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Sample records for investigate microstructural features

  1. Investigation of Microstructural Features Determining the Toughness of 980 MPa Bainitic Weld Metal

    NASA Astrophysics Data System (ADS)

    Cao, R.; Zhang, X. B.; Wang, Z.; Peng, Y.; Du, W. S.; Tian, Z. L.; Chen, J. H.

    2014-02-01

    The microstructural features that control the impact toughness of weld metals of a 980 MPa 8 pct Ni high-strength steel are investigated using instrumented Charpy V tester, optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), electron back-scattered diffraction (EBSD), and finite-element method (FEM) calculation. The results show that the critical event for cleavage fracture in this high-strength steel and weld metals is the propagation of a bainite packet-sized crack across the packet boundary into contiguous packets, and the bainitic packet sizes control the impact toughness. The high-angle misorientation boundaries detected in a bainite packet by EBSD form fine tear ridges on fracture surfaces. However, they are not the decisive factors controlling the cleavage fracture. The effects of Ni content are essential factors for improving the toughness. The extra large cleavage facets seriously deteriorate the toughness, which are formed on the interfaces of large columnar crystals growing in welding pools with high heat input.

  2. Investigation of the crystallization features, atomic structure, and microstructure of chromium-doped monticellite

    NASA Astrophysics Data System (ADS)

    Subbotin, K. A.; Iskhakova, L. D.; Zharikov, E. V.; Lavrishchev, S. V.

    2008-12-01

    A series of Cr4+:CaMgSiO4 single crystals is grown using floating zone melting, and their microstructure, composition, and crystal structure are investigated. It is shown that regions with inclusions of second phases, such as forsterite, akermanite, MgO, and Ca4Mg2Si3O12, can form over the length of the sample. The composition of the single-phase regions of the single crystals varies from the stoichiometric monticellite CaMgSiO4 to the solid solution Ca(1 - x)Mg(1 + x)SiO4( x = 0.22). The Cr:(Ca0.88Mg0.12)MgSiO4 crystal is studied using X-ray diffraction. It is revealed that, in this case, the olivine-like orthorhombic crystal lattice is distorted to the monoclinic lattice with the parameters a = 6.3574(5) Å, b = 4.8164(4) Å, c = 11.0387(8) Å, β = 90.30(1)o, Z = 4, V = 337.98 Å3, and space group P21/ c. In the monoclinic lattice, the M(1) position of the initial olivine structure is split into two nonequivalent positions with the center of symmetry, which are occupied only by Mg2+ cations with the average length of the Mg-O bond R av = 2.128 Å. The overstoichiometric Mg2+ cations partially replace Ca2+ cations (in the M(2) position of the orthorhombic prastructure) with the average bond length of 2.347 Å in the [(Ca,Mg)-O6] octahedron. The average distance in SiO4 distorted tetrahedra is 1.541 Å.

  3. A review on preparation techniques for synthesis of nanocrystalline soft magnetic ferrites and investigation on the effects of microstructure features on magnetic properties

    NASA Astrophysics Data System (ADS)

    Hajalilou, Abdollah; Mazlan, Saiful Amri

    2016-07-01

    Soft magnetic materials have been used in many applications, i.e., electrical and electronic industries, due to their desirable electromagnetic characteristics. The performance of these materials in bulk form, where the size of grains is in micrometer scale, is only limited to a few megahertz frequencies due to their higher conductivity and domain wall resonance. Synthesizing the ferrite particles in nanometer scales before compacting them for sintering would be one way to solve using these materials at higher frequencies. The properties of ferrite depend mainly on the technique and conditions of preparation, which, in turn, affect the cation distribution over the tetrahedral and octahedral sites. Thus, the aim of this study was to introduce some methods used for synthesizing nanocrystalline soft magnetic ferrites. Furthermore, the microstructure features, i.e., grain sizes and porosities, which are influenced by the types of method used for preparation, playing key role on the magnetic properties of the sample, are also highlighted.

  4. Microstructural Features in Aged Erbium Tritide Foils

    SciTech Connect

    Gelles, David S.; Brewer, L. N.; Kotula, Paul G.; Cowgill, Donald F.; Busick, C. C.; Snow, C. S.

    2008-01-01

    Aged erbium tritide foil specimens are found to contain five distinctly different microstructural features. The general structure was of large columnar grains of ErT2. But on a fine scale, precipitates believed to be erbium oxy-tritides and helium bubbles could be identified. The precipitate size was in the range of ~10 nm and the bubbles were of an unusual planar shape on {111} planes with an invariant thickness of ~1 nm and a diameter on the order of 10 nm. Also, an outer layer containing no fine precipitate structure and only a few helium bubbles was present on foils. This layer is best described as a denuded zone which probably grew during aging in air. Finally, large embedded Er2O3 particles were found at low density and non-uniformly distributed, but sometimes extending through the thickness of the foil. A failure mechanism allowing the helium to escape is suggested by observed cracking between bubbles closer to end of life.

  5. Experimental Investigation of Microstructured Evaporators

    NASA Astrophysics Data System (ADS)

    Wibel, W.; Westermann, S.; Maikowske, S.; Brandner, J. J.

    2012-11-01

    Microfluidic devices have become more and more popular over the last decades [1]. Cooling is a topic where microstructures offer significant advantages compared to conventional techniques due the much higher possible surface to volume ratios and short heat transfer lengths. By evaporating of a fluid in microchannels, compact, fast and powerful cooling devices become possible [2]. Experimental results for different designs of microstructured evaporators are presented here. They have been obtained either using water as evaporating coolant or the refrigerant R134a (Tetrafluoroethane). A new microstructured evaporator design consisting of bended microchannels instead of straight channels for a better performance is shown and compared to previous results [2] for the evaporation of R134a in straight microchannels.

  6. Microstructural investigation of some biocompatible ferrofluids

    NASA Astrophysics Data System (ADS)

    Răcuciu, M.; Creangă, D. E.; Bădescu, V.; Sulitanu, N.

    2007-09-01

    Two batches of aqueous ferrofluids based on iron oxide particles as solid nanomagnetic phase have been prepared by applying the chemical precipitation method. Tetramethylammonium hydroxide (N(CH 3) 4OH) and citric acid (C 6H 8O 7) were used to functionalize magnetic cores. Physical tests have been performed in order to reveal the microstructural and magnetic features, both needed for biomedical utilization. The particle size was investigated using transmission electron microscopy (TEM), magnetization measurements and X-ray diffraction (for composition and phase information). The dimensional distribution of the ferrophase physical diameter was comparatively discussed using the box-plot statistical method revealing the fulfilling of the main requirements for ferrofluid stability.

  7. Artificial Microstructures to Investigate Microstructure-Property Relationships in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Sarac, Baran

    Technology has evolved rapidly within the last decade, and the demand for higher performance materials has risen exponentially. To meet this demand, novel materials with advanced microstructures have been developed and are currently in use. However, the already complex microstructure of technological relevant materials imposes a limit for currently used development strategies for materials with optimized properties. For this reason, a strategy to correlate microstructure features with properties is still lacking. Computer simulations are challenged due to the computing size required to analyze multi-scale characteristics of complex materials, which is orders of magnitude higher than today's state of the art. To address these challenges, we introduced a novel strategy to investigate microstructure-property relationships. We call this strategy "artificial microstructure approach", which allows us to individually and independently control microstructural features. By this approach, we defined a new way of analyzing complex microstructures, where microstructural second phase features were precisely varied over a wide range. The artificial microstructures were fabricated by the combination of lithography and thermoplastic forming (TPF), and subsequently characterized under different loading conditions. Because of the suitability and interesting properties of metallic glasses, we proposed to use this toolbox to investigate the different deformation modes in cellular structures and toughening mechanism in metallic glass (MG) composites. This study helped us understand how to combine the unique properties of metallic glasses such as high strength, elasticity, and thermoplastic processing ability with plasticity generated from heterostructures of metallic glasses. It has been widely accepted that metallic glass composites are very complex, and a broad range of contributions have been suggested to explain the toughening mechanism. This includes the shear modulus, morphology

  8. Investigation of Human Nail Microstructure with Ultrasound

    NASA Astrophysics Data System (ADS)

    Maeva, A. R.; Bakulin, E. Y.; Denisova, L. A.; Maev, R. Gr.

    Investigation of a human fingernail and the extraction of the data on its microstructure and elastic properties is important in three main aspects. First of all, various diseases of the nail can be differentiated more precisely; second of all, it is possible to non-invasively track during time the effects of a cosmetic product upon the nail; third of all, because various processes in the organism have a strong influence upon the nail plate growth, the monitoring of the nail morphology and its mechanical properties may be used as additional information for the diagnosis of a number of medical disorders, such as systemic sclerosis, psoriasis, chronic hand eczema, anemia etc. The aim of the present study was to carry out a detailed ultrasound investigation in the high-frequency range (25-50 MHz) of a human nail including micro-anatomical structure imaging and ultrasound velocity evaluation, using B-scans obtained with a scanning acoustic microscope. On the images, exact topology of the nail, nail matrix and the underlying bone have been revealed. Additionally, a certain type of inclined internal layering along the nails of some individuals has been found, which was not reported in previous ultrasonic studies of the nail.

  9. Influence of microstructural features on thermal expansion coefficient in graphene/epoxy composites.

    PubMed

    Shi, Zhan; Li, Xiao-Fei; Bai, Hua; Xu, Wei-Wei; Yang, Shui-Yuan; Lu, Yong; Han, Jia-Jia; Wang, Cui-Ping; Liu, Xing-Jun; Li, Wei-Bin

    2016-03-01

    In this paper, theoretical calculations were conducted to determine the coefficient of thermal expansion (CTE) based on the effective medium approach using Green's function method. The influences of microstructural features were investigated, including volume fraction, aspect ratio, and the orientation of graphene fillers. Calculated results demonstrated strong anisotropy of CTE when all graphene sheets in the composite were aligned in the in-plane direction due to the large difference between the elastic moduli of the graphene and epoxy. The in-plane CTE in the graphene/epoxy composite can be effectively reduced with small additions of graphene additive. Orientation dispersion among the graphene fillers significantly decreases the anisotropy of CTE. Accounting for the influences of all microstructural features, simulation results closely align with current experimental results. This work will provide a general guideline and a solid foundation for the optimal design and preparation of graphene/polymer composites. PMID:27441268

  10. MICROSTRUCTURAL FEATURES AFFECTING PROPERTIES AND AGING OF TRITIUM-EXPOSED AUSTENTIC STAINLESS STEEL

    SciTech Connect

    Subramanian, K; Michael Morgan, M

    2004-01-10

    banding and nitrogen concentration were also included as features of interest. The microstructural features of interest included (1) grain size, shape, and orientation; (2) dislocation structure and distribution, or recovered vs. un-recovered. The grain size and orientation affect the grain boundary fracture stress and the hydrogen solubility and diffusion paths. The dislocation structure and distribution play a role in hydrogen trapping as well as potentially affecting the hydrogen assisted fracture path. The initial mechanical and physical properties that are to be included in the investigation are yield stress, fracture toughness, work-hardening capacity, threshold hydrogen cracking stress intensity and stacking-fault energy.

  11. Microstructural investigation of thermally treated titanium subhydrides

    SciTech Connect

    Wang, P.S.; Wittberg, T.N.; Wolf, J.D.

    1984-09-05

    The ignition of titanium subhydride/potassium perchlorate pyrotechnic blends is influenced by the diffusion of oxygen into the titanium subhydride fuel. The following work is a preliminary study of the microstructural changes that take place during the dehydriding of titanium subhydride. Samples of TiH/sub 1/ /sub 63/ were dehydrided at temperatures between 625 and 775/sup 0/C. In the partially dehydrided samples, evidence of three different phases - ..cap alpha.. Ti (hexagonal), ..beta.. Ti (cubic), and ..gamma.. TiH/sub 2/ (cubic) - was seen. Microstructural examination of a TiH/sub 1/ /sub 15/ sample that had a layered structure is also reported. A furnace constructed for hydriding titanium foils is also described. Titanium subhydride foils having the stoichiometries TiH/sub 1/ /sub 53/ and TiH/sub 0/ /sub 87/ were prepared using this furnace.

  12. Magnetic characterisation of microstructural feature distribution in P9 and T22 steels by major and minor BH loop measurements

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Wilson, John; Strangwood, Martin; Davis, Claire L.; Peyton, Anthony

    2016-03-01

    This paper investigates the magnetic properties and parameters measured from major/minor loops and used to characterise different microstructural feature distributions in P9 and T22 steel in different heat treatment or service conditions. The present study introduces a non-destructive way of selecting microstructural features of interest and/or excluding those of little relevance by examination of minor loop measurements at a selected range of applied fields and discusses the fundamental mechanism in terms of domain processes. There is remarkable consistency in magnetic behaviours and properties such as initial/incremental permeability values between the measurements by different techniques. This behaviour has been ascribed to the similar underlying domain processes and hence similar selected microstructural features that are affecting the domain processes.

  13. Some refractometric features of dual-core chirped microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Velasquez-Botero, Fabian; Reyes-Vera, Erick; Torres, Pedro

    2015-09-01

    Refractometric features of dual-core transversally chirped microstructured optical fibers (MOF) are evaluated. It is shown from numerical results that the chirped MOF could act as a structure with decoupled cores, forming a Mach- Zehnder interferometer in which the analyte directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode. We investigate the influence of the MOF parameters and the analyte refractive index on sensor performance. This novel structure is suitable for measuring refractive indices in the 1.33-1.44 range.

  14. Quantitative analysis and feature recognition in 3-D microstructural data sets

    NASA Astrophysics Data System (ADS)

    Lewis, A. C.; Suh, C.; Stukowski, M.; Geltmacher, A. B.; Spanos, G.; Rajan, K.

    2006-12-01

    A three-dimensional (3-D) reconstruction of an austenitic stainless-steel microstructure was used as input for an image-based finite-element model to simulate the anisotropic elastic mechanical response of the microstructure. The quantitative data-mining and data-warehousing techniques used to correlate regions of high stress with critical microstructural features are discussed. Initial analysis of elastic stresses near grain boundaries due to mechanical loading revealed low overall correlation with their location in the microstructure. However, the use of data-mining and feature-tracking techniques to identify high-stress outliers revealed that many of these high-stress points are generated near grain boundaries and grain edges (triple junctions). These techniques also allowed for the differentiation between high stresses due to boundary conditions of the finite volume reconstructed, and those due to 3-D microstructural features.

  15. As-cast microstructure investigation of two iron aluminides

    NASA Astrophysics Data System (ADS)

    Geraldo Schön, Cláudio; Geoffroy Scuracchio, Bruno

    2006-08-01

    The as-cast microstructure of Fe-30Al-6Cr and Fe-30Al-10Ti high purity alloys was investigated using Electron Backscatter Diffraction. The first alloy is characterized by a highly textured columnar grain microstructure with large grains, while the second is characterized by an equiaxed grain microstructure with small grains and a random texture. These differences are discussed with regard to the higher reactivity of Ti compared with Cr, leading to nanometric nitride or oxide, which may act as sites for heterogeneous nucleation, and the ordered state of the BCC phase in equilibrium with the liquid during solidification and its effect upon dendrite growth kinetics.

  16. Application of Image Analysis for Characterization of Spatial Arrangements of Features in Microstructure

    NASA Technical Reports Server (NTRS)

    Louis, Pascal; Gokhale, Arun M.

    1995-01-01

    A number of microstructural processes are sensitive to the spatial arrangements of features in microstructure. However, very little attention has been given in the past to the experimental measurements of the descriptors of microstructural distance distributions due to the lack of practically feasible methods. We present a digital image analysis procedure to estimate the micro-structural distance distributions. The application of the technique is demonstrated via estimation of K function, radial distribution function, and nearest-neighbor distribution function of hollow spherical carbon particulates in a polymer matrix composite, observed in a metallographic section.

  17. Investigation of the microstructure, mechanical properties and thermal stability of nanocomposite coatings based on amorphous carbon

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Litovchenko, I. Y.; Korotaev, A. D.; Borisov, D. P.

    2015-10-01

    The Ti-C-Ni-Cr and Ti-C-Ni-Cr-Al-Si nanocomposite coatings based on amorphous carbon and the nanosized particles were synthesized by magnetron method. The results of the microstructure features and mechanical properties investigations of these coatings are presented. The thermal stability of microstructure and properties of these coatings at tempering up to 900°C were investigated. These coatings have a high (11-18 GPa) hardness, low (μ < 0.2) the coefficient of friction and high thermal stability of the microstructure and properties up to 700°C. The features of elastically stressed state of nanosized particles in these coatings were founded. A high local internal stresses in the TiC nanoscale particles do not observed.

  18. Supplementary Microstructural Features Induced During Laser Surface Melting of Thermally Sprayed Inconel 625 Coatings

    NASA Astrophysics Data System (ADS)

    Ahmed, Nauman; Voisey, K. T.; McCartney, D. G.

    2014-02-01

    Laser surface melting of thermally sprayed coatings has the potential to enhance their corrosion properties by incorporating favorable microstructural changes. Besides homogenizing the as-sprayed structure, laser melting may induce certain microstructural modifications (i.e., supplementary features) in addition to those that directly improve the corrosion performance. Such features, being a direct result of the laser treatment process, are described in this paper which is part of a broader study in which high velocity oxy-fuel sprayed Inconel 625 coatings on mild-steel substrates were treated with a diode laser and the modified microstructure characterized using optical and scanning electron microscopy and x-ray diffraction. The laser treated coating features several different zones, including a region with a microstructure in which there is a continuous columnar dendritic structure through a network of retained oxide stringers.

  19. Peculiar Features of Microstructure Formation and Microhardness Variations During Torsional Straining of Tantalum Specimens in Bridgman Anvils

    NASA Astrophysics Data System (ADS)

    Ditenberg, I. A.; Tymentsev, A. N.; Korznikov, A. V.

    2015-04-01

    Using the method of transmission electron microscopy, peculiar features of evolution of microstructure and variations in microhardness of Та are investigated under torsional loading in the Bridgman anvil as a function of plastic deformation at room temperature. A quantitative examination of grain and defect's structure of the material under study and the values of local internal stresses is performed in different loading stages. The mechanisms of formation of submicrocrystalline and nanostructured states are analyzed and so is the microstructure variation as a function of the defect-structure characteristics, strain level, and spacing from the axis of torsion.

  20. Rapid characterization of titanium microstructural features for specific modelling of mechanical properties

    NASA Astrophysics Data System (ADS)

    Searles, T.; Tiley, J.; Tanner, A.; Williams, R.; Rollins, B.; Lee, E.; Kar, S.; Banerjee, R.; Fraser, H. L.

    2005-01-01

    Mechanical properties of α/β Ti alloys are closely related to their microstructure. The complexity of the microstructural features involved makes it rather difficult to develop models for predicting properties of these alloys. Advances in stereology and microscopy permit rapid characterization of various features in Ti alloys including Widmanstätten α-laths, grain sizes, grain shapes, colony structures and volume fractions of different phases. This research documents the stereology procedures for characterizing microstructural features in Ti alloys, including the use of three-dimensional serial sectioning and reconstruction procedures for developing through material measurements. The resulting data indicate the powerful characterization processes now available, and the ability to rapidly assess microstructural features in Ti alloys. The processes were tested using Ti-62222 by serial sectioning the sample and conducting automated stereology protocols to determine features. In addition, three-dimensional reconstruction was completed on a Ti-6242 sample to evaluate lath interactions within the alloy. Results indicate the tremendous potential for characterizing microstructures using advanced techniques.

  1. Microstructural Features in Corroded Celtic Iron Age Sword Blades

    NASA Astrophysics Data System (ADS)

    Ghiara, G.; Piccardo, P.; Campodonico, S.; Carnasciali, M. M.

    2014-05-01

    Archaeological artefacts made from iron and steel are often of critical importance for archaeometallurgical studies, which aim to understand the process of manufacturing, as the nearly complete alloy mineralization does not allow for any type of metallographic interpretation. In this study, three Iron Age sword blades dated from the second century BC (LaTène B2/D1) found in the archaeological site of Tintignac (Commune de Naves, Corrèze, France), were investigated. A multianalytical approach was employed to acquire a complete range of data from the partially or totally corroded objects. Analyses were carried out with the use of light optical microscopy, micro Raman spectroscopy, and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy (EDXS). Remnants of metallographic features—ghost microstructure—in the corrosion layers of the blades were observed, allowing for a partial reconstruction of the manufacturing process.

  2. Investigation of sensing properties of microstructured polymer optical fibres

    NASA Astrophysics Data System (ADS)

    Witt, J.; Steffen, M.; Schukar, M.; Krebber, K.

    2010-04-01

    We investigated sensing properties of single mode poly methyl methacrylate (PMMA) microstructured polymer optical fibres (MPOF) with mechanically imprinted long period gratings (LPG). After preparation of the MPOF end-faces the samples were elongated with silica fibres. These samples were used to measure the influence of strain to the LPG wavelength which showed the viscoelastic nature of PMMA. We also measured the influence of temperature and humidity. The results show that MPOF LPGs are well suited for strain sensing. One MPOF LPG was stitched to a textile. Using this textile we measured a simulated respiratory motion.

  3. Experimental investigations of creep in gold RF-MEMS microstructures

    NASA Astrophysics Data System (ADS)

    Somà, Aurelio; De Pasquale, Giorgio; Saleem, Muhammad Mubasher

    2015-05-01

    Lifetime prediction and reliability evaluation of micro-electro-mechanical systems (MEMS) are influenced by permanent deformations caused by plastic strain induced by creep. Creep in microstructures becomes critical in those applications where permanent loads persist for long times and thermal heating induces temperature increasing respect to the ambient. Main goal of this paper is to investigate the creep mechanism in RF-MEMS microstructures by means of experiments. This is done firstly through the detection of permanent deformation of specimens and, then, by measuring the variation of electro-mechanical parameters (resonance frequency, pull-in voltage) that provide indirect evaluation of mechanical stiffness alteration from creep. To prevent the errors caused be cumulative heating of samples and dimensional tolerances, three specimens with the same nominal geometry have been tested per each combination of actuation voltage and temperature. Results demonstrated the presence of plastic deformation due to creep, combined with a component of reversible strain linked to the viscoelastic behavior of the material.

  4. TEM investigations on the local microstructure of electrodeposited galfenol nanowires.

    PubMed

    Pohl, D; Damm, C; Pohl, D; Schultz, L; Schlörb, H

    2016-01-22

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe80±2Ga20±2 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred 〈110〉orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces. PMID:26651087

  5. TEM investigations on the local microstructure of electrodeposited galfenol nanowires

    NASA Astrophysics Data System (ADS)

    Pohl, D.; Damm, C.; Pohl, D.; Schultz, L.; Schlörb, H.

    2016-01-01

    The local microstructure of Fe-Ga nanowires is investigated considering dependence on the deposition technique. Using a complexed electrolyte, smooth and homogeneous Fe80Ga20 nanowires are deposited into anodic aluminum oxide templates by either applying pulse potential or potentiostatic deposition technique. At optimized deposition conditions the wires show the desired composition of Fe80±2Ga20±2 without a gradient along the growth direction. Composition distribution, structure and microstructure are examined in detail and reveal only minor differences. Line EELS and crystal lattice measurements reveal a negligible oxygen content for both preparation routines. Neither Fe/Ga oxides nor hydroxides were found. Both potentiostatically deposited as well as pulse deposited nanowires exhibit a preferred <110> orientation, the latter with slightly larger crystals. Different contrast patterns were found by TEM that appear more pronounced in the case of pulse deposited wires. High resolution transmission electron microscopy analysis and comparison of differently prepared focused ion beam lamellas reveal that these contrasts are caused by defects in the alternating potential deposition itself and are not induced during the TEM preparation process. The alternating potential mode causes periodic growth thereby inducing different layers with reduced wire thickness/defects at the layer interfaces.

  6. Microstructural Investigation of Friction-Stir-Welded 7005 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Xuesong; Lu, Yan; Zheng, Feiyan; Chen, Bin

    2015-11-01

    This paper is aimed to investigate the microstructure of 7005 aluminum sheets joined by friction-stir welding as well as their mechanical properties. Specimens with ten different sets of welding parameters were studied. Tensile test and fracture analysis determined that the joint of the best quality was obtained at the rotation speed of 1000 rpm matching with the travel speed of 200 mm/min, and the travel speed has more impact on the ultimate tensile strength. Optical microscope observation was applied to this high-quality specimen and gave evidence to explaining the formation of the onion ring structure. Electron back-scattered diffraction (EBSD) technique was employed to characterize the textures and revealed the evolution of microstructures during friction stir processing. The EBSD results showed that the grains maintain their original orientations at relatively low deformation while the orientations rotate under increasing strain. Accumulated rotation will turn the textures into mixed shear components, which finally results in grain refinement and contributes to the high quality of the joint.

  7. Microstructural Features Leading to Enhanced Resistance to Grain Boundary Creep Cracking in ALLVAC 718Plus

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Hayes, Robert W.; Mills, Michael J.; Daehn, Glenn S.

    2010-02-01

    This study focuses on the microstructural features that enhance the resistance of ALLVAC 718Plus to grain boundary creep cracking during testing of samples at 704 °C in both dry and moist air. Fully recrystallized structures were found to be susceptible to brittle grain boundary cracking in both environments. Detailed transmission electron microscopy (TEM) microstructural characterization reveals features that are believed to lead to resistance to grain boundary cracking in the resistant microstructures. It is suggested that dislocation substructures found within the grains of resistant structures compete with the high-angle grain boundaries for oxygen, thereby reducing the concentration of oxygen on the grain boundaries and subsequent embrittlement. In addition, electron backscatter diffraction (EBSD) misorientation maps reveal that special boundaries ( i.e., Σ3 boundaries) resist cracking. This is in agreement with previous findings on the superalloy INCONEL 718. Furthermore, it is observed that cracks propagate along high-angle boundaries. This study also shows that in this case, the presence of delta phase at the grain boundaries does not by itself produce materials that are resistant to grain boundary cracking.

  8. Distinctive microstructural features of aged sodium silicate-activated slag concretes

    SciTech Connect

    San Nicolas, Rackel; Bernal, Susan A.; Mejía de Gutiérrez, Ruby; Deventer, Jannie S.J. van; Provis, John L.

    2014-11-15

    Electron microscopic characterisation of 7-year old alkali-activated blast-furnace slag concretes enabled the identification of distinct microstructural features, providing insight into the mechanisms by which these materials evolve over time. Backscattered electron images show the formation of Liesegang-type ring formations, suggesting that the reaction at advanced age is likely to follow an Oswald supersaturation–nucleation–depletion cycle. Segregation of Ca-rich veins, related to the formation of Ca(OH){sub 2}, is observed in microcracked regions due to the ongoing reaction between the pore solution and available calcium from remnant slag grains. A highly dense and uniform interfacial transition zone is identified between siliceous aggregate particles and the alkali activated slag binders, across the concretes assessed. Alkali-activated slag concretes retain a highly dense and stable microstructure at advanced ages, where any microcracks induced at early ages seem to be partially closing, and the remnant slag grains continue reacting.

  9. Effect of vanadium and chromium on the microstructural features of V-Cr-Mn-Ni spheroidal carbide cast irons

    NASA Astrophysics Data System (ADS)

    Efremenko, V. G.; Shimizu, K.; Cheiliakh, A. P.; Kozarevskaya, T. V.; Kusumoto, K.; Yamamoto, K.

    2014-11-01

    The objective of this investigation is to study the influence of vanadium (5.0wt%-10.0wt%) and chromium (0-9.0wt%) on the microstructure and hardness of Cr-V-Mn-Ni white cast irons with spheroidal vanadium carbides. The alloys' microstructural features are presented and discussed with regard to the distribution of phase elements. The structural constituents of the alloys are spheroidal VC, proeutectoid cementite, ledeburite eutectic, rosette-shaped carbide eutectic (based on M7C3), pearlite, martensite, and austenite. Their combinations and area fraction (AF) ratios are reported to be influenced by the alloys' chemical composition. Spheroidized VC particles are found to be sites for the nucleation of carbide eutectics. Cr and V are shown to substitute each other in the VC and M7C3 carbides, respectively. Chromium alloying leads to the formation of a eutectic (γ-Fe + M7C3), preventing the appearance of proeutectoid cementite in the structure. Vanadium and chromium are revealed to increase the total carbide fraction and the amount of austenite in the matrix. Cr is observed to play a key role in controlling the metallic matrix microstructure.

  10. Investigating Surface Features on Nix and Hydra

    NASA Astrophysics Data System (ADS)

    Weaver, Harold A.; Barnouin, O. S.; Cheng, A. F.; Ernst, C. M.; Lauer, T. R.; Stern, S. A.; Olkin, C. B.; Ennico, K.; Young, L. A.

    2015-11-01

    The LORRI (Cheng et al. 2008,Space Sci. Rev. 140, 189) and MVIC (Reuter et al. 2008,Space Sci. Rev. 140, 129) imagers on the New Horizons (NH) spacecraft obtained spatially resolved measurements of Nix and Hydra, two of Pluto's four small moons. Nix was observed by LORRI in panchromatic light (350-850 nm) at resolutions up to 0.30 km/pix, and by MVIC in color (400-550 nm, 540-700 nm, 780-975 nm, 860-910 nm; the latter is centered on a weak CH4 band) at resolutions up to 2.0 km/pix. Hydra was observed by LORRI in panchromatic light at 1.1 km/pix, and by MVIC in color at 4.6 km/pix. The lossless versions of the images, which we will employ in our analysis, are scheduled for downlink in September and October 2015. After image deconvolutions, which typically double the spatial resolution, the NH images provide hundreds to thousands of pixels across the surfaces of Nix and Hydra. We will present results on our searches for craters, lineaments, and other features on the surfaces of Nix and Hydra. We will also present results on any correlations between morphological features and color and albedo variations on the surface. This work was supported by NASA's New Horizons project.

  11. [Investigation of the microstructure of biological systems by triplet label].

    PubMed

    Kotel'niko, A I; Kuznetsov, S N; Fogel', V R; Likhtenshteĭn, G I

    1979-01-01

    A method for investigating the microstruct and dynamics of biological systems by means of triplet-excited molecules is suggested. The method is based on the phenomenon of triplet excitation disactivation by exchange-resonance triplet-triplet energy transfer to the acceptor or by intercombination conversion induced by interaction of an excited molecule with a paramagnetic center. The disactivation efficiency was measured by registrating the phosphorescense decay kinetics. The interaction of the triplet label eosin isothiocyanate, covalently coupled with albumine, lysozyme, sarcoplasmic reticulum membrane and Ca-Mg-dependent sarcoplasmic reticulum ATPase, with O2, the stable nitroxide radicals and ions of Mn2+ was investigated to analyse the potentialities of this method. As a model system the eosin phosphorescence quenching by the same quenchers in glycerine-aguaous solutions was studied. The method permits to investigate the microviscosity and microstructure of biological objects in the label attached region on interaction of the label with a sound-quencher with constants being 10(4) divided by 10(9) M-1 sec-1 and to measure the lateral diffusion of molecules in highly viscosity media (10 divided by 10(5) santypuas). PMID:223037

  12. Transmission electron microscopy characterization of microstructural features of Al-Li-Cu alloys

    NASA Technical Reports Server (NTRS)

    Avalos-Borja, M.; Pizzo, P. P.; Larson, L. A.

    1983-01-01

    A transmission electron microscopy (TEM) examination of aluminum-lithium-copper alloys was conducted. The principal purpose is to characterize the nature, size, and distribution of stringer particles which result from the powder metallurgy (P/M) processing of these alloys. Microstructural features associated with the stringer particles are reported that help explain the stress corrosion susceptibility of the powder metallurgy-processed Al-Li-Cu alloys. In addition, matrix precipitation events are documented for a variety of heat treatments and process variations. Hot rolling is observed to significant alter the nature of matrix precipitation, and the observations are correlated with concomitant mechanical property variations.

  13. Experimental investigation of the serum albumin fascia microstructure

    NASA Astrophysics Data System (ADS)

    Buzoverya, M. E.; Shcherbak, Yu. P.; Shishpor, I. V.

    2012-09-01

    The results of theoretical and experimental investigation of biological liquids are reported. Structural effects observed in fascias are considered with account of the molecular features of albumin and the concept of supramolecular organization of polymers. It is revealed that the morphology of human serum albumin fascias depends on the concentration and quality of the solvent. It is shown that the water-salt fascias of albumin are more structured than water solutions with the same concentration.

  14. Investigation of the Microstructure of Joints of Aluminum Alloys Produced by Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Kolubaev, E. A.

    2015-02-01

    Special features of the microstructure of joints of aluminum-magnesium and aluminum-copper alloys produced by friction stir welding are analyzed. It is demonstrated that a layered structure with ultradisperse grains is produced by friction stir welding at the center of the weld joint. An analogy is drawn between the microstructures of joints produced by friction stir welding and surface layer produced by sliding friction.

  15. Differentiating characteristic microstructural features of cancerous tissues using Mueller matrix microscope.

    PubMed

    Wang, Ye; He, Honghui; Chang, Jintao; Zeng, Nan; Liu, Shaoxiong; Li, Migao; Ma, Hui

    2015-12-01

    Polarized light imaging can provide rich microstructural information of samples, and has been applied to the detections of various abnormal tissues. In this paper, we report a polarized light microscope based on Mueller matrix imaging by adding the polarization state generator and analyzer (PSG and PSA) to a commercial transmission optical microscope. The maximum errors for the absolute values of Mueller matrix elements are reduced to 0.01 after calibration. This Mueller matrix microscope has been used to examine human cervical and liver cancerous tissues with fibrosis. Images of the transformed Mueller matrix parameters provide quantitative assessment on the characteristic features of the pathological tissues. Contrast mechanism of the experimental results are backed up by Monte Carlo simulations based on the sphere-cylinder birefringence model, which reveal the relationship between the pathological features in the cancerous tissues at the cellular level and the polarization parameters. Both the experimental and simulated data indicate that the microscopic transformed Mueller matrix parameters can distinguish the breaking down of birefringent normal tissues for cervical cancer, or the formation of birefringent surrounding structures accompanying the inflammatory reaction for liver cancer. With its simple structure, fast measurement and high precision, polarized light microscope based on Mueller matrix shows a good diagnosis application prospect. PMID:26280279

  16. Internal Microstructure Investigation of Tin Whisker Growth Using FIB Technology

    NASA Astrophysics Data System (ADS)

    Fortier, Aleksandra; Kovacevic, Radovan

    2012-08-01

    The problem of tin (Sn) whiskers has been a significant reliability issue in electronics for the past several decades. Despite the large amount of research conducted on this issue, a solution for mitigating the growth of whiskers remains a challenge for the research community. Whiskers have unpredictable growth and morphology, and a study of a whisker's internal structure may provide further insights into the reason behind their complex growth. This study reports on the internal microstructure and morphology of complex-shaped Sn whiskers grown from an electroplated bright Sn layer on brass substrates exposed to ambient and 95% humid environment. The variables analyzed include surface and microstructure conditions of the film, and morphology and internal microstructure of the Sn whiskers using scanning electron microscopy with focused ion beam technology. Experimental results demonstrated that the whiskers with more complex morphology grow primarily from surfaces exposed to a controlled environment, and some of them have traits of polycrystalline growth rather than only single crystalline, as usually known.

  17. Investigation of efficient features for image recognition by neural networks.

    PubMed

    Goltsev, Alexander; Gritsenko, Vladimir

    2012-04-01

    In the paper, effective and simple features for image recognition (named LiRA-features) are investigated in the task of handwritten digit recognition. Two neural network classifiers are considered-a modified 3-layer perceptron LiRA and a modular assembly neural network. A method of feature selection is proposed that analyses connection weights formed in the preliminary learning process of a neural network classifier. In the experiments using the MNIST database of handwritten digits, the feature selection procedure allows reduction of feature number (from 60 000 to 7000) preserving comparable recognition capability while accelerating computations. Experimental comparison between the LiRA perceptron and the modular assembly neural network is accomplished, which shows that recognition capability of the modular assembly neural network is somewhat better. PMID:22391231

  18. Investigation on multilayer microstructure grating for three-port splitting

    NASA Astrophysics Data System (ADS)

    Shu, Wenhao; Wang, Bo; Pei, Hao; Li, Hongtao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2016-06-01

    A new structure of microstructure reflection three-port beam splitter grating is described in this paper. The grating includes two dielectric layers and a metal slab on the substrate, where incident waves are reflected into the zeroth-order and the ± first-order with polarization-independent property. With the optimized grating profile, reflection efficiencies’ ratios between the first-order and the zeroth-order can reach 0.998 and 1.001 for TE and TM polarizations, respectively. Especially, the reflection grating can diffract efficiencies more than 30% into the ± first-order and the zeroth-order with the incident angular bandwidth of ‑1.9-1.9∘ for TM polarization, which can have merits compared with single-layer transmission grating.

  19. Mechanical Properties and Microstructure Investigation of Lead Free Solder

    NASA Technical Reports Server (NTRS)

    Wang, Qing; Gail, William F.; Johnson, R. Wayne; Strickland, Mark; Blanche, Jim

    2005-01-01

    While the electronics industry appears to be focusing on Sn-Ag-Cu as the alloy of choice for lead free electronics assembly, ,the exact composition varies by geographic region, supplier and user. Add to that dissolved copper and silver from the printed circuit board traces and surface finish, and there can be significant variation in the final solder joint composition. A systematic study of the mechanical and microstructural properties of Sn-Ag-Cu alloys with Ag varying from 2wt% to 4wt% and Cu varying from 0.5wt% to lSwt%, was undertaken in this research study. Different sample preparation techniques (water quenched, oil quenched and water quenched followed by reflow) were explored and the resulting microstructure compared to that of a typical reflowed lead free chip scale package (CSP) solder joint. Tensile properties (modulus, 0.2% yield strength and the ultimate tensile strength) and creep behavior of selected alloy compositions (Sn-4Ag-1 X u , Sn-4Ag-OSCu, Sn- 2Ag-1 X u , Sn-2Ag-OSCu, Sn-3.5Ag-O.SCu) were determined for three conditions: as- cast; aged for 100 hours at 125OC; and aged for 250 hours at 125OC. There was no significant difference in Young's Modulus as a function of alloy composition. After an initial decrease in modulus after 100 hours at 125"C, there was an insignificant change with further aging. The distribution of 0.2% strain yield stress and ultimate tensile strength as a function of alloy composition was more significant and decreased with aging time and temperature. The microstructures of these alloys were examined using light and scanning electron microscopy (LM and SEM) respectively and SEM based energy dispersive x-ray spectroscopy (EDS). Fracture surface and cross-section analysis were performed on the specimens after creep testing. The creep testing results and the effect of high temperature aging on mechanical properties is presented for the oil quenched samples. In general the microstructure of oil quenched specimen exhibited a

  20. Microstructural Investigations On Ni-Ta-Al Ternary Alloys

    SciTech Connect

    Negache, M.; Souami, N.

    2010-01-05

    The Ni-Al-Ta ternary alloys in the Ni-rich part present complex microstructures. They are composed of multiple phases that are formed according to the nominal composition of the alloy, primary Ni(gamma), Ni{sub 3}Al(gamma'), Ni{sub 6}AlTa(tau{sub 3}), Ni{sub 3}Ta(delta) or in equilibrium: two solid phases (gamma'-tau{sub 3}), (tau{sub 3}-delta), (tau{sub 3}-gamma), (gamma-delta) or three solid phases (gamma'-tau{sub 3}-delta). The nature and the volume fraction of these phases give these alloys very interesting properties at high temperature, and this makes them attractive for specific applications. We have developed a series of ternary alloys in electric arc furnace, determining their solidification sequences using Differential Thermal Analysis (DTA), characterized by SEM-EDS, X-ray diffraction and by a microhardness tests. The follow-up results made it possible to make a correlation between the nature of the formed phases and their solidifying way into the Ni{sub 75}Al{sub x}Ta{sub y} (x+y = 25at.%) system, which are varied and complex. In addition to the solid solution Ni (gamma), the formed intermetallics compounds (gamma', tau{sub 3} and delta) has been identified and correlated with a complex balance between phases.We noticed that the hardness increases with the tantalum which has a hardening effect and though the compound Ni{sub 3}Ta(delta) is the hardest. The below results provide a better understanding of the complex microstructure of these alloys.

  1. Investigation on a "tentacle-like" corrosion feature on Bronze Age tin-bronze objects

    NASA Astrophysics Data System (ADS)

    Piccardo, Paolo; Mödlinger, Marianne; Ghiara, Giorgia; Campodonico, Serena; Bongiorno, Valeria

    2013-12-01

    Studying the micro-structure of Austrian, Bosnian and Croatian Bronze Age objects made of tin bronze, a rare kind of corrosion feature, called in the following "tentacle-like" according to its specific way of penetrating the metallic matrix, was noted and investigated. Differing from the more classical intergranular, pitting, or crevice corrosion features, the "tentacle-like" corrosion is not following the grain boundaries, nor precisely positioned under the etching area, but penetrates mainly the crystal matrix without any apparent order. This paper discusses the first results achieved and the following hypotheses formulated in respect of the typology of this corrosion. The analyses were carried out by optical microscopy, Raman microspectroscopy, and scanning electron microscopy equipped with EDX spectroscopy for quantitative analyses.

  2. Microstructural features at the interface between laser ablated YBa2Cu3O7 films and LaAlO3 substrates

    NASA Astrophysics Data System (ADS)

    Guo, L. P.; Tian, Y. J.; Liu, J. Z.; Xu, S. F.; Li, L.; Zhao, Z. X.; Chen, Z. H.; Cui, D. F.; Lu, H. B.; Zhou, Y. L.; Yang, G. Z.

    1995-06-01

    The microstructure at the interface between YBa2Cu3O7(YBCO) thin film and (100)LaAlO3 substrate has been investigated by using transmission electron microscopy. It has been observed that two distinct microstructural features existed in the interface: (1) A thin transitional layer of Ba3Al2O6 was frequently observed and the YBCO thin film grown on it showed stacking faults. (2) Sharp interface with no transitional layer was also occasionally observed and the YBCO film grown on it was single crystalline. In rare cases, a low symmetry phase was observed near the surface of the LaAlO3 substrate, however, the distortion caused by the lattice mismatch between this phase and the YBCO did not affect the quality of the YBCO thin film.

  3. Confined blue iridescence by a diffracting microstructure: an optical investigation of the Cynandra opis butterfly.

    PubMed

    Brink, D J; Lee, M E

    1999-09-01

    When illuminated and viewed along certain well-defined directions, segments on the wings of the butterfly Cynandra opis shows a striking violet-blue to blue-green. We quantify the spectral and the directional properties of these areas of the wings of the insect. Electron microscopy shows that wing scales from these iridescent regions of the wings contain two gratinglike microstructures crossed at right angles. Application of the diffraction theory, as formulated by the Stratton-Silver-Chu integral, to the microstructure can explain all the important features observed experimentally. PMID:18324029

  4. Microstructure investigation of plasma sprayed alumina 13 weight percent titania coatings from nanocrystalline feed powders

    NASA Astrophysics Data System (ADS)

    Goberman, Daniel George

    The development of constituent phases and microstructure in air plasma sprayed alumina (Al2O3) thirteen weight percent titania (TiO2) coatings from reconstituted nanocrystalline feed powder (nanopowder) was investigated as a function of processing conditions and compared to a conventional coating created from micron-sized feed powder. The microstructure of the nanopowder coating was found to consist of a mixture of two distinct regions; one was completely melted and quenched as splats, and the other partially melted with a particulate microstructure retained from the starting powder. The melted regions predominantly consisted of gamma-Al2O 3 with dissolved Ti4+ that varied in morphology and size from a few nanometers to several microns. Based upon these experimental observations, a theory is developed that explains the mechanism behind the morphological differences observed across the melted splat structures. In addition, differences between the melted structures in the nanopowder coatings and the conventional coating are explained using this theory. The partially melted regions were found to be primarily submicrometer-sized alpha-Al2O 3 particles in an amorphous TiO2 matrix containing small amounts of gamma-Al2O3 with dissolved Ti4+ . For the nanopowder coatings, the ratio of the melted splat microstructure to the particulate microstructure and thus the ratio of the gamma-Al 2O3 to alpha-Al2O3 can be controlled by a plasma spray parameter, defined as the critical plasma spray parameter (CPSP). The conventional coating microstructure was insensitive to CPSP, consisting primarily of fully melted splats. The ability to vary the microstructure of the nanopowder coating through CPSP has resulted in bimodal distributions of microstructure and grain size that have allowed these coatings to significantly surpass the conventional coating in several measures of mechanical properties.

  5. Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

    NASA Astrophysics Data System (ADS)

    Hidalgo, Javier; Santofimia, Maria Jesus

    2016-05-01

    Current trends in steels are focusing on refined martensitic microstructures to obtain high strength and toughness. An interesting manner to reduce the size of martensitic substructure is by reducing the size of the prior austenite grain (PAG). This work analyzes the effect of PAGS refinement by thermal cycling on different microstructural features of as-quenched lath martensite in a 0.3C-1.6Si-3.5Mn (wt pct) steel. The application of thermal cycling is found to lead to a refinement of the martensitic microstructures and to an increase of the density of high misorientation angle boundaries after quenching; these are commonly discussed to be key structural parameters affecting strength. Moreover, results show that as the PAGS is reduced, the volume fraction of retained austenite increases, carbides are refined and the concentration of carbon in solid solution as well as the dislocation density in martensite increase. All these microstructural modifications are related with the manner in which martensite forms from different prior austenite conditions, influenced by the PAGS.

  6. Preliminary investigation into sources of uncertainty in quantitative imaging features.

    PubMed

    Fave, Xenia; Cook, Molly; Frederick, Amy; Zhang, Lifei; Yang, Jinzhong; Fried, David; Stingo, Francesco; Court, Laurence

    2015-09-01

    Several recent studies have demonstrated the potential for quantitative imaging features to classify non-small cell lung cancer (NSCLC) patients as high or low risk. However applying the results from one institution to another has been difficult because of the variations in imaging techniques and feature measurement. Our study was designed to determine the effect of some of these sources of uncertainty on image features extracted from computed tomography (CT) images of non-small cell lung cancer (NSCLC) tumors. CT images from 20 NSCLC patients were obtained for investigating the impact of four sources of uncertainty: Two region of interest (ROI) selection conditions (breathing phase and single-slice vs. whole volume) and two imaging protocol parameters (peak tube voltage and current). Texture values did not vary substantially with the choice of breathing phase; however, almost half (12 out of 28) of the measured textures did change significantly when measured from the average images compared to the end-of-exhale phase. Of the 28 features, 8 showed a significant variation when measured from the largest cross sectional slice compared to the entire tumor, but 14 were correlated to the entire tumor value. While simulating a decrease in tube voltage had a negligible impact on texture features, simulating a decrease in mA resulted in significant changes for 13 of the 23 texture values. Our results suggest that substantial variation exists when textures are measured under different conditions, and thus the development of a texture analysis standard would be beneficial for comparing features between patients and institutions. PMID:26004695

  7. Investigation of microstructural alterations in M50 and 52100 steel using nanoindentation

    NASA Astrophysics Data System (ADS)

    Paulson, Kristin R.

    Bearing steels are used in rolling elements and are designed to withstand heavy loads for an extended period of time. At the end of life, microstructural alterations within the material have been observed and are linked to failure. In this study, a three ball-on-rod fatigue tester was used to test M50 and 52100 steel cylindrical rods at differing loads of 4.0 GPa, 4.5 GPa, and 5.0 GPa and in lubricated and unlubricated conditions to 108 cycles in an attempt to produce microstructural alterations. Microstructural alterations characterized as butterflies were observed and investigated further in two M50 samples that were tested at 4.5 GPa to 10 8 cycles in the lubricated and unlubricated condition. Microstructural alterations characterized as dark etching regions (DER), and white etching bands (WEBs) were not observed. Additionally, hardness was investigated cross sectionally as a function of depth and location within the wear track produced by the fatigue test. No conclusive evidence was derived from the hardness measurements as a function of depth in relation to the formation of microstructural alterations or the stress experienced subsurface within the material. Hardness measurements performed specifically within a butterfly wing, however, returned hardness values significantly higher than the matrix hardness values.

  8. Investigation of microstructure and thermal stability of pulsed plasma processed chromium ferritic-martensitic steels

    NASA Astrophysics Data System (ADS)

    Emelyanova, O.; Dzhumaev, P.; Yakushin, V.; Polsky, V.

    2016-04-01

    This paper presents results of the microstructural evolution and thermal stability of the promising Russian ferritic-martensitic steels (EP 823, EP 900, EK 181 and ChS 139) for the nuclear and fusion application after surface modification by high temperature pulsed plasma flows (HTPPF) treatment. Investigations of microstructure, topography and elemental content changes associated with irradiation by nitrogen plasma with energy density 19-28 J/ cm2 and pulse duration 20 μs were carried out. Changes in microstructure and elemental content occurring in the modified surface layer were characterized by means of scanning electron microscopy (SEM) and X-ray microanalysis (EDS and WDS). It was shown that independently of initial microstructure and phase composition, HTPPF treatment of ferritic- martensitic steels leads to formation of ultrafine homogeneous structure in the near surface layers with typical grain size ∼100 nm. Results of microstructure investigations after annealing during 1 hour demonstrates significant thermal stability of nanostructure formed by HTPPF treatment.

  9. Evolution and Control of 2219 Aluminum Microstructural Features Through Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M.; Hafley, Robert A.; Domack, Marcia S.

    2006-01-01

    The layer-additive nature of the electron beam freeform fabrication (EBF3) process results in a tortuous thermal path producing complex microstructures including: small homogeneous equiaxed grains; dendritic growth contained within larger grains; and/or pervasive dendritic formation in the interpass regions of the deposits. Several process control variables contribute to the formation of these different microstructures, including translation speed, wire feed rate, beam current and accelerating voltage. In electron beam processing, higher accelerating voltages embed the energy deeper below the surface of the substrate. Two EBF3 systems have been established at NASA Langley, one with a low-voltage (10-30kV) and the other a high-voltage (30-60 kV) electron beam gun. Aluminum alloy 2219 was processed over a range of different variables to explore the design space and correlate the resultant microstructures with the processing parameters. This report is specifically exploring the impact of accelerating voltage. Of particular interest is correlating energy to the resultant material characteristics to determine the potential of achieving microstructural control through precise management of the heat flux and cooling rates during deposition.

  10. Microstructural Investigation of High Emittance Glass Coatings on Fibrous Ceramic Insulation

    NASA Technical Reports Server (NTRS)

    Ellerby, Don; Leiser, Dan; DiFiore, Robert; Figone, Jeff; Smith, Dane; Loehman, Ron; Kotula, Paul

    2001-01-01

    This viewgraph presentation provides an overview of the Space Shuttle Thermal Protection System (TPS) and the various products incorporated in the TPS. There are three tile systems which include pure silica, fibrous refractory composite insulation (FRCI), and alumina enhanced thermal barrier (AETB). Coating systems include reaction cured glass (RCG) and toughened uni-piece insulation (TUFI). The microstructures of these systems are explored as are the manufacturing processes associated with each. Microstructural investigation using methods such as automated X-ray spectral image analysis (AXSIA) is a crucial part of understanding the mechanical nature of these systems.

  11. Microstructural investigation of copper corrosion: Influence of humidity

    NASA Astrophysics Data System (ADS)

    Campin, Michael J.

    2003-10-01

    Copper is a critical material in electrical components and is subject to atmospheric corrosion. This study characterized the corrosion products formed when copper is exposed to environments containing activated oxygen species or sulfur containing species. Investigation of the oxides formed when copper is exposed to an electron-cyclotron resonance (ECR) O2 plasma has revealed the presence of both Cu2O and CuO. In addition, it was found that the presence of CuO on copper prevents sulfidation. Particular emphasis is placed on the product formed when Cu is exposed to a dilute (50--200 ppb) H2S atmosphere at low (0.5%) to high (80%) relative humidity (RH). An important observation was that the Cu2S growth rate is significantly higher for sulfides formed at low RH compared to high RH. In addition, it is found that for both low and high RH sulfidation, copper reacts to form the low chalcocite phase (Cu2S) as identified by X-ray and electron diffraction. Cross-section and plan-view TEM revealed that the Cu2S grains formed at high RH are 20--50 nm in size with a large amount of porosity, whereas the grains formed at low RH are 75--150+ nm and appear to undergo grain growth with little porosity. Finally, numerical modeling of an ideal diffusion process is used to demonstrate that point like sources can result in behavior similar to that observed for the rate of sulfidation at high RH.

  12. Investigation of flow and microstructure in rheometric and processing flow conditions for liquid crystalline pitch

    NASA Astrophysics Data System (ADS)

    Kundu, Santanu

    The microstructure development within mesophase pitch-based carbon materials depends on the flow history that the pitch is subjected to. Therefore, a fundamental understanding of flow and its influence on the microstructure is required to obtain carbon materials with desired properties. The objective of this research was to investigate the flow and microstructural behavior of a synthetic mesophase pitch (AR-HP) in rheometric and processing flow conditions. In addition, simulation studies were performed to establish a frame work for modeling the flow behavior of this complex material in different flow situations. The steady-shear viscosities obtained from a cone-plate rheometer during increasing rate-sweep experiments exhibited shear-thinning (Region I) and plateau (Region II) responses. However, the slope of the shear-thinning region was only about -0.2, much lower than -0.5 observed in some pitches and liquid-crystalline polymers. This difference could arise from the different molecular constituents of pitches. At higher shear rates, as measured from capillary rheometers, the viscosity values remained almost constant. The transient shear stress responses, as measured from cone-plate rheometer, exhibited nonmonotonic behavior as a function of applied strain at all shear rates and temperatures tested. After rheological experiments, the samples were collected by developing a new experimental protocol for preservation of the sample for microstructural analysis. Microstructural observations obtained from three orthogonal sections, reported for the first time in the literature, indicate that the local maximum in shear stress was due to yielding of initial microstructure. The microstructure became flow oriented with further shearing, and the structure size decreased with increasing shear rates. In addition to high-strain experiments, dynamic experiments were also performed in the linear viscoelastic region where no significant deformation of fluid takes place. The

  13. Evolution and Control of 2219 Aluminum Microstructural Features through Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M.; Hafley, Robert A.; Domack, Marcia S.

    2006-01-01

    Electron beam freeform fabrication (EBF3) is a new layer-additive process that has been developed for near-net shape fabrication of complex structures. EBF3 uses an electron beam to create a molten pool on the surface of a substrate. Wire is fed into the molten pool and the part translated with respect to the beam to build up a 3-dimensional structure one layer at a time. Unlike many other freeform fabrication processes, the energy coupling of the electron beam is extremely well suited to processing of aluminum alloys. The layer-additive nature of the EBF3 process results in a tortuous thermal path producing complex microstructures including: small homogeneous equiaxed grains; dendritic growth contained within larger grains; and/or pervasive dendritic formation in the interpass regions of the deposits. Several process control variables contribute to the formation of these different microstructures, including translation speed, wire feed rate, beam current and accelerating voltage. In electron beam processing, higher accelerating voltages embed the energy deeper below the surface of the substrate. Two EBF3 systems have been established at NASA Langley, one with a low-voltage (10-30kV) and the other a high-voltage (30-60 kV) electron beam gun. Aluminum alloy 2219 was processed over a range of different variables to explore the design space and correlate the resultant microstructures with the processing parameters. This report is specifically exploring the impact of accelerating voltage. Of particular interest is correlating energy to the resultant material characteristics to determine the potential of achieving microstructural control through precise management of the heat flux and cooling rates during deposition.

  14. Microstructural Features of Quenching and Partitioning: A New Martensitic Steel Heat Treatment

    SciTech Connect

    Edmonds, D. V.; He, K.; Miller, Michael K; Rizzo, F. C.; Clarke, A.; Matlock, D. K.; Speer, J. G.

    2007-01-01

    The microstructure following a new martensite heat treatment has been examined, principally by high-resolution microanalytical transmission electron microscopy and by atom probe tomography. The new process involves quenching to a temperature between the martensite-start (Ms) and martensite-finish (Mf) temperatures, followed by ageing either at or above, the initial quench temperature, whereupon carbon can partition from the supersaturated martensite phase to the untransformed austenite phase. Thus the treatment has been termed ''Quenching and Partitioning'' (Q&P). The carbon must be protected from competing reactions, primarily carbide precipitation, during the first quench and partitioning steps, thus enabling the untransformed austenite to be enriched in carbon and largely stabilised against further decomposition to martensite upon final quenching to room temperature. This microstructural objective is almost directly opposed to conventional quenching and tempering of martensite, which seeks to eliminate retained austenite and where carbon supersaturation is relieved by carbide precipitation. This study focuses upon a steel composition representative of a TRIP-assisted sheet steel. The Q&P microstructure is characterised, paying particular attention to the prospect for controlling or suppressing carbide precipitation by alloying, through examination of the carbide precipitation that occurs.

  15. Investigation of Spectral Characteristics for Microstructured Quasi-Optical Bandpass Subteraherz Filters

    NASA Astrophysics Data System (ADS)

    Kuznetsov, S. A.; Gelfand, A. V.

    2016-03-01

    The electrodynamic features of quasi-optical bandpass filters based on multilayer microstructured frequency selective surfaces intended for effective spectral selection of subteraherz electromagnetic radiation are considered. As an optimal solution, the multiplex filters are highlighted wherein tripole-slot self-bearing copper microstructures free from dielectric substrates are employed. The results of the experimental development for such filters are presented by the example of structures with resonant transmission at the frequencies of 0.6 and 1 THz, and the details of testing their spectral performance in the range of 0.1-1.5 THz using a BWO spectroscopy technique are described. Good agreement between the experimental data and the results of theoretical predictions is demonstrated.

  16. A Monte Carlo Potts Investigation of Microstructural Evolution: Particle Assisted Abnormal Grain Growth

    NASA Astrophysics Data System (ADS)

    Guebels, Corentin Alain Pierre Nicolas

    The microstructural changes that occur in metals and alloys due to deformation and heat treatment are often characterized according to the macroscale deformation process (i.e. cold or hot working). The general problem of this type of characterization is that it only distinguishes the general microstructural trends. For many decades, these microstructural phenomena have been described empirically or with limited experimental verification. This shortcoming is apparent for recrystallization and abnormal grain growth processes. Understanding and characterizing the thermal and mechanical processes that compete to control grain boundary kinetics and the subsequent microstructural evolution is critical. These include but are not limited to: the input and recovery of deformation energy, the influence of deformation energy on grain boundary migration, the mechanisms controlling the nucleation of new grains, and the effect of second-phase particles. The present work introduces a new temporal scaling method and investigates the conditions in which some grain boundaries may become unpinned in an otherwise stable, pinned microstructure and extends work done by E. Holm. The temporal scaling method contributes to resolving some of the limitations of Monte Carlo Potts (MCP) simulations in the investigation of the conditions and mechanisms that distinguish recrystallization from dynamic abnormal grain growth (DAGG). Grain boundary unpinning is then investigated for the case of an idealized spherical grain and for a polycrystalline microstructure. The mechanisms of grain boundary pinning and grain growth inhibition by second-phase particles are well known. The influence of simulation temperature on grain boundary unpinning is investigated numerically using a 3D Monte Carlo Potts approach. MCP based models are commonly implemented to simulate microstructural evolution. However, the numerical implementations of recrystallization and other deformation-induced phenomena often elude

  17. Investigation of Magnetic Signatures and Microstructures for Heat-Treated Ferritic/Martensitic HT-9 Alloy

    SciTech Connect

    Henager, Charles H.; McCloy, John S.; Ramuhalli, Pradeep; Edwards, Danny J.; Hu, Shenyang Y.; Li, Yulan

    2013-05-01

    There is increased interest in improved methods for in-situ nondestructive interrogation of materials for nuclear reactors in order to ensure reactor safety and quantify material degradation (particularly embrittlement) prior to failure. Therefore, a prototypical ferritic/martensitic alloy, HT-9, of interest to the nuclear materials community was investigated to assess microstructure effects on micromagnetics measurements – Barkhausen noise emission, magnetic hysteresis measurements, and first-order reversal curve analysis – for samples with three different heat-treatments. Microstructural and physical measurements consisted of high-precision density, resonant ultrasound elastic constant determination, Vickers microhardness, grain size, and texture. These were varied in the HT-9 alloy samples and related to various magnetic signatures. In parallel, a meso-scale microstructure model was created for alpha iron and effects of polycrystallinity and demagnetization factor were explored. It was observed that Barkhausen noise emission decreased with increasing hardness and decreasing grain size (lath spacing) while coercivity increased. The results are discussed in terms of the use of magnetic signatures for nondestructive interrogation of radiation damage and other microstructural changes in ferritic/martensitic alloys.

  18. Microstructural and crystallographic features of ausferrite in as-cast gray iron

    SciTech Connect

    Ferry, M. . E-mail: m.ferry@unsw.edu.au; Xu, W.

    2004-09-15

    Ausferrite has been shown to form during casting of gray iron by carefully controlling the alloying additions Mo, Mn, Si and Cu and consists of an acicular ferrite constituent, termed bainitic ferrite ({alpha}{sub B}), which develops during continuous cooling as a coarse, feathery-type structure within the prior austenite ({gamma}) grains. Regardless of alloy composition, the ausferrite that forms in the microstructure during casting in volume fractions greater than {approx}0.1 was found to have a constant bainitic ferrite/retained austenite ratio ({alpha}{sub B}/{gamma}{approx}3). Electron backscatter diffraction (EBSD) in the scanning electron microscope has demonstrated that {alpha}{sub B} and {gamma} in ausferrite is related by the Kurdjumov-Sachs orientation relationship: {l_brace}111{r_brace}{sub {gamma}}//{l_brace}011{r_brace}{sub {alpha}} and <011>{sub {gamma}}//<111>{sub {alpha}} with a number of {alpha}{sub B} variants possible within a given austenite grain. This study confirms that the ausferrite generated in gray iron by direct casting has comparable microstructural and crystallographic characteristics to that produced in austempered gray and ductile irons.

  19. Damage in dual phase steel DP1000 investigated using digital image correlation and microstructure simulation

    NASA Astrophysics Data System (ADS)

    Alharbi, Khaled; Ghadbeigi, Hassan; Efthymiadis, Panos; Zanganeh, Mohammad; Celotto, Steven; Dashwood, Richard; Pinna, Christophe

    2015-12-01

    Microstructure failure mechanisms and void nucleation in dual-phase (DP) steels during deformation have been studied using a combination of in situ tensile testing in a scanning electron microscope (SEM), digital image correlation (DIC) and finite element (FE) modelling. SEM images acquired during in situ tests were used to follow the evolution of damage within the microstructure of a DP1000 steel. From these images, strain maps were generated using DIC and used as boundary conditions for a FE model to investigate the stress state of martensite and ferrite before the onset of the martensite phase cracking. Based on the simulation results, a maximum principal stress of about 1700 MPa has been estimated for crack initiation in the martensite of the investigated DP1000 steel. The SEM image observations in combination with the FE analyses provide new insights for the development of physically-based damage models for DP-steels.

  20. Effect of processing conditions on microstructural features in Mn–Si sintered steels

    SciTech Connect

    Oro, Raquel; Hryha, Eduard; Campos, Mónica; Torralba, José M.

    2014-09-15

    Sintering of steels containing oxidation sensitive elements is possible if such elements are alloyed with others which present lower affinity for oxygen. In this work, a master alloy powder containing Fe–Mn–Si–C, specifically designed to create a liquid phase during sintering, has been used for such purpose. The effect of processing conditions such as sintering temperature and atmosphere was studied with the aim of describing the microstructural evolution as well as the morphology and distribution of oxides in the sintered material, evaluating the potential detrimental effect of such oxides on mechanical properties. Chemical analyses, metallography and fractography studies combined with X-ray photoelectron spectroscopy analyses on the fracture surfaces were used to reveal the main mechanism of fracture and their correlation with the chemical composition of the different fracture surfaces. The results indicate that the main mechanism of failure in these steels is brittle fracture in the surrounding of the original master alloy particles due to degradation of grain boundaries by the presence of oxide inclusions. Mn–Si oxide inclusions were observed on intergranular decohesive facets. The use of reducing atmospheres and high sintering temperatures reduces the amount and size of such oxide inclusions. Besides, high heating and cooling rates reduce significantly the final oxygen content in the sintered material. A model for microstructure development and oxide evolution during different stages of sintering is proposed, considering the fact that when the master alloy melts, the liquid formed can dissolve some of the oxides as well as the surface of the surrounding iron base particles. - Highlights: • Oxide distribution in steels containing oxidation-sensitive elements • Mn, Si introduced in a master alloy powder, mixed with a base iron powder • Selective oxidation of Mn and Si on iron grain boundaries • Decohesive fracture caused by degradation of grain

  1. Experimental investigation of high aspect ratio tubular microstructuring of glass by means of picosecond Bessel vortices

    NASA Astrophysics Data System (ADS)

    Jedrkiewicz, Ottavia; Bonanomi, Simone; Selva, Marco; Di Trapani, Paolo

    2015-07-01

    We report on experiments on glass material modification using nondiffractive high-order picosecond pulsed Bessel beams, generated by a spatial light phase modulator and then suitably demagnified. We investigate the possibility to generate in single-shot tubular microstructures across 100-μm-thin borosilicate glass, when a suitable energy range is considered, and we highlight the effect of the unstable propagation regime for very high input energies, leading to a breakup of the tubular microstructure. The micromachined glass samples are observed on their top and bottom surfaces as well as longitudinally along their thickness. For the conical beam geometry used, we observe no internal material modification pattern with pulses in the femtosecond range. A comparison with glass machining by means of a focused ring-shaped beam is also presented. The results highlight the role of the conical energy flux for single-shot smooth high aspect ratio material modification in a regime where nonlinear Kerr effects are absent.

  2. Pumice-supported palladium catalysts. I. Chemical preparation and microstructural features

    SciTech Connect

    Fagherazzi, G.; Benedetti, A.; Deganello, G.; Duca, D.; Martorana, A.; Spoto, G.

    1994-11-01

    Two series of pumice-supported palladium catalysts (W = washed, U = unwashed) were prepared by the reaction of [Pd(C{sub 3}H{sub 5}){sub 2}] with the support, followed by reduction using H{sub 2}. W catalysts were washed before reduction to eliminate unreacted [Pd(C{sub 3}H{sub 5}){sub 2}]. U catalysts did not undergo this treatment. Microstructural characterization of the catalysts was performed by small-angle X-ray scattering (SAXS), wide-angle X-ray line broadening, and transmission electron microscopy (TEM). Line-broadening analysis revealed the presence of lattice imperfections, such as growth stacking faults and microstrains in the fcc structure of palladium. The average particle size values determined by SAXS were confirmed by TEM analysis and were employed to calculate the percentage of palladium exposed (catalyst dispersion). W catalysts showed well-dispersed spheroidal particles, whereas the U series displayed agglomerates. 38 refs., 9 figs., 2 tabs.

  3. GALACTIC S STARS: INVESTIGATIONS OF COLOR, MOTION, AND SPECTRAL FEATURES

    SciTech Connect

    Otto, Elizabeth; Green, Paul J.; Gray, Richard O.

    2011-09-01

    Known bright S stars, recognized as such by their enhanced s-process abundances and C/O ratio, are typically members of the asymptotic giant branch (AGB) or the red giant branch. Few modern digital spectra for these objects have been published, from which intermediate resolution spectral indices and classifications could be derived. For published S stars, we find accurate positions using the Two-Micron All Sky Survey (2MASS), and use the FAST spectrograph of the Tillinghast reflector on Mt. Hopkins to obtain the spectra of 57 objects. We make available a digital S star spectral atlas consisting of 14 spectra of S stars with diverse spectral features. We define and derive basic spectral indices that can help distinguish S stars from late-type (M) giants and carbon stars. We convolve all our spectra with the Sloan Digital Sky Survey bandpasses, and employ the resulting gri magnitudes together with 2MASS JHK{sub s} mags to investigate S star colors. These objects have colors similar to carbon and M stars, and are therefore difficult to distinguish by color alone. Using near- and mid-infrared colors from IRAS and Akari, we identify some of the stars as intrinsic (AGB) or extrinsic (with abundances enhanced by past mass transfer). We also use V band and 2MASS magnitudes to calculate a temperature index for stars in the sample. We analyze the proper motions and parallaxes of our sample stars to determine upper and lower limit absolute magnitudes and distances, and confirm that most are probably giants.

  4. Clinical investigation of speech signal features among patients with schizophrenia

    PubMed Central

    ZHANG, Jing; PAN, Zhongde; GUI, Chao; CUI, Donghong

    2016-01-01

    Background A new area of interest in the search for biomarkers for schizophrenia is the study of the acoustic parameters of speech called 'speech signal features'. Several of these features have been shown to be related to emotional responsiveness, a characteristic that is notably restricted in patients with schizophrenia, particularly those with prominent negative symptoms. Aim Assess the relationship of selected acoustic parameters of speech to the severity of clinical symptoms in patients with chronic schizophrenia and compare these characteristics between patients and matched healthy controls. Methods Ten speech signal features-six prosody features, formant bandwidth and amplitude, and two spectral features-were assessed using 15-minute speech samples obtained by smartphone from 26 inpatients with chronic schizophrenia (at enrollment and 1 week later) and from 30 healthy controls (at enrollment only). Clinical symptoms of the patients were also assessed at baseline and 1 week later using the Positive and Negative Syndrome Scale, the Scale for the Assessment of Negative Symptoms, and the Clinical Global Impression-Schizophrenia scale. Results In the patient group the symptoms were stable over the 1-week interval and the 1-week test-retest reliability of the 10 speech features was good (intraclass correlation coefficients [ICC] ranging from 0.55 to 0.88). Comparison of the speech features between patients and controls found no significant differences in the six prosody features or in the formant bandwidth and amplitude features, but the two spectral features were different: the Mel-frequency cepstral coefficient (MFCC) scores were significantly lower in the patient group than in the control group, and the linear prediction coding (LPC) scores were significantly higher in the patient group than in the control group. Within the patient group, 10 of the 170 associations between the 10 speech features considered and the 17 clinical parameters considered were

  5. Investigation of the Dynamic Strain Aging and Mechanical Properties in Alloy-625 with Different Microstructures

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arnomitra; Sharma, Garima; Tewari, R.; Chakravartty, J. K.

    2015-03-01

    Tensile tests were carried out on service exposed Alloy 625 ammonia cracker tube used at heavy water production plant to study the effect of microstructure on the serrated yielding and mechanical properties of the material. Owing to temperature gradient during service exposure, the microstructure was different in top, middle, and bottom sections of the tube. Variation of flow stress, ductility, and average work hardening were monitored with temperature. In the present work, emphasis was given on the study of serrated yielding in the service exposed Alloy 625. Detail investigations were made to study the effect of microstructure on the underlying mechanism of dynamic strain aging of the material. The study revealed that both the normal and the inverse Portevin-Le Chatelier effect (PLC) occured in the material at lower and higher temperature regime, respectively. While the normal PLC dynamics was associated with locking of dislocations by interstitial carbon atoms, the inverse one was accomplished by the dislocation pinning by substitutional Mo atoms. Further analyses identified that the basic deformation mechanism was different in middle and bottom samples as that in the top samples which was reflected in the difference in their respective activation energy and stress drop magnitude.

  6. A microstructural investigation of the depth-dependent response of cartilage during stress relaxation

    NASA Astrophysics Data System (ADS)

    Zhang, Geran; Thambyah, Ashvin; Broom, Neil

    2009-08-01

    The poro-visco-hyperelastic nature of articular cartilage has been studied extensively, yet little has been done to correlate its unique mechanical properties with its microstructural response to load. Making such a correlation would help determine how the microstructure of cartilage, with its zonally-differentiated fibrillar microarchitecture and water-content, influences the overall macro-level mechanical response. A total of eight cartilage-on-bone samples were subjected to stress relaxation tests, conducted via stepwise indentation, and using a 2mm diameter cylindrical indenter. Each step indentation consisted of a 10% compressive strain, up to 80%. At each strain increment the specimen was allowed to fully relax to an equilibrium stress before compressing it further. From the stress relaxation curve at each strain level, peak and equilibrium stresses were recorded. For the microstructural investigation, specimens stress-equilibrated at 20%, 40%, 60% and 80% strain, were chemically fixed to capture the deformed state and then cryo-sectioned and imaged using differential interference contrast (DIC) microscopy. It was found that stress relaxation, i.e. the time from peak stress to equilibrium, occurred at a slower rate at the larger levels of compressive strain. Peak stresses increased exponentially with increasing levels of strain. The equilibrium stress relationship with compressive strain level was largely linear but between 60% and 80% strain, the change in equilibrium stress increased dramatically. The microstructural data showed how at lower strain levels, much of the load was distributed laterally within the upper zones of the cartilage matrix. At higher strain levels (>60%) the deep zone fibrillar alignment was sheared and this may explain the abrupt rise in equilibrium stress levels. Finally, the increase in peak stress at higher strain-levels is likely due to a decreased interstitial fluid permeability associated with an increasingly consolidated matrix.

  7. Investigation of image feature extraction by a genetic algorithm

    NASA Astrophysics Data System (ADS)

    Brumby, Steven P.; Theiler, James P.; Perkins, Simon J.; Harvey, Neal R.; Szymanski, John J.; Bloch, Jeffrey J.; Mitchell, Melanie

    1999-11-01

    We describe the implementation and performance of a genetic algorithm which generates image feature extraction algorithms for remote sensing applications. We describe our basis set of primitive image operators and present our chromosomal representation of a complete algorithm. Our initial application has been geospatial feature extraction using publicly available multi-spectral aerial-photography data sets. We present the preliminary results of our analysis of the efficiency of the classic genetic operations of crossover and mutation for our application, and discuss our choice of evolutionary control parameters. We exhibit some of our evolved algorithms, and discuss possible avenues for future progress.

  8. Microstructure investigation and magnetic study of permalloy thin films grown by thermal evaporation

    NASA Astrophysics Data System (ADS)

    Lamrani, Sabrina; Guittoum, Abderrahim; Schäfer, Rudolf; Pofahl, Stefan; Neu, Volker; Hemmous, Messaoud; Benbrahim, Nassima

    2016-06-01

    We study the effect of thickness on the structural and magnetic properties of permalloy thin films, evaporated on glass substrate. The films thicknesses range from 16 to 90 nm. From X-ray diffraction spectra analysis, we show that the thinner films present a "1,1,1" preferred orientation. However, the thicker films exhibit a random orientation. The grains size increases and the lattice parameter decreases with increasing thickness. The magnetic force microscopy observations display cross-tie walls features only for the two thicker films (60 and 90 nm thick films). The magnetic microstructure, carried out by Kerr microscopy technique, shows the presence of magnetic domains changing with the direction of applied magnetic field. The coercive field, Hc, was found to decrease from 6.5 for 16 to 1.75 Oe for 90 nm. All these results will be discussed and correlated.

  9. Microstructural investigations of materials for low temperature co-fired ceramic (LTCC) based fuel cell using small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Mohamed, A. A.; Ahmad, M. H.; Ibrahim, A.; Azman, A.; Alias, R.; Ambak, Z.; Shapee, S.; Putra, E. G.; Patriati, A.; Sharom, M. A.; Yazid, H.; Mamat, M. R.; Karim, J. A.; Idris, F. M.; Yazid, K.; Zin, M. R.

    2013-06-01

    The concept and the realization fuel cell based on LTCC technology require the investigations of fired LTCC microstructures. The majority of the works involved using small angle neutron scattering studies on the microstructural of LTCC ceramic tape and development of neutron tomography for future tool to visualize channels inside the fired tape. Most SANS characterization were carried out at Smarter SANS instrument at BATAN, Indonesia. Standard sample for resolving tens of micron of object size were measured using simple neutron tomography setup utilizing monochromatic SANS beam at Malaysian Nuclear Agency. The initial microstructural findings indicates that organic additives shape the final microstructural of LTCC after firing with the glassy material possibly fill the space left by the burned organic additives. The tomography results showed that 40 micron size object can be differentiated. The conductor deposited on LTCC is preliminary investigated which will later be used as support for catalyst.

  10. Investigation of mesoscale cloud features viewed by LANDSAT

    NASA Technical Reports Server (NTRS)

    Sherr, P. E. (Principal Investigator); Feteris, P. J.; Lisa, A. S.; Bowley, C. J.; Fowler, M. G.; Barnes, J. C.

    1976-01-01

    The author has identified the following significant results. Some 50 LANDSAT images displaying mesoscale cloud features were analyzed. This analysis was based on the Rayleigh-Kuettner model describing the formation of that type of mesoscale cloud feature. This model lends itself to computation of the average wind speed in northerly flow from the dimensions of the cloud band configurations measured from a LANDSAT image. In nearly every case, necessary conditions of a curved wind profile and orientation of the cloud streets within 20 degrees of the direction of the mean wind in the convective layer were met. Verification of the results by direct observation was hampered, however, by the incompatibility of the resolution of conventional rawinsonde observations with the scale of the banded cloud patterns measured from LANDSAT data. Comparison seems to be somewhat better in northerly flows than in southerly flows, with the largest discrepancies in wind speed being within 8m/sec, or a factor of two.

  11. Orbital-science investigation: Part L: selected volcanic features

    USGS Publications Warehouse

    West, Mareta N.

    1972-01-01

    Preliminary examination of Apollo 15 orbital photographs indicates a large number of volcanic features. One area of exceptionally interesting volcanic activity is depicted in figure 25-74. Located approximately at latitude 25° S and longitude 123° E on the lunar far side, this region also is covered by panoramic camera photographs AS15-9954, 9956, 9958, and 9960 and by stereoscopically overlapping frames AS15-9959, 9961, 9963, and 9965.

  12. Microstructural Investigation of Fe-Ni-Mn-Mo-V-C-N Ferritic Steels by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Baeva, M.; Beskrovnyi, A. I.; Parshorov, I.; Vassilovskii, S. G.

    2010-01-01

    The design of alloys, that economize strategic element as chromium requires detailed physical investigations of their structure and phase composition. In the search for new materials in the last two decades a new class of Fe alloys was composed—the so-called nitrogen steels. The contemporary achievements in the casting technology—the use of nitrogen under high preasure above the melt—made possible the production of Fe alloys with nitrogen concentration even above 0.4 wt%. The wide application of investigated alloy system is connected with creation of alloys without presence of strong carbides-forming elements. The microstructure and phase formation of these new materials are insufficiently studied. The aim of this work is to characterize the microstructure and phase composition of two series Fe-alloys casted with and without nitrogen pressure above the melt. The so cast steels appear as experimental ones and they are directed to demonstrate the possibility for nitrogen doping of steels without presence of Chromium in them. The latter is technologically difficult to fulfil at usual conditions. Six samples [with lower nitrogen, N = 0.0111 wt%] are cast at normal pressure, and six samples [with higher nitrogen, N0.2121 wt%] are cast at pressure of 10.106 Pa. The results of Rietveld structure analysis of Time-Of-Flight neutron diffraction data show that studied steels consist of purely ferritic crystal phase (Body Centered Cubic crystal lattice).

  13. Investigation of grain-scale microstructural variability in tantalum using crystal plasticity-finite element simulations

    DOE PAGESBeta

    Lim, Hojun; Dingreville, Rémi; Deibler, Lisa A.; Buchheit, Thomas E.; Battaile, Corbett C.

    2016-02-27

    In this research, a crystal plasticity-finite element (CP-FE) model is used to investigate the effects of microstructural variability at a notch tip in tantalum single crystals and polycrystals. It is shown that at the macroscopic scale, the mechanical response of single crystals is sensitive to the crystallographic orientation while the response of polycrystals shows relatively small susceptibility to it. However, at the microscopic scale, the local stress and strain fields in the vicinity of the crack tip are completely determined by the local crystallographic orientation at the crack tip for both single and polycrystalline specimens with similar mechanical field distributions.more » Variability in the local metrics used (maximum von Mises stress and equivalent plastic strain at 3% deformation) for 100 different realizations of polycrystals fluctuates by up to a factor of 2–7 depending on the local crystallographic texture. Comparison with experimental data shows that the CP model captures variability in stress–strain response of polycrystals that can be attributed to the grain-scale microstructural variability. In conclusion, this work provides a convenient approach to investigate fluctuations in the mechanical behavior of polycrystalline materials induced by grain morphology and crystallographic orientations.« less

  14. Features of the microstructure development under conditions, reproducing the process of friction stir welding. Molecular-dynamics study

    SciTech Connect

    Nikonov, Anton Yu. E-mail: dmitr@ispms.tsc.ru; Dmitriev, Andrey I. E-mail: dmitr@ispms.tsc.ru; Kolubaev, Evgeniy A. E-mail: rvy@ispms.tsc.ru; Rubtsov, Valeriy E. E-mail: rvy@ispms.tsc.ru

    2014-11-14

    Friction stir welding is a recently developed technology which is used in various branches of modern engineering. The basis of this technology is the friction of the rotating cylindrical or specially shaped tool between two metal plates brought together either to meet their ends of one above another with the overlap. When applying the FSW process in various economical sectors, the important task is to study the mechanisms and identify the physical laws and factors leading to formation of structural inhomogeneities and discontinuities in the weld seam. This paper analyzes the basic mechanisms behind the structural state generation in the material subjected to severe plastic deformation and heating. To investigate the atomic mechanisms of structural changes in FSW, the modeling at atomic scale has been carried out. Results of work can be a basis for new knowledge about the microstructure evolution in FSW.

  15. Microstructure and frictional properties of sheared calcite speleothems: natural vs. experimental investigation

    NASA Astrophysics Data System (ADS)

    Mitrovic, I.; Tesei, T.; Grasemann, B.; Collettini, C.; Plan, L.; Baron, I.

    2015-12-01

    Several alpine caves in Austria preserve evidences related to active faulting, such as broken and scratched speleothems. Here, in order to better understand fault slip behavior and related potential earthquake hazards, microstructures of experimentally deformed speleothems are presented and compared with naturally deformed ones. Speleothems are monomineralitic rocks precipitated in caves, composed of columnar centimeter-scale calcite crystals with strong growth orientation. In order to better study the origin and evolution of deformation in faulted speleothems we performed sliding experiments using a rock deformation biaxial apparatus. In order to recreate the faulting conditions observed in Austrian caves, speleothems were cut into rectangular blocks and sheared against each other, with long growth axes of calcite perpendicular to the shearing direction. The experiments were performed under room conditions, sliding velocity in the range of 0.001-0.01 mm/s, and constant effective normal stress of 3 MPa. The mechanical data show fairly high friction coefficient (0.7-0.95) accompanied by the production of calcite-rich fault gouge which displays Riedel shears within a foliated cataclasite and drastic grain size reduction (nano-scale). The transition from the fault gouge towards the undeformed crystals is characterized first by a series of in situ jigsaw puzzle fracturing, then dense mechanical twin network, which is decreasing in its intensity away from the gouge (i.e. principal slip surface). The similarity between laboratory induced and naturally formed microstructures reinforce the tectonic interpretation of the damaged speleothems. Detailed microstructure investigations, including electron backscattered diffraction technique combined with electron microprobe and cathodoluminescence, are on the way to help distinguishing between seismic slip and/or aseismic creep.

  16. Cross-correlative 3D micro-structural investigation of human bone processed into bone allografts.

    PubMed

    Singh, Atul Kumar; Gajiwala, Astrid Lobo; Rai, Ratan Kumar; Khan, Mohd Parvez; Singh, Chandan; Barbhuyan, Tarun; Vijayalakshmi, S; Chattopadhyay, Naibedya; Sinha, Neeraj; Kumar, Ashutosh; Bellare, Jayesh R

    2016-05-01

    Bone allografts (BA) are a cost-effective and sustainable alternative in orthopedic practice as they provide a permanent solution for preserving skeletal architecture and function. Such BA however, must be processed to be disease free and immunologically safe as well as biologically and clinically useful. Here, we have demonstrated a processing protocol for bone allografts and investigated the micro-structural properties of bone collected from osteoporotic and normal human donor samples. In order to characterize BA at different microscopic levels, a combination of techniques such as Solid State Nuclear Magnetic Resonance (ssNMR), Scanning Electron Microscope (SEM), micro-computed tomography (μCT) and Thermal Gravimetric Analysis (TGA) were used for delineating the ultra-structural property of bone. ssNMR revealed the extent of water, collagen fine structure and crystalline order in the bone. These were greatly perturbed in the bone taken from osteoporotic bone donor. Among the processing methods analyzed, pasteurization at 60 °C and radiation treatment appeared to substantially alter the bone integrity. SEM study showed a reduction in Ca/P ratio and non-uniform distribution of elements in osteoporotic bones. μ-CT and MIMICS (Materialize Interactive Medical Image Control System) demonstrated that pasteurization and radiation treatment affects the BA morphology and cause a shift in the HU unit. However, the combination of all these processes restored all-important parameters that are critical for BA integrity and sustainability. Cross-correlation between the various probes we used quantitatively demonstrated differences in morphological and micro-structural properties between BA taken from normal and osteoporotic human donor. Such details could also be instrumental in designing an appropriate bone scaffold. For the best restoration of bone microstructure and to be used as a biomaterial allograft, a step-wise processing method is recommended that preserves all

  17. Microstructural investigation of hardfacing weld deposit obtained from CrB paste

    SciTech Connect

    Kr. Ray, S.; Sarker, B.; Kr. Bhattacharya, S. )

    1989-05-01

    Hardfacing weld deposits are used as a protective layer on engineering components and tools subjected to different modes of wear. Cheaper iron-based alloys with chromium and carbon or relatively expensive alloys with some niobium or titanium have long been used as standard hardfacing materials. In recent years boron has substituted the costlier alloying elements and the newly developed Fe-B-C alloys have shown encouraging results. The microstructure of the welded hardfacing deposit is one of the most important factors that determine its performance. The amount, size, distribution and hardness of the individual constituents play important roles in imparting the desired properties. Recently Colomonoy sweat on paste containing fine CrB particles (of about 12 {mu}m average size) suspended in an organic binder has been marketed as the new generation hardfacing material. A thin coating of the paste is applied on the component surface, allowed to dry and welded. The welded deposit has been found to offer good wear resistance in many industrial applications. This paper reports the microstructural investigation of the welded deposit obtained from this paste.

  18. Microstructure Evaluation of Fe-BASED Amorphous Alloys Investigated by Doppler Broadening Positron Annihilation Technique

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao

    2013-07-01

    Microstructure of Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Doppler broadening positron annihilation technique (PAT). Doppler broadening measurement reveals that amorphous alloys (Finemet, Type I) which can form a nanocrystalline phase have more defects (free volume) than alloys (Metglas, Type II) which cannot form this microstructure. XRD and TEM characterization indicates that the nanocrystallization of amorphous Finemet alloy occurs at 460°C, where nanocrystallites of α-Fe with an average grain size of a few nanometers are formed in an amorphous matrix. With increasing annealing temperature up to 500°C, the average grain size increases up to around 12 nm. During the annealing of Finemet alloy, it has been demonstrated that positron annihilates in quenched-in defect, crystalline nanophase and amorphous-nanocrystalline interfaces. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of α-Fe(Si) phase during annealing. This study throws new insights into positron behavior in the nanocrystallization of metallic glasses, especially in the presence of single or multiple nanophases embedded in the amorphous matrix.

  19. An Investigation into the Microstructure of Friction-Stir Welded and Artificially Aged AA2017

    NASA Astrophysics Data System (ADS)

    Mirjalili, A.; Aval, H. Jamshidi; Serajzadeh, S.

    2013-11-01

    Microstructural changes in friction-stir welding (FSW) of artificially aged AA2017 were investigated. First, FSW was performed with rotational and linear speeds of 800 rpm and 40 mm/min, respectively. Then, microstructural studies by means of optical metallography and electron microscopy were conducted in different regions of the welded plates. Hardness testing was also employed to determine local strength and subsequent natural aging progress after welding. The results indicate that the considerable hardness degradation occurs in the thermo-mechanically affected zone owing to coarsening of semi-coherent precipitates. Grain refinement also takes place in the weld nugget as a result of dynamic recrystallization and it results in a fine-grained structure with the mean grain size to 5 μm. On the other hand, the initial precipitate distribution is completely vanished in the weld nugget and instead, spherical-shaped particles are formed. Moreover, natural aging after FSW occurs in the welded sample and leads to considerable increase in the hardness of the weld nugget zone.

  20. A Whole-Brain Investigation of White Matter Microstructure in Adolescents with Conduct Disorder

    PubMed Central

    Sarkar, Sagari; Dell’Acqua, Flavio; Froudist Walsh, Seán; Blackwood, Nigel; Scott, Stephen; Craig, Michael C.

    2016-01-01

    Background The biological basis of severe antisocial behaviour in adolescents is poorly understood. We recently reported that adolescents with conduct disorder (CD) have significantly increased fractional anisotropy (FA) of the uncinate fasciculus (a white matter (WM) tract that connects the amygdala to the frontal lobe) compared to their non-CD peers. However, the extent of WM abnormality in other brain regions is currently unclear. Methods We used tract-based spatial statistics to investigate whole brain WM microstructural organisation in 27 adolescent males with CD, and 21 non-CD controls. We also examined relationships between FA and behavioural measures. Groups did not differ significantly in age, ethnicity, or substance use history. Results The CD group, compared to controls, had clusters of significantly greater FA in 7 brain regions corresponding to: 1) the bilateral inferior and superior cerebellar peduncles, corticopontocerebellar tract, posterior limb of internal capsule, and corticospinal tract; 2) right superior longitudinal fasciculus; and 3) left cerebellar WM. Severity of antisocial behavior and callous-unemotional symptoms were significantly correlated with FA in several of these regions across the total sample, but not in the CD or control groups alone. Conclusions Adolescents with CD have significantly greater FA than controls in WM regions corresponding predominantly to the fronto-cerebellar circuit. There is preliminary evidence that variation in WM microstructure may be dimensionally related to behaviour problems in youngsters. These findings are consistent with the hypothesis that antisocial behaviour in some young people is associated with abnormalities in WM ‘connectivity’. PMID:27271503

  1. Investigation of road network features and safety performance.

    PubMed

    Wang, Xuesong; Wu, Xingwei; Abdel-Aty, Mohamed; Tremont, Paul J

    2013-07-01

    The analysis of road network designs can provide useful information to transportation planners as they seek to improve the safety of road networks. The objectives of this study were to compare and define the effective road network indices and to analyze the relationship between road network structure and traffic safety at the level of the Traffic Analysis Zone (TAZ). One problem in comparing different road networks is establishing criteria that can be used to scale networks in terms of their structures. Based on data from Orange and Hillsborough Counties in Florida, road network structural properties within TAZs were scaled using 3 indices: Closeness Centrality, Betweenness Centrality, and Meshedness Coefficient. The Meshedness Coefficient performed best in capturing the structural features of the road network. Bayesian Conditional Autoregressive (CAR) models were developed to assess the safety of various network configurations as measured by total crashes, crashes on state roads, and crashes on local roads. The models' results showed that crash frequencies on local roads were closely related to factors within the TAZs (e.g., zonal network structure, TAZ population), while crash frequencies on state roads were closely related to the road and traffic features of state roads. For the safety effects of different networks, the Grid type was associated with the highest frequency of crashes, followed by the Mixed type, the Loops & Lollipops type, and the Sparse type. This study shows that it is possible to develop a quantitative scale for structural properties of a road network, and to use that scale to calculate the relationships between network structural properties and safety. PMID:23584537

  2. Early Age Characterization and Microstructural Features of Sustainable Binder Systems for Concrete

    NASA Astrophysics Data System (ADS)

    Vance, Kirk

    Concrete is the most widely used infrastructure material worldwide. Production of Portland cement, the main binding component in concrete, has been shown to require significant energy and account for approximately 5-7% of global carbon dioxide production. The expected continued increased use of concrete over the coming decades indicates this is an ideal time to implement sustainable binder technologies. The current work aims to explore enhanced sustainability concretes, primarily in the context of limestone and flow. Aspects such as hydration kinetics, hydration product formation and pore structure add to the understanding of the strength development and potential durability characteristics of these binder systems. Two main strategies for enhancing this sustainability are explored in this work: (i) the use of high volume limestone in combination with other alternative cementitious materials to decrease the Portland cement quantity in concrete and (ii) the use of geopolymers as the binder phase in concrete. The first phase of the work investigates the use of fine limestone as cement replacement from the perspective of hydration, strength development, and pore structure. The nature of the potential synergistic benefit of limestone and alumina will be explored. The second phase will focus on the rheological characterization of these materials in the fresh state, as well as a more general investigation of the rheological characterization of suspensions. The results of this work indicate several key ideas. (i) There is a potential synergistic benefit for strength, hydration, and pore structure by using alumina and in Portland limestone cements, (ii) the limestone in these systems is shown to react to some extent, and fine limestone is shown to accelerate hydration, (iii) rheological characteristics of cementitious suspensions are complex, and strongly dependent on several key parameters including: the solid loading, interparticle forces, surface area of the particles

  3. Surface microstructural features of scales in relation to toxic stress of Basic Violet-1.

    PubMed

    Kaur, Kirandeep; Kaur, Ramandeep; Kaur, Arvinder

    2016-01-01

    The present work deals with scanning electron microscopic (SEM) studies of the scales of Labeo rohita on exposure to lethal and sublethal doses of Basic Violet-1 (an important textile and hair colorant). The dye induced loosening of the scales and caused breakage and disorganization of lepidonts. Erosion of lepidonts occurred mostly in the fish exposed to 0.20 and 0.40 mg/L dye, during acute exposure and to 0.0225 and 0.045 mg/L dye, during the subchronic exposure. However, lepidonts were sloughed off from their sockets in 0.60 and 0.80 mg/L dye during acute exposure and in 0.09 mg/L dye during the subchronic exposure. Circuli, the base that provides anchorage to the lepidonts, got damaged, and tubercles responsible for coloration of a fish became atrophied with an increase in the duration of exposure. The results of the present investigation clearly indicated that exposure to Basic Violet-1 (BV-1) even at a concentration as low as 0.0225 mg was responsible for deleterious changes in the scale morphology of the test fish after 150 days of exposure. Similar changes were observed in the scales of the dead fish also. It can thus be suggested that this noninvasive technique is very helpful for evaluating the health status of an aquatic body. At the same time, the changes in ultramorphology of scales can act as an early indicator of the stress of very minute doses of dyes and even the scales of a dead fish can act as indicators of the untoward changes that would have occurred in the environment of the fish before death. PMID:26432273

  4. White Matter Microstructure in Transsexuals and Controls Investigated by Diffusion Tensor Imaging

    PubMed Central

    Kranz, Georg S.; Hahn, Andreas; Kaufmann, Ulrike; Küblböck, Martin; Hummer, Allan; Ganger, Sebastian; Seiger, Rene; Winkler, Dietmar; Swaab, Dick F.; Windischberger, Christian; Kasper, Siegfried; Lanzenberger, Rupert

    2015-01-01

    Biological causes underpinning the well known gender dimorphisms in human behavior, cognition, and emotion have received increased attention in recent years. The advent of diffusion-weighted magnetic resonance imaging has permitted the investigation of the white matter microstructure in unprecedented detail. Here, we aimed to study the potential influences of biological sex, gender identity, sex hormones, and sexual orientation on white matter microstructure by investigating transsexuals and healthy controls using diffusion tensor imaging (DTI). Twenty-three female-to-male (FtM) and 21 male-to-female (MtF) transsexuals, as well as 23 female (FC) and 22 male (MC) controls underwent DTI at 3 tesla. Fractional anisotropy, axial, radial, and mean diffusivity were calculated using tract-based spatial statistics (TBSS) and fiber tractography. Results showed widespread significant differences in mean diffusivity between groups in almost all white matter tracts. FCs had highest mean diffusivities, followed by FtM transsexuals with lower values, MtF transsexuals with further reduced values, and MCs with lowest values. Investigating axial and radial diffusivities showed that a transition in axial diffusivity accounted for mean diffusivity results. No significant differences in fractional anisotropy maps were found between groups. Plasma testosterone levels were strongly correlated with mean, axial, and radial diffusivities. However, controlling for individual estradiol, testosterone, or progesterone plasma levels or for subjects’ sexual orientation did not change group differences. Our data harmonize with the hypothesis that fiber tract development is influenced by the hormonal environment during late prenatal and early postnatal brain development. PMID:25392513

  5. Bayes factor for investigative assessment of selected handwriting features.

    PubMed

    Taroni, F; Marquis, R; Schmittbuhl, M; Biedermann, A; Thiéry, A; Bozza, S

    2014-09-01

    This paper extends previous research on the use of multivariate continuous data in comparative handwriting examinations, notably for gender classification. A database has been constructed by analyzing the contour shape of loop characters of type a and d by means of Fourier analysis, which allows characters to be described in a global way by a set of variables (e.g., Fourier descriptors). Sample handwritings were collected from right- and left-handed female and male writers. The results reported in this paper provide further arguments in support of the view that investigative settings in forensic science represent an area of application for which the Bayesian approach offers a logical framework. In particular, the Bayes factor is computed for settings that focus on inference of gender and handedness of the author of an incriminated handwritten text. An emphasis is placed on comparing the efficiency for investigative purposes of characters a and d. PMID:25117907

  6. Microstructure investigations of streak formation in 6063 aluminum extrusions by optical metallographic techniques.

    PubMed

    Vander Voort, George; Suárez-Peña, Beatriz; Asensio-Lozano, Juan

    2013-04-01

    The present study investigates the effect of the solidification strategy for AA 6063 alloy on the surface appearance of anodized extrusions. The microstructure of the samples was analyzed using both light optical microscopy and scanning electron microscopy. Results show that if heavy segregation occurs from rapid solidification, coarse Mg2Si particles form, thus reducing the potential for precipitation strengthening by the finer β-Mg2Si developed in the solid state. Differentially-strained regions formed during hot extrusion induce differences in particle size for magnesium silicide (Mg2Si) precipitates. Anodizing generates surface roughness due to Mg2Si particle dissolution and AlFeSi decohesion, which is related to both particle size and deformation. During anodizing, an oxide layer forms on the surface of the extruded products, which can lead to streak formation, usually a subject of rejection due to unacceptable heterogeneous reflectivity. PMID:23481588

  7. Investigation of microstructure changes in ODS-EUROFER after hydrogen loading

    NASA Astrophysics Data System (ADS)

    Emelyanova, O. V.; Ganchenkova, M. G.; Malitskii, E.; Yagodzinskyy, Y. N.; Klimenkov, M.; Borodin, V. A.; Vladimirov, P. V.; Lindau, R.; Möslang, A.; Hänninen, H.

    2016-01-01

    The effect of hydrogen on the microstructure of mechanically tested ODS-EUROFER steel was investigated by means of transmission electron microscopy, thermal desorption spectroscopy, and atomistic simulations. The presence of yttrium oxide particles notably increases hydrogen uptake in ODS-EUROFER steel as compared to ODS-free EUROFER 97. Under tensile loading, hydrogen accumulation promotes the loss of cohesion at the oxide particle interfaces. First-principles molecular dynamics simulations indicate that hydrogen can be trapped at nanoparticle/matrix interface, creating OH-groups. The accumulation of hydrogen atoms at the oxide particle surface can be the reason for the observed hydrogen-induced oxide/matrix interface weakening and de-cohesion under the action of external tensile stress.

  8. Microstructure-Sensitive Investigation of Fracture Using Acoustic Emission Coupled With Electron Microscopy

    NASA Technical Reports Server (NTRS)

    Wisner, Brian; Cabal, Mike; Vanniamparambiland, Prashanth A.; Leser, William; Hochhalter, Jacob; Kontsos, Antonios

    2015-01-01

    A novel technique using Scanning Electron Microscopy (SEM) in conjunction with Acoustic Emission (AE) monitoring is proposed to investigate microstructure-sensitive fatigue and fracture of metals. The coupling between quasi in situ microscopy with actual in situ nondestructive evaluation falls into the ICME framework and the idea of quantitative data-driven characterization of material behavior. To validate the use of AE monitoring inside the SEM chamber, Aluminum 2024-B sharp notch specimen were tested both inside and outside the microscope using a small scale mechanical testing device. Subsequently, the same type of specimen was tested inside the SEM chamber. Load data were correlated with both AE information and observations of microcracks around grain boundaries as well as secondary cracks, voids, and slip bands. The preliminary results are in excellent agreement with similar findings at the mesoscale. Extensions of the application of this novel technique are discussed.

  9. [Effect of technological parameters of sputtering on the microstructure of silicon film investigated by Raman analysis].

    PubMed

    Tian, Gui; Zhu, Jia-qi; Han, Jie-cai; Jiang, Chun-zhu; Jia, Ze-chun

    2010-07-01

    In order to facilitate optical polishing of silicon carbide space telescope, in the present paper, silicon film, which has similar coefficient of thermal expansion with silicon carbide, was fabricated on SiC substrate by radio frequency magnetron sputtering. The effect of substrate temperature, radio frequency power, and substrate bias voltage was investigated by Raman scattering. The results indicate that at lower substrate temperature, the crystalline volume fraction of Si films increases with the increase in deposition temperature. Exceeding a certain temperature, the crystalline volume fraction decreases with further increasing deposition temperature; the increase in substrate bias voltage is bad for forming crystalline structure; the effect of radio power on microstructure of silicon film is comparatively complicated. As the rf power increases, the cluster size and crystallite volume fraction decrease, and both of them increase with further increasing the rf power. But when the rf power is too high, the crystallite volume fraction of the silicon film will decrease slightly. PMID:20827972

  10. Microstructural and magnetic investigations of pseudotachylyte and ultracataclasite in the Hoping River, Tananao Complex, Eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Kuo, Ruo-Lin; Chou, Yu-Min; Ferré, Eric. C.; Yeh, En-Chao; Chu, Hao-Tsu; Hu, Jyr-Ching

    2016-04-01

    Here we investigate seismic rupture processes through the microstructural and magnetic study of pseudotachylyte and ultracataclasite from the Hoping River area. Unlike other fault rocks, pseudotachylytes form through friction-related melting during an earthquake. Therefore, these rocks, regarded as earthquake fossils potentially hold valuable information on seismic deformation. Paradoxically, although Taiwan is a seismically active zone, reports of pseudotachylyte outcrops in Taiwan remain rare. Previous studies reported the first pseudotachylyte outcrop in the Hoping River from which the magnitude, direction and sense of seismic slip were subsequently determined. In this study, we apply new microstructural and magnetic approaches to investigate the pseudotachylyte veins. X- ray fluorescence (XRF) geochemical analyses show that the pseudotachylyte melt, formed by incongruent melting, is depleted in SiO2, Al2O3, Na2O and enriched in Fe2O3, K2O compared with the ultracataclasite and host rock. This observation suggests selective melting of biotite. Scanning electron microscopy (SEM) and transmission X-ray microscopy (TXM) supports the melt origin of the pseudotachylyte although melting occurred only in small spots, manifested by a few microcrystalline aggregates, with low melt percentage (≈10%). Small iron-oxide grains are discovered under TXM, which may be formed by the breakdown of biotite in the host rock during melting. The presence of iron oxide grains appears restricted to the pseudotachylyte. Since the iron content of the pseudotachylyte is slightly higher (4 wt. %) than the ultracataclasite and granitic host rock, magnetic hysteresis measurements were performed under high field (up to 1 Tesla) using a vibrating sample magnetometer (VSM) to determine the nature of ferromagnetic minerals. Magnetic hysteresis curves show the pseudotachylyte veins of the Hoping River are dominated by paramagnetic phases, with a very weak saturation isothermal remanent

  11. Microstructural investigation of MX-80 bentonite and Na/Ca-montmorillonite using basal spacing determination

    NASA Astrophysics Data System (ADS)

    Holmboe, M.; Wold, S.

    2010-12-01

    interlayer swelling as water uptake restricted by volume. Hence saturating clay samples under free swelling conditions vs. RH% may not be representative for describing water uptake and swelling of the bentonite barrier in a deep geological repository. The interlayer porosity dominated the total porosity for all samples investigated. In general, the interparticle, or so-called free porosity, decreases with decreasing water content and was found to be lower than commonly reported in the literature. For the clay buffer dry density planned to be used in the Swedish KBS-3 concept (1.6 g/cm3), the average basal spacing for compacted MX-80 bentonite is approx. 17.3±1 Å compared to the theoretical maximum of 17.8 Å. This means the microstructure is dominated by 2 and 3 H2O layers and the free porosity is approx. < 3%. In order to verify these results, accurate data from neutron or X-ray small-angle scattering and diffraction experiments in transmission mode using pressure cells is needed, as well as more precise layer structure functions at high water contents. [1] Holmboe, M., Wold, S. 2010. To be submitted. [2] Moore & Reynolds, 1997, 2ed. [3] Ferrage et al, 2005, Chem. Mater. 17, 3499-3512.

  12. Investigating the performance of catalyst layer micro-structures with different platinum loadings

    SciTech Connect

    Khakaz-Baboli, Moben; Harvey, David; Pharoah, Jon

    2012-07-01

    In this study a four-phase micro-structure of a PEFC catalyst layer was reconstructed by randomly placing overlapping spheres for each solid catalyst phase. The micro-structure was mirrored to make a micro-structure. A body-fit computational mesh was produced for the reconstructed micro-structure in OpenFOAM. Associated conservation equations were solved within all the phases with electrochemical reaction as the boundary condition at the interface between ionomer and platinum phases. The study is focused on the platinum loading of CL. The polarization curves of the micro-structure performance have been compared for different platinum loadings. This paper gives increased insight into the relatively greater losses at decreased platinum loadings.

  13. Microstructure of 3D-Printed Polymer Composites Investigated by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Kang, Tae Hui; Compton, Brett G.; Heller, William T.; Urban, Voker S.; Duty, Chad E.; Do, Changwoo

    Polymer composites printed from the large scale printer at Manufacturing Demonstration Facility at Oak Ridge National Laboratory have been investigated by small-angle neutron scattering (SANS). For the Acrylonitrile Butadiene Styrene (ABS)/Carbon Fiber (CF) composites, the microstructure of polymer domains and the alignment of CF have been characterized across the layer from the printed piece. CF shows strong anisotropic alignment along the printing direction due to the flow of polymer melt at the nozzle. Order parameter of the anisotropy which ranges from -0.11 to -0.06 exhibits strong correlation with the position within the layer: stronger alignment near the layer interface. It is also confirmed that the existence of CF reduces the polymer domain correlation length significantly and reinforces the mechanical strength of the polymer composites. For the Epoxy/nano-clay platelet composites, the effect of processing condition, nozzle size, and the addition of the another filler, Silicon Carbide (SC), have been investigated by SANS. Nano-clay platelet shows strong anisotropic alignment along the printing direction as well. Order parameter of the anisotropy varies according to nozzle size and presence of the SC, and difference disappears at high Q region. Scientific User Facilities Division and Materials Sciences and Energy Division, Office of Basic Energy Sciences, U.S. Department of Energy.

  14. Investigation of the effect of microstructure on the R-Curve behavior of metal-ceramic composites

    SciTech Connect

    Ellerby, D.T.; Flinn, B.D.; Scott, W.D.; Bordia, R.K.; Ewsuk, K.G.; Loehman, R.E.; Fahrenholtz, W.G.

    1995-07-01

    An investigation was made into the effect of microstructure on the peak toughness and shape of the crack growth resistance curves for two ceramic-metal composites. An Al{sup 2}O{sup 3}/Al composite formed by Reactive Metal Penetration was used along with an AlN/Al composite formed using a reactive infiltration technique. The results indicate that the toughness increases with an increase in the volume fraction of the metal phase for a particular composite composition, and the peak toughness and shape of the R-Curve also depend on the composite microstructure and metal composition.

  15. Investigation of correlation between the microstructure and electrical properties of sol-gel derived ZnO based thin films

    NASA Astrophysics Data System (ADS)

    Zhu, M. W.; Gong, J.; Sun, C.; Xia, J. H.; Jiang, X.

    2008-10-01

    Pure ZnO and aluminum doped ZnO films (ZAO) were prepared by sol-gel method and the effect of Al doping on the microstructure and electrical properties of the films was investigated. The results showed that the transformation from granular to columnar structure could be observed in pure ZnO films with the increase in heating time while in aluminum doped films little structural changes occurred even after a prolonged heating time. Additionally, measurements of electrical properties showed that both microstructural evolution and doping could significantly improve the conductivity of the films, which could be assigned to an increase both in Hall mobility and carrier concentration. The relationship between microstructure and the electrical properties of the films was discussed, and various scattering mechanisms were proposed for sol-gel derived ZnO and ZAO films as a function of the carrier concentration.

  16. Investigation of biological microstructures by using diffraction-enhanced imaging computed tomography

    NASA Astrophysics Data System (ADS)

    Shu, Hang; Liu, Bo; Zhu, Peiping; Gao, Xin; Yin, Hongxia; Yuan, Qingxi; Wang, Junyue; Huang, Wanxia; Gao, Xiulai; Luo, Shuqian; Wu, Ziyu; Fang, Shouxian

    2006-11-01

    Diffraction-enhanced imaging computer tomography (DEI-CT) is a new method to provide the object's inner information. Previous reports demonstrated its applicability in soft and hard tissue imaging. Here, we provide further evidence for the improved overall image quality and for the option to distinguish the inner microstructures of the guinea pig's cochlea. Data has shown the details of the cochlea's inner microstructure such as vestibular membrane which only have 6 μm. A better knowledge of these microstructures may be relevant to achieve progress in the otology of clinical anatomization.

  17. THEORETICAL INVESTIGATION OF MICROSTRUCTURE EVOLUTION AND DEFORMATION OF ZIRCONIUM UNDER CASCADE DAMAGE CONDITIONS

    SciTech Connect

    Barashev, Alexander V; Golubov, Stanislav I; Stoller, Roger E

    2012-06-01

    This work is based on our reaction-diffusion model of radiation growth of Zr-based materials proposed recently in [1]. In [1], the equations for the strain rates in unloaded pure crystal under cascade damage conditions of, e.g., neutron or heavy-ion irradiation were derived as functions of dislocation densities, which include contributions from dislocation loops, and spatial distribution of their Burgers vectors. The model takes into account the intra-cascade clustering of self-interstitial atoms and their one-dimensional diffusion; explains the growth stages, including the break-away growth of pre-annealed samples; and accounts for some striking observations, such as of negative strain in prismatic direction, and co-existence of vacancy- and interstitial-type prismatic loops. In this report, the change of dislocation densities due to accumulation of sessile dislocation loops is taken into account explicitly to investigate the dose dependence of radiation growth. The dose dependence of climb rates of dislocations is calculated, which is important for the climb-induced glide model of radiation creep. The results of fitting the model to available experimental data and some numerical calculations of the strain behavior of Zr for different initial dislocation structures are presented and discussed. The computer code RIMD-ZR.V1 (Radiation Induced Microstructure and Deformation of Zr) developed is described and attached to this report.

  18. Investigation of the response of microstructures under the combined effect of mechanical shock and electrostatic forces

    PubMed Central

    Younis, Mohammad I; Miles, Ronald; Jordy, Daniel

    2009-01-01

    There is strong experimental evidence for the existence of strange modes of failure of microelectromechanical systems (MEMS) devices under mechanical shock and impact. Such failures have not been explained with conventional models of MEMS. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. This work presents modeling and simulation of MEMS devices under the combination of shock loads and electrostatic actuation, which sheds light on the influence of these forces on the pull-in instability. Our results indicate that the reported strange failures can be attributed to early dynamic pull-in instability. The results show that the combination of a shock load and an electrostatic actuation makes the instability threshold much lower than the threshold predicted, considering the effect of shock alone or electrostatic actuation alone. In this work, a single-degree-of-freedom model is utilized to investigate the effect of the shock–electrostatic interaction on the response of MEMS devices. Then, a reduced-order model is used to demonstrate the effect of this interaction on MEMS devices employing cantilever and clamped–clamped microbeams. The results of the reduced-order model are verified by comparing with finite-element predictions. It is shown that the shock–electrostatic interaction can be used to design smart MEMS switches triggered at a predetermined level of shock and acceleration. PMID:21720492

  19. Automated detection and characterization of microstructural features: application to eutectic particles in single crystal Ni-based superalloys

    NASA Astrophysics Data System (ADS)

    Tschopp, M. A.; Groeber, M. A.; Fahringer, R.; Simmons, J. P.; Rosenberger, A. H.; Woodward, C.

    2010-03-01

    Serial sectioning methods continue to produce an abundant amount of image data for quantifying the three-dimensional nature of material microstructures. Here, we discuss a methodology to automate detecting and characterizing eutectic particles taken from serial images of a production turbine blade made of a heat-treated single crystal Ni-based superalloy (PWA 1484). This method includes two important steps for unassisted eutectic particle characterization: automatically identifying a seed point within each particle and segmenting the particle using a region growing algorithm with an automated stop point. Once detected, the segmented eutectic particles are used to calculate microstructural statistics for characterizing and reconstructing statistically representative synthetic microstructures for single crystal Ni-based superalloys. The significance of this work is its ability to automate characterization for analysing the 3D nature of eutectic particles.

  20. Influence of Aging Treatments on Alterations of Microstructural Features and Stress Corrosion Cracking Behavior of an Al-Zn-Mg Alloy

    NASA Astrophysics Data System (ADS)

    Rout, Prasanta Kumar; Ghosh, M. M.; Ghosh, K. S.

    2015-07-01

    7xxx series Al-Zn-Mg-(Cu) alloys have higher strength in their peak-aged (T6) states compared with other age-hardenable aluminum alloys; however, the maximum strength peak-aged state is more susceptible to stress corrosion cracking (SCC) which leads to catastrophic failure. The over-aged (T7) temper with 10-15% lower strength has higher resistance to SCC requiring oversized structural aerospace component applications. The medium-strength AA7017 Al-Zn-Mg weldable alloy without Cu is also prone to SCC under certain environmental conditions. In the present investigation, the SCC behaviors of an AA7017 Al-Zn-Mg alloys of different tempers have been assessed. Specific aging schedules have been adapted to an AA7017 alloy to produce various tempers, e.g., under-, peak-(T6), over-(T7), and highly over-aged tempers. Artificial aging behavior of the AA7017 alloy has been characterized by hardness, electrical conductivity measurements, x-ray diffraction, differential scanning calorimetry, and electrochemical studies. Slow strain rate test technique was used to assess the SCC behaviors of the AA7017 alloys of under-, T6, T7, and highly over-aged tempers in 3.5 wt.% NaCl solution at free corrosion potential (FCP) and at applied anodic potential, as well. Results revealed that the AA7017 alloy tempers are not susceptible to SCC in 3.5 wt.% NaCl solution at FCP, but severely damaging to SCC at applied anodic potentials. Microstructural features, showing a non-recrystallized grain structure and the presence of discrete, widely spaced, not-interconnected η precipitates at the grain boundaries, are the contributive factors by virtue of which the alloy tempers at FCP did not exhibit SCC. However, the applied anodic potential resulted in rapid metal dissolution from the grain boundary region and led to SCC. The local anodic dissolution (LAD) is believed to be the associated SCC mechanism.

  1. An investigation on the crack growth resistance of human tooth enamel: Anisotropy, microstructure and toughening

    NASA Astrophysics Data System (ADS)

    Yahyazadehfar, Mobin

    The enamel of human teeth is generally regarded as a brittle material with low fracture toughness. Consequently, the contributions of this tissue in resisting tooth fracture and the importance of its complex microstructure have been largely overlooked. The primary objective of this dissertation is to characterize the role of enamel's microstructure and degree of decussation on the fracture behavior of human enamel. The importance of the protein content and aging on the fracture toughness of enamel were also explored. Incremental crack growth in sections of human enamel was achieved using a special inset Compact Tension (CT) specimen configuration. Crack extension was achieved in two orthogonal directions, i.e. longitudinal and transverse to the prism axes. Fracture surfaces and the path of crack growth path were evaluated using scanning electron microscopy (SEM) to understand the fundamental mechanisms of crack growth extension. Furthermore, a hybrid approach was adopted to quantify the contribution of toughening mechanisms to the overall toughness. Results of this investigations showed that human enamel exhibits rising R-curve for both directions of crack extension. Cracks extending transverse to the rods in the outer enamel achieved lower rise in toughness with crack extension, and significantly lower toughness (1.23 +/- 0.20 MPa·m 0.5) than in the inner enamel (1.96 +/- 0.28 MPa· 0.5) and in the longitudinal direction (2.01 +/- 0.21 MPa· 0.5). The crack growth resistance exhibited both anisotropy and inhomogeneity, which arise from the complex hierarchical microstructure and the decussated prism structure. Decussation causes deflection of cracks extending from the enamel surface inwards, and facilitates a continuation of transverse crack extension within the outer enamel. This process dissipates fracture energy and averts cracks from extending toward the dentin and vital pulp. This study is the first to investigate the importance of proteins and the effect of

  2. Effects of changes in rock microstructures on permeability: 3-D printing investigation

    NASA Astrophysics Data System (ADS)

    Head, D.; Vanorio, T.

    2016-07-01

    Rocks are naturally heterogeneous; two rock samples with identical bulk properties can vary widely in microstructure. Understanding how the microstructure and bulk properties of rocks then evolve during experiments and computations simulating diagenesis is inherently a multiscale problem. The advent of modern 3-D printing has provided an unprecedented opportunity to link those scales by combining the strengths of digital and experimental rock physics. In this study, we take a computerized tomography-scanned model of a natural carbonate pore space then iteratively digitally manipulate, 3-D print, and measure the flow properties in the laboratory. This approach allows us to access multiple scales digitally and experimentally and test hypotheses about how changes in rock microstructure due to compaction and dissolution affect bulk transport properties in a repeatable manner.

  3. In situ TEM investigation of microstructural behavior of superplastic Al–Mg–Sc alloy

    SciTech Connect

    Dám, Karel; Lejček, Pavel; Michalcová, Alena

    2013-02-15

    Dynamic changes in microstructure of the superplastic ultrafine-grained Al–3Mg–0.2Sc (wt.%) alloy refined by equal-channel angular pressing (ECAP). were observed by in situ transmission electron microscopy at temperatures up to 300 °C (annealing and tensile deformation) in order to simulate the initial stages of superplastic testing. It was found that the microstructure changes significantly during the preheating before the superplastic deformation, which was accompanied by decreased microhardness. During the deformation at 300 °C, high dislocation activity as well as motion of low-angle grain boundaries was observed while high-angle grain boundaries did not move due to the presence of scandium in the alloy. - Highlights: ► We performed in situ TEM annealing and straining on superplastic Al–Mg–Sc alloy. ► We simulated the conditions of early stages of superplastic testing. ► Significant changes in microstructure occur during preheating before deformation.

  4. The Use of Linear Feature Detection to Investigate Thematic Mapper Data Performance and Processing

    NASA Technical Reports Server (NTRS)

    Gurney, C. M.

    1984-01-01

    Geometric and radiometric characteristics of Thematic Mapper data are investigated through analysis of linear features in the data. A linear feature is defined as two close, parallel and opposite edges. Examples in remotely sensed data are such features as rivers and roads. The geometric and radiometric precision TM data is sufficient to allow accurate measurement of linear feature widths. Results also confirm a 28.5m ground IFOV as specified prior to launch. The increase dimensionality of the TM data as compared with MSS data allows the possibility of independent verification of results by using data from several bands.

  5. Specific features of direct formation of graphite-like microstructures in polycarbonate samples by single femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ganin, D. V.; Lapshin, K. E.; Obidin, A. Z.; Vartapetov, S. K.

    2015-11-01

    We present the result of the experiments on producing graphite-like cylindrical microstructures by focusing single femtosecond laser pulses into the bulk of a transparent polymer (polycarbonate). The microstructures are embedded in a cladding with a modified refractive index, possessing waveguide properties. In the experiments with nontransparent screens and diaphragms, placed in the laser beam in front of the entrance pupil of the objective with a large numerical aperture, we have found that the paraxial rays are blocked by the peripheral ones, which reduces the length of the destruction region in the pre-focal zone. In the experiments with transparent screens and diaphragms, introducing optical delays τd between the paraxial and peripheral rays, the quantitative dependence of the destruction region length in the pre-focal zone on the value of τd is determined.

  6. Biomechanical aspects of bone microstructure in vertebrates: potential approach to palaeontological investigations.

    PubMed

    Mishra, S

    2009-11-01

    Biomechanical or biophysical principles can be applied to study biological structures in their modern or fossil form. Bone is an important tissue in paleontological studies as it is a commonly preserved element in most fossil vertebrates, and can often allow its microstructures such as lacuna and canaliculi to be studied in detail. In this context, the principles of Fluid Mechanics and Scaling Laws have been previously applied to enhance the understanding of bone microarchitecture and their implications for the evolution of hydraulic structures to transport fluid. It has been shown that the microstructure of bone has evolved to maintain efficient transport between the nutrient supply and cells, the living components of the tissue. Application of the principle of minimal expenditure of energy to this analysis shows that the path distance comprising five or six lamellar regions represents an effective limit for fluid and solute transport between the nutrient supply and cells; beyond this threshold, hydraulic resistance in the network increases and additional energy expenditure is necessary for further transportation. This suggests an optimization of the size of the bone's building blocks (such as osteon or trabecular thickness) to meet the metabolic demand concomitant to minimal expenditure of energy. This biomechanical aspect of bone microstructure is corroborated from the ratio of osteon to Haversian canal diameters and scaling constants of several mammals considered in this study. This aspect of vertebrate bone microstructure and physiology may provide a basis of understanding of the form and function relationship in both extinct and extant taxa. PMID:20009272

  7. Relationships between microstructure and microfissuring in alloy 718

    NASA Technical Reports Server (NTRS)

    Thompson, R. G.

    1985-01-01

    Microfissures which occur in the weld heat affected zone of alloy 718 can be a limiting factor in the material's weldability. Several studies have attempted to relate microfissuring susceptibility to processing conditions, microstructure, and/or heat-to-heat chemistry differences. The present investigation studies the relationships between microstructure and microfissuring by isolating a particular microstructural feature and measuring microfissuring as a function of that feature. Results to date include the identification of a microstructure-microfissure sequence, microfissuring susceptibility as a function of grain size, and microfissuring susceptibility as a function of solution annealing time.

  8. Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys

    SciTech Connect

    Zhou Tao; Chen Zhenhua; Yang Mingbo; Hu Jianjun; Xia Hua

    2012-01-15

    Rapidly solidified (RS) Mg-Zn-Ca-Ce-La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg-6Zn-5Ca alloy, the stable intermetallic compounds i.e. the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (about 3 at.%), shortened as the T Prime phase, were formed at the expense of the binary Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases, which was possibly beneficial to the enhanced thermal stability of the alloy. In the Mg-6Zn-5Ca-3Ce-0.5La alloy, the composition of the T Prime phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T Prime phase within the grains was close to 2. Moreover, the stable Mg{sub 2}Ca phases were detected around the T Prime phases at the grain boundaries in the alloy. - Research Highlights: Black-Right-Pointing-Pointer The phase constitution of RS Mg-6Zn-5Ca alloy can be improved by RE additions. Black-Right-Pointing-Pointer In the Mg-Zn-Ca-Ce-La alloys, the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (T Prime phase) is formed. Black-Right-Pointing-Pointer The formation of the T Prime phase leads to the loss of the Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases. Black-Right-Pointing-Pointer The composition of the T Prime phase differs from the grain interior to the grain boundary.

  9. Investigation of the microstructure and properties of doped nanocomposite coatings based on titanium nitride

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, S. V.; Korotaev, A. D.; Moshkov, V. Yu.; Borisov, D. P.

    2012-02-01

    The special features of the elemental composition, structure-phase and elastically stressed states, and properties of coatings based on titanium nitride are investigated for different concentrations of Al, Si, Cu, Ni, Cr, and C doping elements using x-ray fluorescent analysis, x-ray microanalysis, dark-field electronmicroscopic analysis of the crystal lattice bending and torsion, microhardness measurements, and scratch tests. Influence of the structure and concentration of the doping elements on the relative fraction of nonmetallic atoms, crystal size, and phase composition of the coating is established. High values (several hundred degrees per micron) of the lattice bending-torsion with dipole configuration are established for nanocrystals with sizes smaller than 20 nm. Residual stresses in nanocrystals are estimated for the disclination model of the structural state. It is demonstrated that the increased degree of coating doping improves the thermal stability of their structure and properties.

  10. Micro-chemical and micro-structural investigation of archaeological bronze weapons from the Ayanis fortress (lake Van, Eastern Anatolia, Turkey)

    NASA Astrophysics Data System (ADS)

    Faraldi, F.; Çilingirǒglu, A.; Angelini, E.; Riccucci, C.; De Caro, T.; Batmaz, A.; Mezzi, A.; Caschera, D.; Cortese, B.

    2013-12-01

    Bronze weapons (VII cen BC) found during the archaeological excavation of the Ayanis fortress (lake Van, eastern Anatolia, Turkey) are investigated in order to determine their chemical composition and metallurgical features as well as to identify the micro-chemical and micro-structural nature of the corrosion products grown during long-term burial. Small fragments were sampled from the artefacts and analysed by means of the combined use of optical microscopy (OM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show that the bronze artefacts have been manufactured by using alloys with a controlled and refined chemical composition demonstrating the high level metallurgical competence and skill of the Urartian craftsmen and artists. Furthermore, the micro-structural and metallurgical investigations evidence the presence of equiaxed grains in the matrix, indicating that the artefact were produced by repeated cycles of mechanical shaping and thermal annealing treatments to restore the alloy ductility. From the degradation point of view, the results show the structures and the chemical composition of the stratified corrosion layers (i.e. the patina) where the copper or tin depletion phenomenon is commonly observed with the surface enrichment of some elements coming from the burial soil, mainly Cl, which is related to the high concentration of chlorides in the Ayanis soil. The results reveal also that another source of degradation is the inter-granular corrosion phenomenon likely increased by the metallurgical features of the alloys caused by the high temperature manufacturing process that induces crystallisation and segregation phenomena along the grain boundaries.

  11. The use of linear feature detection to investigate thematic mapper data performance and processing

    NASA Technical Reports Server (NTRS)

    Gurney, C. M.

    1983-01-01

    The geometric and radiometric characteristics of thematic mapper data through analysis of linear features in the data are investigated. The particular aspects considered are: (1) thematic mapper ground IFOV; (2) radiometric contrast between linear features and background; (3) precision of system geometric correction; (4) band-to-band registration; and (5) potential utility of TM data for linear feature detection especially as compared to MSS data. It is shown that TM data may be used to estimate TM pixel size and to illustrate band-band mis-registration. Further, the geometry and radiometry of the data are sufficiently precise to allow accurate estimation of the widths of linear features. In optimum conditions features one quarter of a pixel in width may be accurately measured. These results have considerable potential for applications for hydrological and topographic mapping.

  12. Investigation of Microstructural Uniformity During Isothermal Forging of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Mirahmadi, S. Javid; Hamedi, Mohsen; Habibi Parsa, Mohammad

    2014-09-01

    The effect of strain on microstructural changes and the primary alpha (αP) volume fraction as well as the workability of Ti-6Al-4V are studied by isothermal compression of wedge-shaped specimens at the initial temperatures of 850, 900, and 950 °C and platen velocities of 2.5, 25, and 250 mm/min in combination with finite element method. The results show that higher platen velocity leads to a lesser αP volume fraction at all of the temperatures. Higher temperature reduces the αP volume fraction, but increases the impact of strain and platen velocity on the microstructure through the specimen. A more uniform distribution of the primary alpha volume fraction can be achieved by decreasing the initial temperature and/or platen velocity. All of the specimens were free from any defects and can withstand a compression with the normalized Cockcroft-Latham damage value of 0.61.

  13. Investigation of Microstructural Uniformity During Isothermal Forging of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Mirahmadi, S. Javid; Hamedi, Mohsen; Habibi Parsa, Mohammad

    2014-12-01

    The effect of strain on microstructural changes and the primary alpha (αP) volume fraction as well as the workability of Ti-6Al-4V are studied by isothermal compression of wedge-shaped specimens at the initial temperatures of 850, 900, and 950 °C and platen velocities of 2.5, 25, and 250 mm/min in combination with finite element method. The results show that higher platen velocity leads to a lesser αP volume fraction at all of the temperatures. Higher temperature reduces the αP volume fraction, but increases the impact of strain and platen velocity on the microstructure through the specimen. A more uniform distribution of the primary alpha volume fraction can be achieved by decreasing the initial temperature and/or platen velocity. All of the specimens were free from any defects and can withstand a compression with the normalized Cockcroft-Latham damage value of 0.61.

  14. The Use of Linear Feature Detection to Investigate Thematic Mapper Data Performance and Processing

    NASA Technical Reports Server (NTRS)

    Gurney, C. M.

    1985-01-01

    The geometric and radiometric characteristics of thematic mapper data through analysis of linear features in the data are investigated. The particular aspects considered are: (1) thematic mapper ground IFUV; (2) radiometric contrast between linear features and background; (3) precision of system geometric correction; (4) band-to-band registration; and (5) potential utility of TM data for linear feature detection especially as compared to MSS data. It is shown that TM data may be used to estimate TM pixel size illustrate band: band mis-registration.

  15. Microstructural Features Controlling the Variability in Low-Cycle Fatigue Properties of Alloy Inconel 718DA at Intermediate Temperature

    NASA Astrophysics Data System (ADS)

    Texier, Damien; Gómez, Ana Casanova; Pierret, Stéphane; Franchet, Jean-Michel; Pollock, Tresa M.; Villechaise, Patrick; Cormier, Jonathan

    2016-03-01

    The low-cycle fatigue behavior of two direct-aged versions of the nickel-based superalloy Inconel 718 (IN718DA) was examined in the low-strain amplitude regime at intermediate temperature. High variability in fatigue life was observed, and abnormally short lifetimes were systematically observed to be due to crack initiation at (sub)-surface non-metallic inclusions. However, crack initiation within (sub)-surface non-metallic inclusions did not necessarily lead to short fatigue life. The macro- to micro-mechanical mechanisms of deformation and damage have been examined by means of detailed microstructural characterization, tensile and fatigue mechanical tests, and in situ tensile testing. The initial stages of crack micro-propagation from cracked non-metallic particles into the surrounding metallic matrix occupies a large fraction of the fatigue life and requires extensive local plastic straining in the matrix adjacent to the cracked inclusions. Differences in microstructure that influence local plastic straining, i.e., the δ-phase content and the grain size, coupled with the presence of non-metallic inclusions at the high end of the size distribution contribute strongly to the fatigue life variability.

  16. Investigation of microstructure in additive manufactured Inconel 625 by spatially resolved neutron transmission spectroscopy

    DOE PAGESBeta

    Tremsin, Anton S.; Gao, Yan; Dial, Laura C.; Grazzi, Francesco; Shinohara, Takenao

    2016-07-08

    Non-destructive testing techniques based on neutron imaging and diffraction can provide information on the internal structure of relatively thick metal samples (up to several cm), which are opaque to other conventional non-destructive methods. Spatially resolved neutron transmission spectroscopy is an extension of traditional neutron radiography, where multiple images are acquired simultaneously, each corresponding to a narrow range of energy. The analysis of transmission spectra enables studies of bulk microstructures at the spatial resolution comparable to the detector pixel. In this study we demonstrate the possibility of imaging (with ~100 μm resolution) distribution of some microstructure properties, such as residual strain,more » texture, voids and impurities in Inconel 625 samples manufactured with an additive manufacturing method called direct metal laser melting (DMLM). Although this imaging technique can be implemented only in a few large-scale facilities, it can be a valuable tool for optimization of additive manufacturing techniques and materials and for correlating bulk microstructure properties to manufacturing process parameters. Additionally, the experimental strain distribution can help validate finite element models which many industries use to predict the residual stress distributions in additive manufactured components.« less

  17. Investigating the Microstructural Correlation of White Matter in Autism Spectrum Disorder.

    PubMed

    Dean, Douglas C; Travers, Brittany G; Adluru, Nagesh; Tromp, Do P M; Destiche, Daniel J; Samsin, Danica; Prigge, Molly B; Zielinski, Brandon A; Fletcher, P Thomas; Anderson, Jeffrey S; Froehlich, Alyson L; Bigler, Erin D; Lange, Nicholas; Lainhart, Janet E; Alexander, Andrew L

    2016-06-01

    White matter microstructure forms a complex and dynamical system that is critical for efficient and synchronized brain function. Neuroimaging findings in children with autism spectrum disorder (ASD) suggest this condition is associated with altered white matter microstructure, which may lead to atypical macroscale brain connectivity. In this study, we used diffusion tensor imaging measures to examine the extent that white matter tracts are interrelated within ASD and typical development. We assessed the strength of inter-regional white matter correlations between typically developing and ASD diagnosed individuals. Using hierarchical clustering analysis, clustering patterns of the pairwise white matter correlations were constructed and revealed to be different between the two groups. Additionally, we explored the use of graph theory analysis to examine the characteristics of the patterns formed by inter-regional white matter correlations and compared these properties between ASD and typical development. We demonstrate that the ASD sample has significantly less coherence in white matter microstructure across the brain compared to that in the typical development sample. The ASD group also presented altered topological characteristics, which may implicate less efficient brain networking in ASD. These findings highlight the potential of graph theory based network characteristics to describe the underlying networks as measured by diffusion magnetic resonance imaging and furthermore indicates that ASD may be associated with altered brain network characteristics. Our findings are consistent with those of a growing number of studies and hypotheses that have suggested disrupted brain connectivity in ASD. PMID:27021440

  18. Investigation of Microstructure and Mechanical Properties of ECAP-Processed AM Series Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Gopi, K. R.; Nayaka, H. Shivananda; Sahu, Sandeep

    2016-07-01

    Magnesium alloy Mg-Al-Mn (AM70) was processed by equal channel angular pressing (ECAP) at 275 °C for up to 4 passes in order to produce ultrafine-grained microstructure and improve its mechanical properties. ECAP-processed samples were characterized for microstructural analysis using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural analysis showed that, with an increase in the number of ECAP passes, grains refined and grain size reduced from an average of 45 to 1 µm. Electron backscatter diffraction analysis showed the transition from low angle grain boundaries to high angle grain boundaries in ECAP 4 pass sample as compared to as-cast sample. The strength and hardness values an showed increasing trend for the initial 2 passes of ECAP processing and then started decreasing with further increase in the number of ECAP passes, even though the grain size continued to decrease in all the successive ECAP passes. However, the strength and hardness values still remained quite high when compared to the initial condition. This behavior was found to be correlated with texture modification in the material as a result of ECAP processing.

  19. An Investigation on Microstructure and Mechanical Properties of Nd:YAG Laser Beam Weld of Copper Beryllium Alloy

    NASA Astrophysics Data System (ADS)

    Akbari Mousavi, S. A. A.; Niknejad, S. T.

    2009-06-01

    Nd:YAG pulsed laser beam welding is conducted on UNS-C17200 copper beryllium sheet. Welding is carried out in the as-annealed and as-aged conditions to investigate the effects of preweld condition on weld microstructure and mechanical properties. Two different heat treatments including direct age treating and solution annealing + subsequent age treating are considered after welding. The mechanical and microstructural characteristics of weld metal regions (WMs) and heat-affected zones (HAZ) of four different samples are considered using tensile tests, hardness measurements, optical microscopy, electron microscopy, and X-ray diffraction (XRD). Results indicate that the microstructural and mechanical properties of the HAZ without postweld treatment are adversely affected by grain boundary liquation observed if welding is carried out in the as-aged condition. Tensile strength and hardness of the WM are improved after a postweld artificial age treatment at 315 °C for 3 hours. However, hardness of the WM is lower than that of the base metal (BM) and HAZ, because the precipitation mechanism in the fusion zone is not as effective as that is in the HAZ and BM. The CuBe secondary phase precipitates during solidification. The precipitates/matrix interface is incoherent, which does not significantly raise the hardness of the weld metal. Incoherent interdendritic precipitates are dissolved in the weld structure after postweld solution annealing. Having performed postweld solution treatment and aging, full strength and hardness throughout the copper beryllium material were observed.

  20. Investigation of the effects of cooling rate on the microstructure of investment cast biomedical grade Co alloys

    NASA Astrophysics Data System (ADS)

    Kaiser, R.; Browne, D. J.; Williamson, K.

    2012-01-01

    The objective of this work is to determine the microstructural characteristics of investment cast cobalt alloy as the cross-sectional area is varied, thus changing the local effective cooling rates and solidification times. The extent of published work on the as-cast properties of cobalt alloys is minimal. The primary aim of this work is therefore to extend knowledge of the behaviour of such alloys as they solidify, which will influence the design of new products as well as the industrial optimisation of the casting process. Wedge-shaped parts were cast from a biomedical grade cobalt alloy employing the method of lost wax investment casting. Analytical techniques such as optical microscopy, image analysis and microhardness testing were used to characterise the as-cast parts. Parameters studied include variations in grain structure, nature of the columnar and equiaxed zones and the spread of porosity (both shrinkage and gas). Changes in microstructure were compared to microhardness values obtained. The solidification profile of the alloy through the prototype cast component was investigated based on measurement of the dendrite arm spacings. A discussion on the physical phenomena controlling the microstructural variations is presented.

  1. On the correlation between irradiation-induced microstructural features and the hardening of reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Lambrecht, M.; Meslin, E.; Malerba, L.; Hernández-Mayoral, M.; Bergner, F.; Pareige, P.; Radiguet, B.; Almazouzi, A.

    2010-11-01

    A correlation is attempted between microstructural observations by various complementary techniques, which have been implemented within the PERFECT project and the hardening measured by tensile tests of reactor pressure vessel steel and model alloys after irradiation to a dose of ˜7 × 10 19 n cm -2. This is done, using the simple hardening model embodied by the Orowan equation and applying the most suitable superposition law, as suggested by a parametric study using the DUPAIR line tension code. It is found that loops are very strong obstacles to dislocation motion, but due to their low concentration, they only play a minor role in the hardening itself. For the precipitates, the contrary is found, although they are quite soft (due to their very small sizes and their coherent nature), they still play the dominant role in the hardening. Vacancy clusters are important for the formation of both loops and precipitates, but they will play almost no role in the hardening by themselves.

  2. Microstructural Investigation of a Wark-Lovering Rim on a Vigarano CAI

    NASA Technical Reports Server (NTRS)

    Han, J.; Keller, L. P.; Needham, A. W.; Messenger, S.; Simon, J. I.

    2015-01-01

    Wark-Lovering (WL) rims are thin multi-layered mineral sequences that surround many CAIs. These rim layers consist of the primary minerals found in the CAI interiors, but vary in their mineralogy. Several models for their origin have been proposed including condensation, reaction with a nebular gas, evaporation, or combinations of these. However, there still is little consensus on how and when the rims formed. Here, we describe the microstructure and mineralogy of a WL rim on a type B CAI from the Vigarano CV(sub red) chondrite using FIB/TEM to better understand the astrophysical significance of WL rim formation.

  3. EBSD investigation of the microstructure and texture characteristics of hot deformed duplex stainless steel.

    PubMed

    Cizek, P; Wynne, B P; Rainforth, W M

    2006-05-01

    The microstructure and crystallographic texture characteristics were studied in a 22Cr-6Ni-3Mo duplex stainless steel subjected to plastic deformation in torsion at a temperature of 1000 degrees C using a strain rate of 1 s(-1). High-resolution EBSD was successfully used for precise phase and substructural characterization of this steel. The austenite/ferrite ratio and phase morphology as well as the crystallographic texture, subgrain size, misorientation angles and misorientation gradients corresponding to each phase were determined over large sample areas. The deformation mechanisms in each phase and the interrelationship between the two are discussed. PMID:16774517

  4. Investigations on Microstructures and Toughness of Fe-B Cast Alloy Containing Titanium and Nitrogen

    NASA Astrophysics Data System (ADS)

    Yi, Dawei; Zhang, Zhiyun; Fu, Hanguang; Yang, Chengyan

    2013-11-01

    The effects of titanium and nitrogen elements on the microstructure and impact toughness of the Fe-B alloy have been studied. The results show that the borides are refined after the additions of titanium and nitrogen elements. With the additions of titanium and nitrogen, titanium nitrides are formed in the Fe-B alloy. Titanium nitride can act as effective heterogeneous nuclei of primary austenite, and promote the refinement of austenite and boride. After heat treatment, the impact toughness of Fe-B alloys modified by titanium and nitrogen elements is higher than that of ordinary alloy.

  5. An Investigation of Some Features of the Psychosocial Learning Environment in Some Nigerian Secondary Schools.

    ERIC Educational Resources Information Center

    Akindehin, Folajimi

    1993-01-01

    Investigated features of the classroom- and school-level psychological learning environments in some secondary schools in Ondo State, Nigeria. It was found that age of a school has no effect on classroom- and school-level psychosocial learning environments. The presumed superiority of old schools over new schools in the provision of favorable…

  6. Investigation of microemulsion microstructure and its impact on skin delivery of flufenamic acid.

    PubMed

    Mahrhauser, Denise-Silvia; Kählig, Hanspeter; Partyka-Jankowska, Ewa; Peterlik, Herwig; Binder, Lisa; Kwizda, Kristina; Valenta, Claudia

    2015-07-25

    Microemulsions are well known penetration enhancing delivery systems. Several properties are described that influence the transdermal delivery of active components. Therefore, this study aimed to characterize fluorosurfactant-based microemulsions and to assess the impact of formulation variables on the transdermal delivery of incorporated flufenamic acid. The microemulsion systems prepared in this study consisted of bistilled water, oleic acid, isopropanol as co-solvent, flufenamic acid as active ingredient and either Hexafor(TM)670 (Hex) or Chemguard S-550-100 (Sin) as fluorosurfactant. Characterization was performed by a combination of techniques including electrical conductivity measurements, small-angle X-ray scattering (SAXS) and nuclear magnetic resonance (NMR) self-diffusion experiments. In vitro skin permeation experiments were performed with each prepared microemulsion using Franz type diffusion cells to correlate their present microstructure with their drug delivery to skin. Electrical conductivity increased with added water content. Consequently, the absence of a conductivity maximum as well as the NMR and SAXS data rather suggest O/W type microemulsions with spherical or rod-like microstructures. Skin permeation data revealed enhanced diffusion for Hex- and Sin-microemulsions if the shape of the structures was rather elongated than spherical implying that the shape of droplets had an essential impact on the skin permeation of flufenamic acid. PMID:26022888

  7. Investigation into Microstructures of Maraging Steel 250 Weldments and Effect of Post-Weld Heat Treatments

    NASA Astrophysics Data System (ADS)

    Tariq, Fawad; Baloch, Rasheed Ahmed; Ahmed, Bilal; Naz, Nausheen

    2010-03-01

    This study was undertaken to gain a better understanding of microstructures obtained by multipass gas tungsten arc welding in maraging steel grade 250. Metallography and microhardness measurements were carried out on sheet and welded joints in as-welded and post-weld aged conditions. It was found that there was a significant amount of reverted austenite formed on cell boundaries of weld metal after aging at 758-823 K for 3-5 h, and was stable at room temperature. Aging at higher temperatures led to an increase in the continuous network of patchy austenite along the cell boundaries. The reason for the above, in our opinion, is the concentrational heterogeneity which characterizes the microstructure of maraging steel welds. No reverted austenite was observed in as-welded specimens. Solution annealing at 1093 K for 1 h did not completely eliminate the chemical heterogeneity associated with weld structures. However, homogenizing at 1373 K produced homogenous structure that on subsequent aging produces austenite-free lath martensitic structure.

  8. Investigation on the evolution of microstructure and texture of electroplated Ni-Ti composite coating by Rietveld method

    NASA Astrophysics Data System (ADS)

    Zhao, Yuantao; Cai, Fei; Wang, Chengxi; Chai, Ze; Zhu, Kaiyuan; Xu, Zhou; Jiang, Chuanhai

    2015-10-01

    Rietveld refinement was utilized to investigate the evolution of microstructure and texture of the Ni-Ti composite coatings electroplated at different applied current densities. Scanning Electron Microscope and Energy Dispersive Spectroscopy were utilized to investigate the morphology and chemical composition of the coatings. Relative texture coefficients (RTC) and measured pole figures were utilized to investigate the texture evolution of the coatings. The results showed that the surface morphology of the coatings changed from a colonial structure to a polyhedral one. And the incorporated Ti content decreased with increasing applied current density. As the applied current density increased, the crystallite sizes increased and their distribution got less uniform, and the microstrain and dislocation density decreased. The results of simulated pole figures obtained from Rietveld refinement illustrated that the texture of the coatings changed from no obvious texture to a strong [2 0 0] fiber texture with increasing applied current density. The texture evolution obtained from simulated pole figures was confirmed by the result of RTC and the measured pole figures. The evolutions of the microstructure and texture were derived from the change of the applied current density and incorporated Ti content in the Ni-Ti composite coatings.

  9. Learning through Feature Prediction: An Initial Investigation into Teaching Categories to Children with Autism through Predicting Missing Features

    ERIC Educational Resources Information Center

    Sweller, Naomi

    2015-01-01

    Individuals with autism have difficulty generalising information from one situation to another, a process that requires the learning of categories and concepts. Category information may be learned through: (1) classifying items into categories, or (2) predicting missing features of category items. Predicting missing features has to this point been…

  10. Microstructural investigation of as-cast uranium rich U-Zr alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Yuting; Wang, Xin; Zeng, Gang; Wang, Hui; Jia, Jianping; Sheng, Liusi; Zhang, Pengcheng

    2016-04-01

    The present study evaluates the microstructure in as-cast uranium rich U-Zr alloys, an important subsystem of U-Pu-Zr ternary metallic nuclear reactor fuel, as a function of the Zr content, from 2wt.% to 15wt.%Zr. It has been previously suggested that the unique intermetallic compound δ phase in U-Zr alloys is only present in as-cast U-Zr alloys with a Zr content exceeding 10wt.%Zr. However, our analysis of transmission electron microscopy (TEM) data shows that the δ phase is common to all as-cast alloys studied in this work. Furthermore, specific coherent orientation relationship is found between the α and δ phases, consistent with previous findings, and a third variant is discovered in this paper.

  11. Crystal plasticity investigation of the microstructural factors influencing dislocation channeling in a model irradiated bcc material

    DOE PAGESBeta

    Patra, Anirban; McDowell, David L.

    2016-03-25

    We use a continuum crystal plasticity framework to study the effect of microstructure and mesoscopic factors on dislocation channeling and flow localization in an irradiated model bcc alloy. For simulated dislocation channeling characteristics we correlate the dislocation and defect densities in the substructure, local Schmid factor, and stress triaxiality, in terms of their temporal and spatial evolution. A metric is introduced to assess the propensity for localization and is correlated to the grain-level Schmid factor. We also found that localization generally takes place in grains with a local Schmid factor in the range 0.42 or higher. Surface slip step heightsmore » are computed at free surfaces and compared to relevant experiments.« less

  12. Investigation of microstructured chitosans by coherent anti-Stokes Raman microscopy.

    PubMed

    Dementjev, A; Mordas, G; Ulevičius, V; Gulbinas, V

    2015-03-01

    This work describes application of coherent anti-Stokes Raman scattering (CARS) microscopy technique for analytical characterization of microstructured materials based on chitosan. We demonstrate that nitrogen-hydrogen vibration band in the high wavenumber region of CARS spectrum prevails over response from oxygen-hydrogen vibrations and can be used as a spectral marker of chitosan. The chemically selective imaging is experimentally demonstrated by applying CARS microscopy to discriminate between chitosan and polystyrene microparticles. CARS microscopy was shown to be a valuable tool for characterization of polluted chitosan fibre from utilized engine filter material. A possibility to observe foreign material pieces on the surface of the polluted chitosan fibre is demonstrated and discussed. PMID:25529768

  13. Three-dimensional microstructural investigation of high magnetization nano-micro composite fluids using x-ray microcomputed tomography

    NASA Astrophysics Data System (ADS)

    Borbáth, T.; Borbáth, I.; Günther, S.; Marinica, O.; Vékás, L.; Odenbach, S.

    2014-05-01

    X-ray microcomputed tomography was used in a three-dimensional investigation of the microstructure of suspensions of multi-domain soft iron particles in magnetic nanofluids. The measurements were performed using two different approaches: with the sample kept frozen, and with the sample under the effect of an external magnetic field. Results show that even a relatively low magnetic field gradient drives the micron-sized iron particles towards the stronger field and thus leads to a redistribution of the ferromagnetic particles in the magnetic nanofluid. Three-dimensional images of the internal microstructure of the composite magnetizable fluid (CMF) were obtained not only for the nano-micro composite system placed in a closed sample holder, but also for the spikes formed at the CMF free surface. It was demonstrated that x-ray microcomputed tomography is an efficient way to investigate the distribution and chain formation of ferromagnetic microparticles in a magnetic nanofluid carrier allowing an analysis even at a single particle level.

  14. Investigation of gait features for stability and risk identification in elders.

    PubMed

    Liang, Jun; Abbott, Carmen C; Skubic, Marjorie; Keller, James

    2009-01-01

    Today, eldercare demands a greater degree of versatility in healthcare. Automatic monitoring devices and sensors are under development to help senior citizens achieve greater autonomy, and, as situations arise, alert healthcare providers. In this paper, we study gait patterns based on extracted silhouettes from image sequences. Three features are investigated through two different image capture perspectives: shoulder level, spinal incline, and silhouette centroid. Through the evaluation of fourteen image sequences representing a range of healthy to frail gait styles, features are extracted and compared to validation results using a Vicon motion capture system. The results obtained show promise for future studies that can increase both the accuracy of feature extraction and pragmatism of machine monitoring for at-risk elders. PMID:19965074

  15. Quantitative investigation of the tensile plastic deformation characteristic and microstructure for friction stir welded 2024 aluminum alloy

    SciTech Connect

    Hu, Z.L.; Wang, X.S.; Yuan, S.J.

    2012-11-15

    The effect of the microstructure heterogeneity on the tensile plastic deformation characteristic of friction stir welded (FSW) 2024 aluminum alloy was investigated for the potential applications on light weight design of vehicles. The microstructure characteristics of the FSW joints, such as the grain structure, dislocation density and the distribution of precipitation, were studied by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The tensile deformation characteristic of the FSW joints was examined using the automatic strain measuring system (ASAME) by mapping the global and local strain distribution, and then was analyzed by mechanics calculation. It is found that the tensile deformation of the FSW joints is highly heterogeneous leading to a significant decrease in global ductility. The FSW joints mainly contain two typical deformation zones, which show great effect on the regional inhomogeneous deformation. One is the nugget zone (NZ) with a region of 8 mm in width, and the other is part of the BM with a region of 10 mm in width. The BM of the joints is the weakest region where the strain localizes early and this localization extends until fracture with a strain over 30%, while the strain in the NZ is only 4%. Differences in regional strain of FSW joints, which are essentially controlled by grain structure, the distribution of precipitation and dislocation density, result in decrease on the overall mechanical properties. - Highlights: Black-Right-Pointing-Pointer Microstructure heterogeneity of welds on tensile deformation behavior is studied. Black-Right-Pointing-Pointer The welds contain two typical deformation zones, affecting the global ductility. Black-Right-Pointing-Pointer Regional strain of welds is controlled by grain structure and dislocation density. Black-Right-Pointing-Pointer Theoretical calculation is in good agreement with experimental result.

  16. Experimental and microstructural investigations of frictional heating and fluidization in clay-rich fault gouge

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Nakakoji, T.; Tsutsumi, A.

    2011-12-01

    Mature faults commonly contain a considerable amount of clay minerals in their core. The frictional properties and the co-seismic deformation mechanisms of clay-rich fault gouges are key controls of the co-seismic fault strength, rupture propagation, and tsunamigenesis in subduction zones. Recent microstructural observations of natural slip zones and high-velocity friction experiments on clay-rich fault gouges suggest that the clay-clast aggregates (CCA; the spherical aggregates defined by clasts surrounded by a cortex of concentric clay layer) and the grain size segregation could be new textural evidence for thermal pressurization associated with water vaporization and fluidization, respectively. However, the physical processes and frictional properties during the development of these textures remain not fully understood. We conducted friction experiments on clay-rich fault gouge taken from the megasplay fault zone in the Nankai subduction zone and examined the resulting microstructures. Friction experiments were conducted at a normal stress of 1.0 MPa and slip rates (V) of 0.0013-1.3 m/s under dry (room humidity) and wet (water saturated) conditions. In the dry tests at V=1.3 m/s, the peak friction of 0.6-0.7 decreases to the steady-state friction of 0.2, over slip weakening distances of ~10.9 m, which is closely correlated to gouge dilation. In contrast, there is no visible slip weakening in the dry tests at V=0.0013-0.13 m/s; friction coefficients remain high in the range of 0.6-0.9 until the end of the experiments and the gouge dilation is small or absent. However, CCA are observed in all dry tests, with their volume content in the fault gouge decreasing with a decrease in V. The calculated temperatures in the fault gouge during the experiments are lower than the temperature for water vaporization at 1.0 MPa (180°C) when V=0.0013-0.013 m/s. These results demonstrate that CCA are neither textural evidence of the reduction in frictional coefficient due to

  17. Investigation of Edge Plasma Features in the HL-1M Tokamak

    NASA Astrophysics Data System (ADS)

    Yan, Long-wen; Yang, Shi-kun; Hong, Wen-yu; Wang, En-yao; Qian, Jun

    1999-12-01

    Edge plasma features in typical HL-1M discharges were presented. Particle confinement and plasma rotation have been investigated in the discharges with lower hybrid current drive (LHCD), molecular beam injection (MBI) and pellet fuelling. LHCD can make particle confinement increase a factor of 2-3 for low-density discharge. Particle confinement time and poloidal rotation can be at least doubled after pellet injection, while MBI can make confinement time increase about one order of magnitude with higher performance.

  18. Micro-structural, electrical and spectroscopic investigations of pulsed laser ablated palladium incorporated nanostructured tungsten oxide films.

    PubMed

    Lethy, K J; Beena, D; Pillai, V P Mahadevan; Suresh, K A

    2009-09-01

    Pure and Pd incorporated (0.5, 1 and 5 wt%) WO3 films are prepared on quartz substrates using pulsed laser ablation (PLD) technique in an oxygen ambient of 0.12 mbar, at a substrate temperature (Ts) of 873 K. Palladium incorporation effects on the microstructure, optical and electrical properties of tungsten oxide films are systematically investigated using techniques like X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), micro-Raman spectroscopy, UV-Vis absorption spectroscopy and temperature dependent electrical resistivity measurements. The micro-structural analysis by XRD and micro-Raman indicates that Pd addition can perturb the tungsten oxide lattice and suppress the grain growth. Optical band gap values of the films increases from 3.17 eV for pure WO3 to 3.29 eV for 5 wt% Pd incorporated WO3 films. All the films present high transparency in the visible spectral range. The electrical resistivity studies of the pure and Pd incorporated films done at room temperature and for the range of temperature; 170-450 K reveal that Pd addition can lower the resistivity of the WO3 thin films. Room temperature resistivity as well as activation energy of the film decreases exponentially with Pd incorporation concentration. Highly transparent, nanocrystalline and semiconducting WO3 films with low resistivity obtained by Pd incorporation can make WO3 suitable for microelectronics industry and for gas sensing applications. PMID:19928224

  19. Investigation of structural properties associated with alkali-silica reaction by means of macro- and micro-structural analysis

    SciTech Connect

    Mo Xiangyin . E-mail: moxiangyin@njnu.edu.cn; Fournier, Benoit

    2007-02-15

    Structural properties associated with alkali-silica reaction were systematically investigated by means of macro-structural accelerated mortar prism expansion levels testing, combined with micro-structural analysis. One part of this study is to determine the reactivity of the aggregate by means of accelerated mortar bar tests, and also to evaluate perlite aggregate constituents, especially the presence of deleterious components and find main causes of the alkali-silica reaction, which was based on the petrographic studies by optical microscope and the implication of X-ray diffraction on the aggregate. Results implied that the aggregate was highly alkali-silica reactive and the main micro-crystalline quartz-intermediate character and matrix that is mainly composed of chalcedony are potentially suitable for alkali-silica reaction. The other part is to study the long-term effect of lithium salts against alkali-silica reaction by testing accelerated mortar prism expansion levels. The macro-structural results were also consistent with the micro-structural mechanisms of alkali-silica reaction of mortar prisms containing this aggregate and the effect of chemical admixtures by means of the methods of scanning electron microscope-X-ray energy-dispersive spectroscopy and X-ray diffraction. It was indicated by these techniques that lithium salts, which were introduced into concrete containing reactive aggregate at the mixing stage, suppressed the alkali-silica reaction by producing non-expansive crystalline materials.

  20. Investigations of high order plasmonic resonance features of the nano hyper ring.

    PubMed

    Wang, C; Li, C X; Wu, Y N; Wang, Z J; Han, Q Y; Zheng, H R; Dong, J

    2016-09-01

    A novel silver hyper ring and its complex nanostructures are designed and its plasmonic properties are investigated numerically. It is found that these hyper ring structures have relative stable optical features. The absorption cross section of the structure changes slightly when the direction and polarization of incident light is adjusting. For the complex structure, the position of each resonance peak does not present obvious change when the relative position of the inner hyper ring and outside larger ring changes. The result of the investigation has great significance for the production of practical nanostructures and the improvement of possible applications. PMID:27385083

  1. Investigations of high order plasmonic resonance features of the nano hyper ring

    NASA Astrophysics Data System (ADS)

    Wang, C.; Li, C. X.; Wu, Y. N.; Wang, Z. J.; Han, Q. Y.; Zheng, H. R.; Dong, J.

    2016-09-01

    A novel silver hyper ring and its complex nanostructures are designed and its plasmonic properties are investigated numerically. It is found that these hyper ring structures have relative stable optical features. The absorption cross section of the structure changes slightly when the direction and polarization of incident light is adjusting. For the complex structure, the position of each resonance peak does not present obvious change when the relative position of the inner hyper ring and outside larger ring changes. The result of the investigation has great significance for the production of practical nanostructures and the improvement of possible applications.

  2. An insight into what superconducts in polycrystalline boron-doped diamonds based on investigations of microstructure

    PubMed Central

    Dubrovinskaia, N.; Wirth, R.; Wosnitza, J.; Papageorgiou, T.; Braun, H. F.; Miyajima, N.; Dubrovinsky, L.

    2008-01-01

    The discovery of superconductivity in polycrystalline boron-doped diamond (BDD) synthesized under high pressure and high temperatures [Ekimov, et al. (2004) Nature 428:542–545] has raised a number of questions on the origin of the superconducting state. It was suggested that the heavy boron doping of diamond eventually leads to superconductivity. To justify such statements more detailed information on the microstructure of the composite materials and on the exact boron content in the diamond grains is needed. For that we used high-resolution transmission electron microscopy and electron energy loss spectroscopy. For the studied superconducting BDD samples synthesized at high pressures and high temperatures the diamond grain sizes are ≈1–2 μm with a boron content between 0.2 (2) and 0.5 (1) at %. The grains are separated by 10- to 20-nm-thick layers and triangular-shaped pockets of predominantly (at least 95 at %) amorphous boron. These results render superconductivity caused by the heavy boron doping in diamond highly unlikely. PMID:18697937

  3. Microstructural properties of superalloys investigated by nanoindentations in an atomic force microscope

    SciTech Connect

    Goeken, M.; Kempf, M.

    1999-02-05

    The microstructure of nickel-base superalloys with differently shaped {gamma}{prime} precipitates determines their excellent high-temperature behavior. A reliable quantitative determination of volume fraction and particle size distribution (PSD) of these precipitates is difficult, since the size of the precipitates is often below 100 nm. With an atomic force microscope (AFM), sections through specimens are analyzed with a resolution in the nanometer range, which allows a quantitative determination of the {gamma}{prime} volume content and PSD for different superalloys. Thus, determined volume fractions for the {gamma}{prime} phase in the superalloys CMSX-6 and Waspaloy amount to 56% and 27%, respectively. A combination of an AFM with a nanoindentation system also allows the measurement of local mechanical properties such as hardness and elasticity. These quantities are determined for the first time directly on the superalloys CMSX-6 and Waspaloy for the {gamma}{prime} and matrix phases, separately. The {gamma}{prime} phase in both alloys shows a significantly higher but different hardness than the matrix phase, whereas the moduli of elasticity are similar. A depth dependence of the hardness was found for very small indentations.

  4. Study of Radiographic Linear Indications and Subsequent Microstructural Features in Gas Tungsten Arc Welds of Inconel 718

    NASA Technical Reports Server (NTRS)

    Walley, J. L.; Nunes, A. C.; Clounch, J. L.; Russell, C. K.

    2007-01-01

    This study presents examples and considerations for differentiating linear radiographic indications produced by gas tungsten arc welds in a 0.05-in-thick sheet of Inconel 718. A series of welds with different structural features, including the enigma indications and other defect indications such as lack of fusion and penetration, were produced, radiographed, and examined metallographically. The enigma indications were produced by a large columnar grain running along the center of the weld nugget occurring when the weld speed was reduced sufficiently below nominal. Examples of respective indications, including the effect of changing the x-ray source location, are presented as an aid to differentiation. Enigma, nominal, and hot-weld specimens were tensile tested to demonstrate the harmlessness of the enigma indication. Statistical analysis showed that there is no difference between the strengths of these three weld conditions.

  5. The mechanical and microstructural behaviour of calcite-dolomite composites: An experimental investigation

    NASA Astrophysics Data System (ADS)

    Kushnir, Alexandra R. L.; Kennedy, L. A.; Misra, Santanu; Benson, Philip; White, J. C.

    2015-01-01

    The styles and mechanisms of deformation associated with many variably dolomitized limestone shear systems are strongly controlled by strain partitioning between dolomite and calcite. Here, we present experimental results from the deformation of four composite materials designed to address the role of dolomite on the strength of limestone. Composites were synthesized by hot isostatic pressing mixtures of dolomite (Dm) and calcite powders (% Dm: 25%-Dm, 35%-Dm, 51%-Dm, and 75%-Dm). In all composites, calcite is finer grained than dolomite. The synthesized materials were deformed in torsion at constant strain rate (3 × 10-4 and 1 × 10-4 s-1), high effective pressure (262 MPa), and high temperature (750 °C) to variable finite shear strains. Mechanical data show an increase in yield strength with increasing dolomite content. Composites with <75% dolomite (the remaining being calcite), accommodate significant shear strain at much lower shear stresses than pure dolomite but have significantly higher yield strengths than anticipated for 100% calcite. The microstructure of the fine-grained calcite suggests grain boundary sliding, accommodated by diffusion creep and dislocation glide. At low dolomite concentrations (i.e. 25%), the presence of coarse-grained dolomite in a micritic calcite matrix has a profound effect on the strength of composite materials as dolomite grains inhibit the superplastic flow of calcite aggregates. In high (>50%) dolomite content samples, the addition of 25% fine-grained calcite significantly weakens dolomite, such that strain can be partially localized along narrow ribbons of fine-grained calcite. Deformation of dolomite grains by shear fracture is observed; there is no intracrystalline deformation in dolomite irrespective of its relative abundance and finite shear strain.

  6. Investigations on the 1.7 micron residual absorption feature in the vegetation reflection spectrum

    NASA Technical Reports Server (NTRS)

    Verdebout, J.; Jacquemoud, S.; Andreoli, G.; Hosgood, B.; Sieber, A.

    1993-01-01

    The detection and interpretation of the weak absorption features associated with the biochemical components of vegetation is of great potential interest to a variety of applications ranging from classification to global change studies. This recent subject is also challenging because the spectral signature of the biochemicals is only detectable as a small distortion of the infrared spectrum which is mainly governed by water. Furthermore, the interpretation is complicated by complexity of the molecules (lignin, cellulose, starch, proteins) which contain a large number of different and common chemical bonds. In this paper, we present investigations on the absorption feature centered at 1.7 micron; these were conducted both on AVIRIS data and laboratory reflectance spectra of leaves.

  7. Investigation of the microstructure and optical properties of Ge films grown by DC magnetron sputtering and in situ annealing

    NASA Astrophysics Data System (ADS)

    Li, Hui-Song; Qiu, Feng; Xin, Zheng-Hang; Wang, Rong-Fei; Yang, Jie; Zhang, Jin; Wang, Chong; Yang, Yu

    2016-06-01

    We investigate the microstructure and optical properties of Ge films on Si substrates prepared at low temperature by DC magnetron sputtering and the effect of in situ annealing on them. With increasing growth temperature, Ge films undergo a transition from amorphous to microcrystalline, then to polycrystalline. After annealing, these thin films transform into polycrystalline films with the (111) preferred orientation and identical crystal sizes. The surfaces of the amorphous and microcrystalline Ge films are severely coarsened, whereas the polycrystalline Ge film still displays a smooth surface. The growth mechanisms of Ge films with different crystalline phases in the annealing process are discussed, which can explain their morphology evolutions. Additionally, their infrared absorptions are enhanced after annealing, and this is useful for fabricating high-efficiency Si-based solar cells.

  8. Dependence of pH on dispersion of SiC fine particulates in boehmite and its correlation with microstructural features of alumina

    SciTech Connect

    Hareesh, U.S.; Ananthakumar, S.; Damodaran, A.D.; Warrier, K.G.K.

    1996-12-31

    The possibility of increasing fracture toughness and strength of alumina ceramics has been achieved recently by incorporating fine SiC particles. One of the many investigated methods for the synthesis of Alumina-SiC composites is by use of pre-coated SiC powders. Gelation of boehmite (AlOOH) in presence of SiC particles have also been attempted. The present study is for obtaining stable, finely dispersed SiC particles in boehmite matrix as precursor material. The effect of pH and solvent medium in the gelation process of boehmite-SiC mixture are followed by optical microscopy coupled with image analysis system and such composites after sintering are evaluated by microstructural observation. Structure-property correlation has been obtained for highly dispersed SiC particles in alumina-SiC nano composites.

  9. Correlation of Fractographic Features with Mechanical Properties in Systematically Varied Microstructures of Cu-Strengthened High-Strength Low-Alloy Steel

    NASA Astrophysics Data System (ADS)

    Das, Arpan; Das, Swapan Kumar; Tarafder, Soumitra

    2009-12-01

    Fracture is often the culmination of continued deformation. Therefore, it is probable that a fracture surface may contain an imprint of the deformation processes that were operative. In this study, the deformation behavior of copper-strengthened high-strength low-alloy (HSLA) 100 steel has been investigated. Systematic variation of the microstructure has been introduced in the steel through various aging treatments. Due to aging, the coherency, size, shape, and distribution of the copper precipitates were changed, while those of inclusions, carbides, and carbonitrides were kept unaltered. Two-dimensional dimple morphologies, quantified from tensile fracture surfaces, have been correlated to the nature of the variation of the deformation parameters with aging treatment.

  10. Investigation on preparation and performance of spinel LiNi0.5Mn1.5O4 with different microstructures for lithium-ion batteries.

    PubMed

    Xue, Yuan; Wang, Zhenbo; Zheng, Lili; Yu, Fuda; Liu, Baosheng; Zhang, Yin; Ke, Ke

    2015-01-01

    The high voltage spinel LiNi0.5Mn1.5O4 is a promising cathode material in next generation of lithium ion batteries. In this study, LiNi0.5Mn1.5O4 with various particle microstructures are prepared by controlling the microstructures of precursors. LiNi0.5Mn1.5O4 spinel samples with solid, hollow and hierarchical microstructures are prepared with solid MnCO3, hollow MnO2 and hierarchical Mn2O3 as precursor, respectively. The homemade spinel materials are investigated and the results show that the content of Mn(3+) and impurity phase differ much in these three spinel samples obtained under the same calcining and annealing conditions. It is revealed for the first time that an inhomogeneous migration of atoms may introduce Mn(3+) and impurity phase in the spinel. The hierarchical microstructure with the primary particles interconnected is optimal for electrode materials because this microstructure has a higher conductivity between the interconnected primary particles and appropriate specific surface area. LiNi0.5Mn1.5O4 in this microstructure has the best rate capability and also the best long-term cycling stability. PMID:26299774

  11. Investigation on preparation and performance of spinel LiNi0.5Mn1.5O4 with different microstructures for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Xue, Yuan; Wang, Zhenbo; Zheng, Lili; Yu, Fuda; Liu, Baosheng; Zhang, Yin; Ke, Ke

    2015-08-01

    The high voltage spinel LiNi0.5Mn1.5O4 is a promising cathode material in next generation of lithium ion batteries. In this study, LiNi0.5Mn1.5O4 with various particle microstructures are prepared by controlling the microstructures of precursors. LiNi0.5Mn1.5O4 spinel samples with solid, hollow and hierarchical microstructures are prepared with solid MnCO3, hollow MnO2 and hierarchical Mn2O3 as precursor, respectively. The homemade spinel materials are investigated and the results show that the content of Mn3+ and impurity phase differ much in these three spinel samples obtained under the same calcining and annealing conditions. It is revealed for the first time that an inhomogeneous migration of atoms may introduce Mn3+ and impurity phase in the spinel. The hierarchical microstructure with the primary particles interconnected is optimal for electrode materials because this microstructure has a higher conductivity between the interconnected primary particles and appropriate specific surface area. LiNi0.5Mn1.5O4 in this microstructure has the best rate capability and also the best long-term cycling stability.

  12. Investigation on preparation and performance of spinel LiNi0.5Mn1.5O4 with different microstructures for lithium-ion batteries

    PubMed Central

    Xue, Yuan; Wang, Zhenbo; Zheng, Lili; Yu, Fuda; Liu, Baosheng; Zhang, Yin; Ke, Ke

    2015-01-01

    The high voltage spinel LiNi0.5Mn1.5O4 is a promising cathode material in next generation of lithium ion batteries. In this study, LiNi0.5Mn1.5O4 with various particle microstructures are prepared by controlling the microstructures of precursors. LiNi0.5Mn1.5O4 spinel samples with solid, hollow and hierarchical microstructures are prepared with solid MnCO3, hollow MnO2 and hierarchical Mn2O3 as precursor, respectively. The homemade spinel materials are investigated and the results show that the content of Mn3+ and impurity phase differ much in these three spinel samples obtained under the same calcining and annealing conditions. It is revealed for the first time that an inhomogeneous migration of atoms may introduce Mn3+ and impurity phase in the spinel. The hierarchical microstructure with the primary particles interconnected is optimal for electrode materials because this microstructure has a higher conductivity between the interconnected primary particles and appropriate specific surface area. LiNi0.5Mn1.5O4 in this microstructure has the best rate capability and also the best long-term cycling stability. PMID:26299774

  13. Determination of optimum threshold values for EMG time domain features; a multi-dataset investigation

    NASA Astrophysics Data System (ADS)

    Nlandu Kamavuako, Ernest; Scheme, Erik Justin; Englehart, Kevin Brian

    2016-08-01

    Objective. For over two decades, Hudgins’ set of time domain features have extensively been applied for classification of hand motions. The calculation of slope sign change and zero crossing features uses a threshold to attenuate the effect of background noise. However, there is no consensus on the optimum threshold value. In this study, we investigate for the first time the effect of threshold selection on the feature space and classification accuracy using multiple datasets. Approach. In the first part, four datasets were used, and classification error (CE), separability index, scatter matrix separability criterion, and cardinality of the features were used as performance measures. In the second part, data from eight classes were collected during two separate days with two days in between from eight able-bodied subjects. The threshold for each feature was computed as a factor (R = 0:0.01:4) times the average root mean square of data during rest. For each day, we quantified CE for R = 0 (CEr0) and minimum error (CEbest). Moreover, a cross day threshold validation was applied where, for example, CE of day two (CEodt) is computed based on optimum threshold from day one and vice versa. Finally, we quantified the effect of the threshold when using training data from one day and test data of the other. Main results. All performance metrics generally degraded with increasing threshold values. On average, CEbest (5.26 ± 2.42%) was significantly better than CEr0 (7.51 ± 2.41%, P = 0.018), and CEodt (7.50 ± 2.50%, P = 0.021). During the two-fold validation between days, CEbest performed similar to CEr0. Interestingly, when using the threshold values optimized per subject from day one and day two respectively, on the cross-days classification, the performance decreased. Significance. We have demonstrated that threshold value has a strong impact on the feature space and that an optimum threshold can be quantified. However, this optimum threshold is highly data and

  14. Micro-chemical and micro-structural investigation of the corrosion products on `` The Dancing Satyr'' (Mazara del Vallo, Sicily, Italy)

    NASA Astrophysics Data System (ADS)

    Ingo, G. M.; Riccucci, C.; Faraldi, F.; Casaletto, M. P.; Guida, G.

    2010-09-01

    The “ Dancing Satyr”, a bronze statue measuring more than 2 metres in height and weighting 108 kg, represents one of the most important recent archaeological finds in Italy. The statue was discovered on the floor of the Sicilian channel (the portion of the Mediterranean sea between Sicily and Tunisia), not far from the south-western Sicilian coast, under 500 metres of seawater in 1998. The bronze statue depicts a nude satyr captured in a frenzied whirling movement during a dance in honour of Dionysus, the God of wine. Though some scholars dated it to the IV century B.C. as an original Praxiteles work or a copy thereof, it could be also dated either back to the Hellenistic period (III or II century B.C.) or possibly to the Roman Empire age (early II century A.D.). The nature and structure of the corrosion products grown on the Dancing Satyr surface and the metallurgical features of the statue were investigated taking into account the nature of the marine environment of provenance. A detailed micro-chemical and micro-structural characterisation was performed by means of the combined use of scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD) and optical microscopy (OM). Results provided good insight into the different corrosion layers and a tentative correlation of the patina nature and the chemical composition of the statue and the marine context is proposed.

  15. Munitions integrity and corrosion features observed during the HUMMA deep-sea munitions disposal site investigations

    NASA Astrophysics Data System (ADS)

    Silva, Jeff A. K.; Chock, Taylor

    2016-06-01

    An evaluation of the current condition of sea-disposed military munitions observed during the 2009 Hawaii Undersea Military Munitions Assessment Project investigation is presented. The 69 km2 study area is located south of Pearl Harbor, Oahu, Hawaii, and is positioned within a former deep-sea disposal area designated as Hawaii-05 or HI-05 by the United States Department of Defense. HI-05 is known to contain both conventional and chemical munitions that were sea-disposed between 1920 and 1951. Digital images and video reconnaissance logs collected during six remotely operated vehicle and 16 human-occupied vehicle surveys were used to classify the integrity and state of corrosion of the 1842 discarded military munitions (DMM) objects encountered. Of these, 5% (or 90 individual DMM objects) were found to exhibit a mild-moderate degree of corrosion. The majority (66% or 1222 DMM objects) were observed to be significantly corroded, but visually intact on the seafloor. The remaining 29% of DMM encountered were found to be severely corroded and breached, with their contents exposed. Chemical munitions were not identified during the 2009 investigation. In general, identified munitions known to have been constructed with thicker casings were better preserved. Unusual corrosion features were also observed, including what are termed here as 'corrosion skirts' that resembled the flow and cementation of corrosion products at and away from the base of many munitions, and 'corrosion pedestal' features resembling a combination of cemented corrosion products and seafloor sediments that were observed to be supporting munitions above the surface of the seafloor. The origin of these corrosion features could not be determined due to the lack of physical samples collected. However, a microbial-mediated formation hypothesis is presented, based on visual analysis, which can serve as a testable model for future field programs.

  16. Glancing angle deposition of SiO{sub 2} thin film microstructures: Investigations of optical and morphological properties

    SciTech Connect

    Tokas, R. B. E-mail: tokasstar@gmail.com; Jena, S. E-mail: tokasstar@gmail.com; Sarkar, P. E-mail: tokasstar@gmail.com; Thakur, S. E-mail: tokasstar@gmail.com; Sahoo, N. K. E-mail: tokasstar@gmail.com

    2014-04-24

    In present work, the optical and the morphological properties of micro-structured SiO{sub 2} thin films fabricated by using glancing angle deposition (GLAD) technique has been carried out. The results are compared with the normally deposited SiO{sub 2} films for the gained advantages. The influence of the glancing angle on the refractive index of porous SiO{sub 2} film was investigated by the spectral transmission measurement in 400–950 nm wavelength regimes. The refractive index has been found to be 1.14@532 nm for the porous SiO{sub 2} film deposited at a glancing angle of 85°. The density and surface qualities of these samples were primarily investigated by using grazing angle X-ray reflectivity (GIXR) and atomic force microscope (AFM) measurements. Results indicate a substantial decrease in film density and refractive index and increase in surface roughness and grain size for GLAD SiO{sub 2} compared to normally deposited SiO{sub 2} films.

  17. Microstructural investigation using synchrotron radiation X-ray microtomography reveals taste-masking mechanism of acetaminophen microspheres.

    PubMed

    Guo, Zhen; Yin, Xianzhen; Liu, Congbiao; Wu, Li; Zhu, Weifeng; Shao, Qun; York, Peter; Patterson, Laurence; Zhang, Jiwen

    2016-02-29

    The structure of solid drug delivery systems has considerable influence on drug release behaviors from particles and granules and also impacts other properties relevant to release characteristics such as taste. In this study, lipid-based microspheres of acetaminophen were prepared to mask the undesirable taste of drug and therefore to identify the optimal formulation for drug release. Synchrotron radiation X-ray computed microtomography (SR-μCT) was used to investigate the fine structural architectures of microspheres non-destructively at different sampling times during drug release test, which were simultaneously determined to quantitatively correlate the structural data with drug release behaviors. The results demonstrated that the polymeric formulation component, namely, cationic polymethacrylate (Eudragit E100), was the key factor to mask the bitter taste of acetaminophen by inhibiting immediate drug release thereby reducing the interaction intensity of the bitter material with the oral cavity taste buds. The structure and morphology of the microspheres were found to be influenced by the shape and particle size of the drug, which was also an important factor for taste-masking performance. The quantitative analysis generated detailed structural information which was correlated well with drug release behaviors. Thus, SR-μCT has been proved as a powerful tool to investigate the fine microstructure of particles and provides a new approach in the design of particles for taste masking. PMID:26712269

  18. Morphological Evolution of Electrochemically Plated/Stripped Lithium Microstructures Investigated by Synchrotron X-ray Phase Contrast Tomography.

    PubMed

    Sun, Fu; Zielke, Lukas; Markötter, Henning; Hilger, André; Zhou, Dong; Moroni, Riko; Zengerle, Roland; Thiele, Simon; Banhart, John; Manke, Ingo

    2016-08-23

    Due to its low redox potential and high theoretical specific capacity, Li metal has drawn worldwide research attention because of its potential use in next-generation battery technologies such as Li-S and Li-O2. Unfortunately, uncontrollable growth of Li microstructures (LmSs, e.g., dendrites, fibers) during electrochemical Li stripping/plating has prevented their practical commercialization. Despite various strategies proposed to mitigate LmS nucleation and/or block its growth, a fundamental understanding of the underlying evolution mechanisms remains elusive. Herein, synchrotron in-line phase contrast X-ray tomography was employed to investigate the morphological evolution of electrochemically deposited/dissolved LmSs nondestructively. We present a 3D characterization of electrochemically stripped Li electrodes with regard to electrochemically plated LmSs. We clarify fundamentally the origin of the porous lithium interface growing into Li electrodes. Moreover, cleavage of the separator caused by growing LmS was experimentally observed and visualized in 3D. Our systematic investigation provides fundamental insights into LmS evolution and enables us to understand the evolution mechanisms in Li electrodes more profoundly. PMID:27463258

  19. Investigation of cellular microstructure and enhanced coercivity in sputtered Sm{sub 2}(CoCuFeZr){sub 17} film

    SciTech Connect

    Bhatt, Ranu Schütz, G.; Bhatt, Pramod

    2014-03-14

    We have investigated the effect of annealing temperature on the microstructure and magnetic properties of Sm{sub 2}(CoCuFeZr){sub 17} films prepared using ion beam sputtering at room temperature. The as-deposited film shows randomly oriented polycrystalline grains and exhibits small coercivity (H{sub C}) of 0.04 T at room temperature. Post annealing of these films at 700 °C under Ar atmosphere shows significant changes in the microstructure transforming it to the development of cellular growth, concomitant with enhanced coercivity up to 1.3 T. The enhanced coercivity is explained using the domain wall pinning mechanism.

  20. Do Online Voting Patterns Reflect Evolved Features of Human Cognition? An Exploratory Empirical Investigation.

    PubMed

    Priestley, Maria; Mesoudi, Alex

    2015-01-01

    Online votes or ratings can assist internet users in evaluating the credibility and appeal of the information which they encounter. For example, aggregator websites such as Reddit allow users to up-vote submitted content to make it more prominent, and down-vote content to make it less prominent. Here we argue that decisions over what to up- or down-vote may be guided by evolved features of human cognition. We predict that internet users should be more likely to up-vote content that others have also up-voted (social influence), content that has been submitted by particularly liked or respected users (model-based bias), content that constitutes evolutionarily salient or relevant information (content bias), and content that follows group norms and, in particular, prosocial norms. 489 respondents from the online social voting community Reddit rated the extent to which they felt different traits influenced their voting. Statistical analyses confirmed that norm-following and prosociality, as well as various content biases such as emotional content and originality, were rated as important motivators of voting. Social influence had a smaller effect than expected, while attitudes towards the submitter had little effect. This exploratory empirical investigation suggests that online voting communities can provide an important test-bed for evolutionary theories of human social information use, and that evolved features of human cognition may guide online behaviour just as it guides behaviour in the offline world. PMID:26066657

  1. Do Online Voting Patterns Reflect Evolved Features of Human Cognition? An Exploratory Empirical Investigation

    PubMed Central

    Priestley, Maria; Mesoudi, Alex

    2015-01-01

    Online votes or ratings can assist internet users in evaluating the credibility and appeal of the information which they encounter. For example, aggregator websites such as Reddit allow users to up-vote submitted content to make it more prominent, and down-vote content to make it less prominent. Here we argue that decisions over what to up- or down-vote may be guided by evolved features of human cognition. We predict that internet users should be more likely to up-vote content that others have also up-voted (social influence), content that has been submitted by particularly liked or respected users (model-based bias), content that constitutes evolutionarily salient or relevant information (content bias), and content that follows group norms and, in particular, prosocial norms. 489 respondents from the online social voting community Reddit rated the extent to which they felt different traits influenced their voting. Statistical analyses confirmed that norm-following and prosociality, as well as various content biases such as emotional content and originality, were rated as important motivators of voting. Social influence had a smaller effect than expected, while attitudes towards the submitter had little effect. This exploratory empirical investigation suggests that online voting communities can provide an important test-bed for evolutionary theories of human social information use, and that evolved features of human cognition may guide online behaviour just as it guides behaviour in the offline world. PMID:26066657

  2. Numerical and experimental investigation on broadband wave propagation features in perforated plates

    NASA Astrophysics Data System (ADS)

    Zhou, C. W.; Lainé, J. P.; Ichchou, M. N.; Zine, A. M.

    2016-06-01

    Perforated plates are widely used in various engineering applications. Their mechanical and dynamical behaviours need to be investigated for the design and optimization purpose. In this work, the wave propagation features on broadband in perforated plates are predicted by a Condensed Wave Finite Element Method (CWFEM). Based on the wave dispersion relation identified by CWFEM, wave-based homogenization methods are proposed to define equivalent solid plates. Three perforated plates with different penetration patterns and hole shapes are considered and the accuracy of the equivalent homogenized model is illustrated by comparing it with finite element method. Experimental validation of the computed wave propagation characteristics on the two models is provided as well. A good correlation is observed not only at low frequency where homogenized model can be found, but also at mid and high frequency, where the wave beaming effect phenomenon occurs.

  3. Investigation of the Phenomenological and Psychopathological Features of Trichotillomania in an Italian Sample.

    PubMed

    Bottesi, Gioia; Cerea, Silvia; Razzetti, Enrico; Sica, Claudio; Frost, Randy O; Ghisi, Marta

    2016-01-01

    Trichotillomania (TTM) is still a scarcely known and often inadequately treated disorder in Italian clinical settings, despite growing evidence about its severe and disabling consequences. The current study investigated the phenomenology of TTM in Italian individuals; in addition, we sought to examine patterns of self-esteem, anxiety, depression, and OCD-related symptoms in individuals with TTM compared to healthy participants. The current study represents the first attempt to investigate the phenomenological and psychopathological features of TTM in Italian hair pullers. One hundred and twenty-two individuals with TTM were enrolled: 24 were assessed face-to-face (face-to-face group) and 98 were recruited online (online group). An additional group of 22 face-to-face assessed healthy controls (HC group) was included in the study. The overall female to male ratio was 14:1, which is slightly higher favoring female than findings reported in literature. Main results revealed that a higher percentage of individuals in the online group reported pulling from the pubic region than did face-to-face participants; furthermore, the former engaged in examining the bulb and running the hair across the lips and reported pulling while lying in bed at higher frequencies than the latter. Interestingly, the online TTM group showed greater functional and psychological impairment, as well as more severe psychopathological characteristics (self-esteem, physiological and social anxiety, perfectionism, overestimation of threat, and control of thoughts), than the face-to-face one. Differences between the two TTM groups may be explained by the anonymity nature of the online group, which may have led to successful recruitment of more serious TTM cases, or fostered more open answers to questions. Overall, results revealed that many of the phenomenological features of Italian TTM participants matched those found in U.S. clinical settings, even though some notable differences were observed

  4. Investigation of the Phenomenological and Psychopathological Features of Trichotillomania in an Italian Sample

    PubMed Central

    Bottesi, Gioia; Cerea, Silvia; Razzetti, Enrico; Sica, Claudio; Frost, Randy O.; Ghisi, Marta

    2016-01-01

    Trichotillomania (TTM) is still a scarcely known and often inadequately treated disorder in Italian clinical settings, despite growing evidence about its severe and disabling consequences. The current study investigated the phenomenology of TTM in Italian individuals; in addition, we sought to examine patterns of self-esteem, anxiety, depression, and OCD-related symptoms in individuals with TTM compared to healthy participants. The current study represents the first attempt to investigate the phenomenological and psychopathological features of TTM in Italian hair pullers. One hundred and twenty-two individuals with TTM were enrolled: 24 were assessed face-to-face (face-to-face group) and 98 were recruited online (online group). An additional group of 22 face-to-face assessed healthy controls (HC group) was included in the study. The overall female to male ratio was 14:1, which is slightly higher favoring female than findings reported in literature. Main results revealed that a higher percentage of individuals in the online group reported pulling from the pubic region than did face-to-face participants; furthermore, the former engaged in examining the bulb and running the hair across the lips and reported pulling while lying in bed at higher frequencies than the latter. Interestingly, the online TTM group showed greater functional and psychological impairment, as well as more severe psychopathological characteristics (self-esteem, physiological and social anxiety, perfectionism, overestimation of threat, and control of thoughts), than the face-to-face one. Differences between the two TTM groups may be explained by the anonymity nature of the online group, which may have led to successful recruitment of more serious TTM cases, or fostered more open answers to questions. Overall, results revealed that many of the phenomenological features of Italian TTM participants matched those found in U.S. clinical settings, even though some notable differences were observed

  5. Associations between white matter microstructure and amyloid burden in preclinical Alzheimer's disease: A multimodal imaging investigation

    PubMed Central

    Racine, Annie M.; Adluru, Nagesh; Alexander, Andrew L.; Christian, Bradley T.; Okonkwo, Ozioma C.; Oh, Jennifer; Cleary, Caitlin A.; Birdsill, Alex; Hillmer, Ansel T.; Murali, Dhanabalan; Barnhart, Todd E.; Gallagher, Catherine L.; Carlsson, Cynthia M.; Rowley, Howard A.; Dowling, N. Maritza; Asthana, Sanjay; Sager, Mark A.; Bendlin, Barbara B.; Johnson, Sterling C.

    2014-01-01

    Some cognitively healthy individuals develop brain amyloid accumulation, suggestive of incipient Alzheimer's disease (AD), but the effect of amyloid on other potentially informative imaging modalities, such as Diffusion Tensor Imaging (DTI), in characterizing brain changes in preclinical AD requires further exploration. In this study, a sample (N = 139, mean age 60.6, range 46 to 71) from the Wisconsin Registry for Alzheimer's Prevention (WRAP), a cohort enriched for AD risk factors, was recruited for a multimodal imaging investigation that included DTI and [C-11]Pittsburgh Compound B (PiB) positron emission tomography (PET). Participants were grouped as amyloid positive (Aβ+), amyloid indeterminate (Aβi), or amyloid negative (Aβ−) based on the amount and pattern of amyloid deposition. Regional voxel-wise analyses of four DTI metrics, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da), and radial diffusivity (Dr), were performed based on amyloid grouping. Three regions of interest (ROIs), the cingulum adjacent to the corpus callosum, hippocampal cingulum, and lateral fornix, were selected based on their involvement in the early stages of AD. Voxel-wise analysis revealed higher FA among Aβ+ compared to Aβ− in all three ROIs and in Aβi compared to Aβ− in the cingulum adjacent to the corpus callosum. Follow-up exploratory whole-brain analyses were consistent with the ROI findings, revealing multiple regions where higher FA was associated with greater amyloid. Lower fronto-lateral gray matter MD was associated with higher amyloid burden. Further investigation showed a negative correlation between MD and PiB signal, suggesting that Aβ accumulation impairs diffusion. Interestingly, these findings in a largely presymptomatic sample are in contradistinction to relationships reported in the literature in symptomatic disease stages of Mild Cognitive Impairment and AD, which usually show higher MD and lower FA. Together with analyses

  6. Synthesis and Microstructural Investigations of Organometallic Pd(II) Thiol-Gold Nanoparticles Hybrids

    PubMed Central

    2008-01-01

    In this work the synthesis and characterization of gold nanoparticles functionalized by a novel thiol-organometallic complex containing Pd(II) centers is presented. Pd(II) thiol,trans, trans-[dithiolate-dibis(tributylphosphine)dipalladium(II)-4,4′-diethynylbiphenyl] was synthesized and linked to Au nanoparticles by the chemical reduction of a metal salt precursor. The new hybrid made of organometallic Pd(II) thiol-gold nanoparticles, shows through a single S bridge a direct link between Pd(II) and Au nanoparticles. The size-control of the Au nanoparticles (diameter range 2–10 nm) was achieved by choosing the suitable AuCl4−/thiol molar ratio. The size, strain, shape, and crystalline structure of these functionalized nanoparticles were determined by a full-pattern X-ray powder diffraction analysis, high-resolution TEM, and X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements of the hybrid system show emission peaks at 418 and 440 nm. The hybrid was exposed to gaseous NOxwith the aim to evaluate the suitability for applications in sensor devices; XPS measurements permitted to ascertain and investigate the hybrid –gas interaction. PMID:21350592

  7. Investigation of internal microstructure and thermo-responsive properties of composite PNIPAM/silica microcapsules.

    PubMed

    Cejková, Jitka; Hanus, Jaroslav; Stepánek, Frantisek

    2010-06-15

    Composite microcapsules consisting of a thermo-responsive hydrogel poly-N-isopropylacrylamide (PNIPAM) and coated by silica (SiO(2)) nanoparticles have been synthesized by the inverse Pickering emulsion polymerization method. The composite capsules, whose mean diameter is in the 25-86 microm range in the expanded state, were characterized by static light scattering, atomic force microscopy (AFM), scanning electron microscopy (SEM), and laser scanning confocal microscopy (LSCM). It is reported that the hydrogel surface is uniformly covered by a monolayer of silica nanoparticles and that depending on the capsule size and degree of polymer cross-linking, either hollow-core or partially-filled hydrogel-core microcapsules can be created. Equilibrium thermo-responsive behavior of the composite microcapsules is investigated and it is found that after heating the particles above the lower critical solution temperature (LCST) of PNIPAM, the shrinkage ratio V/V(max) varies from 0.8 to 0.4 for a cross-linking ratio from 0.6% to 9% on a mass basis. Dynamic temperature cycling studies reveal no hysteresis in the shrinking and recovery phases, but a small measurable dependence of the asymptotic shrinkage ratio V/V(max) on the rate of temperature change exists. The composite capsules are stable under long-term storage in both dried and hydrated states and easily re-dispersible in water. PMID:20304409

  8. Microstructure investigations of hcp phase CoPt thin films with high coercivity

    SciTech Connect

    Yang, Y.; Varghese, B.; Tan, H. K.; Wong, S. K.; Piramanayagam, S. N.

    2014-02-28

    CoPt films have been grown in the past with a high anisotropy in L1{sub 1} or L1{sub 0} phase, and a high coercivity is observed only in L1{sub 0} CoPt films. Recently, we have grown CoPt films which exhibited a high coercivity without exhibiting an ordered phase. In this study, high resolution transmission electron microscopy (HRTEM) investigations have been carried out to understand the strong thickness and deposition pressure dependent magnetic properties. HRTEM studies revealed the formation of an initial growth layer in a metastable hexagonal (hcp) CoPt with high anisotropy. This phase is believed to be aided by the heteroepitaxial growth on Ru as well as the formation of Ru-doped CoPt phase. As the films grew thicker, transformation from hcp phase to an energetically favourable face-centered cubic (fcc) phase was observed. Stacking faults were found predominantly at the hcp-fcc transformation region of the CoPt film. The higher coercivity of thinner CoPt film is attributed to relatively less fcc fraction, less stacking faults, and to the isolated grain structure of these films compared to the thicker films.

  9. Microstructural investigation of the weld HAZ in a modified 800H alloy

    SciTech Connect

    Lundin, C.D.; Qiao, C.Y.P. . Materials Science and Engineering)

    1994-07-01

    Detailed metallographic investigations of Gleeble simulated HAZ samples in modified 800H were performed. Precipitate dissolution, gain growth, HAZ liquation and the hardness degradation behavior in modified 800H were also addressed. Results of this study agree with previous HAZ hot cracking and softening behavior evaluations. Modified 800H is one of the newly developed high-temperature alloys for applications in coal-fired power generating systems (Swindeman, 1991). Modified 800H possesses a greater creep and higher temperature tensile strength as compared to standard alloy 800 and conventional austenitic stainless steels. To achieve excellent creep and high-temperature tensile strength a thermomechanical treatment is applied during alloy fabrication (5--10% cold work). Therefore, grain growth, recrystallization, and precipitate dissolution and redistribution will occur in the weld HAZ during fabrication. Thus, both mechanical and metallurgical degradation may occur in the HAZ. Additionally, metallurgical reactions adjacent to the fusion boundary, including a partially melted region and constitutional liquation, may occur and influence the hot cracking resistance.

  10. Investigation on Strength Development in RBI Grade 81 Stabilized Serian Soil with Microstructural Considerations

    NASA Astrophysics Data System (ADS)

    Taib, S. N. L.; Striprabu, S.; Ahmad, F.; Charmaine, H. J.; Patricia, N. E.

    2016-07-01

    The aim of the research is to investigate the strength development of stabilised local Serian soil with RBI Grade 81 a chemical additive to enhance soil properties in term of strength. Serian is a town which is located about 60 km from Kuching city where the soil was chosen to be treated in this study. The soil sample was mixed with 2%, 6% and 8% of RBI Grade 81 by weight of dry soil and added with water at optimum water content (OWC) to replicate field site conditions. The modified samples were cured in ambient air for 7, 14, and 28 days. Scanning Electron Microscope (SEM) was utilized to analyze surface morphology of the stabilized soil specifically on the formation of bonding between soils and RBI 81 particles. The experimental results show the highest average peak UCS strength achieved was 1071.6 kN/m2 at 14 day curing period with 8% of RBI Grade 81 which is higher than the untreated control sample which was 179.946 kN/m2, showing increment by almost six folds. Hence the RBI 81 stabilization technique enhances the local soil structure by improving the inter-cluster bonding, reducing pore spaces in the soil and subsequently increasing the soil's strength.

  11. A network of disdrometers to investigate the variability of the microstructure of precipitation at the radar pixel scale

    NASA Astrophysics Data System (ADS)

    Jaffrain, J.; Berne, A.; Studzinski, A.; Pantillon, F.

    2009-04-01

    The microstructure of precipitation, in particular the raindrop size distribution (DSD hereafter), is of primary importance for quantitative interpretation of weather radar measurements. As an indirect measurement, radar rain rate estimation depends on the DSD via the Z-R relationship. As precipitation, DSD is characterized by a strong variability in space and time. In order to investigate the effect of the DSD variability at the pixel scale on radar rain rate estimation, a network of disdrometers has been set up. It consists of about 15 optical disdrometers PARSIVEL that are autonomous in terms of power supply (battery, solar panel) as well as data storage (data logger). The network is designed for real-time access and monitoring of data, favoring remote communication (radio modem and GPRS) for data transfer. The network is deployed on EPFL campus over a typical operational radar pixel (~ 1Ã-1 km) since late 2008. The first analyses highlight the uncertainty associated with DSD measurements as well as the variability of the DSD of precipitation over 1 km2.

  12. Dilatometric Analysis and Microstructural Investigation of the Sintering Mechanisms of Blended Elemental Ti-6Al-4V Powders

    NASA Astrophysics Data System (ADS)

    Kim, Youngmoo; Lee, Junho; Lee, Bin; Ryu, Ho Jin; Hong, Soon Hyung

    2016-09-01

    The densification behavior of mixed Ti and Al/V master alloy powders for Ti-6Al-4V was investigated by a series of dilatometry tests to measure the shrinkage of the samples with the sintering temperature. The corresponding microstructural changes were examined under various sintering conditions with optical microscopy, energy-dispersive spectroscopy, and X-ray diffraction analyses. From these results, the consolidation of the mixed powders was divided into two domains: (i) sintering densification and solute homogenization of Ti and Al/V master alloy particles below 1293 K (1020 °C), and (ii) densification of Ti alloy phases above 1293 K (1020 °C). In the lower temperature region, the inter-diffusion between Ti and Al/V master alloy particles dominated the sintering of the mixed powders because the chemical gradient between two types of particles outweighed the surface energy reduction. Following chemical homogenization, the densification induced the shrinkage of the Ti alloy phases to reduce their surface energies. These tendencies are also supported by the density and grain size variations of the sintered specimens with temperature. The apparent activation energies of the sintering and grain growth for Ti alloy particles are 85.91 ± 6.93 and 37.33 kJ/mol, respectively, similar to or slightly lower than those of pure Ti particles. The difference was attributed to the slower self-diffusion of Ti resulting from the alloying of Al and V into in the Ti matrix.

  13. Dilatometric Analysis and Microstructural Investigation of the Sintering Mechanisms of Blended Elemental Ti-6Al-4V Powders

    NASA Astrophysics Data System (ADS)

    Kim, Youngmoo; Lee, Junho; Lee, Bin; Ryu, Ho Jin; Hong, Soon Hyung

    2016-06-01

    The densification behavior of mixed Ti and Al/V master alloy powders for Ti-6Al-4V was investigated by a series of dilatometry tests to measure the shrinkage of the samples with the sintering temperature. The corresponding microstructural changes were examined under various sintering conditions with optical microscopy, energy-dispersive spectroscopy, and X-ray diffraction analyses. From these results, the consolidation of the mixed powders was divided into two domains: (i) sintering densification and solute homogenization of Ti and Al/V master alloy particles below 1293 K (1020 °C), and (ii) densification of Ti alloy phases above 1293 K (1020 °C). In the lower temperature region, the inter-diffusion between Ti and Al/V master alloy particles dominated the sintering of the mixed powders because the chemical gradient between two types of particles outweighed the surface energy reduction. Following chemical homogenization, the densification induced the shrinkage of the Ti alloy phases to reduce their surface energies. These tendencies are also supported by the density and grain size variations of the sintered specimens with temperature. The apparent activation energies of the sintering and grain growth for Ti alloy particles are 85.91 ± 6.93 and 37.33 kJ/mol, respectively, similar to or slightly lower than those of pure Ti particles. The difference was attributed to the slower self-diffusion of Ti resulting from the alloying of Al and V into in the Ti matrix.

  14. Investigation of phase composition and nanoscale microstructure of high-energy ball-milled MgCu sample.

    PubMed

    Ma, Zongqing; Liu, Yongchang; Yu, Liming; Cai, Qi

    2012-01-01

    The ball milling technique has been successfully applied to the synthesis of various materials such as equilibrium intermetallic phases, amorphous compounds, nanocrystalline materials, or metastable crystalline phases. However, how the phase composition and nanoscale microstructure evolute during ball milling in various materials is still controversial due to the complex mechanism of ball milling, especially in the field of solid-state amorphization caused by ball milling. In the present work, the phase evolution during the high-energy ball milling process of the Mg and Cu (atomic ratio is 1:1) mixed powder was investigated. It was found that Mg firstly reacts with Cu, forming the Mg2Cu alloy in the primary stage of ball milling. As the milling time increases, the diffracted peaks of Mg2Cu and Cu gradually disappear, and only a broad halo peak can be observed in the X-ray diffraction pattern of the final 18-h milled sample. As for this halo peak, lots of previous studies suggested that it originated from the amorphous phase formed during the ball milling. Here, a different opinion that this halo peak results from the very small size of crystals is proposed: As the ball milling time increases, the sizes of Mg2Cu and Cu crystals become smaller and smaller, so the diffracted peaks of Mg2Cu and Cu become broader and broader and result in their overlap between 39° and 45°, at last forming the amorphous-like halo peak. In order to determine the origin of this halo peak, microstructure observation and annealing experiment on the milled sample were carried out. In the transmission electron microscopy dark-field image of the milled sample, lots of very small nanocrystals (below 20 nm) identified as Mg2Cu and Cu were found. Moreover, in the differential scanning calorimetry curve of the milled sample during the annealing process, no obvious exothermic peak corresponding to the crystallization of amorphous phase is observed. All the above results confirm that the broad

  15. Dysgraphia in dementia: a systematic investigation of graphemic buffer features in a case series.

    PubMed

    Haslam, Catherine; Kay, Janice; Tree, Jeremy; Baron, Rachel

    2009-08-01

    In this paper we report findings from a systematic investigation of spelling performance in three patients - PR, RH and AC - who despite their different medical diagnoses showed a very consistent pattern of dysgraphia, more typical of graphemic buffer disorder. Systematic investigation of the features characteristic of this disorder in Study 1 confirmed the presence of length effects in spelling, classic errors (i.e., letter substitution, omission, addition, transposition), a bow-shaped curve in the serial position of errors and consistency in substitution of consonants and vowels. However, in addition to this clear pattern of graphemic buffer impairment, evidence of regularity effects and phonologically plausible errors in spelling raised questions about the integrity of the lexical spelling route in each case. A second study was conducted, using a word and non-word immediate delay copy task, in an attempt to minimise the influence of orthographic representations on written output. Persistence of graphemic buffer errors would suggest an additional, independent source of damage. Two patients, PR and AC, took part and in both cases symptoms of graphemic buffer disorder persisted. Together, these findings suggest that damage to the graphemic buffer may be more common than currently suggested in the literature. PMID:19370478

  16. Cicada Wing Surface Topography: An Investigation into the Bactericidal Properties of Nanostructural Features.

    PubMed

    Kelleher, S M; Habimana, O; Lawler, J; O' Reilly, B; Daniels, S; Casey, E; Cowley, A

    2016-06-22

    Recently, the surface of the wings of the Psaltoda claripennis cicada species has been shown to possess bactericidal properties and it has been suggested that the nanostructure present on the wings was responsible for the bacterial death. We have studied the surface-based nanostructure and bactericidal activity of the wings of three different cicadas (Megapomponia intermedia, Ayuthia spectabile and Cryptotympana aguila) in order to correlate the relationship between the observed surface topographical features and their bactericidal properties. Atomic force microscopy and scanning electron microscopy performed in this study revealed that the tested wing species contained a highly uniform, nanopillar structure on the surface. The bactericidal properties of the cicada wings were investigated by assessing the viability of autofluorescent Pseudomonas fluorescens cells following static adhesion assays and targeted dead/live fluorescence staining through direct microscopic counting methods. These experiments revealed a 20-25% bacterial surface coverage on all tested wing species; however, significant bactericidal properties were observed in the M. intermedia and C. aguila species as revealed by the high dead:live cell ratio on their surfaces. The combined results suggest a strong correlation between the bactericidal properties of the wings and the scale of the nanotopography present on the different wing surfaces. PMID:26551558

  17. Three-dimensional microstructural characterization of bulk plutonium and uranium metals using focused ion beam technique

    NASA Astrophysics Data System (ADS)

    Chung, Brandon W.; Erler, Robert G.; Teslich, Nick E.

    2016-05-01

    Nuclear forensics requires accurate quantification of discriminating microstructural characteristics of the bulk nuclear material to identify its process history and provenance. Conventional metallographic preparation techniques for bulk plutonium (Pu) and uranium (U) metals are limited to providing information in two-dimension (2D) and do not allow for obtaining depth profile of the material. In this contribution, use of dual-beam focused ion-beam/scanning electron microscopy (FIB-SEM) to investigate the internal microstructure of bulk Pu and U metals is demonstrated. Our results demonstrate that the dual-beam methodology optimally elucidate microstructural features without preparation artifacts, and the three-dimensional (3D) characterization of inner microstructures can reveal salient microstructural features that cannot be observed from conventional metallographic techniques. Examples are shown to demonstrate the benefit of FIB-SEM in improving microstructural characterization of microscopic inclusions, particularly with respect to nuclear forensics.

  18. Performing effective feature selection by investigating the deep structure of the data

    SciTech Connect

    Richeldi, M.; Lanzi, P.L.

    1996-12-31

    This paper introduces ADHOC (Automatic Discoverer of Fligher-Order Correlation), an algorithm that combines the advantages of both filter and feedback models to enhance the understanding of the given data and to increase the efficiency of the feature selection process. ADHOC partitions the observed features into a number of groups, called factors, that reflect the major dimensions of the phenomenon under consideration. The set of learned factors define the starting point of the search of the best performing feature subset. A genetic algorithm is used to explore the feature space originated by the factors and to determine the set of most informative feature configurations. The feature subset evaluation function is the performance of the induction algorithm. This approach offers three main advantages: (i) the likelihood of selecting good performing features grows; (ii) the complexity of search diminishes consistently; (iii) the possibility of selecting a bad feature subset due to overfitting problems decreases. Extensive experiments on real-world data have been conducted to demonstrate the effectiveness of ADHOC as data reduction technique as well as feature selection method.

  19. Primary combination of phase-field and discrete dislocation dynamics methods for investigating athermal plastic deformation in various realistic Ni-base single crystal superalloy microstructures

    NASA Astrophysics Data System (ADS)

    Gao, Siwen; Rajendran, Mohan Kumar; Fivel, Marc; Ma, Anxin; Shchyglo, Oleg; Hartmaier, Alexander; Steinbach, Ingo

    2015-10-01

    Three-dimensional discrete dislocation dynamics (DDD) simulations in combination with the phase-field method are performed to investigate the influence of different realistic Ni-base single crystal superalloy microstructures with the same volume fraction of {γ\\prime} precipitates on plastic deformation at room temperature. The phase-field method is used to generate realistic microstructures as the boundary conditions for DDD simulations in which a constant high uniaxial tensile load is applied along different crystallographic directions. In addition, the lattice mismatch between the γ and {γ\\prime} phases is taken into account as a source of internal stresses. Due to the high antiphase boundary energy and the rare formation of superdislocations, precipitate cutting is not observed in the present simulations. Therefore, the plastic deformation is mainly caused by dislocation motion in γ matrix channels. From a comparison of the macroscopic mechanical response and the dislocation evolution for different microstructures in each loading direction, we found that, for a given {γ\\prime} phase volume fraction, the optimal microstructure should possess narrow and homogeneous γ matrix channels.

  20. Electron Backscattered Diffraction Analysis Of Narrow Copper Interconnects In Cross-View To Investigate Scale Effect On Microstructure

    SciTech Connect

    Galand, Romain; Clement, Laurent; Waltz, Patrice; Wouters, Yves

    2010-11-24

    In this article, we propose to use Electron Backscattered Diffraction (EBSD) to characterize microstructure of copper interconnects of thin metal level in top view and cross view. These two views give very complementary information about microstructure of copper and thus about recrystallization of copper during annealing. Moreover, for minimum width, as interconnect is two times thicker than wide; It will be easier to analyze smaller interconnect of 45 nm node technology in cross-section. We look for evolution of texture and microstructure of copper with line width in top view and in cross view. We highlight the presence of two recrystallization mechanisms and also the fact that transition from one to the other is progressive with competition of both mechanisms.

  1. Judging a Book by Its Cover: An Investigation of Peritextual Features in Caldecott Award Books

    ERIC Educational Resources Information Center

    Martinez, Miriam; Stier, Catherine; Falcon, Lori

    2016-01-01

    While scholars have recognized the meaning making potential offered by the peritext of picturebooks, there has previously been only limited research on the nature of peritextual features. This content analysis focused on the ways in which various peritextual features (dust jackets, beginning endpapers, illustrations before title page, title pages,…

  2. Explosive crystallization of PZT microstructures by femtosecond infrared radiation

    NASA Astrophysics Data System (ADS)

    Elshin, A. S.; Firsova, N. Yu; Emelianov, V. I.; Pronin, I. P.; Senkevich, S. V.; Zhigalina, O. M.; Mishina, E. D.; Sigov, A. S.

    2015-12-01

    The features of microstructure crystallization into perovskite phase in lead zirconate titanate film by femtosecond laser radiation of near-infrared range were discussed. In-situ crystallization kinetics by method of second harmonic generation (SHG) was studied. The presence of several types of crystallization was shown, including ultra-fast (explosive) crystallization occurring immediately after the start of exposure, and slow (self-sustaining) crystallization, occurring after termination of exposure. The advantage of the second-harmonic generation microscopy for the study of annealed microstructures was shown. The morphology of microstructures was investigated by transmission electron microscopy (TEM).

  3. Investigation of optimal feature value set in false positive reduction process for automated abdominal lymph node detection method

    NASA Astrophysics Data System (ADS)

    Nakamura, Yoshihiko; Nimura, Yukitaka; Kitasaka, Takayuki; Mizuno, Shinji; Furukawa, Kazuhiro; Goto, Hidemi; Fujiwara, Michitaka; Misawa, Kazunari; Ito, Masaaki; Nawano, Shigeru; Mori, Kensaku

    2015-03-01

    This paper presents an investigation of optimal feature value set in false positive reduction process for the automated method of enlarged abdominal lymph node detection. We have developed the automated abdominal lymph node detection method to aid for surgical planning. Because it is important to understand the location and the structure of an enlarged lymph node in order to make a suitable surgical plan. However, our previous method was not able to obtain the suitable feature value set. This method was able to detect 71.6% of the lymph nodes with 12.5 FPs per case. In this paper, we investigate the optimal feature value set in the false positive reduction process to improve the method for automated abdominal lymph node detection. By applying our improved method by using the optimal feature value set to 28 cases of abdominal 3D CT images, we detected about 74.7% of the abdominal lymph nodes with 11.8 FPs/case.

  4. Investigation of context, soft spatial, and spatial frequency domain features for buried explosive hazard detection in FL-LWIR

    NASA Astrophysics Data System (ADS)

    Price, Stanton R.; Anderson, Derek T.; Stone, Kevin; Keller, James M.

    2014-05-01

    It is well-known that a pattern recognition system is only as good as the features it is built upon. In the fields of image processing and computer vision, we have numerous spatial domain and spatial-frequency domain features to extract characteristics of imagery according to its color, shape and texture. However, these approaches extract information across a local neighborhood, or region of interest, which for target detection contains both object(s) of interest and background (surrounding context). A goal of this research is to filter out as much task irrelevant information as possible, e.g., tire tracks, surface texture, etc., to allow a system to place more emphasis on image features in spatial regions that likely belong to the object(s) of interest. Herein, we outline a procedure coined soft feature extraction to refine the focus of spatial domain features. This idea is demonstrated in the context of an explosive hazards detection system using forward looking infrared imagery. We also investigate different ways to spatially contextualize and calculate mathematical features from shearlet filtered candidate image chips. Furthermore, we investigate localization strategies in relation to different ways of grouping image features to reduce the false alarm rate. Performance is explored in the context of receiver operating characteristic curves on data from a U.S. Army test site that contains multiple target and clutter types, burial depths, and times of day.

  5. An investigation of the microstructure and mechanical properties of electrochemically coated Ag(4)Sn dental alloy particles condensed in vitro

    NASA Astrophysics Data System (ADS)

    Marquez, Jose Antonio

    As part of the ongoing scientific effort to develop a new amalgam-like material without mercury, a team of metallurgists and electrochemists at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, announced in 1993 the development of a new Ag-Sn dental alloy system without mercury that sought to replace conventional dental amalgams. They used spherical Ag3Sn and Ag4Sn intermetallic dental alloy particles, commonly used in conventional dental alloys, and coated them with electrodeposited silver with newly-developed electrolytic and immersion techniques. The particles had relatively pure silver coatings that were closely adherent to the intermetalfic cores. These silver-coated particles, due to silver's plasticity at room temperature, were condensed into PlexiglasRTM molds with the aid of an acidic surface activating solution (HBF4) and a mechanical condensing device, producing a metal-matrix composite with Ag3,4Sn filler particles surrounded by a cold-welded silver matrix. Since silver strain hardens rather easily, the layers had to be condensed in less than 0.5 mm increments to obtain a dense structure. Mechanical testing at NIST produced compressive strength values equal to or greater than those of conventional dental amalgams. Because of its potential for eliminating mercury as a constituent in dental amalgam, this material created a stir in dental circles when first developed and conceivably could prove to be a major breakthrough in the field of dental restoratives. To date, the chief impediments to its approval for human clinical applications by the Food and Drug Administration are the potentially-toxic surface activating solution used for oxide reduction, and the high condensation pressures needed for cold welding because of the tendency for silver to strain harden. In this related study, the author, who has practiced general dentistry for 25 years, evaluates some of the mechanical and microstructural properties of these

  6. No place for /h/: an ERP investigation of English fricative place features

    PubMed Central

    Schluter, Kevin; Politzer-Ahles, Stephen; Almeida, Diogo

    2016-01-01

    ABSTRACT The representational format of speech units in long-term memory is a topic of debate. We present novel event-related brain potential evidence from the Mismatch Negativity (MMN) paradigm that is compatible with abstract, non-redundant feature-based models like the Featurally Underspecified Lexicon (FUL). First, we show that the fricatives /s/ and /f/ display an asymmetric pattern of MMN responses, which is predicted if /f/ has a fully specified place of articulation ([Labial]) but /s/ does not ([Coronal], which is lexically underspecified). Second, we show that when /s/ and /h/ are contrasted, no such asymmetric MMN pattern occurs. The lack of asymmetry suggests both that (i) oral and laryngeal articulators are represented distinctly and that (ii) /h/ has no oral place of articulation in long-term memory. The lack of asymmetry between /s/ and /h/ is also in-line with traditional feature-geometric models of lexical representations. PMID:27366758

  7. Experimental investigations and multiscale modeling of the microstructure evolution and the mechanical properties of a ferritic steel grade during the production process

    NASA Astrophysics Data System (ADS)

    Helm, Dirk; Baiker, Maria; Bienger, Pierre

    2013-05-01

    The process chain for sheet metals after casting to produce components made of semi-finished products is complex and the resulting mechanical properties of the produced material depend strongly on the evolution of the microstructure. After casting, a typical process chain consists of hot rolling, cold rolling, annealing, skin pass rolling, and sheet metal forming. In order to represent the microstructure evolution in an adequate way, a multiscale modeling concept is applied for the process steps cold rolling, annealing, and sheet metal forming. In this Integrated Computational Materials Engineering (ICME) concept, the strong microstructure evolution during the production of semi-finished products is modeled by using crystal plasticity for the representation of the cold rolling process and a cellular automaton is incorporated to model the annealing procedure. In both cases, only the microstructure in an adequate unit cell is considered. For sheet metal forming, the whole component has to be simulated together with the interaction between workpiece and the forming tools in order to solve technological problems like springback. For this purpose, classical macroscopic plasticity models have been applied. To connect the different length scales of the modeling approaches, a scale transition on the basis of numerical homogenization is introduced for the determination of the mechanical properties like the multi-axial yield behavior. These information are required to virtually determine the type of the macroscopic plasticity model, the material parameters of the plasticity model, and to simulate sheet metal forming processes. In the article, the different modeling approaches are compared step by step with experimental investigations in order to prove the predictability of each modeling technique.

  8. Toward Automated Multi-Trait Scoring of Essays: Investigating Links among Holistic, Analytic, and Text Feature Scores

    ERIC Educational Resources Information Center

    Lee, Yong-Won; Gentile, Claudia; Kantor, Robert

    2010-01-01

    The main purpose of the study was to investigate the distinctness and reliability of analytic (or multi-trait) rating dimensions and their relationships to holistic scores and "e-rater"[R] essay feature variables in the context of the TOEFL[R] computer-based test (TOEFL CBT) writing assessment. Data analyzed in the study were holistic and…

  9. An Investigation of the 3-μm Feature in M-Type Asteroids

    NASA Astrophysics Data System (ADS)

    Landsman, Zoe A.; Campins, H.; Hargrove, K.; Pinilla-Alonso, N.; Emery, J.; Ziffer, J.

    2013-10-01

    The M-type asteroids had originally been interpreted as the disrupted iron cores of differentiated bodies by spectral analogy with the NiFe meteorites. More detailed studies have since indicated a range of compositions. In particular, the presence of a 3-µm feature, diagnostic of hydration, detected in more than 35% of surveyed M-type asteroids (Jones et al. 1990, Rivkin et al. 1995, 2000) has challenged the notion that these bodies are all metallic. Spectroscopy in the 0.8 - 2.5 µm region has revealed absorption features due to mafic silicates and hydroxides or phyllosilicates (Fornasier et al. 2010, Hardersen et al. 2006, 2010, Ockert-Bell et al. 2010). Radar studies have shown that most M-types are not likely to be iron cores, but they typically have a higher metal content than average (Shepard et al. 2010). Taken together, these results paint a fairly confounding picture of the M-type asteroids. While several interpretations have been suggested, more work is needed to clarify the mineralogy of these bodies. We have started a new spectroscopic study of the M asteroids in the 2 - 4 µm region. We seek to characterize the shape, band center, and band depth of the 3-µm feature where it is present, as these measures are indicative of the type and extent of hydration present on asteroids (Lebofsky et al. 1985, Rivkin et al. 2002, Takir & Emery 2012, Volguardsen et al. 2007). With this work, we hope to shed new light on the origin of hydration on M asteroids and its context within their mineralogy and thermal evolution. In July 2013, we obtained 2 - 4 µm spectra for 69 Hesperia, 136 Austria, and 261 Prymno with the SpeX at NASA’s IRTF, and are in the process of reducing the data. We have also obtained 0.8 - 2.0 µm data for 261 Prymno using the NICS at the TNG in February 2013. We report the presence of an absorption feature near 0.9 µm in Prymno’s spectrum, indicating a partially silicate composition. Based on spectral, physical and orbital similarities to

  10. Investigations of the electron field emission properties and microstructure correlation in sulfur-incorporated nanocrystalline carbon thin films

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Weiner, B. R.; Morell, G.

    2002-06-01

    Results are reported on the electron field emission properties of sulfur (S)-incorporated nanocrystalline carbon (n-C:S) thin films grown on molybdenum (Mo) substrates by hot-filament chemical vapor deposition (HFCVD) technique. In addition to the conventionally used methane (CH4) as carbon precursor with high hydrogen (H2) dilution, hydrogen sulfide-hydrogen (H2)S/H2 premix gas was used for sulfur incorporation. The field emission properties for the S-incorporated films were investigated systematically as a function of substrate temperature (TS) and sulfur concentration. Lowest turn-on field achieved was observed at around 4.0 V/mum for the n-C:S sample grown at TS of 900 degC with 500 ppm of H2S. These results are compared with those films grown without sulfur (n-C) at a particular TS. The turn-on field was found to be almost half for the S-assisted film thus demonstrating the effect of sulfur addition to the chemical vapor deposition process. An inverse relation between turn-on field (EC), growth temperature and sulfur concentration was found. The S incorporation also causes significant microstructural changes, as characterized with non-destructive complementary ex situ techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy (RS). S-assisted films show relatively smoother and finer-grained surfaces than those grown without it. These findings are discussed in terms of the dual role of sulfur in enhancing the field emission properties by controlling the sp2 C cluster size and introducing substantial structural defects through its incorporation. The in-plane correlation length (La) of sp2 C cluster was determined from the intensity ratio of the D- and G-bands I(D)/I(G) in the visible RS as a function of deposition temperature and sulfur concentration using a phenomenological model. The turn-on field was found to decrease with increasing sp2 C cluster size in general ranging from 0.8 to 1.4 nm. The films having sp2 C

  11. Investigating the role of content knowledge, argumentation, and situational features to support genetics literacy

    NASA Astrophysics Data System (ADS)

    Shea, Nicole Anne

    Science curriculum is often used as a means to train students as future scientists with less emphasis placed on preparing students to reason about issues they may encounter in their daily lives (Feinstein, Allen, & Jenkins, 2013; Roth & Barton, 2004). The general public is required to think scientifically to some degree throughout their life and often across a variety of issues. From an empirical standpoint, we do not have a robust understanding of what scientific knowledge the public finds useful for reasoning about socio-scientific issues in their everyday lives (Feinstein, 2011). We also know very little about how the situational features of an issue influences reasoning strategy (i.e., the use of knowledge to generate arguments). Rapid advances in science - particularly in genetics - increasingly challenge the public to reason about socio-scientific issues. This raises questions about the public's ability to participate knowledgeably in socio-scientific debates, and to provide informed consent for a variety of novel scientific procedures. This dissertation aims to answer the questions: How do individuals use their genetic content knowledge to reason about authentic issues they may encounter in their daily lives? Individuals' scientific knowledge is a critical aspect of scientific literacy, but what scientific literacy looks like in practice as individuals use their content knowledge to reason about issues comprised of different situational features is still unclear. The purpose of this dissertation is to explore what knowledge is actually used by individuals to generate and support arguments about a variety of socio-scientific issues, and how the features of those issues influences reasoning strategy. Three studies were conducted to answer questions reflecting this purpose. Findings from this dissertation provide important insights into what scientific literacy looks like in practice.

  12. An investigation of the high-temperature and solidification microstructures of PH 13-8 Mo stainless steel

    NASA Astrophysics Data System (ADS)

    Cieslak, M. J.; Hills, C. R.; Hlava, P. F.; David, S. A.

    1990-09-01

    Differential thermal analysis (DTA), high-temperature water-quench (WQ) experiments, and optical and electron microscopy were used to establish the near-solidus and solidification microstructures in PH 13-8 Mo. On heating at a rate of 0. 33 °C/s, this alloy begins to transform from austenite to δ-ferrite at ≈1350 °C. Transformation is complete by ≈1435 °C. The solidus is reached at ≈1447 °C, and the liquidus is ≈1493 °C. On cooling from the liquid state at a rate of 0. 33 °C/s, solidification is completed as δ-ferrite with subsequent transformation to austenite beginning in the solid state at ≈1364 °C. Insufficient time at temperature is available for complete transformation and the resulting room-temperature microstructure consists of matrix martensite (derived from the shear decomposition of the austenite) and residual δ-ferrite. The residual δ-ferrite in the DTA sample is enriched in Cr (≈16 wt pct), Mo (≈4 wt pct), and Al (≈1. 5 wt pct) and depleted in Ni (≈4 wt pct) relative to the martensite (≈12. 5 wt pct Cr, ≈2 wt pct Mo, ≈1 wt pct Al, ≈9 wt pct Ni). Solid-state transformation of δ σ γ was found to be quench-rate sensitive with large grain, fully ferritic microstructures undergoing a massive transformation as a result of water quenching, while a diffusionally controlled Widmanstätten structure was produced in air-cooled samples.

  13. Submicron scale 3D investigation of kelyphyites after garnet: thermodynamics, crystallographic orientation, microstructure evolution and fluid-rock interactions

    NASA Astrophysics Data System (ADS)

    Dégi, Júlia; Török, Kálmán; Németh, Bianca; Rhede, Dieter; Takács, Ágnes; Habler, Gerlinde; Abart, Rainer

    2016-04-01

    Complex kelyphitic rims after garnet were studied in a lower crustal mafic granulite xenolith from the Bakony-Balaton Highland Volcanic Field, W-Hungary. The xenolith is dominated by a garnet granulite mineral assemblage equilibrated at 900 ° C, 1.4 GPa within the overthickened orogenic root of the Alps. Garnet breakdown was initiated during the extension of the Pannonian Basin and remained continuous until the xenoliths reached the surface. This resulted in the formation of various microstructural domains within the kelyphitic rims which were distinguished to three main types: fine-grained symplectites, recrystallized symplectites and cyrstallized melts. Fine-grained symplectites are the products of isochemical breakdown of garnet to pure anorthite, Al-orthopyroxene and hercynitic spinel. Nanoscale topography built up by curved chains of humps on the garnet surface showing regular spatial distribution is observed at the reaction front in 3D reconstructions. These patterns follow the contours of anorthites nucleating at the reaction front. This suggests that diffusion-controlled material transfer in solid state together with surface energy minimization determines symplectite microstructure. The latter leads to continuous isochemical coarsening getting further from the reaction front. Slight increase of Na and Ti-content in fine-grained symplectites is associated with sudden changes in 3D microstructure reflecting the effect of aquaeous fluids infiltrating to the reaction rim. A similar aquaeous fluid may have induced the formation of nearly isochemical melting and in situ recrystallization of the symplectites to form recrystallized symplectites. Some of these remained pristine, while some experienced ductile deformation and re-melting due to a reaction with an external melt in the lower crust. Well-crystallized melt pockets consisting of complexly zoned pyroxene, spinel and plagioclase grains were formed around 1000 ° C in this stage. Following this, interaction

  14. Jackpot Expiry: An Experimental Investigation of a New EGM Player-Protection Feature.

    PubMed

    Rockloff, Matthew J; Donaldson, Phillip; Browne, Matthew

    2015-12-01

    Given the evidence for the motivating influence of electronic gaming machines (EGM) jackpots on intensifying player behaviour (Rockloff and Hing in J Gambl Stud 1-7, 2013), there is good reason to explore consumer-protection features. Jackpot Expiry is a potential feature of a mandatory pre-commitment system or player identification system (e.g., loyalty program) whereby the availability of jackpots expires after a fixed interval of play. One hundred and thirty volunteers (males = 56, females = 74) played a laptop-simulated EGM with a starting $20 real-money stake. In the test condition, players were shown a "relevant" message stating that the promised jackpot had expired and could no longer be won by the participant (after the 20th trial). In the irrelevant message condition a similar pop-up message simply said to push the button to continue. Lastly, a control condition had no pop-up message about the jackpot expiring. The results showed that betting speeds (one indicator of gambling intensity) were significantly slowed by the relevant 'expiry' message. Most importantly, all wagers past the 20th trial were programmed as losses. Player receiving the 'expiry' message for a cash jackpot quit with significantly more money remaining on the machine. Therefore, jackpot expiry was effective in limiting player losses, while there was no evidence that jackpot expiry reduced self-rated player enjoyment of the simulated EGM experience. PMID:24871299

  15. Investigation of the microstructure and mineralogical composition of urinary calculi fragments by synchrotron radiation X-ray microtomography: a feasibility study.

    PubMed

    Kaiser, Jozef; Holá, Markéta; Galiová, Michaela; Novotný, Karel; Kanický, Viktor; Martinec, Petr; Sčučka, Jiří; Brun, Francesco; Sodini, Nicola; Tromba, Giuliana; Mancini, Lucia; Kořistková, Tamara

    2011-08-01

    The outcomes from the feasibility study on utilization of synchrotron radiation X-ray microtomography (SR-μCT) to investigate the texture and the quantitative mineralogical composition of selected calcium oxalate-based urinary calculi fragments are presented. The comparison of the results obtained by SR-μCT analysis with those derived from current standard analytical approaches is provided. SR-μCT is proved as a potential effective technique for determination of texture, 3D microstructure, and composition of kidney stones. PMID:21161649

  16. Effect of microstructure on the properties of MoSi{sub 2} and its composites

    SciTech Connect

    Newman, A.; Jewett, T.; Sampath, S.; Herman, H.

    1997-12-31

    The effects of processing on the microstructure and properties of MoSi{sub 2} are examined. A diverse array of samples, processed through a variety of means, were investigated for their microstructural features and indentation fracture behavior. Results from this study indicate that a finely dispersed secondary phase enhances tortuous crack paths, crack branching, and microcracking, thereby improving fracture toughness. The effects of substitutional alloying (Re, Al) and composite additions (SiC) have also been investigated.

  17. Investigation of the clinical features in filamentary keratitis in Hangzhou, east of China

    PubMed Central

    Chen, Siming; Ruan, Yimeng; Jin, Xiuming

    2016-01-01

    Abstract Filamentary keratitis (FK) is a chronic and recurrent disorder of the cornea. FK is reportedly associated with various kinds of ocular surface diseases or conditions. Until now, there have been lacks of studies based on quantitative sample analysis concerning FK incidence regularity and inducement characteristics at different ages. This was a retrospective study of 147 patients (162 eyes) with FK who had been continuously and completely recorded from August 2012 to August 2015 at the Second Affiliated Hospital of Zhejiang University in Hangzhou, east of China. Our results suggest that the causative factors of FK varied at different ages and the distribution of filaments on the corneal surface was also diverse with different inducements. By exploring the frequency and clinical features of FK, we believe that the findings from our research will be clinically significant and aid in the early prevention and treatment guidance of the disease. PMID:27583881

  18. Search for DNA conformational features for functional sites. Investigation of the TATA box

    SciTech Connect

    Ponomarenko, M.P.; Ponomarenko, J.V.; Kel, A.E.; Kolchanov, N.A.

    1996-12-31

    A method for searching for DNA conformational features significant for functional sites is developed. The method uses helical angles averaged for known X-ray structures. Nucleotide sequences are assigned mean angles in a given region. Choice of the significant angles is based on their capabilities to discriminate functional sites from random sequences. The yeast, invertebrate, and vertebrate TATA boxes are analyzed using this method. Regions neighboring the TATA boxes are found to have smaller helical twist and roll angles. The results agree with the experimental data on Dickerson-Drew dodecamers. There is a significant decrease in the length of a small roll angle region with increasing complexity of taxon organization. 28 refs., 3 figs., 3 tabs.

  19. Investigation of the clinical features in filamentary keratitis in Hangzhou, east of China.

    PubMed

    Chen, Siming; Ruan, Yimeng; Jin, Xiuming

    2016-08-01

    Filamentary keratitis (FK) is a chronic and recurrent disorder of the cornea. FK is reportedly associated with various kinds of ocular surface diseases or conditions. Until now, there have been lacks of studies based on quantitative sample analysis concerning FK incidence regularity and inducement characteristics at different ages. This was a retrospective study of 147 patients (162 eyes) with FK who had been continuously and completely recorded from August 2012 to August 2015 at the Second Affiliated Hospital of Zhejiang University in Hangzhou, east of China. Our results suggest that the causative factors of FK varied at different ages and the distribution of filaments on the corneal surface was also diverse with different inducements.By exploring the frequency and clinical features of FK, we believe that the findings from our research will be clinically significant and aid in the early prevention and treatment guidance of the disease. PMID:27583881

  20. Investigating chaotic features in solar radiation over a tropical station using recurrence quantification analysis

    NASA Astrophysics Data System (ADS)

    Ogunjo, Samuel T.; Adediji, Adekunle T.; Dada, Joseph B.

    2015-09-01

    The use of solar energy for power generation and other uses is on the increase. This demand necessitate a better understanding of the underlying dynamics for better prediction. Nonlinear dynamics and its associated tools readily lend itself for such analysis. In this paper, nonlinearity in solar radiation data is tested using recurrence plot (RP) and recurrence quantification analysis (RQA) in a tropical station. The data used was obtained from an ongoing campaign at the Federal University of Technology, Akure, Southwestern Nigeria using an Integrated Sensor Suite (Vantage2 Pro). Half hourly and daily values were tested for each month of the year. Both were found to be nonlinear. The dry months of the year exhibit higher chaoticity compared to the wet months of the year. The daily average values were found to be mildly chaotic. Using RQA, features due to external effects such as harmattan and intertropical discontinuity (ITD) on solar radiation data were uniquely identified.

  1. The distinguishing characteristics of narrative identity in adults with features of borderline personality disorder: an empirical investigation.

    PubMed

    Adler, Jonathan M; Chin, Erica D; Kolisetty, Aiswarya P; Oltmanns, Thomas F

    2012-08-01

    While identity disturbance has long been considered one of the defining features of Borderline Personality Disorder (BPD), the present study marks only the third empirical investigation to assess it and the first to do so from the perspective of research on narrative identity. Drawing on the rich tradition of studying narrative identity, the present study examined identity disturbance in a group of 40 mid-life adults, 20 with features of BPD and a matched sample of 20 without BPD. Extensive life story interviews were analyzed for a variety of narrative elements and the themes of agency, communion fulfillment (but not communion), and narrative coherence significantly distinguished the stories of those people with features of BPD from those without the disorder. In addition, associations between the theme of agency and psychopathology were evident six and twelve months following the life story interview. This study seeks to bridge the mutually-informative fields of research on personality disorders and normal identity processes. PMID:22867502

  2. A modelling investigation of solute transport in permeable porous media containing a discrete preferential flow feature

    NASA Astrophysics Data System (ADS)

    Sebben, Megan L.; Werner, Adrian D.

    2016-08-01

    Preferential flow features (PFFs, e.g. fractures and faults) are common features in rocks that otherwise have significant matrix permeability. Despite this, few studies have explored the influence of a PFF on the distribution of solute plumes in permeable rock formations, and the current understanding of PFF effects on solute plumes is based almost entirely on low-permeability rock matrices. This research uses numerical modelling to examine solute plumes that pass through a PFF in permeable rock, to explore the PFF's influence on plume migration. The study adopts intentionally simplified arrangements involving steady-state solute plumes in idealised, moderate-to-high-permeability rock aquifers containing a single PFF. A range of matrix-PFF permeability ratios (4.9 × 10-6-2.5 × 10-2), typical of fractured sedimentary aquifers, is considered. The results indicate that for conditions representative of high-to-moderate-permeability sedimentary rock matrices containing a medium-sized fracture, the effect of the PFF on solute plume displacement and spreading can be considerable. For example, plumes are between 1.3 and 19 times wider than in associated porous media only scenarios, and medium-sized PFFs in moderately permeable matrices can reduce the maximum solute concentration by up to 104 times. Plume displacement and spreading is lower in aquifers of higher matrix-PFF permeability ratios, and where solute plumes are more dispersed at the point of intersection with the PFF. Asymmetry in the plume caused by the passage through the PFF is more pronounced for more dispersive plumes. The current study demonstrates that PFFs most likely govern solute plume characteristics in typical permeable matrices, given that a single PFF of aperture representing a medium-sized fracture (i.e. 5.0 × 10-4m) produces the equivalent spreading effects of 0.22-7.88 m of plume movement through the permeable matrix.

  3. The features of infrared spectrum of bio-polymer and its theoretical investigation

    NASA Astrophysics Data System (ADS)

    Pang, Xiao-Feng

    2015-12-01

    We have here an insight into the features of molecular structures of bio-polymers with α-helix structure using infrared spectrum and elucidated theoretically, its relationship with bio-functions. In this case, we analyzed first the features of molecular structure of collagen and collected further the infrared spectrum of absorption of collagen and bovine serum albumin containing α-helix conformation in 400-4000 cm-1 as well as their changes of strength of infrared absorption with varying temperatures using Fourier Transform-Infrared (FT-IR) spectrometers in the region of 15-95°C. The results show that there is a new band of 1650 cm-1 close to the amide-I band of 1666 cm-1 or 1670 cm-1 in these bio-polymers, its strength decreases exponentially with increasing temperature of the systems, which can be expressed by exp[-(0.437 + 8.987 × 10-6 T2)], but 1666 cm-1 band increases linearly with increasing temperature. We calculated the energy spectrum of the protein molecules with α-helix conformation using the Soliton Theory of bio-energy transport, which are basically same with the experimental results measured by us. From these results and soliton theory we can conclude that the nonlinear soliton excitation, corresponding to 1650 cm-1 band and the exciton excitation, is related to 1666 cm-1 band, exists in the collagen and bovine serum albumin. In the meanwhile, these results also verified that the soliton theory of bio-energy transport along α-helix bio-polymers is appropriate to the protein molecules with α-helix conformation. Therefore, the studied results are helpful to elucidate the relationship between the molecular structure and bio-function of these bio-polymers.

  4. A Microstructural and Kinetic Investigation of the KCl-Induced Corrosion of an FeCrAl Alloy at 600 °C

    SciTech Connect

    Israelsson, Niklas; Unocic, Kinga A.; Hellström, K.; Jonsson, T.; Norell, M.; Svensson, J. -E.; Johansson, L. -G.

    2015-03-18

    In this paper, the corrosion behaviour of a FeCrAl alloy was investigated at 600 °C in O2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that KCl accelerates corrosion and that potassium chromate formation depletes the protective scale in Cr, thus triggering the formation of a fast-growing iron-rich scale. Iron oxide was found to grow both inward and outward, on either side of the initial oxide. A chromia layer is formed with time underneath the iron oxide. Finally, it was found that although the alloy does not form a continuous pure alumina scale at the investigated temperature, aluminium is, however, always enriched at the oxide/alloy interface.

  5. Investigation of the features of polycrystals complex loading using a two-level crystal plasticity theory

    NASA Astrophysics Data System (ADS)

    Volegov, P. S.; Trusov, P. V.; Gribov, D. S.

    2015-01-01

    The article considers a two-level mathematical model of inelastic deformation of metal polycrystals taking into account evolution of the structure. The structure of the model was considered, some special features of its application to describe the intensity of inelastic deformations were marked. The need for a careful physical analysis of the hardening laws construction was highlighted. To evaluate the applicability of multi-level models to describe the known experimental effects of cyclic deformation a number of results of field experiments on the complex proportional and disproportional cyclic deformation was considered, some specific effects that appear in these processes were identified: stresses amplitude output at the stationary value; additional cyclic hardening at a disproportionate loading, which magnitude depends on the so-called degree of disproportionality. Numerical experiments on the disproportionate cyclic loading were carried out, the possibility of modified hardening laws to describe access to the stationary values of the stress intensity was noted, and also the possibility of a qualitative description of the effect of additional cyclic hardening was demonstrated. The A.A. Ilyushin hypothesis by isotropy and the principle of vector properties delay at the turn of the deformation path were validated.

  6. Investigating Neuroanatomical Features in Top Athletes at the Single Subject Level

    PubMed Central

    Taubert, Marco; Wenzel, Uwe; Draganski, Bogdan; Kiebel, Stefan J.; Ragert, Patrick; Krug, Jürgen; Villringer, Arno

    2015-01-01

    In sport events like Olympic Games or World Championships competitive athletes keep pushing the boundaries of human performance. Compared to team sports, high achievements in many athletic disciplines depend solely on the individual’s performance. Contrasting previous research looking for expertise-related differences in brain anatomy at the group level, we aim to demonstrate changes in individual top athlete’s brain, which would be averaged out in a group analysis. We compared structural magnetic resonance images (MRI) of three professional track-and-field athletes to age-, gender- and education-matched control subjects. To determine brain features specific to these top athletes, we tested for significant deviations in structural grey matter density between each of the three top athletes and a carefully matched control sample. While total brain volumes were comparable between athletes and controls, we show regional grey matter differences in striatum and thalamus. The demonstrated brain anatomy patterns remained stable and were detected after 2 years with Olympic Games in between. We also found differences in the fusiform gyrus in two top long jumpers. We interpret our findings in reward-related areas as correlates of top athletes’ persistency to reach top-level skill performance over years. PMID:26079870

  7. Investigation of features of plastic deformation and fracture of fine-crystalline V-4Ti-4Cr alloy

    SciTech Connect

    Grinyaev, Konstantin V. Tyumentsev, Alexander N.; Ditenberg, Ivan A.; Smirnov, Ivan V.; Chernov, Vyacheslav M. E-mail: mmp@bochvar.ru; Potapenko, Mikhail M. E-mail: mmp@bochvar.ru

    2014-11-14

    With the use of transmission electron microscopy the investigation of defect substructure was carried out in the V-4Ti-4Cr-(C, N, O) alloy with disperse strengthening (by nanoparticles of oxy-carbo-nitride phase) after deformation by active tension at temperatures of 20 and 800 °C. It has been shown that an important feature of plastic deformation is deformation localization with crystal lattice reorientation.

  8. Investigating tectonic and bathymetric features of the Indian Ocean using MAGSAT magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Sailor, R. V.; Lazarewicz, A. R. (Principal Investigator)

    1982-01-01

    An equivalent source anomaly map and a map of the relative magnetization for the investigation region were produced. Gravimetry, bathymetry, and MAGSAT anomaly maps were contoured in pseudocolor displays. Finally, an autoregressive spectrum estimation technique was verified with synthetic data and shown to be capable of resolving exponential power spectra using small samples of data. Interpretations were made regarding the relationship between MAGSAT data spectra and crustal anomaly spectra.

  9. Comparative investigation of CuFe2O4 nano and microstructures for structural, morphological, optical and magnetic properties

    NASA Astrophysics Data System (ADS)

    Raja, G.; Gopinath, S.; Raj, R. Azhagu; Shukla, Arun K.; Alhoshan, Mansour S.; Sivakumar, K.

    2016-09-01

    CuFe2O4 nanocrystals were synthesized by the sol-gel method (SGM) and microwave method (MM) by using sucrose as a fuel. The structural, morphological, optical and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). The XRD results confirmed the formation of cubic phase CuFe2O4. The formation of CuFe2O4 nano and microstructures were confirmed by HR-SEM. Photoluminescence emissions were determined by PL spectra, respectively. The relatively high saturation magnetization (78.22 emu/g) of CuFe2O4-MM shows that it is ferromagnetic and low saturation magnetization (35.98 emu/g) of CuFe2O4O-SGM confirms the super paramagnetic behavior.

  10. In Situ Investigation of the 3D Mechanical Microstructure at Nanoscale: Nano-CT Imaging Method of Local Small Region in Large Scale Sample

    PubMed Central

    Xu, Feng; Hu, Xiao-fang; Qu, Hong-yan; Kang, Dan; Xiao, Ti-qiao

    2014-01-01

    To investigate the local micro-/nanoscale region in a large scale sample, an image reconstruction method for nanometer computed tomography (nano-CT) was proposed in this paper. In the algorithm, wavelets were used to localize the filtered-backprojection (FBP) algorithm because of its space-frequency localization property. After the implementation of the algorithm, two simulation local reconstruction experiments were performed to confirm its effectiveness. Three evaluation criteria were used in the experiments to judge the quality of the reconstructed images. The experimental results showed that the algorithm proposed in this paper performed best because (1) the quality of its results had improved 20%–30% compared to the results of FBP and 10%–30% compared to the results of another wavelet algorithm; (2) the new algorithm was stable under different circumstances. Besides, an actual reconstruction experiment was performed using real projection data that had been collected in a CT experiment. Two-dimensional (2D) and three-dimensional (3D) images of the sample were reconstructed. The microstructure of the sample could be clearly observed in the reconstructed images. Since much attention has been directed towards the nano-CT technique to investigate the microstructure of materials, this new wavelet-based local tomography algorithm could be considered as a meaningful effort. PMID:24723829

  11. In situ investigation of the 3D mechanical microstructure at nanoscale: nano-CT imaging method of local small region in large scale sample.

    PubMed

    Dong, Bo; Xu, Feng; Hu, Xiao-fang; Qu, Hong-yan; Kang, Dan; Xiao, Ti-qiao

    2014-01-01

    To investigate the local micro-/nanoscale region in a large scale sample, an image reconstruction method for nanometer computed tomography (nano-CT) was proposed in this paper. In the algorithm, wavelets were used to localize the filtered-backprojection (FBP) algorithm because of its space-frequency localization property. After the implementation of the algorithm, two simulation local reconstruction experiments were performed to confirm its effectiveness. Three evaluation criteria were used in the experiments to judge the quality of the reconstructed images. The experimental results showed that the algorithm proposed in this paper performed best because (1) the quality of its results had improved 20%-30% compared to the results of FBP and 10%-30% compared to the results of another wavelet algorithm; (2) the new algorithm was stable under different circumstances. Besides, an actual reconstruction experiment was performed using real projection data that had been collected in a CT experiment. Two-dimensional (2D) and three-dimensional (3D) images of the sample were reconstructed. The microstructure of the sample could be clearly observed in the reconstructed images. Since much attention has been directed towards the nano-CT technique to investigate the microstructure of materials, this new wavelet-based local tomography algorithm could be considered as a meaningful effort. PMID:24723829

  12. High-Resolution Seismic Investigation of a Surface Collapse Feature at Weeks Island Salt Dome, Louisiana

    NASA Astrophysics Data System (ADS)

    Miller, R. D.; Xia, J.; Harding, R. S.; Steeples, D. W.

    2005-05-01

    Seismic imaging techniques delineated the subsurface expression of an active sinkhole above a former salt mine at Weeks Island, Louisiana, which was used at the time by the U.S. Department of Energy's Strategic Petroleum Reserve. (The Weeks Island salt dome is no longer part of the Reserve.) The sinkhole, which at the time of the survey was approximately 12 m wide and 11 m deep, is directly over the edge of the upper storage chamber and approximately 60 m above the top of the salt dome. Surface seismic reflections imaged a dramatic bowl-shaped depression in a 28-m-deep reflector spatially consistent with the sinkhole. Two reflections (28 m and 60 m) on multichannel VSP data represent the only velocity and/or density contrasts detected above the top of the salt dome. The 28-m reflector identified on both VSP and surface seismic reflection data is at a depth consistent with the piezometric surface. Considering the high measured permeability and relative geometric severity of the reflection geometry, it is questionable whether this drape in the 28-m reflection is consistent with the water table. Localized velocity variations could account for some of the apparent geometry. The 60-m salt reflection, evident on VSP, can be interpreted on selected processed surface seismic shot gathers, but is difficult to confidently and consistently identify on stacked sections. The sinkhole lies along a northeast-trending acoustic lineament, possibly related to or associated with salt dissolution. The acoustic expression of the sinkhole suggests a localized, predominantly vertical feature. No evidence was discovered to confidently ascertain the mechanism responsible for exposing the salt to unsaturated meteoric water.

  13. Microstructural and compositional features of the fibrous and hyaline cartilage on the medial tibial plateau imply a unique role for the hopping locomotion of kangaroo.

    PubMed

    He, Bo; Wu, Jian Ping; Xu, Jiake; Day, Robert E; Kirk, Thomas Brett

    2013-01-01

    Hopping provides efficient and energy saving locomotion for kangaroos, but it results in great forces in the knee joints. A previous study has suggested that a unique fibrous cartilage in the central region of the tibial cartilage could serve to decrease the peak stresses generated within kangaroo tibiofemoral joints. However, the influences of the microstructure, composition and mechanical properties of the central fibrous and peripheral hyaline cartilage on the function of the knee joints are still to be defined. The present study showed that the fibrous cartilage was thicker and had a lower chondrocyte density than the hyaline cartilage. Despite having a higher PG content in the middle and deep zones, the fibrous cartilage had an inferior compressive strength compared to the peripheral hyaline cartilage. The fibrous cartilage had a complex three dimensional collagen meshwork with collagen bundles parallel to the surface in the superficial zone, and with collagen bundles both parallel and perpendicular to the surface in the middle and deep zones. The collagen in the hyaline cartilage displayed a typical Benninghoff structure, with collagen fibres parallel to the surface in the superficial zone and collagen fibres perpendicular to the surface in the deep zone. Elastin fibres were found throughout the entire tissue depth of the fibrous cartilage and displayed a similar alignment to the adjacent collagen bundles. In comparison, the elastin fibres in the hyaline cartilage were confined within the superficial zone. This study examined for the first time the fibrillary structure, PG content and compressive properties of the central fibrous cartilage pad and peripheral hyaline cartilage within the kangaroo medial tibial plateau. It provided insights into the microstructure and composition of the fibrous and peripheral hyaline cartilage in relation to the unique mechanical properties of the tissues to provide for the normal activities of kangaroos. PMID:24058543

  14. Investigation of Antifouling Properties of Surfaces Featuring Zwitterionic α-Aminophosphonic Acid Moieties.

    PubMed

    Wagner, Natalie; Zimmermann, Phyllis; Heisig, Peter; Klitsche, Franziska; Maison, Wolfgang; Theato, Patrick

    2015-12-01

    Zwitterionic thin films containing α-amino phosphonic acid moieties were successfully introduced on silicon surfaces and their antifouling properties were investigated. Initially, the substrates were modified with a hybrid polymer, composed of poly(methylsilsesquioxane) (PMSSQ) and poly(4-vinyl benzaldehyde) (PStCHO). Next, a Kabachnik-Fields post-polymerization modification (sur-KF-PMR) of the functionalized aldehyde surfaces was conducted with different amines and dialkyl phosphonates. After subsequent deprotection reaction of dialkyl phosphonates, the obtained zwitterionic surfaces were characterized by various techniques and we found excellent antifouling properties of the resulting films. PMID:26332285

  15. An NMR and molecular dynamics investigation of the avian prion hexarepeat conformational features in solution

    NASA Astrophysics Data System (ADS)

    Pietropaolo, Adriana; Raiola, Luca; Muccioli, Luca; Tiberio, Giustiniano; Zannoni, Claudio; Fattorusso, Roberto; Isernia, Carla; Mendola, Diego La; Pappalardo, Giuseppe; Rizzarelli, Enrico

    2007-07-01

    The prion protein is a copper binding glycoprotein that in mammals can misfold into a pathogenic isoform leading to prion diseases, as opposed, surprisingly, to avians. The avian prion N-terminal tandem repeat is richer in prolines than the mammal one, and understanding their effect on conformation is of great biological importance. Here we succeeded in investigating the conformations of a single avian hexarepeat by means of NMR and molecular dynamics techniques. We found a high flexibility and a strong conformational dependence on pH: local turns are present at acidic and neutral pH, while unordered regions dominate at basic conditions.

  16. Certain features of the preparation of boron powders in x-ray diffraction investigations

    SciTech Connect

    Tsagareishvili, G.V.; Avlokhashvili, D.A.; Bairamashvili, I.A.; Dolidze, T.V.; Gabuniya, D.L.; Nakashidze, T.G.; Oganezov, K.A.; Tabutsidze, M.L.

    1985-05-01

    It is known that elemental boron is characterized by an increased reaction capacity toward oxygen. Boron powders oxidize especially intensely. Under real conditions, boron powders always contain a certain quantity of oxide phase (primarily in the form of B2O3), the quantity of which depends on their degree of dispersion, the method of production, and the storage conditions. In long exposure to air, as the result of its high hygroscopicity, boric anhydride reacts with particles of moisture, as the result of which orthoboric acid is formed. The mass absorption coefficient of x-rays by elemental boron is significantly lower than by its compounds (anhydride and acid). The presence on the surface of particles of boric anhydride and products of its hydration, the total quantity of which in the powder is large, cannot affect the result of x-ray diffraction investigations of the powders. In this work an investigation is made of the possibility of weakening this influence by preliminary treatment of the powders.

  17. Effects of Microalloying on the Microstructures and Mechanical Properties of Directionally Solidified Ni-33(at.%)Al-31Cr-3Mo Eutectic Alloys Investigated

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2002-01-01

    Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.

  18. Integrated system for investigating sub-surface features of a rock formation

    DOEpatents

    Vu, Cung Khac; Skelt, Christopher; Nihei, Kurt; Johnson, Paul A.; Guyer, Robert; Ten Cate, James A.; Le Bas, Pierre -Yves; Larmat, Carene S.

    2015-08-18

    A system for investigating non-linear properties of a rock formation around a borehole is provided. The system includes a first sub-system configured to perform data acquisition, control and recording of data; a second subsystem in communication with the first sub-system and configured to perform non-linearity and velocity preliminary imaging; a third subsystem in communication with the first subsystem and configured to emit controlled acoustic broadcasts and receive acoustic energy; a fourth subsystem in communication with the first subsystem and the third subsystem and configured to generate a source signal directed towards the rock formation; and a fifth subsystem in communication with the third subsystem and the fourth subsystem and configured to perform detection of signals representative of the non-linear properties of the rock formation.

  19. Characteristic Features of Water Dynamics in Restricted Geometries Investigated with Quasi-Elastic Neutron Scattering

    DOE PAGESBeta

    Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; Wesolowski, David J.; Diallo, S. O.

    2015-12-10

    Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrumentmore » resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.« less

  20. Characteristic Features of Water Dynamics in Restricted Geometries Investigated with Quasi-Elastic Neutron Scattering

    SciTech Connect

    Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; Wesolowski, David J.; Diallo, S. O.

    2015-12-10

    Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrument resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.

  1. Characteristic features of water dynamics in restricted geometries investigated with quasi-elastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Osti, N. C.; Coté, A.; Mamontov, E.; Ramirez-Cuesta, A.; Wesolowski, D. J.; Diallo, S. O.

    2016-02-01

    Understanding the molecular behavior of water in spatially restricted environments is key to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrument resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250 ⩽ T ⩽ 290 K.

  2. Investigating tectonic and bathymetric features of the Indian Ocean using MAGSAT magnetic anomaly data

    NASA Technical Reports Server (NTRS)

    Lazarewicz, A. R.; Sailor, R. V. (Principal Investigator)

    1982-01-01

    MAGSAT Investigator-B tapes were preprocessed by (1) removing all data points with obvious erroneous values and location errors; (2) removing smaller spikes (typically 15 nT or more), and deleting data tracks with fewer than 20 points; and (3) removing a linear trend from each track. The remaining data were recorded on tape for use by the equivalent source mapping (ESMAP) program which uses a least squares algorithm to fit the magnetization parameter of the grid of equivalent source dipoles in the crust to satellite data acquired at different times and locations. ESMAP was implemented on the TASC computing system and modified to read preprocessed MAGSAT tapes and interface with TASC plotting software. Some verification of the software was accomplished. Gridded 1-degree mean values of gravity anomaly and sea surface undulation computed from SEASAT radar altimeter were obtained and brought on line.

  3. A Microstructural and Kinetic Investigation of the KCl-Induced Corrosion of an FeCrAl Alloy at 600 °C

    DOE PAGESBeta

    Israelsson, Niklas; Unocic, Kinga A.; Hellström, K.; Jonsson, T.; Norell, M.; Svensson, J. -E.; Johansson, L. -G.

    2015-03-18

    In this paper, the corrosion behaviour of a FeCrAl alloy was investigated at 600 °C in O2 + H2O with solid KCl applied. A kinetics and microstructural investigation showed that KCl accelerates corrosion and that potassium chromate formation depletes the protective scale in Cr, thus triggering the formation of a fast-growing iron-rich scale. Iron oxide was found to grow both inward and outward, on either side of the initial oxide. A chromia layer is formed with time underneath the iron oxide. Finally, it was found that although the alloy does not form a continuous pure alumina scale at the investigatedmore » temperature, aluminium is, however, always enriched at the oxide/alloy interface.« less

  4. Investigation of Endoscopic and Pathologic Features for Safe Endoscopic Treatment of Superficial Spreading Early Gastric Cancer.

    PubMed

    Lee, Kyong Joo; Pak, Kyung Ho; Hyung, Woo Jin; Noh, Sung Hoon; Kim, Choong Bai; Lee, Yong Chan; Kim, Hee Man; Lee, Sang Kil

    2016-04-01

    Superficial spreading early gastric cancer (EGC) is a rare disease that is treated mainly by surgery. There are few studies on the safety of endoscopic treatment for patients with superficial spreading EGC. The aims of this study were to (1) investigate the risk of lymph node metastasis of superficial spreading EGC and (2) investigate the potential criteria for endoscopic treatment of superficial spreading EGC using surgical specimens.Between 2000 and 2010, patients who received curative surgery of R0 resection at Severance Hospital (Seoul, Korea) for early gastric cancer were enrolled. The superficial spreading EGC was defined as cancer in which the longest tumor length was ≥6 cm. The medical records of the patients were reviewed retrospectively.Of the 3813 patients with EGC, 140 (3.7%) had lesions ≥ 6 cm, whereas 3673 (96.3%) had lesions < 6 cm. Patients with superficial spreading EGC had higher rates of submucosal cancer (59.3% vs 45.7%, P = 0.002), lymphovascular invasion (18.6% vs 9.8%, P < 0.001), and lymph node metastasis (15.7% vs 10.1%, P = 0.033) compared with patients with common EGC (< 6 cm). Multivariate analysis revealed that a tumor ≥ 6 cm was not strongly associated with lymph node metastasis in EGC, as compared with a tumor < 6 cm, but submucosal invasion and lymphovascular invasion were strongly associated with lymph node metastasis in EGC. In mucosal cancer without ulcers, tumors ≥ 6 cm had a higher rate of lymph node metastasis than tumors ≤ 2 cm; however, this trend was not significant (7.7% vs 5.3%, P = 0.455).Superficial spreading EGC was not associated with an increased risk of lymph node metastasis compared with common EGC. We suggest that differentiated intramucosal superficial spreading EGC without ulceration can be treated by endoscopic submucosal dissection. PMID:27057862

  5. Argon broad ion beam tomography in a cryogenic scanning electron microscope: a novel tool for the investigation of representative microstructures in sedimentary rocks containing pore fluid.

    PubMed

    Desbois, G; Urai, J L; Pérez-Willard, F; Radi, Z; Offern, S; Burkart, I; Kukla, P A; Wollenberg, U

    2013-03-01

    The contribution describes the implementation of a broad ion beam (BIB) polisher into a scanning electron microscope (SEM) functioning at cryogenic temperature (cryo). The whole system (BIB-cryo-SEM) provides a first generation of a novel multibeam electron microscope that combines broad ion beam with cryogenic facilities in a conventional SEM to produce large, high-quality cross-sections (up to 2 mm(2)) at cryogenic temperature to be imaged at the state-of-the-art SEM resolution. Cryogenic method allows detecting fluids in their natural environment and preserves samples against desiccation and dehydration, which may damage natural microstructures. The investigation of microstructures in the third dimension is enabled by serial cross-sectioning, providing broad ion beam tomography with slices down to 350 nm thick. The functionalities of the BIB-cryo-SEM are demonstrated by the investigation of rock salts (synthetic coarse-grained sodium chloride synthesized from halite-brine mush cold pressed at 150 MPa and 4.5 GPa, and natural rock salt mylonite from a salt glacier at Qom Kuh, central Iran). In addition, results from BIB-cryo-SEM on a gas shale and Boom Clay are also presented to show that the instrument is suitable for a large range of sedimentary rocks. For the first time, pore and grain fabrics of preserved host and reservoir rocks can be investigated at nm-scale range over a representative elementary area. In comparison with the complementary and overlapping performances of the BIB-SEM method with focused ion beam-SEM and X-ray tomography methods, the BIB cross-sectioning enables detailed insights about morphologies of pores at greater resolution than X-ray tomography and allows the production of large representative surfaces suitable for FIB-SEM investigations of a specific representative site within the BIB cross-section. PMID:23323728

  6. Compositional and technological features of glazed pottery from Aosta Valley (Italy): a SEM-EDS investigation.

    PubMed

    Gulmini, Monica; Appolonia, Lorenzo; Framarin, Patrizia; Mirti, Piero

    2006-11-01

    Twelve finds from archaeological excavations carried out in the Aosta region (Italy) were studied by scanning electron microscopy coupled with energy-dispersive X-ray detection (SEM-EDS). The archaeological samples were shards of glazed pottery dating from the fourth to the seventh century AD. Analysis of ceramic bodies revealed a general homogeneity in composition among the studied samples and the use of a noncalcareous clay for their manufacture; however, two shards stand out due to their high iron contents. Glazes proved to be high-lead products with more than 70% PbO in all of the samples investigated but one. For the latter, a composition poorer in lead and richer in silicon, aluminium and iron was found. SEM observation of the contact region between body and glaze suggests that the vitreous coatings were mostly obtained by applying the glazing components onto the unfired clay body; moreover, a comparison between clay and glaze compositions suggests the use of a lead compound mixed with a silica-rich material, not a lead compound by itself. PMID:17028850

  7. Investigation of microstructure and V-defect formation inInxGa1-xN/GaN MQW grown using temperature-gradient MOCVD

    SciTech Connect

    Johnson, M.C.; Liliental-Weber, Z.; Zakharov, D.N.; McCready,D.E.; Jorgenson, R.J.; Wu, J.; Shan, W.; Bourret-Courchesne, E.D.

    2004-11-19

    Temperature-gradient Metalorganic Chemical Vapor Deposition was used to deposit In{sub x}Ga{sub 1-x}N/GaN multiple quantum well structures with a concentration gradient of indium across the wafer. These multiple quantum well structures were deposited on low defect density (2 x 10{sup 8} cm{sup -2}) GaN template layers for investigation of microstructural properties and V-defect (pinhole) formation. Room temperature photoluminescence and photomodulated transmission were used for optical characterization which show a systematic decrease in emission energy for a decrease in growth temperature. Triple-axis X-ray diffraction, scanning electron microscopy and cross-section transmission electron microscopy were used to obtain microstructural properties of different regions across the wafer. Results show that there is a decrease in crystal quality and an increase in V-defect formation with increasing indium concentration. A direct correlation was found between V-defect density and growth temperature due to increased strain and indium segregation for increasing indium concentration.

  8. Investigation of structural and chemical transitions in copper oxide microstructures produced by combustion waves in a mixture of CuO-Cu2O-Cu and fuel

    NASA Astrophysics Data System (ADS)

    Hwang, Hayoung; Lee, Kang Yeol; Yeo, Taehan; Choi, Wonjoon

    2015-12-01

    The application of micro/nanostructured materials to combustion enables distinctive chemical reactions that can be used to modulate the reaction rates. Simultaneously, combustion is capable of changing the intrinsic properties of micro/nanostructured materials based on chemical interactions in high-temperature conditions. In this work, we investigate the structural-chemical transition of copper oxide microstructures exposed to interfacially driven combustion waves. The high thermal energy and exchange of chemical compounds resulting from the instant combustion waves cause direct transition without any further processes. The precise characterization of the structural and chemical transitions in the copper oxide microstructures and chemical fuels confirm that the self-propagating combustion waves in the layered composites of Cu/Cu2O/CuO microparticle-based films and the chemical fuel layers yield the direct synthesis of Cu(OH)2 flower-like structures and nanowires. The propagation of combustion waves at the interface induces an increase of the surface temperatures over 650 °C and the direct interaction between the copper oxide and chemical compounds of the fuel layers. Further application of these interfacially driven combustion waves will contribute to the development of one-step, fast, low-cost methods for the synthesis of micro/nanostructured materials.

  9. Investigation on the microstructure, mechanical property and corrosion behavior of the selective laser melted CoCrW alloy for dental application.

    PubMed

    Lu, Yanjin; Wu, Songquan; Gan, Yiliang; Li, Junlei; Zhao, Chaoqian; Zhuo, Dongxian; Lin, Jinxin

    2015-04-01

    In this study, an experimental investigation on fabricating Ni-free CoCrW alloys by selective laser melting (SLM) for dental application was conducted in terms of microstructure, hardness, mechanical property, electrochemical behavior, and metal release; and line and island scanning strategy were applied to determine whether these strategies are able to obtain expected CoCrW parts. The XRD revealed that the γ-phase and ε-phase coexisted in the as-SLM CoCrW alloys; The OM and SEM images showed that the microstructure of CoCrW alloys appeared square-like pattern with the fine cellular dendrites at the borders; tensile test suggested that the difference of mechanical properties of line- and island-formed specimens was very small; whilst the outcomes from the electrochemical and metal release tests indicated that the island-formed alloys showed slightly better corrosion resistance than line-formed ones in PBS and Hanks solutions. Considering that the mechanical properties and corrosion resistance of line-formed and island-formed specimens meet the standards of ISO 22674:2006 and EN ISO 10271, CoCrW dental alloys can be successfully fabricated by line and island scanning strategies in the SLM process. PMID:25686979

  10. Investigation on the Microstructure, Interfacial IMC Layer, and Mechanical Properties of Cu/Sn-0.7Cu-xNi/Cu Solder Joints

    NASA Astrophysics Data System (ADS)

    Yang, Li; Ge, Jinguo; Zhang, Yaocheng; Dai, Jun; Liu, Haixiang; Xiang, Jicen

    2016-04-01

    Sn-0.7Cu-xNi composite solder has been fabricated via mechanical mixing of different weight percentages of Ni particles with Sn-0.7Cu solder paste, and the effect of the Ni concentration on the microstructure, wettability, and tensile properties of Cu/Sn-0.7Cu-xNi/Cu solder joints investigated. The results show that refined dot-shaped particles of intermetallic compounds (IMCs) are uniformly dispersed in a primary β-Sn matrix in the Cu/Sn-0.7Cu-(0.05-0.1)Ni/Cu solder joints. The interfacial IMC layer thickness increased slightly when adding Ni content to 0.05 wt.%, then rapidly when further increasing the Ni concentration to 0.4 wt.%. Excellent wettability with bright appearance was obtained for the Sn-0.7Cu-0.05Ni solder due to diminished interfacial tension. The tensile properties improved after adding Ni content to 0.05 wt.% due to the presence of the refined dot-like IMC particles, in agreement with theoretical predictions based on the combination of dispersion and grain-refinement strengthening mechanisms. Refined microstructure and enhanced mechanical properties were obtained for the Cu/Sn-0.7Cu-0.05Ni/Cu solder joint.

  11. Investigation on the Microstructure, Interfacial IMC Layer, and Mechanical Properties of Cu/Sn-0.7Cu- xNi/Cu Solder Joints

    NASA Astrophysics Data System (ADS)

    Yang, Li; Ge, Jinguo; Zhang, Yaocheng; Dai, Jun; Liu, Haixiang; Xiang, Jicen

    2016-07-01

    Sn-0.7Cu- xNi composite solder has been fabricated via mechanical mixing of different weight percentages of Ni particles with Sn-0.7Cu solder paste, and the effect of the Ni concentration on the microstructure, wettability, and tensile properties of Cu/Sn-0.7Cu- xNi/Cu solder joints investigated. The results show that refined dot-shaped particles of intermetallic compounds (IMCs) are uniformly dispersed in a primary β-Sn matrix in the Cu/Sn-0.7Cu-(0.05-0.1)Ni/Cu solder joints. The interfacial IMC layer thickness increased slightly when adding Ni content to 0.05 wt.%, then rapidly when further increasing the Ni concentration to 0.4 wt.%. Excellent wettability with bright appearance was obtained for the Sn-0.7Cu-0.05Ni solder due to diminished interfacial tension. The tensile properties improved after adding Ni content to 0.05 wt.% due to the presence of the refined dot-like IMC particles, in agreement with theoretical predictions based on the combination of dispersion and grain-refinement strengthening mechanisms. Refined microstructure and enhanced mechanical properties were obtained for the Cu/Sn-0.7Cu-0.05Ni/Cu solder joint.

  12. Investigation on the effect of microstructure of proton exchange membrane fuel cell porous layers on liquid water behavior by soft X-ray radiography

    NASA Astrophysics Data System (ADS)

    Sasabe, Takashi; Deevanhxay, Phengxay; Tsushima, Shohji; Hirai, Shuichiro

    2011-10-01

    In order to investigate the effect of microstructure of PEMFC porous layers on the liquid water transport, liquid water accumulation and discharge behavior in the operating PEMFC was visualized by laboratory-based soft X-ray radiography. The utilization of low energy X-ray made it possible to visualize the liquid water behavior in the PEMFC with the spatial resolution of 0.8 μm and the temporal resolution of 2.0 s frame-1, and the cross-sectional imaging can resolve the each components of the PEMFC. The visualization results showed that adding the MPL prevents the accumulation of liquid water in the substrate layer from contacting and forming the liquid water film on the catalyst layer. Furthermore, it was found that the liquid water distribution in the carbon paper and the carbon cloth GDL was completely different. The liquid water in the carbon cloth GDL concentrates at the weaves of fiber bundle and was effectively discharged to the channel. These visualization results suggested that the microstructure of the PEMFC porous layers strongly affect the liquid water behavior in the PEMFC, and the detailed understanding of the pore structures and the network of liquid water is essential for keeping the oxygen transport path to the catalyst site.

  13. Investigation of atmospheric insect wing-beat frequencies and iridescence features using a multispectral kHz remote detection system

    NASA Astrophysics Data System (ADS)

    Gebru, Alem; Rohwer, Erich; Neethling, Pieter; Brydegaard, Mikkel

    2014-01-01

    Quantitative investigation of insect activity in their natural habitat is a challenging task for entomologists. It is difficult to address questions such as flight direction, predation strength, and overall activities using the current techniques such as traps and sweep nets. A multispectral kHz remote detection system using sunlight as an illumination source is presented. We explore the possibilities of remote optical classification of insects based on their wing-beat frequencies and iridescence features. It is shown that the wing-beat frequency of the fast insect events can be resolved by implementing high-sampling frequency. The iridescence features generated from the change of color in two channels (visible and near-infrared) during wing-beat cycle are presented. We show that the shape of the wing-beat trajectory is different for different insects. The flight direction of an atmospheric insect is also determined using a silicon quadrant detector.

  14. Diffusion in polycrystalline microstructures

    SciTech Connect

    Swiler, T.P.; Holm, E.A.

    1995-07-01

    Mass transport properties are important in polycrystalline materials used as protective films. Traditionally, such properties have been studied by examining model polycrystalline structures, such as a regular array of straight grain boundaries. However, these models do not account for a number of features of real grain ensembles, including the grain size distribution and the topological aspects of grain boundaries. In this study, a finite difference scheme is developed to study transient and steady-state mass transport through realistic two-dimensional polycrystalline microstructures. Effects of microstructural parameters such as average grain size and grain boundary topology are examined, as are effects due to limits of the model.

  15. Dimensionality of ICA in resting-state fMRI investigated by feature optimized classification of independent components with SVM

    PubMed Central

    Wang, Yanlu; Li, Tie-Qiang

    2015-01-01

    Different machine learning algorithms have recently been used for assisting automated classification of independent component analysis (ICA) results from resting-state fMRI data. The success of this approach relies on identification of artifact components and meaningful functional networks. A limiting factor of ICA is the uncertainty of the number of independent components (NIC). We aim to develop a framework based on support vector machines (SVM) and optimized feature-selection for automated classification of independent components (ICs) and use the framework to investigate the effects of input NIC on the ICA results. Seven different resting-state fMRI datasets were studied. 18 features were devised by mimicking the empirical criteria for manual evaluation. The five most significant (p < 0.01) features were identified by general linear modeling and used to generate a classification model for the framework. This feature-optimized classification of ICs with SVM (FOCIS) framework was used to classify both group and single subject ICA results. The classification results obtained using FOCIS and previously published FSL-FIX were compared against manually evaluated results. On average the false negative rate in identifying artifact contaminated ICs for FOCIS and FSL-FIX were 98.27 and 92.34%, respectively. The number of artifact and functional network components increased almost linearly with the input NIC. Through tracking, we demonstrate that incrementing NIC affects most ICs when NIC < 33, whereas only a few limited ICs are affected by direct splitting when NIC is incremented beyond NIC > 40. For a given IC, its changes with increasing NIC are individually specific irrespective whether the component is a potential resting-state functional network or an artifact component. Using FOCIS, we investigated experimentally the ICA dimensionality of resting-state fMRI datasets and found that the input NIC can critically affect the ICA results of resting-state fMRI data. PMID

  16. Detailed investigation of optoelectronic and microstructural properties of plasma polymerized cyclohexane thin films: Dependence on the radiofrequency power

    SciTech Connect

    Manaa, C.; Bouaziz, L.; Lejeune, M.; Zellama, K. Benlahsen, M.; Kouki, F.; Mejatty, M.; Bouchriha, H.

    2015-06-07

    Optical properties of polymerized cyclohexane films deposited by radiofrequency plasma enhanced chemical vapor deposition technique at different radiofrequency powers onto glass and silicon substrates, are studied and correlated with the microstructure of the films, using a combination of atomic force microscopy, Raman and Fourier Transformer Infrared spectroscopy and optical measurements. The optical constants such as refractive index n, dielectric permittivity ε and extinction k and absorption α coefficients, are extracted from transmission and reflection spectra through the commercial software CODE. These constants lead, by using common theoretical models as Cauchy, Lorentz, Tauc and single effective oscillator, to the determination of the static refractive index n{sub s} and permittivity ε{sub s}, the plasma frequency ω{sub p}, the carrier density to effective mass ratio N/m{sub e}{sup *}, the optical conductivity σ{sub oc}, the optical band gap E{sub g} and the oscillation and dispersion energies E{sub 0} and E{sub d}, respectively. We find that n, ε{sub s}, ω{sub p}, N/m{sub e}{sup *}, E{sub d}, increase with radiofrequency power, while E{sub g} and E{sub 0} decrease in the same range of power. These results are well correlated with those obtained from atomic force microscopy, Raman and infrared measurements. They also indicate that the increase of the radiofrequency power promotes the fragmentation of the precursor and increases the carbon C-sp{sup 2} hybridization proportion, which results in an improvement of the optoelectronic properties of the films.

  17. Investigation of Microstructure and Mechanical Properties of St37 Steel-Ck60 Steel Joints by Explosive Cladding

    NASA Astrophysics Data System (ADS)

    Yazdani, Majid; Toroghinejad, Mohammad Reza; Hashemi, Seyyed Mohammad

    2015-10-01

    The present work aimed at studying the microstructure and mechanical properties of Ck60/St37 composite plates fabricated by explosive cladding. The explosive ratio and stand-off distance were set to be R = 1.7 and s = 1.5 t, respectively. Optical and scanning electron microscopy revealed that the bonding at the interface had a wavy morphology, but local melted zones were formed along the interface. The chemical composition of the local melted zones was evaluated by energy-dispersive spectroscopy analysis. This analysis showed that the melted zones consisted of both Ck60 and St37 steels. The maximum hardness was obtained near the explosively cladded interface; then these values were decreased by the distance away from the interface. Moreover, it was seen that the local melted zones, especially the vortices, had a high degree of hardness. Shear tests on the cladded metals also showed that the average shear strength was higher than 140 MPa, as set by the ASTM A263-12, implying that composite plates could be used safely. The study was also conducted to consider the strength of bonding by bending test in two ways, one with the cladding metal in tension and the other with the cladding metal in compression. Bending test results showed that these joints could be used safely when the cladded metal was in compression; otherwise, it would be fractured. Finally, impact test results showed that the fracture toughness of cladded samples was higher than that of flyer material due to the higher fracture toughness of the base material.

  18. Investigation of the spectroscopic features of clay-rich rocks in terms of geo-mechanical evaluations

    NASA Astrophysics Data System (ADS)

    Nefeslioglu, Hakan A.

    2013-04-01

    The main purpose of this study is to investigate the spectroscopic features of clay-rich rocks in terms of geo-mechanical evaluations. For the purpose, different types of sedimentary rocks including claystones and mudstones were used. Ultra sonic pulse velocity (Vp) measurements and Uniaxial Compressive Strength (UCS) tests were carried out by using the core samples of these clay-rich rocks, and moduli of elasticity (Ei) values of the samples were calculated. Spectroscopic measurements were also done by using the failed core samples. According to the spectral feature search analyses of the samples 7 spectral bands were differentiated depending on crystal filed effects and charge transfer absorptions of transition elements and water and OH vibrational features. Considering these 7 spectral bands, 8 different genetic rock types were defined. The regression equations of Vp-UCS and Vp-Ei were evaluated for the unclassified and genetic rock types, respectively. The coefficients of correlations of the equations became considerably higher when the genetic rock types were considered, and the equations were found to be statistically significant.

  19. Influence of Cu doping on the microstructure, optical properties and photoluminescence features of Cd0.9Zn0.1S nanoparticles

    NASA Astrophysics Data System (ADS)

    Devadoss, I.; Muthukumaran, S.

    2015-08-01

    Cd0.9-xZn0.1CuxS (0≤x≤0.06) nanoparticles were successfully synthesized by a conventional chemical co-precipitation method at room temperature. Crystalline phases and optical absorption of the nanoparticles have been studied by X-ray diffraction (XRD) and UV-visible spectrophotometer. XRD confirms the phase singularity of the synthesized material, which also confirmed the formation of Cd-Zn-Cu-S alloy nanocrystals rather than separate nucleation or phase formation. Elemental composition was examined by the energy dispersive X-ray analysis and the microstructure was examined by scanning electron microscope. The blue shift of absorption edge below Cu=2% is responsible for dominance of Cu+ while at higher Cu concentration dominated Cu2+, d-d transition may exist. It is suggested that the addition of third metal ion (Cu2+/Cu+) is an effective way to improve the optical property and stability of the Cd0.9Zn0.1S solid solutions. When Cu is introduced, stretching of Cd-Zn-Cu-S bond is shifted lower wave number side from 678 cm-1 (Cu=0%) to 671 cm-1 (Cu=6%) due to the presence of Cu in Cd-Zn-S lattice and also the size effect. The variation in blue band emission peak from 456 nm (∼2.72 eV) to 482 nm (∼2.58 eV) by Cu-doping is corresponding to the inter-band radiation combination of photo-generated electrons and holes. Intensity of red band emission centered at 656 nm significantly increased up to Cu=4%; beyond 4% it is decreased due to the quenching of Cu concentration.

  20. Microstructural Investigation of SexTe100-x Thin Films Deposited on Si(100) Substrates by X-ray Diffractometer and Transmission Electron Microscopy Analysis

    NASA Astrophysics Data System (ADS)

    Kim, Eun Tae; Lee, Jeong Yong; Kim, Yong Tae

    2007-11-01

    The microstructural properties of SexTe100-x (x=16,29,38) thin films are investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. SexTe100-x thin films have a Te hexagonal structure and Te{011} interplanar spacing decreases because some Se atoms occupy Te atomic sites, forming Se helical chains within the Te helical chains. By increasing the Se contents from 16 to 29 at. %, Se5.95Te1.05 monoclinic and Se hexagonal structures coexist in a grain and at 38 at. %, a Se hexagonal structure is observed within the Te hexagonal grain. This means that SexTe100-x thin films maintain the Te hexagonal structure and that phase separation does not occur owing to the short diffusion time.

  1. [Investigation of characteristic microstructures of adhesive interface in wood/bamboo composite material by synchrotron radiation X-ray phase contrast microscopy].

    PubMed

    Peng, Guan-Yun; Wang, Yu-Rong; Ren, Hai-Qing; Yang, Shu-Min; Ma, Hong-Xia; Xie, Hong-Lan; Deng, Biao; Du, Guo-Hao; Xiao, Ti-Qiao

    2013-03-01

    Third-generation synchrotron radiation X-ray phase-contrast microscopy(XPCM)can be used for obtaining image with edge enhancement, and achieve the high contrast imaging of low-Z materials with the spatial coherence peculiarity of X-rays. In the present paper, the characteristic microstructures of adhesive at the interface and their penetration in wood/bamboo composite material were investigated systematically by XPCM at Shanghai Synchrotron Radiation Facility (SSRF). And the effect of several processing techniques was analyzed for the adhesive penetration in wood/bamboo materials. The results show that the synchrotron radiation XPCM is expected to be one of the important precision detection methods for wood-based panels. PMID:23705464

  2. Investigation of microstructure evolution during self-annealing in thin Cu films by combining mesoscale level set and ab initio modeling

    NASA Astrophysics Data System (ADS)

    Hallberg, Håkan; Olsson, Pär A. T.

    2016-05-01

    Microstructure evolution in thin Cu films during room temperature self-annealing is investigated by means of a mesoscale level set model. The model is formulated such that the relative, or collective, influence of anisotropic grain boundary energy, mobility and heterogeneously distributed stored energy can be investigated. Density functional theory (DFT) calculations are performed in the present work to provide the variation of grain boundary energy for different grain boundary configurations. The stability of the predominant (111) fiber texture in the as-deposited state is studied as well as the stability of some special low-Σ grain boundaries. Further, the numerical model allows tracing of the grain size distribution and occurrence of abnormal grain growth during self-annealing. It is found that abnormal grain growth depends mainly on the presence of stored energy variations, whereas anisotropic grain boundary energy or mobility is insufficient to trigger any abnormal growth in the model. However, texture dependent grain boundary properties, mobility in particular, contribute to an increased content of low-Σ boundaries in the annealed microstructure. The increased presence of such boundaries is also promoted by stored energy variations. In addition, if the stored energy variations are sufficient the coexisting (111) and (001) texture components in the as-deposited state will evolve into a (001) dominated texture during annealing. Further, it is found that whereas stored energy variations promote the stability of the (001) texture component, anisotropic grain boundary energy and mobility tend to work the other way and stabilize the (111) component at the expense of (001) grains.

  3. Functional Popliteal Artery Entrapment Syndrome: Poorly Understood and Frequently Missed? A Review of Clinical Features, Appropriate Investigations, and Treatment Options

    PubMed Central

    Hislop, Matthew; Kennedy, Dominic; Cramp, Brendan; Dhupelia, Sanjay

    2014-01-01

    Functional popliteal artery entrapment syndrome (PAES) is an important and possibly underrecognized cause of exertional leg pain (ELP). As it is poorly understood, it is at risk of misdiagnosis and mismanagement. The features indicative of PAES are outlined, as it can share features with other causes of ELP. Investigating functional PAES is also fraught with potential problems and if it is performed incorrectly, it can result in false negative and false positive findings. A review of the current vascular investigations is provided, highlighting some of the limitations standard tests have in determining functional PAES. Once a clinical suspicion for PAES is satisfied, it is necessary to further distinguish the subcategories of anatomical and functional entrapment and the group of asymptomatic occluders. When definitive entrapment is confirmed, it is important to identify the level of entrapment so that precise intervention can be performed. Treatment strategies for functional PAES are discussed, including the possibility of a new, less invasive intervention of guided Botulinum toxin injection at the level of entrapment as an alternative to vascular surgery. PMID:26464888

  4. Microstructural investigation of a locally mirror-like surface collected at 4 km depth in a Pomeranian shale sample

    NASA Astrophysics Data System (ADS)

    Pluymakers, Anne; Renard, Francois

    2016-04-01

    The presence of shiny sliding surfaces, or mirror surfaces, is sometimes thought to have been caused by slip at seismic velocities. Many fault mirrors reported so far are described to occur in carbonate-rich rocks. Here we present microstructural data on a mirror-like slip surface in the Pomeranian shale, recovered from approximately 4 km depth. The accommodated sliding of this fault is probably small, not more than one or two centimeter. The Pomeranian shale is a dark-grey to black shale, composed of 40-60% illite plus mica, 1-10% organic matter, 10% chlorite, and 10 % carbonates plus minor amounts of K-feldspar, plagioclase and kaolinite. In this sample, the surface is optically smooth with striations and some patches that reflect light. Observations using a Hitachi TM3000 (table-top) SEM show that the striations are omnipresent, though more prominent in the carbonate patches (determined using EDS analysis). The smooth surface is locally covered by granular material with a grain size up to 10 μm. This is shown to consist of a mixture of elements and thus likely locally derived fault gouge. The clay-rich parts of the smooth surface are equidimensional grains, with sub-micron grain sizes, whereas in the unperturbed part of the shale core the individual clay platelets are easy to distinguish, with lengths up to 10 μm. The striated calcite-rich patches appear as single grains with sizes up to several millimeters, though they occasionally are smeared out in a direction parallel to the striations. We have analyzed surface roughness at magnifications of 2.5x to 100x using a standard White Light Interferometer, parallel and perpendicular to slip. At low magnifications, 2.5x and 5x, Hurst exponents were anomalously low, around 0.1 to 0.2, interpreted to be related to a lack of sufficient resolution to pick up the striations. At higher magnification the Hurst exponent is 0.34 to 0.43 parallel to the striation, and 0.44 to 0.61 perpendicular to the striation. This

  5. On the role of processing parameters in producing Cu/SiC metal matrix composites via friction stir processing: Investigating microstructure, microhardness, wear and tensile behavior

    SciTech Connect

    Barmouz, Mohsen; Besharati Givi, Mohammad Kazem; Seyfi, Javad

    2011-01-15

    The main aim of this study is to produce copper reinforced metal matrix composite (MMC) layers using micron sized SiC particles via friction stir processing (FSP) in order to enhance surface mechanical properties. Microstructural evaluation using optical microscopy (OM) and scanning electron microscopy (SEM) indicated that an increase in traverse speed and a decrease in rotational speed cause a reduction in the grain size of stir zone (SZ) for the specimens friction stir processed (FSPed) without SiC particles. With the aim of determining the optimum processing parameters, the effect of traverse speed as the main processing variable on microstructure and microhardness of MMC layers was investigated. Higher traverse speeds resulted in poor dispersion of SiC particles and consequently reduced the microhardness values of MMC layers. It was found that upon addition of SiC particles, wear properties were improved. This behavior was further supported by SEM images of wear surfaces. Results demonstrated that the microcomposite produced by FSP exhibited enhanced wear resistance and higher average friction coefficient in comparison with pure copper. Tensile properties and fracture characteristics of the specimens FSPed with and without SiC particles and pure copper were also evaluated. According to the results, the MMC layer produced by FSP showed lower strength and elongation than pure copper while a remarkable elongation was observed for FSPed specimen without SiC particles. Research Highlights: {yields} Decrease in traverse speed leads to good dispersion of SiC particles in composites. {yields} No distinct TMAZ in side regions of SZ of FSPed specimens with SiC particles. {yields} Microhardness of FSPed specimens with SiC particles shows a remarkable increase. {yields} Reinforcement of Cu with SiC particles improves wear and friction behavior of surface. {yields} A weak bonding in tensile due to probable agglomeration for SiC containing samples.

  6. Investigating the use of texture features for analysis of breast lesions on contrast-enhanced cone beam CT

    NASA Astrophysics Data System (ADS)

    Wang, Xixi; Nagarajan, Mahesh B.; Conover, David; Ning, Ruola; O'Connell, Avice; Wismueller, Axel

    2014-04-01

    Cone beam computed tomography (CBCT) has found use in mammography for imaging the entire breast with sufficient spatial resolution at a radiation dose within the range of that of conventional mammography. Recently, enhancement of lesion tissue through the use of contrast agents has been proposed for cone beam CT. This study investigates whether the use of such contrast agents improves the ability of texture features to differentiate lesion texture from healthy tissue on CBCT in an automated manner. For this purpose, 9 lesions were annotated by an experienced radiologist on both regular and contrast-enhanced CBCT images using two-dimensional (2D) square ROIs. These lesions were then segmented, and each pixel within the lesion ROI was assigned a label - lesion or non-lesion, based on the segmentation mask. On both sets of CBCT images, four three-dimensional (3D) Minkowski Functionals were used to characterize the local topology at each pixel. The resulting feature vectors were then used in a machine learning task involving support vector regression with a linear kernel (SVRlin) to classify each pixel as belonging to the lesion or non-lesion region of the ROI. Classification performance was assessed using the area under the receiver-operating characteristic (ROC) curve (AUC). Minkowski Functionals derived from contrastenhanced CBCT images were found to exhibit significantly better performance at distinguishing between lesion and non-lesion areas within the ROI when compared to those extracted from CBCT images without contrast enhancement (p < 0.05). Thus, contrast enhancement in CBCT can improve the ability of texture features to distinguish lesions from surrounding healthy tissue.

  7. Microstructure and mechanical properties of titanium alloys reinforced with titanium boride

    NASA Astrophysics Data System (ADS)

    Hill, Davion M.

    Microstructure features in TiB-reinforced titanium alloys are correlated with mechanical properties. Both laser deposition and arc melting are used to fabricate test alloys where microstructure evolution with heat treatment is examined. SEM and TEM investigations of microstructure are coupled with 3D reconstruction to provide an adequate picture of phases in these alloys. Mechanical properties are then studied. Wear testing of several test alloys is presented, followed by hardness and modulus measurements of individual phases via micro- and nano-indentation as well as a novel micro-compression technique. Bulk mechanical properties are then tested in Ti-6Al-4V and Ti-555 (Ti-5Al-5V-5Mo-3Cr-1Fe) with varying amounts of boron. Image processing methods are then applied to high resolution back-scattered scanning electron microscope images to quantify microstructure features in the tensile test specimens, and these values are then correlated with mechanical properties.

  8. Women with TSC: Relationship between Clinical, Lung Function and Radiological Features in a Genotyped Population Investigated for Lymphangioleiomyomatosis

    PubMed Central

    Imeri, Gianluca; Palumbo, Giuseppina; La Briola, Francesca; Tresoldi, Silvia; Volpi, Angela; Gualandri, Lorenzo; Ghelma, Filippo; Alfano, Rosa Maria; Montanari, Emanuele; Gorio, Alfredo; Lesma, Elena; Peron, Angela; Canevini, Maria Paola; Centanni, Stefano

    2016-01-01

    The advent of pharmacological therapies for lymphangioleiomyomatosis (LAM) has made early diagnosis important in women with tuberous sclerosis complex (TSC), although the lifelong cumulative radiation exposure caused by chest computer tomography (CT) should not be underestimated. We retrospectively investigated, in a cohort of TSC outpatients of San Paolo Hospital (Milan, Italy) 1) the role of pulmonary function tests (PFTs) for LAM diagnosis, 2) the association between LAM and other features of TSC (e.g. demography, extrapulmonary manifestations, genetic mutations, etc.), and 3) the characteristics of patients with multifocal micronodular pneumocyte hyperplasia (MMPH). Eighty-six women underwent chest CT scan; pulmonary involvement was found in 66 patients (77%; 49% LAM with or without MMPH, and 28% MMPH alone). LAM patients were older, with a higher rate of pneumothorax, presented more frequently with renal and hepatic angiomyolipomas, and tended to have a TSC2 mutation profile. PFTs, assessed in 64% of women unaffected by cognitive impairments, revealed a lower lung diffusion capacity in LAM patients. In multivariate analysis, age, but not PFTs, resulted independently associated with LAM diagnosis. Patients with MMPH alone did not show specific clinical, functional or genetic features. A mild respiratory impairment was most common in LAM-TSC patients: In conclusions, PFTs, even if indicated to assess impairment in lung function, are feasible in a limited number of patients, and are not significantly useful for LAM diagnosis in women with TSC. PMID:27171001

  9. The influence of microstructure on the sintering process in crystalline metal powders investigated by positron lifetime spectroscopy: II. Tungsten powders with different powder-particle sizes

    NASA Astrophysics Data System (ADS)

    Staab, T. E. M.; Krause-Rehberg, R.; Vetter, B.; Kieback, B.; Lange, G.; Klimanek, P.

    1999-02-01

    Compacts of tungsten powder with five different powder-particle sizes (from 0953-8984/11/7/010/img7 to 0953-8984/11/7/010/img8) are subjected to pressureless sintering. We investigate the change in microstructure during the sintering process by positron lifetime spectroscopy. So as to be able to distinguish between defects having the same positron lifetime, we investigate their kinetics when the sample is annealed. In particular, we consider the annealing out of vacancy clusters after low-temperature electron irradiation, as well as recovery and recrystallization of a tungsten sheet, in as-manufactured form. Making measurements on uncompacted powder, we find an increasing fraction of positrons annihilating in surface states with decreasing powder-particle size. The powder-particle and grain sizes (influencing the x-ray domain size) are monitored additionally by means of metallography and x-ray diffraction. We find that all of the methods give results in agreement with each other. The small grain sizes at lower temperature, about one fifth of the powder-particle size, cause positrons to annihilate at grain boundaries, leading to vacancy-cluster-like signals. At the intensive-shrinkage stage, there are certainly contributions from different shrinkage mechanisms. The observed shrinkage rates can be explained by Coble creep. It is possible that dislocations also play a role as vacancy sources and sinks, since the intensive-shrinkage stage occurs in a temperature region wherein recrystallization takes place.

  10. Classical molecular dynamics investigation of microstructure evolution and grain boundary diffusion in nano-polycrystalline UO2

    NASA Astrophysics Data System (ADS)

    Govers, K.; Verwerft, M.

    2013-07-01

    The High Burnup Structure (HBS) observed at pellet periphery in conventional Light Water Reactor nuclear fuels and around spots presenting high plutonium content in mixed (U, Pu) oxide fuel - MOX fuel - consists of a restructuration of the original grains into smaller ones. The process is often postulated to occur because of the accumulation of irradiation damage and the retention of fission products in the matrix. The computing power nowadays available enables for simulating larger systems at the atomic scale up to the point that nano-polycrystalline material can now be investigated by empirical potential molecular dynamics. Simulations of nano-polycrystalline UO2 structures have been carried out at various temperatures to investigate atom mobility close to grain boundaries. The variation of Arrhénius parameters for the diffusion coefficient of oxygen, uranium and xenon as a function of the distance from a grain boundary was studied, leading to the distinction of three zones: the grain boundary layers (up to 1 nm depth) presenting enhanced diffusion, an intermediate zone (1 to roughly 2 nm depth) with intermediate diffusion values and the bulk of the grains. The following Arrhénius relations for grain boundary diffusion were derived:

  11. Microstructural features of the La{sub 1−x}Ca{sub x}FeO{sub 3−δ} solid solutions prepared via Pechini route

    SciTech Connect

    Gerasimov, E.Yu.; Isupova, L.A.; Tsybulya, S.V.

    2015-10-15

    Highlights: • La{sub 1−x}Ca{sub x}FeO {sub (3−δ)} (0 ≤ x ≤ 0.7) perovskite were prepared by Pechini method. • Planar defects in direction (1 0 1) were observed in the perovskite surface. • α-Fe{sub 2}O{sub 3} particles (1–10 nm) on the surface of perovskite were revealed. • Amount of α-Fe{sub 2}O{sub 3} particles on the perovskite surface grew with rising x values. - Abstract: Solid solutions with La{sub 1−x}Ca{sub x}FeO{sub 3−δ} (0 ≤ x ≤ 0.7) perovskite-like structure prepared via Pechini route have been investigated by using high resolution transmission electron microscopy and X-ray diffraction. Extended planar defects lying in (1 0 1) crystallographic planes and α-Fe{sub 2}O{sub 3} nanoparticles on the surface of perovskite microcrystals are characteristic of the samples under investigation. It was found that testing of the samples in catalytic deep CH{sub 4} oxidation process results in partial destruction of solid solutions with formation of planar defects in the bulk and α-Fe{sub 2}O{sub 3} particles on the surface.

  12. Investigation on the microstructure and mechanical properties of CuCrZr after manufacturing thermal cycle for plasma facing component

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Yong; Jung, Yang-Il; Choi, Byung-Kwon; Lee, Jung-Suk; Jeong, Yong Hwan; Hong, Bong Guen

    2011-10-01

    The effects of manufacturing thermal cycle on the various mechanical properties of CuCrZr were investigated. Vickers hardness was changed with an aging temperature in an identical manner with the strength change in a wide range of heat treatment. The change of Charpy impact energy with an aging temperature exhibited an opposite trend to the changes of the strength and hardness. At least in terms of the impact energy of CuCrZr, aging at a higher temperate would be preferable if the strength of CuCrZr could be maintained higher than the limitation value after the completion of the fabrication of ITER first wall. The fatigue life of CuCrZr was influenced to a certain extent by the cooling rate and the aging temperature. Especially in the higher strain amplitude, the contribution of the elastic and plastic components to the fatigue response was dependent on the yield strength which is determined by the aging temperature.

  13. Microstructural investigations on as-cast and annealed Al-Sc and Al-Sc-Zr alloys

    SciTech Connect

    Lohar, A.K.; Mondal, B.; Rafaja, D.; Klemm, V.; Panigrahi, S.C.

    2009-11-15

    Al-Sc and Al-Sc-Zr alloys containing 0.05, 0.1 and 0.5 wt.% Sc and 0.15 wt.% Zr were investigated using optical microscopy, electron microscopy and X-ray diffraction. The phase composition of the alloys and the morphology of precipitates that developed during solidification in the sand casting process and subsequent thermal treatment of the samples were studied. XRD analysis shows that the weight percentage of the Al{sub 3}Sc/Al{sub 3}(Sc, Zr) precipitates was significantly below 1% in all alloys except for the virgin Al0.5Sc0.15Zr alloy. In this alloy the precipitates were observed as primary dendritic particles. In the binary Al-Sc alloys, ageing at 470 deg. C for 24 h produced precipitates associated with dislocation networks, whereas the precipitates in the annealed Al-Sc-Zr alloys were free of interfacial dislocations except at the lowest content of Sc. Development of large incoherent precipitates during precipitation heat treatment reduced hardness of all the alloys studied. Growth of the Al{sub 3}Sc/Al{sub 3}(Sc, Zr) precipitates after heat treatment was less at low Sc content and in the presence of Zr. Increase in hardness was observed after heat treatment at 300 deg. C in all alloys. There is a small difference in hardness between binary and ternary alloys slow cooled after sand casting.

  14. An investigation on actuation behavior of polyacrylonitrile gel fibers as a function of microstructure and stabilization temperature

    NASA Astrophysics Data System (ADS)

    Mirbaha, Hamideh; Arbab, Shahram; Zeinolebadi, Ahmad; Nourpanah, Parviz

    2013-04-01

    Polyacrylonitrile (PAN) gel fibers show great potential to be used as actuators due to their mechanical response to chemical stimuli. In this work the response of PAN gel fibers to pH variation is studied. Three commercial grade PAN fibers with different chemical composition are investigated. Fibers are stabilized at temperatures varying from 100 to 275 °C. The stabilized fibers are hydrolyzed in an alkaline solution to obtain gel fibers. Gel fibers are stepwise immersed in solutions with pH varying between 0 and 14. Length/diameter variations are measured by optical microscopy. Results suggest that there is an optimum stabilization temperature at which a maximum response to pH change is obtained. This temperature corresponds to the onset of cyclization reactions, and is determined by the chemical composition of starting material. Thus at low stabilization temperatures (T ≤ 200 °C) only a gel-like shell is formed on the surface of fibers. Fibers stabilized above 200 °C show significant length/diameter variations (up to 325%). Increasing the stabilization temperature above the optimum temperature weakens the response of fibers to pH change. The results also show that the actuation behavior of PAN fibers containing itaconic acid starts at lower stabilization temperatures. This is attributed to the effect of acidic groups in lowering the onset of cyclization reactions.

  15. Investigation of the Influence of the Local Microstructure of Copper Interconnects on Void Formation and Evolution during Electromigration Testing

    SciTech Connect

    Meyer, M. A.; Engelmann, H.-J.; Langer, E.; Zschech, E.; Grafe, M.

    2006-02-07

    The electromigration-induced void evolution has been investigated in-situ on fully embedded inlaid copper test structures inside a SEM, utilizing the method described elsewhere. After the failure of the test structure or after significant voiding had been observed the cathode via region of the samples was prepared for subsequent TEM and/or EBSD analysis in order to reveal the position of grain boundaries and the orientations of the grains in the neighborhood of a void. It was confirmed that intersections of grain boundaries with interfaces of the interconnect lines or clusters of small grains can act as nucleation sites for initial void formation or as trapping sites on which voids can be stopped. Furthermore, it was found that for interconnects with strengthened top interface, where the diffusion rate is significantly lower due to the changed chemical bonding, that the void movement occurs mainly along the copper/liner interface. Such interconnects show significantly longer lifetimes. In this paper, local alloying of copper interconnects with aluminum is reported.

  16. Nucleation mechanisms of refined alpha microstructure in beta titanium alloys

    NASA Astrophysics Data System (ADS)

    Zheng, Yufeng

    Due to a great combination of physical and mechanical properties, beta titanium alloys have become promising candidates in the field of chemical industry, aerospace and biomedical materials. The microstructure of beta titanium alloys is the governing factor that determines their properties and performances, especially the size scale, distribution and volume fraction of precipitate phase in parent phase matrix. Therefore in order to enhance the performance of beta titanium alloys, it is critical to obtain a thorough understanding of microstructural evolution in beta titanium alloys upon various thermal and/or mechanical processes. The present work is focusing on the study of nucleation mechanisms of refined alpha microstructure and super-refined alpha microstructure in beta titanium alloys in order to study the influence of instabilities within parent phase matrix on precipitates nucleation, including compositional instabilities and/or structural instabilities. The current study is primarily conducted in Ti-5Al-5Mo-5V-3Cr (wt%, Ti-5553), a commercial material for aerospace application. Refined and super-refined precipitates microstructure in Ti-5553 are obtained under specific accurate temperature controlled heat treatments. The characteristics of either microstructure are investigated in details using various characterization techniques, such as SEM, TEM, STEM, HRSTEM and 3D atom probe to describe the features of microstructure in the aspect of morphology, distribution, structure and composition. Nucleation mechanisms of refined and super-refined precipitates are proposed in order to fully explain the features of different precipitates microstructure in Ti-5553. The necessary thermodynamic conditions and detailed process of phase transformations are introduced. In order to verify the reliability of proposed nucleation mechanisms, thermodynamic calculation and phase field modeling simulation are accomplished using the database of simple binary Ti-Mo system

  17. Investigating the microstructure of keratin extracted from wool: Peptide sequence (MALDI-TOF/TOF) and protein conformation (FTIR)

    NASA Astrophysics Data System (ADS)

    Cardamone, Jeanette M.

    2010-04-01

    Investigations of keratins extracted from wool by reduction hydrolysis and by alkaline hydrolysis showed that their chemical compositions and secondary structures were similar to original wool. The keratin isolates were similar in amino acid, Amides I and II, and secondary structure to each other and to original wool. From SDS-PAGE electrophoresis, keratin isolated by reduction contained protein homologs of molecular weight, ˜40-60 kDa and keratin isolate from alkaline hydrolysis contained peptide fragments of ˜6-8 kDa. MALDI-TOF/TOF spectrometry confirmed that the reduction isolate contained Type II microfibrillar component 7C, hair Type II intermediate filament, Type I microfibrillar 48 kDa component 8C-1, and Type I microfibrillar 47.6 kDa protein homologs which contained alanine, glutamine, glutamic acid, leucine, serine, leucine, and cystine with highest amounts glutamic acid and leucine amino acids. FTIR spectroscopy was applied to examine secondary structure to confirm the content of α-helix/β-sheet/disordered regions for original wool (58.2%/37.9%/3.9%); keratin from reduction (36.7%/50.2%/13.1%); and keratin from alkaline hydrolysis (25.7%/51.8%/22.5%). The higher content of β-sheet secondary structure and intact α-helical conformation characterized these isolates as viable starting materials for chemical modification to form novel bio-based materials useful in industrial formulations and compositions. In particular keratin extracted by reduction with the molecular weight of original wool and the probability of useful mechanical properties can be transformed into stand-alone products of various shapes and forms such as porous foams, sponges, mats, and films for bio-based, adaptable structures.

  18. Irradiation effects and micro-structural changes in large grain uranium dioxide fuel investigated by micro-beam X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Mieszczynski, C.; Kuri, G.; Degueldre, C.; Martin, M.; Bertsch, J.; Borca, C. N.; Grolimund, D.; Delafoy, Ch.; Simoni, E.

    2014-01-01

    Microstructural changes in a set of commercial grade UO2 fuel samples have been investigated using synchrotron based micro-focused X-ray fluorescence (μ-XRF) and X-ray diffraction (μ-XRD) techniques. The results are associated with conventional UO2 materials and relatively larger grain chromia-doped UO2 fuels, irradiated in a commercial light water reactor plant (average burn-up: 40 MW d kg-1). The lattice parameters of UO2 in fresh and irradiated specimens have been measured and compared with theoretical predictions. In the pristine state, the doped fuel has a somewhat smaller lattice parameter than the standard UO2 as a result of chromia doping. Increase in micro-strain and lattice parameter in irradiated materials is highlighted. All irradiated samples behave in a similar manner with UO2 lattice expansion occurring upon irradiation, where any Cr induced effect seems insignificant and accumulated lattice defects prevail. Elastic strain energy densities in the irradiated fuels are also evaluated based on the UO2 crystal lattice strain and non-uniform strain. The μ-XRD patterns further allow the evaluation of the crystalline domain size and sub-grain formation at different locations of the irradiated UO2 pellets.

  19. Microstructure and mechanical properties investigation of in situ TiB2 and ZrB2 reinforced Al-4Cu composites

    NASA Astrophysics Data System (ADS)

    Lutfi Anis, Ahmad; Ramli, Rosmamuhammadani; Darham, Widyani; Zakaria, Azlan; Talari, Mahesh Kumar

    2016-02-01

    Conventional Al-Cu alloys exhibit coarse grain structure leading to inferior mechanical properties in as-cast condition. Expensive thermo-mechanical treatments are needed to improve microstructure and corresponding mechanical properties. In situ Al-based composites were developed to improve mechanical properties by dispersion strengthening and grain refinement obtained by the presence of particulates in the melt during solidification. In this work Al-4Cu - 3TiB2 and Al-4Cu-3ZrB2 in situ composites were prepared by liquid casting method. XRD, electron microscopy and mechanical tests were performed on suitably sectioned and metallographically prepared surfaces to investigate the phase distribution, hardness and tensile properties. It was found that the reinforcement particles were segregated along the grain boundaries of Al dendrites. Tensile fracture morphology for both Al-4Cu - 3TiB2 and Al-4Cu-3ZrB2 were analyzed and compared to determine the fracture propagation mechanism in the composites. Al-4Cu-3ZrB2 in situ composites displayed higher strength and hardness compared to Al-4Cu-3TiB2 which could be ascribed to the stronger interfacial bonding between the Al dendrites and ZrB2 particulates as evidenced from fractographs.

  20. Microstructure and properties of ceramics

    NASA Technical Reports Server (NTRS)

    Hamano, K.

    1984-01-01

    The history of research into the microstructure and properties of ceramic ware is discussed; methods of producing ceramics with particular characteristics are investigated. Bubbles, sintering, cracks, and electron microscopy are discussed.

  1. Microstructural, optical and electrical investigations of Sb-SnO{sub 2} thin films deposited by spray pyrolysis

    SciTech Connect

    Gupta, Sushant; Yadav, B.C.; Dwivedi, Prabhat K.; Das, B.

    2013-09-01

    Highlights: • We controlled structural, morphological, electrical, optical and physical (such as band gap energy) properties by altering the Sb doping concentration. • Variation in bandgap with Sb concentration is in agreement with the Burstein–Moss hypothesis and this hypothesis was further confirmed by plotting E{sub g} vs n{sup 2/3}. • The resistivity and mobility are in the range of 1.512–6.624 × 10{sup −3} Ω cm and 9.75–22.96 cm{sup 2} V{sup −1} s{sup −1}. The e-density lies between 4.11 × 10{sup 19} and 4.24 × 10{sup 20} cm{sup −3}. • We observed that Sb substitution in SnO{sub 2} lattice decreases the crystallite size and the possible reason for this is the creation of Sb monolayer on the surface of SnO{sub 2} crystallite. - Abstract: The structural, optical and electrical properties of spray deposited antimony (Sb) doped tin oxide (SnO{sub 2}) thin films, prepared from SnCl{sub 4} precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0 to 1.5 wt.% of Sb. The analysis of X-ray diffraction patterns revealed that the as deposited doped and undoped tin oxide thin films are pure crystalline tetragonal rutile phase of tin oxide which belongs to the space group P4{sub 2}/mnm (number 136). The surface morphological examination with field emission scanning electron microscopy (FESEM) revealed the fact that the grains are closely packed and pores/voids between the grains are very few. The resistivity (ρ) and mobility (μ) are in the range of 1.512 × 10{sup −3}–6.624 × 10{sup −3} Ω cm and 9.75–22.96 cm{sup 2} V{sup −1} s{sup −1}. The electron density lies between 4.11 × 10{sup 19} and 4.24 × 10{sup 20} cm{sup −3}. A thorough electrical investigation reveals that the film's resistivity depends on carrier concentration. It is found that ionized impurity scattering is the dominant mechanism, which limits the mobility of the carriers. The transmittance spectra for

  2. Specialized investigations on physical and morphological features of TiC thin films synthesized by PECVD method

    NASA Astrophysics Data System (ADS)

    Alipour, Ramin; Meshkani, Sakineh; Ghoranneviss, Mahmood

    2015-07-01

    Deposition of titanium carbide (TiC) thin film on 304 stainless steel was investigated by the plasma enhanced chemical vapor deposition (PECVD) method using a 5% C2H2 + 95% Ar gas mixture as a reactant gases and carbon source with titanium plate as a target. Physical and mechanical properties of the synthesized TiC thin film on 304 stainless steel were studied to determine its potential application as a protective layer for first wall of Tokamaks. X-ray diffraction (XRD) showed that the crystalline structures of TiC (111 and 220) for sample without annealing and TiC (111, 220 and 311) for sample with annealing at 1000 °C for 1 h, was formed. The XPS Ti 2p spectrum of sample shows two peaks related to the binding energies of 455.3 eV (the photoelectron peaks of Ti 2p 3/2) and 460.9 eV (the photoelectron peaks of Ti 2p 1/2). Also, the C 1s spectra with the binding energy of 281.3 eV was seen in XPS analysis. TiC film of about 10.9 μm thickness was observed on scanning electron microscopy (SEM) image. The morphological feature like statistical parameters, the motifs analysis and the watershed segmentation of the thin film 3D surface of TiC films were investigated by the AFM analysis and MountainsMap Premium 7.2 (64-bit version) and Gwyddion softwares. Also, the effect of annealing on Minkowski functionals of TiC samples were studied. At the end, we can conclude that TiC NPs synthesized in this work by PECVD method have uniformly deposition. All results of AFM analysis provide general insight of nanostructures and properties of these thin films and can be used to achieve to a new topography model of the thin film 3D surface.

  3. Using Unmanned Aerial Vehicle (UAV) Imagery to Investigate Surface Displacements and Surface Features of the Super-Sauze Earthflow (France)

    NASA Astrophysics Data System (ADS)

    James, M. R.; Tizzard, S.; Niethammer, U.

    2014-12-01

    We present the result of using imagery collected with a small rotary wing UAV (unmanned aerial vehicle) to investigate surface displacements and fissures on the Super-Sauze earthflow (France); a slow moving earthflow with the potential to develop into rapid and highly destructive mud flows. UAV imagery acquired in October 2009 was processed using a structure-from-motion and multi-view stereo (SfM-MVS) approach in PhotoScan software. Identification of ~200 ground control points throughout the image set was facilitated by automated image matching in SfM_georef software[1] and the data incorporated into PhotoScan for network optimisation and georeferencing. The completed 2009 model enabled an ~5 cm spatial resolution orthoimage to be generated with an expected accuracy (based on residuals on control) of ~0.3 m. This was supported by comparison to a previously created 2008 model, which gave standard deviations on tie points (located on stationary terrain) of 0.27 m and 0.43 m in Easting and Northing respectively. The high resolution of the orthoimage allowed an investigation into surface displacements and geomorphology of surface features (compared to the 2008 model). The results have produced a comprehensive surface displacement map of the Super-Sauze earthflow, as well as highlighting interesting variations in fissure geomorphology and density between the 2008 and 2009 models. This study underscored the capability for UAV imagery and SfM-MVS to generate highly detailed orthographic imagery and DEMs with a low cost approach that offers significant potential for landslide hazard assessments. [1] http://www.lancaster.ac.uk/staff/jamesm/software/sfm_georef.htm

  4. Microstructural Effects on Materials under Extreme Dynamic Environments

    NASA Astrophysics Data System (ADS)

    Williams, Cyril

    Studies have shown that microstructure and microstructure evolution can play a major role on the shock response of metals and metallic alloys. When metals and metallic alloys are deformed during shock compression, large numbers of lattice defects such as dislocations can be introduced in the material. These dislocations can lead to strengthening effects such as hardening and/or softening such as dynamic recovery which may consequently change the material behavior. Therefore, to better understand the effects of microstructure and microstructure evolution on the spall response of metals, both in-situ and end-state gas gun plate impact experiments were employed to study 1100-O aluminum. The results show a sharp increase in pullback velocity for 1100-O aluminum with increase in peak shock stress between 4.0 and 8.3 GPa due to shock hardening, followed by a decrease for peak shock stresses up to 12.0 GPa due to softening induced by dynamic recovery. addition, the effects of microstructure on the spall properties of two magnesium alloys fabricated via ECAE (AZ31B-4E) and SWAP (AMX602) were also investigated. The pullback velocities were found to decrease by approximately 15% for AZ31B-4E between 1.7 GPa to 4.6 GPa shock stress. On the contrary, the pullback velocities for AMX602 were found to be random for the same shock stress range studied. Residual microstructure of the post-shocked AZ31B-4E magnesium shows that aluminum-manganese intermetallic inclusions were perhaps responsible for the reduction in pullback velocity. Also, the post-shocked residual microstructure of the AMX602 magnesium revealed features that may have been responsible for its random response.

  5. Investigation of the Microstructure and the Mechanical Properties of Cu-NiC Composite Produced by Accumulative Roll Bonding and Coating Processes

    NASA Astrophysics Data System (ADS)

    Shabani, Ali; Toroghinejad, Mohammad Reza

    2015-12-01

    In the present study, Cu-1.8 wt.% NiC (nickel coating) composite was produced by the combination of two methods, including accumulative roll bonding (ARB) and electroplating processes. Electroplating process was done on copper strips in order to produce a nickel-particle-reinforced composite. Microstructure, texture, and the mechanical properties of the produced composite were evaluated during various cycles of ARB using optical and scanning electron microscopes, x-ray diffraction, microhardness, and tensile tests. In addition, the results were compared with Cu-Cu and also Cu-NiS (nickel sheet) samples. It was found that nickel layers were fractured from the first cycle of the process, and nickel fragments were distributed in the copper matrix as the number of cycles was increased. Variation of orientation density of α-, β-, and τ-fibers for the produced composite was examined in different cycles. Microhardness for different elements in different cycles of Cu-NiC was also evaluated. Also, the investigation of the mechanical properties showed that by proceeding the ARB process, the tensile strength of the produced Cu-NiC and Cu-Cu samples was increased. However, improvement in the mechanical properties of composite samples was more noticeable due to the reinforcing effect of nickel particles. The elongation of composite samples showed a decrease in the primary cycles, unlike Cu-Cu ones; however, it was then increased. Finally, by using scanning electron microscopy, the fracture surfaces of Cu-NiC composite were studied to disclose the fracture mechanism of the samples.

  6. Synthesis and microstructural TEM investigation of CaCu{sub 3}Ru{sub 4}O{sub 12} ceramic and thin film

    SciTech Connect

    Brize, Virginie; Autret-Lambert, Cecile; Wolfman, Jerome; Gervais, Monique; Gervais, Francois

    2011-10-15

    CaCu{sub 3}Ru{sub 4}O{sub 12} (CCRO) is a conductive oxide having the same structure as CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and close lattice parameters. The later compound is strongly considered for high density parallel plates capacitors application due to its so-called colossal dielectric constant. The need for an electrode inducing CCTO epitaxial growth with a clean and sharp interface is therefore necessary, and CCRO is a good potential candidate. In this paper, the synthesis of monophasic CCRO ceramic is reported, as well as pulsed laser deposition of CCRO thin film onto (001) NdCaAlO{sub 4} substrate. Structural and physical properties of bulk CCRO were studied by transmission electron microscopy and electron spin resonance. CCRO films and ceramic exhibited a metallic behavior down to low temperature. CCRO films were (001) oriented and promoted a CCTO film growth with the same orientation. - Graphical Abstract: Structure of CaCu{sub 3}Ru{sub 4}O{sub 12} showing the RuO{sub 6} octahedra and the square planar environment for Cu{sup 2+}. Highlights: > In this study, we investigate the structural properties and microstructure of ceramics CaCu{sub 3}Ru{sub 4}O{sub 12}. > We study the conduction properties of polycrystalline material. > Then we synthesize the conductive thin film which is deposited on a high K material with the same structure (CaCu{sub 3}Ti{sub 4}O{sub 12}).

  7. Investigation of the microstructure in the catalyst layer and effects of both perfluorosulfonate ionomer and PTFE-loaded carbon on the catalyst layer of polymer electrolyte fuel cells

    SciTech Connect

    Uchida, Makoto; Aoyama, Yuko; Eda, Nobuo; Ohta, Akira

    1995-12-01

    Effects of a perfluorosulfonate ionomer (PFSI) and of a polytetrafluoroethylene (PTFE) loaded carbon (PTFE-C) on the catalyst layer in the electrode of a polymer electrolyte fuel cell (PEFC) prepared by a new method based on the process of PFSI-colloid formation were investigated by electrochemical techniques and a mercury pore sizer. The microstructure of the catalyst layer and its effect on the PEFC performance were affected by the contents of both PFSI and PTFE-C. The catalyst layer has two distinctive pore distributions with a boundary of ca. 0.04 {micro}m. The volume of larger pore (secondary pore) decreased with an increase of the PFSI content and increased with an increase of the PTFE-C content. The volume of the smaller pore (primary pore) was independent of the content of both PFSI and PTFE-C. The PFSI as well as the PTFE existed only in the secondary pore. The content of PFSI affected the performance of PEFC in the whole current density range. On the other hand, the content of PTFE-C influenced it greatly at high current density due to its gas feeding faculty. In the PEFC, reaction sites were found to exist in the secondary pore coated with the macromolecule PFSI. The hydrophobic PTFE-C works to supply the reaction gas to the reaction sites covered with the PFSI in the secondary pore, and to exhaust the product water from there. The high performance of PEFC at high current density was achieved with the best mixture of the PFSI and the PTFE-C.

  8. Investigation on the Microstructure and Ductility-Dip Cracking Susceptibility of the Butt Weld Welded with ENiCrFe-7 Nickel-Base Alloy-Covered Electrodes

    NASA Astrophysics Data System (ADS)

    Qin, Renyao; Wang, Huang; He, Guo

    2015-03-01

    The weld metal of the ENiCrFe-7 nickel-based alloy-covered electrodes was investigated in terms of the microstructure, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility. Besides the dendritic gamma-Ni(Cr,Fe) phase, several types of precipitates dispersed on the austenitic matrix were observed, which were determined to be the Nb-rich MC-type carbides with "Chinese script" morphology and size of approximately 3 to 10 µm, the Mn-rich MO-type oxides with size of approximately 1 to 2 µm, and the spherical Al/Ti-rich oxides with size of less than 1 µm. The discontinuous Cr-rich M23C6-type carbides predominantly precipitate on the grain boundaries, which tend to coarsen during reheating but begin to dissolve above approximately 1273 K (1000 °C). The threshold strain for DDC at each temperature tested shows a certain degree of correlation with the grain boundary carbides. The DDC susceptibility increases sharply as the carbides coarsen in the temperature range of 973 K to 1223 K (700 °C to 950 °C). The growth and dissolution of the carbides during the welding heat cycles deteriorate the grain boundaries and increase the DDC susceptibility. The weld metal exhibits the minimum threshold strain of approximately 2.0 pct at 1323 K (1050 °C) and the DTR less than 873 K (600 °C), suggesting that the ENiCrFe-7—covered electrode has less DDC susceptibility than the ERNiCrFe-7 bare electrode but is comparable with the ERNiCrFe-7A.

  9. Microstructure and cross-sectional shape of limb bones in Great Horned Owls and Red-tailed Hawks: how do these features relate to differences in flight and hunting behavior?

    PubMed

    Marelli, Crystal A; Simons, Erin L R

    2014-01-01

    The Red-tailed Hawk and Great Horned Owl are two species of raptor that are similar in body size, diet, and habitat. Both species use their hindlimbs during hunting, but differ in foot morphology, how they approach and immobilize prey, and the average size of prey captured. They also differ in primary flight style: the Red-tailed Hawk uses static soaring and the Great Horned Owl uses flap-gliding. The objectives of this study were to characterize the microstructure and cross-sectional shape of limb bones of these species and examine the relationship with flight and hunting behaviors. The mid-shaft of six limb bones from six individuals of each species was sampled. The degree of bone laminarity (proportion of circular primary vascular canals) and cross-sectional geometric parameters were calculated. In both species, the humerus and femur exhibited features that suggest high resistance to torsional loading, whereas the tibiotarsus and phalanges had a shape more likely to resist compression and bending in a specific plane. The femur of the Red-tailed Hawk exhibited higher laminarity and larger polar moment of area than that of the Great Horned Owl. The tibiotarsus was more elliptical than that of the Great Horned Owl. The hawk approaches prey from a more horizontal axis, takes prey of greater mass, and is more likely to pursue prey on the ground, which could potentially be causing more torsional loads on the femur and bending loads on the tibiotarsus. In addition, differences in polar moment of area of the phalanges between the species could relate to differences in foot morphology or digit length. The humerus and ulna of the flap-gliding Great Horned Owl are more elliptical than the static soaring Red-tailed Hawk, a shape that may better resist the bending loads associated with a larger amount of flapping. PMID:25162595

  10. Microstructure and Cross-Sectional Shape of Limb Bones in Great Horned Owls and Red-Tailed Hawks: How Do These Features Relate to Differences in Flight and Hunting Behavior?

    PubMed Central

    Marelli, Crystal A.; Simons, Erin L. R.

    2014-01-01

    The Red-tailed Hawk and Great Horned Owl are two species of raptor that are similar in body size, diet, and habitat. Both species use their hindlimbs during hunting, but differ in foot morphology, how they approach and immobilize prey, and the average size of prey captured. They also differ in primary flight style: the Red-tailed Hawk uses static soaring and the Great Horned Owl uses flap-gliding. The objectives of this study were to characterize the microstructure and cross-sectional shape of limb bones of these species and examine the relationship with flight and hunting behaviors. The mid-shaft of six limb bones from six individuals of each species was sampled. The degree of bone laminarity (proportion of circular primary vascular canals) and cross-sectional geometric parameters were calculated. In both species, the humerus and femur exhibited features that suggest high resistance to torsional loading, whereas the tibiotarsus and phalanges had a shape more likely to resist compression and bending in a specific plane. The femur of the Red-tailed Hawk exhibited higher laminarity and larger polar moment of area than that of the Great Horned Owl. The tibiotarsus was more elliptical than that of the Great Horned Owl. The hawk approaches prey from a more horizontal axis, takes prey of greater mass, and is more likely to pursue prey on the ground, which could potentially be causing more torsional loads on the femur and bending loads on the tibiotarsus. In addition, differences in polar moment of area of the phalanges between the species could relate to differences in foot morphology or digit length. The humerus and ulna of the flap-gliding Great Horned Owl are more elliptical than the static soaring Red-tailed Hawk, a shape that may better resist the bending loads associated with a larger amount of flapping. PMID:25162595

  11. Investigation of effects of deposition parameters on composition, microstructure,a nd emission of RF sputtered SrS:Eu thin film phosphors

    SciTech Connect

    Droes, S.R.; Mueller-Mach, R.; Mueller, G.O.; Ruffner, J.A.

    1996-12-31

    There has been little systematic study of the cause of dead (inactive) layers in II-VI phosphors used in thin film electroluminescent devices. This paper discusses preparation and characterization of rf sputter deposited Eu-doped Sr sulfide (SrS:Eu) thin films for use in a study to determine the cause of the dead layer. (The dead layer`s behavior is likely influenced by thin film composition, crystallinity, and microstructure.) We have deposited SrS:Eu thin films in a repeatable, consistent manner and have characterized properties such as composition, crystallinity, and microstructure as well as photoluminescent (PL) and electroluminescent behavior. The composition was determined using Rutherford backscattering spectrometry and electron microprobe analysis. XRD was used to assess crystalline orientation and grain size, SEM to image thin film microstructure. Measuring the PL decay after subnanosecond laser excitation in the lowest absorption band of the dopant allowed direct measurement of the dopant luminescence efficiency.

  12. INSTRUMENTS AND METHODS OF INVESTIGATION: Microstructure optical fibers for a new generation of fiber-optic sources and converters of light pulses

    NASA Astrophysics Data System (ADS)

    Zheltikov, Aleksei M.

    2007-07-01

    Breakthroughs in microstructure-fiber technologies are pushing the development of a new class of fiber-optic frequency converters, broadband light sources, and short-pulse lasers. The frequency profile of dispersion and the spatial profile of electromagnetic field distribution in waveguide modes of microstructure fibers can be tailored by modifying the core and cladding design on a micro- and nanoscale, suggesting ways of creating novel fiber-optic devices providing the highly efficient spectral and temporal transformation of laser pulses with pulse widths ranging from dozens of nanoseconds to a few optical cycles (several femtoseconds) within a broad range of peak powers from hundreds of watts to several gigawatts. In new fiber lasers, microstructure fibers provide a precise balance of dispersion within a broad spectral range, allowing the creation of compact all-fiber sources of high-power ultrashort light pulses.

  13. Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Ganvir, Ashish; Curry, Nicholas; Markocsan, Nicolaie; Nylén, Per; Joshi, Shrikant; Vilemova, Monika; Pala, Zdenek

    2016-01-01

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  14. Microstructural Control of Additively Manufactured Metallic Materials

    NASA Astrophysics Data System (ADS)

    Collins, P. C.; Brice, D. A.; Samimi, P.; Ghamarian, I.; Fraser, H. L.

    2016-07-01

    In additively manufactured (AM) metallic materials, the fundamental interrelationships that exist between composition, processing, and microstructure govern these materials’ properties and potential improvements or reductions in performance. For example, by using AM, it is possible to achieve highly desirable microstructural features (e.g., highly refined precipitates) that could not otherwise be achieved by using conventional approaches. Simultaneously, opportunities exist to manage macro-level microstructural characteristics such as residual stress, porosity, and texture, the last of which might be desirable. To predictably realize optimal microstructures, it is necessary to establish a framework that integrates processing variables, alloy composition, and the resulting microstructure. Although such a framework is largely lacking for AM metallic materials, the basic scientific components of the framework exist in literature. This review considers these key components and presents them in a manner that highlights key interdependencies that would form an integrated framework to engineer microstructures using AM.

  15. Microstructure and Property Evolution in Advanced Cladding and Duct Materials Under Long-Term and Elevated Temperature Irradiation: Modeling and Experimental Investigation

    SciTech Connect

    Wirth, Brian; Morgan, Dane; Kaoumi, Djamel; Motta, Arthur

    2013-12-01

    The in-service degradation of reactor core materials is related to underlying changes in the irradiated microstructure. During reactor operation, structural components and cladding experience displacement of atoms by collisions with neutrons at temperatures at which the radiation-induced defects are mobile, leading to microstructure evolution under irradiation that can degrade material properties. At the doses and temperatures relevant to fast reactor operation, the microstructure evolves by dislocation loop formation and growth, microchemistry changes due to radiation-induced segregation, radiation-induced precipitation, destabilization of the existing precipitate structure, and in some cases, void formation and growth. These processes do not occur independently; rather, their evolution is highly interlinked. Radiationinduced segregation of Cr and existing chromium carbide coverage in irradiated alloy T91 track each other closely. The radiation-induced precipitation of Ni-Si precipitates and RIS of Ni and Si in alloys T91 and HCM12A are likely related. Neither the evolution of these processes nor their coupling is understood under the conditions required for materials performance in fast reactors (temperature range 300-600°C and doses beyond 200 dpa). Further, predictive modeling is not yet possible as models for microstructure evolution must be developed along with experiments to characterize these key processes and provide tools for extrapolation. To extend the range of operation of nuclear fuel cladding and structural materials in advanced nuclear energy and transmutation systems to that required for the fast reactor, the irradiation-induced evolution of the microstructure, microchemistry, and the associated mechanical properties at relevant temperatures and doses must be understood. Predictive modeling relies on an understanding of the physical processes and also on the development of microstructure and microchemical models to describe their evolution under

  16. Effect of random microstructure on crack propagation in cortical bone tissue under dynamic loading

    NASA Astrophysics Data System (ADS)

    Gao, X.; Li, S.; Adel-Wahab, A.; Silberschmidt, V.

    2013-07-01

    A fracture process in a cortical bone tissue depends on various factors, such as bone loss, heterogeneous microstructure, variation of its material properties and accumulation of microcracks. Therefore, it is crucial to comprehend and describe the effect of microstructure and material properties of the components of cortical bone on crack propagation in a dynamic loading regime. At the microscale level, osteonal bone demonstrates a random distribution of osteons imbedded in an interstitial matrix and surrounded by a thin layer known as cement line. Such a distribution of osteons can lead to localization of deformation processes. The global mechanical behavior of bone and the crack-propagation process are affected by such localization under external loads. Hence, the random distribution of microstructural features plays a key role in the fracture process of cortical bone. The purpose of this study is two-fold: firstly, to develop two-dimensional microstructured numerical models of cortical bone tissue in order to examine the interaction between the propagating crack and bone microstructure using an extended finite-element method under both quasi-static and dynamic loading conditions; secondly, to investigate the effect of randomly distributed microstructural constituents on the crack propagation processes and crack paths. The obtained results of numerical simulations showed the influence of random microstructure on the global response of bone tissue at macroscale and on the crack-propagation process for quasi-static and dynamic loading conditions.

  17. Investigating the Enigmatic Ultraviolet 2175 A Extinction Feature and Correlation with Infrared Aromatic/PAH emission in M101

    NASA Astrophysics Data System (ADS)

    Gordon, Karl

    2011-10-01

    The 2175 Angstrom ultraviolet dust extinction feature has been known for more than 45 years, but the source of the extinction has yet to be positively identified. One of the leading contenders in dust grain models is small aromatic/PAHs grains. Through IR observations of HII regions in the spiral galaxy M101, PAHs have measured emission strengths that dramatically weaken at large radii and ionizations. The parameter space of these HII regions in terms of metallicity, ionization, and PAH emission strengths is the largest of any known galaxy. To explore the connection between the 2175 A extinction feature and IR aromatic/PAH emission strengths, we propose to observe the six regions in M101 {5 HII and the nucleus} using near-UV and far-UV gratings {G230L/G140L} with the MAMA detectors on STIS. The STIS instrument provides the opportunity to obtain high S/N UV spectra integrated over the same large spatial scales of the previous IR observations { 78 square arcsec} in minimal time {2 orbits per region}. From the measured spectra, we will employ stellar evolutionary synthesis and radiative transfer models to extract the intrinsic strength of the 2175 A extinction feature. The 2175 A features strengths will be compared with the published emission strengths of five different aromatic/PAH features in all six regions. If the 2175 A feature is associated with aromatic/PAHs grains, we will see a strong correlation. The lack of a strong correlation will imply the need for significant modification of leading dust models.

  18. The use of a directional solidification technique to investigate the interrelationship of thermal parameters, microstructure and microhardness of Bi–Ag solder alloys

    SciTech Connect

    Spinelli, José Eduardo; Silva, Bismarck Luiz; Cheung, Noé; Garcia, Amauri

    2014-10-15

    Bi–Ag alloys have been stressed as possible alternatives to replace Pb-based solder alloys. Although acceptable melting temperatures and suitable mechanical properties may characterize such alloys, as referenced in literature, there is a lack of comprehension regarding their microstructures (morphologies and sizes of the phases) considering a composition range from 1.5 to 4.0 wt.%Ag. In order to better comprehend such aspects and their correlations with solidification thermal parameters (growth rate, v and cooling rate, T-dot), directional solidification experiments were carried out under transient heat flow conditions. The effects of Ag content on both cooling rate and growth rate during solidification are examined. Microstructure parameters such as eutectic/dendritic spacing, interphase spacing and diameter of the Ag-rich phase were determined by optical microscopy and scanning electron microscopy. The competition between eutectic cells and dendrites in the range from 1.5 to 4.0 wt.%Ag is explained by the coupled zone concept. Microhardness was determined for different microstructures and alloy Ag contents with a view to permitting correlations with microstructure parameters to be established. Hardness is shown to be directly affected by both solute macrosegregation and morphologies of the phases forming the Bi–Ag alloys, with higher hardness being associated with the cellular morphology of the Bi-2.5 and 4.0 wt.%Ag alloys. - Highlights: • Asymmetric zone of coupled growth for Bi–Ag is demonstrated. • Faceted Bi-rich dendrites have been characterized for Bi–1.5 wt.%Ag alloy. • Eutectic cells were shown for the Bi-2.5 and 4.0 wt.%Ag solder alloys. • Interphase spacing relations with G × v are able to represent the experimental scatters. • Hall-Petch type equations are proposed relating microstructural spacings to hardness.

  19. The Role of the L1 and Individual Differences in L2 Sensitivity to Morphosyntactic Features: An ERP Investigation

    ERIC Educational Resources Information Center

    Bond, Kristi

    2013-01-01

    This study used ERP (event-related potentials) to examine both the role of the L1 and the role of individual differences in the processing of agreement violations. Theories of L2 acquisition differ with regard to whether or not native-like acquisition of L2 features is possible (Schwartz and Sprouse, 1994, 1996; Tsimpli and Mastropavlou, 2007),…

  20. Wear and microstructural integrity of ceramic plasma sprayed coatings

    NASA Astrophysics Data System (ADS)

    Erickson, Lynn C.

    1999-10-01

    In this work a series of ceramic plasma sprayed (PS) coatings, both alumina- and chromia-based, were sprayed according to a matrix of deposition parameters in order to produce a broad range of microstructures. To investigate the effect of splat size on the coating response, a series of mono-crystalline a -alumina powders with very narrow particle size ranges, nominally 5, 10 and 18 microns in diameter, was sprayed. The coatings were extensively characterized for a variety of microstructural features, including porosity, the angular distribution and density of microcracks as well as the lamellar, or splat, dimensions, using techniques of metallurgical analysis and electron microscopy. The coatings were then evaluated using a series of micromechanical techniques, including indentation, controlled scratch testing, abrasion and dry particle erosion, to investigate their response to different contact situations. It was found that the microstructural features with the most influence on the behaviour of ceramic PS coatings during contact, or wear, by hard particles include, in order of importance: (1) macro-porosity, (2) horizontal crack density, (3) degree of flattening of the splats and (4) volume of unmelted particles, which are all linked to the level and strength of interlamellar bonding in the coating. The major effect of the inter-lamellar bonding in ceramic PS coatings was seen in the wear mechanism transitions. As the level of inter-splat bonding in the coating decreases, the contact load at which the transition from plastic deformation to splat fracture and debonding occurs does as well. However, the load at which catastrophic brittle fracture and spalling occur is increased. All of the micromechanical and wear methods evaluated in the present work were sensitive to differences in the coating microstructures to varying degrees. The low load abrasion results showed the most sensitivity to the microstructural differences of the coatings, followed by controlled

  1. Hydrophobicity of curved microstructured surfaces

    NASA Astrophysics Data System (ADS)

    Cannon, A. H.; King, W. P.

    2010-02-01

    This paper presents measurements and models for how the macroscopic curvature of microstructured polymers affects hydrophobicity. Flexible polymer substrates were fabricated with arrays of regular microstructures. The interaction of liquid drops with these surfaces was analyzed for flat substrates and substrates flexed into either positive or negative cylindrical shapes. Liquid droplet static contact angle and dynamic slide angle were measured for a range of surfaces. An increase in substrate curvature corresponded with decreased slide angle for liquid droplets suspended on the surface asperities. This phenomenon is investigated in terms of solid-liquid contact line and the periodicity of surface microstructures. We present a model that can be used to understand the observed phenomena and to design microstructure geometries for hydrophobicity.

  2. ProViz-a web-based visualization tool to investigate the functional and evolutionary features of protein sequences.

    PubMed

    Jehl, Peter; Manguy, Jean; Shields, Denis C; Higgins, Desmond G; Davey, Norman E

    2016-07-01

    Low-throughput experiments and high-throughput proteomic and genomic analyses have created enormous quantities of data that can be used to explore protein function and evolution. The ability to consolidate these data into an informative and intuitive format is vital to our capacity to comprehend these distinct but complementary sources of information. However, existing tools to visualize protein-related data are restricted by their presentation, sources of information, functionality or accessibility. We introduce ProViz, a powerful browser-based tool to aid biologists in building hypotheses and designing experiments by simplifying the analysis of functional and evolutionary features of proteins. Feature information is retrieved in an automated manner from resources describing protein modular architecture, post-translational modification, structure, sequence variation and experimental characterization of functional regions. These features are mapped to evolutionary information from precomputed multiple sequence alignments. Data are displayed in an interactive and information-rich yet intuitive visualization, accessible through a simple protein search interface. This allows users with limited bioinformatic skills to rapidly access data pertinent to their research. Visualizations can be further customized with user-defined data either manually or using a REST API. ProViz is available at http://proviz.ucd.ie/. PMID:27085803

  3. ProViz—a web-based visualization tool to investigate the functional and evolutionary features of protein sequences

    PubMed Central

    Jehl, Peter; Manguy, Jean; Shields, Denis C.; Higgins, Desmond G.; Davey, Norman E.

    2016-01-01

    Low-throughput experiments and high-throughput proteomic and genomic analyses have created enormous quantities of data that can be used to explore protein function and evolution. The ability to consolidate these data into an informative and intuitive format is vital to our capacity to comprehend these distinct but complementary sources of information. However, existing tools to visualize protein-related data are restricted by their presentation, sources of information, functionality or accessibility. We introduce ProViz, a powerful browser-based tool to aid biologists in building hypotheses and designing experiments by simplifying the analysis of functional and evolutionary features of proteins. Feature information is retrieved in an automated manner from resources describing protein modular architecture, post-translational modification, structure, sequence variation and experimental characterization of functional regions. These features are mapped to evolutionary information from precomputed multiple sequence alignments. Data are displayed in an interactive and information-rich yet intuitive visualization, accessible through a simple protein search interface. This allows users with limited bioinformatic skills to rapidly access data pertinent to their research. Visualizations can be further customized with user-defined data either manually or using a REST API. ProViz is available at http://proviz.ucd.ie/. PMID:27085803

  4. Investigation on microstructure and mechanical properties of Friction Stir Welded AA6061-4.5Cu-10SiC composite

    NASA Astrophysics Data System (ADS)

    Herbert, Mervin A.; Shettigar, Arun Kumar; Nigalye, Akshay V.; Rao, Shrikantha S.

    2016-02-01

    The application of Metal Matrix Composites (MMCs) is restricted by the availability of properly developed fabrication methods. The main challenge here is the fabrication and welding of MMCs in a cost effective way. In the present study, synthesis of AA6061-4.5%Cu- 10%SiC composite was done by stir casting method. The joining of MMCs was performed by Friction Stir Welding (FSW) using a combination of square and threaded profile pin tool (CSTPP). Further, the welded composite was evaluated for microstructure and joint properties. The microstructural characterization showed uniform distribution of refined fine grains and numerous small particles at nugget zone. The hardness at the stir zone is higher than that of the base material. The tensile test revealed 96% joint efficiency in transverse direction.

  5. Investigation of Microstructure and Microhardness in Self-Reacting Friction Stir Welded AA2014-T6 and AA2219-T87

    NASA Technical Reports Server (NTRS)

    Horton, K. Renee; McGill, Preston; Barkey, Mark

    2011-01-01

    Friction stir welding (FSW) is a solid state welding process with potential advantages for aerospace and automotive industries dealing with light alloys. Self-reacting friction stir welding (SR-FSW) is one variation of the FSW process being developed at the National Aeronautics and Space Administration (NASA) for use in the fabrication of propellant tanks. This work reports on the microstructure and microhardness of SR-FSW between two dissimilar aluminum alloys. Specifically, the study examines the cross section of the weld joint formed between an AA2014-T6 plate on the advancing side and an AA2219-T87 plate on the retreating side. The microstructural analysis shows an irregularly displaced weld seam from the advancing side past the thermo-mechanical affected zone (TMAZ) into the weld nugget region. There are sharp variations in the microhardness across the weld. These variations are described in the paper and mechanisms for their formation are discussed.

  6. Microstructure Investigation of Directionally Solidified NiAl-Cr(Mo)- xDy ( x = 0, 0.1 wt.%) Hypereutectic Alloys at Different Withdrawal Rates

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Shen, Jun; Shang, Zhao; Zhang, Jian-Fei; Du, Yu-Jun; Fu, Heng-Zhi

    2013-11-01

    The microstructures of directionally solidified Ni-31Al-32Cr-6Mo (at.%)- xDy ( x = 0, 0.1 wt.%) hypereutectic alloys were studied at different withdrawal rates. The results show that the microstructure changes from the planar eutectic to the cellular eutectic and the volume fraction of the primary Cr(Mo) dendrites decreases for the Dy-free alloy with the withdrawal rate varying from 6 μm/s to 30 μm/s. The addition of 0.1 wt.% Dy promotes the planar-to-cellular transition. Moreover, the white Dy-containing phase does not form in the alloy for the planar interface growth (6 μm/s), but it can occur in the boundary of eutectic cells for the cellular interface growth (30 μm/s). A sketchy model of the planar and cellular growth is supposed to interpret it.

  7. Investigation of the influence of the chemical composition of HSLA steel grades on the microstructure homogeneity during hot rolling in continuous rolling mills using a fast layer model

    NASA Astrophysics Data System (ADS)

    Schmidtchen, M.; Rimnac, A.; Warczok, P.; Kozeschnik, E.; Bernhard, C.; Bragin, S.; Kawalla, R.; Linzer, B.

    2016-03-01

    The newly developed LaySiMS simulation tool provides new insight for inhomogeneous material flow and microstructure evolution in an endless strip production (ESP) plant. A deepened understanding of the influence of inhomogeneities in initial material state, temperature profile and material flow and their impact on the finished product can be reached e.g. by allowing for variable layer thickness distributions in the roll gap. Coupling temperature, deformation work and work hardening/recrystallization phenomena accounts for covering important effects in the roll gap. The underlying concept of the LaySiMS approach will be outlined and new insight gained regarding microstructural evolution, shear and inhomogeneous stress and strain states in the roll gap as well as local residual stresses will be presented. For the case of thin slab casting and direct rolling (TSDR) the interrelation of inhomogeneous initial state, micro structure evolution and dissolution state of micro alloying elements within the roughing section of an ESP line will be discussed. Special emphasis is put on the influence of the local chemical composition arising from direct charging on throughthickness homogeneity of the final product. It is concluded that, due to the specific combination of large reductions in the high reduction mills (HRM) and the highly inhomogeneous inverse temperature profile, the ESP-concept provides great opportunities for homogenizing the microstructure across the strip thickness.

  8. Role of Microstructural Phenomena in Magnetic Thin Films. Final Report

    SciTech Connect

    Laughlin, D. E.; Lambeth, D. N.

    2001-04-30

    Over the period of the program we systematically varied microstructural features of magnetic thin films in an attempt to better identify the role which each feature plays in determining selected extrinsic magnetic properties. This report summarizes the results.

  9. Investigation of influence of friction stir welding regimes on the features of mass transfer and temperature distribution in forming welds

    NASA Astrophysics Data System (ADS)

    Astafurov, S. V.; Shilko, E. V.; Kolubaev, E. A.; Psakhie, S. G.

    2015-10-01

    Computer simulation by the movable cellular automaton method was performed to study the influence of friction stir welding regimes on the features of intensive mass transfer and temperature distribution in forming welded joints. The calculation results showed that there is a range of optimal values of the ratio of the angular velocity to the welding speed which provides sufficient mass transfer to form a welded joint with a minimum volume content of defects. The use of the optimal FSW regimes allows to obtain joints without significant overheating of the welded materials.

  10. Integration of electrical resistivity imaging and ground penetrating radar to investigate solution features in the Biscayne Aquifer

    NASA Astrophysics Data System (ADS)

    Yeboah-Forson, Albert; Comas, Xavier; Whitman, Dean

    2014-07-01

    The limestone composing the Biscayne Aquifer in southeast Florida is characterized by cavities and solution features that are difficult to detect and quantify accurately because of their heterogeneous spatial distribution. Such heterogeneities have been shown by previous studies to exert a strong influence in the direction of groundwater flow. In this study we use an integrated array of geophysical methods to detect the lateral extent and distribution of solution features as indicative of anisotropy in the Biscayne Aquifer. Geophysical methods included azimuthal resistivity measurements, electrical resistivity imaging (ERI) and ground penetrating radar (GPR) and were constrained with direct borehole information from nearby wells. The geophysical measurements suggest the presence of a zone of low electrical resistivity (from ERI) and low electromagnetic wave velocity (from GPR) below the water table at depths of 4-9 m that corresponds to the depth of solution conduits seen in digital borehole images. Azimuthal electrical measurements at the site reported coefficients of electrical anisotropy as high as 1.36 suggesting the presence of an area of high porosity (most likely comprising different types of porosity) oriented in the E-W direction. This study shows how integrated geophysical methods can help detect the presence of areas of enhanced porosity which may influence the direction of groundwater flow in a complex anisotropic and heterogeneous karst system like the Biscayne Aquifer.

  11. On the complexity of the relationship between microstructure and tensile properties in cast aluminum

    NASA Astrophysics Data System (ADS)

    Bjurenstedt, Anton; Seifeddine, Salem; Jarfors, Anders E. W.

    2015-03-01

    The relationship between microstructure and mechanical properties in cast aluminum alloys is complex and is strongly affected by the casting process conditions and melt handling practices. The aim of the current work is to understand the critical interactions between material microstructure, mechanical properties and process quality in the development of high performance aluminum alloys. The mechanical properties were investigated and correlated with microstructural features such as porosity, Fe-rich particles, secondary dendrite arm spacing (SDAS) and Si-particle length. The correlation with process quality measures such as bifilm index, density index and sludge factor (SF) were also investigated. The Si-particle lengths were found to explain variation in material strength and ductility which factors such as the bifilm index and porosity could not.

  12. Investigation of real-time microstructure evolution in steep thermal gradients using in-situ spatially resolved X-ray diffraction: A case study for Ti fusion welds

    SciTech Connect

    Ressler, T.; Wong, J.; Elmer, J.W. |

    1998-12-24

    A recently developed spatially resolved X-ray diffraction (SRXRD) technique utilizing intense synchrotron radiation has been refined to yield phase and microstructural information down to 200 {micro}m in spatial extent in materials subjected to steep thermal gradients during processing. This SRXRD technique has been applied to map completely the phases and their solid-state transformation in the so-called heat-affected zone (HAZ) in titanium fusion welds in situ during the welding process. Detailed profile analysis of the SRXRD patterns revealed four principal microstructural regions at temperature in the vicinity of the HAZ surrounding the liquid weld pool: (i) a completely transformed {beta}-Ti zone 2--3 mm adjacent to the liquid weld pool; (ii) a mixed {alpha} + {beta}-it region surrounding the pure {beta}-Ti zone, (iii) a back-transformed {alpha}-Ti zone on the backside of the HAZ where pure {beta}-Ti once existed at temperature well above the {alpha} {r_arrow} {beta} transformation isotherm, and (iv) a more diffused region outside the HAZ where annealing and recrystallization of the {alpha}-it base metal occur. The high-temperature microstructures so derived corroborate well the expected transformation kinetics in pure titanium, and the observed phase transformation boundaries are in good agreement with those predicted from the transformation isotherms calculated from a simplified heat-flow model. Based on a detailed assessment of the SRXRD setup employed, improved experimentations such as a smaller beam spot emitted from third generation synchrotron sources, better mechanical stability (tighter scattering geometry), and use of an area detector would enable more quantitative structural information for future phase dynamics studies exemplified by this work.

  13. Can Online Discussion Participation Predict Group Project Performance? Investigating the Roles of Linguistic Features and Participation Patterns

    ERIC Educational Resources Information Center

    Yoo, Jaebong; Kim, Jihie

    2014-01-01

    Although many college courses adopt online tools such as Q&A online discussion boards, there is no easy way to measure or evaluate their effect on learning. As a part of supporting instructional assessment of online discussions, we investigate a predictive relation between characteristics of discussion contributions and student performance.…

  14. Combining seismic reflection and refraction data to investigate tectonic features of the Manila Trench offshore southern Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ping; Liu, Char-Shine

    2015-04-01

    Disastrous earthquakes (Mw>8) were mostly megathrust earthquakes that slipped along plate boundaries as stresses can be easily accumulated in the megathrust fault zone between two plates. Some large thrust faults, called splay faults, have been suggested to emerge from the megathrust fault to the seafloor. The splay fault may enhance tsunami generation by raising the fault plane angle from a low angle megathrust fault to a high angle splay fault, which could increase the vertical displacement of the seafloor once the fault is activated. The Luzon subduction zone has been regarded as one of the high tsunami risk zones. South of Taiwan, the Luzon subduction zone consists of four morphotectonic units from west to east: the Manila Trench, the Hengchun Ridge (accretionary wedge), the North Luzon Trough (forearc basin) and the Luzon volcanic arc. The accretionary wedge can be further divided into a lower slope domain and an upper slope domain by a splay fault. This splay fault separates a folds and thrusts dominated lower slope domain of the accretionary wedge from an intensely deformed upper slope domain. This splay fault system extends from offshore southern Taiwan to offshore southwestern Taiwan in a SSE to NNW direction, and may connect to the Chi-Shan fault onshore. It has been suggested to be a major branch of the megathrust system in the Luzon subduction zone. In this study, we analyze several large-offset multi-channel seismic profile data collected during the TAIGER survey in 2009 across the Manila trench between 18.5°N to 21°N. Special processing procedures to attenuate multiples and to enhance deep signals on seismic reflection profile data have been performed to image tectonic features of the Luzon subduction zone. Velocity structural models from ocean bottom seismometer (OBS) data are constructed for depth conversion. Finally, we map the geometries of decollement, subducting oceanic basement, splay faults, and other structural features across the Manila

  15. Scanning electron microscopy and transmission electron microscopy microstructural investigation of high-speed tool steel after Nd:YAG pulsed laser melting.

    PubMed

    Kac, S; Kusinski, J; Zielinskalipiec, A; Wronska, I

    2006-10-01

    This article presents the microstructure of a pulsed Nd:YAG laser-melted high-speed steel, namely HS6-5-2. The high chemical homogeneity and fine structure of the melted zone was attributed to high cooling rates due to the short duration of interaction with the Nd:YAG pulsed laser radiation and the relatively small volume of the melted material. The structure obtained in the surface layer after laser melting has a high level of hardness and shows improved wear resistance. PMID:17100909

  16. Investigation of a Novel NDE Method for Monitoring Thermomechanical Damage and Microstructure Evolution in Ferritic-Martensitic Steels for Generation IV Nuclear Energy Systems

    SciTech Connect

    Nagy, Peter

    2013-09-30

    The main goal of the proposed project is the development of validated nondestructive evaluation (NDE) techniques for in situ monitoring of ferritic-martensitic steels like Grade 91 9Cr-1Mo, which are candidate materials for Generation IV nuclear energy structural components operating at temperatures up to ~650{degree}C and for steam-generator tubing for sodium-cooled fast reactors. Full assessment of thermomechanical damage requires a clear separation between thermally activated microstructural evolution and creep damage caused by simultaneous mechanical stress. Creep damage can be classified as "negligible" creep without significant plastic strain and "ordinary" creep of the primary, secondary, and tertiary kind that is accompanied by significant plastic deformation and/or cavity nucleation and growth. Under negligible creep conditions of interest in this project, minimal or no plastic strain occurs, and the accumulation of creep damage does not significantly reduce the fatigue life of a structural component so that low-temperature design rules, such as the ASME Section III, Subsection NB, can be applied with confidence. The proposed research project will utilize a multifaceted approach in which the feasibility of electrical conductivity and thermo-electric monitoring methods is researched and coupled with detailed post-thermal/creep exposure characterization of microstructural changes and damage processes using state-of-the-art electron microscopy techniques, with the aim of establishing the most effective nondestructive materials evaluation technique for particular degradation modes in high-temperature alloys that are candidates for use in the Next Generation Nuclear Plant (NGNP) as well as providing the necessary mechanism-based underpinnings for relating the two. Only techniques suitable for practical application in situ will be considered. As the project evolves and results accumulate, we will also study the use of this technique for monitoring other GEN IV

  17. Investigation of the formation mechanism and morphology of the features created in the interior of cornea by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Guo, Yizang; Vukelic, Sinisa

    2015-03-01

    Laser assisted corneal surgeries often rely on the nonlinear absorption effect of ultrafast lasers to induce features in the interior of the cornea without affecting the surface. In particular, corneal flap formation in femtosecond assisted Laser- Assisted in situ Keratomileusis (LASIK) is based on the bubble creation. This study focuses on the interaction between the tissue and the femtosecond laser. Interior of cornea is treated with tightly focused femtosecond laser pulses. Due to the nature of the process, heating of the tissue within and around the focal volume is practically instantaneous. The affected region is subject to thermoelastic stress that arises with the steep temperature elevation. To predict the size of the region subject to the morphological changes due to the laser treatment, the temperature field is calculated. Cavitation bubble initiation and expansion process, which acts as precursor to the stress induced tissue trauma, is studied as well. Theoretical findings are compared against experimental results. High-speed camera is utilized to assess the laser treatment process, showing the temporal development of the cavitation bubbles. The results obtained in this study facilitate a better understanding of the effects of femtosecond laser assisted corneal surgeries and help in choosing optimal laser parameters.

  18. The impact of the stimulus features and task instructions on facial processing in social anxiety: an ERP investigation.

    PubMed

    Peschard, Virginie; Philippot, Pierre; Joassin, Frédéric; Rossignol, Mandy

    2013-04-01

    Social anxiety has been characterized by an attentional bias towards threatening faces. Electrophysiological studies have demonstrated modulations of cognitive processing from 100 ms after stimulus presentation. However, the impact of the stimulus features and task instructions on facial processing remains unclear. Event-related potentials were recorded while high and low socially anxious individuals performed an adapted Stroop paradigm that included a colour-naming task with non-emotional stimuli, an emotion-naming task (the explicit task) and a colour-naming task (the implicit task) on happy, angry and neutral faces. Whereas the impact of task factors was examined by contrasting an explicit and an implicit emotional task, the effects of perceptual changes on facial processing were explored by including upright and inverted faces. The findings showed an enhanced P1 in social anxiety during the three tasks, without a moderating effect of the type of task or stimulus. These results suggest a global modulation of attentional processing in performance situations. PMID:23384510

  19. The effects of magnetic and mechanical microstructures on the twinning stress in Ni-Mn-Ga

    NASA Astrophysics Data System (ADS)

    Faran, Eilon; Benichou, Itamar; Givli, Sefi; Shilo, Doron

    2015-12-01

    The ferromagnetic 10M Ni-Mn-Ga alloy exhibits complex magnetic and mechanical microstructures, which are expected to form barriers for motion of macro twin boundaries. Here, the contributions of both microstructures to the magnitude of the twinning stress property are investigated experimentally. A series of uniaxial loading-unloading curves are taken under different orientation angles of a constant magnetic field. The different 180 ° magnetic domains microstructures that are formed across the twin boundary in each case are visualised using a magneto optical film. Analysis of the different loading curves and the corresponding magnetic microstructures show that the latter does not contribute to the barriers for twin boundary motion. In accordance, the internal resisting stress for twin boundary motion under any magnetic field can be taken as the twinning stress measured in the absence of an external field. In addition, a statistical analysis of the fine features in the loading profiles reveals that the barrier for twinning is associated with a μ m sized characteristic length scale. This length scale corresponds to the typical thickness of micro-twinning laminates that constitute a mechanical microstructure. These findings indicate that the magnitude of the twinning stress in 10M Ni-Mn-Ga is determined by the characteristic fine twinned mechanical microstructure of this alloy.

  20. Laser microstructured biodegradable scaffolds.

    PubMed

    Koroleva, Anastasia; Kufelt, Olga; Schlie-Wolter, Sabrina; Hinze, Ulf; Chichkov, Boris

    2013-10-01

    The two-photon polymerization technique (2PP) uses non-linear absorption of femtosecond laser pulses to selectively polymerize photosensitive materials. 2PP has the ability to fabricate structures with a resolution from tens of micrometers down to hundreds of nanometers. Three-dimensional microstructuring by the 2PP technique provides many interesting possibilities for biomedical applications. This microstructuring technique is suitable with many biocompatible polymeric materials, such as polyethylene glycol, polylactic acid, polycaprolactone, gelatin, zirconium-based hybrids, and others. The process of fabrication does not require clean room conditions and does not use hazard chemicals or high temperatures. The most beneficial property of 2PP is that it is capable of producing especially complex three-dimensional (3-D) structures, including devices with overhangs, without using any supportive structure. The flexibility in controlling geometries and feature sizes and the possibility to fabricate structures without the addition of new material layers makes this technique particularly appealing for fabrication of 3-D scaffolds for tissue engineering. PMID:23729598

  1. Modeling of microstructure formation

    SciTech Connect

    Rappaz, M.; Gandin, C.A.; Jacot, A.; Charbon, C.

    1995-12-31

    As macroscopic models of solidification are now well advanced, the simulation of microstructure formation is becoming increasingly important. Tools based on Greens` functions (i.e., front-tracking) or diffuse interface methods (e.g., phase field) have been developed recently for the calculation of individual dendritic grains or of a few eutectic lamellae. Although very powerful and useful, such methods cannot be extended at present to the scale of a whole process mainly because of the very large computation time involved. At the intermediate mesoscopic scale of the grains, Monte Carlo (MC) or Cellular Automata (CA) methods can integrate nucleation and grain growth mechanisms in order to simulate the formation of grains during solidification. These latter methods have been coupled with Finite Element (FE) heat flow calculations in order to predict the grain structure at the scale of a whole process (computer metallography). The microstructural features which can be predicted using this coupled CA-FE model are: the morphology of the grains (columnar, equiaxed), the columnar-to-equiaxed transition, the selection of grains in the columnar zone, the crystallographic texture of the grains, the extension of grains in open regions of liquid, etc. Calculated parameters of the three-dimensional grain structure can also be related to the same entities obtained in metallographic cross sections (computer stereology).

  2. Three-dimensional investigation of cycling-induced microstructural changes in lithium-ion battery cathodes using focused ion beam/scanning electron microscopy

    NASA Astrophysics Data System (ADS)

    Liu, Hanshuo; Foster, Jamie M.; Gully, Adam; Krachkovskiy, Sergey; Jiang, Meng; Wu, Yan; Yang, Xingyi; Protas, Bartosz; Goward, Gillian R.; Botton, Gianluigi A.

    2016-02-01

    For vehicle electrification, one of the biggest issues for lithium ion batteries is cycle life. Within this context, the mechanisms at the source of capacity degradation during cycling are not yet to be fully understood. In this work, we use state-of-the-art FIB-SEM serial sectioning and imaging techniques to determine the effect of cycling on lithium-ion battery cathodes. The three-dimensional (3D) microstructural study was performed on both pristine and cycled LiNixMnyCo1-x-yO2 (NMC) and Li(Li0.2Ni0.13Mn0.54Co0.13)O2 (HE-NMC) cathodes. The spatial distribution of active material, carbon-doped binder and pore spaces were successfully reconstructed by appropriate image processing. Comparisons of NMC and HE-NMC cathodes after different number of cycles showed only minor increases in the number of smaller active particles, possibly negligible, considering the intrinsic microstructure variation within the cathodes. However, the connectivity between carbon-doped binder additives and active particles in NMC and HE-NMC cathodes, assessed using a "neighbor counting" method, showed an appreciable decrease after cycling which indicates a detachment of carbon-doped binder from active particles. This significant cycling-induced detachment effect between the two phases (e.g., ∼22% for HE-NMC) could indicate a loss in electrical connectivity, which may partially explain the capacity fade in the cells.

  3. Effects of a Destabilization Heat Treatment on the Microstructure and Abrasive Wear Behavior of High-Chromium White Cast Iron Investigated Using Different Characterization Techniques

    NASA Astrophysics Data System (ADS)

    Gasan, Hakan; Erturk, Fatih

    2013-11-01

    The hypoeutectic white cast iron was subjected to various destabilization heat treatment temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C) for 2 hours. The as-cast and destabilized specimens were characterized by optical metallography, classical direct comparison, and the Rietveld method. The volume fractions of carbides were measured by optical metallography. Moreover, the volume fractions of retained austenite and martensite were measured by the classical direct comparison method. Despite the limitations of optical metallography and the classical direct comparison method, the Rietveld method was successively and accurately applied to determine the volume fractions of all phases. In addition, the Rietveld analysis yielded certain results, such as the crystallographic properties of the phases that can be used to explain the relationship between the microstructural parameters and the wear behavior. Abrasive wear tests with different sliding speeds were carried out on the as-cast and destabilized alloys to identify the effect of microstructural parameters on the wear behavior. The results indicated that the morphologies of secondary carbides, the crystallographic properties of the phases, and the proper combination of the amount of martensite, retained austenite, and carbides were the principle parameters that affect the hardness and wear behavior of the alloy.

  4. Geophysical investigations of the Southeast Tyrrhenian Sea (Italy): volcanic features of the Palinuro Seamount enhanced by high resolution DTM

    NASA Astrophysics Data System (ADS)

    Passaro, S.; Milano, G.; Sprovieri, M.; Marsella, E.; Ruggieri, S.

    2009-04-01

    The Palinuro Seamount is a volcanic edifice located in the southeastern Tyrrhenian Sea, the small extensional back-arc basin in the Central Mediterranean Sea. Although several geophysical studies have been performed in the Tyrrhenian Sea, the Palinuro Seamount has not yet been subjected to intensive geophysical exploration, despite its global extension, thus representing the less known Seamount of the area. Previous studies on this Seamount focused on volcanic products, magnetic profiles, single beam data and, recentely, multibeam swath batimetry describing, the latter two, the general physiographic asset of the volcanic complex. On November 2007, a geophysical survey was performed by IAMC-CNR research institute (Naples, Italy) in the southeastern Tyrrhenian Sea within the "Aeolian_2007" cruise onboard the Urania oceanographic vessel. During the second Leg of the survey, detailed multibeam data acquisition was carried out in order to obtain high resolution DTM of the major Seamounts in the study area. Here we report a new, very high resolution Digital Terrain Model (DTM) of the Palinuro Seamount, resulting by multibeam swath bathymetric data. More than 1.000 squared Km of new high resolution multibeam sonar data have been processed and interpreted from IAMC - CNR of Naples. The processed bathymetric data of the seamount cover a depth range -3200 / -84 meters and unreported topographic features were detected both below 1000 m in depth and at the summit. The DEM evidences a global extension larger than that expected, characterized by a roughly elliptical shape extending about 55 km along E-W and 25 km in the N-S direction. The morphology reveals a very articulated summit consisting in a group of overlapped and/or coalescent volcanic cones inside collapsed calderas. Relic domes of calderic collapses are identifiable both in the western and in the central sectors of the Palinuro Seamount.

  5. Morphology and microstructure of composite materials

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.; Srinivansan, K.

    1991-01-01

    Lightweight continuous carbon fiber based polymeric composites are currently enjoying increasing acceptance as structural materials capable of replacing metals and alloys in load bearing applications. As with most new materials, these composites are undergoing trials with several competing processing techniques aimed at cost effectively producing void free consolidations with good mechanical properties. As metallic materials have been in use for several centuries, a considerable database exists on their morphology - microstructure; and the interrelationships between structure and properties have been well documented. Numerous studies on composites have established the crucial relationship between microstructure - morphology and properties. The various microstructural and morphological features of composite materials, particularly those accompanying different processing routes, are documented.

  6. Optimization of microstructure development: Application to hot metal extrusion

    SciTech Connect

    Medina, E.A.; Venugopal, S.; Frazier, W.G.; Medeiros, S.; Mullins, W.M.; Chaudhary, A.; Malas, J.C.; Srinivasan, R.

    1996-12-01

    A new process design method for controlling microstructure development during hot metal deformation processes is presented. This approach is based on modern control theory and involves state-space models for describing the material behavior and the mechanics of the process. The challenge of effectively controlling the values and distribution of important microstructural features can now be systematically formulated and solved in terms of an optimal control problem. This method has been applied to the optimization of grain size and certain process parameters such as die geometry profile and ram velocity during extrusion of plain carbon steel. Various case studies have been investigated, and experimental results show good agreement with those predicted in the design stage.

  7. Optimization of microstructure development: application to hot metal extrusion

    NASA Astrophysics Data System (ADS)

    Medina, E. A.; Venugopal, S.; Frazier, W. G.; Medeiros, S.; Mulhns, W. M.; Chaudhary, A.; Irwin, R. D.; Srinivasan, R.; Malas, J. C.

    1996-12-01

    A new process design method for controlling microstructure development during hot metal deformation processes is presented. This approach is based on modern control theory and involves state- space models for describing the material behavior and the mechanics of the process. The challenge of effectively controlling the values and distribution of important microstructural features can now be systematically formulated and solved in terms of an optimal control problem. This method has been applied to the optimization of grain size and certain process parameters such as die geometry profile and ram velocity during extrusion of plain carbon steel. Various case studies have been investigated, and experimental results show good agreement with those predicted in the design stage.

  8. Biochemical investigations of two 6-DMATS enzymes from Streptomyces reveal new features of L-tryptophan prenyltransferases.

    PubMed

    Winkelblech, Julia; Li, Shu-Ming

    2014-05-01

    Two putative prenyltransferase genes, SAML0654 and Strvi8510, were identified in Streptomyces ambofaciens and Streptomyces violaceusniger, respectively. Their deduced products share 63% sequence identity. Biochemical investigations with recombinant proteins demonstrated that L-tryptophan and derivatives, including D-tryptophan, 4-, 5-, 6- and 7-methyl-dl-tryptophan, were well accepted by both enzymes in the presence of DMAPP. Structural elucidation of the isolated products revealed regiospecific prenylation at C-6 of the indole ring and proved unequivocally the identification of two very similar 6-dimethylallyltryptophan synthases (6-DMATS). Detailed biochemical investigations with SAML0654 proved L-tryptophan to be the best substrate (K(m) 18 μm, turnover 0.3 s(-1)). Incubation with different prenyl donors showed that they also accepted GPP and catalyzed the same specific prenylation. Utilizing GPP as a prenyl donor has not been reported for tryptophan prenyltransferases previously. Both enzymes also catalyzed prenylation of some hydroxynaphthalenes; this has not previously been described for bacterial indole prenyltransferases. Interestingly, SAML0654 transferred prenyl moieties onto the unsubstituted ring of hydroxynaphthalenes. PMID:24692239

  9. An investigation of asymmetric flow features in a scaled-up driven model of the human vocal folds

    NASA Astrophysics Data System (ADS)

    Erath, Byron D.; Plesniak, Michael W.

    2010-07-01

    Flow through a driven, 7.5 times life-size vocal fold model was investigated at corresponding life-size flow rates of Q mean = 89.1 ml/s, 159.4 ml/s, and 253.0 ml/s. The flow was scaled to match physiological values for Reynolds, Strouhal, and Euler numbers. The models were driven at a life-size frequency of 94 Hz. Particle image velocimetry (PIV) data were acquired in the anterior-posterior midplane of the glottis, and the unsteady transglottal pressure drop across the vocal folds was simultaneously measured. Flow and pressure data were obtained at four discrete instances during the closing phases of the phonatory cycle for which t/T open = 0.60, 0.70, 0.80, and 0.90. The glottal jet trajectory exhibited a bimodal distribution of flow attachment between the two medial surfaces of the glottis. Vortex shedding at the trailing edge separation point generated instabilities in the shear layer, which caused large oscillations in the glottal jet orientation downstream of the glottal exit. The development of the Coanda effect during the glottal cycle was found to have minimal impact on the transglottal pressure drop, suggesting that flow orientation does not directly influence the dipole sound source. The change in transglottal pressure drop as a result of jet trajectory was less than 2% for all three investigated flow rates.

  10. Pott’s disease in Moroccan children: Clinical features and investigation of the IL-12/IFN-γ pathway

    PubMed Central

    el Azbaoui, Safa; Mrani, Nidal Alaoui; Sabri, Ayoub; Jouhadi, Zineb; Ailal, Fatima; Bousfiha, Ahmed Aziz; Najib, Jilali; Hafidi, Naima El; Deswarte, Caroline; Schurr, Erwin; Bustamante, Jacinta; Boisson-Dupuis, Stéphanie; Casanova, Jean-Laurent; Abel, Laurent; Baghdadi, Jamila EL

    2016-01-01

    Setting Tuberculosis spondylodiscitis (TS) or Pott’s disease is an extra-pulmonary form of TB that is rare and difficult to diagnose in children. Some cases of severe TB in children were recently explained by inborn errors of immunity affecting the IL-12/IFN-γ axis. Objective To analyze the clinical data for Moroccan children with TS, and to perform immunological and genetic explorations of the IL-12/IFN-γ axis. Design We studied nine children with TS diagnosed between 2012 and 2014. We investigated the IL-12/IFN-γ circuit by both whole-blood assays and sequencing of the coding regions of 14 core genes of this pathway. Results TS diagnosis was based on a combination of clinical, biological, histological, and radiological data. QuantiFERON TB Gold in Tube results were positive in 75% of patients. Whole-blood assays showed normal IL-12 and IFN-γ production in all but one patient, who displayed impaired decreased response to IL-12. No candidate disease-causing mutations were detected in the exonic regions of the 14 genes. Conclusions The diagnosis of TS in children remains challenging, and is based largely on imaging. Further investigations of TS in children are required to determine the role of genetic defects in pathways that may or may not be related to the IL-12/IFN-γ axis. PMID:26614186

  11. System and method for investigating sub-surface features of a rock formation with acoustic sources generating coded signals

    SciTech Connect

    Vu, Cung Khac; Nihei, Kurt; Johnson, Paul A; Guyer, Robert; Ten Cate, James A; Le Bas, Pierre-Yves; Larmat, Carene S

    2014-12-30

    A system and a method for investigating rock formations includes generating, by a first acoustic source, a first acoustic signal comprising a first plurality of pulses, each pulse including a first modulated signal at a central frequency; and generating, by a second acoustic source, a second acoustic signal comprising a second plurality of pulses. A receiver arranged within the borehole receives a detected signal including a signal being generated by a non-linear mixing process from the first-and-second acoustic signal in a non-linear mixing zone within the intersection volume. The method also includes-processing the received signal to extract the signal generated by the non-linear mixing process over noise or over signals generated by a linear interaction process, or both.

  12. A cross-cultural study investigating body features associated with male adolescents' body dissatisfaction in Australia, China, and Malaysia.

    PubMed

    Mellor, David; Hucker, Alice; Waterhouse, Monique; binti Mamat, Norul Hidayah; Xu, Xiaoyan; Cochrane, Jamie; McCabe, Marita; Ricciardelli, Lina

    2014-11-01

    This study investigated how dissatisfaction with particular aspects of the body was associated with overall body dissatisfaction among male adolescents in Western and Asian cultures. One hundred and six Malaysian Malays, 55 Malaysian Chinese, 195 Chinese from China, and 45 non-Asian Australians aged 12 to 19 years completed a questionnaire assessing dissatisfaction with their overall body and dissatisfaction with varying aspects of their body. Dissatisfaction with the face, height, and hair was positively correlated with overall body dissatisfaction among Malaysian Malays after body mass index, age and dissatisfaction with body areas typically included in measures (weight/shape, upper, middle, and lower body, and muscles) had been controlled for. Dissatisfaction with the face was positively correlated with overall body dissatisfaction among Malaysian Chinese. These findings demonstrate the differences in body focus for males from different cultures and the importance of using assessment measures that address all possible areas of body focus. PMID:24707036

  13. Investigation of the Extinguishing Features for Liquid Fuels and Organic Flammable Liquids Atomized by a Water Flow

    NASA Astrophysics Data System (ADS)

    Voytkov, Ivan V.; Zabelin, Maksim V.; Vysokomornaya, Olga V.

    2016-02-01

    The processes of heat and mass transfer were investigated experimentally while moving and evaporating the atomized water flow in high-temperature combustion products of typical liquid fuels and organic flammable liquids: gasoline, kerosene, acetone, crude oil, industrial alcohol. We determined typical periods of liquid extinguishing by an atomized water flow of various dispersability. Data of the discharge of extinguishing medium corresponding to various parameters of atomization and duration of using the atomization devices was presented. It is shown that Um≈3.5 m/s is a minimal outflow velocity of droplets during moving while passing the distance of 1m in the high-temperature gas medium to stop the combustion of organic liquids.

  14. Exploration of the West Florida Shelf Blue Holes Investigation of Physical and Biological Characteristics and Archaeological Implications of Unique Karst Features

    NASA Astrophysics Data System (ADS)

    Culter, J. K.

    2006-12-01

    The west Florida continental shelf is nearly as large as peninsular Florida and embraces a vast mosaic of marine habitats. The dominant shelf habitats have been described and studied to some degree. However, the offshore submerged sinkhole and spring features (blue holes) have not been scientifically described or studied, with the exception of one site called the Mudhole, a saltwater spring off Ft. Myers Beach. These features are relatively small habitats by standards of aerial coverage, but are probably more common than previously thought. These habitats are very unique shelf features, a reef in reverse, representing island habitats on the Florida shelf. This study was initiated in summer 2005 to describe the biota associated with the offshore blue hole features of this region and search for new sites. Eleven sites off the west central Florida coast have been verified and data has been collected at eight locations, all greater than 30 miles offshore. Most blue holes exhibit similar structural features, which divide the biota into zones. Pelagic species, such as amberjack, occupy the water column above the holes and reef species populate the rim. All of the sites investigated harbor one or more goliath grouper (Epinephelus itajara) and most of the features have resident nurse sharks (Ginglymostoma cirratum). Pelagic sharks periodically visit the sites and sea turtles are frequently observed at or near the holes. Whale sharks (Rhincodon typus) also seem to have an affinity for these features. The reef fauna that occupy the rim rapidly decline in abundance and diversity deeper into the holes with the deepest fauna being calcareous tube dwelling polychaetes that grow down to the edges of the hydrogen sulfide layer. There is pronounced temperature stratification within all holes. All of the sites investigated to date are relatively deep, by standards of recreational scuba diving, and divers utilized open circuit trimix to conduct the investigations. The key components

  15. Ocular features in Rubinstein-Taybi syndrome: investigation of 24 patients and review of the literature

    PubMed Central

    van Genderen, M. M; Kinds, G.; Riemslag, F.; Hennekam, R.

    2000-01-01

    AIMS—To delineate the nature and frequency of ocular pathology in Rubinstein-Taybi syndrome (RTs).
METHODS—Literature was searched for reports describing ocular symptoms in patients with RTs. 24 RTs patients (out of a total of 73 Dutch known RTs individuals) were selected for ophthalmological and electrophysiological examination, selection being based only on the distance between a patient's residence and the place of investigation.
RESULTS—Most frequently reported eye anomalies in the literature were lacrimal duct obstruction, corneal abnormalities, congenital glaucoma, congenital cataract, and colobomata. Abnormalities of almost any eye segment have been published in case reports. Ophthalmological examination of 24 Dutch RTs patients showed a visual acuity ⩽0.3 in five patients. The most frequently found eye anomalies were nasolacrimal duct problems (six patients), cataract (six patients, four congenital), and retinal abnormalities (18 patients). VEPs showed an abnormal waveform in 15 patients. It was possible to perform an ERG in 18 patients, of whom 14 were abnormal (eight showed cone dysfunction, six cone-rod dysfunction).
CONCLUSIONS—Ocular abnormalities occur in the majority of RTs patients and can be remarkably diverse. The high frequency of retinal dysfunction (78%) has not been described before. With age, retinal as well as electrophysiological abnormalities occur more frequently. In four patients no signs of retinal dysfunction were observed, indicating phenotypic heterogeneity. Further cytogenetic and molecular examination of the patients is needed before it becomes clear if this also represents genetic heterogeneity. Because of the high frequency of ocular abnormalities, visual function tests and electrophysiological investigations should be performed in every RTs patient at regular intervals.

 PMID:11004107

  16. Microstructure-property relationships in digitally generated three-dimensional, two-phase, liquid phase sintered materials

    NASA Astrophysics Data System (ADS)

    Lee, Sukbin

    In studying microstructure-property relationships, it is of great interest to reveal the effect of individual microstructural parameters on the properties of the materials in all three dimensions. However, it is not easy to obtain experimentally samples in which the individual microstructural features are independently controlled. Even though one can prepare such samples, conventional materials characterization is based on the data obtained from two-dimensional plane sections of the samples. Since many problems related to the properties of materials are three-dimensional in nature, conventional two-dimensional characterization is not always sufficient to describe the microstructure quantitatively. Also, many property experiments are destructive and therefore one needs to repeat the process many times to map the properties as a function of the microstructural parameters. Considerable effort has been made to reconstruct three-dimensional microstructures using serial sectioning in recent years in order to determine three-dimensional microstructural features of two-phase composite materials directly. While this approach yields three-dimensional data on the size, shape, and spatial correlation of particles, it demands difficult and time-consuming steps. Thus, numerical reconstruction or synthesis methods can contribute significantly to modeling three-dimensional microstructures, especially two-phase composite microstructures for this project. One objective of this project is to introduce a procedure for generating three-dimensional digital microstructures representing two-phase composite materials containing isotropically coarsened particles in the surrounding matrix phase. In order to achieve the goal, a three-dimensional, Q-state Monte Carlo Potts model of isotropic particle coarsening in a system with full wetting of particles by matrix is introduced to investigate the coarsening kinetics and microstructures associated with this process. By imposing the condition of

  17. Investigating medical decision-making capacity in patients with cognitive impairment using a protocol based on linguistic features.

    PubMed

    Tallberg, Ing-Mari; Stormoen, Sara; Almkvist, Ove; Eriksdotter, Maria; Sundström, Erik

    2013-10-01

    A critical question is whether cognitively impaired patients have the competence for autonomous decisions regarding participation in clinical trials. The present study aimed to investigate medical decision-making capacity by use of a Swedish linguistic instrument for medical decision-making (LIMD) in hypothetical clinical trials in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). Three comparable groups (age, education) participated in the study: AD (n = 20; MMSE: 24.1 ± 3.3) and MCI (n = 22; MMSE: 26.7 ± 2.4) patients and healthy controls (n = 37; MMSE: 29.1 ± 1.0). Medical decision-making capacity was operationalized as answers to questions regarding participation in three hypothetical clinical trials. Answers were scored regarding comprehension, evaluation and intelligibility of decisions, and a total LIMD score was used as the measure of medical decision-making ability. Groups differed significantly in LIMD with AD patients performing worst and MCI poorer than the control group. A strong association was found between all LIMD scores and diagnosis which supported the assertion that LIMD as it is designed is a one-dimensional instrument of medical decision-making capacity (MDMC). The results indicate that a fundamental communicative ability has an impact on the competence for autonomous decisions in cognitive impairment. PMID:23841467

  18. Investigation of the Effect of Tungsten Substitution on Microstructure and Abrasive Wear Performance of In Situ VC-Reinforced High-Manganese Austenitic Steel Matrix Composite

    NASA Astrophysics Data System (ADS)

    Moghaddam, Emad Galin; Karimzadeh, Neda; Varahram, Naser; Davami, Parviz

    2013-08-01

    Particulate VC-reinforced high-manganese austenitic steel matrix composites with different vanadium and tungsten contents were synthesized by conventional alloying and casting route. Microstructural characterizations showed that the composites processed by in situ precipitation of the reinforcements were composed of V8C7 particulates distributed in an austenitic matrix. It was observed that addition of tungsten to austenite increases work-hardening rate of subsurface layer during pin-on disk wear test. The maximum abrasive wear resistance was achieved at tungsten content equal to 2 wt pct. However, excessive addition of tungsten promoted the formation of W3C phase and reduced the abrasive wear resistance because of decrease in distribution homogeneity and volume fraction of the reinforcing VC particles.

  19. Use of cyclic current reversal polarization voltammetry for investigating the relationship between corrosion resistance and heat-treatment induced variations in microstructures of 400 C martensitic stainless steels

    NASA Technical Reports Server (NTRS)

    Ambrose, John R.

    1992-01-01

    Software for running a cyclic current reversal polarization voltammagram has been developed for use with a EG&G Princeton Applied Research Model 273 potentiostat/galvanostat system. The program, which controls the magnitude, direction and duration of an impressed galvanostatic current, will produce data in ASCII spreadsheets (Lotus, Quattro) for graphical representation of CCRPV voltammograms. The program was used to determine differences in corrosion resistance of 440 C martenstic stainless steel produced as a result of changes in microstructure effected by tempering. It was determined that tempering at all temperatures above 400 F resulted in increased polarizability of the material, with the increased likelihood that pitting would be initiated upon exposure to marine environments. These results will be used in development of remedial procedures for lowering the susceptibility of these alloys toward the stress corrosion cracking experienced in bearings used in high pressure oxygen turbopumps used in the main engines of space shuttle orbiters.

  20. Stability Study of the RERTR Fuel Microstructure

    SciTech Connect

    Jian Gan; Dennis Keiser; Brandon Miller; Daniel Wachs

    2014-04-01

    The irradiation stability of the interaction phases at the interface of fuel and Al alloy matrix as well as the stability of the fission gas bubble superlattice is believed to be very important to the U-Mo fuel performance. In this paper the recent result from TEM characterization of Kr ion irradiated U-10Mo-5Zr alloy will be discussed. The focus will be on the phase stability of Mo2-Zr, a dominated second phase developed at the interface of U-10Mo and the Zr barrier in a monolithic fuel plate from fuel fabrication. The Kr ion irradiations were conducted at a temperature of 200 degrees C to an ion fluence of 2.0E+16 ions/cm2. To investigate the thermal stability of the fission gas bubble superlattice, a key microstructural feature in both irradiated dispersion U-7Mo fuel and monolithic U-10Mo fuel, a FIB-TEM sample of the irradiated U-10Mo fuel (3.53E+21 fission/cm3) was used for a TEM in-situ heating experiment. The preliminary result showed extraordinary thermal stability of the fission gas bubble superlattice. The implication of the TEM observation from these two experiments on the fuel microstructural evolution under irradiation will be discussed.

  1. Effects of temperature, particle features and vent geometry on volcanic jet dynamics, a shock-tube investigation.

    NASA Astrophysics Data System (ADS)

    Cigala, Valeria; Kueppers, Ulrich; Dingwell, Donald B.

    2016-04-01

    The lowermost part of an eruptive plume commonly shows characteristics of an underexpanded jet. The dynamics of this gas-thrust region are likely to be a direct consequence of intrinsic (magma properties, overpressure) and extrinsic (vent geometry, weather) eruption conditions. Additionally, they affect the subsequent evolution of the eruptive column and have, therefore, important hazard assessment implications for both near- and far-field. Direct observation of eruptive events is possible, but often insufficient for complete characterization. Important complementary data can be achieved using controlled and calibrated laboratory experiments. Loose natural particles were ejected from a shock-tube while controlling temperature (25° and 500°C), overpressure (15MPa), starting grain size distribution (1-2 mm, 0.5-1 mm and 0.125-0.250 mm), density (basaltic and phonolitic), gas-particle ratio and vent geometry (nozzle, cylindrical, funnel with a flaring of 15° and 30°, respectively). For each experiment, we quantified the velocity of individual particles, the jet spreading angle, the presence of electric discharges and the production of fines and analysed their dynamic evolution. Data shows velocity of up to 296 m/s and deceleration patterns following nonlinear paths. Gas spreading angles range between 21° and 41° while the particle spreading angles between 3° and 32°. Electric discharges, in the form of lightning, are observed, quantified and described. Moreover, a variation in the production of fines is recognized during the course of single experiments. This experimental investigation, which mechanistically mimics the process of pyroclast ejection, is shown to be capable of constraining the effects of input parameters and conduit/vent geometry on pyroclastic plumes. Therefore, the results should greatly enhance the ability of numerically model explosive ejecta in nature.

  2. Effects of potential geothermal development in the Corwin Springs Known Geothermal Resources Area, Montana, on the thermal features of Yellowstone National Park. Water Resources Investigation

    SciTech Connect

    Sorey, M.L.

    1991-01-01

    A two-year study by the U.S. Geological Survey, in collaboration with the National Park Service, Argonne National Laboratory, and Los Alamos National Laboratory was initiated in 1988 to determine the effects of potential geothermal development in the Corwin Springs Known Geothermal Resources Area (KGRA), Montana, on the thermal features of Yellowstone National Park. The study addressed three principal issues: (1) the sources of thermal water in the hot springs at Mammoth, La Duke, and Bear Creek; (2) the degree of subsurface connection between these areas; and (3) the effects of geothermal development in the Corwin Springs KGRA on the Park's thermal features. The authors investigations included, but were not limited to, geologic mapping, electrical geophysical surveys, chemical sampling and analyses of waters and rocks, determinations of the rates of discharge of various thermal springs, and hydrologic tracer tests.

  3. Investigation of atmospheric insect wing-beat frequencies and iridescence features using a multi-spectral kHz remote detection system

    NASA Astrophysics Data System (ADS)

    Gebru, Alem; Rohwer, Erich; Neethling, Pieter; Brydegaard, Mikkel

    2014-10-01

    Quantitative investigation of insect activity in their natural habitat is a challenging task for entomologist. It is difficult to address questions such as flight direction, predation strength and overall activities using the current techniques such as traps and sweep nets. A multi-spectral kHz remote detection system using sunlight as an illumination source is presented. We explore possibilities of remote optical classification of insects based on their wing-beat frequencies and iridescence features. It is shown that the wing-beat frequency of the fast insect events can be resolved by implementing high sampling frequency. The iridescence features generated from the change of color in two channels (visible and near infrared) during wing-beat cycle is presented. We show that the shape of the wing-beat trajectory is different for different insects. The flight direction of atmospheric insect is also determined using silicon quadrant detector.

  4. Statistical Investigations on Solar Wind Dynamic Pressure Pulses:Basic features and Their Impacts on Geosynchronous Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Zuo, Pingbing; Feng, Xueshang

    2016-07-01

    Solar wind dynamic pressure pulse (DPP) structures, across which the dynamic pressure abruptly changes over timescales from a few seconds to several minutes, are often observed in the near-Earth space environment. Recently we have developed a novel procedure that is able to rapidly identify the DPPs from the plasma data stream, and simultaneously define the transition region and smartly select the upstream and downstream region for analysis. The plasma data with high time-resolution from 3DP instrument on board the WIND spacecraft are inspected with this automatic DPP-searching code, and a complete list of solar wind DPPs of historic WIND observations are built up. We perform a statistical survey on the properties of DPPs near 1 AU based on this event list. It is found that overwhelming majority of DPPs are associated with the solar wind disturbances including the CME-related flows, the corotating interaction regions, as well as the complex ejecta. The annual variations of the averaged occurrence rate of DPPs are roughly in phase with the solar activities. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears no systematic investigations on the response of GMFs to negative DPPs. Here we also study the decompression/compression effects of very strong negative/positive DPPs on GMFs under northward IMFs. In response to the decompression of strong negative DPPs, GMFs on dayside, near the dawn and dusk on nightside are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of events when GOES is located at the midnight sector, GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that on certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Statistically, both the decompression effect of

  5. Influence of the microstructure on the corrosion behavior of magnetron sputter-quenched amorphous metallic alloys

    NASA Technical Reports Server (NTRS)

    Thakoor, A. P.; Khanna, S. K.; Williams, R. M.; Landel, R. F.

    1983-01-01

    The microstructure and corrosion behavior of magnetron sputter deposited amorphous metallic films of (Mo6ORu40)82B18 under varying sputtering atmospheres have been investigated. The microstructural details and topology of the films have been studied by scanning electron microscopy and correlated with the deposition conditions. By reducing the pressure of pure argon gas, the characteristic features of rough surface and columnar growth full of vertical voids can be converted into a mirror-smooth finish with very dense deposits. Films deposited in the presence of O2 or N2 exhibit columnar structure with vertical voids. Film deposited in pure argon at low pressure show remarkably high corrosion resistance due to the formation of a uniform passive surface layer. The influence of the microstructure and surface texture on the corrosion behavior is discussed.

  6. Nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys

    SciTech Connect

    Tashlykova-Bushkevich, Iya I.

    2015-12-31

    The present work summarizes recent progress in the investigation of nanoscale microstructure effects on hydrogen behavior in rapidly solidified aluminum alloys foils produced at exceptionally high cooling rates. We focus here on the potential of modification of hydrogen desorption kinetics in respect to weak and strong trapping sites that could serve as hydrogen sinks in Al materials. It is shown that it is important to elucidate the surface microstructure of the Al alloy foils at the submicrometer scale because rapidly solidified microstructural features affect hydrogen trapping at nanostructured defects. We discuss the profound influence of solute atoms on hydrogen−lattice defect interactions in the alloys. with emphasis on role of vacancies in hydrogen evolution; both rapidly solidified pure Al and conventionally processed aluminum samples are considered.

  7. Injection molding of thermoplastic elastomers for microstructured substrates

    NASA Astrophysics Data System (ADS)

    Birkar, Smita

    Amorphous and semi-crystalline thermoplastic polymers have been widely investigated for injection molding of parts with microstructured surfaces. Microstructured surfaces injection molded from thermoplastic elastomers have emerging applications as superhydrobic surfaces and patterned adhesives, but there is a limited understanding of the factors affecting replication with these materials. This research was a continued investigation of block copolymer thermoplastic elastomers as well as the first in-depth examination of thermoplastic vulcanizates for injection molding microfeatures. The first focus of this research was the interactions between tooling aspect ratio and feature orientation (negative and positive tooling) and thermoplastic elastomer hard segment content on microfeature replication. Electroformed nickel tooling having positive and negative features with different geometries and aspect ratios of 0.02:1 to 2:1 were molded from three copolyester thermoplastic elastomers with similar chemistry and different hardness values. The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry. Results were correlated with elastomer properties. In the second parts of this research, the effects of microfeature spacing on the replication of thermoplastic elastomer features was investigated using micropillars with two diameters (10 and 20 mum) and three spacing ratios (0.5:1, 1:1, and 2:1). The tooling and part features were characterized for feature depth and height as well as feature definition using scanning electron microscopy and optical profilometry. Feature spacing significantly affected the replication of micropillars using a thermoplastic elastomer. This replication was competition between cooling and pressurization of the melt. Wider spacing between smaller features allowed cooling in the tooling lands to dominate the feature filling. Higher pressures did

  8. Paediatric autoimmune encephalopathies: clinical features, laboratory investigations and outcomes in patients with or without antibodies to known central nervous system autoantigens

    PubMed Central

    Hacohen, Yael; Wright, Sukhvir; Waters, Patrick; Agrawal, Shakti; Carr, Lucinda; Cross, Helen; De Sousa, Carlos; DeVile, Catherine; Fallon, Penny; Gupta, Rajat; Hedderly, Tammy; Hughes, Elaine; Kerr, Tim; Lascelles, Karine; Lin, Jean-Pierre; Philip, Sunny; Pohl, Keith; Prabahkar, Prab; Smith, Martin; Williams, Ruth; Clarke, Antonia; Hemingway, Cheryl; Wassmer, Evangeline; Vincent, Angela; Lim, Ming J

    2013-01-01

    Objective To report the clinical and investigative features of children with a clinical diagnosis of probable autoimmune encephalopathy, both with and without antibodies to central nervous system antigens. Method Patients with encephalopathy plus one or more of neuropsychiatric symptoms, seizures, movement disorder or cognitive dysfunction, were identified from 111 paediatric serum samples referred from five tertiary paediatric neurology centres to Oxford for antibody testing in 2007–2010. A blinded clinical review panel identified 48 patients with a diagnosis of probable autoimmune encephalitis whose features are described. All samples were tested/retested for antibodies to N-methyl-D-aspartate receptor (NMDAR), VGKC-complex, LGI1, CASPR2 and contactin-2, GlyR, D1R, D2R, AMPAR, GABA(B)R and glutamic acid decarboxylase. Results Seizures (83%), behavioural change (63%), confusion (50%), movement disorder (38%) and hallucinations (25%) were common. 52% required intensive care support for seizure control or profound encephalopathy. An acute infective organism (15%) or abnormal cerebrospinal fluid (32%), EEG (70%) or MRI (37%) abnormalities were found. One 14-year-old girl had an ovarian teratoma. Serum antibodies were detected in 21/48 (44%) patients: NMDAR 13/48 (27%), VGKC-complex 7/48(15%) and GlyR 1/48(2%). Antibody negative patients shared similar clinical features to those who had specific antibodies detected. 18/34 patients (52%) who received immunotherapy made a complete recovery compared to 4/14 (28%) who were not treated; reductions in modified Rankin Scale for children scores were more common following immunotherapies. Antibody status did not appear to influence the treatment effect. Conclusions Our study outlines the common clinical and paraclinical features of children and adolescents with probable autoimmune encephalopathies. These patients, irrespective of positivity for the known antibody targets, appeared to benefit from immunotherapies and further

  9. Transmission electron microscopy investigation of the microstructure of Fe-Cr alloys induced by neutron and ion irradiation at 300 °C

    NASA Astrophysics Data System (ADS)

    Hernández-Mayoral, M.; Heintze, C.; Oñorbe, E.

    2016-06-01

    Four Fe-Cr binary alloys, with Cr content from 2.5 up to 12wt%, were neutron or ion irradiated up to a dose of 0.6 dpa at 300 °C. The microstructural response to irradiation has been characterised using Transmission Electron Microscopy (TEM). Both, neutrons and ions, gave rise to the formation of dislocation loops. The most striking difference between ion and neutron irradiation is the distribution of these loops in the sample. Except for the lowest Cr content, loops are distributed mainly along grain boundaries and dislocations in the neutron irradiated samples. The inhomogeneous distribution of dislocation loops could be related to the presence of α‧ precipitates in the matrix. In contrast, a homogeneous distribution is observed in all ion irradiated samples. This important difference is attributed to the orders of magnitude difference in dose rate between these two irradiation conditions. Moreover, the density of loops depends non-monotonically on Cr content in case of neutron irradiation, while it seems to increase with Cr content for ion implantation. Differences are also observed in terms of cluster size, with larger sizes for neutron irradiation than for ion implantation, again pointing towards an effect of the dose rate.

  10. An investigation on microstructure evolution and mechanical properties during liquid state diffusion bonding of Al2024 to Ti–6Al–4V

    SciTech Connect

    Samavatian, Majid; Halvaee, Ayoub; Amadeh, Ahmad Ali; Khodabandeh, Alireza

    2014-12-15

    Joining mechanism of Ti/Al dissimilar alloys was studied during liquid state diffusion bonding process using Cu/Sn/Cu interlayer at 510 °C under vacuum of 7.5 × 10{sup −5} Torr for various bonding times. The microstructure and compositional changes in the joint zone were analyzed by scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction. Microhardness and shear strength tests were also applied to study the mechanical properties of the joints. It was found that with an increase in bonding time, the elements of interlayer diffused into the parent metals and formed various intermetallic compounds at the interface. Diffusion process led to the isothermal solidification and the bonding evolution in the joint zone. The results from mechanical tests showed that microhardness and shear strength values have a straight relation with bonding time so that the maximum shear strength of joint was obtained for a bond made with 60 min bonding time. - Highlights: • Liquid state diffusion bonding of Al2024 to Ti–6Al–4V was performed successfully. • Diffusion of the elements caused the formation of various intermetallics at the interface. • Microhardness and shear strength values have a straight relation with bonding time. • The maximum shear strength reached to 36 MPa in 60 min bonding time.

  11. Microstructure-Tensile Properties Correlation for the Ti-6Al-4V Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Shi, Xiaohui; Zeng, Weidong; Sun, Yu; Han, Yuanfei; Zhao, Yongqing; Guo, Ping

    2015-04-01

    Finding the quantitative microstructure-tensile properties correlations is the key to achieve performance optimization for various materials. However, it is extremely difficult due to their non-linear and highly interactive interrelations. In the present investigation, the lamellar microstructure features-tensile properties correlations of the Ti-6Al-4V alloy are studied using an error back-propagation artificial neural network (ANN-BP) model. Forty-eight thermomechanical treatments were conducted to prepare the Ti-6Al-4V alloy with different lamellar microstructure features. In the proposed model, the input variables are microstructure features including the α platelet thickness, colony size, and β grain size, which were extracted using Image Pro Plus software. The output variables are the tensile properties, including ultimate tensile strength, yield strength, elongation, and reduction of area. Fourteen hidden-layer neurons which can make ANN-BP model present the most excellent performance were applied. The training results show that all the relative errors between the predicted and experimental values are within 6%, which means that the trained ANN-BP model is capable of providing precise prediction of the tensile properties for Ti-6Al-4V alloy. Based on the corresponding relations between the tensile properties predicted by ANN-BP model and the lamellar microstructure features, it can be found that the yield strength decreases with increasing α platelet thickness continuously. However, the α platelet thickness exerts influence on the elongation in a more complicated way. In addition, for a given α platelet thickness, the yield strength and the elongation both increase with decreasing β grain size and colony size. In general, the β grain size and colony size play a more important role in affecting the tensile properties of Ti-6Al-4V alloy than the α platelet thickness.

  12. Microstructural diagnosis using electromagnetic wave scattering methodologies

    NASA Astrophysics Data System (ADS)

    Chou, Kevin Jenn Chien

    Scattered electromagnetic waves were used in the present work to characterize the microstructural effects on the performance of metallic materials. A Nisb3Al alloy with a dendritic microstructure has exhibited better creep resistance compared to similar alloys having equiaxed microstructure of grains. X-ray diffraction was applied along the dendritic arms to investigate their orientations. Both the interlocking boundaries and crystallographic texture of the dendritic arms resulted in the superior creep behavior. Non-invasive laser scattering was also used to optically probe smooth fatigue specimens to detect and monitor the development of fatigue damage. Inconel 718 specimens with a cylindrical geometry were tested under low cycle fatigue conditions with constant strain amplitudes ranging from 0.3% to 1%. A detection scheme to minimize computational time and memory was used to achieve in-situ data analysis. Both laser scanning and surface replication procedures were periodically performed throughout the life of the specimens. The scattered light signals were compared with microcrack length and density data from surface replicate SEM images. Three characteristic stages of the scattering signal were observed. The scanning laser light scattering (SLLS) technique was sufficiently robust, and well suited for the non-planar geometry in the leading edge. The SLLS signals correlated well with microstructural features over a large surface area. A physical model of microcrack size distribution within a surface grain was developed. The results of the model suggest that a SLLS signal saturation which coincides with the onset of microcrack density saturation corresponds to a transition from predominately single grain microcracks to microcracks that transverse multiple grains. The saturation of SLLS signal versus mean surface crack length also provided the following findings. Low cycle fatigue cracks were contained and saturated in those surface grains with the highest Schmid

  13. Using prismatic microstructured films for image blending in OLEDS

    SciTech Connect

    Haenichen, Lukas; Pschenitzka, Florian

    2009-09-08

    An apparatus such as a light source is disclosed which has an OLED device and a microstructured film disposed on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The microstructured film contains features which diffuse light emitted by said OLED device and increase the luminance of the device.

  14. Long-term observation of permeability in sedimentary rocks under high-temperature and stress conditions and its interpretation mediated by microstructural investigations

    NASA Astrophysics Data System (ADS)

    Yasuhara, Hideaki; Kinoshita, Naoki; Ohfuji, Hiroaki; Takahashi, Manabu; Ito, Kazumasa; Kishida, Kiyoshi

    2015-07-01

    In this study, a series of long-term, intermittent permeability experiments utilizing Berea sandstone and Horonobe mudstone samples, with and without a single artificial fracture, is conducted for more than 1000 days to examine the evolution of rock permeability under relatively high-temperature and confining pressure conditions. Effluent element concentrations are also measured throughout the experiments. Before and after flow-through experiments, rock samples are prepared for X-ray diffraction, X-ray fluorescence, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy to examine the mineralogical changes between pre and postexperimental samples, and also for microfocus X-ray CT to evaluate the alteration of the microstructure. Although there are exceptions, the observed, qualitative evolution of permeability is found to be generally consistent in both the intact and the fractured rock samples—the permeability in the intact rock samples increases with time after experiencing no significant changes in permeability for the first several hundred days, while that in the fractured rock samples decreases with time. An evaluation of the Damkohler number and of the net dissolution, using the measured element concentrations, reveals that the increase in permeability can most likely be attributed to the relative dominance of the mineral dissolution in the pore spaces, while the decrease can most likely be attributed to the mineral dissolution/crushing at the propping asperities within the fracture. Taking supplemental observations by microfocus X-ray CT and using the intact sandstone samples, a slight increase in relatively large pore spaces is seen. This supports the increase in permeability observed in the flow-through experiments.

  15. Experimental investigation of stress effect on swelling and microstructure of Fe-16Cr-15Ni-3Mo-Nb austenitic stainless steel under low-temperature irradiation up to high damage dose in the BOR-60 reactor

    NASA Astrophysics Data System (ADS)

    Neustroev, V. S.; Ostrovsky, Z. E.; Shamardin, V. K.

    2004-08-01

    The present paper was devoted to investigation of the stress effect on swelling and microstructure evolution of the Fe-15.8Cr-15.3Ni-2.8Mo-0.6Nb steel irradiated in the BOR-60 reactor at temperatures from 395 to 410 °C and damage doses from 79 to 98 dpa. Was found out that the stress increase leads to an increase of swelling, that can be associated with a decrease in incubation period with a practically constant swelling rate. Voids concentration increases at the first stage of irradiation when the void sizes are practically constant, and then the concentration reaches some saturation and swelling increase is caused by void growth.

  16. Phase-field simulation of thermal conductivity in porous polycrystalline microstructures

    SciTech Connect

    Millett, Paul C; Wolf, Dieter W; Tapan Desai; Srujan Rokkam; Anter El-Azab

    2008-08-01

    Mesoscale computer simulations are used to study the effective thermal conductivity of two-dimensional polycrystalline model microstructures containing finely-dispersed, stationary voids. The microstructural evolution is captured by phase-field modeling in which the competing mechanisms of curvature-driven grain-boundary migration and Zener pinning due to void/grain-boundary interactions control the grain-growth kinetics. We investigate porosity fractions between 0 and 8 % by systematically increasing the number of voids in the simulation cell. The temperature distribution throughout the microstructure at progressive instances in time is calculated by solving the solid-state heat-conduction equation. The thermal conductivity of each grid point is assigned a value according to the microstructural feature it represents (grain interiors, GBs, and voids) as determined by the phase-field order parameters. The effective conductivities of the microstructures are analyzed with respect to average grain size as well as porosity fraction, and good agreement with theoretical models is obtained.

  17. Microstructural investigation of phases and pinning properties in MBa2Cu3O7-x (M = Y and/or Gd) coated conductors produced by scale-up facilitie

    NASA Astrophysics Data System (ADS)

    Jin, Hye-Jin; Moon, Han-Kyoul; Yoon, Seokhyun; Jo, William; Kim, Kunsu; Kim, Miyoung; Ko, Rock-Kil; Jo, Young-Sik; Ha, Dong-Woo

    2016-03-01

    To expedite the commercialization of coated conductors, a robust stacking architecture of the wires must be developed and the performance of the critical currents improved. More importantly, the manufacturability, or large-scale delivery, and the capability of sustaining production at a high rate must be considered. The products of three companies, American Superconductor, Superpower Inc., and SuNAM Co., Ltd, were selected because these companies have announced commercial-grade production lines and delivered a significant amounts of wires to the open market that meet the standards demanded by power devices. X-ray diffraction patterns were used to verify the structural properties and the phase formation in the wires, and transmission electron microscopy with energy dispersive spectroscopy was used to investigate the microstructure and composition of the conductors. In addition, Raman scattering spectroscopy was used for the analysis of the phase formation and for the elucidation of secondary phases in the superconducting layers. The field dependence of the critical current was also studied to compare the transport characteristics under relatively low and medium magnetic field at 77 K and 60 K. Pinning forces were obtained from the field dependence of transport properties and pinning characteristics were investigated. The theoretical and experimental analyses were combined together using the Dew-Hughes formula to extract the scaling exponents and estimate the irreversibility lines of the fields. The results showed that the three conductors possess pinning mechanisms that originate from core pinning with a surface pinning geometry. It is remarkable that the wires discussed in this paper exhibit very similar pinning characteristics even though they have different characteristics in terms of chemical composition, microstructure, stacking architectures, and distribution of parasitic phases.

  18. Characterization of microstructure in composites using quantitative stereology

    SciTech Connect

    Gokhale, A.M.

    1995-12-31

    Microstructure of composites consists of features that are geometric in nature. For example, the features such as fibers, microcracks, voids, etc. can be described in terms of their geometric attributes such as size, shape, orientation, and location. Spatial architecture of microstructural features such as fibers, particles, microcracks, etc. affects the damage evolution, mechanical and physical properties, and the performance of composites. The spatial arrangement of microstructural features can be described in terms of attributes such as radial distribution, nearest neighbor distribution, pair-correlation, and n-point correlation functions, etc. The applications of digital image analysis and stereological techniques for statistically reliable estimation of important descriptors of the spatial order in microstructures are discussed in this paper. These techniques are applied to quantify the spatial arrangement of fibers in a metal matrix composite, and to model electrical conductivity of a polymer matrix composite.

  19. Microstructural evolution from stable sliding to fast stick slip: insights from rock deformation experiments on quartz

    NASA Astrophysics Data System (ADS)

    Collettini, Cristiano; Scuderi, Marco M.; Viti, Cecilia; Marone, Chris

    2016-04-01

    Inferring microstructural evolution and associated fault slip behaviour along natural and/or experimental faults is a long-standing problem in fault mechanics. For example, does grain-size reduction and shear localization facilitate earthquake slip or vice versa? We have sheared granular layers of quartz gouge in a double direct shear configuration using a biaxial apparatus. We varied loading stiffness and applied normal stresses to produce a spectrum of slip modes from stable sliding at 10 μm/s, slow stick-slip (average slip velocity 100 μm/s) and fast stick slip (average slip velocity 4 mm/s). At the end of the experiments we collected the experimental fault rocks for microstructural investigations. Additional samples were collected from control experiments to investigate shear fabric development and microstructural features before the onset of stick-slip instabilities. We investigated the role of normal stress and stick-slip properties, including slip velocity, in determining fault zone microstructural features. Ranging from stable sliding to fast stick-slip we observe a progressive localization of deformation along fault parallel boundary shear planes. Only during fast stick-slip is the deformation localized along continuous, thin (1-2 microns wide), boundary parallel shear planes. The shear zones are composed of nanograins dispersed within a patchy matrix. We conducted TEM analyses to characterize these materials. In experiments at the same normal stress, fast stick-slip results in localized shear zones and fabric with nanograins whereas for stable sliding the microstructure does not show a significant grain size reduction and localization. Our results indicate that the fault rheological properties and fault slip behaviour, ranging from stable to unstable slip, plays a significant role in shear localization and fault zone fabric development.

  20. Pore- and micro-structural characterization of a novel structural binder based on iron carbonation

    SciTech Connect

    Das, Sumanta; Stone, David; Convey, Diana; Neithalath, Narayanan

    2014-12-15

    The pore- and micro-structural features of a novel binding material based on the carbonation of waste metallic iron powder are reported in this paper. The binder contains metallic iron powder as the major ingredient, followed by additives containing silica and alumina to facilitate favorable reaction product formation. Compressive strengths sufficient for a majority of concrete applications are attained. The material pore structure is investigated primarily through mercury intrusion porosimetry whereas electron microscopy is used for microstructural characterization. Reduction in the overall porosity and the average pore size with an increase in carbonation duration from 1 day to 4 days is noticed. The pore structure features are used in predictive models for gas and moisture transport (water vapor diffusivity and moisture permeability) through the porous medium which dictates its long-term durability when used in structural applications. Comparisons of the pore structure with those of a Portland cement paste are also provided. The morphology of the reaction products in the iron-based binder, and the distribution of constituent elements in the microstructure are also reported. - Highlights: • Carbonation of iron produces a dense microstructure. • Pore volume in iron carbonate lower, critical size higher than those in OPC pastes • Reaction product contains iron, carbon, silicon, aluminum and calcium. • Power-law for porosity-moisture permeability relationship was established.

  1. Microstructure design for fast oxygen conduction

    SciTech Connect

    Aidhy, Dilpuneet S.; Weber, William J.

    2015-11-11

    Research from the last decade has shown that in designing fast oxygen conducting materials for electrochemical applications has largely shifted to microstructural features, in contrast to material-bulk. In particular, understanding oxygen energetics in heterointerface materials is currently at the forefront, where interfacial tensile strain is being considered as the key parameter in lowering oxygen migration barriers. Nanocrystalline materials with high densities of grain boundaries have also gathered interest that could possibly allow leverage over excess volume at grain boundaries, providing fast oxygen diffusion channels similar to those previously observed in metals. In addition, near-interface phase transformations and misfit dislocations are other microstructural phenomenon/features that are being explored to provide faster diffusion. In this review, the current understanding on oxygen energetics, i.e., thermodynamics and kinetics, originating from these microstructural features is discussed. Moreover, our experimental observations, theoretical predictions and novel atomistic mechanisms relevant to oxygen transport are highlighted. In addition, the interaction of dopants with oxygen vacancies in the presence of these new microstructural features, and their future role in the design of future fast-ion conductors, is outlined.

  2. Microstructure design for fast oxygen conduction

    DOE PAGESBeta

    Aidhy, Dilpuneet S.; Weber, William J.

    2015-11-11

    Research from the last decade has shown that in designing fast oxygen conducting materials for electrochemical applications has largely shifted to microstructural features, in contrast to material-bulk. In particular, understanding oxygen energetics in heterointerface materials is currently at the forefront, where interfacial tensile strain is being considered as the key parameter in lowering oxygen migration barriers. Nanocrystalline materials with high densities of grain boundaries have also gathered interest that could possibly allow leverage over excess volume at grain boundaries, providing fast oxygen diffusion channels similar to those previously observed in metals. In addition, near-interface phase transformations and misfit dislocations aremore » other microstructural phenomenon/features that are being explored to provide faster diffusion. In this review, the current understanding on oxygen energetics, i.e., thermodynamics and kinetics, originating from these microstructural features is discussed. Moreover, our experimental observations, theoretical predictions and novel atomistic mechanisms relevant to oxygen transport are highlighted. In addition, the interaction of dopants with oxygen vacancies in the presence of these new microstructural features, and their future role in the design of future fast-ion conductors, is outlined.« less

  3. Monitoring microstructural evolution in irradiated steel with second harmonic generation

    SciTech Connect

    Matlack, Kathryn H.; Kim, Jin-Yeon; Jacobs, Laurence J.; Wall, James J.; Qu, Jianmin

    2015-03-31

    Material damage in structural components is driven by microstructural evolution that occurs at low length scales and begins early in component life. In metals, these microstructural features are known to cause measurable changes in the acoustic nonlinearity parameter. Physically, the interaction of a monochromatic ultrasonic wave with microstructural features such as dislocations, precipitates, and vacancies, generates a second harmonic wave that is proportional to the acoustic nonlinearity parameter. These nonlinear ultrasonic techniques thus have the capability to evaluate initial material damage, particularly before crack initiation and propagation occur. This paper discusses how the nonlinear ultrasonic technique of second harmonic generation can be used as a nondestructive evaluation tool to monitor microstructural changes in steel, focusing on characterizing neutron radiation embrittlement in nuclear reactor pressure vessel steels. Current experimental evidence and analytical models linking microstructural evolution with changes in the acoustic nonlinearity parameter are summarized.

  4. Computer simulations of realistic three-dimensional microstructures

    NASA Astrophysics Data System (ADS)

    Mao, Yuxiong

    A novel and efficient methodology is developed for computer simulations of realistic two-dimensional (2D) and three-dimensional (3D) microstructures. The simulations incorporate realistic 2D and 3D complex morphologies/shapes, spatial patterns, anisotropy, volume fractions, and size distributions of the microstructural features statistically similar to those in the corresponding real microstructures. The methodology permits simulations of sufficiently large 2D as well as 3D microstructural windows that incorporate short-range (on the order of particle/feature size) as well as long-range (hundred times the particle/feature size) microstructural heterogeneities and spatial patterns at high resolution. The utility of the technique has been successfully demonstrated through its application to the 2D microstructures of the constituent particles in wrought Al-alloys, the 3D microstructure of discontinuously reinforced Al-alloy (DRA) composites containing SiC particles that have complex 3D shapes/morphologies and spatial clustering, and 3D microstructure of boron modified Ti-6Al-4V composites containing fine TiB whiskers and coarse primary TiB particles. The simulation parameters are correlated with the materials processing parameters (such as composition, particle size ratio, extrusion ratio, extrusion temperature, etc.), which enables the simulations of rational virtual 3D microstructures for the parametric studies on microstructure-properties relationships. The simulated microstructures have been implemented in the 3D finite-elements (FE)-based framework for simulations of micro-mechanical response and stress-strain curves. Finally, a new unbiased and assumption free dual-scale virtual cycloids probe for estimating surface area of 3D objects constructed by 2D serial section images is also presented.

  5. Carburizing: Microstructures and properties

    SciTech Connect

    Parrish, G.

    1999-01-01

    Detailed discussions and over 250 graphs and charts describe the effects of microstructure on the properties of carburized steels. In-depth coverage clarifies the causes, interpretation, prevention, and consequences of various microstructural variations and defects in carburized parts. Also covered are the effects of post-hardening heat treatments, surface grinding, and shot peening.

  6. Microstructural examination of the α- ω Two-Phase Shock-Induced Microstructure in Zirconium

    NASA Astrophysics Data System (ADS)

    Morrow, Benjamin M.; Escobedo, J. Pablo; Field, Robert D.; Dickerson, Robert M.; Dickerson, Patricia O.; Trujillo, Carl P.; Cerreta, Ellen K.

    2015-06-01

    Omega phase can be formed in alpha-phase Zr during shock loading. Interestingly, the high pressure phase can be retained upon release allowing for post-mortem study of the omega phase. Currently, the transformation pathway is not well understood. To provide more insight into this pathway during dynamic loading, shocked-induced microstructures of Zr have been studied. Soft recovered, plate impact specimens have been examined via electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) to characterize the orientation relationships (OR) and habit planes (HP) between phases. This enables a better understanding of transformation path that is then compared to Molecular Dynamics (MD) simulations. Based on key microstructural features observed in the post-mortem microstructures, a significant amount of the observed alpha phase appears to have originated from the reverse transformation upon release. Results of microstructural analysis will be discussed, along with implications toward phase transformation pathways.

  7. Texture and microstructure evolution in single-phase Ti{sub x}Ta{sub 1-x}N alloys of rocksalt structure

    SciTech Connect

    Koutsokeras, L. E.; Abadias, G.; Patsalas, P.

    2011-08-15

    The mechanisms controlling the structural and morphological features (texture and microstructure) of ternary transition metal nitride thin films of the Ti{sub x}Ta{sub 1-x}N system, grown by various physical vapor deposition techniques, are reported. Films deposited by pulsed laser deposition, dual cathode magnetron sputtering, and dual ion beam sputtering have been investigated by means of x-ray diffraction in various geometries and scanning electron microscopy. We studied the effects of composition, energetic, and kinetics in the evolution of the microstructure and texture of the films. We obtain films with single and mixed texture as well as films with columnar ''zone-T'' and globular type morphology. The results have shown that the texture evolution of ternary transition metal nitrides as well as the microstructural features of such films can be well understood in the framework of the kinetic mechanisms proposed for their binary counterparts, thus giving these mechanisms a global application.

  8. Correlations of microstructure with dynamic and quasi-static fracture in a plain carbon steel

    NASA Astrophysics Data System (ADS)

    Couque, H.; Asaro, R. J.; Duffy, J.; Lee, S. H.

    1988-09-01

    An investigation was conducted into the effects of temperature, loading rate, and various micro-structural parameters on the initiation of plane strain fracture of a plain carbon AISI 1020 steel. Ferrite and prior austenite grain sizes were chosen as the principal microstructural features to be in-vestigated. The microstructural variations were accomplished by changing the austenitizing tempera-ture and by altering the cooling rate during normalization. Fracture toughness tests were conducted using precracked notched round bars loaded in tension to produce two stress intensity rates, viz., K 1 = 1 MPa √m s-1 and K 1 = 2 × 106 MPa √m s-1. In addition, Charpy impact tests along with quasistatic and high rate plasticity tests were conducted. The plasticity tests were done in torsion at shear strain rates ofoverline γ = 5.0 × 10^{ - 4} s^{ - 1 } and overline γ = 1.5 × 10^{3 } s^{ - 1} . Testing temperatures covered the range from -150 °C to 150 °C which encompassed fracture initiation modes involving transgranular cleavage to fully ductile fracture. Micromechanical processes involved in void and cleavage micro-crack formation were identified and quantified. For these purposes notched round tensile tests and subsequent metallographic observations along with TEM and SEM observations of the plane strain fracture toughness specimens were performed. The experimental results and quantitative micro-modeling using simple fracture models provide a means of correlating both quasistatic and dynamic fracture toughness with microstructures.

  9. Optical and Calorimetric Studies of Cholesterol-Rich Filamentous, Helical Ribbon and Crystal Microstructures

    SciTech Connect

    Miroshnikova, Y. A.; Elsenbeck, M.; Zastavker, Y. V.; Kashuri, K; Iannacchione, G. S.

    2009-04-19

    Formation of biological self-assemblies at all scales is a focus of studies in fields ranging from biology to physics to biomimetics. Understanding the physico-chemical properties of these self-assemblies may lead to the design of bio-inspired structures and technological applications. Here we examine self-assembled filamentous, helical ribbon, and crystal microstructures formed in chemically defined lipid concentrate (CDLC), a model system for cholesterol crystallization in gallbladder bile. CDLC consists of cholesterol, bilayer-forming amphiphiles, micelle-forming amphiphiles, and water. Phase contrast and differential interference contrast (DIC) microscopy indicate the presence of three microstructure types in all samples studied, and allow for an investigation of the structures' unique geometries. Additionally, confocal microscopy is used for qualitative assessment of surface and internal composition. To complement optical observations, calorimetric (differential-scanning and modulation) experiments, provide the basis for an in-depth understanding of collective and individual thermal behavior. Observed ''transition'' features indicate clustering and ''straightening'' of helical ribbons into short, increasingly thickening, filaments that dissolve with increasing temperature. These results suggest that all microstructures formed in CDLC may coexist in a metastable chemical equilibrium. Further investigation of the CDLC thermal profile should uncover the process of cholesterol crystallization as well as the unique design and function of microstructures formed in this system.

  10. Microstructural effects in foam fracture

    NASA Astrophysics Data System (ADS)

    Stewart, Peter; Davis, Stephen; Hilgenfeldt, Sascha

    2015-11-01

    We examine the fracture of a quasi two-dimensional aqueous foam under an applied driving pressure, using a network modelling approach developed for metallic foams by Stewart & Davis (J. Rheol., vol. 56, 2012, p. 543). In agreement with experiments, we observe two distinct mechanisms of failure analogous to those observed in a crystalline solid: a slow ductile mode when the driving pressure is applied slowly, where the void propagates as bubbles interchange neighbours through the T1 process, and a rapid brittle mode for faster application of pressures, where the void advances by successive rupture of liquid films driven by Rayleigh-Taylor instability. The simulations allow detailed insight into the mechanics of the fracturing medium and the role of its microstructure. In particular, we examine the stress distribution around the crack tip and investigate how brittle fracture localizes into a single line of breakages. We also confirm that pre-existing microstructural defects can alter the course of fracture.

  11. Pixels and patterns: A satellite-based investigation of changes to urban features in the Sanya Region, Hainan Special Economic Zone, China

    NASA Astrophysics Data System (ADS)

    Millward, Andrew Allan

    Throughout most of China, and particularly in the coastal areas of its south, ecological resources and traditional culture are viewed by many to be negatively impacted by accelerating urbanization. As a result, achieving an appropriate balance between development and environmental protection has become a significant problem facing policy-makers in these urbanizing areas. The establishment of a Special Economic Zone in the Chinese Province of Hainan has made its coastal areas attractive locations for business and commerce. Development activities that support a burgeoning tourism industry, but which are damaging the environment, are now prominent components of the landscape in the Sanya Region of Hainan. In this study, patterns of urban growth in the Sanya Region of Hainan Province are investigated. Specifically, using several forms of satellite imagery, statistical tools and ancillary data, urban morphology and changes to the extent and spatial arrangement of urban features are researched and documented. A twelve-year chronology of data was collected which consists of four dates of satellite imagery (1987, 1991, 1997, 1999) acquired by three different satellite sensors (SPOT 2 HRV, Landsat 5 TM, Landsat 7 ETM+). A method of assessing inter-temporal variance in unchanged features is developed as a surrogate for traditional evaluations of change detection that require spatially accurate and time-specific data. Results reveal that selective PCA using visible bands with the exclusion of an ocean mask yield the most interpretable components representative of landscape urbanization in the Sanya Region. The geostatistical approach of variography is employed to measure spatial dependence and to test for the presence of directional change in urban morphology across a time series of satellite images. Interpreted time-series geostatistics identify and quantify landscape structure, and changes to structure, and provide a valuable quantitative description of landscape change

  12. Influence of microstructure on fracture toughness of austempered ductile iron

    SciTech Connect

    Rao, P.P.; Putatunda, S.K.

    1997-07-01

    An investigation was carried out to examine the influence of microstructure on the plane strain fracture toughness of austempered ductile iron. Austempered ductile iron (ADI) alloyed with nickel, copper, and molybdenum was austenitized and subsequently austempered over a range of temperatures to produce different microstructures. The microstructures were characterized through optical microscopy and X-ray diffraction. Plane strain fracture toughness of all these materials was determined and was correlated with the microstructure. The results of the present investigation indicate that the lower bainitic microstructure results in higher fracture toughness than upper bainitic microstructure. Both volume fraction of retained austenite and its carbon content influence the fracture toughness. The retained austenite content of 25 vol pct was found to provide the optimum fracture toughness. It was further concluded that the carbon content of the retained austenite should be as high as possible to improve fracture toughness.

  13. H2 binding and splitting on a new-generation [FeFe]-hydrogenase model featuring a redox-active decamethylferrocenyl phosphine ligand: a theoretical investigation.

    PubMed

    Greco, Claudio

    2013-02-18

    [FeFe]-hydrogenases are dihydrogen-evolving metalloenzymes that are able to combine substrate binding and redox functionalities, a feature that has important bearing on their efficiency. New-generation bioinspired systems such as Fe(2)[(SCH(2))(2)NBn](CO)(3)(Cp*Fe(C(5)Me(4)CH(2)PEt(2)))(dppv) were shown to mimic H(2) oxidation and splitting processes performed by the [FeFe]-hydrogenase/ferredoxin system, and key mechanistic aspects of such reaction are theoretically investigated in the present contribution. We found that H(2) binding and heterolytic cleavage take place concomitantly on DFT models of the synthetic catalyst, due to a substrate-dependent intramolecular redox process that promotes dihydrogen activation. Therefore, formation of an iron-dihydrogen complex as a reaction intermediate is excluded in the biomimetic system, at variance with the case of the enzyme. H(2) uptake at the synthetic system also requires an energetically disfavored isomerization of the amine group acting as a base during splitting. A possible strategy to stabilize the conformation competent for H(2) binding is proposed, along with an analysis of the reactivity of a triiron complex in which di(thiomethyl)amine--the chelating group naturally occurring in [FeFe]-hydrogenases--substitutes the benzyl-containing dithiolate ligand. PMID:23374093

  14. Manipulation of microstructure in laser additive manufacturing

    NASA Astrophysics Data System (ADS)

    Bai, Shuang; Yang, Lihmei; Liu, Jian

    2016-05-01

    In this paper, additive manufacturing (AM) of tungsten parts is investigated by using femtosecond fiber lasers. For the first time, manipulating microstructures of AM parts is systematically investigated and reported. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, and microstructural and mechanical properties of the processed components. Fully dense tungsten part with refined grain and increased hardness was obtained for femtosecond laser, compared with parts made with different pulse widths and CW laser. Micro-hardness is investigated for the fabricated samples. This can greatly benefit to the make of complicated structures and materials that could not be achieved before.

  15. Investigation of the microstructure and surface morphology of a Ti6Al4V plate fabricated by vacuum selective laser melting

    NASA Astrophysics Data System (ADS)

    Sato, Yuji; Tsukamoto, Masahiro; Masuno, Shinichiro; Yamashita, Yorihiro; Yamashita, Kensuke; Tanigawa, Daichi; Abe, Nobuyuki

    2016-04-01

    As an additive manufacturing technology, the selective laser melting (SLM) process is useful to directly form complicated shapes. The SLM process in a vacuum has been used to fabricate three-dimensional Ti6Al4V (Ti64) plates because this method can control the phase transformation. To investigate the laser melting and solidification dynamics, the formation of a Ti64 plate by SLM in a vacuum was captured by a high-speed video camera. Due to the effects of temperature and scanning speed on the phase transformation, the crystal orientation was evaluated with X-ray diffraction. A phase transformation of the crystal orientation occurred as the baseplate temperature was heated up from 50 to 150 °C.

  16. PREFACE: Processing, Microstructure and Performance of Materials

    NASA Astrophysics Data System (ADS)

    Chiu, Yu Lung; Chen, John J. J.; Hodgson, Michael A.; Thambyah, Ashvin

    2009-07-01

    A workshop on Processing, Microstructure and Performance of Materials was held at the University of Auckland, School of Engineering, on 8-9 April 2009. Organised by the Department of Chemical and Materials Engineering, University of Auckland, this meeting consisted of international participants and aimed at addressing the state-of-the-art research activities in processing, microstructure characterization and performance integrity investigation of materials. This two-day conference brought together scientists and engineers from New Zealand, Australia, Hong Kong, France, and the United Kingdom. Undoubtedly, this diverse group of participants brought a very international flair to the proceedings which also featured original research papers on areas such as Materials processing; Microstructure characterisation and microanalysis; Mechanical response at different length scales, Biomaterials and Material Structural integrity. There were a total of 10 invited speakers, 16 paper presentations, and 14 poster presentations. Consequently, the presentations were carefully considered by the scientific committee and participants were invited to submit full papers for this volume. All the invited paper submissions for this volume have been peer reviewed by experts in the various fields represented in this conference, this in accordance to the expected standards of the journal's Peer review policy for IOP Conference Series: Materials Science and Engineering. The works in this publication consists of new and original research as well as several expert reviews of current state-of-the art technologies and scientific developments. Knowing some of the real constraints on hard-copy publishing of high quality, high resolution images, the editors are grateful to IOP Publishing for this opportunity to have the papers from this conference published on the online open-access platform. Listed in this volume are papers on a range of topics on materials research, including Ferguson's high strain

  17. An analogue investigation of the relationships among perceived parental criticism, negative affect, and borderline personality disorder features: the role of thought suppression.

    PubMed

    Cheavens, Jennifer S; Zachary Rosenthal, M; Daughters, Stacey B; Nowak, Jennifer; Kosson, David; Lynch, Thomas R; Lejuez, C W

    2005-02-01

    The current study examined the relationships among biological predisposition, social environment, emotion regulation, and features characteristic of Borderline Personality Disorder (BPD). Using an analogue sample, we examined whether thought suppression mediated the relationship of negative affective intensity/reactivity and perceived parental criticism with a composite of BPD features including impulsivity, interpersonal sensitivity, and aggression. Results indicated that thought suppression fully mediated the relationship between negative affect intensity/reactivity and BPD features and partially mediated the relationship between BPD features and perceived parental criticism. Clinical implications, directions for further research, and limitations of the present study are discussed. PMID:15629754

  18. Features of plastic deformation and fracture of dispersion-strengthened V–Cr–Zr–W alloy depending on temperature of tension

    SciTech Connect

    Ditenberg, Ivan A.; Grinyaev, Konstantin V.; Tyumentsev, Alexander N.; Smirnov, Ivan V.; Pinzhin, Yury P.; Tsverova, Anastasiya S.; Chernov, Vyacheslav M.

    2015-10-27

    Influence of tension temperature on features of plastic deformation and fracture of V–4.23Cr–1.69Zr–7.56W alloy was investigated by scanning and transmission electron microscopy. It is shown that temperature increase leads to activation of the recovery processes, which manifests in the coarsening of microstructure elements, reducing the dislocation density, relaxation of continuous misorientations.

  19. Microstructural Characterization of Next Generation Nuclear Graphites

    SciTech Connect

    Karthik Chinnathambi; Joshua Kane; Darryl P. Butt; William E. Windes; Rick Ubic

    2012-04-01

    This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions.

  20. Microstructural investigation of the oxidation behavior of Cu in Ag-coated Cu films using a focused ion beam transmission electron microscopy technique

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hwan; Lee, Jong-Hyun

    2016-06-01

    With the aim of elucidating a detailed mechanism for the oxidation behavior in submicron Cu particles coated with a thin Ag layer, the dewetting of Ag and the oxidation behavior of Cu in Ag-coated Cu films upon heating were investigated with a focused ion beam transmission electron microscopy technique. A slight dewetting of the Ag layer began at approximately 200 °C and aggregates of Cu2O particles were formed on the Ag layer, indicating that the initial Cu2O phase was formed on the thin Ag layer. Voids were formed in the Cu layer because of Cu atoms diffusing through the thin Ag layer to be oxidized in the upper Cu2O aggregates. After being heated to 250 °C, the Ag layer became more irregular, and in some regions, it disappeared because of intensive dewetting. The number and average size of the voids also increased. At 300 °C, a hollow structure with a Cu2O shell was formed. Pillar-like structures of unoxidized Cu and large voids were found under the Cu2O layer.

  1. Microstructure of neat alcohols

    NASA Astrophysics Data System (ADS)

    Perera, Aurélien; Sokolić, Franjo; Zoranić, Larisa

    2007-06-01

    Formation of microstructure in homogeneous associated liquids is analyzed through the density-density pair correlation functions, both in direct and reciprocal space, as well as an effective local one-body density function. This is illustrated through a molecular dynamics study of two neat alcohols, namely, methanol and tert-butanol, which have a rich microstructure: chainlike molecular association for the former and micellelike for the latter. The relation to hydrogen bonding interaction is demonstrated. The apparent failure to find microstructure in water—a stronger hydrogen bonding liquid—with the same tools is discussed.

  2. Amorphous nonstoichiometric Ge1-x-Cx:H compounds obtained by radiolysis-chemical vapor deposition of germane/ethyne or germane/allene systems: A bonding and microstructure investigation performed by x-ray photoelectron spectroscopy and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Benzi, Paola; Bottizzo, Elena; Demaria, Chiara; Infante, Guido; Iucci, Giovanna; Polzonetti, Giovanni

    2007-06-01

    Hydrogenated germanium carbides have been produced by x-ray activated-chemical vapor deposition from germane/ethyne or germane/allene systems. The chemical composition and structure of the reaction products as a function of the hydrocarbon percentage in the irradiated mixture and of the solid annealing temperature have been studied and discussed. Bonding and microstructure of these alloys have been investigated by x-ray photoelectron spectroscopy and Raman spectroscopy. The results indicate that the solids are formed by a randomly bound network of carbon, germanium and hydrogen atoms with composition, and characteristics and properties variable with the radiolysis experimental conditions. The spectra show the presence of Ge-C bonds and a partial polymerlike character of the films with hydrogen atoms bonded both to germanium and carbon. Clustered-germanium zones dispersed in the material matrix are also evidenced. The results suggest that the conductive properties of the materials are related to the density of these amorphous clusters. The annealing causes compositional and structural transformations becoming more drastic with temperature.

  3. Ba3Pt4Al4-Structure, Properties, and Theoretical and NMR Spectroscopic Investigations of a Complex Platinide Featuring Heterocubane [Pt4Al4] Units.

    PubMed

    Stegemann, Frank; Benndorf, Christopher; Bartsch, Timo; Touzani, Rachid St; Bartsch, Manfred; Zacharias, Helmut; Fokwa, Boniface P T; Eckert, Hellmut; Janka, Oliver

    2015-11-16

    Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edges. These are arranged in a hexagonal rod packing by further condensation over Pt and Al atoms with the barium atoms located inside cavities of the [Pt4Al4](δ-) framework. Structural relaxation confirmed the electronic stability of the new phase, while band structure calculations indicate metallic behavior. Crystal orbital Hamilton bonding analysis coupled with Bader effective charge analysis suggest a polar intermetallic phase in which strong Al-Pt covalent bonds are present, while a significant electron transfer from Ba to the [Pt4Al4](δ-) network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f5/2 and 4f7/2 energies for Ba3Pt4Al4 were found in the range of those of elemental Pt due to the electron transfer of Ba, while PtAl and PtAl2 show a pronounced shift toward a more cationic platinum state. (27)Al magic-angle spinning NMR investigations verified the two independent crystallographic Al sites with differently distorted tetrahedrally coordinated [AlPt4] units. Peak assignments could be made based on both geometrical considerations and in relation to electric field gradient calculations. PMID:26536164

  4. A Markov random field approach for microstructure synthesis

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Nguyen, L.; DeGraef, M.; Sundararaghavan, V.

    2016-03-01

    We test the notion that many microstructures have an underlying stationary probability distribution. The stationary probability distribution is ubiquitous: we know that different windows taken from a polycrystalline microstructure are generally ‘statistically similar’. To enable computation of such a probability distribution, microstructures are represented in the form of undirected probabilistic graphs called Markov Random Fields (MRFs). In the model, pixels take up integer or vector states and interact with multiple neighbors over a window. Using this lattice structure, algorithms are developed to sample the conditional probability density for the state of each pixel given the known states of its neighboring pixels. The sampling is performed using reference experimental images. 2D microstructures are artificially synthesized using the sampled probabilities. Statistical features such as grain size distribution and autocorrelation functions closely match with those of the experimental images. The mechanical properties of the synthesized microstructures were computed using the finite element method and were also found to match the experimental values.

  5. Microstructurally based model of fatigue initiation and growth

    NASA Technical Reports Server (NTRS)

    Brockenbrough, J. R.; Hinkle, A. J.; Magnusen, P. E.; Bucci, R. J.

    1994-01-01

    A model to calculate fatigue life is developed based on the assumption that fatigue life is entirely composed of crack growth from an initial microstructural inhomogeneity. Specifically, growth is considered to start from either an ellipsoidal void, a cracked particle, or a debonded particle. The capability of predicting fatigue life from material microstructure is based on linear elastic fracture mechanics principles, the sizes of the crack-initiating microstructural inhomogeneities, and an initiation parameter that is proportional to the cyclic plastic zone size. A key aspect of this modeling approach is that it is linked with a general purpose probability program to analyze the effect of the distribution of controlling microstructural features within the material. This enables prediction of fatigue stress versus life curves for various specimen geometries using distributional statistics obtained from characterizations of the microstructure. Results are compared to experimental fatigue data from an aluminum alloy.

  6. Strain-engineered manufacturing of freeform carbon nanotube microstructures

    NASA Astrophysics Data System (ADS)

    de Volder, M.; Park, S.; Tawfick, S.; Hart, A. J.

    2014-07-01

    The skins of many plants and animals have intricate microscale surface features that give rise to properties such as directed water repellency and adhesion, camouflage, and resistance to fouling. However, engineered mimicry of these designs has been restrained by the limited capabilities of top-down fabrication processes. Here we demonstrate a new technique for scalable manufacturing of freeform microstructures via strain-engineered growth of aligned carbon nanotubes (CNTs). Offset patterning of the CNT growth catalyst is used to locally modulate the CNT growth rate. This causes the CNTs to collectively bend during growth, with exceptional uniformity over large areas. The final shape of the curved CNT microstructures can be designed via finite element modeling, and compound catalyst shapes produce microstructures with multidirectional curvature and unusual self-organized patterns. Conformal coating of the CNTs enables tuning of the mechanical properties independently from the microstructure geometry, representing a versatile principle for design and manufacturing of complex microstructured surfaces.

  7. Influence of simultaneous doping of Sb and Pb on phase formation, superconducting and microstructural characteristics of HgBa 2Ca 2Cu 3O 8+ δ

    NASA Astrophysics Data System (ADS)

    Giri, Rajiv; Tiwari, R. S.; Srivastava, O. N.

    2007-01-01

    We report systematic studies of structural, microstructural and transport properties of (Hg 0.80Sb 0.2- xPb x)Ba 2Ca 2Cu 3O 8+ δ (where x = 0.0, 0.05, 0.1, 0.15, 0.2) compounds. Bulk polycrystalline samples have been prepared by two-step solid-state reaction route at ambient pressure. It has been observed that simultaneous substitution of Sb and Pb at Hg site in oxygen deficient HgO δ layer of HgBa 2Ca 2Cu 3O 8+ δ cuprate high- Tc superconductor leads to the formation of Hg-1223 as the dominant phase. Microstructural investigations of the as grown samples employing scanning electron microscopy reveal single crystal like large grains embodying spiral like features. Superconducting properties particularly transport current density ( Jct) have been found to be sensitive to these microstructural features. As for example (Hg 0.80Sb 0.05Pb 0.15)Ba 2Ca 2Cu 3O 8+ δ compound which exhibits single crystal like large grains (∼50 μm) and appears to result through spiral growth mechanism, shows highest Jct (∼1.85 × 10 3 A/cm 2) at 77 K. A possible mechanism for the generation of spiral like features and correlation between microstructural features and superconducting properties have been put forward.

  8. Deformation Microstructure of a Reduced-Activation Ferritic/Martensitic Steel Irradiated in HFIR

    SciTech Connect

    Hashimoto, N.; Klueh, R.L.; Ando, M.; Tanigawa, H.; Sawai, T.; Shiba, K.

    2003-09-15

    In order to determine the contributions of different microstructural features to strength and to deformation mode, microstructure of deformed flat tensile specimens of irradiated reduced activation F82H (IEA heat) base metal (BM) and its tungsten inert-gas (TIG) weldments (weld metal and weld joint) were investigated by transmission electron microscopy (TEM), following fracture surface examination by scanning electron microscopy (SEM). After irradiation, the fracture surfaces of F82H BM and TIG weldment showed a martensitic mixed quasi-cleavage and ductile-dimple fracture. The microstructure of the deformed region of irradiated F82H BM contained dislocation channels. This suggests that dislocation channeling could be the dominant deformation mechanism in this steel, resulting in the loss of strain-hardening capacity. While, the necked region of the irradiated F82H TIG, where showed less hardening than F82H BM, showed deformation bands only. From these results, it is suggested that the pre-irradiation microstructure, especially the dislocation density, could affect the post-irradiation deformation mode.

  9. Phase-Field Simulation of Microstructure Evolution in Industrial A2214 Alloy During Solidification

    NASA Astrophysics Data System (ADS)

    Wei, Ming; Tang, Ying; Zhang, Lijun; Sun, Weihua; Du, Yong

    2015-07-01

    By linking to the thermodynamic and atomic mobility databases in Al alloys well established in our research group, the microstructure evolution in industrial A2214 alloy (Al-4.5Cu-0.5Mg-1.0Si, in wt pct) during solidification process was studied by means of two-dimensional phase-field simulation via MICRostructure Evolution Simulation Software in the framework of the multi-phase-field formalism. The thermophysical parameters including interfacial energies and interfacial mobilities were carefully chosen for reproducing the experimental features. The solidification sequence due to the present phase-field simulation conforms to both equilibrium calculation and Scheil simulation. The predicted microstructure reproduces the experimental data very well. These facts indicate that a quantitative phase-field simulation was achieved in the present work. Moreover, the mechanisms of characteristic patterns and microstructure formation were revealed with the aid of the phase-field simulation. In addition, the effect of cooling rate on the secondary dendrite arm spacing and microsegregation was also investigated through comprehensive comparison with the experimental data.

  10. Influence of heat treatment on the microstructure and wear behavior of end-chill cast Zn-27Al alloys with different copper content

    NASA Astrophysics Data System (ADS)

    Jeshvaghani, R. Arabi; Ghahvechian, H.; Pirnajmeddin, H.; Shahverdi, H. R.

    2016-04-01

    The aim of this paper was to study the effect of heat treatment on the microstructure and wear behavior of Zn-27Al alloys with different copper content. In order to study the relationship between microstructure features and wear behavior, the alloys prepared by an end-chill cast apparatus and then heat treated. Heat treatment procedure involved solutionizing at temperature of 350 °C for 72 h followed by cooling within the furnace to room temperature. Microstructural characteristics of as-cast and heat-treated alloys at different distances from the chill were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction. Wear tests were performed using a pin-on-disk test machine. To determine the wear mechanisms, the worn surfaces of the samples were also examined by SEM and EDS. Results showed that heat treatment led to the complete dissolution of as-cast dendritic microstructure and formation of a fine lamellar structure with well-distributed microconstituents. Moreover, addition of copper up to 1 wt% had no significant change in the microstructure, while addition of 2 and 4 wt% copper resulted in formation of ɛ (CuZn4) particle in the interdendritic regions. The influence of copper content on the wear behavior of the alloys was explained in terms of microstructural characteristics. Delamination was proposed as the dominant wear mechanism.

  11. Microstructural analysis of radiation effects

    SciTech Connect

    Stoller, R.E.; Rice, P.M.; Farrell, K.

    1995-10-01

    Microstructural characterization was performed on long-term ({approximately}100,000-h) thermally aged and neutron-irradiated surveillance materials obtained from the Babcock & Wilcox Nuclear Technologies and a high phosphorus weld from a Russian reactor. Although mechanical testing indicated that thermal aging did not cause any significant changes in the Charpy impact properties, it is important to determine if there are any changes in the composition of the matrix and if any ultrafine precipitates had formed due to the thermal component of service environment only. The characterization of the Russian weld was performed to determine if the behavior of a steel with a phosphorus level in excess of that typically found in Western steels changes, and to ascertain whether the results for formation of copper-enriched regions are specific to the narrow composition band of the Western steels or a more general phenomenon. The ORNL APFIM is well suited to the microstructural characterization of neutron-irradiated RPV materials because of its near-atomic spatial resolution and ability to chemically analyze all elements. In addition to detecting, chemically identifying, and determining the size, morphology, and approximate number density of ultrafine features, the atom probe is able to quantify the amount of each element remaining in solution in the matrix and the amount of solute segregated to grain or lath boundaries.

  12. Microstructures of negative and positive azeotropes.

    PubMed

    Shephard, J J; Callear, S K; Imberti, S; Evans, J S O; Salzmann, C G

    2016-07-28

    Azeotropes famously impose fundamental restrictions on distillation processes, yet their special thermodynamic properties make them highly desirable for a diverse range of industrial and technological applications. Using neutron diffraction, we investigate the structures of two prototypical azeotropes, the negative acetone-chloroform and the positive benzene-methanol azeotrope. C-HO hydrogen bonding is the dominating interaction in the negative azeotrope but C-ClO halogen bonding contributes as well. Hydrogen-bonded chains of methanol molecules, which are on average longer than in pure methanol, are the defining structural feature of the positive azeotrope illustrating the fundamentally different local mixing in the two kinds of azeotropes. The emerging trend for both azeotropes is that the more volatile components experience the more pronounced structural changes in their local environments as the azeotropes form. The mixing of the acetone-chloroform azeotrope is essentially random above 20 Å, where the running Kirkwood-Buff integrals of our structural model converge closely to the ones expected from thermodynamic data. The benzene-methanol azeotrope on the other hand displays extended methanol-rich regions and consequently the running Kirkwood-Buff integrals oscillate up to at least 60 Å. Our study provides the first experimental insights into the microstructures of azeotropes and a direct link with their thermodynamic properties. Ultimately, this will provide a route for creating tailored molecular environments in azeotropes to improve and fine-tune their performances. PMID:27367534

  13. Control of Cast Iron Microstructure

    NASA Technical Reports Server (NTRS)

    Graham, J.; Lillybeck, N.; Franco, N.; Stefanescu, D. M.

    1985-01-01

    The use of microgravity for industrial research in the processing of cast iron was investigated. Solidification experiments were conducted using the KC-135 and F-104 aircraft, and an experiment plan was developed for follow-on experiments using the Shuttle. Three areas of interest are identified: (1) measurement of thermophysical properties in the melt; (2) understanding of the relative roles of homogeneous nucleation, grain multiplication, and innocultants in forming the microstructure; and (3) exploring the possibility of obtaining an aligned graphite structure in hypereutectic Fe, Ni, and Co.

  14. Beneficial microstructured titania photoanodes for improving DSSC performance

    NASA Astrophysics Data System (ADS)

    Ahmed, Saquib

    Critical assessment of economically viable renewable energy sources is essential for the development of a globally sustainable society. Dye sensitized solar cells (DSSCs) offer a viable alternative to traditional silicon and thin film photovoltaic (PV) technologies owing to their potential low cost and facile manufacturing. The two main challenges in enhancing device cell performance lie in improving the open circuit voltage (VOC), and suppressing recombination in the semiconductor TiO2 matrix. This thesis explores the latter challenge through investigation of a novel microstructured TiO2 photoanode system. In this research, we have synthesized CTAB-templated mesoporous, anatase, high surface area TiO2 using an acidic precursor to enhance dye adsorption. Through simple supramolecular self-assembly of the TiO2 particles during the synthesis, we have discovered a self-assembled system of TiO2 nanocrystallite aggregates with high surface area, which when applied as the photoanode in DSSCs, result in a novel high-roughness film beneficial for dye adsorption, and also lead to enhanced intrinsic light-scattering within the film itself. The TiO2 nanocrystallites are highly crystalline, with good interconnectivity for improved electron conduction. An additional unique and beneficial feature inherent of this novel photoanode film is its hierarchical meso- and macro-porosity, leading to improved electrolyte percolation through the TiO2 matrix---thereby providing better access to dye molecules for regeneration to occur more effectively (enhanced charge transfer). In all, we have fabricated a TiO2 system through a one-step process that incorporates key beneficial microstructural features crucial for enhancing DSSC behavior. We have further carried out critical TiCl4 surface treatment studies of this porous electrode structure of TiO2 aggregates to understand and improve upon recombination kinetics in the photonanode film matrix, together with enhancing its intrinsic light

  15. Microstructures fabricated by dynamically controlled femtosecond patterned vector optical fields.

    PubMed

    Cai, Meng-Qiang; Li, Ping-Ping; Feng, Dan; Pan, Yue; Qian, Sheng-Xia; Li, Yongnan; Tu, Chenghou; Wang, Hui-Tian

    2016-04-01

    We have presented and demonstrated a method for the fabrication of various complicated microstructures based on dynamically controlled patterned vector optical fields (PVOFs). We design and generate dynamic PVOFs by loading patterned holograms displayed on the spatial light modulator and moving traces of focuses with different patterns. We experimentally fabricate the various microstructures in z-cut lithium niobate plates. The method we present has some benefits such as no motion of the fabricated samples and high efficiency due to its parallel feature. Moreover, our approach is able to fabricate three-dimensional microstructures. PMID:27192265

  16. Microstructure and Phase Composition of Cold Isostatically Pressed and Pressureless Sintered Silicon Nitride.

    PubMed

    Lukianova, O A; Krasilnikov, V V; Parkhomenko, A A; Sirota, V V

    2016-12-01

    The microstructure and physical properties of new Y2O3 and Al2O3 oxide-doped silicon nitride ceramics fabricated by cold isostatic pressing and free sintering were investigated. The phase composition of produced material was also studied by X-ray diffraction at room and elevated temperature. The fabricated ceramics featured a microstructure of Si5AlON7 grains with a fine-grained α-Si3N4 with a small amount of Y2SiAlON5. Described ceramics is attractive for many high-temperature structural applications due to beneficial combination of fine-grained structure with improved mechanical properties and small weight loss. PMID:26979726

  17. Microstructure and Phase Composition of Cold Isostatically Pressed and Pressureless Sintered Silicon Nitride

    NASA Astrophysics Data System (ADS)

    Lukianova, O. A.; Krasilnikov, V. V.; Parkhomenko, A. A.; Sirota, V. V.

    2016-03-01

    The microstructure and physical properties of new Y2O3 and Al2O3 oxide-doped silicon nitride ceramics fabricated by cold isostatic pressing and free sintering were investigated. The phase composition of produced material was also studied by X-ray diffraction at room and elevated temperature. The fabricated ceramics featured a microstructure of Si5AlON7 grains with a fine-grained α-Si3N4 with a small amount of Y2SiAlON5. Described ceramics is attractive for many high-temperature structural applications due to beneficial combination of fine-grained structure with improved mechanical properties and small weight loss.

  18. A study of spectrum fatigue crack propagation in two aluminum alloys. 2: Influence of microstructures

    NASA Technical Reports Server (NTRS)

    Telesman, J.; Antolovich, S. D.

    1985-01-01

    The important metallurgical factors that influence both constant amplitude and spectrum crack growth behavior in aluminum alloys were investigated. The effect of microstructural features such as grain size, inclusions, and dispersoids was evaluated. It was shown that a lower stress intensities, the I/M 7050 alloy showed better fatigue crack propagation (FCP) resistance than P/M 7091 alloy for both constant amplitude and spectrum testing. It was suggested that the most important microstructural variable accounting for superior FCP resistance of 7050 alloy is its large grain size. It was further postulated that the inhomogenous planar slip and large grain size of 7050 limit dislocation interactions and thus increase slip reversibility which improves FCP performance. The hypothesis was supported by establishing that the cyclic strain hardening exponent for the 7091 alloy is higher than that of 7050.

  19. Microstructure and Creep Property of Isothermal Forging GH4169G Superalloy

    NASA Astrophysics Data System (ADS)

    Li, Zhenrong; Ma, Chunlei; Tian, Sugui; Chen, Liqing; Liu, Xianghua

    2014-09-01

    By means of direct aging, microstructure observation and creep property measurement, the microstructure and creep behaviors of GH4169G superalloy are investigated. Results show that, after direct aging, the grain size is inhomogeneous in the alloy, and some δ precipitates discontinuously distribute in the grain and along the boundaries, which may improve the bonding strength of the boundaries. Under the experimental conditions, the creep activation energy of the alloy during steady-state creep are calculated to be Q = 594.7 kJ/mol. During creep, the deformation features of the alloy are twinning deformation and dislocations slipping in the matrix. As creep goes on, deformed dislocations pile up near the boundary regions to induce stress concentration for promoting the initiation and propagation of cracks along boundaries.

  20. Microstructure and embrittlement of the fine-grained heat-affected zone of ASTM4130 steel

    NASA Astrophysics Data System (ADS)

    Li, Li-Ying; Wang, Yong; Han, Tao; Li, Chao-Wen

    2011-08-01

    The mechanical properties and microstructure features of the fine-grained heat-affected zone (FGHAZ) of ASTM4130 steel was investigated by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), and welding thermal simulation test. It is found that serious embrittlement occurs in the FGHAZ with an 81.37% decrease of toughness, compared with that of the base metal. Microstructure analysis reveals that the FGHAZ is mainly composed of acicular, equiaxed ferrite, granular ferrite, martensite, and martensite-austenite (M-A) constituent. The FGHAZ embrittlement is mainly induced by granular ferrite because of carbides located at its boundaries and sub-boundaries. Meanwhile, the existence of martensite and M-A constituent, which distribute in a discontinuous network, is also detrimental to the mechanical properties.

  1. An asymptotic theory for waves guided by diffraction gratings or along microstructured surfaces

    PubMed Central

    Antonakakis, T.; Craster, R. V.; Guenneau, S.; Skelton, E. A.

    2014-01-01

    An effective surface equation, that encapsulates the detail of a microstructure, is developed to model microstructured surfaces. The equations deduced accurately reproduce a key feature of surface wave phenomena, created by periodic geometry, that are commonly called Rayleigh–Bloch waves, but which also go under other names, for example, spoof surface plasmon polaritons in photonics. Several illustrative examples are considered and it is shown that the theory extends to similar waves that propagate along gratings. Line source excitation is considered, and an implicit long-scale wavelength is identified and compared with full numerical simulations. We also investigate non-periodic situations where a long-scale geometrical variation in the structure is introduced and show that localized defect states emerge which the asymptotic theory explains. PMID:24399920

  2. Solidification behavior and microstructural analysis of austenitic stainless steel laser welds

    SciTech Connect

    David, S.A.; Vitek, J.M.

    1981-01-01

    Solidification behavior of austenitic stainless steel laser welds has been investigated with a high-power laser system. The welds were made at speeds ranging from 13 to 60 mm/s. The welds sowed a wide variety of microstructural features. The ferrite content in the 13-mm/s weld varied from less than 1% at the root of the weld to about 10% at the crown. The duplex structure at the crown of the weld was much finer than the one observed in conventional weld metal. However, the welds made at 25 and 60 mm/s contained an austenitic structure with less than 1% ferrite throughout the weld. Microstructural analysis of these welds used optical microscopy, transmission electron microscopy, and analytical electron microscopy. The austenitic stainless steel welds were free of any cracking, and the results are explained in terms of the rapid solidification conditions during laser welding.

  3. Lattice Boltzmann simulations of the permeability and capillary adsorption of cement model microstructures

    SciTech Connect

    Zalzale, M.; McDonald, P.J.

    2012-12-15

    The lattice Boltzmann method is used to investigate the permeability of microstructures of cement pastes generated using the numerical models CEMHYD3D (Bentz, 1997) and {mu}IC (Bishnoi and Scrivener, 2009). Results are reported as a function of paste water-to-cement ratio and degree of hydration. The permeability decreases with increasing hydration and decreasing water-to-cement ratio in agreement with experiment. However the permeability is larger than the experimental data recorded using beam bending methods (Vichit-Vadakan and Scherer, 2002). Notwithstanding, the lattice Boltzmann results compare favourably with alternate numerical methods of permeability calculation for cement model microstructures. In addition, we show early results for the liquid/vapour capillary adsorption and desorption isotherms in the same model {mu}IC structures. The broad features of the experimental capillary porosity isotherm are reproduced, although further work is required to adequately parameterise the model.

  4. Damage Tolerant Microstructures for Shock Environments

    NASA Astrophysics Data System (ADS)

    Cerreta, Ellen; Dennis-Koller, Darcie; Escobedo, Juan Pablo; Fensin, Saryu; Valone, Steve; Trujillo, Carl; Bronkhorst, Curt; Lebensohn, Ricardo

    While dynamic failure, due to shock loading, has been studied for many years, our current ability to predict and simulate evolving damage during dynamic loading remains limited. One reason for this is due to the lack of understanding for the linkages between process-induced as well as evolved microstructure and damage. To this end, the role of microstructure on the early stages of dynamic damage has been studied in high purity Ta and Cu. This work, which utilizes plate-impact experiments to interrogate these effects, has recently been extended to a subset to Cu-alloys (Cu-Pb, Cu-Nb, and Cu-Ag). These multi-length scale studies, have identified a number of linkages between damage nucleation and growth and microstructural features such as: grain boundary types, grain boundary orientation with respect to loading direction, grain orientation, and bi-metal interfaces. A combination of modeling and simulation techniques along with experimental observation has been utilized to examine the mechanisms for the ductile damage processes such as nucleation, growth and coalescence. This work has identified differing features of importance for damage nucleation in high purity and alloyed materials, lending insight into features of concern for mitigating shock induced damage in more complicated alloy systems.

  5. An investigation into potential causes of the anomalistic feature observed by the Rosetta Alice spectrograph around 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Noonan, John; Schindhelm, Eric; Parker, Joel Wm.; Steffl, Andrew; Davis, Michael; Stern, S. Alan; Levin, Zuni; Kempf, Sascha; Horanyi, Mihaly

    2016-08-01

    The Alice far-ultraviolet spectrograph in operation around the comet 67P/Churyumov-Gerasimenko on the Rosetta spacecraft experiences an anomalistic feature (AF) that is ubiquitous at comet separations less than 450 km. This feature is highly temporally variable and displays no relation to any studied parameters with the exception of comet separation. This paper tests several possible causes with simulations and finds that positive ions produce a partial explanation for the anomaly, but still finds no definitive source of the AF.

  6. Investigating the role of executive attentional control to self-harm in a non-clinical cohort with borderline personality features

    PubMed Central

    Drabble, Jennifer; Bowles, David P.; Barker, Lynne Ann

    2014-01-01

    Self-injurious behavior (or self-harm) is a frequently reported maladaptive behavior in the general population and a key feature of borderline personality disorder (BPD). Poor affect regulation is strongly linked to a propensity to self-harm, is a core component of BPD, and is linked with reduced attentional control abilities. The idea that attentional control difficulties may provide a link between BPD, negative affect and self-harm has yet to be established, however. The present study explored the putative relationship between levels of BPD features, three aspects of attentional/executive control, affect, and self-harm history in a sample of 340 non-clinical participants recruited online from self-harm forums and social networking sites. Analyses showed that self-reported levels of BPD features and attentional focusing predicted self-harm incidence, and high attentional focusing increased the likelihood of a prior self-harm history in those with high BPD features. Ability to shift attention was associated with a reduced likelihood of self-harm, suggesting that good attentional switching ability may provide a protective buffer against self-harm behavior for some individuals. These attentional control differences mediated the association between negative affect and self-harm, but the relationship between BPD and self-harm appears independent. PMID:25191235

  7. Electronic Mail--A New Style of Communication or Just a New Medium? An Investigation into the Text Features of E-Mail.

    ERIC Educational Resources Information Center

    Gains, Jonathan

    1999-01-01

    A study analyzed and compared the discourse of electronic mail messages from commercial and academic environments. Key text features were examined for style and convention patterns. Results suggest commercial messages follow normal conventions for standard written business English, and academic users may view the medium as a pseudo-conversational…

  8. An Investigation of Non-Thesis Master's Program Geography Teacher Candidates' Attitudes towards Teaching Profession regarding Several Socio-Cultural Features

    ERIC Educational Resources Information Center

    Sezer, Adem; Kara, Hasan; Pinar, Adnan

    2011-01-01

    The purpose of this study is to examine the attitudes of non-thesis master's degree program: geography teacher candidates towards teaching profession regarding several socio-cultural features. The study was conducted in different universities with 218 geography teacher candidates enrolled in the geography education non-thesis master's degree…

  9. Microstructures of A 4(BC)4 star copolymers and the influence of architecture

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Peng, J.; Cheng, M. F.; Fang, J. H.

    2016-07-01

    The self-consistent field theory is used to investigate the microstructures of A 4(BC)4 star copolymers. The phase diagram is mapped out to show different phase regions. Compared with A(BC)4 star copolymers, several microstructures are lost, and more lamellar structures are found due to the stronger topological constraint of the junction. The results may be helpful to understand the influence of molecular architectures on microstructures and provide an effective way to design controllable microstructures.

  10. Mechanical and microstructural characterization of commercial AA5083 aluminum alloys

    NASA Astrophysics Data System (ADS)

    Kulas, Mary Anne

    The superplastic forming (SPF) process has been of interest to automotive manufacturers for several years because of two imperative goals. The first one is the simplification of the manufacturing process for sheet-body panels and the second reason is to follow government regulations to reduce vehicle mass, by using aluminum. However, the high cost associated with superplastic materials and slow production cycle times have limited the use of SPF to niche automobile manufacturing operations. To overcome these limits, research on SPF has been directed to forming at lower temperatures, at faster strain rates and with lower cost materials. AA5083 superplastic materials hold great promise for high-volume SPF production. However, several technical issues related to the material are still not well understood. The present investigation characterizes the mechanical and microstructural behavior of eight commercial 5083 materials. Conclusive evidence on the deformation mechanisms active in the range of conditions typical for SPF operations, low rates and high temperatures, but also at high-rate and low-temperature conditions, are presented. Predictive equations, useful to establish a predictive basis for SPF forming, are constructed. The issue of cavitation in superplastic materials, leading to poor post-formed properties of the material and ductility variations, is treated. A relation between cavitation, ductility and microstructural features is presented. These results should be quite useful in the development of improved commercial superplastic 5083 materials and for enhancing the capabilities of the SPF process.

  11. Microstructural evolution of tungsten oxide thin films

    NASA Astrophysics Data System (ADS)

    Hembram, K. P. S. S.; Thomas, Rajesh; Rao, G. Mohan

    2009-10-01

    Tungsten oxide thin films are of great interest due to their promising applications in various optoelectronic thin film devices. We have investigated the microstructural evolution of tungsten oxide thin films grown by DC magnetron sputtering on silicon substrate. The structural characterization and surface morphology were carried out using X-ray diffraction and Scanning Electron Microscopy (SEM). The as deposited films were amorphous, where as, the films annealed above 400 °C were crystalline. In order to explain the microstructural changes due to annealing, we have proposed a "instability wheel" model for the evolution of the microstructure. This model explains the transformation of mater into various geometries within them selves, followed by external perturbation.

  12. Microstructural characterization of nitrided Timetal 834.

    PubMed

    Moskalewicz, T; Grogger, W; Czyrska-Filemonowicz, A

    2006-09-01

    The microstructure of Timetal 834, in as-received condition and after nitriding under glow discharge has been examined by light microscopy and analytical transmission electorn microscopy (TEM) methods (SAED, EDS, EELS and EFTEM). The microstructure of the as-received alloy consists of the alpha phase and a small amount of the beta phase. Silicide precipitates (Zr5Si4) are present both inside the grains and at the grain boundaries. TEM investigations of cross-sectional thin foils allow for detailed analysis of the nitrided layer microstructure. It was found that the nitrided layer exhibits a graded character with continuously varying nitrogen content. The outermost sublayer consists of nanocrystals of delta-TiN. The following sublayers consist mainly of delta'-Ti2N and epsilon-Ti2N grains. The last sublayer, closest to the substrate, is identified as a nitrogen-rich alpha(N) solid solution containing up to 14 at% of nitrogen. PMID:17059528

  13. Adaptive feature extraction expert

    SciTech Connect

    Yuschik, M.

    1983-01-01

    The identification of discriminatory features places an upper bound on the recognition rate of any automatic speech recognition (ASR) system. One way to structure the extraction of features is to construct an expert system which applies a set of rules to identify particular properties of the speech patterns. However, these patterns vary for an individual speaker and from speaker to speaker so that another expert is actually needed to learn the new variations. The author investigates the problem by using sets of discriminatory features that are suggested by a feature generation expert, improves the selectivity of these features with a training expert, and finally develops a minimally spanning feature set with a statistical selection expert. 12 references.

  14. Investigating the molecular structural features of hulless barley (Hordeum vulgare L.) in relation to metabolic characteristics using synchrotron-based fourier transform infrared microspectroscopy.

    PubMed

    Yang, Ling; Christensen, David A; McKinnon, John J; Beattie, Aaron D; Xin, Hangshu; Yu, Peiqiang

    2013-11-27

    The synchrotron-based Fourier transform infrared microspectroscopy (SR-FTIRM) technique was used to quantify molecular structural features of the four hulless barley lines with altered carbohydrate traits [amylose, 1-40% of dry matter (DM); β-glucan, 5-10% of DM] in relation to rumen degradation kinetics, intestinal nutrient digestion, and predicted protein supply. Spectral features of β-glucan (both area and heights) in hulless barley lines showed a negative correlation with protein availability in the small intestine, including truly digested protein in the small intestine (DVE) (r = -0.76, P < 0.01; r = -0.84, P < 0.01) and total metabolizable protein (MP) (r = -0.71, P < 0.05; r = -0.84, P < 0.01). Variation in absorption intensities of total carbohydrate (CHO) was observed with negative effects on protein degradation, digestion, and potential protein supply (P < 0.05). Molecular structural features of CHO in hulless barley have negative effects on the supply of true protein to ruminants. The results clearly indicated the impact of the carbohydrate-protein structure and matrix. PMID:24156528

  15. The relationship of microstructure to fracture and corrosion behavior of a directionally solidified superalloy

    NASA Astrophysics Data System (ADS)

    Trexler, Matthew D.

    GTD-111 DS is a directionally solidified superalloy currently used in turbine engines. To accurately predict the life of engine components it is essential to examine and characterize the microstructural evolution of the material and its effects on material properties. The as-cast microstructure of GTD-111 is highly inhomogeneous as a result of coring. The current post-casting heat treatments do not effectively eliminate the inhomogeneity. This inhomogeneity affects properties including tensile strength, fracture toughness, fracture path, and corrosion behavior, primarily in terms of the number of grains per specimen. The goal of this work was to link microstructural features to these properties. Quantitative fractography was used to determine that the path of cracks during failure of tensile specimens is influenced by the presence of carbides, which are located in the interdendritic regions of the material as dictated by segregation. The solvus temperature of the precipitate phase, Ni3(Al, Ti), was determined to be 1200°C using traditional metallography, differential thermal analysis, and dilatometry. A heat-treatment was designed to homogenize the microstructure for tensile testing that isolates the carbide by dissolving all of the "eutectic" Ni3(Al, Ti) precipitate phase, which is also found in the interdendritic areas. High temperature oxidation/sulfidation tests were conducted to investigate the corrosion processes involved when GTD-111 DS is utilized in steam and gas combustion turbine engines. The kinetics of corrosion in both oxidizing and sulfidizing atmospheres were determined using thermogravimetric analysis. Additionally, metallography of these samples after TGA revealed a correlation between the presence of grain boundaries and sulfur attack, which led to catastrophic failure of the material under stress-free conditions in a sulfur bearing environment. In summary, this work correlates the inhomogeneous microstructure of GTD-111 DS to tensile fracture

  16. Connectivity Measures in EEG Microstructural Sleep Elements

    PubMed Central

    Sakellariou, Dimitris; Koupparis, Andreas M.; Kokkinos, Vasileios; Koutroumanidis, Michalis; Kostopoulos, George K.

    2016-01-01

    During Non-Rapid Eye Movement sleep (NREM) the brain is relatively disconnected from the environment, while connectedness between brain areas is also decreased. Evidence indicates, that these dynamic connectivity changes are delivered by microstructural elements of sleep: short periods of environmental stimuli evaluation followed by sleep promoting procedures. The connectivity patterns of the latter, among other aspects of sleep microstructure, are still to be fully elucidated. We suggest here a methodology for the assessment and investigation of the connectivity patterns of EEG microstructural elements, such as sleep spindles. The methodology combines techniques in the preprocessing, estimation, error assessing and visualization of results levels in order to allow the detailed examination of the connectivity aspects (levels and directionality of information flow) over frequency and time with notable resolution, while dealing with the volume conduction and EEG reference assessment. The high temporal and frequency resolution of the methodology will allow the association between the microelements and the dynamically forming networks that characterize them, and consequently possibly reveal aspects of the EEG microstructure. The proposed methodology is initially tested on artificially generated signals for proof of concept and subsequently applied to real EEG recordings via a custom built MATLAB-based tool developed for such studies. Preliminary results from 843 fast sleep spindles recorded in whole night sleep of 5 healthy volunteers indicate a prevailing pattern of interactions between centroparietal and frontal regions. We demonstrate hereby, an opening to our knowledge attempt to estimate the scalp EEG connectivity that characterizes fast sleep spindles via an “EEG-element connectivity” methodology we propose. The application of the latter, via a computational tool we developed suggests it is able to investigate the connectivity patterns related to the

  17. MICROSTRUCTURE OF SUPERCONDUCTING MGB(2).

    SciTech Connect

    ZHU,Y.; LI,Q.; WU,L.; VOLKOV,V.; GU,G.; MOODENBAUGH,A.R.

    2001-07-12

    Recently, Akimitsu and co-workers [1] discovered superconductivity at 39 K in the intermetallic compound MgB{sub 2}. This discovery provides a new perspective on the mechanism for superconductivity. More specifically, it opens up possibilities for investigation of structure/properties in a new class of materials. With the exceptions of the cuprate and C{sub 60} families of compounds, MgB{sub 2} possesses the highest superconducting transition temperature T{sub c}. Its superconductivity appears to follow the BCS theory, apparently being mediated by electron-phonon coupling. The coherence length of MgB{sub 2} is reported to be longer than that of the cuprates [2]. In contrast to the cuprates, grain boundaries are strongly coupled and current density is determined by flux pinning [2,3]. Presently, samples of MgB{sub 2} commonly display inhomogeneity and porosity on the nanoscale, and are untextured. In spite of these obstacles, magnetization and transport measurements show that polycrystalline samples may carry large current densities circulating across many grains [3,4]. Very high values of critical current densities and critical fields have been recently observed in thin films [5,6]. These attributes suggest possible large scale and electronic applications. The underlying microstructure can be intriguing, both in terms of basic science and in applied areas. Subsequent to the discovery, many papers were published [1-13], most dealing with synthesis, physical properties, and theory. There have yet been few studies of microstructure and structural defects [11, 14]. A thorough understanding of practical superconducting properties can only be developed after an understanding of microstructure is gained. In this work we review transmission electron microscopy (TEM) studies of sintered MgB{sub 2} pellets [14]. Structural defects, including second phase particles, dislocations, stacking faults, and grain boundaries, are analyzed using electron diffraction, electron

  18. Investigations on the Mechanical Properties of Conducting Polymer Coating-Substrate Structures and Their Influencing Factors

    PubMed Central

    Wang, Xi-Shu; Tang, Hua-Ping; Li, Xu-Dong; Hua, Xin

    2009-01-01

    This review covers recent advances and work on the microstructure features, mechanical properties and cracking processes of conducting polymer film/coating- substrate structures under different testing conditions. An attempt is made to characterize and quantify the relationships between mechanical properties and microstructure features. In addition, the film cracking mechanism on the micro scale and some influencing factors that play a significant role in the service of the film-substrate structure are presented. These investigations cover the conducting polymer film/coating nucleation process, microstructure-fracture characterization, translation of brittle-ductile fractures, and cracking processes near the largest inherent macromolecule defects under thermal-mechanical loadings, and were carried out using in situ scanning electron microscopy (SEM) observations, as a novel method for evaluation of interface strength and critical failure stress. PMID:20054470

  19. About the leak microstructures

    NASA Astrophysics Data System (ADS)

    Lombardi, M.; Guoxiang, H. Huo-J.; Lombardi, F. S.

    2001-04-01

    The capabilities of a new microstructure, anode point based, for the detection of gas ionizing radiations are presented. For every single detected ionizing radiation it gives a pair of "induced" charges (anodic and cathodic) of the same amount (pulses of the same amplitudes), of opposite sign, with the same collection time and essentially in time coincidence, that are proportional to the primary ionization collected. Each pulse of a pair gives the same energy and timing information, thus one can be used for these information and the other for the position. The complete lack of insulating materials in the active volume of this microstructure avoids problems of charging-up and makes its behaviour stable and repeatable. Primary avalanches with a size of more than 2.5×10 7 electrons (4 pC) giving current pulses with a peak of more than 0.26 mA on 100 Ω and about 30 ns duration are possible with 5.9 keV X-rays of 55Fe working in proportional region and in isobutane gas. Single electrons emitted by a heated filament ( Ec<1 eV) were detected in 760 Torr of isobutane; with an estimated gas gain of 1.2×10 6 a counting rate of up to 800 kpulses/s per single microstructure was achieved. Three different types of sensitive-position two-dimensional read-out detectors, based on these microstructures, in development, as well as the best geometry (height of the tip with respect to the cathode) and the shapes and strengths of the electric field in the active volume of these microstructures, evaluated with Poison Superfish and Mafia programs, are presented.

  20. Investigation on the isoform selectivity of novel kinesin-like protein 1 (KIF11) inhibitor using chemical feature based pharmacophore, molecular docking, and quantum mechanical studies.

    PubMed

    Karunagaran, Subramanian; Subhashchandrabose, Subramaniyan; Lee, Keun Woo; Meganathan, Chandrasekaran

    2016-04-01

    Kinesin-like protein (KIF11) is a molecular motor protein that is essential in mitosis. Removal of KIF11 prevents centrosome migration and causes cell arrest in mitosis. KIF11 defects are linked to the disease of microcephaly, lymph edema or mental retardation. The human KIF11 protein has been actively studied for its role in mitosis and its potential as a therapeutic target for cancer treatment. Pharmacophore modeling, molecular docking and density functional theory approaches was employed to reveal the structural, chemical and electronic features essential for the development of small molecule inhibitor for KIF11. Hence we have developed chemical feature based pharmacophore models using Discovery Studio v 2.5 (DS). The best hypothesis (Hypo1) consisting of four chemical features (two hydrogen bond acceptor, one hydrophobic and one ring aromatic) has exhibited high correlation co-efficient of 0.9521, cost difference of 70.63 and low RMS value of 0.9475. This Hypo1 is cross validated by Cat Scramble method; test set and decoy set to prove its robustness, statistical significance and predictability respectively. The well validated Hypo1 was used as 3Dquery to perform virtual screening. The hits obtained from the virtual screening were subjected to various scrupulous drug-like filters such as Lipinski's rule of five and ADMET properties. Finally, six hit compounds were identified based on the molecular interaction and its electronic properties. Our final lead compound could serve as a powerful tool for the discovery of potent inhibitor as KIF11 agonists. PMID:26815769

  1. Fabrication, Micro-structural Analysis, and Mechanical Testing of High Density Polymeric Foam

    NASA Astrophysics Data System (ADS)

    Marks, Trevor Gustov

    Foams, or what are often called cellular solids, are some of the most widely used materials in the modern era. In general, foam is a porous substance formed by the introduction of gas filled pores into condensed matter; the result is typically a light weight substance with properties related to the base (non-porous) medium. Applications of foams include: vibration dampening, energy mitigation (such as packaging and bike helmets), insulation, filtration, and flotation. The focus of this work is on the properties of flexible elastomeric foam of high relative-density. The bulk of existing literature on elastomeric foam is concerned with foam of low relative-density (ratio of the foam density to the density of the material from which the foam is formed ≤ 0.1). The relationship between the micro-structure of high relative-density foam and its mechanical response has, in large part, not been subjected to systematic investigation heretofore. The present work examines how the micro-structural features of pore shape, size, and location affect the macro-structural response of relative high density foam to compressive loading. In order to carry out this study, methods were developed and employed to control a foam's micro-structure, and hence its mechanical response, with the use of temporary pore forming particles and micron scale inclusions. Advanced microscopy techniques were used to observe, in situ, the evolution of a foam's micro-structure under compressive loading, and the results were correlated with the evolution of the foam's stress - strain response. Additionally, quantitative methods were developed and employed to describe numerically the foam's micro-structural features, such as: (i), pore shape, (ii), pore size, and (iii), the arrangement of the pores with respect to each other. Numerous foams were produced, tested, and subjected to the

  2. Intergrowth and other microstructure features in BCSCO superconductor

    SciTech Connect

    Shulin, W.; Jingwei, F.; Chengen, L.

    1989-02-01

    Three compositions of Bi-Ca-Sr-Cu-O superconducting ceramics were studied and characterized by X-ray, EDS and HREM. In addition to the basic lattice structure A/sub 1/ with unit-cell of 5.41 A, B = 5.44 A and c = 30.8 A, other 3 kinds of perovskite-related structures A/sub 0/, A/sub 3/ and A/sub 4/ were found. Furthermore, a prominent structural phenomenon, the intergrowth between A/sub 1/ and other perovskite-related structures (A/sub 0/, A/sub 2/ and A/sub 4/) were found in abundance. The authors had some difficulties isolating pure 120 K phase; the intergrowth may be an obstacle factor.

  3. Snow Micro-Structure Model

    Energy Science and Technology Software Center (ESTSC)

    2014-06-25

    PIKA is a MOOSE-based application for modeling micro-structure evolution of seasonal snow. The model will be useful for environmental, atmospheric, and climate scientists. Possible applications include application to energy balance models, ice sheet modeling, and avalanche forecasting. The model implements physics from published, peer-reviewed articles. The main purpose is to foster university and laboratory collaboration to build a larger multi-scale snow model using MOOSE. The main feature of the code is that it is implementedmore » using the MOOSE framework, thus making features such as multiphysics coupling, adaptive mesh refinement, and parallel scalability native to the application. PIKA implements three equations: the phase-field equation for tracking the evolution of the ice-air interface within seasonal snow at the grain-scale; the heat equation for computing the temperature of both the ice and air within the snow; and the mass transport equation for monitoring the diffusion of water vapor in the pore space of the snow.« less

  4. Snow Micro-Structure Model

    SciTech Connect

    Micah Johnson, Andrew Slaughter

    2014-06-25

    PIKA is a MOOSE-based application for modeling micro-structure evolution of seasonal snow. The model will be useful for environmental, atmospheric, and climate scientists. Possible applications include application to energy balance models, ice sheet modeling, and avalanche forecasting. The model implements physics from published, peer-reviewed articles. The main purpose is to foster university and laboratory collaboration to build a larger multi-scale snow model using MOOSE. The main feature of the code is that it is implemented using the MOOSE framework, thus making features such as multiphysics coupling, adaptive mesh refinement, and parallel scalability native to the application. PIKA implements three equations: the phase-field equation for tracking the evolution of the ice-air interface within seasonal snow at the grain-scale; the heat equation for computing the temperature of both the ice and air within the snow; and the mass transport equation for monitoring the diffusion of water vapor in the pore space of the snow.

  5. Investigation of a Peak-Like Feature Observed in the Triton Energy Spectra from the 152,154 Sm(p,t) Reactions

    NASA Astrophysics Data System (ADS)

    Humby, P.; Wilson, E.; Beausang, C. W.; Simon, A.; Gell, K.; Tarlow, T.; Vyas, G.; Ross, T. J.; Hughes, R. O.; Burke, J. T.; Casperson, R. J.; Koglin, J.; Ota, S.; Allmond, J. M.; McCleskey, M.; McCleskey, E.; Saastamoinen, A.; Chyzh, R.; Dag, M.

    2015-04-01

    Isotopically enriched 152,154 Sm targets were bombarded with 25 MeV protons from the K-150 cyclotron at the Cyclotron Institute of Texas A&M University. The outgoing charged particles and γ rays were detected using the STARLiTeR array, which consists of a highly segmented ΔE-E silicon telescope and six BGO shielded HPGe clover detectors. A peak-like feature was observed in the triton energy spectra from the 152,154 Sm(p,t) reactions at excitation energies of approximately 3 MeV for the 152 Sm(p,t) reaction and 2.2 MeV for the 154 Sm(p,t) reaction. Discrete states with cross sections as large as approximately 9% of the ground state cross section were identified in this feature using particle- γ and particle- γ- γ coincidences. The range of spins populated appears to be unusually large. This work is supported by the U.S. Department of Energy No. DE-FG02-05ER41379, DE-FG52-09NA29467 and DE-NA0001801, the National Science Foundation under PHY-130581, and by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  6. A Combined Statistical-Microstructural Model for Simulation of Sintering

    SciTech Connect

    BRAGINSKY,MICHAEL V.; DEHOFF,ROBERT T.; OLEVSKY,EUGENE A.; TIKARE,VEENA

    1999-10-22

    Sintering theory has been developed either as the application of complex diffusion mechanisms to a simple geometry or as the deformation and shrinkage of a continuum body. They present a model that can treat in detail both the evolution of microstructure and the sintering mechanisms, on the mesoscale, so that constitutive equations with detail microstructural information can be generated. The model is capable of simulating vacancy diffusion by grain boundary diffusion, annihilation of vacancies at grain boundaries resulting in densification, and coarsening of the microstructural features. In this paper, they review the stereological theory of sintering and its application to microstructural evolution and the diffusion mechanism, which lead to sintering. They then demonstrate how these stereological concepts and diffusion mechanisms were incorporated into a kinetic Monte Carlo model to simulate sintering. Finally, they discuss the limitations of this model.

  7. Solidification microstructures: A conceptual approach

    SciTech Connect

    Trivedi, R.; Kurz, W.

    1994-01-01

    Detailed theoretical models have been developed in the literature to correlate microstructural characteristics as a function of processing parameters. These results are examined with a broad perspective to show that various laws for microstructural transitions and microstructural spacings can be represented in terms of three simple characteristic lengths of the important physical processes. Initially, the important physical processes of solute and thermal transport and capillarity effect are considered, and they are related to the microstructural lengths such as dendrite tip radius, primary and secondary spacing, and eutectic spacing. It is shown that these microstructural lengths are simply given by the geometric mean of the characteristic lengths of physical processes that are important in a given problem. New characteristic lengths that become important under rapid solidification are then developed, and how these characteristic lengths influence microstructural transition and microstructural scales is also discussed.

  8. Baseline Microstructural Characterization of Outer 3013 Containers

    SciTech Connect

    Zapp, Phillip E.; Dunn, Kerry A

    2005-07-31

    Three DOE Standard 3013 outer storage containers were examined to characterize the microstructure of the type 316L stainless steel material of construction. Two of the containers were closure-welded yielding production-quality outer 3013 containers; the third examined container was not closed. Optical metallography and Knoop microhardness measurements were performed to establish a baseline characterization that will support future destructive examinations of 3013 outer containers in the storage inventory. Metallography revealed the microstructural features typical of this austenitic stainless steel as it is formed and welded. The grains were equiaxed with evident annealing twins. Flow lines were prominent in the forming directions of the cylindrical body and flat lids and bottom caps. No adverse indications were seen. Microhardness values, although widely varying, were consistent with annealed austenitic stainless steel. The data gathered as part of this characterization will be used as a baseline for the destructive examination of 3013 containers removed from the storage inventory.

  9. Microstructural development of rapid solidification in Al-Si powder

    SciTech Connect

    Jin, F.

    1995-11-01

    The microstructure and the gradient of microstructure that forms in rapidly solidificated powder were investigated for different sized particles. High pressure gas atomization solidification process has been used to produce a series of Al-Si alloys powders between 0.2 {mu}m to 150 {mu}m diameter at the eutectic composition (12.6 wt pct Si). This processing technique provides powders of different sizes which solidify under different conditions (i.e. interface velocity and interface undercooling), and thus give different microstructures inside the powders. The large size powder shows dendritic and eutectic microstructures. As the powder size becomes smaller, the predominant morphology changes from eutectic to dendritic to cellular. Microstructures were quantitatively characterized by using optical microscope and SEM techniques. The variation in eutectic spacing within the powders were measured and compared with the theoretical model to obtain interface undercooling, and growth rate during the solidification of a given droplet. Also, nucleation temperature, which controls microstructures in rapidly solidified fine powders, was estimated. A microstructural map which correlates the microstructure with particle size and processing parameters is developed.

  10. Investigating Short-term Sustainability of Shallow Water Features Within the Canadian Sub- Arctic; A Churchill, Manitoba Case Study (1947-2008)

    NASA Astrophysics Data System (ADS)

    Parrott, J.; Macrae, M.; Duguay, C.

    2009-05-01

    Within the sub-arctic environment, shallow ponds occupy between 15-50% of the landscape and strongly contribute to regional hydrological and energy budgets. Recent remote sensing studies have mainly focused on the sustainability of small water features within Alaska and Siberia; while little is known regarding the Canadian sub-arctic. The overall objectives of this study were to (a) quantify the current distribution and size of ponds within the Churchill region, (b) calculate surface area changes between 1947 and 2008 from a selected number of ponds and to (c) determine the influence of inter- and intra-seasonal hydrological variability on the quality of remote sensing change detection studies within the region. This study focused on detecting surface area distribution and change within 120 surveyed ponds over a 100km study area using SPOT, Landsat and air photo images (7 images total) between 1947 and 2008. Results from the imagery analyses were linked to a regional climate analysis and simple water balance model in order to determine if climate and hydrological changes could have impacted the quality of change detection results over the 61 year period. Although inter-annual variability has been observed, no significant long-term changes were revealed with regards to precipitation over the past 61 years. In 2008, ponds exhibited a mean water depth of 29cm and a mean surface area of 11,000m. An examination of pond bathymetry, field data (subset of 30 ponds) and seasonal/annual hydrological fluctuations (based on simple water balance modeling) indicate the significant variance of seasonal pond hydrologic storage; which can impact the quality of short-term pond sustainability detection. This work suggests that remote sensing studies should be paired with climatic analysis when examining the sustainability of surface water features.

  11. Microstructure-based modelling of multiphase materials and complex structures

    NASA Astrophysics Data System (ADS)

    Werner, Ewald; Wesenjak, Robert; Fillafer, Alexander; Meier, Felix; Krempaszky, Christian

    2015-10-01

    Micromechanical approaches are frequently employed to monitor local and global field quantities and their evolution under varying mechanical and/or thermal loading scenarios. In this contribution, an overview on important methods is given that are currently used to gain insight into the deformational and failure behaviour of multiphase materials and complex structures. First, techniques to represent material microstructures are reviewed. It is common to either digitise images of real microstructures or generate virtual 2D or 3D microstructures using automated procedures (e.g. Voronoï tessellation) for grain generation and colouring algorithms for phase assignment. While the former method allows to capture exactly all features of the microstructure at hand with respect to its morphological and topological features, the latter method opens up the possibility for parametric studies with respect to the influence of individual microstructure features on the local and global stress and strain response. Several applications of these approaches are presented, comprising low and high strain behaviour of multiphase steels, failure and fracture behaviour of multiphase materials and the evolution of surface roughening of the aluminium top metallisation of semiconductor devices.

  12. Stereological investigation of tungsten-copper pseudoalloys. II. Effect of the production method and of the particle-size distribution of the initial tungsten powder on changes of the microstructure of materials

    SciTech Connect

    Paderno, V.N.; Pilyankevich, A.N.; Martynenko, A.N.; Pilipovskii, Yu.L.; Fal'kovich, L.D.

    1987-12-01

    The authors use transmission and scanning electron microscopy to carry out a stereological analysis of the microstructure of a copper-tungsten pseudoalloy and its dependence on tungsten particle size distribution and on production conditions in sintering and hot molding. Comparative data are presented for different process parameters. The correlations they derive make it possible to control the properties of the alloy by targeted control of their structure in the production process.

  13. Emissivity of microstructured silicon.

    PubMed

    Maloney, Patrick G; Smith, Peter; King, Vernon; Billman, Curtis; Winkler, Mark; Mazur, Eric

    2010-03-01

    Infrared transmittance and hemispherical-directional reflectance data from 2.5 to 25 microm on microstructured silicon surfaces have been measured, and spectral emissivity has been calculated for this wavelength range. Hemispherical-total emissivity is calculated for the samples and found to be 0.84 before a measurement-induced annealing and 0.65 after the measurement for the sulfur-doped sample. Secondary samples lack a measurement-induced anneal, and reasons for this discrepancy are presented. Emissivity numbers are plotted and compared with a silicon substrate, and Aeroglaze Z306 black paint. Use of microstructured silicon as a blackbody or microbolometer surface is modeled and presented, respectively. PMID:20197803

  14. Microstructural characterization in nanocrystalline ceramic thin films

    NASA Astrophysics Data System (ADS)

    Kim, Hakkwan

    The primary objective of this research is to investigate the effects of process variables on microstructure in several fluoride and oxide thin films prepared by vapor deposition, in order to predict the properties and behaviors of nanocrystalline thin film materials. There are three distinct stages of this research. The first stage focuses on measuring of the porosity in polycrystalline thin films of a variety of fluorides as a function of the substrate temperature during deposition, and discussing the mechanism by which the porosity varies as a function of the process variables. We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF 2) and calcium fluoride (CaF2) using an atomic force microscope (AFM) and a quartz crystal thickness monitor. The porosity is very sensitive to the substrate temperature and decreases as the substrate temperature increases. Consistent behavior is observed among all of the materials in this study. The second stage is to understand the film microstructure including grain growth and texture development, because these factors are known to influence the behavior and stability of polycrystalline thin films. This study focuses on grain growth and texture development in polycrystalline lithium fluoride thin films using dark field (DF) transmission electron microscopy (TEM). It is demonstrated that we can isolate the size distribution of <111> surface normal grains from the overall size distribution, based on simple and plausible assumptions about the texture. The {111} texture formation and surface morphology were also observed by x-ray diffraction (XRD) and AFM, respectively. The grain size distributions become clearly bimodal as the annealing time increases, and we deduce that the short-time size distributions are also a sum of two overlapping peaks. The smaller grain-size peak in the distribution corresponds to the {111}-oriented grains which do not grow significantly, while

  15. Quantitative ultrasound assessment of cervical microstructure.

    PubMed

    Feltovich, Helen; Nam, Kibo; Hall, Timothy J

    2010-07-01

    The objective of this preliminary study was to determine whether quantitative ultrasound (QUS) can provide insight into, and characterization of, uterine cervical microstructure. Throughout pregnancy, cervical collagen reorganizes (from aligned and anisotropic to disorganized and isotropic) as the cervix changes in preparation for delivery. Premature changes in collagen are associated with premature birth in mammals. Because QUS is able to detect structural anisotropy/isotropy, we hypothesized that it may provide a means of noninvasively assessing cervical microstructure. Thorough study of cervical microstructure has been limited by lack of technology to detect small changes in collagen organization, which has in turn limited our ability to detect abnormal and/or premature changes in collagen that may lead to preterm birth. In order to determine whether QUS may be useful for detection of cervical microstructure, radiofrequency (rf) echo data were acquired from the cervices of human hysterectomy specimens (n = 10). The angle between the acoustic beam and tissue was used to assess anisotropic acoustic propagation by control of transmit/receive angles from -20 degrees to +20 degrees. The power spectrum of the echo signals from within a region of interest was computed in order to investigate the microstructure of the tissue. An identical analysis was performed on a homogeneous phantom with spherical scatterers for system calibration. Power spectra of backscattered rf from the cervix were 6 dB higher for normal (0 degree) than steered (+/- 20 degrees) beams. The spectral power for steered beams decreased monotonically (0.4 dB at +5 degrees to 3.6 dB at +20 degrees). The excess difference (compared to similar analysis for the phantom) in normally-incident (0 degree) versus steered beams is consistent with scattering from an aligned component of the cervical microstructure. Therefore, QUS appears to reliably identify an aligned component of cervical microstructure

  16. Microstructural examination of

    NASA Astrophysics Data System (ADS)

    Fukuoka, C.; Yoshizawa, H.; Nakagawa, Y. G.; Lapides, M. E.

    1993-10-01

    Fatigue tests were performed to examine how microstructural conditioning influences crack initiation and propagation in SA508 class 3 low-carbon steel. A 3-mm-long crack was introduced in compact tension (CT) fatigue test specimens under four different loads in order to obtain crack tip plastic zones at different stress intensity factor ranges, ΔK = 18, 36, 54, and 72 MPa√m. The microstructure of the plastic zones around the crack tip were examined by trans- mission electron microscopy (TEM) and selected area electron diffraction (SAD). Micro- orientation of the dislocation cells in the plastic zones of all of the CT samples increased to 4 deg from the level of an as-received sample. Four-point bending fatigue tests were performed for plate shape samples with a large cyclic strain range. The SAD value of the bending samples was also 4 deg in the damaged area where cracks already initiated at an early stage of the fatigue process. These test results indicate that the microstructural conditioning is a prerequisite for the fatigue crack initiation and propagation in SA508. These observations may lead to better under- standing of how fatigue initiation processes transit to cracks.

  17. Assessment of the Effect of Microstructure on the Magnetic Behavior of Structural Carbon Steels Using an Electromagnetic Sensor

    NASA Astrophysics Data System (ADS)

    Rumiche, F.; Indacochea, J. E.; Wang, M. L.

    2008-08-01

    The magnetic properties of four carbon steels were evaluated using an electromagnetic sensor and correlated with their microstructures. Their composition, microstructure features (such as ferrite volume fraction, grain size, inclusions, etc), and hardness were compared with their saturated magnetic flux density, retentivity, and coercivity. The four steel rods used in this study were hot-rolled AISI 1010, AISI 1018, AISI 1045, and AISI 1045-high manganese/“stress proof.” The results show that microstructures have a notable effect on the magnetic properties of the steels. In addition, the effect of variations in cross-section area of the steel rods on the magnetic response was investigated. The steel rods diameters were systematically reduced by machining and then magnetically evaluated. Consistent relationships between metallurgical characteristics of the structural carbon steels and their magnetic properties measured with the electromagnetic sensor were obtained. In addition, the sensor was found to be able to detect changes in magnetic properties due to variations in cross-section area. These results reveal that the electromagnetic sensor has the potential to be used as a reliable nondestructive tool to detect and monitor microstructural and morphological changes occurring during the different stages of steel manufacturing or alterations caused by a degradation mechanism.

  18. Measurement and characterization of three-dimensional microstructures on precision roller surfaces

    NASA Astrophysics Data System (ADS)

    Kong, L. B.; Cheung, C. F.; Lee, W. B.; To, S.; Ren, M. J.

    2016-01-01

    Precision roller with microstructures is the key tooling component in the precision embossing by roller process such as Roll-to-Roll to manufacture optical plastic plates or films with three dimensional (3D)-microstructures. Measurement and analysis of 3D-microstructures on a precision roller is essential before the embossing process is being undertaken to ensure the quality of the embossed surfaces. Different from 3D-microstructures on a planar surface, it is difficult to measure and characterize the 3D-microstructures on the cylindrical surface of a precision roller due to the geometrical complexity of such integrated surfaces such as V-groove microstructures on a cylindrical surface. This paper presents a study of method and algorithms for the measurement and characterization of 3D-microstructures on a precision roller surface. A feature-based characterization method (FBCM) is proposed to analyze the V-groove microstructures. In this method, a normal template is generated based on the design specifications, and the measured data is fitted with the feature points. Hence alignment and matching of the measured data to the normal template based on the derived feature points are undertaken. After that the V-groove is characterized by some feature parameters such as pitch, depth, angle of the V-grooves. The method also provides an approach for the analysis of burs generated during the machining of Vgroove microstructures. A precision roller with V-groove microstructures has been machined by a Four-axis ultraprecision machine and the machined surface is measured by a contact measuring instrument. The measured data are then characterized and analyzed by the proposed FBCM. The results are presented and discussed, and they indicate the dominant and regular machining errors that are involved in the machining of the V-groove microstructures on roller surfaces.

  19. General features

    SciTech Connect

    Wallace, R.E.

    1990-01-01

    The San Andreas fault system, a complex of faults that display predominantly large-scale strike slip, is part of an even more complex system of faults, isolated segments of the East Pacific Rise, and scraps of plates lying east of the East Pacific Rise that collectively separate the North American plate from the Pacific plate. This chapter briefly describes the San Andreas fault system, its setting along the Pacific Ocean margin of North America, its extent, and the patterns of faulting. Only selected characteristics are described, and many features are left for depictions on maps and figures.

  20. Investigation of electrodeposited cobalt sulphide counter electrodes and their application in next-generation dye sensitized solar cells featuring organic dyes and cobalt-based redox electrolytes

    NASA Astrophysics Data System (ADS)

    Swami, Sanjay Kumar; Chaturvedi, Neha; Kumar, Anuj; Kapoor, Raman; Dutta, Viresh; Frey, Julien; Moehl, Thomas; Grätzel, Michael; Mathew, Simon; Nazeeruddin, Mohammad Khaja

    2015-02-01

    Cobalt sulphide (CoS) films are potentiodynamically deposited on fluorine-doped tin oxide (FTO) coated glass substrates employing one, three and five sweep cycles (CoS-I, CoS-III and CoS-V respectively). Analysis of the CoS-III film by impedance spectroscopy reveals a lower charge transfer resistance (RCT) than that measured for Pt CE (0.75 Ω cm-2 and 0.85 Ω cm-2, respectively). The CoS films are used as counter electrodes (CE) in dye-sensitized solar cells (DSSCs) featuring the combination of a high absorption coefficient organic dye (C218) and the cobalt-based redox electrolyte [Co(bpy)3]2/3+. DSSCs fabricated with the CoS-III CE yield the highest short-circuit current density (JSC) of 12.84 mA cm-2, open circuit voltage (VOC) of 805 mV and overall power conversion efficiency (PCE) of 6.72% under AM 1.5G illumination (100 mW cm-2). These values are comparable to the performance of an analogous cell fabricated with the Pt CE (PCE = 6.94%). Owing to relative lower cost (due to the inherit earth abundance of Co) and non-toxicity, CoS can be considered as a promising alternative to the more expensive Pt as a CE material for next-generation DSSCs that utilize organic dyes and cobalt-based redox electrolytes.

  1. Ground Penetrating Radar Investigation of Sinter Deposits at Old Faithful Geyser and Immediately Adjacent Hydrothermal Features, Yellowstone National Park, Wyoming, USA

    NASA Astrophysics Data System (ADS)

    Foley, D.; Lynne, B. Y.; Jaworowski, C.; Heasler, H.; Smith, G.; Smith, I.

    2015-12-01

    Ground Penetrating Radar (GPR) was used to evaluate the characteristics of the shallow subsurface siliceous sinter deposits around Old Faithful Geyser. Zones of fractures, areas of subsurface alteration and pre-eruption hydrologic changes at Old Faithful Geyser and surrounding hydrothermal mounds were observed. Despite being viewed directly by about 3,000,000 people a year, shallow subsurface geologic and hydrologic conditions on and near Old Faithful Geyser are poorly characterized. GPR transects of 5754 ft (1754m) show strong horizontal to sub-horizontal reflections, which are interpreted as 2.5 to 4.5 meters of sinter. Some discontinuities in reflections are interpreted as fractures in the sinter, some of which line up with known hydrothermal features and some of which have little to no surface expression. Zones with moderate and weak amplitude reflections are interpreted as sinter that has been hydrothermally altered. Temporal changes from stronger to weaker reflections are correlated with the eruption cycle of Old Faithful Geyser, and are interpreted as post-eruption draining of shallow fractures, followed by pre-eruption fracture filling with liquid or vapor thermal fluids.

  2. Systems level approach reveals the correlation of endoderm differentiation of mouse embryonic stem cells with specific microstructural cues of fibrin gels

    PubMed Central

    Task, Keith; D'Amore, Antonio; Singh, Satish; Candiello, Joe; Jaramillo, Maria; Wagner, William R.; Kumta, Prashant; Banerjee, Ipsita

    2014-01-01

    Stem cells receive numerous cues from their associated substrate that help to govern their behaviour. However, identification of influential substrate characteristics poses difficulties because of their complex nature. In this study, we developed an integrated experimental and systems level modelling approach to investigate and identify specific substrate features influencing differentiation of mouse embryonic stem cells (mESCs) on a model fibrous substrate, fibrin. We synthesized a range of fibrin gels by varying fibrinogen and thrombin concentrations, which led to a range of substrate stiffness and microstructure. mESCs were cultured on each of these gels, and characterization of the differentiated cells revealed a strong influence of substrate modulation on gene expression patterning. To identify specific substrate features influencing differentiation, the substrate microstructure was quantified by image analysis and correlated with stem cell gene expression patterns using a statistical model. Significant correlations were observed between differentiation and microstructure features, specifically fibre alignment. Furthermore, this relationship occurred in a lineage-specific manner towards endoderm. This systems level approach allows for identification of specific substrate features from a complex material which are influential to cellular behaviour. Such analysis may be effective in guiding the design of scaffolds with specific properties for tissue engineering applications. PMID:24718448

  3. Effect of polymer microstructure on the docetaxel release and stability of polyurethane formulation.

    PubMed

    Shaikh, Mohsin; Choudhury, Namita Roy; Knott, Robert; Kanwar, Jagat Rakesh; Garg, Sanjay

    2016-04-01

    PurSil®AL20 (PUS), a copolymer of 4,4'-dicyclohexylmethane diisocyanate (HMDI), 1,4-butane diol (BD), poly-tetramethylene oxide (PTMO) and poly-dimethyl siloxane (PDMS) was investigated for stability as a vehicle for Docetaxel (DTX) delivery through oesophageal drug eluting stent (DES). On exposure to stability test conditions, it was found that DTX release rate declined at 4 and 40 °C. In order to divulge reasons underlying this, changes in DTX solid state as well as PUS microstructure were followed. It was found that re-crystallization of DTX in PDMS rich regions was reducing the drug release at both 4 °C and 40 °C samples. So far microstructural features have not been correlated with stability and drug release, and in this study we found that at 40 °C increase in microstructural domain sizes and the inter-domain distances (from ∼85 Å to 129 Å) were responsible for hindering the DTX release in addition to DTX re-crystallization. PMID:26829379

  4. Blindness alters the microstructure of the ventral but not the dorsal visual stream.

    PubMed

    Reislev, Nina L; Kupers, Ron; Siebner, Hartwig R; Ptito, Maurice; Dyrby, Tim B

    2016-07-01

    Visual deprivation from birth leads to reorganisation of the brain through cross-modal plasticity. Although there is a general agreement that the primary afferent visual pathways are altered in congenitally blind individuals, our knowledge about microstructural changes within the higher-order visual streams, and how this is affected by onset of blindness, remains scant. We used diffusion tensor imaging and tractography to investigate microstructural features in the dorsal (superior longitudinal fasciculus) and ventral (inferior longitudinal and inferior fronto-occipital fasciculi) visual pathways in 12 congenitally blind, 15 late blind and 15 normal sighted controls. We also studied six prematurely born individuals with normal vision to control for the effects of prematurity on brain connectivity. Our data revealed a reduction in fractional anisotropy in the ventral but not the dorsal visual stream for both congenitally and late blind individuals. Prematurely born individuals, with normal vision, did not differ from normal sighted controls, born at term. Our data suggest that although the visual streams are structurally developing without normal visual input from the eyes, blindness selectively affects the microstructure of the ventral visual stream regardless of the time of onset. We suggest that the decreased fractional anisotropy of the ventral stream in the two groups of blind subjects is the combined result of both degenerative and cross-modal compensatory processes, affecting normal white matter development. PMID:26134685

  5. Role of Microstructure in Promoting Fracture and Fatigue Resistance in Mo-Si-B Alloys

    SciTech Connect

    Schneibel, Joachim H

    2005-04-01

    An investigation of how microstructural features affect the fracture and fatigue properties of a promising class of high temperature Mo-Si-B based alloys is presented. Fracture toughness and fatigue-crack growth properties are measured at 25 and 1300 C for five Mo-Mo{sub 3}Si-Mo{sub 5}SiB{sub 2} containing alloys produced by powder metallurgy with {alpha}-Mo matrices. Results are compared with previous studies on intermetallic-matrix microstructures in alloys with similar compositions. It is found that increasing the {alpha}-Mo phase volume fraction (17-49%) or ductility (by increasing the temperature) benefits the fracture resistance; in addition, {alpha}-Mo matrix materials show significant improvements over intermetallic-matrix alloys. Fatigue thresholds were also increased with increasing {alpha}-Mo phase content, until a transition to more ductile fatigue behavior occurred with large amounts of {alpha}-Mo phase (49%) and ductility (i.e., at 1300 C). The beneficial role of such microstructural variables are attributed to the promotion of the observed toughening mechanisms of crack trapping and bridging by the relatively ductile {alpha}-Mo phase.

  6. The formation mechanisms of interlocked microstructures in low-carbon high-strength steel weld metals

    SciTech Connect

    Wan, X.L.; Wang, H.H.; Cheng, L.; Wu, K.M.

    2012-05-15

    Microstructural features and the formation mechanisms of interlocked microstructures of acicular ferrite in a low-carbon high-strength steel weld metal were investigated by means of computer-aided three-dimensional reconstruction technique and electron backscattered diffraction analysis. Multiple nucleation on inclusions, sympathetic nucleation or repeated nucleation, hard impingement, mutual intersection, and fixed orientation relationships of acicular ferrite grains were observed. They were all responsible for the formation of interlocked microstructures in the weld metal. During the process of isothermal transformation, the pre-formed acicular ferrite laths or plates partitioned austenite grains into many small and separate regions, and the growth of later formed acicular ferrite grains was confined in these small regions. Thus, the crystallographic grain size became smaller with the increasing holding time. Highlights: Black-Right-Pointing-Pointer Acicular ferrite is formed by multiple nucleation and sympathetic nucleation. Black-Right-Pointing-Pointer Hard impingement and intersection of ferrite grains occur at later stages. Black-Right-Pointing-Pointer The pre-formed ferrite laths partition austenite grains into smaller regions. Black-Right-Pointing-Pointer The growth of later formed ferrite grains is confined in the smaller regions.

  7. From pixels to patches: a cloud classification method based on bag of micro-structures

    NASA Astrophysics Data System (ADS)

    Li, Q.; Zhang, Z.; Lu, W.; Yang, J.; Ma, Y.; Yao, W.

    2015-10-01

    Automatic cloud classification has attracted more and more attention with the increasing development of whole sky imagers, but it is still in progress for ground-based cloud observation. This paper proposes a new cloud classification method, named bag of micro-structures (BoMS). This method treats an all-sky image as a collection of micro-structures mapped from image patches, rather than a collection of pixels. And then it constructs an image representation with a weighted histogram of micro-structures. Lastly, a support vector machine (SVM) classifier is applied on the image representation because SVM is appealing for sparse and high dimensional feature space. Five different sky conditions are identified: cirriform, cumuliform, stratiform, clear sky and mixed cloudiness that often appears in all-sky images but is seldom addressed in literature. BoMS is evaluated on a large dataset, which contains 5000 all-sky images that are captured by a total-sky cloud imager located in Tibet (29.25° N, 88.88° E). BoMS achieves an accuracy of 90.9 % for 10 fold cross-validation, and it outperforms the state-of-the-art method with an increase of about 19 %. Furthermore, influence of key parameters in BoMS are investigated to verify their robustness.

  8. Influence of processing on the microstructure and mechanical properties of 14YWT

    NASA Astrophysics Data System (ADS)

    Hoelzer, D. T.; Unocic, K. A.; Sokolov, M. A.; Byun, T. S.

    2016-04-01

    The investigation of the mechanical alloying (MA) conditions for producing the advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy led to significant improvements in balancing the strength, ductility and fracture toughness properties while still maintaining the salient microstructural features consisting of ultra-fine grains and high concentration of Y-, Ti- and O-enriched nanoclusters. The implemented changes to the processing conditions included reducing the contamination of the powder during ball milling, applying a pre-extrusion annealing treatment on the ball milled powder and exploring different extrusion temperatures at 850 °C (SM170 heat), 1000 °C (SM185) and 1150 °C (SM200). The microstructural studies of the three 14YWT heats showed similarities in the dispersion of nanoclusters and sub-micron size grains, indicating the microstructure was insensitive to the different extrusion conditions. Compared to past 14YWT heats, the three new heats showed lower strength, but higher ductility levels between 25 and 800 °C and significantly higher fracture toughness values between 25 °C and 700 °C. The lower contamination levels of O, C and N achieved with improved ball milling conditions plus the slightly larger grain size were identified as important factors for improving the balance in mechanical properties of the three heats of 14YWT.

  9. Microstructural characterization of dehydrogenated products of the LiBH4-YH3 composite.

    PubMed

    Kim, Ji Woo; Kim, Kee-Bum; Shim, Jae-Hyeok; Cho, Young Whan; Oh, Kyu Hwan

    2014-12-01

    The dehydrogenated microstructure of the lithium borohydride-yttrium hydride (LiBH4-YH3) composite obtained at 350°C under 0.3 MPa of hydrogen and static vacuum was investigated by transmission electron microscopy combined with a focused ion beam technique. The dehydrogenation reaction between LiBH4 and YH3 into LiH and YB4 takes place under 0.3 MPa of hydrogen, which produces YB4 nano-crystallites that are uniformly distributed in the LiH matrix. This microstructural feature seems to be beneficial for rehydrogenation of the dehydrogenation products. On the other hand, the dehydrogenation process is incomplete under static vacuum, leading to the unreacted microstructure, where YH3 and YH2 crystallites are embedded in LiBH4 matrix. High resolution imaging confirmed the presence of crystalline B resulting from the self-decomposition of LiBH4. However, Li2B12H12, which is assumed to be present in the LiBH4 matrix, was not clearly observed. PMID:25347999

  10. Measuring material microstructure under flow using 1-2 plane flow-small angle neutron scattering.

    PubMed

    Gurnon, A Kate; Godfrin, P Douglas; Wagner, Norman J; Eberle, Aaron P R; Butler, Paul; Porcar, Lionel

    2014-01-01

    A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions. PMID:24561395

  11. Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

    PubMed Central

    Gurnon, A. Kate; Godfrin, P. Douglas; Wagner, Norman J.; Eberle, Aaron P. R.; Butler, Paul; Porcar, Lionel

    2014-01-01

    A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions. PMID:24561395

  12. Influence of processing on the microstructure and mechanical properties of 14YWT

    DOE PAGESBeta

    Hoelzer, David T.; Unocic, Kinga A.; Sokolov, Mikhail A.; Byun, Thak Sang

    2015-12-15

    In this study, the investigation of the mechanical alloying (MA) conditions for producing the advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy led to significant improvements in balancing the strength, ductility and fracture toughness properties while still maintaining the salient microstructural features consisting of ultra-fine grains and high concentration of Y-, Ti- and O-enriched nanoclusters. The implemented changes to the processing conditions included reducing the contamination of the powder during ball milling, applying a pre-extrusion annealing treatment on the ball milled powder and exploring different extrusion temperatures at 850 °C (SM170 heat), 1000 °C (SM185) and 1150 °C (SM200). Themore » microstructural studies of the three 14YWT heats showed similarities in the dispersion of nanoclusters and sub-micron size grains, indicating the microstructure was insensitive to the different extrusion conditions. Compared to past 14YWT heats, the three new heats showed lower strength, but higher ductility levels between 25 and 800 °C and significantly higher fracture toughness values between 25 °C and 700 °C. The lower contamination levels of O, C and N achieved with improved ball milling conditions plus the slightly larger grain size were identified as important factors for improving the balance in mechanical properties of the three heats of 14YWT.« less

  13. Influence of processing on the microstructure and mechanical properties of 14YWT

    SciTech Connect

    Hoelzer, David T.; Unocic, Kinga A.; Sokolov, Mikhail A.; Byun, Thak Sang

    2015-12-15

    In this study, the investigation of the mechanical alloying (MA) conditions for producing the advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy led to significant improvements in balancing the strength, ductility and fracture toughness properties while still maintaining the salient microstructural features consisting of ultra-fine grains and high concentration of Y-, Ti- and O-enriched nanoclusters. The implemented changes to the processing conditions included reducing the contamination of the powder during ball milling, applying a pre-extrusion annealing treatment on the ball milled powder and exploring different extrusion temperatures at 850 °C (SM170 heat), 1000 °C (SM185) and 1150 °C (SM200). The microstructural studies of the three 14YWT heats showed similarities in the dispersion of nanoclusters and sub-micron size grains, indicating the microstructure was insensitive to the different extrusion conditions. Compared to past 14YWT heats, the three new heats showed lower strength, but higher ductility levels between 25 and 800 °C and significantly higher fracture toughness values between 25 °C and 700 °C. The lower contamination levels of O, C and N achieved with improved ball milling conditions plus the slightly larger grain size were identified as important factors for improving the balance in mechanical properties of the three heats of 14YWT.

  14. Effect of Multipasses on Microstructure and Electrochemical Behavior of Weldments

    NASA Astrophysics Data System (ADS)

    Makhdoom, Muhammad Atif; Kamran, Muhammad; Awan, Gul Hameed; Mukhtar, Sehrish

    2013-12-01

    Shielded metal arc welding was applied to AISI 1045 medium carbon steel. The microstructural changes and electrochemical corrosion behavior of the heat-affected zone (HAZ), base metal (BM), and weld zone (WZ) were investigated. The effect of welding passes on microstructural changes of BM, HAZ, and WZ were elucidated using optical microscopy, potentiodynamic Tafel scan, and linear polarization resistance (LPR) methods in plain water and 3.5 pct (w/v) NaCl solution under standard temperature and pressure using corrosion kinetic parameters. From microstructural observations, the variations in ferrite morphology in the BM and WZ showed dissimilar electrochemical corrosion behavior and a corrosion rate than that of HAZ.

  15. Microstructural characterization of pipe bomb fragments

    SciTech Connect

    Gregory, Otto; Oxley, Jimmie; Smith, James; Platek, Michael; Ghonem, Hamouda; Bernier, Evan; Downey, Markus; Cumminskey, Christopher

    2010-03-15

    Recovered pipe bomb fragments, exploded under controlled conditions, have been characterized using scanning electron microscopy, optical microscopy and microhardness. Specifically, this paper examines the microstructural changes in plain carbon-steel fragments collected after the controlled explosion of galvanized, schedule 40, continuously welded, steel pipes filled with various smokeless powders. A number of microstructural changes were observed in the recovered pipe fragments: deformation of the soft alpha-ferrite grains, deformation of pearlite colonies, twin formation, bands of distorted pearlite colonies, slip bands, and cross-slip bands. These microstructural changes were correlated with the relative energy of the smokeless powder fillers. The energy of the smokeless powder was reflected in a reduction in thickness of the pipe fragments (due to plastic strain prior to fracture) and an increase in microhardness. Moreover, within fragments from a single pipe, there was a radial variation in microhardness, with the microhardness at the outer wall being greater than that at the inner wall. These findings were consistent with the premise that, with the high energy fillers, extensive plastic deformation and wall thinning occurred prior to pipe fracture. Ultimately, the information collected from this investigation will be used to develop a database, where the fragment microstructure and microhardness will be correlated with type of explosive filler and bomb design. Some analyses, specifically wall thinning and microhardness, may aid in field characterization of explosive devices.

  16. The effect orientation of features in reconstructed atom probe data on the resolution and measured composition of T1 plates in an A2198 aluminium alloy.

    PubMed

    Mullin, Maria A; Araullo-Peters, Vicente J; Gault, Baptiste; Cairney, Julie M

    2015-12-01

    Artefacts in atom probe tomography can impact the compositional analysis of microstructure in atom probe studies. To determine the integrity of information obtained, it is essential to understand how the positioning of features influences compositional analysis. By investigating the influence of feature orientation within atom probe data on measured composition in microstructural features within an AA2198 Al alloy, this study shows differences in the composition of T1 (Al2CuLi) plates that indicates imperfections in atom probe reconstructions. The data fits a model of an exponentially-modified Gaussian that scales with the difference in evaporation field between solutes and matrix. This information provides a guide for obtaining the most accurate information possible. PMID:25896290

  17. Theoretical investigation of some specific features of the electronic structure and optical properties of Benzoic Acid 2-Amino-4,6-Dimethylpyrimidine (1:1) co-crystals

    NASA Astrophysics Data System (ADS)

    Reshak, A. H.

    2015-08-01

    Benzoic Acid 2-Amino-4,6-Dimethylpyrimidine (1:1) co-crystal have been comprehensively investigated by means of density functional theory. The electronic band structure show that the conduction band minimum (CBM) and the valence band maximum (VBM) are situated at the center of the Brillouin zone resulting in a direct band gap. Calculation were performed using the full potential linear augmented plane wave plus local orbitals (FPLAPW + lo) method in a scalar relativistic version as embodied in the WIEN 2 k code within the local density approximation (LDA), gradient approximation (PBE- GGA), Engel-Vosko generalized gradient approximation (EV- GGA) and the recently modified Becke-Johnson potential (mBJ). The calculated density of states explore that the VBM is mainly formed by N-p state while the CBM is formed by the strongly hybridized N-p and C-p states. There exists a strong hybridizations between C-s/p, H-s, N-s/p and O-s/p states above and below the Fermi level (EF). Which may led to covalent bonding between the states. To visualizes the charge transfer and the chemical bonding characters, the valence band's electronic charge density distribution were extensively investigated. The optical properties helps to get deep insight into the electronic structure therefore, details analysis to the calculated optical properties were performed. The optical properties confirm the existence of the band gap and the lossless regions.

  18. The microstructure of minerals in coarse-grained Ca-Al-rich inclusions from the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Barber, D. J.; Martin, P. M.; Hutcheon, I. D.

    1984-01-01

    Transmission electron microscopy (TEM) is used to investigate the microstructure and microchemistry of minerals in Ca-Al-rich, coarse-grained inclusions (CAI) from the meteorite. The spinels contain only low to moderate dislocation densities and are characterized by a ubiquitous, fine black spotty texture that is thought to originate from a slightly nonstoichiometric composition. Whereas the Ti-Al-pyroxenes are relatively devoid of features, they contain veins of secondary phases apparently deposited in unhealed cracks. Chromite is identified in the veins, indicating transport of oxidized iron during alteration. The melilites show the greatest variety of microstructures and are the most heavily altered phase in CAI. High dislocation densities are common and the crystals exhibit considerable internal strain, suggesting that they have not been annealed.

  19. Microstructure and mechanical properties of heat-resistant 12% Cr ferritic-martensitic steel EK-181 after thermomechanical treatment

    NASA Astrophysics Data System (ADS)

    Polekhina, N. A.; Litovchenko, I. Yu.; Tyumentsev, A. N.; Astafurova, E. G.; Chernov, V. M.; Leontyeva-Smirnova, M. V.

    2015-10-01

    The effect of high-temperature thermomechanical treatment (TMT) with the deformation in the austenitic region on the features of microstructure, phase transformations and mechanical properties of low-activation 12% Cr ferritic-martensitic steel EK-181 is investigated. It is established, that directly after thermomechanical treatment (without tempering) the sizes and density of V(CN) particles are comparable with those after a traditional heat treatment (air quenching and tempering at 720°C, 3 h), where these particles are formed only during tempering. It causes the increasing of the yield strength of the steel up to ≈1450 MPa at room temperature and up to ≈430 MPa at the test temperature T = 650°C. The potential of microstructure modification by this treatment aimed at improving heat resistance of steel is discussed.

  20. Nondestructive volumetric imaging of tissue microstructure with benchtop x-ray phase-contrast tomography and critical point drying

    PubMed Central

    Zysk, Adam M.; Garson, Alfred B.; Xu, Qiaofeng; Brey, Eric M.; Zhou, Wei; Brankov, Jovan G.; Wernick, Miles N.; Kuszak, Jerome R.; Anastasio, Mark A.

    2012-01-01

    The in vitro investigation of many optically opaque biological microstructures requires 3D analysis at high resolution over a large field of view. We demonstrate a new nondestructive volumetric imaging technique that eliminates the structural and computational limitations of conventional 2D optical microscopy by combining x-ray phase-contrast tomography with critical point drying sample preparation. We experimentally demonstrate the enhancement of small features afforded by phase-contrast imaging and show the contrast improvement afforded by the drying of a hydrated specimen. We further demonstrate the biological application of this technique by imaging the microstructure of the accommodative apparatus in a primate eye using a benchtop phase-contrast tomography system. PMID:22876355

  1. The microstructure of minerals in coarse-grained Ca-Al-rich inclusions from the Allende meteorite

    NASA Astrophysics Data System (ADS)

    Barber, D. J.; Martin, P. M.; Hutcheon, I. D.

    1984-04-01

    Transmission electron microscopy (TEM) is used to investigate the microstructure and microchemistry of minerals in Ca-Al-rich, coarse-grained inclusions (CAI) from the meteorite. The spinels contain only low to moderate dislocation densities and are characterized by a ubiquitous, fine black spotty texture that is thought to originate from a slightly nonstoichiometric composition. Whereas the Ti-Al-pyroxenes are relatively devoid of features, they contain veins of secondary phases apparently deposited in unhealed cracks. Chromite is identified in the veins, indicating transport of oxidized iron during alteration. The melilites show the greatest variety of microstructures and are the most heavily altered phase in CAI. High dislocation densities are common and the crystals exhibit considerable internal strain, suggesting that they have not been annealed.

  2. Predictions and Experimental Microstructural Characterization of High Strain Rate Failure Modes in Layered Aluminum Composites

    NASA Astrophysics Data System (ADS)

    Khanikar, Prasenjit

    -rate applications. The second major objective of this investigation was the use of recently developed dynamic fracture formulations to model and analyze the crack nucleation and propagation of aluminum layered composites subjected to high strain rate loading conditions and how microstructural effects, such as precipitates, dispersed particles, and GB orientations affect failure evolution. This dynamic fracture approach is used to investigate crack nucleation and crack growth as a function of the different microstructural characteristics of each alloy in layered composites with and without pre-existing cracks. The zigzag nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations ahead of the crack front, and it underscored the capabilities of the fracture methodology. The evolution of dislocation density and the formation of localized shear slip contributed to the blunting of the propagating crack. Extensive geometrical and thermal softening due to the localized plastic slip also affected crack path orientations and directions. These softening mechanisms resulted in the switching of cleavage planes, which affected crack path orientations. Interface delamination can also have an important role in the failure and toughening of the layered composites. Different scenarios of delamination were investigated, such as planar crack growth and crack penetration into the layers. The presence of brittle surface oxide platelets in the interface region also significantly influenced the interface delamination process. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) characterization provided further physical insights and validation of the predictive capabilities. The inherent microstructural features of each alloy play a significant role in the dynamic fracture, shear strain localization, and interface delamination of the layered metallic composite

  3. Microstructural Characterization of Polymers with Positrons

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.

    1997-01-01

    Positrons provide a versatile probe for monitoring microstructural features of molecular solids. In this paper, we report on positron lifetime measurements in two different types of polymers. The first group comprises polyacrylates processed on earth and in space. The second group includes fully-compatible and totally-incompatible Semi-Interpenetrating polymer networks of thermosetting and thermoplastic polyimides. On the basis of lifetime measurements, it is concluded that free volumes are a direct reflection of physical/electromagnetic properties of the host polymers.

  4. Modeling of microstructure property relationships in titanium-aluminum-vanadium

    NASA Astrophysics Data System (ADS)

    Tiley, Jaimie Scott

    Fuzzy logic neural network models were developed to predict the room temperature tensile behavior of Ti-6Al-4V. This involved the development of a database relating microstructure to properties. This necessitated establishing heat treatment processes to develop microstructural features, mechanical testing of samples, creating rigorous stereology procedures, developing numerical models to predict mechanical behavior, and determining trends and inter-relationships relating microstructural features to mechanical properties. Microstructural features were developed using a Gleeble(TM) 1500 Thermal-mechanical simulator. Samples were obtained from mill annealed plate material and both alpha + beta forged and beta forged materials. A total of 72 samples were beta solutionized and heat treated using different heating and cooling conditions. Rigorous stereology procedures were developed to characterize the important microstructural features. The features included Widmanstatten alpha lath thickness, volume fraction of total alpha, volume fraction of Widmanstatten alpha, grain boundary alpha thickness, mean edge length, colony scale factor, and prior beta grain size factor. Chemical composition was also determined using standard chemical analysis and microscopy techniques. The samples were tested for yield strength, ultimate tensile strength, and elongation at room temperature. Results from the tests and the characterization were used to develop fuzzy logic neural network models to predict the mechanical behaviors and develop relationships between the microstructural features (using CubiCalc RTC(TM)). Results were compared to standard multi-variable regression models. The fuzzy logic neural network models were able to predict the yield, and ultimate tensile strength, within acceptable error ranges with a limited number of input data samples. The models also predicted the elongation values but with larger errors. Of particular importance, the models identified the importance of

  5. Microbial composition and ecological features of phototrophic biofilms proliferating in the Moidons Caves (France): investigation at the single-cell level.

    PubMed

    Borderie, Fabien; Denis, Michel; Barani, Aude; Alaoui-Sossé, Badr; Aleya, Lotfi

    2016-06-01

    The authors investigated the microbial composition of phototrophic biofilms proliferating in a show cave using flow cytometry for the first time in such a context. Results are based on several biofilms sampled in the Moidons Caves (France) and concern both heterotrophic prokaryotes and autotrophic microorganisms. Heterotrophic microorganisms with low nucleic acid content were dominant in biofilms, as can be expected from the oligotrophic conditions prevailing within the cave. Analysis of the biofilm autotrophic components revealed the presence of several taxa, particularly the unicellular green algae Chlorella minutissima, specifically well adapted to this cave. Relationships between flow cytometry results and environmental variables determined in the cave were established and discussed so as to better understand biofilm proliferation processes in caves. PMID:26961535

  6. Microstructural studies of advanced austenitic steels

    SciTech Connect

    Todd, J. A.; Ren, Jyh-Ching

    1989-11-15

    This report presents the first complete microstructural and analytical electron microscopy study of Alloy AX5, one of a series of advanced austenitic steels developed by Maziasz and co-workers at Oak Ridge National Laboratory, for their potential application as reheater and superheater materials in power plants that will reach the end of their design lives in the 1990's. The advanced steels are modified with carbide forming elements such as titanium, niobium and vanadium. When combined with optimized thermo-mechanical treatments, the advanced steels exhibit significantly improved creep rupture properties compared to commercially available 316 stainless steels, 17--14 Cu--Mo and 800 H steels. The importance of microstructure in controlling these improvements has been demonstrated for selected alloys, using stress relaxation testing as an accelerated test method. The microstructural features responsible for the improved creep strengths have been identified by studying the thermal aging kinetics of one of the 16Ni--14Cr advanced steels, Alloy AX5, in both the solution annealed and the solution annealed plus cold worked conditions. Time-temperature-precipitation diagrams have been developed for the temperature range 600 C to 900 C and for times from 1 h to 3000 h. 226 refs., 88 figs., 10 tabs.

  7. How fatigue cracks grow, interact with microstructure, and lose similitude

    SciTech Connect

    Davidson, D.L.

    1997-12-01

    This paper reviews the processes by which fatigue cracks grow and interact with applied load and microstructure. Fatigue crack growth processes are remarkably similar irrespective of microstructure, crack size, or nature of the loading. Large strains at fatigue crack tips applied over repeated cycles severely alter, or homogenize, microstructures, followed by crack advance. Microstructure affects fatigue crack growth kinetics more than growth processes. But, under marginal conditions, fatigue crack growth rates are also affected by microstructural features. Examples are small cracks growing under low stresses or large cracks growing near threshold. The prediction of safe lifetimes for machine parts, such as gas turbine components, requires that laboratory-generated fatigue crack growth rate data be transferred to field-operating conditions. This transfer depends on the maintenance of similitude: microstructurely, mechanically, and environmentally. However, for many industrially important conditions, similitude with large fatigue crack growth is lost, partially because of changes in fatigue crack closure. The effect of closure on similitude is discussed. New data are presented to illustrate the loss of similitude between applied loading and crack tip strain response. The resulting strain rates of material within the process zone are unexpected. Environmentally influenced fatigue crack growth rates are likely to be influenced by these strain rates.

  8. Persistence and variation in microstructural design during the evolution of spider silk

    PubMed Central

    Madurga, R.; Blackledge, T. A.; Perea, B.; Plaza, G. R.; Riekel, C.; Burghammer, M.; Elices, M.; Guinea, G.; Pérez-Rigueiro, J.

    2015-01-01

    The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk, and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some key microstructural features are conserved phylogenetically while others show substantial variation even among closely related species. This new understanding helps elucidate which microstructural features need to be copied in order to produce the next generation of biomimetic silk fibers. PMID:26438975

  9. Persistence and variation in microstructural design during the evolution of spider silk.

    PubMed

    Madurga, R; Blackledge, T A; Perea, B; Plaza, G R; Riekel, C; Burghammer, M; Elices, M; Guinea, G; Pérez-Rigueiro, J

    2015-01-01

    The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk, and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some key microstructural features are conserved phylogenetically while others show substantial variation even among closely related species. This new understanding helps elucidate which microstructural features need to be copied in order to produce the next generation of biomimetic silk fibers. PMID:26438975

  10. Persistence and variation in microstructural design during the evolution of spider silk

    NASA Astrophysics Data System (ADS)

    Madurga, R.; Blackledge, T. A.; Perea, B.; Plaza, G. R.; Riekel, C.; Burghammer, M.; Elices, M.; Guinea, G.; Pérez-Rigueiro, J.

    2015-10-01

    The extraordinary mechanical performance of spider dragline silk is explained by its highly ordered microstructure and results from the sequences of its constituent proteins. This optimized microstructural organization simultaneously achieves high tensile strength and strain at breaking by taking advantage of weak molecular interactions. However, elucidating how the original design evolved over the 400 million year history of spider silk, and identifying the basic relationships between microstructural details and performance have proven difficult tasks. Here we show that the analysis of maximum supercontracted single spider silk fibers using X ray diffraction shows a complex picture of silk evolution where some key microstructural features are conserved phylogenetically while others show substantial variation even among closely related species. This new understanding helps elucidate which microstructural features need to be copied in order to produce the next generation of biomimetic silk fibers.

  11. Impact of Nanotopography, Heparin Hydrogel Microstructures, and Encapsulated Fibroblasts on Phenotype of Primary Hepatocytes

    PubMed Central

    2015-01-01

    Hepatocytes, the main epithelial cell type in the liver, perform most of the biochemical functions of the liver. Thus, maintenance of a primary hepatocyte phenotype is crucial for investigations of in vitro drug metabolism, toxicity, and development of bioartificial liver constructs. Here, we report the impact of topographic cues alone and in combination with soluble signals provided by encapsulated feeder cells on maintenance of the primary hepatocyte phenotype. Topographic features were 300 nm deep with pitches of either 400, 1400, or 4000 nm. Hepatocyte cell attachment, morphology and function were markedly better on 400 nm pitch patterns compared with larger scale topographies or planar substrates. Interestingly, topographic features having biomimetic size scale dramatically increased cell adhesion whether or not substrates had been precoated with collagen I. Albumin production in primary hepatocytes cultured on 400 nm pitch substrates without collagen I was maintained over 10 days and was considerably higher compared to albumin synthesis on collagen-coated flat substrates. In order to investigate the potential interaction of soluble cytoactive factors supplied by feeder cells with topographic cues in determining cell phenotype, bioactive heparin-containing hydrogel microstructures were molded (100 μm spacing, 100 μm width) over the surface of the topographically patterned substrates. These hydrogel microstructures either carried encapsulated fibroblasts or were free of cells. Hepatocytes cultured on nanopatterned substrates next to fibroblast carrying hydrogel microstructures were significantly more functional than hepatocytes cultured on nanopatterned surfaces without hydrogels or stromal cells significantly elevated albumin expression and cell junction formation compared to cells provided with topographic cues only. The simultaneous presentation of topographic biomechanical cues along with soluble signaling molecules provided by encapsulated fibroblasts

  12. Evaluating Local Primary Dendrite Arm Spacing Characterization Techniques Using Synthetic Directionally Solidified Dendritic Microstructures

    NASA Astrophysics Data System (ADS)

    Tschopp, Mark A.; Miller, Jonathan D.; Oppedal, Andrew L.; Solanki, Kiran N.

    2015-10-01

    Microstructure characterization continues to play an important bridge to understanding why particular processing routes or parameters affect the properties of materials. This statement certainly holds true in the case of directionally solidified dendritic microstructures, where characterizing the primary dendrite arm spacing is vital to developing the process-structure-property relationships that can lead to the design and optimization of processing routes for defined properties. In this work, four series of simulations were used to examine the capability of a few Voronoi-based techniques to capture local microstructure statistics (primary dendrite arm spacing and coordination number) in controlled (synthetically generated) microstructures. These simulations used both cubic and hexagonal microstructures with varying degrees of disorder (noise) to study the effects of length scale, base microstructure, microstructure variability, and technique parameters on the local PDAS distribution, local coordination number distribution, bulk PDAS, and bulk coordination number. The Voronoi tesselation technique with a polygon-side-length criterion correctly characterized the known synthetic microstructures. By systematically studying the different techniques for quantifying local primary dendrite arm spacings, we have evaluated their capability to capture this important microstructure feature in different dendritic microstructures, which can be an important step for experimentally correlating with both processing and properties in single crystal nickel-based superalloys.

  13. Photoinduced degradation of organic solar cells with different microstructures

    NASA Astrophysics Data System (ADS)

    Lu, Chun-Xi; Yan, Peng; Wang, Jin-Ze; Liu, Ai-Min; Song, De; Jiang, Chao

    2014-08-01

    An in situ measurement setup is established to investigate the photoinduced degradation effects in a controllable inert gas ambient environment for the two different microstructures of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyricacid methyl ester (PCBM) bulk-heterojunction organic solar cells. The two devices are fabricated with the solvent vapor drying process followed by a thermal annealing (vapor drying device) and only a normal thermal annealing process (control device), respectively. Their power conversion efficiencies (PCEs) and aging features are compared. Their different degradation behaviors in light absorption are confirmed. In addition, irradiation-induced changes in both nanostructure and surface morphology of the P3HT:PCBM blend films treated with two different fabrication processes are observed through scanning electron microscopy and atomic force microscopy. Aggregated bulbs are observed at the surfaces for control devices after light irradiation for 50 h, while the vapor drying devices exhibit smooth film surfaces, and the corresponding device features are not easy to degrade under the aging measurement. Thus the devices having solvent vapor drying and thermal annealing show better device stabilities than those having only the thermal annealing process.

  14. Solidification microstructures in single-crystal stainless steel melt pools

    SciTech Connect

    Sipf, J.B.; Boatner, L.A.; David, S.A.

    1994-03-01

    Development of microstructure of stationary melt pools of oriented stainless steel single crystals (70%Fe-15%Ni-15%Cr was analyzed. Stationary melt pools were formed by electron-beam and gas-tungsten-arc heating on (001), (011), and (111) oriented planes of the austenitic, fcc-alloy crystals. Characterization and analysis of resulting microstructure was carried out for each crystallographic plane and welding method. Results showed that crystallography which favors ``easy growth`` along the <100> family of directions is a controlling factor in the microstructural formation along with the melt-pool shape. The microstructure was found to depend on the melting method, since each method forms a unique melt-pool shape. These results are used in making a three-dimensional reconstruction of the microstructure for each plane and melting method employed. This investigation also suggests avenues for future research into the microstructural properties of electron-beam welds as well as providing an experimental basis for mathematical models for the prediction of solidification microstructures.

  15. Directing neuronal cell growth on implant material surfaces by microstructuring.

    PubMed

    Reich, Uta; Fadeeva, Elena; Warnecke, Athanasia; Paasche, Gerrit; Müller, Peter; Chichkov, Boris; Stöver, Timo; Lenarz, Thomas; Reuter, Günter

    2012-05-01

    For best hearing sensation, electrodes of auditory prosthesis must have an optimal electrical contact to the respective neuronal cells. To improve the electrode-nerve interface, microstructuring of implant surfaces could guide neuronal cells toward the electrode contact. To this end, femtosecond laser ablation was used to generate linear microgrooves on the two currently relevant cochlear implant materials, silicone elastomer and platinum. Silicone surfaces were structured by two different methods, either directly, by laser ablation or indirectly, by imprinting using laser-microstructured molds. The influence of surface structuring on neurite outgrowth was investigated utilizing a neuronal-like cell line and primary auditory neurons. The pheochromocytoma cell line PC-12 and primary spiral ganglion cells were cultured on microstructured auditory implant materials. The orientation of neurite outgrowth relative to the microgrooves was determined. Both cell types showed a preferred orientation in parallel to the microstructures on both, platinum and on molded silicone elastomer. Interestingly, microstructures generated by direct laser ablation of silicone did not influence the orientation of either cell type. This shows that differences in the manufacturing procedures can affect the ability of microstructured implant surfaces to guide the growth of neurites. This is of particular importance for clinical applications, since the molding technique represents a reproducible, economic, and commercially feasible manufacturing procedure for the microstructured silicone surfaces of medical implants. PMID:22287482

  16. Microstructure property relationships of urethane magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

    Boczkowska, Anna; Awietjan, Stefan F.; Wroblewski, Rafal

    2007-10-01

    Studies on the structure of urethane magnetorheological elastomers (MREs), with respect to their magnetic and mechanical properties, are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. Samples with different numbers of particles (1.5, 11.5 and 33 vol%) were produced. The microstructure and magnetic properties of the obtained MREs were studied. Also, the displacement of the samples in an external magnetic field was examined using a specially designed experimental set-up. The influences of the number of ferromagnetic particles and their arrangement in relation to the external magnetic field were investigated. It was found that the microstructure of the MREs depends on the number of ferrous particles and the fabrication conditions. The orientation of the iron particles into aligned chains is possible for a lower volume content of the ferromagnetic fillers. The high carbonyl-iron volume content in the matrix leads to the formation of more complex microstructures, similar to three-dimensional lattices. The magnetic measurements also confirmed the existence of the microstructure anisotropy for the MREs with 1.5 and 11.5 vol% of iron particles. The structural and magnetic anisotropy has not been found in the MREs with 33 vol% of Fe. To evaluate the effect of the external magnetic field on the magnetorheological properties, the displacement under magnetic field, the compressive strength, and the rheological properties were measured. The experiments showed that both the particle content and the field strength used during curing have a significant effect on the microstructure of the MREs and, in consequence, on their properties.

  17. An investigation of the effects of interfacial microstructure on the fatigue behavior of a four-ply [75]{sub 4} continuous silicon carbide (SCS-6) fiber-reinforced titanium matrix composite

    SciTech Connect

    Jin, O.; Li, Y.; Rabeeh, B.M.; Soboyejo, W.O.

    1997-12-01

    The effects of interfacial microstructure/thickness on the strength and fatigue behavior of a model four-ply [75]{sub 4} Ti-15V-3Al-3Cr-3Sn/SiC (SCS-6) composite are examined in this article. Interfacial microstructure was controlled by annealing at 815 C for 10, 50, or 100 hours. The reaction layer and coating thickness were observed to increase with increasing annealing duration. Damage initiation/propagation mechanisms were examined in as-received material and composites annealed at 815 C for 10 and 100 hours. Fatigue behavior was observed to be dependent upon the stress amplitude. At high stress amplitudes, the failure was dominated by overload phenomena. However, at all stress levels, fatigue crack initiation occurred by early debonding and matrix deformation by stress-induced precipitation. This was followed by matrix crack growth and fiber fracture prior to the onset of catastrophic failure. Matrix shear failure modes were also observed on the fracture surfaces in addition to fatigue striations in the matrix. Correlations were also established between the observed damage modes and acoustic emission signals that were detected under monotonic and cyclic loading conditions.

  18. Spray features in the near field of a flow-blurring injector investigated by high-speed visualization and time-resolved PIV

    NASA Astrophysics Data System (ADS)

    Jiang, Lulin; Agrawal, Ajay K.

    2015-05-01

    In a flow-blurring (FB) injector, atomizing air stagnates and bifurcates at the gap upstream of the injector orifice. A small portion of the air penetrates into the liquid supply line to create a turbulent two-phase flow. Pressure drop across the injector orifice causes air bubbles to expand and burst thereby disintegrating the surrounding liquid into a fine spray. In previous studies, we have demonstrated clean and stable combustion of alternative liquid fuels, such as biodiesel, straight vegetable oil and glycerol by using the FB injector without requiring fuel pre-processing or combustor hardware modification. In this study, high-speed visualization and time-resolved particle image velocimetry (PIV) techniques are employed to investigate the FB spray in the near field of the injector to delineate the underlying mechanisms of atomization. Experiments are performed using water as the liquid and air as the atomizing gas for air to liquid mass ratio of 2.0. Flow visualization at the injector exit focused on a field of view with physical dimensions of 2.3 mm × 1.4 mm at spatial resolution of 7.16 µm per pixel, exposure time of 1 µs, and image acquisition rate of 100 k frames per second. Image sequences illustrate mostly fine droplets indicating that the primary breakup by FB atomization likely occurs within the injector itself. A few larger droplets appearing mainly at the injector periphery undergo secondary breakup by Rayleigh-Taylor instabilities. Time-resolved PIV is applied to quantify the droplet dynamics in the injector near field. Plots of instantaneous, mean, and root-mean-square droplet velocities are presented to reveal the secondary breakup process. Results show that the secondary atomization to produce fine and stable spray is complete within a few diameters from the injector exit. These superior characteristics of the FB injector are attractive to achieve clean combustion of different fuels in practical systems.

  19. Structural features of a bituminous coal and their changes during low-temperature oxidation and loss of volatiles investigated by advanced solid-state NMR spectroscopy

    USGS Publications Warehouse

    Mao, J.-D.; Schimmelmann, A.; Mastalerz, Maria; Hatcher, P.G.; Li, Y.

    2010-01-01

    Quantitative and advanced 13C solid-state NMR techniques were employed to investigate (i) the chemical structure of a high volatile bituminous coal, as well as (ii) chemical structural changes of this coal after evacuation of adsorbed gases, (iii) during oxidative air exposure at room temperature, and (iv) after oxidative heating in air at 75 ??C. The solid-state NMR techniques employed in this study included quantitative direct polarization/magic angle spinning (DP/MAS) at a high spinning speed of 14 kHz, cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CH, CH2, and CHn selection, 13C chemical shift anisotropy (CSA) filtering, two-dimensional (2D) 1H-13C heteronuclear correlation NMR (HETCOR), and 2D HETCOR with 1H spin diffusion. With spectral editing techniques, we identified methyl CCH 3, rigid and mobile methylene CCH2C, methine CCH, quaternary Cq, aromatic CH, aromatic carbons bonded to alkyls, small-sized condensed aromatic moieties, and aromatic C-O groups. With direct polarization combined with spectral-editing techniques, we quantified 11 different types of functional groups. 1H-13C 2D HETCOR NMR experiments indicated spatial proximity of aromatic and alkyl moieties in cross-linked structures. The proton spin diffusion experiments indicated that the magnetization was not equilibrated at a 1H spin diffusion time of 5 ms. Therefore, the heterogeneity in spatial distribution of different functional groups should be above 2 nm. Recoupled C-H long-range dipolar dephasing showed that the fraction of large charcoal-like clusters of polycondensed aromatic rings was relatively small. The exposure of this coal to atmospheric oxygen at room temperature for 6 months did not result in obvious chemical structural changes of the coal, whereas heating at 75 ??C in air for 10 days led to oxidation of coal and generated some COO groups. Evacuation removed most volatiles and caused a significant reduction in aliphatic signals in its DP

  20. Rate and Microstructure Effects on the Dynamics of Carbon Nanotube Foams

    NASA Astrophysics Data System (ADS)

    Thevamaran, Ramathasan

    Soft hierarchical materials often present unique functional properties that are sensitive to the geometry and organization of their micro- and nano-structural features across different lengthscales. Carbon Nanotube (CNT) foams are hierarchical materials with fibrous morphology that are known for their remarkable physical, chemical and electrical properties. Their complex microstructure has led them to exhibit intriguing mechanical responses at different lengthscales and in different loading regimes. Even though these materials have been studied for mechanical behavior over the past few years, their response at high-rate finite deformations and the influence of their microstructure on bulk mechanical behavior and energy dissipative characteristics remain elusive. In this dissertation, we study the response of aligned CNT foams at the high strain-rate regime of 102 - 104 s -1. We investigate their bulk dynamic response and the fundamental deformation mechanisms at different lengthscales, and correlate them to the microstructural characteristics of the foams. We develop an experimental platform, with which to study the mechanics of CNT foams in high-rate deformations, that includes direct measurements of the strain and transmitted forces, and allows for a full field visualization of the sample's deformation through high-speed microscopy. We synthesize various CNT foams (e.g., vertically aligned CNT (VACNT) foams, helical CNT foams, micro-architectured VACNT foams and VACNT foams with microscale heterogeneities) and show that the bulk functional properties of these materials are highly tunable either by tailoring their microstructure during synthesis or by designing micro-architectures that exploit the principles of structural mechanics. We also develop numerical models to describe the bulk dynamic response using multiscale mass-spring models and identify the mechanical properties at length scales that are smaller than the sample height. The ability to control the

  1. Step-by-Step Growth of Complex Oxide Microstructures.

    PubMed

    Datskos, Panos; Cullen, David A; Sharma, Jaswinder

    2015-07-27

    The synthesis of complex and hybrid oxide microstructures is of fundamental interest and practical applications. However, the design and synthesis of such structures is a challenging task. A solution-phase process to synthesize complex silica and silica-titania hybrid microstructures was developed by exploiting the emulsion-droplet-based step-by-step growth featuring shape control. The strategy is robust and can be extended to the preparation of complex hybrid structures consisting of two or more materials, with each having its own shape. PMID:26095228

  2. Voronoi based microstructure modelling for elastic wave propagation

    NASA Astrophysics Data System (ADS)

    Shivaprasad, S.; Balasubramaniam, Krishnan; Krishnamurthy, C. V.

    2016-02-01

    Ultrasonic assessment of materials and defects are affected by microstructural parameters like grain size and texture. When a beam of ultrasound propagates in a polycrystalline medium, it undergoes extensive scattering by grains, grain boundaries and other microstructural features such as dislocations, voids, micro cracks etc. To understand the role of anisotropy and grain size distribution on an ultrasonic beam, a model system is proposed for carrying out ultrasonic wave propagation in a model characterized by grain size distribution and grain orientation distribution. A 2D polycrystalline medium constructed using Voronoi tessellations with a specific grain size distribution is considered and orientational averaging studies are carried out.

  3. Microstructure and corrosion behavior of shielded metal arc-welded dissimilar joints comprising duplex stainless steel and low alloy steel

    NASA Astrophysics Data System (ADS)

    Srinivasan, P. Bala; Muthupandi, V.; Sivan, V.; Srinivasan, P. Bala; Dietzel, W.

    2006-12-01

    This work describes the results of an investigation on a dissimilar weld joint comprising a boiler-grade low alloy steel and duplex stainless steel (DSS). Welds produced by shielded metal arc-welding with two different electrodes (an austenitic and a duplex grade) were examined for their microstructural features and properties. The welds were found to have overmatching mechanical properties. Although the general corrosion resistance of the weld metals was good, their pitting resistance was found to be inferior when compared with the DSS base material.

  4. A Systematic Study on Tooth Enamel Microstructures of Lambdopsalis bulla (Multituberculate, Mammalia) - Implications for Multituberculate Biology and Phylogeny

    PubMed Central

    Mao, Fangyuan; Wang, Yuanqing; Meng, Jin

    2015-01-01

    Tooth enamel microstructure is a reliable and widely used indicator of dietary interpretations and data for phylogenetic reconstruction, if all levels of variability are investigated. It is usually difficult to have a thorough examination at all levels of enamel structures for any mammals, especially for the early mammals, which are commonly represented by sparse specimens. Because of the random preservation of specimens, enamel microstructures from different teeth in various species are often compared. There are few examples that convincingly show intraspecific variation of tooth enamel microstructure in full dentition of a species, including multituberculates. Here we present a systematic survey of tooth enamel microstructures of Lambdopsalis bulla, a taeniolabidoid multituberculate from the Late Paleocene Nomogen Formation, Inner Mongolia. We examined enamel structures at all hierarchical levels. The samples are treated differently in section orientations and acid preparation and examined using different imaging methods. The results show that, except for preparation artifacts, the crystallites, enamel types, Schmelzmuster and dentition types of Lambdopsalis are relatively consistent in all permanent teeth, but the prism type, including the prism shape, size and density, may vary in different portions of a single tooth or among different teeth of an individual animal. The most common Schmelzmuster of the permanent teeth in Lambdopsalis is a combination of radial enamel in the inner and middle layers, aprismatic enamel in the outer layer, and irregular decussations in tooth crown area with great curvature. The prism seam is another comparably stable characteristic that may be a useful feature for multituberculate taxonomy. The systematic documentation of enamel structures in Lambdopsalis may be generalized for the enamel microstructure study, and thus for taxonomy and phylogenetic reconstruction, of multituberculates and even informative for the enamel study of

  5. A Systematic Study on Tooth Enamel Microstructures of Lambdopsalis bulla (Multituberculate, Mammalia)--Implications for Multituberculate Biology and Phylogeny.

    PubMed

    Mao, Fangyuan; Wang, Yuanqing; Meng, Jin

    2015-01-01

    Tooth enamel microstructure is a reliable and widely used indicator of dietary interpretations and data for phylogenetic reconstruction, if all levels of variability are investigated. It is usually difficult to have a thorough examination at all levels of enamel structures for any mammals, especially for the early mammals, which are commonly represented by sparse specimens. Because of the random preservation of specimens, enamel microstructures from different teeth in various species are often compared. There are few examples that convincingly show intraspecific variation of tooth enamel microstructure in full dentition of a species, including multituberculates. Here we present a systematic survey of tooth enamel microstructures of Lambdopsalis bulla, a taeniolabidoid multituberculate from the Late Paleocene Nomogen Formation, Inner Mongolia. We examined enamel structures at all hierarchical levels. The samples are treated differently in section orientations and acid preparation and examined using different imaging methods. The results show that, except for preparation artifacts, the crystallites, enamel types, Schmelzmuster and dentition types of Lambdopsalis are relatively consistent in all permanent teeth, but the prism type, including the prism shape, size and density, may vary in different portions of a single tooth or among different teeth of an individual animal. The most common Schmelzmuster of the permanent teeth in Lambdopsalis is a combination of radial enamel in the inner and middle layers, aprismatic enamel in the outer layer, and irregular decussations in tooth crown area with great curvature. The prism seam is another comparably stable characteristic that may be a useful feature for multituberculate taxonomy. The systematic documentation of enamel structures in Lambdopsalis may be generalized for the enamel microstructure study, and thus for taxonomy and phylogenetic reconstruction, of multituberculates and even informative for the enamel study of

  6. Light Responsive Microstructured Surfaces of Liquid Crystalline Network with Shape Memory and Tunable Wetting Behaviors.

    PubMed

    Wu, Zi Liang; Wang, Zhi Jian; Keller, Patrick; Zheng, Qiang

    2016-02-01

    Using adaptive soft materials to fabricate microstructured surfaces renders them with tunable topographic feature and thus controllable physical properties. Here, light responsive microstructured surfaces are reported with shape memory and tunable wetting behaviors; the surfaces are covered with micropillar arrays and constructed by lightly crosslinked azo-containing liquid crystalline network (LCN). UV light irradiation induces 25% contraction in length of the micropillars along their long axes and, as a consequence, the variations of topographic feature and wetting behavior of the surfaces. In addition, the LCNs exhibit shape memory properties, which can freeze the temporary topographic feature of microstructured surfaces (formed under UV irradiation and relatively high temperature) and enable application of their functionalities at mild conditions. This light responsiveness makes it feasible to remotely and precisely tune the local regions of microstructured surfaces, which should broaden the applications of adaptive surfaces in regulating the wetting, optical, and adhesion properties in selected regions. PMID:26676211

  7. Metal microstructures in advanced CMOS devices

    SciTech Connect

    Gignac, L.M.; Rodbell, K.P.

    1996-12-31

    As advanced semiconductor device features shrink, grain boundaries and interfaces become increasingly more important to the properties of thin metal film. With film thickness decreasing to the range of 10 nm and the corresponding features also decreasing to sub-micrometer sizes, interface and grain boundary properties become dominant. In this regime the details of the surface and grain boundaries dictate the interactions between film layers and the subsequent electrical properties. Therefore it is necessary to accurately characterize these materials on the proper length scale in order to first understand and then to improve the device effectiveness. In this talk we will examine the importance of microstructural characterization of thin metal films used in semiconductor devices and show how microstructure can influence the electrical performance. Specifically, we will review Co and Ti silicides for silicon contact and gate conductor applications, Ti/TiN liner films used for adhesion and diffusion barriers in chemical vapor deposited (CVD) tungsten vertical wiring (vias) and Ti/AlCu/Ti-TiN films used as planar interconnect metal lines.

  8. Microstructural Effects on the Reactivity of Nano-Aluminum/Iodine (V) Oxide Films

    NASA Astrophysics Data System (ADS)

    Little, B.; Welle, E.; Martinez, L.; Nittinger, J.; Bogle, M.; Emery, S.; Lindsay, C.; Schrand, A.

    2013-06-01

    Recent efforts investigating the self-ignition mechanism of nanoaluminum blended with iodine (V) oxide in the form of powders with and without additives suggests that ignition begins below the decomposition point of either reactant and takes place at the alumina shell surrounding the aluminum nanoparticle. As observed in previous studies of powder composites, microstructural features such as particle morphology are expected to strongly influence properties that govern the combustion behavior of this energetic material (EM). In this study, highly reactive composites containing amorphous and/or crystalline iodine oxide and micron/nano-sized Al was blended with an additive and deposited as films. Physiochemical techniques such as thermal gravimetric analysis, scanning calorimetry, X-ray diffraction, electron microscopy, high-speed imaging and planar doppler velocimetry were employed to characterize these EMs with emphasis on correlating the reaction rate (burn rate) with inherent microstructural features (porosity, thickness, TMD, etc). This work was a continuation of efforts to probe the self-ignition mechanism of Al-iodine (V) oxide composites.

  9. Microstructural Effects on the Reactivity of Nano-Aluminum/Iodine (V) Oxide Films

    NASA Astrophysics Data System (ADS)

    Little, Brian; Langhals, Jarred; Emery, Sam; Martinez, Lucas; Welle, Eric; Lindsay, Michael

    2015-06-01

    Recent efforts investigating the self-ignition mechanism of nanoaluminum blended with iodine (V) oxide in the form of powders with and without additives suggests that ignition begins below the decomposition point of either reactant and takes place at the alumina shell surrounding the aluminum nanoparticle. As observed in previous studies of powder composites, microstructural features such as particle morphology are expected to strongly influence properties that govern the combustion behavior of this energetic material (EM). In this study, highly reactive composites containing amorphous and/or crystalline iodine oxide and nano-sized Al was blended with an additive and deposited as films. Physiochemical techniques such as thermal gravimetric analysis, scanning calorimetry, X-ray diffraction, electron microscopy, high-speed imaging, time of arrival data via photodiodes and planar doppler velocimetry were employed to characterize these EMs with emphasis on correlating the reaction rate (burn rate) with inherent microstructural features (porosity, thickness, TMD, etc). This work was a continuation of efforts to probe the self-ignition mechanism of Al-iodine (V) oxide composites.

  10. Influence of Initial Microstructure on Hot Workability of Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Yeom, Jong-Taek; Kim, Jeoung Han; Hong, Jae-Keun; Park, Nho-Kwang; Lee, Chong Soo

    Hot workability of Ti-6Al-4V alloy with different initial microstructures was investigated by considering processing maps and the dynamic material deformation behavior. The emphasis has been focused on the effect of initial microstructure (equiaxed versus bimodal structure). Process maps were generated using the dynamic material model (DMM), unifying the relationships between constitutive deformation behavior, hot workability and microstructures evolution. Also, the flow instability was investigated using the various flow instability criteria and microstructural analysis. To establish the processing maps with different initial microstructures, high temperature compression tests were carried out at various temperatures and strain rates up to a true strain of 0.7. Microstructural changes occurring during the deformation were analyzed in terms of high temperature deformation mechanisms. Finally the useful instability criterion for predicting the forming defects was suggested through the compression test results with different temperatures and strain rates.

  11. Hemodynamic aspects of reduced platelet adhesion on bioinspired microstructured surfaces.

    PubMed

    Pham, Tam Thanh; Wiedemeier, Stefan; Maenz, Stefan; Gastrock, Gunter; Settmacher, Utz; Jandt, Klaus D; Zanow, Jürgen; Lüdecke, Claudia; Bossert, Jörg

    2016-09-01

    Occlusion by thrombosis due to the absence of the endothelial cell layer is one of the most frequent causes of failure of artificial vascular grafts. Bioinspired surface structures may have a potential to reduce the adhesion of platelets contributing to hemostasis. The aim of this study was to investigate the hemodynamic aspects of platelet adhesion, the main cause of thrombosis, on bioinspired microstructured surfaces mimicking the endothelial cell morphology. We tested the hypothesis that platelet adhesion is statistically significantly reduced on bioinspired microstructured surfaces compared to unstructured surfaces. Platelet adhesion as a function of the microstructure dimensions was investigated under flow conditions on polydimethylsiloxane (PDMS) surfaces by a combined experimental and theoretical approach. Platelet adhesion was statistically significantly reduced (by up to 78%; p≤0.05) on the microstructured PDMS surfaces compared to that on the unstructured control surface. Finite element method (FEM) simulations of blood flow dynamic revealed a micro shear gradient on the microstructure surfaces which plays a pivotal role in reducing platelet adhesion. On the surfaces with the highest differences of the shear stress between the top of the microstructures and the ground areas, platelet adhesion was reduced most. In addition, the microstructures help to reduce the interaction strength between fluid and surfaces, resulting in a larger water contact angle but no higher resistance to flow compared to the unstructured surface. These findings provide new insight into the fundamental mechanisms of reducing platelet adhesion on microstructured bioinspired surfaces and may lay the basis for the development of innovative next generation artificial vascular grafts with reduced risk of thrombosis. PMID:27239904

  12. Weakening mechanisms along Low-Angle Normal Faults in pelagic limestones (Southern Apennine, Italy): insights from microstructural analysis

    NASA Astrophysics Data System (ADS)

    Novellino, R.; Prosser, G.; Viti, C.; Spiess, R.; Agosta, F.; Tavarnelli, E.; Bucci, F.

    2013-12-01

    Low-Angle Normal Faults (LANFs) consist of shallowly-dipping extensional tectonic structures, whose origin relates to a mechanical paradox currently debated by a number of researches. The easy slip along these faults suggests a strain-weakening process active during fault nucleation and growth. Weakening mechanisms may include: i) presence of weak minerals; ii) high fluid pressure which, causing a drastic reduction of the effective stress, and iii) dynamic fault weakening during coseismic rupture. In the Basilicata portion of Southern Apennines, LANFs have been extensively studied by geological mapping and field structural analysis. Differently, a detailed microstructural observations are not hitherto available in the geological literature. For this reason, in this note, we summarize the results of microstructural analysis carried out on fault rock samples collected from a well-exposed mesoscopic LANFs. The present work is aimed at analyzing the weakening mechanisms that took place along the study faults. The incipient study LANFs are characterized by a narrow and discontinuous damage zone surrounding a very thin fault core that include a discrete slip-surface. The offset is in the range of tens of centimeters to few meters. At the microscope scale, the sampled rocks reveal the coexistence of different structural features such as: i) pervasive shape preferred orientation defined by elongated grains of calcite, producing a distinct foliation; ii) Crush Microbreccia (CM), formed of angular clasts locally in contact with each other; iii) several Ultracataclastic Veins (UV), departing from the slip-surfaces and cutting across the slip-zone. TEM investigation reveal the presence of ultrafine to calcite-nanoparticles (<200 nm) aggregate within UV, and iv) decarbonation features, where calcite grains exhibit irregular boundaries, vacuum and vesicles, most likely related to degassing processes. Thermal decomposition results in formation of a calcite aggregate made of

  13. Probing region-specific microstructure of human cortical areas using high angular and spatial resolution diffusion MRI

    PubMed Central

    Aggarwal, Manisha; Nauen, David W.; Troncoso, Juan C.; Mori, Susumu

    2014-01-01

    Regional heterogeneity in cortical cyto- and myeloarchitecture forms the structural basis of mapping of cortical areas in the human brain. In this study, we investigate the potential of diffusion MRI to probe the microstructure of cortical gray matter and its region-specific heterogeneity across cortical areas in the fixed human brain. High angular resolution diffusion imaging (HARDI) data at an isotropic resolution of 92-μm and 30 diffusion-encoding directions were acquired using a 3D diffusion-weighted gradient-and-spin-echo sequence, from the prefrontal (Brodmann area 9), primary motor (area 4), primary somatosensory (area 3b), and primary visual (area 17) cortical specimens (n = 3 each) from three human subjects. Further, the diffusion MR findings in these cortical areas were compared with histological silver impregnation of the same specimens, in order to investigate the underlying architectonic features that constitute the microstructural basis of diffusion-driven contrasts in cortical gray matter. Our data reveal distinct and region-specific diffusion MR contrasts across the studied areas, allowing delineation of intracortical bands of tangential fibers in specific layers layer I, layer VI, and the inner and outer bands of Baillarger. The findings of this work demonstrate unique sensitivity of diffusion MRI to differentiate region-specific cortical microstructure in the human brain, and will be useful for myeloarchitectonic mapping of cortical areas as well as to achieve an understanding of the basis of diffusion NMR contrasts in cortical gray matter. PMID:25449747

  14. Ti-Mo alloys employed as biomaterials: effects of composition and aging heat treatment on microstructure and mechanical behavior.

    PubMed

    Cardoso, Flavia F; Ferrandini, Peterson L; Lopes, Eder S N; Cremasco, Alessandra; Caram, Rubens

    2014-04-01

    The correlation between the composition, aging heat treatments, microstructural features and mechanical properties of β Ti alloys is of primary significance because it is the foundation for developing and improving new Ti alloys for orthopedic biomaterials. However, in the case of Ti-Mo alloys, this correlation is not fully described in the literature. Therefore, the purpose of this study was to experimentally investigate the effect of composition and aging heat treatments on the microstructure, Vickers hardness and elastic modulus of Ti-Mo alloys. These alloys were solution heat-treated and water-quenched, after which their response to aging heat treatments was investigated. Their microstructure, Vickers hardness and elastic modulus were evaluated, and the results allow us to conclude that stabilization of the β phase is achieved with nearly 10% Mo when a very high cooling rate is applied. Young's modulus was found to be more sensitive to phase variations than hardness. In all of the compositions, the highest hardness values were achieved by aging at 723K, which was attributed to the precipitation of α and ω phases. All of the compositions aged at 573K, 623K and 723K showed overaging within 80h. PMID:24394773

  15. Optical Imaging in Microstructures

    SciTech Connect

    Aker, P. M.

    2001-04-11

    This research was focused on developing morphology-dependent stimulated raman scattering (MDSRS) spectroscopy as an analytic optical imaging technique. MDSRS uses the cavity modes (called morphology dependent resonances, MDRs) associated with axisymmetric dielectric microstructures to generate nonlinear optical signals. Since different cavity modes span different regions inside the microstructure, it becomes possible to generate location-specific spectra. The information gotten from MDSRS imaging experiments is analogous with that generated from magnetic resonance imaging (MRI) studies in that spatial variations in chemical composition and molecular configuration within a structure can be mapped out. The authors demonstrated that MDSRS imaging is feasible and is free from nonlinear artifact. They did this by measuring the molecular structure variations that are present in the interfaces of 180 {micro}m dia. charged water droplets. The 4 publications that resulted from these studies are attached. From a chemical perspective a water droplet is, however, a simple thing. Will it be possible to use MDSRS imaging to study more complex systems such as combusting fuel droplets, layered polymer or glass fibers, or biological cells? The long-term goal of the research was to answer this question. The answer they have come up with is yes and no. The results on nitrate aerosols show that it is possible to do imaging studies on optically non-absorbing, ion containing systems, but that the ultimate sensitivity is dictated by ion concentration. hence systems containing large quantities of mobile ions will be difficult to look at, so this essentially eliminates being able to look at biological samples in situ. But on the positive side, organic systems, such as layered polymer and glass fibers, and combusting organic fuel droplets can be looked at with MDSRS imaging.

  16. Dynamic behavior of microstructures

    NASA Astrophysics Data System (ADS)

    Pryputniewicz, Ryszard J.

    2008-11-01

    Continued demand for flexible and sophisticated, yet lightweight and low power as well as small, systems is being satisfied by advances in microelectromechanical systems (MEMS). These advances require use of computational modeling and simulation accompanied by physical measurements. Successful combination of computer aided design (CAD) and multiphysics simulation tools with the state-of-the-art (SOTA) measurement methodology will contribute to reduction of high prototyping costs, long product development cycles, and time-to-market pressures while developing MEMS for a multitude of increasingly diversified applications. In one approach a unique, fully integrated, software environment for multiscale, multiphysics, high fidelity modeling of MEMS is combined with the SOTA optoelectronic laser interferometric microscope (OELIM) methodology for measurements. The OELIM methodology allows remote, noninvasive, full-field-of-view (FFV) measurements of displacements/deformations and vibrations with high spatial resolution, nanometer accuracy, and in near real-time. In this paper, an approach - employing both, the modeling environment (including an analytical process used to quantitatively show the influence that various parameters defining a microstructure, e.g., RF MEMS, a microswitch, or a sensor, may have on its dynamics; using this process dynamic characteristics of a device/sensor can be optimized by constraining its nominal dimensions and finding the optimum set of uncertainties/tolerances in these dimensions) and the OELIM methodology - is described and its applications are illustrated with representative examples. The examples reveal viability of the approach, combining measurements and modeling (i.e., M&M), for the development of MEMS. The representative results demonstrate capacity of the M&M approach to quantitative determination of the effects of dynamic operational loads on performance of selected microstructures of current interest.

  17. Investigation of the effect of aggregates' morphology on concrete creep properties by numerical simulations

    SciTech Connect

    Lavergne, F.; Sab, K.; Sanahuja, J.; Bornert, M.; Toulemonde, C.

    2015-05-15

    Prestress losses due to creep of concrete is a matter of interest for long-term operations of nuclear power plants containment buildings. Experimental studies by Granger (1995) have shown that concretes with similar formulations have different creep behaviors. The aim of this paper is to numerically investigate the effect of size distribution and shape of elastic inclusions on the long-term creep of concrete. Several microstructures with prescribed size distribution and spherical or polyhedral shape of inclusions are generated. By using the 3D numerical homogenization procedure for viscoelastic microstructures proposed by Šmilauer and Bažant (2010), it is shown that the size distribution and shape of inclusions have no measurable influence on the overall creep behavior. Moreover, a mean-field estimate provides close predictions. An Interfacial Transition Zone was introduced according to the model of Nadeau (2003). It is shown that this feature of concrete's microstructure can explain differences between creep behaviors.

  18. Ferroelectric thin film microstructure development and related property enhancement

    SciTech Connect

    Tuttle, B.; Voigt, J.A.; Headley, T.J.; Potter, B.G.; Dimos, D.; Schwartz, R.W.; Dugger, M.T.; Michael, J.; Nasby, R.D.; Garino, T.J.; Goodnow, D.C.

    1993-11-01

    Factors that control phase evolution, microstructural development and ferroelectric domain assemblage are evaluated for chemically prepared lead zirconate titanate (PZT) thin films. Zirconium to titanium stoichiometry is shown to strongly influence microstructure. As Ti content increases, there is an apparent enhancement of the perovskite phase nucleation rate, grain size becomes smaller, and the amount of pyrochlore phase, if present, decreases. While the pyrochlore matrix microstructure for near morphotropic phase boundary composition thin films consists of two interpenetrating nanophases (pyrochlore and an amorphous phase), the pyrochlore microstructure for PZT 20/80 films deposited on MgO substrates is single phase and consists of 10nm grains. Zirconium to titanium stoichiometry also has a substantial influence on process integration. Near morphotropic phase boundary films exhibit extensive reaction with underlying TiO{sub 2} diffusion barriers; conversely, there is no chemical reaction for identically processed PZT 20/80 thin films. The authors have attempted to directly correlate the optical quality of PZT thin films to the following microstructural features: (1) presence of a second phase, (2) domain orientation, and (3) nanometer surface morphology.

  19. Microstructural analysis of the 2195 aluminum-lithium alloy welds

    NASA Technical Reports Server (NTRS)

    Talia, George E.

    1993-01-01

    The principal objective of this research was to explain a tendency of 2195 Al-Li alloy to crack at elevated temperature during welding. Therefore, a study was made on the effect of welding and thermal treatment on the microstructure of Al-Li Alloy 2195. The critical roles of precipitates, boundaries, phases, and other features of the microstructure were inferred from the crack propagation paths and the morphology of fracture surface of the alloy with different microstructures. Particular emphasis was placed on the microstructures generated by the welding process and the mechanisms of crack propagation in such structures. Variation of the welding parameters and thermal treatments were used to alter the micro/macro structures, and they were characterized by optical and scanning electron microscopy. A theoretical model is proposed to explain changes in the microstructure of welded material. This model proposes a chemical reaction in which gases from the air (i.e., nitrogen) release hydrogen inside the alloy. Such a reaction could generate large internal stresses capable to induce porosity and crack-like delamination in the material.

  20. Micro-EDM for silicon microstructure fabrication

    NASA Astrophysics Data System (ADS)

    Song, Xiaozhong; Reynaerts, Dominiek; Meeusen, Wim; Van Brussel, Hendrik

    1999-03-01

    Currently, most silicon microstructures used in microstructures are produced by photolithographic methods. The reason for this is the well-developed etching technology, used in microelectronics, that has been transferred to the microsystem domain. But since the making of an arbitrary shape or angle on silicon mainly depends on the crystal orientation, some severe limits exist in the production of 3D structures. Electro-discharge machining (EDM) is basically a thermal process. During the EDM process material is removed by electric sparking. It is therefore completely different from etching. In this work, micro-EDM is introduce as a potential approach for solving the above mentioned drawbacks. First, this work presents several testing experiments with different process parameters to investigate the influence of the micro-EDM process on the silicon structure. Main emphasis is put on the surface roughness and on avoiding microcracks generated by the sparking process. It is found that microstructures with a sufficiently low surface roughness and with small microcracks can be produced. The remainder of the work concentrates on making small beam structures, which is a common structure in many microsensor designs. It is found that for a wafer thickness of 650 micrometers , the thinnest beam that can be produced is about 30 micrometers wide. This means that micro-EDM can offer an aspect ratio of 20 in combination with a god dimensional control.

  1. Surface and sub-surface anatomy of the landscape: integrating Unmanned Aerial Vehicle Structure from Motion (UAV-SfM) and Ground Penetrating Radar (GRP) to investigate sedimentary features in the field. - an example from NW Australia

    NASA Astrophysics Data System (ADS)

    Callow, Nik; Leopold, Matthias; May, Simon Matthias

    2015-04-01

    Geomorphology is confronted by the challenge of reconstructing landscape features at appropriate scales, resolution and accuracy, that allows meaningful analysis of environmental processes and their implications. Field geomorphology offers a discrete snapshot (i.e. one or two field campaigns) to reconstruct how features have changed, evolved or responded over time. We explore the application of an emerging photogrammetry technique called Structure-from-Motion (SfM), which uses multiple photographs of the same feature (but taken at different locations) to create high-accuracy three-dimensional models of surface of sedimentary fans formed by extreme wave events. This approach is complimented by investigation of the sub-surface morphology using Ground Penetrating Radar (GPR). Using an UAV "octocopter", we captured 1208 photos with a DSLR camera (Canon EoS-M) at the height of 50m with a ground pixel resolution of 9mm, above a cyclone wash-over fan in the Exmouth Gulf (Western Australia) that measured about 500m inland by 300m wide. Based on 38 ground control point targets (with between 4 and 45 individual photographs per target) the SfM surface had an absolute total (XYZ) accuracy of 51mm (39mm X, 29mm Y and 14mm Y), based on RTK-DGPS surveying from a local ground reference station (with an absolute AUSPOS accuracy of 57mm X, 6mm Y, 50mm Z to AHD) and an overall relative point accuracy of 7mm. A sparse point cloud of over 5.5 million data points was generated using only points with a reconstruction accuracy of <50mm, before spectral unsupervised classification (RGB colour of each XYZ pixel) using K-Means clustering within Python. The output was then manually classified into ground and non-ground points, and the geostatistical analyst functionality of ArcGIS used to produce a final bare-earth DEM. This approach has allowed the study team to economically collect an unprecedented high-resolution and accuracy topographic model of this feature to compliment on

  2. Photoconductivity and density of states in microstructural amorphous silicon

    SciTech Connect

    Budaguan, B.G.; Aivazov, A.A.; Radosel'sky, A.G.; Popov, A.A.

    1997-07-01

    It has been reported in previous works that using of RF 55 kHz PECVD method allows to deposit microstructural inhomogeneous a-Si:H films at high deposition rate (10--20{angstrom}/c) and with high photoconductivity. The structural analysis with using of IR spectroscopy and atomic force microscopy (AFM) performed in this work have shown that these films possess a relatively regular microstructure consisting of grains with characteristic size of {approximately}300--500{angstrom}. The regular microstructure of investigated films differs from inhomogeneous a-Si:H with deteriorate electronic properties. At the same time the diffraction analysis didn't reveal the presence of microcrystals. Therefore, the authors denoted their films as microstructural a-Si:H films. In this work they performed the modeling of the photoconductivity of microstructural a-Si:H films to analyze the density-of-states (DOS) responsible for recombination kinetics. For this purpose different approaches to photoconductivity modeling have been used to simulate the experimentally measured temperature dependence of photoconductivity. The comparative analysis of results of these simulations and ESR measurements have shown that recombination in high photoconductive microstructural films is controlled by deep neutral states.

  3. Programming fluid flow with microstructures

    NASA Astrophysics Data System (ADS)

    Amini, Hamed; Masaeli, Mahdokht; di Carlo, Dino

    2011-11-01

    Flow control and fluid interface manipulation in microfluidic platforms are of great importance in a variety of applications. Current approaches to manipulate fluids generally rely on complex designs, difficult-to-fabricate 3D platforms or use of active methods. Here we show that in the presence of simple cylindrical obstacles (i.e. pillars) in a microchannel, at moderate to high flow rates, streamlines tend to turn and stretch in a manner that, unlike intuition for Stokes flow, does not precisely reverse after passing the pillar. The asymmetric flow behavior up- and down-stream of the pillar due to fluid inertia manifests itself as a total deformation of the topology of streamlines that effectively creates a net secondary flow which resembles the recirculating Dean flow in curving channels. Confocal images were taken to investigate the secondary flow for a variety of microstructure settings. We also developed a numerical technique to map the fluid motion in the channel which is utilized to characterize the secondary flow as well as to engineer the fluid patterns within the channel. This passive method creates the possibility of exceptional control of the 3D structure of the fluid within a microfluidic platform which can significantly advance applications requiring fluid interface control (e.g. optofluidics), ultrafast mixing and solution control around cells.

  4. The influence of matrix microstructure

    NASA Astrophysics Data System (ADS)

    Vyletel, G. M.; Allison, J. E.; Aken, D. C.

    1993-11-01

    The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and artificially aged 2219/TiC/15p and unreinforced 2219 Al were investigated utilizing plastic strain-controlled and stress-controlled testing. The cyclic response of both the reinforced and un-reinforced materials was similar for all plastic strain amplitudes tested except that the saturation stress level for the composite was always greater than that of the unreinforced material. The cyclic response of the naturally aged materials exhibited cyclic hardening and, in some cases, cyclic softening, while the cyclic response for the artificially aged materials showed no evidence of either cyclic hardening or softening. The higher ductility of the unreinforced material made it more resistant to fatigue failure at high strains, and thus, at a given plastic strain, it had longer fatigue life. It should be noted that the tensile ductilities of the 2219/TiC/15p were significantly higher than those previously reported for 2XXX-series composites. During stress-controlled test-ing at stresses below 220 MPa, the presence of TiC particles lead to an improvement in fatigue life. Above 220 MPa, no influence of TiC reinforcement on fatigue life could be detected. In both the composite and unreinforced materials, the low-cycle and high-cycle fatigue lives were found to be virtually independent of matrix microstructure.

  5. Computer vision in microstructural analysis

    NASA Technical Reports Server (NTRS)

    Srinivasan, Malur N.; Massarweh, W.; Hough, C. L.

    1992-01-01

    The following is a laboratory experiment designed to be performed by advanced-high school and beginning-college students. It is hoped that this experiment will create an interest in and further understanding of materials science. The objective of this experiment is to demonstrate that the microstructure of engineered materials is affected by the processing conditions in manufacture, and that it is possible to characterize the microstructure using image analysis with a computer. The principle of computer vision will first be introduced followed by the description of the system developed at Texas A&M University. This in turn will be followed by the description of the experiment to obtain differences in microstructure and the characterization of the microstructure using computer vision.

  6. Microstructural investigation of LixNi1/3Mn1/3Co1/3O2 (x 1) and its aged products via magnetic and diffraction study

    SciTech Connect

    Mohanty, Debasish; Gabrisch, Heike

    2012-01-01

    The thermal stability of the layered oxide LiNi1/3Mn1/3Co1/3O2 and its delithiated product is studied by a combination of x-ray and electron diffraction, TEM imaging and magnetic measurements. Diffraction shows that a small fraction of the layered material converts to spinel phase following delithiation. More spinel phase is observed after thermal annealing. The morphology of the particle changes upon thermal annealing of delithiated materials. The selected area electron diffraction and the magnetic measurement results confirm the presence of Ni+2/Li+ disorder in the delithiated material, which increases upon thermal ageing. The oxidation states of the transition metal ions were determined from magnetic data. It is shown that the charge balance due TO removal of Li+ is maintained through oxidation of Ni+2 and that the oxidation states remain stable during subsequent annealing. No anti-ferromagnetic ordering or crystallographic in plane ordering of transition metal ions is observed. These results clearly describe the thermal degradation of LixNi1/3Mn1/3Co1/3O2 (x 1) occur through the significant microstructural changes.

  7. Microstructural investigation of LixNi1/3Mn1/3Co1/3O2 (x ≤ 1) and its aged products via magnetic and diffraction study

    NASA Astrophysics Data System (ADS)

    Mohanty, D.; Gabrisch, H.

    2012-12-01

    The thermal stability of the layered oxide LiNi1/3Mn1/3Co1/3O2 and its delithiated product is studied by a combination of X-ray and electron diffraction, TEM imaging and magnetic measurements. Diffraction shows that a small fraction of the layered material converts to spinel phase following delithiation. More spinel phase is observed after thermal annealing. The morphology of the particle changes upon thermal annealing of delithiated materials. The selected area electron diffraction and the magnetic measurement results confirm the presence of Ni+2/Li+ disorder in the delithiated material, which increases upon thermal ageing. The oxidation states of the transition metal ions were determined from magnetic data. It is shown that the charge balance due to removal of Li+ is maintained through oxidation of Ni+2 and that the oxidation states remain stable during subsequent annealing. No antiferromagnetic ordering or crystallographic in plane ordering of transition metal ions is observed. These results clearly describe the thermal degradation of LixNi1/3Mn1/3Co1/3O2 (x ≤ 1) occur through the significant microstructural changes.

  8. Sulfur Impurities and the Microstructure of Alumina Scales

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1997-01-01

    The relationship between the microstructure of alumina scales, adhesion, and sulfur content was examined through a series of nickel alloys oxidized in 1100 to 1200 deg. C cyclic or isothermal exposures in air. In cyclic tests of undoped NiCrAl, adhesion was produced when the sulfur content was reduced, without any change in scale microstructure. Although interfacial voids were not observed in cyclic tests of NiCrAl, they were promoted by long-term isothermal exposures, by sulfur doping, and in most exposures of NiAl. Two single crystal superalloys, PWA 1480 and Rene' N5, were also tested, either in the as-received condition or after the sulfur content had been reduced to less than 1 ppmw by hydrogen annealing. The unannealed alloys always exhibited spalling to bare metal, but interfacial voids were not observed consistently. Desulfurized PWA 1480 and Rene' N5 exhibited remarkable adhesion and no voidage for either isothermal or cyclic exposures. The most consistent microstructural feature was that, for the cases where voids did form, the scale undersides exhibited corresponding areas with ridged oxide grain boundaries. Voids were not required for spallation nor were other microstructural features essential for adhesion. These observations are consistent with the model whereby scale spallation is controlled primarily by interfacial sulfur segregation and the consequent degradation of oxide-metal bonding.

  9. Modelling of microstructural effects on magnetic hysteresis properties

    NASA Astrophysics Data System (ADS)

    Dupré, L.; Sablik, M. J.; Van Keer, R.; Melkebeek, J.

    2002-09-01

    In this paper, the relationship between microstructural properties of steels and the material parameters in the Preisach model and in the Jiles-Atherton (JA) model is discussed, in the instance where both models describe quasi-static hysteretic magnetic behaviour. It is shown how the material parameters in both hysteresis models should be modified to reflect their dependence on dislocation density and grain size. The dependence of the Preisach material parameters on these microstructural features is identified starting from hysteresis loops calculated by the microstructurally dependent modified JA model. For the Preisach model, a Lorentzian distribution function is used for the distribution function. This makes it possible to compare predictions here to results of an earlier paper in which the Lorentzian distribution was used for Preisach fits to experimental data for steels of different grain sizes. Also, in a different earlier paper, it was shown how the Lorentzian distribution can be formulated so that it connects with salient features of the JA model. The procedure in this paper enables one to examine and predict microstructural variations of Preisach parameters in steels not only for the case of grain size variation but also for the case of variation in dislocation density.

  10. Modelling microstructure evolution during recrystallization

    NASA Astrophysics Data System (ADS)

    Brahme, Abhijit P.

    The main aim of this work was to model microstructural evolution during recrystallization. This was achieved by characterizing it in terms of recrystallization kinetics and texture development and by identifying factors that exert the greatest effect on the recrystallization process. To achieve the above, geometric and crystallographic observations from two orthogonal sections through a polycrystal were used. Using these as input to the computer simulations, a statistically representative three dimensional model was created. Assignment of orientations to the grains was done such that nearest neighbor relationships match the observed distributions. The microstructures thus obtained were allowed to evolve using a Monte-Carlo simulation. A parametric study was done to study the effects of various factors on recrystallization kinetics and texture development during microstructural evolution. A set of software tools (Microstructure builder) were developed to generate the microstructures. The process involved the use of a ellipsoidal packing method combined with a voxel-based tessellation technique to create a 3 dimensional digital microstructure having the desired set of grain aspect ratios. Orientation assignment to the grains in the microstructure was done using a simulated annealing method that minimized the error between the orientation distribution function (ODF) and misorientation distribution function (MDF) of the measured and simulated materials. The effect of grain geometry and placement of nuclei on recrystallization kinetics was studied. A close match in the recrystallization kinetics as measured in the experiments and the simulations was found to be most sensitive to the accuracy with which the geometry of the simulated microstructure matched that observed in experiments. Also the effects of anisotropy, both in energy and in mobility, stored energy and oriented nucleation on overall texture development were studied in the light of various established

  11. Microstructural and continuum evolution modeling of sintering.

    SciTech Connect

    Braginsky, Michael V.; Olevsky, Eugene A.; Johnson, D. Lynn; Tikare, Veena; Garino, Terry J.; Arguello, Jose Guadalupe, Jr.

    2003-12-01

    deformation during. The continuum portion is based on a finite element formulation that allows 3D components to be modeled using SNL's nonlinear large-deformation finite element code, JAS3D. This tool provides a capability to model sintering of complex three-dimensional components. The model was verified by comparing to simulations results published in the literature. The model was validated using experimental results from various laboratory experiments performed by Garino. In addition, the mesoscale simulations were used to study anisotropic shrinkage in aligned, elongated powder compacts. Anisotropic shrinkage occurred in all compacts with aligned, elongated particles. However, the direction of higher shrinkage was in some cases along the direction of elongation and in other cases in the perpendicular direction depending on the details of the powder compact. In compacts of simple-packed, mono-sized, elongated particles, shrinkage was higher in the direction of elongation. In compacts of close-packed, mono-sized, elongated particles and of elongated particles with a size and shape distribution, the shrinkage was lower in the direction of elongation. We also explored the concept of a sintering stress tensor rather than the traditional sintering stress scalar concept for the case of anisotropic shrinkage. A thermodynamic treatment of this is presented. A method to calculate the sintering stress tensor is also presented. A user-friendly code that can simulate microstructural evolution during sintering in 2D and in 3D was developed. This code can run on most UNIX platforms and has a motif-based GUI. The microstructural evolution is shown as the code is running and many of the microstructural features, such as grain size, pore size, the average grain boundary length (in 2D) and area (in 3D), etc. are measured and recorded as a function of time. The overall density as the function of time is also recorded.

  12. Microcontact printing of proteins inside microstructures.

    PubMed

    Foley, Jennifer; Schmid, Heinz; Stutz, Richard; Delamarche, Emmanuel

    2005-11-22

    Microfluidic devices are well suited for the miniaturization of biological assays, in particular when only small volumes of samples and reagents are available, short time to results is desirable, and multiple analytes are to be detected. Microfluidic networks (MFNs), which fill by means of capillary forces, have already been used to detect important biological analytes with high sensitivity and in a combinatorial fashion. These MFNs were coated with Au, onto which a hydrophilic, protein-repellent monolayer of thiolated poly(ethyleneglycol) (HS-PEG) was self-assembled, and the binding sites for analytes were present on a poly(dimethylsiloxane) (PDMS) sealing cover. We report here a set of simple methods to extend previous work on MFNs by integrating binding sites for analytes inside the microstructures of MFNs using microcontact printing (muCP). First, fluorescently labeled antibodies (Abs) were microcontact-printed from stamps onto planar model surfaces such as glass, Si, Si/SiO2, Au, and Au derivatized with HS-PEG to investigate how much candidate materials for MFNs would quench the fluorescence of printed, labeled Abs. Au coated with HS-PEG led to a fluorescence signal that was approximately 65% weaker than that of glass but provided a convenient surface for printing Abs and for rendering the microstructures of the MFNs wettable. Then, proteins were inked from solution onto the surface of PDMS (Sylgard 184) stamps having continuous or discontinuous micropatterns or locally inked onto planar stamps to investigate how the aspect ratio (depth:width) of microstructures and the printing conditions affected the transfer of protein and the accuracy of the resulting patterns. By applying a controlled pressure to the back of the stamp, Abs were accurately microcontact-printed into the recessed regions of MFNs if the aspect ratio of the MFN microstructures was lower than approximately 1:6. Finally, the realization of a simple assay between Abs (used as antigens

  13. The Effects of Microstructure Heterogeneities and Casting Defects on the Mechanical Properties of High-Pressure Die-Cast AlSi9Cu3(Fe) Alloys

    NASA Astrophysics Data System (ADS)

    Timelli, Giulio; Fabrizi, Alberto

    2014-11-01

    Detailed investigations of the salient microstructural features and casting defects of the high-pressure die-cast (HPDC) AlSi9Cu3(Fe) alloy are reported. These characteristics are addressed to the mechanical properties and reliability of separate HPDC tensile bars. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes throughout the tensile specimen. The results indicate that the die-cast microstructure consists of several microstructural heterogeneities such as positive eutectic segregation bands, externally solidified crystals (ESCs), cold flakes, primary Fe-rich intermetallics (sludge), and porosities. In addition, it results that sludge particles, gas porosity, as well as ESCs, and cold flakes are concentrated toward the casting center while low porosity and fine-grained structure is observed on the surface layer of the castings bars. The local variation of the hardness along the cross section as well as the change of tensile test results as a function of gage diameter of the tensile bars seem to be ascribed to the change of porosity content, eutectic fraction, and amount of sludge. Further, this behavior reflects upon the reliability of the die-cast alloy, as evidenced by the Weibull statistics.

  14. Property and microstructural nonuniformity in the yttrium-barium-copper-oxide superconductor determined from electrical, magnetic, and ultrasonic measurements. Ph.D. Thesis - Case Western Reserve Univ.

    NASA Technical Reports Server (NTRS)

    Roth, Don J.

    1991-01-01

    The purpose of this dissertation was the following: (1) to characterize the effect of pore fraction on a comprehensive set of electrical and magnetic properties for the yttrium-barium-copper-oxide (YBCO) high temperature ceramic superconductor; and (2) to determine the viability of using a room-temperature, nondestructive characterization method to aid in the prediction of superconducting (cryogenic) properties. The latter involved correlating ultrasonic velocity measurements at room temperature with property-affecting pore fraction and oxygen content variations. The use of ultrasonic velocity for estimating pore fraction in YBCO is presented, and other polycrystalline materials are reviewed, modeled, and statistically analyzed. This provides the basis for using ultrasonic velocity to interrogate microstructure. The effect of pore fraction (0.10-0.25) on superconductor properties of YBCO samples was characterized. Spatial (within-sample) variations in microstructure and superconductor properties were investigated, and the effect of oxygen content on elastic behavior was examined. Experimental methods used included a.c. susceptibility, electrical, and ultrasonic velocity measurements. Superconductor properties measured included transition temperature, magnetic transition width, transport and magnetic critical current density, magnetic shielding, a.c. loss, and sharpness of the voltage-current characteristics. An ultrasonic velocity image constructed from measurements at 1mm increments across a YBCO sample revealed microstructural variations that correlated with variations in magnetic shielding and a.c. loss behavior. Destructive examination using quantitative image analysis revealed pore fraction to be the varying microstructural feature.

  15. Effect of irradiation spectrum on the microstructural evolution in ceramic insulators

    SciTech Connect

    Zinkle, S.J.

    1995-04-01

    The objective of this study is to determine and examine the effect of variations in the ionizing and displacive radiation environments on the microstructure of oxide ceramic insulators. Cross section transmission electron microscopy has been used to investigate the microstructure of MgAl{sub 2}O{sub 4} (spinel) and Al{sub 2}O{sub 3} (alumina) following irradiation with ions of varying mass and energy at room temperature and 650{degree}C. These results clearly indicate that light ion and electron irradiations produce microstructures which are not representative of the microstructure that would form in these ceramics during fission or fusion neutron irradiation.

  16. Microstructural Evolution of Ti-6Al-4V during High Strain Rate Conditions of Metal Cutting

    NASA Technical Reports Server (NTRS)

    Dong, Lei; Schneider, Judy

    2009-01-01

    The microstructural evolution following metal cutting was investigated within the metal chips of Ti-6Al-4V. Metal cutting was used to impose a high strain rate on the order of approx.10(exp 5)/s within the primary shear zone as the metal was removed from the workpiece. The initial microstructure of the parent material (PM) was composed of a bi-modal microstructure with coarse prior grains and equiaxed primary located at the boundaries. After metal cutting, the microstructure of the metal chips showed coarsening of the equiaxed primary grains and lamellar. These metallographic findings suggest that the metal chips experienced high temperatures which remained below the transus temperature.

  17. Microstructure Evolution in a New Refractory High-Entropy Alloy W-Mo-Cr-Ti-Al

    NASA Astrophysics Data System (ADS)

    Gorr, Bronislava; Azim, Maria; Christ, Hans-Juergen; Chen, Hans; Szabo, Dorothee Vinga; Kauffmann, Alexander; Heilmaier, Martin

    2016-02-01

    The microstructure of a body-centered cubic 20W-20Mo-20Cr-20Ti-20Al alloy in the as-cast condition as well as its microstructural evolution during heat treatment was investigated. Different characterization techniques, such as focused ion beam-scanning electron microscope, X-ray diffraction, and transmission electron microscope, were applied. Experimental observations were supported by thermodynamic calculations. The alloy exhibits a pronounced dendritic microstructure in the as-cast condition with the respective dendritic and interdendritic regions showing significant fluctuations of the element concentrations. Using thermodynamic calculations, it was possible to rationalize the measured element distribution in the dendritic and the interdendritic regions. Observations of the microstructure evolution reveal that during heat treatment, substantial homogenization takes place leading to the formation of a single-phase microstructure. Driving forces for the microstructural evolution were discussed from a thermodynamic point of view.

  18. Microstructure Informed Tractography: Pitfalls and Open Challenges

    PubMed Central

    Daducci, Alessandro; Dal Palú, Alessandro; Descoteaux, Maxime; Thiran, Jean-Philippe

    2016-01-01

    One of the major limitations of diffusion MRI tractography is that the fiber tracts recovered by existing algorithms are not truly quantitative. Local techniques for estimating more quantitative features of the tissue microstructure exist, but their combination with tractography has always been considered intractable. Recent advances in local and global modeling made it possible to fill this gap and a number of promising techniques for microstructure informed tractography have been suggested, opening new and exciting perspectives for the quantification of brain connectivity. The ease-of-use of the proposed solutions made it very attractive for researchers to include such advanced methods in their analyses; however, this apparent simplicity should not hide some critical open questions raised by the complexity of these very high-dimensional problems, otherwise some fundamental issues may be pushed into the background. The aim of this article is to raise awareness in the diffusion MRI community, notably researchers working on brain connectivity, about some potential pitfalls and modeling choices that make the interpretation of the outcomes from these novel techniques rather cumbersome. Through a series of experiments on synthetic and real data, we illustrate practical situations where erroneous and severely biased conclusions may be drawn about the connectivity if these pitfalls are overlooked, like the presence of partial/missing/duplicate fibers or the critical importance of the diffusion model adopted. Microstructure informed tractography is a young but very promising technology, and by acknowledging its current limitations as done in this paper, we hope our observations will trigger further research in this direction and new ideas for truly quantitative and biologically meaningful analyses of the connectivity. PMID:27375412

  19. Microstructure Informed Tractography: Pitfalls and Open Challenges.

    PubMed

    Daducci, Alessandro; Dal Palú, Alessandro; Descoteaux, Maxime; Thiran, Jean-Philippe

    2016-01-01

    One of the major limitations of diffusion MRI tractography is that the fiber tracts recovered by existing algorithms are not truly quantitative. Local techniques for estimating more quantitative features of the tissue microstructure exist, but their combination with tractography has always been considered intractable. Recent advances in local and global modeling made it possible to fill this gap and a number of promising techniques for microstructure informed tractography have been suggested, opening new and exciting perspectives for the quantification of brain connectivity. The ease-of-use of the proposed solutions made it very attractive for researchers to include such advanced methods in their analyses; however, this apparent simplicity should not hide some critical open questions raised by the complexity of these very high-dimensional problems, otherwise some fundamental issues may be pushed into the background. The aim of this article is to raise awareness in the diffusion MRI community, notably researchers working on brain connectivity, about some potential pitfalls and modeling choices that make the interpretation of the outcomes from these novel techniques rather cumbersome. Through a series of experiments on synthetic and real data, we illustrate practical situations where erroneous and severely biased conclusions may be drawn about the connectivity if these pitfalls are overlooked, like the presence of partial/missing/duplicate fibers or the critical importance of the diffusion model adopted. Microstructure informed tractography is a young but very promising technology, and by acknowledging its current limitations as done in this paper, we hope our observations will trigger further research in this direction and new ideas for truly quantitative and biologically meaningful analyses of the connectivity. PMID:27375412

  20. The Effect of Microstructure on the Shock Behaviour of g-TITANIUM Aluminides

    NASA Astrophysics Data System (ADS)

    Jones, I. P.; Millett, J. C. F.; Bourne, N. K.; Gray, G. T., III

    2001-06-01

    Plate impact experiments have been performed on two alloys based on the intermetallic compound TiAl. Previously, workers have shown that microstructural features (such as grain size and phase distribution) significantly effect the mechanical response both at quasi-static and intermediate strain-rates (Hopkinson bar). In this paper, the effects of such microstructural features are extended into the shock-loading regime. In particular, the microstructural effects upon the Hugoniot, the Hugoniot Elastic Limit and the shock induced shear strength are explored. Results show that the differences in the properties of these two alloys under shock loading can be explained in terms of the microstructural differences observed at lower strain-rates.