacterium-like "CaCO(3) cells". Our investigation of the cytotoxicity (MTT assay protocol) also indicates that the CaCO(3) microcapsules have almost no cytotoxicity against HepG2 cells, and they might be useful for future application of detoxifying heavy metal ions after further study. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bond-Energy and Surface-Energy Calculations in Metals

ERIC Educational Resources Information Center

Eberhart, James G.; Horner, Steve

2010-01-01

A simple technique appropriate for introductory materials science courses is outlined for the calculation of bond energies in metals from lattice energies. The approach is applied to body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal-closest-packed (hcp) metals. The strength of these bonds is tabulated for a variety metals and is…

47 CFR 95.219 - (R/C Rule 19) How do I answer correspondence from the FCC?

Code of Federal Regulations, 2010 CFR

2010-10-01

... You Need to Know § 95.219 (R/C Rule 19) How do I answer correspondence from the FCC? (a) If it appears to the FCC that you have violated the Communications Act or FCC rules, the FCC may send you a... 47 Telecommunication 5 2010-10-01 2010-10-01 false (R/C Rule 19) How do I answer correspondence...

Lanthanide-doped NaGdF4 core-shell nanoparticles for non-contact self-referencing temperature sensors.

PubMed

Zheng, Shuhong; Chen, Weibo; Tan, Dezhi; Zhou, Jiajia; Guo, Qiangbing; Jiang, Wei; Xu, Cheng; Liu, Xiaofeng; Qiu, Jianrong

2014-06-07

We report that non-contact self-referencing temperature sensors can be realized with the use of core-shell nanostructures. These lanthanide-based nanothermometers (NaGdF4:Yb(3+)/Tm(3+)@Tb(3+)/Eu(3+)) exhibit higher sensitivity in a wide range from 125 to 300 K based on two emissions of Tb(3+) at 545 nm and Eu(3+) at 615 nm under near-infrared laser excitation.

76 FR 12308 - Modernizing the FCC Form 477 Data Program; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-07

... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Parts 1, 20, and 43 [WCB: WC Docket Nos. 07-38, 09-190, 10-132, 11-10; FCC 11-14] Modernizing the FCC Form 477 Data Program; Correction AGENCY: Federal..., Deputy Manager. [FR Doc. 2011-5095 Filed 3-4-11; 8:45 am] BILLING CODE 6712-01-P ...

Highly aqueous soluble CaF2:Ce/Tb nanocrystals: effect of surface functionalization on structural, optical band gap, and photoluminescence properties.

PubMed

Ansari, Anees A; Parchur, Abdul K; Kumar, Brijesh; Rai, S B

2016-12-01

/Tb nanoparticles via metal complex decomposition rout shows high dispersibility in aqueous solvents with enhanced photoluminescence. The epitaxial growth of inert CaF 2 shell and further amorphous silica, respectively, enhanced their optical and luminescence properties, which is highly usable for luminescent biolabeling, and optical bioprobe etc.

The shell spectrum of HD 94509

NASA Astrophysics Data System (ADS)

Cowley, Charles R.; Przybilla, Norbert; Hubrig, Swetlana

2015-01-01

HD 94509 is a 9th magnitude Be star with an unusually rich metallic-lined shell. The absorption spectrum is rich, comparable to that of an A or F supergiant, but Mg II (4481A), and the Si II (4128 and 4130A), are weak, indicating a dilute radiation field, as described by Otto Struve. The H-alpha emission is double with components of equal intensity and an absorption core that dips well below the stellar continuum. H-beta is weaker, but with a similar structure. H-gamma through H-epsilon have virtually black cores, indicating that the shell covers the stellar disk. The stronger metallic absorption lines are wide near the continuum, but taper to very narrow cores. This line shape is unexplained. However, the total absorption can be modeled to reveal an overall particle densities of 10^{10}-10^{12} cm^{-3}. An electron density log(n_e) = 11.2 is obtained from the Paschen-line convergence and the Inglis-Tellar relation. Column densities are obtained with the help of curves of growth by assuming uniform conditions in the cloud. These indicate a nearly solar composition. The CLOUDY code (Ferland, et al. Rev. Mex. Astron. Astroph. 49, 137, 213) is used to produce a model that predicts matching column densities of the dominant ions, the n = 3 level of hydrogen, the H-alpha strength, and the electron density (± 0.5 dex).

Twin boundary spacing effects on shock response and spall behaviors of hierarchically nanotwinned fcc metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Fuping, E-mail: fpyuan@lnm.imech.ac.cn; Chen, Liu, E-mail: chenliu@imech.ac.cn; Jiang, Ping, E-mail: jping@imech.ac.cn

2014-02-14

Atomistic deformation mechanisms of hierarchically nano-twinned (NT) Ag under shock conditions have been investigated using a series of large-scale molecular dynamics simulations. For the same grain size d and the same spacing of primary twins λ{sub 1}, the average flow stress behind the shock front in hierarchically NT Ag first increases with decreasing spacing of secondary twins λ{sub 2}, achieving a maximum at a critical λ{sub 2}, and then drops as λ{sub 2} decreases further. Above the critical λ{sub 2}, the deformation mechanisms are dominated by three type strengthening mechanisms: (a) partial dislocations emitted from grain boundaries (GBs) travel acrossmore » other boundaries; (b) partial dislocations emitted from twin boundaries (TBs) travel across other TBs; (c) formation of tertiary twins. Below the critical λ{sub 2}, the deformation mechanism are dominated by two softening mechanisms: (a) detwinning of secondary twins; (b) formation of new grains by cross slip of partial dislocations. Moreover, the twin-free nanocrystalline (NC) Ag is found to have lower average flow stress behind the shock front than those of all hierarchically NT Ag samples except the one with the smallest λ{sub 2} of 0.71 nm. No apparent correlation between the spall strength and λ{sub 2} is observed in hierarchically NT Ag, since voids always nucleate at both GBs and boundaries of the primary twins. However, twin-free NC Ag is found to have higher spall strength than hierarchically NT Ag. Voids can only nucleate from GBs for twin-free NC Ag, therefore, twin-free NC Ag has less nucleation sources along the shock direction when compared to hierarchically NT Ag, which requiring higher tensile stress to create spallation. These findings should contribute to the understandings of deformation mechanisms of hierarchically NT fcc metals under extreme deformation conditions.« less

Void Growth and Coalescence in Dynamic Fracture of FCC and BCC Metals - Molecular Dynamics Study

NASA Astrophysics Data System (ADS)

Seppälä, Eira

2004-03-01

In dynamic fracture of ductile metals, the state of tension causes the nucleation of voids, typically from inclusions or grain boundary junctions, which grow and ultimately coalesce to form the fracture surface. Significant plastic deformation occurs in the process, including dislocations emitted to accommodate the growing voids. We have studied at the atomistic scale growth and coalescence processes of voids with concomitant dislocation formation. Classical molecular dynamics (MD) simulations of one and two pre-existing spherical voids initially a few nanometers in radius have been performed in single-crystal face-centered-cubic (FCC) and body-centered-cubic (BCC) lattices under dilational strain with high strain-rates. Million atom simulations of single void growth have been done to study the effect of stress triaxiality,^1 along with strain rate and lattice-structure dependence. An interesting prolate-to-oblate transition in the void shape in uniaxial expansion has been observed and quantitatively analyzed. The simulations also confirm that the plastic strain results directly from the void growth. Interaction and coalescence between two voids have been studied utilizing a parallel MD code in a seven million atom system. In particular, the movement of centers of the voids, linking of the voids, and the shape changes in vicinity of the other void are studied. Also the critical intervoid ligament distance after which the voids can be treated independently has been searched. ^1 E. T. Seppälä, J. Belak, and R. E. Rudd, cond-mat/0310541, submitted to Phys. Rev. B. Acknowledgment: This work was done in collaboration with Dr. James Belak and Dr. Robert E. Rudd, LLNL. It was performed under the auspices of the US Dept. of Energy at the Univ. of Cal./Lawrence Livermore National Laboratory under contract no. W-7405-Eng-48.

Spectroscopy of 70Kr and isospin symmetry in the T =1 f p g shell nuclei

NASA Astrophysics Data System (ADS)

Debenham, D. M.; Bentley, M. A.; Davies, P. J.; Haylett, T.; Jenkins, D. G.; Joshi, P.; Sinclair, L. F.; Wadsworth, R.; Ruotsalainen, P.; Henderson, J.; Kaneko, K.; Auranen, K.; Badran, H.; Grahn, T.; Greenlees, P.; HerzaáÅ, A.; Jakobsson, U.; Konki, J.; Julin, R.; Juutinen, S.; Leino, M.; Sorri, J.; Pakarinen, J.; Papadakis, P.; Peura, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Stolze, S.; Uusitalo, J.; David, H. M.; de Angelis, G.; Korten, W.; Lotay, G.; Mallaburn, M.; Sahin, E.

2016-11-01

The recoil-β tagging technique has been used in conjunction with the 40Ca(32S,2 n ) reaction at a beam energy of 88 MeV to identify transitions associated with the decay of the 2+ and, tentatively, 4+ states in the nucleus 70Kr. These data are used, along with previously published data, to examine the triplet energy differences (TED) for the mass 70 isobars. The experimental TED values are compared with shell model calculations, performed with the JUN45 interaction in the f p g model space, that include a J =0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV. The agreement is found to be very good up to spin 4 and supports the expectation for analog states that all three nuclei have the same oblate shape at low-spin. The A =70 results are compared with the experimental and shell model predicted TED and mirror energy differences (MED) for the mass 66 and 74 systems. The comparisons clearly demonstrate the importance of the isotensor INC interaction in replicating the TED data in this region. Issues related to the observed MED values and their interpretation within the shell model are discussed.

Characterization of an aluminum alloy hemispherical shell fabricated via direct metal laser melting

DOE PAGES

Holesinger, T. G.; Carpenter, J. S.; Lienert, T. J.; ...

2016-01-11

The ability of additive manufacturing to directly fabricate complex shapes provides characterization challenges for part qualification. The orientation of the microstructures produced by these processes will change relative to the surface normal of a complex part. In this work, the microscopy and x-ray tomography of an AlSi10Mg alloy hemispherical shell fabricated using powder bed metal additive manufacturing are used to illustrate some of these challenges. The shell was manufactured using an EOS M280 system in combination with EOS-specified powder and process parameters. The layer-by-layer process of building the shell with the powder bed additive manufacturing approach results in a position-dependentmore » microstructure that continuously changes its orientation relative to the shell surface normal. X-ray tomography was utilized to examine the position-dependent size and distribution of porosity and surface roughness in the 98.6% dense part. Optical and electron microscopy were used to identify global and local position-dependent structures, grain morphologies, chemistry, and precipitate sizes and distributions. The rapid solidification processes within the fusion zone (FZ) after the laser transit results in a small dendrite size. Cell spacings taken from the structure in the middle of the FZ were used with published relationships to estimate a cooling rate of ~9 × 10 5 K/s. Uniformly-distributed, nanoscale Si precipitates were found within the primary α-Al grains. A thin, distinct boundary layer containing larger α-Al grains and extended regions of the nanocrystalline divorced eutectic material surrounds the FZ. Moreover, subtle differences in the composition between the latter layer and the interior of the FZ were noted with scanning transmission electron microscopy (STEM) spectral imaging.« less

Pre-melting Behaviour in fcc Metals

NASA Astrophysics Data System (ADS)

Pamato, M. G.; Wood, I. G.; Dobson, D. P.; Hunt, S.; Vocadlo, L.

2016-12-01

Although the Earth's core is accepted to be made of an iron-nickel alloy with a few percent of light elements, its exact structure and composition are still unknown. Seismological and mineralogical models in the Earth's inner core do not agree, with mineralogical models derived from ab initiocalculations predicting shear-wave velocities up to 30% greater than seismically observed values. Recent computer simulations revealed that such difference may be explained by a dramatic, non-linear, softening of the elastic constants of Fe prior to melting. Up to date, computer calculations are the only result on pre-melting of direct applicability to the Earth's core and it is essential to systematically investigate such phenomena at inner core pressures and temperatures. Measuring the pressure dependence of pre-melting effects at such conditions and to the required precision is however extremely challenging. Also, pre-melting effects have been observed or suggested to occur in other materials, particularly noble metals, which exhibit large departures from linearity (modulus defects) at elevated temperatures. The aim of this study is to investigate to what extent pre-melting behaviour occurs in the physical properties of other metals at more experimentally tractable conditions. In particular, we report measurements of density and thermal expansion coefficients of both pure and alloyed gold (Au) up to their melting points. Au is an ideal test material since it crystallises in a simple monatomic face-centred structure and has a relatively low melting temperature. Precise measurements of unit cell lattice parameters were performed using a PANalytical X'Pert Pro powder diffractometer, equipped with an incident beam monochromator (giving very high resolution diffraction patterns) and with environmental stages covering the range from 40 K to 1373 K, with a readily achievable temperature resolution of 1K. We will discuss the circumstances under which pre-melting occurs, its

Th-Based Endohedral Metallofullerenes: Anomalous Metal Position and Significant Metal-Cage Covalent Interactions with the Involvement of Th 5f Orbitals.

PubMed

Li, Ying; Yang, Le; Liu, Chang; Hou, Qinghua; Jin, Peng; Lu, Xing

2018-05-29

Endohedral metallofullerenes (EMFs) containing actinides are rather intriguing due to potential 5f-orbital participation in the metal-metal or metal-cage bonding. In this work, density functional theory calculations first characterized the structure of recently synthesized ThC 74 as Th@ D 3 h (14246)-C 74 . We found that the thorium atom adopts an unusual off-axis position inside cage due to small metal ion size and the requirement of large coordination number, which phenomenon was further extended to other Th-based EMFs. Significantly, besides the strong metal-cage electrostatic attractions, topological and orbital analysis revealed that all the investigated Th-based EMFs exhibit obvious covalent interactions between metal and cage with substantial contribution from the Th 5f orbitals. The encapsulation by fullerenes is thus proposed as a practical pathway toward the f-orbital covalency for thorium. Interestingly, the anomalous internal position of Th led to a novel three-dimensional metal trajectory at elevated temperatures in the D 3 h -C 74 cavity, as elucidated by the static computations and molecular dynamic simulations.

Low voltage FCC for home and business

NASA Technical Reports Server (NTRS)

Wolf, L.

1972-01-01

A thin pressure-sensitive FCC for low voltage usage is described. It is recommended for installing in speakers, intercoms, doorbells, burglar alarms, and clocks, without running wires between walls. The specifications are given.

Construction of self-supported porous TiO2/NiO core/shell nanorod arrays for electrochemical capacitor application

NASA Astrophysics Data System (ADS)

Wu, J. B.; Guo, R. Q.; Huang, X. H.; Lin, Y.

2013-12-01

High-quality metal oxides hetero-structured nanoarrays have been receiving great attention in electrochemical energy storage application. Self-supported TiO2/NiO core/shell nanorod arrays are prepared on carbon cloth via the combination of hydrothermal synthesis and electro-deposition methods. The obtained core/shell nanorods consist of nanorod core and interconnected nanoflake shell, as well as hierarchical porosity. As cathode materials for pseudo-capacitors, the TiO2/NiO core/shell nanorod arrays display impressive electrochemical performances with both high capacitance of 611 F g-1 at 2 A g-1, and pretty good cycling stability with a retention of 89% after 5000 cycles. Besides, as compared to the single NiO nanoflake arrays on carbon cloth, the TiO2/NiO core/shell nanorod arrays exhibit much better electrochemical properties with higher capacitance, better electrochemical activity and cycling life. This enhanced performance is mainly due to the core/shell nanorods architecture offering fast ion/electron transfer and sufficient contact between active materials and electrolyte.

Deposition of hermetic silver shells onto copper flakes.

PubMed

Njagi, John I; Netzband, Christopher M; Goia, Dan V

2017-02-15

Continuous silver shells were deposited on copper flakes using a two-stage precipitation process. A tightly packed layer of silver nanoparticles was first formed on the surface of the base metal by galvanic displacement. The size of the noble metal particles and their distribution on the substrate were controlled using complexing agents and dispersants. A continuous Ag deposit was subsequently grown by reducing slowly [Ag(NH 3 ) 2 ] + ions with glucose. The final shell thickness was controlled by varying the amount of metal deposited in the second step. The electrical properties of resulting silver coated copper flakes are comparable to those measured for silver flakes of similar size and aspect ratio. By preventing the oxidation of copper cores up to 400°C, the hermetic noble metal shell dramatically extends the temperature range in which Ag/Cu flakes can successfully replace pure silver. Copyright © 2016 Elsevier Inc. All rights reserved.

47 CFR 95.428 - (CB Rule 28) How do I contact the FCC?

Code of Federal Regulations, 2010 CFR

2010-10-01

... SERVICES PERSONAL RADIO SERVICES Citizens Band (CB) Radio Service Other Things You Need to Know § 95.428... Wide Web homepage: http://www.fcc.gov. (c) In writing, to FCC, Attention: CB, 1270 Fairfield Road...

47 CFR 95.422 - (CB Rule 22) How do I answer correspondence from the FCC?

Code of Federal Regulations, 2010 CFR

2010-10-01

... You Need to Know § 95.422 (CB Rule 22) How do I answer correspondence from the FCC? (a) If it appears to the FCC that you have violated the Communications Act or these rules, the FCC may send you a... 47 Telecommunication 5 2010-10-01 2010-10-01 false (CB Rule 22) How do I answer correspondence...

Gastropod (Otala lactea) shell nanomechanical and structural characterization as a biomonitoring tool for dermal and dietary exposure to a model metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allison, Paul G.; Seiter, Jennifer M.; Diaz, Alfredo

Metallic tungsten (W) was initially assumed to be environmentally benign and a green alternative to lead. However, subsequent investigations showed that fishing weights and munitions containing elemental W can fragment and oxidize into complex monomeric and polymeric tungstate (WO 4) species in the environment; this led to increased solubility and mobility in soils and increased bioaccumulation potential in plant and animal tissues. Here we expand on the results of our previous research, which examined tungsten toxicity, bioaccumulation, and compartmentalization into organisms, and present in this research that the bioaccumulation of W was related to greater than 50% reduction in themore » mechanical properties of the snail (Otala lactea), based on depth-sensing nanoindentation. Synchrotron-based X-ray fluorescence maps and X-ray diffraction measurements confirm the integration of W in newly formed layers of the shell matrix with the observed changes in shell biomechanical properties, mineralogical composition, and crystal orientation. With further development, this technology could be employed as a biomonitoring tool for historic metals contamination since unlike the more heavily studied bioaccumulation into soft tissue, shell tissue does not actively eliminate contaminants.« less

Gastropod (Otala lactea) shell nanomechanical and structural characterization as a biomonitoring tool for dermal and dietary exposure to a model metal.

PubMed

Allison, Paul G; Seiter, Jennifer M; Diaz, Alfredo; Lindsay, James H; Moser, Robert D; Tappero, Ryan V; Kennedy, Alan J

2016-01-01

Metallic tungsten (W) was initially assumed to be environmentally benign and a green alternative to lead. However, subsequent investigations showed that fishing weights and munitions containing elemental W can fragment and oxidize into complex monomeric and polymeric tungstate (WO4) species in the environment; this led to increased solubility and mobility in soils and increased bioaccumulation potential in plant and animal tissues. Here we expand on the results of our previous research, which examined tungsten toxicity, bioaccumulation, and compartmentalization into organisms, and present in this research that the bioaccumulation of W was related to greater than 50% reduction in the mechanical properties of the snail (Otala lactea), based on depth-sensing nanoindentation. Synchrotron-based X-ray fluorescence maps and X-ray diffraction measurements confirm the integration of W in newly formed layers of the shell matrix with the observed changes in shell biomechanical properties, mineralogical composition, and crystal orientation. With further development, this technology could be employed as a biomonitoring tool for historic metals contamination since unlike the more heavily studied bioaccumulation into soft tissue, shell tissue does not actively eliminate contaminants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of erosion of metallic materials under cavitation attack in a mineral oil

NASA Technical Reports Server (NTRS)

Rao, B. C. S.; Buckley, D. H.

1984-01-01

Cavitation erosion and erosion rates of eight metallic materials representing three crystal structures were studied using a 20-kHz ultrasonic magnetostrictive oscillator in viscous mineral oil. The erosion rates of the metals with an fcc matrix were 10 to 100 times higher than that of an hcp-matrix titanium alloy. The erosion rates of iron and molybdenum, with bcc matrices, were higher than that of the titanium alloy but lower than those of the fcc metals. Scanning electron microscopy indicates that the cavitation pits are initially formed at the grain boundaries and precipitates and that the pits that formed at the triple points grew faster than the others. Transcrystalline craters formed by cavitation attack over the surface of grains and roughened the surfaces by multiple slip and twinning. Surface roughness measurements show that the pits that formed over the grain boundaries deepended faster than other pits. Computer analysis revealed that a geometric expression describes the nondimensional erosion curves during the time period 0.5 t(0) t 2.5 t(0), where t(0) is the incubation period. The fcc metals had very short incubation periods; the titanium alloy had the longest incubation period.

Synthesis of MnFe2O4@Mn-Co oxide core-shell nanoparticles and their excellent performance for heavy metal removal.

PubMed

Ma, Zichuan; Zhao, Dongyuan; Chang, Yongfang; Xing, Shengtao; Wu, Yinsu; Gao, Yuanzhe

2013-10-21

Magnetic nanomaterials that can be easily separated and recycled due to their magnetic properties have received considerable attention in the field of water treatment. However, these nanomaterials usually tend to aggregate and alter their properties. Herein, we report an economical and environmentally friendly method for the synthesis of magnetic nanoparticles with core-shell structure. MnFe2O4 nanoparticles have been successfully coated with amorphous Mn-Co oxide shells. The synthesized MnFe2O4@Mn-Co oxide nanoparticles have highly negatively charged surface in aqueous solution over a wide pH range, thus preventing their aggregation and enhancing their performance for heavy metal cation removal. The adsorption isotherms are well fitted to a Langmuir adsorption model, and the maximal adsorption capacities of Pb(II), Cu(II) and Cd(II) on MnFe2O4@Mn-Co oxide are 481.2, 386.2 and 345.5 mg g(-1), respectively. All the metal ions can be completely removed from the mixed metal ion solutions in a short time. Desorption studies confirm that the adsorbent can be effectively regenerated and reused.

Microyielding of core-shell crystal dendrites in a bulk-metallic-glass matrix composite

DOE PAGES

Huang, E. -Wen; Qiao, Junwei; Winiarski, Bartlomiej; ...

2014-03-18

In-situ synchrotron x-ray experiments have been used to follow the evolution of the diffraction peaks for crystalline dendrites embedded in a bulk metallic glass matrix subjected to a compressive loading-unloading cycle. We observe irreversible diffraction-peak splitting even though the load does not go beyond half of the bulk yield strength. The chemical analysis coupled with the transmission electron microscopy mapping suggests that the observed peak splitting originates from the chemical heterogeneity between the core (major peak) and the stiffer shell (minor peak) of the dendrites. A molecular dynamics model has been developed to compare the hkl-dependent microyielding of the bulkmore » metallic-glass matrix composite. As a result, the complementary diffraction measurements and the simulation results suggest that the interfaces between the amorphous matrix and the (211) crystalline planes relax under prolonged load that causes a delay in the reload curve which ultimately catches up with the original path.« less

Tuning the Shell Number of Multishelled Metal Oxide Hollow Fibers for Optimized Lithium-Ion Storage.

PubMed

Sun, Jin; Lv, Chunxiao; Lv, Fan; Chen, Shuai; Li, Daohao; Guo, Ziqi; Han, Wei; Yang, Dongjiang; Guo, Shaojun

2017-06-27

Searching the long-life transition-metal oxide (TMO)-based materials for future lithium-ion batteries (LIBs) is still a great challenge because of the mechanical strain resulting from volume change of TMO anodes during the lithiation/delithiation process. To well address this challenging issue, we demonstrate a controlled method for making the multishelled TMO hollow microfibers with tunable shell numbers to achieve the optimal void for efficient lithium-ion storage. Such a particularly designed void can lead to a short diffusion distance for fast diffusion of Li + ions and also withstand a large volume variation upon cycling, both of which are the key for high-performance LIBs. Triple-shelled TMO hollow microfibers are a quite stable anode material for LIBs with high reversible capacities (NiO: 698.1 mA h g -1 at 1 A g -1 ; Co 3 O 4 : 940.2 mA h g -1 at 1 A g -1 ; Fe 2 O 3 : 997.8 mA h g -1 at 1 A g -1 ), excellent rate capability, and stability. The present work opens a way for rational design of the void of multiple shells in achieving the stable lithium-ion storage through the biomass conversion strategy.

1/f noise in semiconductor and metal nanocrystal solids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Heng, E-mail: leophy@gmail.com; Lhuillier, Emmanuel, E-mail: emmanuel.lhuillier@espci.fr; Guyot-Sionnest, Philippe

2014-04-21

Electrical 1/f noise is measured in thin films of CdSe, CdSe/CdS, ZnO, HgTe quantum dots and Au nanocrystals. The 1/f noise, normalized per nanoparticle, shows no systematic dependence on the nanoparticle material and the coupling material. However, over 10 orders of magnitude, it correlates well with the nearest neighbor conductance suggesting some universal magnitude of the 1/f noise in these granular conductors. In the hopping regime, the main mechanism of 1/f noise is determined to be mobility fluctuated. In the metallic regime obtained with gold nanoparticle films, the noise drops to a similar level as bulk gold films and withmore » a similar temperature dependence.« less

Origin of tension-compression asymmetry in ultrafine-grained fcc metals

NASA Astrophysics Data System (ADS)

Tsuru, T.

2017-08-01

A mechanism of anomalous tension-compression (T-C) asymmetry in ultrafine-grained (UFG) metals is proposed using large-scale atomistic simulations and dislocation theory. Unlike coarse-grained metals, UFG Al exhibits remarkable T-C asymmetry of the yield stress. The atomistic simulations reveal that the yield event is not related to intragranular dislocations but caused by dislocation nucleation from the grain boundaries (GBs). The dislocation core structure associated with the stacking fault energy in Al is strongly affected by the external stress compared with Cu; specifically, high tensile stress stabilizes the dissociation into partial dislocations. These dislocations are more likely to be nucleated from GBs and form deformation twins from an energetic viewpoint. The mechanism, which is different from well-known mechanisms for nanocrystalline and amorphous metals, is unique to high-strength UFG metals and can explain the difference in T-C asymmetry between UFG Cu and Al.

Experimental and Theoretical Investigations on d and f Electron Systems under High Pressure

NASA Astrophysics Data System (ADS)

Gupta, Satish C.; Joshi, K. D.; Banerjee, S.

2008-07-01

The pressure-induced electron transfer from sp to d band in transition elements, and spd to f band in the light actinides significantly influences the stability of crystal structures in these metals. Although α → ω → β phase transition with increasing pressure in group IV transition elements is well documented, the β → ω transition under pressure has not been reported until recently. Our experimental study on the β-stabilized Zr-20Nb alloy reveals that it transforms to ω phase on shock compression, whereas this transition is not seen in a hydrostatic pressure condition. The platelike morphology of ω formed under shock compression is in contrast to the fine particle morphology seen in this system under thermal treatment, which clearly indicates that the mechanism of the β → ω transformation under shock treatment involves a large shear component. In this article, we have analyzed why the ω → β transition pressures in Ti, Zr, and Hf do not follow the trend implied by the principle of corresponding states. Our analysis shows that the ω → β transition depends on how the increased d population caused by the sp → d transfer of electron is distributed among various d substates. In Th, we have analyzed the role of 5f electrons in determining the mechanical stability of fcc and bct structures under hydrostatic compressions. Our analysis shows that the fcc to bct transition in this metal, which has been reported by high-pressure experiments, occurs because of softening of the tetragonal shear modulus C' = ( C 11 - C 12)/2 under compression. From the total energy calculated as a function of specific volume, we have determined the 0 K isotherm, which is then used to deduce the shock Hugoniot. The theoretical Hugoniot compares well with the experimental data.

The role of interfacial metal silicates on the magnetism in FeCo/SiO{sub 2} and Fe{sub 49%}Co{sub 49%}V{sub 2%}/SiO{sub 2} core/shell nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desautels, R. D., E-mail: rddesautels@physics.umanitoba.ca; Toyota Research Institute of North America, Ann Arbor, Michigan 48169; Freeland, J. W.

2015-05-07

We have investigated the role of spontaneously formed interfacial metal silicates on the magnetism of FeCo/SiO{sub 2} and Fe{sub 49%}Co{sub 49%}V{sub 2%}/SiO{sub 2} core/shell nanoparticles. Element specific x-ray absorption and photoelectron spectroscopy experiments have identified the characteristic spectral features of metallic iron and cobalt from within the nanoparticle core. In addition, metal silicates of iron, cobalt, and vanadium were found to have formed spontaneously at the interface between the nanoparticle core and silica shell. X-ray magnetic circular dichroism experiments indicated that the elemental magnetism was a result of metallic iron and cobalt with small components from the iron, cobalt, andmore » vanadium silicates. Magnetometry experiments have shown that there was no exchange bias loop shift in the FeCo nanoparticles; however, exchange bias from antiferromagnetic vanadium oxide was measured in the V-doped nanoparticles. These results showed clearly that the interfacial metal silicates played a significant role in the magnetism of these core/shell nanoparticles, and that the vanadium percolated from the FeCo-cores into the SiO{sub 2}-based interfacial shell.« less

78 FR 44121 - FCC Extends Reply Comment Dates for Indecency Cases Policy

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-23

... FEDERAL COMMUNICATIONS COMMISSION [GN Docket No. 13-86; DA 13-1560] FCC Extends Reply Comment... number of this Notice, GN Docket No. 13-86, on the front page. The Public Notice, DA 13-1560, released... documents from BCPI, please provide the appropriate FCC document number DA 13-1560. The Public Notice is...

Transport comparison of multiwall carbon nanotubes by contacting outer shell and all shells.

PubMed

Luo, Qiang; Cui, A-Juan; Zhang, Yi-Guang; Lu, Chao; Jin, Ai-Zi; Yang, Hai-Fang; Gu, Chang-Zhi

2010-11-01

Carbon nanotubes, particularly multiwall carbon nanotubes (MWCNTs) can serve as interconnects in nanoelectronic devices and integrated circuits because of their extremely large current-carrying capacity. Many experimental results about the transport properties of individual MWCNTs by contacting outer shell or all shells have been reported. In this work, a compatible method with integrated circuit manufacturing process was presented to compare the transport property of an individual multiwall carbon nanotube (MWCNT) by contacting outer shell only and all shells successively. First of the Ti/Au electrodes contacting outer shell only were fabricated onto the nanotube through the sequence of electron beam lithography (EBL) patterning, metal deposition and lift-off process. After the characterization of its transport property, focused ion beam (FIB) was used to drill holes through the same nanotube at the as-deposited electrodes. Then new contact to the holes and electrodes were made by ion-induced deposition of tungsten from W(CO)6 precursor gas. The transport results indicated that the new contact to all shells can clear up the intershell resistance and the electrical conductance of the tube can be improved about 8 times compared to that of by contacting outer shell only.

Progress towards next generation hadron colliders: FCC-hh, HE-LHC, and SPPC

NASA Astrophysics Data System (ADS)

Zimmermann, Frank; EuCARD-2 Extreme Beams Collaboration; Future Circular Collider (FCC) Study Collaboration

2017-01-01

A higher-energy circular proton collider is generally considered to be the only path available in this century for exploring energy scales well beyond the reach of the Large Hadron Collider (LHC) presently in operation at CERN. In response to the 2013 Update of the European Strategy for Particle Physics and aligned with the 2014 US ``P5'' recommendations, the international Future Circular Collider (FCC) study, hosted by CERN, is designing such future frontier hadron collider. This so-called FCC-hh will provide proton-proton collisions at a centre-of-mass energy of 100 TeV, with unprecedented luminosity. The FCC-hh energy goal is reached by combining higher-field, 16 T magnets, based on Nb3Sn superconductor, and a new 100 km tunnel connected to the LHC complex. In addition to the FCC-hh proper, the FCC study is also exploring the possibility of a High-Energy LHC (HE-LHC), with a centre-of-mass energy of 25-27 TeV, as could be achieved in the existing 27 km LHC tunnel using the FCC-hh magnet technology. A separate design effort centred at IHEP Beijing aims at developing and constructing a similar collider in China, with a smaller circumference of about 54 km, called SPPC. Assuming even higher-field 20 T magnets, by relying on high-temperature superconductor, the SPPC could reach a c.m. energy of about 70 TeV. This presentation will report the motivation and the present status of the R&D for future hadron colliders, a comparison of the three designs under consideration, the major challenges, R&D topics, the international technology programs, and the emerging global collaboration. Work supported by the European Commission under Capacities 7th Framework Programme project EuCARD-2, Grant Agreement 312453, and the HORIZON 2020 project EuroCirCol, Grant Agreement 654305.

Role of distortion in the hcp vs fcc competition in rare-gas solids

NASA Astrophysics Data System (ADS)

Krainyukova, N. V.

2011-05-01

As a prototype of an initial or intermediate structure between hcp and fcc lattices we consider a distorted bcc crystal. We calculate the temperature and pressure dependences of the lattice parameters for the heavier rare gas solids Ar, Kr, Xe in a quasiharmonic approximation with Aziz potentials, and confirm earlier predictions that the hcp structure predominates over fcc in the bulk within wide ranges of P and T. The situation is different for confined clusters with up to 105 atoms, where, owing to the specific surface energetics and terminations, structures with five-fold symmetry made up of fcc fragments are dominant. As a next step we consider the free relaxation of differently distorted bcc clusters, and show that two types (monoclinic and orthorhombic) of initial distortion are a driving force for the final hcp vs fcc configurations. Possible energy relationships between the initial and final structures are obtained and analyzed.

Current Policy Problems at the FCC.

ERIC Educational Resources Information Center

Wiley, Richard E.

In the past year the Federal Communications Commission (FCC) has instituted new programs and initiatives designed to improve the exchange of information between the Commission and the research and academic community. An Office of Plans and Policy has been formed. As a result of the Future Planning Conference held last year, a research project is…

Single d-metal atoms on F(s) and F(s+) defects of MgO(001): a theoretical study across the periodic table.

PubMed

Neyman, Konstantin M; Inntam, Chan; Matveev, Alexei V; Nasluzov, Vladimir A; Rösch, Notker

2005-08-24

Single d-metal atoms on oxygen defects F(s) and F(s+) of the MgO(001) surface were studied theoretically. We employed an accurate density functional method combined with cluster models, embedded in an elastic polarizable environment, and we applied two gradient-corrected exchange-correlation functionals. In this way, we quantified how 17 metal atoms from groups 6-11 of the periodic table (Cu, Ag, Au; Ni, Pd, Pt; Co, Rh, Ir; Fe, Ru, Os; Mn, Re; and Cr, Mo, W) interact with terrace sites of MgO. We found bonding with F(s) and F(s+) defects to be in general stronger than that with O2- sites, except for Mn-, Re-, and Fe/F(s) complexes. In M/F(s) systems, electron density is accumulated on the metal center in a notable fashion. The binding energy on both kinds of O defects increases from 3d- to 4d- to 5d-atoms of a given group, at variance with the binding energy trend established earlier for the M/O2- complexes, 4d < 3d < 5d. Regarding the evolution of the binding energy along a period, group 7 atoms are slightly destabilized compared to their group 6 congeners in both the F(s) and F(s+) complexes; for later transition elements, the binding energy increases gradually up to group 10 and finally decreases again in group 11, most strongly on the F(s) site. This trend is governed by the negative charge on the adsorbed atoms. We discuss implications for an experimental detection of metal atoms on oxide supports based on computed core-level energies.

Graded core/shell semiconductor nanorods and nanorod barcodes

DOEpatents

Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

2010-12-14

Graded core/shell semiconductor nanorods and shaped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

Graded core/shell semiconductor nanorods and nanorod barcodes

DOEpatents

Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

2013-03-26

Graded core/shell semiconductor nanorods and shapped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

Critical temperature of the Ising ferromagnet on the fcc, hcp, and dhcp lattices

NASA Astrophysics Data System (ADS)

Yu, Unjong

2015-02-01

By an extensive Monte-Carlo calculation together with the finite-size-scaling and the multiple histogram method, the critical coupling constant (Kc = J /kBTc) of the Ising ferromagnet on the fcc, hcp, and double hcp (dhcp) lattices were obtained with unprecedented precision: Kcfcc= 0.1020707(2) , Kchcp= 0.1020702(1) , and Kcdhcp= 0.1020706(2) . The critical temperature Tc of the hcp lattice is found to be higher than those of the fcc and the dhcp lattice. The dhcp lattice seems to have higher Tc than the fcc lattice, but the difference is within error bars.

Glass shell manufacturing in space

NASA Technical Reports Server (NTRS)

Downs, R. L.; Ebner, M. A.; Nolen, R. L., Jr.

1981-01-01

Highly-uniform, hollow glass spheres (shells), which are used for inertial confinement fusion targets, were formed from metal-organic gel powder feedstock in a vertical furnace. As a result of the rapid pyrolysis caused by the furnace, the gel is transformed to a shell in five distinct stages: (a) surface closure of the porous gel; (b) generation of a closed-cell foam structure in the gel; (c) spheridization of the gel and further expansion of the foam; (d) coalescence of the closed-cell foam to a single-void shell; and (e) fining of the glass shell. The heat transfer from the furnace to the falling gel particle was modeled to determine the effective heating rate of the gel. The model predicts the temperature history for a particle as a function of mass, dimensions, specific heat, and absorptance as well as furnace temperature profile and thermal conductivity of the furnace gas. A model was developed that predicts the gravity-induced degradation of shell concentricity in falling molten shells as a function of shell characteristics and time.

Water-soluble core/shell nanoparticles for proton therapy through particle-induced radiation

NASA Astrophysics Data System (ADS)

Park, Jeong Chan; Jung, Myung-Hwan; Kim, Maeng Jun; Kim, Kye-Ryung

2015-02-01

Metallic nanoparticles have been used in biomedical applications such as magnetic resonance imaging (MRI), therapy, and drug delivery systems. Metallic nanoparticles as therapeutic tools have been demonstrated using radio-frequency magnetic fields or near-infrared light. Recently, therapeutic applications of metallic nanomaterials combined with proton beams have been reported. Particle-induced radiation from metallic nanoparticles, which can enhance the therapeutic effects of proton therapy, was released when the nanoparticles were bombarded by a high-energy proton beam. Core/shell nanoparticles, especially Au-coated magnetic nanoparticles, have drawn attention in biological applications due to their attractive characteristics. However, studies on the phase transfer of organic-ligand-based core/shell nanoparticles into water are limited. Herein, we demonstrated that hydrophobic core/shell structured nanomaterials could be successfully dispersed in water through chloroform/surfactant mixtures. The effects of the core/shell nanomaterials and the proton irradiation on Escherichia coli (E. coli) were also explored.

Alternative storage environments for shelled peanuts

USDA-ARS?s Scientific Manuscript database

Studies were conducted in small chambers and commercial storage facilities to evaluate the effect of storing shelled peanuts at 3, 13, and 21 C (38, 55, 70 F) for one year. Shelled medium runner peanuts from the 2014 crop were placed in the three different environments in Feb 2015, sampled at 60-d ...

Alternative Storage Environments for Shelled Peanuts

USDA-ARS?s Scientific Manuscript database

Studies were conducted in small chambers and commercial storage facilities to evaluate the effect of storing shelled peanuts at 3, 13, and 21 C (38, 55, 70 F) for one year. Shelled medium runner peanuts from the 2014 crop were placed in the three different environments in Feb 2015, sampled at 60-d ...

47 CFR 95.225 - (R/C Rule 25) How do I contact the FCC?

Code of Federal Regulations, 2010 CFR

2010-10-01

... SERVICES PERSONAL RADIO SERVICES Radio Control (R/C) Radio Service Other Things You Need to Know § 95.225... Wide Web homepage: http://www.fcc.gov. (c) In writing, to FCC, Attention: R/C, 1270 Fairfield Road...

Polymorphism control of superconductivity and magnetism in Cs(3)C(60) close to the Mott transition.

PubMed

Ganin, Alexey Y; Takabayashi, Yasuhiro; Jeglic, Peter; Arcon, Denis; Potocnik, Anton; Baker, Peter J; Ohishi, Yasuo; McDonald, Martin T; Tzirakis, Manolis D; McLennan, Alec; Darling, George R; Takata, Masaki; Rosseinsky, Matthew J; Prassides, Kosmas

2010-07-08

The crystal structure of a solid controls the interactions between the electronically active units and thus its electronic properties. In the high-temperature superconducting copper oxides, only one spatial arrangement of the electronically active Cu(2+) units-a two-dimensional square lattice-is available to study the competition between the cooperative electronic states of magnetic order and superconductivity. Crystals of the spherical molecular C(60)(3-) anion support both superconductivity and magnetism but can consist of fundamentally distinct three-dimensional arrangements of the anions. Superconductivity in the A(3)C(60) (A = alkali metal) fullerides has been exclusively associated with face-centred cubic (f.c.c.) packing of C(60)(3-) (refs 2, 3), but recently the most expanded (and thus having the highest superconducting transition temperature, T(c); ref. 4) composition Cs(3)C(60) has been isolated as a body-centred cubic (b.c.c.) packing, which supports both superconductivity and magnetic order. Here we isolate the f.c.c. polymorph of Cs(3)C(60) to show how the spatial arrangement of the electronically active units controls the competing superconducting and magnetic electronic ground states. Unlike all the other f.c.c. A(3)C(60) fullerides, f.c.c. Cs(3)C(60) is not a superconductor but a magnetic insulator at ambient pressure, and becomes superconducting under pressure. The magnetic ordering occurs at an order of magnitude lower temperature in the geometrically frustrated f.c.c. polymorph (Néel temperature T(N) = 2.2 K) than in the b.c.c.-based packing (T(N) = 46 K). The different lattice packings of C(60)(3-) change T(c) from 38 K in b.c.c. Cs(3)C(60) to 35 K in f.c.c. Cs(3)C(60) (the highest found in the f.c.c. A(3)C(60) family). The existence of two superconducting packings of the same electronically active unit reveals that T(c) scales universally in a structure-independent dome-like relationship with proximity to the Mott metal-insulator transition

Double-shell CuS nanocages as advanced supercapacitor electrode materials

NASA Astrophysics Data System (ADS)

Guo, Jinxue; Zhang, Xinqun; Sun, Yanfang; Zhang, Xiaohong; Tang, Lin; Zhang, Xiao

2017-07-01

Metal sulfides hollow structures are advanced materials for energy storage applications of lithium-ion batteries and supercapacitors. However, constructing hollow metal sulfides with specific features, such as multi-shell and non-spherical shape, still remains great challenge. In this work, we firstly demonstrate the synthesis of CuS double-shell hollow nanocages using Cu2O nanocubes as precursors. The synthesis processes involve the repeated anion exchange reaction with Na2S and the controllable etching using hydrochloric acid. The whole synthesis processes are well revealed and the obtained double-shell CuS is tested as pseudocapacitive electrode material for supercapacitors. As expected, the CuS double-shell hollow nanocages deliver high specific capacitance, good rate performance and excellent cycling stability due to their unique nano-architecture. The present work contributes greatly to the exploration of hollow metal sulfides with complex architecture and non-spherical shape, as well as their promising application in high-performance electrochemical supercapacitors.

Energy barrier of bcc-fcc phase transition via the Bain path in Yukawa system

NASA Astrophysics Data System (ADS)

Kiyokawa, Shuji

2018-05-01

In the Yukawa system with the dimensionless screening parameter κ>1.5 , when bcc-fcc transition occurs via Bain path, we show that spontaneous transitions do not occur even if the system temperature reaches the transition point of bcc-fcc because it is necessary to increase once the free energy in the process of transition from bcc to fcc through Bain deformation. Here, we refer the temporary increment of the free energy during Bain deformation as Bain barrier. Since there are the Bain barriers at the transitions between bcc and fcc phases, these phases may coexist as metastable state in the wide region (not a coexistence line) of κ and the coupling constant Γ. We study the excess energy of the system and the free energy difference between bcc and fcc phases by the Monte Carlo method, where the simulation box is divided into a large number of elements with small volume and a particle in the box is restricted be placed in one of these elements. By this method, we can tabulate the values of the interparticle potential and can calculate the internal energy fast and precisely.

Enhanced linear photonic nanojet generated by core-shell optical microfibers

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Yen, Tzu-Ping; Chen, Chien-Wen

2017-05-01

The generation of linear photonic nanojet using core-shell optical microfiber is demonstrated numerically and experimentally in the visible light region. The power flow patterns for the core-shell optical microfiber are calculated by using the finite-difference time-domain method. The focusing properties of linear photonic nanojet are evaluated in terms of length and width along propagation and transversal directions. In experiment, the silica optical fiber is etched chemically down to 6 μm diameter and coated with metallic thin film by using glancing angle deposition. We show that the linear photonic nanojet is enhanced clearly by metallic shell due to surface plasmon polaritons. The large-area superresolution imaging can be performed by using a core-shell optical microfiber in the far-field system. The potential applications of this core-shell optical microfiber include micro-fluidics and nano-structure measurements.

Metastability and structural polymorphism in noble metals: the role of composition and metal atom coordination in mono- and bimetallic nanoclusters.

PubMed

Sanchez, Sergio I; Small, Matthew W; Bozin, Emil S; Wen, Jian-Guo; Zuo, Jian-Min; Nuzzo, Ralph G

2013-02-26

This study examines structural variations found in the atomic ordering of different transition metal nanoparticles synthesized via a common, kinetically controlled protocol: reduction of an aqueous solution of metal precursor salt(s) with NaBH₄ at 273 K in the presence of a capping polymer ligand. These noble metal nanoparticles were characterized at the atomic scale using spherical aberration-corrected scanning transmission electron microscopy (C(s)-STEM). It was found for monometallic samples that the third row, face-centered-cubic (fcc), transition metal [(3M)-Ir, Pt, and Au] particles exhibited more coherently ordered geometries than their second row, fcc, transition metal [(2M)-Rh, Pd, and Ag] analogues. The former exhibit growth habits favoring crystalline phases with specific facet structures while the latter samples are dominated by more disordered atomic arrangements that include complex systems of facets and twinning. Atomic pair distribution function (PDF) measurements further confirmed these observations, establishing that the 3M clusters exhibit longer ranged ordering than their 2M counterparts. The assembly of intracolumn bimetallic nanoparticles (Au-Ag, Pt-Pd, and Ir-Rh) using the same experimental conditions showed a strong tendency for the 3M atoms to template long-ranged, crystalline growth of 2M metal atoms extending up to over 8 nm beyond the 3M core.

Quantum and isotope effects in lithium metal

NASA Astrophysics Data System (ADS)

Ackland, Graeme J.; Dunuwille, Mihindra; Martinez-Canales, Miguel; Loa, Ingo; Zhang, Rong; Sinogeikin, Stanislav; Cai, Weizhao; Deemyad, Shanti

2017-06-01

The crystal structure of elements at zero pressure and temperature is the most fundamental information in condensed matter physics. For decades it has been believed that lithium, the simplest metallic element, has a complicated ground-state crystal structure. Using synchrotron x-ray diffraction in diamond anvil cells and multiscale simulations with density functional theory and molecular dynamics, we show that the previously accepted martensitic ground state is metastable. The actual ground state is face-centered cubic (fcc). We find that isotopes of lithium, under similar thermal paths, exhibit a considerable difference in martensitic transition temperature. Lithium exhibits nuclear quantum mechanical effects, serving as a metallic intermediate between helium, with its quantum effect-dominated structures, and the higher-mass elements. By disentangling the quantum kinetic complexities, we prove that fcc lithium is the ground state, and we synthesize it by decompression.

On Campus Web-Monitoring Rules, Colleges and the FCC Have a Bad Connection

ERIC Educational Resources Information Center

Hartle, Terry W.

2006-01-01

A regulation issued by the US Federal Communications Commission (FCC) requires facilities-based Internet services providers who operate their own equipment, including colleges, to make their Internet systems compliant with a statute known as the Communications Assistance for Law Enforcement Act (Calea) by April 2007. However, the FCC does not…

Effect of Steam Deactivation Severity of ZSM-5 Additives on LPG Olefins Production in the FCC Process.

PubMed

Gusev, Andrey A; Psarras, Antonios C; Triantafyllidis, Konstantinos S; Lappas, Angelos A; Diddams, Paul A

2017-10-21

ZSM-5-containing catalytic additives are widely used in oil refineries to boost light olefin production and improve gasoline octanes in the Fluid Catalytic Cracking (FCC) process. Under the hydrothermal conditions present in the FCC regenerator (typically >700 °C and >8% steam), FCC catalysts and additives are subject to deactivation. Zeolites (e.g., Rare Earth USY in the base catalyst and ZSM-5 in Olefins boosting additives) are prone to dealumination and partial structural collapse, thereby losing activity, micropore surface area, and undergoing changes in selectivity. Fresh catalyst and additives are added at appropriate respective levels to the FCC unit on a daily basis to maintain overall targeted steady-state (equilibrated) activity and selectivity. To mimic this process under accelerated laboratory conditions, a commercial P/ZSM-5 additive was hydrothermally equilibrated via a steaming process at two temperatures: 788 °C and 815 °C to simulate moderate and more severe equilibration industrial conditions, respectively. n -Dodecane was used as probe molecule and feed for micro-activity cracking testing at 560 °C to determine the activity and product selectivity of fresh and equilibrated P-doped ZSM-5 additives. The fresh/calcined P/ZSM-5 additive was very active in C 12 cracking while steaming limited its activity, i.e., at catalyst-to-feed (C/F) ratio of 1, about 70% and 30% conversion was obtained with the fresh and steamed additives, respectively. A greater activity drop was observed upon increasing the hydrothermal deactivation severity due to gradual decrease of total acidity and microporosity of the additives. However, this change in severity did not result in any selectivity changes for the LPG (liquefied petroleum gas) olefins as the nature (Brønsted-to-Lewis ratio) of the acid/active sites was not significantly altered upon steaming. Steam deactivation of ZSM-5 had also no significant effect on aromatics formation which was enhanced at higher

The s-process in massive stars: the Shell C-burning contribution

NASA Astrophysics Data System (ADS)

Pignatari, Marco; Gallino, R.; Baldovin, C.; Wiescher, M.; Herwig, F.; Heger, A.; Heil, M.; Käppeler, F.

In massive stars the s¡ process (slow neutron capture process) is activated at different tempera- tures, during He¡ burning and during convective shell C¡ burning. At solar metallicity, the neu- tron capture process in the convective C¡ shell adds a substantial contribution to the s¡ process yields made by the previous core He¡ burning, and the final results carry the signature of both processes. With decreasing metallicity, the contribution of the C¡ burning shell to the weak s¡ process rapidly decreases, because of the effect of the primary neutron poisons. On the other hand, also the s¡ process efficiency in the He core decreases with metallicity.

Applying a Qualitative Modeling Shell to Process Diagnosis: The Caster System.

DTIC Science & Technology

1986-03-01

Process Diagnosis: The Caster System by Timothy F. Thompson and William J. Clancey Department of Computer Science Stanford University Stanford, CA 94303...MODELING SHELL TO PROCESS DIAGNOSIS: THE CASTER SYSTEM 12 PERSONAL AUTHOR(S) TIMOTHY F. THOMPSON. WESTINGHOUSE R&D CENTER, WILLIAM CLANCEY, STANFORD...editions are obsolete. Applying a Qualitative Modeling Shell to Process Diagnosis: The Caster System by Timothy F. Thompson, Westinghouse R&D Center

Study of Shell Zone Formation in Lithographic and Anodizing Quality Aluminum Alloys: Experimental and Numerical Approach

NASA Astrophysics Data System (ADS)

Brochu, Christine; Larouche, André; Hark, Robert

Shell thickness is an important quality factor for lithographic and anodizing quality aluminum alloys. Increasing pressure is placed on casting plants to produce a thinner shell zone for these alloys. This study, based on plant trials and mathematical modelling highlights the most significant parameters influencing shell zone formation. Results obtained show the importance of metal temperature and distribution and mould metal level on shell zone formation. As an answer to specific plant problems, this study led to the development of improved metal distribution systems for DC casting of litho and anodizing quality alloys.

Identification of Second Shell Coordination in Transition Metal Species Using Theoretical XANES: Example of Ti–O–(C, Si, Ge) Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spanjers, Charles S.; Guillo, Pascal; Tilley, T. Don

X-ray absorption near-edge structure (XANES) is a common technique for elucidating oxidation state and first shell coordination geometry in transition metal complexes, among many other materials. However, the structural information obtained from XANES is often limited to the first coordination sphere. In this study, we show how XANES can be used to differentiate between C, Si, and Ge in the second coordination shell of Ti–O–(C, Si, Ge) molecular complexes based on differences in their Ti K-edge XANES spectra. Experimental spectra were compared with theoretical spectra calculated using density functional theory structural optimization and ab initio XANES calculations. The unique featuresmore » for second shell C, Si, and Ge present in the Ti K pre-edge XANES are attributed to the interaction between the Ti center and the O–X (X = C, Si, or Ge) antibonding orbitals.« less

76 FR 20976 - Wireline Competition Bureau Releases 2011 Annual Telecommunications Reporting Worksheet (FCC Form...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-14

... Releases 2011 Annual Telecommunications Reporting Worksheet (FCC Form 499-A) and Accompanying Instructions... Competition Bureau released the revised annual Telecommunications Reporting Worksheet (FCC Form 499-A) and... telecommunications activities) into Appendix B. (5) Noting that email addresses are generally required so that the...

Anisotropic deformation of metallo-dielectric core shell colloids under MeV ion irradiation

NASA Astrophysics Data System (ADS)

Penninkhof, J. J.; van Dillen, T.; Roorda, S.; Graf, C.; van Blaaderen, A.; Vredenberg, A. M.; Polman, A.

2006-01-01

We have studied the deformation of metallo-dielectric core-shell colloids under 4 MeV Xe, 6 and 16 MeV Au, 30 MeV Si and 30 MeV Cu ion irradiation. Colloids of silica surrounded by a gold shell, with a typical diameter of 400 nm, show anisotropic plastic deformation under MeV ion irradiation, with the metal flowing conform the anisotropically deforming silica core. The 20 nm thick metal shell imposes a mechanical constraint on the deforming silica core, reducing the net deformation strain rate compared to that of pure silica. In colloids consisting of a Au core and a silica shell, the silica expands perpendicular to the ion beam, while the metal core shows a large elongation along the ion beam direction, provided the silica shell is thick enough (>40 nm). A minimum electronic energy loss of 3.3 keV/nm is required for shape transformation of the metal core. Silver cores embedded in a silica shell show no elongation, but rather disintegrate. Also in planar SiO2 films, Au and Ag colloids show entirely different behavior under MeV irradiation. We conclude that the deformation model of core-shell colloids must include ion-induced particle disintegration in combination with thermodynamical effects, possibly in combination with mechanical effects driven by stresses around the ion tracks.

Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

NASA Astrophysics Data System (ADS)

Devi, Jutika; Saikia, Rashmi; Datta, Pranayee

2016-10-01

The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications.

fcc-bcc phase transition in plasma crystals using time-resolved measurements

NASA Astrophysics Data System (ADS)

Dietz, C.; Bergert, R.; Steinmüller, B.; Kretschmer, M.; Mitic, S.; Thoma, M. H.

2018-04-01

Three-dimensional plasma crystals are often described as Yukawa systems for which a phase transition between the crystal structures fcc and bcc has been predicted. However, experimental investigations of this transition are missing. We use a fast scanning video camera to record the crystallization process of 70 000 microparticles and investigate the existence of the fcc-bcc phase transition at neutral gas pressures of 30, 40, and 50 Pa. To analyze the crystal, robust phase diagrams with the help of a machine learning algorithm are calculated. This work shows that the phase transition can be investigated experimentally and makes a comparison with numerical results of Yukawa systems. The phase transition is analyzed in dependence on the screening parameter and structural order. We suggest that the transition is an effect of gravitational compression of the plasma crystal. Experimental investigations of the fcc-bcc phase transition will provide an opportunity to estimate the coupling strength Γ by comparison with numerical results of Yukawa systems.

Formation of metal nanoparticles in MgF2, CaF2 and BaF2 crystals under the electron beam irradiation

NASA Astrophysics Data System (ADS)

Bochkareva, Elizaveta S.; Sidorov, Alexander I.; Yurina, Uliana V.; Podsvirov, Oleg A.

2017-07-01

It is shown experimentally that electron beam action with electrons energies of 50 and 70 keV on MgF2, CaF2 and BaF2 crystals results in local formation in the crystal near-surface layer of Mg, Ca or Ba nanoparticles which possess plasmon resonance. In the case of MgF2 spheroidal nanoparticles are formed, in the cases of CaF2 and BaF2 - spherical. The formation of metal nanoparticles is confirmed by computer simulation in dipole quasistatic approximation. The dependence of absorption via electron irradiation dose is non-linear. It is caused by the increase of nanoparticles concentration and by the increase of nanoparticles sizes during irradiation. In the irradiated zones of MgF2 crystals, for irradiation doses less than 80 mC/cm2, the intense luminescence in a visible range appears. The practical application of fabricated composite materials for multilevel optical information recording is discussed.

Synthesis and characterization of silver-copper core-shell nanoparticles using polyol method for antimicrobial agent

NASA Astrophysics Data System (ADS)

Hikmah, N.; Idrus, N. F.; Jai, J.; Hadi, A.

2016-06-01

Silver and copper nanoparticles are well-known as the good antimicrobial agent. The nano-size of particles influences in enhancing the antimicrobial activity. This paper discusses the effect of molarity on the microstructure and morphology of silver-copper core-shell nanoparticles prepared by a polyol method. In this study, silver-copper nanoparticles are synthesized through the green approach of polyol method using ethylene glycol (EG) as green solvent and reductant, and polyoxyethylene-(80)-sorbitan monooleate (Tween 80) as a nontoxic stabilizer. The phase and morphology of silver-copper nanoparticles are characterized by X-ray diffraction (XRD) and Field emission scanning electron microscope (FESEM) and Transmission electron microscope (TEM). The results XRD confirm the pure crystalline of silver and copper nanoparticles with face-centered cubic (FCC) structure. FESEM and TEM analysis confirm the existence of Ag and Cu nanoparticles in core-shell shape.

Facile synthesis of multi-shell structured binary metal oxide powders with a Ni/Co mole ratio of 1:2 for Li-Ion batteries

NASA Astrophysics Data System (ADS)

Choi, Seung Ho; Park, Sun Kyu; Lee, Jung-Kul; Kang, Yun Chan

2015-06-01

Multi-shell structured binary transition metal oxide powders with a Ni/Co mole ratio of 1:2 are prepared by a simple spray drying process. Precursor powder particles prepared by spray drying from a spray solution of citric acid and ethylene glycol have completely spherical shape, fine size, and a narrow size distribution. The precursor powders turn into multi-shell powders after a post heat-treatment at temperatures between 250 and 800 °C. The multi-shell structured powders are formed by repeated combustion and contraction processes. The multi-shell powders have mixed crystal structures of Ni1-xCo2O4-x and NiO phases regardless of the post-treatment temperature. The reversible capacities of the powders post-treated at 250, 400, 600, and 800 °C after 100 cycles are 584, 913, 808, and 481 mA h g-1, respectively. The low charge transfer resistance and high lithium ion diffusion rate of the multi-shell powders post-treated at 400 °C with optimum grain size result in superior electrochemical properties even at high current densities.

Fixture for multiple-FCC chemical stripping and plating

NASA Technical Reports Server (NTRS)

Angele, W.; Norton, W. E.

1971-01-01

For chemical stripping, lead tape applied near ends to be stripped protects insulation. Taped ends are submerged half way in stripping solution. For electroplating, both ends of FCC are stripped - top ends for electric contact, others for submersion in electroplating solution.

Control of the shell structural properties and cavity diameter of hollow magnesium fluoride particles.

PubMed

Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Okuyama, Kikuo

2014-03-26

Control of the shell structural properties [i.e., thickness (8-25 nm) and morphology (dense and raspberry)] and cavity diameter (100-350 nm) of hollow particles was investigated experimentally, and the results were qualitatively explained based on the available theory. We found that the selective deposition size and formation of the shell component on the surface of a core template played important roles in controlling the structure of the resulting shell. To achieve the selective deposition size and formation of the shell component, various process parameters (i.e., reaction temperature and charge, size, and composition of the core template and shell components) were tested. Magnesium fluoride (MgF2) and polystyrene spheres were used as models for shell and core components, respectively. MgF2 was selected because, to the best of our knowledge, the current reported approaches to date were limited to synthesis of MgF2 in film and particle forms only. Therefore, understanding how to control the formation of MgF2 with various structures (both the thickness and morphology) is a prospective for advanced lens synthesis and applications.

Long-range empirical potential model: extension to hexagonal close-packed metals.

PubMed

Dai, Y; Li, J H; Liu, B X

2009-09-23

An n-body potential is developed and satisfactorily applied to hcp metals, Co, Hf, Mg, Re, Ti, and Zr, in the form of long-range empirical potential. The potential can well reproduce the lattice constants, c/a ratios, cohesive energies, and the bulk modulus for their stable structures (hcp) and metastable structures (bcc or fcc). Meanwhile, the potential can correctly predict the order of structural stability and distinguish the energy differences between their stable hcp structure and other structures. The energies and forces derived by the potential can smoothly go to zero at cutoff radius, thus completely avoiding the unphysical behaviors in the simulations. The developed potential is applied to study the vacancy, surface fault, stacking fault and self-interstitial atom in the hcp metals. The calculated formation energies of vacancy and divacancy and activation energies of self-diffusion by vacancies are in good agreement with the values in experiments and in other works. The calculated surface energies and stacking fault energies are also consistent with the experimental data and those obtained in other theoretical works. The calculated formation energies generally agree with the results in other works, although the stable configurations of self-interstitial atoms predicted in this work somewhat contrast with those predicted by other methods. The proposed potential is shown to be relevant for describing the interaction of bcc, fcc and hcp metal systems, bringing great convenience for researchers in constructing potentials for metal systems constituted by any combination of bcc, fcc and hcp metals.

Investigation of Three-Dimensional Stress Fields and Slip Systems for FCC Single Crystal Superalloy Notched Specimens

NASA Technical Reports Server (NTRS)

Arakere, Nagaraj K.; Magnan, Shannon; Ebrahimi, Fereshteh; Ferroro, Luis

2004-01-01

Metals and their alloys, except for a few intermetallics, are inherently ductile, i.e. plastic deformation precedes fracture in these materials. Therefore, resistance to fracture is directly related to the development of the plastic zone at the crack tip. Recent studies indicate that the fracture toughness of single crystals depends on the crystallographic orientation of the notch as well as the loading direction. In general, the dependence of crack propagation resistance on crystallographic orientation arises from the anisotropy of (i) elastic constants, (ii) plastic deformation (or slip), and (iii) the weakest fracture planes (e.g. cleavage planes). Because of the triaxial stress state at the notch tips, many slip systems that otherwise would not be activated during uniaxial testing, become operational. The plastic zone formation in single crystals has been tackled theoretically by Rice and his co-workers and only limited experimental work has been conducted in this area. The study of the stresses and strains in the vicinity of a FCC single crystal notch tip is of relatively recent origin. We present experimental and numerical investigation of 3D stress fields and evolution of slip sector boundaries near notches in FCC single crystal tension test specimens, and demonstrate that a 3D linear elastic finite element model that includes the effect of material anisotropy is shown to predict active slip planes and sectors accurately. The slip sector boundaries are shown to have complex curved shapes with several slip systems active simultaneously near the notch. Results are presented for surface and mid-plane of the specimens. The results demonstrate that accounting for 3D elastic anisotropy is very important for accurate prediction of slip activation near FCC single crystal notches loaded in tension. Results from the study will help establish guidelines for fatigue damage near single crystal notches.

Shaping the photoluminescence from gold nanoshells by cavity plasmons in dielectric-metal core-shell resonators

NASA Astrophysics Data System (ADS)

Sun, Ren; Wan, Mingjie; Wu, Wenyang; Gu, Ping; Chen, Zhuo; Wang, Zhenlin

2016-08-01

We report experimental investigation of the photoluminescence (PL) generated from the gold nanoshells of the dielectric-metal core-shell resonators (DMCSR) that support multipolar electric and magnetic based cavity plasmon resonances. Significantly enhanced and modulated PL spectrum is observed. By comparing the experimental results with analytical Mie calculations, we are able to demonstrate that the observed reshaping effects are due to the excitations of those narrow-band cavity plasmon resonances. We also present that the variation on the dielectric core size allows for tuning the cavity plasmon resonance wavelengths and thus the peak positions of the PL spectrum.

Further Results in Bend-Buckling Analysis of Ring Stiffened Cylindrical Shells.

DTIC Science & Technology

1986-08-01

Submerged Shell Targets, NSWC TR 84-380, Dec 1984. 2. Moussouros, M., "Finite Element Modeling Techniques for Buckling Analysis of Cylindrical Shells...KCR, MBR , M0 , F0 , and I, R is the mean radius as given by R0 ) R0 - Mean radius of circular cylindrical shell (perfect shell or radius of

X-ray Emission Spectroscopy in Magnetic 3d-Transition Metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iota, V; Park, J; Baer, B

2003-11-18

The application of high pressure affects the band structure and magnetic interactions in solids by modifying nearest-neighbor distances and interatomic potentials. While all materials experience electronic changes with increasing pressure, spin polarized, strongly electron correlated materials are expected to undergo the most dramatic transformations. In such materials, (d and f-electron metals and compounds), applied pressure reduces the strength of on-site correlations, leading to increased electron delocalization and, eventually, to loss of its magnetism. In this ongoing project, we study the electronic and magnetic properties of Group VIII, 3d (Fe, Co and Ni) magnetic transition metals and their compounds at highmore » pressures. The high-pressure properties of magnetic 3d-transition metals and compounds have been studied extensively over the years, because of iron being a major constituent of the Earth's core and its relevance to the planetary modeling to understand the chemical composition, internal structure, and geomagnetism. However, the fundamental scientific interest in the high-pressure properties of magnetic 3d-electron systems extends well beyond the geophysical applications to include the electron correlation-driven physics. The role of magnetic interactions in the stabilization of the ''non-standard'' ambient pressure structures of Fe, Co and Ni is still incompletely understood. Theoretical studies have predicted (and high pressure experiments are beginning to show) strong correlations between the electronic structure and phase stability in these materials. The phase diagrams of magnetic 3d systems reflect a delicate balance between spin interactions and structural configuration. At ambient conditions, the crystal structures of {alpha}-Fe(bcc) and {var_epsilon}-Co(hcp) phases depart from the standard sequence (hcp {yields} bcc{yields} hcp {yields} fcc), as observed in all other non-magnetic transition metals with increasing the d-band occupancy

Imaging of single liver tumor cells intoxicated by heavy metals using ToF-SIMS

NASA Astrophysics Data System (ADS)

Mai, Fu-Der; Chen, Bo-Jung; Wu, Li-Chen; Li, Feng-Yin; Chen, Wen-Kang

2006-07-01

Human liver tumor cells intoxicated with five different Cd, Cu, Cr, Hg and Zn metals were analyzed using imaging time-of-flight secondary ion mass spectrometry (ToF-SIMS) to visualize the metal distributions in a single cell basis. A protocol was developed by combining rapid freezing, freeze-fracture and imprinting for transferring the intoxicated cells to a silicon wafer. As shown in the ToF-SIMS images, the cellular morphology was preserved indicating that this protocol can be used to prepare a representative cell for ToF-SIMS imaging analysis. Among the five metal ions investigated in this study, only Cr and Cu ions show preferential diffusion into the cell after simulated intoxication while the signals of the other three ions are either too low to be detected or unable to be distinguished from background intensity.

Crystal grain growth at the α -uranium phase transformation in praseodymium

NASA Astrophysics Data System (ADS)

Cunningham, Nicholas C.; Velisavljevic, Nenad; Vohra, Yogesh K.

2005-01-01

Structural phase transformations under pressure are examined in praseodymium metal for the range 0-40GPa at ambient temperature. Pressure was generated with a diamond-anvil cell, and data were collected using high-resolution synchrotron x-ray diffraction and the image plate technique. The structural sequence double hexagonal close packed (dhcp)→face centered cubic (fcc)→distorted-fcc (d-fcc)→ α -uranium (α-U) is observed with increasing pressure. Rietveld refinement of all crystallographic phases provided confirmation of the hR24 structure for the d-fcc phase while the previously reported monoclinic phase between the d-fcc and the α-U phase was not confirmed. We observe dramatic crystal grain growth during the volume collapse concurrent with the symmetry-lowering transition to the α-U structure. No preferred orientation axis is observed, and the formation process for these large grains is expected to be via a nucleation and growth mechanism. An analogous effect in rare earth metal cerium suggests that the grain growth during transformation to the α-U structure is a common occurrence in f -electron metals at high pressures.

76 FR 69738 - Revised 2011 Annual Telecommunications Reporting Worksheet (FCC Form 499-A) and Accompanying...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-09

... Telecommunications Reporting Worksheet (FCC Form 499-A) and Accompanying Instructions AGENCY: Federal Communications... Telecommunications Reporting Worksheet (FCC Form 499-A) and accompanying instructions that have been approved by the... INFORMATION CONTACT: Ernesto Beckford, Wireline Competition Bureau, Telecommunications Access Policy Division...

Carbon flow analysis and Carbon emission reduction of FCC in Chinese oil refineries

NASA Astrophysics Data System (ADS)

Jia, Fengrui; Wei, Na; Ma, Danzhu; Liu, Guangxin; Wu, Ming; Yue, Qiang

2017-08-01

The major problem of the energy production in oil refineries is the high emission of CO2 in China. The fluid catalytic cracking unit (FCC) is the key source of carbon emission in the oil refineries. According to the statistical data, the carbon emission of FCC unit accounts for more than 31% for the typical oil refineries. The carbon flow of FCC in the typical Chinese oil refineries were evaluated and analysed, which aimed at the solution of CO2 emission reduction. The method of substances flow analysis (SFA) and the mathematical programming were used to evaluate the carbon metabolism and optimize the carbon emission. The results indicated that the combustion emission of the reaction-regeneration subsystem (RRS) was the major source of FCC. The quantity of CO2 emission of RSS was more than 90%. The combustion efficiency and the amount of residual oil affected the carbon emission of RRS most according to the optimized analysis of carbon emission reduction. Moreover, the fractionation subsystem (TFS) had the highest environmental efficiency and the absorption-stabilization subsystem (ASS) had the highest resource efficiency (approximately to 1) of carbon.

Nitrogen Chemistry and Coke Transformation of FCC Coked Catalyst during the Regeneration Process

NASA Astrophysics Data System (ADS)

Shi, Junjun; Guan, Jianyu; Guo, Dawei; Zhang, Jiushun; France, Liam John; Wang, Lefu; Li, Xuehui

2016-06-01

Regeneration of the coked catalyst is an important process of fluid catalytic cracking (FCC) in petroleum refining, however, this process will emit environmentally harmful gases such as nitrogen and carbon oxides. Transformation of N and C containing compounds in industrial FCC coke under thermal decomposition was investigated via TPD and TPO to examine the evolved gaseous species and TGA, NMR and XPS to analyse the residual coke fraction. Two distinct regions of gas evolution are observed during TPD for the first time, and they arise from decomposition of aliphatic carbons and aromatic carbons. Three types of N species, pyrrolic N, pyridinic N and quaternary N are identified in the FCC coke, the former one is unstable and tends to be decomposed into pyridinic and quaternary N. Mechanisms of NO, CO and CO2 evolution during TPD are proposed and lattice oxygen is suggested to be an important oxygen resource. Regeneration process indicates that coke-C tends to preferentially oxidise compared with coke-N. Hence, new technology for promoting nitrogen-containing compounds conversion will benefit the in-situ reduction of NO by CO during FCC regeneration.

Nitrogen Chemistry and Coke Transformation of FCC Coked Catalyst during the Regeneration Process

PubMed Central

Shi, Junjun; Guan, Jianyu; Guo, Dawei; Zhang, Jiushun; France, Liam John; Wang, Lefu; Li, Xuehui

2016-01-01

Regeneration of the coked catalyst is an important process of fluid catalytic cracking (FCC) in petroleum refining, however, this process will emit environmentally harmful gases such as nitrogen and carbon oxides. Transformation of N and C containing compounds in industrial FCC coke under thermal decomposition was investigated via TPD and TPO to examine the evolved gaseous species and TGA, NMR and XPS to analyse the residual coke fraction. Two distinct regions of gas evolution are observed during TPD for the first time, and they arise from decomposition of aliphatic carbons and aromatic carbons. Three types of N species, pyrrolic N, pyridinic N and quaternary N are identified in the FCC coke, the former one is unstable and tends to be decomposed into pyridinic and quaternary N. Mechanisms of NO, CO and CO2 evolution during TPD are proposed and lattice oxygen is suggested to be an important oxygen resource. Regeneration process indicates that coke-C tends to preferentially oxidise compared with coke-N. Hence, new technology for promoting nitrogen-containing compounds conversion will benefit the in-situ reduction of NO by CO during FCC regeneration. PMID:27270486

The microstructure and magnetic properties of Cu/CuO/Ni core/multi-shell nanowire arrays

NASA Astrophysics Data System (ADS)

Yang, Feng; Shi, Jie; Zhang, Xiaofeng; Hao, Shijie; Liu, Yinong; Feng, Chun; Cui, Lishan

2018-04-01

Multifunctional metal/oxide/metal core/multi-shell nanowire arrays were prepared mostly by physical or chemical vapor deposition. In our study, the Cu/CuO/Ni core/multi-shell nanowire arrays were prepared by AAO template-electrodeposition and oxidation processes. The Cu/Ni core/shell nanowire arrays were prepared by AAO template-electrodeposition method. The microstructure and chemical compositions of the core/multi-shell nanowires and core/shell nanowires have been characterized using transmission electron microscopy with HADDF-STEM and X-ray diffraction. Magnetization measurements revealed that the Cu/CuO/Ni and Cu/Ni nanowire arrays have high coercivity and remanence ratio.

Shape transformation of bimetallic Au–Pd core–shell nanocubes to multilayered Au–Pd–Au core–shell hexagonal platelets

DOE PAGES

Bhattarai, Nabraj; Prozorov, Tanya

2015-11-05

Transformation of metallic or bimetallic (BM) nanoparticles (NPs) from one shape to another desired shape is of importance to nanoscience and nanotechnology, where new morphologies of NPs lead to enhancement of their exploitable properties. In this report, we present the shape transformation of Au octahedral NPs to Au–Pd core–shell nanocubes, followed by their transformation to nanostars and finally to multilayered Au–Pd–Au core–shell hexagonal platelets in the presence of T30 DNA. The weaker binding affinity of T30 DNA directs the growth to favor the formation of lower energy {111} facets, changing the morphology from nanocubes to nanostar. The nanostars, exhibiting unusualmore » intermediate morphologies, are comprised two sets of shell layers and have Au core, Pd intermediate shell, and Au outer shell. Similarly, the hexagonal platelets, which also have Au core and inner Pd shell, are encased in an external gold shell. As a result, the formation of multilayered Au–Pd–Au core–shell hexagonal platelets from Au–Pd core–shell nanocubes via the multilayered nanostars is monitored using scanning/transmission electron microscopy analysis.« less

Shape transformation of bimetallic Au–Pd core–shell nanocubes to multilayered Au–Pd–Au core–shell hexagonal platelets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattarai, Nabraj; Prozorov, Tanya

Transformation of metallic or bimetallic (BM) nanoparticles (NPs) from one shape to another desired shape is of importance to nanoscience and nanotechnology, where new morphologies of NPs lead to enhancement of their exploitable properties. In this report, we present the shape transformation of Au octahedral NPs to Au–Pd core–shell nanocubes, followed by their transformation to nanostars and finally to multilayered Au–Pd–Au core–shell hexagonal platelets in the presence of T30 DNA. The weaker binding affinity of T30 DNA directs the growth to favor the formation of lower energy {111} facets, changing the morphology from nanocubes to nanostar. The nanostars, exhibiting unusualmore » intermediate morphologies, are comprised two sets of shell layers and have Au core, Pd intermediate shell, and Au outer shell. Similarly, the hexagonal platelets, which also have Au core and inner Pd shell, are encased in an external gold shell. As a result, the formation of multilayered Au–Pd–Au core–shell hexagonal platelets from Au–Pd core–shell nanocubes via the multilayered nanostars is monitored using scanning/transmission electron microscopy analysis.« less

Metal-in-metal localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Smith, G. B.; Earp, A. A.

2010-01-01

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result.

Lattice vibrations and electronic transitions in the rare-earth metals: yttrium, gadolinium and lutetium

NASA Astrophysics Data System (ADS)

Olijnyk, Helmut

2005-01-01

Lattice vibrations in high-pressure phases of Y, Gd and Lu were studied by Raman spectroscopy. The observed phonon frequencies decrease towards the transitions to the dhcp and fcc phases. There is evidence that the entire structural sequence {\\mathrm {hcp \\to Sm\\mbox {-}type \\to dhcp \\to fcc}} under pressure for the individual regular rare-earth metals and along the lanthanide series at ambient pressure involve softening of certain acoustic and optical phonon modes and of the elastic shear modulus C44. Comparison is made to transitions between close-packed lattices in other metals, and possible correlations to s-d electron transfer are discussed.

Multi-Shell Hybrid Diffusion Imaging (HYDI) at 7 Tesla in TgF344-AD Transgenic Alzheimer Rats.

PubMed

Daianu, Madelaine; Jacobs, Russell E; Weitz, Tara M; Town, Terrence C; Thompson, Paul M

2015-01-01

Diffusion weighted imaging (DWI) is widely used to study microstructural characteristics of the brain. Diffusion tensor imaging (DTI) and high-angular resolution imaging (HARDI) are frequently used in radiology and neuroscience research but can be limited in describing the signal behavior in composite nerve fiber structures. Here, we developed and assessed the benefit of a comprehensive diffusion encoding scheme, known as hybrid diffusion imaging (HYDI), composed of 300 DWI volumes acquired at 7-Tesla with diffusion weightings at b = 1000, 3000, 4000, 8000 and 12000 s/mm2 and applied it in transgenic Alzheimer rats (line TgF344-AD) that model the full clinico-pathological spectrum of the human disease. We studied and visualized the effects of the multiple concentric "shells" when computing three distinct anisotropy maps-fractional anisotropy (FA), generalized fractional anisotropy (GFA) and normalized quantitative anisotropy (NQA). We tested the added value of the multi-shell q-space sampling scheme, when reconstructing neural pathways using mathematical frameworks from DTI and q-ball imaging (QBI). We show a range of properties of HYDI, including lower apparent anisotropy when using high b-value shells in DTI-based reconstructions, and increases in apparent anisotropy in QBI-based reconstructions. Regardless of the reconstruction scheme, HYDI improves FA-, GFA- and NQA-aided tractography. HYDI may be valuable in human connectome projects and clinical research, as well as magnetic resonance research in experimental animals.

Revisiting chameleon gravity: Thin-shell and no-shell fields with appropriate boundary conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamaki, Takashi; Department of Physics, Rikkyo University, Toshima, Tokyo 171-8501; Tsujikawa, Shinji

2008-10-15

We derive analytic solutions of a chameleon scalar field {phi} that couples to a nonrelativistic matter in the weak gravitational background of a spherically symmetric body, paying particular attention to a field mass m{sub A} inside of the body. The standard thin-shell field profile is recovered by taking the limit m{sub A}r{sub c}{yields}{infinity}, where r{sub c} is a radius of the body. We show the existence of 'no-shell' solutions where the field is nearly frozen in the whole interior of the body, which does not necessarily correspond to the 'zero-shell' limit of thin-shell solutions. In the no-shell case, under themore » condition m{sub A}r{sub c}>>1, the effective coupling of {phi} with matter takes the same asymptotic form as that in the thin-shell case. We study experimental bounds coming from the violation of equivalence principle as well as solar-system tests for a number of models including f(R) gravity and find that the field is in either the thin-shell or the no-shell regime under such constraints, depending on the shape of scalar-field potentials. We also show that, for the consistency with local gravity constraints, the field at the center of the body needs to be extremely close to the value {phi}{sub A} at the extremum of an effective potential induced by the matter coupling.« less

X-ray-diffraction study of californium metal to 16 GPa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, J.R.; Benedict, U.; Dufour, C.

1983-01-01

The first series of measurements to determine the structural behavior of californium (Cf) metal under pressure has been carried out. The initial dhcp structure transformed sluggishly with increasing pressure to a fcc structure. A bulk modulus of 50(5) GPa was derived for dhcp Cf metal from the relative volume (V/V/sub 0/) data to 10 GPa.

Dropping macadamia nuts-in-shell reduces kernel roasting quality.

PubMed

Walton, David A; Wallace, Helen M

2010-10-01

Macadamia nuts ('nuts-in-shell') are subjected to many impacts from dropping during postharvest handling, resulting in damage to the raw kernel. The effect of dropping on roasted kernel quality is unknown. Macadamia nuts-in-shell were dropped in various combinations of moisture content, number of drops and receiving surface in three experiments. After dropping, samples from each treatment and undropped controls were dry oven-roasted for 20 min at 130 °C, and kernels were assessed for colour, mottled colour and surface damage. Dropping nuts-in-shell onto a bed of nuts-in-shell at 3% moisture content or 20% moisture content increased the percentage of dark roasted kernels. Kernels from nuts dropped first at 20%, then 10% moisture content, onto a metal plate had increased mottled colour. Dropping nuts-in-shell at 3% moisture content onto nuts-in-shell significantly increased surface damage. Similarly, surface damage increased for kernels dropped onto a metal plate at 20%, then at 10% moisture content. Postharvest dropping of macadamia nuts-in-shell causes concealed cellular damage to kernels, the effects not evident until roasting. This damage provides the reagents needed for non-enzymatic browning reactions. Improvements in handling, such as reducing the number of drops and improving handling equipment, will reduce cellular damage and after-roast darkening. Copyright © 2010 Society of Chemical Industry.

3718-F Alkali Metal Treatment and Storage Facility Closure Plan. Revision 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The Hanford Site, located northwest of the city of Richland, Washington, houses reactors, chemical-separation systems, and related facilities used for the production of special nuclear materials, as well as for activities associated with nuclear energy development. The 300 Area of the Hanford Site contains reactor fuel manufacturing facilities and several research and development laboratories. The 3718-F Alkali Metal Treatment and Storage Facility (3718-F Facility), located in the 300 Area, was used to store and treat alkali metal wastes. Therefore, it is subject to the regulatory requirements for the storage and treatment of dangerous wastes. Closure will be conducted pursuant tomore » the requirements of the Washington Administrative Code (WAC) 173-303-610 (Ecology 1989) and 40 CFR 270.1. Closure also will satisfy the thermal treatment facility closure requirements of 40 CFR 265.381. This closure plan presents a description of the 3718-F Facility, the history of wastes managed, and the approach that will be followed to close the facility. Only hazardous constituents derived from 3718-F Facility operations will be addressed.« less

ZnS-Sb2S3@C Core-Double Shell Polyhedron Structure Derived from Metal-Organic Framework as Anodes for High Performance Sodium Ion Batteries.

PubMed

Dong, Shihua; Li, Caixia; Ge, Xiaoli; Li, Zhaoqiang; Miao, Xianguang; Yin, Longwei

2017-06-27

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-Sb 2 S 3 @C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn 2+ dissociated from ZIF-8 and S 2- from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn 2+ and Sb 3+ , in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and Sb 2 S 3 /C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex Sb 2 S 3 /C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices.

New insights into micro/nanoscale combined probes (nanoAuger, μXPS) to characterize Ag/Au@SiO2 core-shell assemblies

NASA Astrophysics Data System (ADS)

Ledeuil, J. B.; Uhart, A.; Soulé, S.; Allouche, J.; Dupin, J. C.; Martinez, H.

2014-09-01

This work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2 particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming electron signal (potentially affected by the topography of the material) during analysis. SEM experiments have unambiguously revealed the hollow-morphology of the metal core, while Auger spectroscopy observations showed chemical heterogeneity within the particles (as silver and gold are randomly found in the core ring). To our knowledge, this is the first time that Auger nano probe spectroscopy has been used and successfully optimized for the study of some complex metal/inorganic interfaces at such a high degree of resolution (~12 nm). Complementarily, XPS Au 4f and Ag 3d peaks were finally detected attesting the possibility of access to the whole chemistry of such nanostructured assemblies.This work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2 particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming

Adsorption of cadmium on cerium oxide nanoparticles and oyster shells

NASA Astrophysics Data System (ADS)

Ji, Yongbo; Liu, Zhuomiao; Dang, Yonghui; Xu, Lina; Ning, Fangyuan; Xue, Yinhao; Wei, Yongpeng; Dai, Yanhui

2018-03-01

This study investigated the adsorption of cadmium (Cd(II)) by cerium oxide nanoparticles (CeO2 NPs) and oyster shells in seawater. The results showed that the addition of Cd(II) significantly inhibited the agglomeration of CeO2 NPs both in DI water and seawater, increased the positive charges of CeO2 NPs in DI water and neutralized the negative charges of CeO2 NPs in seawater. Additionally, CeO2 NPs could adsorb Cd and the bioavailability of Cd was reduced in the presence of oyster shells. This study demonstrated that the adsorption of metals on shells should not be neglected for the accumulation of metals by shellfish.

The extremely metal-poor galaxy DDO 68: the luminous blue variable, Hα shells and the most luminous stars

NASA Astrophysics Data System (ADS)

Pustilnik, S. A.; Makarova, L. N.; Perepelitsyna, Y. A.; Moiseev, A. V.; Makarov, D. I.

2017-03-01

This paper presents new results from the ongoing study of the unusual Lynx-Cancer void galaxy DDO 68, which has star-forming regions of record low metallicity [12+log (O/H) ˜7.14]. The results include the following. (I) A new spectrum and photometry have been obtained with the 6-m SAO RAS telescope (BTA) for the luminous blue variable (LBV = DDO68-V1). Photometric data sets were complemented with others based on the Sloan Digital Sky Survey (SDSS) and the Hubble Space Telescope (HST) archive images. (II) We performed an analysis of the DDO 68 supergiant shell (SGS) and the prominent smaller Hα arcs/shells visible in the HST image coupled with kinematic maps in Hα obtained with the Fabry-Perot interferometer (FPI) at the BTA. (III) We compiled a list of about 50 of the most luminous stars (-9.1 mag < MV < -6.0 mag) identified from the HST images associated with the star-forming regions with known extremely low O/H. This is intended to pave the path for the current science to be investigated with the next generation of giant telescopes. We have confirmed earlier hints of significant variation of the LBV optical light, deriving its amplitude as ΔV ≳ 3.7 mag for the first time. New data suggest that in 2008-2010 the LBV reached MV = -10.5 mag and probably underwent a giant eruption. We argue that the structure of star-forming complexes along the SGS ('Northern Ring') perimeter provides evidence for sequential induced star-formation episodes caused by the shell gas instabilities and gravitational collapse. The variability of some luminous extremely metal-poor stars in DDO 68 can currently be monitored with medium-size telescopes at sites with superb seeing.

Dislocation Multiplication by Single Cross Slip for FCC at Submicron Scales

NASA Astrophysics Data System (ADS)

Cui, Yi-Nan; Liu, Zhan-Li; Zhuang, Zhuo

2013-04-01

The operation mechanism of single cross slip multiplication (SCSM) is investigated by studying the response of one dislocation loop expanding in face-centered-cubic (FCC) single crystal using three-dimensional discrete dislocation dynamic (3D-DDD) simulation. The results show that SCSM can trigger highly correlated dislocation generation in a short time, which may shed some light on understanding the large strain burst observed experimentally. Furthermore, we find that there is a critical stress and material size for the operation of SCSM, which agrees with that required to trigger large strain burst in the compression tests of FCC micropillars.

Molecular dynamics study of melting and fcc-bcc transitions in Xe.

PubMed

Belonoshko, A B; Ahuja, R; Johansson, B

2001-10-15

We have investigated the phase diagram of Xe over a wide pressure-temperature range by molecular dynamics. The calculated melting curve is in good agreement with earlier experimental data. At a pressure of around 25 GPa and a temperature of about 2700 K we find a triple fcc-bcc liquid point. The calculated fcc-bcc boundary is in nice agreement with the experimental points, which, however, were interpreted as melting. This finding suggests that the transition from close-packed to bcc structure might be more common at high pressure and high temperature than was previously anticipated.

Characterization of erosion of metallic materials under cavitation attack in a mineral oil

NASA Technical Reports Server (NTRS)

Rao, B. C. S.; Buckley, D. H.

1985-01-01

Cavitation erosion and erosion rates of eight metallic materials representing three crystal structures were studied. The erosion experiments were conducted with a 20-kHz ultrasonic magnetostrictive oscillator in a viscous mineral oil. The erosion rates of the metals with an fcc matrix were 10 to 100 times higher than that of an hop-matrix titanium alloy. The erosion rates of iron and molybdenum, with bcc matrices, were higher than that of the titanium alloy but lower than those of those of the fcc materials. Studies with scanning electron microscopy indicated that the cavitation pits were initially formed at the grain boundaries and precipitates and that the pits formed at the junction of grain boundaries grew faster than the others. Transcrystalline craters formed by cavitation attack over the surface of grains and roughened the surfaces by multiple slip and twinning. Surface roughness measurements showed that the pits that formed over the grain boundaries deepened faster than pits. Computer analysis revealed that a geometric expression describes the nondimensional erosion curves during the time period 0.5 t (sub 0) t 2.5 t (sub 0), where t (sub 0) is the incubation period. The fcc metals had very short incubation periods; the titanium alloy had the longest incubation period.

Phonons and superconductivity in fcc and dhcp lanthanum

NASA Astrophysics Data System (ADS)

Baǧcı, S.; Tütüncü, H. M.; Duman, S.; Srivastava, G. P.

2010-04-01

We have investigated the structural and electronic properties of lanthanum in the face-centered-cubic (fcc) and double hexagonal-close-packed (dhcp) phases using a generalized gradient approximation of the density functional theory and the ab initio pseudopotential method. It is found that double hexagonal-close-packed is the more stable phase for lanthanum. Differences in the density of states at the Fermi level between these two phases are pointed out and discussed in detail. Using the calculated lattice constant and electronic band structure for both phases, a linear response approach based on the density functional theory has been applied to study phonon modes, polarization characteristics of phonon modes, and electron-phonon interaction. Our phonon results show a softening behavior of the transverse acoustic branch along the Γ-L direction and the Γ-M direction for face-centered-cubic and double hexagonal-close-packed phases, respectively. Thus, the transverse-phonon linewidth shows a maximum at the zone boundary M(L) for the double hexagonal-close-packed phase (face-centered-cubic phase), where the transverse-phonon branch exhibits a dip. The electron-phonon coupling parameter λ is found to be 0.97 (1.06) for the double hexagonal-close-packed phase (face-centered-cubic phase), and the superconducting critical temperature is estimated to be 4.87 (dhcp) and 5.88 K (fcc), in good agreement with experimental values of around 5.0 (dhcp) and 6.0 K (fcc). A few superconducting parameters for the double hexagonal-close-packed phase have been calculated and compared with available theoretical and experimental results. Furthermore, the calculated superconducting parameters for both phases are compared between each other in detail.

Effects of Co doping on the metamagnetic states of the ferromagnetic fcc Fe-Co alloy.

PubMed

Ortiz-Chi, Filiberto; Aguayo, Aarón; de Coss, Romeo

2013-01-16

The evolution of the metamagnetic states in the ferromagnetic face centered cubic (fcc) Fe(1-x)Co(x) alloy as a function of Co concentration has been studied by means of first-principles calculations. The ground state properties were obtained using the full-potential linear augmented plane wave method and the generalized gradient approximation for the exchange-correlation functional. The alloying was modeled using the virtual crystal approximation and the magnetic states were obtained from the calculations of the total energy as a function of the spin moment, using the fixed spin moment method. For ferromagnetic fcc Fe, the binding-energy curve shows metamagnetic behavior, with two minima corresponding to a small-volume, low-spin (LS) state and a large-volume, high-spin (HS) state, which are separated by a small energy (E(LS) ≲ E(HS)). The evolution of the magnetic moment, the exchange integral (J), and the binding-energy curve is analyzed in the whole range of Co concentrations (x). The magnetic moment corresponding to the HS state decreases monotonically from 2.6 μ(B)/atom in fcc Fe to 1.7 μ(B)/atom in fcc Co. In contrast, the exchange integral for the HS state shows a maximum at around x = 0.45. The thermal dependence of the lattice parameter is evaluated with a method based on statistical mechanics using the binding-energy curve as an effective potential. It is observed that the behavior of the lattice parameter with temperature is tuned by Co doping, from negative thermal expansion in fcc Fe to positive thermal expansion in fcc Co, through the modification of the energetics of the metamagnetic states.

Metallic Sn spheres and SnO2@C core-shells by anaerobic and aerobic catalytic ethanol and CO oxidation reactions over SnO2 nanoparticles

PubMed Central

Kim, Won Joo; Lee, Sung Woo; Sohn, Youngku

2015-01-01

SnO2 has been studied intensely for applications to sensors, Li-ion batteries and solar cells. Despite this, comparatively little attention has been paid to the changes in morphology and crystal phase that occur on the metal oxide surface during chemical reactions. This paper reports anaerobic and aerobic ethanol and CO oxidation reactions over SnO2 nanoparticles (NPs), as well as the subsequent changes in the nature of the NPs. Uniform SnO2@C core-shells (10 nm) were formed by an aerobic ethanol oxidation reaction over SnO2 NPs. On the other hand, metallic Sn spheres were produced by an anaerobic ethanol oxidation reaction at 450 °C, which is significantly lower than that (1200 °C) used in industrial Sn production. Anaerobic and aerobic CO oxidation reactions were also examined. The novelty of the methods for the production of metallic Sn and SnO2@C core-shells including other anaerobic and aerobic reactions will contribute significantly to Sn and SnO2-based applications. PMID:26300041

Hyperfine structure of 2Σ molecules containing alkaline-earth-metal atoms

NASA Astrophysics Data System (ADS)

Aldegunde, Jesus; Hutson, Jeremy M.

2018-04-01

Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF, and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth-metal and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

Synthesis and characterization of Na(Gd0.5Lu0.5)F4: Nd3+,a core-shell free multifunctional contrast agent.

PubMed

Mimun, L Christopher; Ajithkumar, G; Rightsell, Chris; Langloss, Brian W; Therien, Michael J; Sardar, Dhiraj K

2017-02-25

Compared to conventional core-shell structures, core-shell free nanoparticles with multiple functionalities offer several advantages such as minimal synthetic complexity and low production cost. In this paper, we present the synthesis and characterization of Nd 3+ doped Na(Gd 0.5 Lu 0.5 )F 4 as a core-shell free nanoparticle system with three functionalities. Nanocrystals with 20 nm diameter, high crystallinity and a narrow particle size distributions were synthesized by the solvothermal method and characterized by various analytical techniques to understand their phase and morphology. Fluorescence characteristics under near infrared (NIR) excitation at 808 nm as well as X-ray excitation were studied to explore their potential in NIR optical and X-ray imaging. At 1.0 mol% Nd concentration, we observed a quantum yield of 25% at 1064 nm emission with 13 W/cm 2 excitation power density which is sufficiently enough for imaging applications. Under 130 kVp (5 mA) power of X-ray excitation, Nd 3+ doped Na(Gd 0.5 Lu 0.5 )F 4 shows the characteristic emission bands of Gd 3+ and Nd 3+ with the strongest emission peak at 1064 nm due to Nd 3+ . Furthermore, magnetization measurements show that the nanocrystals are paramagnetic in nature with a calculated magnetic moment per particle of ~570 μB at 2T. These preliminary results support the suitability of the present nanophosphor as a multimodal contrast agent with three imaging features viz. optical, magnetic and X-ray.

Elasto-plastic impact of hemispherical shell impacting on hard rigid sphere

NASA Technical Reports Server (NTRS)

Raftopoulos, D. D.; Spicer, A. L.

1976-01-01

An analysis of plastic stress waves for cylindrical metallic projectile in impact is extended to an analysis of a hemispherical shell suffereing plastic deformation during the process of impact. It is assumed that the hemispherical shell with a prescribed launch velocity impinges a fixed rigid sphere of diameter equal to the internal diameter of the shell. The dynamic biaxial state of stress present in the shell during deformation is investigated. The analysis is valuable for studying the state of stress during large plastic deformation of a hemispherical shell.

Subwavelength core/shell cylindrical nanostructures for novel plasmonic and metamaterial devices

NASA Astrophysics Data System (ADS)

Kim, Kyoung-Ho; No, You-Shin

2017-12-01

In this review, we introduce novel plasmonic and metamaterial devices based on one-dimensional subwavelength nanostructures with cylindrical symmetry. Individual single devices with semiconductor/metal core/shell or dielectric/metal core/multi-shell structures experience strong light-matter interaction and yield unique optical properties with a variety of functions, e.g., invisibility cloaking, super-scattering/super-absorption, enhanced luminescence and nonlinear optical activities, and deep subwavelength-scale optical waveguiding. We describe the rational design of core/shell cylindrical nanostructures and the proper choice of appropriate constituent materials, which allow the efficient manipulation of electromagnetic waves and help to overcome the limitations of conventional homogeneous nanostructures. The recent developments of bottom-up synthesis combined with the top-down fabrication technologies for the practical applications and the experimental realizations of 1D subwavelength core/shell nanostructure devices are briefly discussed.

47 CFR 95.422 - (CB Rule 22) How do I answer correspondence from the FCC?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false (CB Rule 22) How do I answer correspondence from the FCC? 95.422 Section 95.422 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED... You Need to Know § 95.422 (CB Rule 22) How do I answer correspondence from the FCC? (a) If it appears...

Achieving the broader frequency electromagnetic absorber by development of magnetic core-shell composite with tunable shell/core sizes

NASA Astrophysics Data System (ADS)

Cheng, Ye; Guo, Yuhang; Zhang, Zhenya; Dong, Songtao; Liu, Suwei; Wang, Hongying

2018-03-01

Magnetic absorber has been regarded as the advanced electromagnetic energy transfer material to solve the increasingly high frequency electromagnetic interference issue. Even so, the pure magnetic material, in particular magnetic metal nanoparticle, suffering from the poor chemical stability and strong eddy current effect, thus limits it further application. To overcome this shortage, surrounded the magnetic metal nanoparticle (MPs) with insulated oxide shell has been considered to be an efficient route to suppress such an eddy current effect. Meanwhile, the combined insulated shell with good impedance matching feature, shows a positive role on the electromagnetic energy transfer intensity. In this regard, the binary Fe@α-Fe2O3 composite with the average size of ∼ 20 nm was prepared by a facile self-oxidation reaction. Interestingly, both the core diameter and shell thickness is controllable by controlling the oxide degree. The electromagnetic energy transfer performance revealed the maximum absorption frequency bandwidth of the optimal Fe@α-Fe2O3 composite is up to 5.3 G(8.2-13.5 GHz)under a small coating thickness of 1.5 mm.

Cesium under pressure: First-principles calculation of the bcc-to-fcc phase transition

NASA Astrophysics Data System (ADS)

Carlesi, S.; Franchini, A.; Bortolani, V.; Martinelli, S.

1999-05-01

In this paper we present the ab initio calculation of the structural properties of cesium under pressure. The calculation of the total energy is done in the local-density approximation of density-functional theory, using a nonlocal pseudopotential including the nonlinear core corrections proposed by Louie et al. The calculation of the pressure-volume diagram for both bcc and fcc structures allows us to prove that the transition from bcc to fcc structure is a first-order transition.

Sub-molecular modulation of a 4f driven Kondo resonance by surface-induced asymmetry

NASA Astrophysics Data System (ADS)

Warner, Ben; El Hallak, Fadi; Atodiresei, Nicolae; Seibt, Philipp; Prüser, Henning; Caciuc, Vasile; Waters, Michael; Fisher, Andrew J.; Blügel, Stefan; van Slageren, Joris; Hirjibehedin, Cyrus F.

2016-09-01

Coupling between a magnetic impurity and an external bath can give rise to many-body quantum phenomena, including Kondo and Hund's impurity states in metals, and Yu-Shiba-Rusinov states in superconductors. While advances have been made in probing the magnetic properties of d-shell impurities on surfaces, the confinement of f orbitals makes them difficult to access directly. Here we show that a 4f driven Kondo resonance can be modulated spatially by asymmetric coupling between a metallic surface and a molecule containing a 4f-like moment. Strong hybridization of dysprosium double-decker phthalocyanine with Cu(001) induces Kondo screening of the central magnetic moment. Misalignment between the symmetry axes of the molecule and the surface induces asymmetry in the molecule's electronic structure, spatially mediating electronic access to the magnetic moment through the Kondo resonance. This work demonstrates the important role that molecular ligands have in mediating electronic and magnetic coupling and in accessing many-body quantum states.

Native CB1 receptor affinity, intrinsic activity and accumbens shell dopamine stimulant properties of third generation SPICE/K2 cannabinoids: BB-22, 5F-PB-22, 5F-AKB-48 and STS-135.

PubMed

De Luca, Maria Antonietta; Castelli, M Paola; Loi, Barbara; Porcu, Alessandra; Martorelli, Mariella; Miliano, Cristina; Kellett, Kathryn; Davidson, Colin; Stair, Jacqueline L; Schifano, Fabrizio; Di Chiara, Gaetano

2016-06-01

In order to investigate the in vivo dopamine (DA) stimulant properties of selected 3rd generation Spice/K2 cannabinoids, BB-22, 5F-PB-22, 5F-AKB-48 and STS-135, their in vitro affinity and agonist potency at native rat and mice CB1 receptors was studied. The compounds bind with high affinity to CB1 receptors in rat cerebral cortex homogenates and stimulate CB1-induced [(35)S]GTPγS binding with high potency and efficacy. BB-22 and 5F-PB-22 showed the lowest Ki of binding to CB1 receptors (0.11 and 0.13 nM), i.e., 30 and 26 times lower respectively than that of JWH-018 (3.38 nM), and a potency (EC50, 2.9 and 3.7 nM, respectively) and efficacy (Emax, 217% and 203%, respectively) as CB1 agonists higher than JWH-018 (EC50, 20.2 nM; Emax, 163%). 5F-AKB-48 and STS-135 had higher Ki for CB1 binding, higher EC50 and lower Emax as CB1 agonists than BB-22 and 5F-PB-22 but still comparatively more favourable than JWH-018. The agonist properties of all the compounds were abolished or drastically reduced by the CB1 antagonist/inverse agonist AM251 (0.1 μM). No activation of G-protein was observed in CB1-KO mice. BB-22 (0.003-0.01 mg/kg i.v.) increased dialysate DA in the accumbens shell but not in the core or in the medial prefrontal cortex, with a bell shaped dose-response curve and an effect at 0.01 mg/kg and a biphasic time-course. Systemic AM251 (1.0 mg/kg i.p.) completely prevented the stimulant effect of BB-22 on dialysate DA in the NAc shell. All the other compounds increased dialysate DA in the NAc shell at doses consistent with their in vitro affinity for CB1 receptors (5F-PB-22, 0.01 mg/kg; 5F-AKB-48, 0.1 mg/kg; STS-135, 0.15 mg/kg i.v.). 3rd generation cannabinoids can be even more potent and super-high CB1 receptor agonists compared to JWH-018. Future research will try to establish if these properties can explain the high toxicity and lethality associated with these compounds. Copyright © 2015 Elsevier Ltd. All rights reserved.

Shear response of Σ3{112} twin boundaries in face-centered-cubic metals

NASA Astrophysics Data System (ADS)

Wang, J.; Misra, A.; Hirth, J. P.

2011-02-01

Molecular statics and dynamics simulations were used to study the mechanisms of sliding and migration of Σ3{112} incoherent twin boundaries (ITBs) under applied shear acting in the boundary in the face-centered-cubic (fcc) metals, Ag, Cu, Pd, and Al, of varying stacking fault energies. These studies revealed that (i) ITBs can dissociate into two phase boundaries (PBs), bounding the hexagonal 9R phase, that contain different arrays of partial dislocations; (ii) the separation distance between the two PBs scales inversely with increasing stacking fault energy; (iii) for fcc metals with low stacking fault energy, one of the two PBs migrates through the collective glide of partials, referred to as the phase-boundary-migration (PBM) mechanism; (iv) for metals with high stacking energy, ITBs experience a coupled motion (migration and sliding) through the glide of interface disconnections, referred to as the interface-disconnection-glide (IDG) mechanism.

Porous Core-Shell Nanostructures for Catalytic Applications

NASA Astrophysics Data System (ADS)

Ewers, Trevor David

Porous core-shell nanostructures have recently received much attention for their enhanced thermal stability. They show great potential in the field of catalysis, as reactant gases can diffuse in and out of the porous shell while the core particle is protected from sintering, a process in which particles coalesce to form larger particles. Sintering is a large problem in industry and is the primary cause of irreversible deactivation. Despite the obvious advantages of high thermal stability, porous core-shell nanoparticles can be developed to have additional interactive properties from the combination of the core and shell together, rather than just the core particle alone. This dissertation focuses on developing new porous core-shell systems in which both the core and shell take part in catalysis. Two types of systems are explored; (1) yolk-shell nanostructures with reducible oxide shells formed using the Kirkendall effect and (2) ceramic-based porous oxide shells formed using sol-gel chemistry. Of the Kirkendall-based systems, Au FexOy and Cu CoO were synthesized and studied for catalytic applications. Additionally, ZnO was explored as a potential shelling material. Sol-gel work focused on optimizing synthetic methods to allow for coating of small gold particles, which remains a challenge today. Mixed metal oxides were explored as a shelling material to make dual catalysts in which the product of a reaction on the core particle becomes a reactant within the shell.

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE PAGES

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; ...

2014-04-03

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

High-value utilization of egg shell to synthesize Silver and Gold-Silver core shell nanoparticles and their application for the degradation of hazardous dyes from aqueous phase-A green approach.

PubMed

Sinha, Tanur; Ahmaruzzaman, M

2015-09-01

The common household material, egg shell of Anas platyrhynchos is utilized for the synthesis of Silver and Gold-Silver core shell nanoparticles using greener, environment friendly and economic way. The egg shell extracts were acting as a stabilizing and reducing agents. This method avoids the use of external reducing and stabilizing agents, templates and solvents. The effects of various reaction parameters, such as reaction temperature, concentration in the formation of nanoparticles have also been investigated. The compositional abundance of gelatin may be envisaged for the effective reductive as well as stabilizing potency. The mechanisms for the formation of NPs have also been presented. The synthesized Ag NPs formed were predominantly spherical in nature with an average size of particles in the range of 6-26 nm. While, Au-Ag core shell nanoparticles formed were spherical and oval shaped, within a narrow size spectrum of 9-18 nm. Both the Ag NPs Au-and Ag core shell nanoparticles showed characteristic Bragg's reflection planes of fcc structure and surface plasmon resonance at 430 nm and 365 nm, respectively. The NPs were utilized for the removal of toxic and hazardous dyes, such as Rose Bengal, Methyl Violet 6 B and Methylene Blue from aqueous phase. Approximately 98.2%, 98.4% and 97% degradations of Rose Bengal, Methyl Violet 6 B, and Methylene Blue were observed with Ag NPs, while the percentage degradation of these dyes was 97.3%, 97.6% and 96% with Au-Ag NPs, respectively. Therefore, the present study has opened up an innovative way for synthesizing Ag NPs and Au-Ag bimetallic nanostructures of different morphologies and sizes involving the utilization of egg shell extract. The high efficiency of the NPs as photocatalysts has opened a promising application for the removal of hazardous dyes from the industrial effluents. Copyright © 2015 Elsevier Inc. All rights reserved.

Large-area super-resolution optical imaging by using core-shell microfibers

NASA Astrophysics Data System (ADS)

Liu, Cheng-Yang; Lo, Wei-Chieh

2017-09-01

We first numerically and experimentally report large-area super-resolution optical imaging achieved by using core-shell microfibers. The particular spatial electromagnetic waves for different core-shell microfibers are studied by using finite-difference time-domain and ray tracing calculations. The focusing properties of photonic nanojets are evaluated in terms of intensity profile and full width at half-maximum along propagation and transversal directions. In experiment, the general optical fiber is chemically etched down to 6 μm diameter and coated with different metallic thin films by using glancing angle deposition. The direct imaging of photonic nanojets for different core-shell microfibers is performed with a scanning optical microscope system. We show that the intensity distribution of a photonic nanojet is highly related to the metallic shell due to the surface plasmon polaritons. Furthermore, large-area super-resolution optical imaging is performed by using different core-shell microfibers placed over the nano-scale grating with 150 nm line width. The core-shell microfiber-assisted imaging is achieved with super-resolution and hundreds of times the field-of-view in contrast to microspheres. The possible applications of these core-shell optical microfibers include real-time large-area micro-fluidics and nano-structure inspections.

Teaching Valence Shell Electron Pair Repulsion (VSEPR) Theory

ERIC Educational Resources Information Center

Talbot, Christopher; Neo, Choo Tong

2013-01-01

This "Science Note" looks at the way that the shapes of simple molecules can be explained in terms of the number of electron pairs in the valence shell of the central atom. This theory is formally known as valence shell electron pair repulsion (VSEPR) theory. The article explains the preferred shape of chlorine trifluoride (ClF3),…

The stability of the epitaxially introduced metastable metallic structures of thin layers and multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cadeville, M.C.

Among the very large number of metallic thin films, sandwiches and multilayers which have been elaborated by epitaxy on various single crystalline substrates during the last decade, few new structures are reported. Limiting to the case of 3d metals, one finds with a great confidence bcc Cobalt, possibly bee Nickel and a non-compact hexagonal (hp) iron. Moreover structures existing at high temperature under ambient pressure are epitaxially stabilized at room temperature (RT) like fcc Cobalt, fcc Iron, fcc and bcc Manganese. The hcp iron which is stable under high pressure at RT would not be epitaxially stabilized at ambient pressuremore » conversely to first findings. The critical thickness of the metastable phase is generally limited to some monolayers in thin films, being slightly increased in sandwiches or multilayers, even if the phenomenological wetting criterion to build superlattices is not satisfied. No increased magnetic moment has been found up to now in the expanded lattices, contrary to band structure calculation predictions. 56 refs.« less

Insights into chromatographic separation using core-shell metal-organic frameworks: Size exclusion and polarity effects.

PubMed

Qin, Weiwei; Silvestre, Martin E; Kirschhöfer, Frank; Brenner-Weiss, Gerald; Franzreb, Matthias

2015-09-11

Porous metal-organic frameworks (MOFs) [Cu3(BTC)2(H2O)3]n (also known as HKUST-1; BTC, benzene-1,3,5-tricarboxylic acid) were synthesized as homogeneous shell onto carboxyl functionalized magnetic microparticles through a liquid phase epitaxy (LPE) process. The as-synthesized core-shell HKUST-1 magnetic microparticles composites were characterized by XRD and SEM, and used as stationary phase in high performance liquid chromatography (HPLC). The effects of the unique properties of MOFs onto the chromatographic performance are demonstrated by the experiments. First, remarkable separation of pyridine and bipyridine is achieved, although both molecules show a strong interaction between the Cu-ions in HKUST-1 and the nitrogen atoms in their heterocyles. The difference can be explained due to size exclusion of bipyridine from the well defined pore structure of crystalline HKUST-1. Second, the enormous variety of possible interactions of sample molecules with the metal ions and linkers within MOFs allows for specifically tailored solid phases for challenging separation tasks. For example, baseline separation of three chloroaniline (CLA) isomers tested can be achieved without the need for gradient elution modes. Along with the experimental HPLC runs, in-depth modelling with a recently developed chromatography modelling software (ChromX) was applied and proofs the software to be a powerful tool for exploring the separation potential of thin MOF films. The pore diffusivity of pyridine and CLA isomers within HKUST-1 are found to be around 2.3×10(-15)m(2)s(-1). While the affinity of HKUST-1 to the tested molecules strongly differs, the maximum capacities are in the same range, with 0.37molL(-1) for pyridine and 0.23molL(-1) for CLA isomers, corresponding to 4.0 and 2.5 molecules per MOF unit cell, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

Self-assembly of noble metal monolayers on transition metal carbide nanoparticle catalysts

DOE PAGES

Hunt, Sean T.; Milina, Maria; Alba-Rubio, Ana C.; ...

2016-05-20

Here, we demonstrated the self-assembly of transition metal carbide nanoparticles coated with atomically thin noble metal monolayers by carburizing mixtures of noble metal salts and transition metal oxides encapsulated in removable silica templates. This approach allows for control of the final core-shell architecture, including particle size, monolayer coverage, and heterometallic composition. Carbon-supported Ti 0.1W 0.9C nanoparticles coated with Pt or bimetallic PtRu monolayers exhibited enhanced resistance to sintering and CO poisoning, achieving an order of magnitude increase in specific activity over commercial catalysts for methanol electrooxidation after 10,000 cycles. These core-shell materials provide a new direction to reduce the loading,more » enhance the activity, and increase the stability of noble metal catalysts.« less

False-positive 18F-fluorodeoxyglucose positron emission tomography/computed tomography in a patient with metallic implants following chondrosarcoma resection.

PubMed

Zhou, P U; Tang, Jinliang; Zhang, Dong; Li, Guanghui

2016-05-01

Positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose ( 18 F-FDG) has been used for the staging and evaluation of recurrence in cancer patients. We herein report a false-positive result of 18 F-FDG PET/computed tomography (CT) scan in a patient following chondrosarcoma resection and metallic implanting. A 35-year-old male patient with chondrosarcoma of the left iliac bone underwent radical resection, metal brace implanting and radiotherapy. A high uptake of 18 F-FDG was observed in the metallic implants and adjacent tissue during PET/CT scanning in the 5th year of follow-up. Tissue biopsy and follow-up examination identified no tumor recurrence or infection at these sites, suggesting that the results of 18 F-FDG PET/CT must be interpreted with caution in cancer patients with metallic implants.

Determination on the chemical composition of Ammonia beccarii shell using SEM and EDX: Preliminary study of benthic foraminifera capacity in response to anthropogenic metal contamination in coastal areas

NASA Astrophysics Data System (ADS)

Rositasari, R.; Suratno; Yogaswara, D.

2018-02-01

The use of single-celled and shelled biota, such as foraminifera that lives as benthic, in coastal environmental monitoring activity is very efficient. Several species of the Ammonia have been used as a proxy of various aquatic environmental monitoring activities. Chemical constituents screening in foraminiferal shell is a step ahead to identify the capacity of benthic foraminifera in responding to anthropogenic metal contamination in coastal water areas. The initial hypothesis of this study is the calcite test of Ammonia beccarii binds the anthropogenic metal in its shell structure and triggers the deformation test. The normal and abnormal shells of Ammonia specimens from Jakarta Bay and Batam waters are used in this study. The Ponar grab was used to sample surface sediment in Jakarta Bay and Batam waters in 2015, and the short core was used to acquire substratum sediment in Jakarta Bay in 2011.The Ammonia beccarii shell was analyzed using SEM and EDX detectors (Scanning Electron Microscope and Energy Dispersive X-ray). The shooting was performed three times in each test, i.e. in the first chamber (proloculus), the last chamber and the chamber between the two. The main building blocks of the foraminifera test are oxygen with an average weight range of 42.86 - 58.79% and carbon with an average weight range of 17.69 - 26.32%. There is a tendency for low levels of C and O elements in the abnormal tests.

Nanosized (mu12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x approximately 7) containing Pt-centered four-shell 165-atom Pd-Pt core with unprecedented intershell bridging carbonyl ligands: comparative analysis of icosahedral shell-growth patterns with geometrically related Pd145(CO)x(PEt3)30 (x approximately 60) containing capped three-shell Pd145 core.

PubMed

Mednikov, Evgueni G; Jewell, Matthew C; Dahl, Lawrence F

2007-09-19

Presented herein are the preparation and crystallographic/microanalytical/magnetic/spectroscopic characterization of the Pt-centered four-shell 165-atom Pd-Pt cluster, (mu(12)-Pt)Pd(164-x)Pt(x)(CO)(72)(PPh(3))(20) (x approximately 7), 1, that replaces the geometrically related capped three-shell icosahedral Pd(145) cluster, Pd(145)(CO)(x)(PEt(3))(30) (x approximately 60), 2, as the largest crystallographically determined discrete transition metal cluster with direct metal-metal bonding. A detailed comparison of their shell-growth patterns gives rise to important stereochemical implications concerning completely unexpected structural dissimilarities as well as similarities and provides new insight concerning possible synthetic approaches for generation of multi-shell metal clusters. 1 was reproducibly prepared in small yields (<10%) from the reaction of Pd(10)(CO)(12)(PPh(3))(6) with Pt(CO)(2)(PPh(3))(2). Its 165-atom metal-core geometry and 20 PPh(3) and 72 CO ligands were established from a low-temperature (100 K) CCD X-ray diffraction study. The well-determined crystal structure is attributed largely to 1 possessing cubic T(h) (2/m3) site symmetry, which is the highest crystallographic subgroup of the noncrystallographic pseudo-icosahedral I(h) (2/m35) symmetry. The "full" four-shell Pd-Pt anatomy of 1 consists of: (a) shell 1 with the centered (mu(12)-Pt) atom encapsulated by the 12-atom icosahedral Pt(x)Pd(12-x) cage, x = 1.2(3); (b) shell 2 with the 42-atom nu(2) icosahedral Pt(x)Pd(42-x) cage, x = 3.5(5); (c) shell 3 with the anti-Mackay 60-atom semi-regular rhombicosidodecahedral Pt(x)Pd(60-x) cage, x = 2.2(6); (d) shell 4 with the 50-atom nu(2) pentagonal dodecahedral Pd(50) cage. The total number of crystallographically estimated Pt atoms, 8 +/- 3, which was obtained from least-squares (Pt(x)/Pd(1-x))-occupancy analysis of the X-ray data that conclusively revealed the central atom to be pure Pt (occupancy factor, x = 1.00(3)), is fortuitously in agreement

The rates of charge separation and energy destructive charge recombination processes within an organic dyad in presence of metal-semiconductor core shell nanocomposites.

PubMed

Mandal, Gopa; Bhattacharya, Sudeshna; Das, Subrata; Ganguly, Tapan

2012-01-01

Steady state and time resolved spectroscopic measurements were made at the ambient temperature on an organic dyad, 1-(4-Chloro-phenyl)-3-(4-methoxy-naphthalen-1-yl)-propenone (MNCA), where the donor 1-methoxynaphthalene (1 MNT) is connected with the acceptor p-chloroacetophenone (PCA) by an unsaturated olefinic bond, in presence of Ag@TiO2 nanoparticles. Time resolved fluorescence and absorption measurements reveal that the rate parameters associated with charge separation, k(CS), within the dyad increases whereas charge recombination rate k(CR) reduces significantly when the surrounding medium is changed from only chloroform to mixture of chloroform and Ag@TiO2 (noble metal-semiconductor) nanocomposites. The observed results indicate that the dyad being combined with core-shell nanocomposites may form organic-inorganic nanocomposite system useful for developing light energy conversion devices. Use of metal-semiconductor nanoparticles may provide thus new ways to modulate charge recombination processes in light energy conversion devices. From comparison with the results obtained in our earlier investigations with only TiO2 nanoparticles, it is inferred that much improved version of light energy conversion device, where charge-separated species could be protected for longer period of time of the order of millisecond, could be designed by using metal-semiconductor core-shell nanocomposites rather than semiconductor nanoparticles only.

Hydrogen sorption in Pd-decorated Mg-MgO core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Callini, E.; Pasquini, L.; Piscopiello, E.; Montone, A.; Antisari, M. Vittori; Bonetti, E.

2009-06-01

Mg nanoparticles with metal-oxide core-shell morphology were synthesized by inert-gas condensation and decorated by in situ Pd deposition. Transmission electron microscopy and x-ray diffraction underline the formation of a noncontinuous layer with Pd clusters on top of the MgO shell. Even in the presence of a thick MgO interlayer, a modest (2 at. %) Pd decoration deeply enhances the hydrogen sorption properties: previously inert nanoparticles exhibit metal-hydride transformation with fast kinetics and gravimetric capacity above 5 wt %.

False-positive 18F-fluorodeoxyglucose positron emission tomography/computed tomography in a patient with metallic implants following chondrosarcoma resection

PubMed Central

ZHOU, PU; TANG, JINLIANG; ZHANG, DONG; LI, GUANGHUI

2016-01-01

Positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose (18F-FDG) has been used for the staging and evaluation of recurrence in cancer patients. We herein report a false-positive result of 18F-FDG PET/computed tomography (CT) scan in a patient following chondrosarcoma resection and metallic implanting. A 35-year-old male patient with chondrosarcoma of the left iliac bone underwent radical resection, metal brace implanting and radiotherapy. A high uptake of 18F-FDG was observed in the metallic implants and adjacent tissue during PET/CT scanning in the 5th year of follow-up. Tissue biopsy and follow-up examination identified no tumor recurrence or infection at these sites, suggesting that the results of 18F-FDG PET/CT must be interpreted with caution in cancer patients with metallic implants. PMID:27123290

Influence of SiO2 shell thickness on power conversion efficiency in plasmonic polymer solar cells with Au nanorod@SiO2 core-shell structures

PubMed Central

Zhang, Ran; Zhou, Yongfang; Peng, Ling; Li, Xue; Chen, Shufen; Feng, Xiaomiao; Guan, Yuqiao; Huang, Wei

2016-01-01

Locating core-shell metal nanoparticles into a photoactive layer or at the interface of photoactive layer/hole extraction layer is beneficial for fully employing surface plasmon energy, thus enhancing power conversion efficiency (PCE) in plasmonic organic photovoltaic devices (OPVs). Herein, we first investigated the influence of silica shell thickness in Au nanorods (NRs)@SiO2 core-shell structures on OPV performances by inserting them into poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) and thieno[3,4-b]thiophene/benzodithiophene (PTB7) interface, and amazedly found that a 2–3 nm silica shell onto Au NRs induces a highest short-circuit current density of 21.2 mA cm−2 and PCE of 9.55%. This is primarily due to an extremely strong local field and a much slower attenuation of localized surface plasmon resonance around ultrathin silica-coated Au NRs, with which the field intensity remains a high value in the active layer, thus sufficiently improves the absorption of PTB7. Our work provides a clear design concept on precise control of the shell of metal nanoparticles to realize high performances in plasmonic OPVs. PMID:27125309

Influence of SiO2 shell thickness on power conversion efficiency in plasmonic polymer solar cells with Au nanorod@SiO2 core-shell structures.

PubMed

Zhang, Ran; Zhou, Yongfang; Peng, Ling; Li, Xue; Chen, Shufen; Feng, Xiaomiao; Guan, Yuqiao; Huang, Wei

2016-04-29

Locating core-shell metal nanoparticles into a photoactive layer or at the interface of photoactive layer/hole extraction layer is beneficial for fully employing surface plasmon energy, thus enhancing power conversion efficiency (PCE) in plasmonic organic photovoltaic devices (OPVs). Herein, we first investigated the influence of silica shell thickness in Au nanorods (NRs)@SiO2 core-shell structures on OPV performances by inserting them into poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) and thieno[3,4-b]thiophene/benzodithiophene (PTB7) interface, and amazedly found that a 2-3 nm silica shell onto Au NRs induces a highest short-circuit current density of 21.2 mA cm(-2) and PCE of 9.55%. This is primarily due to an extremely strong local field and a much slower attenuation of localized surface plasmon resonance around ultrathin silica-coated Au NRs, with which the field intensity remains a high value in the active layer, thus sufficiently improves the absorption of PTB7. Our work provides a clear design concept on precise control of the shell of metal nanoparticles to realize high performances in plasmonic OPVs.

Detection of MgCn in IRC + 10216: A new metal-bearing free radical

NASA Technical Reports Server (NTRS)

Ziurys, L. M.; Apponi, A. J.; Guelin, M.; Cernicharo, J.

1995-01-01

A new metal-containing molecule, MgCN, has been detected toward the late-type star IRC + 10216, using the NRAO 12 m and IRAM 30 m telescopes. The N = 11 approaches 10, 10 approaches 9, and 9 approaches 8 transtions of this species which has a (sup 2)Sigma(sup +) ground state, have been observed in the outer envelope of this object at 3 mm. For the N = 11 approaches 10 transitions, the two spin-rotation components are clearly resolved and conclusively identify this new radical. These measurements imply a column of density for MgCN of N(sub tot) approximately 10(exp 12)/sq cm in the outer shell, which corresponds to a fractional abundance of f approximately 7x10(exp -10). This molecule, the metastable isomer of MgNC, is the third metal-bearing species thus far identified in the outer shell of IRC + 10216, and its detection implies a ratio of MgNC/MgCN approximately 22/1. MgCN may be formed through a reaction scheme involving magnesium and HNC or CN, both prominent outer shell molecules, or through synthesis on grains.

Stretched proton-neutron configurations in fp-shell nuclei (II). Systematics

NASA Astrophysics Data System (ADS)

von Neumann-Cosel, P.; Fister, U.; Jahn, R.; Schenk, P.; Trelle, T. K.; Wenzel, D.; Wienands, U.

1994-03-01

The systematics of the binding energies of stretched proton-neutron configurations ( f{7}/{2}, g{9}/{2}) 8 -, ( p{3}/{2}, g{9}/{2}) 6 -, ( g{9}/{2}, p{3}/{2}) 6- and ( g{9}/{2}) 29 + are studied over a wide range of f p-shell nuclei. The effective proton-neutron interaction energies deduced from the data are nearly constant for ( p{3}/{2}, g{9}/{2}) 6 -and ( g{9}/{2}) 29 + states while the ( f{7}/{2}, g{9}/{2}) 8 - configuration reveals an additional repulsive term proportional to the partial filling of the f{7}/{2} orbit in the target ground state. Two-body matrix elements are extracted. A crude shell model, which predicts that the excitation energy of a stretched state is equal to the sum of the single-particle energies, works well for the 6 - and 9 + states, but fails for the 8 - levels due to neglect of the additional interactions described above. The physics underlying the empirically introduced basic assumptions of the crude shell model is discussed. The binding energies are found to be linearly dependent on the mass number A and the isospin Tz component and are well described by the weak-coupling model of Bansal and French. The derived parameters agree with averaged values of a similar analysis for the single-particle states in the corresponding odd-even neighbours. The data indicate a significant change of the particle-hole energies with closure of the proton f{7}/{2} shell.

Surface shift of the occupied and unoccupied 4f levels of the rare-earth metals

NASA Astrophysics Data System (ADS)

Aldén, M.; Johansson, B.; Skriver, H. L.

1995-02-01

The surface energy shifts of the occupied and unoccupied 4f levels for the lanthanide metals have been calculated from first principles by means of a Green's-function technique within the tight-binding linear muffin-tin orbitals method. We use the concept of complete screening to identify the occupied and unoccupied 4f energy level shifts as the surface segregation energy of a 4fn-1 and 4fn+1 impurity atom, respectively, in a 4fn host metal. The calculations include both initial- and final-state effects and give values that are considerably lower than those measured on polycrystalline samples as well as those found in previous initial-state model calculations. The present theory agrees well with very recent high-resolution, single-crystal film measurements for Gd, Tb, Dy, Ho, Er, Tm, and Lu. We furthermore utilize the unique possibility offered by the lanthanide metals to clarify the roles played by the initial and the different final states of the core-excitation process, permitted by the fact that the so-called initial-state effect is identical upon 4f removal and 4f addition. Surface energy and work function calculations are also reported.

A numerical investigation of the scale-up effects on flow, heat transfer, and kinetics processes of FCC units.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, S. L.

1998-08-25

Fluid Catalytic Cracking (FCC) technology is the most important process used by the refinery industry to convert crude oil to valuable lighter products such as gasoline. Process development is generally very time consuming especially when a small pilot unit is being scaled-up to a large commercial unit because of the lack of information to aide in the design of scaled-up units. Such information can now be obtained by analysis based on the pilot scale measurements and computer simulation that includes controlling physics of the FCC system. A Computational fluid dynamic (CFD) code, ICRKFLO, has been developed at Argonne National Laboratorymore » (ANL) and has been successfully applied to the simulation of catalytic petroleum cracking risers. It employs hybrid hydrodynamic-chemical kinetic coupling techniques, enabling the analysis of an FCC unit with complex chemical reaction sets containing tens or hundreds of subspecies. The code has been continuously validated based on pilot-scale experimental data. It is now being used to investigate the effects of scaled-up FCC units. Among FCC operating conditions, the feed injection conditions are found to have a strong impact on the product yields of scaled-up FCC units. The feed injection conditions appear to affect flow and heat transfer patterns and the interaction of hydrodynamics and cracking kinetics causes the product yields to change accordingly.« less

Magnetic states, correlation effects and metal-insulator transition in FCC lattice

NASA Astrophysics Data System (ADS)

Timirgazin, M. A.; Igoshev, P. A.; Arzhnikov, A. K.; Irkhin, V. Yu

2016-12-01

The ground-state magnetic phase diagram (including collinear and spiral states) of the single-band Hubbard model for the face-centered cubic lattice and related metal-insulator transition (MIT) are investigated within the slave-boson approach by Kotliar and Ruckenstein. The correlation-induced electron spectrum narrowing and a comparison with a generalized Hartree-Fock approximation allow one to estimate the strength of correlation effects. This, as well as the MIT scenario, depends dramatically on the ratio of the next-nearest and nearest electron hopping integrals {{t}\\prime}/t . In contrast with metallic state, possessing substantial band narrowing, insulator one is only weakly correlated. The magnetic (Slater) scenario of MIT is found to be superior over the Mott one. Unlike simple and body-centered cubic lattices, MIT is the first order transition (discontinuous) for most {{t}\\prime}/t . The insulator state is type-II or type-III antiferromagnet, and the metallic state is spin-spiral, collinear antiferromagnet or paramagnet depending on {{t}\\prime}/t . The picture of magnetic ordering is compared with that in the standard localized-electron (Heisenberg) model.

Core-Shell Composite Fibers for High-Performance Flexible Supercapacitor Electrodes.

PubMed

Lu, Xiaoyan; Shen, Chen; Zhang, Zeyang; Barrios, Elizabeth; Zhai, Lei

2018-01-31

Core-shell nanofibers containing poly(acrylic acid) (PAA) and manganese oxide nanoparticles as the core and polypyrrole (PPy) as the shell were fabricated through electrospinning the solution of PAA and manganese ions (PAA/Mn 2+ ). The obtained nanofibers were stabilized by Fe 3+ through the interaction between Fe 3+ ions and carboxylate groups. Subsequent oxidation of Mn 2+ by KMnO 4 produced uniform manganese dioxide (MnO 2 ) nanoparticles in the fibers. A PPy shell was created on the fibers by immersing the fibers in a pyrrole solution where the Fe 3+ ions in the fiber polymerized the pyrrole on the fiber surfaces. In the MnO 2 @PAA/PPy core-shell composite fibers, MnO 2 nanoparticles function as high-capacity materials, while the PPy shell prevents the loss of MnO 2 during the charge/discharge process. Such a unique structure makes the composite fibers efficient electrode materials for supercapacitors. The gravimetric specific capacity of the MnO 2 @PAA/PPy core-shell composite fibers was 564 F/g based on cyclic voltammetry curves at 10 mV/s and 580 F/g based on galvanostatic charge/discharge studies at 5 A/g. The MnO 2 @PAA/PPy core-shell composite fibers also present stable cycling performance with 100% capacitance retention after 5000 cycles.

Matrix infrared spectroscopy and quantum-chemical calculations for the coinage-metal fluorides: comparisons of Ar-AuF, Ne-AuF, and Molecules MF2 and MF3.

PubMed

Wang, Xuefeng; Andrews, Lester; Brosi, Felix; Riedel, Sebastian

2013-01-21

The reactions of laser-ablated Au, Ag, and Cu atoms with F(2) in excess argon and neon gave new absorptions in the M-F stretching region of their IR spectra, which were assigned to metal-fluoride species. For gold, a Ng-AuF bond was identified in mixed neon/argon samples. However, this bonding was much weaker with AgF and CuF. Molecules MF(2) and MF(3) (M=Au, Ag, Cu) were identified from the isotopic distribution of the Cu and Ag atoms, comparison of the frequencies for three metal fluorides, and theoretical frequency calculations. The AuF(5) molecule was characterized by its strongest stretching mode and theoretical frequency calculations. Additional evidence was observed for the formation of the Au(2) F(6) molecule. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly anisotropic exchange interactions of j eff = 1 2 iridium moments on the fcc lattice in La 2 B IrO 6   ( B = Mg , Zn )

DOE PAGES

Aczel, A. A.; Cook, A. M.; Williams, T. J.; ...

2016-06-20

Here we have performed inelastic neutron scattering (INS) experiments to investigate the magnetic excitations in the weakly distorted face-centered-cubic (fcc) iridate double perovskites Lamore » $$_2$$ZnIrO$$_6$$ and La$$_2$$MgIrO$$_6$$, which are characterized by A-type antiferromagnetic ground states. The powder inelastic neutron scattering data on these geometrically frustrated $$j_{\\rm eff}=1/2$$ Mott insulators provide clear evidence for gapped spin wave excitations with very weak dispersion. The INS results and thermodynamic data on these materials can be reproduced by conventional Heisenberg-Ising models with significant uniaxial Ising anisotropy and sizeable second-neighbor ferromagnetic interactions. Such a uniaxial Ising exchange interaction is symmetry-forbidden on the ideal fcc lattice, so that it can only arise from the weak crystal distortions away from the ideal fcc limit. This may suggest that even weak distortions in $$j_{\\rm eff}=1/2$$ Mott insulators might lead to strong exchange anisotropies. More tantalizingly, however, we find an alternative viable explanation of the INS results in terms of spin models with a dominant Kitaev interaction. In contrast to the uniaxial Ising exchange, the highly-directional Kitaev interaction is a type of exchange anisotropy which is symmetry-allowed even on the ideal fcc lattice. The Kitaev model has a magnon gap induced by quantum order-by-disorder, while weak anisotropies of the Kitaev couplings generated by the symmetry-lowering due to lattice distortions can pin the order and enhance the magnon gap. In conclusion, our findings highlight how even conventional magnetic orders in heavy transition metal oxides may be driven by highly-directional exchange interactions rooted in strong spin-orbit coupling.« less

Hypersonic vibrations of Ag@SiO2 (cubic core)-shell nanospheres.

PubMed

Sun, Jing Ya; Wang, Zhi Kui; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Tran, Toan Trong; Lu, Xianmao

2010-12-28

The intriguing optical and catalytic properties of metal-silica core-shell nanoparticles, inherited from their plasmonic metallic cores together with the rich surface chemistry and increased stability offered by their silica shells, have enabled a wide variety of applications. In this work, we investigate the confined vibrational modes of a series of monodisperse Ag@SiO(2) (cubic core)-shell nanospheres synthesized using a modified Stöber sol-gel method. The particle-size dependence of their mode frequencies has been mapped by Brillouin light scattering, a powerful tool for probing hypersonic vibrations. Unlike the larger particles, the observed spheroidal-like mode frequencies of the smaller ones do not scale with inverse diameter. Interestingly, the onset of the deviation from this linearity occurs at a smaller particle size for higher-energy modes than for lower-energy ones. Finite element simulations show that the mode displacement profiles of the Ag@SiO(2) core-shells closely resemble those of a homogeneous SiO(2) sphere. Simulations have also been performed to ascertain the effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole. As the vibrational modes of a particle have a bearing on its thermal and mechanical properties, the findings would be of value in designing core-shell nanostructures with customized thermal and mechanical characteristics.

Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations.

PubMed

Reeh, S; Kasprzak, M; Klusmann, C D; Stalf, F; Music, D; Ekholm, M; Abrikosov, I A; Schneider, J M

2013-06-19

The elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys with additions of up to 8 at.% X were studied by combinatorial thin film growth and characterization and by ab initio calculations using the disordered local moments (DLM) approach. The lattice parameter and Young's modulus values change only marginally with X. The calculations and experiments are in good agreement. We demonstrate that the elastic properties of transition metal alloyed Fe-Mn can be predicted by the DLM model.

Reduction of silver (I) using defatted cashew nut shell starch and its structural comparison with commercial product.

PubMed

Velmurugan, Palanivel; Park, Jung-Hee; Lee, Sang-Myeong; Jang, Jum-Suk; Yi, Young-Joo; Han, Sang-Sub; Lee, Sang-Hyun; Cho, Kwang-Min; Cho, Min; Oh, Byung-Taek

2015-11-20

In this current study, we report on the reduction of noble metal silver into silver nanoparticles using defatted cashew nut shell (CNS) starch as both the reducing and capping agents. Furthermore, it was compared with commercially available silver nanopowder for the first time. Color changes, ultraviolet-visible spectra (433.76nm), X-ray diffraction peaks (2θ=37.8, 46.3, 66.2, and 77.92) revealed the face-centered cubic (fcc) geometry of silver nanoparticles, scanning electron microscopy-energy dispersive spectroscopy confirmed the presence of elemental silver nanoparticles and the defatted CNS starch silver nanoparticle structures was in accordance to commercial silver nanopowder. The size of both the nanoparticles was found to be similar in the range of 10-50nm as analyzed using high resolution-transmission electron micrographs. The FT-IR spectroscopy revealed the shifting of NH and OH of defatted CNS starch, starch based silver nanoparticle and commercial silver nanopowder has parallel functional groups. The use of environmentally benign and renewable materials like defatted CNS starch offers an alternative to large scale synthesis of silver nanoparticle and includes numerous benefits like eco-friendly and compatibility for pharmaceutical and biomedical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Laboratory astrophysics on ASDEX Upgrade: Measurements and analysis of K-shell O, F, and Ne spectra in the 9 - 20 A region

NASA Technical Reports Server (NTRS)

Hansen, S. B.; Fournier, K. B.; Finkenthal, M. J.; Smith, R.; Puetterich, T.; Neu, R.

2006-01-01

High-resolution measurements of K-shell emission from O, F, and Ne have been performed at the ASDEX Upgrade tokamak in Garching, Germany. Independently measured temperature and density profiles of the plasma provide a unique test bed for model validation. We present comparisons of measured spectra with calculations based on transport and collisional-radiative models and discuss the reliability of commonly used diagnostic line ratios.

47 CFR 95.219 - (R/C Rule 19) How do I answer correspondence from the FCC?

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false (R/C Rule 19) How do I answer correspondence from the FCC? 95.219 Section 95.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED... You Need to Know § 95.219 (R/C Rule 19) How do I answer correspondence from the FCC? (a) If it appears...

Thermodynamics of impurity-enhanced vacancy formation in metals

NASA Astrophysics Data System (ADS)

Bukonte, Laura; Ahlgren, Tommy; Heinola, Kalle

2017-01-01

Hydrogen induced vacancy formation in metals and metal alloys has been of great interest during the past couple of decades. The main reason for this phenomenon, often referred to as the superabundant vacancy formation, is the lowering of vacancy formation energy due to the trapping of hydrogen. By means of thermodynamics, we study the equilibrium vacancy formation in fcc metals (Pd, Ni, Co, and Fe) in correlation with the H amounts. The results of this study are compared and found to be in good agreement with experiments. For the accurate description of the total energy of the metal-hydrogen system, we take into account the binding energies of each trapped impurity, the vibrational entropy of defects, and the thermodynamics of divacancy formation. We demonstrate the effect of vacancy formation energy, the hydrogen binding, and the divacancy binding energy on the total equilibrium vacancy concentration. We show that the divacancy fraction gives the major contribution to the total vacancy fraction at high H fractions and cannot be neglected when studying superabundant vacancies. Our results lead to a novel conclusion that at high hydrogen fractions, superabundant vacancy formation takes place regardless of the binding energy between vacancies and hydrogen. We also propose the reason of superabundant vacancy formation mainly in the fcc phase. The equations obtained within this work can be used for any metal-impurity system, if the impurity occupies an interstitial site in the lattice.

The puzzling spectrum of HD 94509. Sounding out the extremes of Be shell star spectral morphology

NASA Astrophysics Data System (ADS)

Cowley, C. R.; Przybilla, N.; Hubrig, S.

2015-06-01

Context. The spectral features of HD 94509 are highly unusual, adding an extreme to the zoo of Be and shell stars. The shell dominates the spectrum, showing lines typical for spectral types mid-A to early-F, while the presence of a late/mid B-type central star is indicated by photospheric hydrogen line wings and helium lines. Numerous metallic absorption lines have broad wings but taper to narrow cores. They cannot be fit by Voigt profiles. Aims: We describe and illustrate unusual spectral features of this star, and make rough calculations to estimate physical conditions and abundances in the shell. Furthermore, the central star is characterized. Methods: We assume mean conditions for the shell. An electron density estimate is made from the Inglis-Teller formula. Excitation temperatures and column densities for Fe i and Fe ii are derived from curves of growth. The neutral H column density is estimated from high Paschen members. The column densities are compared with calculations made with the photoionization code Cloudy. Atmospheric parameters of the central star are constrained employing non-LTE spectrum synthesis. Results: Overall chemical abundances are close to solar. Column densities of the dominant ions of several elements, as well as excitation temperatures and the mean electron density are well accounted for by a simple model. Several features, including the degree of ionization, are less well described. Conclusions: HD 94509 is a Be star with a stable shell, close to the terminal-age main sequence. The dynamical state of the shell and the unusually shaped, but symmetric line profiles, require a separate study.

Electronic transport properties of inner and outer shells in near ohmic-contacted double-walled carbon nanotube transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yuchun; Zhou, Liyan; Zhao, Shangqian

2014-06-14

We investigate electronic transport properties of field-effect transistors based on double-walled carbon nanotubes, of which inner shells are metallic and outer shells are semiconducting. When both shells are turned on, electron-phonon scattering is found to be the dominant phenomenon. On the other hand, when outer semiconducting shells are turned off, a zero-bias anomaly emerges in the dependence of differential conductance on the bias voltage, which is characterized according to the Tomonaga-Luttinger liquid model describing tunneling into one-dimensional materials. We attribute these behaviors to different contact conditions for outer and inner shells of the double-walled carbon nanotubes. A simple model combiningmore » Luttinger liquid model for inner metallic shells and electron-phonon scattering in outer semiconducting shells is given here to explain our transport data at different temperatures.« less

Assembly of metals and nanoparticles into novel nanocomposite superstructures

PubMed Central

Xu, Jiaquan; Chen, Lianyi; Choi, Hongseok; Konish, Hiromi; Li, Xiaochun

2013-01-01

Controlled assembly of nanoscale objects into superstructures is of tremendous interests. Many approaches have been developed to fabricate organic-nanoparticle superstructures. However, effective fabrication of inorganic-nanoparticle superstructures (such as nanoparticles linked by metals) remains a difficult challenge. Here we show a novel, general method to assemble metals and nanoparticles rationally into nanocomposite superstructures. Novel metal-nanoparticle superstructures are achieved by self-assembly of liquid metals and nanoparticles in immiscible liquids driven by reduction of free energy. Superstructures with various architectures, such as metal-core/nanoparticle-shell, nanocomposite-core/nanoparticle-shell, network of metal-linked core/shell nanostructures, and network of metal-linked nanoparticles, were successfully fabricated by simply tuning the volume ratio between nanoparticles and liquid metals. Our approach provides a simple, general way for fabrication of numerous metal-nanoparticle superstructures and enables a rational design of these novel superstructures with desired architectures for exciting applications.

[Aseptic, simultaneous and bilateral mobilisation due to an acetabular shell fracture in a 43 year-old patient].

PubMed

Ceretti, M; Fanelli, M; Pappalardo, S

2014-01-01

The acetabular shell mobilization is the main long-term complication in total hip replacement. Metal-back fracture has also to be considered among the possible causes of shell mobilization. A case is presented of bilateral acetabular shell mobilization due to the trabecular covering de-soldering from the metal-back in a 43 year-old patient, 13-14 years after the first surgery. Copyright © 2013 SECOT. Published by Elsevier Espana. All rights reserved.

Uranium 5f shell in UPd2Al3 and URu2Si2 studied by x-ray magnetic circular dichroism

NASA Astrophysics Data System (ADS)

Yaouanc, A.; Dalmas de Réotier, P.; van der Laan, G.; Hiess, A.; Goulon, J.; Neumann, C.; Lejay, P.; Sato, N.

1998-10-01

We report x-ray magnetic circular dichroism (XMCD) measurements performed at the uranium M4,5 edges in the paramagnetic phase of the heavy fermion superconductors UPd2Al3 and URu2Si2. The analysis of the spectra with the first sum rule yields the orbital moment of the 5f shell for both compounds. The shape of the dichroic spectrum at the M5 edge for the two compounds is qualitatively different: a single lobe is observed for URu2Si2 and two lobes are detected for UPd2Al3. This two lobe structure reflects the strong effect of the interaction of the uranium 5f electrons with their environment in the latter compound.

Invertebrate shells (mollusca, foraminifera) as pollution indicators, Red Sea Coast, Egypt

NASA Astrophysics Data System (ADS)

Youssef, Mohamed; Madkour, Hashem; Mansour, Abbas; Alharbi, Wedad; El-Taher, Atef

2017-09-01

To assess the degree of pollution and its impact on the environment along the Red Sea Coast, the most abundant nine species of recent benthic foraminifera and three species of molluscan shells have been selected for the analysis of Fe, Mn, Zn, Cu, Pb, Ni, Co, and Cd concentrations. The selected foraminiferal species are: Textularia agglutinans, Amphispsorus hemprichii, Sorites marginalis, Peneroplis planatus, Borelis schlumbergeri, Amphistegina lessonii, Ammonia beccarii, Operculina gaimairdi, and Operculinella cumingii. The selected molluscan shells are: Lambis truncata and Strombus tricornis (gastropods) and Tridacana gigas (bivalves). The inorganic material analysis of foraminifera and molluscs from the Quseir and Safaga harbors indicates that foraminifera tests include higher concentrations of heavy metals such as Fe and Mn than molluscan shells. These results are supported by the black tests of porcelaneous foraminifera and reflect iron selectivity. The Cd and Pb concentrations in molluscan shells are high in the El Esh Area because of oil pollution at this site. The Cu, Zn, and Ni concentrations in the studied invertebrates are high at Quseir Harbor and in the El Esh Area because of the strong influence of terrigenous materials that are rich in these metals. The heavy metal contamination is mostly attributed to anthropogenic sources.

Creation of half-metallic f -orbital Dirac fermion with superlight elements in orbital-designed molecular lattice

NASA Astrophysics Data System (ADS)

Cui, Bin; Huang, Bing; Li, Chong; Zhang, Xiaoming; Jin, Kyung-Hwan; Zhang, Lizhi; Jiang, Wei; Liu, Desheng; Liu, Feng

2017-08-01

Magnetism in solids generally originates from the localized d or f orbitals that are hosted by heavy transition-metal elements. Here, we demonstrate a mechanism for designing a half-metallic f -orbital Dirac fermion from superlight s p elements. Combining first-principles and model calculations, we show that bare and flat-band-sandwiched (FBS) Dirac bands can be created when C20 molecules are deposited into a two-dimensional hexagonal lattice, which are composed of f -molecular orbitals (MOs) derived from s p -atomic orbitals (AOs). Furthermore, charge doping of the FBS Dirac bands induces spontaneous spin polarization, converting the system into a half-metallic Dirac state. Based on this discovery, a model of a spin field effect transistor is proposed to generate and transport 100% spin-polarized carriers. Our finding illustrates a concept to realize exotic quantum states by manipulating MOs, instead of AOs, in orbital-designed molecular crystal lattices.

A Plasmonic Colloidal Photocatalyst Composed of a Metal-Organic Framework Core and a Gold/Anatase Shell for Visible-Light-Driven Wastewater Purification from Antibiotics and Hydrogen Evolution.

PubMed

Tilgner, Dominic; Kempe, Rhett

2017-03-02

Porous coordination polymers (PCP) or metal- organic frameworks (MOF) are promising materials for the generation of photocatalytically active composite materials. Here, a novel synthesis concept is reported, which permits the formation of PCP/MOF-core-Au/anatase-shell materials. These materials are photocatalysts for wastewater purification and hydrogen generation from water under visible-light illumination. MIL-101 (Cr) is utilized as the core material, which directs the size of the core-shell compound and ensures the overall stability. In addition, its excellent reversible large molecule sorption behavior allows the materials synthesis. The crystalline anatase shell is generated stepwise under mild conditions using titanium(IV) isopropoxide as a precursor. The high degree of control of the vapor phase deposition process permits the precise anatase shell formation. The generation of plasmonic active gold particles on the TiO 2 shell leads to an efficient material for visible-light-driven photocatalysis with a higher activity than gold-decorated P25 (Degussa). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced Upconversion Luminescence in Yb3+/Tm3+-Codoped Fluoride Active Core/Active Shell/Inert Shell Nanoparticles through Directed Energy Migration

PubMed Central

Qiu, Hailong; Yang, Chunhui; Shao, Wei; Damasco, Jossana; Wang, Xianliang; Ågren, Hans; Prasad, Paras N.; Chen, Guanying

2014-01-01

The luminescence efficiency of lanthanide-doped upconversion nanoparticles is of particular importance for their embodiment in biophotonic and photonic applications. Here, we show that the upconversion luminescence of typically used NaYF4:Yb3+30%/Tm3+0.5% nanoparticles can be enhanced by ~240 times through a hierarchical active core/active shell/inert shell (NaYF4:Yb3+30%/Tm3+0.5%)/NaYbF4/NaYF4 design, which involves the use of directed energy migration in the second active shell layer. The resulting active core/active shell/inert shell nanoparticles are determined to be about 11 times brighter than that of well-investigated (NaYF4:Yb3+30%/Tm3+0.5%)/NaYF4 active core/inert shell nanoparticles when excited at ~980 nm. The strategy for enhanced upconversion in Yb3+/Tm3+-codoped NaYF4 nanoparticles through directed energy migration might have implications for other types of lanthanide-doped upconversion nanoparticles. PMID:28348285

Equations of state of anhydrous AlF3 and AlI3: Modeling of extreme condition halide chemistry

NASA Astrophysics Data System (ADS)

Stavrou, Elissaios; Zaug, Joseph M.; Bastea, Sorin; Crowhurst, Jonathan C.; Goncharov, Alexander F.; Radousky, Harry B.; Armstrong, Michael R.; Roberts, Sarah K.; Plaue, Jonathan W.

2015-06-01

Pressure dependent angle-dispersive x-ray powder diffraction measurements of alpha-phase aluminum trifluoride (α-AlF3) and separately, aluminum triiodide (AlI3) were conducted using a diamond-anvil cell. Results at 295 K extend to 50 GPa. The equations of state of AlF3 and AlI3 were determined through refinements of collected x-ray diffraction patterns. The respective bulk moduli and corresponding pressure derivatives are reported for multiple orders of the Birch-Murnaghan (B-M), finite-strain (F-f), and higher pressure finite-strain (G-g) EOS analysis models. Aluminum trifluoride exhibits an apparent isostructural phase transition at approximately 12 GPa. Aluminum triiodide also undergoes a second-order atomic rearrangement: applied stress transformed a monoclinically distorted face centered cubic (fcc) structure into a standard fcc structural arrangement of iodine atoms. Results from semi-empirical thermochemical computations of energetic materials formulated with fluorine containing reactants were obtained with the aim of predicting the yield of halogenated products.

Voltage Control of Rare-Earth Magnetic Moments at the Magnetic-Insulator-Metal Interface

NASA Astrophysics Data System (ADS)

Leon, Alejandro O.; Cahaya, Adam B.; Bauer, Gerrit E. W.

2018-01-01

The large spin-orbit interaction in the lanthanides implies a strong coupling between their internal charge and spin degrees of freedom. We formulate the coupling between the voltage and the local magnetic moments of rare-earth atoms with a partially filled 4 f shell at the interface between an insulator and a metal. The rare-earth-mediated torques allow the power-efficient control of spintronic devices by electric-field-induced ferromagnetic resonance and magnetization switching.

Magnetic state and phase composition of carbon-encapsulated Co@C nanoparticles according to 59Co, 13C NMR data and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Mikhalev, K. N.; Germov, A. Yu; Uimin, M. A.; Yermakov, A. E.; Konev, A. S.; Novikov, S. I.; Gaviko, V. S.; Ponosov, Yu S.

2018-05-01

59Co, 13C NMR spectra, magnetization and Raman spectra of Co@C nanoparticles encapsulated in carbon have been analyzed. It has been shown that the cores of the nanoparticles consist of metallic cobalt with FCC structure and perhaps the carbide of cobalt Co3C. Carbon shell have been characterized as a highly defective structure similar to amorphous or glassy-like carbon, however, it may include a small amount of the carbon nanotubes.

The formation of nanopores in metal materials after irradiation by beams of Ar+ with energy of 30 keV

NASA Astrophysics Data System (ADS)

Ivchenko, V. A.

2017-01-01

In this paper are the results of direction observations of nanopores in the subsurface volume of metals materials Pt and Pd(CuAg) using field-ion microscopy (FIM). Radiation of tip specimens was carried out with ions having an energy ˜ 25-30 keV in the fluency range of 1016 - 1018 ions/cm2, the current density lying within 150- 340 µA/cm2. Nanopores have been observed immediately after removal of the first atomic layers from the irradiated surface. It was established that, the threshold for ion-implanted platinum corresponds to fluence F = 1017 ions/cm2. For Pd(CuAg) it was revealed that nanopores have been down to 80 nm deep with current density 340 µA/cm2. Their dimensions and volume fractions were determined. The obtained results can be used for prediction of radiation stability of materials based on fcc metals.

Turning the halide switch in the synthesis of Au–Pd alloy and core–shell nanoicosahedra with terraced shells: Performance in electrochemical and plasmon-enhanced catalysis

DOE PAGES

Hsu, Shih -Cheng; Chuang, Yu -Chun; Sneed, Brian T.; ...

2016-01-01

Au Pd nanocrystals are an intriguing system to study the integrated functions of localized surface plasmon resonance (LSPR) and heterogeneous catalysis. Gold is both durable and can harness incident light energy to enhance the catalytic activity of another metal, such as Pd, via the SPR effect in bimetallic nanocrystals. Despite the superior catalytic performance of icosahedral (IH) nanocrystals compared to alternate morphologies, the controlled synthesis of alloy and core shell IH is still greatly challenged by the disparate reduction rates of metal precursors and lack of continuous epigrowth on multiply twinned boundaries of such surfaces. Herein, we demonstrate a one-stepmore » strategy for the controlled growth of monodisperse Au Pd alloy and core shell IH with terraced shells by turning an ionic switch between [Br ]/[Cl –] in the coreduction process. The core shell IH nanocrystals contain AuPd alloy cores and ultrathin Pd shells (<2 nm). They not only display more than double the activity of the commercial Pd catalysts in ethanol electrooxidation attributed to monatomic step terraces but also show SPR-enhanced conversion of 4-nitrophenol. Furthermore, this strategy holds promise toward the development of alternate bimetallic IH nanocrystals for electrochemical and plasmon-enhanced catalysis.« less

Influences of the third and fourth nearest neighbouring interactions on the surface anisotropy of face-centred-cubic metals

NASA Astrophysics Data System (ADS)

Luo, Yongkun; Qin, Rongshan

2014-06-01

The structure and the anisotropic properties of the surfaces of face-centred-cubic (FCC) metals have been studied using the broken-bond model while considering the third and fourth nearest neighbouring (3rd and 4th NN) interactions. The pair potential expressions are obtained using the Rose-Vinet universal potential equation. The model is suitable for calculation of the property of a surface with arbitrary crystallographic orientations and can provide absolute unrelaxed surface energy values using three input parameters, namely the lattice constant, bulk modulus and cohesive energy. These parameters are available for the majority of FCC metals. The numerical results for 7 FCC metals have been obtained and compared with these obtained from ab initio calculations and experimental measurements. Good agreement is observed between the two. Taking into account up to the 4th NN interactions, the overall surface energy anisotropy for FCC metals was found to be between 12% to 16%, and the ratio between the surface energies at (100) and (111) planes was found to be 1.05. These values are less than those reported by conventional calculations but more similar to experimental measurements. It is found that the strength of 3rd and 4th NN interactions differs from one element to another, the Ni and Cu interactions being the most significant while the Au, Pt and Pb interactions are the least significant. This suggests that the polar diagrams of the surface energy of Ni and Cu are different from those of Au, Pt and Pb by showing cusps of the unconventional {110} and high-index {210}, {311} and possibly {135} poles. This provides explanations to the recent experimental observations of the {110}, {210}, {311} and {135} facets in equilibrated Ni and Cu crystallines.

Effect of the fcc-hcp martensitic transition on the equation of state of solid krypton up to 140 GPa

NASA Astrophysics Data System (ADS)

Rosa, A. D.; Garbarino, G.; Briggs, R.; Svitlyk, V.; Morard, G.; Bouhifd, M. A.; Jacobs, J.; Irifune, T.; Mathon, O.; Pascarelli, S.

2018-03-01

Solid krypton (Kr) undergoes a pressure-induced martensitic phase transition from a face-centered cubic (fcc) to a hexagonal close-packed (hcp) structure. These two phases coexist in a very wide pressure domain inducing important modifications of the bulk properties of the resulting mixed phase system. Here, we report a detailed in situ x-ray diffraction and absorption study of the influence of the fcc-hcp phase transition on the compression behavior of solid krypton in an extended pressure domain up to 140 GPa. The onset of the hcp-fcc transformation was observed in this study at around 2.7 GPa and the coexistence of these two phases up to 140 GPa, the maximum investigated pressure. The appearance of the hcp phase is also evidenced by the pressure-induced broadening and splitting of the first peak in the XANES spectra. We demonstrate that the transition is driven by a continuous nucleation and intergrowth of nanometric hcp stacking faults that evolve in the fcc phase. These hcp stacking faults are unaffected by high-temperature annealing, suggesting that plastic deformation is not at their origin. The apparent small Gibbs free-energy differences between the two structures that decrease upon compression may explain the nucleation of hcp stacking faults and the large coexistence domain of fcc and hcp krypton. We observe a clear anomaly in the equation of state of the fcc solid at ˜20 GPa when the proportion of the hcp form reaches ˜20 % . We demonstrate that this anomaly is related to the difference in stiffness between the fcc and hcp phases and propose two distinct equation of states for the low and high-pressure regimes.

New insights into micro/nanoscale combined probes (nanoAuger, μXPS) to characterize Ag/Au@SiO2 core-shell assemblies.

PubMed

Ledeuil, J B; Uhart, A; Soulé, S; Allouche, J; Dupin, J C; Martinez, H

2014-10-07

This work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2 particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming electron signal (potentially affected by the topography of the material) during analysis. SEM experiments have unambiguously revealed the hollow-morphology of the metal core, while Auger spectroscopy observations showed chemical heterogeneity within the particles (as silver and gold are randomly found in the core ring). To our knowledge, this is the first time that Auger nano probe spectroscopy has been used and successfully optimized for the study of some complex metal/inorganic interfaces at such a high degree of resolution (≈12 nm). Complementarily, XPS Au 4f and Ag 3d peaks were finally detected attesting the possibility of access to the whole chemistry of such nanostructured assemblies.

A Guide to Federal Regulation; Understanding the FCC Rules.

ERIC Educational Resources Information Center

Cable Television Information Center, Washington, DC.

While it is apparent that the Federal Communications Commission (FCC) has given a great deal of thought to the regulation of cable systems, the basic success or failure of cable as a communications service will depend on local development. Relatively little guidance has been provided to local franchising authorities for selecting among applicants,…

Reuse of nuclear byproducts, NaF and HF in metal glass industries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J.W.; Lee, H.W.; Yoo, S.H.

1997-02-01

A study has been performed to evaluate the radiological safety and feasibility associated with reuse of NaF(Sodium Fluoride) and HF(Hydrofluoric Acid) which are generated as byproducts from the nuclear fuel fabrication process. The investigation of oversea`s experience reveals that the byproduct materials are most often used in the metal and glass industries. For the radiological safety evaluation, the uranium radioactivities in the byproduct materials were examined and shown to be less than radioactivities in natural materials. The radiation doses to plant personnel and the general public were assessed to be very small and could be ignored. The Korea nuclear regulatorymore » body permits the reuse of NaF in the metal industry on the basis of associated radioactivity being {open_quote}below regulatory concern{close_quote}. HF is now under review for reuse acceptability in the steel and glass industries.« less

Semiconductor@metal-organic framework core-shell heterostructures: a case of ZnO@ZIF-8 nanorods with selective photoelectrochemical response.

PubMed

Zhan, Wen-wen; Kuang, Qin; Zhou, Jian-zhang; Kong, Xiang-jian; Xie, Zhao-xiong; Zheng, Lan-sun

2013-02-06

Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for their applications in gas storage/separation as well as catalysis. In contrast, research concerning potential uses in electronic devices (such as sensors) is in its infancy, which might be due to a great challenge in the fabrication of MOFs and semiconductor composites with well-designed structures. In this paper, we proposed a simple self-template strategy to fabricate metal oxide semiconductor@MOF core-shell heterostructures, and successfully obtained freestanding ZnO@ZIF-8 nanorods as well as vertically standing arrays (including nanorod arrays and nanotube arrays). In this synthetic process, ZnO nanorods not only act as the template but also provide Zn(2+) ions for the formation of ZIF-8. In addition, we have demonstrated that solvent composition and reaction temperature are two crucial factors for successfully fabricating well-defined ZnO@ZIF-8 heterostructures. As we expect, the as-prepared ZnO@ZIF-8 nanorod arrays display distinct photoelectrochemical response to hole scavengers with different molecule sizes (e.g., H(2)O(2) and ascorbic acid) owing to the limitation of the aperture of the ZIF-8 shell. Excitingly, such ZnO@ZIF-8 nanorod arrays were successfully applied to the detection of H(2)O(2) in the presence of serous buffer solution. Therefore, it is reasonable to believe that the semiconductor@MOFs heterostructure potentially has promising applications in many electronic devices including sensors.

Supergiants and their shells in young globular clusters

NASA Astrophysics Data System (ADS)

Szécsi, Dorottya; Mackey, Jonathan; Langer, Norbert

2018-04-01

Context. Anomalous surface abundances are observed in a fraction of the low-mass stars of Galactic globular clusters, that may originate from hot-hydrogen-burning products ejected by a previous generation of massive stars. Aims: We aim to present and investigate a scenario in which the second generation of polluted low-mass stars can form in shells around cool supergiant stars within a young globular cluster. Methods: Simulations of low-metallicity massive stars (Mi 150-600 M⊙) show that both core-hydrogen-burning cool supergiants and hot ionizing stellar sources are expected to be present simulaneously in young globular clusters. Under these conditions, photoionization-confined shells form around the supergiants. We have simulated such a shell, investigated its stability and analysed its composition. Results: We find that the shell is gravitationally unstable on a timescale that is shorter than the lifetime of the supergiant, and the Bonnor-Ebert mass of the overdense regions is low enough to allow star formation. Since the low-mass stellar generation formed in this shell is made up of the material lost from the supergiant, its composition necessarily reflects the composition of the supergiant wind. We show that the wind contains hot-hydrogen-burning products, and that the shell-stars therefore have very similar abundance anomalies that are observed in the second generation stars of globular clusters. Considering the mass-budget required for the second generation star-formation, we offer two solutions. Either a top-heavy initial mass function is needed with an index of -1.71 to -2.07. Alternatively, we suggest the shell-stars to have a truncated mass distribution, and solve the mass budget problem by justifiably accounting for only a fraction of the first generation. Conclusions: Star-forming shells around cool supergiants could form the second generation of low-mass stars in Galactic globular clusters. Even without forming a photoionizaton-confined shell, the

Electronic shell structure in Ga12 icosahedra and the relation to the bulk forms of gallium.

PubMed

Schebarchov, D; Gaston, N

2012-07-28

The electronic structure of known cluster compounds with a cage-like icosahedral Ga(12) centre is studied by first-principles theoretical methods, based on density functional theory. We consider these hollow metalloid nanostructures in the context of the polymorphism of the bulk, and identify a close relation to the α phase of gallium. This previously unrecognised connection is established using the electron localisation function, which reveals the ubiquitous presence of radially-pointing covalent bonds around the Ga(12) centre--analogous to the covalent bonds between buckled deltahedral planes in α-Ga. Furthermore, we find prominent superatom shell structure in these clusters, despite their hollow icosahedral motif and the presence of covalent bonds. The exact nature of the electronic shell structure is contrasted with simple electron shell models based on jellium, and we demonstrate how the interplay between gallium dimerisation, ligand- and crystal-field effects can alter the splitting of the partially filled 1F shell. Finally, in the unique compound where the Ga(12) centre is bridged by six phosphorus ligands, the electronic structure most closely resembles that of δ-Ga and there are no well-defined superatom orbitals. The results of this comprehensive study bring new insights into the nature of chemical bonding in metalloid gallium compounds and the relation to bulk gallium metal, and they may also guide the development of more general models for ligand-protected clusters.

Metal-Organic Frameworks Derived Porous Core/Shell Structured ZnO/ZnCo2O4/C Hybrids as Anodes for High-Performance Lithium-Ion Battery.

PubMed

Ge, Xiaoli; Li, Zhaoqiang; Wang, Chengxiang; Yin, Longwei

2015-12-09

Metal-organic frameworks (MOFs) derived porous core/shell ZnO/ZnCo2O4/C hybrids with ZnO as a core and ZnCo2O4 as a shell are for the first time fabricated by using core/shell ZnCo-MOF precursors as reactant templates. The unique MOFs-derived core/shell structured ZnO/ZnCo2O4/C hybrids are assembled from nanoparticles of ZnO and ZnCo2O4, with homogeneous carbon layers coated on the surface of the ZnCo2O4 shell. When acting as anode materials for lithium-ion batteries (LIBs), the MOFs-derived porous ZnO/ZnCo2O4/C anodes exhibit outstanding cycling stability, high Coulombic efficiency, and remarkable rate capability. The excellent electrochemical performance of the ZnO/ZnCo2O4/C LIB anodes can be attributed to the synergistic effect of the porous structure of the MOFs-derived core/shell ZnO/ZnCo2O4/C and homogeneous carbon layer coating on the surface of the ZnCo2O4 shells. The hierarchically porous core/shell structure offers abundant active sites, enhances the electrode/electrolyte contact area, provides abundant channels for electrolyte penetration, and also alleviates the structure decomposition induced by Li(+) insertion/extraction. The carbon layers effectively improve the conductivity of the hybrids and thus enhance the electron transfer rate, efficiently prevent ZnCo2O4 from aggregation and disintegration, and partially buffer the stress induced by the volume change during cycles. This strategy may shed light on designing new MOF-based hybrid electrodes for energy storage and conversion devices.

High-Pressure Geophysical Properties of Fcc Phase FeHX

NASA Astrophysics Data System (ADS)

Thompson, E. C.; Davis, A. H.; Bi, W.; Zhao, J.; Alp, E. E.; Zhang, D.; Greenberg, E.; Prakapenka, V. B.; Campbell, A. J.

2018-01-01

Face centered cubic (fcc) FeHX was synthesized at pressures of 18-68 GPa and temperatures exceeding 1,500 K. Thermally quenched samples were evaluated using synchrotron X-ray diffraction (XRD) and nuclear resonant inelastic X-ray scattering (NRIXS) to determine sample composition and sound velocities to 82 GPa. To aid in the interpretation of nonideal (X ≠ 1) stoichiometries, two equations of state for fcc FeHX were developed, combining an empirical equation of state for iron with two distinct synthetic compression curves for interstitial hydrogen. Matching the density deficit of the Earth's core using these equations of state requires 0.8-1.1 wt % hydrogen at the core-mantle boundary and 0.2-0.3 wt % hydrogen at the interface of the inner and outer cores. Furthermore, a comparison of Preliminary Reference Earth Model (PREM) to a Birch's law extrapolation of our experimental results suggests that an iron alloy containing ˜0.8-1.3 wt % hydrogen could reproduce both the density and compressional velocity (VP) of the Earth's outer core.

Solvation structures and dynamics of alkaline earth metal halides in supercritical water: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Keshri, Sonanki; Mandal, Ratnamala; Tembe, B. L.

2016-09-01

Constrained molecular dynamics simulations of alkaline earth metal halides have been carried out to investigate their structural and dynamical properties in supercritical water. Potentials of mean force (PMFs) for all the alkaline earth metal halides in supercritical water have been computed. Contact ion pairs (CIPs) are found to be more stable than all other configurations of the ion pairs except for MgI2 where solvent shared ion pair (SShIP) is more stable than the CIP. There is hardly any difference in the PMFs between the M2+ (M = Mg, Ca, Sr, Ba) and the X- (X = F, Cl, Br, I) ions whether the second X- ion is present in the first coordination shell of the M2+ ion or not. The solvent molecules in the solvation shells diffuse at a much slower rate compared to the bulk. Orientational distribution functions of solvent molecules are sharper for smaller ions.

One-Pot Synthesis of Tunable Crystalline Ni3 S4 @Amorphous MoS2 Core/Shell Nanospheres for High-Performance Supercapacitors.

PubMed

Zhang, Yu; Sun, Wenping; Rui, Xianhong; Li, Bing; Tan, Hui Teng; Guo, Guilue; Madhavi, Srinivasan; Zong, Yun; Yan, Qingyu

2015-08-12

Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS(2) is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni(3)S(4)@MoS(2)) is prepared by a facile one-pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni(3)S(4) @amorphous MoS(2) nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g(-1) at 2 A g(-1) and a good capacitance retention of 90.7% after 3000 cycles at 10 A g(-1). This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The influence of shell thickness of Au@TiO2 core-shell nanoparticles on the plasmonic enhancement effect in dye-sensitized solar cells.

PubMed

Liu, Wei-Liang; Lin, Fan-Cheng; Yang, Yu-Chen; Huang, Chen-Hsien; Gwo, Shangjr; Huang, Michael H; Huang, Jer-Shing

2013-09-07

Plasmonic core-shell nanoparticles (PCSNPs) can function as nanoantennas and improve the efficiency of dye-sensitized solar cells (DSSCs). To achieve maximum enhancement, the morphology of PCSNPs needs to be optimized. Here we precisely control the morphology of Au@TiO2 PCSNPs and systematically study its influence on the plasmonic enhancement effect. The enhancement mechanism was found to vary with the thickness of the TiO2 shell. PCSNPs with a thinner shell mainly enhance the current, whereas particles with a thicker shell improve the voltage. While pronounced plasmonic enhancement was found in the near infrared regime, wavelength-independent enhancement in the visible range was observed and attributed to the plasmonic heating effect. Emission lifetime measurement confirms that N719 molecules neighboring nanoparticles with TiO2 shells exhibit a longer lifetime than those in contact with metal cores. Overall, PCSNPs with a 5 nm shell give the highest efficiency enhancement of 23%. Our work provides a new synthesis route for well-controlled Au@TiO2 core-shell nanoparticles and gains insight into the plasmonic enhancement in DSSCs.

Modification of emission photon statistics from single quantum dots using metal/SiO2 core/shell nanostructures.

PubMed

Naiki, Hiroyuki; Oikawa, Hidetoshi; Masuo, Sadahiro

2017-04-12

Emission photon statistics, i.e., single-photon and multi-photon emissions, of isolated QDs is required for tailoring optoelectronic applications. In this article, we demonstrate that the emission photon statistics can be modified by the control of the spectral overlap of the QDs with the localized surface plasmon resonance (LSPR) of the metal nanoparticle (metal NP) and by the distance between the QD and the metal NP. Moreover, the contribution to the modification of the emission photon statistics, which is the excitation and emission enhancements and the quenching generated by the spectral overlap and the distance, is elucidated. By fabricating well-defined SiO 2 -coated AgNPs and AuNPs (metal/SiO 2 ), the spectral overlap originated from the metal species of Ag and Au and the distance constituted by the thickness of the SiO 2 shell are controlled. The probability of single-photon emission of single QD was increased by the enhancement of the excitation rate via adjusting the distance using Ag/SiO 2 while the single-photon emission was converted to multi-photon emission by the effect of exciton quenching at a short distance and a small spectral overlap. By contrast, the probability of multi-photon emission was increased by enhancement of the multi-photon emission rate and the quenching via the spectral overlap using Au/SiO 2 . These results indicated the fundamental finding to control emission photon statistics in single QDs by controlling the spectral overlap and the distance, and understand the interaction of plasmonic nanostructures and single QD systems.

Nano-engineering of three-dimensional core/shell nanotube arrays for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Grote, Fabian; Wen, Liaoyong; Lei, Yong

2014-06-01

Large-scale arrays of core/shell nanostructures are highly desirable to enhance the performance of supercapacitors. Here we demonstrate an innovative template-based fabrication technique with high structural controllability, which is capable of synthesizing well-ordered three-dimensional arrays of SnO2/MnO2 core/shell nanotubes for electrochemical energy storage in supercapacitor applications. The SnO2 core is fabricated by atomic layer deposition and provides a highly electrical conductive matrix. Subsequently a thin MnO2 shell is coated by electrochemical deposition onto the SnO2 core, which guarantees a short ion diffusion length within the shell. The core/shell structure shows an excellent electrochemical performance with a high specific capacitance of 910 F g-1 at 1 A g-1 and a good rate capability of remaining 217 F g-1 at 50 A g-1. These results shall pave the way to realize aqueous based asymmetric supercapacitors with high specific power and high specific energy.

Squid inks-derived nanocarbons with unique ;shell@pearls; structure for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Cheng, Fengli; Liu, Wei; Zhang, Yuan; Wang, Huanlei; Liu, Shuang; Hao, Enchao; Zhao, Shuping; Yang, Hongzhan

2017-06-01

Porous carbons derived from biomass are one current hotspot in exploring advanced electrode materials for supercapacitors. In this work, based on nanoparticles from squid inks, an N-doping porous carbons with a unique "shell@pearls" structure has been fabricated through a direct carbonization/activation procedure. Remarkably, a fantastic structural evolution from core-shell, yolk-shell to the porous matrix embedded with small spheres (like pears in shell) has been observed. The as-obtained products exhibit a hierarchical porosity comprised of micro-, meso- and macropores, as well with a large surface area (1957 m2 g-1) and N-doping (2.09%). As the electrode materials for supercapacitors, the "shell@pearls"bio-carbons show the very high capacitance of 329 F g-1 at 0.5 A g-1 and 265 F g-1 at 30 A g-1 and also a superior retention of 99.5% after 10000 cycles at 5 A g-1.

Timoshenko-Type Theory in the Stability Analysis of Corrugated Cylindrical Shells

NASA Astrophysics Data System (ADS)

Semenyuk, N. P.; Neskhodovskaya, N. A.

2002-06-01

A technique is proposed for stability analysis of longitudinally corrugated shells under axial compression. The technique employs the equations of the Timoshenko-type nonlinear theory of shells. The geometrical parameters of shells are specified on discrete set of points and are approximated by segments of Fourier series. Infinite systems of homogeneous algebraic equations are derived from a variational equation written in displacements to determine the critical loads and buckling modes. Specific types of corrugated isotropic metal and fiberglass shells are considered. The calculated results are compared with those obtained within the framework of the classical theory of shells. It is shown that the Timoshenko-type theory extends significantly the possibility of exact allowance for the geometrical parameters and material properties of corrugated shells compared with Kirchhoff-Love theory.

The influence of MOVPE growth conditions on the shell of core-shell GaN microrod structures

NASA Astrophysics Data System (ADS)

Schimpke, Tilman; Avramescu, Adrian; Koller, Andreas; Fernando-Saavedra, Amalia; Hartmann, Jana; Ledig, Johannes; Waag, Andreas; Strassburg, Martin; Lugauer, Hans-Jürgen

2017-05-01

A core-shell geometry is employed for most next-generation, three-dimensional opto-electric devices based on III-V semiconductors and grown by metal organic vapor phase epitaxy (MOVPE). Controlling the shape of the shell layers is fundamental for device optimization, however no detailed analysis of the influence of growth conditions has been published to date. We study homogeneous arrays of gallium nitride core-shell microrods with height and diameter in the micrometer range and grown in a two-step selective area MOVPE process. Changes in shell shape and homogeneity effected by deliberately altered shell growth conditions were accurately assessed by digital analysis of high-resolution scanning electron microscope images. Most notably, two temperature regimes could be established, which show a significantly different behavior with regard to material distribution. Above 900 °C of wafer carrier temperature, the shell thickness along the growth axis of the rods was very homogeneous, however variations between vicinal rods increase. In contrast, below 830 °C the shell thickness is higher close to the microrod tip than at the base of the rods, while the lateral homogeneity between neighboring microrods is very uniform. This temperature effect could be either amplified or attenuated by changing the remaining growth parameters such as reactor pressure, structure distance, gallium precursor, carrier gas composition and dopant materials. Possible reasons for these findings are discussed with respect to GaN decomposition as well as the surface and gas phase diffusion of growth species, leading to an improved control of the functional layers in next-generation 3D V-III devices.

Enhancement of luminescence in white emitting strontium fluoride core @ calcium fluoride shell nanoparticles

NASA Astrophysics Data System (ADS)

Kumam, Nandini; Singh, Ningthoujam Premananda; Singh, Laishram Priyobarta; Srivastava, Sri Krishna

2015-09-01

Synthesis of lanthanide-doped fluoride SrF2:3Dy and SrF2:3Dy@CaF2 nanoparticles with different ratios of core to shell (1:0.5, 1:1 and 1:2) has been carried out by employing ethylene glycol route. X-ray diffraction (XRD) patterns reveal that the structure of the prepared nanoparticles was of cubical shape, which is also evident in TEM images. The size of the nanoparticles for core (SrF2:3Dy) is found to increase when core is covered by shell (CaF2). It is also evident from Fourier transform infrared spectroscopy (FTIR) that ethylene glycol successfully controls the growth and acts as a shape modifier by regulating growth rate. In the photoluminescence investigation, emission spectra of SrF2:3Dy is found to be highly enhanced when SrF2:3Dy is covered by CaF2 due to the decrease of cross relaxation amongst the Dy3+-Dy3+ ions. Such type of enhancement of luminescence in homonanostructure SrF2:3Dy@CaF2 (core@shell) has not been studied so far, to the best of the authors' knowledge. This luminescent material exhibits prominently white light emitting properties as shown by the Commission Internationale d'Eclairage (CIE) chromaticity diagram. The calculated correlate colour temperature (CCT) values for SrF2:3Dy, SrF2:3Dy@CaF2 (1:0.05), SrF2:3Dy@CaF2 (1:1) and SrF2:3Dy@CaF2 (1:2) are 5475, 5476, 5384 and 5525 K, respectively, which lie in the cold white region.

An Analysis of Explosion-Induced Bending Damage in Submerged Shell Targets,

DTIC Science & Technology

1984-12-01

AD-R169 009 AN ANRLYSIS OF EXPLOSION-INDUCED SENDING DfIMAhE IN SUBMERGED SHELL TRRGETS(U) NRVRL SURFACE HERPONS CENTER OANLOREN YR N NOUSSOUROS DEC...BENDING DAMAGE IN SUBMERGED SHELL TARGETS 0 o BY MINOS MOUSSOUROS RESEARCH AND TECHNOLOGY DEPARTMENT < DECEMBER 1984 Aptroved f u, blic release...IN SUBMERGED ) SHELL TARGETS 6. PERFORMING ORG. REPORT NUMBER 7 AUTHOR(&) S. CONTRACT OR GRANT NUMERI(s) jMlNoS MOUSSoUROS 9 PERFORMING

Coexistence of a metastable double hcp phase in bcc-fcc structure transition of Te under high pressure

NASA Astrophysics Data System (ADS)

Akahama, Yuichi; Okawa, Naoki; Sugimoto, Toshiyuki; Fujihisa, Hiroshi; Hirao, Naoshisa; Ohishi, Yasuo

2018-02-01

The structural phase transitions of tellurium (Te) are investigated at pressures of up to 330 GPa at 298 K using an X-ray powder diffraction technique. In the experiments, it was found that the high-pressure bcc phase (Te-V) transitioned to the fcc phase (Te-VI) at 99 GPa, although a double hcp phase (dhcp) coexisted with the fcc phase. As the pressure was increased and decreased, the dhcp phase vanished at 255 and 100 GPa, respectively. These results suggest that the dhcp phase is metastable at 298 K and the structure of the highest-pressure phase of Te is fcc. The present results provide important information regarding the high-pressure behavior of group-16 elements.

Use of extracts from oyster shell and soil for cultivation of Spirulina maxima.

PubMed

Jung, Joo-Young; Kim, Sunmin; Lee, Hansol; Kim, Kyochan; Kim, Woong; Park, Min S; Kwon, Jong-Hee; Yang, Ji-Won

2014-12-01

Calcium ion and trace metals play important roles in various metabolisms of photosynthetic organisms. In this study, simple methods were developed to extract calcium ion and micronutrients from oyster shell and common soil, and the prepared extracts were tested as a replacement of the corresponding chemicals that are essential for growth of microalgae. The oyster shell and soil were treated with 0.1 M sodium hydroxide or with 10 % hydrogen peroxide, respectively. The potential application of these natural sources to cultivation was investigated with Spirulina maxima. When compared to standard Zarrouk medium, the Spirulina maxima cultivated in a modified Zarrouk media with elements from oyster shell and soil extract exhibited increases in biomass, chlorophyll, and phycocyanin by 17, 16, and 64 %, respectively. These results indicate that the extracts of oyster shell and soil provide sufficient amounts of calcium and trace metals for successful cultivation of Spirulina maxima.

ITS America's petition to the FCC requesting allocation for DSRC [memorandum

DOT National Transportation Integrated Search

1997-05-20

This memorandum summarizes a petition from the Intelligent Transportation Society of America (ITSA) to the Federal Communications Commission (FCC) to request that the frequency band between 5850-5925MHz be reallocated to allow DSRC (Dedicated Short R...

Investigation of Thermal Hardening of the FCC Material Containing Strengthening Particles with an L12 Superstructure

NASA Astrophysics Data System (ADS)

Daneyko, O. I.; Kulaeva, N. A.; Kovalevskaya, C. A.; Kolupaeva, S. N.

2015-07-01

A mathematical model of plastic deformation of dispersion-hardened materials with an fcc matrix containing strengthening particles with an L12 superstructure having a coherent relationship with the matrix is presented. The model is based on the balance equations of deformation defects of different types with taking into account their transformation during plastic deformation. The influence of scale characteristics of the hardening phase, temperature, and deformation rate on the evolution of the dislocation subsystem and strain hardening of an alloy with an fcc matrix hardened by particles with an L12 super structure is studied. A temperature anomaly of mechanical properties is found for the materials with different fcc matrices (Al,Cu, Ni). It is shown that the temperature anomaly is more pronounced for the material with larger volume fraction of the hardening phase.

De novo modeling of the F420-reducing [NiFe]-hydrogenase from a methanogenic archaeon by cryo-electron microscopy

PubMed Central

Mills, Deryck J; Vitt, Stella; Strauss, Mike; Shima, Seigo; Vonck, Janet

2013-01-01

Methanogenic archaea use a [NiFe]-hydrogenase, Frh, for oxidation/reduction of F420, an important hydride carrier in the methanogenesis pathway from H2 and CO2. Frh accounts for about 1% of the cytoplasmic protein and forms a huge complex consisting of FrhABG heterotrimers with each a [NiFe] center, four Fe-S clusters and an FAD. Here, we report the structure determined by near-atomic resolution cryo-EM of Frh with and without bound substrate F420. The polypeptide chains of FrhB, for which there was no homolog, was traced de novo from the EM map. The 1.2-MDa complex contains 12 copies of the heterotrimer, which unexpectedly form a spherical protein shell with a hollow core. The cryo-EM map reveals strong electron density of the chains of metal clusters running parallel to the protein shell, and the F420-binding site is located at the end of the chain near the outside of the spherical structure. DOI: http://dx.doi.org/10.7554/eLife.00218.001 PMID:23483797

Design and synthesis of magnetic nanoparticles with gold shells for single particle optical tracking

NASA Astrophysics Data System (ADS)

Lim, Jitkang

The design, synthesis, and characterization of iron oxide core, gold shell nanoparticles are studied in this thesis. Firstly, nanoparticles with 18 +/- 1.7 nm diameter iron oxide cores with ˜5 nm thick gold shells were synthesized via a new seed-mediated electroless deposition method. The nanoparticles were superparamagnetic at room temperature and could be reversibly collected by a permanent magnet. These nanoparticles displayed a sharp localized surface plasmon resonance peak at 605 nm, as predicted by scattering theory, and their large scattering cross-section allowed them to be individually resolved in darkfield optical microscopy while undergoing Brownian motion in aqueous suspension. Later, commercially available 38 +/- 3.8 nm diameter spherical iron oxide nanoparticles (from Ocean Nanotech, Inc) were employed to make core-shell particles. These particles were decorated with cationic poly(diallyldimethylammonium chloride) (PDDA) which further promotes the attachment of small gold clusters. After gold seeding, the average hydrodynamic diameter of the core-shell particles is 172 +/- 65.9 nm. The magnetophoretic motion of these particles was guided by a piece of magnetized mu-metal. Individual particle trajectories were observed by darkfield optical microscopy. The typical magnetophoretic velocity achieved was within the range of 1--10 mum/sec. Random walk analysis performed on these particles while undergoing Brownian motion confirmed that individual particles were indeed being imaged. The particle size variation within the observed sample obtained through random walk analysis was within the size distribution obtained by dynamic light scattering. When the current to the solenoid used to magnetize the mu-metal was turned off, all the collected core-shell particles were readily redispersed by diffusion back into the surrounding environment. A Peclet number analysis was performed to probe the convective motion of nanospheres and nanorods under the influence of

Phase stability, ordering tendencies, and magnetism in single-phase fcc Au-Fe nanoalloys

DOE PAGES

Zhuravlev, I. A.; Barabash, S. V.; An, J. M.; ...

2017-10-01

Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L1 0 and L1 2 orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L1 0 AuFe, L1 2 Au 3Fe,more » and L1 2 AuFe 3 structures are unstable in DFT. But, a tendency to form concentration waves at the corresponding [001] ordering vector is revealed in nearly-random alloys in a certain range of concentrations. Furthermore, this incipient ordering requires enrichment by Fe relative to the equiatomic composition, which may occur in the core of a nanoparticle due to the segregation of Au to the surface. Effects of magnetism on the chemical ordering are also discussed.« less

Phase stability, ordering tendencies, and magnetism in single-phase fcc Au-Fe nanoalloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravlev, I. A.; Barabash, S. V.; An, J. M.

Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L1 0 and L1 2 orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L1 0 AuFe, L1 2 Au 3Fe,more » and L1 2 AuFe 3 structures are unstable in DFT. But, a tendency to form concentration waves at the corresponding [001] ordering vector is revealed in nearly-random alloys in a certain range of concentrations. Furthermore, this incipient ordering requires enrichment by Fe relative to the equiatomic composition, which may occur in the core of a nanoparticle due to the segregation of Au to the surface. Effects of magnetism on the chemical ordering are also discussed.« less

Design and performance studies of a hadronic calorimeter for a FCC-hh experiment

NASA Astrophysics Data System (ADS)

Faltova, J.

2018-03-01

The hadron-hadron Future Circular Collider (FCC-hh) project studies the physics reach of a proton-proton machine with a centre-of-mass-energy of 100 TeV and five times greater peak luminosities than at the High-Luminosity LHC (HL-LHC). The high-energy regime of the FCC-hh opens new opportunities for the discovery of physics beyond the standard model. At 100 TeV a large fraction of the W, Z, H bosons and top quarks are produced with a significant boost. It implies an efficient reconstruction of very high energetic objects decaying hadronically. The reconstruction of those boosted objects sets the calorimeter performance requirements in terms of energy resolution, containment of highly energetic hadron showers, and high transverse granularity. We present the current baseline technologies for the calorimeter system in the barrel region of the FCC-hh reference detector: a liquid argon electromagnetic and a scintillator-steel hadronic calorimeters. The focus of this paper is on the hadronic calorimeter and the performance studies for hadrons. The reconstruction of single particles and the achieved energy resolution for the combined system of the electromagnetic and hadronic calorimeters are discussed.

Stacking fault energy of face-centered cubic metals: thermodynamic and ab initio approaches

NASA Astrophysics Data System (ADS)

Li, Ruihuan; Lu, Song; Kim, Dongyoo; Schönecker, Stephan; Zhao, Jijun; Kwon, Se Kyun; Vitos, Levente

2016-10-01

The formation energy of the interface between face-centered cubic (fcc) and hexagonal close packed (hcp) structures is a key parameter in determining the stacking fault energy (SFE) of fcc metals and alloys using thermodynamic calculations. It is often assumed that the contribution of the planar fault energy to the SFE has the same order of magnitude as the bulk part, and thus the lack of precise information about it can become the limiting factor in thermodynamic predictions. Here, we differentiate between the interfacial energy for the coherent fcc(1 1 1)/hcp(0 0 0 1) interface and the ‘pseudo-interfacial energy’ that enters the thermodynamic expression for the SFE. Using first-principles calculations, we determine the coherent and pseudo-interfacial energies for six elemental metals (Al, Ni, Cu, Ag, Pt, and Au) and three paramagnetic Fe-Cr-Ni alloys. Our results show that the two interfacial energies significantly differ from each other. We observe a strong chemistry dependence for both interfacial energies. The calculated pseudo-interfacial energies for the Fe-Cr-Ni steels agree well with the available literature data. We discuss the effects of strain on the description of planar faults via thermodynamic and ab initio approaches.

Stacking fault energy of face-centered cubic metals: thermodynamic and ab initio approaches.

PubMed

Li, Ruihuan; Lu, Song; Kim, Dongyoo; Schönecker, Stephan; Zhao, Jijun; Kwon, Se Kyun; Vitos, Levente

2016-10-05

The formation energy of the interface between face-centered cubic (fcc) and hexagonal close packed (hcp) structures is a key parameter in determining the stacking fault energy (SFE) of fcc metals and alloys using thermodynamic calculations. It is often assumed that the contribution of the planar fault energy to the SFE has the same order of magnitude as the bulk part, and thus the lack of precise information about it can become the limiting factor in thermodynamic predictions. Here, we differentiate between the interfacial energy for the coherent fcc(1 1 1)/hcp(0 0 0 1) interface and the 'pseudo-interfacial energy' that enters the thermodynamic expression for the SFE. Using first-principles calculations, we determine the coherent and pseudo-interfacial energies for six elemental metals (Al, Ni, Cu, Ag, Pt, and Au) and three paramagnetic Fe-Cr-Ni alloys. Our results show that the two interfacial energies significantly differ from each other. We observe a strong chemistry dependence for both interfacial energies. The calculated pseudo-interfacial energies for the Fe-Cr-Ni steels agree well with the available literature data. We discuss the effects of strain on the description of planar faults via thermodynamic and ab initio approaches.

Specific features of defect and mass transport in concentrated fcc alloys

DOE PAGES

Osetsky, Yuri N.; Béland, Laurent K.; Stoller, Roger E.

2016-06-15

We report that diffusion and mass transport are basic properties that control materials performance, such as phase stability, solute decomposition and radiation tolerance. While understanding diffusion in dilute alloys is a mature field, concentrated alloys are much less studied. Here, atomic-scale diffusion and mass transport via vacancies and interstitial atoms are compared in fcc Ni, Fe and equiatomic Ni-Fe alloy. High temperature properties were determined using conventional molecular dynamics on the microsecond timescale, whereas the kinetic activation-relaxation (k-ART) approach was applied at low temperatures. The k-ART was also used to calculate transition states in the alloy and defect transport coefficients.more » The calculations reveal several specific features. For example, vacancy and interstitial defects migrate via different alloy components, diffusion is more sluggish in the alloy and, notably, mass transport in the concentrated alloy cannot be predicted on the basis of diffusion in its pure metal counterparts. Lastly, the percolation threshold for the defect diffusion in the alloy is discussed and it is suggested that this phenomenon depends on the properties and diffusion mechanisms of specific defects.« less

Interface Mediated Nucleation and Growth of Dislocations in fcc-bcc nanocomposite

NASA Astrophysics Data System (ADS)

Zhang, Ruifeng; Wang, Jian; Beyerlein, Irene J.; Germann, Timothy C.

2011-03-01

Heterophase interfaces play a crucial role in determining material strength for nanostructured materials because they can block, store, nucleate, and remove dislocations, the essential defects that enable plastic deformation. Much recent theoretical and experimental effort has been conducted on nanostructured Cu-Nb multilayer composites that exhibited extraordinarily high strength, ductility, and resistance to radiation and mechanical loading. In decreasing layer thicknesses to the order of a few tens of nanometers or less, the deformation behavior of such composites is mainly controlled by the Cu/Nb interface. In this work, we focus on the cooperative mechanisms of dislocation nucleation and growth from Cu/Nb interfaces, and their interaction with interface. Two types of experimentally observed Cu/Nb incoherent interfaces are comparatively studied. We found that the preferred dislocation nucleation sites are closely related to atomic interface structure, which in turn, depend on the orientation relationship. The activation stress and energies for an isolated Shockley dislocation loop of different sizes from specific interface sites depend strongly on dislocation size, atomic interface pattern, and loading conditions. Such findings provide important insight into the mechanical response of a wide range of fcc/bcc metallic nanocomposites via atomic interface design.

47 CFR 3.53 - FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s). 3.53 Section 3.53 Telecommunication FEDERAL COMMUNICATIONS... telecommunications service to U.S. registered vessel(s). An accounting authority must inform the FCC immediately...

47 CFR 3.53 - FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s). 3.53 Section 3.53 Telecommunication FEDERAL COMMUNICATIONS... telecommunications service to U.S. registered vessel(s). An accounting authority must inform the FCC immediately...

47 CFR 3.53 - FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 1 2012-10-01 2012-10-01 false FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s). 3.53 Section 3.53 Telecommunication FEDERAL COMMUNICATIONS... telecommunications service to U.S. registered vessel(s). An accounting authority must inform the FCC immediately...

47 CFR 3.53 - FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s). 3.53 Section 3.53 Telecommunication FEDERAL COMMUNICATIONS... telecommunications service to U.S. registered vessel(s). An accounting authority must inform the FCC immediately...

47 CFR 3.53 - FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC notification of refusal to provide telecommunications service to U.S. registered vessel(s). 3.53 Section 3.53 Telecommunication FEDERAL COMMUNICATIONS... telecommunications service to U.S. registered vessel(s). An accounting authority must inform the FCC immediately...

Accurate Monte Carlo simulations on FCC and HCP Lennard-Jones solids at very low temperatures and high reduced densities up to 1.30

NASA Astrophysics Data System (ADS)

Adidharma, Hertanto; Tan, Sugata P.

2016-07-01

Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T∗ ≤ 1.20) and high densities (0.96 ≤ ρ∗ ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe the properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.

Projections for neutral Di-Boson and Di-Higgs interactions at FCC-he collider

NASA Astrophysics Data System (ADS)

Kuday, S.; Saygın, H.; Hoş, İ.; Çetin, F.

2018-07-01

As a high energy e-p collider, FCC-he, has been recently proposed with sufficient energy options to investigate Higgs couplings. To analyze the sensitivity on Higgs boson couplings, we focus specifically on the CP-even and CP-odd Wilson coefficients with hhZZ and hhγγ four-point interactions of Higgs boson with Effective Lagrangian Model through the process e- p → hhje-. We simulate the related processes in FCC-he, with 60 GeV and 120 GeV e- beams and 50 TeV proton beam collisions. We present the exclusion limits on these couplings both for 68% and 95% C.L. in terms of integrated luminosities.

Ni@Ru and NiCo@Ru Core-Shell Hexagonal Nanosandwiches with a Compositionally Tunable Core and a Regioselectively Grown Shell.

PubMed

Hwang, Hyeyoun; Kwon, Taehyun; Kim, Ho Young; Park, Jongsik; Oh, Aram; Kim, Byeongyoon; Baik, Hionsuck; Joo, Sang Hoon; Lee, Kwangyeol

2018-01-01

The development of highly active electrocatalysts is crucial for the advancement of renewable energy conversion devices. The design of core-shell nanoparticle catalysts represents a promising approach to boost catalytic activity as well as save the use of expensive precious metals. Here, a simple, one-step synthetic route is reported to prepare hexagonal nanosandwich-shaped Ni@Ru core-shell nanoparticles (Ni@Ru HNS), in which Ru shell layers are overgrown in a regioselective manner on the top and bottom, and around the center section of a hexagonal Ni nanoplate core. Notably, the synthesis can be extended to NiCo@Ru core-shell nanoparticles with tunable core compositions (Ni 3 Co x @Ru HNS). Core-shell HNS structures show superior electrocatalytic activity for the oxygen evolution reaction (OER) to a commercial RuO 2 black catalyst, with their OER activity being dependent on their core compositions. The observed trend in OER activity is correlated to the population of Ru oxide (Ru 4+ ) species, which can be modulated by the core compositions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly selective removal of Hg2+ and Pb2+ by thiol-functionalized Fe3O4@metal-organic framework core-shell magnetic microspheres

NASA Astrophysics Data System (ADS)

Ke, Fei; Jiang, Jing; Li, Yizhi; Liang, Jing; Wan, Xiaochun; Ko, Sanghoon

2017-08-01

In this work, we report a novel type of thiol-functionalized magnetic core-shell metal-organic framework (MOF) microspheres that can be potentially used for selective removal of Hg2+ and Pb2+ in the presence of other background ions from wastewater. The monodisperse Fe3O4@Cu3(btc)2 core-shell magnetic microspheres have been fabricated by a versatile step-by-step assembly strategy. Further, the thiol-functionalized Fe3O4@Cu3(btc)2 magnetic microspheres were successfully synthesized by utilizing a facile postsynthetic strategy. Significantly, the thiol-functionalized Fe3O4@Cu3(btc)2 magnetic microspheres exhibit remarkably selective adsorption affinity for Hg2+ (Kd = 5.98 × 104 mL g-1) and Pb2+ (Kd = 1.23 × 104 mL g-1), while a weaker binding affinity occurred for the other background ions such as Ni2+, Na+, Mg2+, Ca2+, Zn2+ and Cd2+. The adsorption kinetics follow the pseudo-second-order rate equation and with an almost complete removal of Hg2+ and Pb2+ from the mixed heavy metal ions wastewater (0.5 mM) within 120 min. Moreover, this adsorbent can be easily recycled because of the presence of the magnetic Fe3O4 core. This work provides a promising functionalized porous magnetic Fe3O4@MOF-based adsorbent with easy recycling property for the selective removal of heavy metal ions from wastewater.

Optical properties of MgF2 nano-composite films dispersed with noble metal nanoparticles synthesized by sol-gel method

NASA Astrophysics Data System (ADS)

Wakaki, Moriaki; Soujima, Nobuaki; Shibuya, Takehisa

2015-03-01

Porous MgF2 films synthesized by a sol-gel method exhibit the lowest refractive index among the dielectric optical materials and are the most useful materials for the anti-reflection coatings. On the other hand, surface plasmon resonance (SPR) absorptions of noble metal nanoparticles in various solid matrices have been extensively studied. New functional materials like a SERS (Surface Enhanced Raman Spectroscopy) tips are expected by synthesizing composite materials between porous MgF2 films featured by the network of MgF2 nanoparticles and noble metal nanoparticles introduced within the network. In this study, fundamental physical properties including morphology and optical properties are characterized for these materials to make clear the potential of the composite system. Composite materials of MgF2 films dispersed with noble metal (Ag, Au) nanoparticles were prepared using the sol-gel technique with various annealing temperatures and densities of noble metal nanoparticles. The structural morphology was analyzed by an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The size and shape distributions of the metal nanoparticles were observed using a transmission electron microscope (TEM). The optical properties of fabricated composite films were characterized by UV-Vis-NIR and FT-IR spectrophotometers. The absorption spectra due to the surface plasmon resonance (SPR) of the metal nanoparticles were analyzed using the dielectric function considering the effective medium approximation, typically Maxwell-Garnett model. The Raman scattering spectra were also studied to check the enhancement effect of specimen dropped on the MgF2: Ag nano-composite films deposited on Si substrate. Enhancement of the Raman intensity of pyridine solution specimen was observed.

Ab initio study of the diatomic fluorides FeF, CoF, NiF, and CuF.

PubMed

Koukounas, Constantine; Mavridis, Aristides

2008-11-06

The late-3d transition-metal diatomic fluorides MF = FeF, CoF, NiF, and CuF have been studied using variational multireference (MRCI) and coupled-cluster [RCCSD(T)] methods, combined with large to very large basis sets. We examined a total of 35 (2S+1)|Lambda| states, constructing as well 29 full potential energy curves through the MRCI method. All examined states are ionic, diabatically correlating to M(+)+F(-)((1)S). Notwithstanding the "eccentric" character of the 3d transition metals and the difficulties to accurately be described with all-electron ab initio methods, our results are, in general, in very good agreement with available experimental numbers.

Trends in Ionization Energy of Transition-Metal Elements

ERIC Educational Resources Information Center

Matsumoto, Paul S.

2005-01-01

A rationale for the difference in the periodic trends in the ionization energy of the transition-metal elements versus the main-group elements is presented. The difference is that in the transition-metal elements, the electrons enter an inner-shell electron orbital, while in the main-group elements, the electrons enter an outer-shell electron…

Statement on CATV from the FCC to the Senate Committee.

ERIC Educational Resources Information Center

Federal Communications Commission, Washington, DC.

In this statement to the Senate, the Federal Communications Commission (FCC) describes in detail their specific policies relevant to cable television (CATV) regulation under four general areas. The rules for the first of these, television broadcast signal carriage, are outlined in terms of three classifications which would divide all signals:…

Facile preparation of core-shell magnetic metal-organic framework nanospheres for the selective enrichment of endogenous peptides.

PubMed

Xiong, Zhichao; Ji, Yongsheng; Fang, Chunli; Zhang, Quanqing; Zhang, Lingyi; Ye, Mingliang; Zhang, Weibing; Zou, Hanfa

2014-06-10

Facile preparation of core-shell magnetic metal-organic framework nanospheres by a layer-by-layer approach is presented. The nanospheres have high surface area (285.89 cm(2)  g(-1)), large pore volume (0.18 cm(3)  g(-1)), two kinds of mesopores (2.50 and 4.72 nm), excellent magnetic responsivity (55.65 emu g(-1)), structural stability, and good dispersibility. The combination of porosity, hydrophobicity, and uniform magnetism was exploited for effective enrichment of peptides with simultaneous exclusion of high molecular weight proteins. The nanospheres were successfully applied in the selective enrichment of endogenous peptides in human serum. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Discussion on Microwave-Matter Interaction Mechanisms by In Situ Observation of "Core-Shell" Microstructure during Microwave Sintering.

PubMed

Liu, Wenchao; Xu, Feng; Li, Yongcun; Hu, Xiaofang; Dong, Bo; Xiao, Yu

2016-02-23

This research aims to deepen the understanding of the interaction mechanisms between microwave and matter in a metal-ceramic system based on in situ synchrotron radiation computed tomography. A special internal "core-shell" microstructure was discovered for the first time and used as an indicator for the interaction mechanisms between microwave and matter. Firstly, it was proved that the microwave magnetic field acted on metal particles by way of inducing an eddy current in the surface of the metal particles, which led to the formation of a "core-shell" microstructure in the metal particles. On this basis, it was proposed that the ceramic particles could change the microwave field and open a way for the microwave, thereby leading to selective heating in the region around the ceramic particles, which was verified by the fact that all the "core-shell" microstructure was located around ceramic particles. Furthermore, it was indicated that the ceramic particles would gather the microwaves, and might lead to local heating in the metal-ceramic contact region. The focusing of the microwave was proved by the quantitative analysis of the evolution rate of the "core-shell" microstructure in a different region. This study will help to reveal the microwave-matter interaction mechanisms during microwave sintering.

Inner and Outer Coordination Shells of Mg(2+) in CorA Selectivity Filter from Molecular Dynamics Simulations.

PubMed

Kitjaruwankul, Sunan; Wapeesittipan, Pattama; Boonamnaj, Panisak; Sompornpisut, Pornthep

2016-01-28

Structural data of CorA Mg(2+) channels show that the five Gly-Met-Asn (GMN) motifs at the periplasmic loop of the pentamer structure form a molecular scaffold serving as a selectivity filter. Unfortunately, knowledge about the cation selectivity of Mg(2+) channels remains limited. Since Mg(2+) in aqueous solution has a strong first hydration shell and apparent second hydration sphere, the coordination structure of Mg(2+) in a CorA selectivity filter is expected to be different from that in bulk water. Hence, this study investigated the hydration structure and ligand coordination of Mg(2+) in a selectivity filter of CorA using molecular dynamics (MD) simulations. The simulations reveal that the inner-shell structure of Mg(2+) in the filter is not significantly different from that in aqueous solution. The major difference is the characteristic structural features of the outer shell. The GMN residues engage indirectly in the interactions with the metal ion as ligands in the second shell of Mg(2+). Loss of hydrogen bonds between inner- and outer-shell waters observed from Mg(2+) in bulk water is mostly compensated by interactions between waters in the first solvation shell and the GMN motif. Some water molecules in the second shell remain in the selectivity filter and become less mobile to support the metal binding. Removal of Mg(2+) from the divalent cation sensor sites of the protein had an impact on the structure and metal binding of the filter. From the results, it can be concluded that the GMN motif enhances the affinity of the metal binding site in the CorA selectivity filter by acting as an outer coordination ligand.

75 FR 13540 - Notice of Public Information Collections Being Submitted to the Office of Management and Budget...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-22

... INFORMATION: OMB Control Number: 3060-0874. Title: FCC Form 2000 A through F, FCC Form 475-B, FCC Form 1088 A...): FCC Form 2000 A through F, FCC Form 475-B, FCC Form 1088 A through H, and FCC Form 501. Type of Review... indecent programming. The FCC Form 475-B will remain unchanged. The FCC Form 1088 Consumer Complaint Form...

Shell-Isolated Tip-Enhanced Raman and Fluorescence Spectroscopy.

PubMed

Huang, Ya-Ping; Huang, Sheng-Chao; Wang, Xiang-Jie; Bodappa, Nataraju; Li, Chao-Yu; Yin, Hao; Su, Hai-Sheng; Meng, Meng; Zhang, Hua; Ren, Bin; Yang, Zhi-Lin; Zenobi, Renato; Tian, Zhong-Qun; Li, Jian-Feng

2018-06-18

Tip-enhanced Raman spectroscopy can provide molecular fingerprint information with ultrahigh spatial resolution, but the tip will be easily contaminated, thus leading to artifacts. It also remains a great challenge to establish tip-enhanced fluorescence because of the quenching resulting from the proximity of the metal tip. Herein, we report shell-isolated tip-enhanced Raman and fluorescence spectroscopies by employing ultrathin shell-isolated tips fabricated by atomic layer deposition. Such shell-isolated tips not only show outstanding electromagnetic field enhancement in TERS but also exclude interference by contaminants, thus greatly promoting applications in solution. Tip-enhanced fluorescence has also been achieved using these shell-isolated tips, with enhancement factors of up to 1.7×10 3 , consistent with theoretical simulations. Furthermore, tip-enhanced Raman and fluorescence signals are acquired simultaneously, and their relative intensities can be manipulated by changing the shell thickness. This work opens a new avenue for ultrahigh resolution surface analysis using plasmon-enhanced spectroscopies. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biodegradable Core-shell Dual-Metal-Organic-Frameworks Nanotheranostic Agent for Multiple Imaging Guided Combination Cancer Therapy

PubMed Central

Wang, Dongdong; Zhou, Jiajia; Shi, Ruohong; Wu, Huihui; Chen, Ruhui; Duan, Beichen; Xia, Guoliang; Xu, Pengping; Wang, Hui; Zhou, Shu; Wang, Chengming; Wang, Haibao; Guo, Zhen; Chen, Qianwang

2017-01-01

Metal-organic-frameworks (MOFs) possess high porosity, large surface area, and tunable functionality are promising candidates for synchronous diagnosis and therapy in cancer treatment. Although large number of MOFs has been discovered, conventional MOF-based nanoplatforms are mainly limited to the sole MOF source with sole functionality. In this study, surfactant modified Prussian blue (PB) core coated by compact ZIF-8 shell (core-shell dual-MOFs, CSD-MOFs) has been reported through a versatile stepwise approach. With Prussian blue as core, CSD-MOFs are able to serve as both magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI) agents. We show that CSD-MOFs crystals loading the anticancer drug doxorubicin (DOX) are efficient pH and near-infrared (NIR) dual-stimuli responsive drug delivery vehicles. After the degradation of ZIF-8, simultaneous NIR irradiation to the inner PB MOFs continuously generate heat that kill cancer cells. Their efficacy on HeLa cancer cell lines is higher compared with the respective single treatment modality, achieving synergistic chemo-thermal therapy efficacy. In vivo results indicate that the anti-tumor efficacy of CSD-MOFs@DOX+NIR was 7.16 and 5.07 times enhanced compared to single chemo-therapy and single thermal-therapy respectively. Our strategy opens new possibilities to construct multifunctional theranostic systems through integration of two different MOFs. PMID:29158848

Equations of state of anhydrous AlF 3 and AlI 3 : Modeling of extreme condition halide chemistry

DOE PAGES

Stavrou, Elissaios; Zaug, Joseph M.; Bastea, Sorin; ...

2015-06-04

Pressure dependent angle-dispersive x-ray powder diffraction measurements of alpha-phase aluminum trifluoride (α-AlF 3) and separately, aluminum triiodide (AlI 3) were conducted using a diamond-anvil cell. Results at 295 K extend to 50 GPa. The equations of state of AlF 3 and AlI 3 were determined through refinements of collected x-ray diffraction patterns. The respective bulk moduli and corresponding pressure derivatives are reported for multiple orders of the Birch-Murnaghan (B-M), finite-strain (F-f), and higher pressure finite-strain (G-g) EOS analysis models. Aluminum trifluoride exhibits an apparent isostructural phase transition at approximately 12 GPa. Aluminum triiodide also undergoes a second-order atomic rearrangement: appliedmore » stress transformed a monoclinically distorted face centered cubic (fcc) structure into a standard fcc structural arrangement of iodine atoms. In conclusion, results from semi-empirical thermochemical computations of energetic materials formulated with fluorine containing reactants were obtained with the aim of predicting the yield of halogenated products.« less

Equations of state of anhydrous AlF 3 and AlI 3 : Modeling of extreme condition halide chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stavrou, Elissaios; Zaug, Joseph M.; Bastea, Sorin

Pressure dependent angle-dispersive x-ray powder diffraction measurements of alpha-phase aluminum trifluoride (α-AlF 3) and separately, aluminum triiodide (AlI 3) were conducted using a diamond-anvil cell. Results at 295 K extend to 50 GPa. The equations of state of AlF 3 and AlI 3 were determined through refinements of collected x-ray diffraction patterns. The respective bulk moduli and corresponding pressure derivatives are reported for multiple orders of the Birch-Murnaghan (B-M), finite-strain (F-f), and higher pressure finite-strain (G-g) EOS analysis models. Aluminum trifluoride exhibits an apparent isostructural phase transition at approximately 12 GPa. Aluminum triiodide also undergoes a second-order atomic rearrangement: appliedmore » stress transformed a monoclinically distorted face centered cubic (fcc) structure into a standard fcc structural arrangement of iodine atoms. In conclusion, results from semi-empirical thermochemical computations of energetic materials formulated with fluorine containing reactants were obtained with the aim of predicting the yield of halogenated products.« less

78 FR 34099 - FCC Extends Pleading Cycle for Indecency Cases Policy

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-06

... FEDERAL COMMUNICATIONS COMMISSION [GN Docket No. 13-86; DA 13-1071] FCC Extends Pleading Cycle for Indecency Cases Policy AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: In this document, the Federal Communications Commission Enforcement Bureau and Office of General Counsel extend the...

Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

PubMed Central

Park, Nam-Hee; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2015-01-01

To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell) along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface. PMID:28793420

Investigation of radiation damage tolerance in interface-containing metallic nano structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greer, Julia R.

The proposed work seeks to conduct a basic study by applying experimental and computational methods to obtain quantitative influence of helium sink strength and proximity on He bubble nucleation and growth in He-irradiated nano-scale metallic structures, and the ensuing deformation mechanisms and mechanical properties. We utilized a combination of nano-scale in-situ tension and compression experiments on low-energy He-irradiated samples combined with site-specific microstructural characterization and modeling efforts. We also investigated the mechanical deformation of nano-architected materials, i.e. nanolattices which are comprised of 3-dimensional interwoven networks of hollow tubes, with the wall thickness in the nanometer range. This systematic approach willmore » provide us with critical information for identifying key factors that govern He bubble nucleation and growth upon irradiation as a function of both sink strength and sink proximity through an experimentally-confirmed physical understanding. As an outgrowth of these efforts, we performed irradiations with self-ions (Ni 2+) on Ni-Al-Zr metallic glass nanolattices to assess their resilience against radiation damage rather than He-ion implantation. We focused our attention on studying individual bcc/fcc interfaces within a single nano structure (nano-pillar or a hollow tube): a single Fe (bcc)-Cu (fcc) boundary per pillar oriented perpendicular to the pillar axes, as well as pure bcc and fcc nano structures. Additional interfaces of interest include bcc/bcc and metal/metallic glass all within a single nano-structure volume. The model material systems are: (1) pure single crystalline Fe and Cu, (2) a single Fe (bcc)-Cu (fcc) boundary per nano structure (3) a single metal–metallic glass, all oriented non-parallel to the loading direction so that their fracture strength can be tested. A nano-fabrication approach, which involves e-beam lithography and templated electroplating, as well as two

Federal Communications Commission (FCC) Transponder Loading Data Conversion Software. User's guide and software maintenance manual, version 1.2

NASA Technical Reports Server (NTRS)

Mallasch, Paul G.

1993-01-01

This volume contains the complete software system documentation for the Federal Communications Commission (FCC) Transponder Loading Data Conversion Software (FIX-FCC). This software was written to facilitate the formatting and conversion of FCC Transponder Occupancy (Loading) Data before it is loaded into the NASA Geosynchronous Satellite Orbital Statistics Database System (GSOSTATS). The information that FCC supplies NASA is in report form and must be converted into a form readable by the database management software used in the GSOSTATS application. Both the User's Guide and Software Maintenance Manual are contained in this document. This volume of documentation passed an independent quality assurance review and certification by the Product Assurance and Security Office of the Planning Research Corporation (PRC). The manuals were reviewed for format, content, and readability. The Software Management and Assurance Program (SMAP) life cycle and documentation standards were used in the development of this document. Accordingly, these standards were used in the review. Refer to the System/Software Test/Product Assurance Report for the Geosynchronous Satellite Orbital Statistics Database System (GSOSTATS) for additional information.

Reduced Magnetism in Core–Shell Magnetite@MOF Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elsaidi, Sameh K.; Sinnwell, Michael A.; Banerjee, Debasis

Rare-earth elements (REEs) have significant commercial and military uses.1-3 However, REE extraction through conventional mining processes is expensive and feasible at only a few locations worldwide. Alternative methods are needed to produce REEs from more geographically disperse resources and in a cost effective, environmental friendly manner.4,5 Among various sources, geothermal brine, used for generating geothermal energy can possess attractive concentrations (ppb to ppm level) of REEs along with other dissolved metal ions.6 A system that can selectively trap the REEs using an existing geothermal power plant infrastructure would be an attractive additional revenue stream for the plant operator that couldmore » accelerate the development and deployment of geothermal plants in the United States and rest of the world.7,8 Here, we demonstrate a magnetic core-shell approach that can effectively extract REEs in their ionic form from aqueous solution with up to 99.99% removal efficiency. The shell, composed of thermally and chemically stable functionalized metal-organic framework (MOF), is grown over a synthesized Fe3O4 magnetic core. Magnetic susceptibility of the particles was found to decline significantly after in situ growth of a MOF shell, which resulted from oxidation of Fe2+ species of the magnetite (Fe3O4) to Fe3+ species (maghemite). The core-shell particles can be completely removed from the mixture under an applied magnetic field, offering a practical, economic, and efficient REE-removal process.« less

Denitrification by the mix-culturing of fungi and bacteria with shell.

PubMed

Liu, Deli; Zhang, Shan; Zheng, Yongliang; Shoun, Hirofumi

2006-01-01

Denitrification by pure and mixed culture of Fusarium oxysporum and Pseudomonas stutzeri in different mineral medium and in synthetic wastewater were examined. The results obtained revealed that a rapid N2 evolution by F. oxysporum and P. stutzeri in mineral medium and synthetic wastewater was observed. In co-cultures of F. oxysporum and P. stutzeri, N2O produced by F. oxysporum was rapidly consumed by P. stutzeri. This indicated that mixed culture of F. oxysporum and P. stutzeri could be used for efficient nitrate and nitrite removal. Using synthetic wastewater, about 87% of nitrate was reduced by co-denitrification of F. oxysporum and P. stutzeri after incubation for 6 days. In the further denitrification tests, the interaction of shell and mixed culture of F. oxysporum and P. stutzeri was investigated. The dinitrogen was rapidly evolved (442.48 micromol N2 produced from 1.0 mmol of NO3(-) in 36 h). These results clearly showed that shell provide a suitable microenvironment for P. stutzeri, which is beneficial to the denitrification.

Double-shell target fabrication workshop-2016 report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Y. Morris; Oertel, John; Farrell, Michael

On June 30, 2016, over 40 representatives from Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), General Atomics (GA), Laboratory for Laser Energetics (LLE), Schafer Corporation, and NNSA headquarter attended a double-shell (DS) target fabrication workshop at Livermore, California. Pushered-single-shell (PSS) and DS metalgas platforms potentially have a large impact on programmatic applications. The goal of this focused workshop is to bring together target fabrication scientists, physicists, and designers to brainstorm future PSS and DS target fabrication needs and strategies. This one-day workshop intends to give an overall view of historical information, recent approaches, and future research activitiesmore » at each participating organization. Five topical areas have been discussed that are vital to the success of future DS target fabrications, including inner metal shells, foam spheres, outer ablators, fill tube assembly, and metrology.« less

Is there a rationale to use a dual mobility poly insert for failed Birmingham metal-on-metal hip replacements? A retrieval analysis.

PubMed

Renner, Lisa; Faschingbauer, Martin; Boettner, Friedrich

2015-08-01

Previous studies showed poor outcomes for patients undergoing revision of failed metal-on-metal total hip arthroplasty (MoM-THA) and resurfacing (RS) with an increased risk of dislocation. Dual mobility inserts are an option to retain the acetabular component and change the metal-on-metal bearing to plastic-on-metal. The current study analyzes the rationale for the off-label use of a dual mobility poly insert (MDM X3, Stryker, Mahwah, NJ) in a Birmingham metal shell (Smith & Nephew, Memphis, TN). Based on retrievals from the implant database the study compared the clearance between 20 BHR shells, 31 MDM poly inserts and 24 ADM acetabular components of different sizes. The radial clearance was calculated for each possible combination of implants [n = 81 (MDM/BHR) and n = 119 (MDM/ADM)]. An MDM mobile bearing poly insert in an ADM shell has an average clearance of 0.314 mm (SD 0.031) compared to 0.234 mm (SD 0.030) in a BHR shell (p < 0.01). The minimal clearance is 0.246 and 0.163 mm, respectively. 30.9 % of the MDM/BHR clearances were within the range of the MDM/ADM bearing and 88.9 % had a clearance of more than 0.2 mm. Clearances of the MDM poly insert in a BHR shell are reduced, and although the majority of combinations appear safe, the indication needs to be made on an individual base carefully considering alternative treatment options.

Ion-beam-induced magnetic transformation of CO-stabilized fcc Fe films on Cu(100)

NASA Astrophysics Data System (ADS)

Shah Zaman, Sameena; Oßmer, Hinnerk; Jonner, Jakub; Novotný, Zbyněk; Buchsbaum, Andreas; Schmid, Michael; Varga, Peter

2010-12-01

We have grown 22-ML-thick Fe films on a Cu(100) single crystal. The films were stabilized in the face-centered-cubic (fcc) γ phase by adsorption of carbon monoxide during growth, preventing the transformation to the body-centered-cubic (bcc) α phase. A structural transformation of these films from fcc to bcc can be induced by Ar+ ion irradiation. Scanning-tunneling microscopy images show the nucleation of bcc crystallites, which grow with increasing Ar+ ion dose and eventually result in complete transformation of the film to bcc. Surface magneto-optic Kerr effect measurements confirm the transformation of the Fe film from paramagnetic (fcc) to ferromagnetic (bcc) with an in-plane easy axis. The transformation can also be observed by low-energy electron diffraction. We find only very few nucleation sites of the bcc phase and argue that nucleation of the bcc phase happens under special circumstances during resolidification of the molten iron in the thermal spike after ion impact. Intermixing with the Cu substrate impedes the transformation. We also demonstrate the transformation of films coated with Au to protect them from oxidation at ambient conditions.

F4TCNQ on Cu, Ag, and Au as prototypical example for a strong organic acceptor on coinage metals

NASA Astrophysics Data System (ADS)

Rangger, Gerold M.; Hofmann, Oliver T.; Romaner, Lorenz; Heimel, Georg; Bröker, Benjamin; Blum, Ralf-Peter; Johnson, Robert L.; Koch, Norbert; Zojer, Egbert

2009-04-01

Metal work-function modification with the help of organic acceptors is an efficient tool to significantly enhance the performance of modern state-of-the-art organic molecular electronic devices. Here, the prototypical organic acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, F4TCNQ, is characterized on Ag(111), Au(111), and Cu(111) metal surfaces by means of density-functional theory calculations. Particular attention is paid to charge-transfer processes at the metal-organic interface; a subtle balance between charge forward and backward donations in combination with a strong adsorption-induced geometry change are found to be responsible for the observed increase in the system work function. A larger effect is obtained for the metals with larger initial work function. Interestingly, this results in similar charge-injection barriers from the substrate metal into an organic semiconductor deposited on top of the F4TCNQ layer. The impact of the F4TCNQ packing density of the electronic properties of the interface is also addressed. Comparing the calculated energy-level alignments and work-function modifications to experimental data from ultraviolet photoelectron spectroscopy yields good agreement between experiments and simulations.

Types and analysis of defects in welding junctions of the header to steam generator shells on power-generating units with VVER-1000

NASA Astrophysics Data System (ADS)

Ozhigov, L. S.; Voevodin, V. N.; Mitrofanov, A. S.; Vasilenko, R. L.

2016-10-01

Investigation objects were metal templates, which were cut during the repair of welding junction no. 111 (header to the steam generator shell) on a power-generating unit with VVER-1000 of the South-Ukraine NPP, and substances of mud depositions collected from walls of this junction. Investigations were carried out using metallography, optical microscopy, and scanning electron microscopy with energy dispersion microanalysis by an MMO-1600-AT metallurgical microscope and a JEOL JSM-7001F scanning electron microscope with the Shottky cathode. As a result of investigations in corrosion pits and mud depositions in the area of welding junction no. 111, iron and copper-enriched particles were revealed. It is shown that, when contacting with the steel header surface, these particles can form microgalvanic cells causing reactions of iron dissolution and the pit corrosion of metal. Nearby corrosion pits in metal are microcracks, which can be effect of the stress state of metal under corrosion pits along with revealed effects of twinning. The hypothesis is expressed that pitting corrosion of metal occurred during the first operation period of the power-generating unit in the ammonia water chemistry conditions (WCC). The formation of corrosion pits and nucleating cracks from them was stopped with the further operation under morpholine WCC. The absence of macrocracks in metal of templates verifies that, during operation, welding junction no. 111 operated under load conditions not exceeding the permissible ones by design requirements. The durability of the welding junction of the header to the steam generator shell significantly depends on the technological schedule of chemical cleaning and steam generator shut-down cooling.

Can the shell of the green-lipped mussel Perna viridis from the west coast of Peninsular Malaysia be a potential biomonitoring material for Cd, Pb and Zn?

NASA Astrophysics Data System (ADS)

Yap, C. K.; Ismail, A.; Tan, S. G.; Abdul Rahim, I.

2003-07-01

The distributions of Cd, Pb and Zn in the total soft tissues and total shells of the green-lipped mussel Perna viridis were studied in field collected samples as well as from laboratory experimental samples. The results showed that Cd, Pb and Zn were readily accumulated in the whole shells. In mussels sampled from 12 locations along the west coast of Peninsular Malaysia, the ratios of the shell metals to the soft tissue metals were different at each sampling site. Nevertheless, the Cd and Pb levels in the shells were always higher than those in the soft tissues, while the Zn level was higher in the soft tissues than in the shells. In comparison with soft tissues, the degrees of variability for Pb and Cd concentrations in the shells were lower. The lower degrees of variability and significant ( P<0.05) correlation coefficients of Cd and Pb within the shells support the use of the mussel shell as a suitable biomonitoring material for the two metals rather than the soft tissue since this indicated that there is more precision (lower CV) in the determination of metal concentrations in the shell than in the soft tissue. Experimental work showed that the pattern of depuration in the shell was not similar to that of the soft tissue although their patterns of accumulation were similar. This indicated that the depuration of heavy metals in the shell was not affected by the physiological conditions of the mussels. Although Zn could be regulated by the soft tissue, the incorporated Cd, Pb and Zn remained in the shell matrices. The present results support the use of the total shell of P. viridis as a potential biomonitoring material for long-term contamination of Cd, Pb and Zn.

Determination of K shell absorption jump factors and jump ratios of 3d transition metals by measuring K shell fluorescence parameters.

PubMed

Kaçal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

2015-01-01

Energy dispersive X-ray fluorescence technique (EDXRF) has been employed for measuring K-shell absorption jump factors and jump ratios for Ti, Cr, Fe, Co, Ni and Cu elements. The jump factors and jump ratios for these elements were determined by measuring K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to-Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using a Cd-109 radioactive point source and an Si(Li) detector in direct excitation and transmission experimental geometry. The measured values for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Two-Layer 16 Tesla Cosθ Dipole Design for the FCC

DOE PAGES

Holik, Eddie Frank; Ambrosio, Giorgio; Apollinari, G.

2018-02-13

The Future Circular Collider or FCC is a study aimed at exploring the possibility to reach 100 TeV total collision energy which would require 16 tesla dipoles. Upon the conclusion of the High Luminosity Upgrade, the US LHC Accelerator Upgrade Pro-ject in collaboration with CERN will have extensive Nb3Sn magnet fabrication experience. This experience includes robust Nb3Sn conductor and insulation scheming, 2-layer cos2θ coil fabrication, and bladder-and-key structure and assembly. By making im-provements and modification to existing technology the feasibility of a two-layer 16 tesla dipole is investigated. Preliminary designs indicate that fields up to 16.6 tesla are feasible withmore » conductor grading while satisfying the HE-LHC and FCC specifications. Key challenges include accommodating high-aspect ratio conductor, narrow wedge design, Nb3Sn conductor grading, and especially quench protection of a 16 tesla device.« less

Two-Layer 16 T Cos θ Dipole Design for the FCC

DOE PAGES

Holik, Eddie Frank; Ambrosio, Giorgio; Apollinari, Giorgio

2018-02-22

Here, the Future Circular Collider or FCC is a study aimed at exploring the possibility to reach 100 TeV total collision energy which would require 16 tesla dipoles. Upon the conclusion of the High Luminosity Upgrade, the US LHC Accelerator Upgrade Pro-ject in collaboration with CERN will have extensive Nb 3Sn magnet fabrication experience. This experience includes robust Nb 3Sn conductor and insulation scheming, 2-layer cos2θ coil fabrication, and bladder-and-key structure and assembly. By making im-provements and modification to existing technology the feasibility of a two-layer 16 tesla dipole is investigated. Preliminary designs indicate that fields up to 16.6 teslamore » are feasible with conductor grading while satisfying the HE-LHC and FCC specifications. Key challenges include accommodating high-aspect ratio conductor, narrow wedge design, Nb 3Sn conductor grading, and especially quench protection of a 16 tesla device.« less

Two-Layer 16 T Cos θ Dipole Design for the FCC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holik, Eddie Frank; Ambrosio, Giorgio; Apollinari, Giorgio

Here, the Future Circular Collider or FCC is a study aimed at exploring the possibility to reach 100 TeV total collision energy which would require 16 tesla dipoles. Upon the conclusion of the High Luminosity Upgrade, the US LHC Accelerator Upgrade Pro-ject in collaboration with CERN will have extensive Nb 3Sn magnet fabrication experience. This experience includes robust Nb 3Sn conductor and insulation scheming, 2-layer cos2θ coil fabrication, and bladder-and-key structure and assembly. By making im-provements and modification to existing technology the feasibility of a two-layer 16 tesla dipole is investigated. Preliminary designs indicate that fields up to 16.6 teslamore » are feasible with conductor grading while satisfying the HE-LHC and FCC specifications. Key challenges include accommodating high-aspect ratio conductor, narrow wedge design, Nb 3Sn conductor grading, and especially quench protection of a 16 tesla device.« less

Engineered magnetic core shell nanoprobes: Synthesis and applications to cancer imaging and therapeutics.

PubMed

Mandal, Samir; Chaudhuri, Keya

2016-02-26

Magnetic core shell nanoparticles are composed of a highly magnetic core material surrounded by a thin shell of desired drug, polymer or metal oxide. These magnetic core shell nanoparticles have a wide range of applications in biomedical research, more specifically in tissue imaging, drug delivery and therapeutics. The present review discusses the up-to-date knowledge on the various procedures for synthesis of magnetic core shell nanoparticles along with their applications in cancer imaging, drug delivery and hyperthermia or cancer therapeutics. Literature in this area shows that magnetic core shell nanoparticle-based imaging, drug targeting and therapy through hyperthermia can potentially be a powerful tool for the advanced diagnosis and treatment of various cancers.

Controlled Synthesis and Utilization of Metal and Oxide Hybrid Nanoparticles

NASA Astrophysics Data System (ADS)

Crane, Cameron

This dissertation reports the development of synthetic methods concerning rationally-designed, hybrid, and multifunctional nanomaterials. These methods are based on a wet chemical, solution phase approach that utilizes the knowledge of synthetic organic and inorganic chemistry to generate building blocks in solution for the growth of nanocrystals and hybrid nanostructures. This work builds on the prior knowledge of shape-controlled synthesis of noble metal nanocrystals and expands into the challenging realm of the more reactive first row transition metals. Specifically, a microemulsion sol-gel method was developed to synthesize Au-SiO2 dimers as precursors for the synthesis of segmented heterostructures of noble metals that can be used for catalysis. This microemulsion sol-gel method was modified to synthesize an aqueous suspension of oxidation-resistant Cu-SiO2 core-shell nanoparticles that can be used for sensing and catalysis. A thermal decomposition approach was developed, wherein zero-valence metal precursor complexes in the presence of seed nanoparticles produced metal-metal oxide core-shell structures with well-controlled shell thickness. This method was demonstrated on AuCu 3-Fe3O4, AuCu3-NiO, and AuCu3 -MnO core-shell systems. Switching the core from AuCu3 alloy to pure Cu, this method could extend to Cu-Fe3O4 and Cu-MnO systems. Further etching the Cu core in these core-shell structures led to the formation of the hollow metal oxides which provides a versatile route to hollow nanostructures of metal oxides. This work develops the synthetic library of tools for the production of hybrid nanostructures with multiple functionalities.

47 CFR 73.4060 - Citizens agreements.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., Docket 20495, FCC 75-1359, adopted December 10, 1975. 57 F.C.C. 2d 42; 40 F.R. 49730, December 30, 1975. (b) See Memorandum Opinion and Order, FCC 78-875, adopted December 21, 1978. 70 F.C.C. 2d 1672. [44...

Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts

NASA Astrophysics Data System (ADS)

Sun, Ligang; He, Xiaoqiao; Lu, Jian

2018-02-01

The recent studies on nanotwinned (NT) and hierarchical nanotwinned (HNT) face-centered cubic (FCC) metals are presented in this review. The HNT structures have been supposed as a kind of novel structure to bring about higher strength/ductility than NT counterparts in crystalline materials. We primarily focus on the recent developments of the experimental, atomistic and theoretical studies on the NT and HNT structures in the metallic materials. Some advanced bottom-up and top-down techniques for the fabrication of NT and HNT structures are introduced. The deformation induced HNT structures are available by virtue of severe plastic deformation (SPD) based techniques while the synthesis of growth HNT structures is so far almost unavailable. In addition, some representative molecular dynamics (MD) studies on the NT and HNT FCC metals unveil that the nanoscale effects such as twin spacing, grain size and plastic anisotropy greatly alter the performance of NT and HNT metals. The HNT structures may initiate unique phenomena in comparison with the NT ones. Furthermore, based on the phenomena and mechanisms revealed by experimental and MD simulation observations, a series of theoretical models have been proposed. They are effective to describe the mechanical behaviors of NT and HNT metals within the applicable scope. So far the development of manufacturing technologies of HNT structures, as well as the studies on the effects of HNT structures on the properties of metals are still in its infancy. Further exploration is required to promote the design of advanced materials.

X-ray Fluorescence Tomography of Aged Fluid-Catalytic-Cracking Catalyst Particles Reveals Insight into Metal Deposition Processes.

PubMed

Kalirai, Sam; Boesenberg, Ulrike; Falkenberg, Gerald; Meirer, Florian; Weckhuysen, Bert M

2015-11-01

Microprobe X-ray fluorescence tomography was used to investigate metal poison deposition in individual, intact and industrially deactivated fluid catalytic cracking (FCC) particles at two differing catalytic life-stages. 3 D multi-element imaging, at submicron resolution was achieved by using a large-array Maia fluorescence detector. Our results show that Fe, Ni and Ca have significant concentration at the exterior of the FCC catalyst particle and are highly co-localized. As concentrations increase as a function of catalytic life-stage, the deposition profiles of Fe, Ni, and Ca do not change significantly. V has been shown to penetrate deeper into the particle with increasing catalytic age. Although it has been previously suggested that V is responsible for damaging the zeolite components of FCC particles, no spatial correlation was found for V and La, which was used as a marker for the embedded zeolite domains. This suggests that although V is known to be detrimental to zeolites in FCC particles, a preferential interaction does not exist between the two.

Modelling of Surfaces. Part 1: Monatomic Metallic Surfaces Using Equivalent Crystal Theory

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John; Rodriguez, Agustin M.

1994-01-01

We present a detailed description of equivalent crystal theory focusing on its application to the study of surface structure. While the emphasis is in the structure of the algorithm and its computational aspects, we also present a comprehensive discussion on the calculation of surface energies of metallic systems with equivalent crystal theory and other approaches. Our results are compared to experiment and other semiempirical as well as first-principles calculations for a variety of fcc and bcc metals.

Catalytic performance of M@Ni (M = Fe, Ru, Ir) core-shell nanoparticles towards ammonia decomposition for CO x -free hydrogen production

NASA Astrophysics Data System (ADS)

Chen, Xin; Zhou, Junwei; Chen, Shuangjing; Zhang, Hui

2018-06-01

To reduce the use of precious metals and maintain the catalytic activity for NH3 decomposition reaction, it is an effective way to construct bimetallic nanoparticles with special structures. In this paper, by using density functional theory methods, we investigated NH3 decomposition reaction on three types of core-shell nanoparticles M@Ni (M = Fe, Ru, Ir) with 13 core M atoms and 42 shell Ni atoms. The size of these three particles is about 1 nm. Benefit from alloying with Ru in this nanocluster, Ru@Ni core-shell nanoparticles exhibit catalytic activity comparable to that of single metal Ru, based on the analysis of the adsorption energy and potential energy diagram of NH3 decomposition, as well as N2 desorption processes. However, as for Fe@Ni and Ir@Ni core-shell nanoparticles, their catalytic activities are still unsatisfactory compared to the active metal Ru. In addition, in order to further explain the synergistic effect of bimetallic core-shell nanoparticles, the partial density of states were also calculated. The results show that d-band electrons provided by the core metal are the main factors affecting the entire catalytic process.