WorldWideScience

Sample records for single ice crystal

  1. Angular correlation of annihilation photons in ice single crystals

    DEFF Research Database (Denmark)

    Mogensen, O. E.; Kvajic, G.; Eldrup, Morten Mostgaard

    1971-01-01

    -lattice vectors g⃗ on the direction perpendicular to the slits and the sample surface. The relative area of the central plus the side peaks was (15.2 ± 0.4)% for all curves. All the peaks are interpreted as due to parapositronium annihilation. The side peaks are explained as evidence for the positronium center......Linear-slit angular-correlation curves were obtained at - 148 °C for the [0001], [10¯10], and [11¯20] directions in single crystals of ice. Besides the narrow central peak, pronounced narrow side peaks were also observed. They occurred at angles θ=2πℏgz/mc, where gz is the projection of reciprocal...

  2. Single particle measurements of the chemical composition of cirrus ice residue during CRYSTAL-FACE

    Science.gov (United States)

    Cziczo, D. J.; Murphy, D. M.; Hudson, P. K.; Thomson, D. S.

    2004-02-01

    The first real-time, in situ, investigation of the chemical composition of the residue of cirrus ice crystals was performed during July 2002. This study was undertaken on a NASA WB-57F high-altitude research aircraft as part of CRYSTAL-FACE, a field campaign which sought to further our understanding of the relation of clouds, water vapor, and climate by characterizing, among other parameters, anvil cirrus formed about the Florida peninsula. A counter flow virtual impactor (CVI) was used to separate cirrus ice from the unactivated interstitial aerosol particles and evaporate condensed-phase water. Residual material, on a crystal-by-crystal basis, was subsequently analyzed using the NOAA Aeronomy Laboratory's Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Sampling was performed from 5 to 15 km altitude and from 12° to 28° north latitude within cirrus originating over land and ocean. Chemical composition measurements provided several important results. Sea salt was often incorporated into cirrus, consistent with homogeneous ice formation by aerosol particles from the marine boundary layer. Size measurements showed that large particles preferentially froze over smaller ones. Meteoritic material was found within ice crystals, indicative of a relation between stratospheric aerosol particles and tropospheric clouds. Mineral dust was the dominant residue observed in clouds formed during a dust transport event from the Sahara, consistent with a heterogeneous freezing mechanism. These results show that chemical composition and size are important determinants of which aerosol particles form cirrus ice crystals.

  3. On Spectral Invariance of Single Scattering Albedo for Water Droplets and Ice Crystals at Weakly Absorbing Wavelengths

    Science.gov (United States)

    Marshak, Alexander; Knyazikhin, Yuri; Chiu, J. Christine; Wiscombe, Warren J.

    2012-01-01

    The single scattering albedo omega(sub O lambda) in atmospheric radiative transfer is the ratio of the scattering coefficient to the extinction coefficient. For cloud water droplets both the scattering and absorption coefficients, thus the single scattering albedo, are functions of wavelength lambda and droplet size r. This note shows that for water droplets at weakly absorbing wavelengths, the ratio omega(sub O lambda)(r)/omega(sub O lambda)(r (sub O)) of two single scattering albedo spectra is a linear function of omega(sub O lambda)(r). The slope and intercept of the linear function are wavelength independent and sum to unity. This relationship allows for a representation of any single scattering albedo spectrum omega(sub O lambda)(r) via one known spectrum omega(sub O lambda)(r (sub O)). We provide a simple physical explanation of the discovered relationship. Similar linear relationships were found for the single scattering albedo spectra of non-spherical ice crystals.

  4. Single particle analysis of ice crystal residuals observed in orographic wave clouds over Scandinavia during INTACC experiment

    Directory of Open Access Journals (Sweden)

    A. C. Targino

    2006-01-01

    Full Text Available Individual ice crystal residual particles collected over Scandinavia during the INTACC (INTeraction of Aerosol and Cold Clouds experiment in October 1999 were analyzed by Scanning Electron Microscopy (SEM equipped with Energy-Dispersive X-ray Analysis (EDX. Samples were collected onboard the British Met Office Hercules C-130 aircraft using a Counterflow Virtual Impactor (CVI. This study is based on six samples collected in orographic clouds. The main aim of this study is to characterize cloud residual elemental composition in conditions affected by different airmasses. In total 609 particles larger than 0.1 μm diameter were analyzed and their elemental composition and morphology were determined. Thereafter a hierarchical cluster analysis was performed on the signal detected with SEM-EDX in order to identify the major particle classes and their abundance. A cluster containing mineral dust, represented by aluminosilicates, Fe-rich and Si-rich particles, was the dominating class of particles, accounting for about 57.5% of the particles analyzed, followed by low-Z particles, 23.3% (presumably organic material and sea salt (6.7%. Sulfur was detected often across all groups, indicating ageing and in-cloud processing of particles. A detailed inspection of samples individually unveiled a relationship between ice crystal residual composition and airmass origin. Cloud residual samples from clean airmasses (that is, trajectories confined to the Atlantic and Arctic Oceans and/or with source altitude in the free troposphere were dominated primarily by low-Z and sea salt particles, while continentally-influenced airmasses (with trajectories that originated or traveled over continental areas and with source altitude in the continental boundary layer contained mainly mineral dust residuals. Comparison of residual composition for similar cloud ambient temperatures around –27°C revealed that supercooled clouds are more likely to persist in conditions where

  5. Fundamental Ice Crystal Accretion Physics Studies

    Science.gov (United States)

    Struk, Peter M.; Broeren, Andy P.; Tsao, Jen-Ching; Vargas, Mario; Wright, William B.; Currie, Tom; Knezevici, Danny; Fuleki, Dan

    2012-01-01

    Due to numerous engine power-loss events associated with high-altitude convective weather, ice accretion within an engine due to ice crystal ingestion is being investigated. The National Aeronautics and Space Administration (NASA) and the National Research Council (NRC) of Canada are starting to examine the physical mechanisms of ice accretion on surfaces exposed to ice-crystal and mixed-phase conditions. In November 2010, two weeks of testing occurred at the NRC Research Altitude Facility utilizing a single wedge-type airfoil designed to facilitate fundamental studies while retaining critical features of a compressor stator blade or guide vane. The airfoil was placed in the NRC cascade wind tunnel for both aerodynamic and icing tests. Aerodynamic testing showed excellent agreement compared with CFD data on the icing pressure surface and allowed calculation of heat transfer coefficients at various airfoil locations. Icing tests were performed at Mach numbers of 0.2 to 0.3, total pressures from 93 to 45 kPa, and total temperatures from 5 to 15 C. Ice and liquid water contents ranged up to 20 and 3 g/m3, respectively. The ice appeared well adhered to the surface in the lowest pressure tests (45 kPa) and, in a particular case, showed continuous leading-edge ice growth to a thickness greater than 15 mm in 3 min. Such widespread deposits were not observed in the highest pressure tests, where the accretions were limited to a small area around the leading edge. The suction surface was typically ice-free in the tests at high pressure, but not at low pressure. The icing behavior at high and low pressure appeared to be correlated with the wet-bulb temperature, which was estimated to be above 0 C in tests at 93 kPa and below 0 C in tests at lower pressure, the latter enhanced by more evaporative cooling of water. The authors believe that the large ice accretions observed in the low pressure tests would undoubtedly cause the aerodynamic performance of a compressor component

  6. Eulerian method for ice crystal icing in turbofan engines

    NARCIS (Netherlands)

    Norde, Ellen

    2017-01-01

    The newer generations of high-bypass-ratio engines are susceptible to the ingestion of small ice crystals which may cause engine power loss or damage. The research presented in this thesis focusses on the development of a computational method for in-engine ice crystal accretion. The work has been

  7. Ice crystallization in water's "no-man's land".

    Science.gov (United States)

    Moore, Emily B; Molinero, Valeria

    2010-06-28

    The crystallization of water at 180 K is studied through large-scale molecular dynamics simulations with the monatomic water model mW. This temperature is in the middle of water's "no-man's land," where rapid ice crystallization prevents the elucidation of the structure of liquid water and its transformation into ice with state of the art experimental methods. We find that critical ice nuclei (that contain less than ten water molecules) form in a time scale shorter than the time required for the relaxation of the liquid, suggesting that supercooled liquid water cannot be properly equilibrated in this region. We distinguish three stages in the crystallization of water at 180 K: concurrent nucleation and growth of ice, followed by consolidation that decreases the number density of ice nuclei, and finally, slow growth of the crystallites without change in their number density. The kinetics of the transformation along the three stages is well described by a single compacted exponential Avrami equation with n approximately 1.7. This work confirms the coexistence of ice and liquid after water is crystallized in "no-man's land": the formation of ice plateaus when there is still 15%-20% of liquid water in the systems, thinly dispersed between ice I crystals with linear dimensions ranging from 3 to 10 nm. We speculate that the nanoscopic size of the crystallites decreases their melting point and slows their evolution toward the thermodynamically most stable fully crystalline state.

  8. Ice crystal precipitation at Dome C site (East Antarctica)

    Science.gov (United States)

    Santachiara, G.; Belosi, F.; Prodi, F.

    2016-01-01

    For the first time, falling ice crystals were collected on glass slides covered with a thin layer of 2% formvar in chloroform at the Dome Concordia site (Dome C), Antarctica. Samplings were performed in the framework of the 27th Italian Antarctica expedition of the Italian National Program for Research in Antarctica in the period 21 February-6 August 2012. Events of clear-sky precipitations and precipitations from clouds were considered and the replicas obtained were examined under Scanning Electron Microscope (SEM). Several shapes of ice crystals were identified, including ;diamond dust; (plates, pyramids, hollow and solid columns), and crystal aggregates varying in complexity. Single events often contained both small (10 μm to 50 μm) and large (hundreds of microns) crystals, suggesting that crystals can form simultaneously near the ground (height of a few hundred metres) and at higher layers (height of thousands of metres). Images of sampled crystal replicas showed that single bullets are not produced separately, but by the disintegration of combinations of bullets. Rimed ice crystals were absent in the Dome C samples, i.e. the only mode of crystal growth was water vapour diffusion. On considering the aerosol in the sampled crystals, we reached the conclusion that inertial impaction, interception and Brownian motion were insufficient to explain the scavenged aerosol. We therefore presume that phoretic forces play a role in scavenging during the crystal growth process.

  9. An ice crystal model for jupiter's moon Europa

    DEFF Research Database (Denmark)

    Dahl-Jensen, Dorthe; schmidt, Karen Guldbae

    2003-01-01

    A simple model for crystal growth in the ice shell of Europa has been made in order to estimate the size of ice crystals at Europa's surface. If mass is lost from the surface of Europa due to sputtering processes, and the ice thickness is constant in time, ice crystals will be transported upwards...

  10. Study on application of single-crystal ice `Kurobe ice column` to high-speed skating rinks. Demonstration test result at Olympic memorial arena `M wave` in Nagano city; Tankesshohyo `Kurobe no hyojun` no kosoku skate link eno tekiyosei kenkyu. Naganoshi olympic kinen arina `Emu Wave` deno jissho shiken kekka

    Energy Technology Data Exchange (ETDEWEB)

    Iwasaki, M. [Kansai Electric Power Co. Inc., Osaka (Japan)

    1999-06-10

    For high-speed low-friction skating rinks, research was made on sticking artificial ice columns (ice bamboo shoot). The ice columns were fabricated with the ice column production equipment equipped with 4-line water droplet dropping devices which were installed at intervals of 0.3m on both sides of a pathway of 200m long, 2.6m wide and 1.8m high in the lateral adit of Kurobegawa No.4 hydroelectric power station. The grown ice columns were processed for high-speed skating rinks through cutting, confirmation of single crystal and crystal orientation, slicing for every 7mm thickness and packaging. The ice columns were spread all over the rink while sliding them to prevent mixing of bubbles after spraying distilled water of nearly 25 degreesC onto base ices. In addition, hot water of nearly 40 degreesC was sprayed to produce the final ice rink of 30mm thick by nearly 5mm a day. The dynamic friction coefficient of the ice column rink reduced to 0.0038 by nearly 16% as compared with 0.0045 of conventional rinks. (NEDO)

  11. Impact of aerosols on ice crystal size

    Science.gov (United States)

    Zhao, Bin; Liou, Kuo-Nan; Gu, Yu; Jiang, Jonathan H.; Li, Qinbin; Fu, Rong; Huang, Lei; Liu, Xiaohong; Shi, Xiangjun; Su, Hui; He, Cenlin

    2018-01-01

    The interactions between aerosols and ice clouds represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. In particular, the impact of aerosols on ice crystal effective radius (Rei), which is a key parameter determining ice clouds' net radiative effect, is highly uncertain due to limited and conflicting observational evidence. Here we investigate the effects of aerosols on Rei under different meteorological conditions using 9-year satellite observations. We find that the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters. While there is a significant negative correlation between Rei and aerosol loading in moist conditions, consistent with the "Twomey effect" for liquid clouds, a strong positive correlation between the two occurs in dry conditions. Simulations based on a cloud parcel model suggest that water vapor modulates the relative importance of different ice nucleation modes, leading to the opposite aerosol impacts between moist and dry conditions. When ice clouds are decomposed into those generated from deep convection and formed in situ, the water vapor modulation remains in effect for both ice cloud types, although the sensitivities of Rei to aerosols differ noticeably between them due to distinct formation mechanisms. The water vapor modulation can largely explain the difference in the responses of Rei to aerosol loadings in various seasons. A proper representation of the water vapor modulation is essential for an accurate estimate of aerosol-cloud radiative forcing produced by ice clouds.

  12. Mesoscopic surface roughness of ice crystals pervasive across a wide range of ice crystal conditions

    Science.gov (United States)

    Magee, N. B.; Miller, A.; Amaral, M.; Cumiskey, A.

    2014-11-01

    Here we show high-magnification images of hexagonal ice crystals acquired by environmental scanning electron microscopy (ESEM). Most ice crystals were grown and sublimated in the water vapor environment of an FEI-Quanta-200 ESEM, but crystals grown in a laboratory diffusion chamber were also transferred intact and imaged via ESEM. All of these images display prominent mesoscopic topography including linear striations, ridges, islands, steps, peaks, pits, and crevasses; the roughness is not observed to be confined to prism facets. The observations represent the most highly magnified images of ice surfaces yet reported and expand the range of conditions in which rough surface features are known to be conspicuous. Microscale surface topography is seen to be ubiquitously present at temperatures ranging from -10 °C to -40 °C, in supersaturated and subsaturated conditions, on all crystal facets, and irrespective of substrate. Despite the constant presence of surface roughness, the patterns of roughness are observed to be dramatically different between growing and sublimating crystals, and transferred crystals also display qualitatively different patterns of roughness. Crystals are also demonstrated to sometimes exhibit inhibited growth in moderately supersaturated conditions following exposure to near-equilibrium conditions, a phenomenon interpreted as evidence of 2-D nucleation. New knowledge about the characteristics of these features could affect the fundamental understanding of ice surfaces and their physical parameterization in the context of satellite retrievals and cloud modeling. Links to supplemental videos of ice growth and sublimation are provided.

  13. Inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate.

    Science.gov (United States)

    Damodaran, Srinivasan

    2007-12-26

    The inhibition of ice crystal growth in ice cream mix by gelatin hydrolysate produced by papain action was studied. The ice crystal growth was monitored by thermal cycling between -14 and -12 degrees C at a rate of one cycle per 3 min. It is shown that the hydrolysate fraction containing peptides in the molecular weight range of about 2000-5000 Da exhibited the highest inhibitory activity on ice crystal growth in ice cream mix, whereas fractions containing peptides greater than 7000 Da did not inhibit ice crystal growth. The size distribution of gelatin peptides formed in the hydrolysate was influenced by the pH of hydrolysis. The optimum hydrolysis conditions for producing peptides with maximum ice crystal growth inhibitory activity was pH 7 at 37 degrees C for 10 min at a papain to gelatin ratio of 1:100. However, this may depend on the type and source of gelatin. The possible mechanism of ice crystal growth inhibition by peptides from gelatin is discussed. Molecular modeling of model gelatin peptides revealed that they form an oxygen triad plane at the C-terminus with oxygen-oxygen distances similar to those found in ice nuclei. Binding of this oxygen triad plane to the prism face of ice nuclei via hydrogen bonding appears to be the mechanism by which gelatin hydrolysate might be inhibiting ice crystal growth in ice cream mix.

  14. Factors Affecting the Changes of Ice Crystal Form in Ice Cream

    Science.gov (United States)

    Wang, Xin; Watanabe, Manabu; Suzuki, Toru

    In this study, the shape of ice crystals in ice cream was quantitatively evaluated by introducing fractal analysis. A small droplet of commercial ice cream mix was quickly cooled to about -30°C on the cold stage of microscope. Subsequently, it was heated to -5°C or -10°C and then held for various holding time. Based on the captured images at each holding time, the cross-sectional area and the length of circumference for each ice crystal were measured to calculate fractal dimension using image analysis software. The results showed that the ice crystals were categorized into two groups, e.g. simple-shape and complicated-shape, according to their fractal dimensions. The fractal dimension of ice crystals became lower with increasing holding time and holding temperature. It was also indicated that the growing rate of complicated-shape ice crystals was relatively higher because of aggregation.

  15. A Flexible Parameterization for Shortwave Optical Properties of Ice Crystals

    Science.gov (United States)

    VanDiedenhoven, Bastiaan; Ackerman, Andrew S.; Cairns, Brian; Fridlind, Ann M.

    2014-01-01

    A parameterization is presented that provides extinction cross section sigma (sub e), single-scattering albedo omega, and asymmetry parameter (g) of ice crystals for any combination of volume, projected area, aspect ratio, and crystal distortion at any wavelength in the shortwave. Similar to previous parameterizations, the scheme makes use of geometric optics approximations and the observation that optical properties of complex, aggregated ice crystals can be well approximated by those of single hexagonal crystals with varying size, aspect ratio, and distortion levels. In the standard geometric optics implementation used here, sigma (sub e) is always twice the particle projected area. It is shown that omega is largely determined by the newly defined absorption size parameter and the particle aspect ratio. These dependences are parameterized using a combination of exponential, lognormal, and polynomial functions. The variation of (g) with aspect ratio and crystal distortion is parameterized for one reference wavelength using a combination of several polynomials. The dependences of g on refractive index and omega are investigated and factors are determined to scale the parameterized (g) to provide values appropriate for other wavelengths. The parameterization scheme consists of only 88 coefficients. The scheme is tested for a large variety of hexagonal crystals in several wavelength bands from 0.2 to 4 micron, revealing absolute differences with reference calculations of omega and (g) that are both generally below 0.015. Over a large variety of cloud conditions, the resulting root-mean-squared differences with reference calculations of cloud reflectance, transmittance, and absorptance are 1.4%, 1.1%, and 3.4%, respectively. Some practical applications of the parameterization in atmospheric models are highlighted.

  16. Possible Mechanisms for Turbofan Engine Ice Crystal Icing at High Altitude

    Science.gov (United States)

    Tsao, Jen-Ching; Struk, Peter M.; Oliver, Michael J.

    2016-01-01

    A thermodynamic model is presented to describe possible mechanisms of ice formation on unheated surfaces inside a turbofan engine compression system from fully glaciated ice crystal clouds often formed at high altitude near deep convective weather systems. It is shown from the analysis that generally there could be two distinct types of ice formation: (1) when the "surface freezing fraction" is in the range of 0 to 1, dominated by the freezing of water melt from fully or partially melted ice crystals, the ice structure is formed from accretion with strong adhesion to the surface, and (2) when the "surface melting fraction" is the range of 0 to 1, dominated by the further melting of ice crystals, the ice structure is formed from accumulation of un-melted ice crystals with relatively weak bonding to the surface. The model captures important qualitative trends of the fundamental ice-crystal icing phenomenon reported earlier (Refs. 1 and 2) from the research collaboration work by NASA and the National Research Council (NRC) of Canada. Further, preliminary analysis of test data from the 2013 full scale turbofan engine ice crystal icing test (Ref. 3) conducted in the NASA Glenn Propulsion Systems Laboratory (PSL) has also suggested that (1) both types of ice formation occurred during the test, and (2) the model has captured some important qualitative trend of turning on (or off) the ice crystal ice formation process in the tested engine low pressure compressor (LPC) targeted area under different icing conditions that ultimately would lead to (or suppress) an engine core roll back (RB) event.

  17. Remote Sensing of Crystal Shapes in Ice Clouds

    Science.gov (United States)

    van Diedenhoven, Bastiaan

    2017-01-01

    Ice crystals in clouds exist in a virtually limitless variation of geometries. The most basic shapes of ice crystals are columnar or plate-like hexagonal prisms with aspect ratios determined by relative humidity and temperature. However, crystals in ice clouds generally display more complex structures owing to aggregation, riming and growth histories through varying temperature and humidity regimes. Crystal shape is relevant for cloud evolution as it affects microphysical properties such as fall speeds and aggregation efficiency. Furthermore, the scattering properties of ice crystals are affected by their general shape, as well as by microscopic features such as surface roughness, impurities and internal structure. To improve the representation of ice clouds in climate models, increased understanding of the global variation of crystal shape and how it relates to, e.g., location, cloud temperature and atmospheric state is crucial. Here, the remote sensing of ice crystal macroscale and microscale structure from airborne and space-based lidar depolarization observations and multi-directional measurements of total and polarized reflectances is reviewed. In addition, a brief overview is given of in situ and laboratory observations of ice crystal shape as well as the optical properties of ice crystals that serve as foundations for the remote sensing approaches. Lidar depolarization is generally found to increase with increasing cloud height and to vary with latitude. Although this variation is generally linked to the variation of ice crystal shape, the interpretation of the depolarization remains largely qualitative and more research is needed before quantitative conclusions about ice shape can be deduced. The angular variation of total and polarized reflectances of ice clouds has been analyzed by numerous studies in order to infer information about ice crystal shapes from them. From these studies it is apparent that pristine crystals with smooth surfaces are generally

  18. Diffraction. Single crystal, magnetic

    International Nuclear Information System (INIS)

    Heger, G.

    1999-01-01

    The analysis of crystal structure and magnetic ordering is usually based on diffraction phenomena caused by the interaction of matter with X-rays, neutrons, or electrons. Complementary information is achieved due to the different character of X-rays, neutrons and electrons, and hence their different interactions with matter and further practical aspects. X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (K.A.)

  19. Study on application of single-crystal ice 'Kurobe ice column' to high-speed skating rinks. Demonstration test result at Olympic memorial arena 'M wave' in Nagano city. Tankesshohyo 'Kurobe no hyojun' no kosoku skate link eno tekiyosei kenkyu. Naganoshi olympic kinen arina 'Emu Wave' deno jissho shiken kekka

    Energy Technology Data Exchange (ETDEWEB)

    Iwasaki, M. (Kansai Electric Power Co. Inc., Osaka (Japan))

    1999-06-10

    For high-speed low-friction skating rinks, research was made on sticking artificial ice columns (ice bamboo shoot). The ice columns were fabricated with the ice column production equipment equipped with 4-line water droplet dropping devices which were installed at intervals of 0.3m on both sides of a pathway of 200m long, 2.6m wide and 1.8m high in the lateral adit of Kurobegawa No.4 hydroelectric power station. The grown ice columns were processed for high-speed skating rinks through cutting, confirmation of single crystal and crystal orientation, slicing for every 7mm thickness and packaging. The ice columns were spread all over the rink while sliding them to prevent mixing of bubbles after spraying distilled water of nearly 25 degreesC onto base ices. In addition, hot water of nearly 40 degreesC was sprayed to produce the final ice rink of 30mm thick by nearly 5mm a day. The dynamic friction coefficient of the ice column rink reduced to 0.0038 by nearly 16% as compared with 0.0045 of conventional rinks. (NEDO)

  20. Single Crystal Surfaces

    Science.gov (United States)

    Aguilar-Santillan, Joaquin

    2014-06-01

    The present work studies (0001) Al2O3 and (111) Al2MgO4 wetting with pure molten Al by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) under Ar at PO2 10-15 Pa. Al pure liquid wets a smooth and chemically homogeneous surface of an inert solid, the wetting driving force ( t, T) can be readily studied when surface solid roughness increases in the system. Both crystals planes (0001) Al2O3 and (111) Al2MgO4 have crystallographic surfaces with identical O-2 crystalline positions however considering Mg2+ content in Al2MgO4 structure may influence a reactive mode. Kinetic models results under similar experimental conditions show that Al wetting on (0001) Al2O3 is less reactive than (111) Al2MgO4, however at >1273 K (1000 °C) (0001) Al2O3 transformation occurs and a transition of wetting improves. The (111) Al2MgO4 and Al system promotes interface formations that slow its wetting process.

  1. Laboratory Investigation of Contact Freezing and the Aerosol to Ice Crystal Transformation Process

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, Raymond A. [Michigan Technological Univ., Houghton, MI (United States)

    2014-10-28

    This project has been focused on the following objectives: 1. Investigations of the physical processes governing immersion versus contact nucleation, specifically surface-induced crystallization; 2. Development of a quadrupole particle trap with full thermodynamic control over the temperature range 0 to –40 °C and precisely controlled water vapor saturation ratios for continuous, single-particle measurement of the aerosol to ice crystal transformation process for realistic ice nuclei; 3. Understanding the role of ice nucleation in determining the microphysical properties of mixed-phase clouds, within a framework that allows bridging between laboratory and field measurements.

  2. Crystal ball single event display

    International Nuclear Information System (INIS)

    Grosnick, D.; Gibson, A.; Allgower, C.; Alyea, J.; Argonne National Lab., IL

    1997-01-01

    The Single Event Display (SED) is a routine that is designed to provide information graphically about a triggered event within the Crystal Ball. The SED is written entirely in FORTRAN and uses the CERN-based HICZ graphing package. The primary display shows the amount of energy deposited in each of the NaI crystals on a Mercator-like projection of the crystals. Ten different shades and colors correspond to varying amounts of energy deposited within a crystal. Information about energy clusters is displayed on the crystal map by outlining in red the thirteen (or twelve) crystals contained within a cluster and assigning each cluster a number. Additional information about energy clusters is provided in a series of boxes containing useful data about the energy distribution among the crystals within the cluster. Other information shown on the event display include the event trigger type and data about π o 's and η's formed from pairs of clusters as found by the analyzer. A description of the major features is given, along with some information on how to install the SED into the analyzer

  3. Ice Crystal Icing Engine Testing in the NASA Glenn Research Center's Propulsion Systems Laboratory: Altitude Investigation

    Science.gov (United States)

    Oliver, Michael J.

    2014-01-01

    The National Aeronautics and Space Administration (NASA) conducted a full scale ice crystal icing turbofan engine test using an obsolete Allied Signal ALF502-R5 engine in the Propulsion Systems Laboratory (PSL) at NASA Glenn Research Center. The test article used was the exact engine that experienced a loss of power event after the ingestion of ice crystals while operating at high altitude during a 1997 Honeywell flight test campaign investigating the turbofan engine ice crystal icing phenomena. The test plan included test points conducted at the known flight test campaign field event pressure altitude and at various pressure altitudes ranging from low to high throughout the engine operating envelope. The test article experienced a loss of power event at each of the altitudes tested. For each pressure altitude test point conducted the ambient static temperature was predicted using a NASA engine icing risk computer model for the given ambient static pressure while maintaining the engine speed.

  4. Transport of pollutants by gravitational settling of ice crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hauf, T.; Alheit, R. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

    1997-12-01

    A numerical box model was developed which simulates the cloud microphysical development within an air parcel of a developing contrail. In a series of simulations it could be shown that in most cases the effective size of the ice crystals is less than 10 {mu}m. Only for high supersaturation (over ice) in the environment and relatively low supersaturation (over water) within the contrail ice crystals larger than 20 {mu}m develop and fall out of the contrail. The hypothesised related transport of pollutants by gravitational settling of ice crystals, therefore, is an unimportant effect when the large-scale dispersion of aircraft exhausts is considered. (orig.) 144 figs., 42 tabs., 497 refs.

  5. Gypsum crystals observed in experimental and natural sea ice

    DEFF Research Database (Denmark)

    Geilfus, Nicolas-Xavier; Galley, Ryan; Cooper, Marc

    2013-01-01

    of authigenic gypsum in sea ice during its formation represents a new observation of precipitate formation and potential marine deposition in polar seas. Citation: Geilfus, N.-X., R. J. Galley, M. Cooper, N. Halden, A. Hare, F. Wang, D. H. Søgaard, and S. Rysgaard (2013), Gypsum crystals observed......Although gypsum has been predicted to precipitate in sea ice, it has never been observed. Here we provide the first report on gypsum precipitation in both experimental and natural sea ice. Crystals were identified by X-ray diffraction analysis. Based on their apparent distinguishing characteristics......, the gypsum crystals were identified as being authigenic. The FREeZing CHEMistry (FREZCHEM) model results support our observations of both gypsum and ikaite precipitation at typical in situ sea ice temperatures and confirms the “Gitterman pathway” where gypsum is predicted to precipitate. The occurrence...

  6. Ice crystal properties retrieval using radar spectral polarimetric measurements within ice/mixed-phase clouds

    NARCIS (Netherlands)

    Dufournet, Y.

    2010-01-01

    In the field of atmospheric research, ground-based radar systems are often employed to study ice/mixed-phase cloud properties based on retrieval techniques. These techniques convert the radar signal backscattered by each bulk of ice crystals being probed within the same radar resolution volume to

  7. Patterning of Perovskite Single Crystals

    KAUST Repository

    Corzo, Daniel

    2017-06-12

    As the internet-of-things hardware integration continues to develop and the requirements for electronics keep diversifying and expanding, the necessity for specialized properties other than the classical semiconductor performance becomes apparent. The success of emerging semiconductor materials depends on the manufacturability and cost as much as on the properties and performance they offer. Solution-based semiconductors are an emerging concept that offers the advantage of being compatible with large-scale manufacturing techniques and have the potential to yield high-quality electronic devices at a lower cost than currently available solutions. In this work, patterns of high-quality MAPbBr3 perovskite single crystals in specific locations are achieved through the modification of the substrate properties and solvent engineering. The fabrication of the substrates involved modifying the surface adhesion forces through functionalization with self-assembled monolayers and patterning them by photolithography processes. Spin coating and blade coating were used to deposit the perovskite solution on the modified silicon substrates. While single crystal perovskites were obtained with the modification of substrates alone, solvent engineering helped with improving the Marangoni flows in the deposited droplets by increasing the contact angle and lowering the evaporation rate, therefore controlling and improving the shape of the grown perovskite crystals. The methodology is extended to other types of perovskites such as the transparent MAPbCl3 and the lead-free MABi2I9, demonstrating the adaptability of the process. Adapting the process to electrode arrays opened up the path towards the fabrication of optoelectronic devices including photodetectors and field-effect transistors, for which the first iterations are demonstrated. Overall, manufacturing and integration techniques permitting the fabrication of single crystalline devices, such as the method in this thesis work, are

  8. Separation of ice crystals from interstitial aerosol particles using virtual impaction at the Fifth International Ice Nucleation Workshop FIN-3

    Science.gov (United States)

    Roesch, M.; Garimella, S.; Roesch, C.; Zawadowicz, M. A.; Katich, J. M.; Froyd, K. D.; Cziczo, D. J.

    2016-12-01

    In this study, a parallel-plate ice chamber, the SPectrometer for Ice Nuclei (SPIN, DMT Inc.) was combined with a pumped counterflow virtual impactor (PCVI, BMI Inc.) to separate ice crystals from interstitial aerosol particles by their aerodynamic size. These measurements were part of the FIN-3 workshop, which took place in fall 2015 at Storm Peak Laboratory (SPL), a high altitude mountain top facility (3220 m m.s.l.) in the Rocky Mountains. The investigated particles were sampled from ambient air and were exposed to cirrus-like conditions inside SPIN (-40°C, 130% RHice). Previous SPIN experiments under these conditions showed that ice crystals were found to be in the super-micron range. Connected to the outlet of the ice chamber, the PCVI was adjusted to separate all particulates aerodynamically larger than 3.5 micrometer to the sample flow while smaller ones were rejected and removed by a pump flow. Using this technique reduces the number of interstitial aerosol particles, which could bias subsequent ice nucleating particle (INP) analysis. Downstream of the PCVI, the separated ice crystals were evaporated and the flow with the remaining INPs was split up to a particle analysis by laser mass spectrometry (PALMS) instrument a laser aerosol spectrometer (LAS, TSI Inc.) and a single particle soot photometer (SP2, DMT Inc.). Based on the sample flow and the resolution of the measured particle data, the lowest concentration threshold for the SP2 instrument was 294 INP L-1 and for the LAS instrument 60 INP L-1. Applying these thresholds as filters to the measured PALMS time series 944 valid INP spectra using the SP2 threshold and 445 valid INP spectra using the LAS threshold were identified. A sensitivity study determining the number of good INP spectra as a function of the filter threshold concentration showed a two-phase linear growth when increasing the threshold concentration showing a breakpoint around 100 INP L-1.

  9. Preparation of TiC single crystals

    International Nuclear Information System (INIS)

    Scheerer, B.; Fink, J.; Reichardt, W.

    1975-07-01

    TiC single crystals were prepared by vertical zone melting for measurements of the phonon dispersion by inelastic neutron scattering. The influence of the starting material and of the growing conditions on the growth of the crystal were studied. The crystals were characterized by chemical methods, EMX and neutron diffraction. It was possible to grow single crystals with a volume of up to 0.6 cm 3 and mosaic spread of less then 0.4 0 . (orig.) [de

  10. Specific findings on ice crystal microphysical properties from in-situ observation

    Science.gov (United States)

    Coutris, Pierre; Leroy, Delphine; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter

    2017-04-01

    This study focuses on microphysical properties of ice particles populating high ice water content areas in Mesoscale Convective Systems (MCS). These clouds have been extensively sampled during the High Altitude Ice Crystal - High Ice Water Content international projects (HAIC-HIWC, Dezitter et al. 2013, Strapp et al. 2015) with the objective of characterizing ice particle properties such as size distribution, radar reflectivity and ice water content. The in-situ data collected during these campaigns at different temperature levels and in different type of MCS (oceanic, continental) make the HAIC-HIWC data set a unique opportunity to study ice particle microphysical properties. Recently, a new approach to retrieve ice particle mass from in-situ measurements has been developed: a forward model that relates ice particles' mass to Particle Size Distribution (PSD) and Ice Water Content (IWC) is formulated as a linear system of equations and the retrieval process consists in solving the inverse problem with numerical optimization tools (Coutris et al. 2016). In this study, this new method is applied to HAIC-HIWC data set and main outcomes are discussed. First, the method is compared to a classical power-law based method using data from one single flight performed in Darwin area on February, 7th 2014. The observed differences in retrieved quantities such as ice particle mass, ice water content or median mass diameter, highlight the potential benefit of abandoning the power law simplistic assumption. The method is then applied to data measured at different cloud temperatures ranging from -40°C to -10°C during several flights of both Darwin 2014 and Cayenne 2015 campaigns. Specific findings about ice microphysical properties such as variations of effective density with particle size and the influence of cloud temperature on particle effective density are presented.

  11. Ice Crystal Icing Engine Testing in the NASA Glenn Research Center's Propulsion Systems Laboratory (PSL): Altitude Investigation

    Science.gov (United States)

    Oliver, Michael J.

    2015-01-01

    The National Aeronautics and Space Administration conducted a full scale ice crystal icing turbofan engine test in the NASA Glenn Research Centers Propulsion Systems Laboratory (PSL) Facility in February 2013. Honeywell Engines supplied the test article, an obsolete, unmodified Lycoming ALF502-R5 turbofan engine serial number LF01 that experienced an un-commanded loss of thrust event while operating at certain high altitude ice crystal icing conditions. These known conditions were duplicated in the PSL for this testing.

  12. Growth-melt asymmetry in ice crystals under the influence of spruce budworm antifreeze protein

    Energy Technology Data Exchange (ETDEWEB)

    Pertaya, Natalya [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); Celik, Yeliz [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); DiPrinzio, Carlos L [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); Wettlaufer, J S [Department of Geology and Geophysics, Yale University, New Haven, CT 06520-8109 (United States); Davies, Peter L [Department of Biochemistry, Queen' s University, Kingston, ON K7L 3N6 (Canada); Braslavsky, Ido [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States)

    2007-10-17

    Here we describe studies of the crystallization behavior of ice in an aqueous solution of spruce budworm antifreeze protein (sbwAFP) at atmospheric pressure. SbwAFP is an ice binding protein with high thermal hysteresis activity, which helps protect Choristoneura fumiferana (spruce budworm) larvae from freezing as they overwinter in the spruce and fir forests of the north eastern United States and Canada. Different types of ice binding proteins have been found in many other species. They have a wide range of applications in cryomedicine and cryopreservation, as well as the potential to protect plants and vegetables from frost damage through genetic engineering. However, there is much to learn regarding the mechanism of action of ice binding proteins. In our experiments, a solution containing sbwAFP was rapidly frozen and then melted back, thereby allowing us to produce small single crystals. These maintained their hexagonal shapes during cooling within the thermal hysteresis gap. Melt-growth-melt sequences in low concentrations of sbwAFP reveal the same shape transitions as are found in pure ice crystals at low temperature (-22 deg. C) and high pressure (2000 bar) (Cahoon et al 2006 Phys. Rev. Lett. 96 255502); while both growth and melt shapes display faceted hexagonal morphology, they are rotated 30 deg. relative to one another. Moreover, the initial melt shape and orientation is recovered in the sequence. To visualize the binding of sbwAFP to ice, we labeled the antifreeze protein with enhanced green fluorescent protein (eGFP) and observed the sbwAFP-GFP molecules directly on ice crystals using confocal microscopy. When cooling the ice crystals, facets form on the six primary prism planes (slowest growing planes) that are evenly decorated with sbwAFP-GFP. During melting, apparent facets form on secondary prism planes (fastest melting planes), leaving residual sbwAFP at the six corners of the hexagon. Thus, the same general growth-melt behavior of an apparently

  13. Scattering phase functions of horizontally oriented hexagonal ice crystals

    International Nuclear Information System (INIS)

    Chen Guang; Yang Ping; Kattawar, George W.; Mishchenko, Michael I.

    2006-01-01

    Finite-difference time domain (FDTD) solutions are first compared with the corresponding T-matrix results for light scattering by circular cylinders with specific orientations. The FDTD method is then utilized to study the scattering properties of horizontally oriented hexagonal ice plates at two wavelengths, 0.55 and 12 μm. The phase functions of horizontally oriented ice plates deviate substantially from their counterparts obtained for randomly oriented particles. Furthermore, we compute the phase functions of horizontally oriented ice crystal columns by using the FDTD method along with two schemes for averaging over the particle orientations. It is shown that the phase functions of hexagonal ice columns with horizontal orientations are not sensitive to the rotation about the principal axes of the particles. Moreover, hexagonal ice crystals and circular cylindrical ice particles have similar optical properties, particularly, at a strongly absorbing wavelength, if the two particle geometries have the same length and aspect ratio defined as the ratio of the radius or semi-width of the cross section of a particle to its length. The phase functions for the two particle geometries are slightly different in the case of weakly absorbing plates with large aspect ratios. However, the solutions for circular cylinders agree well with their counterparts for hexagonal columns

  14. Principles of crystallization, and methods of single crystal growth

    International Nuclear Information System (INIS)

    Chacra, T.

    2010-01-01

    Most of single crystals (monocrystals), have distinguished optical, electrical, or magnetic properties, which make from single crystals, key elements in most of technical modern devices, as they may be used as lenses, Prisms, or grating sin optical devises, or Filters in X-Ray and spectrographic devices, or conductors and semiconductors in electronic, and computer industries. Furthermore, Single crystals are used in transducer devices. Moreover, they are indispensable elements in Laser and Maser emission technology.Crystal Growth Technology (CGT), has started, and developed in the international Universities and scientific institutions, aiming at some of single crystals, which may have significant properties and industrial applications, that can attract the attention of international crystal growth centers, to adopt the industrial production and marketing of such crystals. Unfortunately, Arab universities generally, and Syrian universities specifically, do not give even the minimum interest, to this field of Science.The purpose of this work is to attract the attention of Crystallographers, Physicists and Chemists in the Arab universities and research centers to the importance of crystal growth, and to work on, in the first stage to establish simple, uncomplicated laboratories for the growth of single crystal. Such laboratories can be supplied with equipment, which are partly available or can be manufactured in the local market. Many references (Articles, Papers, Diagrams, etc..) has been studied, to conclude the most important theoretical principles of Phase transitions,especially of crystallization. The conclusions of this study, are summarized in three Principles; Thermodynamic-, Morphologic-, and Kinetic-Principles. The study is completed by a brief description of the main single crystal growth methods with sketches, of equipment used in each method, which can be considered as primary designs for the equipment, of a new crystal growth laboratory. (author)

  15. Single Particle Laser Mass Spectrometry Applied to Differential Ice Nucleation Experiments at the AIDA Chamber

    International Nuclear Information System (INIS)

    Gallavardin, S. J.; Froyd, Karl D.; Lohmann, U.; Moehler, Ottmar; Murphy, Daniel M.; Cziczo, Dan

    2008-01-01

    Experiments conducted at the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) chamber located in Karlsruhe, Germany permit investigation of particle properties that affect the nucleation of ice at temperature and water vapor conditions relevant to cloud microphysics and climate issues. Ice clouds were generated by heterogeneous nucleation of Arizona test dust (ATD), illite, and hematite and homogeneous nucleation of sulfuric acid. Ice crystals formed in the chamber were inertially separated from unactivated, or 'interstitial' aerosol particles with a pumped counterflow virtual impactor (PCVI), then evaporated. The ice residue (i.e., the aerosol which initiated ice nucleation plus any material which was scavenged from the gas- and/or particle-phase), was chemically characterized at the single particle level using a laser ionization mass spectrometer. In this manner the species that first nucleated ice could be identified out of a mixed aerosol population in the chamber. Bare mineral dust particles were more effective ice nuclei (IN) than similar particles with a coating. Metallic particles from contamination in the chamber initiated ice nucleation before other species but there were few enough that they did not compromise the experiments. Nitrate, sulfate, and organics were often detected on particles and ice residue, evidently from scavenging of trace gas-phase species in the chamber. Hematite was a more effective ice nucleus than illite. Ice residue was frequently larger than unactivated test aerosol due to the formation of aggregates due to scavenging, condensation of contaminant gases, and the predominance of larger aerosol in nucleation

  16. Neutron forward diffraction by single crystal prisms

    Indian Academy of Sciences (India)

    November 2008 physics pp. 1109–1114. Neutron forward diffraction by single crystal prisms. SOHRAB ABBAS1,∗, APOORVA G WAGH1, MARKUS STROBL2 and. WOLFGANG ... vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an ... Bragg reflection, for several single crystal prisms.

  17. Ultratough single crystal boron-doped diamond

    Science.gov (United States)

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  18. Growth of emerald single crystals

    International Nuclear Information System (INIS)

    Bukin, G.V.; Godovikov, A.A.; Klyakin, V.A.; Sobolev, V.S.

    1986-01-01

    In addition to its use for jewelry, emerald can also be used in low-noise microwave amplifiers. The authors discuss flux crystallization of emerald and note that when emerald is grown by this method, it is desirable to use solvents which dissolve emerald with minimum deviations from congruence but at the same time with sufficient high efficiency. Emerald synthesis and crystal growth from slowly cooled solutions is discussed as another possibility. The techniques are examined. Vapor synthesis and growht of beryl crystals re reviewed and the authors experimentally study the seeded CVD crystallization of beryl from BeO, Al 2 O 3 and SiO 2 oxides, by using complex compounds as carrier agents. The color of crystals of emerald and other varieties of beryl is detemined by slelective light absorption in teh visible part of the spectrum and depends on the density and structural positions of chromphore ions: chromium, iron, vanadium, nickel, manganese and cobalt

  19. Relaxor-PT Single Crystal Piezoelectric Sensors

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2014-07-01

    Full Text Available Relaxor-PbTiO3 piezoelectric single crystals have been widely used in a broad range of electromechanical devices, including piezoelectric sensors, actuators, and transducers. This paper reviews the unique properties of these single crystals for piezoelectric sensors. Design, fabrication and characterization of various relaxor-PT single crystal piezoelectric sensors and their applications are presented and compared with their piezoelectric ceramic counterparts. Newly applicable fields and future trends of relaxor-PT sensors are also suggested in this review paper.

  20. Single crystal preparation of CuO

    NARCIS (Netherlands)

    Pieters, Th.W.J.; Nedermeyer, J.

    Single crystals of CuO are prepared by means of sublimation in a closed quartz capsule at 900 °C. The crystals have dimensions of 5 × 2 × 0.2 mm. Doping of the CuO with a few percent In2O3 (1 to 5% In/In + Cu) was necessary for the growth of the crystals. The residue contained CuO-In2O3 spinel.

  1. Observations of amplified roughness from crystal accretion in the sub-ice ocean boundary layer

    Science.gov (United States)

    Robinson, N. J.; Stevens, C. L.; McPhee, M. G.

    2017-02-01

    Ice crystal accretion on the underside of sea ice and ice shelves, a signature of pressure-induced supercooling, has the potential to alter the energy balance in the ocean boundary layer through enhanced hydrodynamic roughness. Here we present estimates of crystal-driven ocean boundary layer roughness in supercooled water beneath sea ice adjacent to the McMurdo/Ross Ice Shelf. Data were collected from four sites in McMurdo Sound, Antarctica, between 2007 and 2015, and represent a range of ice shelf-affected conditions. The results show that drag of the rough ice underside in the presence of platelets is 6-30 times larger than typical levels homogeneously applied in ice-ocean interaction models. The crystal-enhanced drag promotes increased entrainment into the boundary layer from the upper ocean, which has the potential to affect ice shelf evolution and sea ice growth through enhanced turbulent exchange of heat and momentum.

  2. EVAPORATION FORM OF ICE CRYSTALS IN SUBSATURATED AIR AND THEIR EVAPORATION MECHANISM

    OpenAIRE

    ゴンダ, タケヒコ; セイ, タダノリ; Takehiko, GONDA; Tadanori, SEI

    1987-01-01

    The evaporation form and the evaporation mechanism of dendritic ice crystals grown in air of 1.0×(10)^5 Pa and at water saturation and polyhedral ice crystals grown in air of 4.0×10 Pa and at relatively low supersaturation are studied. In the case of dendritic ice crystals, the evaporation preferentially occurs in the convex parts of the crystal surfaces and in minute secondary branches. On the other hand, in the case of polyhedral ice crystals, the evaporation preferentially occurs in the pa...

  3. Defect free single crystal thin layer

    KAUST Repository

    Elafandy, Rami Tarek Mahmoud

    2016-01-28

    A gallium nitride film can be a dislocation free single crystal, which can be prepared by irradiating a surface of a substrate and contacting the surface with an etching solution that can selectively etch at dislocations.

  4. Neutron forward diffraction by single crystal prisms

    International Nuclear Information System (INIS)

    Abbas, Sohrab; Wagh, Apoorva G.; Strobl, Markus; Treimer, Wolfgang

    2008-01-01

    We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to the incidence angle. We have measured the variation of neutron deflection and transmission across a Bragg reflection, for several single crystal prisms. The results agree well with theory. (author)

  5. Electrically Anisotropic Layered Perovskite Single Crystal

    KAUST Repository

    Li, Ting-You

    2016-04-01

    Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.

  6. Optical Properties of Small Ice Crystals with Black Carbon Inclusions

    Science.gov (United States)

    Yang, X.; Geier, M.; Arienti, M.

    2013-12-01

    The optical properties of ice crystals play a fundamental role in modeling atmospheric radiation and hydrological cycle, which are critical in monitoring climate change. While Black Carbon (BC) is recognized as the dominant absorber with positive radiative forcing (warming) (Ramanathan & Carmichael, 2008), in-situ observations (Cappa, et al, 2012) indicate that the characterization of the mixing state of BC with ice crystals and other non-BC particles in global climate models (Ghan & Schwartz, 2007) needs further investigation. The limitation in the available mixing models is due to the drastically different absorbing properties of BC compared to other aerosols. We explore the scattering properties of ice crystals (in shapes commonly found in cirrus clouds and contrails - Yang, et al. 2012) with the inclusion of BC particles. The Discrete Dipole Approximation (DDA) (Yurkin & Hoekstra, 2011) is utilized to directly calculate the optical properties of the crystals with multiple BC inclusions, modeled as a distribution of spheres. The results are then compared with the most popular models of internal and external mixing (Liou, et al. 2011). The DDA calculations are carried out over a broad range of BC particle sizes and volume fractions within the crystal at the 532 nm wavelength and for ice crystals smaller than 50 μm. The computationally intensive database generated in this study is critical for understanding the effect of different types of BC inclusions on the atmosphere radiative forcing. Examples will be discussed to illustrate the modification of BC optical properties by encapsulation in ice crystals and how the parameterization of the BC mixing state in global climate models can be improved. Acknowledgements Support by Sandia National Laboratories' LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of

  7. Single Crystals Grown Under Unconstrained Conditions

    Science.gov (United States)

    Sunagawa, Ichiro

    Based on detailed investigations on morphology (evolution and variation in external forms), surface microtopography of crystal faces (spirals and etch figures), internal morphology (growth sectors, growth banding and associated impurity partitioning) and perfection (dislocations and other lattice defects) in single crystals, we can deduce how and by what mechanism the crystal grew and experienced fluctuation in growth parameters through its growth and post-growth history under unconstrained condition. The information is useful not only in finding appropriate way to growing highly perfect and homogeneous single crystals, but also in deciphering letters sent from the depth of the Earth and the Space. It is also useful in discriminating synthetic from natural gemstones. In this chapter, available methods to obtain molecular information are briefly summarized, and actual examples to demonstrate the importance of this type of investigations are selected from both natural minerals (diamond, quartz, hematite, corundum, beryl, phlogopite) and synthetic crystals (SiC, diamond, corundum, beryl).

  8. Light Emitting Transistors of Organic Single Crystals

    Science.gov (United States)

    Iwasa, Yoshihiro

    2009-03-01

    Organic light emitting transistors (OLETs) are attracting considerable interest as a novel function of organic field effect transistors (OFETs). Besides a smallest integration of light source and current switching devices, OLETs offer a new opportunity in the fundamental research on organic light emitting devices. The OLET device structure allows us to use organic single crystals, in contrast to the organic light emitting diodes (OLEDs), the research of which have been conducted predominantly on polycrystalline or amorphous thin films. In the case of OFETs, use of single crystals have produced a significant amount of benefits in the studies of pursuit for the highest performance limit of FETs, intrinsic transport mechanism in organic semiconductors, and application of the single crystal transistors. The study on OLETs have been made predominantly on polycrystalline films or multicomponent heterojunctions, and single crystal study is still limited to tetracene [1] and rubrene [2], which are materials with relatively high mobility, but with low photoluminescence efficiency. In this paper, we report fabrication of single crystal OLETs of several kinds of highly luminescent molecules, emitting colorful light, ranging from blue to red. Our strategy is single crystallization of monomeric or oligomeric molecules, which are known to have a very high photoluminescence efficiency. Here we report the result on single crystal LETs of rubrene (red), 4,4'-bis(diphenylvinylenyl)-anthracene (green), 1,4-bis(5-phenylthiophene-2-yl)benzene (AC5) (green), and 1,3,6,8-tetraphenylpyrene (TPPy) (blue), all of which displayed ambipolar transport as well as peculiar movement of voltage controlled movement of recombination zone, not only from the surface of the crystal but also from the edges of the crystals, indicting light confinement inside the crystal. Realization of ambipolar OLET with variety of single crystals indicates that the fabrication method is quite versatile to various light

  9. Settling and collision between small ice crystals in turbulent flows

    Science.gov (United States)

    Jucha, Jennifer; Naso, Aurore; Lévêque, Emmanuel; Pumir, Alain

    2018-01-01

    Ice crystals are present in a variety of clouds, at sufficiently low temperature. We consider here mixed-phase clouds which, at temperature ≳-20 ∘C , contain ice crystals, shaped approximately as thin oblate ellipsoids. We investigate the motion of these particles transported by an isotropic turbulent flow and, in particular, the collision between these crystals, a key process in the formation of graupels. Using fully resolved direct numerical simulations, and neglecting the effects of fluid inertia on the particle motion, we determine the influence of the turbulence intensity and of gravitational settling, in a realistic range of parameters. At small turbulent energy dissipation rate, collisions are induced mainly by differential gravitational settling between particles with different orientations. The effect has a clear signature on the relative orientation of colliding ellipsoids. As the turbulent energy dissipation rate increases, however, the influence of the turbulent velocity fluctuations becomes the dominant effect determining the collision rate. Using simple estimates, we propose an elementary understanding of the relative importance of gravitational settling and turbulent fluctuations.

  10. Crystal plasticity study of single crystal tungsten by indentation tests

    International Nuclear Information System (INIS)

    Yao, Weizhi

    2012-01-01

    Owing to its favorable material properties, tungsten (W) has been studied as a plasma-facing material in fusion reactors. Experiments on W heating in plasma sources and electron beam facilities have shown an intense micro-crack formation at the heated surface and sub-surface. The cracks go deep inside the irradiated sample, and often large distorted areas caused by local plastic deformation are present around the cracks. To interpret the crack-induced microscopic damage evolution process in W, one needs firstly to understand its plasticity on a single grain level, which is referred to as crystal plasticity. In this thesis, the crystal plasticity of single crystal tungsten (SCW) has been studied by spherical and Berkovich indentation tests and the finite element method with a crystal plasticity model. Appropriate values of the material parameters included in the crystal plasticity model are determined by fitting measured load-displacement curves and pile-up profiles with simulated counterparts for spherical indentation. The numerical simulations reveal excellent agreement with experiment. While the load-displacement curves and the deduced indentation hardness exhibit little sensitivity to the indented plane at small indentation depths, the orientation of slip directions within the crystals governs the development of deformation hillocks at the surface. It is found that several factors like friction, indentation depth, active slip systems, misoriented crystal orientation, misoriented sample surface and azimuthal orientation of the indenter can affect the indentation behavior of SCW. The Berkovich indentation test was also used to study the crystal plasticity of SCW after deuterium irradiation. The critical load (pop-in load) for triggering plastic deformation under the indenter is found to depend on the crystallographic orientation. The pop-in loads decrease dramatically after deuterium plasma irradiation for all three investigated crystallographic planes.

  11. Circular depolarization ratios of single water droplets and finite ice circular cylinders: a modeling study

    Directory of Open Access Journals (Sweden)

    M. Nicolet

    2012-05-01

    Full Text Available Computations of the phase matrix elements for single water droplets and ice crystals in fixed orientations are presented to determine if circular depolarization δC is more accurate than linear depolarization for phase discrimination. T-matrix simulations were performed to calculate right-handed and left-handed circular depolarization ratios δ+C, respectively δ−C and to compare them with linear ones. Ice crystals are assumed to have a circular cylindrical shape where their surface-equivalent diameters range up to 5 μm. The circular depolarization ratios of ice particles were generally higher than linear depolarization and depended mostly on the particle orientation as well as their sizes. The fraction of non-detectable ice crystals (δ<0.05 was smaller considering a circular polarized light source, reaching 4.5%. However, water droplets also depolarized light circularly for scattering angles smaller than 179° and size parameters smaller than 6 at side- and backscattering regions. Differentiation between ice crystals and water droplets might be difficult for experiments performed at backscattering angles which deviate from 180° unlike LIDAR applications. Instruments exploiting the difference in the P44/P11 ratio at a scattering angle around 115° are significantly constrained in distinguishing between water and ice because small droplets with size parameters between 5 and 10 do cause very high circular depolarizations at this angle. If the absence of the liquid phase is confirmed, the use of circular depolarization in single particle detection is more sensitive and less affected by particle orientation.

  12. Interference phenomena at backscattering by ice crystals of cirrus clouds.

    Science.gov (United States)

    Borovoi, Anatoli; Kustova, Natalia; Konoshonkin, Alexander

    2015-09-21

    It is shown that light backscattering by hexagonal ice crystals of cirrus clouds is formed within the physical-optics approximation by both diffraction and interference phenomena. Diffraction determines the angular width of the backscattering peak and interference produces the interference rings inside the peak. By use of a simple model for distortion of the pristine hexagonal shape, we show that the shape distortion leads to both oscillations of the scattering (Mueller) matrix within the backscattering peak and to a strong increase of the depolarization, color, and lidar ratios needed for interpretation of lidar signals.

  13. The growth of sapphire single crystals

    Directory of Open Access Journals (Sweden)

    STEVAN DJURIC

    2001-06-01

    Full Text Available Sapphire (Al2O3 single crystals were grown by the Czochralski technique both in air and argon atmospheres. The conditions for growing sapphire single crystals were calculated by using a combination of Reynolds and Grashof numbers. Acritical crystal diameter dc = 20 mm and the critical rate of rotation wc = 20 rpm were calculated from the hydrodynamics of the melt. The value of the rate of crystal growth was experimentally found to be 3.5 mm/h. According to our previous experiments, it was confirmed that three hours exposures to conc. H3PO4 at 593 K was suitable for chemical polishing. Also, three hours exposure to conc.H3PO4 at 523 K was found to be a suitable etching solution. The lattice parameters a = 0.47573 nm and c = 1.29893 nm were determined by X-ray powder diffraction. The obtained results are discussed and compared with published data.

  14. Single Crystal Diffuse Neutron Scattering

    Directory of Open Access Journals (Sweden)

    Richard Welberry

    2018-01-01

    Full Text Available Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.

  15. Growth and characterization of nonlinear optical single crystals: bis ...

    Indian Academy of Sciences (India)

    methoxy benzoate (C4MB) single crystals were successfully grown by the slow evaporation solution growth technique. The harvested crystals were subjected to single-crystal X-ray diffraction, spectral, optical, thermal and mechanical studies in ...

  16. Single crystal LaB/sub 6/

    Energy Technology Data Exchange (ETDEWEB)

    Noack, M.A.

    1979-07-01

    Single crystals of LaB/sub 6/ were prepared by float zone refining of hot pressed blocks of LaB/sub 6/. The orientations studied were (001), (110), and a high index plane. The resulting crystals and the as-received material were chemically analyzed by vacuum fusion, combustion analysis, self-arc mass spectroscopy, and wet chemical analysis. The first two provided accurate analysis for O, N, H, and C. The remaining elements except for La and B were determined by mass spectroscopy. The wet chemical analyses determined the B/La ratio. Two batches of as-received material had B/La ratios of 6.0 and 5.8, respectively. Slightly lower B/La ratios were obtained in the single crystals grown by the float zone technique from these materials. The single crystals were further characterized by measurements of lattice parameter and density. Work function values were determined by the FERP method and the thermionic method. Work function measurements in conjunction with Auger analysis of the crystals provided insight into the electron emission character of LaB/sub 6/. Results indicate that for maximum emission from a crystal plane a proper heat treatment is necessary. Brightness of the crystals was measured in a Cambridge S-4 scanning electron microscope using a Broers type gun. Results show that a brightness of 10/sup 6/ amp/cm/sup 2/ steradian (20kV) may be achieved with a single crystal LaB/sub 6/ cathode operating at a temperature of 1900/sup 0/K which corresponds to a lifetime greater than 500 hrs for 1 mm cathodes.

  17. Sputtering yield measurements on single crystal cobalt

    International Nuclear Information System (INIS)

    Chernysh, V.S.; Johansen, A.; Sarholt-Kristensen, L.

    1981-01-01

    Single crystals of cobalt have been bombarded with 80 keV A + ions in the direction of the h.c.p. structure and in the direction of the f.c.c. structure. The sputtering yields, measured by the weight loss method, depend on the crystal structure, and damage, introduced by the ion bombardment, is shown to play a significant role in the explanation of the measured sputtering yields. (Auth.)

  18. Single chirality through crystal grinding

    NARCIS (Netherlands)

    Noorduin, W.L.

    2010-01-01

    The properties of chiral molecules in living organisms can be different for left- and right-handed molecules. Therefore, ways to produce molecules of single handedness are of paramount importance, especially for economical, high yielding processes to synthesize pharmaceutical compounds that must be

  19. Ice crystal growth under the presence of krypton and methane at low temperature

    Science.gov (United States)

    Kawauchi, Taizo; Yoda, Yoshitaka; Fukutani, Katsuyuki

    2018-02-01

    To investigate the influence of foreign gas inclusion on the crystallization of ice, we studied the low-temperature (74 0.2) of Kr and CH4 enhance the formation of ice Ih and increase the crystal size, while at high foreign gas contents (R ⩽ 0.2) that may develop Kr or CH4 crystals below 92 K, the crystal size and relative amount of ice decrease strongly. The maximum ice Ih crystal size in the order of 200 nm was observed with either Kr or CH4 at 92 K for R = 0.2. We propose that Kr and CH4 induce the crystallization of ice by acting as a surfactant.

  20. Mechanical Properties Of Single Crystal Ceramics

    Science.gov (United States)

    Rowcliffe, D. J.; Johnson, S. M.

    1987-03-01

    Approaches to characterizing the mechanical behavior of single crystal ceramics are reviewed. Consideration is given to techniques applicable to large crystals and to indentation techniques that can be used on crystals of 1 mm or less. The importance of flaws in controlling the mechanical behavior of brittle ceramics is discussed, leading to an emphasis on fracture mechanics methods. These techniques are applicable to the determination of fracture toughness and to the measurement of slow crack growth in aggresive environments. Indentation processes have been analyzed extensively and the good understanding of stress fields and micro-mechanics of indentation has led to techniques to measure hardness, toughness and elastic modulus. Measurements of hardness anistropy can be used to determine slip planes and also provide considerable information on local plastic flow in brittle crystals.

  1. Mineralogical and Crystal Chemical Characterization of Dust Particles From Antarctica Ice Cores

    Science.gov (United States)

    Sala, M.; Dapiaggi, M.; Artioli, G.; Marino, F.; Delmonte, B.; Maggi, V.; Frezzotti, M.

    2006-12-01

    Antarctic ice cores are actively studied to understand and reconstruct past climatic changes. Valuable data to this aim are the physical and chemical characteristics of the very cold ice, that in several places in Antarctica laid undisturbed since the time of deposition, carrying information on depostion rates and trapped chemical components, and especially the aeolian mineral particles, which is mainly transported by the wind, its mineralogical and chemical composition being influenced by a complex interplay of atmospheric, hydrological, geographical and geological parameters. Besides a few pioneering studies in the eighties there are no recent detailed investigations on the mineralogical composition of the dust particulate enclosed in the Antarctic ice cores, so that its compostion is commonly evaluated indirectly, by means of recalculations from chemical analyses. A recent project was started to set up an analytical protocol to define the mineralogical and crystal chemical composition of ice dust material. The main challenge is the very small amount of solid particles, which is generally below the ppm range (1-100 mg of dust per kg of melted ice), which makes sample preparation for the different analytical techniques very difficult and prone to external contamination. The developed protocol encompasses X-ray powder diffraction (XRPD), high-resolution transmission electron microscopy (HR-TEM) coupled to energy dispersive X-ray fluorescence analysis (ED-XRF), and proton induced X-ray emission analysis (PIXE) on the same sample, so to combine single-particle and bulk analysis of the material. The results from the different techniques provide for robust procedures for mineral phases identification, as the XRPD informations are cross-checked with single particle TEM results. At the same time XRPD provides for the statistics intrinsically lacking in single particle TEM evaluation. Moreover, the TEM-associated ED-XRF analysis yields an approximate crystal chemistry of

  2. Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data

    Directory of Open Access Journals (Sweden)

    A. Diez

    2015-02-01

    This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred crystal orientations.

  3. Update on the NASA Glenn Propulsion Systems Lab Ice Crystal Cloud Characterization (2015, 2016)

    Science.gov (United States)

    Van Zante, Judith; Bencic, Timothy; Ratvasky, Thomas

    2016-01-01

    NASA Glenn's Propulsion Systems Lab, an altitude engine test facility, was outfitted with a spray system to generate ice crystals in 2011. Turbine engines and driven rigs can experience ice crystal icing at flight altitudes, temperatures and Mach numbers. To support these tests, four ice crystal characterizations have been conducted in two different facility configurations. In addition, super-cooled liquid and mixed phase clouds have also been generated. This paper represents a work in progress. It will describe some of the 11-parameter calibration space, and how those parameters interact with each other, the instrumentation used to characterize the cloud and present a sample of the cloud characterization results.

  4. Systematic hardness measurements on single crystals and ...

    Indian Academy of Sciences (India)

    Vickers and knoop hardness measurements were carried out on CsBr and CsI single crystals. Polycrystalline blanks of CsCl, CsBr and CsI were prepared by melting and characterized by X-ray diffraction. Vickers hardness measurements were carried out on these blanks. The hardness values were correlated with the lattice ...

  5. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker

    1975-01-01

    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...

  6. Neutron forward diffraction by single crystal prisms

    Indian Academy of Sciences (India)

    Abstract. We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater ...

  7. Neutron forward diffraction by single crystal prisms

    Indian Academy of Sciences (India)

    We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to ...

  8. Antiferromagnetism in chromium alloy single crystals

    DEFF Research Database (Denmark)

    Bjerrum Møller, Hans; Trego, A.L.; Mackintosh, A.R.

    1965-01-01

    The antiferromagnetism of single crystals of dilute alloys of V, Mn and Re in Cr has been studied at 95°K and 300°K by neutron diffraction. The addition of V causes the diffraction peaks to decrease in intensity and move away from (100), while Mn and Re cause them to increase and approach (100) s...

  9. Lattice effects in YVO3 single crystal

    NARCIS (Netherlands)

    Marquina, C; Sikora, M; Ibarra, MR; Nugroho, AA; Palstra, TTM

    In this paper we report on the lattice effects in the Mott insulator yttrium orthovanadate (YVO3). Linear thermal expansion and magnetostriction experiments have been performed on a single crystal, in the temperature range from 5 K to room temperature. The YVO3 orders antiferromagnetically at T-N =

  10. Method for manufacturing a single crystal nanowire

    NARCIS (Netherlands)

    van den Berg, Albert; Bomer, Johan G.; Carlen, Edwin; Chen, S.; Kraaijenhagen, Roderik Adriaan; Pinedo, Herbert Michael

    2013-01-01

    A method for manufacturing a single crystal nano-structure is provided comprising the steps of providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing

  11. Method for manufacturing a single crystal nanowire

    NARCIS (Netherlands)

    van den Berg, Albert; Bomer, Johan G.; Carlen, Edwin; Chen, S.; Kraaijenhagen, R.A.; Pinedo, Herbert Michael

    2010-01-01

    A method for manufacturing a single crystal nano-structure is provided comprising the steps of providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing

  12. Single-Crystal Germanium Core Optoelectronic Fibers

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Xiaoyu [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Page, Ryan L. [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Chaudhuri, Subhasis [Department of Chemistry, Pennsylvania State University, University Park PA 16802 USA; Liu, Wenjun [Advanced Photon Source, Argonne National Laboratory, Argonne IL 60439 USA; Yu, Shih-Ying [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Mohney, Suzanne E. [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Badding, John V. [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA; Department of Chemistry, Pennsylvania State University, University Park PA 16802 USA; Department of Physics, Pennsylvania State University, University Park PA 16802 USA; Gopalan, Venkatraman [Department of Materials Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park PA 16802 USA

    2016-09-19

    Synthesis and fabrication of high-quality, small-core single-crystal germanium fibers that are photosensitive at the near-infrared and have low optical losses ≈1 dB cm-1 at 2 μm are reported. These fibers have potential applications in fiber-based spectroscopic imaging, nonlinear optical devices, and photodetection at the telecommunication wavelengths.

  13. Derivation of Physical and Optical Properties of Midlatitude Cirrus Ice Crystals for a Size-Resolved Cloud Microphysics Model

    Science.gov (United States)

    Fridlind, Ann M.; Atlas, Rachel; Van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-01-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by approx. 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from approx. 0:05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  14. Friction stir welding of single crystal aluminium

    DEFF Research Database (Denmark)

    Fonda, Richard Warren; Wert, John A.; Reynolds, A.P.

    2007-01-01

    Friction stir welds were prepared in different orientations in an aluminium single crystal. The welds were quenched to preserve the microstructure surrounding the tool and then electron backscattered diffraction was used to reveal the generation of grain boundaries and the evolution...... to new crystal orientations, producing new grain boundaries in the process. These refined grains develop a {112}. texture closer to the tool. Large conventionally recrystallised grains sometimes form in the outer regions of the refined grain structure, but become ever more deformed as they approach...

  15. Irradiation creep in zirconium single crystals

    International Nuclear Information System (INIS)

    MacEwen, S.R.; Fidleris, V.

    1976-07-01

    Two identical single crystals of crystal bar zirconium have been creep tested in reactor. Both specimens were preirradiated at low stress to a dose of about 4 x 10 23 n/m 2 (E > 1 MeV), and were then loaded to 25 MPa. The first specimen was loaded with reactor at full power, the second during a shutdown. The loading strain for both crystals was more than an order of magnitude smaller than that observed when an identical unirradiated crystal was loaded to the same stress. Both crystals exhibited periods of primary creep, after which their creep rates reached nearly constant values when the reactor was at power. During shutdowns the creep rates decreased rapidly with time. Electron microscopy revealed that the irradiation damage consisted of prismatic dislocation loops, approximately 13.5 nm in diameter. Cleared channels, identified as lying on (1010) planes, were also observed. The results are discussed in terms of the current theories for flux enhanced creep in the light of the microstructures observed. (author)

  16. Interaction of Tenebrio Molitor Antifreeze Protein with Ice Crystal: Insights from Molecular Dynamics Simulations.

    Science.gov (United States)

    Ramya, L; Ramakrishnan, Vigneshwar

    2016-07-01

    Antifreeze proteins (AFP) observed in cold-adapting organisms bind to ice crystals and prevent further ice growth. However, the molecular mechanism of AFP-ice binding and AFP-inhibited ice growth remains unclear. Here we report the interaction of the insect antifreeze protein (Tenebrio molitor, TmAFP) with ice crystal by molecular dynamics simulation studies. Two sets of simulations were carried out at 263 K by placing the protein near the primary prism plane (PP) and basal plane (BL) of the ice crystal. To delineate the effect of temperatures, both the PP and BL simulations were carried out at 253 K as well. The analyses revealed that the protein interacts strongly with the ice crystal in BL simulation than in PP simulation both at 263 K and 253 K. Further, it was observed that the interactions are primarily mediated through the interface waters. We also observed that as the temperature decreases, the interaction between the protein and the ice increases which can be attributed to the decreased flexibility and the increased structuring of the protein at low temperature. In essence, our study has shed light on the interaction mechanism between the TmAFP antifreeze protein and the ice crystal. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Update on the NASA Glenn Propulsion Systems Lab Ice Crystal Cloud Characterization (2015)

    Science.gov (United States)

    Van Zante, Judith F.; Bencic, Timothy J.; Ratvasky, Thomas P.

    2016-01-01

    NASA Glenn's Propulsion Systems Lab (PSL), an altitude engine test facility, was outfitted with a spray system to generate ice crystals. The first ice crystal characterization test occurred in 2012. At PSL, turbine engines and driven rigs can experience ice crystal icing at flight altitudes, temperatures and Mach numbers. To support these tests, four ice crystal characterizations have been conducted in two different facility configurations. In addition, super-cooled liquid and mixed phase clouds have also been generated. This paper will discuss the recent learning from the previous two calibrations. It will describe some of the 12-parameter calibration space, and how those parameters interact with each other, the instrumentation used to characterize the cloud and present a sample of the cloud characterization results.

  18. Growth of 2-amino-5-chlorobenzophenone single crystal by ...

    Indian Academy of Sciences (India)

    Abstract. Organic single crystals of 2-amino-5-chlorobenzophenone (2A5CB) were grown by Microtube Czochral- ski method using Microtube as a seed. The grown crystals were characterized by single crystal and powder X-ray diffraction. The functional groups of the grown crystal were found using Fourier transform ...

  19. Charge transport in single crystal organic semiconductors

    Science.gov (United States)

    Xie, Wei

    Organic electronics have engendered substantial interest in printable, flexible and large-area applications thanks to their low fabrication cost per unit area, chemical versatility and solution processability. Nevertheless, fundamental understanding of device physics and charge transport in organic semiconductors lag somewhat behind, partially due to ubiquitous defects and impurities in technologically useful organic thin films, formed either by vacuum deposition or solution process. In this context, single-crystalline organic semiconductors, or organic single crystals, have therefore provided the ideal system for transport studies. Organic single crystals are characterized by their high chemical purity and outstanding structural perfection, leading to significantly improved electrical properties compared with their thin-film counterparts. Importantly, the surfaces of the crystals are molecularly flat, an ideal condition for building field-effect transistors (FETs). Progress in organic single crystal FETs (SC-FETs) is tremendous during the past decade. Large mobilities ~ 1 - 10 cm2V-1s-1 have been achieved in several crystals, allowing a wide range of electrical, optical, mechanical, structural, and theoretical studies. Several challenges still remain, however, which are the motivation of this thesis. The first challenge is to delineate the crystal structure/electrical property relationship for development of high-performance organic semiconductors. This thesis demonstrates a full spectrum of studies spanning from chemical synthesis, single crystal structure determination, quantum-chemical calculation, SC-OFET fabrication, electrical measurement, photoelectron spectroscopy characterization and extensive device optimization in a series of new rubrene derivatives, motivated by the fact that rubrene is a benchmark semiconductor with record hole mobility ~ 20 cm2V-1s-1. With successful preservation of beneficial pi-stacking structures, these rubrene derivatives form

  20. In situ inward epitaxial growth of bulk macroporous single crystals.

    Science.gov (United States)

    Chen, Chenlong; Sun, Shujing; Chou, Mitch M C; Xie, Kui

    2017-12-19

    The functionalities of porous materials could be significantly enhanced if the materials themselves were in single-crystal form, which, owing to structural coherence, would reduce electronic and optical scattering effects. However, growing macroporous single crystals remains a fundamental challenge, let alone manufacturing crystals large enough to be of practical use. Here we demonstrate a straightforward, inexpensive, versatile method for creating macroporous gallium nitride single crystals on a centimetre scale. The synthetic strategy is built upon a disruptive crystal growth mechanism that utilises direct nitridation of a parent LiGaO 2 single crystal rendering an inward epitaxial growth process. Strikingly, the resulting single crystals exhibit electron mobility comparable to that for bulk crystals grown by the conventional sodium flux method. This approach not only affords control of both crystal and pore size through synthetic modification, but proves generic, thus opening up the possibility of designing macroporous crystals in a wealth of other materials.

  1. Ice-Crystallization Kinetics during Fuel-Cell Cold-Start

    Science.gov (United States)

    Dursch, Thomas James, Jr.

    Proton-exchange-membrane fuel cells (PEMFCs) show promise in automotive applications because of their high efficiency, high power density, and potentially low emissions. To be successful in automobiles, PEMFCs must permit rapid startup with minimal energy from subfreezing temperatures, known as cold-start. In a PEMFC, reduction of oxygen to water occurs in the cathode catalyst layer (CL). Under subfreezing conditions, water generated during startup solidifies and hinders access of gaseous oxygen to the catalytic sites in the cathode CL, severely inhibiting cell performance and potentially causing cell failure. Achieving cold-start is difficult in practice, due to potential flooding, sluggish reaction kinetics, durability loss, and rapid ice crystallization. Currently, however, few studies focus on the fundamentals of ice crystallization during cold-start. Elucidation of the mechanisms and kinetics of ice formation within PEMFC porous media is, therefore, critical to successful cell startup and high performance at low temperatures. First, an experimental method is presented for obtaining isothermal ice-crystallization kinetics in water-saturated gas-diffusion layers (GDLs). Ice formation is initially studied in the GDL because this layer retains a significant amount of product water during cold-start. Isothermal ice-crystallization and ice-nucleation rates are obtained in commercial Toray GDLs as functions of subcooling using differential scanning calorimetry (DSC). A nonlinear ice-crystallization rate expression is developed using Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Predicted ice-crystallization rates are in excellent agreement with experiment. A validated rate expression is thus available for predicting ice-crystallization kinetics in GDLs. Ice-crystallization kinetics is also considered under experimental settings similar to real PEMFC operating

  2. Some effects of ice crystals on the FSSP measurements in mixed phase clouds

    Directory of Open Access Journals (Sweden)

    G. Febvre

    2012-10-01

    Full Text Available In this paper, we show that in mixed phase clouds, the presence of ice crystals may induce wrong FSSP 100 measurements interpretation especially in terms of particle size and subsequent bulk parameters. The presence of ice crystals is generally revealed by a bimodal feature of the particle size distribution (PSD. The combined measurements of the FSSP-100 and the Polar Nephelometer give a coherent description of the effect of the ice crystals on the FSSP-100 response. The FSSP-100 particle size distributions are characterized by a bimodal shape with a second mode peaked between 25 and 35 μm related to ice crystals. This feature is observed with the FSSP-100 at airspeed up to 200 m s−1 and with the FSSP-300 series. In order to assess the size calibration for clouds of ice crystals the response of the FSSP-100 probe has been numerically simulated using a light scattering model of randomly oriented hexagonal ice particles and assuming both smooth and rough crystal surfaces. The results suggest that the second mode, measured between 25 μm and 35 μm, does not necessarily represent true size responses but corresponds to bigger aspherical ice particles. According to simulation results, the sizing understatement would be neglected in the rough case but would be significant with the smooth case. Qualitatively, the Polar Nephelometer phase function suggests that the rough case is the more suitable to describe real crystals. Quantitatively, however, it is difficult to conclude. A review is made to explore different hypotheses explaining the occurrence of the second mode. However, previous cloud in situ measurements suggest that the FSSP-100 secondary mode, peaked in the range 25–35 μm, is likely to be due to the shattering of large ice crystals on the probe inlet. This finding is supported by the rather good relationship between the concentration of particles larger than 20 μm (hypothesized to be ice shattered-fragments measured by the

  3. Growth of single crystals of BaFe12O19 by solid state crystal growth

    International Nuclear Information System (INIS)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-01-01

    Single crystals of BaFe 12 O 19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe 12 O 19 are buried in BaFe 12 O 19 +1 wt% BaCO 3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe 12 O 19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe 12 O 19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth. - Highlights: • Single crystals of BaFe 12 O 19 are grown by solid state crystal growth. • A single crystal up to ∼130 μm thick (c-axis direction) grows on the seed crystal. • The single crystal and surrounding ceramic matrix have similar composition. • Micro-Raman scattering shows the single crystal has the BaFe 12 O 19 structure.

  4. Chemical vapor deposition of graphene single crystals.

    Science.gov (United States)

    Yan, Zheng; Peng, Zhiwei; Tour, James M

    2014-04-15

    As a two-dimensional (2D) sp(2)-bonded carbon allotrope, graphene has attracted enormous interest over the past decade due to its unique properties, such as ultrahigh electron mobility, uniform broadband optical absorption and high tensile strength. In the initial research, graphene was isolated from natural graphite, and limited to small sizes and low yields. Recently developed chemical vapor deposition (CVD) techniques have emerged as an important method for the scalable production of large-size and high-quality graphene for various applications. However, CVD-derived graphene is polycrystalline and demonstrates degraded properties induced by grain boundaries. Thus, the next critical step of graphene growth relies on the synthesis of large graphene single crystals. In this Account, we first discuss graphene grain boundaries and their influence on graphene's properties. Mechanical and electrical behaviors of CVD-derived polycrystalline graphene are greatly reduced when compared to that of exfoliated graphene. We then review four representative pathways of pretreating Cu substrates to make millimeter-sized monolayer graphene grains: electrochemical polishing and high-pressure annealing of Cu substrate, adding of additional Cu enclosures, melting and resolidfying Cu substrates, and oxygen-rich Cu substrates. Due to these pretreatments, the nucleation site density on Cu substrates is greatly reduced, resulting in hexagonal-shaped graphene grains that show increased grain domain size and comparable electrical properties as to exfoliated graphene. Also, the properties of graphene can be engineered by its shape, thickness and spatial structure. Thus, we further discuss recently developed methods of making graphene grains with special spatial structures, including snowflakes, six-lobed flowers, pyramids and hexagonal graphene onion rings. The fundamental growth mechanism and practical applications of these well-shaped graphene structures should be interesting topics and

  5. Optical properties of lithium niobate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Palatnikov, M.N.; Sidorov, N.V.; Biryukova, I.V.; Kalinnikov, V.T. [Institute of Chemistry, Kola Science Centre RAS, 26a Fersman str., 184200 Apatity, Murmansk region (Russian Federation); Bormanis, K. [Institute of Solid State Physics, University of Latvia, 8 Kengaraga str., Riga, LV-1063 (Latvia)

    2005-01-01

    Studies of thermal and {gamma}-irradiation effects on the optical properties in congruous lithium niobate single crystals containing Y, Mg, Gd, B, and Zn dopants including samples with double dopants Y, Mg and Gd, Mg are reported. Formation of defects at irradiation and thermal treatment of the samples is explored by electron absorption spectra. Considerable increase of absorption with the dose of {gamma}-radiation is observed at 500 nm. The changes of absorption examined under different conditions are explained by creation and destruction of Nb{sup 4+} defects. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. NMR studies of single crystal chromium diboride

    Energy Technology Data Exchange (ETDEWEB)

    Michioka, C. [Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)]. E-mail: michioka@kuchem.kyoto-u.ac.jp; Itoh, Y. [Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Yoshimura, K. [Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Watabe, Y. [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 229-8558 (Japan); Kousaka, Y. [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 229-8558 (Japan); Ichikawa, H. [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 229-8558 (Japan); Akimitsu, J. [Department of Physics and Mathematics, Aoyama Gakuin University, Sagamihara, Kanagawa 229-8558 (Japan)

    2007-03-15

    We report {sup 11}B NMR studies of a single crystal CrB{sub 2}. From the temperature dependence of the Fourier-transformed NMR spectra in the paramagnetic state, the hyperfine coupling constants are estimated to be A{sub Cr-B} = -0.64,-0.74 and -0.71kOe/{mu}{sub B} for H parallel c, H parallel a and H parallel [210], respectively. In the magnetically ordered state, the spectra in H parallel a and H parallel [210] consist of superposition of a broad hump and five peaks, which correspond to the incommensurate and commensurate spin structures.

  7. Photoelectric studies of gallium monosulfide single crystals

    Science.gov (United States)

    Gamal, G. A.; Azad, M. I.

    2005-10-01

    Photoconductivity studies were carried out on GaS single crystals prepared from melt by directional solidification. We studied the effect of light intensity, applied voltage on both the photoconductivity and the lifetime of carriers. The V-I characteristics and the absorption spectra were checked for different sample thickness. The present investigation was extended to study the spectral distribution of the photocurrent for GaS. It was found that the photocurrent curves are practically independent on the bias voltage. The energy gap for GaS was found to be 2.5 eV.

  8. Theory of isotopic fractionation on facetted ice crystals

    Directory of Open Access Journals (Sweden)

    J. Nelson

    2011-11-01

    Full Text Available The currently used "kinetic-fractionation" (KF model of the differential incorporation of water-molecule isotopologues into vapor-grown ice omits surface processes on crystal facets that may be important in temperature reconstructions. This article introduces the "surface-kinetic" fractionation model, a model that includes such surface processes, and shows that differences in deposition coefficients for water isotopologues can produce isotopic fractionation coefficients that significantly differ from those of KF theory. For example, if the deposition coefficient of H218O differs by just 5% from that of ordinary water (H216O, the resulting fractionation coefficient at 20% supersaturation may deviate from the KF value by up to about ±17‰, and even more at greater supersaturation. As a result, the surface-kinetic theory may significantly change how fractionation depends on supersaturation. Moreover, the model introduces possible new temperature dependencies from the deposition coefficients. These parameters need to be constrained by new laboratory measurements.

  9. Properties of horizontally oriented ice crystals observed by polarization lidar over summit, Greenland

    Directory of Open Access Journals (Sweden)

    Neely Ryan R.

    2018-01-01

    Full Text Available A source of error in microphysical retrievals and model simulations is the assumption that clouds are composed of only randomly oriented ice crystals. This assumption is frequently not true, as evidenced by optical phenomena such as parhelia. Here, observations from the Cloud, Aerosol and Polarization Backscatter Lidar at Summit, Greenland are utilized along with other sensors and beam imaging to examine the properties of horizontally oriented ice crystals and the environment conditions in which they occur.

  10. Ikaite crystal distribution in winter sea ice and implications for CO2 system dynamics

    DEFF Research Database (Denmark)

    Rysgaard, Søren; Søgaard, D.H.; Cooper, M.

    2013-01-01

    The precipitation of ikaite (CaCO3 ⋅ 6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite...... in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74° N, 20° W) of NE Greenland. Ikaite crystals, ranging......–900 μmol kg−1 ice (~25 × 106 crystals kg−1) to values of 100–200 μmol kg−1 ice (1–7 × 106 crystals kg−1) near the sea ice–water interface, all of which are much higher (4–10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within...

  11. Ikaite crystal distribution in winter sea ice and implications for CO2 system dynamics

    DEFF Research Database (Denmark)

    Rysgaard, Søren; Søgaard, Dorthe H.; Cooper, M.

    2013-01-01

    The precipitation of ikaite (CaCO3·6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite...... in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1m thick land-fast ice site and a 0.3m thick polynya site, both in the Young Sound area (74 N, 20 W) of NE Greenland. Ikaite crystals, ranging in size......−1 ice (25×106 crystals kg−1) to values of 100–200 μmol kg−1 ice (1–7×106 crystals kg−1) near the sea ice–water interface, all of which are much higher (4–10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within the same...

  12. Structural perfection and residual electric resistance of tungsten single crystals

    International Nuclear Information System (INIS)

    Tagirova, D.M.; Dyakina, V.P.; Startsev, V.E.; Esin, V.O.

    1997-01-01

    A study was made into residual relative resistance (RRR) and structural perfection (SP) of tungsten single crystals, grown by electron beam zone melting using seeding crystals of several orientations, namely, , , , . The single crystals were of 99.98 and 99.9995 wt.% purity. The RRR value is found to depend on crystallographic orientation of an axis of crystal growth and to correlate with SP. Single crystals of different purity are differ in the nature of orientational dependences. It is shown that the correlation between RRR and SP of crystals is mainly due to conduction electron scattering by subgrain boundaries (internal size effect)

  13. The new single crystal diffractometer SC3

    Energy Technology Data Exchange (ETDEWEB)

    Schefer, J.; Koch, M.; Keller, P.; Fischer, S.; Thut, R. [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland)

    1996-11-01

    Single crystal diffraction is a powerful method for the determination of precise structure parameters, superlattices, stress. Neutron single crystal diffraction gives additionally to X-rays information on magnetic structures, both commensurate and incommensurate, hydrogen positions, hydrogen bonding behavior and accurate bondlengths, e.g. important in cuprates. The method is therefore especially powerful if combined with X-ray diffraction results. The new instrument at SINQ has been designed for inorganic materials and is positioned at a thermal beam tube, pointing on a water scatterer. This scatterer is presently operating with H{sub 2}O at ambient temperature, but a change to another medium at different temperature is possible. The instrument will be equipped with three area detectors, moving at fixed difference in 2{Theta}. each detector may be individually moved around a vertical circle (tilting angle {gamma}), allowing to use not only 4-circle geometry in the temperature range from 1.5 to 380 K, but also any equipment from a dilution refrigerator (7 mK) to a heavy magnet. A high temperature furnace for 4-circle geometry is foreseen as a future option. (author) 6 figs., 1 tab., 7 refs.

  14. The new single crystal diffractometer SC3

    International Nuclear Information System (INIS)

    Schefer, J.; Koch, M.; Keller, P.; Fischer, S.; Thut, R.

    1996-01-01

    Single crystal diffraction is a powerful method for the determination of precise structure parameters, superlattices, stress. Neutron single crystal diffraction gives additionally to X-rays information on magnetic structures, both commensurate and incommensurate, hydrogen positions, hydrogen bonding behavior and accurate bondlengths, e.g. important in cuprates. The method is therefore especially powerful if combined with X-ray diffraction results. The new instrument at SINQ has been designed for inorganic materials and is positioned at a thermal beam tube, pointing on a water scatterer. This scatterer is presently operating with H 2 O at ambient temperature, but a change to another medium at different temperature is possible. The instrument will be equipped with three area detectors, moving at fixed difference in 2Θ. each detector may be individually moved around a vertical circle (tilting angle γ), allowing to use not only 4-circle geometry in the temperature range from 1.5 to 380 K, but also any equipment from a dilution refrigerator (7 mK) to a heavy magnet. A high temperature furnace for 4-circle geometry is foreseen as a future option. (author) 6 figs., 1 tab., 7 refs

  15. Electron-irradiation of oxide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Caulfield, K.J.; Cooper, R.; Guy, L. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1996-12-31

    Full text: Point defects created in single crystals of CaO, MgO and {alpha}-Al{sub 2}O{sub 3} (sapphire) by electron-irradiation give rise to luminescence from colour centres. The luminescence may be used to monitor the formation of point defects by elastic collision processes. Such processes have great technological importance, in thermoluminescent dosimetry, the development of colour centre lasers, and particularly with the use of sapphire as a first-wall insulator in nuclear fusion reactors. Point defect formation is the initial process which can ultimately lead to dielectric breakdown. By controlling the energy of incident electrons irradiating single crystals, thresholds may be determined for atomic displacement. The time-dependent spectroscopy and decay kinetics of luminescence may also be studied. Displacement thresholds, luminescence spectroscopy and decay kinetics have been studied for CaO, MgO and {alpha}-Al{sub 2}O{sub 3}. Sapphire irradiated with 0.50 MeV electrons, exhibits a broad luminescence emission band around 300 nm at room temperature, which at temperatures below 60 K broadens into two distinct bands around 300 nm and 400 nm. Analysis of the logarithmic decay kinetics of the 300 nm band reveals distinctive features observed in similar oxides by other workers, namely a rapid decrease in intensity punctuated by discrete plateau regions. A model comprising bimolecular electron-hole recombination, in conjunction with unimolecular electron-detrapping, is able to account for these features. 4 refs.

  16. Growth features of ammonium hydrogen d-tartrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    Ammonium hydrogen d-tartrate (d-AHT) single crystals were grown in silica gel. The growth fea- tures of these crystals with variation of parameters like specific gravity of the gel, gel pH, acid concentrations, concentration of the feed solution and gel age were studied in detail. Keywords. d-AHT single crystals; growth features ...

  17. Growth of single crystals of BaFe12O19 by solid state crystal growth

    Science.gov (United States)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-10-01

    Single crystals of BaFe12O19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe12O19 are buried in BaFe12O19+1 wt% BaCO3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe12O19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe12O19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth.

  18. Ikaite crystal distribution in Arctic winter sea ice and implications for CO2 system dynamics

    DEFF Research Database (Denmark)

    Rysgaard, Søren; Søgaard, D. H.; Cooper, M.

    2012-01-01

    concentration whereas TA concentrations in bottom layers were twice as high. This depth-related discrepancy suggests interior ice processes where ikaite crystals form in surface sea ice layers and partly dissolved in bottom layers. From these findings and model calculations we relate sea ice formation and melt......The precipitation of ikaite (CaCO3·6H2O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite...... in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74° N, 20° W) of NE Greenland. Ikaite crystals, ranging...

  19. Physics-Based Crystal Plasticity Modeling of Single Crystal Niobium

    Science.gov (United States)

    Maiti, Tias

    Crystal plasticity models based on thermally activated dislocation kinetics has been successful in predicting the deformation behavior of crystalline materials, particularly in face-centered cubic (fcc) metals. In body-centered cubic (bcc) metals success has been limited owing to ill-defined slip planes. The flow stress of a bcc metal is strongly dependent on temperature and orientation due to the non-planar splitting of a/2 screw dislocations. As a consequence of this, bcc metals show two unique deformation characteristics: (a) thermally-activated glide of screw dislocations--the motion of screw components with their non-planar core structure at the atomistic level occurs even at low stress through the nucleation (assisted by thermal activation) and lateral propagation of dislocation kink pairs; (b) break-down of the Schmid Law, where dislocation slip is driven only by the resolved shear stress. Since the split dislocation core has to constrict for a kink pair formation (and propagation), the non-planarity of bcc screw dislocation cores entails an influence of (shear) stress components acting on planes other than the primary glide plane on their mobility. Another consequence of the asymmetric core splitting on the glide plane is a direction-sensitive slip resistance, which is termed twinning/atwinning sense of shear and should be taken into account when developing constitutive models. Modeling thermally-activated flow including the above-mentioned non-Schmid effects in bcc metals has been the subject of much work, starting in the 1980s and gaining increased interest in recent times. The majority of these works focus on single crystal deformation of commonly used metals such as Iron (Fe), Molybdenum (Mo), and Tungsten (W), while very few published studies address deformation behavior in Niobium (Nb). Most of the work on Nb revolves around fitting parameters of phenomenological descriptions, which do not capture adequately the macroscopic multi-stage hardening

  20. Cascaded adaptive-mask algorithm for twin-image removal and its application to digital holograms of ice crystals.

    Science.gov (United States)

    Raupach, Sebastian M F

    2009-01-10

    An iterative Gerchberg-Saxton-type algorithm with a support constraint for twin-image removal from reconstructed Gabor inline holograms of single plane objects is described. It is applied to simulated holograms and to holograms of ice crystals recorded in the laboratory and in atmospheric clouds in situ. The algorithm is characterized by a distinction between object and background region and an iterative adaption of the object mask. Applying the algorithm to recorded inline holograms of atmospheric objects, the twin-image artifacts are removed successfully, for the first time allowing for a proper access to the in situ phase information on atmospheric ice crystals. It is also demonstrated that, after application of the algorithm, previously indiscernible internal object features can become visible for large Fresnel numbers.

  1. None-destructive Measurement of Ice Crystals in Frozen Gelatin Gel

    Science.gov (United States)

    Ueno, Shigeakii; Shirakashi, Ryo; Do, Gab-Soo; Sagara, Yasuyuki; Kudoh, Ken-Ichi; Higuchi, Toshiro

    The relationship between the ice polycrystalline structure and the dielectric properties of a frozen gelatin gel were investigated. The Micro-Slicer Image Processing System (MSIPS) was applied to measure the diameter, the perimeter density and the number density of ice crystals. The dielectric property of frozen gelatin gel at various freezing rate was measured in the frequency range of 100Hz to 100kHz at -40°C. The characteristic value of dielectric property, σ0 and ɛ0-ɛ∞ have good correlation with structural parameters of ice crystals, such as diameter, perimeter density and number density, while other characteristic value, the relaxation time, τ has no relation to the structure of ice polycrystalline. The resu1ts showed that the possibility of non-destructive measurement of ice structure by dielectric property.

  2. Solid state single crystal growth of three-dimensional faceted LaFeAsO crystals

    Science.gov (United States)

    Kappenberger, Rhea; Aswartham, Saicharan; Scaravaggi, Francesco; Blum, Christian G. F.; Sturza, Mihai I.; Wolter, Anja U. B.; Wurmehl, Sabine; Büchner, Bernd

    2018-02-01

    Solid state single crystal growth (SSCG) is a crystal growth technique where crystals are grown from a polycrystalline matrix. Here, we present single crystals of the iron pnictide LaFeAsO grown via SSCG using NaAs as a liquid phase to aid crystallization. The size of the as-grown crystals are up to 2 × 3 × 0.4 mm3. Typical for this method, but very uncommon for crystals of the pnictide superconductors and especially for the oxypnictides, the crystals show pronounced facets caused by considerable growth in c direction. The crystals were characterized regarding their composition, structure, magnetic, and thermodynamic properties. This sets the stage for further measurements for which single crystals are crucial such as any c axis and reciprocal space dependent measurements.

  3. Solar cell structure incorporating a novel single crystal silicon material

    Science.gov (United States)

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  4. The Ice Selective Inlet: a novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds

    Directory of Open Access Journals (Sweden)

    P. Kupiszewski

    2015-08-01

    Full Text Available Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol–cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of much more numerous liquid droplets. The Ice Selective Inlet (ISI, presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterization. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI, the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 μm in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artefacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the optical particle size spectrometers and a characterization of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterization Experiment (CLACE 2013 and 2014 – two extensive international field campaigns encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaigns provided an important

  5. The Ice Selective Inlet: a novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds

    Science.gov (United States)

    Kupiszewski, P.; Weingartner, E.; Vochezer, P.; Schnaiter, M.; Bigi, A.; Gysel, M.; Rosati, B.; Toprak, E.; Mertes, S.; Baltensperger, U.

    2015-08-01

    Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol-cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of much more numerous liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel inlet designed to selectively sample pristine ice crystals in mixed-phase clouds and extract the ice residual particles contained within the crystals for physical and chemical characterization. Using a modular setup composed of a cyclone impactor, droplet evaporation unit and pumped counterflow virtual impactor (PCVI), the ISI segregates particles based on their inertia and phase, exclusively extracting small ice particles between 5 and 20 μm in diameter. The setup also includes optical particle spectrometers for analysis of the number size distribution and shape of the sampled hydrometeors. The novelty of the ISI is a droplet evaporation unit, which separates liquid droplets and ice crystals in the airborne state, thus avoiding physical impaction of the hydrometeors and limiting potential artefacts. The design and validation of the droplet evaporation unit is based on modelling studies of droplet evaporation rates and computational fluid dynamics simulations of gas and particle flows through the unit. Prior to deployment in the field, an inter-comparison of the optical particle size spectrometers and a characterization of the transmission efficiency of the PCVI was conducted in the laboratory. The ISI was subsequently deployed during the Cloud and Aerosol Characterization Experiment (CLACE) 2013 and 2014 - two extensive international field campaigns encompassing comprehensive measurements of cloud microphysics, as well as bulk aerosol, ice residual and ice nuclei properties. The campaigns provided an important opportunity for a

  6. In-situ observations and modeling of small nitric acid-containing ice crystals

    Directory of Open Access Journals (Sweden)

    C. Voigt

    2007-06-01

    Full Text Available Measurements in nascent ice forming regions are very rare and help understand cirrus cloud formation and the interactions of trace gases with ice crystals. A tenuous cirrus cloud has been probed with in-situ and remote sensing instruments onboard the high altitude research aircraft Geophysica M55 in the tropical upper troposphere. Besides microphysical and optical particle properties, water (H2O and reactive nitrogen species (NOy have been measured. In slightly ice supersaturated air between 14.2 and 14.9 km altitude, an unusually low ice water content of 0.031 mg m−3 and small ice crystals with mean radii of 5 µm have been detected. A high nitric acid to water molar ratio (HNO3/H2O of 5.4×10−5 has been observed in the ice crystals, about an order of magnitude higher compared to previous observations in cirrus at temperatures near 202 K. A model describing the trapping of HNO3 in growing ice particles shows that a high HNO3 content in ice crystals is expected during early growth stages, mainly originating from uptake in aerosol particles prior to freezing. Water vapor deposition on ice crystals and trapping of additional HNO3 reduces the molar ratio to values close to the ratio of HNO3/H2O in the gas phase while the cloud ages.

  7. Conduction in ion implanted single crystal diamond

    International Nuclear Information System (INIS)

    Hunn, J.D.; Parikh, N.R.; Swanson, M.L.

    1992-01-01

    We have implanted sodium, phosphorus and arsenic into single crystal type IIa diamond as possible n-type dopants. Particular emphasis was applied to the implantation of sodium at different temperatures and doses; combined implantation energies of 55,80 and 120 keV were used to provide a uniformly doped layer over approximately 100 nm depth. The implanted layers exhibited semiconducting behavior with a single exponential activation energy between 0.40 and 0.48 eV, as determined by temperature dependent resistance measurements. A sample implanted to a concentration of 5.10 19 Na + /cm 3 at 550 degrees C exhibited a single activation energy of 0.415 eV over a temperature range from 25 to 500 degrees C. Thermal annealing above 900 degrees C was found to remove implantation damage as measured by optical absorption and RBS/channeling. However, concomitant increases in the resistance and the activation energy were observed. Implantation of 22 Ne was used to introduce a damage density equivalent to the 23 Na implant, while not introducing an electrically active species. The activation energy and electrical resistance were similar but higher than those produced by implantation with sodium. We conclude that the electrical properties of the Na-implanted samples were at least partly due to electrically active Na, but that residual implantation damage was still important

  8. Photoluminescent properties of single crystal diamond microneedles

    Science.gov (United States)

    Malykhin, Sergey A.; Ismagilov, Rinat R.; Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Fedotov, Pavel V.; Ermakova, Anna; Siyushev, Petr; Katamadze, Konstantin G.; Jelezko, Fedor; Rakovich, Yury P.; Obraztsov, Alexander N.

    2018-01-01

    Single crystal needle-like diamonds shaped as rectangular pyramids were produced by combination of chemical vapor deposition and selective oxidation with dimensions and geometrical characteristics depending on the deposition process parameters. Photoluminescence spectra and their dependencies on wavelength of excitation radiation reveal presence of nitrogen- and silicon-vacancy color centers in the diamond crystallites. Photoluminescence spectra, intensity mapping, and fluorescence lifetime imaging microscopy indicate that silicon-vacancy centers are concentrated at the crystallites apex while nitrogen-vacancy centers are distributed over the whole crystallite. Dependence of the photoluminescence on excitation radiation intensity demonstrates saturation and allows estimation of the color centers density. The combination of structural parameters, geometry and photoluminescent characteristics are prospective for advantageous applications of these diamond crystallites in quantum information processing and optical sensing.

  9. Instrumentation for ice crystal characterization in laboratory using interferometric out-of-focus imaging

    Science.gov (United States)

    Brunel, M.; Demange, G.; Fromager, M.; Talbi, M.; Zapolsky, H.; Patte, R.; Aït Ameur, K.; Jacquot-Kielar, J.; Coetmellec, S.; Gréhan, G.; Quevreux, B.

    2017-08-01

    Airborne characterization of ice crystals has important applications. The extreme difficulty of realizing in situ tests requires the development of a complete instrumentation in the laboratory. Such an installation should enable design, development, test, and calibration of instruments in conditions as close as possible to real ones. We present a set of numerical and experimental tools that have been developed to realize ice crystal sensors based on interferometric particle imaging. The set of tools covers the development of complementary simulators for crystal growth and interferometric particle imaging predictions, experimental generation of "programmable" ice crystals, and instrumentation of a freezing column where different techniques as in-focus imaging, out-of-focus imaging, and digital in-line holography can be combined simultaneously for test and calibration.

  10. Development of novel growth methods for halide single crystals

    Science.gov (United States)

    Yokota, Yuui; Kurosawa, Shunsuke; Shoji, Yasuhiro; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

    2017-03-01

    We developed novel growth methods for halide scintillator single crystals with hygroscopic nature, Halide micro-pulling-down [H-μ-PD] method and Halide Vertical Bridgman [H-VB] method. The H-μ-PD method with a removable chamber system can grow a single crystal of halide scintillator material with hygroscopicity at faster growth rate than the conventional methods. On the other hand, the H-VB method can grow a large bulk single crystal of halide scintillator without a quartz ampule. CeCl3, LaBr3, Ce:LaBr3 and Eu:SrI2 fiber single crystals could be grown by the H-μ-PD method and Eu:SrI2 bulk single crystals of 1 and 1.5 inch in diameter could be grown by the H-VB method. The grown fiber and bulk single crystals showed comparable scintillation properties to the previous reports using the conventional methods.

  11. Particle Size Measurements From the First Fundamentals of Ice Crystal Icing Physics Test in the NASA Propulsion Systems Laboratory

    Science.gov (United States)

    King, Michael C.; Bachalo, William; Kurek, Andrzej

    2017-01-01

    This paper presents particle measurements by the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments from the first Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The work focuses on humidity sweeps at a larger and a smaller median volumetric diameter. The particle size distribution, number density, and water content measured by the Phase Doppler Interferometer and High Speed Imaging instruments from the sweeps are presented and compared. The current capability for these two instruments to measure and discriminate ICI conditions is examined.

  12. Development of n- and p-type Doped Perovskite Single Crystals Using Solid-State Single Crystal Growth (SSCG) Technique

    Science.gov (United States)

    2017-10-09

    tried. Among them “n- and p-type doped” BaTiO3 single crystals have been successfully fabricated . And their bi- crystals containing a twin or twist...boundary are also fabricated using diffusion bonding process of two single crystal plates. These results demonstrate that the SSCG (solid-state...or Bridgman method have critical limitations; high production cost and compositional inhomogeneity throughout the crystal. These limitations result

  13. Ultratough CVD single crystal diamond and three dimensional growth thereof

    Science.gov (United States)

    Hemley, Russell J [Washington, DC; Mao, Ho-kwang [Washington, DC; Yan, Chih-shiue [Washington, DC

    2009-09-29

    The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

  14. Composite single crystal silicon scan mirror substrates, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Single crystal silicon is a desirable mirror substrate for scan mirrors in space telescopes. As diameters of mirrors become larger, existing manufacturing...

  15. Lattice Boltzmann simulation of water isotope fractionation during ice crystal growth in clouds

    Science.gov (United States)

    Lu, Guoping; DePaolo, Donald J.

    2016-05-01

    We describe a lattice Boltzmann (LB) method for simulating water isotope fractionation during diffusion-limited ice crystal growth by vapor deposition from water-oversaturated air. These conditions apply to the growth of snow crystals in clouds where the vapor composition is controlled by the presence of both ice crystals and water droplets. Modeling of water condensation with the LB method has the advantage of allowing concentration fields to evolve based on local conditions so that the controls on grain shapes of the condensed phase can be studied simultaneously with the controls on isotopic composition and growth rate. Water isotope fractionation during snow crystal growth involves kinetic effects due to diffusion of water vapor in air, which requires careful consideration of the boundary conditions at the ice-vapor interface. The boundary condition is relatively simple for water isotopes because the molecular exchange rate for water at the interface is large compared to the crystal growth rate. Our results for the bulk crystal isotopic composition are consistent with simpler models using analytical solutions for radial geometry. However, the model results are sufficiently different for oxygen isotopes that they could affect the interpretation of D-excess values of snow and ice. The extent of vapor oversaturation plays a major role in determining the water isotope fractionation as well as the degree of dendritic growth. Departures from isotopic equilibrium increase at colder temperatures as diffusivity decreases. Dendritic crystals are isotopically heterogeneous. Isotopic variations within individual snow crystals could yield information on the microphysics of ice condensation as well as on the accommodation or sticking coefficient of water associated with vapor deposition. Our results are ultimately a first step in implementing LB models for kinetically controlled condensation or precipitation reactions, but needs to be extended also to cases where the

  16. Global Statistics of Microphysical Properties of Cloud-Top Ice Crystals

    Science.gov (United States)

    Van Diedenhoven, Bastiaan; Fridlind, Ann; Cairns, Brian; Ackerman, Andrew; Riedl, Jerome

    2017-01-01

    Ice crystals in clouds are highly complex. Their sizes, macroscale shape (i.e., habit), mesoscale shape (i.e., aspect ratio of components) and microscale shape (i.e., surface roughness) determine optical properties and affect physical properties such as fall speeds, growth rates and aggregation efficiency. Our current understanding on the formation and evolution of ice crystals under various conditions can be considered poor. Commonly, ice crystal size and shape are related to ambient temperature and humidity, but global observational statistics on the variation of ice crystal size and particularly shape have not been available. Here we show results of a project aiming to infer ice crystal size, shape and scattering properties from a combination of MODIS measurements and POLDER-PARASOL multi-angle polarimetry. The shape retrieval procedure infers the mean aspect ratios of components of ice crystals and the mean microscale surface roughness levels, which are quantifiable parameters that mostly affect the scattering properties, in contrast to a habit. We present global statistics on the variation of ice effective radius, component aspect ratio, microscale surface roughness and scattering asymmetry parameter as a function of cloud top temperature, latitude, location, cloud type, season, etc. Generally, with increasing height, sizes decrease, roughness increases, asymmetry parameters decrease and aspect ratios increase towards unity. Some systematic differences are observed for clouds warmer and colder than the homogeneous freezing level. Uncertainties in the retrievals will be discussed. These statistics can be used as observational targets for modeling efforts and to better constrain other satellite remote sensing applications and their uncertainties.

  17. Single-crystal growth of ceria-based materials

    International Nuclear Information System (INIS)

    Ulbrich, Gregor

    2015-01-01

    In this work it could be shown that Skull-Melting is a suitable method for growing ceria single crystals. Twenty different ceria-based single crystals could be manufactured. It was possible to dope ceria single crystals with Gd, Sm, Y, Zr, Ti, Ta, and Pr in different concentrations. Also co-doping with the named metals was realized. However, there remain some problems for growing ceria-based single crystals by Skull-Melting. As ignition metal zirconium was used because no ceria-based material works well. For that reason all single crystals show small zirconium contamination. Another problem is the formation of oxygen by the heat-induced reduction of ceria during the melting process. Because of that the skull of sintered material is often destroyed by gas pressure. This problem had to be solved individually for every single crystal. The obtained single crystals were characterized using different methods. To ensure the single crystal character the y were examined by Laue diffraction. All manufactured crystals are single crystals. Also powder diffraction patterns of the milled and oxidized samples were measured. For the determination of symmetry and metric the structural parameters were analyzed by the Rietveld method. All synthesized materials crystallize in space group Fm-3m known from calcium fluoride. The cubic lattice parameter a was determined for all crystals. In the case of series with different cerium and zirconium concentrations a linear correlation between cerium content and cubic lattice parameter was detected. The elemental composition was determined by WDX. All crystals show a homogeneous elemental distribution. The oxygen content was calculated because the WDX method isn't useful for determination.

  18. Growth of Ce-Doped LSO Single Crystals by Stockbarger-Bridgman Modified Crystallization Method

    International Nuclear Information System (INIS)

    Namtalishvili, M.; Sanadze, T.; Basharuli, N.; Magalashvili, P.; Mikaberidze, A.; Razmadze, Z.; Gabeskiria, M.

    2006-01-01

    The modified Stockbarger-Bridgman method was suggested for the growth of optically perfect LSO:Ce single crystals. Our investigations have shown that the most perfect crystals are grown by by the horizontally directed crystallization. In this case the elements of directional crystallyzation are combined with the zone melting. Crystallization is carried out in the conditions of sufficiently developed mirror of meltin. As a result in this case the chemical purity of grown crystals increases. (author)

  19. High-quality single crystals for neutron experiments

    Indian Academy of Sciences (India)

    Abstract. To make headway on any problem in physics, high-quality single crystals are required. In this talk, special emphasis will be placed on the crystal growth of various oxides (superconductors and magnetic materials), borides and carbides using the image furnaces at Warwick. The floating zone method of crystal ...

  20. High-quality single crystals for neutron experiments

    Indian Academy of Sciences (India)

    To make headway on any problem in physics, high-quality single crystals are required. In this talk, special emphasis will be placed on the crystal growth of various oxides (superconductors and magnetic materials), borides and carbides using the image furnaces at Warwick. The floating zone method of crystal growth used in ...

  1. Polytypism of Pb-doped single crystals of cadmium iodide

    International Nuclear Information System (INIS)

    Tyagi, U.P.; Trigunayat, G.C.

    1986-01-01

    The zone refining technique has been used both for the purification of cadmium iodide and for the growth of lead-doped single crystals of cadmium iodide. The as-grown crystals when studied by X-ray diffraction show exclusive presence of the most common polytype 4H. The hexagonal plate-shaped crystals of the doped material, grown from aqueous solution, shown polytypism, but of a different nature than the crystals of pure cadmium iodide. The results have been discussed. (author)

  2. Growth and Characterization on PMN-PT-Based Single Crystals

    Directory of Open Access Journals (Sweden)

    Jian Tian

    2014-07-01

    Full Text Available Lead magnesium niobate—lead titanate (PMN-PT single crystals have been successfully commercialized in medical ultrasound imaging. The superior properties of PMN-PT crystals over the legacy piezoelectric ceramics lead zirconate titanate (PZT enabled ultrasound transducers with enhanced imaging (broad bandwidth and improved sensitivity. To obtain high quality and relatively low cost single crystals for commercial production, PMN-PT single crystals were grown with modified Bridgman method, by which crystals were grown directly from stoichiometric melt without flux. For ultrasound imaging application, [001] crystal growth is essential to provide uniform composition and property within a crystal plate, which is critical for transducer performance. In addition, improvement in crystal growth technique is under development with the goals of improving the composition homogeneity along crystal growth direction and reducing unit cost of crystals. In recent years, PIN-PMN-PT single crystals have been developed with higher de-poling temperature and coercive field to provide improved thermal and electrical stability for transducer application.

  3. Oxygen diffusion in single crystal barium titanate.

    Science.gov (United States)

    Kessel, Markus; De Souza, Roger A; Martin, Manfred

    2015-05-21

    Oxygen diffusion in cubic, nominally undoped, (100) oriented BaTiO3 single crystals has been studied by means of (18)O2/(16)O2 isotope exchange annealing and subsequent determination of the isotope profiles in the solid by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experiments were carried out as a function of temperature 973 < T/K < 1173, at an oxygen activity of aO2 = 0.200, and as a function of oxygen activity 0.009 < aO2 < 0.900 at T = 1073 K. The oxygen isotope profiles comprise two parts: slow diffusion through a space-charge zone at the surface depleted of oxygen vacancies followed by faster diffusion in a homogeneous bulk phase. The entire isotope profile can be described by a single solution to the diffusion equation involving only three fitting parameters: the surface exchange coefficient ks*, the space-charge potential Φ0 and the bulk diffusion coefficient D*(∞). Analysis of the temperature and oxygen activity dependencies of D*(∞) and Φ0 yields a consistent picture of both the bulk and the interfacial defect chemistry of BaTiO3. Values of the oxygen vacancy diffusion coefficient DV extracted from measured D*(∞) data are compared with literature data; consequently a global expression for the vacancy diffusivity in BaTiO3 for the temperature range 466 < T/K < 1273 is obtained, with an activation enthalpy of vacancy migration, ΔHmig,V = (0.70 ± 0.04) eV.

  4. Czochralski method of growing single crystals. State-of-art

    International Nuclear Information System (INIS)

    Bukowski, A.; Zabierowski, P.

    1999-01-01

    Modern Czochralski method of single crystal growing has been described. The example of Czochralski process is given. The advantages that caused the rapid progress of the method have been presented. The method limitations that motivated the further research and new solutions are also presented. As the example two different ways of the technique development has been described: silicon single crystals growth in the magnetic field; continuous liquid feed of silicon crystals growth. (author)

  5. Magnetoresistance in terbium and holmium single crystals

    International Nuclear Information System (INIS)

    Singh, R.L.; Jericho, M.H.; Geldart, D.J.W.

    1976-01-01

    The longitudinal magnetoresistance of single crystals of terbium and holmium metals in their low-temperature ferromagnetic phase has been investigated in magnetic fields up to 80 kOe. Typical magnetoresistance isotherms exhibit a minimum which increases in depth and moves to higher fields as the temperature increases. The magnetoresistance around 1 0 K, where inelastic scattering is negligible, has been interpreted as the sum of a negative contribution due to changes in the domain structure and a positive contribution due to normal magnetoresistance. At higher temperatures, a phenomenological approach has been developed to extract the inelastic phonon and spin-wave components from the total measured magnetoresistance. In the temperature range 4--20 0 K (approximately), the phonon resistivity varies as T 3 . 7 for all samples. Approximate upper and lower bounds have been placed on the spin-wave resistivity which is also found to be described by a simple power law in this temperature range. The implications of this result for theoretical treatments of spin-wave resistivity due to s-f exchange interactions are considered. It is concluded that the role played by the magnon energy gap is far less transparent than previously suggested

  6. Update on the NASA Glenn PSL Ice Crystal Cloud Characterization (2016)

    Science.gov (United States)

    Van Zante, J.; Bencic, T.; Ratvasky, Thomas P.; Struk, Peter M.

    2016-01-01

    NASA Glenn's Propulsion Systems Laboratory (PSL) is an altitude engine research test facility capable of producing ice-crystal and supercooled liquid clouds. The cloud characterization parameter space is fairly large and complex, but the phase of the cloud seems primarily governed by wet bulb temperature. The presentation will discuss some of the issues uncovered through four cloud characterization efforts to date, as well as some of instrumentation that has been used to characterize cloud parameters including cloud uniformity, bulk total water content, median volumetric diameter and max-diameter, percent freeze-out, relative humidity, and an update on the NASA Glenn PSL Ice Crystal Cloud Characterization (2016).

  7. Reshock and release response of aluminum single crystal

    International Nuclear Information System (INIS)

    Huang, H.; Asay, J. R.

    2007-01-01

    Reshock and release experiments were performed on single crystal aluminum along three orientations and on polycrystalline 1050 aluminum with 50 μm grain size at shock stresses of 13 and 21 GPa to investigate the mechanisms for previously observed quasielastic recompression behavior. Particle velocity profiles obtained during reshocking both single crystals and polycrystalline aluminum from initial shock stresses of 13-21 GPa show similar quasielastic recompression behavior. Quasielastic release response is also observed in all single crystals, but the magnitude of the effect is crystal orientation dependent, with [111] and [110] exhibiting more ideal elastic-plastic release for unloading from the shocked state than for the [100] orientation and polycrystalline aluminum. The quasielastic response of 1050 aluminum is intermediate to that of the [100] and [111] orientations. Comparison of the wave profiles obtained for both unloading and reloading of single crystals and polycrystalline 1050 aluminum from shocked states suggests that the observed quasielastic response of polycrystalline aluminum results from the averaging response of single crystals for shock propagation along different orientations, and that the response of 1050 aluminum with large grain boundaries is not significantly different from the results obtained on single crystal aluminum. The yield strength of the single crystals and 1050 aluminum is found to increase with shock stress, which is consistent with previous results [H. Huang and I. R. Asay, J. Appl. Phys. 98, 033524 (2005)

  8. A single crystal neutron diffraction study on mixed crystal (K)0.25 ...

    Indian Academy of Sciences (India)

    41

    environment affects the hydrogen bonding is very important from the point of view of improving the ... obtained from single crystal diffraction data gives a time as well as space average picture of the crystal. 1. 2. 3. 4. 5. 6 ... KDPX(ADP)1-X mixed crystals are obtained from the aqueous solutions containing AR grade KDP and.

  9. 75 FR 8116 - Notice Pursuant to the National Cooperative Research and Production Act of 1993-Ice Crystal...

    Science.gov (United States)

    2010-02-23

    ... DEPARTMENT OF JUSTICE Antitrust Division Notice Pursuant to the National Cooperative Research and Production Act of 1993--Ice Crystal Consortium Notice is hereby given that, on December 31, 2009, pursuant to.... (``the Act''), the Ice Crystal Consortium (``ICC'') has filed written notifications simultaneously with...

  10. A finite-strain homogenization model for viscoplastic porous single crystals: II - Applications

    Science.gov (United States)

    Song, Dawei; Ponte Castañeda, P.

    2017-10-01

    In part I of this work (Song and Ponte Castañeda, 2017a), a new homogenization-based constitutive model was developed for the finite-strain, macroscopic response of porous viscoplastic single crystals. In this second part, the new model is first used to investigate the instantaneous response and the evolution of the microstructure for porous FCC single crystals for a wide range of loading conditions. The loading orientation, Lode angle and stress triaxiality are found to have significant effects on the evolution of porosity and average void shape, which play crucial roles in determining the overall hardening/softening behavior of porous single crystals. The predictions of the model are found to be in fairly good agreement with numerical simulations available from the literature for all loadings considered, especially for low triaxiality conditions. The model is then used to investigate the strong effect of crystal anisotropy on the instantaneous response and the evolution of the microstructure for porous HCP single crystals. For uniaxial tension and compression, the overall hardening/softening behavior of porous HCP crystals is found to be controlled mostly by the evolution of void shape, and not so much by the evolution of porosity. In particular, porous HCP crystals exhibit overall hardening behavior with increasing porosity, while they exhibit overall softening behavior with decreasing porosity. This interesting behavior is consistent with corresponding results for porous FCC crystals, but is found to be more significant for porous HCP crystals with large anisotropy, such as porous ice, where the non-basal slip systems are much harder than the basal systems.

  11. Systematic hardness measurements on single crystals and ...

    Indian Academy of Sciences (India)

    Unknown

    nuclear fuel container technology (Fullam 1972). While there is an enormous amount of work on the crystal growth of alkali halides with NaCl structure, work ..... Grateful thanks are due to D E Schuele, Michelson. Professor, Case Western Reserve University, for keeping the expensive CsBr and CsI crystals at our disposal.

  12. Unidirectional seeded single crystal growth from solution of benzophenone

    Science.gov (United States)

    Sankaranarayanan, K.; Ramasamy, P.

    2005-07-01

    A novel crystal growth method has been established for the growth of single crystal with selective orientation at room temperature. Using volatile solvent, the saturated solution containing the material to be crystallized was taken in an ampoule and allowed to crystallize by slow solvent evaporation assisted with a ring heater. The orientation of the growing crystal was imposed by means of a seed fixed at the bottom of the ampoule. By selecting a suitable ring heater voltage and by controlling the ring heater voltage, nucleation and the growth rate of the crystal were controlled more effectively. By employing this novel method, benzophenone single crystal ingots of diameters 10 and 20 mm and length more than 50 mm were successfully grown using xylene as solvent. The ease in scaling up of diameter from 10 to 20 mm shows the vital advantage of this technique. It was possible to achieve solute-crystal conversion efficiency of 100 percent. The grown benzophenone crystal was characterized by FTIR, TG and DTA, powder X-ray diffraction, X-ray rocking curve, optical transmission study and powder SHG measurement. The results show that the crystal quality is at least as good as the quality of the crystal grown by other known methods. Also, microbial growth was naturally avoided in this method, as the fresh solution is constantly made available for the growing crystal.

  13. High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

    KAUST Repository

    Saidaminov, Makhsud I.

    2015-07-06

    Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization.

  14. The effect of ice crystals formations on the flesh quality of frozen horse mackerel (Trachurus japonicus).

    Science.gov (United States)

    Wang, Yao; Miyazaki, Riho; Saitou, Shinobu; Hirasaka, Katsuya; Takeshita, Satoshi; Tachibana, Katsuyasu; Taniyama, Shigeto

    2017-11-15

    It is known that the formation of ice crystals has a negative impact on the flesh quality of frozen meat. This study focuses on how the formation of ice crystals in the dorsal ordinary muscle affects the flesh quality of frozen horse mackerel (Trachurus japonicus). Freeze-thawed muscle specimens (F-TMS) of horse mackerel were first stored at -24C and then thawed. The K-value, expressible water, breaking strength of unfrozen muscle specimens (UMS) and F-TMS, and histological structure (light microscope [LM], scanning electron microscope [SEM] of UMS, frozen muscle specimens [FMS], and F-TMS) were investigated. K-values were higher in the F-TMS than in the UMS, and the increasing rate of K-value in F-TMS was approximately 1.4-fold higher than UMS. Similarly, the percentage of expressible water was higher in the F-TMS than in the UMS. The breaking strength of the UMS decreased with storage period, but it remained at a higher level than that of F-TMS. Numerous ice crystal formations in muscle cells of FMS and small interstices between cells of F-TMS were observed under LM. Moreover, we observed a relatively collapsed honeycomb structure of the extracellular matrix (ECM) under SEM, and found that collagen fibril networks of endomysiums became looser after thawing. Therefore, ice crystals contribute to vulnerabilities in the ECM. These results suggest that a decrease of freshness and the degradation of physical properties caused by ECM destruction may be due to the formation of ice crystals in muscle structures during freezing, leading to the deterioration of flesh quality during storage. The flesh quality deteriorated after thawing on the basis of degradation of physical properties. Moreover, it could be presumed that the K-value increase was exacerbated by ice crystals, and the decreasing speed of chemical freshness was sped up accompanied by ice storage after thawing. Thus, the formation of ice crystals, which destroyed the muscle cells and structures, may be one of

  15. Excitonic polaritons of zinc diarsenide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Syrbu, N.N., E-mail: sirbunn@yahoo.com [Technical University of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Stamov, I.G. [T.G. Shevchenko State University of Pridnestrovie, Tiraspol, Republic of Moldova (Moldova, Republic of); Zalamai, V.V. [Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Dorogan, A. [Technical University of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of)

    2017-02-01

    Excitonic polaritons of ZnAs{sub 2} single crystals had been investigated. Parameters of singlet excitons with Г{sub 2}¯(z) symmetry and orthoexcitons 2Г{sub 1}¯(y)+Г{sub 2}¯(x) had been determined. Spectral dependencies of ordinary and extraordinary dispersion of refractive index had been calculated using interferential reflection and transmittance spectra. It was shown, that A excitonic series were due to hole (V{sub 1}) and electron (C{sub 1}) bands. The values of effective masses of electrons (m{sub c}{sup *}=0.10 m{sub 0}) and holes (m{sub v1}{sup *}=0.89 m{sub 0}) had been estimated. It was revealed that the hole mass m{sub v1}{sup *} changes from 1.03 m{sub 0} to 0.55 m{sub 0} at temperature increasing from 10 K up to 230 K and that the electron mass m{sub c}{sup *} does not depend on temperature. The integral absorption A (eV cm{sup −1}) of the states n=1, 2 and 3 of Г{sub 2}¯(z) excitons depends on the A{sub n}≈n{sup −3} equality, which it is characteristic for S-type excitonic functions. Temperature dependences of the integral absorption of ground states for Г{sub 2}¯(z) and Г{sub 2}¯(Ñ…) excitons differ. The ground states of B and C excitons formed by V{sub 3} – C{sub 1} and V{sub 4} – C{sub 1} bands and its parameters had been determined.

  16. Prospects for the synthesis of large single-crystal diamonds

    International Nuclear Information System (INIS)

    Khmelnitskiy, R A

    2015-01-01

    The unique properties of diamond have stimulated the study of and search for its applications in many fields, including optics, optoelectronics, electronics, biology, and electrochemistry. Whereas chemical vapor deposition allows the growth of polycrystalline diamond plates more than 200 mm in diameter, most current diamond application technologies require large-size (25 mm and more) single-crystal diamond substrates or films suitable for the photolithography process. This is quite a challenge, because the largest diamond crystals currently available are 10 mm or less in size. This review examines three promising approaches to fabricating large-size diamond single crystals: growing large-size single crystals, the deposition of heteroepitaxial diamond films on single-crystal substrates, and the preparation of composite diamond substrates. (reviews of topical problems)

  17. Method for harvesting rare earth barium copper oxide single crystals

    Science.gov (United States)

    Todt, Volker R.; Sengupta, Suvankar; Shi, Donglu

    1996-01-01

    A method of preparing high temperature superconductor single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid.

  18. Improving the Representation of Snow Crystal Properties Within a Single-Moment Microphysics Scheme

    Science.gov (United States)

    Molthan, Andrew L.; Petersen, Walter A.; Case, Jonathan L.; Dembek, S. R.

    2010-01-01

    As computational resources continue their expansion, weather forecast models are transitioning to the use of parameterizations that predict the evolution of hydrometeors and their microphysical processes, rather than estimating the bulk effects of clouds and precipitation that occur on a sub-grid scale. These parameterizations are referred to as single-moment, bulk water microphysics schemes, as they predict the total water mass among hydrometeors in a limited number of classes. Although the development of single moment microphysics schemes have often been driven by the need to predict the structure of convective storms, they may also provide value in predicting accumulations of snowfall. Predicting the accumulation of snowfall presents unique challenges to forecasters and microphysics schemes. In cases where surface temperatures are near freezing, accumulated depth often depends upon the snowfall rate and the ability to overcome an initial warm layer. Precipitation efficiency relates to the dominant ice crystal habit, as dendrites and plates have relatively large surface areas for the accretion of cloud water and ice, but are only favored within a narrow range of ice supersaturation and temperature. Forecast models and their parameterizations must accurately represent the characteristics of snow crystal populations, such as their size distribution, bulk density and fall speed. These properties relate to the vertical distribution of ice within simulated clouds, the temperature profile through latent heat release, and the eventual precipitation rate measured at the surface. The NASA Goddard, single-moment microphysics scheme is available to the operational forecast community as an option within the Weather Research and Forecasting (WRF) model. The NASA Goddard scheme predicts the occurrence of up to six classes of water mass: vapor, cloud ice, cloud water, rain, snow and either graupel or hail.

  19. "Predicting" Polymorphs of Pharmaceuticals Using Hydrogen Bond Propensities: Probenecid and Its Two Single-Crystal-to-Single-Crystal Phase Transitions.

    Science.gov (United States)

    Nauha, Elisa; Bernstein, Joel

    2015-06-01

    The recently developed hydrogen-bonding propensity tool in the Cambridge Structural Database software package (Mercury) was tested to predict polymorphs. The compounds for the study were chosen from a list of approximately 300 pharmaceutically important compounds, for which multiple crystal forms had not been previously reported. The hydrogen-bonding propensity analysis was carried out on approximately 60 randomly selected compounds from this list. Several compounds with a high probability for exhibiting polymorphism in the analysis were chosen for a limited experimental crystal form screening. One of the compounds, probenecid, did not yield polymorphs by traditional solution crystallization screening, but differential scanning calorimetry revealed three polymorphs. All of them exhibit the same hydrogen bonding and transform via two reversible single-crystal-to single-crystal transformations, which have been characterized in detail through three single-crystal structure determinations at appropriate temperatures. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  20. Ultra-large single crystals by abnormal grain growth.

    Science.gov (United States)

    Kusama, Tomoe; Omori, Toshihiro; Saito, Takashi; Kise, Sumio; Tanaka, Toyonobu; Araki, Yoshikazu; Kainuma, Ryosuke

    2017-08-25

    Producing a single crystal is expensive because of low mass productivity. Therefore, many metallic materials are being used in polycrystalline form, even though material properties are superior in a single crystal. Here we show that an extraordinarily large Cu-Al-Mn single crystal can be obtained by abnormal grain growth (AGG) induced by simple heat treatment with high mass productivity. In AGG, the sub-boundary energy introduced by cyclic heat treatment (CHT) is dominant in the driving pressure, and the grain boundary migration rate is accelerated by repeating the low-temperature CHT due to the increase of the sub-boundary energy. With such treatment, fabrication of single crystal bars 70 cm in length is achieved. This result ensures that the range of applications of shape memory alloys will spread beyond small-sized devices to large-scale components and may enable new applications of single crystals in other metallic and ceramics materials having similar microstructural features.Growing large single crystals cheaply and reliably for structural applications remains challenging. Here, the authors combine accelerated abnormal grain growth and cyclic heat treatments to grow a superelastic shape memory alloy single crystal to 70 cm.

  1. Hall Effect in Bulk-Doped Organic Single Crystals.

    Science.gov (United States)

    Ohashi, Chika; Izawa, Seiichiro; Shinmura, Yusuke; Kikuchi, Mitsuru; Watase, Seiji; Izaki, Masanobu; Naito, Hiroyoshi; Hiramoto, Masahiro

    2017-06-01

    The standard technique to separately and simultaneously determine the carrier concentration per unit volume (N, cm -3 ) and the mobility (μ) of doped inorganic single crystals is to measure the Hall effect. However, this technique has not been reported for bulk-doped organic single crystals. Here, the Hall effect in bulk-doped single-crystal organic semiconductors is measured. A key feature of this work is the ultraslow co-deposition technique, which reaches as low as 10 -9 nm s -1 and enables us to dope homoepitaxial organic single crystals with acceptors at extremely low concentrations of 1 ppm. Both the hole concentration per unit volume (N, cm -3 ) and the Hall mobility (μ H ) of bulk-doped rubrene single crystals, which have a band-like nature, are systematically observed. It is found that these rubrene single crystals have (i) a high ionization rate and (ii) scattering effects because of lattice disturbances, which are peculiar to this organic single crystal. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Resistivity distribution of silicon single crystals using codoping

    Science.gov (United States)

    Wang, Jong Hoe

    2005-07-01

    Numerous studies including continuous Czochralski method and double crucible technique have been reported on the control of macroscopic axial resistivity distribution in bulk crystal growth. The simple codoping method for improving the productivity of silicon single-crystal growth by controlling axial specific resistivity distribution was proposed by Wang [Jpn. J. Appl. Phys. 43 (2004) 4079]. Wang [J. Crystal Growth 275 (2005) e73] demonstrated using numerical analysis and by experimental results that the axial specific resistivity distribution can be modified in melt growth of silicon crystals and relatively uniform profile is possible by B-P codoping method. In this work, the basic characteristic of 8 in silicon single crystal grown using codoping method is studied and whether proposed method has advantage for the silicon crystal growth is discussed.

  3. Single crystal Processing and magnetic properties of gadolinium nickel

    Energy Technology Data Exchange (ETDEWEB)

    Shreve, Andrew John [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd2O3 W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

  4. Zinc (tris) thiourea sulphate (ZTS): A single crystal neutron diffraction ...

    Indian Academy of Sciences (India)

    near IR laser radiations. In this study, the crystal structure of ZTS has been ob- tained in detail by single crystal neutron diffraction technique. Using the structural parameters and an existing formalism [1] based on the theory of bond polarizability, the contributions from each of the structural groups in the unit cell to the total.

  5. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot

    DEFF Research Database (Denmark)

    Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal

    2016-01-01

    We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offe...

  6. Detection of anomalies in NLO sulphamic acid single crystals by ...

    Indian Academy of Sciences (India)

    The ultrasonic pulse echo overlap technique (PEO) has been used to measure the velocities of 10 MHz acoustic waves in sulphamic acid single crystals in the range of 300–400 K. This study evaluated all the elastic stiffnessconstants, compliance constants and Poisson's ratios of the crystal. The temperature variations of the ...

  7. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    menon, especially those involved in the gel technique. With an aim of controlling nucleation and improving the size, in the present study, we have grown pure calcium tartrate tetrahydrate single crystals using calcium formate mixed with formic acid as the supernatant solution. The grown crystals have been characterized by ...

  8. Single crystal growth of europium and ytterbium based intermetallic ...

    Indian Academy of Sciences (India)

    Abstract. This article covers the use of indium as a potential metal solvent for the crystal growth of europium and ytterbium-based intermetallic compounds. A brief view about the advantage of metal flux technique and the use of indium as reactive and non-reactive flux are outlined. Large single crystals of EuGe2, EuCoGe3.

  9. Ellipsometric studies of ErMnO3 single crystals

    DEFF Research Database (Denmark)

    Babonas, G.-J.; Grivel, Jean-Claude; Reza, A.

    2007-01-01

    Ellipsometric studies of ErMnO3 single crystals have been carried out in the spectral range of 1-5 eV by means of photometric ellipsometers. Experimental ellipsometric data were analysed in the uniaxial crystal model. For the first time, the components of dielectric function of ErMnO3 were...

  10. Single crystal neutron diffraction study of triglycine sulphate revisited

    Indian Academy of Sciences (India)

    atom positions in TGS crystals, neutron diffraction study on TGS was once again undertaken, since neutron diffraction is known to be the only method, which gives exact hydrogen atom position. 2. Experiment. A clear rectangular single crystal of TGS of dimension 3×3.5×3 mm was loaded on a goniometer, which was then ...

  11. A Study of the Optical Properties of Ice Crystals with Black Carbon Inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Arienti, Marco [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Yang, Xiaoyuan [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Kopacz, Adrian M [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Geier, Manfred [Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

    2015-09-01

    The report focu ses on the modification of the optical properties of ice crystals due to atmospheric black car bon (BC) contamination : the objective is to advance the predictive capabilities of climate models through an improved understanding of the radiative properties of compound particles . The shape of the ice crystal (as commonly found in cirrus clouds and cont rails) , the volume fraction of the BC inclusion , and its location inside the crystal are the three factors examined in this study. In the multiscale description of this problem, where a small absorbing inclusion modifies the optical properties of a much la rger non - absorbing particle, state - of - the - art discretization techniques are combined to provide the best compromise of flexibility and accuracy over a broad range of sizes .

  12. Process for Forming a High Temperature Single Crystal Canted Spring

    Science.gov (United States)

    DeMange, Jeffrey J (Inventor); Ritzert, Frank J (Inventor); Nathal, Michael V (Inventor); Dunlap, Patrick H (Inventor); Steinetz, Bruce M (Inventor)

    2017-01-01

    A process for forming a high temperature single crystal canted spring is provided. In one embodiment, the process includes fabricating configurations of a rapid prototype spring to fabricate a sacrificial mold pattern to create a ceramic mold and casting a canted coiled spring to form at least one canted coil spring configuration based on the ceramic mold. The high temperature single crystal canted spring is formed from a nickel-based alloy containing rhenium using the at least one coil spring configuration.

  13. Dielectric behaviour of strontium tartrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    on second harmonic generation, crystal oscillators and rescuators, and devices to central laser emission are ... molecular structure of tartrate, monohydrotartrate and water indents. Since the data on dielectric properties .... Design of sample holder used for measurements. Evacuation of the holder is not required. 1. Sample ...

  14. Crystal growth and scintillation properties of Pr-doped SrI2 single crystals

    Science.gov (United States)

    Yokota, Yuui; Ito, Tomoki; Yoshino, Masao; Yamaji, Akihiro; Ohashi, Yuji; Kurosawa, Shunsuke; Kamada, Kei; Yoshikawa, Akira

    2018-04-01

    Pr-doped SrI2 (Pr:SrI2) single crystals with various Pr concentrations were grown by the halide-micro-pulling-down (H-μ-PD) method, and the scintillation properties were investigated. Pr1%:SrI2 single crystal with high transparency could be grown by the H-μ-PD method while Pr2, 3 and 5%:SrI2 single crystals included some cracks and opaque parts. In the photoluminescence spectrum of the Pr1%:SrI2 single crystal, an emission peak originated from the Pr3+ ion was observed around 435 nm while the radioluminescence spectra showed an emission peak around 535 nm for the undoped SrI2 and Pr:SrI2 single crystals. Light yields of Pr1, 2, 3 and 5%:SrI2 single crystals under γ-ray irradiation were 7700, 8700, 7200 and 6700 photons/MeV, respectively. Decay times of Pr1 and 2%:SrI2 single crystals under γ-ray irradiation were 55.9 and 35.0 ns of the fast decay component, and 435 and 408 ns of the slow decay component, respectively.

  15. Is increasing ice crystal sedimentation velocity in geoengineering simulations a good proxy for cirrus cloud seeding?

    Science.gov (United States)

    Gasparini, Blaž; Münch, Steffen; Poncet, Laure; Feldmann, Monika; Lohmann, Ulrike

    2017-04-01

    The complex microphysical details of cirrus seeding with ice nucleating particles (INPs) in numerical simulations are often mimicked by increasing ice crystal sedimentation velocities. So far it has not been tested whether these results are comparable to geoengineering simulations in which cirrus clouds are seeded with INPs. We compare simulations where the ice crystal sedimentation velocity is increased at temperatures colder than -35 °C with simulations of cirrus seeding with INPs using the ECHAM-HAM general circulation model. The radiative flux response of the two methods shows a similar behaviour in terms of annual and seasonal averages. Both methods decrease surface temperature but increase precipitation in response to a decreased atmospheric stability. Moreover, simulations of seeding with INPs lead to a decrease in liquid clouds, which counteracts part of the cooling due to changes in cirrus clouds. The liquid cloud response is largely avoided in a simulation where seeding occurs during night only. Simulations with increased ice crystal sedimentation velocity, however, lead to counteracting mixed-phase cloud responses. The increased sedimentation velocity simulations can counteract up to 60 % of the radiative effect of CO2 doubling with a maximum net top-of-the-atmosphere forcing of -2. 2 W m-2. They induce a 30 % larger surface temperature response, due to their lower altitude of maximum diabatic forcing compared with simulations of seeding with INPs.

  16. Iron single crystal growth from a lithium-rich melt

    Science.gov (United States)

    Fix, M.; Schumann, H.; Jantz, S. G.; Breitner, F. A.; Leineweber, A.; Jesche, A.

    2018-03-01

    α -Fe single crystals of rhombic dodecahedral habit were grown from a Li84N12Fe∼3 melt. Crystals of several millimeter along a side form at temperatures around T ≈ 800 ° C. Upon further cooling the growth competes with the formation of Fe-doped Li3N. The b.c.c. structure and good sample quality of α -Fe single crystals were confirmed by X-ray and electron diffraction as well as magnetization measurements and chemical analysis. A nitrogen concentration of 90 ppm was detected by means of carrier gas hot extraction. Scanning electron microscopy did not reveal any sign of iron nitride precipitates.

  17. Ice Multiplication by Crystal Growth?Ice growing from the vapor along with tiny amounts of salt solution sheds free ice crystals, at -5C and saturation with respect to liquid water, in quiescent conditions. This is a more appealing explanation for the Hallett-Mossop effect than rime splintering, if it occurs primarily at temperatures near -5C.

    Science.gov (United States)

    Knight, C. A.

    2015-12-01

    Ice growing from the vapor, at -5C and liquid water supersaturation, often sheds crystals when it grows along with a small amount of salt solution. The experiments are done with single crystals growing in a temperature-controlled chamber with 5 ml of water in the bottom to maintain and control supersaturation, and the new crystals are detected when they fall into and nucleate the water in the bottom. Crystal growth is initiated by inserting into the growth chamber a pipet tip that contained a few microliters of very dilute salt solution that had been supercooled to -5C and nucleated at the tip. Growth from the vapor ensues, with condensation directly onto ice and onto whatever salt solution is exposed. The results are not completely reproducible, no doubt because the starting details of the exposure of ice and solution is not controllable. However, the shedding of crystals often occurs with starting NaCl concentrations of the order of 0.01 wt. percent, and almost never occurs with "pure" water. The shedding events themselves have not been identified, and an attractive hypothesis for how the shedding of ice occurs has not been found at the time of writing this abstract. By the time of the AGU meeting it is hoped that enough experiments will have been performed in order to say whether this effect is found only near -5C. If it requires a temperature near -5C then it seems to be an attractive explanation of the Hallett-Mossop process. It also, of course, is hoped that an attractive hypothesis for the mechanism of the shedding will have been found.

  18. Studies of propane flame soot acting as heterogeneous ice nuclei in conjunction with single particle soot photometer measurements

    Directory of Open Access Journals (Sweden)

    I. Crawford

    2011-09-01

    Full Text Available The ice nucleation efficiency of propane flame soot particles with and without a sulphuric acid coating was investigated using the aerosol and cloud chamber facility AIDA (Aerosol Interaction and Dynamics in the Atmosphere. The test soot for cloud formation simulations was produced using a propane flame Combustion Aerosol Standard generator (CAST, Jing-CAST Technologies. The organic carbon content (OC of the test soot was altered in a reproducible fashion by changing the fuel/air mixture of the generator. The soot content of ice nuclei was subsequently investigated using a combination of a pumped counterflow virtual impactor (PCVI to separate and evaporate the ice crystals, and a DMT single particle soot photometer (SP2 to examine the mixing state of the BC containing ice residuals.

    Ice nucleation was found to be most efficient for uncoated soot of low organic carbon content (~5 % organic carbon content where deposition freezing occurred at an ice saturation ratio Sice ~ 1.22 at a temperature T = 226.6 K with 25 % of the test soot becoming active as ice nuclei. Propane flame soot of higher organic carbon content (~30 % and ~70 % organic carbon content showed significantly lower ice nucleation efficiency (an activated fraction of the order of a few percent in the experiments than the low organic carbon content soot, with water saturation being required for freezing to occur. Ice nucleation occurred over the range Sice = 1.22–1.70, and T = 223.2–226.6 K. Analysis of the SP2 data showed that the 5 % organic carbon content soot had an undetectable OC coating whereas the 30 % organic carbon content soot had a thicker or less volatile OC coating.

    The application of a sulphuric acid coating to the flame soot shifted the threshold of the onset of freezing towards that of the homogeneous freezing of sulphuric acid; for the minimum OC flame soot this inhibited nucleation since the

  19. Supercooling, ice nucleation and crystal growth: a systematic study in plant samples.

    Science.gov (United States)

    Zaragotas, Dimitris; Liolios, Nikolaos T; Anastassopoulos, Elias

    2016-06-01

    This paper presents an innovative technological platform which is based on infrared video recording and is used for monitoring multiple ice nucleation events and their interactions, as they happen in 96 well microplates. Thousands of freezing curves were obtained during this study and the following freezing parameters were measured: cooling rate, nucleation point, freezing point, solidus point, degree of supercooling, duration of dendritic phase and duration of crystal growth. We demonstrate the use of this platform in the detection of ice nuclei in plant samples. Future applications of this platform may include breeding for frost tolerance, cryopreservation, frozen food technology and atmospheric sciences. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Raman spectra of deuteriated taurine single crystals

    Science.gov (United States)

    Souza, J. M. de; Lima, R. J. C.; Freire, P. T. C.; Sasaki, J. M.; Melo, F. E. A.; Filho, J. Mendes; Jones, Derry W.

    2005-05-01

    The polarized Raman spectra of partially deuteriated taurine [(ND 3+) 0.65(NH 3+) 0.35(CH 2) 2SO 3-] crystals from x( zz) x and x( zy) x scattering geometries of the A g and B g irreducible representations of the factor group C 2h are reported. The temperature-dependent Raman spectra of partially deuteriated taurine do not reveal any evidence of the structural phase transition undergone by normal taurine at about 250 K, but an anomaly observed in the 180 cm -1 band at ˜120 K implies a different dynamic for this band (which is involved in a pressure-induced phase transition) in the deuteriated crystal.

  1. Solid State Recrystallization of Single Crystal Ce:LSO Scintillator Crystals for High Resolution Detectors

    Science.gov (United States)

    2012-06-01

    Advances in our knowledge of scintillation and semiconductor materials, plastics , organics, glass, synthesized nano-crystal fabrics and fluids as...are few electron traps leading to non-radioactive transitions that quench the primary scintillation mechanisms. In addition the host lattice has a...TR-10-69 Solid State Recrystallization of Single Crystal Ce:LSO Scintillator Crystals for High Resolution Detectors Approved for public release

  2. Controlled growth of filamentary crystals and fabrication of single-crystal whisker probes

    International Nuclear Information System (INIS)

    Givargizov, E. I.

    2006-01-01

    The growth of filamentary crystals (whiskers) on a single-crystal substrate through the vapour-liquid-solid mechanism is described. The possibility of fabricating oriented systems of whiskers on the basis of this mechanism of crystal growth is noted. A phenomenon that is important for nanotechnology is noted: the existence of a critical diameter of whiskers, below which they are not formed. The phenomenon of radial periodic instability, which is characteristic of nanowhiskers, is described and the ways of its elimination are shown. The possibility of transforming whiskers into single-crystal tips and the growth of crystalline diamond particles at their apices are noted as important for practice. Possible applications of systems of whiskers and tips are described briefly. Particular attention is paid to the latest direction in whisker technology-fabrication of single-crystal whisker probes for atomic force microscopy

  3. Elastic properties of Ti-24Nb-4Zr-8Sn single crystals with bcc crystal structure

    International Nuclear Information System (INIS)

    Zhang, Y.W.; Li, S.J.; Obbard, E.G.; Wang, H.; Wang, S.C.; Hao, Y.L.; Yang, R.

    2011-01-01

    Research highlights: → The single crystals of Ti2448 alloy with the bcc crystal structure were prepared. → The elastic moduli and constants were measured by several resonant methods. → The crystal shows significant elastic asymmetry in tension and compression. → The crystal exhibits weak nonlinear elasticity with large elastic strain ∼2.5%. → The crystal has weak atomic interactions against crystal distortion to low symmetry. - Abstract: Single crystals of Ti2448 alloy (Ti-24Nb-4Zr-8Sn in wt.%) were grown successfully using an optical floating-zone furnace. Several kinds of resonant methods gave consistent Young's moduli of 27.1, 56.3 and 88.1 GPa and shear moduli of 34.8, 11.0 and 14.6 GPa for the , and oriented single crystals, and C 11 , C 12 and C 44 of 57.2, 36.1 and 35.9 GPa respectively. Uniaxial testing revealed asymmetrical elastic behaviors of the crystals: tension caused elastic softening with a large reversible strain of ∼4% and a stress plateau of ∼250 MPa, whereas compression resulted in gradual elastic stiffening with much smaller reversible strain. The crystals exhibited weak nonlinear elasticity with a large elastic strain of ∼2.5% and a high strength, approaching ∼20% and ∼30% of its ideal shear and ideal tensile strength respectively. The crystals showed linear elasticity with a small elastic strain of ∼1%. These elastic deformation characteristics have been interpreted in terms of weakened atomic interactions against crystal distortion to low crystal symmetry under external applied stresses. These results are consistent with the properties of polycrystalline Ti2448, including high strength, low elastic modulus, large recoverable strain and weak strengthening effect due to grain refinement.

  4. Mesoporous Zeolite Single Crystals for Catalytic Hydrocarbon Conversion

    DEFF Research Database (Denmark)

    Schmidt, I.; Christensen, Claus H.; Kustova, Marina

    2005-01-01

    Recently, mesoporous zeolite single crystals were discovered. They constitute a novel family of materials that features a combined micropore and mesopore architecture within each individual crystal. Here, we briefly summarize recent catalytic results from cracking and isomerization of alkalies......, alkylation of aromatics and present new results on isomerization of aromatics. Specifically, the shape-selective isomerization of meta-xylenc into para-xylene and ortho-xylene is studied. In all these reactions, rnesoporous zeolite single crystals prove to be unique catalysts since they provide easy...... transport to and from active sites and at the same time maintain the shape-selectivity required. Thus, all these results support the idea that the beneficial effect of the mesopores system in the mesoporous zeolite single crystals call be solely attributed to enhanced mass transport....

  5. Measurements of high number densities of ice crystals in the tops of tropical cumulonimbus

    Science.gov (United States)

    Knollenberg, R. G.; Kelly, K.; Wilson, J. C.

    1993-05-01

    Imaging and light scattering instruments were used during the January/February 1987 STEP Tropical Experiment at Darwin, Australia, to measure ice crystal size distributions in the tops of tropical cumulonimbus anvils associated with tropical cyclones and related cloud systems. Two light scattering instruments covered particles from 0.1-μm to 78-μm diameter. Particles larger than 50-μm diameter were imaged with a two-dimensional Grey optical array imaging probe. The measurements were made at altitudes ranging from 13 to 18 km at temperatures ranging from -60° to -90°C. Additional measurements made in continental cumulonimbus anvils in the western United States offer a comparative data set. The tropical anvil penetrations revealed surprisingly high concentrations of ice crystals. Number densities were typically greater than 10 cm-3 with up to 100 cm-3 if one includes all particles larger than 0.1 μm and can approach condensation nuclei in total concentration. In order to explain the high number densities, ice crystal nucleation at altitude is proposed with the freezing of fairly concentrated solution droplets in equilibrium at low relative humidities. Any dilute liquid phase is hypothesized to be transitory with a vanishingly short lifetime and limited to cloud levels nearer -40°C. Homogeneous nucleation of ice involving H2SO4 nuclei is attractive in explaining the high number densities of small ice crystals observed near cloud top at temperatures below -60°C. The tropical size distributions were converted to mass using a spherical equivalent size, while the continental anvil data were treated as crystalline plates. Comparisons of the ice water contents integrated from the mass distributions with total water contents measured with NOAA Lyman-alpha instruments require bulk densities equivalent to solid ice for best agreement. Correlation between the two data sets for a number of flight passes was quite good and was further improved by subtraction of water

  6. A single crystal neutron diffraction study on mixed crystal (K) 0. 25 ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 41; Issue 1. A single crystal neutron diffraction study on mixed crystal (K) 0.25 ( N H _4 ) _{0.75}H 2 PO 4 : tuning of short strong hydrogen bonds by ionic interactions. RAJUL RANJAN CHOUDHURY R CHITRA. Volume 41 Issue 1 February 2018 Article ID 8 ...

  7. Mesoscale martensitic transformation in single crystals of topological defects

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiao; Martínez-González, José A.; Hernández-Ortiz, Juan P.; Ramírez-Hernández, Abelardo; Zhou, Ye; Sadati, Monirosadat; Zhang, Rui; Nealey, Paul F.; de Pablo, Juan J.

    2017-09-05

    Liquid crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of doubletwisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with considerable precision by relying on chemically nano-patterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of meso-crystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local re-organization of the crystalline array, without diffusion of the double twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the sub-micron regime, is found to be martensitic in nature, with the diffusion-less feature associated to the collective behavior of the double twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal-nucleation and the controlled growth of soft matter.

  8. Anisotropy of Single-Crystal Silicon in Nanometric Cutting.

    Science.gov (United States)

    Wang, Zhiguo; Chen, Jiaxuan; Wang, Guilian; Bai, Qingshun; Liang, Yingchun

    2017-12-01

    The anisotropy exhibited by single-crystal silicon in nanometric cutting is very significant. In order to profoundly understand the effect of crystal anisotropy on cutting behaviors, a large-scale molecular dynamics model was conducted to simulate the nanometric cutting of single-crystal silicon in the (100)[0-10], (100)[0-1-1], (110)[-110], (110)[00-1], (111)[-101], and (111)[-12-1] crystal directions in this study. The simulation results show the variations of different degrees in chip, subsurface damage, cutting force, and friction coefficient with changes in crystal plane and crystal direction. Shear deformation is the formation mechanism of subsurface damage, and the direction and complexity it forms are the primary causes that result in the anisotropy of subsurface damage. Structurally, chips could be classified into completely amorphous ones and incompletely amorphous ones containing a few crystallites. The formation mechanism of the former is high-pressure phase transformation, while the latter is obtained under the combined action of high-pressure phase transformation and cleavage. Based on an analysis of the material removal mode, it can be found that compared with the other crystal direction on the same crystal plane, the (100)[0-10], (110)[-110], and (111)[-101] directions are more suitable for ductile cutting.

  9. Benzothiazolium Single Crystals: A New Class of Nonlinear Optical Crystals with Efficient THz Wave Generation.

    Science.gov (United States)

    Lee, Seung-Heon; Lu, Jian; Lee, Seung-Jun; Han, Jae-Hyun; Jeong, Chan-Uk; Lee, Seung-Chul; Li, Xian; Jazbinšek, Mojca; Yoon, Woojin; Yun, Hoseop; Kang, Bong Joo; Rotermund, Fabian; Nelson, Keith A; Kwon, O-Pil

    2017-08-01

    Highly efficient nonlinear optical organic crystals are very attractive for various photonic applications including terahertz (THz) wave generation. Up to now, only two classes of ionic crystals based on either pyridinium or quinolinium with extremely large macroscopic optical nonlinearity have been developed. This study reports on a new class of organic nonlinear optical crystals introducing electron-accepting benzothiazolium, which exhibit higher electron-withdrawing strength than pyridinium and quinolinium in benchmark crystals. The benzothiazolium crystals consisting of new acentric core HMB (2-(4-hydroxy-3-methoxystyryl)-3-methylbenzo[d]thiazol-3-ium) exhibit extremely large macroscopic optical nonlinearity with optimal molecular ordering for maximizing the diagonal second-order nonlinearity. HMB-based single crystals prepared by simple cleaving method satisfy all required crystal characteristics for intense THz wave generation such as large crystal size with parallel surfaces, moderate thickness and high optical quality with large optical transparency range (580-1620 nm). Optical rectification of 35 fs pulses at the technologically very important wavelength of 800 nm in 0.26 mm thick HMB crystal leads to one order of magnitude higher THz wave generation efficiency with remarkably broader bandwidth compared to standard inorganic 0.5 mm thick ZnTe crystal. Therefore, newly developed HMB crystals introducing benzothiazolium with extremely large macroscopic optical nonlinearity are very promising materials for intense broadband THz wave generation and other nonlinear optical applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Corelli: Efficient single crystal diffraction with elastic discrimination

    Indian Academy of Sciences (India)

    corporates only the source, a pseudorandom chopper, a sample, and a single point detector at a fixed scattering angle. For the simulations we utilized parameters relevant to Corelli, the dedicated single crystal diffuse scattering instrument under development at SNS, i.e., facing the high-resolution water moderator [17], ...

  11. Application of a multiple scattering model to estimate optical depth, lidar ratio and ice crystal effective radius of cirrus clouds observed with lidar.

    Directory of Open Access Journals (Sweden)

    Gouveia Diego

    2018-01-01

    Full Text Available Lidar measurements of cirrus clouds are highly influenced by multiple scattering (MS. We therefore developed an iterative approach to correct elastic backscatter lidar signals for multiple scattering to obtain best estimates of single-scattering cloud optical depth and lidar ratio as well as of the ice crystal effective radius. The approach is based on the exploration of the effect of MS on the molecular backscatter signal returned from above cloud top.

  12. Ice Surfaces

    Science.gov (United States)

    Shultz, Mary Jane

    2017-05-01

    Ice is a fundamental solid with important environmental, biological, geological, and extraterrestrial impact. The stable form of ice at atmospheric pressure is hexagonal ice, Ih. Despite its prevalence, Ih remains an enigmatic solid, in part due to challenges in preparing samples for fundamental studies. Surfaces of ice present even greater challenges. Recently developed methods for preparation of large single-crystal samples make it possible to reproducibly prepare any chosen face to address numerous fundamental questions. This review describes preparation methods along with results that firmly establish the connection between the macroscopic structure (observed in snowflakes, microcrystallites, or etch pits) and the molecular-level configuration (detected with X-ray or electron scattering techniques). Selected results of probing interactions at the ice surface, including growth from the melt, surface vibrations, and characterization of the quasi-liquid layer, are discussed.

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

    Science.gov (United States)

    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.

  14. Effect of Orientation of Ice Crystals in Cirrus on Direct and Scattered Solar Radiation Fluxes

    Science.gov (United States)

    Samokhvalov, I. V.

    2018-03-01

    The problem of solar radiation transfer by cirrus containing horizontally oriented ice crystals urgent today is considered. The results of a complex radiation experiment are described in which solar radiation fluxes at the Earth's surface are measured and high-level clouds are vertically sensed by a polarization lidar. The lidar allows the full backscattering phase matrix (BSPM) to be determined. The degree of orientation of ice crystals in cirrus is estimated from the form of the BSPM elements and their interrelations. It is shown experimentally for the first time that the degree of orientation of crystalline particles in cirrus has a significant effect on the direct and scattered solar radiation fluxes arriving at the Earth's surface.

  15. The accretion of the new ice layer on the surface of hexagonal ice crystal and the influence of the local electric field on this process

    Science.gov (United States)

    Grabowska, Joanna; Kuffel, Anna; Zielkiewicz, Jan

    2017-11-01

    The process of creation of a new layer of ice on the basal plane and on the prism plane of a hexagonal ice crystal is analyzed. It is demonstrated that the ordering of water molecules in the already existing crystal affects the freezing. On the basal plane, when the orientations of water molecules in the ice block are random, the arrangement of the new layer in a cubic manner is observed more frequently—approximately 1.7 times more often than in a hexagonal manner. When the water molecules in the ice block are more ordered, it results in the predominance of the oxygen atoms or the hydrogen atoms on the most outer part of the surface of the ice block. In this case, the hexagonal structure is formed more frequently when the supercooling of water exceeds 10 K. This phenomenon is explained by the influence of the oriented electric field, present as a consequence of the ordering of the dipoles of water molecules in the ice block. This field modifies the structure of solvation water (i.e., the layer of water in the immediate vicinity of the ice surface). We showed that the structure of solvation water predetermines the kind of the newly created layer of ice. This effect is temperature-dependent: when the temperature draws nearer to the melting point, the cubic structure becomes the prevailing form. The temperature at which the cubic and the hexagonal structures are formed with the same probabilities is equal to about 260 K. In the case of the prism plane, the new layer that is formed is always the hexagonal one, which is independent of the arrangement of water molecules in the ice block and is in agreement with previous literature data. For the basal plane, as well as for the prism plane, no evident dependence on the ordering of water molecules that constitute the ice block on the rate of crystallization can be observed.

  16. Crystal growth and characterization of a semiorganic nonlinear optical single crystal of gamma glycine

    International Nuclear Information System (INIS)

    Prakash, J. Thomas Joseph; Kumararaman, S.

    2008-01-01

    Gamma glycine has been successfully synthesized by taking glycine and potassium chloride and single crystals have been grown by solvent evaporation method for the first time. The grown single crystals have been analyzed with XRD, Fourier transform infrared (FTIR), and thermo gravimetric and differential thermal analyses (TG/DTA) measurements. Its mechanical behavior has been assessed by Vickers microhardness measurements. Its nonlinear optical property has been tested by Kurtz powder technique. Its optical behavior was examined by UV-vis., and found that the crystal is transparent in the region between 240 and 1200 nm. Hence, it may be very much useful for the second harmonic generation (SHG) applications

  17. Microscopic single-crystal refractometry as a function of wavelength

    International Nuclear Information System (INIS)

    DeLoach, L.D.

    1994-01-01

    The refractive indices of crystal fragments 50--200 μm in size can be measured for light wavelengths between 365 and 1100 nm with a spindle-stage refractometer. Established methods from optical crystallograpy are used to orient a crystal on the microscope spindle stage and then to match its refractive index to an immersion fluid. The refractive index of the fluid for the wavelength of light and matching temperature is determined by comparison of a reference crystal on a second spindle axis with the fluid under the match conditions. Investigations of new nonlinear-optical crystals admirably demonstrate the advantages of measuring the refractive index to ± 0.0004 in small single crystals

  18. Enhancing the mechanical properties of single-crystal CVD diamond.

    Science.gov (United States)

    Liang, Qi; Yan, Chih-Shiue; Meng, Yufei; Lai, Joseph; Krasnicki, Szczesny; Mao, Ho-Kwang; Hemley, Russell J

    2009-09-09

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness (∼78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

  19. Structural, spectral and mechanical studies of bimetallic crystal: cadmium manganese thiocyanate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, M.; Vijaya Prasath, G.; Mahalingam, T.; Ravi, G. [Alagappa University, Department of Physics, Karaikudi (India); Bhagavannarayan, G.; Vijayan, N. [National Physical Laboratory, Materials Characterization Division, New Delhi (India)

    2012-09-15

    A nonlinear optical bimetallic thiocyanate complex crystal, cadmium manganese thiocyanate (CMTC) has been successfully synthesized. The growth of single crystals of cadmium manganese thiocyanate has been accomplished from aqueous solution using slow evaporation method. The presence of manganese and cadmium in the synthesized material was confirmed through energy dispersive spectrum (EDS) analysis. Structural analysis was carried out using powder X-ray diffractometer (PXRD) and crystalline perfection of the grown crystals was ascertained by high-resolution X-ray diffraction (HRXRD) analysis. Fourier transform infrared (FTIR) spectrum was taken to confirm the functional groups. The transmittance spectrum of the crystal in the UV-visible region has been recorded and the cutoff wavelength has been determined. The dielectric measurements for the crystals were performed for various frequencies and temperatures. The mechanical properties were evaluated by Vickers microhardness testing, which reveals hardness and stiffness constant of the crystals. (orig.)

  20. Luminescence of YAB:Er single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Foeldvari, I.; Beregi, E.; Watterich, A. [Research Institute for Solid State Physics and Optics, HAS, Konkoly-Thege u. 29-33, 1121 Budapest (Hungary); Solarz, P.; Dominiak-Dzik, G.; Ryba-Romanowski, W. [Institute of Low Temperature and Structure Research, PAS, Okolna 2, 50422 Wroclaw (Poland)

    2007-03-15

    Luminescence spectra of YAB:Er crystals were studied in the ultraviolet-visible region and in the 10-300 K temperature range. The dominant Er{sup 3+}-emission belonged to the {sup 4}S{sub 3/2} {yields} {sup 4}I{sub 15/2} transition (18000-18500 cm{sup -1}). Its Stark components were assigned and found to be consistent with those derived from the absorption spectra. The lifetime of the luminescence was determined as a function of temperature and Er-concentration, and the decay kinetics was analyzed. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Exploration of NVE classical trajectories as a tool for molecular crystal structure prediction, with tests on ice polymorphs

    Science.gov (United States)

    Buch, V.; Martoňák, R.; Parrinello, M.

    2006-05-01

    Following an initial Communication [Buch et al., J. Chem. Phys. 123, 051108 (2005)], a new molecular-dynamics-based approach is explored to search for candidate crystal structures of molecular solids corresponding to minima of the enthalpy. The approach is based on the observation of phase transitions in an artificial periodic system with a small unit cell and relies on the existence of an optimal energy range for observing freezing to low-lying minima in the course of classical trajectories. Tests are carried out for O structures of nine H2O-ice polymorphs. NVE trajectories for a range of preimposed box shapes display freezing to the different crystal polymorphs whenever the box dimensions approximate roughly the appropriate unit cell; the exception is ice II for which freezing requires unit cell dimensions close to the correct ones. In an alternate version of the algorithm, an initial box shape is picked at random and subsequently readjusted at short trajectory intervals by enthalpy minimization. Tests reveal the existence of ice forms which are "difficult" and "easy" to locate in this way. The former include ice IV, which is also difficult to crystallize experimentally from the liquid, and ice II, which does not interface with the liquid in the phase diagram. On the other hand, the latter crystal search procedure located successfully the remaining seven ice polymorphs, including ice V, which corresponds to the most complicated structure of all ice phases, with a monoclinic cell of 28molecules.

  2. Large Silver Halide Single Crystals as Charged Particle Track Detectors

    Science.gov (United States)

    Kusmiss, J. H.

    1972-01-01

    The trajectory of the particle is made visible under a microscope by the accumulation of metallic silver at regions of the lattice damaged by the particle. This decoration of the particle track is accomplished by exposure of the crystal to light. The decoration of normally present lattice imperfections such as dislocations can be suppressed by the addition to the crystal of less than ten parts per million of a suitable polyvalent metal impurity. An account of some preliminary attempts to grow thin single crystals of AgCl is given also, and suggestions for a more refined technique are offered.

  3. Characteristics of trapped electrons and electron traps in single crystals

    International Nuclear Information System (INIS)

    Budzinski, E.E.; Potter, W.R.; Potienko, G.; Box, H.C.

    1979-01-01

    Two additional carbohydrates are reported whose crystal structures trap electrons intermolecularly in single crystals x irradiated at low temperature, namely sucrose and rhamnose. Five carbohydrate and polyhydroxy compounds are now known which exhibit this phenomenon. The following characteristics of the phenomenon were investigated: (1) the hyperfine couplings of the electron with protons of the polarized hydroxy groups forming the trap; (2) the distances between these protons and the trapped electron; (3) the spin density of the electron at the protons and (4) the relative stabilities of the electron trapped in various crystal structures

  4. Single crystal surface structure by bragg scattering

    DEFF Research Database (Denmark)

    Nielsen, Mogens

    1985-01-01

    X-ray diffraction is becoming an important tool in the measurements of surface structures. Single crystalline samples are used as in Low Energy Electron Diffraction (LEED)-studies. The X-ray technique is somewhat more involved due to the need of bright, collimated photon sources, in general...

  5. Blocking rapid ice crystal growth through nonbasal plane adsorption of antifreeze proteins.

    Science.gov (United States)

    Olijve, Luuk L C; Meister, Konrad; DeVries, Arthur L; Duman, John G; Guo, Shuaiqi; Bakker, Huib J; Voets, Ilja K

    2016-04-05

    Antifreeze proteins (AFPs) are a unique class of proteins that bind to growing ice crystal surfaces and arrest further ice growth. AFPs have gained a large interest for their use in antifreeze formulations for water-based materials, such as foods, waterborne paints, and organ transplants. Instead of commonly used colligative antifreezes such as salts and alcohols, the advantage of using AFPs as an additive is that they do not alter the physicochemical properties of the water-based material. Here, we report the first comprehensive evaluation of thermal hysteresis (TH) and ice recrystallization inhibition (IRI) activity of all major classes of AFPs using cryoscopy, sonocrystallization, and recrystallization assays. The results show that TH activities determined by cryoscopy and sonocrystallization differ markedly, and that TH and IRI activities are not correlated. The absence of a distinct correlation in antifreeze activity points to a mechanistic difference in ice growth inhibition by the different classes of AFPs: blocking fast ice growth requires rapid nonbasal plane adsorption, whereas basal plane adsorption is only relevant at long annealing times and at small undercooling. These findings clearly demonstrate that biomimetic analogs of antifreeze (glyco)proteins should be tailored to the specific requirements of the targeted application.

  6. Growth of Ti or Fe doped lithium niobate single crystals

    International Nuclear Information System (INIS)

    Lee, J.H.; Kim, J.N.; Ro, J.H.; Kim, J.W.; Jeen, G.S.; Kim, Y.C.; Lee, H.S.

    1982-01-01

    This paper reprots a study of the growth of Ti or Fe doped LiNbO 3 single crystals by Czochralski method and its physical properties. On the basis of this study we have developed a growth procedure that produces a high yield of twin-free boules. The quality is better for crystals that are lightly doped with Ti than for those of high concentrations. However there are no significant quality differences among the crystals with concentrations of less than 0.5wt% of Fe. The crystals are characterized by optical absorption and magnetic susceptibility. Undoped crystals show the magnetic susceptibility of -10x10 -6 cgs, which is diamagnetic. The crystals with 0.01wt% and 0.5wt% of ferromagnetic susceptibilities of 2.6x1a -6 cgs, and 80x10 -6 cgs, respectively. Therefore, Fe-doped crystals are paramagnetic. Very small changes of magnetic susceptibilities have been observed in the Ti-doped crystals. (Author)

  7. Preparation for Scaling Studies of Ice-Crystal Icing at the NRC Research Altitude Test Facility

    Science.gov (United States)

    Struk, Peter M.; Bencic, Timothy J.; Tsao, Jen-Ching; Fuleki, Dan; Knezevici, Daniel C.

    2013-01-01

    This paper describes experiments conducted at the National Research Council (NRC) of Canadas Research Altitiude Test Facility between March 26 and April 11, 2012. The tests, conducted collaboratively between NASA and NRC, focus on three key aspects in preparation for later scaling work to be conducted with a NACA 0012 airfoil model in the NRC Cascade rig: (1) cloud characterization, (2) scaling model development, and (3) ice-shape profile measurements. Regarding cloud characterization, the experiments focus on particle spectra measurements using two shadowgraphy methods, cloud uniformity via particle scattering from a laser sheet, and characterization of the SEA Multi-Element probe. Overviews of each aspect as well as detailed information on the diagnostic method are presented. Select results from the measurements and interpretation are presented which will help guide future work.

  8. Spin and charge transport study in single crystal organic semiconductors

    Science.gov (United States)

    Raman, Karthik V.; Mulder, Carlijn L.; Baldo, Marc A.; Moodera, Jagadeesh S.

    2009-03-01

    Spin transport studies in amorphous rubrene films have shown exciting and promising results [1]. A large spin diffusion length in these amorphous films has increased the motivation to perform spin transport study in high purity single crystal rubrene. This will provide the fundamental understanding on the spin transport behavior in OS; not influenced by defects or traps. We will present work on small channel single crystal rubrene FET device with magnetic electrodes. For example, our preliminary studies have show mobility for FET with Co electrode to be 0.014cm^2/V-s. A study on the spin and charge transport properties in single crystals of OS with magnetic electrodes is being done and the results will be reported. The influence of gate voltage and applied magnetic field on the transport properties will be discussed. [1] J.H. Shim et al., PRL 100, 226603 (2008)

  9. Deformation Induced Microtwins and Stacking Faults in Aluminum Single Crystal

    Science.gov (United States)

    Han, W. Z.; Cheng, G. M.; Li, S. X.; Wu, S. D.; Zhang, Z. F.

    2008-09-01

    Microtwins and stacking faults in plastically deformed aluminum single crystal were successfully observed by high-resolution transmission electron microscope. The occurrence of these microtwins and stacking faults is directly related to the specially designed crystallographic orientation, because they were not observed in pure aluminum single crystal or polycrystal before. Based on the new finding above, we propose a universal dislocation-based model to judge the preference or not for the nucleation of deformation twins and stacking faults in various face-centered-cubic metals in terms of the critical stress for dislocation glide or twinning by considering the intrinsic factors, such as stacking fault energy, crystallographic orientation, and grain size. The new finding of deformation induced microtwins and stacking faults in aluminum single crystal and the proposed model should be of interest to a broad community.

  10. Mechanical properties of hydroxyapatite single crystals from nanoindentation data

    Science.gov (United States)

    Zamiri, A.; De, S.

    2011-01-01

    In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals. PMID:21262492

  11. Characterization of MnO4-/KBr Single Crystal

    International Nuclear Information System (INIS)

    Win Kyaw; Win Zaw; Thein Soe; Pho Kaung; Sein Htoon

    2006-06-01

    Manually operated X- ray diffractometer (Tel-X-Ometer 580) was upgraded successfully into the Personal Computer (PC) based instrument. Utilizing this together with Fourier Transform Infrared (FTIR) Spectrophotometer investigates the effect of doping Permanganate, MnO4- , ions into Potassium Bromide, KBr, single crystal. XRD spectra of the pure KBr single crystal and the MnO4 doped KBr (MnO4- / KBr) single crystal are found to be similar irrespective of the dopant MnO4- ion. The IR spectrum, however, confirms the existence of MnO4- matrix isolated in KBr. The high intensity of the resonance Raman transitions is employed to examine the dopants in substrate which are present in such low abundances that conventional Raman Spectroscopy cannot detect

  12. Superfast domain walls in KTP single crystals

    Science.gov (United States)

    Shur, V. Ya.; Esin, A. A.; Alam, M. A.; Akhmatkhanov, A. R.

    2017-10-01

    Potassium titanyl phosphate KTiOPO4 (KTP) crystals with periodical ferroelectric domain structures are one of the most promising materials for nonlinear optics, in which the main types of nonlinear optical interactions have been demonstrated. Despite the crucial importance of the in situ visualization of domain structure kinetics for creation of high quality periodical domain gratings, there are only a few works concerning KTP. We present the results of in situ visualization of domain kinetics in KTP with the time resolution down to 12.5 μs and simultaneous recording of the switching current data. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field. The kinetic maps allowed analyzing the spatial distribution of wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast types of domain walls differed by their orientation. It was shown that the fast and slow domain walls provided the smooth input to the switching current, whereas the short-lived superfast walls resulted in short current peaks. The mobility and the threshold fields for all types of domain walls were estimated. The revealed increase in the wall velocity with deviation from low-index crystallographic planes for slow and fast walls was considered in terms of determined step generation and anisotropic kink motion. The obtained results are important for further development of domain engineering in KTP required for creation of high power, reliable, and effective coherent light sources.

  13. Effects of ice crystal surface roughness and air bubble inclusions on cirrus cloud radiative properties from remote sensing perspective

    International Nuclear Information System (INIS)

    Tang, Guanglin; Panetta, R. Lee; Yang, Ping; Kattawar, George W.; Zhai, Peng-Wang

    2017-01-01

    We study the combined effects of surface roughness and inhomogeneity on the optical scattering properties of ice crystals and explore the consequent implications to remote sensing of cirrus cloud properties. Specifically, surface roughness and inhomogeneity are added to the Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 (MC6) cirrus cloud particle habit model. Light scattering properties of the new habit model are simulated using a modified version of the Improved Geometric Optics Method (IGOM). Both inhomogeneity and surface roughness affect the single scattering properties significantly. In visible bands, inhomogeneity and surface roughness both tend to smooth the phase function and eliminate halos and the backscattering peak. The asymmetry parameter varies with the degree of surface roughness following a U shape - decreases and then increases - with a minimum at around 0.15, whereas it decreases monotonically with the air bubble volume fraction. Air bubble inclusions significantly increase phase matrix element -P 12 for scattering angles between 20°–120°, whereas surface roughness has a much weaker effect, increasing -P 12 slightly from 60°–120°. Radiative transfer simulations and cirrus cloud property retrievals are conducted by including both the factors. In terms of surface roughness and air bubble volume fraction, retrievals of cirrus cloud optical thickness or the asymmetry parameter using solar bands show similar patterns of variation. Polarimetric simulations using the MC6 cirrus cloud particle habit model are shown to be more consistent with observations when both surface roughness and inhomogeneity are simultaneously considered. - Highlights: • Surface roughness and air bubble inclusions affect optical properties of ice crystals significantly. • Including both factors improves simulations of ice cloud.• Cirrus cloud particle habit model of the MODIS collection 6 achieves better self-consistency and consistency with

  14. Communication: Anti-icing characteristics of superhydrophobic surfaces investigated by quartz crystal microresonators

    Science.gov (United States)

    Lee, Moonchan; Yim, Changyong; Jeon, Sangmin

    2015-01-01

    We investigated the anti-icing characteristics of superhydrophobic surfaces with various morphologies by using quartz crystal microresonators. Anodic aluminum oxide (AAO) or ZnO nanorods were synthesized directly on gold-coated quartz crystal substrates and their surfaces were rendered hydrophobic via chemical modifications with octyltrichlorosilane (OTS), octadecyltrichlorosilane (ODS), or octadecanethiol (ODT). Four different hydrophobic nanostructures were prepared on the quartz crystals: ODT-modified hydrophobic plain gold (C18-Au), an OTS-modified AAO nanostructure (C8-AAO), an ODS-modified AAO nanostructure (C18-AAO), and ODT-modified ZnO nanorods (C18-ZnO). The water contact angles on the C18-Au, C8-AAO, C18-AAO, and C18-ZnO surfaces were measured to be 91.4°, 147.2°, 156.3°, and 157.8°, respectively. A sessile water droplet was placed on each quartz crystal and its freezing temperature was determined by monitoring the drastic changes in the resonance frequency and Q-factor upon freezing. The freezing temperature of a water droplet was found to decrease with decreases in the water contact radius due to the decreases in the number of active sites available for ice nucleation.

  15. Regularities of recrystallization in rolled Zr single crystals

    International Nuclear Information System (INIS)

    Isaenkova, M; Perlovich, Yu; Fesenko, V; Krymskaya, O; Krapivka, N; Thu, S S

    2015-01-01

    Experiments by rolled single crystals give a more visible conception of the operating mechanisms of plastic deformation and the following recrystallization, than experiments by polycrystals. Studies by usage of X-ray diffraction methods were conducted by Zr single crystals. It was revealed, that regions of the α-Zr matrix, deformed mainly by twinning, are characterized with decreased tendency to recrystallization. Orientations of recrystallized α-Zr grains correspond to “slopes” of maxima in the rolling texture, where the level of crystalline lattice distortion is maximal and the number of recrystallization nuclei is most of all. (paper)

  16. Charge transient spectroscopy of C 60 single crystals

    Science.gov (United States)

    Baranc̆ok, D.; Halus̆ka, M.; Kuzmany, H.; Nádaz̆dy, V.

    1994-01-01

    Suitability of the charge transient spectroscopy — QTS for the investigation of fullerites is demonstrated. QTS can yield an information on the electrical properties of both the bulk and the interface of fullerites interfaced with metals (insulators, semiconductors) as well as on its bulk phase transition. Our measurements were carried out on C60 single crystals. We observed a single QTS peak which reflects most probably a thermally activated relaxation process (polarization or trap - limited charge emission) in the crystal. The expected phase transition was detected as a step of QTS signal at 255 K. The influence of a thermal treatment in air on the QTS peak was also observed.

  17. Preparation of single-crystal copper ferrite nanorods and nanodisks

    International Nuclear Information System (INIS)

    Du Jimin; Liu Zhimin; Wu Weize; Li Zhonghao; Han Buxing; Huang Ying

    2005-01-01

    This article, for the first time, reports the preparation of single-crystal copper ferrite nanorods and nanodisks. Using amorphous copper ferrite nanoparticles synthesized by reverse micelle as reaction precursor, single-crystal copper ferrite nanorods were synthesized via hydrothermal method in the presence of surfactant polyethylene glycol (PEG), however, copper ferrite nanodisks were prepared through the same procedures except the surfactant PEG. The resulting nanomaterials have been characterized by powder X-ray diffraction (XRD), selected electron area diffraction (SEAD), and transmission electron microscopy (TEM). The bulk composition of the samples was determined by means of X-ray photoelectron spectroscopy (XPS)

  18. Studies on growth, crystal structure and characterization of novel organic nicotinium trifluoroacetate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dhanaraj, P.V. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Rajesh, N.P., E-mail: rajeshnp@hotmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Sundar, J. Kalyana; Natarajan, S. [Department of Physics, Madurai Kamaraj University, Madurai 625 021 (India); Vinitha, G. [Department of Physics, Crescent Engineering College, Chennai 600 048 (India)

    2011-09-15

    Highlights: {yields} Good quality crystals of nicotinium trifluoroacetate in monoclinic system were grown for first time. {yields} Nicotinium trifluoroacetate crystal exhibits third order nonlinear optical properties. {yields} The optical spectrum of nicotinium trifluoroacetate crystal reveals the wide transmission in the entire range with cutoff wavelength at 286 nm. {yields} Nicotinium trifluoroacetate is a low dielectric constant material. - Abstract: An organic material, nicotinium trifluoroacetate (NTF) was synthesized and single crystals in monoclinic system were grown from aqueous solution for the first time. Its solubility and metastable zone width were estimated. The crystal structure of NTF was analyzed to reveal the molecular arrangements and the formation of hydrogen bonds in the crystal. High-resolution X-ray diffraction rocking curve measurements were performed to analyze the structural perfection of the grown crystals. Functional groups in NTF were identified by Fourier transform infrared spectral analysis. Thermal behaviour and stability of NTF were studied by thermogravimetric and differential thermal analysis and differential scanning calorimetry. Mechanical and dielectric properties of NTF crystals were analyzed. Optical studies reveal that NTF crystals are transparent in the wavelength range 286-1100 nm. The third order nonlinear optical parameters of NTF were derived by the Z-scan technique.

  19. A laboratory investigation on the influence of adsorbed gases and particles from the exhaust of a kerosene burner on the evaporation rate of ice crystals and the ice nucleating ability of the exhaust particles

    Energy Technology Data Exchange (ETDEWEB)

    Diehl, K.; Mitra, S.K.; Pruppacher, H.R. [Johannes Gutenberg Univ., Mainz (Germany). Inst. fuer Physik der Atmosphaere

    1997-12-31

    Laboratory experiments are described during which the influence of the exhausts of a kerosene burner on microphysical processes were studied. In one experimental investigation the evaporation rates of polluted ice crystals were compared with the evaporation rates of pure ice crystals. During another experimental investigation the ice nucleating ability of the exhaust particles was studied. The results show that the evaporation rate of polluted ice crystals was significantly reduced and also that ice nucleation takes place between -20 and -38 deg C. (author) 7 refs.

  20. Stacking fault tetrahedron induced plasticity in copper single crystal

    International Nuclear Information System (INIS)

    Zhang, Liang; Lu, Cheng; Tieu, Kiet; Su, Lihong; Zhao, Xing; Pei, Linqing

    2017-01-01

    Stacking fault tetrahedron (SFT) is the most common type of vacancy clustered defects in fcc metals and alloys, and can play an important role in the mechanical properties of metallic materials. In this study, molecular dynamics (MD) simulations were carried out to investigate the incipience of plasticity and the underlying atomic mechanisms in copper single crystals with SFT. Different deformation mechanisms of SFT were reported due to the crystal orientations and loading directions (compression and tension). The results showed that the incipient plasticity in crystals with SFT resulted from the heterogeneous dislocation nucleation from SFT, so the stress required for plastic deformation was less than that needed for perfect single crystals. Three crystal orientations ([1 0 0], [1 1 0] and [1 1 1]) were specified in this study because they can represent most of the typical deformation mechanisms of SFT. MD simulations revealed that the structural transformation of SFT was frequent under the applied loading; a metastable SFT structure and the collapse of SFT were usually observed. The structural transformation resulted in a different reduction of yield stress in compression and tension, and also caused a decreased or reversed compression/tension asymmetry. Compressive stress can result in the unfaulting of Frank loop in some crystal orientations. According to the elastic theory of dislocation, the process of unfaulting was closely related to the size of the dislocation loop and the stacking fault energy.

  1. Roflumilast - A reversible single-crystal to single-crystal phase transition at 50 °C

    Science.gov (United States)

    Viertelhaus, Martin; Holst, Hans Christof; Volz, Jürgen; Hummel, Rolf-Peter

    2013-01-01

    Roflumilast is a selective phosphodiesterase type 4 inhibitor and is marketed under the brand names Daxas®, Daliresp® and Libertec®. A phase transition of the drug substance roflumilast was observed at 50 °C. The low temperature form, the high temperature form and the phase transition were characterised by differential scanning calorimetry, variable temperature powder X-ray diffraction and single crystal X-ray diffraction, Raman spectroscopy and solid state NMR spectroscopy. The phase transition of roflumilast at 50 °C is completely reversible, the high temperature form cannot be stabilised by quench cooling and the phase transition does not influence the quality of the active pharmaceutical ingredient (API) and the drug product. It was observed to be a single crystal to single crystal phase transition.

  2. Crystal growth, spectral and laser properties of Nd:LSAT single crystal

    Science.gov (United States)

    Hu, P. C.; Yin, J. G.; Zhao, C. C.; Gong, J.; He, X. M.; Zhang, L. H.; Liang, X. Y.; Hang, Y.

    2011-10-01

    Nd:(La, Sr)(Al, Ta)O3 (Nd:LSAT) crystal was grown by the Czochralski method. The absorption and fluorescence spectra of Nd:LSAT crystal at room temperature were investigated. With a fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Nd:LSAT crystal was demonstrated. The result of diode-pumped laser operation of Nd:LSAT crystal single crystal is reported for what is to our knowledge the first time. The maximum output power at 1064 nm was obtained to be 165 mW under the incident pump power of 3 W, with the slope efficiency 10.9%.

  3. Polarization properties and crystal structures of ferroelectric (Ba,CaTiO3 single crystals

    Directory of Open Access Journals (Sweden)

    Ryota Imura

    2014-01-01

    Full Text Available We have investigated the spontaneous polarization (Ps of Ba1-xCaxTiO3 (BCT by polarization hysteresis measurements using single crystals and by density functional theory (DFT calculations. Single crystals of BCT (x = 0.07 were grown by a top-seeded solution growth (TSSG method. The polarization measurements show that the crystals (x = 0.07 have a Ps of 26.0 μC/cm2, which is slightly small compared with BaTiO3 (27.3 μC/cm2. Our DFT calculations based on a supercell approach show that Ca atoms are markedly displaced cooperatively with the adjacent Ti atoms along the Ps direction. It is suggested that the CaTiO3-like octahedral rotation is constructed in the BCT supercell around the Ca atoms, which is the origin of the smaller Ps observed for the BCT crystals.

  4. Ikaite crystals in melting sea ice - implications for pCO(2) and pH levels in Arctic surface waters

    DEFF Research Database (Denmark)

    Rysgaard, Søren; Glud, Ronnie N.; Lennert, Kunuk

    2012-01-01

    A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3 center dot 6H(2)O) in Arctic and Antarctic sea ice, which indicate......, melt reduced the ice floe thickness by 0.2m per week and resulted in an estimated 3.8 ppm decrease of pCO(2) in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 10.6 mmol m(-2) sea ice d(-1) or to 3.3 ton km(-2) ice floe week(-1). This is markedly higher than the estimated...... that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km(2) (0.5-1m thick) drifting ice floe...

  5. Ordered macro-microporous metal-organic framework single crystals

    Science.gov (United States)

    Shen, Kui; Zhang, Lei; Chen, Xiaodong; Liu, Lingmei; Zhang, Daliang; Han, Yu; Chen, Junying; Long, Jilan; Luque, Rafael; Li, Yingwei; Chen, Banglin

    2018-01-01

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional–ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent–induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  6. Ordered macro-microporous metal-organic framework single crystals

    KAUST Repository

    Shen, Kui

    2018-01-16

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional-ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent-induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  7. Monitoring Lidocaine Single-Crystal Dissolution by Ultraviolet Imaging

    DEFF Research Database (Denmark)

    Ostergaard, Jesper; Ye, Fengbin; Rantanen, Jukka

    2011-01-01

    ) imaging for conducting single‐crystal dissolution studies was performed. Using lidocaine as a model compound, the aim was to develop a setup capable of monitoring and quantifying the dissolution of lidocaine into a phosphate buffer, pH 7.4, under stagnant conditions. A single crystal of lidocaine...... was placed in the quartz dissolution cell and UV imaging was performed at 254 nm. Spatially and temporally resolved mapping of lidocaine concentration during the dissolution process was achieved from the recorded images. UV imaging facilitated the monitoring of lidocaine concentrations in the dissolution...... media adjacent to the single crystals. The concentration maps revealed the effects of natural convection due to density gradients on the dissolution process of lidocaine. UV imaging has great potential for in vitro drug dissolution testing...

  8. Extrinsic doping of CuGaSe2 single crystals

    Science.gov (United States)

    Schön, J. H.

    2000-02-01

    Technological applications of semiconductors depend critically on the ability to dope them. Single crystals of CuGaSe2 were doped during crystal growth either by a post-growth diffusion step or by ion-implantation, in order to study the limits of extrinsic doping. The electrical and optical properties of the doped samples are analysed by Hall effect and photoluminescence (PL) measurements. The carrier concentration at room temperature can be adjusted between 2 × 1019 cm-3 (p-type) and 1017 cm-3 (n-type). Various donor and acceptor levels are identified and ascribed to dopant-induced point defects taking into account the dopant concentration and/or the post-growth treatment of the single crystals.

  9. Single Crystals of Organolead Halide Perovskites: Growth, Characterization, and Applications

    KAUST Repository

    Peng, Wei

    2017-04-01

    With the soaring advancement of organolead halide perovskite solar cells rising from a power conversion efficiency of merely 3% to more than 22% shortly in five years, researchers’ interests on this big material family have been greatly spurred. So far, both in-depth studies on the fundamental properties of organolead halide perovskites and their extended applications such as photodetectors, light emitting diodes, and lasing have been intensively reported. The great successes have been ascribed to various superior properties of organolead halide hybrid perovskites such as long carrier lifetimes, high carrier mobility, and solution-processable high quality thin films, as will be discussed in Chapter 1. Notably, most of these studies have been limited to their polycrystalline thin films. Single crystals, as a counter form of polycrystals, have no grain boundaries and higher crystallinity, and thus less defects. These characteristics gift single crystals with superior optical, electrical, and mechanical properties, which will be discussed in Chapter 2. For example, organolead halide perovskite single crystals have been reported with much longer carrier lifetimes and higher carrier mobilities, which are especially intriguing for optoelectronic applications. Besides their superior optoelectronic properties, organolead halide perovskites have shown large composition versatility, especially their organic components, which can be controlled to effectively adjust their crystal structures and further fundamental properties. Single crystals are an ideal platform for such composition-structure-property study since a uniform structure with homogeneous compositions and without distraction from grain boundaries as well as excess defects can provide unambiguously information of material properties. As a major part of work of this dissertation, explorative work on the composition-structure-property study of organic-cation-alloyed organolead halide perovskites using their single

  10. Single crystal growth, crystal structure and characterization of a novel crystal: L-arginine 4-nitrophenolate 4-nitrophenol dehydrate (LAPP)

    Science.gov (United States)

    Wang, L. N.; Wang, X. Q.; Zhang, G. H.; Liu, X. T.; Sun, Z. H.; Sun, G. H.; Wang, L.; Yu, W. T.; Xu, D.

    2011-07-01

    A novel organic crystal, L-arginine 4-nitrophenolate 4-nitrophenol dehydrate (LAPP), synthesized and grown from aqueous solution, is presented. X-ray single diffraction shows that LAPP belongs to the monoclinic crystallographic system with space group P2 1. FT-IR and UV/vis/NIR transmission spectra have been employed to characterize the crystal. The computational calculation based on the density functional theory at the B3LYP/6-31G (d, p) level has been used to compute the first-order hyperpolarizability of LAPP relating to different molecular models. The morphology, nonlinear characteristic and thermal stability of the crystal have also been investigated.

  11. Corelli: Efficient single crystal diffraction with elastic discrimination

    Indian Academy of Sciences (India)

    Here, we discuss the potential of the cross-correlation technique for efficient measurement of single crystal diffuse scattering with energy discrimination, as will be implemented in a novel instrument, Corelli. Utilizing full experiment simulations, we show that this technique readily leads up to a fifty-fold gain in efficiency, ...

  12. Some Debye temperatures from single-crystal elastic constant data

    Science.gov (United States)

    Robie, R.A.; Edwards, J.L.

    1966-01-01

    The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single-crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures ??De for these materials. Models of the three wave velocity surfaces for calcite are illustrated. ?? 1966 The American Institute of Physics.

  13. Single crystal neutron diffraction study of triglycine sulphate revisited

    Indian Academy of Sciences (India)

    Abstract. In order to get the exact hydrogen-bonding scheme in triglycine sulphate. (TGS), which is an important hydrogen bonded ferroelectric, a single crystal neutron diffraction study was undertaken. The structure was refined to an R-factor of R[F2] = 0.034. Earlier neutron structure of TGS was reported with a very limited ...

  14. Organic field-effect transistors using single crystals.

    Science.gov (United States)

    Hasegawa, Tatsuo; Takeya, Jun

    2009-04-01

    Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm 2 Vs -1 , achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

  15. Organic field-effect transistors using single crystals

    Directory of Open Access Journals (Sweden)

    Tatsuo Hasegawa and Jun Takeya

    2009-01-01

    Full Text Available Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs, the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

  16. Single crystal ternary oxide ferroelectric integration with Silicon

    Science.gov (United States)

    Bakaul, Saidur; Serrao, Claudy; Youun, Long; Khan, Asif; Salahuddin, Sayeef

    2015-03-01

    Integrating single crystal, ternary oxide ferroelectric thin film with Silicon or other arbitrary substrates has been a holy grail for the researchers since the inception of microelectronics industry. The key motivation is that adding ferroelectric materials to existing electronic devices could bring into new functionality, physics and performance improvement such as non-volatility of information, negative capacitance effect and lowering sub-threshold swing of field effect transistor (FET) below 60 mV/decade in FET [Salahuddin, S, Datta, S. Nano Lett. 8, 405(2008)]. However, fabrication of single crystal ferroelectric thin film demands stringent conditions such as lattice matched single crystal substrate and high processing temperature which are incompatible with Silicon. Here we report on successful integration of PbZr0.2Ti0.8O3 in single crystal form with by using a layer transfer method. The lattice structure, surface morphology, piezoelectric coefficient d33, dielectric constant, ferroelectric domain switching and spontaneous and remnant polarization of the transferred PZT are as good as these characteristics of the best PZT films grown by pulsed laser deposition on lattice matched oxide substrates. We also demonstrate Si based, FE gate controlled FET devices.

  17. Microhardness studies on nonlinear optical L-alanine single crystals

    Indian Academy of Sciences (India)

    Sci., Vol. 36, No. 3, June 2013, pp. 471–474. c Indian Academy of Sciences. Microhardness studies on nonlinear optical L-alanine single crystals. R HANUMANTHARAO† and S KALAINATHAN‡,∗ ... ter to the area of the impression left on the specimen. Both ... where P is the applied load in kg, d is in mm and Hv is in kg mm.

  18. Magnetic structure of URhSi single crystal

    Czech Academy of Sciences Publication Activity Database

    Prokeš, K.; Andreev, Alexander V.; Honda, F.; Sechovský, V.

    2003-01-01

    Roč. 261, - (2003), s. 131-138 ISSN 0304-8853 R&D Projects: GA ČR GA202/02/0739 Institutional research plan: CEZ:AV0Z1010914 Keywords : URhSi single crystal * magnetization * neutron diffraction * magnetic structure determination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.910, year: 2003

  19. Bulk study of a DyNiAl single crystal

    Czech Academy of Sciences Publication Activity Database

    Prchal, J.; Andreev, Alexander V.; Javorský, P.; Honda, F.; Jurek, Karel

    272-276, - (2004), e419-e420 ISSN 0304-8853 R&D Projects: GA ČR GA106/02/0943 Keywords : rare-earth * DyNiAl * magnetic anisotropy * single crystal Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.031, year: 2004

  20. Area detectors in single-crystal neutron diffraction

    Science.gov (United States)

    McIntyre, Garry J.

    2015-12-01

    The introduction of area detectors has brought about a gentle revolution in the routine application of single-crystal neutron diffractometry. Implemented first for macromolecular crystallography, electronic detectors subsequently gradually spread to chemical and physics-oriented crystallography at steady-state sources. The volumetric surveying of reciprocal space implicit in the Laue technique has required area detectors right from the start, whether using film and more recently image plates and CCD-based detectors at reactors, or scintillation detectors at spallation sources. Wide-angle volumetric data collection has extended application of neutron single-crystal diffractometry to chemical structures, sample volumes, and physical phenomena previously deemed impossible. More than 30 of the dedicated single-crystal neutron diffractometers at steady-state reactor and neutron spallation sources worldwide and accessible via peer-review proposal mechanisms are currently equipped with area detectors. Here we review the historical development of the various types of area detectors used for single crystals, discuss experimental aspects peculiar to experiments with such detectors, highlight the scientific fields where the use of area detectors has had a special impact, and forecast future developments in hardware, implementation, and software.

  1. Area detectors in single-crystal neutron diffraction

    International Nuclear Information System (INIS)

    McIntyre, Garry J

    2015-01-01

    The introduction of area detectors has brought about a gentle revolution in the routine application of single-crystal neutron diffractometry. Implemented first for macromolecular crystallography, electronic detectors subsequently gradually spread to chemical and physics-oriented crystallography at steady-state sources. The volumetric surveying of reciprocal space implicit in the Laue technique has required area detectors right from the start, whether using film and more recently image plates and CCD-based detectors at reactors, or scintillation detectors at spallation sources. Wide-angle volumetric data collection has extended application of neutron single-crystal diffractometry to chemical structures, sample volumes, and physical phenomena previously deemed impossible. More than 30 of the dedicated single-crystal neutron diffractometers at steady-state reactor and neutron spallation sources worldwide and accessible via peer-review proposal mechanisms are currently equipped with area detectors. Here we review the historical development of the various types of area detectors used for single crystals, discuss experimental aspects peculiar to experiments with such detectors, highlight the scientific fields where the use of area detectors has had a special impact, and forecast future developments in hardware, implementation, and software. (review)

  2. Effect of pressure on electrical resistance of WSe single crystal

    Indian Academy of Sciences (India)

    Abstract. The results of electrical resistance measurements under pressure on single crystals of. WSe2 are reported. Measurements up to 8.5 GPa are carried out using Bridgman anvil set up and beyond it using diamond anvil cell (DAC) up to a pressure of 27 GPa. There is no clear indication of any phase transition till the ...

  3. Lattice effects in HoVo(3) single crystal

    NARCIS (Netherlands)

    Sikora, M.; Marquina, C.; Ibarra, M. R.; Nugroho, A. A.; Palstra, T. T. M.

    We report the study of lattice effects in the Mott insulator HoVO3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO3 reveals gradual orbital ordering (OO) below T-OO = 200K and orders antiferromagnetically at T-N =

  4. Lattice location of helium in uranium dioxide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Garrido, F.; Nowicki, L. E-mail: lech.nowicki@fuw.edu.pl; Sattonnay, G.; Sauvage, T.; Thome, L

    2004-06-01

    Lattice location of {sup 3}He atoms implanted into UO{sub 2} single crystals was performed by means of the channeling technique combined with nuclear reaction analysis (NRA) and Rutherford backscattering spectrometry (RBS). The {sup 3}He(d,p){sup 4}He reaction was used. The experimental angular scans show that helium atoms occupy octahedral interstitial positions.

  5. METHOD FOR MANUFACTURING A SINGLE CRYSTAL NANO-WIRE.

    NARCIS (Netherlands)

    Van Den Berg, Albert; Bomer, Johan; Carlen Edwin, Thomas; Chen, Songyue; Kraaijenhagen Roderik, Adriaan; Pinedo Herbert, Michael

    2011-01-01

    A method for manufacturing a single crystal nano-structure is provided comprising the steps of providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing

  6. METHOD FOR MANUFACTURING A SINGLE CRYSTAL NANO-WIRE

    NARCIS (Netherlands)

    Van Den Berg, Albert; Bomer, Johan; Carlen Edwin, Thomas; Chen, Songyue; Kraaijenhagen Roderik, Adriaan; Pinedo Herbert, Michael

    2012-01-01

    A method for manufacturing a single crystal nano-structure includes providing a device layer with a 100 structure on a substrate; providing a stress layer onto the device layer; patterning the stress layer along the 110 direction of the device layer; selectively removing parts of the stress layer to

  7. Double minimum creep of single crystal Ni-base superalloys

    Czech Academy of Sciences Publication Activity Database

    WU, X.; Wollgramm, P.; Somsen, C.; Dlouhý, Antonín; Kostka, A.; Eggeler, G.

    2016-01-01

    Roč. 112, JUN (2016), s. 242-260 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA14-22834S Institutional support: RVO:68081723 Keywords : Single crystal Ni-base superalloys * Primary creep * Transmission electron microscopy * Dislocations * Stacking fault s Subject RIV: JG - Metallurgy Impact factor: 5.301, year: 2016

  8. Growth features of ammonium hydrogen d-tartrate single crystals

    Indian Academy of Sciences (India)

    Unknown

    Most of the tartrate compounds are insoluble in water and decompose before melting. Hence, single crystals of such type cannot be grown either by slow evaporation or by melt technique, but can be grown easily by gel method. Gel method is an alternative method to solution growth with controlled diffusion and the growth ...

  9. Determining ice water content from 2D crystal images in convective cloud systems

    Science.gov (United States)

    Leroy, Delphine; Coutris, Pierre; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter

    2016-04-01

    Cloud microphysical in-situ instrumentation measures bulk parameters like total water content (TWC) and/or derives particle size distributions (PSD) (utilizing optical spectrometers and optical array probes (OAP)). The goal of this work is to introduce a comprehensive methodology to compute TWC from OAP measurements, based on the dataset collected during recent HAIC (High Altitude Ice Crystals)/HIWC (High Ice Water Content) field campaigns. Indeed, the HAIC/HIWC field campaigns in Darwin (2014) and Cayenne (2015) provide a unique opportunity to explore the complex relationship between cloud particle mass and size in ice crystal environments. Numerous mesoscale convective systems (MCSs) were sampled with the French Falcon 20 research aircraft at different temperature levels from -10°C up to 50°C. The aircraft instrumentation included an IKP-2 (isokinetic probe) to get reliable measurements of TWC and the optical array probes 2D-S and PIP recording images over the entire ice crystal size range. Based on the known principle relating crystal mass and size with a power law (m=α•Dβ), Fontaine et al. (2014) performed extended 3D crystal simulations and thereby demonstrated that it is possible to estimate the value of the exponent β from OAP data, by analyzing the surface-size relationship for the 2D images as a function of time. Leroy et al. (2015) proposed an extended version of this method that produces estimates of β from the analysis of both the surface-size and perimeter-size relationships. Knowing the value of β, α then is deduced from the simultaneous IKP-2 TWC measurements for the entire HAIC/HIWC dataset. The statistical analysis of α and β values for the HAIC/HIWC dataset firstly shows that α is closely linked to β and that this link changes with temperature. From these trends, a generalized parameterization for α is proposed. Finally, the comparison with the initial IKP-2 measurements demonstrates that the method is able to predict TWC values

  10. Calorimetric determination of inhibition of ice crystal growth by antifreeze protein in hydroxyethyl starch solutions.

    Science.gov (United States)

    Hansen, T N; Carpenter, J F

    1993-01-01

    Differential scanning calorimetry and cryomicroscopy were used to investigate the effects of type I antifreeze protein (AFP) from winter flounder on 58% solutions of hydroxyethyl starch. The glass, devitrification, and melt transitions noted during rewarming were unaffected by 100 micrograms/ml AFP. Isothermal annealing experiments were undertaken to detect the effects of AFP-induced inhibition of ice crystal growth using calorimetry. A premelt endothermic peak was detected during warming after the annealing procedure. Increasing the duration or the temperature of the annealing for the temperature range from -28 and -18 degrees C resulted in a gradual increase in the enthalpy of the premelt endotherm. This transition was unaffected by 100 micrograms/ml AFP. Annealing between -18 and -10 degrees C resulted in a gradual decrease in the premelt peak enthalpy. This process was inhibited by 100 micrograms/ml AFP. Cryomicroscopic examination of the samples revealed that AFP inhibited ice recrystallization during isothermal annealing at -10 degrees C. Annealing at lower temperatures resulted in minimal ice recrystallization and no visible effect of AFP. Thus, the 100 micrograms/ml AFP to have a detectable influence on thermal events in the calorimeter, conditions must be used that result in significant ice growth without AFP and visible inhibition of this process by AFP. Images FIGURE 8 PMID:7690257

  11. Sensitivity of Cirrus and Mixed-phase Clouds to the Ice Nuclei Spectra in McRAS-AC: Single Column Model Simulations

    Science.gov (United States)

    Betancourt, R. Morales; Lee, D.; Oreopoulos, L.; Sud, Y. C.; Barahona, D.; Nenes, A.

    2012-01-01

    The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice formation parameterizations of Liu and Penner (LP) and Barahona and Nenes (BN). The performance of LP and BN ice nucleation parameterizations were assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments where established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to described the availability of IN for heterogeneous ice nucleation. The results show large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there are some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to transfer liquid to ice efficiently, so that on average, the clouds were fully glaciated at T approximately 260K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted 20 average values of IWP within plus or minus 15% of the observations.

  12. Electronic Transport Properties of Single Crystal THALLIUM-2201 Superconductors

    Science.gov (United States)

    Yandrofski, Robert Michael

    1992-11-01

    Four-probe resistance measurements on single crystals of the calcium-free thallium-based superconducting rm Tl_2Ba_2CuO_{6+delta } phase (Tl-2201) were performed in magnetic fields up to 12 Telsa. Single crystals of sizes approaching 5mm x 1mm x.2mm were grown by a self-flux technique and were characterized by single crystal X-ray diffraction and X-ray Dispersive Analysis. Field measurements were taken both at dc and at low frequencies using a lock-in technique. Techniques were developed to oxygen-anneal the as-grown single crystals to generate single crystal samples of the same Tl-2201 phase with varying transition temperature T_{rm c}. Resistivity measurements indicate a gradual cross-over from linear temperature-dependent resistivity at high T_ {rm c} (i.e., low oxygen doping), to a predominantly quadratic temperature dependent resistivity at low T_{rm c} (i.e., high oxygen doping). These results are correlated with theories describing the gradual change in the nature of charge carrier scattering as the system is over-doped with holes. Four-probe resistivity measurements indicate that severe anisotropies in the resistivity profiles exist at all oxygen concentrations, with the out-of-plane resistivity measuring two to three orders of magnitude higher than the in-plane resistivity. Magnetic field results indicate the presence of an irreversibility transition, with a signature for a Kosterlitz-Thouless (or "melting") transition in the vortex lattice at low fields occuring in samples with the lower T_{rm c}. Such data suggest a quasi-two-dimensional behavior in this system. Measurements of the fluctuation conductivity also suggest a quasi-two -dimensional fluctuation regime. Experimental results are discussed within the framework of Fermi liquid theory.

  13. Single-crystal metal growth on amorphous insulating substrates.

    Science.gov (United States)

    Zhang, Kai; Pitner, Xue Bai; Yang, Rui; Nix, William D; Plummer, James D; Fan, Jonathan A

    2018-01-23

    Metal structures on insulators are essential components in advanced electronic and nanooptical systems. Their electronic and optical properties are closely tied to their crystal quality, due to the strong dependence of carrier transport and band structure on defects and grain boundaries. Here we report a method for creating patterned single-crystal metal microstructures on amorphous insulating substrates, using liquid phase epitaxy. In this process, the patterned metal microstructures are encapsulated in an insulating crucible, together with a small seed of a differing material. The system is heated to temperatures above the metal melting point, followed by cooling and metal crystallization. During the heating process, the metal and seed form a high-melting-point solid solution, which directs liquid epitaxial metal growth. High yield of single-crystal metal with different sizes is confirmed with electron backscatter diffraction images, after removing the insulating crucible. Unexpectedly, the metal microstructures crystallize with the [Formula: see text] direction normal to the plane of the film. This platform technology will enable the large-scale integration of high-performance plasmonic and electronic nanosystems.

  14. Effect of zinc acetate addition on crystal growth, structural, optical, thermal properties of glycine single crystals

    Directory of Open Access Journals (Sweden)

    S. Anbu Chudar Azhagan

    2017-05-01

    Full Text Available In the present study, γ-glycine has been crystallized by using zinc acetate dihydrate as an additive for the first time by slow solvent evaporation method. The second harmonic conversion efficiency of γ-glycine crystal was determined using Kurtz and Perry powder technique and was found to be 3.66 times greater than that of standard inorganic material potassium dihydrogen phosphate (KDP. The analytical grade chemicals of glycine and zinc acetate dihydrate were taken in six different molar ratios: 1:0.2, 1:0.4, 1:0.6, 1:0.7, 1:0.8, and 1:0.9 respectively to find out the γ-polymorph of glycine. The lower molar concentration of zinc acetate yield only α-polymorph where as the higher molar concentration of zinc acetate inhibits the γ-polymorph of glycine which was confirmed by single crystal XRD and powder XRD studies. Inductively coupled plasma optical emission spectrometry (ICP-OES was carried out to quantify the concentration of zinc element in the grown glycine single crystals. The concentration of zinc element in the presence of grown γ-glycine single crystal is found to be 0.73 ppm. UV–Visible–NIR transmittance spectra were recorded for the samples to analyse the transparency in visible and near infrared region (NIR. The optical band gap Eg was estimated for γ-glycine single crystal using UV–Visible–NIR study. Functional groups present in the samples were identified by FTIR spectroscopic analysis. Differential scanning calorimetry technique was employed to determine the phase transition, thermal stability and melting point of the grown crystal.

  15. The growth of single crystals of Ni-W alloy under conditions of high temperature gradient

    International Nuclear Information System (INIS)

    Azhazha, V.M.; Gorbenko, Yu.V.; Kovtun, G.P.; Ladygin, A.N.; Malykhin, D.G.; Rudycheva, T.Yu.; Sverdlov, V.Ya.; Shcherban', A.P.; Zhemanyuk, P.D.; Klochikhin, V.V.

    2004-01-01

    The structure of single crystals of the NV-4 nickel alloy containing 32-36 wt % W is investigated. The temperature gradient at the crystallization front and the velocity of the crystallization front are the variable parameters of directional crystallization. The degrees of structural perfection of the single crystals grown under different conditions are compared. The crystallization parameters providing growth of single crystals that have high structural perfection and can be successfully used as seeds for the growth of single-crystal blades are determined. Typical defects formed upon directional crystallization of single crystals of the Ni-W (35 wt %) alloy are examined. The studied defects are classified, and the factors responsible for the disturbance of the single-crystal structure are analyzed

  16. Twinning processes in Cu-Al-Ni martensite single crystals investigated by neutron single crystal diffraction method

    Czech Academy of Sciences Publication Activity Database

    Molnar, P.; Šittner, P.; Novák, V.; Lukáš, Petr

    2008-01-01

    Roč. 481, Sp.Iss.SI (2008), s. 513-517 ISSN 0921-5093 R&D Projects: GA AV ČR IAA100480704 Institutional research plan: CEZ:AV0Z10480505 Keywords : Cu-Al-Ni * single crystals * neutron diffraction Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.806, year: 2008

  17. Thermal and electrical transport properties of ? single crystals

    Science.gov (United States)

    Gamal, G. A.; Nassary, M. M.; Nagat, A. T.; Abou-Alwafa, A. M.

    1996-04-01

    Electrical conductivity, Hall effect and thermoelectric power measurements are made for the compound 0268-1242/11/4/009/img2. This compound, which is a semiconductor grown in a single-crystal form, is studied over a wide range of temperature from 150 to 375 K. The crystal is grown by a modification of the Bridgman method. The combination of the electrical and thermal measurements in the present investigation makes it possible to find various physical parameters and to reveal the general behaviour of this semiconductor.

  18. Ferroelectric phase transition in Ga2Te3 single crystals

    Science.gov (United States)

    Gamal, G. A.; Abdalrahman, M. M.; Ashraf, M. I.; Eman, H. J.

    2005-01-01

    Measurements of the electrical conductivity and Hall effect were carried out in a wide temperature range (200-500 K) for Ga2Te3 crystals. The crystals were grown in single crystalline form by making a modification of the travelling heater method technique. The measurements revealed unusual observations in the electric conductivity and Hall mobility indicating the presence of some type of phase transitions at about 430 K. So, ferroelectric behavior was examined for confirming the presence of second-order (ferroelectric) phase transition. An energy gap of 1.21 eV and depth of the impurity center of 0.11 eV were found.

  19. Growth and Characterization of Tl2S Single Crystals

    Science.gov (United States)

    Gamal, G. A.; Zied, M. Abou; Gerges, M. K.; Galal, E. M.

    2003-09-01

    Single crystals of the Tl2S compound were grown for the first time in our laboratory by a new crystal growth technique based on a modification of the traveling heater method technique (THM). This growth was performed in our laboratory. Electrical conductivity, Hall effect and thermoelectric power (TEP) measurements were carried out in the temperature range (200-575 K). Throughout these measurements, various physical parameters such as effective mass of charge carriers, carrier mobility, diffusion length, diffusion coefficient, and the relaxation time for both majority and minority carriers were found. In conjunction with electrical conductivity and charge carrier concentration, thermoelectric power is discussed.

  20. Trapezoidal diffraction grating beam splitters in single crystal diamond

    Science.gov (United States)

    Kiss, Marcell; Graziosi, Teodoro; Quack, Niels

    2018-02-01

    Single Crystal Diamond has been recognized as a prime material for optical components in high power applications due to low absorption and high thermal conductivity. However, diamond microstructuring remains challenging. Here, we report on the fabrication and characterization of optical diffraction gratings exhibiting a symmetric trapezoidal profile etched into a single crystal diamond substrate. The optimized grating geometry diffracts the transmitted optical power into precisely defined proportions, performing as an effective beam splitter. We fabricate our gratings in commercially available single crystal CVD diamond plates (2.6mm x 2.6mm x 0.3mm). Using a sputter deposited hard mask and patterning by contact lithography, the diamond is etched in an inductively coupled oxygen plasma with zero platen power. The etch process effectively reveals the characteristic {111} diamond crystal planes, creating a precisely defined angled (54.7°) profile. SEM and AFM measurements of the fabricated gratings evidence the trapezoidal shape with a pitch of 3.82μm, depth of 170 nm and duty cycle of 35.5%. Optical characterization is performed in transmission using a 650nm laser source perpendicular to the sample. The recorded transmitted optical power as function of detector rotation angle shows a distribution of 21.1% in the 0th order and 23.6% in each +/-1st order (16.1% reflected, 16.6% in higher orders). To our knowledge, this is the first demonstration of diffraction gratings with trapezoidal profile in single crystal diamond. The fabrication process will enable beam splitter gratings of custom defined optical power distribution profiles, while antireflection coatings can increase the efficiency.

  1. Annealing effect of H+ -implanted single crystal silicon on strain and crystal structure

    International Nuclear Information System (INIS)

    Duo Xinzhong; Liu Weili; Zhang Miao; Gao Jianxia; Fu Xiaorong; Lin Chenglu

    2000-01-01

    The work focuses on the rocking curves of H + -implanted single silicon crystal detected by Four-Crystal X-ray diffractometer. The samples were annealed under different temperatures. Lattice defect in H + -implanted silicon crystals was detected by Rutherford Backscattering Spectrometry. It appeared that H-related complex did not crush until annealing temperature reached about 400 degree C. At that temperature H 2 was formed, deflated in silicon lattice and strained the lattice. But defects did not come into being in large quantity. The lattice was undamaged. When annealing temperature reached 500 degree C, strain induced by H 2 deflation crashed the silicon lattice. A large number of defects were formed. At the same time bubbles in the crystal and blister/flaking on the surface could be observed

  2. "Crystals within Crystals: The Story of Sea Ice". A Classroom-Based Outreach Project Communicating Cutting-Edge Ocean Science to School Pupils

    Science.gov (United States)

    Butler, B.

    2016-02-01

    'Crystals within Crystals: The story of sea ice' is a UK based outreach project based that uses a range practical tools to engage school students with cutting edge scientific research that relates to the use of some of the world's most powerful X-rays in sea ice research. The project is delivered in the form of a classroom workshop that first introduces school pupils (aged 11-14) to seawater and the salts that give it a salinity. The pupils are then shown how the presence of salts within seawater results in very important physical changes when the liquid freezes, which includes different structural and optical properties of the ice. The properties of the ice are then linked to the presence of countless microscopic salt crystals that are trapped within the microstructure of the frozen seawater, which is explained with use of a novel crystal growth demonstration. Given that there is currently no way of successfully removing these salt crystals from the ice, the workshop culminates in explaining how some of the worlds most powerful X-rays can be used to investigate processes that otherwise remain elusive. The workshop introduces students to the fundamental principles of scientific enquiry, the sea ice environment, and the power of X-rays in investigating the properties of crystals. Here we present information that outlines a host of practical and project management tools that are applicacble to outreach projects in the the field of ocean sciences, with the aim of seeding ideas and interest for other graduate student to enage with the public during their studies.

  3. Fluid inclusions and microstructures in experimentally deformed quartz single crystals

    Science.gov (United States)

    Thust, A.; Tarantola, A.; Heilbronner, R.; Stünitz, H.

    2009-04-01

    The "H2O-weakening" effect that reduces the strength of quartz dramatically (e.g. Griggs & Blacic 1965) is still not understood. For example, Kronenberg & Tullis (1984) conclude that the weakening effect is pressure dependent while Paterson (1989) infers a glide and recovery control of water. Obviously, the spatial distribution and transport of H2O are important factors (Kronenberg et al. 1986, FitzGerald et al. 1991). We have carried out experiments on milky quartz in a Griggs deformation apparatus. Cylinders (6.5 mm in diameter, 12-13 mm in length) from a milky zone of a natural quartz single crystal have been cored in orientations (1) normal to one of the prism planes and (2) 45˚ to and 45˚ to (O+orientation). At 1 GPa confining pressure, 900˚ C and 10-6s-1, the flow strength is 150 MPa for samples with orientation (1). Further experiments are needed to establish the flow strength for orientation (2). FTIR measurements on double-polished thick sections (200-500 μm) in the undeformed quartz material yield an average H2O content of approximately 100 H/106Si. The water is heterogeneously distributed in the sample. Direct measurements on fluid inclusions yield a H2O content of more than 25 000 H/106Si. Thus, the H2O in the undeformed material is predominantly present in fluid inclusions of size from tens to hundred microns. Micro-thermometric measurements at low temperature indicate the presence of different salts in the fluid inclusions. The ice melting temperature, between -6.9 and -7.4˚ C, indicate an average salinity of 10.5 wt% NaCl. After deformation the distribution of H2O is more homogeneous throughout the sample. The majority of the big inclusions have disappeared and very small inclusions of several microns to sub-micron size have formed. FTIR measurements in zones of undulatory extinction and shear bands show an average H2O content of approximately 3000 H/106Si. Moreover, the larger fluid inclusions are characterized by a higher salinity (12 wt%) due

  4. Twinning structures in near-stoichiometric lithium niobate single crystals

    International Nuclear Information System (INIS)

    Yao, Shuhua; Chen, Yanfeng

    2010-01-01

    A near-stoichiometric lithium niobate single crystal has been grown by the Czochralski method in a hanging double crucible with a continuous powder supply system. Twins were found at one of the three characteristic growth ridges of the as-grown crystal. The twin structure was observed and analyzed by transmission synchrotron topography. The image shifts ΔX and ΔY in the transmission synchrotron topograph were calculated for the 3 anti 2 anti 12 and 0 anti 222 reflections based on results from high-resolution X-ray diffractometry. It is confirmed that one of the {01 anti 1 anti 2} m planes is the composition face of the twin and matrix crystals. The formation mechanism of these twins is discussed. (orig.)

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

    Science.gov (United States)

    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.

  6. Crystal growth, structure analysis and characterisation of 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Sankari, R. Siva, E-mail: sivasankari.sh@act.edu.in [Department of Physics, Agni College of Technology, Thalambur, Chennai-603103 (India); Perumal, Rajesh Narayana [Department of Physics, SSN College of Engineering, Kalavakkam, Chennai-603110 (India)

    2014-04-24

    Single crystal of dielectric material 2 - (1, 3 - dioxoisoindolin - 2 - yl) acetic acid has been grown by slow evaporation solution growth method. The grown crystal was harvested in 25 days. The crystal structure was analyzed by Single crystal X - ray diffraction. UV-vis-NIR analysis was performed to examine the optical property of the grown crystal. The thermal property of the grown crystal was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The dielectric measurements were carried out and the dielectric constant was calculated and plotted at all frequencies.

  7. Frictional properties of single crystals HMX, RDX and PETN explosives.

    Science.gov (United States)

    Wu, Y Q; Huang, F L

    2010-11-15

    The frictional properties of single crystals of cyclotetramethylene tetranitramine (HMX), cyclotrimethylene trinitramine (RDX) and pentaerythritol tetranitrate (PETN) secondary explosives are examined using a sensitive friction machine. The explosive crystals used for the measurements are at least 3.5 mm wide. The friction coefficients between crystals of the same explosive (i.e., HMX on HMX, etc.), crystals of different explosives (i.e., HMX on RDX, etc.), and each explosive and a well-polished gauge steel surface are determined. The frictional surfaces are also studied under an environmental scanning electron microscope (ESEM) to analyze surface microstructural changes under increasing loading forces. The friction coefficients vary considerably with increasing normal loading forces and are particularly sensitive to slider shapes, crystal roughness and the mechanical properties of both the slider and the sample. With increasing loading forces, most friction experiments show surface damage, consisting of grooves, debris, and nano-particles, on both the slider and sample. In some cases, a strong evidence of a localized molten state is found in the central region of the friction track. Possible mechanisms that affect the friction coefficient are discussed based on microscopic observations. Copyright © 2010 Elsevier B.V. All rights reserved.

  8. Chemical composition of ambient aerosol, ice residues and cloud droplet residues in mixed-phase clouds: single particle analysis during the Cloud and Aerosol Characterization Experiment (CLACE 6

    Directory of Open Access Journals (Sweden)

    M. Kamphus

    2010-08-01

    Full Text Available Two different single particle mass spectrometers were operated in parallel at the Swiss High Alpine Research Station Jungfraujoch (JFJ, 3580 m a.s.l. during the Cloud and Aerosol Characterization Experiment (CLACE 6 in February and March 2007. During mixed phase cloud events ice crystals from 5–20 μm were separated from larger ice aggregates, non-activated, interstitial aerosol particles and supercooled droplets using an Ice-Counterflow Virtual Impactor (Ice-CVI. During one cloud period supercooled droplets were additionally sampled and analyzed by changing the Ice-CVI setup. The small ice particles and droplets were evaporated by injection into dry air inside the Ice-CVI. The resulting ice and droplet residues (IR and DR were analyzed for size and composition by the two single particle mass spectrometers: a custom-built Single Particle Laser-Ablation Time-of-Flight Mass Spectrometer (SPLAT and a commercial Aerosol Time-of-Flight Mass Spectrometer (ATOFMS, TSI Model 3800. During CLACE 6 the SPLAT instrument characterized 355 individual IR that produced a mass spectrum for at least one polarity and the ATOFMS measured 152 IR. The mass spectra were binned in classes, based on the combination of dominating substances, such as mineral dust, sulfate, potassium and elemental carbon or organic material. The derived chemical information from the ice residues is compared to the JFJ ambient aerosol that was sampled while the measurement station was out of clouds (several thousand particles analyzed by SPLAT and ATOFMS and to the composition of the residues of supercooled cloud droplets (SPLAT: 162 cloud droplet residues analyzed, ATOFMS: 1094. The measurements showed that mineral dust was strongly enhanced in the ice particle residues. Close to all of the SPLAT spectra from ice residues did contain signatures from mineral compounds, albeit connected with varying amounts of soluble compounds. Similarly, close to all of the ATOFMS IR spectra show a

  9. Mutiple Czochralski growth of silicon crystals from a single crucible

    Science.gov (United States)

    Lane, R. L.; Kachare, A. H.

    1980-01-01

    An apparatus for the Czochralski growth of silicon crystals is presented which is capable of producing multiple ingots from a single crucible. The growth chamber features a refillable crucible with a water-cooled, vacuum-tight isolation valve located between the pull chamber and the growth furnace tank which allows the melt crucible to always be at vacuum or low argon pressure when retrieving crystal or introducing recharge polysilicon feed stock. The grower can thus be recharged to obtain 100 kg of silicon crystal ingots from one crucible, and may accommodate crucibles up to 35 cm in diameter. Evaluation of the impurity contents and I-V characteristics of solar cells fabricated from seven ingots grown from two crucibles reveals a small but consistent decrease in cell efficiency from 10.4% to 9.6% from the first to the fourth ingot made in a single run, which is explained by impurity build-up in the residual melt. The crystal grower thus may offer economic benefits through the extension of crucible lifetime and the reduction of furnace downtime.

  10. Microwave single-scattering properties of randomly oriented soft-ice hydrometeors

    Directory of Open Access Journals (Sweden)

    D. Casella

    2008-11-01

    Full Text Available Large ice hydrometeors are usually present in intense convective clouds and may significantly affect the upwelling radiances that are measured by satellite-borne microwave radiometers – especially, at millimeter-wavelength frequencies. Thus, interpretation of these measurements (e.g., for precipitation retrieval requires knowledge of the single scattering properties of ice particles. On the other hand, shape and internal structure of these particles (especially, the larger ones is very complex and variable, and therefore it is necessary to resort to simplifying assumptions in order to compute their single-scattering parameters.

    In this study, we use the discrete dipole approximation (DDA to compute the absorption and scattering efficiencies and the asymmetry factor of two kinds of quasi-spherical and non-homogeneous soft-ice particles in the frequency range 50–183 GHz. Particles of the first kind are modeled as quasi-spherical ice particles having randomly distributed spherical air inclusions. Particles of the second kind are modeled as random aggregates of ice spheres having random radii. In both cases, particle densities and dimensions are coherent with the snow hydrometeor category that is utilized by the University of Wisconsin – Non-hydrostatic Modeling System (UW-NMS cloud-mesoscale model. Then, we compare our single-scattering results for randomly-oriented soft-ice hydrometeors with corresponding ones that make use of: a effective-medium equivalent spheres, b solid-ice equivalent spheres, and c randomly-oriented aggregates of ice cylinders. Finally, we extend to our particles the scattering formulas that have been developed by other authors for randomly-oriented aggregates of ice cylinders.

  11. Raman analysis of gold on WSe2 single crystal film

    International Nuclear Information System (INIS)

    Mukherjee, Bablu; Sun Leong, Wei; Li, Yida; Thong, John T L; Gong, Hao; Sun, Linfeng; Xiang Shen, Ze; Simsek, Ergun

    2015-01-01

    Synthesis and characterization of high-quality single-crystal tungsten diselenide (WSe 2 ) films on a highly insulating substrate is presented. We demonstrate for the first time that the presence of gold (Au) nanoparticles in the basal plane of a WSe 2 film can enhance its Raman scattering intensity. The experimentally observed enhancement ratio in the Raman signal correlates well with the simulated electric field intensity using both three-dimensional electromagnetic software and theoretical calculation considering layered medium coupled-dipole approximation (LM-CDA). This work serves as a guideline for the use of Au nanoparticles on WSe 2 single-crystal thin films for surface enhanced Raman scattering (SERS) applications in the future. (paper)

  12. Single crystal studies of platinum alloys for oxygen reduction electrodes

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese

    the behavior of bulk single crystals, deposition of yttrium and gadolinium on a clean, annealed Pt(111) crystal were investigated in UHV. PtxY and PtxGd alloys terminated with a single atomic layer of platinum were formed after annealing to 500 °C in UHV. These alloys will be referred to as Y/Pt(111) and Gd.......89×1.89 structure, and the Gd/Pt(111) sample has formed a 1.90×1.90 structure compared to pure platinum. From the XPS measurements, it is most likely that alloys with the Pt5Y and Pt5Gd stoichiometry have been formed. The reactivity of the surfaces were probed using TPD. These measurements showed sharp desorption...

  13. Frequency dispersion of flexoelectricity in PMN-PT single crystal

    Science.gov (United States)

    Shu, Longlong; Wan, Meiqian; Jiang, Xiaoning; Li, Fei; Zhou, Naigen; Huang, Wenbin; Wang, Tong

    2017-01-01

    The mechanism of the recent discovered enhanced flexoelectricity in perovskites has brought about numerous controversies which still remain unclear. In this paper, we employed relaxor 0.68Pb(Mg2/3Nb1/3)O3 -0.32PbTiO3 (PMN-PT) single crystals for study. The observed flexoelectric coefficient in PMN-PT single crystal reaches up to 100 μ C /m , and in a relative low frequency range, exhibits an abnormal frequency dispersion phenomenon with a positive relationship with frequency. Such frequency dispersion regulation is different from the normal relaxation behavior that usually occur a time delay, and hence proves the flexoelectricity acting more like bulk effect rather than surface effect in this kind of materials.

  14. Frequency dispersion of flexoelectricity in PMN-PT single crystal

    Directory of Open Access Journals (Sweden)

    Longlong Shu

    2017-01-01

    Full Text Available The mechanism of the recent discovered enhanced flexoelectricity in perovskites has brought about numerous controversies which still remain unclear. In this paper, we employed relaxor 0.68Pb(Mg2/3Nb1/3O3 -0.32PbTiO3 (PMN-PT single crystals for study. The observed flexoelectric coefficient in PMN-PT single crystal reaches up to 100 μC/m, and in a relative low frequency range, exhibits an abnormal frequency dispersion phenomenon with a positive relationship with frequency. Such frequency dispersion regulation is different from the normal relaxation behavior that usually occur a time delay, and hence proves the flexoelectricity acting more like bulk effect rather than surface effect in this kind of materials.

  15. Mechanisms for tertiary creep of single crystal superalloy

    Science.gov (United States)

    Staroselsky, Alexander; Cassenti, Brice

    2008-12-01

    During the thermal-mechanical loading of high temperature single crystal turbine components, all three creep—stages: primary, secondary and tertiary, manifest themselves and, hence, none of them can be neglected. The development of a creep law that includes all three stages is especially important in the case of non-homogeneous thermal loading of the component where significant stress redistribution and relaxation will result. Thus, local creep analysis is crucial for proper design of damage tolerant airfoils. We have developed a crystallographic-based constitutive model and fully coupled it with damage kinetics. The model extends existing approaches for cyclic and thermal-cyclic loading of anisotropic elasto-viscoplastic deformation behavior and damage kinetics of single-crystal materials, allowing prediction of tertiary creep and failure initiation of high temperature components. Our damage model bridges the gap between dislocation dynamics and the continuum mechanics scales and can be used to represent tertiary as well as primary and secondary creep.

  16. Scintillation activity in an unirradiated single crystal of 3-hydroxyxanthine

    International Nuclear Information System (INIS)

    Cooke, D.W.; Jahan, M.S.; Alexander, C. Jr.

    1976-01-01

    A method of growing single crystals (approximately 4mm long) of 3-hydroxyxanthine is described. Observed scintillations occurring in an unirradiated single crystal of this potent oncogen as the temperature is lowered from 300 to 90 K are shown. It was found that these scintillations occur upon heating or cooling and do not diminish in activity as the number of heating and cooling cycles increase. It was found that a short duration u.v. exposure would terminate the scintillation activity and various attempts (such as annealing and pressure changes) to rejuvenate them were unsuccessful. With these observations in mind speculation is made concerning the mechanisms associated with the production of purine N-oxide derivatives. (U.K.)

  17. Influence of solvents on the habit modification of alpha lactose monohydrate single crystals

    Science.gov (United States)

    Parimaladevi, P.; Srinivasan, K.

    2013-02-01

    Restricted evaporation of solvent method was adopted for the growth of alpha lactose monohydrate single crystals from different solvents. The crystal habits of grown crystals were analysed. The form of crystallization was confirmed by powder x-ray diffraction analysis. Thermal behaviour of the grown crystals was studied by using differential scanning calorimetry.

  18. Character, distribution and biological implications of ice crystallization in cryopreserved rabbit ovarian tissue revealed by cryo-scanning electron microscopy.

    Science.gov (United States)

    Gosden, Roger G; Yin, Hang; Bodine, Richard J; Morris, G John

    2010-02-01

    Ovarian tissue banking is an emerging strategy for fertility preservation which has led to several viable pregnancies after transplantation. However, the standard method of slow cooling was never rigorously optimized for human tissue nor has the extent and location of ice crystals in tissue been investigated. To address this, we used cryo-scanning electron microscopy (cryo-SEM) to study ice formation in cryopreserved ovarian tissue. Rabbit ovarian tissue slices were equilibrated in 1,2-propanediol-sucrose solution and cooled at either 0.3 degrees C/min or 3.0 degrees C/min after nucleating ice at -7 degrees C, or snap-frozen by plunging in liquid nitrogen. Frozen tissues were fractured, etched and coated with gold or prepared by freeze substitution and sectioning for cryo-SEM. The size, location and orientation of extracellular ice crystals were revealed as pits and channels that had grown radially between freeze-concentrated cellular materials. They represented 60% of the total volume in slowly cooled samples that were nucleated at -7 degrees C and the crystals, often >30 microm in length, displaced cells without piercing them. Samples cooled more rapidly were much less dehydrated, accounting for the presence of small ice crystals inside cells and possibly in organelles. Cryo-SEM revealed the internal structure of ovarian tissue in the frozen state was dominated by elongated ice crystals between islands of freeze-concentrated cellular matrix. Despite the grossly distorted anatomy, the greater degree of dehydration and absence of intracellular ice confirmed the superiority of a very slow rate of cooling for optimal cell viability. These ultrastructural methods will be useful for validating and improving new protocols for tissue cryopreservation.

  19. X-ray diffraction analysis of some single crystals with special properties

    Energy Technology Data Exchange (ETDEWEB)

    Antipin, M.Yu. [Russian Academy of Sciences, Moscow (Russian Federation). Inst. of Organoelement Compounds

    1996-12-31

    New possibilities of the X-ray diffraction method for studies of some single crystals with special physical properties are analyzed. It is demonstrated that wide range temperature diffraction data, special single crystals experiments under strong electric fields, and charge density analysis in crystals might enrich the knowledge on the nature of the crystal properties.

  20. A macroscopic model for magnetic shape-memory single crystals

    Czech Academy of Sciences Publication Activity Database

    Bessoud, A. L.; Kružík, Martin; Stefanelli, U.

    2013-01-01

    Roč. 64, č. 2 (2013), s. 343-359 ISSN 0044-2275 R&D Projects: GA AV ČR IAA100750802; GA ČR GAP201/10/0357 Institutional support: RVO:67985556 Keywords : magneto striction * evolution Subject RIV: BA - General Mathematics Impact factor: 1.214, year: 2013 http://library.utia.cas.cz/separaty/2012/MTR/kruzik-a macroscopic model for magnetic shape-memory single crystals.pdf

  1. Ion implantation induced blistering of rutile single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Bing-Xi [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Jiao, Yang [College of Physics and Electronics, Shandong Normal University, Jinan, Shandong 250100 (China); Guan, Jing [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Wang, Lei [School of Physics, Shandong University, Jinan, Shandong 250100 (China); Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (China)

    2015-07-01

    The rutile single crystals were implanted by 200 keV He{sup +} ions with a series fluence and annealed at different temperatures to investigate the blistering behavior. The Rutherford backscattering spectrometry, optical microscope and X-ray diffraction were employed to characterize the implantation induced lattice damage and blistering. It was found that the blistering on rutile surface region can be realized by He{sup +} ion implantation with appropriate fluence and the following thermal annealing.

  2. Single crystal analyser accepting the narrowest neutron angular profile

    International Nuclear Information System (INIS)

    Abbas, Sohrab; Wagh, Apoorva G.; Strobl, Markus; Treimer, Wolfgang

    2007-01-01

    We have designed, fabricated and tested a novel silicon single crystal analyser. It accepts a 0.21 arcsec (FWHM) wide angular profile of a monochromatic 5.24 A neutron beam, in agreement with its design. This is the narrowest and sharpest acceptance angular profile attained to date in the world with a neutron analyser. This analyser will facilitate SUSANS experiments probing wave vector transfers Q ∼ 10 -6 A -1 . (author)

  3. Blue luminescence in ZnO single crystals, nanopowders, ceramic

    International Nuclear Information System (INIS)

    LGrigorjeva; Millers, D; Pankratov, V; Kalinko, A; Grabis, J; Monty, C

    2007-01-01

    The luminescence spectra and luminescence decay processes were studied in a ZnO single crystal, nanopowders and ceramic at liquid helium and room temperature under VUV synchrotron radiation as well as under pulsed laser excitation. The exciton-exciton and exciton-multiphonon processes were compared in different ZnO nanopowders (commercial powder, powders obtained by vaporization-condensation technique) and ceramic. The possibility of luminescence decay time modification by Al 3+ doping was shown

  4. Application of GRID to Foreign Atom Localization in Single Crystals.

    Science.gov (United States)

    Karmann, A; Wesch, W; Weber, B; Börner, H G; Jentschel, M

    2000-01-01

    The application of GRID (Gamma Ray Induced Doppler broadening) spectroscopy to the localization of foreign atoms in single crystals is demonstrated on erbium in YAP. By the investigation of the Doppler broadened secondary γ line for two crystalline directions, the Er was determined to be localized on the Y site. Conditions for the nuclear parameters of the impurity atoms used for the application of GRID spectroscopy are discussed.

  5. Study of diffusion of Ag in Cu single crystals

    CERN Document Server

    Wang, R

    2002-01-01

    4.0 MeV sup 7 Li sup + sup + RBS and AES were used for investigations of thermal diffusion of Ag in Cu single crystals. The annealing of samples was carried out in vacuum in the temperature range from 498 to 613 K. The element depth concentration profiles transformed from RBS spectra indicate that the diffusion of Ag into Cu is a typical volume diffusion. The Arrhenius parameters corresponding to the diffusion were obtained.

  6. Luminescence properties of piezoelectric single crystals with langasite structure

    International Nuclear Information System (INIS)

    Itoh, Minoru; Takagi, Shinya; Kitaura, Mamoru; Fujita, Masami; Endo, Naoyuki

    2007-01-01

    Luminescence properties of single crystals of langasite (LGS), langataite (LGT), and langanite (LGN) are investigated at 5 K by using synchrotron radiation as an exciting light source. Two emission bands are observed at 420 and 500 nm in LGS, at 410 and 460 nm in LGT, and at 500 and 535 nm in LGN. The origin of these bands is discussed by reference to the electronic structure of LGS

  7. Growth and characterisation of lead iodide single crystals

    International Nuclear Information System (INIS)

    Tonn, Justus

    2012-01-01

    The work in hand deals with the growth and characterisation of lead iodide (PbI 2 ) single crystals. PbI 2 is regarded as a promising candidate for low-noise X- and gamma ray detection at room temperature. Its benefits if compared to conventional materials like HgI 2 , CdTe, Si, or GaAs lie in a band gap energy of 2.32 eV, an excellent ability to absorb radiation, and a high electrical resistivity. For an application of PbI 2 as detector material the growth and characterisation of crystals with high chemical and structural quality is extremely challenging. In light of this, the effectiveness of zone purification of the PbI 2 used for crystal growth was confirmed by spectroscopic analysis. Furthermore, technological aspects during processing of purified PbI 2 were investigated. With the help of thermal analysis, a correlation was found between the degree of exposing the source material to oxygen from the air and the structural quality of the resulting crystals. A hydrogen treatment was applied to PbI 2 as an effective method for the removal of oxidic pollutions, which resulted in a significant reduction of structural defects like polytypic growth and stress-induced cracking. The growth of PbI 2 single crystals was, among others, carried out by the Bridgman-Stockbarger method. In this context, much effort was put on the investigation of influences resulting from the design and preparation of ampoules. For the first time, crystal growth of PbI 2 was also carried out by the Czochralski method. If compared to the Bridgman-Stockbarger method, the Czochralski technique allowed a significantly faster growth of nearly crack-free crystals with a reproducible predetermination of crystallographic orientation. By an optimised sample preparation of PbI 2 , surface orientations perpendicular to the usually cleaved (0001) plane were realised. It is now possible to determine the material properties along directions which were so far not accessible. Thus, for example, the ratio of

  8. SINGLE-CRYSTAL SAPPHIRE OPTICAL FIBER SENSOR INSTRUMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    A. Wang; G. Pickrell; R. May

    2002-09-10

    In this research program, several optical instruments for high temperature measurement based on single crystal sapphire material are introduced and tested for real-time, reliable, long-term monitoring of temperatures for coal gasifier. These are sapphire fiber extrinsic Fabry-Perot interferometric (EFPI) sensor; intensity-measurement based polarimetric sapphire sensor and broadband polarimetric differential interferometric (BPDI) sapphire sensor. Based on current evaluation and analysis of the experimental results, the broadband polarimetric differential interferometric (BPDI) sensor system was chosen for further prototype instrumentation development. This approach is based on the self-calibrating measurement of optical path differences (OPD) in a single-crystal sapphire disk, which is a function of both the temperature dependent birefringence and the temperature dependent dimensional changes. The BPDI sensor system extracts absolute temperature information by absolute measurement of phase delays. By encoding temperature information in optical spectrum instead of optical intensity, this sensor guarantees its relative immunity to optical source power fluctuations and fiber losses, thus providing a high degree of long-term measurement stability which is highly desired in industrial applications. The entire prototype for BPDI system including the single crystal sapphire probe, zirconia prism, alumina extension tube, optical components and signal processing hardware and software have shown excellent performance in the laboratory experiments shown in this report.

  9. Interfacial dislocation motion and interactions in single-crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Raabe, D. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Roters, F. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Arsenlis, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-10-01

    The early stage of high-temperature low-stress creep in single-crystal superalloys is characterized by the rapid development of interfacial dislocation networks. Although interfacial motion and dynamic recovery of these dislocation networks have long been expected to control the subsequent creep behavior, direct observation and hence in-depth understanding of such processes has not been achieved. Incorporating recent developments of discrete dislocation dynamics models, we simulate interfacial dislocation motion in the channel structures of single-crystal superalloys, and investigate how interfacial dislocation motion and dynamic recovery are affected by interfacial dislocation interactions and lattice misfit. Different types of dislocation interactions are considered: self, collinear, coplanar, Lomer junction, glissile junction, and Hirth junction. The simulation results show that strong dynamic recovery occurs due to the short-range reactions of collinear annihilation and Lomer junction formation. The misfit stress is found to induce and accelerate dynamic recovery of interfacial dislocation networks involving self-interaction and Hirth junction formation, but slow down the steady interfacial motion of coplanar and glissile junction forming dislocation networks. The insights gained from these simulations on high-temperature low-stress creep of single-crystal superalloys are also discussed.

  10. Single crystal plasticity by modeling dislocation density rate behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Benjamin L [Los Alamos National Laboratory; Bronkhorst, Curt [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory; Cerreta, E. K. [Los Alamos National Laboratory; Dennis-Koller, Darcie [Los Alamos National Laboratory

    2010-12-23

    The goal of this work is to formulate a constitutive model for the deformation of metals over a wide range of strain rates. Damage and failure of materials frequently occurs at a variety of deformation rates within the same sample. The present state of the art in single crystal constitutive models relies on thermally-activated models which are believed to become less reliable for problems exceeding strain rates of 10{sup 4} s{sup -1}. This talk presents work in which we extend the applicability of the single crystal model to the strain rate region where dislocation drag is believed to dominate. The elastic model includes effects from volumetric change and pressure sensitive moduli. The plastic model transitions from the low-rate thermally-activated regime to the high-rate drag dominated regime. The direct use of dislocation density as a state parameter gives a measurable physical mechanism to strain hardening. Dislocation densities are separated according to type and given a systematic set of interactions rates adaptable by type. The form of the constitutive model is motivated by previously published dislocation dynamics work which articulated important behaviors unique to high-rate response in fcc systems. The proposed material model incorporates thermal coupling. The hardening model tracks the varying dislocation population with respect to each slip plane and computes the slip resistance based on those values. Comparisons can be made between the responses of single crystals and polycrystals at a variety of strain rates. The material model is fit to copper.

  11. Point defects and electric compensation in gallium arsenide single crystals

    International Nuclear Information System (INIS)

    Kretzer, Ulrich

    2007-01-01

    In the present thesis the point-defect budget of gallium arsenide single crystals with different dopings is studied. It is shown, in which way the concentration of the single point defects depende on the concentration of the dopants, the stoichiometry deviation, and the position of the Fermi level. For this serve the results of the measurement-technical characterization of a large number of samples, in the fabrication of which these parameters were directedly varied. The main topic of this thesis lies in the development of models, which allow a quantitative description of the experimentally studied electrical and optical properties of gallium arsenide single crystals starting from the point-defect concentrations. Because from point defects charge carriers can be set free, their concentration determines essentially the charge-carrier concentration in the bands. In the ionized state point defects act as scattering centers for free charge carriers and influence by this the drift mobility of the charge carriers. A thermodynamic modeling of the point-defect formation yields statements on the equilibrium concentrations of the point defects in dependence on dopant concentration and stoichiometry deviation. It is show that the electrical properties of the crystals observed at room temperature result from the kinetic suppression of processes, via which the adjustment of a thermodynamic equilibrium between the point defects is mediated [de

  12. Chiral multichromic single crystals for optical devices (LDRD 99406).

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Richard Alan; Felix, Ana M. (University of New Mexico, Albuquerque, NM)

    2006-12-01

    This report summarizes our findings during the study of a novel system that yields multi-colored materials as products. This system is quite unusual as it leads to multi-chromic behavior in single crystals, where one would expect that only a single color would exist. We have speculated that these novel solids might play a role in materials applications such as non-linear optics, liquid crystal displays, piezoelectric devices, and other similar applications. The system examined consisted of a main-group alkyl compound (a p block element such as gallium or aluminum) complexed with various organic di-imines. The di-imines had substituents of two types--either alkyl or aromatic groups attached to the nitrogen atoms. We observed that single crystals, characterized by X-ray crystallography, were obtained in most cases. Our research during January-July, 2006, was geared towards understanding the factors leading to the multi-chromic nature of the complexes. The main possibilities put forth initially considered (a) the chiral nature of the main group metal, (b) possible reduction of the metal to a lower-valent, radical state, (c) the nature of the ligand(s) attached to the main group metal, and (d) possible degradation products of the ligand leading to highly-colored products. The work carried out indicates that the most likely explanation considered involves degradation of the aromatic ligands (a combination of (c) and (d)), as the experiments performed can clearly rule out (a) and (b).

  13. Diamond turning of Si and Ge single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Blake, P.; Scattergood, R.O.

    1988-12-01

    Single-point diamond turning studies have been completed on Si and Ge crystals. A new process model was developed for diamond turning which is based on a critical depth of cut for plastic flow-to-brittle fracture transitions. This concept, when combined with the actual machining geometry for single-point turning, predicts that {open_quotes}ductile{close_quotes} machining is a combined action of plasticity and fracture. Interrupted cutting experiments also provide a meant to directly measure the critical depth parameter for given machining conditions.

  14. Method for thermal processing alumina-enriched spinel single crystals

    Science.gov (United States)

    Jantzen, Carol M.

    1995-01-01

    A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

  15. Grating coupler on single-crystal lithium niobate thin film

    Science.gov (United States)

    Chen, Zhihua; Wang, Yiwen; Jiang, Yunpeng; Kong, Ruirui; Hu, Hui

    2017-10-01

    The grating coupler on single-crystal lithium niobate thin film (lithium niobate on insulator, LNOI) was designed. A bottom reflector was added in the LNOI material to improve the coupling efficiency. The grating structure was optimized by FDTD method. The material parameters such as layer thickness of lithium niobate thin film, SiO2 thickness were discussed with respect to the coupling efficiency, and the tolerances of grating period, etch depth, groove width and fiber position were also studied systematically. The simulated maximum coupling efficiency from a grating coupler with (without) bottom reflector to a single-mode fiber is about 78% (40%) in z-cut LNOI for TE polarization.

  16. Single mode dye-doped polymer photonic crystal lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Buss, Thomas; Smith, Cameron

    2010-01-01

    Dye-doped polymer photonic crystal (PhC) lasers fabricated by combined nanoimprint and photolithography are studied for their reproducibility and stability characteristics. We introduce a phase shift in the PhC lattice that substantially improves the yield of single wavelength emission. Single mode...... emission and reproducibility of laser characteristics are important if the lasers are to be mass produced in, e. g., optofluidic sensor chips. The fabrication yield is above 85% with highly reproducible wavelengths (within 0.5%), and the temperature dependence on the wavelength is found to be -0.045 or -0...

  17. Acquisition of Single Crystal Growth and Characterization Equipment. Final report

    International Nuclear Information System (INIS)

    Maple, M. Brian; Zocco, Diego A.

    2008-01-01

    Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As a result, many user facilities are not being used optimally. The number of proficient crystal growers is too small. In addition, insufficient attention is being paid to the enterprise of finding new and interesting materials, which is the driving force behind much of condensed matter research and, ultimately, technology. While a detailed assessment of this situation is clearly needed, enough evidence of a problem already exists to compel a general consensus that the situation must be addressed promptly. This final report describes the work carried out during the last four years in our group, in which a state-of-the-art single crystal growth and characterization facility was established for the study of novel oxides and intermetallic compounds of rare earth, actinide and transition metal elements. Research emphasis is on the physics of superconducting (SC), magnetic, heavy fermion (HF), non-Fermi liquid (NFL) and other types of strongly correlated electron phenomena in bulk single crystals. Properties of these materials are being studied as a function of concentration of chemical constituents, temperature, pressure, and magnetic field, which provide information about the electronic, lattice, and magnetic excitations at the root of various strongly correlated electron phenomena. Most importantly, the facility makes possible the investigation of material properties that can only be achieved in high quality bulk single crystals, including magnetic and transport phenomena, studies of the effects of disorder, properties in the clean limit, and spectroscopic and scattering

  18. Acquisition of Single Crystal Growth and Characterization Equipment

    Energy Technology Data Exchange (ETDEWEB)

    Maple, M. Brian; Zocco, Diego A.

    2008-12-09

    Final Report for DOE Grant No. DE-FG02-04ER46178 'Acquisition of Single Crystal Growth and Characterization Equipment'. There is growing concern in the condensed matter community that the need for quality crystal growth and materials preparation laboratories is not being met in the United States. It has been suggested that there are too many researchers performing measurements on too few materials. As a result, many user facilities are not being used optimally. The number of proficient crystal growers is too small. In addition, insufficient attention is being paid to the enterprise of finding new and interesting materials, which is the driving force behind much of condensed matter research and, ultimately, technology. While a detailed assessment of this situation is clearly needed, enough evidence of a problem already exists to compel a general consensus that the situation must be addressed promptly. This final report describes the work carried out during the last four years in our group, in which a state-of-the-art single crystal growth and characterization facility was established for the study of novel oxides and intermetallic compounds of rare earth, actinide and transition metal elements. Research emphasis is on the physics of superconducting (SC), magnetic, heavy fermion (HF), non-Fermi liquid (NFL) and other types of strongly correlated electron phenomena in bulk single crystals. Properties of these materials are being studied as a function of concentration of chemical constituents, temperature, pressure, and magnetic field, which provide information about the electronic, lattice, and magnetic excitations at the root of various strongly correlated electron phenomena. Most importantly, the facility makes possible the investigation of material properties that can only be achieved in high quality bulk single crystals, including magnetic and transport phenomena, studies of the effects of disorder, properties in the clean limit, and spectroscopic and

  19. Prognostic description of ice using a single category in the GCM ECHAM-HAM

    Science.gov (United States)

    Dietlicher, Remo; Neubauer, David; Lohmann, Ulrike

    2017-04-01

    A new scheme for stratiform cloud microphysics has been implemented in a general circulation model. It features a widely used description of cloud water with the two categories for cloud droplets and rain. The unique aspect of the scheme is the break with the traditional approach to describe cloud ice analogously. Here we parametrize cloud ice with a single, prognostic category, as it has been done in recent regional models. The intrinsicly hard to parametrize processes of aggregation and accretion are replaced by the explicit computation of ice particle collection and fall speeds within the prognosed particle size distribution. This work shows that a single category is a viable approach to describe cloud ice in climate models. Performance is evaluated in idealized single column model setups as well as global runs. We find that a nested approach for substepping the microphysics scheme yields good results in terms of numerical stability and computational cost. The scheme is compared to an established description of cloud ice with two categories for in-cloud ice and snow. We find that especially in clouds where aggregation is weak but fall-speeds are not negligible due to strong depositional growth or riming, the new scheme produces much more reasonable results.

  20. Advanced Optical Diagnostics for Ice Crystal Cloud Measurements in the NASA Glenn Propulsion Systems Laboratory

    Science.gov (United States)

    Bencic, Timothy J.; Fagan, Amy; Van Zante, Judith F.; Kirkegaard, Jonathan P.; Rohler, David P.; Maniyedath, Arjun; Izen, Steven H.

    2013-01-01

    A light extinction tomography technique has been developed to monitor ice water clouds upstream of a direct connected engine in the Propulsion Systems Laboratory (PSL) at NASA Glenn Research Center (GRC). The system consists of 60 laser diodes with sheet generating optics and 120 detectors mounted around a 36-inch diameter ring. The sources are pulsed sequentially while the detectors acquire line-of-sight extinction data for each laser pulse. Using computed tomography algorithms, the extinction data are analyzed to produce a plot of the relative water content in the measurement plane. To target the low-spatial-frequency nature of ice water clouds, unique tomography algorithms were developed using filtered back-projection methods and direct inversion methods that use Gaussian basis functions. With the availability of a priori knowledge of the mean droplet size and the total water content at some point in the measurement plane, the tomography system can provide near real-time in-situ quantitative full-field total water content data at a measurement plane approximately 5 feet upstream of the engine inlet. Results from ice crystal clouds in the PSL are presented. In addition to the optical tomography technique, laser sheet imaging has also been applied in the PSL to provide planar ice cloud uniformity and relative water content data during facility calibration before the tomography system was available and also as validation data for the tomography system. A comparison between the laser sheet system and light extinction tomography resulting data are also presented. Very good agreement of imaged intensity and water content is demonstrated for both techniques. Also, comparative studies between the two techniques show excellent agreement in calculation of bulk total water content averaged over the center of the pipe.

  1. Self-templated synthesis of single-crystal and single-domain ferroelectric nanoplates

    KAUST Repository

    Chao, Chunying

    2012-08-15

    Free-standing single-crystal PbTiO 3 nanoplates (see picture) were synthesized by a facile hydrothermal method. A "self-templated" crystal growth is presumed to lead to the formation of the PbTiO 3 nanoplates, which have ferroelectric single-domain structures, whose polarization areas can be manipulated by writing and reading. The nanoplates are also effective catalysts for the oxidation of carbon monoxide. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Computational Modeling of Photonic Crystal Microcavity Single-Photon Emitters

    Science.gov (United States)

    Saulnier, Nicole A.

    Conventional cryptography is based on algorithms that are mathematically complex and difficult to solve, such as factoring large numbers. The advent of a quantum computer would render these schemes useless. As scientists work to develop a quantum computer, cryptographers are developing new schemes for unconditionally secure cryptography. Quantum key distribution has emerged as one of the potential replacements of classical cryptography. It relics on the fact that measurement of a quantum bit changes the state of the bit and undetected eavesdropping is impossible. Single polarized photons can be used as the quantum bits, such that a quantum system would in some ways mirror the classical communication scheme. The quantum key distribution system would include components that create, transmit and detect single polarized photons. The focus of this work is on the development of an efficient single-photon source. This source is comprised of a single quantum dot inside of a photonic crystal microcavity. To better understand the physics behind the device, a computational model is developed. The model uses Finite-Difference Time-Domain methods to analyze the electromagnetic field distribution in photonic crystal microcavities. It uses an 8-band k · p perturbation theory to compute the energy band structure of the epitaxially grown quantum dots. We discuss a method that combines the results of these two calculations for determining the spontaneous emission lifetime of a quantum dot in bulk material or in a microcavity. The computational models developed in this thesis are used to identify and characterize microcavities for potential use in a single-photon source. The computational tools developed are also used to investigate novel photonic crystal microcavities that incorporate 1D distributed Bragg reflectors for vertical confinement. It is found that the spontaneous emission enhancement in the quasi-3D cavities can be significantly greater than in traditional suspended slab

  3. Shock-induced optical emission from yttria-doped cubic zircon single crystal: crystal orientation effects

    Science.gov (United States)

    Cao, Xiuxia; Zhou, Xianming; Meng, Chuanmin

    2015-06-01

    The shock-induced optical emission from yttria (Y2O3) -doped cubic zircon single crystal ( and crystal orientations) under the pressure range from 30 to 52 GPa was measured by the time-resolved 40-channel optical pyrometer at discrete wavelengths ranging from 400 to 800 nm. Clear periodic fluctuation was observed in spectral radiance history of ZrO2, while a noise fluctuation was found in ZrO2. The gray-body function was used to fit the spectral radiance histories. We found that the obtained apparent temperature varied slightly with time, but the emissivity history showed a fluctuate increase with time. Moreover, all the temperature data were independent of shock stress and were well above the calculated Lindeman melting temperature. Present result suggests that the optical emission relates to the shock-induced local hot spots, and its crystal orientation effect is attributed to the different dynamic deformation response between and ZrO2.

  4. Growth of high quality bulk size single crystals of inverted solubility lithium sulphate monohydrate

    Energy Technology Data Exchange (ETDEWEB)

    Silambarasan, A.; Rajesh, P., E-mail: rajeshp@ssn.edu.in; Ramasamy, P. [Center for Crystal Growth, SSN College of Engineering, Kalavakkam-603110 (India)

    2015-06-24

    The paper summarizes the processes of growing large lithium sulfate monohydrate (LSMH) single crystals. We have established a procedure to grow high quality bulk size single crystals of inverted solubility LSMH by a newly developed unidirectional crystallization technique called the Sankeranarayenan - Ramasamy (SR) method. The convective flow of crystal growth processes from solution and the conditions of growing crystals of various aspects were discussed. Good quality LSMH single crystal is grown of the size 20 mmX80 mm without cracks, localized-defects and inclusions. The as-grown crystals are suitable for piezoelectric and nonlinear optical applications.

  5. Large pyramid shaped single crystals of BiFeO{sub 3} by solvothermal synthesis method

    Energy Technology Data Exchange (ETDEWEB)

    Sornadurai, D.; Ravindran, T. R.; Paul, V. Thomas; Sastry, V. Sankara [Condensed Matter Physics Division, Materials Science Group, Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu (India); Condensed Matter Physics Division, Materials Science Group (India)

    2012-06-05

    Synthesis parameters are optimized in order to grow single crystals of multiferroic BiFeO{sub 3}. 2 to 3 mm size pyramid (tetrahedron) shaped single crystals were successfully obtained by solvothermal method. Scanning electron microscopy with EDAX confirmed the phase formation. Raman scattering spectra of bulk BiFeO3 single crystals have been measured which match well with reported spectra.

  6. Ice crystallization in porous building materials: assessing damage using real-time 3D monitoring

    Science.gov (United States)

    Deprez, Maxim; De Kock, Tim; De Schutter, Geert; Cnudde, Veerle

    2017-04-01

    Frost action is one of the main causes of deterioration of porous building materials in regions at middle to high latitudes. Damage will occur when the internal stresses due to ice formation become larger than the strength of the material. Hence, the sensitivity of the material to frost damage is partly defined by the structure of the solid body. On the other hand, the size, shape and interconnection of pores manages the water distribution in the building material and, therefore, the characteristics of the pore space control potential to form ice crystals (Ruedrich et al., 2011). In order to assess the damage to building materials by ice crystallization, lot of effort was put into identifying the mechanisms behind the stress build up. First of all, volumetric expansion of 9% (Hirschwald, 1908) during the transition of water to ice should be mentioned. Under natural circumstances, however, water saturation degrees within natural rocks or concrete cannot reach a damaging value. Therefore, linear growth pressure (Scherer, 1999), as well as several mechanisms triggered by water redistribution during freezing (Powers and Helmuth, 1953; Everett, 1961) are more likely responsible for damage due to freezing. Nevertheless, these theories are based on indirect observations and models and, thus, direct evidence that reveals the exact damage mechanism under certain conditions is still lacking. To obtain this proof, in-situ information needs to be acquired while a freezing process is performed. X-ray computed tomography has proven to be of great value in material research. Recent advances at the Ghent University Centre for Tomography (UGCT) have already allowed to dynamically 3D image crack growth in natural rock during freeze-thaw cycles (De Kock et al., 2015). A great potential to evaluate the different stress build-up mechanisms can be found in this imaging technique consequently. It is required to cover a range of materials with different petrophysical properties to achieve

  7. On size-effects in single crystal wedge indentation

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2012-01-01

    Wedge indentation in single crystals is studied numerically, with emphasis on size-effects on the micron scale. Under the assumption of a perfectly sharp wedge indenter, a linear relationship between indentation force and indentation depth would be predicted from conventional theories lacking con...... are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. The finite element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles.......Wedge indentation in single crystals is studied numerically, with emphasis on size-effects on the micron scale. Under the assumption of a perfectly sharp wedge indenter, a linear relationship between indentation force and indentation depth would be predicted from conventional theories lacking...... constitutive length parameters to model sizeeffects. The problem is studied numerically using a strain gradient crystal visco-plasticity theory formulated along the lines proposed by Fleck andWillis (2009). It is shown how the force-indentation relation is affected due to size-dependence in the material. Size-effects...

  8. ESR Study on Irradiated Ascorbic Acid Single Crystal

    International Nuclear Information System (INIS)

    Tuner, H.; Korkmaz, M.

    2007-01-01

    Food irradiation is a 'cold' process for preserving food and has been established as a safe and effective method of food processing and preservation after more than five decades of research and development. The small temperature increase, absence of residue and effectiveness of treatment of pre-packed food are the main advantages. In food industry, ascorbic acid and its derivatives are frequently used as antioxidant agents. However, irradiation is expected to produces changes in the molecules of food components and of course in the molecules of the agents added as preservation agents such as ascorbic acid. These changes in the molecular structures could cause decreases in the antioxidant actions of these agents. Therefore, the radiation resistance of these agents must be known to determine the amount of radiation dose to be delivered. Electron spin resonance (ESR) is one of the leading methods for identification of intermediates produced after irradiation. ESR spectrum of irradiated solid powder of ascorbic acid is fairly complex and determinations of involved radical species are difficult. In the present work, single crystals of ascorbic acid irradiated by gamma radiation are used to determine molecular structures of radiation induced radicalic species and four radicalic species related in pair with P21 crystal symmetry are found to be responsible from experimental ESR spectrum of gamma irradiated single crystal of ascorbic acid

  9. Plastic deformation of Ni3Nb single crystals

    International Nuclear Information System (INIS)

    Hagihara, Kouji; Nakano, Takayoshi; Umakoshi, Yukichi

    1999-01-01

    Temperature dependence of yield stress and operative slip system in Ni 3 Nb single crystals with the D0 a structure was investigated in comparison with that in an analogous L1 2 structure. Compression tests were performed at temperatures between 20 C and 1,200 C for specimens with loading axes perpendicular to (110), (331) and (270). (010)[100] slip was operative for three orientations, while (010)[001] slip for (331) and [211] twin for (270) orientations were observed, depending on deformation temperature. The critical resolved shear stress (CRSS) for the (010)[100] slip anomaly increased with increasing temperature showing a maximum peak between 400 C and 800 C depending on crystal orientation. The CRSS showed orientation dependence and no significant strain rate dependence in the temperature range for anomalous strengthening. The [100] dislocations with a screw character were aligned on the straight when the anomalous strengthening occurred. The anomalous strengthening mechanism for (010)[100] slip in Ni 3 Nb single crystals is discussed on the basis of a cross slip model which has been widely accepted for some L1 2 -type compounds

  10. Strength anomaly in B2 FeAl single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimi, K.; Hanada, S.; Yoo, M.H. [Oak Ridge National Lab., TN (United States); Matsumoto, N. [Tohoku Univ. (Japan). Graduate School

    1994-12-31

    Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

  11. Single-crystal neutron diffraction analysis in chemistry

    International Nuclear Information System (INIS)

    Hosoya, Takaaki; Ohhara, Takashi

    2010-01-01

    Single-crystal neutron diffraction technique is a powerful method to analyze the reaction mechanism whose hydrogen atom or proton has a key role in the reaction. Especially hydrogen atom or proton transfer(HT/PT) is one of the most elemental phenomena and often observed in many organic, inorganic, enzymatic and catalytic reactions. We describe several applications in chemistry. At first, hydrogen atom in metal hydride complexes, which is quite difficult to do using X-ray diffraction because of the great cloud of electrons of central metal atom. Secondary, hydrogen atom in hydrogen-bonding network, e.g., low-barrier hydrogen bond(LBHB) system. Neutron diffraction can refine the thermal motion of hydrogen atom. Finally, our results, photo-induced HT/PTs using 'deuterium atom labeling' technique and 'crystalline-state reaction' technique, which are currently developing applications. Despite the success illustrated by the many studies presented here or many other studies, we have many problems in using single-crystal neutron diffraction technique. For example, extremely limited flux and the requirement for mm-size sample crystals. Now, these limitations are being solved by the operation of powerful instruments at a new generation of pulsed neutron sources, including iBIX diffractometer running at Japan Proton Accelerator Research Complex(J-PARC) in Japan. (author)

  12. Crystal growth and anisotropy of high temperature thermoelectric properties of yttrium borosilicide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, M. Anwar [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Center for Crystal Science and Technology, University of Yamanashi, Miyamae 7-32, Kofu, Yamanashi 400-8511 (Japan); Tanaka, Isao [Center for Crystal Science and Technology, University of Yamanashi, Miyamae 7-32, Kofu, Yamanashi 400-8511 (Japan); Tanaka, Takaho; Khan, A. Ullah [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Mori, Takao, E-mail: MORI.Takao@nims.go.jp [International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8671 (Japan)

    2016-01-15

    We studied thermoelectric properties of YB{sub 41}Si{sub 1.3} single crystals grown by the floating zone method. The composition of the grown crystal was confirmed by electron probe micro-analysis. We have determined the growth direction for the first time for these borosilicides, and discovered relatively large anisotropy in electrical properties. We measured the electrical resistivity and Seebeck coefficient along [510] (the growth direction) and [052] directions and we found that this crystal exhibits strong electrical anisotropy with a maximum of more than 8 times. An interesting layered structural feature is revealed along [510] with dense boron cluster layers and yttrium layers, with conductivity enhanced along this direction. We obtained 3.6 times higher power factor along [510] compared to that along [052]. Although the ZT of the present system is low, anisotropy in the thermoelectric properties of a boride was reported for the first time, and can be a clue in developing other boride systems also. - Graphical abstract: The growth direction ([510]) was determined for the first time in YB{sub 41}Si{sub 1.3} single crystals and revealed an interesting layered feature of boron clusters and metal atoms, along which the electrical conductivity and thermoelectric power factor was strongly enhanced. - Highlights: • We have grown YB{sub 41}Si{sub 1.3} single crystals by the floating zone method. • Growth direction of [510] determined for first time in REB{sub 41}Si{sub 1.2}. • Electrical resistivity was strongly anisotropic with possible enhancement along metal layers. • The obtained power factor along [510] is 3.6 times higher than that along [052].

  13. Micromechanical Behavior of Single-Crystal Superalloy with Different Crystal Orientations by Microindentation

    Directory of Open Access Journals (Sweden)

    Jinghui Li

    2015-01-01

    Full Text Available In order to investigate the anisotropic micromechanical properties of single-crystal nickel-based superalloy DD99 of four crystallographic orientations, (001, (215, (405, and (605, microindentation test (MIT was conducted with different loads and loading velocities by a sharp Berkovich indenter. Some material parameters reflecting the micromechanical behavior of DD99, such as microhardness H, Young’s modulus E, yield stress σy, strain hardening component n, and tensile strength σb, can be obtained from load-displacement relations. H and E of four different crystal planes evidently decrease with the increase of h. The reduction of H is due to dislocation hardening while E is related to interplanar spacing and crystal variable. σy of (215 is the largest among four crystal planes, followed by (605, and (001 has the lowest value. n of (215 is the lowest, followed by (605, and that of (001 is the largest. Subsequently, a simplified elastic-plastic material model was employed for 3D microindentation simulation of DD99 with various crystal orientations. The simulation results agreed well with experimental, which confirmed the accuracy of the simplified material model.

  14. Crystal growth and optical properties of Sm:CaNb2O6 single crystal

    International Nuclear Information System (INIS)

    Di Juqing; Xu Xiaodong; Xia Changtai; Zeng Huidan; Cheng Yan; Li Dongzhen; Zhou Dahua; Wu Feng; Cheng Jimeng; Xu Jun

    2012-01-01

    Highlights: ► Sm:CaNb 2 O 6 single crystal was grown by the Czochralski method. ► Thermal expansion coefficients and J–O parameters were calculated. ► We found that this crystal had high quantum efficiency of 97%. - Abstract: Sm:CaNb 2 O 6 single crystal has been grown by the Czochralski method. Its high-temperature X-ray powder diffraction, optical absorption, emission spectroscopic as well as lifetime have been studied. Thermal expansion coefficients (α), J–O parameters (Ω i ), radiative lifetime (τ rad ), branching ratios (β) and stimulated emission cross-sections (σ e ) were calculated. The quantum efficiency (η) was calculated to be 97%. The intense peak emission cross section at 610, 658 nm were calculated to be 2.40 × 10 −21 , 2.42 × 10 −21 cm 2 . These results indicate that Sm:CaNb 2 O 6 crystal has potential use in visible laser and photonic devices area.

  15. Crystal growth and luminescence properties of Pr-doped LuLiF4 single crystal

    International Nuclear Information System (INIS)

    Sugiyama, Makoto; Yanagida, Takayuki; Yokota, Yuui; Kurosawa, Shunsuke; Fujimoto, Yutaka; Yoshikawa, Akira

    2013-01-01

    0.1, 1, and 3% Pr (with respect to Lu) doped LuLiF 4 (Pr:LuLiF 4 ) single crystals were grown by the micro-pulling-down (μ-PD) method. Transparency of the grown crystals was higher than 70% in the visible wavelength region with some absorption bands due to Pr 3+ 4f-4f transitions. Intense absorption bands related with the Pr 3+ 4f-5d transitions were observed at 190 and 215 nm. In radioluminescence spectra, Pr 3+ 5d-4f emissions were observed at 220, 240, 340, and 405 nm. In the pulse height spectra recorded under 137 Cs γ-ray excitation, the Pr 3% doped sample showed the highest light yield of 2050 photons/MeV and the scintillation decay time of it exhibited 23 and 72 ns also excited by 137 Cs γ-ray. -- Highlights: ► 0.1, 1, and 3% Pr-doped LuLiF 4 single crystals were grown by the μ-PD method. ► Pr 3+ 5d-4f emission peaks appeared at 220, 240, 340, and 405 nm ► The Pr 3%:LuLiF 4 crystal showed the highest light yield of 2050 photons/MeV

  16. The Effect of Roughness Model on Scattering Properties of Ice Crystals.

    Science.gov (United States)

    Geogdzhayev, Igor V.; Van Diedenhoven, Bastiaan

    2016-01-01

    We compare stochastic models of microscale surface roughness assuming uniform and Weibull distributions of crystal facet tilt angles to calculate scattering by roughened hexagonal ice crystals using the geometric optics (GO) approximation. Both distributions are determined by similar roughness parameters, while the Weibull model depends on the additional shape parameter. Calculations were performed for two visible wavelengths (864 nm and 410 nm) for roughness values between 0.2 and 0.7 and Weibull shape parameters between 0 and 1.0 for crystals with aspect ratios of 0.21, 1 and 4.8. For this range of parameters we find that, for a given roughness level, varying the Weibull shape parameter can change the asymmetry parameter by up to about 0.05. The largest effect of the shape parameter variation on the phase function is found in the backscattering region, while the degree of linear polarization is most affected at the side-scattering angles. For high roughness, scattering properties calculated using the uniform and Weibull models are in relatively close agreement for a given roughness parameter, especially when a Weibull shape parameter of 0.75 is used. For smaller roughness values, a shape parameter close to unity provides a better agreement. Notable differences are observed in the phase function over the scattering angle range from 5deg to 20deg, where the uniform roughness model produces a plateau while the Weibull model does not.

  17. Single-Photon Source for Quantum Information Based on Single Dye Molecule Fluorescence in Liquid Crystal Host

    International Nuclear Information System (INIS)

    Lukishova, S.G.; Knox, R.P.; Freivald, P.; McNamara, A.; Boyd, R.W.; Stroud, Jr. C.R.; Schmid, A.W.; Marshall, K.L.

    2006-01-01

    This paper describes a new application for liquid crystals: quantum information technology. A deterministically polarized single-photon source that efficiently produces photons exhibiting antibunching is a pivotal hardware element in absolutely secure quantum communication. Planar-aligned nematic liquid crystal hosts deterministically align the single dye molecules which produce deterministically polarized single (antibunched) photons. In addition, 1-D photonic bandgap cholesteric liquid crystals will increase single-photon source efficiency. The experiments and challenges in the observation of deterministically polarized fluorescence from single dye molecules in planar-aligned glassy nematic-liquid-crystal oligomer as well as photon antibunching in glassy cholesteric oligomer are described for the first time

  18. Conoscopic study of strontium-barium niobate single crystals

    Science.gov (United States)

    Kolesnikov, Aleksandr; Grechishkin, Rostislav; Malyshkina, Olga; Malyshkin, Yury; Dec, Jan; Łukasiewicz, Tadeusz; Ivanova, Aleksandra

    2013-12-01

    Optically transparent single crystals of strontium-barium niobate, SrxBa1-xNb2O6, of different compositions (x = 0.26...0.7) were examined with the aid of conoscopic light interference figures. A regular change of the isochrome concentric ring number and diameters consistent with the temperature variation of the value of birefringence is demonstrated by direct observations of polar cuts of optically uniaxial samples. Anomalous violations of the conventional (uniaxial) interference patterns occur occasionaly in some samples being indicative of the existence of biaxial trait in their behaviour even though no voltage is applied. These features may depend on annealing treatments at elevated temperatures. The results of the study show that conoscopic images may serve as a sensitive indicator of the structural state of SBN crystals related to the effects of stress-induced change of optical anisotropy and temperature dependent birefringence parameters.

  19. Thermal conductivity of niobium single crystals in a magnetic field

    International Nuclear Information System (INIS)

    Gladun, C.; Vinzelberg, H.

    1980-01-01

    The thermal conductivity in longitudinal magnetic fields up to 5 T and in the temperature range 3.5 to 15 K is measured in two high purity niobium single crystals having residual resistivity ratios of 22700 and 19200 and orientations of the rod axis [110] and [100]. The investigations show that by means of the longitudinal magnetic field the thermal conductivity may decrease only to a limiting value. In the crystal directions [110] and [100] for the ratio of the thermal conductivity in zero field and the thermal conductivity in the saturation field the temperature-independent factors 1.92 and 1.27, respectively, are determined. With the aid of these factors the thermal conductivity in the normal state is evaluated from the measured values of thermal conductivity below Tsub(c) in the magnetic field. The different conduction and scattering mechanisms are discussed. (author)

  20. Preparation of high purity yttrium single crystals by electrotransport

    International Nuclear Information System (INIS)

    Volkov, V.T.; Nikiforova, T.V.; Ionov, A.M.; Pustovit, A.N.; Sikharulidse, G.G.

    1981-01-01

    The possibility of obtaining yttrium crystals of high purity by the method of solid state electrotransport (SSE) was investigated in the present work. The behaviour of low contents of iron, aluminium, silicon, tantalum, copper, silver and vanadium as metallic impurities was studied using mass spectrometry. It is shown that all the impurities investigated, except copper, migrate to the anode. During electrotransfer a purification with respect to these impurities by a factor of 4 - 6 is obtained. It is proposed that the diffusion coefficients of the metallic impurities investigated are anomalously high and that the behaviour of the impurities during SSE in adapters necessitates further investigation. By using a three-stage process with intermediate removal of the anode end yttrium single crystals with a resistance ratio rho 293 /rhosub(4.2)=570 were produced. (Auth.)

  1. The Ice Selective Inlet: A novel technique for exclusive extraction of pristine ice crystals in mixed-phase clouds

    OpenAIRE

    Kupiszewski, P; Weingartner, E.; Vochezer, P.; Schnaiter, M.; Bigi, A.; Gysel, M.; Rosati, B.; Toprak, E.; Mertes, S.; Baltensperger, U.

    2015-01-01

    Climate predictions are affected by high uncertainties partially due to an insufficient knowledge of aerosol–cloud interactions. One of the poorly understood processes is formation of mixed-phase clouds (MPCs) via heterogeneous ice nucleation. Field measurements of the atmospheric ice phase in MPCs are challenging due to the presence of much more numerous liquid droplets. The Ice Selective Inlet (ISI), presented in this paper, is a novel i...

  2. Importance of crystal orientation in linear friction joining of single crystal to polycrystalline nickel-based superalloys

    International Nuclear Information System (INIS)

    Karadge, M.; Preuss, M.; Withers, P.J.; Bray, S.

    2008-01-01

    Effects of crystal orientation on weldability and microstructural evolution occurring during linear friction joining of single crystal nickel-base superalloy to polycrystalline nickel-base superalloy were studied. Electron microscopy was used to characterize deformation and microstructural development. Changes in friction coefficient with changes in crystal orientation were observed and correlated to the metallurgical adhesion. These changes were explained by taking into consideration the single crystal deformation mechanisms. It was concluded that the orientation of the single crystal with reference to the principal axes of the pressure force is of utmost importance during linear friction welding (LFW) due to changes in orientation of the primary slip system in the fcc-based single crystal lattice

  3. A 4-D dataset for validation of crystal growth in a complex three-phase material, ice cream

    International Nuclear Information System (INIS)

    Rockett, P; Karagadde, S; Guo, E; Kingsley, M; Lee, P D; Bent, J; Hazekamp, J; Vila-Comamala, J

    2015-01-01

    Four dimensional (4D, or 3D plus time) X-ray tomographic imaging of phase changes in materials is quickly becoming an accepted tool for quantifying the development of microstructures to both inform and validate models. However, most of the systems studied have been relatively simple binary compositions with only two phases. In this study we present a quantitative dataset of the phase evolution in a complex three-phase material, ice cream. The microstructure of ice cream is an important parameter in terms of sensorial perception, and therefore quantification and modelling of the evolution of the microstructure with time and temperature is key to understanding its fabrication and storage. The microstructure consists of three phases, air cells, ice crystals, and unfrozen matrix. We perform in situ synchrotron X-ray imaging of ice cream samples using in-line phase contrast tomography, housed within a purpose built cold-stage (-40 to +20 o C) with finely controlled variation in specimen temperature. The size and distribution of ice crystals and air cells during programmed temperature cycling are determined using 3D quantification. The microstructural evolution of three-phase materials has many other important applications ranging from biological to structural and functional material, hence this dataset can act as a validation case for numerical investigations on faceted and non-faceted crystal growth in a range of materials. (paper)

  4. A 4-D dataset for validation of crystal growth in a complex three-phase material, ice cream

    Science.gov (United States)

    Rockett, P.; Karagadde, S.; Guo, E.; Bent, J.; Hazekamp, J.; Kingsley, M.; Vila-Comamala, J.; Lee, P. D.

    2015-06-01

    Four dimensional (4D, or 3D plus time) X-ray tomographic imaging of phase changes in materials is quickly becoming an accepted tool for quantifying the development of microstructures to both inform and validate models. However, most of the systems studied have been relatively simple binary compositions with only two phases. In this study we present a quantitative dataset of the phase evolution in a complex three-phase material, ice cream. The microstructure of ice cream is an important parameter in terms of sensorial perception, and therefore quantification and modelling of the evolution of the microstructure with time and temperature is key to understanding its fabrication and storage. The microstructure consists of three phases, air cells, ice crystals, and unfrozen matrix. We perform in situ synchrotron X-ray imaging of ice cream samples using in-line phase contrast tomography, housed within a purpose built cold-stage (-40 to +20oC) with finely controlled variation in specimen temperature. The size and distribution of ice crystals and air cells during programmed temperature cycling are determined using 3D quantification. The microstructural evolution of three-phase materials has many other important applications ranging from biological to structural and functional material, hence this dataset can act as a validation case for numerical investigations on faceted and non-faceted crystal growth in a range of materials.

  5. Tectonics of icy satellites driven by melting and crystallization of water bodies inside their ice shells

    Science.gov (United States)

    Johnston, Stephanie Ann

    Enceladus and Europa are icy satellites that currently support bodies of liquid water in the outer solar system Additionally, they show signs of being geologically active. Developing numerical models informed by observations of these icy satellites allows for the development of additional constraints and an improved understanding of the tectonics and evolution of icy satellites. The formation mechanisms for both chaos and ridges on Europa are thought to involve water as albedo changes observed in association with them imply the deposition of salt-rich water near these features. Ridges are the most ubiquitous feature on Europa and are described as central troughs flanked by two raised edifices, range in height from tens to hundreds of meters. Europan ridges can extend hundreds of km continuously along strike but are only about 2 km across. A model of a crystallizing dike--like water intrusion is able to match the overall morphology of ridges, and is consistent the long continuous strike. However, the intrusion of a large volume of water is required to match the most common heights of the ridges. Chaos on Europa is defined as a large area of disrupted ice that contain blocks of pre-existing material separated by a hummocky matrix. A proposed mechanism for the formation of Chaos is that a region of heterogeneous ice within the shell is melted and then recrystallizes. Comparing the model results with the geology of Thera Macula, a region where it has been proposed that Chaos is currently forming, suggests that additional processes may be needed to fully understand the development of Chaos. Water-rich plumes erupt from the south pole of Enceladus, suggesting the presence of a pressurized water reservoir. If a pressurized sea is located beneath the south polar terrain, its geometry and size in the ice shell would contribute to the stress state in the ice shell. The geometry and location of such an ocean, as well as the boundary conditions and thickness of an ice shell

  6. Magnetic order of Nd5Pb3 single crystals

    Science.gov (United States)

    Yan, J.-Q.; Ochi, M.; Cao, H. B.; Saparov, B.; Cheng, J.-G.; Uwatoko, Y.; Arita, R.; Sales, B. C.; Mandrus, D. G.

    2018-04-01

    We report millimeter-sized Nd5Pb3 single crystals grown out of a Nd-Co flux. We experimentally study the magnetic order of Nd5Pb3 single crystals by measuring the anisotropic magnetic properties, electrical resistivity under high pressure up to 8 GPa, specific heat, and neutron single crystal diffraction. Two successive magnetic orders are observed at T N1  =  44 K and T N2  =  8 K. The magnetic cells can be described with a propagation vector k=(0.5, 0, 0) . Cooling below T N1, Nd1 and Nd3 order forming ferromagnetic stripes along the b-axis, and the ferromagnetic stripes are coupled antiferromagnetically along the a-axis for the k=(0.5, 0, 0) magnetic domain. Cooling below T N2, Nd2 orders antiferromagnetically to nearby Nd3 ions. All ordered moments align along the crystallographic c-axis. The magnetic order at T N1 is accompanied by a quick drop of electrical resistivity upon cooling and a lambda-type anomaly in the temperature dependence of specific heat. At T N2, no anomaly was observed in electrical resistivity but there is a weak feature in specific heat. The resistivity measurements under hydrostatic pressures up to 8 GPa suggest a possible phase transition around 6 GPa. Our first-principles band structure calculations show that Nd5Pb3 has the same electronic structure as does Y5Si3 which has been reported to be a one-dimensional electride with anionic electrons that do not belong to any atom. Our study suggests that R 5Pb3 (R  =  rare earth) can be a materials playground for the study of magnetic electrides. This deserves further study after experimental confirmation of the presence of anionic electrons.

  7. The effect of roughness model on scattering properties of ice crystals

    International Nuclear Information System (INIS)

    Geogdzhayev, Igor; Diedenhoven, Bastiaan van

    2016-01-01

    We compare stochastic models of microscale surface roughness assuming uniform and Weibull distributions of crystal facet tilt angles to calculate scattering by roughened hexagonal ice crystals using the geometric optics (GO) approximation. Both distributions are determined by similar roughness parameters, while the Weibull model depends on the additional shape parameter. Calculations were performed for two visible wavelengths (864 nm and 410 nm) for roughness values between 0.2 and 0.7 and Weibull shape parameters between 0 and 1.0 for crystals with aspect ratios of 0.21, 1 and 4.8. For this range of parameters we find that, for a given roughness level, varying the Weibull shape parameter can change the asymmetry parameter by up to about 0.05. The largest effect of the shape parameter variation on the phase function is found in the backscattering region, while the degree of linear polarization is most affected at the side-scattering angles. For high roughness, scattering properties calculated using the uniform and Weibull models are in relatively close agreement for a given roughness parameter, especially when a Weibull shape parameter of 0.75 is used. For smaller roughness values, a shape parameter close to unity provides a better agreement. Notable differences are observed in the phase function over the scattering angle range from 5° to 20°, where the uniform roughness model produces a plateau while the Weibull model does not. - Highlights: • We compare scattering by hexagonal crystals for uniform and Weibull roughness models. • The Weibull shape parameter has a stronger effect on the phase function at backscattering. • DoLP is mostly affected at the side-scattering angles. • For high roughness, the two models are in relatively close agreement for a given roughness. • A plateau from 5° to 20° is observed in the phase function when using the uniform model.

  8. Depressurization amorphization of single-crystal boron carbide.

    Science.gov (United States)

    Yan, X Q; Tang, Z; Zhang, L; Guo, J J; Jin, C Q; Zhang, Y; Goto, T; McCauley, J W; Chen, M W

    2009-02-20

    We report depressurization amorphization of single-crystal boron carbide (B4C) investigated by in situ high-pressure Raman spectroscopy. It was found that localized amorphization of B4C takes place during unloading from high pressures, and nonhydrostatic stresses play a critical role in the high-pressure phase transition. First-principles molecular dynamics simulations reveal that the depressurization amorphization results from pressure-induced irreversible bending of C-B-C atomic chains cross-linking 12 atom icosahedra at the rhombohedral vertices.

  9. Single Molecule Studies on Dynamics in Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Daniela Täuber

    2013-09-01

    Full Text Available Single molecule (SM methods are able to resolve structure related dynamics of guest molecules in liquid crystals (LC. Highly diluted small dye molecules on the one hand explore structure formation and LC dynamics, on the other hand they report about a distortion caused by the guest molecules. The anisotropic structure of LC materials is used to retrieve specific conformation related properties of larger guest molecules like conjugated polymers. This in particular sheds light on organization mechanisms within biological cells, where large molecules are found in nematic LC surroundings. This review gives a short overview related to the application of highly sensitive SM detection schemes in LC.

  10. Aluminum-rich mesoporous MFI - type zeolite single crystals

    DEFF Research Database (Denmark)

    Kustova, Marina; Kustov, Arkadii; Christensen, Christina Hviid

    2005-01-01

    are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature programmed desorption (NH3-TPD), and N-2 adsorption measurements. The obtained zeolites combine the high crystallinity and the characteristic micropores of zeolites with an intracrystalline mesopore system....... With this technique, only zeolites with relatively low Al contents were reported (Si/Al ratio about 100). In this work, the preparation of aluminum-rich mesoporous MFI-type zeolite single crystals (Si/Al similar to 16-50) using aluminum isopropoxide as the aluminum Source is reported for the first time. All samples...

  11. EPR studies of gamma-irradiated taurine single crystals

    International Nuclear Information System (INIS)

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Koeksal, F.

    2000-01-01

    An EPR study of gamma-irradiated taurine [C 2 H 7 NO 3 S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32 SO - 2 and 33 SO - 2 radicals. The hyperfine values of 33 SO - 2 radical were used to obtain O-S-O bond angle for both sites

  12. EPR studies of gamma-irradiated taurine single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Bulut, A. E-mail: abulut@samsun.omu.edu.tr; Karabulut, B.; Tapramaz, R.; Koeksal, F

    2000-04-01

    An EPR study of gamma-irradiated taurine [C{sub 2}H{sub 7}NO{sub 3}S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of {sup 32}SO{sup -}{sub 2} and {sup 33}SO{sup -}{sub 2} radicals. The hyperfine values of {sup 33}SO{sup -}{sub 2} radical were used to obtain O-S-O bond angle for both sites.

  13. EPR studies of gamma-irradiated taurine single crystals

    Science.gov (United States)

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Köksal, F.

    2000-04-01

    An EPR study of gamma-irradiated taurine [C 2H 7NO 3S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32ṠO -2 and 33ṠO -2 radicals. The hyperfine values of 33ṠO -2 radical were used to obtain O-S-O bond angle for both sites.

  14. Lattice effects in HoVo3 single crystal

    International Nuclear Information System (INIS)

    Sikora, M.; Marquina, C.; Ibarra, M.R.; Nugroho, A.A.; Palstra, T.T.M.

    2007-01-01

    We report the study of lattice effects in the Mott insulator HoVO 3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO 3 reveals gradual orbital ordering (OO) below T OO =200 K and orders antiferromagnetically at T N =113 K. A first-order structural phase transition takes place at T S ∼38 K, which is probably accompanied by change of the OO type and hence the type of antiferromagnetic spin ordering

  15. Single molecule studies on dynamics in liquid crystals.

    Science.gov (United States)

    Täuber, Daniela; von Borczyskowski, Christian

    2013-09-26

    Single molecule (SM) methods are able to resolve structure related dynamics of guest molecules in liquid crystals (LC). Highly diluted small dye molecules on the one hand explore structure formation and LC dynamics, on the other hand they report about a distortion caused by the guest molecules. The anisotropic structure of LC materials is used to retrieve specific conformation related properties of larger guest molecules like conjugated polymers. This in particular sheds light on organization mechanisms within biological cells, where large molecules are found in nematic LC surroundings. This review gives a short overview related to the application of highly sensitive SM detection schemes in LC.

  16. Point defects in electron-irradiated oxide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Caulfield, K.J.; Cooper, R. [Univ. of Melbourne, Parkville, Victoria (Australia). Dept. of Chemistry; Boas, J.F. [Australian Radiation Lab., Yallambie, Victoria (Australia)

    1995-04-01

    Point defects have been produced in CaO, MgO, and {alpha}-Al{sub 2}O{sub 3} single crystals by electron irradiation, and thresholds for atomic displacement have been measured using time-resolved luminescence spectroscopy. Oxygen displacement energies of approximately 50 eV have been determined; however, a temperature-dependent threshold observed for an emission band in MgO may arise from a magnesium displacement. A 300-nm emission in {alpha}-Al{sub 2}O{sub 3} may be due to an F-center transition. Studies of radiative recombination kinetics are consistent with an electron-detrapping model.

  17. Thermal conductivity of bulk GaN single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jezowski, A.; Stachowiak, P.; Suski, T.; Krukowski, S.; Bockowski, M.; Grzegory, I.; Danilchenko, B

    2003-05-01

    We have measured thermal conductivity, {kappa}, in the wide temperature range 4-300 K of GaN bulk single crystals grown by high-pressure, high-temperature synthesis. Obtained results (1600 W/Km at 45 K) are the highest {kappa} values reported on GaN material. At the room temperature {kappa} is about 210 W/Km. The contributions to the GaN thermal resistance of Umklapp process, mass point defects as well as phonon scattering on dislocations and sample boundary are discussed.

  18. T-1020 NaI crystal test for DM-Ice

    International Nuclear Information System (INIS)

    Maruyama, Reina; Heeger, Karsten; Pierpoint, Zachary; Pettus, Walter; Broerman, Benjamin; Hilgenberg, Chris; Webber, David

    2011-01-01

    This is a memorandum of understanding between the Fermi National Accelerator Laboratory (Fermilab) and the experiments of the NaI Crystal Test for DM-Ice from the University of Wisconsin who have committed to participate in detector tests to be carried out during the 2011-2012 Fermilab Neutrino program. The memorandum is intended primarily for the purpose of recording expectations for budget estimates and work allocations for Fermilab, the funding agencies and the participating institutions. It reflects an arrangement that currently is satisfactory to the parties; however, it is recognized and anticipated that changing circumstances of the evolving research program will necessitate revisions. The parties agree to modify this memorandum to reflect such required adjustments. Actual contractual obligations will be set forth in separate documents. The DM-Ice collaboration is designing a sodium-iodide (NaI) based detector for a direct dark matter search. The detectors should have low readout noise and background levels to carry out a sensitive search. A 17-kg version of the experiment is running at the South Pole, 2500 m deep in the Antarctic ice, and a large scale experiment is currently being designed. One of the keys to the success of the experiment is to have a good understanding of the background levels intrinsic in the NaI detectors. To measure the background level, the detectors have to be shielded against cosmic rays. The lead shielding used for DAMIC in the Minos Underground Areas is a well-suited location for this test since it offers enough overburden to shield against cosmic rays, lead shielding, and experimental infrastructure. The goal of the test is to assess the background levels in the detector and to assess the characteristics of phosphorescence induced by muons and 100 keV-3 MeV gamma rays.

  19. Defect sensitive etching of hexagonal boron nitride single crystals

    Science.gov (United States)

    Edgar, J. H.; Liu, S.; Hoffman, T.; Zhang, Yichao; Twigg, M. E.; Bassim, Nabil D.; Liang, Shenglong; Khan, Neelam

    2017-12-01

    Defect sensitive etching (DSE) was developed to estimate the density of non-basal plane dislocations in hexagonal boron nitride (hBN) single crystals. The crystals employed in this study were precipitated by slowly cooling (2-4 °C/h) a nickel-chromium flux saturated with hBN from 1500 °C under 1 bar of flowing nitrogen. On the (0001) planes, hexagonal-shaped etch pits were formed by etching the crystals in a eutectic mixture of NaOH and KOH between 450 °C and 525 °C for 1-2 min. There were three types of pits: pointed bottom, flat bottom, and mixed shape pits. Cross-sectional transmission electron microscopy revealed that the pointed bottom etch pits examined were associated with threading dislocations. All of these dislocations had an a-type burgers vector (i.e., they were edge dislocations, since the line direction is perpendicular to the [ 2 11 ¯ 0 ]-type direction). The pit widths were much wider than the pit depths as measured by atomic force microscopy, indicating the lateral etch rate was much faster than the vertical etch rate. From an Arrhenius plot of the log of the etch rate versus the inverse temperature, the activation energy was approximately 60 kJ/mol. This work demonstrates that DSE is an effective method for locating threading dislocations in hBN and estimating their densities.

  20. Synthesis and Single Crystal X-Ray Structure Determination of 3,3',5 ...

    African Journals Online (AJOL)

    Single crystal structure determination at 100 K revealed needle-like crystals in an orthorhombic crystal system. The asymmetric unit of the cell consists of an isolated chloride ion, one half of a tetrahedral [MnCl4]2- anion, a [H2Me4bpz]2+ dication and one half of a molecule of water. Keywords: Crystal Engineering, Hydrogen ...

  1. Investigation on the bulk growth of α-LiIO 3 single crystals and the ...

    Indian Academy of Sciences (India)

    2017-07-26

    Jul 26, 2017 ... Herein, we investigate to grow bulk size good quality crystals of α-LiIO3 based on the observed problems during its crystallization process. A systematic investigation was carried out to find the effect of pH on solubility, crystal growth, structural, surface and laser damage properties of α-LiIO3 single crystals.

  2. Ice crystal characterization in cirrus clouds: a sun-tracking camera system and automated detection algorithm for halo displays

    Science.gov (United States)

    Forster, Linda; Seefeldner, Meinhard; Wiegner, Matthias; Mayer, Bernhard

    2017-07-01

    Halo displays in the sky contain valuable information about ice crystal shape and orientation: e.g., the 22° halo is produced by randomly oriented hexagonal prisms while parhelia (sundogs) indicate oriented plates. HaloCam, a novel sun-tracking camera system for the automated observation of halo displays is presented. An initial visual evaluation of the frequency of halo displays for the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign from October to mid-November 2014 showed that sundogs were observed more often than 22° halos. Thus, the majority of halo displays was produced by oriented ice crystals. During the campaign about 27 % of the cirrus clouds produced 22° halos, sundogs or upper tangent arcs. To evaluate the HaloCam observations collected from regular measurements in Munich between January 2014 and June 2016, an automated detection algorithm for 22° halos was developed, which can be extended to other halo types as well. This algorithm detected 22° halos about 2 % of the time for this dataset. The frequency of cirrus clouds during this time period was estimated by co-located ceilometer measurements using temperature thresholds of the cloud base. About 25 % of the detected cirrus clouds occurred together with a 22° halo, which implies that these clouds contained a certain fraction of smooth, hexagonal ice crystals. HaloCam observations complemented by radiative transfer simulations and measurements of aerosol and cirrus cloud optical thickness (AOT and COT) provide a possibility to retrieve more detailed information about ice crystal roughness. This paper demonstrates the feasibility of a completely automated method to collect and evaluate a long-term database of halo observations and shows the potential to characterize ice crystal properties.

  3. Thermally reversible single-crystal to single-crystal transformation of mononuclear to dinuclear Zn(II) complexes by [2+2] cycloaddition reaction.

    Science.gov (United States)

    Medishetty, Raghavender; Yap, Terence Teck Sheng; Koh, Lip Lin; Vittal, Jagadese J

    2013-10-25

    Two Zn(II) complexes of trans-4-styrylpyridine ligands undergo [2+2] cycloaddition reaction forming Zn(II) complex dimers in a single-crystal to single-crystal (SCSC) manner which were thermally reversible. The dimers are presumed to be the stable intermediates in the formation of 1D coordination polymers upon prolonged exposure to UV light.

  4. CH3NH3PbCl3 Single Crystals: Inverse Temperature Crystallization and Visible-Blind UV-Photodetector

    KAUST Repository

    Maculan, Giacomo

    2015-09-02

    Single crystals of hybrid perovskites have shown remarkably improved physical properties compared to their polycrystalline film counterparts, underscoring their importance in the further development of advanced semiconductor devices. Here we present a new method of sizeable CH3NH3PbCl3 single crystal growth based on retrograde solubility behavior of hybrid perovskites. We show, for the first time, the energy band structure, charge-carrier recombination and transport properties of single crystal CH3NH3PbCl3. The chloride-based perovskite crystals exhibit trap-state density, charge carriers concentration, mobility and diffusion length comparable with the best quality crystals of methylammonium lead iodide or bromide perovskites reported so far. The high quality of the crystal along with its suitable optical bandgap enabled us to design and build an efficient visible-blind UV-photodetector, demonstrating the potential of this material to be employed in optoelectronic applications.

  5. Temperature dependence of magnetoresistance in copper single crystals

    Science.gov (United States)

    Bian, Q.; Niewczas, M.

    2018-03-01

    Transverse magnetoresistance of copper single crystals has been measured in the orientation of open-orbit from 2 K to 20 K for fields up to 9 T. The experimental Kohler's plots display deviation between individual curves below 16 K and overlap in the range of 16 K-20 K. The violation of the Kohler's rule below 16 K indicates that the magnetotransport can not be described by the classical theory of electron transport on spherical Fermi surface with a single relaxation time. A theoretical model incorporating two energy bands, spherical and cylindrical, with different relaxation times has been developed to describe the magnetoresistance data. The calculations show that the electron-phonon scattering rates at belly and neck regions of the Fermi surface have different temperature dependencies, and in general, they do not follow T3 law. The ratio of the relaxation times in belly and neck regions decreases parabolically with temperature as A - CT2 , with A and C being constants.

  6. Real-time analysis of insoluble particles in glacial ice using single-particle mass spectrometry

    Science.gov (United States)

    Osman, Matthew; Zawadowicz, Maria A.; Das, Sarah B.; Cziczo, Daniel J.

    2017-11-01

    Insoluble aerosol particles trapped in glacial ice provide insight into past climates, but analysis requires information on climatically relevant particle properties, such as size, abundance, and internal mixing. We present a new analytical method using a time-of-flight single-particle mass spectrometer (SPMS) to determine the composition and size of insoluble particles in glacial ice over an aerodynamic size range of ˜ 0.2-3.0 µm diameter. Using samples from two Greenland ice cores, we developed a procedure to nebulize insoluble particles suspended in melted ice, evaporate condensed liquid from those particles, and transport them to the SPMS for analysis. We further determined size-dependent extraction and instrument transmission efficiencies to investigate the feasibility of determining particle-class-specific mass concentrations. We find SPMS can be used to provide constraints on the aerodynamic size, composition, and relative abundance of most insoluble particulate classes in ice core samples. We describe the importance of post-aqueous processing to particles, a process which occurs due to nebulization of aerosols from an aqueous suspension of originally soluble and insoluble aerosol components. This study represents an initial attempt to use SPMS as an emerging technique for the study of insoluble particulates in ice cores.

  7. The peculiarities of water crystallization and ice melting processes in the roots of one-year plants (Plantago major L.).

    Science.gov (United States)

    Bakradze, N; Kiziria, E; Sokhadze, V; Gogichaishvili, S

    2008-01-01

    Results are presented of a water phase transition study in plantain (Plantago major L.) roots, which were used as a model system to research the peculiarities of water crystallization and ice melting processes in complex heterogeneous biological systems. It was confirmed that water in such systems is crystallized in two clearly distinguished temperature ranges: -10 to -25 degree capital ES, Cyrillic and -25 to -45 degree capital ES, Cyrillic. These water fractions are conditionally attributed to extracellular (-10 to -25 degree capital ES, Cyrillic) and intracellular (-25 to -45 degree capital ES, Cyrillic) solutions. A possible explanation is given for such significant supercooling of the intracellular solution. The values of osmotic pressures of extra- and intracellular solutions were determined according to ice melting curves. It is noted that the intracellular solution, which crystallized at lower temperatures, had a lower osmotic pressure.

  8. Strength and deformation of shocked diamond single crystals: Orientation dependence

    Science.gov (United States)

    Lang, J. M.; Winey, J. M.; Gupta, Y. M.

    2018-03-01

    Understanding and quantifying the strength or elastic limit of diamond single crystals is of considerable scientific and technological importance, and has been a subject of long standing theoretical and experimental interest. To examine the effect of crystalline anisotropy on strength and deformation of shocked diamond single crystals, plate impact experiments were conducted to measure wave profiles at various elastic impact stresses up to ˜120 GPa along [110] and [111] crystal orientations. Using laser interferometry, particle velocity histories and shock velocities in the diamond samples were measured and were compared with similar measurements published previously for shock compression along the [100] direction. Wave profiles for all three orientations showed large elastic wave amplitudes followed by time-dependent inelastic deformation. From the measured wave profiles, the elastic limits were determined under well characterized uniaxial strain loading conditions. The measured elastic wave amplitudes for the [110] and [111] orientations were lower for higher elastic impact stress (stress attained for an elastic diamond response), consistent with the result reported previously for [100] diamond. The maximum resolved shear stress (MRSS) on the {111}⟨110⟩ slip systems was determined for each orientation, revealing significant orientation dependence. The MRSS values for the [100] and [110] orientations (˜33 GPa) are 25%-30% of theoretical estimates; the MRSS value for the [111] orientation is significantly lower (˜23 GPa). Our results demonstrate that the MRSS depends strongly on the stress component normal to the {111} planes or the resolved normal stress (RNS), suggesting that the RNS plays a key role in inhibiting the onset of inelastic deformation. Lower elastic wave amplitudes at higher peak stress and the effect of the RNS are inconsistent with typical dislocation slip mechanisms of inelastic deformation, suggesting instead an inelastic response

  9. Joint Development of a Fourth Generation Single Crystal Superalloy

    Science.gov (United States)

    Walston, S.; Cetel, A.; MacKay, R.; OHara, K.; Duhl, D.; Dreshfield, R.

    2004-01-01

    A new, fourth generation, single crystal superalloy has been jointly developed by GE Aircraft Engines, Pratt & Whitney, and NASA. The focus of the effort was to develop a turbine airfoil alloy with long-term durability for use in the High Speed Civil Transport. In order to achieve adequate long-time strength improvements at moderate temperatures and retain good microstructural stability, it was necessary to make significant composition changes from 2nd and 3rd generation single crystal superalloys. These included lower chromium levels, higher cobalt and rhenium levels and the inclusion of a new alloying element, ruthenium. It was found that higher Co levels were beneficial to reducing both TCP precipitation and SRZ formation. Ruthenium caused the refractory elements to partition more strongly to the ' phase, which resulted in better overall alloy stability. The final alloy, EPM 102, had significant creep rupture and fatigue improvements over the baseline production alloys and had acceptable microstructural stability. The alloy is currently being engine tested and evaluated for advanced engine applications.

  10. Ultrafast dynamic response of single crystal β-HMX

    Science.gov (United States)

    Zaug, Joseph M.; Armstrong, Michael R.; Crowhurst, Jonathan C.; Radousky, Harry B.; Ferranti, Louis; Swan, Raymond; Gross, Rick; Teslich, Nick E.; Wall, Mark A.; Austin, Ryan A.; Fried, Laurence E.

    2017-01-01

    We report results from ultrafast compression experiments conducted on β-HMX single crystals. Results consist of nominally 12 picosecond time-resolved wave profile data, (ultrafast time domain interferometry -TDI measurements), that were analyzed to determine high-velocity wave speeds as a function of piston velocity. TDI results are used to validate calculations of anisotropic stress-strain behavior of shocked loaded energetic materials. Our previous results derived using a 350 ps duration compression drive revealed anisotropic elastic wave response in single crystal β-HMX from (110) and (010) impact planes. Here we present results using a 1.05 ns duration compression drive with a 950 ps interferometry window to extend knowledge of the anisotropic dynamic response of β-HMX within eight microns of the initial impact plane. We observe two distinct wave profiles from (010) and three wave profiles from (010) impact planes. The (110) impact plane wave speeds typically exceed (010) impact plane wave speeds at the same piston velocities. The development of multiple hydrodynamic wave profiles begins at 20 GPa for the (110) impact plane and 28 GPa for the (10) impact plane. We compare our ultrafast TDI results with previous gun and plate impact results on β-HMX and PBX9501.

  11. Steps to detect catalytic ethylene oxide formation on single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boecklein, Sebastian; Guenther, Sebastian; Reichelt, Robert; Seibald, Markus; Preimesser, Andreas; Ehrensberger, Martin; Rozsa, Gergely; Wintterlin, Joost [Ludwig-Maximilians-Universitaet, 81377 Muenchen (Germany)

    2010-07-01

    As part of a project to bridge the ''pressure gap'' for the catalytic synthesis of ethylene oxide (EtO) on Ag surfaces we have undertaken extensive studies in a model reactor. The investigations aimed at finding conditions under which the production of EtO can be unambiguously and quantitatively detected on single crystal Ag surfaces, a challenging task because of the extremely low ethylene-to-EtO reaction probability. The experiments were performed in a specially designed reactor, and they involved the variation of partial pressures, temperature, and type of Ag samples (powders and polycrystalline sheets), and great effort was expended for proper background subtraction. We find that for the sheets an essential ingredient is an activation treatment by annealing in oxygen, which raises the activity by more than one order of magnitude. There are indications that subsurface O atoms are created by this pretreatment. The maximum values obtained for activity, selectivity, yield, and reaction probability allow us to predict that EtO produced on a single Ag crystal can indeed be detected under flow conditions in a UHV chamber. Experiments on the deactivation show that sintering plays an important role for the dispersed samples, but that there is an additional deactivation process for the sheets that is not caused by sintering or poisoning.

  12. Single-crystal study on the heavy-fermion antiferromagnet UZn12

    NARCIS (Netherlands)

    Gonçalves, A.P.; Estrela, P.; de Visser, A.; Lopes, E.B.; Catarino, I.; Bonfait, G.; Godinho, M.; Almeida, M.; Gnida, D.; Kaczorowski, D.

    2011-01-01

    Millimetre size UZn12 single crystals were grown by the high temperature solution growth method using zinc as the solvent. Single-crystal x-ray diffraction data confirm that this compound crystallizes in the hexagonal high temperature form of SmZn12 (S.G. P6/mmm) and points to a U1.01(1)Zn11.7(1)

  13. Strain gradient crystal plasticity analysis of a single crystal containing a cylindrical void

    DEFF Research Database (Denmark)

    Borg, Ulrik; Kysar, J.W.

    2007-01-01

    The effects of void size and hardening in a hexagonal close-packed single crystal containing a cylindrical void loaded by a far-field equibiaxial tensile stress under plane strain conditions are studied. The crystal has three in-plane slip systems oriented at the angle 60 degrees with respect...... plasticity formulation. The stress and deformation fields obtained with a local non-hardening constitutive formulation are compared to those obtained from a local hardening formulation and to those from a non-local formulation. Compared to the case of the non-hardening local constitutive formulation......, it is shown that a local theory with hardening has only minor effects on the deformation field around the void, whereas a significant difference is obtained with the non-local constitutive relation. Finally, it is shown that the applied stress state required to activate plastic deformation at the void is up...

  14. Imatinib (Gleevec@) conformations observed in single crystals, protein-Imatinib co-crystals and molecular dynamics: Implications for drug selectivity

    Science.gov (United States)

    Golzarroshan, B.; Siddegowda, M. S.; Li, Hong qi; Yathirajan, H. S.; Narayana, B.; Rathore, R. S.

    2012-06-01

    Structure and dynamics of the Leukemia drug, Imatinib, were examined using X-ray crystallography and molecular dynamics studies. Comparison of conformations observed in single crystals with several reported co-crystals of protein-drug complexes suggests existence of two conserved conformations of Imatinib, extended and compact (or folded), corresponding to two binding modes of interaction with the receptor. Furthermore, these conformations are conserved throughout a dynamics simulation. The present study attempts to draw a parallel on conformations and binding patterns of interactions, obtained from small-molecule single-crystal and macromolecule co-crystal studies, and provides structural insights for understanding the high selectivity of this drug molecule.

  15. Ice VII from aqueous salt solutions: From a glass to a crystal with broken H-bonds

    Science.gov (United States)

    Klotz, S.; Komatsu, K.; Pietrucci, F.; Kagi, H.; Ludl, A.-A.; Machida, S.; Hattori, T.; Sano-Furukawa, A.; Bove, L. E.

    2016-08-01

    It has been known for decades that certain aqueous salt solutions of LiCl and LiBr readily form glasses when cooled to below ≈160 K. This fact has recently been exploited to produce a « salty » high-pressure ice form: When the glass is compressed at low temperatures to pressures higher than 4 GPa and subsequently warmed, it crystallizes into ice VII with the ionic species trapped inside the ice lattice. Here we report the extreme limit of salt incorporation into ice VII, using high pressure neutron diffraction and molecular dynamics simulations. We show that high-pressure crystallisation of aqueous solutions of LiCl•RH2O and LiBr•RH2O with R = 5.6 leads to solids with strongly expanded volume, a destruction of the hydrogen-bond network with an isotropic distribution of water-dipole moments, as well as a crystal-to-amorphous transition on decompression. This highly unusual behaviour constitutes an interesting pathway from a glass to a crystal where translational periodicity is restored but the rotational degrees of freedom remaining completely random.

  16. Crystal growth, structural, thermal and mechanical behavior of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals

    Science.gov (United States)

    Mahadevan, M.; Ramachandran, K.; Anandan, P.; Arivanandhan, M.; Bhagavannarayana, G.; Hayakawa, Y.

    2014-12-01

    Single crystals of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) have been grown successfully from the solution of L-arginine and 4-nitrophenol. Slow evaporation of solvent technique was adopted to grow the bulk single crystals. Single crystal X-ray diffraction analysis confirms the grown crystal has monoclinic crystal system with space group of P21. Powder X-ray diffraction analysis shows the good crystalline nature. The crystalline perfection of the grown single crystals was analyzed by HRXRD by employing a multicrystal X-ray diffractometer. The functional groups were identified from proton NMR spectroscopic analysis. Linear and nonlinear optical properties were determined by UV-Vis spectrophotometer and Kurtz powder technique respectively. It is found that the grown crystal has no absorption in the green wavelength region and the SHG efficiency was found to be 2.66 times that of the standard KDP. The Thermal stability of the crystal was found by obtaining TG/DTA curve. The mechanical behavior of the grown crystal has been studied by Vicker's microhardness method.

  17. Ice Protection of Turbojet Engines by Inertia Separation of Water II : Single-offset-duct System

    Science.gov (United States)

    Von Glahn, Uwe

    1948-01-01

    Investigation of a single-offset-duct system designed to prevent entrance of water into a turbojet engine was conducted on a half-scale nacelle model. An investigation was made to determine ram-pressure recovery and radial velocity profiles at the compressor section and icing characteristics of such a duct system. At a design inlet velocity of 0.77, the maximum ram-pressure recovery attained with effective water-separating inlet was 77 percent, which is considerably less than attainable with a direct-ram inlet. Continuous heating of the accessory-housing surface would be required for inlets that have a small ice storage space.

  18. Ignition and growth modeling of detonation reaction zone experiments on single crystals of PETN and HMX

    Science.gov (United States)

    White, Bradley W.; Tarver, Craig M.

    2017-01-01

    It has long been known that detonating single crystals of solid explosives have much larger failure diameters than those of heterogeneous charges of the same explosive pressed or cast to 98 - 99% theoretical maximum density (TMD). In 1957, Holland et al. demonstrated that PETN single crystals have failure diameters of about 8 mm, whereas heterogeneous PETN charges have failure diameters of less than 0.5 mm. Recently, Fedorov et al. quantitatively determined nanosecond time resolved detonation reaction zone profiles of single crystals of PETN and HMX by measuring the interface particle velocity histories of the detonating crystals and LiF windows using a PDV system. The measured reaction zone time durations for PETN and HMX single crystal detonations were approximately 100 and 260 nanoseconds, respectively. These experiments provided the necessary data to develop Ignition and Growth (I&G) reactive flow model parameters for the single crystal detonation reaction zones. Using these parameters, the calculated unconfined failure diameter of a PETN single crystal was 7.5 +/- 0.5 mm, close to the 8 mm experimental value. The calculated failure diameter of an unconfined HMX single crystal was 15 +/- 1 mm. The unconfined failure diameter of an HMX single crystal has not yet been determined precisely, but Fedorov et al. detonated 14 mm diameter crystals confined by detonating a HMX-based plastic bonded explosive (PBX) without initially overdriving the HMX crystals.

  19. Effects of ice crystal surface roughness and air bubble inclusions on cirrus cloud radiative properties from remote sensing perspective

    Science.gov (United States)

    Tang, Guanglin; Panetta, R. Lee; Yang, Ping; Kattawar, George W.; Zhai, Peng-Wang

    2017-07-01

    We study the combined effects of surface roughness and inhomogeneity on the optical scattering properties of ice crystals and explore the consequent implications to remote sensing of cirrus cloud properties. Specifically, surface roughness and inhomogeneity are added to the Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 (MC6) cirrus cloud particle habit model. Light scattering properties of the new habit model are simulated using a modified version of the Improved Geometric Optics Method (IGOM). Both inhomogeneity and surface roughness affect the single scattering properties significantly. In visible bands, inhomogeneity and surface roughness both tend to smooth the phase function and eliminate halos and the backscattering peak. The asymmetry parameter varies with the degree of surface roughness following a U shape - decreases and then increases - with a minimum at around 0.15, whereas it decreases monotonically with the air bubble volume fraction. Air bubble inclusions significantly increase phase matrix element -P12 for scattering angles between 20°-120°, whereas surface roughness has a much weaker effect, increasing -P12 slightly from 60°-120°. Radiative transfer simulations and cirrus cloud property retrievals are conducted by including both the factors. In terms of surface roughness and air bubble volume fraction, retrievals of cirrus cloud optical thickness or the asymmetry parameter using solar bands show similar patterns of variation. Polarimetric simulations using the MC6 cirrus cloud particle habit model are shown to be more consistent with observations when both surface roughness and inhomogeneity are simultaneously considered.

  20. Growth and characterization of 2-methylquinolinium L-malate single crystal

    Science.gov (United States)

    Bharathi, M. Divya; Ahila, G.; Mohana, J.; Anbalagan, G.

    2017-05-01

    An organic nonlinear optical single crystal, 2-methylquinolinium L-malate (MLM) was grown from ethanol solvent using slow evaporation solution growth technique. The single crystal X-ray diffraction studies confirmed that the crystal belongs to the monoclinic system with the non-centrosymmetric space group P21. The crystal is transparent in the entire visible region. The second harmonic generation efficiency of the grown crystal has been obtained by the Kurtz-Perry powder technique. The laser damage threshold value 5.58 GW/cm2 indicates that this crystal can be used for high-power laser applications.

  1. Luminescence Properties of ScPO{sub 4} Single Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, L.A.; Trukhin, A.N.

    1999-08-16

    Flux-grown ScPO{sub 4} single crystals exhibit a number of luminescence bands in their x-ray-excited luminescence spectra - including sharp lines arising from rare-earth elements plus a number of broad bands at 5.6 cV, 4.4 eV, and 3 eV. The band at 5.6 eV was attributed to a self-trapped exciton (STE) [l], and it could be excited at 7 eV and higher energies. This luminescence is strongly polarized (P = 70 %) along the optical axes of the crystal and exhibits a kinetic decay time constant that varies from several ns at room temperature to {approximately}10 {micro}s at 60 K and up to {approximately}1 ms at 10 K. It is assumed that the STE is localized on the SC ions. The band at 3 eV can be excited in the range of the ScPO{sub 4} crystal transparency (decay time = 3 to 4 {micro}s.) This band is attributed to a lead impurity that creates different luminescence centers. At high temperatures, the band at 4.4 eV is dominant in the x-ray-excited TSL and afterglow spectra. Its intensity increases with irradiation time beginning at zero at the initial irradiation time. The 4.4 eV band does not appear in a fast process under a pulsed electron beam, showing that accumulation is necessary for its observation. A sample of ScPO{sub 4} doped with vanadium exhibited a prevalent band at 4.4 eV at T = 480 K.

  2. Studies on crystal growth and physical properties of 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline single crystal

    Science.gov (United States)

    Jebin, R. P.; Suthan, T.; Rajesh, N. P.; Vinitha, G.; Dhas, S. A. Britto

    2016-07-01

    The organic material 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline has been grown by slow evaporation technique. Single crystal and Powder X-ray diffraction studies have been carried out to conform the grown crystal. FTIR and FT-Raman spectra were recorded to identify the functional groups present in the crystal. The optical property of the grown crystal was analysed by UV-Vis-NIR measurement. The thermal property of the grown crystal was analysed by thermogravimetric (TG) and differential thermal analyses (DTA). Thermal diffusivity of the grown crystal was analysed by Photo acoustic spectroscopic (PAS) studies. The third order nonlinear optical properties of 4-(dimethylamino)benzaldehyde-2,4-dinitroaniline was measured by the Z-scan technique using 532 nm diode pumped continuous wave (CW) Nd:YAG laser. The mechanical property of the grown crystal was analysed by using microhardness studies.

  3. Defects induced in cerium dioxide single crystals by electron irradiation

    Science.gov (United States)

    Costantini, Jean-Marc; Miro, Sandrine; Touati, Nadia; Binet, Laurent; Wallez, Gilles; Lelong, Gérald; Guillaumet, Maxime; Weber, William J.

    2018-01-01

    Micro-Raman spectroscopy, X-band electron paramagnetic resonance (EPR) spectroscopy, and UV-visible optical absorption spectroscopy were used to study the damage production in cerium dioxide (CeO2) single crystals by electron irradiation for three energies (1.0, 1.4, and 2.5 MeV). The Raman-active T2g peak was left unchanged after 2.5-MeV electron irradiation at a high fluence. This shows that no structural modifications occurred for the cubic fluorite structure. UV-visible optical absorption spectra exhibited a characteristic sub band-gap tail for 1.4-MeV and 2.5-MeV energies, but not for 1.0 MeV. Narrow EPR lines were recorded near liquid-helium temperature after 2.5-MeV electron irradiation; whereas no such signal was found for the virgin un-irradiated crystal or after 1.0-MeV irradiation for the same fluence. The angular variation of these lines in the {111} plane revealed a weak g-factor anisotropy assigned to Ce3+ ions (with the 4f1 configuration) in a high-symmetry local environment. It is concluded that Ce3+ ions may be produced by a reduction resulting from the displacement damage process. However, no evidence of F+ or F0 center or hole center formation due to irradiation was found from the present EPR and optical absorption spectra.

  4. From Protein Structure to Function via Single Crystal Optical Spectroscopy

    Directory of Open Access Journals (Sweden)

    Luca eRonda

    2015-04-01

    Full Text Available The more than 100.000 protein structures determined by X-ray crystallography provide a wealth of information for the characterization of biological processes at the molecular level. However, several crystallographic artifacts, including conformational selection, crystallization conditions and radiation damages, may affect the quality and the interpretation of the electron density map, thus limiting the relevance of structure determinations. Moreover, for most of these structures no functional data have been obtained in the crystalline state, thus posing serious questions on their validity in the inference for protein mechanisms. In order to solve these issues, spectroscopic methods have been applied for the determination of equilibrium and kinetic properties of proteins in the crystalline state. These methods are UV-vis spectrophotometry, spectrofluorimetry, IR, EPR, Raman and resonance Raman spectroscopy. Some of these approaches have been implemented with on-line instruments at X-ray synchrotron beamlines. Here, we provide an overview of investigations predominantly carried out in our laboratory by single crystal polarized absorption UV-vis microspectrophotometry, the most applied technique for the functional characterization of proteins in the crystalline state. Studies on hemoglobins, pyridoxal 5’-phosphate dependent enzymes and green fluorescent protein in the crystalline state have addressed key biological issues, leading to either straightforward structure-function correlations or limitations to structure-based mechanisms.

  5. Solidification microstructures in single-crystal stainless steel melt pools

    Energy Technology Data Exchange (ETDEWEB)

    Sipf, J.B.; Boatner, L.A.; David, S.A.

    1994-03-01

    Development of microstructure of stationary melt pools of oriented stainless steel single crystals (70%Fe-15%Ni-15%Cr was analyzed. Stationary melt pools were formed by electron-beam and gas-tungsten-arc heating on (001), (011), and (111) oriented planes of the austenitic, fcc-alloy crystals. Characterization and analysis of resulting microstructure was carried out for each crystallographic plane and welding method. Results showed that crystallography which favors ``easy growth`` along the <100> family of directions is a controlling factor in the microstructural formation along with the melt-pool shape. The microstructure was found to depend on the melting method, since each method forms a unique melt-pool shape. These results are used in making a three-dimensional reconstruction of the microstructure for each plane and melting method employed. This investigation also suggests avenues for future research into the microstructural properties of electron-beam welds as well as providing an experimental basis for mathematical models for the prediction of solidification microstructures.

  6. A discrete dislocation dynamics model of creeping single crystals

    Science.gov (United States)

    Rajaguru, M.; Keralavarma, S. M.

    2018-04-01

    Failure by creep is a design limiting issue for metallic materials used in several high temperature applications. Current theoretical models of creep are phenomenological with little connection to the underlying microscopic mechanisms. In this paper, a bottom-up simulation framework based on the discrete dislocation dynamics method is presented for dislocation creep aided by the diffusion of vacancies, known to be the rate controlling mechanism at high temperature and stress levels. The time evolution of the creep strain and the dislocation microstructure in a periodic unit cell of a nominally infinite single crystal is simulated using the kinetic Monte Carlo method, together with approximate constitutive laws formulated for the rates of thermal activation of dislocations over local pinning obstacles. The deformation of the crystal due to dislocation glide between individual thermal activation events is simulated using a standard dislocation dynamics algorithm, extended to account for constant stress periodic boundary conditions. Steady state creep conditions are obtained in the simulations with the predicted creep rates as a function of stress and temperature in good agreement with experimentally reported values. Arrhenius scaling of the creep rates as a function of temperature and power-law scaling with the applied stress are also reproduced, with the values of the power-law exponents in the high stress regime in good agreement with experiments.

  7. Simulations of surface stress effects in nanoscale single crystals

    Science.gov (United States)

    Zadin, V.; Veske, M.; Vigonski, S.; Jansson, V.; Muszinsky, J.; Parviainen, S.; Aabloo, A.; Djurabekova, F.

    2018-04-01

    Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the surface and subsurface layers in the presence of high electric fields. Thermally activated processes, as well as plastic deformation caused by tensile stress due to an applied electric field, are usually not accessible by atomistic simulations because of the long time needed for these processes to occur. On the other hand, finite element methods, able to describe the process of plastic deformations in materials at realistic stresses, do not include surface properties. The latter are particularly important for the problems where the surface plays crucial role in the studied process, as for instance, in the case of plastic deformations at a nanovoid. In the current study by means of molecular dynamics (MD) and finite element simulations we analyse the stress distribution in single crystal copper containing a nanovoid buried deep under the surface. We have developed a methodology to incorporate the surface effects into the solid mechanics framework by utilizing elastic properties of crystals, pre-calculated using MD simulations. The method leads to computationally efficient stress calculations and can be easily implemented in commercially available finite element software, making it an attractive analysis tool.

  8. Thermal expansion of C60 single crystals under pressure

    International Nuclear Information System (INIS)

    Grube, K.D.

    1995-12-01

    The thermal expansion and compressibility of C 60 single crystals have been investigated by a newly developed capacitive dilatometer. The dilatometer was integrated in a high pressure cell and exposed to a hydrostatic pressure of maximal 0.85 GPa with He or Ar as pressure transmitting medium. The relative length change of the C 60 -samples was measured with a resolution of ΔL/L∼10 -9 . The crystals consist of weakly bonded C 60 -molecules which can rotate nearly free at room temperature. The gradual freezing-in of the rotational motions leads to a first order phase transition at 260 K and a glass transition at 90 K. The pressure dependence of these transitions was determined in a temperature range from 50 K to 325 K up to a pressure of 0.85 GPa. The phase transition at 260 K shows a positive pressure dependence of 174 K/GPa. The glass transition temperature first increases with 75 K/GPa under pressure, then it jumps discontinuously by 10 K at 0.15 GPa followed by a further increase with a slope of 54 K/GPa. The jump in the glass transition temperature at 0.15 GPa can be explained with an orientation-dependent interaction between the C 60 -molecules. (orig.) [de

  9. Growth and microtopographic study of CuInSe{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Sanjaysinh M.; Chaki, Sunil, E-mail: sunilchaki@yahoo.co.in; Deshpande, M. P. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat - 388120 (India); Tailor, J. P. [Applied Physics Department, S.V.N.I.T., Surat, Gujarat - 395007 (India)

    2016-05-23

    The CuInSe{sub 2} single crystals were grown by chemical vapour transport (CVT) technique using iodine as transporting agent. The elemental composition of the as-grown CuInSe{sub 2} single crystals was determined by energy dispersive analysis of X-ray (EDAX). The unit cell crystal structure and lattice parameters were determined by X-ray diffraction (XRD) technique. The surface microtopographic study of the as-grown CuInSe{sub 2} single crystals surfaces were done to study the defects, growth mechanism, etc. of the CVT grown crystals.

  10. Single crystal growth and X-ray structure analysis of non-peripheral octahexyl phthalocyanine

    Science.gov (United States)

    Ohmori, Masashi; Nakano, Chika; Higashi, Takuya; Miyano, Tetsuya; Tohnai, Norimitsu; Fujii, Akihiko; Ozaki, Masanori

    2016-07-01

    The single-crystal structure of metal-free non-peripheral octahexyl-substituted phthalocyanine (C6PcH2) has been investigated by single-crystal X-ray structure analysis. Two types of C6PcH2 single crystal, bulk and needle crystals, were separately grown by controlling the recrystallization conditions. The structures of the two types of crystal were determined, and were found to be completely different, that is, C6PcH2 exhibits structural polymorphism. It has been clarified that the C6PcH2 microcrystals in thin films used in previously reported electronic devices have the needle structure.

  11. Phonon interactions with methyl radicals in single crystals

    Directory of Open Access Journals (Sweden)

    James W. Wells

    2017-04-01

    Full Text Available The high temperature ESR spectra’s anomalous appearance at very low temperatures for the methyl radical created in single crystals is explained by magnetic dipole interactions with neighboring protons. These protons acting via phonon vibrations induce resonant oscillations with the methyl group to establish a very temperature sensitive ‘‘relaxation’’ mode that allows the higher energy ‘‘E’’ state electrons with spin 12 to ‘‘decay’’ into ‘‘A’’ spin 12 states. Because of the amplitude amplification with temperature, the ‘‘E’’ state population is depleted and the ‘‘A’’ state population augmented to produce the high temperature ESR spectrum. This phenomenon is found to be valid for all but the very highest barriers to methyl group tunneling. In support, a time dependent spin population study shows this temperature evolution in the state populations under this perturbation.

  12. Non-linear friction in a single crystal of zirconium

    International Nuclear Information System (INIS)

    Ritchie, I.G.; Atrens, A.; Sprungmann, K.W.

    1980-04-01

    Non-linear internal friction phenomena in a single crystal of zirconium are investigated. Both the interactions between dislocations and immobile obstacles and between dislocations and mobile pinning points are involved. It is shown that vibration conditioning and programmed vibration annealing can be used to separate the time-dependent and strain-amplitude-dependent components of the internal friction. An impurity peaking effect has been generated by altering the effective concentration of obstacles by step changes in strain amplitude and vibration conditioning. Repeated thermal cycling at low strain amplitudes, through the terminal solid solubility boundary for hydrogen in zirconium, does not lead to the cumulative increase in dislocation density observed when polycrystalline samples are treated similarly. (auth)

  13. EPR of Mn2+ in strontium tartrate trihydrate single crystals

    International Nuclear Information System (INIS)

    Korkmaz, M.; Aktas, B.

    1985-01-01

    Electron paramagnetic resonance spectra of Mn 2+ doped in single crystals of strontium tartrate trihydrate grown by a diffusion technique are investigated at room temperature. Mn 2+ enters the lattice substitutionally and is trapped at two magnetically equivalent but crystallographically inequivalent sites. The EPR measurements give the following values for the spin-Hamiltonian parameters: g/sub x/(= g/sub y/) = 1.9781, g/sub z/ = 2.0012, A/sub x/(= A/sub y/) = -94.9 x 10 -4 T, A/sub z/ = -96.2 x 10 -4 T, B 0 2 (= D/3) = +160.9 x 10 -4 T, B 2 2 (= E) = +101.2 x 10 -4 T, B 0 4 = +0.013 x 10 -4 T, and B 2 4 = +0.088 x 10 -4 T. (author)

  14. Hydrogen solid solutions in niobium - molybdenum single crystal alloys

    International Nuclear Information System (INIS)

    Silva, J.R.G. da; Ishikawa, T.T.

    1981-01-01

    The temperature variation of the hydrogen solubility in a series of single crystal Nb-Mo alloys ('binary solvents') in equilibrium with the gaseous phase at atmospheric pressure is presented. The partial thermodynamic properties of the intersticially dissolved hydrogen atoms were calculated from of solubility versus temperature curves. The hydrogen solution obeys the quasi-regular model at all the compositions of the investigated alloys. The variation of the partial entalphy Hu sup(-) with the solvent alloys composition (Mo/Nb + Mo ratio) is compared with the variation of the electronic structure of the solvent. The non-random solute distribution in the binary solvent lattice is shown, with the H atoms prefering interstitial sites next to Nb atoms. (Author) [pt

  15. Superconductivity in SrNi2P2 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Park, Tuscon [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory

    2009-01-01

    Heat capacity, magnetic susceptibility, and resistivity of SrNi{sub 2}P{sub 2} single crystals are presented, illustrating the structural transition at 325 K, and bulk superconductivity at 1.4 K. The magnitude of {Tc}, fits to the heat capacity data, the small upper critical field H{sub c2} = 390 Oe, and {kappa} = 2.1 suggests a conventional fully gapped superconductor. With applied pressure we find that superconductivity persists into the so-called 'collapsed tetragonal' phase, although the transition temperature is monotonically suppressed with increasing pressure. This argues that reduced dimensionality can be a mechanism for increasing the transition temperatures of layered NiP, as well as layered FeAs and NiAs, superconductors.

  16. Optical properties of reduced lithium niobate single crystals

    Science.gov (United States)

    Dhar, Ajay; Mansingh, Abhai

    1990-12-01

    The optical transmission of LiNbO3 single crystals has been measured in the wavelength range 200-900 nm, for different degrees of reduction, to study the effect of reduction on the optical characteristics of LiNbO3 near the fundamental absorption edge. The optical transitions in LiNbO3 were found to be indirect and the band gap decreased with increasing degree of reduction. The band observed at 2.48 eV in the absorption spectrum in heavily reduced samples has been attributed to the formation of polarons, and the theoretical model of Reik and Heese [J. Chem. Solids 28, 581 (1967)] for small polarons is used to correlate the optical and electrical properties.

  17. Quantum nernst effect in a bismuth single crystal

    International Nuclear Information System (INIS)

    Matsuo, M.; Endo, A.; Hatano, N.; Nakamura, H.; Shirasaki, R.; Sugihara, K.

    2009-07-01

    We calculate the phonon-drag contribution to the transverse (Nernst) thermoelectric power S yx in a bismuth single crystal subjected to a quantizing magnetic field. The calculated heights of the Nernst peaks originating from the hole Landau levels and their temperature dependence reproduce the right order of magnitude for those of the pronounced magneto-oscillations recently reported by Behnia et al. A striking experimental finding that S yx is much larger than the longitudinal (Seebeck) thermoelectric power S xx can be naturally explained as the effect of the phonon drag, combined with the well-known relation between the longitudinal and the Hall resistivity ρ xx >> |ρ yx | in a semi-metal bismuth. The calculation that includes the contribution of both holes and electrons suggests that some of the hitherto unexplained minor peaks located roughly at the fractional filling of the hole Landau levels are attributable to the electron Landau levels. (author)

  18. Growth of single-crystal YAG fiber optics.

    Science.gov (United States)

    Nie, Craig D; Bera, Subhabrata; Harrington, James A

    2016-07-11

    Single-crystal YAG (Y3Al5O12) fibers have been grown by the laser heated pedestal growth technique with losses as low as 0.3 dB/m at 1.06 μm. These YAG fibers are as long as about 60 cm with diameters around 330 μm. The early fibers were grown from unoriented YAG seed fibers and these fibers exhibited facet steps or ridges on the surface of the fiber. However, recently we have grown fibers using an oriented seed to grow step-free fibers. Scattering losses made on the fibers indicate that the scattering losses are equal to about 30% of the total loss.

  19. Shock compression experiments on Lithium Deuteride single crystals.

    Energy Technology Data Exchange (ETDEWEB)

    Knudson, Marcus D.; Desjarlais, Michael Paul; Lemke, Raymond W.

    2014-10-01

    S hock compression exper iments in the few hundred GPa (multi - Mabr) regime were performed on Lithium Deuteride (LiD) single crystals . This study utilized the high velocity flyer plate capability of the Sandia Z Machine to perform impact experiments at flyer plate velocities in the range of 17 - 32 km/s. Measurements included pressure, density, and temperature between %7E200 - 600 GPa along the Principal Hugoniot - the locus of end states achievable through compression by large amplitude shock waves - as well as pressure and density of re - shock states up to %7E900 GPa . The experimental measurements are compared with recent density functional theory calculations as well as a new tabular equation of state developed at Los Alamos National Labs.

  20. Trapped electrons in irradiated single crystals of polyhydroxy compounds

    International Nuclear Information System (INIS)

    Box, H.C.; Budzinski, E.E.; Freund, H.G.; Potter, W.R.

    1979-01-01

    The intermolecular trapping of electrons has been observed in single crystals of dulcitol and L(+) arabinose x-irradiated at 4.2 0 K. Attribution of a major component of the ESR absorption to trapped electrons is based upon the character of the hyperfine pattern, which arises from multiple anisotropic hyperfine interactions with exchangeable protons, and on the g value of the absorption, which is always less than the free spin value. The removal of the trapped electron absorption upon irradiation with visible light has also been demonstrated. In these experiments all of the electrons are trapped in identical sites. This circumstance provides some important advantages in the study of the factors affecting the stabilization of charge in an environment of polarizable molecules

  1. X-ray conductivity of ZnSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Degoda, V. Ya., E-mail: degoda@univ.kiev.ua; Podust, G. P. [Taras Shevchenko Kyiv National University, Physics Department (Ukraine)

    2016-05-15

    The experimental I–V and current–illuminance characteristics of the X-ray conductivity and X-ray luminescence of zinc-selenide single crystals feature a nonlinear shape. The performed theoretical analysis of the kinetics of the X-ray conductivity shows that even with the presence of shallow and deep traps for free charge carriers in a semiconductor sample, the integral characteristics of the X-ray conductivity (the current–illuminance and I–V dependences) should be linear. It is possible to assume that the nonlinearity experimentally obtained in the I–V and current–illuminance characteristics can be caused by features of the generation of free charge carriers upon X-ray irradiation, i.e., the generation of hundreds of thousands of free charge carriers of opposite sign in a local region with a diameter of <1 μm and Coulomb interaction between the free charge carriers of opposite signs.

  2. Bulk crystal growth and their effective third order nonlinear optical properties of 2-(4-fluorobenzylidene) malononitrile (FBM) single crystal

    Science.gov (United States)

    Priyadharshini, A.; Kalainathan, S.

    2018-04-01

    2-(4-fluorobenzylidene) malononitrile (FBM), an organic third order nonlinear (TONLO) single crystal with the dimensions of 32 × 7 × 11 mm3, has been successfully grown in acetone solution by slow evaporation technique at 35 °C. The crystal system (triclinic), space group (P-1) and crystalline purity of the titular crystal were measured by single crystal and powder X-ray diffraction, respectively. The molecular weight and the multiple functional groups of the FBM material were confirmed through the mass and FT-IR spectral analysis. UV-Vis-NIR spectral study enroles that the FBM crystal exhibits excellent transparency (83%) in the entire visible and near infra-red region with a wide bandgap 2.90 eV. The low dielectric constant (εr) value of FBM crystal is appreciable for microelectronics industry applications. Thermal stability and melting point (130.09 °C) were ascertained by TGA-DSC analysis. The laser-induced surface damage threshold (LDT) value of FBM specimen is found to be 2.14 GW/cm2, it is fairly good compared to other reported NLO crystals. The third - order nonlinear optical character of the FBM crystal was confirmed through the typical single beam Z-scan technique. All these finding authorized that the organic crystal of FBM is favorably suitable for NLO applications.

  3. Single crystal diamond detectors grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    Tuve, C.; Angelone, M.; Bellini, V.; Balducci, A.; Donato, M.G.; Faggio, G.; Marinelli, M.; Messina, G.; Milani, E.; Morgada, M.E.; Pillon, M.; Potenza, R.; Pucella, G.; Russo, G.; Santangelo, S.; Scoccia, M.; Sutera, C.; Tucciarone, A.; Verona-Rinati, G.

    2007-01-01

    The detection properties of heteropitaxial (polycrystalline, pCVD) and homoepitaxial (single crystal, scCVD) diamond films grown by microwave chemical vapor deposition (CVD) in the Laboratories of Roma 'Tor Vergata' University are reported. The pCVD diamond detectors were tested with α-particles from different sources and 12 C ions produced by 15MV Tandem accelerator at Southern National Laboratories (LNS) in Catania (Italy). pCVDs were also used to monitor 14MeV neutrons produced by the D-T plasma at Joint European Torus (JET), Culham, U.K. The limit of pCVDs is the poor energy resolution. To overcome this problem, we developed scCVD diamonds using the same reactor parameters that optimized pCVD diamonds. scCVD were grown on a low cost (100) HPHT single crystal substrate. A detector 110μm thick was tested under α-particles and under 14MeV neutron irradiation. The charge collection efficiency spectrum measured under irradiation with a triple α-particle source shows three clearly resolved peaks, with an energy resolution of about 1.1%. The measured spectra under neutron irradiation show a well separated C(n,α 0 ) 9 Be12 reaction peak with an energy spread of 0.5MeV for 14.8MeV neutrons and 0.3MeV for 14.1MeV neutrons, which are fully compatible with the energy spread of the incident neutron beams

  4. Isothermal equation of state of a lithium fluoride single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.Y.

    1975-01-01

    An isothermal equation of state of a LiF single crystal was determined from length change measurements of the specimen as a function of hydrostatic pressure up to approximately 7 kbars at 28 to 41/sup 0/C. The length change was measured with an accuracy of approximately 500 A by using a Fabry Perot type He--Ne laser interferometer for a 1-m long specimen at temperatures constant to less than 0.002/sup 0/C. Several two- and three-parameter equations of state were used in analyzing the measured pressure-volume data. The computer fit for each equation of state determines not only the value of its parameters but also the standard deviations associated with them and one dependent variable, either pressure or volume. With the parameters determined, the equations of state are extrapolated to approximately 5 megabars in order to see discrepancies. Using the Born model of ionic solids, two equations of state were derived both from a power law potential and from an exponential form for the repulsive energy of alkali metal halides and used to fit the pressure-volume data of a LiF single crystal. They are also extrapolated to approximately 5 megabars. The Birch's two-parameter equation and the Grover, Getting, and Kennedy equation are indistinguishable from the two equations of state derived from the Born model for pressures approximately equal to or less than 800 kbars within +-20 kbars. The above four equations of state also fit closely the Pagannone and Drickamer static compression data, the Christian shock wave data, and the Kormer et al. shock wave data. The isothermal bulk modulus and its first pressure derivative at atmospheric pressure and 28.83/sup 0/C are 664.5 +- 0.5 kbars and 5.40 +- 0.18, respectively, in close agreement with those values ultrasonically measured by R. A. Miller and C. S. Smith. (auth)

  5. Modification of ion implanted or irradiated single crystal sapphire

    International Nuclear Information System (INIS)

    Song Yin; Zhang Chonghong; Wang Zhiguang; Zhao Zhiming; Yao Cunfeng; Zhou Lihong; Jin Yunfan

    2006-01-01

    Single crystal sapphire (Al 2 O 3 ) samples were implanted at 600 K by He, Ne and Ar ions with energy of 110 keV to doses ranging from 5 x 10 16 to 2 x 10 17 ion/cm 2 or irradiated at 320 K by 208 Pb 27+ ion with energy of 1.1 MeV/u to the fluences ranging from 1 x 10 12 to 5 x 10 14 ion/cm 2 . The modification of structure and optical properties induced by ion implantation or irradiation were analyzed by using photoluminescence (PL) and Fourier transformation infrared spectrum (FTIR) spectra and transmission electron microscopy (TEM) measurements. The PL measurements showed that absorption peaks located at 375, 413 and 450 nm appeared in all the implanted or irradiated samples, the PL intensities reached up to the maximum for the 5 x 10 16 ion/cm 2 implanted samples. After Pb-ion irradiation, a new peak located at 390 nm formed. TEM analyses showed that small size voids (1-2 nm) with high density were formed in the region from the surface till to about 100 nm in depth and also large size Ne-bubble formed in the Ne-doped region. Form the obtained FTIR spectra, it was found that Pb-ion irradiation induced broadening of the absorption band in 460-510 cm -1 and position shift of the absorption band in 1000-1300 cm -1 towards to high wavenumber. The possible damage mechanism in single crystal sapphire induced by energetic ion implantation or irradiation was briefly discussed. (authors)

  6. Synthesis, crystal growth, optical, thermal, and mechanical properties of a nonlinear optical single crystal: ammonium sulfate hydrogen sulphamate (ASHS)

    Science.gov (United States)

    Sudhakar, K.; Nandhini, S.; Muniyappan, S.; Arumanayagam, T.; Vivek, P.; Murugakoothan, P.

    2018-04-01

    Ammonium sulfate hydrogen sulphamate (ASHS), an inorganic nonlinear optical crystal, was grown from the aqueous solution by slow evaporation solution growth technique. The single-crystal XRD confirms that the grown single crystal belongs to the orthorhombic system with the space group of Pna21. Powder XRD confirms the crystalline nature and the diffraction planes were indexed. Crystalline perfection of grown crystal was analysed by high-resolution X-ray diffraction rocking curve technique. UV-Vis-NIR studies revealed that ASHS crystal has optical transparency 65% and lower cut-off wavelength at 218 nm. The violet light emission of the crystal was identified by photoluminescence studies. The particle size-dependent second-harmonic generation efficiency for ASHS crystal was evaluated by Kurtz-Perry powder technique using Nd:YAG laser which established the existence of phase matching. Surface laser damage threshold value was evaluated using Nd:YAG laser. Optical homogeneity of the crystal was evaluated using modified channel spectrum method through birefringence study. Thermal analysis reveals that ASHS crystal is stable up to 213 °C. The mechanical behaviour of the ASHS crystal was analysed using Vickers microhardness study.

  7. A dislocation-based crystal plasticity framework for dynamic ductile failure of single crystals

    Science.gov (United States)

    Nguyen, Thao; Luscher, D. J.; Wilkerson, J. W.

    2017-11-01

    A framework for dislocation-based viscoplasticity and dynamic ductile failure has been developed to model high strain rate deformation and damage in single crystals. The rate-dependence of the crystal plasticity formulation is based on the physics of relativistic dislocation kinetics suited for extremely high strain rates. The damage evolution is based on the dynamics of void growth, which are governed by both micro-inertia as well as dislocation kinetics and dislocation substructure evolution. An averaging scheme is proposed in order to approximate the evolution of the dislocation substructure in both the macroscale as well as its spatial distribution at the microscale. Additionally, a concept of a single equivalent dislocation density that effectively captures the collective influence of dislocation density on all active slip systems is proposed here. Together, these concepts and approximations enable the use of semi-analytic solutions for void growth dynamics developed in (Wilkerson and Ramesh, 2014), which greatly reduce the computational overhead that would otherwise be required. The resulting homogenized framework has been implemented into a commercially available finite element package, and a validation study against a suite of direct numerical simulations was carried out.

  8. Structure of cleaved (001) USb2 single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shao-ping [Los Alamos National Laboratory; Hawley, Marilyn [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Stockum, Phil B [STANFORD UNIV.; Manoharan, Hari C [STANFORD UNIV

    2009-01-01

    We have achieved what we believe to be the first atomic resolution STM images for a uranium compound taken at room temperature. The a, b, and c lattice parameters in the images confirm that the USb{sub 2} crystals cleave on the (001) basal plane as expected. The a and b dimensions were equal, with the atoms arranged in a cubic pattern. Our calculations indicate a symmetric cut between Sb planes to be the most favorable cleavage plane and U atoms to be responsible for most of the DOS measured by STM. Some strange features observed in the STM will be discussed in conjunction with ab initio calculations. The purpose of this work is to demonstrate the power of scanning tunneling microscopy (STM) techniques combined with a theoretical underpinning to determine the surface atomic structure and properties of actinide materials, such as the quasi 2-dimensional uranium dipnictide USb{sub 2} single crystal, thereby contributing to the understanding of their surface structural and electronic properties. The members of this interesting UX{sub 2} (X=P, As, Sb, Bi) series of compounds display dual localized and itinerant 5f electron behavior within the same compound due to the hybridization of the 5f orbitals with the conduction band. With the exception of UO{sub 2}, which has to be studied at elevated temperature to generate enough carriers for STM imaging, STM techniques have not been applied successfully to the characterization of the surface atomic structure of any other single crystal actinide compound, to the best of our knowledge. However, STM has been used to a limited extent for the study of some cerium compounds. STM probes electronic properties at the atomic level and can directly provide information about the local density of filled and empty states (LDOS) states simultaneously. A STM topograph provides the local atomic arrangement and spacing of the atoms on the surface, local defect structures (e.g. steps, vacancies, and kink sites) and the presence of contaminants

  9. 3D Micro-topography of Transferred Laboratory and Natural Ice Crystal Surfaces Imaged by Cryo and Environmental Scanning Electron Microscopy

    Science.gov (United States)

    Magee, N. B.; Boaggio, K.; Bancroft, L.; Bandamede, M.

    2015-12-01

    Recent work has highlighted micro-scale roughness on the surfaces of ice crystals grown and imaged in-situ within the chambers of environmental scanning electron microscopes (ESEM). These observations appear to align with theoretical and satellite observations that suggest a prevalence of rough ice in cirrus clouds. However, the atmospheric application of the lab observations are indeterminate because the observations have been based only on crystals grown on substrates and in pure-water vapor environments. In this work, we present details and results from the development of a transfer technique which allows natural and lab-grown ice and snow crystals to be captured, preserved, and transferred into the ESEM for 3D imaging. Ice crystals were gathered from 1) natural snow, 2) a balloon-borne cirrus particle capture device, and 3) lab-grown ice crystals from a diffusion chamber. Ice crystals were captured in a pre-conditioned small-volume (~1 cm3) cryo-containment cell. The cell was then sealed closed and transferred to a specially-designed cryogenic dewer (filled with liquid nitrogen or crushed dry ice) for transport to a new Hitachi Field Emission, Variable Pressure SEM (SU-5000). The cryo-cell was then removed from the dewer and quickly placed onto the pre-conditioned cryo transfer stage attached to the ESEM (Quorum 3010T). Quantitative 3D topographical digital elevation models of ice surfaces are reported from SEM for the first time, including a variety of objective measures of statistical surface roughness. The surfaces of the transported crystals clearly exhibit signatures of mesoscopic roughening that are similar to examples of roughness seen in ESEM-grown crystals. For most transported crystals, the habits and crystal edges are more intricate that those observed for ice grown directly on substrates within the ESEM chamber. Portions of some crystals do appear smooth even at magnification greater than 1000x, a rare observation in our ESEM-grown crystals. The

  10. Investigation on crystalline perfection, mechanical, piezoelectric and ferroelectric properties of L-tartaric acid single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Murugan, G. Senthil, E-mail: nanosen@gmail.com; Ramasamy, P., E-mail: nanosen@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Tamilnadu - 603110 (India)

    2014-04-24

    Polar organic nonlinear optical material, L-tartaric acid single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study indicates that the grown crystal crystallized in monoclinic system with space group P2{sub 1}. Crystalline perfection of the crystal has been evaluated by high resolution X-ray diffraction technique and it reveals that the crystal quality is good and free from structural grain boundaries. Mechanical stability of the crystal has been analyzed by Vickers microhardness measurement and it exhibits reverse indentation size effect. Piezoelectric d{sub 33} co-efficient for the crystal has been examined and its value is 47 pC/N. The ferroelectric behaviour of the crystal was analyzed by polarization-electric field hysteresis loop measurement.

  11. Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates.

    Science.gov (United States)

    Chadwick, F Mark; McKay, Alasdair I; Martinez-Martinez, Antonio J; Rees, Nicholas H; Krämer, Tobias; Macgregor, Stuart A; Weller, Andrew S

    2017-08-01

    Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(η 2 η 2 -NBA)][BAr F 4 ] (NBA = norbornane; Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(alkene) x ][BAr F 4 ] are formed. The ethene ( x = 2) complex, [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(ethene) 2 ][BAr F 4 ]-Oct , has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy. Rapid, low temperature recrystallization using solution methods results in a different crystalline modification, [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(ethene) 2 ][BAr F 4 ]-Hex , that has a hexagonal microporous structure ( P 6 3 22). The propene complex ( x = 1) [Rh(Cy 2 PCH 2 CH 2 PCy 2 )(propene)][BAr F 4 ] is characterized as having a π-bound alkene with a supporting γ-agostic Rh···H 3 C interaction at low temperature by single-crystal X-ray diffraction, variable temperature solution and solid-state NMR spectroscopy, as well as periodic density functional theory (DFT) calculations. A fluxional process occurs in both the solid-state and solution that is proposed to proceed via a tautomeric allyl-hydride. Gas/solid catalytic isomerization of d 3 -propene, H 2 C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111

  12. Snow and Ice Particle Sizes and Mass Concentrations at Altitudes Up to 9 km (30,000 ft)

    National Research Council Canada - National Science Library

    Jeck, Richard

    1998-01-01

    About 7600 nautical miles (nm) (14,000 km) of select ice particle measurements over the United States have been compiled into a single, computerized database for use in characterizing ice crystal and snowflake...

  13. Structural and optical properties of Cd2+ ion on the growth of sulphamic acid single crystals

    Science.gov (United States)

    Rajyalakshmi, S.; Rao, Valluru Srinivasa; Reddy, P. V. S. S. S. N.; Krishna, V. Y. Rama; Samatha, K.; Rao, K. Ramachandra

    2016-05-01

    Transparent single crystals of Cadmium doped Sulphamic acid (SA) was grown by Conventional slow evaporation solution technique (SEST) which had the size of 13 × 8 × 7 mm3. The grown single crystals have been characterized using single crystal X-ray diffraction UV-visible Spectral studies and Second harmonic generation (SHG) efficiency and the results were discussed. The lattice parameters of the grown Cd2+ ion doped SA crystal are confirmed by single crystal X-ray diffraction and belong to orthorhombic system. Optical transmittance of the crystal was recorded using UV-vis NIR spectrophotometer with its lower cut off wavelength around 259nm. SHG measurements indicate that the SHG efficiency of the grown Cd2+ ion doped SA crystal at a fundamental wavelength of 1064 nm is approximately equal to KDP.

  14. Cryogenic Fluid Transfer Components Using Single Crystal Piezoelectric Actuators, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid transfer components using single crystal piezoelectric actuators are proposed to enable low thermal mass, minimal heat leak, low power consumption...

  15. Cryogenic Fluid Transfer Components Using Single Crystal Piezoelectric Actuators, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid transfer components using single crystal piezoelectric actuators are proposed to enable low thermal mass, minimal heat leak, low power consumption...

  16. Advanced Electroactive Single Crystal and Polymer Actuator Concepts for Passive Optics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes large stroke and high precision piezoelectric single crystal and electroactive polymer actuator concepts?HYBrid Actuation System (HYBAS)...

  17. Cryogenic Clamp-on Ultrasonic Flowmeters using Single Crystal Piezoelectric Transducers, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Clamp-on ultrasound cryogenic flowmeters using single crystal piezoelectric transducers are proposed to enable reliable, accurate cryogenic instrumentation needs in...

  18. Ion beam synthesis of buried single crystal erbium silicide

    International Nuclear Information System (INIS)

    Golanski, A.; Feenstra, R.; Galloway, M.D.; Park, J.L.; Pennycook, S.J.; Harmon, H.E.; White, C.W.

    1990-01-01

    High doses (10 16 --10 17 /cm 2 ) of 170 keV Er + were implanted into single-crystal left-angle 111 right-angle Si at implantation temperatures between 350 degree C and 520 degree C. Annealing at 800 degree C in vacuum following the implant, the growth and coalescence of ErSi 2 precipitates leads to a buried single crystalline ErSi 2 layer. This has been studied using Rutherford backscattering/channeling, X-ray diffraction, cross-sectional TEM and resistance versus temperature measurements. Samples implanted at 520 degree C using an Er dose of 7 x 10 16 /cm 2 and thermally annealed were subsequently used as seeds for the mesoepitaxial growth of the buried layer during a second implantation and annealing process. Growth occurs meso-epitaxially along both interfaces through beam induced, defect mediated mobility of Er atoms. The crystalline quality of the ErSi 2 layer strongly depends on the temperature during the second implantation. 12 refs., 4 figs

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

    Science.gov (United States)

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

    2014-10-06

    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.

  20. Mixed-Phase Ice Crystal and Droplet Characterization and Thermometry Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This effort proposes to design, build, and demonstrate a new instrument for icing research and flight safety capable of discriminating liquid water from ice while...

  1. Mixed-Phase Ice Crystal and Droplet Characterization and Thermometry, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This effort proposes to design, build, and demonstrate a new instrument for icing research and flight safety capable of discriminating liquid water from ice while...

  2. Crystal Structure and Physical Properties of U3T3Sn4 (T = Ni, Cu) Single-Crystals

    OpenAIRE

    Shlyk, L.; Estrela, P.; Waerenborgh, J. C.; De Long, L. E.; de Visser, A.; Rojas, D. P.; Gandra, F.; Almeida, M.

    2000-01-01

    Heat capacity experiments, crystal structure determination and transmission electron microscopy have been carried out on U3Cu3Sn4 single-crystals. U3Cu3Sn4 was confirmed to be a heavy-fermion antiferromagnet (TN=13(1) K) with a low temperature electronic heat capacity coefficient gamma=390 mJ/molUK2. Low temperature heat capacity experiments on a U3Ni3Sn4 single-crystal indicate that below 0.4 K there is a crossover between the previously observed non-Fermi liquid behavior and a Fermi liquid ...

  3. Diffuse scattering in Ih ice

    International Nuclear Information System (INIS)

    Wehinger, Björn; Krisch, Michael; Bosak, Alexeï; Chernyshov, Dmitry; Bulat, Sergey; Ezhov, Victor

    2014-01-01

    Single crystals of ice Ih, extracted from the subglacial Lake Vostok accretion ice layer (3621 m depth) were investigated by means of diffuse x-ray scattering and inelastic x-ray scattering. The diffuse scattering was identified as mainly inelastic and rationalized in the frame of ab initio calculations for the ordered ice XI approximant. Together with Monte-Carlo modelling, our data allowed reconsidering previously available neutron diffuse scattering data of heavy ice as the sum of thermal diffuse scattering and static disorder contribution. (paper)

  4. Synthesis and Single Crystal X-Ray Crystallographic Analysis of 2 ...

    African Journals Online (AJOL)

    dihydropyrimidin-1-ium) tetrachlorocobaltate(II) [H2pymo]2[CoCl4]. The compound was re-crystallized in diethyl ether to obtain a suitable single crystal for X-ray diffraction analysis which revealed a molecule crystallizes in the orthorhombic ...

  5. D.C. electrical conductivity measurements on ADP single crystals ...

    Indian Academy of Sciences (India)

    Unknown

    beaker (corning glass vessel) and allowed to equilibrate at the desired temperature. The crystals were grown in unstirred condition. The temperature and volume were kept constant, respectively at 30°C and 20 ml in all the crystal growth experiments. Small crystals appeared in the beginning due to slow evaporation and ...

  6. Thiourea-doped ammonium dihydrogen phosphate: A single crystal ...

    Indian Academy of Sciences (India)

    Thiourea-doped ammonium dihydrogen phosphate (TADP) exhibits nonlinear optical property and the second harmonic generation efficiency of these crystals is three times that of pure ammonium dihydrogen phosphate (ADP) crystal. In this context, the study of structural distortion in the thiourea-doped ADP crystal is ...

  7. Single-crystal elastic constants of natural ettringite

    KAUST Repository

    Speziale, Sergio

    2008-07-01

    The single-crystal elastic constants of natural ettringite were determined by Brillouin spectroscopy at ambient conditions. The six non-zero elastic constants of this trigonal mineral are: C11 = 35.1 ± 0.1 GPa, C12 = 21.9 ±0.1 GPa, C13 = 20.0 ± 0.5 GPa, C14 = 0.6 ± 0.2 GPa, C33 = 55 ± 1 GPa, C44 = 11.0 ± 0.2 GPa. The Hill average of the aggregate bulk, shear modulus and the polycrystal Young\\'s modulus and Poisson\\'s ratio are 27.3 ± 0.9 GPa, 9.5 ± 0.8 GPa, 25 ± 2 GPa and 0.34 ± 0.02 respectively. The longitudinal and shear elastic anisotropy are C33/C11 = 0.64 ± 0.01 and C66/C44 =0.60 ± 0.01. The elastic anisotropy in ettringite is connected to its crystallographic structure. Stiff chains of [Al(OH)6]3- octahedra alternating with triplets of Ca2+ in eight-fold coordination run parallel to the c-axis leading to higher stiffness along this direction. The determination of the elastic stiffness tensor can help in the prediction of the early age properties of cement paste when ettringite crystals precipitate and in the modeling of both internal and external sulfate attack when secondary ettringite formation leads to expansion of concrete. © 2008 Elsevier Ltd. All rights reserved.

  8. Synthesis and ultrastructure of plate-like apatite single crystals as a model for tooth enamel

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Zhi, E-mail: zhuang@meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Yoshimura, Hideyuki, E-mail: hyoshi@isc.meiji.ac.jp [Department of Physics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Aizawa, Mamoru, E-mail: mamorua@isc.meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan)

    2013-07-01

    Hydroxyapatite (HAp) is an inorganic constituent compound of human bones and teeth, with superior biocompatibility and bioactivity characteristics. Its crystal structure is hexagonal, characterized by a(b)- and c-planes. In vertebrate long bones, HAp crystals have a c-axis orientation, while in tooth enamel, they have an a(b)-axis orientation. Many methods can be used to synthesize c-axis oriented HAp single crystals; however, to the best of our knowledge, there have been no reports on a synthesis method for a(b)-axis oriented HAp single crystals. In this study, we successfully synthesized plate-like HAp crystals at the air–liquid interface of a starting solution via an enzyme reaction of urea with urease. Crystal phase analysis and ultrastructure observations were carried out, and the results indicated that the particles were single crystals, with almost the same a(b)-axis orientation as tooth enamel. It is hoped that by utilizing their unique surface charge and atomic arrangement, the resulting particles can be used as a high-performance biomaterial, capable of adsorbing bio-related substances and a model for tooth enamel. - Highlights: ► Synthesis of plate-like hydroxyapatite crystals at air–liquid interface ► Ultrastructural analysis of plate-like hydroxyapatite crystals ► Plate-like hydroxyapatite single crystals with a high a(b)-axis orientation ► Plate-like hydroxyapatite single crystals as a model for tooth enamel.

  9. Seed crystal in growth of KDP single crystal for optical harmonic generation

    International Nuclear Information System (INIS)

    Shimomura, Osamu

    1985-01-01

    As for the crystal growth of KDP for optical harmonic generation, the employment of (101) seed crystal plate could reduce crystal growth period in comparison with the employment of conventional (001) seed crystal plate except the case of low phase matching angle. This paper describes seed crystal in the case of types I and II of phase matching, evaluation of minimum crystal volume to cut necessary volume crystal plate for optical harmonic generation in the case of types I and II for (001) and (101) crystal plates, results and discussion of numerical analysis of KDP crystal growth for the above-mentioned cases and experimental results of actual KDP crystal growth. It was clarified from these examinations that the use of a (101) crystal plate as a seed showed faster crystal growth regardless of theta m, a phase matching angle. It was also shown that the minimum crystal volume to cut the necessary volume crystal for optical harmonic generation became less by employing a (101) crystal plate than employing a (001) crystal in the case of high phase matching angle, namely theta m > 23.7 0 for type I and theta m > 11.6 0 for type II. Example calculations showed that 54.4 % of crystal growth period for type I and 33.8 % of that for type II was needed for the (101) seed crystal plate in comparison with the case of the (001) seed crystal plate. It was speculated that this conclusion might be applicable also for DKDP or ADP crystals growth. (Takagi, S.)

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

    Science.gov (United States)

    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.

  11. Crystal structure of La2Mo2O9 single crystals doped with bismuth

    International Nuclear Information System (INIS)

    Alekseeva, O. A.; Verin, I. A.; Sorokina, N. I.; Krasil'nikova, A. E.; Voronkova, V. I.

    2010-01-01

    Precision X-ray diffraction studies of La 2-x Bi x Mo 2 O 9 (x = 0.04, 0.06, and 0.18) single crystals are performed. It is found that in the compounds doped with bismuth, analogously with the structure of the metastable β ms phase of pure La 2 Mo 2 O 9 (LM), the La, Mo1, and O1 atoms deviate from the threefold axis on which they are located in the high-temperature β phase. It is shown that bismuth atoms substitute for part of lanthanum atoms and occupy a position at the threefold axis in the neighborhood of the split lanthanum position. The implantation of bismuth atoms in the LM structure results in the return of a part of the molybdenum atoms to the position at the threefold axis. The occupancy of this position is equal to the occupancy of the bismuth atomic position.

  12. SINGLE-CRYSTAL SAPPHIRE OPTICAL FIBER SENSOR INSTRUMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    A. Wang; G. Pickrell; R. May

    2002-09-10

    Accurate measurement of temperature is essential for the safe and efficient operation and control of a wide range of industrial processes. Appropriate techniques and instrumentation are needed depending on the temperature measurement requirements in different industrial processes and working environments. Harsh environments are common in many industrial applications. These harsh environments may involve extreme physical conditions, such as high-temperature, high-pressure, corrosive agents, toxicity, strong electromagnetic interference, and high-energy radiation exposure. Due to these severe environmental conditions, conventional temperature sensors are often difficult to apply. This situation has opened a new but challenging opportunity for the sensor society to provide robust, high-performance, and cost-effective temperature sensors capable of operating in those harsh environments. The focus of this research program has been to develop a temperature measurement system for temperature measurements in the primary and secondary stages of slagging gasifiers. For this application the temperature measurement system must be able to withstand the extremely harsh environment posed by the high temperatures and corrosive agents present in these systems. Real-time, accurate and reliable monitoring of temperature for the coal gasification process is important to realize the full economic potential of these gasification systems. Long life and stability of operation in the high temperature environment is essential for the temperature measurement system to ensure the continuous running of the coal gasification system over the long term. In this high temperature and chemically corrosive environment, rather limited high temperature measurement techniques such as high temperature thermocouples and optical/acoustic pyrometers are available, each with their own limitations. In this research program, five different temperature sensing schemes based on the single crystal sapphire

  13. SINGLE-CRYSTAL SAPPHIRE OPTICAL FIBER SENSOR INSTRUMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    A. Wang; G. Pickrell; R. May

    2002-10-18

    Accurate measurement of temperature is essential for the safe and efficient operation and control of a wide range of industrial processes. Appropriate techniques and instrumentation are needed depending on the temperature measurement requirements in different industrial processes and working environments. Harsh environments are common in many industrial applications. These harsh environments may involve extreme physical conditions, such as high-temperature, high-pressure, corrosive agents, toxicity, strong electromagnetic interference, and high-energy radiation exposure. Due to these severe environmental conditions, conventional temperature sensors are often difficult to apply. This situation has opened a new but challenging opportunity for the sensor society to provide robust, high-performance, and cost-effective temperature sensors capable of operating in those harsh environments. The focus of this research program has been to develop a temperature measurement system for temperature measurements in the primary and secondary stages of slagging gasifiers. For this application the temperature measurement system must be able to withstand the extremely harsh environment posed by the high temperatures and corrosive agents present in these systems. Real-time, accurate and reliable monitoring of temperature for the coal gasification process is important to realize the full economic potential of these gasification systems. Long life and stability of operation in the high temperature environment is essential for the temperature measurement system to ensure the continuous running of the coal gasification system over the long term. In this high temperature and chemically corrosive environment, rather limited high temperature measurement techniques such as high temperature thermocouples and optical/acoustic pyrometers are available, each with their own limitations. In this research program, five different temperature sensing schemes based on the single crystal sapphire

  14. Growth of ultra radiation hard NaBi(WO4)2 single crystal

    International Nuclear Information System (INIS)

    Govind Singh, S.; Tyagi, Mohit; Singh, Awadh K.; Sangeeta

    2009-01-01

    Single crystals of undoped NaBi(WO 4 ) 2 were grown under different condition by Czochralski technique. Radiation hardness of the crystals was studied by irradiating them up to 10''5 and 10''6 Gy dose at a fast rate (2 Gy/sec) using 60 Co as a gamma source. Transmission spectra of the crystal samples were recorded and analyzed. It is found that crystal grown from recrystalized charge shows very good optical quality and excellent radiation hardness. (author)

  15. Growth and characterization of 4-chloro-3-nitrobenzophenone single crystals using vertical Bridgman technique

    Energy Technology Data Exchange (ETDEWEB)

    Aravinth, K., E-mail: anandcgc@gmail.com; Babu, G. Anandha, E-mail: anandcgc@gmail.com; Ramasamy, P., E-mail: anandcgc@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam -603110, Tamilnadu (India)

    2014-04-24

    4-chloro-3-nitrobenzophenone (4C3N) has been grown by using vertical Bridgman technique. The grown crystal was confirmed by Powder X-ray diffraction analysis. The crystalline perfection of the grown crystal was examined by high-resolution X-ray diffraction study. The fluorescence spectra of grown 4C3N single crystals exhibit emission peak at 575 nm. The micro hardness measurements were used to analyze the mechanical property of the grown crystal.

  16. Electrolytic coloration and spectral properties of hydroxyl-doped potassium chloride single crystals

    International Nuclear Information System (INIS)

    Gu Hongen; Wu Yanru

    2011-01-01

    Hydroxyl-doped potassium chloride single crystals are colored electrolytically at various temperatures and voltages using a pointed cathode and a flat anode. Characteristic OH - spectral band is observed in the absorption spectrum of uncolored single crystal. Characteristic O - , OH - , U, V 2 , V 3 , O 2- -V a + , F, R 2 and M spectral bands are observed simultaneously in absorption spectra of colored single crystals. Current-time curve for electrolytic coloration of hydroxyl-doped potassium chloride single crystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained. - Highlights: → Expanded the traditional electrolysis method. → Hydroxyl-doped potassium chloride crystals were colored electrolytically for the first time. → Useful V, F and F-aggregate color centers were produced in colored crystals. → V color centers were produced directly and F and F-aggregate color centers indirectly.

  17. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    Science.gov (United States)

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Effects of Ice-Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray-Tracing Modeling Studies

    Science.gov (United States)

    Sassen, Kenneth; Knight, Nancy C.; Takano, Yoshihide; Heymsfield, Andrew J.

    1994-01-01

    During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22 deg halo-producing cirrus clouds were studied jointly from a ground-based polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow-ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds.

  19. Temperature effect on phase states of quartz nano-crystals in silicon single crystal

    International Nuclear Information System (INIS)

    Kalanov, M.U.; Ibragimova, E.M.; Khamraeva, R.N.; Rustamova, V.M.; Ummatov, Kh.D.

    2006-01-01

    Full text: Oxygen penetrates into the silicon lattice up to the concentration of 2·10 18 cm -3 in the course of growing [1]. By the author's opinion at a low oxygen content the formation of solid solution is possible in the local defect places of the silicon single crystal lattice due to the difference in effective ion radius of oxygen and silicon (r O 0.176 and r Si = 0.065 nm). Upon reaching some critical content (∼ 10 17 cm -3 ), it becomes favorable energetically for oxygen ions to form precipitates (SiO x ) and finally a dielectric layer (stoichiometric inclusions of SiO 2 ). It was shown later that depending on the growth conditions, indeed the quartz crystal inclusions are formed in the silicon single crystals at an amount of 0.3 /0.5 wt. % [2]. However the authors did not study a phase state of the quartz inclusions. Therefore the aim of this work was to study a phase state of the quartz inclusions in silicon crystal at various temperatures. We examined the silicon single crystals grown by Czochralski technique, which were cut in (111) plane in the form of disk of 20 mm diameter and 1.5 thickness and had hole conductivity with the specific resistance ρ o ≅ 1/10 Ohm cm. The dislocation density was N D ≅ 10 1 /10 3 cm -2 , the concentrations of oxygen and boron were N 0 ≅ 2/ 4·10 17 cm -3 and N B ≅ 3*10 15 cm -3 . Structure was analyzed at the set-up DRON-UM1 with high temperature supply UVD-2000 ( CuK = 0.1542 nm) at the temperatures of 300, 1173 and 1573 K measured with platinum-platinum-rhodium thermocouple. The high temperature diffraction spectrum measured at 1573 K in the angle range (2Θ≅10/70 d egree ) there is only one main structure reflection (111) with a high intensity and d/n ≅ 0.3136 nm (2 Θ≅ 28.5 d egree ) from the matrix lattice of silicon single crystal. The weak line at 2 Θ≅ 25.5 d egree ( d/n≅0.3136 nm) is β component of the main reflection (111), and the weak structure peak at 2Θ≅59 d egree ( d/n≅ 0.1568 nm

  20. Piezoelectric properties of Sr3 Ga2 Ge4 O14 single crystals

    Indian Academy of Sciences (India)

    ... determined with resonance and anti-resonance frequencies method by using the impedance analyzer (Agilent 4294A). The results show that the piezoelectric strain constants and electromechanical coupling factors of SGG single crystal are higher than those of LGS single crystals making it a potential substrate material ...

  1. Arc-melting preparation of single crystal LaB6 cathodes

    International Nuclear Information System (INIS)

    Gibson, E.D.; Verhoeven, J.D.

    1977-01-01

    A method for preparing single crystals of lanthanum hexaboride (LaB 6 ) by arc melting a rod of compacted LaB 6 powder is discussed. The method is especially suitable for preparing single-crystal LaB 6 cathodes for use in scanning electron microscopes (SEM) and scanning transmission electron microscopes (STEM). 1 figure, 1 table

  2. Probing the crossover in CO desorption from single crystal to nanoparticulate Ru model catalysts

    DEFF Research Database (Denmark)

    Murphy, Shane; Strebel, Christian Ejersbo; Vendelbo, Søren Bastholm

    2011-01-01

    Crossover in CO desorption behavior and nanoscale structure probed with STM from ruthenium single crystals to PVD and mass-selected nanoparticles.......Crossover in CO desorption behavior and nanoscale structure probed with STM from ruthenium single crystals to PVD and mass-selected nanoparticles....

  3. Growth and study of some gel grown group II single crystals of iodate

    Indian Academy of Sciences (India)

    Unknown

    Page 1 ... Abstract. Single crystals of calcium iodate and barium iodate were grown by simple gel technique by single diffusion method. The optimum conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of the reactants etc. Crystals having ...

  4. DEVELOPMENT OF PROTECTIVE COATINGS FOR SINGLE CRYSTAL TURBINE BLADES

    Energy Technology Data Exchange (ETDEWEB)

    Amarendra K. Rai

    2006-12-04

    Turbine blades in coal derived syngas systems are subject to oxidation and corrosion due to high steam temperature and pressure. Thermal barrier coatings (TBCs) are developed to address these problems. The emphasis is on prime-reliant design and a better coating architecture, having high temperature and corrosion resistance properties for turbine blades. In Phase I, UES Inc. proposed to develop, characterize and optimize a prime reliant TBC system, having smooth and defect-free NiCoCrAlY bond layer and a defect free oxide sublayer, using a filtered arc technology. Phase I work demonstrated the deposition of highly dense, smooth and defect free NiCoCrAlY bond coat on a single crystal CMSX-4 substrate and the deposition of alpha-alumina and yttrium aluminum garnet (YAG) sublayer on top of the bond coat. Isothermal and cyclic oxidation test and pre- and post-characterization of these layers, in Phase I work, (with and without top TBC layer of commercial EB PVD YSZ) revealed significant performance enhancement.

  5. ZnO powders as multi-facet single crystals.

    Science.gov (United States)

    Haque, Francia; Chenot, Stéphane; Viñes, Francesc; Illas, Francesc; Stankic, Slavica; Jupille, Jacques

    2017-04-19

    Oxides are most commonly found in divided forms with properties difficult to control since their crystallographic orientations usually escape analysis. To overcome this an appropriate model system can be provided by ZnO smoke which, obtained by combustion of Zn in air, exhibits nanoparticles with well-defined surface facets. The present work focuses on the interaction of water with ZnO smokes by combining density functional theory based simulations and infrared spectroscopy measurements with applied pressures from 10 -7 to 1 mbar. We demonstrate that the use of ultra-high vacuum allows the analysis of the very first stages of the adsorption, and report on water structures on ZnO(112[combining macron]0) for the first time. We further show that ZnO powders behave as multi-facet single crystals involving (101[combining macron]0), (112[combining macron]0), (0001), and (0001[combining macron]) surfaces with the polar orientations corresponding to 25% of the total surface area. A great deal of cross-agreements between experimental results and simulation provides a simple approach for the examination of hydroxylated/hydrated ZnO smokes and can be widely applied on other ZnO-related powders.

  6. Radiation tolerance of piezoelectric bulk single-crystal aluminum nitride.

    Science.gov (United States)

    Parks, David A; Tittmann, Bernhard R

    2014-07-01

    For practical use in harsh radiation environments, we pose selection criteria for piezoelectric materials for non-destructive evaluation (NDE) and material characterization. Using these criteria, piezoelectric aluminum nitride is shown to be an excellent candidate. The results of tests on an aluminum-nitride- based transducer operating in a nuclear reactor are also presented. We demonstrate the tolerance of single-crystal piezoelectric aluminum nitride after fast and thermal neutron fluences of 1.85 x 10(18) neutron/cm(2) and 5.8 x 10(18) neutron/ cm(2), respectively, and a gamma dose of 26.8 MGy. The radiation hardness of AlN is most evident from the unaltered piezoelectric coefficient d33, which measured 5.5 pC/N after a fast and thermal neutron exposure in a nuclear reactor core for over 120 MWh, in agreement with the published literature value. The results offer potential for improving reactor safety and furthering the understanding of radiation effects on materials by enabling structural health monitoring and NDE in spite of the high levels of radiation and high temperatures, which are known to destroy typical commercial ultrasonic transducers.

  7. Understanding surface structure and chemistry of single crystal lanthanum aluminate

    KAUST Repository

    Pramana, Stevin S.

    2017-03-02

    The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

  8. The CCP14 for single crystal and powder diffraction

    International Nuclear Information System (INIS)

    Cranswick, L.M.D.

    1999-01-01

    Full text: The Collaborative Computation Project Number 14 for Single Crystal and Powder Diffraction (CCP14) is continuing in its objective to provide freely available software and resources for the powder diffraction and crystallographic community. Using the Internet and World Wide Web, we are presently compiling software and web resources, creating tutorials and help files. It also endeavours to encourage and provide resources to assist program authors with developing their software. The CCP14 presently has its web-site at and a mirror at (at CSIRO, Melbourne, Australia). Auto web-mirroring is being implemented to allow users to obtain software and access to resources in a more time effective manner. For people in countries isolated from the Internet, the CCP14 on CD-ROM can be snail mailed on request. This is in the form of a Virtual World Wide Web/Virtual Internet; in the same vein as the existing Crystallographic Nexus CD-ROM. Copyright (1999) Australian X-ray Analytical Association Inc

  9. What is the role of rhenium in single crystal superalloys?

    Directory of Open Access Journals (Sweden)

    Mottura Alessandro

    2014-01-01

    Full Text Available Rhenium plays a critical role in single-crystal superalloys –its addition to first generation alloys improves creep life by a factor of at least two, with further benefits for fatigue performance. Its use in alloys such as PWA1484, CMSX-4 and Rene N5 is now widespread, and many in this community regard Re as the “magic dust”. In this paper, the latest thinking concerning the origins of the “rhenium-effect” is presented. We start by reviewing the hypothesis that rhenium clusters represent barriers to dislocation motion. Recent atom probe tomography experiments have shown that Re may instead form a solid solution with Ni at low concentrations (< 7 at.%. Density functional theory calculations indicate that, in the solid solution, short range ordering of Re may be expected. Finally, Re has been shown to diffuse slowly in the γ-Ni phase. Calculations using a semi-analytical dislocation climb/glide model based upon the work of McLean and Dyson have been used to rationalise the composition-dependence of creep deformation in these materials. All evidence points to two important factors: (i the preferred partitioning of Re to the γ phase, where dislocation activity preferentially occurs during the tertiary creep regime and (ii a retardation effect on dislocation segments at γ/γ′ interfaces, which require non-conservative climb and thus an associated vacancy flux.

  10. Deformation of periodic nanovoid structures in Mg single crystals

    Science.gov (United States)

    Xu, Shuozhi; Su, Yanqing; Zare Chavoshi, Saeed

    2018-01-01

    Large scale molecular dynamics (MD) simulations in Mg single crystal containing periodic cylindrical voids subject to uniaxial tension along the z direction are carried out. Models with different initial void sizes and crystallographic orientations are explored using two interatomic potentials. It is found that (i) a larger initial void always leads to a lower yield stress, in agreement with an analytic prediction; (ii) in the model with x[\\bar{1}100]–y[0001]–z[11\\bar{2}0] orientations, the two potentials predict different types of tension twins and phase transformation; (iii) in the model with x[0001]–y[11\\bar{2}0]–z[\\bar{1}100] orientations, the two potentials identically predict the nucleation of edge dislocations on the prismatic plane, which then glide away from the void, resulting in extrusions at the void surface; in the case of the smallest initial void, these surface extrusions pinch the void into two voids. Besides bringing new physical understanding of the nanovoid structures, our work highlights the variability and uncertainty in MD simulations arising from the interatomic potential, an issue relatively lightly addressed in the literature to date.

  11. Radiation attenuation by single-crystal diamond windows

    Energy Technology Data Exchange (ETDEWEB)

    Guthrie, M.; Pruteanu, C. G.; Donnelly, M. -E.; Molaison, J. J.; dos Santos, A. M.; Loveday, J. S.; Boehler, R.; Tulk, C. A.

    2017-02-01

    As artificial diamond becomes more cost effective it is likely to see increasing use as a window for sample environment equipment used in diffraction experiments. Such windows are particularly useful as they exhibit exceptional mechanical properties in addition to being highly transparent to both X-ray and neutron radiation. A key application is in high-pressure studies, where diamond anvil cells (DACs) are used to access extreme sample conditions. However, despite their utility, an important consideration when using single-crystal diamond windows is their interaction with the incident beam. In particular, the Bragg condition will be satisfied for specific angles and wavelengths, leading to the appearance of diamond Bragg spots on the diffraction detectors but also, unavoidably, to loss of transmitted intensity of the beam that interacts with the sample. This effect can be particularly significant for energy-dispersive measurements, for example, in time-of-flight neutron diffraction work using DACs. This article presents a semi-empirical approach that can be used to correct for this effect, which is a prerequisite for the accurate determination of diffraction intensities.

  12. Buckling of Single-Crystal Silicon Nanolines under Indentation

    Directory of Open Access Journals (Sweden)

    Min K. Kang

    2008-01-01

    Full Text Available Atomic force microscope-(AFM- based indentation tests were performed to examine mechanical properties of parallel single-crystal silicon nanolines (SiNLs of sub-100-nm line width, fabricated by a process combining electron-beam lithography and anisotropic wet etching. The SiNLs have straight and nearly atomically flat sidewalls, and the cross section is almost perfectly rectangular with uniform width and height along the longitudinal direction. The measured load-displacement curves from the indentation tests show an instability with large displacement bursts at a critical load ranging from 480 μN to 700 μN. This phenomenon is attributed to a transition of the buckling mode of the SiNLs under indentation. Using a set of finite element models with postbuckling analyses, we analyze the indentation-induced buckling modes and investigate the effects of tip location, contact friction, and substrate deformation on the critical load of mode transition. The results demonstrate a unique approach for the study of nanomaterials and patterned nanostructures via a combination of experiments and modeling.

  13. Polymorphic transitions in single crystals: A new molecular dynamics method

    Energy Technology Data Exchange (ETDEWEB)

    Parrinello, M.; Rahman, A.

    1981-12-01

    A new Lagrangian formulation is introduced. It can be used to make molecular dynamics (MD) calculations on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamical equations given by this Lagrangian. This new MD technique is well suited to the study of structural transformations in solids under external stress and at finite temperature. As an example of the use of this technique we show how a single crystal of Ni behaves under uniform uniaxial compressive and tensile loads. This work confirms some of the results of static (i.e., zero temperature) calculations reported in the literature. We also show that some results regarding the stress-strain relation obtained by static calculations are invalid at finite temperature. We find that, under compressive loading, our model of Ni shows a bifurcation in its stress-strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. It is suggested that such a transformation could perhaps be observed experimentally under extreme conditions of shock.

  14. Reduction of precursor decay anomaly in single crystal lithium fluoride

    Science.gov (United States)

    Sano, Yukio

    2000-08-01

    The purpose of this study is to reveal that the precursor decay anomaly in single crystal lithium fluoride is reduced by Sano's decay curve [Y. Sano, J. Appl. Phys. 85, 7616 (1999)], which is much smaller in slope than Asay's decay curve [J. R. Asay, G. R. Fowles, G. E. Duvall, M. H. Miles, and R. F. Tinder, J. Appl. Phys. 43, 2132 (1972)]. To this end, strain, particle, velocity, and stress in a precursor and near the leading edge of the follower changing with time along Sano's decay curve are first analyzed quantitatively. The analysis verified the existence of degenerate contraction waves I and II and a subrarefaction wave R', and the decay process [Y. Sano, J. Appl. Phys. 77, 3746 (1995)] caused in sequence by evolving followers C, I, II, R', Rb. Next, inequalities relating decay rates qualitatively to plastic strain rates at the leading edge of the follower, which are derived using the properties of the followers, are incorporated into the analysis. Calculation results showed that the plastic strain rates were reduced by low decay rates. This indicates that the precursor decay anomaly might be greatly reduced by Sano's decay curve.

  15. Analysis of ripple formation in single crystal spot welds

    Energy Technology Data Exchange (ETDEWEB)

    Rappaz, M. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab de Metallurgie Physique; Corrigan, D.; Boatner, L.A. [Oak Ridge National Lab., TN (United States). Solid State Div.

    1997-10-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 {micro}m) and spacing (typically {approximately} 60 {micro}m) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f{sub 0} given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v{sub s}/f{sub 0}, where v{sub s} is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  16. Effect of crystal shape on neutron rocking curves of perfect single crystals designed for ultra-small-angle scattering experiments

    International Nuclear Information System (INIS)

    Freund, A K; Rehm, C

    2014-01-01

    The present study has been conducted in the framework of the channel-cut crystal design for the Kookaburra ultra-small-angle neutron scattering (USANS) instrument to be installed at the OPAL reactor of ANSTO. This facility is based on the classical Bonse-Hart method that uses two multiple-reflection crystal systems. The dynamical theory of diffraction by perfect crystals distinguishes two cases: the Darwin case applying to infinitely thick crystals and the Ewald solution for very small absorption taking into account the reflection from the rear face of a plane-parallel crystal reflecting in Bragg geometry. The former is preferable because it yields narrower rocking curves. To prevent the neutrons to 'see' the rear face, grooves were machined into the backside of perfect Si test crystals for single reflection and filled with neutron absorbing material. These samples were examined at the S18 instrument of the Institut Laue-Langevin. Unexpectedly the crystals with empty slots showed an increase of the rocking curve width. When filling the slots with an absorber the widths decreased, but without reaching that of the Darwin curve. Understanding the results and achieving a successful crystal design call for the development of a theory that permits to describe neutron diffraction from crystals with a structured back face.

  17. Effect of crystal shape on neutron rocking curves of perfect single crystals designed for ultra-small-angle scattering experiments

    Science.gov (United States)

    Freund, A. K.; Rehm, C.

    2014-07-01

    The present study has been conducted in the framework of the channel-cut crystal design for the Kookaburra ultra-small-angle neutron scattering (USANS) instrument to be installed at the OPAL reactor of ANSTO. This facility is based on the classical Bonse-Hart method that uses two multiple-reflection crystal systems. The dynamical theory of diffraction by perfect crystals distinguishes two cases: the Darwin case applying to infinitely thick crystals and the Ewald solution for very small absorption taking into account the reflection from the rear face of a plane-parallel crystal reflecting in Bragg geometry. The former is preferable because it yields narrower rocking curves. To prevent the neutrons to "see" the rear face, grooves were machined into the backside of perfect Si test crystals for single reflection and filled with neutron absorbing material. These samples were examined at the S18 instrument of the Institut Laue-Langevin. Unexpectedly the crystals with empty slots showed an increase of the rocking curve width. When filling the slots with an absorber the widths decreased, but without reaching that of the Darwin curve. Understanding the results and achieving a successful crystal design call for the development of a theory that permits to describe neutron diffraction from crystals with a structured back face.

  18. The evolution of machining-induced surface of single-crystal FCC copper via nanoindentation.

    Science.gov (United States)

    Zhang, Lin; Huang, Hu; Zhao, Hongwei; Ma, Zhichao; Yang, Yihan; Hu, Xiaoli

    2013-05-04

    The physical properties of the machining-induced new surface depend on the performance of the initial defect surface and deformed layer in the subsurface of the bulk material. In this paper, three-dimensional molecular dynamics simulations of nanoindentation are preformed on the single-point diamond turning surface of single-crystal copper comparing with that of pristine single-crystal face-centered cubic copper. The simulation results indicate that the nucleation of dislocations in the nanoindentation test on the machining-induced surface and pristine single-crystal copper is different. The dislocation embryos are gradually developed from the sites of homogeneous random nucleation around the indenter in the pristine single-crystal specimen, while the dislocation embryos derived from the vacancy-related defects are distributed in the damage layer of the subsurface beneath the machining-induced surface. The results show that the hardness of the machining-induced surface is softer than that of pristine single-crystal copper. Then, the nanocutting simulations are performed along different crystal orientations on the same crystal surface. It is shown that the crystal orientation directly influences the dislocation formation and distribution of the machining-induced surface. The crystal orientation of nanocutting is further verified to affect both residual defect generations and their propagation directions which are important in assessing the change of mechanical properties, such as hardness and Young's modulus, after nanocutting process.

  19. Unidirectional growth and characterization of L-arginine monohydrochloride monohydrate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sangeetha, K. [Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu 620 024 (India); Babu, R. Ramesh, E-mail: rampap2k@yahoo.co.in [Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu 620 024 (India); Bhagavannarayana, G. [Materials Characterization Division, National Physical Laboratory, New Delhi 110 012 (India); Ramamurthi, K. [Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu 620 024 (India)

    2011-10-17

    Highlights: {yields} L-Arginine monohydrochloride monohydrate (LAHCl) single crystal was grown successfully by unidirectional solution growth method for the first time. {yields} High crystalline perfection was observed for UDS grown crystal compared to CS grown crystal. {yields} The optical transparency and mechanical stability are high for UDS grown LAHCl single crystal. {yields} Optical birefringence measurement on this material. {yields} The piezoelectric resonance frequencies observation - first time observation on this material. - Abstract: L-Arginine monohydrochloride monohydrate (LAHCl) single crystals were grown successfully by conventional and unidirectional solution growth methods. The crystalline perfection of grown crystals was analyzed by high-resolution X-ray diffraction. The linear optical transmittance, mechanical stability of conventional and unidirectional grown LAHCl single crystals were analyzed and compared along (0 0 1) plane. The refractive index and birefringence of LAHCl single crystals were also measured using He-Ne laser source. From the dielectric studies, piezoelectric resonance frequencies were observed in kHz frequency range for both conventional and unidirectional grown LAHCl single crystals along (0 0 1) plane.

  20. Photoelectron diffraction studies of small adsorbates on single crystal surfaces

    International Nuclear Information System (INIS)

    Pascal, Mathieu

    2002-01-01

    The structural determination of small molecules adsorbed on single crystal surfaces has been investigated using scanned energy mode photoelectron diffraction (PhD). The experimental PhD data were compared to theoretical models using a simulation program based on multiple scattering calculations. Three adsorption systems have been examined on Ag(110), Cu(110) and Cu(111) crystals. The structure of the (2x1)-O adsorption phase on Ag(110) revealed that the O atoms occupied the long bridge site and are almost co-planar with the top layer of Ag atoms. The best agreement between multiple scattering theory and experiment has been obtained for a missing-row (or equivalently an 'added- row') reconstruction. Alternative buckled-row and unreconstructed surface models can be excluded. The adsorption of the benzoate species on Cu(110) has been found to occur via the carboxylate group. The molecules occupy short bridge sites with the O atoms being slightly displaced from atop sites and are aligned along the close-packed azimuth. The tilt of the molecule with respect to the surface and the degree to which the surface is relaxed have also been investigated. The adsorption of methyl on Cu(111) was studied using either azomethane or methyl iodide to prepare the surface layers. At saturation coverage the preferred adsorption site is the fcc threefold hollow site, whereas at half saturation coverage ∼ 30 % of the methyl species occupy the hop threefold hollow sites. Best agreement between theory and experiment corresponded to a methyl group adsorbed with C 3v symmetry. The height of the C above the surface in a pure methyl layer was 1.66 ± 0.02 A, but was reduced to 1.62 ± 0.02 A in the presence of co-adsorbed iodine, suggesting that iodine increases the strength of adsorption. Iodine was also found to occupy the fee threefold hollow sites with a Cu-l bondlength of 2.61 ± 0.02 A. (author)

  1. Correlation between crystal structure and mobility in organic field-effect transistors based on single crystals of tetrathiafulvalene derivatives.

    Science.gov (United States)

    Mas-Torrent, Marta; Hadley, Peter; Bromley, Stefan T; Ribas, Xavi; Tarrés, Judit; Mas, Montserrat; Molins, Elies; Veciana, Jaume; Rovira, Concepció

    2004-07-14

    Recently, it was reported that crystals of the organic material dithiophene-tetrathiafulvalene (DT-TTF) have a high field-effect charge carrier mobility of 1.4 cm(2)/(V x s). These crystals were formed by a simple drop-casting method, making this material interesting to investigate for possible applications in low-cost electronics. Here, organic single-crystal field-effect transistors based on materials related to DT-TTF are presented and a clear correlation between the crystal structure and the electrical characteristics is observed. The observed relationship between the mobilities in the different crystal structures is strongly corroborated by calculations of both the molecular reorganization energies and the maximum intermolecular transfer integrals. The most suitable materials described here exhibit mobilities that are among the highest reported for organic field-effect transistors and that are the highest reported for solution-processed materials.

  2. Growth of niobium single crystals by pulling from a melt on a pedestal. II

    International Nuclear Information System (INIS)

    Naramoto, H.; Kamada, K.

    1975-01-01

    The following improvements were made in growing niobium single crystals by pulling from a melt in a pedestal heated by electron beam bombardment: (1) use of single crystalline seed; (2) rotation of the seed crystal as well as the pedestal; and (3) reduction of the pulling rate down to about 0.15 mm/min. The perfection of these crystals were assessed by taking both projection and section topographs under both the thick crystal case and thin crystal case. In the former case, diffusion of defect-images, which might overlook the grown-in dislocations, was critically examined. As a result of these measurements it was established that the niobium crystals are free from any grown-in dislocations. No propagation of dislocations from the seed to the grown crystal was observed. (Auth.)

  3. Thermal behaviour of strontium tartrate single crystals grown in gel

    Indian Academy of Sciences (India)

    Thermal behaviour of strontium tartrate crystals grown with the aid of sodium metasilicate gel is investigated using thermogravimetry (TG) and differential thermal analysis (DTA). Effect of magnetic field and dopant (Pb)2+ on the crystal stability is also studied using thermal analysis. This study reveals that water molecules are ...

  4. Synthesis, growth, crystal structure, optical and third order nonlinear optical properties of quinolinium derivative single crystal: PNQI

    Science.gov (United States)

    Karthigha, S.; Krishnamoorthi, C.

    2018-03-01

    An organic quinolinium derivative nonlinear optical (NLO) crystal, 1-ethyl-2-[2-(4-nitro-phenyl)-vinyl]-quinolinium iodide (PNQI) was synthesized and successfully grown by slow evaporation solution growth technique. Formation of a crystalline compound was confirmed by single crystal X-ray diffraction. The quinolinium compound PNQI crystallizes in the triclinic crystal system with a centrosymmetric space group of P-1 symmetry. The molecular structure of PNQI was confirmed by 1H NMR and 13C NMR spectral studies. The thermal properties of the crystal have been investigated by thermogravimetric (TG) and differential scanning calorimetry (DSC) studies. The optical characteristics obtained from UV-Vis-NIR spectral data were described and the cut-off wavelength observed at 506 nm. The etching study was performed to analyse the growth features of PNQI single crystal. The third order NLO properties such as nonlinear refractive index (n2), nonlinear absorption coefficient (β) and nonlinear susceptibility (χ (3)) of the crystal were investigated using Z-scan technique at 632.8 nm of Hesbnd Ne laser.

  5. Single-Crystal Sapphire Optical Fiber Sensor Instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Pickrell, Gary [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Scott, Brian [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Wang, Anbo [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Yu, Zhihao [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States)

    2013-12-31

    This report summarizes technical progress on the program “Single-Crystal Sapphire Optical Fiber Sensor Instrumentation,” funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. This project was completed in three phases, each with a separate focus. Phase I of the program, from October 1999 to April 2002, was devoted to development of sensing schema for use in high temperature, harsh environments. Different sensing designs were proposed and tested in the laboratory. Phase II of the program, from April 2002 to April 2009, focused on bringing the sensor technologies, which had already been successfully demonstrated in the laboratory, to a level where the sensors could be deployed in harsh industrial environments and eventually become commercially viable through a series of field tests. Also, a new sensing scheme was developed and tested with numerous advantages over all previous ones in Phase II. Phase III of the program, September 2009 to December 2013, focused on development of the new sensing scheme for field testing in conjunction with materials engineering of the improved sensor packaging lifetimes. In Phase I, three different sensing principles were studied: sapphire air-gap extrinsic Fabry-Perot sensors; intensity-based polarimetric sensors; and broadband polarimetric sensors. Black body radiation tests and corrosion tests were also performed in this phase. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. At the beginning of Phase II, in June 2004, the BPDI sensor was tested at the Wabash River coal gasifier

  6. Compositional Effects on Nickel-Base Superalloy Single Crystal Microstructures

    Science.gov (United States)

    MacKay, Rebecca A.; Gabb, Timothy P.; Garg,Anita; Rogers, Richard B.; Nathal, Michael V.

    2012-01-01

    Fourteen nickel-base superalloy single crystals containing 0 to 5 wt% chromium (Cr), 0 to 11 wt% cobalt (Co), 6 to 12 wt% molybdenum (Mo), 0 to 4 wt% rhenium (Re), and fixed amounts of aluminum (Al) and tantalum (Ta) were examined to determine the effect of bulk composition on basic microstructural parameters, including gamma' solvus, gamma' volume fraction, volume fraction of topologically close-packed (TCP) phases, phase chemistries, and gamma - gamma'. lattice mismatch. Regression models were developed to describe the influence of bulk alloy composition on the microstructural parameters and were compared to predictions by a commercially available software tool that used computational thermodynamics. Co produced the largest change in gamma' solvus over the wide compositional range used in this study, and Mo produced the largest effect on the gamma lattice parameter and the gamma - gamma' lattice mismatch over its compositional range, although Re had a very potent influence on all microstructural parameters investigated. Changing the Cr, Co, Mo, and Re contents in the bulk alloy had a significant impact on their concentrations in the gamma matrix and, to a smaller extent, in the gamma' phase. The gamma phase chemistries exhibited strong temperature dependencies that were influenced by the gamma and gamma' volume fractions. A computational thermodynamic modeling tool significantly underpredicted gamma' solvus temperatures and grossly overpredicted the amount of TCP phase at 982 C. Furthermore, the predictions by the software tool for the gamma - gamma' lattice mismatch were typically of the wrong sign and magnitude, but predictions could be improved if TCP formation was suspended within the software program. However, the statistical regression models provided excellent estimations of the microstructural parameters based on bulk alloy composition, thereby demonstrating their usefulness.

  7. Synthesis and photocatalytic activity of mesoporous – (001) facets TiO{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Yeshuo [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Fei, Xuening, E-mail: xueningfei@126.com [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); School of Science, Tianjin Chengjian University, Tianjin 300384 (China); Zhou, Yongzhu [School of Science, Tianjin Chengjian University, Tianjin 300384 (China)

    2017-05-01

    Highlights: • The (001) facets of TiO{sub 2} single crystals with mesoporous structure. • The (010) and (100) facets of TiO{sub 2} single crystals were covered by the flower – shaped TiO{sub 2} crystals. • This special structure could promote charge separation and provide more active sites, which will lead to a substantial increase in photocatalytic activity. - Abstract: In this work, the mesoporous – (001) facets TiO{sub 2} single crystals have been successfully synthesized through a two-step solvothermal route without any template. Their structure and morphology were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV–vis) diffuse reflectance spectroscopy and energy dispersive X-ray spectrometer (EDX). Based on the different characteristics and atomic arrangements on each facet of anatase TiO{sub 2} single crystals, we synthesized these mesoporous – (001) facets TiO{sub 2} single crystals by controlling the interaction characteristics of hydrofluoric acid (HF) and isopropanol (i-PrOH) on the crystal facets. It can been seen that the (001) facets of these as-synthesized TiO{sub 2} single crystals have a clear mesoporous structure through the SEM images and BET methods. Moreover, the other four facets were covered by the flower – shaped TiO{sub 2} crystals with the generation of the mesoporous – (001) facets. This special and interesting morphology could promote charge separation and provide more active sites, which will lead to a substantial increase in photocatalytic activity. Moreover, it is more intuitive to reflect that the different crystal facets possess the different properties due to their atomic arrangement. Besides, according to the different synthetic routes, we proposed and discussed a plausible synthesis mechanism of these mesoporous – (001) facets TiO{sub 2} single crystals.

  8. Mechanism of the superior mechanical strength of nanometer-sized metal single crystals revealed

    KAUST Repository

    Afify, N. D.

    2013-10-01

    Clear understanding of the superior mechanical strength of nanometer-sized metal single crystals is required to derive advanced mechanical components retaining such superiority. Although high quality studies have been reported on nano-crystalline metals, the superiority of small single crystals has neither been fundamentally explained nor quantified to this date. Here we present a molecular dynamics study of aluminum single crystals in the size range from 4.1 nm to 40.5 nm. We show that the ultimate mechanical strength deteriorates exponentially as the single crystal size increases. The small crystals superiority is explained by their ability to continuously form vacancies and to recover them. © 2013 Published by Elsevier B.V.

  9. Surface relief grating formation on a single crystal of 4-(dimethylamino)azobenzene

    International Nuclear Information System (INIS)

    Nakano, Hideyuki; Tanino, Takahiro; Shirota, Yasuhiko

    2005-01-01

    Surface relief grating (SRG) formation on an organic single crystal by irradiation with two coherent laser beams has been demonstrated by using 4-(dimethylamino)azobenzene (DAAB). It was found that the SRG formation was greatly depending upon both the coordination of the crystal and the polarization of the writing beams. The dependence of the polarization of writing beams on the SRG formation using the single crystal was found to be quite different from that reported for amorphous polymers and photochromic amorphous molecular materials, suggesting that the mechanism of the SRG formation on the organic crystal is somewhat different from that on amorphous materials

  10. A Novel Approach to Determine Strides, Ice Contact, and Swing Phases During Ice Hockey Skating Using a Single Accelerometer.

    Science.gov (United States)

    Stetter, Bernd J; Buckeridge, Erica; von Tscharner, Vinzenz; Nigg, Sandro R; Nigg, Benno M

    2016-02-01

    This study presents a new approach for automated identification of ice hockey skating strides and a method to detect ice contact and swing phases of individual strides by quantifying vibrations in 3D acceleration data during the blade-ice interaction. The strides of a 30-m forward sprinting task, performed by 6 ice hockey players, were evaluated using a 3D accelerometer fixed to a hockey skate. Synchronized plantar pressure data were recorded as reference data. To determine the accuracy of the new method on a range of forward stride patterns for temporal skating events, estimated contact times and stride times for a sequence of 5 consecutive strides was validated. Bland-Altman limits of agreement (95%) between accelerometer and plantar pressure derived data were less than 0.019 s. Mean differences between the 2 capture methods were shown to be less than 1 ms for contact and stride time. These results demonstrate the validity of the novel approach to determine strides, ice contact, and swing phases during ice hockey skating. This technology is accurate, simple, effective, and allows for in-field ice hockey testing.

  11. Single-particle characterization of ice-nucleating particles and ice particles residuals sampled by three different techniques

    Science.gov (United States)

    Kandler, Konrad; Worringen, Annette; Benker, Nathalie; Dirsch, Thomas; Mertes, Stephan; Schenk, Ludwig; Kästner, Udo; Frank, Fabian; Nillius, Björn; Bundke, Ulrich; Rose, Diana; Curtius, Joachim; Kupiszewski, Piotr; Weingartner, Ernest; Vochezer, Paul; Schneider, Johannes; Schmidt, Susan; Weinbruch, Stephan; Ebert, Martin

    2015-04-01

    During January/February 2013, at the High Alpine Research Station Jungfraujoch a measurement campaign was carried out, which was centered on atmospheric ice-nucleating particles (INP) and ice particle residuals (IPR). Three different techniques for separation of INP and IPR from the non-ice-active particles are compared. The Ice Selective Inlet (ISI) and the Ice Counterflow Virtual Impactor (Ice-CVI) sample ice particles from mixed phase clouds and allow for the analysis of the residuals. The combination of the Fast Ice Nucleus Chamber (FINCH) and the Ice Nuclei Pumped Counterflow Virtual Impactor (IN-PCVI) provides ice-activating conditions to aerosol particles and extracts the activated INP for analysis. Collected particles were analyzed by scanning electron microscopy and energy-dispersive X-ray microanalysis to determine size, chemical composition and mixing state. All INP/IPR-separating techniques had considerable abundances (median 20 - 70 %) of instrumental contamination artifacts (ISI: Si-O spheres, probably calibration aerosol; Ice-CVI: Al-O particles; FINCH+IN-PCVI: steel particles). Also, potential sampling artifacts (e.g., pure soluble material) occurred with a median abundance of metal oxides were the major INP/IPR particle types separated by all three techniques. Soot was a minor contributor. Lead was detected in less than 10 % of the particles, of which the majority were internal mixtures with other particle types. Sea-salt and sulfates were identified by all three methods as INP/IPR. Most samples showed a maximum of the INP/IPR size distribution at 400 nm geometric diameter. In a few cases, a second super-micron maximum was identified. Soot/carbonaceous material and metal oxides were present mainly in the submicron range. ISI and FINCH yielded silicates and Ca-rich particles mainly with diameters above 1 µm, while the Ice-CVI also separated many submicron IPR. As strictly parallel sampling could not be performed, a part of the discrepancies between

  12. Crystallization behavior of single isotactic poly(methyl methacrylate) chains visualized by atomic force microscopy.

    Science.gov (United States)

    Anzai, Takahiro; Kawauchi, Mariko; Kawauchi, Takehiro; Kumaki, Jiro

    2015-01-08

    We have, for the first time, successfully visualized the crystallization behavior of a single isolated polymer chain at the molecular level by atomic force microscopy (AFM). Previously, we found that isotactic poly(methyl methacrylate) (it-PMMA) formed two-dimensional folded chain crystals composed of double-stranded helices upon compression of its Langmuir monolayer on a water surface, and the molecular images of the crystals deposited on mica were clearly visualized by AFM (Kumaki, J.; et al. J. Am. Chem. Soc. 2005, 127, 5788). In the present study, a high-molecular-weight it-PMMA was diluted in a monolayer of an it-PMMA oligomer which cannot crystallize at the experimental temperature due to its low molecular weight. At a low surface pressure, isolated amorphous chains of the high-molecular-weight it-PMMA solubilized in the oligomer monolayer were observed. On compression, the isolated chains converted to crystals composed of a single chain, typically some small crystallites linked by an amorphous chain like a necklace. Detailed AFM observations of the crystals indicated that the crystalline nuclei preferentially formed at the ends of the chains, and the size of the nuclei was almost independent of the molecular weight of it-PMMA over a wide range. At an extremely slow compression, crystallization was promoted, resulting in crystallization of the whole chain. The crystallization behavior of a single isolated chain provides new insights in understanding the polymer crystallization process.

  13. Single shot ultrafast dynamic ellipsometry (UDE) of laser-driven shocks in single crystal explosives

    Energy Technology Data Exchange (ETDEWEB)

    Whitley, Von H [Los Alamos National Laboratory; Mcgrane, Shawn D [Los Alamos National Laboratory; Moore, David S [Los Alamos National Laboratory; Eakins, Dan E [Los Alamos National Laboratory; Bolme, Cindy A [Los Alamos National Laboratory

    2009-01-01

    We report on the first experiments to measure states in shocked energetic single crystals with dynamic ellipsometry. We demonstrate that these ellipsometric techniques can produce reasonable Hugoniot values using small amounts of crystalline RDX and PETN. Pressures, particle velocities and shock velocities obtained using shocked ellipsometry are comparable to those found using gas-gun flyer plates and molecular dynamics calculations. The adaptation of the technique from uniform thin films of polymers to thick non-perfect crystalline materials was a significant achievement. Correct sample preparation proved to be a crucial component. Through trial and error, we were able to resolve polishing issues, sample quality problems, birefringence effects and mounting difficulties that were not encountered using thin polymer films.

  14. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)

    The grown crystals were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction analysis (XRD), microhardness measurement, Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential thermal analysis (DTA). The results obtained are compared with the previous work.

  15. Crystal growth, optical properties, and laser operation of Yb3+-doped NYW single crystal

    Science.gov (United States)

    Cheng, Y.; Xu, X. D.; Yang, X. B.; Xin, Z.; Cao, D. H.; Xu, J.

    2009-11-01

    Laser crystal Yb3+-doped NaY(WO4)2 (Yb:NYW) with excellent quality has been grown by Czochralski technique. The rocking curves from (400) plane of as-grown Yb:NYW crystal was measured and the full-width value at half-maximum was 19.92″. The effective segregation coefficients were measured by the X-ray fluorescence method. The polarized absorption spectra and the fluorescence spectra of Yb:NYW crystal were measured at room temperature. The fluorescence decay lifetime of Yb3+ ion in NYW crystal has been investigated. The spectroscopic parameters of Yb:NYW crystal are calculated and compared with those of Yb:YAG crystal. A continuous wave output power of 3.06 W at 1031 nm was obtained with a slope efficiency of 42% by use of diode pumping.

  16. A = Rb, K: Single crystal X-ray diffraction studies

    Indian Academy of Sciences (India)

    Unknown

    X-ray diffraction on structural phase transition. 475. Figure 2. Powder X-ray diffraction pattern of KLHS at 298 and 100 K. 3. Structure determination and refinement. 3.1 Structure of RLHS at 293 K. A crystal of size 0⋅7 × 0⋅3 × 0⋅4 mm was mounted on a BRUKER AXS SMART APEX. CCD9 diffractometer with a crystal to ...

  17. The tensile effect on crack formation in single crystal silicon irradiated by intense pulsed ion beam

    Science.gov (United States)

    Liang, Guoying; Shen, Jie; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Yan, Sha; Zhang, Xiaofu; Yu, Xiao; Le, Xiaoyun

    2017-10-01

    Improving antifatigue performance of silicon substrate is very important for the development of semiconductor industry. The cracking behavior of silicon under intense pulsed ion beam irradiation was studied by numerical simulation in order to understand the mechanism of induced surface peeling observed by experimental means. Using molecular dynamics simulation based on Stillinger Weber potential, tensile effect on crack growth and propagation in single crystal silicon was investigated. Simulation results reveal that stress-strain curves of single crystal silicon at a constant strain rate can be divided into three stages, which are not similar to metal stress-strain curves; different tensile load velocities induce difference of single silicon crack formation speed; the layered stress results in crack formation in single crystal silicon. It is concluded that the crack growth and propagation is more sensitive to strain rate, tensile load velocity, stress distribution in single crystal silicon.

  18. Experimental study and numerical simulation of the plastic deformation of zirconium single crystals

    International Nuclear Information System (INIS)

    Lebon, C.

    2011-01-01

    There is only few experimental data in the literature on the zirconium single crystals and no constitutive laws for this single crystal material are provided. The goal of this work is then to create an experimental database like the Critical Resolved Shear Stress (CRSS) for the prismatic slip, the strain-hardening, the activation of the prismatic glide system and the activation volumes. We determine theses parameters from image correlation method. Then, we develop a new multi-scale approach using dislocations dynamics concept and finite element computations. Finally, a first single crystal constitutive law for the zirconium is proposed and a good agreement with the experimental data is obtained. (author) [fr

  19. Highly efficient single-pass sum frequency generation by cascaded nonlinear crystals

    DEFF Research Database (Denmark)

    Hansen, Anders Kragh; Andersen, Peter E.; Jensen, Ole Bjarlin

    2015-01-01

    The cascading of nonlinear crystals has been established as a simple method to greatly increase the conversion efficiency of single-pass second-harmonic generation compared to a single-crystal scheme. Here, we show for the first time that the technique can be extended to sum frequency generation......, despite differences in the phase relations of the involved fields. An unprecedented 5.5 W of continuous-wave diffraction-limited green light is generated from the single-pass sum frequency mixing of two diode lasers in two periodically poled nonlinear crystals (conversion efficiency 50%). The technique...

  20. Synthesis and characterization of nonlinear optical L-arginine semi-oxalate single crystal

    Science.gov (United States)

    Vasudevan, P.; Gokul Raj, S.; Sankar, S.

    2013-04-01

    L-arginine semi-oxalate single crystals have been synthesized by slow evaporation method at room temperature. Single crystal and powder X-ray diffraction analyses has been made to confirm the triclinic structure with non-centrosymmetric space group P1. The presence of functional groups of L-arginine semi-oxalate crystals was identified and confirmed by using the Fourier transform infrared spectroscopy. Molecular structure of the grown crystal was analyzed by 1H NMR and 13C NMR studies. Optical absorption studies carried out in wavelength range from 250 nm to 1200 nm have revealed that the material is completely transparent for the entire wavelength range studied. Thermal characterization using thermogravimetric analysis and differential scanning calorimetry studies show that the crystal is thermally stable up to 146 °C. The presence of second harmonic generation of the grown crystal was tested and its efficiency was determined by using Kurtz and Perry powder technique.

  1. Structure of sodium above 100 GPa by single-crystal x-ray diffraction.

    Science.gov (United States)

    McMahon, M I; Gregoryanz, E; Lundegaard, L F; Loa, I; Guillaume, C; Nelmes, R J; Kleppe, A K; Amboage, M; Wilhelm, H; Jephcoat, A P

    2007-10-30

    At pressures above a megabar (100 GPa), sodium crystallizes in a number of complex crystal structures with unusually low melting temperatures, reaching as low as 300 K at 118 GPa. We have utilized this unique behavior at extreme pressures to grow a single crystal of sodium at 108 GPa, and have investigated the complex crystal structure at this pressure using high-intensity x-rays from the new Diamond synchrotron source, in combination with a pressure cell with wide angular apertures. We confirm that, at 108 GPa, sodium is isostructural with the cI16 phase of lithium, and we have refined the full crystal structure of this phase. The results demonstrate the extension of single-crystal structure refinement beyond 100 GPa and raise the prospect of successfully determining the structures of yet more complex phases reported in sodium and other elements at extreme pressures.

  2. Thermoluminescent properties of undoped and Ce-doped lutetium orthosilicate and yttrium orthosilicate single crystals and single crystalline films scintillators

    Czech Academy of Sciences Publication Activity Database

    Twardak, A.; Bilski, B.; Zorenko, Yu.; Zorenko, T.; Gorbenko, V.; Mandowska, E.; Mandowski, A.; Sidletskiy, O.; Mareš, Jiří A.

    2014-01-01

    Roč. 61, č. 1 (2014), s. 276-281 ISSN 0018-9499 Institutional support: RVO:68378271 Keywords : LSO * single crystalline films * single crystals * thermoluminescence * YSO Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.283, year: 2014

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    Highlights: • The interdiffusion behavior between the NiAlHf coating and the superalloy substrate was influenced by the crystal orientation of the substrate alloy. • The structure of TCP phases formed in SRZ and IDZ was studied. • Studying the effect of orientation crystal of substrate on the formation of SRZ. - Abstract: 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

  4. Study of dopamine reactivity on platinum single crystal electrode surfaces

    International Nuclear Information System (INIS)

    Chumillas, Sara; Figueiredo, Marta C.; Climent, Víctor; Feliu, Juan M.

    2013-01-01

    Dopamine is the biological molecule responsible, among other functions, of the heart beat and blood pressure regulation. Its loss, in the human body, can result in serious diseases such as Parkinson's, schizophrenia or depression. Structurally, this molecule belongs to the group of catecholamines, together with epinephrine (adrenaline) and norepinephrine (noradrenaline). The hydroquinone moiety of the molecule can be easily oxidized to quinone, rendering the electrochemical methods a convenient approach for the development of dopamine biosensors. The reactivity of similar aromatic molecules, such as catechol and hydroquinone, at well-ordered platinum surfaces, has recently been investigated in our group. In this paper, we extend these studies to the structurally related molecule dopamine. The study has been performed in neutral pH, since this is closer to the natural conditions for these molecules in biological media. Cyclic voltammetry and in situ infra-red spectroscopy have been combined to extract information about the behavior of this molecule on well-defined platinum surfaces. Dopamine appears to be electrochemically active and reveals interesting adsorption phenomena at low potentials (0.15–0.25 V vs RHE), sensitive to the single crystal orientation. The adsorption of dopamine on these surfaces is very strong, taking place at much lower potentials than the electron transfer from solution species. Specifically, the voltammetry of Pt(1 1 1) and Pt(1 0 0) in dopamine solutions shows an oxidation peak at potentials close to the onset of hydrogen evolution, which is related to the desorption of hydrogen and the adsorption of dopamine. On the other hand, adsorption on Pt(1 1 0) is irreversible and the surface appears totally blocked. Spectroscopic results indicate that dopamine is adsorbed flat on the surface. At potentials higher than 0.6 V vs RHE the three basal planes show a common redox process. The initial formation of the quinone moiety is followed by a

  5. Gallium arsenide single crystal solar cell structure and method of making

    Science.gov (United States)

    Stirn, Richard J. (Inventor)

    1983-01-01

    A production method and structure for a thin-film GaAs crystal for a solar cell on a single-crystal silicon substrate (10) comprising the steps of growing a single-crystal interlayer (12) of material having a closer match in lattice and thermal expansion with single-crystal GaAs than the single-crystal silicon of the substrate, and epitaxially growing a single-crystal film (14) on the interlayer. The material of the interlayer may be germanium or graded germanium-silicon alloy, with low germanium content at the silicon substrate interface, and high germanium content at the upper surface. The surface of the interface layer (12) is annealed for recrystallization by a pulsed beam of energy (laser or electron) prior to growing the interlayer. The solar cell structure may be grown as a single-crystal n.sup.+ /p shallow homojunction film or as a p/n or n/p junction film. A Ga(Al)AS heteroface film may be grown over the GaAs film.

  6. Preliminary experiments on phase conjugation for flow visualization. [barium titanate single crystals

    Science.gov (United States)

    Weimer, D.; Howes, W. L.

    1984-01-01

    Barium titanate single crystals are discussed in the context of: the procedure for polarizing a crystal; a test for phase conjugation; transients in the production of phase conjugation; real time readout by a separate laser of a hologram induced within the crystal, including conjugation response times to on-off switching of each beam; and a demonstration of a Twyman-Green interferometer utilizing phase conjugation.

  7. Direct fabrication of diffraction grating onto organic single crystals by electron beam lithography

    Science.gov (United States)

    Kawata, Yoshihiro; Aoki, Kazuki; Inada, Yuhi; Yamao, Takeshi; Hotta, Shu

    2018-03-01

    We have directly fabricated a diffraction grating onto platelike single crystals made of an organic semiconducting oligomer by electron beam lithography followed by reactive-ion etching. The decrease in the grating period resulted in photoexcited spectrally narrowed emission peaks related to the first-order diffraction from the crystal edge without outstanding quenching of the crystal. This work is expected to lead to the realization of organic semiconductor lasers.

  8. Experimental realization of highly efficient broadband coupling of single quantum dots to a photonic crystal waveguide

    DEFF Research Database (Denmark)

    Lund-Hansen, Toke; Stobbe, Søren; Julsgaard, Brian

    2008-01-01

    We present time-resolved spontaneous emission measurements of single quantum dots embedded in photonic crystal waveguides. Quantum dots that couple to a photonic crystal waveguide are found to decay up to 27 times faster than uncoupled quantum dots. From these measurements -factors of up to 0.89 ...... taking into account that the light-matter coupling is strongly enhanced due to the significant slow-down of light in the photonic crystal waveguides....

  9. Study on the temperature field of large-sized sapphire single crystal furnace

    Science.gov (United States)

    Zhai, J. P.; Jiang, J. W.; Liu, K. G.; Peng, X. B.; Jian, D. L.; Li, I. L.

    2018-01-01

    In this paper, the temperature field of large-sized (120kg, 200kg and 300kg grade) sapphire single crystal furnace was simulated. By keeping the crucible diameter ratio and the insulation system unchanged, the power consumption, axial and radial temperature gradient, solid-liquid surface shape, stress distribution and melt flow were studied. The simulation results showed that with the increase of the single crystal furnace size, the power consumption increased, the temperature field insulation effect became worse, the growth stress value increased and the stress concentration phenomenon occurred. To solve these problems, the middle and bottom insulation system should be enhanced during designing the large-sized sapphire single crystal furnace. The appropriate radial and axial temperature gradient was favorable to reduce the crystal stress and prevent the occurrence of cracking. Expanding the interface between the seed and crystal was propitious to avoid the stress accumulation phenomenon.

  10. Sea ice local surface topography from single-pass satellite InSAR measurements: a feasibility study

    Directory of Open Access Journals (Sweden)

    W. Dierking

    2017-08-01

    Full Text Available Quantitative parameters characterizing the sea ice surface topography are needed in geophysical investigations such as studies on atmosphere–ice interactions or sea ice mechanics. Recently, the use of space-borne single-pass interferometric synthetic aperture radar (InSAR for retrieving the ice surface topography has attracted notice among geophysicists. In this paper the potential of InSAR measurements is examined for several satellite configurations and radar frequencies, considering statistics of heights and widths of ice ridges as well as possible magnitudes of ice drift. It is shown that, theoretically, surface height variations can be retrieved with relative errors  ≤  0.5 m. In practice, however, the sea ice drift and open water leads may contribute significantly to the measured interferometric phase. Another essential factor is the dependence of the achievable interferometric baseline on the satellite orbit configurations. Possibilities to assess the influence of different factors on the measurement accuracy are demonstrated: signal-to-noise ratio, presence of a snow layer, and the penetration depth into the ice. Practical examples of sea surface height retrievals from bistatic SAR images collected during the TanDEM-X Science Phase are presented.

  11. The Effect of Cracks and Voids on the Dynamic Yield of Rdx Single Crystals

    Science.gov (United States)

    Hooks, D. E.; Ramos, K. J.; Bahr, D. F.

    2007-12-01

    To further understand the deformation mechanisms associated with the dynamic yield point and shock initiation of single crystals of explosives, shock wave loading experiments were performed on oriented crystals of RDX at impact stresses of approximately 1 GPa. Defect content in the crystals and the surface polishing technique were varied and the resulting materials were characterized by optical microscopy. In previous experiments on (100) oriented crystals, multiple loading inflections in the proximity of the dynamic yield point were thought to be due to cracks introduced during experiment assembly. Experiments were performed to try to reproduce these features on other crystal orientations by deliberately inducing cracks and/or choosing crystals with voids. Previously observed inflections in the proximity of the dynamic yield point can be interpreted as discrete yielding events potentially caused by one or more defects that eventually lead to a disperse elastic-plastic transition as observed in randomly oriented powders or perhaps sufficiently defective single crystals. The intent of this effort is to understand the effects of orientation dependent crystal plasticity and large defects, such as surface finish, cracks, and voids, on dynamic deformation separately so that the efficiencies and importance of deformation mechanisms in the initiation process can begin to be delineated for energetic molecular single crystals.

  12. Crystal growth, spectral and laser properties of Nd:LuAG single crystal

    International Nuclear Information System (INIS)

    Xu, X D; Meng, J Q; Cheng, Y; Li, D Z; Cheng, S S; Wu, F; Zhao, Z W; Wang, X D; Xu, J

    2009-01-01

    Nd:LuAG (Nd:Lu 3 Al 5 O 12 ) crystal was grown by the Czochralski method. X-ray powder diffraction experiments show that the Nd:LuAG crystal crystallizes in the cubic with space group Ia3d and has the cell parameter: a = 1.1907 nm, V = 1.6882 nm 3 . The absorption and fluorescence spectra of Nd:LuAG crystal at room temperature were investigated. With a fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Nd:LuAG crystal was demonstrated. The maximum output power at 1064 nm was obtained to be 3.8 W under the incident pump power of 17.3 W, with the optical conversion efficiency 22.0% and the slope efficiency 25.7%

  13. Crystal growth, spectral and laser properties of Nd:LuAG single crystal

    Science.gov (United States)

    Xu, X. D.; Wang, X. D.; Meng, J. Q.; Cheng, Y.; Li, D. Z.; Cheng, S. S.; Wu, F.; Zhao, Z. W.; Xu, J.

    2009-09-01

    Nd:LuAG (Nd:Lu3Al5O12) crystal was grown by the Czochralski method. X-ray powder diffraction experiments show that the Nd:LuAG crystal crystallizes in the cubic with space group Ia3d and has the cell parameter: a = 1.1907 nm, V = 1.6882 nm3. The absorption and fluorescence spectra of Nd:LuAG crystal at room temperature were investigated. With a fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Nd:LuAG crystal was demonstrated. The maximum output power at 1064 nm was obtained to be 3.8 W under the incident pump power of 17.3 W, with the optical conversion efficiency 22.0% and the slope efficiency 25.7%.

  14. Synthesis, growth and characterization of L-Phenylalaninium methanesulfonate nonlinear optical single crystal

    Science.gov (United States)

    Mangaiyarkarasi, K.; Ravichandran, A. T.; Anitha, K.; Manivel, A.

    2018-03-01

    The titled compound, L-Phenylalaninium methanesulfonate (LPA-MS) was synthesized and grown into single crystals by slow solvent evaporation solution growth technique in aqueous solution containing equimolar concentrations of L-phenylalanine and methanesulfonic acid at room temperature. The grown crystals were subjected to single crystal X-ray diffraction studies. It crystallizes in the monoclinic crystal structure with P21 space group and the unit cell parameters are a = 5.312 (10) Å, b = 8.883 (2) Å and c = 25.830 (7) Å. The functional groups of the LPA-MS crystal were confirmed with FT-IR and FT-Raman analysis. The carbon-hydrogen skeleton was confirmed with 1H NMR and 13C NMR analysis. TG-DTG and DSC studies were carried out to determine the thermal stability of the crystals. The optical transparency ranges were studied through UV-vis-spectroscopy and the crystal was found to be transparent in the visible region. The second Harmonic generation (SHG) efficiency of the grown LPA-MS crystal was measured by the Kurtz-Perry powder technique. The dipolar nature of the L-phenylalaninium methanesulfonate and the presence of the intermolecular hydrogen bonding between the molecules are the vital factors responsible for the existence of SHG activity in the crystal.

  15. Piezoelectric properties of Sr3 Ga2 Ge4 single crystals

    Indian Academy of Sciences (India)

    TECS

    Abstract. A new piezoelectric single crystal, Sr3Ga2Ge4O14 (SGG), has been grown successfully by the verti- cal Bridgman method with crucible-sealing technique. SGG crystal up to 2″ in diameter has been obtained. The relative dielectric constants, the piezoelectric strain constants, elastic compliance constants and ...

  16. The twisting of LiNbO3 single crystals grown by the Czochralski method

    International Nuclear Information System (INIS)

    Erdei, S.; Gabrieljan, V.T.

    1989-01-01

    As a result of our experimental work of mainly practical importance we established that for LiNbO 3 single crystals the Mg and Fe dopants promote spirality whereas decreasing of the pulling velocity strongly reduces the propensity of the system to produce spiral-shaped crystals. (author)

  17. Highly Luminescent Solution-Grown Thiophene-Phenylene Co-Oligomer Single Crystals

    NARCIS (Netherlands)

    Kudryashova, Lyudmila G.; Kazantsev, Maxim S.; Postnikov, Valery A.; Bruevich, Vladimir V.; Luponosov, Yuriy N.; Surin, Nikolay M.; Borshchev, Oleg V.; Ponomarenko, Sergei A.; Pshenichnikov, Maxim S.; Paraschuk, Dmitry Yu.

    2016-01-01

    Thiophene-phenylene co-oligomers (TPCOs) are among the most promising materials for organic light emitting devices. Here we report on record high among TPCO single crystals photoluminescence quantum yield reaching 60%. The solution-grown crystals are stronger luminescent than the vapor-grown ones,

  18. Single crystal EPR study of VO(II)-doped cadmium potassium ...

    Indian Academy of Sciences (India)

    A good single crystal of the proper axis is selected and mounted on to the goniometer with a particular axis (e.g. a axis) and is inserted into the EPR cavity for room temperature measurements. A few EPR spectra, at two different orientation of the crystal in the bc plane, recorded at room temperature are shown in figure 1.

  19. Crystal growth and optical properties of indium doped LiCaAlF.sub.6./sub. scintillator single crystals

    Czech Academy of Sciences Publication Activity Database

    Tanaka, Ch.; Yokota, Y.; Kurosawa, S.; Yamaji, A.; Jarý, Vítězslav; Babin, Vladimir; Pejchal, Jan; Ohashi, Y.; Kamada, K.; Nikl, Martin

    2017-01-01

    Roč. 65, Mar (2017), s. 69-72 ISSN 0925- 3467 R&D Projects: GA MŠk(CZ) LH14266 Institutional support: RVO:68378271 Keywords : scintillator * LiCaAlF6 * single crystal * Indium Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.238, year: 2016

  20. Methods for producing single crystal mixed halide perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Kai; Zhao, Yixin

    2017-07-11

    An aspect of the present invention is a method that includes contacting a metal halide and a first alkylammonium halide in a solvent to form a solution and maintaining the solution at a first temperature, resulting in the formation of at least one alkylammonium halide perovskite crystal, where the metal halide includes a first halogen and a metal, the first alkylammonium halide includes the first halogen, the at least one alkylammonium halide perovskite crystal includes the metal and the first halogen, and the first temperature is above about 21.degree. C.

  1. Single Crystal Piezoelectric Deformable Mirrors with High Actuator Density and Large Stroke, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Single crystal piezoelectric deformable mirrors with high actuator density, fine pitch, large stroke and no floating wires will be developed for future NASA science...

  2. Single crystal particles of a mesoporous mixed transition metal oxide with a wormhole structure.

    Science.gov (United States)

    Lee, B; Lu, D; Kondo, J N; Domen, K

    2001-10-21

    A new type of mesoporous mixed transition metal oxide of Nb and Ta (NbTa-TIT-1) has been prepared through a two-step calcination, which consists of single crystal particles with wormhole mesoporous structure.

  3. Polycrystal deformation and single crystal deformation: Dislocation structure and flow stress in copper

    DEFF Research Database (Denmark)

    Huang, X.; Borrego, A.; Pantleon, W.

    2001-01-01

    The relation between the polycrystal deformation and single crystal deformation has been studied for pure polycrystalline copper deformed in tension. The dislocation microstructure has been analyzed for grains of different orientation by transmission electron microscopy (TEM) and three types...

  4. Single Crystal Piezomotor for Large Stroke, High Precision and Cryogenic Actuations, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes a novel single crystal piezomotor for large stroke, high precision, and cryogenic actuations with capability of position set-hold with...

  5. Advanced Electroactive Single Crystal and Polymer Actuators for Passive Optics, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Large stroke and high precision electroactive single crystal and polymer actuators are desired for cryogenic passive optics such as Fabry-Perot Interferometer (FPI)...

  6. Growth and Characteristics of Bulk Single Crystals Grown from Solution on Earth and in Microgravity

    Science.gov (United States)

    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. Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride

    Science.gov (United States)

    2015-08-01

    Aluminum Nitride by GA Gazonas and JW McCauley Weapons and Materials Research Directorate, ARL JJ Guo, KM Reddy, A Hirata, T Fujita, and MW Chen...Sample Size Induced Brittle-to-Ductile Transition of Single-Crystal Aluminum Nitride 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...their microscopic structure. In this study, we report a size induced brittle-to-ductile transition in single-crystal aluminum nitride (AlN). When the

  8. DS-a 3D graphics simulation program for single-crystal diffractometry

    International Nuclear Information System (INIS)

    Zheng Chaode; Min Yao; Tanaka, I.

    1995-01-01

    A brief description of a 3D graphics simulation program for single-crystal diffractometry is presented. The program displays both χ- and κ-type diffractometers with a zero-dimensional (conventional) counter or a two-dimensional area detector and simulates the process of data collection. This program has been designed for assisting actual data collection using these devices, but it could also be useful as a tutorial aid for those starting to learn single-crystal diffractometry. (orig.)

  9. An Investigation of Ni2P Single Crystal Surfaces : Structure, Electronic State and Reactivity

    OpenAIRE

    Yuan, Qiuyi; Ariga, Hiroko; Asakura, Kiyotaka

    2015-01-01

    Ni2P has demonstrated high catalytic activity for hydrodesulfurization and has recently been employed as a catalyst in a variety of other reactions. We have thoroughly reviewed the literature concerning Ni2P single crystal surfaces, with the aim of determining the relationship between surface structure and catalytic properties. Published results to date indicate that Ni2P single crystal surfaces exhibit reconstructed structures, and so the bulk terminated structure may not be stable. We have ...

  10. Single-particle characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques

    Science.gov (United States)

    Worringen, A.; Kandler, K.; Benker, N.; Dirsch, T.; Mertes, S.; Schenk, L.; Kästner, U.; Frank, F.; Nillius, B.; Bundke, U.; Rose, D.; Curtius, J.; Kupiszewski, P.; Weingartner, E.; Vochezer, P.; Schneider, J.; Schmidt, S.; Weinbruch, S.; Ebert, M.

    2015-04-01

    In the present work, three different techniques to separate ice-nucleating particles (INPs) as well as ice particle residuals (IPRs) from non-ice-active particles are compared. The Ice Selective Inlet (ISI) and the Ice Counterflow Virtual Impactor (Ice-CVI) sample ice particles from mixed-phase clouds and allow after evaporation in the instrument for the analysis of the residuals. The Fast Ice Nucleus Chamber (FINCH) coupled with the Ice Nuclei Pumped Counterflow Virtual Impactor (IN-PCVI) provides ice-activating conditions to aerosol particles and extracts the activated particles for analysis. The instruments were run during a joint field campaign which took place in January and February 2013 at the High Alpine Research Station Jungfraujoch (Switzerland). INPs and IPRs were analyzed offline by scanning electron microscopy and energy-dispersive X-ray microanalysis to determine their size, chemical composition and mixing state. Online analysis of the size and chemical composition of INP activated in FINCH was performed by laser ablation mass spectrometry. With all three INP/IPR separation techniques high abundances (median 20-70%) of instrumental contamination artifacts were observed (ISI: Si-O spheres, probably calibration aerosol; Ice-CVI: Al-O particles; FINCH + IN-PCVI: steel particles). After removal of the instrumental contamination particles, silicates, Ca-rich particles, carbonaceous material and metal oxides were the major INP/IPR particle types obtained by all three techniques. In addition, considerable amounts (median abundance mostly a few percent) of soluble material (e.g., sea salt, sulfates) were observed. As these soluble particles are often not expected to act as INP/IPR, we consider them as potential measurement artifacts. Minor types of INP/IPR include soot and Pb-bearing particles. The Pb-bearing particles are mainly present as an internal mixture with other particle types. Most samples showed a maximum of the INP/IPR size distribution at 200

  11. Theoretical study of diaquamalonatozinc(II) single crystal for ...

    Indian Academy of Sciences (India)

    MITESH CHAKRABORTY

    2017-11-28

    Nov 28, 2017 ... [37] D J Newman and B T Ng, Crystal field handbook. (Cambridge University Press, Cambridge, 2000). [38] R Kripal and D Yadav, Solid State Commun. 150, 1621. (2010). [39] M G Mishra and R Kripal, Mol. Phys. 110, 3001 (2012). [40] T H Yeom, S H Choh, M L Du and M S Jang, Phys. Rev. B 53, 6 (1996).

  12. Frustration and single crystal morphology of isotactic poly(2-vinylpyridine)

    NARCIS (Netherlands)

    Okihara, T; Cartier, L; van Ekenstein, GORA; Lotz, B

    The crystal structure of isotactic poly(2-vinylpyridine) (iP2VP) established in 1977 by Puterman et al. is shown to conform to a recently proposed frustrated packing scheme which involves three isochiral three-fold helices packed in a trigonal unit-cell, and observed in a number of polymers and

  13. Growth and characterization of nonlinear optical single crystals: bis ...

    Indian Academy of Sciences (India)

    Administrator

    telecommunication, optical switching, optical frequency conversion, THz generation, electro-optical and inte- grated optics.1,2 In recent times, polar aromatic organic molecules have received great attention for NLO applica- tions. However, NLO properties of several inorganic crystals such as LiNbO3, GaP have been widely ...

  14. Singly-resonant optical parametric oscillator based on KTA crystal

    Indian Academy of Sciences (India)

    Since the first demonstration of OPO by Giordmaine and Miller in 1965 using. LiNbO3 crystal [1] there has been a lot of improvement in this front making it a real tool for different applications. This becomes possible due to the advent of novel non-linear materials having wide transparency range with very low optical losses,.

  15. Thermal behaviour of strontium tartrate single crystals grown in gel

    Indian Academy of Sciences (India)

    Unknown

    lengths of the diffusing ions increase which slow down the vertical displacement of the ions due to the increased resistance of the extra path which the ions have to travel. In effect this is equivalent to reducing the diffusion coeffi- cient of the medium. The observed delay in the time of formation of the crystal in magnetic field is ...

  16. On the growth of calcium tartrate tetrahydrate single crystals

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... The grown crystals were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction analysis (XRD), microhardness measurement, Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential thermal analysis (DTA). The results obtained are compared with the ...

  17. Pyroelectric electron emissions and domain inversion of LiNbO3 single crystals

    International Nuclear Information System (INIS)

    Kim, Dong-Wook; Bourim, E.M.; Jeong, Soo-Hwan; Yoo, In K.

    2004-01-01

    We investigated the electron emissions from a congruent LiNbO 3 single crystal with variation in temperature. When there was a small gap between the crystal and detector (<2 mm), we observed abrupt drops in the emission current and polarization domain inversion of the crystal. The current burst was distributed in tree-like patterns that suggested plasma generation. A sufficient gap and a crystal with a high coercive field appear to be factors that allow reproducible electron emissions from pyroelectric materials

  18. Preparation of HfC single crystals by a floating zone technique

    International Nuclear Information System (INIS)

    Otani, S.; Tanaka, T.

    1981-01-01

    HfC single crystals have been prepared using a floating zone technique by controlling the compositions of the initial molten zone and the feed rod. The obtained crystal rods were 6 cm long and 0.9 cm in diameter. The various parts of the crystal rods have nearly constant compositions (C/Hf(ZR) = 0.956-0.977), and do not contain any free carbon. The impurities in the crystal, evaporation product, and starting material were examined by fluorescence X-ray spectroscopy. The refining effect due to evaporation was discussed. (orig.)

  19. Perovskite single crystals and thin films for optoelectronic devices (Conference Presentation)

    Science.gov (United States)

    Li, Gang; Han, Qifeng; Yang, Yang; Bae, Sang-Hoon; Sun, Pengyu

    2016-09-01

    Hybrid organolead trihalide perovskite (OTP) solar cells have developed as a promising candidate in photovoltaics due to their excellent properties including a direct bandgap, strong absorption coefficient, long carrier lifetime, and high mobility. Most recently, formamidinium (NH2CH=NH2+ or FA) lead iodide (FAPbI3) has attracted significant attention due to several advantages: (1) the larger organic FA cation can replace the MA cation and form a more symmetric crystal structure, (2) the smaller bandgap of FAPbI3 allows for near infrared (NIR) absorption, and (3) FAPbI3 has an elevated decomposition temperature and thus potential to improve stability. Single crystals provide an excellent model system to study the intrinsic electrical and optical properties of these materials due to their high purity, which is particularly important to understand the limits of these materials. In this work, we report the growth of large ( 5 millimeter size) single crystal FAPbI3 using a novel liquid based crystallization method. The single crystal FAPbI3 demonstrated a δ-phase to α-phase transition with a color change from yellow to black when heated to 185°C within approximately two minutes. The crystal structures of the two phases were identified and the PL emission peak of the α-phase FAPbI3 (820 nm) shows clear red-shift compared to the FAPbI3 thin film (805 nm). The FAPbI3 single crystal shows a long carrier lifetime of 484 ns, a high carrier mobility of 4.4 cm2·V-1·s-1, and even more interestingly a conductivity of 1.1 × 10-7(ohm·cm)-1, which is approximately one order of magnitude higher than that of the MAPbI3 single crystal. Finally, high performance photoconductivity type photodetectors were successfully demonstrated using the single crystal FAPbI3.

  20. High Performance Relaxor-Based Ferroelectric Single Crystals for Ultrasonic Transducer Applications

    Directory of Open Access Journals (Sweden)

    Yan Chen

    2014-07-01

    Full Text Available Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3O3-PbTiO3 (PMN-PT have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60% near the morphotropic phase boundary (MPB. Ternary Pb(In1/2Nb1/2O3-Pb(Mg1/3Nb2/3O3-PbTiO3 (PIN-PMN-PT single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed.

  1. Ice Nuclei Production in Volcanic Clouds

    Science.gov (United States)

    Few, A. A.

    2012-12-01

    The paper [Durant et al., 2008] includes a review of research on ice nucleation in explosive volcanic clouds in addition to reporting their own research on laboratory measurements focused on single-particle ice nucleation. Their research as well as the research they reviewed were concerned with the freezing of supercooled water drops (250 to 260 K) by volcanic ash particles acting as ice freezing nuclei. Among their conclusions are: Fine volcanic ash particles are very efficient ice freezing nuclei. Volcanic clouds likely contain fine ash concentrations 104 to 105 times greater than found in meteorological clouds. This overabundance of ice nuclei will produce a cloud with many small ice crystals that will not grow larger as they do in meteorological clouds because the cloud water content is widely distributed among the numerous small ice crystals. The small ice crystals have a small fall velocity, thus volcanic clouds are very stable. The small ice crystals are easily lofted into the stratosphere transporting water and adsorbed trace gasses. In this paper we examine the mechanism for the production of the small ice nuclei and develop a simple model for calculating the size of the ice nuclei based upon the distribution of magma around imbedded bubbles. We also have acquired a volcanic bomb that exhibits bubble remnants on its entire surface. The naturally occurring fragments from the volcanic bomb reveal a size distribution consistent with that predicted by the simple model. Durant, A. J., R. A. Shaw, W. I. Rose, Y. Mi, and G. G. J. Ernst (2008), Ice nucleation and overseeding of ice in volcanic clouds, J. Geophys. Res., 113, D09206, doi:10.1029/2007JD009064.

  2. Reversible Single-Crystal-to-Single-Crystal Structural Transformation in a Mixed-Ligand 2D Layered Metal-Organic Framework: Structural Characterization and Sorption Study

    Directory of Open Access Journals (Sweden)

    Chih-Chieh Wang

    2017-12-01

    Full Text Available A 3D supramolecular network, [Cd(bipy(C4O4(H2O2]·3H2O (1 (bipy = 4,4′-bipyridine and C4O42− = dianion of H2C4O4, constructed by mixed-ligand two-dimensional (2D metal-organic frameworks (MOFs has been reported and structurally determined by the single-crystal X-ray diffraction method and characterized by other physicochemical methods. In 1, the C4O42− and bipy both act as bridging ligands connecting the Cd(II ions to form a 2D layered MOF, which are then extended to a 3D supramolecular network via the mutually parallel and interpenetrating arrangements among the 2D-layered MOFs. Compound 1 shows a two-step dehydration process with weight losses of 11.0% and 7.3%, corresponding to the weight-loss of three guest and two coordinated water molecules, respectively, and exhibits an interesting reversible single-crystal-to-single-crystal (SCSC structural transformation upon de-hydration and re-hydration for guest water molecules. The SCSC structural transformation have been demonstrated and monitored by single-crystal and X-ray powder diffraction, and thermogravimetic analysis studies.

  3. Crystal growth and scintillation properties of Lu substituted CeBr.sub.3./sub. single crystals

    Czech Academy of Sciences Publication Activity Database

    Ito, T.; Yokota, Y.; Kurosawa, S.; Král, Robert; Kamada, K.; Pejchal, Jan; Ohashi, Y.; Yoshikawa, A.

    2016-01-01

    Roč. 452, Oct (2016), s. 65-68 ISSN 0022-0248. [American Conference on Crystal Growth and Epitaxy /20./ (ACCGE) / 17th Biennial Workshop on Organometallic Vapor Phase Epitaxy (OMVPE) / 2nd 2D Electronic Materials Symposium. Big Sky, MT, 02.08.2015-07.08.2015] Institutional support: RVO:68378271 Keywords : radiation * halides * scintillator materials * crystal growth Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.751, year: 2016

  4. Morphological and mechanical characterization of composite calcite/SWCNT-COOH single crystals.

    Science.gov (United States)

    Calvaresi, Matteo; Falini, Giuseppe; Pasquini, Luca; Reggi, Michela; Fermani, Simona; Gazzadi, Gian Carlo; Frabboni, Stefano; Zerbetto, Francesco

    2013-08-07

    A growing number of classes of organic (macro)molecular materials have been trapped into inorganic crystalline hosts, such as calcite single crystals, without significantly disrupting their crystalline lattices. Inclusion of an organic phase plays a key role in enhancing the mechanical properties of the crystals, which are believed to share structural features with biogenic minerals. Here we report the synthesis and mechanical characterization of composite calcite/SWCNT-COOH single crystals. Once entrapped into the crystals SWCNT-COOH appeared both as aggregates of entangled bundles and nanoropes. Their observation was possible only after crystal etching, fracture or FIB (focused ion beam) cross-sectioning. SWCNT-COOHs occupied a small volume fraction and were randomly distributed into the host crystal. They did not strongly affect the crystal morphology. However, although the Young's modulus of composite calcite/SWCNT-COOH single crystals was similar to that of pure calcite their hardness increased by about 20%. Thus, SWCNT-COOHs provide an obstacle against the dislocation-mediated propagation of plastic deformation in the crystalline slip systems, in analogy with the well-known hardness increase in fiber-reinforced composites.

  5. Synthesis and optical characterization of Nickel doped Thiourea Barium Chloride (TBC) single crystals

    Science.gov (United States)

    Mahendra, K.; K, Udayashankar N.

    2018-03-01

    Organometallic Thiourea barium chloride (TBC) single crystals were synthesized using solution evaporation process at room temperature. Synthesized thiourea barium chloride crystals were recrystallized and during the recrystallization process 1M%, 2M% and 5M% of nickel (Ni) was added to the solution and kept for crystallization. The variation of intensity peaks and the shift in the XRD peaks were observed due to the incorporation of nickel in the host matrix. Variations in the absorbance and transmittance spectra of the pure and Ni doped crystals further confirms the presence of nickel in TBC single crystal. The optical bandgap of the pure and nickel doped single crystals were calculated using Touc’s relation. The results show that bandgap decreased with the dopant concentration in the thiourea barium chloride crystal. The optical constants such as extinction coefficient and reflectance were also studied using the absorption spectrum. The FTIR absorption also shows minute shift in the absorption peaks due to the presence of nickel in the host matrix. Photoluminescence spectra of pure and doped crystals were studied.

  6. Results on the Coherent Interaction of High Energy Electrons and Photons in Oriented Single Crystals

    CERN Document Server

    Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.

    2005-01-01

    The CERN-NA-59 experiment examined a wide range of electromagnetic processes for multi-GeV electrons and photons interacting with oriented single crystals. The various types of crystals and their orientations were used for producing photon beams and for converting and measuring their polarisation. The radiation emitted by 178 GeV unpolarised electrons incident on a 1.5 cm thick Si crystal oriented in the Coherent Bremsstrahlung (CB) and the String-of-Strings (SOS) modes was used to obtain multi-GeV linearly polarised photon beams. A new crystal polarimetry technique was established for measuring the linear polarisation of the photon beam. The polarimeter is based on the dependence of the Coherent Pair Production (CPP) cross section in oriented single crystals on the direction of the photon polarisation with respect to the crystal plane. Both a 1 mm thick single crystal of Germanium and a 4 mm thick multi-tile set of synthetic Diamond crystals were used as analyzers of the linear polarisation. A birefringence ...

  7. Growth and characterization of Sm3+ doped cerium oxalate single crystals

    Directory of Open Access Journals (Sweden)

    Minu Mary C

    2016-07-01

    Full Text Available Single crystals of Sm3+ doped cerium oxalate decahydrate were synthesized using single diffusion gel technique and the conditions influencing the size, morphology, nucleation density and quality of the crystals were optimized. Highly transparent single crystals of average size 3 mm × 2 mm × 1 mm with well-defined hexagonal morphology were grown during a time period of two weeks. X-ray powder diffraction analysis revealed that the grown crystals crystallize in the monoclinic system with space group P21/c as identical with the pure cerium oxalate. The various functional groups of the oxalate ligand and the water of crystallization were identified by Fourier transform infrared spectroscopy. The photoluminescence spectrum of the Sm3+ doped cerium oxalate indicated that the Sm3+ ions are optically active in the cerium oxalate matrix. The crystal has a strong and efficient orange red emission with a wavelength peak at 595 nm and hence can be effectively used for optical amplification. Microhardness measurements of the crystal revealed that they belong to the soft material category.

  8. Scanning electron microscope study of polytetrafluoroethylene sliding on aluminum single crystals

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1973-01-01

    Friction experiments were conducted in air with polytetrafluoroethylene (PTFE) sliding on aluminum single crystals. Mechanical scoring of the crystals with (110) and (100) orientations was observed with a single pass of the PTFE slider. No scoring was observed on the (111). The degree of scoring of the crystals is related to the hardness, with the hardest surface (111) showing no damage and the softest surface (110) showing the most severe scoring. Scoring is caused by work-hardened pieces of aluminum which, as a consequence of the adhesion between PTFE and aluminum, were pulled out of the bulk and became embedded in the PTFE polymer.

  9. Effects of microscopic boundary conditions on plastic deformations of small-sized single crystals

    DEFF Research Database (Denmark)

    Kuroda, Mitsutoshi; Tvergaard, Viggo

    2009-01-01

    The finite deformation version of the higher-order gradient crystal plasticity model proposed by the authors is applied to solve plane strain boundary value problems, in order to obtain an understanding of the effect of the higher-order boundary conditions. Numerical solutions are carried out...... for uniaxial plane strain compression of a single crystal block and for uniform pure bending of a single crystal foil. The compressed block has loading surfaces that are penetrable or impenetrable to dislocations. This allows for a study of the two types of higher-order boundaries available, and a significant...

  10. Antiferromagnetic transition in EuCu sub 2 Ge sub 2 single crystals

    CERN Document Server

    Hossain, Z; Yuan, H Q; Sparn, G

    2003-01-01

    Single crystals of EuCu sub 2 Ge sub 2 were grown and characterized using electrical resistivity, magnetization, specific heat and magnetoresistance measurements. The crystals exhibit antiferromagnetic transitions at T sub N sub 1 = 9 K and T sub N sub 2 = 5 K. The T sub N of the flux-grown single crystals reported here are lower than that reported for the polycrystalline sample (T sub N = 13 K) in the literature (Felner and Nowik 1978 J. Phys. Chem. Solids 39 763). The magnetoresistance is positive in the ordered state and negative in the paramagnetic state. The magnetic order could not be suppressed up to a pressure of 25 kbar.

  11. Method for single crystal growth of photovoltaic perovskite material and devices

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jinsong; Dong, Qingfeng

    2017-11-07

    Systems and methods for perovskite single crystal growth include using a low temperature solution process that employs a temperature gradient in a perovskite solution in a container, also including at least one small perovskite single crystal, and a substrate in the solution upon which substrate a perovskite crystal nucleates and grows, in part due to the temperature gradient in the solution and in part due to a temperature gradient in the substrate. For example, a top portion of the substrate external to the solution may be cooled.

  12. Optical power limiting and transmitting properties of cadmium iodide single crystals: Temperature dependence

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish, E-mail: m.miah@griffith.edu.a [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)] [Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)] [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

    2009-09-14

    Optical limiting properties of the single crystals of cadmium iodide are investigated using ns laser pulses. It is found that the transmissions in the crystals increase with increasing temperature. However, they limit the transmissions at high input powers. The limiting power is found to be higher at higher temperature. From the measured transmission data, the photon absorption coefficients are estimated. The temperature dependence of the coefficients shows a decrease in magnitude with increasing temperature. This might be due to the temperature-dependent bandgap shift of the material. The results demonstrate that the cadmium iodide single crystals are promising materials for applications in optical power limiting devices.

  13. Optical power limiting and transmitting properties of cadmium iodide single crystals: Temperature dependence

    International Nuclear Information System (INIS)

    Miah, M. Idrish

    2009-01-01

    Optical limiting properties of the single crystals of cadmium iodide are investigated using ns laser pulses. It is found that the transmissions in the crystals increase with increasing temperature. However, they limit the transmissions at high input powers. The limiting power is found to be higher at higher temperature. From the measured transmission data, the photon absorption coefficients are estimated. The temperature dependence of the coefficients shows a decrease in magnitude with increasing temperature. This might be due to the temperature-dependent bandgap shift of the material. The results demonstrate that the cadmium iodide single crystals are promising materials for applications in optical power limiting devices.

  14. Self-cavity lasing in optically pumped single crystals of p-sexiphenyl

    Energy Technology Data Exchange (ETDEWEB)

    Yanagi, Hisao, E-mail: yanagi@ms.naist.jp; Tamura, Kenji [Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Sasaki, Fumio [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2016-08-15

    Organic single-crystal self-cavities are prepared by solution growth of p-sexiphenyl (p-6P). Based on Fabry-Pérot feedback inside a quasi-lozenge-shaped platelet crystal, edge-emitting laser is obtained under optical pumping. The multimode lasing band appears at the 0-1 or 0-2 vibronic progressions depending on the excitation conditions which affect the self-absorption effect. Cavity-size dependence of amplified spontaneous emission (ASE) is investigated with laser-etched single crystals of p-6P. As the cavity length of square-shaped crystal is reduced from 100 to 10 μm, ASE threshold fluence is decreased probably due to size-dependent light confinement in the crystal cavity.

  15. Growth and characterization of 2-Methylimidazolium D-tartrate single crystal

    Science.gov (United States)

    Srinivasan, T. P.; Anandhi, S.; Gopalakrishnan, R.

    2011-03-01

    Single crystal of 2-Methylimidazolium D-tartrate (2MImdT; C8N2O6H12) has been grown by slow evaporation solution growth technique at room temperature using mixed solvents of ethanol and deionized water. Single crystal X-ray diffraction study confirms that 2-Methylimidazolium D-tartrate belongs to monoclinic crystal system with non-centrosymmetric space group P21. The Fourier transform infrared spectrum of 2-Methylimidazolium D-tartrate reveals the presence of methyl and carboxyl functional groups in the compound. The mechanical properties of 2MImdT crystal were studied. The theoretical factor group analysis predicts 168 optical modes in the title compound. The dielectric behavior of 2MImdT crystals was studied at different frequencies and temperatures. Decomposition and melting point of 2MImdT were found using thermal measurements. SHG behavior of the title compound was demonstrated using Q-switched Nd:YAG laser.

  16. The influence of orientation on the stress rupture properties of nickel-base superalloy single crystals

    Science.gov (United States)

    Mackay, R. A.; Maier, R. D.

    1982-01-01

    Constant load creep rupture tests were performed on MAR-M247 single crystals at 724 MPa and 774 C where the effect of anisotropy is prominent. The initial orientations of the specimens as well as the final orientations of selected crystals after stress rupture testing were determined by the Laue back-reflection X-ray technique. The stress rupture lives of the MAR-M247 single crystals were found to be largely determined by the lattice rotations required to produce intersecting slip, because second-stage creep does not begin until after the onset of intersecting slip. Crystals which required large rotations to become oriented for intersecting slip exhibited the shortest stress rupture lives, whereas crystals requiring little or no rotations exhibited the lowest minimum creep rates, and consequently, the longest stress rupture lives.

  17. Effects of orientation on the rolling and recrystallization behavior of tantalum single crystals

    International Nuclear Information System (INIS)

    Snyder, W.B. Jr.

    1976-12-01

    Some deformed single crystals are more difficult to recrystallize than others. Tantalum single crystals were rolled unidirectionally at room temperature to a thickness reduction of 80 percent. Optical and electron metallography, X-ray line broadening and pole figure analyses, and microhardness testing were used to study the deformed, recovered, and recrystallized structures of these crystals. Crystal stability, reorientation, and deformation banding was interpreted in terms of the Taylor theory of plasticity as applied to pencil glide in body-centered-cubic metals. Experimental results were in partial agreement with the theory. Nucleation of recrystallization was found to occur by the polygonization and growth of dislocation cells originally present in the deformed structure. Impingement of these growing nuclei resulted in a fully recrystallized structure whose orientations were present in the deformed crystal

  18. Anisotropic surface hole-transport property of triphenylamine-derivative single crystal prepared by solution method

    Energy Technology Data Exchange (ETDEWEB)

    Umeda, Minoru, E-mail: mumeda@vos.nagaokaut.ac.jp [Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Katagiri, Mitsuhiko; Shironita, Sayoko [Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Nagayama, Norio [Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Ricoh Company, Ltd., Nishisawada, Numazu, Shizuoka 410-0007 (Japan)

    2016-12-01

    Highlights: • A hole transport molecule was investigated based on its electrochemical redox characteristics. • The solubility and supersolubility curves of the molecule were measured in order to prepare a large crystal. • The polarization micrograph and XRD results revealed that a single crystal was obtained. • An anisotropic surface conduction, in which the long-axis direction exceeds that of the amorphous layer, was observed. • The anisotropic surface conduction was well explained by the molecular stacked structure. - Abstract: This paper reports the anisotropic hole transport at the triphenylamine-derivative single crystal surface prepared by a solution method. Triphenylamine derivatives are commonly used in a hole-transport material for organic photoconductors of laser-beam printers, in which the materials are used as an amorphous form. For developing organic photovoltaics using the photoconductor’s technology, preparation of a single crystal seems to be a specific way by realizing the high mobility of an organic semiconductor. In this study, a single crystal of 4-(2,2-diphenylethenyl)-N,N-bis(4-methylphenyl)-benzenamine (TPA) was prepared and its anisotropic hole-transport property measured. First, the hole-transport property of the TPA was investigated based on its chemical structure and electrochemical redox characteristics. Next, a large-scale single crystal formation at a high rate was developed by employing a solution method based on its solubility and supersolubility curves. The grown TPA was found to be a single crystal based on the polarization micrograph observation and crystallographic analysis. For the TPA single crystal, an anisotropic surface conduction was found, which was well explained by its molecular stack structure. The measured current in the long-axis direction is one order of magnitude greater than that of amorphous TPA.

  19. Single crystal growth and neutron study of Bi-2212 high temperature superconductor

    International Nuclear Information System (INIS)

    Gu, G.D.; Miles, P.A.; Russell, G. J.; Ivanov, A.; Koshizuka, N.; Kennedy, S.J.

    1999-01-01

    Full text: Many physical properties of the cuprate high temperature superconductors appear to defy the conventional (one-electron) theory of metals. The neutron diffraction and inelastic neutron scattering of the high T c single crystals can provides incisive information about collective magnetic excitations which is required to guide the development of new theories incorporating strong electron correlations. For lack of the suitably large single crystals, inelastic neutron scattering measurements have thus far proven possible for only two of the many families of high temperature superconductors, La 2-x Sr x CuO 4 and YBa 2 Cu 3 O x . While the magnetic pronounced differences that have hampered a unified description of the spin dynamics in the cuprates. In particular, a sharp resonant spin excitation dominates the spectrum in the superconducting state of YBa 2 Cu 3 0 x , but is not found in La 2-x Sr x CuO 4 . We have successfully grown large size Bi-2212 single crystals up to 10*5*1.2 mm 3 by floating zone method, and have studied neutron diffraction and neutron scattering in the single crystals. The Neutron diffraction of the single crystals shows that the crystals are high quality. Here we report the discovery of a magnetic resonance peak in the superconducting state of a third high temperature superconductor of Bi-2212 single crystal by modern neutron optics. The discovery provides evidence of the generality of this unusual phenomenon among the cuprates and greatly extends the empirical basis for its theoretical description. The magnetic resonance peak in Bi-2212 single crystals rules out the possibility or chemical parameters peculiar to YBCO superconductor. Rather, it is an intrinsic feature of the copper oxides whose explanation must be in an integral part of any theory of high temperature superconductivity

  20. Seeded growth of boron arsenide single crystals with high thermal conductivity

    Science.gov (United States)

    Tian, Fei; Song, Bai; Lv, Bing; Sun, Jingying; Huyan, Shuyuan; Wu, Qi; Mao, Jun; Ni, Yizhou; Ding, Zhiwei; Huberman, Samuel; Liu, Te-Huan; Chen, Gang; Chen, Shuo; Chu, Ching-Wu; Ren, Zhifeng

    2018-01-01

    Materials with high thermal conductivities are crucial to effectively cooling high-power-density electronic and optoelectronic devices. Recently, zinc-blende boron arsenide (BAs) has been predicted to have a very high thermal conductivity of over 2000 W m-1 K-1 at room temperature by first-principles calculations, rendering it a close competitor for diamond which holds the highest thermal conductivity among bulk materials. Experimental demonstration, however, has proved extremely challenging, especially in the preparation of large high quality single crystals. Although BAs crystals have been previously grown by chemical vapor transport (CVT), the growth process relies on spontaneous nucleation and results in small crystals with multiple grains and various defects. Here, we report a controllable CVT synthesis of large single BAs crystals (400-600 μm) by using carefully selected tiny BAs single crystals as seeds. We have obtained BAs single crystals with a thermal conductivity of 351 ± 21 W m-1 K-1 at room temperature, which is almost twice as conductive as previously reported BAs crystals. Further improvement along this direction is very likely.