Science.gov

Sample records for characteristic crystal orientation

  1. Control of liquid crystal molecular orientation using ultrasound vibration

    NASA Astrophysics Data System (ADS)

    Taniguchi, Satoki; Koyama, Daisuke; Shimizu, Yuki; Emoto, Akira; Nakamura, Kentaro; Matsukawa, Mami

    2016-03-01

    We propose a technique to control the orientation of nematic liquid crystals using ultrasound and investigate the optical characteristics of the oriented samples. An ultrasonic liquid crystal cell with a thickness of 5-25 μm and two ultrasonic lead zirconate titanate transducers was fabricated. By exciting the ultrasonic transducers, the flexural vibration modes were generated on the cell. An acoustic radiation force to the liquid crystal layer was generated, changing the molecular orientation and thus the light transmission. By modulating the ultrasonic driving frequency and voltage, the spatial distribution of the molecular orientation of the liquid crystals could be controlled. The distribution of the transmitted light intensity depends on the thickness of the liquid crystal layer because the acoustic field in the liquid crystal layer is changed by the orientational film.

  2. Liquid crystal orientation control in photonic liquid crystal fibers

    NASA Astrophysics Data System (ADS)

    Chychlowski, M. S.; Nowinowski-Kruszelnicki, E.; Woliński, T. R.

    2011-05-01

    Similarly to liquid crystal displays technology in photonic liquid crystal fibers (PLCFs) a molecular orientation control is a crucial issue that influences proper operation of PLCF-based devices. The paper presents two distinct configurations: planar and radial escaped orientation of the LC molecules inside capillaries as well as methods of their application to photonic liquid crystal fibers. Possibilities of LC orientation control influence both: attenuation and transmitting spectra of the PLCF The orienting method is based on creation of an additional orienting layer on the inner surface of the capillary or air hole of the photonic liquid crystal fiber. Aligning materials used in the experiment are commercially available polyimides SE1211 and SE130 which induce liquid crystal homeotropic and planar anchoring conditions. The orienting layer increase an order parameter of the liquid crystal improving propagation properties and stability of photonic liquid crystal fiber-based devices.

  3. Light scattering by randomly oriented crystals

    NASA Astrophysics Data System (ADS)

    Muinonen, Karri; Lumme, Kari; Peltoniemi, Jouni; Irvine, William M.

    The scattering phase function and the degree of linear polarization for small crystals oriented randomly in space have been computed using the geometric ray tracing theory and assuming that the crystals are homogeneous and isotropic. Calculations have been carried out for the main crystal geometries. Detection of halos from crystals other than hexagonal water ice is briefly discussed. The crystal size and shape parameters have also been averaged over some simple distributions in order to examine general light scattering properties of sharp-edged particles. A scalar physical optics correction has been developed for the geometric optics phase functions. Results can be applied to light scattering from regoliths and planetary rings, and possibly also to atmospheric halos. Retroreflecting crystals in the regolith would cause an opposition spike, a phenomenon observed for many bright satellites.

  4. Light scattering by randomly oriented crystals

    NASA Technical Reports Server (NTRS)

    Muinonen, Karri; Lumme, Kari; Peltoniemi, Jouni; Irvine, William M.

    1989-01-01

    The scattering phase function and the degree of linear polarization for small crystals oriented randomly in space have been computed using the geometric ray tracing theory and assuming that the crystals are homogeneous and isotropic. Calculations have been carried out for the main crystal geometries. Detection of halos from crystals other than hexagonal water ice is briefly discussed. The crystal size and shape parameters have also been averaged over some simple distributions in order to examine general light scattering properties of sharp-edged particles. A scalar physical optics correction has been developed for the geometric optics phase functions. Results can be applied to light scattering from regoliths and planetary rings, and possibly also to atmospheric halos. Retroreflecting crystals in the regolith would cause an opposition spike, a phenomenon observed for many bright satellites.

  5. Laser alexandrite crystals grown by horizontal oriented crystallization technique

    NASA Astrophysics Data System (ADS)

    Gurov, V. V.; Tsvetkov, E. G.; Yurkin, A. M.

    2008-05-01

    Comparative studies were performed for alexandrite crystals, Al 2BeO 4:Cr 3+, employed in solid state lasers and grown by the horizontal oriented crystallization (HOC) technique and alexandrite crystals grown by the Czochralski (Cz) method. It was shown that the structural quality and possibilities of generation of stimulated emission HOC-crystals are similar to Cz-crystals, whereas their damage threshold is about three times higher. The obtained results and considerably lower cost price of HOC-alexandrite crystals prove their advantageous application in powerful laser systems, which require large laser rods with a higher resistance to laser beam. It is emphasized that application of HOC technique is promising for growth of laser crystals of other high-temperature oxide compounds.

  6. Characteristics Orientation, Needs and Expectations. Symposium.

    ERIC Educational Resources Information Center

    2002

    This document contains three papers from a symposium on characteristics orientation, needs, and expectations. "Characteristics Orientation of Emerging Professions: Implications for Research, Policy, and Practice of Continuing Professional Education" (William H. Young, Margot B. Weinstein) reports on a qualitative study that examined emerging…

  7. Controlling laser emission by selecting crystal orientation

    NASA Astrophysics Data System (ADS)

    Chen, Lijuan; Han, Shujuan; Wang, Zhengping; Wang, Jiyang; Zhang, Huanjin; Yu, Haohai; Han, Shuo; Xu, Xinguang

    2013-01-01

    Based on the anisotropy of laser crystal, we demonstrate a method of adjusting laser emission by selecting crystal orientation. When the light propagating direction varies from a to c axis of Nd:LiGd(MoO4)2 crystal, emission wavelength exhibits a sensitive change of 1061 nm → 1061/1062 + 1068 nm → 1068 nm. The experimental discipline is well explained by a theoretical study of simulating on the spatial distribution of stimulated emission cross-section. This letter manifests that the laser property along non-principal-axis direction is also valuable for research and application, which breaks through the traditional custom of using laser materials processed along principal-axis.

  8. Method of controlling defect orientation in silicon crystal ribbon growth

    NASA Technical Reports Server (NTRS)

    Leipold, M. H. (Inventor)

    1978-01-01

    The orientation of twinning and other effects in silicon crystal ribbon growth is controlled by use of a starting seed crystal having a specific (110) crystallographic plane and (112) crystallographic growth direction.

  9. Distinctive characteristics of sexual orientation bias crimes.

    PubMed

    Stacey, Michele

    2011-10-01

    Despite increased attention in the area of hate crime research in the past 20 years, sexual orientation bias crimes have rarely been singled out for study. When these types of crimes are looked at, the studies are typically descriptive in nature. This article seeks to increase our knowledge of sexual orientation bias by answering the question: What are the differences between sexual orientation motivated bias crimes and racial bias crimes? This question is examined using data from the National Incident Based Reporting System (NIBRS) and multiple regression techniques. This analysis draws on the strengths of NIBRS to look at the incident characteristics of hate crimes and distinguishing characteristics of sexual orientation crimes. Specifically this analysis looks at the types and seriousness of offenses motivated by sexual orientation bias as opposed to race bias as well as victim and offender characteristics. The findings suggest that there are differences between these two types of bias crimes, suggesting a need for further separation of the bias types in policy and research. PMID:21156686

  10. Germanium Detector Crystal Axis Orientation for the MAJORANA Demonstrator

    NASA Astrophysics Data System (ADS)

    Letourneau, Hannah

    2013-10-01

    The MAJORANA Demonstrator, currently being constructed at Sanford Underground Research Facility in Lead, South Dakota, is an array of germanium detectors which will be used to search for neutrinoless double beta decay, which would demonstrate that neutrinos have a Majorana mass term and lepton number is not conserved. An important characteristic of semiconductor detectors is the crystal axis orientation, because the propagation of electromagnetic signals is attenuated by the location of the interaction relative to the axis of the crystal. Conventionally, a goniometer is used to position a collimated low energy gamma source in many small increments around the detector to measure the rise time at each position. However, due to physical constraints from the casing of the Demonstrator, a different method must be developed. At the University of Washington this summer, I worked with a 76 Ge point-contact detector. I found the crystal axis orientation first with Americium 241, a lower energy gamma source. Then, I used a higher energy source, Thorium 232, in conjunction with the only a few angular reference points to also calculate rise time. Also, I wrote code to process the data. The success of this method will be evaluated and discussed. NSF

  11. Dynamic theory of morphological characteristics of crystals of ɛ and γ phases, including Headley-Brooks orientation relationships upon the α-ɛ and α-ɛ-γ martensitic transformations

    NASA Astrophysics Data System (ADS)

    Kashchenko, M. P.; Chashchina, V. G.

    2015-10-01

    Different variants of the formation of martensite crystals upon the α-γ transformation caused by the tension-compression deformation of {110}α planes have been considered according to the dynamic theory of martensitic transformations. In contrast to previous works, here we take into account the deviation (angle θ) of the principal directions of deformation from the symmetry axes < {1bar 10} rangle _α and <001>α. It has been shown that the requirement of the symmetry of the arrangement of atoms in the basal plane {0001}ɛ is satisfied in the range of angular deviations-arctan √ {2/3} ≤slant θ ≤slant arctan √ {2/3}. The algorithm for calculating the morphological characteristics is illustrated based on the example of an elastically isotropic medium, which does not require assigning concrete values of elastic moduli. The estimations performed make it possible, in particular, to explain the physical nature of the Headley-Brooks orientation relationships as a result of the inheritance of one of the variants of permissible material orientation relationships for the α-ɛ transformation in the course of the ɛ-γ transformation at θ 35°. The changes in the other morphological signs are also discussed.

  12. Orientation of nematic liquid crystal in open glass microstructures

    NASA Astrophysics Data System (ADS)

    Azarinia, H.; Beeckman, J.; Neyts, K.; Schacht, E.; Gironès, J.; James, R.; Fernandez, F. A.

    2009-09-01

    Liquid crystal materials can have bulk reorientation due to surface interaction and are therefore of interest for biosensing applications. We present a setup, with holes etched in a substrate, filled with liquid crystal and covered by a sample fluid. The influence of the depth of the microcavities and the type of liquid on the liquid crystal orientation is investigated by experiments and simulations.

  13. Orientation-dependent impurity partitioning of colloidal crystals

    NASA Astrophysics Data System (ADS)

    Nozawa, Jun; Uda, Satoshi; Hu, Sumeng; Fujiwara, Kozo; Koizumi, Haruhiko

    2016-04-01

    Impurity partitioning during colloidal crystallization was investigated for grains with different orientations. Particles of various sizes were doped as impurities during the growth of colloidal polycrystals. The effective partition coefficient, keff, which is the impurity concentration in the solid (CS) divided by that in initial solution (CL), was measured for grains oriented in the [111] and [100] directions normal to the growth direction. The [111]-oriented grains were found to have a larger keff than [100]-oriented grains. This was analyzed by using the Thurmond and Struthers model. Though both [111]- and [100]-oriented grains were face centered cubic (fcc) structures, within several layers of crystals, the volume fraction of [111]-oriented grains was larger than that of [100]-oriented grains, yielding a larger driving force for nucleation, ΔGTr, and thus a larger equilibrium partition coefficient, k0, for [111]-oriented grains.

  14. Polarization lidar observations of backscatter phase matrices from oriented ice crystals and rain.

    PubMed

    Hayman, Matthew; Spuler, Scott; Morley, Bruce

    2014-07-14

    Oriented particles can exhibit different polarization properties than randomly oriented particles. These properties cannot be resolved by conventional polarization lidar systems and are capable of corrupting the interpretation of depolarization ratio measurements. Additionally, the typical characteristics of backscatter phase matrices from atmospheric oriented particles are not well established. The National Center for Atmospheric Research High Spectral Resolution Lidar was outfitted in spring of 2012 to measure the backscatter phase matrix, allowing it to fully characterize the polarization properties of oriented particles. The lidar data analyzed here considers operation at 4°, 22° and 32° off zenith in Boulder, CO, USA (40.0°N,105.2°W). The HSRL has primarily observed oriented ice crystal signatures at lidar tilt angles near 32° off zenith which corresponds to an expected peak in backscatter from horizontally oriented plates. The maximum occurrence frequency of oriented ice crystals is measured at 5 km, where 2% of clouds produced significant oriented ice signatures by exhibiting diattenuation in their scattering matrices. The HSRL also observed oriented particle characteristics of rain at all three tilt angles. Oriented signatures in rain are common at all three tilt angles. As many as 70% of all rain observations made at 22° off zenith exhibited oriented signatures. The oriented rain signatures exhibit significant linear diattenuation and retardance. PMID:25090513

  15. Shear induced orientation of edible fat and chocolate crystals

    NASA Astrophysics Data System (ADS)

    Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.

    2003-03-01

    Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.

  16. Alignment of crystal orientations of the multi-domain photonic crystals in Parides sesostris wing scales.

    PubMed

    Yoshioka, S; Fujita, H; Kinoshita, S; Matsuhana, B

    2014-03-01

    It is known that the wing scales of the emerald-patched cattleheart butterfly, Parides sesostris, contain gyroid-type photonic crystals, which produce a green structural colour. However, the photonic crystal is not a single crystal that spreads over the entire scale, but it is separated into many small domains with different crystal orientations. As a photonic crystal generally has band gaps at different frequencies depending on the direction of light propagation, it seems mysterious that the scale is observed to be uniformly green under an optical microscope despite the multi-domain structure. In this study, we have carefully investigated the structure of the wing scale and discovered that the crystal orientations of different domains are not perfectly random, but there is a preferred crystal orientation that is aligned along the surface normal of the scale. This finding suggests that there is an additional factor during the developmental process of the microstructure that regulates the crystal orientation. PMID:24352678

  17. Alignment of crystal orientations of the multi-domain photonic crystals in Parides sesostris wing scales

    PubMed Central

    Yoshioka, S.; Fujita, H.; Kinoshita, S.; Matsuhana, B.

    2014-01-01

    It is known that the wing scales of the emerald-patched cattleheart butterfly, Parides sesostris, contain gyroid-type photonic crystals, which produce a green structural colour. However, the photonic crystal is not a single crystal that spreads over the entire scale, but it is separated into many small domains with different crystal orientations. As a photonic crystal generally has band gaps at different frequencies depending on the direction of light propagation, it seems mysterious that the scale is observed to be uniformly green under an optical microscope despite the multi-domain structure. In this study, we have carefully investigated the structure of the wing scale and discovered that the crystal orientations of different domains are not perfectly random, but there is a preferred crystal orientation that is aligned along the surface normal of the scale. This finding suggests that there is an additional factor during the developmental process of the microstructure that regulates the crystal orientation. PMID:24352678

  18. Elastic response of zone axis (001)-oriented PWA 1480 single crystal: The influence of secondary orientation

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

    1991-01-01

    The influence of secondary orientation on the elastic response of a zone axis (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical loading conditions by applying finite element techniques. Elastic stress analyses were performed with a commercially available finite element code. Secondary orientation of the single-crystal superalloy was offset with respect to the global coordinate system in increments from 0 to 90 deg and stresses developed within the single crystal were determined for each loading condition. The results indicated that the stresses were strongly influenced by the angular offset between the secondary crystal orientation and the global coordinate system. The degree of influence was found to vary with the type of loading condition (mechanical, thermal, or combined) imposed on the single-crystal superalloy.

  19. Growth Of Oriented Crystals At Polymerized Membranes

    DOEpatents

    Charych, Deborah H. , Berman, Amir

    2000-01-25

    The present invention relates to methods and compositions for the growth and alignment of crystals at biopolymeric films. The methods and compositions of the present invention provide means to generate a variety of dense crystalline ceramic films, with totally aligned crystals, at low temperatures and pressures, suitable for use with polymer and plastic substrates.

  20. Optical-diffraction method for determining crystal orientation

    DOEpatents

    Sopori, B.L.

    1982-05-07

    Disclosed is an optical diffraction technique for characterizing the three-dimensional orientation of a crystal sample. An arbitrary surface of the crystal sample is texture etched so as to generate a pseudo-periodic diffraction grating on the surface. A laser light beam is then directed onto the etched surface, and the reflected light forms a farfield diffraction pattern in reflection. Parameters of the diffraction pattern, such as the geometry and angular dispersion of the diffracted beam are then related to grating shape of the etched surface which is in turn related to crystal orientation. This technique may be used for examining polycrystalline silicon for use in solar cells.

  1. Crystal orientation dependence of elastic precursor strength in pentaerythritol tetranitrate

    SciTech Connect

    Dick, J.J.; Whitehead, M.C.; Martinez, A.R.

    1993-08-01

    Elastic precursor shock strengths were measured using VISAR instrumentation on pentaerythritol tetranitrate crystals 2.9 to 6.4 mm thick. Input shock strength was 1.2 GPa. A factor of 3 difference in elastic shock strength and a factor of 2 difference in critical resolved shear stress were observed depending on the crystal orientation. The order of increasing elastic shock strength was [100], [101],[110], and [001]. This is the same order as that obtained in our analysis for increasing steric hindrance to shear, indicating that the relative strength of different orientations of this molecular crystal under shock conditions is governed by steric hindrance to shear.

  2. Crystal orientation dependence of polarized infrared reflectance response of hexagonal sapphire crystal

    NASA Astrophysics Data System (ADS)

    Lee, S. C.; Ng, S. S.; Abu Hassan, H.; Hassan, Z.; Dumelow, T.

    2014-11-01

    Polarized infrared (IR) reflectance responses of c-, a- and r-plane sapphire crystals were investigated. The sapphire crystals with differently oriented surfaces exhibited different reststrahlen features. Except for c-plane sapphire, the polarized IR reflectance responses were sensitive to the orientation of the samples. The spectral features for a- and r-plane sapphire crystals were modulated by just rotating the samples about their surface normal. To analyze the observations, a theoretical model for the polarized IR reflectivity that considers the effects of crystal orientation of a hexagonal crystal system was employed. Overall, the theoretical predictions were in good agreement with experimental data. The crystal orientation information deduced from the polarized IR reflectance spectra is consistent with that acquired from X-ray diffraction measurements.

  3. Backscatter by azimuthally oriented ice crystals of cirrus clouds.

    PubMed

    Konoshonkin, Alexander; Wang, Zhenzhu; Borovoi, Anatoli; Kustova, Natalia; Liu, Dong; Xie, Chenbo

    2016-09-01

    The backscattering Mueller matrix has been calculated for the first time for the hexagonal ice columns and plates with both zenith and azimuth preferential orientations. The possibility of a vertically pointing polarization lidar measuring the full Mueller matrix for retrieving the orientation distributions of the crystals is considered. It is shown that the element m44 or, equivalently, the circular depolarization ratio distinguishes between the low and high zenith tilts of the crystals. Then, at their low or high zenith tilts, either the element m22 or m34, respectively, should be measured to retrieve the azimuth tilts. PMID:27607728

  4. Solar glint from oriented crystals in cirrus clouds.

    PubMed

    Lavigne, Claire; Roblin, Antoine; Chervet, Patrick

    2008-11-20

    Solar scattering on oriented cirrus crystals near the specular reflection direction is modeled using a mix method combining geometric optics and diffraction effects at three wavelengths in the visible and infrared domains. Different potential sources of phase function broadening around the specular direction, such as multiple scattering, solar disk, or tilt effects, are studied by means of a Monte Carlo method. The radiance detected by an airborne sensor located a few kilometers above the cirrus cloud and pointing in the specular scattering direction is calculated at four solar zenith angles showing a dramatic increase of the signal in relation to the usual assumption of random crystal orientation. PMID:19023393

  5. Oriental transitions in nematic liquid crystals on grooved substrates

    SciTech Connect

    Krekhov, A.P.; Khasimullin, M.V.; Lebedev, Y.A.

    1995-12-31

    An expression for the surface energy of a nematic liquid crystal (NLC) on a fine-grooved substrate is obtained with the phenomenological approach. Temperature-induced orientational transitions in nematic liquid crystals are analyzed as functions of the surface-profile parameters. A planar{yields}tilted{yields}homeotropic alignment transition was observed near the clearing point of an MBBA layer sandwiched between two grooved glass substrates, with a microrelief obtained by oblique evaporation of silicon monoxide. 15 refs., 1 fig.

  6. The Crystallization Clinic-A TA Orientation Exercise

    NASA Astrophysics Data System (ADS)

    Kandel, Marjorie

    1999-01-01

    Our orientation exercise for TAs in the organic laboratories is a Crystallization Clinic, and the main feature is a contest. Each TA has a different unknown solid to recrystallize. The products are judged by the students in the organic lab courses. Beauty of the crystals is the single criterion. The contest serves to refresh the TAs' technique and to give them empathy with the beginning students.

  7. Orientation-dependent shock response of explosive crystals

    SciTech Connect

    Dick, J.J.

    1995-09-01

    Some orientations of PETN crystals have anomalously high shock initiation sensitivity around 4 to 5 GPa. Results of a series of laser interferometry experiments at 4.2 GPa show that this is associated with an elastic-plastic, two-wave structure with large elastic precursors. Implications for the initiation mechanism in single crystals is discussed. Initial work on beta phase, monoclinic HMX is also described.

  8. Molecular Orientation of Liquid Crystals on Topographic Nanopatterns.

    PubMed

    Ryu, Seong Ho; Yoon, Dong Ki

    2016-07-13

    Controlling the orientation of building blocks in soft matter on the substrate has been a big challenge in material sciences. We have controlled the molecular orientation of liquid crystal (LC) materials on the porous anodic aluminum oxide (AAO) film having hexagonal pore arrays on the top surface. In our method, anchoring conditions can be varied by changing the pore size (Dp) and the porosity (P). As a proof-of-concept, the orientation of smectic A (SmA) structure at different anchoring conditions was successfully controlled in a sandwich cell consisting of AAO and a glass substrate, which has not been successfully controlled by conventional methods. PMID:27322013

  9. Director orientation of nematic liquid crystal using orientated nanofibers obtained by electrospinning

    NASA Astrophysics Data System (ADS)

    Toan, Duong Quoc; Ozaki, Ryotaro; Moritake, Hiroshi

    2014-01-01

    Nanofibers with diameters less than 1000 nm assembled by electrospinning and with a large surface area per unit mass have been attracting considerable attention and are expected to affect the orientation of liquid crystals (LCs). Firstly, to determine the orientated nanofibers on an indium-tin-oxide (ITO) glass surface, the spectral analysis technique of using fast Fourier transform is applied. Optical observation is performed to confirm the orientation of LC molecules in a twisted nematic LC cell. Finally, optical measurement of an LC cell is carried out to estimate the threshold voltage of the LC in two types of twisted nematic LC cell: one with rubbed polyimide and the other with orientated nanofibers as the alignment layer. A twisted nematic LC is oriented in the cell using orientated nanofibers as the alignment layer and the threshold voltage of this cell agrees with that of the conventional polyimide rubbed cell.

  10. Automated crystal orientation and phase mapping in TEM

    SciTech Connect

    Rauch, E.F. Véron, M.

    2014-12-15

    The paper describes an automated crystal orientation and phase mapping technique that allows nanoscale characterization of crystalline materials with a transmission electron microscope. The template matching strategy used to identify the diffraction patterns is detailed and the resulting outputs of the technique are illustrated. Some examples of applications are used to demonstrate the capability of the tool and potential developments are discussed.

  11. Distinctive Characteristics of Sexual Orientation Bias Crimes

    ERIC Educational Resources Information Center

    Stacey, Michele

    2011-01-01

    Despite increased attention in the area of hate crime research in the past 20 years, sexual orientation bias crimes have rarely been singled out for study. When these types of crimes are looked at, the studies are typically descriptive in nature. This article seeks to increase our knowledge of sexual orientation bias by answering the question:…

  12. Direction-Specific Interactions Control Crystal Growth by Oriented Attachment

    NASA Astrophysics Data System (ADS)

    Li, Dongsheng; Nielsen, Michael H.; Lee, Jonathan R. I.; Frandsen, Cathrine; Banfield, Jillian F.; De Yoreo, James J.

    2012-05-01

    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment.

  13. Direction-specific interactions control crystal growth by oriented attachment.

    PubMed

    Li, Dongsheng; Nielsen, Michael H; Lee, Jonathan R I; Frandsen, Cathrine; Banfield, Jillian F; De Yoreo, James J

    2012-05-25

    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment. PMID:22628650

  14. Crystal orientation results in different amorphization of olivine during solar wind implantation

    NASA Astrophysics Data System (ADS)

    Li, Yang; Li, Xiongyao; Wang, Shijie; Li, Shijie; Tang, Hong; Coulson, Ian M.

    2013-10-01

    Crystal orientation plays an important role in mineral amorphization during solar wind implantation. To discuss these effects, ion implantation experiments were carried out to irradiate natural olivine grains by 1 × 1017 cm-2 50 keV He+. Based on the olivine grains irradiated in our experiment, residual crystal planes have been identified by reference to the crystal plane's spacing shown in diffraction images. It is found that He+ ions injected along [010] damages the olivine structure more effectively than with other orientations and that this possibly relates to the higher atomic density and the vertical impact of the flux on MO6 (where M commonly represents Fe2+ and Mg2+) octahedra chains. Crystal planes perpendicular or approximately perpendicular to [010] may be destroyed easily during the early stages of irradiation, particularly for (040). However, crystal planes, such as (041), (021), (022), (120), and (140), parallel to [100] or [001] may survive until the final stages of olivine amorphization. These different characteristics affected by crystal orientation in ion implantation might help researchers to better understand the process of solar wind weathering and in dating the exposure time of lunar and asteroidal soil grains as well as interplanetary dust particles affected by the solar wind.

  15. Effect of the Surface Affinity of Liquid Crystals and Monomers on the Orientation of Polymer-Dispersed Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Hoon; Yoon, Tae-Hoon

    2013-09-01

    We investigated the effect of the surface affinity of liquid crystals and reactive monomers on liquid crystal orientation. Liquid crystals and monomers having different contact angles with the vertical alignment polyimide were mixed and photo-polymerized using a UV light. Liquid crystals with smaller contact angles and reactive monomers with greater contact angles promoted a uniform vertical orientation of liquid crystals with a vertical polymer morphology. On the other hand, liquid crystals with greater contact angles and monomers with smaller contact angles resulted in a deformed liquid crystal orientation with an elliptical polymer structure.

  16. Refraction characteristics of phononic crystals

    NASA Astrophysics Data System (ADS)

    Nemat-Nasser, Sia

    2015-08-01

    Some of the most interesting refraction properties of phononic crystals are revealed by examining the anti-plane shear waves in doubly periodic elastic composites with unit cells containing rectangular and/or elliptical multi-inclusions. The corresponding band structure, group velocity, and energy-flux vector are calculated using a powerful mixed variational method that accurately and efficiently yields all the field quantities over multiple frequency pass-bands. The background matrix and the inclusions can be anisotropic, each having distinct elastic moduli and mass densities. Equifrequency contours and energy-flux vectors are readily calculated as functions of the wave-vector components. By superimposing the energy-flux vectors on equifrequency contours in the plane of the wave-vector components, and supplementing this with a three-dimensional graph of the corresponding frequency surface, a wealth of information is extracted essentially at a glance. This way it is shown that a composite with even a simple square unit cell containing a central circular inclusion can display negative or positive energy and phase velocity refractions, or simply performs a harmonic vibration (standing wave), depending on the frequency and the wave-vector. Moreover, that the same composite when interfaced with a suitable homogeneous solid can display: (1) negative refraction with negative phase velocity refraction; (2) negative refraction with positive phase velocity refraction; (3) positive refraction with negative phase velocity refraction; (4) positive refraction with positive phase velocity refraction; or even (5) complete reflection with no energy transmission, depending on the frequency, and direction and the wavelength of the plane-wave that is incident from the homogeneous solid to the interface. For elliptical and rectangular inclusion geometries, analytical expressions are given for the key calculation quantities. Expressions for displacement, velocity, linear momentum

  17. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, N. K.; Swanson, G.

    2002-01-01

    High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297

  18. Some Personality Characteristics of Elite Orienteers.

    ERIC Educational Resources Information Center

    Zsheliaskova-Koynova, Zshivka

    1991-01-01

    Administered questionnaires to 80 Bulgarian orienteers (cross-country racers who navigate a course) measuring extroversion, neuroticism, psychoticism, social desirability, trait anxiety, need for achievement, and locus of control. Examined the effects of sex, age, sport experience, level of sport qualification, and kind of sport specialization on…

  19. Orientational disorder: A key to understand polarity of molecular crystals

    NASA Astrophysics Data System (ADS)

    Hulliger, J.; Brahimi, K.; Burgener, M.; Dulcevscaia, G.

    2014-12-01

    Polarity of molecular crystals is understood here as a result of 180° orientational disorder of asymmetrical building blocks. Symmetry arguments based on (i) a single rotational degree of freedom, (ii) the finite size of crystals and (iii) interactions in between asymmetrical molecules lead to the conclusion that such crystals should express a bi-polar (∞/∞m) average state of zero polarity. This basic property of molecular crystals is exemplified by forming solid solutions of 4-iodo-4‧-nitro-biphenyl (INBP) and symmetrical bi-phenyls (BP: A-π-A, D-π-D; A: acceptor; D: donor). Monte Carlo simulations based on a layer-by-layer growth model predict a reversal of the bi-polar state of pure INBP by forming a solid solution of (INBP)1-x(D-π-D)x. In the case of the addition of A-π-A reversal as found for pure INBP is promoted, i.e. needs less growth steps (layers) to be accomplished. Real crystals representing solid solutions were grown from 2-butanon solutions using symmetrical BPs. Scanning pyroelectric microscopy confirmed the qualitative behavior seen in Monte Carlo simulations. These findings represent an experimentum crucis supporting the general validity of the theory of stochastic polarity formation applied to single component or solid solution molecular crystals.

  20. Plastic Deformation of O+ Oriented Quartz Single Crystals

    NASA Astrophysics Data System (ADS)

    Poston, E. J.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    The strength of wet quartz deforming by dislocation creep significantly influences the strength of mid to lower crust. Dislocation creep of quartz in Earth's crust is dominated by slip on the basal slip system. However, very little is known about the temperature, strain rate, or water fugacity dependence of this slip system. In order to better understand the rheology of the basal slip system, we deformed single crystals of synthetic quartz, with the basal slip system oriented at 45° to the compression direction (O+ orientation). Each core was annealed at 900°C and 1 atm for 24 hours to convert the gel-type water defects found in synthetic quartz into fluid inclusions, like those observed in milky quartz. FTIR analysis indicate that water contents (200-450 H/106Si) were not affected by the annealing process. The annealed single crystals were then deformed in a Griggs piston-cylinder rock deformation apparatus using a solid salt assembly, at temperatures from 800 to 900°C, strain rates from 10-6 to 10-4/s, and a confining pressure of 1.5 GPa. The strength of the quartz crystals increases with faster strain rates and decreases with increasing temperature. During some of the faster strain rate steps at 800°C, the crystals did not deform plastically before the differential stress reached the confining pressure, whereas they deformed at low stresses at 800°C and 10-6/s. The microstructures visible in the deformed samples are consistent with dislocation creep. The samples exhibit undulatory extinction, and show no deformation lamellae or subgrain formation. The strength of synthetic quartz crystals with low water contents deformed in this study is greater than milky quartz single crystals with high water contents deformed at the same conditions in other studies. These results indicate that the strength of basal slip system in quartz is affected by both water content and water fugacity.

  1. Optical properties of planar nematic liquid crystals samples which are parallel oriented by nanofibers

    NASA Astrophysics Data System (ADS)

    Yusuf, Yusril; Kusumasari, Ervanggis Minggar; Ula, Nur Mufidatul; Jahidah, Khannah; Triyana, Kuwat; Sosiati, Harini; Harsojo

    2016-04-01

    Optical properties of two nematic liquid crystals, i.e., 4-methoxybenzylidene-4-butylaniline (MBBA) and 4-cyano-4'-pentylbiphenyl (5 CB) which are parallel oriented by nanofibers has been successfully performed. Planar samples of liquid crystals were made using polyvinyl alcohol (PVA) nanofiber from electrospinning process. Electrospinning method was modified using copper (Cu) as gap collector. These planar samples area are 15 mm x 25 mm. Optical characteristic of these samples were studied by using optical polarizing microscope. The optical intensity changes by a rotationof crossed polarizers is observed. The sinusoidal intensity change was observedin these samples as such as in the planar sample prepared by the rubbing method.

  2. Determining the Orientations of Ice Crystals Using Electron Backscatter Patterns

    NASA Astrophysics Data System (ADS)

    Iliescu, D.; Baker, I.; Chang, H.

    2004-05-01

    The presentation will show how electron backscatter diffraction can be employed to determine crystal orientations in ice. The technique involves obtaining and indexing electron back-scatter patterns (EBSPs) from uncoated ice using a scanning electron microscope equipped with a custom-built cold-stage and an Orientation Imaging System. Unlike any of the currently-used methods, the EBSP-based technique has considerably higher angular and spatial resolution and is significantly faster. We also present an orientation image map of a muti-grain region in laboratory-grown ice constructed by automatically indexing the EBSPs using an HKL, Inc Channel 5 Orientation Imaging System and discuss possible applications of the technique to the study of natural ice. Primarily, the focus will be on the characterization of the microstructure of dynamically recrystallized glacier ice whose texture is intrinsically related the flow process. Other applications include obtaining orientation images from frozen water-containing materials, such as clathrate hydrates. This research was supported by Army Research Office grant DAAD 19-03-1-0110 and National Science Foundation grants OPP-9981379 and OPP-0221120.

  3. Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite

    PubMed Central

    Checa, Antonio G.; Bonarski, Jan T.; Willinger, Marc G.; Faryna, Marek; Berent, Katarzyna; Kania, Bogusz; González-Segura, Alicia; Pina, Carlos M.; Pospiech, Jan; Morawiec, Adam

    2013-01-01

    The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research. PMID:23804442

  4. Effect of Crystal Orientation on Analysis of Single-Crystal, Nickel-Based Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Swanson, G. R.; Arakere, N. K.

    2000-01-01

    High-cycle fatigue-induced failures in turbine and turbopump blades is a pervasive problem. Single-crystal nickel turbine blades are used because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant and complicating factor. A fatigue failure criterion based on the maximum shear stress amplitude on the 24 octahedral and 6 cube slip systems is presented for single-crystal nickel superalloys (FCC crystal). This criterion greatly reduces the scatter in uniaxial fatigue data for PWA 1493 at 1,200 F in air. Additionally, single-crystal turbine blades used in the Space Shuttle main engine high pressure fuel turbopump/alternate turbopump are modeled using a three-dimensional finite element (FE) model. This model accounts for material orthotrophy and crystal orientation. Fatigue life of the blade tip is computed using FE stress results and the failure criterion that was developed. Stress analysis results in the blade attachment region are also presented. Results demonstrate that control of crystallographic orientation has the potential to significantly increase a component's resistance to fatigue crack growth without adding additional weight or cost.

  5. Effect of Crystal Orientation on Nanoindentation Behavior in Magnesium

    NASA Astrophysics Data System (ADS)

    Somekawa, Hidetoshi; Schuh, Christopher A.

    2016-06-01

    The effect of crystal orientation on nanoindentation behavior at both quasi-static and high strain rates was investigated using single-crystalline magnesium oriented in basal and prismatic configurations. Both the basal and prismatic planes had similar activation volumes, 55 and 73 b 3 for deformation at room temperature, as well as a small temperature dependence up to 423 K (150 °C). Microstructural observations beneath the indentations revealed that { 10bar{1}2 } type deformation twins were formed in both orientations irrespective of testing temperature. With twins forming beneath the indenter and multiple orientations of loading, it is believed that cross-slip and/or multiple slip are likely rate-controlling for global deformation, which also aligns with observations on nanoindentation of polycrystalline coarse-grained magnesium. The locations of the twins were consistent with expectations based on indentation mechanics as assessed by finite element simulations. The finite element simulations also predicted that an indenter tip with a shaper tip radius would tend to promote { 10bar{1}2 } twins.

  6. Effect of Crystal Orientation on Nanoindentation Behavior in Magnesium

    NASA Astrophysics Data System (ADS)

    Somekawa, Hidetoshi; Schuh, Christopher A.

    2016-04-01

    The effect of crystal orientation on nanoindentation behavior at both quasi-static and high strain rates was investigated using single-crystalline magnesium oriented in basal and prismatic configurations. Both the basal and prismatic planes had similar activation volumes, 55 and 73b 3 for deformation at room temperature, as well as a small temperature dependence up to 423 K (150 °C). Microstructural observations beneath the indentations revealed that { 10bar{1}2 } type deformation twins were formed in both orientations irrespective of testing temperature. With twins forming beneath the indenter and multiple orientations of loading, it is believed that cross-slip and/or multiple slip are likely rate-controlling for global deformation, which also aligns with observations on nanoindentation of polycrystalline coarse-grained magnesium. The locations of the twins were consistent with expectations based on indentation mechanics as assessed by finite element simulations. The finite element simulations also predicted that an indenter tip with a shaper tip radius would tend to promote { 10bar{1}2 } twins.

  7. Process and apparatus for making oriented crystal layers

    DOEpatents

    Springer, Robert W.

    2002-01-01

    Thin films of single crystal-like materials are made by using flow-through ion beam deposition during specific substrate rotation around an axis in a clocking action. The substrate is quickly rotated to a selected deposition position, paused in the deposition position for ionized material to be deposited, then quickly rotated to the next selected deposition position. The clocking motion can be achieved by use of a lobed cam on the spindle with which the substrate is rotated or by stopping and starting a stepper motor at long and short intervals. Other symmetries can be programmed into the process, allowing virtually any oriented inorganic crystal to be grown on the substrate surface.

  8. Orientational dynamics of nematic liquid crystals under shear flow

    NASA Astrophysics Data System (ADS)

    Rienäcker, G.; Hess, S.

    The orientational dynamics of low molecular weight and polymeric nematic liquid crystals in a flow field is investigated, based on a nonlinear relaxation equation for the second rank alignment tensor. Various approximations are discussed: Assuming uniaxial alignment with a constant order parameter, the results of the Ericksen-Leslie theory are recovered. The detailed analysis to be presented here for plane Couette flow concerns (i) uniaxial alignment with a variable degree of order and (ii) the tensorial analysis involving the three symmetry-adapted components of the five components of the alignment tensor. The transitions between tumbling, wagging and aligning behavior observed in polymeric liquid crystals and described by the Doi theory of rod-like nematic polymers are recovered. Consequences for the rheological behavior are indicated.

  9. Orientational order parameter measurements of discotic liquid crystal

    NASA Astrophysics Data System (ADS)

    Kaur, Supreet; Raina, K. K.; Kumar, S.; Pratibha, R.

    2014-04-01

    The IR dichroism technique is a convenient method which can be used to measure the molecular order parameter corresponding to the IR bands exclusively present in the disc -like molecules in discotic liquid crystal (DLC). To measure orientational order parameter, homeotropic alignment of discotic liquid crystal was attained by slow cooling of sample from isotropic phase on untreated flat CaF2 substrate. The homeotropic alignment thus achieved was found to be thermodynamically stable in the discotic mesophase. IR spectra were recorded at different temperatures for the DLC. The order parameter was calculated by comparing the spectra of discotic phase with that of the isotropic phase. Order parameter has been presented as function of temperature for different significant IR bands present in the DLC.

  10. Orientational order parameter measurements of discotic liquid crystal

    SciTech Connect

    Kaur, Supreet; Raina, K. K.; Kumar, S.; Pratibha, R.

    2014-04-24

    The IR dichroism technique is a convenient method which can be used to measure the molecular order parameter corresponding to the IR bands exclusively present in the disc –like molecules in discotic liquid crystal (DLC). To measure orientational order parameter, homeotropic alignment of discotic liquid crystal was attained by slow cooling of sample from isotropic phase on untreated flat CaF{sub 2} substrate. The homeotropic alignment thus achieved was found to be thermodynamically stable in the discotic mesophase. IR spectra were recorded at different temperatures for the DLC. The order parameter was calculated by comparing the spectra of discotic phase with that of the isotropic phase. Order parameter has been presented as function of temperature for different significant IR bands present in the DLC.

  11. Liquid crystal orientational order in confined geometries: A NMR perspective

    NASA Astrophysics Data System (ADS)

    Zeng, Huairen

    Liquid crystals are a very rich physical system where it is possible to study many phenomena both theoretically as well as experimentally. In almost all applications, liquid crystals exist in contact with some kind of substrate. Liquid crystals properties are greatly affected by a nearby surface: confinement alignment, phase transition temperatures, the critical behavior of the thermodynamic quantities and several other of their properties change. Researching confined liquid crystals to study surface effects will be beneficial for basic physics understanding and provide results perhaps extrapolated to the applied world. An important concept in a microscopic description of a liquid crystal phase is the order parameter, each of the phases is characterized by one or more such parameters. It is therefore of interest to quantify and measure the degree of order of a particular phase 2H-NMR, as a microscopic measurement at the molecular level, has a number of unique features that make it a useful technique to study liquid crystals. NMR can distinguish between spatial and time averages whereas other methods such as birefringence can not. And, most importantly, deuterium NMR is sensitive to the orientational order present in the system. In fact, through NMR lineshape analysis, we can derive the configuration of the nematic director field, and thus determine liquid crystal alignment in random interconnected host. In this work I will use thermotropic liquid crystals and confine them in Millipore membranes, silica Aerogel porous glass and silica Aerosil spheres. Millipore membranes are made from pure, biologically inert mixtures of cellulose acetate and cellulose nitrate. It is a randomly interconnected host geometry with a high porosity, and available in a variety of void sizes, for my research I will use sizes from 8.0 mum to 0.025 mum. Silica Aerogel is a connected pore network, available in many different densities. Our work will cover densities ranging from 0.068 to 0

  12. Growth of oriented p-aminobenzoic acid crystals by directional freezing

    PubMed Central

    Ko, Young Gun

    2012-01-01

    Oriented long needle-like p-aminobenzoic acid (PABA) crystals are successfully prepared by directional freezing of PABA solution in this work. The width of the oriented crystals is controlled by changing the directional cooling rate, resulting in varying crystal morphologies and thermodynamic properties while maintaining the same chemical structure. PMID:23144588

  13. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory R.

    2000-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine engines is a pervasive problem affecting a wide range of components and materials. HCF is currently the primary cause of component failures in gas turbine aircraft engines. Turbine blades in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys. Single-crystal Nickel-base superalloys were developed to provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys previously used in the production of turbine blades and vanes. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. PWA1493, identical to PWA1480, but with tighter chemical constituent control, is used in the NASA SSME (Space Shuttle Main Engine) alternate turbopump, a liquid hydrogen fueled rocket engine. Objectives for this paper are motivated by the need for developing failure criteria and fatigue life evaluation procedures for high temperature single crystal components, using available fatigue data and finite element modeling of turbine blades. Using the FE (finite element) stress analysis results and the fatigue life relations developed, the effect of variation of primary and secondary crystal orientations on life is determined, at critical blade locations. The most advantageous crystal orientation for a given blade design is determined. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to optimize blade design by increasing its resistance to fatigue crack growth without adding additional weight or cost.

  14. Oriented lead zirconate titanate thin films: Characterization of film crystallization

    SciTech Connect

    Voigt, J.A.; Tuttle, B.A.; Headley, T.J.; Eatough, M.O.; Lamppa, D.L.; Goodnow, D.

    1993-11-01

    Film processing temperature and time was varied to characterize the pyrochlore-to-perovskite crystallization of solution-derived PZT 20/80 thin films. 3000 {Angstrom} thick films were prepared by spin deposition using <100> single crystal MgO as substrate. By controlled rapid thermal processing, films at different stages in the perovskite crystallization process were prepared with the tetragonal PZT 20/80 phase being <100>/<001> oriented relative to the MgO surface. An activation energy for the conversion process of 326 kJ/mole was determined by use of an Arrhenius expression using rate constants found by application of the method of Avrami. Activation energy for formation of the PZT 20/80 perovskite phase of the solution-derived films compared favorably with that calculated from data by Kwok and Desu for sputter-deposited 3500 {Angstrom} thick PZT 55/45 films. Similarity in activation energies indicates that the energetics of the conversion process are not strongly dependent on the method used for film deposition.

  15. Liquid crystal orientation on solution processed zinc oxide inorganic films according to molecular concentration

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Jin; Han, Jae-Jun; Park, Hong-Gyu; Kim, Dai-Hyun; Byun, Sang-Un; Seo, Dae-Shik

    2013-10-01

    In this paper we present the characteristics of molar concentration-dependent zinc oxide (ZnO) inorganic films deposited by the solution process for application in liquid crystal displays. ZnO surfaces supported homogeneously aligned liquid crystal (LC) molecules based on an ion-beam (IB) irradiation system. Uniform LC alignment was obtained at ZnO molar concentrations greater than 0.25 mol l-1. X-ray photoelectron spectroscopic (XPS) analysis revealed that changes in the orientation of LC molecules occurred on the ZnO layer. The electro-optic characteristics of the aligned homogenous LCs and twisted nematic (TN) mode based on the ZnO layer were comparable to those based on polyimide, which showed good potential as ZnO surfaces as an alignment layer.

  16. Early oriented isothermal crystallization of polyethylene studied by high-time-resolution SAXS/WAXS.

    PubMed

    Stribeck, N; Almendarez Camarillo, A; Nöchel, U; Bösecke, P; Bayer, R K

    2007-01-01

    During cooling from the quiescent melt of a highly oriented polyethylene rod, highly oriented proto-lamellae are formed first, which are not crystalline. This is shown in scattering data which are recorded on two-dimensional detectors with a cycle time of 1 s and an exposure of 0.1 s. In the experiments small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) are registered simultaneously during the first 3 min after quenching to a crystallization temperature. A non-uniform thickness between 20 and 100 nm is characteristic for the ensemble of proto-lamellae. During the first minute of isothermal treatment the number of proto-lamellae slowly increases without a change of the thickness distribution. As crystallization starts, the crystallites are not oriented in contrast to the proto-lamellae. During crystallization the layer thickness distribution narrows. The number of lamellae rapidly increases during the following 2 min of isothermal treatment (at 128 degrees C and 124 degrees C). The results are obtained by interpretation of the WAXS and of the multidimensional chord distribution function (CDF), a model-free real-space visualization of the nanostructure information contained in the SAXS data. PMID:17089099

  17. Assessment of crystal quality and unit cell orientation in epitaxial Cu₂ZnSnSe₄ layers using polarized Raman scattering.

    PubMed

    Krämmer, Christoph; Lang, Mario; Redinger, Alex; Sachs, Johannes; Gao, Chao; Kalt, Heinz; Siebentritt, Susanne; Hetterich, Michael

    2014-11-17

    We use polarization-resolved Raman spectroscopy to assess the crystal quality of epitaxial kesterite layers. It is demonstrated for the example of epitaxial Cu₂ZnSnSe₄ layers on GaAs(001) that "standing" and "lying" kesterite unit cell orientations (c'-axis parallel / perpendicular to the growth direction) can be distinguished by the application of Raman tensor analysis. From the appearance of characteristic intensity oscillations when the sample is rotated one can distinguish polycrystalline and epitaxial layers. The method can be transferred to kesterite layers oriented in any crystal direction and can shed light on the growth of such layers in general. PMID:25402065

  18. Driving voltage properties sensitive to microscale liquid crystal orientation pattern in twisted nematic liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Takahashi, Koki; Yamaguchi, Rumiko; Nose, Toshiaki

    2016-04-01

    We investigated the micropattern-sensitive driving voltage properties of twisted nematic liquid crystal (LC) cells and found that the threshold voltage for inducing the Fréedericksz transition strongly depends on the micropatterned LC molecular orientation state. We discuss the effects of various cell parameters such as the period of the micropattern Λ, the LC layer thickness d, and the twist angle Φ on the threshold voltage. By a computer simulation of the LC molecular orientation, we found that the threshold voltage V th varies in response to the deformation factor Δ (= d 2/Λ2 + Φ2/π2) of the spatially distributed LC molecular orientation. We confirm that V\\text{th}2 is proportional to 1 - Δ from both theoretical and experimental standpoints.

  19. Orthogonal orientation of chromonic liquid crystals by rubbed polyamide films.

    PubMed

    Mcguire, Aya; Yi, Youngwoo; Clark, Noel A

    2014-05-19

    Chromonic liquid crystals (CLCs) have drawn attention for applications to organic electronics and optical films as well as biological materials. Understanding the alignment mechanism of CLCs is important for those applications. Using a polarized transmission optical microscope, we observe the optical texture, dichroism, and birefringence of CLC films of sunset yellow (SSY) confined by polyamide (nylon) films that are rubbed with a brush. The films align with the stacks of SSY molecules oriented, surprisingly, perpendicular to the rubbing direction. We propose that this alignment is stabilized by molecular interaction between the stretched nylon chains and molecular grooves of the SSY stacks rather than elastic energy of the CLCs due to surface topography induced by the rubbing. PMID:24470318

  20. Phase diagrams of orientational transitions in absorbing nematic liquid crystals

    SciTech Connect

    Zolot’ko, A. S. Ochkin, V. N.; Smayev, M. P.; Shvetsov, S. A.

    2015-05-15

    A theory of orientational transitions in nematic liquid crystals (NLCs), which employs the expansion of optical torques acting on the NLC director with respect to the rotation angle, has been developed for NLCs with additives of conformationally active compounds under the action of optical and low-frequency electric and magnetic fields. Phase diagrams of NLCs are constructed as a function of the intensity and polarization of the light field, the strength of low-frequency electric field, and a parameter that characterizes the feedback between the rotation of the NLC director and optical torque. Conditions for the occurrence of first- and second-order transitions are determined. The proposed theory agrees with available experimental data.

  1. Structure of polarization-resolved conoscopic patterns of planar oriented liquid crystal cells

    SciTech Connect

    Kiselev, A. D. Vovk, R. G.

    2010-05-15

    The geometry of distributions of the polarization of light in conoscopic patterns of planar oriented nematic and cholesteric liquid crystal (LC) cells is described in terms of the polarization singularities including C-points (points of circular polarization) and L lines (lines of linear polarization). Conditions for the formation of polarization singularities (C-points) in an ensemble of conoscopic patterns parametrized by the polarization azimuth and ellipticity of the incident light wave have been studied. A characteristic feature of these conditions is selectivity with respect to the polarization parameters of the incident light wave. The polarization azimuth and ellipticity are determining parameters for nematic and cholesteric LC cells, respectively.

  2. Interdiffusion behavior between NiAlHf coating and Ni-based single crystal superalloy with different crystal orientations

    NASA Astrophysics Data System (ADS)

    Wang, Ruili; Gong, Xueyuan; Peng, Hui; Ma, Yue; Guo, Hongbo

    2015-01-01

    NiAlHf coatings were deposited onto Ni-based single crystal (SC) superalloy with different crystal orientations by electron beam physical vapor deposition (EB-PVD). The effects of the crystal orientations of the superalloy substrate on inter-diffusion behavior between the substrate and the NiAlHf coating were investigated. Substrate diffusion zone (SDZ) containing needle-like μ phases and interdiffusion zone (IDZ) mainly consisting of the ellipsoidal and rod-like μ phases were formed in the SC alloy after heat-treatment 10 h at 1100 °C. The thickness of secondary reaction zone (SRZ) formed in the SC alloy with (0 1 1) crystal orientation is about 14 μm after 50 h heat-treatment at 1100 °C, which is relatively thicker than that in the SC alloy with (0 0 1) crystal orientation, whereas the IDZ revealed similar thickness.

  3. Substrate-induced orientational order in the isotropic phase of liquid crystals

    NASA Technical Reports Server (NTRS)

    Mauger, A.; Zribi, G.; Mills, D. L.; Toner, J.

    1984-01-01

    Nematic order induced near a solid boundary in an otherwise isotropic liquid crystal is studied theoretically, at temperatures just above the bulk nematic-isotropic phase transition. Three distinct regimes are found, depending on the strength of orientational torques at the boundary: (1) strong orientational order, (2) strong orientational order followed by a first-order transition to a state of weak orientational order as temperature is raised, and (3) a state of weak orientational order.

  4. Evaluation of Crystal Orientation for (K,Na)NbO3 Films Using X-ray Diffraction Reciprocal Space Map and Relationship between Crystal Orientation and Piezoelectric Coefficient

    NASA Astrophysics Data System (ADS)

    Shibata, Kenji; Suenaga, Kazufumi; Watanabe, Kazutoshi; Horikiri, Fumimasa; Mishima, Tomoyoshi; Shiratani, Masaharu

    2012-07-01

    We have found an effective method for the evaluation of the crystal orientation of (K,Na)NbO3 (KNN) films in the (K,Na)NbO3/Pt/Ti/SiO2/Si structure using X-ray diffraction (XRD) reciprocal space maps. Previously, the crystal structure and orientation of such (K,Na)NbO3 films were evaluated using 2θ/θ XRD, and were considered to be the pseudocubic perovskite structure with preferential (001) orientation and no (111) orientation. Here, we applied the new method using XRD reciprocal space maps, and discovered that the (K,Na)NbO3 films had some degree of KNN(111) orientation. We calculated the KNN(001)- and KNN(111)-orientation volume fractions for the (K,Na)NbO3 films from the (101) diffraction peaks originating from the KNN(001)- and KNN(111)-orientation elements in the XRD reciprocal space maps, considering the calibration factors obtained from pole-figure simulations, and examined the relationship between the crystal orientation and d31 piezoelectric coefficient in the (K,Na)NbO3 films. The results indicated that the d31 piezoelectric coefficient increases with increasing (001)-orientation volume fraction.

  5. Snow Crystal Orientation Effects on the Scattering of Passive Microwave Radiation

    NASA Technical Reports Server (NTRS)

    Foster, J. L.; Barton, J. S.; Chang, A. T. C.; Hall, D. K.

    1999-01-01

    For this study, consideration is given to the role crystal orientation plays in scattering and absorbing microwave radiation. A discrete dipole scattering model is used to measure the passive microwave radiation, at two polarizations (horizontal and vertical), scattered by snow crystals oriented in random and non random positions, having various sizes (ranging between 1 micrometers to 10,000 micrometers in radius), and shapes (including spheroids, cylinders, hexagons). The model results demonstrate that for the crystal sizes typically found in a snowpack, crystal orientation is insignificant compared to crystal size in terms of scattering microwave energy in the 8,100 gm (37 GHz) region of the spectrum. Therefore, the assumption used in radiative transfer approaches, where snow crystals are modeled as randomly oriented spheres, is adequate to account for the transfer of microwave energy emanating from the ground and passing through a snowpack.

  6. Orientation, interaction and laser assisted self-assembly of organic single-crystal micro-sheets in a nematic liquid crystal.

    PubMed

    Rasna, M V; Zuhail, K P; Ramudu, U V; Chandrasekar, R; Dontabhaktuni, J; Dhara, Surajit

    2015-10-14

    Colloidal self-assembly has been one of the major driving themes in material science to obtain functional and advanced optical materials with complex architecture. Most of the nematic colloids reported so far are based on the optically isotropic spherical microparticles. We study organic single crystal micro-sheets and investigate their orientation, interaction and directed assembly in a nematic liquid crystal. The micro-sheets induce planar surface anchoring of the liquid crystal. The elasticity mediated pair interaction of micro-sheets shows quadrupolar characteristics. The average orientation angle of the micro-sheets in a planar cell and the angle between two micro-sheets in a homeotropic cell are supported by the Landau-de Gennes Q-tensor modeling. The self-assembly of the micro-sheets is assisted by a laser tweezer to form larger two-dimensional structures which have the potential for application of colloids in photonics. PMID:26299670

  7. Crystallization, Crystal Orientation and Morphology of Poly(ethylene oxide) under 1D Defect-Free Nanoscale Confinement

    NASA Astrophysics Data System (ADS)

    Hsiao, Ming-Siao; Zheng, Joseph X.; van Horn, Ryan M.; Quirk, Roderic P.; Thomas, Edwin L.; Lotz, Bernard; Cheng, Stephen Z. D.

    2009-03-01

    One-dimensional (1-D) defect-free nanoscale confinement is created by growing single crystals of PS-b-PEO block copolymers in dilute solution. Those defect-free, 1-D confined lamellae having different PEO layer thicknesses in PS-b-PEO lamellar single crystals (or crystal mats) were used to study the polymer recrystallization and crystal orientation evolution as a function of recrystallization temperature (Trx) because the Tg^PS is larger than Tm^PEO in the PS-b-PEO single crystal. The results are summarized as follows. First, by the combination of electron diffraction and known PEO crystallography, the crystallization of PEO only takes place at Trx<-5^oC. Meanwhile a unique tilted PEO orientation is formed at Trx >-5^oC after self-seeding. The origin of the formation of tilted chains in the PEO crystal will be addressed. Second, from the analysis of 2D WAXD patterns of crystal mats, it is shown that the change in PEO c-axis orientation from homogeneous at low Trx to homeotropic at higher Trx transitions sharply, within 1^oC. The mechanism inducing this dramatic change in crystal orientation will be investigated in detail.

  8. Secondary orientation effects in a single crystal superalloy under mechanical and thermal loads

    NASA Technical Reports Server (NTRS)

    Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

    1991-01-01

    The nickel-base single crystal superalloy PWA 1480 is a candidate blading material for the advanced turbopump development program of the SSME. In order to improve thermal fatigue resistance of the turbine blades, the single crystal superalloy PWA 1480 is grown along the low modulus zone axes (001) crystal orientation by a directional solidification process. Since cubic single crystal materials such as PWA 1480 exhibit anisotropic elastic behavior, the stresses developed within the single crystal superalloy due to mechanical and thermal loads are likely to be affected by the exact orientation of the secondary crystallographic direction with respect to the geometry of the turbine blade. The effects of secondary crystal orientation on the elastic response of single crystal PWA 1480 superalloy were investigated.

  9. Orientational coupling enhancement in a carbon nanotube dispersed liquid crystal.

    PubMed

    Basu, Rajratan; Iannacchione, Germano S

    2010-05-01

    We present a detailed study of a dilute suspension of carbon nanotubes (CNTs) in a pentylcyanobiphenyl (5CB) liquid crystal (LC) by probing the dielectric properties as a function of applied ac voltage and frequency. In principle, to minimize the elastic distortion in the nematic matrix, the monodispersed CNTs follow the nematic director without disturbing the director field significantly. A strong anchoring energy due to π-π electron stacking between LC-CNT molecules results in an increase in the dielectric anisotropy for the hybrid system, indicating a significant enhancement in the orientational order parameter. The frequency-dependent dielectric anisotropy for the composite system reveals the intrinsic frequency response of the LC-CNT anchoring mechanism. As a matter of consequence, the extracted value of splay elastic constant suggests that LC-CNT anchoring has an impact on the structural modification of the hybrid LC+CNT system. This strong anchoring energy stabilizes local pseudonematic domains, giving rise to a nonzero dielectric anisotropy in the isotropic phase that also shows an intrinsic frequency response. PMID:20866245

  10. Orientational coupling enhancement in a carbon nanotube dispersed liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan; Iannacchione, Germano S.

    2010-05-01

    We present a detailed study of a dilute suspension of carbon nanotubes (CNTs) in a pentylcyanobiphenyl (5CB) liquid crystal (LC) by probing the dielectric properties as a function of applied ac voltage and frequency. In principle, to minimize the elastic distortion in the nematic matrix, the monodispersed CNTs follow the nematic director without disturbing the director field significantly. A strong anchoring energy due to π-π electron stacking between LC-CNT molecules results in an increase in the dielectric anisotropy for the hybrid system, indicating a significant enhancement in the orientational order parameter. The frequency-dependent dielectric anisotropy for the composite system reveals the intrinsic frequency response of the LC-CNT anchoring mechanism. As a matter of consequence, the extracted value of splay elastic constant suggests that LC-CNT anchoring has an impact on the structural modification of the hybrid LC+CNT system. This strong anchoring energy stabilizes local pseudonematic domains, giving rise to a nonzero dielectric anisotropy in the isotropic phase that also shows an intrinsic frequency response.

  11. Zinc oxide nanolevel surface transformation for liquid crystal orientation by ion bombardment

    SciTech Connect

    Oh, Byeong-Yun; Lee, Won-Kyu; Kim, Young-Hwan; Seo, Dae-Shik

    2009-03-01

    This paper introduces the characteristics of the zinc oxide (ZnO) inorganic film deposited by radio-frequency magnetron sputtering as an alternative alignment layer for liquid crystal display (LCD) applications. The crystalline structure related to the texture formation of ZnO (1013) was observed with a tilt angle of approximately 28.1 deg. to the ZnO (0001) plane, leading to a smooth surface and high-density structure. Ion beam (IB) bombardment at various incident angles was used to induce liquid crystal (LC) alignment and cause the measured pretilt angle on ZnO films to assume a triangular contour. The orientation order of liquid crystal molecules was due to the van der Waals force for the vertical alignment of LCs with selective breaking of O-Zn bonds by IB bombardment. The contact angle contour as a function of the IB incident angle resembled the behavior of the pretilt angle. The pretilt angle is controllable by adjusting the surface features on ZnO films with IB bombardment. The electro-optic characteristics of vertically aligned (VA)-LCD based on ZnO film were comparable to those of VA-LCD based on polyimide, showing good potential of ZnO film as a LC alignment layer.

  12. Side-polished fiber sensing for determination of azimuthal orientation of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Han, Yuqi; Chen, Zhe; Yu, Jianhui; Li, Haozhi; He, Xiaoli

    2013-09-01

    The orientation of nematic liquid crystal (NLC) can be used in biosensor. The sensing characteristics of side-polished fiber (SPF) for determination of azimuthal orientation of NLC have been investigated. The relationship between the azimuthal angle of NLC director and the optical transmission power in SPF was derived by empirical approach. Experimental results showed that the azimuthal transition of liquid crystal affected the optical transmission power in SPF. While the azimuthal angle increased from 0° to 90°, the optical transmission power increased by 28.10dB, which is similar to the variation tendency of the empirical analysis. When it changes from 0° to 30°, the azimuthal angle is linear to the change of optical transmission power. The respondence of azimuthal angle for optical sensing is averagely 0.359dB/°. Experiments indicate that SPF can be used in determination of the azimuzal transition of NLC. It would be used for a new fiber optical biosensor based on the SPF and NLC.

  13. Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs

    SciTech Connect

    Buckley, Sonia Radulaski, Marina; Vučković, Jelena; Biermann, Klaus

    2013-11-18

    We demonstrate second harmonic generation at telecommunications wavelengths in photonic crystal cavities in (111)-oriented GaAs. We fabricate 30 photonic crystal structures in both (111)- and (100)-oriented GaAs and observe an increase in generated second harmonic power in the (111) orientation, with the mean power increased by a factor of 3, although there is a large scatter in the measured values. We discuss possible reasons for this increase, in particular, the reduced two photon absorption for transverse electric modes in (111) orientation, as well as a potential increase due to improved mode overlap.

  14. Two-stage magnetic orientation of uric acid crystals as gout initiators

    NASA Astrophysics Data System (ADS)

    Takeuchi, Y.; Miyashita, Y.; Mizukawa, Y.; Iwasaka, M.

    2014-01-01

    The present study focuses on the magnetic behavior of uric acid crystals, which are responsible for gout. Under a sub-Tesla (T)-level magnetic field, rotational motion of the crystals, which were caused by diamagnetic torque, was observed. We used horizontal magnetic fields with a maximum magnitude of 500 mT generated by an electromagnet to observe the magnetic orientation of the uric acid microcrystals by a microscope. The uric acid crystals showed a perpendicular magnetic field orientation with a minimum threshold of 130 mT. We speculate that the distinct diamagnetic anisotropy in the uric acid crystals resulted in their rotational responses.

  15. Orientation Dependence of Electromechanical Characteristics of Defect-free InAs Nanowires.

    PubMed

    Zheng, Kun; Zhang, Zhi; Hu, Yibin; Chen, Pingping; Lu, Wei; Drennan, John; Han, Xiaodong; Zou, Jin

    2016-03-01

    Understanding the electrical properties of defect-free nanowires with different structures and their responses under deformation are essential for design and applications of nanodevices and strain engineering. In this study, defect-free zinc-blende- and wurtzite-structured InAs nanowires were grown using molecular beam epitaxy, and individual nanowires with different structures and orientations were carefully selected and their electrical properties and electromechanical responses were investigated using an electrical probing system inside a transmission electron microscope. Through our careful experimental design and detailed analyses, we uncovered several extraordinary physical phenomena, such as the electromechanical characteristics are dominated by the nanowire orientation, rather than its crystal structure. Our results provide critical insights into different responses induced by deformation of InAs with different structures, which is important for nanowire-based devices. PMID:26837494

  16. Orientational bonding of phases accompanying directed crystallization of the eutectic of the system Si-TiSi2

    NASA Astrophysics Data System (ADS)

    Derevyagina, L. S.; Butkevich, L. M.

    1987-09-01

    The characteristic features of structure formation in cast and direct crystallized alloys of the system Si-TiSi2 were studied. It is shown that the predominant orientation of the bonding of the phases in directionally crystallized eutectics (DE) of the system Si-TiSi2, observed at the stage of steady-state growth, already appears on the surface of nucleation, which apparently indicates that the nucleation of the phases in the alloys of this system is of an epitaxial character.

  17. Coupled crystal orientation-size effects on the strength of nano crystals

    NASA Astrophysics Data System (ADS)

    Yuan, Rui; Beyerlein, Irene J.; Zhou, Caizhi

    2016-05-01

    We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textured materials and our values are in agreement with experimental measurements from numerous studies. We find that the Hall-Petch slope increases with texture strength, indicating that preferred orientations intensify the enhancements in strength that accompany grain size reductions. These findings reveal that texture is too influential to be neglected when analyzing and engineering grain size effects for increasing nanomaterial strength.

  18. Coupled crystal orientation-size effects on the strength of nano crystals

    PubMed Central

    Yuan, Rui; Beyerlein, Irene J.; Zhou, Caizhi

    2016-01-01

    We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textured materials and our values are in agreement with experimental measurements from numerous studies. We find that the Hall-Petch slope increases with texture strength, indicating that preferred orientations intensify the enhancements in strength that accompany grain size reductions. These findings reveal that texture is too influential to be neglected when analyzing and engineering grain size effects for increasing nanomaterial strength. PMID:27185364

  19. Effect of crystal orientation on conductivity and electron mobility in single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

    1992-01-01

    The electrical conductivity of high-purity, single-crystal alumina is determined parallel to and perpendicular to the c-axis. The mean conductivity of four samples of each orientation is a factor 3.3 higher parallel to the c-axis than perpendicular to it. The conductivity as a function of temperature is attributed to extrinsic electron conduction at temperatures from 400 to 900 C, and intrinsic semiconduction at temperatures from 900 to 1300 C. In the high-temperature regime, the slope on all eight specimens is 4.7 +/- 0.1 eV. Hence, the thermal bandgap at O K is 9.4 +/- 0.2 eV.

  20. Imposed Orientation of Dye Molecules by Liquid Crystals and an Electric Field.

    ERIC Educational Resources Information Center

    Sadlej-Sosnowska, Nina

    1980-01-01

    Describes experiments using dye solutions in liquid crystals in which polar molecules are oriented in an electrical field and devices are constructed to change their color in response to an electric signal. (CS)

  1. Crystal orientation mapping via ion channeling: An alternative to EBSD.

    PubMed

    Langlois, C; Douillard, T; Yuan, H; Blanchard, N P; Descamps-Mandine, A; Van de Moortèle, B; Rigotti, C; Epicier, T

    2015-10-01

    A new method, which we name ion CHanneling ORientation Determination (iCHORD), is proposed to obtain orientation maps on polycrystals via ion channeling. The iChord method exploits the dependence between grain orientation and ion beam induced secondary electron image contrast. At each position of the region of interest, intensity profiles are obtained from a series of images acquired with different orientations with respect to the ion beam. The profiles are then compared to a database of theoretical profiles of known orientation. The Euler triplet associated to the most similar theoretical profile gives the orientation at that position. The proof-of-concept is obtained on a titanium nitride sample. The potentialities of iCHORD as an alternative to EBSD are then discussed. PMID:26094201

  2. Inducing uniform single-crystal like orientation in natural rubber with constrained uniaxial stretch.

    PubMed

    Zhou, Weiming; Meng, Lingpu; Lu, Jie; Wang, Zhen; Zhang, Wenhua; Huang, Ningdong; Chen, Liang; Li, Liangbin

    2015-07-01

    The effect of flow on crystallization is commonly attributed to entropic reduction, which is caused by stretch and orientation of polymer chains but overlooks the role of flow on final-state free energy. With the aid of in situ synchrotron radiation wide-angle X-ray diffraction (WAXD) and a homemade constrained uniaxial tensile testing machine, polycrystals possessing single-crystal-like orientation rather than uniaxial orientation are found during the constrained stretch of natural rubber, whereas the c-axis and a-axis align in the stretch direction (SD) and constrained direction (CD), respectively. Molecular dynamics simulation shows that aligning the a-axis of crystal nuclei in CD leads to the lowest free energy increase and favors crystal nucleation. This indicates that the nomenclature of strain-induced crystallization may not fully account for the nature of flow-induced crystallization (FIC) as strain mainly emphasizes the entropic reduction of initial melt, whereas stress rather than strain plays the dominant role in crystal deformation. The current work not only contributes to a comprehensive understanding of the mechanism of flow-induced crystallization but also demonstrates the potential application of constrained uniaxial tensile stretch for the creation of functional materials containing polycrystals that possess single-crystal-like orientation. PMID:26021287

  3. Surface Tension Drives the Orientation of Crystals at the Air-Water Interface.

    PubMed

    Chevalier, Nicolas R; Guenoun, Patrick

    2016-07-21

    The fabrication of oriented crystalline thin films is essential for a range of applications ranging from semiconductors to optical components, sensors, and catalysis. Here we show by depositing micrometric crystal particles on a liquid interface from an aerosol phase that the surface tension of the liquid alone can drive the crystallographic orientation of initially randomly oriented particles. The X-ray diffraction patterns of the particles at the interface are identical to those of a monocrystalline sample cleaved along the {104} (CaCO3) or {111} (CaF2) face. We show how this orientation effect can be used to produce thin coatings of oriented crystals on a solid substrate. These results also have important implications for our understanding of heterogeneous crystal growth beneath amphiphile monolayers and for 2D self-assembly processes at the air-liquid interface. PMID:27389283

  4. Growth and Raman spectra of single-crystal trilayer graphene with different stacking orientations.

    PubMed

    Zhao, Haiming; Lin, Yung-Chang; Yeh, Chao-Hui; Tian, He; Chen, Yu-Chen; Xie, Dan; Yang, Yi; Suenaga, Kazu; Ren, Tian-Ling; Chiu, Po-Wen

    2014-10-28

    Understanding the growth mechanism of graphene layers in chemical vapor deposition (CVD) and their corresponding Raman properties is technologically relevant and of importance for the application of graphene in electronic and optoelectronic devices. Here, we report CVD growth of single-crystal trilayer graphene (TLG) grains on Cu and show that lattice defects at the center of each grain persist throughout the growth, indicating that the adlayers share the same nucleation site with the upper layers and these central defects could also act as a carbon pathway for the growth of a new layer. Statistics shows that ABA, 30-30, 30-AB, and AB-30 make up the major stacking orientations in the CVD-grown TLG, with distinctive Raman 2D characteristics. Surprisingly, a high level of lattice defects results whenever a layer with a twist angle of θ = 30° is found in the multiple stacks of graphene layers. PMID:25295851

  5. Orientation dependence of the stress rupture properties of Nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.

    1981-01-01

    The influence of orientation of the stress rupture behavior of Mar-M247 single crystals was studied. Stress rupture tests were performed at 724 MPa and 774 C where the effect of anisotropy is prominent. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factors for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The stress rupture lives were found to be greatly influenced by the lattice rotations required to produce intersecting slip, because steady-state creep does not begin until after the onset of intersecting slip. Crystals which required large rotations to become oriented for intersecting slip exhibited a large primary creep strain, a large effective stress level at the onset of steady-state creep, and consequently a short stress rupture life. A unified analysis was attained for the stress rupture behavior of the Mar-M247 single crystals tested in this study at 774 C and that of the Mar-M200 single crystals tested in a prior study at 760 C. In this analysis, the standard 001-011-111 stereographic triangle was divided into several regions of crystallographic orientation which were rank ordered according to stress rupture life for this temperature regime. This plot indicates that those crystals having orientations within about 25 deg of the 001 exhibited significantly longer lives when their orientations were closer to the 001-011 boundary of the stereographic triangle than to the 001-111 boundary.

  6. Orientational photorefractive effects observed in poly(vinyl alcohol)/liquid crystal composites

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

    1998-04-01

    We successfully observed orientational photorefractive gratings generated in poly(vinyl alcohol) (PVA)/liquid crystal (LC) composites doped with a fullerene (C60) as a photoconductive sensitizer under an applied dc field. Orientational photorefractivity was demonstrated by observing Raman-Nath diffraction beams with an external dc field. The photorefractive gratings were partially memorized even in the absence of the applied dc field.

  7. Electric-field-assisted position and orientation control of organic single crystals.

    PubMed

    Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

    2014-12-01

    We have investigated the motion of growing pentacene single crystals in solution under various electric fields. The pentacene single crystals in 1,2,4-trichlorobenzene responded to the electric field as if they were positively charged. By optimizing the strength and frequency of an alternating electric field, the pentacene crystals automatically bridged the electrodes on SiO2. The pentacene crystal with a large aspect ratio tended to direct the [1̅10] orientation parallel to the conduction direction, which will be suitable from a viewpoint of anisotropy in mobility. The present result shows a possibility of controlling the position and orientation of organic single crystals by the use of an electric field, which leads to high throughput and low cost industrial manufacturing of the single crystal array from solution. PMID:25360544

  8. Plasmonic Photopatterning of Complex Molecular Orientations in Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Guo, Yubing; Jiang, Miao; Peng, Chenhui; Sun, Kai; Yaroshchuk, Oleg; Lavrentovich, Oleg; Wei, Qi-Huo

    Aligning liquid crystal (LC) molecules in spatially non-uniform patterns are highly demanded for applications such as programmable origami and liquid crystal enabled nonlinear electrokinetics. We developed a high resolution projection photoalignment technique for patterning arbitrary LC alignment fields. The photoalignment is based on carefully engineered metasurfaces, or dubbed as plasmonic metamasks (PMMs). When illuminated by light, the PMMs generate patterns of both light intensity and polarization. By projecting the light transmitted through the PMMs onto liquid crystal cells coated with photosensitive materials, alignment patterns predesigned in polarization patterns of the PMMs can be imposed in liquid crystals. This technique makes the liquid crystal alignment a repeatable and scalable process similar to conventional photolithography, promising various applications. National Science Foundation CMMI-1436565.

  9. Orientation dependence of shock induced dislocations in Tantalum single crystals

    NASA Astrophysics Data System (ADS)

    Pang, Bo; Jones, I.; Chiu, Yulung; Millett, J.; Whiteman, Glenn; Bourne, N.

    2013-06-01

    Shock wave deformation of monocrystalline tantalum to a pressure of 6.2 GPa and duration of 1.7 μs generates profuse dislocations. Three orientations (100),(110),(111) were tested to examine the orientation dependence of the dislocation generation. The dislocations were characterised by transmission electron microscopy. The difference in the Burgers vectors of the primary dislocations in the specimens with different orientations showed a distinct anisotropy and will be discussed in light of the models of slip behaviour in one-dimensional strain (Smith 1958) and (Meyers 1978). The front and rear surfaces of the specimens were both investigated to examine the effects of wave duration.

  10. Backscatter ratios for arbitrary oriented hexagonal ice crystals of cirrus clouds.

    PubMed

    Borovoi, Anatoli; Konoshonkin, Alexander; Kustova, Natalia

    2014-10-01

    Three dimensionless ratios widely used for interpretation of lidar signals, i.e., the color ratio, lidar ratio, and depolarization ratio, have been calculated for hexagonal ice crystals of cirrus clouds as functions of their spatial orientation. The physical-optics algorithm developed earlier by the authors is applied. It is shown that these ratios are minimal at the horizontal crystal orientation. Then these quantities increase with the effective tilt angle approaching the asymptotic values of the random particle orientation. The values obtained are consistent with the available experimental data. PMID:25360985

  11. Orientational Order of Molecular Assemblies on Inorganic Crystals

    NASA Astrophysics Data System (ADS)

    Chun, Jaehun; Saville, Dudley; Li, Je-Luen; Schniepp, Hannes; Car, Roberto; Aksay, Ilhan

    2006-03-01

    Surfactant micelles form oriented arrays on crystalline substrates such as HOPG (Highly Ordered Pyrolytic Graphite) although registration is unexpected since the template unit cell is small compared to the size of a rod-like micelle. In addition, with atomic force microscopy, we show that orientational ordering is a dynamic, multi-molecule process. Interaction energy calculations based on molecular simulations reveal that orientational energy differences on a molecular scale are too small to explain matters. However, treating the cooperative processes as a balance between van der Waals torque on a large, rod-like micellar assembly and Brownian motion shows that orientation is favored. Our study provides a physical insight on regulation of self-assembly structures at small length scale.

  12. Orientational ordering of Janus colloids in cholesteric liquid crystals.

    PubMed

    Rudyak, Vladimir Yu; Emelyanenko, Alexander V

    2015-10-01

    In this paper we show that Janus colloids, which are spherical particles with hybrid anchoring conditions, have preferable orientations in cholesteric media depending on the cholesteric wave vector. Simulations reveal that the tilt angle of a particle varies greatly with variation of the particle diameter to the cholesteric pitch ratio, which makes it possible to stabilize the appropriate particle orientation and to control it by variation of the cholesteric pitch. PMID:26291514

  13. Recrystallization of plane strain compressed Al-1 wt.% Mn alloy single crystals of typical unstable orientations.

    PubMed

    Bijak, M; Paul, H; Driver, J H

    2010-03-01

    A systematic study of crystal lattice reorientation in early stages of recrystallization has been carried out to correlate the orientations of recrystallization nuclei with the deformation microtexture and with slip systems. Microstructure and texture of Al-1 wt.% Mn single crystals of unstable initial orientations of {112}111, {100}001 and {001}110 have been examined by high-resolution field-emission gun scanning electron microscope local orientation measurements. All single crystals were channel-die deformed at room temperature and then annealed for a short time. It was shown that often observed presence of the 112 directions as rotation axes in the formation of new nuclei orientation directly suggested a close link with the deformation process. PMID:20500369

  14. Graphene-Assisted Solution Growth of Vertically Oriented Organic Semiconducting Single Crystals.

    PubMed

    Wang, Yue; Torres, Jaime A; Stieg, Adam Z; Jiang, Shan; Yeung, Michael T; Rubin, Yves; Chaudhuri, Santanu; Duan, Xiangfeng; Kaner, Richard B

    2015-10-27

    Vertically oriented structures of single crystalline conductors and semiconductors are of great technological importance due to their directional charge carrier transport, high device density, and interesting optical properties. However, creating such architectures for organic electronic materials remains challenging. Here, we report a facile, controllable route for producing oriented vertical arrays of single crystalline conjugated molecules using graphene as the guiding substrate. The arrays exhibit uniform morphological and crystallographic orientations. Using an oligoaniline as an example, we demonstrate this method to be highly versatile in controlling the nucleation densities, crystal sizes, and orientations. Charge carriers are shown to travel most efficiently along the vertical interfacial stacking direction with a conductivity of 12.3 S/cm in individual crystals, the highest reported to date for an aniline oligomer. These crystal arrays can be readily patterned and their current harnessed collectively over large areas, illustrating the promise for both micro- and macroscopic device applications. PMID:26322526

  15. Hexapole-Oriented Molecule Beams Scattered by Single Crystal Surfaces.

    NASA Astrophysics Data System (ADS)

    Curtiss, Thomas J.

    A newly constructed machine capable of producing beams of spatially oriented molecules is described in detail. Beam molecules are focused and state-selected by a 2.85 m electrostatic hexapole. The machine consists of seven differentially pumped chambers with an overall length from nozzle to final collimator in the surface scattering configuration of 3.78 m. For symmetric top molecules pure (>95%) {mid}JKM> rotational state selection has been achieved. The distribution of orientations among CH_3I beam molecules has been quantitatively measured using the photodissociation/multiphoton ionization time of flight technique. Results accord with simulated ion time of flight distributions using theoretical orientational probability distribution functions which include the nuclear hyperfine interaction. Oriented molecule beams of seven different molecules have been scattered by a graphite (0001) surface. The results show a large diversity in the sign and magnitude of the steric effects (i.e., "heads" vs. "tails"). The steric effects have been quantitatively measured, and have been analyzed in terms of a two component model: a trapping/desorption component and a direct scattering component. Analysis of the scattered angular distribution data yields estimates for the anisotropy of the trapping probability (e.g., for CHF_3 there is 25% higher trapping probability when the H "end" of the molecule is incident on the graphite surface than for the F_3 "end"). The magnitude of the steric effect is found to be a linear function of the degree of orientation of the beam molecules for all systems studied. Over the limited range of the present data, the steric effect increases with incident kinetic energy. A null steric effect result was observed for the scattering of oriented CH_3Cl by a W(110) surface. However, the initial sticking probability for randomly oriented CH_3Cl was measured to be unity. It is not surprising that there is no observable steric effect in the scattering of CH _3

  16. Investigating the orientational order in smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Wang, Shun

    This thesis is composed of two projects. The first one is the investigation of a reversed phase sequence, which subsequently leads to the discovery of a novel Smectic-C liquid crystal phase. The 10OHFBBB1M7 (10OHF) compound shows a reversed phase sequence with the SmC*d4 phase occurring at a higher temperature than the SmC* phase. This phase sequence is stabilized by moderate doping of 9OTBBB1M7 (C9) or 11OTBBB1M7 (C11). To further study this unique phase sequence, the mixtures of 10OHFBBB1M7 and its homologs have been characterized by optical techniques. In order to perform the resonant X-ray diffraction experiment, we have added C9 and C11 compounds to the binary mixtures and pure 10OHF. In two of the studied mixtures, a new smectic-C* liquid crystal phase with six-layer periodicity has been discovered. Upon cooling, the new phase appears between the SmC*a phase having a helical structure and the SmC*d4 phase with four-layer periodicity. The SmC*d6 phase shows a distorted clock structure. Three theoretical models have predicted the existence of a six-layer phase. However, our experimental findings are not consistent with the theories. The second project involves the mixtures of liquid crystals with different shapes. The role of different interactions in stabilizing the antiferroelectric smectic liquid crystal phases have been a long-standing questions in the community. By mixing the antiferroelectric smectic liquid crystal with achiral liquid crystal molecules with rod and hockey-stick shapes, distinct different behaviors are obtained. In the case of the mixtures of chiral smectic liquid crystals with rod-like molecules, all the smectic-C* variant phases vanish with a small amount of doping. However, the hockey-stick molecule is much less destructive compared to the rod-like molecule. This suggests that the antiferroelectric smectic liquid crystal molecules may have a shape closer to a hockey-stick rather than a rod.

  17. Oriented growth of inorganic crystals at organic templates: Synchrotron X-ray scattering studies

    NASA Astrophysics Data System (ADS)

    Kewalramani, Sumit

    Living organisms grow precisely controlled assemblies of inorganic crystals using organic substrates. This observation has inspired the strategy of using synthetic organic templates for the growth of tailored inorganic thin films. It has been previously shown that monomolecular organic layers floating on supersaturated aqueous subphases (Langmuir monolayers) select the structure (where more than one is possible) and the orientation of the inorganic crystals nucleating under them. However, the mechanisms governing such selective crystal nucleation process remained unclear. This project attempts to understand the roles played by geometric influences such as structural match between the interfacial lattices and the interactions between monolayer headgroups and aqueous ions in determining the orientation and structure of the inorganic nucleate. To perform such studies we have monitored the organic-inorganic interface during the nucleation process using grazing incidence X-ray diffraction (GID). Scanning electron microscopy (SEM) was used to perform morphological studies on grown crystals. Our studies show that different mechanisms govern the early and late stages of crystal growth. In the early stages interplay between the monolayer headgroup - aqueous ion interactions and ion specific effects determine the inorganic species that nucleates. During crystal growth of barium fluoride and barium fluoride chloride under a fatty acid monolayer, we found that both the inorganic forms nucleate in an oriented manner. However, when the monolayer is in a deprotonated state, only barium fluoride nucleation was observed. In nearly all the cases of oriented crystal growth we found a lattice match between the interfacial structures. During barium fluoride and barium fluoride chloride crystal growth under a fatty acid monolayer, the interfacial lattices demonstrated sufficient flexibility; to achieve an epitaxial match. A variant was observed during hydrocerussite (2PbCO3·Pb(OH) 2

  18. Orientational defects near colloidal particles in a nematic liquid crystal.

    PubMed

    Feng, James J; Zhou, Chixing

    2004-01-01

    We study the interaction between a surface-anchoring colloidal particle and a liquid-crystalline host, and in particular the formation of orientational defects near the particle. A mean-field theory based on the nonlocal Marrucci-Greco nematic potential is used to represent molecular interactions in an inhomogeneous orientational field. An evolution equation for the molecular configuration tensor is solved numerically whose steady state minimizes the total free energy of the system. With strong homeotropic anchoring on the particle surface, three types of solutions may appear depending on initial conditions and particle size: Saturn rings, satellite point defects, and polar rings. The Saturn ring remains stable on micrometer-sized particles, contrary to previous calculations but consistent with experiments. A phase diagram is constructed for the three regimes. Based on the free energy, the most stable state is the Saturn ring for smaller particles and the satellite defect for larger ones. PMID:14651897

  19. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires.

    PubMed

    Fu, Mengqi; Tang, Zhiqiang; Li, Xing; Ning, Zhiyuan; Pan, Dong; Zhao, Jianhua; Wei, Xianlong; Chen, Qing

    2016-04-13

    We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (VT), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (ΦOFF). The SS increases while VT, ON-OFF ratio, and ΦOFF decrease one by one in the sequence of WZ ⟨0001⟩, ZB ⟨131⟩, ZB ⟨332⟩, ZB ⟨121⟩, and ZB ⟨011⟩. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at VBG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs. PMID:27002386

  20. Insights Into the Solution Crystallization of Oriented Alq3 and Znq2 Microprisms and Nanorods.

    PubMed

    Boulet, Joel; Mohammadpour, Arash; Shankar, Karthik

    2015-09-01

    Optimized solution-based methods to grow high quality micro- and nanocrystals of organic semi-conductors with defined size, shape and orientation are important to a variety of optoelectronic applications. In this context, we report the growth of single crystal micro- and nanostructures of the organic semiconductors Tris(8-hydroxyquinoline)aluminum (Alq3) and bis(8-hydroxyquinoline)zinc (Znq2) terminating in flat crystal planes using a combination of evaporative and antisolvent crystallization. By controlling substrate-specific nucleation and optimizing the conditions of growth, we generate vertically-oriented hexagonal prism arrays of Alq3, and vertical half-disks and sharp-edged rectangular prisms of Znq2. The effect of process variables such as ambient vapour pressure, choice of anti-solvent and temperature on the morphology and crystal habit of the nanostructures were studied and the results of varying them catalogued to gain a better understanding of the mechanism of growth. PMID:26716228

  1. Orientational fluctuation study in nematic liquid crystals by high speed micrograph

    NASA Astrophysics Data System (ADS)

    Yoon, Beom-Jin; Park, Min Sang; Park, Jung O.; Srinivasarao, Mohan

    2009-03-01

    The orientational fluctuations in uniaxial and biaxial nematic liquid crystals were investigated with a polarized microscope and a high speed TV camera. Liquid crystals usually have fluctuations with respect to their director, even when the molecular axes tend to be aligned to each other. These fluctuations are sufficiently slow and large, have long wave length and increase with temperature. Herein, we describe our study on fluctuation dynamics by direct observations in real space, while it has been typically done by the photon scattering in reciprocal space. The twinkling of liquid crystals due to orientational fluctuations was observed with a high speed camera up to 500 frames/sec. The time correlation function of the intensity was computed via 2D spatial Fourier transform of each image and then the relaxation frequency was estimated from it. The elastic constant to the viscosity ratio was computed from the relaxation frequency. This approach provides facile route to analyze fluctuation dynamics in liquid crystals.

  2. Orientational optical nonlinearity induced by comb-shaped polymers in a nematic liquid crystal

    SciTech Connect

    Budagovsky, I. A.; Zolot'ko, A. S. Ochkin, V. N.; Smayev, M. P.; Bobrovsky, A. Yu.; Shibaev, V. P.; Barnik, M. I.

    2008-01-15

    The effect of optical orientation in nematic liquid crystals containing small additions of high-molecular compounds, i.e., comb-shaped polymers with light-absorbing azobenzene side fragments, was studied. The effects of light-induced reorientation of the director of nematic liquid crystals caused by light absorption of polymers and a low-molecular compound with a structure similar to side fragments of the polymers were compared in detail. An explanation was proposed for large values of the orientational nonlinearity induced by polymers.

  3. Effects of the Coordinates Planes Crystal Orientation on the Structural Strength of Single-Crystal Turbine Vanes and Blades

    NASA Astrophysics Data System (ADS)

    Chen, Jinxiang; Hashimoto, Ryosaku; Fukuyama, Yoshitaka; Matsushita, Masahiro; Ogawa, Akinori; Osawa, Makoto; Yokokawa, Tadaharu; Harada, Hiroshi

    The effects of crystal orientation (θ) on the structural strength of single crystal turbine vanes and blades calculated with the finite element method (FEM) are discussed in this paper. TMS-75, a 3rd generation single-crystal Ni-base superalloy, is chosen as the model material for turbine vanes and blades. It became clear that, (1) the elastic constant matrix changes were equivalence for each of three coordinate due to the orientation variation (0° < θ < 90°), and the strength of the turbine vane and blade were strongly related to θ, and also depended on the load and model shape. (2) The strength dependence of the turbine vane on the crystal orientation was depended on coordinate plane: there are lower Mises stress in XY plane and maximum Mises stress in near the θ=45° at both YZ and ZX Planes. (3) In the case of a blade, the influence is similar to the vane on blade tip, but the converse holds for the blade root. It is clear that the creep rupture time can be extended, when the <100> crystallographic axes is the Y or X axis of the blade under higher rotation speed.

  4. Simplification for Fraunhofer diffracting pattern of various randomly oriented ice crystals in cirrus.

    PubMed

    Pujol, Olivier; Brogniez, Gérard; Labonnote, Laurent

    2012-09-01

    This paper deals with Fraunhofer diffraction by an ensemble of independent randomly oriented ice crystals of assorted shapes, like those of cirrus clouds. There is no restriction on the shape of each crystal. It is shown that light flux density in the Fourier plane is azimuth-invariant and varies as 1/sin(4)θ, θ being the angle of diffraction. The analytical formula proposed is exact. The key point of this study is conservation of electromagnetic energy. PMID:23201960

  5. Revealing the preferred interlayer orientations and stackings of two-dimensional bilayer gallium selenide crystals

    DOE PAGESBeta

    Li, Xufan; Basile Carrasco, Leonardo A.; Yoon, Mina; Ma, Cheng; Puretzky, Alexander A.; Lee, Jaekwang; Idrobo Tapia, Juan Carlos; Chi, Miaofang; Rouleau, Christopher M.; Geohegan, David B.; et al

    2015-01-21

    Characterizing and controlling the interlayer orientations and stacking order of bilayer two-dimensional (2D) crystals and van der Waals (vdW) heterostructure is crucial to optimize their electrical and optoelectronic properties. The four polymorphs of layered gallium selenide (GaSe) that result from different layer stacking provide an ideal platform to study the stacking configurations in bilayer 2D crystals. Here, through a controllable vapor-phase deposition method we selectively grow bilayer GaSe crystals and investigate their two preferred 0° or 60° interlayer rotations. The commensurate stacking configurations (AA' and AB-stacking) in as-grown 2D bilayer GaSe crystals are clearly observed at the atomic scale andmore » the Ga-terminated edge structure are identified for the first time by using atomic-resolution scanning transmission electron microscopy (STEM). Theoretical analysis of the interlayer coupling energetics vs. interlayer rotation angle reveals that the experimentally-observed orientations are energetically preferred among the bilayer GaSe crystal polytypes. Here, the combined experimental and theoretical characterization of the GaSe bilayers afforded by these growth studies provide a pathway to reveal the atomistic relationships in interlayer orientations responsible for the electronic and optical properties of bilayer 2D crystals and vdW heterostructures.« less

  6. Revealing the preferred interlayer orientations and stackings of two-dimensional bilayer gallium selenide crystals

    SciTech Connect

    Li, Xufan; Basile Carrasco, Leonardo A.; Yoon, Mina; Ma, Cheng; Puretzky, Alexander A.; Lee, Jaekwang; Idrobo Tapia, Juan Carlos; Chi, Miaofang; Rouleau, Christopher M.; Geohegan, David B.; Xiao, Kai

    2015-01-21

    Characterizing and controlling the interlayer orientations and stacking order of bilayer two-dimensional (2D) crystals and van der Waals (vdW) heterostructure is crucial to optimize their electrical and optoelectronic properties. The four polymorphs of layered gallium selenide (GaSe) that result from different layer stacking provide an ideal platform to study the stacking configurations in bilayer 2D crystals. Here, through a controllable vapor-phase deposition method we selectively grow bilayer GaSe crystals and investigate their two preferred 0° or 60° interlayer rotations. The commensurate stacking configurations (AA' and AB-stacking) in as-grown 2D bilayer GaSe crystals are clearly observed at the atomic scale and the Ga-terminated edge structure are identified for the first time by using atomic-resolution scanning transmission electron microscopy (STEM). Theoretical analysis of the interlayer coupling energetics vs. interlayer rotation angle reveals that the experimentally-observed orientations are energetically preferred among the bilayer GaSe crystal polytypes. Here, the combined experimental and theoretical characterization of the GaSe bilayers afforded by these growth studies provide a pathway to reveal the atomistic relationships in interlayer orientations responsible for the electronic and optical properties of bilayer 2D crystals and vdW heterostructures.

  7. Faraday rotator based on TSAG crystal with <001> orientation.

    PubMed

    Yasuhara, Ryo; Snetkov, Ilya; Starobor, Aleksey; Mironov, Evgeniy; Palashov, Oleg

    2016-07-11

    A Faraday isolator (FI) for high-power lasers with kilowatt-level average power and 1-µm wavelength was demonstrated using a terbium scandium aluminum garnet (TSAG) with its crystal axis aligned in the <001> direction. Furthermore, no compensation scheme for thermally induced depolarization in a magnetic field was used. An isolation ratio of 35.4 dB (depolarization ratio γ of 2.9 × 10-4) was experimentally observed at a maximum laser power of 1470 W. This result for room-temperature FIs is the best reported, and provides a simple, practical solution for achieving optical isolation in high-power laser systems. PMID:27410823

  8. Structural, morphological and optical characteristics of KGd(WO4)2 crystals

    NASA Astrophysics Data System (ADS)

    Ananyeva, G. V.; Afanasyev, I. I.; Glazov, A. I.; Mamontov, I. Y.; Merkulyayeva, T. I.

    1984-02-01

    A KGd (WO sub 4) (sub 2) crystal, suitable as active laser material with Nd (sup + 3) doping, has a low-order symmetry which makes determination and normalization of its optical characteristics difficult. Its atomic structure is described by the P/2m group of spatial symmetry. A correspondence between the principal axes and the structure of this biaxial crystal was established by X-ray structural analyses with a URS-50IM X-ray diffractometer and a model F goniometer and optical measurements. Based on this study and plotting of the stereographic projection of such a crystal, its lattice parameters and optical indicatrix are found. Its optical orientation can be described as n sub g = b and n sub pc = 20 deg with the optical axes at an 86.5 deg angle to one another lying in the plane of the crystallographic b-axis zone.

  9. Point-group sensitive orientation mapping of non-centrosymmetric crystals

    SciTech Connect

    Winkelmann, Aimo; Nolze, Gert

    2015-02-16

    We demonstrate polarity-sensitive orientation mapping of non-centrosymmetric phases by Electron Backscatter Diffraction (EBSD). The method overcomes the restrictions of kinematic orientation determination by EBSD, which is limited to the centro-symmetric Laue-groups according to Friedel's rule. Using polycrystalline GaP as an example, we apply a quantitative pattern matching approach based on simulations using the dynamical theory of electron diffraction. This procedure results in a distinct assignment of the local orientation according to the non-centrosymmetric point group of the crystal structure under investigation.

  10. Preferential Crystal Growth of (100)-Oriented BiFeO3 Films on Si Substrate

    NASA Astrophysics Data System (ADS)

    Hayashi, M.; Yasui, S.; Funakubo, H.; Uchida, H.

    2011-10-01

    Bi-based perovskite-type oxide materials such as BiFeO3 (BFO) and the related compounds receive much attention and have been developed actively as important candidates for Pb-free ferroelectric / piezoelectric materials instead of toxic Pb-based perovskite oxide materials. Recently, many researches have been reported for thin films of BFO by various film-deposition techniques for actual application of semiconductive devices, microactuators, etc. In this report, we tried preferential crystal growth of BFO films on semiconductive silicon substrates using uniaxial-(100)-oriented LaNiO3 (LNO) buffer layer. BFO films were fabricated via chemical solution deposition (CSD) technique on platinized silicon wafer [(111)Pt/TiO2/(100)Si] and (100)LNO-coated platinized silicon [(100)LNO/(111)Pt/TiO2/(100)Si] substrates. XRD analysis indicated that the films fabricated on (111)Pt/TiO2/(100)Si substrate consisted of randomly-oriented BFO crystal with lower crystallinity and trace amount of the second Bi2Fe4O9 phase. On the other hand, the films on (100)LNO/(111)Pt/TiO2/(100)Si consisted of uniaxial-(100)-oriented BFO crystal with higher crystallinity. The crystallization temperature these films were 450 and 400°C, respectively. These results suggest that the BFO crystal was grown epitaxially on uniaxial oriented (100)LNO plane which also had perovskite-type crystal structure. Consequently, (100)-oriented BFO films were prepared on Si substrate successfully using (100)LNO buffer layer.

  11. Crystal Orientation Controlled Photovoltaic Properties of Multilayer GaAs Nanowire Arrays.

    PubMed

    Han, Ning; Yang, Zai-Xing; Wang, Fengyun; Yip, SenPo; Li, Dapan; Hung, Tak Fu; Chen, Yunfa; Ho, Johnny C

    2016-06-28

    In recent years, despite significant progress in the synthesis, characterization, and integration of various nanowire (NW) material systems, crystal orientation controlled NW growth as well as real-time assessment of their growth-structure-property relationships still presents one of the major challenges in deploying NWs for practical large-scale applications. In this study, we propose, design, and develop a multilayer NW printing scheme for the determination of crystal orientation controlled photovoltaic properties of parallel GaAs NW arrays. By tuning the catalyst thickness and nucleation and growth temperatures in the two-step chemical vapor deposition, crystalline GaAs NWs with uniform, pure ⟨110⟩ and ⟨111⟩ orientations and other mixture ratios can be successfully prepared. Employing lift-off resists, three-layer NW parallel arrays can be easily attained for X-ray diffraction in order to evaluate their growth orientation along with the fabrication of NW parallel array based Schottky photovoltaic devices for the subsequent performance assessment. Notably, the open-circuit voltage of purely ⟨111⟩-oriented NW arrayed cells is far higher than that of ⟨110⟩-oriented NW arrayed counterparts, which can be interpreted by the different surface Fermi level pinning that exists on various NW crystal surface planes due to the different As dangling bond densities. All this indicates the profound effect of NW crystal orientation on physical and chemical properties of GaAs NWs, suggesting the careful NW design considerations for achieving optimal photovoltaic performances. The approach presented here could also serve as a versatile and powerful platform for in situ characterization of other NW materials. PMID:27223050

  12. Orientation Dependence in Molecular Dynamics Simulations of Shocked Single Crystals

    SciTech Connect

    Germann, Timothy C.; Holian, Brad Lee; Lomdahl, Peter S.; Ravelo, Ramon

    2000-06-05

    We use multimillion-atom molecular dynamics simulations to study shock wave propagation in fcc crystals. As shown recently, shock waves along the <100> direction form intersecting stacking faults by slippage along {l_brace}111{r_brace} close-packed planes at sufficiently high shock strengths. We find even more interesting behavior of shocks propagating in other low-index directions: for the <111> case, an elastic precursor separates the shock front from the slipped (plastic) region. Shock waves along the <110> direction generate a leading solitary wave train, followed (at sufficiently high shock speeds) by an elastic precursor, and then a region of complex plastic deformation. (c) 2000 The American Physical Society.

  13. Structural Correspondence of the Oriented Attachment Growth Mechanism of Crystals of the Pharmaceutical Dirithromycin.

    PubMed

    Liang, Zuozhong; Wang, Yuan; Wang, Wei; Han, Xianglong; Chen, Jian-Feng; Xue, Chunyu; Zhao, Hong

    2015-12-29

    The oriented attachment (OA) mechanism is promising for designing novel nanomaterials, yet an intensive understanding of the relationship between the crystal structure and attachment orientation is still lacking. In this work, we report layered hexagonal crystals of the pharmaceutical dirithromycin (DIR) containing multiple layers fabricated via a solvothermal method for a certain period of time at 40 °C. These elongated hexagonal crystals experience an OA that is preferentially on the face (001) of the initial crystals to assemble the final crystals into layered stacks. Through agreement with molecular modeling calculations, we predicted the final crystal growth morphology and confirmed the favored attachment surface based on the energy change ΔE following an OA event. These simulation results at the molecular level yielded good agreement with the crystal growth experiments. This study demonstrates the critical importance of combining experiments with a computational approach to understand the intrinsic molecular details of the OA growth mechanism of other compounds and to design nanomaterials with a desirable morphology and physical and chemical properties. PMID:26632998

  14. Adaptation of BAp crystal orientation to stress distribution in rat mandible during bone growth

    NASA Astrophysics Data System (ADS)

    Nakano, T.; Fujitani, W.; Ishimoto, T.; Umakoshi, Y.

    2009-05-01

    Biological apatite (BAp) c-axis orientation strongly depends on stress distribution in vivo and tends to align along the principal stress direction in bones. Dentulous mandible is subjected to a complicated stress condition in vivo during chewing but few studies have been carried out on the BAp c-axis orientation; so the adaptation of BAp crystal orientation to stress distribution was examined in rat dentulous mandible during bone growth and mastication. Female SD rats 4 to 14 weeks old were prepared, and the bone mineral density (BMD) and BAp crystal orientation were analyzed in a cross-section of mandible across the first molar focusing on two positions: separated from and just under the tooth root on the same cross-section perpendicular to the mesiodistal axis. The degree of BAp orientation was analyzed by a microbeam X-ray diffractometer using Cu-Kα radiation equipped with a detector of curved one-dimensional PSPC and two-dimensional PSPC in the reflection and transmission optics, respectively. BMD quickly increased during bone growth up to 14 weeks, although it was independent of the position from the tooth root. In contrast, BAp crystal orientation strongly depended on the age and the position from the tooth root, even in the same cross-section and direction, especially along the mesiodistal and the biting axes. With increased biting stress during bone growth, the degree of BAp orientation increased along the mesiodistal axis in a position separated from the tooth root more than that near the tooth root. In contrast, BAp preferential alignment clearly appeared along the biting axis near the tooth root. We conclude that BAp orientation rather than BMD sensitively adapts to local stress distribution, especially from the chewing stress in vivo in the mandible.

  15. Crystallographic Orientation Determination of Hexagonal Structure Crystals by Laser Ultrasonic Technique

    NASA Astrophysics Data System (ADS)

    Li, W.; Coulson, J.; Marrow, P.; Smith, R. J.; Lainé, S. J.; Clark, M.; Sharples, S. D.

    2016-01-01

    Spatially resolved acoustic spectroscopy (SRAS) is a laser ultrasonic technique that shows qualitative contrast between grains of different orientation, illustrating the sensitivity of acoustic waves to the material structure. The technique has been improved significantly on determining the full orientation of multigrain cubic metals, by comparing the measured surface acoustic wave (SAW) velocity to a pre-calculated model. In this paper we demonstrate the ability of this technique to determine the orientation of hexagonal structure crystals, such as magnesium and titanium based alloys. Because of the isotropy of the SAW velocity on the basal plane (0001) of hexagonal crystals, the slowness surface is shown as a circle. As the plane moves from (0001) towards (112¯0) or towards (101¯0), the slowness surface gradually turns into an oval. These acoustic properties increase the difficulty in orientation determination. The orientation results of a grade 1 commercially pure titanium by SRAS is presented, with comparison with electron backscattered diffraction (EBSD) results. Due to the nature of SAWs on hexagonal structure crystals, only the results of Euler angles 1 and 2 are discussed. The error between SRAS and EBSD is also investigated.

  16. Anisotropic light absorption, refractive indices, and orientational order parameter of unidirectionally aligned columnar liquid crystal films.

    PubMed

    Charlet, Emilie; Grelet, Eric

    2008-10-01

    The anisotropic optical properties of thermotropic columnar liquid crystals absorbing in the visible range are investigated for different discotic compounds unidirectionally oriented in open supported thin films. Two methods to monitor the alignment of columnar mesophases in thin films are reported, making possible to achieve either homeotropic anchoring (columns normal to the substrate) by a specific thermal annealing, or unidirectional planar orientation (columns parallel to the substrate) by using a rubbed Teflon coating. The columnar liquid crystal anchoring is found to depend on the nature of the compound, either parallel or perpendicular to the Teflon orientation. Based on this control of the mesophase alignment, the dichroic ratio and the orientational order parameter of oriented samples are measured, and a high order parameter of 0.9 is found in the case of parallel alignment. From the polarized absorption data of the columnar liquid crystal films, the light wavelength dependence of the birefringence and of the real and imaginary parts (refractive index and extinction coefficient, respectively) of the anisotropic optical indices are determined over the whole visible range. PMID:18999445

  17. Choice of scalar measure for crystal curvature to image dislocation substructure in terms of discrete orientation data

    NASA Astrophysics Data System (ADS)

    Zisman, Alexander

    2016-04-01

    Starting from Nye's tensor, alternative characteristics of crystal curvature indicative of dislocation content are considered subject to very low thickness of investigated matter under the free surface and discreteness of orientation sampling. Analysis within the framework of continuum mechanics, undertaken to allow for such conditions peculiar to the electron backscatter diffraction (EBSD) technique, has shown the variable part of orientations expressed in a vector form to be most sensitive to lattice defects when projected to the free surface plane. Hence, as verified with EBSD data on a grain junction in a low deformed IF steel, magnitude of the projected field allows one to map plastic strains inhomogeneous within grains whereas divergence of this field distinctly images and quantifies low-angle dislocation boundaries formed at low strains.

  18. Orientation Dependent Polarized Micro-XAS Study of U, Th and Sr in Single Crystal Apatites

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Rakovan, J.; Wright, S.

    2009-05-01

    In order to evaluate apatite as a potential solid nuclear waste form and a contaminant sequestration agent, the complimentary use of single crystal X-ray diffraction and X-ray absorption spectroscopy (XAS) is applied to the study of U, Th, and Sr doped apatite single crystals to investigate the site preference, oxidation state, and structural distortions created by these substituents. Single crystal X-ray diffraction provides average information regarding the site occupancy of U and Th in apatites. Extended X-ray absorption fine-structure (EXAFS) yields quantitative information of the local structure of these substituents, which includes near-neighbor distances, coordination numbers and variations in bond distances; while X-ray absorption near edge structure (XANES) is used to determine the oxidation states of U. Restricted by the typical small size (20-100 μm) and volume of our synthetic samples, Micro-XAS is required. Different from studies which take full advantage of the polarization of synchrotron radiation, our Micro- XAS study on single crystal apatites was hampered by the polarization effects. In order to extract precise information of valence state and structural variation from XAS, it is necessary to know the crystallographic orientation of the sample with respect to the polarization direction of the incident X-ray beam during data collection. To do this we have designed and built a portable goniometer that duplicates the geometry of our laboratory standard Bruker Apex diffractometer goniometer. Crystal orientation is determined by X-ray diffraction at our home institution. The portable goniometer is then set up on the experimental table at synchrotron facilities and the crystal can be set in any specific known orientation. The lattice orientation determined by X-ray diffraction is applied to XAS data analysis, specifically calculation of scattering amplitudes and phase shifts, to account for polarization effects of synchrotron radiation. The goniometer

  19. Long-range orientational order, local-field anisotropy, and mean molecular polarizability in liquid crystals

    SciTech Connect

    Aver'yanov, E. M.

    2009-01-15

    The problems on the relation of the mean effective molecular polarizability {gamma}-bar to the long-range orientational order of molecules (the optical anisotropy of the medium) in uniaxial and biaxial liquid crystals, the local anisotropy on mesoscopic scales, and the anisotropy of the Lorentz tensor L and the local-field tensor f are formulated and solved. It is demonstrated that the presence of the long-range orientational order of molecules in liquid crystals imposes limitations from below on the molecular polarizability {gamma}-bar, which differs for uniaxial and biaxial liquid crystals. The relation between the local anisotropy and the molecular polarizability {gamma}-bar is investigated for calamitic and discotic uniaxial liquid crystals consisting of lath- and disk-shaped molecules. These liquid crystals with identical macroscopic symmetry differ in the local anisotropy and the relationships between the components L{sub parallel} < L{sub perpendicular} , f{sub parallel} < f{sub perpendicular} (calamitic) and L{sub parallel} > L{sub perpendicular} , f{sub parallel} > f{sub perpendicular} (discotic) for an electric field oriented parallel and perpendicular to the director. The limitations from below and above on the molecular polarizability {gamma}-bar due to the anisotropy of the tensors L and f are established for liquid crystals of both types. These limitations indicate that the molecular polarizability {gamma}-bar depends on the phase state and the temperature. The factors responsible for the nonphysical consequences of the local-field models based on the approximation {gamma}-bar = const are revealed. The theoretical inferences are confirmed by the experimental data for a number of calamitic nematic liquid crystals with different values of birefringence and the discotic liquid crystal Col{sub ho}.

  20. The manipulation of self-collimated beam in phononic crystals composed of orientated rectangular inclusions

    NASA Astrophysics Data System (ADS)

    Tsai, Chia-Nien; Chen, Lien-Wen

    2016-07-01

    Self-collimation is wave propagation in straight path without diffraction. The performance is evaluated by bandwidth, angular collimating range and straightness of equi-frequency contours. The present study aims to manipulate the self-collimated beam in square-array phononic crystals by means of orientated rectangular inclusions. Finite element simulations are performed to investigate the effects of the aspect ratio and orientation angle of rectangular inclusions on the self-collimated beam. The simulation results show that the proposed design successfully achieves all-angle self-collimation phenomenon. In addition, it also shows that the propagation direction of a self-collimated beam can be effectively manipulated by varying the orientation angle of inclusions. Numerical simulation result of the S-shaped bend demonstrates that acoustic collimated beam can be steered with negligible diffraction. Overall, the proposed design has significant potential for the realization of applications such as collimators, acoustic waveguides and other phononic crystals-based systems.

  1. Critical CuI buffer layer surface density for organic molecular crystal orientation change

    SciTech Connect

    Ahn, Kwangseok; Kim, Jong Beom; Lee, Dong Ryeol; Kim, Hyo Jung; Lee, Hyun Hwi

    2015-01-21

    We have determined the critical surface density of the CuI buffer layer inserted to change the preferred orientation of copper phthalocyanine (CuPc) crystals grown on the buffer layer. X-ray reflectivity measurements were performed to obtain the density profiles of the buffer layers and out-of-plane and 2D grazing-incidence X-ray diffraction measurements were performed to determine the preferred orientations of the molecular crystals. Remarkably, it was found that the preferred orientation of the CuPc film is completely changed from edge-on (1 0 0) to face-on (1 1 −2) by a CuI buffer layer with a very low surface density, so low that a large proportion of the substrate surface is bare.

  2. Vapor deposition of a smectic liquid crystal: highly anisotropic, homogeneous glasses with tunable molecular orientation.

    PubMed

    Gómez, Jaritza; Jiang, Jing; Gujral, Ankit; Huang, Chengbin; Yu, Lian; Ediger, M D

    2016-03-01

    Physical vapor deposition (PVD) has been used to prepare glasses of itraconazole, a smectic A liquid crystal. Glasses were deposited onto subtrates at a range of temperatures (Tsubstrate) near the glass transition temperature (Tg), with Tsubstrate/Tg ranging from 0.70 to 1.02. Infrared spectroscopy and spectroscopic ellipsometry were used to characterize the molecular orientation using the orientational order parameter, Sz, and the birefringence. We find that the molecules in glasses deposited at Tsubstrate = Tg are nearly perpendicular to the substrate (Sz = +0.66) while at lower Tsubstrate molecules are nearly parallel to the substrate (Sz = -0.45). The molecular orientation depends on the temperature of the substrate during preparation, allowing layered samples with differing orientations to be readily prepared. In addition, these vapor-deposited glasses are macroscopically homogeneous and molecularly flat. We interpret the combination of properties obtained for vapor-deposited glasses of itraconazole to result from a process where molecular orientation is determined by the structure and dynamics at the free surface of the glass during deposition. Vapor deposition of liquid crystals is likely a general approach for the preparation of highly anisotropic glasses with tunable molecular orientation for use in organic electronics and optoelectronics. PMID:26875700

  3. Crystal Shape, Rotation and Preferred Orientation in Rocks

    NASA Astrophysics Data System (ADS)

    Hiraga, T.; Maruyama, G.; Miyazaki, T.

    2014-12-01

    Recently, we have shown that a significant crystallographic preferred orientation (CPO) of forsterite develops during Newtonian flow of the forsterite aggregate (Miyazaki et al., 2013 Nature). Since the aggregate also exhibits (i) superplasticity (>>100 % tensile strain) (Hiraga, 2010 Nature), (ii) the same phase aggregation at the direction of compression (Hiraga et al. 2013 Geology) and (iii) essentially no change in grain shape before and after the deformation, we concluded that grain boundary sliding (GBS) should have accommodated a majority of the sample strain. One of the distinct natures of the observed CPO was that the preexisting grain shape, which is controlled by crystallography of forsterite, controls CPO development and its pattern. Based on these results, we concluded that the preferential GBS at the boundary parallel to the specific crystallographic plane (i.e., low-index plane grain boundary) resulted in CPO. The development of CPO requires a grain rotation toward the specific direction in the sample geometry. Such rotation was well identified by the shape change of line markers imposed on the sample surface prior to the sample deformation. Further, scanning probe microscopy on the sample surface reveals the anisotropic grain rotation, that is, a significant rotation around the axis perpendicular to the compression axis whereas essentially zero rotation around the axis parallel to the compression axis. We will demonstrate that such CPO, which is originated from crystallography-controlled GBS, is not limited to forsterite system but it is a common process in various mineral systems. CPO in rocks has been considered as a consequence of dislocation creep. Here we show an alternative model of CPO development in the earth's interior.

  4. Theory of two-dimensional self-assembly of Janus colloids: crystallization and orientational ordering.

    PubMed

    Shin, Homin; Schweizer, Kenneth S

    2014-01-14

    We study the rich crystalline phase behavior of amphiphilic spherical Janus colloids using a new formulation of self-consistent phonon theory that includes coupled translational and rotational entropic and enthalpic contributions to the free energy. In contrast to homogeneous spheres, broken rotational symmetry can result in more exotic crystals that possess distinct orientational patterns, and also plastic crystals. Ground states are identified based on the compatibility between the patch geometry of particles (e.g., patch coverage, number, shape) and lattice symmetry. We derive the explicit coupled self-consistent equations for translational and rotational localization parameters for effectively 2-dimensional dense monolayers of Janus crystals. The equations are numerically solved for a given crystal symmetry, thermodynamic state, and patch orientational order, and the thermodynamic stability of different phases is determined. For hexagonal packing, we predict with increasing temperature or decreasing attraction strength the possibility of a phase sequence of maximally bonded zigzag stripe, trimer, and rotationally disordered plastic crystal phases (or a phase sequence of trimer, dimer, and plastic crystal), which depends sensitively on particle chemical composition (Janus balance) and pressure. The role of rotational entropy in stabilizing the intermediate trimer (or dimer) phase at intermediate temperatures and high pressures is discussed in detail. Evolution of the center-of-mass vibrational and rotational amplitudes with thermodynamic state and Janus balance is also determined. PMID:24651877

  5. Orientational bistability and magneto-optical response in compensated ferronematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Zakhlevnykh, A. N.; Petrov, D. A.

    2016-03-01

    In the framework of continuum theory we consider magnetic field induced transitions in soft compensated ferronematic liquid crystals, i.e., suspensions of ferromagnetic nanoparticles in nematic solvents with equiprobable distribution of the particles parallel and antiparallel to the director. Such systems are liquid-crystalline analogs of antiferromagnetics. We study the sequence of re-entrant transitions (uniform compensated phase - non-uniform phase - uniform saturation phase - non-uniform phase) between phases with different orientations of the director and magnetization. These transitions take place under the magnetic field action in the case of weak coupling between disperse magnetic phase and nematic matrix. We show that these transitions can be first or second order, and obtain the expressions for determining the order of orientational transitions. For the case of first order transitions, when the ferronematic shows orientational bistability, we study magnetic field influence on the orientational behavior of the director and magnetization, redistribution of magnetic impurity, and magneto-optical response.

  6. Preresonance Raman single-crystal measurements of electronic transition moment orientations in N-acetylglycinamide

    SciTech Connect

    Pajcini, V.; Asher, S.A.

    1999-12-01

    The authors have examined electronic coupling between the two amide electronic transitions in a dipeptide and have found strong excitonic interactions in a case where the amide planes are almost perpendicular. The absorption and resonance Raman spectra of N-methylacetamide (NMA) and acetamide (AM) are compared to that of the dipeptide N-acetylglycinamide (NAGA), which is composed of linked primary and secondary amides. The authors measured the transition moment magnitudes of each of these species and also determined the orientation of the preresonance Raman tensor of NAGA in a single crystal. From these single-crystal tensor values, the NAGA diagonal Raman tensor orientations were calculated and compared to those expected for unperturbed primary and secondary amides oriented as in the NAGA crystal. Because the primary and secondary amide III vibrations are vibrationally uncoupled and nonoverlapping, their intensities can be used to determine the contributions to their resonance enhancement from the coupled NAGA electronic transitions. The Raman tensor major axes of the primary and secondary amide III and amide I vibrations do not lie in their corresponding amide planes, indicating excitonically coupled states which mix the primary and secondary amide transitions. These results are relevant to the understanding of amide coupling in peptides and proteins; the NAGA crystal conformation is similar to that of a type I {beta}-turn in peptides and proteins, with the amide planes nearly perpendicular to each other (dihedral angle 85{degree}).

  7. Molecular relaxations, molecular orientation, and the friction characteristics of polyimide films. [wear characteristics of polymeric lubricant

    NASA Technical Reports Server (NTRS)

    Fusaro, R. L.

    1975-01-01

    The friction characteristics of polyimide films bonded to metallic substrates were studied from 25 to 500 C. These results were interpreted in terms of molecular orientation and thermomechanical data obtained by torsional braid analysis (TBA). A large friction transition was found to occur at 40 + or - 10 C in a dry argon atmosphere (10 ppm H2O). It was postulated that the mechanical stresses of sliding transform or reorder the molecules on the surface into a configuration conducive to easy shear, such as an extended chain. The molecular relaxation which occurs in this temperature region appears to give the molecules the necessary freedom for this reordering process to occur. The effects of velocity, reversibility, and thermal prehistory on the friction properties of polyimide were also studied.

  8. The role of crystal orientation and surface proximity in the self-similar behavior of deformed Cu single crystals

    SciTech Connect

    Pang, Judy; Ice, Gene E; Liu, W.

    2010-01-01

    We report on novel 3D spatially resolved X-ray diffraction microscopy studies of self-affine behavior in deformed single crystals. This study extends surface profile measurements of self-affined morphology changes in single crystals during deformation to include local lattice rotations and sub-surface behavior. Investigations were made on the spatial correlation of the local lattice rotations in 8% tensile deformed Cu single crystals oriented with [1 2 3], [1 1 1] and [0 0 1] axes parallel to the tensile axis. The nondestructive depth-resolved measurements were made over a length scale of one to hundreds of micrometers. Self-affined correlation was found both at the surface and below the surface of the samples. A universal exponent for the power-law similar to that observed with surface profile methods is found at the surface of all samples but crystallographically sensitive changes are observed as a function of depth. Correlation lengths of the self-affine behavior vary with the [1 2 3] crystal exhibiting the longest self-affine length scale of 70 m with only 18 m for the [1 1 1] and [0 0 1] crystals. These measurements illuminate the transition from surface-like to bulk-like deformation behavior and provide new quantitative information to guide emerging models of self-organized structures in plasticity.

  9. Orientation characteristics in the RF electric shielding effects of superconducting BPSCCO plates

    NASA Astrophysics Data System (ADS)

    Nishikubo, T.; Endo, H.; Itoh, M.

    2010-06-01

    As one of the basic areas of research for improvement of the electromagnetic environment by use of a bulk high-critical temperature superconductor (HTS), the present paper has developed a Bi-Pb-Sr-Ca-Cu-O (BPSCCO) plate that displays orientation characteristics of the plane wave. To achieve these orientation characteristics, a slit was cut into the surface of the BPSCCO plate. The values of SDEH and SDEP are defined as the radio frequency (RF) electric shielding degrees when orienting the slit horizontal and perpendicular to the ground, respectively. The shieldings exhibit similar characteristics in the frequency region from 1 MHz (55 dB) to 100 MHz (30 dB). The values of SDEH, in the frequency region of 100 MHz (30 dB) to 3 GHz (52 dB), increased with frequency. The values of SDEP indicated an average value of 30 dB in this frequency region. Namely, the difference in the RF electric shielding degree, SDEH - SDEP, with respect to the orientation of the slit, represents the orientation characteristics. Experimental results revealed several characteristics of the BPSCCO plate that include the dependencies of the orientation characteristics on the length, width, and number of slits. Also examined were the orientation characteristics in the RF magnetic shielding effect of the BPSCCO plate as a function of radio frequency.

  10. New type of instrument for the orientation of the optical axis of crystal

    NASA Astrophysics Data System (ADS)

    Cao, Tianning

    1992-10-01

    In modern optical industry and optical research the anisotropic crystals, such as iceland, KDP, ADP, LiNbO3, crystalline quartz, etc., have been widely used for making various types of polarizers, optical shutters, interference polarization filters, and light modulators, etc. In order to improve the quality of crystal elements, the accuracy of crystal optical axis orientation must be improved. In this paper a new type of instrument is described for determining the perpendicular orientation of the crystal optical axis of a crystal plate to the plate surface. A converging bundle of polarized rays passes through the plate and forms a set of ring interferogram and a dark cross image in the interferogram. As the working stage is rotated, the center of the cross and the rings move along a circle, if the surface of the plate is not perpendicular to the optical axis. The accuracy of data read directly from a beeswax screen of (phi) 150 mm does not exceed six arc minutes. If the data and other parameters are input to a microcomputer IBM/PC to remove the theoretical deviations of the instrument the accuracy of two arc minutes can be obtained. The size of crystal under test can be (phi) 100 X (0.5 - 100) mm. Theoretical calculation shows that the accuracy of a thick crystal plate under test and the data read from an interferential ring of lower order of interference are improved. In this instrument the crystal cone interferogram, clean and bright, is projected on a screen, and it is suitable for teaching demonstration and shop testing. The cost of this instrument is lower because of its simple structure.

  11. Analysis of compression behavior of a [011] Ta single crystal with orientation imaging microscopy and crystal plasticity

    SciTech Connect

    Adams, B L; Campbell, G H; King, W E; Lassila, D H; Stolken, J S; Sun, S; Swartz, A J

    1999-02-03

    High-purity tantalum single crystal cylinders oriented with [011] parallel to the cylinder axis were deformed 10, 20, and 30 percent in compression. The engineering stress-strain curve exhibited an up-turn at strains greater than {approximately}20% while the samples took on an ellipsoidal shape during testing, elongated along the [100] direction with almost no dimensional change along [0{bar 1}1]. Two orthogonal planes were selected for characterization using Orientation Imaging Microscopy (OIM): one plane containing [100] and [011] (longitudinal) and the other in the plane containing [0{bar 1}1] and [011] (transverse). OIM revealed patterns of alternating crystal rotations that develop as a function of strain and exhibit evolving length scales. The spacing and magnitude of these alternating misorientations increases in number density and decreases in spacing with increasing strain. Classical crystal plasticity calculations were performed to simulate the effects of compression deformation with and without the presence of friction. The calculated stress-strain response, local lattice reorientations, and specimen shape are compared with experiment.

  12. Determination of crystal grain orientations by optical microscopy at textured surfaces

    SciTech Connect

    Lausch, D.; Gläser, M.; Hagendorf, C.

    2013-11-21

    In this contribution, a new method to determine the crystal orientation with the example of chemical treated silicon wafers by means of optical microscopy has been demonstrated. The introduced procedure represents an easy method to obtain all relevant parameters to describe the crystal structure of the investigated material, i.e., the crystal grain orientation and the grain boundary character. The chemical treatment is a standard mono-texture for solar cells, well known in the solar industry. In general, this concept can also be applied to other crystalline materials, i.e., GaAs, SiC, etc., the only thing that needs to be adjusted is the texturing method to reveal specific crystal planes and the calculation model. In conclusion, an application of this method is shown with the example of the defect classification of recombination active defects in mc-Si solar cell. The introduced method demonstrates a simple and quick opportunity to improve the crystallization process and the quality of electronic devices by means of an optical microscope and a chemical treatment of the material.

  13. Determination of the Crystal Axis Orientations of Ge detectors for the Majorana Demonstrator

    NASA Astrophysics Data System (ADS)

    Xu, Wenqin; Busch, Matthew; Elliott, Steven; Green, Matthew; Hegai, Alex; Henning, Reyco; Ronquest, Michael; Snavely, Kyle; Zitin, Ari

    2013-04-01

    High purity germanium (HPGe) crystals will be used for the Majorana Demonstrator, where they serve as both the source and the detector for neutrinoless double beta decays. Sophisticated pulse shape analysis (PSA) is crucial in distinguishing certain background events in the energy region of interest. It is also well known that the charge-carrier mobility in Ge crystals has considerable dependence on the crystallographic axes, resulting in a crystal axis dependence of the PSA. Meanwhile, as within the Peccei-Quinn solution to the strong CP problem and as a dark matter candidate, axions have been searched for in many experiments. It has been suggested that the postulated solar axions could coherently covert to photons by the Primakeoff effect in a periodic lattice, such as that found in the Ge crystals used by the Demonstrator, with conversion rates depending on the crystal axis orientation. In order to use the Demonstrator to search for solar axions, the Ge crystal axes need to be measured. In this talk, we will present our experimental measurements to characterize crystal axes with P-type point contact (PPC) HPGe detectors, which are cylindrical in shape with point contacts at the bottom.

  14. Characterization of the influence of polarization orientation on bulk damage in KDP crystals at different wavelengths

    NASA Astrophysics Data System (ADS)

    Zheng, YinBo; Ding, Lei; Zhou, XinDa; Ba, RongSheng; Yuan, Jing; Xu, HongLei; Na, Jin; Li, YaJun; Yang, XiaoYu; Chai, Liqun; Chen, Bo; Zheng, WanGuo

    2016-08-01

    The investigation of polarization orientation on damage performance of type I doubler KDP crystals under different wavelengths pulses irradiation is presented in this work. Pinpoints densities (PPD) and the size distribution of pinpoints are extracted through light scattering pictures captured by microscope. The obtained results indicate that the measured PPD as a function of the fluence is both wavelength and polarization dependent, although neither fluence nor polarization have impact on the size distribution of pinpoints. We also find that the damage performances can separate into three groups depending on the wavelength, which suggests the existence of different categories of precursors and different mechanisms responsible for bulk damage initiation in SHG KDP crystals.

  15. Investigating the role of oriented nucleus in polymer shish-kebab crystal growth via phase-field method

    NASA Astrophysics Data System (ADS)

    Wang, Xiaodong; Ouyang, Jie; Su, Jin; Zhou, Wen

    2014-03-01

    The phase-field method has been developed to simulate the shish-kebab crystal growth in polymer crystallization by introducing the oriented nucleus. With the help of this developed phase-field model, the role of oriented nucleus in polymer shish-kebab crystal growth has been investigated. It appears that the growth mechanisms of shish-kebab crystal on a preformed oriented nucleus may be attributed to epitaxial growth and lattice match. First the oriented nucleus (early shish) further grows into stable shish entity through epitaxial growth, and then lattice match supplies the sites for kebabs and epitaxial lateral growth from these sites forms the kebabs. It also has been verified that kebabs can be grown on oriented nucleus in the total absence of any flow. Therefore, with regard to flow induced shish-kebab crystal, the oriented nucleus plays a major role in the growth of shish-kebab morphology and the flow mainly helps to generate the oriented nucleus. Besides, when the nucleus possesses a rod-like profile, the kebabs are generally parallel and equidistantly distributed, and the well-defined interval between adjacent kebabs is strongly influenced by the orientation angle of the rod-like nucleus. On the other hand, when the nucleus is slightly curved and presents a thread-like profile, the distribution of kebabs on the shish is no longer equidistant and the influence of orientation angle on the kebab density becomes weak.

  16. Orientated Crystallization in Discontinuous Aramid Fiber/isotactic Polypropylene Composites under Shear Flow Conditions

    SciTech Connect

    Larin,B.; Marom, G.; Avila-Orta, C.; Somani, R.Hsiao, B.

    2005-01-01

    Melt blends of short aramid fibers (AF) and isotactic polypropylene (iPP) are subjected to shear at 145 C and the structural evolution and final morphology are examined by in situ synchrotron X-ray scattering/diffraction and high-resolution scanning electron microscopy, respectively. The results indicate that the presence of short AFs significantly enhances the crystallization of iPP. It is argued that shear flow in this system exerts a twofold orientating action, namely, on the bulk iPP molecules and on the short AFs. The resultant crystalline morphology reflects the combined effects of crystallization on orientated iPP molecules to facilitate a shish kebab morphology and at the interface of the aligned fibers, to form transcrystallinity.

  17. Smart dust: self-assembling, self-orienting photonic crystals of porous Si.

    PubMed

    Link, Jamie R; Sailor, Michael J

    2003-09-16

    Micrometer-sized one-dimensional photonic crystals of porous Si that spontaneously assemble, orient, and sense their local environment are prepared. The photonic crystals are generated by electrochemically etching two discrete porous multilayered dielectric mirrors into Si, one on top of the other. The first mirror is chemically modified by hydrosilylation with dodecene before the etching of the second mirror, which is prepared with an optical reflectivity spectrum that is distinct from the first. The entire film is removed from the substrate, and the second mirror is then selectively modified by mild thermal oxidation. The films are subsequently fractured into small particles by sonication. The chemically asymmetric particles spontaneously align at an organic liquid-water interface, with the hydrophobic side oriented toward the organic phase and the hydrophilic side toward the water. Sensing is accomplished when liquid at the interface infuses into the porous mirrors, inducing predictable shifts in the optical spectra of both mirrors. PMID:12947036

  18. Anisotropy and crystal orientation of silicon--application to the modeling of a bent mirror

    SciTech Connect

    Zhang Lin

    2010-06-23

    Matrix formula and MATLAB algorithm are proposed to calculate the stiffness coefficient matrix C, the Young's modulus, shear modulus and Poisson ratio for the silicon crystal in any orientation. Results for Si(110) and Si(311) are given as an example. The anisotropic material properties of the silicon have been used in the mirror width profile optimization for the nano-imaging end-station ID22NI at the ESRF. As the Si(110) is used as the substrate of this multilayer coated KB mirror, the silicon crystal axis [0 0 1] is proposed to orient to the mirror axis. This is the case to have low stress in the mirror and low bending forces from actuators.

  19. Homeotropic orientation of a nematic liquid crystal by bent-core molecules adsorbed on its surface

    NASA Astrophysics Data System (ADS)

    Hwang, Jiyong; Yang, Seungbin; Lee, Hyojin; Kim, Jongyoon; Lee, Ji-Hoon; Kang, Shin-Woong; Choi, E.-Joon

    2015-06-01

    We reported the promotion of a homeotropic alignment of a nematic liquid crystal (NLC) by bent-core liquid-crystal (BLC) Molecules adsorbed its surface. The BLC was mixed at various concentrations with the NLC, and the mixtures were injected into an empty cell with a cell gap of 13 μm. Although the pure NLC showed a heterogeneous orientation, the BLC-NLC mixture was gradually transformed to a homeotropic alignment with increasing concentration of the BLC. We investigated the surface topography of the samples by using an atomic force microscopy (AFM) and found that the BLC molecules were segregated into a polyimide (PI) surface and formed protrusion domains with diameters of 50-100 nm. The BLC protrusions might promote the homeotropic orientation of the NLC molecules.

  20. Effect of crystal orientation on anisotropic etching and MOCVD growth of grooves on GaAs

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Landis, Geoffrey A.; Wilt, David M.

    1989-01-01

    Grooves can be formed on GaAs by wet-chemical anisotropic etching of surfaces masked by photoresist stripes. The effect of crystal orientation on the shape of the grooves etched and on subsequent epitaxial growth by MOCVD is presented. The polar lattice increases the complexity of the etching and growth processes. The slow-etch planes defined by anisotropic etching are not always the same as the growth facets produced during MOCVD deposition, especially for deposition on higher order planes.

  1. Orientation control of liquid crystals using carbon-nanotube-magnetic particle hybrid materials.

    PubMed

    Jeong, Hyeon Su; Youn, Sang Cheon; Kim, Yun Ho; Jung, Hee-Tae

    2013-06-28

    We have developed a simple yet versatile method for aligning liquid crystals (LCs) by using magnetic-field oriented single-walled carbon nanotubes (SWNTs) that were modified with magnetic particles. A high degree of homeotropic/planar LC alignment was achieved by SWNTs being exposed to a very low strength magnetic field, combined with strong π-π interactions between the biphenyl group in the LCs and the wall of the SWNTs. PMID:23676827

  2. Joint investigation of the local material rotation and lattice spin in a cube {100} <001> oriented single crystal

    NASA Astrophysics Data System (ADS)

    Darrieulat, M.; Fillit, R. Y.; Mondon, M.; Sao-Joao, S.

    2010-07-01

    Cube {100} <001> oriented single crystals of Al 1% Mn were compressed in channel-die. Their lateral faces were covered with transferable carbon grids with a step of 100mm . At a deformation of about 0.3, the vertical bars of the grids show undulations whose characteristic length is of the order of the millimetre and which become sharper and smaller as the deformation proceeds. Fiducial golden grids with a step of 20 mm remain largely unaffected. This shows that the investigated heterogeneity is typical of the mesoscopic scale and has no directly related patterns at the macroscopic and microscopic level. Microfocussed X-rays were used to measure the crystallographic rotations during the process. The investigated spot was a few 0.1 mm2. At a deformation of 0.6, the lateral faces of the crystal undergo a split into two Cube orientations each rotated of about 15° around the transverse axis. This is put in relation with the undulations of the bars. At 0.9 an additional rotation around the longitudinal axis appears. The local material rotation and the lattice spin at the mesoscopic scale are interpreted in accordance with previous analyses of the evolution of the Cube texture based on EBSD and the observation of the traces of slip systems.

  3. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    NASA Astrophysics Data System (ADS)

    Miura, Terumitsu; Fujii, Katsuhiko; Fukuya, Koji; Takashima, Keisuke

    2011-10-01

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe 2+ ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  4. Device and method of optically orienting biaxial crystals for sample preparation

    NASA Astrophysics Data System (ADS)

    Thomas, Timothy; Rossman, George R.; Sandstrom, Mark

    2014-09-01

    An optical instrument we refer to as the "biaxial orientation device" has been developed for finding the optical plane, acute bisectrix, and obtuse bisectrix in biaxial crystals by means of optically aligning conoscopically formed melatopes and measuring the angular coordinates of the melatopes, where the angular values allow for determination of the optical plane containing the optical axes using a vector algebra approach. After determination of the optical plane, the instrument allows for the sample to be aligned in the acute bisectrix or obtuse bisectrix orientations and to be transferred to a simple mechanical component for subsequent grinding and polishing, while preserving the orientation of the polished faces relative to the optical plane, acute bisectrix, and obtuse bisectrix during the grinding and polishing process. Biaxial crystalline material samples prepared in the manner are suitable for accurate spectroscopic absorption measurements in the acute bisectrix and obtuse bisectrix directions as well as perpendicular to the optical plane.

  5. Transient Liquid Phase Bonding Single-Crystal Superalloys with Orientation Deviations: Creep Properties

    NASA Astrophysics Data System (ADS)

    Sheng, Naicheng; Liu, Jide; Jin, Tao; Sun, Xiaofeng; Hu, Zhuangqi

    2015-12-01

    Superalloys single crystals with various orientation deviations were bonded using transient liquid phase bonding method, then the creep properties of the bonded specimens were tested at 1033 K (760 °C)/780 MPa. It is found that the creep life of the bonded specimens decreases with the increase of the relative orientation deviations. Despite the fracture of the specimens appears on the bonding region, the deformation mechanism changes from specimens with low angle boundary to high angle boundary. In low angle boundary specimens, cleavage originated from the defects grows perpendicularly to the tensile stress and connects through the different slip planes around the cleavage planes. In this case, the deformation proceeds by the dislocations and stacking faults on multi-planes. With increasing orientation deviation, dislocation and stacking faults moved on single plane. As a result, the dislocations interact with the grain boundary and lead to fracture. Based on the present investigation, the orientation of the bonded superalloys single crystal should be controlled so that the introduced grain boundaries are relatively small and exhibit higher creep strength.

  6. Ultraweak azimuthal anchoring of a nematic liquid crystal on a planar orienting photopolymer

    SciTech Connect

    Nespoulous, Mathieu; Blanc, Christophe; Nobili, Maurizio

    2007-10-01

    The search of weak anchoring is an important issue for a whole class of liquid crystal displays. In this paper we present an orienting layer showing unreached weak planar azimuthal anchoring for 4-n-pentyl-4{sup '}-cyanobiphenyl nematic liquid crystal (5CB). Azimuthal extrapolation lengths as large as 80 {mu}m are easily obtained. Our layers are made with the commercial photocurable polymer Norland optical adhesive 60. The anisotropy of the film is induced by the adsorption of oriented liquid crystal molecules under a 2 T magnetic field applied parallel to the surfaces. We use the width of surface {pi}-walls and a high-field electro-optical method to measure, respectively, the azimuthal and the zenithal anchorings. The azimuthal anchoring is extremely sensitive to the ultraviolet (UV) dose and it also depends on the magnetic field application duration. On the opposite, the zenithal anchoring is only slightly sensitive to the preparation parameters. All these results are discussed in terms of the adsorption/desorption mechanisms of the liquid crystal molecules on the polymer layer and of the flexibility of the polymer network.

  7. Determination of the orientation of the ice crystals in a cloud

    NASA Astrophysics Data System (ADS)

    Kaul, Bruno V.; Werner, Christian; Herrmann, H.

    1995-09-01

    Theoretical grounds are given in this paper for two methods of determining preferred orientation of crystal particles in a cloud. The methods proposed in the paper enable one to do this in a much simpler way than it could be done when measuring full backscattering phase matrix. One of the methods proposed assumes that a polarization lidar can be rotated as a whole, while the second technique uses rotation of the polariztion plane of a linearly polarized sounding beam. Feasibility of the former technique is illustrated in the paper with the results of field experiments on sounding of a snowfall. Recent experimental studies of crystal clouds conducted with a polarization lidar capable of measuring backscattering phase matrices (BPM) have revealed the fact that preferred orientation of symmetry axes of particles in crystal clouds is very often observed to be in horizontal plane. This conclusion is drawn from the fact that off-diagonal elements of BPMs measured differ from zero. Using a model ensemble of crystal particles of axially symmetric plates and columns one can determine the direction of preferred orientation and the degree of particles orientation about this direction. For many practical reasons it is quite desirable to try to construct a technique for detecting situations in clouds under study when a preferred orientation of crystal particles occurs, which is more simple than that based on measurements of BPMs of clouds. Below we describe two possible versions of lidar measurements using a polarization lidar with a linearly polarized sounding radiation. Such a lidar can record two cross polarized components of lidar returns from scattering medium, i.e. two first Stokes parameters. One of the versions assumes that a lidar facility can be turned around the sounding beam axis as a whole, white in the second version we need to use a (lambda) /2 phase plate in the lidar transmitter to enable changes of sounding beam polarization. In order to make understanding of

  8. Thermophysical characteristics of EuF2.136 crystal

    NASA Astrophysics Data System (ADS)

    Popov, P. A.; Moiseev, N. V.; Karimov, D. N.; Sorokin, N. I.; Sulyanova, E. A.; Sobolev, B. P.

    2015-09-01

    Single crystals of EuF2.136 solid solution with a f luorite-type structure (sp. gr. , a = 5.82171(5) Å) have been grown by the Bridgeman method from a melt. Their thermal conductivity k( T) in the temperature range of 50-300 K and heat capacity С Р ( T) at 63-300 K have been studied experimentally for the first time. At T = 300 K the thermophysical characteristics are as follows: thermal conductivity k = 2.13 W/(m K), heat capacity С Р = 73 J/(mol K), and phonon mean free path l ≈ 11 Å. The temperature dependences of entropy S( T), enthalpy H( T), and phonon mean free path l( T) in EuF2.136 crystal are determined.

  9. Protein crystal structure from non-oriented, single-axis sparse X-ray data

    PubMed Central

    Wierman, Jennifer L.; Lan, Ti-Yen; Tate, Mark W.; Philipp, Hugh T.; Elser, Veit; Gruner, Sol M.

    2016-01-01

    X-ray free-electron lasers (XFELs) have inspired the development of serial femtosecond crystallography (SFX) as a method to solve the structure of proteins. SFX datasets are collected from a sequence of protein microcrystals injected across ultrashort X-ray pulses. The idea behind SFX is that diffraction from the intense, ultrashort X-ray pulses leaves the crystal before the crystal is obliterated by the effects of the X-ray pulse. The success of SFX at XFELs has catalyzed interest in analogous experiments at synchrotron-radiation (SR) sources, where data are collected from many small crystals and the ultrashort pulses are replaced by exposure times that are kept short enough to avoid significant crystal damage. The diffraction signal from each short exposure is so ‘sparse’ in recorded photons that the process of recording the crystal intensity is itself a reconstruction problem. Using the EMC algorithm, a successful reconstruction is demonstrated here in a sparsity regime where there are no Bragg peaks that conventionally would serve to determine the orientation of the crystal in each exposure. In this proof-of-principle experiment, a hen egg-white lysozyme (HEWL) crystal rotating about a single axis was illuminated by an X-ray beam from an X-ray generator to simulate the diffraction patterns of microcrystals from synchrotron radiation. Millions of these sparse frames, typically containing only ∼200 photons per frame, were recorded using a fast-framing detector. It is shown that reconstruction of three-dimensional diffraction intensity is possible using the EMC algorithm, even with these extremely sparse frames and without knowledge of the rotation angle. Further, the reconstructed intensity can be phased and refined to solve the protein structure using traditional crystallographic software. This suggests that synchrotron-based serial crystallography of micrometre-sized crystals can be practical with the aid of the EMC algorithm even in cases where the data

  10. Protein crystal structure from non-oriented, single-axis sparse X-ray data.

    PubMed

    Wierman, Jennifer L; Lan, Ti-Yen; Tate, Mark W; Philipp, Hugh T; Elser, Veit; Gruner, Sol M

    2016-01-01

    X-ray free-electron lasers (XFELs) have inspired the development of serial femtosecond crystallography (SFX) as a method to solve the structure of proteins. SFX datasets are collected from a sequence of protein microcrystals injected across ultrashort X-ray pulses. The idea behind SFX is that diffraction from the intense, ultrashort X-ray pulses leaves the crystal before the crystal is obliterated by the effects of the X-ray pulse. The success of SFX at XFELs has catalyzed interest in analogous experiments at synchrotron-radiation (SR) sources, where data are collected from many small crystals and the ultrashort pulses are replaced by exposure times that are kept short enough to avoid significant crystal damage. The diffraction signal from each short exposure is so 'sparse' in recorded photons that the process of recording the crystal intensity is itself a reconstruction problem. Using the EMC algorithm, a successful reconstruction is demonstrated here in a sparsity regime where there are no Bragg peaks that conventionally would serve to determine the orientation of the crystal in each exposure. In this proof-of-principle experiment, a hen egg-white lysozyme (HEWL) crystal rotating about a single axis was illuminated by an X-ray beam from an X-ray generator to simulate the diffraction patterns of microcrystals from synchrotron radiation. Millions of these sparse frames, typically containing only ∼200 photons per frame, were recorded using a fast-framing detector. It is shown that reconstruction of three-dimensional diffraction intensity is possible using the EMC algorithm, even with these extremely sparse frames and without knowledge of the rotation angle. Further, the reconstructed intensity can be phased and refined to solve the protein structure using traditional crystallographic software. This suggests that synchrotron-based serial crystallography of micrometre-sized crystals can be practical with the aid of the EMC algorithm even in cases where the data are

  11. Epitaxy versus oriented heterogeneous nucleation of organic crystals on ionic substrates

    NASA Astrophysics Data System (ADS)

    Sarma, K. R.; Shlichta, P. J.; Wilcox, W. R.; Lefever, R. A.

    1997-04-01

    It is plausible to assume that epitaxy is a special case of heterogeneous nucleation in which a restrictive crystallographic relationship exists between substrate and deposit orientations. This would mean that epitaxial substrates should always induce a perceptible reduction in the critical supercooling for nucleation of the deposit. To test this hypothesis, the critical supercoolings of six organic compounds were measured on glass and 11 single-crystal cleaved substrates including (0001) graphite, (001) mica, (111) BaF 2, SrF 2, and CaF 2, and (100) KCl, KBr, KI, NaCl, NaF, and LiF. Reductions in supercooling (with reference to glass substrates) were checked many times for repeatability and reproducibility and shown in almost all cases to have a standard deviation of 1 C or less. Acetanilide, benzoic acid, and p-bromochlorobenzene showed a wide range of supercooling reductions and were oriented on all crystalline substrates. Naphthalene and p-dibromobenzene showed only slight supercooling reductions but were oriented on all substrates, including glass. Benzil showed strong supercooling reductions only for mica and KI but was oriented not only in these cases but also with KI, BaF 2, CaF 2, and graphite. There was little correlation between degree of lattice match and either supercooling reduction or degree of preferred orientation. These results suggest that, for the systems and geometry studied, forces such as molecular dipole binding and growth anisotropy had a stronger effect than lattice match.

  12. Stresses and orientational order in shearing flows of granular liquid crystals

    NASA Astrophysics Data System (ADS)

    Berzi, Diego; Thai-Quang, Nha; Guo, Yu; Curtis, Jennifer

    2016-04-01

    We perform discrete element simulations of homogeneous shearing of frictionless cylinders and show that the particles are characterized by orientational order and form a granular liquid crystal. For elongated and flat cylinders, the alignment is in the plane of shearing, while cylinders having an aspect ratio equal to 1 and 0.8 show no orientational order. We show that the particle pressure is insensitive to the cylinder aspect ratio and well predicted by the kinetic theory of granular gases, with a singularity in the radial distribution function at contact different from that for frictionless spheres. The numerical results quantitatively agree with physical experiments on different geometries. The particle shear stress is affected by orientational anisotropy. We postulate that, for frictionless cylinders, the viscosity is roughly due to the motion of the orientationally disordered fraction of the particles, and show that it is proportional, through the order parameter, to the expression of kinetic theory. Finally, we suggest that the orientational order is the result of the competing effects of the shear rate, which induces alignment, and the granular temperature, which ramdomizes.

  13. Effects of crystal orientation on electronic band structure and anomalous shift of higher critical point in VO2 thin films during the phase transition process

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Huang, Ting; You, Qinghu; Zhang, Jinzhong; Li, Wenwu; Wu, Jiada; Hu, Zhigao; Chu, Junhao

    2015-12-01

    The phase transition behaviour of vanadium dioxide (VO2) with different thicknesses has been investigated by temperature-dependent optical transmittance and Raman spectra. It is found that the crystal orientation has a great effect on the metal-insulator transition (MIT) of VO2 films. The x-ray diffraction (XRD) analysis shows that the films are polycrystalline and exhibit the characteristics of the monoclinic phase. The preferential growth crystal orientation (0 2 0) is converted to the (\\bar{1} 1 1) plane with the film thickness increasing. It is believed that the (\\bar{1} 1 1) plane is the reflection of a twinned structure with (0 1 1) crystal orientation, which will lead to the arrangements of oxygen atoms and vanadium atoms deviating from the pure monoclinic structure. It is found that the highest order transition (E 3) is highly susceptible to the crystal orientation, whereas the lowest order transition (E 1) is nearly unaffected by it. The E 3 exhibits an anomalous temperature dependence with an abrupt blue-shift (˜0.5 eV) in the vicinity of the metal-insulator transition (MIT) for VO2 film with a thickness of 84 nm. The findings show that the empty {σ*} band can be driven close to the Fermi level when the (0 2 0) orientation is converted to the (\\bar{1} 1 1) orientation. Compared to the VO2 films with thicknesses of 39 and 57 nm, the E 3 decreases by 0.8 eV and the E 2 increases by about 0.1 eV at the insulator state for the VO2 film with a thickness of 84 nm. The abnormal electronic transition and the variation of energy band is likely caused by the lattice distortion and V-V dimerisation deviation from the monoclinic {{a}\\text{m}} axis.

  14. Effect of crystallographic orientation on plastic deformation of single crystal nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Westbrooke, Eboni F.

    Nickel-base superalloys, with gamma/gamma' microstructure, are the primary material used in turbines for aerospace applications. The blades in the hottest region of the turbine engine are made of single crystal Ni-base superalloys. It has been shown that the critical resolved shear stress (CRSS) of these materials is orientation dependent (also known as non-Schmid effect). The purpose of this research was to investigate the plastic deformation mechanisms of single crystal Ni-base superalloys as a function of crystallographic orientation in order to understand the factors that contribute to the non-Schmid effect. The superalloys in this study possessed alloying elements in amounts which defined them as 1st and 2nd generation superalloys. Tensile samples of various orientations were loaded to different strain levels. The mechanisms of plastic deformation were characterized by optical and scanning electron microscopy (SEM) observations of deformation bands as well as the dislocation structures using transmission electron microscopy (TEM). It was confirmed that the CRSS of the single crystals did not follow Schmid's law and the near <111> specimens showed the lowest values. The degree of non-Schmid behavior in the <111> specimens was diminished by HIP'ing, which resulted in closure of solidification pores. Furthermore, it was shown that the CRSS for the <100> loaded samples was smallest when loaded along the secondary dendrite arms. The slip analysis by optical microscopy showed that the deformation bands did not follow the expected {111} slip planes for all samples. Studies in SEM proved that those slip bands that followed the {111} planes were associated with extensive shearing of gamma' particles. In addition, it was found that the presence of tri-axial stress states within the macrostructure influenced the deformation path significantly. The TEM observations of deformed specimens revealed that plastic deformation took place mainly in the gamma channels in specimens

  15. Development of crystal preferred orientation of olivine during diffusion creep: a matter of olivine crystal shape

    NASA Astrophysics Data System (ADS)

    Miyazaki, T.; Sueyoshi, K.; Hiraga, T.

    2013-12-01

    Crystalloagraphic preferred orientation (CPO) of olivine produced during dislocation creep is considered the primary cause of elastic anisotropy in the upper mantle of Earth and is used by seismologists to determine the direction of flow. Here we show that synthetic Fe-free olivine aggregates with either diopside or melt develop strong to weak CPO during grain boundary sliding (GBS) accommodated by diffusion. GBS on boundaries that correspond to specific crystallographic planes produces CPO. By combining the CPO patterns developed during tension and compression experiments, we predict formation in the mantle of three different CPO patterns depending on temperature and the presence of melt. Strong radial anisotropy is anticipated for GBS accommodated by diffusion during simple shear deformation at temperatures from 0.92*Ts to Ts (Ts: solidus temperature). These conditions correspond to depths where melting initiates to 50-100 km deeper and where strongly anisotropic and low seismic velocities are detected.

  16. Vertical Liquid Crystal Orientation on Amorphous Tantalum Pentoxide Surfaces Depending on Anisotropic Dipole-Dipole Interaction via Ion Beam Irradiation

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Jin; Kim, Hyung-Jun; Kang, Young-Gu; Kim, Young-Hwan; Park, Hong-Gyu; Kim, Byoung-Yong; Seo, Dae-Shik

    2011-03-01

    We achieved vertically aligned (VA) liquid crystals (LCs) on amorphous tantalum pentoxide (Ta2O5) alignment films deposited by radio frequency (rf) magnetron sputtering using ion beam (IB) irradiation. By analyzing measurements by X-ray photoelectron spectroscopy (XPS), we confirmed the bond breaking, as detected from the O 1s spectra, which caused an isotropic dipole-dipole interaction between the LC molecules and the Ta2O5 alignment film to uniformly align the vertical LC molecular orientation as a function of IB energy density. Moreover, by examining the electro-optical (EO) characteristics of the Ta2O5 surfaces compared with those of the polyimide (PI) alignment layer, we confirmed that Ta2O5 has a low threshold voltage and a low power consumption when used as an LC alignment layer.

  17. Polarization orientation dependence of the far infrared spectra of oriented single crystals of 1,3,5,-trinitro-s-triazine (RDX) using terahertz-time-domain spectroscopy

    SciTech Connect

    Whitley, Von H; Hooks, Dan E; Ramos, Kyle J; O' Hara, John F; Azad, A K; Taylor, A J; Barber, J; Averitt, R D

    2008-01-01

    The far infrared spectra of (100), (010), and (001)-oriented RDX single crystals were measured as the crystal was rotated about the axis perpendicular to the polarization plane of the incident radiation. Absorption measurements were taken at temperatures of both 20 K and 295 K for all rotations using terahertz time-domain spectroscopy. A number of discrete absorptions were found ranging from 10-100 cm(-1) (0.3-3 THz). The absorptions are highly dependent on the orientation of the terahertz polarization with respect to crystallographic axes.

  18. The Influence of Job Characteristics and Self-Directed Learning Orientation on Workplace Learning

    ERIC Educational Resources Information Center

    Raemdonck, Isabel; Gijbels, David; van Groen, Willemijn

    2014-01-01

    Given the increasing importance of learning at work, we set out to examine the factors which influence workplace learning behaviour. The study investigated the influence of the job characteristics from Karasek's Job Demand Control Support model and the personal characteristic self-directed learning orientation on workplace learning. A total…

  19. Mechanisms for Species-Selective Oriented Crystal Growth at Organic Templates

    SciTech Connect

    Kewalramani,S.; Kim, K.; Evmenenko, G.; Zschack, P.; Karapetrova, E.; Bai, J.; Dutta, P.

    2007-01-01

    Langmuir monolayers floating on supersaturated aqueous subphases can act as templates for the growth of oriented inorganic films--a 'bioinspired' nucleation process. We have performed in situ grazing incidence x-ray diffraction studies of the selective nucleation of BaClF and BaF2 under fatty acid monolayers. The arrangement of the fatty acid headgroups, the monolayer charge, and ion-specific effects all play important roles in selecting the inorganic species. When the monolayer is in a neutral state, both BaClF and BaF2 nucleate at the interface and are well aligned, but when the monolayer headgroup is deprotonated, only oriented BaF2 grows at the interface. We also observe an enhanced alignment of BaF2 crystals during growth from highly supersaturated solutions, presumably due to reorganization of preformed crystals at the organic template. These results show that a delicate interplay between multiple factors governs the oriented growth of inorganic films at organic templates.

  20. Localization and orientation of heavy-atom cluster compounds in protein crystals using molecular replacement

    PubMed Central

    Dahms, Sven O.; Kuester, Miriam; Streb, Carsten; Roth, Christian; Sträter, Norbert; Than, Manuel E.

    2013-01-01

    Heavy-atom clusters (HA clusters) containing a large number of specifically arranged electron-dense scatterers are especially useful for experimental phase determination of large complex structures, weakly diffracting crystals or structures with large unit cells. Often, the determination of the exact orientation of the HA cluster and hence of the individual heavy-atom positions proves to be the critical step in successful phasing and subsequent structure solution. Here, it is demonstrated that molecular replacement (MR) with either anomalous or isomorphous differences is a useful strategy for the correct placement of HA cluster compounds. The polyoxometallate cluster hexasodium α-metatungstate (HMT) was applied in phasing the structure of death receptor 6. Even though the HA cluster is bound in alternate partially occupied orientations and is located at a special position, its correct localization and orientation could be determined at resolutions as low as 4.9 Å. The broad applicability of this approach was demonstrated for five different derivative crystals that included the compounds tantalum tetradeca­bromide and trisodium phosphotungstate in addition to HMT. The correct placement of the HA cluster depends on the length of the intramolecular vectors chosen for MR, such that both a larger cluster size and the optimal choice of the wavelength used for anomalous data collection strongly affect the outcome. PMID:23385464

  1. Orientation dependent oxygen exchange kinetics on single crystal SrTiO3 surfaces.

    PubMed

    Kerman, Kian; Ko, Changhyun; Ramanathan, Shriram

    2012-09-14

    The perovskite SrTiO(3) is arguably one of the most important oxide systems in condensed matter research. In this study, we report measurement of the orientation dependence of oxygen exchange on SrTiO(3) single crystal surfaces by dynamic conductivity measurements under electrochemical perturbations. Activation energy for electrical conduction in the 923-1223 K range at an oxygen partial pressure of ∼10(-11) Pa of (100), (111), and (110) single crystals was found to be 2.6 eV, 2.7 eV, and 3.1 eV, respectively. The equilibration kinetics show profound dependence on the surface orientation and are modelled using a heterogeneous relaxation process. All surfaces show similar cationic sub-lattice limited rate behavior with (111), (100), and (110) having the fastest, intermediate, and slowest rates, respectively. We discuss the orientation dependence and its relation to local atomic structure in light of previous experimental and theoretical studies. PMID:22850487

  2. Improved crystal orientation and physical properties from single-shot XFEL stills

    SciTech Connect

    Sauter, Nicholas K. Hattne, Johan; Brewster, Aaron S.; Echols, Nathaniel; Zwart, Petrus H.; Adams, Paul D.

    2014-12-01

    X-ray free-electron laser crystallography relies on the collection of still-shot diffraction patterns. New methods are developed for optimal modeling of the crystals’ orientations and mosaic block properties. X-ray diffraction patterns from still crystals are inherently difficult to process because the crystal orientation is not uniquely determined by measuring the Bragg spot positions. Only one of the three rotational degrees of freedom is directly coupled to spot positions; the other two rotations move Bragg spots in and out of the reflecting condition but do not change the direction of the diffracted rays. This hinders the ability to recover accurate structure factors from experiments that are dependent on single-shot exposures, such as femtosecond diffract-and-destroy protocols at X-ray free-electron lasers (XFELs). Here, additional methods are introduced to optimally model the diffraction. The best orientation is obtained by requiring, for the brightest observed spots, that each reciprocal-lattice point be placed into the exact reflecting condition implied by Bragg’s law with a minimal rotation. This approach reduces the experimental uncertainties in noisy XFEL data, improving the crystallographic R factors and sharpening anomalous differences that are near the level of the noise.

  3. Estimation of diffusion anisotropy in microporous crystalline materials and optimization of crystal orientation in membranes.

    PubMed

    Gounaris, Chrysanthos E; First, Eric L; Floudas, Christodoulos A

    2013-09-28

    The complex nature of the porous networks in microporous materials is primarily responsible for a high degree of intracrystalline diffusion anisotropy. Although this is a well-understood phenomenon, little attention has been paid in the literature with regards to classifying such anisotropy and elucidating its effect on the performance of membrane-based separation systems. In this paper, we develop a novel methodology to estimate full diffusion tensors based on the detailed description of the porous network geometry through our recent advances for the characterization of such networks. The proposed approach explicitly accounts for the tortuosity and complex connectivity of the porous framework, as well as for the variety of diffusion regimes that may be experienced by a guest molecule while it travels through the different localities of the crystal. Results on the diffusion of light gases in silicalite demonstrate good agreement with results from experiments and other computational techniques that have been reported in the literature. A comprehensive computational study involving 183 zeolite frameworks classifies these structures in terms of a number of anisotropy metrics. Finally, we utilize the computed diffusion tensors in a membrane optimization model that determines optimal crystal orientations. Application of the model in the context of separating carbon dioxide from nitrogen demonstrates that optimizing crystal orientation can offer significant benefit to membrane-based separation processes. PMID:24089791

  4. Mechanisms of liquid crystal and biopolymer alignment on highly-oriented polymer thin films

    NASA Astrophysics Data System (ADS)

    Dennis, John Raymond

    1998-12-01

    Molecular order can strongly enhance material properties, or produce materials which perform advanced functions. Many materials, from small crystals to large macromolecules, may be aligned on highly-oriented poly(tetrafluoroethylene) (PTFE) or high-density polyethylene (HDPE) thin films, prepared by a simple shear deposition procedure. Here, processes by which these films produce order are examined, first in a well- characterized liquid crystal, then in two more complex polymer liquid crystals, and finally in an adsorbed motor protein system. Optical second harmonic generation (SHG) was used to study surface molecular order in the liquid crystal 4'-n-octyl-4-cyano-biphenyl (8CB) on PTFE and HDPE films. In nematic 8CB cells with bulk alignment along the polymer orientation axis, the surface monolayers of 8CB were also aligned, and showed C2ν symmetry. In the isotropic phase, the surface monolayer alignment was lost. Monolayers of 8CB evaporated onto either polymer showed little or no alignment. The bulk 8CB alignment appears to be primarily caused by surface ridges through an elastic, bulk- mediated mechanism, unlike the epitaxy-like alignment found on some cloth-rubbed polymer surfaces. For the polymer liquid crystal poly-γ-benzyl- glutamate (PBG), uniform homogeneous surface alignment was observed on PTFE films; this is the first report of PBG surface alignment. However, liquid crystalline samples of microtubules were not aligned. PTFE films show promise for aligning some other polymer liquid crystals via elastic interactions. The motor protein kinesin, adsorbed to PTFE films, transported fluorescently labeled microtubules predominantly in straight lines along the films' orientation axis, not in random directions as observed on glass surfaces. As the kinesin surface density was increased, the degree of alignment peaked and then declined. The results indicate that directed motion occurs because active kinesin preferentially adsorbs to surface sites along linear

  5. The effect of crystal orientation on the cryogenic strength of hydroxide catalysis bonded sapphire

    NASA Astrophysics Data System (ADS)

    Haughian, K.; Douglas, R.; van Veggel, A. A.; Hough, J.; Khalaidovski, A.; Rowan, S.; Suzuki, T.; Yamamoto, K.

    2015-04-01

    Hydroxide catalysis bonding has been used in gravitational wave detectors to precisely and securely join components of quasi-monolithic silica suspensions. Plans to operate future detectors at cryogenic temperatures has created the need for a change in the test mass and suspension material. Mono-crystalline sapphire is one candidate material for use at cryogenic temperatures and is being investigated for use in the KAGRA detector. The crystalline structure of sapphire may influence the properties of the hydroxide catalysis bond formed. Here, results are presented of studies of the potential influence of the crystal orientation of sapphire on the shear strength of the hydroxide catalysis bonds formed between sapphire samples. The strength was tested at approximately 8 K; this is the first measurement of the strength of such bonds between sapphire at such reduced temperatures. Our results suggest that all orientation combinations investigated produce bonds of sufficient strength for use in typical mirror suspension designs, with average strengths >23 MPa.

  6. Recording of polarization holograms in a liquid crystal cell with a photosensitive chalcogenide orientation layer [Invited].

    PubMed

    Sheremet, Nina; Kurioz, Yuriy; Slyusarenko, Kostyantyn; Trunov, Michael; Reznikov, Yuriy

    2013-08-01

    Polarization gratings have been recorded in a combined liquid crystal (LC) cell made of a substrate covered with a photosensitive chalcogenide orientation layer and a reference substrate covered with a rubbed polyimide film. The gratings are formed due to the spatially modulated light-induced easy orientation axis on the chalcogenide surface recorded by two beams with opposite circular polarizations. The gratings are permanent, but they can be erased by one of the recording beams and re-recorded. The diffraction intensity of the circularly polarized light is achromatic and does not depend on the birefringence of the LC. The diffraction efficiency of the grating is of the order of a few percents. Application of an ac field causes a strong increase of the diffraction efficiency up to 45%. PMID:23913086

  7. Homeotropic orientation behavior of nematic liquid crystals induced by copper ions.

    PubMed

    Li, Guang; Gao, Bin; Yang, Meng; Chen, Long-Cong; Xiong, Xing-Liang

    2015-06-01

    A homeotropic ordering film of nematic liquid crystal (LC) induced by copper ions (Cu(2+)) had been developed. The Cu(ClO4)2 was directly spin-coated on the glass substrate without any other chemical modification. A homeotropic orientation of LC thin-film was generated by the interfacial chemical interaction between nitrile-containing LC and copper ions on the surface. Results showed that an appropriate density of Cu(2+) could shorten the response time of orientation, but a shelf-time was prolonged. The LC film fabrication not only offered a simple process, but also presented a great repeatability to detect organophosphonates (DMMP). This study provided guidance for the design of LC films responding to organic molecules as a biosensor. PMID:25935262

  8. Graphite edge controlled registration of monolayer MoS{sub 2} crystal orientation

    SciTech Connect

    Lu, Chun-I; Butler, Christopher John; Yang, Hung-Hsiang; Chu, Yu-Hsun; Luo, Chi-Hung; Sun, Yung-Che; Hsu, Shih-Hao; Yang, Kui-Hong Ou; Huang, Jing-Kai; Hsing, Cheng-Rong; Wei, Ching-Ming Li, Lain-Jong; Lin, Minn-Tsong

    2015-05-04

    Transition metal dichalcogenides such as the semiconductor MoS{sub 2} are a class of two-dimensional crystals. The surface morphology and quality of MoS{sub 2} grown by chemical vapor deposition are examined using atomic force and scanning tunneling microscopy techniques. By analyzing the moiré patterns from several triangular MoS{sub 2} islands, we find that there exist at least five different superstructures and that the relative rotational angles between the MoS{sub 2} adlayer and graphite substrate lattices are typically less than 3°. We conclude that since MoS{sub 2} grows at graphite step-edges, it is the edge structure which controls the orientation of the islands, with those growing from zig-zag (or armchair) edges tending to orient with one lattice vector parallel (perpendicular) to the step-edge.

  9. Rapid, all-optical crystal orientation imaging of two-dimensional transition metal dichalcogenide monolayers

    SciTech Connect

    David, Sabrina N.; Zhai, Yao; Zande, Arend M. van der; O'Brien, Kevin; Huang, Pinshane Y.; Chenet, Daniel A.; Hone, James C.; Zhang, Xiang; Yin, Xiaobo

    2015-09-14

    Two-dimensional (2D) atomic materials such as graphene and transition metal dichalcogenides (TMDCs) have attracted significant research and industrial interest for their electronic, optical, mechanical, and thermal properties. While large-area crystal growth techniques such as chemical vapor deposition have been demonstrated, the presence of grain boundaries and orientation of grains arising in such growths substantially affect the physical properties of the materials. There is currently no scalable characterization method for determining these boundaries and orientations over a large sample area. We here present a second-harmonic generation based microscopy technique for rapidly mapping grain orientations and boundaries of 2D TMDCs. We experimentally demonstrate the capability to map large samples to an angular resolution of ±1° with minimal sample preparation and without involved analysis. A direct comparison of the all-optical grain orientation maps against results obtained by diffraction-filtered dark-field transmission electron microscopy plus selected-area electron diffraction on identical TMDC samples is provided. This rapid and accurate tool should enable large-area characterization of TMDC samples for expedited studies of grain boundary effects and the efficient characterization of industrial-scale production techniques.

  10. Theoretical characterization of a model of aragonite crystal orientation in red abalone nacre

    NASA Astrophysics Data System (ADS)

    Coppersmith, S N; Gilbert, P U P A; Metzler, R A

    2009-03-01

    Nacre, commonly known as mother-of-pearl, is a remarkable biomineral that in red abalone consists of layers of 400 nm thick aragonite crystalline tablets confined by organic matrix sheets, with the [0 0 1] crystal axes of the aragonite tablets oriented to within ±12° from the normal to the layer planes. Recent experiments demonstrate that greater orientational order develops over a distance of tens of layers from the prismatic boundary at which nacre formation begins. Our previous simulations of a model in which the order develops because of differential tablet growth rates (oriented tablets growing faster than misoriented ones) yield patterns of tablets that agree qualitatively and quantitatively with the experimental measurements. This paper presents an analytical treatment of this model, focusing on how the dynamical development and eventual degree of order depend on model parameters. Dynamical equations for the probability distributions governing tablet orientations are introduced whose form can be determined from symmetry considerations and for which substantial analytic progress can be made. Numerical simulations are performed to relate the parameters used in the analytic theory to those in the microscopic growth model. The analytic theory demonstrates that the dynamical mechanism is able to achieve a much higher degree of order than naive estimates would indicate.

  11. Influence of Simple Electrolytes on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    PubMed Central

    Carlton, Rebecca J.; Gupta, Jugal K.; Swift, Candice L.; Abbott, Nicholas L.

    2011-01-01

    We report orientational anchoring transitions at aqueous interfaces of a water-immiscible, thermotropic liquid crystal (LC; nematic phase of 4′-pentyl-4-cyanobiphenyl) that are induced by changes in pH of the aqueous solution and the addition of simple electrolytes (NaCl) to the aqueous phase. Whereas measurements of the zeta potential on the aqueous side of the interface of LC-in-water emulsions prepared with 5CB confirm pH-dependent formation of an electrical double layer extending into the aqueous phase, quantification of the orientational ordering of the LC leads to the proposition that an electrical double layer is also formed on the LC-side of the interface with an internal electric field that drives the LC anchoring transition. Further support for this conclusion is obtained from measurements of the dependence of LC ordering on pH and ionic strength, as well as a simple model based on the Poisson-Boltzmann equation from which we calculate the contribution of an electrical double layer to the orientational anchoring energy of the LC. Overall, the results presented herein provide new fundamental insights into ionic phenomena at LC-aqueous interfaces, and expand the range of solutes known to cause orientational anchoring transitions at LC-aqueous interfaces beyond previously examined amphiphilic adsorbates. PMID:22106820

  12. Influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures and lattice defects accumulation

    SciTech Connect

    Sedao, Xxx; Garrelie, Florence Colombier, Jean-Philippe; Reynaud, Stéphanie; Pigeon, Florent; Maurice, Claire; Quey, Romain

    2014-04-28

    The influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures (LIPSS) has been investigated on a polycrystalline nickel sample. Electron Backscatter Diffraction characterization has been exploited to provide structural information within the laser spot on irradiated samples to determine the dependence of LIPSS formation and lattice defects (stacking faults, twins, dislocations) upon the crystal orientation. Significant differences are observed at low-to-medium number of laser pulses, outstandingly for (111)-oriented surface which favors lattice defects formation rather than LIPSS formation.

  13. Observation of an Organic-Inorganic Lattice Match during Biomimetic Growth of (001)-Oriented Calcite Crystals under Floating Sulfate Monolayers

    SciTech Connect

    Kewalramani, S.; Kim, K; Stripe, B; Evmenenko, G; Dommett, G; Dutta, P

    2008-01-01

    Macromolecular layers rich in amino acids and with some sulfated polysaccharides appear to control oriented calcite growth in living organisms. Calcite crystals nucleating under floating acid monolayers have been found to be unoriented on average. We have now observed directly, using in situ grazing incidence X-ray diffraction, that there is a 1:1 match between the monolayer unit cell and the unit cell of the (001) plane of calcite. Thus, sulfate head groups appear to act as templates for the growth of (001)-oriented calcite crystals, which is the orientation commonly found in biominerals.

  14. Surface-assisted unidirectional orientation of ZnO nanorods hybridized with nematic liquid crystals.

    PubMed

    Kubo, Shoichi; Taguchi, Rei; Hadano, Shingo; Narita, Mamiko; Watanabe, Osamu; Iyoda, Tomokazu; Nakagawa, Masaru

    2014-01-22

    Inorganic semiconductor nanorods are regarded as the primary components of optical and electrical nanoscale devices. In this paper, we demonstrate the unidirectional alignment of monolayered and dispersed ZnO nanorods on a rubbed polyimide alignment layer, which was achieved by a conventional liquid crystal alignment technique. The outermost surfaces of the ZnO nanorods (average diameter 7 nm; length 50 nm) were modified by polymerization initiator moieties, and nematic liquid crystalline (LC) methacrylate polymers were grown by atom transfer radical polymerization. By regulating the densities of the polymerization initiator moieties, we successfully hybridized LC-polymer-grafted ZnO nanorods and small nematic LC molecules. The LC-polymer-modified ZnO nanorods were hierarchically aligned on the substrate via cooperative molecular interactions among the liquid crystal mesogens, which induced molecular orientation on the rubbed polyimide alignment layer. PMID:24299205

  15. 1300 K Creep Behavior of [001] Oriented Ni-49Al-1Hf (at.%) Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Locci, I. E.; Darolia, Ram; Bowman, R.

    1999-01-01

    A study of the 1300 K compressive and tensile creep properties of [001]-oriented NiAl-1Hf (D209) single crystals has been undertaken. Neither post homogenization cooling treatment, minor chemical variations within an ingot or from ingot-to-ingot, nor testing procedure had a significant effect on mechanical behavior; however a heat treatment which dissolved the initial G-phase precipitates and promoted formation of Heusler particles led to a strength reduction. Little primary creep was found utilizing direct measurement of strain, and a misorientation of 18 deg from the [001] did not reduce the creep strength. The effects of heat treatments on properties and a comparison of the flow stress-strain rate data to those predicted by the Jaswon-Cottrell solid solution hardening model indicate that the 1300 K strength in NiAl-1Hf single crystals is mainly due to precipitation hardening mechanisms.

  16. Orientational Order of a Lyotropic Chromonic Liquid Crystal Measured by Polarized Raman Spectroscopy.

    PubMed

    Yao, Xuxia; Nayani, Karthik; Park, Jung Ok; Srinivasarao, Mohan

    2016-05-19

    Lyotropic chromonic liquid crystals are distinct from thermotropic nematics from a fundamental standpoint as the structure of the aggregating columns is a function of both the temperature and concentration. We report on the thermal evolution of orientational order parameters, both the second (=scalar) (⟨P200⟩ (=S)) and fourth (⟨P400⟩) order, of sunset yellow FCF aqueous solutions, measured using polarized Raman spectroscopy for different concentrations. The order parameter increases with the concentration, and their values are high in comparison with those of thermotropic liquid crystals. On the basis of Raman spectroscopy, we provide the strongest evidence yet that the hydrozone tautomer of SSY is the predominant form in aqueous solutions in the isotropic, nematic, and columnar phases, as well as what we believe to be the first measurements of (⟨P400⟩) for this system. PMID:27074395

  17. Shape-controlled orientation and assembly of colloids with sharp edges in nematic liquid crystals.

    PubMed

    Beller, Daniel A; Gharbi, Mohamed A; Liu, Iris B

    2015-02-14

    The assembly of colloids in nematic liquid crystals via topological defects has been extensively studied for spherical particles, and investigations of other colloid shapes have revealed a wide array of new assembly behaviors. We show, using Landau-de Gennes numerical modeling, that nematic defect configurations and colloidal assembly can be strongly influenced by fine details of colloid shape, in particular the presence of sharp edges. For cylinder, microbullet, and cube colloid geometries, we obtain the particles' equilibrium alignment directions and effective pair interaction potentials as a function of simple shape parameters. We find that defects pin at sharp edges, and that the colloid consequently orients at an oblique angle relative to the far-field nematic director that depends on the colloid's shape. This shape-dependent alignment, which we confirm in experimental measurements, raises the possibility of selecting self-assembly outcomes for colloids in liquid crystals by tuning particle geometry. PMID:25523158

  18. Selective liquid crystal molecule orientation on ion beam irradiated tantalum oxide ultrathin films

    SciTech Connect

    Lim, Ji-Hun; Oh, Byeong-Yun; Lee, Won-Kyu; Lee, Kang-Min; Na, Hyun-Jae; Kim, Byoung-Yong; Seo, Dae-Shik; Han, Jeong-Min; Hwang, Jeong-Yeon

    2009-09-21

    We recently achieved the homogeneous alignment of liquid crystal (LC) on amorphous Ta{sub 2}O{sub 5} layers. This study demonstrates that LC layers could be aligned either homogeneously or vertically by increasing the growth temperature of rf magnetron sputtering device and the irradiation time of the DuoPIGatron type Ar ion beam device causing uniform and dense plasma. We attained two LC orientations by observing Ta 4f and O 1s peak shifts with x-ray photoelectron spectroscopy. Moreover, the decreased thickness of layers with high-k dielectric constants helped to decrease driving LC voltages and in turn to achieve low power consumption.

  19. Chaotic orientational behavior of a nematic liquid crystal subjected to a steady shear flow.

    PubMed

    Rienäcker, Götz; Kröger, Martin; Hess, Siegfried

    2002-10-01

    Based on a relaxation equation for the second rank alignment tensor characterizing the molecular orientation in liquid crystals, we report on a number of symmetry-breaking transient states and simple periodic and irregular, chaotic out-of-plane orbits under steady flow. Both an intermittency route and a period-doubling route to chaos are found for this five-dimensional dynamic system in a certain range of parameters (shear rate, tumbling parameter at isotropic-nematic coexistence, and reduced temperature). A link to the corresponding rheochaotic states, present in complex fluids, is made. PMID:12443167

  20. The spectroscopy of a benzil-bibenzyl mixed crystal system. Lifetime and optical spin orientation studies

    NASA Astrophysics Data System (ADS)

    Kohler, Bryan E.; Loda, Richard T.

    1981-09-01

    Phosphorescence decay curves for three isotopic derivatives of a benzil-bibenzyl mixed crystal have been measured as a function of temperature over the range from 2-310 K. Optical spin orientation occurs between 40 and 4.2 K for all of the three isotopic derivatives. The results are consistent with the model where benzil has one active zero-field spin sublevel radiatively connected to the ground state. The other two sublevels are, to a good approximation, nonradiative. Effective spin-lattice relaxation rates, measured at 16 and 30 K, were found to increase with increasing temperature.

  1. cm-scale variations of crystal orientation fabric in cold Alpine ice core from Colle Gnifetti

    NASA Astrophysics Data System (ADS)

    Kerch, Johanna; Weikusat, Ilka; Eisen, Olaf; Wagenbach, Dietmar; Erhardt, Tobias

    2015-04-01

    Analysis of the microstructural parameters of ice has been an important part of ice core analyses so far mainly in polar cores in order to obtain information about physical processes (e.g. deformation, recrystallisation) on the micro- and macro-scale within an ice body. More recently the influence of impurities and climatic conditions during snow accumulation on these processes has come into focus. A deeper understanding of how palaeoclimate proxies interact with physical properties of the ice matrix bears relevance for palaeoclimatic interpretations, improved geophysical measurement techniques and the furthering of ice dynamical modeling. Variations in microstructural parameters e.g. crystal orientation fabric or grain size can be observed on a scale of hundreds and tens of metres but also on a centimetre scale. The underlying processes are not necessarily the same on all scales. Especially for the short-scale variations many questions remain unanswered. We present results from a study that aims to investigate following hypotheses: 1. Variations in grain size and fabric, i.e. strong changes of the orientation of ice crystals with respect to the vertical, occur on a centimetre scale and can be observed in all depths of an ice core. 2. Palaeoclimate proxies like dust and impurities have an impact on the microstructural processes and thus are inducing the observed short-scale variations in grain size and fabric. 3. The interaction of proxies with the ice matrix leads to depth intervals that show correlating behaviour as well as ranges with anticorrelation between microstructural parameters and palaeoclimatic proxies. The respective processes need to be identified. Fabric Analyser measurements were conducted on more than 80 samples (total of 8 m) from different depth ranges of a cold Alpine ice core (72 m length) drilled in 2013 at Colle Gnifetti, Switzerland/Italy. Results were obtained by automatic image processing, providing estimates for grain size distributions

  2. Localization and orientation of heavy-atom cluster compounds in protein crystals using molecular replacement

    SciTech Connect

    Dahms, Sven O. Kuester, Miriam; Streb, Carsten; Roth, Christian; Sträter, Norbert; Than, Manuel E.

    2013-02-01

    A new approach is presented that allows the efficient localization and orientation of heavy-atom cluster compounds used in experimental phasing by a molecular replacement procedure. This permits the calculation of meaningful phases up to the highest resolution of the diffraction data. Heavy-atom clusters (HA clusters) containing a large number of specifically arranged electron-dense scatterers are especially useful for experimental phase determination of large complex structures, weakly diffracting crystals or structures with large unit cells. Often, the determination of the exact orientation of the HA cluster and hence of the individual heavy-atom positions proves to be the critical step in successful phasing and subsequent structure solution. Here, it is demonstrated that molecular replacement (MR) with either anomalous or isomorphous differences is a useful strategy for the correct placement of HA cluster compounds. The polyoxometallate cluster hexasodium α-metatungstate (HMT) was applied in phasing the structure of death receptor 6. Even though the HA cluster is bound in alternate partially occupied orientations and is located at a special position, its correct localization and orientation could be determined at resolutions as low as 4.9 Å. The broad applicability of this approach was demonstrated for five different derivative crystals that included the compounds tantalum tetradecabromide and trisodium phosphotungstate in addition to HMT. The correct placement of the HA cluster depends on the length of the intramolecular vectors chosen for MR, such that both a larger cluster size and the optimal choice of the wavelength used for anomalous data collection strongly affect the outcome.

  3. Face-on and Edge-on Orientation Transition and Self-epitaxial Crystallization of All-conjugated Diblock Copolymer

    NASA Astrophysics Data System (ADS)

    Yang, Hua; Han, Yanchun

    The orientation transition and self-epitaxial crystallization of all-conjugated diblock copolymers poly(p-phenylene)-block-(3-hexylthiophene) (PPP- b-P3HT, BmTn) were systematically investigated by in-situ temperature-resolved two-dimensional grazing incidence X-ray diffraction (2D GIXD) in step-by-step heating and cooling process. B39T18 was selected, the results of 2D GIXD showed that the PPP block crystal adopted a face-on orientation while the crystallization of P3HT block was hindered in as-casted films. Three different molecular orientations transition were obtained in self-epitaxial crystallization circles. First, P3HT crystallize with edge-on during the heating process and induced the PPP blocks crystallized with edge-on during the cooling process. Then, the as-casted film was heated in the melting temperature region of PPP blocks and isothermally crystallized. The partial melting of PPP blocks promoted the P3HT blocks crystallize in a face-on due to the steric limitation effect, PPP blocks crystallized with a face-on via the self-epitaxy during cooling. Furthermore, the face-on transformed to thermodynamically stable edge-on in the melt annealing process. The financial support from the National Basic Research Program of China (973 Program, 2012CB821500) is gratefully acknowledged.

  4. Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt

    PubMed Central

    Soares, Alexei S.; Mullen, Jeffrey D.; Parekh, Ruchi M.; McCarthy, Grace S.; Roessler, Christian G.; Jackimowicz, Rick; Skinner, John M.; Orville, Allen M.; Allaire, Marc; Sweet, Robert M.

    2014-01-01

    X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltd in situ micro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ∼100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face that preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. High-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies. PMID:25343789

  5. Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt.

    PubMed

    Soares, Alexei S; Mullen, Jeffrey D; Parekh, Ruchi M; McCarthy, Grace S; Roessler, Christian G; Jackimowicz, Rick; Skinner, John M; Orville, Allen M; Allaire, Marc; Sweet, Robert M

    2014-11-01

    X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltd in situ micro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ∼100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face that preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. High-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies. PMID:25343789

  6. Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt

    DOE PAGESBeta

    Soares, Alexei S.; Mullen, Jeffrey D.; Parekh, Ruchi M.; McCarthy, Grace S.; Roessler, Christian G.; Jackimowicz, Rick; Skinner, John M.; Orville, Allen M.; Allaire, Marc; Sweet, Robert M.

    2014-10-09

    X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltdin situmicro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ~100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face thatmore » preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. Lastly, high-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies.« less

  7. Unoccupied electronic structure and molecular orientation of rubrene; from evaporated films to single crystals

    NASA Astrophysics Data System (ADS)

    Ueba, T.; Park, J.; Terawaki, R.; Watanabe, Y.; Yamada, T.; Munakata, T.

    2016-07-01

    Two-photon photoemission (2PPE) spectroscopy and ultraviolet photoemission spectroscopy (UPS) have been performed for rubrene single crystals and evaporated thin films on highly oriented pyrolytic graphite (HOPG). The changes in the 2PPE intensity from the single crystals by the polarization of the light and by the angle of the light incident plane against the crystalline axes indicate that the molecular arrangement on the surface is similar to that in the bulk crystal. On the other hand, in the case of evaporated films, the polarization dependence of 2PPE indicates that the tetracene backbone becomes standing upright as the thickness increases. In spite of the alignment of molecules, the broadened 2PPE spectral features for thick films suggest that the films are amorphous and molecules are in largely different environments. The film structures are confirmed by scanning tunneling microscopy (STM). The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) derived levels of the single crystal are shifted by + 0.18 and - 0.20 eV, respectively, from those of the 0.8 ML film. The shifts are attributed to the packing density of molecules. It is shown that the unoccupied electronic structure is more sensitively affected by the film structure than the occupied electronic structure.

  8. Improved crystal orientation and physical properties from single-shot XFEL stills

    DOE PAGESBeta

    Sauter, Nicholas K.; Hattne, Johan; Brewster, Aaron S.; Echols, Nathaniel; Zwart, Petrus H.; Adams, Paul D.

    2014-11-28

    X-ray diffraction patterns from still crystals are inherently difficult to process because the crystal orientation is not uniquely determined by measuring the Bragg spot positions. Only one of the three rotational degrees of freedom is directly coupled to spot positions; the other two rotations move Bragg spots in and out of the reflecting condition but do not change the direction of the diffracted rays. This hinders the ability to recover accurate structure factors from experiments that are dependent on single-shot exposures, such as femtosecond diffract-and-destroy protocols at X-ray free-electron lasers (XFELs). Here, additional methods are introduced to optimally model themore » diffraction. The best orientation is obtained by requiring, for the brightest observed spots, that each reciprocal-lattice point be placed into the exact reflecting condition implied by Bragg's law with a minimal rotation. This approach reduces the experimental uncertainties in noisy XFEL data, improving the crystallographic R factors and sharpening anomalous differences that are near the level of the noise.« less

  9. Improved crystal orientation and physical properties from single-shot XFEL stills

    PubMed Central

    Sauter, Nicholas K.; Hattne, Johan; Brewster, Aaron S.; Echols, Nathaniel; Zwart, Petrus H.; Adams, Paul D.

    2014-01-01

    X-ray diffraction patterns from still crystals are inherently difficult to process because the crystal orientation is not uniquely determined by measuring the Bragg spot positions. Only one of the three rotational degrees of freedom is directly coupled to spot positions; the other two rotations move Bragg spots in and out of the reflecting condition but do not change the direction of the diffracted rays. This hinders the ability to recover accurate structure factors from experiments that are dependent on single-shot exposures, such as femtosecond diffract-and-destroy protocols at X-ray free-electron lasers (XFELs). Here, additional methods are introduced to optimally model the diffraction. The best orientation is obtained by requiring, for the brightest observed spots, that each reciprocal-lattice point be placed into the exact reflecting condition implied by Bragg’s law with a minimal rotation. This approach reduces the experimental uncertainties in noisy XFEL data, improving the crystallographic R factors and sharpening anomalous differences that are near the level of the noise. PMID:25478847

  10. Improved crystal orientation and physical properties from single-shot XFEL stills

    SciTech Connect

    Sauter, Nicholas K.; Hattne, Johan; Brewster, Aaron S.; Echols, Nathaniel; Zwart, Petrus H.; Adams, Paul D.

    2014-11-28

    X-ray diffraction patterns from still crystals are inherently difficult to process because the crystal orientation is not uniquely determined by measuring the Bragg spot positions. Only one of the three rotational degrees of freedom is directly coupled to spot positions; the other two rotations move Bragg spots in and out of the reflecting condition but do not change the direction of the diffracted rays. This hinders the ability to recover accurate structure factors from experiments that are dependent on single-shot exposures, such as femtosecond diffract-and-destroy protocols at X-ray free-electron lasers (XFELs). Here, additional methods are introduced to optimally model the diffraction. The best orientation is obtained by requiring, for the brightest observed spots, that each reciprocal-lattice point be placed into the exact reflecting condition implied by Bragg's law with a minimal rotation. This approach reduces the experimental uncertainties in noisy XFEL data, improving the crystallographic R factors and sharpening anomalous differences that are near the level of the noise.

  11. Bandgap characteristics of one-dimensional plasma photonic crystal

    SciTech Connect

    Yin Yan; Ma Yanyun; Tian Chenglin; Shao Fuqiu; Xu Han; Zhuo Hongbin; Yu, M. Y.

    2009-10-15

    When two pump laser pulses intersect in an underdense plasma, plasma Bragg grating (PBG) is induced by the slow-varying ponderomotive force [Z. M. Sheng et al., Appl. Phys. B: Lasers Opt. 77, 673 (2003)]. Such a PBG can be considered as a one-dimensional (1D) plasma photonic crystal (PPC). Here the bandgap characteristic of 1D PPC composed of plasma layers of different densities is investigated theoretically and numerically. It is found that when the maximum density is lower than the critical density of the pump laser, there is only one normal-incidence bandgap. When the maximum density is higher than the critical density of the pump laser, high-order bandgaps are found. The theoretical results are verified by 1D particle-in-cell simulations.

  12. Orientations of Chromonic Liquid Crystals by Imprinted or Rubbed Polymer Films

    NASA Astrophysics Data System (ADS)

    Yi, Youngwoo; McGuire, Aya; Clark, Noel

    2014-03-01

    A variety of novel alignment effects of chromonic liquid crystal phases of sunset yellow (SSY)/water, disodium cromoglycate (DSCG)/water, and their mixtures by thiol-ene polymer films topographically imprinted with linear channels are observed using polarizing optical microscopy. Nematic DSCG and SSY at low concentration and their nematic mixtures orient with the long axes of stacked chromonic aggregates on average parallel to the channels, that is, with the molecular planes normal to the channel axis. On the contrary, nematic SSY in contact with the rubbed polyimide films orients with the long axes on average in-plane perpendicular to the rubbing direction, arguably, due to a tongue-groove interaction between SSY and the stretched PI chains. Furthermore, multi-stable alignments are observed in SSY solutions of sufficiently high concentration, including preferential in-plane orientation of the long axes of the aggregates parallel to, perpendicular to, and 45° rotated from the channels. This work was supported by NSF grant DMR 1207606, NSF MRSEC grant DMR 0820579, and NSF Research Experience for Undergraduate programs.

  13. Influence of 4-cyano-4'-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces.

    PubMed

    Park, Joon-Seo; Jang, Chang-Hyun; Tingey, Matthew L; Lowe, Aaron M; Abbott, Nicholas L

    2006-12-15

    We report two methods that involve tailoring of the chemical composition of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl to achieve control over the orientational ordering of the liquid crystal on chemically functionalized surfaces. The first method involves the direct addition of 4-cyano-4'-biphenylcarboxylic acid to 4-cyano-4'-pentylbiphenyl. The second method involves exposure of 4-cyano-4'-pentylbiphenyl to ultraviolet light and photochemical generation of a range of products, including 4-cyano-4'-biphenylcarboxylic acid. The addition of the acid or exposure to ultraviolet light accelerated the rate at which the liquid crystal exhibited an orientational transition from planar to perpendicular (homeotropic) alignment on surfaces presenting ammonium groups. The appearance of the homeotropic orientation of the UV-treated 4-cyano-4'-pentylbiphenyl on ammonium-terminated surfaces was dependent on the thickness of the film of liquid crystal (13-50 mum), consistent with a dipolar coupling between the liquid crystal and the electric field associated with an electrical double layer generated at the ammonium surface. Although the addition of 4-cyano-4'-biphenylcarboxylic acid or UV treatment of the liquid crystal also promoted homeotropic orientations on surfaces presenting hydroxyl groups, the orientations of the UV-treated liquid crystal on the hydroxyl-terminated surface did not change with thickness of the film of liquid crystal in the manner observed on the ammonium-terminated surfaces. The latter result indicates that the mechanism leading to homeotropic anchoring on hydroxyl-terminated surfaces is distinct from that on ammonium-terminated surfaces. Measurements performed using polarization modulation infrared reflection-absorption spectroscopy suggest that hydrogen bonding between the 4-cyano-4'-biphenylcarboxylic acid and the hydroxyl-terminated surface is responsible for the homeotropic anchoring on the surface. Finally, the orientation of the liquid

  14. Development of the Shielding Materials Having the Highly Orientation Characteristics in the RF Magnetic Field

    NASA Astrophysics Data System (ADS)

    Nishikubo, Tokoh; Itoh, Mineo

    The conventional electromagnetic shielding technique is all but impossible to fundamental solution of the problems in the information and communication fields, such as virtual image for radar. Namely, it is necessary to receive a required electromagnetic wave as the information signal, and to shield a needless electromagnetic wave as the noise. the present research has developed the carbon, copper, ferrite, and BPSCCO plates, as the typical shielding material, having the orientation characteristics in the RF (radio frequency) magnetic field. To exhibit the orientation characteristics in the plane wave, it has formed the slit on the surface of typical shielding materials; termed the slit plate. For example, the value of RF magnetic shielding degree SDHP of slit carbon plate for holding the slit perpendicularly to the ground increased with frequency in the region from 1 MHz (7 dB) to 3 GHz (70 dB). And, the value of SDHH when holding the slit horizontally is indicated an average value of approximately 10 dB in this frequency region. That is, the difference values, SDHP-SDHH, indicated the orientation characteristics. Experimental results revealed several characteristics of the slit plates that include the influences of orientation characteristics on the slit length, slit width, and slit number. In the present paper, it was succeeded to improved the difference average value of approximately 35 dB for SDHP-SDHH, by the sandwich of slit ferrite plate over a slit carbon plate, in the civilian communication frequency region from 1 MHz to 3 GHz. In addition, important criteria are discussed for the design of an effective RF magnetic shielding plate having orientation characteristics.

  15. Orientation dependence of high temperature creep strength and internal stress in Ni{sub 3}Al alloy single crystals

    SciTech Connect

    Miura, Seiji; Peng, Z.L.; Mishima, Yoshinao

    1997-12-31

    High temperature creep behavior of a nickel-rich Ni{sub 3}(Al,Ta) with the L1{sub 2} structure is investigated in order to clarify the influence of crystallographic orientation with respect to the stress axis. The single crystals with four different orientations are deformed in compressive creep at temperatures ranging from 1,123 to 1,273 K under a constant load, initial shear stress being 35 to 120 MPa for (111)[{bar 1}01] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent of the orientation. It is shown, however, the internal stress, being measured by strain transient dip tests, is found to be orientation dependent and the creep behavior is independent on orientation if it is interpreted using the effective stress instead of the applied shear stress.

  16. Dependence of Initial Grain Orientation on the Evolution of Anisotropy in FCC and BCC Metals Using Crystal Plasticity and Texture Analysis

    NASA Astrophysics Data System (ADS)

    Raja, Daniel Selvakumar

    Abundant experimental analyses and theoretical computational analyses that had been performed on metals to understand anisotropy and its evolution and its dependence on initial orientation of grains have failed to provide theories that can be used in macro-scale plasticity. Ductile metals fracture after going through a large amount of plastic deformation, during which the anisotropy of the material changes significantly. Processed metal sheets or slabs possess anisotropy due to textures produced by metal forming processes (such as drawing, bending and press braking). Metals that were initially isotropic possess anisotropy after undergoing forming processes, i.e., through texture formation due to large amount of plastic deformation before fracture. It is therefore essential to consider the effect of anisotropy to predict the characteristics of fracture and plastic flow performances in the simulation of ductile fracture and plastic flow of materials. Crystal plasticity simulations carried out on grains at the meso-scale level with different initial orientations (ensembles) help to derive the evolution of anisotropy at the macro-scale level and its dependence on initial orientation of grains. This paper investigates the evolution of anisotropy in BCC and FCC metals and its dependence on grain orientation using crystal plasticity simulations and texture analysis to reveal the mechanics behind the evolution of anisotropy. A comparison of anisotropy evolution between BCC and FCC metals is made through the simulation, which can be used to propose the theory of anisotropy evolution in macro-scale plasticity. Keywords: ensembles; grains; initial orientation; anisotropy; evolution of anisotropy; crystal plasticity; textures; homogeneity; isotropy; inelastic; equivalent strain.

  17. Effects of substrate crystallographic orientations on crystal growth and microstructure development in laser surface-melted superalloy single crystals. Mathematical modeling of single-crystal growth in a melt pool (Part II)

    SciTech Connect

    Liu Weiping . E-mail: wel2@lehigh.edu; DuPont, J.N.

    2005-03-01

    The mathematical model developed for single-crystalline solidification in laser surface melting (LSM) described in Part I [Acta Mater 2004;52:4833-4847] was used to compute the dendrite growth pattern and velocity distribution in the 3D melt pool for various substrate orientations. LSM experiments with single-crystal nickel-base superalloys were conducted for different orientations to verify the computational results. Results show that the substrate orientation has a predominant effect on crystal growth pattern, and simultaneously influences the magnitude and distribution of dendrite growth velocity in the melt pool. The selected <100> growth variants and the number of the chosen growth variants are dependent on the substrate orientation. The maximum velocity ratio (dendrite growth velocity over the beam velocity, V/V{sub b}) in the melt pool is a function of melt-pool geometrical parameters and the substrate orientation. The largest maximum velocity-ratio among the symmetric orientations is 1.414 for the (001)/[110] and (011)/[011-bar] orientations, while that value for asymmetric orientations is 1.732 for the (011)/[111-bar] orientation. Good agreement was obtained between the predicted and experimentally observed microstructures. The results are discussed with the susceptibility to stray grain formation as a function of substrate orientations and melt-pool geometrical parameters. These findings have some important implications for single-crystal surface processing.

  18. Characteristics and crystal structure of bacterial inosine-5'-monophosphate dehydrogenase.

    SciTech Connect

    Zhang, R.; Evans, G.; Rotella, F. J.; Westbrook, E. M.; Beno, D.; Huberman, E.; Joachimiak, A.; Collart, F. R.

    1999-01-01

    IMP dehydrogenase (IMPDH) is an essential enzyme that catalyzes the first step unique to GTP synthesis. To provide a basis for the evaluation of IMPDH inhibitors as antimicrobial agents, we have expressed and characterized IMPDH from the pathogenic bacterium Streptococcus pyogenes. Our results show that the biochemical and kinetic characteristics of S. pyogenes IMPDH are similar to other bacterial IMPDH enzymes. However, the lack of sensitivity to mycophenolic acid and the K{sub m} for NAD (1180 {mu}M) exemplify some of the differences between the bacterial and mammalian IMPDH enzymes, making it an attractive target for antimicrobial agents. To evaluate the basis for these differences, we determined the crystal structure of the bacterial enzyme at 1.9 {angstrom} with substrate bound in the catalytic site. The structure was determined using selenomethionine-substituted protein and multiwavelength anomalous (MAD) analysis of data obtained with synchrotron radiation from the undulator beamline (19ID) of the Structural Biology Center at Argonne's Advanced Photon Source. S. pyogenes IMPDH is a tetramer with its four subunits related by a crystallographic 4-fold axis. The protein is composed of two domains: a TIM barrel domain that embodies the catalytic framework and a cystathione {beta}-synthase (CBS) dimer domain of so far unknown function. Using information provided by sequence alignments and the crystal structure, we prepared several site-specific mutants to examine the role of various active site regions in catalysis. These variants implicate the active site flap as an essential catalytic element and indicate there are significant differences in the catalytic environment of bacterial and mammalian IMPDH enzymes. Comparison of the structure of bacterial IMPDH with the known partial structures from eukaryotic organisms will provide an explanation of their distinct properties and contribute to the design of specific bacterial IMPDH inhibitors.

  19. Liquid crystal quenched orientational disorder at an AFM-scribed alignment surface.

    PubMed

    Pendery, J S; Atherton, T J; Nobili, M; Petschek, R G; Lacaze, E; Rosenblatt, C

    2015-03-21

    A polyimide substrate was scribed using the stylus of an atomic force microscope, then covered with a nematic liquid crystal. The fiber from a near field scanning optical microscope was immersed into the liquid crystal and rastered approximately 80 nm above the surface, thereby obviating smearing effects that occur in thicker samples. By appropriate averaging of multiple data sets, a histogram of the "frozen-in" director deviation Δφ from the average easy axis was obtained, having a full-width-half-maximum of ∼0.02 rad. Additionally, the spatial autocorrelation function of Δφ was extracted, where the primary correlation length was found to be comparable to, but larger than, the liquid crystal's extrapolation length. A secondary characteristic length scale of a few μm was observed, and is thought to be an artifact due to material ejection during the scribing process. Our results demonstrate the utility of nanoscale imaging of the interface behavior inside the liquid crystal. PMID:25643289

  20. Photoreactive self-assembled monolayer for the stabilization of tilt orientation of a director in vertically aligned nematic liquid crystals.

    PubMed

    Oh, Su Yeon; Kang, Shin-Woong

    2013-12-16

    Photo-reactive self-assembled monolayer (PR-SAM) is employed to mediate alignment of liquid crystals (LC) and stabilize the tilt orientation of a nematic director for a vertically aligned liquid crystal. Bifunctional PR-SAM formed by silane coupling reaction to oxide surfaces efficiently induces a homeotropic alignment and stabilizes LC director by the photo-polymerization under applied electric field. As a result, the substantial enhancement of electro-optic performance has been achieved after the PR-SAM assisted stabilization of tilt orientation of director. This approach for pretilt stabilization has multifarious advantages over the conventional PSVA. PMID:24514711

  1. Light-induced first-order orientational transitions in a nematic liquid crystal in the presence of an ordinary wave

    SciTech Connect

    Zolot'ko, A S; Smaev, Mikhail P; Shvetsov, S A; Boiko, N I; Barnik, M I

    2012-04-30

    The effects of light-induced reorientation of the director of a nematic liquid crystal doped with dendrimer are investigated experimentally. The influence of light polarisation on the firstorder orientational transition that occurs with changing the light beam power is studied. An irreversible first-order orientational transition when changing the polarisation of light is discovered and examined. A theoretical description of the observed effects is presented.

  2. Molecular conformation and orientational order in nCB liquid crystals

    NASA Astrophysics Data System (ADS)

    Kobinata, Shunsuke; Kobayashi, Takamichi; Yoshida, Hiroshi; Chandani, A. D. L.; Maeda, Shiro

    1986-08-01

    A resonance Raman probe method for determining the second and fourth orientational order parameters ( P¯2 and P¯4) in liquid crystals is described. The method was applied to a series of nematic nCB near the nematic—isotropic transition temperature, using all trans β-carotene as a resonant probe. Both P¯2 and P¯4, thus obtained show a distinct even—odd effect, that is, zigzag change of the parameter value against the length of alkyl end chain. The origin of the even—odd effect was investigated by the mean field theory, taking the conformation variety of end chain into account following the method of Marcelja. On the basis of calculation, the function of the alkyl chain in the formation of the liquid crystalline state is discussed.

  3. Crystal preferred orientation of an amphibole experimentally deformed by simple shear.

    PubMed

    Ko, Byeongkwan; Jung, Haemyeong

    2015-01-01

    Seismic anisotropy has been widely observed in crust and mantle materials and plays a key role in the understanding of structure and flow patterns. Although seismic anisotropy can be explained by the crystal preferred orientation (CPO) of highly anisotropic minerals in the crust, that is, amphibole, experimental studies on the CPO of amphibole are limited. Here we present the results of novel experiments on simple shear deformation of amphibolite at high pressure and temperatures (1 GPa, 480-700 °C). Depending on the temperature and stress, the deformed amphibole produced three types of CPOs and resulted in a strong seismic anisotropy. Our data provide a new understanding of the observed seismic anisotropy. The seismic data obtained from the amphibole CPOs revealed that anomalous seismic anisotropy observed in the deep crust, subducting slab and mantle wedge can be attributed to the CPO of amphibole. PMID:25858349

  4. Tilt plane orientation in antiferroelectric liquid crystal cells and the origin of the pretransitional effect.

    PubMed

    Rudquist, P; Lagerwall, J P F; Meier, J G; D'havé, K; Lagerwall, S T

    2002-12-01

    The optic, electro-optic, and dielectric properties of antiferroelectric liquid crystals (AFLCs) are analyzed and discussed in terms of the local tilt plane orientation. We show that the so-called pretransitional effect is a combination of two different electro-optic modes: the field-induced antiphase distortion of the antiferroelectric structure and the field-induced reorientation of the tilt plane. In the presence of a helix, the latter corresponds to a field-induced distortion of the helix. Both electro-optic modes are active only when the electric field has a component along the tilt plane. Thus, by assuring a horizontal surface-stabilized condition, where the helix is unwound by surface action and the tilt plane is everywhere parallel to the cell plates, the pretransitional effect should be suppressed. We also discuss the dielectrically active modes in AFLCs and under which circumstances they contribute to the measured dielectric permittivity. PMID:12513306

  5. Orientational photorefractive properties in polymer-dispersed liquid crystals with different polymer matrixes

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

    1998-10-01

    We report orientational photorefractive effects observed in photoconductive liquid crystals (LCs) contained with three kinds of polymer, i.e., poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA) and a side-chain liquid crystalline polymer (SLCP1). The morphology of the photorefractive composites depended on the kind of polymer strongly. In both PMMA and PVA cases, LC and polymer were phase-separated and the composite showed memory effects. In SLCP1 case, the phase-separation in the composite dose not occur and the high resolution could be achieved. In this case, the photorefractive Bragg gratings were generated and a high two-beam coupling gain coefficient with a low applied field of 4 V/micrometers was observed.

  6. Nuclear quadrupole spin-lattice relaxation due to molecular reorientations in crystals with orientational disorder

    NASA Astrophysics Data System (ADS)

    Meriles, C. A.; Pérez, S. C.; Brunetti, A. H.

    1997-08-01

    p-chloronitrobenzene (PCNB) and p-chlorobromobenzene (PCBB) crystallize in the centrosymmetric space group P21/c with two molecules per unit cell. The space lattice will have an equal number of points with molecules facing in opposite directions. As a consequence, these compounds exhibit an orientational rigid disorder. In this work, we have measured the temperature dependence of the chlorine nuclear quadrupole spin-lattice relaxation time (T1), linewidth, and resonance frequency for both compounds for temperatures higher than 80 K. Both compounds exhibit an inhomogeneously broadened line shape and a "normal" Bayer-type temperature dependence of the resonance frequency. The analysis focuses on the identification of the dominant relaxation process at high temperatures (T>240 K in PCNB and T>260 K in PCBB). It is shown that T1(T) reflects the existence of 180° molecular reorientations through a modulation of the crystalline contribution to the electric field gradient.

  7. Crystal preferred orientation of an amphibole experimentally deformed by simple shear

    PubMed Central

    Ko, Byeongkwan; Jung, Haemyeong

    2015-01-01

    Seismic anisotropy has been widely observed in crust and mantle materials and plays a key role in the understanding of structure and flow patterns. Although seismic anisotropy can be explained by the crystal preferred orientation (CPO) of highly anisotropic minerals in the crust, that is, amphibole, experimental studies on the CPO of amphibole are limited. Here we present the results of novel experiments on simple shear deformation of amphibolite at high pressure and temperatures (1 GPa, 480–700 °C). Depending on the temperature and stress, the deformed amphibole produced three types of CPOs and resulted in a strong seismic anisotropy. Our data provide a new understanding of the observed seismic anisotropy. The seismic data obtained from the amphibole CPOs revealed that anomalous seismic anisotropy observed in the deep crust, subducting slab and mantle wedge can be attributed to the CPO of amphibole. PMID:25858349

  8. Characterization of the crystal orientation in mono-oriented films of HDPE/LLDPE blends by IR dichroism

    NASA Astrophysics Data System (ADS)

    Canevarolo, Sebastião V.; Elias, Marcelo; Ravazzi, Camila; Silva, Jorge

    2016-03-01

    Polyethylene films are a common packaging material. The level and type of chain orientation in these films are a very important property which is of great care and concern of the converter personnel during the conformation process. Usually bi-orientation is the conventional procedure but when easy tear in one direction is needed mono-orientation is sought. This paper deal with the characterization of the crystalline orientation in films of polyethylene blends (HDPE/LLDPE) which have being oriented in two steps: initially the polymer was bi-oriented via extrusion-blown, cooled, and then in a second process hot stretched along the machine direction in order to produce mono-oriented films. In order to evaluate the orientation of the film, the polarization of the FT-IR beam was rotated 360° in steps of 5° by rotating the polarizer. In each step the absorbance spectrum was recorded and the corresponding dichroic ratio (DR) calculated after subtracting the baseline. With differential scanning calorimetry (DSC) was possible to infer about the changes in the morphology caused by the stretching.

  9. Creep property and microstructure evolution of a nickel-base single crystal superalloy in [011] orientation

    SciTech Connect

    Han, G.M. Yu, J.J.; Hu, Z.Q.; Sun, X.F.

    2013-12-15

    The creep property and microstructure evolution of a single crystal superalloy with [011] orientation were investigated at the temperatures of 700 °C, 900 °C and 1040 °C. It is shown that there exist stages of primary, steady-state, and tertiary creep under the lower temperature 700 °C. As the temperature increases to high temperatures of 900 °C and 1040 °C, steady-state creep stage is reduced or disappears and the shape of creep curves is dominated by an extensive tertiary stage. The minimum creep strain rate exhibits power law dependence on the applied stress; the stress exponents at 700 °C, 900 °C and 1040 °C are 28, 13 and 6.5, respectively. Microstructure observation shows that the morphologies of γ′ phase almost keep original shape at the lower temperature 700 °C and high applied stress. With the increasing creep temperature, γ′ precipitates tend to link together and form lamellar structure at an angle of 45° inclined to the applied stress. Transmission electron microscopy (TEM) investigations reveal that multiple < 110 > (111) slip systems gliding in the matrix channels and shearing γ′ precipitates by stacking faults or bending dislocation pairs are the main deformation mechanism at the lower temperature of 700 °C. At the high temperatures of 900 °C and 1040 °C, dislocation networks are formed at γ/γ′ interfaces and the γ′ rafts are sheared by dislocation pairs. - Highlights: • Creep properties of < 011 >-oriented single crystal superalloys were investigated. • γ′ phases become rafting at an angle of 45° inclined to the applied stress. • Creep deformation mechanisms depend on temperature and stress.

  10. Effects of Crystallographic Orientation on Corrosion Behavior of Magnesium Single Crystals

    NASA Astrophysics Data System (ADS)

    Shin, Kwang Seon; Bian, Ming Zhe; Nam, Nguyen Dang

    2012-06-01

    The corrosion behavior of magnesium single crystals with various crystallographic orientations was examined in this study. To identify the effects of surface orientation on the corrosion behavior in a systematic manner, single-crystal specimens with ten different rotation angles of the plane normal from the [0001] direction to the [ 10overline{1} 0] direction at intervals of 10° were prepared and subjected to potentiodynamic polarization and potentiostatic tests as well as electrochemical impedance spectroscopy (EIS) measurements in 3.5 wt.% NaCl solution. Potentiodynamic polarization results showed that the pitting potential ( E pit) first decreased from -1.57 V SCE to -1.64 V SCE with an increase in the rotation angle from 0° to 40°, and then increased to -1.60 V SCE with a further increase in the rotation angle to 90°. The results obtained from potentiostatic tests are also in agreement with the trend in potentiodynamic polarization tests as a function of rotation angle. A similar trend was also observed for the depressed semicircle and the total resistances in the EIS measurements due to the facile formation of MgO and Mg(OH)2 passive films on the magnesium surface. In addition, the amount of chloride in the passive film was found first to increase with an increase in rotation angle from 0° to 40°, then decrease with a further increase in rotation angle, indicating that the tendency to form a more protective passive film increased for rotation angle near 0° [the (0001) plane] or 90° [the ( 10overline{1} 0) plane].

  11. Influence of Specific Anions on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    PubMed Central

    Carlton, Rebecca J.; Ma, C. Derek; Gupta, Jugal K.; Abbott, Nicholas L.

    2012-01-01

    We report that specific anions (of sodium salts) added to aqueous phases at molar concentrations can trigger rapid, orientational ordering transitions in water-immiscible, thermotropic liquid crystals (LCs; e.g., nematic phase of 4′-pentyl-4-cyanobiphenyl, 5CB) contacting the aqueous phases. Anions classified as chaotropic, specifically iodide, perchlorate and thiocyanate, cause 5CB to undergo continuous, concentration-dependent transitions from planar to homeotropic (perpendicular) orientations at LC-aqueous interfaces within 20 s of addition of the anions. In contrast, anions classified as relatively more kosmotropic in nature (fluoride, sulfate, phosphate, acetate, chloride, nitrate, bromide, and chlorate) do not perturb the LC orientation from that observed without added salts (i.e., planar orientation). Surface pressure-area isotherms of Langmuir films of 5CB supported on aqueous salt solutions reveal ion-specific effects ranking in a manner similar to the LC ordering transitions. Specifically, chaotropic salts stabilized monolayers of 5CB to higher surface pressures and areal densities (12.6 mN/m at 27 Å2/molec. for NaClO4) and thus smaller molecular tilt angles (30° from the surface normal for NaClO4) than kosmotropic salts (5.0 mN/m at 38 Å2/molec. with a corresponding tilt angle of 53° for NaCl). These results and others reported herein suggest that anion-specific interactions with 5CB monolayers lead to bulk LC ordering transitions. Support for the proposition that these ion-specific interactions involve the nitrile group was obtained by using a second LC with nitrile groups (E7; ion-specific effects similar to 5CB were observed) and a third LC with fluorine-substituted aromatic groups (TL205; weak dipole and no ion-specific effects were measured). Finally, we also establish that anion-induced orientational transitions in micrometer-thick LC films involve a change in the easy axis of the LC. Overall, these results provide new insights into ionic

  12. Influence of cluster defects of variable composition on the optical and radiative characteristics of oxide crystals

    NASA Astrophysics Data System (ADS)

    Burachas, S. F.; Vasil'Ev, A. A.; Ippolitov, M. S.; Man'ko, V. I.; Savel'Ev, Yu. A.; Tamulaitis, G.

    2007-11-01

    It is shown that oxide crystals contain cluster defects of variable composition, which cause absorption of light in the transparency region of crystals. The model based on the presence of cluster defects in oxide crystals explains well the experimental data on the thermal and radiative coloring of these crystals. It is noted that cluster defects accumulate oxygen in oxide crystals. These defects are responsible also for the photochromic effect in them. Application of the noted model made it possible to fabricate lead tungstate scintillators at North Crystals Company for the ALICE project (CERN) with almost 100% reproducibility of their operating characteristics.

  13. Liquid crystals with patterned molecular orientation as an electrolytic active medium.

    PubMed

    Peng, Chenhui; Guo, Yubing; Conklin, Christopher; Viñals, Jorge; Shiyanovskii, Sergij V; Wei, Qi-Huo; Lavrentovich, Oleg D

    2015-11-01

    Transport of fluids and particles at the microscale is an important theme in both fundamental and applied science. One of the most successful approaches is to use an electric field, which requires the system to carry or induce electric charges. We describe a versatile approach to generate electrokinetic flows by using a liquid crystal (LC) with surface-patterned molecular orientation as an electrolyte. The surface patterning is produced by photoalignment. In the presence of an electric field, the spatially varying orientation induces space charges that trigger flows of the LC. The active patterned LC electrolyte converts the electric energy into the LC flows and transport of embedded particles of any type (fluid, solid, gaseous) along a predesigned trajectory, posing no limitation on the electric nature (charge, polarizability) of these particles and interfaces. The patterned LC electrolyte exhibits a quadratic field dependence of the flow velocities; it induces persistent vortices of controllable rotation speed and direction that are quintessential for micro- and nanoscale mixing applications. PMID:26651712

  14. Robustness of the periodic and chaotic orientational behavior of tumbling nematic liquid crystals.

    PubMed

    Heidenreich, Sebastian; Ilg, Patrick; Hess, Siegfried

    2006-06-01

    The dynamical behavior of molecular alignment strongly affects physical properties of nematic liquid crystals. A theoretical description can be made by a nonlinear relaxation equation of the order parameter and leads to the prediction that rather complex even chaotic orientational behavior occur. Here the influence of fluctuating shear rates on the orientational dynamics especially on chaotic solutions is discussed. With the help of phase portraits and time evolution diagrams, we investigated the influence of different fluctuation strengths on the flow aligned, isotropic, and periodic solutions. To explore the effect of fluctuations on the chaotic behavior, we calculated the largest Lyapunov exponent for different fluctuation strengths. We found in all cases that small fluctuations of the shear rate do not affect the basic features of the dynamics of tumbling nematics. Furthermore, we present an amended potential modeling the isotropic to nematic transition and discuss the equivalence and difference to the commonly used Landau-de Gennes potential. In contrast to the Landau-de Gennes potential, our potential has the advantage to restrict the order parameter to physically admissible values. In the case of extensional flow, we show that the amended potential leads for increasing extensional rate to a better agreement with experimental results. PMID:16906852

  15. Using chemically patterns with different anchoring behavior to control the orientation of nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Armas Perez, Julio; Martinez-Gonzalez, Jose Adrian; Xie, Helou; de Pablo, Juan; Nealey, Paul

    2015-03-01

    We present experimental and theoretical study of nematic liquid crystal (5CB) confined to a thin cell between homeotropic anchoring top surface and chemically patterned planar/homeotropic anchoring bottom substrates. The chemically patterned substrate with different dimensions and ~ 4 nm depth topography induce the 5CB to align as the pattern direction as non-degenerate behavior, until the width of the straight line pattern is too wide to confine the 5CB to one direction and back to degenerate behavior. By changing the width of the straight line pattern, a brightness change of the intensity is shown by their corresponding crossed polarizer images. This change is mainly due to a discontinuity of the average angle between the molecules and the surface in function of line width, which is in excellent agreement with the Landan-de Gennes theory when the balance between the elastic deformation in the bulk and orientation of molecules close to the surface is simulated for different pattern dimensions. An elastic free energy transition is also observed from the numerical analysis when the strong planar anchoring for presented experiments is changed to weak. This 3D confinement by chemically patterns and small depth topography offers a new way to generate any geometry pattern controllable non-degenerate orientation, achieving switchable optical properties.

  16. Young's Modulus, Residual Stress, and Crystal Orientation of Doubly Clamped Silicon Nanowire Beams.

    PubMed

    Calahorra, Y; Shtempluck, O; Kotchetkov, V; Yaish, Y E

    2015-05-13

    Initial or residual stress plays an important role in nanoelectronics. Valley degeneracy in silicon nanowires (SiNWs) is partially lifted due to built-in stresses, and consequently, electron-phonon scattering rate is reduced and device mobility and performance are improved. In this study we use a nonlinear model describing the force-deflection relationship to extract the Young's modulus, the residual stress, and the crystallographic growth orientation of SiNW beams. Measurements were performed on suspended doubly clamped SiNWs subjected to atomic force microscopy (AFM) three-point bending constraints. The nanowires comprised different growth directions and two SiO2 sheath thicknesses, and underwent different rapid thermal annealing processes. Analysis showed that rapid thermal annealing introduces compressive strains into the SiNWs and may result in buckling of the SiNWs. Furthermore, the core-shell model together with the residual stress analysis accurately describe the Young's modulus of oxide covered SiNWs and the crystal orientation of the measured nanowires. PMID:25826449

  17. Liquid crystals with patterned molecular orientation as an electrolytic active medium

    NASA Astrophysics Data System (ADS)

    Peng, Chenhui; Guo, Yubing; Conklin, Christopher; Viñals, Jorge; Shiyanovskii, Sergij V.; Wei, Qi-Huo; Lavrentovich, Oleg D.

    2015-11-01

    Transport of fluids and particles at the microscale is an important theme in both fundamental and applied science. One of the most successful approaches is to use an electric field, which requires the system to carry or induce electric charges. We describe a versatile approach to generate electrokinetic flows by using a liquid crystal (LC) with surface-patterned molecular orientation as an electrolyte. The surface patterning is produced by photoalignment. In the presence of an electric field, the spatially varying orientation induces space charges that trigger flows of the LC. The active patterned LC electrolyte converts the electric energy into the LC flows and transport of embedded particles of any type (fluid, solid, gaseous) along a predesigned trajectory, posing no limitation on the electric nature (charge, polarizability) of these particles and interfaces. The patterned LC electrolyte exhibits a quadratic field dependence of the flow velocities; it induces persistent vortices of controllable rotation speed and direction that are quintessential for micro- and nanoscale mixing applications.

  18. Robustness of the periodic and chaotic orientational behavior of tumbling nematic liquid crystals

    SciTech Connect

    Heidenreich, Sebastian; Hess, Siegfried; Ilg, Patrick

    2006-06-15

    The dynamical behavior of molecular alignment strongly affects physical properties of nematic liquid crystals. A theoretical description can be made by a nonlinear relaxation equation of the order parameter and leads to the prediction that rather complex even chaotic orientational behavior occur. Here the influence of fluctuating shear rates on the orientational dynamics especially on chaotic solutions is discussed. With the help of phase portraits and time evolution diagrams, we investigated the influence of different fluctuation strengths on the flow aligned, isotropic, and periodic solutions. To explore the effect of fluctuations on the chaotic behavior, we calculated the largest Lyapunov exponent for different fluctuation strengths. We found in all cases that small fluctuations of the shear rate do not affect the basic features of the dynamics of tumbling nematics. Furthermore, we present an amended potential modeling the isotropic to nematic transition and discuss the equivalence and difference to the commonly used Landau-de Gennes potential. In contrast to the Landau-de Gennes potential, our potential has the advantage to restrict the order parameter to physically admissible values. In the case of extensional flow, we show that the amended potential leads for increasing extensional rate to a better agreement with experimental results.

  19. Control of the spatial distribution and crystal orientation of self-organized Au nanoparticles.

    PubMed

    Yasukawa, Yukiko; Liu, Xiaoxi; Shirsath, Sagar E; Suematsu, Hisayuki; Kotaki, Yukio; Nemoto, Yoshihiro; Takeguchi, Masaki; Morisako, Akimitsu

    2016-09-23

    Ordered, two-dimensional, self-organized Au nanoparticles were fabricated using radiofrequency (RF) magnetron sputtering. The particles were uniformly spherical in shape and ultrafine in size (3-7 nm) and showed an ultrahigh density in the order of ∼10(12) inch(-2). A custom-developed sputtering apparatus that employs low sputtering power density and a minimized sputtering time (1 min) was used to markedly simplify the preparation conditions for Au nanoparticle fabrication. The spatial distribution of Au nanoparticles was rigorously controlled by placing a Ta interfacial layer between the Au nanoparticles and substrate as well as by post-annealing samples in an Ar atmosphere after the formation of Au nanoparticles. The interfacial layer and the post-annealing step caused approximately 40% of the Au nanoparticles on the substrate surface to orient in the (111) direction. This method was shown to produce ultrafine Au nanoparticles showing an ultrahigh surface density. The crystal orientation of the nanoparticles can be precisely controlled with respect to the substrate surface. Therefore, this technique promises to deliver tunable nanostructures for applications in the field of high-performance electronic devices. PMID:27528598

  20. Prediction of Fretting Crack Location and Orientation in a Single Crystal Nickel Alloy

    NASA Technical Reports Server (NTRS)

    Matlik, J. F.; Farris, T. N.; Haynes, J.; Swanson, G. R.; Ham-Battista, G.

    2005-01-01

    Fretting is a structural damage mechanism arising between two nominally clamped surfaces subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high- temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact that could potentially foster crack growth leading to component failure. These contact stresses drive crack nucleation in fretting and are very sensitive to the geometry of the contacting bodies, the contact loads, materials, temperature, and contact surface tribology (friction). Recently, a high-frequency, high-temperature load frame has been designed for experimentally investigating fretting damage of single crystal nickel materials employed in aircraft and spacecraft turbomachinery. A modeling method for characterizing the fretting stresses of the spherical fretting contact stress behavior in this experiment is developed and described. The calculated fretting stresses for a series of experiments are then correlated to the observed fretting damage. Results show that knowledge of the normal stresses and resolved shear stresses on each crystal plane can aid in predicting crack locations and orientations.

  1. Orientational disorder and phase transitions in crystals of (NH4)2NbOF5

    PubMed Central

    Udovenko, Anatoly A.; Laptash, Natalia M.

    2008-01-01

    Ammonium oxopentafluoroniobate, (NH4)2NbOF5, was synthesized in a single-crystal form and the structures of its different phases were determined by X-ray diffraction at three temperatures: phase (I) at 297 K, phase (II) at 233 K and phase (III) at 198 K. The distorted [NbOF5]2− octahedra are of similar geometry in all three structures, with the central atom shifted towards the O atom. The structure of (I) is disordered, with three spatial orientations of the [NbOF5]2− octahedron related by a jump rotation around the pseudo-threefold local axis such that the disorder observed is of a dynamic nature. As the temperature decreases, the compound undergoes two phase transitions. The first is accompanied by full anionic ordering and partial ordering of the ammonium groups (phase II). The structure of (III) is completely ordered. The F and O atoms in the structures investigated were identified via the Nb—X (X = O and F) distances. The crystals of all three phases are twinned. PMID:18799840

  2. Homoepitaxial meso- and microscale crystal co-orientation and organic matrix network structure in Mytilus edulis nacre and calcite.

    PubMed

    Griesshaber, Erika; Schmahl, Wolfgang W; Ubhi, Harbinder Singh; Huber, Julia; Nindiyasari, Fitriana; Maier, Bernd; Ziegler, Andreas

    2013-12-01

    New developments in high-resolution, low accelaration voltage electron backscatter diffraction (EBSD) enable us to resolve and quantify the co-orientation of nanocrystals constituting biological carbonate crystals with a scan step resolution of 125 nm. This allows the investigation of internal structures in carbonate tablets and tower biocrystals in the nacre of mollusc shells, and it provides details on the calcite-aragonite polymorph interface in bivalves. Within the aragonite tablets of Mytilus edulis nacre we find a mesoscale crystallographic mosaic structure with a misorientation distribution of 2° full width at half maximum. Selective etching techniques with critical point drying reveal an organic matrix network inside the nacre tablets. The size scales of the visible aragonite tablet subunits and nanoparticles correspond to those of the open pore system in the organic matrix network. We further observe by EBSD that crystal co-orientation spans over tablet boundaries and forms composite crystal units of up to 20 stacked co-oriented tablets (tower crystals). Statistical evaluation of the misorientation data gives a probability distribution of grain boundary misorientations with two maxima: a dominant peak for very-small-angle grain boundaries and a small maximum near 64°, the latter corresponding to {110} twinning orientations. However, the related twin boundaries are typically the membrane-lined {001} flat faces of the tablets and not {110} twin walls within tablets. We attribute this specific pattern of misorientation distribution to growth by particle accretion and subsequent semicoherent homoepitaxial crystallization. The semicoherent crystallization percolates between the tablets through mineral bridges and across matrix membranes surrounding the tablets. In the "prismatic" calcite layer crystallographic co-orientation of the prisms reaches over more than 50 micrometers. PMID:23896564

  3. Crystal preferred orientation of amphibole and implications for seismic anisotropy in the crust

    NASA Astrophysics Data System (ADS)

    Jung, Haemyeong

    2016-04-01

    Strong seismic anisotropy is often observed in the middle to lower crust and it has been considered to be originated from the crystal preferred orientation (CPO) of anisotropic minerals such as amphibole. Amphibolite is one of the dominant rocks in the middle to lower crust. In this study, crystal preferred orientations of hornblende in amphibolites at Yeoncheon and Chuncheon areas in South Korea were determined by using the electron backscattered diffraction (EBSD)/SEM with HKL Channel 5 software. In Yeoncheon area, hornblende showed two types of CPOs. Type-I CPO is characterized as (100) poles of hornblende aligned subnormal to foliation and [001] axes aligned subparallel to lineation. Type-II CPO is characterized as (100) poles of hornblende aligned subnormal to foliation and (010) poles aligned subparallel to lineation (refer to Ko and Jung, 2015, Nature Communications). In Chuncheon area, three types of CPOs of hornblende were observed. In addition to the type-I and -II CPOs described above, type-III CPO of hornblende was observed in Chuncheon area and it is characterized as (100) poles of hornblende aligned subnormal to foliation and both [001] axes and (010) poles aligned as a girdle subparallel to foliation. Using the observed CPO and the single crystal elastic constant of hornblende, seismic anisotropy of hornblende was calculated. Seismic anisotropy of P-wave was strong in the range of 10.2 - 13.5 %. Seismic anisotropy of S-wave was also strong in the range of 6.9 - 11.2 %. These results show that hornblende deformed in nature can produce a strong CPO, resulting in a strong seismic anisotropy in the middle to lower crust. Taking into account of the CPO of plagioclase in the rock, seismic anisotropies of whole rock turned out to be maximum P-wave anisotropy (Vp) of 9.8% and maximum S-wave anisotropy (Vs) of 8.2%. Therefore, strong seismic anisotropy found in the middle to lower crust in nature can be attributed to the CPO of hornblende in amphibolite.

  4. Precise Characterisation of Molecular Orientation in a Single Crystal Field-Effect Transistor Using Polarised Raman Spectroscopy.

    PubMed

    Wood, Sebastian; Rigas, Grigorios-Panagiotis; Zoladek-Lemanczyk, Alina; Blakesley, James C; Georgakopoulos, Stamatis; Mas-Torrent, Marta; Shkunov, Maxim; Castro, Fernando A

    2016-01-01

    Charge transport in organic semiconductors is strongly dependent on the molecular orientation and packing, such that manipulation of this molecular packing is a proven technique for enhancing the charge mobility in organic transistors. However, quantitative measurements of molecular orientation in micrometre-scale structures are experimentally challenging. Several research groups have suggested polarised Raman spectroscopy as a suitable technique for these measurements and have been able to partially characterise molecular orientations using one or two orientation parameters. Here we demonstrate a new approach that allows quantitative measurements of molecular orientations in terms of three parameters, offering the complete characterisation of a three-dimensional orientation. We apply this new method to organic semiconductor molecules in a single crystal field-effect transistor in order to correlate the measured orientation with charge carrier mobility measurements. This approach offers the opportunity for micrometre resolution (diffraction limited) spatial mapping of molecular orientation using bench-top apparatus, enabling a rational approach towards controlling this orientation to achieve optimum device performance. PMID:27619423

  5. Peculiar orientational disorder in 4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP) leading to bipolar crystals.

    PubMed

    Burgener, Matthias; Aboulfadl, Hanane; Labat, Gaël Charles; Bonin, Michel; Sommer, Martin; Sankolli, Ravish; Wübbenhorst, Michael; Hulliger, Jürg

    2016-05-01

    180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP)] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals. The spatial inhomogeneous distribution of polarity was investigated by scanning pyroelectric microscopy (SPEM), phase-sensitive second harmonic microscopy (PS-SHM) and selected volume X-ray diffraction (SVXD). As a result, the acceptor groups (NO2 or CN) are predominantly present at crystal surfaces. However, the stochastic process of polarity formation can be influenced by adding a symmetrical biphenyl to a growing system. For this case, Monte Carlo simulations predict an inverted net polarity compared with the growth of pure BNBP and BCNBP. SPEM results clearly demonstrate that 4,4'-dibromobiphenyl (DBBP) can invert the polarity for both crystals. Phenomena reported in this paper belong to the most striking processes seen for molecular crystals, demonstrated by a stochastic process giving rise to symmetry breaking. We encounter here further examples supporting the general thesis that monodomain polar molecular crystals for fundamental reasons cannot exist. PMID:27158508

  6. What does pressure decide to cook with orientationally disordered plastic phase of cubane: An orientational glass or crystal?

    NASA Astrophysics Data System (ADS)

    Arul Murugan, N.

    2005-12-01

    The effect of pressure on the structure and reorientational motion of molecules in orientationally disordered (OD) crystalline phase of cubane has been investigated in detail using variable shape molecular simulations in constant-pressure constant-temperature ensemble. Complete orientational ordering occurs at a pressure of 1.0 GPa and the OD phase transforms to an orientationally ordered phase at this pressure. The transition is associated with a kink in the variation of structural parameters such as cell parameters, unit-cell volume, and interaction energy. This transition is also associated with an anomaly in specific heat. Above this transition pressure, the structural quantities display only smaller changes with further increase in pressure. The structure of high-pressure orientationally ordered (HPOO) phase has been characterized using radial distribution functions and orientational distribution function. From detailed analysis of the structure of HPOO phase we conclude that it is isostructural with low-temperature orientationally ordered phase. The OD phase has four times larger compressibility than the HPOO phase.

  7. Hydrogen induced fracture characteristics of single crystal nickel-based superalloys

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Wilcox, Roy C.

    1990-01-01

    A stereoscopic method for use with x ray energy dispersive spectroscopy of rough surfaces was adapted and applied to the fracture surfaces single crystals of PWA 1480E to permit rapid orientation determinations of small cleavage planes. The method uses a mathematical treatment of stereo pair photomicrographs to measure the angle between the electron beam and the surface normal. One reference crystal orientation corresponding to the electron beam direction (crystal growth direction) is required to perform this trace analysis. The microstructure of PWA 1480E was characterized before fracture analysis was performed. The fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was studied. The hydrogen-induced fracture behavior of single crystals of the PWA 1480E nickel-based superalloy was also studied. In order to understand the temperature dependence of hydrogen-induced embrittlement, notched single crystals with three different crystal growth orientations near zone axes (100), (110), and (111) were tensile tested at 871 C (1600 F) in both helium and hydrogen atmospheres at 34 MPa. Results and conclusions are given.

  8. Influence of crystal orientation and ion bombardment on the nitrogen diffusivity in single-crystalline austenitic stainless steel

    SciTech Connect

    Martinavicius, A.; Abrasonis, G.; Moeller, W.

    2011-10-01

    The nitrogen diffusivity in single-crystalline AISI 316L austenitic stainless steel (ASS) during ion nitriding has been investigated at different crystal orientations ((001), (110), (111)) under variations of ion flux (0.3-0.7 mA cm{sup -2}), ion energy (0.5-1.2 keV), and temperature (370-430 deg. C). The nitrogen depth profiles obtained from nuclear reaction analysis are in excellent agreement with fits using the model of diffusion under the influence of traps, from which diffusion coefficients were extracted. At fixed ion energy and flux, the diffusivity varies by a factor up to 2.5 at different crystal orientations. At (100) orientation, it increases linearly with increasing ion flux or energy. The findings are discussed on the basis of atomistic mechanisms of interstitial diffusion, potential lattice distortions, local decomposition, and ion-induced lattice vibrational excitations.

  9. Influence of crystal orientation and ion bombardment on the nitrogen diffusivity in single-crystalline austenitic stainless steel

    NASA Astrophysics Data System (ADS)

    Martinavičius, A.; Abrasonis, G.; Möller, W.

    2011-10-01

    The nitrogen diffusivity in single-crystalline AISI 316L austenitic stainless steel (ASS) during ion nitriding has been investigated at different crystal orientations ((001), (110), (111)) under variations of ion flux (0.3-0.7 mA cm-2), ion energy (0.5-1.2 keV), and temperature (370-430 °C). The nitrogen depth profiles obtained from nuclear reaction analysis are in excellent agreement with fits using the model of diffusion under the influence of traps, from which diffusion coefficients were extracted. At fixed ion energy and flux, the diffusivity varies by a factor up to 2.5 at different crystal orientations. At (100) orientation, it increases linearly with increasing ion flux or energy. The findings are discussed on the basis of atomistic mechanisms of interstitial diffusion, potential lattice distortions, local decomposition, and ion-induced lattice vibrational excitations.

  10. Vapor phase growth of GaN crystals with different morphologies and orientations on graphite and sapphire substrates

    SciTech Connect

    Miura, Akira; Shimada, Shiro . E-mail: shimashi@eng.hokudai.ac.jp

    2006-09-14

    GaN crystals were grown on graphite and sapphire substrates at 990-1050 deg. C by reaction of Ga{sub 2}O with flowing NH{sub 3}. Ga{sub 2}O gas was produced at a constant rate (1.3 wt% min{sup -1}) by reaction of Ga{sub 2}O{sub 3} with carbon at 1000-1060 deg. C. The effect of NH{sub 3} concentration (3-100 vol%) and the nature of the substrate on the morphology and orientation of the GaN crystals were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and selected area electron diffraction. It was found that sheet and plate-like crystals grew at different orientations to the substrate with different NH{sub 3} concentrations and substrates.

  11. Preferential growth orientation of laser-patterned LiNbO{sub 3} crystals in lithium niobium silicate glass

    SciTech Connect

    Komatsu, T.; Koshiba, K.; Honma, T.

    2011-02-15

    Dots and lines consisting of LiNbO{sub 3} crystals are patterned on the surface of 1CuO-40Li{sub 2}O-32Nb{sub 2}O{sub 5}-28SiO{sub 2} (mole ratio) glass by irradiations of continuous-wave Nd:YAG laser (wavelength: {lambda}=1064 nm), diode laser ({lambda}=795 nm), and Yb:YVO{sub 4} fiber laser ({lambda}=1080 nm), and the feature of laser-patterned LiNbO{sub 3} crystal growth is examined from linearly polarized micro-Raman scattering spectrum measurements. LiNbO{sub 3} crystals with the c-axis orientation are formed at the edge parts of the surface and cross-section of dots. The growth direction of an LiNbO{sub 3} along the laser scanning direction is the c-axis. It is proposed that the profile of the temperature distribution in the laser-irradiated region and its change along laser scanning would be one of the most important conditions for the patterning of crystals with a preferential growth orientation. Laser irradiation giving a narrow width is also proposed to be one of the important factors for the patterning of LiNbO{sub 3} crystal lines with homogeneous surface morphologies. -- Graphical abstract: Polarized optical microscope observations for the surface and cross-section of the dot obtained by LD laser ({lambda}=795 nm) irradiations of P=1.4 W and t=20 s in Cu-LNS glass. Schematic model for the orientation of LiNbO{sub 3} crystals at the edge parts of the surface and cross-section of the dot is also shown. Display Omitted Research highlights: > Dots and lines with LiNbO{sub 3} crystals are patterned on the glass surface by laser irradiations. > LiNbO{sub 3} crystals with the c-axis orientation are formed at the edge parts of the surface and cross-section of dots. > The profile of the temperature distribution in the laser-irradiated region is one of the most important conditions for the patterning of highly oriented crystals.

  12. Microstructure Evolution and Analysis of A [011] Orientation, Single-Crystal, Nickel-Based Superalloy During Tensile Creep

    NASA Astrophysics Data System (ADS)

    Tian, Sugui; Zhang, Shu; Li, Chenxi; Yu, Huichen; Su, Yong; Yu, Xingfu; Yu, Lili

    2012-10-01

    By means of the elastic-plastic finite-element method (FEM) for calculating the distribution features of the von Mises stress and strain energy density, the influences of the applied stress on the von Mises stress of the γ'/ γ phases and the rafting of the γ' phase for the [011] orientation, single-crystal, nickel-based superalloy are investigated. The results show that, after being fully heat treated, the microstructure of the [011] orientation, single-crystal, nickel-based superalloy consists of the cuboidal γ' phase embedded coherently in the γ matrix, and the cuboidal γ' phase on (100) plane is regularly arranged along a 45 deg angle relative to the [011] orientation. Compared with the matrix channel of [010] orientation, the bigger von Mises stress is produced within the [001] matrix channel when the tensile stress is applied along the [011] orientation. Under the action of the larger principal stress component, the bigger expanding lattice strain occurs on the (001) plane of the cuboidal γ' phase along the [010] direction, which may trap the Al, Ti atoms with a bigger atomic radius for promoting the directional growth of the γ' phase into the stripe-like rafted structure along the [001] orientation. The changes of the interatomic potential energy, misfit stress, and interfacial energy during the tensile creep are thought to be the driving forces of promoting the elements' diffusion and directional growth of the γ' phase.

  13. Orientational coupling between the vortex lattice and the crystalline lattice in a weakly pinned Co0.0075NbSe2 single crystal

    NASA Astrophysics Data System (ADS)

    Ganguli, Somesh Chandra; Singh, Harkirat; Ganguly, Rini; Bagwe, Vivas; Thamizhavel, Arumugam; Raychaudhuri, Pratap

    2016-04-01

    We report experimental evidence of strong orientational coupling between the crystal lattice and the vortex lattice in a weakly pinned Co-doped NbSe2 single crystal through direct imaging using low temperature scanning tunneling microscopy/spectroscopy. When the magnetic field is applied along the six-fold symmetric c-axis of the NbSe2 crystal, the basis vectors of the vortex lattice are preferentially aligned along the basis vectors of the crystal lattice. The orientational coupling between the vortex lattice and crystal lattice becomes more pronounced as the magnetic field is increased. This orientational coupling enhances the stability of the orientational order of the vortex lattice, which persists even in the disordered state at high fields where dislocations and disclinations have destroyed the topological order. Our results underpin the importance of crystal lattice symmetry on the vortex state phase diagram of weakly pinned type II superconductors.

  14. Processing of X-ray snapshots from crystals in random orientations

    PubMed Central

    Kabsch, Wolfgang

    2014-01-01

    A functional expression is introduced that relates scattered X-ray intensities from a still or a rotation snapshot to the corresponding structure-factor amplitudes. The new approach was implemented in the program nXDS for processing monochromatic diffraction images recorded by a multi-segment detector where each exposure could come from a different crystal. For images containing indexable spots, the intensities of the expected reflections and their variances are obtained by profile fitting after mapping the contributing pixel contents to the Ewald sphere. The varying intensity decline owing to the angular distance of the reflection from the surface of the Ewald sphere is estimated using a Gaussian rocking curve. This decline is dubbed ‘Ewald offset correction’, which is well defined even for still images. Together with an image-scaling factor and other corrections, an explicit expression is defined that predicts each recorded intensity from its corresponding structure-factor amplitude. All diffraction parameters, scaling and correction factors are improved by post-refinement. The ambiguous case of a lower point group than the lattice symmetry is resolved by a method reminiscent of the technique of ‘selective breeding’. It selects the indexing alternative for each image that yields, on average, the highest correlation with intensities from all other images. Processing a test set of rotation images by XDS and treating the same images by nXDS as snapshots of crystals in random orientations yields data of comparable quality, clearly indicating an anomalous signal from Se atoms. PMID:25084339

  15. Crystal Orientation and Temperature Effects on the Double Hysteresis Loop Behavior of a PVDF- g-PS Graft Copolymer

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Yang, Lianyun; Guan, Fangxiao

    2013-03-01

    In a recent report, double hysteresis loop behavior is observed in a nanoconfined poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene)-graft-polystyrene [P(VDF-TrFE-CTFE)- g-PS] copolymer. It is considered that the PS grafts are capable of reducing the compensation polarization and thus the polarization electric field during the reverse poling process, resulting in the double hysteresis loop behavior. In this study, we further investigated crystal orientation and temperature effects on this novel ferroelectric behavior. It is observed that with increasing the orientation factor, the electric displacement-electric field (D-E) loop changes from linear for non-oriented film to double loop for the well-oriented film. With increasing the temperature, the double hysteresis loop is gradually replaced by the single and open loop, which is attributed to the impurity ion migrational loss in the sample. This work is supported by NSF (DMR-0907580).

  16. Crystal orientation mechanism of ZnTe epilayers formed on different orientations of sapphire substrates by molecular beam epitaxy

    SciTech Connect

    Nakasu, T. Yamashita, S.; Aiba, T.; Hattori, S.; Sun, W.; Taguri, K.; Kazami, F.; Kobayashi, M.

    2014-10-28

    The electrooptic effect in ZnTe has recently attracted research attention, and various device structures using ZnTe have been explored. For application to practical terahertz wave detector devices based on ZnTe thin films, sapphire substrates are preferred because they enable the optical path alignment to be simplified. ZnTe/sapphire heterostructures were focused upon, and ZnTe epilayers were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. Epitaxial relationships between the ZnTe thin films and the sapphire substrates with their various orientations were investigated using an X-ray diffraction pole figure method. (0001) c-plane, (1-102) r-plane, (1-100) m-plane, and (11-20) a-plane oriented sapphire substrates were used in this study. The epitaxial relationship between ZnTe and c-plane sapphire was found to be (111) ZnTe//(0001) sapphire with an in-plane orientation relationship of [−211] ZnTe//[1-100] sapphire. It was found that the (211)-plane ZnTe layer was grown on the m-plane of the sapphire substrates, and the (100)-plane ZnTe layer was grown on the r-plane sapphire. When the sapphire substrates were inclined from the c-plane towards the m-axis direction, the orientation of the ZnTe thin films was then tilted from the (111)-plane to the (211)-plane. The c-plane of the sapphire substrates governs the formation of the (111) ZnTe domain and the ZnTe epilayer orientation. These crystallographic features were also related to the atom arrangements of ZnTe and sapphire.

  17. Crystal orientation mechanism of ZnTe epilayers formed on different orientations of sapphire substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Nakasu, T.; Yamashita, S.; Aiba, T.; Hattori, S.; Sun, W.; Taguri, K.; Kazami, F.; Kobayashi, M.

    2014-10-01

    The electrooptic effect in ZnTe has recently attracted research attention, and various device structures using ZnTe have been explored. For application to practical terahertz wave detector devices based on ZnTe thin films, sapphire substrates are preferred because they enable the optical path alignment to be simplified. ZnTe/sapphire heterostructures were focused upon, and ZnTe epilayers were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. Epitaxial relationships between the ZnTe thin films and the sapphire substrates with their various orientations were investigated using an X-ray diffraction pole figure method. (0001) c-plane, (1-102) r-plane, (1-100) m-plane, and (11-20) a-plane oriented sapphire substrates were used in this study. The epitaxial relationship between ZnTe and c-plane sapphire was found to be (111) ZnTe//(0001) sapphire with an in-plane orientation relationship of [-211] ZnTe//[1-100] sapphire. It was found that the (211)-plane ZnTe layer was grown on the m-plane of the sapphire substrates, and the (100)-plane ZnTe layer was grown on the r-plane sapphire. When the sapphire substrates were inclined from the c-plane towards the m-axis direction, the orientation of the ZnTe thin films was then tilted from the (111)-plane to the (211)-plane. The c-plane of the sapphire substrates governs the formation of the (111) ZnTe domain and the ZnTe epilayer orientation. These crystallographic features were also related to the atom arrangements of ZnTe and sapphire.

  18. Orientation epitaxy of Ge1–xSnx films grown on single crystal CaF2 substrates

    DOE PAGESBeta

    A. J. Littlejohn; Zhang, L. H.; Lu, T. -M.; Kisslinger, K.; and Wang, G. -C.

    2016-03-15

    Ge1–xSnx films were grown via physical vapor deposition below the crystallization temperature of Ge on single crystal (111) and (100) CaF2 substrates to assess the role of Sn alloying in Ge crystallization. By studying samples grown at several growth temperatures ranging from 250 °C to 400 °C we report temperature-dependent trends in several of the films' properties. X-ray diffraction theta vs. two-theta (θ/2θ) scans indicate single orientation Ge1–xSnx(111) films are grown on CaF2(111) substrates at each temperature, while a temperature-dependent superposition of (111) and (100) orientations are exhibited in films grown on CaF2(100) above 250 °C. This is the firstmore » report of (111) oriented Ge1–xSnx grown on a (100) oriented CaF2 substrate, which is successfully predicted by a superlattice area matching model. These results are confirmed by X-ray diffraction pole figure analysis. θ/2θ results indicate substitutional Sn alloying in each film of about 5%, corroborated by energy dispersive spectroscopy. In addition, morphological and electrical properties are measured by scanning electron microscopy, atomic force microscopy and Hall mobility measurements and are also shown to be dependent upon growth temperature.« less

  19. Combined Effect of Shear and Fibrous Fillers on Orientation-Induced Crystallization in Discontinuous Aramid Fiber-Isotactic Polypropylene Composites

    SciTech Connect

    Larin,B.; Avila-Orta, C.; Somani, R.; Hsiao, B.; Marom, G.

    2008-01-01

    The shear-induced crystallization behavior in isotactic polypropylene (iPP) composite melt containing short aramid fibers was investigated by means of WAXD (wide-angle X-ray diffraction) and SAXS (small-angle X-ray scattering) techniques using synchrotron radiation. The study was carried out in a post-shear isothermal crystallization mode at temperatures of 140-160 C. Parameters pertaining to the crystallization morphology and kinetics were analyzed, including total crystallinity, orientated crystalline and amorphous fractions, dimensions of the formed shish-kebab structure, as well as induction time and rate of crystallization. The individual contributions of shear and fibers were evaluated and the combined effect was compared. The results clearly indicated that the effect is synergistic rather than additive.

  20. Mechanical property enhancement in laminates through control of morphology and crystal orientation

    NASA Astrophysics Data System (ADS)

    Zeilinger, A.; Daniel, R.; Stefenelli, M.; Sartory, B.; Chitu, L.; Burghammer, M.; Schöberl, T.; Kolednik, O.; Keckes, J.; Mitterer, C.

    2015-07-01

    This article shows the successful implementation of biological design principles into synthetic laminate materials in order to enhance their mechanical properties. We demonstrate and provide a strategy for laminate thin films, which reveals that the control of local crystal anisotropy across laminates together with the optimized layered arrangement are essential for their mechanical behavior. By the example of a laminate consisting of brittle CrN and ductile Cr layers, enhanced material properties are achieved by taking advantage of the self assembly mechanisms of the heterogeneous material during film growth. The usage of local microstructure analysis by a synchrotron based technique as well as miniature mechanical tests allow to understand the relationship between the apparent local microstructure and the accompanied mechanical properties. A crystallographic orientation relationship between Cr and CrN is elucidated, which leads to decisive mechanical enhancement due to microstructural benefits in terms of texture. This results in enhanced strength and fracture toughness of the laminate compared to its single constituents. The systematic approach gives an insight into the complex coherences of laminate materials, where the used techniques and design principles are universally applicable.

  1. Utilization of oriented crystal growth for screening of aromatic carboxylic acids cocrystallization with urea

    NASA Astrophysics Data System (ADS)

    Przybyłek, Maciej; Ziółkowska, Dorota; Kobierski, Mirosław; Mroczyńska, Karina; Cysewski, Piotr

    2016-01-01

    The possibility of molecular complex formation in the solid state of urea with benzoic acid analogues was measured directly on the crystallite films deposited on the glass surface using powder X-ray diffractometry (PXRD). Obtained solid mixtures were also analyzed using Fourier transform infrared spectroscopy (FTIR). The simple droplet evaporation method was found to be efficient, robust, fast and cost-preserving approach for first stage cocrystal screening. Additionally, the application of orientation effect to cocrystal screening simplifies the analysis due to damping of majority of diffraction signals coming from coformers. During validation phase the proposed approach successfully reproduced both positive cases of cocrystallization (urea:salicylic acid and urea:4-hydroxy benzoic acid) as well as pairs of co-formers immiscible in the solid state (urea:benzoic acid and urea:acetylsalicylic acids). Based on validated approach new cocrystals of urea were identified in complexes with 3-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid and 3,5-dihydroxybenzoic acid. In all cases formation of multicomponent crystal phase was confirmed by the appearance of new reflexes on the diffraction patterns and FTIR absorption band shifts of O-H and N-H groups.

  2. Assessment of the Characteristics of Orientation Distribution Functions in HARDI Using Morphological Metrics

    PubMed Central

    Sun, Chang-yu; Zhu, Yue-min; Chu, Chun-yu; Yang, Feng; Liu, Wan-yu; Korenberg, Julie R.; Hsu, Edward W.

    2016-01-01

    Orientation distribution functions (ODFs) are widely used to resolve fiber crossing problems in high angular resolution diffusion imaging (HARDI). The characteristics of the ODFs are often assessed using a visual criterion, although the use of objective criteria is also reported, which are directly borrowed from classic signal and image processing theory because they are intuitive and simple to compute. However, they are not always pertinent for the characterization of ODFs. We propose a more general paradigm for assessing the characteristics of ODFs. The idea consists in regarding an ODF as a three-dimensional (3D) point cloud, projecting the 3D point cloud onto an angle-distance map, constructing an angle-distance matrix, and calculating metrics such as length ratio, separability, and uncertainty. The results from both simulated and real data show that the proposed metrics allow for the assessment of the characteristics of ODFs in a quantitative and relatively complete manner. PMID:26919477

  3. The Extent to Which the Characteristics of a Metacognitive Oriented Learning Environment Predict the Characteristics of a Thinking-Friendly Classroom

    ERIC Educational Resources Information Center

    Alkin-Sahin, Senar

    2015-01-01

    Problem Statement: Based on information presented in previous literature, that the characteristics of learning environments foster metacognition and thinking, it is believed that metacognitive oriented classrooms can contribute to the formation of environments needed to teach thinking, and when metacognitive oriented learning environment…

  4. Optical characteristics of LGP depending on the scattering pattern orientation for flat-type LED lighting

    NASA Astrophysics Data System (ADS)

    Park, Sohee; Shin, Yongjin; Oh, Kwanghwan; Bang, Taehwan

    2016-04-01

    In flat-type light-emitting-diode (LED) lighting systems, a planar light is formed using a luminance source positioned on the side of the system and light guide panel (LGP) or reflecting plates. Thus, such systems are favorable for their thinness, which allows a relatively small number of LEDs to be used. However, the application of a high-power LED light to a large-area lighting system yields Lambertian luminaires; therefore, a point or a discomfort glare is produced, which generally causes degradation of the luminance efficiency and uniformity. In this study, we solved the problems of luminance non-uniformity and inefficiency by adjusting the orientation of an applied LGP scattered pattern and removing the remaining glare. Through computer simulation, optical characteristics that increase the efficiency even in the case of low-output LEDs were found. Specifically, a scattered pattern vertically oriented relative to the direction of the incident light improves the luminance uniformity at the side of the system, while a scattered pattern oriented parallel to the direction of the incident light plays the role of a waveguide. We implemented a flat-type LED lighting system by fabricating a large-area LGP based on the computer-simulation results and using an extremely sensitive laser. The optical characteristics observed using the laser-processed LGP were identical to those obtained in the computer simulation. Therefore, for large-area flat-type LED lighting systems, we confirmed that adjusting the orientation of the LGP scattered pattern can increase the luminance efficiency and uniformity.

  5. Ferroelectric, Thermal, and Magnetic Characteristics of Praseodymium Malonate Hexahydrate Crystals

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2016-04-01

    Gel-grown single crystals of [Pr2(C3H2O4)3(H2O)6] exhibit remarkably flat habit faces, the most predominant being {110}. High-resolution x-ray diffraction analysis showed that the crystals are free from structural grain boundaries, which is the key requirement for single crystals for use in the microelectronics industry to serve as low-dielectric-constant ferroelectric material. The dielectric behavior recorded on {110} planes of single crystals shows that the crystal is ferroelectric with transition temperature T c = 135°C, which differs from the Curie-Weiss temperature T 0 by 2°C (T 0 < T c). Material in pellet form is shown to exhibit slightly different dielectric behavior. Polarization versus electric field confirms the ferroelectric behavior of the material. The dielectric behavior is also supported by the results of thermal studies, viz. thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The magnetic susceptibility and magnetic moment are calculated to be 30.045 × 10-6 emu and 3.092 BM, respectively.

  6. Influence of crack orientation on the ductile-brittle behavior in Fe-3 wt.% Si single crystals

    SciTech Connect

    Spielmannova, Alena Landa, Michal; Machova, Anna; Hausild, Petr; Lejcek, Pavel

    2007-10-15

    In this paper we present experimental results from fracture tests performed at room temperature on bcc iron-silicon single crystals with edge cracks of two different orientations (001)[110] and (- 110)[110]. The cracks were loaded under mode I. The fracture toughness and acoustic emission response were measured, and a fractographic analysis obtained via scanning electron microscopy was carried out. Experimental results confirm the basic predictions pertaining to the influence of crack orientation on crack stability from continuum modeling and molecular dynamic simulations in bcc iron.

  7. Nematic order-disorder state transition in a liquid crystal analogue formed by oriented and migrating amoeboid cells

    NASA Astrophysics Data System (ADS)

    Kemkemer, R.; Teichgräber, V.; Schrank-Kaufmann, S.; Kaufmann, D.; Gruler, H.

    2000-10-01

    In cell culture, liquid crystal analogues are formed by elongated, migrating, and interacting amoeboid cells. An apolar nematic liquid crystal analogue is formed by different cell types like human melanocytes (=pigment cells of the skin), human fibroblasts (=connective tissue cells), human osteoblasts (=bone cells), human adipocytes (=fat cells), etc. The nematic analogue is quite well described by i) a stochastic machine equation responsible for cell orientation and ii) a self-organized extracellular guiding signal, E_2, which is proportional to the orientational order parameter as well as to the cell density. The investigations were mainly made with melanocytes. The transition to an isotropic state analogue can be accomplished either by changing the strength of interaction (e.g. variation of the cell density) or by influencing the cellular machinery by an externally applied signal: i) An isotropic gaseous state analogue is observed at low cell density (ρ < 110melanocytes/mm^2) and a nematic liquid crystal state analogue at higher cell density. ii) The nematic state analogue disappears if the bipolar shaped melanocytes are forced to become a star-like shape (induced by colchicine or staurosporine). The analogy between nematic liquid crystal state analogue formed by elongated, migrating and interacting cells and the nematic liquid crystal phase formed by interacting elongated molecules is discussed.

  8. Some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening

    NASA Technical Reports Server (NTRS)

    Bahadur, H.; Parshad, R.

    1983-01-01

    The paper reports some new results on irradiation characteristics of synthetic quartz crystals and their application to radiation hardening. The present results show how the frequency shift in quartz crystals can be influenced by heat processing prior to irradiation and how this procedure can lead to radiation hardening for obtaining precise frequencies and time intervals from quartz oscillators in space.

  9. Spectroscopic characteristics of GdVO4: Dy3+ crystal

    NASA Astrophysics Data System (ADS)

    Ning, Kaijie; He, Xiaoming; Zhang, Lianhan; Liu, Youchen; Yin, Jigang; Zhang, Peixing; Chen, Guangzhu; Wang, Xiangyong; Chen, Zhe; Shi, Chunjun; Hong, Jiaqi; Hang, Yin

    2014-11-01

    Room temperature optical absorption, emission spectrum of GdVO4: Dy3+ crystal grown by Czochralski (CZ) method were measured and analyzed. Spectral parameters were calculated in the framework of the Judd-Ofelt theory. The GdVO4: Dy3+ crystal showed two intense and relatively broad absorption bands in UV wavelength range centered at 390 and 453 nm and two prominent emission peaks located at blue 485 and yellow 575 nm. The corresponding absorption and emission cross sections were estimated and the luminescence decay curve was analyzed. Optical spectroscopy investigations indicate that GdVO4: Dy3+ crystal would be a promising blue and yellow solid state laser material.

  10. Transmission characteristics of a twisted nematic liquid-crystal layer

    NASA Technical Reports Server (NTRS)

    Grinberg, J.; Jacobson, A. D.

    1976-01-01

    An approximate analytical expression is calculated for the transmission of thin twisted nematic layers situated between a polarizer/analyzer pair. The approximation assumes that the twist angle of the nematic liquid crystal is smaller than the maximum retardation of the cell. The direction of the incident light is assumed to be parallel to the normal of the electrode. This configuration is analyzed for a general arrangement of polarizer and analyzer; the general result is evaluated for the case of the polarizer parallel and analyzer perpendicular to the liquid-crystal optical axis on the input and output electrodes, respectively. The results show that in the case of a thin twisted nematic layer the transmission depends on the thickness of the layer, on the birefringence of the liquid crystal, and on the wavelength of the light. This is a departure from the well-known independence of the transmission on these parameters for a thick twisted nematic layer.

  11. Cathodoluminescence and scintillation characteristics of YAG:Ce crystals grown by horizontal directional crystallization in a protective atmosphere

    NASA Astrophysics Data System (ADS)

    Nizhankovsky, S. V.; Dan'ko, A. Ya.; Zelenskaya, O. V.; Tarasov, V. A.; Zorenko, Yu. V.; Puzikov, V. M.; Grin', L. A.; Trushkovskii, A. G.; Savchin, V. P.

    2009-10-01

    YAG:Ce crystals have been grown by a new gas-phase horizontal directional crystallization (HDC) technique in a protective atmosphere and their cathodoluminescence (CL) spectra and scintillation characteristics have been studied. Using this HDC technology, it is possible to obtain large (110 × 150 × 35 mm) crystals with a high specific light yield (15 000-18 000 Ph/MeV) and good amplitude resolution (8-10%) for the excitation with 5.15-MeV α particles from a 239Pu source. In addition to an intense band at 550 nm due to Ce3+ ions, the CL spectra of crystals display an intrinsic emission band of YAG in the UV spectral range, which is due to the presence of YAl antisite defects.

  12. The polarization trajectory of terahertz magnetic dipole radiation in (110)-oriented PrFeO3 single crystal

    NASA Astrophysics Data System (ADS)

    Song, Gaibei; Jin, Zuanming; Lin, Xian; Jiang, Junjie; Wang, Xinyan; Wu, Hailong; Ma, Guohong; Cao, Shixun

    2014-04-01

    By using the polarized terahertz (THz) time-domain spectroscopy, the macro-magnetization motion in (110)-oriented PrFeO3 single crystal was constructed. We emphasize that the trajectory of the emitted THz waveforms relies on not only the motion of macroscopic magnetization vector, but also the spin configuration in the ground state and the propagation of THz pulse. The azimuthal angle (the incident THz pulse polarization with respect to the crystal axes) enables us to control the polarization trajectories of the quasiferromagnetic and quasiantiferromagnetic mode radiations that can lead to further applications on multiple information storing and quantum processing.

  13. The polarization trajectory of terahertz magnetic dipole radiation in (110)-oriented PrFeO{sub 3} single crystal

    SciTech Connect

    Song, Gaibei; Jin, Zuanming; Lin, Xian; Jiang, Junjie; Wang, Xinyan; Wu, Hailong; Ma, Guohong E-mail: sxcao@shu.edu.cn; Cao, Shixun E-mail: sxcao@shu.edu.cn

    2014-04-28

    By using the polarized terahertz (THz) time-domain spectroscopy, the macro-magnetization motion in (110)-oriented PrFeO{sub 3} single crystal was constructed. We emphasize that the trajectory of the emitted THz waveforms relies on not only the motion of macroscopic magnetization vector, but also the spin configuration in the ground state and the propagation of THz pulse. The azimuthal angle (the incident THz pulse polarization with respect to the crystal axes) enables us to control the polarization trajectories of the quasiferromagnetic and quasiantiferromagnetic mode radiations that can lead to further applications on multiple information storing and quantum processing.

  14. Characteristic Pressure Dependence of Spontaneous Polarization in Ferroelectric Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Uehara, Hiroyuki

    2008-09-01

    The spontaneous polarization and rotational viscosity of the c-director of the ferroelectric liquid crystal 4'-octyloxy-biphenyl-4-carboxylic acid 4-(1-methyl-heptyloxy)-phenyl ester at various pressures were investigated. Spontaneous polarization as a function of T-TCA( p) decreased markedly when pressure was changed from 0.1 to 20 MPa and was independent of pressure as pressure was further increased. Rotational viscosity decreased when pressure was applied. These results suggest that the conformation of liquid crystal molecules changes at pressures below 20 MPa.

  15. Modeling the effects of stress state and crystal orientation on the stress-induced transformation of NiTi single crystals

    NASA Astrophysics Data System (ADS)

    Buchheit, T. E.; Wert, J. A.

    1994-11-01

    A model that combines the phenomenological theory of martensite with a generalized Schmid’s law has been used to predict the principal stress combinations required to induce the martensitic transformation in unconstrained NiTi shape memory alloy (SMA) single crystals. The transformation surfaces prescribed by the model are anisotropic and asymmetric, reflecting the unidirectional character of shear on individual martensite habit planes. Model predictions of the transformation strain as a function of stress axis orientation for a uniaxial applied stress further demonstrate the anisotropy of the stress-induced transformation in NiTi single crystals. Model results for the uniaxial stress case compare favorably with previously published experimental observations for aged NiTi single crystals.

  16. Modeling the effects of stress state and crystal orientation on the stress-induced transformation of NiTi single crystals

    SciTech Connect

    Buchheit, T.E.; Wert, J.A. . Dept. of Materials Science and Engineering)

    1994-11-01

    A model that combines the phenomenological theory of martensite with a generalized Schmid's law has been used to predict the principal stress combinations required to induce the martensitic transformation in unconstrained NiTi shape memory alloy (SMA) single crystals. The transformation surfaces prescribed by the model are anisotropic and asymmetric, reflecting the unidirectional character of shear on individual martensite habit planes. Model predictions of the transformation strain as a function of stress axis orientation for uniaxial applied stress further demonstrate the anisotropy of the stress-induced transformation in NiTi single crystals. Model results for the uniaxial stress case compare favorably with previously published experimental observations for aged NiTi single crystals.

  17. Genetic variation in eggshell crystal size and orientation is large and these traits are correlated with shell thickness and are associated with eggshell matrix protein markers.

    PubMed

    Dunn, I C; Rodríguez-Navarro, A B; Mcdade, K; Schmutz, M; Preisinger, R; Waddington, D; Wilson, P W; Bain, M M

    2012-08-01

    The size and orientation of calcium carbonate crystals influence the structure and strength of the eggshells of chickens. In this study, estimates of heritability were found to be high (0.6) for crystal size and moderate (0.3) for crystal orientation. There was a strong positive correlation (0.65) for crystal size and orientation with the thickness of the shell and, in particular, with the thickness of the mammillary layer. Correlations with shell breaking strength were positive but with a high standard error. This was contrary to expectations, as in man-made materials smaller crystals would be stronger. We believe the results of this study support the hypothesis that the structural organization of shell, and in particular the mammillary layer, is influenced by crystal size and orientation, especially during the initial phase of calcification. Genetic associations for crystal measurements were observed between haplotype blocks or individual markers for a number of eggshell matrix proteins. Ovalbumin and ovotransferrin (LTF) markers for example were associated with crystal size, while ovocleidin-116 and ovocalyxin-32 (RARRES1) markers were associated with crystal orientation. The location of these proteins in the eggshell is consistent with different phases of the shell-formation process. In conclusion, the variability of crystal size, and to a lesser extent orientation, appears to have a large genetic component, and the formation of calcite crystals are intimately related to the ultrastructure of the eggshell. Moreover, this study also provides evidence that proteins in the shell influence the variability of crystal traits and, in turn, the shell's thickness profile. The crystal measurements and/or the associated genetic markers may therefore prove to be useful in selection programs to improve eggshell quality. PMID:22497523

  18. The anisotropy of the basic characteristics of Lamb waves in a (001)-Bi12SiO20 piezoelectric crystal

    NASA Astrophysics Data System (ADS)

    Anisimkin, V. I.

    2016-03-01

    The orientation dependences of the phase velocity, the effective electromechanical coupling coefficient, and the angle between the wave normal and the energy flux vector are numerically calculated for zeroand first-order Lamb waves propagating in the (001) basal plane of a Bi12SiO20 cubic piezoelectric crystal. It is shown that the anisotropies of these modes are different and depend on the plate thickness h and the wavelength λ. For h/λ < 1, the mode anisotropy can exceed the anisotropy of the corresponding characteristics of surface acoustic waves propagating in the same plane; for h/λ > 1, it approximately coincides with the SAW anisotropy for all the characteristics.

  19. Smectic C liquid crystal growth through surface orientation by ZnxCd1-xSe thin films

    NASA Astrophysics Data System (ADS)

    Katranchev, B.; Petrov, M.; Bineva, I.; Levi, Z.; Mineva, M.

    2012-12-01

    A smectic C liquid crystal (LC) texture, consisting of distinct local single crystals (DLSCs) was grown using predefined orientation of ternary nanocrystalline thin films of ZnxCd1-xSe. The surface morphology and orientation features of the ZnxCd1-xSe films were investigated by AFM measurements and micro-texture polarization analysis. The ZnxCd1-xSe surface causes a substantial enlargement of the smectic C DLSCs and induction of a surface bistable state. The specific character of the morphology of this coating leads to the decrease of the corresponding anchoring energy. Two new chiral states, not typical for this LC were indicated. The physical mechanism providing these new effects is presented.

  20. Differential analysis of band-edge photoluminescence spectra of germanium single crystals with different orientations under biaxial tensile strains

    NASA Astrophysics Data System (ADS)

    Emel'yanov, A. M.

    2016-06-01

    The previously published photoluminescence spectra of bulk germanium single crystals with orientations (100), (110), and (111) under different biaxial tensile strains have been investigated using the differential method proposed by the author for the analysis of luminescence spectra of semiconductors. An increase in the strain for all these orientations of the single crystals leads to a shift in the maxima of the differential spectra in the region of direct radiative transitions toward lower photon energies due to the narrowing of the germanium direct band gap. At the same time, the positions of the maxima of the differential spectra in the region of indirect radiative transitions remain almost unchanged. This indicates that the germanium indirect band gap does not depend on the tensile strains, at least for their values of ˜0.2-0.3%.

  1. Development of olivine Crystal Preferred Orientation in Oshima peridotite body as a remnant of oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Tasaka, M.; Toriumi, M.; Wataru, N.

    2008-12-01

    To know the mantle flow kinematics, investigation of the seismic anisotropy is common method in upper mantle. Anisotropy is linked to crystal preferred orientations (CPOs) of olivine which is most abundant and weakest mineral in upper mantle. However the quantitative investigation analyses of natural CPO data have not succeeded yet. So, we must understand how olivine CPOs develops with strain in deformation settings. The Oshima peridotite body is the lower part of the Yakuno ophiolite in SW Japan (Ishiwatari, 1985a, b). This body consists dominantly of dunite and harzburgite deformed in upper mantle. This peridotites display various microstructures such as coarse grained granoblastic texture (0.7-1.0mm), elongated porphyroclastic texture (1.0mm-) and fine grained equigranular texture (0.1mm-). We analyzed CPOs of olivine using EBSD method. The results show that CPOs of olivine was formed by (0kl)[100] or (010)[100] slip system. In order to characterize the CPOs, we first determined the fabric strength and orientation distribution density of the principal crystallographic axes (J-index and M-index; Tommasi et al., 2000 and Skemer et al., 2005). According to those studies with increasing monotonously strain, the value of J- and M-index also increases. The Oshima peridotite body shows the various fabric strength from J=2.95 to 16.26 (M=0.040 to 0.384). On this presentation, we propose a new inversion method of mantle deformation by matching the model CPO patterns with natural CPOs in the Alpine type peridotites. Furthermore, we investigated two kind of angles of olivine together with CPOs at the same time to analyze CPOs development during mantle deformation. There are; (1) Angles between slip plane of each olivine grain and sample lineation. (2) Misorientation angles between adjacent olivine grains. The different angles between the slip plane of olivine grains and the rock lineation (1) are controlled by lattice rotation due to dislocation glide (Sevillano et al

  2. Investigation of vibrational characteristics in BBO crystals by femtosecond CARS

    NASA Astrophysics Data System (ADS)

    Xia, Yuanqin; Zhao, Yang; Wang, Zi; Zhang, Sheng; Dong, Zhiwei; Chen, Deying; Zhang, Zhonghua

    2012-10-01

    Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) is utilized to study the ultrafast vibrational dynamics in BBO crystals at room temperature. Time-resolved two-beam and three-beam CARS are detected. The vibrational dephasing time is analyzed and the changes of vibrational mode intensities with the polarization of pump pulses are observed.

  3. Quasicharacteristic radiation of relativistic electrons at orientation motion in lithium halides crystals along charged planes and axes

    NASA Astrophysics Data System (ADS)

    Maksyuta, N. V.; Vysotskii, V. I.; Efimenko, S. V.

    2016-07-01

    The paper deals with the investigation of the orientation motion of relativistic electrons in charged (111) planes and charged [110] axes of lithium halides ionic crystals of LiF, LiCl, LiBr and LiI. On the basis of these investigations the spectra of quasicharacteristic radiation for the electron beams with various Lorentz-factors both in planar and axial cases have been calculated numerically.

  4. Layers of quasi-horizontally oriented ice crystals in cirrus clouds observed by a two-wavelength polarization lidar.

    PubMed

    Borovoi, Anatoli; Balin, Yurii; Kokhanenko, Grigorii; Penner, Iogannes; Konoshonkin, Alexander; Kustova, Natalia

    2014-10-01

    Layers of quasi-horizontally oriented ice crystals in cirrus clouds are observed by a two-wavelength polarization lidar. These layers of thickness of several hundred meters are identified by three attributes: the backscatter reveals a sharp ridge while the depolarization ratio and color ratio become deep minima. These attributes have been justified by theoretical calculations of these quantities within the framework of the physical-optics approximation. PMID:25322032

  5. Bond orientational ordering in a metastable supercooled liquid: a shadow of crystallization and liquid-liquid transition

    NASA Astrophysics Data System (ADS)

    Tanaka, Hajime

    2010-12-01

    It is widely believed that a liquid state can be characterized by a single order parameter, density, and that a transition from a liquid to solid can be described by density ordering (translational ordering). For example, this type of theory has had great success in describing the phase behaviour of hard spheres. However, there are some features that cannot be captured by such theories. For example, hard spheres crystallize into either hcp or fcc structures, without a tendency of bcc ordering which is expected by the Alexander-McTague theory based on the Landau-type free energy of the density order parameter. We also found hcp-like bond orientational ordering in a metastable supercooled liquid, which promotes nucleation of hcp crystals. Furthermore, theories based on the single order parameter cannot explain water-like thermodynamic and kinetic anomalies of a liquid and liquid-liquid transition in a single-component liquid. Based on these facts, we argue that we need an additional order parameter to describe a liquid state. It is bond orientational order, which is induced by dense packing in hard spheres or by directional bonding in molecular and atomic liquids. Bond orientational order is intrinsically of local nature, unlike translational order which is of global nature. This feature plays a unique role in crystallization and quasicrystal formation. We also reveal that bond orientational ordering is a cause of dynamic heterogeneity near a glass transition and is linked to slow dynamics. In relation to this, we note that, for describing the structuring of a highly disordered liquid, we need a structural signature of low configurational entropy, which is more general than bond orientational order. Finally, the water-like anomaly and liquid-liquid transition can be explained by bond orientational ordering due to hydrogen or covalent bonding and its cooperativity, respectively. So we argue that bond orientational ordering is a key to the physical understanding of

  6. [Analysis of anti-ultraviolet characteristic of liquid-crystal display].

    PubMed

    Huang, Chong; Ouyang, Yan-dong; Wu, Yong-jun; Zhan, Qian-xian

    2004-05-01

    As liquid-crystal display is developing to be used outside and becomes colorful and larger, the influence of ultraviolet on liquid-crystal display is becoming more and more apparent. And the anti-ultraviolet character of liquid-crystal display becomes more important. In this paper, the spectroscopic characteristics of ITO glass and polaroid were measured with ultraviolet of various wavelengths. By comparing the ultraviolet transmission spectrum of normal polaroid (LN-1205T) with that of anti-ultraviolet polaroid (F-1225DU), the anti-ultraviolet characteristic of a new style liquid-crystal display (LCD) was discussed. And the results show, the anti-ultraviolet polaroid (F-1225DU) is better in the absorption of ultraviolet. The anti-ultraviolet polaroid (F-1225DU) can enhance the performance of liquid-crystal display used outside. PMID:15769069

  7. Substrate Orientation and Catalysis at the Molybdenum Site in Xanthine Oxidase CRYSTAL STRUCTURES IN COMPLEX WITH XANTHINE AND LUMAZINE

    SciTech Connect

    Pauff, James M.; Cao, Hongnan; Hille, Russ

    2010-01-12

    Xanthine oxidoreductase is a ubiquitous cytoplasmic protein that catalyzes the final two steps in purine catabolism. We have previously investigated the catalytic mechanism of the enzyme by rapid reaction kinetics and x-ray crystallography using the poor substrate 2-hydroxy-6-methylpurine, focusing our attention on the orientation of substrate in the active site and the role of Arg-880 in catalysis. Here we report additional crystal structures of as-isolated, functional xanthine oxidase in the course of reaction with the pterin substrate lumazine at 2.2 {angstrom} resolution and of the nonfunctional desulfo form of the enzyme in complex with xanthine at 2.6 {angstrom} resolution. In both cases the orientation of substrate is such that the pyrimidine subnucleus is oriented opposite to that seen with the slow substrate 2-hydroxy-6-methylpurine. The mechanistic implications as to how the ensemble of active site functional groups in the active site work to accelerate reaction rate are discussed.

  8. Effects of crystal orientation and ferroelastic domain structure on the photochemical reactivity of BiVO4 and related compounds

    NASA Astrophysics Data System (ADS)

    Munprom, Ratiporn

    Bismuth vanadate, BiVO4, has been recognized for its high efficiency as a photoanode for water splitting. However, its performance is limited by photogenerated electron--hole recombination. Thus, researchers have attempted to modify BiVO4 to improve its performance. One strategy to improve charge separation is to utilize an internal field arising from surface termination differences. Previous studies concentrated on polygonal single crystals of BiVO4, providing limited information about the orientation-reactivity relationship. The current research focuses on polycrystalline BiVO4, which makes it possible to study the photochemical reactivity of all possible orientations and determine the complete orientation dependence of the photochemical reactivity of BiVO4. (Abstract shortened by UMI.).

  9. Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array

    PubMed Central

    Liew, Weng Heng; Mirshekarloo, Meysam Sharifzadeh; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock

    2015-01-01

    Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers. PMID:25966301

  10. Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array.

    PubMed

    Liew, Weng Heng; Mirshekarloo, Meysam Sharifzadeh; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock

    2015-01-01

    Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers. PMID:25966301

  11. The deformation micro-structures and the relationships of crystal orientation between olivine and antigorite in serpentinized peridotite from Toba area, SW Japan

    NASA Astrophysics Data System (ADS)

    Soda, Y.; Morishita, T.; Wenk, H.-R.

    2012-04-01

    Foliated serpentinite with lattice preferred orientation (LPO) has strong elastic anisotropy, and is considered as a cause for seismic anisotropy observed in subduction zones (Katayama et al., 2009; Jung, 2011). However, deformation mechanisms of antigorite LPO are unclear. We measured crystal orientation of antigorite and olivine, to clarify the chronological relations between shear deformation and formation of antigorite LPO. The crystal orientations are measured by the U-stage optically. In addition, we try to measure the antigorite orientations by EBSD. The studied samples are from lenticular serpentinite bodies intruded in a Jurassic accretionary complex, Toba area, southwest Japan. Shear zones (

  12. Orientation and optical properties of methylene blue crystal for better understanding of interactions with clay mineral surface

    NASA Astrophysics Data System (ADS)

    Milošević, Maja; Logar, Mihovil

    2013-04-01

    The properties of cationic dye Methylene blue (MB) adsorbed on diferent surfaces have been investigated intensively over the years and various models for the orientation of its cations have been proposed (Hang and Brindley, 1970; Bujdak et al., 2003; Li and Zare, 2004; Marr III et al., 1973; Bujdak, 2006).The main objective of this work is to investigate and determine orientation and optical properties of metylene blue crystal upon its crystallization on a glass slate and to use those findings in better understanding of interactions with clay minerals. Cationic dyes have very high affinity for clay surfaces and those interactions are easily detected, therefore these dyes are used to determine several properties of clay surfaces (morphology, layer charge, CEC). For this study, we have selected a group of MB crystal and carried out XRD analysis, polarized absorption spectra measurement (400 - 900 nm) and determination of optical properties (pleochroism, determination of twining and extinction angle) using polarizing microscope. Methylene blue crystals are exhibiting mostly needle like habitus with huge difference in width - length ratio. According to X-ray diffraction it is quite obvious that the y (b) axis is perpendicular to the crystal surface. The x (a) and z (c) axis lie in the crystal plane (010). Crystals exhibit prominent dichroism: from blue (E || elong.) to colorless. In accordance with current interpretation of MB spectra peaks at 647 and 570 nm can be assigned as dimer aggregation and peaks at 475 and 406 nm as higher level of aggregation. All of them exhibit pronounced polarization dependence. The group of peaks at lower energy (700 to 900 nm) do not show significant polarization dependence and they correspond to the J - aggregates. Peak at around 800 nm have been noticed as fluorescence active. In dependence with thickness of the crystals and vibration direction we have observed presence of polysynthetic twinning which can be compared with polysynthetic

  13. Optical and electrical characteristics of pure and doped potassium hydrogen tartrate single crystals

    NASA Astrophysics Data System (ADS)

    Quasim, I.; Firdous, A.; Khosa, S. K.; Kotru, P. N.

    2009-08-01

    The optical and electrical characteristics of pure, sodium- and lithium-doped potassium hydrogen tartrate crystals grown by the gel technique are reported. An optical absorption study conducted in the UV-Vis range of 200-800 nm reveals the transparency of these crystals in the entire visible range but not in the ultraviolet range. The optical band gap of pure potassium hydrogen tartrate crystals is found to be dependent on doping by Na or Li ions. The non-linear optical behaviour of these crystals is reported and explained. The electrical properties of pure and doped potassium hydrogen tartrate crystals are studied by measuring electrical resistivity from 80 to 300 K. It is shown that while pure potassium hydrogen tartrate crystal is an insulator at room temperature (300 K), doping by Na or Li ions makes it a semiconductor. The results have been explained in terms of the variable range hopping model.

  14. Study on dipolar orientation and relaxation characteristics of guest-host polymers affected by corona poling parameters

    NASA Astrophysics Data System (ADS)

    Yun, Binfeng; Hu, Guohua; Lu, Changgui; Cui, Yiping

    2009-05-01

    The dipolar orientation and relaxation characteristics of guest-host polymers poled by corona poling have been studied in detail. The mechanisms of dipolar orientation affected by poling parameters (voltage, temperature, time and cooling velocity) in polymers have been analyzed by UV-Vis absorption spectra and microscope. The results show that with increasing poling voltage, the orientation order parameter increases to maximum and then drops. Also the same trend of orientation order parameter has been obtained with increasing poling temperature. While the orientation order parameter increases to saturation with increasing poling time. With the biexponential model analyzing, it is shown that the relaxation of dipolar orientation can be slowed by slowing the cooling velocity during the poling process.

  15. Threshold Characteristics of Slow-Light Photonic Crystal Lasers

    NASA Astrophysics Data System (ADS)

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa; Chen, Yaohui; Semenova, Elizaveta; Yvind, Kresten; Mork, Jesper

    2016-02-01

    The threshold properties of photonic crystal quantum dot lasers operating in the slow-light regime are investigated experimentally and theoretically. Measurements show that, in contrast to conventional lasers, the threshold gain attains a minimum value for a specific cavity length. The experimental results are explained by an analytical theory for the laser threshold that takes into account the effects of slow light and random disorder due to unavoidable fabrication imperfections. Longer lasers are found to operate deeper into the slow-light region, leading to a trade-off between slow-light induced reduction of the mirror loss and slow-light enhancement of disorder-induced losses.

  16. Lasing characteristics of Ho:YAG single crystal fiber.

    PubMed

    Li, Yuan; Miller, Keith; Johnson, Eric G; Nie, Craig D; Bera, Subhabrata; Harrington, James A; Shori, Ramesh

    2016-05-01

    Lasing was demonstrated for the first time at 2.09 μm in 0.5% Holmium (Ho) doped YAG single crystal fiber (SCF) fabricated using the Laser Heated Pedestal Growth (LHPG) method. Output power of 23.5 W with 67.5% optical-to-optical slope efficiency is, to the best of our knowledge, the highest output power achieved at 2 µm from a SCF fabricated using LHPG. With continued improvement in the quality of the SCF and better thermal management, output power of few 100s W and higher, especially in the 2 µm spectral region, is realizable in the very near future. PMID:27137589

  17. Threshold Characteristics of Slow-Light Photonic Crystal Lasers.

    PubMed

    Xue, Weiqi; Yu, Yi; Ottaviano, Luisa; Chen, Yaohui; Semenova, Elizaveta; Yvind, Kresten; Mork, Jesper

    2016-02-12

    The threshold properties of photonic crystal quantum dot lasers operating in the slow-light regime are investigated experimentally and theoretically. Measurements show that, in contrast to conventional lasers, the threshold gain attains a minimum value for a specific cavity length. The experimental results are explained by an analytical theory for the laser threshold that takes into account the effects of slow light and random disorder due to unavoidable fabrication imperfections. Longer lasers are found to operate deeper into the slow-light region, leading to a trade-off between slow-light induced reduction of the mirror loss and slow-light enhancement of disorder-induced losses. PMID:26918991

  18. Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization: Bond orientational order in liquids.

    PubMed

    Tanaka, Hajime

    2012-10-01

    There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases a complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is the most poorly understood. We argue that it is crucial for a better understanding of liquids to recognize that a liquid generally has the tendency to have a local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many-body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing a low local free-energy configuration, which is a bond orientational order parameter in many cases, in addition to a density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena is also discussed. PMID:23104614

  19. Epitaxially-crystallized oriented naphthalene bis(dicarboximide) morphology for significant performance improvement of electron-transporting thin-film transistors.

    PubMed

    Liu, Lili; Ren, Zhongjie; Xiao, Chengyi; He, Bing; Dong, Huanli; Yan, Shouke; Hu, Wenping; Wang, Zhaohui

    2016-04-01

    Large-area highly-ordered F-NDI films were obtained by epitaxial-crystallization on highly-oriented PE substrates through vacuum deposition. An electron mobility of 0.2 cm(2) V(-1) s(-1) was achieved based on such epitaxially-crystallized F-NDI films, which is 4 times higher than that of its un-oriented thin film devices. PMID:26974522

  20. Rheologic effects of crystal preferred orientation in upper mantle flow near plate boundaries

    NASA Astrophysics Data System (ADS)

    Blackman, Donna; Castelnau, Olivier; Dawson, Paul; Boyce, Donald

    2016-04-01

    Observations of anisotropy provide insight into upper mantle processes. Flow-induced mineral alignment provides a link between mantle deformation patterns and seismic anisotropy. Our study focuses on the rheologic effects of crystal preferred orientation (CPO), which develops during mantle flow, in order to assess whether corresponding anisotropic viscosity could significantly impact the pattern of flow. We employ a coupled nonlinear numerical method to link CPO and the flow model via a local viscosity tensor field that quantifies the stress/strain-rate response of a textured mineral aggregate. For a given flow field, the CPO is computed along streamlines using a self-consistent texture model and is then used to update the viscosity tensor field. The new viscosity tensor field defines the local properties for the next flow computation. This iteration produces a coupled nonlinear model for which seismic signatures can be predicted. Results thus far confirm that CPO can impact flow pattern by altering rheology in directionally-dependent ways, particularly in regions of high flow gradient. Multiple iterations run for an initial, linear stress/strain-rate case (power law exponent n=1) converge to a flow field and CPO distribution that are modestly different from the reference, scalar viscosity case. Upwelling rates directly below the spreading axis are slightly reduced and flow is focused somewhat toward the axis. Predicted seismic anisotropy differences are modest. P-wave anisotropy is a few percent greater in the flow 'corner', near the spreading axis, below the lithosphere and extending 40-100 km off axis. Predicted S-wave splitting differences would be below seafloor measurement limits. Calculations with non-linear stress/strain-rate relation, which is more realistic for olivine, indicate that effects are stronger than for the linear case. For n=2-3, the distribution and strength of CPO for the first iteration are greater than for n=1, although the fast seismic

  1. A database of crystal preferred orientation of olivine in upper mantle rocks

    NASA Astrophysics Data System (ADS)

    Mainprice, D.

    2012-12-01

    Olivine is the most volumetrically abundant mineral in the Earth's upper mantle, as such it dominates the mechanical and physical properties and has a controlling influence of the geodynamics of plate tectonics. Since the pioneering work of Hess and others we know that seismic anisotropy of the shallow mantle is related to olivine and it's crystal preferred orientation (CPO). With advent of plate tectonics the understanding of the key role of peridotite rocks became a major scientific objective and the measurement CPO of olivine in upper mantle samples became an important tool for studying the kinematics of these rocks. Our group originally lead by Adolphe Nicolas introduced the systematic use of CPO measured by U-stage for field studies all over the world for over 30 years, this tradition was extended in last 15 years by the use of electron back-scattered diffraction (EBSD) to study of CPO and the associated digital microstructure. It is an appropriate time to analysis this significant database of olivine CPO, which represents the work of our group, both present and former members, as well as collaborating colleagues. It is also interesting to compare the natural record as illustrated by our database in the light of recent experimental results stimulated by the extended ranges in temperature, pressure and finite strain, as well as intrinsic olivine variables such as hydrogen content. To analysis the database, which is heterogeneous because it is constructed from the individual work of many people over a 45 year period containing U-stage data and EBSD measurements (manual indexing point per grain, automatic indexing one point per grain, automatic indexing gridded mapping data) of various formats, we need a flexible software tool that can handle large volumes of data in consistent way. We have used the state-of-art open source MTEX toolbox for quantitative texture analysis. MTEX is a scriptable MATLAB toolbox, which permits all aspects of quantitative texture

  2. Impedance spectroscopy investigation of electrophysical characteristics of the electrode-liquid crystal interface

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Drokin, N. A.

    2015-01-01

    The behavior of frequency dependences of the impedance of a capacitive measuring cell with a liquid crystal has been investigated in the frequency range from 10-1 to 105 Hz. A method for determining electrophysical characteristics of the liquid crystal in the bulk and at the liquid crystal-metal electrode interface has been proposed and tested for liquid crystals of the alkyl cyanobiphenyl series, which are doped with ionic surfactants. The method is based on the use of an equivalent electrical circuit, which makes it possible to approximate the impedance spectra with the required accuracy, and also on the determination of the frequency at the singular point in the impedance spectra, at which the reactive component of the electric current flowing through the liquid-crystal cell is negligible compared to the active component.

  3. Structural study of growth, orientation and defects characteristics in the functional microelectromechanical system material aluminium nitride

    SciTech Connect

    Hrkac, Viktor Schürmann, Ulrich; Kienle, Lorenz; Kobler, Aaron; Kübel, Christian; Marauska, Stephan; Wagner, Bernhard; Petraru, Adrian; Kohlstedt, Hermann; Kiran Chakravadhanula, Venkata Sai; Duppel, Viola; Lotsch, Bettina Valeska

    2015-01-07

    The real structure and morphology of piezoelectric aluminum nitride (AlN) thin films as essential components of magnetoelectric sensors are investigated via advanced transmission electron microscopy methods. State of the art electron diffraction techniques, including precession electron diffraction and automated crystal orientation mapping (ACOM), indicate a columnar growth of the AlN grains optimized for piezoelectric application with a (0 0 0 1) texture. Comparing ACOM with piezoresponse force microscopy measurements, a visual correlation of the structure and the piezoelectric properties is enabled. With a quantitative analysis of the ACOM measurements, a statistical evaluation of grain rotations is performed, indicating the presence of coincidence site lattices with Σ7, Σ13a, Σ13b, Σ25. Using a geometric phase analysis on high resolution micrographs, the occurrence of strain is detected almost exclusively at the grain boundaries. Moreover, high resolution imaging was applied for solving the atomic structure at stacking mismatch boundaries with a displacement vector of 1/2 〈1 0 -1 1〉. All real structural features can be interpreted via simulations based on crystallographic computing in terms of a supercell approach.

  4. Orientation Characteristics of Non-regiocontrolled Poly (3-hexyl-thiophene) Film by FTM on Various Liquid Substrates

    NASA Astrophysics Data System (ADS)

    Pandey, M.; Nagamatsu, S.; Pandey, S. S.; Hayase, S.; Takashima, W.

    2016-04-01

    Orientation characteristics of non-regiocontrolled poly (3-hexylthiophene) (NR-P3HT) films prepared by dynamic casting of floating film and transferring method (FTM) has been investigated. The film was first cast on liquid-substrate to obtain as a floating-film followed by its transfer on solid-substrate such as white-glass or Si-wafer in order to evaluate their optoelectronic characteristics. As a possible key-factor to generate the orientation of conjugated polymer in this method we focused on the components of liquid-substrate in this study. The orientation dependence upon various liquid-substrates reveals that dichroic ratio strongly changes with liquid-substrates. Pictures of floating-film show the change in size of floating-parts depending upon the liquid-substrate, representing the expansion length of casting solution upon the viscosity. These findings have indicated that spreading speed of polymer solution and solvent evaporation speed controls the size of floating-film leading to change in the orientation intensity. The multilayer coatings of oriented NR-P3HT films were used for polarized FTIR analysis exhibiting clear dichroism. The obtained dichroic characteristics were well corresponded with in-plane, out-of-plane and non-oriented vibronic modes of P3HT.

  5. Fabrication and optical transmission characteristics of polymers woodpile photonic crystal structures with different crystal planes

    NASA Astrophysics Data System (ADS)

    Chen, Ling-Jing; Dong, Xian-Zi; Zhao, Yuan-Yuan; Zhang, Yong-Liang; Liu, Jie; Zheng, Mei-Ling; Duan, Xuan-Ming; Zhao, Zhen-Sheng

    2015-10-01

    The photonic band gap effect which originates from the translational invariance of the periodic lattice of dielectrics has been widely applied in the technical applications of microwave, telecommunication and visible wavelengths. Among the various examples, polymers based three dimensional (3D) photonic crystals (PhCs) have attracted considerable interest because they can be easily fabricated by femo-second (fs) ultrafast laser direct writing (DLW) method. However, it is difficult to realize complete band gap in polymers PhCs due to the low index contrast between polymers and air. Here, we report the design and experimental realization of light's nonreciprocal propagation in woodpile PhCs fabricated with DLW method. Firstly, we fabricated several polymers woodpile PhCs on glass substrate with different crystal planes. The Fourier transform infrared spectroscopy (FTIR) measurements are in agreement with the theoretical predictions, which proves the validity and the accuracy of our DLW method. Further measurements of the transmission spectra with respect to the incident angle reveal that the surface crystal planes and incident wave vectors play important roles in the optical response. Furthermore, we designed and fabricated a 30° PhC wedge. And we find nonreciprocal transmission effect between the forward and backward waves, resulting from the nonsymmetrical refraction of the light in different planes. Our results may find potential applications in future 3D photonic integrated circuits and pave the way for the fabrication of other photonic and optical devices with DLW method.

  6. Boosting Photon Harvesting in Organic Solar Cells with Highly Oriented Molecular Crystals via Graphene-Organic Heterointerface.

    PubMed

    Jo, Sae Byeok; Kim, Hyun Ho; Lee, Hansol; Kang, Boseok; Lee, Seongkyu; Sim, Myungsun; Kim, Min; Lee, Wi Hyoung; Cho, Kilwon

    2015-08-25

    Photon harvesting in organic solar cells is highly dependent on the anisotropic nature of the optoelectronic properties of photoactive materials. Here, we demonstrate an efficient approach to dramatically enhance photon harvesting in planar heterojunction solar cells by using a graphene-organic heterointerface. A large area, residue-free monolayer graphene is inserted at anode interface to serve as an atomically thin epitaxial template for growing highly orientated pentacene crystals with lying-down orientation. This anisotropic orientation enhances the overall optoelectronic properties, including light absorption, charge carrier lifetime, interfacial energetics, and especially the exciton diffusion length. Spectroscopic and crystallographic analysis reveal that the lying-down orientation persists until a thickness of 110 nm, which, along with increased exciton diffusion length up to nearly 100 nm, allows the device optimum thickness to be doubled to yield significantly enhanced light absorption within the photoactive layers. The resultant photovoltaic performance shows simultaneous increment in Voc, Jsc, and FF, and consequently a 5 times increment in the maximum power conversion efficiency than the equivalent devices without a graphene layer. The present findings indicate that controlling organic-graphene heterointerface could provide a design strategy of organic solar cell architecture for boosting photon harvesting. PMID:26166186

  7. Crystal orientation effects on electronic and optical properties of wurtzite ZnO/CdZnO quantum well lasers

    NASA Astrophysics Data System (ADS)

    Hebal, Hamza; Abid, Hamza

    2014-11-01

    The study of electronic and optical properties of ZnO/CdZnO quantum well (QW) structures, considering the crystal orientation dependence and Gaussian line shape function for optical gain are explored including many body effects and spontaneous-piezoelectric built-in field. Results are confronted with those for GaN-based QW structures. The effect of internal field in the c-plane oriented ZnO/CdZnO QW structure is relatively small compared to that of GaN/InGaN QW structure and thus, a larger optical gain is shown while it disappears in the a- and m-planes for both QW structures where the optical gain as a result is match larger. Energy dispersion, transition strength and the average hole effective masses are anisotropic in non-polar structures. The bandgap transition wavelength of the QW structure with a-plane orientation is smaller than that of m-plane orientation by 2 nm in ZnO/CdZnO QW while it is 10 nm in the case of GaN/InGaN QW structure.

  8. Laser-driven microflow-induced bistable orientation of a nematic liquid crystal in perfluoropolymer-treated unrubbed cells.

    PubMed

    Jampani, V S R; Skarabot, M; Takezoe, H; Muševič, I; Dhara, S

    2013-01-14

    We demonstrate laser-driven microflow-induced orientational change (homeotropic to planar) in a dye-doped nematic liquid crystal. The homeotropic to planar director alignment is achieved in unrubbed cells in the thermal hysteresis range of a discontinuous anchoring reorientation transition due to the local heating by light absorption in dye-doped sample. Various bistable patterns were recorded in the cell by a programmable laser tweezers. The width of the patterns depend on the scanning speed of the tightly focussed laser beam and the minimum width obtained is approximately equal to 0.57μm which is about 35 times smaller than the earlier report in the rubbed cells. We show that the motion of the microbeam spot causes local flow as a result the liquid crystal director is aligned along that direction. PMID:23388965

  9. NH4+-mediated growth of hematite tire-like single crystals by oriented attachment and their unique photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Ma, J.; Chen, K.

    2014-04-01

    In this work, hematite tire-like single crystals were fabricated by a facile hydrothermal procedure. The presence of NH4+ cations in the reaction was proved to be decisive to the formation of hematite single-crystalline tires. It was found that the (001) crystallographic plane, doubly-coordinated by surface hydroxyl groups, preferably distributes at the edge of originally-formed oblate spheroids and dynamically adsorbs NH4+ cations in solution, which would greatly protect this plane from being etched by [Fe(HPO4)]+ and H+ cations during the reaction. Meanwhile, these remanent etch-proof nanoparticles would co-align, followed by the oriented attachment mechanism, and finally form tire-like single crystals enclosed by (001) surface. Even though these single-crystalline tires were bound by low-index facet, their photocatalytic properties were quite unique due to their high density of surface hydroxyl radicals.

  10. Birefringence imaging and orientation of laser patterned β-BaB{sub 2}O{sub 4} crystals with bending and curved shapes in glass

    SciTech Connect

    Ogawa, Kazuki; Honma, Tsuyoshi; Komatsu, Takayuki

    2013-11-15

    Nonlinear optical β-BaB{sub 2}O{sub 4} crystals (β-BBO) with bending and curved shapes were patterned at the surface of 8Sm{sub 2}O{sub 3}–42BaO–50B{sub 2}O{sub 3} glass by laser irradiations (Yb:YVO{sub 4} laser with a wavelength of 1080 nm, power of 0.8 W, and scanning speed of 4 μm/s), and the orientation state of β-BBO crystals was examined from the birefringence imaging obtained by polarization optical microscope (POM) observations. The formation (crystallization) of β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes at a certain point within the bending angle of 60°. The birefringence images indicate that the formation of highly c-axis oriented β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of β-BBO crystals changes gradually at the bending point. The model for the orientation of the c-axis of β-BBO near the bending point is proposed. The present study proposes that the laser-induced crystallization opens a new door for the science and technology in crystal growth engineering. - Graphical abstract: This figure shows the birefringence images obtained by the Abrio IM imaging system (λ=546 nm) for the laser-patterned β-BaB{sub 2}O{sub 4} crystal line with the bending angle of 45° in the glass. The relation between the direction of slow axis and color is also shown. It is demonstrated that the formation (crystallization) of highly c-axis oriented β-BaB{sub 2}O{sub 4} crystals follows along laser scanning direction even if the laser scanning direction changes. Display Omitted - Highlights: • β-BaB{sub 2}O{sub 4} crystals with bending and curved shapes were patterned by laser irradiations. • The orientation was examined from the birefringence imaging. • Highly c-axis oriented crystals follows along laser scanning direction. • The c-axis direction changes gradually at the bending point. • The

  11. REVIEW ARTICLE: Effects of light on molecular orientation of liquid crystals

    NASA Astrophysics Data System (ADS)

    Simoni, F.; Francescangeli, O.

    1999-10-01

    A review of basic physical phenomena underlying the light-induced molecular reorientation in nematic liquid crystals is presented. A detailed description of the mechanisms of direct optical torque, photoisomerization and photorefractivity and of their effect on the macroscopic order of liquid crystals is reported. The first part of the article deals with the study of reorientation effects in transparent liquid crystalline materials. Here, the effects of photo-induced molecular reorientation are fully interpreted within the framework of classical electrodynamics and standard continuum theory of liquid crystals. We investigate the peculiar properties related to the macroscopic anisotropy and the collective behaviour of liquid crystals that result in extraordinarily large nonlinear optical response. Afterwards, the behaviour of liquid crystals in the presence of light absorption is considered and the related reorientation effects are discussed. We give a review of the wide phenomenology which is met in liquid crystals when doped with absorbing azo-dye molecules. The photoisomerization process that in this case drives the evolution of the dye-liquid crystal mixture consequent to the interaction with the light is discussed in detail. Finally, the relatively new field of photorefractivity in liquid crystals as a source of molecular reorientation is considered. We describe the different mechanisms contributing to the creation of a space-charge field such as conductivity anisotropy, dielectric anisotropy and photocharge production. A theoretical discussion of the fundamental mechanisms regulating the dc-field-assisted optically induced space-charge fields and the optical molecular reorientation in nematic liquid crystal films is also given.

  12. Effects of membrane orientation on fouling characteristics of forward osmosis membrane in concentration of microalgae culture.

    PubMed

    Honda, Ryo; Rukapan, Weerapong; Komura, Hitomi; Teraoka, Yuta; Noguchi, Mana; Hoek, Eric M V

    2015-12-01

    Application of forward osmosis (FO) membrane to microalgae cultivation processes enables concentration of microalgae and nutrients with low energy consumption. To understand fouling characteristics of FO membrane in concentration of microalgae culture, we studied flux decline, flux recovery by cleaning, and foulants characteristics, in different membrane orientation of active-layer-facing-feed-solution (AL-FS) and active-layer-facing-draw-solution (AL-DS) modes. Batch concentration of Chlorella vulgaris was conducted with a cellulose-triacetate FO membrane. Rapid flux decline and lower flux recovery was observed in AL-DS mode because of inner-membrane fouling including internal pore clogging, adsorption and internal concentration polarization in the support layer. A proportion of polysaccharides in extracellular polymeric substances to soluble microbial products were larger in chemical cleaning effluent than physical one in AL-DS mode, although those were not significantly different in AL-FS mode. Excitation-emission matrix analysis revealed that proteins and humic-like substances were also possible irreversible foulants both in AL-DS and AL-FS modes. PMID:26356114

  13. Dense layers of vertically oriented WO 3 crystals as anodes for photoelectrochemical water oxidation

    SciTech Connect

    Qin, Dong-Dong; Tao, Chun-Lan; Friesen, Stuart A.; Wang, Tsing-Hai; Varghese, Oomman K.; Bao, Ning-Zhong; Yang, Zheng-Yin; Mallouk, Thomas E.; Grimes, Craig A.

    2011-11-25

    Films of crystalline WO₃ nanosheets oriented perpendicular to tungsten substrates were grown by a surfactant-free hydrothermal method, followed by sintering. The films exhibit photoelectrochemical oxygen evolution at low overpotential.

  14. Orientational order of some liquid crystal/dye mixtures obtained from optical birefringence

    NASA Astrophysics Data System (ADS)

    Bielejewska, Natalia

    2016-04-01

    This study presents optical birefringence measurements as a function of temperature for the liquid crystal/dye mixtures. The optical birefringence of the liquid crystals used in liquid crystal displays technology is related to the order parameter , which is crucial from the development point of view. The properties of the dyes (4-dimethylamino-4‧-nitrostilbene and N,N‧-bis(2,5-di-tert-buthylphenyl)-3,4,9,10-perylenedicarboximide) as a guest molecule are tested over the whole region of nematic phase occurrence by three different methods: measurement with use of the plano-convex lens, Berek's compensator and photoelastic modulator.

  15. Self-Assembly of Graphene Single Crystals with Uniform Size and Orientation: The First 2D Super-Ordered Structure.

    PubMed

    Zeng, Mengqi; Wang, Lingxiang; Liu, Jinxin; Zhang, Tao; Xue, Haifeng; Xiao, Yao; Qin, Zhihui; Fu, Lei

    2016-06-29

    The challenges facing the rapid developments of highly integrated electronics, photonics, and microelectromechanical systems suggest that effective fabrication technologies are urgently needed to produce ordered structures using components with high performance potential. Inspired by the spontaneous organization of molecular units into ordered structures by noncovalent interactions, we succeed for the first time in synthesizing a two-dimensional superordered structure (2DSOS). As demonstrated by graphene, the 2DSOS was prepared via self-assembly of high-quality graphene single crystals under mutual electrostatic force between the adjacent crystals assisted by airflow-induced hydrodynamic forces at the liquid metal surface. The as-obtained 2DSOS exhibits tunable periodicity in the crystal space and outstanding uniformity in size and orientation. Moreover, the intrinsic property of each building block is preserved. With simplicity, scalability, and continuously adjustable feature size, the presented approach may open new territory for the precise assembly of 2D atomic crystals and facilitate its application in structurally derived integrated systems. PMID:27313075

  16. Photoanodes with Fully Controllable Texture: The Enhanced Water Splitting Efficiency of Thin Hematite Films Exhibiting Solely (110) Crystal Orientation.

    PubMed

    Kment, Stepan; Schmuki, Patrik; Hubicka, Zdenek; Machala, Libor; Kirchgeorg, Robin; Liu, Ning; Wang, Lei; Lee, Kiyoung; Olejnicek, Jiri; Cada, Martin; Gregora, Ivan; Zboril, Radek

    2015-07-28

    Hematite, α-Fe2O3, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing up to 4 orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet. Here, we present a strategy for controlling the crystal orientation of very thin hematite films by adjusting energy of ion flux during advanced pulsed reactive magnetron sputtering technique. The texture and effect of the deposition mode on the film properties were monitored by XRD, conversion electron Mössbauer spectroscopy, XPS, SEM, AFM, PEC water splitting, IPCE, transient photocurrent measurements, and Mott-Schottky analysis. The precise control of the synthetic conditions allowed to fabricate hematite photoanodes exhibiting fully textured structures along (110) and (104) crystal planes with huge differences in photocurrents of 0.65 and 0.02 mA cm(-2) (both at 1.55 V versus RHE), respectively. The photocurrent registered for fully textured (110) film is among record values reported for thin planar films. Moreover, the developed fine-tuning of crystal orientation having a huge impact on the photoefficiency would induce further improvement of thin hematite films mainly if cation doping will be combined with the controllable texture. PMID:26083741

  17. Numerical simulation of the flow fields around falling ice crystals with inclined orientation and the hydrodynamic torque

    NASA Astrophysics Data System (ADS)

    Hashino, Tempei; Chiruta, Mihai; Polzin, Dierk; Kubicek, Alexander; Wang, Pao K.

    2014-12-01

    The flow field and orientation of ice particles are fundamental information to understand cloud microphysical processes, optical phenomena, and electric-field induced orientation and to improve remote sensing of ice clouds. The purpose of this study is to investigate the flow fields and hydrodynamic torques of falling ice columns and hexagonal plates with their largest dimension inclined with respect to the airflow. The Reynolds numbers range from 2 to 70 for columns and 2 to 120 for plates. The flow fields are obtained by numerically solving the relevant Navier-Stokes equations under the assumption of air incompressibility. It was found that for the intermediate Reynolds number the streamlines around the inclined crystals exhibit less spiral rotation behind them than those around the stable posture. The vorticity magnitude was larger in the upstream side and broader in the downstream than the one without inclination. For plates, a high-pressure dome on the center of the lower basal face disappears with inclination, possibly leading to an increase of riming there. The torques acting on the crystals have a local maximum over the inclined angle and exhibit almost symmetric around 45° over the range of Reynolds numbers. The torque parameterization was performed under pressures of 300, 500, and 800 hPa as a function of Reynolds number and aspect ratio. It was found that the time scale of rotation for plates is smaller than the one for columns. Furthermore, the torque formula was applied to assess alignment of crystals along electric fields. It was found that these crystals of millimeter size require 120 kV/m for the electrical alignment, which agrees with previous studies.

  18. Confinement-Induced Orientational Order in a Ferroelectric Liquid Crystal Containing Dispersed Aerosils

    NASA Astrophysics Data System (ADS)

    Cordoyiannis, George; Nounesis, George; Bobnar, Vid; Kralj, Samo; Kutnjak, Zdravko

    2005-01-01

    The study of the smectic-A to chiral smectic-C* phase transition of the liquid crystal S-(+)-[4-(2'-methyl butyl) phenyl 4'-n-octylbiphenyl-4-carboxylate] (CE8) containing dispersed hydrophilic aerosils reveals novel properties, important to understanding quenched disorder and confinement in ferroelectric liquid crystals. Smectic layer compression leads to a distribution of transition temperatures inducing smearing of the macroscopic data across the transition. A pronounced confinement-induced pretransitional tilted order is observed.

  19. Influence law of structural characteristics on the surface roughness of a magnetorheological-finished KDP crystal.

    PubMed

    Chen, Shaoshan; Li, Shengyi; Hu, Hao; Li, Qi; Tie, Guipeng

    2014-11-01

    A new nonaqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing potassium dihydrogen phosphate (KDP) crystal due to its low hardness, high brittleness, temperature sensitivity, and water solubility. This paper researches the influence of structural characteristics on the surface roughness of MRF-finished KDP crystal. The material removal by dissolution is uniform layer by layer when the polishing parameters are stable. The angle between the direction of the polishing wheel's linear velocity and the initial turning lines will affect the surface roughness. If the direction is perpendicular to the initial turning lines, the polishing can remove the lines. If the direction is parallel to the initial turning lines, the polishing can achieve better surface roughness. The structural characteristic of KDP crystal is related to its internal chemical bonds due to its anisotropy. During the MRF finishing process, surface roughness will be improved if the structural characteristics of the KDP crystal are the same on both sides of the wheel. The processing results of (001) plane crystal show we can get the best surface roughness (RMS of 0.809 nm) if the directions of cutting and MRF polishing are along the (110) direction. PMID:25402879

  20. Analysis of crystal orientation in AlN layers grown on m-plane sapphire

    NASA Astrophysics Data System (ADS)

    Mogilatenko, A.; Kirmse, H.; Stellmach, J.; Frentrup, M.; Mehnke, F.; Wernicke, T.; Kneissl, M.; Weyers, M.

    2014-08-01

    Our study reports on the microstructure of AlN layers grown on m-plane sapphire by metal organic vapor phase epitaxy. We have found that AlN can nucleate with three different orientations on the m-plane sapphire surface: semipolar (112¯2) and (11¯03) as well as m-plane (11¯00). Depending on the growth conditions, i.e. V/III ratio, the differently oriented crystallites exhibit different lateral and vertical growth rates. At a low V/III ratio of 626 the vertical growth rate of semipolar (112¯2) AlN regions is much lower than that of the (11¯03) and (11¯00) oriented grains, which results in an almost complete lateral overgrowth of the (112¯2) AlN oriented regions. In contrast, a high V/III ratio of 1043 leads to the formation of uniform semipolar (112¯2) AlN layers. Nevertheless, the formation of differently oriented AlN crystallites could not be suppressed completely. These randomly appearing crystallites still show a high vertical growth rate and lead to a deterioration of the surface morphology.

  1. Influence of Acoustic Field Structure on Polarization Characteristics of Acousto-optic Interaction in Crystals

    NASA Astrophysics Data System (ADS)

    Muromets, A. V.; Trushin, A. S.

    Influence of acoustic field structure on polarization characteristics of acousto-optic interaction is investigated. It is shown that inhomogeneity of acoustic field and mechanism of ultrasound excitation causes changes in values of acousto-optic figure of merit for ordinary and extraordinary light beams in comparison with theoretic values. The theoretic values were derived under assumption that acoustic wave is homogeneous. Experimental analysis was carried out in acousto-optic cell based on lithium niobate crystal where the acoustic wave propagates at the angle 13 degrees to Z axis of the crystal. We used three different methods of ultrasound generation in the crystal: by means of external piezotransducer, by interdigital transducer and by two sets of electrodes placed on top of the crystal surface. In the latter case, the first pair of the electrodes was directed along X crystal axis, while the second pair of the electrodes was directed orthogonally to X crystal axis and the direction of ultrasound. Obtained values for diffraction efficiencies for ordinary and extraordinary polarized optical beams were qualitatively different which may be caused by spatial inhomogeneity of the generated acoustic waves in the crystal. Structure of acoustic field generated by these sets of electrodes was examined by laser probing. We performed the analysis of the acoustic field intensity using acousto-optic method. A relation of diffraction efficiencies for ordinary and extraordinary light waves was measured during each iteration of the laser probing.

  2. The effect of crystal orientation on the aluminum anodes of the aluminum-air batteries in alkaline electrolytes

    NASA Astrophysics Data System (ADS)

    Fan, Liang; Lu, Huimin; Leng, Jing; Sun, Zegao; Chen, Chunbo

    2015-12-01

    Recently, aluminum-air (Al-air) batteries have received attention from researchers as an exciting option for safe and efficient batteries. The electrochemical performance of Aluminum anode remains an active area of investigation. In this paper, the electrochemical properties of polycrystalline Al, Al (001), (110) and (111) single crystals are investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 4 M NaOH and KOH. Hydrogen corrosion rates of the Al anodes are determined by hydrogen collection. Battery performance using the anodes is tested by constant current discharge at 10 mA cm-2. This is the first report showing that the electrochemical properties of Al are closely related to the crystallographic orientation in alkaline electrolytes. The (001) crystallographic plane has good corrosion resistance but (110) is more sensitive. Al (001) single crystals display higher anode efficiency and capacity density. Controlling the crystallographic orientation of the Al anode is another way to improve the performance of Al-air batteries in alkaline electrolytes.

  3. Birefringence imaging and orientation of laser patterned β-BaB2O4 crystals with bending and curved shapes in glass

    NASA Astrophysics Data System (ADS)

    Ogawa, Kazuki; Honma, Tsuyoshi; Komatsu, Takayuki

    2013-11-01

    Nonlinear optical β-BaB2O4 crystals (β-BBO) with bending and curved shapes were patterned at the surface of 8Sm2O3-42BaO-50B2O3 glass by laser irradiations (Yb:YVO4 laser with a wavelength of 1080 nm, power of 0.8 W, and scanning speed of 4 μm/s), and the orientation state of β-BBO crystals was examined from the birefringence imaging obtained by polarization optical microscope (POM) observations. The formation (crystallization) of β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes at a certain point within the bending angle of 60°. The birefringence images indicate that the formation of highly c-axis oriented β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of β-BBO crystals changes gradually at the bending point. The model for the orientation of the c-axis of β-BBO near the bending point is proposed. The present study proposes that the laser-induced crystallization opens a new door for the science and technology in crystal growth engineering.

  4. Bearing alloys with hexagonal crystal structures provide improved friction and wear characteristics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Johnson, R. L.

    1966-01-01

    Bearings of titanium, cobalt, and other hexagonal crystal alloys are used in vacuum and high temperature environments. These temperature-stabilized alloys have reduced friction and wear characteristics and therefore have potential use in aircraft seals, hydraulic equipment, and artificial human joints.

  5. Orientational behaviour of thermotropic and lyotropic liquid crystal polymer systems under shear flow

    NASA Astrophysics Data System (ADS)

    Andresen, E. M.; Mitchell, G. R.

    1998-08-01

    A comparison is made of the development of global orientation during shearing of lyotropic solutions of hydroxypropylcellulose with that observed for the thermotropic phase of hydroxypropylcellulose. At shear rates > 10 s-1 the behaviour of the two systems is similar, both during steady-state shear, and in terms of relaxation following cessation of shear flow. At low shear rates, the levels of orientation observed for the thermotropic system are substantially greater than observed for the lyotropic solutions. The relationship of these differences to variations in molecular parameters, viscous stress and to director tumbling is discussed.

  6. Effect of applied stress, crystal orientation, and phases on type-II hot corrosion of CMSX-4

    NASA Astrophysics Data System (ADS)

    Lortrakul, Pongpat

    Gas turbine blades encounter corrosion problems, especially at the bare metal connection between the blades and the rotor. Elevated temperatures, a corrosive environment, and high stress are factors that can reduce blade lifespan. Thus, understanding the relation between corrosion behavior and stress is key to improving the design of turbine blades and their operation. Type-II hot corrosion mechanisms (700 °C in flowing 1000 ppm-SO2 with Na2SO4 on the specimen surface) are representative of this problem, and Meier and Luthra have expertly established the mechanisms of Ni-alloy and Co-alloy systems. However, little research has focused on CMSX-4, which is a Ni-based superalloy single crystal. Moreover, research on the effects of phases (eutectic and gamma' size), crystal orientations, and applied stress is lacking. In this research, tests of the early stages of hot corrosion---from 3 minutes to 50 hours of exposure---are performed to develop an understanding of type-II hot corrosion mechanism in CMSX-4.The discovery is that a single Cobalt oxide rich layer is initially formed above NiO in the outward oxidation and turns into spheroids afterward. A unique remnant gamma' precipitate structure is observed in the inward oxidation zone and this evidence indicates the preferential corrosion behavior. Sulfur layer above the original surface is one of the causes influencing the overall oxidation thickness by pushing the outward oxidation scale. As-cast CMSX-4 with a wide variety of phases is used to examine the phase effects. With short exposure, coarse gamma' phase influences the inward oxidation thickness but the effect becomes less with time. Specimens with different orientations (growth and transverse directions) are used to examine orientation effect. A notched specimen with a wedge was invented to maintain a stress gradient during hot corrosion test. The results suggest that there may be an effect of stress on the overall oxidation thickness.

  7. Microstructure evolution and FEM analysis of a [111] oriented single crystal nickel-based superalloy during tensile creep

    NASA Astrophysics Data System (ADS)

    Tian, Sugui; Li, Qiuyang; Su, Yong; Yu, Huichen; Xie, Jun; Zhang, Shu

    2015-03-01

    By means of the elastic-plastic stress-strain finite element method (FEM), the distribution of the von Mises stress and strain energy density in the regions near the interfaces of the cuboidal γ/ γ' phases is calculated to investigate the rafted behaviors of γ' phase in a [111] oriented single crystal (SC) nickel-based superalloy. Results show that, after fully heat treated, the microstructure of the superalloy consists of the cuboidal γ' phase embedded coherently in the γ matrix and arranged regularly along the <100> orientation. And the parameters and misfits of γ'/ γ phases in the alloy increase with the temperature. After crept for 50 h, the γ' phase in alloy has transformed into the mesh-like rafted structure on (010) plane along [001] and [100] orientations. When the tensile stress is applied along [111] direction, the change of the strain energy on the planes of the cuboidal γ' phase results in the directional diffusion of the elements. Thereinto, compared with (010) plane, the bigger expanding strain occurs on (100) and (001) planes along the [010], [001] and [010], [100] directions, which may trap the Al and Ti atoms with bigger radius to promote the directional growth of γ' phase on (010) plane along [100] and [001] directions. This is thought to be the main reason for the γ' phase directionally growing into the mesh-like rafted structure on (010) plane.

  8. Kinematic characteristics of the stroke and orientation of the hand during front crawl resisted swimming.

    PubMed

    Gourgoulis, Vassilios; Antoniou, Panagiotis; Aggeloussis, Nikolaos; Mavridis, Georgios; Kasimatis, Panagiotis; Vezos, Nikolaos; Boli, Alexia; Mavromatis, Georgios

    2010-09-01

    The aim of this study was to examine the acute effect of front crawl sprint resisted swimming with different added resistances on the kinematic characteristics of the stroke and the orientation of the hand. Ten female swimmers swam four maximal trials (25 m) with small, moderate, large, and no added resistance respectively. Four camcorders were used to record the underwater motion of the right hand and digitizing was undertaken using the Ariel Performance Analysis System. Stroke rate, the stroke length, and mean swimming velocity were significantly decreased, whereas the total duration of the stroke and the relative duration of the pull and push phases were significantly increased during resisted swimming. The increase in the total duration of the stroke was accompanied by an increase in absolute pull length, while no alterations were observed in relative pull length or medial-lateral displacements of the hand. Moreover, the mean resultant velocity of the hand, as well as the pitch and the sweepback angles of the hand were not modified. In conclusion, resisted swimming appears to be a specific form of training, at least regarding its acute effect, although long-term effects should be investigated further. PMID:20845217

  9. Suicidality and sexual orientation: Characteristics of symptom severity, disclosure, and timing across the life course.

    PubMed

    Blosnich, John R; Nasuti, Laura J; Mays, Vickie M; Cochran, Susan D

    2016-01-01

    This investigation explored suicide-related characteristics and help-seeking behavior by sexual orientation. Population-based data are from the California Quality of Life Surveys, which included 1,478 sexual minority (lesbian, gay, bisexual, and homosexually experienced individuals) and 3,465 heterosexual individuals. Bisexual women had a nearly six-fold increased risk of lifetime suicide attempts than heterosexual women (RR = 5.88, 95%CI: 3.89-8.90), and homosexually experienced men had almost 7 times higher risk of lifetime suicide attempts than heterosexual men (RR = 6.93, 95%CI: 3.65-13.15). Sexual minority men and women were more likely than heterosexual men and women to have disclosed suicide attempts to a medical professional (RR = 1.48 and RR = 1.44, respectively). Among persons who ever attempted suicide, sexual minority women had a younger age of index attempt than heterosexual women (15.9 vs. 19.6 years of age, respectively). Healthcare professionals should be aware of suicidal risk heterogeneity among sexual minority individuals, including vulnerable points of risk and evidenced-based treatments. PMID:26752446

  10. Stability of tetragonal <0 0 1> oriented PZN-12PT single crystals

    NASA Astrophysics Data System (ADS)

    Touhtouh, S.; Hajjaji, A.; Boughaleb, Y.; Benkhouja, K.; Arbaoui, A.; Rguiti, M.; Guyomar, D.

    2012-08-01

    The present paper reports on the synthesis and electromechanical characterization of tetragonal (1 - x)Pb(Zn1/3-Nb2/3)O3-xPbTiO3 (x = 12) single crystals as a function of various external disturbances. Tetragonal PZN-12PT single crystals were grown using the flux method. The set of piezoelectric coefficients in the lateral mode was measured. Samples with size of 10 × 2 × 1 mm3 were polled in the <0 0 1> and <1 1 0> crystallographic directions and were found to possess a high Curie temperature (>170 °C). Moreover, no ferroelectric-ferroelectric phase transition was observed for the positive temperatures, which expanded the usage range significantly. Tetragonal crystals were also found to have high coercive field, mechanical quality factors, and good optical properties, attracting much effort on the characterization of tetragonal PZN-12PT crystals. However, the most interesting properties in the lateral mode were obtained for <0 0 1>. Finally, the thermal stability and stress dependence were studied in order to determine the working conditions.

  11. Band structure and transmission characteristics of complex phononic crystals by multi-level substructure scheme

    NASA Astrophysics Data System (ADS)

    Yin, J.; Zhang, S.; Zhang, H. W.; Chen, B. S.

    2015-10-01

    A fast scheme based on the multi-level substructure technique is proposed for the band structure and transmission characteristics calculation of phononic crystals uniformly. The main idea is that finite element models of phononic crystals are divided into several domains by a special multi-level decomposition. For the band structure calculation, the upscaling calculation is employed to condense the internal stiffness matrix of the unit cell into the Bloch boundary. Due to the internal stiffness matrix does not change along with reduced wave vectors in an iteration process, the scheme can reduce the computational scale and improve the efficiency greatly, meanwhile it does not introduce approximation into the traditional finite element model. For the transmission characteristics calculation, the unit cell of the phononic crystal is periodic which is taken as a substructure with the same coefficient matrix. Moreover, the downscaling calculation of internal displacements can be selected flexibly. Some closely watched examples of the three-dimensional locally resonant, defect state of Lamb wave and Bragg waveguide are analyzed. Numerical results indicate that the proposed scheme is efficient and accurate, which may widely be applicable and suitable for complex phononic crystal problems, and provides a reliable numerical tool to optimize and design crystal devices.

  12. Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt

    SciTech Connect

    Soares, Alexei S.; Mullen, Jeffrey D.; Parekh, Ruchi M.; McCarthy, Grace S.; Roessler, Christian G.; Jackimowicz, Rick; Skinner, John M.; Orville, Allen M.; Allaire, Marc; Sweet, Robert M.

    2014-10-09

    X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltdin situmicro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ~100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face that preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. Lastly, high-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies.

  13. Cloud radar with hybrid mode towards estimation of shape and orientation of ice crystals

    NASA Astrophysics Data System (ADS)

    Myagkov, A.; Seifert, P.; Bauer-Pfundstein, M.; Wandinger, U.

    2016-02-01

    This paper is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data are obtained using a newly developed 35 GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing back-scattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. The developed algorithm is applied to a measurement of the hybrid-mode cloud radar taken on 20 October 2014 in Cabauw, the Netherlands, in the framework of the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) campaign. The case study shows the retrieved polarizability ratio and degree of orientation of ice particles for a cloud system of three cloud layers at different heights. Retrieved polarizability ratios are 0.43, 0.85, and 1.5 which correspond to oblate, quasi-spherical, and columnar ice particles, respectively. It is shown

  14. Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

    NASA Astrophysics Data System (ADS)

    Zhou, Bite; Zhou, Quan; Bieler, Thomas R.; Lee, Tae-kyu

    2015-03-01

    Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy x-ray diffraction were used to obtain Sn grain orientations and the average coefficient of thermal expansion normal to the board in every joint of the package for samples in the as-fabricated and thermally cycled conditions. The results indicated a near-random distribution of joint orientation. Optical, scanning electron microscopy, and EBSD methods were used to characterize microstructure changes in pre-cross-sectioned samples due to thermal cycling. Slip trace analysis and Orientation Imaging Microscopy™ (OIM) show that slip systems with high Schmid factors (estimated global shear stress based on the package neutral point) are responsible for the observed microstructure evolution during thermal cycling, which provides information about slip systems that are more easily activated. Two joints were analyzed in detail to evaluate slip activity at different stages of their thermal history. The first case showed that a solidification twin grain boundary misorientation deviated from the twin relationship due to slip activity during thermal cycling, which can influence damage development and the path of crack propagation. The second case showed a new grain orientation developing due to gradual lattice rotation about the Sn [110] axis by a continuous recrystallization mechanism. This rotation was correlated with the operation of slip system . Small tin whiskers emerged from the initially polished chip interface and grew with increasing thermal cycles until a crack developed in the solder that relieved the stress. As the local stresses are not known experimentally, this analysis provides observations that can be compared with a crystal plasticity model simulation.

  15. Laser patterning and preferential orientation of two-dimensional planar {beta}-BaB{sub 2}O{sub 4} crystals on the glass surface

    SciTech Connect

    Suzuki, F.; Ogawa, K.; Honma, T.; Komatsu, T.

    2012-01-15

    The laser-induced crystallization method is applied to pattern two-dimensional planar {beta}-BaB{sub 2}O{sub 4} crystals on the surface of Sm{sub 2}O{sub 3}-BaO-B{sub 2}O{sub 3} glass. By scanning Yb:YVO{sub 4} fiber lasers (wavelength: 1080 nm) continuously with a small step (0.5 {mu}m) between laser irradiated areas, homogeneous planar {beta}-BaB{sub 2}O{sub 4} crystals are patterned successfully, and a preferential growth orientation of {beta}-BaB{sub 2}O{sub 4} crystals is confirmed from linearly polarized micro-Raman scattering spectrum and second harmonic intensity measurements. It is found that the crystal growth direction is perpendicular to the laser scanning direction. This relation, i.e., the perpendicular relation, is different from the behavior in discrete crystal line patterning, where the crystal growth direction is consistent with the laser scanning direction. The present study proposes the possibility of the control of crystal growth direction in laser-induced crystallization in glasses. - Graphical abstract: This figure shows confocal scanning laser microscope and polarized optical microscope photographs for {beta}-BaB{sub 2}O{sub 4} crystals obtained by laser irradiations. The laser scanning was repeated with a step of 0.5 {mu}m between the lines using the condition of the power of P=0.8 W and a laser scanning speed of S=8 {mu}m/s. It is suggested that {beta}-BaB{sub 2}O{sub 4} crystals in the overlapped laser-irradiated region are highly oriented and the c-axis direction of {beta}-BaB{sub 2}O{sub 4} crystals is perpendicular to the laser scanning direction. Highlights: Black-Right-Pointing-Pointer Laser-induced crystallization method is applied to pattern {beta}-BaB{sub 2}O{sub 4} crystals. Black-Right-Pointing-Pointer Two-dimensional planar crystals are patterned on the glass surface. Black-Right-Pointing-Pointer Preferential growth orientation of {beta}-BaB{sub 2}O{sub 4} crystals is confirmed. Black-Right-Pointing-Pointer Crystal growth

  16. Preferred Ice Crystal Orientation Fabric Measurements within the Greenland Ice Sheet Using Multi-Polarization Radar Data

    NASA Astrophysics Data System (ADS)

    Velez-Gonzalez, J. A.; JiLu, L.; Leuschen, C.; Gogineni, P.; Van der Veen, C. J.; Tsoflias, G. P.; Drews, R.; Harish, A. R.

    2013-12-01

    Discharge of ice from the Greenland Ice Sheet to the ocean has increased significantly over the last 25 years due to the acceleration of important outlet glaciers. It was reported that the Greenland Ice Sheet contributed about 2.5 m out of about 6 m of sea-level rise during the Eemian interglacial period. The temperatures during Eemian were reported to be about 8o×4o C higher than the mean of the past millennium. Laboratory measurements have shown that glacial ice, characterized by preferred crystal orientation fabric (COF), is three times more deformable than ice with randomly oriented crystalline structures. Layers characterized by preferred ice COF can influence the flow behavior of a glacier or ice sheet. However, COF measurements are typically obtained from ice cores, and thus are very spatially limited and mostly constrained to areas with little ice flow. A more efficient technique to map the extent of ice fabric over larger regions of ice sheets is needed to better understand the effects on large scale ice flow processes. Radar measurements are capable of discriminating between reflections caused by changes in density, electrical permittivity and COF by exploiting the anisotropic and birefringent properties of ice crystals. For this investigation two radar datasets were collected during the survey of the Greenland Eemian Ice Drilling Site (77.45°N 51.06°W) in August 2008, using a ground-based and chirped-pulse Multi-Channel Radar Depth Sounder (MCRDS) developed by the Center for Remote Sensing of Ice Sheets (CReSIS). The radar used two transmit and eight receive antennas at the center frequency of 150 MHz with a bandwidth of 30 MHz. The first data set consisted of polarimatric measurements acquired in a circular pattern (radius: 35 m) with two co-polarized antenna orientations (one transmitter and four receivers oriented with 90° offsets in the directions of the incident H-Field and E-Field, respectively). Analysis of the circular data shows a periodic

  17. Effects of crystal orientation on cellulose nanocrystals-cellulose acetate nanocomposite fibers prepared by dry spinning.

    PubMed

    Chen, Si; Schueneman, Greg; Pipes, R Byron; Youngblood, Jeffrey; Moon, Robert J

    2014-10-13

    This work presents the development of dry spun cellulose acetate (CA) fibers using cellulose nanocrystals (CNCs) as reinforcements. Increasing amounts of CNCs were dispersed into CA fibers in efforts to improve the tensile strength and elastic modulus of the fiber. A systematic characterization of dispersion of CNCs in the polymer fiber and their effect on the nanocomposites' mechanical properties is described. The birefringence, thermal properties, and degree of CNC orientation of the fibers are discussed. 2D X-ray diffraction was used to quantify the degree of CNC alignment within the fibers. It is shown that the CNC alignment directly correlates to the mechanical properties of the composite. Maximum improvements of 137% in tensile strength and 637% in elastic modulus were achieved. Empirical micromechanical models Halpin-Tsai equation and an orientation modified Cox model were used to predict the fiber performance and compared with experimental results. PMID:25226382

  18. Theoretical study of interfacial damping in perpendicular anisotropy superlattices along multiple crystal orientations

    NASA Astrophysics Data System (ADS)

    Qu, T.; Victora, R. H.

    2016-06-01

    Damping, representing the loss of magnetic energy from the electrons to the lattice through the spin-orbit interaction, is calculated for Co/Pt and Co/Pd superlattices grown along the (001), (111), and (011) orientations. The damping consists of two contributions: interfacial and, usually, bulk. The interfacial damping shows dependence on the superlattice orientation. The origin of the interfacial damping is due to both the distorted electronic states at the interface and the spin-orbit interaction in the weakly polarized nonmagnetic Pt/Pd layers deposited on Co layers. The density of states around the Fermi level provides the spin-flip channels and closely correlates with the damping value. The damping shows asymmetry in the two transverse directions of the spin for spins at most angles. The damping for out-of-plane magnetization can be as much as 1.7 times larger than that of in-plane magnetization.

  19. Modeling the effect of subgrain rotation recrystallization on the evolution of olivine crystal preferred orientations in simple shear

    NASA Astrophysics Data System (ADS)

    Signorelli, Javier; Tommasi, Andréa

    2015-11-01

    Homogenization models are widely used to predict the evolution of texture (crystal preferred orientations) and resulting anisotropy of physical properties in metals, rocks, and ice. They fail, however, in predicting two main features of texture evolution in simple shear (the dominant deformation regime on Earth) for highly anisotropic crystals, like olivine: (1) the fast rotation of the CPO towards a stable position characterized by parallelism of the dominant slip system and the macroscopic shear and (2) the asymptotical evolution towards a constant intensity. To better predict CPO-induced anisotropy in the mantle, but limiting computational costs and use of poorly-constrained physical parameters, we modified a viscoplastic self-consistent code to simulate the effects of subgrain rotation recrystallization. To each crystal is associated a finite number of fragments (possible subgrains). Formation of a subgrain corresponds to introduction of a disorientation (relative to the parent) and resetting of the fragment strain and internal energy. The probability of formation of a subgrain is controlled by comparison between the local internal energy and the average value in the polycrystal. A two-level mechanical interaction scheme is applied for simulating the intracrystalline strain heterogeneity allowed by the formation of low-angle grain boundaries. Within a crystal, interactions between subgrains follow a constant stress scheme. The interactions between grains are simulated by a tangent viscoplastic self-consistent approach. This two-level approach better reproduces the evolution of olivine CPO in simple shear in experiments and nature. It also predicts a marked weakening at low shear strains, consistently with experimental data.

  20. Template Adaptability is Key in the Oriented Crystallization of CaCO3

    SciTech Connect

    Popescu,D.; Smulders, M.; Pichon, B.; Chebotareva, N.; Kwak, S.; van Asselen, O.; Sijbesma, R.; DiMasi, E.; Sommerdijk, N.

    2007-01-01

    In CaCO3, biomineralization nucleation and growth of the crystals are related to the presence of carboxylate-rich proteins within a macromolecular matrix, often with organized {beta}-sheet domains. To understand the interplay between the organic template and the mineral crystal it is important to explicitly address the issue of structural adaptation of the template during mineralization. To this end we have developed a series of self-organizing surfactants (1-4) consisting of a dodecyl chain connected via a bisureido-heptylene unit to an amino acid head group. In Langmuir monolayers the spacing of these molecules in one direction is predetermined by the hydrogen-bonding distances between the bis-urea units. In the other direction, the intermolecular distance is determined by steric interactions introduced by the side groups (-R) of the amino acid moiety. Thus, by the choice of the amino acid we can systematically alter the density of the surfactant molecules in a monolayer and their ability to respond to the presence of calcium ions. The monolayer films are characterized by surface pressure-surface area (p-A) isotherms, Brewster angle microscopy, in-situ synchrotron X-ray scattering at fixed surface area, and also infrared reflection absorption spectroscopy (IRRAS) of films transferred to solid substrates. The developing crystals are studied with scanning and transmission electron microscopy (SEM, TEM), selected area electron diffraction (SAED), and crystal modeling. The results demonstrate that although all compounds are active in the nucleation of calcium carbonate, habit modification is only observed when the size of the side group allows the molecules to rearrange and adapt their organization in response to the mineral phase.

  1. Orientational order of solutes in liquid crystals: The effect of distributed electric quadrupoles

    NASA Astrophysics Data System (ADS)

    Lee, J. S. J.; Sokolovskii, R. O.; Berardi, R.; Zannoni, C.; Burnell, E. E.

    2008-03-01

    We perform Monte Carlo simulations of a mixture of soft ellipsoids with embedded quadrupoles as a model of various small molecules dissolved in nematic liquid crystals. We find that Gay-Berne ellipsoids with distributed embedded quadrupoles qualitatively reproduce the trend in the order parameters observed experimentally in NMR spectra. In contrast, ellipsoids with a single embedded quadrupole cannot reproduce the negative order parameter of acetylene in EBBA.

  2. The Relationships between Different Personality Characteristics and Styles of Coping with Stress in Elite Orienteers.

    ERIC Educational Resources Information Center

    Zsheliaskova-Koynova, Zshivka

    1993-01-01

    Eighty orienteers, divided into three groups according to level of expertise in orienteering, completed questionnaires measuring extraversion, neuroticism, trait anxiety, social desirability, need for achievement, and locus of control. Subject interviews revealed individual styles of coping with precompetitive stress. A combination of high sport…

  3. Dependences of the Diffraction Efficiency of Photorefractive Holograms on the Sample Thickness and Orientation Angle in a (ī ī 0)-cut Bi12SiO20 Crystal

    NASA Astrophysics Data System (ADS)

    Shepelevich, V. V.; Makarevich, A. V.; Shandarov, S. M.; Ropot, P. I.; Zagorskii, A. E.

    2016-02-01

    We present the results of experimental studies of the dependence of the diffraction efficiency of nonoblique transmission holograms formed in the sample of a (īī0)-cut photorefractive piezoelectric Bi12SiO20 crystal on the sample thickness and orientation angle of the grating vector at two fixed mutually orthogonal orientations of the linear polarization vector of the reading beam. It is shown that only if along with optical activity of the crystal, the electrooptic, inverse piezoelectric, and photoelastic effects are taken into account in the analytical diffraction model, it is possible to carry out satisfactory theoretical interpretation of the experimental data.

  4. High magneto-optical characteristics of Holmium-doped terbium gallium garnet crystal.

    PubMed

    Chen, Zhe; Yang, Lei; Wang, Xiangyong; Yin, Hang

    2016-06-01

    Magneto-optical characteristics of a new magneto-active material, (Tb(1-x)Hox)3Ga5O12 crystal, have been grown by the Czochralski (Cz) method. A high value of the Verdet constant was obtained at room temperature-namely, 214.9 and 77.8  rad·m-1 T-1 for 632.8 and 1064 nm, respectively. The Verdet constant of the Ho-doped terbium gallium garnet crystal at 1064 nm is about 2 times higher than that of terbium gallium garnet crystal. High value of magneto-optical figure-of-merit makes it an attractive next-generation magneto-optics material for high-power Faraday isolators. PMID:27244419

  5. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study

    PubMed Central

    Zhou, Li-li; Liu, Rang-su; Tian, Ze-an; Liu, Hai-rong; Hou, Zhao-yang; Peng, Ping

    2016-01-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90–150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule. PMID:27526660

  6. Low-energy electron diffraction study of potassium adsorbed on single-crystal graphite and highly oriented pyrolytic graphite

    SciTech Connect

    Ferralis, N.; Diehl, R.D.; Pussi, K.; Lindroos, M.; Finberg, S.E.; Smerdon, J.; McGrath, R.

    2004-12-15

    Potassium adsorption on graphite has been a model system for the understanding of the interaction of alkali metals with surfaces. The geometries of the (2x2) structure of potassium on both single-crystal graphite (SCG) and highly oriented pyrolytic graphite (HOPG) were investigated for various preparation conditions for graphite temperatures between 55 and 140 K. In all cases, the geometry was found to consist of K atoms in the hollow sites on top of the surface. The K-graphite average perpendicular spacing is 2.79{+-}0.03 A , corresponding to an average C-K distance of 3.13{+-}0.03 A , and the spacing between graphite planes is consistent with the bulk spacing of 3.35 A. No evidence was observed for a sublayer of potassium. The results of dynamical LEED studies for the clean SCG and HOPG surfaces indicate that the surface structures of both are consistent with the truncated bulk structure of graphite.

  7. Elevated temperature tension, compression and creep-rupture behavior of (001)-oriented single crystal superalloy PWA 1480

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Miner, Robert V.

    1987-01-01

    Tensile and compressive flow behavior at various temperatures and strain rates, and tensile creep rupture behavior at 850 and 1050 C and various stresses were studied for (001)-oriented single crystals of the Ni-base superalloy PWA 1480. At temperatures up to 760 C, the flow stress is insensitive to strain rate and of greater magnitude in tension than in compression. At temperatures of 800 C and above, the flow stress decreases continuously with decreasing strain rate and the tension/compression anisotropy diminishes. The second stage creep rate and rupture time exhibited power law relationships with the applied stress for both 850 and 1050 C, however with different stress dependencies. The stress exponent for the steady state creep rate was about 7 at 1050 C, but much higher at 850 C, about 12. Directional coarsening of the gamma' phase occurred during creep at 1050 C, but not at 850 C.

  8. Stepwise heat-capacity change at an orientation transition in liquid crystals

    NASA Astrophysics Data System (ADS)

    Aya, Satoshi; Sasaki, Yuji; Pociecha, Damian; Araoka, Fumito; Górecka, Ewa; Ema, Kenji; Muševič, Igor; Orihara, Hiroshi; Ishikawa, Ken; Takezoe, Hideo

    2014-02-01

    During a phase transition in a bulk material, heat is exchanged with matter to balance the changes in the internal energy and the entropy of the system. Here we report on the thermal detection of a surface-mediated anchoring transition, a spontaneous and discontinuous orientation change between planar (P) and homeotropic (H) alignments within a single nematic phase by changing temperature. In this case a stepwise change in the heat flow, similar to a glass transition, is observed by means of high-resolution differential scanning calorimetry. We found that the jump in the specific heat does not depend on the sample volume, although the contribution of molecules in the vicinity of surfaces, which trigger the transition, becomes less with increasing the sample volume. This means that different molecular orientations, H and P, with respect to surfaces have different thermodynamic free energies. We also address why the anchoring transition occurs by means of grazing-incidence x-ray diffraction measurements, which clearly reveal the formation of quasismectic layers parallel to surfaces in the nematic phase.

  9. Temperature characteristics of Pockels electro-optic voltage sensor with double crystal compensation

    NASA Astrophysics Data System (ADS)

    Sima, Wenxia; Liu, Tong; Yang, Qing; Han, Rui; Sun, Shangpeng

    2016-05-01

    Voltage sensors based on the Pockels electro-optic effect in LiNbO3 crystals have been applied to practical engineering measurements because of their passive nature, wide operating bands, and low transmission loss. However, the temperature of the measurement environment can greatly affect the dynamic responses of these sensors because the natural birefringence of a single LiNbO3 crystal voltage sensor (SVS) is related to its temperature. To improve the stability of this sensor over a wide temperature range, a double crystal compensation method is introduced in this paper to compensate for the natural birefringence of the SVS. A double LiNbO3 crystal voltage sensor (DVS) was fabricated, and its working point drift characteristics and amplitude-frequency response were investigated over the temperature range from 0°C to 50°C. The effects of two intrinsic parameters of the LiNbO3 crystal were also investigated. Comparison between an existing SVS and the proposed DVS showed that the DVS resisted environmental temperature fluctuations more strongly.

  10. Fully Atomistic Simulations of the Ionic Liquid Crystal [C16mim][NO3]: Orientational Order Parameters and Voids Distribution.

    PubMed

    Saielli, Giacomo

    2016-03-10

    We present a fully atomistic molecular dynamics simulation of the smectic phase of the ionic liquid crystal (ILC) 1-hexadecyl-3-methylimidazolium nitrate, [C16MIm][NO3]. We have characterized the structure of the phase by means of a set of radial distribution functions resolved along the director and in the plane of the smectic layers. The results obtained allow us to discuss the similarities in the microscopic structure of ionic liquids (ILs) and ILCs. In addition to this, we have calculated the orientational order parameters, S, of the methylene groups of the alkyl chain and compared them with the results obtained for phospholipidic membranes from (2)H NMR experiments. We also discuss the orientational order parameters of the imidazolium ring. Finally, we analyze the distribution of voids in the ILC phase. We have found that voids of considerable volume to host a nonpolar gas, e.g. xenon, are localized in the hydrophobic layers and almost absent in the ionic layers. PMID:26849800

  11. Orientational Coherent Effects of High-Energy Particles in a LiNbO3 Crystal

    NASA Astrophysics Data System (ADS)

    Bagli, E.; Guidi, V.; Mazzolari, A.; Bandiera, L.; Germogli, G.; Sytov, A. I.; De Salvador, D.; Argiolas, A.; Bazzan, M.; Carnera, A.; Berra, A.; Bolognini, D.; Lietti, D.; Prest, M.; Vallazza, E.

    2015-07-01

    A bent lithium niobate strip was exposed to a 400 -GeV /c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3 ) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (1 04 per cm2 ) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2 ). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.

  12. Orientational Coherent Effects of High-Energy Particles in a LiNbO3 Crystal.

    PubMed

    Bagli, E; Guidi, V; Mazzolari, A; Bandiera, L; Germogli, G; Sytov, A I; De Salvador, D; Argiolas, A; Bazzan, M; Carnera, A; Berra, A; Bolognini, D; Lietti, D; Prest, M; Vallazza, E

    2015-07-01

    A bent lithium niobate strip was exposed to a 400-GeV/c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (10(4) per cm2) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations. PMID:26182106

  13. Crystallization of Polymer Chains Chemically Attached on a Surface: Lamellar Orientation from Flat-on to Edge-on.

    PubMed

    Chen, Yihuang; Gan, Tiansheng; Ma, Chunfeng; Wang, Linge; Zhang, Guangzhao

    2016-05-26

    Crystallization of polymer chains confined on a surface greatly influences surface properties. We have grafted comb-like copolymer, consisting of poly(2-hydroxyethyl methacrylate) (PHEMA) backbone and semicrystalline poly(ε-caprolactone) (PCL) side chains, on silicon surface and investigated the crystallization of such confined PCL chains upon solvent evaporation by using atomic force microscopy (AFM), grazing incidence wide-angle X-ray scattering (GI-WAXS), and polarized optical microscope (POM). Our studies reveal that the PCL chains align and form "flat-on" lamellae at a low PCL chain density. As the chain density increases, the comb-like polymer (PHEMA-g-PCL) chains undergo pancake-to-mushroom-to-brush transition, and the lamellae turn from "flat-on" to "edge-on" in orientation. Further increasing PCL chain density leads the "edge-on" lamellae to change from a quasi-two-dimensional (quasi-2D) to quasi-three-dimensional (quasi-3D). Because of the confinements of polymer chains, we can observe the evolution of spherulites at different stages during the mushroom-to-brush transition of PHEMA-g-PCL chains. The confinements also result in knobbly substructures in the edge-on lamellae. PMID:27149242

  14. Indentation Schmid factor and orientation dependence of nanoindentation pop-in behavior of NiAl single crystals

    SciTech Connect

    Li, Tianlei; Gao, Yanfei; Bei, Hongbin; George, Easo P

    2011-01-01

    Instrumented nanoindentation techniques have been widely used to characterize the small-scale mechanical behavior of materials. The elastic-plastic transition during nanoindentation is often indicated by a sudden displacement burst (pop-in) in the measured load-displacement curve. In defect-free single crystals, the pop-in is believed to be the result of homogeneous dislocation nucleation because the maximum shear stress corresponding to the pop-in load approaches the theoretical strength of the materials and because the statistical distribution of pop-in stresses is consistent with what is expected for a thermally activated process of homogeneous dislocation nucleation. This paper investigates whether this process is affected by crystallography and stress components other than the resolved shear stress. A Stroh formalism coupled with the two-dimensional Fourier transformation is used to derive the analytical stress fields in elastically anisotropic solids under Hertzian contact, which allows the determination of an indentation Schmid factor, namely, the ratio of maximum resolved shear stress to the maximum contact pressure. Nanoindentation tests were conducted on B2-structured NiAl single crystals with different surface normal directions. This material was chosen because it deforms at room temperature by {110}<001> slip and thus avoids the complexity of partial dislocation nucleation. Good agreement is obtained between the experimental data and the theoretically predicted orientation dependence of pop-in loads based on the indentation Schmid factor. Pop-in load is lowest for indentation directions close to <111> and highest for those close to <001>. In nanoindentation, since the stress component normal to the slip plane is typically comparable in magnitude to the resolved shear stress, we find that the pressure sensitivity of homogeneous dislocation nucleation cannot be determined from pop-in tests. Our statistical measurements generally confirm the thermal

  15. Orientational order and translational dynamics of magnetic particle assemblies in liquid crystals.

    PubMed

    Peroukidis, Stavros D; Klapp, Sabine H L

    2016-08-10

    Implementing extensive molecular dynamics simulations we explore the organization of magnetic particle assemblies (clusters) in a uniaxial liquid crystalline matrix comprised of rodlike particles. The magnetic particles are modelled as soft dipolar spheres with diameter significantly smaller than the width of the rods. Depending on the dipolar strength coupling the magnetic particles arrange into head-to-tail configurations forming various types of clusters including rings (closed loops) and chains. In turn, the liquid crystalline matrix induces long range orientational ordering to these structures and promotes their diffusion along the director of the phase. Different translational dynamics are exhibited as the liquid crystalline matrix transforms either from isotropic to nematic or from nematic to smectic state. This is caused due to different collective motion of the magnetic particles into various clusters in the anisotropic environments. Our results offer a physical insight for understanding both the structure and dynamics of magnetic particle assemblies in liquid crystalline matrices. PMID:27460190

  16. Orientational dynamics of a ferronematic liquid crystal in a rotating magnetic field

    SciTech Connect

    Boychuk, A. N. Zakhlevnykh, A. N.; Makarov, D. V.

    2015-09-15

    The behavior of the orientational structure of a ferronematic in a rotating uniform magnetic field is investigated using the continual theory. The time-dependent system of equations describing the dynamics of the ferronematic is derived. The dependences of the angles of rotation of the director and of the magnetization of the ferronematic on the velocity of field rotation are determined for various values of the material parameters. Two regimes (synchronous and asynchronous) of rotation of the ferronematic structure are detected. In the synchronous regime, the director rotates with the frequency of the magnetic field and a constant phase delay. The asynchronous regime is characterized by a time-dependent phase delay. The dependence of the critical angular velocity of magnetic field rotation, which determines the boundary between the synchronous and asynchronous regimes, on the magnetic field strength is derived.

  17. Electrically tunable birefringence of a polymer composite with long-range orientational ordering of liquid crystals.

    PubMed

    Choi, Byeongdae; Song, Seongkyu; Jeong, Soon Moon; Chung, Seok-Hwan; Glushchenko, Anatoliy

    2014-07-28

    We report an optical film with electrically tunable birefringence in which the liquid crystals (LCs), mixed with the host polymer, form long-range ordering. The film was prepared through polymerization without phase separation between the LCs and polymers. Driving voltage below 30 V for full switching of birefringence is achieved in a 6 μm-thick film. Electro-optical investigations for the film suggest that the long-range ordering of the LCs mixed in the film caused by polymerization lead to rotations of the LCs as well as optical anisotropy in the film. These films with electrically tunable birefringence could have applications as flexible light modulators and phase retardation films for 2D-3D image switching. PMID:25089422

  18. Peculiar orientational disorder in 4-bromo-4′-nitrobiphenyl (BNBP) and 4-bromo-4′-cyanobiphenyl (BCNBP) leading to bipolar crystals

    PubMed Central

    Burgener, Matthias; Aboulfadl, Hanane; Labat, Gaël Charles; Bonin, Michel; Sommer, Martin; Sankolli, Ravish; Wübbenhorst, Michael; Hulliger, Jürg

    2016-01-01

    180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4′-nitrobiphenyl (BNBP) and 4-bromo-4′-cyanobiphenyl (BCNBP)] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals. The spatial inhomogeneous distribution of polarity was investigated by scanning pyroelectric microscopy (SPEM), phase-sensitive second harmonic microscopy (PS-SHM) and selected volume X-ray diffraction (SVXD). As a result, the acceptor groups (NO2 or CN) are predominantly present at crystal surfaces. However, the stochastic process of polarity formation can be influenced by adding a symmetrical biphenyl to a growing system. For this case, Monte Carlo simulations predict an inverted net polarity compared with the growth of pure BNBP and BCNBP. SPEM results clearly demonstrate that 4,4′-dibromobiphenyl (DBBP) can invert the polarity for both crystals. Phenomena reported in this paper belong to the most striking processes seen for molecular crystals, demonstrated by a stochastic process giving rise to symmetry breaking. We encounter here further examples supporting the general thesis that monodomain polar molecular crystals for fundamental reasons cannot exist. PMID:27158508

  19. Influence of body-wave velocity characteristic on the seismic data interpretation in TI media with arbitrary spatial orientation

    NASA Astrophysics Data System (ADS)

    Hao, C.; Yao, C.

    2007-12-01

    TI media with arbitrary spatial orientation (ATI) is the actual anisotropic model used to describe tilted PTL (period thin layers) and no vertical fractured rock. We devote our paper to study the Influence of body-wave velocity characteristic on the seismic data interpretation in the ATI media. Based on the method of coordinates transformation for the TI media with arbitrary strength of anisotropy and arbitrary spatial orientation, we present the characteristic of body-wave velocity with incident angle and azimuth variation in the ATI media. The result shows that patterns of body-wave velocity are fixed relative to the symmetry axis, and these fixed patterns are closely relative to Thomsen's anisotropic parameters. Body-wave velocity characteristic depends just on the angle between the propagation direction and the symmetry axis. Therefore, with variations of spatial orientation of the symmetry axis and the surveying line azimuth, patterns of body-wave velocity have a variety, and have some symmetries, gradual changes and repetitions. The result is useful to processing and explaining of seismic data.

  20. Domain Structure and Orientational Ordering of NO{sub 2} Groups in K{sub 2}Ba(NO{sub 2}){sub 4} Crystals

    SciTech Connect

    Kirpichnikova, L. F.; Shakhmatov, V. S.; Szczesniak, L. Polomska, M.

    2010-11-15

    Polarization-optical studies of the domain structure of K{sub 2}Ba(NO{sub 2}){sub 4} crystals and differentialscanning calorimetric measurements have been performed in the vicinity of the high-temperature phase transition. The orientational ordering of NO{sub 2} atomic groups is analyzed and the temperature dependence of the birefringence coefficient is theoretically described.

  1. Correction: Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Muñoz Rojo, Miguel; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2015-03-01

    Correction for 'Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865. PMID:25668105

  2. Physical matching of metals: grain orientation association at fracture edge.

    PubMed

    Lograsso, Barbara K

    2015-01-01

    The objective of this study was to examine whether surface crystal orientation can be used to associate or differentiate metal fracture fragments. The orientations of individual crystals and crystals across the fracture plane were measured on polished steel and iron alloy surfaces using Electron Backscattered Diffraction/ Orientation Imaging Microscopy (EBSD/OIM). This investigation examined crystallographic characteristics within a metal. This study showed that for transgranular fracture, it is feasible that pieces of grains could be associated across the fracture surface with the difference in orientation between grains (misorientation) along a length sequence of grain orientations on one side of the fracture surface to associate the other side of a fracture surface. Regarding pair comparisons of crystals on fracture surfaces, it was estimated that the probability for an ordered sequence of six distinct oriented grains along a fracture surface to occur again is about 1 in 4.82 (10)(30) or 2.07 (10)(-31). PMID:25619870

  3. Manifestations of Dynamic Strain Aging in Soft-Oriented NiAl Single Crystals

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1996-01-01

    The tensile and compressive properties of six NiAl-base single-crystal alloys have been investigated at temperatures between 77 and 1200 K. The normalized critical resolved shear stresses (CRSS/E) and work-hardening rates (Theta/E) for these alloys generally decreased with increasing temperature. However, anomalous peaks or plateaus for these properties were observed in conventional purity (CPNiAl), Si-doped (NiAl-Si), C-doped low Si (UF-NiAl1), and Mo-doped (NiAl-Mo) alloys at intermediate temperatures (600 to 1000 K). This anomalous behavior was not observed in high-purity, low interstitial material (HP-NiAl). Low or negative strain-rate sensitivities (SRS) also were observed in all six alloys in this intermediate temperature range. Coincident with the occurrence of negative strain-rate sensitivities was the observation of serrated stress-strain curves in the CPNiAl and NiAl-Si alloys. These phenomena have been attributed to dynamic strain aging (DSA). Chemical analysis of the alloys used in this study suggests that the main specie responsible for strain aging in NiAl is C but indicate that residual Si impurities can enhance the strain aging effects. The corresponding dislocation microstructures at low temperatures (300 to 600 K) were composed of well-defined cells. At intermediate temperatures (600 to 900 K), either poorly defined cells or coarse bands of localized slip, reminiscent of the vein structures observed in low-cycle fatigue specimens deformed in the DSA regime, were observed in conventional purity, Si-doped, and in Mo-doped alloys. In contrast, a well-defined cell structure persisted in the low interstitial, high-purity alloy. At elevated temperatures (greater than or equal to 1000 K), more uniformly distributed dislocations and sub-boundaries were observed in all alloys. These observations are consistent with the occurrence of DSA in NiAl single-crystal alloys at intermediate temperatures.

  4. The luminescence characteristics of CsI(Na) crystal under {alpha} and X/{gamma} excitation

    SciTech Connect

    Liu Jinliang; Liu Fang; Ouyang Xiaoping; Liu Bin; Chen Liang; Ruan Jinlu; Zhang Zhongbing; Liu Jun

    2013-01-14

    In this paper, we study the effective decay time characteristic of CsI(Na) crystal under {sup 239}Pu alpha particle and {sup 137}Cs gamma-ray excitation using a single photon counting decay time measurement system. The measurement system employs a silicon optical fiber to couple and transit single photon. The slow decay time component of CsI(Na) crystal is 460-550 ns. We observe a 15 ns fast decay component under alpha particle excitation. In addition, we find that the primary stage of the falling edge in the decay time curve is non-exponential and drops rapidly when CsI(Na) crystal is excited by {sup 239}Pu alpha particles. Since the high density of self-trapped-excitons (STEs) is produced in alpha particle excitation process, we propose that the fast falling edge is corresponding to the quenching process of STEs which transit with non-radiation in the case of high excitation density. To prove this proposal, we excited the CsI(Na) crystal with sub-nanosecond intensive pulsed X-ray radiation. Our X-ray impinging results show that the fast falling edge also exists under low energy (average 100 keV) bremsstrahlung X-ray excitation.

  5. Workplace Learning within Teacher Education: The Role of Job Characteristics and Goal Orientation

    ERIC Educational Resources Information Center

    Kyndt, Eva; Donche, Vincent; Gijbels, David; Van Petegem, Peter

    2014-01-01

    Within teacher education, it is widely recognised that internships play a major role in preparing prospective teachers. The current research examines if the learning activities students' undertake in the workplace can be explained by students' goal orientation and their perceptions of the workplace. In addition, it will be investigated…

  6. Associations of Parental and Peer Characteristics with Adolescents' Social Dominance Orientation

    ERIC Educational Resources Information Center

    Cross, Jennifer Riedl; Fletcher, Kathryn L.

    2011-01-01

    Studies with adults of social dominance orientation (SDO), a preference for inequality among social groups, have found correlations with various prejudices and support for discriminatory practices. This study explores the construct among adolescents at an age when they are beginning to recognize the social groups in their environment, particularly…

  7. Surface-Controlled Orientational Transitions in Elastically Strained Films of Liquid Crystal That Are Triggered by Vapors of Toluene.

    PubMed

    Bedolla Pantoja, Marco A; Abbott, Nicholas L

    2016-05-25

    We report the fabrication of chemically patterned microwells that enable the rapid and facile preparation (by spin coating and patterned dewetting) of thin films of liquid crystals (LCs) that have precise thicknesses (0.7-30 μm), are supported on chemically defined substrates, and have free upper surfaces. We use these microwells to prepare elastically strained nematic LC films supported on silica glass, gold, or polystyrene substrates and thereby characterize the response of the strained LC films to vapors of toluene. We report that low concentrations of toluene vapor (<500 ppm) can partition into the LC to lower the anchoring energy of the LC on these substrates, thus allowing the elastic energy of the strained LC film to drive the LC films through an orientational transition. The central role of the toluene-induced change in surface anchoring energy is supported by additional experiments in which the response of the nematic LC to changes in film thickness and substrate identity are quantified. A simple thermodynamic model captures these trends and yielded estimates of anchoring energies (8-22 μJ/m(2)). Significantly, the orientational transitions observed in these strained LC thin films occur at concentrations of toluene vapor that are almost 1 order of magnitude below those which lead to bulk phase transitions, and they are not triggered by exposure to water vapor. Overall, these results hint at principles for the design of responsive LC-based materials that can be triggered by concentrations of aromatic, volatile organic compounds that are relevant to human health. PMID:27070511

  8. Silver as Seed-Particle Material for GaAs Nanowires—Dictating Crystal Phase and Growth Direction by Substrate Orientation

    PubMed Central

    2016-01-01

    Here we investigate the feasibility of silver as seed-particle material to synthesize GaAs nanowires and show that both crystal phase and growth direction can be controlled by choice of substrate orientation. A (111)B substrate orientation can be used to form vertically aligned wurtzite GaAs nanowires and a (100) substrate orientation to form vertically aligned zinc blende GaAs nanowires. A 45–50% yield of vertical nanowire growth is achieved on the (100) substrate orientation without employing any type of surface modification or nucleation strategy to promote a vertical growth direction. In addition, photoluminescence measurements reveal that the photon emission from the silver seeded wurtzite GaAs nanowires is characterized by a single and narrow emission peak at 1.52 eV. PMID:26998550

  9. Silver as Seed-Particle Material for GaAs Nanowires--Dictating Crystal Phase and Growth Direction by Substrate Orientation.

    PubMed

    Lindberg, Caroline; Whiticar, Alexander; Dick, Kimberly A; Sköld, Niklas; Nygård, Jesper; Bolinsson, Jessica

    2016-04-13

    Here we investigate the feasibility of silver as seed-particle material to synthesize GaAs nanowires and show that both crystal phase and growth direction can be controlled by choice of substrate orientation. A (111)B substrate orientation can be used to form vertically aligned wurtzite GaAs nanowires and a (100) substrate orientation to form vertically aligned zinc blende GaAs nanowires. A 45-50% yield of vertical nanowire growth is achieved on the (100) substrate orientation without employing any type of surface modification or nucleation strategy to promote a vertical growth direction. In addition, photoluminescence measurements reveal that the photon emission from the silver seeded wurtzite GaAs nanowires is characterized by a single and narrow emission peak at 1.52 eV. PMID:26998550

  10. Radially oriented mesoporous TiO2 microspheres with single-crystal-like anatase walls for high-efficiency optoelectronic devices.

    PubMed

    Liu, Yong; Che, Renchao; Chen, Gang; Fan, Jianwei; Sun, Zhenkun; Wu, Zhangxiong; Wang, Minghong; Li, Bin; Wei, Jing; Wei, Yong; Wang, Geng; Guan, Guozhen; Elzatahry, Ahmed A; Bagabas, Abdulaziz A; Al-Enizi, Abdullah M; Deng, Yonghui; Peng, Huisheng; Zhao, Dongyuan

    2015-05-01

    Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m(2)/g), a large pore volume (0.164 cm(3)/g), and highly single-crystal-like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials. PMID:26601185

  11. Morphology and orientation of β-BaB{sub 2}O{sub 4} crystals patterned by laser in the inside of samarium barium borate glass

    SciTech Connect

    Nishii, Akihito; Shinozaki, Kenji; Honma, Tsuyoshi; Komatsu, Takayuki

    2015-01-15

    Nonlinear optical β-BaB{sub 2}O{sub 4} crystal lines (β-BBO) were patterned in the inside of 8Sm{sub 2}O{sub 3}–42BaO–50B{sub 2}O{sub 3} glass by irradiations of continuous-wave Yb:YVO{sub 4} lasers with a wavelength of 1080 nm (power: P=0.8–1.0 W, scanning speed: S=0.2–2.5 μm/s), in which the laser focal position was moved gradually from the surface to the inside. The morphology, size, and orientation of β-BBO crystals were examined from polarization optical microscope and birefringence imaging observations. It was demonstrated that c-axis oriented β-BBO crystals with long lengths (e.g., 20 mm) were patterned in the inside of the glass. The morphology of β-BBO in the cross-section of lines was a rectangular shape with rounded corners, and the volume of β-BBO formed increased with increasing laser power and with decreasing laser scanning speed. The maximum depth in the inside from the surface for β-BBO patterning increased with increasing laser power, e.g., D{sub max}∼100 μm at P=0.8 W, D{sub max}∼170 μm at P=0.9 W, and D{sub max}∼200 μm at P=1 W. The present study proposes that the laser-induced crystallization opens a new door for applied engineering in glassy solids. - Graphical abstract: This figure shows the POM photographs for β-BaB{sub 2}O{sub 4} crystal lines patterned by cw Yb:YVO{sub 4} fiber laser irradiations with a laser power of P=0.8 W and a laser scanning speed S=2 μm/s in the glass. The laser focal point was moved gradually from the surface into the inside. The results shown in Fig. 1 demonstrate that it is possible to pattern highly oriented β-BaB{sub 2}O{sub 4} crystals even in the inside of glasses. - Highlights: • β-BaB{sub 2}O{sub 4} crystal lines were patterned in the inside of a glass by lasers. • Laser focal position was moved gradually from the surface to the inside. • Birefringence imaging was observed. • Morphology, size, and orientation of crystals were clarified. • Crystal lines with long lengths

  12. The Influence of Hydrogen on Shape Memory Effect and Superelasticity in [001]-Oriented FeNiCoAlTi Single Crystals

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Platonova, Yu. N.

    2016-04-01

    Using [001]-oriented single crystals of an iron-based alloy (Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Ti at.%), which were aged at 973 K for 7 h, the influence of hydrogen on the axial-stress temperature response σ0.1(T), the values of shape-memory effect (SME) and superelasticity (SE) is investigated during thermoelastic γ-α'-martensitic transformation (MT) (γ-FCC - face centered lattice, α'-BCT - body centered tetragonal lattice) under tensile conditions. It is found that saturation of [001]-oriented single crystals of the Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Ti alloy with hydrogen within 2 h at T = 300 K and current density j = 50 mA/cm2 results in lower starting temperature, Ms, of a forward MT during cooling and Md temperature, increased strength properties of the high-temperature phase at Md temperature and wider temperature range of SE observation compared to hydrogen-free crystals. It is shown that hydrogen affects but only slightly the SME and SE values, the temperature and stress hysteresis under the above saturation mode. In [001]-oriented crystals aged at 973 K for 7 h, which are saturated with hydrogen and hydrogen-free, the SME and SE values are found to be equal to 7.8-8 and 6.5-6.9%, respectively.

  13. Ferroelectric domain structures in <001>-oriented K{sub 0.15}Na{sub 0.85}NbO{sub 3} lead-free single crystal

    SciTech Connect

    Chen, Yan; Wong, Chi-Man; Yau, Hei-Man; Dai, Jiyan; Deng, Hao; Luo, Haosu; Wang, Danyang; Yan, Zhibo; Chan, Helen L. W.

    2015-03-15

    In this work, ferroelectric domain structures of <001 >-oriented K{sub 0.15}Na{sub 0.85}NbO{sub 3} single crystal are characterized. Transmission electron microscopy (TEM) observation revealed high-density of laminate domain structures in the crystal and the lattices of the neighboring domains are found to be twisted in a small angle. Superlattice diffraction spots of 1/2 (eeo) and 1/2 (ooe) in electron diffraction patterns are observed in the crystal, revealing the a{sup +}a{sup +}c{sup −} tilting of oxygen octahedral in the perovskite structure. The piezoresponse of domains and in-situ poling responses of K{sub 0.15}Na{sub 0.85}NbO{sub 3} crystal are observed by piezoresponse force microscopy (PFM), and the results assure its good ferroelectric properties.

  14. Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal

    NASA Astrophysics Data System (ADS)

    Shan, Pai; Sun, Tongqing; Chen, Hong; Liu, Hongde; Chen, Shaolin; Liu, Xuanwen; Kong, Yongfa; Xu, Jingjun

    2016-04-01

    Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4.

  15. Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal.

    PubMed

    Shan, Pai; Sun, Tongqing; Chen, Hong; Liu, Hongde; Chen, Shaolin; Liu, Xuanwen; Kong, Yongfa; Xu, Jingjun

    2016-01-01

    Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4. PMID:27126353

  16. Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal

    PubMed Central

    Shan, Pai; Sun, Tongqing; Chen, Hong; Liu, Hongde; Chen, Shaolin; Liu, Xuanwen; Kong, Yongfa; Xu, Jingjun

    2016-01-01

    Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4. PMID:27126353

  17. Discovery of room-temperature spin-glass behaviors in two-dimensional oriented attached single crystals

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Chen, Kezheng

    2016-05-01

    In this study, room-temperature spin-glass behaviors were observed in flake-like oriented attached hematite (α-Fe2O3) and iron phosphate hydroxide hydrate (Fe5(PO4)4(OH)3·2H2O) single crystals. Remarkably, their coercivity (HC) values were found to be almost invariable at various given temperatures from 5 to 300 K. The spin topographic map in these flakes was assumed as superparamagnetic (SPM) "islands" isolated by spin glass (SG)-like "bridges". A spin-glass model was then proposed to demonstrate the spin frustration within these "bridges", which were formed by the staggered atomic planes in the uneven surfaces belonging to different attached nanoparticles. Under the spatial limitation and coupling shield of these "bridges", the SPM "islands" were found to be collectively frozen to form a superspin glass (SSG) state below 80 K in weak applied magnetic fields; whereas, when strong magnetic fields were applied, the magnetic coupling of these "islands" would become superferromagnetic (SFM) through tunneling superexchange, so that, these SFM spins could antiferromagnetically couple with the SG-like "bridges" to yield pronounced exchange bias (EB) effect.

  18. Decomposition of a<111> and a<101> dislocations in hard-oriented NiAl single crystals

    SciTech Connect

    Srinivasan, R.; Savage, M.F.; Mills, M.J.; Daw, M.S.; Noebe, R.D.

    1998-08-04

    The B2 intermetallic compound NiAl and its alloys have been subjects of extensive study for potential use as high temperature structural materials, particularly in the aerospace industry. The factors that make them attractive candidates are their low density (5.85 g/cm{sup 3}), excellent oxidation and corrosion resistance and high melting points. But they suffer from lack of ductility at low temperatures and poor strength at higher temperatures. There are still several issues regarding deformation behavior in NiAl and other B2 alloys (e.g., FeAl) that merit further research. Study of the deformation behavior in NiAl should provide further insight into some of the outstanding issues in B2 alloys: chiefly, the nature of slip transition and the effect of various parameters such as temperature, strain rate and stoichiometry on the deformation behavior. The preferred slip system in NiAl involves a <100> slip. But on stressing along the cube axes, also known as the hard orientation, single crystals of NiAl deform at much higher stresses through the motion of a<111> dislocations at lower temperatures. Non-a<111> slip dominates at higher temperatures, with an associated increase in ductility and dramatic decrease in strength. There is also some confusion regarding the mode of deformation beyond the slip transition temperature. The exact process of this slip transition needs to be addressed in its entirety to completely understand the mechanical response of NiAl.

  19. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. II - Low cycle fatigue behavior

    NASA Technical Reports Server (NTRS)

    Gabb, T. P.; Gayda, J.; Miner, R. V.

    1986-01-01

    The low cycle fatigue (LCF) properties of a single-crystal nickel-base superalloy Rene N4, have been examined at 760 and 980 C in air. Specimens having crystallographic orientations near the 001, 011, -111, 023, -236, and -145 lines were tested in fully reversed, total-strain-controlled LCF tests at a frequency of 0.1 Hz. At 760 C, this alloy exhibited orientation dependent tension-compression anisotropies of yielding which continued to failure. Also at 760 C, orientations exhibiting predominately single slip exhibited serrated yielding for many cycles. At 980 C, orientation dependencies of yielding behavior were smaller. In spite of the tension-compression anisotropies, cyclic stress range-strain range behavior was not strongly orientation dependent for either test temperature. Fatigue life on a total strain range basis was highly orientation dependent at 760 and 980 C and was related chiefly to elastic modulus, low modulus orientations having longer lives. Stage I crack growth on 111 planes was dominant at 760 C, while Stage II crack growth occurred at 980 C. Crack initiation generally occurred at near-surface micropores, but occasionally at oxidation spikes in the 980 C tests.

  20. Surface-Induced Orientation Control of CuPc Molecules for the Epitaxial Growth of Highly Ordered Organic Crystals on Graphene

    SciTech Connect

    Xiao, Kai; Deng, Wan; Keum, Jong Kahk; Yoon, Mina; Vlassiouk, Ivan V; Clark, Kendal W; Li, An-Ping; Kravchenko, Ivan I; Gu, Gong; Payzant, E Andrew; Sumpter, Bobby; Smith, Sean C; Browning, Jim; Geohegan, David B

    2013-01-01

    The epitaxial growth and preferred molecular orientation of copper phthalocyanine (CuPc) molecules on graphene has been systematically investigated and compared with growth on Si substrates, demonstrating the role of surface-mediated interactions in determining molecular orientation. X-ray scattering and diffraction, scanning tunneling microscopy, scanning electron microscopy, and first-principles theoretical calculations were used to show that the nucleation, orientation and packing of CuPc molecules on films of graphene are fundamentally different compared to those grown on Si substrates. Interfacial dipole interactions induced by charge transfer between CuPc molecules and graphene are shown to epitaxially align the CuPc mole-cules in a face-on orientation in a series of ordered superstructures. At high temperatures, CuPc molecules lie flat with respect to the graphene substrate to form strip-like CuPc crystals with micron sizes containing monocrystalline grains. Such large epitaxial crystals may potentially enable bulk-like properties to improve the device properties in organic electronics, which charge transport, exciton diffusion and dissociation are currently limited by grain size effects and molecular orientation.

  1. Single crystal growth and enhancing effect of glycine on characteristic properties of bis-thiourea zinc acetate crystal

    NASA Astrophysics Data System (ADS)

    Anis, Mohd; Muley, G. G.

    2016-08-01

    A single crystal of glycine-doped bis-thiourea zinc acetate (G-BTZA) with a dimension of 15 × 6 × 4 mm3 has been grown using the slow solution evaporation technique. The structural parameters of the crystals were determined using the single crystal XRD technique. The increase in optical transparency of the doped BTZA crystal was ascertained in the range of 200 to 900 nm using UV–visible spectral analysis. The improved optical band gap of the G-BTZA crystal is found to be 4.19 eV, and vital optical constants have been calculated using the transmittance data. The influence of glycine on the mechanical parameters of the BTZA crystal has been investigated via microhardness studies. The thermal stability of pure and doped BTZA crystals has been determined by employing the thermogravimetric and differential thermal analysis technique. The improvement in the dielectric properties of the BTZA crystal after the addition of glycine has been evaluated in a temperature range of 30 to 120 °C at a frequency of 100 KHz. The SHG efficiency of the glycine-doped BTZA crystal is found to be much higher than KDP and BTZA crystal material in a Kurtz–Perry powder analysis.

  2. Single crystal growth, structural characteristics and magnetic properties of chromium substituted M-type ferrites

    NASA Astrophysics Data System (ADS)

    Shlyk, L.; Vinnik, D. A.; Zherebtsov, D. A.; Hu, Z.; Kuo, C.-Y.; Chang, C.-F.; Lin, H.-J.; Yang, L.-Y.; Semisalova, A. S.; Perov, N. S.; Langer, T.; Pöttgen, R.; Nemrava, S.; Niewa, R.

    2015-12-01

    Two different types of fluxes, namely sodium based and chloride based fluxes were used to grow Cr substituted barium and strontium hexaferrite ferrite crystals, (Sr,Ba)Fe12 - xCrxO19 at comparatively low temperatures of about 1300 °C. The sodium based flux led to growth of larger crystals up to 5 mm, but with only minor Cr contents x ≤ 0.07. From the chloride based flux the obtained Cr contents are significantly higher with x = 5.7 (Sr) and x = 3.4 (Ba), however, crystals reach only sizes in the sub-mm range. X-ray absorption spectroscopy data support exclusively isovalent substitution of Fe3+ by Cr3+ even for very low Cr contents. 57Fe Mößbauer spectroscopy reveals Cr to preferentially occupy the six-fold by oxygen coordinated site at 12k and, to a lower degree, 2a and 4f2 in space group P63/mmc. All characteristic magnetic properties drop upon Cr substitution, e. g., the Curie temperature from 728 K for pure BaFe12O19 to 465 K for BaFe8.6Cr3.4O19, the saturation magnetization from 71 emu/g to 29.7 emu/g and the coercive field from 363 Oe to 45 Oe.

  3. Surface reformation and electro-optical characteristics of liquid crystal alignment layers using ion beam irradiation

    SciTech Connect

    Oh, Byeong-Yun; Lee, Kang-Min; Kim, Byoung-Yong; Kim, Young-Hwan; Han, Jin-Woo; Han, Jeong-Min; Lee, Sang-Keuk; Seo, Dae-Shik

    2008-09-15

    The surface modification characteristics of liquid crystal (LC) alignment layers irradiated with various argon (Ar) ion beam (IB) energies were investigated as a substitute for rubbing technology. Various pretilt angles were created on the IB-irradiated polyimide (PI) surfaces after IB irradiation, but the Ar ions did not alter the morphology on the PI surface, indicating that the pretilt angle was not due to microgrooves. The chemical bonding states of the IB-irradiated PI surfaces were analyzed in detail by x-ray photoelectron spectroscopy to verify the compositional behavior for the LC alignment. Chemical structure analysis showed that the alignment ability of LCs was due to the preferential reorientation of the carbon network due to the breaking of C=O double bonds in the imide ring parallel to the incident IB direction. The potential of applying nonrubbing technology to display devices was further supported by the superior electro-optical characteristics compared to rubbed PI.

  4. Polarization filter characteristics of photonic crystal fibers with square lattice and selectively filled gold wires.

    PubMed

    Zhang, Wan; Li, Shu-Guang; An, Guo-Wen; Fan, Zhen-Kai; Bao, Ya-Jie

    2014-04-10

    A novel design of Au-filled photonic crystal fiber (PCF) with square lattice has been proposed in this paper. The resonance strength of the surface plasmon mode and the impacts of structural parameters of the PCF on the polarization filter characteristics are studied through the finite element method. Numerical results show that the sizes of Au wires and the symmetry of the air holes near the fiber core have a great effect on the polarization filter characteristics. In the optimization process, it was found that the resonance strengths can reach 279.10 and 399.18  dB/cm at wavelengths of 1.02 μm and 1.55 μm, respectively, which can be applied in many polarization filter devices. PMID:24787416

  5. Electric and magnetic field-assisted orientational transitions in the ensembles of domains in a nematic liquid crystal on the polymer surface.

    PubMed

    Parshin, Alexander M; Gunyakov, Vladimir A; Zyryanov, Victor Y; Shabanov, Vasily F

    2014-01-01

    Using electro- and magneto-optical techniques, we investigated orientational transitions in the ensembles of domains in a nematic liquid crystal on the polycarbonate film surface under the conditions of competing surface forces that favor radial and uniform planar alignment of nematic molecules. Having analyzed field dependences of the intensity of light passed through a sample, we established the threshold character of the orientational effects, plotted the calculated intensity versus magnetic coherence length, and compared the latter with the equilibrium length that characterizes the balance of forces on the polymer surface. PMID:25279586

  6. Electric and Magnetic Field-Assisted Orientational Transitions in the Ensembles of Domains in a Nematic Liquid Crystal on the Polymer Surface

    PubMed Central

    Parshin, Alexander M.; Gunyakov, Vladimir A.; Zyryanov, Victor Y.; Shabanov, Vasily F.

    2014-01-01

    Using electro- and magneto-optical techniques, we investigated orientational transitions in the ensembles of domains in a nematic liquid crystal on the polycarbonate film surface under the conditions of competing surface forces that favor radial and uniform planar alignment of nematic molecules. Having analyzed field dependences of the intensity of light passed through a sample, we established the threshold character of the orientational effects, plotted the calculated intensity versus magnetic coherence length, and compared the latter with the equilibrium length that characterizes the balance of forces on the polymer surface. PMID:25279586

  7. X-ray crystal structure of rac-[Ru(phen)2dppz]2+ with d(ATGCAT)2 shows enantiomer orientations and water ordering.

    PubMed

    Hall, James P; Cook, Daniel; Morte, Sara Ruiz; McIntyre, Patrick; Buchner, Katrin; Beer, Hanna; Cardin, David J; Brazier, John A; Winter, Graeme; Kelly, John M; Cardin, Christine J

    2013-08-28

    We report an atomic resolution X-ray crystal structure containing both enantiomers of rac-[Ru(phen)2dppz](2+) with the d(ATGCAT)2 DNA duplex (phen = phenanthroline; dppz = dipyridophenazine). The first example of any enantiomeric pair crystallized with a DNA duplex shows different orientations of the Λ and Δ binding sites, separated by a clearly defined structured water monolayer. Job plots show that the same species is present in solution. Each enantiomer is bound at a TG/CA step and shows intercalation from the minor groove. One water molecule is directly located on one phenazine N atom in the Δ-enantiomer only. PMID:23875832

  8. Shape-Dependent Oriented Trapping and Scaffolding of Plasmonic Nanoparticles by Topological Defects for Self-Assembly of Colloidal Dimers in Liquid Crystals

    SciTech Connect

    Senyuk, B.; Evans, J. S.; Ackerman, P. J.; Lee, T.; Manna, P.; Vigderman, L.; Zubarey, E. R.; van de Lagemaat, J.; Smalyukh, I. I.

    2012-02-08

    We demonstrate scaffolding of plasmonic nanoparticles by topological defects induced by colloidal microspheres to match their surface boundary conditions with a uniform far-field alignment in a liquid crystal host. Displacing energetically costly liquid crystal regions of reduced order, anisotropic nanoparticles with concave or convex shapes not only stably localize in defects but also self-orient with respect to the microsphere surface. Using laser tweezers, we manipulate the ensuing nanoparticle-microsphere colloidal dimers, probing the strength of elastic binding and demonstrating self-assembly of hierarchical colloidal superstructures such as chains and arrays.

  9. Shape-dependent oriented trapping and scaffolding of plasmonic nanoparticles by topological defects for self-assembly of colloidal dimers in liquid crystals.

    PubMed

    Senyuk, Bohdan; Evans, Julian S; Ackerman, Paul J; Lee, Taewoo; Manna, Pramit; Vigderman, Leonid; Zubarev, Eugene R; van de Lagemaat, Jao; Smalyukh, Ivan I

    2012-02-01

    We demonstrate scaffolding of plasmonic nanoparticles by topological defects induced by colloidal microspheres to match their surface boundary conditions with a uniform far-field alignment in a liquid crystal host. Displacing energetically costly liquid crystal regions of reduced order, anisotropic nanoparticles with concave or convex shapes not only stably localize in defects but also self-orient with respect to the microsphere surface. Using laser tweezers, we manipulate the ensuing nanoparticle-microsphere colloidal dimers, probing the strength of elastic binding and demonstrating self-assembly of hierarchical colloidal superstructures such as chains and arrays. PMID:22233163

  10. The impact of MgO-doped near-stoichiometric lithium niobate crystals on the THz wave output characteristics

    NASA Astrophysics Data System (ADS)

    Xianbin, Zhang; Yunfeng, Li; lijuan, Ma; ke, Yuan; Wei, Shi

    2011-02-01

    The control experimental study on the THz wave parametric oscillator (TPO) output characteristics based on the congruent LiNbO3 crystal (CLN) and stoichiometric MgO-doped lithium niobate (SLN) crystal is performed. As a nonlinear medium in the aspect of the THz wave output experiments show that the congruent LiNbO3 crystal is more stable than the SLN crystal. Compared with the CLN crystal SLN showed significant photorefractive effect which adversely the stability of the THz wave output. Experiments indicated that different molar concentration of MgO doped can significantly change the photorefractive properties of SLN crystal. The results showed that with the increase of MgO doping concentration the photorefractive of SLN gradually become weaker and THz wave output stability has the significantly increase. The output stability of mol 5.0% MgO droped SLN crystal has not significantly different with the CLN. In the contrast experiment of TPO with the 160mm cavity length and 65mm crystal length the pump laser threshold of the 5% mol MgO: SLN crystal decreased by 23% than the CLN crystal while the peak THz energy output increased 28%.

  11. Polymer stabilized vertical alignment liquid crystal display: effect of monomer structures and their stabilizing characteristics

    NASA Astrophysics Data System (ADS)

    Kwon, You Ri; Choi, Young Eun; Wen, Pushen; Lee, Byeong Hoon; Kim, Jong Chan; Lee, Myong-Hoon; Jeong, Kwang-Un; Lee, Seung Hee

    2016-04-01

    A polymer-stabilized vertical alignment (PS-VA) mode using a new type of photoreactive monomer for polymer stabilization of the liquid crystal (LC) director was developed. Conventional reactive mesogens having a higher molecular weight than those of the host LC tend to aggregate and form large-sized polymer grains when exposed to ultraviolet (UV) light, subsequently deteriorating the quality of the dark state. To address these problems, bis(4-hydroxyphenyl) diacrylates were synthesized with four different linking groups as stabilizing monomers (SMs) which have molecular weights similar to that of the host LC. Their stabilizing characteristics with respect to the molecular size and polarity of SMs were evaluated by examining the electro-optic characteristics of LC cells after UV irradiation. The results showed that the SM containing a small linking group in size between biphenyls with high polarity was favored to achieve excellent polymer stabilization. The SM containing an ether linkage showed excellent electro-optic characteristics with no large-sized polymer grains even in the absence of a photo-initiator. Consequently, we anticipate that SMs, polar and smaller in size, can improve the electro-optic characteristics in PS-VA mode.

  12. Influence of sputter rate and crystal orientation on the distribution of carbon in polycrystalline copper surfaces treated by plasma immersion ion implantation

    SciTech Connect

    Flege, S.; Kraft, G.; Bruder, E.; Ensinger, W.; Baba, K.; Hatada, R.

    2009-07-15

    The sputter rate influences the resulting thickness of the carbon containing layer within a surface that was treated by plasma immersion ion implantation. Choosing a polycrystalline substrate with rather large crystals and a material with an inherent high sputter rate, inhomogeneous distributions of carbon over the substrate area due to different thicknesses of the incorporated carbon can be detected. A correlation of three factors namely the carbon x-ray intensity in electron probe microanalysis, the thickness of the carbon layer, and the sputter rate in depth profiling measurements via secondary ion mass spectrometry can be shown. Essential for these factors is the crystal orientation that is visualized by mapping via electron backscatter diffraction. The differences in carbon content due to the orientation are most likely one of the reasons that the adhesion of diamond-like carbon films on copper does not improve with an interlayer of implanted carbon.

  13. Molecular orientation behavior of chiral nematic liquid crystals based on the presence of blue phases using polarized microscopic FT-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsumura, Masanori; Katayama, Norihisa

    2016-07-01

    Study on molecular orientation behavior of highly twisted chiral nematic liquid crystals (N∗LCs) expressing blue phases (BPs) is important for developing new devices. This study examines the change of molecular orientation of N∗LCs due to the presence of BPs. Polarized microscopic FT-IR spectroscopy was used to study the in- and out-of-plane molecular orientations of N∗LCs that undergo a phase transition involving BPs. The band intensity ratio of CN to CH2 stretching modes (CN/CH2) in the IR spectra was used to determine the orientation of N∗LC molecules. The measured spectra indicated that the helical axis of N∗LC molecules was perpendicular to the substrate before heating and inclined on the substrate after cooling the sample which has phase transition from BP I to chiral nematic (N∗). The N∗LC molecule in the cell of rubbed orientation film exhibited the in-plane anisotropy after a heating-cooling ramp only in samples that passed through BP I. These results indicate that the changes of molecular orientation of N∗LC by phase transition are affected by BP I.

  14. Characteristics of covert and overt visual orienting: Evidence from attentional and oculomotor capture

    NASA Technical Reports Server (NTRS)

    Wu, Shu-Chieh; Remington, Roger W.

    2003-01-01

    Five visual search experiments found oculomotor and attentional capture consistent with predictions of contingent orienting, contrary to claims that oculomotor capture is purely stimulus driven. Separate saccade and attend-only conditions contained a color target appearing either singly, with an onset or color distractor, or both. In singleton mode, onsets produced oculomotor and attentional capture. In feature mode, capture was absent or greatly reduced, providing evidence for top-down modulation of both types of capture. Although attentional capture by color abstractors was present throughout, oculomotor capture by color occurred only when accompanied by transient change, providing evidence for a dissociation between oculomotor and attentional capture. Oculomotor and attentional capture appear to be mediated by top-down attentional control settings, but transient change may be necessary for oculomotor capture. ((c) 2003 APA, all rights reserved).

  15. Effect of pre-deposition RF plasma etching on wafer surface morphology and crystal orientation of piezoelectric AlN thin films.

    PubMed

    Felmetsger, V; Mikhov, M; Laptev, P

    2015-02-01

    In this work, we describe the design and operation of a planarized capacitively coupled RF plasma module and investigate the effects of non-reactive RF plasma etching on Si (100) wafer surface morphology and crystal orientation of Al bottom electrodes and subsequently deposited AlN films. To ensure formation of highly (111) textured Al electrode, a thin 25-nm AlN seed layer was grown before the Al deposition. The seed layer's orientation efficiency improved with increasing the RF power from 70 to 300 W and resulted in narrowing the Al (111) rocking curves. AFM and XRD data have shown that crystal orientations of both the electrode and reactively sputtered AlN film are considerably improved when the substrate micro roughness is reduced from an ordinary level of a few nanometers to atomic level corresponding to root mean square roughness as low as about 0.2 to 0.3 nm. The most perfectly crystallized film stacks of 100-nm Al and 500-nm AlN were obtained in this work using etching in Ar plasma optimized to create an atomically smooth, epi-ready Si surface morphology that enables superior AlN seed layer nucleation conditions. X-ray rocking curves around the Al (111) and AlN (0002) diffraction peaks exhibited extremely low FWHM values of 0.68° and 1.05°, respectively. PMID:25643087

  16. Israeli Teachers' Perceptions of Gifted Teachers' Desired Characteristics: A Case of Cultural Orientation

    ERIC Educational Resources Information Center

    Vidergor, Hava E.; Eilam, Billie

    2012-01-01

    The aim of this study was to assess Israeli Jewish and Arab teachers' perceptions of the desired characteristics of teachers of the gifted. The research sample comprised 217 teachers (134 Jews and 83 Arabs) representing three groups: (a) teachers entering a professional development program for teachers of gifted students; (b) teachers of gifted…

  17. Polar-axis-oriented crystal growth of tetragonal PZT films on stainless steel substrate using pseudo-perovskite nanosheet buffer layer

    NASA Astrophysics Data System (ADS)

    Minemura, Yoshiki; Ichinose, Daichi; Nagasaka, Kohei; Kim, Jin Woon; Shima, Hiromi; Nishida, Ken; Kiguchi, Takanori; Konno, Toyohiko J.; Oshima, Naoya; Funakubo, Hiroshi; Uchida, Hiroshi

    2015-07-01

    Lead zirconate titanate (PZT) film with polar axis orientation was grown on a SUS 316L stainless steel substrate with the help of a Ca2Nb3O10 nanosheet (ns-CN) layer that had a pseudo-perovskite-type crystal structure. The ns-CN buffer layer was supported on a platinized SUS 316L (Pt/SUS) substrate, followed by chemical solution deposition (CSD) of the PZT films with tetragonal symmetry (Zr/Ti =40/60). The PZT films consisting of c-domain, with [001]-axis orientation of the perovskite unit cell, were deposited on the ns-CN/Pt/SUS substrate owing to (i) epitaxial lattice matching between the unit cell of PZT and substrate surface and (ii) in-plane thermal stress applied to the PZT film during cooling-down step of CSD procedure. The c-domain-oriented PZT film on ns-CN/Pt/SUS substrate exhibited enhanced remanent polarization of approximately 52 μC/cm2 and lowered dielectric permittivity of approximately 230, which are superior to those of conventional PZT films with random crystal orientation and comparable to those of epitaxial PZT films grown on (100)SrRuO3//(100)SrTiO3 substrates.

  18. Influence of the spin-orientation of free and unpaired protons of ortho-water on the crystallization of the (0 0 1) face of TGS crystal: “in situ” investigation

    NASA Astrophysics Data System (ADS)

    Bikov, A. Z.; Genova, R. V.; Vassilev, N. G.

    2014-06-01

    The influence of the spin orientation of free and unpaired protons of ortho-water in a growth solution on the morphological and kinetic parameters of the dislocation centers of growth of the (0 0 1) face of a TGS (triglycine sulfate) crystal was studied by precision methods. It was shown that the protons' spin orientation towards the crystal surface has no noticeable effect on the hills' shape and causes a decrease of about 11% of the normal growth rate. The spin-lattice relaxation time (T1) of the growth solution has been experimentally determined for the first time. The experimental result of 2.1±0.1 s and that calculated based on literature data are in good agreement.

  19. Morphology and orientation of β-BaB2O4 crystals patterned by laser in the inside of samarium barium borate glass

    NASA Astrophysics Data System (ADS)

    Nishii, Akihito; Shinozaki, Kenji; Honma, Tsuyoshi; Komatsu, Takayuki

    2015-01-01

    Nonlinear optical β-BaB2O4 crystal lines (β-BBO) were patterned in the inside of 8Sm2O3-42BaO-50B2O3 glass by irradiations of continuous-wave Yb:YVO4 lasers with a wavelength of 1080 nm (power: P=0.8-1.0 W, scanning speed: S=0.2-2.5 μm/s), in which the laser focal position was moved gradually from the surface to the inside. The morphology, size, and orientation of β-BBO crystals were examined from polarization optical microscope and birefringence imaging observations. It was demonstrated that c-axis oriented β-BBO crystals with long lengths (e.g., 20 mm) were patterned in the inside of the glass. The morphology of β-BBO in the cross-section of lines was a rectangular shape with rounded corners, and the volume of β-BBO formed increased with increasing laser power and with decreasing laser scanning speed. The maximum depth in the inside from the surface for β-BBO patterning increased with increasing laser power, e.g., Dmax~100 μm at P=0.8 W, Dmax~170 μm at P=0.9 W, and Dmax~200 μm at P=1 W. The present study proposes that the laser-induced crystallization opens a new door for applied engineering in glassy solids.

  20. Cyclic stability of superelasticity in the aged [ {bar{1}}23 ]-oriented Ni49Fe18Ga27Co6 single crystals

    NASA Astrophysics Data System (ADS)

    Panchenko, E. Yu.; Chumlyakov, Yu. I.; Timofeeva, E. E.; Vetoshkina, N. G.; Maier, H.

    2013-02-01

    The results of investigation of the effect of precipitates of different sizes, from 5 to 300 nm, on the character of stress-induced martensitic transformations, the value of stress hysteresis and cyclic stability of superelasticity in Ni49Fe18Ga27Со6 (at.%) ferromagnetic single crystals oriented along the [ {bar{1}}23 ] axis are presented. It is shown that a martensitic transformation in single crystals of Ni49Fe18Ga27Со6 containing dispersed particles of the γ- and γ'-phases measuring up to 30 nm (ageing at 673 K for 1 and 4 hours) is characterized by storing considerable elastic energy. It is revealed that these single crystals exhibit higher cyclic stability of superelasticity and a narrower stress hysteresis compared to those in the initial state and aged at 823 K for 0.5 hour, the latter containing much larger (150-300 nm) particles.

  1. Linear-dichroic infrared spectroscopy—Validation and experimental design of the new orientation technique of solid samples as suspension in nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Ivanova, B. B.; Simeonov, V. D.; Arnaudov, M. G.; Tsalev, D. L.

    2007-05-01

    A validation of the developed new orientation method of solid samples as suspension in nematic liquid crystal (NLC), applied in linear-dichroic infrared (IR-LD) spectroscopy has been carried out using a model system DL-isoleucine ( DL-isoleu). Accuracy, precision and the influence of the liquid crystal medium on peak positions and integral absorbances of guest molecules have been presented. Optimization of experimental conditions has been performed as well. An experimental design for quantitative evaluation of the impact of four input factors: the number of scans, the rubbing-out of KBr-pellets, the amount of studied compounds included in the liquid crystal medium and the ratios of Lorentzian to Gaussian peak functions in the curve fitting procedure on the spectroscopic signal at five different frequencies, indicating important specifities of the system has been studied.

  2. Influence of samarium impurity on spectral characteristics of calcium iodide crystals

    NASA Astrophysics Data System (ADS)

    Novosad, S. S.; Novosad, I. S.

    2013-03-01

    The influence of a SmBr3 impurity on optical absorption spectra and x-ray-, photo-, and thermally stimulated luminescence of CaI2 scintillator was studied in the temperature range 90-295 K. Activation of CaI2 from the melt by SmBr3 caused absorption bands related to 4 f 6 → 4 f 55 d electronic transitions in Sm2+ to appear in the spectra. Excitation and emission spectra of CaI2:SmBr3 (0.01 mol%) were represented mainly by bands characteristic of the matrix. The photoluminescence spectrum at 90 K upon optical excitation of the crystal in the impurity absorption region (λex = 280 nm) was approximated by individual Gaussian bands with maxima near 345, 395, 430, 470, 500, and 520 nm. The photoluminescence spectrum of CaI2:SmBr3 (0.5 mol%) at 295 K with excitation by radiation from an LGI-21 nitrogen laser (λex = 337.1 nm) was represented mainly by a band at 465 nm. The intensity of this band weakened, its maximum shifted to 470 nm, luminescence in the 520 nm region increased, and weak emission with a maximum near 585 nm was also observed upon lowering the crystal temperature to 90 K. Doping CaI2 with the Sm impurity decreased the yield and changed the spectral composition of its x-ray-luminescence. CaI2:SmBr3 stored a small light sum in shallow trapping levels upon x-ray excitation at 90 K. The nature of the emission and trapping centers in the investigated crystals was discussed.

  3. Surface and subsurface cracks characteristics of single crystal SiC wafer in surface machining

    SciTech Connect

    Qiusheng, Y. Senkai, C. Jisheng, P.

    2015-03-30

    Different machining processes were used in the single crystal SiC wafer machining. SEM was used to observe the surface morphology and a cross-sectional cleavages microscopy method was used for subsurface cracks detection. Surface and subsurface cracks characteristics of single crystal SiC wafer in abrasive machining were analysed. The results show that the surface and subsurface cracks system of single crystal SiC wafer in abrasive machining including radial crack, lateral crack and the median crack. In lapping process, material removal is dominated by brittle removal. Lots of chipping pits were found on the lapping surface. With the particle size becomes smaller, the surface roughness and subsurface crack depth decreases. When the particle size was changed to 1.5µm, the surface roughness Ra was reduced to 24.0nm and the maximum subsurface crack was 1.2µm. The efficiency of grinding is higher than lapping. Plastic removal can be achieved by changing the process parameters. Material removal was mostly in brittle fracture when grinding with 325# diamond wheel. Plow scratches and chipping pits were found on the ground surface. The surface roughness Ra was 17.7nm and maximum subsurface crack depth was 5.8 µm. When grinding with 8000# diamond wheel, the material removal was in plastic flow. Plastic scratches were found on the surface. A smooth surface of roughness Ra 2.5nm without any subsurface cracks was obtained. Atomic scale removal was possible in cluster magnetorheological finishing with diamond abrasive size of 0.5 µm. A super smooth surface eventually obtained with a roughness of Ra 0.4nm without any subsurface crack.

  4. Vertically self-ordered orientation of nanocrystalline hexagonal boron nitride thin films for enhanced thermal characteristics

    NASA Astrophysics Data System (ADS)

    Cometto, Olivier; Sun, Bo; Tsang, Siu Hon; Huang, Xi; Koh, Yee Kan; Teo, Edwin Hang Tong

    2015-11-01

    Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm-2. Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m-1 K-1. The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature growth could outperform SiO2 in high power density electronic applications.Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm-2. Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m-1 K-1. The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature

  5. Spectral and Lensing Characteristics of Gel-Derived Strontium Tartrate Single Crystals Using Dual-Beam Thermal Lens Technique.

    PubMed

    Rejeena, I; Thomas, V; Mathew, S; Lillibai, B; Nampoori, V P N; Radhakrishnan, P

    2016-09-01

    The Dual Beam mode-matched thermal lens spectrometry is a sensible technique for direct measurements of the thermal properties of tartrate crystalline materials. Here we report the measurement of thermal diffusivity of Strontium Tartrate single crystals incorporated with Rhodamine 6G using the thermal lens experiment. The respective crystals were prepared by solution-gel method at room temperature. The absorption characteristics of three different Strontium Tartrate crystals viz. pure, electric field applied and magnetic field applied were also carried out. PMID:27465706

  6. Pyrolysis characteristics and pyrolysis products separation for recycling organic materials from waste liquid crystal display panels.

    PubMed

    Wang, Ruixue; Xu, Zhenming

    2016-01-25

    Waste liquid crystal display (LCD) panels mainly contain inorganic materials (glass substrate with indium-tin oxide film), and organic materials (polarizing film and liquid crystal). The organic materials should be removed beforehand since the organic matters would hinder the indium recycling process. In the present study, pyrolysis process is used to remove the organic materials and recycle acetic as well as and triphenyl phosphate (TPP) from waste LCD panels in an environmental friendly way. Several highlights of this study are summarized as follows: (i) Pyrolysis characteristics and pyrolysis kinetics analysis are conducted which is significant to get a better understanding of the pyrolysis process. (ii) Optimum design is developed by applying Box-Behnken Design (BBD) under response surface methodology (RSM) for engineering application which is significant to guide the further industrial recycling process. The oil yield could reach 70.53 wt% and the residue rate could reach 14.05 wt% when the pyrolysis temperature is 570 °C, nitrogen flow rate is 6 L min(-1) and the particle size is 0.5 mm. (iii) Furthermore, acetic acid and TPP are recycled, and then separated by rotary evaporation, which could reduce the consumption of fossil energy for producing acetic acid, and be reused in electronics manufacturing industry. PMID:26444486

  7. Evaluation of curving characteristics of flexible liquid crystal displays fabricated using polycarbonate substrates

    NASA Astrophysics Data System (ADS)

    Sato, Akihito; Ishinabe, Takahiro; Fujikake, Hideo

    2016-01-01

    The improvement of the contrast ratio of flexible liquid crystal displays (LCDs) fabricated using plastic substrates in a curved state is an important problem to achieve high-quality flexible LCDs. In this study, we evaluated the distributions of in-plane phase retardation and slow axis direction of polycarbonate substrates and the effects of curvature on the electro-optical properties of flexible LCDs. As a result, we clarified that the polycarbonate substrates have high uniformity in the in-plane phase retardation and slow axis direction, and that the change in the phase retardation of the polycarbonate substrate caused by the curvature deformation has a small effect on the electro-optical characteristics of flexible LCDs. We successfully achieved a high contrast ratio of 1042:1 by fabricating the device using polycarbonate substrates. This result indicates that it is possible to realize high-quality images in flexible LCDs fabricated using polycarbonate substrates even in the curved state.

  8. Associations of parental and peer characteristics with adolescents' social dominance orientation.

    PubMed

    Cross, Jennifer Riedl; Fletcher, Kathryn L

    2011-06-01

    Studies with adults of social dominance orientation (SDO), a preference for inequality among social groups, have found correlations with various prejudices and support for discriminatory practices. This study explores the construct among adolescents at an age when they are beginning to recognize the social groups in their environment, particularly adolescent crowds. The relationship of SDO and perceptions of parents' responsiveness and demandingness were also investigated. Subjects were in grades 9-12 (N = 516, 53% female, 96% White). Mother's and father's responsiveness significantly predicted adolescent's SDO scores, with greater perceived responsiveness associated with lower SDO. To analyze the multiple crowd memberships of the 76% belonging to more than one crowd, two-step cluster analysis was used to identify patterns, resulting in 8 clusters of distinct, heterogeneous composition. SDO differed significantly among males in different clusters, but not females. The importance of membership was positively associated with SDO among high-status crowds and negatively associated with SDO among the academic and normal crowds. The findings have implications for prejudices that may be developing in adolescence and indicate a need for further research into the social context of SDO and its development. PMID:20820895

  9. Vertically self-ordered orientation of nanocrystalline hexagonal boron nitride thin films for enhanced thermal characteristics.

    PubMed

    Cometto, Olivier; Sun, Bo; Tsang, Siu Hon; Huang, Xi; Koh, Yee Kan; Teo, Edwin Hang Tong

    2015-12-01

    Vertically self-ordered hexagonal boron nitride (ordered h-BN) is a highly ordered turbostratic BN (t-BN) material similar to hexagonal BN, with its planar structure perpendicularly oriented to the substrate. The ordered h-BN thin films were grown using a High Power Impulse Magnetron Sputtering (HiPIMS) system with a lanthanum hexaboride (LaB6) target reactively sputtered in nitrogen gas. The best vertical alignment was obtained at room temperature, with a grounded bias and a HiPIMS peak power density of 60 W cm(-2). Even though the film contains up to 7.5 at% lanthanum, it retains its highly insulative properties and it was observed that an increase in compressive stress is correlated to an increase in film ordering quality. Importantly, the thermal conductivity of vertically ordered h-BN is considerably high at 5.1 W m(-1) K(-1). The favourable thermal conductivity coupled with the dielectric properties of this novel material and the low temperature growth could outperform SiO2 in high power density electronic applications. PMID:26510890

  10. Determination of the Origin of Crystal Orientation for Nanocrystalline Bismuth Telluride-Based Thin Films Prepared by Use of the Flash Evaporation Method

    NASA Astrophysics Data System (ADS)

    Takashiri, M.; Tanaka, S.; Miyazaki, K.

    2014-06-01

    We have investigated the origin of crystal orientation for nanocrystalline bismuth telluride-based thin films. Thin films of p-type bismuth telluride antimony (Bi-Te-Sb) and n-type bismuth telluride selenide (Bi-Te-Se) were fabricated by a flash evaporation method, with exactly the same deposition conditions except for the elemental composition of the starting powders. For p-type Bi-Te-Sb thin films the main x-ray diffraction (XRD) peaks were from the c-axis (Σ{00l}/Σ{ hkl} = 0.88) whereas n-type Bi-Te-Se thin films were randomly oriented (Σ{00l}/Σ{ hkl} = 0.40). Crystal orientation, crystallinity, and crystallite size were improved for both types of thin film by sintering. For p-type Bi-Te-Sb thin films, especially, high-quality structures were obtained compared with those of n-type Bi-Te-Se thin films. We also estimated the thermoelectric properties of the as-grown and sintered thin films. The power factor was enhanced by sintering; maximum values were 34.9 μW/cm K2 for p-type Bi-Te-Sb thin films at a sintering temperature of 300°C and 23.9 μW/cm K2 for n-type Bi-Te-Se thin films at a sintering temperature of 350°C. The exact mechanisms of film growth are not yet clear but we deduce the crystal orientation originates from the size of nano-clusters generated on the tungsten boat during flash evaporation.

  11. Effects of substrate annealing and post-crystallization thermal treatments on the functional properties of preferentially oriented (Pb,Ca)TiO3 thin films

    NASA Astrophysics Data System (ADS)

    Poyato, R.; Calzada, M. L.; Pardo, L.

    2003-04-01

    <111> and <001>,<100> preferentially oriented calcium-modified lead titanate thin films have been studied. Effects of the substrate annealing and post-crystallization thermal treatment of the films on the texture and ferro-, piezo-, and pyroelectric properties have been analyzed and discussed. The annealing of the substrate has effect on the texture of <001>,<100>-oriented films and, as a consequence, produces an increase in the net polarization in the perpendicular direction to the plane of the film and in the pyroelectric coefficient. The annealing of the substrate does not affect the texture of <111>-oriented films, but the electrical properties at the electrode-substrate interface and, as a consequence, gives place to high internal electric fields leading to the highest spontaneous piezo- (5 pm V-1) and pyroelectric coefficients (25.0×10-9 C cm-2 K-1). The asymmetry that characterizes the functional properties of <111>-oriented films under poling with negative or positive polarity is also consequence of such a high internal field. This is accompanied with a remarkable field stability of the piezoelectric d33 coefficient when poling in the sense of the spontaneous polarization (d33˜45 pm V-1 under ±200 kV cm-1). The application of post-crystallization thermal treatment results in an enhancement of the ferroelectric and pyroelectric properties in all the films, by liberation of domains that were clamped by charged defects. Both the substrate and post-crystallization film annealing treatments lead to reach the highest values of remanent polarization (43 μC cm-2), pyroelectric coefficient (42.0×10-9 C cm-2 K-1), and figure of merit [13.3×10-6 (N m-2)-1/2] reported to date for sol-gel PTC films.

  12. Comparative study of electrical characteristics in (1 0 0) and (1 1 0) surface-oriented nMOSFETs with direct contact La-silicate/Si interface structure

    NASA Astrophysics Data System (ADS)

    Kawanago, T.; Kakushima, K.; Ahmet, P.; Kataoka, Y.; Nishiyama, A.; Sugii, N.; Tsutsui, K.; Natori, K.; Hattori, T.; Iwai, H.

    2013-06-01

    This study reports on the electrical characteristics of (1 1 0)-oriented nMOSFETs with a direct contact La-silicate/Si interface structure and the detailed comparison with (1 0 0)-oriented nMOSFETs. Precise control of oxygen partial pressure can provide the scaled EOT down to 0.73 nm on (1 1 0) orientation in common with (1 0 0) orientation. No frequency dispersion in Cgc-V characteristic for (1 1 0)-oriented nMOSFETs is successfully demonstrated at scaled EOT region, while higher amount of available bonds on (1 1 0) surface results in a larger interface state density, leading to the degradation of sub-threshold slope. High breakdown voltages of 2.85 V and 2.9 V for (1 0 0)- and (1 1 0)-oriented nMOSFETs are considered to be due to superior interfacial property. The electron mobility on (1 1 0) orientation is lower than that on (1 0 0) orientation because of the smaller energy split between fourfold valleys and twofold valleys as well as the larger density of states for lower-energy valleys in the (1 1 0) surface. Moreover, electron mobility is reduced with decreasing EOT in both (1 0 0)- and (1 1 0)-oriented nMOSFETs. It is found that threshold voltage instability by positive bias stress is mainly responsible for bulk trapping of electron even with a larger interface state density in (1 1 0) orientation and influence of surface orientation on threshold voltage instability is negligibly small.

  13. Orientational order parameters of a de Vries-type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction.

    PubMed

    Sanchez-Castillo, A; Osipov, M A; Jagiella, S; Nguyen, Z H; Kašpar, M; Hamplovă, V; Maclennan, J; Giesselmann, F

    2012-06-01

    The orientational order parameters (P{2}) and (P{4}) of the ferroelectric, de Vries-type liquid crystal 9HL have been determined in the SmA and SmC phases by means of polarized Raman spectroscopy, and in the SmA phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a "sugar loaf" orientational distribution in the SmA phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries-type behavior is considered. PMID:23005110

  14. Comprehensive study of Al-induced layer-exchange growth for orientation-controlled Si crystals on SiO{sub 2} substrates

    SciTech Connect

    Kurosawa, Masashi; Sadoh, Taizoh; Miyao, Masanobu

    2014-11-07

    Orientation-controlled crystalline Si films on insulating substrates are strongly required to achieve high-performance thin-film devices for next-generation electronics. We have comprehensively investigated the layer-exchange kinetics of Al-induced crystallization (AIC) in stacked structures, i.e., amorphous-Si/Al-oxide/Al/SiO{sub 2}-substrates, as a function of the air-exposure time of Al surfaces (t{sub air}: 0–24 h) to form Al-oxide interface-layers, the thickness of Al and Si layers (d{sub Al,} d{sub Si}: 50–200 nm), the annealing temperature (450–500 °C), and the annealing time (0–50 h). It has been clarified that longer t{sub air} (>60 min) and/or thinner d{sub Al} and d{sub Si} (<50 nm) lead to the (111) oriented growth; in contrast, shorter t{sub air} (<60 min) and/or thicker d{sub Al} and d{sub Si} (>100 nm) lead to the (100) oriented growth. No correlation between the annealing temperature and the crystal orientation is observed. Detailed analysis reveals that the layer-exchange kinetics are dominated by “supply-limited” processing, i.e., diffusion of Si atoms into Al layers through Al-oxide layer. Based on the growth rate dependent Si concentration profiles in Al layers, and the free-energy of Si at Al-oxide/Al or Al/SiO{sub 2} interfaces, a comprehensive model for layer-exchange growth is proposed. This well explains the experimental results of not only Si-AIC but also another material system such as gold-induced crystallization of Ge. In this way, a growth technique achieving the orientation-controlled Si crystals on insulating substrates is established from both technological and scientific points of view.

  15. Effects of 3 dimensional crystal geometry and orientation on 1D and 2D time-scale determinations of magmatic processes using olivine and orthopyroxene

    NASA Astrophysics Data System (ADS)

    Shea, Thomas; Krimer, Daniel; Costa, Fidel; Hammer, Julia

    2014-05-01

    One of the achievements in recent years in volcanology is the determination of time-scales of magmatic processes via diffusion in minerals and its addition to the petrologists' and volcanologists' toolbox. The method typically requires one-dimensional modeling of randomly cut crystals from two-dimensional thin sections. Here we address the question whether using 1D (traverse) or 2D (surface) datasets exploited from randomly cut 3D crystals introduces a bias or dispersion in the time-scales estimated, and how this error can be improved or eliminated. Computational simulations were performed using a concentration-dependent, finite-difference solution to the diffusion equation in 3D. The starting numerical models involved simple geometries (spheres, parallelepipeds), Mg/Fe zoning patterns (either normal or reverse), and isotropic diffusion coefficients. Subsequent models progressively incorporated more complexity, 3D olivines possessing representative polyhedral morphologies, diffusion anisotropy along the different crystallographic axes, and more intricate core-rim zoning patterns. Sections and profiles used to compare 1, 2 and 3D diffusion models were selected to be (1) parallel to the crystal axes, (2) randomly oriented but passing through the olivine center, or (3) randomly oriented and sectioned. Results show that time-scales estimated on randomly cut traverses (1D) or surfaces (2D) can be widely distributed around the actual durations of 3D diffusion (~0.2 to 10 times the true diffusion time). The magnitude over- or underestimations of duration are a complex combination of the geometry of the crystal, the zoning pattern, the orientation of the cuts with respect to the crystallographic axes, and the degree of diffusion anisotropy. Errors on estimated time-scales retrieved from such models may thus be significant. Drastic reductions in the uncertainty of calculated diffusion times can be obtained by following some simple guidelines during the course of data

  16. Growth and Faraday rotation characteristics of TbVO4 crystals

    NASA Astrophysics Data System (ADS)

    Guo, Feiyun; Chen, Xin; Gong, Zhongliang; Chen, Xiang; Zhao, Bin; Chen, Jianzhong

    2015-09-01

    TbVO4 (TV) single crystals with dimensions of 18 × 18 × 16 mm3 were grown by Czochralski method under different atmosphere. XPS studies revealed the presence of V4+ and Tb4+ in TV crystal grown at 99.9% N2 atmosphere, which caused a wide absorption peak centered at 950 nm in the transmission spectrum. TV crystal grown at 80% N2 + 20% CO2 mixed atmosphere has high transmittance at 600-1500 nm waveband. Faraday rotation spectra of TV crystal were measured. TV crystal has a larger Faraday rotation than terbium gallium garnet (TGG) crystal at 500-1500 nm waveband.

  17. Performance characteristics of thermal neutron detectors based on Li6Y(BO3)3:Ce single crystals

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Tyagi, M.; Singh, S. G.; Tiwari, B.; Desai, D. G.; Sen, S.; Desai, S. S.; Ghodke, S. S.; Gadkari, S. C.

    2015-12-01

    Crack-free single crystals of Ce doped Li6Y(BO3)3 (LYBO:Ce) have been grown using the Czochralski technique. Grown crystals were characterized for their optical and scintillation characteristics to explore their potential as neutron detectors. Scintillator detectors based on LYBO:Ce crystal were used successfully to record the pulse height spectra from various neutron sources in the flux range from 10 n/cm2/s to 107 n/cm2/s. The detection efficiency for thermal neutrons was found to be over 80% for a 2 mm thick LYBO:Ce crystal. The scintillation decay times measured for neutron and gamma radiations were about 27 ns and 49 ns, respectively.

  18. Effect of magnetic properties of non-oriented electrical steel on torque characteristics of interior-permanent-magnet synchronous motor

    NASA Astrophysics Data System (ADS)

    Fujimura, Hiroshi; Nitomi, Hirokatsu; Yashiki, Hiroyoshi

    The torque characteristics of interior-permanent-magnet synchronous motor (IPMSM), in which core materials were our conventional non-oriented electrical steel 35SX250 and our developed steels 35SXH, 27SXH with high permeability, were measured by a pulse wave modulation (PWM) inverter control. The torque characteristics of the motor with developed steels were superior to that of conventional steel. The advantage of developed steels was remarkable in the high-toque region. Experimental torque separation using current phase control showed that reluctance torque was strongly affected by the magnetic properties of core materials. And we did magnetic field analysis of the motors by finite element method (FEM). The flux density in the teeth of the stator core was higher in the high permeability steels than that in the conventional steel under the same current condition. The developed steels are expected to be suited to the stator material of IPMSM used as drive motors for electric vehicles and compressor motors for air conditioner.

  19. Effect of water absorption of dielectric underlayers on crystal orientation in Al-Si-Cu/Ti/TiN/Ti metallization

    NASA Astrophysics Data System (ADS)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Hosokawa, Hideki; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1997-05-01

    The influence of the exposure of underlying dielectric (phophosilicate glass and borophosphosilicate glass) films to a humid air ambient on crystallographic orientations in Al-Si-Cu/Ti/TiN/Ti layered structures has been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered structures was found to improve drastically with increasing boron content and exposure time of the dielectric films. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and the average grain size increases as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. The mechanism of the improved Ti(002) orientation was investigated. It was confirmed that the improved orientation is closely related with the surface concentration of the absorbed water in the dielectric films. Further, it was demonstrated that interconnects fabricated from the improved layered structure have excellent electromigration performance.

  20. Crystallographic Texture and Orientation Variants in Al2O3-Y3Al5O12 Directionally Solidified Eutectic Crystals

    NASA Technical Reports Server (NTRS)

    Frazer, Colleen S.; Dickey, Elizabeth C.; Sayir, Ali; Farmer, Serene (Technical Monitor)

    2001-01-01

    Eutectic rods of Al2O3 and Y3Al5O12 were grown by a laser-heated float zone method, and their microstructure and crystallographic texture were studied by scanning electron microscopy, electron backscattered diffraction and x-ray diffraction. The composites were found to be highly textured with two twin-related crystallographic orientation relationships between the phases. Electron backscattered diffraction was employed to determine the spatial distribution of the orientational variants within the samples and to define the crystallographic orientation of various microstructural features.

  1. Highly effective strain-induced band-engineering of (111) oriented, direct-gap GeSn crystallized on amorphous SiO2 layers

    NASA Astrophysics Data System (ADS)

    Li, Haofeng; Wang, Xiaoxin; Liu, Jifeng

    2016-03-01

    We demonstrate highly effective strain-induced band-engineering of (111) oriented direct-gap Ge1-xSnx thin films (0.074 < x < 0.085) crystallized on amorphous SiO2 towards 3D photonic integration. Due to a much smaller Poisson's ratio for (111) vs. (100) orientation, 0.44% thermally induced biaxial tensile strain reduces the direct-gap by 0.125 eV towards enhanced direct-gap semiconductor properties, twice as effective as the tensile strain in Ge(100) films. Correspondingly, the optical response is extended to λ = 2.8 μm. A dilatational deformation potential of a = -12.8 ± 0.8 eV is derived. These GeSn films also demonstrate high thermal stability, offering both excellent direct-gap optoelectronic properties and fabrication/operation robustness for integrated photonics.

  2. Disordering of the vortex lattice through successive destruction of positional and orientational order in a weakly pinned Co0.0075NbSe2 single crystal

    PubMed Central

    Chandra Ganguli, Somesh; Singh, Harkirat; Saraswat, Garima; Ganguly, Rini; Bagwe, Vivas; Shirage, Parasharam; Thamizhavel, Arumugam; Raychaudhuri, Pratap

    2015-01-01

    The vortex lattice in a Type II superconductor provides a versatile model system to investigate the order-disorder transition in a periodic medium in the presence of random pinning. Here, using scanning tunnelling spectroscopy in a weakly pinned Co0.0075NbSe2 single crystal, we show that the vortex lattice in a 3-dimensional superconductor disorders through successive destruction of positional and orientational order, as the magnetic field is increased across the peak effect. At the onset of the peak effect, the equilibrium quasi-long range ordered state transforms into an orientational glass through the proliferation of dislocations. At a higher field, the dislocations dissociate into isolated disclination giving rise to an amorphous vortex glass. We also show the existence of a variety of additional non-equilibrium metastable states, which can be accessed through different thermomagnetic cycling. PMID:26039699

  3. High-performance poly-Si thin film transistors with highly biaxially oriented poly-Si thin films using double line beam continuous-wave laser lateral crystallization

    NASA Astrophysics Data System (ADS)

    Yamano, Masayuki; Kuroki, Shin-Ichiro; Sato, Tadashi; Kotani, Koji

    2014-01-01

    Highly biaxially oriented poly-Si thin films were formed by double-line beam continuous-wave laser lateral crystallization (DLB-CLC). The crystallinities of the DLB-CLC poly-Si thin films were (110), (111), and (211) for the laser scan, transverse, and surface directions, respectively, and an energetically stable Σ3 grain boundary was observed to be dominant. All silicon grains were elongated in the laser scan direction and one-dimensionally very large silicon grains with lengths of more than 100 µm were fabricated. Using these biaxially oriented polycrystalline silicon (poly-Si) films, low-temperature poly-Si TFTs (LTPS-TFTs) were fabricated at low temperatures (≦550 °C) by a metal gate self-aligned process. As a result, a TFT with a high electron field effect mobility of μFE = 450 cm2 V-1 s-1 in a linear region was realized.

  4. Molecular orientation and the infrared dichroism of a chiral smectic liquid crystal in a homogeneously aligned cell at different temperature and bias fields.

    PubMed

    Sigarev, A A; Vij, J K; Lewis, R A; Hird, M; Goodby, J W

    2003-09-01

    The molecular orientation and the dichroic behavior of the vibrational bands of a homogeneously aligned helical cell containing chiral smectic liquid crystal (R)-(-)-1-methylheptyl 4-(4(')-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate are studied at various temperatures as a function of the bias field. These temperatures correspond to the various phase states of the sample at zero field. For those bands that exhibit significant dichroism, the field dependencies of the dichroic parameters (the dichroic ratio and the polarization angle of maximum absorbance) are found to be dependent on temperature, phase state, and helical unwinding. For the SmA* and SmC(*)(alpha) phases, the phenyl band dichroic ratio and the corresponding orientational order parameter are found to be almost independent of the bias field. The temperature dependence of the orientational order for zero field is discussed by taking into account the structures of the phases and the molecular tilt angles. The field dependencies of the phenyl band dichroic parameters for the SmC(*)(A) and SmC(*)(gamma) phases yield results about the distribution of directors in the layers of their unit cells and the state of helical unwinding. The azimuthal orientational distribution function of the carbonyl transition moments with respect to the long molecular axis has been determined. It is found that the degrees of the polar and quadrupolar biasing increase with decrease in temperature and the azimuthal biasing angle for the chiral carbonyl group increases significantly with a reduction in temperature. PMID:14524788

  5. Temperature and orientation dependence of surface relief gratings based on dye-doped polymer film with the interface of nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Huang, Shuan-Yu; Huang, Bing-Yau; Hung, Wen-Chi; Yu, Kai-Yu; Cheng, Wen-Shou; Kuo, Chie-Tong

    2011-02-01

    The formation of surface relief grating on dye-doped polymer film with the interface of nematic liquid crystals has been investigated by means of the holographic technique. The first-order diffraction efficiency of surface relief grating depends on the temperature and the orientation of molecular director in the interface of nematic liquid crystals. The diffraction efficiency is roughly independent of thermal fluctuations of molecular director in the most part of nematic temperature range and apparently drops near the transition temperature. The morphology of surface relief grating demonstrates that the surface modulation is larger for molecular director parallel to the groove direction. The experimental result also shows that the first-order diffraction efficiency is dependent on the surface modulation of surface relief grating.

  6. Growth and Characteristics of Bulk Single Crystals Grown from Solution on Earth and in Microgravity

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D.; Batra, A. K.; Lal, R. B.; Penn, Benjamin G.; Frazier, Donald O.

    2011-01-01

    The growth of crystals has been of interest to physicists and engineers for a long time because of their unique properties. Single crystals are utilized in such diverse applications as pharmaceuticals, computers, infrared detectors, frequency measurements, piezoelectric devices, a variety of high technology devices and sensors. Solution crystal growth is one of the important techniques to grow a variety of crystals when the material decomposes at the melting point and a suitable solvent is available to make a saturated solution at a desired temperature. In this chapter an attempt is made to give some fundamentals of growing crystals from solution including improved designs of various crystallizers. Since the same solution crystal growth technique could not be used in microgravity, authors had proposed a new cooled sting technique to grow crystals in space. Authors? experiences of conducting two space shuttle experiments relating to solution crystal growth are also detailed in this work. The complexity of these solution growth experiments to grow crystals in space are discussed. These happen to be some of the early experiments performed in space, and various lessons learned are described. A brief discussion of protein crystal growth that also shares basic principles of solution growth technique is given along with some flight hardware information for its growth in microgravity.

  7. Spectroscopy of discrete vertically oriented single-crystals of n-type tetraazaterrylene: understanding the role of defects in molecular semiconductor photovoltaics.

    PubMed

    Wise, A J; Zhang, Y; Fan, J; Wudl, F; Briseno, A L; Barnes, M D

    2014-08-14

    Recent synthetic work has realized a novel (n-type) small-molecule acceptor, 7,8,15,16-tetra-aza-terrylene (TAT), single-crystals of which can be grown oriented along the c-axis crystallographic direction, and over-coated with pentacene to form a highly ordered donor/acceptor interface for use in organic photovoltaic devices. However, characterization of single TAT crystals reveals highly variable emission spectra and excited state dynamics - properties which strongly influence photovoltaic performance. Through the use of single-crystal widefield imaging, photoluminescence spectroscopy, time correlated single photon counting, and resonant Raman studies, we conclude that this variability is a result of long-lived low-energy trap-emission from packing defects. Interestingly, we also discovered that TAT crystals whose width exceeds ∼200 nm begin acting as waveguides and optical microcavity resonators for their own photoluminescence. Several strategies are proposed for leveraging the size-dependant optical properties of TAT pillars to further enhance device performance using this active layer design. PMID:24676385

  8. Crystal preferred orientations of minerals from mantle xenoliths in alkali basaltic rocks form the Catalan Volcanic Zone (NE Spain)

    NASA Astrophysics Data System (ADS)

    Fernández-Roig, Mercè; Galán, Gumer; Mariani, Elisabetta

    2015-04-01

    Mantle xenoliths in alkali basaltic rocks from the Catalan Volcanic Zone, associated with the Neogene-Quaternary rift system in NE Spain, are formed of anhydrous spinel lherzolites and harzburgites with minor olivine websterites. Both peridotites are considered residues of variable degrees of partial melting, later affected by metasomatism, especially the harzburgites. These and the websterites display protogranular microstructures, whereas lherzolites show continuous variation between protogranular, porphyroclastic and equigranular forms. Thermometric data of new xenoliths indicate that protogranular harzburgites, lherzolites and websterites were equilibrated at higher temperatures than porphyroclastic and equigranular lherzolites. Mineral chemistry also indicates lower equilibrium pressure for porphyroclastic and equigranular lherzolites than for the protogranular ones. Crystal preferred orientations (CPOs) of olivine and pyroxenes from these new xenoliths were determined with the EBSD-SEM technique to identify the deformation stages affecting the lithospheric mantle in this zone and to assess the relationships between the deformation fabrics, processes and microstructures. Olivine CPOs in protogranular harzburgites, lherzolites and a pyroxenite display [010]-fiber patterns characterized by a strong point concentration of the [010] axis normal to the foliation and girdle distribution of [100] and [001] axes within the foliation plane. Olivine CPO symmetry in porphyroclastic and equigranular lherzolites varies continuously from [010]-fiber to orthorhombic and [100]-fiber types. The orthorhombic patterns are characterized by scattered maxima of the three axes, which are normal between them. The rare [100]-fiber patterns display strong point concentration of [100] axis, with normal girdle distribution of the other two axes, which are aligned with each other. The patterns of pyroxene CPOs are more dispersed than those of olivine, especially for clinopyroxene, but

  9. Cladding modes in photonic crystal fiber: characteristics and sensitivity to surrounding refractive index

    NASA Astrophysics Data System (ADS)

    Jiang, Xiuli; Gu, Zhengtian; Zheng, Li

    2016-01-01

    Characteristics of cladding modes in a photonic crystal fiber (PCF) with triangular air-hole lattice in the cladding are numerically analyzed using a finite element method. The transition for LP11 cladding mode to core mode with variation of the normalized wavelength has been shown. The transition of the LP01 cladding mode to the outer silica mode and reorganization of the LP0m cladding modes caused by varying the fiber radius has been investigated. By choosing the optimized fiber radius, which is located in the cladding modes' reorganization region, the sensitivity of the coupled wavelength between the core mode LP01 and cladding mode LP03 to surrounding refractive index is increased by a factor of five and reaches to 2660 nm/refractive index unit over the range of 1.40 to 1.42. The sensitivity is competitive with that of long-period grating in PCF in response to changes in refractive indices of the medium contained in the cladding air channels.

  10. Frequency characteristics of defect states in a two-dimensional phononic crystal with slit structure

    NASA Astrophysics Data System (ADS)

    Wang, X. P.; Jiang, P.; Chen, T. N.; Yu, K. P.

    2016-02-01

    In this paper, the defect state and band gap characteristics in a two-dimensional slit structure phononic crystal, consisting of slotted steel tubes embedded in an air matrix, are investigated theoretically and experimentally. Using the finite element method and supercell technique, the dispersion relationships and power transmission spectra of the slit structures are calculated. The vibration modes of the band gap edges are analyzed to clarify the mechanism of the generation of the band gaps. Additionally, the influence of the slit width on the band gaps in slit structure is investigated. The slit width was found to influence the band gaps; this is critical to understand for practical applications. Based on this finding, a method to form defect scatterers by changing the slit width of a single central scatterer, or one row of scatterers, in the perfect PC was developed. Defect bands can be induced by creating defects inside the original complete band gaps. The frequency can then be tuned by changing the slit width of defect scatterers. Meanwhile, the relationship between point defect and line defect is investigated. Finally, we verify the results of theoretical research by experiments. These results will help in fabricating devices such as acoustic filters and waveguides whose band frequency can be modulated.

  11. Studies on output characteristics of stable dual-wavelength ytterbium-doped photonic crystal fiber laser

    NASA Astrophysics Data System (ADS)

    Tian, Hongchun; Zhang, Sa; Hou, Zhiyun; Xia, Changming; Zhou, Guiyao; Zhang, Wei; Liu, Jiantao; Wu, Jiale; Fu, Jian

    2016-06-01

    A stable dual-wavelength ytterbium-doped photonic crystal fiber laser pumped by a 976 nm laser diode has been demonstrated at room temperature. Single-wavelength, dual-wavelength laser oscillations are observed when the fiber laser operates under different pump power by using different length of fibers. Stable dual-wavelength radiation around 1045 nm and 1075 nm has been generated simultaneously at a high pump power directly from an ytterbium-doped fiber laser without using any spectral control mechanism. A small core ytterbium-doped PCF fabricated by the powder sinter direction drawn rod technology is used as gain medium. The pump power and fiber length which can affect the output characteristics of dual-wavelength fiber laser are analyzed in the experiment. Experiments confirm that higher pump power and longer fiber length favors 1075 nm output; lower pump power and shorter fiber length favors 1045 nm output. Those results have a good reference in multi-wavelength fiber laser.

  12. Control and design of fiber birefringence characteristics based on selective-filled hybrid photonic crystal fibers.

    PubMed

    Han, Tingting; Liu, Yan-Ge; Wang, Zhi; Guo, Junqi; Wu, Zhifang; Luo, Mingming; Li, Shuo; Wang, Jing; Wang, Wei

    2014-06-16

    We demonstrated a kind of birefringence-controllable hybrid photonic crystal fibers (HPCFs) by selectively infiltrating air holes of PCFs with index-tunable liquids processing higher index than silica background. Detailed theoretical investigations on mode couplings from fundamental core mode to high-index-liquid-rod modes and birefringence properties of several HPCFs were presented. Strong wavelength dependence of phase and group birefringence was found, and HPCFs with different arrangements of high index liquid rods possess distinct birefringence characteristics. Then, the Sagnac interferometers (SIs) based on two typical HPCFs with different liquid-rod arrangements were theoretically and experimentally studied. The results indicated the SIs exhibit different transmission spectra and temperature responses due to the distinct birefringence features of HPCFs. A temperature sensitivity of -45.8 nm/°C at 56.5 °C was achieved using one HPCF, and a sensitivity of -11.6 nm/°C from 65 °C to 85 °C was achieved using the other HPCF. The thermal tunable HPCFs with birefringence-controllable properties will provide great potential for a variety of tunable optical devices and sensors. PMID:24977594

  13. Point Defect Distributions in ZnSe Crystals: Effects of Gravity Vector Orientation During Physical Vapor Transport Growth

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, S.; Hirschfeld, D.; Smith, T. M.; Wang, Ling Jun; Volz, M. P.; Lehoczky, S. L.

    1999-01-01

    ZnSe crystals were grown by the physical vapor transport technique under horizontal and vertical (stabilized and destabilized) configurations. Secondary ion mass spectroscopy and photoluminescence measurements were performed on the grown ZnSe samples to map the distributions of [Si], [Fe], [Cu], [Al] and [Li or Na] impurities as well as Zn vacancy, [V (sub Zn)]. Annealings of ZnSe under controlled Zn pressures were studied to correlate the measured photoluminescence emission intensity to the equilibrium Zn partial pressure. In the horizontal grown crystals the segregations of [Si], [Fe], [Al] and [V (sub Zn)] were observed along the gravity vector direction whereas in the vertically stabilized grown crystal the segregation of these point defects was radially symmetrical. No apparent pattern was observed on the measured distributions in the vertically destabilized grown crystal. The observed segregations in the three growth configurations were interpreted based on the possible buoyancy-driven convection in the vapor phase.

  14. Ice crystal c-axis orientation and mean grain size measurements from the Dome Summit South ice core, Law Dome, East Antarctica

    NASA Astrophysics Data System (ADS)

    Treverrow, Adam; Jun, Li; Jacka, Tim H.

    2016-06-01

    We present measurements of crystal c-axis orientations and mean grain area from the Dome Summit South (DSS) ice core drilled on Law Dome, East Antarctica. All measurements were made on location at the borehole site during drilling operations. The data are from 185 individual thin sections obtained between a depth of 117 m below the surface and the bottom of the DSS core at a depth of 1196 m. The median number of c-axis orientations recorded in each thin section was 100, with values ranging from 5 through to 111 orientations. The data from all 185 thin sections are provided in a single comma-separated value (csv) formatted file which contains the c-axis orientations in polar coordinates, depth information for each core section from which the data were obtained, the mean grain area calculated for each thin section and other data related to the drilling site. The data set is also available as a MATLAB™ structure array. Additionally, the c-axis orientation data from each of the 185 thin sections are summarized graphically in figures containing a Schmidt diagram, histogram of c-axis colatitudes and rose plot of c-axis azimuths. All these data are referenced by doi:10.4225/15/5669050CC1B3B and are available free of charge at https://data.antarctica.gov.au.<

  15. Growth and optical characteristics of coumarin 6 doped potassium hydrogen phthalate (KAP) crystals

    NASA Astrophysics Data System (ADS)

    Enculescu, Monica

    2009-12-01

    Single-crystals of potassium hydrogen phthalate (KAP) doped with coumarin 6 (C6) were grown by solution evaporation technique. Powder X-ray diffraction, optical transmission and luminescence measurements were performed. The structure and morphology of the KAP crystals are not changed with the incorporation of the dye. Transparency of the dye-doped crystals is suited for non-linear optical (NLO) applications and UV cut-off is not changed when compared with the pure KAP crystals. The dye-doped crystals present an absorption band at 350 nm while the growth solution exhibits a peak at 400 nm. The doped crystals have a strong emission band at 450 nm that is excited at 350 nm and the second harmonic generating (SHG) properties are demonstrated using luminescence measurements.

  16. Some new results on the frequency characteristics on quartz crystals irradiated by ionizing and particle radiations

    NASA Technical Reports Server (NTRS)

    Bahadur, H.; Parshad, R.

    1981-01-01

    The frequency behavior of AT-cut quartz crystals irradiated by X -, gamma rays and fast neutrons. Initial instability in frequency for gamma and neutron irradiated crystals was found. All the different radiations first give a negative frequency shift at lower doses which are followed by positive frequency shift for increased doses. Results are explained in terms of the fundamental crystal structure. Applications of the frequency results for radiation hardening are proposed.

  17. Magnetic properties of epitaxial Fe{sub 3}O{sub 4} films with various crystal orientations and tunnel magnetoresistance effect at room temperature

    SciTech Connect

    Nagahama, Taro Matsuda, Yuya; Tate, Kazuya; Kawai, Tomohiro; Takahashi, Nozomi; Hiratani, Shungo; Watanabe, Yusuke; Yanase, Takashi; Shimada, Toshihiro

    2014-09-08

    Fe{sub 3}O{sub 4} is a ferrimagnetic spinel ferrite that exhibits electric conductivity at room temperature (RT). Although the material has been predicted to be a half metal according to ab-initio calculations, magnetic tunnel junctions (MTJs) with Fe{sub 3}O{sub 4} electrodes have demonstrated a small tunnel magnetoresistance (TMR) effect. Not even the sign of the tunnel magnetoresistance ratio has been experimentally established. Here, we report on the magnetic properties of epitaxial Fe{sub 3}O{sub 4} films with various crystal orientations. The films exhibited apparent crystal orientation dependence on hysteresis curves. In particular, Fe{sub 3}O{sub 4}(110) films exhibited in-plane uniaxial magnetic anisotropy. With respect to the squareness of hysteresis, Fe{sub 3}O{sub 4} (111) demonstrated the largest squareness. Furthermore, we fabricated MTJs with Fe{sub 3}O{sub 4}(110) electrodes and obtained a TMR effect of −12% at RT. The negative TMR ratio corresponded to the negative spin polarization of Fe{sub 3}O{sub 4} predicted from band calculations.

  18. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. 3: Tension-compression anisotropy

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gaab, T. P.; Gayda, J.; Hemker, K. J.

    1985-01-01

    Single crystal superalloy specimens with various crystallographic directions along their axes were tested in compression at room temperature, 650, 760, 870, and 980 deg C. These results are compared with the tensile behavior studied previously. The alloy, Rene N4, was developed for gas turbine engine blades and has the nominal composition 3.7 Al, 4.2 Ti, 4 Ta, 0.5 Nb, 6 W, 1.5 Mo 9 Cr. 7.5 Co, balance Ni, in weight percent. Slip trace analysis showed that primary cube slip occurred even at room temperature for the 111 specimens. With increasing test temperature more orientations exhibited primary cube slip, until at 870 deg C only the 100 and 011 specimens exhibited normal octahedral slip. The yield strength for octahedral slip was numerically analysed using a model proposed by Lall, Chin, and Pope to explain deviations from Schmid's Law in the yielding behavior of a single phase Gamma prime alloy, Ni3(Al, Nb). The Schmid's Law deviations in Rene N4 were found to be largely due to a tension-compression anisotropy. A second effect, which increases trength for orientations away from 001, was found to be small in Rene N4. Analysis of recently published data on the single crystal superalloy PWA 1480 yielded the same result.

  19. Influencing Work-Related Learning: The Role of Job Characteristics and Self-Directed Learning Orientation in Part-Time Vocational Education

    ERIC Educational Resources Information Center

    Gijbels, David; Raemdonck, Isabel; Vervecken, Dries

    2010-01-01

    Based on the Demand-Control-Support (DCS) model, the present paper aims to investigate the influence of job characteristics such as job demands, job control, social support at work and self-directed learning orientation on the work-related learning behaviour of workers. The present study was conducted in a centre for part-time vocational education…

  20. Anomalies in the sound velocities of [011]-oriented Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals studied by using Brillouin light scattering

    NASA Astrophysics Data System (ADS)

    Kim, Tae Hyun; Kojima, Seiji; Ko, Jae-Hyeon

    2016-06-01

    The acoustic properties of [011]-oriented Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals were studied by using Brillouin spectroscopy over a wide temperature range under unpoled and poled conditions. Poling the crystal along the [011] direction induced significant changes in the sound velocity and the acoustic attenuation coefficient of both the longitudinal and the transverse acoustic modes at several characteristic temperatures. These acoustic anomalies could be attributed to changes in the polar character from macroscopic ferroelectric domains to mesoscopic polar regions along with quasi-static polar nanoregions and then to dynamic polar nanoregions upon heating the poled crystal.

  1. The role of the crystal orientation (c-axis) on switching field distribution and the magnetic domain configuration in electrodeposited hcp Co–Pt nanowires

    NASA Astrophysics Data System (ADS)

    Shahid Arshad, Muhammad; Proenca, Mariana P.; Trafela, Spela; Neu, Volker; Wolff, Ulrike; Stienen, Sven; Vazquez, Manuel; Kobe, Spomenka; Žužek Rožman, Kristina

    2016-05-01

    In this report, Co–Pt nanowires (NWs) were produced via potentiostatic electrodeposition into commonly used commercial ordered-alumina and disordered-polycarbonate membranes with similar pore diameters (≈200 nm). The pore diameter of the membranes and the deposition conditions were chosen such that the Co–Pt NWs fabricated into both membranes had a hexagonal close packed (hcp) crystal structure with a crystallographic texturing of the c-axis in the direction perpendicular to the NWs’ long axis; this effect was more pronounced in the alumina membranes. Due to the local fluctuation in electrodeposition conditions (pore diameter, pore shape), we have found a small variation in the c-axis orientations in the plane perpendicular to the NWs’ long axis. Magnetic characterizations suggested that there is uniaxial anisotropy perpendicular to the Co–Pt NWs’ long axis and the small variation in the orientation of the hcp c-axis plays an important role in the switching-field distribution and the magnetic domain structure of the Co–Pt NWs. First order reversal curves (FORCs) revealed week magnetostatic interactions between Co–Pt NWs, thus suggesting that the different pore alignments are not influencing much the magnetic properties in both membranes. The micromagnetic simulation revealed that the transverse-stripe (TS) and longitudinal stripe (LS) domains are energetically most favorable structures in such NWs. This study accentuates the influence of the crystal orientation (c-axis) of the high-anisotropy materials on their functional magnetic properties and thus is of great importance for the fabrication of nanodevices based on such NWs.

  2. The effects of alloy purity on the mechanical behavior of soft oriented NiAl single crystals

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1993-01-01

    Preliminary results of the effects of alloy purity on the mechanical properties of NiAl single crystals are presented. Two stoichiometric NiAl single crystals with different impurity contents were studied. It is concluded that reductions in the interstitial and substitutional levels cause reduced yield strengths in NiAl. Heat treatment also results in reduced yield and flow stresses in both CP-NiAl and Hp-NiAl which are considered to be due to a reduction in the concentration of thermal vacancies due to vacancy coalescence during heat treatment.

  3. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

    PubMed Central

    Shirsath, Sagar E.; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-01-01

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate. PMID:27435010

  4. Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film.

    PubMed

    Shirsath, Sagar E; Liu, Xiaoxi; Yasukawa, Yukiko; Li, Sean; Morisako, Akimitsu

    2016-01-01

    Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate. PMID:27435010

  5. Controlled sputtering of AlN (002) and (101) crystal orientations on epitaxial 3C-SiC-on-Si (100) substrate

    NASA Astrophysics Data System (ADS)

    Iqbal, A.; Walker, G.; Iacopi, A.; Mohd-Yasin, F.

    2016-04-01

    Aluminum Nitride (AlN) thin films are successfully deposited on epitaxial 3C-SiC-on-Si (100) substrates using DC magnetron sputterer. The sputtered films are characterized on the following parameters: crystal orientations (Siemens D500 X-Ray diffraction tool), deposition rate (Nanospec AFT 180), surface roughness (Park NX20 Atomic Force Microscopy), refractive index (Rudolph AutoEL IV Ellipsometer), in-plane stress (Tencor Flexus 2320 System) and Raman Spectra (Rennishaw InVia Spectrometer). XRD results demonstrate that the orientation of the AlN thin films can be changed from (002) to (101) by increasing the Nitrogen to Argon ratio from 40% to 80% at the total gas flow of 50 sccm. We are also able to tune the in-plane stress via RF biasing on the substrate. Both controlling abilities enable the applications of these thin films for low cost longitudinal piezoelectric devices and a quasi-shear mode devices using (002) and (101) orientations, respectively.

  6. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. I - Tensile behavior

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Gayda, J.; Gabb, T. P.; Voigt, R. C.

    1986-01-01

    Single crystal specimens of a nickel-base superalloy with axes near 001, 011, and -112 were tested in tension at room temperature, 760, and 980 C. The alloy Rene N-4, was developed for gas turbine engine blades and has the nominal composition 3.7 Al, 4.2 Ti, 4 Ta, 0.5 Nb, 6 W, 1.5 Mo, 9 Cr, 7.5 Co, balance Ni, (all in weight percent). Analysis of slip band traces, specimen axis rotation, and dislocation Burgers vectors showed that at 760 and 980 C primary cube slip supplanted normal octahedral slip for the -112 line-oriented specimens. The other two orientations, which have lower resolved shear stresses on the cube system, exhibited octahedral slip at all three temperatures. The critical resolved shear stress is considerably greater on the cube system than on the octahedral system at room temperature. However, at 760 and 980 C the critical resolved shear stresses on the two systems are about the same. While the room temperature and 980 C yield strengths for the two orientations exhibiting octahedral slip could be rationalized on the basis of resolved shear stress, those at 760 C could not. Such violations of Schmid's law have previously been observed in other superalloys and single phase gamma-prime.

  7. Growth of Large-Size SnS Thin Crystals Driven by Oriented Attachment and Applications to Gas Sensors and Photodetectors.

    PubMed

    Wang, Jun; Lian, Gang; Xu, Zhenghao; Fu, Chen; Lin, Zhaojun; Li, Liyi; Wang, Qilong; Cui, Deliang; Wong, Ching-Ping

    2016-04-20

    Freestanding large-size SnS thin crystals are synthesized via two-dimensional oriented attachment (OA) growth of colloidal quantum dots (CQDs) in a novel high-pressure solvothermal reaction. The SnS thin crystals present a uniform rectangular shape with a lateral size of 20-30 um and thickness of <10 nm. The evolution process demonstrates that a synergetic effect of pressure, aging time and organic ligands results in polycrystal-to-monocrystal formation and defect annihilation. Furthermore, gas sensor and photodetector devices, based on SnS thin single crystals, are also prepared. The sensing devices present high sensitivity, superior selectivity, low detection limit (≪100 ppb) and reversibility to NO2 at room temperature. The fabricated photodetector devices exhibit a high responsivity of 2.04 × 10(3) A W(1-) and high external quantum efficiency of ∼4.75 × 10(5) % at 532 nm, which are much higher than most of the photodetector devices. PMID:27054920

  8. Size-dependent plasticity in KCl and LiF single crystals: influence of orientation, temperature, pre-straining and doping

    NASA Astrophysics Data System (ADS)

    Zou, Yu; Spolenak, Ralph

    2015-06-01

    Size effects in plasticity are mostly studied in metallic systems, but they are rarely investigated in ionic crystals. In this study, single-crystalline KCl and LiF pillars were fabricated by focused ion beam technique and compressed using a flat punch tip in a nanoindenter. The materials were investigated with regards to crystal orientation, test temperature, pre-straining and doping. The results show: (1) [1 1 1] LiF pillars do exhibit size effect with an exponent of -0.38, in contrary to no size effect in [1 1 1] LiF reported in literature; (2) [0 0 1] LiF, and [0 0 1] and [1 1 1] KCl have similar size-effect exponents of -0.68, -0.71 and -0.65, respectively; (3) the size effect of [1 1 1] LiF pillars is more sensitive to the temperature change than that of [0 0 1] LiF pillars; (4) pre-straining of [1 1 1] LiF pillars results in a reduced size effect; (5) the 0.05 mol% CaCl2 doping in [0 0 1] KCl slightly increases strength levels and does not change the size effect much. The magnitude of the size effects in ionic crystals can be attributed to the bulk stress level, but not the slip systems. In addition, a correlation between critical temperatures and size-effect slopes is illustrated, and the additivity of strengthening mechanisms is critically discussed.

  9. Investigation of thermophysical characteristics of SrMoO4 crystals, nominally pure and doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Popov, P. A.; Skrobov, S. A.; Matovnikov, A. V.; Ivleva, L. I.; Dunaeva, E. E.; Shekhovtsov, A. N.; Kosmyna, M. B.

    2015-11-01

    Thermophysical characteristics of SrMoO4 crystals (grown by the Czochralski method from intrinsic melts), nominally pure and doped with rare earth ions, have been investigated. The temperature and concentration dependences of the thermal conductivity are obtained for SrMoO4 samples containing Nd3+ (0.28, 0.56, 0.84, and 1.33 at %), Pr3+ (0.01 and 0.41 at %), Ho3+ (0.01 and 0.06 at %), and Ho3+ (0.13 at %) + Tm3+ (0.13 at %) in a temperature range of 50-300 K. The thermal conductivities are measured in the directions parallel and/or perpendicular to the crystal optical axis. The thermal conductivity of nominally pure SrMoO4 at 300 K in the direction perpendicular to the c axis has been found to be 4.2 W/(m K). The introduction of impurities of rare earth metals reduces the thermal conductivity of SrMoO4 crystals. The anisotropy of the thermal conductivity is weak. The measured molar specific heat C P ( T) of a nominally pure SrMoO4 crystal is 116.2 J/(mol K) at 300 K. The temperature dependence of the phonon mean free path l( T) in a SrMoO4 crystal is calculated for the temperature range of 80-300 K based on experimental data.

  10. Current instability with Z- and N-shaped current-voltage characteristics in inhomogeneous In2Se3 crystals

    NASA Astrophysics Data System (ADS)

    Drapak, S. I.; Gavrilyuk, S. V.; Kovalyuk, Z. D.

    2009-06-01

    Layered In2Se3 crystals with a defect structure grown from a stoichiometric melt using the Bridgman technique are characterized by the electric current instability with Z- and N-shaped features in the current-voltage characteristics, which are typical of superlattices and multiple-quantum-well heterostructures. It is established that the observed behavior is related to the presence of nanodimensional In6Se7 inclusions in the α-In2Se3 matrix possessing a wider bandgap.

  11. Characteristics and optical spectra of U:CaF 2 crystal grown by TGT

    NASA Astrophysics Data System (ADS)

    Su, Liangbi; Xu, Jun; Dong, Yongjun; Yang, Weiqiao; Zhou, Guoqing; Zhao, Guangjun

    2004-02-01

    Transparent and integral U:CaF 2 single crystals with diameters 75 mm were grown by temperature gradient technique. Distribution of uranium in the 0.3 wt% doped CaF 2 crystal was determined by inductively coupled plasma-mass spectrometry. For the first time, the segregation coefficient of U in U:CaF 2 crystal was calculated, which is equal to 0.53 depending on either the formula, K0= Cs/ Cl or the general distribution equation, Cs= K0C0(1- g) K0-1 . The solute-enriched strips parallel to growth direction were observed under optical microscopy. The color of U:CaF 2 crystal is almost all red but for 5-mm-thickness periphery which is yellow. From the crystal growth initiating part to the finishing, the shape of absorption spectrum of red crystal does not change, but the density of all peaks gradually increases with color deepening. The red crystal mostly contains U 3+, while the yellow contains more U 2+ ions according to the comparison of optical absorption spectra.

  12. Growth and magneto-optical characteristic of Ho2Ti2O7 crystal

    NASA Astrophysics Data System (ADS)

    Kang, Junbiao; Xu, Wenming; Zhang, Wenhui; Chen, Xiang; Liu, Wei; Guo, Feiyun; Wu, Shuting; Chen, Jianzhong

    2014-06-01

    A pyrochlore crystal with magneto-optical effect-Ho2Ti2O7 crystal has been grown by Czochralski method. X-ray powder diffraction, magnetic susceptibility, transmission spectrum and Faraday rotation of single crystal Ho2Ti2O7 were measured. The results of Rietveld refinement revealed that the crystal belongs to cubic system and the lattice parameters calculated by Jade 7.0 (Materials Data, Inc.) were a=1.00915(7) nm and V=1.0277 nm3. The effective magnetic moment and Curie-Weiss temperature of Ho2Ti2O7 crystal are 10.4 μB and 1.86 K, respectively. The transmittance of Ho2Ti2O7 crystals grown in Ar can be more than 72% in 700-1080 nm and 1260-1500 nm. The Verdet constant of Ho2Ti2O7 crystal at 1064 nm comes up to -54.1 rad/(mT), which is 1.35 times as large as that of Tb3Ga5O12 reported.

  13. What Drives Juvenile Probation Officers? Relating Organizational Contexts, Status Characteristics, and Personal Convictions to Treatment and Punishment Orientations

    ERIC Educational Resources Information Center

    Ward, Geoff; Kupchik, Aaron

    2010-01-01

    Data from surveys of juvenile court probation officers in four states are analyzed to understand professional orientations toward two seemingly contrasting goals of contemporary juvenile justice systems: punishment and treatment. These self-reported juvenile probation officer orientations are considered in relation to three clusters of variables…

  14. Predicting the orientation-dependent stress-induced transformation and detwinning response of shape memory alloy single crystals

    NASA Astrophysics Data System (ADS)

    Buchheit, T. E.; Wert, J. A.

    1996-02-01

    The present investigation examines three models that predict the orientation dependence of the stress-induced transformation strain in shape memory alloys (SMAs). The merits of each model are con-sidered in light of experimental results for three SMAs: NiTi, Cu-Ni-Al, and Ni-Al. Published experimental results fit model predictions well in most cases; the few exceptions can be accounted for by factors not included in the present models. As part of the comparison of model results with experimental observations, Ni-Al stress-strain curves generated by one of the models are found to closely match experimental stress-strain curves for the [001], [011], and [111] stress axis orientations. Finally, the predicted transformation stress anisotropy is analyzed in detail to examine the effect of detwinning of the stress-induced martensite.

  15. Predicting the orientation-dependent stress-induced transformation and detwinning response of shape memory alloy single crystals

    SciTech Connect

    Buchheit, T.E.; Wert, J.A.

    1996-02-01

    The present investigation examines three models that predict the orientation dependence of the stress-induced transformation strain in shape memory alloys (SMAs). The merits of each model are considered in light of experimental results for three SMAs: NiTi, Cu-Ni-Al, and Ni-Al. Published experimental results fit model predictions well in most cases; the few exceptions can be accounted for by factors not included in the present models. As part of the comparison of model results with experimental observations, Ni-Al stress-strain curves generated by one of the models are found to closely match experimental stress-strain curves for the [001], [011], and [111] stress axis orientations. Finally, the predicted transformation stress anisotropy is analyzed in detail to examine the effect of detwinning of the stress-induced martensite.

  16. Casimir interaction in smectic-A liquid crystals caused by coupled fluctuations of positional and orientational order

    NASA Astrophysics Data System (ADS)

    Markun, B.; Žumer, S.

    2006-03-01

    A theoretical study of the Casimir interaction in smectic-A systems, considering fluctuations of both types of smectic ordering—positional and orientational—including the coupling between them, is presented. Two model systems with plan-parallel geometry are studied: homeotropic cell and free-standing film. At large thicknesses of the system the behavior of the Casimir force is found to be primarily determined by positional fluctuations, whereas at small thicknesses also the orientational degrees of freedom greatly contribute to the interaction. The influence of different coupling strengths between orientational and positional order is presented. The dependence of the Casimir force on the director anchoring and surface-tension parameters is studied. The possibilities of experimental detection of the interaction are discussed.

  17. Crystal Organic Light-Emitting Diodes with Perfectly Oriented Non-Doped Pt-Based Emitting Layer.

    PubMed

    Kim, Kwon-Hyeon; Liao, Jia-Ling; Lee, Si Woo; Sim, Bomi; Moon, Chang-Ki; Lee, Gene-Hsiang; Kim, Hyo Jung; Chi, Yun; Kim, Jang-Joo

    2016-04-01

    Organic light-emitting diodes with external quantum efficiency of 38.8% are realized using a Pt-based thin-film emitting layer with photoluminescence quantum yield of 96% and transition dipole ratio of 93%. The emitting dipole orientation of the thin films fabricated using Pt complexes is investigated and the structural relationship between X-ray structural analysis and the structures in thin films are discussed based on quantum chemical calculations. PMID:26833629

  18. Crystal orientation effects on helium ion depth distributions and adatom formation processes in plasma-facing tungsten

    SciTech Connect

    Hammond, Karl D.; Wirth, Brian D.

    2014-10-14

    We present atomistic simulations that show the effect of surface orientation on helium depth distributions and surface feature formation as a result of low-energy helium plasma exposure. We find a pronounced effect of surface orientation on the initial depth of implanted helium ions, as well as a difference in reflection and helium retention across different surface orientations. Our results indicate that single helium interstitials are sufficient to induce the formation of adatom/substitutional helium pairs under certain highly corrugated tungsten surfaces, such as (1 1 1)-orientations, leading to the formation of a relatively concentrated layer of immobile helium immediately below the surface. The energies involved for helium-induced adatom formation on (1 1 1) and (2 1 1) surfaces are exoergic for even a single adatom very close to the surface, while (0 0 1) and (0 1 1) surfaces require two or even three helium atoms in a cluster before a substitutional helium cluster and adatom will form with reasonable probability. This phenomenon results in much higher initial helium retention during helium plasma exposure to (1 1 1) and (2 1 1) tungsten surfaces than is observed for (0 0 1) or (0 1 1) surfaces and is much higher than can be attributed to differences in the initial depth distributions alone. The layer thus formed may serve as nucleation sites for further bubble formation and growth or as a source of material embrittlement or fatigue, which may have implications for the formation of tungsten “fuzz” in plasma-facing divertors for magnetic-confinement nuclear fusion reactors and/or the lifetime of such divertors.

  19. Impact of additional Pt and NiSi crystal orientation on channel stress induced by Ni silicide film in metal-oxide-semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Mizuo, Mariko; Yamaguchi, Tadashi; Kudo, Shuichi; Hirose, Yukinori; Kimura, Hiroshi; Tsuchimoto, Jun-ichi; Hattori, Nobuyoshi

    2014-01-01

    The impact of additional Pt and Ni monosilicide (NiSi) crystal orientation on channel stress from Ni silicide in metal-oxide-semiconductor field-effect transistors (MOSFETs) has been demonstrated. The channel stress generation mechanism can be explained by the NiSi crystal orientation. In pure Ni silicide films, the channel stress in the p-type substrate is much larger than that in the n-type one, since the NiSi a-axis parallel to the channel direction is strongly aligned on the p-type substrate compared with on the n-type one. On the other hand, in NiPt silicide films, the difference in the channel stress between the p- and n-type substrates is small, because the NiSi crystal orientation on the p-type substrate is similar to that on the n-type one. These results can be explained by the Pt segregation at the interface between the NiSi film and the Si surface. Segregated Pt atoms cause the NiSi b-axis to align normal to the Si(001) surface in the nucleation step owing to the expansion of the NiSi lattice spacing at the NiSi/Si interface. Furthermore, the Pt segregation mechanism is considered to be caused by the grain boundary diffusion in the Ni2Si film during NiSi formation. We confirmed that the grains of Ni2Si on the p-type substrate are smaller than those on the n-type one. The Ni2Si film on the p-type substrate has more grain boundary diffusion paths than that on the n-type one. Therefore, the amount of Pt segregation at the NiSi/Si interface on the p-type substrate is larger than that on the n-type one. Consequently, the number of NiSi grains with the b-axis aligned normal to the Si(001) in the p-type substrate is larger than that in the n-type one. As a result, the channel stress induced by NiPt silicide in PMOS is larger than that in NMOS. According to this mechanism, controlling the Pt concentration at the NiSi/Si interface is one of the key factors for channel stress engineering.

  20. Performance characteristics of pixelated CZT crystals used on the GammaTracker project

    NASA Astrophysics Data System (ADS)

    Becker, Eric M.; Seifert, Carolyn E.; Myjak, Mitchell J.; Erikson, Luke E.; Morris, Scott J.; Balvage, Duane T.; Lundy, Richard P.

    2011-09-01

    GammaTracker is a handheld radioisotope identification device in development at Pacific Northwest National Laboratory that uses eighteen pixelated Cadmium-Zinc Telluride (CZT) crystals to provide energy resolution approaching that of high-purity germanium without the need for cryogenic cooling. Additionally, these crystals can be used to provide directional and imaging capabilities that cannot be found in other handheld detectors. A significant number of CZT crystals have been procured during the development of the GammaTracker system; the majority of these were procured with the same set of specifications. Each of these detectors has been characterized in terms of key parameters, including current-voltage response and pixel-by-pixel energy resolution. The results of this testing indicate that the overall quality of CZT crystals is improving over time.

  1. Ultraviolet fast-response photoelectric effect in tilted orientation SrTiO{sub 3} single crystals

    SciTech Connect

    Zhao Kun; Jin Kuijuan; Huang Yanhong; Zhao Songqing; Lu Huibin; He Meng; Chen Zhenghao; Zhou Yueliang; Yang Guozhen

    2006-10-23

    Ultraviolet photoelectricity based on the vicinal cut as-supplied SrTiO{sub 3} single crystals has been experimentally studied in the absence of an applied bias at room temperature. An open-circuit photovoltage of 130 ps rise time and 230 ps full width at half maximum was observed under the irradiation of a 355 nm pulsed laser of 25 ps in duration. The dependence of the photoelectric effect on the tilting angles was studied, and the optimum angle is 20.9 deg. . Seebeck effect is proposed to elucidate the tilting angle dependence of laser-induced photovoltage. This work demonstrates the potential of SrTiO{sub 3} single crystals in ultraviolet detection.

  2. Numerical simulation of the scavenging rates of ice crystals of various microphysical characteristics

    NASA Astrophysics Data System (ADS)

    Pitter, Richard L.; Zhang, Renyi

    1991-06-01

    Numerical models of trajectories of small aerosol spheres relative to oblate spheroids were used to determine ice crystal scavenging efficiencies. The models included the effects of aerodynamic flow about the ice particle, gravity, aerosol particle inertia and drag and electrostatic effects. Two electric configurations of the ice particle were investigated in detail. The first applied a net charge to the ice particle, of magnitude equal to the mean thunderstorm charge distribution, while the second applied a charge distribution, with no net charge, to the ice particle to model the electric multipole charge distribution. The results show that growing ice crystals with electric multipoles are better scavengers than single ice crystals with net thunderstorm charges, especially in the Greenfield gap (0.1 to 1.0 μm), and that larger single crystals are better scavengers than smaller single crystals. The results also show that the low density ice crystals are more effective scavengers with net charges than they are with charge distribution.

  3. Physicochemical characteristics of drip waters: Influence on mineralogy and crystal morphology of recent cave carbonate precipitates

    NASA Astrophysics Data System (ADS)

    Riechelmann, Sylvia; Schröder-Ritzrau, Andrea; Wassenburg, Jasper A.; Schreuer, Jürgen; Richter, Detlev K.; Riechelmann, Dana F. C.; Terente, Mihai; Constantin, Silviu; Mangini, Augusto; Immenhauser, Adrian

    2014-11-01

    Speleothems are one of the most intensively explored continental archives for palaeoclimate variability. The parameters, however, that control speleothem petrography and its changes with time and space, specifically calcite crystal morphology and carbonate mineralogy, are still poorly understood. In order to shed light on processes and their products, precipitation experiments of recent carbonate crystals on watch glasses and glass plates were performed in seven selected caves. Drip water sites were analysed for their fluid Mg/Ca molar ratio, pH, degree of saturation for calcite and aragonite and drip rates. Corresponding precipitates were analysed with respect to their mineralogy, calcite crystal morphology and Mg/Ca molar ratio of calcite. The following results are found: High fluid Mg/Ca ratios are found only for caves situated in dolostone, thus the hostrock lithology indirectly controls the carbonate mineralogy and calcite crystal morphology of speleothems. The precipitation of aragonite in place of calcite occurred only in dolostone caves and is bound to very specific conditions. These are: high fluid Mg/Ca ratios (⩾0.5), high fluid pH (>8.2) and low fluid saturation indices for calcite (<0.8). These specific conditions are induced by slow drip rates of <0.2 ml/min as often under more arid conditions, causing the precipitation of calcite/aragonite prior to reaching the stalagmite top. Due to this, fluid chemistry is altered, which in turn leads to changes in carbonate mineralogy and geochemistry on the stalagmite top. Calcite growth is inhibited at high fluid Mg/Ca ratios and hence, aragonite precipitation is kinetically stabilised. An increase of the drip water Mg/Ca ratio leads to an increased incorporation of Mg2+ into the calcite crystal lattice and thus, to a change in calcite crystal morphology. Four distinctive changes occur with increasing Mg2+ incorporation: (i) development of new forms (steeper rhombohedra and base pinacoid) at the edges and

  4. Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material

    PubMed Central

    Tan, Yanli; Gao, Qiuming; Li, Zeyu; Tian, Weiqian; Qian, Weiwei; Yang, Chunxiao; Zhang, Hang

    2016-01-01

    A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li+ ion storage capacity of 986 mAh g−1 was obtained at 100 mA g−1 after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g−1). Even at the higher current density of 1 A g−1, the electrode could still deliver a remarkable discharge capacity of 720 mAh g−1 over 150 cycles. PMID:27217201

  5. Magnetic anisotropy in the SDW state of metallic V 2- yO 3 observed by magnetotransport measurements on oriented single crystals

    NASA Astrophysics Data System (ADS)

    Klimm, S.; Gerstmeier, G.; Paulin, H.; Klemm, M.; Horn, S.

    1997-02-01

    The compound V 2O 3 is often considered to be a Mott-Hubbard insulator at low temperatures. The development of a spin-density wave (SDW) in samples with V-deficiency, i.e. upon hole-doping of the stoichiometric system, is regarded to corroborate this view. This transition into a metallic antiferromagnetic state at TN = 10 K leads to a minimum in the resistivity. We show that this minimum varies only slightly when an external magnetic field is applied ( ΔTN = -1 K for B = 12 T). The Hall resistivity is linear in field and the Hall constant R H shows a strong temperature dependence with a maximum at about TN. For T < TN the magnetoresistance is negative and we observe metamagnetic behavior, which depends on the orientation of the magnetic field with respect to the crystal axes.

  6. Microstructure and Sn Crystal Orientation Evolution in Sn-3.5Ag Lead-Free Solders in High-Temperature Packaging Applications

    NASA Astrophysics Data System (ADS)

    Zhou, Bite; Muralidharan, Govindarajan; Kurumadalli, Kanth; Parish, Chad M.; Leslie, Scott; Bieler, Thomas R.

    2014-01-01

    Understanding the reliability of eutectic Sn-3.5Ag lead-free solders in high-temperature packaging applications is of significant interest in power electronics for the next-generation electric grid. Large-area (2.5 mm × 2.5 mm) Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates were thermally cycled between 5°C and 200°C. Sn crystal orientation and microstructure evolution during thermal cycling were characterized by electron backscatter diffraction in the scanning electron microscope. Comparisons were made between the observed initial texture and microstructure and its evolution during thermal cycling. Gradual lattice rotation and grain boundary misorientation evolution observed due to thermal cycling suggested a continuous recrystallization mechanism. Recrystallization behavior was correlated with dislocation slip activities.

  7. Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material.

    PubMed

    Tan, Yanli; Gao, Qiuming; Li, Zeyu; Tian, Weiqian; Qian, Weiwei; Yang, Chunxiao; Zhang, Hang

    2016-01-01

    A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li(+) ion storage capacity of 986 mAh g(-1) was obtained at 100 mA g(-1) after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g(-1)). Even at the higher current density of 1 A g(-1), the electrode could still deliver a remarkable discharge capacity of 720 mAh g(-1) over 150 cycles. PMID:27217201

  8. Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material

    NASA Astrophysics Data System (ADS)

    Tan, Yanli; Gao, Qiuming; Li, Zeyu; Tian, Weiqian; Qian, Weiwei; Yang, Chunxiao; Zhang, Hang

    2016-05-01

    A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li+ ion storage capacity of 986 mAh g‑1 was obtained at 100 mA g‑1 after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g‑1). Even at the higher current density of 1 A g‑1, the electrode could still deliver a remarkable discharge capacity of 720 mAh g‑1 over 150 cycles.

  9. Microstructure and Sn crystal orientation evolution in Sn-3.5Ag lead-free solders in high temperature packaging applications

    SciTech Connect

    Zhou, Bite; Muralidharan, Govindarajan; Kurumaddali, Nalini Kanth; Parish, Chad M; Leslie, Dr Scott; Bieler, T. R.

    2014-01-01

    Understanding the reliability of eutectic Sn-3.5Ag lead-free solders in high temperature packaging applications is of significant interest in power electronics for the next generation electric grid. Large area (2.5mm 2.5mm) Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates were thermally cycled between 5 C and 200 C. Sn crystal orientation and microstructure evolution during thermal cycling were characterized by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Comparisons are made between observed initial texture and microstructure and its evolution during thermal cycling. Gradual lattice rotation and grain boundary misorientation evolution suggested the continuous recrystallization mechanism. Recrystallization behavior was correlated with dislocation slip activities.

  10. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2014-07-21

    To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented. PMID:24933655

  11. Three-point bending analysis of doubly clamped silicon nanowire beams; Young's modulus, initial stress, and crystal orientation

    SciTech Connect

    Yaish, Y. E. Calahorra, Y.; Shtempluck, O.; Kotchetkov, V.

    2015-04-28

    A non-linear model is introduced describing the force-deflection relation of doubly clamped beams, including initial stress. Several approximations for the exact model are developed and compared, revealing the importance of considering the initial stress during 3-point bending measurements analysis. A novel approximation is found to be better than others, and both the exact model and this approximation are in perfect agreement with finite element simulations. A brief experimental example of silicon nanowires is presented in which the Young's modulus, the initial stress, and the crystallographic growth orientation are extracted by 3-point bending analysis.

  12. Observations of Glide and Decomposition of a<101> Dislocations at High Temperatures in Ni-Al Single Crystals Deformed along the Hard Orientation

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Daw, M. S.; Noebe, R. D.; Mills, M. J.

    2003-01-01

    Ni-44at.% Al and Ni-50at.% single crystals were tested in compression in the hard (001) orientations. The dislocation processes and deformation behavior were studied as a function of temperature, strain and strain rate. A slip transition in NiAl occurs from alpha(111) slip to non-alphaaaaaaaaaaa9111) slip at intermediate temperatures. In Ni-50at.% Al single crystal, only alpha(010) dislocations are observed above the slip transition temperature. In contrast, alpha(101)(101) glide has been observed to control deformation beyond the slip transition temperature in Ni-44at.%Al. alpha(101) dislocations are observed primarily along both (111) directions in the glide plane. High-resolution transmission electron microscopy observations show that the core of the alpha(101) dislocations along these directions is decomposed into two alpha(010) dislocations, separated by a distance of approximately 2nm. The temperature window of stability for these alpha(101) dislocations depends upon the strain rate. At a strain rate of 1.4 x 10(exp -4)/s, lpha(101) dislocations are observed between 800 and 1000K. Complete decomposition of a alpha(101) dislocations into alpha(010) dislocations occurs beyond 1000K, leading to alpha(010) climb as the deformation mode at higher temperature. At lower strain rates, decomposition of a alpha(101) dislocations has been observed to occur along the edge orientation at temperatures below 1000K. Embedded-atom method calculations and experimental results indicate that alpha(101) dislocation have a large Peieris stress at low temperature. Based on the present microstructural observations and a survey of the literature with respect to vacancy content and diffusion in NiAl, a model is proposed for alpha(101)(101) glide in Ni-44at.%Al, and for the observed yield strength versus temperature behavior of Ni-Al alloys at intermediate and high temperatures.

  13. KDP crystal doped with L-arginine amino acid: growth, structure perfection, optical and strength characteristics

    NASA Astrophysics Data System (ADS)

    Pritula, I. M.; Kostenyukova, E. I.; Bezkrovnaya, O. N.; Kolybaeva, M. I.; Sofronov, D. S.; Dolzhenkova, E. F.; Kanaev, A.; Tsurikov, V.

    2016-07-01

    Potassium Dihydrogen Phosphate (KDP) crystal doped with L-arginine (L-arg) amino acid with 1.4 wt% concentration in the solution was grown onto a point seed by the method of temperature reduction. For the first time an attempt was made to grow large-size (7 × 6 × 8 cm3) optically transparent crystals, which allowed to analyze the effect of L-arg additive on the physical properties of the different growth sectors ({100} and {101}) of KDP. The incorporation of L-arg into both growth sectors of the crystal was confirmed by the methods of optical and IR spectroscopy and found to be caused by the ability of the amino acid to form hydrogen bonds with the face {100} and electrostatically interact with the positively charged face {101} of KDP crystal. A slight variation in the unit cell parameters was reported, the elementary cell volume of KDP:L-arg crystal increased in comparison with the one of pure KDP by 2·10-2 and 2.07·10-2 Å3 in the sectors {100} and {101}, respectively. It was found that the doping of L-arg enhanced the SHG efficiency of KDP and depended on the crystal growth sectors. The SHG efficiency of KDP:L-arg was by a factor 2.53 and 3.95 higher in comparison with those of pure KDP for {101} and {100} growth sector, respectively. The doping was found to lead to softening of both faces by ∼3-10% and ∼14-17% in the sectors {101} and {100}, respectively. Investigation of the influence of L-arg molecules on the bulk laser damage threshold of the crystals showed that the bulk laser damage threshold of the samples of KDP:L-arg crystal was higher than the one of the pure crystal in the sector {101} and lower in the sector {100}. The correlation between microhardness and laser damage threshold were discussed. The study is helpful for further searching, designing and simulation of hybrid NLO materials.

  14. Orientating layers with adjustable pretilt angles for liquid crystals deposited by a linear atmospheric pressure plasma source

    SciTech Connect

    Jian, Shih-Jie; Kou, Chwung-Shan; Hwang, Jennchang; Lee, Chein-Dhau; Lin, Wei-Cheng

    2013-06-15

    A method for controlling the pretilt angles of liquid crystals (LC) was developed. Hexamethyldisiloxane polymer films were first deposited on indium tin oxide coated glass plates using a linear atmospheric pressure plasma source. The films were subsequently treated with the rubbing method for LC alignment. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements were used to characterize the film composition, which could be varied to control the surface energy by adjusting the monomer feed rate and input power. The results of LC alignment experiments showed that the pretilt angle continuously increased from 0 Degree-Sign to 90 Degree-Sign with decreasing film surface energy.

  15. Effect of an electric field on the orientation of a liquid crystal in a cell with a nonuniform director distribution

    NASA Astrophysics Data System (ADS)

    Aksenova, E. V.; Karetnikov, A. A.; Karetnikov, N. A.; Kovshik, A. P.; Ryumtsev, E. I.; Sakhatskii, A. S.; Svanidze, A. V.

    2016-05-01

    The electric field-induced reorientation of a nematic liquid crystal in cells with a planar helicoidal or a homeoplanar structure of a director field is studied theoretically and experimentally. The dependences of the capacitances of these systems on the voltage in an applied electric field below and above the Fréedericksz threshold are experimentally obtained and numerically calculated. The calculations use the director distribution in volume that is obtained by direct minimization of free energy at various voltages. The inhomogeneity of the electric field inside a cell is taken into account. The calculation results are shown to agree with the experimental data.

  16. Non-polar InGaN quantum dot emission with crystal-axis oriented linear polarization

    SciTech Connect

    Reid, Benjamin P. L. Chan, Christopher C. S.; Taylor, Robert A.; Kocher, Claudius; Zhu, Tongtong; Oehler, Fabrice; Oliver, Rachel A.

    2015-04-27

    Polarization sensitive photoluminescence is performed on single non-polar InGaN quantum dots. The studied InGaN quantum dots are found to have linearly polarized emission with a common polarization direction defined by the [0001] crystal axis. Around half of ∼40 studied dots have a polarization degree of 1. For those lines with a polarization degree less than 1, we can resolve fine structure splittings between −800 μeV and +800 μeV, with no clear correlation between fine structure splitting and emission energy.

  17. Analysis of transmission characteristics of doubly clad fibers with an inner cladding made of uniaxial crystal materials

    NASA Astrophysics Data System (ADS)

    Xiaoping, Zhang; Zhihong, Tan

    2002-04-01

    A doubly clad optical fiber with an inner cladding made of a uniaxial crystal material whose optical axis is parallel to the fiber axis was proposed, and exact characteristic equations of vector modes were derived. The influence of the ratio ( kcl) of the extraordinary to the ordinary ray indexes upon the waveguide dispersion was examined in detail. In view of the impossibility to deduce the expression of waveguide dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate waveguide dispersion was established. The calculated results indicate that the values of waveguide dispersion can be effectively changed through variation of kcl without changing the geometrical and optical parameters ( S and R). The influences of kcl, S and R on the propagation and cutoff characteristics of the low order modes are also analyzed.

  18. Numerical investigation of the influence of crystallization of ultrafine particles of aluminum oxide on energy characteristics of solid-propellant rocket engine

    NASA Astrophysics Data System (ADS)

    Dyachenko, N. N.; Dyachenko, L. I.

    2014-08-01

    The results of numerical investigation of a multiphase flow considering coagulation, crushing and crystallization of the particles of polydispersed condensate in the nozzles of solid-propellant rocket engine are presented. The influence of particles crystallization on the energy characteristics of the engine is shown.

  19. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores.

    PubMed

    Całus, Sylwia; Kityk, Andriy V; Borowik, Lech; Lefort, Ronan; Morineau, Denis; Krause, Christina; Schönhals, Andreas; Busch, Mark; Huber, Patrick

    2015-07-01

    We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PMID:26274191

  20. Interfacial dislocations in (111) oriented (Ba0.7Sr0.3)TiO3 films on SrTiO3 single crystal

    DOE PAGESBeta

    Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; Kamo, Takafumi; Funakubo, Hiroshi; Wu, Di; Xin, Huolin L.; Su, Dong

    2015-10-08

    In this study, we have investigated the interfacial structure of epitaxial (Ba,Sr)TiO3 films grown on (111)-oriented SrTiO3 single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a<110> comprised of a misfit dislocation along <112>, and threading dislocations along <110> or <100>. The misfit dislocation with Burgers vector of a <110> can dissociate into two ½ a <110> partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrievedmore » the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba0.7Sr0.3)TiO3 films.« less

  1. The photorefractive characteristics of bismuth-oxide doped lithium niobate crystals

    SciTech Connect

    Zheng, Dahuai; Yao, Jiaying; Kong, Yongfa; Liu, Shiguo; Zhang, Ling; Chen, Shaolin; Xu, Jingjun

    2015-01-15

    Bismuth-doped lithium niobate (LN:Bi) crystals were grown by Czochralski method and their optical damage resistance, photorefraction, absorption spectra, and defect energy levels were investigated. The experimental results indicate that the photorefractive properties of LN:Bi were enhanced as compared with congruent one, the photorefractive response time was greatly shortened, the photorefractive sensitivity was increased, and the diffraction efficiency of near-stoichiometric LN:Bi (SLN:Bi) reached 31.72% and 49.08% at 532 nm and 488 nm laser, respectively (light intensity of 400 mW/cm{sup 2}). An absorption peak at about 350 nm was observed in the absorption spectrum of LN:Bi. And the defect energy levels simulation indicates new defect levels appear in the forbidden gap of LN:Bi crystals. Therefore bismuth can act as photorefractive centers in LN crystals.

  2. Superior characteristics of organic chalcone single crystals as efficient nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Kiran, A. John; Kim, H. C.; Kim, K.; Rotermund, F.; Ravindra, H. J.; Dharmaprakash, S. M.; Lim, H.

    2008-03-01

    High-quality biaxial single crystals of chalcone derivatives were grown by solution growth technique. Their molecular structures were designed to possess large second-order nonlinearities by choosing proper donor/acceptor groups while retaining a high transparency in the visible and infrared spectral regions. The second-order nonlinear optical coefficients, determined by applying the Maker fringe technique, were found to be much larger than those of LiB3O5, KTiOPO4, KH2PO4, and urea. The advantages, such as easy synthesis and crystal growth, low cutoff wavelength (<450nm ), large optical nonlinearity, and high damage threshold (>7.2GW/cm2), make these organic crystals promising for efficient frequency doubling.

  3. Kinetic characteristics of crystallization from model solutions of the oral cavity

    NASA Astrophysics Data System (ADS)

    Golovanova, O. A.; Chikanova, E. S.

    2015-11-01

    The kinetic regularities of crystallization from model solutions of the oral cavity are investigated and the growth order and constants are determined for two systems: saliva and dental plaque fluid (DPF). It is found that the stage in which the number of particles increases occurs in the range of mixed kinetics and their growth occurs in the diffusion range. The enhancing effect of additives HCO- 3 > C6H12O6 > F- and the retarding effect of Mg2+ are demonstrated. The HCO- 3 and Mg2+ additives, taken in high concentrations, affect the corresponding rate constants. It is revealed the crystallization in DPF is favorable for the growth of small crystallites, while the model solution of saliva is, vice versa, favorable for the growth of larger crystals.

  4. Ionic conductivity in gem-quality single-crystal alkali feldspar from the Eifel: temperature, orientation and composition dependence

    NASA Astrophysics Data System (ADS)

    El Maanaoui, Hamid; Wilangowski, Fabian; Maheshwari, Aditya; Wiemhöfer, Hans-Dieter; Abart, Rainer; Stolwijk, Nicolaas A.

    2016-05-01

    We measured the ion conductivity of single-crystal alkali feldspar originating from two different locations in the Eifel/Germany, named Volkesfeld and Rockeskyller sanidine and having potassium site fractions C_K of 0.83 and 0.71, respectively. The dc conductivities resulting from electrochemical impedance spectroscopy over the temperature range of 300-900°C show a weak composition dependence but pronounced differences between the b-direction [perp (010)] and c^{*}-direction [perp (001)] of the monoclinic feldspar structure. Conductivity activation energies obtained from the observed linear Arrhenius plots are close to 1.2 eV in all cases, which is closely similar to the activation energies of the ^{22}Na tracer diffusivity in the same crystals. Taking into account literature data on K tracer diffusion and diffusion correlation effects, the present results point to a predominance of the interstitialcy mechanism over the vacancy mechanism in mass and charge transport on the alkali sublattice in potassium-rich alkali feldspar.

  5. Orientation relationships of copper crystals on sapphire (1 0 1¯ 0) m-plane and (1 0 1¯ 2) r-plane substrates

    NASA Astrophysics Data System (ADS)

    Chatain, Dominique; Curiotto, Stefano; Wynblatt, Paul; Meltzman, Hila; Kaplan, Wayne D.; Rohrer, Gregory S.

    2015-05-01

    Copper films deposited on m- and r-plane sapphire substrates have been dewetted in either the solid or the liquid state, and equilibrated at 1253 K. The orientation relationships (ORs) between the dewetted copper crystals and the sapphire substrates have been investigated by electron backscatter diffraction. In addition, the shape of the copper/sapphire interface has been studied by scanning electron microscopy. Although the as-deposited films develop {1 1 1} surfaces parallel to both substrates, after solid state dewetting the copper crystals on the m-plane substrate are found to change their interface plane from Cu{1 1 1}||Al2O3(m-plane) to Cu{1 1 1}|| Al2O3 (a-plane), and after liquid state dewetting the preferred OR of copper on both m- and r-plane substrates may be expressed as: Cu{1 1 1}<1 1 0> || Al2O3 {1 1 2bar 0}<0 0 0 1>. This OR is identical to that previously observed for copper on the sapphire a-plane.

  6. Optical characteristics of C{sub 60} single crystals grown in microgravity conditions

    SciTech Connect

    Steinman, E.A.; Avdeev, S.V.; Efimov, V.B.

    2000-05-01

    This work is devoted to the growing and characterization of perfect C{sub 60} single crystals with the aim of further understanding of the physical properties of this material related to the low energy excited states which determine in a considerable degree its electronic properties, which, in turn, are important for its possible application. Here the authors present several characterization techniques based on optical properties of C{sub 60} crystals and the first results of the investigation of the C{sub 60} samples grown at the orbital space station MIR.

  7. Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

    NASA Astrophysics Data System (ADS)

    Vdovichenko, G. A.; Krivchikov, A. I.; Korolyuk, O. A.; Tamarit, J. Ll.; Pardo, L. C.; Rovira-Esteva, M.; Bermejo, F. J.; Hassaine, M.; Ramos, M. A.

    2015-08-01

    The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl2F-CClF2, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl2F-CCl2F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range.

  8. Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

    SciTech Connect

    Vdovichenko, G. A.; Krivchikov, A. I.; Korolyuk, O. A.; Tamarit, J. Ll. Pardo, L. C.; Rovira-Esteva, M.; Bermejo, F. J.; Hassaine, M.; Ramos, M. A.

    2015-08-28

    The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl{sub 2}F–CClF{sub 2}, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl{sub 2}F–CCl{sub 2}F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range.

  9. Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom.

    PubMed

    Vdovichenko, G A; Krivchikov, A I; Korolyuk, O A; Tamarit, J Ll; Pardo, L C; Rovira-Esteva, M; Bermejo, F J; Hassaine, M; Ramos, M A

    2015-08-28

    The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl2F-CClF2, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl2F-CCl2F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range. PMID:26328859

  10. One-dimensional photonic crystals with a planar oriented nematic layer: Temperature and angular dependence of the spectra of defect modes

    SciTech Connect

    Arkhipkin, V. G. Gunyakov, V. A.; Myslivets, S. A.; Gerasimov, V. P.; Zyryanov, V. Ya.; Vetrov, S. Ya.; Shabanov, V. F.

    2008-02-15

    Transmission spectra of a one-dimensional photonic crystal (PC) formed by two multilayer dielectric mirrors and a planar oriented layer of 5CB nematic liquid crystal (LC) that is sandwiched between these mirrors and serves as a structure defect are investigated experimentally. Specific features of the behavior of the spectrum of defect modes as a function of the angle of incidence of light on the crystal are studied for two polarizations: parallel and perpendicular to the director of the LC; the director either lies in the plane of incidence or is perpendicular to it. It is shown that, for the configurations considered, the maxima of the defect modes shift toward the short-wavelength region as the tilt angle of incidence radiation increases; this tendency is more manifest for the parallel-polarized component, when the director lies in the plane of incidence. In the latter case, the width of the photonic band gap (PBG) appreciably decreases. The temperature dependence of the polarization components of the transmission spectra of a PC is investigated in the case of normal incidence of light. The spectral shift of defect modes due to the variation of the refractive index of the LC at the nematic-isotropic liquid phase transition point is measured. It is shown that, in real PCs, the amplitude of defect modes decreases when approaching the center of the band gap, as well as when the number of layers in the dielectric mirrors increases. Theoretical transmission spectra of the PCs calculated by the method of recurrence relations with regard to the decay of defect modes are in good agreement with experimental data.

  11. One-dimensional photonic crystals with a planar oriented nematic layer: Temperature and angular dependence of the spectra of defect modes

    NASA Astrophysics Data System (ADS)

    Arkhipkin, V. G.; Gunyakov, V. A.; Myslivets, S. A.; Gerasimov, V. P.; Zyryanov, V. Ya.; Vetrov, S. Ya.; Shabanov, V. F.

    2008-02-01

    Transmission spectra of a one-dimensional photonic crystal (PC) formed by two multilayer dielectric mirrors and a planar oriented layer of 5CB nematic liquid crystal (LC) that is sandwiched between these mirrors and serves as a structure defect are investigated experimentally. Specific features of the behavior of the spectrum of defect modes as a function of the angle of incidence of light on the crystal are studied for two polarizations: parallel and perpendicular to the director of the LC; the director either lies in the plane of incidence or is perpendicular to it. It is shown that, for the configurations considered, the maxima of the defect modes shift toward the short-wavelength region as the tilt angle of incidence radiation increases; this tendency is more manifest for the parallel-polarized component, when the director lies in the plane of incidence. In the latter case, the width of the photonic band gap (PBG) appreciably decreases. The temperature dependence of the polarization components of the transmission spectra of a PC is investigated in the case of normal incidence of light. The spectral shift of defect modes due to the variation of the refractive index of the LC at the nematic-isotropic liquid phase transition point is measured. It is shown that, in real PCs, the amplitude of defect modes decreases when approaching the center of the band gap, as well as when the number of layers in the dielectric mirrors increases. Theoretical transmission spectra of the PCs calculated by the method of recurrence relations with regard to the decay of defect modes are in good agreement with experimental data.

  12. Characteristics of Heavy Snowfall and Snow Crystal Habits in the ESSAY (Experiment on Snow Storms At Yeongdong) Campaign in Korea

    NASA Astrophysics Data System (ADS)

    Seong, D. K.; Seok, S. W.; Eun, S. H.; Kim, B. G.; Reum, K. A.; Lee, K. M.; Jeon, H. R.; Byoung Choel, C.; Park, Y. S.

    2015-12-01

    Characteristics of heavy snowfall and snow crystal habits have been investigated in the campaign of Experiment on Snow Storms At Yeongdong (ESSAY) using radiosonde soundings, Global Navigation Satellite System (GNSS), and a digital camera with a magnifier for taking a photograph of snowfall crystals. The analysis period is mainly both winters of 2014 and 2015. The synoptic situations are similar to those of the previous studies such as the Low pressure system passing by the far South of the Korean peninsula along with the Siberian High extending to northern Japan, which eventually results in the northeasterly or easterly flows and the long-lasting snowfall episodes in the Yeongdong region. The snow crystal habits observed in the ESSAY campaign were mainly dendrite, consisting of 70% of the entire habits. The rimed habits were frequently captured when two-layered clouds were observed, probably through the process of freezing of super-cooled droplets on the ice particles. The homogeneous habit such as dendrite was shown in case of shallow clouds with its thickness of below 500 m whereas various habits were captured such as graupel, dendrites, rimed dendrites, aggregates of dendrites, plates, rimed plates, etc in the thick cloud with its thickness greater than 1.5 km. The dendrites appeared to be dominant in the condition of cloud top temperature specifically ranging -12~-16℃. Interestingly temporal evolutions of snow crystal habits were consistently shown for several snowfall events such as changes from rimed particles to dendrites(or aggregated dendrites). The association of snow crystal habits with temperature and super-saturation in the cloud will be in detail examined. However, better understandings of characteristics of snow crystal habits would contribute to preventing breakdown accidents such as a greenhouse destruction and collapse of a temporary building due to heavy snowfall, and traffic accidents due to snow-slippery road condition, providing a higher

  13. Crystal Systems.

    ERIC Educational Resources Information Center

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  14. Optical characteristics of ZnO single crystal grown by the hydrothermal method

    NASA Astrophysics Data System (ADS)

    Chen, G. Z.; Yin, J. G.; Zhang, L. H.; Zhang, P. X.; Wang, X. Y.; Liu, Y. C.; Zhang, C. L.; Gu, S. L.; Hang, Y.

    2015-12-01

    ZnO single crystals have been grown by the hydrothermal method. Raman scattering and Photoluminescence spectroscopy (PL) have been used to study samples of ZnO that were unannealed or annealed in different ambient gases. It is suggested that the green emission may originate from defects related to copper in our samples.

  15. Optical characteristics of ZnO single crystal grown by the hydrothermal method

    SciTech Connect

    Chen, G. Z.; Yin, J. G. E-mail: yjg@siom.ac.cn; Zhang, L. H.; Zhang, P. X.; Wang, X. Y.; Liu, Y. C.; Zhang, C. L.; Gu, S. L.; Hang, Y.

    2015-12-15

    ZnO single crystals have been grown by the hydrothermal method. Raman scattering and Photoluminescence spectroscopy (PL) have been used to study samples of ZnO that were unannealed or annealed in different ambient gases. It is suggested that the green emission may originate from defects related to copper in our samples.

  16. Physical characteristics of Medicago truncatula calcium oxalate crystals determine their effectiveness in insect defense

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant structural traits can act as defense against herbivorous insects, causing them to avoid feeding on a given plant or tissue. Mineral crystals of calcium oxalate in leaves of Medicago truncatula Gaertn. have previously been shown to be effective deterrents of lepidopteran insect feeding. They ar...

  17. The High Mosaicity Illusion: Revealing the True Physical Characteristics of Macromolecular Crystals

    NASA Technical Reports Server (NTRS)

    Bellamy, Henry; Snell, Edward H.; Borgstahl, Gloria

    2000-01-01

    An experimental system and software have been developed for simultaneously measuring the diffraction resolution and mosaic spread of macromolecular crystals. Hundreds of reflection profiles over a wide resolution range were rapidly measured by using a charge coupled device (CCD) area detector in combination with superfine phi slicing data collection. The contributions of the X-ray beam to the reflection widths were minimized by using a highly-parallel, highly-monochromatic synchrotron source. These contributions and Lorentz effects were evaluated and deconvoluted from the recorded data. Data collection and processing is described. From one degree of superfine phi slice data collected on a crystal of manganese superoxide dismutase the mosaicity of 261 reflections were measured. The average mosaicity was 0.0101 degrees (0.0035) at the full-width-at-half-maximum (FWHM) and ranged from 0.0011 degrees to 0.0188 degrees. Each reflection profile was individually fit with two gaussian profiles with the first gaussian contributing 55% and the second contributing 35% of the reflection. On average, the mosaicity of the first gaussian was 0.0054 degrees (0.0015) and the second was 0.0061 degrees (0.0023). The mosaicity of the crystal was anisotropic with fh, f k, and fl values of 0.0068 degrees, 0.0140 degrees and 0.0046 degrees, respectively at the FWHM. The anisotropic mosaicity analysis indicates that the crystal is the most perfect in the I direction which corresponds to the favored growth direction of the crystal.

  18. Influence of the thickness of a crystal on the electrical characteristics of Cd(Zn)Te detectors

    SciTech Connect

    Sklyarchuk, V.; Fochuk, p.; Rarenko, I.; Zakharuk, Z.; Sklyarchuk, O. F.; Bolotnikov, A. E.; James, R. B.

    2015-08-01

    We studied the electrical characteristics of Cd(Zn)Te detectors with rectifying contacts and varying thicknesses, and established that their geometrical dimensions affect the measured electrical properties. We found that the maximum value of the operating-bias voltage and the electric field in the detector for acceptable values of the dark current can be achieved when the crystal has an optimum thickness. This finding is due to the combined effect of generation-recombination in the space-charge region and space-charge limited currents (SCLC).

  19. Improvement of the characteristics of ZnSe single-crystal semiconductor lasers pumped longitudinally by an electron beam

    SciTech Connect

    Akimova, I.V.; Dudenkova, A.V.; Kozlovskii, V.I.; Korostelin, Y.V.; Nasibov, A.S.; Reznikov, P.V.; Tishina, E.M.; Shapkin, P.V.

    1982-10-01

    The cathodoluminescence spectrum of ZnSe single crystals grown from the vapor and liquid phases was investigated in the range 400--800 nm and the internal quantum efficiency eta was measured at T = 77 /sup 0/K. A correlation was found between eta and the free-electron line intensity, but there was no correlation between eta and other luminescence lines. A comparison of the photoluminescence spectra recorded at 4.2 /sup 0/K for zinc selenide samples annealed in zinc and selenium with the spectra of the original samples indicated that the saturation with zinc during annealing increased eta and improved the laser characteristics.

  20. The grinding tip of the sea urchin tooth exhibits exquisite control over calcite crystal orientation and Mg distribution.

    PubMed

    Ma, Yurong; Aichmayer, Barbara; Paris, Oskar; Fratzl, Peter; Meibom, Anders; Metzler, Rebecca A; Politi, Yael; Addadi, Lia; Gilbert, P U P A; Weiner, Steve

    2009-04-14

    The sea urchin tooth is a remarkable grinding tool. Even though the tooth is composed almost entirely of calcite, it is used to grind holes into a rocky substrate itself often composed of calcite. Here, we use 3 complementary high-resolution tools to probe aspects of the structure of the grinding tip: X-ray photoelectron emission spectromicroscopy (X-PEEM), X-ray microdiffraction, and NanoSIMS. We confirm that the needles and plates are aligned and show here that even the high Mg polycrystalline matrix constituents are aligned with the other 2 structural elements when imaged at 20-nm resolution. Furthermore, we show that the entire tooth is composed of 2 cooriented polycrystalline blocks that differ in their orientations by only a few degrees. A unique feature of the grinding tip is that the structural elements from each coaligned block interdigitate. This interdigitation may influence the fracture process by creating a corrugated grinding surface. We also show that the overall Mg content of the tooth structural elements increases toward the grinding tip. This probably contributes to the increasing hardness of the tooth from the periphery to the tip. Clearly the formation of the tooth, and the tooth tip in particular, is amazingly well controlled. The improved understanding of these structural features could lead to the design of better mechanical grinding and cutting tools. PMID:19332795

  1. The grinding tip of the sea urchin tooth exhibits exquisite control over calcite crystal orientation and Mg distribution

    PubMed Central

    Ma, Yurong; Aichmayer, Barbara; Paris, Oskar; Fratzl, Peter; Meibom, Anders; Metzler, Rebecca A.; Politi, Yael; Addadi, Lia; Gilbert, P. U. P. A.; Weiner, Steve

    2009-01-01

    The sea urchin tooth is a remarkable grinding tool. Even though the tooth is composed almost entirely of calcite, it is used to grind holes into a rocky substrate itself often composed of calcite. Here, we use 3 complementary high-resolution tools to probe aspects of the structure of the grinding tip: X-ray photoelectron emission spectromicroscopy (X-PEEM), X-ray microdiffraction, and NanoSIMS. We confirm that the needles and plates are aligned and show here that even the high Mg polycrystalline matrix constituents are aligned with the other 2 structural elements when imaged at 20-nm resolution. Furthermore, we show that the entire tooth is composed of 2 cooriented polycrystalline blocks that differ in their orientations by only a few degrees. A unique feature of the grinding tip is that the structural elements from each coaligned block interdigitate. This interdigitation may influence the fracture process by creating a corrugated grinding surface. We also show that the overall Mg content of the tooth structural elements increases toward the grinding tip. This probably contributes to the increasing hardness of the tooth from the periphery to the tip. Clearly the formation of the tooth, and the tooth tip in particular, is amazingly well controlled. The improved understanding of these structural features could lead to the design of better mechanical grinding and cutting tools. PMID:19332795

  2. The molecular characteristics of a human pancreatic acidic phosphoprotein that inhibits calcium carbonate crystal growth.

    PubMed Central

    De Caro, A; Multigner, L; Lafont, H; Lombardo, D; Sarles, H

    1984-01-01

    A CaCO3-crystal-growth inhibitor was isolated from human pancreatic stones by using EDTA demineralization, followed by DEAE-Trisacryl chromatography. The isolated inhibitor was found to be a phosphoglycoprotein with Mr 14017 and having an unusual chemical composition. It is characterized by a high (42%) acidic amino acid content, but lacks methionine and gamma-carboxyglutamic acid. The protein contains 2.65 mol of P/mol of protein, as phosphoserine (2 mol) and phosphothreonine (0.5 mol). Isoelectric focusing of the protein yields one major band corresponding to an isoelectric point of 4.2. Immunochemical quantification of the crystal-growth inhibitor in pure pancreatic juice reveals that it constitutes 14% of the normal exocrine secretion. Our findings demonstrate that this is a novel secretory protein, which has no enzymic activity and which maintains pancreatic juice in a supersaturated state with respect to CaCO3. Images Fig. 3. Fig. 4. PMID:6487269

  3. Self-Efficacy, Self-Regulation, and Goal Orientation: Learner Motivational Characteristics That Influence Online Student Performance

    ERIC Educational Resources Information Center

    Wintling, Cheral Ann

    2012-01-01

    Learner motivational constructs of self-efficacy, self-regulation, and goal orientation in predicting successful student performance in online courses were explored. Thirty-three undergraduate students from the online courses Introduction to Educational Technology and Introduction to Education completed sections of the Motivated Strategies for…

  4. Rupture Orientation and Strain-induced Crystallization of Polymer Chain and Network in Vulcanized Polyisoprene During Uniaxial Deformation by in-situ Electron Spin Resonance(ESR) and Synchrotron X-ray Analysis

    SciTech Connect

    S Toki; R Takagi; M Ito; B Hsiao

    2011-12-31

    Different network structures of vulcanized polyisoprene rubbers were studied by in-situ ESR and synchrotron X-ray during deformation to analyze the rupture, orientation, and strain-induced crystallization of polymer chains and network points. Rupture of network points occur, depending on network structure, and create an un-reversible change in vulcanized rubber. The flexibility of network points affects the possibility of rupture, polymer orientation and strain-induced crystallization. Peroxide vulcanized network is rigid and un-rupturable. Poly-sulfide rich vulcanized network is more flexible and less rupturable than mono-sulfide rich vulcanized network. Chain flexibility and rupturability of network points affect the strain-induced crystallization and stress-strain relation.

  5. Flow Characteristics of a Liquid Crystal Mixture in a Circular Pipe Electrode

    NASA Astrophysics Data System (ADS)

    Tsukiji, Tetsuhiro; Koyabu, Eitaro

    A circular pipe electrode was developed to control the pressure and the flow rate of the ER(Electro-rheological) fluids by one of the authors. The shape of the electrode is a circular pipe and some parts of the inner surface of the pipe are the electrode. The diameter of the tube is 1mm and the four pairs of the electrode are used. In the present study a liquid crystal mixture is selected for a homogeneous ER fluid and the pressure drop of the circular pipe electrode is measured for the constant flow rates under application of the voltages. The voltages are added in the peripheral direction. The director which is the average direction of the molecular of the liquid crystal is perpendicular to the flow direction. On the other hands, numerical analysis of the electric fields and the flow in the circular pipe electrode is conducted and the relations between the flow rate and the pressure are obtained for various electric field intensities, which almost agree with experimental results. The emphasized point of the present flow analysis is assuming that the viscosity of a liquid crystal mixture distributes in the flow field. Furthermore the pulse-wave voltages are added to the electrodes to control the pressure drop using the pulse width modulation. It is found that the pressure can be controlled using the pulse width modulation in the some range of the parameters.

  6. Thermoluminescence characteristics of Li2B4O7 single crystal dosimeters doped with Mn

    NASA Astrophysics Data System (ADS)

    Ekdal, E.; Karalı, T.; Kelemen, A.; Ignatovych, M.; Holovey, V.; Harmansah, C.

    2014-03-01

    In this study, thermoluminescence (TL) characterization of newly developed Li2B4O7:Mn single crystal phosphor is reported. It is a very attractive material in personal dosimetry because of its near tissue equivalency (Zeff=7.25). The crystal was grown by the Czochralski method from high purity compounds. Glow curve, dose response, and fading and reproducibility properties of this material were investigated. Its TL glow curve showed two well separated peaks at about 105 and 220 °C with a heating rate of 2 °C s-1. The main peak at 220 °C has a linear dose response of up to 60 Gy. The thermal fading ratio of the material is about 8% for the main peak in 10 days. The results showed that there is no significant variation of TL responses for 15 sequential measurements. Apart from the dosimetric properties above, the TL kinetic parameters of the main peak at 220 °C of Li2B4O7:Mn single crystal phosphor were also calculated using the various heating rates method. Activation energy and frequency factor were found as 1.21 eV and 3.75×1011 s-1, respectively.

  7. Laser characteristics of TGT-grown Nd,Y-codoped:SrF2 single crystal

    NASA Astrophysics Data System (ADS)

    Jelínek, Michal; Kubeček, Václav; Su, Liangbi; Jiang, Dapeng; Ma, Fengkai; Zhang, Qian; Cao, Yuexin; Xu, Jun

    2014-05-01

    In this contribution we present spectroscopic and laser properties of TGT (temperature gradient technique) grown Nd,Y:SrF2 crystals with neodymium concentration of 0.4, 0.65 and 0.8 at.%. The absorption cross-section, fluorescence spectra and fluorescence decay time were measured. For the laser experiments, the noncoated crystal samples 3.5 or 5 mm thick were pumped by a 796 nm laser diode matching the Nd:SrF2 absorption peak. Several output couplers with reflectivity ranging from 70 to 98 % at the generated wavelength were tested. In the pulsed pumping regime (pulseduration 2 ms, frequency 10 Hz), the maximum average output power of 75 mW was obtained with the slope efficiency as high as 48 % and the optical-to-optical efficiency of 42 % with respect to the absorbed pump power. The output beam spatial profile was nearly Gaussian in both axes, oscillations started at the wavelength of 1057 nm. At higher pumping levels, the second emission line at 1050 nm appears corresponding to our fluorescence measurements. Wavelength tuning using birefringent filter from 1048 to 1070 nm is probably given by crystal-field splitting of the 4F3/2 manifold in Nd3+. True-CW laser operation was also successfully obtained at lower pumping level with the maximum output power of 90 mW using output coupler reflectivity of 98 %.

  8. Effect of electric field and temperature gradient on the orientational dynamics of liquid crystals in a microvolume cylindrical cavity

    NASA Astrophysics Data System (ADS)

    Zakharov, A. V.; Vakulenko, A. A.; Romano, Silvano

    2009-10-01

    We have considered a homogeneously aligned liquid crystal (HALC) microvolume confined between two infinitely long horizontal coaxial cylinders and investigated dynamic field pumping, i.e., studied the interactions between director, velocity, and electric E fields as well as a radially applied temperature gradient ∇T, where the inner cylinder is kept at a lower temperature than the outer one. In order to elucidate the role of ∇T in producing hydrodynamic flow u, we have carried out a numerical study of a system of hydrodynamic equations including director reorientation, fluid flow, and temperature redistribution across the HALC cavity. Calculations show that only under the influence of ∇T does the initially quiescent HALC sample settle down to a stationary flow regime with horizontal component of velocity ueq(r). The effects of ∇T and of the size of the HALC cavity on magnitude and direction of ueq(r) have been investigated for a number of hydrodynamic regimes. Calculations also showed that E influences only the director redistribution across the HALC but not the magnitude of the velocity ueq(r).

  9. Planar scanning method for detecting refraction characteristics of two-dimensional photonic quasi-crystal wedge-shaped prisms.

    PubMed

    Liu, Jianjun; Tan, Wei; Liu, Exian; Hu, Haili; Fan, Zhigang; Zhang, Tianhua; Zhang, Xiong

    2016-05-01

    In this study, a planar scanning method is proposed. This novel method adapts two monitors moving along double planar tracks that can be used to detect refraction characteristics of two-dimensional (2D) photonic quasi-crystal (PQC) wedge-shaped prisms. Refraction of a decagonal Penrose-type PQC prism is analyzed for a given incident beam and two polarization modes at different incident positions in the prism using this method. Refraction from the prism is irregular, indicating that nonuniformity in the arrangement of scatterers in the prism causes Bragg-like scattering irregularities. Numerical results show that this method can be used for guiding the design of a 2D PQC prism and for the analysis of its refraction characteristics. PMID:27140896

  10. Effect of surface anchoring energy on electro-optic characteristics of a fringe-field switching liquid crystal cell

    NASA Astrophysics Data System (ADS)

    Kim, Jin Hyun; Kang, Wan Seok; Sol Choi, Han; Park, Kiwoong; Lee, Joong Hee; Yoon, Sangho; Yoon, Sukin; Lee, Gi-Dong; Lee, Seung Hee

    2015-11-01

    Surface anchoring strength of the alignment layer on liquid crystal (LC) determines electro-optic characteristics in the LC devices. This paper investigates how azimuthal and polar anchoring strength affects the electro-optic performance of a fringe-field switching (FFS) mode associated with electrode structure, cell gap and dielectric anisotropy of the LC by numerical simulation. Our important findings in the FFS mode are that both azimuthal and polar anchoring energy can considerably affect the operating voltage and also maximum transmittance when using a LC with positive dielectric anisotropy; however, when using a LC with negative dielectric anisotropy only azimuthal anchoring energy affects electro-optic characteristics. The study proposes an optimal design of an alignment layer for maximizing transmittance in the FFS mode.

  11. Effect of dispersed CdSe/ZnS quantum dots on optical and electrical characteristics of nematic liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Konshina, E. A.; Gavrish, E. O.; Orlova, A. O.; Artem'ev, M. V.

    2011-11-01

    We have studied the electrical and optical characteristics of cells filled with nematic liquid crystal (NLC) based on cyanobiphenyls with positive dielectric anisotropy, containing dispersed 3.5-nm-sized CdSe/ZnS composite semiconductor nanoparticles (quantum dots, QDs) with a concentration of 0.1-0.2 wt %. In addition to a decrease in the threshold voltage of the electrooptical splay effect, the doping with QDs leads also to a decrease in the phase delay of light and the effective dielectric permittivity of NLC cells. These characteristics are reduced by half during the storage of NLC cells containing about 0.2 wt % QDs, which is related to the self-organization of QDs.

  12. Orientation Dependence of Functional Properties in Heterophase Single Crystals of the Ti36.5Ni51.0Hf12.5 and Ti48.5Ni51.5 Alloys

    NASA Astrophysics Data System (ADS)

    Panchenko, E. Yu.; Chumlyakov, Yu. I.; Surikov, N. Yu.; Tagiltsev, A. I.; Vetoshkina, N. G.; Osipovich, K. S.; Maier, H.; Sehitoglu, H.

    2016-03-01

    The features of orientation dependence of stress-induced thermoelastic B2-( R)- B19'-martensitic transformations in single crystals of the Ti48.5Ni51.5 and Ni51.0Ti36.5Hf12.5 (at.%) alloys, which contain disperse particles of the Ti3Ni4 and H-phase, respectively, are revealed along with those of their shape-memory effects (SME) and superelasticity (SE). It is experimentally demonstrated that irrespective of the crystal structure of disperse particles measuring more than 100 nm, for their volume fraction f > 16% there is a weaker orientation dependence of the reversible strain in the cases of manifestation of SME and SE. In the orientations of Class I, wherein martensitic detwinning introduces a considerable contribution into transformation strain, the values of SME |ɛ SME | and SE |ɛ SE | decrease by over a factor of two compared to the theoretical lattice strain value |ɛ tr0 | for a B2- B19'-transformation and the experimental values of reversible strain for quenched TiNi crystals. In the orientations of Class 2, wherein detwinning of the martensite is suppressed as is the case in quenched single-phase single crystals, the reversible strain is maintained close to its theoretical value |ɛ tr0 |. Micromechanical models of interaction between the martensite and the disperse particles are proposed, which account for the weaker orientation dependence of |ɛ SME | and |ɛ SE | due to suppression of detwinning of the B19'-martensite crystals by the particles and a transition from a single-variant evolution of the stress-induced martensitic transformations to a multiple-variant evolution of transformations in the cases of increased size of the particles and their larger volume fractions.

  13. Crystal synthesis and effects of epitaxial perovskite manganite underlayer conditions on characteristics of ZnO nanostructured heterostructures

    NASA Astrophysics Data System (ADS)

    Liang, Yuan-Chang; Hu, Chia-Yen; Zhong, Hua; Wang, Jyh-Liang

    2013-02-01

    This study presents the synthesis of high-density aligned wurtzite ZnO nanostructures using thermal evaporation on perovskite (La,Sr)MnO3(LSMO) epitaxy to form a heterostructure without the assistance of metallic catalysis. LSMO epitaxial films are RF-sputtered with various crystal qualities to examine the correlation between the interface and electrical characteristics of the heterostructures. The ZnO nanostructures-LSMO epitaxial heterostructures show electrical rectifying behavior without inserting an ultrathin insulating layer at the hetero-interface. Misfit strain, intrinsic strain, and crystal defects are major factors in causing a phase separation in the as-prepared manganite LSMO epitaxial films. The coexistence of a charge-ordered insulating domain and a ferromagnetic metallic domain causes inhomogeneous electrical contact at the ZnO-LSMO heterointerfaces, further deteriorating the junction characteristics. A high-temperature annealing procedure and moderate LSMO epitaxy film thickness are required for the construction of an efficient ZnO nanostructures-LSMO epitaxy junction.

  14. Polarization-independent characteristics of the metasurfaces with the symmetrical axis’s orientation angle of 45° or 135°

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Guo, Zhongyi; Ran, Lingling; Sun, Yongxuan; Shen, Fei; Li, Yan; Mao, Xiaoqin; Wang, Benyang; Fan, Guanghua; Qu, Shiliang

    2016-03-01

    A series of symmetrical nanoantennas with a symmetrical axis orientation angle of 45° or 135°, which are suitable for both X/Y linear and circular polarizations incidences simultaneously, have been designed and investigated in detail. We have deduced the transmitted matrix of the metasurface structure by rigorous mathematical theory, and found that the essential reason for the polarization-independence characteristics is that there are the same transmitted amplitudes and phases under the incidences of X/Y linear and circular polarization lights due to metasurface structure with the symmetrical axis’s orientation angles of 45° or 135°. Based on the V-shaped, C-shaped, U-shaped and elliptical slit nanoantennas, we have verified the proposed theory fully by numerical simulations. The independence of the incident polarizations is very important for the practical applications and developments of the metasurfaces.

  15. Magnetoresistance characteristics in individual Fe{sub 3}O{sub 4} single crystal nanowire

    SciTech Connect

    Reddy, K. M. Punnoose, Alex; Hanna, Charles; Padture, Nitin P.

    2015-05-07

    We report on the magnetoresistance (MR) and electron transport measurements observed on a single crystal magnetite nanowire prepared using a hydrothermal synthesis method. High-resolution electron microscopy revealed the single crystal magnetite nanowires with 80–120 nm thickness and up to 8 μm in length. Magnetic measurements showed the typical Verwey transition around 120 K with a 100 Oe room temperature coercivity and 45 emu/g saturation magnetization, which are comparable to bulk magnetite. Electrical resistance measurements in 5–300 K temperature range were performed by scanning gate voltage and varying applied magnetic field. Electrical resistivity of the nanowire was found to be around 5 × 10{sup −4} Ω m, slightly higher than the bulk and has activation energy of 0.07 eV. A negative MR of about 0.7% is observed for as-synthesized nanowires at 0.3 T applied field. MR scaled with increasing applied magnetic field representing the field-induced alignment of magnetic domain. These results are attributed to the spin-polarized electron transport across the antiphase boundaries, which implicate promising applications for nanowires in magnetoelectronics.

  16. High carrier mobility in orientation-controlled large-grain (≥50 μm) Ge directly formed on flexible plastic by nucleation-controlled gold-induced-crystallization

    NASA Astrophysics Data System (ADS)

    Park, Jong-Hyeok; Kasahara, Kenji; Hamaya, Kohei; Miyao, Masanobu; Sadoh, Taizoh

    2014-06-01

    High-carrier-mobility semiconductors on flexible-plastic are essential to realize flexible electronics. For this purpose, electrical properties of orientation-controlled large-grain Ge crystals on flexible-plastic directly formed by nucleation-controlled gold-induced-crystallization (GIC) are examined, and compared with those obtained by aluminum-induced-crystallization (AIC). The Ge crystals show p-type conductions. Here, hole concentrations are 2.2 × 1017 and 5.8 × 1020 cm-3 for GIC-Ge and AIC-Ge, respectively, which are explained on the basis of the solubility of Au and Al in Ge. Thanks to the low hole concentration, GIC-Ge shows high hole mobility (160 cm2 V-1 s-1) compared with AIC-Ge (37 cm2 V-1 s-1). These demonstrate significant advantage of GIC to realize high-performance flexible-electronics.

  17. Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage.

    PubMed

    Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X S

    2015-05-21

    Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a "platelet-on-sheet" LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (∼56 mA h g(-1) at 60 C) and long life cycling stability (∼87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (∼98% capacity retention over 1000 cycles at 10 C). PMID:25908535

  18. Temperature-dependent Raman study of ammonium perchlorate single crystals: The orientational dynamics of the NH + 4 ions and phase transitions

    NASA Astrophysics Data System (ADS)

    Chakraborty, T.; Khatri, S. S.; Verma, A. L.

    1986-06-01

    A detailed temperature-dependent study of the Raman spectra of oriented single crystals of NH4ClO4 is reported in the spectral regions of lattice modes and internal vibrations of the ClO-4 and NH+4 ions between 10 and 300 K. The internal modes of the ClO-4 ions show splitting into several components due to site and correlation field effects. The linewidth, frequency shift, and intensities of some of the internal modes of the ClO-4 and NH+4 ions and the frequency shift of a few lattice modes show anomalous temperature dependence around 180 and at 40 K. These anomalies have been explained in terms of phase transformations associated with the changes in hydrogen bonding strength and reorientational freedom of the NH+4 ions in the lattice. The low temperature transition at 40 K exhibits a sharp and discontinuous anomaly in some of the spectral parameters measured in this study which is associated with order-disorder-type transition. The measured linewidth of the ν'1 mode in the diagonal scattering configuration can be understood in terms of vibrational dephasing of the ν1 excited state due to vibrational-librational coupling. The estimated activation energies in the 50-160 K and 10-40 K temperature ranges are found to be 141 and 51 cm-1, respectively, which correspond to the observed NH+4 librational frequencies.

  19. Prediction of photonic crystal fiber characteristics by Neuro-Fuzzy system

    NASA Astrophysics Data System (ADS)

    Pourmahyabadi, M.; Mohammad Nejad, S.

    2009-10-01

    The most common methods applied in the analysis of photonic crystal fibers (PCFs) are finite difference time/frequency domain (FDTD/FDFD) method and finite element method (FEM). These methods are very general and reliable (well tested). They describe arbitrary structure but are numerically intensive and require detailed treatment of boundaries and complex definition of calculation mesh. So these conventional models that simulate the photonic response of PCFs are computationally expensive and time consuming. Therefore, a practical design process with trial and error cannot be done in a reasonable amount of time. In this article, an artificial intelligence method such as Neuro-Fuzzy system is used to establish a model that can predict the properties of PCFs. Simulation results show that this model is remarkably effective in predicting the properties of PCF such as dispersion, dispersion slope and loss over the C communication band.

  20. Temperature-independent strain sensing characteristics of coupled photonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Liu, Hai; Leng, Lemeng; Ma, Hanlin; Li, Lei; Zhang, Sheng; Cheng, Deqiang

    2016-05-01

    A highly sensitive strain sensor based on coupled two-dimensional (2D) photonic crystal waveguides consisting of dielectric rods array immersed in air is designed. The effective side-coupling between directional coupled waveguides and surrounding defect cavities gives flexibility in the choice of the sensing monitoring band. The coupling process and transmission spectral properties are analyzed by the finite difference time domain (FDTD) method. The influence of strain and temperature on the transmission spectrum is investigated by monitoring the wavelength shift in the loss peaks. The dual-channel sensing method is proposed to eliminate the cross sensitivity effect between the strain and ambient temperature, and render a new category of temperature-independent strain sensing devices.