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Sample records for single-crystal diamond-based thermal

  1. Thermal diffusion boron doping of single-crystal natural diamond

    NASA Astrophysics Data System (ADS)

    Seo, Jung-Hun; Wu, Henry; Mikael, Solomon; Mi, Hongyi; Blanchard, James P.; Venkataramanan, Giri; Zhou, Weidong; Gong, Shaoqin; Morgan, Dane; Ma, Zhenqiang

    2016-05-01

    With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.

  2. Thermally induced single crystal to single crystal transformation leading to polymorphism

    NASA Astrophysics Data System (ADS)

    Saha, Rajat; Biswas, Susobhan; Dey, Sanjoy Kumar; Sen, Arijit; Roy, Madhusudan; Steele, Ian M.; Dey, Kamalendu; Ghosh, Ashutosh; Kumar, Sanjay

    2014-09-01

    The robust complex [La(1,10-phen)2(NO3)3] (1,10-phen = 1,10-phenanthroline) exhibits thermally induced single crystal to single crystal transformation from one polymorphic phase to another. The complex crystallizes in monoclinic C2/c space group with C2 molecular symmetry at 293 K while at 100 K it shows P21/c space group with C1 molecular symmetry. Supramolecular investigation shows that at 100 K the complex forms 2D achiral sheets whereas at 293 K forms two different homochiral 2D sheets. Low temperature DSC analysis indicates that this structural transformation occurs at 246 K and also this transformation is reversible in nature. We have shown that thermally induced coherent movement of ligands changes the molecular symmetry of the complex and leads to polymorphism. Photoluminescence property of complex has been studied in both solid state and in methanolic solution at room temperature. The effect of the presence low-lying LUMO orbital of π-character in the complex is elucidated by theoretical calculation using DFT method.

  3. Limits to Fourier theory in high thermal conductivity single crystals

    NASA Astrophysics Data System (ADS)

    Wilson, R. B.; Cahill, David G.

    2015-11-01

    We report the results of time-domain thermoreflectance (TDTR) experiments that examine the ability of Fourier theory to predict the thermal response in single crystals when heater dimensions are small. We performed TDTR measurements on Al-coated diamond, 6H-SiC, GaP, Ge, MgO, GaAs, and GaSb single crystals with a wide range of laser spot size radii, 0.7 μm < w 0 < 12 μm. When the laser spot-size is large, w 0 ≈ 12 μm, TDTR data for all crystals are in agreement with predictions of Fourier theory with bulk thermal conductivity values. When the laser spot-size is small, w 0 < 2 μm, there are significant differences between the predictions of Fourier theory and TDTR data for all crystals except MgO.

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

    DOEpatents

    Jantzen, C.M.

    1995-05-09

    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. 12 figs.

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

    DOEpatents

    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.

  6. Thermal and Nonthermal Processes on Single Crystal Transition Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Guo, Xingcai

    This dissertation contains three parts. Part I, "Fundamentals", provides concise description of concepts, detailed accounts of historic studies, and extensive reviews of current activities. Chapter 1 deals with thermal processes (adsorption and desorption), and Chapter 2 with nonthermal processes induced by electrons and by photons. Part II, "Experimental" (Chapter 3), describes the ultrahigh vacuum apparatus, surface science techniques, and procedures for single crystal preparation and gas exposure. Part III, "Results", is a collection of ten selected publications in refereed journals. Each chapter is self-contained. Thermal desorption of CO from Pd(111) (Chapter 4) has been studied by temperature programmed desorption. It is demonstrated that the effective desorption kinetic parameters extracted from desorption spectra are correlated with the adlayer structures and dependent on the sizes of ordered domains--a nonequilibrium effect. Site exchange of CO (Chapter 5) and site retention of O_2 (Chapter 6) on Pt(112) during thermal desorption are observed with isotope labeled adsorption on specific sites--steps or terraces. The adsorption and desorption kinetics of O _2 are compared on Pt(111) and Pt(112) surfaces (Chapter 7). The mechanisms of adsorption and the effect of well-defined defects are elucidated. O_2 adsorbed on Pd(111) is studied with thermal activation (Chapter 8), electron impact (Chapter 9), and photon irradiation (Chapter 10 -12). Various thermal processes are delineated with isotopic mixing experiments. Electron-induced conversion, dissociation, and desorption processes are observed. Cross sections (10^{-17} cm^2 ) and their electron energy dependences (0-500 eV) are measured. A resonance-enhanced desorption of atomic oxygen from Pd(111) is found at ~10 eV. Photon-induced conversion, dissociation, and desorption processes are observed. Cross sections (10^ {-19} cm^2) and photon energy dependence (1.4-5.4 eV) are extracted. Possible mechanisms are

  7. Growth, mechanical, thermal and dielectric properties of pure and doped KHP single crystal

    NASA Astrophysics Data System (ADS)

    M, Lakshmipriya.; Babu, D. Rajan; Vizhi, R. Ezhil

    2015-06-01

    L-Arginine doped potassium hydrogen phthalate and L-Histidine doped potassium hydrogen phthalate single crystals were grown by slow evaporation method at room temperature. The grown crystal crystallizes in orthorhombic system which is confirmed by single crystal XRD analysis. The grown crystals are subjected to thermal, mechanical and dielectric analysis.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  9. Thermal decomposition study of Mo0.6W0.4Se2 single crystals

    NASA Astrophysics Data System (ADS)

    Chaki, Sunil H.; Deshpande, M. P.; Tailor, Jiten P.

    2013-06-01

    The Mo0.6W0.4Se2 single crystals were grown by direct vapour transport (DVT) technique. The thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential thermogravimetric (DTG) analysis were carried out on the as-grown Mo0.6W0.4Se2 single crystals in inert nitrogen atmosphere. All these thermal analysis were done from ambient temperature to 1223 K. The activation energy, enthalpy, entropy and Gibbs free energy of Mo0.6W0.4Se2 single crystals were determined from the thermal curves using Broido, Horowitz-Metzger (H-M), Piloyan-Novikova (P-N) and Coats-Redfern (C-R) relations. The results are reported in this paper.

  10. Thermal Shock Behavior of Single Crystal Oxide Refractive Concentrators for High Temperatures Solar Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Choi, Sung R.; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium-aluminum-garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) have been considered as refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermal mechanical reliability of the oxide components in severe thermal environments during space mission sun/shade transitions is of great concern. In this paper, critical mechanical properties of these oxide crystals are determined by the indentation technique. Thermal shock resistance of the oxides is evaluated using a high power CO, laser under high temperature-high thermal gradients. Thermal stress fracture behavior and failure mechanisms of these oxide materials are investigated under various temperature and heating conditions.

  11. Thermal-Diffusivity Dependence on Temperature of Gadolinium Calcium Oxoborate Single Crystals

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.; Łukasiewicz, T.

    2013-05-01

    Thermal diffusivities of pure and doped gadolinium calcium oxoborate (GdCOB) single crystals were measured as a function of the temperature along optical indicatrix axes X, Y, and Z. Three GdCOB samples were investigated, chemically pure single crystal, the one doped with 4 at% of Nd and the next one doped with 7 at% of Yb. Measurements were carried out for temperature range 40 °C to 300 °C. Determination of the thermal diffusivity based on an analysis of thermal wave propagation in the sample. For a detection of temperature disturbance propagating in the sample the mirage effect was used. Obtained results show that the thermal diffusivity decreases with the increase of sample temperature for all investigated crystals. The GdCOB single crystals reveal a strong anisotropy. The thermal diffusivity along Y direction has the highest value while values obtained in X and Z axes are much lower. Dopants cause decrease in the thermal diffusivity for all investigated directions.

  12. Silver- and Gold-Ordered Structures on Single-Crystal Silicon Surface After Thermal Deposition

    NASA Astrophysics Data System (ADS)

    Karbivskyy, Vladimir; Karbivska, Love; Artemyuk, Viktor

    2016-02-01

    The formation mechanisms of Ag- and Au-ordered structures on single-crystal silicon (Si) (111) and Si (110) surfaces were researched using high-resolution scanning tunneling microscopy method. It was shown that different patterns of self-assembled nanostructures with very precise and regular geometric shapes can be produced by controlling process parameters of thermal metal spraying on the substrate. The surfaces of nanorelieves at each stage of deposition were researched, and the main stages of morphological transformation were fixed.

  13. Work function engineering of SnO single crystal microplates with thermal annealing.

    PubMed

    Doh, Won Hui; Jeong, Wooseok; Lee, Hyunsoo; Park, Jonghyurk; Park, Jeong Young

    2016-08-19

    We synthesized black SnO single-crystal microplates via a sonochemical process and engineered the work function of the SnO microplates using thermal treatments. The as-synthesized SnO microplates have a wide (001) plane, as is clearly evident from TEM images and diffraction patterns. Surface potential measurements on the SnO microplates show that the work function changes as the annealing temperature increases. The TEM and XAS results after thermal treatments imply that the micro-sized SnO(001) single-crystals are stable up to about 400 °C in air, after which the surface starts to become locally oxidized. Consequently, the long-range ordering and lattice parameter of the SnO(001) single crystals started to change to make polycrystalline SnO2 at about 600 °C. These results demonstrate the ability to tune the work function of the microplates and suggest an intriguing way to engineer the electrical properties of nanostructures. PMID:27389518

  14. Work function engineering of SnO single crystal microplates with thermal annealing

    NASA Astrophysics Data System (ADS)

    Doh, Won Hui; Jeong, Wooseok; Lee, Hyunsoo; Park, Jonghyurk; Park, Jeong Young

    2016-08-01

    We synthesized black SnO single-crystal microplates via a sonochemical process and engineered the work function of the SnO microplates using thermal treatments. The as-synthesized SnO microplates have a wide (001) plane, as is clearly evident from TEM images and diffraction patterns. Surface potential measurements on the SnO microplates show that the work function changes as the annealing temperature increases. The TEM and XAS results after thermal treatments imply that the micro-sized SnO(001) single-crystals are stable up to about 400 °C in air, after which the surface starts to become locally oxidized. Consequently, the long-range ordering and lattice parameter of the SnO(001) single crystals started to change to make polycrystalline SnO2 at about 600 °C. These results demonstrate the ability to tune the work function of the microplates and suggest an intriguing way to engineer the electrical properties of nanostructures.

  15. Thermal effects in Yb:YAG single-crystal thin-rod amplifier.

    PubMed

    Kuznetsov, Ivan; Mukhin, Ivan; Vadimova, Olga; Palashov, Oleg; Ueda, Ken-Ichi

    2015-09-01

    This work presents a new design for the laser gain module based on a ytterbium-doped yttrium aluminum garnet (Yb:YAG) single-crystal thin rod. Thermal effects (temperature, phase, and polarization distortion of laser radiation) and small signal gain are investigated both experimentally and theoretically. We then analyzed the influence of thermal effects and amplified spontaneous emission on the power scaling of the laser based on the gain module. A small signal gain as high as 3.3 per pass was experimentally achieved. PMID:26368900

  16. Precision control of thermal transport in cryogenic single-crystal silicon devices

    NASA Astrophysics Data System (ADS)

    Rostem, K.; Chuss, D. T.; Colazo, F. A.; Crowe, E. J.; Denis, K. L.; Lourie, N. P.; Moseley, S. H.; Stevenson, T. R.; Wollack, E. J.

    2014-03-01

    We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path ℓ is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than ℓ, even when the surface is fairly smooth, 5-10 nm rms, and the peak thermal wavelength is 0.6 μm. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order ℓ, the conductance is dominated by ballistic transport and is effectively set by the beam cross-sectional area. We have demonstrated a uniformity of ±8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

  17. Precision control of thermal transport in cryogenic single-crystal silicon devices

    SciTech Connect

    Rostem, K.; Chuss, D. T.; Colazo, F. A.; Crowe, E. J.; Denis, K. L.; Lourie, N. P.; Moseley, S. H.; Stevenson, T. R.; Wollack, E. J.

    2014-03-28

    We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path ℓ is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than ℓ, even when the surface is fairly smooth, 5–10 nm rms, and the peak thermal wavelength is 0.6 μm. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order ℓ, the conductance is dominated by ballistic transport and is effectively set by the beam cross-sectional area. We have demonstrated a uniformity of ±8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

  18. Precision Control of Thermal Transport in Cryogenic Single-Crystal Silicon Devices

    NASA Technical Reports Server (NTRS)

    Rostem, K.; Chuss, D. T.; Colazo, F. A.; Crowe, E. J.; Denis, K. L.; Lourie, N. P.; Moseley, S. H.; Stevenson, T. R.; Wollack, E. J.

    2014-01-01

    We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than, even when the surface is fairly smooth, 510 nm rms, and the peak thermal wavelength is 0.6 microns. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order, the conductance is dominated by ballistic transport and is effectively set by the beam cross-sectional area. We have demonstrated a uniformity of +/-8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

  19. Thermal property characterization of single crystal diamond with varying isotopic composition

    SciTech Connect

    Wei, L.

    1993-01-01

    The mirage-effect/thermal wave technique as a modern technique for thermal property characterization is described. The thermal diffusivity of a material is determined by measuring the time and space varying temperature distribution (thermal wave) in the material generated by an intensity modulated heating laser beam. These thermal waves are detected through the deflection of a probe laser beam due to modulation of gradient of the index of refraction (mirage effect) either in the air above the specimens (the in-air technique) or in the specimen itself (the in-solid technique). Three-dimensional theories, for both in-air and in-solid mirage techniques, are represented. In order to extract the material parameters by comparing the theory with experimental data, an extensive data analysis procedure based on multiparameter-least-squares has been developed. The experimental and data analysis details are discussed. Topics concerns with the quality and reliability of the measurements are addressed. This technique has been successfully applied to the thermal property characterization of single crystal diamond with varying isotope contents. The results showed a 50% enhancement in the thermal conductivity by removal of C[sup 13] content from 1.1% to 0.1% in diamond at room temperature. The technique has also been adapted to function in cryogenic temperatures. The temperature dependence of thermal conductivity in the temperature range 80-378K for natural IIA specimen and 187-375K for isotopically enriched specimen are obtained, the former results agree with previous works and the latter results demonstrate the isotope effect on the thermal conductivity of single crystal diamond consistently in a large temperature range. The physical source of this enhancement in diffusivity due to the isotope effect in diamond is discussed. The discussion is based on the full Callaway's theory with emphasizing the role of N-processes in the phonon scattering mechanism.

  20. Large anisotropic thermal transport properties observed in bulk single crystal black phosphorus

    NASA Astrophysics Data System (ADS)

    Wang, Yue; Xu, Guizhou; Hou, Zhipeng; Yang, Bingchao; Zhang, Xiaoming; Liu, Enke; Xi, Xuekui; Liu, Zhongyuan; Zeng, Zhongming; Wang, Wenhong; Wu, Guangheng

    2016-02-01

    The anisotropy of thermal transport properties for bulk black phosphorus (BP) single crystal, which might be of particular interest in the fabrication of thermoelectric/optoelectronic devices, was investigated by using angular dependent thermal conductivity and Seebeck coefficient measurements at various temperatures. We found that the maximum thermal conductivities in x (zigzag), y (armchair), and z (perpendicular to the puckered layers) directions are 34, 17, and 5 W m-1 K-1, respectively, exhibiting large anisotropy. At temperature around 200 K, a large Seebeck coefficient up to +487 ± 10 μV/K has been obtained in x direction, which is 1.5 times higher than that in z direction. The large anisotropy of thermal transport properties can be understood from the crystal structure and bonding characters of BP. In addition, the energy gap has been obtained from nuclear spin lattice relaxation measurements, which is consistent with the value derived from temperature-dependent Seebeck coefficient measurements.

  1. Low-temperature thermal decomposition of large single crystals of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Majda, Dorota; Korobov, Alexander; Filek, Urszula; Sulikowski, Bogdan; Midgley, Paul; Vowles, David; Klinowski, Jacek

    2008-03-01

    Similarities and differences in the thermal behaviour of deuterated and nondeuterated ammonium perchlorate provide insights into the mechanism of its thermal decomposition. Thermal decomposition of NHClO and NDClO always begins in the bulk of the crystals. In both cases decomposition stops when the degree of conversion is about 30%, giving porous products which undergo the same phase transition as the parent single crystals. Thermal decomposition of the deuterated sample is slower, the volume fraction of pores appears to be lower and the sample has a small quantity of 'snow' on the surface. These effects are best rationalized as caused by proton transfer at the intersections of dislocations in the bulk of the crystals.

  2. Silver- and Gold-Ordered Structures on Single-Crystal Silicon Surface After Thermal Deposition.

    PubMed

    Karbivskyy, Vladimir; Karbivska, Love; Artemyuk, Viktor

    2016-12-01

    The formation mechanisms of Ag- and Au-ordered structures on single-crystal silicon (Si) (111) and Si (110) surfaces were researched using high-resolution scanning tunneling microscopy method. It was shown that different patterns of self-assembled nanostructures with very precise and regular geometric shapes can be produced by controlling process parameters of thermal metal spraying on the substrate. The surfaces of nanorelieves at each stage of deposition were researched, and the main stages of morphological transformation were fixed.Self-ordered hexagonal pyramid-shaped nanostructures were formed at thermal deposition of gold on the Si (111), whereas only monolayer hexagonal formation could be observed on the plane Si (110). Gold monolayer flake nanostructures were obtained under certain technological parameters.Atomically smooth Ag film cannot be obtained on the Si (111) surface by means of thermal spraying at room temperature. The formation of two-dimensional (2D) clusters takes place; heating of these clusters at several hundred degrees Celsius leads to their transformation into atomically smooth covering.The weak interaction between Ag multilayer coatings and substrate was established that allows to clear crystal surface from metal with reproduction of the reconstructed Si (111) 7 × 7 surface by slight warming. The offered method can be used for single-crystal surface protection from destruction. PMID:26847695

  3. Structural, thermal and optical characterization of an organic NLO material—Benzaldehyde thiosemicarbazone monohydrate single crystals

    NASA Astrophysics Data System (ADS)

    Santhakumari, R.; Ramamurthi, K.

    2011-02-01

    Single crystals of the organic NLO material, benzaldehyde thiosemicarbazone (BTSC) monohydrate, were grown by slow evaporation method. Solubility of BTSC monohydrate was determined in ethanol at different temperatures. The grown crystals were characterized by single crystal X-ray diffraction analysis to determine the cell parameters and by FT-IR technique to study the presence of the functional groups. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. UV-vis-NIR spectrum shows excellent transmission in the region of 200-1100 nm. Theoretical calculations were carried out to determine the linear optical constants such as extinction coefficient and refractive index. Further the optical nonlinearities of BTSC have been investigated by Z-scan technique with He-Ne laser radiation of wavelength 632.8 nm. Mechanical properties of the grown crystal were studied using Vickers microhardness tester. Second harmonic generation efficiency of the powdered BTSC monohydrate was tested using Nd:YAG laser and it is found to be ˜5.3 times that of potassium dihydrogen orthophosphate.

  4. Structural, thermal and optical characterization of an organic NLO material--benzaldehyde thiosemicarbazone monohydrate single crystals.

    PubMed

    Santhakumari, R; Ramamurthi, K

    2011-02-01

    Single crystals of the organic NLO material, benzaldehyde thiosemicarbazone (BTSC) monohydrate, were grown by slow evaporation method. Solubility of BTSC monohydrate was determined in ethanol at different temperatures. The grown crystals were characterized by single crystal X-ray diffraction analysis to determine the cell parameters and by FT-IR technique to study the presence of the functional groups. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. UV-vis-NIR spectrum shows excellent transmission in the region of 200-1100 nm. Theoretical calculations were carried out to determine the linear optical constants such as extinction coefficient and refractive index. Further the optical nonlinearities of BTSC have been investigated by Z-scan technique with He-Ne laser radiation of wavelength 632.8 nm. Mechanical properties of the grown crystal were studied using Vickers microhardness tester. Second harmonic generation efficiency of the powdered BTSC monohydrate was tested using Nd:YAG laser and it is found to be ∼5.3 times that of potassium dihydrogen orthophosphate. PMID:21186136

  5. Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet and magnesium oxide.

  6. Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet, and magnesium oxide.

  7. Fabrication of Fe nanowires on yittrium-stabilized zirconia single crystal substrates by thermal CVD methods

    SciTech Connect

    Kawahito, A.; Yanase, T.; Endo, T.; Nagahama, T.; Shimada, T.

    2015-05-07

    Magnetic nanowires (NWs) are promising as material for use in spintronics and as the precursor of permanent magnets because they have unique properties due to their high aspect ratio. The growth of magnetic Fe whiskers was reported in the 1960s, but the diameter was not on a nanoscale level and the growth mechanism was not fully elucidated. In the present paper, we report the almost vertical growth of Fe NWs on a single crystal yttrium-stabilized zirconia (Y{sub 0.15}Zr{sub 0.85}O{sub 2}) by a thermal CVD method. The NWs show a characteristic taper part on the bottom growing from a trigonal pyramidal nucleus. The taper angle and length can be controlled by changing the growth condition in two steps, which will lead to obtaining uniformly distributed thin Fe NWs for applications.

  8. Thermal spray forming of refractory sample ampoule cartridges for single crystal growth space furnaces

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank; Poorman, Richard; Holmes, Richard; Mckechnie, Timothy; Krotz, Phil; Liaw, Yoon

    1993-01-01

    A thermal spray process is being used to build up refractory metals and ceramics into a containment cartridge for high temperature, single crystal semiconductor growth experiments. This process uses high energy plasma inside a low pressure (100-200 torr) inert environment to apply layers of material onto a removable mandrel. A variety of materials are being characterized and evaluated against a demanding set of requirements, including high service temperature (1700 C), oxidation resistance, and resistance to liquid metal attack. Techniques to spray form refractory metals (tungsten, molybdenum, niobium, tantalum) and ceramics (alumina, boron nitride) are being developed in the Plasma Spray Cell at Marshall Space Flight Center. These plasma spray formed materials have been evaluated for mechanical properties, density, microstructure, and resistance to liquid metal attack. Forming techniques and the resultant mechanical and metallurgical properties will be presented.

  9. Thermal spray forming of refractory sample ampoule cartridges for single crystal growth space furnaces

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank; Poorman, Richard; Holmes, Richard; Mckechnie, Timothy; Krotz, Phil; Liaw, Yoon

    1993-01-01

    A thermal spray process is being used to build up refractory metals and ceramics into a containment cartridge for high temperature, single crystal semiconductor growth experiments. This process uses high energy plasma inside a low pressure (100-200 torr) inert environment to apply layers of material onto a removable mandrel. A variety of materials are being characterized and evaluated against a demanding set of requirements, including high service temperature (1700 C), oxidation resistance, and resistance to liquid metal attack. Techniques to spray form refractory metals (tungsten, molybdenum, niobium, tantalum) and ceramics (alumina, boron nitride) are being developed in the Plasma Spray Cell at Marshall Space Flight Center. These plasma spray formed materials have been evaluated for mechanical properties, density, microstructure, and resistance to liquid metal attack. Forming techniques and the resultant mechanical and metallurgical properties are presented.

  10. Fabrication of Fe nanowires on yittrium-stabilized zirconia single crystal substrates by thermal CVD methods

    NASA Astrophysics Data System (ADS)

    Kawahito, A.; Yanase, T.; Endo, T.; Nagahama, T.; Shimada, T.

    2015-05-01

    Magnetic nanowires (NWs) are promising as material for use in spintronics and as the precursor of permanent magnets because they have unique properties due to their high aspect ratio. The growth of magnetic Fe whiskers was reported in the 1960s, but the diameter was not on a nanoscale level and the growth mechanism was not fully elucidated. In the present paper, we report the almost vertical growth of Fe NWs on a single crystal yttrium-stabilized zirconia (Y0.15Zr0.85O2) by a thermal CVD method. The NWs show a characteristic taper part on the bottom growing from a trigonal pyramidal nucleus. The taper angle and length can be controlled by changing the growth condition in two steps, which will lead to obtaining uniformly distributed thin Fe NWs for applications.

  11. Synthesis, thermal and nonlinear optical characterization of L-arginine semi-oxalate single crystals

    NASA Astrophysics Data System (ADS)

    Vasudevan, P.; Gokulraj, S.; Sankar, S.

    2012-06-01

    Optically good quality L-arginine semi-oxalate, an organic nonlinear optical crystal, has been synthesized from aqueous solution by slow evaporation method. Single crystal X-ray diffraction (XRD) analysis reveals that the synthesized L-arginine semi-oxalate crystal possesses triclinic structure with unit cell dimensions as a=5.05Å, b=9.73Å, c=13.12Å, α=111.030, β=92.790 and γ=91.910. The Fourier transform infra-red (FTIR) spectroscopy was analyzed and the presence of functional groups of L-arginine semi-oxalate was confirmed. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies show that the material is thermally stable up to 1460C and the melting point is 1500C. Kurtz and Perry powder technique confirms that the second harmonic generation (SHG) efficiency is 0.32 times that of standard organic materials urea and KDP.

  12. Behavior of nickel-base superalloy single crystals under thermal-mechanical fatigue

    NASA Astrophysics Data System (ADS)

    Fleury, E.; Rémy, L.

    1994-12-01

    The thermal-mechanical fatigue behavior of AM1 nickel-base superalloy single crystals is studied using a cycle from 600 °C to 1100 °C. It is found to be strongly dependent on crystallo-graphic orientation, which leads to different shapes of the stress-strain hysteresis loops. The cyclic stress-strain response is influenced by variation in Young’s modulus, flow stress, and cyclic hardening with temperature for every crystallographic orientation. The thermalmechanical fatigue life is mainly spent in crack growth. Two main crack-initiation mechanisms occur, depending on the mechanical strain range. Oxidation-induced cracking is the dominant damage mechanism in the lifetime of interest for turbine blades.

  13. Thermal Transport in CuSb2O6 single crystals

    NASA Astrophysics Data System (ADS)

    Prasai, Narayan; Cohn, Joshua L.; Smith, Michael G.; Rebello, Alwyn; Neumeier, John J.

    2012-02-01

    CuSb2O6 behaves as a uniform, one-dimensional (1D) S=1/2 Heisenberg spin chain with long-range, antiferromagnetic ordering below TN˜8.5 K.ootnotetextA. Nakua et al., J. Solid State Chem. 91, 105 (1991); B. J. Gibson et al., J. Magn. Magn. Mater. 272-276, 927 (2004). Unusual for cuprates, the Cu^2+ ions lie within quite regular CuO6 octahedra and 1D magnetism appears to arise from orbital ordering driven by correlation effects.ootnotetextDeepa Kasinathan, Klaus Koepernik, and Helge Rosner, Phys. Rev. Lett. 100, 237202 (2008). We will report the results of thermal conductivity measurements on single crystals over the temperature range 5K<=T<=330 K.

  14. Faraday isolator based on a TSAG single crystal with compensation of thermally induced depolarization inside magnetic field

    NASA Astrophysics Data System (ADS)

    Snetkov, Ilya; Palashov, Oleg

    2015-04-01

    A Faraday isolator based on a terbium scandium aluminum garnet (TSAG) single crystal with compensation of thermally induced depolarization inside magnetic field was demonstrated. An isolation ratio of 32 dB at 350 W cw laser radiation power was achieved. Thermally induced depolarization and thermal lens were studied and compared with similar thermal effects arising in the widely used terbium gallium garnet crystal (TGG) for the first time.

  15. Growth and thermal properties of GeSePb0.4 single crystals

    NASA Astrophysics Data System (ADS)

    Solanki, G. K.; Patel, K. D.; Gosai, N. N.; Patel, Ruchita R.

    2012-06-01

    Single crystals of GeSePb0.4 were grown by Direct Vapor Transport (DVT) technique, in a two zone horizontal furnace with temperature difference of 50 K between growth and source zones. The material crystallizes in the form of shining gray and platelets like crystals at the end of growth cycles. Thermogravimetric analysis (TGA) has been used for many years to evaluate thermal stability of material as it will determine the range of stable operation for a device made up out of these materials under investigation. Thermal characteristics of GeSePb0.4 crystals were studied employing thermoanalytical techniques, viz. TGA and DTA. Thermal analysis experiments were carried out with constant heating rate of 10°C/ min in air. The DTA pattern of GeSePb0.4 crystals shows a strong endothermic peak at 472°C. The objective of this study is to determine activation energy and other kinetic parameters of GeSePb0.4 crystals. Broido and Coats-Redfern models are used to evaluate different kinetic parameters of GeSePb0.4 crystals viz. activation energy, entropy, enthalpy, Gibbs mean free energy etc.

  16. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Neutron Diffraction Measurements of a Thermally Fatigued Single Crystal Superalloy

    NASA Astrophysics Data System (ADS)

    Sun, Guang-Ai; Chen, Bo; Wu, Er-Dong; Li, Jin-Chao; Pirling, T.; Hughes, D.

    2009-08-01

    The thermally fatigued single crystal superalloy DZ125L is investigated by neutron diffraction measurements. The measurements, made using the phi angle oscillating method, provide more detailed and reliable data than those with the phi angle fixed. Diffraction studies show that the influence of thermal fatigue on the lattice parameters of the alloy is very limited. The stress analysis reveals that triaxial elastic hydrostatic stress plays a major role during thermal fatigue. The magnitude of the macrostress increases with the fatigue cycles, with the stress of the γ phase increasing more significantly than that of the γ' phase, and becoming fragile after many cycles. The changes in the microstrain are dependent on the reflection planes. The microstrains at the center of the sample are released by the thermal fatigue in comparison with those at the outlying locations, which has been attributed to the advance of the dislocation slips.

  17. Thermal Mechanical Stability of Single-Crystal-Oxide Refractive Concentrators Evaluated for High-Temperature Solar-Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Recently, refractive secondary solar concentrator systems were developed for solar thermal power and propulsion (ref. 1). Single-crystal oxides-such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO), and sapphire (Al2O3)-are candidate refractive secondary concentrator materials. However, the refractive concentrator system will experience high-temperature thermal cycling in the solar thermal engine during the sun/shade transition of a space mission. The thermal mechanical reliability of these components in severe thermal environments is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions. In this research at the NASA Lewis Research Center, a controlled heat flux test approach was developed for investigating the thermal mechanical stability of the candidate oxide. This approach used a 3.0-kW continuous-wave (wavelength, 10.6 mm) carbon dioxide (CO2) laser (ref. 2). The CO2 laser is especially well-suited for single-crystal thermal shock tests because it can directly deliver well-characterized heat energy to the oxide surfaces. Since the oxides are opaque at the 10.6-mm wavelength of the laser beam, the light energy is absorbed at the surfaces rather than transmitting into the crystals, and thus generates the required temperature gradients within the specimens. The following figure is a schematic diagram of the test rig.

  18. Investigation of thermal diffusivity dependence on temperature in a group of optical single crystals doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.

    2015-07-01

    The group of YAG, YVO4 and GdCOB single crystals was examined to determine the thermal diffusivity as a function of temperature in range from 30 °C to 300 °C. Further investigations concerned on analysis of the influence of dopants on these dependencies. The experimental setup based on thermal wave method with mirage detection was used. The samples represented different crystallographic systems such as cubic (YAG) tetragonal (YVO4) and monoclinic (GdCOB). The anisotropy of thermal conductivity of investigated samples was taken into account in the investigations. The crystals were doped with calcium ions, rare earth ions such as ytterbium, neodymium, and thulium, and also with transition metal vanadium. The results confirmed that influence of doping on the thermal diffusivity of investigated materials strongly depends on temperature. In general the thermal diffusivity decreases with increasing of sample temperature from 30 °C to 300 °C, however the drop in thermal diffusivity is the highest for pure single crystals. Doping is another factor reducing the heat transport in single crystals. Introduction of dopant ions into a crystal lattice leads to a significant decrease in the thermal diffusivity at lower temperatures in comparison with pure crystals. However, the influence of dopants becomes less pronounced with increasing temperature, and in case of weakly doped crystals it becomes negligible at higher temperatures. The interpretation of thermal diffusivity dependence on temperature for single crystals was based on the Debye model of lattice thermal conductivity of solids. The results allowed to conclude that the decrease of thermal diffusivity with temperature and increasing concentration of impurities is caused by shortening of the phonons mean free path due to phonon-phonon and phonon-point defect scatterings.

  19. Structural, optical, thermal and mechanical properties of Urea tartaric acid single crystals

    NASA Astrophysics Data System (ADS)

    Vinothkumar, P.; Rajeswari, K.; Kumar, R. Mohan; Bhaskaran, A.

    2015-06-01

    Urea tartaric acid (UT) an organic nonlinear optical (NLO) material was synthesized from aqueous solution and the crystals were grown by the slow evaporation technique. The single crystal X-ray diffraction (XRD) analysis revealed that the UT crystal belongs to the orthorhombic system. The functional groups of UT have been identified by the Fourier transform infrared spectral studies. The optical transparent window in the visible and near the IR regions was investigated. The transmittance of UT has been used to calculate the refractive index (n) as a function of the wavelength. The nonlinear optical property of the grown crystal has been confirmed by the Kurtz powder second harmonic generation test. The birefringence of the crystal was determined using a tungsten halogen lamp source. The laser induced surface damage threshold for the grown crystal was measured using the Nd:YAG laser. The anisotropic in mechanical property of the grown crystals was studied using Vicker's microhardness tester at different planes. The etch pit density of UT crystals was investigated. The thermal behavior of UT was investigated using the TG-DTA and DSC studies.

  20. Thermal oxidation of 3C silicon carbide single-crystal layers on silicon

    NASA Technical Reports Server (NTRS)

    Fung, C. D.; Kopanski, J. J.

    1984-01-01

    Thermal oxidation of thick single-crystal 3C SiC layers on silicon substrates was studied. The oxidations were conducted in a wet O2 atmosphere at temperatures from 1000 to 1250 C for times from 0.1 to 50 h. Ellipsometry was used to determine the thickness and index of refraction of the oxide films. Auger analysis showed them to be homogeneous with near stoichiometric composition. The oxide growth followed a linear parabolic relationship with time. Activation energy of the parabolic rate constant was found to be 50 kcal/mole, while the linear rate constant was 74 kcal/mole. The latter value corresponds approximately to the energy required to break a Si-C bond. Electrical measurements show an effective density of 4-6 x 10 to the 11th per sq cm for fixed oxide charges at the oxide-carbide interface, and the dielectric strength of the oxide film is aproximately 6 x 10 to the 6th V/cm.

  1. Structural, optical, thermal and mechanical properties of Urea tartaric acid single crystals.

    PubMed

    Vinothkumar, P; Rajeswari, K; Kumar, R Mohan; Bhaskaran, A

    2015-06-15

    Urea tartaric acid (UT) an organic nonlinear optical (NLO) material was synthesized from aqueous solution and the crystals were grown by the slow evaporation technique. The single crystal X-ray diffraction (XRD) analysis revealed that the UT crystal belongs to the orthorhombic system. The functional groups of UT have been identified by the Fourier transform infrared spectral studies. The optical transparent window in the visible and near the IR regions was investigated. The transmittance of UT has been used to calculate the refractive index (n) as a function of the wavelength. The nonlinear optical property of the grown crystal has been confirmed by the Kurtz powder second harmonic generation test. The birefringence of the crystal was determined using a tungsten halogen lamp source. The laser induced surface damage threshold for the grown crystal was measured using the Nd:YAG laser. The anisotropic in mechanical property of the grown crystals was studied using Vicker's microhardness tester at different planes. The etch pit density of UT crystals was investigated. The thermal behavior of UT was investigated using the TG-DTA and DSC studies. PMID:25766476

  2. Characterization of oxide scales thermally formed on single-crystal silicon carbide.

    PubMed

    Chayasombat, B; Kato, T; Hirayama, T; Tokunaga, T; Sasaki, K; Kuroda, K

    2010-08-01

    Microstructures of oxide scales thermally formed on single-crystal silicon carbide were investigated using transmission electron microscopy. The oxide scales were formed on the Si-face of 6H-SiC at 1273-1473 K in dry oxygen. Spherical patterns were observed on the surfaces of the oxidized samples by an optical microscope in some regions. In these regions, cross-sectional transmission electron microscopy (TEM) observations show that the oxide scale was divided into two layers; the upper layer (surface side) was composed of crystalline silica, and the lower layer on the silicon carbide substrate was amorphous silica, while the oxide scales in the surroundings of the patterns were composed of only amorphous silica. The oxidation activation energy in the amorphous silica layer of the Si-face of 6H-SiC was found to be 408 kJ/mol by the evolution of thickness directly measured from the cross-sectional scanning electron microscopy and TEM images. PMID:20554755

  3. Growth Stresses in Thermally Grown Oxides on Nickel-Based Single-Crystal Alloys

    NASA Astrophysics Data System (ADS)

    Rettberg, Luke H.; Laux, Britta; He, Ming Y.; Hovis, David; Heuer, Arthur H.; Pollock, Tresa M.

    2016-03-01

    Growth stresses that develop in α-Al2O3 scale that form during isothermal oxidation of three Ni-based single crystal alloys have been studied to elucidate their role in coating and substrate degradation at elevated temperatures. Piezospectroscopy measurements at room temperature indicate large room temperature compressive stresses in the oxides formed at 1255 K or 1366 K (982 °C or 1093 °C) on the alloys, ranging from a high of 4.8 GPa for René N4 at 1366 K (1093 °C) to a low of 3.8 GPa for René N5 at 1255 K (982 °C). Finite element modeling of each of these systems to account for differences in coefficients of thermal expansion of the oxide and substrate indicates growth strains in the range from 0.21 to 0.44 pct at the oxidation temperature, which is an order of magnitude higher than the growth strains measured in the oxides on intermetallic coatings that are typically applied to these superalloys. The magnitudes of the growth strains do not scale with the parabolic oxidation rate constants measured for the alloys. Significant spatial inhomogeneities in the growth stresses were observed, due to (i) the presence of dendritic segregation and (ii) large carbides in the material that locally disrupts the structure of the oxide scale. The implications of these observations for failure during cyclic oxidation, fatigue cycling, and alloy design are considered.

  4. Thermal conductivity of Zn, Pr and Tb doped YBCO single crystals: Theory and experiment

    SciTech Connect

    Henning, P.F.; Cao, G.; Crow, J.E.

    1995-08-01

    The thermal conductivity K(T) vs temperature has been measured for (Y,Pr)Ba{sub 2}Cu{sub 3}O{sub 7}, (Y,Tb)Ba{sub 2}Cu{sub 3}O{sub 7} and YBa{sub 2}(Cu,Zn){sub 3}O{sub 7} single crystals from 10{le}T{le}280K. For YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO), a strong enhancement in K(T) is observed for T{le}T{sub c} with a peak in K(T) at approximately T{approx}T{sub c}/2 with a sharp change in slope of K(T) at T{sub c}. These results are similar to those reported previously. For the selectively doped YBCO, the peak in K(T) is shifted to lower temperatures and occurs at T{approx}20K independent of T{sub c} and the impurity concentration. In addition, the sharp change in slope of K(T) at T{sub c} is not apparent for the doped crystals. These results are discussed along with a theoretical model for electronic conduction including both impurity and inelastic scattering from spin fluctuations.

  5. Thermal Diffused Scattering (TDS) - a new tool for determining single crystal elasticity at high-pressure condition

    NASA Astrophysics Data System (ADS)

    Zhang, J.

    2015-12-01

    X-ray thermal diffuse scattering (TDS) has been used to determine phonon dispersion relation of solids since 1940s (Wehinger et al. 2013; Ding et al. 2006; Xu and Chiang 2005). However, its application in high-pressure mineral physics has not been widely recognized. Sound velocities of Earth materials at relevant high pressure (P) and temperature (T) conditions are essential for interpreting seismic data, which provides by now the most accurate image of the Earth interior. Comparing with other commonly used techniques for measuring sound velocities in the high-pressure mineral physics community, it has significant advantages and disadvantages. Firstly, it could be used for measuring any single crystals at extreme P-T conditions using diamond anvil cell (DAC), not limited to transparent samples or nuclear resonant isotopes; Secondly, single-crystal elastic constants could be obtained through TDS, and hence directional dependences of sound velocities are available; Finally, experimental setup for TDS measurement is very easy, essentially identical to what is used for routine high-pressure single-crystal X-ray diffraction experiments. However, TDS is much less straightforward in data interpretation, which usually involves micro force constant modeling between the nearest neighbor atoms. We developed dependable data collection procedures for TDS measurement under high-pressure conditions. Measurements with single-crystal Si and foresterite under ambient and high-pressure conditions are successful. Using the python code package we developed for analyzing TDS data, we successfully reproduced the previously determined single-crystal elastic moduli of Si and foresterite using Brillouin spectroscopy and ultrasonics. The experimental uncertainty of the single crystal elastic moduli determined from TDS approach is within 4% or better.

  6. Thermal expansion and elastic anisotropy in single crystal Al2O3 and SiC reinforcements

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Li, Zhuang; Bradt, Richard C.

    1994-01-01

    In single crystal form, SiC and Al2O3 are attractive reinforcing components for high temperature composites. In this study, the axial coefficients of thermal expansion and single crystal elastic constants of SiC and Al2O3 were used to determine their coefficients of thermal expansion and Young's moduli as a function of crystallographic orientation and temperature. SiC and Al2O3 exhibit a strong variation of Young's modulus with orientation; however, their moduli and anisotropies are weak functions of temperature below 1000 C. The coefficients of thermal expansion exhibit significant temperature dependence, and that of the non-cubic Al2O3 is also a function of crystallographic orientation.

  7. Thermal diffusivity of pyroxene, feldspar, and silica melts, glasses, and single-crystals at high temperature

    NASA Astrophysics Data System (ADS)

    Pertermann, M.; Branlund, J.; Whittington, A.; Hofmeister, A.

    2007-12-01

    Thermal diffusivity (D) due to phonon transport (the lattice component) was measured using laser-flash analysis from oriented single-crystals and of glasses above the glass transition, which proxy as melts. Compositions include SiO2, CaMgSi2O6, LiAlSi2O6, NaAlSi3O8, and CaAl2Si2O8. KAlSi3O8 was studied previously. Viscosity measurements of the supercooled liquids, in the range 106.8 to 1012.3 Pas, confirm near-Arrhenian behavior. For all compositions and for crystal and glass, D decreases with T, approaching a constant generally near 1000 K: Dsat, which is larger in the crystal than in the glass. A rapid decrease in D as T is increased further (ca 1400 K for orthoclase) is consistent with crossing the glass transition, verified from our viscosity data on these systems. The amount of the decrease depends on the chemical composition and similar to the relative decrease observed in heat capacity. Orthoclase values for Dsat are 0.65± 0.3 mm2/s for bulk crystal and 0.53+/-0.03 mm2/s for the glass. Constant D = 0.475+/-.01 mm2/s represents melt. Thermal conductivity (klat) of orthoclase glass, calculated using previous results for heat capacity (CP) and our density data, increases with T due to CP strongly increasing with T, reaching a plateau near 1.45 W/m-K for melt, but is always below klat of the crystal. Similar results were obtained from the other systems studied. Melting of silica, pyroxene, and feldspars impedes heat transport, providing positive thermal feedback that may promote further melting in the continental crust. The consistency of the behavior for these different compositions and structures suggests that our results are universal, holding for oceanic lithosphere as well. Melts, due to being disordered, are poor transporters of heat via vibrations. However, d(ln klat)/dP depends inversely on bulk modulus, suggesting that at some high pressure, the thermal conductivity of the melt and corresponding crystal become equal so that retention of heat by melts

  8. Spectral and Lensing Characteristics of Gel-Derived Strontium Tartrate Single Crystals Using Dual-Beam Thermal Lens Technique.

    PubMed

    Rejeena, I; Thomas, V; Mathew, S; Lillibai, B; Nampoori, V P N; Radhakrishnan, P

    2016-09-01

    The Dual Beam mode-matched thermal lens spectrometry is a sensible technique for direct measurements of the thermal properties of tartrate crystalline materials. Here we report the measurement of thermal diffusivity of Strontium Tartrate single crystals incorporated with Rhodamine 6G using the thermal lens experiment. The respective crystals were prepared by solution-gel method at room temperature. The absorption characteristics of three different Strontium Tartrate crystals viz. pure, electric field applied and magnetic field applied were also carried out. PMID:27465706

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Growth of N-Glycyl-L-Valine (GV) single crystal and its spectral, thermal and optical characterization

    NASA Astrophysics Data System (ADS)

    Janarthanan, S.; Sugaraj Samuel, R.; Rajan, Y. C.; Suresh, P.; Thangaraj, K.

    2013-03-01

    A nonlinear optical crystal of N-Glycyl-L-Valine (GV) single crystals was grown by slow evaporation solution growth technique from an aqueous solution. The unit cell parameters and the crystal structure were determined by single crystal X-ray diffraction study. The Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectral studies were carried out to identify the functional groups of the grown crystals. The ultraviolet visible near infrared (UV-Vis-NIR) spectrum was recorded to study the optical transparency of the grown crystal. The thermogravimetric (TG) and differential thermal (DTA) analyses revealed the thermal stability of the sample. The presence of second harmonic generation (SHG) for the grown crystal was confirmed by Kurtz-Perry powder technique.

  11. Studies on the growth, thermal and optical properties of 4-aminopyridinium p-aminobenzoate dihydrate single crystals

    NASA Astrophysics Data System (ADS)

    Sornamurthy, B. M.; Peramaiyan, G.; Pandi, P.; Das, S.; Bhagavannarayana, G.; Manivannan, V.; Mohan Kumar, R.

    2014-07-01

    4-aminopyridinium p-aminobenzoate dihydrate (4APAB) compound was synthesized successfully and single crystals were grown by slow evaporation solution growth technique. Single crystal X-ray diffraction study was conducted to evaluate the cell parameters of grown crystal. The crystalline perfection of 4APAB crystal was assessed by HRXRD studies. Thermal studies revealed the thermal stability of grown crystal up to 126 °C. The optical transmittance window and lower cut-off wavelength of 4APAB crystal were estimated by using UV-vis-NIR studies. The second harmonic efficiency of 4APAB was measured by powder test using Nd:YAG laser radiation. The dielectric tensor studies revealed that 4APAB crystal shows normal dielectric behavior. The single and multiple shots laser damage threshold values of grown crystal were measured.

  12. Crystallographic, electronic, thermal, and magnetic properties of single-crystal SrCo2As2

    DOE PAGESBeta

    Pandey, Abhishek; Quirinale, D. G.; Jayasekara, W.; Sapkota, A.; Kim, M. G.; Dhaka, R. S.; Lee, Y.; Heitmann, T. W.; Stephens, P. W.; Ogloblichev, V.; et al

    2013-07-01

    In tetragonal SrCo2As2 single crystals, inelastic neutron scattering measurements demonstrated that strong stripe-type antiferromagnetic (AFM) correlations occur at a temperature T = 5 K [W. Jayasekara et al., arXiv:1306.5174] that are the same as in the isostructural AFe2As2 (A = Ca, Sr, Ba) parent compounds of high-Tc superconductors. This surprising discovery suggests that SrCo2As2 may also be a good parent compound for high-Tc superconductivity. Here, structural and thermal expansion, electrical resistivity ρ, angle-resolved photoemission spectroscopy (ARPES), heat capacity Cp, magnetic susceptibility χ, 75As NMR and neutron diffraction measurements of SrCo2As2 crystals are reported together with LDA band structure calculations thatmore » shed further light on this fascinating material. The c-axis thermal expansion coefficient αc is negative from 7 to 300 K, whereas αa is positive over this T range. The ρ(T) shows metallic character. The ARPES measurements and band theory confirm the metallic character and in addition show the presence of a flat band near the Fermi energy EF. The band calculations exhibit an extremely sharp peak in the density of states D(EF) arising from a flat dx2-y2 band. A comparison of the Sommerfeld coefficient of the electronic specific heat with χ(T → 0) suggests the presence of strong ferromagnetic itinerant spin correlations which on the basis of the Stoner criterion predicts that SrCo2As2 should be an itinerant ferromagnet, in conflict with the magnetization data. The χ(T) does have a large magnitude, but also exhibits a broad maximum at 115 K suggestive of dynamic short-range AFM spin correlations, in agreement with the neutron scattering data. The measurements show no evidence for any type of phase transition between 1.3 and 300 K and we propose that metallic SrCo2As2 has a gapless quantum spin-liquid ground state.« less

  13. A NEW SINGLE-CRYSTAL FILTERED THERMAL NEUTRON SOURCE FOR NEUTRON CAPTURE THERAPY RESEARCH AT THE UNIVERSITY OF MISSOURI

    SciTech Connect

    John D. Brockman; David W. Nigg; M. Frederick Hawthorne

    2008-09-01

    Parameter studies, design calculations and initial neutronic performance measurements have been completed for a new thermal neutron beamline to be used for neutron capture therapy cell and small-animal radiobiology studies at the University of Missouri Research Reactor. The beamline features the use of single-crystal silicon and bismuth sections for neutron filtering and for reduction of incident gamma radiation. The calculated and measured thermal neutron flux produced at the irradiation location is on the order of 9.5x108 neutrons/cm2-s, with a measured cadmium ratio (Au foils) of 105, indicating a well-thermalized spectrum.

  14. Spectral and Non Radiative Decay Studies of Lead Di Bromide Single Crystals by Mode Matched Thermal Lens Technique.

    PubMed

    Rejeena, I; Lillibai, B; Thomas, V; Nampoori, V P N; Radhakrishnan, P

    2016-07-01

    In the present paper, the investigations on the non radiative decay mechanism, optical band gap determination from absorption spectroscopic studies and fluorescence emission by photo luminescence techniques using different excitation wavelengths on gel derived lead di bromide single crystals are reported. Non radiative decay of the sample is studied using high sensitive dual beam mode matched thermal lens technique. For the thermal lensing experiment the crystal in solution phase is incorporated with rhodamine 6G dye for enhancing the absorption of the crystal sample. The thermal diffusivity of lead di bromide is determined using the probe beam intensity v/s time measurements. PMID:27165040

  15. Growth, spectral, thermal, optical, mechanical and etching studies of L-lysine semi-maleate (L-LSM) single crystals

    NASA Astrophysics Data System (ADS)

    Vasudevan, V.; Renuka, N.; Ramesh Babu, R.; Ramamurthi, K.

    2015-02-01

    Organic nonlinear optical material, L-lysine semi-maleate (L-LSM) single crystals were grown by slow cooling solution growth technique. The crystal system of grown L-LSM was confirmed by single crystal and powder X-ray diffraction analyzes. Functional groups of the grown crystal have been identified by Fourier Transform Infrared spectral analysis. The proton and carbon NMR spectral studies confirm the presence of hydrogen and carbon in the grown L-LSM. The melting and thermal decomposition temperatures of the crystal were determined using thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. Optical transparency, second harmonic generation efficiency, micro hardness, dielectric constant and loss, refractive index and birefringence have also been measured. Further, the growth patterns and dislocations present in the grown crystal are studied.

  16. Growth, optical, thermal and mechanical studies of methyl 4-hydroxybenzoate single crystals

    NASA Astrophysics Data System (ADS)

    Vijayan, N.; Ramesh Babu, R.; Gunasekaran, M.; Gopalakrishnan, R.; Ramasamy, P.

    2003-08-01

    Bulk single crystals of methyl 4-hydroxy benzoate have been successfully grown by slow evaporation solution growth technique at room temperature. The grown crystals have been subjected to spectroscopic studies like FT-IR and FT-Raman. The hardness of the crystal was measured by Vicker's microhardness tester. The lattice parameters have been calculated by X-ray diffraction technique and the values are in good agreement with the reported JCPDS file.

  17. Constraints on the Thermal History of Martian Meteorites ALH84001 and MIL03346 by Single Crystal XRD, Electron Microprobe and Mössbauer Analyses of Ortho- and Clinopyroxene

    NASA Astrophysics Data System (ADS)

    Domeneghetti, M. C.; Fioretti, A. M.; Cámara, F.; Carraro, A.; McCammon, C.; Tazzoli, V.

    2007-07-01

    Constraints on the thermal history of meteorites can be established by estimating the Fe2+-Mg order degree in their pyroxene using single-crystal XRD. We present here the data obtained on martian meteorites ALH84001 and MIL03346.

  18. Thermally programmable gas storage and release in single crystals of an organic van der Waals host.

    PubMed

    Enright, Gary D; Udachin, Konstantin A; Moudrakovski, Igor L; Ripmeester, John A

    2003-08-20

    A single crystal of a low density form of guest-free p-tert-butylcalix[4]arene can take up and release small guest molecules by controlling the temperature and pressure without changing the structure. Using NMR spectroscopy with flowing hyperpolarized xenon, we have shown that at room temperature access of xenon to the pore system is difficult, whereas it is relatively easy at 100 degrees C. There are good prospects for simple van der Waals materials such as the title material to be used as programmable zeolite mimics. PMID:12914432

  19. Formation of Semi-Insulating Layers on Semiconducting β-Ga2O3 Single Crystals by Thermal Oxidation

    NASA Astrophysics Data System (ADS)

    Oshima, Takayoshi; Kaminaga, Kenichi; Mukai, Akira; Sasaki, Kohei; Masui, Takekazu; Kuramata, Akito; Yamakoshi, Shigenobu; Fujita, Shizuo; Ohtomo, Akira

    2013-05-01

    Semi-insulating layers (SIL) were formed on the surfaces of nominally undoped β-Ga2O3 (010) single crystals by thermal oxidation. Capacitance-voltage measurement with double Schottky configuration was performed to evaluate the increase in the thickness of the SIL as a function of annealing temperature and time. A SiO2 layer prepared on the surface prevented the extension of the SIL, indicating that oxygen incorporation from air and successive bulk diffusion dominated the carrier compensation process. The activation energy of oxygen diffusion coefficient was estimated to be 4.1 eV.

  20. Investigation on growth, structural, optical, thermal, dielectric and mechanical properties of organic L-prolinium trichloroacetate single crystals

    SciTech Connect

    Boopathi, K.; Rajesh, P.; Ramasamy, P.

    2012-09-15

    Graphical abstract: L-Prolinium trichloroacetate is an organic nonlinear optical crystal has been grown from the aqueous solution by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis reveals that L-PTCA crystallizes in trigonal crystal system. The optical band gab is found to be 4.26 eV. Second harmonic conversion efficiency of L-PTCA has been found to be half that of KDP. Highlights: ► It deals with the synthesis, growth and characterization of L-PTCA an organic NLO crystal. ► Wide optical transparency window between 260 nm and 1100 nm. ► Thermal study reveals that the grown crystal is stable up to 127 °C. ► L-PTCA crystal exhibits the second order nonlinear optical properties. -- Abstract: A new organic nonlinear optical material L-prolinium trichloroacetate (L-PTCA) single crystal has been synthesized and grown by slow solvent evaporation technique at room temperature using water as solvent. Single-crystal X-ray diffractometer was utilized to measure unit cell parameters and to confirm lattice parameter. The powder X-ray diffraction pattern of the grown L-PTCA has been indexed. The modes of vibration of different molecular groups present in the sample were identified by the FTIR spectral analysis. The optical transmittance window and the lower cutoff wavelength of the L-PTCA have been identified by UV–vis–NIR studies. Thermal stability of the L-prolinium trichloroacetate was determined by TGA/DTA measurements. Dielectric measurements were carried out at various temperatures at frequency range 10–1 MHz. The mechanical properties of the grown crystals have been analyzed by Vickers microhardness method. The chemical etching studies were carried out on the grown crystals. Its SHG efficiency has been tested by Kurtz powder method.

  1. The effect of contained fluids during rocksalt heating: insights from thermal expansion experiments on halite single crystals.

    NASA Astrophysics Data System (ADS)

    Speranza, Giulio; Vona, Alessandro; Di Genova, Danilo; Romano, Claudia

    2015-04-01

    Rocksalt overall characteristics and peculiarity are well known and have made rocksalt bodies one of the most favorable choice for nuclear waste storage purposes. Low to medium temperature effects related to nuclear waste heat generation have been studied by several authors. However, high temperature related salt behavior has been poorly investigated as well as studies focused on the effect of temperature increase on fluids contained in halite. Here we present the results of thermal expansion experiments in the range 50 - 700°C made on halite single crystals with different fluid contents. Our results show that thermally unaltered halite is subjected, upon heating, to thermal instability around 300 - 450°C, with sudden increase in expansivity, sample cracking and fluids emission. Moreover, thermal expansion results higher for fluid-rich salts. In contrast, thermally altered halite, lacks the instability occurrence, showing a constant linear thermal expansion regardless its fluid contents. Rocksalt thermal instability, that is likely to be due to fluids overpressure development upon heating, lead also to a bulk density reduction. Thus, unaltered salt heated to temperature around 300°C or more could cause damage, fluids emission and density drop, increasing the salt mobility. For this reason, a detailed and quantitative study of fluid type, abundance and arrangement within crystals, as well as their response to stress and thermal changes is fundamental for both scientific and applicative purposes regarding halite.

  2. Single-crystal sapphire resonator at millikelvin temperatures: Observation of thermal bistability in high- Q factor whispering gallery modes

    NASA Astrophysics Data System (ADS)

    Creedon, Daniel L.; Tobar, Michael E.; Le Floch, Jean-Michel; Reshitnyk, Yarema; Duty, Timothy

    2010-09-01

    Resonance modes in single crystal sapphire (α-Al2O3) exhibit extremely high electrical and mechanical Q factors ( ≈109 at 4 K), which are important characteristics for electromechanical experiments at the quantum limit. We report the cool down of a bulk sapphire sample below superfluid liquid-helium temperature (1.6 K) to as low as 25 mK. The electromagnetic properties were characterized at microwave frequencies, and we report the observation of electromagnetically induced thermal bistability in whispering gallery modes due to the material T3 dependence on thermal conductivity and the ultralow dielectric loss tangent. We identify “magic temperatures” between 80 and 2100 mK, the lowest ever measured, at which the onset of bistability is suppressed and the frequency-temperature dependence is annulled. These phenomena at low temperatures make sapphire suitable for quantum metrology and ultrastable clock applications, including the possible realization of the quantum-limited sapphire clock.

  3. Spectroscopic, thermal and cw dual-wavelength laser characteristics of Nd:LaF3 single crystal

    NASA Astrophysics Data System (ADS)

    Hong, Jiaqi; Zhang, Lianhan; Li, Jing; Wang, Zhaowei; He, Jingliang; Zhang, Peixiong; Wang, Yaqi; Hang, Yin

    2016-03-01

    A Nd-doped LaF3 crystal was grown by Czochralski method, and the rocking curves of (0 0 2) and (1 1 0) diffraction planes show good crystallinity quality of the as-grown crystal. Room-temperature fluorescence spectrum and transmittance spectrum of Nd:LaF3 crystal were investigated, both indicating probable dual-wavelength emissions at ∼1.04 μm and ∼1.06 μm. The thermal diffusivity and thermal conductivity of Nd:LaF3 crystal were detailed studied. Cw dual-wavelength laser operation of Nd:LaF3 single crystal at 1040 nm and around 1065 nm with LD pumping was demonstrated. A maximum output power of 302 mW was obtained with a slope efficiency of about 18.5% with respect to the pump power. The results of our study indicate the Nd:LaF3 crystal a promising laser crystal.

  4. Growth, structural, optical, thermal and laser damage threshold studies of an organic single crystal: 1,3,5 - triphenylbenzene (TPB)

    NASA Astrophysics Data System (ADS)

    Raja, R. Subramaniyan; Babu, G. Anandha; Ramasamy, P.

    2016-05-01

    Good quality single crystals of pure hydrocarbon 1,3,5-Triphenylbenzene (TPB) have been successfully grown using toluene as a solvent using controlled slow cooling solution growth technique. TPB crystallizes in orthorhombic structure with the space group Pna21. The structural perfection of the grown crystal has been analysed by high resolution X-ray diffraction measurements. The range and percentage of the optical transmission are ascertained by recording the UV-vis spectrum. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) were used to study its thermal properties. Powder second harmonic generation studies were carried out to explore its NLO properties. Laser damage threshold value has been determined using Nd:YAG laser operating at 1064 nm.

  5. Growth and dielectric, mechanical, thermal and etching studies of an organic nonlinear optical L-arginine trifluoroacetate (LATF) single crystal

    SciTech Connect

    Arjunan, S.; Mohan Kumar, R.; Mohan, R.; Jayavel, R.

    2008-08-04

    L-arginine trifluoroacetate, an organic nonlinear optical material, has been synthesized from aqueous solution. Bulk single crystal of dimension 57 mm x 5 mm x 3 mm has been grown by temperature lowering technique. Powder X-ray diffraction studies confirmed the monoclinic structure of the grown L-arginine trifluoroacetate crystal. Linear optical property of the grown crystal has been studied by UV-vis spectrum. Dielectric response of the L-arginine trifluoroacetate crystal was analysed for different frequencies and temperatures in detail. Microhardness study on the sample reveals that the crystal possesses relatively higher hardness compared to many organic crystals. Thermal analyses confirmed that the L-arginine trifluoroacetate material is thermally stable upto 212 deg. C. The etching studies have been performed to assess the perfection of the L-arginine trifluoroacetate crystal. Kurtz powder second harmonic generation test confirms the nonlinear optical properties of the as-grown L-arginine trifluoroacetate crystal.

  6. Synthesis, growth, structural, optical, thermal and mechanical properties of an organic Urea maleic acid single crystals for nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Vinothkumar, P.; Kumar, R. Mohan; Jayavel, R.; Bhaskaran, A.

    2016-07-01

    A potential organic urea maleic acid (UMA) was synthesized and single crystals were grown at room temperature by slow evaporation and seed rotation methods. The grown crystal has been subjected to single crystal XRD analysis and found to have been crystallized in a noncentrosymmetric monoclinic crystal system with Cc as space group. The High resolution X-ray diffraction analysis revealed that the specimen is free from structural grain boundaries. The transparency of the grown crystal was confirmed by optical absorption and transmittance spectra with lower cut-off wavelength of 285 nm. The microhardness test was carried out on different planes to study the load dependent hardness values. The dislocation density of the UMA crystal was estimated from the etching studies. The dielectric permittivity and dielectric loss of the grown crystal was carried out as a function of frequency for different temperatures along three crystallographic axes. Thermal properties of UMA crystals were studied by TG-DTA analysis and it is stable upto 112 °C. The laser induced surface damage threshold of the grown crystal was measured using Nd: YAG laser. The birefringence of the crystal measured in the visible region was found to vary with the wavelength. The particle size dependent SHG of the sample was measured with different input energies by Kurtz's powder method using Nd:YAG laser.

  7. Synthesis, structure, spectral, thermal and first-order molecular hyperpolarizability of 4-benzoylpyridine isonicotinyl hydrazone monohydrate single crystals.

    PubMed

    Meenatchi, V; Muthu, K; Rajasekar, M; Meenakshisundaram, S P

    2014-04-24

    Single crystals of 4-benzoylpyridine isonicotinyl hydrazone monohydrate were grown by slow evaporation solution growth technique from ethanol at room temperature. It belongs to triclinic system with space group P1¯ and the cell parameters are, a=8.9250(2) Å, b=9.1540(2) Å, c=10.87500(10) Å and V=797.88(3) Å(3). Powder XRD closely resembles with that of simulated pattern from single crystal XRD. The characteristic functional groups present in the molecule are confirmed by FT-IR and FT-Raman analyses. The crystal is transparent in the visible region having a lower optical cut-off at ∼420 nm and the band gap energies are estimated by the application of Kubelka-Munk algorithm. Thermal analysis by TG/DTA indicates the stability of the material. The scanning electron microscopy studies reveal the surface morphology of the as-grown crystal. Mass spectrometry provides information pertaining to the structure and molecular weight of the compound. Theoretical calculations were performed using Hartree-Fock method with 6-31G(d,p) as the basis set for to derive the optimized geometry, dipole moment and first-order molecular hyperpolarizality (β) values. PMID:24508881

  8. Growth of large aluminum nitride single crystals with thermal-gradient control

    SciTech Connect

    Bondokov, Robert T; Rao, Shailaja P; Gibb, Shawn Robert; Schowalter, Leo J

    2015-05-12

    In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.

  9. Thermal analysis of Bridgman-Stockbarger growth. [mercury cadmium telluride single crystals

    NASA Technical Reports Server (NTRS)

    Knopf, F. W.

    1979-01-01

    A thermal analysis of a cylindrical HgCdTe sample in a Bridgman-Stockbarger crystal growth configuration was conducted with emphasis on the thermal profile, interface shape and position, and the thermal gradients at the liquid-solid interface. Alloys of HgTe and CdTe with compositions approximating 20 percent CdTe, 80 percent HgTe were used. This composition results in a bandgap suited for the detection of 10.6 micron CO2 radiation. The sensitivity of the sample thermal characteristics to important growth parameters, such as thermal diffusivities, thermal conductivities, furnace temperature profile, ampoule dimensions, and growth velocity was assessed. Numerical techniques and associated computational models necessary to analyze the heat transfer process within the sample and the Bridgman-Stockbarger boundary conditions were developed. This thermal analysis mode was programmed in FORTRAN V, and is currently operational on the MSFC Univac 1100 system.

  10. Structural, optical, thermal, mechanical and dielectric studies of Sulfamic acid single crystals: An influence of dysprosium (Dy3+) doping

    NASA Astrophysics Data System (ADS)

    Singh, Budhendra; Shkir, Mohd.; AlFaify, S.; Kaushal, Ajay; Nasani, Narendar; Bdikin, Igor; Shoukry, H.; Yahia, I. S.; Algarni, H.

    2016-09-01

    Sulfamic acid is a potential material that exhibits excellent optical properties. A good quality, pure and dysprosium (Dy3+) doped (2.5 and 5 mol %) Sulfamic acid (SA) single crystals were grown successfully by slow cooling method. Structural study revealed a slight change in its lattice parameters and volume, suggesting the successful incorporation of Dy3+ in crystal system. The existence of dysprosium in the system was also confirmed. Presence of various vibrational modes was confirmed. Optical transparency was found to have a significant effect with variation in the doping concentration. Furthermore, a marked enhancement in its mechanical parameters with doping was also identified by nanoindentation technique. Etching study was also performed on the grown crystals to study the etch-pit formation and growth mechanism. Effect of doping on the thermal stability was analysed. All the results were compared and discussed in detail to get insight of the effect of doping concentration on Sulfamic acid crystal.

  11. Performance characteristics of thermal neutron detectors based on Li6Y(BO3)3:Ce single crystals

    NASA Astrophysics Data System (ADS)

    Singh, A. K.; Tyagi, M.; Singh, S. G.; Tiwari, B.; Desai, D. G.; Sen, S.; Desai, S. S.; Ghodke, S. S.; Gadkari, S. C.

    2015-12-01

    Crack-free single crystals of Ce doped Li6Y(BO3)3 (LYBO:Ce) have been grown using the Czochralski technique. Grown crystals were characterized for their optical and scintillation characteristics to explore their potential as neutron detectors. Scintillator detectors based on LYBO:Ce crystal were used successfully to record the pulse height spectra from various neutron sources in the flux range from 10 n/cm2/s to 107 n/cm2/s. The detection efficiency for thermal neutrons was found to be over 80% for a 2 mm thick LYBO:Ce crystal. The scintillation decay times measured for neutron and gamma radiations were about 27 ns and 49 ns, respectively.

  12. Thermal and Electrical Conduction of Single-crystal Bi2Te3 Nanostructures grown using a one step process

    PubMed Central

    Park, Dambi; Park, Sungjin; Jeong, Kwangsik; Jeong, Hong-Sik; Song, Jea Yong; Cho, Mann–Ho

    2016-01-01

    Single-crystal Bi2Te3 nanowires (NWs) and nanoribbons (NRs) were synthesized by a vapor-liquid-solid (VLS) method from Bi2Te3 powder. To investigate the thermal properties of the Bi2Te3 nanostructure, a nondestructive technique based on temperature dependent Raman mapping was carried out. The Raman peaks were red shifted with increasing temperature. In addition, the fraction of the laser power absorbed inside the Bi2Te3 nanostructures was estimated by optical simulation and used to calculate the thermal conductivity value (κ). The thermal conductivity value obtained for the Bi2Te3 NW and NR was 1.47 Wm−1K−1 and 1.81 Wm−1K−1 at 300 K, respectively. The electrical conductivity of the Bi2Te3 nanostructure was also measured. In particular, an excellent electrical conductivity value of 1.22 * 103 Ω−1 cm−1 was obtained for the Bi2Te3 NW at 300 K. This result can be attributed to topological insulator surface states. As a result of our study, the figure of merit (ZT) for the Bi2Te3 NW and NR can be significantly improved. PMID:26750563

  13. Study of Thermally Induced Damage and its Recovery in ZnO Single Crystals by Elastic Resonant Ion Channeling

    NASA Astrophysics Data System (ADS)

    Dhar, S.; Pugel, D.; Hullavarad, S. S.; Vispute, R. D.; Ogale, S. B.; Venkatesan, T.

    2006-03-01

    ZnO is widely considered as the next generation wide-band gap material for optoelectronic device applications due to its excellent material properties. Although in recent years various studies on ZnO crystal have been made, very little is known about its response after thermal treatments. In this work, we studied the influence of thermal annealing on ZnO (0001) bulk single crystal in the temperature range of 30-1000 ^oC by elastic resonant ion channeling and Rutherford backscattering (RBS) techniques using a 3.05 MeV He beam. After an isochronal1 h anneal, RBS-Ion channeling analysis showed the evolution of disorder in the Zn sub-lattice of the crystal with increasing annealing temperature. The maximum disorder was observed at 200 ^oC above which it decreased. The induced disorder in the Zn sub-lattice at lower temperature (< 400 ^oC) can almost be recovered by further annealing above 800 ^oC. Elastic resonant ion channeling analysis, which monitors the oxygen in the near-surface region clearly revealed the evolution of thermally induced disorder in the oxygen sub-lattice with increasing temperature. In contrast to the disorder recovery of Zn sub-lattice, the disorder in oxygen sub-lattice did not recover completely. Possible mechanism on the disorder and its recovery will be discussed.

  14. Thermal and fast neutron detection in chemical vapor deposition single-crystal diamond detectors

    NASA Astrophysics Data System (ADS)

    Almaviva, S.; Marinelli, M.; Milani, E.; Prestopino, G.; Tucciarone, A.; Verona, C.; Verona-Rinati, G.; Angelone, M.; Lattanzi, D.; Pillon, M.; Montereali, R. M.; Vincenti, M. A.

    2008-03-01

    Recently, a compact solid-state neutron detector capable of simultaneously detecting thermal and fast neutrons was proposed [M. Marinelli et al., Appl. Phys. Lett. 89, 143509 (2006)]. Its design is based on a p-type/intrinsic/metal layered structure obtained by Microwave Plasma Chemical Vapor Deposition (CVD) of homoepitaxial diamond followed by thermal evaporation of an Al contact and a L6iF converting layer. Fast neutrons are directly detected in the CVD diamond bulk, since they have enough energy to produce the C12(n,α)B9e reaction in diamond. Thermal neutrons are instead converted into charged particles in the L6iF layer through the L6i(n ,α)T nuclear reaction. These charged particles are then detected in the diamond layer. The thickness of the L6iF converting layer and the CVD diamond sensing layer affect the counting efficiency and energy resolution of the detector both for low- (thermal) and high-energy neutrons. An analysis is carried out on the dynamics of the L6i(n ,α)T and the C12(n,α)B9e reactions products, and the distribution of the energy released inside the sensitive layer is calculated. The detector counting efficiency and energy resolution were accordingly derived as a function of the thickness of the L6iF and CVD diamond layers, both for thermal and fast neutrons, thus allowing us to choose the optimum detector design for any particular application. Comparison with experimental results is also reported.

  15. Thermal, mechanical, electrical, linear and nonlinear optical properties of L-arginine dihydrofluoride single crystal

    NASA Astrophysics Data System (ADS)

    Sankar, D.; Menon, Vinay Raj; Sagayaraj, P.; Madhavan, J.

    2010-01-01

    L-arginine dihydrofluoride of dimensions upto 15×10×9 mm 3 was successfully grown by slow evaporation technique from aqueous solution. The crystal was characterized by X-ray diffractometry, Elemental analysis, FT-IR, UV-Vis-NIR spectroscopy, thermal and microhardness studies. The dielectric constant and dielectric loss of the crystal were studied as function of frequency. Photoconductivity studies were also carried out on the sample. Kurtz powder SHG measurement confirms the NLO property of the grown crystals.

  16. Growth, crystalline perfection, optical, thermal, laser damage threshold and electrical characterization of melaminium levulinate monohydrate single crystal

    NASA Astrophysics Data System (ADS)

    Sivakumar, N.; Kanagathara, N.; Bhagavannarayana, G.; Kalainathan, S.; Anbalagan, G.

    2015-09-01

    Equimolar amounts of melamine and levulinic acid results an organic crystal of melaminium levulinate monohydrate (MLM) at room temperature. MLM belongs to a monoclinic crystal structure having P21/c space group which was confirmed by single crystal X-ray diffraction study. Functional groups present in the MLM crystal were identified by FT-IR spectral study. HRXRD study dictates the quality of MLM crystal. UV-visble spectrum of MLM reveals the lower cut-off wavelength of 293 nm with 55% optical transparency and optical band gap was found to be 4.20 eV for the prominent plane (1 0 -1). Refractive indices for the three axes of MLM crystal were found to be nx=2.6, ny=2.4 and nz=2.2 respectively. Further the thermal stability and melting point of MLM crystal were investigated by TG/DTA study. Dielectric permittivity tensor components were estimated for the planes (1 0 -1), (0 1 0) and (1 1 1) respectively. The thermal conductivity of the crystal by Wiedemann-Franz law was found to be 5.99×10-11 W/mK at 70 °C. LDT value (2.84 GW/cm2) of MLM was estimated for laser optical device applications.

  17. Single-crystal sapphire resonator at millikelvin temperatures: Observation of thermal bistability in high-Q factor whispering gallery modes

    SciTech Connect

    Creedon, Daniel L.; Tobar, Michael E.; Le Floch, Jean-Michel; Reshitnyk, Yarema; Duty, Timothy

    2010-09-01

    Resonance modes in single crystal sapphire ({alpha}-Al{sub 2}O{sub 3}) exhibit extremely high electrical and mechanical Q factors ({approx_equal}10{sup 9} at 4 K), which are important characteristics for electromechanical experiments at the quantum limit. We report the cool down of a bulk sapphire sample below superfluid liquid-helium temperature (1.6 K) to as low as 25 mK. The electromagnetic properties were characterized at microwave frequencies, and we report the observation of electromagnetically induced thermal bistability in whispering gallery modes due to the material T{sup 3} dependence on thermal conductivity and the ultralow dielectric loss tangent. We identify ''magic temperatures'' between 80 and 2100 mK, the lowest ever measured, at which the onset of bistability is suppressed and the frequency-temperature dependence is annulled. These phenomena at low temperatures make sapphire suitable for quantum metrology and ultrastable clock applications, including the possible realization of the quantum-limited sapphire clock.

  18. Structural, vibrational, thermal and optical studies of organic single crystal: Benzotriazolium p-toluene sulfonate (BTPTS)

    NASA Astrophysics Data System (ADS)

    Kumar, R. Ramesh; Sathya, P.; Gopalakrishnan, R.

    2016-05-01

    Benzotriazolium p-toluene sulfonate (BTPTS) was grown by solution growth technique. The powder X-ray diffraction analysis was carried out to evaluate crystal system of the compound. LeBail Profile fitting analysis was performed to extract the individual peak intensities. FTIR spectrum analysis was recorded to study vibration frequencies of the prepared organic salt. Thermal studies were carried out using TG-DSC analysis. Optical absorption and energy band gap of the title compound was evaluated by UV-Vis spectral study.

  19. Hydrogen retrapping after thermal charging of hydrogen in iron single crystal

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Lam; Lee, Jai-Young

    1989-09-01

    A theory to estimate and describe the behavior of supersaturated hydrogen in interstitial sites of a normal lattice and in trap sites is suggested, and the experimental proof is provided by thermal analysis. In this theory, variation with temperature changes of the equilibrium state between hydrogen in trapping sites and in normal lattice sites, which occurs during rapid cooling after hydrogen charging at high temperature, is considered. Two evolution rate peaks of hy-drogen corresponding to a reversible trap, a dislocation, and to an irreversible trap, a microvoid, are observed, respectively, at 388 and 538 K in a thermal analysis plot. The hydrogen amount released from the reversible trap is increased with decreasing microvoid concentration, even though the reversible trap density is maintained at the same level. According to the theoretical analysis, supersaturated hydrogen dissolved in a normal lattice site by a rapid cooling of hydrogen-charged iron from high temperature is predominantly retrapped into the vacant irreversible trap-ping sites. The remaining hydrogen exists in the normal lattice interstitial sites and will maintain local equilibrium with hydrogen in the reversible trap sites. The apparent hydrogen diffusivities at 293 K with each type of trap are estimated to be 1 × 10-6 cm2/s for reversible traps and 4 × 10-8 cm2/s for microvoid traps, based on changes in the hydrogen amount released from each type of trap with the room-temperature anneal time in vacuum.

  20. Coupled theoretical interpretation and experimental investigation of the lattice thermal conductivity of Bi2Te3 single crystal

    NASA Astrophysics Data System (ADS)

    Jacquot, A.; Bayer, B.; Winkler, M.; Jaegle, M.

    2012-06-01

    An essential challenge in thermoelectric material research is the selection of materials having potentially a high figure-of-merit and their improvement by the reduction of their lattice thermal conductivity. In the present article the Debye model is modified for the calculation of the lattice thermal conductivity and used to gain insight into the anisotropy of single crystalline bismuth telluride (Bi2Te3). In this article the minimum wavelength of phonons that moved, which is closely related to the concept of cutoff frequency, is not taken twice the atoms separation. The Debye temperature is in fact not used to estimate the cutoff frequencies of the phonons that carry heat. The cutoff frequencies are defined in this work by setting an upper limit to the energy of acoustic phonons using the complete dispersion relations. Our work indicates that the cutoff frequencies of acoustic phonons are anisotropic in Bi2Te3. The anisotropy of the thermal conductivity is surprisingly found to be unrelated to the anisotropy of the sound velocities that are calculated as a function of the tensor of the elastic constants. The sound velocity is in fact almost isotropic when the longitudinal and two transversal waves are added together. In addition it is suggested that the relaxation time is also a function of the cutoff frequencies and that this may counterbalance the anisotropy arising from the variation of the number of acoustic phonons traveling in various directions. Finally, the anisotropy of the thermal conductivity of Bi2Te3 single crystal is found to be mostly related to the Grüneisen's constant if the main scattering mechanism is a phonon-phonon interaction.

  1. Thermal oxidation of single-crystal silicon carbide - Kinetic, electrical, and chemical studies

    NASA Technical Reports Server (NTRS)

    Petit, J. B.; Neudeck, P. G.; Matus, L. G.; Powell, J. A.

    1992-01-01

    This paper presents kinetic data from oxidation studies of the polar faces for 3C and 6H SiC in wet and dry oxidizing ambients. Values for the linear and parabolic rate constants were obtained, as well as preliminary results for the activation energies of the rate constants. Examples are presented describing how thermal oxidation can be used to map polytypes and characterize defects in epitaxial layers grown on low tilt angle 6H SiC substrates. Interface widths were measured using Auger electron spectroscopy (AES) with Ar ion beam depth profiling and variable angle spectroscopic ellipsometry (VASE) with effective medium approximation (EMA) models. Preliminary electrical measurements of MOS capacitors are also presented.

  2. Significant Gas Adsorption and Catalytic Performance by a Robust Cu(II) -MOF Derived through Single-Crystal to Single-Crystal Transmetalation of a Thermally Less-Stable Zn(II) -MOF.

    PubMed

    Pal, Tapan K; De, Dinesh; Neogi, Subhadip; Pachfule, Pradip; Senthilkumar, S; Xu, Qiang; Bharadwaj, Parimal K

    2015-12-21

    By using a bent tetracarboxylic acid ligand that incorporates a pendent-NH2 functional group, a 3D Zn(II)-framework (1) based on Zn2 (CO2)4 secondary building units and Zn12 (CO2)24 supramolecular building blocks has been synthesized. Framework 1 is thermally less stable, which precludes its application as a porous framework for gas adsorption or catalytic studies. This framework undergoes single-crystal to single-crystal transmetalation to give isostructural 1Cu. Unlike 1, the Cu(II) analogue is very stable and can be activated by removing metal-bound lattice solvent molecules by heating to afford 1Cu'. The activated 1Cu' exhibits excellent H2 storage (2.29 wt%) at 77 K and a high 32.1 wt% CO2 uptake at 273 K. Additionally, it displays significant selectivity for CO2 adsorption over N2 and H2 and can catalyse size-selective Knoevenagel condensation reactions. PMID:26586229

  3. Thermally-induced single-crystal-to-single-crystal transformations from a 2D two-fold interpenetrating square lattice layer to a 3D four-fold interpenetrating diamond framework and its application in dye-sensitized solar cells.

    PubMed

    Gao, Song; Fan, Rui Qing; Wang, Xin Ming; Wei, Li Guo; Song, Yang; Du, Xi; Xing, Kai; Wang, Ping; Yang, Yu Lin

    2016-07-28

    In this work, a rare 2D → 3D single-crystal-to-single-crystal transformation (SCSC) is observed in metal-organic coordination complexes, which is triggered by thermal treatment. The 2D two-fold interpenetrating square lattice layer [Cd(IBA)2]n (1) is irreversibly converted into a 3D four-fold interpenetrating diamond framework {[Cd(IBA)2(H2O)]·2.5H2O}n (2) (HIBA = 4-(1H-imidazol-1-yl)benzoic acid). Consideration is given to these two complexes with different interpenetrating structures and dimensionality, and their influence on photovoltaic properties are studied. Encouraged by the UV-visible absorption and HOMO-LUMO energy states matched for sensitizing TiO2, the two complexes are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate absorption in the ultraviolet and blue-violet region, offset competitive visible light absorption of I3(-) and reducing charge the recombination of injected electrons. After co-sensitization with 1 and 2, the device co-sensitized by 1/N719 and 2/N719 to yield overall efficiencies of 7.82% and 8.39%, which are 19.94% and 28.68% higher than that of the device sensitized only by N719 (6.52%). Consequently, high dimensional interpenetrating complexes could serve as excellent co-sensitizers and have application in DSSCs. PMID:27356177

  4. Magnetic and Thermal Properties of SmRh2Zn20 Single Crystal

    NASA Astrophysics Data System (ADS)

    Isikawa, Yosikazu; Mizushima, Toshio; Fujita, Aika; Kuwai, Tomohiko

    2016-02-01

    The magnetization, magnetic susceptibility, and specific heat of the single crystalline sample SmRh2Zn20 were measured. The valence of Sm ions in SmRh2Zn20 was found to be trivalent. No evidence of valence fluctuations was detected. SmRh2Zn20 is an antiferromagnet with TN = 2.46 K. The observed magnetic phase transition temperature in the C(T,H) curves showed that TN splits into two in the external field H along the [001] and [101] directions. On the other hand, TN in H along the [111] direction did not split, decreasing to 2.20 K at H = 7 T. At 2 K, the magnetization M111 in H along the [111] direction increased linearly with increasing field, while M001 and M101 deviated upward slightly from the linear dependence. We analyzed the observed magnetic and thermal properties of SmRh2Zn20 taking into account the crystalline-electric-field effect, the Zeeman energy, and the exchange interaction. The theoretical calculation well reproduced the experimental χ(T), M(H), C(T,H), and TN(H), suggesting that the energy scheme of Sm3+ is composed of the ground state Γ7 and the excited state Γ8 with an energy gap of 10.8 K. The sublattice magnetic moments are expected to be along the <111> direction below TN at H = 0 T. Variations of the magnetic structures induced by the external magnetic fields in a narrow temperature region around TN are inferred on the basis of theoretical calculations.

  5. Growth, spectral, optical, thermal, and mechanical behaviour of an organic single crystal: Quinolinium 2-carboxy 6-nitrophthalate monohydrate

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Organic single crystals of quinolinium 2-carboxy 6-nitrophthalate monohydrate (QN) were grown by slow evaporation solution growth technique using ethanol and water as a mixed solvent. X-ray powder diffraction analysis revealed that the crystal belongs to the monoclinic crystal system with space group of P21/c. The functional groups present in the crystallized material confirmed its molecular structure. The optical transparency range and the lower cutoff wavelength were identified from the UV-vis spectrum. The optical constants were determined by UV-visible transmission spectrum at normal incidence, measured over the 200-700 nm spectral range. The dispersion of the refractive index was discussed in terms of the single-oscillator Wemple and DiDomenico model. The calculated HOMO and LUMO energies show that the charge transfer occur within the molecule. Electronic excitation properties were discussed within the framework of two level model on the basis of an orbital analysis. The nonlinear optical absorption coefficient (β) and nonlinear refraction (n2) of QN was measured by Z-scan technique and reported here. Thermal stability of QN was determined using TGA/DSC curves. Vicker's microhardness studies were carried out on the (1 1 ̅0) plane to understand the mechanical properties of the grown crystal. The microhardness measurements showed a Vickers hardness value as 18.4 kg/mm2 which is comparable to well-known organic crystal, urea.

  6. Synthesis, growth, spectral, X-ray diffraction, magnetic and thermal studies of metal-organic complex: Diiodobis(2-aminopyridine)Cadmium(II) single crystal

    NASA Astrophysics Data System (ADS)

    Venkatesan, G.; Anandha Babu, G.; Ramasamy, P.; Rajnikant

    2013-06-01

    The metal-organic hybrid complex, [Cd(2ap)2I2] (DIAC), (2ap = 2-aminopyridine) was synthesized, DIAC single crystal has been grown and characterized by FT-IR, FT-Raman, FT-1H NMR, single crystal X-ray diffraction, high resolution X-ray diffraction (HRXRD), UV-Vis-NIR transmission, magnetic and thermal studies. The metal-ligand formation of the title complex was analyzed by FT-IR, FT-Raman and 1H NMR spectroscopic studies. The DIAC crystallizes in monoclinic crystal system, space group P21/n. The coordination geometry around the Cd(II) center is a distorted tetrahedral. The single-crystal structure analysis showed that DIAC displayed three-dimensional structures containing inorganic-organic motifs with two-dimensional layers pillar-connected through hydrogen bonding framework. The high resolution X-ray diffraction studies (HRXRD) reveals that the crystalline perfection of as grown single crystal is fairly good. Thermal stability of title compound was studied by TG/DTA analysis.

  7. Adsorption and thermal chemistry of formic acid on clean and oxygen-predosed Cu(110) single-crystal surfaces revisited

    NASA Astrophysics Data System (ADS)

    Yao, Yunxi; Zaera, Francisco

    2016-04-01

    The thermal chemistry of formic acid on clean and oxygen-predosed Cu(110) single-crystal surfaces was studied under ultrahigh-vacuum (UHV) conditions by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Key results reported in the past were confirmed, including the partial switchover from H2 to H2O desorption upon oxygen addition on the surface and the development of a second decomposition regime at 420 K, in addition to the one observed at 460 K on the clean substrate. In addition, new observations were added, including the previously missed desorption of H2 at 420 K and the existence of a normal kinetic isotope effect in both TPD peaks. Peak fitting of the XPS data afforded the identification of an asymmetric geometry for the formate intermediate, which was established to form by 200 K, and the presence of coadsorbed molecular formic acid up to the temperatures of decomposition, probably in a second layer and held by hydrogen bonding. Quantitative analysis of the TPD data indicated a one-to-one correspondence between the increase in oxygen coverage beyond θO = 0.5 ML and a decrease in formic acid uptake that mainly manifests itself in a decrease in the decomposition seen in the 460 K TPD peak. All these observations were interpreted in terms of a simple decomposition mechanism involving hydrogen abstraction from adsorbed formate species, possibly aided by coadsorbed oxygen, and a change in reaction activation energy as a function of the structure of the oxygen overlayer, which reverts from a O-c(6 × 2) structure at high oxygen coverages to the O-(2 × 1) order seen at θO = 0.5 ML.

  8. Influence of doping on thermal diffusivity of single crystals used in photonics: measurements based on thermal wave methods.

    PubMed

    Bodzenta, Jerzy; Kaźmierczak-Bałata, Anna; Wokulska, Krystyna B; Kucytowski, Jacek; Łukasiewicz, Tadeusz; Hofman, Władysław

    2009-03-01

    Three crystals used in solid-state lasers, namely, yttrium aluminum garnet (YAG), yttrium orthovanadate (YVO(4)), and gadolinium calcium oxoborate (GdCOB), were investigated to determine the influence of dopants on their thermal diffusivity. The thermal diffusivity was measured by thermal wave method with a signal detection based on mirage effect. The YAG crystals were doped with Yb or V, the YVO(4) with Nd or Ca and Tm, and the GdCOB crystals contained Nd or Yb. In all cases, the doping caused a decrease in thermal diffusivity. The analysis of complementary measurements of ultrasound velocity changes caused by dopants leads to the conclusion that impurities create phonon scattering centers. This additional scattering reduces the phonon mean free path and accordingly results in the decrease of the thermal diffusivity of the crystal. The influence of doping on lattice parameters was investigated, additionally. PMID:19252616

  9. Thermal chemistry of hydrazine on clean and oxygen- and water-predosed Cu(110) single-crystal surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Yunxi; Zaera, Francisco

    2016-08-01

    The chemistry of hydrazine on Cu(110) single-crystal surfaces was probed under ultrahigh vacuum (UHV) conditions by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Survey TPD experiments identified molecular nitrogen and ammonia as the main desorbing products from thermal activation of the adsorbate, but small amounts of diazene and NH2· radicals were also detected. At saturation coverage, N2 production leads NH3 desorption by approximately 10 K (with TPD peaks at 350 K versus 360 K, respectively), indicating a preference for dehydrogenation over N-N bond scission steps, and additional nitrogen was seen at even lower temperatures (320 K) in experiments starting with even higher doses of hydrazine. On the other hand, the formation of NH3 and NH2·, which desorb in a wide range of temperatures between approximately 300 K and 700 K, dominates in experiments with low N2H4 doses, presumably because a stronger interaction of the N-N bond with the metal in the flat adsorption geometry expected at such low coverages. Dosing at room temperature seems to also facilitate the dissociative adsorption, albeit via dehydrogenation steps that lead to the subsequent production of more significant amounts of diazene and of molecular hydrogen (in addition to N2, NH3, and NH2·). Preadsorption of oxygen on the Cu(110) surface helps stabilize the hydrazine, increasing its desorption temperature and helping with the low-temperature (320 K) production of N2. Coadsorption of hydrazine with water leads to facile proton exchange, as indicated by the production of NH2D in TPD experiments with N2H4 + D2O. This isotope scrambling must occur at cryogenic temperatures because all water desorbs from the surface below 200 K and no other changes in surface chemistry are observed after that. The implications of all this chemistry to practical applications that may use hydrazine in surface reactions with copper, including its use as a reducing agent in atomic layer

  10. Determination of Thermal-Diffusivity Dependence on Temperature of YAG Single Crystals with Different Concentrations of Yb3+ and V3+ Doping Ions

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.; Kaźmierczak-Bałata, A.; Łukasiewicz, T.

    2012-04-01

    Thermal diffusivities of pure and doped yttrium aluminum garnet single crystals were measured as a function of temperature. Samples doped with rare earth ions (3 at% and 25 at% of Yb 3+, and 0.8 at% and 2.1 at% of V 3+) were investigated in the temperature range from 34 °C to 300 °C. Determination of the thermal diffusivity was based on an analysis of propagation of a thermal wave in the sample. The frequency of the thermal wave was 100 mHz. A temperature disturbance connected with the thermal wave propagating in the sample was detected using the mirage effect. The results showed that the thermal diffusivity of all investigated samples decreases with an increase of sample temperature. A drop in the thermal diffusivity is more pronounced for pure and low-doped crystals.

  11. Thermal stability and electrical transport properties of β-Zn4Sb3 single crystal prepared by Sn-flux method

    NASA Astrophysics Data System (ADS)

    Shai, Xuxia; Deng, Shukang; Meng, Daiyi; Shen, Lanxian; Li, Decong

    2014-11-01

    In this work, β-Zn4Sb3 single crystals with space group R3barc were prepared by Sn-flux method according to the stoichiometric ratios of Zn4+x(0-0.8)Sb3Sn3. thermogravimetric-differential thermal analysis (TG-DTA) shows that there has no weight loss untill temperature reaches to melting point of 821 K. All crystals behave characteristic of p-type conduction and the carrier densities are independent on the initial composition. Comparing with β-Zn4Sb3 polycrystalline sample, the carrier mobility of the present single crystals are increased. The crystals with X>0 possess higher electrical conductivity, and the highest power factor of 1.18×10-3 Wm-1 K-2 is obtained at 585 K for the sample with X=0.8.

  12. Thermal-independent properties of PIN-PMN-PT single-crystal linear-array ultrasonic transducers.

    PubMed

    Chen, Ruimin; Wu, Jinchuan; Ho Lam, Kwok; Yao, Liheng; Zhou, Qifa; Tian, Jian; Han, Pengdi; Shung, K Kirk

    2012-12-01

    In this paper, low-frequency 32-element linear-array ultrasonic transducers were designed and fabricated using both ternary Pb(In(1/2)Nb(1/2))-Pb(Mg(1/3)Nb(2/3))-PbTiO(3) (PIN-PMN-PT) and binary Pb(Mg(1/3)Nb(2/3))-PbTiO(3) (PMNPT) single crystals. Performance of the array transducers was characterized as a function of temperature ranging from room temperature to 160°C. It was found that the array transducers fabricated using the PIN-PMN-PT single crystal were capable of satisfactory performance at 160°C, having a -6-dB bandwidth of 66% and an insertion loss of 37 dB. The results suggest that the potential of PIN-PMN-PT linear-array ultrasonic transducers for high-temperature ultrasonic transducer applications is promising. PMID:23221227

  13. Growth, structural, thermal, dielectric, mechanical and optical characterization of 2, 3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Krishnan, P.; Gayathri, K.; Jayasakthi, M.; Gunasekaran, S.; Anbalagan, G.

    2013-11-01

    Single crystal of 2, 3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate has been grown by slow evaporation solution growth technique (SEST) using ethanol-water solution at room temperature. It crystallizes in the orthorhombic system with space group of P212121. The crystalline perfection of the grown single crystal has been examined by high resolution X-ray diffraction analysis (HRXRD). The optical absorption studies show that the crystal is transparent in the visible region with a lower cut-off wavelength of 342 nm and the optical energy band gap Eg is found to be 3.52 eV. The electrical properties have been assessed by dielectric measurement at different temperatures. Hardness values measured using Vickers hardness indenter show considerable anisotropy. Laser damage threshold study is also carried out for the grown crystal.

  14. Synthesis, crystal growth, structural, thermal, optical and mechanical properties of solution grown 4-methylpyridinium 4-hydroxybenzoate single crystal.

    PubMed

    Sudhahar, S; Krishna Kumar, M; Sornamurthy, B M; Mohan Kumar, R

    2014-01-24

    Organic nonlinear optical material, 4-methylpyridinium 4-hydroxybenzoate (4MPHB) was synthesized and single crystal was grown by slow evaporation solution growth method. Single crystal and powder X-ray diffraction analyses confirm the structure and crystalline perfection of 4MPHB crystal. Infrared, Raman and NMR spectroscopy techniques were used to elucidate the functional groups present in the compound. TG-DTA analysis was carried out in nitrogen atmosphere to study the decomposition stages, endothermic and exothermic reactions. UV-visible and Photoluminescence spectra were recorded for the grown crystal to estimate the transmittance and band gap energy respectively. Linear refractive index, birefringence, and SHG efficiency of the grown crystal were studied. Laser induced surface damage threshold and mechanical properties of grown crystal were studied to assess the suitability of the grown crystals for device applications. PMID:24184578

  15. Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): A potential NLO material

    NASA Astrophysics Data System (ADS)

    Dinakaran, Paul M.; Kalainathan, S.

    2013-07-01

    4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6 × 2 × 3 mm3) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and 1H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV).

  16. Mechanical and thermal transitions in morphotropic PZN-pT and PMN-PT single crystals and their implication for sound projectors.

    PubMed

    Amin, Ahmed; McLaughlin, Elizabeth; Robinson, Harold; Ewart, Lynn

    2007-06-01

    Isothermal compression experiments on multidomain [001] oriented and poled ferroelectric rhombohedral PZN-0.07PT and PMN-0.30PT single crystals revealed elastic instabilities corresponding to zero field ferroelectric-ferroelectric phase transition under mechanical compression. The application of an appropriate dc bias field doubled the stability range of the ferroelectric rhombohedral state under uniaxial compression for both crystals and maintained a linear elastic response. Young's modulus as derived from the quasistatic, zero field stress-strain linear response agreed well with that derived from small signal resonance for the ferroelectric rhombohedral FR state of both PZN-PT and PMN-PT. Elastic compliances s(E)33 as determined from high temperature resonance revealed a monotonically decreasing Young's modulus as a function of temperature in the ferroelectric rhombohedral state with a sudden stiffening near the ferroelectric rhombohedral (FR)-ferroelectric tetragonal (FT) transition. The reversible ferroelectric-ferroelectric transition of morphotropic PZN-PT and PMN-PT single crystals as accessed by mechanical compression is discussed in terms of strain calculations from Devonshire's theory, domain unfolding, and morphotropic phase boundary shift with mechanical stress. The mechanically-induced and thermally-induced ferroelectric-ferroelectric transition trajectories are discussed in terms of the Devonshire theory. Implications of these observations for sound projectors are discussed. A single crystal tonpilz projector fabricated into a 16-element array and a segmented cylinder transducer demonstrated the outstanding capabilities of single crystals to achieve compact, broadband, and high-source level projectors when compared to conventional lead zirconate-titanate PZT8 projectors. PMID:17571807

  17. Structural, magnetic, thermal, and transport properties of X{sub 8}Ga{sub 16}Ge{sub 30} (X=Eu,Sr,Ba) single crystals

    SciTech Connect

    Sales, B. C.; Chakoumakos, B. C.; Jin, R.; Thompson, J. R.; Mandrus, D.

    2001-06-15

    Structural, magnetic, electrical and thermal transport, and heat-capacity measurements are reported on single crystals of Eu{sub 8}Ga{sub 16}Ge{sub 30}, Sr{sub 8}Ga{sub 16}Ge{sub 30}, and Ba{sub 8}Ga{sub 16}Ge{sub 30}. These compounds all crystallize in a cubic type-I ice clathrate structure, and are of interest as potential thermoelectric materials. Neutron-diffraction measurements were made on a single crystal of Eu{sub 8}Ga{sub 16}Ge{sub 30} that was grown using isotopically pure Eu{sup 153}. Nuclear density maps clearly show that Eu atoms at the 6d sites 1/4,0 can move away from the cage center to one of four nearby positions. Ferromagnetism is observed in Eu{sub 8}Ga{sub 16}Ge{sub 30} for temperatures below 32 K, with the preferred direction of the Eu spins along the (100) axis. Ferromagnetism in these heavily doped semiconductors ({approx}10{sup 21} electrons/cm{sup 3}) is likely due to a Rudermann-Kittel-Kasuya-Yoshida-type interaction. A large ({approx}10% at 8 T) negative magnetoresistance was measured near the Curie temperature of Eu{sub 8}Ga{sub 16}Ge{sub 30}. The lattice thermal conductivities of Eu{sub 8}Ga{sub 16}Ge{sub 30} and Sr{sub 8}Ga{sub 16}Ge{sub 30} single crystals show all of the characteristics of a structural glass. The thermal conductivity of Ba{sub 8}Ga{sub 16}Ge{sub 30} is low at room temperature (1.3 W/m K), but exhibits a temperature dependence characteristic of a crystal. A magnetic field has no significant effect on the thermal conductivity of any of the crystals for temperatures between 2 and 300 K. Heat-capacity measurements indicated Einstein contributions from each of the rattlers, with characteristic temperatures of 60, 53, and 30 K for Ba, Sr, and Eu atoms respectively. No superconductivity was observed in heavily doped single crystals of Ba{sub 8}Ga{sub 16}Ge{sub 30} for temperatures above 2 K, contrary to a previous report.

  18. The influence of high thermal gradient casting, hot isostatic pressing and alternate heat treatment on the structure and properties of a single crystal nickel base superalloy

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.

    1988-01-01

    A development program has been conducted to improve the cyclic properties of the PWA 1480 single-crystal superalloy by reducing or entirely eliminating casting porosity at fatigue-initiation sites, through the use of improved casting process parameters and HIPing; potential mechanical property improvements in a high-pressure hydrogen environment were also sought in alternatives to the standard coating and heat-treatment cycle. High thermal gradient casting was found to yield a reduction in overall casting porosity density and pore sizes. The most dramatic mechanical property improvement resulted from HIPing.

  19. Thermal-Independent Properties of PIN-PMN-PT Single-Crystal Linear-Array Ultrasonic Transducers

    PubMed Central

    Chen, Ruimin; Wu, Jinchuan; Lam, Kwok Ho; Yao, Liheng; Zhou, Qifa; Tian, Jian; Han, Pengdi; Shung, K. Kirk

    2013-01-01

    In this paper, low-frequency 32-element linear-array ultrasonic transducers were designed and fabricated using both ternary Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN-PMN-PT) and binary Pb(Mg1/3Nb2/3)–PbTiO3 (PMN-PT) single crystals. Performance of the array transducers was characterized as a function of temperature ranging from room temperature to 160°C. It was found that the array transducers fabricated using the PIN-PMN-PT single crystal were capable of satisfactory performance at 160°C, having a −6-dB bandwidth of 66% and an insertion loss of 37 dB. The results suggest that the potential of PIN-PMN-PT linear-array ultrasonic transducers for high-temperature ultrasonic transducer applications is promising. PMID:23221227

  20. Nucleation kinetics, growth, crystalline perfection, mechanical, thermal, optical and electrical characterization of brucinium 2-carboxy-6-nitrophthalate dihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Krishnan, P.; Gayathri, K.; Sivakumar, N.; Gunasekaran, S.; Anbalagan, G.

    2014-06-01

    Single crystals of brucinium 2-carboxy-6-nitrophthalate dihydrate (B2C6ND) have been grown by the slow evaporation solution technique at room temperature using water-ethanol (1:1) mixed solvent. The metastable zone width and induction period have been experimentally determined for the growth conditions. Nucleation kinetics and fundamental growth parameters such as surface free energy, critical radius and critical free energy change are also evaluated according to the experimental data. The crystal system and the lattice parameters have been confirmed by single crystal X-ray diffraction. The crystalline perfection of the grown B2C6ND crystals has been characterized by HRXRD method. Optical band gap and Urbach tail width of the sample have been studied employing UV-Vis absorption spectroscopy. The Vickers microhardness number (Hv), yield strength (σv) and stiffness constant (C11) of the grown crystal have been evaluated. The dielectric permittivity and dielectric loss of the grown B2C6ND crystal have been investigated as a function of frequency in the temperature range 313-353 K. The laser damage threshold value of B2C6ND crystal was estimated to be 2.8 GW/cm2 using a Nd:YAG laser.

  1. Single crystal growth, structural characterization, thermal and optical properties of a novel organometallic nonlinear optical crystal: MnHg(SCN) 4(C 2H 5NO) 2

    NASA Astrophysics Data System (ADS)

    Wang, X. Q.; Cheng, X. F.; Zhang, S. J.; Xu, D.; Zhang, G. H.; Sun, Z. H.; Yu, F. P.; Liu, X. J.; Liu, W. L.; Chen, C. L.

    2010-02-01

    A novel potentially useful organometallic nonlinear optical crystal, manganese mercury thiocyanate-bis(N-methylformamide), MnHg(SCN) 4(C 2H 5NO) 2 (MMTN) has been prepared, and large highly-optical quality single crystals with dimensions up to 29×28×14 mm 3 have been grown. The structural characterization, thermal and optical properties of the grown crystals are investigated. The growth morphology was obtained by indexing the X-ray powder diffraction data and compared with that deducing from the single crystal structure data using the Bravais-Friedel-Donnay-Harker model. The thermal analysis reveals that MMTN crystal possesses good physicochemical stability. The specific heat of the crystal is 635.1 J mol -1 K -1 at 300 K. The thermal expansion coefficient along the a, b, and c axis is α1=6.18×10 -5 K -1, α2=3.91×10 -5 K -1 and α3=9.53×10 -6 K -1, respectively. The laser damage threshold of MMTN crystal is about 225.7 MW/cm 2 with pulse width of 18 ns at 1064 nm. The powder second harmonic efficiency of the crystal is about 1.1 pm/V and the UV transparency cutoff is 354 nm, which are interpreted on the basis of the crystal structure with the Molecular Orbital theory using a GAUSSIAN03 program.

  2. Growth, optical, luminescence, thermal and mechanical behavior of an organic single crystal: 3-Acetyl-2-methyl-4-phenylquinolin-1-ium chloride.

    PubMed

    Nirosha, M; Kalainathan, S; Sarveswari, S; Vijayakumar, V

    2014-04-01

    A single crystal of 3-acetyl-2-methyl-4-phenylquinolin-1-ium chloride has grown by slow evaporation solution growth technique using ethanol as solvent. The structural, thermal, optical and mechanical property has studied for the grown crystal. Single crystal XRD revealed that the crystal belongs to monoclinic system with space group P21/c. The presences of Functional groups in the crystallized material have confirmed using the FTIR vibrational spectrum. The optical absorbance spectrum recorded from 190 to 1100nm shows the cut-off wavelength occurs at 371nm. The material shows its transparency in the entire region of the visible spectrum. The photoluminescence spectrum shows the ultraviolet and blue emission in the crystal. Thermogravimetric and differential thermal analysis reveal the thermal stability of the grown crystal. Etching study shows the grown mechanism and surface features of the crystal. Vickers microhardness studies have carried out on the (01-1) plane to understand the mechanical properties of the grown crystal. The hardness of the title compound increases on increasing the load. The Meyer's index number (n), and the stiffness constants for different loads has calculated and reported. PMID:24389003

  3. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    DOE PAGESBeta

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivitymore » decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.« less

  4. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    SciTech Connect

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivity decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.

  5. Structural, optical, thermal, photoconductivity, laser damage threshold and fluorescence analysis of an organic material: β-P-amino benzoic acid single crystal

    NASA Astrophysics Data System (ADS)

    Chandran, SenthilKumar; Paulraj, Rajesh; Ramasamy, P.

    2016-02-01

    β-P-amino benzoic acid, an organic single crystal was grown by slow evaporation technique. Single crystal X-ray diffraction studies show that the grown crystal has β-polymorph of P-amino benzoic acid [β-PABA] form and the lattice parameters are a = 6.30 Å, b = 8.61 Å, c = 12.43 Å α = γ = 90° and β = 100.20°. FTIR analysis confirms that bands at 1588 cm-1, 1415 cm-1 are assigned to ring skeletal vibrations of title compound. The molecular structure of the grown crystal has been identified by Nuclear Magnetic Resonance spectral study. The optical absorbance spectrum from 200 to 1100 nm shows that there is an edge absorbance in UV region. Optical band gap of the crystal has been assessed from the absorbance spectrum. The thermal properties of crystals were evaluated from TG-DTA analysis, it exhibits that there is no weight loss up to 187 °C. Laser damage threshold indicates that the grown crystal has no surface damage up to 35 mJ. Photoconductivity and fluorescence spectral experiments are also carried out and the results are discussed.

  6. Dynamical control of the spin transition inside the thermal hysteresis loop of a spin-crossover single crystal

    NASA Astrophysics Data System (ADS)

    Boukheddaden, Kamel; Sy, Mouhamadou; Paez-Espejo, Miguel; Slimani, Ahmed; Varret, François

    2016-04-01

    We have succeeded to achieve experimentally, using an adapted optical microscopy setup, the reversible control of the front transformation between the low-spin (LS)-high-spin (HS) interface in the spin-crossover (SC) single crystal [{Fe(NCSe)(py)2}2(m-bpypz)] undergoing a first-order transition at 112 K with a 7 K hysteresis width. For that, we first generate a phase separation state (a HS/LS interface at equilibrium) inside the hysteresis loop by tuning the light intensity of the microscope. In the second step, this intensity is monitored in such a way to drive, through a photo-heating process, the interface motion. This photo-control is found to be reversible, accurate and requiring a very small amount of energy. In addition the integrity of the crystal is maintained even after a large number of cycling. The experimental observations, are well described as a reaction diffusion process accounting for the front propagation and the photo-heating effects.

  7. Materials Chemistry Issues in the Development of a Single-Crystal Solar/Thermal Refractive Secondary Concentrator

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Biering, Robert C.

    2005-01-01

    A translucent crystal concentrates and transmits energy to a heat exchanger, which in turn heats a propellant gas, working gas of a dynamic power system, or a thermopile. Materials are the limiting issue in such a system. Central is the durability of the crystal, which must maintain the required chemical, physical/optical, and mechanical properties as it is heated and cooled. This report summarizes available data to date on the materials issues with this system. We focus on the current leading candidate materials, which are sapphire (Al2O3) for higher temperatures and silica (SiO2) for lower temperatures. We use data from thermochemical calculations; laboratory coupon tests with silica and sapphire; and system tests with sapphire. The required chemical properties include low-vapor pressure and interfacial stability with supporting structural materials. Optical properties such as transmittance and index of refraction must be maintained. Thermomechanical stability is a major challenge for a large, single-crystal ceramic and has been discussed in another report. In addition to the crystal, other materials in the proposed system include refractory metals (Nb, Ta, Mo, W, and Re), carbon (C), and high-temperature ceramic insulation. The major issue here is low levels of oxygen, which lead to volatile refractory metal oxides and rapid consumption of the refractory metal. Interfacial reactions between the ceramic crystal and refractory metal are also discussed. Finally, high-temperature ceramic insulating materials are also likely to be used in this system. Outgassing is a major issue for these materials. The products of outgassing are typically reactive with the refractory metals and must be minimized.

  8. New organic single crystal of (benzylthio)acetic acid: Synthesis, crystal structure, spectroscopic (ATR-FTIR, 1H and 13C NMR) and thermal characterization

    NASA Astrophysics Data System (ADS)

    Sienkiewicz-Gromiuk, Justyna; Tarasiuk, Bogdan; Mazur, Liliana

    2016-04-01

    (Benzylthio)acetic acid (Hbta) was synthesized with 78% yield from benzyl chloride and thiourea as substrates. Well-shaped crystals of Hbta were grown by slow solvent evaporation technique from pure methanol. The compound was investigated by single-crystal X-ray and powder diffraction techniques and was also characterized by other analytical methods, like ATR-FTIR, 1H and 13C NMR and TG/DSC. The acid molecule adopts bent conformation in the solid state. The crystal structure of Hbta is stabilized by numerous intermolecular interactions, including O-H···O, C-H···O, C-H···S and C-H···π contacts. Thermal decomposition of the obtained material takes place above 150 °C.

  9. Performance of a New Composite Single-Crystal Filtered Thermal Neutron Beam for Neutron Capture Therapy Research at the University of Missouri

    SciTech Connect

    John D. Brockman; David W. Nigg; M. Frederick Hawthorne; Charles McKibben

    2008-11-01

    The University of Missouri (MU) Institute for Nano and Molecular Medicine, the Idaho National Laboratory (INL) and the University of Missouri Research Reactor (MURR) have undertaken a new collaborative research initiative to further the development of improved boron delivery agents for BNCT. The first step of this effort has involved the design and construction of a new thermal neutron beam irradiation facility for cell and small-animal radiobological research at the MURR. In this paper we present the beamline design with the results of pertinent neutronic design calculations. Results of neutronic performance measurements, initiated in February 2008, will also be available for inclusion in the final paper. The new beam will be located in an existing 152.4 mm (6’) diameter MURR beam tube extending from the core to the right in Figure 1. The neutron beam that emanates from the berylium reflector around the reactor is filtered with single-crystal silicon and single-crystal bismuth segments to remove high energy, fission spectrum neutrons and reactor gamma ray contamination. The irradiation chamber is downstream of the bismuth filter section, and approximately 3.95 m from the central axis of the reactor. There is sufficient neutron flux available from the MURR at its rated power of 10 MW to avoid the need for cryogenic cooling of the crystals. The MURR operates on average 150 hours per week, 52 weeks a year. In order to take advantage of 7800 hours of operation time per year the small animal BNCT facility will incorparate a shutter constucuted of boral, lead, steel and polyethylene that will allow experimenters to access the irradiation chamber a few minutes after irradiation. Independent deterministic and stochastic models of the coupled reactor core and beamline were developed using the DORT two-dimensional radiation transport code and the MCNP-5 Monte Carlo code, respectively. The BUGLE-80 47-neutron, 20-gamma group cross section library was employed for the DORT

  10. Single-crystal growth, crystallography, magnetic susceptibility, heat capacity, and thermal expansion of the antiferromagnetic S=1 chain compound CaV[subscript 2]O[subscript 4

    SciTech Connect

    Niazi, A.; Bud'ko, S.L.; Schlagel, D.L.; Yan, J.Q.; Lograsso, T.A.; Kreyssig, A.; Das, S.; Nandi, S.; Goldman, A.I.; Honecker, A.; McCallum, R.W.; Reehuis, M.; Pieper, O.; Lake, B.; Johnston, D.C.

    2009-05-01

    The compound CaV{sub 2}O{sub 4} contains V{sup +3} cations with spin S=1 and has an orthorhombic structure at room temperature containing zigzag chains of V atoms running along the c axis. We have grown single crystals of CaV{sub 2}O{sub 4} and report crystallography, static magnetization, magnetic susceptibility x, ac magnetic susceptibility, heat capacity C{sub p}, and thermal expansion measurements in the temperature T range of 1.8--350 K on the single crystals and on polycrystalline samples. An orthorhombic-to-monoclinic structural distortion and a long-range antiferromagnetic (AF) transition were found at sample-dependent temperatures T{sub S}{approx}108--145 K and T{sub N}{approx}51--76 K, respectively. In two annealed single crystals, another transition was found at {approx}200 K. In one of the crystals, this transition is mostly due to V{sub 2}O{sub 3} impurity phase that grows coherently in the crystals during annealing. However, in the other crystal the origin of this transition at 200 K is unknown. The x(T) shows a broad maximum at {approx}300 K associated with short-range AF ordering and the anisotropy of x above T{sub N} is small. The anisotropic x(T{yields}0) data below T{sub N} show that the (average) easy axis of the AF magnetic structure is the b axis. The C{sub p}(T) data indicate strong short-range AF ordering above T{sub N}, consistent with the x(T) data. We fitted our x data by a J{sub 1}-J{sub 2} S=1 Heisenberg chain model, where J{sub 1}(J{sub 2}) is the (next)-nearest-neighbor exchange interaction. We find J{sub 1}{approx}230 K and surprisingly, J{sub 2}/J{sub 1}{approx}0 (or J{sub 1}/J{sub 2}{approx}0). The interaction J{sub {perpendicular}} between these S=1 chains leading to long-range AF ordering at T{sub N} is estimated to be J{sub {perpendicular}}/J{sub 1}{approx_equal}0.04.

  11. Single Crystal Membranes

    NASA Technical Reports Server (NTRS)

    Stormont, R. W.; Morrison, A.

    1974-01-01

    Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

  12. Effect of fast neutron, gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate single crystals

    NASA Technical Reports Server (NTRS)

    Herley, P. J.; Wang, C. S.; Varsi, G.; Levy, P. W.

    1974-01-01

    The thermal decomposition kinetics have been determined for ammonium perchlorate crystals subjected to a fast neutron irradiation or to a fast neutron irradiation followed by a gamma-ray irradiation. Qualitatively, the radiation induced changes are similar to those obtained in this and in previous studies, with samples exposed only to gamma rays. The induction period is shortened and the rate constants, obtained from an Avrami-Erofeyev kinetic analysis, are modified. The acceleratory period constant increases and the decay period constant decreases. When compared on an equal deposited energy basis, the fast neutron induced changes are appreciably larger than the gamma-ray induced changes. Some, or all, of the fast neutron induced effects might be attributable to the introduction of localized regions of concentrated radiation damage ('spikes') by lattice atom recoils which become thermal decomposition sites when the crystals are heated.

  13. Solid state parameters, structure elucidation, High Resolution X-Ray Diffraction (HRXRD), phase matching, thermal and impedance analysis on L-Proline trichloroacetate (L-PTCA) NLO single crystals

    NASA Astrophysics Data System (ADS)

    Kalaiselvi, P.; Raj, S. Alfred Cecil; Jagannathan, K.; Vijayan, N.; Bhagavannarayana, G.; Kalainathan, S.

    2014-11-01

    Nonlinear optical single crystal of L-Proline trichloroacetate (L-PTCA) was successfully grown by Slow Evaporation Solution Technique (SEST). The grown crystals were subjected to single crystal X-ray diffraction analysis to confirm the structure. From the single crystal XRD data, solid state parameters were determined for the grown crystal. The crystalline perfection has been evaluated using high resolution X-ray diffractometer. The frequencies of various functional groups were identified from FTIR spectral analysis. The percentage of transmittance was obtained from UV Visible spectral analysis. TGA-DSC measurements indicate the thermal stability of the crystal. The dielectric constant, dielectric loss and ac conductivity were measured by the impedance analyzer. The DC conductivity was calculated by the cole-cole plot method.

  14. Crystal growth, structural and thermal studies of amino acids admixtured L-arginine phosphate monohydrate single crystals

    NASA Astrophysics Data System (ADS)

    Anandan, P.; Saravanan, T.; Parthipan, G.; Kumar, R. Mohan; Bhagavannarayana, G.; Ravi, G.; Jayavel, R.

    2011-05-01

    To study the improved characteristics of L-arginine phosphate monohydrate (LAP) crystals, amino acids mixed LAP crystals have been grown by slow cooling method. Amino acids like glycine, L-alanine, and L-valine have been selected for doping. Optical quality bulk crystals have been harvested after a typical growth period of about twenty days. The effect of amino acids in the crystal lattice and molecular vibrational frequencies of various functional groups in the crystals have been studied using X-ray powder diffraction and Fourier Transform infrared (FTIR) analyses respectively. Thermal behavior of the amino acids mixed LAP crystals have been studied from the TG and DTG analyses. High-resolution X-ray diffraction studies have been carried out to find the crystalline nature. Optical transmission studies have been carried out by UV-vis spectrophotometer. The cut off wavelength is below 240 nm for the grown crystals.

  15. Spectroscopic, thermal and mechanical studies on 4-methylanilinium p-toluenesulfonate - a new organic NLO single crystal.

    PubMed

    Shanmugam, G; Brahadeeswaran, S

    2012-09-01

    Bulk crystals of newly identified organic nonlinear optical material 4-methylanilinium p-toluenesulfonate (PMPT) were grown by slow evaporation solution growth method using ethanol as a solvent. It crystallizes in monoclinic system with a noncentrosymmetric space group P2(1). The formation of the title compound was confirmed through microanalysis, X-ray diffraction and density measurements. The proton positions and functional groups have been identified and confirmed through nuclear magnetic resonance and Fourier transform infrared spectrums respectively. Optical properties are determined by UV-Visible and photoluminescence spectroscopic studies to explore its efficacy towards device fabrications. Thermal studies exhibited that the newly obtained PMPT crystals are stable up to 199 °C. Its mechanical strength was studied by Vickers micro hardness studies. PMID:22634406

  16. Phase separation and superconductivity in K1-xFe2-ySe2 single crystals under different thermal treatments

    NASA Astrophysics Data System (ADS)

    Wen, Hai-Hu; Ding, Xiaxin; Tao, Jian; Yang, Huan

    2013-03-01

    Single crystals with the starting composition of K0.8Fe2Se2 have been thermally treated in three different ways: slow furnace cooling (SFC) from 1020 °C, retreated for 2 hours at 250 °C (S250) and 350 °C (S350:) and followed by quenching. The DC magnetization measurements on them exhibit very different behavior: the SFC samples show a tiny diamagnetic signal, while the sample S350 shows a quite large Meissner shielding volume with the S250 in the middle. The resistive measurements on the sample S350 show zero resistance below 31 K with a sharp transition; while those from the sample SFC or S250 show much larger residual resistance together with a much wider transition. By using the SEM, we have successfully identified that, in SFC, the superconducting areas have relatively larger sizes (about one micrometer) and are widely separated; the superconducting area change into many thin but well connected networks in the sample S350, which construct a 3D spider-web. This explains both the magnetic shielding and the resistive transitions in the three samples. In addition, the superconducting area has a composition of about K0.64Fe1.8Se2. We suggest that the thermodynamically stable phase for the superconducting state has probably one vacancy in every 10 Fe-sites.

  17. Investigations on the growth, optical, thermal, dielectric, and laser damage threshold properties of crystal violet dye-doped potassium acid phthalate single crystal

    NASA Astrophysics Data System (ADS)

    Rao, G. Babu; Rajesh, P.; Ramasamy, P.

    2016-03-01

    Influence of crystal violet dye with different concentration on potassium acid phthalate single crystal grown by conventional method has been studied. No change has been observed in the structure, whereas changes have been observed in the external morphology of the crystal when the dyes are incorporated in the crystal lattice. Thermogravimetric and differential thermal analyses show the onset decomposition temperatures to be at 302, 285, 284, and 285 °C for pure, 0.1, 0.3, and 0.5 mol% crystal violet-doped potassium acid phthalate crystals, respectively. The dielectric measurement was carried out on the grown crystals as a function of frequency at various temperatures. In addition, strong luminescent emission bands at 638, 648, and 640 nm were observed in which the relative intensity was found to be reversed as a result of doping concentration. The laser damage threshold value significantly increased for dye-doped crystal in comparison with pure crystal which may make it suitable for the solid-state dye laser applications.

  18. Low interfacial trap density and high-temperature thermal stability in atomic layer deposited single crystal Y2O3/n-GaAs(001)

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Hsun; Fu, Chien-Hua; Lin, Keng-Yung; Chen, Kuan-Hsiung; Chang, Tsong-Wen; Raynien Kwo, J.; Hong, Minghwei

    2016-08-01

    A low interfacial trap density (D it) of 2.2 × 1011 eV‑1 cm‑2 has been achieved with an atomic layer deposited (ALD) single crystal Y2O3 epitaxially on n-GaAs(001), along with a small frequency dispersion of 10.3% (2.6%/decade) at the accumulation region in the capacitance–voltage (C–V) curves. The D it and frequency dispersion in the C–V curves in this work are the lowest among all of the reported ALD-oxides on n-type GaAs(001). The D it was measured using the conductance–voltage (G–V) and quasi-static C–V (QSCV) methods. Moreover, the heterostructure was thermally stable with rapid annealing at 900 °C under various durations in He and N2, which has not been achieved in the heterostructures of ALD-Al2O3 or HfO2 on GaAs.

  19. Single-Crystal Springs For Accelerometers

    NASA Technical Reports Server (NTRS)

    Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

    1995-01-01

    Thermal noise reduced, enabling use of smaller proof masses. Spring-and-mass accelerometers in which springs made of single-crystal material being developed. In spring-and-mass accelerometer, proof mass attached to one end of spring, and acceleration of object at other end of spring measured in terms of deflection of spring, provided frequency spectrum of acceleration lies well below resonant frequency of spring-and-proof-mass system. Use of single-crystal spring materials instead of such polycrystalline spring materials as ordinary metals makes possible to construct highly sensitive accelerometers (including seismometers) with small proof masses.

  20. Bioengineering single crystal growth.

    PubMed

    Wu, Ching-Hsuan; Park, Alexander; Joester, Derk

    2011-02-16

    Biomineralization is a "bottom-up" synthesis process that results in the formation of inorganic/organic nanocomposites with unrivaled control over structure, superior mechanical properties, adaptive response, and the capability of self-repair. While de novo design of such highly optimized materials may still be out of reach, engineering of the biosynthetic machinery may offer an alternative route to design advanced materials. Herein, we present an approach using micro-contact-printed lectins for patterning sea urchin embryo primary mesenchyme cells (PMCs) in vitro. We demonstrate not only that PMCs cultured on these substrates show attachment to wheat germ agglutinin and concanavalin A patterns but, more importantly, that the deposition and elongation of calcite spicules occurs cooperatively by multiple cells and in alignment with the printed pattern. This allows us to control the placement and orientation of smooth, cylindrical calcite single crystals where the crystallographic c-direction is parallel to the cylinder axis and the underlying line pattern. PMID:21265521

  1. Upper critical fields and thermally-activated transport of Nd(0.7Fe0.3) FeAs single crystal

    SciTech Connect

    Balakirev, Fedor F; Jaroszynski, J; Hunte, F; Balicas, L; Jo, Youn - Jung; Raicevic, I; Gurevich, A; Larbalestier, D C; Fang, L; Cheng, P; Jia, Y; Wen, H H

    2008-01-01

    We present measurements of the resistivity and the upper critical field H{sub c2} of Nd(O{sub 0.7}F{sub 0.3})FeAs single crystals in strong DC and pulsed magnetic fields up to 45 T and 60 T, respectively. We found that the field scale of H{sub c2} is comparable to {approx}100 T of high T{sub c} cuprates. H{sub c2}(T) parallel to the c-axis exhibits a pronounced upward curvature similar to what was extracted from earlier measurements on polycrystalline samples. Thus this behavior is indeed an intrinsic feature of oxypnictides, rather than manifestation of vortex lattice melting or granularity. The orientational dependence of H{sub c2} shows deviations from the one-band Ginzburg-Landau scaling. The mass anisotropy decreases as T decreases, from 9.2 at 44K to 5 at 34K. Spin dependent magnetoresistance and nonlinearities in the Hall coefficient suggest contribution to the conductivity from electron-electron interactions modified by disorder reminiscent that of diluted magnetic semiconductors. The Ohmic resistivity measured below T{sub c} but above the irreversibility field exhibits a clear Arrhenius thermally activated behavior over 4--5 decades. The activation energy has very different field dependencies for H{parallel}ab and H{perpendicular}ab. We discuss to what extent different pairing scenarios can manifest themselves in the observed behavior of H{sub c2}, using the two-band model of superconductivity. The results indicate the importance of paramagnetic effects on H{sub c2}(T), which may significantly reduce H{sub c2}(0) as compared to H{sub c2}(0) {approx}200--300 T based on extrapolations of H{sub c2}(T) near T{sub c} down to low temperatures.

  2. Investigations on the spin-glass state in Dy0.5Sr0.5MnO3 single crystals through structural, magnetic and thermal properties

    NASA Astrophysics Data System (ADS)

    Harikrishnan, S.; Naveen Kumar, C. M.; Bhat, H. L.; Elizabeth, Suja; Rößler, U. K.; Dörr, K.; Rößler, S.; Wirth, S.

    2008-07-01

    Single crystals of Dy0.5Sr0.5MnO3 are grown using the optical floating zone technique, and their structural, magnetic, transport and thermal properties have been investigated. Magnetization measurements under field-cooled and zero-field-cooled conditions display irreversibility below 35 K. The magnetization does not saturate up to fields of 5 T in the temperature range 5-350 K. AC susceptibility shows a cusp around 32 K that shifts to higher temperature with increasing frequency. This frequency dependence of the peak temperature follows a critical slowing down with exponent zν = 3.6. Electrical resistivity shows insulating behavior, and the application of magnetic fields up to 10 T does not change this qualitative behavior. However, a marked negative magnetoresistance is observed in the paramagnetic phase reaching 80% at 70 K and 10 T. The observed resistivity behavior does not obey an activated type of conduction. These features are characteristic of spin-glass behavior in this half-doped insulating manganite. It is argued that the spin-glass-like state originates from the A-site disorder, which in turn results from the random distribution of cations with different ionic radii. Specific-heat measurements reveal a sizable linear contribution at low temperature that may be associated with the glassy magnetic ordering and a Schottky-like anomaly in a wide temperature range between 8 and 40 K. The distribution of Schottky levels is explained by the inhomogeneity of the molecular field in the spin-glass state that leads to variable splitting of the Kramers ground-state doublets in Dy3+.

  3. Diamond based photonic crystal microcavities.

    PubMed

    Tomljenovic-Hanic, S; Steel, M J; de Sterke, C Martijn; Salzman, J

    2006-04-17

    Diamond based technologies offer a material platform for the implementation of qubits for quantum computing. The photonic crystal architecture provides the route for a scalable and controllable implementation of high quality factor (Q) nanocavities, operating in the strong coupling regime for cavity quantum electrodynamics. Here we compute the photonic band structures and quality factors of microcavities in photonic crystal slabs in diamond, and compare the results with those of the more commonly-used silicon platform. We find that, in spite of the lower index contrast, diamond based photonic crystal microcavities can exhibit quality factors of Q=3.0x10(4), sufficient for proof of principle demonstrations in the quantum regime. PMID:19516502

  4. Crystallographic, electronic, thermal, and magnetic properties of single-crystal SrCo2As2

    SciTech Connect

    Pandey, Abhishek; Quirinale, D. G.; Jayasekara, W.; Sapkota, A.; Kim, M. G.; Dhaka, R. S.; Lee, Y.; Heitmann, T. W.; Stephens, P. W.; Ogloblichev, V.; Kreyssig, A.; McQueeney, R. J.; Goldman, A. I.; Kaminski, Adam; Harmon, B. N.; Furukawa, Y.; Johnston, D. C.

    2013-07-01

    In tetragonal SrCo2As2 single crystals, inelastic neutron scattering measurements demonstrated that strong stripe-type antiferromagnetic (AFM) correlations occur at a temperature T = 5 K [W. Jayasekara et al., arXiv:1306.5174] that are the same as in the isostructural AFe2As2 (A = Ca, Sr, Ba) parent compounds of high-Tc superconductors. This surprising discovery suggests that SrCo2As2 may also be a good parent compound for high-Tc superconductivity. Here, structural and thermal expansion, electrical resistivity ρ, angle-resolved photoemission spectroscopy (ARPES), heat capacity Cp, magnetic susceptibility χ, 75As NMR and neutron diffraction measurements of SrCo2As2 crystals are reported together with LDA band structure calculations that shed further light on this fascinating material. The c-axis thermal expansion coefficient αc is negative from 7 to 300 K, whereas αa is positive over this T range. The ρ(T) shows metallic character. The ARPES measurements and band theory confirm the metallic character and in addition show the presence of a flat band near the Fermi energy EF. The band calculations exhibit an extremely sharp peak in the density of states D(EF) arising from a flat dx2-y2 band. A comparison of the Sommerfeld coefficient of the electronic specific heat with χ(T → 0) suggests the presence of strong ferromagnetic itinerant spin correlations which on the basis of the Stoner criterion predicts that SrCo2As2 should be an itinerant ferromagnet, in conflict with the magnetization data. The χ(T) does have a large magnitude, but also exhibits a broad maximum at 115 K suggestive of dynamic short-range AFM spin correlations, in agreement with the neutron scattering data. The measurements show no evidence for any type of phase

  5. Stacking fault, microtopography and thermal decomposition studies of CrxW1-xSe2 (x=0.25, 0.50, 0.75) single crystals

    NASA Astrophysics Data System (ADS)

    Patel, D. D.; Desai, Priyanka; Jani, A. R.

    2014-08-01

    The single crystals of CrxW1-xSe2 (x=0.25, 0.50, 0.75) have been grown by the chemical vapour transport (CVT) technique using iodine as a transporting agent. The structural characterisation of these crystals has been made by the X-ray diffraction (XRD) method. The lattice parameters, unit cell volume, crystallite size, strain and dislocation densities have also been evaluated for these new crystals. The estimation of growth and deformation fault probabilities is further calculated. The grown crystals were examined under an optical zoom microscope for their surface topography. Thermo gravimetry analysis (TGA) and differential thermogravimetry (DTG) were carried for the CVT grown CrxW1-xSe2 single crystals. The different kinetic parameters: entropy, enthalpy and Gibbs free energy were calculated using Piloyan-Novikova (P-N) and Coats-Redfern (C-R) relations.

  6. Fabrication and electrical characterization of three-dimensional graphitic microchannels in single crystal diamond

    NASA Astrophysics Data System (ADS)

    Picollo, F.; Gatto Monticone, D.; Olivero, P.; Fairchild, B. A.; Rubanov, S.; Prawer, S.; Vittone, E.

    2012-05-01

    We report on the systematic characterization of conductive micro-channels fabricated in single-crystal diamond with direct ion microbeam writing. Focused high-energy (˜MeV) helium ions are employed to selectively convert diamond with micrometric spatial accuracy to a stable graphitic phase upon thermal annealing, due to the induced structural damage occurring at the end-of-range. A variable-thickness mask allows the accurate modulation of the depth at which the microchannels are formed, from several μm deep up to the very surface of the sample. By means of cross-sectional transmission electron microscopy (TEM), we demonstrate that the technique allows the direct writing of amorphous (and graphitic, upon suitable thermal annealing) microstructures extending within the insulating diamond matrix in the three spatial directions, and in particular, that buried channels embedded in a highly insulating matrix emerge and electrically connect to the sample surface at specific locations. Moreover, by means of electrical characterization at both room temperature and variable temperature, we investigate the conductivity and the charge-transport mechanisms of microchannels obtained by implantation at different ion fluences and after subsequent thermal processes, demonstrating that upon high-temperature annealing, the channels implanted above a critical damage density convert into a stable graphitic phase. These structures have significant impact for different applications, such as compact ionizing radiation detectors, dosimeters, bio-sensors and more generally diamond-based devices with buried three-dimensional all-carbon electrodes.

  7. Single crystal XRD, vibrational spectra, quantum chemical and thermal studies on a new semi-organic crystal: 4-Aminium antipyrine chloride

    NASA Astrophysics Data System (ADS)

    Chitradevi, A.; Suresh Kumar, S.; Athimoolam, S.; Asath Bahadur, S.; Sridhar, B.

    2015-11-01

    The new semi-organic crystal of 4-aminium antipyrine chloride was grown as a single crystal by slow evaporation solution growth method. The crystal and molecular structure of the grown crystal was determined by single crystal diffraction techniques. The single crystal XRD studies reveal that the phenyl ring and pyrazolone ring of the cation has been inclined at an angle of 52.3 (1)°. The molecular aggregations were stabilized through intricate three dimensional hydrogen bonding network formed by the classical N-H⋯O and N-H⋯Cl hydrogen bonds. The cationic dimer R22(10) motif formed through N-H⋯O intermolecular hydrogen bonds was observed around the inversion center of the unit cell. The amino group from the cation and the chlorine anion was linked through N-H⋯Cl intermolecular hydrogen bond leading to a R24 (8) ring motif. These two ring motifs were extended along the a-axis of the unit cell and forms a hydrophilic layer at z = 0 and 1, which is sandwiched between the hydrophobic layer at z = 1/2. Geometry optimization of the molecules was done by Density Functional Theory (DFT) using the B3LYP function and Hartree-Fock (HF) level with 6-311++G(d,p) basis set. The optimized molecular geometry and computed vibrational spectra were compared with experimental results which show a significant agreement. The natural bond orbital (NBO) analysis was carried out to interpret hyperconjucative interaction and intramolecular charge transfer (ICT). The chemical hardness, electro-negativity and chemical potential of the molecule were carried out by HOMO-LUMO plot. The lower band gap value of the frontier orbitals shows the possible bioactivity of the molecule.

  8. Structural, thermal, laser damage, photoconductivity, NLO and mechanical properties of modified vertical Bridgman method grown AgGa0.5In0.5Se2 single crystal

    NASA Astrophysics Data System (ADS)

    Vijayakumar, P.; Ramasamy, P.

    2016-08-01

    AgGa0.5In0.5Se2 single crystal was grown using modified vertical Bridgman method. The structural perfection of the AgGa0.5In0.5Se2 single crystal has been analyzed by high-resolution X-ray diffraction rocking curve measurements. The structural and compositional uniformities of AgGa0.5In0.5Se2 were studied using Raman scattering spectroscopy at room temperature. The FWHM of the Γ1 (W1) and Γ5L (Γ15) measured at different regions of the crystal confirms that the composition throughout its length is fairly uniform. Thermal properties of the as-grown crystal, including specific heat, thermal diffusivity and thermal conductivity have been investigated. The multiple shot surface laser damage threshold value was measured using Nd:YAG laser. Photoconductivity measurements with different temperatures have confirmed the positive photoconducting behavior. Second harmonic generation (SHG) on powder samples has been measured using the Kurtz and Perry technique and the results display that AgGa0.5In0.5Se2 is a phase-matchable NLO material. The hardness behavior has been measured using Vickers micro hardness measurement and the indentation size effect has been observed. The classical Meyer's law, propositional resistance model and modified propositional resistance model have been used to analyse the micro hardness behavior.

  9. 250 W single-crystal fiber Yb:YAG laser.

    PubMed

    Délen, Xavier; Piehler, Stefan; Didierjean, Julien; Aubry, Nicolas; Voss, Andreas; Ahmed, Marwan Abdou; Graf, Thomas; Balembois, Francois; Georges, Patrick

    2012-07-15

    We demonstrate an Yb:YAG single-crystal fiber laser with 251 W output power in continuous-wave and an optical efficiency of 44%. This performance can be explained by the high overlap between pump and signal beams brought by the pump guiding and by the good thermal management provided by the single-crystal fiber geometry. The oscillator performance with a reflectivity of the output coupler as low as 20% also shows high potential for power amplification. PMID:22825171

  10. Physical properties of superconducting single crystal iron sulfide

    NASA Astrophysics Data System (ADS)

    Rodriguez, Efrain E.; Borg, Christopher K. H.; Zhou, Xiuquan; Paglione, Johnpierre; University of Maryland Collaboration

    Recently, the simple binary tetragonal iron sulfide, FeS, was found to be a superconductor with a Tc = 5 K. We have prepared single crystals of tetragonal iron sulfide through hydrothermal de-intercalation of KxFe2-yS2. The KxFe2-yS2 single crystal precursors were grown by slow cooling of stoichiometric melts of K, Fe and S. The silver, plate-like FeS single crystals were highly crystalline with a superconducting transition temperature (Tc) of 4 K. The high quality of the FeS crystals revealed highly anisotropic nature of the magnetic and electronic properties intrinsic to FeS. The physical properties and thermal stability of single crystal FeS will be discussed in detail.

  11. Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb (Zr0.80Ti0. 20)O3 single crystal

    DOE PAGESBeta

    Frantti, Johannes; Fujioka, Y.; Puretzky, Alexander A.; Xie, Y; Ye, Z. -G.; Parish, Chad M.; Glazer, A. M.

    2014-12-22

    Zirconium-rich lead-zirconate-titanate (PZT) Pb(Zr0.80Ti0.20)O3 single crystal is studied by polarized-Raman scattering experiments as a function of temperature. We show that the crystal possesses complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition. The boundary stabilized the domains which had the same orientation after cyclic heating and cooling up to 773 K. The domains transformed normally to the cubic paraelectric phase, but returned to their original state after cooling. Physical mechanism behind the reversible behavior is related to the strain between the boundary region and domain, which forces the domain to grow similarlymore » after each heating and cooling cycle. Electron backscattering diffraction measurements show that macroscopic domains, lengths scale in hundreds of microns, are divided into regions whose Pb-displacements are not correlated. The results are notably interesting for non-volatile memory development as it implies that the original ferroelectric state can be restored after the material has been transformed to a paraelectric phase. Incoherent Pbdisplacements play a role for polarization switching.« less

  12. Growth of organic benzimidazole (BMZ) single crystal by vertical Bridgman technique and its structural, spectral, thermal, optical, mechanical and dielectric properties

    NASA Astrophysics Data System (ADS)

    Muthuraja, A.; Kalainathan, S.

    2015-09-01

    Benzimidazole (BMZ) single crystal was successfully grown by the vertical Bridgman technique (VBT). The crystal system was identified and lattice parameters have been measured from the powder X-ray diffraction (PXRD) measurement. Fourier transforms infrared spectral studies have been carried out to find out the functional groups of BMZ crystal. The optical transmittance and the cut-off wavelength of BMZ were identified using UV-Vis NIR studies and the cut-off wavelength was found to be 294 nm. The dielectric permittivity and dielectric loss as a function of frequency and temperature was measured for the grown BMZ crystal. Vickers microhardness analysis was carried out to identify the mechanical stability of the grown crystal. Chemical etching study was carried out using different etchants and the etch pit density (EPD) was calculated and compared. The third order nonlinear optical property of BMZ crystal was studied by using Z-scan technique with He-Ne laser (632.8 nm). The magnitude of nonlinear refractive index (n2), nonlinear absorption (β) and third order nonlinear susceptibility (χ3) have been found to be in the range of 10-11 m2/W, 10-4 m/W and 10-5 esu respectively. Photoluminescence spectrum was recorded using a xenon lamp in the range of 330-585 nm and it exhibits ultraviolet light emission.

  13. Thermal energy harvesting from Pb(Zn1/3Nb2/3)0.955Ti0.045O3 single crystals phase transitions

    NASA Astrophysics Data System (ADS)

    Zhu, Hongying; Pruvost, Sébastien; Guyomar, Daniel; Khodayari, Akram

    2009-12-01

    This paper describes the effect of the frequency on energy harvesting in Pb(Zn1/3Nb2/3)0.955Ti0.045O3 single crystals with an Ericsson cycle. At the lowest frequency of 0.01 Hz (which corresponds to the slope for the application of the electric field), the maximum harvested energy was equal to 86 mJ cm-3. With an increase in frequency, the harvested energy demonstrated a nonlinear decrease, and the diminution was particularly rapid at frequencies above the critical frequency of 1 Hz. The inherent mechanism of the frequency effect is discussed in detail. In the present case, the phase transitions due to domain engineering, e.g., R-O during the charge process at low temperature and O-T during the discharging process at high temperature, greatly improved the harvested energy. The study also revealed that various parameters, such as the electric field associated with the phase transition, the polarization relaxation, and polarization variations, influenced the capability of energy harvesting to a certain extent. This capability depended significantly on the electric field frequency. Especially at high frequency, the reduction in the polarization time resulted in an inadequate phase transition, and subsequently gave rise to the coexistence of orthorhombic and rhombohedral phases. This had an adverse effect on the energy harvesting, and consequently, the harvested energy exhibited a decreasing tendency with an increasing electric field. Based on the result of the frequency effect, two asymmetric Ericsson cycles were attempted: an L-H cycle and an H-L cycle. These cycles employed different imposed frequencies at the charge and the discharge of the sample. Both asymmetric cycles agreed well with the performed analysis on the influence of the frequency. The H-L cycle greatly promoted energy harvesting, and its harvested energy reached 106 mJ cm-3, thus corresponding to the most effective energy harvesting cycle for this material.

  14. Stacking fault energy in some single crystals

    NASA Astrophysics Data System (ADS)

    Vora, Aditya M.

    2012-06-01

    The stacking fault energy of single crystals has been reported using the peak shift method. Presently studied all single crystals are grown by using a direct vapor transport (DVT) technique in the laboratory. The structural characterizations of these crystals are made by XRD. Considerable variations are shown in deformation (α) and growth (β) probabilities in single crystals due to off-stoichiometry, which possesses the stacking fault in the single crystal.

  15. Lattice effects in YVO 3 single crystal

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    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 TN=116 K and orbital ordering was reported to appear below TOO=196 K. A first-order structural phase transition takes place at TS=77 K, accompanied by changes in the antiferromagnetic type of ordering as well as in the orbital-ordering type. Our results reveal that the thermal expansion measurement technique is a very powerful tool in order to clearly detect the existence of the above-mentioned transitions. The magnetostriction results point to the stability of the low-temperature-magnetic ground state under such high applied magnetic field.

  16. Single-crystal gallium nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Goldberger, Joshua; He, Rongrui; Zhang, Yanfeng; Lee, Sangkwon; Yan, Haoquan; Choi, Heon-Jin; Yang, Peidong

    2003-04-01

    Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an `epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200nm and wall thicknesses of 5-50nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

  17. Micro- and nanostructures in lithium niobate single crystals doped with lanthanides

    SciTech Connect

    Palatnikov, M. N. Shcherbina, O. B.; Sidorov, N. V.; Bormanis, K.

    2010-09-15

    Lithium niobate single crystals doped with lanthanides (Gd, Er) and nominally pure single crystals of congruent and stoichiometric compositions have been grown under time-dependent thermal conditions. Regular growth domain microstructures and periodic nanostructures have been investigated by optical microscopy and atomic force microscopy with a step from 10 to 100 nm. Comparative investigations of the Raman spectra of lithium niobate single crystals of different compositions have been performed.

  18. Coupled theoretical interpretation and experimental investigation of the anisotropy of the lattice thermal conductivity of Bi{sub 2}Te{sub 3} single crystal

    SciTech Connect

    Jacquot, A.; Bayer, B.; Winkler, M.; Boettner, H.; Jaegle, M.

    2012-09-15

    The Debye model is modified for the calculation of the lattice thermal conductivity and used to gain insight into the anisotropy of Bi{sub 2}Te{sub 3}. In this work, the Debye temperature is not used to estimate the cutoff frequencies of the phonons that carry heat. The cutoff frequencies are defined by setting an upper limit to the energy of acoustic phonons using the complete dispersion relations. The anisotropy of the thermal conductivity is found to be unrelated to the anisotropy of the sound velocities. It is found that the sound velocity is almost isotropic when the longitudinal and two transversal waves are added together. In addition the relaxation time must be a function of the cutoff frequencies and counterbalances the anisotropy arising from the variation of the number of acoustic phonons traveling in various directions. It is concluded that the anisotropy of the thermal conductivity is mostly related to the Grueneisen's constant. - Graphical abstract: Dispersion relations of Bi{sub 2}Te{sub 3} along c-axis. The cutoff frequencies are found to be anisotropic and are defined exactly in this article where the acoustic branch crosses the optical branch. This affects both the number of phonons that carry heat in a given direction and the number of phonons that can scatter them. This is decisive for understanding the lattice thermal conductivity. Highlights: Black-Right-Pointing-Pointer Prediction of the anisotropy of the lattice thermal conductivity. Black-Right-Pointing-Pointer Provide a definition of the cutoff frequencies that makes sense. Black-Right-Pointing-Pointer Reduction of the number of frees parameter in phenomenological model. Black-Right-Pointing-Pointer Prediction that the anisotropy is a function of the scattering mechanism. Black-Right-Pointing-Pointer Means of experimental verification of theory.

  19. Fabrication of diamond based sensors for use in extreme environments

    DOE PAGESBeta

    Samudrala, Gopi K.; Moore, Samuel L.; Vohra, Yogesh K.

    2015-04-23

    Electrical and magnetic sensors can be lithographically fabricated on top of diamond substrates and encapsulated in a protective layer of chemical vapor deposited single crystalline diamond. This process when carried out on single crystal diamond anvils employed in high pressure research is termed as designer diamond anvil fabrication. These designer diamond anvils allow researchers to study electrical and magnetic properties of materials under extreme conditions without any possibility of damaging the sensing elements. We describe a novel method for the fabrication of designer diamond anvils with the use of maskless lithography and chemical vapor deposition in this paper. This methodmore » can be utilized to produce diamond based sensors which can function in extreme environments of high pressures, high and low temperatures, corrosive and high radiation conditions. Here, we demonstrate applicability of these diamonds under extreme environments by performing electrical resistance measurements during superconducting transition in rare earth doped iron-based compounds under high pressures to 12 GPa and low temperatures to 10 K.« less

  20. Fabrication of diamond based sensors for use in extreme environments

    SciTech Connect

    Samudrala, Gopi K.; Moore, Samuel L.; Vohra, Yogesh K.

    2015-04-23

    Electrical and magnetic sensors can be lithographically fabricated on top of diamond substrates and encapsulated in a protective layer of chemical vapor deposited single crystalline diamond. This process when carried out on single crystal diamond anvils employed in high pressure research is termed as designer diamond anvil fabrication. These designer diamond anvils allow researchers to study electrical and magnetic properties of materials under extreme conditions without any possibility of damaging the sensing elements. We describe a novel method for the fabrication of designer diamond anvils with the use of maskless lithography and chemical vapor deposition in this paper. This method can be utilized to produce diamond based sensors which can function in extreme environments of high pressures, high and low temperatures, corrosive and high radiation conditions. Here, we demonstrate applicability of these diamonds under extreme environments by performing electrical resistance measurements during superconducting transition in rare earth doped iron-based compounds under high pressures to 12 GPa and low temperatures to 10 K.

  1. Growth and characterization of organic single crystal benzyl carbamate

    NASA Astrophysics Data System (ADS)

    Bala Solanki, S. Siva; Perumal, Rajesh Narayana; Suthan, T.; Bhagavannarayana, G.

    2015-10-01

    Benzyl carbamate single crystal is grown by a solution and vertical Bridgman technique for the first time. The cell parameters and morphologies are assessed from single crystal X-ray diffraction analysis. High resolution X-ray diffraction analysis indicates the crystalline perfection of the grown benzyl carbamate crystal. Fourier Transforms Infrared spectroscopy study has been applied to arrive at the different functional groups. Thermo gravimetric analysis and differential scanning calorimetry are used to study its thermal behavior. The microhardness test is carried out and the load dependent hardness is measured.

  2. Hg-1212 and Hg-1223 single crystals: Synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Gatt, R.; Olsson, E.; Morawski, A.; Lada, T.; Paszewin, A.; Bryntse, I.; Grishin, A. M.; Eeltsev, Yu.; Berastegui, P.; Johansson, L.-G.

    1997-02-01

    Single crystals of HgBa 2CaCu 2O 6+δ (Hg-1212) and HgBa 2Ca 2Cu 3O 8+δ (Hg-1223) were grown from the melt at an argon pressure of 10 kbar. Electron microscopy, as well as single crystal X-ray diffraction studies show that the crystals are well ordered. The EDS analysis indicates the presence of a minor amount of other cations replacing Hg, Ba and Ca in the structure. Refined fractional coordinates and thermal parameters are given for a crystal of Hg-1223 type. Magnetic and resistive measurements show a Tc of 133 K for the Hg-1223 phase.

  3. Apparatus And Method For Producing Single Crystal Metallic Objects

    DOEpatents

    Huang, Shyh-Chin; Gigliotti, Jr., Michael Francis X.; Rutkowski, Stephen Francis; Petterson, Roger John; Svec, Paul Steven

    2006-03-14

    A mold is provided for enabling casting of single crystal metallic articles including a part-defining cavity, a sorter passage positioned vertically beneath and in fluid communication with the part-defining cavity, and a seed cavity positioned vertically beneath and in fluid communication with the sorter passage. The sorter passage includes a shape suitable for encouraging a single crystal structure in solidifying molten metal. Additionally, a portion of the mold between the sorter passage and the part-defining cavity includes a notch for facilitating breakage of a cast article proximate the notch during thermal stress build-up, so as to prevent mold breakage or the inclusion of part defects.

  4. Development of single crystal membranes

    NASA Technical Reports Server (NTRS)

    Stormont, R. W.; Cocks, F. H.

    1972-01-01

    The design and construction of a high pressure crystal growth chamber was accomplished which would allow the growth of crystals under inert gas pressures of 2 MN/sq m (300 psi). A novel crystal growth technique called EFG was used to grow tubes and rods of the hollandite compounds, BaMgTi7O16, K2MgTi7O16, and tubes of sodium beta-alumina, sodium magnesium-alumina, and potassium beta-alumina. Rods and tubes grown are characterized using metallographic and X-ray diffraction techniques. The hollandite compounds are found to be two or three-phase, composed of coarse grained orientated crystallites. Single crystal c-axis tubes of sodium beta-alumina were grown from melts containing excess sodium oxide. Additional experiments demonstrated that crystals of magnesia doped beta-alumina and potassium beta-alumina also can be achieved by this EFG technique.

  5. Single Crystal Synthesis and STM Studies of High Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Barrientos, Alfonso

    1997-01-01

    This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

  6. Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films. PMID:21673933

  7. Thermal properties and radiation damage in NaNH[sub 4]XO[sub 4][center dot]2H[sub 2]O single crystals (XO[sub 4] = SO[sub 4], SeO[sub 4])

    SciTech Connect

    Hilczer, B.; Szczepanska, L. ); Piskunowicz, P. ); Darwish, H.G. )

    1992-07-01

    Differential thermal analysis (DTA) studies of NaNH[sub 4]SO[sub 4][center dot]2H[sub 2]O, NaND[sub 4]SO[sub 4][center dot]2H[sub 2]O, and NANH[sub 4]SeO[sub 4][center dot]2H[sub 2]O single crystals were performed in the temperature range of the ferroelectric-paraelectric phase transition and of the dehydration process. The first-order phase transition at the Curie point was confirmed for NaNH[sub 4]SO[sub 4][center dot]2H[sub 2]O, whereas the transition in the isomorphous NaNH[sub 4]SeO[sub 4][center dot]2H[sub 2]O at the Curie temperature was found to be similar to a continuous (second order) with considerable higher transition enthalpy. Dehydration process of the crystals studied was found to proceed in two stages, with maximum dehydration rates at [approximately]355 and [approximately]400 K. A linear decrease in thermal energy related to the long-range ordering in NaNH[sub 4]SO[sub 4][center dot]2H[sub 2]O crystals was observed with the dose of [gamma]-cobalt-60 irradiation and discussed with respect to the radiation induced decrease in spontaneous polarization. 17 refs., 5 figs., 2 tabs.

  8. Isotropic behavior of an anisotropic material: single crystal silicon

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.; Paquin, Roger A.

    2013-09-01

    Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si

  9. Advanced single crystal for SSME turbopumps

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.

    1989-01-01

    The objective of this program was to evaluate the influence of high thermal gradient casting, hot isostatic pressing (HIP) and alternate heat treatments on the microstructure and mechanical properties of a single crystal nickel base superalloy. The alloy chosen for the study was PWA 1480, a well characterized, commercial alloy which had previously been chosen as a candidate for the Space Shuttle Main Engine high pressure turbopump turbine blades. Microstructural characterization evaluated the influence of casting thermal gradient on dendrite arm spacing, casting porosity distribution and alloy homogeneity. Hot isostatic pressing was evaluated as a means of eliminating porosity as a preferred fatigue crack initiation site. The alternate heat treatment was chosen to improve hydrogen environment embrittlement resistance and for potential fatigue life improvement. Mechanical property evaluation was aimed primarily at determining improvements in low cycle and high cycle fatigue life due to the advanced processing methods. Statistically significant numbers of tests were conducted to quantitatively demonstrate life differences. High thermal gradient casting improves as-cast homogeneity, which facilitates solution heat treatment of PWA 1480 and provides a decrease in internal pore size, leading to increases in low cycle and high cycle fatigue lives.

  10. A Coupled Thermal, Fluid Flow, and Solidification Model for the Processing of Single-Crystal Alloy CMSX-4 Through Scanning Laser Epitaxy for Turbine Engine Hot-Section Component Repair (Part I)

    NASA Astrophysics Data System (ADS)

    Acharya, Ranadip; Bansal, Rohan; Gambone, Justin J.; Das, Suman

    2014-12-01

    Scanning laser epitaxy (SLE) is a new laser-based additive manufacturing technology under development at the Georgia Institute of Technology. SLE is aimed at the creation of equiaxed, directionally solidified, and single-crystal deposits of nickel-based superalloys through the melting of alloy powders onto superalloy substrates using a fast scanning Nd:YAG laser beam. The fast galvanometer control movement of the laser (0.2 to 2 m/s) and high-resolution raster scanning (20 to 200 µm line spacing) enables superior thermal control over the solidification process and allows the production of porosity-free, crack-free deposits of more than 1000 µm thickness. Here, we present a combined thermal and fluid flow model of the SLE process applied to alloy CMSX-4 with temperature-dependent thermo-physical properties. With the scanning beam described as a moving line source, the instantaneous melt pool assumes a convex hull shape with distinct leading edge and trailing edge characteristics. Temperature gradients at the leading and trailing edges are of order 2 × 105 and 104 K/m, respectively. Detailed flow analysis provides insights on the flow characteristics of the powder incorporating into the melt pool, showing velocities of order 1 × 10-4 m/s. The Marangoni effect drives this velocity from 10 to 15 times higher depending on the operating parameters. Prediction of the solidification microstructure is based on conditions at the trailing edge of the melt pool. Time tracking of solidification history is incorporated into the model to couple the microstructure prediction model to the thermal-fluid flow model, and to predict the probability of the columnar-to-equiaxed transition. Qualitative agreement is obtained between simulation and experimental result.

  11. Single crystals for welding research

    SciTech Connect

    David, S.A.; Boatner, L.A.

    1991-01-01

    Most welds last for many years, but a few fail after a relatively short time. Knowing the reasons why welds fail is important because cracks in welds can threaten the safety of people in buildings, airplanes, ships, automobiles, and power plants. Bad welds can lead to costly, extended shutdowns of industrial facilities such as petroleum refineries. Thus, research on this very important fabrication technology is critical to the multibillion-dollar welding industry. Research at ORNL and elsewhere strives to determine the structural features that make some welds strong and others weak. The goals are to find cost-effective ways to characterize the structure and strength of a new weld, correctly predict whether it will last a long time, and determine the welding conditions most likely to produce high-quality welds. There is more to welding than meets the eye. The cracks that make welds fail result from the complexities of microstructures formed during welding. Thus weld microstructure is linked to weld properties such as mechanical strength. As the hot weld material cools from a liquid into a solid, the crystalline grains grow at different speeds and in different directions, forming a new microstructure. By using single crystals rather than polycrystalline alloys to study different weld microstructures, scientists at ORNL have developed a way to predict more accurately the microstructures of various welds. The results could guide welders in providing the right conditions (correct welding speed, heat input, and weld thickness) for producing safer, higher-quality, and longer-lasting welds.

  12. Large magnetic penetration depth and thermal fluctuations in a superconducting Ca10(Pt3As8)[(Fe1 xPtx)2As2]5 (x = 0.097) single crystal

    SciTech Connect

    Kim J.; Nazaretski E.; Ronning, F.; Haberkorn, N.; Civale, L.; Ni, N.; Cava, R.J.; Thompson, J.D.; Movshovich, R.

    2012-05-18

    We have measured the temperature dependence of the absolute value of the magnetic penetration depth {lambda}(T) in a Ca{sub 10}(Pt{sub 3}As{sub 8})[(Fe{sub 1-x}Pt{sub x}){sub 2}As{sub 2}]{sub 5} (x = 0.097) single crystal using a low-temperature magnetic force microscope (MFM). We obtain {lambda}{sub ab}(0) {approx} 1000 nm via extrapolating the data to T = 0. This large {lambda} and pronounced anisotropy in this system are responsible for large thermal fluctuations and the presence of a liquid vortex phase in this low-temperature superconductor with a critical temperature of 11 K, consistent with the interpretation of the electrical transport data. The superconducting parameters obtained from {lambda} and coherence length {zeta} place this compound in the extreme type II regime. Meissner responses (via MFM) at different locations across the sample are similar to each other, indicating good homogeneity of the superconducting state on a submicron scale.

  13. Metal-ion directed synthesis of N2O2 type chelate complexes of Ni(II), Cu(II) and Zn(II): spectral, thermal and single crystal studies.

    PubMed

    Yadav, Seema; Ahmad, Musheer; Siddiqi, K S

    2012-12-01

    A set of Ni(II), Cu(II) and Zn(II) complexes of Schiff base have been synthesized by one pot condensation reaction of 2-hydroxy-4-methoxybenzophenone with 1,3-diaminopropane in 1:2:1 molar ratio. They have been characterized by elemental analysis, conductance measurement, thermal analysis (TGA/DTA), FT-IR, (1)H-NMR, EPR spectra, ESI-MS and electronic spectral studies. In order to establish the geometry, a single crystal X-ray structure for [Ni(L)] complex was determined. It crystallizes in monoclinic system having unit cell parameters a=14.015(5)Å, b=13.391(5)Å, c=14.931(5)Å and α=90.000(5)(o), β=112.237(5)(o), γ=90.000(5)(o) with P 2(1)/c space group. No π-π stacking interaction was obtained in molecular packing diagram. A square-planar geometry has been confirmed for Ni(II) complex. Furthermore, on the basis of elemental analysis, IR, UV-visible and EPR data a square-planar geometry for Cu(II) and a distorted octahedral geometry for the Zn(II) complex has been established. In case of Zn(II) complex NO(3)(-) group was found to be coordinated in monodentate fashion. The low molar conductivity values of the complexes measured in chloroform and DMSO suggest their non-ionic nature. PMID:22960327

  14. Metal-ion directed synthesis of N2O2 type chelate complexes of Ni(II), Cu(II) and Zn(II): Spectral, thermal and single crystal studies

    NASA Astrophysics Data System (ADS)

    Yadav, Seema; Ahmad, Musheer; Siddiqi, K. S.

    2012-12-01

    A set of Ni(II), Cu(II) and Zn(II) complexes of Schiff base have been synthesized by one pot condensation reaction of 2-hydroxy-4-methoxybenzophenone with 1,3-diaminopropane in 1:2:1 molar ratio. They have been characterized by elemental analysis, conductance measurement, thermal analysis (TGA/DTA), FT-IR, 1H-NMR, EPR spectra, ESI-MS and electronic spectral studies. In order to establish the geometry, a single crystal X-ray structure for [Ni(L)] complex was determined. It crystallizes in monoclinic system having unit cell parameters a = 14.015(5) Å, b = 13.391(5) Å, c = 14.931(5) Å and α = 90.000(5)o, β = 112.237(5)o, γ = 90.000(5)o with P 21/c space group. No π-π stacking interaction was obtained in molecular packing diagram. A square-planar geometry has been confirmed for Ni(II) complex. Furthermore, on the basis of elemental analysis, IR, UV-visible and EPR data a square-planar geometry for Cu(II) and a distorted octahedral geometry for the Zn(II) complex has been established. In case of Zn(II) complex NO3- group was found to be coordinated in monodentate fashion. The low molar conductivity values of the complexes measured in chloroform and DMSO suggest their non-ionic nature.

  15. Reliability analysis of single crystal NiAl turbine blades

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

    1995-01-01

    As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

  16. Ames Lab 101: Single Crystal Growth

    ScienceCinema

    Schlagel, Deborah

    2014-06-04

    Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

  17. Ames Lab 101: Single Crystal Growth

    SciTech Connect

    Schlagel, Deborah

    2013-09-27

    Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

  18. Ultratough single crystal boron-doped diamond

    DOEpatents

    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.

  19. Mechanisms for tertiary creep of single crystal superalloy

    NASA Astrophysics Data System (ADS)

    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.

  20. Unified constitutive model for single crystal deformation behavior with applications

    NASA Technical Reports Server (NTRS)

    Walker, K. P.; Meyer, T. G.; Jordan, E. H.

    1988-01-01

    Single crystal materials are being used in gas turbine airfoils and are candidates for other hot section components because of their increased temperature capabilities and resistance to thermal fatigue. Development of a constitutive model which assesses the inelastic behavior of these materials has been studied in 2 NASA programs: Life Prediction and Constitutive Models for Engine Hot Section Anisotropic Materials and Biaxial Constitutive Equation Development for Single Crystals. The model has been fit to a large body of constitutive data for single crystal PWA 1480 material. The model uses a unified approach for computing total inelastic strains (creep plus plasticity) on crystallographic slip systems reproducing observed directional and strain rate effects as a natural consequence of the summed slip system quantities. The model includes several of the effects that have been reported to influence deformation in single crystal materials, such as shear stress, latent hardening, and cross slip. The model is operational in a commercial Finite Element code and is being installed in a Boundary Element Method code.

  1. Advanced piezoelectric single crystal based actuators

    NASA Astrophysics Data System (ADS)

    Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.; Smith, Edward; Dong, Shuxiang; Viehland, Dwight; Moore, Jim, Jr.; Patrick, Brian

    2005-05-01

    TRS is developing new actuators based on single crystal piezoelectric materials such as Pb(Zn1/3Nb2/3)1-xTixO3 (PZN-PT) and Pb(Mg1/3Nb2/3)x-1TixO3 (PMN-PT) which exhibit very high piezoelectric coefficients (d33 = 1800-2200 pC/N) and electromechanical coupling factors (k33 > 0.9), respectively, for a variety of applications, including active vibration damping, active flow control, high precision positioning, ultrasonic motors, deformable mirrors, and adaptive optics. The d32 cut crystal plate actuators showed d32 ~ -1600 pC/N, inter-digital electroded (IDE) plate actuators showed effective d33 ~ 1100 pC/N. Single crystal stack actuators with stroke of 10 μm-100 μm were developed and tested at both room temperature and cryogenic temperatures. Flextensional single crystal piezoelectric actuators with either stack driver or plate driver were developed with stroke 70 μm - > 250 μm. For large stroke cryogenic actuation (> 1mm), a single crystal piezomotor was developed and tested at temperature of 77 K-300K and stroke of > 10mm and step resolution of 20 nm were achieved. In order to demonstrate the significance of developed single crystal actuators, modeling on single crystal piezoelectric deformable mirrors and helicopter flap control using single crystal actuators were conducted and the modeling results show that more than 20 wavelength wavefront error could be corrected by using the single crystal deformable mirrors and +/- 5.8 ° flap deflection will be obtained for a 36" flap using single crystal stack actuators.

  2. Single Crystal Sapphire Optical Fiber Sensor Instrumentation

    SciTech Connect

    Anbo Wang; Russell May; Gary R. Pickrell

    2000-10-28

    The goal of this 30 month program is to develop reliable accurate temperature sensors based on single crystal sapphire materials that can withstand the temperatures and corrosive agents present within the gasifier environment. The research for this reporting period has been segregated into two parallel paths--corrosion resistance measurements for single crystal sapphire fibers and investigation of single crystal sapphire sensor configurations. The ultimate goal of this phase one segment is to design, develop and demonstrate on a laboratory scale a suitable temperature measurement device that can be field tested in phase two of the program.

  3. Ion implantation induced blistering of rutile single crystals

    NASA Astrophysics Data System (ADS)

    Xiang, Bing-Xi; Jiao, Yang; Guan, Jing; Wang, Lei

    2015-07-01

    The rutile single crystals were implanted by 200 keV He+ 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+ ion implantation with appropriate fluence and the following thermal annealing.

  4. Fiber-integrated diamond-based magnetometer

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodi; Cui, Jinming; Sun, Fangwen; Song, Xuerui; Feng, Fupan; Wang, Junfeng; Zhu, Wei; Lou, Liren; Wang, Guanzhong

    2013-09-01

    We demonstrated a fiber-integrated diamond-based magnetometer in this paper. In the system, the fluorescence of nitrogen vacancy (NV) centers in nanodiamonds deposited on a tapered fiber was coupled to the tapered fiber effectively and detected at the output end of the fiber. By using this scheme, optically detected electron spin resonance spectra were recorded for single NV centers. The results confirmed that such a tapered fiber-nanodiamond system can act as a magnetometer. Featured with excellent portability, convenient fabrication, and potential for further integration, the constructed system has been demonstrated to be a practical magnetometer prototype.

  5. Single crystal plasticity by modeling dislocation density rate behavior

    SciTech Connect

    Hansen, Benjamin L; Bronkhorst, Curt; Beyerlein, Irene; Cerreta, E. K.; Dennis-Koller, Darcie

    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.

  6. Growth and properties of InP single crystals

    NASA Astrophysics Data System (ADS)

    Dun-fu, Fang; Xiang-xi, Wang; Yong-quan, Xu; Li-tong, Tan

    1984-04-01

    InP single crystals with various dopants including S, Sn, Zn and Fe have been grown successfully by the Czochralski method under high pressure with liquid encapsulation. It is found that by carefully adjusting the thermal symmetry of the heating field and by further improving the quality of the polycrystals and by dehydrating B 2O 3, twin-free InP crystals can be obtained even with a shoulder angle of up to 54°, and defects caused by thermal decomposition appear on the surface of the crystals during pulling. Furthermore, a comparison of the crystal perfection and uniformity between S-doped and Sn-doped InP crystals shows that the quality of the former is better than that of the latter. Dislocation-free Zn-doped p-InP single crystals without precipitates have also been easily obtained when the carrier concentration is greater than 2×10 18 cm -3 and the diameter less than 30 mm. By controlling the iron content, semi-insulating thermally stable single crystals of InP doped with ⩽0.03 wt% of Fe without precipitates and with a homogeneous resistivity can be produced.

  7. Ultrafast dynamics of excitons in tetracene single crystals

    NASA Astrophysics Data System (ADS)

    Birech, Zephania; Schwoerer, Markus; Schmeiler, Teresa; Pflaum, Jens; Schwoerer, Heinrich

    2014-03-01

    Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states Sn on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S1 on a 40 ps timescale. The high energy Davydov component of the S1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.

  8. Ultrafast dynamics of excitons in tetracene single crystals.

    PubMed

    Birech, Zephania; Schwoerer, Markus; Schmeiler, Teresa; Pflaum, Jens; Schwoerer, Heinrich

    2014-03-21

    Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S(n) on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S1 on a 40 ps timescale. The high energy Davydov component of the S1 exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale. PMID:24655187

  9. Nanofluidics of Single-Crystal Diamond Nanomechanical Resonators.

    PubMed

    Kara, V; Sohn, Y-I; Atikian, H; Yakhot, V; Lončar, M; Ekinci, K L

    2015-12-01

    Single-crystal diamond nanomechanical resonators are being developed for countless applications. A number of these applications require that the resonator be operated in a fluid, that is, a gas or a liquid. Here, we investigate the fluid dynamics of single-crystal diamond nanomechanical resonators in the form of nanocantilevers. First, we measure the pressure-dependent dissipation of diamond nanocantilevers with different linear dimensions and frequencies in three gases, He, N2, and Ar. We observe that a subtle interplay between the length scale and the frequency governs the scaling of the fluidic dissipation. Second, we obtain a comparison of the surface accommodation of different gases on the diamond surface by analyzing the dissipation in the molecular flow regime. Finally, we measure the thermal fluctuations of the nanocantilevers in water and compare the observed dissipation and frequency shifts with theoretical predictions. These findings set the stage for developing diamond nanomechanical resonators operable in fluids. PMID:26509332

  10. Growth and characterization of ammonium acid phthalate single crystals

    NASA Astrophysics Data System (ADS)

    Arunkumar, A.; Ramasamy, P.

    2013-04-01

    Ammonium acid phthalate (AAP) has been synthesized and single crystals were grown by slow evaporation solution growth technique. The unit cell parameters were confirmed by single crystal X-ray diffraction analysis and it belongs to orthorhombic system with the space group of Pcab. The high resolution X-ray diffraction studies revealed the crystalline perfection of the grown crystal. The various functional groups of AAP were identified by FT-IR and Raman spectral analyses. Thermal stability of the grown crystals was studied by TGA/DTA. The optical properties of the grown crystals were analyzed by UV-Vis-NIR and photoluminescence spectral studies. The mechanical property of the grown crystal was studied by Vickers microhardness measurement. The growth features of AAP were analyzed by chemical etching.

  11. Ultrafast dynamics of excitons in tetracene single crystals

    SciTech Connect

    Birech, Zephania; Schwoerer, Heinrich; Schwoerer, Markus; Schmeiler, Teresa; Pflaum, Jens

    2014-03-21

    Ultrafast exciton dynamics in free standing 200 nm thin tetracene single crystals were studied at room temperature by femtosecond transient absorption spectroscopy in the visible spectral range. The complex spectrally overlapping transient absorption traces of single crystals were systematically deconvoluted. From this, the ultrafast dynamics of the ground, excited, and transition states were identified including singlet exciton fission into two triplet excitons. Fission is generated through both, direct fission of higher singlet states S{sub n} on a sub-picosecond timescale, and thermally activated fission of the singlet exciton S{sub 1} on a 40 ps timescale. The high energy Davydov component of the S{sub 1} exciton is proposed to undergo fission on a sub-picoseconds timescale. At high density of triplet excitons their mutual annihilation (triplet-triplet annihilation) occurs on a <10 ps timescale.

  12. Diamond-based heat spreaders for power electronic packaging applications

    NASA Astrophysics Data System (ADS)

    Guillemet, Thomas

    As any semiconductor-based devices, power electronic packages are driven by the constant increase of operating speed (higher frequency), integration level (higher power), and decrease in feature size (higher packing density). Although research and innovation efforts have kept these trends continuous for now more than fifty years, the electronic packaging technology is currently facing a challenge that must be addressed in order to move toward any further improvements in terms of performances or miniaturization: thermal management. Thermal issues in high-power packages strongly affect their reliability and lifetime and have now become one of the major limiting factors of power modules development. Thus, there is a strong need for materials that can sustain higher heat flux levels while safely integrating into the electronic package architecture. In such context, diamond is an attractive candidate because of its outstanding thermal conductivity, low thermal expansion, and high electrical resistivity. Its low heat capacity relative to metals such as aluminum or copper makes it however preferable for heat spreading applications (as a heat-spreader) rather than for dissipating the heat flux itself (as a heat sink). In this study, a dual diamond-based heat-spreading solution is proposed. Polycrystalline diamond films were grown through laser-assisted combustion synthesis on electronic substrates (in the U.S) while, in parallel, diamond-reinforced copper-matrix composite films were fabricated through tape casting and hot pressing (in France). These two types of diamond-based heat-spreading films were characterized and their microstructure and chemical composition were related to their thermal performances. Particular emphasize was put on the influence of interfaces on the thermal properties of the materials, either inside a single material (grain boundaries) or between dissimilar materials (film/substrate interface, matrix/reinforcement interface). Finally, the packaging

  13. Growth and optical property of methyl para hydroxybenzoate sodium dihydrate single crystals

    NASA Astrophysics Data System (ADS)

    Karunagaran, N.; Ramasamy, P.

    2013-06-01

    Methyl parahydroxybenzoate sodium dihydrate (MHBN), a novel semiorganic single crystal has been grown by slow evaporation solution technique (SEST). Single crystal of MHBN with the size of 30 × 30 × 10 mm3 has been grown using methanol as a solvent. The crystal structure of MHBN has been confirmed by single crystal X-ray diffraction. The grown crystals were subjected to powder X-ray diffraction studies. The optical transparency was studied using UV-VIS spectrophotometer and it was found that the crystal is having good optical transparency. The mechanical strength of the grown crystal is measured using Vickers microhardness tester. Thermal properties of the MHBN crystals were studied.

  14. Design and fabrication of PIN-PMN-PT single-crystal high-frequency ultrasound transducers.

    PubMed

    Sun, Ping; Zhou, Qifa; Zhu, Benpeng; Wu, Dawei; Hu, Changhong; Cannata, Jonathan M; Tian, Jin; Han, Pengdi; Wang, Gaofeng; Shung, K Kirk

    2009-12-01

    High-frequency PIN-PMN-PT single crystal ultrasound transducers at center frequencies of 35 MHz and 60 MHz were successfully fabricated using lead indium niobate-lead magnesium niobate-lead titanate (0.23PIN- 0.5PMN-0.27PT) single crystal. The new PIN-PMN-PT single crystal has higher coercivity (6.0 kV/cm) and higher Curie temperature (160 degrees C) than PMN-PT crystal. Experimental results showed that the PIN-PMN-PT transducers have similar performance but better thermal stability compared with the PMN-PT transducers. PMID:20040413

  15. Remarkable structural diversity and single-crystal-to-single-crystal transformations in sulfone functionalized lanthanide MOFs

    SciTech Connect

    Neofotistou, Eleftheria; Malliakas, Christos D.; Trikalitis, Pantelis N.

    2010-04-13

    We report the formation of novel open framework lanthanide (La, Ce, Pr and Dy) MOFs using the ligand 4,4{prime}-bibenzoic acid-2,2{prime}-sulfone. In the case of Ce and Pr, an unprecedented single-crystal-to-single-crystal transformation at room temperature was discovered.

  16. Single-Crystal-to-Single-Crystal Transformations in One Dimensional Ag-Eu Helical System

    SciTech Connect

    Cai, Yue-Peng; Zhout, Xiu-Xia; Zhout, Zheng-Yuan; Zhu, Shi-Zheng; Thallapally, Praveen K.; Liu, Jun

    2009-07-06

    Single-crystal-to-single-crystal transformation of 1-D 4d-4f coordination polymers have been investigated for the first time. It displays high selectivity for Mg2+ and can be used as magnesium ion-selective luminescent probe. More importantly, we observed the transformation of meso-helical chain to rac-helical chain as a function of temperature.

  17. Growth of lithium triborate single crystals from molten salt solution under various temperature gradients

    NASA Astrophysics Data System (ADS)

    Guretskii, S. A.; Ges, A. P.; Zhigunov, D. I.; Ignatenko, A. A.; Kalanda, N. A.; Kurnevich, L. A.; Luginets, A. M.; Milovanov, A. S.; Molchan, P. V.

    1995-12-01

    Single crystals of lithium triborate LiB 3O 5 (LBO) have been grown by the top-seeded solution growth method with B 2O 3 as a solvent using different temperature gradients in the zone of crystallization. Optical and nonlinear optical properties of LBO single crystals have been investigated. The influence of post-growth thermal treatment in oxygen atmosphere on the optical properties has been studied.

  18. The growth of Ho:YAG single crystals by Czochralski method and investigating the formed cores

    SciTech Connect

    Hasani Barbaran, J. Ghani Aragi, M. R.; Javaheri, I.; Baharvand, B.; Tabasi, M.; Layegh Ahan, R.; Jangjo, E.

    2015-12-15

    Ho:YAG single crystals were grown by Czochralski technique, and investigated by the X-ray diffraction (XRD) and optical methods. The crystals were cut and polished in order to observe and analyze their cores. It was found that the deviation of the cores formed in the Czochralski grown Ho:YAG single crystals are resulted from non-symmetrical status of thermal insulation around the Iridium crucible.

  19. Graphene single crystals: size and morphology engineering.

    PubMed

    Geng, Dechao; Wang, Huaping; Yu, Gui

    2015-05-13

    Recently developed chemical vapor deposition (CVD) is considered as an effective way to large-area and high-quality graphene preparation due to its ultra-low cost, high controllability, and high scalability. However, CVD-grown graphene film is polycrystalline, and composed of numerous grains separated by grain boundaries, which are detrimental to graphene-based electronics. Intensive investigations have been inspired on the controlled growth of graphene single crystals with the absence of intrinsic defects. As the two most concerned parameters, the size and morphology serve critical roles in affecting properties and understanding the growth mechanism of graphene crystals. Therefore, a precise tuning of the size and morphology will be of great significance in scale-up graphene production and wide applications. Here, recent advances in the synthesis of graphene single crystals on both metals and dielectric substrates by the CVD method are discussed. The review mainly covers the size and morphology engineering of graphene single crystals. Furthermore, recent progress in the growth mechanism and device applications of graphene single crystals are presented. Finally, the opportunities and challenges are discussed. PMID:25809643

  20. Photocurrent multiplication in organic single crystals

    NASA Astrophysics Data System (ADS)

    Hiramoto, Masahiro; Miki, Ayako; Yoshida, Manabu; Yokoyama, Masaaki

    2002-08-01

    A photocurrent multiplication of up to 200 times has been observed in single crystals of naphthalene tetracarboxylic anhydride sandwiched between metal electrodes. Photocurrent multiplication arises from photoinduced electron injection occurring at the crystal/metal interface. The high-speed response of the multiplied photocurrent reached 500 ms.

  1. Nonlinear spectroscopy of C60 single crystal

    NASA Astrophysics Data System (ADS)

    Zamboni, Roberto; Muccini, Michele; Danieli, R.; Taliani, Carlo; Mohn, H.; Muller, W.; ter Meer, Hans-Ulrich

    1994-11-01

    Two-photon excitation measurements of C60 single crystal at 4 K have been performed. The TPE spectrum shows a sharp band at 1.846 eV which is assigned to the C60 lowest forbidden Frenkel singlet exciton of T1g symmetry. This assignment is supported by the analysis of Herzberg-Teller induced photoluminescence.

  2. Environmental Qualification of a Single-Crystal Silicon Mirror for Spaceflight Use

    NASA Technical Reports Server (NTRS)

    Hagopian, John; Chambers, John; Rohrback. Scott; Bly, Vincent; Morell, Armando; Budinoff, Jason

    2013-01-01

    This innovation is the environmental qualification of a single-crystal silicon mirror for spaceflight use. The single-crystal silicon mirror technology is a previous innovation, but until now, a mirror of this type has not been qualified for spaceflight use. The qualification steps included mounting, gravity change measurements, vibration testing, vibration- induced change measurements, thermal cycling, and testing at the cold operational temperature of 225 K. Typical mirrors used for cold applications for spaceflight instruments include aluminum, beryllium, glasses, and glass-like ceramics. These materials show less than ideal behavior after cooldown. Single-crystal silicon has been demonstrated to have the smallest change due to temperature change, but has not been spaceflight-qualified for use. The advantage of using a silicon substrate is with temperature stability, since it is formed from a stress-free single crystal. This has been shown in previous testing. Mounting and environmental qualification have not been shown until this testing.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  4. TEM in-situ study of dislocation motion in B2 NiAl single crystals

    SciTech Connect

    Ghosh, B.; Crimp, M.A.

    1997-12-31

    In an effort to understand dislocation mobility in stoichiometric NiAl single crystals, in-situ tensile deformation experiments have been performed in a transmission electron microscope. Commercially pure and high purity single crystals with <001> and <110> orientations have been examined. Two different thermal treatments were adopted in order to effect the mechanical response. Dislocation motion was observed in all samples. Pre-existing dislocations, either isolated or tangled, were not observed to move at any point leading up to sample failure. Cross-slip of the mobile dislocations was observed in some cases. In commercially pure single crystals, dislocations were found to move at a much slower rate and uniform manner in contrast to motion in high purity single crystals which occurs by rapid jumps.

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

    PubMed

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

    2016-05-01

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

  6. Lattice effects in HoVo 3 single crystal

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    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 TOO=200 K and orders antiferromagnetically at TN=113 K. A first-order structural phase transition takes place at TS˜38 K, which is probably accompanied by change of the OO type and hence the type of antiferromagnetic spin ordering.

  7. Lightweight optical mirrors formed in single crystal substrate

    NASA Technical Reports Server (NTRS)

    Bly, Vincent T. (Inventor)

    2006-01-01

    This invention is directed to a process for manufacturing a lightweight mirror from a single crystal material, such as single crystal silicon. As a near perfect single crystal material, single crystal silicon has much lower internal stress than a conventional material. This means much less distortion of the optical surface during the light weighting process. After being ground and polished, a single crystal silicon mirror is light weighted by removing material from the back side using ultrasonic machining. After the light weighting process, the single crystal silicon mirror may be used as-is or further figured by conventional polishing or ion milling, depending on the application and the operating wavelength.

  8. Structural and optical properties of a new chalcone single crystal

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Poojary, Boja

    2012-09-01

    A new nonlinear optical material 1-(4-methylthiophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one with molecular formula C17H16O2S was synthesized by using the Claisen-Schmidt condensation reaction method. The Various functional groups present in the compound were identified using recorded FT-IR spectrum. The crystal growth parameters have been studied using solubility test and acetone is found to be a very good solvent for the crystal growth at an ambient temperature. The transparent high quality single crystals up to a size of 26×2×2 mm3 were grown using the slow evaporation solution growth technique. UV-visible study was carried out and the spectrum reveals that the crystal is transparent in the entire visible region and absorptive in the UV region. The refractive index is determined using Brewster's angle method. The optical energy band gap of the material is measured using Tauc's plot and the direct method. The single crystal XRD of MMPP crystal shows the following cell parameters: a=5.9626(2) Å, b=15.3022(6) Å, c=16.0385(7) Å, α=β=γ=90°, volume=1463.37(10) Å3 with a space group of Pna21. The compound MMPP exhibits optical nonlinearity (NLO) and its second order NLO efficiency is 3.15 times to that of urea. The effect of functional groups OCH3 and SCH3 on the non-linearity as well as the structural property of the compound has been discussed. The crystal is thermally stable. High NLO efficiency, good thermal stability, good transparency and ability to grow as a high quality single crystal make this material very attractive for opto-electronic applications.

  9. Neutron detection with single crystal organic scintillators

    SciTech Connect

    Zaitseva, N; Newby, J; Hamel, S; Carman, L; Faust, M; Lordi, V; Cherepy, N; Stoeffl, W; Payne, S

    2009-07-15

    Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10-diphenylanthracene and diphenylacetylene.

  10. Biomineralization of nanoscale single crystal hydroxyapatite.

    PubMed

    Omokanwaye, Tiffany; Wilson, Otto C; Gugssa, Ayelle; Anderson, Winston

    2015-11-01

    The chemical and physical characteristics of nanocrystalline hydroxyapatite particles which formed during the subcutaneous implantation of crab shell in Sprague-Dawley rats were studied using selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The initial SAED characterization evidence indicated the presence of an amorphous calcium phosphate phase. The electron dense nanophase particles which formed in the wound healing zone displayed broad diffuse rings which usually indicate a low crystalline order or amorphous phase. High resolution transmission electron microscopy (HRTEM) revealed that these mineralized regions contained discrete single crystal particles less than 5nm in size. Micrographs taken at successively higher magnifications revealed very small nanoparticles with a hexagonal arrangement of ion channels with characteristic spacing of 0.54nm and 0.23nm. This study revealed that single crystal hydroxyapatite nanoparticles consisting of only a few unit cells formed via a biomineralization directed process. PMID:26249568

  11. Neutron detection with single crystal organic scintillators

    NASA Astrophysics Data System (ADS)

    Zaitseva, Natalia P.; Newby, Jason; Hamel, Sebastien; Carman, Leslie; Faust, Michelle; Lordi, Vincenzo; Cherepy, Nerine J.; Stoeffl, Wolfgang; Payne, Stephen A.

    2009-08-01

    Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10- diphenylanthracene and diphenylacetylene.

  12. Single Crystals Grown Under Unconstrained Conditions

    NASA Astrophysics Data System (ADS)

    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).

  13. Macrodeformation Twins in Single-Crystal Aluminum.

    PubMed

    Zhao, F; Wang, L; Fan, D; Bie, B X; Zhou, X M; Suo, T; Li, Y L; Chen, M W; Liu, C L; Qi, M L; Zhu, M H; Luo, S N

    2016-02-19

    Deformation twinning in pure aluminum has been considered to be a unique property of nanostructured aluminum. A lingering mystery is whether deformation twinning occurs in coarse-grained or single-crystal aluminum at scales beyond nanotwins. Here, we present the first experimental demonstration of macrodeformation twins in single-crystal aluminum formed under an ultrahigh strain rate (∼10^{6}  s^{-1}) and large shear strain (200%) via dynamic equal channel angular pressing. Large-scale molecular dynamics simulations suggest that the frustration of subsonic dislocation motion leads to transonic deformation twinning. Deformation twinning is rooted in the rate dependences of dislocation motion and twinning, which are coupled, complementary processes during severe plastic deformation under ultrahigh strain rates. PMID:26943543

  14. Titania single crystals with a curved surface.

    PubMed

    Yang, Shuang; Yang, Bing Xing; Wu, Long; Li, Yu Hang; Liu, Porun; Zhao, Huijun; Yu, Yan Yan; Gong, Xue Qing; Yang, Hua Gui

    2014-01-01

    Owing to its scientific and technological importance, crystallization as a ubiquitous phenomenon has been widely studied over centuries. Well-developed single crystals are generally enclosed by regular flat facets spontaneously to form polyhedral morphologies because of the well-known self-confinement principle for crystal growth. However, in nature, complex single crystalline calcitic skeleton of biological organisms generally has a curved external surface formed by specific interactions between organic moieties and biocompatible minerals. Here we show a new class of crystal surface of TiO₂, which is enclosed by quasi continuous high-index microfacets and thus has a unique truncated biconic morphology. Such single crystals may open a new direction for crystal growth study since, in principle, crystal growth rates of all facets between two normal {101} and {011} crystal surfaces are almost identical. In other words, the facet with continuous Miller index can exist because of the continuous curvature on the crystal surface. PMID:25373513

  15. Titania single crystals with a curved surface

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Yang, Bing Xing; Wu, Long; Li, Yu Hang; Liu, Porun; Zhao, Huijun; Yu, Yan Yan; Gong, Xue Qing; Yang, Hua Gui

    2014-11-01

    Owing to its scientific and technological importance, crystallization as a ubiquitous phenomenon has been widely studied over centuries. Well-developed single crystals are generally enclosed by regular flat facets spontaneously to form polyhedral morphologies because of the well-known self-confinement principle for crystal growth. However, in nature, complex single crystalline calcitic skeleton of biological organisms generally has a curved external surface formed by specific interactions between organic moieties and biocompatible minerals. Here we show a new class of crystal surface of TiO2, which is enclosed by quasi continuous high-index microfacets and thus has a unique truncated biconic morphology. Such single crystals may open a new direction for crystal growth study since, in principle, crystal growth rates of all facets between two normal {101} and {011} crystal surfaces are almost identical. In other words, the facet with continuous Miller index can exist because of the continuous curvature on the crystal surface.

  16. Crack growth in single-crystal silicon

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Leipold, M. H.

    1986-01-01

    Crack growth in single-crystal silicon at room temperature in air was evaluated by double torsion (DT) load-relaxation method and monitored by acoustic emission (AE) technique. Both DT and AE methods indicated lack of subcritical crack growth in silicon. At the critical stress intensity factor, the crack front was found to be jumping several times in a 'mirror' region and then followed by fast crack growth in a 'hackle' region. Hackle marks were found to be associated with plastic deformation at the tip of the fast moving crack. No dislocation etch pits were found in the 'mirror' region, in which crack growth may result from interatomic bonds broken at the crack tip under stress without any plastic deformation. Acoustic emission appears to be spontaneously generated from both interatomic bonds broken and dislocation generation at the moving crack tip during the crack growth in single-crystal silicon.

  17. Oxygen Incorporation in Rubrene Single Crystals

    PubMed Central

    Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

    2014-01-01

    Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed. PMID:24786311

  18. Optimizing Scale Adhesion on Single Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Pint, Bruce A.

    2000-01-01

    To improve scale adhesion, single crystal superalloys have been desulfurized to levels below 1 ppmw by hydrogen annealing. A transition to fully adherent behavior has been shown to occur at a sulfur level of about 0.2 ppmw, as demonstrated for PWA 1480, PWA 1484, and Rene N5 single crystal superalloys in 1100-1150 C cyclic oxidation tests up to 2000 h. Small additions of yttrium (15 ppmw) also have been effective in producing adhesion for sulfur contents of about 5 ppmw. Thus the critical Y/S ratio required for adhesion was on the order of 3-to-1 by weight (1-to-1 atomic), in agreement with values estimated from solubility products for yttrium sulfides. While hydrogen annealing greatly improved an undoped alloy, yielding <= 0.01 ppmw S, it also produced benefits for Y-doped alloys without measurably reducing the sulfur content.

  19. Crack Growth in Single-Crystal Silicon

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Leipold, M. H.

    1986-01-01

    Report describes experiments on crack growth in single-crystal silicon at room temperature in air. Crack growth in (111) cleavage plane of wafers, 50 by 100 by 0.76 mm in dimension, cut from Czochralski singlecrystal silicon studied by double-torsion load-relaxation method and by acoustic-emission measurements. Scanning electron microscopy and X-ray topography also employed. Results aid in design and fabrication of silicon photovoltaic and microelectronic devices.

  20. Ionic diffusion in single crystals of vermiculite

    SciTech Connect

    Maraqah, H.R.

    1993-01-01

    Novel guest-host compounds, based on single crystal vermiculite, were synthesized by diffusive techniques through a new hydrogen vermiculite. Single crystals were chosen because of the ease of characterization. An investigation of the ion transport properties of these single crystals was done to determine the mechanism of conductivity including the predominant charge carrier. Measurements of the ionic conductivity using impedance spectroscopy and X-ray lattice parameters of the ion-exchanged samples strongly suggest that the native cations and not protons are the major current carriers. Single crystals of hydrogen vermiculite were synthesized at room temperature by ion exchange from sodium-vermiculite using 1 molar acetic acid for a one week. Subsequent ion exchange with other cations was found to be much enhanced. Thus transition metals were exchanged in about a week in contrast to the need of several months using previous methods. The ionic conductivity of hydrogen vermiculite was measured and shown to be much lower than that of many other monovalent cations in the same host lattice. Its enthalpy of motion is also much lower. These marked differences suggest that protonic species do not play a significant role in charge transport in these layered materials. These materials were characterized by x-ray powder diffraction, thermogravimetric analysis and acid-base titration. Hydrogen-vermiculite was found to react with organic bases, like methylamine, ethylamine, n-butylamine, n-hexylamine, n-octylamine, n-decylamine, aniline, acrylamide, methacrylaminde, urea, 1,10phenanthroline, and 1,1phenanthroline ferrous sulfate complex, to undergo ion exchange with metal cations like sodium, zinc, copper(II) ions and polymerization reactions could be performed in the galleries of the structure like pyrrole and aniline. Its behavior was compared with that of powdered montmorillonite.

  1. Single crystal diffraction by synchrotron radiation

    SciTech Connect

    Kvick, A.

    1988-01-01

    The tunability and access to short wavelengths in combination with high intensity and the low divergence of the x-ray radiation produced by synchrotron storage rings opens up new and challenging fields for single crystal diffraction. These areas include microcrystal diffraction, studies of time-dependent phenomena, element selective diffraction, studies of materials under extreme conditions, solution of the crystallographic phase problem either by the use of the wavelength dependency of the anomalous scattering or by direct experimental determination of the phases. Single crystal diffraction from proteins and macromolecules using photographic film as a detection medium has already reached considerable maturity, but high-precision data collections using diffractometers at storage rings are still not routine because of the severe requirements for beam stability over extended periods of time. Development work at institutions such as the National Synchrotron Light Source, The Photon Factory, SSRL, CHESS, Hasylab and Daresbury, however, suggest that synchrotron single-crystal diffraction will become an essential part of the research at the synchrotron storage rings in the near future. 9 refs., 2 figs.

  2. Anisotropy of sapphire single crystal sputtering

    SciTech Connect

    Minnebaev, K. F.; Tolpin, K. A.; Yurasova, V. E.

    2015-08-15

    We have studied the spatial distribution of particles sputtered from the base (0001) plane of a sapphire single crystal with trigonal crystalline lattice (α-Al{sub 2}O{sub 3}) that can be considered a superposition of two hexagonal close packed (hcp) structures–the ideal sublattice of oxygen and a somewhat deformed sublattice of aluminum. It is established that the particles sputtered from the base plane of sapphire are predominantly deposited along the sides of an irregular hexagon with spots at its vertices. The patterns of spots have been also studied for sputtering of particles from the (0001) face of a zinc single crystal with the hcp lattice. The spots of sputtered Zn atoms are arranged at the vertices of concentric equilateral hexagons. In both cases, the observed anisotropy of sputtering is related to focused collisions (direct and assisted focusing) and the channeling process. The chemical composition of spots has been determined in various regions of sputtered sapphire deposition. The results are discussed in comparison to analogous earlier data for secondary ion emission from an α-Al{sub 2}O{sub 3} single crystal.

  3. An improved single crystal adsorption calorimeter

    NASA Astrophysics Data System (ADS)

    Stuck, A.; Wartnaby, C. E.; Yeo, Y. Y.; Stuckless, J. T.; Al-Sarraf, N.; King, D. A.

    1996-04-01

    Significant improvements to the single crystal adsorption calorimeter (SCAC) of Borroni-Bird and King are described. The calorimeter comprises a pulsed molecular beam source, an ultrathin single crystal and an infrared detector. It is calibrated using a chopped laser beam, and the amount of gas adsorbed or reacted per pulse is measured using the King and Wells reflection detector technique. Refinements in the molecular beam system, the optical calibration system, flux calibration system and sticking probability measurement technique have been made. The calorimeter response is accurately linear over a useful energy range; the detection limit is estimated as 10 kJ mol -1; and the accuracy in heats of adsorption for heats above ˜ 80 kJ mol -1 is estimated as ˜ 6%. Comparisons of calorimetric heats with isosteric heats and with desorption energies obtained for reversible systems, such as CO on Ni and Pt single crystal surfaces, generally yield good agreement and give support to the estimate for the absolute accuracy of the instrument.

  4. Single crystal cylinder transducers for sonar applications

    NASA Astrophysics Data System (ADS)

    Robinson, Harold; Stevens, Gerald; Buffman, Martin; Powers, James

    2005-04-01

    A segmented cylinder transducer constructed of single crystal lead magnesium niobate-lead titanate (PMN-PT) has been under development at NUWC and EDO Corporation for several years. The purpose of this development was to provide an extremely compact, high power broadband source. By virtue of their extraordinary material properties, ferroelectric single crystals are the ideal transduction material for developing such compact broadband systems. This presentation shall review the evolution of the transducer design as well as present the results of a successful in-water test conducted at NUWC in October of 2003. It shall be shown that design changes intended to eliminate spurious modes limiting the transducer bandwidth first observed in 2002 were successful, resulting in a transducer with a clean frequency response and an effective coupling factor of 0.85. The measured transducer admittance was in nearly exact agreement with theoretical predictions. The NUWC in-water tests demonstrated that the single crystal cylinder achieved an admittance bandwidth (based on the Stansfield criterion) of over 100%, while the tuned power factor was 0.8 or more over 2.5 octaves of frequency. Additionally, the transducer produced 12 dB higher source levels than a similarly sized PZT transducer. [Work sponsored by DARPA.

  5. Growth of shaped single crystals of proteins

    NASA Astrophysics Data System (ADS)

    Moreno, Abel; Rondón, Deyanira; García-Ruiz, Juan Ma.

    1996-09-01

    We present a procedure for obtaining protein single crystals that fill the capillary tubes in which they grow. The implementation was typical of the gel acupuncture method and the four different proteins are used as examples: lysozyme (HEW), thaumatin I, ferritin and insulin. Rod- and prismatic-shaped protein single crystals of these four proteins were grown inside capillary tubes of 0.2, 0.3, 0.5 mm in diameter and, for the case of lysozyme, up to 1.2 mm in diameter. The maximum length measured along the long axes of the rod crystals was 1.6 mm again for lysozyme crystals. It was observed that, once the capillary tube was filled, the crystal continues to grow by diffusion of the precipitating agent throughout the porous network formed by the protein crystal structure. We also discuss the possibility of growing these cylinders of crystalline proteins by the addition of protein solution to the mother liquor through the upper end of the glass capillary while the precipitating agent diffuses through the protein crystal itself. X-ray diffraction patterns confirm the single crystal character of the protein rods.

  6. Single crystal complex oxide on flexible substrate

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Lee, Oukjae; Salahuddin, Sayeef

    Flexible ferroelectrics are needed for various applications such as biocompatible energy harvesting and flexible memory. In this sector, most of the current research is focused on organic piezoelectric materials which have advantage of flexibility but suffers severely from poor energy conversion and generation efficiency. On the contrary, owing to very high electromechanical coupling factor (representing energy conversion efficiency) complex oxides are the best choices as energy harvesting and transduction elements, especially for transforming mechanical energies into electronic energy. Still their usage in energy harvesting is very limited mainly due to the stringent growth conditions of single crystals, high temperature needed for crystallization and lack of flexibility and stretchability. We have shown that single crystal Pb0.8Zr0.2TiO3 can be epitaxially transferred on flexible plastic substrate. The transferred PZT shows 70 uC/cm2 remnant polarization and dielectric constant over 100 even when it is bent. These results suggest the possibility of single crystal complex oxide devices on flexible platform.

  7. Single-crystal disk drive miniactuators

    NASA Astrophysics Data System (ADS)

    Giovanardi, Marco; McKenney, Kevin B.; Rule, John A.; Yoshikawa, Shoko

    2001-08-01

    As hard disk drive areal densities increase at a compound annual growth rate (CAGR) of 60%, disk drives must position the head over increasingly small areas while moving more rapidly to reach the desired position. This results in an increase in vibration disturbance. To meet this demand, many hard disk drive manufactures have created prototype dual-stage actuators employing piezoelectric ceramics for the second stage. These are an attractive means of obtaining higher-bandwidth control due to the low inertia and size of the actuator element. As the technology improves, the next limiting factor will be the amount of displacement obtainable with traditional piezoceramic elements. Under the AXIS (Advanced Crystal Integrated System) Consortium program funded by DARPA, the application of PZN-PT single crystal piezoceramic as a second stage disk drive actuator was studied, based on the fact that the single crystal material provides larger stroke than its traditional PZT counterparts. The transverse (d31) strain of PZN-PT single crystal was measured to be about two times larger than that of PZT-5H ceramic. Both materials were integrated into a disk drive system and compared as second stage actuators. The methodologies used and the servo control techniques applied are also discussed in the paper.

  8. Optical and structural properties of chalcone NLO single crystals

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, P. C.; Ravindrachary, V.; Janardhana, K.; Manjunath, H. R.; Karegouda, Prakash; Crasta, Vincent; Sridhar, M. A.

    2011-11-01

    Organic compound (E)-1-(4-methoxyphenyl)-3-(2,3,5-trichlorophenyl)prop-2-en-1-one [MPTCPP] with molecular formula C 16H 11Cl 3O 2 was synthesized using Claisen-Schmidt condensation reaction method. 1H NMR spectra was recorded to identify the various functional groups present in the compound and confirm the chemical structure. The single crystals were grown using slow evaporation solution growth technique. The UV-Visible spectrum study reveals that the crystal is transparent in the entire visible region and the absorption is observed at 364 nm. The Kurtz powder second harmonic generation (SHG) test shows that the MPTCPP is NLO active and its SHG efficiency is three times that of urea. Single crystal XRD study shows that the compound crystallizes in the monoclinic system with a space group Cc. The corresponding lattice parameters of the crystal are a = 28.215(5) Å, b = 3.9740(4) Å, c = 16.178(3) Å and V = 1503.0(4) Å 3. The micro hardness test was carried out and the work hardening coefficient value ( n) of the crystal was found to be 1.48. This indicates that the crystal is hard and is suitable for device application. The thermal study reveals that the thermal stability of the crystal is good.

  9. Gallium arsenide single crystal solar cell structure and method of making

    NASA Technical Reports Server (NTRS)

    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.

  10. Shock response of He bubbles in single crystal Cu

    NASA Astrophysics Data System (ADS)

    Li, B.; Wang, L.; E, J. C.; Ma, H. H.; Luo, S. N.

    2014-12-01

    With large-scale molecular dynamics simulations, we investigate shock response of He nanobubbles in single crystal Cu. For sufficient bubble size or internal pressure, a prismatic dislocation loop may form around a bubble in unshocked Cu. The internal He pressure helps to stabilize the bubble against plastic deformation. However, the prismatic dislocation loops may partially heal but facilitate nucleation of new shear and prismatic dislocation loops. For strong shocks, the internal pressure also impedes internal jetting, while a bubble assists local melting; a high speed jet breaks a He bubble into pieces dispersed among Cu. Near-surface He bubbles may burst and form high velocity ejecta containing atoms and small fragments, while the ejecta velocities do not follow the three-dimensional Maxwell-Boltzmann distributions expected for thermal equilibrium. The biggest fragment size deceases with increasing shock strength. With a decrease in ligament thickness or an increase in He bubble size, the critical shock strength required for bubble bursting decreases, while the velocity range, space extension and average velocity component along the shock direction, increase. Small bubbles are more efficient in mass ejecting. Compared to voids and perfect single crystal Cu, He bubbles have pronounced effects on shock response including bubble/void collapse, Hugoniot elastic limit (HEL), deformation mechanisms, and surface jetting. HEL is the highest for perfect single crystal Cu with the same orientations, followed by He bubbles without pre-existing prismatic dislocation loops, and then voids. Complete void collapse and shear dislocations occur for embedded voids, as opposed to partial collapse, and shear and possibly prismatic dislocations for He bubbles. He bubbles lower the threshhold shock strength for ejecta formation, and increase ejecta velocity and ejected mass.

  11. Shock response of He bubbles in single crystal Cu

    SciTech Connect

    Li, B.; Wang, L.; E, J. C.; Luo, S. N.; Ma, H. H.

    2014-12-07

    With large-scale molecular dynamics simulations, we investigate shock response of He nanobubbles in single crystal Cu. For sufficient bubble size or internal pressure, a prismatic dislocation loop may form around a bubble in unshocked Cu. The internal He pressure helps to stabilize the bubble against plastic deformation. However, the prismatic dislocation loops may partially heal but facilitate nucleation of new shear and prismatic dislocation loops. For strong shocks, the internal pressure also impedes internal jetting, while a bubble assists local melting; a high speed jet breaks a He bubble into pieces dispersed among Cu. Near-surface He bubbles may burst and form high velocity ejecta containing atoms and small fragments, while the ejecta velocities do not follow the three-dimensional Maxwell-Boltzmann distributions expected for thermal equilibrium. The biggest fragment size deceases with increasing shock strength. With a decrease in ligament thickness or an increase in He bubble size, the critical shock strength required for bubble bursting decreases, while the velocity range, space extension and average velocity component along the shock direction, increase. Small bubbles are more efficient in mass ejecting. Compared to voids and perfect single crystal Cu, He bubbles have pronounced effects on shock response including bubble/void collapse, Hugoniot elastic limit (HEL), deformation mechanisms, and surface jetting. HEL is the highest for perfect single crystal Cu with the same orientations, followed by He bubbles without pre-existing prismatic dislocation loops, and then voids. Complete void collapse and shear dislocations occur for embedded voids, as opposed to partial collapse, and shear and possibly prismatic dislocations for He bubbles. He bubbles lower the threshhold shock strength for ejecta formation, and increase ejecta velocity and ejected mass.

  12. Method of Promoting Single Crystal Growth During Melt Growth of Semiconductors

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua (Inventor)

    2013-01-01

    The method of the invention promotes single crystal growth during fabrication of melt growth semiconductors. A growth ampoule and its tip have a semiconductor source material placed therein. The growth ampoule is placed in a first thermal environment that raises the temperature of the semiconductor source material to its liquidus temperature. The growth ampoule is then transitioned to a second thermal environment that causes the semiconductor source material in the growth ampoule's tip to attain a temperature that is below the semiconductor source material's solidus temperature. The growth ampoule so-transitioned is then mechanically perturbed to induce single crystal growth at the growth ampoule's tip.

  13. Single crystal and polycrystalline CVD diamond for demanding optical applications

    NASA Astrophysics Data System (ADS)

    Dodson, J. M.; Brandon, J. R.; Dhillon, H. K.; Friel, I.; Geoghegan, S. L.; Mollart, T. P.; Santini, P.; Scarsbrook, G. A.; Twitchen, D. J.; Whitehead, A. J.; Wilman, J. J.; de Wit, H.

    2011-06-01

    Diamond's extremely wide transparency, combined with its other exceptional properties including hardness, strength and thermal conductivity make it a desirable material for optical windows. Polycrystalline diamond grown by chemical vapour deposition (CVD) has become the preferred window material for high power CO2 laser systems since its development in the 1990s. The range and availability of diamond materials is expanding, and in recent years has been extended to include CVD single crystal diamond. This paper reviews the quality of these materials, looking at optical scatter and absorption around 1 and 10 microns, along with their thermal and mechanical properties. We also discuss selection of appropriate grades and how they may best be integrated into demanding optical applications.

  14. Chemical vapor deposition of graphene single crystals.

    PubMed

    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

  15. Characterization of zinc selenide single crystals

    NASA Technical Reports Server (NTRS)

    Gerhardt, Rosario A.

    1996-01-01

    ZnSe single crystals of high quality and low impurity levels are desired for use as substrates in optoelectronic devices. This is especially true when the device requires the formation of homoepitaxial layers. While ZnSe is commercially available, it is at present extremely expensive due to the difficulty of growing single crystal boules with low impurity content and the resultant low yields. Many researchers have found it necessary to heat treat the crystals in liquid Zn in order to remove the impurities, lower the resistivity and activate the photoluminescence at room temperature. The physical vapor transport method (PVT) has been successfully used at MSFC to grow many single crystals of II-VI semiconducting materials including ZnSe. The main goal at NASA has been to try to establish the effect of gravity on the growth parameters. To this effect, crystals have been grown vertically upwards or horizontally. Both (111) and (110) oriented ZnSe crystals have been obtained via unseeded PVT growth. Preliminary characterization of the horizontally grown crystals has revealed that Cu is a major impurity and that the low temperature photoluminescence spectra is dominated by the copper peak. The ratio of the copper peak to the free exciton peak is being used to determine variations in composition throughout the crystal. It was the intent of this project to map the copper composition of various crystals via photoluminescence first, then measure their electrical resistivity and capacitance as a function of frequency before proceeding with a heat treatment designed to remove the copper impurities. However, equipment difficulties with the photoluminescence set up, having to establish a procedure for measuring the electrical properties of the as-grown crystals and time limitations made us re-evaluate the project goals. Vertically grown samples designated as ZnSe-25 were chosen to be measured electrically since they were not expected to show as much variation in their

  16. Single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

    1974-01-01

    The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

  17. Growth rate study of canavalin single crystals

    NASA Technical Reports Server (NTRS)

    Demattei, R. C.; Feigelson, R. S.

    1989-01-01

    The dependence on supersaturation of the growth rate of single crystals of the protein canavalin is studied. In the supersaturation ranges studied, the rate-limiting step for growth is best described by a screw dislocation mechanism associated with interface attachment kinetics. Using a ln-ln plot, the growth-rate data is found to fit a predictive relationship of the form G = 0.012 x the supersaturation to the 6.66, which, together with the solubility curves, allows the growth rate to be estimated under a variety of conditions.

  18. Charge transport in single crystal organic semiconductors

    NASA Astrophysics Data System (ADS)

    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

  19. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

  20. Growth and characterization of diammonium copper disulphate hexahydrate single crystal

    SciTech Connect

    Siva Sankari, R.; Perumal, Rajesh Narayana

    2014-03-01

    Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a function of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function

  1. Growth and studies of cyclohexylammonium 4-methoxy benzoate single crystal for nonlinear optical applications

    SciTech Connect

    Sathya, P.; Gopalakrishnan, R.

    2015-06-24

    Cyclohexylammonium 4-Methoxy Benzoate (C4MB) was synthesised and the functional groups were confirmed by FTIR analysis. The purified C4MB (by repeated recrystallisation) was used for single crystal growth. Single crystal of cyclohexylammonium 4-methoxy benzoate was successfully grown by slow evaporation solution growth method at ambient temperature. Structural orientations were determined from single crystal X-ray diffractometer. Optical absorption and cut off wavelength were identified by UV-Visible spectroscopy. Thermal stability of the crystal was studied from thermogravimetric and differential thermal analyses curves. Mechanical stability of the grown crystal was analysed by Vicker’s microhardness tester. The Second Harmonic Generation (SHG) study revealed that the C4MB compound exhibits the SHG efficiency 3.3 times greater than KDP crystal.

  2. Growth and properties of new nonlinear LiKB 4O 7 single crystals

    NASA Astrophysics Data System (ADS)

    Adamiv, V. T.; Burak, Ya. V.; Teslyuk, I. M.

    2006-03-01

    Successful growth of new nonlinear LiKB 4O 7 single crystals by the Czochralsky technique are reported. Peculiarities of thermal expansion and its influence on the post-growth cooling have been analyzed. The LiKB 4O 7 single crystal is optically biaxial, n>n>n, and the optical axes are located in plane (0 0 1); bisector of acute angle between these ( ϕ˜56°) coincides with crystallographic axis [0 1 0]. Coefficients of thermal expansion at 293 K: α=16×10 K, α=11×10 K, α=12×10 K and β=39×10 K. The Moose hardness is equal to 5. Second harmonic generation has been observed in LiKB 4O 7 single crystal.

  3. Single crystal growth and characterization of holmium tartrate trihydrate

    NASA Astrophysics Data System (ADS)

    Want, Basharat; Ahmad, Farooq; Kotru, P. N.

    2007-02-01

    The growth of holmium tartrate trihydrate (HTT) single crystals is achieved in organic (agar-agar) as well as in inorganic (silica) gels by single gel diffusion method. Results of the study on nucleation kinetics of crystals grown in silica gel are described. The crystals exhibit the morphological form of a tetragonal dipyramidal class with {0 0 1} and {1 1 1} as dominant faces. Elemental and thermogravimetric analysis (TGA) supplemented by energy dispersive analysis of X-rays (EDAX) support the suggested chemical formula of the grown crystals to be [Ho (C 4H 4O 6) (C 4H 5O 6)·3H 2O]. Single crystal X-ray diffraction (XRD) studies indicate that the crystals belong to tetragonal system with the cell parameters a=5.97 Å, c=36.09 Å, bearing the space group P4 1. Fourier transform infrared (FT-IR) spectroscopic study indicates the presence of tartrate ligands and suggests that one of the tartrate ions is singly ionized. TGA suggests that the material is thermally stable up to 220 °C.

  4. OSL studies of alkali fluoroperovskite single crystals for radiation dosimetry

    NASA Astrophysics Data System (ADS)

    Daniel, D. Joseph; Raja, A.; Madhusoodanan, U.; Annalakshmi, O.; Ramasamy, P.

    2016-08-01

    This paper presents a preliminary investigation of the optically stimulated luminescence (OSL) of alkali fluoroperovskite single crystals for radiation dosimetry. The perovskite-like KMgF3, NaMgF3 and LiBaF3 polycrystalline compounds doped with rare earths (Eu2+ and Ce3+) were synthesized by standard solid state reaction technique. Phase purity of the synthesized compounds was analyzed by powder X-ray diffraction technique. Single crystals of these compounds have been grown from melt by using vertical Bridgman-Stockbarger method. The Linearly Modulated OSL and Continuous Wave OSL measurements were performed in these alkali fluorides using blue light stimulation. Thermal bleaching experiments have shown that OSL signals originate from traps which are unstable near 200 °C, thus proving the suitability of the signals for dosimetric purposes. Optical bleaching measurements were also performed for these fluoride samples. OSL dose response was studied as a function of dose which was found to increase with beta dose.

  5. Shear mode properties of single crystal ferroelectrics

    NASA Astrophysics Data System (ADS)

    McLaughlin, E. A.; Robinson, H. C.

    2003-10-01

    Single crystal ferroelectrics or piezocrystals were recently introduced into the electroactive materials community. The 33-mode electromechanical coupling factor of piezocrystals is typically greater than 0.90, which is significantly larger than typical values for piezoelectric ceramics (0.62-0.74). For sonar projector applications this large k33 has been responsible for more than doubling the bandwidth of active sonar arrays over what is currently achievable with ceramics. Last year a crystal grower produced a cut of lead magnesium niobate-lead titanate (PMN-PT) single crystal with piezoelectric shear coefficient values of 7000 pm/V and shear coupling factors of 0.97. (For PZT5H, d15 is 730 pm/V.) This piezocrystal d15 coefficient implies significantly improved sensitivity and signal-to-noise ratio for accelerometers and hydrophones, while the high coupling promises bandwidth increases greater than those realized in 33-mode projectors using piezocrystals. This research studies the shear-mode behavior of PMN-PT piezocrystals for use in sensors and projectors. By measuring the response of the materials to high and low level electrical bias and excitation fields, frequency, and temperature, the materials' effective material properties as a function of these operational variables were determined. [Work sponsored by ONR and NUWC ILIR.

  6. Infrared investigations of 4-hydroxycyanobenzene single crystals.

    PubMed

    Capria, E; Benevoli, L; Perucchi, A; Fraboni, B; Tessarolo, M; Lupi, Stefano; Fraleoni-Morgera, A

    2013-08-01

    4-Hydroxycyanobenzene (4HCB) single crystals (SCs) and polycrystals (PCs) have been analyzed by means of both unpolarized and linearly polarized (LP) infrared (IR) beams. Most of the signals found at room temperature (298 K) were assigned to well-defined vibrational modes. Using an LP-IR beam and keeping the beam polarization aligned with either the a or the b crystal axis, anisotropic spectra of SCs were also attributed. The differences between the LP and unpolarized spectra of SCs are discussed in view of spatially anisotropic vibronic couplings between the benzenic π electrons and the molecular functional groups (FGs), with reference to the overall lattice arrangement and the polarizability of the FGs. In addition, signals suggesting the low-concentration presence of tautomers within the crystal were detected. LP-IR measurements of SCs in the temperature range between 298 and 120 K are also reported and discussed, with particular reference to the hydrogen-bonding-related functional groups of 4HCB, allowing the assignment of OH bending signals that were otherwise not clearly attributable and the inference of an anisotropic shrinking of the crystals. Overall, the presented results show that LP-IR spectroscopy is a valuable tool for noncontact, nondestructive characterization of organic semiconducting single crystals. PMID:23829587

  7. Oscillatory reactions on single crystal surfaces

    NASA Astrophysics Data System (ADS)

    Imbihl, R.

    1993-12-01

    Heterogeneous catalytic reactions exhibit under certain conditions kinetic oscillations which have been investigated both with polycrystalline materials and with single crystal surfaces as catalysts. The present paper reviews single-crystal experiments conducted under isothermal, low pressure conditions ( p < 10 -3 mbar). Two different reaction systems have been investigated: catalytic CO oxidation on various Pt and Pd orientations and catalytic NO reduction on Pt(100) using CO, H 2, or NH 3 as the reducing agent. The different reaction systems exhibit a wide variety of interesting phenomena which are well-known in nonlinear dynamics, for example, such as spatiotemporal pattern formation, the existence of Turing structures and the appearance of deterministic chaos, and chemical turbulence. The mechanistic steps leading to the observed phenomena have been investigated and appropriate mathematical models have been formulated and analyzed using bifurcation theory. The driving force for the rate oscillations has been shown to result from structural changes of the substrate in the case of catalytic CO oxidation on Pt surfaces, subsurface oxygen formation in the case of catalytic CO oxidation on Pd surfaces, and in the chemical reaction network described by a vacancy model in the case of the NO reduction reactions.

  8. Constitutive modeling for single crystal superalloys

    NASA Technical Reports Server (NTRS)

    Stouffer, D. C.; Jayaraman, N.; Sheh, M.; Alden, D.

    1986-01-01

    The inelastic response of single crystal gamma/gamma prime superalloys is quite different from the behavior of polycrystalline nickel base superalloys. Upto a critical temperature the yield stress of single crystal alloys is a function of the material orientation relative to the direction of the applied stress and the material exhibits significant tension/compression asymmetry. This behavior is primarily due to slip on the octahedral slip system. Above the critical temperature there is a sharp drop in the yield stress, cube slip becomes more predominant and the tension/compression asymmetry is reduced. Similar orientation and tension/compression asymmetry is observed in creep and secondary creep above the critical temperature is inferred to occur by octahedral slip. There are two exceptions to this behavior. First, loading near the (111) orientation exhibits cube slip at all temperatures, and; second, loading near the (001) orientation produces only octahedral slip at all temperatures. The constitutive model is based on separating the total global strain into elastic and inelastic components. This model is developed and briefly discussed.

  9. A nanoporous two-dimensional polymer by single-crystal-to-single-crystal photopolymerization

    NASA Astrophysics Data System (ADS)

    Kissel, Patrick; Murray, Daniel J.; Wulftange, William J.; Catalano, Vincent J.; King, Benjamin T.

    2014-09-01

    In contrast to the wide number and variety of available synthetic routes to conventional linear polymers, the synthesis of two-dimensional polymers and unambiguous proof of their structure remains a challenge. Two-dimensional polymers—single-layered polymers that form a tiling network in exactly two dimensions—have potential for use in nanoporous membranes and other applications. Here, we report the preparation of a fluorinated hydrocarbon two-dimensional polymer that can be exfoliated into single sheets, and its characterization by high-resolution single-crystal X-ray diffraction analysis. The procedure involves three steps: preorganization in a lamellar crystal of a rigid monomer bearing three photoreactive arms, photopolymerization of the crystalline monomers by [4 + 4] cycloaddition, and isolation of individual two-dimensional polymer sheets. This polymer is a molecularly thin (~1 nm) material that combines precisely defined monodisperse pores of ~9 Å with a high pore density of 3.3 × 1013 pores cm-2. Atomic-resolution single-crystal X-ray structures of the monomer, an intermediate dimer and the final crystalline two-dimensional polymer were obtained and prove the single-crystal-to-single-crystal nature and molecular precision of the two-dimensional photopolymerization.

  10. Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb (Zr0.80Ti0. 20)O3 single crystal

    SciTech Connect

    Frantti, Johannes; Fujioka, Y.; Puretzky, Alexander A.; Xie, Y; Ye, Z. -G.; Parish, Chad M.; Glazer, A. M.

    2014-12-22

    Zirconium-rich lead-zirconate-titanate (PZT) Pb(Zr0.80Ti0.20)O3 single crystal is studied by polarized-Raman scattering experiments as a function of temperature. We show that the crystal possesses complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition. The boundary stabilized the domains which had the same orientation after cyclic heating and cooling up to 773 K. The domains transformed normally to the cubic paraelectric phase, but returned to their original state after cooling. Physical mechanism behind the reversible behavior is related to the strain between the boundary region and domain, which forces the domain to grow similarly after each heating and cooling cycle. Electron backscattering diffraction measurements show that macroscopic domains, lengths scale in hundreds of microns, are divided into regions whose Pb-displacements are not correlated. The results are notably interesting for non-volatile memory development as it implies that the original ferroelectric state can be restored after the material has been transformed to a paraelectric phase. Incoherent Pbdisplacements play a role for polarization switching.

  11. Experimental dynamic metamorphism of mineral single crystals

    USGS Publications Warehouse

    Kirby, S.H.; Stern, L.A.

    1993-01-01

    This paper is a review of some of the rich and varied interactions between non-hydrostatic stress and phase transformations or mineral reactions, drawn mainly from results of experiments done on mineral single crystals in our laboratory or our co-authors. The state of stress and inelastic deformation can enter explicitly into the equilibrium phase relations and kinetics of mineral reactions. Alternatively, phase transformations can have prominent effects on theology and on the nature of inelastic deformation. Our examples represent five types of structural phase changes, each of which is distinguished by particular mechanical effects. In increasing structural complexity, these include: (1) displacive phase transformations involving no bond-breaking, which may produce anomalous brittle behavior. A primary example is the a-?? quartz transition which shows anomalously low fracture strength and tertiary creep behavior near the transition temperature; (2) martensitic-like transformations involving transformation strains dominated by shear deformation. Examples include the orthoenstatite ??? clinoenstatite and w u ??rtzite ??? sphalerite transformations; (3) coherent exsolution or precipitation of a mineral solute from a supersaturated solid-solution, with anisotropy of precipitation and creep rates produced under nonhydrostatic stress. Examples include exsolution of corundum from MgO ?? nAl2O3 spinels and Ca-clinopyroxene from orthopyroxene; (4) order-disorder transformations that are believed to cause anomalous plastic yield strengthening, such as MgO - nAl2O3 spinels; and (5) near-surface devolatilization of hydrous silicate single-crystals that produces a fundamental brittleness thought to be connected with dehydration at microcracks at temperatures well below nominal macroscopic dehydration temperatures. As none of these interactions between single-crystal phase transformations and non-hydrostatic stress is understood in detail, this paper serves as a challenge to

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Path to meter class single crystal silicon (SCSi) space optics

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.

    2012-03-01

    With the global financial crisis affecting funding for space systems development, customers are calling for lower cost systems. Yet, at the same time, these lower cost systems must have increased thermal response to operational environments and load survivability. We submit that single crystal silicon (SCSi) meets both of these requirements. This paper will highlight some key SCSi material properties, discuss the opportunities that led to the development of McCarter processing methods, and present the latest steps in the manufacturing path of McCarter Mirrors using SCSi, GFB (glass frit bonding) and MSF (McCarter super finish), including the concept drawing of a one meter SCSi lightweight mirror, which together sets up the last step toward a lower cost, high performing one meter SCSi space optic.

  14. Electrical conduction in nanodomains in congruent lithium tantalate single crystal

    SciTech Connect

    Cho, Yasuo

    2014-01-27

    The electrical current flow behavior was investigated for nanodomains formed in a thin congruent lithium tantalate (LiTaO{sub 3}) single-crystal plate. When the nanodomains were relatively large, with diameters of about 100 nm, current flow was detected along the domain wall. However, when they were about 40 nm or smaller, the current flowed through the entire nanodomain. Schottky-like rectifying behavior was observed. Unlike the case of LiNbO{sub 3}, optical illumination was not required for current conduction in LiTaO{sub 3}. A clear temperature dependence of the current was found indicating that the conduction mechanism for nanodomains in LiTaO{sub 3} may involve thermally activated carrier hopping.

  15. Cloning polymer single crystals through self-seeding

    NASA Astrophysics Data System (ADS)

    Xu, Jianjun; Ma, Yu; Hu, Wenbing; Rehahn, Matthias; Reiter, Günter

    2009-04-01

    In general, when a crystal is molten, all molecules forget about their mutual correlations and long-range order is lost. Thus, a regrown crystal does not inherit any features from an initially present crystal. Such is true for materials exhibiting a well-defined melting point. However, polymer crystallites have a wide range of melting temperatures, enabling paradoxical phenomena such as the coexistence of melting and crystallization. Here, we report a self-seeding technique that enables the generation of arrays of orientation-correlated polymer crystals of uniform size and shape (`clones') with their orientation inherited from an initial single crystal. Moreover, the number density and locations of these cloned crystals can to some extent be predetermined through the thermal history of the starting crystal. We attribute this unique behaviour of polymers to the coexistence of variable fold lengths in metastable crystalline lamellae, typical for ordering of complex chain-like molecules.

  16. Growth and characterization of nonlinear optical single crystal: Nicotinic L-tartaric

    SciTech Connect

    Sheelarani, V.; Shanthi, J.

    2015-06-24

    Nonlinear optical single crystals were grown from Nicotinic and L-Tartaric acid by slow evaporation technique at room temperature. Structure of the grown crystal was confirmed by single crystal X-ray diffraction studies, The crystallinity of the Nicotinic L-Tartaric (NLT) crystals was confirmed from the powder XRD pattern. The transparent range and cut off wavelength of the grown crystal was studied by the UV–Vis spectroscopic analysis.The thermal stability of the crystal was studied by TG-DTA. The second harmonic generation (SHG) efficiency of NLT was confirmed by Kurtz Perry technique.

  17. Growth of Bulk Single Crystals of Dicyanovinyl-Ansiole and its Derivatives for Nonlinear Optical Applications

    NASA Technical Reports Server (NTRS)

    Gebre, T.; Choi, J.; Wang, W. S.; Metzl, R.; Aggarwal, M. D.; Romero, Melvin; Clark, Ronald D.; Penn, Benjamin G.; Frazier, Donald O.

    1998-01-01

    Bulk single crystals of a series of thermally stable nonlinear optical organic materials, Dicyanovinyl-anisole (DIVA) and their methoxy derivatives, have been successfully grown using the Bridgman-Stockbarger technique. The growth conditions are chosen to be temperature gradient of 5 to 10 C/cm and lowering rate of 0.1 to 0.3 mm/h. Single crystals of DIVA and its derivatives, of 8 x 8 x 50 cu mm in size, have been grown while maintaining a flat solid-liquid growth interface.

  18. Studies on novel single crystals of tri-nitrophenol methyl p-hydroxybenzoate

    NASA Astrophysics Data System (ADS)

    Vesta, C.; Uthrakumar, R.; Vinitha, G.; Ramalingam, A.; Jerome Das, S.

    2009-08-01

    Good quality single crystal of tri-nitrophenol methyl p-hydroxybenzoate (TNMPHB) has been successfully grown from aqueous solution by a slow evaporation technique. Single-crystal X-ray diffraction analysis confirms that the crystal formed by crystallizing in triclinic system with space group P1¯ is of a new kind. The functional groups of the compound are confirmed qualitatively by FT-IR spectral analysis. An optical absorption study on this sample reveals the minimum absorption region is well suited for optical applications. Thermal analysis carried out on the compound reveals that the sample is stable up to 187 °C.

  19. Iron-based composition for magnetocaloric effect (MCE) applications and method of making a single crystal

    DOEpatents

    Evans, III, Boyd Mccutchen; Kisner, Roger A.; Ludtka, Gail Mackiewicz; Ludtka, Gerard Michael; Melin, Alexander M.; Nicholson, Donald M.; Parish; , Chad M.; Rios, Orlando; Sefat, Athena S.; West, David L.; Wilgen, John B.

    2016-02-09

    A method of making a single crystal comprises heating a material comprising magnetic anisotropy to a temperature T sufficient to form a melt of the material. A magnetic field of at least about 1 Tesla is applied to the melt at the temperature T, where a magnetic free energy difference .DELTA.G.sub.m between different crystallographic axes is greater than a thermal energy kT. While applying the magnetic field, the melt is cooled at a rate of about 30.degree. C./min or higher, and the melt solidifies to form a single crystal of the material.

  20. Low-cobalt single crystal Rene 150

    NASA Technical Reports Server (NTRS)

    Scheuermann, C. M.

    1982-01-01

    The effects of cobalt content on a single crystal version of the advanced, high gamma prime content turbine airfoil alloy Rene 150 were investigated. Cobalt contents under investigation include 12 wt.% (composition level of Rene 150), 6 wt.%, and 0 wt.%. Preliminary test results are presented and compared with the properties of standard DS Rene 150. DTA results indicate that the liquidus goes through a maximum of about 1435 C near 6 wt.% Co. The solidus remains essentially constant at 1390 C with decreasing Co content. The gamma prime solvus appears to go through a minimum of about 1235 C near 6 wt.% Co content. Preliminary as-cast tensile and stress rupture results are presented along with heat treat schedules and future test plans.

  1. Hydrogen Annealing Of Single-Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Schaeffer, John C.; Murphy, Wendy

    1995-01-01

    Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.

  2. Shock Hugoniot of Single Crystal Copper

    SciTech Connect

    Chau, R; Stolken, J; Asoka-Kumar, P; Kumar, M; Holmes, N C

    2009-08-28

    The shock Hugoniot of single crystal copper is reported for stresses below 66 GPa. Symmetric impact experiments were used to measure the Hugoniots of three different crystal orientations of copper, [100], [110], [111]. The photonic doppler velocimetry (PDV) diagnostic was adapted into a very high precision time of arrival detector for these experiments. The measured Hugoniots along all three crystal directions were nearly identical to the experimental Hugoniot for polycrystalline Cu. The predicted orientation dependence of the Hugoniot from MD calculations was not observed. At the lowest stresses, the sound speed in Cu was extracted from the PDV data. The measured sound speeds are in agreement with values calculated from the elastic constants for Cu.

  3. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

    Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

    1973-01-01

    Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

  4. Single-crystal superalloy drives turbine advances

    SciTech Connect

    Harris, K.

    1995-04-01

    In searching for ways to improve power-to-weight ratios and fuel efficiency, gas turbine engine manufacturers invest heavily in the development and testing of new alloys. Their goal is to find turbine airfoil materials that can handle the higher operating temperatures, increased component stresses, and faster rotational speeds that are needed to increase turbine performance. Major turbine engine manufacturers find they can achieve these objectives through ultra-high performance, single-crystal superalloys -- a group of nickel-base materials that exhibit outstanding strength and surface stability at temperatures up to 85{percent} of their melting points. One such superalloy is CMSX-4, co-engineered by ingot maker Cannon-Muskegon and turbine engine manufacturers Rolls-Royce and Allison Engine Company. It is currently being used in such applications as Allison`s advanced airfoil programs.

  5. Single crystal functional oxides on silicon

    PubMed Central

    Bakaul, Saidur Rahman; Serrao, Claudy Rayan; Lee, Michelle; Yeung, Chun Wing; Sarker, Asis; Hsu, Shang-Lin; Yadav, Ajay Kumar; Dedon, Liv; You, Long; Khan, Asif Islam; Clarkson, James David; Hu, Chenming; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2016-01-01

    Single-crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism and so on that have the potential for completely new electronic applications. Direct synthesis of such oxides on silicon remains challenging because of the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces. Here we report integration of thin (down to one unit cell) single crystalline, complex oxide films onto silicon substrates, by epitaxial transfer at room temperature. In a field-effect transistor using a transferred lead zirconate titanate layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single-crystal functional oxides on-demand on silicon. PMID:26853112

  6. Submicron diameter single crystal sapphire optical fiber

    SciTech Connect

    Hill, Cary; Homa, Daniel; Liu, Bo; Yu, Zhihao; Wang, Anbo; Pickrell, Gary

    2014-10-02

    In this work, a submicron-diameter single crystal sapphire optical fiber was demonstrated via wet acid etching at elevated temperatures. Etch rates on the order 2.3 µm/hr were achievable with a 3:1 molar ratio sulfuric-phosphoric acid solution maintained at a temperature of 343°C. A sapphire fiber with an approximate diameter of 800 nm was successfully fabricated from a commercially available fiber with an original diameter of 50 µm. The simple and controllable etching technique provides a feasible approach to the fabrication of unique waveguide structures via traditional silica masking techniques. The ability to tailor the geometry of sapphire optical fibers is the first step in achieving optical and sensing performance on par with its fused silica counterpart.

  7. Single-crystal AlN nanonecklaces.

    PubMed

    Wang, Huatao; Xie, Zhipeng; Wang, Yiguang; Yang, Weiyou; Zeng, Qingfeng; Xing, Feng; An, Linan

    2009-01-14

    Distinct single-crystal aluminum nitride nanonecklaces with uniform [1011] faceted beads are synthesized via catalyst-assisted nitriding of Al. The detailed morphology and structure of the nanonecklaces have been characterized. The growth process has been investigated by comparing the products obtained at different synthesis times. The results reveal that the formation of the nanonecklaces is via a process consisting of facet formation and bead unification. The formation of the [1011] facets is due to the presence of a liquid phase that lowers the surface tension of otherwise high-energy [1011] planes. The bead unification is driven by minimizing the energy contributed by surface energy and electrostatic energy. The unique morphology of the nanonecklaces could be useful for studying fundamental physical phenomena and fabricating nanodevices. PMID:19417280

  8. Electrical switching in cadmium boracite single crystals

    NASA Technical Reports Server (NTRS)

    Takahashi, T.; Yamada, O.

    1981-01-01

    Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

  9. Cutting fluid study for single crystal silicon

    SciTech Connect

    Chargin, D.

    1998-05-05

    An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.

  10. Microhardness studies of sulfamic acid single crystal

    NASA Astrophysics Data System (ADS)

    Santhosh Kumar, A.; Joseph, Cyriac; Paulose, Reshmi; R, Rajesh; Joseph, Georgekutty; Louis, Godfrey

    2015-02-01

    Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal sulfamic acid have been reported. Single crystals of sulfamic acid have been grown by slow evaporation method. The load dependence of the Vickers microhardness of sulfamic acid crystal were investigated and analyzed from the stand point of various theoretical models. Crystal samples in a, b and c-axes exhibit reverse indentation effect which is best described by Meyer's law, Hays-Kendall's approach and proportional specimen resistance (PSR) models. The negative values of load dependent quantities in Hays-Kendall's approach and PSR model suggest that the origin of indentation size effect is associated with the process of relaxation of indentation stresses.

  11. The Creep of Single Crystals of Aluminum

    NASA Technical Reports Server (NTRS)

    Johnson, R D; Shober, F R; Schwope, A D

    1953-01-01

    The creep of single crystals of high-purity aluminum was investigated in the range of temperatures from room temperature to 400 F and at resolved-shear-stress levels of 200, 300, and 400 psi. The tests were designed in an attempt to produce data regarding the relation between the rate of strain and the mechanism of deformation. The creep data are analyzed in terms of shear strain rate and the results are discussed with regard to existing creep theories. Stress-strain curves were determined for the crystals in tinsel and constant-load-rate tests in the same temperature range to supplement the study of plastic deformation by creep with information regarding the part played by crystal orientation, differences in strain markings, and other variables in plastic deformation.

  12. Submicron diameter single crystal sapphire optical fiber

    DOE PAGESBeta

    Hill, Cary; Homa, Daniel; Liu, Bo; Yu, Zhihao; Wang, Anbo; Pickrell, Gary

    2014-10-02

    In this work, a submicron-diameter single crystal sapphire optical fiber was demonstrated via wet acid etching at elevated temperatures. Etch rates on the order 2.3 µm/hr were achievable with a 3:1 molar ratio sulfuric-phosphoric acid solution maintained at a temperature of 343°C. A sapphire fiber with an approximate diameter of 800 nm was successfully fabricated from a commercially available fiber with an original diameter of 50 µm. The simple and controllable etching technique provides a feasible approach to the fabrication of unique waveguide structures via traditional silica masking techniques. The ability to tailor the geometry of sapphire optical fibers ismore » the first step in achieving optical and sensing performance on par with its fused silica counterpart.« less

  13. Shock Compression of Ammonium Perchlorate Single Crystals

    NASA Astrophysics Data System (ADS)

    Gupta, Y. M.; Yuan, Gang; Feng, Ruqiang

    1997-07-01

    The shock response of ammonium perchlorate (AP) single crystals has been examined for uniaxial strain compression along the [210] and [001] directions. Quartz gauge and VISAR measurements have provided the wave profiles at the impact surface and after propagation through thin samples (1-3 mm thickness) for peak stresses ranging between 10 and 65 kbar. A two wave structure due to elastic-plastic deformation was observed for both orientations. The measured HEL values for the [210] and [001] orientations were about 4.3 and 3.5 kbar, respectively. Data for the two orientations reveal small stress relaxation effects and small differences due to crystal orientation effects. We have chosen to fit both sets of results with a simple elastic-perfectly plastic model used for isotropic materials. Reasonable agreement between the calculations and experimental results was obtained. Over the stress range examined to date, no evidence of chemical decomposition was observed for the time durations in our experiments.

  14. Method of Making Lightweight, Single Crystal Mirror

    NASA Technical Reports Server (NTRS)

    Bly, Vincent T. (Inventor)

    2015-01-01

    A method of making a mirror from a single crystal blank may include fine grinding top and bottom surfaces of the blank to be parallel. The blank may then be heat treated to near its melting temperature. An optical surface may be created on an optical side of the blank. A protector may be bonded to the optical surface. With the protector in place, the blank may be light weighted by grinding a non-optical surface of the blank using computer controlled grinding. The light weighting may include creating a structure having a substantially minimum mass necessary to maintain distortion of the mirror within a preset limit. A damaged layer of the non-optical surface caused by light weighting may be removed with an isotropic etch and/or repaired by heat treatment. If an oxide layer is present, the entire blank may then be etched using, for example, hydrofluoric acid. A reflecting coating may be deposited on the optical surface.

  15. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Gillies, Donald C.; Watring, Dale A.

    1999-01-01

    The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

  16. Loop polymer brushes from polymer single crystals

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Li, Christopher

    2014-03-01

    Loop polymer brushes represent a category of polymer brushes with both chain ends being tethered to a surface or interface with sufficiently high density. Due to this morphological difference, loop brushes exhibit distinct properties compared with traditional polymer brushes with single chain end being tethered. In our study, α, ω-functionalized polycaprolactone (PCL) single crystals were prepared as templates for polymer brush synthesis. By carefully controlling crystallization condition and immobilization, looped polymer brushes were successfully prepared. Comprehensive studies on the morphology and physical properties of these polymer brushes were carried out using Atomic Force Microscopy and FTIR. Advantages of using this method include exclusive loop morphology, high grafting density, controlled tethering sites and tunable loop size.

  17. Advanced piezoelectric single crystal based transducers for naval sonar applications

    NASA Astrophysics Data System (ADS)

    Snook, Kevin A.; Rehrig, Paul W.; Hackenberger, Wesley S.; Jiang, Xiaoning; Meyer, Richard J., Jr.; Markley, Douglas

    2006-03-01

    Transducers incorporating single crystal piezoelectric Pb(Mg 1/3Nb 2/3) x-1Ti xO 3 (PMN-PT) exhibit significant advantages over ceramic piezoelectrics such as PZT, including both high electromechanical coupling (k 33 > 90%) and piezoelectric coefficients (d 33 > 2000 pC/N). Conventional <001> orientation gives inherently larger bandwidth and output power than PZT ceramics, however, the anisotropy of the crystal also allows for tailoring of the performance by orienting the crystal along different crystallographic axes. This attribute combined with composition refinements can be used to improve thermal or mechanical stability, which is important in high power, high duty cycle sonar applications. By utilizing the "31" resonance mode, the high power performance of PMN-PT can be improved over traditional "33" mode single crystal transducers, due to an improved aspect ratio. Utilizing novel geometries, effective piezoelectric constants of -600 pC/N to -1200 pC/N have been measured. The phase transition point induced by temperature, pre-stress or field is close to that in the "33" mode, and since the prestress is applied perpendicular to the poling direction in "31" mode elements, they exhibit lower loss and can therefore be driven harder. The high power characteristics of tonpilz transducers can also be affected by the composition of the PMN-PT crystal. TRS modified the composition of PMN-PT to improve the thermal stability of the material, while keeping the loss as low as possible. Three dimensional modeling shows that the useable bandwidth of these novel compositions nearly equals that of conventional PMN-PT. A decrease in the source level of up to 6 dB was calculated, which can be compensated for by the higher drive voltages possible.

  18. Single Crystal Growth of High Temperature Superconductors and Investigation of Their Physical Properties

    NASA Astrophysics Data System (ADS)

    Tatarchenko, V. A.; Emel'Chenko, G. A.; Abrosimov, N. V.; Borodin, V. A.; Vinnikov, L. Ya.; Zharikov, O. V.; Zhokhov, A. A.; Kononovich, P. A.; Masalov, V. M.; Romanenko, I. M.; Ryazanov, V. V.; Chernyshova, L. I.

    Part of the phase diagram of the La2O3-CuO system has been studied and single crystals of La2CuO4, (LaSr)2CuO4 (up to 20 × 8 × 6 mm3), YBa2Cu3O7-δ (up to 8 × 6 × 0.1 mm3) and HoBa2Cu3O7-(up to 3 × 2.5 × 1 mm3) have been grown by the method of spontaneous crystallisation, using a rotational crucible. It has been established that thermal treatment of "123" single crystals under oxygen pressure to 10 bars improves their superconducting properties. Electrical, magnetic, optical properties, and the real structure of the single crystals produced have been studied.

  19. Single-crystal X-ray diffraction at megabar pressures and temperatures of thousands of degrees

    SciTech Connect

    Dubrovinsky, L.; Boffa-Ballaran, T.; Glazyrin, K.; Kurnosov, A.; Frost, D.; Merlini, M.; Hanfland, M.; Prakapenka, V.B.; Schouwink, P.; Pippinger, T.; Dubrovinskaia, N.

    2011-08-09

    The most reliable information about crystal structures and their response to changes in pressure and temperature is obtained from single-crystal diffraction experiments. We have developed a methodology to perform single-crystal X-ray diffraction experiments in laser-heated diamond anvil cells and demonstrate that structural refinements and accurate measurements of the thermal equation of state of metals, oxides and silicates from single-crystal intensity data are possible in pressures ranging up to megabars and temperatures of thousands of degrees. A new methodology was applied to solve the in situ high pressure, high temperature structure of iron oxide and study structural variations of iron and aluminum bearing silicate perovskite at conditions of the Earth's lower mantle.

  20. Piezoelectric single crystals for ultrasonic transducers in biomedical applications.

    PubMed

    Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K Kirk

    2014-10-01

    Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state-of-art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN-PT and PIN-PMN-PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single-element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

  1. Piezoelectric single crystals for ultrasonic transducers in biomedical applications

    PubMed Central

    Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K. Kirk

    2014-01-01

    Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state–of–art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN–PT and PIN–PMN–PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single–element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

  2. Comparison of the optical parameters of a CaF{sub 2} single crystal and optical ceramics

    SciTech Connect

    Palashov, O V; Khazanov, E A; Mukhin, I B; Mironov, I A; Smirnov, A N; Dukel'skii, K V; Fedorov, Pavel P; Osiko, Vyacheslav V; Basiev, Tasoltan T

    2007-01-31

    Single crystal and optical ceramic CaF{sub 2} samples are studied by the method of thermally induced depolarisation of laser radiation at 1076 nm. The absorption coefficients of the single crystal and ceramics are estimated as {alpha} < 4.5x10{sup -4} cm{sup -1} and {alpha} < 1.33x10{sup -3} cm{sup -1}, respectively. (letters)

  3. Neutron-induced defects in the lithium tetraborate single crystals

    NASA Astrophysics Data System (ADS)

    Burak, Y. V.; Padlyak, B. V.; Shevel, V. M.

    The X-band (nucongruent to9.4 GHz) electron spin resonance (ESR) spectra of the un-doped isotopically enriched lithium tetraborate (LTB) Li2B4O7 single crystals, irradiated by thermal neutrons (fluences Phi(n) =2.74x 10(15) divided by 1.79 x 10(18) cm(-2) ) were investigated at 300 and 77 K. The LTB crystals of high chemical purity and optical quality with different isotope compositions (Li-6(2) (B4O7)-B-10 , Li-6(2) (B4O7)-B-11 , Li-7(2) (B4O7)-B-10 and Li-7(2) (B4O7)-B-11) were grown by Czochralski technique. The thermal neutrons (the total quantity >90%) with fluence near 10(18) cm(-2) induce at least 4 different types of stable paramagnetic centers in the Li and B isotopically enriched LTB crystals. The ESR spectra, electron structure and efficiency of generation for centers, induced by thermal neutrons, essentially depend on neutron fluence and isotope composition of the LTB crystals. The local symmetry and the spin Hamiltonian parameters of the observed paramagnetic centers were determined and their electron structure were established. The possible models and formation mechanism of the radiation defects, induced by thermal neutrons in the LTB lattice, are proposed.

  4. Large-scale single-crystal growth of (CH3)2NH2CuCl3 for neutron scattering experiments

    NASA Astrophysics Data System (ADS)

    Park, Garam; Oh, In-Hwan; Park, J. M. Sungil; Park, Seong-Hun; Hong, Chang Seop; Lee, Kwang-Sei

    2016-05-01

    Neutron scattering studies on low-dimensional quantum spin systems require large-size single-crystals. Single-crystals of (CH3)2NH2CuCl3 showing low-dimensional magnetic behaviors were grown by a slow solvent evaporation method in a two-solvent system at different temperature settings. The best results were obtained for the bilayer solution of methanol and isopropanol with a molar ratio of 2:1 at 35 °C. The quality of the obtained single-crystals was tested by powder and single-crystal X-ray diffraction and single-crystal neutron diffraction. In addition, to confirm structural phase transitions (SPTs), thermal analysis and single-crystal X-ray diffraction at 300 K and 175 K, respectively, were conducted, confirming the presence of a SPT at Tup=288 K on heating and Tdown=285 K on cooling.

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

    DOEpatents

    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.

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

    DOEpatents

    Hemley, Russell J.; Mao, Ho-kwang; Yan, Chih-shiue

    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.

  7. Standard Reference Material (SRM 1990) For Single Crystal Diffractometer Alignment

    PubMed Central

    Wong-Ng, W.; Siegrist, T.; DeTitta, G. T.; Finger, L. W.; Evans, H. T.; Gabe, E. J.; Enright, G. D.; Armstrong, J. T.; Levenson, M.; Cook, L. P.; Hubbard, C. R.

    2001-01-01

    An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and (2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material® for single crystal diffractometer alignment. This SRM is a set of ≈3500 units of Cr-doped Al2O3, or ruby spheres [(0.420.011 mole fraction % Cr (expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals: the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a=4.7608 ű0.0062 Å, and c=12.9979 ű0.020 Å (95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at (Bell Laboratories) Lucent Technologies and at NRC of Canada (39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Hägg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies– are rhombohedral, with space group R3¯c. The certified mean unit cell parameters are a=4.76080±0.00029 Å, and c=12.99568 ű0.00087 Å (expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Hägg transmission measurements on five samples of powdered rubies (a=4.7610 ű0.0013 Å, and c = 12

  8. Standard Reference Material (SRM 1990) For Single Crystal Diffractometer Alignment.

    PubMed

    Wong-Ng, W; Siegrist, T; DeTitta, G T; Finger, L W; Evans, H T; Gabe, E J; Enright, G D; Armstrong, J T; Levenson, M; Cook, L P; Hubbard, C R

    2001-01-01

    An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and (2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material(®) for single crystal diffractometer alignment. This SRM is a set of ≈3500 units of Cr-doped Al2O3, or ruby spheres [(0.420.011 mole fraction % Cr (expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals: the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a=4.7608 ű0.0062 Å, and c=12.9979 ű0.020 Å (95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at (Bell Laboratories) Lucent Technologies and at NRC of Canada (39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Hägg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies- are rhombohedral, with space group [Formula: see text]. The certified mean unit cell parameters are a=4.76080±0.00029 Å, and c=12.99568 ű0.00087 Å (expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Hägg transmission measurements on five samples of powdered rubies (a=4.7610 ű0.0013

  9. Standard Reference Material (SRM 1990) for Single Crystal Diffractometer Alignment

    USGS Publications Warehouse

    Wong-Ng, W.; Siegrist, T.; DeTitta, G.T.; Finger, L.W.; Evans, H.T., Jr.; Gabe, E.J.; Enright, G.D.; Armstrong, J.T.; Levenson, M.; Cook, L.P.; Hubbard, C.R.

    2001-01-01

    An international project was successfully completed which involved two major undertakings: (1) a round-robin to demonstrate the viability of the selected standard and (2) the certification of the lattice parameters of the SRM 1990, a Standard Reference Material?? for single crystal diffractometer alignment. This SRM is a set of ???3500 units of Cr-doped Al2O3, or ruby spheres [(0 420.011 mole fraction % Cr (expanded uncertainty)]. The round-robin consisted of determination of lattice parameters of a pair of crystals' the ruby sphere as a standard, and a zeolite reference to serve as an unknown. Fifty pairs of crystals were dispatched from Hauptman-Woodward Medical Research Institute to volunteers in x-ray laboratories world-wide. A total of 45 sets of data was received from 32 laboratories. The mean unit cell parameters of the ruby spheres was found to be a=4.7608 A?? ?? 0.0062 A??, and c=12.9979 A?? ?? 0.020 A?? (95 % intervals of the laboratory means). The source of errors of outlier data was identified. The SRM project involved the certification of lattice parameters using four well-aligned single crystal diffractometers at (Bell Laboratories) Lucent Technologies and at NRC of Canada (39 ruby spheres), the quantification of the Cr content using a combined microprobe and SEM/EDS technique, and the evaluation of the mosaicity of the ruby spheres using a double-crystal spectrometry method. A confirmation of the lattice parameters was also conducted using a Guinier-Ha??gg camera. Systematic corrections of thermal expansion and refraction corrections were applied. These rubies_ are rhombohedral, with space group R3c. The certified mean unit cell parameters are a=4.76080 ?? 0.00029 A??, and c=12 99568 A?? ?? 0.00087 A?? (expanded uncertainty). These certified lattice parameters fall well within the results of those obtained from the international round-robin study. The Guinier-Ha??gg transmission measurements on five samples of powdered rubies (a=4.7610 A?? ?? 0

  10. Single Crystal DMs for Space-Based Observatories

    NASA Astrophysics Data System (ADS)

    Bierden, Paul

    etched independently: one for the substrate and fixed electrode layer, one for the actuator layer, and one for the mirror layer. Subsequently, each of these wafers will be bonded through a thermal fusion process to the others. In an innovative new processing technique, we will employ sacrificial oxide pillars to add temporary support to the otherwise compliant device structures. These pillars will be dissolved after assembly. The result will be a stress-free, single crystal silicon device with broadly expanded design space for geometric parameters such as actuator pitch, mirror diameter, array size, and actuator gap. Consequently, this approach will allow us to make devices with characteristics that are needed for some important NASA applications in space-based coronography, especially where larger array sizes, greater actuator pitch, and better optical surface quality are needed. The significance of this work is that it will provide a technology platform that meets or exceeds the superb optical performance that has been demonstrated in conventional pizezoelectrically actuated DMs, while retaining the advantages in cost, repeatability, and thermal insensitivity that have been demonstrated in the newer generation of MEMS electrostatically actuated DMs. The shift to bonded single-crystal structures will eliminate the single biggest drawback in previously reported NASA-fielded MEMS DM technology: device susceptibility to stress-induced scalloping and print through artifacts resulting from polycrystalline thin film surface micromachining. With single crystal structures bonded at atomic scales, uncorrected surface topography can be controlled to subnanometer levels, enabling the advancement of NASA s next-generation space-based coronagraphs.

  11. Experimental Investigation of Orthoenstatite Single Crystal Rheology

    NASA Astrophysics Data System (ADS)

    fraysse, G.; Girard, J.; Holyoke, C. W.; Raterron, P.

    2013-12-01

    The plasticity of enstatite, upper mantle second most abundant mineral, is still poorly constrained, mostly because of its high-temperature (T) transformation into proto- and clino-enstatite at low pressure (P). Mackwell (1991, GRL, 18, 2027) reports a pioneer study of protoenstatite (Pbcn) single-crystal rheology, but the results do not directly apply to the orthorhombic (Pbca) mantle phase. Ohuchi et al. (2011, Contri. Mineral. Petrol , 161, 961) carried out deformation experiments at P=1.3 GPa on oriented orthoenstatite crystals, investigating the activity of [001](100) and [001](010) dislocation slip systems; they report the first rheological laws for orthoenstatite crystals. However, strain and stress were indirectly constrained in their experiments, which questioned whether steady state conditions of deformation were achieved. Also, data reported for [001](100) slip system were obtained after specimens had transformed by twinning into clinoenstatite. We report here new data from deformation experiments carried out at high T and P ranging from 3.5 to 6.2 GPa on natural Fe-bearing enstatite single crystals, using the Deformation-DIA apparatus (D-DIA) that equipped the X17B2 beamline of the NSLS (NY, USA). The applied stress and specimen strain rates were measured in situ by X-ray diffraction and imaging techniques (e.g., Raterron & Merkel, 2009, J. Sync. Rad., 16, 748; Raterron et al., 2013, Rev. Sci. Instr., 84, 043906). Three specimen orientations were tested: i) with the compression direction along [101]c crystallographic direction, which forms a 45° angle with both [100] and [001] axes, to investigate [001](100) slip-system activity; ii) along [011]c direction to investigate [001](010) system activity; iii) and along enstatite [125] axis, to activate both slip systems together. Crystals were deformed two by two, to compare slip system activities, or against enstatite aggregates or orientated olivine crystals of known rheology for comparison. Run products

  12. Direct Shear of Olivine Single Crystals

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob; Zimmerman, Mark; Kohlstedt, David

    2016-04-01

    Knowledge of the strength of individual dislocation slip systems in olivine is fundamental to understanding the flow behavior and the development of lattice-preferred orientation in olivine-rich rocks. The most direct measurements of the strengths of individual slip systems are from triaxial compression experiments on olivine single crystals. However, such experiments only allow for determination of flow laws for two of the four dominate slip systems in olivine. In order to measure the strengths of the (001)[100] and (100)[001] slip systems independently, we performed deformation experiments on single crystals of San Carlos olivine in a direct shear geometry. Experiments were carried out at temperatures of 1000° to 1300°C, a confining pressure of 300 MPa, shear stresses of 60 to 334 MPa, and resultant shear strain rates of 7.4 x 10‑6 to 6.7 x 10‑4 s‑1. At high-temperature (≥1200°C) and low-stress (≤200 MPa) conditions, the strain rate of crystals oriented for direct shear on either the (001)[100] or the (100)[001] slip system follows a power law relationship with stress, whereas at lower temperatures and higher stresses, strain rate depends exponentially on stress. The flow laws derived from the mechanical data in this study are consistent with a transition from the operation of a climb-controlled dislocation mechanism during power-law creep to the operation of a glide-controlled dislocation mechanism during exponential creep. In the climb-controlled regime, crystals oriented for shear on the (001)[100] slip system are weaker than crystals orientated for shear on the (100)[001] slip system. In contrast, in the glide-controlled regime the opposite is observed. Extrapolation of flow laws determined for crystals sheared in orientations favorable for slip on these two slip systems to upper mantle conditions reveals that the (001)[100] slip system is weaker at temperatures and stresses that are typical of the asthenospheric mantle, whereas the (100

  13. Single Crystal Structure Determination of Alumina to 1 Mbar

    NASA Astrophysics Data System (ADS)

    Dong, H.; Zhang, L.; Prakapenka, V.; Mao, H.

    2014-12-01

    Aluminum oxide (Al2O3) is an important ceramic material and a major oxide in the earth. Additionally, alumina is a widely used pressure standard in static high-pressure experiments (Cr3+-bearing corundum, ruby). The changes of its crystal structure with pressure (P) and temperature (T) are important for its applications and understanding its physical properties in the deep Earth. There have been numerous reports on the high P-T polymorphs of alumina. Previous theoretical calculations and experiments suggest that the crystal structure of Al2O3 evolves greatly at high P-T. In this study, we used the newly developed multigrain crystallography method combined with single-crystal x-ray diffraction analysis technique for the structure determination of alumina at high P-T to provide single-crystal structure refinement for high-pressure phases of Al2O3. Alumina powder was mixed with ~10% Pt and Ne was used as both pressure transmitting media and thermal insulating layers during laser-heating. Coarse-grained aggregates of Al2O3 were synthesized in a laser-heated diamond anvil cell. The structure change of Al2O3 was monitored by in situ x-ray diffraction at ~1 Mbar and 2700 K. The results allow us to distinguish the structural differences between the Rh2O3 (II) structure (space group Pbcn) and perovskite structure (space group Pbnm) for the first high-pressure phase of Al2O3. More detailed results will be discussed in the later work.

  14. Flux free growth of superconducting FeSe single crystals

    NASA Astrophysics Data System (ADS)

    Maheshwari, P. K.; Joshi, L. M.; Gahtori, Bhasker; Srivastava, A. K.; Gupta, Anurag; Patnaik, S. P.; Awana, V. P. S.

    2016-07-01

    We report flux free growth of superconducting FeSe single crystals by an easy and versatile high temperature melt and slow cooling method for first time. The room temperature x-ray diffraction (XRD) on the surface of the piece of such obtained crystals showed single [101] plane of β-FeSe tetragonal phase. The bulk powder XRD, being obtained by crushing the part of crystal chunk showed majority (∼87%) β-FeSe tetragonal (space group P4/nmm) and minority (∼13%) δ-FeSe hexagonal (space group P63/mmc) crystalline phases. Detailed high resolution transmission electron microscope images along with selected area electron diffraction showed the abundance of both majority β-FeSe and minority δ-FeSe phases. Both transport (ρ-T) and magnetization exhibited superconductivity at below around 10 K. Interestingly, the magnetization signal of these crystals is dominated by the magnetism of minority δ-FeSe magnetic phase, and hence the isothermal magnetization at 4 K was seen to be ferromagnetic like. Transport (ρ-T) measurements under magnetic field showed superconductivity onset at below 12 K, and ρ = 0 (T c) at 9 K. Superconducting transition temperature (T c) decreases with applied field to around 6 K at 7 T, with dT c/dH of ∼0.4 K T‑1, giving rise to an H c2(0) value of around 50 , 30 and 20 T for normal resistivity ρ n = 90%, 50% and 10% respectively, which are calculated from conventional one band Werthamer–Helfand–Hohenberg equation. FeSe single crystal activation energy is calculated from thermally activated flux flow model which is found to decreases with field from 12.1 meV for 0.2 T to 3.77 meV for 7 T.

  15. Thermodynamic forces in single crystals with dislocations

    NASA Astrophysics Data System (ADS)

    Van Goethem, Nicolas

    2014-06-01

    A simple model for the evolution of macroscopic dislocation regions in a single crystal is presented. This model relies on maximal dissipation principle within Kröner's geometric description of the dislocated crystal. Mathematical methods and tools from shape optimization theory provide equilibrium relations at the dislocation front, similarly to previous work achieved on damage modelling (J Comput Phys 33(16):5010-5044, 2011). The deformation state variable is the incompatible strain as related to the dislocation density tensor by a relation involving the Ricci curvature of the crystal underlying elastic metric. The time evolution of the model variables follows from a novel interpretation of the Einstein-Hilbert flow in terms of dislocation microstructure energy. This flow is interpreted as the dissipation of non-conservative dislocations, due to the climb mechanism, modelled by an average effect of mesoscopic dislocations moving normal to their glide planes by adding or removing points defects. The model equations are a fourth-order tensor parabolic equation involving the operator "incompatibility," here appearing as a tensorial counterpart of the scalar Laplacian. This work encompasses and generalizes results previously announced (C R Acad Sci Paris Ser I 349:923-927, 2011), with in addition a series of physical interpretations to give a meaning to the newly introduced concepts.

  16. Double bragg reflections in single crystals and textured polycrystals

    NASA Astrophysics Data System (ADS)

    Skrytnyy, V. I.; Yaltsev, V. N.

    2016-04-01

    Analysis of the detection of the double Bragg reflections (DBR) in single crystals and polycrystals is carried out. Technique of the detection of the double Bragg reflection in single crystals and textured polycrystalline samples using X-ray synchrotron radiation is proposed.

  17. A Quick Method for Determining the Density of Single Crystals.

    ERIC Educational Resources Information Center

    Roman, Pascual; Gutierrez-Zorrilla, Juan M.

    1985-01-01

    Shows how the Archimedes method is used to determine the density of a single crystal of ammonium oxalate monohydrate. Also shows how to calculate the density of other chemicals when they are available as single crystals. Experimental procedures and materials needed are included. (JN)

  18. Characterization of a synthetic single crystal diamond Schottky diode for radiotherapy electron beam dosimetry

    SciTech Connect

    Di Venanzio, C.; Marinelli, Marco; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Falco, M. D.; Bagala, P.; Santoni, R.; Pimpinella, M.

    2013-02-15

    Purpose: To investigate the dosimetric properties of synthetic single crystal diamond based Schottky diodes under irradiation with therapeutic electron beams from linear accelerators. Methods: A single crystal diamond detector was fabricated and tested under 6, 8, 10, 12, and 15 MeV electron beams. The detector performances were evaluated using three types of commercial detectors as reference dosimeters: an Advanced Markus plane parallel ionization chamber, a Semiflex cylindrical ionization chamber, and a p-type silicon detector. Preirradiation, linearity with dose, dose rate dependence, output factors, lateral field profiles, and percentage depth dose profiles were investigated and discussed. Results: During preirradiation the diamond detector signal shows a weak decrease within 0.7% with respect to the plateau value and a final signal stability of 0.1% (1{sigma}) is observed after about 5 Gy. A good linear behavior of the detector response as a function of the delivered dose is observed with deviations below {+-}0.3% in the dose range from 0.02 to 10 Gy. In addition, the detector response is dose rate independent, with deviations below 0.3% in the investigated dose rate range from 0.17 to 5.45 Gy/min. Percentage depth dose curves obtained from the diamond detector are in good agreement with the ones from the reference dosimeters. Lateral beam profile measurements show an overall good agreement among detectors, taking into account their respective geometrical features. The spatial resolution of solid state detectors is confirmed to be better than that of ionization chambers, being the one from the diamond detector comparable to that of the silicon diode. A good agreement within experimental uncertainties was also found in terms of output factor measurements between the diamond detector and reference dosimeters. Conclusions: The observed dosimetric properties indicate that the tested diamond detector is a suitable candidate for clinical electron beam dosimetry.

  19. Molecular dynamics simulation of fast particle irradiation on the single crystal CeO2

    NASA Astrophysics Data System (ADS)

    Sasajima, Y.; Ajima, N.; Osada, T.; Ishikawa, N.; Iwase, A.

    2013-11-01

    We used a molecular dynamics method to simulate structural relaxation caused by the high-energy-ion irradiation of single crystal CeO2. As the initial condition, we assumed high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order diameter located in the center of the single crystal. The potential proposed by Inaba et al. was utilized to calculate interactions between atoms [H. Inaba, R. Sagawa, H. Hayashi, K. Kawamura, Solid State Ionics 122 (1999) 95-103]. The supplied thermal energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it was dissipated in the crystal. We compared the obtained results with those of computer simulations for UO2 and found that CeO2 was more stable than UO2 when supplied with high thermal energy.

  20. Synthesis, crystal growth and characterization of an organic material: 2-Aminopyridinium succinate succinic acid single crystal.

    PubMed

    Magesh, M; Bhagavannarayana, G; Ramasamy, P

    2015-11-01

    The 2-aminopyridinium succinate succinic acid (2APS) single crystal was synthesized and grown by slow evaporation method. The crystal structure has been confirmed by powder X-ray diffraction as well as single crystal X-ray diffraction analysis. The crystal perfection has been evaluated by high resolution X-ray diffraction (HRXRD). The grown crystal is transparent in the visible and near infrared region. The optical absorption edge was found to be 348 nm. The fluorescence study was carried out by spectrofluorophotometer. The thermal stability of grown crystal was analyzed by thermal gravimetric and differential thermal gravimetric (TG-DTA) analysis. Vicker's hardness study carried out at room temperature shows increased hardness while increasing the load. Laser damage threshold value was determined by Nd:YAG laser operating at 1064 nm. The grown 2APS crystal was characterized by etching studies using water as etchant. PMID:26099828

  1. Oxygen binding by single crystals of hemoglobin.

    PubMed

    Rivetti, C; Mozzarelli, A; Rossi, G L; Henry, E R; Eaton, W A

    1993-03-23

    Reversible oxygen binding curves for single crystals of hemoglobin in the T quaternary structure have been measured using microspectrophotometry. Saturations were determined from complete visible spectra measured with light linearly polarized parallel to the a and c crystal axes. Striking differences were observed between the binding properties of hemoglobin in the crystal and those of hemoglobin in solution. Oxygen binding to the crystal is effectively noncooperative, the Bohr effect is absent, and there is no effect of chloride ion. Also, the oxygen affinity is lower than that of the T quaternary structure in solution. The absence of the Bohr effect supports Perutz's hypothesis on the key role of the salt bridges, which are known from X-ray crystallography to remain intact upon oxygenation. The low affinity and absence of the Bohr effect can be explained by a generalization of the MWC-PSK model (Monod, Wyman, & Changeux, 1965; Perutz, 1970; Szabo & Karplus, 1972) in which both high- and low-affinity tertiary conformations, with broken and unbroken salt bridges, respectively, are populated in the T quaternary structure. Because the alpha and beta hemes make different projections onto the two crystal axes, separate binding curves for the alpha and beta subunits could be calculated from the two measured binding curves. The approximately 5-fold difference between the oxygen affinities of the alpha and beta subunits is much smaller than that predicted from the crystallographic study of Dodson, Liddington, and co-workers, which suggested that oxygen binds only to the alpha hemes.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8457555

  2. Radiation tolerance of piezoelectric bulk single-crystal aluminum nitride.

    PubMed

    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. PMID:24960710

  3. Radiation tolerance of piezoelectric bulk single-crystal aluminum nitride

    SciTech Connect

    David A. Parks; Bernhard R. Tittmann

    2014-07-01

    For practical use in harsh radiation environments, we pose selection criteria for piezoelectric materials for nondestructive evaluation (NDE) and material characterization. Using these criteria, piezoelectric aluminum nitride is shown to be an excellent candidate. The results of tests on an aluminumnitride-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 × 1018 neutron/cm2 and 5.8 × 1018 neutron/cm2, 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.

  4. Birefringence simulation of annealed ingot of calcium fluoride single crystal

    NASA Astrophysics Data System (ADS)

    Ogino, H.; Miyazaki, N.; Mabuchi, T.; Nawata, T.

    2008-01-01

    We developed a method for simulating birefringence of an annealed ingot of calcium fluoride single crystal caused by the residual stress after annealing process. The method comprises the heat conduction analysis that provides the temperature distribution during the ingot annealing, the elastic thermal stress analysis using the assumption of the stress-free temperature that provides the residual stress after annealing, and the birefringence analysis of an annealed ingot induced by the residual stress. The finite element method was applied to the heat conduction analysis and the elastic thermal stress analysis. In these analyses, the temperature dependence of material properties and the crystal anisotropy were taken into account. In the birefringence analysis, the photoelastic effect gives the change of refractive indices, from which the optical path difference in the annealed ingot is calculated by the Jones calculus. The relation between the Jones calculus and the approximate method using the stress components averaged along the optical path is discussed theoretically. It is found that the result of the approximate method agrees very well with that of the Jones calculus in birefringence analysis. The distribution pattern of the optical path difference in the annealed ingot obtained from the present birefringence calculation methods agrees reasonably well with that of the experiment. The calculated values also agree reasonably well with those of the experiment, when a stress-free temperature is adequately selected.

  5. Theoretical and experimental investigations in characterizing and developing multiplexed diamond-based neutron spectrometers

    NASA Astrophysics Data System (ADS)

    Lukosi, Eric

    In this work a novel technique of multiplexing diamond is presented where electronic grade diamond plates are connected electrically in series and in parallel to increase the overall detection efficiency of diamond-based neutron detection systems. Theoretical results utilizing MCNPX indicate that further development in this simulation software is required to accurately predict the response of diamond to various interrogating neutron energies. However, the results were accurate enough to indicate that an equivalent diamond plate 1cm thick only lowers the energy resolution of the 12 C(n,αo)9Be peak from a 14.1 MeV interrogating neutron reference field by a factor of two compared to a single diamond plate 0.5mm thick while increasing the detection efficiency from 1.34 percent for a single diamond plate to 25.4 percent for the 1cm thick diamond plate. Further, the number of secondary neutron interactions is minimal, approximately 5.3 percent, with a detection medium this size. It is also shown that photons can interfere with lower energy neutron signals when multiplexing is used, especially at lower impinging photon energies, although the full energy peak still does not dominantly present itself in the pulse height spectrum for multiplexed arrays approaching 1cm with respect to the interrogating neutron reference field vector. Experimental results indicate that series multiplexing is not capable for use as a means of increasing the active detection volume of a diamond-based neutron spectrometer because of the interaction of diamond detection mediums in series with each other and the input capacitor of a charge sensitive preamplifier, where severe signal degradation is seen due to the equal impedances of the single crystal diamond plates. However, parallel multiplexing is shown to have great promise, although there are limitations to this technique due to the large capacitance at the preamplifier input for a large parallel multiplexed array. Still, the latter

  6. Diamond-based capacitive micromachined ultrasonic transducers in immersion.

    PubMed

    Cetin, Ahmet M; Bayram, Baris

    2013-02-01

    Diamond is a superior membrane material for capacitive micromachined ultrasonic transducers (CMUTs). By using ultrananocrystalline diamond (UNCD) membrane and plasma-activated wafer bonding technology, a single diamond-based circular CMUT is demonstrated and operated in immersion for the first time. The diamond-based CMUT, biased at 100 V, is excited with a 10-cycle burst of 36 V(p-p) sine signal at 3.5 MHz. Pressure generated on a 2-D plane coincident with the normal of the CMUT is measured using a broadband hydrophone. Peak-to-peak hydrophone voltage measurements along the scan area clearly indicate the main lobe and the side lobes, as theoretically predicted by our directivity function calculations. The peak-to-peak hydrophone voltage on the axial direction of the CMUT is found to be in agreement with our theoretical calculations in the Fraunhofer region (-45 mm diamond-based CMUT is measured for a dc bias of 100 V, and ac excitation with 30-cycle bursts of 9, 36, and 54 V(p-p) sine signal. A peak response at 5.6 MHz is measured for all ac amplitudes. Overall, diamond is shown to be an applicable membrane for CMUT devices and applications. PMID:23357916

  7. Investigation of Advanced Processed Single-Crystal Turbine Blade Alloys

    NASA Technical Reports Server (NTRS)

    Peters, B. J.; Biondo, C. M.; DeLuca, D. P.

    1995-01-01

    This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal turbine blade alloy that is specifically tailored for use in hydrogen fueled rocket engine turbopumps. High-gradient casting, hot isostatic pressing (HIP), and alternate heat treatment (HT) processing parameters were developed to produce pore-free, eutectic-free microstructures with different (gamma)' precipitate morphologies. Test materials were cast in high thermal gradient solidification (greater than 30 C/cm (137 F/in.)) casting furnaces for reduced dendrite arm spacing, improved chemical homogeneity, and reduced interdendritic pore size. The HIP processing was conducted in 40 cm (15.7 in.) diameter production furnaces using a set of parameters selected from a trial matrix study. Metallography was conducted on test samples taken from each respective trial run to characterize the as-HIP microstructure. Post-HIP alternate HT processes were developed for each of the two alloys. The goal of the alternate HT processing was to fully solution the eutectic gamma/(gamma)' phase islands and to develop a series of modified (gamma)' morphologies for subsequent characterization testing. This was accomplished by slow cooling through the (gamma)' solvus at controlled rates to precipitate volume fractions of large (gamma)'. Post-solution alternate HT parameters were established for each alloy providing additional volume fractions of finer precipitates. Screening tests included tensile, high-cycle fatigue (HCF), smooth and notched low-cycle fatigue (LCF), creep, and fatigue crack growth evaluations performed in air and high pressure (34.5 MPa (5 ksi)) hydrogen at room and elevated temperature. Under the most severe embrittling conditions (HCF and smooth and notched LCF in 34.5 MPa (5 ksi) hydrogen at 20 C (68 F), screening test

  8. Spectroscopy and Photochemistry in Single Crystals of Uranyl Formate Monohydrate.

    NASA Astrophysics Data System (ADS)

    Cox, Jack Neal

    1982-03-01

    UO(,2)CH(OO)(,2)(.)H(,2)O, (UFM) is an orthorhombic crystal (Fdd2, C(,2v)('19)) with two uranyls per unit cell. Above 210(DEGREES)K, when uranyl is excited by visible light, a two-step reaction occurs. The primary photochemical step is. U(VI)O(,2)('++) + HCOO('-) (--->) U(V) + (HCOO(.) or CO(,2)('-)). (1). A study of UFM in the oriented solid explores one of the most basic chemical reactions--the redox reaction. High resolution, polarized absorption and excitation specta were taken on single crystals at liquid helium temperatures. Eight electronic origins are identified, each split into doublets by factor group interactions. Uranyl (a)symmetric stretch vibronic progressions (do not) preserve the factor group splittings and polarizations of their origins. The spectrum of UFM lies closer to the (omega)-(omega) limit, as opposed to Russell-Saunders, than Cs(,2)UO(,2)Cl(,4). Low site symmetry depolarizes the B-symmetry components of the origins. Below 2(DEGREES)K, where UFM exhibits non-single exponential luminescence decay, migration to traps is limited. By 20(DEGREES)K, where the curves become single exponential and drop tenfold in the value of the lifetime, emission is occurring from UFM in thermal equilibrium with a population of killer traps. Above 70(DEGREES)K, the lifetime slowly rises. It peaks at 135(DEGREES)K, and then drops steeply, falling below detectability by 210(DEGREES)K. The drop is accompanied by the onset of photoreactivity. The rise in emission is attributed either to a decrease in trapping efficiency or to a hindered migration to traps due to a thermal population of bound (DELTA)(,g) excitons. ESR studies show that a signal at g = 2.0 observed at 77(DEGREES)K is from surface radicals. Below 20(DEGREES)K, a signal near g = 2.1 is due to organic radicals in the bulk generated by the photochemical step. Studies on a single crystal resolve these signals into components that reflect the crystallographic symmetry elements. A signal near g = 3.4 is

  9. Reshock and release response of aluminum single crystal

    NASA Astrophysics Data System (ADS)

    Huang, H.; Asay, J. R.

    2007-03-01

    Reshock and release experiments were performed on single crystal aluminum along three orientations and on polycrystalline 1050 aluminum with 50μm grain size at shock stresses of 13 and 21GPa 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 13-21GPa 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)].

  10. Single crystal x-ray diffraction: optical and micro hardness studies on chalcone derivative single crystal

    NASA Astrophysics Data System (ADS)

    Crasta, Vincent; Ravindrachary, V.; Bhajantri, R. F.; Naveen, S.; Shridar, M. A.; Shashidhara Prasad, J.

    2005-08-01

    1-(4-methylphenyl)-3-(4- N, N dimethyl amino phenyl)-2-propen-1-one, a chalcone derivative nonlinear optical material has been synthesized by standard method. FT-IR and NMR spectral studies have been performed to confirm the molecular structure of the synthesized compound. The single crystals up to a dimension of 13 x 9 x 3 mm3 were grown by slow evaporation method. The grown crystals were transparent in the entire visible region and absorbs in the UV-region. The refractive index has been measured using a He-Ne laser. The grown crystals have been subjected to single crystal X-ray diffraction studies to determine the crystal structure and hence the cell parameters of the crystal. From this study it is found that this compound crystallizes in orthorhombic system with a space group P212121 and corresponding lattice parameters are, a = 7.3610(13) Å, b = 11.651(2) Å, c = 17.6490(17) Å. The Kurtz powder second harmonic generation test shows that the compound is a potential candidate for Photonic application. The micro hardness test on these crystals were carried out and the load dependence hardness was observed

  11. Single-crystal diamond nanomechanical resonators with quality factors exceeding one million.

    PubMed

    Tao, Y; Boss, J M; Moores, B A; Degen, C L

    2014-01-01

    Diamond has gained a reputation as a uniquely versatile material, yet one that is intricate to grow and process. Resonating nanostructures made of single-crystal diamond are expected to possess excellent mechanical properties, including high-quality factors and low dissipation. Here we demonstrate batch fabrication and mechanical measurements of single-crystal diamond cantilevers with thickness down to 85 nm, thickness uniformity better than 20 nm and lateral dimensions up to 240 μm. Quality factors exceeding one million are found at room temperature, surpassing those of state-of-the-art single-crystal silicon cantilevers of similar dimensions by roughly an order of magnitude. The corresponding thermal force noise for the best cantilevers is ~5·10(-19) N Hz(-1/2) at millikelvin temperatures. Single-crystal diamond could thus directly improve existing force and mass sensors by a simple substitution of resonator material. Presented methods are easily adapted for fabrication of nanoelectromechanical systems, optomechanical resonators or nanophotonic devices that may lead to new applications in classical and quantum science. PMID:24710311

  12. Analysis of laser-generated plasma ionizing radiation by synthetic single crystal diamond detectors

    NASA Astrophysics Data System (ADS)

    Marinelli, M.; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Cutroneo, M.; Torrisi, L.; Margarone, D.; Velyhan, A.; Krasa, J.; Krousky, E.

    2013-05-01

    Diamond based detectors have been used in order to analyze the ionizing radiation emitted from the laser-generated plasma. High energy proton/ion beams were generated at Prague Asterix Laser System (PALS) Centre by the sub-nanosecond kJ-class laser at intensities above 1016 W/cm2. The tested detectors consisted of a photoconductive device based on high quality chemical vapor deposition (CVD) single crystal diamond, produced at Rome "Tor Vergata" University. They have been operated in planar configuration, having inter-digitized electrodes. The proposed diamond detectors were able to measure UV, X-rays, electrons and ions. They have been employed in time-of-flight (TOF) configuration and their reliability was checked by comparison with standard ion collectors (mostly used at PALS). Both the forward and backward expanding plasma was characterized in the experiment. The results indicate that diamond detectors are very promising for the characterization of fast proton and ion beams produced by high power laser systems.

  13. Supramolecular self-organisation and conformational isomerism of a binuclear O,O'-dipropyl dithiophosphate gold(I) complex, [Au2{S2P(OC3H7)2}2]: Synthesis, (13)C and (31)P CP/MAS NMR spectroscopy, single-crystal X-ray diffraction study and thermal behaviour.

    PubMed

    Rodina, Tatyana A; Korneeva, Eugenia V; Antzutkin, Oleg N; Ivanov, Alexander V

    2015-10-01

    Crystalline one-dimensional polymeric catena-poly[bis(μ2-O,O'-dipropyldithiophosphato-S,S')digold(I)] (Au-Au) (1) was prepared and studied using (13)C and (31)P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. To elucidate the structural function of Dtph ligands in crystalline gold(I) O,O'-dipropyl dithiophosphate, the chemical shift anisotropy parameters (δaniso and η) were calculated from spinning sideband manifolds in (31)P MAS NMR spectra. A novel structure of the gold(I) compound comprises two isomeric, non-centrosymmetric binuclear molecules of [Au2{S2P(OC3H7)2}2] (isomers 'A' and 'B'), whose four Dtph groups display structural inequivalence. In each isomeric binuclear molecule of 1, a pair of μ2-bridging dipropyl Dtph ligands almost symmetrically links two neighbouring gold atoms, forming an extensive eight-membered metallocycle [Au2S4P2], while the intramolecular aurophilic Au⋯Au bond additionally stabilises this central cyclic moiety. At the supramolecular level of complex 1, intermolecular aurophilic Au⋯Au bonds yield almost linear infinite polymeric chains (⋯'A'⋯'B'⋯'A'⋯'B'⋯)n. The thermal behaviour of this compound was studied by the simultaneous thermal analysis (STA) technique (a combination of TG and DSC) under an argon atmosphere. PMID:26004097

  14. Relaxor-PT single crystals for broad bandwidth, high power sonar projectors

    NASA Astrophysics Data System (ADS)

    Sherlock, Nevin P.

    2010-06-01

    The high piezoelectric response of the ferroelectric relaxor (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 (PMNT) in single crystal form has generated significant interest in producing broad bandwidth SONAR systems. Both the piezoelectric coefficient (d33 > 2000 pC/N) and coupling coefficient (k33 > 0.90) are superior to those of conventional piezoelectric ceramics. Within the context of a high power acoustic projector, its high losses and low temperature stability have limited its development. Second generation single crystals with compositions modified from the base PMNT have been recently developed to decrease the electromechanical losses and mitigate the thermal property dependence. In this work, the electromechanical properties were measured using single crystals which have been modified in various ways. The modified crystals exhibit electromechanically "hard" behavior with lower losses (tan delta = 0.1--0.2% and QM = 230--950) than unmodified PMNT (tan delta = 0.26% and QM = 190). The measured d33 values of modified single crystals (d33 = 760--1490 pm/V) are also lower than unmodified PMNT (d33 = 1540 pm/V), but the lower piezoelectric response is compensated by the greater stability of the modified single crystals. These modified single crystal properties were also compared to conventional high power piezoelectric ceramics ( d33 = 240 pm/V and QM = 1050) to show similar losses but significantly greater response in the modified PMNT single crystals. Although most piezoelectric materials are measured under small signal conditions (small signal defined by a completely linear relationship between the input and output signals), the high power nature of SONAR projectors demands that these modified single crystals also be evaluated under high power conditions. A test procedure was developed to measure the electromechanical properties of each material as a function of applied electric field over a frequency range which includes the resonance frequency. Modified single crystals

  15. UCN Production With a Single Crystal of Ortho-Deuterium

    PubMed Central

    Utsuro, M.; Tanaka, M.; Mishima, K.; Nagai, Y.; Shima, T.; Fukuda, Y.; Kohmoto, T.; Momose, T.; Moriai, A.; Okumura, K.; Yoshino, H.

    2005-01-01

    The present paper reports on the preliminary experimental results concerning a new concept of ultracold neutron production with a single crystal converter of ortho-deuterium lying in the ground rotational state at the low temperature of about 10 K, which should make it possible to utilize a guided cold neutron beam instead of irradiating the converter material in the inside of high radiation fields. The successful observation of the clear Bragg scattering pattern from the single crystal converter and the reasonable results from the first experimental trial of the ultracold neutron production with the single crystal are shown. PMID:27308135

  16. UCN Production With a Single Crystal of Ortho-Deuterium.

    PubMed

    Utsuro, M; Tanaka, M; Mishima, K; Nagai, Y; Shima, T; Fukuda, Y; Kohmoto, T; Momose, T; Moriai, A; Okumura, K; Yoshino, H

    2005-01-01

    The present paper reports on the preliminary experimental results concerning a new concept of ultracold neutron production with a single crystal converter of ortho-deuterium lying in the ground rotational state at the low temperature of about 10 K, which should make it possible to utilize a guided cold neutron beam instead of irradiating the converter material in the inside of high radiation fields. The successful observation of the clear Bragg scattering pattern from the single crystal converter and the reasonable results from the first experimental trial of the ultracold neutron production with the single crystal are shown. PMID:27308135

  17. Transport in organic single-crystal microbelt for conformal electronics

    NASA Astrophysics Data System (ADS)

    Cui, Nan; Tong, Yanhong; Tang, Qingxin; Liu, Yichun

    2016-03-01

    We showed the advantages of flexible rubrene organic single-crystal microbelts in high-performance devices and circuits towards conformal electronics. The anisotropic transport based on the only one organic microbelt was studied by a "cross-channel" method, and the rubrene microbelt showed the highest mobility up to 26 cm2/V s in the length direction. Based on an individual rubrene microbelt, the organic single-crystal circuit with good adherence on a pearl ball and the gain as high as 18 was realized. These results present great potential for applications of organic single-crystal belts in the next-generation conformal electronics.

  18. Microstructure and superconductivity of MgB2 single crystals

    SciTech Connect

    Kim, Kijoon H.P.; Jung, C.U.; Kang, B.W.; Kim, Kyung Hee; Lee, Hyun-Sook; Lee, Sung-Ik; Tamura, N.; Caldwell, W.A.; Patel, J.R.

    2004-07-19

    The hexagonal-disc-shaped MgB2 single crystals were synthesized under the high-pressure conditions. The crystal symmetry, lattice constants as well as the Laue pattern of these single crystals were obtained from X-ray micro-diffraction. A crystallographic mapping showed that the edge and the c-axis of hexagonal-disc shape exactly matched the [1 0 1 bar 0] and [0 0 0 1] directions of the MgB2 phase. This clearly confirmed that above well-shaped single crystals could be excellent samples to study the unsolved direction dependencies of the physical properties.

  19. A simple low-cost single-crystal NMR setup

    NASA Astrophysics Data System (ADS)

    Vinding, Mads S.; Kessler, Tommy O.; Vosegaard, Thomas

    2016-08-01

    A low-cost single-crystal NMR kit is presented along with a web-based post-processing software. The kit consists of a piezo-crystal motor and a goniometer for the crystal, both embedded in a standard wide-bore NMR probe with a 3D printed scaffold. The NMR pulse program controls the angle setting automatically, and the post-processing software incorporates a range of orientation-angle discrepancies present in the kit and other single-crystal setups. Results with a NaNO3 single-crystal show a high degree of reproducibility and excellent agreement with previous findings for the anisotropic quadrupolar interaction.

  20. Synthesis and characterization of nonlinear optical L-arginine semi-oxalate single crystal

    NASA Astrophysics Data System (ADS)

    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. Growth and characterization of the nonlinear optical single crystal: L-lysine acetate

    NASA Astrophysics Data System (ADS)

    Sun, Z. H.; Zhang, G. H.; Wang, X. Q.; Cheng, X. F.; Liu, X. J.; Zhu, L. Y.; Fan, H. L.; Yu, G.; Xu, D.

    2008-05-01

    Single crystals of L-lysine acetate, an organic nonlinear optical (NLO) material, were grown by the controlled evaporation of its aqueous solutions. Its solubility in aqueous solution was determined gravimetrically. The grown crystals were characterized by the single-crystal diffraction, X-ray powder diffraction, Fourier transform infrared and Raman spectra. The structure analysis reveals that it belongs to the monoclinic crystallographic system, space group P2 1, with cell parameters: a=5.420(2) Å, b=7.542(4) Å, c=12.653(1) Å, β=91.73(1)°, Z=2 and V=516.8 Å 3. Experiments of thermogravimetric (TG) and differential thermal analysis (DTA) were carried out to study its thermal properties. The optical behaviours, including transmission spectrum and second harmonic generation (SHG), were investigated to study its linear and NLO properties.

  2. Temperature and Field Induced Strain Measurements in Single Crystal Gd5Si2Ge2

    NASA Astrophysics Data System (ADS)

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-06-01

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of -8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of -8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.

  3. Thermographic analyses of the growth of Cd1-xZnxTe single crystals

    SciTech Connect

    Kopach, O.V.; Bolotnikov, A.; Shcherbak, Larysa P.; Fochuk, Petro M.; and James, Ralph B.

    2010-08-01

    Bulk Cd1-xZnxTe (0single crystals for gamma-ray detectors are grown mainly from near-stoichiometric melts. We discuss the influence of the thermal pre-history of the melts (superheating, thermo-cycling, and cooling rate) on various physical properties based on our thermographic analyses, electrical conductivity and viscosity measurements. Increasing the Zn content causes non-monotonic dependencies in the quality of the crystals structure.

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

    SciTech Connect

    Sankari, R. Siva; Perumal, Rajesh Narayana

    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.

  5. Growth and electrical properties of mercury indium telluride single crystals

    SciTech Connect

    Wang Linghang Dong Yangchun; Jie Wanqi

    2007-11-06

    A novel photoelectronic single crystal, mercury indium telluride (MIT), has been successfully grown by using vertical Bridgman method (VB). The crystallinity, thermal and electrical properties of the MIT crystal were investigated. The results of X-ray rocking curve show that the as-grown MIT crystal has good crystal quality with the FWHM on (3 1 1) face of about 173 in. DSC measurement reveals that the Hg element is easy to solely evaporate from the compound when the temperature is higher than 387.9 deg. C in the open system. Hall measurements at room temperature show that the resistivity, carrier density and mobility of the MIT crystal were 4.79 x 10{sup 2} {omega} cm, 2.83 x 10{sup 13} cm{sup -3} and 4.60 x 10{sup 2} cm{sup 2} V{sup -1} s{sup -1}, respectively. The reduction of carrier mobility and the increase of the resistivity are related to the adding of In{sub 2}Te{sub 3} into HgTe, which changes the energy band structure of the crystal.

  6. DEVELOPMENT OF PROTECTIVE COATINGS FOR SINGLE CRYSTAL TURBINE BLADES

    SciTech Connect

    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.

  7. Properties of salt-grown uranium single crystals.

    SciTech Connect

    Cooley, J. C.; Hanrahan, R. J.; Hults, W. L.; Lashley, J. C.; Manley, M. E.; Mielke, C. H.; Smith, J. L.; Thoma, D. J.; Clark, R. G.; Hamilton, A. R.; O'Brien, J. L.; Gay, E. C.; Lumpkin, N. E.; McPheeters, C. C.; Willit, J.; Schmiedeshoff, G. M.; Touton, S.; Woodfield, B. F.; Lang, B. E.; Boerio-Goates, Juliana

    2001-01-01

    Recently single crystals of {alpha}-uranium were grown from a liquid salt bath. The electrical, magnetic and thermal properties of these crystals have been surveyed. The ratio of the room temperature resistivity of these crystals to the saturation value at low temperature is three times larger than any previously reported demonstrating that the crystals are of higher purity and quality than those in past work. The resistive signatures of the CDW transitions at 43, 37 and 22 K are obvious to the naked eye. The transition at 22 K exhibits temperature hysteresis that increases with magnetic field. In addition the superconducting transition temperature from resistivity is 820 mK and the critical field is 80 mT. Contrary to earlier work where the Debye temperature ranged from 186 to 218 K, the Debye temperature extracted from the heat capacity is 254 K in good agreement with the predicted value of 250 K. Magnetoresistance, Hall effect and magnetic susceptibility measurements are underway. In time, measurements made on these crystals may help us to understand the origin of superconductivity and its relation to the CDW transitions in pure uranium.

  8. Electrical transport properties of single-crystal Al nanowires.

    PubMed

    Brunbauer, Florian M; Bertagnolli, Emmerich; Majer, Johannes; Lugstein, Alois

    2016-09-23

    Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10(-9) Ω m, i.e. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 10(12) A m(-2) before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron-phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K. PMID:27533003

  9. A Single Crystal Niobium RF Cavity of the TESLA Shape

    SciTech Connect

    Singer, W.; Singer, X.; Kneisel, P.

    2007-08-09

    A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was build. An accelerating gradient of 37.5 MV/m was reached after approximately 110 {mu}m of Buffered Chemical Polishing (BCP) and in situ baking at 120 deg. C for 6 hrs with a quality factor exceeding 2x1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

  10. High-temperature alloys: Single-crystal performance boost

    NASA Astrophysics Data System (ADS)

    Schütze, Michael

    2016-08-01

    Titanium aluminide alloys are lightweight and have attractive properties for high-temperature applications. A new growth method that enables single-crystal production now boosts their mechanical performance.

  11. A Single Crystal Niobium RF Cavity of the TESLA Shape

    SciTech Connect

    W. Singer; X. Singer; P. Kneisel

    2007-09-01

    A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was built. An accelerating gradient of 37.5 MV/m was reached after approximately 110 mu-m of Buffered Chanical Polishing (BCP) and in situ baking at 120°C for 6 hrs with a quality factor exceeding 2x1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

  12. Inhomogeneities in single crystals of cuprate oxide superconductors

    NASA Technical Reports Server (NTRS)

    Moorjani, K.; Bohandy, J.; Kim, B. F.; Adrian, F. J.

    1991-01-01

    The next stage in the evolution of experimental research on the high temperature superconductors will require high quality single crystals and epitaxially grown crystalline films. However, inhomogeneities and other defects are not uncommon in single crystals of cuprate oxide superconductors, so a corollary requirement will be a reliable method for judging the quality of these materials. The application of magnetically modulated resistance methods in this task is briefly described and illustrated.

  13. Anomalous magneto-resistance in single crystals of silver chalcogenides

    NASA Astrophysics Data System (ADS)

    Zhang, Chenglong; Liu, Haiwen; Hua, Wei; Yuan, Zhunjun; Sun, Junliang; Xie, Xincheng; Jia, Shuang

    2015-03-01

    Silver chalcogenides have been known as quantum materials for over fifteen years but no single crystal was ever studied before. Very recently, we developed a method for growth of single crystals. Our measurements of magneto-resistance (MR) showed strong Shubnikov-de Haas (SdH) oscillations associated with a very low quantum limit. When the field is beyond this limit we observed a negative, longitudinal MR, which is believed as a fingerprint of chiral anomaly in Weyl Fermion systems.

  14. Synthesis and Single-Crystal Growth of Ca

    SciTech Connect

    Nakatsuji, Satoru; Maeno, Yoshiteru

    2001-01-01

    For the study of the quasi-two-dimensional Mott transition system Ca{sub 2-x}Sr{sub x}RuO{sub 4}, we have succeeded in synthesizing polycrystalline samples and also growing single crystals by a floating-zone method. Details of the preparations for the entire solution range are described. The structural, transport, and magnetic properties of both polycrystalline and single-crystal samples are fully in agreement.

  15. Single crystal growth and characterization of URu2Si2

    NASA Astrophysics Data System (ADS)

    Haga, Yoshinori; Matsuda, Tatsuma D.; Tateiwa, Naoyuki; Yamamoto, Etsuji; Ōnuki, Yoshichika; Fisk, Zachary

    2014-11-01

    We review recent progress in single crystal growth and study of electronic properties in ?. Czocharalski pulling, using purified uranium metal and subsequent annealing under ultra-high vacuum, is successfully applied to this compound, and it yields the highest residual resistivity ratio. These high-quality single crystals allow us to investigate Fermi surfaces using quantum oscillation and to make detailed transport measurements at low temperature.

  16. Single crystal Processing and magnetic properties of gadolinium nickel

    SciTech Connect

    Shreve, Andrew John

    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.

  17. Fatigue damage modeling for coated single crystal superalloys

    NASA Technical Reports Server (NTRS)

    Nissley, David M.

    1988-01-01

    A high temperature, low-cycle fatigue life prediction method for coated single crystal nickel-base superalloys is being developed. The method is being developed for use in predicting crack initiation life of coated single crystal turbine airfoils. Although the models are being developed using coated single crystal PWA 1480, they should be readily adaptable to other coated nickel-base single crystal materials. The coatings choosen for this effort were of two generic types: a low pressure plasma sprayed NiCoCrAlY overlay, designated PWA 286, and an aluminide diffusion, designated PWA 273. In order to predict the useful crack initiation life of airfoils, the constitutive and failure behavior of the coating/substrate combination must be taken into account. Coatings alter the airfoil surface microstructure and are a primary source from which cracks originate. The adopted life prediction approach addresses this complexity by separating the coating and single crystal crack initiation regimes. This provides a flexible means for using different life model formulations for the coating and single crystal materials. At the completion of this program, all constitutive and life model formulations will be available in equation form and as software. The software will use the MARC general purpose finite element code to drive the constitutive models and calculate life parameters.

  18. Effect of L-Valine on the growth and characterization of Sodium Acid Phthalate (SAP) single crystals

    NASA Astrophysics Data System (ADS)

    Nirmala, L. Ruby; Prakash, J. Thomas Joseph

    2013-06-01

    Undoped and amino acid doped good quality single crystals of Sodium Acid Phthalate crystals (SAP) were grown by slow evaporation solution growth technique which are semiorganic in nature. The effect of amino acid (L-Valine) dopant on the growth and the properties of SAP single crystal was investigated. The single crystal X-ray diffraction studies and FT-IR studies were carried out to identify the crystal structure and the presence of functional groups in undoped and L-Valine doped SAP crystals. The transparent nature of the grown crystal was observed using UV-Visible spectrum. The thermal decomposition of the doped SAP crystals was investigated by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The enhancement in the NLO property of the undoped and L-Valine doped SAP crystals using KDP crystal as a reference was studied using SHG measurements. Vickers micro hardness measurements are used for the study of mechanical strength of the grown crystals.

  19. Anisotropic electrical and thermal conductivity in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} [AE = Ca, Sr{sub 1−x}Ba{sub x} (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals

    SciTech Connect

    Dong, Song-Tao; Zhang, Bin-Bin; Lv, Yang-Yang; Zhou, Jian; Zhang, Shan-Tao; Xiong, Ye; Yao, Shu-Hua E-mail: ybchen@nju.edu.cn; Chen, Y. B. E-mail: ybchen@nju.edu.cn; Chen, Yan-Feng

    2015-09-28

    Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE represents alkaline earth), constructed by stacking of rock-salt Bi{sub 2}AE{sub 2}O{sub 4} and triangle CoO{sub 2} layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ}, as reported previously, is their electrical conductivity mainly lying along CoO{sub 2} plane, adjusting Bi{sub 2}AE{sub 2}O{sub 4} layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE = Ca, Sr, Ba, Sr{sub 1−x}Ba{sub x}) single crystals. The results substantiate that isovalence replacement in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi{sub 2}AE{sub 2}O{sub 4} layer in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.

  20. Measurement of single crystal surface parameters

    NASA Technical Reports Server (NTRS)

    Swanson, L. W.; Bell, A. E.; Strayer, R. W.

    1972-01-01

    The sticking coefficient and thermal desorption spectra of Cs from the (110) plane of W was investigated. A sticking coefficient of unity for the monolayer region was measured for T 250 K. Several distinct binding states were observed in the thermal desorption spectrum. Work function and electron reflection measurements were made on the (110) and (100) crystal faces of Mo. Both LEED and Auger were used to determine the orientation and cleanliness of the crystal surfaces. The work function values obtained for the (110) and (100) planes of Mo were 4.92 and 4.18 eV respectively.

  1. Single crystal diamond for infrared sensing applications

    SciTech Connect

    Majdi, S. Kovi, K. K.; Isberg, J.; Kolahdouz, M.; Moeen, M.; Radamson, H. H.; Balmer, R. S.

    2014-10-20

    The synthesis of new materials for thermal infrared (IR) detection has been an intensive research area in recent years. Among new semiconductor materials, synthetic diamond has the ability to function even under very high temperature and high radiation conditions. In the present work, diamond Schottky diodes with boron concentrations in the range of 10{sup 14 }< B < 10{sup 17 }cm{sup −3} are presented as candidates for IR thermal sensors with an excellent temperature coefficient of resistance (−8.42%/K) and very low noise levels around 6.6 × 10{sup −15} V{sup 2}/Hz. This enables huge performance enhancements for a wide variety of systems, e.g., automotive and space applications.

  2. Mesoporous TiO2 single crystals delivering enhanced mobility and optoelectronic device performance.

    PubMed

    Crossland, Edward J W; Noel, Nakita; Sivaram, Varun; Leijtens, Tomas; Alexander-Webber, Jack A; Snaith, Henry J

    2013-03-14

    Mesoporous ceramics and semiconductors enable low-cost solar power, solar fuel, (photo)catalyst and electrical energy storage technologies. State-of-the-art, printable high-surface-area electrodes are fabricated from thermally sintered pre-formed nanocrystals. Mesoporosity provides the desired highly accessible surfaces but many applications also demand long-range electronic connectivity and structural coherence. A mesoporous single-crystal (MSC) semiconductor can meet both criteria. Here we demonstrate a general synthetic method of growing semiconductor MSCs of anatase TiO2 based on seeded nucleation and growth inside a mesoporous template immersed in a dilute reaction solution. We show that both isolated MSCs and ensembles incorporated into films have substantially higher conductivities and electron mobilities than does nanocrystalline TiO2. Conventional nanocrystals, unlike MSCs, require in-film thermal sintering to reinforce electronic contact between particles, thus increasing fabrication cost, limiting the use of flexible substrates and precluding, for instance, multijunction solar cell processing. Using MSC films processed entirely below 150 °C, we have fabricated all-solid-state, low-temperature sensitized solar cells that have 7.3 per cent efficiency, the highest efficiency yet reported. These high-surface-area anatase single crystals will find application in many different technologies, and this generic synthetic strategy extends the possibility of mesoporous single-crystal growth to a range of functional ceramics and semiconductors. PMID:23467091

  3. Growth of propyl-p-hydroxybenzoate single crystals and its characterizations

    NASA Astrophysics Data System (ADS)

    Karunagaran, N.; Ramasamy, P.

    2012-06-01

    Single crystals of Propyl-p-hydroxybenzoate (PHB) crystals have been grown by slow evaporation solution technique (SEST) using methanol as a solvent. The PHB single crystal of dimension up to 27×16×8 mm3 has been grown in a period of 18 days at room temperature. The optical transparency of the grown PHB crystal has been measured on (212) plane by UV-Vis-NIR spectrophotometer. The crystal has 60% of transparency in the entire visible region. The thermo gravimetric analysis (TG) and differential thermal analysis (DTA) studies reveal that the crystal is thermally stable up to 99°C. The mechanical strength of the grown PHB crystal is measured using Vickers microhardness tester. The chemical etching studies were carried out on (212) plane using methanol etchant. The laser damage threshold of PHB crystal is 1.3 GW/cm2. The dielectric properties have been investigated. The birefringence value is found to be 0.10148 at the wavelength of 504 nm. The refractive index of grown PHB single crystal is 1.6753.

  4. Growth and surface morphology of ErFeO3 single crystal

    NASA Astrophysics Data System (ADS)

    Chang, Fenfen; Yuan, Shujuan; Wang, Yabin; Zhan, Sheng; Cao, Shixun; Wu, Anhua; Xu, Jun

    2011-03-01

    ErFeO3 single crystal 7 mm in diameter and up to 70 mm in length has been grown by the floating zone technique using a four-mirror image furnace. Particular attention was given to the surface morphology of different cross-sections of the single crystal perpendicular to the growth direction. There are many cracks, bubbles, and precipitations on the cross-sections of the crystal observed by scanning electron microscopy. The thermal stress induced by the high growth rate might play an important role in the formation of the cracks. The bubbles might be mainly caused by high growth rate and the voids within the sintered feed rod. The energy-dispersive X-ray spectroscopy analysis indicates that there is Fe deficiency in the crystal especially in the precipitations.

  5. Single-crystal diamond pyramids: synthesis and application for atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Ismagilov, Rinat R.

    2016-03-01

    Here we present the results of investigations aimed at the development and testing of robust, chemically inert single-crystal diamond probes for atomic force microscopy (AFM). The probes were prepared by assembling common silicon probes with micrometer-sized pyramid-shaped single-crystal diamonds (SCD). The SCD were obtained by the selective thermal oxidation of the polycrystalline films grown by chemical vapor deposition. Electrostatic spray of adhesive coating onto silicon probes was used to attach individual SCD. Geometrical parameters of produced AFM SCD probes were revealed with transmission electron microscopy: the apex angle of the pyramidal diamond crystallite was ˜10 deg, and the curvature radius at the apex was ˜2 to 10 nm. The diamond AFM probes were used for surface imaging of deoxyribonucleic acid deposited on graphite substrate. Obtained results demonstrate high efficiency of the diamond AFM probes, allowing improvement of the image quality compared to standard silicon probes.

  6. Preparation and characterization of single crystal samples for high-pressure experiments

    SciTech Connect

    Farber, D; Antonangeli, D; Aracne, C; Benterou, J

    2005-10-26

    To date, most research utilizing the diamond anvil cell (DAC) has been conducted with polycrystalline samples, thus the results are limited to addressing average bulk properties. However, experiments on single crystals can yield data on a range of orientation dependent properties such as thermal and electrical conductivity, magnetic susceptibility, elasticity and plasticity. Here we report new procedures to produce extremely high-quality metallic single crystal samples of size compatible with DAC experiments in the Mbar range. So far, we have produced samples of zinc, Al{sub 2}O{sub 3}, cobalt, molybdenum and cerium, and have evaluated the quality of the finished samples with white-light interferometry, synchrotron x-ray diffraction and inelastic x-ray scattering.

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

    PubMed

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

    2009-09-01

    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. PMID:21832321

  8. Low-cost single-crystal turbine blades, volume 2

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Dennis, R. E.; Heath, B. R.

    1984-01-01

    The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through extensive mechanical property testing, rig testing, and 200 hours of endurance engine testing. These Program objectives were achieved. The exothermic casting process was successfully developed into a low-cost nonproperietary method for producing single-crystal castings. Single-crystal MAR-M 247 and two derivatives DS alloys developed during this project, NASAIR 100 and SC Alloy 3, were fully characterized through mechanical property testing. SC MAR-M 247 shows no significant improvement in strength over directionally solidified (DS) MAR-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. Firtree testing, holography, and strain-gauge rig testing were used to determine the effects of the anisotropic characteristics of single-crystal materials. No undesirable characteristics were found. In general, the single-crystal material behaved similarly to DS MAR-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined. These blades were successfully engine-tested.

  9. Thermal desorption of metals from tungsten single crystal surfaces

    NASA Technical Reports Server (NTRS)

    Bauer, E.; Bonczek, F.; Poppa, H.; Todd, G.

    1975-01-01

    After a short review of experimental methods used to determine desorption energies and frequencies the assumptions underlying the theoretical analysis of experimental data are discussed. Recent experimental results on the flash desorption of Cu, Ag, and Au from clean, well characterized W (110) and (100) surfaces are presented and analyzed in detail with respect to the coverage dependence. The results obtained clearly reveal the limitations of previous analytical methods and of the experimental technique per se (such as structure and phase changes below and in the temperature region in which desorption occurs).

  10. Thermal behaviour of helium-implanted spinel single crystals

    NASA Astrophysics Data System (ADS)

    Velisa, G.; Debelle, A.; Vincent, L.; Thomé, L.; Declémy, A.; Pantelica, D.; Antohe, S.

    2011-09-01

    The study of the microstructural modifications induced in spinel implanted with 4He + at 4.7 at.% and subsequently annealed at 1075 K is addressed in this paper. The combination of three analysis techniques Rutherford backscattering spectrometry in channeling geometry (RBS/C), X-ray diffraction and transmission electron microscopy was used in order to gain information about the damage depth distribution, the nature of radiation defects, and the occurrence of microstructural modifications. In as-implanted crystals the disorder level is weak, and the damage principally consists of small helium-vacancy clusters. These defects induce a tensile strain in the direction normal to the implanted crystal surface. After annealing, a surprising increase of the disorder level is measured by RBS/C. This increased backscattering yield is due to the formation of a particular type of He-vacancy clusters, namely He platelets, which also induce a relaxation of the strain.

  11. Preparation and characterization of pure and Pr(III)-doped lead chloride single crystals grown by modified micro-pulling-down method

    NASA Astrophysics Data System (ADS)

    Král, R.; Nitsch, K.; Jarý, V.; Yokota, Y.; Futami, F.; Yoshikawa, A.; Nikl, M.

    2013-07-01

    Single crystals of lead chloride pure and doped with Pr(III) were grown for the first time using the modified micro-pulling-down method. Due to hygroscopicity of both lead chloride and doping Pr(III) chloride the standard micro-pulling-down apparatus had to be equipped with a removable protective chamber. Prepared single crystals 25 mm long and 3 mm in diameter were characterized by powder X-ray diffraction and DSC thermal analysis. Optical and luminescence characteristics of lead chloride single crystals, such as absorption, radioluminescence, photoluminescence, and decay curves, were measured as well.

  12. The effects of alloy purity on the mechanical behavior of soft oriented NiAl single crystals

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1993-01-01

    Preliminary results of the effects of alloy purity on the mechanical properties of NiAl single crystals are presented. Two stoichiometric NiAl single crystals with different impurity contents were studied. It is concluded that reductions in the interstitial and substitutional levels cause reduced yield strengths in NiAl. Heat treatment also results in reduced yield and flow stresses in both CP-NiAl and Hp-NiAl which are considered to be due to a reduction in the concentration of thermal vacancies due to vacancy coalescence during heat treatment.

  13. Growth and properties of Lithium Salicylate single crystals

    SciTech Connect

    Zaitseva, N; Newby, J; Hull, G; Saw, C; Carman, L; Cherepy, N; Payne, S

    2009-02-13

    An attractive feature of {sup 6}Li containing fluorescence materials that determines their potential application in radiation detection is the capture reaction with slow ({approx}< 100 keV) neutrons: {sup 6}Li + n = {sup 4}He + {sup 3}H + 4.8MeV. The use of {sup 6}Li-salicylate (LiSal, LiC{sub 6}H{sub 5}O{sub 3}) for thermal neutron detection was previously studied in liquid and polycrystalline scintillators. The studies showed that both liquid and polycrystalline LiSal scintillators could be utilized in pulse shape discrimination (PSD) techniques that enable separation of neutrons from the background gamma radiation. However, it was found that the efficiency of neutron detection using LiSal in liquid solutions was severely limited by its low solubility in commonly used organic solvents like, for example, toluene or xylene. Better results were obtained with neutron detectors containing the compound in its crystalline form, such as pressed pellets, or microscopic-scale (7-14 micron) crystals dispersed in various media. The expectation drown from these studies was that further improvement of pulse height, PSD, and efficiency characteristics could be reached with larger and more transparent LiSal crystals, growth of which has not been reported so far. In this paper, we present the first results on growth and characterization of relatively large, a cm-scale size, single crystals of LiSal with good optical quality. The crystals were grown both from aqueous and anhydrous (methanol) media, mainly for neutron detection studies. However, the results on growth and structural characterization may be interesting for other fields where LiSal, together with other alkali metal salicylates, is used for biological, medical, and chemical (as catalyst) applications.

  14. Charged-particle spectroscopy in organic semiconducting single crystals

    NASA Astrophysics Data System (ADS)

    Ciavatti, A.; Sellin, P. J.; Basiricò, L.; Fraleoni-Morgera, A.; Fraboni, B.

    2016-04-01

    The use of organic materials as radiation detectors has grown, due to the easy processability in liquid phase at room temperature and the possibility to cover large areas by means of low cost deposition techniques. Direct charged-particle detectors based on solution-grown Organic Semiconducting Single Crystals (OSSCs) are shown to be capable to detect charged particles in pulse mode, with very good peak discrimination. The direct charged-particle detection in OSSCs has been assessed both in the planar and in the vertical axes, and a digital pulse processing algorithm has been used to perform pulse height spectroscopy and to study the charge collection efficiency as a function of the applied bias voltage. Taking advantage of the charge spectroscopy and the good peak discrimination of pulse height spectra, an Hecht-like behavior of OSSCs radiation detectors is demonstrated. It has been possible to estimate the mobility-lifetime value in organic materials, a fundamental parameter for the characterization of radiation detectors, whose results are equal to μτcoplanar = (5 .5 ± 0.6 ) × 10-6 cm2/V and μτsandwich = (1 .9 ± 0.2 ) × 10-6 cm2/V, values comparable to those of polycrystalline inorganic detectors. Moreover, alpha particles Time-of-Flight experiments have been carried out to estimate the drift mobility value. The results reported here indicate how charged-particle detectors based on OSSCs possess a great potential as low-cost, large area, solid-state direct detectors operating at room temperature. More interestingly, the good detection efficiency and peak discrimination observed for charged-particle detection in organic materials (hydrogen-rich molecules) are encouraging for their further exploitation in the detection of thermal and high-energy neutrons.

  15. Growing intermetallic single crystals using in situ decanting

    SciTech Connect

    Petrovic, Cedomir; Canfield, Paul; Mellen, Jonathan

    2012-05-16

    High temperature metallic solution growth is one of the most successful and versatile methods for single crystal growth, and is particularly suited for exploratory synthesis. The method commonly utilizes a centrifuge at room temperature and is very successful for the synthesis of single crystal phases that can be decanted from the liquid below the melting point of the silica ampoule. In this paper, we demonstrate the extension of this method that enables single crystal growth and flux decanting inside the furnace at temperatures above 1200°C. This not only extends the number of available metallic solvents that can be used in exploratory crystal growth but also can be particularly well suited for crystals that have a rather narrow exposed solidification surface in the equilibrium alloy phase diagram.

  16. A simple low-cost single-crystal NMR setup.

    PubMed

    Vinding, Mads S; Kessler, Tommy O; Vosegaard, Thomas

    2016-08-01

    A low-cost single-crystal NMR kit is presented along with a web-based post-processing software. The kit consists of a piezo-crystal motor and a goniometer for the crystal, both embedded in a standard wide-bore NMR probe with a 3D printed scaffold. The NMR pulse program controls the angle setting automatically, and the post-processing software incorporates a range of orientation-angle discrepancies present in the kit and other single-crystal setups. Results with a NaNO3 single-crystal show a high degree of reproducibility and excellent agreement with previous findings for the anisotropic quadrupolar interaction. PMID:27295612

  17. Preparation and tensile properties of DD5 single crystal castings

    NASA Astrophysics Data System (ADS)

    Liang, Xiang-feng; Zhao, Yu-tao; Jia, Zhi-hong; Zhang, Chi

    2016-06-01

    The preparation procedure of DD5 single crystal castings was optimized. The microstructure characteristics of DD5 single crystal superalloy were investigated by microstructure observation and segregation behavior examination. The results show that the grain orientation is optimized by constraining the spiral crystallizer in [001] orientation and spatial scale. Also, the γ' phase of inter-dendrites is larger and more irregular than that in dendrite arms. High temperature tensile tests of DD5 single crystal castings exhibit that the peak stress increases with increasing temperature, while the area reduction shows an opposite trend, when the temperature is below 800°C; meanwhile, when the temperature is between 800°C and 1000°C, the fracture stress of the alloy is the same as the peak stress. The fracture mode changes from shear to ductile with increasing temperature from 600°C and 1000°C.

  18. The Load Capability of Piezoelectric Single Crystal Actuators

    NASA Technical Reports Server (NTRS)

    Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

    2007-01-01

    Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

  19. The Load Capability of Piezoelectric Single Crystal Actuators

    NASA Technical Reports Server (NTRS)

    Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

    2006-01-01

    Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

  20. Twisted Single Crystals of Meta-Aromatic Polyamides

    NASA Astrophysics Data System (ADS)

    Lawrence, D. P.; Martin, D. C.

    1996-03-01

    The morphology of single crystals of the aromatic polyamide poly(metaphenylene isophthalamide) (MPDI or Nomex) was studied by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The single crystals of MPDI were slowly grown from 0.1 weight percent solution. MPDI forms elongated crystals which aggregate together to form highly regular twisted helical bundles. The repeat periods of the helices typically range from 240 nm to 1000 nm and the bundle diameters vary from 36 nm to 120 nm. The angle between the edge of the crystal and the bundle axis varies from 40 to 65 degrees. The regular twisting evidently arises from a bending moment induced by the triclinic symmetry of the MPDI unit cell and the lamellar geometry of the chain-folded single crystal.

  1. A study of the structure and scattering mechanisms of subterahertz phonons in lithium fluoride single crystals and optical ceramics

    SciTech Connect

    Khazanov, E. N. Taranov, A. V.; Gainutdinov, R. V.; Akchurin, M. Sh.; Basiev, T. T.; Konyushkin, V. A.; Fedorov, P. P.; Kuznetsov, S. V.; Osiko, V. V.

    2010-06-15

    The methods of optical, electron, and atomic force microscopy (AFM) are applied to the study of the real structure of optical lithium fluoride ceramic obtained by hot deformation of single crystals. A comparative analysis is carried out of the scattering mechanisms of weakly nonequilibrium thermal phonons at liquid helium temperatures in LiF single crystals and ceramics. It is demonstrated that the phonon scattering in the original single crystals is determined by the forced vibrations of dislocations in the stress field of an elastic plane wave (a phonon), i.e., by the flutter mechanism. As the degree of deformation of the original material increases, the ceramics exhibit a change in the plastic deformation mechanisms, which leads to a decrease in the average size of grains and to an ordered structure. In this case, the dominant scattering is that by intergrain boundaries. The thickness and the acoustic impedance of these boundaries are evaluated.

  2. Comparative Investigation of the Downward and Upward Directionally Solidified Single-Crystal Blades of Superalloy CMSX-4

    NASA Astrophysics Data System (ADS)

    Wang, Fu; Ma, Dexin; Bogner, Samuel; Bührig-Polaczek, Andreas

    2016-05-01

    Single-crystal blades of Ni-base superalloys CMSX-4 have been directionally solidified using the downward directional solidification (DWDS) process. The possible benefits of the process were comparatively evaluated with respect to the Bridgman process' results. The DWDS process exhibits good capabilities for casting the single-crystal components. The thermal gradients of this process are approximately seven times higher than those of the Bridgman process. It provides more advantages for solidifying the single-crystal superalloy blades by reducing the casting defects, refining the microstructure, decreasing the size of the γ/ γ' eutectic pools, refining the γ' precipitates, alleviating the degree of the microsegregation, and minimizing the size and volume fraction of the micropores.

  3. Silicon single-crystal cryogenic optical resonator.

    PubMed

    Wiens, Eugen; Chen, Qun-Feng; Ernsting, Ingo; Luckmann, Heiko; Rosowski, Ulrich; Nevsky, Alexander; Schiller, Stephan

    2014-06-01

    We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 h. This stability allowed sensitive measurements of the resonator thermal expansion coefficient (α). We found that α=4.6×10(-13)  K(-1) at 1.6 K. At 16.8 K α vanishes, with a derivative equal to -6×10(-10)  K(-2). The temperature of the resonator was stabilized to a level below 10 μK for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-10(-17) level. PMID:24876023

  4. Method for harvesting single crystals from a peritectic melt

    DOEpatents

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

    1996-01-01

    A method of preparing 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, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals 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 unmelted, allowing the wicking away of the peritectic liquid.

  5. Method for harvesting single crystals from a peritectic melt

    DOEpatents

    Todt, V.R.; Sengupta, S.; Shi, D.

    1996-08-27

    A method of preparing single crystals is disclosed. 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, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals 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 unmelted, allowing the wicking away of the peritectic liquid. 2 figs.

  6. Two-photon-induced singlet fission in rubrene single crystal

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Galstyan, Gegham; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E.; Gurzadyan, Gagik G.

    2013-05-01

    The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm/GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data.

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

    SciTech Connect

    Du Jimin; Liu Zhimin . E-mail: liuzm@iccas.ac.cn; Wu Weize; Li Zhonghao; Han Buxing . E-mail: hanbx@iccas.ac.cn; Huang Ying

    2005-06-15

    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)

  8. Growth and surface topography of WSe2 single crystal

    NASA Astrophysics Data System (ADS)

    Dixit, Vijay; Vyas, Chirag; Pataniya, Pratik; Jani, Mihir; Pathak, Vishal; Patel, Abhishek; Pathak, V. M.; Patel, K. D.; Solanki, G. K.

    2016-05-01

    Tungsten Di-Selenide belongs to the family of TMDCs showing their potential applications in the fields of Optoelectronics and PEC solar cells. Here in the present investigation single crystals of WSe2 were grown by Direct Vapour Transport Technique in a dual zone furnace having temperature difference of 50 K between the two zones. These single crystals were characterized by EDAX which confirms the stiochiometry of the grown crystals. Surface topography of the crystal was studied by optical micrograph showing the left handed spirals on the surface of WSe2 crystals. Single crystalline nature of the crystals was confirmed by SAED.

  9. Optical and photoelectrochemical study of WTe2 single crystals

    NASA Astrophysics Data System (ADS)

    Desai, P. F.; Patel, D. D.; Bhavsar, D. N.; Jani, A. R.

    2013-06-01

    Single crystals of Tungsten Ditelluride (WTe2) having a layered structure grown by chemical vapor transport method using iodine as the transporting agent are studied here. The optical response of these crystals has been obtained by UV-Vis-NIR spectroscopy at room temperature. Results of optical spectra have been analyzed on the basis of three dimensional models. Photoelectrochemical (PEC) characterization of WTe 2 single crystals have been carried out. Photo response measurements were obtained at different intensities of light source to illuminate the photoanode. The effect of intensity in the efficiency of PEC solar cell has been studied. The implications of the results have been discussed.

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

    DOEpatents

    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.

  11. Constitutive Modeling of Superalloy Single Crystals and Directionally Solidified Materials

    NASA Technical Reports Server (NTRS)

    Walker, K. P.; Jordan, E. H.

    1985-01-01

    A unified viscoplastic constitutive relation based on crystallographic slip theory was developed for the deformation analysis of nickel base face centered cubic superalloy single crystals at elevated temperature. The single crystal theory is embedded in a self consistent method to derive a constitutive relation for a directionally solidified material comprised of a polycrystalline aggregate of columnar cylindrical grains. One of the crystallographic axes of the cylindrical crystals points in the columnar direction while the remaining crystallographic axes are oriented at random in the basal plane perpendicular to the columnar direction. These constitutive formulations are coded in FORTRAN for use in nonlinear finite element and boundary element programs.

  12. Single crystal niobium tubes for particle colliders accelerator cavities

    SciTech Connect

    Murphy, James E

    2013-02-28

    The objective of this research project is to produce single crystal niobium (Nb) tubes for use as particle accelerator cavities for the Fermi laboratory’s International Linear Collider project. Single crystal Nb tubes may have superior performance compared to a polycrystalline tubes because the absence of grain boundaries may permit the use of higher accelerating voltages. In addition, Nb tubes that are subjected to the high temperature, high vacuum crystallization process are very pure and well annealed. Any impurity with a significantly higher vapor pressure than Nb should be decreased by the relatively long exposure at high temperature to the high vacuum environment. After application of the single crystal process, the surfaces of the Nb tubes are bright and shiny, and the tube resembles an electro polished Nb tube. For these reasons, there is interest in single crystal Nb tubes and in a process that will produce single crystal tubes. To convert a polycrystalline niobium tube into a single crystal, the tube is heated to within a few hundred °C of the melting temperature of niobium, which is 2477 °C. RF heating is used to rapidly heat the tube in a narrow zone and after reaching the operating temperature, the hot zone is slowly passed along the length of the tube. For crystallization tests with Nb tubes, the traverse rate was in the range of 1-10 cm per hour. All the crystallization tests in this study were performed in a water-cooled, stainless steel chamber under a vacuum of 5 x10-6 torr or better. In earliest tests of the single crystal growth process, the Nb tubes had an OD of 1.9 cm and a wall thickness of 0.15 mm. With these relatively small Nb tubes, the single crystal process was always successful in producing single crystal tubes. In these early tests, the operating temperature was normally maintained at 2200 °C, and the traverse rate was 5 cm per hour. In the next test series, the Nb tube size was increased to 3.8 cm OD and the wall thickness was

  13. Raman spectroscopic study of cation disorder in poly- and single crystals of the nickel aluminate spinel

    NASA Astrophysics Data System (ADS)

    Laguna-Bercero, M. A.; Sanjuán, M. L.; Merino, R. I.

    2007-05-01

    The Raman spectrum of NiAl2O4 inverse spinel has been studied in quenched polycrystalline pellets produced by solid-state reaction and in single crystals grown by the floating zone method. The lattice parameters and inversion degrees were determined by x-ray diffraction. Polarization measurements in single crystals allow mode symmetry assignment. Then, a correlation is established between the bands observed in polycrystalline samples and those of single crystals. Both kinds of sample present more bands than the five expected (A1g+Eg+3T2g) in a cubic Fd3m spinel. This multiplicity is attributed to the almost fully inverted cation distribution in NiAl2O4, with inversion parameter xap0.9. The multiplicity of the high-frequency A1g band, in particular, is attributed to the different possible configurations of Ni2+ and Al3+ cations occupying the three octahedral sites close to a given oxygen ion. A strong downshift of the Eg mode frequency, as compared to the normal spinel MgAl2O4, is attributed to the longer bonding distance between oxygen and octahedral cations in inverse II-III spinels. Due to the small range of variation of x upon thermal treatment in NiAl2O4, no significant differences were found between the spectra of samples quenched at different temperatures, from 800 to 1200 °C.

  14. Single Crystal Preparation for High-Pressure Experiments in the Diamond Anvil Cell

    SciTech Connect

    Aracne, C; Farber, D; Benterou, J; Occelli, F; Krisch, M; Antonangeli, D; Requardt, H; Fiquet, G

    2003-07-01

    Most research conducted in diamond anvil cells (DAC) is performed on polycrystalline samples. While data from polycrystalline samples are sufficient for determining the bulk properties, high-pressure experiments on single crystals allow for measurements on a range of tensor properties such as: thermal and electrical conductivity; magnetic susceptibility; elasticity; and plasticity. However, in order to achieve pressures above 1 Mbar in a DAC, single crystal samples must be <50 m in diameter and <15 m thick while maintaining a high degree of crystallinity. Thus, we have developed new procedures for producing extremely high-quality micro single crystal samples from commercially available material. Our sample preparation steps include cutting, classical metallographic polishing, and laser ablation. The key to our new process is the preservation of crystallinity during cutting and thinning. We have been successful in maintaining orientation, along with an extremely high degree of crystallinity in completed metal samples. To date, we have analyzed cobalt and molybdenum samples with both white-light interferometry and synchrotron x-ray diffraction, and are in the process of extending these methods to other metals and ceramics.

  15. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

    1999-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the

  16. Could one make a diamond-based quantum computer?

    PubMed

    Stoneham, A Marshall; Harker, A H; Morley, Gavin W

    2009-09-01

    We assess routes to a diamond-based quantum computer, where we specifically look towards scalable devices, with at least 10 linked quantum gates. Such a computer should satisfy the deVincenzo rules and might be used at convenient temperatures. The specific examples that we examine are based on the optical control of electron spins. For some such devices, nuclear spins give additional advantages. Since there have already been demonstrations of basic initialization and readout, our emphasis is on routes to two-qubit quantum gate operations and the linking of perhaps 10-20 such gates. We analyse the dopant properties necessary, especially centres containing N and P, and give results using simple scoping calculations for the key interactions determining gate performance. Our conclusions are cautiously optimistic: it may be possible to develop a useful quantum information processor that works above cryogenic temperatures. PMID:21832328

  17. Focus on diamond-based photonics and spintronics

    NASA Astrophysics Data System (ADS)

    Jelezko, Fedor; Wrachtrup, Jörg

    2012-10-01

    The ability to control the state of individual atoms is a new challenge for science and technology in the 21st century. Currently, experiments on individual quantum systems such as trapped ions, single molecules, quantum dots, superconducting qubits and photons are crucial for the rapidly growing field of quantum information processing and communication. In general, solid state systems are preferable for scaling and the choice of material plays a crucial role; for example, in classical electronic devices continual performance enhancement and miniaturization is strongly linked to the success of silicon-based technology. For quantum applications, diamond has the potential to become the material of choice, because its large bandgap enables the control of optically active impurities and higher operation temperature. This focus issue collates original research contributions from some of the leading groups in the field as a showcase for the very latest developments in diamond-based quantum technologies.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. 3D crack tip fields for FCC single crystals

    SciTech Connect

    Cuitino, A.M.; Ortiz, M.

    1995-12-31

    Cracks in single crystals are of concern in a number of structural and non-structural applications, ranging form single-crystal turbine blades and rotors to metal interconnect lines in microcircuits. In this paper we present 3D numerical simulations of the crack-tip fields of a Cu single crystal, including stress, strain and slip activity patterns. The orientation of the crack tip is along the crystallographic orientation (101), while the crack plane is (010). A material model based on dislocation mechanics is used in these simulations. This model correctly predicts the observed behavior of Cu, including the basic hardening characteristics of single crystals, orientation dependence and stage I-II-III structure of the stress-strain curves, the observed levels of latent hardening and their variation with orientation and deformation in the primary system and slip activities and dislocation densities. We use the FEM within the context of finite deformation plasticity. In the figure below, we show the finite element mesh composed by 12-noded tetrahedrons with 6-noded triangular faces. The model simulates half of a beam, which is subjected to a concentrated load at 1/8 of total length from the support. Detailed results of the stress, deformation and slip activity are presented at different radii from crack tip and at different depths from the surface. In general, the results show a strong difference in the slip activity pattern form the interior to the exterior, while smaller differences are encountered in the stress and strain fields.

  20. Low-cost single-crystal turbine blades, volume 1

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Heath, B.; Fujii, M.

    1983-01-01

    The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. NASAIR 100 and SC Alloy 3 were fully characterized through mechanical property testing. SC Mar-M 247 shows no significant improvement in strength over directionally solidified (DS) Mar-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. In general, the single crystal material behaved similarly to DS Mar-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined.

  1. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

    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.

  2. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Dreshfield, R. L.; Maier, R. D.

    1980-01-01

    The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factor contours for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The tensile properties correlated well with the appropriate Schmid factor contours. The stress rupture lives at lower testing temperatures were greatly influenced by the lattice rotations required to produce cross slip. A unified analysis was attained for the stress rupture life data generated for the Mar-M247 single crystals at 760 and 774 C under a stress of 724 MPa and the data reported for Mar-M200 single crystals tested at 760 C under a stress of 689 MPa. Based on this analysis, the stereographic triangle was divided into several regions which were rank ordered according to stress rupture life for this temperature regime.

  3. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Maier, R. D.; Dreshfield, R. L.

    1980-01-01

    The effects of crystal orientation on the mechanical properties of single crystals of the nickel-based superalloy Mar-M247 are investigated. Tensile tests at temperatures from 23 to 1093 C and stress rupture tests at temperatures from 760 to 1038 C were performed for 52 single crystals at various orientations. During tensile testing between 23 and 760 C, single crystals with high Schmid factors were found to be favorably oriented for slip and to exhibit lower strength and higher ductility than those with low Schmid factors. Crystals which required large rotations to become oriented for cross slip were observed to have the shortest stress rupture lives at 760 C, while those which required little or no rotation had the longest lives. In addition, stereographic triangles obtained for Mar-M247 and Mar-M200 single crystals reveal that crystals with orientations near the -111 had the highest lives, those near the 001 had high lives, and those near the 011 had low lives.

  4. Dynamic actuation of single-crystal diamond nanobeams

    SciTech Connect

    Sohn, Young-Ik; Burek, Michael J.; Lončar, Marko; Kara, Vural; Kearns, Ryan

    2015-12-14

    We show the dielectrophoretic actuation of single-crystal diamond nanomechanical devices. Gradient radio-frequency electromagnetic forces are used to achieve actuation of both cantilever and doubly clamped beam structures, with operation frequencies ranging from a few MHz to ∼50 MHz. Frequency tuning and parametric actuation are also studied.

  5. TOPICAL REVIEW: Organic field-effect transistors using single crystals

    NASA Astrophysics Data System (ADS)

    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 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.

  6. Low temperature magnetic transitions of single crystal HoBi

    SciTech Connect

    Fente, A.; Suderow, H.; Vieira, S.; Nemes, N. M.; Garcia-Hernandez, M.; Budko, Sergei L.; Canfield, Paul C.

    2013-09-04

    We present resistivity, specific heat and magnetization measurements in high quality single crystals of HoBi, with a residual resistivity ratio of 126. We find, from the temperature and field dependence of the magnetization, an antiferromagnetic transition at 5.7 K, which evolves, under magnetic fields, into a series of up to five metamagnetic phases.

  7. Transverse Mode Multi-Resonant Single Crystal Transducer

    NASA Technical Reports Server (NTRS)

    Snook, Kevin A. (Inventor); Liang, Yu (Inventor); Luo, Jun (Inventor); Hackenberger, Wesley S. (Inventor); Sahul, Raffi (Inventor)

    2015-01-01

    A transducer is disclosed that includes a multiply resonant composite, the composite having a resonator bar of a piezoelectric single crystal configured in a d(sub 32) transverse length-extensional resonance mode having a crystallographic orientation set such that the thickness axis is in the (110) family and resonance direction is the (001) family.

  8. Area detectors in single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    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.

  9. Effect of gamma ray irradiation on sodium borate single crystals

    NASA Astrophysics Data System (ADS)

    Kalidasan, M.; Asokan, K.; Baskar, K.; Dhanasekaran, R.

    2015-12-01

    In this work, the effects of 5 kGy, 10 kGy and 20 kGy doses of gamma ray irradiation on sodium borate, Na2[B4O5(OH)4]·(H2O)8 single crystals have been studied. Initially these crystals were grown by solution growth technique and identified as monoclinic using X-ray diffraction analysis. X-ray rocking curves confirm the formation of crystalline defects due to gamma rays in sodium borate single crystals. The electron paramagnetic resonance spectra have been recorded to identify the radicals created due to gamma ray irradiation in sodium borate single crystals. The thermoluminescence glow curves due to the defects created by gamma rays in this crystal have been observed and their kinetic parameters were calculated using Chen's peak shape method. The optical absorption increases and photoluminescence spectral intensity decreases for 5 kGy and 20 kGy doses gamma ray irradiated crystals compared to pristine and 10 kGy dose irradiated one. The effect of various doses of gamma rays on vibrational modes of the sodium borate single crystals was studied using FT-Raman and ATR-FTIR spectral analysis. The dielectric permittivity, conductance and dielectric loss versus frequency graphs of these crystals have been analyzed to know the effect of gamma ray irradiation on these parameters.

  10. Multifunctional Charge-Transfer Single Crystals through Supramolecular Assembly.

    PubMed

    Xu, Beibei; Luo, Zhipu; Wilson, Andrew J; Chen, Ke; Gao, Wenxiu; Yuan, Guoliang; Chopra, Harsh Deep; Chen, Xing; Willets, Katherine A; Dauter, Zbigniew; Ren, Shenqiang

    2016-07-01

    Centimeter-sized segregated stacking TTF-C60 single crystals are crystallized by a mass-transport approach combined with solvent-vapor evaporation for the first time. The intermolecular charge-transfer interaction in the long-range ordered superstructure enables the crystals to demonstrate external stimuli-controlled multifunctionalities and angle/electrical-potential-dependent luminescence. PMID:27146726

  11. Single-crystal semiconductor films grown on foreign substrates

    NASA Technical Reports Server (NTRS)

    Vohl, P.

    1966-01-01

    Intermediate alloy formed between foreign substrates and semiconductor material enable the growth of single crystal semiconductor films on the alloy layer. The melted film must not ball up on the surface of the substrate and neither chemically react nor alloy with the intermediate alloy formed on the substrate.

  12. Adhesion of single crystals on modified surfaces in crystallization fouling

    NASA Astrophysics Data System (ADS)

    Mayer, Moriz; Augustin, Wolfgang; Scholl, Stephan

    2012-12-01

    In crystallization fouling it has been observed that during a certain initial phase the fouling is formed by a non-uniform layer consisting of a population of single crystals. These single crystals are frequently formed by inverse soluble salts such as CaCO3. During heterogeneous nucleation and heterogeneous growth an interfacial area between the crystal and the heat transfer surface occurs. The development of this interfacial area is the reason for the adhesion of each single crystal and of all individual crystals, once a uniform layer has been built up. The emerging interfacial area is intrinsic to the heterogeneous nucleation of crystals and can be explained by the thermodynamic principle of the minimum of the Gibbs free energy. In this study CaCO3 crystals were grown heterogeneously on untreated and on modified surfaces inside a flow channel. An untreated stainless steel (AISI 304) surface was used as a reference. Following surface modifications were investigated: enameled and electropolished stainless steel as well as diamond-like-carbon based coatings on stainless steel substrate. The adhesion was measured through a novel measurement technique using a micromanipulator to shear off single crystals from the substrate which was fixed to a spring table inside a SEM.

  13. Growth of large single crystals of the orthorhombic paracetamol

    NASA Astrophysics Data System (ADS)

    Mikhailenko, M. A.

    2004-05-01

    A new procedure for the growth of large (cm-range) single crystals of the metastable orthorhombic (s.g. Pcab) polymorph of paracetamol is described. The crystals were grown by very slow cooling of hot water solutions under the conditions, when the multiple nucleation was prevented. The samples were characterized by DSC and X-ray diffraction.

  14. Fatigue Failure Criteria for Single Crystal Nickel Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.

    1999-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine and rocket engine turbopump blades is a pervasive problem. Single crystal turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry and NASA because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the pan geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades is complicated to predict due to the material orthotropy and variations in crystal orientations. A fatigue failure criteria based on the maximum shear stress amplitude [delta t max] on the 30 slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criteria reduces the scatter in uniaxial LCF test data, for four different specimen orientations, for PWA 1484 at 1200 F in air, quite well. A power law curve fit of the failure parameter, delta t max, vs. cycles to failure is presented.

  15. Study of single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Doty, J. P.; Reising, J. A.

    1973-01-01

    The parameters and requirements for growing single crystals of relatively high melting point metals in a zero gravity environment are studied. The crystal growth of metals such as silver, copper, gold, and alloys with a melting point between 900-1100 C is examined.

  16. Growth and nonlinear optical characterization of organic single crystal films

    NASA Astrophysics Data System (ADS)

    Zhou, Ligui

    1997-12-01

    Organic single crystal films are important for various future applications in photonics and integrated optics. The conventional method for inorganic crystal growth is not suitable for organic materials, and the high temperature melting method is not good for most organic materials due to decomposition problems. We developed a new method-modified shear method-to grow large area organic single crystal thin films which have exceptional nonlinear optical properties and high quality surfaces. Several organic materials (NPP, PNP and DAST) were synthesized and purified before the thin film crystal growth. Organic single crystal thin films were grown from saturated organic solutions using modified shear method. The area of single crystal films were about 1.5 cm2 for PNP, 1 cm2 for NPP and 5 mm2 for DAST. The thickness of the thin films which could be controlled by the applied pressure ranged from 1μm to 10 μm. The single crystal thin films of organic materials were characterized by polarized microscopy, x-ray diffraction, polarized UV-Visible and polarized micro-FTIR spectroscopy. Polarized microscopy showed uniform birefringence and complete extinction with the rotation of the single crystal thin films under crossed- polarization, which indicated high quality single crystals with no scattering. The surface orientation of single crystal thin films was characterized by x-ray diffraction. The molecular orientation within the crystal was further studied by the polarized UV-Visible and Polarized micro-FTIR techniques combined with the x-ray and polarized microscopy results. A Nd:YAG laser with 35 picosecond pulses at 1064nm wavelength was employed to perform the nonlinear optical characterization of the organic single crystal thin films. Two measurement techniques were used to study the crystal films: second harmonic generation (SHG) and electro-optic (EO) effect. SHG results showed that the nonlinear optical coefficient of NPP was 18 times that of LiNbO3, a standard

  17. Growth and characterization of large CdSiP 2 single crystals

    NASA Astrophysics Data System (ADS)

    Zawilski, Kevin T.; Schunemann, Peter G.; Pollak, Thomas C.; Zelmon, David E.; Fernelius, Nils C.; Kenneth Hopkins, F.

    2010-04-01

    Large, optically transparent crystals of CdSiP 2 (CSP) have been grown for the first time from a stoichiometric melt. The material is a high temperature analog to ZnGeP 2 with promising characteristics for IR frequency conversion. Crystals are birefringent and are transparent from 0.5 to 9 μm. Polycrystalline charges were successfully synthesized from high purity elemental starting materials by two-temperature vapor transport despite the very high equilibrium vapor pressure (˜22 atm) at the melting point of CdSiP 2 (1133 °C). Single crystals were grown using the horizontal gradient freeze (HGF) technique in high-temperature transparent furnaces. Over the course of several growth runs, the material proved to be prone to cracking and to twinning along (1 1 2) planes. Twinning was eliminated by seeded growth along directions normal to the 112 planar boundaries. Further modifications to growth conditions resulted in high optical quality, crack- and twin-free single crystals 70×25×8 mm 3. The largest CdSiP 2 single crystals previously reported in the literature were grown through either halogen assisted vapor transport or from a molten Sn flux and measured 2×2×0.2 mm 3. The HGF growth of large CdSiP 2 crystals has allowed several bulk properties to be measured for the first time, including the thermal expansion coefficients, thermal conductivity, and wavelength dependent birefringence and dispersion. Measurements of the optical and thermal properties reveal this to be an extremely promising material for 1-, 1.5-, and 2 μm-pumped mid-IR lasers.

  18. Fluorescence from rubrene single crystals: Interplay of singlet fission and energy trapping

    NASA Astrophysics Data System (ADS)

    Ma, Lin; Zhang, Keke; Kloc, Christian; Sun, Handong; Soci, Cesare; Michel-Beyerle, Maria E.; Gurzadyan, Gagik G.

    2013-05-01

    We have studied fluorescence in rubrene single crystals by use of fluorescence up-conversion, fluorescence anisotropy, and temperature-dependent time-resolved fluorescence techniques. Thermally activated singlet fission was demonstrated to play an important role in the quenching of two intrinsic fluorescence bands, 565 and 610 nm. At low temperatures, singlet fission is suppressed while another process, namely energy trapping, becomes pronounced. The 650 nm fluorescence originates from the hole trap states located 0.27 eV above the valence band.

  19. Amplification of cylindrically polarized laser beams in single crystal fiber amplifiers.

    PubMed

    Piehler, Stefan; Délen, Xavier; Rumpel, Martin; Didierjean, Julien; Aubry, Nicolas; Graf, Thomas; Balembois, Francois; Georges, Patrick; Ahmed, Marwan Abdou

    2013-05-01

    Yb:YAG single crystal fiber (SCF) amplifiers have recently drawn much attention in the field of amplification of ultra-short pulses. In this paper, we report on the use of SCF amplifiers for the amplification of cylindrically polarized laser beams, as such beams offer promising properties for numerous applications. While the amplification of cylindrically polarized beams is challenging with other amplifier designs due to thermally induced depolarization, we demonstrate the amplification of 32 W cylindrically polarized beams to an output power of 100 W. A measured degree of radial polarization after the SCF of about 95% indicates an excellent conservation of polarization. PMID:23669994

  20. Growth and characterization of NLO based L-arginine maleate dihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Baraniraj, T.; Philominathan, P.

    2010-01-01

    Single crystals of L-arginine maleate dihydrate (LAMD) were successfully grown from aqueous solution by solvent evaporation technique. As-grown crystals were analyzed by different instrumentation techniques such as X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectra and UV-vis near infrared (NIR) transmittance spectra. Thermal behavior has been studied with TGA/DTA analyses. The optical second harmonic generation (SHG) conversion efficiency of LAMD was determined using Kurtz powder technique and found to be 1.5 times that of KDP.

  1. Temperature dependence dielectric behavior of Ge-doped lead scandium tantalate single crystals

    NASA Astrophysics Data System (ADS)

    Dixit, Chandra Kumar; Srivastava, Anil Kumar

    2012-07-01

    The doping of Pb2SeTaO6 with Ge ferroelectrics was produced by a high-temperature solution method. We measure dielectric constant, dielectric loss and conductivity in the temperature range -30°C to 200°C and frequency range 1 to 100 KHz. The value of dielectric constant of the Pb2SeTaO6 (PST) crystal remained the same after thermal annealing whereas they decreased after Ge doping in the phase transition temperature range of the PST single crystal. All samples were investigated for conductivity with increasing temperature.

  2. Exploiting polymer single crystals to assemble and functionalize nanomaterials

    NASA Astrophysics Data System (ADS)

    Li, Bing

    Nanomaterials are fundamental building blocks for nanoscience and nanotechnology. They can generally be categorized into three classes: zero-dimensional (0D) (e.g. nanoparticles), one-dimensional (1D) (e.g. carbon nanotubes) and two-dimensional (2D) (e.g. thin films) nanomaterials. Assembly of nanomaterials is the key step to transfer their fascinating mechanical, electronic and optical properties from nano- to micro- or macro-scale. Among all types of assemblies, assembling across different nanomaterial classes is of particular interest. For example, assembling 0D nanoparticles with 1D nanotubes or 2D thin films. These assembled structures have the advantage of possessing properties from both classes of nanomaterials. Functionalization of nanomaterials is important from both scientific and technological points of view. A newly developed field of functionalization is called "patchy particles". Multiple types of functional molecules form different domains on particle surface. Each domain contains only one type of functional molecules. These domains are called patches. These patchy particles are advanced building blocks, which may assemble into useful complex structures. In this thesis, polymer single crystals are exploited to assemble and functionalize nanomaterials. Polymer single crystals have a lamellar structure. Since the thickness of these lamellae is ˜10 nm, polymer single crystals are introduced as a new type of 2D nanomaterials. Different from the traditional 2D nanomaterials such as Langmuir-Blodgett films, self-assembled monolayers and thin films made by Layer-by-Layer technique, these polymer single crystals are free-standing, which means no substrate is needed. Furthermore, the surface of these polymer single crystals can be readily functionalized by crystallizing end-functionalized polymers. Based on the studied polymers, this thesis is divided into two parts. The first part is focused on single crystals of poly(ethylene oxide) (PEO). Thiol

  3. Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

    SciTech Connect

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, John S.

    2015-02-21

    Initially, the alkaline-earth scintillator, CaI2:Eu2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI2:Eu2+ has the potential to exceed the excellent scintillation performance of SrI2:Eu2+. In fact, theoretical predictions for the light yield of CaI2:Eu2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI2:Eu2+ scintillator, the performance of CaI2:Eu2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI2:Eu2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI2:Eu2+ and pure CaI2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI2:Eu2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI2:Eu2+ and un-doped CaI2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the

  4. Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

    DOE PAGESBeta

    Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.; Neal, John S.

    2015-02-21

    Initially, the alkaline-earth scintillator, CaI2:Eu2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI2:Eu2+ has the potential to exceed the excellent scintillation performance of SrI2:Eu2+. In fact, theoretical predictions for the light yield of CaI2:Eu2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI2:Eu2+ scintillator, the performance of CaI2:Eu2+ scintillators has traditionally suffered due, atmore » least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI2:Eu2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI2:Eu2+ and pure CaI2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI2:Eu2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI2:Eu2+ and un-doped CaI2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI2:Eu2+ and pure CaI2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.« less

  5. ac conductance of surface layer in lithium tetraborate single crystals

    NASA Astrophysics Data System (ADS)

    Kim, Chung-Sik; Park, Jong-Ho; Moon, Byung Kee; Seo, Hyo-Jin; Choi, Byung-Chun; Hwang, Yoon-Hwae; Kim, Hyung Kook; Kim, Jung Nam

    2003-12-01

    ac conductance for the electrode effect in Li2B4O7 single crystal was investigated by use of a coplanar electrode applied on the surface of a (001) plate. A coplanar electrode in this material more clearly shows conduction of the electrode effect than a conventional parallel planar electrode. The electrode effect in ac conductance is likely to be controlled by the surface layer, which is a poorly conductive depletion layer possibly filled with vacancies of lithium ions. We found that the surface layer is not locally distributed near the electrodes, but, rather, on the broad area of the surface (001) plane of the material. So we conclude that the electrode effect in ac conduction of Li2B4O7 single crystal is mainly due to the poor conductive surface layer distributed over the whole surface of the (001) plane and is not a secondary phase formed by reaction with the electrode material.

  6. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Budraa, N. K.; Jackson, H. W.; Barmatz, M.

    1999-01-01

    We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

  7. Characterization of hydrogen embrittlement in nickel base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Chene, J.; Baker, C. L.; Bernstein, I. M.; Williams, J. C.

    1986-01-01

    In order to study the role of CMSX2 single crystal microstructure on the combined stress-hydrogen environment effects, hydrogen was introduced by cathodic charging. Concentration measurements were carried out to investigate the dependence of hydrogen solubility and trapping on microstructure. Mechanical properties were measured at room temperature on smooth tensile specimens as a function of heat treatment, crystal orientation and H charging conditions. SEM and TEM allow to study H induced cracks initiation and propagation. A large amount of hydrogen can be dissolved and trapped in CMSX2 single crystals when exposed to a high hydrogen fugacity environment. The strong H trapping evidenced in voids explains the predominant role of these defects as crack initiation sites. The strong detrimental effect of hydrogen on the material tenacity is discussed.

  8. Flextensional Single Crystal Piezoelectric Actuators for Membrane Deformable Mirrors

    NASA Technical Reports Server (NTRS)

    Jiang, Xiaoning; Sahul, Raffi; Hackenberger, Wesley S.

    2006-01-01

    Large aperture and light weight space telescopes requires adaptive optics with deformable mirrors capable of large amplitude aberration corrections at a broad temperature range for space applications including NASA missions such as SAFIR, TPF, Con-X, etc. The single crystal piezoelectric actuators produced at TRS offer large stroke, low hysteresis, and an excellent cryogenic strain response. Specifically, the recently developed low profile, low voltage flextensional single crystal piezoelectric actuators with dimensions of 18 x 5 x 1 mm showed stroke larger than 95 microns under 300 V. Furthermore, flextensional actuator retained approx. 40-50% of its room temperature strain at liquid Nitrogen environment. In this paper, ATILA FEM design of flextensional actuators, actuator fabrication, and characterization results will be presented for the future work on membrane deformable mirror.

  9. Plastic Deformation of Aluminum Single Crystals at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Johnson, R D; Young, A P; Schwope, A D

    1956-01-01

    This report describes the results of a comprehensive study of plastic deformation of aluminum single crystals over a wide range of temperatures. The results of constant-stress creep tests have been reported for the temperature range from 400 degrees to 900 degrees F. For these tests, a new capacitance-type extensometer was designed. This unit has a range of 0.30 inch over which the sensitivity is very nearly linear and can be varied from as low a sensitivity as is desired to a maximum of 20 microinches per millivolt with good stability. Experiments were carried out to investigate the effect of small amounts of prestraining, by two different methods, on the creep and tensile properties of these aluminum single crystals. From observations it has been concluded that plastic deformation takes place predominantly by slip which is accompanied by the mechanisms of kinking and polygonization.

  10. Single crystal plasticity with bend-twist modes

    NASA Astrophysics Data System (ADS)

    Elkhodary, Khalil I.; Bakr, Mohamed A.

    2015-06-01

    In this work a formulation is proposed and computationally implemented for rate dependent single crystal plasticity, which incorporates plastic bend-twist modes that arise from dislocation density based poly-slip mechanisms. The formulation makes use of higher order continuum theory and may be viewed as a generalized micromechanics model. The formulation is then linked to the burgers and Nye tensors, showing how their material rates are derivable from a newly proposed third-rank tensor Λp, which incorporates a crystallographic description of bend-twist plasticity through selectable slip-system level constitutive laws. A simple three-dimensional explicit finite element implementation is outlined and employed in three simulations: (a) bi-crystal bending; (b) tension on a notched single crystal; and (c) the large compression of a microstructure to induce the plastic buckling of secondary phases. All simulation are transient, for computational expediency. The results shed light on the physics resulting from dynamic inhomogeneous plastic deformation.

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

    DOEpatents

    Todt, V.R.; Sengupta, S.; Shi, D.

    1996-04-02

    A method of preparing high temperature superconductor single crystals is disclosed. 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. 2 figs.

  12. Single-Crystal Structure of a Covalent Organic Framework

    SciTech Connect

    Zhang, YB; Su, J; Furukawa, H; Yun, YF; Gandara, F; Duong, A; Zou, XD; Yaghi, OM

    2013-11-06

    The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 degrees C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m(2)/g and a methane total uptake of 15.0 wt % (176 cm(3)/cm(3)) at 25 degrees C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry.

  13. Fabry-Perot microcavity for diamond-based photonics

    NASA Astrophysics Data System (ADS)

    Janitz, Erika; Ruf, Maximilian; Dimock, Mark; Bourassa, Alexandre; Sankey, Jack; Childress, Lilian

    2015-10-01

    Open Fabry-Perot microcavities represent a promising route for achieving a quantum electrodynamics (cavity-QED) platform with diamond-based emitters. In particular, they offer the opportunity to introduce high-purity, minimally fabricated material into a tunable, high quality factor optical resonator. Here, we demonstrate a fiber-based microcavity incorporating a thick (>10 μ m ) diamond membrane with a finesse of 17 000, corresponding to a quality factor Q ˜106 . Such minimally fabricated thick samples can contain optically stable emitters similar to those found in bulk diamond. We observe modified microcavity spectra in the presence of the membrane, and we develop analytic and numerical models to describe the effect of the membrane on cavity modes, including loss and coupling to higher-order transverse modes. We estimate that a Purcell enhancement of approximately 20 should be possible for emitters within the diamond in this device, and we provide evidence that better diamond surface treatments and mirror coatings could increase this value to 200 in a realistic system.

  14. Creep Properties of NiAl-1Hf Single Crystals Re-Investigated

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    NiAl-1Hf single crystals have been shown to be quite strong at 1027 C, with strength levels approaching those of advanced Ni-based superalloys. Initial testing, however, indicated that the properties might not be reproducible. Study of the 1027 C creep behavior of four different NiAl-1Hf single-crystal ingots subjected to several different heat treatments indicated that strength lies in a narrow band. Thus, we concluded that the mechanical properties are reproducible. Recent investigations of the intermetallic NiAl have confirmed that minor alloying additions combined with single-crystal growth technology can produce elevated temperature strength levels approaching those of Ni-based superalloys. For example, General Electric alloy AFN 12 {Ni-48.5(at.%) Al-0.5Hf-1Ti-0.05Ga} has a creep rupture strength equivalent to Rene 80 combined with a approximately 30-percent lower density, a fourfold improvement in thermal conductivity, and the ability to form a self-protective alumina scale in aggressive environments. Although the compositions of strong NiAl single crystals are relatively simple, the microstructures are complex and vary with the heat treatment and with small ingot-toingot variations in the alloy chemistry. In addition, initial testing suggested a strong dependence between microstructure and creep strength. If these observations were true, the ability to utilize NiAl single-crystal rotating components in turbine machinery could be severely limited. To investigate the possible limitations in the creep response of high-strength NiAl single crystals, the NASA Glenn Research Center at Lewis Field initiated an in depth investigation of the effect of heat treatment on the microstructure and subsequent 1027 C creep behavior of [001]-oriented NiAl-1Hf with a nominal chemistry of Ni-47.5Al-1Hf-0.5Si. This alloy was selected since four ingots, grown over a number of years and possessing slightly different compositions, were available for study. Specimens taken from the

  15. Growth of large single crystals of MgO

    SciTech Connect

    Boatner, L.A.; Urbanik, M.

    1997-06-12

    The progressive identification of new high-technology applications and requirements for MgO single crystals in the commercial realm, as well as in DOE and other government-agency project areas, has resulted in an increased demand and international market for this material. Specifically, the demand for MgO crystals in large sizes and quantities is presently increasing due to existing and developing applications that include: (a) MgO substrates for the formation of electro-optic thin films and devices, (b) epitaxial substrates for high-temperature thin-film superconducting devices MgO optical components - including high-temperature windows, lenses, and prisms, and (d) specialty MgO crucibles and evaporation sources for thin-film production. In the course of CRADA ORNL92-0091, carried out with Commercial Crystal Laboratories of Naples, Florida as the commercial participant, we have made major progress in increasing the size of single crystals of MgO produced by means of the submerged-arc-fusion technique-thereby increasing the commercial utility of this material. Prior to the accomplishments realized in the course of this CRADA, the only commercially available single crystals of MgO were produced in Japan, Israel, and Russia. The results achieved in the course of CRADA ORNL92-0091 have now led to the establishment of a domestic commercial source of MgO single-crystal substrates and components, and the U.S. is no longer totally dependent on foreign sources of this increasingly important material.

  16. Yb:YAG single crystal fiber image amplifier

    NASA Astrophysics Data System (ADS)

    Wan, Peng; Liu, Jian; Yang, Lih-Mei; Bai, Shuang

    2014-02-01

    In the paper, a Yb:YAG single crystal fiber is used for the first time to amplify week image signal. It was longitudinally pumped by a fiber-coupled laser diode with a maximum power of 150W at 940 nm. The image amplifier provided low noise and high gain amplification. A spatially uniform amplification gain of up to 10.2 dB at wavelength of 1030 nm was obtained.

  17. Creep in single crystal Ni{sub 3}Al

    SciTech Connect

    Zhu, W.; Jones, I.P.; Fort, D.; Smallman, R.E.

    1997-12-31

    Single crystals of Ni{sub 3}Al (1 at.%Ta) with a compression axis of [{bar 1}23] were subject to creep at a stress of 550 MPa and a temperature of 520 C. Slip trace and TEM microstructural observations reveal that primary octahedral slip is responsible for the primary creep. In the secondary stage, cube cross slip (010) is operative. There is no obvious sign of inverse creep.

  18. Superconductivity in binary FeS single crystals

    NASA Astrophysics Data System (ADS)

    Campbell, Daniel; Eckberg, Chris; Saha, Shanta; Borg, Chris; Zhou, Xiuquan; Rodriguez, Efrain; Paglione, Johnpierre

    FeS is the third recently discovered member of the superconducting binary iron-chalcogenide series that includes the well-known FeSe and FeSe1-xTex members. Grown via hydrothermal techniques, single crystals of FeS have been characterized using transport, thermodynamic and magnetic techniques. We will review experimental results and compare with the unconventional superconducting properties of the selenide and telluride counterparts.

  19. Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves

  20. Growth and characterization of lithium yttrium borate single crystals

    SciTech Connect

    Singh, A. K.; Singh, S. G.; Tyagi, M.; Desai, D. G.; Sen, Shashwati

    2014-04-24

    Single crystals of 0.1% Ce doped Li{sub 6}Y(BO{sub 3}){sub 3} have been grown using the Czochralski technique. The photoluminescence study of these crystals shows a broad emission at ∼ 420 nm corresponding to Ce{sub 3+} emission from 5d→4f energy levels. The decay profile of this emission shows a fast response of ∼ 28 ns which is highly desirable for detector applications.

  1. Nodal superconducting state in clean single crystals of FeSe

    NASA Astrophysics Data System (ADS)

    Kasahara, S.; Mikami, T.; Mizukami, Y.; Kawamoto, Y.; Kurata, S.; Watanabe, D.; Shibauchi, T.; Matsuda, Y.; Böhmer, A. E.; Wolf, T.; Meingast, C.; Löhneysen, H. V.

    2014-03-01

    Among iron-based superconductors, the binary ``11'' family offers the possibility to investigate systems consisting of just the iron arsenic/selenium layers without the intermediate layers which are present in the ``111'', ``122'' and ``1111'' families. This simplest iron based superconductor may therefore yield vital information about the origin of superconductivity in the iron pnictides/chalcogenides. Here we measured the penetration depth and thermal conductivity in very clean single crystals of FeSe with RRR > 200. Presence of line nodes is evident by the quasi T-linear dependence of the penetration depth. Moreover, a large residual thermal conductivity, which is much larger than that expected for d-wave symmetry, suggests that nodes are accidental and nearly vanishing. The field dependence of thermal conductivity suggests a possible field induced phase transition in the superconducting state.

  2. Spin reorientation transition in dysprosium-samarium orthoferrite single crystals

    NASA Astrophysics Data System (ADS)

    Zhao, Weiyao; Cao, Shixun; Huang, Ruoxiang; Cao, Yiming; Xu, Kai; Kang, Baojuan; Zhang, Jincang; Ren, Wei

    2015-03-01

    We report the control of spin reorientation (SR) transition in perovskite D y1 -xS mxFe O3 , a whole family of single crystals grown by an optical floating zone method from x =0 to 1 with an interval of 0.1. Powder x-ray diffractions and Rietveld refinements indicate that lattice parameters a and c increase linearly with Sm doping concentration, whereas b keeps a constant. Temperature dependence of the magnetizations under zero-field-cooling (ZFC) and field-cooling (FC) processes are studied in detail. We have found a remarkable linear change of SR transition temperature in Sm-rich samples for x >0.2 , which covers an extremely wide temperature range including room temperature. The a -axis magnetization curves under the FC during cooling (FCC) process bifurcate from and then jump back to that of the ZFC and FC warming process in single crystals when x =0.5 -0.9 , suggesting complicated 4 f -3 d electron interactions among D y3 + -S m3 +,D y3 + -F e3 + , and S m3 + -F e3 + sublattices of diverse magnetic configurations. The magnetic properties from the doping effect on SR transition temperature in these single crystals might be useful in the material physics and device design applications.

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

    SciTech Connect

    Liu, B.; Raabe, D.; Roters, F.; Arsenlis, A.

    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.

  4. MOFs under pressure: the reversible compression of a single crystal.

    PubMed

    Gagnon, Kevin J; Beavers, Christine M; Clearfield, Abraham

    2013-01-30

    The structural change and resilience of a single crystal of a metal-organic framework (MOF), Zn(HO(3)PC(4)H(8)PO(3)H)·2H(2)O (ZAG-4), was investigated under high pressures (0-9.9 GPa) using in situ single crystal X-ray diffraction. Although the unit cell volume decreases over 27%, the quality of the single crystal is retained and the unit cell parameters revert to their original values after pressure has been removed. This framework is considerably compressible with a bulk modulus calculated at ∼11.7 GPa. The b-axis also exhibits both positive and negative linear compressibility. Within the applied pressures investigated, there was no discernible failure or amorphization point for this compound. The alkyl chains in the structure provide a spring-like cushion to stabilize the compression of the system allowing for large distortions in the metal coordination environment, without destruction of the material. This intriguing observation only adds to the current speculation as to whether or not MOFs may find a role as a new class of piezofunctional solid-state materials for application as highly sensitive pressure sensors, shock absorbing materials, pressure switches, or smart body armor. PMID:23320490

  5. Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik C.; Duke, Greg; Battista, Gilda; Swanson, Greg

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.

  6. Subsurface Stress Fields in Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.

    2003-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and fatigue stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. Techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts are presented in this report. Figure 1 shows typical damper contact locations in a turbine blade. The subsurface stress results are used for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades.

  7. Single-Crystal Elasticity of Earth Materials: An Appraisal

    NASA Astrophysics Data System (ADS)

    Duffy, T. S.

    2015-12-01

    The elastic properties of minerals are of central importance for interpreting seismic data for the Earth's crust, mantle, and core. Mineral elasticity data also have more general applications towards understanding equations of state, phase equilibria, interatomic forces, material strength, and phase transitions. The singe-crystal elastic properties are the most generally useful as they provide complete information on the anisotropy of elastic moduli (e.g. Poisson's ratio, Young's modulus), sound velocities, and compressibility. Measurement of the full set of single-crystal elastic properties remains challenging especially for lower symmetry crystals. In this talk, I present an overview of our current understanding of single-crystal elasticity based on a newly constructed database of single-crystal elastic properties. At ambient conditions the full elastic tensor of about 150 minerals have now been measured, along with about another 60 related compounds that are not formally minerals. About two-thirds of the measured minerals are oxides or silicates. A limitation of the existing database is that only about 10% of the measurements are on crystals of monoclinic or triclinic symmetry, while these two systems account for about 40% of known minerals. Additionally, only a smaller subset of minerals have been examined at high pressure or temperature conditions. Several applications of the database will be presented emphasizing trends in elastic anisotropy. The pyroxenes will be used as an illustrative example.

  8. Single-crystal phosphors for high-brightness white LEDs/LDs

    NASA Astrophysics Data System (ADS)

    Víllora, Encarnación G.; Arjoca, Stelian; Inomata, Daisuke; Shimamura, Kiyoshi

    2016-03-01

    White light-emitting diodes (wLEDs) are the new environmental friendly sources for general lighting purposes. For applications requiring a high-brightness, current wLEDs present overheating problems, which drastically decrease their emission efficiency, color quality and lifetime. This work gives an overview of the recent investigations on single-crystal phosphors (SCPs), which are proposed as novel alternative to conventional ceramic powder phosphors (CPPs). This totally new approach takes advantage of the superior properties of single-crystals in comparison with ceramic materials. SCPs exhibit an outstanding conversion efficiency and thermal stability up to 300°C. Furthermore, compared with encapsulated CPPs, SCPs possess a superior thermal conductivity, so that generated heat can be released efficiently. The conjunction of all these characteristics results in a low temperature rise of SCPs even under high blue irradiances, where conventional CPPs are overheated or even burned. Therefore, SCPs represent the ideal, long-demanded all-inorganic phosphors for high-brightness white light sources, especially those involving the use of high-density laser-diode beams.

  9. Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing.

    PubMed

    Liao, Ting-Wei; Chen, Hung-Ming; Shen, Kuan-Yuan; Kuan, Chieh-Hsiung

    2015-04-24

    In this paper, a sandwich structure comprising a SiO2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si-Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm(-2), the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows a highly symmetric Ge transversal optical peak with a full width at half maximum of 4.2 cm(-1) at 300.7 cm(-1), which is close to that of the original Ge wafer. In addition, the high-resolution transmission electron microscopy image for the Ge NDs and the corresponding selected area electron diffraction pattern shows a clear single crystalline structure without any impurities. PMID:25815515

  10. Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Liao, Ting-Wei; Chen, Hung-Ming; Shen, Kuan-Yuan; Kuan, Chieh-Hsiung

    2015-04-01

    In this paper, a sandwich structure comprising a SiO2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si-Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm-2, the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows a highly symmetric Ge transversal optical peak with a full width at half maximum of 4.2 cm-1 at 300.7 cm-1, which is close to that of the original Ge wafer. In addition, the high-resolution transmission electron microscopy image for the Ge NDs and the corresponding selected area electron diffraction pattern shows a clear single crystalline structure without any impurities.

  11. Preparation and characterization of highly transparent Ce3+ doped terbium gallium garnet single crystal

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Yang, Lei; Hang, Yin; Wang, Xiangyong

    2015-09-01

    A Ce3+ doped terbium gallium garnet crystal (TCGG) with 30 mm in diameter and 25 mm in length has been grown by the Czochralski (Cz) method. The cation distributions in the TCGG crystal and thermal expansion coefficient have been investigated. Absorption spectrum was evaluated in the visible and near-infrared region (VIS-NIR) at room temperature, which indicated the crystal had low absorption coefficient at 500-1500 nm. The specific Faraday rotation of single crystal was measured at room temperature in 532, 633, and 1064 nm. The Verdet constant of the crystal at 633 nm comes up to 164.3 rad m-1 T-1, 26.3% larger than that of TGG at 633 nm. The thermal conductivity and laser induced damage threshold (LIDT) were also measured. Overall, the TCGG single crystal studied here exhibits superior properties than the commercial TGG so far, therefore it has potential to cover the increasing demand for new and improved Faraday rotators in the VIS-NIR region.

  12. Temperature and field induced strain measurements in single crystal Gd5Si2Ge2

    DOE PAGESBeta

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-03-29

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of –8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of –8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Furthermore,more » using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.« less

  13. Single crystal growth and characterization of lanthanum-neodymium oxalate octahydrate

    NASA Astrophysics Data System (ADS)

    Want, Basharat

    2011-11-01

    Single crystals of mixed lanthanum-neodymium oxalates are grown by gel diffusion method using agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having (001), (110) and (010) as habit faces. Single crystal X-ray diffraction results show that the crystals belong to monoclinic system with cell parameters; a=10.344(2) Å, b=9.643(6) Å, c=11.721(2) Å, β=118.7 (2)° , bearing the space group P2/c. Fourier transform infrared spectrum of the crystals indicates the presence of water and other functional groups associated with the oxalate ions. Thermogravimetric and differential thermal analysis support the presence of 8H 2O molecules attached to the lanthanum-neodymium crystal lattice. The thermal decomposition in the nitrogen atmosphere leads to the formation of mixed lanthanum-neodymium oxide as the final product. Energy dispersive analysis of X-rays along with elemental analysis suggests the stoichiometry of the gel grown crystals to be La 1.5Nd 0.5(C 2O 4) 3·8H 2O.

  14. Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

    SciTech Connect

    McGuire, Michael A.; Cao, Huibo; Chakoumakos, Bryan C.; Sales, Brian C.

    2014-11-18

    Here we report structural and physical properties determined by measurements on large single crystals of the anisotropic ferromagnet MnBi. The findings support the importance of magnetoelastic effects in this material. X-ray diffraction reveals a structural phase transition at the spin reorientation temperature TSR = 90 K. The distortion is driven by magneto-elastic coupling, and upon cooling transforms the structure from hexagonal to orthorhombic. Heat capacity measurements show a thermal anomaly at the crystallographic transition, which is suppressed rapidly by applied magnetic fields. Effects on the transport and anisotropic magnetic properties of the single crystals are also presented. Increasing anisotropy of the atomic displacement parameters for Bi with increasing temperature above TSR is revealed by neutron diffraction measurements. It is likely that this is directly related to the anisotropic thermal expansion in MnBi, which plays a key role in the spin reorientation and magnetocrystalline anisotropy. Finally, the identification of the true ground state crystal structure reported here may be important for future experimental and theoretical studies of this permanent magnet material, which have to date been performed and interpreted using only the high temperature structure.

  15. Symmetry-lowering lattice distortion at the spin reorientation in MnBi single crystals

    DOE PAGESBeta

    McGuire, Michael A.; Cao, Huibo; Chakoumakos, Bryan C.; Sales, Brian C.

    2014-11-18

    Here we report structural and physical properties determined by measurements on large single crystals of the anisotropic ferromagnet MnBi. The findings support the importance of magnetoelastic effects in this material. X-ray diffraction reveals a structural phase transition at the spin reorientation temperature TSR = 90 K. The distortion is driven by magneto-elastic coupling, and upon cooling transforms the structure from hexagonal to orthorhombic. Heat capacity measurements show a thermal anomaly at the crystallographic transition, which is suppressed rapidly by applied magnetic fields. Effects on the transport and anisotropic magnetic properties of the single crystals are also presented. Increasing anisotropy ofmore » the atomic displacement parameters for Bi with increasing temperature above TSR is revealed by neutron diffraction measurements. It is likely that this is directly related to the anisotropic thermal expansion in MnBi, which plays a key role in the spin reorientation and magnetocrystalline anisotropy. Finally, the identification of the true ground state crystal structure reported here may be important for future experimental and theoretical studies of this permanent magnet material, which have to date been performed and interpreted using only the high temperature structure.« less

  16. Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory

    2000-01-01

    Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal nickel base turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. Furthermore, crystallographic crack growth on octahedral planes under fretting induced mixed mode loading can be an order of magnitude faster than under pure mode I loading. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate Advanced High Pressure Fuel Turbo Pump (HPFTP/AT) for the Space Shuttle Main Engine (SSME). Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale 3D finite element (FE) model capable of accounting for contact friction, material orthotrophy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation, Stress results are used to discuss fretting fatigue failure analysis of SSME blades. Attachment stresses are seen to reach

  17. Optimization of Weld Conditions and Alloy Composition for Welding of Single-Crystal Nickel-Based Superalloys

    SciTech Connect

    Vitek, John Michael; David, Stan A; Babu, Sudarsanam S

    2007-01-01

    Calculations were carried out to identify optimum welding conditions and weld alloy compositions to avoid stray grain formation during welding of single-crystal nickel-based superalloys. The calculations were performed using a combination of three models: a thermal model to describe the weld pool shape and the local thermal gradient and solidification front velocity; a geometric model to identify the local active dendrite growth variant, and a nucleation and growth model to describe the extent of stray grain formation ahead of the advancing solidification front. Optimum welding conditions (low weld power, high weld speed) were identified from the model calculations. Additional calculations were made to determine potential alloy modifications that reduce the solidification temperature range while maintaining high gamma prime content. The combination of optimum weld conditions and alloy compositions should allow for weld repair of single-crystal nickel-based superalloys without sacrificing properties or performance.

  18. Single Crystal Preparation for High Pressure Experiments in the Diamond Anvil Cell.

    NASA Astrophysics Data System (ADS)

    Aracne, C. M.; Farber, D. L.; Occelli, F.; Antonangeli, D.; Badro, J.

    2003-12-01

    Measuring the effects of pressure on geomaterials in deep Earth's P-T conditions using the diamond anvil cell (DAC) is essential for understanding the phase transition mechanisms, the mechanical properties (which derives directly from the determination of the elastic constants), and the transport properties of deep-Earth materials. To date, most DAC research has been performed with polycrystalline samples. While these are sufficient for determining orientationally averaged properties of solids (i.e. bulk modulus, P-waves and S-wave aggregate velocities, etc\\ldots), single crystals offer the ability to measure a range of direction dependent properties (i.e. thermal and electrical conductivity, elasticity and plasticity, etc\\ldots). Subsequent comparison of measurements on single-\\ and poly-crystalline materials can, for instance, make it possible to address the effects of pressure on the elastic anisotropy and preferred orientations in deep Earth's conditions. In order to achieve pressures above 1 Mbar, one must produce single crystal samples ˜25 μ m in diameter and less than 10 μ m thick. We have developed procedures to produce extremely high-quality metallic single crystals of this size from commercially available material with millimeter dimensions. Critical to the final product is the preservation of crystallinity during thinning and cutting. Our surface preparation methods include the use of selected abrasives, colloidal silica polishing and chemical etching. Samples are cut to final shape using a laser-ablation facility that can handle both conductive and insulating materials. To date, we have been successful in maintaining an extremely high degree of crystallinity and orientation in the final samples. Presently, we have analyzed cobalt and molybdenum samples with both white-light interferometry and synchrotron x-ray diffraction and are in the process of extending these methods to other metals and minerals, such as zinc, sapphire, and olivine.

  19. Calculations of single crystal elastic constants for yttria partially stabilised zirconia from powder diffraction data

    NASA Astrophysics Data System (ADS)

    Lunt, A. J. G.; Xie, M. Y.; Baimpas, N.; Zhang, S. Y.; Kabra, S.; Kelleher, J.; Neo, T. K.; Korsunsky, A. M.

    2014-08-01

    Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.

  20. Calculations of single crystal elastic constants for yttria partially stabilised zirconia from powder diffraction data

    SciTech Connect

    Lunt, A. J. G. Xie, M. Y.; Baimpas, N.; Korsunsky, A. M.; Zhang, S. Y.; Kabra, S.; Kelleher, J.; Neo, T. K.

    2014-08-07

    Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.

  1. Growth of tourmaline single crystals containing transition metal elements in hydrothermal solutions

    NASA Astrophysics Data System (ADS)

    Setkova, Tatiana; Shapovalov, Yury; Balitsky, Vladimir

    2011-03-01

    Interest in the growth of tourmaline single crystals is based on the promising piezoelectric and pyroelectric properties of this material compared to quartz crystals currently in use. Moreover, synthetic tourmaline can be used as a substitute for the natural stone in the jewelry industry similar to other synthetic analogues of gemstones. Single crystals of colored Co-, Ni-, Fe-, (Ni,Cr)-, (Ni,Fe)-, and (Co,Ni,Cr)-containing tourmalines with concentration of transition metal elements up to 16 wt% on a seed have been grown from complex boron-containing hydrothermal solutions at a range of temperatures 400-750 °C and pressures 100 MPa. Experiments were conducted under conditions of a thermal gradient in titanium and chromium-nickel autoclaves. Tourmaline growth on a seed crystal occurs only if separate tourmaline-forming components (monocrystalline corundum and quartz bars) are used as charge. All tourmalines specified above grow in analogous (+) direction of the optical axis with a speed of 0.05 mm/day by faces of the trigonal pyramid, except tourmalines containing chromium. They grow in analogous (+0001) direction with a speed 0.05 mm/day, and in antilogous (-0001) direction with a speed of 0.01 mm/day by faces of the trigonal pyramid and in prism direction with a speed of 0.001 mm/day. Along with the large single crystals, a great amount of finest (30-150 μm in size) tourmaline crystals was formed during the runs by spontaneous nucleation both on the surface of the seed crystals and in the charge.

  2. Characterization of <0 1 0> directed KAP single crystals grown by Sankaranarayanan Ramasamy (SR) method

    NASA Astrophysics Data System (ADS)

    Senthil Pandian, M.; Balamurugan, N.; Bhagavannarayana, G.; Ramasamy, P.

    2008-08-01

    Single crystals of potassium acid phthalate (KAP), a semi-organic compound, have been grown at an average growth rate of 4 mm/day from aqueous solution by using the uniaxial crystal growth method of Sankaranarayanan-Ramasamy (SR). Transparent, cylindrical KAP crystal of size 70 mm length and 15 mm diameter was grown. The grown crystals were characterized by etching and UV-vis NIR analysis. HRXRD analysis indicates that the crystalline perfection of SR method-grown KAP is good. The KAP crystals grown by SR method have 9% higher transmittance than conventional method-grown crystal. The microhardness test was carried out on the (0 1 0) face and a load-dependent hardness was observed. TG-DTA evaluated the thermal properties of the grown crystal. KAP was found to be thermally stable up to 290 °C. The dielectric constant and dielectric loss of the crystal were studied as function of frequency and temperature.

  3. Synthesis of mesoporous zeolite single crystals with cheap porogens

    SciTech Connect

    Tao Haixiang; Li Changlin; Ren Jiawen; Wang Yanqin; Lu Guanzhong

    2011-07-15

    Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, {sup 27}Al magic angle spinning nuclear magnetic resonance ({sup 27}Al MAS NMR), temperature-programmed desorption of ammonia (NH{sub 3}-TPD) and ultraviolet-visible spectroscopy (UV-vis). The SEM images clearly show that all zeolite crystals possess the similar morphology with particle size of about 300 nm, the TEM images reveal that irregular intracrystal pores are randomly distributed in the whole crystal. {sup 27}Al MAS NMR spectra indicate that nearly all of the Al atoms are in tetrahedral co-ordination in ZSM-5, UV-vis spectra confirm that nearly all of titanium atoms are incorporated into the framework of TS-1. The catalytic activity of meso-ZSM-5 in acetalization of cyclohexanone and meso-TS-1 in hydroxylation of phenol was also studied. The synthesis method reported in this paper is cost-effective and environmental friendly, can be easily expended to prepare other hierarchical structured zeolites. - Graphical abstract: Mesoporous zeolite single crystals were synthesized by using cheap porogens as template. Highlights: > Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals were synthesized. > Soluble starch or sodium carboxymethyl cellulose (CMC) was used as porogens. > The mesoporous zeolites had connected mesopores although closed pores existed. > Higher catalytic activities were obtained.

  4. Advanced piezoelectric single crystal based transducers for naval sonar applications

    NASA Astrophysics Data System (ADS)

    Snook, Kevin A.; Rehrig, Paul W.; Hackenberger, Wesley S.; Jiang, Xiaoning; Meyer, Richard J., Jr.; Markley, Douglas

    2005-05-01

    TRS is developing new transducers based on single crystal piezoelectric materials such as Pb(Mg1/3Nb2/3)x-1TixO3 (PMN-PT). Single crystal piezoelectrics such as PMN-PT exhibit very high piezoelectric coefficients (d33 ~ 1800 to >2000 pC/N) and electromechanical coupling factors (k33 > 0.9), respectively, which may be exploited for improving the performance of broad bandwidth and high frequency sonar. Apart from basic performance, much research has been done on reducing the size and increasing the output power of tonpilz transducers for sonar applications. Results are presented from two different studies. "33" mode single crystal tonpilz transducers have reduced stack lengths due to their low elastic stiffness relative to PZTs, however, this produces non-ideal aspect ratios due to large lateral dimensions. Alternative "31" resonance mode tonpilz elements are proposed to improve performance over these "33" designs. d32 values as high as 1600 pC/N have been observed, and since prestress is applied perpendicular to the poling direction, "31" mode Tonpilz elements exhibit lower loss and higher reliability than "33" mode designs. Planar high power tonpilz arrays are the optimum way to obtain the required acoustic pressure and bandwidth for small footprint, high power sensors. An important issue for these sensors is temperature and prestress stability, since fluctuations in tonpilz properties affects power delivery and sensing electronic design. TRS used the approach of modifying the composition of PMN-PT to improve the temperature dependence of properties of the material. Results show up to a 50% decrease in temperature change while losing minimal source level.

  5. Plastic Deformation of O+ Oriented Quartz Single Crystals

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  6. Free-standing nanomechanical and nanophotonic structures in single-crystal diamond

    NASA Astrophysics Data System (ADS)

    Burek, Michael John

    Realizing complex three-dimensional structures in a range of material systems is critical to a variety of emerging nanotechnologies. This is particularly true of nanomechanical and nanophotonic systems, both relying on free-standing small-scale components. In the case of nanomechanics, necessary mechanical degrees of freedom require physically isolated structures, such as suspended beams, cantilevers, and membranes. For nanophotonics, elements like waveguides and photonic crystal cavities rely on light confinement provided by total internal reflection or distributed Bragg reflection, both of which require refractive index contrast between the device and surrounding medium (often air). Such suspended nanostructures are typically fabricated in a heterolayer structure, comprising of device (top) and sacrificial (middle) layers supported by a substrate (bottom), using standard surface nanomachining techniques. A selective, isotropic etch is then used to remove the sacrificial layer, resulting in free-standing devices. While high-quality, crystalline, thin film heterolayer structures are readily available for silicon (as silicon-on-insulator (SOI)) or III-V semiconductors (i.e. GaAs/AlGaAs), there remains an extensive list of materials with attractive electro-optic, piezoelectric, quantum optical, and other properties for which high quality single-crystal thin film heterolayer structures are not available. These include complex metal oxides like lithium niobate (LiNbO3), silicon-based compounds such as silicon carbide (SiC), III-V nitrides including gallium nitride (GaN), and inert single-crystals such as diamond. Diamond is especially attractive for a variety of nanoscale technologies due to its exceptional physical and chemical properties, including high mechanical hardness, stiffness, and thermal conductivity. Optically, it is transparent over a wide wavelength range (from 220 nm to the far infrared), has a high refractive index (n ~ 2.4), and is host to a vast

  7. Fluidized-Bed Deposition Of Single-Crystal Silicon

    NASA Technical Reports Server (NTRS)

    Hsu, George C.; Rohatgi, Naresh K.

    1988-01-01

    Uniformly thin single-crystal films of silicon produced by modification of fluidized-bed-reactor technique producing polysilicon by chemical vapor deposition. Proposed for silicon wafers for flat-plate solar arrays and results in different structural and electronic properties in deposition layer desirable for specific microelectronic or solar-cell processing. In process deposition occurs on silicon wafers, kept individually at temperatures above 1,000 degree C. Heated wafers held in unheated and minimally-agitated-fluidized bed of silicon particles and in low concentration of silane.

  8. EPR studies of gamma-irradiated taurine single crystals

    NASA Astrophysics Data System (ADS)

    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.

  9. Acquisition of Single Crystal Growth and Characterization Equipment

    SciTech Connect

    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 scattering

  10. Raman Investigations of Rare Earth Arsenate Single Crystals

    SciTech Connect

    Barros, G; Santos, C. C.; Ayala, A. P.; Guedes, I.; Boatner, Lynn A; Loong, C. K.

    2010-01-01

    Polarized Raman Spectroscopy was used to investigate the room-temperature phonon characteristics of a series of rare-earth arsenate (REAsO4, RE = Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu) single crystals. The Raman data were interpreted in a systematic manner based on the known tetragonal zircon structure of these compounds, and assignments and correlations were made for the observed bands. We found that the wavenumber of the internal modes of the AsO4 tetrahedron increased with increasing atomic number, and for three out of four lattice wavenumbers observed, this tendency was not nearly so marked as in the case of the internal mode wavenumber.

  11. Skylab experiments on semiconductors and alkali halides. [single crystal growth

    NASA Technical Reports Server (NTRS)

    Lundquist, C. A.

    1974-01-01

    The space processing experiments performed during the Skylab missions included one on single crystal growth of germanium selenide and telluride, one on pure and doped germanium crystals, two on pure and doped indium antimonide, one on gallium-indium-antimony systems, and one on a sodium chloride-sodium fluoride eutectic. In each experiment, three ampoules of sample were processed in the multipurpose electric furnace within the Skylab Materials Processing Facility. All were successful in varying degrees and gave important information about crystal growth removed from the effects of earth surface gravity.

  12. Heavy ion passive dosimetry with silver halide single crystals

    NASA Technical Reports Server (NTRS)

    Childs, C. B.; Parnell, T. A.

    1972-01-01

    A method of detecting radiation damage tracks due to heavy particles in large single crystals of the silver halides is described. The tracks, when made visible with a simple electrical apparatus, appear similar to tracks in emulsions. The properties of the crystals, the technique of printing out the tracks, and evidence concerning the threshold energy for registering particles indicates that this method may find application in heavy ion dosimetry. The method has been found to be sensitive to stopping He nuclei and relativistic M group cosmic rays. Some impurities strongly influence the printout of the tracks, and the effects of these impurities are discussed.

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

    NASA Technical Reports Server (NTRS)

    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.

  14. Structural examination of iridium-based single-crystal preparations

    NASA Astrophysics Data System (ADS)

    Axler, K. M.; Roof, R. B.

    A high-temperature crystal growth experiment produced discrete single-crystal products of AlIr and IrSi. The preparation and examination of these phases is described within. This project is part of a materials compatibility study relating to radioisotopic heat sources. These heat sources are comprised of a PuO2 fuel pellet encapsulated in an Ir alloy containment shell. Th is introduced as an additive within the Ir to maintain ductility. Si and P are picked up inadvertently in the fuel processing. The compatibility of the heat sources with Al is of interest because of potential interactions with Al alloy hardware associated with the heat source environment.

  15. Synthesis and characterization of Mo 3Si single crystal

    NASA Astrophysics Data System (ADS)

    Rosales, I.

    2008-08-01

    Mo 3Si single crystals were successfully produced using an optical floating zone furnace. Reoriented specimens were obtained from the original crystal with <1 1 1>, <1 1 0> and <1 0 0> orientations. Cracking behavior of the crystals shows an interesting relation regarding their crystal orientation. Fracture toughness values show small orientation dependence. The hardness test shows that the hard plane is the (1 0 0), and the softest plane was the (1 1 0) and not the (1 1 1) as it was expected.

  16. PHz current switching in calcium fluoride single crystal

    NASA Astrophysics Data System (ADS)

    Kwon, Ojoon; Kim, D.

    2016-05-01

    We demonstrate that a current can be induced and switched in a sub-femtosecond time-scale in an insulating calcium fluoride single crystal by an intense optical field. This measurement indicates that a sizable current can be generated and also controlled by an optical field in a dielectric medium, implying the capability of rapid current switching at a rate of optical frequency, PHz (1015 Hz), which is a couple of orders of magnitude higher than that of contemporary electronic signal processing. This demonstration may serve to facilitate the development of ultrafast devices in PHz frequency.

  17. Polarization-dependent exciton dynamics in tetracene single crystals.

    PubMed

    Zhang, Bo; Zhang, Chunfeng; Xu, Yanqing; Wang, Rui; He, Bin; Liu, Yunlong; Zhang, Shimeng; Wang, Xiaoyong; Xiao, Min

    2014-12-28

    We conduct polarization-dependent ultrafast spectroscopy to study the dynamics of singlet fission (SF) in tetracene single crystals. The spectrotemporal species for singlet and triplet excitons in transient absorption spectra are found to be strongly dependent on probe polarization. By carefully analyzing the polarization dependence, the signals contributed by different transitions related to singlet excitons have been disentangled, which is further applied to construct the correlation between dynamics of singlet and triplet excitons. The anisotropy of exciton dynamics provides an alternative approach to tackle the long-standing challenge in understanding the mechanism of singlet fission in organic semiconductors. PMID:25554147

  18. Polarization-dependent exciton dynamics in tetracene single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Zhang, Chunfeng; Xu, Yanqing; Wang, Rui; He, Bin; Liu, Yunlong; Zhang, Shimeng; Wang, Xiaoyong; Xiao, Min

    2014-12-01

    We conduct polarization-dependent ultrafast spectroscopy to study the dynamics of singlet fission (SF) in tetracene single crystals. The spectrotemporal species for singlet and triplet excitons in transient absorption spectra are found to be strongly dependent on probe polarization. By carefully analyzing the polarization dependence, the signals contributed by different transitions related to singlet excitons have been disentangled, which is further applied to construct the correlation between dynamics of singlet and triplet excitons. The anisotropy of exciton dynamics provides an alternative approach to tackle the long-standing challenge in understanding the mechanism of singlet fission in organic semiconductors.

  19. Lithium niobate single-crystal and photo-functional device

    DOEpatents

    Gopalan, Venkatraman; Mitchell, Terrence E.; Kitamura, Kenji; Furukawa, Yasunori

    2001-01-01

    Provided are lithium niobate single-crystal that requires a low voltage of not larger than 10 kV/nm for its ferroelectric polarization inversion and of which the polarization can be periodically inverted with accuracy even at such a low voltage, and a photo-functional device comprising the crystal. The crystal has a molar fraction of Li.sub.2 O/(Nb.sub.2 O.sub.5 +Li.sub.2 O) of falling between 0.49 and 0.52. The photo-functional device can convert a laser ray being incident thereon.

  20. Nonlinear microwave switching response of BSCCO single crystals

    SciTech Connect

    Jacobs, T.; Sridhar, S.; Willemsen, B.A. |; Li, Qiang; Gu, G.D.; Koshizuka, N.

    1996-06-01

    Measurements of the surface impedance in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystal with microwave currents flowing along the {cflx c} axis show clear evidence of a step-like nonlinearity. The surface resistance switches between apparently quantized levels for microwave field strength changes < 1 mG. This nonlinear response can arise from the presence of intrinsic Josephson junctions along the {cflx c} axis of these samples driven by the microwave current.

  1. Optical spectroscopy of single crystals and nanoscale films of pentacene

    NASA Astrophysics Data System (ADS)

    He, Rui

    Growing interest in organic molecular semiconductors is stimulated by their promising applications in flexible devices. Transistors based on pentacene have reached device mobilities comparable to amorphous Si. This creates incentives for fundamental studies of organic molecular crystals and nanoscale structures. The research presented in this dissertation demonstrates optical spectroscopy venues for studies of organic molecular semiconductors. Pentacene single crystals and nanoscale films, reaching sub-monolayer thickness, are probed by photoluminescence and resonance Raman spectroscopies. The studies of single crystals reveal new physics linked to intrinsic and extrinsic excitations and provide benchmarks for evaluating the results in nanoscale films. By studying single crystals with different degrees of purities, I identified extrinsic luminescence bands in high quality crystals. Large resonance enhancements of Raman intensities occur when photon energies overlap intrinsic luminescence bands of free and self-trapped excitons. A four-step Raman scattering mechanism is proposed to describe the resonance processes with the self-trapped state. Photoluminescence spectra of discontinuous clusters and ultra-thin films with few monolayers in thickness reveal two fundamental excitations that are assigned to Davydov doublets of the lowest singlet exciton. The observations suggest that pentacene nanoscale films develop a structure with two molecules per unit cell. Pentacene monolayers deposited on substrates functionalized with the polymer of poly alpha-methylstyrene exhibit great lateral uniformity. These monolayers display sharp and intense free exciton luminescence bands which offer giant resonance enhancements of Raman scattering intensities. The enhancements enable the first observations of low-lying lattice modes from pentacene monolayers. The lattice modes show characteristic changes when the number of layers is increased. The low-lying lattice modes reveal inter

  2. Growth of bulk gadolinium pyrosilicate single crystals for scintillators

    NASA Astrophysics Data System (ADS)

    Gerasymov, I.; Sidletskiy, O.; Neicheva, S.; Grinyov, B.; Baumer, V.; Galenin, E.; Katrunov, K.; Tkachenko, S.; Voloshina, O.; Zhukov, A.

    2011-03-01

    Ce, Pr, and La-doped gadolinium pyrosilicate Gd2Si2O7 (GPS) single crystals were grown by the Czochralski and Top Seeded Solution Growth (TSSG) techniques for the first time. Formation conditions of different pyrosilicate phases were determined. X-ray luminescence integral intensity of Ce-doped GPS is about one order of magnitude higher in comparison with gadolinium oxyorthosilicate Gd2SiO5:Ce (GSO:Ce). All samples demonstrate temperature stability of luminescence yield up to 400 K.

  3. Annealing of cold-rolled Fe-40Al single crystals

    SciTech Connect

    Yang, Y.; Baker, I.

    1997-12-31

    Single crystals of Fe-40Al were cold-rolled to plastic strains in the range 5% to 48%. Discs cut from the rolled crystals at different rolling strains were heated at 10 K/min in a differential scanning calorimeter from room temperature to 973 K. Three exothermic peaks were observed in the temperature ranges of 440--550 K, 610--650 K, and 860--930 K, all the peaks shifting to lower temperatures with increasing strain. The origins of these peaks are discussed in terms of the disorder and vacancies introduced during rolling.

  4. Oxygen tracer diffusion in single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Cawley, James D.; Halloran, John W.; Cooper, Alfred R.

    1991-01-01

    Oxygen tracer diffusion coefficients are determined in single-crystal alumina samples with differing dopant levels using the gas-exchange technique. The diffusion direction is parallel to the c-axis and the ambient PO2 is 1 atm (100,000 Pa) for all experiments except a single run with a low PO2, approximately 10 to the -15th atm (10 to the -10th Pa) produced by a CO/CO2 mixture. The diffusion is insensitive to both impurities and ambient PO2. The insensitivities are discussed in terms of point-defect clustering. Prior tracer studies are compared and discussed.

  5. How a silver dendritic mesocrystal converts to a single crystal

    SciTech Connect

    Fang, J.; Ding, B.; Song, X.; Han, Y.

    2008-05-02

    In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the transformation, there is a crystallographic fusion process, dominated by oriented attachment mechanism. Ostwald ripening also plays an important role in forming smooth surface and regular shape of the final nanocrystal.

  6. ATMOSPHERIC EFFECTS ON THE PERFORMANCE OF CDZNTE SINGLE CRYSTAL DETECTORS

    SciTech Connect

    Washington, A.; Duff, M.; Teague, L.

    2010-05-12

    The production of high-quality ternary single-crystal materials for radiation detectors has progressed over the past 15 years. One of the more common materials being studied is CdZnTe (CZT), which can be grown using several methods to produce detector-grade materials. The work presented herein examines the effects of environmental conditions including temperature and humidity on detector performance [full-width at half-maximum (FWHM)] using the single pixel with guard detector configuration. The effects of electrical probe placement, reproducibility, and aging are also presented.

  7. Carrier doping and interlayer coupling in HTSC single crystals

    SciTech Connect

    Kishio, K.; Shimoyama, J.; Kimura, T.; Kotaka, Y.; Kitazawa, K.; Yamafuji, K.; Li, Q.; Suenaga, M.

    1994-09-01

    Experimental results of the effect of carrier doping on the irreversibility lines in (La,Sr){sub 2}CuO{sub 4{minus}{delta}} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8 + {delta}} single crystals are summarized. As a function of Sr or oxygen contents, systematic and dramatic widening of the irreversible regions in the B {minus} T phase diagram was observed in both systems. The present study suggests the critical importance of carrier concentration which directly affects the interlayer coupling strength and dimensionality of the flux line lattice in all the layered HTSC compounds as a universal feature.

  8. Polarization-dependent exciton dynamics in tetracene single crystals

    SciTech Connect

    Zhang, Bo; Zhang, Chunfeng Xu, Yanqing; Wang, Rui; He, Bin; Liu, Yunlong; Zhang, Shimeng; Wang, Xiaoyong; Xiao, Min

    2014-12-28

    We conduct polarization-dependent ultrafast spectroscopy to study the dynamics of singlet fission (SF) in tetracene single crystals. The spectrotemporal species for singlet and triplet excitons in transient absorption spectra are found to be strongly dependent on probe polarization. By carefully analyzing the polarization dependence, the signals contributed by different transitions related to singlet excitons have been disentangled, which is further applied to construct the correlation between dynamics of singlet and triplet excitons. The anisotropy of exciton dynamics provides an alternative approach to tackle the long-standing challenge in understanding the mechanism of singlet fission in organic semiconductors.

  9. Integrated experimental and computational studies of deformation of single crystal copper at high strain rates

    NASA Astrophysics Data System (ADS)

    Rawat, S.; Chandra, S.; Chavan, V. M.; Sharma, S.; Warrier, M.; Chaturvedi, S.; Patel, R. J.

    2014-12-01

    Quasi-static (0.0033 s-1) and dynamic (103 s-1) compression experiments were performed on single crystal copper along ⟨100⟩ and ⟨110⟩ directions and best-fit parameters for the Johnson-Cook (JC) material model, which is an important input to hydrodynamic simulations for shock induced fracture, have been obtained. The deformation of single crystal copper along the ⟨110⟩ direction showed high yield strength, more strain hardening, and less strain rate sensitivity as compared to the ⟨100⟩ direction. Although the JC model at the macro-scale is easy to apply and describes a general response of material deformation, it lacks physical mechanisms that describe the influence of texture and initial orientation on the material response. Hence, a crystal plasticity model based on the theory of thermally activated motion of dislocations was used at the meso-scale, in which the evolution equations permit one to study and quantify the influence of initial orientation on the material response. Hardening parameters of the crystal plasticity model show less strain rate sensitivity along the ⟨110⟩ orientation as compared to the ⟨100⟩ orientation, as also shown by the JC model. Since the deformation process is inherently multiscale in nature, the shape changes observed in the experiments due to loading along ⟨100⟩ and ⟨110⟩ directions are also validated by molecular dynamics simulations at the nano-scale.

  10. Vertically-Aligned Single-Crystal Nanocone Arrays: Controlled Fabrication and Enhanced Field Emission.

    PubMed

    Duan, Jing Lai; Lei, Dang Yuan; Chen, Fei; Lau, Shu Ping; Milne, William I; Toimil-Molares, M E; Trautmann, Christina; Liu, Jie

    2016-01-13

    Metal nanostructures with conical shape, vertical alignment, large ratio of cone height and curvature radius at the apex, controlled cone angle, and single-crystal structure are ideal candidates for enhancing field electron-emission efficiency with additional merits, such as good mechanical and thermal stability. However, fabrication of such nanostructures possessing all these features is challenging. Here, we report on the controlled fabrication of large scale, vertically aligned, and mechanically self-supported single-crystal Cu nanocones with controlled cone angle and enhanced field emission. The Cu nanocones were fabricated by ion-track templates in combination with electrochemical deposition. Their cone angle is controlled in the range from 0.3° to 6.2° by asymmetrically selective etching of the ion tracks and the minimum tip curvature diameter reaches down to 6 nm. The field emission measurements show that the turn-on electric field of the Cu nanocone field emitters can be as low as 1.9 V/μm at current density of 10 μA/cm(2) (a record low value for Cu nanostructures, to the best of our knowledge). The maximum field enhancement factor we measured was as large as 6068, indicating that the Cu nanocones are promising candidates for field emission applications. PMID:26666466

  11. Thermoelectric Properties of n-type SnSe Single Crystal

    NASA Astrophysics Data System (ADS)

    Nguyen, Phuong; Duong, Anh Tuan; Rhim, S. H.; Nguyen, Van Quang; Duong, Van Thiet; Shin, Yooleemi; Cho, Sunglae; Kwon, Suyong; Song, Jae Yong; Park, Hyun Min

    Although thermoelectric materials are well known for their reliability and have been used for many years, even in the field of space engineering, their performance is quite small due to low energy conversion efficiency. Dimensionless figure of merit, ZT = S2. σ.T.κ-1 (where S, σ, T, κ are Seebeck coefficient, electrical conductivity, absolute temperature and thermal conductivity, respectively) is conveniently used to evaluate the conversion efficiency of a thermoelectric materials. Recently, the highest value of ZT to date has been reported for single crystal SnSe, ZT = 2.6 along the b axis of unit cell at 923 K. This temperature is rather high and the range of temperature for high reported ZT is quite narrow. Here we report an attempt to modify the thermoelectric properties of SnSe by using group V and VII as n-type dopant. A negative value of Seebeck coefficient was observed and the power factor reached a peak of 10 μW.K-2.cm-1 at around 600 K. The maximum n-type ZT was 0.57 at 650 K. We will discuss on dopant dependent thermoelectric properties of n-type SnSe single crystals.

  12. Optimized growth and characterization of cadmium oxalate single crystals in silica gel

    NASA Astrophysics Data System (ADS)

    Ezhil Raj, A. Moses; Jayanthi, D. Deva; Jothy, V. Bena

    2008-05-01

    Single crystals of cadmium oxalate hydrate have been grown in silica gel in the presence of divalent Cd 2+ ions impregnated with oxalic acid at room temperature. Gel aging technique was adopted to reduce the nucleation density and hence larger and more perfect single crystals were harvested. Obtained crystals exhibit triclinic structure with unit cell dimensions a = 6.0059 Å, b = 6.66 Å, c = 8.49 Å, α = 105.71°, β = 98.99° and γ = 74.66°. IR spectrum indicates the presence of oxalate ligands and water of crystallization. Thermal behavior and stability of the grown cadmium oxalate crystals were investigated in the temperature range of 30-600 °C. A.C. electrical conductivity of Cd(C 2O 4)·3H 2O was measured for different frequencies and was found to lie between usual conductivities of semiconductor and insulator. The activation energy required to move permanent intrinsic defects in the crystal lattice was found and was equal to 0.15 eV.

  13. Experimental investigations on the synthesis, growth and characterization of MCCTC single crystals

    NASA Astrophysics Data System (ADS)

    Ramesh, V.; Kumar, K. Sendil; Subashini, A.; Shihabuddeen, A.; Jaganathan, K.; Rajarajan, K.

    2012-06-01

    Single crystals of mercury cadmium chloride thiocyanate [Hg3CdCl2(SCN)6; (MCCTC)] were grown from ethanol solvent using slow solvent evaporation technique for the first time. The cell parameters of the grown crystals of MCCTC were confirmed by single crystal X-ray diffraction technique. The various functional groups of resulting compound were well-identified using FT-IR analysis. The UV-Vis-NIR studies revealed that the ultra violet cut off wavelength lies at 270 nm. It is also interesting to note that the sample exhibited wide range of optical transparency from 270 to 2000 nm in ethanol solution, which might be due to the incorporation of the halogen ion (Cl-) in the grown crystal of MCCTC. The second harmonic generation efficiency of MCCTC is found to be superior (about seventeen times) to KDP and (about three times) urea. TGA-DTA and DSC analysis showed that the thermal stability of the sample is retained up to 171.3°C above which phase change occurred from HgCdCl2(SCN)6 to CdHg(SCN)4 with other fragments. The latent heat of the sample is found to be 0.7652 J/Kg.

  14. Unidirectional growth and characterization of 1,3,5-triphenylbenzene single crystals

    NASA Astrophysics Data System (ADS)

    Govindan, V.; Dhatchayani, S.; Sarala, N.; Sankaranarayanan, K.

    2016-05-01

    1,3,5-Triphenylbenzene single crystals has been grown by both conventional slow evaporation and Unidirectional Sankaranarayanan-Ramasamy method. Colourless, highly transparent crystal of size 20 mm × 10 mm × 3mm with well defined morphology was grown from slow evaporation solution method and <111>-oriented unidirectional bulk single crystal of size 23 mm length and 23 mm diameter was grown by the SR method. From the PXRD measurement the material has been crystallized in orthorhombic crystal system. The functional groups were assessed by the use of FTIR analysis. The optical parameter of the grown crystal was obtained from UV-visible spectral analysis and the cutoff wavelength was observed at 247 nm. Mechanical and thermal properties of the grown crystals were carried out from Vicker's hardness test method and TG-DSC analysis respectively. From the TG-DSC studies, the melting points were confirmed at 172°C and no decompose or dissociation was observed. The powder Kurtz method confirms that 1,3,5-Triphenylbenzene has second harmonic generation (SHG) and the SHG efficiency was found to be 0.7 times that of KDP.

  15. Energy efficient engine high-pressure turbine single crystal vane and blade fabrication technology report

    NASA Technical Reports Server (NTRS)

    Giamei, A. F.; Salkeld, R. W.; Hayes, C. W.

    1981-01-01

    The objective of the High-Pressure Turbine Fabrication Program was to demonstrate the application and feasibility of Pratt & Whitney Aircraft-developed two-piece, single crystal casting and bonding technology on the turbine blade and vane configurations required for the high-pressure turbine in the Energy Efficient Engine. During the first phase of the program, casting feasibility was demonstrated. Several blade and vane halves were made for the bonding trials, plus solid blades and vanes were successfully cast for materials evaluation tests. Specimens exhibited the required microstructure and chemical composition. Bonding feasibility was demonstrated in the second phase of the effort. Bonding yields of 75 percent for the vane and 30 percent for the blade were achieved, and methods for improving these yield percentages were identified. A bond process was established for PWA 1480 single crystal material which incorporated a transient liquid phase interlayer. Bond properties were substantiated and sensitivities determined. Tooling die materials were identified, and an advanced differential thermal expansion tooling concept was incorporated into the bond process.

  16. Growth of ZnTe single crystals from Te solution by vertical Bridgman method with ACRT

    NASA Astrophysics Data System (ADS)

    Yang, Rui; Jie, Wanqi; Liu, Hang

    2014-08-01

    ZnTe ingots 30 mm in diameter and about 60 mm in length were grown from Te solution based on vertical Bridgman method with accelerated crucible rotation technique (ACRT). The composition homogeneity and the optical and electrical properties of the crystals were investigated using optical transmission microscope, energy dispersive spectrometer (EDS), scanning electron microscope (SEM), electron probe micro-analyzer (EPMA), ultraviolet-visible (UV-Vis) spectrophotometer, Fourier transform infrared (FT-IR) spectrometer and digital electrometer. The growth method was found efficient for mass transfer, and produced large size single crystal with the volume up to 10 mm×10 mm×40 mm. Single crystals formed in the earlier stage of growth process are larger in size with less Te inclusions. Secondary inclusions formed due to thermal migration and crystal cracking were found. The IR transmittance over the wavenumber range from 500 to 4000 cm-1 is about 60%, and the band gap is about 2.23 eV at room temperature (RT). Its resistivity can reach up to about 700 Ω cm, which is the highest ever reported for unintentionally doped ZnTe crystal.

  17. Growth and characterization of Mn 2+-activated magnesium aluminate spinel single crystals

    NASA Astrophysics Data System (ADS)

    Jouini, Anis; Yoshikawa, Akira; Fukuda, Tsuguo; Boulon, Georges

    2006-08-01

    Several concentrations of Mn 2+-doped MgAl 2O 4 single crystals have been successfully grown using the micro-pulling-down (μ-PD) method. Due to their high melting temperature, the use of special Ir-Re crucibles was necessary. Because of the wide solubility range, the dependence of the behavior of the solid-liquid interface on the growth parameters was carefully studied to establish the growth conditions of stoichiometric MgAl 2O 4 spinel. Rod shaped <1 0 0> oriented single crystals of undoped and manganese doped MgAl 2O 4 spinel with 3 mm in diameter and a few centimeters in length were obtained in reducing argon atmosphere. The composition of Mn ions along the growth a-axis was controlled by the electron probe micro-analysis (EPMA). The optical transmission, crystallinity and thermal expansion of the grown crystals are investigated as well the annealing effect under oxidizing atmosphere will be detailed.

  18. Ultra-thin distributed Bragg reflectors via stacked single-crystal silicon nanomembranes

    SciTech Connect

    Cho, Minkyu; Seo, Jung-Hun; Lee, Jaeseong; Mi, Hongyi; Kim, Munho; Ma, Zhenqiang; Zhao, Deyin; Zhou, Weidong; Yin, Xin; Wang, Xudong

    2015-05-04

    In this paper, we report ultra-thin distributed Bragg reflectors (DBRs) via stacked single-crystal silicon (Si) nanomembranes (NMs). Mesh hole-free single-crystal Si NMs were released from a Si-on-insulator substrate and transferred to quartz and Si substrates. Thermal oxidation was applied to the transferred Si NM to form high-quality SiO{sub 2} and thus a Si/SiO{sub 2} pair with uniform and precisely controlled thicknesses. The Si/SiO{sub 2} layers, as smooth as epitaxial grown layers, minimize scattering loss at the interface and in between the layers. As a result, a reflection of 99.8% at the wavelength range from 1350 nm to 1650 nm can be measured from a 2.5-pair DBR on a quartz substrate and 3-pair DBR on a Si substrate with thickness of 0.87 μm and 1.14 μm, respectively. The high reflection, ultra-thin DBRs developed here, which can be applied to almost any devices and materials, holds potential for application in high performance optoelectronic devices and photonics applications.

  19. Growth and characterization of new semiorganic nonlinear optical and piezoelectric lithium sulfate monohydrate oxalate single crystals

    SciTech Connect

    Yadav, Harsh; Sinha, Nidhi; Kumar, Binay

    2015-04-15

    Highlights: • A new semiorganic single crystal of LSO grown by slow evaporation technique. • Morphological studies of the LSO crystal deduced by BFDH law. • In the UV–vis spectrum wide transparent region and large band gap were found. • SHG is equal to KDP crystal and d{sub 33} was found to be equal to 6pC/N. • Grown crystal belongs to softer category. - Abstract: New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application was synthesized by controlled slow evaporation method. The growth rate of various planes of the grown crystal was estimated by morphological study. Single crystal XRD analysis confirmed that the crystal belongs to triclinic lattice with space group P1. High transparency (∼95%) with large band gap (4.57 eV) was analyzed by UV–vis studies. FTIR and Raman spectroscopy were used to identify various functional groups present in the LSO crystal. SHG efficiency was found to be equal to the KDP crystal. Thermal stability (up to 117.54 °C) and melting point (242 °C) of the crystal were studied by TG-DTA. In dielectric measurements, the value of dielectric constant decreases with increase in frequency. Hardness studies confirmed soft nature of crystals. The piezoelectric coefficient was found to be 6pC/N along [0 0 1].

  20. Ultra-thin distributed Bragg reflectors via stacked single-crystal silicon nanomembranes

    NASA Astrophysics Data System (ADS)

    Cho, Minkyu; Seo, Jung-Hun; Lee, Jaeseong; Zhao, Deyin; Mi, Hongyi; Yin, Xin; Kim, Munho; Wang, Xudong; Zhou, Weidong; Ma, Zhenqiang

    2015-05-01

    In this paper, we report ultra-thin distributed Bragg reflectors (DBRs) via stacked single-crystal silicon (Si) nanomembranes (NMs). Mesh hole-free single-crystal Si NMs were released from a Si-on-insulator substrate and transferred to quartz and Si substrates. Thermal oxidation was applied to the transferred Si NM to form high-quality SiO2 and thus a Si/SiO2 pair with uniform and precisely controlled thicknesses. The Si/SiO2 layers, as smooth as epitaxial grown layers, minimize scattering loss at the interface and in between the layers. As a result, a reflection of 99.8% at the wavelength range from 1350 nm to 1650 nm can be measured from a 2.5-pair DBR on a quartz substrate and 3-pair DBR on a Si substrate with thickness of 0.87 μm and 1.14 μm, respectively. The high reflection, ultra-thin DBRs developed here, which can be applied to almost any devices and materials, holds potential for application in high performance optoelectronic devices and photonics applications.

  1. Interaction of hydrogen with surfaces of silicates: single crystal vs. amorphous.

    PubMed

    He, Jiao; Frank, Paul; Vidali, Gianfranco

    2011-09-21

    We have studied how the formation of molecular hydrogen on silicates at low temperature is influenced by surface morphology. At low temperature (<30 K), the formation of molecular hydrogen occurs chiefly through weak physical adsorption processes. Morphology then plays a role in facilitating or hindering the formation of molecular hydrogen. We studied the formation of molecular hydrogen on a single crystal forsterite and on thin films of amorphous silicate of general composition (Fe(x)Mg((x-1)))(2)SiO(4), 0 < x < 1. The samples were studied ex situ by Atom Force Microscopy (AFM), and in situ using Thermal Programmed Desorption (TPD). The data were analysed using a rate equation model. The main outcome of the experiments is that TPD features of HD desorbing from an amorphous silicate after its formation are much wider than the ones from a single crystal; correspondingly typical energy barriers for diffusion and desorption of H, H(2) are larger as well. The results of our model can be used in chemical evolution codes of space environments, where both amorphous and crystalline silicates have been detected. PMID:21808801

  2. Growth of dislocation-free ZnSe single crystal by CVT method

    NASA Astrophysics Data System (ADS)

    Fujiwara, S.; Namikawa, Y.; Irikura, M.; Matsumoto, K.; Kotani, T.; Nakamura, T.

    2000-11-01

    ZnSe single crystals with a diameter of 12 mm and a length of 28 mm were grown by the CVT method using iodine as a transport agent. The ampoule wall, which has direct contact with the crystal during growth, was formed of pBN. The seed crystal, which was the CVT grown ZnSe single crystal with a reduced dislocation density (EPD) of less than 1×10 4 cm -2, was used. The seed crystal was protected against thermal stress from the ampoule end wall by inserting the undoped polycrystalline ZnSe between the back of the seed crystal and the ampoule end wall. The EPD of the grown ZnSe crystal was less than 1×10 4 cm -2 even near the seed crystal, and reduced to 0 at the tail part of the crystal. The shallow pits were found to exist on the etched surface of dislocation-free part. The dislocation-free part was annealed in Zn atmosphere, and crystallographic, electrical and optical characterizations were evaluated in relation to the annealing conditions.

  3. Low Temperature Rhombohedral Single Crystal SiGe Epitaxy on c-plane Sapphire

    NASA Technical Reports Server (NTRS)

    Duzik, Adam J.; Choi, Sang H.

    2016-01-01

    Current best practice in epitaxial growth of rhombohedral SiGe onto (0001) sapphire (Al2O3) substrate surfaces requires extreme conditions to grow a single crystal SiGe film. Previous models described the sapphire surface reconstruction as the overriding factor in rhombohedral epitaxy, requiring a high temperature Al-terminated surface for high quality films. Temperatures in the 850-1100 C range were thought to be necessary to get SiGe to form coherent atomic matching between the (111) SiGe plane and the (0001) sapphire surface. Such fabrication conditions are difficult and uneconomical, hindering widespread application. This work proposes an alternative model that considers the bulk sapphire structure and determines how the SiGe film nucleates and grows. Accounting for thermal expansion effects, calculations using this new model show that both pure Ge and SiGe can form single crystal films in the 450-550 C temperature range. Experimental results confirm these predictions, where x-ray diffraction and atomic force microscopy show the films fabricated at low temperature rival the high temperature films in crystallographic and surface quality. Finally, an explanation is provided for why films of comparable high quality can be produced in either temperature range.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  5. Growth, characterization, and crystal structure of a new chalcone derivative single crystal

    NASA Astrophysics Data System (ADS)

    Shettigar, Venkataraya; Dharmaprakash, S. M.

    2006-09-01

    A new organic nonlinear optical (NLO) chalcone derivative viz.1- ( 4- methoxyphenyl )-3- (3,4 - dimethoxy phenyl ) - 2 - propene-1-one, has been synthesized by Claisen-Schmidt condensation method. The synthesized compound was purified by repeated recrystallization process. To confirm the identity of the synthesized compound, FTIR spectra was recorded and various functional groups present were identified. NMR spectra were recorded for structural identity and purity confirmation of the synthesized compound. Good quality single crystals were grown by solvent evaporation and slow cooling technique using acetone as solvent. The grown crystals were characterized by UV-Visible , differential thermal analysis and linear refractive index measurement. The hardness of the crystal was determined using Vicker's indentation method. The single crystal structure analysis of the crystal was performed and it is found that the crystal belongs to monoclinic system with space group P2 I. The powder second harmonic generation(SHG)frequency conversion efficiency of the crystal was determined using Nd: YAG laser(λ = 1064nm)and it is 15 times that of Urea.

  6. Thermoluminescence characteristics of Li2B4O7 single crystal dosimeters doped with Mn

    NASA Astrophysics Data System (ADS)

    Ekdal, E.; Karalı, T.; Kelemen, A.; Ignatovych, M.; Holovey, V.; Harmansah, C.

    2014-03-01

    In this study, thermoluminescence (TL) characterization of newly developed Li2B4O7:Mn single crystal phosphor is reported. It is a very attractive material in personal dosimetry because of its near tissue equivalency (Zeff=7.25). The crystal was grown by the Czochralski method from high purity compounds. Glow curve, dose response, and fading and reproducibility properties of this material were investigated. Its TL glow curve showed two well separated peaks at about 105 and 220 °C with a heating rate of 2 °C s-1. The main peak at 220 °C has a linear dose response of up to 60 Gy. The thermal fading ratio of the material is about 8% for the main peak in 10 days. The results showed that there is no significant variation of TL responses for 15 sequential measurements. Apart from the dosimetric properties above, the TL kinetic parameters of the main peak at 220 °C of Li2B4O7:Mn single crystal phosphor were also calculated using the various heating rates method. Activation energy and frequency factor were found as 1.21 eV and 3.75×1011 s-1, respectively.

  7. Rare earth magnetism in CeFeAsO: a single crystal study

    NASA Astrophysics Data System (ADS)

    Jesche, A.; Krellner, C.; de Souza, M.; Lang, M.; Geibel, C.

    2009-10-01

    Single crystals of CeFeAsO, large enough to study the anisotropy of the magnetic properties, were grown by an optimized Sn-flux technique. The high quality of our single crystals is apparent from the highest residual resistivity ratio (RRR)≈12, reported among undoped RFeAsO compounds (R=rare earth) as well as sharp anomalies in resistivity, specific heat, C(T), and thermal expansion at the different phase transitions. The magnetic susceptibility χ(T) presents a large easy-plane anisotropy consistent with the lowest crystal electric field doublet having a dominant Γ6 character. Curie-Weiss-like susceptibilities for magnetic field parallel and perpendicular to the crystallographic c-axis do not reveal an influence of a staggered field on the Ce site induced by magnetic ordering of the Fe. Furthermore, the standard signatures for antiferromagnetic order of Ce at TN4f=3.7 K observed in χ(T) and C(T) are incompatible with a Zeeman splitting Δ≈10 K of the CEF ground state doublet at low temperature due to the Fe-magnetic order as previously proposed. Our results can be reconciled with the earlier observation by assuming a comparatively stronger effect of the Ce-Ce exchange leading to a reduction of this Zeeman splitting below 15 K.

  8. Modal reduction in single crystal sapphire optical fiber

    NASA Astrophysics Data System (ADS)

    Cheng, Yujie; Hill, Cary; Liu, Bo; Yu, Zhihao; Xuan, Haifeng; Homa, Daniel; Wang, Anbo; Pickrell, Gary

    2015-10-01

    A type of single crystal sapphire optical fiber (SCSF) design is proposed to reduce the number of guided modes via a highly dispersive cladding with a periodic array of high- and low-index regions in the azimuthal direction. The structure retains a "core" region of pure single crystal (SC) sapphire in the center of the fiber and a "cladding" region of alternating layers of air and SC sapphire in the azimuthal direction that is uniform in the radial direction. The modal characteristics and confinement losses of the fundamental mode were analyzed via the finite element method by varying the effective core diameter and the dimensions of the "windmill"-shaped cladding. The simulation results showed that the number of guided modes was significantly reduced in the windmill fiber design, as the radial dimension of the air and SC sapphire cladding regions increase with corresponding decrease in the azimuthal dimension. It is anticipated that the windmill SCSF will readily improve the performance of current fiber optic sensors in the harsh environment and potentially enable those that were limited by the extremely large modal volume of unclad SCSF.

  9. Folding in FCC metal single crystals under compression

    NASA Astrophysics Data System (ADS)

    Lychagin, D. V.; Alfyorova, E. A.

    2015-10-01

    Results of the analysis of folding during compression deformation of metals with fcc lattice are presented. Single crystals with orientations at angles of the standard stereographic triangle and different crystallographic orientations of lateral faces have been studied. It has been found that the major factor affecting the folding intensity is the slip plane shear with respect to lateral faces. Such a shear results in face bending and the formation of fold systems in maximum curvature regions. It has been shown that, among all considered orientations, the maximum susceptibility to the formation of different folds is inherent in single crystals with bar 1 compression axis orientation. For this orientation, the development of shear and rotational components during folding is traced by interference microscopy and electron backscatter diffraction methods. It has been found that an excess dislocation density is accumulated when shear is activated in the folding region, which results in an increase in fold misorientation. The activation of this process in fcc metals is promoted by an increase in the homologous deformation temperature and stacking fault energy.

  10. High yield, single crystal ice via the Bridgman method

    NASA Astrophysics Data System (ADS)

    Bisson, Patrick; Groenzin, Henning; Barnett, Irene Li; Shultz, Mary Jane

    2016-03-01

    The surface chemistry of ice and of water is an important topic of study, especially given the role of ice and water in shaping the environment. Although snow, granular, and polycrystalline ice are often used in research, there are applications where large surface areas of a known crystallographic plane are required. For example, fundamental spectroscopy or scattering studies rely on large area samples of known crystalline orientation. In addition, due to its slower dynamics and decreased number of molecular configurations, ice can be viewed as a reduced complexity model for the complex hydrogen bonding environment found at the surface and within the bulk of liquid water. In our studies using Sum Frequency Generation (SFG) vibrational spectroscopy, we have shown that each crystalline face has a unique spectral signature and therefore a unique chemistry and chemical activity. A reliable, reproducible, high performance method of producing large single crystal samples is needed to support this surface chemistry research. The design, construction, and use of a computer-controlled, ice-growth machine based on the Stockbarger modified Bridgeman technique is described. The instrument reliably produces relatively large single crystals that are optically flawless (that is, no visible flaws when viewed in a crossed polarizer), and in very high yield. Success rates of 95% are typical. Such performance has not been observed in the literature.

  11. High yield, single crystal ice via the Bridgman method.

    PubMed

    Bisson, Patrick; Groenzin, Henning; Barnett, Irene Li; Shultz, Mary Jane

    2016-03-01

    The surface chemistry of ice and of water is an important topic of study, especially given the role of ice and water in shaping the environment. Although snow, granular, and polycrystalline ice are often used in research, there are applications where large surface areas of a known crystallographic plane are required. For example, fundamental spectroscopy or scattering studies rely on large area samples of known crystalline orientation. In addition, due to its slower dynamics and decreased number of molecular configurations, ice can be viewed as a reduced complexity model for the complex hydrogen bonding environment found at the surface and within the bulk of liquid water. In our studies using Sum Frequency Generation (SFG) vibrational spectroscopy, we have shown that each crystalline face has a unique spectral signature and therefore a unique chemistry and chemical activity. A reliable, reproducible, high performance method of producing large single crystal samples is needed to support this surface chemistry research. The design, construction, and use of a computer-controlled, ice-growth machine based on the Stockbarger modified Bridgeman technique is described. The instrument reliably produces relatively large single crystals that are optically flawless (that is, no visible flaws when viewed in a crossed polarizer), and in very high yield. Success rates of 95% are typical. Such performance has not been observed in the literature. PMID:27036790

  12. Bithermal fatigue of a nickel-base superalloy single crystal

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.

    1988-01-01

    The thermomechanical fatigue behavior of a nickel-base superalloy single crystal was investigated using a bithermal test technique. The bithermal fatigue test was used as a simple alternative to the more complex thermomechanical fatigue test. Both in-phase and out-of-phase bithermal tests were performed on (100)-oriented coated and bare Rene N4 single crystals. In out-of-plane bithermal tests, the tensile and compressive halves of the cycle were applied isothermally at 760 and 982 C, respectively, while for the in-phase bithermal tests the temperature-loading sequence was reversed. The bithermal fatigue lives of bare specimens were shorter than the isothermal fatigue lives at either temperature extreme when compared on an inelastic strain basis. Both in-phase and out-of-phase bithermal fatigue life curves converged in the large strain regime and diverged in the small strain regime, out-of-phase resulting in the shortest lives. The coating had no effect on life for specimens cycled in-phase; however, the coating was detrimental for isothermal fatigue at 760 C and for out-of-phase fatigue under large strains.

  13. ESR Study on Irradiated Ascorbic Acid Single Crystal

    SciTech Connect

    Tuner, H.; Korkmaz, M.

    2007-04-23

    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.

  14. Self-assembled single-crystal silicon circuits on plastic

    PubMed Central

    Stauth, Sean A.; Parviz, Babak A.

    2006-01-01

    We demonstrate the use of self-assembly for the integration of freestanding micrometer-scale components, including single-crystal, silicon field-effect transistors (FETs) and diffusion resistors, onto flexible plastic substrates. Preferential self-assembly of multiple microcomponent types onto a common platform is achieved through complementary shape recognition and aided by capillary, fluidic, and gravitational forces. We outline a microfabrication process that yields single-crystal, silicon FETs in a freestanding, powder-like collection for use with self-assembly. Demonstrations of self-assembled FETs on plastic include logic inverters and measured electron mobility of 592 cm2/V-s. Finally, we extend the self-assembly process to substrates each containing 10,000 binding sites and realize 97% self-assembly yield within 25 min for 100-μm-sized elements. High-yield self-assembly of micrometer-scale functional devices as outlined here provides a powerful approach for production of macroelectronic systems. PMID:16968780

  15. Tribological properties of sintered polycrystalline and single crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.; Srinivasan, M.

    1982-01-01

    Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on both the friction properties and the surface chemistry of silicon carbide. The main contaminants on the as received sintered polycrystalline silicon carbide surfaces are adsorbed carbon, oxygen, graphite, and silicon dioxide. The surface revealed a low coefficient of friction. This is due to the presence of the graphite on the surface. At temperatures of 400 to 600 C graphite and copious amount of silicon dioxide were observed on the polycrystalline silicon carbide surface in addition to silicon carbide. At 800 C, the amount of the silicon dioxide decreased rapidly and the silicon carbide type silicon and carbon peaks were at a maximum intensity in the XPS spectra. The coefficients of friction were high in the temperature range 400 to 800 C. Small amounts of carbon and oxygen contaminants were observed on the as received single crystal silicon carbide surface below 250 C. Silicon carbide type silicon and carbon peaks were seen on the silicon carbide in addition to very small amount of graphite and silicon dioxide at temperatures of 450 to 800 C.

  16. Strength anomaly in B2 FeAl single crystals

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H.; Matsumoto, N.

    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.

  17. Joint Development of a Fourth Generation Single Crystal Superalloy

    NASA Technical Reports Server (NTRS)

    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.

  18. EPR study of gamma-irradiated single crystal 4-phenylsemicarbazide

    NASA Astrophysics Data System (ADS)

    Sayin, U.; Türkkan, E.; Dereli, Ö.; Yüksel, H.; Birey, M.

    2010-08-01

    Single crystals of 4-phenylsemicarbazide (4PSC) were investigated using an electron paramagnetic resonance (EPR) technique, with γ irradiation of the crystals at different orientations in the magnetic field between temperatures of 120 and 450 K, and the spectra were found to be temperature independent. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal 4PSC, we assumed that one or more paramagnetic species were produced, each having an unpaired electron delocalized in the phenyl ring. Pursuant to this assumption, six possible radicals were modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radicals using the B3LYP method and TZVP basis set. The calculated hyperfine coupling constants were used as starting points for simulations. The experimental and simulated spectra for each of the three crystallographic axes were well matched for the modeled radical R6. We thus identified the R6 (C 6H 5NH) radical as a paramagnetic species produced in 4PSC. The experimental g-factor and hyperfine coupling constants of the C 6H 5NH radical were found to be anisotropic, with the average values g=2.00431, aNHN(8)=8.85 G, aNHH(9)=16.85 G, ao,pH(14,16,20)=6.47 G, and amH(18,19)=2.80 G.

  19. Plastic strain arrangement in copper single crystals in sliding

    SciTech Connect

    Chumaevskii, Andrey V. Lychagin, Dmitry V.; Tarasov, Sergei Yu.

    2014-11-14

    Deformation of tribologically loaded contact zone is one of the wear mechanisms in spite of the fact that no mass loss may occur during this process. Generation of optimal crystallographic orientations of the grains in a polycrystalline materials (texturing) may cause hardening and reducing the deformation wear. To reveal the orientation dependence of an individual gain and simplify the task we use copper single crystals with the orientations of the compression axis along [111] and [110]. The plastic deformation was investigated by means of optical, scanning electron microscopy and EBSD techniques. It was established that at least four different zones were generated in the course of sliding test, such as non-deformed base metal, plastic deformation layer sliding, crystalline lattice reorientation layer and subsurface grain structure layer. The maximum plastic strain penetration depth was observed on [110]-single crystals. The minimum stability of [111]-crystals with respect to rotation deformation mode as well as activation of shear in the sliding contact plane provide for rotation deformation localization below the worn surface. The high-rate accumulation of misorientations and less strain penetration depth was observed on [111]-crystals as compared to those of [110]-oriented ones.

  20. ESR and Microwave Absorption in Boron Doped Diamond Single Crystals

    NASA Astrophysics Data System (ADS)

    Timms, Christopher

    2015-03-01

    Superconductivity has been reportedly found in boron-doped diamond. Most research to date has only studied superconductivity in polycrystalline and thin film boron-diamonds, as opposed to a single crystal. In fact, only one other group has examined a macro scale boron-doped diamond crystal. Our group has successfully grown large single crystals by using the High Temperature High Pressure method (HTHP) and observed a transition to metallic and superconducting states for high B concentrations. For the present, we are studying BDD crystal using Electron Spin Resonance. We conducted our ESR analysis over a range of temperatures (2K to 300K) and found several types of signals, proving the existence of charge carriers with spin 1/2 in BDD. Moreover, we have found that with increasing B concentrations, from n ~ 1018 cm-3 to n of over 1020 cm-3, the ESR signal changes from that of localized spins to the Dysonian shape of free carriers. The low magnetic field microwave absorption has also been studied in BDD samples at various B concentrations and the clear transition to superconducting state has been found below Tc that ranges from 2K to 4 K depending on concentration and quality of crystal. Sergey Polyakov, Victor Denisov, Vladimir Blank, Ray Baughman, Anvar Zakhidov.

  1. Study of single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Doty, J. P.; Reising, J. A.

    1973-01-01

    The growth of single crystals of relatively high melting point metals such as silver, copper, gold, and their alloys was investigated. The purpose was to develop background information necessary to support a space flight experiment and to generate ground based data for comparison. The ground based data, when compared to the data from space grown crystals, are intended to identify any effects which zero-gravity might have on the basic process of single crystal growth of these metals. The ultimate purposes of the complete investigation are to: (1) determine specific metals and alloys to be investigated; (2) grow single metal crystals in a terrestrial laboratory; (3) determine crystal characteristics, properties, and growth parameters that will be effected by zero-gravity; (4) evaluate terrestrially grown crystals; (5) grow single metal crystals in a space laboratory such as Skylab; (6) evaluate the space grown crystals; (7) compare for zero-gravity effects of crystal characteristics, properties, and parameters; and (8) make a recommendation as to production of these crystals as a routine space manufacturing proceses.

  2. Synthesis of millimeter-scale transition metal dichalcogenides single crystals

    DOE PAGESBeta

    Gong, Yongji; Ye, Gonglan; Lei, Sidong; Shi, Gang; Vajtai, Robert; Pantelides, Sokrates T.; Zhou, Wu; Li, Bo; Ajayan, Pullikel M.

    2016-02-10

    The emergence of semiconducting transition metal dichalcogenide (TMD) atomic layers has opened up unprecedented opportunities in atomically thin electronics. Yet the scalable growth of TMD layers with large grain sizes and uniformity has remained very challenging. Here is reported a simple, scalable chemical vapor deposition approach for the growth of MoSe2 layers is reported, in which the nucleation density can be reduced from 105 to 25 nuclei cm-2, leading to millimeter-scale MoSe2 single crystals as well as continuous macrocrystalline films with millimeter size grains. The selective growth of monolayers and multilayered MoSe2 films with well-defined stacking orientation can also bemore » controlled via tuning the growth temperature. In addition, periodic defects, such as nanoscale triangular holes, can be engineered into these layers by controlling the growth conditions. The low density of grain boundaries in the films results in high average mobilities, around ≈42 cm2 V-1 s-1, for back-gated MoSe2 transistors. This generic synthesis approach is also demonstrated for other TMD layers such as millimeter-scale WSe2 single crystals.« less

  3. Method of making macrocrystalline or single crystal semiconductor material

    NASA Technical Reports Server (NTRS)

    Shlichta, P. J. (Inventor); Holliday, R. J. (Inventor)

    1986-01-01

    A macrocrystalline or single crystal semiconductive material is formed from a primary substrate including a single crystal or several very large crystals of a relatively low melting material. This primary substrate is deposited on a base such as steel or ceramic, and it may be formed from such metals as zinc, cadmium, germanium, aluminum, tin, lead, copper, brass, magnesium silicide, or magnesium stannide. These materials generally have a melting point below about 1000 C and form on the base crystals the size of fingernails or greater. The primary substrate has an epitaxial relationship with a subsequently applied layer of material, and because of this epitaxial relationship, the material deposited on the primary substrate will have essentially the same crystal size as the crystals in the primary substrate. If required, successive layers are formed, each of a material which has an epitaxial relationship with the previously deposited layer, until a layer is formed which has an epitaxial relationship with the semiconductive material. This layer is referred to as the epitaxial substrate, and its crystals serve as sites for the growth of large crystals of semiconductive material. The primary substrate is passivated to remove or otherwise convert it into a stable or nonreactive state prior to deposition of the seconductive material.

  4. Relaxor-PT Single crystals: Observations and Developments

    PubMed Central

    Zhang, Shujun; Shrout, Thomas R.

    2011-01-01

    Relaxor-PT based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) attracted lot of attentions in last decade due to their ultra high electromechanical coupling factors and piezoelectric coefficients. However, owing to a strongly curved morphotropic phase boundary (MPB), the usage temperature of these perovskite single crystals is limited by TRT - the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature TC. Furthermore, the low mechanical quality factors and coercive fields of these crystals, usually being on the order of ~70 and 2–3kV/cm, respectively, restrict their usage in high power applications. Thus, it is desirable to have high performance crystals with high temperature usage range and high power characteristics. In this survey, different binary and ternary crystal systems were explored, with respect to their temperature usage range, general trends of dielectric and piezoelectric properties of relaxor-PT crystal systems were discussed related to their TC/TRT. In addition, two approaches were proposed to improve mechanical Q values, including acceptor dopant strategy, analogous to “hard” polycrystalline ceramics, and anisotropic domain engineering configurations. PMID:20889397

  5. Modal reduction in single crystal sapphire optical fiber

    SciTech Connect

    Cheng, Yujie; Hill, Cary; Liu, Bo; Yu, Zhihao; Xuan, Haifeng; Homa, Daniel; Wang, Anbo; Pickrell, Gary

    2015-10-12

    A new type of single crystal sapphire optical fiber (SCSF) design is proposed to reduce the number of guided modes via a highly dispersive cladding with a periodic array of high and low index regions in the azimuthal direction. The structure retains a “core” region of pure single crystal (SC) sapphire in the center of the fiber and a “cladding” region of alternating layers of air and SC sapphire in the azimuthal direction that is uniform in the radial direction. The modal characteristics and confinement losses of the fundamental mode were analyzed via the finite element method by varying the effective core diameter and the dimensions of the “windmill” shaped cladding. The simulation results showed that the number of guided modes were significantly reduced in the “windmill” fiber design, as the radial dimension of the air and SC sapphire cladding regions increase with corresponding decrease in the azimuthal dimension. It is anticipated that the “windmill” SCSF will readily improve the performance of current fiber optic sensors in the harsh environment and potentially enable those that were limited by the extremely large modal volume of unclad SCSF.

  6. Magnetic field controlled FZ single crystal growth of intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Hermann, R.; Behr, G.; Gerbeth, G.; Priede, J.; Uhlemann, H.-J.; Fischer, F.; Schultz, L.

    2005-02-01

    Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

  7. Modified single crystals for high-power underwater projectors.

    PubMed

    Sherlock, Nevin P; Meyer, Richard J

    2012-06-01

    Underwater electroacoustic projectors using single crystals based on the lead magnesium niobate-lead titanate (PMNT) composition were investigated. The large electromechanical coupling coefficient (k(33) > 0.90) and piezoelectric coefficient (d(33) > 1500 pC/N) of PMNT have been demonstrated to improve transducer bandwidth and source level relative to conventional piezoelectric ceramics. The low mechanical quality factor (Q(M) < 200) and low temperature stability (T(RT) < 95°C) of PMNT, however, limit its utility in high-power, high-duty-cycle applications. Use of modified single crystals was shown to result in transducers which exhibit up to 5 dB improvement in source level over PMNT when operated at resonance. Compared with a PZT4 transducer, these modified crystals offer similar source level and power handling capability at resonance, but the available bandwidth is doubled and a 6 dB improvement in maximum source level is achieved when driven off resonance. PMID:22718879

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

    SciTech Connect

    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).

  9. Lithium containing chalcogenide single crystals for neutron detection

    NASA Astrophysics Data System (ADS)

    Tupitsyn, E.; Bhattacharya, P.; Rowe, E.; Matei, L.; Cui, Y.; Buliga, V.; Groza, M.; Wiggins, B.; Burger, A.; Stowe, A.

    2014-05-01

    Lithium containing semiconductor-grade chalcogenide single crystals were grown using the vertical Bridgman method. The source material was synthesized from elementary precursors in two steps, (i) preparing the metal alloy LiIn or LiGa, and (ii) reaction with chalcogen - Se or Te. In a number of experiments, enriched 6Li isotope was used for synthesis and growth. The composition and structure of the synthesized materials was verified using powder X-Ray diffraction. The energy band gaps of the crystals were determined using optical absorption measurements. The resistivity of LiInSe2 and LiGaSe2, obtained using current-voltage measurements is on the order of 108-1011 Ω cm. Photoconductivity measurement of a yellow LiInSe2 sample showed a peak in the photocurrent around 445 nm. Nuclear radiation detectors were fabricated from single crystal wafers and the responses to alpha particles, neutrons and gammas were measured and presented. It suggests that this material is a promising candidate for neutron detection applications.

  10. A crystallographic model for nickel base single crystal alloys

    NASA Technical Reports Server (NTRS)

    Dame, L. T.; Stouffer, D. C.

    1988-01-01

    The purpose of this research is to develop a tool for the mechanical analysis of nickel-base single-crystal superalloys, specifically Rene N4, used in gas turbine engine components. This objective is achieved by developing a rate-dependent anisotropic constitutive model and implementing it in a nonlinear three-dimensional finite-element code. The constitutive model is developed from metallurgical concepts utilizing a crystallographic approach. An extension of Schmid's law is combined with the Bodner-Partom equations to model the inelastic tension/compression asymmetry and orientation-dependence in octahedral slip. Schmid's law is used to approximate the inelastic response of the material in cube slip. The constitutive equations model the tensile behavior, creep response and strain-rate sensitivity of the single-crystal superalloys. Methods for deriving the material constants from standard tests are also discussed. The model is implemented in a finite-element code, and the computed and experimental results are compared for several orientations and loading conditions.

  11. Modal reduction in single crystal sapphire optical fiber

    DOE PAGESBeta

    Cheng, Yujie; Hill, Cary; Liu, Bo; Yu, Zhihao; Xuan, Haifeng; Homa, Daniel; Wang, Anbo; Pickrell, Gary

    2015-10-12

    A new type of single crystal sapphire optical fiber (SCSF) design is proposed to reduce the number of guided modes via a highly dispersive cladding with a periodic array of high and low index regions in the azimuthal direction. The structure retains a “core” region of pure single crystal (SC) sapphire in the center of the fiber and a “cladding” region of alternating layers of air and SC sapphire in the azimuthal direction that is uniform in the radial direction. The modal characteristics and confinement losses of the fundamental mode were analyzed via the finite element method by varying themore » effective core diameter and the dimensions of the “windmill” shaped cladding. The simulation results showed that the number of guided modes were significantly reduced in the “windmill” fiber design, as the radial dimension of the air and SC sapphire cladding regions increase with corresponding decrease in the azimuthal dimension. It is anticipated that the “windmill” SCSF will readily improve the performance of current fiber optic sensors in the harsh environment and potentially enable those that were limited by the extremely large modal volume of unclad SCSF.« less

  12. Physics of Heavily Implanted Single Crystal Complex Oxides

    NASA Astrophysics Data System (ADS)

    Ofan, Avishai

    Ion implantation is known to result in a significant amount of damage in solid single crystals. In this work a battery of material probes is used to study the effect of a very high-dose He implantation in ferroelectric lithium niobate (LiNbO3) and the implantation-induced formation of defects. In addition, the evolution of these defects with post-implantation annealing is examined. After irradiation, a high concentration of defects is found to collect and create a network of thick prismatic planar defects having typical dimensions of ˜1.5 microm and 200 nm parallel and perpendicular to the Z axis, respectively. Optical microscopy shows that there is strong temperature dependence for forming the network; the density of these defects reaches a maximum value for an annealing temperature of 250 °C. However, annealing to temperatures above 380 °C fully eliminates the defects. High-resolution TEM studies indicate that the defects are likely localized twinning and dislocation pileups due to plastic deformation of the lattice to relieve He-implantation-induced stress. During this deformation He accumulates at the twin boundaries. A second type of implantation induced defects is studied using room temperature, high- resolution electron microscopy; this study shows that implanted He in LiNbO3 nucleates and accumulates as bubbles. These He inclusions are at ˜20 GPa pressure and most probably in the solid phase. In addition, the energetically favored shape of the inclusions in their as-implanted form is spherical and not oblate; this spherical shape is due to the fact their diameter is below a critical radius for balancing the surface and elastics energies as predicted by elastic theory. When annealed, the characteristic length scale of the He inclusions increases, forming faceted bubbles. Annealing also causes the He inclusions to migrate and accumulate into strings due to the preferred {1014}-pyramidal-twinning planes. The ion implantation-induced defects are found to be

  13. Synthesis, crystal structure, and magnetic properties of two-dimensional divalent metal glutarate/dipyridylamine coordination polymers, with a single crystal-to-single crystal transformation in the copper derivative

    SciTech Connect

    Montney, Matthew R.; Supkowski, Ronald M.; Staples, Richard J.; LaDuca, Robert L.

    2009-01-15

    Hydrothermal reaction of divalent metal chlorides with glutaric acid and 4,4'-dipyridylamine (dpa) has afforded an isostructural family of coordination polymers with formulation [M(glu)(dpa)]{sub n} (M=Co (1), Ni (2), Cu (3); glu=glutarate). Square pyramidal coordination is seen in 1-3, with semi-ligation of a sixth donor to produce a '5+1' extended coordination sphere. Neighboring metal atoms are linked into 1D [M(glu)]{sub n} neutral chains through chelating/monodentate bridging glutarate moieties with a syn-anti binding mode, and semi-chelation of the pendant carboxylate oxygen. These chains further connect into 2D layers through dipodal dpa ligands. Neighboring layers stack into the pseudo 3D crystal structure of 1-3 through supramolecular hydrogen bonding between dpa amine units and the semi-chelated glutarate oxygen atoms. The variable temperature magnetic behavior of 1-3 was explored and modeled as infinite 1D Heisenberg chains. Notably, complex 3 undergoes a thermally induced single crystal-to-single crystal transformation between centric and acentric space groups, with a conformationally disordered unilayer structure at 293 K and an ordered bilayer structure at 173 K. All materials were further characterized via infrared spectroscopy and elemental and thermogravimetric analyses. - Graphical abstract: The coordination polymers [M(glu)(dpa)]{sub n} (M=Co (1), Ni (2), Cu (3); glu=glutarate, dpa=4,4'-dipyridylamine) exhibit 2D layer structures based on 1D [M(glu)]{sub n} chains linked through dpa tethers. Antiferromagnetic coupling is observed for 2 and 3, while ferromagnetism is predominant in 1. Compound 3 undergoes a thermally induced single crystal-to-single crystal transformation from an acentric to a centrosymmetric space group.

  14. Growth and characterization studies of sodium Di(L-Malato) borate bulk single crystal: A promising nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Senthil, A.; Loganayaki, M.; Lenin, M.; Ramasamy, P.

    2012-06-01

    A semi-organic nonlinear optical material, sodium di(L-malato) borate (NaDMB) has been synthesized. Optically good quality bulk single crystal of NaDMB was successfully grown by slow evaporation solution technique (SEST) and Sankaranarayanan-Ramasamy (SR) method at 36 °C. Transparent, colourless crystal of size 22 mm X 8 mm X 6 mm with well defined morphology was grown by SEST and <100> oriented unidirectional bulk single crystal of size 48 mm length and 16 mm diameter was grown by SR method. The grown crystals were subjected to single crystal X-ray diffraction studies. The crystal belongs to monoclinic structure with space group P21. The grown crystals were characterized by UV-vis studies. The structural perfection of the grown crystal has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The differential thermal (DTA) and thermogravimetric (TG) analysis traces reveal the thermal stability of the sample. The second-harmonic generation efficiency was estimated by Kurtz and Perry powder technique.

  15. Crucial role of molecular planarity on the second order nonlinear optical property of pyridine based chalcone single crystals

    NASA Astrophysics Data System (ADS)

    Menezes, Anthoni Praveen; Jayarama, A.; Ng, Seik Weng

    2015-05-01

    An efficient nonlinear optical material 2E-3-(4-bromophenyl)-1-(pyridin-3-yl) prop-2-en-1-one (BPP) was synthesized and single crystals were grown using slow evaporation solution growth technique at room temperature. Grown crystal had prismatic morphology and its structure was confirmed by various spectroscopic studies, elemental analysis, and single crystal X-ray diffraction (XRD) technique. The single crystal XRD of the crystal showed that BPP crystallizes in monoclinic system with noncentrosymmetric space group P21 and the cell parameters are a = 5.6428(7) Å, b = 3.8637(6) Å, c = 26.411(2) Å, β = 97.568(11) deg and v = 575.82(12) Å3. The UV-Visible spectrum reveals that the crystal is optically transparent and has high optical energy band gap of 3.1 eV. The powder second harmonic generation efficiency (SHG) of BPP is 6.8 times that of KDP. From thermal analysis it is found that the crystal melts at 139 °C and decomposes at 264 °C. High optical transparency down to blue region, higher powder SHG efficiency and better thermal stability than that of urea makes this chalcone derivative a promising candidate for SHG applications. Furthermore, effect of molecular planarity on SHG efficiency and role of pyridine ring adjacent to carbonyl group in forming noncentrosymmetric crystal systems of chalcone family is also discussed.

  16. Studies on semi-organic non linear optical single crystal: Lithium formate monohydrate (HCO2LiṡH2O)

    NASA Astrophysics Data System (ADS)

    Joseph Daniel, D.; Ramasamy, P.

    2014-03-01

    A semi-organic nonlinear optical single crystal, of lithium formate monohydrate (LFMH), has been grown by slow evaporation solution growth technique. The single crystal XRD analysis confirms that the crystal belongs to the orthorhombic system with non-centrosymmetric space group Pbn21. Powder X-ray diffraction analysis was carried out for the grown crystal in the 2θ range 20-80°. The crystalline perfection was analyzed by high-resolution X-ray diffraction (HRXRD) and found that the quality of the grown single crystal is quite good. The UV-Vis spectrum shows that it has a good transmittance in the entire visible region with the lower cut-off wavelength at 240 nm. The presence of the functional groups was confirmed by using FT-IR spectral analysis. The thermal characteristics of LFMH were analyzed by thermogravimetric (TGA) and differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Dielectric studies have been carried out for the grown crystal at different frequencies from 100 Hz to 5 MHz. Both dielectric constant and dielectric loss values are found to decrease with increasing frequency. The mechanical behavior of the grown crystal was studied using Vickers microhardness tester. Nonlinear optical characteristics of LFMH have been studied using Q-switched Nd:YAG laser (λ = 1064 nm). The second harmonic generation conversion efficiency of LFMH is 0.9 times that of standard KDP crystal. The laser damage threshold value of LFMH is found to be 1.5 GW/cm2.

  17. Growth and characterization of diaquatetrakis (thiocyanato) cobalt (II) mercury (II) N-methyl-2-pyrolidone (CMTWMP) single crystals

    NASA Astrophysics Data System (ADS)

    Potheher, I. Vetha; Madhavan, J.; Rajarajan, K.; Nagaraja, K. S.; Sagayaraj, P.

    2008-01-01

    Single crystals of diaquatetrakis (thiocyanato) cobalt (II) mercury (II) N-methyl-2-pyrolidone, (CoHg(SCN) 4·(H 2O) 2·2(C 3H 6CONCH 3) (abbreviated as CMTWMP) were grown using slow solvent evaporation technique. The structure of the grown crystals was confirmed by single-crystal X-ray diffraction (XRD) technique. The optical properties of the crystals were investigated by Fourier transform infrared (FTIR) and UV-Vis-NIR transmission spectra. The grown crystals of CMTWMP were also subjected to dielectric, photoconductivity, thermal and microhardness studies. The photoconductivity study of CMTWMP confirms the electrochromism behaviour in the sample. The SHG efficiency of the sample was measured by Kurtz and Perry powder technique and its value is almost comparable with KDP.

  18. Single-crystal growth of Na xCo 2O 4 via a novel low-temperature flux method

    NASA Astrophysics Data System (ADS)

    Tang, Xiaofeng; He, Jian; Aaron, Kelvin; Abbott, Ed; Kolis, Joseph K.; Tritt, Terry M.

    2008-02-01

    Na xCo 2O 4 single-crystals have been grown using a novel low-temperature flux method. As compared to the formerly reported recipe, the growth temperature has been lowered almost by half to 550 °C via using pure Co as the Co source and the NaOH/NaCl admixture as the flux. The issue of significant loss of Na due to its high vapor pressure at elevated temperatures is much better controlled. Various growth conditions, such as the NaOH to NaCl ratio in the flux, the ratio of Co element to the flux, the firing temperature,the soaking time,the warming/cooling rates and the atmosphere control, have been optimized. The as-grown Na xCo 2O 4 single-crystals, in form of platelets with growth direction along the ab-plane and with a typical size of ˜ few mm on one edge, are found to be Na deficient ( x˜0.3-0.8), which is consistent with the observed electrical resistivity, thermopower and magnetic susceptibility behavior. Despite the single-crystal nature, the directly measured in-plane thermal conductivity κ exhibited an amorphous-like temperature dependence; with the room temperature κ value is ˜7 W/m-K. In addition, the thermal stability and the associated surface micro-morphology changes have been studied by means of the differential scanning calorimetry-thermogravimetry analysis and scanning electron microscope. The results showed that the as-grown Na xCo 2O 4 single-crystals start losing Na above ˜900 °C.

  19. Postsynthetic Improvement of the Physical Properties in a Metal-Organic Framework through a Single Crystal to Single Crystal Transmetallation.

    PubMed

    Grancha, Thais; Ferrando-Soria, Jesús; Zhou, Hong-Cai; Gascon, Jorge; Seoane, Beatriz; Pasán, Jorge; Fabelo, Oscar; Julve, Miguel; Pardo, Emilio

    2015-05-26

    A single crystal to single crystal transmetallation process takes place in the three-dimensional (3D) metal-organic framework (MOF) of formula Mg(II) 2 {Mg(II) 4 [Cu(II) 2 (Me3 mpba)2 ]3 }⋅45 H2 O (1; Me3 mpba(4-) =N,N'-2,4,6-trimethyl-1,3-phenylenebis(oxamate)). After complete replacement of the Mg(II) ions within the coordination network and those hosted in the channels by either Co(II) or Ni(II) ions, 1 is transmetallated to yield two novel MOFs of formulae Co2 (II) {Co(II) 4 [Cu(II) 2 (Me3 mpba)2 ]3 }⋅56 H2 O (2) and Ni2 (II) {Ni(II) 4 [Cu(II) 2 (Me3 mpba)2 ]3 }⋅ 54 H2 O (3). This unique postsynthetic metal substitution affords materials with higher structural stability leading to enhanced gas sorption and magnetic properties. PMID:25873186

  20. Deformation of Single Crystal Molybdenum at High Pressure

    SciTech Connect

    Bonner, B P; Aracne, C; Farber, D L; Boro, C O; Lassila, D H

    2004-02-24

    Single crystal samples of micron dimensions oriented in the [001] direction were shortened 10 to 40% in uniaxial compression with superposed hydrostatic pressure to begin investigation of how the onset of yielding evolves with pressure. A testing machine based on opposed anvil geometry with precision pneumatic control of the applied force and capability to measure sub micron displacements was developed to produce shape changing deformation at pressure. The experiments extend observations of pressure dependent deformation to {approx}5Gpa at shortening rates of {approx}2*10{sup -4}. Samples have been recovered for post run characterization and analysis to determine if deformation mechanisms are altered by pressure. Experiments under hydrostatic pressure provide insight into the nature of materials under extreme conditions, and also provide a means for altering deformation behavior in a controlled fashion. The approach has a long history demonstrating that pressure enhances ductility in general, and produces enhanced hardening relative to that expected from normal cold work in the BCC metals Mo, Ta and Nb{sup 2}. The pressure hardening is in excess of that predicted from the measured increase in shear modulus at pressure, and therefore is likely due to a dislocation mechanism, such as suppression of kink pair formation or the interaction of forest dislocation cores, and not from lattice resistance. The effect has not been observed in FCC metals, suggesting a fundamental difference between deformation mechanisms at pressure for the two classes. The purpose of this letter is to investigate the origin of pressure hardening with new experiments that extend the pressure range beyond 3 GPa, the upper limit of conventional large sample (1cm{sup 3}) testing methods. Most previous high pressure deformation studies have been on poly crystals, relying on model dependent analysis to infer the maximum deviatoric stress that a deformed sample can support. In one experiment, a