Anode materials for lithium-ion batteries

DOEpatents

Sunkara, Mahendra Kumar; Meduri, Praveen; Sumanasekera, Gamini

2014-12-30

An anode material for lithium-ion batteries is provided that comprises an elongated core structure capable of forming an alloy with lithium; and a plurality of nanostructures placed on a surface of the core structure, with each nanostructure being capable of forming an alloy with lithium and spaced at a predetermined distance from adjacent nanostructures.

Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

2004-01-01

The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

In-situ synthetize multi-walled carbon nanotubes@MnO2 nanoflake core-shell structured materials for supercapacitors

NASA Astrophysics Data System (ADS)

Zheng, Huajun; Wang, Jiaoxia; Jia, Yi; Ma, Chun'an

2012-10-01

A new type of core-shell structured material consisting of multi-walled carbon nanotubes (MWCNTs) and manganese dioxide (MnO2) nanoflake is synthesized using an in-situ co-precipitation method. By scanning electron microscopy and transition electron microscope, it is confirmed that the core-shell nanostructure is formed by the uniform incorporation of birnessite-type MnO2 nanoflake growth round the surface of the activated-MWCNTs. That core-shell structured material electrode presents excellent electrochemical capacitance properties with the specific capacitance reaching 380 F g-1 at the current density of 5 A g-1 in 0.5 M Na2SO4 electrolyte. In addition, the electrode also exhibits good performance (the power density: 11.28 kW kg-1 at 5 A g-1) and long-term cycling stability (retaining 82.7% of its initial capacitance after 3500 cycles at 5 A g-1). It mainly attributes to MWCNTs not only providing considerable specific surface area for high mass loading of MnO2 nanoflakes to ensure effective utilization of MnO2 nanoflake, but also offering an electron pathway to improve electrical conductivity of the electrode materials. It is clearly indicated that such core-shell structured materials including MWCNTs and MnO2 nanoflake may find important applications for supercapacitors.

Structural materials for NASP

NASA Astrophysics Data System (ADS)

Ronald, Terence M. F.

1991-12-01

Structural materials for the NASP X-30 experimental vehicle are briefly reviewed including titanium alloys, titanium-based metal-matrix composites, carbon-carbon composites, ceramic-matrix composites, and copper-matrix composites. Areas of application of these materials include the airframe where these materials would be used as lightweight skin panels for honeycomb-core, truss-core, or integrally stiffened thin sheet configuration; and the engine, where they would be used in the hot gas path of the ramjet/scramjet, and in the inlet and nozzle areas.

Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Dexter, Benson H.

1996-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

Fabrication method for cores of structural sandwich materials including star shaped core cells

DOEpatents

Christensen, Richard M.

1997-01-01

A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded.

Structural materials issues for the next generation fission reactors

NASA Astrophysics Data System (ADS)

Chant, I.; Murty, K. L.

2010-09-01

Generation-IV reactor design concepts envisioned thus far cater to a common goal of providing safer, longer lasting, proliferation-resistant, and economically viable nuclear power plants. The foremost consideration in the successful development and deployment of Gen-W reactor systems is the performance and reliability issues involving structural materials for both in-core and out-of-core applications. The structural materials need to endure much higher temperatures, higher neutron doses, and extremely corrosive environments, which are beyond the experience of the current nuclear power plants. Materials under active consideration for use in different reactor components include various ferritic/martensitic steels, austenitic stainless steels, nickel-base superalloys, ceramics, composites, etc. This article addresses the material requirements for these advanced fission reactor types, specifically addressing structural materials issues depending on the specific application areas.

High performance carbon nanotube-Si core-shell wires with a rationally structured core for lithium ion battery anodes.

PubMed

Fan, Yu; Zhang, Qing; Lu, Congxiang; Xiao, Qizhen; Wang, Xinghui; Tay, Beng Kang

2013-02-21

Core-shell Si nanowires are very promising anode materials. Here, we synthesize vertically aligned carbon nanotubes (CNTs) with relatively large diameters and large inter-wire spacing as core wires and demonstrate a CNT-Si core-shell wire composite as a lithium ion battery (LIB) anode. Owing to the rationally engineered core structure, the composite shows good capacity retention and rate performance. The excellent performance is superior to most core-shell nanowires previously reported.

Method of laminating structural members

NASA Technical Reports Server (NTRS)

Heier, W. C. (Inventor)

1974-01-01

A laminate is obtained by providing a lightweight core material, such as a honeycombed plastic or metal, within the cavity defined by an annular mold cavity frame. Face sheets, which are to be bonded to the core material, are provided on opposite sides of the frame and extend over the frame, thus sealing the core material in the cavity. An adhesive is provided between the core material and the face sheets and the combined thickness of the core material and adhesive is a close fit within the opposed face sheets. A gas tight seal, such as an O-ring gasket, is provided between the frame and the face sheet members to form a gas tight cavity between the face sheet members and the frame. External heat and pressure are used to bond the face sheets to the core material. Gas pressure is introduced into the sealed cavity to minimize out-gasing of the adhesive.

Analysis of Stainless Steel Sandwich Panels with a Metal Foam Care for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

2004-01-01

The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. Traditionally, these components have been fabricated using expensive materials such as light weight titanium alloys, polymeric composite materials and carbon-carbon composites. The present study investigates the use of P sandwich foam fan blade made up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The stiffness of the sandwich structure is increased by separating the two face sheets by a foam core. The resulting structure possesses a high stiffness while being lighter than a similar solid construction. Since the face sheets carry the applied bending loads, the sandwich architecture is a viable engineering concept. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of the sandwich structure for a fan blade application. A vibration analysis for natural frequencies and P detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of skin thickness and core volume %re presented with a comparison to a solid titanium blade.

Fabrication method for cores of structural sandwich materials including star shaped core cells

DOEpatents

Christensen, R.M.

1997-07-15

A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells is disclosed. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded. 3 figs.

Honeycomb-laminate composite structure

NASA Technical Reports Server (NTRS)

Gilwee, W. J., Jr.; Parker, J. A. (Inventor)

1977-01-01

A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.

Systematic technology evaluation program for SiC/SiC composite-based accident-tolerant LWR fuel cladding and core structures: Revision 2015

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

Katoh, Yutai; Terrani, Kurt A.

2015-08-01

Fuels and core structures in current light water reactors (LWR’s) are vulnerable to catastrophic failure in severe accidents as unfortunately evidenced by the March 2011 Fukushima Dai-ichi Nuclear Power Plant Accident. This vulnerability is attributed primarily to the rapid oxidation kinetics of zirconium alloys in a water vapor environment at very high temperatures. Zr alloys are the primary material in LWR cores except for the fuel itself. Therefore, alternative materials with reduced oxidation kinetics as compared to zirconium alloys are sought to enable enhanced accident-tolerant fuels and cores.

Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

NASA Technical Reports Server (NTRS)

Yasensky, John; Christiansen, Eric L.

2007-01-01

A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

Synthesis of carbon core–shell pore structures and their performance as supercapacitors

DOE PAGES

Ariyanto, Teguh; Dyatkin, Boris; Zhang, Gui-Rong; ...

2015-07-15

High-power supercapacitors require excellent electrolyte mobility within the pore network and high electrical conductivity for maximum capacitance and efficiency. Achieving high power typically requires sacrificing energy densities, as the latter demands a high specific surface area and narrow porosity that impedes ion transport. Here, we present a novel solution for this optimization problem: a nanostructured core–shell carbonaceous material that exhibits a microporous carbon core surrounded by a mesoporous, graphitic shell. The tunable synthesis parameters yielded a structure that features either a sharp or a gradual transition between the core and shell sections. Electrochemical supercapacitor testing using organic electrolyte revealed thatmore » these novel core–shell materials outperform carbons with homogeneous pore structures. The hybrid core–shell materials showed a combination of good capacitance retention, typical for the carbon present in the shell and high specific capacitance, typical for the core material. These materials achieved power densities in excess of 40 kW kg -1 at energy densities reaching 27 Wh kg -1.« less

Influence of the supporting die structures on the fracture strength of all-ceramic materials.

PubMed

Yucel, Munir Tolga; Yondem, Isa; Aykent, Filiz; Eraslan, Oğuz

2012-08-01

This study investigated the influence of the elastic modulus of supporting dies on the fracture strengths of all-ceramic materials used in dental crowns. Four different types of supporting die materials (dentin, epoxy resin, brass, and stainless steel) (24 per group) were prepared using a milling machine to simulate a mandibular molar all-ceramic core preparation. A total number of 96 zirconia cores were fabricated using a CAD/CAM system. The specimens were divided into two groups. In the first group, cores were cemented to substructures using a dual-cure resin cement. In the second group, cores were not cemented to the supporting dies. The specimens were loaded using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture occurred. Data were statistically analyzed using two-way analysis of variance and Tukey HSD tests (α = 0.05). The geometric models of cores and supporting die materials were developed using finite element method to obtain the stress distribution of the forces. Cemented groups showed statistically higher fracture strength values than non-cemented groups. While ceramic cores on stainless steel dies showed the highest fracture strength values, ceramic cores on dentin dies showed the lowest fracture strength values among the groups. The elastic modulus of the supporting die structure is a significant factor in determining the fracture resistance of all-ceramic crowns. Using supporting die structures that have a low elastic modulus may be suitable for fracture strength tests, in order to accurately reflect clinical conditions.

Energy-Absorbing Beam Member

NASA Technical Reports Server (NTRS)

Littell, Justin D. (Inventor)

2017-01-01

An energy-absorbing (EA) beam member and having a cell core structure is positioned in an aircraft fuselage proximate to the floor of the aircraft. The cell core structure has a length oriented along a width of the fuselage, a width oriented along a length of the fuselage, and a depth extending away from the floor. The cell core structure also includes cell walls that collectively define a repeating conusoidal pattern of alternating respective larger and smaller first and second radii along the length of the cell core structure. The cell walls slope away from a direction of flight of the aircraft at a calibrated lean angle. An EA beam member may include the cell core structure and first and second plates along the length of the cell core structure on opposite edges of the cell material.

GVIPS Models and Software

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Gendy, Atef; Saleeb, Atef F.; Mark, John; Wilt, Thomas E.

2007-01-01

Two reports discuss, respectively, (1) the generalized viscoplasticity with potential structure (GVIPS) class of mathematical models and (2) the Constitutive Material Parameter Estimator (COMPARE) computer program. GVIPS models are constructed within a thermodynamics- and potential-based theoretical framework, wherein one uses internal state variables and derives constitutive equations for both the reversible (elastic) and the irreversible (viscoplastic) behaviors of materials. Because of the underlying potential structure, GVIPS models not only capture a variety of material behaviors but also are very computationally efficient. COMPARE comprises (1) an analysis core and (2) a C++-language subprogram that implements a Windows-based graphical user interface (GUI) for controlling the core. The GUI relieves the user of the sometimes tedious task of preparing data for the analysis core, freeing the user to concentrate on the task of fitting experimental data and ultimately obtaining a set of material parameters. The analysis core consists of three modules: one for GVIPS material models, an analysis module containing a specialized finite-element solution algorithm, and an optimization module. COMPARE solves the problem of finding GVIPS material parameters in the manner of a design-optimization problem in which the parameters are the design variables.

Light-weight sandwich panel honeycomb core with hybrid carbon-glass fiber composite skin for electric vehicle application

NASA Astrophysics Data System (ADS)

Cahyono, Sukmaji Indro; Widodo, Angit; Anwar, Miftahul; Diharjo, Kuncoro; Triyono, Teguh; Hapid, A.; Kaleg, S.

2016-03-01

The carbon fiber reinforced plastic (CFRP) composite is relative high cost material in current manufacturing process of electric vehicle body structure. Sandwich panels consisting polypropylene (PP) honeycomb core with hybrid carbon-glass fiber composite skin were investigated. The aim of present paper was evaluate the flexural properties and bending rigidity of various volume fraction carbon-glass fiber composite skins with the honeycomb core. The flexural properties and cost of panels were compared to the reported values of solid hybrid Carbon/Glass FRP used for the frame body structure of electric vehicle. The finite element model of represented sandwich panel was established to characterize the flexural properties of material using homogenization technique. Finally, simplified model was employed to crashworthiness analysis for engine hood of the body electric vehicle structure. The good cost-electiveness of honeycomb core with hybrid carbon-glass fiber skin has the potential to be used as a light-weight alternative material in body electric vehicle fabricated.

Development and modeling of multi-phase polymeric origami inspired architecture by using pre-molded geometrical features

NASA Astrophysics Data System (ADS)

Kshad, Mohamed Ali E.; Naguib, Hani E.

2017-02-01

Using Origami folded cores in sandwich structures for lightweight applications has attracted attention in different engineering applications, especially in the applications where the stiffness to weight ratio is a critical design parameter. Recently, common sandwich cores such as honey-comb and foamed cores have been replaced with origami core panels due to their way of force redistribution and energy absorption; these unique characteristics give origami cores high stiffness to weight ratio and high bending and twisting resistance. This paper presents the results of experimental investigations of the effect of base material on the mechanical properties and the impact resistance of Miura-Origami sandwich cores; then, the experimental results are compared with FEA simulation results. The materials used in the study for the origami cores were polymer blends composed of polylactic acid (PLA) and thermoplastic polyurethane (TPU). PLA/TPU blend compositions are (100/0, 80/20, 65/35, 50/50, 20/80, and 0/100) as a weight percentage. The geometrical parameters of the unit cell, base material thickness, and the panel thickness were considered to be constants in this study. The study shows the behavior of the origami cores under impact test and the energy absorbed by the origami folded cores. It was found that 20/80 PLA/TPU blend demonstrated the highest specific energy absorption efficiency both in quasi-static compression and impact tests. Fractured Origami structures were observed to fail at folded edges (creases lines), while the facets exhibit rigid body rotations. The FEM simulation showed a consistency in the impact behavior of the origami cores, and the directional deformational of origami core units which explain the ability of the structure to redistribute the applied force and absorb energy. In this work the origami folded core features were molded directly from the blended material.

Design, synthesis and applications of core-shell, hollow core, and nanorattle multifunctional nanostructures.

PubMed

El-Toni, Ahmed Mohamed; Habila, Mohamed A; Labis, Joselito Puzon; ALOthman, Zeid A; Alhoshan, Mansour; Elzatahry, Ahmed A; Zhang, Fan

2016-02-07

With the evolution of nanoscience and nanotechnology, studies have been focused on manipulating nanoparticle properties through the control of their size, composition, and morphology. As nanomaterial research has progressed, the foremost focus has gradually shifted from synthesis, morphology control, and characterization of properties to the investigation of function and the utility of integrating these materials and chemical sciences with the physical, biological, and medical fields, which therefore necessitates the development of novel materials that are capable of performing multiple tasks and functions. The construction of multifunctional nanomaterials that integrate two or more functions into a single geometry has been achieved through the surface-coating technique, which created a new class of substances designated as core-shell nanoparticles. Core-shell materials have growing and expanding applications due to the multifunctionality that is achieved through the formation of multiple shells as well as the manipulation of core/shell materials. Moreover, core removal from core-shell-based structures offers excellent opportunities to construct multifunctional hollow core architectures that possess huge storage capacities, low densities, and tunable optical properties. Furthermore, the fabrication of nanomaterials that have the combined properties of a core-shell structure with that of a hollow one has resulted in the creation of a new and important class of substances, known as the rattle core-shell nanoparticles, or nanorattles. The design strategies of these new multifunctional nanostructures (core-shell, hollow core, and nanorattle) are discussed in the first part of this review. In the second part, different synthesis and fabrication approaches for multifunctional core-shell, hollow core-shell and rattle core-shell architectures are highlighted. Finally, in the last part of the article, the versatile and diverse applications of these nanoarchitectures in catalysis, energy storage, sensing, and biomedicine are presented.

An assessment of fracture resistance of three composite resin core build-up materials on three prefabricated non-metallic posts, cemented in endodontically treated teeth: an in vitro study

PubMed Central

Pal, Bhupinder; Pujari, Prashant

2015-01-01

Endodontically treated teeth with excessive loss of tooth structure would require to be restored with post and core to enhance the strength and durability of the tooth and to achieve retention for the restoration. The non-metallic posts have a superior aesthetic quality. Various core build-up materials can be used to build-up cores on the posts placed in endodontically treated teeth. These materials would show variation in their bonding with the non-metallic posts thus affecting the strength and resistance to fracture of the remaining tooth structure. Aims. The aim of the study was to assess the fracture resistance of three composite resin core build-up materials on three prefabricated non-metallic posts, cemented in extracted endodontically treated teeth. Material and Methods. Forty-five freshly extracted maxillary central incisors of approximately of the same size and shape were selected for the study. They were divided randomly into 3 groups of 15 each, depending on the types of non-metallic posts used. Each group was further divided into 3 groups (A, B and C) of 5 samples each depending on three core build-up material used. Student’s unpaired ‘t’ test was also used to analyse and compare each group with the other groups individually, and decide whether their comparisons were statistically significant. Results. Luxacore showed the highest fracture resistance among the three core build-up materials with all the three posts systems. Ti-core had intermediate values of fracture resistance and Lumiglass had the least values of fracture resistance. PMID:25755926

Magnetic Behavior of Ni-Fe Core-Shell and Alloy Nanowires

NASA Astrophysics Data System (ADS)

Tripathy, Jagnyaseni; Vargas, Jose; Spinu, Leonard; Wiley, John

2013-03-01

Template assisted synthesis was used to fabricate a series of Ni-Fe core-shell and alloy nanowires. By controlling reaction conditions as well as pore structure, both systems could be targeted and magnetic properties followed as a function of architectures. In the core-shell structure coercivity increases with decrease in shell thickness while for the alloys, coercivity squareness improve with increase pore diameter. Details on the systematic studies of these materials will be presented in terms of hysteretic measurements, including first order reversal curves (FORC), and FMR data. Magnetic variation as a function of structure and nanowire aspect ratios will be presented and the origins of these behaviors discussed. Advanced Material Research Institute

Failure modes and materials design for biomechanical layer structures

NASA Astrophysics Data System (ADS)

Deng, Yan

Ceramic materials are finding increasing usage in the area of biomechanical replacements---dental crowns, hip and bone implants, etc.---where strength, wear resistance, biocompatibility, chemical durability and even aesthetics are critical issues. Aesthetic ceramic crowns have been widely used in dentistry to replace damaged or missing teeth. However, the failure rates of ceramic crowns, especially all-ceramic crowns, can be 1%˜6% per year, which is not satisfactory to patients. The materials limitations and underlying fracture mechanisms of these prostheses are not well understood. In this thesis, fundamental fracture and damage mechanisms in model dental bilayer and trilayer structures are studied. Principle failure modes are identified from in situ experimentation and confirmed by fracture mechanics analysis. In bilayer structures of ceramic/polycarbonate (representative of ceramic crown/dentin structure), three major damage sources are identified: (i) top-surface cone cracks or (ii) quasiplasticity, dominating in thick ceramic bilayers; (iii) bottom-surface radial cracks, dominating in thin ceramic bilayers. Critical load P for each damage mode are measured in six dental ceramics: Y-TZP zirconia, glass-infiltrated zirconia and alumina (InCeram), glass-ceramic (Empress II), Porcelain (Mark II and Empress) bonded to polymer substrates, as a function of ceramic thickness d in the range of 100 mum to 10 mm. P is found independent of d for mode (i) and (ii), but has a d 2 relations for mode (iii)---bottom surface radial cracking. In trilayer structures of glass/core-ceramic/polycarbonate (representing veneer porcelain/core/dentin structures), three inner fracture origins are identified: radial cracks from the bottom surface in the (i) first and (ii) second layers; and (iii) quasiplasticity in core-ceramic layer. The role of relative veneer/core thickness, d1/d 2 and materials properties is investigated for three core materials with different modulus (114--270GPa) and strength (400--1400MPa): Y-TZP zirconia, InCeram alumina and Empress II glass-ceramic. Explicit relations for the critical loads P to produce these different damage modes in bilayer and trilayer structures are developed in terms of basic material properties (modulus E, strength, hardness H and toughness T) and geometrical variables (thickness d and contact sphere radius r). These experimentally validated relations are used to design of optimal material combinations for improved fracture resistance and to predict mechanical performance of current dental materials.

Broadband absorption and enhanced photothermal conversion property of octopod-like Ag@Ag2S core@shell structures with gradually varying shell thickness.

PubMed

Jiang, Qian; Zeng, Wenxia; Zhang, Canying; Meng, Zhaoguo; Wu, Jiawei; Zhu, Qunzhi; Wu, Daxiong; Zhu, Haitao

2017-12-19

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag 2 S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag 2 S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag 2 S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag 2 S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Study on micro-bend light transmission performance of novel liquid-core optical fiber

NASA Astrophysics Data System (ADS)

Ma, Junyan; Zhao, Zhimin; Wang, Kaisheng; Guo, Linfeng

2007-01-01

With the increasing development of material technology and electronic integration technology, optical fiber and its using in smart structure have become hot in the field of material research. And liquid-core optical fiber is a special kind of optical fiber, which is made using liquid material as core and polymer material as optical layer and protective covering, and it has the characteristics of large core diameter, high numerical aperture, large-scope and efficient spectrum transmission and long life for using. So the liquid-core optical fiber is very suitable for spectrum cure, ultraviolet solidification, fluorescence detection, criminal investigation and evidence obtainment, etc, and especially as light transfer element in some new structures for the measurement of some signals, such as concentration, voltage, temperature, light intensity and so on. In this paper, the novel liquid-core optical fiber is self-made, and then through the test of its light transmission performance in free state, the relation between axial micro-bend and light-intensity loss are presented. When the liquid-core optical fiber is micro-bent axially, along with the axial displacement's increase, output power of light is reducing increasingly, and approximately has linear relation to micro-displacement in a range. According to the results liquid-core fiber-optic micro-bend sensor can be designed to measure micro-displacement of the tested objects. Experimental data and analysis provide experimental basis for further application of liquid-core optical fiber.

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

Wang Shumin; Tian Hongwei; Pei Yanhui

A novel hedgehog-like core/shell structure, consisting of a high density of vertically aligned graphene sheets and a thin graphene shell/a copper core (VGs-GS/CC), has been synthesized via a simple one-step synthesis route using radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Scanning and transmission electron microscopy investigations show that the morphology of this core/shell material could be controlled by deposition time. For a short deposition time, only multilayer graphene shell tightly surrounds the copper particle, while as the deposition time is relative long, graphene sheets extend from the surface of GS/CC. The GS can protect CC particles from oxidation. The growth mechanismmore » for the obtained GS/CC and VGs-GS/CC has been revealed. Compared to VGs, VGs-GS/CC material exhibits a better electron field emission property. This investigation opens a possibility for designing a core/shell structure of different carbon-metal hybrid materials for a wide variety of practical applications. - Graphical abstract: With increasing deposition time, graphene sheets extend from the surface of GS/CC, causing the multilayer graphene encapsulated copper to be converted into vertically aligned graphene sheets-graphene shell/copper core structure. Highlights: Black-Right-Pointing-Pointer A novel hedgehog-like core/shell structure has been synthesized. Black-Right-Pointing-Pointer The structure consists of vertical graphene sheets-graphene shell and copper core. Black-Right-Pointing-Pointer The morphology of VGs-GS/CC can be controlled by choosing a proper deposition time. Black-Right-Pointing-Pointer With increasing deposition time, graphene sheets extend from the surface of GS/CC. Black-Right-Pointing-Pointer VGs-GS/CC exhibits a better electron field emission property as compared with VGs.« less

Synthesis of Engineered Zeolitic Materials: From Classical Zeolites to Hierarchical Core-Shell Materials.

PubMed

Masoumifard, Nima; Guillet-Nicolas, Rémy; Kleitz, Freddy

2018-04-01

The term "engineered zeolitic materials" refers to a class of materials with a rationally designed pore system and active-sites distribution. They are primarily made of crystalline microporous zeolites as the main building blocks, which can be accompanied by other secondary components to form composite materials. These materials are of potential importance in many industrial fields like catalysis or selective adsorption. Herein, critical aspects related to the synthesis and modification of such materials are discussed. The first section provides a short introduction on classical zeolite structures and properties, and their conventional synthesis methods. Then, the motivating rationale behind the growing demand for structural alteration of these zeolitic materials is discussed, with an emphasis on the ongoing struggles regarding mass-transfer issues. The state-of-the-art techniques that are currently available for overcoming these hurdles are reviewed. Following this, the focus is set on core-shell composites as one of the promising pathways toward the creation of a new generation of highly versatile and efficient engineered zeolitic substances. The synthesis approaches developed thus far to make zeolitic core-shell materials and their analogues, yolk-shell, and hollow materials, are also examined and summarized. Finally, the last section concisely reviews the performance of novel core-shell, yolk-shell, and hollow zeolitic materials for some important industrial applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computational Investigation of Shock-Mitigation Efficacy of Polyurea When Used in a Combat Helmet

DTIC Science & Technology

2012-01-01

Multidiscipline Modeling in Materials and Structures Emerald Article: Computational investigation of shock-mitigation efficacy of polyurea when used...mitigation efficacy of polyurea when used in a combat helmet: A core sample analysis", Multidiscipline Modeling in Materials and Structures, Vol. 8 Iss...to 00-00-2012 4. TITLE AND SUBTITLE Computational investigation of shock-mitigation efficacy of polyurea when used in a combat helmet: A core

Development of a core sheath process for production of oxide fibers

NASA Technical Reports Server (NTRS)

Freske, S.

1972-01-01

Improvements were sought in an oxide fiber of a core sheath configuration intended for structural applications at 2000 F (1093 C). Discontinuities in the core were eliminated by using core materials other than pure alumina, and continuous core sheath fibers were produced. In the case of some core materials, the continuous sections were sufficiently long for applications in short fiber composites. Creep at 2000 F (1093 C) was found to be due, in most cases, to breaks in the core, allowing the glass sheath to creep. Evidence was obtained indicating that a closer match between the thermal expansion coefficient of the sheath and the core would greatly improve the strength.

Prepreg effects on honeycomb composite manufacturing

NASA Astrophysics Data System (ADS)

Martin, Cary Joseph

Fiber reinforced composites offer many advantages over traditional materials and are widely utilized in aerospace applications. Advantages include a high stiffness to weight ratio and excellent fatigue resistance. However, the pace of new implementation is slow. The manufacturing processes used to transform composite intermediates into final products are poorly understood and are a source of much variability. This limits new implementation and increases the manufacturing costs of existing designs. One such problem is honeycomb core crush, in which a core-stiffened structure collapses during autoclave manufacture, making the structure unusable and increasing the overall manufacturing cost through increased scrap rates. Consequently, the major goal of this research was to investigate the scaling of core crush from prepreg process-structure-property relations to commercial composite manufacture. The material dependent nature of this defect was of particular interest. A methodology and apparatus were developed to measure the frictional resistance of prepreg materials under typical processing conditions. Through a characterization of commercial and experimental prepregs, it was found that core crush behavior was the result of differences in prepreg frictional resistance. This frictional resistance was related to prepreg morphology and matrix rheology and elasticity. Resin composition and prepreg manufacturing conditions were also found to affect manufacturing behavior. Mechanical and dimensional models were developed and demonstrated utility for predicting this crushing behavior. Collectively, this work explored and identified the process-structure-property relations as they relate to the manufacture of composite materials and suggested several avenues by which manufacturing-robust materials may be developed.

Zirconium(IV) oxide: New coating material for nanoresonators for shell-isolated nanoparticle-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Krajczewski, Jan; Abdulrahman, Heman Burhanalden; Kołątaj, Karol; Kudelski, Andrzej

2018-03-01

One tool that can be used for determining the structure and composition of surfaces of various materials (even in in situ conditions) is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). In SHINERS measurements, the surface under investigation is covered with a layer of surface-protected plasmonic nanoparticles, and then the Raman spectrum of the surface analysed is recorded. The plasmonic cores of the used core-shell structures act as electromagnetic nanoresonators, significantly locally enhancing the intensity of the electric field of the incident radiation, leading to a large increase in the efficiency of the generation of the Raman signal from molecules in the close proximity to the deposited SHINERS nanoresonators. A protective layer (from transparent dielectrics such as SiO2, Al2O3 or TiO2) prevents direct interaction between the plasmonic metal and the analysed surface (such interactions may lead to changes in the structure of the surface) and, in the case of plasmonic cores other than gold cores, the dielectric layer increases the chemical stability of the metal core. In this contribution, we show for the first time that core-shell nanoparticles having a silver core (both a solid and hollow one) and a shell of zirconium(IV) oxide are very efficient SHINERS nanoresonators that are significantly more stable in acidic and alkaline media than the silver-silica core-shell structures typically used for SHINERS experiments.

Unusual behavior in magnesium-copper cluster matter produced by helium droplet mediated deposition.

PubMed

Emery, S B; Xin, Y; Ridge, C J; Buszek, R J; Boatz, J A; Boyle, J M; Little, B K; Lindsay, C M

2015-02-28

We demonstrate the ability to produce core-shell nanoclusters of materials that typically undergo intermetallic reactions using helium droplet mediated deposition. Composite structures of magnesium and copper were produced by sequential condensation of metal vapors inside the 0.4 K helium droplet baths and then gently deposited onto a substrate for analysis. Upon deposition, the individual clusters, with diameters ∼5 nm, form a cluster material which was subsequently characterized using scanning and transmission electron microscopies. Results of this analysis reveal the following about the deposited cluster material: it is in the un-alloyed chemical state, it maintains a stable core-shell 5 nm structure at sub-monolayer quantities, and it aggregates into unreacted structures of ∼75 nm during further deposition. Surprisingly, high angle annular dark field scanning transmission electron microscopy images revealed that the copper appears to displace the magnesium at the core of the composite cluster despite magnesium being the initially condensed species within the droplet. This phenomenon was studied further using preliminary density functional theory which revealed that copper atoms, when added sequentially to magnesium clusters, penetrate into the magnesium cores.

Nuclear reactor melt-retention structure to mitigate direct containment heating

DOEpatents

Tutu, Narinder K.; Ginsberg, Theodore; Klages, John R.

1991-01-01

A light water nuclear reactor melt-retention structure to mitigate the extent of direct containment heating of the reactor containment building. The structure includes a retention chamber for retaining molten core material away from the upper regions of the reactor containment building when a severe accident causes the bottom of the pressure vessel of the reactor to fail and discharge such molten material under high pressure through the reactor cavity into the retention chamber. In combination with the melt-retention chamber there is provided a passageway that includes molten core droplet deflector vanes and has gas vent means in its upper surface, which means are operable to deflect molten core droplets into the retention chamber while allowing high pressure steam and gases to be vented into the upper regions of the containment building. A plurality of platforms are mounted within the passageway and the melt-retention structure to direct the flow of molten core material and help retain it within the melt-retention chamber. In addition, ribs are mounted at spaced positions on the floor of the melt-retention chamber, and grid means are positioned at the entrance side of the retention chamber. The grid means develop gas back pressure that helps separate the molten core droplets from discharged high pressure steam and gases, thereby forcing the steam and gases to vent into the upper regions of the reactor containment building.

Solar reflection panels

DOEpatents

Diver, Jr., Richard B.; Grossman, James W [Albuquerque, NM; Reshetnik, Michael [Boulder, CO

2006-07-18

A solar collector comprising a glass mirror, and a composite panel, wherein the back of the mirror is affixed to a front surface of the composite panel. The composite panel comprises a front sheet affixed to a surface of a core material, preferably a core material comprising a honeycomb structure, and a back sheet affixed to an opposite surface of the core material. The invention may further comprise a sealing strip, preferably comprising EPDM, positioned between the glass mirror and the front surface of the composite panel. The invention also is of methods of making such solar collectors.

Core design for use with precision composite reflectors

NASA Technical Reports Server (NTRS)

Porter, Christopher C. (Inventor); Jacoy, Paul J. (Inventor); Schmitigal, Wesley P. (Inventor)

1992-01-01

A uniformly flexible core, and method for manufacturing the same, is disclosed for use between the face plates of a sandwich structure. The core is made of a plurality of thin corrugated strips, the corrugations being defined by a plurality of peaks and valleys connected to one another by a plurality of diagonal risers. The corrugated strips are orthogonally criss-crossed to form the core. The core is particularly suitable for use with high accuracy spherically curved sandwich structures because undesirable stresses in the curved face plates are minimized due to the uniform flexibility characteristics of the core in both the X and Y directions. The core is self venting because of the open geometry of the corrugations. The core can be made from any suitable composite, metal, or polymer. Thermal expansion problems in sandwich structures may be minimized by making the core from the same composite materials that are selected in the manufacture of the curved face plates because of their low coefficients of thermal expansion. Where the strips are made of a composite material, the core may be constructed by first cutting an already cured corrugated sheet into a plurality of corrugated strips and then secondarily bonding the strips to one another or, alternatively, by lying a plurality of uncured strips orthogonally over one another in a suitable jig and then curing and bonding the entire plurality of strips to one another in a single operation.

Development of SiO2@TiO2 core-shell nanospheres for catalytic applications

NASA Astrophysics Data System (ADS)

Kitsou, I.; Panagopoulos, P.; Maggos, Th.; Arkas, M.; Tsetsekou, A.

2018-05-01

Silica-titania core-shell nanospheres, CSNp, were prepared via a simple and environmentally friendly two step route. First, silica cores were prepared through the hydrolysis-condensation reaction of silicic acid in the presence of hyperbranched poly(ethylene)imine (HBPEI) followed by repeating washing, centrifugation and, finally, calcination steps. To create the core-shell structure, various amounts of titanium isopropoxide were added to the cores and after that a HBPEI-water solution was added to hydrolyze the titanium precursor. Washing with ethanol and heat treatment followed. The optimization of processing parameters led to well-developed core-shell structures bearing a homogeneous nanocrystalline anatase coating over each silica core. The photocatalytic activity for NO was examined in a continuous flux photocatalytic reactor under real environmental conditions. The results revealed a very potent photocatalyst as the degradation percentage reached 84.27% for the core-shell material compared to the 82% of pure titania with the photodecomposition rates measured at 0.62 and 0.55 μg·m-2·s-1, respectively. In addition, catalytic activities of the CSNp and pure titania were investigated by monitoring the reduction of 4-nitrophenol to 4-aminophenol by an excess of NaBH4. Both materials exhibited excellent catalytic activity (100%), making the core-shell material a promising alternative catalyst to pure titania for various applications.

Evidence for Radial Anisotropy in Earth's Upper Inner Core from Normal Modes

NASA Astrophysics Data System (ADS)

Lythgoe, K.; Deuss, A. F.

2017-12-01

The structure of the uppermost inner core is related to solidification of outer core material at the inner core boundary. Previous seismic studies using body waves indicate an isotropic upper inner core, although radial anisotropy has not been considered since it cannot be uniquely determined by body waves. Normal modes, however, do constrain radial anisotropy in the inner core. Centre frequency measurements indicate 2-5 % radial anisotropy in the upper 100 km of the inner core, with a fast direction radially outwards and a slow direction along the inner core boundary. This seismic structure provides constraints on solidification processes at the inner core boundary and appears consistent with texture predicted due to anisotropic inner core growth.

Finite element simulation of core inspection in helicopter rotor blades using guided waves.

PubMed

Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

2015-09-01

This paper extends the work presented earlier on inspection of helicopter rotor blades using guided Lamb modes by focusing on inspecting the spar-core bond. In particular, this research focuses on structures which employ high stiffness, high density core materials. Wave propagation in such structures deviate from the generic Lamb wave propagation in sandwich panels. To understand the various mode conversions, finite element models of a generalized helicopter rotor blade were created and subjected to transient analysis using a commercial finite element code; ANSYS. Numerical simulations showed that a Lamb wave excited in the spar section of the blade gets converted into Rayleigh wave which travels across the spar-core section and mode converts back into Lamb wave. Dispersion of Rayleigh waves in multi-layered half-space was also explored. Damage was modeled in the form of a notch in the core section to simulate a cracked core, and delamination was modeled between the spar and core material to simulate spar-core disbond. Mode conversions under these damaged conditions were examined numerically. The numerical models help in assessing the difficulty of using nondestructive evaluation for complex structures and also highlight the physics behind the mode conversions which occur at various discontinuities. Copyright © 2015 Elsevier B.V. All rights reserved.

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.

High renewable content sandwich structures based on flax-basalt hybrids and biobased epoxy polymers

NASA Astrophysics Data System (ADS)

Colomina, S.; Boronat, T.; Fenollar, O.; Sánchez-Nacher, L.; Balart, R.

2014-05-01

In the last years, a growing interest in the development of high environmental efficiency materials has been detected and this situation is more accentuated in the field of polymers and polymer composites. In this work, green composite sandwich structures with high renewable content have been developed with core cork materials. The base resin for composites was a biobased epoxy resin derived from epoxidized vegetable oils. Hybrid basalt-flax fabrics have been used as reinforcements for composites and the influence of the stacking sequence has been evaluated in order to optimize the appropriate laminate structure for the sandwich bases. Core cork materials with different thickness have been used to evaluate performance of sandwich structures thus leading to high renewable content composite sandwich structures. Results show that position of basalt fabrics plays a key role in flexural fracture of sandwich structures due to differences in stiffness between flax and basalt fibers.

Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

NASA Technical Reports Server (NTRS)

Smeltzer, Stanley S., III (Inventor); Lundgren, Eric C. (Inventor)

2016-01-01

Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life.

Systems, Apparatuses, and Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

NASA Technical Reports Server (NTRS)

Smeltzer, III, Stanley S. (Inventor); Lundgren, Eric C. (Inventor)

2014-01-01

Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life.

Coupled Monte Carlo neutronics and thermal hydraulics for power reactors

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

Bernnat, W.; Buck, M.; Mattes, M.

The availability of high performance computing resources enables more and more the use of detailed Monte Carlo models even for full core power reactors. The detailed structure of the core can be described by lattices, modeled by so-called repeated structures e.g. in Monte Carlo codes such as MCNP5 or MCNPX. For cores with mainly uniform material compositions, fuel and moderator temperatures, there is no problem in constructing core models. However, when the material composition and the temperatures vary strongly a huge number of different material cells must be described which complicate the input and in many cases exceed code ormore » memory limits. The second problem arises with the preparation of corresponding temperature dependent cross sections and thermal scattering laws. Only if these problems can be solved, a realistic coupling of Monte Carlo neutronics with an appropriate thermal-hydraulics model is possible. In this paper a method for the treatment of detailed material and temperature distributions in MCNP5 is described based on user-specified internal functions which assign distinct elements of the core cells to material specifications (e.g. water density) and temperatures from a thermal-hydraulics code. The core grid itself can be described with a uniform material specification. The temperature dependency of cross sections and thermal neutron scattering laws is taken into account by interpolation, requiring only a limited number of data sets generated for different temperatures. Applications will be shown for the stationary part of the Purdue PWR benchmark using ATHLET for thermal- hydraulics and for a generic Modular High Temperature reactor using THERMIX for thermal- hydraulics. (authors)« less

Structure modeling and manufacturing PCFs for the range of 2-25 μm

NASA Astrophysics Data System (ADS)

Lvov, Alexandr; Salimgareev, Dmitrii; Korsakov, Michail; Korsakov, Alexandr; Zhukova, Liya

2017-11-01

Photostable and flexible materials transparent at the wide spectral range are necessary for the development of optical fiber units. Solid solutions of silver and monadic thallium halides are the most suitable crystal media for this purpose. The goal of our research was the search of optimum structure for the fibers with a single mode operation and a rather large core diameter. We modelled fiber structures (solid-core, hollow-core, active-core PCF) with various ratio of inserts diameters and increments between the inserts, basing on two crystal systems: AgCl-AgBr and AgBr-TlI. Then we chose the single mode fiber structure and manufactured it by means of extrusion.

Fabrication of Fe3O4@CuO core-shell from MOF based materials and its antibacterial activity

NASA Astrophysics Data System (ADS)

Rajabi, S. K.; Sohrabnezhad, Sh.; Ghafourian, S.

2016-12-01

Magnetic Fe3O4@CuO nanocomposite with a core/shell structure was successfully synthesized via direct calcinations of magnetic Fe3O4@HKUST-1 in air atmosphere. The morphology, structure, magnetic and porous properties of the as-synthesized nano composites were characterized by using scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and vibration sample magnetometer (VSM). The results showed that the nanocomposite material included a Fe3O4 core and a CuO shell. The Fe3O4@CuO core-shell can be separated easily from the medium by a small magnet. The antibacterial activity of Fe3O4-CuO core-shell was investigated against gram-positive and gram-negative bacteria. A new mechanism was proposed for inactivation of bacteria over the prepared sample. It was demonstrated that the core-shell exhibit recyclable antibacterial activity, acting as an ideal long-acting antibacterial agent.

Investigation of Quasi-Static Indentation Response of Inkjet Printed Sandwich Structures under Various Indenter Geometries

PubMed Central

Dikshit, Vishwesh; Nagalingam, Arun Prasanth; Yap, Yee Ling; Sing, Swee Leong; Yeong, Wai Yee; Wei, Jun

2017-01-01

The objective of this investigation was to determine the quasi-static indentation response and failure mode in three-dimensional (3D) printed trapezoidal core structures, and to characterize the energy absorbed by the structures. In this work, the trapezoidal sandwich structure was designed in the following two ways. Firstly, the trapezoidal core along with its facesheet was 3D printed as a single element comprising a single material for both core and facesheet (type A); Secondly, the trapezoidal core along with facesheet was 3D printed, but with variation in facesheet materials (type B). Quasi-static indentation was carried out using three different indenters, namely standard hemispherical, conical, and flat indenters. Acoustic emission (AE) technique was used to capture brittle cracking in the specimens during indentation. The major failure modes were found to be brittle failure and quasi-brittle fractures. The measured indentation energy was at a maximum when using a conical indenter at 9.40 J and 9.66 J and was at a minimum when using a hemispherical indenter at 6.87 J and 8.82 J for type A and type B series specimens respectively. The observed maximum indenter displacements at failure were the effect of material variations and composite configurations in the facesheet. PMID:28772649

Investigation of Quasi-Static Indentation Response of Inkjet Printed Sandwich Structures under Various Indenter Geometries.

PubMed

Dikshit, Vishwesh; Nagalingam, Arun Prasanth; Yap, Yee Ling; Sing, Swee Leong; Yeong, Wai Yee; Wei, Jun

2017-03-14

The objective of this investigation was to determine the quasi-static indentation response and failure mode in three-dimensional (3D) printed trapezoidal core structures, and to characterize the energy absorbed by the structures. In this work, the trapezoidal sandwich structure was designed in the following two ways. Firstly, the trapezoidal core along with its facesheet was 3D printed as a single element comprising a single material for both core and facesheet (type A); Secondly, the trapezoidal core along with facesheet was 3D printed, but with variation in facesheet materials (type B). Quasi-static indentation was carried out using three different indenters, namely standard hemispherical, conical, and flat indenters. Acoustic emission (AE) technique was used to capture brittle cracking in the specimens during indentation. The major failure modes were found to be brittle failure and quasi-brittle fractures. The measured indentation energy was at a maximum when using a conical indenter at 9.40 J and 9.66 J and was at a minimum when using a hemispherical indenter at 6.87 J and 8.82 J for type A and type B series specimens respectively. The observed maximum indenter displacements at failure were the effect of material variations and composite configurations in the facesheet.

Core-shell-structured nanothermites synthesized by atomic layer deposition

NASA Astrophysics Data System (ADS)

Qin, Lijun; Gong, Ting; Hao, Haixia; Wang, Keyong; Feng, Hao

2013-12-01

Thermite materials feature very exothermic solid-state redox reactions. However, the energy release rates of traditional thermite mixtures are limited by the reactant diffusion velocities. In this work, atomic layer deposition (ALD) is utilized to synthesize thermite materials with greatly enhanced reaction rates. By depositing certain types of metal oxides (oxidizers) onto a commercial Al nanopowder, core-shell-structured nanothermites can be produced. The average film deposition rate on the Al nanopowder is 0.17 nm/cycle for ZnO and 0.031 nm/cycle for SnO2. The thickness of the oxidizer layer can be precisely controlled by adjusting the ALD cycle number. The compositions, morphologies, and structures of the ALD nanothermites are characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The characterization results reveal nearly perfect coverage of the Al nanoparticles by uniform ALD oxidizer layers and confirm the formation of core-shell nanoparticles. Combustion properties of the nanothermites are probed by laser ignition technique. Reactions of the core-shell-structured nanothermites are several times faster than the mixture of nanopowders. The promoted reaction rate is mostly attributed to the uniform distribution of reactants on the nanometer scale. These core-shell-structured nanothermites provide a potential pathway to control and enhance thermite reactions.

Three-phase inductive-coupled structures for contactless PHEV charging system

NASA Astrophysics Data System (ADS)

Lee, Jia-You; Shen, Hung-Yu; Li, Cheng-Bin

2016-07-01

In this article, a new-type three-phase inductive-coupled structure is proposed for the contactless plug-in hybrid electric vehicle (PHEV) charging system regarding with SAE J-1773. Four possible three-phase core structures are presented and subsequently investigated by the finite element analysis. To study the correlation between the core geometric parameter and the coupling coefficient, the magnetic equivalent circuit model of each structure is also established. In accordance with the simulation results, the low reluctance and the sharing of flux path in the core material are achieved by the proposed inductive-coupled structure with an arc-shape and three-phase symmetrical core material. It results in a compensation of the magnetic flux between each phase and a continuous flow of the output power in the inductive-coupled structure. Higher coupling coefficient between inductive-coupled structures is achieved. A comparison of coupling coefficient, mutual inductance, and self-inductance between theoretical and measured results is also performed to verify the proposed model. A 1 kW laboratory scale prototype of the contactless PHEV charging system with the proposed arc-shape three-phase inductive-coupled structure is implemented and tested. An overall system efficiency of 88% is measured when two series lithium iron phosphate battery packs of 25.6 V/8.4 Ah are charged.

Highly selective and sensitive methanol gas sensor based on molecular imprinted silver-doped LaFeO3 core-shell and cage structures

NASA Astrophysics Data System (ADS)

Rong, Qian; Zhang, Yumin; Lv, Tianping; Shen, Kaiyuan; Zi, Baoye; Zhu, Zhongqi; Zhang, Jin; Liu, Qingju

2018-04-01

Silver-doped LaFeO3 molecularly imprinted polymers (SLMIPs) were synthesized by a sol-gel method combined with molecularly imprinted technology as precursors. The precursors were then used to prepare SLMIPs cage (SLM-cage) and SLMIPs core-shell (SLM-core-shell) structures by using a carbon sphere as the template and hydrothermal synthesis, respectively. The structures, morphologies, and surface areas of these materials were determined, as well as their gas-sensing properties and related mechanisms. The SLM-cage and SLM-core-shell samples exhibited good responses to methanol gas, with excellent selectivity. The response and optimum working temperature were 16.98 °C and 215 °C, 33.7 °C and 195 °C, respectively, with corresponding response and recovery times of 45 and 50 s (SLM-cage) and 42 and 57 s (SLM-core-shell) for 5 ppm methanol gas. Notably, the SLM-cage and SLM-core-shell samples exhibited lower responses (≤5 and ≤7, respectively) to other gases, including ethanol, ammonia, benzene, acetone, and toluene. Thus, these materials show potential as practical methanol detectors.

Highly selective and sensitive methanol gas sensor based on molecular imprinted silver-doped LaFeO3 core-shell and cage structures.

PubMed

Rong, Qian; Zhang, Yumin; Lv, Tianping; Shen, Kaiyuan; Zi, Baoye; Zhu, Zhongqi; Zhang, Jin; Liu, Qingju

2018-04-06

Silver-doped LaFeO 3 molecularly imprinted polymers (SLMIPs) were synthesized by a sol-gel method combined with molecularly imprinted technology as precursors. The precursors were then used to prepare SLMIPs cage (SLM-cage) and SLMIPs core-shell (SLM-core-shell) structures by using a carbon sphere as the template and hydrothermal synthesis, respectively. The structures, morphologies, and surface areas of these materials were determined, as well as their gas-sensing properties and related mechanisms. The SLM-cage and SLM-core-shell samples exhibited good responses to methanol gas, with excellent selectivity. The response and optimum working temperature were 16.98 °C and 215 °C, 33.7 °C and 195 °C, respectively, with corresponding response and recovery times of 45 and 50 s (SLM-cage) and 42 and 57 s (SLM-core-shell) for 5 ppm methanol gas. Notably, the SLM-cage and SLM-core-shell samples exhibited lower responses (≤5 and ≤7, respectively) to other gases, including ethanol, ammonia, benzene, acetone, and toluene. Thus, these materials show potential as practical methanol detectors.

Dye-sensitized solar cells employing a SnO2-TiO2 core-shell structure made by atomic layer deposition.

PubMed

Karlsson, Martin; Jõgi, Indrek; Eriksson, Susanna K; Rensmo, Håkan; Boman, Mats; Boschloo, Gerrit; Hagfeldt, Anders

2013-01-01

This paper describes the synthesis and characterization of core-shell structures, based on SnO2 and TiO2, for use in dye-sensitized solar cells (DSC). Atomic layer deposition is employed to control and vary the thickness of the TiO2 shell. Increasing the TiO2 shell thickness to 2 nm improved the device performance of liquid electrolyte-based DSC from 0.7% to 3.5%. The increase in efficiency originates from a higher open-circuit potential and a higher short-circuit current, as well as from an improvement in the electron lifetime. SnO2-TiO2 core-shell DSC devices retain their photovoltage in darkness for longer than 500 seconds, demonstrating that the electrons are contained in the core material. Finally core-shell structures were used for solid-state DSC applications using the hole transporting material 2,2',7,7',-tetrakis(N, N-di-p-methoxyphenyl-amine)-9,9',-spirofluorene. Similar improvements in device performance were obtained for solid-state DSC devices.

Functional Polymer Opals and Porous Materials by Shear-Induced Assembly of Tailor-Made Particles.

PubMed

Gallei, Markus

2018-02-01

Photonic band-gap materials attract enormous attention as potential candidates for a steadily increasing variety of applications. Based on the preparation of easily scalable monodisperse colloids, such optically attractive photonic materials can be prepared by an inexpensive and convenient bottom-up process. Artificial polymer opals can be prepared by shear-induced assembly of core/shell particles, yielding reversibly stretch-tunable materials with intriguing structural colors. This feature article highlights recent developments of core/shell particle design and shear-induced opal formation with focus on the combination of hard and soft materials as well as crosslinking strategies. Structure formation of opal materials relies on both the tailored core/shell architecture and the parameters for polymer processing. The emphasis of this feature article is on elucidating the particle design and incorporation of addressable moieties, i.e., stimuli-responsive polymers as well as elaborated crosslinking strategies for the preparation of smart (inverse) opal films, inorganic/organic opals, and ceramic precursors by shear-induced ordering. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fatigue Characterization of Fire Resistant Syntactic Foam Core Material

NASA Astrophysics Data System (ADS)

Hossain, Mohammad Mynul

Eco-Core is a fire resistant material for sandwich structural application; it was developed at NC A&T State University. The Eco-Core is made of very small amount of phenolic resin and large volume of flyash by a syntactic process. The process development, static mechanical and fracture, fire and toxicity safety and water absorption properties and the design of sandwich structural panels with Eco-Core material was established and published in the literature. One of the important properties that is needed for application in transportation vehicles is the fatigue performance under different stress states. Fatigue data are not available even for general syntactic foams. The objective of this research is to investigate the fatigue performance of Eco-Core under three types of stress states, namely, cyclic compression, shear and flexure, then document failure modes, and develop empherical equations for predicting fatigue life of Eco-Core under three stress states. Compression-Compression fatigue was performed directly on Eco-Core cylindrical specimen, whereas shear and flexure fatigue tests were performed using sandwich beam made of E glass-Vinyl Ester face sheet and Eco-Core material. Compression-compression fatigue test study was conducted at two values of stress ratios (R=10 and 5), for the maximum compression stress (sigmamin) range of 60% to 90% of compression strength (sigmac = 19.6 +/- 0.25 MPa) for R=10 and 95% to 80% of compression strength for R=5. The failure modes were characterized by the material compliance change: On-set (2% compliance change), propagation (5%) and ultimate failure (7%). The number of load cycles correspond to each of these three damages were characterized as on-set, propagation and total lives. A similar approach was used in shear and flexure fatigue tests with stress ratio of R=0.1. The fatigue stress-number of load cycles data followed the standard power law equation for all three stress states. The constant of the equation were established for the three stress states and three types of the failure modes. This equation was used to estimate endurance limit (106 cycles) of the material. Like metallic materials, the compression fatigue life of Eco-Core was found to be dependent on the stress range instead of maximum or mean cyclic stress. Furthermore shear and flexural ultimate failure of the core material was found to be due to a combination of shear and tensile stress.

Solid oxide fuel cell having monolithic cross flow core and manifolding

DOEpatents

Poeppel, Roger B.; Dusek, Joseph T.

1984-01-01

This invention discloses a monolithic core construction having the flow passageways for the fuel and for the oxidant gases extended transverse to one another, whereby full face core manifolding can be achieved for these gases and their reaction products. The core construction provides that only anode material surround each fuel passageway and only cathode material surround each oxidant passageway, each anode and each cathode further sandwiching at spaced opposing sides electrolyte and interconnect materials to define electrolyte and interconnect walls. Webs of the cathode and anode material hold the electrolyte and interconnect walls spaced apart to define the flow passages. The composite anode and cathode wall structures are further alternately stacked on one another (with the separating electrolyte or interconnect material typically being a single common layer) whereby the fuel passageway and the oxidant passageways are disposed transverse to one another.

Solid oxide fuel cell having monolithic cross flow core and manifolding

DOEpatents

Poeppel, R.B.; Dusek, J.T.

1983-10-12

This invention discloses a monolithic core construction having the flow passageways for the fuel and for the oxidant gases extended transverse to one another, whereby full face core manifolding can be achieved for these gases and their reaction products. The core construction provides that only anode material surround each fuel passageway and only cathode material surround each oxidant passageway, each anode and each cathode further sandwiching at spaced opposing sides electrolyte and interconnect materials to define electrolyte and interconnect walls. Webs of the cathode and anode material hold the electrolyte and interconnect walls spaced apart to define the flow passages. The composite anode and cathode wall structures are further alternately stacked on one another (with the separating electrolyte or interconnect material typically being a single common layer) whereby the fuel passageways and the oxidant passageways are disposed transverse to one another.

Method of manufacturing lightweight thermo-barrier material

NASA Technical Reports Server (NTRS)

Blair, Winford (Inventor)

1987-01-01

A method of manufacturing thermal barrier structures comprising at least three dimpled cores separated by flat plate material with the outer surface of the flat plate material joined together by diffusion bonding.

An Analysis of Nondestructive Evaluation Techniques for Polymer Matrix Composite Sandwich Materials

NASA Technical Reports Server (NTRS)

Cosgriff, Laura M.; Roberts, Gary D.; Binienda, Wieslaw K.; Zheng, Diahua; Averbeck, Timothy; Roth, Donald J.; Jeanneau, Philippe

2006-01-01

Structural sandwich materials composed of triaxially braided polymer matrix composite material face sheets sandwiching a foam core are being utilized for applications including aerospace components and recreational equipment. Since full scale components are being made from these sandwich materials, it is necessary to develop proper inspection practices for their manufacture and in-field use. Specifically, nondestructive evaluation (NDE) techniques need to be investigated for analysis of components made from these materials. Hockey blades made from sandwich materials and a flat sandwich sample were examined with multiple NDE techniques including thermographic, radiographic, and shearographic methods to investigate damage induced in the blades and flat panel components. Hockey blades used during actual play and a flat polymer matrix composite sandwich sample with damage inserted into the foam core were investigated with each technique. NDE images from the samples were presented and discussed. Structural elements within each blade were observed with radiographic imaging. Damaged regions and some structural elements of the hockey blades were identified with thermographic imaging. Structural elements, damaged regions, and other material variations were detected in the hockey blades with shearography. Each technique s advantages and disadvantages were considered in making recommendations for inspection of components made from these types of materials.

Vibroacoustic Characterization of Corrugated-Core and Honeycomb-Core Sandwich Panels

NASA Technical Reports Server (NTRS)

Allen, Albert; Schiller, Noah

2016-01-01

The vibroacoustic characteristics of two candidate launch vehicle fairing structures, corrugated- core and honeycomb-core sandwich designs, were studied. The study of these structures has been motivated by recent risk reduction efforts focused on mitigating high noise levels within the payload bays of large launch vehicles during launch. The corrugated-core sandwich concept is of particular interest as a dual purpose structure due to its ability to harbor resonant noise control systems without appreciably adding mass or taking up additional volume. Specifically, modal information, wavelength dispersion, and damping were determined from a series of vibrometer measurements and subsequent analysis procedures carried out on two test panels. Numerical and analytical modeling techniques were also used to assess assumed material properties and to further illuminate underlying structural dynamic aspects. Results from the tests and analyses described herein may serve as a reference for additional vibroacoustic studies involving these or similar structures.

Using Indigenous Materials for Construction

DTIC Science & Technology

2015-07-01

Theoretical models were devised for prediction of the structural attributes of indigenous ferrocement sheets and sandwich composite panels comprising the...indigenous ferrocement skins and aerated concrete core. Structural designs were developed for these indigenous sandwich composite panels in typical...indigenous materials and building systems developed in the project were evaluated. Numerical modeling capabilities were developed for structural

Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Odegard, Gregory M.; Herring, Helen M.

2003-01-01

The next generation of space transportation vehicles will require advances in lightweight structural materials and related design concepts to meet the increased demands on performance. One potential source for significant structural weight reduction is the replacement of traditional metallic cryogenic fuel tanks with new designs for polymeric matrix composite tanks. These new tank designs may take the form of thin-walled sandwich constructed with lightweight core and composite facesheets. Life-time durability requirements imply the materials must safely carry pressure loads, external structural loads, resist leakage and operate over an extremely wide temperature range. Aside from catastrophic events like tank wall penetration, one of the most likely scenarios for failure of a tank wall of sandwich construction is the permeation of cryogenic fluid into the sandwich core and the subsequent delamination of the sandwich facesheet due to the build-up of excessive internal pressure. The research presented in this paper was undertaken to help understand this specific problem of core to facesheet delamination in cryogenic environments and relate this data to basic mechanical properties. The experimental results presented herein provide data on the strain energy release rate (toughness) of the interface between the facesheet and the core of a composite sandwich subjected to simulated internal pressure. A unique test apparatus and associated test methods are described and the results are presented to highlight the effects of cryogenic temperature on the measured material properties.

Integral manifolding structure for fuel cell core having parallel gas flow

DOEpatents

Herceg, Joseph E.

1984-01-01

Disclosed herein are manifolding means for directing the fuel and oxidant gases to parallel flow passageways in a fuel cell core. Each core passageway is defined by electrolyte and interconnect walls. Each electrolyte and interconnect wall consists respectively of anode and cathode materials layered on the opposite sides of electrolyte material, or on the opposite sides of interconnect material. A core wall projects beyond the open ends of the defined core passageways and is disposed approximately midway between and parallel to the adjacent overlaying and underlying interconnect walls to define manifold chambers therebetween on opposite sides of the wall. Each electrolyte wall defining the flow passageways is shaped to blend into and be connected to this wall in order to redirect the corresponding fuel and oxidant passageways to the respective manifold chambers either above or below this intermediate wall. Inlet and outlet connections are made to these separate manifold chambers respectively, for carrying the fuel and oxidant gases to the core, and for carrying their reaction products away from the core.

Integral manifolding structure for fuel cell core having parallel gas flow

DOEpatents

Herceg, J.E.

1983-10-12

Disclosed herein are manifolding means for directing the fuel and oxidant gases to parallel flow passageways in a fuel cell core. Each core passageway is defined by electrolyte and interconnect walls. Each electrolyte and interconnect wall consists respectively of anode and cathode materials layered on the opposite sides of electrolyte material, or on the opposite sides of interconnect material. A core wall projects beyond the open ends of the defined core passageways and is disposed approximately midway between and parallel to the adjacent overlaying and underlying interconnect walls to define manifold chambers therebetween on opposite sides of the wall. Each electrolyte wall defining the flow passageways is shaped to blend into and be connected to this wall in order to redirect the corresponding fuel and oxidant passageways to the respective manifold chambers either above or below this intermediate wall. Inlet and outlet connections are made to these separate manifold chambers respectively, for carrying the fuel and oxidant gases to the core, and for carrying their reaction products away from the core.

Magnetic nuclear core restraint and control

DOEpatents

Cooper, Martin H.

1979-01-01

A lateral restraint and control system for a nuclear reactor core adaptable to provide an inherent decrease of core reactivity in response to abnormally high reactor coolant fluid temperatures. An electromagnet is associated with structure for radially compressing the core during normal reactor conditions. A portion of the structures forming a magnetic circuit are composed of ferromagnetic material having a curie temperature corresponding to a selected coolant fluid temperature. Upon a selected signal, or inherently upon a preselected rise in coolant temperature, the magnetic force is decreased a given amount sufficient to relieve the compression force so as to allow core radial expansion. The expanded core configuration provides a decreased reactivity, tending to shut down the nuclear reaction.

Magnetic nuclear core restraint and control

DOEpatents

Cooper, Martin H.

1978-01-01

A lateral restraint and control system for a nuclear reactor core adaptable to provide an inherent decrease of core reactivity in response to abnormally high reactor coolant fluid temperatures. An electromagnet is associated with structure for radially compressing the core during normal reactor conditions. A portion of the structures forming a magnetic circuit are composed of ferromagnetic material having a curie temperature corresponding to a selected coolant fluid temperature. Upon a selected signal, or inherently upon a preselected rise in coolant temperature, the magnetic force is decreased a given amount sufficient to relieve the compression force so as to allow core radial expansion. The expanded core configuration provides a decreased reactivity, tending to shut down the nuclear reaction.

EVALUATIONS ON ASR DAMAGE OF CONCRETE STRUCTURE AND ITS STRUCTURAL PERFORMANCE

NASA Astrophysics Data System (ADS)

Ueda, Naoshi; Nakamura, Hikaru; Kunieda, Minoru; Maeno, Hirofumi; Morishit, Noriaki; Asai, Hiroshi

In this paper, experiments and finite element analyses were conducted in order to evaluate effects of ASR on structural performance of RC and PC structures. From the experimental results, it was confirmed that the ASR expansion was affected by the restraint of reinforcement and the magnitude of prestress. The material properties of concrete damaged by ASR had anisotropic characteristics depending on the degree of ASR expansion. Therefore, when the structural performance of RC and PC structures were evaluated by using the material properties of core concrete, the direction and place where cylinder specimens were cored should be considered. On the other hand, by means of proposed analytical method, ASR expansion behaviors of RC and PC beams and changing of their structural performance were evaluated. As the results, it was confirmed that PC structure had much advantage comparing with RC structure regarding the structural performance under ASR damage because of restraint by prestress against the ASR.

Thermoelectric-pyroelectric hybrid energy generation from thermopower waves in core-shell structured carbon nanotube-PZT nanocomposites.

PubMed

Yeo, Taehan; Hwang, Hayoung; Shin, Dongjoon; Seo, Byungseok; Choi, Wonjoon

2017-02-10

There is an urgent need to develop a suitable energy source owing to the rapid development of various innovative devices using micro-nanotechnology. The thermopower wave (TW), which produces a high specific power during the combustion of solid fuel inside micro-nanostructure materials, is a unique energy source for unusual platforms that cannot use conventional energy sources. Here, we report on the significant enhancement of hybrid energy generation of pyroelectrics and thermoelectrics from TWs in carbon nanotube (CNT)-PZT (lead zirconate titanate, P(Z 0.5 -T 0.5 )) composites for the first time. Conventional TWs use only charge carrier transport driven by the temperature gradient along the core materials to produce voltage. In this study, a core-shell structure of CNTs-PZTs was prepared to utilize both the temperature gradient along the core material (thermoelectrics) and the dynamic change in the temperature of the shell structure (pyroelectrics) induced by TWs. The dual mechanism of energy generation in CNT-PZT composites amplified the average peak and duration of the voltage up to 403 mV and 612 ms, respectively, by a factor of 2 and 60 times those for the composites without a PZT layer. Furthermore, dynamic voltage measurements and structural analysis in repetitive TWs confirmed that CNT-PZT composites maintain the original performance in multiple TWs, which improves the reusability of materials. The advanced TWs obtained by the application of a PZT layer as a pyroelectric material contributes to the extension of the usable energy portion as well as the development of TW-based operating devices.

A high-performance ternary Si composite anode material with crystal graphite core and amorphous carbon shell

NASA Astrophysics Data System (ADS)

Sui, Dong; Xie, Yuqing; Zhao, Weimin; Zhang, Hongtao; Zhou, Ying; Qin, Xiting; Ma, Yanfeng; Yang, Yong; Chen, Yongsheng

2018-04-01

Si is a promising anode material for lithium-ion batteries, but suffers from sophisticated engineering structures and complex fabrication processes that pose challenges for commercial application. Herein, a ternary Si/graphite/pyrolytic carbon (SiGC) anode material with a structure of crystal core and amorphous shell using low-cost raw materials is developed. In this ternary SiGC composite, Si component exists as nanoparticles and is spread on the surface of the core graphite flakes while the sucrose-derived pyrolytic carbon further covers the graphite/Si components as the amorphous shell. With this structure, Si together with the graphite contributes to the high specific capacity of this Si ternary material. Also the graphite serves as the supporting and conducting matrix and the amorphous shell carbon could accommodate the volume change effect of Si, reinforces the integrity of the composite architecture, and prevents the graphite and Si from direct exposing to the electrolyte. The optimized ternary SiGC composite displays high reversible specific capacity of 818 mAh g-1 at 0.1 A g-1, initial Coulombic efficiency (CE) over 80%, and excellent cycling stability at 0.5 A g-1 with 83.6% capacity retention (∼610 mAh g-1) after 300 cycles.

Compression Behavior of Fluted-Core Composite Panels

NASA Technical Reports Server (NTRS)

Schultz, Marc R.; Oremont, Leonard; Guzman, J. Carlos; McCarville, Douglas; Rose, Cheryl A.; Hilburger, Mark W.

2011-01-01

In recent years, fiber-reinforced composites have become more accepted for aerospace applications. Specifically, during NASA s recent efforts to develop new launch vehicles, composite materials were considered and baselined for a number of structures. Because of mass and stiffness requirements, sandwich composites are often selected for many applications. However, there are a number of manufacturing and in-service concerns associated with traditional honeycomb-core sandwich composites that in certain instances may be alleviated through the use of other core materials or construction methods. Fluted-core, which consists of integral angled web members with structural radius fillers spaced between laminate face sheets, is one such construction alternative and is considered herein. Two different fluted-core designs were considered: a subscale design and a full-scale design sized for a heavy-lift-launch-vehicle interstage. In particular, axial compression of fluted-core composites was evaluated with experiments and finite-element analyses (FEA); axial compression is the primary loading condition in dry launch-vehicle barrel sections. Detailed finite-element models were developed to represent all components of the fluted-core construction, and geometrically nonlinear analyses were conducted to predict both buckling and material failures. Good agreement was obtained between test data and analyses, for both local buckling and ultimate material failure. Though the local buckling events are not catastrophic, the resulting deformations contribute to material failures. Consequently, an important observation is that the material failure loads and modes would not be captured by either linear analyses or nonlinear smeared-shell analyses. Compression-after-impact (CAI) performance of fluted core composites was also investigated by experimentally testing samples impacted with 6 ft.-lb. impact energies. It was found that such impacts reduced the ultimate load carrying capability by approximately 40% on the subscale test articles and by less than 20% on the full-scale test articles. Nondestructive inspection of the damage zones indicated that the detectable damage was limited to no more than one flute on either side of any given impact. More study is needed, but this may indicate that an inherent damage-arrest capability of fluted core could provide benefits over traditional sandwich designs in certain weight-critical applications.

The influence of anisotropy on the core structure of Shockley partial dislocations within FCC materials

NASA Astrophysics Data System (ADS)

Szajewski, B. A.; Hunter, A.; Luscher, D. J.; Beyerlein, I. J.

2018-01-01

Both theoretical and numerical models of dislocations often necessitate the assumption of elastic isotropy to retain analytical tractability in addition to reducing computational load. As dislocation based models evolve towards physically realistic material descriptions, the assumption of elastic isotropy becomes increasingly worthy of examination. We present an analytical dislocation model for calculating the full dissociated core structure of dislocations within anisotropic face centered cubic (FCC) crystals as a function of the degree of material elastic anisotropy, two misfit energy densities on the γ-surface ({γ }{{isf}}, {γ }{{usf}}) and the remaining elastic constants. Our solution is independent of any additional features of the γ-surface. Towards this pursuit, we first demonstrate that the dependence of the anisotropic elasticity tensor on the orientation of the dislocation line within the FCC crystalline lattice is small and may be reasonably neglected for typical materials. With this approximation, explicit analytic solutions for the anisotropic elasticity tensor {B} for both nominally edge and screw dislocations within an FCC crystalline lattice are devised, and employed towards defining a set of effective isotropic elastic constants which reproduce fully anisotropic results, however do not retain the bulk modulus. Conversely, Hill averaged elastic constants which both retain the bulk modulus and reasonably approximate the dislocation core structure are employed within subsequent numerical calculations. We examine a wide range of materials within this study, and the features of each partial dislocation core are sufficiently localized that application of discrete linear elasticity accurately describes the separation of each partial dislocation core. In addition, the local features (the partial dislocation core distribution) are well described by a Peierls-Nabarro dislocation model. We develop a model for the displacement profile which depends upon two disparate dislocation length scales which describe the core structure; (i) the equilibrium stacking fault width between two Shockley partial dislocations, R eq and (ii) the maximum slip gradient, χ, of each Shockley partial dislocation. We demonstrate excellent agreement between our own analytic predictions, numerical calculations, and R eq computed directly by both ab-initio and molecular statics methods found elsewhere within the literature. The results suggest that understanding of various plastic mechanisms, e.g., cross-slip and nucleation may be augmented with the inclusion of elastic anisotropy.

Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures

NASA Astrophysics Data System (ADS)

Lares, Alan

Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the previous insert designs. A casting process for manufacturing the v.3 inserts was developed. The developed casting process, when producing more than 13 inserts, becomes more economical than machining. An exploratory study was conducted looking at the effects of dynamic loading on the v.3 insert performance. The results of this study highlighted areas for improving dynamic testing of foam-core sandwich structure inserts. Correlations were developed relating design variables such as face-sheet thickness and insert diameter to a failure load for different load cases. This was done through simulations using Computer Aided Engineering (CAE) software, and experimental testing. The resulting correlations were integrated into a computer program which outputs the required insert dimensions given a set of design parameters, and load values.

F Ring Bright Core Clumps

NASA Image and Video Library

2010-07-20

Bright clumps of ring material and a fan-like structure appear near the core of Saturn tenuous F ring in this mosaic of images from NASA Cassini spacecraft. Such features suggest the existence of additional objects in the F ring.

High ink absorption performance of inkjet printing based on SiO2@Al13 core-shell composites

NASA Astrophysics Data System (ADS)

Chen, YiFan; Jiang, Bo; Liu, Li; Du, Yunzhe; Zhang, Tong; Zhao, LiWei; Huang, YuDong

2018-04-01

The increasing growth of the inkjet market makes the inkjet printing more necessary. A composite material based on core-shell structure has been developed and applied to prepare inkjet printing layer. In this contribution, the ink printing record layers based on SiO2@Al13 core-shell composite was elaborated. The prepared core-shell composite materials were characterized by X-ray photoelectron spectroscopy (XPS), zeta potential, X-ray diffraction (XRD), scanning electron microscopy (SEM). The results proved the presence of electrostatic adsorption between SiO2 molecules and Al13 molecules with the formation of the well-dispersed system. In addition, based on the adsorption and the liquid permeability analysis, SiO2@Al13 ink printing record layer achieved a relatively high ink uptake (2.5 gmm-1) and permeability (87%), respectively. The smoothness and glossiness of SiO2@Al13 record layers were higher than SiO2 record layers. The core-shell structure facilitated the dispersion of the silica, thereby improved its ink absorption performance and made the clear printed image. Thus, the proposed procedure based on SiO2@Al13 core-shell structure of dye particles could be applied as a promising strategy for inkjet printing.

Structural Basis for Near Unity Quantum Yield Core/Shell Nanostructures

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

McBride, James; Treadway, Joe; Pennycook, Stephen J

2006-01-01

Aberration-corrected Z-contrast scanning transmission electron microscopy of core/shell nanocrystals shows clear correlations between structure and quantum efficiency. Uniform shell coverage is obtained only for a graded CdS/ZnS shell material and is found to be critical to achieving near 100% quantum yield. The sublattice sensitivity of the images confirms that preferential growth takes place on the anion-terminated surfaces. This explains the three-dimensional "nanobullet" shape observed in the case of core/shell nanorods.

Core–Shell to Doped Quantum Dots: Evolution of the Local Environment Using XAFS

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

Saha, Avijit; Chattopadhyay, Soma; Shibata, Tomohiro

2016-09-30

Internal structure study at an atomic level is a challenging task with far reaching consequences to its material properties, specifically in the field of transition metal doping in quantum dots. Diffusion of transition metal ions in and out of quantum dots forming magnetic clusters has been a major bottleneck in this class of materials. Diffusion of the magnetic ions from the core into the nonmagnetic shell in a core/shell heterostructure architecture to attain uniform doping has been recently introduced and yet to be understood. In this work, we have studied the local structure variation of Fe as a function ofmore » CdS matrix thickness and annealing time during the overcoating of Fe 3O 4 core with CdS using X-ray absorption spectroscopy. The data reveals that Fe 3O 4 core initially forms a core/shell structure with CdS followed by alloying at the interface eventually completely diffusing all the way through the CdS matrix to form homogeneously Fe-doped CdS QDs with excellent control over size and size distribution. Study of Fe K-edge shows a complete change of Fe local environment from Fe–O to FeS.« less

Effects of pore topology and iron oxide core on doxorubicin loading and release from mesoporous silica nanoparticles

NASA Astrophysics Data System (ADS)

Ronhovde, Cicily J.; Baer, John; Larsen, Sarah C.

2017-06-01

Mesoporous silica nanoparticles (MSNs) have a network of pores that give rise to extremely high specific surface areas, making them attractive materials for applications such as adsorption and drug delivery. The pore topology can be readily tuned to achieve a variety of structures such as the hexagonally ordered Mobil Crystalline Material 41 (MCM-41) and the disordered "wormhole" (WO) mesoporous silica (MS) structure. In this work, the effects of pore topology and iron oxide core on doxorubicin loading and release were investigated using MSNs with pore diameters of approximately 3 nm and sub-100 nm particle diameters. The nanoparticles were loaded with doxorubicin, and the drug release into phosphate-buffered saline (PBS, 10 mM, pH 7.4) at 37 °C was monitored by fluorescence spectroscopy. The release profiles were fit using the Peppas model. The results indicated diffusion-controlled release for all samples. Statistically significant differences were observed in the kinetic host-guest parameters for each sample due to the different pore topologies and the inclusion of an iron oxide core. Applying a static magnetic field to the iron oxide core WO-MS shell materials did not have a significant impact on the doxorubicin release. This is the first time that the effects of pore topology and iron oxide core have been isolated from pore diameter and particle size for these materials.

Improvements on the interior structure of Mercury expected from geodesy measurements

NASA Astrophysics Data System (ADS)

Rivoldini, A.; van Hoolst, T.; Verhoeven, O.

2008-09-01

ABSTRACT We assess the improvements on the interior structure of Mercury provided by expected data from geodesy experiments to be performed with the MESSENGER and BepiColombo orbiters. The observation of obliquity will allow estimating the moment of inertia, whereas measurements of libration will determine the moment of inertia of the silicate shell (mantle and crust). Tidal measurements will constrain the Love numbers that characterize the response of Mercury to the solar tidal forcing. Here, we construct depth-dependent interior structure models of Mercury for several plausible chemical compositions of the core and of the mantle using recent data on core and mantle materials. In particular we study the core structure for different mantle mineralogies and two different temperature profiles. We investigate the influence of the core light element concentration, temperature, and melting law on core state and inner core size. We compute libration amplitude, obliquity, tidal deformation, and tidal changes in the external potential for our models.

NUCLEAR REACTOR

DOEpatents

Grebe, J.J.

1961-01-24

A core structure for neutronic reactors adapted for the propulsion of aircraft and rockets is offered. The core is designed for cooling by gaseous media, and comprises a plurality of hollow tapered tubular segments of a porous moderating material impregniated with fissionable fuel nested about a common axis. Alternate ends of the segments are joined. In operation a coolant gas passes through the porous structure and is heated.

Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets

NASA Technical Reports Server (NTRS)

Hoffmann, E. K.; Bird, R. K.; Bales, T. T.

1989-01-01

A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

Advanced Technology Composite Fuselage - Materials and Processes

NASA Technical Reports Server (NTRS)

Scholz, D. B.; Dost, E. F.; Flynn, B. W.; Ilcewicz, L. B.; Nelson, K. M.; Sawicki, A. J.; Walker, T. H.; Lakes, R. S.

1997-01-01

The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program was to develop the technology required for cost and weight efficient use of composite materials in transport fuselage structure. This contractor report describes results of material and process selection, development, and characterization activities. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of monolithic and sandwich skin panels. Circumferential frames and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant section stiffening elements. Drape forming was chosen for stringers and other stiffening elements. Significant development efforts were expended on the AFP, braiding, and RTM processes. Sandwich core materials and core edge close-out design concepts were evaluated. Autoclave cure processes were developed for stiffened skin and sandwich structures. The stiffness, strength, notch sensitivity, and bearing/bypass properties of fiber-placed skin materials and braided/RTM'd circumferential frame materials were characterized. The strength and durability of cocured and cobonded joints were evaluated. Impact damage resistance of stiffened skin and sandwich structures typical of fuselage panels was investigated. Fluid penetration and migration mechanisms for sandwich panels were studied.

Ultrasonic, microwave, and millimeter wave inspection techniques for adhesively bonded stacked open honeycomb core composites

NASA Astrophysics Data System (ADS)

Thomson, Clint D.; Cox, Ian; Ghasr, Mohammad Tayeb Ahmed; Ying, Kuang P.; Zoughi, Reza

2015-03-01

Honeycomb sandwich composites are used extensively in the aerospace industry to provide stiffness and thickness to lightweight structures. A common fabrication method for thick, curved sandwich structures is to stack and bond multiple honeycomb layers prior to machining core curvatures. Once bonded, each adhesive layer must be inspected for delaminations and the presence of unwanted foreign materials. From a manufacturing and cost standpoint, it can be advantageous to inspect the open core prior to face sheet closeout in order to reduce end-article scrap rates. However, by nature, these honeycomb sandwich composite structures are primarily manufactured from low permittivity and low loss materials making detection of delamination and some of the foreign materials (which also are low permittivity and low loss) quite challenging in the microwave and millimeter wave regime. Likewise, foreign materials such as release film in adhesive layers can be sufficiently thin as to not cause significant attenuation in through-transmission ultrasonic signals, making them difficult to detect. This paper presents a collaborative effort intended to explore the efficacy of different non-contact NDI techniques for detecting flaws in a stacked open fiberglass honeycomb core panel. These techniques primarily included air-coupled through-transmission ultrasonics, single-sided wideband synthetic aperture microwave and millimeter-wave imaging, and lens-focused technique. The goal of this investigation has been to not only evaluate the efficacy of these techniques, but also to determine their unique advantages and limitations for evaluating parameters such as flaw type, flaw size, and flaw depth.

Natural Biowaste-Cocoon-Derived Granular Activated Carbon-Coated ZnO Nanorods: A Simple Route To Synthesizing a Core-Shell Structure and Its Highly Enhanced UV and Hydrogen Sensing Properties.

PubMed

Saravanan, Adhimoorthy; Huang, Bohr-Ran; Kathiravan, Deepa; Prasannan, Adhimoorthy

2017-11-15

Granular activated carbon (GAC) materials were prepared via simple gas activation of silkworm cocoons and were coated on ZnO nanorods (ZNRs) by the facile hydrothermal method. The present combination of GAC and ZNRs shows a core-shell structure (where the GAC is coated on the surface of ZNRs) and is exposed by systematic material analysis. The as-prepared samples were then fabricated as dual-functional sensors and, most fascinatingly, the as-fabricated core-shell structure exhibits better UV and H 2 sensing properties than those of as-fabricated ZNRs and GAC. Thus, the present core-shell structure-based H 2 sensor exhibits fast responses of 11% (10 ppm) and 23.2% (200 ppm) with ultrafast response and recovery. However, the UV sensor offers an ultrahigh photoresponsivity of 57.9 A W -1 , which is superior to that of as-grown ZNRs (0.6 A W -1 ). Besides this, switching photoresponse of GAC/ZNR core-shell structures exhibits a higher switching ratio (between dark and photocurrent) of 1585, with ultrafast response and recovery, than that of as-grown ZNRs (40). Because of the fast adsorption ability of GAC, it was observed that the finest distribution of GAC on ZNRs results in rapid electron transportation between the conduction bands of GAC and ZNRs while sensing H 2 and UV. Furthermore, the present core-shell structure-based UV and H 2 sensors also well-retained excellent sensitivity, repeatability, and long-term stability. Thus, the salient feature of this combination is that it provides a dual-functional sensor with biowaste cocoon and ZnO, which is ecological and inexpensive.

Single-wall nanohorn structure and distribution of incorporated materials

NASA Astrophysics Data System (ADS)

Maigne, Alan; Gloter, Alexandre; Ajima, Kumiko; Colliex, Christian; Iijima, Sumio

2005-03-01

Single-wall carbon nanohorns (SWNHs) are unique spherical-aggregates of single-wall carbon quasi-nanotubes. So far, the observable area has been limited to the aggregate surfaces. We studied core-region structure with TEM using thickness measurement method, EELS, and EDS, and found that carbon density was uniform over the whole aggregate. This result allows to modelize the core-region and to clarify previous models of SWNHs. We used same tools to investigate the incorporation of materials such as fullerenes or platinium compounds. We found that particles can even be incorporated in the core-region and that their distribution in the aggregate depends on their concentration. The information available with these models should be useful in the study of SWNH applications to, for example, drug delivery system.

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material

DOEpatents

Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

1986-12-09

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front there through. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique. 12 figs.

Measuring of electrical changes induced by in situ combustion through flow-through electrodes in a laboratory sample of core material

DOEpatents

Lee, David O.; Montoya, Paul C.; Wayland, Jr., James R.

1986-01-01

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front therethrough. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique.

Interfacial effect on the structural and optical properties of pure SnO2 and dual shells (ZnO; SiO2) coated SnO2 core-shell nanospheres for optoelectronic applications

NASA Astrophysics Data System (ADS)

Selvi, N.; Sankar, S.; Dinakaran, K.

2014-12-01

Nanocrystallites of SnO2 core and dual shells (ZnO, SiO2) coated SnO2 core-shell nanospheres were successfully synthesized by co-precipitation method. The as prepared and annealed samples were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM) and UV-Vis analysis. XRD pattern confirms the obtained SnO2 core with tetragonal rutile crystalline structure and the shell ZnO with hexagonal structure. FTIR result shows the functional groups present in the samples. The spherical morphology and the formation of the core-shell structures have been confirmed by HRTEM measurements. The UV-Vis showed that band gap is red shifted for as-prepared and the shells coated core-shell samples. From this investigation it can be concluded that the surface modification with different metal and insulating oxides strongly influences the optical properties of the core-shell materials which enhance their potential applications towards optical devices fabrication.

Inverse Photonic Glasses by Packing Bidisperse Hollow Microspheres with Uniform Cores.

PubMed

Kim, Seung-Hyun; Magkiriadou, Sofia; Rhee, Do Kyung; Lee, Doo Sung; Yoo, Pil J; Manoharan, Vinothan N; Yi, Gi-Ra

2017-07-19

A major fabrication challenge is producing disordered photonic materials with an angle-independent structural red color. Theoretical work has shown that such a color can be produced by fabricating inverse photonic glasses with monodisperse, nontouching voids in a silica matrix. Here, we demonstrate a route toward such materials and show that they have an angle-independent red color. We first synthesize monodisperse hollow silica particles with precisely controlled shell thickness and then make glassy colloidal structures by mixing two types of hollow particles with the same core size and different shell thicknesses. We then infiltrate the interstices with index-matched polymers, producing disordered porous materials with uniform, nontouching air voids. This procedure allows us to control the light-scattering form factor and structure factor of these porous materials independently, which is not possible to do in photonic glasses consisting of packed solid particles. The structure factor can be controlled by the shell thickness, which sets the distance between pores, whereas the pore size determines the peak wave vector of the form factor, which can be set below the visible range to keep the main structural color pure. By using a binary mixture of 246 and 268 nm hollow silica particles with 180 nm cores in an index-matched polymer matrix, we achieve angle-independent red color that can be tuned by controlling the shell thickness. Importantly, the width of the reflection peak can be kept constant, even for larger interparticle distances.

Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.

PubMed

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades.

Insights into Mercury's interior structure from geodesy measurements and global contraction

NASA Astrophysics Data System (ADS)

Rivoldini, A.; Van Hoolst, T.

2014-04-01

The measurements of the gravitational field of Mercury by MESSENGER [6] and improved measurements of the spin state of Mercury [3] provide important insights on its interior structure. In particular, these data give strong constraints on the radius and density of Mercury's core [5, 2]. However, present geodesy data do not provide strong constraints on the radius of the inner core. The data allow for models with a fully molten liquid core to models which have an inner core radius that is smaller than about 1760km [5], if it is assumed that sulfur is the only light element in the core. Models without an inner core are, however, at odds with the observed internally generated magnetic field of Mercury since Mercury's dynamo cannot operate by secular cooling alone at present. The present radius of the inner core depends mainly on Mercury's thermal state and light elements inside the core. Because of the secular cooling of the planet,the temperature inside the core drops below the liquidus temperature of the core material somewhere in the core and leads to the formation of an inner core and to the global contraction of the planet. The amount of contraction depends on the temperature decrease, on the thermal expansion of the materials inside the planet, and on the volume of crystallized liquid core alloy. In this study we use geodesy data, the recent estimate about the radial contraction of Mercury [1], and thermo-chemical evolution calculations in order to improve our knowledge about Mercury's inner core radius and thermal state. Since data from remote sensing of Mercury's surface [4] indicate that Mercury formed under reducing conditions we consider models that have sulfur and silicon as light elements inside their core. Unlike sulfur, which does almost not partition into solid iron under Mercury's core pressure and temperature conditions, silicon partitions virtually equally between solid and liquid iron. As a consequence, the density difference between the liquid and the crystallized material is smaller than for sulfur as only light element inside the core and therefore, for a given inner core radius the contraction of the planet is likely smaller.

Application of fiber-reinforced bismaleimide materials to aircraft nacelle structures

NASA Technical Reports Server (NTRS)

Peros, Vasilios; Ruth, John; Trawinski, David

1992-01-01

Existing aircraft engine nacelle structures employ advanced composite materials to reduce weight and thereby increase overall performance. Use of advanced composite materials on existing aircraft nacelle structures includes fiber-reinforced epoxy structures and has typically been limited to regions furthest away from the hot engine core. Portions of the nacelle structure that are closer to the engine require materials with a higher temperature capability. In these portions, existing nacelle structures employ aluminum sandwich construction and skin/stringer construction. The aluminum structure is composed of many detail parts and assemblies and is usually protected by some form of ablative, insulator, or metallic thermal shield. A one-piece composite inner cowl for a new-generation engine nacelle structure has been designed using fiber-reinforced bismaleimide (BMI) materials and honeycomb core in a sandwich construction. The new composite design has many advantages over the existing aluminum structure. Multiple details were integrated into the one-piece composite design, thereby significantly reducing the number of detail parts and fasteners. The use of lightweight materials and the reduction of the number of joints result in a significant weight reduction over the aluminum design; manufacturing labor and the overall number of tools required have also been reduced. Several significant technical issues were addressed in the development of a BMI composite design. Technical evaluation of the available BMI systems led to the selection of a toughened BMI material which was resistant to microcracking under thermal cyclic loading and enhanced the damage tolerance of the structure. Technical evaluation of the degradation of BMI materials in contact with aluminum and other metals validated methods for isolation of the various materials. Graphite-reinforced BMI in contact with aluminum and some steels was found to degrade in salt spray testing. Isolation techniques such as those used for graphite-reinforced epoxy structures were shown to provide adequate protection. The springback and producibility of large BMI structures were evaluated by manufacturing prototype hardware which had the full-scale cross section of the one-piece composite structure.

3D FDM production and mechanical behavior of polymeric sandwich specimens embedding classical and honeycomb cores

NASA Astrophysics Data System (ADS)

Brischetto, Salvatore; Ferro, Carlo Giovanni; Torre, Roberto; Maggiore, Paolo

2018-04-01

Desktop 3D FDM (Fused Deposition Modelling) printers are usually employed for the production of nonstructural objects. In recent years, the present authors tried to use this technology also to produce structural elements employed in the construction of small UAVs (Unmanned Aerial Vehicles). Mechanical stresses are not excessive for small multirotor UAVs. Therefore, the FDM technique combined with polymers, such as the ABS (Acrylonitrile Butadiene Styrene) and the PLA(Poly Lactic Acid), can be successfully employed to produce structural components. The present new work is devoted to the production and preliminary structural analysis of sandwich configurations. These new lamination schemes could lead to an important weight reduction without significant decreases of mechanical properties. Therefore, it could be possible, for the designed application (e.g., a multifunctional small UAV produced via FDM), to have stiffener and lighter structures easy to be manufactured with a low-cost 3D printer. The new sandwich specimens here proposed are PLA sandwich specimens embedding a PLA honeycomb core produced by means of the same extruder, multilayered specimens with ABS external layers and an internal homogeneous PLA core using different extruders for the two materials, sandwich specimens with external ABS skins and an internal PLA honeycomb core using different extruders for the two materials, and sandwich specimens where two different extruders have been employed for PLA material used for skins and for the internal honeycomb core. For all the proposed configurations, a detailed description of the production activity is given.Moreover, several preliminary results about three-point bending tests, different mechanical behaviors and relative delamination problems for each sandwich configuration will be discussed in depth.

COOLED NEUTRONIC REACTOR

DOEpatents

Binner, C.R.; Wilkie, C.B.

1958-03-18

This patent relates to a design for a reactor of the type in which a fluid coolant is flowed through the active portion of the reactor. This design provides for the cooling of the shielding material as well as the reactor core by the same fluid coolant. The core structure is a solid moderator having coolant channels in which are disposed the fuel elements in rod or slug form. The coolant fluid enters the chamber in the shield, in which the core is located, passes over the inner surface of said chamber, enters the core structure at the center, passes through the coolant channels over the fuel elements and out through exhaust ducts.

MEANS FOR COOLING REACTORS

DOEpatents

Wheeler, J.A.

1957-11-01

A design of a reactor is presented in which the fuel elements may be immersed in a liquid coolant when desired without the necessity of removing them from the reactor structure. The fuel elements, containing the fissionable material are in plate form and are disposed within spaced slots in a moderator material, such as graphite to form the core. Adjacent the core is a tank containing the liquid coolant. The fuel elements are mounted in spaced relationship on a rotatable shaft which is located between the core and the tank so that by rotation of the shaft the fuel elements may be either inserted in the slots in the core to sustain a chain reaction or immersed in the coolant.

Unveiling the composite structures of emissive consolidated p-i-n junction nanocells for white light emission.

PubMed

Lee, Kyu Seung; Shim, Jaeho; Lee, Hyunbok; Yim, Sang-Youp; Angadi, Basavaraj; Lim, Byungkwon; Son, Dong Ick

2018-06-08

Hybrid organic-Red-Green-Blue (RGB) color quantum dots were incorporated into consolidated p(polymer)-i(RGB quantum dots)-n(small molecules) junction structures to fabricate a single active layer for a light emitting diode device for white electroluminescence. The semiconductor RGB quantum dots, as an intrinsic material, were electrostatically bonded between functional groups of the p-type polymer organic material core surface and the n-type small molecular organic material shell surface. The ZnCdSe/ZnS and CdSe/ZnS quantum dots distributed uniformly and isotropically surrounding the polymer core which in turn was surrounded by small molecular organic materials. In the present study, we have identified the mechanisms of chemical synthesis and interactions of the p-i-n junction nanocell structure through modeling studies by DFT calculations. We have also investigated optical, structural and electrical properties along with the carrier transport mechanism of the light emitting diodes which have a single active layer of consolidated p-i-n junction nanocells for white electroluminescence.

Elastic stability of cylindrical shells with soft elastic cores: Biomimicking natural tubular structures

NASA Astrophysics Data System (ADS)

Karam, Gebran Nizar

1994-01-01

Thin walled cylindrical shell structures are widespread in nature: examples include plant stems, porcupine quills, and hedgehog spines. All have an outer shell of almost fully dense material supported by a low density, cellular core. In nature, all are loaded in combination of axial compression and bending: failure is typically by buckling. Natural structures are often optimized. Here we have analyzed the elastic buckling of a thin cylindrical shell supported by an elastic core to show that this structural configuration achieves significant weight saving over a hollow cylinder. The results of the analysis are compared with data from an extensive experimental program on uniaxial compression and four point bending tests on silicone rubber shells with and without compliant foam cores. The analysis describes the results of the mechanical tests well. Characterization of the microstructures of several natural tubular structures with foamlike cores (plant stems, quills, and spines) revealed them to be close to the optimal configurations predicted by the analytical model. Biomimicking of natural cylindrical shell structures and evolutionary design processes may offer the potential to increase the mechanical efficiency of engineering cylindrical shells.

Evaluation of Ceramic Honeycomb Core Compression Behavior at Room Temperature

NASA Technical Reports Server (NTRS)

Bird, Richard K.; Lapointe, Thomas S.

2013-01-01

Room temperature flatwise compression tests were conducted on two varieties of ceramic honeycomb core specimens that have potential for high-temperature structural applications. One set of specimens was fabricated using strips of a commercially-available thin-gage "ceramic paper" sheet molded into a hexagonal core configuration. The other set was fabricated by machining honeycomb core directly from a commercially available rigid insulation tile material. This paper summarizes the results from these tests.

Experimental investigation of fiberglass sandwich composite bending behaviour after severe aging condition

NASA Astrophysics Data System (ADS)

Gambaro, Carla; Lertora, Enrico; Mandolfino, Chiara

2016-10-01

Fiber Reinforced Polymer (FRP) sandwich panels are increasing their application as structural and non-structural components in all kinds of construction. By varying the material and thickness of core and face sheets, it is possible to obtain sandwich structures with different properties and performance. In particular, their advantages as lightweight and high mechanical properties make them extremely suitable for the transport industry. One of the most critical aspects regarding composite materials for engineering application is their performance after hygrothermal aging. The panels used in this study are composed of low density core, made by thermosetting resin foam with microspheres and glass fibers rolled until obtaining the required thickness, and two face sheets of the same material but realized in high density. In this study, the authors focused on the bending behaviour of this kind of sandwich panel, as received and after severe aging cycles.

Patched bimetallic surfaces are active catalysts for ammonia decomposition.

PubMed

Guo, Wei; Vlachos, Dionisios G

2015-10-07

Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

Patched bimetallic surfaces are active catalysts for ammonia decomposition

NASA Astrophysics Data System (ADS)

Guo, Wei; Vlachos, Dionisios G.

2015-10-01

Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

Silicon as a potential anode material for Li-ion batteries: where size, geometry and structure matter.

PubMed

Ashuri, Maziar; He, Qianran; Shaw, Leon L

2016-01-07

Silicon has attracted huge attention in the last decade because it has a theoretical capacity ∼10 times that of graphite. However, the practical application of Si is hindered by three major challenges: large volume expansion during cycling (∼300%), low electrical conductivity, and instability of the SEI layer caused by repeated volume changes of the Si material. Significant research efforts have been devoted to addressing these challenges, and significant breakthroughs have been made particularly in the last two years (2014 and 2015). In this review, we have focused on the principles of Si material design, novel synthesis methods to achieve such structural designs, and the synthesis-structure-performance relationships to enhance the properties of Si anodes. To provide a systematic overview of the Si material design strategies, we have grouped the design strategies into several categories: (i) particle-based structures (containing nanoparticles, solid core-shell structures, hollow core-shell structures, and yolk-shell structures), (ii) porous Si designs, (iii) nanowires, nanotubes and nanofibers, (iv) Si-based composites, and (v) unusual designs. Finally, our personal perspectives on outlook are offered with an aim to stimulate further discussion and ideas on the rational design of durable and high performance Si anodes for the next generation Li-ion batteries in the near future.

Unusual behavior in magnesium-copper cluster matter produced by helium droplet mediated deposition

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

Emery, S. B., E-mail: samuel.emery@navy.mil; Little, B. K.; Air Force Research Laboratory, Munitions Directorate, 2306 Perimeter Rd., Eglin AFB, Florida 32542

2015-02-28

We demonstrate the ability to produce core-shell nanoclusters of materials that typically undergo intermetallic reactions using helium droplet mediated deposition. Composite structures of magnesium and copper were produced by sequential condensation of metal vapors inside the 0.4 K helium droplet baths and then gently deposited onto a substrate for analysis. Upon deposition, the individual clusters, with diameters ∼5 nm, form a cluster material which was subsequently characterized using scanning and transmission electron microscopies. Results of this analysis reveal the following about the deposited cluster material: it is in the un-alloyed chemical state, it maintains a stable core-shell 5 nm structuremore » at sub-monolayer quantities, and it aggregates into unreacted structures of ∼75 nm during further deposition. Surprisingly, high angle annular dark field scanning transmission electron microscopy images revealed that the copper appears to displace the magnesium at the core of the composite cluster despite magnesium being the initially condensed species within the droplet. This phenomenon was studied further using preliminary density functional theory which revealed that copper atoms, when added sequentially to magnesium clusters, penetrate into the magnesium cores.« less

Rigid polyurethane foam – kenaf core composites for structural applications

USDA-ARS?s Scientific Manuscript database

Kenaf (Hibiscus cannabinus L.) is a fast growing summer annual crop with numerous commercial applications (fibers, biofuels, bioremediation, paper pulp, building materials, cover crops, and livestock forages). The stalks of the kenaf plants contain two distinct fiber types, bast and core fibers. The...

Metal-Organic Frameworks-Derived Hierarchical Co3O4 Structures as Efficient Sensing Materials for Acetone Detection.

PubMed

Zhang, Rui; Zhou, Tingting; Wang, Lili; Zhang, Tong

2018-03-21

Highly sensitive and stable gas sensors have attracted much attention because they are the key to innovations in the fields of environment, health, energy savings and security, etc. Sensing materials, which influence the practical sensing performance, are the crucial parts for gas sensors. Metal-organic frameworks (MOFs) are considered as alluring sensing materials for gas sensors because of the possession of high specific surface area, unique morphology, abundant metal sites, and functional linkers. Herein, four kinds of porous hierarchical Co 3 O 4 structures have been selectively controlled by optimizing the thermal decomposition (temperature, rate, and atmosphere) using ZIF-67 as precursor that was obtained from coprecipitation method with the co-assistance of cobalt salt and 2-methylimidazole in the solution of methanol. These hierarchical Co 3 O 4 structures, with controllable cross-linked channels, meso-/micropores, and adjustable surface area, are efficient catalytic materials for gas sensing. Benefits from structural advantages, core-shell, and porous core-shell Co 3 O 4 exhibit enhanced sensing performance compared to those of porous popcorn and nanoparticle Co 3 O 4 to acetone gas. These novel MOF-templated Co 3 O 4 hierarchical structures are so fantastic that they can be expected to be efficient sensing materials for development of low-temperature operating gas sensors.

Template-free synthesis of ordered ZnO@ZnS core-shell arrays for high performance supercapacitors.

PubMed

Yan, Hailong; Li, Tong; Lu, Yang; Cheng, Jinbing; Peng, Tao; Xu, Jinyou; Yang, Linying; Hua, Xiangqiang; Liu, Yunxin; Luo, Yongsong

2016-11-28

In this article, ordered ZnO@ZnS core-shell structures have been produced on a stainless mesh by a two-step approach without using a template. ZnO nanorods fabricated by a chemical vapor method are transferred into a 50 ml autoclave for a second stage ion-exchange reaction followed by heating at 120 °C for 4-16 h. The ZnO core is prepared as the conducting channel and ZnS as the active material. Such unique architecture exhibits remarkable electrochemical performance with high capacitance and desirable cycle life. When evaluating as the electrode for supercapacitors, the ZnO@ZnS core-shell structure delivers a high specific capacitance of 603.8 F g -1 at a current density of 2 A g -1 , with 9.4% capacitance loss after cycling 3000 times. The fabrication strategy presented here is simple and cost-effective, which can open new avenues for large-scale applications of the novel materials in energy storage.

Structural materials for Gen-IV nuclear reactors: Challenges and opportunities

NASA Astrophysics Data System (ADS)

Murty, K. L.; Charit, I.

2008-12-01

Generation-IV reactor design concepts envisioned thus far cater toward a common goal of providing safer, longer lasting, proliferation-resistant and economically viable nuclear power plants. The foremost consideration in the successful development and deployment of Gen-IV reactor systems is the performance and reliability issues involving structural materials for both in-core and out-of-core applications. The structural materials need to endure much higher temperatures, higher neutron doses and extremely corrosive environment, which are beyond the experience of the current nuclear power plants. Materials under active consideration for use in different reactor components include various ferritic/martensitic steels, austenitic stainless steels, nickel-base superalloys, ceramics, composites, etc. This paper presents a summary of various Gen-IV reactor concepts, with emphasis on the structural materials issues depending on the specific application areas. This paper also discusses the challenges involved in using the existing materials under both service and off-normal conditions. Tasks become increasingly complex due to the operation of various fundamental phenomena like radiation-induced segregation, radiation-enhanced diffusion, precipitation, interactions between impurity elements and radiation-produced defects, swelling, helium generation and so forth. Further, high temperature capability (e.g. creep properties) of these materials is a critical, performance-limiting factor. It is demonstrated that novel alloy and microstructural design approaches coupled with new materials processing and fabrication techniques may mitigate the challenges, and the optimum system performance may be achieved under much demanding conditions.

Impact damage detection in sandwich composite structures using Lamb waves and laser vibrometry

NASA Astrophysics Data System (ADS)

Lamboul, B.; Passilly, B.; Roche, J.-M.; Osmont, D.

2013-01-01

This experimental study explores the feasibility of impact damage detection in composite sandwich structures using Lamb wave excitation and signals acquired with a laser Doppler vibrometer. Energy maps are computed from the transient velocity wave fields and used to highlight defect areas in impacted coupons of foam core and honeycomb core sandwich materials. The technique performs well for the detection of barely visible damage in this type of material, and is shown to be robust in the presence of wave reverberation. Defect extent information is not always readily retrieved from the obtained defect signatures, which depend on the wave - defect interaction mechanisms.

High-Performance One-Body Core/Shell Nanowire Supercapacitor Enabled by Conformal Growth of Capacitive 2D WS2 Layers.

PubMed

Choudhary, Nitin; Li, Chao; Chung, Hee-Suk; Moore, Julian; Thomas, Jayan; Jung, Yeonwoong

2016-12-27

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have emerged as promising capacitive materials for supercapacitor devices owing to their intrinsically layered structure and large surface areas. Hierarchically integrating 2D TMDs with other functional nanomaterials has recently been pursued to improve electrochemical performances; however, it often suffers from limited cyclic stabilities and capacitance losses due to the poor structural integrity at the interfaces of randomly assembled materials. Here, we report high-performance core/shell nanowire supercapacitors based on an array of one-dimensional (1D) nanowires seamlessly integrated with conformal 2D TMD layers. The 1D and 2D supercapacitor components possess "one-body" geometry with atomically sharp and structurally robust core/shell interfaces, as they were spontaneously converted from identical metal current collectors via sequential oxidation/sulfurization. These hybrid supercapacitors outperform previously developed any stand-alone 2D TMD-based supercapacitors; particularly, exhibiting an exceptional charge-discharge retention over 30,000 cycles owing to their structural robustness, suggesting great potential for unconventional energy storage technologies.

Synthesis and Characterization of Mn3O4 - Graphene Core - Shell Quantum Dots for Electrochemical Pseudocapacitor Applications

NASA Astrophysics Data System (ADS)

Ko, Yohan; Son, Dong Ick

2018-05-01

We report on the in-situ chemical growth of unique core-shell quantum dots (QDs) with single layer graphene on the surfaces of the Mn3O4 QDs and on their structural, optical and electrical properties. The Mn3O4-graphene QDs were synthesized through a simple hydrothermal technique. In order to enhance performance for electrochemical energy storage, we developed core (active material) - shell (conductive material)-type Mn3O4 - graphene QDs as electrode materials by using an aqueous electrolyte (6M KOH). As a result, the performance of electrochemical energy storage exhibit a specific capacitance of 452.72 Fg-1 at a current density of 1 Ag-1.

Role of Absorbing Nanocrystal Cores in Soft Photonic Crystals: A Spectroscopy and SANS Study.

PubMed

Rauh, Astrid; Carl, Nico; Schweins, Ralf; Karg, Matthias

2018-01-23

Periodic superstructures of plasmonic nanoparticles have attracted significant interest because they can support coupled plasmonic modes, making them interesting for plasmonic lasing, metamaterials, and as light-management structures in thin-film optoelectronic devices. We have recently shown that noble metal hydrogel core-shell colloids allow for the fabrication of highly ordered 2-dimensional plasmonic lattices that show surface lattice resonances as the result of plasmonic/diffractive coupling (Volk, K.; Fitzgerald, J. P. S.; Ruckdeschel, P.; Retsch, M.; König, T. A. F.; Karg, M. Reversible Tuning of Visible Wavelength Surface Lattice Resonances in Self-Assembled Hybrid Monolayers. Adv. Optical Mater. 2017, 5, 1600971, DOI: 10.1002/adom.201600971). In the present work, we study the photonic properties and structure of 3-dimensional crystalline superstructures of gold hydrogel core-shell colloids and their pitted counterparts without gold cores. We use far-field extinction spectroscopy to investigate the optical response of these superstructures. Narrow Bragg peaks are measured, independently of the presence or absence of the gold cores. All crystals show a significant reduction in low-wavelength scattering. This leads to a significant enhancement of the plasmonic properties of the samples prepared from gold-nanoparticle-containing core-shell colloids. Plasmonic/diffractive coupling is not evident, which we mostly attribute to the relatively small size of the gold cores limiting the effective coupling strength. Small-angle neutron scattering is applied to study the crystal structure. Bragg peaks of several orders clearly assignable to an fcc arrangement of the particles are observed for all crystalline samples in a broad range of volume fractions. Our results indicate that the nanocrystal cores do not influence the overall crystallization behavior or the crystal structure. These are important prerequisites for future studies on photonic materials built from core-shell particles, in particular, the development of new photonic materials from plasmonic nanocrystals.

Enhanced flexibility and electron-beam-controlled shape recovery in alumina-coated Au and Ag core-shell nanowires

NASA Astrophysics Data System (ADS)

Vlassov, Sergei; Polyakov, Boris; Vahtrus, Mikk; Mets, Magnus; Antsov, Mikk; Oras, Sven; Tarre, Aivar; Arroval, Tõnis; Lõhmus, Rünno; Aarik, Jaan

2017-12-01

The proper choice of coating materials and methods in core-shell nanowire (NW) engineering is crucial to assuring improved characteristics or even new functionalities of the resulting composite structures. In this paper, we have reported electron-beam-induced reversible elastic-to-plastic transition in Ag/Al2O3 and Au/Al2O3 NWs prepared by the coating of Ag and Au NWs with Al2O3 by low-temperature atomic layer deposition. The observed phenomenon enabled freezing the bent core-shell NW at any arbitrary curvature below the yield strength of the materials and later restoring its initially straight profile by irradiating the NW with electrons. In addition, we demonstrated that the coating efficiently protects the core material from fracture and plastic yield, allowing it to withstand significantly higher deformations and stresses in comparison to uncoated NW.

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

Photoenergy Harvesting Organic PV Cells Using Modified Photosynthetic Light-Harvesting Complex for Energy Harvesting Materials

DTIC Science & Technology

2008-07-03

complex is still unclear even in the crystal structure of RC-LH1 core complex from Rhodopseudomonas (Rps.) palustris [1]. In this study, we use a...complex of R. palustris . 16 The NIR absorption spectra of these core complexes on the electrode indicate that these complexes are stable when...as the LH or the core complex. For example, the core complex, isolated from the photosynthetic bacterium, Rps. palustris , was successfully

Synthesis and characterization of metal oxide-polyaniline emeraldine salt based nanocomposite

NASA Astrophysics Data System (ADS)

Kumar, K. Siva; Kavitha, B.; Prabakar, K.; Srinivasu, D.; Srinivas, Ch.; Narsimlu, N.

2013-02-01

This paper describes the synthesis of TiO2 (core)/Polyaniline (shell) core-shell structured nanocomposites and characterization of the synthesized material. The morphological characterization is performed with XRD, SEM, DLS and SANS. Spectroscopic characterization is performed with FTIR, UV/Visible and ESR techniques.

Mold with improved core for metal casting operation

DOEpatents

Gritzner, Verne B.; Hackett, Donald W.

1977-01-01

The present invention is directed to a mold containing an improved core for use in casting hollow, metallic articles. The core is formed of, or covered with, a layer of cellular material which possesses sufficient strength to maintain its structural integrity during casting, but will crush to alleviate the internal stresses that build up if the normal contraction during solidification and cooling is restricted.

Kohn-Sham Band Structure Benchmark Including Spin-Orbit Coupling for 2D and 3D Solids

NASA Astrophysics Data System (ADS)

Huhn, William; Blum, Volker

2015-03-01

Accurate electronic band structures serve as a primary indicator of the suitability of a material for a given application, e.g., as electronic or catalytic materials. Computed band structures, however, are subject to a host of approximations, some of which are more obvious (e.g., the treatment of the exchange-correlation of self-energy) and others less obvious (e.g., the treatment of core, semicore, or valence electrons, handling of relativistic effects, or the accuracy of the underlying basis set used). We here provide a set of accurate Kohn-Sham band structure benchmarks, using the numeric atom-centered all-electron electronic structure code FHI-aims combined with the ``traditional'' PBE functional and the hybrid HSE functional, to calculate core, valence, and low-lying conduction bands of a set of 2D and 3D materials. Benchmarks are provided with and without effects of spin-orbit coupling, using quasi-degenerate perturbation theory to predict spin-orbit splittings. This work is funded by Fritz-Haber-Institut der Max-Planck-Gesellschaft.

Propagation of Electromagnetic Waves in Slab Waveguide Structure Consisting of Chiral Nihility Claddings and Negative-Index Material Core Layer

NASA Astrophysics Data System (ADS)

Helal, Alaa N. Abu; Taya, Sofyan A.; Elwasife, Khitam Y.

2018-06-01

The dispersion equation of an asymmetric three-layer slab waveguide, in which all layers are chiral materials is presented. Then, the dispersion equation of a symmetric slab waveguide, in which the claddings are chiral materials and the core layer is negative index material, is derived. Normalized cut-off frequencies, field profile, and energies flow of right-handed and left-handed circularly polarized modes are derived and plotted. We consider both odd and even guided modes. Numerical results of guided low-order modes are provided. Some novel features, such as abnormal dispersion curves, are found.

Electronic, Optical, and Thermal Properties of Reduced-Dimensional Semiconductors

NASA Astrophysics Data System (ADS)

Huang, Shouting

Reduced-dimensional materials have attracted tremendous attention because of their new physics and exotic properties, which are of great interests for fundamental science. More importantly, the manipulation and engineering of matter on an atomic scale yield promising applications for many fields including nanoelectronics, nanobiotechnology, environments, and renewable energy. Because of the unusual quantum confinement and enhanced surface effect of reduced-dimensional materials, traditional empirical models suffer from necessary but unreliable parameters extracted from previously-studied bulk materials. In this sense, quantitative, parameter-free approaches are highly useful for understanding properties of reduced-dimensional materials and, furthermore, predicting their novel applications. The first-principles density functional theory (DFT) is proven to be a reliable and convenient tool. In particular, recent progress in many-body perturbation theory (MBPT) makes it possible to calculate excited-state properties, e.g., quasiparticle (QP) band gap and optical excitations, by the first-principles approach based on DFT. Therefore, during my PhD study, I employed first-principles calculations based on DFT and MBPT to systematically study fundamental properties of typical reduced-dimensional semiconductors, i.e., the electronic structure, phonons, and optical excitations of core-shell nanowires (NWs) and graphene-like two-dimensional (2D) structures of current interests. First, I present first-principles studies on how to engineer band alignments of nano-sized radial heterojunctions, Si/Ge core-shell NWs. Our calculation reveals that band offsets in these one-dimensional (1D) nanostructures can be tailored by applying axial strain or varying core-shell sizes. In particular, the valence band offset can be efficiently tuned across a wide range and even be diminished via applied strain. Two mechanisms contribute to this tuning of band offsets. Furthermore, varying the size of Si/Ge core-shell NWs and corresponding quantum confinement is shown to be efficient for modifying both valence and conduction band offsets simultaneously. Our proposed approaches to control band offsets in nano-sized heterojunctions may be of practical interest for nanoelectronic and photovoltaic applications. Additionally, I also studied the lattice vibrational modes of Si/Ge core-shell N-Ws. Our calculations show that the internal strain induced by the lattice mismatch between core and shell plays an important role in significantly shifting the frequency of characteristic optical modes of core-shell NWs. In particular, our simulation demonstrates that these frequency shifts can be detected by Raman-scattering experiments, giving rise to a convenient and nondestructive way to obtain structural information of core-shell materials. Meanwhile, another type of collective modes, the radial breathing modes (RBM), is identified in Si-core/Ge-shell NWs and their frequency dependence is explained by an elastic media model. Our studied vibrational modes and their frequency evolution are useful for thermoelectric applications based on core-shell nanostructures. Then I studied optical properties and exciton spectra of 2D semiconducting carbon structures. The energy spectra and wavefunctions of excitons in the 2D graphene derivatives, i.e., graphyne and graphane, are found to be strongly modified by quantum confinement, making them qualitatively different from the usual Rydberg series. However, their parity and optical selection rules are preserved. Thus a one-parameter hydrogenic model is applied to quantitatively explain the ab initio exciton spectra, and allows one to extrapolate the electron-hole binding energy from optical spectroscopies of 2D semiconductors without costly simulations. Meanwhile, our calculated optical absorption spectrum and enhanced spin singlet-triplet splitting project graphyne, an allotrope of graphene, as a good candidate for intriguing energy and biomedical applications. Lastly, we report first-principles results on electronic structures of 2D graphene-like system, i.e., silicene. For planar and simply buckled silicene structures, we confirm their zero-gap nature and show a significant renormalization of their Fermi velocity by including many-electron effects. However, the other two recently proposed silicene structures exhibit a finite band gap, indicating that they are gapped semiconductors instead of expected Dirac-fermion semimetals. This finite band gap of the latter two structures is preserved even with the Ag substrate included. The gap opening is explained by the symmetry breaking of the buckled structures. Moreover, our GW calculation reveals enhanced many-electron effects in these 2D structures. Finally the band gap of the latter two structures can be tuned in a wide range by applying strain.

In situ TEM and analytical STEM studies of ZnO nanotubes with Sn cores and Sn nanodrops

NASA Astrophysics Data System (ADS)

Ortega, Y.; Jäger, W.; Piqueras, J.; Häussler, D.; Fernández, P.

2013-10-01

ZnO nanorods with Sn core regions grown by a thermal evaporation-deposition method from a mixture of SnO2 and ZnS powders as precursors, are used to study the behaviour of liquid metal in the nanotubes' core regions and the formation of liquid metal nanodrops at the tube ends by in situ TEM experiments. The compositions of the core materials and of the nanodrops were assessed by employing HAADF-STEM imaging and spatially resolved EDXS measurements. By applying variable thermal load through changing the electron-beam flux of the electron microscope, melting of the metallic core can be induced and the behaviour of the liquid metal of the nanorods can be monitored locally. Within the nanorod core, melting and reversible thermal expansion and contraction of Sn core material is reproducibly observed. For nanotubes with core material near-tip regions, a nanodrop emerges from the tip upon melting the core material, followed by reabsorption of the melt into the core and re-solidification upon decreasing the heat load, being reminiscent of a ‘soldering nanorod’. The radius of the liquid nanodrop can reach a few tens of nanometres, containing a total volume of 10-20 up to 10-18 l of liquid Sn. In situ TEM confirms that the radius of the nanodrop can be controlled via the thermal load: it increases with increasing temperature and decreases with decreasing temperature. In addition, some phenomena related to structure modifications during extended electron-beam exposure are also described.

Effects of core-to-dentin thickness ratio on the biaxial flexural strength, reliability, and fracture mode of bilayered materials of zirconia core (Y-TZP) and veneer indirect composite resins.

PubMed

Su, Naichuan; Liao, Yunmao; Zhang, Hai; Yue, Li; Lu, Xiaowen; Shen, Jiefei; Wang, Hang

2017-01-01

Indirect composite resins (ICR) are promising alternatives as veneering materials for zirconia frameworks. The effects of core-to-dentin thickness ratio (C/Dtr) on the mechanical property of bilayered veneer ICR/yttria-tetragonal zirconia polycrystalline (Y-TZP) core disks have not been previously studied. The purpose of this in vitro study was to assess the effects of C/Dtr on the biaxial flexural strength, reliability, and fracture mode of bilayered veneer ICR/ Y-TZP core disks. A total of 180 bilayered 0.6-mm-thick composite resin disks in core material and C/Dtr of 2:1, 1:1, and 1:2 were tested with either core material placed up or placed down for piston-on-3-ball biaxial flexural strength. The mean biaxial flexural strength, Weibull modulus, and fracture mode were measured to evaluate the variation trend of the biaxial flexural strength, reliability, and fracture mode of the bilayered disks with various C/Dtr. One-way analysis of variance (ANOVA) and chi-square tests were used to evaluate the variation tendency of fracture mode with the C/Dtr or material placed down during testing (α=.05). Light microscopy was used to identify the fracture mode. The mean biaxial flexural strength and reliability improved with the increase in C/Dtr when specimens were tested with the core material either up and down, and depended on the materials that were placed down during testing. The rates of delamination, Hertzian cone cracks, subcritical radial cracks, and number of fracture fragments partially depended on the C/Dtr and the materials that were placed down during testing. The biaxial flexural strength, reliability, and fracture mode in bilayered structures of Y-TZP core and veneer ICR depend on both the C/Dtr and the material that was placed down during testing. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Rocky core solubility in Jupiter and giant exoplanets.

PubMed

Wilson, Hugh F; Militzer, Burkhard

2012-03-16

Gas giants are believed to form by the accretion of hydrogen-helium gas around an initial protocore of rock and ice. The question of whether the rocky parts of the core dissolve into the fluid H-He layers following formation has significant implications for planetary structure and evolution. Here we use ab initio calculations to study rock solubility in fluid hydrogen, choosing MgO as a representative example of planetary rocky materials, and find MgO to be highly soluble in H for temperatures in excess of approximately 10,000 K, implying the potential for significant redistribution of rocky core material in Jupiter and larger exoplanets.

Investigation of mechanical properties and deformation behavior of single-crystal Al-Cu core-shell nanowire generated using non-equilibrium molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Sarkar, Jit

2018-06-01

Molecular dynamics (MD) simulation studies were carried out to generate a cylindrical single-crystal Al-Cu core-shell nanowire and its mechanical properties like yield strength and Young's modulus were evaluated in comparison to a solid aluminum nanowire and hollow copper nanowire which combines to constitute the core-shell structure respectively. The deformation behavior due to changes in the number of Wigner-Seitz defects and dislocations during the entire tensile deformation process was thoroughly studied for the Al-Cu core-shell nanowire. The single-crystal Al-Cu core-shell nanowire shows much higher yield strength and Young's modulus in comparison to the solid aluminum core and hollow copper shell nanowire due to tangling of dislocations caused by lattice mismatch between aluminum and copper. Thus, the Al-Cu core-shell nanowire can be reinforced in different bulk matrix to develop new type of light-weight nanocomposite materials with greatly enhanced material properties.

An Investigation on Low Velocity Impact Response of Multilayer Sandwich Composite Structures

PubMed Central

Jedari Salami, S.; Sadighi, M.; Shakeri, M.; Moeinfar, M.

2013-01-01

The effects of adding an extra layer within a sandwich panel and two different core types in top and bottom cores on low velocity impact loadings are studied experimentally in this paper. The panel includes polymer composite laminated sheets for faces and the internal laminated sheet called extra layer sheet, and two types of crushable foams are selected as the core material. Low velocity impact tests were carried out by drop hammer testing machine to the clamped multilayer sandwich panels with expanded polypropylene (EPP) and polyurethane rigid (PUR) in the top and bottom cores. Local displacement of the top core, contact force and deflection of the sandwich panel were obtained for different locations of the internal sheet; meanwhile the EPP and PUR were used in the top and bottom cores alternatively. It was found that the core material type has made significant role in improving the sandwich panel's behavior compared with the effect of extra layer location. PMID:24453804

Full-Color Biomimetic Photonic Materials with Iridescent and Non-Iridescent Structural Colors

PubMed Central

Kawamura, Ayaka; Kohri, Michinari; Morimoto, Gen; Nannichi, Yuri; Taniguchi, Tatsuo; Kishikawa, Keiki

2016-01-01

The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers. The size of the core-shell particles was controlled by adjusting the core polystyrene (PSt) particles’ diameter and the PDA shell thicknesses. The blackness and refractive index of the colloidal particles could be adjusted by controlling the thickness of the PDA shell. The arrangement of the particles was controlled by adjusting the surface roughness of the core-shell particles. This method enabled the production of both iridescent and non-iridescent structural colors from only one component. This simple and novel process of using core-shell particles containing PDA shell layers can be used in basic research on structural colors in nature and their practical applications. PMID:27658446

Full-Color Biomimetic Photonic Materials with Iridescent and Non-Iridescent Structural Colors.

PubMed

Kawamura, Ayaka; Kohri, Michinari; Morimoto, Gen; Nannichi, Yuri; Taniguchi, Tatsuo; Kishikawa, Keiki

2016-09-23

The beautiful structural colors in bird feathers are some of the brightest colors in nature, and some of these colors are created by arrays of melanin granules that act as both structural colors and scattering absorbers. Inspired by the color of bird feathers, high-visibility structural colors have been created by altering four variables: size, blackness, refractive index, and arrangement of the nano-elements. To control these four variables, we developed a facile method for the preparation of biomimetic core-shell particles with melanin-like polydopamine (PDA) shell layers. The size of the core-shell particles was controlled by adjusting the core polystyrene (PSt) particles' diameter and the PDA shell thicknesses. The blackness and refractive index of the colloidal particles could be adjusted by controlling the thickness of the PDA shell. The arrangement of the particles was controlled by adjusting the surface roughness of the core-shell particles. This method enabled the production of both iridescent and non-iridescent structural colors from only one component. This simple and novel process of using core-shell particles containing PDA shell layers can be used in basic research on structural colors in nature and their practical applications.

Reversed Cherenkov emission of terahertz waves from an ultrashort laser pulse in a sandwich structure with nonlinear core and left-handed cladding.

PubMed

Bakunov, M I; Mikhaylovskiy, R V; Bodrov, S B; Luk'yanchuk, B S

2010-01-18

We propose a scheme for an experimental verification of the reversed Cherenkov effect in left-handed media. The scheme uses optical-to-terahertz conversion in a planar sandwichlike structure that consists of a nonlinear core cladded with a material that exhibits left-handedness at terahertz frequencies. The focused into a line femtosecond laser pulse propagates in the core and emits Cherenkov wedge of terahertz waves in the cladding. We developed a theory that describes terahertz generation in such a structure and calculated spatial distribution of the generated terahertz field, its energy spectrum, and optical-to-terahertz conversion efficiency. The proposed structure can be a useful tool for characterization of the electromagnetic properties of metamaterials in the terahertz frequency range.

Theoretical prediction on corrugated sandwich panels under bending loads

NASA Astrophysics Data System (ADS)

Shu, Chengfu; Hou, Shujuan

2018-05-01

In this paper, an aluminum corrugated sandwich panel with triangular core under bending loads was investigated. Firstly, the equivalent material parameters of the triangular corrugated core layer, which could be considered as an orthotropic panel, were obtained by using Castigliano's theorem and equivalent homogeneous model. Secondly, contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory, and these equivalent material parameters were compared with finite element analysis solutions. Then, based on the Mindlin orthotropic plate theory, this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions, and parameters study and comparison by the finite element method were executed simultaneously.

Four-terminal circuit element with photonic core

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

Sampayan, Stephen

A four-terminal circuit element is described that includes a photonic core inside of the circuit element that uses a wide bandgap semiconductor material that exhibits photoconductivity and allows current flow through the material in response to the light that is incident on the wide bandgap material. The four-terminal circuit element can be configured based on various hardware structures using a single piece or multiple pieces or layers of a wide bandgap semiconductor material to achieve various designed electrical properties such as high switching voltages by using the photoconductive feature beyond the breakdown voltages of semiconductor devices or circuits operated basedmore » on electrical bias or control designs. The photonic core aspect of the four-terminal circuit element provides unique features that enable versatile circuit applications to either replace the semiconductor transistor-based circuit elements or semiconductor diode-based circuit elements.« less

Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

NASA Technical Reports Server (NTRS)

Ryan, Shannon; Christiansen, Eric; Lear, Dana

2009-01-01

Metallic foams are a relatively new class of materials with low density and novel physical, mechanical, thermal, electrical and acoustic properties. Although incompletely characterized, they offer comparable mechanical performance to traditional spacecraft structural materials (i.e. honeycomb sandwich panels) without detrimental through-thickness channeling cells. There are two competing types of metallic foams: open cell and closed cell. Open cell foams are considered the more promising technology due to their lower weight and higher degree of homogeneity. Leading micrometeoroid and orbital debris shields (MMOD) incorporate thin plates separated by a void space (i.e. Whipple shield). Inclusion of intermediate fabric layers, or multiple bumper plates have led to significant performance enhancements, yet these shields require additional non-ballistic mass for installation (fasteners, supports, etc.) that can consume up to 35% of the total shield weight [1]. Structural panels, such as open cell foam core sandwich panels, that are also capable of providing sufficient MMOD protection, represent a significant potential for increased efficiency in hypervelocity impact shielding from a systems perspective through a reduction in required non-ballistic mass. In this paper, the results of an extensive impact test program on aluminum foam core sandwich panels are reported. The effect of pore density, and core thickness on shielding performance have been evaluated over impact velocities ranging from 2.2 - 9.3 km/s at various angles. A number of additional tests on alternate sandwich panel configurations of comparable-weight have also been performed, including aluminum honeycomb sandwich panels (see Figure 1), Nomex honeycomb core sandwich panels, and 3D aluminum honeycomb sandwich panels. A total of 70 hypervelocity impact tests are reported, from which an empirical ballistic limit equation (BLE) has been derived. The BLE is in the standard form suitable for implementation in risk analysis software, and includes the effect of panel thickness, core density, and facesheet material properties. A comparison between the shielding performance of foam core sandwich panel structures and common MMOD shielding configurations is made for both conservative (additional 35% non-ballistic mass) and optimistic (additional mass equal to 30% of bumper mass) considerations. Suggestions to improve the shielding performance of foam core sandwich panels are made, including the use of outer mesh layers, intermediate fabric/composite layers, and varying pore density.

Integrally rigidized acoustic interior spacecraft panel

NASA Technical Reports Server (NTRS)

1976-01-01

A sandwich panel concept is described which utilizes a monolithic I-beam design as the core. The core and skins are integrally bonded with thermosetting resin into a homogeneous structure. In addition to possessing a high strength to weight ratio, the panel resists combustion, delamination, aging due to fatigue, localized stresses, and exhibits good acoustic properties. Since the panel concept has definite potential as a high flame retardant and low smoke emission panel with excellent structural integrity, aerospace materials were used to optimize the construction for highly demanding space shuttle applications. The specific materials of construction were chosen for low flammability and off-gassing properties as well as for strength, light weight, and sound dampening.

Facile one-pot transformation using structure-guided combustion waves of micro-nanostructured β-Bi2O3 to α-Bi2O3@C and analysis of electrochemical capacitance

NASA Astrophysics Data System (ADS)

Hwang, Hayoung; Shin, Jung-ho; Lee, Kang Yeol; Choi, Wonjoon

2018-01-01

Precise phase-transformation can facilitate control of the properties of various materials, while an organic coating surrounding inorganic materials can yield useful characteristics. Herein, we demonstrate facile, selective manipulation of micro-nanostructured bismuth oxide (Bi2O3) for phase transformation from microflower-like β-Bi2O3 to micropill-like α-Bi2O3, with carbon-coating layer deposition, using structure-guided combustion waves (SGCWs). Microflower-like β-Bi2O3 are synthesized as core materials and nitrocellulose is coated on their surfaces for the formation of core-shell hybrid structures of Bi2O3 and chemical fuel. The SGCWs, which propagate along the core-material and fuel interfaces, apply high thermal energy (550-600 °C) and deposit incompletely combusted carbonaceous fuel on the microflower-like β-Bi2O3 to enable transformation to α-phase and carbon-coating-layer synthesis. SGCW-induced improvements to the electrochemical characteristics of the developed micropill-like α-Bi2O3@C, compared with the microflower-like β-Bi2O3, are investigated. The enhanced stability from the α-phase Bi2O3 and micropill-like structures during charge-discharge cycling improves the specific capacitance, while the carbon-coating layers facilitate increased electrical conductivity. SGCW-based methods exhibit high potential for selective phase manipulation and synthesis of carbon coatings surrounding micro-nanomaterials. They constitute a low-cost, fast, large-scale process for metal oxides, ceramics, and hybrid materials, implemented through control of the processing parameters by tuning the temperature, chemical fuel, and ambient conditions.

Progress Towards a Rad-Hydro Code for Modern Computing Architectures LA-UR-10-02825

NASA Astrophysics Data System (ADS)

Wohlbier, J. G.; Lowrie, R. B.; Bergen, B.; Calef, M.

2010-11-01

We are entering an era of high performance computing where data movement is the overwhelming bottleneck to scalable performance, as opposed to the speed of floating-point operations per processor. All multi-core hardware paradigms, whether heterogeneous or homogeneous, be it the Cell processor, GPGPU, or multi-core x86, share this common trait. In multi-physics applications such as inertial confinement fusion or astrophysics, one may be solving multi-material hydrodynamics with tabular equation of state data lookups, radiation transport, nuclear reactions, and charged particle transport in a single time cycle. The algorithms are intensely data dependent, e.g., EOS, opacity, nuclear data, and multi-core hardware memory restrictions are forcing code developers to rethink code and algorithm design. For the past two years LANL has been funding a small effort referred to as Multi-Physics on Multi-Core to explore ideas for code design as pertaining to inertial confinement fusion and astrophysics applications. The near term goals of this project are to have a multi-material radiation hydrodynamics capability, with tabular equation of state lookups, on cartesian and curvilinear block structured meshes. In the longer term we plan to add fully implicit multi-group radiation diffusion and material heat conduction, and block structured AMR. We will report on our progress to date.

Characterization of basin concrete in support of structural integrity demonstration for extended storage

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

Duncan, A.

Concrete core samples from C basin were characterized through material testing and analysis to verify the design inputs for structural analysis of the L Basin and to evaluate the type and extent of changes in the material condition of the concrete under extended service for fuel storage. To avoid the impact on operations, core samples were not collected from L area, but rather, several concrete core samples were taken from the C Basin prior to its closure. C basin was selected due to its similar environmental exposure and service history compared to L Basin. The microstructure and chemical composition ofmore » the concrete exposed to the water was profiled from the water surface into the wall to evaluate the impact and extent of exposure. No significant leaching of concrete components was observed. Ingress of carbonation or deleterious species was determined to be insignificant. No evidence of alkali-silica reactions (ASR) was observed. Ettringite was observed to form throughout the structure (in air voids or pores); however, the sulfur content was measured to be consistent with the initial concrete that was used to construct the facility. Similar ettringite trends were observed in the interior segments of the core samples. The compressive strength of the concrete at the mid-wall of the basin was measured, and similar microstructural analysis was conducted on these materials post compression testing. The microstructure was determined to be similar to near-surface segments of the core samples. The average strength was 4148 psi, which is well-above the design strength of 2500 psi. The analyses showed that phase alterations and minor cracking in a microstructure did not affect the design specification for the concrete.« less

Mechatronic Materials and Systems. Design and Demonstration of High Aughtority Shape Morphing Structures

DTIC Science & Technology

2005-09-01

thermal expansion of these truss elements. One side of the structure is fully clamped, while the other is free to displace. As in prior assessments [6...levels, by using the finite element package ABAQUS . To simulate the complete system, the core and the Kagome face members are modeled using linear...code ABAQUS . To simulate the complete actuation system, the core and Kagome members are modeled using linear Timoshenko-type beams, while the solid

Initial Comparison of Direct and Legacy Modeling Approaches for Radial Core Expansion Analysis

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

Shemon, Emily R.

2016-10-10

Radial core expansion in sodium-cooled fast reactors provides an important reactivity feedback effect. As the reactor power increases due to normal start up conditions or accident scenarios, the core and surrounding materials heat up, causing both grid plate expansion and bowing of the assembly ducts. When the core restraint system is designed correctly, the resulting structural deformations introduce negative reactivity which decreases the reactor power. Historically, an indirect procedure has been used to estimate the reactivity feedback due to structural deformation which relies upon perturbation theory and coupling legacy physics codes with limited geometry capabilities. With advancements in modeling andmore » simulation, radial core expansion phenomena can now be modeled directly, providing an assessment of the accuracy of the reactivity feedback coefficients generated by indirect legacy methods. Recently a new capability was added to the PROTEUS-SN unstructured geometry neutron transport solver to analyze deformed meshes quickly and directly. By supplying the deformed mesh in addition to the base configuration input files, PROTEUS-SN automatically processes material adjustments including calculation of region densities to conserve mass, calculation of isotopic densities according to material models (for example, sodium density as a function of temperature), and subsequent re-homogenization of materials. To verify the new capability of directly simulating deformed meshes, PROTEUS-SN was used to compute reactivity feedback for a series of contrived yet representative deformed configurations for the Advanced Burner Test Reactor design. The indirect legacy procedure was also performed to generate reactivity feedback coefficients for the same deformed configurations. Interestingly, the legacy procedure consistently overestimated reactivity feedbacks by 35% compared to direct simulations by PROTEUS-SN. This overestimation indicates that the legacy procedures are in fact not conservative and could be overestimating reactivity feedback effects that are closely tied to reactor safety. We conclude that there is indeed value in performing direct simulation of deformed meshes despite the increased computational expense. PROTEUS-SN is already part of the SHARP multi-physics toolkit where both thermal hydraulics and structural mechanical feedback modeling can be applied but this is the first comparison of direct simulation to legacy techniques for radial core expansion.« less

Laser Heating of the Core-Shell Nanowires

NASA Astrophysics Data System (ADS)

Astefanoaei, Iordana; Dumitru, Ioan; Stancu, Alexandru

2016-12-01

The induced thermal stress in a heating process is an important parameter to be known and controlled in the magnetization process of core-shell nanowires. This paper analyses the stress produced by a laser heating source placed at one end of a core-shell type structure. The thermal field was computed with the non-Fourier heat transport equation using a finite element method (FEM) implemented in Comsol Multiphysics. The internal stresses are essentially due to thermal gradients and different expansion characteristics of core and shell materials. The stress values were computed using the thermo elastic formalism and are depending on the laser beam parameters (spot size, power etc.) and system characteristics (dimensions, thermal characteristics). Stresses in the GPa range were estimated and consequently we find that the magnetic state of the system can be influenced significantly. A shell material as the glass which is a good thermal insulator induces in the magnetic core, the smaller stresses and consequently the smaller magnetoelastic energy. These results lead to a better understanding of the switching process in the magnetic materials.

Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

2004-01-01

The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful operating range. Operating a blade at or near the resonance frequencies leads to high-cycle fatigue, which ultimately limits the blade's durability and life. So the aim of this study is to determine the variation of the resonance frequencies for an idealized sandwich blade as a function of its face-sheet thickness, core thickness, and foam density. The finite element method is used to determine the natural frequencies for an idealized rectangular sandwich blade. The proven Lanczos method (ref. 7) is used in the study to extract the natural frequency.

Megablocks and melt pockets in the Chesapeake Bay impact structure constrained by magnetic field measurements and properties of the Eyreville and Cape Charles cores

USGS Publications Warehouse

Shah, A.K.; Daniels, D.L.; Kontny, A.; Brozena, J.

2009-01-01

We use magnetic susceptibility and remanent magnetization measurements of the Eyreville and Cape Charles cores in combination with new and previously collected magnetic field data in order to constrain structural features within the inner basin of the Chesapeake Bay impact structure. The Eyreville core shows the first evidence of several-hundred-meter-thick basement-derived megablocks that have been transported possibly kilometers from their pre-impact location. The magnetic anomaly map of the structure exhibits numerous short-wavelength (<2 km) variations that indicate the presence of magnetic sources within the crater fill. With core magnetic properties and seismic reflection and refraction results as constraints, forward models of the magnetic field show that these sources may represent basementderived megablocks that are a few hundred meters thick or melt bodies that are a few dozen meters thick. Larger-scale magnetic field properties suggest that these bodies overlie deeper, pre-impact basement contacts between materials with different magnetic properties such as gneiss and schist or gneiss and granite. The distribution of the short-wavelength magnetic anomalies in combination with observations of small-scale (1-2 mGal) gravity field variations suggest that basement-derived megablocks are preferentially distributed on the eastern side of the inner crater, not far from the Eyreville core, at depths of around 1-2 km. A scenario where additional basement-derived blocks between 2 and 3 km depth are distributed throughout the inner basin-and are composed of more magnetic materials, such as granite and schist, toward the east over a large-scale magnetic anomaly high and less magnetic materials, such as gneiss, toward the west where the magnetic anomaly is lower-provides a good model fi t to the observed magnetic anomalies in a manner that is consistent with both gravity and seismic-refraction data. ?? 2009 The Geological Society of America.

Fabrication of Fe{sub 3}O{sub 4}@CuO core-shell from MOF based materials and its antibacterial activity

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

Rajabi, S.K.; Sohrabnezhad, Sh., E-mail: sohrabnezhad@guilan.ac.ir; Ghafourian, S.

Magnetic Fe{sub 3}O{sub 4}@CuO nanocomposite with a core/shell structure was successfully synthesized via direct calcinations of magnetic Fe{sub 3}O{sub 4}@HKUST-1 in air atmosphere. The morphology, structure, magnetic and porous properties of the as-synthesized nano composites were characterized by using scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), and vibration sample magnetometer (VSM). The results showed that the nanocomposite material included a Fe{sub 3}O{sub 4} core and a CuO shell. The Fe{sub 3}O{sub 4}@CuO core-shell can be separated easily from the medium by a small magnet. The antibacterial activity of Fe{sub 3}O{sub 4}-CuO core-shell was investigated againstmore » gram-positive and gram-negative bacteria. A new mechanism was proposed for inactivation of bacteria over the prepared sample. It was demonstrated that the core-shell exhibit recyclable antibacterial activity, acting as an ideal long-acting antibacterial agent. - Graphical abstract: Fe{sub 3}O{sub 4}@CuO core-shell release of copper ions. These Cu{sup 2+} ions were responsible for the exhibited antibacterial activity. - Highlights: • The Fe{sub 3}O{sub 4}@CuO core-shell was prepared by MOF method. • This is the first study of antibacterial activity of core-shell consist of CuO and Fe{sub 3}O{sub 4}. • The core-shell can be reused effectively. • Core-shell was separated from the reaction solution by external magnetic field.« less

How cores grow by pebble accretion. I. Direct core growth

NASA Astrophysics Data System (ADS)

Brouwers, M. G.; Vazan, A.; Ormel, C. W.

2018-03-01

Context. Planet formation by pebble accretion is an alternative to planetesimal-driven core accretion. In this scenario, planets grow by the accretion of cm- to m-sized pebbles instead of km-sized planetesimals. One of the main differences with planetesimal-driven core accretion is the increased thermal ablation experienced by pebbles. This can provide early enrichment to the planet's envelope, which influences its subsequent evolution and changes the process of core growth. Aims: We aim to predict core masses and envelope compositions of planets that form by pebble accretion and compare mass deposition of pebbles to planetesimals. Specifically, we calculate the core mass where pebbles completely evaporate and are absorbed before reaching the core, which signifies the end of direct core growth. Methods: We model the early growth of a protoplanet by calculating the structure of its envelope, taking into account the fate of impacting pebbles or planetesimals. The region where high-Z material can exist in vapor form is determined by the temperature-dependent vapor pressure. We include enrichment effects by locally modifying the mean molecular weight of the envelope. Results: In the pebble case, three phases of core growth can be identified. In the first phase (Mcore < 0.23-0.39 M⊕), pebbles impact the core without significant ablation. During the second phase (Mcore < 0.5M⊕), ablation becomes increasingly severe. A layer of high-Z vapor starts to form around the core that absorbs a small fraction of the ablated mass. The rest of the material either rains out to the core or instead mixes outwards, slowing core growth. In the third phase (Mcore > 0.5M⊕), the high-Z inner region expands outwards, absorbing an increasing fraction of the ablated material as vapor. Rainout ends before the core mass reaches 0.6 M⊕, terminating direct core growth. In the case of icy H2O pebbles, this happens before 0.1 M⊕. Conclusions: Our results indicate that pebble accretion can directly form rocky cores up to only 0.6 M⊕, and is unable to form similarly sized icy cores. Subsequent core growth can proceed indirectly when the planet cools, provided it is able to retain its high-Z material.

Chemical and thermal stability of core-shelled magnetite nanoparticles and solid silica

NASA Astrophysics Data System (ADS)

Cendrowski, Krzysztof; Sikora, Pawel; Zielinska, Beata; Horszczaruk, Elzbieta; Mijowska, Ewa

2017-06-01

Pristine nanoparticles of magnetite were coated by solid silica shell forming core/shell structure. 20 nm thick silica coating significantly enhanced the chemical and thermal stability of the iron oxide. Chemical and thermal stability of this structure has been compared to the magnetite coated by mesoporous shell and pristine magnetite nanoparticles. It is assumed that six-membered silica rings in a solid silica shell limit the rate of oxygen diffusion during thermal treatment in air and prevent the access of HCl molecules to the core during chemical etching. Therefore, the core/shell structure with a solid shell requires a longer time to induce the oxidation of iron oxide to a higher oxidation state and, basically, even strong concentrated acid such as HCl is not able to dissolve it totally in one month. This leads to the desired performance of the material in potential applications such as catalysis and environmental protection.

NEUTRON SHIELDING STRUCTURE

DOEpatents

Mattingly, J.T.

1962-09-25

A lightweight neutron shielding structure comprises a honeycomb core which is filled with a neutron absorbing powder. The honeycomb core is faced with parallel planar facing sheets to form a lightweight rigid unit. Suitable absorber powders are selected from among the following: B, B/sub 4/C, B/sub 2/O/ sub 3/, CaB/sub 6/, Li/sub 2/CO3, LiOH, LiBO/sub 2/, Li/s ub 2/O. The facing sheets are constructed of a neutron moderating material, so that fast neutrons will be moderated while traversing the facing sheets, and ultimately be absorbed by the absorber powder in the honeycomb. Beryllium is a preferred moderator material for use in the facing sheets. The advantage of the structure is that it combines the rigidity and light weight of a honeycomb construction with the neutron absorption properties of boron and lithium. (AEC)

All-Dielectric Multilayer Cylindrical Structures for Invisibility Cloaking

PubMed Central

Mirzaei, Ali; Miroshnichenko, Andrey E.; Shadrivov, Ilya V.; Kivshar, Yuri S.

2015-01-01

We study optical response of all-dielectric multilayer structures and demonstrate that the total scattering of such structures can be suppressed leading to optimal invisibility cloaking. We use experimental material data and a genetic algorithm to reduce the total scattering by adjusting the material and thickness of various layers for several types of dielectric cores at telecommunication wavelengths. Our approach demonstrates 80-fold suppression of the total scattering cross-section by employing just a few dielectric layers. PMID:25858295

Hollow-structured mesoporous materials: chemical synthesis, functionalization and applications.

PubMed

Li, Yongsheng; Shi, Jianlin

2014-05-28

Hollow-structured mesoporous materials (HMMs), as a kind of mesoporous material with unique morphology, have been of great interest in the past decade because of the subtle combination of the hollow architecture with the mesoporous nanostructure. Benefitting from the merits of low density, large void space, large specific surface area, and, especially, the good biocompatibility, HMMs present promising application prospects in various fields, such as adsorption and storage, confined catalysis when catalytically active species are incorporated in the core and/or shell, controlled drug release, targeted drug delivery, and simultaneous diagnosis and therapy of cancers when the surface and/or core of the HMMs are functionalized with functional ligands and/or nanoparticles, and so on. In this review, recent progress in the design, synthesis, functionalization, and applications of hollow mesoporous materials are discussed. Two main synthetic strategies, soft-templating and hard-templating routes, are broadly sorted and described in detail. Progress in the main application aspects of HMMs, such as adsorption and storage, catalysis, and biomedicine, are also discussed in detail in this article, in terms of the unique features of the combined large void space in the core and the mesoporous network in the shell. Functionalization of the core and pore/outer surfaces with functional organic groups and/or nanoparticles, and their performance, are summarized in this article. Finally, an outlook of their prospects and challenges in terms of their controlled synthesis and scaled application is presented. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and gas sensing properties of α-Fe(2)O(3)@ZnO core-shell nanospindles.

PubMed

Zhang, Jun; Liu, Xianghong; Wang, Liwei; Yang, Taili; Guo, Xianzhi; Wu, Shihua; Wang, Shurong; Zhang, Shoumin

2011-05-06

α-Fe(2)O(3)@ZnO core-shell nanospindles were synthesized via a two-step hydrothermal approach, and characterized by means of SEM/TEM/XRD/XPS. The ZnO shell coated on the nanospindles has a thickness of 10-15 nm. Considering that both α-Fe(2)O(3) and ZnO are good sensing materials, we have investigated the gas sensing performances of the core-shell nanocomposite using ethanol as the main probe gas. It is interesting to find that the gas sensor properties of the core-shell nanospindles are significantly enhanced compared with pristine α-Fe(2)O(3). The enhanced sensor properties are attributed to the unique core-shell nanostructure. The detailed sensing mechanism is discussed with respect to the energy band structure and the electron depletion theory. The core-shell nanostructure reported in this work provides a new path to fabricate highly sensitive materials for gas sensing applications.

Carbon-silicon core-shell nanowires as high capacity electrode for lithium ion batteries.

PubMed

Cui, Li-Feng; Yang, Yuan; Hsu, Ching-Mei; Cui, Yi

2009-09-01

We introduce a novel design of carbon-silicon core-shell nanowires for high power and long life lithium battery electrodes. Amorphous silicon was coated onto carbon nanofibers to form a core-shell structure and the resulted core-shell nanowires showed great performance as anode material. Since carbon has a much smaller capacity compared to silicon, the carbon core experiences less structural stress or damage during lithium cycling and can function as a mechanical support and an efficient electron conducting pathway. These nanowires have a high charge storage capacity of approximately 2000 mAh/g and good cycling life. They also have a high Coulmbic efficiency of 90% for the first cycle and 98-99.6% for the following cycles. A full cell composed of LiCoO(2) cathode and carbon-silicon core-shell nanowire anode is also demonstrated. Significantly, using these core-shell nanowires we have obtained high mass loading and an area capacity of approximately 4 mAh/cm(2), which is comparable to commercial battery values.

Amyloid Fibrils as Building Blocks for Natural and Artificial Functional Materials.

PubMed

Knowles, Tuomas P J; Mezzenga, Raffaele

2016-08-01

Proteinaceous materials based on the amyloid core structure have recently been discovered at the origin of biological functionality in a remarkably diverse set of roles, and attention is increasingly turning towards such structures as the basis of artificial self-assembling materials. These roles contrast markedly with the original picture of amyloid fibrils as inherently pathological structures. Here we outline the salient features of this class of functional materials, both in the context of the functional roles that have been revealed for amyloid fibrils in nature, as well as in relation to their potential as artificial materials. We discuss how amyloid materials exemplify the emergence of function from protein self-assembly at multiple length scales. We focus on the connections between mesoscale structure and material function, and demonstrate how the natural examples of functional amyloids illuminate the potential applications for future artificial protein based materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon nano fibers reinforced composites origami inspired mechanical metamaterials with passive and active properties

NASA Astrophysics Data System (ADS)

Kshad, Mohamed Ali E.; D'Hondt, Clement; Naguib, Hani E.

2017-10-01

Core panels used for compression or impact damping are designed to dissipate energy and to reduce the transferred force and energy. They are designed to have high strain and deformation with low density. The geometrical configuration of such cores plays a significant role in redistributing the applied forces to dampen the compression and impact energy. Origami structures are renowned for affording large macroscopic deformation which can be employed for force redistribution and energy damping. The material selection for the fabrication of origami structures affects the core capacity to withstand compression and impact loads. Polymers are characterized by their high compression and impact resistance; the drawback of polymers is the low stiffness and elastic moduli compared with metallic materials. This work is focused on the study of the effect of Carbon Nano Fibers (CNF) on the global mechanical properties of the origami panel cores made of polymeric blends. The base matrix materials used were Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) blends, and the percentages of the PLA/TPU were 100/0, 20/80, 65/35, 50/50, 20/80, and 0/100 as a percentage of weight. The weight percentages of CNF added to the polymeric blends were 1%, 3%, and 5%. This paper deals with the fabrication process of the polymeric reinforced blends and the origami cores, in order to predict the best fabrication conditions. The dynamic scanning calorimetry and the dynamic mechanical analyzer were used to test the reinforced blended base material for thermomechanical and viscoelastic properties. The origami core samples were fabricated using per-molded geometrical features and then tested for compression and impact properties. The results of the study were compared with previous published results which showed that there is considerable enhancement in the mechanical properties of the origami cores compared with the pure blended polymeric origami cores. The active properties of the origami unit cell made of composite polymers containing a low percentage of CNF were also investigated in this study, in which the shape memory effect test conducted on the origami unit cell.

Evaluation of Materials and Concepts for Aircraft Fire Protection

NASA Technical Reports Server (NTRS)

Anderson, R. A.; Price, J. O.; Mcclure, A. H.; Tustin, E. A.

1976-01-01

Woven fiberglass fluted-core simulated aircraft interior panels were flame tested and structurally evaluated against the Boeing 747 present baseline interior panels. The NASA-defined panels, though inferior on a strength-to-weight basis, showed better structural integrity after flame testing, due to the woven fiberglass structure.

Ion dynamics in nanocrystalline LiMnPO{sub 4} synthesised by novel template free hydrothermal approach

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

Vijayan, Lakshmi, E-mail: lakshmivijayan@gmail.com; Cheruku, Rajesh; Govindaraj, G.

A dense core rectangular shaped nanocrystalline LiMnPO{sub 4} material was synthesized by template free sucrose assisted hydrothermal synthesis. The material possess orthorhombic crystal structure with Pnma, space group having four formula units. The structural characterization was accomplished through X-ray diffraction, thermo gravimetry/differential thermal analysis. Morphology was identified by the SEM, VSM was used to verify the magnetic behavior of the material and electrical characterization was done through impedance spectroscopy and the results were reported.

Epitaxial Growth of Lattice-Mismatched Core-Shell TiO2 @MoS2 for Enhanced Lithium-Ion Storage.

PubMed

Dai, Rui; Zhang, Anqi; Pan, Zhichang; Al-Enizi, Abdullah M; Elzatahry, Ahmed A; Hu, Linfeng; Zheng, Gengfeng

2016-05-01

Core-shell structured nanohybrids are currently of significant interest due to their synergetic properties and enhanced performances. However, the restriction of lattice mismatch remains a severe obstacle for heterogrowth of various core-shells with two distinct crystal structures. Herein, a controlled synthesis of lattice-mismatched core-shell TiO2 @MoS2 nano-onion heterostructures is successfully developed, using unilamellar Ti0.87 O2 nanosheets as the starting material and the subsequent epitaxial growth of MoS2 on TiO2 . The formation of these core-shell nano-onions is attributed to an amorphous layer-induced heterogrowth mechanism. The number of MoS2 layers can be well tuned from few to over ten layers, enabling layer-dependent synergistic effects. The core-shell TiO2 @MoS2 nano-onion heterostructures exhibit significantly enhanced energy storage performance as lithium-ion battery anodes. The approach has also been extended to other lattice-mismatched systems such as TiO2 @MoSe2 , thus suggesting a new strategy for the growth of well-designed lattice-mismatched core-shell structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dominance of debonding defect of CFST on PZT sensor response considering the meso-scale structure of concrete with multi-scale simulation

NASA Astrophysics Data System (ADS)

Xu, Bin; Chen, Hongbing; Mo, Y.-L.; Zhou, Tianmin

2018-07-01

Piezoelectric-lead-zirconate-titanate(PZT)-based interface debonding defects detection for concrete filled steel tubulars (CFSTs) has been proposed and validated through experiments, and numerical study on its mechanism has been carried out recently by assuming that concrete material is homogenous. However, concrete is composed of coarse and fine aggregates, mortar and interface transition zones (ITZs) and even initial defects and is a typical nonhomogeneous material and its mesoscale structure might affect the wave propagation in the concrete core of CFST members. Therefore, it is significantly important to further investigate the influence of mesoscale structure of concrete on the stress wave propagation and the response of embedded PZT sensor for the interface debonding detection. In this study, multi-physical numerical simulation on the wave propagation and embedded PZT sensor response of rectangular CFST members with numerical concrete core considering the randomness in circular aggregate distribution, and coupled with surface-mounted PZT actuator and embedded PZT sensor is carried out. The effect of randomness in the circular aggregates distribution and the existence of ITZs are discussed. Both a local stress wave propagation behavior including transmission, reflection, and diffraction at the interface between concrete core and steel tube under a pulse signal excitation and a global wave field in the cross-section of the rectangular CFST models without and with interface debonding defects under sweep frequency excitation are simulated. The sensitivity of an evaluation index based on wavelet packet analysis on the embedded PZT sensor response on the variation of mesoscale parameters of concrete core without and with different interface debonding defects under sweep frequency voltage signal is investigated in details. The results show that the effect of the interface debondings on the embedded PZT measurement is dominant when compared to the meso-scale structures of concrete core. This study verified the feasibility of the PZT based debonding detection for rectangular CFST members even the meso-scale structure of concrete core is considered.

Magnetic response of hybrid ferromagnetic and antiferromagnetic core-shell nanostructures

NASA Astrophysics Data System (ADS)

Khan, U.; Li, W. J.; Adeela, N.; Irfan, M.; Javed, K.; Wan, C. H.; Riaz, S.; Han, X. F.

2016-03-01

The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3&cmb.macr;. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ~25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required.The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3&cmb.macr;. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ~25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07946b

The past, present, and future of hockey-stick-shaped liquid crystals

NASA Astrophysics Data System (ADS)

Choi, E.-Joon

2014-02-01

Recently, the liquid crystalline materials with a bent-core mesogen have attracted attentions because their interesting properties such as polarity and biaxiality of the mesophase. There are several types of bent-core mesogenic structures have been reported, for instance, banana-shaped, V-shaped molecules, boomerang-shaped, hockey stick-shaped, and Yshaped molecules. In this study, the liquid crystals and the reactive mesogens with the hockey-stick shaped mesogens will be described concerning with the structure-property relationship.

Advanced Aerospace Materials by Design

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Djomehri, Jahed; Wei, Chen-Yu

2004-01-01

The advances in the emerging field of nanophase thermal and structural composite materials; materials with embedded sensors and actuators for morphing structures; light-weight composite materials for energy and power storage; and large surface area materials for in-situ resource generation and waste recycling, are expected to :revolutionize the capabilities of virtually every system comprising of future robotic and :human moon and mars exploration missions. A high-performance multiscale simulation platform, including the computational capabilities and resources of Columbia - the new supercomputer, is being developed to discover, validate, and prototype next generation (of such advanced materials. This exhibit will describe the porting and scaling of multiscale 'physics based core computer simulation codes for discovering and designing carbon nanotube-polymer composite materials for light-weight load bearing structural and 'thermal protection applications.

Using Powder Cored Tubular Wire Technology to Enhance Electron Beam Freeform Fabricated Structures

NASA Technical Reports Server (NTRS)

Gonzales, Devon; Liu, Stephen; Domack, Marcia; Hafley, Robert

2016-01-01

Electron Beam Freeform Fabrication (EBF3) is an additive manufacturing technique, developed at NASA Langley Research Center, capable of fabricating large scale aerospace parts. Advantages of using EBF3 as opposed to conventional manufacturing methods include, decreased design-to-product time, decreased wasted material, and the ability to adapt controls to produce geometrically complex parts with properties comparable to wrought products. However, to fully exploit the potential of the EBF3 process development of materials tailored for the process is required. Powder cored tubular wire (PCTW) technology was used to modify Ti-6Al-4V and Al 6061 feedstock to enhance alloy content, refine grain size, and create a metal matrix composite in the as-solidified structures, respectively.

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.

Atomically informed nonlocal semi-discrete variational Peierls-Nabarro model for planar core dislocations

PubMed Central

Liu, Guisen; Cheng, Xi; Wang, Jian; Chen, Kaiguo; Shen, Yao

2017-01-01

Prediction of Peierls stress associated with dislocation glide is of fundamental concern in understanding and designing the plasticity and mechanical properties of crystalline materials. Here, we develop a nonlocal semi-discrete variational Peierls-Nabarro (SVPN) model by incorporating the nonlocal atomic interactions into the semi-discrete variational Peierls framework. The nonlocal kernel is simplified by limiting the nonlocal atomic interaction in the nearest neighbor region, and the nonlocal coefficient is directly computed from the dislocation core structure. Our model is capable of accurately predicting the displacement profile, and the Peierls stress, of planar-extended core dislocations in face-centered cubic structures. Our model could be extended to study more complicated planar-extended core dislocations, such as <110> {111} dislocations in Al-based and Ti-based intermetallic compounds. PMID:28252102

Enhanced exchange bias and improved ferromagnetic properties in Permalloy-BiFe0.95Co0.05O3 core-shell nanostructures.

PubMed

Javed, K; Li, W J; Ali, S S; Shi, D W; Khan, U; Riaz, S; Han, X F

2015-12-14

Hybrid core-shell nanostructures consisting of permalloy (Ni80Fe20) and multiferroic(BiFeO3, BFO/BiFe0.95Co0.05O3, BFC) materials were synthesized by a two-step method, based on wet chemical impregnation and subsequent electrodeposition within porous alumina membranes. Structural and magnetic characterizations have been done to investigate doping effect on magnetic properties and exchange bias. The magnetometry analysis revealed significant enhancements of the exchange bias and coercivity in NiFe-BFC core-shell nanostructures as compared with NiFe-BFO core-shell nanostructures. The enhancements can be attributed to the effective reduction of ferromagnet domain sizes between adjacent layers of core-shell structure. It indicates that it is possible to improve properties of multiferroic composites by site-engineering method. Our approach opens a pathway to obtain optimized nanostructured multiferroic composites exhibiting tunable magnetic properties.

Foam patterns

DOEpatents

Chaudhry, Anil R; Dzugan, Robert; Harrington, Richard M; Neece, Faurice D; Singh, Nipendra P; Westendorf, Travis

2013-11-26

A method of creating a foam pattern comprises mixing a polyol component and an isocyanate component to form a liquid mixture. The method further comprises placing a temporary core having a shape corresponding to a desired internal feature in a cavity of a mold and inserting the mixture into the cavity of the mold so that the mixture surrounds a portion of the temporary core. The method optionally further comprises using supporting pins made of foam to support the core in the mold cavity, with such pins becoming integral part of the pattern material simplifying subsequent processing. The method further comprises waiting for a predetermined time sufficient for a reaction from the mixture to form a foam pattern structure corresponding to the cavity of the mold, wherein the foam pattern structure encloses a portion of the temporary core and removing the temporary core from the pattern independent of chemical leaching.

Development of a wear-resistant flux cored wire of Fe-C-Si-Mn-Cr-Ni-Mo-V system for deposit welding of mining equipment parts

NASA Astrophysics Data System (ADS)

Osetkovsky, I. V.; Kozyrev, N. A.; Kryukov, R. E.; Usoltsev, A. A.; Gusev, A. I.

2017-09-01

The effect of introduction of cobalt in the charge of the flux cored wire of Fe-C-Si-Mn-Cr-Ni-Mo-V system operating under abrasive and abrasive-shock loads is studied. In the laboratory conditions samples of flux cored wires were made, deposition was performed, the effect of cobalt on the hardness and the degree of wear was evaluated, metallographic studies were carried out. The influence of cobalt introduced into the charge of the flux cored wire of Fe-C-Si-Mn-Cr-Ni-Mo-V system on the structure, nature of nonmetallic inclusions, hardness and wear resistance of the weld metal was studied. In the laboratory conditions samples flux cored wire were made using appropriate powdered materials. As a carbon-fluorine-containing material dust from gas cleaning units of aluminum production was used. In the course of the study the chemical composition of the weld metal was determined, metallographic analysis was performed, mechanical properties were determined. As a result of the metallographic analysis the size of the former austenite grain, martensite dispersion in the structure of the weld metal, the level of contamination with its nonmetallic inclusions were established.

Effects of Oxidation on Oxidation-Resistant Graphite

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

Windes, William; Smith, Rebecca; Carroll, Mark

2015-05-01

The Advanced Reactor Technology (ART) Graphite Research and Development Program is investigating doped nuclear graphite grades that exhibit oxidation resistance through the formation of protective oxides on the surface of the graphite material. In the unlikely event of an oxygen ingress accident, graphite components within the VHTR core region are anticipated to oxidize so long as the oxygen continues to enter the hot core region and the core temperatures remain above 400°C. For the most serious air-ingress accident which persists over several hours or days the continued oxidation can result in significant structural damage to the core. Reducing the oxidationmore » rate of the graphite core material during any air-ingress accident would mitigate the structural effects and keep the core intact. Previous air oxidation testing of nuclear-grade graphite doped with varying levels of boron-carbide (B4C) at a nominal 739°C was conducted for a limited number of doped specimens demonstrating a dramatic reduction in oxidation rate for the boronated graphite grade. This report summarizes the conclusions from this small scoping study by determining the effects of oxidation on the mechanical strength resulting from oxidation of boronated and unboronated graphite to a 10% mass loss level. While the B4C additive did reduce mechanical strength loss during oxidation, adding B4C dopants to a level of 3.5% or more reduced the as-fabricated compressive strength nearly 50%. This effectively minimized any benefits realized from the protective film formed on the boronated grades. Future work to infuse different graphite grades with silicon- and boron-doped material as a post-machining conditioning step for nuclear components is discussed as a potential solution for these challenges in this report.« less

Core-shelled mesoporous CoFe2O4-SiO2 material with good adsorption and high-temperature magnetic recycling capabilities

NASA Astrophysics Data System (ADS)

Li, Zhi'ang; Wang, Jianlin; Liu, Min; Chen, Tong; Chen, Jifang; Ge, Wen; Fu, Zhengping; Peng, Ranran; Zhai, Xiaofang; Lu, Yalin

2018-04-01

Residues of organic dye in industrial effluents cause severe water system pollution. Although several methods, such as biodegradation and activated carbon adsorption, are available for treating these effluents before their discharge into waterbodies, secondary pollution by adsorbents and degrading products remains an issue. Therefore, new materials should be identified to solve this problem. In this work, CoFe2O4-SiO2 core-shell structures were synthesized using an improved Stöber method by coating mesoporous silica onto CoFe2O4 nanoparticles. The specific surface areas of the synthesized particles range from 30 m2/g to 150 m2/g and vary according to the dosage amount of tetraethoxysilane. Such core-shelled nanoparticles have the following advantages for treating industrial effluents mixed with dye: good adsorption capability, above-room-temperature magnetic recycling capability, and heat-enduring stability. Through adsorption of methylene blue, a typical dyeing material, the core-shell-structured particles show a good adsorption capability of approximately 33 mg/L. The particles are easily and completely collected by magnets, which is possible due to the magnetic property of core CoFe2O4. Heat treatment can burn out the adsorbed dyes and good adsorption performance is sustained even after several heat-treating loops. This property overcomes the common problem of particles with Fe3O4 as a core, by which Fe3O4 is oxidized to nonmagnetic α-Fe2O3 at the burning temperature. We also designed a miniature of effluent-treating pipeline, which demonstrates the potential of the application.

Intercalation compounds and electrodes for batteries

DOEpatents

Chiang, Yet-Ming; Sadoway, Donald R.; Jang, Young-Il; Huang, Biyan

2004-09-07

This invention concerns intercalation compounds and in particular lithium intercalation compounds which have improved properties for use in batteries. Compositions of the invention include particulate metal oxide material having particles of multicomponent metal oxide, each including an oxide core of at least first and second metals in a first ratio, and each including a surface coating of metal oxide or hydroxide that does not include the first and second metals in the first ratio formed by segregation of at least one of the first and second metals from the core. The core may preferably comprise Li.sub.x M.sub.y N.sub.z O.sub.2 wherein M and N are metal atom or main group elements, x, y and z are numbers from about 0 to about 1 and y and z are such that a formal charge on M.sub.y N.sub.z portion of the compound is (4-x), and having a charging voltage of at least about 2.5V. The invention may also be characterized as a multicomponent oxide microstructure usable as a lithium intercalation material including a multiphase oxide core and a surface layer of one material, which is a component of the multiphase oxide core, that protects the underlying intercalation material from chemical dissolution or reaction. In a particular preferred example the multicomponent oxide may be an aluminum-doped lithium manganese oxide composition. Such aluminum-doped lithium manganese oxide compositions, having an orthorhombic structure, also form a part of the invention. In addition, the invention includes articles, particularly electrodes, for batteries formed from the compositions of the invention, and batteries including such electrodes. The invention further relates to a composite intercalation material comprising at least two compounds in which at least one compound has an orthorhombic structure Li.sub.x Al.sub.y Mn.sub.1-y O.sub.2, where y is nonzero, or a mixture of orthorhombic and monoclinic Li.sub.x Al.sub.y Mn.sub.1-y O.sub.2.

Block coordination copolymers

DOEpatents

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2014-11-11

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Block coordination copolymers

DOEpatents

Koh, Kyoung Moo; Wong-Foy, Antek G.; Matzger, Adam J.; Benin, Annabelle I.; Willis, Richard R.

2012-12-04

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Block coordination copolymers

DOEpatents

Koh, Kyoung Moo; Wong-Foy, Antek G; Matzger, Adam J; Benin, Annabelle I; Willis, Richard R

2012-11-13

The present invention provides compositions of crystalline coordination copolymers wherein multiple organic molecules are assembled to produce porous framework materials with layered or core-shell structures. These materials are synthesized by sequential growth techniques such as the seed growth technique. In addition, the invention provides a simple procedure for controlling functionality.

Analysis of a new composite material for watercraft manufacturing

NASA Astrophysics Data System (ADS)

Wahrhaftig, Alexandre; Ribeiro, Henrique; Nascimento, Ademar; Filho, Milton

2016-09-01

In this paper, we investigate the properties of an alternative material for use in marine engineering, namely a rigid and light sandwich-structured composite made of expanded polystyrene and fiberglass. Not only does this material have an improved section modulus, but it is also inexpensive, light, easy to manipulate, and commercially available in various sizes. Using a computer program based on the finite element method, we calculated the hogging and sagging stresses and strains acting on a prismatic boat model composed of this material, and determined the minimum sizes and maximum permissible stresses to avoid deformation. Finally, we calculated the structural weight of the resulting vessel for comparison with another structure of comparable dimensions constructed from the commonly used core material Divinycell.

Polymorphism in magic-sized Au144(SR)60 clusters

NASA Astrophysics Data System (ADS)

Jensen, Kirsten M. Ø.; Juhas, Pavol; Tofanelli, Marcus A.; Heinecke, Christine L.; Vaughan, Gavin; Ackerson, Christopher J.; Billinge, Simon J. L.

2016-06-01

Ultra-small, magic-sized metal nanoclusters represent an important new class of materials with properties between molecules and particles. However, their small size challenges the conventional methods for structure characterization. Here we present the structure of ultra-stable Au144(SR)60 magic-sized nanoclusters obtained from atomic pair distribution function analysis of X-ray powder diffraction data. The study reveals structural polymorphism in these archetypal nanoclusters. In addition to confirming the theoretically predicted icosahedral-cored cluster, we also find samples with a truncated decahedral core structure, with some samples exhibiting a coexistence of both cluster structures. Although the clusters are monodisperse in size, structural diversity is apparent. The discovery of polymorphism may open up a new dimension in nanoscale engineering.

Enhanced oxidation stability of quasi core-shell alloyed CdSeS quantum dots prepared through aqueous microwave synthesis technique.

PubMed

Zhan, Hong-Ju; Zhou, Pei-Jiang; Ma, Rong; Liu, Xi-Jing; He, Yu-Ning; Zhou, Chuan-Yun

2014-01-01

Quasi core shell alloyed CdSeS quantum dots (QDs) have been prepared through a facile aqueous-phase route employing microwave irradiation technique. The optical spectroscopy and structure characterization evidenced the quasi core shell alloyed structures of CdSeS QDs. The X-ray diffraction patterns of the obtained CdSeS QDs displayed peak positions very close to those of bulk cubic CdS crystal structures and the result of X-ray photoelectron spectroscopy data re-confirmed the thick CdS shell on the CdSe core. The TEM images and HRTEM images of the CdSeS QDs ascertained the well-defined spherical particles and a relatively narrow size distribution. On the basis, the stability of the obtained QDs in an oxidative environment was also discussed using etching reaction by H2O2. The experiments result showed the as-prepared QDs present high tolerance towards H2O2, obviously superior to the commonly used CdTe QDs and core-shell CdTe/CdS QDs, which was attributed to the unique quasi core-shell CdSeS crystal structure and the small lattice mismatch between CdSe and CdS semiconductor materials. This assay provided insight to obtain high stable crystal structured semiconductor nanocrystals in the design and synthesis process.

Bandgap Engineering of InP QDs Through Shell Thickness and Composition

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

Dennis, Allison M.; Mangum, Benjamin D.; Piryatinski, Andrei

2012-06-21

Fields as diverse as biological imaging and telecommunications utilize the unique photophysical and electronic properties of nanocrystal quantum dots (NQDs). The development of new NQD compositions promises material properties optimized for specific applications, while addressing material toxicity. Indium phosphide (InP) offers a 'green' alternative to the traditional cadmium-based NQDs, but suffers from extreme susceptibility to oxidation. Coating InP cores with more stable shell materials significantly improves nanocrystal resistance to oxidation and photostability. We have investigated several new InP-based core-shell compositions, correlating our results with theoretical predictions of their optical and electronic properties. Specifically, we can tailor the InP core-shell QDsmore » to a type-I, quasi-type-II, or type-II bandgap structure with emission wavelengths ranging from 500-1300 nm depending on the shell material used (ZnS, ZnSe, CdS, or CdSe) and the thickness of the shell. Single molecule microscopy assessments of photobleaching and blinking are used to correlate NQD properties with shell thickness.« less

Measuring Moisture Levels in Graphite Epoxy Composite Sandwich Structures

NASA Technical Reports Server (NTRS)

Nurge, Mark; Youngquist, Robert; Starr, Stanley

2011-01-01

Graphite epoxy composite (GEC) materials are used in the construction of rocket fairings, nose cones, interstage adapters, and heat shields due to their high strength and light weight. However, they absorb moisture depending on the environmental conditions they are exposed to prior to launch. Too much moisture absorption can become a problem when temperature and pressure changes experienced during launch cause the water to vaporize. The rapid state change of the water can result in structural failure of the material. In addition, heat and moisture combine to weaken GEC structures. Diffusion models that predict the total accumulated moisture content based on the environmental conditions are one accepted method of determining if the material strength has been reduced to an unacceptable level. However, there currently doesn t exist any field measurement technique to estimate the actual moisture content of a composite structure. A multi-layer diffusion model was constructed with Mathematica to predict moisture absorption and desorption from the GEC sandwich structure. This model is used in conjunction with relative humidity/temperature sensors both on the inside and outside of the material to determine the moisture levels in the structure. Because the core materials have much higher diffusivity than the face sheets, a single relative humidity measurement will accurately reflect the moisture levels in the core. When combined with an external relative humidity measurement, the model can be used to determine the moisture levels in the face sheets. Since diffusion is temperaturedependent, the temperature measurements are used to determine the diffusivity of the face sheets for the model computations.

The curious case of Mercury's internal structure

NASA Astrophysics Data System (ADS)

Hauck, Steven A.; Margot, Jean-Luc; Solomon, Sean C.; Phillips, Roger J.; Johnson, Catherine L.; Lemoine, Frank G.; Mazarico, Erwan; McCoy, Timothy J.; Padovan, Sebastiano; Peale, Stanton J.; Perry, Mark E.; Smith, David E.; Zuber, Maria T.

2013-06-01

The recent determination of the gravity field of Mercury and new Earth-based radar observations of the planet's spin state afford the opportunity to explore Mercury's internal structure. These observations provide estimates of two measures of the radial mass distribution of Mercury: the normalized polar moment of inertia and the fractional polar moment of inertia of the solid portion of the planet overlying the liquid core. Employing Monte Carlo techniques, we calculate several million models of the radial density structure of Mercury consistent with its radius and bulk density and constrained by these moment of inertia parameters. We estimate that the top of the liquid core is at a radius of 2020 ± 30 km, the mean density above this boundary is 3380 ± 200 kg m-3, and the density below the boundary is 6980 ± 280 kg m-3. We find that these internal structure parameters are robust across a broad range of compositional models for the core and planet as a whole. Geochemical observations of Mercury's surface by MESSENGER indicate a chemically reducing environment that would favor the partitioning of silicon or both silicon and sulfur into the metallic core during core-mantle differentiation. For a core composed of Fe-S-Si materials, the thermodynamic properties at elevated pressures and temperatures suggest that an FeS-rich layer could form at the top of the core and that a portion of it may be presently solid.

Process engineering of polynanomeric layered and infused composites

NASA Astrophysics Data System (ADS)

Williams, Ebonee Porche Marie

As the application of advanced polymeric composites expands, the continued adaptation of traditional as well as the incorporation and/or implementation of new technologies continue to be at the core of development for engineers. One of these traditional technologies is honeycomb sandwich composites. This technology has been around for more than fifty years and there have been minimal alterations to the materials used to produce the parts and the process used to manufacture the structures. This is where the depth of this work focused. Traditional honeycomb core dip resin systems were modified to incorporate nano scale fillers. This adaptation is one of the defining aspects of polynanomeric systems, the concept of which is that modifications of the nano scale in a polymer system create nano layered structures that emulate the properties of both the polymer and the nano filler, a nano composite. The modified resin systems were characterized to investigate morphology, thermal and mechanical properties as well as electrical characteristics. It was observed that the nano altered resin system exhibited increased mechanical, 50 to 60%, and thermal properties, burn temperatures extended by 30°C, while also demonstrating improved electrical properties. These were significant results given that the main applications of honeycomb sandwich structures are on the interior of aircrafts. These results could open the door to some new applications of the modified resin system. This work also implemented a new processing technique to produce honeycomb sandwich structures. The technique was Vacuum Assisted Resin Transfer Molding, VARTM, which has gained interest over the last decade due to the reduced up front cost to initiate production, the ease of processing, and the overall health benefits. This process was successfully performed to produce sandwich structures by incorporating a permeable scrim layer at the core face sheet interface. This was the first successful production of unfilled honeycomb core sandwich part production. Overall this work is at the tip of implementing new materials and processing techniques into honeycomb core and honeycomb sandwich composite structures.

Shear properties evaluation of a truss core of sandwich beams

NASA Astrophysics Data System (ADS)

Wesolowski, M.; Ludewicz, J.; Domski, J.; Zakrzewski, M.

2017-10-01

The open-cell cores of sandwich structures are locally bonded to the face layers by means of adhesive resin. The sandwich structures composed of different parent materials such as carbon fibre composites (laminated face layers) and metallic core (aluminium truss core) brings the need to closely analyse their adhesive connections which strength is dominated by the shear stress. The presented work considers sandwich beams subjected to the static tests in the 3-point bending with the purpose of estimation of shear properties of the truss core. The main concern is dedicated to the out-of plane shear modulus and ultimate shear stress of the aluminium truss core. The loading of the beam is provided by a static machine. For the all beams the force - deflection history is extracted by means of non-contact optical deflection measurement using PONTOS system. The mode of failure is identified for each beam with the corresponding applied force. A flexural rigidity of the sandwich beams is also discussed based on force - displacement plots.

Structural and electronic properties of CdS/ZnS core/shell nanowires: A first-principles study

NASA Astrophysics Data System (ADS)

Kim, Hyo Seok; Kim, Yong-Hoon

2015-03-01

Carrying out density functional theory (DFT) calculation, we studied the relative effects of quantum confinement and strain on the electronic structures of II-IV semiconductor compounds with a large lattice-mismatch, CdS and ZnS, in the core/shell nanowire geometry. We considered different core radii and shell thickness of the CdS/ZnS core/shell nanowire, different surface facets, and various defects in the core/shell interface and surface regions. To properly describe the band level alignment at the core/shell boundary, we adopted the self-interaction correction (SIC)-DFT scheme. Implications of our findings in the context of device applications will be also discussed. This work was supported by the Basic Science Research Grant (No. 2012R1A1A2044793), Global Frontier Program (No. 2013-073298), and Nano-Material Technology Development Program (2012M3A7B4049888) of the National Research Foundation funded by the Ministry of Education, Science and Technology of Korea. Corresponding author

Fabrication and characterization of ZnS/ZnO core shell nanostructures on silver wires

NASA Astrophysics Data System (ADS)

Kao, Chyuan Haur; Su, Wei Ming; Li, Cheng Yuan; Weng, Wei Chih; Weng, Chen Yuan; Cheng, Chin-Chi; Lin, Yung-Sen; Lin, Chia Feng; Chen, Hsiang

2018-06-01

In this research, ZnS nanoparticles were synthesized on ZnO/silver wires to form ZnS/ZnO core shell structures. Various outward appearance and colors could be observed by different ZnO growth and sulfurization conditions. To evaluate the properties of these nanostructures, optical properties and chemical bindings were analyzed by photoluminescence, Raman analysis, and X-ray photoelectron spectroscopy. Furthermore, material characterizations including transmission electron microscopy and X-ray diffraction confirmed that cubic ZnS (311)/ZnO nanostructures were grown on silver wires for the first time. ZnS/ZnO core shell structures on silver wires are promising for future optoelectronic and biomedical applications.

Materials and structures for stretchable energy storage and conversion devices.

PubMed

Xie, Keyu; Wei, Bingqing

2014-06-11

Stretchable energy storage and conversion devices (ESCDs) are attracting intensive attention due to their promising and potential applications in realistic consumer products, ranging from portable electronics, bio-integrated devices, space satellites, and electric vehicles to buildings with arbitrarily shaped surfaces. Material synthesis and structural design are core in the development of highly stretchable supercapacitors, batteries, and solar cells for practical applications. This review provides a brief summary of research development on the stretchable ESCDs in the past decade, from structural design strategies to novel materials synthesis. The focuses are on the fundamental insights of mechanical characteristics of materials and structures on the performance of the stretchable ESCDs, as well as challenges for their practical applications. Finally, some of the important directions in the areas of material synthesis and structural design facing the stretchable ESCDs are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Disruption of a coronal streamer by an eruptive prominence and coronal mass ejection

NASA Technical Reports Server (NTRS)

Illing, R. M. E.; Hundhausen, A. J.

1986-01-01

The coronal mass ejection of August 18, 1980 is analyzed using images from the coronagraph on the Solar Maximum Mission (SMM) satellite. The event occurred at the site of a large coronal helmet streamer and evolved into the three-part structure of a bright frontal shell, followed by a relatively dark space surrounding a bright filamentary core as seen in many mass ejections of the SMM epoch. The bright core can be identified as material from a prominence whose eruption was observed from the ground. The mass of the frontal shell is equal to that of the coronal helmet streamer, indicating that the shell is the coronal material previously in the helmet streamer, displaced and set into motion by the erupting prominence and surrounding cavity. The mass ejected in the bright core (or prominences) is estimated to be 50 percent larger than the 'coronal' material in the front loop.

Synthesis and Structure of an Extended Cluster Lead(II) Carboxylate, [Pb{(CO)(9)Co(3)(&mgr;(3)-CCO(2))}(2)](n)(). Role of Core Metals in Cluster-Derived Hydrogenation Catalysts.

PubMed

Lei, Xinjian; Shang, Maoyu; Patil, Atul; Wolf, Eduardo E.; Fehlner, Thomas P.

1996-05-22

The reaction of lead acetate with (CO)(9)Co(3)(&mgr;(3)-CCOOH) leads to the formation of [Pb{(CO)(9)Co(3)(&mgr;(3)-CCO(2))}(2)](n)(), I, in high yield. The structure of I exhibits unusual six-coordinate Pb(II) centers with two asymmetrical chelating cluster carboxylates (C(22)Co(6)PbO(22); triclinic P&onemacr;; a = 8.119(1), b = 14.346(2), c = 14.660(2) Å; alpha = 102.18(1), beta = 99.01(1), gamma = 97.30(1) degrees; Z = 2). One oxygen of each cluster carboxylate ligand bridges between adjacent lead atoms such that a chainlike extended structure is found in the solid state without the presence of solvent or water. I is converted stepwise on pyrolysis into two metastable forms of solid materials (designated LT and HT), each of which has been characterized spectroscopically. The hydrogenation of 2-butenal as a test reaction shows that the LT catalyst exhibits selectivities similar to previous LT materials derived from other cobalt cluster metal carboxylates and that the HT material is totally inactive. The observed release of the lead core metal under HT activation conditions totally inactivates the catalyst and demonstrates exposure of the core metal in the HT form of these novel catalysts.

Fractal analysis and its impact factors on pore structure of artificial cores based on the images obtained using magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Wang, Heming; Liu, Yu; Song, Yongchen; Zhao, Yuechao; Zhao, Jiafei; Wang, Dayong

2012-11-01

Pore structure is one of important factors affecting the properties of porous media, but it is difficult to describe the complexity of pore structure exactly. Fractal theory is an effective and available method for quantifying the complex and irregular pore structure. In this paper, the fractal dimension calculated by box-counting method based on fractal theory was applied to characterize the pore structure of artificial cores. The microstructure or pore distribution in the porous material was obtained using the nuclear magnetic resonance imaging (MRI). Three classical fractals and one sand packed bed model were selected as the experimental material to investigate the influence of box sizes, threshold value, and the image resolution when performing fractal analysis. To avoid the influence of box sizes, a sequence of divisors of the image was proposed and compared with other two algorithms (geometric sequence and arithmetic sequence) with its performance of partitioning the image completely and bringing the least fitted error. Threshold value selected manually and automatically showed that it plays an important role during the image binary processing and the minimum-error method can be used to obtain an appropriate or reasonable one. Images obtained under different pixel matrices in MRI were used to analyze the influence of image resolution. Higher image resolution can detect more quantity of pore structure and increase its irregularity. With benefits of those influence factors, fractal analysis on four kinds of artificial cores showed the fractal dimension can be used to distinguish the different kinds of artificial cores and the relationship between fractal dimension and porosity or permeability can be expressed by the model of D = a - bln(x + c).

Growth Mechanism of a Unique Hierarchical Vaterite Structure

NASA Astrophysics Data System (ADS)

Ma, Guobin; Xu, Yifei; Wang, Mu

2013-03-01

Calcium carbonate is one of the most significant minerals in nature as well as in biogenic sources. Calcium carbonate occurs naturally in three crystalline polymorphs, i.e., calcite, aragonite, and vaterite. Although it has been attracted much research attention to understanding of the formation mechanisms of the material, the properties of the vaterite polymorph is not well known. Here we report synthesis and formation mechanism of a unique hierarchical structure of vaterite. The material is grown by a controlled diffusion method. The structure possesses a core and an outer part. The core is convex lens-like and is formed by vaterite nanocrystals that have small misorientations. The outer part is separated into six garlic clove-like segments. Each segment possesses piles of plate-like vaterite crystals, and the orientations of the plates continuously change from pile to pile. Based on real-time experimental results and the structural analysis, a growth mechanism is presented. Work supported by NSFC (Grant No. 51172104) and MOST of China (Grant No. 2101CB630705)

Realization of Both High-Performance and Enhanced Durability of Fuel Cells: Pt-Exoskeleton Structure Electrocatalysts.

PubMed

Kim, Ok-Hee; Cho, Yoon-Hwan; Jeon, Tae-Yeol; Kim, Jung Won; Cho, Yong-Hun; Sung, Yung-Eun

2015-07-01

Core-shell structure nanoparticles have been the subject of many studies over the past few years and continue to be studied as electrocatalysts for fuel cells. Therefore, many excellent core-shell catalysts have been fabricated, but few studies have reported the real application of these catalysts in a practical device actual application. In this paper, we demonstrate the use of platinum (Pt)-exoskeleton structure nanoparticles as cathode catalysts with high stability and remarkable Pt mass activity and report the outstanding performance of these materials when used in membrane-electrode assemblies (MEAs) within a polymer electrolyte membrane fuel cell. The stability and degradation characteristics of these materials were also investigated in single cells in an accelerated degradation test using load cycling, which is similar to the drive cycle of a polymer electrolyte membrane fuel cell used in vehicles. The MEAs with Pt-exoskeleton structure catalysts showed enhanced performance throughout the single cell test and exhibited improved degradation ability that differed from that of a commercial Pt/C catalyst.

Preliminary Structural Sizing and Alternative Material Trade Study of CEV Crew Module

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steve M.; Collier, Craig S.; Yarrington, Phillip W.

2007-01-01

This paper presents the results of a preliminary structural sizing and alternate material trade study for NASA s Crew Exploration Vehicle (CEV) Crew Module (CM). This critical CEV component will house the astronauts during ascent, docking with the International Space Station, reentry, and landing. The alternate material design study considers three materials beyond the standard metallic (aluminum alloy) design that resulted from an earlier NASA Smart Buyer Team analysis. These materials are graphite/epoxy composite laminates, discontinuously reinforced SiC/Al (DRA) composites, and a novel integrated panel material/concept known as WebCore. Using the HyperSizer (Collier Research and Development Corporation) structural sizing software and NASTRAN finite element analysis code, a comparison is made among these materials for the three composite CM concepts considered by the 2006 NASA Engineering and Safety Center Composite Crew Module project.

Seaurchin-like hierarchical NiCo2O4@NiMoO4 core-shell nanomaterials for high performance supercapacitors.

PubMed

Zhang, Qiang; Deng, Yanghua; Hu, Zhonghua; Liu, Yafei; Yao, Mingming; Liu, Peipei

2014-11-14

A novel electrode material of the three-dimensional (3D) multicomponent oxide NiCo2O4@NiMoO4 core-shell was synthesized via a facile two-step hydrothermal method using a post-annealing procedure. The uniform NiMoO4 nanosheets were grown on the seaurchin-like NiCo2O4 backbone to form a NiCo2O4@NiMoO4 core-shell material constructed by interconnected ultrathin nanosheets, so as to produce hierarchical mesopores with a large specific surface area of 100.3 m(2) g(-1). The porous feature and core-shell structure can facilitate the penetration of electrolytic ions and increases the number of electroactive sites. Hence, the NiCo2O4@NiMoO4 material exhibited a high specific capacitance of 2474 F g(-1) and 2080 F g(-1) at current densities of 1 A g(-1) and 20 A g(-1) respectively, suggesting that it has not only a very large specific capacitance, but also a good rate performance. In addition, the capacitance loss was only 5.0% after 1000 cycles of charge and discharge tests at the current density of 10 A g(-1), indicating high stability. The excellent electrochemical performance is mainly attributed to its 3D core-shell and hierarchical mesoporous structures which can provide unobstructed pathways for the fast diffusion and transportation of ions and electrons, a large number of active sites and good strain accommodation.

Mould design and manufacturing considerations of honeycomb biocomposites with transverse fibre direction for aerospace application

NASA Astrophysics Data System (ADS)

Manan, N. H.; Majid, D. L.; Romli, F. I.

2016-10-01

Sandwich structures with honeycomb core are known to significantly improve stiffness at lower weight and possess high flexural rigidity. They have found wide applications in aerospace as part of the primary structures, as well as the interior paneling and floors. High performance aluminum and aramid are the typical materials used for the purpose of honeycomb core whereas in other industries, materials such as fibre glass, carbon fibre, Nomex and also Kevlar reinforced with polymer are used. Recently, growing interest in developing composite structures with natural fibre reinforcement has also spurred research in natural fibre honeycomb material. The majority of the researches done, however, have generally emphasized on the usage of random chopped fibre and only a few are reported on development of honeycomb structure using unidirectional fibre as the reinforcement. This is mainly due to its processing difficulties, which often involve several stages to account for the arrangement of fibres and curing. Since the use of unidirectional fibre supports greater strength compared to random chopped fibre, a single-stage process in conjunction with vacuum infusion is suggested with a mould design that supports fibre arrangement in the direction of honeycomb loading.

Generation of a mesoporous silica MSU shell onto solid core silica nanoparticles using a simple two-step sol-gel process.

PubMed

Allouche, Joachim; Dupin, Jean-Charles; Gonbeau, Danielle

2011-07-14

Silica core-shell nanoparticles with a MSU shell have been synthesized using several non-ionic poly(ethylene oxide) based surfactants via a two step sol-gel method. The materials exhibit a typical worm-hole pore structure and tunable pore diameters between 2.4 nm and 5.8 nm.

Finsler Geometry of Nonlinear Elastic Solids with Internal Structure

DTIC Science & Technology

2017-01-01

should enable regularized numerical solutions with discretization -size independence for representation of materials demonstrating softening, e.g...additional possibility of a discrete larger void/cavity forming at the core of the sphere. In the second case, comparison with the classical...core of the domain. This hollow sphere physically represents a discrete cavity, while the constant field ξH physically represents a continuous

Preparation, characterization and luminescence properties of core-shell ternary terbium composites SiO2(600)@Tb(MABA-Si)•L

NASA Astrophysics Data System (ADS)

Ma, Yang-Yang; Li, Wen-Xian; Zheng, Yu-Shan; Bao, Jin-Rong; Li, Yi-Lian; Feng, Li-Na; Yang, Kui-Suo; Qiao, Yan; Wu, An-Ping

2018-03-01

Two novel core-shell structure ternary terbium composites SiO2(600)@Tb(MABA-Si)·L(L:dipy/phen) nanometre luminescence materials were prepared by ternary terbium complexes Tb(MABA-Si)·L2·(ClO4)3·2H2O shell grafted onto the surface of SiO2 microspheres. And corresponding ternary terbium complexes were synthesized using (CONH(CH2)3Si(OCH2CH3)3)2 (denoted as MABA-Si) as first ligand and L as second ligand coordinated with terbium perchlorate. The as-synthesized products were characterized by means of IR spectra, 1HNMR, element analysis, molar conductivity, SEM and TEM. It was found that the first ligand MABA-Si of terbium ternary complex hydrolysed to generate the Si-OH and the Si-OH condensate with the Si-OH on the surface of SiO2 microspheres; then ligand MABA-Si grafted onto the surface of SiO2 microspheres. The diameter of SiO2 core of SiO2(600)@Tb(MABA-Si)·L was approximately 600 nm. Interestingly, the luminescence properties demonstrate that the two core-shell structure ternary terbium composites SiO2(600)Tb(MABA-Si)·L(dipy/phen) exhibit strong emission intensities, which are 2.49 and 3.35 times higher than that of the corresponding complexes Tb(MABA-Si)·L2·(ClO4)3·2H2O, respectively. Luminescence decay curves show that core-shell structure ternary terbium composites have longer lifetime. Excellent luminescence properties enable the core-shell materials to have potential applications in medicine, industry, luminescent fibres and various biomaterials fields.

Preparation, characterization and luminescence properties of core-shell ternary terbium composites SiO2(600)@Tb(MABA-Si)•L.

PubMed

Ma, Yang-Yang; Li, Wen-Xian; Zheng, Yu-Shan; Bao, Jin-Rong; Li, Yi-Lian; Feng, Li-Na; Yang, Kui-Suo; Qiao, Yan; Wu, An-Ping

2018-03-01

Two novel core-shell structure ternary terbium composites SiO 2(600) @Tb(MABA-Si)·L(L:dipy/phen) nanometre luminescence materials were prepared by ternary terbium complexes Tb(MABA-Si)·L 2 ·(ClO 4 ) 3 ·2H 2 O shell grafted onto the surface of SiO 2 microspheres. And corresponding ternary terbium complexes were synthesized using (CONH(CH 2 ) 3 Si(OCH 2 CH 3 ) 3 ) 2 (denoted as MABA-Si) as first ligand and L as second ligand coordinated with terbium perchlorate. The as-synthesized products were characterized by means of IR spectra, 1 HNMR, element analysis, molar conductivity, SEM and TEM. It was found that the first ligand MABA-Si of terbium ternary complex hydrolysed to generate the Si-OH and the Si-OH condensate with the Si-OH on the surface of SiO 2 microspheres; then ligand MABA-Si grafted onto the surface of SiO 2 microspheres. The diameter of SiO 2 core of SiO 2(600) @Tb(MABA-Si)·L was approximately 600 nm. Interestingly, the luminescence properties demonstrate that the two core-shell structure ternary terbium composites SiO 2(600) Tb(MABA-Si)·L(dipy/phen) exhibit strong emission intensities, which are 2.49 and 3.35 times higher than that of the corresponding complexes Tb(MABA-Si)·L 2 ·(ClO 4 ) 3 ·2H 2 O, respectively. Luminescence decay curves show that core-shell structure ternary terbium composites have longer lifetime. Excellent luminescence properties enable the core-shell materials to have potential applications in medicine, industry, luminescent fibres and various biomaterials fields.

Preparation and characterization of core-shell structured LiFePO4/C composite using a novel carbon source for lithium-ion battery cathode

NASA Astrophysics Data System (ADS)

Huang, Zan; Luo, Peifang; Wang, Daxiang

2017-03-01

Core-shell structured LiFePO4/C1 cathode material is synthesized via a rapid microwave irradiation route using ethylene diamine tetraacetic acid (EDTA) as the novel carbon source. XRD results reveal that all the patterns can be indexed as the olivine-type structured LiFePO4 with the space group of Pnma. TEM images show that the obtained carbon is an amorphous layer with a thickness of about 3-4 nm. When the LiFePO4/C1 used as cathode material for lithium-ion battery, it delivers an initial discharge capacity of 163.1 mAh g-1 at 0.1 C which is about 96% of the theoretical capacity. Moreover, it also shows excellent rate performance and good cycle stability due to the enhanced electronic conductivity as proved by the electrochemical impedance spectroscopy (EIS). Thus, this carbon decorated LiFePO4 composite synthesized via the rapid microwave irradiation method is a promising cathode material for high-performance lithium-ion battery.

Facile synthesis and lithium storage properties of a porous NiSi2/Si/carbon composite anode material for lithium-ion batteries.

PubMed

Jia, Haiping; Stock, Christoph; Kloepsch, Richard; He, Xin; Badillo, Juan Pablo; Fromm, Olga; Vortmann, Britta; Winter, Martin; Placke, Tobias

2015-01-28

In this work, a novel, porous structured NiSi2/Si composite material with a core-shell morphology was successfully prepared using a facile ball-milling method. Furthermore, the chemical vapor deposition (CVD) method is deployed to coat the NiSi2/Si phase with a thin carbon layer to further enhance the surface electronic conductivity and to mechanically stabilize the whole composite structure. The morphology and porosity of the composite material was evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption measurements (BJH analysis). The as-prepared composite material consists of NiSi2, silicon, and carbon phases, in which the NiSi2 phase is embedded in a silicon matrix having homogeneously distributed pores, while the surface of this composite is coated with a carbon layer. The electrochemical characterization shows that the porous and core-shell structure of the composite anode material can effectively absorb and buffer the immense volume changes of silicon during the lithiation/delithiation process. The obtained NiSi2/Si/carbon composite anode material displays an outstanding electrochemical performance, which gives a stable capacity of 1272 mAh g(-1) for 200 cycles at a charge/discharge rate of 1C and a good rate capability with a reversible capacity of 740 mAh g(-1) at a rate of 5C.

A convergent approach to biocompatible polyglycerol "click" dendrons for the synthesis of modular core-shell architectures and their transport behavior.

PubMed

Wyszogrodzka, Monika; Haag, Rainer

2008-01-01

Dendrimers are an important class of polymeric materials for a broad range of applications in which monodispersity and multivalency are of interest. Here we report on a highly efficient synthetic route towards bifunctional polyglycerol dendrons on a multigram scale. Commercially available triglycerol (1), which is highly biocompatible, was used as starting material. By applying Williamson ether synthesis followed by an ozonolysis/reduction procedure, glycerol-based dendrons up to the fourth generation were prepared. The obtained products have a reactive core, which was further functionalized to the corresponding monoazido derivatives. By applying copper(I)-catalyzed 1,3-dipolar cycloaddition, so-called "click" coupling, a library of core-shell architectures was prepared. After removal of the 1,2-diol protecting groups, water-soluble core-shell architectures 24-27 of different generations were obtained in high yields. In the structure-transport relationship with Nile red we observe a clear dependence on core size and generation of the polyglycerol dendrons.

Preparation and electrochemical properties of core-shell carbon coated Mn-Sn complex metal oxide as anode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Ruixue; Fang, Guoqing; Liu, Weiwei; Xia, Bingbo; Sun, Hongdan; Zheng, Junwei; Li, Decheng

2014-02-01

In this study, we synthesized a carbon coated Mn-Sn metal oxide composite with core-shell structure (MTO@C) via a simple glucose hydrothermal reaction and subsequent carbonization approach. When the MTO@C composite was applied as an anode material for lithium-ion batteries, it maintained a reversible capacity of 409 mA h g-1 after 200 cycles at a current density of 100 mA g-1. The uniformed and continuous carbon layer formed on the MTO nanoparticles, effectively buffered the volumetric change of the active material and increased electronic conductivity, which thus prolonged the cycling performance of the MTO@C electrode.

Predictable Particle Engineering: Programming the Energy Level, Carrier Generation, and Conductivity of Core-Shell Particles.

PubMed

Yuan, Conghui; Wu, Tong; Mao, Jie; Chen, Ting; Li, Yuntong; Li, Min; Xu, Yiting; Zeng, Birong; Luo, Weiang; Yu, Lingke; Zheng, Gaofeng; Dai, Lizong

2018-06-20

Core-shell structures are of particular interest in the development of advanced composite materials as they can efficiently bring different components together at nanoscale. The advantage of this structure greatly relies on the crucial design of both core and shell, thus achieving an intercomponent synergistic effect. In this report, we show that decorating semiconductor nanocrystals with a boronate polymer shell can easily achieve programmable core-shell interactions. Taking ZnO and anatase TiO 2 nanocrystals as inner core examples, the effective core-shell interactions can narrow the band gap of semiconductor nanocrystals, change the HOMO and LUMO levels of boronate polymer shell, and significantly improve the carrier density of core-shell particles. The hole mobility of core-shell particles can be improved by almost 9 orders of magnitude in comparison with net boronate polymer, while the conductivity of core-shell particles is at most 30-fold of nanocrystals. The particle engineering strategy is based on two driving forces: catechol-surface binding and B-N dative bonding and having a high ability to control and predict the shell thickness. Also, this approach is applicable to various inorganic nanoparticles with different components, sizes, and shapes.

Synthesis of suitable SiO2 nano particles as the core in core-shell nanostructured materials.

PubMed

Ghahari, Mehdi; Aghababazadeh, Roya; Ebadzadeh, Touradj; Mirhabibi, Alireza; Brydson, Rik; Fabbri, Paola; Najafi, Farhod

2011-06-01

The effect of surfactant on the luminescent intensity of SiO2 @Y2O3:Eu3+ particles with a core shell structure is described. Core-shell particles are used in phosphor materials and employing spherical particles with a narrow size distribution is vital for the enhancement of luminescent properties. Three kinds of different surfactants were used to synthesis SiO2 nano particles via a sol gel process. The results demonstrated that comb polycarboxylic acid surfactant had a significant influence on the morphology and particle size distribution. Somehow, particles with 100 nm size and narrow size distribution were produced. These particles had relatively uniform packing, unlike particles produced with other surfactants or without surfactant which had irregular assembly. The photoluminescence intensity of SiO2 @Y2O3:Eu3+ particles that was synthesized by comb polycarboxylic acid surfactant was higher than those which were produced without surfactant.

Behavior of composite sandwich panels with several core designs at different impact velocities

NASA Astrophysics Data System (ADS)

Jiga, Gabriel; Stamin, Ştefan; Dinu, Gabriela

2018-02-01

A sandwich composite represents a special class of composite materials that is manufactured by bonding two thin but stiff faces to a low density and low strength but thick core. The distance between the skins given by the core increases the flexural modulus of the panel with a low mass increase, producing an efficient structure able to resist at flexural and buckling loads. The strength of sandwich panels depends on the size of the panel, skins material and number or density of the cells within it. Sandwich composites are used widely in several industries, such as aerospace, automotive, medical and leisure industries. The behavior of composite sandwich panels with different core designs under different impact velocities are analyzed in this paper by numerical simulations performed on sandwich panels. The modeling was done in ANSYS and the analysis was performed through LS-DYNA.

Gravity investigations of the Chesapeake Bay impact structure

USGS Publications Warehouse

Plescia, J.B.; Daniels, D.L.; Shah, A.K.

2009-01-01

The Chesapeake Bay impact structure is a complex impact crater, ??85 km in diameter, buried beneath postimpact sediments. Its main structural elements include a central uplift of crystalline bedrock, a surrounding inner crater filled with impact debris, and an annular faulted margin composed of block-faulted sediments. The gravity anomaly is consistent with that of a complex impact consisting of a central positive anomaly over the central uplift and an annular negative anomaly over the inner crater. An anomaly is not recognized as being associated with the faulted margin or the outer edge of the structure. Densities from the Eyreville drill core and modeling indicate a density contrast of ??0.3-0.6 g cm-3 between crystalline basement and the material that fills the inner crater (e.g., Exmore breccia and suevite). This density contrast is somewhat higher than for other impact structures, but it is a function of the manner in which the crater fill was deposited (as a marine resurge deposit). Modeling of the gravity data is consistent with a depth to basement of ??1600 m at the site of Eyreville drill hole and 800 m at the central uplift. Both depths are greater than the depth at which crystalline rocks were encountered in the cores, suggesting that the cored material is highly fractured para-allochthonous rock. ?? 2009 The Geological Society of America.

High performance of SDC and GDC core shell type composite electrolytes using methane as a fuel for low temperature SOFC

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

Irshad, Muneeb; Siraj, Khurram, E-mail: razahussaini786@gmail.com, E-mail: khurram.uet@gmail.com; Javed, Fayyaz

Nanocomposites Samarium doped Ceria (SDC), Gadolinium doped Ceria (GDC), core shell SDC amorphous Na{sub 2}CO{sub 3} (SDCC) and GDC amorphous Na{sub 2}CO{sub 3} (GDCC) were synthesized using co-precipitation method and then compared to obtain better solid oxide electrolytes materials for low temperature Solid Oxide Fuel Cell (SOFCs). The comparison is done in terms of structure, crystallanity, thermal stability, conductivity and cell performance. In present work, XRD analysis confirmed proper doping of Sm and Gd in both single phase (SDC, GDC) and dual phase core shell (SDCC, GDCC) electrolyte materials. EDX analysis validated the presence of Sm and Gd in bothmore » single and dual phase electrolyte materials; also confirming the presence of amorphous Na{sub 2}CO{sub 3} in SDCC and GDCC. From TGA analysis a steep weight loss is observed in case of SDCC and GDCC when temperature rises above 725 °C while SDC and GDC do not show any loss. The ionic conductivity and cell performance of single phase SDC and GDC nanocomposite were compared with core shell GDC/amorphous Na{sub 2}CO{sub 3} and SDC/ amorphous Na{sub 2}CO{sub 3} nanocomposites using methane fuel. It is observed that dual phase core shell electrolytes materials (SDCC, GDCC) show better performance in low temperature range than their corresponding single phase electrolyte materials (SDC, GDC) with methane fuel.« less

Correlative Microscopy of Neutron-Irradiated Materials

DOE PAGES

Briggs, Samuel A.; Sridharan, Kumar; Field, Kevin G.

2016-12-31

A nuclear reactor core is a highly demanding environment that presents several unique challenges for materials performance. Materials in modern light water reactor (LWR) cores must survive several decades in high-temperature (300-350°C) aqueous corrosion conditions while being subject to large amounts of high-energy neutron irradiation. Next-generation reactor designs seek to use more corrosive coolants (e.g., molten salts) and even greater temperatures and neutron doses. The high amounts of disorder and unique crystallographic defects and microchemical segregation effects induced by radiation inevitably lead to property degradation of materials. Thus, maintaining structural integrity and safety margins over the course of the reactor'smore » service life thus necessitates the ability to understand and predict these degradation phenomena in order to develop new, radiation-tolerant materials that can maintain the required performance in these extreme conditions.« less

Degradation of Si/Ge core/shell nanowire heterostructures during lithiation and delithiation at 0.8 and 20 A g-1.

PubMed

Kim, Dongheun; Li, Nan; Sheehan, Chris J; Yoo, Jinkyoung

2018-04-26

Si/Ge core/shell nanowire heterostructures have been expected to provide high energy and power densities for lithium ion battery anodes due to the large capacity of Si and the high electrical and ionic conductivities of Ge. Although the battery anode performances of Si/Ge core/shell nanowire heterostructures have been characterized, the degradation of Si/Ge core/shell nanowire heterostructures has not been thoroughly investigated. Here we report the compositional and structural changes of the Si/Ge core/shell nanowire heterostructure over cycling of lithiation and delithiation at different charging rates. The Si/Ge core/shell nanowire heterostructure holds the core and shell structure at a charging rate of 0.8 A g-1 up to 50 cycles. On the other hand, compositional intermixing and loss of Si occur at a charging rate of 20 A g-1 within 50 cycles. The operation condition-dependent degradation provides a new aspect of materials research for the development of high performance lithium ion battery anodes with a long cycle life.

Porous and Cellular Materials for Structural Applications; Symposium Held in San Francisco, California on April 13-15, 1998

DTIC Science & Technology

1998-04-01

Industrial Scale 179 M. Schmidt and F. Schwertfeger Structural Graphitic Carbon Foams 185 Kristen M. Kearns, David P. Anderson, and Heather J...Nanostructured Powders and Their Industrial Application, Q. Beaucage, J.E. Mark, Q. Burns, H. Duen-Wu, 1998, ISBN: 1-55899-426-2 Volume 521—Porous and Cellular...has faces which are 0.03" thick and the core is 0.4" thick. Bonding between the core and face is achieved using a standard industrial epoxy adhesive

Size-Independent Exciton Localization Efficiency in Colloidal CdSe/CdS Core/Crown Nanosheet Type-I Heterostructures.

PubMed

Li, Qiuyang; Wu, Kaifeng; Chen, Jinquan; Chen, Zheyuan; McBride, James R; Lian, Tianquan

2016-03-22

CdSe/CdS core/crown nanoplatelet type I heterostructures are a class of two-dimensional materials with atomically precise thickness and many potential optoelectronic applications. It remains unclear how the precise thickness and lack of energy disorder affect the properties of exciton transport in these materials. By steady-state photoluminescence excitation spectroscopy and ultrafast transient absorption spectroscopy, we show that in five CdSe/CdS core/crown structures with the same core and increasing crown size (with thickness of ∼1.8 nm, width of ∼11 nm, and length from 20 to 40 nm), the crown-to-core exciton localization efficiency is independent of crown size and increases with photon energy above the band edge (from 70% at 400 nm to ∼100% at 370 nm), while the localization time increases with the crown size. These observations can be understood by a model that accounts for the competition of in-plane exciton diffusion and selective hole trapping at the core/crown interface. Our findings suggest that the exciton localization efficiency can be further improved by reducing interfacial defects.

Theoretical and experimental investigation of architected core materials incorporating negative stiffness elements

NASA Astrophysics Data System (ADS)

Chang, Chia-Ming; Keefe, Andrew; Carter, William B.; Henry, Christopher P.; McKnight, Geoff P.

2014-04-01

Structural assemblies incorporating negative stiffness elements have been shown to provide both tunable damping properties and simultaneous high stiffness and damping over prescribed displacement regions. In this paper we explore the design space for negative stiffness based assemblies using analytical modeling combined with finite element analysis. A simplified spring model demonstrates the effects of element stiffness, geometry, and preloads on the damping and stiffness performance. Simplified analytical models were validated for realistic structural implementations through finite element analysis. A series of complementary experiments was conducted to compare with modeling and determine the effects of each element on the system response. The measured damping performance follows the theoretical predictions obtained by analytical modeling. We applied these concepts to a novel sandwich core structure that exhibited combined stiffness and damping properties 8 times greater than existing foam core technologies.

Integration of Biosafety into Core Facility Management

PubMed Central

Fontes, Benjamin

2013-01-01

This presentation will discuss the implementation of biosafety policies for small, medium and large core laboratories with primary shared objectives of ensuring the control of biohazards to protect core facility operators and assure conformity with applicable state and federal policies, standards and guidelines. Of paramount importance is the educational process to inform core laboratories of biosafety principles and policies and to illustrate the technology and process pathways of the core laboratory for biosafety professionals. Elevating awareness of biohazards and the biosafety regulatory landscape among core facility operators is essential for the establishment of a framework for both project and material risk assessment. The goal of the biohazard risk assessment process is to identify the biohazard risk management parameters to conduct the procedure safely and in compliance with applicable regulations. An evaluation of the containment, protective equipment and work practices for the procedure for the level of risk identified is facilitated by the establishment of a core facility registration form for work with biohazards and other biological materials with potential risk. The final step in the biocontainment process is the assumption of Principal Investigator role with full responsibility for the structure of the site-specific biosafety program plan by core facility leadership. The presentation will provide example biohazard protocol reviews and accompanying containment measures for core laboratories at Yale University.

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.

Ordered three- and five-ply nanocomposites from ABC block terpolymer microphase separation with niobia and aluminosilicate sols

PubMed Central

Stefik, Morgan; Mahajan, Surbhi; Sai, Hiroaki; Epps, Thomas H.; Bates, Frank S.; Gruner, Sol M; DiSalvo, Francis J.; Wiesner, Ulrich

2009-01-01

We report the first use of a non-frustrated block terpolymer for the synthesis of highly ordered oxide nanocomposites containing multiple plies. The morphological behavior of 15 ISO-oxide nanocomposites was investigated spanning a large range of compositions along the ƒI=ƒS isopleth using aluminosilicate and niobia sols. Morphologies were determined by TEM and SAXS measurements. Four morphologies were identified, including core-shell hexagonal, core-shell double gyroid, three-domain lamellae, and core-shell inverse-hexagonal, in order of increasing O+oxide vol fraction. All of the resulting nanocomposites had three- or five-ply morphologies containing domains that were continuous in one, two, or three dimensions. The five-ply core-shell double gyroid phase was only found to be stable when the O+oxide domain was a minority. Removal of the polymer enabled simple and direct synthesis of mesoporous oxide materials while retaining the ordered network structure. We believe that advances in the synthesis of multi-ply nanocomposites will lead to advanced materials and devices containing multiple plies of functional materials. PMID:20209023

Ordered three- and five-ply nanocomposites from ABC block terpolymer microphase separation with niobia and aluminosilicate sols.

PubMed

Stefik, Morgan; Mahajan, Surbhi; Sai, Hiroaki; Epps, Thomas H; Bates, Frank S; Gruner, Sol M; Disalvo, Francis J; Wiesner, Ulrich

2009-11-24

We report the first use of a non-frustrated block terpolymer for the synthesis of highly ordered oxide nanocomposites containing multiple plies. The morphological behavior of 15 ISO-oxide nanocomposites was investigated spanning a large range of compositions along the ƒ(I)=ƒ(S) isopleth using aluminosilicate and niobia sols. Morphologies were determined by TEM and SAXS measurements. Four morphologies were identified, including core-shell hexagonal, core-shell double gyroid, three-domain lamellae, and core-shell inverse-hexagonal, in order of increasing O+oxide vol fraction. All of the resulting nanocomposites had three- or five-ply morphologies containing domains that were continuous in one, two, or three dimensions. The five-ply core-shell double gyroid phase was only found to be stable when the O+oxide domain was a minority. Removal of the polymer enabled simple and direct synthesis of mesoporous oxide materials while retaining the ordered network structure. We believe that advances in the synthesis of multi-ply nanocomposites will lead to advanced materials and devices containing multiple plies of functional materials.

Saturable inductor and transformer structures for magnetic pulse compression

DOEpatents

Birx, Daniel L.; Reginato, Louis L.

1990-01-01

Saturable inductor and transformer for magnetic compression of an electronic pulse, using a continuous electrical conductor looped several times around a tightly packed core of saturable inductor material.

MC carbide structures in M(lc2)ar-M247. M.S. Thesis - Final Report

NASA Technical Reports Server (NTRS)

Wawro, S. W.

1982-01-01

The morphologies and distribution of the MC carbides in Mar-M247 ingot stock and castings were investigated using metallographic, X-ray diffraction and energy-dispersive X-ray analysis techniques. The MC carbides were found to form script structures during solidification. The script structures were composed of three distinct parts. The central cores and elongated arms of the MC carbide script structures had compositions (Ti, Cr, Hf, Ta, W)C and lattice parameters of 4.39 A. The elongated script arms terminated in enlarged, angular "heads". The heads had compositions (Ti, Hf, Ta, W)C and lattice parameters of approximately 4.50 A. The heads had a higher Hf content than the cores and arms. The size of the script structures, as well as the relative amount of head-type to core and arm-type MC carbide, was found to be determined by solidification conditions. No carryover of the MC carbides from the ingot stock to the remelted and cast material was observed.

Comparison of the performance of concrete-filled steel tubular and hollow steel diagrid buildings

NASA Astrophysics Data System (ADS)

Peter, Minu Ann; S, Sajith A.; Nagarajan, Praveen

2018-03-01

In the recent construction scenario, diagrid structures are becoming a popular high-rise building structural system. Diagrid structures consist of diagonals in the perimeter and an interior core. The corner and interior vertical columns are not required due to the structural efficiency of diagrid structural systems. Steel and concrete are commonly used material for diagrid. An alternate material for diagrid is concrete-filled steel tube (CFST). CFST incorporates the advantages of both steel and concrete. In CFST, the inward buckling of the steel tube is effectively prevented by the filled concrete. The compressive strength of concrete increases due to the tri-axial state of stress in concrete induced by the steel tube. The longitudinal as well as lateral reinforcement to the concrete core is also provided by the steel tube. This paper compares the performance of CFST and steel diagrid buildings using linear static analysis. For this purpose, a 12 storey and 36 storey building are analysed using finite element method and CFST diagrid building is found to perform better.

Polymorphism in magic-sized Au144(SR)60 clusters

DOE PAGES

Jensen, Kirsten M. O.; Juhas, Pavol; Tofanelli, Marcus A.; ...

2016-06-14

Ultra-small, magic-sized metal nanoclusters represent an important new class of materials with properties between molecules and particles. However, their small size challenges the conventional methods for structure characterization. We present the structure of ultra-stable Au144(SR)60 magic-sized nanoclusters obtained from atomic pair distribution function analysis of X-ray powder diffraction data. Our study reveals structural polymorphism in these archetypal nanoclusters. Additionally, in order to confirm the theoretically predicted icosahedral-cored cluster, we also find samples with a truncated decahedral core structure, with some samples exhibiting a coexistence of both cluster structures. Although the clusters are monodisperse in size, structural diversity is apparent. Finally,more » the discovery of polymorphism may open up a new dimension in nanoscale engineering.« less

Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core-Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes.

PubMed

Ma, Zhipeng; Shao, Guangjie; Fan, Yuqian; Wang, Guiling; Song, Jianjun; Shen, Dejiu

2016-04-13

Poor electrical conductivity and mechanical instability are two major obstacles to realizing high performance of MnO2 as pseudocapacitor material. The construction of unique hierarchical core-shell nanostructures, therefore, plays an important role in the efficient enhancement of the rate capacity and the stability of this material. We herein report the fabrication of a hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure by adopting a facile and practical solution-phase technique. The novel hierarchical nanostructures are composed of ultrathin δ-MnO2 nanosheets with a few atomic layers growing well on the surface of the ultralong α-MnO2 nanowires. The first specific capacitance of hierarchical core-shell nanostructure reached 153.8 F g(-1) at the discharge current density of as high as 20 A g(-1), and the cycling stability is retained at 98.1% after 10,000 charge-discharge cycles, higher than those in the literature. The excellent rate capacity and stability of the hierarchical core-shell nanostructures can be attributed to the structural features of the two MnO2 crystals, in which a 1D α-MnO2 nanowire core provides a stable structural backbone and the ultrathin 2D δ-MnO2 nanosheet shell creates more reactive active sites. The synergistic effects of different dimensions also contribute to the superior rate capability.

Design and intestinal mucus penetration mechanism of core-shell nanocomplex.

PubMed

Zhang, Xin; Cheng, Hongbo; Dong, Wei; Zhang, Meixia; Liu, Qiaoyu; Wang, Xiuhua; Guan, Jian; Wu, Haiyang; Mao, Shirui

2018-02-28

The objective of this study was to design intestinal mucus-penetrating core-shell nanocomplex by functionally mimicking the surface of virus, which can be used as the carrier for peroral delivery of macromolecules, and further understand the influence of nanocomplex surface properties on the mucosal permeation capacity. Taking insulin as a model drug, the core was formed by the self-assembly among positively charged chitosan, insulin and negatively charged sodium tripolyphosphate, different types of alginates were used as the shell forming material. The nanocomplex was characterized by dynamic light scattering (DLS), atomic force microscopy (AFM) and FTIR. Nanocomplex movement in mucus was recorded using multiple particle tracking (MPT) method. Permeation and uptake of different nanocomplex were studied in rat intestine. It was demonstrated that alginate coating layer was successfully formed on the core and the core-shell nanocomplex showed a good physical stability and improved enzymatic degradation protection. The mucus penetration and MPT study showed that the mucus penetration capacity of the nanocomplex was surface charge and coating polymer structure dependent, nanocomplex with negative alginate coating had 1.6-2.5 times higher mucus penetration ability than that of positively charged chitosan-insulin nanocomplex. Moreover, the mucus penetration ability of the core-shell nanocomplex was alginate structure dependent, whereas alginate with lower G content and lower molecular weight showed the best permeation enhancing ability. The improvement of intestine permeation and intestinal villi uptake of the core-shell nanocomplex were further confirmed in rat intestine and multiple uptake mechanisms were involved in the transport process. In conclusion, core-shell nanocomplex composed of oppositely charged materials could provide a strategy to overcome the mucus barrier and enhance the mucosal permeability. Copyright © 2018 Elsevier B.V. All rights reserved.

High temperature, flexible, fiber-preform seal

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor); Strocky, Paul J. (Inventor)

1992-01-01

A seal is mounted in a rectangular groove in a movable structural panel. The seal comprises a fiber preform constructed of multiple layers of fiber having a uniaxial core. Helical fibers are wound over the core. The fibers are of materials capable of withstanding high temperatures and are both left-hand and right-hand wound. An outer layer wrapped over said helical fibers prevents abrasion damage.

The Sociological Core: Conceptual Patterns and Idiosyncrasies in the Structure and Content of Introductory Sociology Textbooks, 1940-2000

ERIC Educational Resources Information Center

Keith, Bruce; Ender, Morten G.

2004-01-01

Sociology is often portrayed as an errant discipline, driving forward without any apparent direction or purpose. We contend that these perceptions about the central tenets of our discipline derive from a lack of standardization of core material, which reduces the social value of sociology as a scientific field and erodes its credibility as a…

Three-dimensional engineered fiberboard : opportunities for the use of low valued timber and recycled material

Treesearch

John F. Hunt; David P. Harper; Katherine A. Friedrich

2004-01-01

Fiberboard sandwich panels constructed of a structural core with exterior skins can be produced with high strength and stiffness values that compare to other wood-based panels. At the same time, as much as two-thirds less material is used in the process compared to commercial wood composite products. This offers large savings in raw material and weight. The panel...

Production of three-dimensional quantum dot lattice of Ge/Si core-shell quantum dots and Si/Ge layers in an alumina glass matrix.

PubMed

Buljan, M; Radić, N; Sancho-Paramon, J; Janicki, V; Grenzer, J; Bogdanović-Radović, I; Siketić, Z; Ivanda, M; Utrobičić, A; Hübner, R; Weidauer, R; Valeš, V; Endres, J; Car, T; Jerčinović, M; Roško, J; Bernstorff, S; Holy, V

2015-02-13

We report on the formation of Ge/Si quantum dots with core/shell structure that are arranged in a three-dimensional body centered tetragonal quantum dot lattice in an amorphous alumina matrix. The material is prepared by magnetron sputtering deposition of Al2O3/Ge/Si multilayer. The inversion of Ge and Si in the deposition sequence results in the formation of thin Si/Ge layers instead of the dots. Both materials show an atomically sharp interface between the Ge and Si parts of the dots and layers. They have an amorphous internal structure that can be crystallized by an annealing treatment. The light absorption properties of these complex materials are significantly different compared to films that form quantum dot lattices of the pure Ge, Si or a solid solution of GeSi. They show a strong narrow absorption peak that characterizes a type II confinement in accordance with theoretical predictions. The prepared materials are promising for application in quantum dot solar cells.

Optical fiber sensors for materials and structures characterization

NASA Technical Reports Server (NTRS)

Lindner, D. K.; Claus, R. O.

1991-01-01

The final technical report on Optical Fiber Sensors for Materials and Structures Characterization, covering the period August 1990 through August 1991 is presented. Research programs in the following technical areas are described; sapphire optical fiber sensors; vibration analysis using two-mode elliptical core fibers and sensors; extrinsic Fabry-Perot interferometer development; and coatings for fluorescent-based sensor. Research progress in each of these areas was substantial, as evidenced by the technical publications which are included as appendices.

Core-Sheath Paraffin-Wax-Loaded Nanofibers by Electrospinning for Heat Storage.

PubMed

Lu, Yuan; Xiao, Xiudi; Zhan, Yongjun; Huan, Changmeng; Qi, Shuai; Cheng, Haoliang; Xu, Gang

2018-04-18

Paraffin wax (PW) is widely used for smart thermoregulation materials due to its good thermal performance. However, the leakage and low thermal conductivity of PW hinder its application in the heat storage field. Accordingly, developing effective methods to address these issues is of great importance. In this study, we explored a facile approach to obtain PW-loaded core-sheath structured flexible nanofibers films via coaxial electrospinning technique. The PW as the core layer was successfully encapsulated by the sheath-layer poly(methyl methacrylate). The diameter of the fiber core increased from 395 to 848 nm as the core solution speed rate increased from 0.1 to 0.5 mL/h. In addition, it can be seen that higher core solution speed rate could lead to higher PW encapsulation efficiency according to the transmission electron microscopy results. The core-sheath nanofiber films, moreover, possessed the highest latent heat of 58.25 J/g and solidifying enthalpy of -56.49 J/g. In addition, we found that after 200 thermal cycles, there was little change in latent heat, which demonstrated that it is beneficial for the PW-loaded core-sheath structure to overcome the leakage issue and enhance thermal stability properties for the thermoregulation film.

An unusual type of polymorphism in a liquid crystal

DOE PAGES

Li, Lin; Salamonczyk, Miroslaw; Shadpour, Sasan; ...

2018-02-19

Polymorphism is a remarkable concept in chemistry, materials science, computer science, and biology. Whether it is the ability of a material to exist in two or more crystal structures, a single interface connecting to two different entities, or alternative phenotypes of an organism, polymorphism determines function and properties. In materials science, polymorphism can be found in an impressively wide range of materials, including crystalline materials, minerals, metals, alloys, and polymers. Here in this paper we report on polymorphism in a liquid crystal. A bent-core liquid crystal with a single chiral side chain forms two structurally and morphologically significantly different liquidmore » crystal phases solely depending on the cooling rate from the isotropic liquid state. On slow cooling, the thermodynamically more stable oblique columnar phase forms, and on rapid cooling, a not heretofore reported helical microfilament phase. Since structure determines function and properties, the structural color for these phases also differs.« less

An unusual type of polymorphism in a liquid crystal

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

Li, Lin; Salamonczyk, Miroslaw; Shadpour, Sasan

Polymorphism is a remarkable concept in chemistry, materials science, computer science, and biology. Whether it is the ability of a material to exist in two or more crystal structures, a single interface connecting to two different entities, or alternative phenotypes of an organism, polymorphism determines function and properties. In materials science, polymorphism can be found in an impressively wide range of materials, including crystalline materials, minerals, metals, alloys, and polymers. Here in this paper we report on polymorphism in a liquid crystal. A bent-core liquid crystal with a single chiral side chain forms two structurally and morphologically significantly different liquidmore » crystal phases solely depending on the cooling rate from the isotropic liquid state. On slow cooling, the thermodynamically more stable oblique columnar phase forms, and on rapid cooling, a not heretofore reported helical microfilament phase. Since structure determines function and properties, the structural color for these phases also differs.« less

Concentration-Driven Assembly and Sol–Gel Transition of π-Conjugated Oligopeptides

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

Zhou, Yuecheng; Li, Bo; Li, Songsong

Advances in supramolecular assembly have enabled the design and synthesis of functional materials with well-defined structures across multiple length scales. Biopolymer-synthetic hybrid materials can assemble into supramolecular structures with a broad range of structural and functional diversity through precisely controlled noncovalent interactions between subunits. Despite recent progress, there is a need to understand the mechanisms underlying the assembly of biohybrid/synthetic molecular building blocks, which ultimately control the emergent properties of hierarchical assemblies. Here in this work, we study the concentration-driven self-assembly and gelation of π-conjugated synthetic oligopeptides containing different π-conjugated cores (quaterthiophene and perylene diimide) using a combination of particlemore » tracking microrheology, confocal fluorescence microscopy, optical spectroscopy, and electron microscopy. Our results show that π-conjugated oligopeptides self-assemble into β-sheet-rich fiber-like structures at neutral pH, even in the absence of electrostatic screening of charged residues. A critical fiber formation concentration c fiber and a critical gel concentration c gel are determined for fiber-forming π-conjugated oligopeptides, and the linear viscoelastic moduli (storage modulus G' and loss modulus G") are determined across a wide range of peptide concentrations. These results suggest that the underlying chemical structure of the synthetic π-conjugated cores greatly influences the self-assembly process, such that oligopeptides appended to π-conjugated cores with greater torsional flexibility tend to form more robust fibers upon increasing peptide concentration compared to oligopeptides with sterically constrained cores. Overall, our work focuses on the molecular assembly of π-conjugated oligopeptides driven by concentration, which is controlled by a combination of enthalpic and entropic interactions between oligopeptide subunits.« less

Concentration-Driven Assembly and Sol–Gel Transition of π-Conjugated Oligopeptides

DOE PAGES

Zhou, Yuecheng; Li, Bo; Li, Songsong; ...

2017-08-17

Advances in supramolecular assembly have enabled the design and synthesis of functional materials with well-defined structures across multiple length scales. Biopolymer-synthetic hybrid materials can assemble into supramolecular structures with a broad range of structural and functional diversity through precisely controlled noncovalent interactions between subunits. Despite recent progress, there is a need to understand the mechanisms underlying the assembly of biohybrid/synthetic molecular building blocks, which ultimately control the emergent properties of hierarchical assemblies. Here in this work, we study the concentration-driven self-assembly and gelation of π-conjugated synthetic oligopeptides containing different π-conjugated cores (quaterthiophene and perylene diimide) using a combination of particlemore » tracking microrheology, confocal fluorescence microscopy, optical spectroscopy, and electron microscopy. Our results show that π-conjugated oligopeptides self-assemble into β-sheet-rich fiber-like structures at neutral pH, even in the absence of electrostatic screening of charged residues. A critical fiber formation concentration c fiber and a critical gel concentration c gel are determined for fiber-forming π-conjugated oligopeptides, and the linear viscoelastic moduli (storage modulus G' and loss modulus G") are determined across a wide range of peptide concentrations. These results suggest that the underlying chemical structure of the synthetic π-conjugated cores greatly influences the self-assembly process, such that oligopeptides appended to π-conjugated cores with greater torsional flexibility tend to form more robust fibers upon increasing peptide concentration compared to oligopeptides with sterically constrained cores. Overall, our work focuses on the molecular assembly of π-conjugated oligopeptides driven by concentration, which is controlled by a combination of enthalpic and entropic interactions between oligopeptide subunits.« less

From the molecular structure to spectroscopic and material properties: computational investigation of a bent-core nematic liquid crystal.

PubMed

Greco, Cristina; Marini, Alberto; Frezza, Elisa; Ferrarini, Alberta

2014-05-19

We present a computational investigation of the nematic phase of the bent-core liquid crystal A131. We use an integrated approach that bridges density functional theory calculations of molecular geometry and torsional potentials to elastic properties through the molecular conformational and orientational distribution function. This unique capability to simultaneously access different length scales enables us to consistently describe molecular and material properties. We can reassign (13)C NMR chemical shifts and analyze the dependence of phase properties on molecular shape. Focusing on the elastic constants we can draw some general conclusions on the unconventional behavior of bent-core nematics and highlight the crucial role of a properly-bent shape. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advanced composites: Fabrication processes for selected resin matrix materials

NASA Technical Reports Server (NTRS)

Welhart, E. K.

1976-01-01

This design note is based on present state of the art for epoxy and polyimide matrix composite fabrication technology. Boron/epoxy and polyimide and graphite/epoxy and polyimide structural parts can be successfully fabricated. Fabrication cycles for polyimide matrix composites have been shortened to near epoxy cycle times. Nondestructive testing has proven useful in detecting defects and anomalies in composite structure elements. Fabrication methods and tooling materials are discussed along with the advantages and disadvantages of different tooling materials. Types of honeycomb core, material costs and fabrication methods are shown in table form for comparison. Fabrication limits based on tooling size, pressure capabilities and various machining operations are also discussed.

Design and Synthesis of Novel Discotic Liquid Crystals

NASA Astrophysics Data System (ADS)

Kayal, Himadri Sekhar

Columnar mesophases of discotic liquid crystals (DLCs) have attracted much attention as organic semiconductors and have been tested as active materials in light-emitting diodes, photovoltaic solar cells, and field-effect transistors. However, devices based on DLCs have shown lower performance than devices based on polymeric and small molecule glass semiconductors, despite their superior charge conducting and advantages self-organizing properties. Most DLCs also require relatively complex processing conditions for the preparation of electronic devices, which is another significant disadvantage. Consequently, new types of DLCs are sought-after to overcome these limitations and described in this thesis are new types of discotic materials and their synthesis. Chapters 2 and 3 describe star-shaped discotic molecules for donor-acceptor columnar structures and as novel flexible core discotic molecules. Presented are the first examples of star-shaped heptamers of donor and acceptor discotic molecules which have six hexaalkoxy triphenylene ligands and a hexaazatriphenylene hexacarboxylate core or a hexaazatriphenylene hexaamide core. The hexaazatriphenylene cores were chosen because of their electron deficient character while the hexaalkoxy triphenylenes are known to be electron rich. Envisioned is the formation of super-columns in which the heptamers stack on top of each other and generate a material with electron acceptor and electron donor channels separated by aliphatic chains. This is an important difference to previously reported donor-acceptor star-shaped structures that were connected via conjugated linkers and do not form separate columnar stacks. Star-shaped DLCs based on small aromatic groups linked together by short flexible spacers may represent a novel type of discotic core structure that does not require peripheral flexible chains. Softening of the core by the spacer group is expected to sufficiently lower melting points and not interfere with the columnar stacking as long as a disc-shaped structure can be adopted. Presented here are synthetic approaches towards novel hexa(thiophen-2-yl)alkyl)benzene derivatives as star-shaped hetero-heptamer discotic cores. New ionic and polymerizable discotic liquid crystals based on the commercial dye tetraazaporphyrin are presented in Chapters 4 and 5. Both areas have been given little attention despite their importance for the preparation of stable films for devices. Tetraazaporphyrins containing azide and acetylene groups at the end of aliphatic spacers have been prepared and cross-linked by cycloaddition (click chemistry). Some derivatives form columnar mesophases and could be thermally cross-linked in their columnar mesophase and their copper catalyzed cross-linking in Langmuir and Langmuir-Blodgett layers was also successful.

Core/shell structure NiCo2O4@MnCo2O4 nanofibers fabricated by different temperatures for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Qing; Qin, Xuefeng; Jiang, Pengcheng; Dai, Jianfeng; Li, Weixue; Gao, Haoran

2018-03-01

Core/shell structure NiCo2O4@MnCo2O4 nanofibers (NiCo2O4@MnCo2O4 NFs) were prepared by a facile co-electrospinning method and heat treatment. The composites annealed at 500 °C have a complete, continuously obvious core/shell structure, and clear interface of composites with good morphology, while annealed at 600 °C were stacked on each other and were unable to sustain three-dimensional network structures and 700 °C calcination have completely lost one-dimensional structure. The core NiCo2O4 is about 70 nm in diameter and the MnCo2O4 shell behaves a thickness about 60 nm. When investigated as an electrode material for supercapacitors, the NiCo2O4@MnCo2O4 NFs annealed at 500 °C exihibited the specific capacitance of 463 F g-1 (0.926 F cm-2) at 1 A g-1, higher than that annealed at 600 °C 362 F g-1, 1 A g-1 (0.724 F cm-2, 1 A g-1) and 700 °C 283 F g-1, 1 A g-1 (0.566 F cm-2, 1 A g-1). These results suggest that core/shell NiCo2O4@MnCo2O4 NFs annealed at 500 °C have formed a good morphology with continuously complete core/shell structure which lead to good properties would be potential electrodes for supercapacitors.

A continuous structural characterisation of Atlantis Massif using an integrated analysis of oriented downhole imagery and logging data

NASA Astrophysics Data System (ADS)

Pressling, Nicola; Morris, Antony; John, Barbara; MacLeod, Christopher

2010-05-01

Continuous wireline logging data are invaluable when less than 100% of drilled core material is recovered. The data provide information on missing units, record the true depth of features and uniquely constrain spatial orientation. Only by fully integrating continuous, oriented logging data and discrete, finer-scale core data can we develop a complete structural interpretation for drill holes that is not limited by sampling bias. Integrated Ocean Drilling Program (IODP) Expedition 304/305 sampled the Atlantis Massif oceanic core complex at the intersection between the Mid-Atlantic Ridge and the Atlantis Transform fault at 30°N. Hole U1309D penetrated 1415.5m into the central dome of the massif, which exposes the corrugated detachment fault surface denuding the lower crust and upper mantle. The recovered section is dominated by gabbro compositions that are complexly faulted and layered on a variety of scales, reflecting the complicated interplay between magmatic and tectonic processes controlling the formation, evolution and deformation of oceanic crust at slow-spreading ridges. The average core recovery at Atlantis Massif was 74%. Therefore, to augment and constrain structural interpretations based on limited core material, we used the Formation MicroScanner (FMS) wireline logging tool that measures microresistivity contrasts in the immediate vicinity of the borehole wall formation. The data are presented as an unwrapped image of the borehole cylinder, and inclined planar structural features that intersect the borehole, such as faults or veins, are shown as darker (more conductive) sinusoidal traces. The true dip and azimuth of these features can be calculated directly due to the inclusion of an accelerometer and magnetometer on the toolstring, which record the position and spatial orientation (with respect to magnetic north) of the tool within the borehole, respectively. 4324 distinct structural features have been identified in the FMS images between 97 and 1415mbsf (metres below sea floor). Distinctly different structural trends are seen across the five sub-units that are based on petrological and geochemical observations of the recovered core. In addition, variations in the borehole dimensions are used to define 115 zones of borehole breakout, with a cumulative extent of 434.76m (31% of the total drilled). Such regions often correspond to areas of poor recovery and are consequently poorly characterised using core samples. The extensive FMS-based structural database allows the variation in fracture networks and areas of weakness to be quantified at a high-resolution, leading to improved understanding of the hydrothermal fluid flow and melt pathways in the footwall section.

Alternating current dielectrophoresis of core-shell nanoparticles: Experiments and comparison with theory

NASA Astrophysics Data System (ADS)

Yang, Chungja

Nanoparticles are fascinating where physical and optical properties are related to size. Highly controllable synthesis methods and nanoparticle assembly are essential for highly innovative technological applications. Well-defined shaped and sized nanoparticles enable comparisons between experiments, theory and subsequent new models to explain experimentally observed phenomena. Among nanoparticles, nonhomogeneous core-shell nanoparticles (CSnp) have new properties that arise when varying the relative dimensions of the core and the shell. This CSnp structure enables various optical resonances, and engineered energy barriers, in addition to the high charge to surface ratio. Assembly of homogeneous nanoparticles into functional structures has become ubiquitous in biosensors (i.e. optical labeling), nanocoatings, and electrical circuits. Limited nonhomogenous nanoparticle assembly has only been explored. Many conventional nanoparticle assembly methods exist, but this work explores dielectrophoresis (DEP) as a new method. DEP is particle polarization via non-uniform electric fields while suspended in conductive fluids. Most prior DEP efforts involve microscale particles. Prior work on core-shell nanoparticle assemblies and separately, nanoparticle characterizations with dielectrophoresis and electrorotation, did not systematically explore particle size, dielectric properties (permittivity and electrical conductivity), shell thickness, particle concentration, medium conductivity, and frequency. This work is the first, to the best of our knowledge, to systematically examine these dielectrophoretic properties for core-shell nanoparticles. Further, we conduct a parametric fitting to traditional core-shell models. These biocompatible core-shell nanoparticles were studied to fill a knowledge gap in the DEP field. Experimental results (chapter 5) first examine medium conductivity, size and shell material dependencies of dielectrophoretic behaviors of spherical CSnp into 2D and 3D particle-assemblies. Chitosan (amino sugar) and poly-L-lysine (amino acid, PLL) CSnp shell materials were custom synthesized around a hollow (gas) core by utilizing a phospholipid micelle around a volatile fluid templating for the shell material; this approach proves to be novel and distinct from conventional core-shell models wherein a conductive core is coated with an insulative shell. Experiments were conducted within a 100 nl chamber housing 100 um wide Ti/Au quadrapole electrodes spaced 25 um apart. Frequencies from 100kHz to 80MHz at fixed local field of 5Vpp were tested with 10-5 and 10-3 S/m medium conductivities for 25 seconds. Dielectrophoretic responses of ~220 and 340(or ~400) nm chitosan or PLL CSnp were compiled as a function of medium conductivity, size and shell material. Experiments further examined shell thickness and particle concentration (chapter 6) dependencies on ~530 nm CSnp dielectrophoretic and electrorotational responses with ~30nm and ~80 nm shell thicknesses and at particle concentration count rates of 5000 +/- 500, 10000 +/- 500, and 15000 +/- 500 counts per second. Using similar experimental conditions, both dielectrophoretic and electrorotational CSnp responses were compiled versus frequency, shell thickness, and particle concentration. Knowledge gained from this study includes a unique resonance-like dielectrophoretic and electrorotational spectrum, which is significantly distinct from other cells and particles. CSnp dielectric properties were then calculated by parametrically fitting parameters to an existing core-shell model. The optimum conductivity and relative permittivity for the core and the shell are 1E-15 S/m, 1, 0.6 S/m, and 90, respectively. These properties can be exploited to rapidly assemble these unique core-shell particles for future structural color production in fabrics, vehicle, and wall painting.

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

Field-assisted organization, substrate effects and magnetic behavior of Ag 30Co 70 core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Crisan, A. D.; Angelakeris, M.; Simeonidis, K.; Tsiaoussis, I.; Crisan, O.

2010-11-01

In core-shell systems with non-magnetic core and magnetic shell, the electron transport and magnetic properties are expected to show enhanced behavior due to the particular morpho-structural features of the conductive and magnetic regions. This may lead to novel advanced GMR materials and spin valves. This is the case of core-shell Ag-Co colloidal nanoscale particles that organize into regular arrays. An insight on the structure and morphology of the newly synthesized Ag-Co nanoparticles deposited on different substrates will be presented. The influence of the substrate on different morphologies and organization dynamics is discussed. It is shown that the magnetic behavior of the Ag-Co nanoparticles is highly influenced by the corona-like morphology of Co shell, chemical environment of the magnetic atoms and by the fact that they exhibit strongly reduced coordination due to the surface states.

Magnetic response of hybrid ferromagnetic and antiferromagnetic core-shell nanostructures.

PubMed

Khan, U; Li, W J; Adeela, N; Irfan, M; Javed, K; Wan, C H; Riaz, S; Han, X F

2016-03-21

The synthesis of FeTiO3-Ni(Ni80Fe20) core-shell nanostructures by a two-step method (sol-gel and DC electrodeposition) has been demonstrated. XRD analysis confirms the rhombohedral crystal structure of FeTiO3(FTO) with space group R3[combining macron]. Transmission electron microscopy clearly depicts better morphology of nanostructures with shell thicknesses of ∼25 nm. Room temperature magnetic measurements showed significant enhancement of magnetic anisotropy for the permalloy (Ni80Fe20)-FTO over Ni-FTO core-shell nanostructures. Low temperature magnetic measurements of permalloy-FeTiO3 core-shell structure indicated a strong exchange bias mechanism with magnetic coercivity below the antiferromagnetic Neel temperature (TN = 59 K). The exchange bias is attributed to the alignment of magnetic moments in the antiferromagnetic material at low temperature. Our scheme opens a path towards optimum automotive systems and wireless communications wherein broader bandwidths and smaller sizes are required.

NEUTRONIC REACTOR FUEL ELEMENT AND CORE SYSTEM

DOEpatents

Moore, W.T.

1958-09-01

This patent relates to neutronic reactors and in particular to an improved fuel element and a novel reactor core system for facilitating removal of contaminating fission products, as they are fermed, from association with the flssionable fuel, so as to mitigate the interferent effects of such fission products during reactor operation. The fuel elements are comprised of tubular members impervious to fluid and contatning on their interior surfaces a thin layer of fissionable material providing a central void. The core structure is comprised of a plurality of the tubular fuel elements arranged in parallel and a closed manifold connected to their ends. In the reactor the core structure is dispersed in a water moderator and coolant within a pressure vessel, and a means connected to said manifuld is provided for withdrawing and disposing of mobile fission product contamination from the interior of the feel tubes and manifold.

Microscopic insight into the bilateral formation of carbon spirals from a symmetric iron core

PubMed Central

Shiozawa, Hidetsugu; Bachmatiuk, Alicja; Stangl, Andreas; Cox, David C.; Silva, S. Ravi P.; Rümmeli, Mark H.; Pichler, Thomas

2013-01-01

Mirrored carbon-spirals have been produced from pressured ferrocene via the bilateral extrusion of the spiral pairs from an iron core. A parametric plot of the surface geometry displays the fractal growth of the conical helix made with the logarithmic spiral. Electron microscopy studies show the core is a crystalline cementite which grows and transforms its shape from spherical to biconical as it extrudes two spiralling carbon arms. In a cross section along the arms we observe graphitic flakes arranged in a herringbone structure, normal to which defects propagate. Local-wave-pattern analysis reveals nanoscale defect patterns of two-fold symmetry around the core. The data suggest that the bilateral growth originates from a globular cementite crystal with molten surfaces and the nano-defects shape emerging hexagonal carbon into a fractal structure. Understanding and knowledge obtained provide a basis for the controlled production of advanced carbon materials with designed geometries. PMID:23670649

Description of gravity cores from San Pablo Bay and Carquinez Strait, San Francisco Bay, California

USGS Publications Warehouse

Woodrow, Donald L.; John L. Chin,; Wong, Florence L.; Fregoso, Theresa A.; Jaffe, Bruce E.

2017-06-27

Seventy-two gravity cores were collected by the U.S. Geological Survey in 1990, 1991, and 2000 from San Pablo Bay and Carquinez Strait, California. The gravity cores collected within San Pablo Bay contain bioturbated laminated silts and sandy clays, whole and broken bivalve shells (mostly mussels), fossil tube structures, and fine-grained plant or wood fragments. Gravity cores from the channel wall of Carquinez Strait east of San Pablo Bay consist of sand and clay layers, whole and broken bivalve shells (less than in San Pablo Bay), trace fossil tubes, and minute fragments of plant material.

Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization

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

Joy, Lija K.; Sooraj, V.; Sethulakshmi, N.

2014-03-24

Commercial samples of Magnetite with size ranging from 25–30 nm were coated with polyaniline by using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle (core)–Polyaniline (shell). High resolution transmission electron microscopy images confirm the core shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a Maxwell–Wagner capacitor model. A plausible mechanism for the enhancement of dielectric permittivity is proposed.

Core-shell structured polystyrene/BaTiO3 hybrid nanodielectrics prepared by in situ RAFT polymerization: a route to high dielectric constant and low loss materials with weak frequency dependence.

PubMed

Yang, Ke; Huang, Xingyi; Xie, Liyuan; Wu, Chao; Jiang, Pingkai; Tanaka, Toshikatsu

2012-11-23

A novel route to prepare core-shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO(3) by an in situ RAFT polymerization. The core-shell structured PS/BaTiO(3) nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental studies on metallic fuel relocation in a single-pin core structure of a sodium-cooled fast reactor

DOE PAGES

Kim, Taeil; Harbaruk, Dzmitry; Gerardi, Craig; ...

2017-07-10

Experiments dropping molten uranium into test sections of single fuel pin geometry filled with sodium were conducted to investigate relocation behavior of metallic fuel in the core structures of sodium-cooled fast reactors during a hypothetical core disruptive accident. Metallic uranium was used as a fuel material and HT-9M was used as a fuel cladding material in the experiment in order to accurately mock-up the thermo-physical behavior of the relocation. The fuel cladding failed due to eutectic formation between the uranium and HT-9M for all experiments. The extent of the eutectic formation increased with increasing molten uranium temperature. Voids in themore » relocated fuel were observed for all experiments and were likely formed by sodium boiling in contact with the fuel. In one experiment, numerous fragments of the relocated fuel were found. In conclusion, it could be concluded that the injected metallic uranium fuel was fragmented and dispersed in the narrow coolant channel by sodium boiling« less

Experimental studies on metallic fuel relocation in a single-pin core structure of a sodium-cooled fast reactor

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

Kim, Taeil; Harbaruk, Dzmitry; Gerardi, Craig

Experiments dropping molten uranium into test sections of single fuel pin geometry filled with sodium were conducted to investigate relocation behavior of metallic fuel in the core structures of sodium-cooled fast reactors during a hypothetical core disruptive accident. Metallic uranium was used as a fuel material and HT-9M was used as a fuel cladding material in the experiment in order to accurately mock-up the thermo-physical behavior of the relocation. The fuel cladding failed due to eutectic formation between the uranium and HT-9M for all experiments. The extent of the eutectic formation increased with increasing molten uranium temperature. Voids in themore » relocated fuel were observed for all experiments and were likely formed by sodium boiling in contact with the fuel. In one experiment, numerous fragments of the relocated fuel were found. In conclusion, it could be concluded that the injected metallic uranium fuel was fragmented and dispersed in the narrow coolant channel by sodium boiling« less

Designing for time-dependent material response in spacecraft structures

NASA Technical Reports Server (NTRS)

Hyer, M. W.; Oleksuk, Lynda L. S.; Bowles, D. E.

1992-01-01

To study the influence on overall deformations of the time-dependent constitutive properties of fiber-reinforced polymeric matrix composite materials being considered for use in orbiting precision segmented reflectors, simple sandwich beam models are developed. The beam models include layers representing the face sheets, the core, and the adhesive bonding of the face sheets to the core. A three-layer model lumps the adhesive layers with the face sheets or core, while a five-layer model considers the adhesive layers explicitly. The deformation response of the three-layer and five-layer sandwich beam models to a midspan point load is studied. This elementary loading leads to a simple analysis, and it is easy to create this loading in the laboratory. Using the correspondence principle of viscoelasticity, the models representing the elastic behavior of the two beams are transformed into time-dependent models. Representative cases of time-dependent material behavior for the facesheet material, the core material, and the adhesive are used to evaluate the influence of these constituents being time-dependent on the deformations of the beam. As an example of the results presented, if it assumed that, as a worst case, the polymer-dominated shear properties of the core behave as a Maxwell fluid such that under constant shear stress the shear strain increases by a factor of 10 in 20 years, then it is shown that the beam deflection increases by a factor of 1.4 during that time. In addition to quantitative conclusions, several assumptions are discussed which simplify the analyses for use with more complicated material models. Finally, it is shown that the simpler three-layer model suffices in many situations.

Structural Characterization of Bimetallic Nanocrystal Electrocatalysts

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

Cullen, David A

2016-01-01

Late transition metal nanocrystals find applications in heterogeneous catalysis such as plasmon-enhanced catalysis and as electrode materials for fuel cells, a zero-emission and sustainable energy technology. Their commercial viability for automotive transportation has steadily increased in recent years, almost exclusively due to the discovery of more efficient bimetallic nanocatalysts for the oxygen reduction reaction (ORR) at the cathode. Despite improvements to catalyst design, achieving high activity while maintaining durability is essential to further enhance their performance for this and other important applications in catalysis. Electronic effects arising from the generation of metal-metal interfaces, from plasmonic metals, and from lattice distortions,more » can vastly improve sorption properties at catalytic surfaces, while increasing durability.[1] Multimetallic lattice-strained nanoparticles are thus an interesting opportunity for fundamental research.[2,3] A colloidal synthesis approach is demonstrated to produce AuPd alloy and Pd@Au core-shell nanoicosahedra as catalysts for electro-oxidations. The nanoparticles are characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and large solid angle energy dispersive X-ray spectroscopy (EDS) on an FEI Talos 4-detector STEM/EDS system. Figure 1 shows bright-field (BF) and high-angle annular dark-field (HAADF) ac-STEM images of the alloy and core-shell nanoicosahedra together with EDS line-scans and elemental maps. These structures are unique in that the presence of twin boundaries, alloying, and core-shell morphology could create highly strained surfaces and interfaces. The shell thickness of the core-shell structures observed in HAADF-STEM images is tuned by adjusting the ratio between metal precursors (Figure 2a-f) to produce shells ranging from a few to several monolayers. Specific activity was measured in ethanol electro-oxidation to examine the effect of shell thickness on catalytic activity. A volcano relationship was observed for the core-shell nanoicosahedra having different Pd-shell thicknesses as Pd content is increased (Figure 2g). Durability tests are ongoing for the AuPd system; however, promising ORR materials and morphologies have also been synthesized for a more cost-effective Cu-based system of Cu-CuM (M = Pd, Rh, Pt) core-alloy-shell nanocrystals. The synthesis, characterization, and catalytic behavior of different high-index faceted morphologies of Cu-based materials towards ORR and methanol oxidation catalysis will be discussed, where we show how they exceed the performance of commercial Pd- and Pt- based catalysts. The development of new materials and their characterization is critical to understanding the effects of structure and composition on catalysis. Future efforts are directed at resolving these structures and more industrially relevant fuel cell catalysts in 3D through electron tomography.[4] References: [1] X. Huang, et al., Science 348 (2015) p. 1230. [2] P. Strasser, et al., Nat. Chem. 2 (2010) p. 454. [3] C. Chen, et al., Science 343 (2014) p. 1339. [4] Microscopy performed as part of a user project through ORNL s Center for Nanophase Materials Sciences, which is a U.S. DOE Office of Science User Facility, and instrumentation provided by the U.S. DOE Office of Nuclear Energy, Fuel Cycle R&D Program, and the Nuclear Science User Facilities.« less

Facet-selective nucleation and conformal epitaxy of Ge shells on Si nanowires

DOE PAGES

Nguyen, Binh -Minh; Swartzentruber, Brian; Ro, Yun Goo; ...

2015-10-08

Knowledge of nanoscale heteroepitaxy is continually evolving as advances in material synthesis reveal new mechanisms that have not been theoretically predicted and are different than what is known about planar structures. In addition to a wide range of potential applications, core/shell nanowire structures offer a useful template to investigate heteroepitaxy at the atomistic scale. We show that the growth of a Ge shell on a Si core can be tuned from the theoretically predicted island growth mode to a conformal, crystalline, and smooth shell by careful adjustment of growth parameters in a narrow growth window that has not been exploredmore » before. In the latter growth mode, Ge adatoms preferentially nucleate islands on the {113} facets of the Si core, which outgrow over the {220} facets. Islands on the low-energy {111} facets appear to have a nucleation delay compared to the {113} islands; however, they eventually coalesce to form a crystalline conformal shell. As a result, synthesis of epitaxial and conformal Si/Ge/Si core/multishell structures enables us to fabricate unique cylindrical ring nanowire field-effect transistors, which we demonstrate to have steeper on/off characteristics than conventional core/shell nanowire transistors.« less

NEUTRONIC REACTOR CORE

DOEpatents

Thomson, W.B.; Corbin, A. Jr.

1961-07-18

An improved core for a gas-cooled power reactor which admits gas coolant at high temperatures while affording strong integral supporting structure and efficient moderation of neutrons is described. The multiplicities of fuel elements constituting the critical amassment of fissionable material are supported and confined by a matrix of metallic structure which is interspersed therebetween. Thermal insulation is interposed between substantially all of the metallic matrix and the fuel elements; the insulation then defines the principal conduit system for conducting the coolant gas in heat-transfer relationship with the fuel elements. The metallic matrix itseif comprises a system of ducts through which an externally-cooled hydrogeneous liquid, such as water, is circulated to serve as the principal neutron moderant for the core and conjointly as the principal coolant for the insulated metallic structure. In this way, use of substantially neutron transparent metals, such as aluminum, becomes possible for the supporting structure, despite the high temperatures of the proximate gas. The Aircraft Nuclear Propulsion program's "R-1" reactor design is a preferred embodiment.

Hybrid metal–organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly

DOE PAGES

Yan, Hao; Hohman, J. Nathan; Li, Fei Hua; ...

2016-12-26

Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal–organic frameworks and coordination polymers. However, the lack of ‘solid’ inorganic cores requires charge transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal–organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires. The strong van der Waals attraction between diamondoids overcomes steric repulsion leading to a cis configuration at the active growth front, enabling face-on additionmore » of precursors for nanowire elongation. These nanowires have band-like electronic properties, low effective carrier masses and three orders-of-magnitude conductivity modulation by hole doping. Furthermore, this discovery highlights a previously unexplored regime of structure-directing agents compared with traditional surfactant, block copolymer or metal–organic framework linkers.« less

Three-dimensional core-shell Fe2O3 @ carbon/carbon cloth as binder-free anode for the high-performance lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Xiaohua; Zhang, Miao; Liu, Enzuo; He, Fang; Shi, Chunsheng; He, Chunnian; Li, Jiajun; Zhao, Naiqin

2016-12-01

A facile and scalable strategy is developed to fabricate three dimensional core-shell Fe2O3 @ carbon/carbon cloth structure by simple hydrothermal route as binder-free lithium-ion battery anode. In the unique structure, carbon coated Fe2O3 nanorods uniformly disperse on carbon cloth which forms the conductive carbon network. The hierarchical porous Fe2O3 nanorods in situ grown on the carbon cloth can effectively shorten the transfer paths of lithium ions and reduce the contact resistance. The carbon coating significantly inhibits pulverization of active materials during the repeated Li-ion insertion/extraction, as well as the direct exposure of Fe2O3 to the electrolyte. Benefiting from the structural integrity and flexibility, the nanocomposites used as binder-free anode for lithium-ion batteries, demonstrate high reversible capacity and excellent cyclability. Moreover, this kind of material represents an alternative promising candidate for flexible, cost-effective, and binder-free energy storage devices.

High-temperature gas-cooled reactor technology development program. Annual progress report for period ending December 31, 1982

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

Kasten, P.R.; Rittenhouse, P.L.; Bartine, D.E.

1983-06-01

During 1982 the High-Temperature Gas-Cooled Reactor (HTGR) Technology Program at Oak Ridge National Laboratory (ORNL) continued to develop experimental data required for the design and licensing of cogeneration HTGRs. The program involves fuels and materials development (including metals, graphite, ceramic, and concrete materials), HTGR chemistry studies, structural component development and testing, reactor physics and shielding studies, performance testing of the reactor core support structure, and HTGR application and evaluation studies.

Modeling the Creep of Rib-Reinforced Composite Media Made from Nonlinear Hereditary Phase Materials 2. Verification of the Model

NASA Astrophysics Data System (ADS)

Yankovskii, A. P.

2015-05-01

An indirect verification of a structural model describing the creep of a composite medium reinforced by honeycombs and made of nonlinear hereditary phase materials obeying the Rabotnov theory of creep is presented. It is shown that the structural model proposed is trustworthy and can be used in practical calculations. For different kinds of loading, creep curves for a honeycomb core made of a D16T aluminum alloy are calculated.

Nanostructured microtubes based on TiO2 doped by Zr and Hf oxides with the anatase structure

NASA Astrophysics Data System (ADS)

Zheleznov, VV; Voit, EI; Sushkov, YV; Sarin, SA; Kuryavyi, VG; Opra, DP; Gnedenkov, SV; Sinebryukhov, SL; Sokolov, AA

2016-01-01

The nanostructured microtubes based on TiO2 have been prepared on the carbon fiber template using the sol-gel method. The microtubes consist of nanoparticles of metal oxides: TiO2/ZrO2 and TiO2/HfO2. The dependence of microtubes morphology and nanoparticles structure on the synthesis conditions has been studied using the methods of SEM, SAXS, and Raman spectroscopy. It has been demonstrated that at the stoichiometric ratio of up to 0.04 for Zr/Ti and up to 0.06 for Hf/Ti microtubes consist of uniform nanoparticles with the anatase structure. Along with further increase of the dopants content in the microtubes composition, nanoparticles acquire the core-shell structure. It has been suggested that nanoparticles have a core composed of the solid solutions Ti1-xZrxO2 or Ti1-xHfxO2 and a shell consisting of zirconium or hafnium titanate. The fabricated Zr- and Hf-doped TiO2 materials were investigated in view of their possible use as anode materials for Li-ion batteries. Charge- discharge measurements showed that the doped samples manifested significantly higher reversibility in comparison with the undoped TiO2. The method opens new prospects in synthesis of nanostructured materials for Li-ion batteries application.

Solution softening in magnesium alloys: the effect of solid solutions on the dislocation core structure and nonbasal slip.

PubMed

Tsuru, T; Udagawa, Y; Yamaguchi, M; Itakura, M; Kaburaki, H; Kaji, Y

2013-01-16

There is a pressing need to improve the ductility of magnesium alloys so that they can be applied as lightweight structural materials. In this study, a mechanism for enhancing the ductility of magnesium alloys has been pursued using the atomistic method. The generalized stacking fault (GSF) energies for basal and prismatic planes in magnesium were calculated by using density functional theory, and the effect of the GSF energy on the dislocation core structures was examined using a semidiscrete variational Peierls-Nabarro model. Yttrium was found to have an anomalous influence on the solution softening owing to a reduction in the GSF energy gradient.

Method and apparatus for low-loss signal transmission

NASA Technical Reports Server (NTRS)

Shimabukuro, Fred (Inventor); Yeh, Cavour (Inventor); Fraser, Scott (Inventor); Siegel, Peter (Inventor)

2008-01-01

The present invention relates to the field of radio-frequency (RF) waveguides. More specifically, the present invention pertains to a method and apparatus that provides ultra-low-loss RF waveguide structures targeted between approximately 300 GHz and approximately 30 THz. The RF waveguide includes a hollow core and a flexible honeycomb, periodic-bandgap structure surrounding the hollow core. The flexible honeycomb, periodic-bandgap structure is formed of a plurality of tubes formed of a dielectric material such as of low-loss quartz, polyethylene, or high-resistivity silicon. Using the RF waveguide, a user may attach a terahertz signal source to the waveguide and pass signals through the waveguide, while a terahertz signal receiver receives the signals.

Spectral engineering of optical fiber through active nanoparticle doping

NASA Astrophysics Data System (ADS)

Lindstrom-James, Tiffany

The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions. Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result of different host materials, varying rare earth doping levels and processing conditions, indicated the ability to influence the spectral behavior of the doped nanoparticle. By using photoluminescence to predict diffusion behavior, the application of a simple one dimensional model for diffusion provided a method for predicting the diffusion coefficient of europium ions in alkaline earth fluorides with order of magnitude accuracy. Modified chemical vapor deposition derived silica preforms were individually solution doped with europium doped alkaline earth fluoride nanoparticles. By using the rare earth doped alkaline earth fluoride nanoparticles as the dopant materials in the core of optical fiber preforms, the resultant optical properties of the glass were significantly influenced by their presence in the core. The incorporation of these rare earth doped alkaline earth fluoride nanoparticles was found to significantly influence the local chemical and structural environment about the rare earth ion, demonstrated homogeneity and uniform distribution of the rare earth dopant and resulted in specifically unique spectral behavior when compared to conventional doping methods. A more detailed structural model of the doped core glass region has been developed based on the spectral behavior of these active fiber preforms. It has been shown that rare earth doping of alkaline earth fluoride nanoparticles provides a material which can be 'tuned' to specific applications through the use of different host materials, processing conditions and doping levels of the rare earth and when used as dopant materials for active optical fibers, provides a means to tailor the optical behavior.

Plasmonic core-satellite assemblies with high stability and yield (Conference Presentation)

NASA Astrophysics Data System (ADS)

Huang, Li-Ching; Lin, Tien-Hsin; Liu, Zhi-Yan; Chen, Jyun-Hao; Wang, Yi-Chen; Chen, Shiuan-Yeh

2016-09-01

Plasmonic structures are attractive due to their optical properties in the near-field and far-field. In the near-field, the enhanced field they generated strongly interacts with materials in proximity to the surface and even produces the quantum hybrid states in the strong coupling regime. In the far-field, the larger scattering cross section of plasmonic particles provides better contrast for tissue imaging. In addition, the strong absorption can generate substantial amount of heat for cancer cell elimination. These optical properties are usually engineered through tuning the size and morphology of individual nanoparticles by various chemical synthesis methods. The alternative way is to use coupled structure based on existing particles. The molecule-linked structure is a common way for 3D plasmonic materials. However, to produce a stable coupled structure in the solution phase is challenging. The formation of linkage between linker molecules is usually time-consuming and at low efficiency. Increasing the concentration of linker molecules may raise the reaction speed but also result in the random aggregation of particles. In this work, a polyelectrolyte coating is used to connect spherical nanoparticles of different sizes to form core-satellite assemblies (CSA). The coupled core-satellite structure is formed almost immediately after the solutions of two particles are mixed. The output efficiency is nearly 100%. The CSA is robust under the additional silica shell coating and strong laser illumination. The stability of this CSA is confirmed by the Raman spectra and this assembly can potentially be used as Raman tags.

Advanced Na-NiCl2 Battery Using Nickel-Coated Graphite with Core-Shell Microarchitecture.

PubMed

Chang, Hee-Jung; Canfield, Nathan L; Jung, Keeyoung; Sprenkle, Vincent L; Li, Guosheng

2017-04-05

Stationary electric energy storage devices (rechargeable batteries) have gained increasing prominence due to great market needs, such as smoothing the fluctuation of renewable energy resources and supporting the reliability of the electric grid. With regard to raw materials availability, sodium-based batteries are better positioned than lithium batteries due to the abundant resource of sodium in Earth's crust. However, the sodium-nickel chloride (Na-NiCl 2 ) battery, one of the most attractive stationary battery technologies, is hindered from further market penetration by its high material cost (Ni cost) and fast material degradation at its high operating temperature. Here, we demonstrate the design of a core-shell microarchitecture, nickel-coated graphite, with a graphite core to maintain electrochemically active surface area and structural integrity of the electron percolation pathway while using 40% less Ni than conventional Na-NiCl 2 batteries. An initial energy density of 133 Wh/kg (at ∼C/4) and energy efficiency of 94% are achieved at an intermediate temperature of 190 °C.

Core-melt source reduction system

DOEpatents

Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

1995-04-25

A core-melt source reduction system for ending the progression of a molten core during a core-melt accident and resulting in a stable solid cool matrix. The system includes alternating layers of a core debris absorbing material and a barrier material. The core debris absorbing material serves to react with and absorb the molten core such that containment overpressurization and/or failure does not occur. The barrier material slows the progression of the molten core debris through the system such that the molten core has sufficient time to react with the core absorbing material. The system includes a provision for cooling the glass/molten core mass after the reaction such that a stable solid cool matrix results. 4 figs.

Core-melt source reduction system

DOEpatents

Forsberg, Charles W.; Beahm, Edward C.; Parker, George W.

1995-01-01

A core-melt source reduction system for ending the progression of a molten core during a core-melt accident and resulting in a stable solid cool matrix. The system includes alternating layers of a core debris absorbing material and a barrier material. The core debris absorbing material serves to react with and absorb the molten core such that containment overpressurization and/or failure does not occur. The barrier material slows the progression of the molten core debris through the system such that the molten core has sufficient time to react with the core absorbing material. The system includes a provision for cooling the glass/molten core mass after the reaction such that a stable solid cool matrix results.

Three-Year High School Science Core Curriculum: A Framework.

ERIC Educational Resources Information Center

Bardeen, Marjorie; Freeman, Wade; Lederman, Leon; Marshall, Stephanie; Thompson, Bruce; Young, M. Jean

It is time to start a complete re-structuring of the high school science sequence: new content, new instructional materials, new laboratories, new assessment tools, and new teacher preparation. This white paper initiates re-structuring by proposing organization, pedagogy, and content for a new sequence of science courses. The proposal respects the…

Atomic Structure of Au 329(SR) 84 Faradaurate Plasmonic Nanomolecules

DOE PAGES

Kumara, Chanaka; Zuo, Xiaobing; Ilavsky, Jan; ...

2015-04-03

To design novel nanomaterials, it is important to precisely control the composition, determine the atomic structure, and manipulate the structure to tune the materials property. Here we present a comprehensive characterization of the material whose composition is Au 329(SR) 84 precisely, therefore referred to as a nanomolecule. The size homogeneity was shown by electron microscopy, solution X-ray scattering, and mass spectrometry. We proposed its atomic structure to contain the Au 260 core using experiments and modeling of a total-scattering-based atomic-pair distribution functional analysis. HAADF-STEM images shows fcc-like 2.0 ± 0.1 nm diameter nanomolecules.

Radiation Effects in M and NEMS

DTIC Science & Technology

2016-03-31

10.1117/12.876968 casing mobile core AFM tip Pt wire x δ a Figure 5. Proposed approach to combine single crystal silicon MEMS (Sandia) fab capabilities and form supporting structure for 2D materials (VU). 198

Zigzag-Elongated Fused π-Electronic Core: A Molecular Design Strategy to Maximize Charge-Carrier Mobility.

PubMed

Yamamoto, Akito; Murata, Yoshinori; Mitsui, Chikahiko; Ishii, Hiroyuki; Yamagishi, Masakazu; Yano, Masafumi; Sato, Hiroyasu; Yamano, Akihito; Takeya, Jun; Okamoto, Toshihiro

2018-01-01

Printed and flexible electronics requires solution-processable organic semiconductors with a carrier mobility (μ) of ≈10 cm 2 V -1 s -1 as well as high chemical and thermal durability. In this study, chryseno[2,1- b :8,7- b ']dithiophene (ChDT) and its derivatives, which have a zigzag-elongated fused π-electronic core (π-core) and a peculiar highest occupied molecular orbital (HOMO) configuration, are reported as materials with conceptually new semiconducting π-cores. ChDT and its derivatives are prepared by a versatile synthetic procedure. A comprehensive investigation reveals that the ChDT π-core exhibits increasing structural stability in the bulk crystal phase, and that it is unaffected by a variation of the transfer integral, induced by the perpetual molecular motion of organic materials owing to the combination of its molecular shape and its particular HOMO configuration. Notably, ChDT derivatives exhibit excellent chemical and thermal stability, high charge-carrier mobility under ambient conditions (μ ≤ 10 cm 2 V -1 s -1 ), and a crystal phase that is highly stable, even at temperatures above 250 °C.

MODULAR CORE UNITS FOR A NEUTRONIC REACTOR

DOEpatents

Gage, J.F. Jr.; Sherer, D.B.

1964-04-01

A modular core unit for use in a nuclear reactor is described. Many identical core modules can be placed next to each other to make up a complete core. Such a module includes a cylinder of moderator material surrounding a fuel- containing re-entrant coolant channel. The re-entrant channel provides for the circulation of coolant such as liquid sodium from one end of the core unit, through the fuel region, and back out through the same end as it entered. Thermal insulation surrounds the moderator exterior wall inducing heat to travel inwardly to the coolant channel. Spaces between units may be used to accommodate control rods and support structure, which may be cooled by a secondary gas coolant, independently of the main coolant. (AEC)

Scalable Synthesis of Triple-Core-Shell Nanostructures of TiO2 @MnO2 @C for High Performance Supercapacitors Using Structure-Guided Combustion Waves.

PubMed

Shin, Dongjoon; Shin, Jungho; Yeo, Taehan; Hwang, Hayoung; Park, Seonghyun; Choi, Wonjoon

2018-03-01

Core-shell nanostructures of metal oxides and carbon-based materials have emerged as outstanding electrode materials for supercapacitors and batteries. However, their synthesis requires complex procedures that incur high costs and long processing times. Herein, a new route is proposed for synthesizing triple-core-shell nanoparticles of TiO 2 @MnO 2 @C using structure-guided combustion waves (SGCWs), which originate from incomplete combustion inside chemical-fuel-wrapped nanostructures, and their application in supercapacitor electrodes. SGCWs transform TiO 2 to TiO 2 @C and TiO 2 @MnO 2 to TiO 2 @MnO 2 @C via the incompletely combusted carbonaceous fuels under an open-air atmosphere, in seconds. The synthesized carbon layers act as templates for MnO 2 shells in TiO 2 @C and organic shells of TiO 2 @MnO 2 @C. The TiO 2 @MnO 2 @C-based electrodes exhibit a greater specific capacitance (488 F g -1 at 5 mV s -1 ) and capacitance retention (97.4% after 10 000 cycles at 1.0 V s -1 ), while the absence of MnO 2 and carbon shells reveals a severe degradation in the specific capacitance and capacitance retention. Because the core-TiO 2 nanoparticles and carbon shell prevent the deformation of the inner and outer sides of the MnO 2 shell, the nanostructures of the TiO 2 @MnO 2 @C are preserved despite the long-term cycling, giving the superior performance. This SGCW-driven fabrication enables the scalable synthesis of multiple-core-shell structures applicable to diverse electrochemical applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

A scaling and experimental approach for investigating in-vessel cooling

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

Henry, R.E.

1997-02-01

The TMI-2 accident experienced the relocation of a large quantity of core material to the lower plenum. The TMI-2 vessel investigation project concluded that approximately 20 metric tonnes of once molten fuel material drained into the RPV lower head. As a result, the lower head wall experienced a thermal transient that has been characterized as reaching temperatures as high as 1100{degrees}C, then a cooling transient with a rate of 10 to 100{degrees}C/min. Two mechanisms have been proposed as possible explanations for this cooling behavior. One is the ingression of water through core material as a result of interconnected cracks inmore » the frozen debris and/or water ingression around the crust which is formed on internal structures (core supports and in-core instrumentation) in the lower head. The second focuses on the lack of adhesion of oxidic core debris to the RPV wall when the debris contacts the wall. Furthermore, the potential for strain of the RPV lower head when the wall is overheated could provide for a significant cooling path for water to ingress between the RPV and the frozen core material next to the wall. To examine these proposed mechanisms, a set of scaled experiments have been developed to examine the potential for cooling. These are performed in a scaled system in which the high temperature molten material is iron termite and the RPV wall is carbon steel. A termite mass of 40 kg is used and the simulated reactor vessels have water in the lower head at pressures up to 2.2 MPa. Furthermore, two different thicknesses of the vessel wall are examined with the thicker vessel having virtually no potential for material creep during the experiment and the thinner wall having the potential for substantial creep. Moreover, the experiment includes the option of having molten iron as the first material to drain into the RPV lower head or molten aluminum oxide being the only material that drains into the test configuration.« less

Application of Ni-Oxide@TiO₂ Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors.

PubMed

Lee, Seungwon; Lee, Jisuk; Nam, Kyusuk; Shin, Weon Gyu; Sohn, Youngku

2016-12-20

Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO₂ core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO₂ overlayer coating.

Abnormal elastic modulus behavior in a crystalline-amorphous core-shell nanowire system.

PubMed

Lee, Jeong Hwan; Choi, Su Ji; Kwon, Ji Hwan; Van Lam, Do; Lee, Seung Mo; Kim, An Soon; Baik, Hion Suck; Ahn, Sang Jung; Hong, Seong Gu; Yun, Yong Ju; Kim, Young Heon

2018-06-13

We investigated the elastic modulus behavior of crystalline InAs/amorphous Al2O3 core-shell heterostructured nanowires with shell thicknesses varying between 10 and 90 nm by conducting in situ tensile tests inside a transmission electron microscope (TEM). Counterintuitively, the elastic modulus behaviors of InAs/Al2O3 core-shell nanowires differ greatly from those of bulk-scale composite materials, free from size effects. According to our results, the elastic modulus of InAs/Al2O3 core-shell nanowires increases, peaking at a shell thickness of 40 nm, and then decreases in the range of 50-90 nm. This abnormal behavior is attributed to the continuous decrease in the elastic modulus of the Al2O3 shell as the thickness increases, which is caused by changes in the atomic/electronic structure during the atomic layer deposition process and the relaxation of residual stress/strain in the shell transferred from the interfacial mismatch between the core and shell materials. A novel method for estimating the elastic modulus of the shell in a heterostructured core-shell system was suggested by considering these two effects, and the predictions from the suggested method coincided well with the experimental results. We also found that the former and latter effects account for 89% and 11% of the change in the elastic modulus of the shell. This study provides new insight by showing that the size dependency, which is caused by the inhomogeneity of the atomic/electronic structure and the residual stress/strain, must be considered to evaluate the mechanical properties of heterostructured nanowires.

In vitro evaluation of five core materials.

PubMed

Gu, Steven; Rasimick, Brian J; Deutsch, Allan S; Musikant, Barry L

2007-01-01

This in vitro study determined the fracture strength of five core materials supported by two different endodontic dowels. Diametral tensile strength and microhardness of the three resin composite core materials used in this study were also tested. The fracture strength study used one lanthanide-reinforced flowable resin composite (Ti-Core Auto E), one titanium- and lanthanide-reinforced composite (Ti-Core), one lanthanide-reinforced composite (Ti-Core Natural), and two metal-reinforced glass ionomer core materials (Ketac Silver and GC Miracle Mix). Two types of dowels were used: a multitiered, split-shank threaded dowel with a flange (#1 Flexi-Flange) and one without a flange design (#1 Flexi-Post). The specimens were divided into ten groups. Each tooth/dowel and core specimen was placed in a special jig at 45 degrees and subjected to a load by a universal testing machine. The diametral tensile strength and the microhardness of the three resin composite core materials were measured by a universal testing machine and Barcol hardness tester, respectively. All test groups contained ten specimens. The fracture strength value of the resin composite core materials was significantly larger ( p < 0.0001) than those for the metal-reinforced glass-ionomer core materials. Analysis of variance (ANOVA) also showed that the Flexi-Flange dowel interacted with Ti-Core and Ti-Core Auto E to significantly ( p < 0.0013) increase the fracture strength relative to the Flexi-Post. One-way ANOVA revealed that there were no significant differences between them in terms of diametral tensile strength. The Barcol hardness values of the composite core materials were statistically different ( p < 0.0001), with the Ti-Core the highest, followed by Ti-Core Natural, then Ti-Core Auto E. Resin composite core material performed better than glass ionomer material in this in vitro study. The flowable composite core material performed about the same in terms of fracture strength and diametral tensile strength compared with nonflowable composites. Combined with certain core materials, the flange design increased the fracture strength of the tooth/dowel and core combination.

Understanding the Antifungal Mechanism of Ag@ZnO Core-shell Nanocomposites against Candida krusei.

PubMed

Das, Bhaskar; Khan, Md Imran; Jayabalan, R; Behera, Susanta K; Yun, Soon-Il; Tripathy, Suraj K; Mishra, Amrita

2016-11-04

In the present paper, facile synthesis of Ag@ZnO core-shell nanocomposites is reported where zinc oxide is coated on biogenic silver nanoparticles synthesized using Andrographis paniculata and Aloe vera leaf extract. Structural features of as synthesized nanocomposites are characterized by UV-visible spectroscopy, XRD, and FTIR. Morphology of the above core-shell nanocomposites is investigated by electron microscopy. As synthesized nanocomposite material has shown antimicrobial activity against Candida krusei, which is an opportunistic pathogen known to cause candidemia. The possible mode of activity of the above material has been studied by in-vitro molecular techniques. Our investigations have shown that surface coating of biogenic silver nanoparticles by zinc oxide has increased its antimicrobial efficiency against Candida krusei, while decreasing its toxicity towards A431 human epidermoid carcinoma cell lines.

Rational growth of branched nanowire heterostructures with synthetically encoded properties and function

PubMed Central

Jiang, Xiaocheng; Tian, Bozhi; Xiang, Jie; Qian, Fang; Zheng, Gengfeng; Wang, Hongtao; Mai, Liqiang; Lieber, Charles M.

2011-01-01

Branched nanostructures represent unique, 3D building blocks for the “bottom-up” paradigm of nanoscale science and technology. Here, we report a rational, multistep approach toward the general synthesis of 3D branched nanowire (NW) heterostructures. Single-crystalline semiconductor, including groups IV, III–V, and II–VI, and metal branches have been selectively grown on core or core/shell NW backbones, with the composition, morphology, and doping of core (core/shell) NWs and branch NWs well controlled during synthesis. Measurements made on the different composition branched NW structures demonstrate encoding of functional p-type/n-type diodes and light-emitting diodes (LEDs) as well as field effect transistors with device function localized at the branch/backbone NW junctions. In addition, multibranch/backbone NW structures were synthesized and used to demonstrate capability to create addressable nanoscale LED arrays, logic circuits, and biological sensors. Our work demonstrates a previously undescribed level of structural and functional complexity in NW materials, and more generally, highlights the potential of bottom-up synthesis to yield increasingly complex functional systems in the future. PMID:21730174

Influence of extrusion rate and magma rheology on the growth of lava domes: Insights from particle-dynamics modeling

NASA Astrophysics Data System (ADS)

Husain, Taha; Elsworth, Derek; Voight, Barry; Mattioli, Glen; Jansma, Pamela

2014-09-01

Lava domes are structures that grow by the extrusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Repeated cycles of growth are punctuated by collapse, as the structure becomes oversized for the strength of the composite magma that rheologically stiffens and strengthens at its surface. Here we explore lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional carapace that caps a ductile magma core. Extrusion rate and magma rheology together with crystallization temperature and volatile content govern the distribution of strength in the composite structure. This new model is calibrated against existing observational models of lava dome growth. Results show that the shape and extent of the ductile core and the overall structure of the lava dome are strongly controlled by the infusion rate. The effects of extrusion rate on magma rheology are sensitive to material stiffness, which in turn is a function of volatile content and crystallinity. Material stiffness and material strength are key model parameters which govern magma rheology and subsequently the morphological character of the lava dome and in turn stability. Degassing induced crystallization causes material stiffening and enhances material strength reflected in non-Newtonian magma behavior. The increase in stiffness and strength of the injected magma causes a transition in the style of dome growth, from endogenous expansion of a ductile core, to stiffer and stronger intruding material capable of punching through the overlying material and resulting in the development of a spine or possibly inducing dome collapse. Simulation results mimic development of a megaspine upon the influx of fresh magma which leads to the re-direction of magma flow, creating a new shear zone and the switching of dome growth from one side to the other. Our model shows similar dome growth dynamics as observed at Soufriere Hills Volcano, Montserrat, indicating a strong correlation between extrusion rate and its subsequent effect on mechanical properties and variations in magma rheology.

Electronic and Optical Properties of Core/Shell Pb16X16/Cd52X52 (X =S, Se, Te) Quantum Dots

NASA Astrophysics Data System (ADS)

Tamukong, Patrick; Mayo, Michael; Kilina, Svetlana

2015-03-01

The electronic and optoelectronic properties of semiconductor quantum dots (QDs) are mediated by surface defects due to the presence of dangling bonds producing trap states within the HOMO-LUMO energy gap, and contributing to fluorescence quenching. Surface capping ligands are generally used to alleviate this problem and increase the quantum yields of QDs. An alternative way is to synthesize core-shell QD structures; i.e., a QD core with a shell of another semiconductor material. We have investigated the effects of Cd52X52 shells on the photoexcited dynamics of Pb16X16 (X =S, Se, Te) QDs. The thin (~ 0.50 nm) shells were found to result largely in type I core/shell structures and a blue shift of the absorption spectra. Our studies revealed fairly strong core-shell hybridization in the electronic states close to the conduction band (CB) edge for Pb16S16andPb16Se16 cores, whereas for the Pb16Te16 core, such CB states were largely shell-like in nature. Nonadiabatic DFT-based dynamics, coupled with the surface hopping method, was used to study the effects of the core and shell compositions on energy relaxation rates in these systems.

Synthesis and luminescent properties of CaCO3:Eu3+@SiO2 phosphors with core-shell structure

NASA Astrophysics Data System (ADS)

Liu, Min; Kang, Ming; Chen, Kexu; Mou, Yongren; Sun, Rong

2018-03-01

Integrating the processes of preparation of CaCO3:Eu3+ and its surface-coating, core-shell structured CaCO3:Eu3+@SiO2 phosphors with red emission were synthesized by the carbonation method and surface precipitation procedure using sodium silicate as silica source. The phase structure, thermal stability, morphology and luminescent property of the as-synthesized samples were characterized by X-ray diffraction, Fourier transform infrared spectrum, thermal analysis, field-emission scanning electron microscopy, transmission electron microscope and photoluminescence spectra. The experimental results show that Eu3+ ions as the luminescence center are divided into two types: one is at the surface of the CaCO3 and the other inhabits the site of Ca2+. For CaCO3:Eu3+@SiO2 phosphors, the SiO2 layers are continuously coated on the surface of CaCO3:Eu3+ and show a typical core-shell structure. After coated with SiO2 layer, the luminous intensity and the compatibility with the rubber matrix increase greatly. Additionally, the luminous intensity increases with the increasing of Eu3+ ions concentration in CaCO3 core and concentration quenching occurs when Eu3+ ions concentration exceeds 7.0 mol%, while it is 5.0 mol% for CaCO3:Eu3+ phosphors. Therefore, preparation of CaCO3:Eu3+@SiO2 phosphors can not only simplify the experimental process through integrating the preparation of CaCO3:Eu3+ and SiO2 layer, but also effectively increase the luminous intensities of CaCO3:Eu3+ phosphors. The as-obtained phosphors may have potential applications in the fields of optical materials and functional polymer composite materials, such as plastics and rubbers.

Contamination assessment in microbiological sampling of the Eyreville core, Chesapeake Bay impact structure

USGS Publications Warehouse

Gronstal, A.L.; Voytek, M.A.; Kirshtein, J.D.; Von der, Heyde; Lowit, M.D.; Cockell, C.S.

2009-01-01

Knowledge of the deep subsurface biosphere is limited due to difficulties in recovering materials. Deep drilling projects provide access to the subsurface; however, contamination introduced during drilling poses a major obstacle in obtaining clean samples. To monitor contamination during the 2005 International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) deep drilling of the Chesapeake Bay impact structure, four methods were utilized. Fluorescent microspheres were used to mimic the ability of contaminant cells to enter samples through fractures in the core material during retrieval. Drilling mud was infused with a chemical tracer (Halon 1211) in order to monitor penetration of mud into cores. Pore water from samples was examined using excitation-emission matrix (EEM) fl uorescence spectroscopy to characterize dissolved organic carbon (DOC) present at various depths. DOC signatures at depth were compared to signatures from drilling mud in order to identify potential contamination. Finally, microbial contaminants present in drilling mud were identified through 16S ribosomal deoxyribonucleic acid (rDNA) clone libraries and compared to species cultured from core samples. Together, these methods allowed us to categorize the recovered core samples according to the likelihood of contamination. Twenty-two of the 47 subcores that were retrieved were free of contamination by all the methods used and were subsequently used for microbiological culture and culture-independent analysis. Our approach provides a comprehensive assessment of both particulate and dissolved contaminants that could be applied to any environment with low biomass. ?? 2009 The Geological Society of America.

Functionalized core-shell hydrogel microsprings by anisotropic gelation with bevel-tip capillary

PubMed Central

Yoshida, Koki; Onoe, Hiroaki

2017-01-01

This study describes a novel microfluidic-based method for the synthesis of hydrogel microsprings that are capable of encapsulating various functional materials. A continuous flow of alginate pre-gel solution can spontaneously form a hydrogel microspring by anisotropic gelation around the bevel-tip of the capillary. This technique allows fabrication of hydrogel microsprings using only simple capillaries and syringe pumps, while their complex compartmentalization characterized by a laminar flow inside the capillary can contribute to the optimization of the microspring internal structure and functionality. Encapsulation of several functional materials including magnetic-responsive nanoparticles or cell dispersed collagen for tissue scaffold was demonstrated to functionalize the microsprings. Our core-shell hydrogel microsprings have immense potential for application in a number of fields, including biological/chemical microsensors, biocompatible soft robots/microactuators, drug release, self-assembly of 3D structures and tissue engineering. PMID:28378803

Evolution of petrophysical properties of across natural faults: a study on cores from the Tournemire underground research laboratory (France)

NASA Astrophysics Data System (ADS)

Bonnelye, Audrey; David, Christian; Schubnel, Alexandre; Wassermann, Jérôme; Lefèvre, Mélody; Henry, Pierre; Guglielmi, Yves; Castilla, Raymi; Dick, Pierre

2017-04-01

Faults in general, and in clay materials in particular, have complex structures that can be linked to both a polyphased tectonic history and the anisotropic nature of the material. Drilling through faults in shaly materials allows one to measure properties such as the structure, the mineralogical composition, the stress orientation or physical properties. These relations can be investigated in the laboratory in order to have a better understanding on in-situ mechanisms. In this study we used shales of Toarcian age from the Tournemire underground research laboratory (France). We decided to couple different petrophysical measurements on core samples retrieved from a borehole drilled perpendicularly to a fault plane, and the fault size is of the order of tens of meters. This 25m long borehole was sampled in order to perform several types of measurements: density, porosity, saturation directly in the field, and velocity of elastic waves and magnetic susceptibility anisotropy in the laboratory. For all these measurements, special protocols were developed in order to preserve as much as possible the saturation state of the samples. All these measurements were carried out in three zones that intersects the borehole: the intact zone , the damaged zone and the fault core zone. From our measurements, we were able to associate specific properties to each zone of the fault. We then calculated Thomsen's parameters in order to quantify the elastic anisotropy across the fault. Our results show strong variations of the elastic anisotropy with the distance to the fault core as well as the occurrence of anisotropy reversal.

Linear complexions: Confined chemical and structural states at dislocations

NASA Astrophysics Data System (ADS)

Kuzmina, M.; Herbig, M.; Ponge, D.; Sandlöbes, S.; Raabe, D.

2015-09-01

For 5000 years, metals have been mankind’s most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe-9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states.

Nanoscale alloys and core-shell materials: Model predictions of the nanostructure and mechanical properties

NASA Astrophysics Data System (ADS)

Zhurkin, E. E.; van Hoof, T.; Hou, M.

2007-06-01

Atomic scale modeling methods are used to investigate the relationship between the properties of clusters of nanometer size and the materials that can be synthesized by assembling them. The examples of very different bimetallic systems are used. The first one is the Ni3Al ordered alloy and the second is the AgCo core-shell system. While the Ni3Al cluster assembled materials modeling is already reported in our previous work, here we focus on the prediction of new materials synthesized by low energy deposition and accumulation of AgCo clusters. It is found that the core-shell structure is preserved by deposition with energies typical of low energy cluster beam deposition, although deposition may induce substantial cluster deformation. In contrast with Ni3Al deposited cluster assemblies, no grain boundary between clusters survives deposition and the silver shells merge into a noncrystalline system with a layered structure, in which the fcc Co grains are embedded. To our knowledge, such a material has not yet been synthesized experimentally. Mechanical properties are discussed by confronting the behaviors of Ni3Al and AgCo under the effect of a uniaxial load. To this end, a molecular dynamics scheme is established in view of circumventing rate effects inherent to short term modeling and thereby allowing to examine large plastic deformation mechanisms. Although the mechanisms are different, large plastic deformations are found to improve the elastic properties of both the Ni3Al and AgCo systems by stabilizing their nanostructure. Beyond this improvement, when the load is further increased, the Ni3Al system displays reduced ductility while the AgCo system is superplastic. The superplasticity is explained by the fact that the layered structure of the Ag system is not modified by the deformation. Some coalescence of the Co grains is identified as a geometrical effect and is suggested to be a limiting factor to superplasticity.

Stability of a Bifunctional Cu-Based Core@Zeolite Shell Catalyst for Dimethyl Ether Synthesis Under Redox Conditions Studied by Environmental Transmission Electron Microscopy and In Situ X-Ray Ptychography.

PubMed

Baier, Sina; Damsgaard, Christian D; Klumpp, Michael; Reinhardt, Juliane; Sheppard, Thomas; Balogh, Zoltan; Kasama, Takeshi; Benzi, Federico; Wagner, Jakob B; Schwieger, Wilhelm; Schroer, Christian G; Grunwaldt, Jan-Dierk

2017-06-01

When using bifunctional core@shell catalysts, the stability of both the shell and core-shell interface is crucial for catalytic applications. In the present study, we elucidate the stability of a CuO/ZnO/Al2O3@ZSM-5 core@shell material, used for one-stage synthesis of dimethyl ether from synthesis gas. The catalyst stability was studied in a hierarchical manner by complementary environmental transmission electron microscopy (ETEM), scanning electron microscopy (SEM) and in situ hard X-ray ptychography with a specially designed in situ cell. Both reductive activation and reoxidation were applied. The core-shell interface was found to be stable during reducing and oxidizing treatment at 250°C as observed by ETEM and in situ X-ray ptychography, although strong changes occurred in the core on a 10 nm scale due to the reduction of copper oxide to metallic copper particles. At 350°C, in situ X-ray ptychography indicated the occurrence of structural changes also on the µm scale, i.e. the core material and parts of the shell undergo restructuring. Nevertheless, the crucial core-shell interface required for full bifunctionality appeared to remain stable. This study demonstrates the potential of these correlative in situ microscopy techniques for hierarchically designed catalysts.

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

Singh, Paviter; Kaur, Manpreet; Singh, Bikramjeet

Boron-carbon core shell structures have been synthesized by solvo-thermal synthesis route. The synthesized material is highly pure. X-ray diffraction analysis confirms the reduction of reactants in to boron and carbon. Scanning Electron Microscopy (SEM) analysis showed that the shell is uniform with average thickness of 340 nm. Photo luminescence studies showed that the material is blue light emitting with CIE color coordinates: x=0.16085, y=0.07554.

Nanoparticles of CdCl2 with closed cage structures

NASA Astrophysics Data System (ADS)

Popovitz-Biro, R.; Twersky, A.; Hacohen, Y. Rosenfeld; Tenne, R.

2000-11-01

Nanoparticles of various layered compounds having a closed cage or nanotubular structure, designated also inorganic fullerene-like (IF) materials, have been reported in the past. In this work IF-CdCl2 nanoparticles were synthesized by electron beam irradiation of the source powder leading to its recrystallization into closed nanoparticles with a nonhollow core. This process created polyhedral nanoparticles with hexagonal or elongated rectangular characters. The analysis also shows that, while the source (dried) powder is orthorhombic cadmium chloride monohydrate, the crystallized IF cage consists of the anhydrous 3R polytype which is not stable as bulk material in ambient atmosphere. Consistent with previous observations, this study shows that the seamless structure of the IF materials can stabilize phases, which are otherwise unstable in ambient conditions.

New materials and structures for photovoltaics

NASA Astrophysics Data System (ADS)

Zunger, Alex; Wagner, S.; Petroff, P. M.

1993-01-01

Despite the fact that over the years crystal chemists have discovered numerous semiconducting substances, and that modern epitaxial growth techniques are able to produce many novel atomic-scale architectures, current electronic and opto-electronic technologies are based but on a handful of ˜10 traditional semiconductor core materials. This paper surveys a number of yet-unexploited classes of semiconductors, pointing to the much-needed research in screening, growing, and characterizing promising members of these classes. In light of the unmanageably large number of a-priori possibilities, we emphasize the role that structural chemistry and modern computer-aided design must play in screening potentially important candidates. The basic classes of materials discussed here include nontraditional alloys, such as non-isovalent and heterostructural semiconductors, materials at reduced dimensionality, including superlattices, zeolite-caged nanostructures and organic semiconductors, spontaneously ordered alloys, interstitial semiconductors, filled tetrahedral structures, ordered vacancy compounds, and compounds based on d and f electron elements. A collaborative effort among material predictor, material grower, and material characterizer holds the promise for a successful identification of new and exciting systems.

Synthesis and structure of an extended cluster lead(II) carboxylate, [Pb((CO){sub 9}Co{sub 3}({mu}{sub 3}-CCO{sub 2})){sub 2}]{sub n}. Role of core metals in cluster-derived hydrogenation catalysts

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

Xinjian Lei; Maoyu Shang; Fehlner, T.P.

The reaction of lead acetate with (CO){sub 9}Co{sub 3}({mu}{sub 3}-CCOOH) leads to the formation of [Pb((CO){sub 9}Co{sub 3}({mu}{sub 3}-CCO{sub 2})){sub 2}]{sub n}, I, in high yield. The structure of I exhibits unusual six-coordinate Pb(II) centers with two asymmetrical chelating cluster carboxylates (C{sub 22}Co{sub 6}PbO{sub 22}; triclinic P1; a = 8.119(1), b = 14.346(2), c = 14.660(2) {Angstrom}; {alpha} = 102.18(1), {beta} = 99.01(1), {gamma} = 97.30(1){degrees}; Z = 2). One oxygen of each cluster carboxylate ligand bridges between adjacent lead atoms such that a chainlike extended structure is found in the solid state without the presence of solvent or water.more » I is converted stepwide on pyrolysis into two metastable forms of solid materials (designated LT and HT), each of which has been characterized spectroscopically. The hydrogenation of 2-butenal as a test reaction shows that the LT catalyst exhibits selectivities similar to previous LT materials derived from other cobalt cluster metal carboxylates and that the HT material is totally inactive. The observed release of the lead core metal under HT activation conditions totally inactivates the catalyst and demonstrates exposure of the core metal in the HT form of these novel catalysts.« less

Fuel elements of thermionic converters

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

Hunter, R.L.; Gontar, A.S.; Nelidov, M.V.

1997-01-01

Work on thermionic nuclear power systems has been performed in Russia within the framework of the TOPAZ reactor program since the early 1960s. In the TOPAZ in-core thermionic convertor reactor design, the fuel element`s cladding is also the thermionic convertor`s emitter. Deformation of the emitter can lead to short-circuiting and is the primary cause of premature TRC failure. Such deformation can be the result of fuel swelling, thermocycling, or increased unilateral pressure on the emitter due to the release of gaseous fission products. Much of the work on TRCs has concentrated on preventing or mitigating emitter deformation by improving themore » following materials and structures: nuclear fuel; emitter materials; electrical insulators; moderator and reflector materials; and gas-exhaust device. In addition, considerable effort has been directed toward the development of experimental techniques that accurately mimic operational conditions and toward the creation of analytical and numerical models that allow operational conditions and behavior to be predicted without the expense and time demands of in-pile tests. New and modified materials and structures for the cores of thermionic NPSs and new fabrication processes for the materials have ensured the possibility of creating thermionic NPSs for a wide range of powers, from tens to several hundreds of kilowatts, with life spans of 5 to 10 years.« less

The influence of temperature on a nutty-cake structural material: LiMn1-xFexPO4 composite with LiFePO4 core and carbon outer layer for lithium-ion battery

NASA Astrophysics Data System (ADS)

Huo, Zhen-Qing; Cui, Yu-Ting; Wang, Dan; Dong, Yue; Chen, Li

2014-01-01

The extremely low electronic conductivity, slow ion diffusion kinetics, and the Jahn-Teller effect of LiMnPO4 limit its electrochemical performance. In this work, a nutty-cake structural C-LiMn1-xFexPO4-LiFePO4 cathode material is synthesized by hydrothermal method and further calcined at different temperatures. The influence of calcination temperature on the electrochemical behavior is investigated by X-ray diffractometer, scanning electron microscope, field-emission high-resolution transmission electron microscope, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and charge-discharge tests. And the performance of C-LiMn1-xFexPO4-LiFePO4 materials has a relationship with its crystal structure. The well-crystallized Sample-600 calcined at 600 °C shows the smallest charge transfer resistance, the largest lithium ion diffusion coefficient (DLi) and the best cycling stability. The discharge capacity of Sample-600 holds around 112 mAh g-1 after the 3rd cycle at 0.1 C rate. The performances improvement of C-LiMn1-xFexPO4-LiFePO4 material can be mainly attributed to the iron diffusion from the LiFePO4 core to the outer LiMnPO4 layer under appropriate calcination temperature.

Electronically cloaked nanoparticles

NASA Astrophysics Data System (ADS)

Shen, Wenqing

The concept of electronic cloaking is to design objects invisible to conduction electrons. The approach of electronic cloaking has been recently suggested to design invisible nanoparticle dopants with electronic scattering cross section smaller than 1% of the physical cross section (pi a2), and therefore to enhance the carrier mobility of bulk materials. The proposed nanoparticles have core-shell structures. The dopants are incorporated inside the core, while the shell layer serves both as a spacer to separate the charge carriers from their parent atoms and as a cloaking shell to minimize the scattering cross section of the electrons from the ionized nanoparticles. Thermoelectric materials are usually highly doped to have enough carrier density. Using invisible dopants could achieve larger thermoelectric power factors by enhancing the electronic mobility. Core-shell nanoparticles show an advantage over one-layer nanoparticles, which are proposed in three-dimensional modulation doping. However designing such nanoparticles is not easy as there are too many parameters to be considered. This thesis first shows an approach to design hollow nanoparticles by applying constrains on variables. In the second part, a simple mapping approach is introduced where one can identify possible core-shell particles by comparing the dimensionless parameters of chosen materials with provided maps. In both parts of this work, several designs with realistic materials were made and proven to achieve electronic cloaking. Improvement in the thermoelectric power factor compared to the traditional impurity doping method was demonstrated in several cases.

Fracture zone drilling through Atotsugawa fault in central Japan - geological and geophysical structure -

NASA Astrophysics Data System (ADS)

Omura, K.; Yamashita, F.; Yamada, R.; Matsuda, T.; Fukuyama, E.; Kubo, A.; Takai, K.; Ikeda, R.; Mizuochi, Y.

2004-12-01

Drilling is an effective method to investigate the structure and physical state in and around the active fault zone, such as, stress and strength distribution, geological structure and materials properties. In particular, the structure in the fault zone is important to understand where and how the stress accumulates during the earthquake cycle. In previous studies, we did integrate investigation on active faults in central Japan by drilling and geophysical prospecting. Those faults are estimated to be at different stage in the earthquake cycle, i.e., Nojima fault which appeared on the surface by the 1995 Great Kobe earthquake (M=7.2), the Neodani fault which appeared by the 1891 Nobi earth-quake (M=8.0), the Atera fault, of which some parts have seemed to be dislocated by the 1586 Tensyo earthquake (M=7.9), and Gofukuji Fault that is considered to have activated about 1200 years ago. Each faults showed characteristic features of fracture zone structure according to their geological and geophysical situations. In a present study, we did core recovery and down hole measurements at the Atotsugawa fault, central Japan, that is considered to have activated at 1858 Hida earthquake (M=7.0). The Atotsugawa fault is characterized by active seismicity along the fault. But, at the same time, the shallow region in the central segment of the fault seems to have low seismicity. The high seismicity segment and low seismicity segments may have different mechanical, physical and material properties. A 350m depth borehole was drilled vertically beside the surface trace of the fault in the low seismicity segment. Recovered cores were overall heavily fractured and altered rocks. In the cores, we observed many shear planes holding fault gouge. Logging data showed that the apparent resistance was about 100 - 600 ohm-m, density was about 2.0 - 2.5g/cm3, P wave velocity was approximately 3.0 - 4.0 km/sec, neutron porosity was 20 - 40 %. Results of physical logging show features of fault fracture zone that were the same as the fault fracture zones of other active faults that we have drilled previously. By the BHTV logging, we detected many fractures of which the strikes are not only parallel to the fault trace bur also oblique to the fault trace. The observations of cores and logging data indicate that the borehole passed in the fracture zone down to the bottom, and that the fracture zone has complicate internal structure including foliation not parallel to the fault trace. The core samples are significant for further investigation on material properties in the fracture zone. And we need data of geophysical prospecting to infer the deeper structure of the fracture zone.

Development of lightweight graphite/polyimide sandwich panels.

NASA Technical Reports Server (NTRS)

Poesch, J. G.

1972-01-01

Lightweight graphite/polyimide composite honeycomb core and sandwich panels were fabricated and tested. Honeycomb cores of 1/4-in. and 3/8-in. cell sizes of hexagonal configuration were produced from thin plus or minus 45 deg cross plied sheets of prepreg producing core weights between 1.8 and 3.6 lb/cu ft. Thin gauge prepreg using Hercules graphite tow and Monsanto Skybond 710 polyimide resin were manufactured to produce cured ply thicknesses of 0.001 to 0.002 in. Graphite core properties measured at temperatures from -150 to 600 F are reported. Core properties which are superior to available materials were obtained. Sandwich panels weighing less than 0.5 lb/sq ft were designed and fabricated which meet the support structure loads for the shuttle orbiter thermal protection system.

16 CFR § 1633.9 - Glossary of terms.

Code of Federal Regulations, 2013 CFR

2013-01-01

... FOR THE FLAMMABILITY (OPEN FLAME) OF MATTRESS SETS The Standard § 1633.9 Glossary of terms. (a... structure may include constructed frames, foam, box springs or other materials used alone or in combination..., solid foam core segments. ...

Simplified method to solve sound transmission through structures lined with elastic porous material.

PubMed

Lee, J H; Kim, J

2001-11-01

An approximate analysis method is developed to calculate sound transmission through structures lined with porous material. Because the porous material has both the solid phase and fluid phase, three wave components exist in the material, which makes the related analysis very complicated. The main idea in developing the approximate method is very simple: modeling the porous material using only the strongest of the three waves, which in effect idealizes the material as an equivalent fluid. The analysis procedure has to be conducted in two steps. In the first step, sound transmission through a flat double panel with a porous liner of infinite extents, which has the same cross sectional construction as the actual structure, is solved based on the full theory and the strongest wave component is identified. In the second step sound transmission through the actual structure is solved modeling the porous material as an equivalent fluid while using the actual geometry of the structure. The development and validation of the method are discussed in detail. As an application example, the transmission loss through double walled cylindrical shells with a porous core is calculated utilizing the simplified method.

An MR/MRI compatible core holder with the RF probe immersed in the confining fluid.

PubMed

Shakerian, M; Balcom, B J

2018-01-01

An open frame RF probe for high pressure and high temperature MR/MRI measurements was designed, fabricated, and tested. The open frame RF probe was installed inside an MR/MRI compatible metallic core holder, withstanding a maximum pressure and temperature of 5000 psi and 80 °C. The open frame RF probe was tunable for both 1 H and 19 F resonance frequencies with a 0.2 T static magnetic field. The open frame structure was based on simple pillars of PEEK polymer upon which the RF probe was wound. The RF probe was immersed in the high pressure confining fluid during operation. The open frame structure simplified fabrication of the RF probe and significantly reduced the amount of polymeric materials in the core holder. This minimized the MR background signal detected. Phase encoding MRI methods were employed to map the spin density of a sulfur hexafluoride gas saturating a Berea core plug in the core holder. The SF 6 was imaged as a high pressure gas and as a supercritical fluid. Copyright © 2017 Elsevier Inc. All rights reserved.

An MR/MRI compatible core holder with the RF probe immersed in the confining fluid

NASA Astrophysics Data System (ADS)

Shakerian, M.; Balcom, B. J.

2018-01-01

An open frame RF probe for high pressure and high temperature MR/MRI measurements was designed, fabricated, and tested. The open frame RF probe was installed inside an MR/MRI compatible metallic core holder, withstanding a maximum pressure and temperature of 5000 psi and 80 °C. The open frame RF probe was tunable for both 1H and 19F resonance frequencies with a 0.2 T static magnetic field. The open frame structure was based on simple pillars of PEEK polymer upon which the RF probe was wound. The RF probe was immersed in the high pressure confining fluid during operation. The open frame structure simplified fabrication of the RF probe and significantly reduced the amount of polymeric materials in the core holder. This minimized the MR background signal detected. Phase encoding MRI methods were employed to map the spin density of a sulfur hexafluoride gas saturating a Berea core plug in the core holder. The SF6 was imaged as a high pressure gas and as a supercritical fluid.

NDE of Fiber Reinforced Foam Composite Structures for Future Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Walker, james; Roth, Don; Hopkins, Dale

2010-01-01

This slide presentation reviews the complexities of non-destructive evaluation (NDE) of fiber reinforced foam composite structures to be used for aerospace vehicles in the future.Various views of fiber reinforced foam materials are shown and described. Conventional methods of NDE for composites are reviewed such as Micro-computed X-Ray Tomography, Thermography, Shearography, and Phased Array Ultrasonics (PAUT). These meth0ods appear to work well on the face sheet and face sheet ot core bond, they do not provide adequate coverage for the webs. There is a need for additional methods that will examine the webs and web to foam core bond.

VISCEL: A general-purpose computer program for analysis of linear viscoelastic structures (user's manual), volume 1

NASA Technical Reports Server (NTRS)

Gupta, K. K.; Akyuz, F. A.; Heer, E.

1972-01-01

This program, an extension of the linear equilibrium problem solver ELAS, is an updated and extended version of its earlier form (written in FORTRAN 2 for the IBM 7094 computer). A synchronized material property concept utilizing incremental time steps and the finite element matrix displacement approach has been adopted for the current analysis. A special option enables employment of constant time steps in the logarithmic scale, thereby reducing computational efforts resulting from accumulative material memory effects. A wide variety of structures with elastic or viscoelastic material properties can be analyzed by VISCEL. The program is written in FORTRAN 5 language for the Univac 1108 computer operating under the EXEC 8 system. Dynamic storage allocation is automatically effected by the program, and the user may request up to 195K core memory in a 260K Univac 1108/EXEC 8 machine. The physical program VISCEL, consisting of about 7200 instructions, has four distinct links (segments), and the compiled program occupies a maximum of about 11700 words decimal of core storage.

Innovative use of wood-plastic-composites (WPC) as a core material in the sandwich injection molding process

NASA Astrophysics Data System (ADS)

Moritzer, Elmar; Martin, Yannick

2016-03-01

The demand for materials based on renewable raw materials has risen steadily in recent years. With society's increasing interest for climate protection and sustainability, natural-based materials such as wood-plastic-composites (WPC) have gained market share thanks to their positive reputation. Due to advantages over unreinforced plastics such as cost reduction and weight savings it is possible to use WPC in a wide area of application. Additionally, an increase in mechanical properties such as rigidity and strength is achieved by the fibers compared to unreinforced polymers. The combination of plastic and wood combines the positive properties of both components in an innovative material. Despite the many positive properties of wood-plastic-composite, there are also negative characteristics that prevent the use of WPC in many product areas, such as automotive interiors. In particular, increased water intake, which may result in swelling of near-surface particles, increased odor emissions, poor surface textures and distortion of the components are unacceptable for many applications. The sandwich injection molding process can improve this situation by eliminating the negative properties of WPC by enclosing it with a pure polymer. In this case, a layered structure of skin and core material is produced, wherein the core component is completely enclosed by the skin component. The suitability of WPC as the core component in the sandwich injection molding has not yet been investigated. In this study the possibilities and limitations of the use of WPC are presented. The consideration of different fiber types, fiber contents, skin materials and its effect on the filling behavior are the focus of the presented analysis.

Review of Repair Materials for Fire-Damaged Reinforced Concrete Structures

NASA Astrophysics Data System (ADS)

Zahid, MZA Mohd; Abu Bakar, BH; Nazri, FM; Ahmad, MM; Muhamad, K.

2018-03-01

Reinforced concrete (RC) structures perform well during fire and may be repaired after the fire incident because their low heat conductivity prevents the loss or degradation of mechanical strength of the concrete core and internal reinforcing steel. When an RC structure is heated to more than 500 °C, mechanical properties such as compressive strength, stiffness, and tensile strength start to degrade and deformations occur. Although the fire-exposed RC structure shows no visible damage, its residual strength decreases compared with that in the pre-fire state. Upon thorough assessment, the fire-damaged RC structure can be repaired or strengthened, instead of subjecting to partial or total demolition followed by reconstruction. The structure can be repaired using several materials, such as carbon fiber-reinforced polymer, glass fiber-reinforced polymer, normal strength concrete, fiber-reinforced concrete, ferrocement, epoxy resin mortar, and high-performance concrete. Selecting an appropriate repair material that must be compatible with the substrate or base material is a vital step to ensure successful repair. This paper reviews existing repair materials and factors affecting their performance. Of the materials considered, ultra-high-performance fiber-reinforced concrete (UHPFRC) exhibits huge potential for repairing fire-damaged RC structures but lack of information available. Hence, further studies must be performed to assess the potential of UHPFRC in rehabilitating fire-damaged RC structures.

Generalized Ellipsometry on Complex Nanostructures and Low-Symmetry Materials

NASA Astrophysics Data System (ADS)

Mock, Alyssa Lynn

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with monoclinic and triclinic symmetries. A model eigendielectric displacement vector approach is developed, described and utilized to characterize monoclinic materials. Materials are investigated in spectral regions spanning from the far-infrared to the vacuum ultraviolet. Examples are demonstrated for phonon mode determination in cadmium tungstate and yttrium silicate and for band-to-band transitions in gallia (beta-Ga2O3) single crystals. Furthermore, the anisotropic optical properties of an emerging class of spatially coherent heterostructure materials with nanostructure dimensions are investigated. The so-called anisotropic effective medium approximation for slanted columnar thin films is extended to the concept of slanted columnar heterostructure thin films as well as core-shell heterostructure thin films. Examples include the determination of band-to-band transitions, phonon modes and oxidation properties of cobalt-oxide core shell structures and gas-liquid-solid distribution during controlled adsorption of organic solvents in silicon slanted columnar thin films.

A SOLAR TORNADO OBSERVED BY AIA/SDO: ROTATIONAL FLOW AND EVOLUTION OF MAGNETIC HELICITY IN A PROMINENCE AND CAVITY

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

Li, Xing; Morgan, Huw; Leonard, Drew

During 2011 September 24, as observed by the Atmospheric Imaging Assembly instrument of the Solar Dynamic Observatory and ground-based H{alpha} telescopes, a prominence and associated cavity appeared above the southwest limb. On 2011 September 25 8:00 UT, material flows upward from the prominence core along a narrow loop-like structure, accompanied by a rise ({>=}50,000 km) of the prominence core and the loop. As the loop fades by 10:00, small blobs and streaks of varying brightness rotate around the top part of the prominence and cavity, mimicking a cyclone. The most intense and coherent rotation lasts for over three hours, withmore » emission in both hot ({approx}1 MK) and cold (hydrogen and helium) lines. We suggest that the cyclonic appearance and overall evolution of the structure can be interpreted in terms of the expansion of helical structures into the cavity, and the movement of plasma along helical structures which appears as a rotation when viewed along the helix axis. The coordinated movement of material between prominence and cavity suggests that they are structurally linked. Complexity is great due to the combined effect of these actions and the line-of-sight integration through the structure which contains tangled fields.« less

Fat emulsions based on structured lipids (1,3-specific triglycerides): an investigation of the in vivo fate.

PubMed

Hedeman, H; Brøndsted, H; Müllertz, A; Frokjaer, S

1996-05-01

Structured lipids (1,3-specific triglycerides) are new chemical entities made by enzymatic transesterification of the fatty acids in the 1,3 positions of the triglyceride. The purpose of this study is to characterize structured lipids with either short chain fatty acids or medium chain fatty acids in the 1,3 positions with regard to their hydrophobicity, and investigate the in vivo fate in order to evaluate the potential of structured lipids as core material in fat emulsions used as parenteral drug delivery system. The lipids were characterized by employing reversed phase high performance liquid chromatography. The biodistribution of radioactively labeled emulsions was studied in rats. By employing high performance liquid chromatography a rank order of the hydrophobicities of the lipids could be given, with the triglycerides containing long chain fatty acids being the most hydrophobic and the structured lipid with short chain fatty acids in the 1,3 positions the least. When formulated as fat emulsions, the emulsion based on structured lipids with short fatty acids in the 1,3 positions was removed slower from the general blood circulation compared to emulsions based on lipids with long chain fatty acids in the 1,3 positions. The type of core material influences the in vivo circulation time of fat emulsions.

Intricate Estimation and Assessment of Surface Conditioning of Posts to improve Interfacial Adhesion in Post-core Restorations: An in vitro Study.

PubMed

Gupta, Priyanka; Sharma, Amil; Pathak, Vivek K; Mankeliya, Saurabh; Bhardwaj, Shivanshu; Dhanare, Poorvasha

2017-12-01

Post and core restorations are routinely used for restoring grossly decayed tooth structures. Various chemical agents are known to affect the interfacial adhesions between the post and the core. Hence, we planned the present study to evaluate the effect of various post-surface treatments on the interfacial strength between the posts and composite materials that are used for building up the core portion. The present study included assessment of the effect of surface conditioning of posts on the interfacial adhesion in post-core restorations. A total of 80 clear post-tapers were included and were divided broadly into four study groups based on the type of chemical testing protocols used. Various chemical treatments included alkaline potassium permanganate, hydrogen peroxide, and phosphoric acid. The fourth group was the control group. The composite core material was used for building up the core. Testing of the tensile load was done on a universal testing machine. All the results were analyzed by the Statistical Package for the Social Sciences (SPSS) software. The highest bond strength was observed in the study group treated with alkaline potassium permanganate, while the lowest was observed in the control group followed by the hydrogen peroxide group. While comparing the mean bond strength in between various study groups, significant results were obtained. Chemical treatment protocol significantly alters the mean bond strength of the post and core restoration. Potassium permanganate significantly increases the bond strength between the fiber post and core restoration.

Simplifying the design of microstructured optical fibre pressure sensors.

PubMed

Osório, Jonas H; Chesini, Giancarlo; Serrão, Valdir A; Franco, Marcos A R; Cordeiro, Cristiano M B

2017-06-07

In this paper, we propose a way to simplify the design of microstructured optical fibres with high sensitivity to applied pressure. The use of a capillary fibre with an embedded core allows the exploration of the pressure-induced material birefringence due to the capillary wall displacements and the photoelastic effect. An analytical description of pressure-induced material birefringence is provided, and fibre modal characteristics are explored through numerical simulations. Moreover, a capillary fibre with an embedded core is fabricated and used to probe pressure variations. Even though the embedded-core fibre has a non-optimized structure, measurements showed a pressure sensitivity of (1.04 ± 0.01) nm/bar, which compares well with more complex, specially designed fibre geometries reported in the literature. These results demonstrate that this geometry enables a novel route towards the simplification of microstructured fibre-based pressure sensors.

Environmental implications of the use of sulfidic back-bay sediments for dune reconstruction — Lessons learned post Hurricane Sandy

USGS Publications Warehouse

Plumlee, Geoffrey S.; Benzel, William M.; Hoefen, Todd M.; Hageman, Philip L.; Morman, Suzette A.; Reilly, Timothy J.; Adams, Monique; Berry, Cyrus J.; Fischer, Jeffrey; Fisher, Irene

2016-01-01

Some barrier-island dunes damaged or destroyed by Hurricane Sandy's storm surges in October 2012 have been reconstructed using sediments dredged from back bays. These sand-, clay-, and iron sulfide-rich sediments were used to make berm-like cores for the reconstructed dunes, which were then covered by beach sand. In November 2013, we sampled and analyzed partially weathered materials collected from the cores of reconstructed dunes. There are generally low levels of metal toxicants in the reconstructed dune materials. However oxidation of reactive iron sulfides by percolating rainwater produces acid-sulfate pore waters, which evaporate during dry periods to produce efflorescent gypsum and sodium jarosite salts. The results suggest use of sulfidic sediments in dune reconstruction has both drawbacks (e.g., potential to generate acid runoff from dune cores following rainfall, enhanced corrosion of steel bulwarks) and possible benefits (e.g., efflorescent salts may enhance structural integrity).

Green synthesis of CuInS2/ZnS core-shell quantum dots by facile solvothermal route with enhanced optical properties

NASA Astrophysics Data System (ADS)

Jindal, Shikha; Giripunje, Sushama M.; Kondawar, Subhash B.; Koinkar, Pankaj

2018-03-01

We report an eco-friendly green synthesis of highly luminescent CuInS2/ZnS core-shell quantum dots (QDs) with average particle size ∼ 3.9 nm via solvothermal process. The present study embodies the intensification of CuInS2/ZnS QDs properties by the shell growth on the CuInS2 QDs. The as-prepared CuInS2 core and CuInS2/ZnS core-shell QDs have been characterized using a range of optical and structural techniques. By adopting a low temperature growth of CuInS2 core and high temperature growth of CuInS2/ZnS core-shell growth, the tuning of absorption and photoluminescence emission spectra were observed. Optical absorption and photoluminescence spectroscopy probe the effect of ZnS passivation on the electronic structure of the CuInS2 dots. In addition, QDs have been scrutinized using ultra violet photoelectron spectroscopy (UPS) to explore their electronic band structure. The band level positions of CuInS2 and CuInS2/ZnS QDs suffices the demand of non-toxic acceptor material for electronic devices. The variation in electronic energy levels of CuInS2 core with the coating of wide band gap ZnS shell influence the removal of trap assisted recombination on the surface of the core. QDs exhibited tunable emission from red to orange region. These studies reveal the feasibility of QDs in photovoltaic and light emitting diodes.

Comparison of the fractional power motor with cores made of various magnetic materials

NASA Astrophysics Data System (ADS)

Gmyrek, Zbigniew; Lefik, Marcin; Cavagnino, Andrea; Ferraris, Luca

2017-12-01

The optimization of the motor cores, coupled with new core shapes as well as powering the motor at high frequency are the primary reasons for the use of new materials. The utilization of new materials, like SMC (soft magnetic composite), reduce the core loss and/or provide quasi-isotropic core's properties in any magnetization direction. Moreover, the use of SMC materials allows for avoiding degradation of the material portions, resulting from punching process, thereby preventing the deterioration of operating parameters of the motor. The authors examine the impact of technological parameters on the properties of a new type of SMC material and analyze the possibility of its use as the core of the fractional power motor. The result of the work is an indication of the shape of the rotor core made of a new SMC material to achieve operational parameters similar to those that have a motor with a core made of laminations.

Research on the relationship between the structural properties of bedding layer in spring mattress and sleep quality.

PubMed

Shen, Liming; Chen, Yu-xia; Guo, Yong; Zhong, ShiLu; Fang, Fei; Zhao, Jing; Hu, Tian-Yi

2012-01-01

Mattress, as a sleep platform, its types and physical properties has an important effect on sleep quality and rest efficiency. In this paper, by subjective evaluations, analysis of sleeping behaviors and tests of depth of sleep, the relationship between characteristics of the bedding materials, the structure of mattress, sleep quality and sleep behaviors were studied. The results showed that: (1) Characteristics of the bedding materials and structure of spring mattress had a remarkable effect on sleep behaviors and sleep quality. An optimum combination of the bedding materials, the structure of mattress and its core could improve the overall comfort of mattress, thereby improving the depth of sleep and sleep quality. (2) Sleep behaviors had a close relationship with sleeping postures and sleep habits. The characteristics of sleep behaviors vary from person to person.

Single-polarization hollow-core square photonic bandgap waveguide

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

Eguchi, Masashi, E-mail: megu@ieee.org; Tsuji, Yasuhide, E-mail: y-tsuji@mmm.muroran-it.ac.jp

Materials with a periodic structure have photonic bandgaps (PBGs), in which light can not be guided within certain wavelength ranges; thus light can be confined within a low-index region by the bandgap effect. In this paper, rectangular-shaped hollow waveguides having waveguide-walls (claddings) using the PBG have been discussed. The design principle for HE modes of hollow-core rectangular PBG waveguides with a Bragg cladding consisting of alternating high- and low-index layers, based on a 1D periodic multilayer approximation for the Bragg cladding, is established and then a novel single-polarization hollow-core square PBG waveguide using the bandgap difference between two polarized wavesmore » is proposed. Our results demonstrated that a single-polarization guiding can be achieved by using the square Bragg cladding structure with different layer thickness ratios in the mutually orthogonal directions and the transmission loss of the guided mode in a designed hollow-core square PBG waveguide is numerically estimated to be 0.04 dB/cm.« less

An efficient strategy for designing ambipolar organic semiconductor material: Introducing dehydrogenated phosphorus atoms into pentacene core

NASA Astrophysics Data System (ADS)

Tang, Xiao-Dan

2017-09-01

The charge transport properties of phosphapentacene (P-PEN) derivatives were systematically explored by theoretical calculation. The dehydrogenated P-PENs have reasonable frontier molecular orbital energy levels to facilitate both electron and hole injection. The reduced reorganization energies of dehydrogenated P-PENs could be intimately connected to the bonding nature of phosphorus atoms. From the idea of homology modeling, the crystal structure of TIPSE-4P-2p is constructed and fully optimized. Fascinatingly, TIPSE-4P-2p shows the intrinsic property of ambipolar transport in both hopping and band models. Thus, introducing dehydrogenated phosphorus atoms into pentacene core could be an efficient strategy for designing ambipolar material.

Application of Ni-Oxide@TiO2 Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors

PubMed Central

Lee, Seungwon; Lee, Jisuk; Nam, Kyusuk; Shin, Weon Gyu; Sohn, Youngku

2016-01-01

Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO2 core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO2 overlayer coating. PMID:28774145

Bonding and Sealing Evaluations for Cryogenic Tanks

NASA Technical Reports Server (NTRS)

Glass, David E.

1997-01-01

Several different cryogenic tank concepts are being considered for reusable launch vehicles (RLV'S) . Though different tank concepts are being considered, many will require that the cryogenic insulation be evacuated and be bonded to a structure. In this work, an attempt was made to evaluate the effectiveness of maintaining a vacuum on a specimen where foam or honeycomb core was encased within Gr/Ep. In addition to these tests, flatwise adhesion pull off tests were performed at room temperature with PR 1664, EA 9394, FM-300, Crest 3170, and HT 435 adhesives. The materials bonded included Gr/Ep, Gr/BMI, Al, and stainless steel facesheets, and Ti honeycomb, Hexcel honeycomb, and Rohacell foam core materials.

Estimation of photonic band gap in the hollow core cylindrical multilayer structure

NASA Astrophysics Data System (ADS)

Chourasia, Ritesh Kumar; Singh, Vivek

2018-04-01

The propagation characteristic of two hollow core cylindrical multilayer structures having high and low refractive index contrast of cladding regions have been studied and compared at two design wavelengths i.e. 1550 nm and 632.8 nm. With the help of transfer matrix method a relation between the incoming light wave and outgoing light wave has been developed using the boundary matching technique. In high refractive index contrast, small numbers of layers are sufficient to provide perfect band gap in both design wavelengths. The spectral position and width of band gap is highly depending on the optical path of incident light in all considered cases. For sensing application, the sensitivity of waveguide can be obtained either by monitoring the width of photonic band gap or by monitoring the spectral shift of photonic band gap. Change in the width of photonic band gap with the core refractive index is larger in high refractive index contrast of cladding materials. However, in the case of monitoring the spectral shift of band gap, the obtained sensitivity is large for low refractive index contrast of cladding materials and further it increases with increase of design wavelength.

Hybrid photoluminescent materials containing a benzobisthiazole core for liquid crystal and gel applications.

PubMed

Díaz, E; Elgueta, E; Sanchez, S A; Barberá, J; Vergara, J; Parra, M; Dahrouch, M

2017-03-01

Tetra- and hexacatenar amide compounds containing a linear centrosymmetric benzobisthiazole core were synthesized with good yields. These compounds were characterized and their structures confirmed by elemental analysis, and FT-IR, Maldi mass and NMR spectroscopy. All compounds exhibited excellent thermal stability up to 330 °C. The tetracatenar series containing a double substitution in the meta positions did not show mesomorphic behaviour, whereas the hexacatenar and tetracatenar series having a double substitution in the meta and para positions showed liquid crystal properties with optical textures typical of columnar mesophases corroborated by POM analysis. The mesomorphic properties were dependent on the length, number and position of alkoxy chains attached at the end of the rigid core. XRD studies of the hexacatenar series showed the hexagonal columnar structure of the mesophases. Photoluminescence properties in solution were observed in the visible region, with good quantum yields. In the solid state, these compounds behave as blue emitters and they are able to change colour with acid or base addition. The hexacatenar benzobisthiazole compound with an alkoxy chain of 14 carbons presented properties of a supergelator in chloroform, leading to the formation of a fluorescent organogel material with fluorescence emission in the blue region.

Role Of Impurities On Deformation Of HCP Crystal: A Multi-Scale Approach

NASA Astrophysics Data System (ADS)

Bhatia, Mehul Anoopkumar

Commercially pure (CP) and extra low interstitial (ELI) grade Ti-alloys present excellent corrosion resistance, lightweight, and formability making them attractive materials for expanded use in transportation and medical applications. However, the strength and toughness of CP titanium are affected by relatively small variations in their impurity/solute content (IC), e.g., O, Al, and V. This increase in strength is due to the fact that the solute either increases the critical stress required for the prismatic slip systems ({10- 10}) or activates another slip system ((0001), {10-11}). In particular, solute additions such as O can effectively strengthen the alloy but with an attendant loss in ductility by changing the behavior from wavy (cross slip) to planar nature. In order to understand the underlying behavior of strengthening by solutes, it is important to understand the atomic scale mechanism. This dissertation aims to address this knowledge gap through a synergistic combination of density functional theory (DFT) and molecular dynamics. Further, due to the long-range strain fields of the dislocations and the periodicity of the DFT simulation cells, it is difficult to apply ab initio simulations to study the dislocation core structure. To alleviate this issue we developed a multiscale quantum mechanics/molecular mechanics approach (QM/MM) to study the dislocation core. We use the developed QM/MM method to study the pipe diffusion along a prismatic edge dislocation core. Complementary to the atomistic simulations, the Semi-discrete Variational Peierls-Nabarro model (SVPN) was also used to analyze the dislocation core structure and mobility. The chemical interaction between the solute/impurity and the dislocation core is captured by the so-called generalized stacking fault energy (GSFE) surface which was determined from DFT-VASP calculations. By taking the chemical interaction into consideration the SVPN model can predict the dislocation core structure and mobility in the presence and absence of the solute/impurity and thus reveal the effect of impurity/solute on the softening/hardening behavior in alpha-Ti. Finally, to study the interaction of the dislocation core with other planar defects such as grain boundaries (GB), we develop an automated method to theoretically generate GBs in HCP type materials.

Facile Synthesis of Free-Standing NiO/MnO2 Core-Shell Nanoflakes on Carbon Cloth for Flexible Supercapacitors.

PubMed

Xi, Shuang; Zhu, Yinlong; Yang, Yutu; Jiang, Shulan; Tang, Zirong

2017-12-01

Free-standing NiO/MnO 2 core-shell nanoflake structure was deposited on flexible carbon cloth (CC) used as electrode for high-performance supercapacitor (SC). The NiO core was grown directly on CC by hydrothermal process and the following annealing treatment. MnO 2 thin film was then covered on NiO structures via a self-limiting process in aqueous solution of 0.5 M KMnO 4 and 0.5 M Na 2 SO 4 with a carbon layer serving as the sacrificial layer. Both the core and shell materials are good pseudocapacitive materials, the compounds of binary metal oxides can provide the synergistic effect of all individual constituents, and thus enhance the performance of SC electrode. The obtained CC/NiO/MnO 2 heterostructure was directly used as SC electrodes, showing an enhanced electrochemical performance including areal capacitance of 316.37 mF/cm 2 and special gravimetric capacitance of 204.3 F/g at the scan rate of 50 mV/s. The electrode also shows excellent cycling stability, which retains 89% of its initial discharge capacitance after 2200 cycles with >97% Coulombic efficiency. The synthesized binder-free hierarchical composite electrode with superior electrochemical properties demonstrates enormous potential in the application of flexible SCs.

Impact Resistance of Lightweight Hybrid Structures for Gas Turbine Engine Fan Containment Applications

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G.; Noebe, Ronald D.; Revilock, Duane M.

2003-01-01

The ballistic impact resistance of hybrid composite sandwich structures was evaluated with the ultimate goal of developing new materials or structures for potential gas turbine engine fan containment applications. The sandwich structures investigated consisted of GLARE-5 laminates as face sheets with lightweight cellular metallic materials such as honeycomb, foam, and lattice block as a core material. The impact resistance of these hybrid sandwich structures was compared to GLARE-5 laminates and 2024-T3 Al sheet, which were tested as a function of areal weight (material thickness). The GLARE-5 laminates exhibited comparable impact properties to that of 2024-T3 Al at low areal weights, even though there were significant differences in the static tensile properties of these materials. The GLARE-5, however, did have a greater ballistic limit than straight aluminum sheet at higher areal weights. Furthermore, there is up to a 25% advantage in ballistic limit for the GLARE-5/foam sandwich structures compared to straight 2024-T3 Al. But no advantage in ballistic limit was observed between any of the hybrid sandwich structures and thicker versions of GLARE-5. Recommendations for future work are provided, based on these preliminary data.

Armor systems including coated core materials

DOEpatents

Chu, Henry S [Idaho Falls, ID; Lillo, Thomas M [Idaho Falls, ID; McHugh, Kevin M [Idaho Falls, ID

2012-07-31

An armor system and method involves providing a core material and a stream of atomized coating material that comprises a liquid fraction and a solid fraction. An initial layer is deposited on the core material by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is less than the liquid fraction of the stream of atomized coating material on a weight basis. An outer layer is then deposited on the initial layer by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is greater than the liquid fraction of the stream of atomized coating material on a weight basis.

Armor systems including coated core materials

DOEpatents

Chu, Henry S; Lillo, Thomas M; McHugh, Kevin M

2013-10-08

An armor system and method involves providing a core material and a stream of atomized coating material that comprises a liquid fraction and a solid fraction. An initial layer is deposited on the core material by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is less than the liquid fraction of the stream of atomized coating material on a weight basis. An outer layer is then deposited on the initial layer by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is greater than the liquid fraction of the stream of atomized coating material on a weight basis.

High Water Tolerance of a Core-Shell-Structured Zeolite for CO2 Adsorptive Separation under Wet Conditions.

PubMed

Miyamoto, Manabu; Ono, Shumpei; Kusukami, Kodai; Oumi, Yasunori; Uemiya, Shigeyuki

2018-06-11

Dehumidification in CO 2 adsorptive separation processes is an important issue, owing to its high energy consumption. However, available adsorbents such as low-silica zeolites show a significant decrease in CO 2 adsorption capacity when water vapor is present. A core-shell-structured MFI-type zeolite with a hydrophilic ZSM-5 coated with a hydrophobic silicalite-1 shell layer was applied in CO 2 adsorptive separation under wet conditions. This hybrid material demonstrated remarkably high water tolerance with stable CO 2 adsorption performance without additional thermal treatment for regeneration, whereas a significant decrease in the CO 2 adsorption amount because of water vapor was observed on the parent ZSM-5. The core-shell structure of zeolites with high pore volumes, such as LTA or CHA, could also be suitable candidates for high CO 2 adsorption capacity and high water tolerance for practical applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sandwich Panels Evaluated With Ultrasonic Spectroscopy

NASA Technical Reports Server (NTRS)

Cosgriff, Laura M.

2004-01-01

Enhanced, lightweight material systems, such as 17-4PH stainless steel sandwich panels are being developed for use as fan blades and fan containment systems for next-generation engines. The bond strength between the core and face sheets is critical in maintaining the structural integrity of the sandwich structure. To improve the inspection and production of these systems, researchers at the NASA Glenn Research Center are using nondestructive evaluation (NDE) techniques, such as ultrasonic spectroscopy, to evaluate the brazing quality between the face plates and the metallic foam core. The capabilities and limitations of a swept-frequency approach to ultrasonic spectroscopy were evaluated with respect to these sandwich structures. This report discusses results from three regions of a sandwich panel representing different levels of brazing quality between the outer face plates and a metallic foam core. Each region was investigated with ultrasonic spectroscopy. Then, on the basis of the NDE results, three shear specimens sectioned from the sandwich panel to contain each of these regions were mechanically tested.

Characterization and modeling of an advanced flexible thermal protection material for space applications

NASA Technical Reports Server (NTRS)

Clayton, Joseph P.; Tinker, Michael L.

1991-01-01

This paper describes experimental and analytical characterization of a new flexible thermal protection material known as Tailorable Advanced Blanket Insulation (TABI). This material utilizes a three-dimensional ceramic fabric core structure and an insulation filler. TABI is the leading candidate for use in deployable aeroassisted vehicle designs. Such designs require extensive structural modeling, and the most significant in-plane material properties necessary for model development are measured and analytically verified in this study. Unique test methods are developed for damping measurements. Mathematical models are developed for verification of the experimental modulus and damping data, and finally, transverse properties are described in terms of the inplane properties through use of a 12-dof finite difference model of a simple TABI configuration.

Structural assessment of metal foam using combined NDE and FEA

NASA Astrophysics Data System (ADS)

Ghosn, Louis J.; Abdul-Aziz, Ali; Young, Philippe G.; Rauser, Richard W.

2005-05-01

Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a high fidelity finite element analysis is conducted on as fabricated metal foam microstructures, to compare the calculated mechanical properties with the idealized theory. The high fidelity geometric models for the FEA are generated using series of 2D CT scans of the foam structure to reconstruct the 3D metal foam geometry. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile, compressive, and shear mechanical properties are deduced from the FEA model and compared with the theoretical values. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

Micro-size antenna structure with vertical nanowires for wireless power transmission and communication.

PubMed

Kang, Jong-Gu; Jeong, Yeri; Shin, Jeong Hee; Choi, Ji-Woong; Sohn, Jung Inn; Cha, Seung Nam; Jang, Jae Eun

2014-11-01

For biomedical implanted devices, a wireless power or a signal transmission is essential to protect an infection and to enhance durability. In this study, we present a magnetic induction technique for a power transmission without any wire connection between transmitter (Tx) and receiver (Rx) in a micro scale. Due to a micro size effect of a flat spiral coil, a magnetic inductance is not high. To enhance the magnetic inductance, a three dimensional magnetic core is added to an antenna structure, which is consisted of ZnO nano wires coated by a nickel (Ni) layer. ZnO nano wires easily supply a large effective surface area with a vertical structural effect to the magnetic core structure, which induces a higher magnetic inductance with a ferro-magnetic material Ni. The magnetic induction antenna with the magnetic core shows a high inductance value, a low reflection power and a strong power transmission. The power transmission efficiencies are tested under the air and the water medium are almost the same values, so that the magnetic induction technique is quite proper to body implanted systems.

A flattened cloud core in NGC 2024

NASA Technical Reports Server (NTRS)

Ho, Paul T. P.; Peng, Yun-Lou; Torrelles, Jose M.; Gomez, Jose F.; Rodriguez, Luis F.; Canto, Jorge

1993-01-01

The (J, K) (1, 1) and (2, 2) NH3 lines were mapped toward a molecular cloud core in NGC 2024 using the VLA in its C/D-configuration. This region is associated with one of the most highly collimated molecular outflows. We find that the molecular condensations associated with the far-infrared sources FIR 5, FIR 6, and FIR 7 have kinetic temperatures of about 40 K. We also find line broadening toward FIR 6 and FIR 7. This suggests that these condensations may not be protostars heated by gravitational energy released during collapse but that they have an internal heating source. A flattened structure of ammonia emission is found extending parallel to the unipolar CO outflow structure, but displaced systematically to the east. If the NH3 emission traces the denser gas environment, there is no evidence that a dense gas structure is confining the molecular outflow. Instead, the location of the high-velocity outflow along the surface of the NH3 structure suggests that a wind is sweeping material from the surface of this elongated cloud core.

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.

Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

NASA Astrophysics Data System (ADS)

Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

2017-12-01

Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

Hierarchically Structured Electrospun Fibers

DTIC Science & Technology

2013-01-07

polymeric materials such as ceramics and metals, can be fabricated into nanofibers via electrospinning . An assortment of natural polymers, such as the...are traditionally made by electrospinning of the core material, which serves as a template for the deposition of the shell layer via chemical vapor...been made from the contraction of a manganese oxide sol gel upon solvent evaporation, as well as from zinc oxide and silicon dioxide using vapor

Zigzag‐Elongated Fused π‐Electronic Core: A Molecular Design Strategy to Maximize Charge‐Carrier Mobility

PubMed Central

Yamamoto, Akito; Murata, Yoshinori; Mitsui, Chikahiko; Yamagishi, Masakazu; Yano, Masafumi; Sato, Hiroyasu; Yamano, Akihito; Takeya, Jun

2017-01-01

Abstract Printed and flexible electronics requires solution‐processable organic semiconductors with a carrier mobility (μ) of ≈10 cm2 V−1 s−1 as well as high chemical and thermal durability. In this study, chryseno[2,1‐b:8,7‐b′]dithiophene (ChDT) and its derivatives, which have a zigzag‐elongated fused π‐electronic core (π‐core) and a peculiar highest occupied molecular orbital (HOMO) configuration, are reported as materials with conceptually new semiconducting π‐cores. ChDT and its derivatives are prepared by a versatile synthetic procedure. A comprehensive investigation reveals that the ChDT π‐core exhibits increasing structural stability in the bulk crystal phase, and that it is unaffected by a variation of the transfer integral, induced by the perpetual molecular motion of organic materials owing to the combination of its molecular shape and its particular HOMO configuration. Notably, ChDT derivatives exhibit excellent chemical and thermal stability, high charge‐carrier mobility under ambient conditions (μ ≤ 10 cm2 V−1 s−1), and a crystal phase that is highly stable, even at temperatures above 250 °C. PMID:29375963

Linear complexions: Confined chemical and structural states at dislocations.

PubMed

Kuzmina, M; Herbig, M; Ponge, D; Sandlöbes, S; Raabe, D

2015-09-04

For 5000 years, metals have been mankind's most essential materials owing to their ductility and strength. Linear defects called dislocations carry atomic shear steps, enabling their formability. We report chemical and structural states confined at dislocations. In a body-centered cubic Fe-9 atomic percent Mn alloy, we found Mn segregation at dislocation cores during heating, followed by formation of face-centered cubic regions but no further growth. The regions are in equilibrium with the matrix and remain confined to the dislocation cores with coherent interfaces. The phenomenon resembles interface-stabilized structural states called complexions. A cubic meter of strained alloy contains up to a light year of dislocation length, suggesting that linear complexions could provide opportunities to nanostructure alloys via segregation and confined structural states. Copyright © 2015, American Association for the Advancement of Science.

TiO2/ZnO and ZnO/TiO2 core/shell nanofibers prepared by electrospinning and atomic layer deposition for photocatalysis and gas sensing

NASA Astrophysics Data System (ADS)

Boyadjiev, Stefan I.; Kéri, Orsolya; Bárdos, Péter; Firkala, Tamás; Gáber, Fanni; Nagy, Zsombor K.; Baji, Zsófia; Takács, Máté; Szilágyi, Imre M.

2017-12-01

In the present work, core TiO2 and ZnO oxide nanofibers were prepared by electrospinning, then shell oxide (ZnO, TiO2) layers were deposited on them by atomic layer deposition (ALD). The aim of preparing ZnO and TiO2 nanofibers, as well as ZnO/TiO2 and TiO2/ZnO nanocomposites is to study the interaction between the oxide materials when a pure oxide fiber is covered with thin film of the other oxide, and explore the influence of exchanging the core and shell materials on their photocatalytic and gas sensing properties. The composition, structure and morphology of the pure and composite nanofibers were studied by SEM-EDX, TEM, XRD, FTIR, UV-vis and Raman. The photocatalytic activity of the as-prepared materials was analyzed by UV-vis spectroscopy through decomposing aqueous methyl orange under UV irradiation. The gas sensing of the nanofibers was investigated by detecting 100 ppm NH3 at 150 and 220 °C using interdigital electrode based sensors.

Light weight fire resistant graphite composites

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A.; Hsu, M. T. S.

1986-01-01

Composite structures with a honeycomb core and characterized by lightweight and excellent fire resistance are provided. These sandwich structures employ facesheets made up of bismaleimide-vinyl styrylpyridine copolymers with fiber reinforcement such as carbon fiber reinforcement. In preferred embodiments the facesheets are over layered with a decorative film. The properties of these composites make them attractive materials of construction aircraft and spacecraft.

A Best Practice Modular Design of a Hybrid Course Delivery Structure for an Executive Education Program

ERIC Educational Resources Information Center

Klotz, Dorothy E.; Wright, Thomas A.

2017-01-01

This article highlights a best practice approach that showcases the highly successful deployment of a hybrid course delivery structure for an Operations core course in an Executive MBA Program. A key design element of the approach was the modular design of both the course itself and the learning materials. While other hybrid deployments may stress…

Theoretical study on the optical response behavior to hydrogen chloride gas of a series of Schiff-base-based star-shaped structures.

PubMed

Wang, Fei; Qi, Tianhong; Su, Zhongmin; Xie, Yuzhong

2018-02-17

Schiff-base compounds have many applications in the field of optoelectronic materials and chemical sensing because of their appealing coordination ability, and simple and easily accessible use in structural modification. Herein, five kinds of star-shaped Schiff-base compounds were designed and their optical response behavior to hydrogen chloride (HCl) gas was studied using dependent/time-dependent density functional theory (DFT/TDDFT). Moreover, the relationship between structures and properties was investigated upon changing the benzene group into N atom or triazine group at the core-position and introducing a methoxyl (-OCH 3 ) or nitro (-NO 2 ) group into the star-shaped Schiff-bases at the tail of the branches. The results show that all five Schiff-bases could be candidates for HCl gas sensing materials. Furthermore, introducing an electron-donating group at either the core or the tail forms a charge transfer channel with the electron deficient H-bonded imino group, which is convenient for charge transfer and subsequently promotes a red-shift in absorption spectra and fluorescence quenching.

The foamed structures in numerical testing

NASA Astrophysics Data System (ADS)

John, Antoni; John, Małgorzata

2018-01-01

In the paper numerical simulation of the foamed metal structures using numerical homogenization algorithm is prescribed. From the beginning, numerical model of heterogeneous porous simplified structures of typical foamed metal, based on the FEM was built and material parameters (coefficients of elasticity matrix of the considered structure) were determined with use of numerical homogenization algorithm. During the work the different RVE models of structure were created and their properties were compared at different relative density, different numbers and the size and structure of the arrangement of voids. Finally, obtained results were used in modeling of typical elements made from foam metals structures - sandwich structure and profile filled with metal foam. Simulation were performed for different dimensions of cladding and core. Additionally, the test of influence material orientation (arrangement of voids in RVE element) on the maximum stresses and displacement during bending test was performed.

Mode I Toughness Measurements of Core/Facesheet Bonds in Honeycomb Sandwich Structures

NASA Technical Reports Server (NTRS)

Nettles, Alan T.; Ratcliffe, James G.

2006-01-01

Composite sandwich structures will be used in many future applications in aerospace, marine and offshore industries due to the fact that the strength and stiffness to mass ratios surpass any other structural type. Sandwich structure also offers advantages over traditional stiffened panels such as ease of manufacturing and repair. During the last three decades, sandwich structure has been used extensively for secondary structure in aircraft (fuselage floors, rudders and radome structure). Sandwich structure is also used as primary structure in rotorcraft, the most common example being the trailing edge of rotor blades. As with other types of composite construction, sandwich structure exhibits several types of failure mode such as facesheet wrinkling, core crushing and sandwich buckling. Facesheet/core debonding has also been observed in the marine and aerospace industry. During this failure mode, peel stresses applied to an existing facesheet/core debond or an interface low in toughness, results in the facesheet being peeled from the core material, possibly leading to a significant loss in structural integrity of the sandwich panel. In an incident during a test on a liquid hydrogen fuel tank of the X-33 prototype vehicle, the outer graphite/epoxy facesheet and honeycomb core became debonded from the inner facesheet along significant areas, leading to failure of the tank. As a consequence of the accident; significant efforts were made to characterize the toughness of the facesheet/core bond. Currently, the only standardized method available for assessing the quality of the facesheet/core interface is the climbing drum peel test (ASTM D1781). During this test a sandwich beam is removed from a panel and the lip of one of the facesheets is attached to a drum, as shown in Fig. 1. The drum is then rotated along the sandwich beam, causing the facesheet to peel from the core. This method has two major drawbacks. First, it is not possible to obtain quantitative fracture data from the test and so the results can only be used in a qualitative manner. Second, only sandwich structure with thin facesheets can be tested (to facilitate wrapping of the facesheet around the climbing drum). In recognition of the need for a more quantitative facesheet/core fracture test, several workers have devised experimental techniques for characterizing the toughness of the facesheet/core interface. In all of these cases, the tests are designed to yield a mode I-dominated fracture toughness of the facesheet/core interface in a manner similar to that used to determine mode I fracture toughness of composite laminates. In the current work, a modified double cantilever beam is used to measure the mode I-dominated fracture toughness of the interface in a sandwich consisting of glass/phenolic honeycomb core reinforced with graphite epoxy facesheets. Two specimen configurations were tested as shown in Fig 2. The first configuration consisted of reinforcing the facesheets with aluminum blocks (Fig. 2a). In the second configuration unreinforced specimens were tested (Fig. 2b). Climbing drum peel tests were also conducted to compare the fracture behavior observed between this test and the modified double cantilever beam. This paper outlines the test procedures and data reduction strategies used to compute fracture toughness values from the tests. The effect of specimen reinforcement on fracture toughness of the facesheet/core interface is discussed.

Microstructure-based hyperelastic models for closed-cell solids

PubMed Central

Wyatt, Hayley

2017-01-01

For cellular bodies involving large elastic deformations, mesoscopic continuum models that take into account the interplay between the geometry and the microstructural responses of the constituents are developed, analysed and compared with finite-element simulations of cellular structures with different architecture. For these models, constitutive restrictions for the physical plausibility of the material responses are established, and global descriptors such as nonlinear elastic and shear moduli and Poisson’s ratio are obtained from the material characteristics of the constituents. Numerical results show that these models capture well the mechanical responses of finite-element simulations for three-dimensional periodic structures of neo-Hookean material with closed cells under large tension. In particular, the mesoscopic models predict the macroscopic stiffening of the structure when the stiffness of the cell-core increases. PMID:28484340

Microstructure-based hyperelastic models for closed-cell solids.

PubMed

Mihai, L Angela; Wyatt, Hayley; Goriely, Alain

2017-04-01

For cellular bodies involving large elastic deformations, mesoscopic continuum models that take into account the interplay between the geometry and the microstructural responses of the constituents are developed, analysed and compared with finite-element simulations of cellular structures with different architecture. For these models, constitutive restrictions for the physical plausibility of the material responses are established, and global descriptors such as nonlinear elastic and shear moduli and Poisson's ratio are obtained from the material characteristics of the constituents. Numerical results show that these models capture well the mechanical responses of finite-element simulations for three-dimensional periodic structures of neo-Hookean material with closed cells under large tension. In particular, the mesoscopic models predict the macroscopic stiffening of the structure when the stiffness of the cell-core increases.

Microstructure-based hyperelastic models for closed-cell solids

NASA Astrophysics Data System (ADS)

Mihai, L. Angela; Wyatt, Hayley; Goriely, Alain

2017-04-01

For cellular bodies involving large elastic deformations, mesoscopic continuum models that take into account the interplay between the geometry and the microstructural responses of the constituents are developed, analysed and compared with finite-element simulations of cellular structures with different architecture. For these models, constitutive restrictions for the physical plausibility of the material responses are established, and global descriptors such as nonlinear elastic and shear moduli and Poisson's ratio are obtained from the material characteristics of the constituents. Numerical results show that these models capture well the mechanical responses of finite-element simulations for three-dimensional periodic structures of neo-Hookean material with closed cells under large tension. In particular, the mesoscopic models predict the macroscopic stiffening of the structure when the stiffness of the cell-core increases.

Dynamics of Metamorphic Core Complexes Inferred From Modeling and Metamorphic Petrology

NASA Astrophysics Data System (ADS)

Whitney, D. L.; Rey, P.; Teyssier, C.

2008-12-01

Orogenic collapse involves extension and thinning of thick, hot, and in some cases partially molten, crust, leading to the formation of metamorphic core complexes (MCC) that are commonly cored by migmatite domes. 2D numerical modeling predicts that the geometry and P-T-t history of MCC varies as a function of the presence/absence of a partially molten layer in the deep crust; the nature of heterogeneities that localize the MCC (e.g. normal fault in upper crust vs. point-like anomaly in the deep crust); and extensional strain rate. The presence of melt in particular has a significant effect on the thermal and structural history of MCC because the presence of partially molten crust or magma bodies at depth enhances upward advection of material and heat. At high extension rate (cm/year in the region of the MCC), partially molten crust crystallizes as migmatite and cools along a high geothermal gradient (35-65 C/km); material remains partially molten during ascent, forming a migmatite dome when it crystallizes at shallower crustal levels (e.g. cordierite/sillimanite stability field). At low strain rate (mm/yr in the MCC region), the partially molten crust crystallizes at high pressure (e.g. kyanite zone); this material is subsequently deformed in the solid-state along a cooler geothermal gradient (20-35 C/km) during ascent. MCC that develop during extension of partially molten crust may therefore record distinct crystallization versus exhumation histories as a function of extensional strain rate. The mineral assemblages, metamorphic reaction histories, and structures of migmatite-cored (Mc) MCC can therefore be used to interpret the dynamics of MCC formation, e.g. "fast" McMCC in the northern N American Cordillera and Aegean regions.

Structure factor of blends of solvent-free nanoparticle-organic hybrid materials: density-functional theory and small angle X-ray scattering.

PubMed

Yu, Hsiu-Yu; Srivastava, Samanvaya; Archer, Lynden A; Koch, Donald L

2014-12-07

We investigate the static structure factor S(q) of solvent-free nanoparticle-organic hybrid materials consisting of silica nanocores and space-filling polyethylene glycol coronas using a density-functional theory and small angle X-ray scattering measurements. The theory considers a bidisperse suspension of hard spheres with different radii and tethered bead-spring oligomers with different grafting densities to approximate the polydispersity effects in experiments. The experimental systems studied include pure samples with different silica core volume fractions and the associated mean corona grafting densities, and blends with different mixing ratios of the pure samples, in order to introduce varying polydispersity of corona grafting density. Our scattering experiments and theory show that, compared to the hard-sphere suspension with the same core volume fraction, S(q) for pure samples exhibit both substantially smaller values at small q and stronger particle correlations corresponding to a larger effective hard core at large q, indicating that the tethered incompressible oligomers enforce a more uniform particle distribution, and the densely grafted brush gives rise to an additional exclusionary effect between the nanoparticles. According to the theory, polydispersity in the oligomer grafting density controls the deviation of S(q) from the monodisperse system at smaller q, and the interplay of the enhanced effective core size and the entropic attraction among the particles is responsible for complex variations in the particle correlations at larger q. The successful comparison between the predictions and the measurements for the blends further suggests that S(q) can be used to assess the uniformity of grafting density in polymer-grafted nanoparticle materials.

Eco-friendly synthesis of core-shell structured (TiO2/Li2CO3) nanomaterials for low cost dye-sensitized solar cells.

PubMed

Karuppuchamy, S; Brundha, C

2016-12-01

Core-shell structured TiO 2 /Li 2 CO 3 electrode was successfully synthesized by eco-friendly solution growth technique. TiO 2 /Li 2 CO 3 electrodes were characterized using X-ray Diffractometer (XRD), Scanning electron microscopy (SEM) and photocurrent-voltage measurements. The synthesized core-shell electrode material was sensitized with tetrabutylammonium cis-di(thiocyanato)-N,N'-bis(4-carboxylato-4'-carboxylic acid-2,2'-bipyridine)ruthenate(II) (N-719). The performance of dye-sensitized solar cells (DSCs) based on N719 dye modified TiO 2 /Li 2 CO 3 electrodes was investigated. The effect of various shell thickness on the photovoltaic performance of the core-shell structured electrode is also investigated. We found that Li 2 CO 3 shells of all thicknesses perform as inert barriers which improve open-circuit voltage (V oc ) of the DSCs. The energy conversion efficiency was greatly dependent on the thickness of Li 2 CO 3 on TiO 2 film, and the highest efficiency of 3.7% was achieved at the optimum Li 2 CO 3 shell layer. Copyright © 2015 Elsevier Inc. All rights reserved.

Us army corps of engineers - Engineering research and development center - Petrographic analysis of section 3 personnel tunnel concrete

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

Carter, J. M.

The Concrete and Materials Branch (CMB) of the Geotechnical and Structures Laboratory was requested to perform an analysis on concrete cores collected from the north and south walls of the H-Canyon Section 3 Personnel Tunel, Savannah River Site, Aiken, South Carolina to determine the cause of the lower than expected compressive strength. This study examined five cores provided to the ERDC by the Department of Energy. The cores were logged in as CMB No. 170051-1 to 170051-5 and subjected to petrographic examination, air void analysis, chemical sprays, scanning electron microscopy, and x-ray diffraction.

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.

Effect of Different Concentration of Sodium Hydroxide [NaOH] on Kenaf Sandwich Structures

NASA Astrophysics Data System (ADS)

Aziz, M.; Halim, Z.; Othman, M.

2018-01-01

Sandwich panels are structures that made of three layers, low-density core inserted in between thin skin layers. This structures allow the achievement of excellent mechanical performance with low weight, thus this characteristic fulfil requirement to be use in aircraft application. In recent time, sandwich structures have been studied due to it has multifunction properties and lightweight. The aim of this study is to fabricate a composite sandwich structures with biodegradable material for face sheet [skin] where the fibre being treat with different concentration of sodium hydroxide [NaOH] with 10 and 20 hours of soaking time. Kenaf fibre [treated] reinforced epoxy will be used as skins and Nomex honeycomb is chosen to perform as core for this sandwich composite structure. The mechanical properties that are evaluated such as flexural strength and impact energy of kenaf fibre-reinforced epoxy sandwich structures. For flexural test, the optimum flexural strength is 13.4 MPa and impact strength is 18.3 J.

Development of Modified Titanium Nitride Nanoparticles as Potential Contrast Material for Photoacoustic Imaging

DTIC Science & Technology

2014-05-10

based on modified fullerenes , carbon nanotubes and gold nanoparticles (including nanocages and nanorods) were very recently reported.4 Nevertheless, this...ratios of 1:1.6 and 1:16, in order to form an onion- like core-shell structure, containing TiN core and shells of TPP (inner shell) and chitosan (outer...These results nicely correlate with the cells viability results and the formation of the ROS is most likely the cause of the cells death (Figure 24

Synthesis and properties of nickel cobalt boron nanoparticles

NASA Astrophysics Data System (ADS)

Patel, J.; Pankhurst, Q. A.; Parkin, I. P.

2005-01-01

Amorphous cobalt nickel boride nanoparticles were synthesised by chemical reduction synthesis in aqueous solution. Careful control of synthesis conditions and post reaction oxidation enabled the nanoparticles to be converted into a core-shell structure comprising of an amorphous Co-Ni-B core and an outer metal oxide sheet. These particles had interesting magnetic properties including saturation magnetisations and coercivities of the order of 80 emu/g and 170 Oe respectively, making them suitable for a potential use as an exchange-pinned magnetic material.

Terminal structure

DOEpatents

Schmidt, Frank [Langenhagen, DE; Allais, Arnaud [Hannover, DE; Mirebeau, Pierre [Villebon sur Yvette, FR; Ganhungu, Francois [Vieux-Reng, FR; Lallouet, Nicolas [Saint Martin Boulogne, FR

2009-10-20

A terminal structure (2) for a superconducting cable (1) is described. It consists of a conductor (2a) and an insulator (2b) that surrounds the conductor (2a), wherein the superconducting cable (1) has a core with a superconducting conductor (5) and a layer of insulation that surrounds the conductor (5), and wherein the core is arranged in such a way that it can move longitudinally in a cryostat. The conductor (2a) of the terminal structure (2) is electrically connected with the superconducting conductor (5) or with a normal conductor (6) that is connected with the superconducting conductor (5) by means of a tubular part (7) made of an electrically conductive material, wherein the superconducting conductor (5) or the normal conductor (6) can slide in the part (7) in the direction of the superconductor.

Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

NASA Astrophysics Data System (ADS)

Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

2016-05-01

Silica/polyaniline (PANI) core-shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core-shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

Efficient implementation of core-excitation Bethe-Salpeter equation calculations

NASA Astrophysics Data System (ADS)

Gilmore, K.; Vinson, John; Shirley, E. L.; Prendergast, D.; Pemmaraju, C. D.; Kas, J. J.; Vila, F. D.; Rehr, J. J.

2015-12-01

We present an efficient implementation of the Bethe-Salpeter equation (BSE) method for obtaining core-level spectra including X-ray absorption (XAS), X-ray emission (XES), and both resonant and non-resonant inelastic X-ray scattering spectra (N/RIXS). Calculations are based on density functional theory (DFT) electronic structures generated either by ABINIT or QuantumESPRESSO, both plane-wave basis, pseudopotential codes. This electronic structure is improved through the inclusion of a GW self energy. The projector augmented wave technique is used to evaluate transition matrix elements between core-level and band states. Final two-particle scattering states are obtained with the NIST core-level BSE solver (NBSE). We have previously reported this implementation, which we refer to as OCEAN (Obtaining Core Excitations from Ab initio electronic structure and NBSE) (Vinson et al., 2011). Here, we present additional efficiencies that enable us to evaluate spectra for systems ten times larger than previously possible; containing up to a few thousand electrons. These improvements include the implementation of optimal basis functions that reduce the cost of the initial DFT calculations, more complete parallelization of the screening calculation and of the action of the BSE Hamiltonian, and various memory reductions. Scaling is demonstrated on supercells of SrTiO3 and example spectra for the organic light emitting molecule Tris-(8-hydroxyquinoline)aluminum (Alq3) are presented. The ability to perform large-scale spectral calculations is particularly advantageous for investigating dilute or non-periodic systems such as doped materials, amorphous systems, or complex nano-structures.

Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition

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

Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Pizá-Ruiz, P.

2015-07-15

Core–shell nanorod structures were prepared by a sequential synthesis using an aerosol assisted chemical vapor deposition technique. Several samples consisting of ZnO nanorods were initially grown over TiO{sub 2} film-coated borosilicate glass substrates, following the synthesis conditions reported elsewhere. Later on, a uniform layer consisting of individual Al, Ni, Ti or Fe oxides was grown onto ZnO nanorod samples forming the so-called single MO{sub x}/ZnO nanorod core–shell structures, where MO{sub x} was the metal oxide shell. Additionally, a three-layer core–shell sample was developed by growing Fe, Ti and Fe oxides alternately, onto the ZnO nanorods. The microstructure of the core–shellmore » materials was characterized by grazing incidence X-ray diffraction, scanning and transmission electron microscopy. Energy dispersive X-ray spectroscopy was employed to corroborate the formation of different metal oxides. X-ray diffraction outcomes for single core–shell structures showed solely the presence of ZnO as wurtzite and TiO{sub 2} as anatase. For the multi-layered shell sample, the existence of Fe{sub 2}O{sub 3} as hematite was also detected. Morphological observations suggested the existence of an outer material grown onto the nanorods and further microstructural analysis by HR-STEM confirmed the development of core–shell structures in all cases. These studies also showed that the individual Al, Fe, Ni and Ti oxide layers are amorphous; an observation that matched with X-ray diffraction analysis where no apparent extra oxides were detected. For the multi-layered sample, the development of a shell consisting of three different oxide layers onto the nanorods was found. Overall results showed that no alteration in the primary ZnO core was produced during the growth of the shells, indicating that the deposition technique used herein was and it is suitable for the synthesis of homogeneous and complex nanomaterials high in quality and purity. In addition, materials absorptance determined from the total transmittance and reflectance spectra revealed a broader absorption interval including visible light, indicating potential uses of these nanostructures on solar energy appliances. - Graphical abstract: Display Omitted - Highlights: • Uniform ZnO nanorods (core)–metal oxide (shell) were obtained sequentially by AACVD. • Shells were structured of homogeneous single or multi-layered non-mixed metal oxides. • ZnO nanorod core was preserved during the shell synthesis. • Optical absorptance revealed visible interval absorption for FeO{sub x} shell samples. • Materials can be suitable for photocatalytic or photovoltaic applications.« less

Effect of an adhesive resin luting agent on the dowel-head retention of three different core materials.

PubMed

Aksoy, Gokhan; Cotert, H Serdar; Korkut, Levent

2005-05-01

A dowel-and-core restoration may fail due to failure at either the dowel-tooth or dowel head-core material interface. Long-term clinical success of a dowel-and-core restoration depends on retention of both the dowel to the tooth and the dowel head to the core material. Thus, strengthening of the dowel head-core interface is important. This study evaluated the retention between a prefabricated dowel and 3 different core materials with or without a dual-polymerized adhesive resin luting agent. Sixty prefabricated dowels (Gold Plated Anchorage Post) were divided into 3 groups (n=20) consisting of 1 of 3 core materials, amalgam (Standalloy F), light-polymerized resin composite (Clearfil Ray), or glass ionomer (Chelon-Silver). Each core group was divided into 2 subgroups (n=10), and a dual-polymerized adhesive resin luting agent (Panavia F) was applied to the dowel heads of 1 of these subgroups before application of the core material. The manufacturing procedure was standardized by using a plastic index (4.5-mm internal diameter and 5-mm height) and a custom-made dowel holder, which held the dowel head. Prepared specimens were stored in water at room temperature for 3 months and then loaded to fracture in a universal testing machine with a crosshead speed of 0.05 mm/min until failure. Bond strengths were recorded (MPa). Data were analyzed with 2-way analysis of variance (ANOVA) in a 2 x 3 factorial randomized design (alpha=.05). Afterward, core material differences were computed with 1-way ANOVA for both of the bonded and nonbonded groups. Post hoc multiple comparisons were made with the Dunnett C multiple range test. Dowel-head retention values (MPa) of the tested core materials (mean +/- SD) from the highest to the lowest were as follows: bonded amalgam core, 296.1 +/- 108; bonded composite core, 284.3 +/- 38.3; nonbonded composite core, 177.0 +/- 53.7; nonbonded amalgam core, 128.5 +/- 35.0; bonded glass-ionomer core (GIC), 128.0 +/- 24.5; nonbonded GIC, 61.8 +/- 13.3. Two-way ANOVA revealed significant differences between the core material groups and between the bonded and nonbonded groups (P <.001). The interaction between the core material and bond variables was also significant (P =.018). One-way ANOVA revealed statistically significant differences between the bonded (P <.001) and also between the nonbonded core material groups (P <.001). Post hoc multiple comparisons showed that the dowel-head retention of the GIC was significantly weaker than the post-head retention for amalgam and resin composite, whether bonded or not. Within the limitations of this study, the adhesive resin luting agent tested appeared to have a significant strengthening effect on the dowel-head retention of the core materials.

He-Ion Microscopy as a High-Resolution Probe for Complex Quantum Heterostructures in Core-Shell Nanowires.

PubMed

Pöpsel, Christian; Becker, Jonathan; Jeon, Nari; Döblinger, Markus; Stettner, Thomas; Gottschalk, Yeanitza Trujillo; Loitsch, Bernhard; Matich, Sonja; Altzschner, Marcus; Holleitner, Alexander W; Finley, Jonathan J; Lauhon, Lincoln J; Koblmüller, Gregor

2018-06-13

Core-shell semiconductor nanowires (NW) with internal quantum heterostructures are amongst the most complex nanostructured materials to be explored for assessing the ultimate capabilities of diverse ultrahigh-resolution imaging techniques. To probe the structure and composition of these materials in their native environment with minimal damage and sample preparation calls for high-resolution electron or ion microscopy methods, which have not yet been tested on such classes of ultrasmall quantum nanostructures. Here, we demonstrate that scanning helium ion microscopy (SHeIM) provides a powerful and straightforward method to map quantum heterostructures embedded in complex III-V semiconductor NWs with unique material contrast at ∼1 nm resolution. By probing the cross sections of GaAs-Al(Ga)As core-shell NWs with coaxial GaAs quantum wells as well as short-period GaAs/AlAs superlattice (SL) structures in the shell, the Al-rich and Ga-rich layers are accurately discriminated by their image contrast in excellent agreement with correlated, yet destructive, scanning transmission electron microscopy and atom probe tomography analysis. Most interestingly, quantitative He-ion dose-dependent SHeIM analysis of the ternary AlGaAs shell layers and of compositionally nonuniform GaAs/AlAs SLs reveals distinct alloy composition fluctuations in the form of Al-rich clusters with size distributions between ∼1-10 nm. In the GaAs/AlAs SLs the alloy clustering vanishes with increasing SL-period (>5 nm-GaAs/4 nm-AlAs), providing insights into critical size dimensions for atomic intermixing effects in short-period SLs within a NW geometry. The straightforward SHeIM technique therefore provides unique benefits in imaging the tiniest nanoscale features in topography, structure and composition of a multitude of diverse complex semiconductor nanostructures.

Tunable Free-Standing Core-Shell CNT@MoSe2 Anode for Lithium Storage.

PubMed

Yousaf, Muhammad; Wang, Yunsong; Chen, Yijun; Wang, Zhipeng; Aftab, Waseem; Mahmood, Asif; Wang, Wei; Guo, Shaojun; Han, Ray P S

2018-05-02

Heterogeneous nanostructuring of MoSe 2 over a carbon nanotube (CNT) sponge as a free-standing electrode not only brings higher performance but also eliminates the need for dead elements such as a binder, conductive carbon, and supportive current collectors. Further, the porous CNT sponge can be easily compacted via an intense densification of the active material MoSe 2 to produce an electrode with a high mass loading for a significantly improved areal capacity. In this work, we present a tunable coating of MoSe 2 on a CNT sponge to fabricate a core-shell MoSe 2 @CNT anode. The three-dimensional nanotubular sponge is synthesized via a solvothermal process, followed by thermal annealing to improve crystallization. Structural and morphological studies revealed that MoSe 2 grew as a layered structure ( d = 0.66 nm), where numbers of layers can be controlled to yield optimized results for Li + storage. We showed that the 10-layer core-shell CNT@MoSe 2 hybrid sponge delivered a discharge capacity of 820.5 mAh g -1 after 100 cycles at 100 mA g -1 with a high cyclic stability and rate capability. Further, an ex situ structural and morphological analysis revealed that ionic storage causes a phase change in MoSe 2 from a crystalline to a partial amorphous state for a continuous increase in the capacity with extended cycling. We believe that the strategy developed here will assist users to tune the electrode materials for future energy-storage devices, especially how the materials are changing with the passage of time and their effects on the device performance.

Direct Determination of Atomic Structure and Magnetic Coupling of Magnetite Twin Boundaries.

PubMed

Chen, Chunlin; Li, Hongping; Seki, Takehito; Yin, Deqiang; Sanchez-Santolino, Gabriel; Inoue, Kazutoshi; Shibata, Naoya; Ikuhara, Yuichi

2018-03-27

Clarifying how the atomic structure of interfaces/boundaries in materials affects the magnetic coupling nature across them is of significant academic value and will facilitate the development of state-of-the-art magnetic devices. Here, by combining atomic-resolution transmission electron microscopy, atomistic spin-polarized first-principles calculations, and differential phase contrast imaging, we conduct a systematic investigation of the atomic and electronic structures of individual Fe 3 O 4 twin boundaries (TBs) and determine their concomitant magnetic couplings. We demonstrate that the magnetic coupling across the Fe 3 O 4 TBs can be either antiferromagnetic or ferromagnetic, which directly depends on the TB atomic core structures and resultant electronic structures within a few atomic layers. Revealing the one-to-one correspondence between local atomic structures and magnetic properties of individual grain boundaries will shed light on in-depth understanding of many interesting magnetic behaviors of widely used polycrystalline magnetic materials, which will surely promote the development of advanced magnetic materials and devices.

Enhanced exchange bias and improved ferromagnetic properties in Permalloy–BiFe0.95Co0.05O3 core–shell nanostructures

PubMed Central

Javed, K.; Li, W. J.; Ali, S. S.; Shi, D. W.; Khan, U.; Riaz, S.; Han, X. F.

2015-01-01

Hybrid core–shell nanostructures consisting of permalloy (Ni80Fe20) and multiferroic(BiFeO3, BFO/BiFe0.95Co0.05O3, BFC) materials were synthesized by a two-step method, based on wet chemical impregnation and subsequent electrodeposition within porous alumina membranes. Structural and magnetic characterizations have been done to investigate doping effect on magnetic properties and exchange bias. The magnetometry analysis revealed significant enhancements of the exchange bias and coercivity in NiFe-BFC core-shell nanostructures as compared with NiFe-BFO core-shell nanostructures. The enhancements can be attributed to the effective reduction of ferromagnet domain sizes between adjacent layers of core-shell structure. It indicates that it is possible to improve properties of multiferroic composites by site-engineering method. Our approach opens a pathway to obtain optimized nanostructured multiferroic composites exhibiting tunable magnetic properties. PMID:26658956

Highly birefringent elliptical core photonic crystal fiber for terahertz application

NASA Astrophysics Data System (ADS)

Sultana, Jakeya; Islam, Md. Saiful; Faisal, Mohammad; Islam, Mohammad Rakibul; Ng, Brian W.-H.; Ebendorff-Heidepriem, Heike; Abbott, Derek

2018-01-01

We present a novel strategy for designing a highly birefringent photonic crystal fiber (PCF) with near zero flattened dispersion properties by applying elliptical air holes in the core area. The elliptical structure of the air holes in the porous-core region introduces asymmetry between x and y polarization modes, which consequently offers ultra-high birefringence. Also the compact geometry of the conventional hexagonal structure in the cladding confines most of the useful power. The optical properties including birefringence, dispersion, confinement loss, effective material loss (EML) and single modeness of the fiber are investigated using a full-vector finite element method. Simulation results show an ultra-high birefringence of 0 . 086 ultra-flattened near zero dispersion of 0 . 53 ± 0 . 07 ps/THz/cm in a broad frequency range. The practical implementation of the proposed fiber is feasible using existing fabrication technology and is applicable to the areas of terahertz sensing and polarization maintaining systems.

Composite sandwich structure and method for making same

NASA Technical Reports Server (NTRS)

Magurany, Charles J. (Inventor)

1995-01-01

A core for a sandwich structure which has multi-ply laminate ribs separated by voids is made as an integral unit in one single curing step. Tooling blocks corresponding to the voids are first wrapped by strips of prepreg layup equal to one half of each rib laminate so a continuous wall of prepreg material is formed around the tooling blocks. The wrapped tooling blocks are next pressed together laterally, like tiles, so adjoining walls from two tooling blocks are joined. The assembly is then cured by conventional methods, and afterwards the tooling blocks are removed so voids are formed. The ribs can be provided with integral tabs forming bonding areas for face sheets, and face sheets may be co-cured with the core ribs. The new core design is suitable for discrete ribcores used in space telescopes and reflector panels, where quasiisotropic properties and zero coefficient of thermal expansion are required.

Nanoparticles of CdI 2 with closed cage structures obtained via electron-beam irradiation

NASA Astrophysics Data System (ADS)

Sallacan, N.; Popovitz-Biro, R.; Tenne, R.

2003-06-01

Nanoparticles of various layered compounds were shown to form closed cage or nanotubular structures, which were designated as inorganic fullerene-like ( IF) materials. In particular, closed cage structures and nanotubes were synthesized from NiCl 2 and CdCl 2 in the past. In the present work IF-CdI 2 nanoparticles were synthesized by electron-beam irradiation of the source powder leading to evaporation and subsequent recrystallization into closed nanoparticles with a non-hollow core. This process created polyhedral nanoparticles with hexagonal or elongated rectangular characters. Consistent with previous observations, this study shows that the seamless structure of the IF materials can stabilize phases, which are otherwise unstable under the electron-beam irradiation.

An Efficient Analysis Methodology for Fluted-Core Composite Structures

NASA Technical Reports Server (NTRS)

Oremont, Leonard; Schultz, Marc R.

2012-01-01

The primary loading condition in launch-vehicle barrel sections is axial compression, and it is therefore important to understand the compression behavior of any structures, structural concepts, and materials considered in launch-vehicle designs. This understanding will necessarily come from a combination of test and analysis. However, certain potentially beneficial structures and structural concepts do not lend themselves to commonly used simplified analysis methods, and therefore innovative analysis methodologies must be developed if these structures and structural concepts are to be considered. This paper discusses such an analysis technique for the fluted-core sandwich composite structural concept. The presented technique is based on commercially available finite-element codes, and uses shell elements to capture behavior that would normally require solid elements to capture the detailed mechanical response of the structure. The shell thicknesses and offsets using this analysis technique are parameterized, and the parameters are adjusted through a heuristic procedure until this model matches the mechanical behavior of a more detailed shell-and-solid model. Additionally, the detailed shell-and-solid model can be strategically placed in a larger, global shell-only model to capture important local behavior. Comparisons between shell-only models, experiments, and more detailed shell-and-solid models show excellent agreement. The discussed analysis methodology, though only discussed in the context of fluted-core composites, is widely applicable to other concepts.

Growth of GaN@InGaN Core-Shell and Au-GaN Hybrid Nanostructures for Energy Applications

DOE PAGES

Kuykendall, Tevye; Aloni, Shaul; Jen-La Plante, Ilan; ...

2009-01-01

We demonstrated a method to control the bandgap energy of GaN nanowires by forming GaN@InGaN core-shell hybrid structures using metal organic chemical vapor deposition (MOCVD). Furthermore, we show the growth of Au nanoparticles on the surface of GaN nanowires in solution at room temperature. The work shown here is a first step toward engineering properties that are crucial for the rational design and synthesis of a new class of photocatalytic materials. The hybrid structures were characterized by various techniques, including photoluminescence (PL), energy dispersive x-ray spectroscopy (EDS), transmission and scanning electron microscopy (TEM and SEM), and x-ray diffraction (XRD).

Fabrication of a magnetic helical mesostructured silica rod

NASA Astrophysics Data System (ADS)

Zhang, Lei; Zhang Qiao, Shi; Cheng, Lina; Yan, Zifeng; Qing Lu, Gao Max

2008-10-01

We report a one-step synthesis of magnetic helical mesostructured silica (MHMS) by self-assembly of an achiral surfactant, magnetic nanocrystals with stearic acid ligands and silicate. This core-shell structured material consists of an Fe3O4 superparamagnetic nanocrystal core and a highly ordered periodic helical mesoporous silica shell. We propose that the formation of the helical structure is induced by the interaction between the surfactant and dissociated stearic acid ligands. The MHMS obtained possesses superparamagnetism, uniform mesostructure, narrow pore size distribution, high surface area, and large pore volume. Furthermore, the drug release process is demonstrated using aspirin as a drug model and MHMS as a drug carrier in a sodium phosphate buffer solution.

Liquid-phase pulsed laser ablation synthesis of graphitized carbon-encapsulated palladium core-shell nanospheres for catalytic reduction of nitrobenzene to aniline

NASA Astrophysics Data System (ADS)

Kim, Yu-jin; Ma, Rory; Reddy, D. Amaranatha; Kim, Tae Kyu

2015-12-01

Graphitized carbon-encapsulated palladium (Pd) core-shell nanospheres were produced via pulsed laser ablation of a solid Pd foil target submerged in acetonitrile. The microstructural features and optical properties of these nanospheres were characterized via high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy. Microstructural analysis indicated that the core-shell nanostructures consisted of single-crystalline cubic metallic Pd spheres that serve as the core material, over which graphitized carbon was anchored as a heterogeneous shell. The absorbance spectrum of the synthesized nanostructures exhibited a broad (absorption) band at ∼264 nm; this band corresponded to the typical inter-band transition of a metallic system and resulted possibly from the absorbance of the ionic Pd2+. The catalytic properties of the Pd and Pd@C core-shell nanostructures were investigated using the reduction of nitrobenzene to aniline by an excess amount of NaBH4 in an aqueous solution at room temperature, as a model reaction. Owing to the graphitized carbon-layered structure and the high specific surface area, the resulting Pd@C nanostructures exhibited higher conversion efficiencies than their bare Pd counterparts. In fact, the layered structure provided access to the surface of the Pd nanostructures for the hydrogenation reaction, owing to the synergistic effect between graphitized carbon and the nanostructures. Their unique structure and excellent catalytic performance render Pd@C core-shell nanostructures highly promising candidates for catalysis applications.

Preparation and microwave absorption properties of honeycomb core structures coated with composite absorber

NASA Astrophysics Data System (ADS)

Luo, Hui; Chen, Fu; Wang, Fang; Wang, Xian; Dai, Weiyong; Hu, Sheng; Gong, Rongzhou

2018-05-01

Honeycomb structure coated with paraffin filled with composite of graphene and flaky carbonyl iron powder (FCIP) as lossy filler have been studied. The composite of graphene/FCIP with different weight ratio were synthesized via mechanical milling, the electromagnetic properties of the samples were measured by transmission/reflection method in the frequency range of 8-12 GHz. The microwave absorbing properties of the microwave absorbing honeycomb structure (MAHS) and microwave absorbing honeycomb sandwich structure (MAHSS) were studied based on the Finite Element Method with periodical boundary conditions. The matching layer on the top of the honeycomb sandwich structure can enhanced the microwave absorption properties. It was shown that a light weight and broadband MAHSS could be implemented with the use of the magnetic material and dielectric material.

[Comparative investigation of compressive resistance of glass-cermet cements used as a core material in post-core systems].

PubMed

Ersoy, E; Cetiner, S; Koçak, F

1989-09-01

In post-core applications, addition to the cast designs restorations that are performed on fabrication posts with restorative materials are being used. To improve the physical properties of glass-ionomer cements that are popular today, glass-cermet cements have been introduced and those materials have been proposed to be an alternative restorative material in post-core applications. In this study, the compressive resistance of Ketac-Silver as a core material was investigated comparatively with amalgam and composite resins.

Novel techniques for optical sensor using single core multi-layer structures for electric field detection

NASA Astrophysics Data System (ADS)

Ali, Amir R.; Kamel, Mohamed A.

2017-05-01

This paper studies the effect of the electrostriction force on the single optical dielectric core coated with multi-layers based on whispering gallery mode (WGM). The sensing element is a dielectric core made of polymeric material coated with multi-layers having different dielectric and mechanical properties. The external electric field deforming the sensing element causing shifts in its WGM spectrum. The multi-layer structures will enhance the body and the pressure forces acting on the core of the sensing element. Due to the gradient on the dielectric permittivity; pressure forces at the interface between every two layers will be created. Also, the gradient on Young's modulus will affect the overall stiffness of the optical sensor. In turn the sensitivity of the optical sensor to the electric field will be increased when the materials of each layer selected properly. A mathematical model is used to test the effect for that multi-layer structures. Two layering techniques are considered to increase the sensor's sensitivity; (i) Pressure force enhancement technique; and (ii) Young's modulus reduction technique. In the first technique, Young's modulus is kept constant for all layers, while the dielectric permittivity is varying. In this technique the results will be affected by the value dielectric permittivity of the outer medium surrounding the cavity. If the medium's dielectric permittivity is greater than that of the cavity, then the ascending ordered layers of the cavity will yield the highest sensitivity (the core will have the smallest dielectric permittivity) to the applied electric field and vice versa. In the second technique, Young's modulus is varying along the layers, while the dielectric permittivity has a certain constant value per layer. On the other hand, the descending order will enhance the sensitivity in the second technique. Overall, results show the multi-layer cavity based on these techniques will enhance the sensitivity compared to the typical polymeric optical sensor.

Electrostatics of Nanowire Radial p-n Heterojunctions

NASA Astrophysics Data System (ADS)

Borblik, Vitalii

2018-04-01

The electrostatics of a nanowire radial heterostructure p-n junction is considered theoretically. It is shown that when the radius of the core-shell interface decreases, depletion width of the core increases, but depletion width of the shell, on the contrary, decreases. This is the consequence of cylindrical symmetry of the structure. Thereby, the relative contribution from the constituent materials into performance characteristics of the devices, which use a heterostructure p-n junction, changes substantially. Values of the depletion widths in the heterostructure p-n junction prove to be intermediate between those in radial homostructure p-n junctions made of the constituent materials at the same doping levels. An analogous situation takes place for a barrier capacitance of the radial heterostructure p-n junction.

Benchmark results and theoretical treatments for valence-to-core x-ray emission spectroscopy in transition metal compounds

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

Mortensen, D. R.; Seidler, G. T.; Kas, Joshua J.

We report measurement of the valence-to-core (VTC) region of the K-shell x-ray emission spectra from several Zn and Fe inorganic compounds, and their critical comparison with several existing theoretical treatments. We find generally good agreement between the respective theories and experiment, and in particular find an important admixture of dipole and quadrupole character for Zn materials that is much weaker in Fe-based systems. These results on materials whose simple crystal structures should not, a prior, pose deep challenges to theory, will prove useful in guiding the further development of DFT and time-dependent DFT methods for VTC-XES predictions and their comparisonmore » to experiment.« less

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic-Inorganic Lead Halide Perovskites.

PubMed

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; Sadoughi, Golnaz; Habisreutinger, Severin N; Félix, Roberto; Wilks, Regan G; Snaith, Henry J; Bär, Marcus; Draxl, Claudia

2018-04-19

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3 ) hybrid inorganic-organic perovskite and its binary phase PbI 2 . The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. The theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.

FWP executive summaries, Basic Energy Sciences Materials Sciences Programs (SNL/NM)

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

Samara, G.A.

1997-05-01

The BES Materials Sciences Program has the central theme of Scientifically Tailored Materials. The major objective of this program is to combine Sandia`s expertise and capabilities in the areas of solid state sciences, advanced atomic-level diagnostics and materials synthesis and processing science to produce new classes of tailored materials as well as to enhance the properties of existing materials for US energy applications and for critical defense needs. Current core research in this program includes the physics and chemistry of ceramics synthesis and processing, the use of energetic particles for the synthesis and study of materials, tailored surfaces and interfacesmore » for materials applications, chemical vapor deposition sciences, artificially-structured semiconductor materials science, advanced growth techniques for improved semiconductor structures, transport in unconventional solids, atomic-level science of interfacial adhesion, high-temperature superconductors, and the synthesis and processing of nano-size clusters for energy applications. In addition, the program includes the following three smaller efforts initiated in the past two years: (1) Wetting and Flow of Liquid Metals and Amorphous Ceramics at Solid Interfaces, (2) Field-Structured Anisotropic Composites, and (3) Composition-Modulated Semiconductor Structures for Photovoltaic and Optical Technologies. The latter is a joint effort with the National Renewable Energy Laboratory. Separate summaries are given of individual research areas.« less

To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin.

PubMed

Shori, Deepa; Pandey, Swapnil; Kubde, Rajesh; Rathod, Yogesh; Atara, Rahul; Rathi, Shravan

2013-10-01

Fiber posts are widely used for restoration of mutilated teeth that lack adequate coronal tooth structure to retain a core for definitive restoration, bond between the fiber post and composite material depends upon the chemical reaction between the post surface and the resin material used for building up the core. In attempt to maximize the resin bonding with fiber post, different post surface conditioning is advocated. Therefore the purpose of the study is to examine the interfacial strength between fiber post and composite, as core build-up material after different surface treatments of fiber posts. Twenty fiber posts were split into four groups off five each according to different surface treatments viz. Group I-(Negative Control), Group II-Silanization (Positive control), Group III-(37% Phosphoric Acid & Silanization) ,Group IV- (10% Hydrogen Peroxide and Silanization). With the preformed plastic mould, a core of dual cure composite resin around the fiber post having the uniform thickness was created. Tensile bond strength of each specimen was measured under Universal Testing Machine (UTM) at the cross head speed of 3mm/min. The results achieved with 10% Hydrogen peroxide had a marked effect on micro tensile bond strength values between the tested materials. Immense enhancement in the silanization efficiency of quartz fiber phase was observed with different surface chemical treatment of the resin phase of fiber posts with the marked increase in the micro-tensile bond strength between fiber post and composite core. Shori D, Pandey S, Kubde R, Rathod Y, Atara R, Rathi S. To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin. J Int Oral Health 2013; 5(5):27-32.

Mechanical properties of commercial high strength ceramic core materials.

PubMed

Rizkalla, A S; Jones, D W

2004-02-01

The objective of the present study is to evaluate and compare the flexural strength, dynamic elastic moduli and true hardness (H(o)) values of commercial Vita In-Ceram alumina core and Vita In-Ceram matrix glass with the standard aluminous porcelain (Hi-Ceram and Vitadur), Vitadur N and Dicor glass and glass-ceramic. The flexural strength was evaluated (n=5) using 3-point loading and a servo hydraulic Instron testing machine at a cross head speed of 0.5 mm/min. The density of the specimens (n=3) was measured by means of the water displacement technique. Dynamic Young's shear and bulk moduli and Poisson's ratio (n=3) were measured using a non-destructive ultrasonic technique using 10 MHz lithium niobate crystals. The true hardness (n=3) was measured using a Knoop indenter and the fracture toughness (n=3) was determined using a Vickers indenter and a Tukon hardness tester. Statistical analysis of the data was conducted using ANOVA and a Student-Newman-Keuls (SNK) rank order multiple comparative test. The SNK rank order test analysis of the mean flexural strength was able to separate five commercial core materials into three significant groups at p=0.05. Vita In-Ceram alumina and IPS Empress 2 exhibited significantly higher flexural strength than aluminous porcelains and IPS Empress at p=0.05. The dynamic elastic moduli and true hardness of Vita In-Ceram alumina core were significantly higher than the rest of the commercial ceramic core materials at p=0.05. The ultrasonic test method is a valuable mechanical characterization tool and was able to statistically discriminate between the chemical and structural differences within dental ceramic materials. Significant correlation was obtained between the dynamic Young's modulus and true hardness, p=0.05.

A New Star-shaped Carbazole Derivative with Polyhedral Oligomeric Silsesquioxane Core: Crystal Structure and Unique Photoluminescence Property.

PubMed

Xu, Zixuan; Yu, Tianzhi; Zhao, Yuling; Zhang, Hui; Zhao, Guoyun; Li, Jianfeng; Chai, Lanqin

2016-01-01

A new inorganic–organic hybrid material based on polyhedral oligomeric silsesquioxane (POSS) capped with carbazolyl substituents, octakis[3-(carbazol-9-yl)propyldimethylsiloxy]-silsesquioxane (POSS-8Cz), was successfully synthesized and characterized. The X-ray crystal structure of POSS-8Cz were described. The photophysical properties of POSS-8Cz were investigated by using UV–vis,photoluminescence spectroscopic analysis. The hybrid material exhibits blue emission in the solution and the solid film.The morphology and thermal stablity properties were measured by X-ray diffraction (XRD) and TG-DTA analysis.

Core-shell rhodium sulfide catalyst for hydrogen evolution reaction / hydrogen oxidation reaction in hydrogen-bromine reversible fuel cell

NASA Astrophysics Data System (ADS)

Li, Yuanchao; Nguyen, Trung Van

2018-04-01

Synthesis and characterization of high electrochemical active surface area (ECSA) core-shell RhxSy catalysts for hydrogen evolution oxidation (HER)/hydrogen oxidation reaction (HOR) in H2-Br2 fuel cell are discussed. Catalysts with RhxSy as shell and different percentages (5%, 10%, and 20%) of platinum on carbon as core materials are synthesized. Cyclic voltammetry is used to evaluate the Pt-equivalent mass specific ECSA and durability of these catalysts. Transmission electron microscopy (TEM), X-ray Photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDX) techniques are utilized to characterize the bulk and surface compositions and to confirm the core-shell structure of the catalysts, respectively. Cycling test and polarization curve measurements in the H2-Br2 fuel cell are used to assess the catalyst stability and performance in a fuel cell. The results show that the catalysts with core-shell structure have higher mass specific ECSA (50 m2 gm-Rh-1) compared to a commercial catalyst (RhxSy/C catalyst from BASF, 6.9 m2 gm-Rh-1). It also shows better HOR/HER performance in the fuel cell. Compared to the platinum catalyst, the core-shell catalysts show more stable performance in the fuel cell cycling test.

Highly Efficient Parallel Multigrid Solver For Large-Scale Simulation of Grain Growth Using the Structural Phase Field Crystal Model

NASA Astrophysics Data System (ADS)

Guan, Zhen; Pekurovsky, Dmitry; Luce, Jason; Thornton, Katsuyo; Lowengrub, John

The structural phase field crystal (XPFC) model can be used to model grain growth in polycrystalline materials at diffusive time-scales while maintaining atomic scale resolution. However, the governing equation of the XPFC model is an integral-partial-differential-equation (IPDE), which poses challenges in implementation onto high performance computing (HPC) platforms. In collaboration with the XSEDE Extended Collaborative Support Service, we developed a distributed memory HPC solver for the XPFC model, which combines parallel multigrid and P3DFFT. The performance benchmarking on the Stampede supercomputer indicates near linear strong and weak scaling for both multigrid and transfer time between multigrid and FFT modules up to 1024 cores. Scalability of the FFT module begins to decline at 128 cores, but it is sufficient for the type of problem we will be examining. We have demonstrated simulations using 1024 cores, and we expect to achieve 4096 cores and beyond. Ongoing work involves optimization of MPI/OpenMP-based codes for the Intel KNL Many-Core Architecture. This optimizes the code for coming pre-exascale systems, in particular many-core systems such as Stampede 2.0 and Cori 2 at NERSC, without sacrificing efficiency on other general HPC systems.

Fracture resistance of five pin-retained core build-up materials on teeth with and without extracoronal preparation.

PubMed

Burke, F J; Shaglouf, A G; Combe, E C; Wilson, N H

2000-01-01

Core build-ups should provide satisfactory strength and resistance to fracture both before and after crown preparation. This paper examines the resistance to fracture of core build-ups in different materials and the fracture resistance of core build-ups when these have been reduced for full crown preparation. Standardized core build-ups were made on groups of extracted molar teeth of similar size, with 10 teeth per group. Three resin-composite (prisma APH: Dentsply, Weybridge, UK; Ti-Core, Essential Dental Systems, NJ, US and Coradent, Vivadent, Liechtenstein), one cermet (Ketac-Silver, ESPE GmbH, Seefeld, Germany) and one amalgam material (Duralloy, Degussa Ltd, Cheshire, UK). These specimens were subjected to compressive force on a universal testing machine and the force at fracture noted. Standardized full crown preparations were made on a further five groups of core build-up specimens using the same materials as above. These prepared specimens were subjected to compressive force on a universal testing machine and the force to fracture noted. The results indicated that amalgam core build-ups demonstrated higher fracture resistance than the other materials examined. There was a general decrease in the fracture strength of the specimens following crown preparation, with the teeth restored with the amalgam core build-ups showing a greater percentage reduction in fracture strength than the other materials tested. Prepared core build-ups in a hybrid composite material provided the highest fracture resistance. The cermet material used provided the lowest resistance to fracture in both the core build-up and crown preparation specimens. In terms of fracture resistance, no advantage was apparent in using the two composite materials designated as being specifically appropriate for core build-ups.

Molecular Designs for Enhancement of Polarity in Ferroelectric Soft Materials

NASA Astrophysics Data System (ADS)

Ohtani, Ryo; Nakaya, Manabu; Ohmagari, Hitomi; Nakamura, Masaaki; Ohta, Kazuchika; Lindoy, Leonard F.; Hayami, Shinya

2015-11-01

The racemic oxovanadium(IV) salmmen complexes, [VO((rac)-(4-X-salmmen))] (X = C12C10C5 (1), C16 (2), and C18 (3); salmmen = N,N‧-monomethylenebis-salicylideneimine) with “banana shaped” molecular structures were synthesized, and their ferroelectric properties were investigated. These complexes exhibit well-defined hysteresis loops in their viscous phases, moreover, 1 also displays liquid crystal behaviour. We observed a synergetic effect influenced by three structural aspects; the methyl substituents on the ethylene backbone, the banana shaped structure and the square pyramidal metal cores all play an important role in generating the observed ferroelectricity, pointing the way to a useful strategy for the creation of advanced ferroelectric soft materials.

Band structure engineering strategies of metal oxide semiconductor nanowires and related nanostructures: A review

NASA Astrophysics Data System (ADS)

Piyadasa, Adimali; Wang, Sibo; Gao, Pu-Xian

2017-07-01

The electronic band structure of a solid state semiconductor determines many of its physical and chemical characteristics such as electrical, optical, physicochemical, and catalytic activity. Alteration or modification of the band structure could lead to significant changes in these physical and chemical characteristics, therefore we introduce new mechanisms of creating novel solid state materials with interesting properties. Over the past three decades, research on band structure engineering has allowed development of various methods to modify the band structure of engineered materials. Compared to bulk counterparts, nanostructures generally exhibit higher band structure modulation capabilities due to the quantum confinement effect, prominent surface effect, and higher strain limit. In this review we will discuss various band structure engineering strategies in semiconductor nanowires and other related nanostructures, mostly focusing on metal oxide systems. Several important strategies of band structure modulation are discussed in detail, such as doping, alloying, straining, interface and core-shell nanostructuring.

Experimental and simulation of split semi-torus key in PVC foam core to improve the debonding resistance of composite sandwich panel

NASA Astrophysics Data System (ADS)

Juliyana, M.; Santhana Krishnan, R.

2018-02-01

The sandwich composite panels consisting of facesheet and core material are used as a primary structural member for aerospace, civil and marine areas due to its high stiffness to weight ratio. But the debonding nature of facesheet from the foam core under shear loading conditions leads to failure of the composite structure. To inhibit the debonding, an innovative methodology of introducing semi-torus key is used in the present study. The polyvinyl chloride foam core(PVC) is grooved and filled with semi-torus shaped chopped strand prepregs which are sandwiched between alternate layers of woven roven(WR) and chopped strand mat(CSM) skins by vacuum infusion process. The sandwich panel manufactured with semi-torus keys is evaluated regarding experimental and numerical simulations under shear loading conditions. The present innovative concept delays the debonding between face-sheet and foam core with enhancement the shear load carrying capability as the initial stiffness is higher than the conventional model. Also, the shear behaviour of the proposed concept is in good agreement with experimental results. The split semi-torus keys sustain the shear failure resulting in resistance to debonding capability.

Electronic structure of CdSe-ZnS 2D nanoplatelets

NASA Astrophysics Data System (ADS)

Cruguel, Hervé; Livache, Clément; Martinez, Bertille; Pedetti, Silvia; Pierucci, Debora; Izquierdo, Eva; Dufour, Marion; Ithurria, Sandrine; Aubin, Hervé; Ouerghi, Abdelkarim; Lacaze, Emmanuelle; Silly, Mathieu G.; Dubertret, Benoit; Lhuillier, Emmanuel

2017-04-01

Among colloidal nanocrystals, 2D nanoplatelets (NPLs) made of cadmium chalcogenides have led to especially well controlled optical features. However, the growth of core shell heterostructures has so far been mostly focused on CdS shells, while more confined materials will be more promising to decouple the emitting quantum states of the core from their external environment. Using k.p simulation, we demonstrate that a ZnS shell reduces by a factor 10 the leakage of the wavefunction into the surrounding medium. Using X-ray photoemission (XPS), we confirm that the CdSe active layer is indeed unoxidized. Finally, we build an effective electronic spectrum for these CdSe/ZnS NPLs on an absolute energy scale which is a critical set of parameters for the future integration of this material into optoelectronic devices. We determine the work function (WF) to be 4.47 eV while the material is behaving as an n-type semiconductor.

Carbon materials-functionalized tin dioxide nanoparticles toward robust, high-performance nitrogen dioxide gas sensor.

PubMed

Zhang, Rui; Liu, Xiupeng; Zhou, Tingting; Wang, Lili; Zhang, Tong

2018-08-15

Carbon (C) materials, which process excellent electrical conductivity and high carrier mobility, are promising sensing materials as active units for gas sensors. However, structural agglomeration caused by chemical processes results in a small resistance change and low sensing response. To address the above issues, structure-derived carbon-coated tin dioxide (SnO 2 ) nanoparticles having distinct core-shell morphology with a 3D net-like structure and highly uniform size are prepared by careful synthesis and fine structural design. The optimum carbon-coated SnO 2 nanoparticles (SnO 2 /C)-based gas sensor exhibits a low working temperature, excellent selectivity and fast response-recovery properties. In addition, the SnO 2 /C-based gas sensor can maintain a sensitivity to nitrogen dioxide (NO 2 ) of 3 after being cycled 4 times at 140 °C for, suggesting its good long-term stability. The structural integrity, good synergistic properties, and high gas-sensing performance of SnO 2 /C render it a promising sensing material for advanced gas sensors. Copyright © 2018 Elsevier Inc. All rights reserved.

JOYO-1 Irradiation Test Campaign Technical Close-out, For Information

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

G. Borges

2006-01-31

The JOYO-1 irradiation testing was designed to screen the irradiation performance of candidate cladding, structural and reflector materials in support of space reactor development. The JOYO-1 designation refers to the first of four planned irradiation tests in the JOYO reactor. Limited irradiated material performance data for the candidate materials exists for the expected Prometheus-1 duration, fluences and temperatures. Materials of interest include fuel element cladding and core materials (refractory metal alloys and silicon carbide (Sic)), vessel and plant structural materials (refractory metal alloys and nickel-base superalloys), and control and reflector materials (BeO). Key issues to be evaluated were long termmore » microstructure and material property stability. The JOYO-1 test campaign was initiated to irradiate a matrix of specimens at prototypical temperatures and fluences anticipated for the Prometheus-1 reactor [Reference (1)]. Enclosures 1 through 9 describe the specimen and temperature monitors/dosimetry fabrication efforts, capsule design, disposition of structural material irradiation rigs, and plans for post-irradiation examination. These enclosures provide a detailed overview of Naval Reactors Prime Contractor Team (NRPCT) progress in specific areas; however, efforts were in various states of completion at the termination of NRPCT involvement with and restructuring of Project Prometheus.« less

Comparison of clast frequency and size in the resurge deposits at the Chesapeake Bay impact structure (Eyreville A and Langley cores): Clues to the resurge process

USGS Publications Warehouse

Ormo, J.; Sturkell, E.; Horton, J. Wright; Powars, D.S.; Edwards, L.E.

2009-01-01

Collapse and inward slumping of unconsolidated sedimentary strata expanded the Chesapeake Bay impact structure far beyond its central basement crater. During crater collapse, sediment-loaded water surged back to fill the crater. Here, we analyze clast frequency and granulometry of these resurge deposits in one core hole from the outermost part of the collapsed zone (i.e., Langley) as well as a core hole from the moat of the basement crater (i.e., Eyreville A). Comparisons of clast provenance and flow dynamics show that at both locations, there is a clear change in clast frequency and size between a lower unit, which we interpret to be dominated by slumped material, and an upper, water-transported unit, i.e., resurge deposit. The contribution of material to the resurge deposit was primarily controlled by stripping and erosion. This includes entrainment of fallback ejecta and sediments eroded from the surrounding seafloor, found to be dominant at Langley, and slumped material that covered the annular trough and basement crater, found to be dominant at Eyreville. Eyreville shows a higher content of crystalline clasts than Langley. There is equivocal evidence for an anti-resurge from a collapsing central water plume or, alternatively, a second resurge pulse, as well as a transition into oscillating resurge. The resurge material shows more of a debris-flow-like transport compared to resurge deposits at some other marine target craters, where the ratio of sediment to water has been relatively low. This result is likely a consequence of the combination of easily disaggregated host sediments and a relatively shallow target water depth. ?? 2009 The Geological Society of America.

Reconfigurable Polymer Shells on Shape-Anisotropic Gold Nanoparticle Cores.

PubMed

Kim, Juyeong; Song, Xiaohui; Kim, Ahyoung; Luo, Binbin; Smith, John W; Ou, Zihao; Wu, Zixuan; Chen, Qian

2018-05-03

Reconfigurable hybrid nanoparticles made by decorating flexible polymer shells on rigid inorganic nanoparticle cores can provide a unique means to build stimuli-responsive functional materials. The polymer shell reconfiguration has been expected to depend on the local core shape details, but limited systematic investigations have been undertaken. Here, two literature methods are adapted to coat either thiol-terminated polystyrene (PS) or polystyrene-poly(acrylic acid) (PS-b-PAA) shells onto a series of anisotropic gold nanoparticles of shapes not studied previously, including octahedron, concave cube, and bipyramid. These core shapes are complex, rendering shell contours with nanoscale details (e.g., local surface curvature, shell thickness) that are imaged and analyzed quantitatively using the authors' customized analysis codes. It is found that the hybrid nanoparticles based on the chosen core shapes, when coated with the above two polymer shells, exhibit distinct shell segregations upon a variation in solvent polarity or temperature. It is demonstrated for the PS-b-PAA-coated hybrid nanoparticles, the shell segregation is maintained even after a further decoration of the shell periphery with gold seeds; these seeds can potentially facilitate subsequent deposition of other nanostructures to enrich structural and functional diversity. These synthesis, imaging, and analysis methods for the hybrid nanoparticles of anisotropically shaped cores can potentially aid in their predictive design for materials reconfigurable from the bottom up. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermally Sprayed High Temperature Sandwich Structures: Physical Properties and Mechanical Performance

NASA Astrophysics Data System (ADS)

Salavati, Saeid

Metallic foam core sandwich structures have been of particular interest for engineering applications in recent decades due to their unique physical and mechanical properties. One of the potential applications of open pore metallic foam core sandwich structures is in heat exchangers. An investigation of sandwich structures fabricated from materials suitable for application at high temperatures and in corrosive environments was undertaken in this project. A novel method for fabrication of metallic foam core sandwich structures is thermal spray deposition of the faces on the prepared surfaces of the metallic foam substrate. The objective of the current study was to optimize the twin wire arc spray process parameters for the deposition of alloy 625 faces with controllable porosity content on the nickel foam substrate, and to characterize the physical and mechanical properties of the sandwich structure. The experimental investigations consisted of microstructural evaluation of the skin material and the foam substrate, investigation of the effect of alloying on the mechanical and thermal properties of the nickel foam, optimization of the grit-blasting and arc spray processes, observation of mechanical properties of the alloy 625 deposit by tensile testing and evaluation of the overall mechanical properties of the sandwich structure under flexural loading condition. The optimization of arc spraying process parameters allowed deposition of alloy 625 faces with a porosity of less than 4% for heat exchanger applications. Modification of the arc spraying process by co-deposition of polyester powder enabled 20% porosity to be obtained in the deposited faces for heat shield applications with film cooling. The effects of nickel foam alloying and heat treatment on the flexural rigidity of the sandwich structures were investigated and compared with as-received foam and as-fabricated sandwich structures. Available analytical models were employed to describe the effect of constituents' mechanical properties on the overall mechanical performance of the sandwich structures. Finite element modeling using ANSYS Structural was used to simulate the behaviour of the sandwich structures in four-point bending. The analytical and simulation results were compared with the experimental results obtained from the flexural tests.

Apparatus and Method for Increasing the Diameter of Metal Alloy Wires Within a Molten Metal Pool

DOEpatents

Hartman, Alan D.; Argetsinger, Edward R.; Hansen, Jeffrey S.; Paige, Jack I.; King, Paul E.; Turner, Paul C.

2002-01-29

In a dip forming process the core material to be coated is introduced directly into a source block of coating material eliminating the need for a bushing entrance component. The process containment vessel or crucible is heated so that only a portion of the coating material becomes molten, leaving a solid portion of material as the entrance port of, and seal around, the core material. The crucible can contain molten and solid metals and is especially useful when coating core material with reactive metals. The source block of coating material has been machined to include a close tolerance hole of a size and shape to closely fit the core material. The core material moves first through the solid portion of the source block of coating material where the close tolerance hole has been machined, then through a solid/molten interface, and finally through the molten phase where the diameter of the core material is increased. The crucible may or may not require water-cooling depending upon the type of material used in crucible construction. The system may operate under vacuum, partial vacuum, atmospheric pressure, or positive pressure depending upon the type of source material being used.

Apparatus and method for increasing the diameter of metal alloy wires within a molten metal pool

DOEpatents

Hartman, Alan D.; Argetsinger, Edward R.; Hansen, Jeffrey S.; Paige, Jack I.; King, Paul E.; Turner, Paul C.

2002-01-29

In a dip forming process the core material to be coated is introduced directly into a source block of coating material eliminating the need for a bushing entrance component. The process containment vessel or crucible is heated so that only a portion of the coating material becomes molten, leaving a solid portion of material as the entrance port of, and seal around, the core material. The crucible can contain molten and solid metals and is especially useful when coating core material with reactive metals. The source block of coating material has been machined to include a close tolerance hole of a size and shape to closely fit the core material. The core material moves first through the solid portion of the source block of coating material where the close tolerance hole has been machined, then through a solid/molten interface, and finally through the molten phase where the diameter of the core material is increased. The crucible may or may not require water-cooling depending upon the type of material used in crucible construction. The system may operate under vacuum, partial vacuum, atmospheric pressure, or positive pressure depending upon the type of source material being used.

A Study on the Plasmonic Properties of Silver Core Gold Shell Nanoparticles: Optical Assessment of the Particle Structure

NASA Astrophysics Data System (ADS)

Mott, Derrick; Lee, JaeDong; Thi Bich Thuy, Nguyen; Aoki, Yoshiya; Singh, Prerna; Maenosono, Shinya

2011-06-01

This paper reports a qualitative comparison between the optical properties of a set of silver core, gold shell nanoparticles with varying composition and structure to those calculated using the Mie solution. To achieve this, silver nanoparticles were synthesized in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing-capping agent. The particles were then coated with a layer of gold with controllable thickness through a reduction-deposition process. The resulting nanoparticles reveal well defined optical properties that make them suitable for comparison to ideal calculated results using the Mie solution. The discussion focuses on the correlation between the synthesized core shell nanoparticles with varying Au shell thickness and the Mie solution results in terms of the optical properties. The results give insight in how to design and synthesize silver core, gold shell nanoparticles with controllable optical properties (e.g., SPR band in terms of intensity and position), and has implications in creating nanoparticle materials to be used as biological probes and sensing elements.

Single-mode tunable laser emission in the single-exciton regime from colloidal nanocrystals

PubMed Central

Grivas, Christos; Li, Chunyong; Andreakou, Peristera; Wang, Pengfei; Ding, Ming; Brambilla, Gilberto; Manna, Liberato; Lagoudakis, Pavlos

2013-01-01

Whispering-gallery-mode resonators have been extensively used in conjunction with different materials for the development of a variety of photonic devices. Among the latter, hybrid structures, consisting of dielectric microspheres and colloidal core/shell semiconductor nanocrystals as gain media, have attracted interest for the development of microlasers and studies of cavity quantum electrodynamic effects. Here we demonstrate single-exciton, single-mode, spectrally tuned lasing from ensembles of optical antenna-designed, colloidal core/shell CdSe/CdS quantum rods deposited on silica microspheres. We obtain single-exciton emission by capitalizing on the band structure of the specific core/shell architecture that strongly localizes holes in the core, and the two-dimensional quantum confinement of electrons across the elongated shell. This creates a type-II conduction band alignment driven by coulombic repulsion that eliminates non-radiative multi-exciton Auger recombination processes, thereby inducing a large exciton–bi-exciton energy shift. Their ultra-low thresholds and single-mode, single-exciton emission make these hybrid lasers appealing for various applications, including quantum information processing. PMID:23974520

Ni foam supported quasi-core-shell structure of ultrathin Ti3C2 nanosheets through electrostatic layer-by-layer self-assembly as high rate-performance electrodes of supercapacitors

NASA Astrophysics Data System (ADS)

Tian, Yapeng; Yang, Chenhui; Que, Wenxiu; He, Yucheng; Liu, Xiaobin; Luo, Yangyang; Yin, Xingtian; Kong, Ling Bing

2017-11-01

Supercapacitor, as an important energy storage device, is a critical component for next generation electric power system, due to its high power density and long cycle life. In this study, a novel electrode material with quasi-core-shell structure, consisting of negatively charged few layer Ti3C2 nanosheets (FL-Ti3C2) and positively charged polyethyleneimine as building blocks, has been prepared by using an electrostatic layer-by-layer self-assembly method, with highly conductive Ni foam to be used as the skeleton. The unique quasi-core-shell structured ultrathin Ti3C2 nanosheets provide an excellent electron channel, ion transport channel and large effective contact area, thus leading to a great improvement in electrochemical performance of the material. The specific capacitance of the binder-free FL-Ti3C2@Ni foam electrodes reaches 370 F g-1 at the scan rate of 2 mV s-1 and a specific capacitance of 117 F g-1 is obtained even at the scan rate of 1000 mV s-1 in the electrolyte of Li2SO4, indicating a high rate performance. In addition, this electrode shows a long-term cyclic stability with a loss of only 13.7% after 10,000 circles. Furthermore, quantitative analysis has been conducted to ensure the relationship between the capacitive contribution and the rate performance of the as-fabricated electrode.

Enhanced magnetocaloric effect material

DOEpatents

Lewis, Laura J. H.

2006-07-18

A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.

The Synthesis of a Core-Shell Photocatalyst Material YF3:Ho3+@TiO2 and Investigation of Its Photocatalytic Properties

PubMed Central

Xu, Xuan; Zhou, Shiyu; Long, Jun; Wu, Tianhu; Fan, Zihong

2017-01-01

In this paper, YF3:Ho3+@TiO2 core-shell nanomaterials were prepared by hydrolysis of tetra-n-butyl titanate (TBOT) using polyvinylpyrrolidone K-30 (PVP) as the coupling agent. Characterization methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) under TEM, X-ray photoelectron spectroscopy (XPS), fluorescence spectrometry, ultraviolet-visible diffuse reflectance spectroscopy, and electron spin resonance (ESR) were used to characterize the properties and working mechanism of the prepared photocatalyst material. They indicated that the core phase YF3 nanoparticles were successfully coated with a TiO2 shell and the length of the composite was roughly 100 nm. The Ho3+ single-doped YF3:Ho3+@TiO2 displayed strong visible absorption peaks with wavelengths of 450, 537, and 644 nm, respectively. By selecting these three peaks as excitation wavelengths, we could observe 288 nm (5D4→5I8) ultraviolet emission, which confirmed that there was indeed an energy transfer from YF3:Ho3+ to anatase TiO2. In addition, this paper investigated the influences of different TBOT dosages on photocatalysis performance of the as-prepared photocatalyst material. Results showed that the YF3:Ho3+@TiO2 core-shell nanomaterial was an advanced visible-light-driven catalyst, which decomposed approximately 67% of rhodamine b (RhB) and 34.6% of phenol after 10 h of photocatalysis reaction. Compared with the blank experiment, the photocatalysis efficiency was significantly improved. Finally, the visible-light-responsive photocatalytic mechanism of YF3:Ho3+@TiO2 core-shell materials and the influencing factors of photocatalytic degradation were investigated to study the apparent kinetics, which provides a theoretical basis for improving the structural design and functions of this new type of catalytic material. PMID:28772662

Vibration control of beams using constrained layer damping with functionally graded viscoelastic cores: theory and experiments

NASA Astrophysics Data System (ADS)

El-Sabbagh, A.; Baz, A.

2006-03-01

Conventionally, the viscoelastic cores of Constrained Layer Damping (CLD) treatments are made of materials that have uniform shear modulus. Under such conditions, it is well-recognized that these treatments are only effective near their edges where the shear strains attain their highest values. In order to enhance the damping characteristics of the CLD treatments, we propose to manufacture the cores from Functionally Graded ViscoElastic Materials (FGVEM) that have optimally selected gradient of the shear modulus over the length of the treatments. With such optimized distribution of the shear modulus, the shear strain can be enhanced, and the energy dissipation can be maximized. The theory governing the vibration of beams treated with CLD, that has functionally graded viscoelastic cores, is presented using the finite element method (FEM). The predictions of the FEM are validated experimentally for plain beams, beams treated conventional CLD, and beams with CLD/FGVEM of different configurations. The obtained results indicate a close agreement between theory and experiments. Furthermore, the obtained results demonstrate the effectiveness of the new class of CLD with functionally graded cores in enhancing the energy dissipation over the conventional CLD over a broad frequency band. Extension of the proposed one-dimensional beam/CLD/FGVEM system to more complex structures is a natural extension to the present study.

Monodisperse MnO2@NiCo2O4 core/shell nanospheres with highly opened structures as electrode materials for good-performance supercapacitors

NASA Astrophysics Data System (ADS)

Zhou, You; Ma, Li; Gan, Mengyu; Ye, Menghan; Li, Xiurong; Zhai, Yanfang; Yan, Fabing; Cao, Feifei

2018-06-01

The monodisperse MnO2@NiCo2O4 core/shell nanospheres for good-performance supercapacitors are designed and synthesized by a two-step solution-based method and a simple post annealing process. In the composite, both MnO2 (the "core") and NiCo2O4 (the "shell") are formed by the accumulation of nanoflakes. Thus, nearly all the core/shell nanoflakes are highly opened and accessible to electrolyte, making them give full play to the Faradaic reaction. Our results demonstrate that the composite electrode exhibits desirable pseudocapacitive behaviors with higher specific capacitance (1127.27 F g-1 at a current density of 1 A g-1), better rate capability (81.0% from 1 to 16 A g-1) and superior cycling stability (actually 126.8% capacitance retention after 1000 cycles and only 3.7% loss after 10,000 cycles at 10 A g-1) in 3 M KOH aqueous solution. Moreover, it offers the excellent specific energy density of 26.6 Wh kg-1 at specific power density of 800 W kg-1. The present MnO2@NiCo2O4 core/shell nanospheres with remarkable electrochemical properties are considered as potential electrode materials for the next generation supercapacitors.

16 CFR 1632.1 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... which contain upholstery material between the ticking and the mattress core, and any detachable... which do not contain upholstery material between the ticking and the mattress core, upholstered... outermost layer of fabric or related material that encloses the core and upholstery materials of a mattress...

Synthesis of fly ash based core-shell composites for use as functional pigment in paints

NASA Astrophysics Data System (ADS)

Sharma, Richa; Tiwari, Sangeeta

2016-04-01

Fly ash is a combustion residue, mainly composed of silica, alumina and iron oxides. It is produced by the power industries in very large amounts and usually disposed in landfills, which have represented an environmental problem in recent years1. The need to generate a market for fly ash consumption is the main reason why alternative applications have been studied. It has been applied as an additive in construction materials like cement and pavements2. The present work describes the synthesis of Flyash-Titania core-shell particles by precipitation technique using Titanium tetra isopropoxide (TTIP) which can be used for variety of applications such as NIR reflecting materials for cool coatings, Photocatalysis etc. In this work, Fly ash is used in core and Nano -TiO2 is coated as shell on it. Surfactants are used to improve the adhesion of Nano Titania shell on fly ash core. Effect on adhesion of TiO2 on Fly ash is studied by using different types of surfactant. The preparation of core shells was carried out in absence of surfactant as well as using anionic and non-ionic surfactants. The percentage of surfactant was varied to study the effect of amount of surfactant on the uniformity and size of particles in the shell using Kubelka-Munk transformed reflectance spectra. The morphology of core shell structures was studied using SEM technique. Use of anionic surfactant results in more uniform coating with reduced particle size of the shell material. The composite particles prepared by using anionic surfactant are having good pigment properties and also shows good reflectance in Near Infrared region and hence can be used as a pigment in cool coatings.

Adaptation of adhesive post and cores to dentin after in vitro occlusal loading: evaluation of post material influence.

PubMed

Dietschi, Dider; Ardu, Stefano; Rossier-Gerber, Anne; Krejci, Ivo

2006-12-01

Fatigue resistance of post and cores is critical to the long term behavior of restored nonvital teeth. The purpose of this in vitro trial was to evaluate the influence of the post material's physical properties on the adaptation of adhesive post and core restorations after cyclic mechanical loading. Composite post and cores were made on endodontically treated deciduous bovine teeth using 3 anisotropic posts (made of carbon, quartz, or quartz-and-carbon fibers) and 3 isotropic posts (zirconium, stainless steel, titanium). Specimens were submitted to 3 successive loading phases--250,000 cycles at 50 N, 250,000 at 75 N, and 500,000 at 100 N--at a rate of 1.5 Hz. Restoration adaptation was evaluated under SEM, before and during loading (margins) and after test completion (margins and internal interfaces). Six additional samples were fabricated for the characterization of interface micromorphology using confocal microscopy. Mechanical loading increased the proportion of marginal gaps in all groups; carbon fiber posts presented the lowest final gap proportion (7.11%) compared to other stiffer metal-ceramic or softer fiber posts (11.0% to 19.1%). For internal adaptation, proportions of debonding between dentin and core or cement varied from 21.69% (carbon post) to 47.37% (stainless steel post). Debonding at the post-cement interface occurred only with isotropic materials. Confocal microscopy observation revealed that gaps were generally associated with an incomplete hybrid layer and reduced resin tags. Regardless of their rigidity, metal and ceramic isotropic posts proved less effective than fiber posts at stabilizing the post and core structure in the absence of the ferrule effect, due to the development of more interfacial defects with either composite or dentin.

Controlled generation of different orbital angular momentum states in a hybrid optical fiber

NASA Astrophysics Data System (ADS)

Heng, Xiaobo; Gan, Jiulin; Zhang, Zhishen; Qian, Qi; Xu, Shanhui; Yang, Zhongmin

2017-11-01

A new kind of hybrid optical fiber for different orbital angular momentum (OAM) states generation is proposed and investigated by simulation. The hybrid fiber is composed of three main regions: the core, the cladding and the bow-tie-shaped stress-applying zones (SAZs). The SAZs are symmetrically distributed on both sides of the core and filled with piezoelectric material PZT-5H which would generate radial mechanical movement when subjected to an electric field. The strain applied by the SAZs introduces anisotropic variation of the material permittivity which affect the propagation of the guided modes along the fiber core. The OAM modes of | l | = 1 , 2 , 3 can be generated by setting the appropriate electric potential applied in the SAZs. This fiber-based structure and electric control design enable the generation and adjustment of OAM states with the merits of accuracy, compactness and practicality, which would have potential application in OAM optical fiber communication systems and other systems utilizing OAM light.

Zero-valent iron treatment of dark brown colored coffee effluent: Contributions of a core-shell structure to pollutant removals.

PubMed

Tomizawa, Mayuka; Kurosu, Shunji; Kobayashi, Maki; Kawase, Yoshinori

2016-12-01

The decolorization and total organic carbon (TOC) removal of dark brown colored coffee effluent by zero-valent iron (ZVI) have been systematically examined with solution pH of 3.0, 4.0, 6.0 and 8.0 under oxic and anoxic conditions. The optimal decolorization and TOC removal were obtained at pH 8.0 with oxic condition. The maximum efficiencies of decolorization and TOC removal were 92.6 and 60.2%, respectively. ZVI presented potential properties for pollutant removal at nearly neutral pH because of its core-shell structure in which shell or iron oxide/hydroxide layer on ZVI surface dominated the decolorization and TOC removal of coffee effluent. To elucidate the contribution of the core-shell structure to removals of color and TOC at the optimal condition, the characterization of ZVI surface by scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscope (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) was conducted. It was confirmed that the core-shell structure was formed and the shell on ZVI particulate surface and the precipitates formed during the course of ZVI treatment consisted of iron oxides and hydroxides. They were significantly responsible for decolorization and TOC removal of coffee effluent via adsorption to shell on ZVI surface and inclusion into the precipitates rather than the oxidative degradation by OH radicals and the reduction by emitted electrons. The presence of dissolved oxygen (DO) enhanced the formation of the core-shell structure and as a result improved the efficiency of ZVI treatment for the removal of colored components in coffee effluents. ZVI was found to be an efficient material toward the treatment of coffee effluents. Copyright © 2016 Elsevier Ltd. All rights reserved.

Germanium–Tin/Cadmium Sulfide Core/Shell Nanocrystals with Enhanced Near-Infrared Photoluminescence

DOE PAGES

Boote, Brett W.; Men, Long; Andaraarachchi, Himashi P.; ...

2017-06-27

Ge 1–xSn x alloy nanocrystals and Ge 1–xSn x/CdS core/shell nanocrystals were prepared via solution phase synthesis, and their size, composition, and optical properties were characterized. We found that the diameter of the nanocrystal samples ranged from 6 to 13 nm. Furthermore, the crystal structure of the Ge 1–xSn x materials was consistent with a cubic diamond phase, while the CdS shell was consistent with the zinc blende polytype. Inclusion of Sn alone does not result in enhanced photoluminescence intensity; however, adding an epitaxial CdS shell onto the Ge 1–xSn x nanocrystals does enhance the photoluminescence up to 15-fold versusmore » that of Ge/CdS nanocrystals with a pure Ge core. There is more effective passivation of surface defects, and a consequent decrease in the level of surface oxidation, by the CdS shell as a result of improved epitaxy (smaller lattice mismatch) is the most likely explanation for the increased photoluminescence observed for the Ge 1–xSn x/CdS materials. With enhanced photoluminescence in the near-infrared region, Ge 1–xSn x core/shell nanocrystals might be useful alternatives to other materials for energy capture and conversion applications and as imaging probes.« less

The beetle elytron plate: a lightweight, high-strength and buffering functional-structural bionic material.

PubMed

Zhang, Xiaoming; Xie, Juan; Chen, Jinxiang; Okabe, Yoji; Pan, Longcheng; Xu, Mengye

2017-06-30

To investigate the characteristics of compression, buffering and energy dissipation in beetle elytron plates (BEPs), compression experiments were performed on BEPs and honeycomb plates (HPs) with the same wall thickness in different core structures and using different molding methods. The results are as follows: 1) The compressive strength and energy dissipation capacity in the BEP are 2.44 and 5.0 times those in the HP, respectively, when the plates are prepared using the full integrated method (FIM). 2) The buckling stress is directly proportional to the square of the wall thickness (t). Thus, for core structures with equal wall thicknesses, although the core volume of the BEP is 42 percent greater than that of the HP, the mechanical properties of the BEP are several times higher than those of the HP. 3) It is also proven that even when the single integrated method (SIM) is used to prepare BEPs, the properties discussed above remain superior to those of HPs by a factor of several; this finding lays the foundation for accelerating the commercialization of BEPs based on modern manufacturing processes.

Effect of cavitation on flow structure of a tip vortex

NASA Astrophysics Data System (ADS)

Matthieu, Dreyer; Reclari, Martino; Farhat, Mohamed

2013-11-01

Tip vortices, which may develop in axial turbines and marine propellers, are often associated with the occurrence of cavitation because of the low pressure in their core. Although this issue has received a great deal of attention, it is still unclear how the phase transition affects the flow structure of such a vortex. In the present work, we investigate the change of the vortex structure due to cavitation incipience. The measurement of the velocity field is performed in the case of a tip vortex generated by an elliptical hydrofoil placed in the test section of EPFL high speed cavitation tunnel. To this end, a 3D stereo PIV is used with fluorescent seeding particles. A cost effective method is developed to produce in-house fluorescent seeding material, based on polyamide particles and Rhodamine-B dye. The amount of cavitation in the vortex core is controlled by the inlet pressure in the test section, starting with the non-cavitating case. We present an extensive analysis of the vorticity distribution, the vortex intensity and core size for various cavitation developments. This research is supported by CCEM and swisselectric research.

Multicharged and/or water-soluble fluorescent dendrimers: properties and uses.

PubMed

Caminade, Anne-Marie; Hameau, Aurélien; Majoral, Jean-Pierre

2009-09-21

The fluorescence of water-soluble dendritic compounds can be due to the whole structure or to fluorophores used as core, as peripheral groups, or as branches. Highly sophisticated precisely defined structures with other functional groups usable for material or biological purposes have been synthesised, but many recent examples have shown that dendrimers can be used as versatile platforms for statistically linking various types of functional groups.

Coated armor system and process for making the same

DOEpatents

Chu, Henry S.; Lillo, Thomas M.; McHugh, Kevin M.

2010-11-23

An armor system and method involves providing a core material and a stream of atomized coating material that comprises a liquid fraction and a solid fraction. An initial layer is deposited on the core material by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is less than the liquid fraction of the stream of atomized coating material on a weight basis. An outer layer is then deposited on the initial layer by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is greater than the liquid fraction of the stream of atomized coating material on a weight basis.

Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

NASA Astrophysics Data System (ADS)

Dey, Vikram

The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and correlate the behavior of these structural composites under uniaxial tension and flexural loading responses. Development and use of analytical models enables optimal design for application of these materials in structural applications. Another area of immediate focus is the development of new construction products from SHCC laminates such as angles, channels, hat sections, closed sections with optimized cross sections. Sandwich composites with stress skin-cellular core concept were also developed to utilize strength and ductility of fabric reinforced skin in addition to thickness, ductility, and thermal benefits of cellular core materials. The proposed structurally efficient and durable sections promise to compete with wood and light gage steel based sections for lightweight construction and panel application.

Expression of a cloned lipopolysaccharide antigen from Neisseria gonorrhoeae on the surface of Escherichia coli K-12.

PubMed Central

Palermo, D A; Evans, T M; Clark, V L

1987-01-01

A gonococcal gene bank maintained in Escherichia coli K-12 was screened by colony immunoblotting, and a transformant expressing a surface antigen reactive to anti-gonococcal outer membrane antiserum was isolated. The isolate carried a recombinant plasmid, pTME6, consisting of approximately 9 kilobases of Neisseria gonorrhoeae DNA inserted into the BamHI site of pBR322. Surface labeling of E. coli HB101(pTME6) confirmed that the antigen was expressed on the E. coli cell surface. The antigenic material was resistant to proteinase K digestion and sensitive to periodate oxidation, indicating that the material was carbohydrate. Purified lipopolysaccharide (LPS) from HB101(pTME6) produced a unique band on silver-stained polyacrylamide gels that contained immunoreactive material as seen on Western blots of LPS samples. Only two of three E. coli LPS mutant strains carrying pTME6 reacted with the antigonococcal antiserum, suggesting that a certain E. coli core structure is necessary for antigen expression. We conclude that pTME6 contains one or more gonococcal genes encoding an LPS core biosynthetic enzyme(s) which can modify E. coli core LPS to produce a gonococcuslike epitope(s). Images PMID:3117695

Keeping the ball rolling: fullerene-like molecular clusters.

PubMed

Kong, Xiang-Jian; Long, La-Sheng; Zheng, Zhiping; Huang, Rong-Bin; Zheng, Lan-Sun

2010-02-16

The discovery of fullerenes in 1985 opened a new chapter in the chemistry of highly symmetric molecules. Fullerene-like metal clusters, characterized by (multi)shell-like structures, are one rapidly developing class of molecules that share this shape. In addition to creating aesthetically pleasing molecular structures, the ordered arrangement of metal atoms within such frameworks provides the opportunity to develop materials with properties not readily achieved in corresponding mononuclear or lower-nuclearity complexes. In this Account, we survey the great variety of fullerene-like metal-containing clusters with an emphasis on their synthetic and structural chemistry, a first step in the discussion of this fascinating field of cluster chemistry. We group the compounds of interest into three categories based on the atomic composition of the cluster core: those with formal metal-metal bonding, those characterized by ligand participation, and those supported by polyoxometalate building blocks. The number of clusters in the first group, containing metal-metal bonds, is relatively small. However, because of the unique and complex bonding scenarios observed for some of these species, these metalloid clusters present a number of research questions with significant ramifications. Because these cores contain molecular clusters of precious metals at the nanoscale, they offer an opportunity to study chemical properties at size ranges from the molecular to nanoscale and to gain insights into the electronic structures and properties of nanomaterials of similar chemical compositions. Clusters of the second type, whose core structures are facilitated by ligand participation, could aid in the development of functional materials. Of particular interest are the magnetic clusters containing both transition and lanthanide elements. A series of such heterometallic clusters that we prepared demonstrates diverse magnetic properties including antiferromagnetism, ferrimagnetism, and ferromagnetism. Considering the diversity of their composition, their distinct electronic structures, and the disparate coordination behaviors of the different metal elements, these materials suggest abundant opportunities for designing multifunctional materials with varied structures. The third type of clusters that we discuss are based on polyoxometalates, in particular those containing pentagonal units. However, unlike in fullerene chemistry, which does not allow the use of discrete pentagonal building blocks, the metal oxide-based pentagonal units can be used as fundamental building blocks for constructing various Keplerate structures. These structures also have a variety of functions, including intriguing magnetic properties in some cases. Coupled with different linking groups, such pentagonal units can be used for the assembly of a large number of spherical molecules whose properties can be tuned and optimized. Although this Account focuses on the topological aspects of fullerene-like metal clusters, we hope that this topical review will stimulate more efforts in the exploratory synthesis of new fullerene-like clusters. More importantly, we hope that further study of the bonding interactions and properties of these molecules will lead to the development of new functional materials.

Hybrid porous core low loss dispersion flattened fiber for THz propagation

NASA Astrophysics Data System (ADS)

Ali, Sharafat; Ahmed, Nasim; Aljunid, Syed; Ahmad, Badlishah

2016-11-01

This manuscript represents a novel porous core fiber design for Terahertz (THz) propagation with low loss and near zero flat dispersion properties. In this proposed fiber a hexagonal arrangement is used as cladding structure and a hybrid core containing circular and triangular designs is used as the central porous region. The Effective Material Loss (EML), confinement loss and bending loss are investigated for the proposed fiber along with dispersion characteristics. Simulation results show a very low EML of 0.01944 cm-1 at 1 THz operating frequency with negligible confinement and bending loss. The proposed novel porous design shows 0.55 THz range near zero flat dispersion of ±0.05 ps/THz/cm at 0.95 ps/THz/cm. The reported design consists of only circular shaped air holes with proper core diameter and porosity to simplify the fabrication process. The newly proposed hybrid design in the porous core region can be considered as an improved edition in the research of THz porous core fibers.

Investigation of novel inverted NiO@NixCo1-xO core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Hasan, Samiul; Mayanovic, R. A.; Benamara, Mourad

2018-05-01

Inverse core-shell nanoparticles, comprised of an antiferromagnetic (AFM) core covered by a ferromagnetic (FM) or ferrimagnetic (FiM) shell, are of current interest due to their different potential application and due to the tunability of their magnetic properties. The antiferromagnetic nature of NiO and high Néel temperature (523 K) makes this material well suited for inverse core-shell nanoparticle applications. Our primary objective in this project has been to synthesize and characterize inverted core-shell nanoparticles (CSNs) comprised of a NiO (AFM) core and a shell consisting of a NixCo1-xO (FiM) compound. The synthesis of the CSNs was made using a two-step process. The NiO nanoparticles were synthesized using a chemical reaction method. Subsequently, the NiO nanoparticles were used to grow the NiO@NixCo1-xO CSNs using our hydrothermal nano-phase epitaxy method. XRD structural characterization shows that the NiO@NixCo1-xO CSNs have the rock salt cubic crystal structure. SEM-EDS data indicates the presence of Co in the CSNs. Magnetic measurements show that the CSNs exhibit AFM/FiM characteristics with a small coercivity field of 30 Oe at 5 K. The field cooled vs zero field cooled hysteresis loop measurements show a magnetization axis shift which is attributed to the exchange bias effect between the AFM NiO core and an FiM NixCo1-xO shell of the CSNs. Our ab initio based calculations of the NixCo1-xO rock salt structure confirm a weak FiM character and a charge transfer insulator property of the compound.

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

Steel skin - SMC laminate structures for lightweight automotive manufacturing

NASA Astrophysics Data System (ADS)

Quagliato, Luca; Jang, Changsoon; Murugesan, Mohanraj; Kim, Naksoo

2017-09-01

In the present research work an innovative material, made of steel skin and sheet molding compound core, is presented and is aimed to be utilized for the production of automotive body frames. For a precise description of the laminate structure, the material properties of all the components, including the adhesive utilized as an interlayer, have been carried out, along with the simple tension test of the composite material. The result have shown that the proposed laminate structure has a specific yield strength 114% higher than 6061 T6 aluminum, 34% higher than 7075 T6 aluminum, 186% higher than AISI 304 stainless steel (30HRC) and 42% than SK5 high-strength steel (52HRC), showing its reliability and convenience for the realization of automotive components. After calibrating the material properties of the laminate structure, and utilizing as reference the simple tension results of the laminate structure, the derived material properties have been utilized for the simulation of the mechanical behavior of an automotive B-pillar. The results have been compared with those of a standard B-pillar made of steel, showing that the MS-SMC laminate structure manifests load and impact carry capacity comparable with those of high strength steel, while granting, at least, an 11% weight reduction.

Toward a New Chemotherapy for Breast Cancer: Structural and Functional Mechanism of the Retinoid Receptors Addressed by a Novel Computer Approach

DTIC Science & Technology

1999-05-01

substitution of the second leucine in an LxxLL core with isoleucine still permits a strong hydrophobic interaction with the liganded receptor (Table 2...through electrostatic interactions. Figure 10 illustrates that the two leucines and one isoleucine (green and cyan) of the LxxlL motif are predicted to be...RARox was carried out as described in Materials and methods. The side chains of the two leucines (green) and one isoleucine (cyan) of the LxxIL core fit

A novel durable double-conductive core-shell structure applying to the synthesis of silicon anode for lithium ion batteries

NASA Astrophysics Data System (ADS)

Xing, Yan; Shen, Tong; Guo, Ting; Wang, Xiuli; Xia, Xinhui; Gu, Changdong; Tu, Jiangping

2018-04-01

Si/C composites are currently the most commercially viable next-generation lithium-ion battery anode materials due to their high specific capacity. However, there are still many obstacles need to be overcome such as short cycle life and poor conductivity. In this work, we design and successfully synthesis an excellent durable double-conductive core-shell structure p-Si-Ag/C composites. Interestingly, this well-designed structure offers remarkable conductivity (both internal and external) due to the introduction of silver particles and carbon layer. The carbon layer acts as a protective layer to maintain the integrity of the structure as well as avoids the direct contact of silicon with electrolyte. As a result, the durable double-conductive core-shell structure p-Si-Ag/C composites exhibit outstanding cycling stability of roughly 1000 mAh g-1 after 200 cycles at a current density of 0.2 A g-1 and retain 765 mAh g-1 even at a high current density of 2 A g-1, indicating a great improvement in electrochemical performance compared with traditional silicon electrode. Our research results provide a novel pathway for production of high-performance Si-based anodes to extending the cycle life and specific capacity of commercial lithium ion batteries.

Time-efficient simulations of tight-binding electronic structures with Intel Xeon PhiTM many-core processors

NASA Astrophysics Data System (ADS)

Ryu, Hoon; Jeong, Yosang; Kang, Ji-Hoon; Cho, Kyu Nam

2016-12-01

Modelling of multi-million atomic semiconductor structures is important as it not only predicts properties of physically realizable novel materials, but can accelerate advanced device designs. This work elaborates a new Technology-Computer-Aided-Design (TCAD) tool for nanoelectronics modelling, which uses a sp3d5s∗ tight-binding approach to describe multi-million atomic structures, and simulate electronic structures with high performance computing (HPC), including atomic effects such as alloy and dopant disorders. Being named as Quantum simulation tool for Advanced Nanoscale Devices (Q-AND), the tool shows nice scalability on traditional multi-core HPC clusters implying the strong capability of large-scale electronic structure simulations, particularly with remarkable performance enhancement on latest clusters of Intel Xeon PhiTM coprocessors. A review of the recent modelling study conducted to understand an experimental work of highly phosphorus-doped silicon nanowires, is presented to demonstrate the utility of Q-AND. Having been developed via Intel Parallel Computing Center project, Q-AND will be open to public to establish a sound framework of nanoelectronics modelling with advanced HPC clusters of a many-core base. With details of the development methodology and exemplary study of dopant electronics, this work will present a practical guideline for TCAD development to researchers in the field of computational nanoelectronics.

X-ray Magnetic Linear Dichroism of Fe-Ni Alloys on Cu(111)

DTIC Science & Technology

2001-04-01

the study of magnetism and magnetic materials. This control allows for the study of the relationship between magnetic and structural properties for...effect in NiFe /Cu systems that are relevant to magnetic disk drive heads. Using core-level photoelectron spectroscopies on magnetized samples allows

Fusing porphyrins with polycyclic aromatic hydrocarbons and heterocycles for optoelectronic applications

DOEpatents

Thompson, Mark E.; Diev, Viacheslav; Hanson, Kenneth; Forrest, Stephen R.

2015-08-18

A compound that can be used as a donor material in organic photovoltaic devices comprising a non-activated porphyrin fused with one or more non-activated polycyclic aromatic rings or one or more non-activated heterocyclic rings can be obtained by a thermal fusion process. The compounds can include structures of Formula I: ##STR00001## By heating the reaction mixture of non-activated porphyrins with non-activated polycyclic aromatic rings or heterocyclic rings to a fusion temperature and holding for a predetermined time, fusion of one or more polycyclic rings or heterocyclic rings to the non-activated porphyrin core in meso,.beta. fashion is achieved resulting in hybrid structures containing a distorted porphyrin ring with annulated aromatic rings. The porphyrin core can be olygoporphyrins.

Method and apparatus for improved observation of in-situ combustion processes

DOEpatents

Lee, D.O.; Montoya, P.C.; Wayland, J.R. Jr.

Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front there-through. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique. 6 figures, 2 tables.

Size-controlled, magnetic, and core-shell nanoparticles synthesized by inert-gas condensation

NASA Astrophysics Data System (ADS)

Koten, Mark A.

Interest in nanoparticles (2 to 100 nm in diameter) and clusters of atoms (0.5 to 2 nm in diameter) has heightened over the past two and a half decades on both fundamental and functional levels. Nanoparticles and clusters of atoms are an exciting branch of materials science because they do not behave like normal bulk matter, nor do they act like molecules. They can have shockingly different physical, chemical, optical, or magnetic properties from the same material at a larger scale. In the case of nanoparticles, the surface-to-volume ratio can change fundamental properties like melting temperature, binding energy, or electron affinity. The definitions of markers used to distinguish between metallic, semiconducting, and insulating bulk condensed matter, such as the band gap and polarizability, can even be blurred or confused on the nanoscale. Similarly, clusters of atoms can form in structures that are only stable at finite sizes, and do not translate to bulk condensed matter. Thermodynamics of finite systems changes dramatically in nanovolumes such as wires, rods, cubes, and spheres, which can lead to complex core-shell and onion-like nanostructures. Consequently, these changes in properties and structure have led to many new possibilities in the field of materials engineering. Inert-gas condensation (IGC) is a well-established method of producing nanoparticles that condense from the gas phase. Its first use dates back to the early 1990s, and it has been used to fabricate nanoparticles both commercially and in research and development for applications in magnetism, biomedicine, and catalysts. In this dissertation, IGC was used to produce a wide variety of nanoparticles. First, control over the size distributions of Cu nanoparticles and how it relates to the plasma properties inside the nucleation chamber was investigated. Next, the formation of phase pure WFe2 nanoparticles revealed that this Laves phase is ferromagnetic instead of non-magnetic. Finally, core-shell nanoparticles were produced using three thermodynamically different systems, which showed that IGC could be used to produce a wide variety of core-shell particles. These three projects are presented in the context of size-dependent structural and magnetic properties.

Solid oxide fuel cell having monolithic core

DOEpatents

Ackerman, J.P.; Young, J.E.

1983-10-12

A solid oxide fuel cell is described for electrochemically combining fuel and oxidant for generating galvanic output, wherein the cell core has an array of electrolyte and interconnect walls that are substantially devoid of any composite inert materials for support. Instead, the core is monolithic, where each electrolyte wall consists of thin layers of cathode and anode materials sandwiching a thin layer of electrolyte material therebetween. The electrolyte walls are arranged and backfolded between adjacent interconnect walls operable to define a plurality of core passageways alternately arranged where the inside faces thereof have only the anode material or only the cathode material exposed. Means direct the fuel to the anode-exposed core passageways and means direct the oxidant to the anode-exposed core passageways and means direct the oxidant to the cathode-exposed core passageway; and means also direct the galvanic output to an exterior circuit. Each layer of the electrolyte and interconnect materials is of the order of 0.002 to 0.01 cm thick; and each layer of the cathode and anode materials is of the order of 0.002 to 0.05 cm thick.

Influence of dimensionality and interface type on optical and electronic properties of CdS/ZnS core-shell nanocrystals—A first-principles study

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

Kocevski, V., E-mail: vancho.vk@gmail.com, E-mail: vancho.kocevski@physics.uu.se; Eriksson, O.; Gerard, C.

2015-10-28

Semiconducting nanocrystals (NCs) have become one of the leading materials in a variety of applications, mainly due to their size tunable band gap and high intensity emission. Their photoluminescence (PL) properties can be notably improved by capping the nanocrystals with a shell of another semiconductor, making core-shell structures. We focus our study on the CdS/ZnS core-shell nanocrystals that are closely related to extensively studied CdSe/CdS NCs, albeit exhibiting rather different photoluminescence properties. We employ density functional theory to investigate the changes in the electronic and optical properties of these nanocrystals with size, core/shell ratio, and interface structure between the coremore » and the shell. We have found that both the lowest unoccupied eigenstate (LUES) and the highest occupied eigenstate (HOES) wavefunction (WF) are localized in the core of the NCs, with the distribution of the LUES WF being more sensitive to the size and the core/shell ratio. We show that the radiative lifetimes are increasing, and the Coulomb interaction energies decrease with increasing NC size. Furthermore, we investigated the electronic and optical properties of the NCs with different interfaces between the core and the shell and different core types. We find that the different interfaces and core types have rather small influence on the band gaps and the absorption indexes, as well as on the confinement of the HOES and LUES WFs. Also the radiative lifetimes are found to be only slightly influenced by the different structural models. In addition, we compare these results with the previous results for CdSe/CdS NCs, reflecting the different PL properties of these two types of NCs. We argue that the difference in their Coulomb interaction energies is one of the main reasons for their distinct PL properties.« less

Plateau-Rayleigh Crystal Growth of Nanowire Heterostructures: Strain-Modified Surface Chemistry and Morphological Control in One, Two, and Three Dimensions.

PubMed

Day, Robert W; Mankin, Max N; Lieber, Charles M

2016-04-13

One-dimensional (1D) structures offer unique opportunities for materials synthesis since crystal phases and morphologies that are difficult or impossible to achieve in macroscopic crystals can be synthesized as 1D nanowires (NWs). Recently, we demonstrated one such phenomenon unique to growth on a 1D substrate, termed Plateau-Rayleigh (P-R) crystal growth, where periodic shells develop along a NW core to form diameter-modulated NW homostructures with tunable morphologies. Here we report a novel extension of the P-R crystal growth concept with the synthesis of heterostructures in which Ge (Si) is deposited on Si (Ge) 1D cores to generate complex NW morphologies in 1, 2, or 3D. Depositing Ge on 50 nm Si cores with a constant GeH4 pressure yields a single set of periodic shells, while sequential variation of GeH4 pressure can yield multimodulated 1D NWs with two distinct sets of shell periodicities. P-R crystal growth on 30 nm cores also produces 2D loop structures, where Ge (Si) shells lie primarily on the outside (inside) of a highly curved Si (Ge) core. Systematic investigation of shell morphology as a function of growth time indicates that Ge shells grow in length along positive curvature Si cores faster than along straight Si cores by an order of magnitude. Short Ge deposition times reveal that shells develop on opposite sides of 50 and 100 nm Si cores to form straight 1D morphologies but that shells develop on the same side of 20 nm cores to produce 2D loop and 3D spring structures. These results suggest that strain mediates the formation of 2 and 3D morphologies by altering the NW's surface chemistry and that surface diffusion of heteroatoms on flexible freestanding 1D substrates can facilitate this strain-mediated mechanism.

An Evolutionarily Conserved Family of Virion Tail Needles Related to Bacteriophage P22 gp26: Correlation between Structural Stability and Length of the -Helical Trimeric Coiled Coil

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

Bhardwaj, A.; Walker-Kopp, N; Casjens, S

2009-01-01

Bacteriophages of the Podoviridae family use short noncontractile tails to inject their genetic material into Gram-negative bacteria. In phage P22, the tail contains a thin needle, encoded by the phage gene 26, which is essential both for stabilization and for ejection of the packaged viral genome. Bioinformatic analysis of the N-terminal domain of gp26 (residues 1-60) led us to identify a family of genes encoding putative homologues of the tail needle gp26. To validate this idea experimentally and to explore their diversity, we cloned the gp26-like gene from phages HK620, Sf6 and HS1, and characterized these gene products in solution.more » All gp26-like factors contain an elongated {alpha}-helical coiled-coil core consisting of repeating, adjacent trimerization heptads and form trimeric fibers with length ranging between about 240 to 300 {angstrom}. gp26 tail needles display a high level of structural stability in solution, with Tm (temperature of melting) between 85 and 95 C. To determine how the structural stability of these phage fibers correlates with the length of the {alpha}-helical core, we investigated the effect of insertions and deletions in the helical core. In the P22 tail needle, we identified an 85-residue-long helical domain, termed MiCRU (minimal coiled-coil repeat unit), that can be inserted in-frame inside the gp26 helical core, preserving the straight morphology of the fiber. Likewise, we were able to remove three quarters of the helical core of the HS1 tail needle, minimally decreasing the stability of the fiber. We conclude that in the gp26 family of tail needles, structural stability increases nonlinearly with the length of the {alpha}-helical core. Thus, the overall stability of these bacteriophage fibers is not solely dependent on the number of trimerization repeats in the {alpha}-helical core.« less

Bio-Inspired Bright Structurally Colored Colloidal Amorphous Array Enhanced by Controlling Thickness and Black Background.

PubMed

Iwata, Masanori; Teshima, Midori; Seki, Takahiro; Yoshioka, Shinya; Takeoka, Yukikazu

2017-07-01

Inspired by Steller's jay, which displays angle-independent structural colors, angle-independent structurally colored materials are created, which are composed of amorphous arrays of submicrometer-sized fine spherical silica colloidal particles. When the colloidal amorphous arrays are thick, they do not appear colorful but almost white. However, the saturation of the structural color can be increased by (i) appropriately controlling the thickness of the array and (ii) placing the black background substrate. This is similar in the case of the blue feather of Steller's jay. Based on the knowledge gained through the biomimicry of structural colored materials, colloidal amorphous arrays on the surface of a black particle as the core particle are also prepared as colorful photonic pigments. Moreover, a structural color on-off system is successfully built by controlling the background brightness of the colloidal amorphous arrays. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

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

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

DOE PAGES

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; ...

2018-03-23

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Rotational spectral variations of asteroid (8) Flora Implications for the nature of the S-type asteroids and for the parent bodies of the ordinary chondrites

NASA Technical Reports Server (NTRS)

Gaffey, M. J.

1984-01-01

The surface material and the surface material heterogeneities of the asteroid Flora are characterized using the best available data sets and the most sophisticated interpretive calibrations. Five spectrally derived mineralogic and patrologic properties of the surface assemblage of Flora which are relevant to whether this body is a differentiated or undifferentiated object are considered: bulk mineralogy, mafic mineral assemblage, metallic phase, pyroxene composition and structural type, and mineralogic variation. All of these properties indicate that Flora is a differentiated body. Flora is probably the residual core of an intensely heated, thermally evolved, and magnetically differentiated planetesimal which was subsequently disrupted. The present surface sample layers formed at or near the core-mantle boundary in the parent body.

The behaviour of post-retained core materials supported by coronal tooth structure in vitro.

PubMed

Russell, M D; Masood, M; Cunningham, L

1997-11-01

This study was designed to investigate the effect of retaining coronal tooth substance on the performance of post-retained core materials, and to compare the fracture resistance of the system with an intact tooth prepared to similar dimensions. Ten teeth restored with post-retained silver amalgam, and 10 teeth restored with silver-glass cermet, all with a retained single wall of coronal tooth substance, were compared with 10 unrestored teeth prepared to similar dimensions when subjected to a shearing load. The results showed no statistically significant difference between the unrestored teeth and those restored with a silver-glass cermet. Whilst the teeth restored with silver amalgam had a significantly higher fracture resistance (P > 0.01) there was greater tendency to root fracture.

Nickel/silicon core/shell nanosheet arrays as electrode materials for lithium ion batteries

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

Huang, X.H., E-mail: drhuangxh@hotmail.com; Zhang, P.; Wu, J.B.

Highlights: • Ni nanosheet arrays is the core and Si layer is the shell. • Ni nanosheet arrays act as a three-dimensional current collector to support Si. • Ni nanosheet arrays can improve the conductivity and stability of the electrode. • Ni/Si nanosheet arrays exhibit excellent cyclic and rate performance. - Abstract: Ni/Si core/shell nanosheet arrays are proposed to enhance the electrochemical lithium-storage properties of silicon. The arrays are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The arrays are micro-sized in height, which are constructed by interconnected Ni nanosheet as themore » core and Si coating layer as the shell. The electrochemical properties as anode materials of lithium ion batteries are investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. The arrays can achieve high reversible capacity, good cycle stability and high rate capability. It is believed that the enhanced electrochemical performance is attributed to the electrode structure, because the interconnected Ni nanosheet can act as a three-dimensional current collector, and it has the ability of improving the electrode conductivity, enlarging the electrochemical reaction interface, and suppressing the electrode pulverization.« less

Optimal Damping Behavior of a Composite Sandwich Beam Reinforced with Coated Fibers

NASA Astrophysics Data System (ADS)

Lurie, S.; Solyaev, Y.; Ustenko, A.

2018-04-01

In the present paper, the effective damping properties of a symmetric foam-core sandwich beam with composite face plates reinforced with coated fibers is studied. A glass fiber-epoxy composite with additional rubber-toughened epoxy coatings on the fibers is considered as the material of the face plates. A micromechanical analysis of the effective properties of the unidirectional lamina is conducted based on the generalized self-consistent method and the viscoelastic correspondence principle. The effective complex moduli of composite face plates with a symmetric angle-ply structure are evaluated based on classical lamination theory. A modified Mead-Markus model is utilized to evaluate the fundamental modal loss factor of a simply supported sandwich beam with a polyurethane core. The viscoelastic frequency-dependent behaviors of the core and face plate materials are both considered. The properties of the face plates are evaluated based on a micromechanical analysis and found to implicitly depend on frequency; thus, an iterative procedure is applied to find the natural frequencies of the lateral vibrations of the beam. The optimal values of the coating thickness, lamination angle and core thickness for the best multi-scale damping behavior of the beam are found.

An Overview of Materials Structures for Extreme Environments Efforts for 2015 SBIR Phases I and II

NASA Technical Reports Server (NTRS)

Nguyen, Hung D.; Steele, Gynelle C.

2017-01-01

Technological innovation is the overall focus of NASA's Small Business Innovation Research (SBIR) program. The program invests in the development of innovative concepts and technologies to help NASA's mission directorates address critical research and development needs for Agency projects. This report highlights innovative SBIR 2015 Phase I and II projects that specifically address areas in Materials and Structures for Extreme Environments, one of six core competencies at NASA Glenn Research Center. Each article describes an innovation, defines its technical objective, and highlights NASA applications as well as commercial and industrial applications. Ten technologies are featured: metamaterials-inspired aerospace structures, metallic joining to advanced ceramic composites, multifunctional polyolefin matrix composite structures, integrated reacting fluid dynamics and predictive materials degradation models for propulsion system conditions, lightweight inflatable structural airlock (LISA), copolymer materials for fused deposition modeling 3-D printing of nonstandard plastics, Type II strained layer superlattice materials development for space-based focal plane array applications, hydrogenous polymer-regolith composites for radiation-shielding materials, a ceramic matrix composite environmental barrier coating durability model, and advanced composite truss printing for large solar array structures. This report serves as an opportunity for NASA engineers, researchers, program managers, and other personnel to learn about innovations in this technology area as well as possibilities for collaboration with innovative small businesses that could benefit NASA programs and projects.

Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis.

PubMed

Lee, Ki-Sun; Shin, Joo-Hee; Kim, Jong-Eun; Kim, Jee-Hwan; Lee, Won-Chang; Shin, Sang-Wan; Lee, Jeong-Yol

2017-01-01

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of 45° to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems.

Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis

PubMed Central

Shin, Joo-Hee; Kim, Jong-Eun; Kim, Jee-Hwan; Lee, Won-Chang; Shin, Sang-Wan

2017-01-01

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of 45° to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems. PMID:28386547

St. Petersburg Coastal and Marine Science Center's Core Archive Portal

USGS Publications Warehouse

Reich, Chris; Streubert, Matt; Dwyer, Brendan; Godbout, Meg; Muslic, Adis; Umberger, Dan

2012-01-01

This Web site contains information on rock cores archived at the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center (SPCMSC). Archived cores consist of 3- to 4-inch-diameter coral cores, 1- to 2-inch-diameter rock cores, and a few unlabeled loose coral and rock samples. This document - and specifically the archive Web site portal - is intended to be a 'living' document that will be updated continually as additional cores are collected and archived. This document may also contain future references and links to a catalog of sediment cores. Sediment cores will include vibracores, pushcores, and other loose sediment samples collected for research purposes. This document will: (1) serve as a database for locating core material currently archived at the USGS SPCMSC facility; (2) provide a protocol for entry of new core material into the archive system; and, (3) set the procedures necessary for checking out core material for scientific purposes. Core material may be loaned to other governmental agencies, academia, or non-governmental organizations at the discretion of the USGS SPCMSC curator.

Methods of producing armor systems, and armor systems produced using such methods

DOEpatents

Chu, Henry S; Lillo, Thomas M; McHugh, Kevin M

2013-02-19

An armor system and method involves providing a core material and a stream of atomized coating material that comprises a liquid fraction and a solid fraction. An initial layer is deposited on the core material by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is less than the liquid fraction of the stream of atomized coating material on a weight basis. An outer layer is then deposited on the initial layer by positioning the core material in the stream of atomized coating material wherein the solid fraction of the stream of atomized coating material is greater than the liquid fraction of the stream of atomized coating material on a weight basis.

Passive zero-gravity leg restraint

NASA Technical Reports Server (NTRS)

Miller, Christopher R. (Inventor)

1989-01-01

A passive zero or microgravity leg restraint is described which includes a central support post with a top and a bottom. Extending from the central support post are a calf pad tab, to which calf pad is attached, and a foot pad tab, to which foot tab is attached. Also extending from central support post are knee pads. When the restraint is in use the user's legs are forced between pads by a user imposed scissors action of the legs. The user's body is then supported in a zero or microgravity neutral body posture by the leg restraint. The calf pad has semi-ridig elastic padding material covering structural stiffener. The foot pad has padding material and a structural stiffener. Knee pads have s structural tube stiffener at their core.

Multi-scale predictive modeling of nano-material and realistic electron devices

NASA Astrophysics Data System (ADS)

Palaria, Amritanshu

Among the challenges faced in further miniaturization of electronic devices, heavy influence of the detailed atomic configuration of the material(s) involved, which often differs significantly from that of the bulk material(s), is prominent. Device design has therefore become highly interrelated with material engineering at the atomic level. This thesis aims at outlining, with examples, a multi-scale simulation procedure that allows one to integrate material and device aspects of nano-electronic design to predict behavior of novel devices with novel material. This is followed in four parts: (1) An approach that combines a higher time scale reactive force field analysis with density functional theory to predict structure of new material is demonstrated for the first time for nanowires. Novel stable structures for very small diameter silicon nanowires are predicted. (2) Density functional theory is used to show that the new nanowire structures derived in 1 above have properties different from diamond core wires even though the surface bonds in some may be similar to the surface of bulk silicon. (3) Electronic structure of relatively large-scale germanium sections of realistically strained Si/strained Ge/ strained Si nanowire heterostructures is computed using empirical tight binding and it is shown that the average non-homogeneous strain in these structures drives their interesting non-conventional electronic characteristics such as hole effective masses which decrease as the wire cross-section is reduced. (4) It is shown that tight binding, though empirical in nature, is not necessarily limited to the material and atomic structure for which the parameters have been empirically derived, but that simple changes may adapt the derived parameters to new bond environments. Si (100) surface electronic structure is obtained from bulk Si parameters.

Band alignment and charge transfer predictions of ZnO/ZnX (X = S, Se or Te) interfaces applied to solar cells: a PBE+U theoretical study.

PubMed

Flores, Efracio Mamani; Gouvea, Rogério Almeida; Piotrowski, Maurício Jeomar; Moreira, Mário Lucio

2018-02-14

The engineering of semiconductor materials for the development of solar cells is of great importance today. Two topics are considered to be of critical importance for the efficiency of Grätzel-type solar cells, the efficiency of charge separation and the efficiency of charge carrier transfer. Thus, one research focus is the combination of semiconductor materials with the aim of reducing charge recombination, which occurs by spatial charge separation. From an experimental point of view, the combining of materials can be achieved by decorating a core with a shell of another material resulting in a core-shell system, which allows control of the desired photoelectronic properties. In this context, a computational simulation is mandatory for the atomistic understanding of possible semiconductor combinations and for the prediction of their properties. Considering the construction of ZnO/ZnX (X = S, Se or Te) interfaces, we seek to investigate the electronic influence of the shell (ZnX) on the core (ZnO) and, consequently, find out which of the interfaces would present the appropriate properties for (Grätzel-type) solar cell applications. To perform this study, we have employed density functional theory (DFT) calculations, considering the Perdew-Burke-Ernzerhof (PBE) functional. However, it is well-known that plain DFT fails to describe strong electronic correlated materials where, in general, an underestimation of the band gap is obtained. Thus, to obtain the correct description of the electronic properties, a Hubbard correction was employed, i.e. PBE+U calculations. The PBE+U methodology provided the correct electronic structure properties for bulk ZnO in good agreement with experimental values (99.4%). The ZnO/ZnX interfaces were built and were composed of six ZnO layers and two ZnX layers, which represents the decoration process. The core-shell band gap was 2.2 eV for ZnO/ZnS, ∼1.71 eV for ZnO/ZnSe and ∼0.95 eV for ZnO/ZnTe, which also exhibited a type-II band alignment. Bader charge analysis showed an accumulation of charges in the 6th layer of ZnO for the three ZnO/ZnX interfaces. On the basis of these results, we have proposed that ZnO/ZnS and ZnO/ZnSe core-shell structures can be applied as good candidates (with better efficiency) for photovoltaic devices.

Plasmon modes supported by left-handed material slab waveguide with conducting interfaces

NASA Astrophysics Data System (ADS)

Taya, Sofyan A.

2018-07-01

Theoretical analysis of left-handed material core layer waveguide in the presence of interface free charge layers is presented. The thickness of the interface charge layer can be neglected compared with the incident wavelength. The tangential component of the magnetic field is no longer continuous due to the conducting interfaces. The non-homogeneous boundary conditions are solved and the corresponding dispersion relation is found. The dispersion properties are studied. The proposed structure is found to support even as well as odd plasmon modes. Moreover, the structure shows abnormal dispersion property of decreasing the effective index with the increase of the frequency which means negative group velocity.

Advanced concepts for transformers pressboard dielectric constant and mechanical strength

NASA Astrophysics Data System (ADS)

1982-03-01

Of the numerous electrical considerations in a material, the value of the dielectric constant serves as an important criterion in designing proper insulation systems. Ways to reduce the dielectric constant of solid (fibrous) insulating materials were investigated. A literature search was made on cellulosic and synthetic fibers and also additives which offered the potential for dielectric constant reduction of the solid insulation. Sample board structures were produced in the laboratory and tested for electrical, mechanical and chemical characteristics. Electrical tests determined the suitability of the material at transformer test and operating conditions. The mechanical tests established the physical characteristics of the modified board structures. Chemical tests checked the conductivity of the aqueous extract, acidity, and ash content. Further, compatibility with transformer oil and some aging tests were performed. An actual computer transformer design was made based on one of the modified board structures and the reduction in core steel and transformer losses were shown.

Crystal MD: The massively parallel molecular dynamics software for metal with BCC structure

NASA Astrophysics Data System (ADS)

Hu, Changjun; Bai, He; He, Xinfu; Zhang, Boyao; Nie, Ningming; Wang, Xianmeng; Ren, Yingwen

2017-02-01

Material irradiation effect is one of the most important keys to use nuclear power. However, the lack of high-throughput irradiation facility and knowledge of evolution process, lead to little understanding of the addressed issues. With the help of high-performance computing, we could make a further understanding of micro-level-material. In this paper, a new data structure is proposed for the massively parallel simulation of the evolution of metal materials under irradiation environment. Based on the proposed data structure, we developed the new molecular dynamics software named Crystal MD. The simulation with Crystal MD achieved over 90% parallel efficiency in test cases, and it takes more than 25% less memory on multi-core clusters than LAMMPS and IMD, which are two popular molecular dynamics simulation software. Using Crystal MD, a two trillion particles simulation has been performed on Tianhe-2 cluster.

Braided reinforced composite rods for the internal reinforcement of concrete

NASA Astrophysics Data System (ADS)

Gonilho Pereira, C.; Fangueiro, R.; Jalali, S.; Araujo, M.; Marques, P.

2008-05-01

This paper reports on the development of braided reinforced composite rods as a substitute for the steel reinforcement in concrete. The research work aims at understanding the mechanical behaviour of core-reinforced braided fabrics and braided reinforced composite rods, namely concerning the influence of the braiding angle, the type of core reinforcement fibre, and preloading and postloading conditions. The core-reinforced braided fabrics were made from polyester fibres for producing braided structures, and E-glass, carbon, HT polyethylene, and sisal fibres were used for the core reinforcement. The braided reinforced composite rods were obtained by impregnating the core-reinforced braided fabric with a vinyl ester resin. The preloading of the core-reinforced braided fabrics and the postloading of the braided reinforced composite rods were performed in three and two stages, respectively. The results of tensile tests carried out on different samples of core-reinforced braided fabrics are presented and discussed. The tensile and bending properties of the braided reinforced composite rods have been evaluated, and the results obtained are presented, discussed, and compared with those of conventional materials, such as steel.

Adhesion of resin composite core materials to dentin.

PubMed

O'Keefe, K L; Powers, J M

2001-01-01

This study determined (1) the effect of polymerization mode of resin composite core materials and dental adhesives on the bond strength to dentin, and (2) if dental adhesives perform as well to dentin etched with phosphoric acid as to dentin etched with self-etching primer. Human third molars were sectioned 2 mm from the highest pulp horn and polished. Three core materials (Fluorocore [dual cured], Core Paste [self-cured], and Clearfil Photo Core [light cured]) and two adhesives (Prime & Bond NT Dual Cure and Clearfil SE Bond [light cured]) were bonded to dentin using two dentin etching conditions. After storage, specimens were debonded in microtension and bond strengths were calculated. Scanning electron micrographs of representative bonding interfaces were analyzed. Analysis showed differences among core materials, adhesives, and etching conditions. Among core materials, dual-cured Fluorocore had the highest bond strengths. There were incompatibilities between self-cured Core Paste and Prime & Bond NT in both etched (0 MPa) and nonetched (3.0 MPa) dentin. Among adhesives, in most cases Clearfil SE Bond had higher bond strengths than Prime & Bond NT and bond strengths were higher to self-etched than to phosphoric acid-etched dentin. Scanning electron micrographs did not show a relationship between resin tags and bond strengths. There were incompatibilities between a self-cured core material and a dual-cured adhesive. All other combinations of core materials and adhesives produced strong in vitro bond strengths both in the self-etched and phosphoric acid-etched conditions.

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

Altay, A.; Carter, C.B., E-mail: cbcarter@engr.uconn.ed; Rulis, P.

Calcium aluminates, compounds in the CaO-Al{sub 2}O{sub 3} phase system, are used in high-temperature cements and refractory oxides and have wide range of potential technological applications due to their interesting optical, electrical, thermal, and mechanical properties. They are used in both crystalline and glassy form; the glass is an isotropic material while the crystalline materials may be highly anisotropic. This paper will consider two particular crystalline materials, CA{sub 2} and CA{sub 6}, but the results should be applicable to all calcium aluminates. Although CA{sub 2} and CA{sub 6} crystals contain the same chemical species, Ca, Al, and O, the coordinationmore » and local environments of these species are different in the two structures and hence they show very different energy-loss near-edge structures (ELNES) when examined by electron energy-loss spectroscopy (EELS) in the TEM. The data obtained using ELNES can effectively provide a fingerprint for each compound and a map for their electronic structure. Once such fingerprints are obtained, they can be used to identify nano-sized particles/grains or material at interfaces and grain boundaries. In the present study, the local symmetry fingerprints for CA{sub 2} and CA{sub 6} structures are reported combining experimental spectra with electronic-structure calculations that allow the different features in the spectra to be interpreted. Al-L{sub 2,3} and O-K edge core-loss spectra from CA{sub 2} and CA{sub 6} were measured experimentally using electron energy-loss spectroscopy in a monochromated scanning transmission electron microscope. The near-edge structures were calculated for the different phases using the orthogonalized linear combination of atomic-orbitals method, and took account of core-hole interactions. It is shown that CA{sub 2} and CA{sub 6} structures exhibit distinctive experimental ELNES fingerprints so that these two phases can be separately identified even when present in small volumes. - Graphical abstract: Projection of the CA{sub 2} structure viewed in the [010] direction. Green atoms represent the Ca{sup 2+} ions and blue atoms represent the Al{sup 3+} ions. Two unit cells are outlined..« less

Preparation of PPy-Coated MnO2 Hybrid Micromaterials and Their Improved Cyclic Performance as Anode for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Feng, Lili; Zhang, Yinyin; Wang, Rui; Zhang, Yanli; Bai, Wei; Ji, Siping; Xuan, Zhewen; Yang, Jianhua; Zheng, Ziguang; Guan, Hongjin

2017-09-01

MnO2@PPy core-shell micromaterials are prepared by chemical polymerization of pyrrole on the MnO2 surface. The polypyrrole (PPy) is formed as a homogeneous organic shell on the MnO2 surface. The thickness of PPy shell can be adjusted by the usage of pyrrole. The analysis of SEM, FT-IR, X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and XRD are used to confirm the formation of PPy shell. Galvanostatic cell cycling and electrochemical impedance spectroscopy (EIS) are used to evaluate the electrochemical performance as anode for lithium-ion batteries. The results show that after formation of MnO2@PPy core-shell micromaterials, the cyclic performance as anode for lithium-ion batteries is improved. Fifty microliters of PPy-coated caddice-clew-like MnO2 has the best cyclic performances as has 620 mAh g-1 discharge specific capacities after 300 cycles. As a comparison, the discharge specific capacity of bare MnO2 materials falls to below 200 mAh g-1 after 10 cycles. The improved lithium-storage cyclic stability of the MnO2@PPy samples attributes to the core-shell hybrid structure which can buffer the structural expansion and contraction of MnO2 caused by the repeated embedding and disengagement of Li ions and can prevent the pulverization of MnO2. This experiment provides an effective way to mitigate the problem of capacity fading of the transition metal oxide materials as anode materials for (lithium-ion batteries) LIBs.

Preparation of PPy-Coated MnO2 Hybrid Micromaterials and Their Improved Cyclic Performance as Anode for Lithium-Ion Batteries.

PubMed

Feng, Lili; Zhang, Yinyin; Wang, Rui; Zhang, Yanli; Bai, Wei; Ji, Siping; Xuan, Zhewen; Yang, Jianhua; Zheng, Ziguang; Guan, Hongjin

2017-09-02

MnO 2 @PPy core-shell micromaterials are prepared by chemical polymerization of pyrrole on the MnO 2 surface. The polypyrrole (PPy) is formed as a homogeneous organic shell on the MnO 2 surface. The thickness of PPy shell can be adjusted by the usage of pyrrole. The analysis of SEM, FT-IR, X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and XRD are used to confirm the formation of PPy shell. Galvanostatic cell cycling and electrochemical impedance spectroscopy (EIS) are used to evaluate the electrochemical performance as anode for lithium-ion batteries. The results show that after formation of MnO 2 @PPy core-shell micromaterials, the cyclic performance as anode for lithium-ion batteries is improved. Fifty microliters of PPy-coated caddice-clew-like MnO 2 has the best cyclic performances as has 620 mAh g -1 discharge specific capacities after 300 cycles. As a comparison, the discharge specific capacity of bare MnO 2 materials falls to below 200 mAh g -1 after 10 cycles. The improved lithium-storage cyclic stability of the MnO 2 @PPy samples attributes to the core-shell hybrid structure which can buffer the structural expansion and contraction of MnO 2 caused by the repeated embedding and disengagement of Li ions and can prevent the pulverization of MnO 2 . This experiment provides an effective way to mitigate the problem of capacity fading of the transition metal oxide materials as anode materials for (lithium-ion batteries) LIBs.

STRESS AND FAILURE ANALYSIS OF RAPIDLY ROTATING ASTEROID (29075) 1950 DA

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

Hirabayashi, Masatoshi; Scheeres, Daniel J., E-mail: masatoshi.hirabayashi@colorado.edu

Rozitis et al. recently reported that near-Earth asteroid (29075) 1950 DA, whose bulk density ranges from 1.0 g cm{sup –3} to 2.4 g cm{sup –3}, is a rubble pile and requires a cohesive strength of at least 44-76 Pa to keep from failing due to its fast spin period. Since their technique for giving failure conditions required the averaged stress over the whole volume, it discarded information about the asteroid's failure mode and internal stress condition. This paper develops a finite element model and revisits the stress and failure analysis of 1950 DA. For the modeling, we do not consider material hardening andmore » softening. Under the assumption of an associated flow rule and uniform material distribution, we identify the deformation process of 1950 DA when its constant cohesion reaches the lowest value that keeps its current shape. The results show that to avoid structural failure the internal core requires a cohesive strength of at least 75-85 Pa. It suggests that for the failure mode of this body, the internal core first fails structurally, followed by the surface region. This implies that if cohesion is constant over the whole volume, the equatorial ridge of 1950 DA results from a material flow going outward along the equatorial plane in the internal core, but not from a landslide as has been hypothesized. This has additional implications for the likely density of the interior of the body.« less

Diametral and compressive strength of dental core materials.

PubMed

Cho, G C; Kaneko, L M; Donovan, T E; White, S N

1999-09-01

Strength greatly influences the selection of core materials. Many disparate material types are now recommended for use as cores. Cores must withstand forces due to mastication and parafunction for many years. This study compared the compressive and diametral tensile strengths of 8 core materials of various material classes and formulations (light-cured hybrid composite, autocured titanium containing composite, amalgam, glass ionomer, glass ionomer cermet, resin-modified glass ionomer, and polyurethane). Materials were manipulated according to manufacturers' instructions for use as cores. Mean compressive and diametral strengths with associated standard errors were calculated for each material (n = 10). Analyses of variance were computed (P <.0001) and multiple comparisons tests discerned many differences among materials. Compressive strengths varied widely from 61.1 MPa for a polyurethane to 250 MPa for a resin composite. Diametral tensile strengths ranged widely from 18.3 MPa for a glass ionomer cermet to 55.1 MPa for a resin composite. Some resin composites had compressive and tensile strengths equal to those of amalgam. Light-cured hybrid resin composites were stronger than autocured titanium containing composites. The strengths of glass ionomer-based materials and of a polyurethane material were considerably lower than for resin composites or amalgam.

Core-Cutoff Tool

NASA Technical Reports Server (NTRS)

Gheen, Darrell

2007-01-01

A tool makes a cut perpendicular to the cylindrical axis of a core hole at a predetermined depth to free the core at that depth. The tool does not damage the surrounding material from which the core was cut, and it operates within the core-hole kerf. Coring usually begins with use of a hole saw or a hollow cylindrical abrasive cutting tool to make an annular hole that leaves the core (sometimes called the plug ) in place. In this approach to coring as practiced heretofore, the core is removed forcibly in a manner chosen to shear the core, preferably at or near the greatest depth of the core hole. Unfortunately, such forcible removal often damages both the core and the surrounding material (see Figure 1). In an alternative prior approach, especially applicable to toxic or fragile material, a core is formed and freed by means of milling operations that generate much material waste. In contrast, the present tool eliminates the damage associated with the hole-saw approach and reduces the extent of milling operations (and, hence, reduces the waste) associated with the milling approach. The present tool (see Figure 2) includes an inner sleeve and an outer sleeve and resembles the hollow cylindrical tool used to cut the core hole. The sleeves are thin enough that this tool fits within the kerf of the core hole. The inner sleeve is attached to a shaft that, in turn, can be attached to a drill motor or handle for turning the tool. This tool also includes a cutting wire attached to the distal ends of both sleeves. The cutting wire is long enough that with sufficient relative rotation of the inner and outer sleeves, the wire can cut all the way to the center of the core. The tool is inserted in the kerf until its distal end is seated at the full depth. The inner sleeve is then turned. During turning, frictional drag on the outer core pulls the cutting wire into contact with the core. The cutting force of the wire against the core increases with the tension in the wire and, hence, with the frictional drag acting on the outer sleeve. As the wire cuts toward the center of the core, the inner sleeve rotates farther with respect to the outer sleeve. Once the wire has cut to the center of the core, the tool and the core can be removed from the hole. The proper choice of cutting wire depends on the properties of the core material. For a sufficiently soft core material, a nonmetallic monofilament can be used. For a rubber-like core material, a metal wire can be used. For a harder core material, it is necessary to use an abrasive wire, and the efficiency of the tool can be increased greatly by vacuuming away the particles generated during cutting. For a core material that can readily be melted or otherwise cut by use of heat, it could be preferable to use an electrically heated cutting wire. In such a case, electric current can be supplied to the cutting wire, from an electrically isolated source, via rotating contact rings mounted on the sleeves.

A combined NDE/FEA approach to evaluate the structural response of a metal foam

NASA Astrophysics Data System (ADS)

Ghosn, Louis J.; Abdul-Aziz, Ali; Raj, Sai V.; Rauser, Richard W.

2007-04-01

Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight metal foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans. The series of the 2D images are assembled to construct a high precision solid model capturing all the fine details within the metal foam as detected by the CT scanning technique. Moreover, a finite element analysis is then performed on as fabricated metal foam microstructures, to calculate the foam mechanical properties with the idealized theory. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile and compressive mechanical properties are deduced from the FEA model and compared with the theoretical values for three different foam densities. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

Porous HKUST-1 derived CuO/Cu2O shell wrapped Cu(OH)2 derived CuO/Cu2O core nanowire arrays for electrochemical nonenzymatic glucose sensors with ultrahigh sensitivity

NASA Astrophysics Data System (ADS)

Yu, Cuiping; Cui, Jiewu; Wang, Yan; Zheng, Hongmei; Zhang, Jianfang; Shu, Xia; Liu, Jiaqin; Zhang, Yong; Wu, Yucheng

2018-05-01

Self-supported CuO/Cu2O@CuO/Cu2O core-shell nanowire arrays (NWAs) are successfully fabricated by a simple and efficient method in this paper. Anodized Cu(OH)2 NWAs could in-situ convert to HKUST-1 at room temperature easily. Cu(OH)2 NWAs cores and HKUST-1 shells transform into CuO/Cu2O simultaneously after calcinations and form CuO/Cu2O@CuO/Cu2O core-shell NWAs. This smart configuration of the core-shell structure not only avoids the agglomeration of the traditional MOF-derived materials in particle-shape, but also facilitates the ion diffusion and increases the active sites. This novel structure is employed as substrate to construct nonenzymatic glucose sensors. The results indicate that glucose sensor based on CuO/Cu2O@CuO/Cu2O core-shell NWAs presents ultrahigh sensitivity (10,090 μA mM-1 cm-2), low detection limit (0.48 μM) and wide linear range (0.99-1,330 μM). In addition, it also shows excellent anti-interference ability toward uric acid, ascorbic acid and L-Cysteine co-existing with glucose, good reproducibility and superior ability of real sample analysis.

Solvent-free nanofluid with three structure models based on the composition of a MWCNT/SiO2 core and its adsorption capacity of CO2

NASA Astrophysics Data System (ADS)

Yang, R. L.; Zheng, Y. P.; Wang, T. Y.; Li, P. P.; Wang, Y. D.; Yao, D. D.; Chen, L. X.

2018-01-01

A series of core/shell nanoparticle organic/inorganic hybrid materials (NOHMs) with different weight ratios of two components, consisting of multi-walled carbon nanotubes (MWCNTs) and silicon dioxide (SiO2) as the core were synthesized. The NOHMs display a liquid-like state in the absence of solvent at room temperature. Five NOHMs were categorized into three kinds of structure states based on different weight ratio of two components in the core, named the power strip model, the critical model and the collapse model. The capture capacities of these NOHMs for CO2 were investigated at 298 K and CO2 pressures ranging from 0 to 5 MPa. Compared with NOHMs having a neat MWCNT core, it was revealed that NOHMs with the power strip model show better adsorption capacity toward CO2 due to its lower viscosity and more reactive groups that can react with CO2. In addition, the capture capacities of NOHMs with the critical model were relatively worse than the neat MWCNT-based NOHM. The result is attributed to the aggregation of SiO2 in these samples, which may cause the consumption and hindrance of reactive groups. However, the capture capacity of NOHMs with the collapse model was the worst of all the NOHMs, owing to its lowest content of reactive groups and hollow structure in MWCNTs. In addition, they presented non-interference of MWCNTs and SiO2 without aggregation state.

Radiation Shielding System Using a Composite of Carbon Nanotubes Loaded with Electropolymers

NASA Technical Reports Server (NTRS)

McKay, Chris; Chen, Bin

2012-01-01

Single-wall carbon nanotubes (SWCNTs) coated with a hydrogen-rich, electrically conducting polymer such as polyethylene, receive and dissipate a portion of incoming radiation pulse energy to electrical signals that are transmitted along the CNT axes, and are received at energy-dissipating terminals. In this innovation, an array of highly aligned nanowires is grown using a strong electric field or another suitable orientation procedure. Polyethylene (PE), polymethymlethacrylate (PMMA), or other electrically conducting polymer is spin-coated onto the SWCNTs with an average thickness of a few hundred nanometers to a few tenths of micrometers to form a PE/SWCNT composite. Alternatively, the polymer is spin-coated onto the nanowire array or an anodized alumina membrane (AAM) to form a PE/metal core shell structure, or PE can be electropolymerized using the SWCNTs or the metal nanowires as an electrode to form a PE/SWCNT core shell structure. The core shell structures can be extruded as anisotropic fibers. A monomer can be polymerized in the presence of SWCNTs to form highly cross-linked PE/SWCNT films. Alternatively, Pb colloid solution can be impregnated into a three-dimensional PE/SWCNT nanostructure to form a PW/SWCNT/Pb composite structure. A face-centered cubic (FCC) arrangement provides up to 12 interconnection channels connected to each core, with transverse channel dimensions up to 20 nm, with adequate mechanical compressive strength, and with an associated electrical conductivity of around 3 Seimens/cm for currents ranging from 0.01 to 10 mA. This threedimensional nanostructure is used as a host material to house appropriate radiation shielding material such as hydrogen- rich polymer/CNT structures, metal nanoparticles, and nanowires. Thicknesses of this material required to attenuate 10 percent, 50 percent, and 90 percent of an incident beam (gamma, X-ray, ultraviolet, neutron, proton, and electron) at energies in the range of 0 440 MeV are being determined, for example, by measuring fluence rate reduction. For example, a radiation field arrives first at an exposed surface of the innovation and produces an associated first electric field within the metal-like fingers of the three-dimensional nanostructure. This field is intensified near the exposed tips of the fingers, and this intensified field generates an intensified second electric field near the adjacent exposed tips of the coated CNSs. This generates an associated electrical current in the CNSs, and the associated electropolymer coating. The current is received by the second substrate transport component and is transported to the dissipation mechanism located contiguously to the second substrate.

Ni-Co alloy plaque for cathode of Ni-Cd battery

NASA Astrophysics Data System (ADS)

Lander, J. J.

1986-03-01

The present invention relates generally to Ni-Cd batteries, and, in particular, relates to the plaque material attached to the cathode. Because of the wide use of nickel-cadmium batteries, the corrosion rates of nickel and nickel-cobalt alloys are of interest to nickel-cadmium battery electrochemical theory and its technology. The plaque material of the cathode consists of a Ni-Co alloy in solid solution wherein the cobalt is by weight percent one to ten percent of the alloy. Conventional methods of applying the plaque material to the nickel core may be used. It is therefore an object of the present invention to provide an improved cathode for a nickel-cadmium battery wherein the nickel corrosion is substantially lessened in the plaque material. One process of making the plaque uses a nickel powder slurry that is applied to a nickel-plated steel core. This is then sintered at a high temperature which results in a very porous structure and an welding of the nickel grains to the core. This plaque is then soaked in appropriate salts to make either a positive or a negative plate; nickel salts make a positive plate and a cadmium salts a negative plate, for example. After impregnation, the plaque is placed in an electrolyte and an electric current is passed therethrough to convert the salts to their final form. In the nickel-cadmium cell, nickel hydroxide is the active material in the positive plate.

Next Generation Car — Example of Function Integration at the Light Urban Vehicle (LUV) Vehicle Concept

NASA Astrophysics Data System (ADS)

Kopp, G.; Brückmann, S.; Kriescher, M.; Friedrich, H. E.

In times of climate change vehicle emissions have to be reduced clearly. One possibility is to reduce the mass of the body in white using lightweight sandwich structures. The department `Lightweight and Hybrid Design Methods' of the Institute of Vehicle Concepts develops a vehicle body structure by using sandwiches with aluminum top layers and polyurethane foam as core material. For that the foam and the sandwiches were investigated under different load cases, e.g. pressure loading and in-plane tests. In tests with components the high potential of the sandwich materials were shown. On the dynamic component test facility of the institute, vehicle front structures were tested successfully. The results of all investigations regarding sandwich materials, integration of functions (e.g. crash, thermal) in vehicle structures and the concept LUV are developed under the research program of Next Generation Car of the DLR. We will show the development and results of the LUV.

Modulated nematic structures induced by chirality and steric polarization

NASA Astrophysics Data System (ADS)

Longa, Lech; PajÄ k, Grzegorz

2016-04-01

What kind of one-dimensional modulated nematic structures (ODMNS) can form nonchiral and chiral bent-core and dimeric materials? Here, using the Landau-de Gennes theory of nematics, extended to account for molecular steric polarization, we study a possibility of formation of ODMNS, both in nonchiral and intrinsically chiral liquid crystalline materials. Besides nematic and cholesteric phases, we find four bulk ODMNS for nonchiral materials, two of which, to the best of our knowledge, have not been reported so far. These two structures are longitudinal (NLP) and transverse (NTP) periodic waves where the polarization field being periodic in one dimension stays parallel and perpendicular, respectively, to the wave vector. The other two phases are the twist-bend nematic phase (NTB) and the splay-bend nematic phase (NSB), but their fine structure appears more complex than that considered so far. The presence of molecular chirality converts nonchiral NTP and NSB into new NTB phases. Surprisingly, the nonchiral NLP phase can stay stable even in the presence of intrinsic chirality.

Hierarchical MoO3/SnS2 core-shell nanowires with enhanced electrochemical performance for lithium-ion batteries.

PubMed

Hu, Chenli; Shu, Haibo; Shen, Zihong; Zhao, Tianfeng; Liang, Pei; Chen, Xiaoshuang

2018-06-27

Two-dimensional (2D) tin disulfide (SnS2) is a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. The main challenges associated with the SnS2 electrodes are the poor cycling stability and low rate capability due to structural degradation in the discharge/charge process. Here, a facile two-step synthesis method is developed to fabricate hierarchical MoO3/SnS2 core-shell nanowires, where ultrathin SnS2 nanosheets are vertically anchored on MoO3 nanobelts to induce a heterointerface. Benefiting from the unique structural and compositional characteristics, the hierarchical MoO3/SnS2 core-shell nanowires exhibit excellent electrochemical performance and deliver a high reversible capacity of 504 mA h g-1 after 100 stable cycles at a current density of 100 mA g-1, which is far superior to the MoO3 and SnS2 electrodes. An analysis of lithiation dynamics based on ab initio molecular dynamics simulations demonstrates that the formation of a hierarchical MoO3/SnS2 core-shell heterostructure can effectively suppress the rapid dissociation of shell-layer SnS2 nanosheets via the interfacial coupling effect and the central MoO3 backbone can trap and support the polysulfide in the discharge/charge process. The results are responsible for the high storage capacity and rate capability of MoO3/SnS2 electrode materials. This work provides a novel design strategy for constructing high-performance electrodes for LIBs.

Necroplanetology: Disrupted Planetary Material Transiting WD 1145+017

NASA Astrophysics Data System (ADS)

Manideep Duvvuri, Girish; Redfield, Seth; Veras, Dimitri

2018-06-01

The WD 1145+017 system shows irregular transit features that are consistent with the tidal disruption of differentiated asteroids with bulk densities < 4 g cm-3 and bulk masses < 1021 kg. We use the open-source N-body code REBOUND to simulate this disruption with different internal structures: varying the core volume fraction, mantle/core density ratio, and the presence/absence of a thin low-density crust. We show that these parameters have observationally distinguishable effects on the transit light curve as the asteroid is disrupted and fit the simulation-generated lightcurves to data. We find that an asteroid with a low core fraction, low mantle/density ratio, and without a crust is most consistent with the A1 feature present for multiple weeks circa April 2017. This combination of observations and simulations to study the interior structure and chemistry of exoplanetary bodies via their destruction in action is an early example of necroplanetology, a field that will hopefully grow with the discovery of other systems like WD 1145+017.

Core-shell VO2@TiO2 nanorods that combine thermochromic and photocatalytic properties for application as energy-saving smart coatings

PubMed Central

Li, Yamei; Ji, Shidong; Gao, Yanfeng; Luo, Hongjie; Kanehira, Minoru

2013-01-01

Vanadium dioxide (VO2) is a Mott phase transition compound that can be applied as a thermochromic smart material for energy saving and comfort, and titanium dioxide (TiO2) is a well-known photocatalyst for self-cleaning coatings. In this paper, we report a VO2@TiO2 core-shell structure, in which the VO2 nanorod core exhibits a remarkable modulation ability for solar infrared light, and the TiO2 anatase shell exhibits significant photocatalytic degradation of organic dye. In addition, the TiO2 overcoating not only increased the luminous transmittance of VO2 based on an antireflection effect, but also modified the intrinsic colour of VO2 films from yellow to light blue. The TiO2 also enhanced the chemical stability of VO2 against oxidation. This is the first report of such a single nanoparticle structure with both thermochromic and photocatalytic properties that offer significant potential for creating a multifunctional smart coating. PMID:23546301

Core-shell VO2@TiO2 nanorods that combine thermochromic and photocatalytic properties for application as energy-saving smart coatings.

PubMed

Li, Yamei; Ji, Shidong; Gao, Yanfeng; Luo, Hongjie; Kanehira, Minoru

2013-01-01

Vanadium dioxide (VO2) is a Mott phase transition compound that can be applied as a thermochromic smart material for energy saving and comfort, and titanium dioxide (TiO2) is a well-known photocatalyst for self-cleaning coatings. In this paper, we report a VO2@TiO2 core-shell structure, in which the VO2 nanorod core exhibits a remarkable modulation ability for solar infrared light, and the TiO2 anatase shell exhibits significant photocatalytic degradation of organic dye. In addition, the TiO2 overcoating not only increased the luminous transmittance of VO2 based on an antireflection effect, but also modified the intrinsic colour of VO2 films from yellow to light blue. The TiO2 also enhanced the chemical stability of VO2 against oxidation. This is the first report of such a single nanoparticle structure with both thermochromic and photocatalytic properties that offer significant potential for creating a multifunctional smart coating.

DNA nanoparticles with core-shell morphology.

PubMed

Chandran, Preethi L; Dimitriadis, Emilios K; Lisziewicz, Julianna; Speransky, Vlad; Horkay, Ferenc

2014-10-14

Mannobiose-modified polyethylenimines (PEI) are used in gene therapy to generate nanoparticles of DNA that can be targeted to the antigen-presenting cells of the immune system. We report that the sugar modification alters the DNA organization within the nanoparticles from homogenous to shell-like packing. The depth-dependent packing of DNA within the nanoparticles was probed using AFM nano-indentation. Unmodified PEI-DNA nanoparticles display linear elastic properties and depth-independent mechanics, characteristic of homogenous materials. Mannobiose-modified nanoparticles, however, showed distinct force regimes that were dependent on indentation depth, with 'buckling'-like response that is reproducible and not due to particle failure. By comparison with theoretical studies of spherical shell mechanics, the structure of mannobiosylated particles was deduced to be a thin shell with wall thickness in the order of few nanometers, and a fluid-filled core. The shell-core structure is also consistent with observations of nanoparticle denting in altered solution conditions, with measurements of nanoparticle water content from AFM images, and with images of DNA distribution in Transmission Electron Microscopy.

Peculiar bonding associated with atomic doping and hidden honeycombs in borophene

NASA Astrophysics Data System (ADS)

Lee, Chi-Cheng; Feng, Baojie; D'angelo, Marie; Yukawa, Ryu; Liu, Ro-Ya; Kondo, Takahiro; Kumigashira, Hiroshi; Matsuda, Iwao; Ozaki, Taisuke

2018-02-01

Engineering atomic-scale structures allows great manipulation of physical properties and chemical processes for advanced technology. We show that the B atoms deployed at the centers of honeycombs in boron sheets, borophene, behave as nearly perfect electron donors for filling the graphitic σ bonding states without forming additional in-plane bonds by first-principles calculations. The dilute electron density distribution owing to the weak bonding surrounding the center atoms provides easier atomic-scale engineering and is highly tunable via in-plane strain, promising for practical applications, such as modulating the extraordinarily high thermal conductance that exceeds the reported value in graphene. The hidden honeycomb bonding structure suggests an unusual energy sequence of core electrons that has been verified by our high-resolution core-level photoelectron spectroscopy measurements. With the experimental and theoretical evidence, we demonstrate that borophene exhibits a peculiar bonding structure and is distinctive among two-dimensional materials.

Design of a composite wing extension for a general aviation aircraft

NASA Technical Reports Server (NTRS)

Adney, P. S.; Horn, W. J.

1984-01-01

A composite wing extension was designed for a typical general aviation aircraft to improve lift curve slope, dihedral effect, and lift to drag ratio. Advanced composite materials were used in the design to evaluate their use as primary structural components in general aviation aircraft. Extensive wind tunnel tests were used to evaluate six extension shapes. The extension shape chosen as the best choice was 28 inches long with a total area of 17 square feet. Subsequent flight tests showed the wing extension's predicted aerodynamic improvements to be correct. The structural design of the wing extension consisted of a hybrid laminate carbon core with outer layers of Kevlar - layed up over a foam interior which acted as an internal support. The laminate skin of the wing extension was designed from strength requirements, and the foam core was included to prevent buckling. A joint lap was recommended to attach the wing extension to the main wing structure.

Failure Predictions for VHTR Core Components using a Probabilistic Contiuum Damage Mechanics Model

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

Fok, Alex

2013-10-30

The proposed work addresses the key research need for the development of constitutive models and overall failure models for graphite and high temperature structural materials, with the long-term goal being to maximize the design life of the Next Generation Nuclear Plant (NGNP). To this end, the capability of a Continuum Damage Mechanics (CDM) model, which has been used successfully for modeling fracture of virgin graphite, will be extended as a predictive and design tool for the core components of the very high- temperature reactor (VHTR). Specifically, irradiation and environmental effects pertinent to the VHTR will be incorporated into the modelmore » to allow fracture of graphite and ceramic components under in-reactor conditions to be modeled explicitly using the finite element method. The model uses a combined stress-based and fracture mechanics-based failure criterion, so it can simulate both the initiation and propagation of cracks. Modern imaging techniques, such as x-ray computed tomography and digital image correlation, will be used during material testing to help define the baseline material damage parameters. Monte Carlo analysis will be performed to address inherent variations in material properties, the aim being to reduce the arbitrariness and uncertainties associated with the current statistical approach. The results can potentially contribute to the current development of American Society of Mechanical Engineers (ASME) codes for the design and construction of VHTR core components.« less

Bioinspired Single-Walled Carbon Nanotubes as a Spider Silk Structure for Ultrahigh Mechanical Property.

PubMed

Luo, Chengzhi; Li, Fangying; Li, Delong; Fu, Qiang; Pan, Chunxu

2016-11-16

Due to its unique hierarchical structure, natural spider silk features exceptional mechanical properties such as high tensile strength and great extensibility, making it one of the toughest materials. Herein, we design bioinspired spider silk single-walled carbon nanotubes (BISS-SWCNTs) that combine the hierarchical structure of spider silk and the high strength and conductivity of SWCNTs. To imitate the hierarchical structure, Fe nanoparticles are embedded on the surface of directly synthesized SWCNTs skeleton followed by coating an amorphous carbon layer. The carbon layer forms the spider silk-featured skin-core structure with SWCNTs, thus making the tube junction tougher. The embedded Fe nanoparticles act as glue spots for preventing interfacial slippages between the BISS-SWCNTs and the reinforced matrix. With only 2.1 wt % BISS-SWCNTs added, the tensile strength and Young's modulus of the BISS-SWCNTs/PMMA composites can be improved by 300%. More importantly, the BISS-SWCNTs also retain the high conductivity and transmittance of the pristine SWCNTs film. This unique bioinspired material will be of great importance in applications of multifunctional composite materials and has important implications for the future of biomimetic materials.

Fluorescent aromatic sensors and their methods of use

NASA Technical Reports Server (NTRS)

Meador, Michael A. (Inventor); Tyson, Daniel S. (Inventor); Ilan, Ulvi F. (Inventor)

2012-01-01

Aromatic molecules that can be used as sensors are described. The aromatic sensors include a polycyclic aromatic hydrocarbon core with a five-membered imide rings fused to the core and at least two pendant aryl groups. The aromatic sensor molecules can detect target analytes or molecular strain as a result of changes in their fluorescence, in many cases with on-off behavior. Aromatic molecules that fluoresce at various frequencies can be prepared by altering the structure of the aromatic core or the substituents attached to it. The aromatic molecules can be used as sensors for various applications such as, for example, the detection of dangerous chemicals, biomedical diagnosis, and the detection of damage or strain in composite materials. Methods of preparing aromatic sensor molecules are also described.

Preparation of ZnS@In2S3 Core@shell Composite for Enhanced Photocatalytic Degradation of Gaseous o-Dichlorobenzene under Visible Light.

PubMed

Liu, Baojun; Hu, Xia; Li, Xinyong; Li, Ying; Chen, Chang; Lam, Kwok-Ho

2017-11-27

In this study, novel ZnS@In 2 S 3 core@shell hollow nanospheres were fabricated by a facile refluxing method for the first time, and the formation mechanism of hollow structure with interior architecture was discussed based on ion-exchange Ostwald ripening. As the photocatalytic material for degradation of gaseous o-Dichlorobenzene (o-DCB), the as-synthesized core@shell hollow nanospheres were found to show significantly enhanced catalytic performance for effective separation of photo-generated charges. Moreover, the mechanisms of enhanced activity were elucidated by band alignment and unique configuration. Such photocatalyst would meet the demands for the control of persistent organic pollutant (POPs) in the atmospheric environment.

S&TR Preview: Smashing Materials to Reveal Unusual Behavior

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

Hunsberger, Maren; Akin, Minta; Chau, Ricky

2016-01-13

Squeeze a material hard enough, and its structure and properties will change, sometimes dramatically so. With enough heat and pressure, scientists can turn pencil lead (graphite), one of Earth’s softest materials, into diamond, one of its hardest. Apply even more pressure—such as might be found in explosions, detonating nuclear weapons, laser fusion experiments, meteorite impacts, or the hearts of stars and planets—and materials can take stranger forms. Deep in Jupiter’s core, for instance, where pressures likely reach 50 to 100 million times that of Earth’s atmosphere, hydrogen is predicted to be a metallic liquid rather than the familiar transparent gas.

Solid oxide fuel cell having monolithic core

DOEpatents

Ackerman, John P.; Young, John E.

1984-01-01

A solid oxide fuel cell for electrochemically combining fuel and oxidant for generating galvanic output, wherein the cell core has an array of electrolyte and interconnect walls that are substantially devoid of any composite inert materials for support. Instead, the core is monolithic, where each electrolyte wall consists of thin layers of cathode and anode materials sandwiching a thin layer of electrolyte material therebetween, and each interconnect wall consists of thin layers of the cathode and anode materials sandwiching a thin layer of interconnect material therebetween. The electrolyte walls are arranged and backfolded between adjacent interconnect walls operable to define a plurality of core passageways alternately arranged where the inside faces thereof have only the anode material or only the cathode material exposed. Means direct the fuel to the anode-exposed core passageways and means direct the oxidant to the cathode-exposed core passageway; and means also direct the galvanic output to an exterior circuit. Each layer of the electrolyte and interconnect materials is of the order of 0.002-0.01 cm thick; and each layer of the cathode and anode materials is of the order of 0.002-0.05 cm thick.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, David S.; Catchings, Rufus D.; Goldman, Mark R.; Gohn, Gregory S.; Horton, J. Wright; Edwards, Lucy E.; Rymer, Michael J.; Gandhok, Gini

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (~5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientific Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderate-amplitude, discontinuous, dipping reflections below ~527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ~527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fill sediments and postimpact Eocene to Pleistocene sediments. Reflections with ~20-30 m of relief in the uppermost part of the crater-fill and lowermost part of the postimpact section suggest differential compaction of the crater-fill materials during early postimpact time. The top of the crater-fill section also shows ~20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostrati-graphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the first possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postim-pact section unrelated to structures in the crater fill indicates postimpact sediment compaction.

Study of CT Scan Flooding System at High Temperature and Pressure

NASA Astrophysics Data System (ADS)

Chen, X. Y.

2017-12-01

CT scan flooding experiment can scan micro-pore in different flooding stages by the use of CT scan technology, without changing the external morphology and internal structure of the core, and observe the distribution characterization in pore medium of different flooding fluid under different pressure.thus,it can rebuilt the distribution images of oil-water distribution in different flooding stages. However,under extreme high pressure and temperature conditions,the CT scan system can not meet the requirements. Container of low density materials or thin shell can not resist high pressure,while high density materials or thick shell will cause attenuation and scattering of X-ray. The experiment uses a simple Ct scanning systems.X ray from a point light source passing trough a micro beryllium shell on High pressure stainless steal container,continuously irradiates the core holder that can continuously 360° rotate along the core axis. A rare earth intensifying screen behind the core holder emitting light when irradiated with X ray can show the core X ray section image. An optical camera record the core X ray images through a transparency high pressure glazing that placed on the High pressure stainless steal container.Thus,multiple core X ray section images can reconstruct the 3D core reconstruction after a series of data processing.The experiment shows that both the micro beryllium shell and rare earth intensifying screen can work in high temperature and high pressure environment in the stainless steal container. This way that X-ray passes through a thin layer of micro beryllium shell , not high pressure stainless steal shell,avoid the attenuation and scattering of X-ray from the container shell,while improving the high-pressure experiment requirements.

Developing core-shell upconversion nanoparticles for optical encoding

NASA Astrophysics Data System (ADS)

Huang, Kai

Lanthanide-doped upconversion nanoparticles (UCNPs) are an emerging class of luminescent materials that emit UV or visible light under near infra-red (NIR) excitations, thereby possessing a large anti-Stokes shift property. Also considering their sharp emission bands, excellent photo- and chemical stability, and almost zero auto-fluorescence of their NIR excitation, UCNPs are advantageous for optical encoding. Fabricating core-shell structured UCNPs provides a promising strategy to tune and enhance their upconverting luminescence. However, the energy transfer between core and shell had been rarely studied. Moreover, this strategy had been limited by the difficulty of coating thick shells onto the large cores of UCNPs. To overcome these constraints, the overall aim of this project is to study the inter-layers energy transfer in core-shell UCNPs and to develop an approach for coating thicker shell onto the core UCNPs, in order to fabricate UCNPs with enhanced and tunable luminescence for optical encoding. The strategy for encapsulating UCNPs into hydrogel droplet to fabricate multi-color bead barcodes has also been developed. Firstly, to study the inter-layers energy transfer between the core and shell of coreshell UCNPs, the activator and sensitizer ions were separately doped in the core or shell by fabricating NaYF4:Er NaYF4:Yb and NaYF4:Yb NaYF4:Er UCNPs. This eliminated the intra-layer energy transfer, resulting in a luminescence that is solely based on the energy transfer between layers, which facilitated the study of inter-layers energy transfer. The results demonstrated that the NaYF4:Yb NaYF4:Er structure, with sensitizer ions doped in the core, was preferable because of the strong luminescence, through minimizing the cross relaxations between Er3+ and Yb3+ and the surface quenching. Based on these information, a strategy of enhancing and tuning upconversion luminescence of core-shell UCNPs by accumulating sensitizer in the core has been developed. Next, a strategy of coating a thick shell by lutetium doping has been developed. With a smaller ion radius compared to Y3+, when Lu3+ partially replace Y3+ in the NaYF4 UCNPs during nanoparticle synthesis, nucleation process is suppressed and the growth process is promoted, which are favorable for increasing the nanoparticle size and coating a thicker shell onto the core UCNPs. Through the rational doping of Lu3+, core UCNPs with bigger sizes and enhanced luminescence were produced. Using NaLuF4 as the shell material, shells with tremendous thickness were coated onto core UCNPs, with the shell/core ratio of up to 10:1. This led to the fabrication of multi-color UCNPs with well-designed core-shell structures with multiple layers and controllable thicknesses. Finally, a strategy of encapsulating these UCNPs to produce optically encoded micro-beads through high-throughput microfluidics has been developed. The hydrophobic UCNPs were first modified with Pluronic F127 to render them hydrophilic and uniformly distributed in the poly (ethylene glycol) diacrylate (PEGDA) hydrogel precursor. Droplets of the hydrogel precursor were formed in a microfluidic device and cross-linked into micro-beads under UV irradiation. Through encapsulation of multi-color UCNPs and by controlling their ratio, optically encoded multi-color micro-beads have been easily fabricated. These multi-color UCNPs and micro-bead barcodes have great potential for use in multiplexed bioimaging and detection.

Structural Analysis and Optimization of a Composite Fan Blade for Future Aircraft Engine

NASA Astrophysics Data System (ADS)

Coroneos, Rula M.; Gorla, Rama Subba Reddy

2012-09-01

This paper addresses the structural analysis and optimization of a composite sandwich ply lay-up of a NASA baseline solid metallic fan blade comparable to a future Boeing 737 MAX aircraft engine. Sandwich construction with a polymer matrix composite face sheet and honeycomb aluminum core replaces the original baseline solid metallic fan model made of Titanium. The focus of this work is to design the sandwich composite blade with the optimum number of plies for the face sheet that will withstand the combined pressure and centrifugal loads while the constraints are satisfied and the baseline aerodynamic and geometric parameters are maintained. To satisfy the requirements a sandwich construction for the blade is proposed with composite face sheets and a weak core made of honeycomb aluminum material. For aerodynamic considerations, the thickness of the core is optimized where as the overall blade thickness is held fixed in order not to alter the original airfoil geometry. Weight reduction is taken as the objective function by varying the core thickness of the blade within specified upper and lower bounds. Constraints are imposed on radial displacement limitations and ply failure strength. From the optimum design, the minimum number of plies, which will not fail, is back-calculated. The ply lay-up of the blade is adjusted from the calculated number of plies and final structural analysis is performed. Analyses were carried out by utilizing the OpenMDAO Framework, developed at NASA Glenn Research Center combining optimization with structural assessment.

The structural conversion from α-AgVO3 to β-AgVO3: Ag nanoparticle decorated nanowires with application as cathode materials for Li-ion batteries.

PubMed

McNulty, David; Ramasse, Quentin; O'Dwyer, Colm

2016-09-15

The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO 3 nanowires (NWs) and their conversion to tunnel structured β-AgVO 3 NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO 3 to β-AgVO 3 is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO 3 NWs offers insight into the true β-AgVO 3 structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO 3 NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO 3 NWs have a core-shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO 3 NWs core material. Electrochemical comparison of α-AgVO 3 and β-AgVO 3 NWs confirms that β-AgVO 3 offers improved electrochemical performance. An ex situ structural characterization of β-AgVO 3 NWs after the first galvanostatic discharge and charge offers new insight into the Li + reaction mechanism for β-AgVO 3 . Ag + between the van der Waals layers of the vanadium oxide is reduced during discharge and deposited as metallic Ag, the vacant sites are then occupied by Li + .

Thermal conductivity at the nanoscale: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Lyver, John W., IV

With the growing use of nanotechnology and nanodevices in many fields of engineering and science, a need for understanding the thermal properties of such devices has increased. The ability for nanomaterials to conduct heat is highly dependent on the purity of the material, internal boundaries due to material changes and the structure of the material itself. Experimentally measuring the heat transport at the nanoscale is extremely difficult and can only be done as a macro output from the device. Computational methods such as various Monte Carlo (MC) and molecular dynamics (MD) techniques for studying the contribution of atomic vibrations associated with heat transport properties are very useful. The Green--Kubo method in conjunction with Fourier's law for calculating the thermal conductivity, kappa, has been used in this study and has shown promise as one approach well adapted for understanding nanosystems. Investigations were made of the thermal conductivity using noble gases, modeled with Lennard-Jones (LJ) interactions, in solid face-centered cubic (FCC) structures. MC and MD simulations were done to study homogeneous monatomic and binary materials as well as slabs of these materials possessing internal boundaries. Additionally, MD simulations were done on silicon carbide nanowires, nanotubes, and nanofilaments using a potential containing two-body and three-body terms. The results of the MC and MD simulations were matched against available experimental and other simulations and showed that both methods can accurately simulate real materials in a fraction of the time and effort. The results of the study show that in compositionally disordered materials the selection of atomic components by their mass, hard-core atomic diameter, well depth, and relative concentration can change the kappa by as much as an order of magnitude. It was found that a 60% increase in mass produces a 25% decrease in kappa. A 50% increase in interatomic strength produces a 25% increase in kappa, while as little as a 10% change in the hard core radius can almost totally suppress a materials ability to conduct heat. Additionally, for two LJ materials sharing an interface, the atomic vibrations altering the heat energy depend on the type of internal boundary in the material. Mass increases across the interfacial boundary enhance excitation of the very low frequency (ballistic) vibrational modes, while the opposite effect is seen as increases in hard core radius and interatomic strength enhance excitation of higher frequency vibrational modes. Additionally, it was found that this effect was diminished for higher temperatures around half the Debye temperatures. In nanodevices and nanomachines, there is an additional factor that degrades heat transport at the boundary. In fact, the interface induces a temperature jump consistent with a thermal resistance created by the boundary. It was found that the temperature jump, which is due to a boundary resistance, was significant in boundaries involving small mass changes, lesser in changes in hard core radii changes and even lesser for interatomic strength changes. The study of SiC nanowires and nanotubes showed that the structural changes produced vastly different kappa. The kappa in closely packed structures like nanowires and nanofilaments approximated that of the bulk SiC, yet were less sensitive to temperature than the 1/T relationship traditionally found in bulk systems. The more open nanostructures, like nanotubes, had vastly lower kappa values and are almost totally insensitive to temperature variation. The results of this study can be used in the design of nano-machines where heat generation and transport is a concern. Additionally, the design of nano-machines which transport heat like nano-refrigerators or nano-heaters may be possible due to a better selection of materials with the understanding of how the materials affect their nanothermal properties at the nano scale.

Improving the Durability of Methanol Oxidation Reaction Electro-Catalysts Through the Modification of Carbon Architectures

DTIC Science & Technology

2014-01-01

zeolite template was used in conjunction with liquid cyanamide to form a carbon nitride structure with a better 2D mesoporous hexagonal framework, resulting...the core. Both hybrid inorganic–organic polymer networks and 139 zeolitic inorganic–organic polymer electrolyte materials were used to impregnate an

Electrochemical characteristics of discrete, uniform, and monodispersed hollow mesoporous carbon spheres in double-layered supercapacitors.

PubMed

Chen, Xuecheng; Kierzek, Krzysztof; Wenelska, Karolina; Cendrowski, Krzystof; Gong, Jiang; Wen, Xin; Tang, Tao; Chu, Paul K; Mijowska, Ewa

2013-11-01

Core-shell-structured mesoporous silica spheres were prepared by using n-octadecyltrimethoxysilane (C18TMS) as the surfactant. Hollow mesoporous carbon spheres with controllable diameters were fabricated from core-shell-structured mesoporous silica sphere templates by chemical vapor deposition (CVD). By controlling the thickness of the silica shell, hollow carbon spheres (HCSs) with different diameters can be obtained. The use of ethylene as the carbon precursor in the CVD process produces the materials in a single step without the need to remove the surfactant. The mechanism of formation and the role played by the surfactant, C18TMS, are investigated. The materials have large potential in double-layer supercapacitors, and their electrochemical properties were determined. HCSs with thicker mesoporous shells possess a larger surface area, which in turn increases their electrochemical capacitance. The samples prepared at a lower temperature also exhibit increased capacitance as a result of the Brunauer-Emmett-Teller (BET) area and larger pore size. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Volumetric dimensional change of six direct core materials.

PubMed

Chutinan, Supattriya; Platt, Jeffrey A; Cochran, Michael A; Moore, B Keith

2004-05-01

This study evaluated the influence of water on the volumetric dimensional change of six direct placement core build-up materials by using Archimedes' principle. The effect on dimensional change due to the setting reaction was determined through the use of a silicone oil storage medium. The materials used were two dual-cured resin composites (CoreStore and Build-It FR), two chemically activated resin composites (CorePaste and Ti-Core), one metal-reinforced glass ionomer cement (Ketac-Silver), and one resin-modified glass ionomer (Fuji II LC Core). Using the manufacturers' instructions for each material, cylindrical specimens were prepared with dimensions of 7+/-0.1 mm in diameter and 2+/-0.1 mm in height. Each material had four groups (n = 5) based on storage conditions; silicone oil at 23 and 37 degrees C and distilled water at 23 and 37 degrees C. A 0.01 mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 min after mixing, and at the time intervals of 1, 14, and 56 days. All materials exhibited dimensional change. Ketac-Silver had the most shrinkage in silicone oil and Fuji II LC showed the highest expansion in distilled water. The glass ionomer materials showed more change than did any of the resin composite materials. Current direct placement core materials show variation in the amount of volumetric dimensional change seen over a period of 56 days.

A Comparison of Four Techniques for Producing High-Grade Furniture Core Material From Low-Grade Yellow-Poplar

Treesearch

Philip A. Araman

1978-01-01

Four Methods of converting low-grade yellow-poplar lumber into high-grade furniture core material (lumber core) were compared. High-grade core material is used in tops, shelves, doors, and drawer fronts and only minor defects are allowed. Three gang-rip first and the conventional crosscut-first manufacturing sequences were evaluated in combination with 1 Common, 2A...

Research on Shock Responses of Three Types of Honeycomb Cores

NASA Astrophysics Data System (ADS)

Peng, Fei; Yang, Zhiguang; Jiang, Liangliang; Ren, Yanting

2018-03-01

The shock responses of three kinds of honeycomb cores have been investigated and analyzed based on explicit dynamics analysis. According to the real geometric configuration and the current main manufacturing methods of aluminum alloy honeycomb cores, the finite element models of honeycomb cores with three different cellular configurations (conventional hexagon honeycomb core, rectangle honeycomb core and auxetic honeycomb core with negative Poisson’s ratio) have been established through FEM parametric modeling method based on Python and Abaqus. In order to highlight the impact response characteristics of the above three honeycomb cores, a 5 mm thick panel with the same mass and material was taken as contrast. The analysis results showed that the peak values of longitudinal acceleration history curves of the three honeycomb cores were lower than those of the aluminum alloy panel in all three reference points under the loading of a longitudinal pulse pressure load with the peak value of 1 MPa and the pulse width of 1 μs. It could be concluded that due to the complex reflection and diffraction of stress wave induced by shock in honeycomb structures, the impact energy was redistributed which led to a decrease in the peak values of the longitudinal acceleration at the measuring points of honeycomb cores relative to the panel.

Mode structure of a quantum cascade laser

NASA Astrophysics Data System (ADS)

Bogdanov, A. A.; Suris, R. A.

2011-03-01

We analyze the mode structure of a quantum cascade laser (QCL) cavity considering the surface plasmon-polariton modes and familiar modes of hollow resonator jointly, within a single model. We present a comprehensive mode structure analysis of the laser cavity, varying its geometric parameters and free electron concentration inside cavity layers within a wide range. Our analysis covers, in particular, the cases of metal-insulator-metal and insulator-metal-insulator waveguides. We discuss the phenomenon of negative dispersion for eigenmodes in detail and explain the nature of this phenomenon. We specify a waveguide parameters domain in which negative dispersion exists. The mode structure of QCL cavity is considered in the case of the anisotropic electrical properties of the waveguide materials. We show that anisotropy of the waveguide core results in propagation of Langmuir modes that are degenerated in the case of the isotropic core. Comparative analysis of optical losses due to free carrier absorption is presented for different modes within the frequency range from terahertz to ultraviolet frequencies.

Discovery of core-structurally novel PTP1B inhibitors with specific selectivity containing oxindole-fused spirotetrahydrofurochroman by one-pot reaction.

PubMed

Dong, Suzhen; Lei, Yubing; Jia, Shikun; Gao, Lixin; Li, Jia; Zhu, Tong; Liu, Shunying; Hu, Wenhao

2017-02-15

Protein tyrosine phosphatase 1B (PTP1B) has been proposed to be an ideal target for treatment of type II diabetes and obesity. However, no druggable PTP1B inhibitor has been established and there is still an urgent demand for the development of structurally novel PTPIB inhibitor. Herein, we reported core-structurally novel PTP1B inhibitors with low micromole-ranged inhibitory activity by one-pot reaction from simple starting materials. Further studies demonstrated some of these active compounds had a specific selectivity over other PTPs. The structure and activity relationship was also described. The best active and selective compound 5e inhibited PTP1B activity with an IC 50 of 4.53μM. Molecular docking analysis further demonstrated that compound 5e bound to the active pocket of PTP1B. The results might provide some insights for further development of new drugs for type II diabetes and obesity. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nanodiamond-Based Composite Structures for Biomedical Imaging and Drug Delivery.

PubMed

Rosenholm, Jessica M; Vlasov, Igor I; Burikov, Sergey A; Dolenko, Tatiana A; Shenderova, Olga A

2015-02-01

Nanodiamond particles are widely recognized candidates for biomedical applications due to their excellent biocompatibility, bright photoluminescence based on color centers and outstanding photostability. Recently, more complex architectures with a nanodiamond core and an external shell or nanostructure which provides synergistic benefits have been developed, and their feasibility for biomedical applications has been demonstrated. This review is aimed at summarizing recent achievements in the fabrication and functional demonstrations of nanodiamond-based composite structures, along with critical considerations that should be taken into account in the design of such structures from a biomedical point of view. A particular focus of the review is core/shell structures of nanodiamond surrounded by porous silica shells, which demonstrate a remarkable increase in drug loading efficiency; as well as nanodiamonds decorated with carbon dots, which have excellent potential as bioimaging probes. Other combinations are also considered, relying on the discussed inherent properties of the inorganic materials being integrated in a way to advance inorganic nanomedicine in the quest for better health-related nanotechnology.

A tunable optofluidic circular liquid fiber

NASA Astrophysics Data System (ADS)

Li, Lei; Wu, Wei; Shi, Yang; Gong, Enze; Yang, Yi

2016-01-01

This paper presents a tunable optofluidic circular liquid fiber through the numerical simulation. Fiber is a significant optical device and has been widely applied on optical fiber communication. But the fiber based solid has limited tunability. Compared to solid fiber, the fiber based liquid material is relatively infrequent. Cause for the liquid optical device has more freedom tunable properties than solid counterpart, it has attracted more interest. The traditional optofluidic waveguide is designed like a sandwich in planar channel. This two-dimensional (2D) structure liquid waveguide will face huge transmission loss in the perpendicular direction of the flow streams. In this paper, a curving microchannel is designed inside the microchip to produce centrifugal effect. Two different liquids are injected into the chip by external pumps. In a particular situation, the core flow will be totally surrounded by the cladding flow. So the liquid can form an optical waveguide. Its structure is similar to an optical fiber which high refractive index (RI) liquid is core of the waveguide and the low RI liquid is cladding of the waveguide. Profit from the reconfigurability of liquid material, this liquid fiber has excellent tunability. The diameter of the core flow can be tuned in a wider range by changing the volume ratio of the flows through the finite element analysis. It is predictable that such a tunable liquid fiber may find wider applications in lab-on-a-chip systems and integrated optical devices.