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Sample records for synthetic sapphire crystal

  1. Sapphire shaped crystals for medicine

    NASA Astrophysics Data System (ADS)

    Shikunova, A.; Kurlov, V. N.

    2016-01-01

    The favorable combination of excellent optical and mechanical properties of sapphire makes it an attractive structural material for medicine. We have developed a new kind of medical instruments and devices for laser photodynamic and thermal therapy, laser surgery, fluorescent diagnostics, and cryosurgery based on sapphire crystals of various shapes with capillary channels in their volume.

  2. Morphological stability of sapphire crystallization front

    NASA Astrophysics Data System (ADS)

    Baranov, V. V.; Nizhankovskyi, S. V.

    2016-03-01

    The main factors and specificity of growth conditions for sapphire and Ti:sapphire crystals, which affect the morphological stability of the crystal-melt interface, have been investigated with allowance for the concentration and radiative melt supercooling. It is shown that the critical sapphire growth rate is determined to a great extent by the optical transparency of the melt and the mixing conditions near the crystallization front.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Laser induced damage of sapphire and titanium doped sapphire crystals under femtosecond to nanosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Bussière, B.; Utéza, O.; Sanner, N.; Sentis, M.; Riboulet, G.; Vigroux, L.; Commandré, M.; Wagner, F.; Natoli, J.-Y.; Chambaret, J.-P.

    2009-10-01

    The use of large Ti:Sapphire crystals in ultra fast high peak power laser amplifiers makes crucial the problem of crystal laser induced damage. These works aim to quantify the laser induced damage threshold (LIDT) of Sapphire and Ti:Sapphire crystals under femtosecond, picosecond and nanosecond laser pulse irradiations, which are typically encountered in such laser chains. Furthermore, a study of the influence of cryogenic conditions on the LIDT of Ti:Sapphire crystals and of their anti-reflection coating has been performed. The results are important to understand the mechanisms leading to the damage, and to reveal the key parameters which will have to be optimized in future high peak power laser chains.

  8. Study of the crystal structure of silicon nanoislands on sapphire

    SciTech Connect

    Krivulin, N. O. Pirogov, A. V.; Pavlov, D. A.; Bobrov, A. I.

    2015-02-15

    The results of studies of the crystal structure of silicon nanoislands on sapphire are reported. It is shown that the principal defects in silicon nanoislands on sapphire are twinning defects. As a result of the formation of such defects, different crystallographic orientations are formed in silicon nanoislands on sapphire. In the initial stages of the molecular-beam epitaxy of silicon on sapphire, there are two basic orientations: the (001) orientation parallel to the surface and the (001) orientation at an angle of 70° to the surface.

  9. Liquid-crystal tunable filter based on sapphire microspheres.

    PubMed

    Gilardi, Giovanni; Donisi, Domenico; Serpengüzel, Ali; Beccherelli, Romeo

    2009-11-01

    We design an integrated optoelectronic device based on the whispering-gallery modes of a sapphire microsphere integrated with a liquid-crystal tuning medium to produce a narrowband, electrically tunable, channel-dropping filter. The sapphire microsphere is glued over a diffused waveguide in a glass substrate. At the base of the microsphere, a small volume of liquid crystal is infiltrated. We numerically evaluate the performance of the device and demonstrate a voltage tuning of the narrowband resonances. PMID:19881558

  10. Numerical analysis of sapphire crystal growth by the Kyropoulos technique

    NASA Astrophysics Data System (ADS)

    Demina, S. E.; Bystrova, E. N.; Lukanina, M. A.; Mamedov, V. M.; Yuferev, V. S.; Eskov, E. V.; Nikolenko, M. V.; Postolov, V. S.; Kalaev, V. V.

    2007-09-01

    A numerical model has been suggested to analyze processes occurring during sapphire crystal growth by the Kyropoulos technique. The model accounts for the radiative heat exchange in the crystal and melt convection together with the crystallization front formation. The theoretical predictions agree well with available experimental data.

  11. A peek into the history of sapphire crystal growth

    NASA Astrophysics Data System (ADS)

    Harris, Daniel C.

    2003-09-01

    After the chemical compositions of sapphire and ruby were unraveled in the middle of the 19th century, chemists set out to grow artificial crystals of these valuable gemstones. In 1885 a dealer in Geneva began to sell ruby that is now believed to have been created by flame fusion. Gemnologists rapidly concluded that the stones were artificial, but the Geneva ruby stimulated A. V. L. Verneuil in Paris to develop a flame fusion process to produce higher quality ruby and sapphire. By 1900 there was brisk demand for ruby manufactured by Verneuil's method, even though Verneuil did not publicly announce his work until 1902 and did not publish details until 1904. The Verneuil process was used with little alteration for the next 50 years. From 1932-1953, S. K. Popov in the Soviet Union established a capability for manufacturing high quality sapphire by the Verneuil process. In the U.S., under government contract, Linde Air Products Co. implemented the Verneuil process for ruby and sapphire when European sources were cut off during World War II. These materials were essential to the war effort for jewel bearings in precision instruments. In the 1960s and 1970s, the Czochralski process was implemented by Linde and its successor, Union Carbide, to make higher crystal quality material for ruby lasers. Stimulated by a government contract for structural fibers in 1966, H. LaBelle invented edge-defined film-fed growth (EFG). The Saphikon company, which is currently owned by Saint-Gobain, evolved from this effort. Independently and simultaneously, Stepanov developed edge-defined film-fed growth in the Soviet Union. In 1967 F. Schmid and D. Viechnicki at the Army Materials Research Lab grew sapphire by the heat exchanger method (HEM). Schmid went on to establish Crystal Systems, Inc. around this technology. Rotem Industries, founded in Israel in 1969, perfected the growth of sapphire hemispheres and near-net-shape domes by gradient solidification. In the U.S., growth of near

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  13. 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.

  14. 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.

  15. 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

  16. Single-Crystal Sapphire Optical Fiber Sensor Instrumentation

    SciTech Connect

    Pickrell, Gary; Scott, Brian; Wang, Anbo; Yu, Zhihao

    2013-12-31

    This report summarizes technical progress on the program “Single-Crystal Sapphire Optical Fiber Sensor Instrumentation,” funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. This project was completed in three phases, each with a separate focus. Phase I of the program, from October 1999 to April 2002, was devoted to development of sensing schema for use in high temperature, harsh environments. Different sensing designs were proposed and tested in the laboratory. Phase II of the program, from April 2002 to April 2009, focused on bringing the sensor technologies, which had already been successfully demonstrated in the laboratory, to a level where the sensors could be deployed in harsh industrial environments and eventually become commercially viable through a series of field tests. Also, a new sensing scheme was developed and tested with numerous advantages over all previous ones in Phase II. Phase III of the program, September 2009 to December 2013, focused on development of the new sensing scheme for field testing in conjunction with materials engineering of the improved sensor packaging lifetimes. In Phase I, three different sensing principles were studied: sapphire air-gap extrinsic Fabry-Perot sensors; intensity-based polarimetric sensors; and broadband polarimetric sensors. Black body radiation tests and corrosion tests were also performed in this phase. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. At the beginning of Phase II, in June 2004, the BPDI sensor was tested at the Wabash River coal gasifier

  17. Polarized infrared attenuated total reflection study of sapphire crystals with different crystallographic planes

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Polarized infrared (IR) attenuated total reflection (ATR) measurements were performed on c- (polar) and r-plane (semi-polar) sapphire crystals. For c-plane sapphire crystal, spectral features due to the surface phonon polariton (SPhP) modes are only observable in the p-polarized ATR spectrum. Calculation of the SPhP dispersion spectra revealed that the SPhP modes of r-plane sapphire crystal are possible to be observed in both the s- and p-polarized ATR spectra. ATR measurements verified that excitation of the SPhP modes are still easier in the p-polarized ATR spectra. Taking into account the effects of anisotropy and the crystal orientation of hexagonal crystal system, the ATR spectra of r-plane sapphire crystal with arbitrary orientations were simulated. Through a best fit of experimental with simulated spectra, information about the crystal orientation of sapphire crystals was deduced.

  18. SINGLE-CRYSTAL SAPPHIRE OPTICAL FIBER SENSOR INSTRUMENTATION

    SciTech Connect

    A. Wang; G. Pickrell; R. May

    2002-09-10

    Accurate measurement of temperature is essential for the safe and efficient operation and control of a wide range of industrial processes. Appropriate techniques and instrumentation are needed depending on the temperature measurement requirements in different industrial processes and working environments. Harsh environments are common in many industrial applications. These harsh environments may involve extreme physical conditions, such as high-temperature, high-pressure, corrosive agents, toxicity, strong electromagnetic interference, and high-energy radiation exposure. Due to these severe environmental conditions, conventional temperature sensors are often difficult to apply. This situation has opened a new but challenging opportunity for the sensor society to provide robust, high-performance, and cost-effective temperature sensors capable of operating in those harsh environments. The focus of this research program has been to develop a temperature measurement system for temperature measurements in the primary and secondary stages of slagging gasifiers. For this application the temperature measurement system must be able to withstand the extremely harsh environment posed by the high temperatures and corrosive agents present in these systems. Real-time, accurate and reliable monitoring of temperature for the coal gasification process is important to realize the full economic potential of these gasification systems. Long life and stability of operation in the high temperature environment is essential for the temperature measurement system to ensure the continuous running of the coal gasification system over the long term. In this high temperature and chemically corrosive environment, rather limited high temperature measurement techniques such as high temperature thermocouples and optical/acoustic pyrometers are available, each with their own limitations. In this research program, five different temperature sensing schemes based on the single crystal sapphire

  19. Effect of power arrangement on the crystal shape during the Kyropoulos sapphire crystal growth process

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Hung; Chen, Jyh-Chen; Lu, Chung-Wei; Liu, Che-Ming

    2012-08-01

    The Kyropoulos (KY) method is commonly used to grow large sized sapphire single crystals. The shape of the sapphire crystal thus grown is determined by the heater arrangement and the power reduction history in the Kyropoulos furnace. In order to grow high-quality sapphire single crystal, the heater arrangement should allow different power inputs in different sections in order to control the thermal field in the melt during the growth process. In this study, a numerical computation is performed to investigate the effects of the heater arrangement on the thermal and flow transport, the shape of the crystal-melt interface, and the power requirements during the Kyropoulos sapphire crystal growth process in a resistance heated furnace. Four different power ratio arrangements in a three-zone heater are considered. The results show that for the power arrangements considered herein, the temperature gradients along the crystallization front do not exceed 0.05 K/mm, and that, after the growth of the crown, the crystal maintains an almost constant diameter. The remelting phenomenon may occur during growth when the input power of the upper side of the heater is higher than that of the lower side of the heater.

  20. Growth of sapphire crystals for optoelectronics from alumina in a protective medium

    NASA Astrophysics Data System (ADS)

    Dan'ko, A. Ja.; Nizhankovskiy, S. V.; Puzikov, V. M.; Grin', L. A.; Sidelnikova, N. S.; Adonkin, G. T.; Kanishchev, V. N.

    2008-12-01

    This paper reports on the results obtained during the development of the technological process of growth of sapphire crystals for optoelectronics through horizontal directional crystallization in a gaseous argon medium at a pressure of 800 mmHg. The sapphire crystals intended for the use in optoelectronics have been grown from purified molten alumina according to the authors’ technology. It has been demonstrated that, under conditions of a high temperature gradient across the crystallization front and at a low content of reducing components (H2, CO) in the growth medium, it is possible to grow sapphire crystals satisfying the requirements of optoelectronics.

  1. Study on crystal-melt interface shape of sapphire crystal growth by the KY method

    NASA Astrophysics Data System (ADS)

    Liu, Weina; Lu, Jijun; Chen, Hongjian; Yan, Wenbo; Min, Chunhua; Lian, Qingqing; Wang, Yunman; Cheng, Peng; Liu, Caichi; Xu, Yongliang

    2015-12-01

    In this article, the influence of the flow field structure and temperature gradient of forefront interface on the shape of crystal-melt interface which may reflect the interface stability were analyzed through the method of numerical simulation by using CGSim software. In order to get a suitable interface shape and grow high-quality sapphire crystal, the heater arrangement should be adjusted during the KY process. The results indicate that the effect of Marangoni convection cannot be neglected at the last stage, the crystal-melt interface is governed by the flow field structure and the temperature gradient in melt at the crystal-melt interface. The phenomenon of shoulder concave appears at the stage of shoulder turning and interface inversion appears at the last stage during the crystal growth is discussed. Adjusting heater arrangement may effectively optimize the shape of crystal-melt interface.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  3. Synthetic thermoelectric materials comprising phononic crystals

    SciTech Connect

    El-Kady, Ihab F; Olsson, Roy H; Hopkins, Patrick; Reinke, Charles; Kim, Bongsang

    2013-08-13

    Synthetic thermoelectric materials comprising phononic crystals can simultaneously have a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Such synthetic thermoelectric materials can enable improved thermoelectric devices, such as thermoelectric generators and coolers, with improved performance. Such synthetic thermoelectric materials and devices can be fabricated using techniques that are compatible with standard microelectronics.

  4. High temperature sensing using higher-order-mode rejected sapphire-crystal fiber gratings

    NASA Astrophysics Data System (ADS)

    Zhan, Chun; Kim, Jae Hun; Lee, Jon; Yin, Stuart; Ruffin, Paul; Luo, Claire

    2007-09-01

    In this paper, we report the fabrication of higher-order-mode rejected fiber Bragg gratings (FBGs) in sapphire crystal fiber using infrared (IR) femtosecond laser illumination. The grating is tested in high temperature furnace up to 1600 degree Celsius. As sapphire fiber is only available as highly multimode fiber, a scheme to filter out higher order modes in favor for the fundamental mode is theoretically evaluated and experimentally demonstrated. The approach is to use an ultra thin sapphire crystal fiber (60 micron in diameter) to decrease the number of modes. The small diameter fiber also enables bending the fiber to certain radius which is carefully chosen to provide low loss for the fundamental mode LP01 and high loss for the other high-order modes. After bending, less-than-2-nm resonant peak bandwidth is achieved. The grating spectrum is improved, and higher resolution sensing measurement can be achieved. This mode filtering method is very easy to implement. Furthermore, the sapphire fiber is sealed with hi-purity alumina ceramic cement inside a flexible high temperature titanium tube, and the highly flexible titanium tube offers a robust packaging to sapphire fiber. Our high temperature sapphire grating sensor is very promising in extremely high temperature sensing application.

  5. Low phase-noise sapphire crystal microwave oscillators: current status.

    PubMed

    Ivanov, Eugene N; Tobar, Michael E

    2009-02-01

    This work demonstrates that ultra-low phase-noise oscillators with a single-sideband phase-noise spectral density approaching -160 dBc/Hz at Fourier frequency of 1 kHz can be constructed at microwave frequencies (8 to 10 GHz). Such noise performance has been achieved by frequency locking a conventional loop oscillator to a temperature-stabilized sapphire dielectric resonator operating at a relatively high level of dissipated microwave power (approximately 0.5 W). Principles of microwave circuit interferometry have been employed to generate the error signal for the oscillator frequency control system. No cryogens were used. Two almost identical oscillators were built to perform the classical 2-oscillator phase noise measurements. The phase referencing of one oscillator to another was achieved by varying microwave power dissipated in the sapphire resonator. PMID:19251513

  6. Broadband and high-brightness light source: glass-clad Ti:sapphire crystal fiber.

    PubMed

    Wang, Shih-Chang; Yang, Teng-I; Jheng, Dong-Yo; Hsu, Chun-Yang; Yang, Tzu-Te; Ho, Tuan-Shu; Huang, Sheng-Lung

    2015-12-01

    High-brightness near-infrared broadband amplified spontaneous emission (ASE) was generated by glass-clad Ti:sapphire crystal fibers, which were developed using the co-drawing laser-heated pedestal growth method. As much as 29.2 mW of ASE power was generated using 520 nm laser diodes as the excitation source on an a-cut, 18 μm core-diameter Ti:sapphire crystal fiber (CF). The 3 dB bandwidth was 163.8 nm, and the radiance was 53.94  W·mm(-2) sr(-1). The propagation loss of the glass-clad sapphire CF measured using the cutback method was 0.017  cm(-1) at 780 nm. For single-mode applications, more than 100 μW of power was coupled into a SM600 single-mode fiber. PMID:26625059

  7. Properties Data for Adhesion and Surface Chemistry of Aluminum: Sapphire-Aluminum, Single-Crystal Couple

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Pohlchuck, Bobby; Whitle, Neville C.; Hector, Louis G., Jr.; Adams, Jim

    1998-01-01

    An investigation was conducted to examine the adhesion and surface chemistry of single-crystal aluminum in contact with single-crystal sapphire (alumina). Pull-off force (adhesion) measurements were conducted under loads of 0. I to I mN in a vacuum of 10(exp -1) to 10(exp -9) Pa (approx. 10(exp -10) to 10(exp -11) torr) at room temperature. An Auger electron spectroscopy analyzer incorporated directly into an adhesion-measuring vacuum system was primarily used to define the chemical nature of the surfaces before and after adhesion measurements. The surfaces were cleaned by argon ion sputtering. With a clean aluminum-clean -sapphire couple the mean value and standard deviation of pull-off forces required to separate the surfaces were 3015 and 298 micro-N, respectively. With a contaminated aluminum-clean sapphire couple these values were 231 and 241 micro-N. The presence of a contaminant film on the aluminum surface reduced adhesion by a factor of 13. Therefore, surfaces cleanliness, particularly aluminum cleanliness, played an important role in the adhesion of the aluminum-sapphire couples. Pressures on the order of 10(exp -8) to 10(exp -9) Pa (approx. 10(exp -10) to 10(exp -11) torr) maintained a clean aluminum surface for only a short time (less then 1 hr) but maintained a clean sapphire surface, once it was achieved, for a much longer time.

  8. Light refraction in sapphire plates with a variable angle of crystal optical axis to the surface

    SciTech Connect

    Vetrov, V. N. Ignatenkov, B. A.

    2013-05-15

    The modification of sapphire by inhomogeneous plastic deformation makes it possible to obtain plates with a variable angle of inclination of the crystal optical axis to the plate surface. The refraction of light in this plate at perpendicular and oblique incidence of a parallel beam of rays is considered. The algorithm of calculating the refractive index of extraordinary ray and the birefringence is proposed.

  9. Design and analysis of large-core single-mode windmill 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

    2016-06-01

    We present a large-core single-mode "windmill" single crystal sapphire optical fiber (SCSF) design, which exhibits single-mode operation by stripping off the higher-order modes (HOMs) while maintaining the fundamental mode. The "windmill" SCSF design was analyzed using the finite element analysis method, in which all the HOMs are leaky. The numerical simulation results show single-mode operation in the spectral range from 0.4 to 2 μm in the windmill SCSF, with an effective core diameter as large as 14 μm. Such fiber is expected to improve the performance of many of the current sapphire fiber optic sensor structures.

  10. Single-crystal sapphire tubes as economical probes for optical pyrometry in harsh environments

    SciTech Connect

    Ruzicka, Jakub; Houzvicka, Jindrich; Bok, Jiri; Praus, Petr; Mojzes, Peter

    2011-12-20

    One-end-sealed single-crystal sapphire tubes are presented as a simple, robust, and economical alternative for bulky lightpipe probes. Thermal radiation from a blackbody cavity created at the inner surface of the sealed end is gathered by a simple lens-based collecting system and transmitted via optical fiber to the remote detection unit. Simplicity and applicability of the concept are demonstrated by the combination of commercially available sapphire tubes with a common optical pyrometer. Radiation thermometers with sapphire tubes as invasive probes can be useful for applications requiring immunity to electromagnetic interference, resistance to harsh environments, simple replacement in the case of failure, and enhanced mechanical firmness, enabling wider range probe positioning inside the medium of interest.

  11. Use of numerical simulation for growing high-quality sapphire crystals by the Kyropoulos method

    NASA Astrophysics Data System (ADS)

    Demina, S. E.; Bystrova, E. N.; Postolov, V. S.; Eskov, E. V.; Nikolenko, M. V.; Marshanin, D. A.; Yuferev, V. S.; Kalaev, V. V.

    2008-04-01

    In the present work, an advanced numerical model is suggested to analyze heat transfer and flow pattern in sapphire crystal growth by the Kyropoulos technique. The new approach accounts for radiative heat exchange in the crystal and convection in the melt, and provides prediction of the crystallization front shape. The model allowed the analysis of several growth setup designs and selection of an optimal configuration. The numerical predictions performed with the CGSim software ( www.semitech.us) agree well with available experimental data obtained in optimized crystal growth process reported for the first time.

  12. A century of sapphire crystal growth: origin of the EFG method

    NASA Astrophysics Data System (ADS)

    Harris, Daniel C.

    2009-08-01

    A. Verneuil developed flame fusion to grow sapphire and ruby on a commercial scale around 1890. Flame fusion was further perfected by Popov in the Soviet Union in the 1930s and by Linde Air Products Co. in the U.S. during World War II. Union Carbide Corp., the successor to Linde, developed Czochralski crystal growth for sapphire laser materials in the 1960s. Edge-Defined Film-Fed Growth (EFG) was invented by H. Labelle in the 1960s and the Heat Exchanger Method (HEM) was invented by F. Schmid and D. Viechnicki in 1967. Both methods were commercialized in the 1970s. Gradient solidification was invented in Israel in the 1970s by J. Makovsky. The Horizontal Directional Solidification Method (HDSM) was invented by Kh. S. Bagdasorov in the Soviet Union in the 1960s. Kyropoulos growth of sapphire, known as GOI crystal growth in the Soviet Union, was developed by M. Musatov at the State Optical Institute in St. Petersburg in the 1970s. Today, half of the world's sapphire is produced by the GOI method.

  13. 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.

  14. Parametric sensitivity and temporal dynamics of sapphire crystal growth via the micro-pulling-down method

    NASA Astrophysics Data System (ADS)

    Samanta, Gaurab; Yeckel, Andrew; Bourret-Courchesne, Edith D.; Derby, Jeffrey J.

    2012-11-01

    The micro-pulling-down (μ-PD) crystal growth of sapphire fibers, whose steady-state limits were the focus of our prior study [Samanta et al., Journal of Crystal Growth 335 (2011) 148-159], is further examined using a parametric sensitivity computation derived by linearizing the nonlinear model around a quasi-steady-state (QSS). In addition, transient analyses are performed to assess inherent stability and dynamic responses in this μ-PD system. Information from these two approaches enlarges our understanding of this particular process, and the approaches themselves are put forth as valuable complements to classical QSS analysis.

  15. 3D unsteady computer modeling of industrial scale Ky and Cz sapphire crystal growth

    NASA Astrophysics Data System (ADS)

    Demina, S. E.; Kalaev, V. V.

    2011-04-01

    In the present work, 3D features of melt convection during sapphire growth of 100 mm diameter Cz and of 200 mm diameter Ky crystals are studied. The approach accounting for radiative heat exchange with absorption and a specular reflection in the crystal, which we applied in 2D modeling [1-3], has been extended to 3D computational domains and coupled to 3D heat transfer in the melt, crystal, and crucible. 3D melt unsteady convection together with crystallization front formation are taken into account within the Direct Numerical Simulation (DNS) approach. Results of 3D modeling are discussed in detail and quantitatively compared to the previously reported data of 2D modeling and experiments [2,3]. It has been found that the features of unsteady melt convection during the "before seeding", "seeding", and "shouldering" growth stages are quite different from each other, which necessitates a flexible control of the radial and vertical temperature gradients in the crucible to provide optimal conditions for stable growth of high quality sapphire crystals.

  16. Design and analysis of large-core single-mode windmill single crystal sapphire optical fiber

    DOE PAGESBeta

    Cheng, Yujie; Hill, Cary; Liu, Bo; Yu, Zhihao; Xuan, Haifeng; Homa, Daniel; Wang, Anbo; Pickrell, Gary

    2016-06-01

    We present a large-core single-mode “windmill” single crystal sapphire optical fiber (SCSF) design, which exhibits single-mode operation by stripping off the higher-order modes (HOMs) while maintaining the fundamental mode. The “windmill” SCSF design was analyzed using the finite element analysis method, in which all the HOMs are leaky. The numerical simulation results show single-mode operation in the spectral range from 0.4 to 2 μm in the windmill SCSF, with an effective core diameter as large as 14 μm. Such fiber is expected to improve the performance of many of the current sapphire fiber optic sensor structures.

  17. Intense THz source based on BNA organic crystal pumped at Ti:sapphire wavelength

    NASA Astrophysics Data System (ADS)

    Shalaby, Mostafa; Vicario, Carlo; Thirupugalmani, Karunanithi; Brahadeeswaran, Srinivasan; Hauri, Christoph P.

    2016-04-01

    We report on high energy terahertz pulses by optical rectification (OR) in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) directly pumped by a conventional Ti:Sapphire (Ti:Sa) amplifier. The simple scheme provides an optical to terahertz conversion efficiency of 0.25% when pumped by a collimated laser pulses with duration of 50 fs and central wavelength of 800nm. The generated radiation spans frequencies between 0.2 and 3 THz. We measured the damage threshold as well as the dependency of the conversion efficiency on the pump fluence, pump wavelength, and pulse duration.

  18. Single-crystal sapphire microstructure for high-resolution synchrotron X-ray monochromators

    DOE PAGESBeta

    Asadchikov, Victor E.; Butashin, Andrey V.; Buzmakov, Alexey V.; Deryabin, Alexander N.; Kanevsky, Vladimir M.; Prokhorov, Igor A.; Roshchin, Boris S.; Volkov, Yuri O.; Zolotov, Dennis A.; Jafari, Atefeh; et al

    2016-03-22

    We report on the growth and characterization of several sapphire single crystals for the purpose of x-ray optics applications. Structural defects were studied by means of laboratory double-crystal X-ray diffractometry and white beam synchrotron-radiation topography. The investigations confirmed that the main defect types are dislocations. The best quality crystal was grown using the Kyropoulos technique with a dislocation density of 102-103 cm-2 and a small area with approximately 2*2 mm2 did not show dislocation contrast in many reflections and has suitable quality for application as a backscattering monochromator. As a result, a clear correlation between growth rate and dislocation densitymore » is observed, though growth rate is not the only parameter impacting the quality.« less

  19. 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.

  20. Thermal conductivity of synthetic garnet laser crystals

    NASA Astrophysics Data System (ADS)

    Wang, B. S.; Jiang, H. H.; Zhang, Q. L.; Yin, S. T.

    2007-07-01

    The thermal conductivities of nine different synthetic garnet laser crystals at various temperatures, range from 273 to 393K have been investigated by instantaneous measurement method. The results show that the thermal conductivity of each crystal decreases exponentially with the temperature increasing. It is notable that, different host crystals, such as YAG, GGG, and GSGG have different thermal conductivity, which is attributed to the crucial influence of crystal structure and composition on the absolute value of their thermal conductivity. Moreover, with respect to the same host crystals, the impurity scattering also results in the change of their thermal conductivities. This is because that a higher concentration of doped ions leads to a more phonon scattering modes, which results in a shorter mean free path of the phonons and a lower thermal conductivity. In addition, different host crystals have various dependences of thermal conductivity on dopant concentration. This works provides reliable and useful information for designing high power, high quality, and high stability laser devices.

  1. An ESR Investigation of Synthetic Pyrite Crystals

    NASA Astrophysics Data System (ADS)

    Siebert, D.; Dahlem, J.; Fiechter, S.; Hartmann, A.

    1989-01-01

    Synthetic pyrite crystals doped with halogen (CI, Br) or manganese (Mn) were investigated by ESR at 78 K with an X-band spectrometer and a TE102 cavity with 100 kc field modulation. The crystals were preferably measured with the directions <100>, <110>, and <111> parallel to the static magnetic field HO. The ESR spectrum of Mn-doped crystals showed a sextet which can be explained by a spin-Hamiltonian for an electron spin S = 1/2 in interaction with the nuclear spin I = 5/2 of the Mn nucleus for axial symmetry. Due to the observed spin and due to the orientation of the paramagnetic centers the spectra were assigned to Mn2+ in the low spin state which resides on cation site in the FeS2, lattice. In halogen-doped crystals four pairs of lines can be interpreted by the interaction of the two isotopes of I = 3/2, 79Br, 81Br and 35Cl, 37Cl, respectively, with an electron spin S = 1/2. According to the observed symmetry of the ESR signals the paramagnetic centers can be explained as (S-X)2- radicals (X = CI, Br) which substitute for the (S2)2- dumb-bells of pyrite. All crystals evoked extremely narrow ESR lines, especially the halogen-doped crystals with linewidths down to 0.03 mT. Excellent agreement between measured and calculated spectra up to the finest details has been obtained.

  2. Tunable integrated optical filters based on sapphire microspheres and liquid crystals

    NASA Astrophysics Data System (ADS)

    Gilardi, Giovanni; Yilmaz, Hasan; Sharif Murib, Mohammed; Asquini, Rita; d'Alessandro, Antonio; Serpengüzel, Ali; Beccherelli, Romeo

    2010-05-01

    We present an integrated optical narrowband electrically tunable filter based on the whispering gallery modes of sapphire microspheres and double ion-exchanged channel BK7 glass waveguides. Tuning is provided by a liquid crystal infiltrated between the spheres and the glass substrate. By suitably choosing the radii of the spheres and of the circular apertures, upon which the spheres are positioned, arrays of different filters can be realized on the same substrate with a low cost industrial process. We evaluate the performance in terms of quality factor, mode spacing, and tuning range by comparing the numerical results obtained by the numerical finite element modeling approach and with the analytical approach of the Generalized Lorenz-Mie Theory for various design parameters. By reorienting the LC in an external electrical field, we demonstrate the tuning of the spectral response of the sapphire microsphere based filter. We find that the value of the mode spacing remains nearly unchanged for the different values of the applied electric field. An increase of the applied electric field strength, changes the refractive index of the liquid crystal, so that for a fixed geometry the mode spacing remains unchanged.

  3. Laser-diode pumped glass-clad Ti:sapphire crystal fiber laser.

    PubMed

    Wang, Shih-Chang; Hsu, Chun-Yang; Yang, Tzu-Te; Jheng, Dong-Yo; Yang, Teng-I; Ho, Tuan-Shu; Huang, Sheng-Lung

    2016-07-15

    Efficient glass-clad crystal fiber (CF) lasers were demonstrated using a Ti:sapphire crystalline core as the gain medium. With a core diameter of 18 μm, the laser diode (LD) pump source can be effectively coupled and guided throughout the crystal fiber for a low threshold and high slope efficiency laser operation. The advantage of high heat dissipation efficiency of the fiber structure can be derived from the low core temperature rising measurement (i.e., 17 K/W) with passive cooling. At an output transmittance of 23%, the lowest absorbed threshold of 118.2 mW and highest slope efficiency of 29.6% were achieved, with linear laser polarization. PMID:27420499

  4. Mid-infrared silicon-on-sapphire waveguide coupled photonic crystal microcavities

    SciTech Connect

    Zou, Yi E-mail: swapnajit.chakravarty@omegaoptics.com Chen, Ray T. E-mail: swapnajit.chakravarty@omegaoptics.com; Chakravarty, Swapnajit E-mail: swapnajit.chakravarty@omegaoptics.com

    2015-08-24

    We experimentally demonstrate a photonic crystal (PC) microcavity side coupled to a W1.05 photonic crystal waveguide fabricated in silicon-on-sapphire working in mid-IR regime at 3.43 μm. Using a fixed wavelength laser source, propagation characteristics of PC waveguides without microcavity are characterized as a function of lattice constant to determine the light line position, stop gap, and guided mode transmission behavior. The resonance of an L21 PC microcavity coupled to the W1.05 PCW in the guided mode transmission region is then measured by thermal tuning of the cavity resonance across the source wavelength. Resonance quality factor ∼3500 is measured from the temperature dependency curve.

  5. Synthesis and Transfer of Large-Area Monolayer WS2 Crystals: Moving Toward the Recyclable Use of Sapphire Substrates.

    PubMed

    Xu, Zai-Quan; Zhang, Yupeng; Lin, Shenghuang; Zheng, Changxi; Zhong, Yu Lin; Xia, Xue; Li, Zhipeng; Sophia, Ponraj Joice; Fuhrer, Michael S; Cheng, Yi-Bing; Bao, Qiaoliang

    2015-06-23

    Two-dimensional layered transition metal dichalcogenides (TMDs) show intriguing potential for optoelectronic devices due to their exotic electronic and optical properties. Only a few efforts have been dedicated to large-area growth of TMDs. Practical applications will require improving the efficiency and reducing the cost of production, through (1) new growth methods to produce large size TMD monolayer with less-stringent conditions, and (2) nondestructive transfer techniques that enable multiple reuse of growth substrate. In this work, we report to employ atmospheric pressure chemical vapor deposition (APCVD) for the synthesis of large size (>100 μm) single crystals of atomically thin tungsten disulfide (WS2), a member of TMD family, on sapphire substrate. More importantly, we demonstrate a polystyrene (PS) mediated delamination process via capillary force in water which reduces the etching time in base solution and imposes only minor damage to the sapphire substrate. The transferred WS2 flakes are of excellent continuity and exhibit comparable electron mobility after several growth cycles on the reused sapphire substrate. Interestingly, the photoluminescence emission from WS2 grown on the recycled sapphire is much higher than that on fresh sapphire, possibly due to p-type doping of monolayer WS2 flakes by a thin layer of water intercalated at the atomic steps of the recycled sapphire substrate. The growth and transfer techniques described here are expected to be applicable to other atomically thin TMD materials. PMID:25961515

  6. Complete characterization of damage threshold in titanium doped sapphire crystals with nanosecond, picosecond, and femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Canova, F.; Chambaret, J.-P.; Mourou, G.; Sentis, M.; Uteza, O.; Delaporte, P.; Itina, T.; Natoli, J.-Y.; Commandre, M.; Amra, C.

    2005-12-01

    The major bottleneck for the development of robust and cost-effective femtosecond amplification systems is the uncertainty concerning the damage threshold of Ti: Sapphire crystals. Up to now, Ti: Sapphire is the only material that supports the generation of temporally short pulses (few femtosecond) at high repetition rates, and overcoming this bottleneck will represent a major advance in laser performance for all the femtosecond community. Currently, when pumped at 532nm, the uncertainty on Ti:Sapphire damage threshold, is about a factor of ten. The empirically estimated threshold is 10J/cm2 but for safety reasons the femtosecond laser community (especially the companies producing the lasers) uses the conservative value of 1J/cm2. Such a low pumping fluency means low extraction efficiency during the amplification process and a great waste of pumping energy, the most expensive part of a Ti:Sapphire amplifier. In order to remove this bottleneck, we launch a complete analysis of all the factors that influence the damage threshold in Ti:Sapphire Crystals. Our program is to first measure the bulk threshold to define the upper threshold limit, and the influence of Ti ion concentration in the crystal garnet. Then, we will analyze all the surface effects that influence the value of the threshold. These effects depend on the polishing, on the cleaning process, as well as the type of anti-reflective coating. Only a complete understanding of all the mechanisms involved in threshold limitation will allow us to produce Ti:Sa crystals with the best performances. The study of the characteristics of the Ti:Sapphire damage threshold will not be complete and reliable without a complete characterization of the pump beams (temporal and spatial modulations), and this analysis will be done with nanosecond and picosecond pulses at 532nm. Finally, to complete the exploration of the the behavior of the titanium doped sapphire crystal, we will characterize the damage threshold with

  7. Characterization of AFB sapphire single crystal composites for infrared window application

    NASA Astrophysics Data System (ADS)

    Lee, H.-C.; Meissner, H. E.

    2007-04-01

    Next generation weapons platforms may require 30" x 30" sapphire windows. Since these sizes exceed what can be manufactured directly, a concept is proposed and experimental data are furnished in this report on the viability of increasing the window dimensions by Adhesive-Free-Bonding (AFB®) of smaller starting components by their edges. The bonding scheme has been evaluated for single crystal sapphire but is expected to also work equally well for other IR window materials. The bonding mechanism is explained with Van der Waals theory of attractive forces and confirmed experimentally by applying the bending plate theory. The gap at the interface between two components is deduced from the measured roughness of the polished surfaces that are brought into optical contact and subsequently heat-treated, and is estimated to be about 2 Å rms. Stress relief at AFB® interfaces has been established. Experimental data of flexural strength determined by four-point bending at room temperature is reported. The data indicates that AFB® composite specimens and equivalently prepared blank samples fracture at statistically same loads under standardized testing conditions. Failure of composites has not been observed at the interface and only at random flaws that are a result of sample preparation.

  8. The study on the nanomachining property and cutting model of single-crystal sapphire by atomic force microscopy.

    PubMed

    Huang, Jen-Ching; Weng, Yung-Jin

    2014-01-01

    This study focused on the nanomachining property and cutting model of single-crystal sapphire during nanomachining. The coated diamond probe is used to as a tool, and the atomic force microscopy (AFM) is as an experimental platform for nanomachining. To understand the effect of normal force on single-crystal sapphire machining, this study tested nano-line machining and nano-rectangular pattern machining at different normal force. In nano-line machining test, the experimental results showed that the normal force increased, the groove depth from nano-line machining also increased. And the trend is logarithmic type. In nano-rectangular pattern machining test, it is found when the normal force increases, the groove depth also increased, but rather the accumulation of small chips. This paper combined the blew by air blower, the cleaning by ultrasonic cleaning machine and using contact mode probe to scan the surface topology after nanomaching, and proposed the "criterion of nanomachining cutting model," in order to determine the cutting model of single-crystal sapphire in the nanomachining is ductile regime cutting model or brittle regime cutting model. After analysis, the single-crystal sapphire substrate is processed in small normal force during nano-linear machining; its cutting modes are ductile regime cutting model. In the nano-rectangular pattern machining, due to the impact of machined zones overlap, the cutting mode is converted into a brittle regime cutting model. PMID:25241676

  9. ON-LINE SELF-CALIBRATING SINGLE CRYSTAL SAPPHIRE OPTICAL SENSOR INSTRUMENTATION FOR ACCURATE AND RELIABLE COAL GASIFIER TEMPERATURE MEASUREMENT

    SciTech Connect

    Kristie Cooper; Gary Pickrell; Anbo Wang

    2003-04-01

    This report summarizes technical progress over the first six months of the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the BPDI sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Research efforts were focused on analyzing and testing factors that impact performance degradation of the initially designed sensor prototype, including sensing element movement within the sensing probe and optical signal quality degradation. Based these results, a new version of the sensing system was designed by combining the sapphire disk sensing element and the single crystal zirconia right angle light reflector into one novel single crystal sapphire right angle prism. The new sensor prototype was tested up to 1650 C.

  10. Simulation of heat transfer and convection during sapphire crystal growth in a modified heat exchanger method

    NASA Astrophysics Data System (ADS)

    Zhang, Nan; Park, Hyun Gyoon; Derby, Jeffrey J.

    2013-03-01

    Quasi-steady-state (QSS) and transient models, developed using the CrysMAS code, are employed to study the effects of transport mechanisms and cold finger design on the temperature distribution, melt flow field, and melt-crystal interface shape during the crystal growth of sapphire by a small-scale, modified heat exchanger method (HEM). QSS computations show the importance and effects of various heat transfer mechanisms in the crystal and melt, including conduction, internal radiation, and melt convection driven by buoyant and Marangoni forces. The design of the cold finger is demonstrated to have significant effects on growth states. Notably, transient computations on an idealized heat transfer model, supplemented with QSS calculations of a model with rigorous heat transfer representation, show that non-uniform growth conditions arise under uniform cooling of the system via a linear decrease in furnace set points. We suggest that more uniform HEM growth conditions may be achieved by using non-linear cool-down strategies.

  11. Surface phonon polariton responses of hexagonal sapphire crystals with non-polar and semi-polar crystallographic planes.

    PubMed

    Lee, Sai Cheong; Ng, Sha Shiong; Hassan, Haslan Abu; Hassan, Zainuriah; Dumelow, Thomas

    2014-09-15

    The surface phonon polariton (SPhP) characteristics of hexagonal sapphire crystals with non-polar and semi-polar crystallographic planes are investigated. A formulation that considers the effects of crystal orientation is employed to calculate the SPhP dispersion curves of the samples. The SPhP dispersion curves indicate that the SPhP responses of sapphire crystals in non-polar and semi-polar orientations are directionally sensitive. Resonance frequencies and spectral strengths of the SPhP modes can be modulated simply by tuning the angular positions of the samples. The validity of the theoretical results is confirmed by the polarized infrared attenuated total reflection measurements. PMID:26466299

  12. Defect Analysis of Boron Phosphide Thin Films and Sapphire Single Crystal Using Synchrotron X-ray Topography

    NASA Astrophysics Data System (ADS)

    Ding, Zihao

    Boron phosphide is an ideal semiconductor material used for neutron detectors because of its superior material properties, such as wide band gap and large thermal neutron capture cross-section of 10B. Since bulk BP is not readily available for neutron detector application, BP thin films are mainly synthesized by chemical vapor deposition (CVD). Among all the feasible substrates for BP deposition, SiC stands out due to its small lattice mismatch (4.5%) with BP, however it is necessary to optimize the growth condition to synthesize high quality BP thin films on SiC. In chapter III, BP thin film samples deposited on 4H-SiC and 6H-SiC under different growth conditions are characterized, mainly using synchrotron X-ray topography and other techniques such as optical microscopy and scanning electron microscopy. The relationship between BP thin film crystal quality and substrate material and orientation and other growth conditions is investigated. It can be concluded from the experimental data that the crystal quality of BP thin films on 4H-SiC substrate is much better than that on 6H-SiC substrate. Besides, poor crystalline quality of substrate will likely degrade the crystalline quality of epitaxial thin films. Sapphire single crystal has been widely used in high-technology industry because of its excellent combination between optical, electrical and mechanical properties. In this thesis, a-plane sapphire ribbon grown by Edge-defined Film-fed Growth method (EFG) is analyzed by characterizing the seed crystals used and the quality of as-grown ribbon, by reflection X-ray topography. Distributions and formation mechanisms of defects inside both the sapphire seed crystal and ribbon crystal are studied. Transmission topographs reveal the presence of two sets of slip bands that are nucleated from either edge, the distribution of which is symmetric in the used seed crystal and asymmetric in the pristine seed crystal. This phenomenon could be caused by the unstable growth

  13. Effects of RF coil position on the transport processes during the stages of sapphire Czochralski crystal growth

    NASA Astrophysics Data System (ADS)

    Lu, Chung-Wei; Chen, Jyh-Chen; Chen, Chien-Hung; Chen, Chun-Hung; Hsu, Wen-Ching; Liu, Che-Ming

    2010-04-01

    The effect of the RF coil position during the stages of sapphire crystal growth process in an inductively heated Czochralski crystal growth furnace on the thermal and flow transport, the shape of the crystal-melt interface shape, and the power requirements is investigated numerically. The results show that although the maximum values of temperature and velocity decrease, the convexity of the crystal-melt interface increases as the crystal length grows. It is found that the least input power is required if the central position of the RF coil is maintained below the central position of the melt during the crystal growth process. Under such crystal growth conditions, the temperature gradients along the crystalline front are small.

  14. Bulk vertical micromachining of single-crystal sapphire using inductively coupled plasma etching for x-ray resonant cavities

    NASA Astrophysics Data System (ADS)

    Chen, P.-C.; Lin, P.-T.; Mikolas, D. G.; Tsai, Y.-W.; Wang, Y.-L.; Fu, C.-C.; Chang, S.-L.

    2015-01-01

    To provide coherent x-ray sources for probing the dynamic structures of solid or liquid biological substances on the picosecond timescale, a high-aspect-ratio x-ray resonator cavity etched from a single crystal substrate with a nearly vertical sidewall structure is required. Although high-aspect-ratio resonator cavities have been produced in silicon, they suffer from unwanted multiple beam effects. However, this problem can be avoided by using the reduced symmetry of single-crystal sapphire in which x-ray cavities may produce a highly monochromatic transmitted x-ray beam. In this study, we performed nominal 100 µm deep etching and vertical sidewall profiles in single crystal sapphire using inductively coupled plasma (ICP) etching. The large depth is required to intercept a useful fraction of a stopped-down x-ray beam, as well as for beam clearance. An electroplated Ni hard mask was patterned using KMPR 1050 photoresist and contact lithography. The quality and performance of the x-ray cavity depended upon the uniformity of the cavity gap and therefore verticality of the fabricated vertical sidewall. To our knowledge, this is the first report of such deep, vertical etching of single-crystal sapphire. A gas mixture of Cl2/BCl3/Ar was used to etch the sapphire with process variables including BCl3 flow ratio and bias power. By etching for 540 min under optimal conditions, we obtained an x-ray resonant cavity with a depth of 95 µm, width of ~30 µm, gap of ~115 µm and sidewall profile internal angle of 89.5°. The results show that the etching parameters affected the quality of the vertical sidewall, which is essential for good x-ray resonant cavities.

  15. ON-LINE SELF-CALIBRATING SINGLE CRYSTAL SAPPHIRE OPTICAL SENSOR INSTRUMENTATION FOR ACCURATE AND RELIABLE COAL GASIFIER TEMPERATURE MEASUREMENT

    SciTech Connect

    Kristie Cooper; Gary Pickrell; Anbo Wang

    2003-11-01

    This report summarizes technical progress over the second six month period of the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the BPDI sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Research efforts were focused on evaluating corrosion effects in single crystal sapphire at temperatures up to 1400 C, and designing the sensor mechanical packaging with input from Wabash River Power Plant. Upcoming meetings will establish details for the gasifier field test.

  16. 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.

  17. Optical mode confinement and selection in single-crystal sapphire fibers by formation of nanometer scale cavities with hydrogen ion implantation

    NASA Astrophysics Data System (ADS)

    Spratt, William; Huang, Mengbing; Murray, Thomas; Xia, Hua

    2013-11-01

    The excellent material properties of single crystal sapphire fibers promise great advantages in applications related to harsh environment optical sensing, high laser power delivery, and high-resolution/sensitivity optical spectroscopy. However, the lack of viable cladding for confining light propagation in sapphire fibers with negligible transmission loss has restricted their practical applications. Despite great efforts in engineering either a low-refractive-index cladding layer or highly reflective mirror layer as sapphire fiber surface coatings, confining light propagation within sapphire fibers remains difficult in practice since such surface coatings fail to function due to increased thermal stress and fast erosion in environments with extremely high temperatures (>1000 °C) and chemically reactive species/gases. Here, we demonstrate a method for creating nanoscale cavities/voids in sapphire as effective fiber cladding structures that are thermally robust even at 1700 °C using hydrogen ion implantation. Material analysis of implanted sapphire crystals indicates that such nanoscale cavities play a key role in reducing the refractive index in sapphire crystals.

  18. Progress in the growth of large scale Ti:sapphire crystals by the heat exchanger method (HEM) for petawatt class lasers

    NASA Astrophysics Data System (ADS)

    Joyce, David B.; Schmid, Frederick

    2010-04-01

    In modelocked laser systems, the shortest possible pulse width is determined by the Fourier transform of the spectral bandwidth of the pulse; the wider the spectral bandwidth, the shorter the pulse. Titanium-doped sapphire (Ti:sapphire) offers the widest gain bandwidth of any currently available laser gain material, enabling systems to deliver pulse widths shorter than 10 fs (10 -14 s). Because of the short pulse durations, the peak power can be extremely high, and therefore Ti:sapphire lasers have been at the forefront of research into ultrafast, ultrahigh power lasers. These intense ultrashort laser pulses are the light source for fundamental studies of light-matter interactions. Interesting scientific results have been achieved with these lasers in the fields of high order harmonic and short pulse X-ray generations, high density plasmas, relativistic acceleration, relativistic nonlinear optics, time resolved X-ray diffraction with unprecedented time resolution and others. Researchers have recently achieved near petawatt (10 15 W) peak power laser operation using large diameter Ti:sapphire amplifiers, and are developing higher power lasers for research into high energy physics. However, the saturation fluence of the Ti:sapphire gain medium is limited to about 1 J/cm 2. Thus, continued scale up in peak laser energy requires the scale up of high-quality Ti:sapphire crystals for laser amplifiers. Current demand is for 100 mm diameter crystals, and this requirement is projected to grow up to 250 mm diameter crystals in a few years. To address this technological bottleneck, Crystal Systems has upgraded its heat exchanger method (HEM) furnaces and fabrication and metrology to scale up the production of Ti:sapphire crystals. Currently, 175 mm diameter Ti:sapphire amplifier crystals are being fabricated from high-quality 208 mm boules.

  19. DOE SAPPHIRE PROJECT

    SciTech Connect

    Dr. Gary R. Pickrell

    2000-03-01

    Since this is the first report for this project an extensive background section follows on the theory of operation of the single crystal sapphire sensor technology which will be developed and field tested at the Wabash River Coal Gasification Facility. Requirements for the temperature sensors for implementation in the coal gasifiers has been established in conjunction with the industrial partner, Dynegy. Coal slag immersion tests indicate good corrosion resistance of the single crystal sapphire. However, a more sophisticated corrosion apparatus has been constructed in order to test the optical attenuation of a single crystal sapphire fiber immersed in the coal slag at high temperature. These results will be reported in the next period. The data to date for sapphire sensor development is promising. More extensive data on the sapphire fiber sensor development will be reported for the next period.

  20. On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement

    SciTech Connect

    Kristie Cooper; Anbo Wang

    2007-03-31

    This report summarizes technical progress October 2006 - March 2007 on the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. During the second phase, an alternative high temperature sensing system based on Fabry-Perot interferometry was developed that offers a number of advantages over the BPDI solution. The objective of this program is to bring the sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. The sapphire wafer-based interferometric sensing system that was installed at TECO's Polk Power Station remained in operation for seven months. Our efforts have been focused on monitoring and analyzing the real-time data collected, and preparing for a second field test.

  1. Optical anomalies and residual stresses in basal-plane-faceted ribbons of Stepanov-grown sapphire crystals

    NASA Astrophysics Data System (ADS)

    Denisov, A. V.; Krymov, V. M.; Punin, Yu. O.

    2007-03-01

    The effects of an anomalous biaxiality and a residual-stress field in basal-plane-faceted single-crystal sapphire ribbons were studied by an optical polarization method using a conoscopic light beam. Formulas that relate the difference between the principal stresses to the angle of optical-axis divergence are obtained. It is shown that the central regions of the ribbons undergo compressive stresses whereas their edges undergo tensile stresses. As compared to block-free ribbons, the stresses in block-containing ribbons increase more intensely with distance from the seed.

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

    SciTech Connect

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

    2006-09-14

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

  3. Structure analysis on synthetic emerald crystals

    NASA Astrophysics Data System (ADS)

    Lee, Pei-Lun; Lee, Jiann-Shing; Huang, Eugene; Liao, Ju-Hsiou

    2013-05-01

    Single crystals of emerald synthesized by means of the flux method were adopted for crystallographic analyses. Emerald crystals with a wide range of Cr3+-doping content up to 3.16 wt% Cr2O3 were examined by X-ray single crystal diffraction refinement method. The crystal structures of the emerald crystals were refined to R 1 (all data) of 0.019-0.024 and w R 2 (all data) of 0.061-0.073. When Cr3+ substitutes for Al3+, the main adjustment takes place in the Al-octahedron and Be-tetrahedron. The effect of substitution of Cr3+ for Al3+ in the beryl structure results in progressively lengthening of the Al-O distance, while the length of the other bonds remains nearly unchanged. The substitution of Cr3+ for Al3+ may have caused the expansion of a axis, while keeping the c axis unchanged in the emerald lattice. As a consequence, the Al-O-Si and Al-O-Be bonding angles are found to decrease, while the angle of Si-O-Be increases as the Al-O distance increases during the Cr replacement.

  4. ON-LINE SELF-CALIBRATING SINGLE CRYSTAL SAPPHIRE OPTICAL SENSOR INSTRUMENTATION FOR ACCURATE AND RELIABLE COAL GASIFIER TEMPERATURE MEASUREMENT

    SciTech Connect

    Kristie Cooper; Gary Pickrell; Anbo Wang; Zhengyu Huang

    2004-04-01

    This report summarizes technical progress over the third six month period of the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the BPDI sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Research efforts were focused on sensor probe design and machining, sensor electronics design, software algorithm design, sensor field installation procedures, and sensor remote data access and control. Field testing will begin in the next several weeks.

  5. On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement

    SciTech Connect

    Kristie Cooper; Gary Pickrell; Anbo Wang

    2005-11-01

    This report summarizes technical progress April-September 2005 on the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Due to the difficulties described on the last report, field testing of the BPDI system has not continued to date. However, we have developed an alternative high temperature sensing solution, which is described in this report. The sensing system will be installed and tested at TECO's Polk Power Station. Following a site visit in June 2005, our efforts have been focused on preparing for that field test, including he design of the sensor mechanical packaging, sensor electronics, the data transfer module, and the necessary software codes to accommodate this application.. We are currently ready to start sensor fabrication.

  6. ON-LINE SELF-CALIBRATING SINGLE CRYSTAL SAPPHIRE OPTICAL SENSOR INSTRUMENTATION FOR ACCURATE AND RELIABLE COAL GASIFIER TEMPERATURE MEASUREMENT

    SciTech Connect

    Kristie Cooper; Gary Pickrell; Anbo Wang; Zhengyu Huang; Yizheng Zhu

    2005-04-01

    This report summarizes technical progress October 2004-March 2005 on the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the BPDI sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Due to the difficulties described on the last report, field testing of the BPDI system has not continued to date. However, we have developed an alternative high temperature sensing solution, which is described in this report.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  8. High performance sapphire windows

    NASA Technical Reports Server (NTRS)

    Bates, Stephen C.; Liou, Larry

    1993-01-01

    High-quality, wide-aperture optical access is usually required for the advanced laser diagnostics that can now make a wide variety of non-intrusive measurements of combustion processes. Specially processed and mounted sapphire windows are proposed to provide this optical access to extreme environment. Through surface treatments and proper thermal stress design, single crystal sapphire can be a mechanically equivalent replacement for high strength steel. A prototype sapphire window and mounting system have been developed in a successful NASA SBIR Phase 1 project. A large and reliable increase in sapphire design strength (as much as 10x) has been achieved, and the initial specifications necessary for these gains have been defined. Failure testing of small windows has conclusively demonstrated the increased sapphire strength, indicating that a nearly flawless surface polish is the primary cause of strengthening, while an unusual mounting arrangement also significantly contributes to a larger effective strength. Phase 2 work will complete specification and demonstration of these windows, and will fabricate a set for use at NASA. The enhanced capabilities of these high performance sapphire windows will lead to many diagnostic capabilities not previously possible, as well as new applications for sapphire.

  9. Crystallization by Particle Attachment in Synthetic, Biogenic, and Geologic Environments

    SciTech Connect

    De Yoreo, James J.; Gilbert, Pupa U.; Sommerdijk, Nico; Penn, R. Lee; Whitelam, Stephen B.; Joester, Derk; Zhang, Hengzhong; Rimer, Jeffrey D.; Navrotsky, Alexandra; Banfield, Jillian F.; Wallace, Adam F.; Michel, F. M.; Meldrum, Fiona C.; Colfen, Helmut; Dove, Patricia M.

    2015-07-31

    Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. These non-classical pathways to crystallization are diverse, in contrast to classical models that consider the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle attachment processes and show that multiple pathways result from the interplay of free energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects; particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems and patterns of mineralization in natural environments.

  10. Spatial Coherence Preservation By Synthetic Single Diamond Crystals

    NASA Astrophysics Data System (ADS)

    Hoszowska, J.; Freund, A. K.; Guigay, J.-P.; Rommeveaux, A.

    2004-05-01

    The degree of spatial coherence after x-ray diffraction by synthetic single diamond crystals was investigated. The coherence preservation was measured by means of the Talbot effect for x-rays at the optics beamline BM5 at the ESRF. The (111)- and (100)- oriented specimens of type Ib and IIa were grown by De Beers. To establish a correlation between the coherence degradation and the surface quality, 3D surface topography was measured with an optical interferometric profiler and an AFM. Likewise, to pinpoint the relationship with crystalline quality, the samples were characterized by means of double crystal x-ray diffractometry with microscopic resolution.

  11. Spatial Coherence Preservation By Synthetic Single Diamond Crystals

    SciTech Connect

    Hoszowska, J.; Freund, A. K.; Guigay, J.-P.; Rommeveaux, A.

    2004-05-12

    The degree of spatial coherence after x-ray diffraction by synthetic single diamond crystals was investigated. The coherence preservation was measured by means of the Talbot effect for x-rays at the optics beamline BM5 at the ESRF. The (111)- and (100)- oriented specimens of type Ib and IIa were grown by De Beers. To establish a correlation between the coherence degradation and the surface quality, 3D surface topography was measured with an optical interferometric profiler and an AFM. Likewise, to pinpoint the relationship with crystalline quality, the samples were characterized by means of double crystal x-ray diffractometry with microscopic resolution.

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

    SciTech Connect

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

    2014-10-28

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  14. Optical Properties of Natural and Synthetic Beryl Crystals

    NASA Astrophysics Data System (ADS)

    Skvortsova, V.; Mironova-Ulmane, N.; Trinkler, L.; Merkulov, V.

    2015-03-01

    The results of investigation of photoluminescence and UV-Visible absorption spectra of natural beryl crystals from Ural Mountains before and after fast neutron irradiation and synthetic crystal grown in Belarus and Russia are presented. Photoluminescence (PL) spectra of synthetic beryl crystals contain a broad band with maxima 740 nm excited both by UV light (λex = 260 nm, 271 nm) and laser excitation (λex =263 nm). This band is connected with Fe2+ ions. The temperature lowering down to 8 K leads to appearance of narrow lines in the 680 - 720 nm regions. Emission lines observed in the luminescence spectra are connected with electron transition 2Eg→4A2g of the Cr3+ ions: R-lines (682.5 nm) arise from isolated Cr3+ ions occupying Al3+ sites; N-lines (691, 698, 703, 706 and 711 nm) arise from several types of exchange-coupled pairs of Cr3+ ions occupying first, second and third nearest and related neighbour Al3+ sites. It is shown that the absorption bands in the 690-580 nm region of natural pale blue beryl crystals caused by neutron irradiation belong to a complex center, which consists of Cr3+ ions and radiation defect - F or F+- center. Presence of Fe2+ ions contributes to the persistence of the complex defect.

  15. Effect of surface pretreatment of r-plane sapphire substrates on the crystal quality of a-plane AlN

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Hung; Yasui, Daiki; Tamaki, Shinya; Miyake, Hideto; Hiramatsu, Kazumasa

    2016-05-01

    Single-crystal a-plane AlN(11\\bar{2}0) films were grown on r-plane sapphire (1\\bar{1}02) substrates by hydride vapor phase epitaxy (HVPE). We performed the optimization of thermal cleaning and nitridation conditions for r-plane sapphire substrates, and investigated the effect of ammonia (NH3) preflow on the crystallinity of a-plane AlN. An r-plane sapphire substrate with uniformly straight atomic steps was formed at 1000 °C, and NH3 preflow was subsequently supplied. The growth mode of a-plane AlN was promoted to be three-dimensional (3D) growth by the nitridation of r-plane sapphire substrates, and sizes of 3D islands were modified by changing the NH3 preflow time. The crystallinity of a-plane AlN films was improved by varying the NH3 preflow time from 30 to 90 s. The optimum crystal quality of a-plane AlN films was obtained with NH3 preflow for 30 s.

  16. Orientation relationships of copper crystals on sapphire (1 0 1¯ 0) m-plane and (1 0 1¯ 2) r-plane substrates

    NASA Astrophysics Data System (ADS)

    Chatain, Dominique; Curiotto, Stefano; Wynblatt, Paul; Meltzman, Hila; Kaplan, Wayne D.; Rohrer, Gregory S.

    2015-05-01

    Copper films deposited on m- and r-plane sapphire substrates have been dewetted in either the solid or the liquid state, and equilibrated at 1253 K. The orientation relationships (ORs) between the dewetted copper crystals and the sapphire substrates have been investigated by electron backscatter diffraction. In addition, the shape of the copper/sapphire interface has been studied by scanning electron microscopy. Although the as-deposited films develop {1 1 1} surfaces parallel to both substrates, after solid state dewetting the copper crystals on the m-plane substrate are found to change their interface plane from Cu{1 1 1}||Al2O3(m-plane) to Cu{1 1 1}|| Al2O3 (a-plane), and after liquid state dewetting the preferred OR of copper on both m- and r-plane substrates may be expressed as: Cu{1 1 1}<1 1 0> || Al2O3 {1 1 2bar 0}<0 0 0 1>. This OR is identical to that previously observed for copper on the sapphire a-plane.

  17. Characterization of critically cleaned sapphire single-crystal substrates by atomic force microscopy, XPS and contact angle measurements

    NASA Astrophysics Data System (ADS)

    Zhang, Dan; Wang, You; Gan, Yang

    2013-06-01

    A contaminant-free surface of single-crystal α-Al2O3 (or sapphire) substrates is key to the experimental studies of its surface and interfacial properties at ambient conditions. Here we critically evaluated methods reported in the literature using comprehensive surface analysis techniques including atomic force microscopy, XPS and contact angle measurements. We found that reported methods did not perform well in terms of removing both organic and particulate contaminants from the (0 0 0 1) basal surface. After thoroughly examining the cleaning effect of various chemical solutions and UV light and plasma irradiation, and based on modified RCA cleaning protocols, we proposed a new wet-cleaning method showing outstanding cleaning performance. This new reliable method will be very useful for the next-step surface chemistry study of single-crystal α-Al2O3. It was also demonstrated that AFM, due to its high spatial resolution and sensitivity as a local probe technique, was an indispensable tool for surface contamination control studies.

  18. The crystallization of new synthetic organo-clays

    SciTech Connect

    Carrado, K.A.

    1994-03-01

    A novel method for the preparation of new synthetic, potentially catalytic clays has been discovered. In this method, a diverse variety of organic and-organometallic molecules can be directly incorporated during crystallization of the clay. This method has great potential for the incorporation of catalytically active species to create new heterogeneous catalysts. The catalyst precursors are organic-inorganic composites comprised of a layered silicate intercalated with such molecules as porphyrins or metalloporphyrins, organic aromatic dyes, a Cu(II) phthalocyanine dye, or bulky transition metal chelates. This procedure is readily applicable for introducing specific molecules for highly tailored applications, because successful templates include a variety of catalytically, electrochemically, and photochemically active species. Characterization studies were performed to establish the composition of the synthetic products, including x-ray absorption spectroscopy at NSLS.

  19. Synthetic Strategies Toward DNA-Coated Colloids that Crystallize.

    PubMed

    Wang, Yufeng; Wang, Yu; Zheng, Xiaolong; Ducrot, Étienne; Lee, Myung-Goo; Yi, Gi-Ra; Weck, Marcus; Pine, David J

    2015-08-26

    We report on synthetic strategies to fabricate DNA-coated micrometer-sized colloids that, upon thermal annealing, self-assemble into various crystal structures. Colloids of a wide range of chemical compositions, including poly(styrene), poly(methyl methacrylate), titania, silica, and a silica-methacrylate hybrid material, are fabricated with smooth particle surfaces and a dense layer of surface functional anchors. Single-stranded oligonucleotides with a short sticky end are covalently grafted onto particle surfaces employing a strain-promoted alkyne-azide cycloaddition reaction resulting in DNA coatings with areal densities an order of magnitude higher than previously reported. Our approach allows the DNA-coated colloids not only to aggregate upon cooling but also to anneal and rearrange while still bound together, leading to the formation of colloidal crystal compounds when particles of different sizes or different materials are combined. PMID:26192470

  20. Histological characteristics of peri-implant mucosa around Brånemark and single-crystal sapphire implants.

    PubMed

    Arvidson, K; Fartash, B; Hilliges, M; Köndell, P A

    1996-03-01

    Soft tissues surrounding Brånemark titanium implants and single crystal sapphire implants were studied by conventional light- and transmission electron microscopy and by immunohistochemical markers for cytokeratin, protein S-100, Factor VIII and KP1. Histological sections of biopsies obtained from clinically healthy peri-implant mucosa were separated into a keratinized outer implant epithelium and an inner, non-keratinized epithelium, both immunoreactive towards cytokeratin. The inner implant epithelium terminated in a junctional epithelium, apically not a few cell layers thick. The cells adjacent to the implant showed a condensed cytoplasm, resembling hemidesmosomes. In the underlying connective tissue, rich in fibroblasts and factor VIII immunoreactive blood vessels, the bundles of collagen ran in different directions. S-100 immunoreactive nerve structures were more frequently found beneath the outer than the inner implant epithelium. Inflammatory cell infiltrates, some KP1 positive, were observed in the apical parts of the inner implant epithelium. S-100 positive Langerhans' cells were present mainly within the the outer implant epithelium. For the two implant systems, the techniques disclosed no qualitative structural differences in the adjacent soft tissues. PMID:9002817

  1. Crystallization and textural porosity of synthetic clay minerals.

    SciTech Connect

    Carrado, K. A.; Csencsits, R.; Thiyagarajan, P.; Seifert, S.; Macha, S. M.; Harwood, J.; Univ. of Illinois at Chicago; IIT

    2002-12-01

    The crystallization of synthetic layered magnesium silicate hectorite clays from both silica sol and organosilane sources is compared. For the silica sol-derived clays, a templating method is employed wherein organic or polymeric molecules are included during clay crystallization that are then removed from the composites via calcination. The mechanism of silane-derived hectorite formation is followed by XRD, TGA, 29Si MAS NMR, and small angle X-ray scattering (SAXS), and results are compared to those obtained for the sol-derived hectorite. The mechanism appears to be similar but the rate is approximately doubled when the silane is used rather than silica sol. Analytical transmission electron microscopy (TEM) is exploited to glean structural morphology information towards resolving the nature of the resulting pore network structures. Results are compared with nitrogen adsorption-desorption isotherm behavior; dominant hysteresis loops are present in the type IV isotherms. Pore size distributions based on both the adsorption and desorption isotherms are compared. Small angle neutron scattering (SANS) experiments reveal that the average particle size increases as synthetic laponite < sol-derived hectorite < silane-derived hectorite < natural hectorite. Contrast matching SANS studies in aqueous and organic solvents are carried out to extract information about pore accessibility.

  2. The crystal structures of semi-synthetic aequorins

    PubMed Central

    Toma, Sachiko; Chong, Khoon Tee; Nakagawa, Atsushi; Teranishi, Katsunori; Inouye, Satoshi; Shimomura, Osamu

    2005-01-01

    The photoprotein aequorin emits light by an intramolecular reaction in the presence of a trace amount of Ca2+. Semi-synthetic aequorins, produced by replacing the coelenterazine moiety in aequorin with the analogues of coelenterazine, show widely different sensitivities to Ca2+. To understand the structural basis of the Ca2+-sensitivity, we determined the crystal structures of four semi-synthetic aequorins (cp-, i-, br- and n-aequorins) at resolutions of 1.6–1.8 Å. In general, the protein structures of these semi-synthetic aequorins are almost identical to native aequorin. Of the four EF-hand domains in the molecule, EF-hand II does not bind Ca2+, and the loop of EF-hand IV is clearly deformed. It is most likely that the binding of Ca2+ with EF-hands I and III triggers luminescence. Although little difference was found in the overall structures of aequorins investigated, some significant differences were found in the interactions between the substituents of coelenterazine moiety and the amino acid residues in the binding pocket. The coelenterazine moieties in i-, br-, and n-aequorins have bulky 2-substitutions, which can interfere with the conformational changes of protein structure that follow the binding of Ca2+ to aequorin. In cp-aequorin, the cyclopentylmethyl group that substitutes for the original 8-benzyl group does not interact hydrophobically with the protein part, giving the coelenterazine moiety more conformational freedom to promote the light-emitting reaction. The differences of various semi-synthetic aequorins in Ca2+-sensitivity and reaction rate are explained by the capability of the involved groups and structures to undergo conformational changes in response to the Ca2+-binding. PMID:15632284

  3. Synthetic routes and applications of photonic crystal composites

    NASA Astrophysics Data System (ADS)

    Jiang, Ping

    This dissertation focuses on: (1) the development of synthetic routes to fabricate robust photonic crystal composites that allows for a wide range of monomeric systems to be utilized in the encapsulation procedure to a priori design the final optical and thermomechanical characteristics of the composite and (2) the characterization of the optical and thermomechanical properties of the composites and their exploitation in potential applications. In the first section, two strategies were developed, one using poly(ethylene glycol) (PEG) and its acrylate derivatives as matrixes to encapsulate the CCA of polystyrene spheres and to form a photonic crystal hydrogel (PCH) composite. The second strategy employs the technique of first dehydrating the PCH composite, then swelling it in a monomeric solution, and finally photopolymerizing it in situ, to form a water-free photonic crystal, or photonic band gap (PBG) composite. In the second section, the mechanochromic and solvatochromic responses of the PBG composite composed of poly(EGMEA) were characterized. This composite exhibited a reversible color variation at deformation frequencies up to 200 Hz and a 172 nm total stop band tuning range between +/-120V applied voltages when it was coupled with a piezoelectric actuator. Based on this effect, approaches for generating complex permanent multicolor patterns in both PBG and PCH films were developed. Finally, two types of potential sensing systems were explored in this dissertation. One is a chemical vapor sensing system composed of the poly(EGMEA)-based PBG composite film. The second is a label-free optical bio-recognition system composed of an antigen-selective photonic crystal hydrogel (PCH). The avidin molecules were first covalently immobilized in the PCH film. The biotinylated capture antibody was then introduced into the film through the non-covalent avidin-biotin binding. (Abstract shortened by UMI.)

  4. CRYSTAL GROWTH. Crystallization by particle attachment in synthetic, biogenic, and geologic environments.

    PubMed

    De Yoreo, James J; Gilbert, Pupa U P A; Sommerdijk, Nico A J M; Penn, R Lee; Whitelam, Stephen; Joester, Derk; Zhang, Hengzhong; Rimer, Jeffrey D; Navrotsky, Alexandra; Banfield, Jillian F; Wallace, Adam F; Michel, F Marc; Meldrum, Fiona C; Cölfen, Helmut; Dove, Patricia M

    2015-07-31

    Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments. PMID:26228157

  5. Differences in crystal habitus of natural and synthetic colloids

    NASA Astrophysics Data System (ADS)

    Wieczorek, Arkadiusz K.; Händel, Matthias; Totsche, Kai Uwe

    2014-05-01

    The formation of colloids from natural aqueous solutions is influenced by a multitude of biogeochemical and physicochemical processes and the presence of a large diversity of geogen and biogen, inorganic and organic solution phase components. A thereby frequently neglected class of components is the dissolved and colloidal phase organic matter (DOM). As DOM will interact with other solution phase components, we hypothesize that nanosized and colloidal particles formed in DOM bearing solutions may differ from synthetic precipitates either by size, shape, crystal habitus, crystallinity, composition or combinations of that. To investigate this, we analyzed natural colloidal particles collected from a limestone aquifer of the Upper Muschelkalk formation at Hainich National Park, Thuringia, Germany. Major groundwater components are Ca2+, Mg2+, Na+, SO42-, Cl-, HCO3- , and about 1 ppm of total organic carbon (TOC) in dissolved and colloidal form. Synthetic nanoparticles were precipitated from a series of oversaturated solutions containing single or mixtures of the following salts CaSO4, MgSO4, Ca(HCO3)2 NaCl typical for limestone environments. The solutions were produced with both natural groundwater and pure water (milli-Q). Droplets of such produced colloidal suspension were pipetted on silicon wafers and subject to air drying. The wafers were then analyzed by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). We found that particles from oversaturated CaSO4 solution in pure water precipitate as large needle shaped crystals, whereas precipitates from CaSO4 solution in natural water were much smaller and showed a rosette like shape - similar in size and shape to gypsum crystals collected from the limestone formation water. Similar differences we found for other aqueous solution compositions. From this pilot study we presume that even minute amounts of dissolved and colloidal phase organic matter in

  6. Ion Milling of Sapphire

    NASA Technical Reports Server (NTRS)

    Gregory, Don A.

    2002-01-01

    The ion figuring system at the Marshall Space Flight Center has been successfully used for at least three previous investigations into the ion milling of metals. The research was directed toward improving the surface quality of X-ray directing optics. These studies were performed on surfaces that were already hand polished to an excellent surface quality and were intended to remove the residual unwanted figure left by those techniques. The ion milling was typically carried out on test surfaces or mandrels that were several centimeters in width and length. The good thermal conductivity of the metal samples allowed the ion beam to be directed onto the sample for an indefinite period of time. This is not true of sapphire or most electrical insulators and problems have arisen in recent attempts to ion mill thin samples of sapphire. The failure and fracture of the material was likely due to thermal stresses and the relatively low thermal conductivity of sapphire (compared to most metals), These assumed stresses actually provided the key as to how they might be monitored. A thermal gradient in the sapphire sample will induce an effective index of refraction change and because of the shape constraint and the crystal structure and simple thermal expansion, this index change will be nonuniform across the sample. In all but simple cubic crystal structures, this leads to a spatially nonuniform optical retardance induced on any polarized optical beam traversing the sample, and it is this retardance that can be monitored using standard polarimetric procedures.

  7. Ureaplasma urealyticum-induced crystallization of magnesium ammonium phosphate and calcium phosphates in synthetic urine.

    PubMed

    Grenabo, L; Brorson, J E; Hedelin, H; Pettersson, S

    1984-10-01

    Crystallization of struvite and calcium phosphates was studied in vitro as encrustations on glass rods immersed in synthetic urine, to evaluate the crystallization capacity of Ureaplasma urealyticum and compare it with that of known urease and non-urease-producing bacteria. Inoculation of the synthetic urine with Ureaplasma urealyticum resulted in alkalinization of the synthetic urine and crystallization of struvite and brushite. Inoculation with Proteus mirabilis caused a faster and more pronounced alkalinization as well as crystallization of struvite and apatite. The alkalinization and crystallization caused by Ureaplasma urealyticum and Proteus mirabilis was completely prevented by acetohydroxamic acid, a potent urease inhibitor, linking the crystallization to the urease activity of the microorganisms. When the synthetic urine was inoculated with urease-negative Escherichia coli no alkalinization and no crystallization were seen. PMID:6381769

  8. Crystal chemistry of natural and synthetic trioctahedral micas: Exploring the limits of geometric crystal chemical models

    NASA Astrophysics Data System (ADS)

    Mercier, Patrick H. J.

    Seventy-five synthetic powder trioctahedral mica samples (between Mg, Co, Ni, and Fe end members, with different degrees of oxidation, vacancy and Al/Si contents, and including an OH/F substitution series) were studied by room-temperature powder X-ray diffraction. The iron-bearing samples were studied by 57Fe Mossbauer spectroscopy. Subsets of the samples were also characterized by scanning electron microscopy combined with energy dispersive spectroscopy, optical microscopy, X-ray fluorescence spectroscopy, and gas chromatography. Lattice parameters (refined under the 1M stacking polytype, space group C2/m) were determined for all powder samples and iron site populations ([4]Fe 3+, [6]Fe2+, and [6]Fe 2+) were obtained from Mossbauer spectroscopy. The relation (c/a)cosbeta* = 113 was found to hold exactly (within experimental error) for all synthetic powders whereas it does not hold in general for synthetic and natural 1M single-crystals. The above relation is predicted to hold for geometric home-octahedral sheets (having equal M1 and M2 site bond lengths) and not to hold for geometric meso-octahedral sheets (having unequal M1 and M2 site bond lengths). The counter-rotation of the M2 site of 1M single-crystals exactly (within experimental error) follows the geometric meso-octahedral sheet model, which, assuming a uniform octahedral sheet height and site-specific M1 and M2 bond lengths, predicts site-specific flattening angles and a counter-rotation angle for the M2 site which is uniquely determined by the bond length difference between the M1 and M2 sites. A geometric meso-octahedral 2:1 layer silicate was shown to require corrugated tetrahedral sheets composed of bond-distorted tetrahedra. Key geometric meso-octahedral distortions in 1M single-crystals were identified and elucidated: (i) intra-layer top-bottom displacements within a TOT layer; and (ii) a tetrahedral bending angle between the apical bond and the pyramidal base formed by the three basal bonds. Plots

  9. Morphology and structural perfection of shaped sapphire

    NASA Astrophysics Data System (ADS)

    Dobrovinskaya, E. R.; Litvinov, L. A.; Pishchik, V. V.

    1980-09-01

    This paper is concerned with an investigation of the characteristic features in the structural perfection of sapphire crystals grown by the Stepanov method. It was shown that the formation of the mosaic grains was considerably dependent on the growth rate. When growing tubular shaped crystals the defect density is relatively insensitive to the growth rate. The structural perfection of shaped sapphire depends on the ratio of the emitting outer surface area to the volume of the crystal. Growth of sapphire shapes occurs by addition of separate atoms and also by the joining of the complexes first formed in the melt before the crystallization front. Upon incoherent crystal twinning, formation of dislocations and boundaries with small angle misorientations takes place. The observed features in the morphology and the structural perfection of shaped sapphire obtained by the Stepanov technique are caused by the considerable differences in crystallization conditions characteristic of this method. These differences result in a change in the growth mechanism.

  10. System and method for forming synthetic protein crystals to determine the conformational structure by crystallography

    DOEpatents

    Craig, G.D.; Glass, R.; Rupp, B.

    1997-01-28

    A method is disclosed for forming synthetic crystals of proteins in a carrier fluid by use of the dipole moments of protein macromolecules that self-align in the Helmholtz layer adjacent to an electrode. The voltage gradients of such layers easily exceed 10{sup 6}V/m. The synthetic protein crystals are subjected to x-ray crystallography to determine the conformational structure of the protein involved. 2 figs.

  11. System and method for forming synthetic protein crystals to determine the conformational structure by crystallography

    DOEpatents

    Craig, George D.; Glass, Robert; Rupp, Bernhard

    1997-01-01

    A method for forming synthetic crystals of proteins in a carrier fluid by use of the dipole moments of protein macromolecules that self-align in the Helmholtz layer adjacent to an electrode. The voltage gradients of such layers easily exceed 10.sup.6 V/m. The synthetic protein crystals are subjected to x-ray crystallography to determine the conformational structure of the protein involved.

  12. Sapphire statistical characterization and risk reduction program

    NASA Astrophysics Data System (ADS)

    McClure, Donald R.; Cayse, Robert; Black, David R.; Goodrich, Steven M.; Lagerloef, K. Peter D.; Harris, Daniel C.; McCullum, Dale; Platus, Daniel H.; Patty, Charles E., Jr.; Polvani, Robert S.

    2001-09-01

    The Sapphire Statistical Characterization and Risk Reduction Program tested 1400 4-point flexure bars with different crystal orientations at different temperatures to establish a mechanical strength database for engineering design. Sapphire coupons were selected to represent surfaces on two different missile windows and a missile dome. Sapphire was obtained from the same suppliers used for the windows or dome and, as much as possible, coupons were fabricated in the same manner as the corresponding part of the window or dome. For one missile window, sapphire from one fabricator was 50% stronger than sapphire made to the same specifications from the same blanks by another fabricator. In laser thermal shock tests, sapphire performed better than predicted from flexure tests. Of several nondestructive methods evaluated for their ability to identify mechanically weak specimens, only x-ray topography was correlated with strength for a limited set of specimens.

  13. Eutectic bonding of sapphire to sapphire

    NASA Technical Reports Server (NTRS)

    Deluca, J. J.

    1973-01-01

    Eutectic mixture of aluminum oxide and zirconium oxide provides new bonding technique for sapphires and rubies. Technique effectively reduces possibility of contamination. Bonding material is aluminum oxide and zirconium oxide mixture that matches coefficient of thermal expansion of sapphire.

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

    NASA Technical Reports Server (NTRS)

    Bahadur, H.; Parshad, R.

    1983-01-01

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

  15. An approach to crystallizing proteins by metal-mediated synthetic symmetrization

    SciTech Connect

    Laganowsky, Arthur; Zhao, Minglei; Soriaga, Angela B.; Sawaya, Michael R.; Cascio, Duilio; Yeates, Todd O.

    2011-12-09

    Combining the concepts of synthetic symmetrization with the approach of engineering metal-binding sites, we have developed a new crystallization methodology termed metal-mediated synthetic symmetrization. In this method, pairs of histidine or cysteine mutations are introduced on the surface of target proteins, generating crystal lattice contacts or oligomeric assemblies upon coordination with metal. Metal-mediated synthetic symmetrization greatly expands the packing and oligomeric assembly possibilities of target proteins, thereby increasing the chances of growing diffraction-quality crystals. To demonstrate this method, we designed various T4 lysozyme (T4L) and maltose-binding protein (MBP) mutants and cocrystallized them with one of three metal ions: copper (Cu2+), nickel (Ni2+), or zinc (Zn2+). The approach resulted in 16 new crystal structures-eight for T4L and eight for MBP-displaying a variety of oligomeric assemblies and packing modes, representing in total 13 new and distinct crystal forms for these proteins. We discuss the potential utility of the method for crystallizing target proteins of unknown structure by engineering in pairs of histidine or cysteine residues. As an alternate strategy, we propose that the varied crystallization-prone forms of T4L or MBP engineered in this work could be used as crystallization chaperones, by fusing them genetically to target proteins of interest.

  16. An approach to crystallizing proteins by metal-mediated synthetic symmetrization.

    PubMed

    Laganowsky, Arthur; Zhao, Minglei; Soriaga, Angela B; Sawaya, Michael R; Cascio, Duilio; Yeates, Todd O

    2011-11-01

    Combining the concepts of synthetic symmetrization with the approach of engineering metal-binding sites, we have developed a new crystallization methodology termed metal-mediated synthetic symmetrization. In this method, pairs of histidine or cysteine mutations are introduced on the surface of target proteins, generating crystal lattice contacts or oligomeric assemblies upon coordination with metal. Metal-mediated synthetic symmetrization greatly expands the packing and oligomeric assembly possibilities of target proteins, thereby increasing the chances of growing diffraction-quality crystals. To demonstrate this method, we designed various T4 lysozyme (T4L) and maltose-binding protein (MBP) mutants and cocrystallized them with one of three metal ions: copper (Cu²⁺, nickel (Ni²⁺), or zinc (Zn²⁺). The approach resulted in 16 new crystal structures--eight for T4L and eight for MBP--displaying a variety of oligomeric assemblies and packing modes, representing in total 13 new and distinct crystal forms for these proteins. We discuss the potential utility of the method for crystallizing target proteins of unknown structure by engineering in pairs of histidine or cysteine residues. As an alternate strategy, we propose that the varied crystallization-prone forms of T4L or MBP engineered in this work could be used as crystallization chaperones, by fusing them genetically to target proteins of interest. PMID:21898649

  17. Thermal characteristics of sapphire contact probe delivery systems for laser angioplasty.

    PubMed

    Ashley, S; Brooks, S G; Gehani, A A; Kester, R C; Rees, M R

    1990-01-01

    Contact probes made from synthetic sapphire crystal, designed for general laser surgery, are currently being evaluated for use in laser angioplasty. Their mode of action and safety in the context of arterial recanalisation is unknown, particularly with respect to the degree of probe and catheter heating. Infrared thermal imaging was used to investigate the surface temperature rise of various rounded sapphire probes during emission of continuous wave Nd-YAG (1,064 nm) laser energy. Catheter safety was addressed by analyzing the temperature of the metal interface between the optical fiber and sapphire, as well as the catheter proximal to this junction. Transmission of Nd-YAG energy through each probe was also measured. Five rounded probes of 1.8-3.0 mm diameter (three supplied by Surgical Laser Technologies [SLT], two by Living Technology [LT]), along with their respective optical catheters, were compared. There was a large temperature gradient between the front and rim of the probes. The maximum surface temperature rise of the sapphire (at 20 W, 5-second exposure) was 314-339 degrees C (SLT) and 90-108 degrees C (LT) [P less than 0.001, 3-way ANOVA]. The reason for this difference may be related to "crazing" of the front surface of the SLT sapphires. At all energy levels sapphire temperatures were considerably lower than attained by metal laser thermal angioplasty probes. Forward transmission was slightly higher in the SLT probes (75-85%) than the LT sapphires (54-69%). With fiber perfusion at 2 ml/minute, a minor degree of heating of the metal sapphire holders was recorded (maximum rise 35 degrees C), but heating of the catheter proximal to this was negligible. Therefore, it would appear that the risk of tip detachment or arterial injury due to heating of the connecting metal interface is extremely low. Without perfusion, however, there was a greater degree of interface heating in the LT delivery system suggestive of more laser backscattering by these sapphires

  18. Characterization of single crystal films of molybdenum (011) grown by molecular beam epitaxy on sapphire (112¯0) and studied by low-energy electron microscopy

    NASA Astrophysics Data System (ADS)

    Świȩch, W.; Mundschau, M.; Flynn, C. P.

    1999-08-01

    Films of molybdenum grown on the (112¯0) plane of sapphire (Al 2O 3) are characterized using low-energy microscopy and low-energy electron diffraction. Stress fields observed on the Mo surface originate at dislocations and at miscut steps of the buried molybdenum-alumina vicinal interface. As-grown films contain small-angle grain boundaries. These are largely eliminated upon heating to 1700 K as edge dislocations that form the boundaries become extremely mobile. Edge dislocations attract and annihilate one another, and the small-angle grain boundaries disappear. Mobility of edge dislocations is correlated with rapid diffusion of carbon, which apparently pins dislocations up to temperatures that allow diffusion of carbon from dislocations into the bulk. The main contaminants of the Mo surface are carbon, oxygen and carbon monoxide. The most stable impurities are carbides that persist to 1700 K. Oxygen promotes bunching of monatomic steps into groups of two, three and four. Electron beams dissociate CO with energy less than 1 eV and deposit residues of carbon. Fairly ideal single crystal films of Mo produced by annealing exhibit monatomic surface step and terrace structure, and a minimum of dislocations. The quality of surfaces on these films exceeds that of typical single crystal bulk samples and is well suited for fundamental studies in surface science.

  19. Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

    SciTech Connect

    Nian, Qiong; Zhang, Martin Y.; Schwartz, Bradley D.; Cheng, Gary J.

    2014-05-19

    One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm{sup 2}/V s at a low carrier concentration of 7.9 × 10{sup +19} cm{sup −3}. This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity.

  20. Cleaved thioredoxin fusion protein enables the crystallization of poorly soluble ERα in complex with synthetic ligands

    SciTech Connect

    Cura, Vincent; Gangloff, Monique; Eiler, Sylvia; Moras, Dino; Ruff, Marc

    2008-01-01

    A new crystallization strategy: the presence of cleaved thioredoxin fusion is critical for crystallization of the estrogen nuclear receptor ligand binding domain in complex with synthetic ligands. This novel technique should be regarded as an interesting alternative for crystallization of difficult proteins. The ligand-binding domain (LBD) of human oestrogen receptor α was produced in Escherichia coli as a cleavable thioredoxin (Trx) fusion in order to improve solubility. Crystallization trials with either cleaved and purified LBD or with the purified fusion protein both failed to produce crystals. In another attempt, Trx was not removed from the LBD after endoproteolytic cleavage and its presence promoted nucleation and subsequent crystal growth, which allowed the structure determination of two different LBD–ligand–coactivator peptide complexes at 2.3 Å resolution. This technique is likely to be applicable to other low-solubility proteins.

  1. High-temperature strength of sapphire

    NASA Astrophysics Data System (ADS)

    Harris, Daniel C.

    2000-10-01

    The Sapphire Statistical Characterization and Risk Reduction Program tested approximately 1500 4-point flexure bars with different crystal orientations at different temperatures to establish a mechanical strength database for engineering design. Sapphire coupons were selected to represent surfaces on two different missile windows and a missile dome. Sapphire was obtained from the same suppliers used for the windows or dome and, as much as possible, coupons were fabricated in the same manner as the corresponding part of the window or dome. Perhaps the most interesting result was that sapphire from one fabricator was 50% stronger than sapphire made to the same specifications from the same blanks by another fabricator. In laser heating tests, sapphire performed better than predicted from flexure tests. When a compliant layer of graphite was used as a pad between the test specimens and the load fixture, sapphire in which the principal axis of tension and compression was parallel to the c-axis increased in apparent strength by a factor of 2 - 3. Strengths of other crystal orientations were not significantly affected by the graphite pads, but the incidence of twinning at 883 K was reduced by graphite.

  2. Control of macromolecule distribution within synthetic and biogenic single calcite crystals

    SciTech Connect

    Aizenberg, J.; Weiner, S.; Addadi, L.; Hanson, J.; Koetzle, T.F.

    1997-02-05

    The ability of organisms to exercise control over crystal growth is wonderfully exemplified by skeleton formation in echinoderms. A sea urchin spine is a unique composite of a single crystal of calcite and glycoproteins intercalated inside the crystal during its growth. Here we performed a detailed morphological and high-resolution synchrotron X-ray diffraction study of the textures of synthetic and biogenic calcite crystals. We show that the intracrystalline macromolecules from sea urchin spines, when allowed to interact with growing calcite crystals in vitro, selectively reduce the coherence lengths and degrees of alignment of the perfect domains in specific crystallographic directions. These directions also correspond to the newly-developed stable faces. In contrast, the defect distribution of young sea urchin spines composed entirely of spongy stereomic structure is much more isotropic. In mature spines containing secondarily filled-in wedges of calcite, the degree of anisotropy is intermediate between that of the synthetic crystals and the young spines. The macromolecules extracted from young and mature spines are, however, very similar. These observations demonstrate the inherent capability of occluded matrix macromolecules to finely differentiate between crystal planes by stereochemical recognition processes. 20 refs., 5 figs., 2 tabs.

  3. A neutron sensor based on synthetic single crystal diamond

    SciTech Connect

    Schmid, G J; Koch, J A; Lerche, R A; Moran, M J

    2003-10-17

    We report the first neutron data for a single crystal Chemical Vapor Deposition (CVD) diamond sensor. Results are presented for 2.5, 14.1, and 14.9 MeV incident neutrons. We show that the energy resolution for 14.1 MeV neutrons is at least 2.9% (as limited by the energy spread of the incident neutrons), and perhaps as good as 0.4% (as extrapolated from high resolution {alpha} particle data). This result could be relevant to fusion neutron spectroscopy at machines like the International Thermonuclear Experimental Reactor (ITER). We also show that our sensor has a high neutron linear attenuation coefficient, due to the high atomic density of diamond, and this could lead to applications in fission neutron detection.

  4. Transformation and Crystallization Energetics of Synthetic and Biogenic Amorphous Calcium Carbonate

    SciTech Connect

    Radha, A. V.; Forbes, Tori Z.; Killian, Christopher E.; Gilbert, P.U.P.A; Navrotsky, Alexandra

    2010-01-01

    Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC→anhydrous ACC ~ biogenic anhydrous ACC→vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO₂ sequestration.

  5. The effect of nucleation layer thickness on the structural evolution and crystal quality of bulk GaN grown by a two-step process on cone-patterned sapphire substrate

    NASA Astrophysics Data System (ADS)

    Shang, Lin; Zhai, Guangmei; Mei, Fuhong; Jia, Wei; Yu, Chunyan; Liu, Xuguang; Xu, Bingshe

    2016-05-01

    The role of nucleation layer thickness on the GaN crystal quality grown on cone-patterned sapphire substrate (PSS) was explored. The morphologies of epitaxial GaN at different growth stages were investigated by a series of growth interruption in detail. After 10- and 15-min three-dimensional growth, the nucleation sites are very important for the bulk GaN crystal quality. They have a close relationship with the nucleation layer thickness, as confirmed through the scanning electron microscope (SEM) analysis. Nucleation sites formed mainly on patterns are bad for bulk GaN crystal quality and nucleation sites formed mainly in the trenches of PSS mounds are good for bulk GaN crystal quality, as proved by X-ray diffraction analysis. Nucleation layer thickness can effectively control the nucleation sites and thus determine the crystal quality of bulk GaN.

  6. Advances in sapphire optical fiber sensors

    NASA Technical Reports Server (NTRS)

    Wang, Anbo; Wang, George Z.; Gollapudi, Sridhar; May, Russell G.; Murphy, Kent A.; Claus, Richard O.

    1993-01-01

    We describe the development and testing of two sapphire fiber sensor designs intended for use in high temperature environments. The first is a birefringence-balanced polarimetric sapphire fiber sensor. In this sensor, two single crystal sapphire rods, acting as the birefringence sensing element, are connected to each other in such a way that the slow axis of the first rod is aligned along with the fast axis of the second rod, and the fast axis of the first rod is along the slow axis of the second rod. This sensor has been demonstrated for measurement of temperature up to 1500 C. The second is a sapphire-fiber-based intrinsic interferometric sensor. In this sensor, a length of uncoated, unclad, structural-graded multimode sapphire fiber is fusion spliced to a singlemode silica fiber to form a Fabry-Perot cavity. The reflections from the silica-to-sapphire fiber splice and the free endface of the sapphire fiber give rise to the interfering fringe output. This sensor has been demonstrated for the measurement of temperature above 1510 C, and a resolution of 0.1 C has been obtained.

  7. Effects of Cr 3+ impurity concentration on the crystallography of synthetic emerald crystals

    NASA Astrophysics Data System (ADS)

    Lee, Pei-Lun; Huang, Eugene; Lee, Jan-Shing; Yu, Shu-Cheng

    2011-06-01

    Flux method has been adopted for the synthesis of emerald crystals using PbO-V 2O 5 as a flux in order to study the crystallography of the synthetic crystals. In general, the hue of green color of emerald deepens with the addition of Cr 3+. The molar volume of the synthesized crystals was found to increase with the incorporation of Cr 2O 3 dopant. The substitution of Cr 3+ for Al 3+ in the octahedral sites of beryl results in the expansion of a-axis, while c-axis remains nearly unchanged. The maximum Cr 2O 3-content allowed in the crystal lattice of emerald has been found to be about 3.5 wt%. When the doping Cr 2O 3-content exceeds 3.5 wt%, a significant anomaly in lattice parameters starts to take place, accompanying the precipitation of an unknown phase in the emerald matrix.

  8. Enhancement of spin-wave nonreciprocity in magnonic crystals via synthetic antiferromagnetic coupling

    PubMed Central

    Di, K.; Feng, S. X.; Piramanayagam, S. N.; Zhang, V. L.; Lim, H. S.; Ng, S. C.; Kuok, M. H.

    2015-01-01

    Spin-wave nonreciprocity arising from dipole-dipole interaction is insignificant for magnon wavelengths in the sub-100 nm range. Our micromagnetic simulations reveal that for the nanoscale magnonic crystals studied, such nonreciprocity can be greatly enhanced via synthetic antiferromagnetic coupling. The nonreciprocity is manifested as highly asymmetric magnon dispersion curves of the magnonic crystals. Furthermore, based on the study of the dependence of the nonreciprocity on an applied magnetic field, the antiparallel alignment of the magnetizations is shown to be responsible for the enhancement. Our findings would be useful for magnonic and spintronics applications. PMID:25950082

  9. Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate

    PubMed Central

    Radha, A. V.; Forbes, Tori Z.; Killian, Christopher E.; Gilbert, P. U. P. A.; Navrotsky, Alexandra

    2010-01-01

    Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC⇒anhydrous ACC ∼ biogenic anhydrous ACC⇒vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO2 sequestration. PMID:20810918

  10. Analysis of synthetic diamond single crystals by X-ray topography and double-crystal diffractometry

    SciTech Connect

    Prokhorov, I. A.; Ralchenko, V. G.; Bolshakov, A. P.; Polskiy, A. V.; Vlasov, A. V.; Subbotin, I. A.; Podurets, K. M.; Pashaev, E. M.; Sozontov, E. A.

    2013-12-15

    Structural features of diamond single crystals synthesized under high pressure and homoepitaxial films grown by chemical vapor deposition (CVD) have been analyzed by double-crystal X-ray diffractometry and topography. The conditions of a diffraction analysis of diamond crystals using Ge monochromators have been optimized. The main structural defects (dislocations, stacking faults, growth striations, second-phase inclusions, etc.) formed during crystal growth have been revealed. The nitrogen concentration in high-pressure/high-temperature (HPHT) diamond substrates is estimated based on X-ray diffraction data. The formation of dislocation bundles at the film-substrate interface in the epitaxial structures has been revealed by plane-wave topography; these dislocations are likely due to the relaxation of elastic macroscopic stresses caused by the lattice mismatch between the substrate and film. The critical thicknesses of plastic relaxation onset in CVD diamond films are calculated. The experimental techniques for studying the real diamond structure in optimizing crystal-growth technology are proven to be highly efficient.

  11. Crystals, colloids, or molecules?: Early controversies about the origin of life and synthetic life.

    PubMed

    Deichmann, Ute

    2012-01-01

    Crystals, colloids, and (macro-)molecules have played major roles in theoretical concepts and experimental approaches concerning the generation of life from the mid-19th century on. The notion of the crystallization of life out of a nonliving fluid, a special case of the doctrine of spontaneous generation, was most prominently incorporated into Schleiden's and Schwann's version of cell theory. Refutation at the end of the 19th century of spontaneous generation of life and cells, in particular by Pasteur, Remak, and Virchow, not only gave rise to the flourishing fields of microbiology and cytology, but it also opened up research on synthetic life. These approaches focused on growth and form and colloidal chemistry on the one hand, and on the specificity of organisms' macromolecules and chemical reactions on the other. This article analyzes the contribution of these approaches to synthetic life research and argues that researchers' philosophical predilections and basic beliefs have played important roles in the choice of experimental and theoretical approaches towards synthetic life. PMID:23502562

  12. Photonic detection and characterization of DNA using sapphire microspheres.

    PubMed

    Murib, Mohammed Sharif; Yeap, Weng-Siang; Martens, Daan; Bienstman, Peter; De Ceuninck, Ward; van Grinsven, Bart; Schöning, Michael J; Michiels, Luc; Haenen, Ken; Ameloot, Marcel; Serpengüzel, Ali; Wagner, Patrick

    2014-09-01

    A microcavity-based deoxyribonucleic acid (DNA) optical biosensor is demonstrated for the first time using synthetic sapphire for the optical cavity. Transmitted and elastic scattering intensity at 1510 nm are analyzed from a sapphire microsphere (radius 500 µm, refractive index 1.77) on an optical fiber half coupler. The 0.43 nm angular mode spacing of the resonances correlates well with the optical size of the sapphire sphere. Probe DNA consisting of a 36-mer fragment was covalently immobilized on a sapphire microsphere and hybridized with a 29-mer target DNA. Whispering gallery modes (WGMs) were monitored before the sapphire was functionalized with DNA and after it was functionalized with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The shift in WGMs from the surface modification with DNA was measured and correlated well with the estimated thickness of the add-on DNA layer. It is shown that ssDNA is more uniformly oriented on the sapphire surface than dsDNA. In addition, it is shown that functionalization of the sapphire spherical surface with DNA does not affect the quality factor (Q . ≈ 04) of the sapphire microspheres. The use of sapphire is especially interesting because this material is chemically resilient, biocompatible, and widely used for medical implants. PMID:25260868

  13. The characterization of strain, impurity content, and crush strength of synthetic diamond crystals

    SciTech Connect

    McCormick, T.L.; Jackson, W.E.; Nemanich, R.J.

    1997-01-01

    This study addresses the correlation of the macroscopic and microscopic characteristics of synthetic diamond crystals produced by high pressure, high temperature conditions. Microscopic properties were characterized using Raman spectroscopy, birefringence, and photoluminescence (PL). Macroscopic properties characterized included inclusion content and crush force. Raman measurements detected measurable stress shifts in only two samples. The PL measurements indicated an increased presence of the H3 center in areas of high strain. The absence of the H3 center and the presence of the N-V PL center was correlated to lower average crush force. A hierarchy has been developed that relates microscopic properties to average crush force. {copyright} {ital 1997 Materials Research Society.}

  14. Boron analysis by electron microprobe using MoB4C layered synthetic crystals

    USGS Publications Warehouse

    McGee, J.J.; Slack, J.F.; Herrington, C.R.

    1991-01-01

    Preliminary electron microprobe studies of B distribution in minerals have been carried out using MoB4C-layered synthetic crystals to improve analytical sensitivity for B. Any microprobe measurements of the B contents of minerals using this crystal must include analyses for Cl to assess and correct for the interference of Cl X-rays on the BK?? peak. Microprobe analyses for B can be made routinely in tourmaline and other B-rich minerals, and minor B contents also can be determined in common rock-forming minerals. Incorporation of unusually high B contents in minerals other than borosilicates has been discovered in prograde and retrograde minerals in tourmalinites from the Broken Hill district, Australia, and may reflect high B activities produced during the metamorphism of tourmaline-rich rocks. -from Authors

  15. Sapphire tube pressure vessel

    SciTech Connect

    Outwater, J.O.

    2000-05-23

    A pressure vessel is provided for observing corrosive fluids at high temperatures and pressures. A transparent Teflon bag contains the corrosive fluid and provides an inert barrier. The Teflon bag is placed within a sapphire tube, which forms a pressure boundary. The tube is received within a pipe including a viewing window. The combination of the Teflon bag, sapphire tube and pipe provides a strong and inert pressure vessel. In an alternative embodiment, tie rods connect together compression fittings at opposite ends of the sapphire tube.

  16. Sapphire tube pressure vessel

    DOEpatents

    Outwater, John O.

    2000-01-01

    A pressure vessel is provided for observing corrosive fluids at high temperatures and pressures. A transparent Teflon bag contains the corrosive fluid and provides an inert barrier. The Teflon bag is placed within a sapphire tube, which forms a pressure boundary. The tube is received within a pipe including a viewing window. The combination of the Teflon bag, sapphire tube and pipe provides a strong and inert pressure vessel. In an alternative embodiment, tie rods connect together compression fittings at opposite ends of the sapphire tube.

  17. High Resolution Sapphire Bragg Backscattering Monochromator

    SciTech Connect

    Linden, P. van der; Wille, H.-C.; Shvyd'ko, Yu. V.

    2007-01-19

    We present a temperature stabilised high resolution sapphire backscattering monochromator. The device consists of a sapphire crystal inside a cold nitrogen gas cooled, temperature stabilised chamber with a passively temperature stabilised screen. The achieved temperature stability of {+-}2mK allows for an energy resolution of {delta}E/E {<=} 10-7 at energies in the range of 30-70 keV. The device was developed for nuclear resonant scattering above 30 keV, where appropriate solutions did not exist until now.

  18. Characterization and Origin of Zonal Sapphire from Shandong Province, China

    NASA Astrophysics Data System (ADS)

    Yu, Xiaoyan; Niu, Xiaowei; Zhao, Linghao

    2015-02-01

    Shandong Province is the main producer of sapphire in China. Among the sapphire deposits discovered in China, Shandong sapphire hosted in Cenzoic basalt shows a great variety of features, especially for in zoning. These sapphire crystals are generally large in size, with depth in color and well-developed zoning. In this article, the characteristics of zonal sapphire have been studied by using petrography, trace element data from laser ablation inductively coupled with plasma-mass spectrometry, and Raman spectrometry. The trace elements variation is proposed to correspond with their parent magma composition, and the changes in growth environment of sapphire have resulted in the formation of zoning features. Sapphires from different geological settings have different characteristics. Trace elements in sapphire not only affect the color but also reflect the changes of physical and chemical conditions of sapphire growth. The concentration of impurity elements in the zoning core of Shandong sapphire is the highest, indicating that the parent magma of Shandong sapphire-host basaltic rock is rich in trace elements. Fe content is more than 2.00% in the zoning core, which causes the deepest color in the samples. It also suggests that the total content of Fe is positively correlated to the band color. The Raman spectrum shows that the spectrum peaks at 246 cm-1 caused by Fe3+ vary regularly with the band color, which shows that Fe is dominated by Fe3+ in Shandong sapphire. With the changes of forming condition, the parent magma composition has changed accordingly, which causes the zoning formation.

  19. Improvement of crystal quality and optical property in (11-22) semipolar InGaN/GaN LEDs grown on patterned m-plane sapphire substrate

    NASA Astrophysics Data System (ADS)

    Jang, Jongjin; Lee, Kwanhyun; Hwang, Junghwan; Jung, Joocheol; Lee, Seunga; Lee, Kyuho; Kong, Bohyun; Cho, Hyunghoun; Nam, Okhyun

    2012-12-01

    Semipolar GaN layers were grown on the m-plane hemispherical patterned sapphire substrates (HPSS) using metal organic chemical vapor deposition in order to reduce the defect density and enhance the extraction efficiency of light. The roughness values of the GaN surface grown on the planar sapphire and the HPSS were 30 and 23 nm root-mean-square roughness for a 20×20-μm2 area, respectively. The reduction of basal stacking fault density was demonstrated by x-ray rocking curve of off-axis planes and cross-sectional transmission electron microscopy. The low-temperature photoluminescence measurement showed that the near band-edge emission from HPSS semipolar GaN was approximately one order of magnitude stronger than that from planar semipolar GaN layer. The InGaN light emitting diode grown on the HPSS showed an output power approximately 1.5 times that on the planar m-sapphire.

  20. Bismuth-ceramic nanocomposites through ball milling and liquid crystal synthetic methods

    NASA Astrophysics Data System (ADS)

    Dellinger, Timothy Michael

    Three methods were developed for the synthesis of bismuth-ceramic nanocomposites, which are of interest due to possible use as thermoelectric materials. In the first synthetic method, high energy ball milling of bismuth metal with either MgO or SiO2 was found to produce nanostructured bismuth dispersed on a ceramic material. The morphology of the resulting bismuth depended on its wetting behavior with respect to the ceramic: the metal wet the MgO, but did not wet on the SiO2. Differential Scanning Calorimetry measurements on these composites revealed unusual thermal stability, with nanostructure retained after multiple cycles of heating and cooling through the metal's melting point. The second synthesis methodology was based on the use of lyotropic liquid crystals. These mixtures of water and amphiphilic molecules self-assemble to form periodic structures with nanometer-scale hydrophilic and hydrophobic domains. A novel shear mixing methodology was developed for bringing together reactants which were added to the liquid crystals as dissolved salts. The liquid crystals served to mediate synthesis by acting as nanoreactors to confine chemical reactions within the nanoscale domains of the mesophase, and resulted in the production of nanoparticles. By synthesizing lead sulfide (PbS) and bismuth (Bi) particles as proof-of-concept, it was shown that nanoparticle size could be controlled by controlling the dimensionality of the nanoreactors through control of the liquid crystalline phase. Particle size was shown to decrease upon going from three-dimensionally percolating nanoreactors, to two dimensional sheet-like nanoreactors, to one dimensional rod-like nanoreactors. Additionally, particle size could be controlled by varying the precursor salt concentration. Since the nanoparticles did not agglomerate in the liquid crystal immediately after synthesis, bismuth-ceramic nanocomposites could be prepared by synthesizing Bi nanoparticles and mixing in SiO2 particles which

  1. Secondary nucleation of gibbsite crystals from synthetic Bayer liquors: effect of alkali metal ions

    NASA Astrophysics Data System (ADS)

    Li, Jun; Prestidge, Clive A.; Addai-Mensah, Jonas

    2000-11-01

    The effect of alkali metal ions (Na + versus K +) on secondary nucleation of gibbsite ( γ-Al(OH) 3) from synthetic Bayer liquors has been investigated under seeded, isothermal, batch crystallisation conditions. The nucleation kinetics showed a fourth-order dependence upon Al(III) relative supersaturation and a strong temperature effect. An activation energy of 132 kJ mol -1, which was independent of alkali metal ion, was calculated. Secondary nucleation and subsequent crystal growth rates however, were greater in sodium than in potassium aluminate solution. The Arrhenius, pre-exponential factor was at least three times larger in sodium than in potassium aluminate solutions at equivalent crystal surface area, similar supersaturation and temperature. The results indicated that secondary nucleation of Al(OH) 3 is a chemical reaction-controlled process which is alkali metal ion-mediated. Na + ions provide a more favourable pathway than potassium ions for the formation of Al(III)-containing clusters, higher collision frequency between the species and crystal surface, and faster growth of potential secondary nuclei in the solutions.

  2. Sapphire mirror for the KAGRA gravitational wave detector

    NASA Astrophysics Data System (ADS)

    Hirose, Eiichi; Bajuk, Dan; Billingsley, GariLynn; Kajita, Takaaki; Kestner, Bob; Mio, Norikatsu; Ohashi, Masatake; Reichman, Bill; Yamamoto, Hiroaki; Zhang, Liyuan

    2014-03-01

    KAGRA, the Japanese interferometric gravitational wave detector currently under construction, will employ sapphire test masses for its cryogenic operation. Sapphire has an advantage in its higher thermal conductivity near the operating temperature 20 K compared to fused silica used in other gravitational wave detectors, but there are some uncertain properties for the application such as hardness, optical absorption, and birefringence. We introduce an optical design of the test masses and our recent R&D results to address the above properties. Test polish of sapphire substrate has especially proven that specifications on the surface are sufficiently met. Recent measurements of absorption and inhomogeneity of the refractive index of the sapphire substrate indicate that the other properties are also acceptable to use sapphire crystal as test masses.

  3. Low current operation of GaN-based blue-violet laser diodes fabricated on sapphire substrate using high-temperature-grown single-crystal AlN buffer layer

    NASA Astrophysics Data System (ADS)

    Ohba, Yasuo; Gotoda, Toru; Kaneko, Kei

    2007-01-01

    Low current laser operation at 405 nm has been demonstrated for the first time for the devices fabricated on sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using a high-temperature-grown single-crystal AlN buffer. The thick optical guiding layers were adopted to improve optical confinement. The device structure was the 2-μm-wide ridge-stripe type without facet coating. The minimum threshold current and current density were 60 mA and 3.8 kA/cm 2 for cavity lengths of 500 mm and 1 mm, respectively. These data were comparable to those reported using the special dislocation reduction techniques. The threshold current density linearly decreases with decreasing inverse of cavity length. It was expected that the low threshold current density ranging from 1 to 2 kA/cm 2 could be realized by adapting high reflection coating for laser facets. This expected current density was comparable to values realized for devices grown on the thick freestanding GaN as substrates. These findings support the promising potential of the HT-AlN buffer technique for production of advanced short-wavelength light-emitting devices on sapphire substrates.

  4. Synthetical bone-like and biological hydroxyapatites: a comparative study of crystal structure and morphology.

    PubMed

    Marković, Smilja; Veselinović, Ljiljana; Lukić, Miodrag J; Karanović, Ljiljana; Bračko, Ines; Ignjatović, Nenad; Uskoković, Dragan

    2011-08-01

    Phase composition, crystal structure and morphology of biological hydroxyapatite (BHAp) extracted from human mandible bone, and carbonated hydroxyapatite (CHAp), synthesized by the chemical precipitation method, were studied by x-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman (R) spectroscopy techniques, combined with transmission electron microscopy (TEM). Structural and microstructural parameters were determined through Rietveld refinement of recorded XRD data, performed using the FullProf computing program, and TEM. Microstructural analysis shows anisotropic extension along the [00l] crystallographic direction (i.e. elongated crystallites shape) of both investigated samples. The average crystallite sizes of 10 and 8 nm were estimated for BHAp and CHAp, respectively. The FTIR and R spectroscopy studies show that carbonate ions substitute both phosphate and hydroxyl ions in the crystal structure of BHAp as well as in CHAp, indicating that both of them are mixed AB-type of CHAp. The thermal behaviour and carbonate content were analysed using thermogravimetric and differential thermal analysis. The carbonate content of about 1 wt.% and phase transition, at near 790 °C, from HAp to β-tricalcium phosphate were determined in both samples. The quality of synthesized CHAp powder, particularly, the particle size distribution and uniformity of morphology, was analysed by a particle size analyser based on laser diffraction and field emission scanning electron microscopy, respectively. These data were used to discuss similarity between natural and synthetic CHAp. Good correlation between the unit cell parameters, average crystallite size, morphology, carbonate content and crystallographic positions of carbonate ions in natural and synthetic HAp samples was found. PMID:21659698

  5. Damage testing of sapphire and Ti: sapphire laser materials

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Diffusion bonded sapphire and Ti (Titanium). Sapphire laser materials that will be damage tested to determine if there is an increase in damage threshold. Photographed in building 1145, photographic studio.

  6. General Synthetic Strategy for Hollow Hybrid Microspheres through a Progressive Inward Crystallization Process.

    PubMed

    Yang, Li-Ping; Lin, Xi-Jie; Zhang, Xing; Zhang, Wei; Cao, An-Min; Wan, Li-Jun

    2016-05-11

    Hollow hybrid microspheres have found great potential in different areas, such as drug delivery, nanoreactors, photonics, and lithium-ion batteries. Here, we report a simple and scalable approach to construct high-quality hollow hybrid microspheres through a previously unexplored growth mechanism. Starting from uniform solid microspheres with low crystallinity, we identified that a hollowing process can happen through the progressive inward crystallization process initiated on the particle surface: the gradual encroachment of the crystallization frontline toward the core leads to the depletion of the center and forms the central cavity. We showed that such a synthetic platform was versatile and can be applicable for a large variety of materials. By using the production of Li4Ti5O12-carbon hollow hybrid microspheres as an example, we demonstrated that high-performance anode materials could be achieved through synthesis and structure control. We expect that our findings offer new perspectives in different areas ranging from materials chemistry, energy storage devices, catalysis, to drug delivery. PMID:27096883

  7. Crystallization of synthetic coal-petcoke slag mixtures simulating those encountered in entrained bed slagging gasifiers

    SciTech Connect

    Jinichiro Nakano; Seetharaman Sridhar; Tyler Moss; James Bennett; Kyei-Sing Kwong

    2009-09-15

    Commercial entrained bed slagging gasifiers use a carbon feedstock of coal, petcoke, or combinations of them to produce CO and H{sub 2}. These carbon sources contain mineral impurities that liquefy during gasification and flow down the gasification sidewall, interacting with the refractory linear and solidifying in the cooler zones of the gasifier. Proper slag flow is critical to good gasifier operation. A hot-stage confocal scanning laser microscope (CSLM) was used to analyze the kinetic behavior of slag crystallization for a range of synthetic coal-petcoke mixtures. On the basis of the observed precipitation during cool down studies in the 1200-1700{sup o}C temperature range, a time-temperature-transformation (TTT) diagram was created. The crystallization studies were conducted with a CO/CO{sub 2} (=1.8) corresponding to a gasification PO{sub 2} of approximately 10-8 atm at 1500{sup o}C. Ash chemistries were chosen such that they correspond to coal-petcoke feedstock mixtures with coal ash amounts of 0, 10, 30, 50, 70, and 100% (by weight), with the balance being petcoke ash. The TTT diagram exhibited two crystallization areas, one above and one below 1350{sup o}C. At the nose of the higher temperature curves, karelianite (V{sub 2}O{sub 3}) crystallization occurred and was fastest for a 30% coal-petcoke ash mixture. The second nose was located below 1350{sup o}C and had spinel-type phases that formed at 1200{sup o}C, in which preferred atomic occupation at the octahedral and tetrahedral sites varied depending upon the ash composition. At 1200{sup o}C, an Al-rich spinel formed for 100% coal slag and a Fe-rich spinel formed in petcoke-enriched slags. The addition of petcoke ash to coal ash promoted crystallization in the slag, with additional crystalline phases, such as V-rich spinel, forming at the lower temperatures. These phases were not predicted using commercially available databases. 30 refs., 18 figs.

  8. Study of high-temperature Smart Cut™: Application to silicon-on-sapphire films and to thin foils of single crystal silicon

    NASA Astrophysics Data System (ADS)

    Meyer, Raphaël; Kononchuck, Oleg; Moriceau, Hubert; Lemiti, Mustapha; Bruel, Michel

    2016-01-01

    Two novel processes of elaboration of silicon thin films and silicon foils are proposed, based on the knowledge brought from the Smart Cut™. The first relies on the laser-beam annealing of an implanted silicon wafer in order to induce a separation layer within the implanted wafer and a transfer upon a transparent wafer. The second consists in depositing a layer of liquid silicon upon an implanted silicon wafer and to form a silicon foil by liquid phase epitaxial growth that can be separated from the substrate by Smart Cut™. The separation kinetics of an implanted silicon wafer is characterized for temperature between 450 °C and 700 °C, considering doses of implantation from 3.5 ∗ 1016 H cm-2 to 1.0 ∗ 1017 H cm-2. The out-diffusion of hydrogen is studied by Energy Recoil Detection Analysis and a model of diffusion of hydrogen in implanted silicon is proposed. Based on this analysis, a model for the kinetics of splitting at high temperature is established. Smart Cut™ separation is demonstrated for temperature up to 1250 °C, considering an implanted silicon wafer bonded with a sapphire wafer, through which a laser beam anneals the structure. The kinetics of separation by laser beam annealing is characterized and compared to the kinetics established between 450 °C and 700 °C. The roughness of the silicon on sapphire film is characterized by Atomic Force Microscopy and a transfer is realized considering an implanted silicon bonded with a glass wafer of 200 mm of diameter. Finally, this article presents results of liquid silicon deposition onto an implanted silicon substrate. These results demonstrate the possibility to detach the film grown by liquid phase epitaxy and the upper part of the implanted substrate by Smart Cut™. Electron Backscattering Diffraction Pattern analysis is considered in order to demonstrate the occurrence of epitaxy of the deposited liquid onto the implanted substrate.

  9. The kinetics of desilication of synthetic spent Bayer liquor seeded with cancrinite and cancrinite/sodalite mixed-phase crystals

    NASA Astrophysics Data System (ADS)

    Barnes, Mark C.; Addai-Mensah, Jonas; Gerson, Andrea R.

    1999-04-01

    Isothermal, batch desilication kinetics of synthetic, sodium aluminate solution (spent Bayer liquor) via cancrinite and cancrinite/sodalite mixed-phase crystal growth, have been studied under conditions at which sodium aluminosilicate scale forms at the surfaces of steel heat exchangers of alumina plant. Seeding with the pure cancrinite and mixed-phase crystals results in the suppression of scale formation and a faster rate of liquor desilication in comparison with its sodalite dimorph. Cancrinite seed crystals prepared from NO -3-rich solutions exhibited crystal growth mechanism and kinetic behaviour different from dimorphic mixed-phase crystals prepared from CO 2-3-rich solutions, when both were used to desilicate CO 2-3-rich spent Bayer liquor. The rate of desilication due to crystal growth on CO 2-3-cancrinite/sodalite mixed phase crystals followed a second-order dependence on the relative supersaturation of SiO 2. An activation energy of 52 kJ mol -1 was estimated for the crystal growth process. For desilication kinetics involving NO -3-cancrinite seed crystal growth, a third-order dependence on relative supersaturation of SiO 2 and an activation energy of 63 kJ mol -1 were obtained.

  10. 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.

  11. Layer matching epitaxy of NiO thin films on atomically stepped sapphire (0001) substrates

    PubMed Central

    Yamauchi, Ryosuke; Hamasaki, Yosuke; Shibuya, Takuto; Saito, Akira; Tsuchimine, Nobuo; Koyama, Koji; Matsuda, Akifumi; Yoshimoto, Mamoru

    2015-01-01

    Thin-film epitaxy is critical for investigating the original properties of materials. To obtain epitaxial films, careful consideration of the external conditions, i.e. single-crystal substrate, temperature, deposition pressure and fabrication method, is significantly important. In particular, selection of the single-crystal substrate is the first step towards fabrication of a high-quality film. Sapphire (single-crystalline α-Al2O3) is commonly used in industry as a thin-film crystal-growth substrate, and functional thin-film materials deposited on sapphire substrates have found industrial applications. However, while sapphire is a single crystal, two types of atomic planes exist in accordance with step height. Here we discuss the need to consider the lattice mismatch for each of the sapphire atomic layers. Furthermore, through cross-sectional transmission electron microscopy analysis, we demonstrate the uniepitaxial growth of cubic crystalline thin films on bistepped sapphire (0001) substrates. PMID:26402241

  12. Crystal and molecular structure and spectroscopic behavior of isotypic synthetic analogs of the oxalate minerals stepanovite and zhemchuzhnikovite

    NASA Astrophysics Data System (ADS)

    Piro, Oscar E.; Echeverría, Gustavo A.; González-Baró, Ana C.; Baran, Enrique J.

    2016-04-01

    The crystal structure of synthetic stepanovite, Na[Mg(H2O)6][Fe(C2O4)3]·3H2O, and zhemchuzhnikovite, Na[Mg(H2O)6][Al0.55Fe0.45(C2O4)3]·3H2O, has been determined by single-crystal X-ray diffraction methods. The compounds are isotypic to each other and to the previously reported Na[Mg(H2O)6][M(C2O4)3]·3H2O (M: Cr, Al). They crystallize in the trigonal P3 c1 space group with Z = 6 molecules per unit cell and (hexagonal axes) a = 17.0483(4), c = 12.4218(4) Å for the iron compound, and a = 16.8852(5), c = 12.5368(5) Å for the Al/Fe solid solution. Comparison of our crystallographic results with previous X-ray diffraction and chemical data of type stepanovite and zhemchuzhnikovite minerals provides compelling evidence that these natural materials possess the same crystal and molecular structure as their synthetic counterparts. It is shown that the originally reported unit cell for stepanovite represents a pronounced sub-cell and that the correct unit cell and space group are based on weak superstructure reflections. The infrared and Raman spectra of both synthetic analogs were also recorded and are briefly discussed.

  13. Ion Milling of Sapphire

    NASA Technical Reports Server (NTRS)

    Gregory, Don A.; Herren, Kenneth A.

    2004-01-01

    The ion milling of sapphire is a complicated operation due to several characteristics of the material itself. It is a relatively hard transparent nonconductive crystalline material that does not transfer heat nearly as well as metals that have been successfully ion milled in the past. This investigation involved designing an experimental arrangement, using existing ion milling equipment, as the precursor to figuring the surface of sapphire and other insulating optical materials. The experimental arrangement employs a laser probe beam to constantly monitor the stresses being induced in the material, as it is being ion milled. The goal is to determine if the technique proposed would indeed indicate the stress being induced in the material so that these stresses can be managed to prevent failure of the optic.

  14. Evolution of the sapphire industry: Rubicon Technology and Gavish

    NASA Astrophysics Data System (ADS)

    Harris, Daniel C.

    2009-05-01

    A. Verneuil developed flame fusion to grow sapphire and ruby on a commercial scale around 1890. Flame fusion was further perfected by Popov in the Soviet Union in the 1930s and by Linde Air Products Co. in the U.S. during World War II. Union Carbide Corp., the successor to Linde, developed Czochralski crystal growth for sapphire laser materials in the 1960s. Stepanov in the Soviet Union published his sapphire growth method in 1959. Edge-Defined Film-Fed Growth (EFG), which is similar to the Stepanov method, was developed by H. Labelle in the U. S. in the 1960s and 1970s. The Heat Exchanger Method (HEM), invented by F. Schmid and D. Viechnicki in 1967 was commercialized in the 1970s. Gradient solidification was invented in Israel in the 1970s by J. Makovsky. The Horizontal Directional Solidification Method (HDSM) proposed by Kh. S. Bagdasorov in the Soviet Union in the 1960s was further developed at the Institute for Single Crystals in Ukraine. Kyropoulos growth of sapphire, known as GOI crystal growth in the Soviet Union, was developed by M. Musatov at the State Optical Institute in St. Petersburg in the 1970s and 1980s. At the Institute for Single Crystals in Ukraine, E. Dobrovinskaya characterized Verneuil, Czochralsky, Bagdasarov, and GOI sapphire. In 1995, she emigrated to the United States and joined S&R Rubicon, founded near Chicago by R. Mogilevsky initially to import sapphire and ruby. Mogilevsky began producing sapphire by the Kyropoulos method in 1999. In 2000 the company name was changed to Rubicon Technology. Today, Dobrovinskaya is Chief Scientist and Rubicon produces high quality Kyropoulos sapphire substrates for solid-state lighting. In 1995, H. Branover of Ben Gurion University and a sole investor founded Gavish, which is Hebrew for "crystal." They invited another veteran of the Ukrainian Institute for Single Crystals, V. Pishchik, to become Chief Scientist. Under Pishchik's technical leadership and J. Sragowicz's business leadership, Gavish now

  15. Refinement of the crystal structures of synthetic nickel- and cobalt-bearing tourmalines

    NASA Astrophysics Data System (ADS)

    Rozhdestvenskaya, I. V.; Setkova, T. V.; Vereshchagin, O. S.; Shtukenberg, A. G.; Shapovalov, Yu. B.

    2012-01-01

    The crystal structures of synthetic tourmalines with a unique composition containing 3 d elements (Ni, Fe, and Co) have been refined: (Ca0.12▭0.88)(Al1.69Ni{0.81/2+}Fe{0.50/2+})(Al5.40Fe{0.60/3+})(Si5.82Al0.18O18)(BO3)3(OH)3.25O0.75 I, a = 15.897(5), c = 7.145(2) Å, V = 1564(1) Å; Na0.91(Ni{1.20/2+}Cr{0.96/3+}Al0.63Fe{0.18/2+}Mg0.03)(Al4.26Ni{1.20/2+}Cr{0.48/3+}Ti0.06)(Si5.82Al0.18)O18(BO3)3(OH)3.73O0.27 II, a = 15.945(5), c = 7.208(2) Å, V = 1587(1) Å3 and Na0.35(Al1.80Co{1.20/2+})(Al5.28Co{0.66/2+}Ti0.06)(Si5.64B0.36)O18(BO3)3(OH)3.81O0.19 III, a = 15.753(8), c = 7.053(3) Å, V = 1516(2) Å3. The reliability factors are R 1 = 0.038-0.057 and wR 2 = 0.041-0.060. It is found that 3 d elements occupy both Y- and Z positions in all structures. The excess positive charge is compensated for due to the incorporation of divalent oxygen anions into the O3(V)+O1(W) positions.

  16. Optimization of the structural quality of sapphire rods grown by the Stepanov method in a reducing atmosphere

    SciTech Connect

    Kryvonosov, Ye. V.; Konevskiy, P. V. Lytvynov, L. A.; Tkachenko, V. F.

    2015-03-15

    Historically, the Stepanov method has been used for growing long shaped sapphire crystals (rods, tubes, and ribbons) for practical design. The recent intense development of this technique was stimulated by sapphire applications in optics and electronics; thus, the optical and structural quality of these crystals is of great importance. The results of studying the structural quality of sapphire rods up to 18 mm in diameter grown under optimized conditions are reported.

  17. Epitaxial growth of hexagonal silicon polytypes on sapphire

    SciTech Connect

    Pavlov, D. A.; Pirogov, A. V. Krivulin, N. O.; Bobrov, A. I.

    2015-01-15

    The formation of a single-crystal silicon polytype is observed in silicon-on-sapphire structures by high-resolution transmission electron microscopy. The appearance of inclusions with a structure different from that of diamond is attributed to the formation of strong-twinning regions and the aggregation of stacking faults, which form their own crystal structure in the crystal lattice of silicon. It is demonstrated that the given modification belongs to the 9R silicon polytype.

  18. TH-C-19A-06: Measurements with a New Commercial Synthetic Single Crystal Diamond Detector

    SciTech Connect

    Laub, W; Crilly, R

    2014-06-15

    Purpose: A commercial version of a synthetic single crystal diamond detector in a Scottky diode configuration was recently released as the new type 60019 microDiamond detector (PTW-Freiburg). In this study we investigate the dosimetric properties of this detector and explore if the use of the microDiamond detector can be expanded to high energy photon beams of up to 15MV and to large field measurements. Methods: Energy dependency was investigated. Photon and electron depth-dose curves were measured. Photon PDDs were measured with the Semiflex type 31010, microLion type 31018, P-Diode type 60016, SRS Diode type 60018, and the microDiamond type 60019 detector. Electron depth-dose curves were measured with a Markus chamber type 23343, an E Diode type 60017 and the microDiamond type 60019 detector (all PTW-Freiburg). Profiles were measured with the E-Diode and microDiamond at dose maximum depths. Results: The microDiamond detector shows no energy dependence in high energy photon or electron dosimetry. Electron PDD measurements with the E-Diode and microDiamond are in good agreement except for the bremsstrahlungs region, where values are about 0.5 % lower with the microDiamond detector. Markus detector measurements agree with E-Diode measurements in this region. For depths larger than dmax, depth-dose curves of photon beams measured with the microDiamond detector are in close agreement to those measured with the microLion detector for small fields and with those measured with a Semiflex 0.125cc ionization chamber for large fields. For profile measurements, microDiamond detector measurements agree well with microLion and P-Diode measurements in the high-dose region and the penumbra region. For areas outside the open field, P-Diode measurements are about 0.5–1.0% higher than microDiamond and microLion measurements. Conclusion: The investigated diamond detector is suitable for a wide range of applications in high energy photon and electron dosimetry and is interesting

  19. The growth of an epitaxial Mg Al spinel layer on sapphire by solid-state reactions

    NASA Astrophysics Data System (ADS)

    Liu, Che-Ming; Chen, Jyh-Chen; Chen, Chun-Jen

    2005-11-01

    In this work an epitaxial Mg-Al spinel layer was successfully grown on a sapphire single crystal surface by solid-state reactions. An Mg film (15 μm) was sputtered onto the sapphire crystal using RF magnetron sputtering. An epitaxial Mg-Al spinel layer was formed on the sapphire surface; an MgO layer was formed on top of the spinel layer by solid-state reactions that occurred around 1300-1600 °C, in an air atmosphere. When the reaction time was lengthened to over 30 h at 1600 °C, these layers were almost completely transformed into an epitaxial Mg-Al spinel layer. The thickness of the epitaxial layer could be controlled by the length of the reaction time and the temperature. The results of X-ray diffraction analysis indicate that the orientation of the MgO and the spinel growth was dependent on the plane of the sapphire, that is (0 0 0 1) sapphire||(1 1 1) spinel||(1 1 1) MgO and (1 1 2¯ 0) sapphire||(1 1 1) spinel||(1 1 1) MgO. It was confirmed that the in-plane orientation of the spinel with respect to the C- and A-sapphire surface was [1 1¯ 0 0] sapphire||[1¯ 1 0] spinel, [1 1 2¯ 0] sapphire||[1¯ 1¯ 2] spinel and [1 0 1¯ 0] sapphire||[1¯ 1 0] spinel, [0 0 0 1] sapphire||[1¯ 1¯ 2] spinel, and there would be (1¯ 1 0)-oriented spinel growth on the M-plane sapphire substrate.

  20. Morphology of synthetic chrysoberyl and alexandrite crystals: Analysis of experimental data and theoretical modeling

    NASA Astrophysics Data System (ADS)

    Gromalova, N. A.; Eremin, N. N.; Dorokhova, G. I.; Urusov, V. S.

    2012-07-01

    A morphological analysis of chrysoberyl and alexandrite crystals obtained by flux crystallization has been performed. Seven morphological types of crystals are selected. The surface energies of the faces of chrysoberyl and alexandrite crystals and their isostructural analogs, BeCr2O4 and BeFe2O4, have been calculated by atomistic computer modeling using the Metadise program. A "combined" approach is proposed which takes into account both the structural geometry and the surface energy of the faces and thus provides better agreement between the theoretical and experimentally observed faceting of chrysoberyl and alexandrite crystals.

  1. Raman Gain Coefficient of Barium Nitrate Measured for the Spectral Region of TI:SAPPHIRE Laser

    NASA Astrophysics Data System (ADS)

    Lisinetskii, V. A.; Mishkel', I. I.; Chulkov, R. V.; Grabtchikov, A. S.; Apanasevich, P. A.; Eichler, H.-J.; Orlovich, V. A.

    We report the measurements of the Raman gain coefficient for a barium nitrate crystal in the spectral region of a Ti:Sapphire laser using Raman amplification. The experimentally-obtained data are well described by the known empirical formula.

  2. Clinical radiation therapy measurements with a new commercial synthetic single crystal diamond detector.

    PubMed

    Laub, Wolfram U; Crilly, Richard

    2014-01-01

    A commercial version of a synthetic single crystal diamond detector (SCDD) in a Schottky diode configuration was recently released as the new type 60019 microDiamond detector (PTW-Freiburg, Germany). In this study we investigate the dosimetric properties of this detector to independently confirm that findings from the developing group of the SCDDs still hold true for the commercial version of the SCDDs. We further explore if the use of the microDiamond detector can be expanded to high-energy photon beams of up to 15 MV and to large field measure- ments. Measurements were performed with an Elekta Synergy linear accelerator delivering 6, 10, and 15 MV X-rays, as well as 6, 9, 12, 15, and 20 MeV electron beams. The dependence of the microdiamond detector response on absorbed dose after connecting the detector was investigated. Furthermore, the dark current of the diamond detector was observed after irradiation. Results are compared to similar results from measurements with a diamond detector type 60003. Energy dependency was investigated, as well. Photon depth-dose curves were measured for field sizes 3 × 3, 10 × 10, and 30 × 30 cm2. PDDs were measured with the Semiflex type 31010 detector, microLion type 31018 detector, P Diode type 60016, SRS Diode type 60018, and the microDiamond type 60019 detector (all PTW-Freiburg). Photon profiles were measured at a depth of 10 cm. Electron depth-dose curves normalized to the dose maximum were measured with the 14 × 14 cm2 electron cone. PDDs were measured with a Markus chamber type 23343, an E Diode type 60017 and the microDiamond type 60019 detector (all PTW-Freiburg). Profiles were measured with the E Diode and microDiamond at half of D90, D90, D70, and D50 depths and for electron cone sizes of 6 × 6 cm2, 14 × 14 cm2, and 20 × 20 cm2. Within a tol- erance of 0.5% detector response of the investigated detector was stable without any preirradiation. After preirradition with approximately 250 cGy the detector response

  3. Optical and crystalline characteristics of large EFG sapphire sheet

    NASA Astrophysics Data System (ADS)

    Bates, Herbert E.; Jones, Christopher D.; Locher, John W.

    2005-05-01

    Edge Defined Film-fed Growth (EFGTM) Saphikon® sapphire crystals have been grown as large, thick sheet. The sheet is then precision-polished and coated into an infrared or laser transmission compatible window. The sapphire windows are subsequently assembled into a multi-panel configuration for advanced targeting, navigation, or reconnaissance applications. As future aerospace programs will require windows with larger apertures, material characteristics and uniformity such as refractive index homogeneity will increase in importance. Optical measurements, x-ray topography data and rocking curve analysis are presented The crystalline properties as they relate to refractive index inhomogeneity and wave front distortion are discussed.

  4. Herbal preparations affect the kinetic factors of calcium oxalate crystallization in synthetic urine: implications for kidney stone therapy.

    PubMed

    Rodgers, Allen L; Webber, Dawn; Ramsout, Ronica; Gohel, Mayur Danny I

    2014-06-01

    Herbal remedies are increasingly being considered as suitable long-term treatments for renal dysfunction. The objective of the present study was to investigate the effect of some herbal extracts, all previously identified in published studies as influencing kidney stone formation, on the crystallization characteristics of calcium oxalate (CaOx) in synthetic urine (SU). Five herbal extracts were selected for the study: Folium pyrrosiae, Desmodium styracifolium, Phyllanthus niruri, Orthosiphon stamineus and Cystone(®). Concentrated stock solutions of each herbal extract were prepared and were tested at their recommended dosages in in vitro crystallization studies in SU. CaOx crystallization experiments were performed in which the metastable limit (MSL), average particle size, and nucleation and growth rates were determined. The CaOx MSL of SU was unaltered by the five herbal extracts. Three of the herbs (Desmodium styracifolium, Orthosiphon stamineus and Cystone(®)) significantly reduced the average particle size of precipitated crystals relative to undosed SU. All of the extracts increased the rate of nucleation and decreased the rate of growth significantly in SU. Cystone(®) showed the greatest effect on the measured risk factors. It is concluded that all of the herbs have the potential to serve as inhibitors of calcium oxalate stone formation and warrant investigation in clinical trials. PMID:24648109

  5. Cleaved thioredoxin fusion protein enables the crystallization of poorly soluble ERα in complex with synthetic ligands

    PubMed Central

    Cura, Vincent; Gangloff, Monique; Eiler, Sylvia; Moras, Dino; Ruff, Marc

    2008-01-01

    The ligand-binding domain (LBD) of human oestrogen receptor α was produced in Escherichia coli as a cleavable thioredoxin (Trx) fusion in order to improve solubility. Crystallization trials with either cleaved and purified LBD or with the purified fusion protein both failed to produce crystals. In another attempt, Trx was not removed from the LBD after endoproteolytic cleavage and its presence promoted nucleation and subsequent crystal growth, which allowed the structure determination of two different LBD–ligand–coactivator peptide complexes at 2.3 Å resolution. This technique is likely to be applicable to other low-solubility proteins. PMID:18097104

  6. Sapphire Fiber Optics Sensors for Engine Test Instrumentation

    SciTech Connect

    Janney, MA

    2003-09-19

    This document is the final report for the Cooperative Research and Development Agreement (CRADA) between UT-Battelle and Prime Photonics, Inc. The purpose of this CRADA was to improve the properties of single crystal sapphire optical fibers for sensor applications. A reactive coating process was developed to form a magnesium aluminate spinel cladding on sapphire optical fibers. The resulting clad fiber had a numerical aperture, NA, of 0.09 as compared with 0.83 for the unclad fiber, dramatically enhancing its usefulness for sensor applications. Because the process allows one to control the diameter of the sapphire core within the fiber, it may be possible using this technology to develop waveguides that approach single-mode transmission character.

  7. Spherical-sapphire-based whispering gallery mode resonator thermometer

    NASA Astrophysics Data System (ADS)

    Yu, Lili; Fernicola, V.

    2012-09-01

    A novel microwave whispering gallery mode (WGM) resonator based on a spherical sapphire crystal was developed at INRIM and its use as a thermometer was tested. The temperature dependence of the WGM frequencies was studied and the most promising resonance near to 13.6 GHz, with a loaded quality factor as large as 82 000, was carefully investigated. Its potential use in thermometry was evaluated through a study of its main metrological characteristics, such as the temperature sensitivity, the frequency stability, the repeatability, and the resolution at several temperatures over the temperature range -40 °C to 85 °C. Finally, the INRIM spherical sapphire thermometer was compared with the NIST SWGT, a dielectric thermometer based on a cylindrical sapphire resonator [V. B. Braginsky, V. S. Ilchenko, and Kh. S. Bagdassarov, Phys. Lett. A 120(3), 300 (1987), 10.1016/0375-9601(87)90676-1].

  8. Spherical-sapphire-based whispering gallery mode resonator thermometer.

    PubMed

    Yu, Lili; Fernicola, V

    2012-09-01

    A novel microwave whispering gallery mode (WGM) resonator based on a spherical sapphire crystal was developed at INRIM and its use as a thermometer was tested. The temperature dependence of the WGM frequencies was studied and the most promising resonance near to 13.6 GHz, with a loaded quality factor as large as 82 000, was carefully investigated. Its potential use in thermometry was evaluated through a study of its main metrological characteristics, such as the temperature sensitivity, the frequency stability, the repeatability, and the resolution at several temperatures over the temperature range -40 °C to 85 °C. Finally, the INRIM spherical sapphire thermometer was compared with the NIST SWGT, a dielectric thermometer based on a cylindrical sapphire resonator [V. B. Braginsky, V. S. Ilchenko, and Kh. S. Bagdassarov, Phys. Lett. A 120(3), 300 (1987)]. PMID:23020404

  9. Study of green light-emitting diodes grown on semipolar (11-22) GaN/m-sapphire with different crystal qualities

    NASA Astrophysics Data System (ADS)

    Oh, Dong-Sub; Jang, Jong-Jin; Nam, Okhyun; Song, Keun-Man; Lee, Sung-Nam

    2011-07-01

    We investigated the anisotropic optical and structural properties of semipolar (11-22) InGaN-based green light emitting diodes (LEDs) grown on GaN templates with the different crystallographic properties. By introducing the N 2-GaN as a seed layer grown at a N 2 atmosphere, the full width at half maximum (FWHMs) of X-ray rocking curves (XRCs) for semipolar GaN templates were decreased from 1331 to 727 arcsec and from 1955 to 1076 arcsec with the incident beam directions of [11-2-3] and [1-100], respectively. It was found that the interfacial qualities of InGaN/GaN quantum wells (QWs) would be improved by reducing the FWHMs of XRCs with regardless of crystallographic directions. However, the thickness uniformity of InGaN QWs was significantly deteriorated for the direction of [11-2-3] rather than [1-100]. In addition, the EL intensity of semipolar green LEDs would be increased by enhancing the crystal quality of semipolar GaN template, which could also be resulted in the formation of abrupt interface and the enhancement of homogeneity at InGaN/GaN QWs.

  10. Combined protein construct and synthetic gene engineering for heterologous protein expression and crystallization using Gene Composer

    SciTech Connect

    Raymond, Amy; Lovell, Scott; Lorimer, Don; Walchli, John; Mixon, Mark; Wallace, Ellen; Thompkins, Kaitlin; Archer, Kimberly; Burgin, Alex; Stewart, Lance

    2009-12-01

    With the goal of improving yield and success rates of heterologous protein production for structural studies we have developed the database and algorithm software package Gene Composer. This freely available electronic tool facilitates the information-rich design of protein constructs and their engineered synthetic gene sequences, as detailed in the accompanying manuscript. In this report, we compare heterologous protein expression levels from native sequences to that of codon engineered synthetic gene constructs designed by Gene Composer. A test set of proteins including a human kinase (P38{alpha}), viral polymerase (HCV NS5B), and bacterial structural protein (FtsZ) were expressed in both E. coli and a cell-free wheat germ translation system. We also compare the protein expression levels in E. coli for a set of 11 different proteins with greatly varied G:C content and codon bias. The results consistently demonstrate that protein yields from codon engineered Gene Composer designs are as good as or better than those achieved from the synonymous native genes. Moreover, structure guided N- and C-terminal deletion constructs designed with the aid of Gene Composer can lead to greater success in gene to structure work as exemplified by the X-ray crystallographic structure determination of FtsZ from Bacillus subtilis. These results validate the Gene Composer algorithms, and suggest that using a combination of synthetic gene and protein construct engineering tools can improve the economics of gene to structure research.

  11. Single-crystal structure and Raman spectroscopy of synthetic titanite analog CaAlSiO4F

    NASA Astrophysics Data System (ADS)

    Krüger, Hannes; Többens, Daniel M.; Tropper, Peter; Haefeker, Udo; Kahlenberg, Volker; Fuchs, Martin R.; Olieric, Vincent; Troitzsch, Ulrike

    2015-10-01

    Synthetic CaAlSiO4F, the Al-F analog of titanite, has been investigated using single-crystal synchrotron diffraction experiments at Beamline X06DA (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland) and Raman spectroscopy. The presented structural model with 40 parameters was refined against 506 unique reflections to a final R o b s of 0.026 (space group A2/ a, a = 6.9120(11), b = 8.5010(10), c = 6.435(2) Å, β = 114.670(11)°, and Z = 4) and exhibits less distorted coordination polyhedra than earlier models from powder data. Vibrational spectra were calculated in harmonic approximation at the Γ point from fully relaxed energy optimisations of the crystal structure, using 3D-periodic density functional theory with Gaussian basis sets and the software CRYSTAL06. The lattice parameters of the fully relaxed structure were in good agreement with the experimental values, with the calculated values 0.8 ± 0.4 % too large; the monoclinic angle was calculated 0.4° too large. The agreement of the calculated Raman frequencies with the observed ones was very good, with standard deviation ±3 cm-1 and maximum deviations of ±7 cm-1. Furthermore, a detailed discussion of the atomic displacements associated with each Raman mode is given.

  12. Miniature Sapphire Acoustic Resonator - MSAR

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Tjoelker, Robert L.

    2011-01-01

    A room temperature sapphire acoustics resonator incorporated into an oscillator represents a possible opportunity to improve on quartz ultrastable oscillator (USO) performance, which has been a staple for NASA missions since the inception of spaceflight. Where quartz technology is very mature and shows a performance improvement of perhaps 1 dB/decade, these sapphire acoustic resonators when integrated with matured quartz electronics could achieve a frequency stability improvement of 10 dB or more. As quartz oscillators are an essential element of nearly all types of frequency standards and reference systems, the success of MSAR would advance the development of frequency standards and systems for both groundbased and flight-based projects. Current quartz oscillator technology is limited by quartz mechanical Q. With a possible improvement of more than x 10 Q with sapphire acoustic modes, the stability limit of current quartz oscillators may be improved tenfold, to 10(exp -14) at 1 second. The electromagnetic modes of sapphire that were previously developed at JPL require cryogenic temperatures to achieve the high Q levels needed to achieve this stability level. However sapphire fs acoustic modes, which have not been used before in a high-stability oscillator, indicate the required Q values (as high as Q = 10(exp 8)) may be achieved at room temperature in the kHz range. Even though sapphire is not piezoelectric, such a high Q should allow electrostatic excitation of the acoustic modes with a combination of DC and AC voltages across a small sapphire disk (approximately equal to l mm thick). The first evaluations under this task will test predictions of an estimated input impedance of 10 kilohms at Q = 10(exp 8), and explore the Q values that can be realized in a smaller resonator, which has not been previously tested for acoustic modes. This initial Q measurement and excitation demonstration can be viewed similar to a transducer converting electrical energy to

  13. Evaluation of the dosimetric properties of a synthetic single crystal diamond detector in high energy clinical proton beams

    SciTech Connect

    Mandapaka, A. K.; Ghebremedhin, A.; Patyal, B.; Marinelli, Marco; Prestopino, G.; Verona, C.; Verona-Rinati, G.

    2013-12-15

    Purpose: To investigate the dosimetric properties of a synthetic single crystal diamond Schottky diode for accurate relative dose measurements in large and small field high-energy clinical proton beams.Methods: The dosimetric properties of a synthetic single crystal diamond detector were assessed by comparison with a reference Markus parallel plate ionization chamber, an Exradin A16 microionization chamber, and Exradin T1a ion chamber. The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of Fractional depth dose curves and lateral beam profiles in clinical proton beams of energies 155 and 250 MeV for a 14 cm square cerrobend aperture and 126 MeV for 3, 2, and 1 cm diameter circular brass collimators. ICRU Report No. 78 recommended beam parameters were used to compare fractional depth dose curves and beam profiles obtained using the diamond detector and the reference ionization chamber. Warm-up/stability of the detector response and linearity with dose were evaluated in a 250 MeV proton beam and dose rate dependence was evaluated in a 126 MeV proton beam. Stem effect and the azimuthal angle dependence of the diode response were also evaluated.Results: A maximum deviation in diamond detector signal from the average reading of less than 0.5% was found during the warm-up irradiation procedure. The detector response showed a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range from 50 to 500 cGy. The detector response was dose rate independent, with deviations below 0.5% in the investigated dose rates ranging from 85 to 300 cGy/min. Stem effect and azimuthal angle dependence of the diode signal were within 0.5%. Fractional depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those measured using reference dosimeters.Conclusions: The observed dosimetric properties of the synthetic single

  14. Growth of Mg-Al spinel microcrystals on a sapphire surface using a solution-precipitation method

    NASA Astrophysics Data System (ADS)

    Liu, Che-Ming; Chen, Jyh-Chen

    2006-07-01

    A solution-precipitation process was used to grow Mg-Al spinel microcrystals at etched pits in a c-axial sapphire single crystal surface. In the proposed innovative growth process, the etched pits function as heterogeneous nucleation points. The quenching and aging treatment causes Mg ions to diffuse into the sapphire crystal, precipitating as microcrystals at the etched pits. We found the precipitated crystals to be (111) Mg-Al spinels with a triangular pyramidal shape.

  15. LASE Ti: Sapphire Laser

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In the photo, Mr. Leroy F. Matthews (Lockheed Engineering & Sciences Co.) is connecting the Thermal Control Unit cables in preparing the Lidar Atmospheric Sensing Experiment (LASE) Instrument for integration into a NASA/ER-2 aircraft for a field mission. LASE is the first fully-engineered, autonomous differential Absorption Lidar (DIAL) System for the measurement of water vapor, aerosol and cloud in the troposphere. LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150 mJ/pulse. The laser beam is seeded to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere with accuracy having less than 6% of error. No other instrument can provide the spatial coverage and accuracy of LASE. Water vapor is the most radiative active gas in the troposphere, and the lack of understanding about its distribution provides one of the largest uncertainties in modeling climate change. LASE has demonstrated the necessary potential in providing high resolution water vapor measurements that can advance the studies of tropospheric water vapor distributions. LASE has flown 19 times during the development of the instrument and the validation of the science data. A joint international field mission was completed in the summer of 1996; adding 9 more successful flights. The LASE Instument is being adapted to other aircraft platforms to support planned missions and to increase its utility.

  16. LASE Ti: Sapphire Laser

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In the photo, Messrs. Leroy F. Matthews (left) and Frank J. Novak (Lockheed Engineering & Sciences Co.) are preparing the Lidar Atmospheric Sensing Experiment (LASE) Instrument for integration into a NASA/ER-2 aircraft for a field mission. LASE is the first fully- engineered, autonomous differential Absorption Lidar (DIAL) System for the measurement of water vapor, aerosol and cloud in the troposphere. LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150 mJ/pulse. The laser beam is seeded to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere with accuracy having less than 6% of error. No other instrument can provide the spatial coverage and accuracy of LASE. Water vapor is the most radiative active gas in the troposphere, and the lack of understanding about its distribution provides one of the largest uncertainties in modeling climate change. LASE has demonstrated the necessary potential in providing high resolution water vapor measurements that can advance the studies of tropospheric water vapor distributions. LASE has flown 19 times during the development of the instrument and the validation of the science data. A joint international field mission was completed in the summer of 1996; adding 9 more successful flights. The LASE Instrument is being adapted to other aircraft platforms to support planned missions and to increase its utility.

  17. The crystal structure of synthetic simmonsite, Na 2LiAlF 6

    NASA Astrophysics Data System (ADS)

    Ross, Kirk C.; Mitchell, Roger H.; Chakhmouradian, Anton R.

    2003-04-01

    The structure of the synthetic fluoroperovskite, Na 2LiAlF 6 (simmonsite), has been determined by powder X-ray diffraction using the Rietveld method of structure refinement. The compound adopts space group P2 1/ n [#14; a=5.2842(1); b=5.3698(1); c=7.5063(2) Å; β=89.98(1)°; Z=4), and is a member of the cryolite (Na 2NaAlF 6) structural group characterized by ordering of the B-site cations (Li, Al) and tilting of the BF 6 octahedra according to the tilt scheme a-b-c+. Rotations of the B-site polyhedra are less ( ΦLi=14.9°; ΦAl=17.0°) than those found in cryolite ( ΦNa=18.6; ΦAl=23.5°) because of the larger difference in the ionic radii of the B-site cations in cryolite as compared to those in simmonsite. Na at the A-site is displaced from the special position resulting in 10- and 8-fold coordination in simmonsite and cryolite, respectively. By analogy with the synthetic compound, naturally occurring simmonsite is considered to adopt space group P2 1/ n (#14) and not the P2 1(#4) or P2 1/ m(#11) space groups.

  18. Optical Extinction of Sapphire Shock Loaded to 250-260 GPa

    SciTech Connect

    Hare, D E; Webb, D J; Lee, S H; Holmes, N

    2001-08-21

    Sapphire, a common optical window material used in shock-compression studies, displays significant shock-induced optical emission and extinction. It is desirable to quantify such non-ideal window behavior to enhance the usefulness of sapphire in optical studies of opaque shock-compressed samples, such as metals. At the highest stresses we can achieve with a two-stage gas gun it is technically very difficult to study the optical properties of sapphire without the aid of some opaque backing material, hence one is invariably compelled to deconvolve the optical effects of the opaque surface and the sapphire. In an effort to optimize this deconvolution process, we have constructed sapphire/thin-film/sapphire samples using two basic types of thin films: one optimized to emit copious optical radiation (the hot-film sample), the other designed to yield minimal emission (the cold-film sample). This sample geometry makes it easy to maintain the same steady shock-stress in the sapphire window (255 GPa in our case) while varying the window/film interface temperature. A six-channel time-resolved optical pyrometer is used to measure the emission from the sample assemblies. Two different sapphire crystal orientations were evaluated. We also comment on finite thermal conductivity effects of the thin-film geometry on the interpretation of our data.

  19. Sapphire hard X-ray Fabry-Perot resonators for synchrotron experiments.

    PubMed

    Tsai, Yi Wei; Wu, Yu Hsin; Chang, Ying Yi; Liu, Wen Chung; Liu, Hong Lin; Chu, Chia Hong; Chen, Pei Chi; Lin, Pao Te; Fu, Chien Chung; Chang, Shih Lin

    2016-05-01

    Hard X-ray Fabry-Perot resonators (FPRs) made from sapphire crystals were constructed and characterized. The FPRs consisted of two crystal plates, part of a monolithic crystal structure of Al2O3, acting as a pair of mirrors, for the backward reflection (0 0 0 30) of hard X-rays at 14.3147 keV. The dimensional accuracy during manufacturing and the defect density in the crystal in relation to the resonance efficiency of sapphire FPRs were analyzed from a theoretical standpoint based on X-ray cavity resonance and measurements using scanning electron microscopic and X-ray topographic techniques for crystal defects. Well defined resonance spectra of sapphire FPRs were successfully obtained, and were comparable with the theoretical predictions. PMID:27140144

  20. Rare earth elements in synthetic zircon. 2. a single-crystal x-ray study of xenotime substitution.

    SciTech Connect

    Finch, R. J.; Hanchar, J. M.; Hoskin, P. W. O.; Burns, P. C.; Chemical Engineering; Australian National Univ.; Univ. of Notre Dame

    2001-05-01

    Zircon crystals synthesized in a Li-Mo oxide melt and doped with trivalent lanthanides and Y (REE), both with and without P, were examined by single-crystal X-ray diffraction (XRD). REE are incorporated into the Zr site in the zircon structure, and some Zr appears to be displaced to the Si site. Crystals doped with middle REE (MREE, Sm to Dy) and Y, plus P follow the xenotime substitution (REE{sup 3+} + P{sup 5+} = Zr{sup 4+} + Si{sup 4+}) rather closely, whereas crystals doped with heavy REE (HREE, Er to Lu) deviate from the xenotime substitution, having REE:P atomic ratios significantly greater than one. Xenotime substitution requires that P{sup 5+} replace Si{sup 4+}, but this substitution becomes limited by strain at the Si site in HREE-doped crystals. As Si sites become saturated with P{sup 5+}, additional charge balance in synthetic zircon crystals may be provided by Mo{sup 6+} and Li{sup +} from the flux entering interstitial sites, accounting for an additional 0.3 to 0.6 at% HREE beyond that balanced by P{sup 5+} ions. Heavy REE are more compatible in the zircon structure than are LREE and MREE, and HREE substitution is ultimately limited by the inability of the zircon structure to further accommodate charge-compensating elements. Thus the limit on REE concentrations in zircon is not a simple function of REE{sup 3+} ionic radii but depends in a complex way on structural strain at Zr and Si sites, which act together to limit REE and P incorporation. The mechanisms that limit the coupled xenotime substitution change from LREE to HREE. This change means that REE fractionation in zircon may vary according to the availability of charge-compensating elements. REE partition coefficients between zircon and melt must also depend in part on the availability of charge-compensating elements and their compatibility in the zircon structure.

  1. Single-crystal X-ray diffraction study of synthetic sodium-hydronium jarosite

    NASA Astrophysics Data System (ADS)

    Najorka, Jens; Lewis, James M. T.; Spratt, John; Sephton, Mark A.

    2016-05-01

    Na-H3O jarosite was synthesized hydrothermally at 413 K for 8 days and investigated using single-crystal X-ray diffraction (XRD) and electron microprobe analysis (EMPA). The chemical composition of the studied crystal is [Na0.57(3) (H3O)0.36 (H2O)0.07]A Fe2.93(3) (SO4)2 (OH)5.70 (H2O)0.30, and Fe deficiency was confirmed by both EMPA and XRD analysis. The single-crystal XRD data were collected at 298 and 102 K, and crystal structures were refined in space group Roverline{3}m. The room-temperature data match structural trends of the jarosite group, which vary linearly with the c axis. The low-temperature structure at 102 K shows an anisotropic decrease in the unit cell parameters, with c and a decreasing by 0.45 and 0.03 %, respectively. Structural changes are mainly confined to the A site environment. Only minor changes occur in FeO6 and SO4 polyhedra. The structure responds upon cooling by increasing bond length distortion and by decreasing quadratic elongation of the large AO12 polyhedra. The structural parameters at low temperature follow very similar patterns to structural changes that correspond to compositional variation in the jarosite group, which is characterised by the flexibility of AO12 polyhedra and rigidity of Fe(OH)4O2-SO4 layers. The most flexible areas in the jarosite structure are localized at AO12 edges that are not shared with neighbouring FeO6 octahedra. Importantly, for the application of XRD in planetary settings, the temperature-related changes in jarosite can mimic compositional change.

  2. Isolation of brassicasterol, its synthetic prodrug-crystal structure, stereochemistry and theoretical studies

    NASA Astrophysics Data System (ADS)

    Sethi, Arun; Prakash, Rohit; Srivastava, Sangeeta; Amandeep; Bishnoi, Abha; Singh, Ranvijay Pratap

    2014-07-01

    In the present study brassicasterol (1), was isolated from the chloroform extract of the flowers of Allamanda violacea and identified with the help of different spectroscopic techniques like 1H, 13C, 2D NMR (1H-1H COSY), IR, UV and mass spectrometry. A novel prodrug was synthesized by carrying out esterification of brassicasterol (1) with the well known drug naproxen using Steglich esterification to give 3β-(2-(6-methoxynaphthalene-2yl) propionoxy) 24 methyl cholest-5, 22-dien (2). Compounds 2 was subjected to single crystal X-ray diffraction technique and crystallized out in monoclinic form having P21 space group and stabilized by CH-π interactions. Structure and stereochemistry of compound 2 was established with the help of modern spectroscopic techniques like 1H NMR, IR, UV, mass spectrometry as well as with single crystal X-ray diffraction. Molecular geometry and vibrational frequencies of compounds 1 and 2 were calculated by density functional method (DFT/B3LYP) using 6-31G (d, p) basis set, bond parameters and IR frequencies were correlated with the experimental data. 1H and 13C chemical shifts of compound 1 and 1H chemical shifts of compound 2 were calculated with GIAO method and correlated with experimental data. Hyperconjugative interactions were studied with the help of natural bond order analysis (NBO). Electronic properties of both the compounds such as HOMO-LUMO energies were measured with the help of time dependent DFT method.

  3. Fabrication of a new substrate for atomic force microscopic observation of DNA molecules from an ultrasmooth sapphire plate.

    PubMed Central

    Yoshida, K; Yoshimoto, M; Sasaki, K; Ohnishi, T; Ushiki, T; Hitomi, J; Yamamoto, S; Sigeno, M

    1998-01-01

    A new stable substrate applicable to the observation of DNA molecules by atomic force microscopy (AFM) was fabricated from a ultrasmooth sapphire (alpha-Al2O3 single crystal) plate. The atomically ultrasmooth sapphire as obtained by high-temperature annealing has hydrophobic surfaces and could not be used for the AFM observation of DNA. However, sapphire treated with Na3PO4 aqueous solution exhibited a hydrophilic character while maintaining a smooth surface structure. The surface of the wet-treated sapphire was found by x-ray photoelectron spectroscopy and AFM to be approximately 0.3 nm. The hydrophilic surface character of the ultrasmooth sapphire plate made it easy for DNA molecules to adhere to the plate. Circular molecules of the plasmid DNA could be imaged by AFM on the hydrophilic ultrasmooth sapphire plate. PMID:9545030

  4. Role of Stearic Acid in the Strain-Induced Crystallization of Crosslinked Natural Rubber and Synthetic Cis-1,4-Polyisoprene

    SciTech Connect

    Kohjiya,S.; Tosaka, M.; Furutani, M.; Ikeda, Y.; Toki, S.; Hsiao, B.

    2007-01-01

    Strain-induced crystallization of crosslinked natural rubber (NR) and its synthetic analogue, cis-1,4-polyisoprene (IR), both mixed with various amounts of stearic acid (SA), were investigated by time-resolved X-ray diffraction using a powerful synchrotron radiation source and simultaneous mechanical (tensile) measurement. No acceleration or retardation was observed on NR in spite of the increase of SA amount. Even the SA-free IR crystallized upon stretching, and the overall crystallization behavior of IR shifted to the larger strain ratio with increasing SA content. No difference due to the SA was detected in the deformation of crystal lattice by stress for both NR and IR. These results suggested that the extended network chains are effective for the initiation of crystallization upon stretching, while the role of SA is trivial. These behaviors are much different from their crystallization at low temperature by standing, where SA acts as a nucleating agent.

  5. Oxidation states of Fe and Ti in blue sapphire

    NASA Astrophysics Data System (ADS)

    Wongrawang, P.; Monarumit, N.; Thammajak, N.; Wathanakul, P.; Wongkokua, W.

    2016-02-01

    X-ray absorption near-edge spectroscopy (XANES) can be used to study the oxidation state of a dilute system such as transition metal defects in solid-state samples. In blue sapphire, Fe and Ti are defects that cause the blue color. Inter-valence charge transfer (IVCT) between Fe2+ and Ti4+ has been proposed to describe the optical color’s origin. However, the existence of divalent iron cations has not been thoroughly investigated. Fluorescent XANES is therefore employed to study K-edge absorptions of Fe and Ti cations in various blue sapphire samples including natural, synthetic, diffused and heat-treated sapphires. All the samples showed an Fe absorption edge at 7124 eV, corresponding to the Fe3+ state; and Ti at 4984 eV, corresponding to Ti4+. From these results, we propose Fe3+-Ti4+ mixed acceptor states located at 1.75 eV and 2.14 eV above the valence band of corundum, that correspond to 710 nm and 580 nm bands of UV-vis absorption spectra, to describe the cause of the color of blue sapphire.

  6. Effects of compression direction on the plasticity and rheology of hydrolytically weakened synthetic quartz crystals at atmospheric pressure

    SciTech Connect

    Linker, M.F.; Kirby, S.H.; Ord, A.; Christie, J.M.

    1984-06-10

    A hydrothermally grown synthetic quartz crystal with 370 +- 60 ppm hydroxyl impurity was cut into right rectangular prisms in eight crystallographic orientations. We compressed the prisms under constant axial force corresponding to a uniaxial stress of 140.0 +- 0.5 MPa, and temperatures of 510/sup 0/ and 750/sup 0/C. All but one of the samples sustained permanent axial strains of 2--3%. We established the operating slip systems from specimen shape change, slip bands and dislocation etch pits on polished surfaces, crystallographic orientation changes, stress optical features in thin sections, and transmission electron microscopy. The observed creep behavior and plasticity divided the samples into three groups: (1) Crystals compressed at 45/sup 0/ to (0001) and (2110) and those compressed perpendicular(0111) and perpendicular(0111) deformed principally by slip parallel to (0001). Creep rates were relatively high and were not strongly sensitive to test temperature. Dislocation arrays approximately parallel to (2110) are common. Dislocation loops are elongate parallel to (0001), indicating that the edge segments were more mobile than the screw segements. (2) The second groups of samples were loaded normal to (0001) in three orientation: perpendicular(2110), perpendicular(0110), and at 45/sup 0/ to (1100). These samples deformed primarily by 0 )1010) slip with some evidence for secondary slip on the other systems. They were more creep resistant than the first group and displayed a much higher sensitivity of creep rate to test temperature.

  7. Multiscale experimental investigation of crystal plasticity and grain boundary sliding in synthetic halite using digital image correlation

    NASA Astrophysics Data System (ADS)

    Bourcier, M.; Bornert, M.; Dimanov, A.; HéRipré, E.; Raphanel, J. L.

    2013-02-01

    is a renewed interest in the study of the rheology of halite since salt cavities are considered for waste repositories or energy storage. This research benefits from the development of observation techniques at the microscale, which allow precise characterizations of microstructures, deformation mechanisms, and strain fields. These techniques are applied to uniaxial compression tests on synthetic halite done with a classical press and with a specific rig implemented in a scanning electron microscope. Digital images of the surface of the sample have been recorded at several loading stages. Surface markers allow the measurement of displacements by means of digital image correlation techniques. Global and local strain fields may then be computed using ad hoc data processing. Analysis of these results provides a measure of strain heterogeneity at various scales, an estimate of the size of the representative volume element, and most importantly an identification of the deformation mechanisms, namely crystal slip plasticity and grain boundary sliding, which are shown to be in a complex local interaction. Indeed, the applied macroscopic loading gives rise locally to complex stress states owing to relative crystallographic orientations, density and orientation of interfaces, and local deformation history. We have quantitatively estimated the relative importance of crystal slip plasticity and grain boundary sliding for different microstructures and evidenced their dependence on grain size. The two mechanisms of deformation and their link to the microstructure should thus be considered when modeling polycrystalline viscoplasticity.

  8. Epitaxial neodymium-doped sapphire films, a new active medium for waveguide lasers.

    PubMed

    Kumaran, Raveen; Webster, Scott E; Penson, Shawn; Li, Wei; Tiedje, Thomas; Wei, Peng; Schiettekatte, Francois

    2009-11-01

    Epitaxial films of neodymium-doped sapphire have been grown by molecular beam epitaxy on R-, A-, and M-plane sapphire substrates. The emission spectrum features sharp lines consistent with single-site doping of the Nd(3+) ion into the host crystal. This material is believed to be a nonequilibrium phase, inaccessible by conventional high-temperature growth methods. Neodymium-doped sapphire has a promising lasing line at 1096 nm with an emission cross section of 11.9x10(-19) cm(2), similar to the 1064 nm line of Nd:YVO(4). PMID:19881593

  9. Temperature Compensated Sapphire Resonator for Ultra-Stable Oscillator Capability at Temperatures Above 77 Kelvin

    NASA Technical Reports Server (NTRS)

    Dick, G.; Santiago, D.; Wang, R.

    1994-01-01

    We report on the design and test of a whispering gallery sapphire resonator for which the dominant (WGH xxxsubn11) microwave mode family shows frequency-stable, compensated operation for temperatures above 77 Kelvin. The resonator makes possible a new ultra-stable oscillator (USO) capability that promises performance improvements over the best available crystal quartz oscillators in a compact cryogenic package. A mechanical compensation mechanism, enabled by the difference between copper and sapphire expansion coefficients, tunes the resonator to cancel the temperature variation of sapphire's dielectric constant.

  10. Phosphate adsorption and desorption in relation to morphology and crystal properties of synthetic hematites

    NASA Astrophysics Data System (ADS)

    Colombo, C.; Barrón, V.; Torrent, J.

    1994-02-01

    Phosphate adsorption and desorption by iron hydr(oxides) are geochemically important processes affecting water quality and soil fertility. Relatively little is known, however, about the interaction between phosphate and hematite, which after goethite is the most abundant iron hydr(oxide) in nature. To study the effect of morphology and other crystal properties of hematite on phosphorous adsorption and desorption, thirty hematites synthesized by different methods and differing widely in properties were used. Phosphate adsorption curves 1 and 124 days after P addition were adequately described by the Freundlich equation. The P adsorbed at an equilibrium concentration of 1 mg P/L (32 μM) at 1 and 124 days ( A 1, A 124) ranged between 0.31 and 2.07 ( X¯ = 1.03; SD = 0.53) μmol/m 2, and between 0.54 and 2.72 ( X¯ = 1.59; SD = 0.65) μmol/m 2, respectively. The values of A decreased when the crystals and the X-ray coherently scattering domains became more platy in the c with respect to the a direction, supporting the hypothesis that the P-adsorbing faces are the nonbasal ones. Exponent b of the Freundlich equation, which gives a measure of the relative affinity of the adsorption sites, increased when domains and crystals became more platy, i.e., the more platy the crystal, the lower the proportion of high-affinity sites. The ratio between slow (1-124 days) and total (124 days) adsorption increased with decreasing affinity (higher b values) and was not related to microporosity. In comparison to goethite, the present results show that hematite has more variability in P-adsorption capacity, adsorbs on average less P per unit surface area, has less affinity for phosphate, and exhibits a more important slow adsorption component. The proportion of the adsorbed phosphate that could be desorbed by an anion-exchange resin or by electroultrafiltration was affected by those hematite properties affecting diffusion (e.g., microporosity). Isotopically exchangeable P did not depend

  11. Methodology of growing gigantic sapphire for GSLW project

    NASA Astrophysics Data System (ADS)

    Abgaryan, Artoush A.; Hartounian, Gomidas

    2005-09-01

    In our present world the Crystal Growth Technology does not have the necessary and sufficient conditions to manufacture large sizes; especially in the Sapphire Crystal world. We have a theoretical and methodological development for growing gigantic Sapphire Crystal Lenses. Our gigantic Sapphire Crystal Lenses have a unique optical characteristic which will be used in the Global System of Laser Weapons (GSLW); hence solving one of the crucial problems in the Relay Mirror System; where it captures the Laser beam from the earth surface, cleaning the beam in the Satellite and redirecting the laser energy to the precise desired target. Developed and solution for the temperature and heat-elasticity fields in growth systems are considered theoretical, in order to assess their effects on the optical symmetry of the growing crystal. The process is modeled using three-dimensional curvilinear coordinates to describe a closed, low-strain heat-elasticity system, with allowance made for the temperature variations of the thermal properties of the multilayer growth system, and nonlinear and unsteady-state process with arbitrary boundary conditions. The results presented as plots of the strain, stress, displacement, and temperature fields; demonstrate the potential of the method for designing new growth units and improving the existing ones and suggesting that crystals, in general, without frustration of optical symmetry can, in principle, be grown. In order to solve generalized problem for large optics. It is required to have super and correct mathematical computing calculations, and using basic fundamental laws of nature regarding optical symmetry in the crystal, and discovering the radical "new wave method" for crystal growth technology.

  12. Jones calculus modeling and analysis of the thermal distortion in a Ti:sapphire laser amplifier.

    PubMed

    Cho, Seryeyohan; Jeong, Jihoon; Yu, Tae Jun

    2016-06-27

    The mathematical modeling of an anisotropic Ti:sapphire crystal with a significant thermal load is performed. The model is expressed by the differential Jones matrix. A thermally induced distortion in the chirped-pulse amplification process is shown by the solution of the differential Jones matrix. Using this model, the thermally distorted spatio-temporal laser beam shape is calculated for a high-power and high-repetition-rate Ti:sapphire amplifier. PMID:27410590

  13. Spectroscopic studies of excitons in cuprous oxide: Natural crystals and synthetic thick films on magnesium oxide

    NASA Astrophysics Data System (ADS)

    Sun, Yi

    2001-10-01

    We observed exciton photoluminescence from Cu2O natural bulk crystals under two-photon excitation to the 1s, as well as to the 2s level, over a wide temperature range. The direct recombination emission, denoted as Xo, and a phonon- assisted, electric-dipole radiative transition involving G-12 longitudinal optical phonons, denoted as Xo- G-12 , were observed for 1s excitation. We have studied the angular (at 1.8K) and temperature (from 1.8K to 297K) dependence of the time integrated photoluminescence intensity of both emission features. For resonant pumping to the 1s level, the direct emission is strongly enhanced at low temperature. It is forward directed, however, with an angular width substantially larger than the divergence of the excitation beam; excitation to the 2s level (which subsequently decays into a 1s level) results in a more isotropic angular distribution of Xo emission. The lifetime of the Xo emission resulting from resonant excitation to the 1s level at 1.8K is ~2ns, shorter than the decay time of thermalized orthoexcitons. The results support the idea that resonant two-photon excitation to the 1s level results primarily in a quadrupole-orthoexciton-polariton formation. A theory involving the Green's function and coupled photon-exciton wave equations was developed to simulate the coherent polariton propagation. To study excitons in a spatially confined geometry, we developed an ex situ growth technique to obtain single-crystal like Cu2O thick films on MgO substrates. The optical absorption spectrum exhibits the exciton absorption series up to n = 5p at low temperature. 1s orthoexciton direct emission and phonon-assisted emission features were observed to split into three (on MgO (110)) and two (on MgO (111)) peaks. The distortion of film crystal structure and the effective Hamiltonian including a deformation potential were used to explain the energy level splitting and shift of the 1s orthoexcitons in Cu2O films. Cu2O dots and waveguides were also

  14. Crystal chemical properties of synthetic lazulite-scorzalite solid-solution series

    NASA Astrophysics Data System (ADS)

    Schmid-Beurmann, P.; Knitter, St.; Cemič, L.

    Members of the lazulite-scorzalite (MgAl2- (PO4)2(OH)2-FeAl2(PO4)2(OH)2) solid-solution series were synthesized in compositional steps of 12.5mol% at T=485°C and P=0.3GPa under hydrothermal conditions and controlled oxygen fugacities of the Ni/NiO-buffer. X-ray powder diffraction and 57Fe-Mössbauer studies show that under these conditions a complete solid-solution series is formed which is characterized by the substitution of Mg2+ and Fe2+ on the octahedral Me2+ site. The 57Fe-Mössbauer spectra which reveal the presence of both ferrous and ferric iron and the compositional data were interpreted in terms of a defect model with a distribution of the ferric ions over both the Me2+ and the Al3+ positions and vacancies on the Me2+ site. The 57Fe-Mössbauer parameters of the synthetic compounds correspond to those of natural lazulites except for the total absorption ratio of the ferric iron A(Fe3+)/(A(Fe3+)+A(Fe2+)), which is significantly higher in natural lazulites of the same composition. The total absorption ratio of the ferric iron increases from 4% in pure scorzalite to 15% in a Mg-rich solid-solution with xFe=12(1)%

  15. Characterization of synthetic nanocrystalline mackinawite: crystal structure, particle size, and specific surface area

    PubMed Central

    Jeong, Hoon Y.; Lee, Jun H.; Hayes, Kim F.

    2010-01-01

    Iron sulfide was synthesized by reacting aqueous solutions of sodium sulfide and ferrous chloride for 3 days. By X-ray powder diffraction (XRPD), the resultant phase was determined to be primarily nanocrystalline mackinawite (space group: P4/nmm) with unit cell parameters a = b = 3.67 Å and c = 5.20 Å. Iron K-edge XAS analysis also indicated the dominance of mackinawite. Lattice expansion of synthetic mackinawite was observed along the c-axis relative to well-crystalline mackinawite. Compared with relatively short-aged phase, the mackinawite prepared here was composed of larger crystallites with less elongated lattice spacings. The direct observation of lattice fringes by HR-TEM verified the applicability of Bragg diffraction in determining the lattice parameters of nanocrystalline mackinawite from XRPD patterns. Estimated particle size and external specific surface area (SSAext) of nanocrystalline mackinawite varied significantly with the methods used. The use of Scherrer equation for measuring crystallite size based on XRPD patterns is limited by uncertainty of the Scherrer constant (K) due to the presence of polydisperse particles. The presence of polycrystalline particles may also lead to inaccurate particle size estimation by Scherrer equation, given that crystallite and particle sizes are not equivalent. The TEM observation yielded the smallest SSAext of 103 m2/g. This measurement was not representative of dispersed particles due to particle aggregation from drying during sample preparation. In contrast, EGME method and PCS measurement yielded higher SSAext (276–345 m2/g by EGME and 424 ± 130 m2/g by PCS). These were in reasonable agreement with those previously measured by the methods insensitive to particle aggregation. PMID:21085620

  16. The Crystal Structure of Synthetic Autunite, Ca[(UO2)(PO4)]2(H2O)11

    NASA Astrophysics Data System (ADS)

    Locock, A. J.; Burns, P. C.

    2002-05-01

    Autunite, Ca[(UO2)(PO4)]2(H2O)11, is amongst the most abundant and widely distributed of the uranyl phosphate minerals, yet because of its pseudo-tetragonal symmetry and rapid dehydration behavior, the details of its symmetry, stoichiometry and structure remain uncertain. The crystal structure of autunite was solved by direct methods and refined by full-matrix least-squares techniques to agreement indices wR2 = 0.125 for all data, and R1 = 0.042, calculated for the 1497 unique observed reflections. Autunite is orthorhombic, space group Pnma, Z = 4, a = 14.0135(6), b = 20.7121(8), c = 6.9959(3) Å, V = 2030.55(15) Å 3. Intensity data were collected using MoK-alpha radiation and a CCD-based area detector. The structure contains the well-known autunite type sheet with composition [(UO2)(PO4)]1-, resulting from the sharing of equatorial vertices of the uranyl square bipyramids with the phosphate tetrahedra. Calcium in the interlayer is coordinated by seven H2O groups and two longer distances to uranyl ion oxygen atoms. In addition, there are two symmetrically independent H2O groups held in the structure only by H-bonding. The structures of other members of the autunite group: orthorhombic synthetic Sr[(UO2)(PO4)]2(H2O)11, triclinic synthetic Ni[(UO2)(PO4)]2(H2O)12 and tetragonal zeunerite, Cu[(UO2)(AsO4)]2(H2O)12, will also be discussed.

  17. An Insight into the Pharmacophores of Phosphodiesterase-5 Inhibitors from Synthetic and Crystal Structural Studies

    SciTech Connect

    Chen,G.; Wang, H.; Robinson, H.; Cai, J.; Wan, Y.; Ke, H.

    2008-01-01

    Selective inhibitors of cyclic nucleotide phosphodiesterase-5 (PDE5) have been used as drugs for treatment of male erectile dysfunction and pulmonary hypertension. An insight into the pharmacophores of PDE5 inhibitors is essential for development of second generation of PDE5 inhibitors, but has not been completely illustrated. Here we report the synthesis of a new class of the sildenafil derivatives and a crystal structure of the PDE5 catalytic domain in complex with 5-(2-ethoxy-5-(sulfamoyl)-3-thienyl)-1-methyl-3-propyl-1, 6-dihydro-7H-pyrazolo[4, 3-d]pyrimidin-7-one (12). Inhibitor 12 induces conformational change of the H-loop (residues 660-683), which is different from any of the known PDE5 structures. The pyrazolopyrimidinone groups of 12 and sildenafil are well superimposed, but their sulfonamide groups show a positional difference of as much as 1.5 Angstroms . The structure-activity analysis suggests that a small hydrophobic pocket and the H-loop of PDE5 are important for the inhibitor affinity, in addition to two common elements for binding of almost all the PDE inhibitors: the stack against the phenylalanine and the hydrogen bond with the invariant glutamine. However, the PDE5-12 structure does not provide a full explanation to affinity changes of the inhibitors. Thus alternatives such as conformational change of the M-loop are open and further structural study is required.

  18. 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.

  19. Seven Post-synthetic Covalent Reactions in Tandem Leading to Enzyme-like Complexity within Metal-Organic Framework Crystals.

    PubMed

    Fracaroli, Alejandro M; Siman, Peter; Nagib, David A; Suzuki, Mitsuharu; Furukawa, Hiroyasu; Toste, F Dean; Yaghi, Omar M

    2016-07-13

    The design of enzyme-like complexity within metal-organic frameworks (MOFs) requires multiple reactions to be performed on a MOF crystal without losing access to its interior. Here, we show that seven post-synthetic reactions can be successfully achieved within the pores of a multivariate MOF, MTV-IRMOF-74-III, to covalently incorporate tripeptides that resemble the active sites of enzymes in their spatial arrangement and compositional heterogeneity. These reactions build up H2N-Pro-Gly-Ala-CONHL and H2N-Cys-His-Asp-CONHL (where L = organic struts) amino acid sequences by covalently attaching them to the organic struts in the MOFs, without losing porosity or crystallinity. An enabling feature of this chemistry is that the primary amine functionality (-CH2NHBoc) of the original MOF is more reactive than the commonly examined aromatic amines (-NH2), and this allowed for the multi-step reactions to be carried out in tandem within the MOF. Preliminary findings indicate that the complexity thus achieved can affect reactions that were previously accomplished only in the presence of enzymes. PMID:27346625

  20. Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

    NASA Technical Reports Server (NTRS)

    Choi, Sang; King, Glen; Park, Yeonjoon

    2009-01-01

    SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than

  1. SAPPHIRE: scenarios, architecture, and process.

    PubMed

    Kay, S; Redman, R; McWilliams, A; Bradley, P; Daniels, A

    1994-06-01

    General Medical Practice (GMP) information systems within the UK are becoming more sophisticated and more complex and are widely available from numerous suppliers. Although such systems are viewed as being important, they are problematic in terms of interpreting and assessing their usefulness, and their impact upon work and the organisation (G. Walsham, Interpreting Information Systems in Organizations (Wiley, Chichester, 1993)). In particular, it is difficult for any who have an interest in these systems to apply existing technical specifications to a specific situation, and to match individual requirements with the supplier's products. The research project SAPPHIRE seeks to inform the decision making of stakeholders, e.g. GPs, facilitators and suppliers, with respect to procurement, update, design and supply of GMP systems by developing the means of evaluating such systems, and by facilitating an accreditation process through that evaluation. This extended paper introduces the multi-faceted approach, scenarios, architecture and process of SAPPHIRE. PMID:7956163

  2. Germanium Nanocrystals Embedded in Sapphire

    SciTech Connect

    Xu, Q.; Sharp, I.D.; Liao, C.Y.; Yi, D.O.; Ager III, J.W.; Beeman, J.W.; Yu, K.M.; Chrzan, D.C.; Haller, E.E.

    2005-04-15

    {sup 74}Ge nanocrystals are formed in a sapphire matrix by ion implantation followed by damage. Embedded nanocrystals experience large compressive stress relative to bulk, as embedded in sapphire melt very close to the bulk melting point (Tm = 936 C) whereas experience considerably lower stresses. Also, in situ TEM reveals that nanocrystals ion-beam-synthesized nanocrystals embedded in silica are observed to be spherical and measured by Raman spectroscopy of the zone center optical phonon. In contrast, reveals that the nanocrystals are faceted and have a bi-modal size distribution. Notably, the matrix remains crystalline despite the large implantation dose and corresponding thermal annealing. Transmission electron microscopy (TEM) of as-grown samples those embedded in silica exhibit a significant melting point hysteresis around T{sub m}.

  3. Erbium localized doping into various cuts of lithium niobate and sapphire: a comparative study

    NASA Astrophysics Data System (ADS)

    Nekvindova, Pavla; Mackova, Anna; Perina, Vratislav; Cervena, Jarmila; Capek, Pavel; Schroefel, Josef; Spirkova, Jarmila; Oswald, Jiri

    2003-07-01

    Medium temperature (350 °C) localized doping of Er3+ was studied in lithium niobate (LN) and sapphire single crystal wafers that were cut in various crystallographic directions. It was found that the efficiency of the doping was connected with orientations of the substrate wafers of both LN and sapphire, and with the presence of mobile lithium ions in the structure of LN. The basic interstitial mechanism of erbium incorporation into the structure of sapphire and LN is in the latter accompanied with erbium for lithium ion exchange. While the rate of the interstitial diffusion was higher in the wafers oriented perpendicularly towards the cleavage planes of the crystals, ion exchange process was significant in the wafers cut in cleavage planes. Waveguiding properties in erbium doped lithium niobate originated rather from presence of erbium in the structure of the crystals than being a consequence of a weak proton exchange. Luminescence properties of the fabricated samples are also presented.

  4. Formation of twins in sapphire under shock wave loading: Atomistic simulations

    NASA Astrophysics Data System (ADS)

    Kuksin, A. Yu.; Yanilkin, A. V.

    2012-02-01

    This work is devoted to molecular dynamics (MD) simulation of shock-wave loading of sapphire (α-Al2 O3). Defect free sapphire and sapphire with the microcrack are considered. Homogeneous nucleation and growth of rhombohedral twins are observed in single crystal alumina. A fast mechanism of plastic deformation is revealed under shock-wave loading of sapphire with microcrack. Rhombohedral twins nucleate and grow as a result of a two stage process. At the first stage the formation of a new type of linear defect takes place in the shock wave front, which is initiated at the surface of the microcrack. At the second stage the rhombohedral twins grow from the primary linear defects and combine with each other. The results are confirmed by first principles calculations.

  5. Forced polarization of α-sapphire induced by coated LiNbO3 and LiTaO3 films

    NASA Astrophysics Data System (ADS)

    Yang, X.; Wu, X. L.; Feng, Y.; Li, J.; Jiang, M.

    2004-04-01

    We have investigated the formation mechanism of the interfacial electric field in LiNbO3(or LiTaO3)/α-sapphire crystal structures, which is important in understanding the photoluminescence properties of this kind of ferroelectric film-coated crystal material. It is revealed that the interfacial electric field arises from the interfacial polarization charge generated during poling of LiNbO3(or LiTaO3) film near Curie temperature, which induces forced polarization of the α-sapphire crystal. As a result, lattice distortions of the α-sapphire crystal change the crystal field of Cr3+ ion in the sapphire crystal and therefore lead to intensity enhancement of R-line luminescence from Cr3+ centers.

  6. Microwave Frequency Discriminator With Sapphire Resonator

    NASA Technical Reports Server (NTRS)

    Santiago, David G.; Dick, G. John

    1994-01-01

    Cooled sapphire resonator provides ultralow phase noise. Apparatus comprises microwave oscillator operating at nominal frequency of about 8.1 GHz, plus frequency-discriminator circuit measuring phase fluctuations of oscillator output. One outstanding feature of frequency discriminator is sapphire resonator serving as phase reference. Sapphire resonator is dielectric ring resonator operating in "whispering-gallery" mode. Functions at room temperature, but for better performance, typically cooled to operating temperature of about 80 K. Similar resonator described in "Sapphire Ring Resonator for Microwave Oscillator" (NPO-18082).

  7. Computer simulation of growth process in synthetic quartz crystals grown from X-bar, Y-bar and rectangular Z-plate seeds

    NASA Astrophysics Data System (ADS)

    Iwasaki, H.; Iwasaki, F.; Yokokawa, H.; Kurashige, M.; Oba, K.

    2002-02-01

    The growth simulations of synthetic quartz crystals grown on seeds with industrialized sizes and orientations were shown on the procedure by means of the setting of virtual lengths between the seed center and principal crystal faces to be grown. The virtual lengths needed for simulations are calculated on the given sizes and shapes of seeds, X-bar, Y-bar and rectangular Z-plate. The simulations of growth processes are executed as a function of growth time under the model values of growth rates on principal crystal faces, m, R, r, Z, and the so-called S. By the comparison of geometrical sizes of as-grown crystal faces with simulated faces, the growth rates of principal faces are quantitatively evaluated in the commercially produced quartz crystals grown from the rectangular Z-plate seeds. The growth rates of R- and r-faces at the upper and lower sides of grown crystals show somewhat different values which may be due to the direction of convection flow in autoclave.

  8. Experimental analysis of sapphire contact probes for Nd-YAG laser angioplasty.

    PubMed

    Ashley, S; Brooks, S G; Gehani, A A; Kester, R C; Rees, M R

    1990-06-01

    Laser angioplasty may offer percutaneous recanalization of occluded vessels where conventional guidewire and balloon techniques fail. Metal laser thermal angioplasty probes may, however, cause excessive thermal damage due to high tip temperatures (greater than 400.C). Therefore, contact probes made from artificial sapphire crystal designed for general laser surgery are currently being evaluated for use in laser angioplasty with continuous wave Nd-YAG energy. The sapphire modifies the laser energy in various ways, and this paper examines the physical characteristics of five types of rounded sapphire probe (SMTR, MTR, MTRL, OS, LT) and how these properties are affected by clinical usage. The laser beam profile emitted by these probes demonstrates a focal spot 1-2 mm in front of the tip. However, the forward transmission of Nd-YAG energy through the sapphires varied (SMTR, 85%; MTR, 83%; MTRL, 75%; OS, 54%; LT, 69%). Probe heating occurs owing to energy absorption within the sapphire. The surface temperature of the sapphires was measured in air by infrared thermography and the hottest region within the probes localized by an isothermographic technique. At energy settings used clinically (20 J, 10 watts for 2 s) the SMTR, MTR, and MTRL probes exhibited higher temperature rises (94-112.C) than the OS and LT probes (30.C), and heating was localized to the front surface of the former probes. Peak sapphire temperatures remained lower than those of metal probes even at higher energies. After clinical use, the MTR probe demonstrated reduced transmission, beam defocusing, and increased heating, due to surface pitting. Thus, recanalization with sapphire probes occurs by a combination of photothermal and contact thermal effects that are localized to the probe tip and may reduce the degree of thermal injury associated with metal probes. Understanding these basic properties is important to the application and development of contact probes for laser recanalization. PMID:2142867

  9. Design and preparation of laser film on sapphire substrate

    NASA Astrophysics Data System (ADS)

    Dang, Shao-kun; Xu, Jun-qi; Su, Jun-hong; Guo, Fang; Cheng, Yao-jin

    2014-08-01

    Sapphire crystal as a kind of good material has a good transmittance in the ultraviolet, visible, infrared, which was widely used in the high-intensity laser system as the window material. Anti-reflection thin films on sapphire substrate were commonly used in high-energy laser system in the middle infrared bands 3~5μm and these thin films are very easily damaged for high energy laser system. In this paper, we adopt thermal evaporation technique on the sapphire substrate was prepared by design of single layer and multilayer anti-reflection coatings system so that the infrared transmittance satisfy the design requirements. The results of transmittance and laser damage performance tests show that the anti-reflection coating of 3~5μm transmittance is more than 97% on average, Laser-induced damage threshold (LIDT) is more than 5J/cm2 (1064nm), which means that this method could obtain a high-quality laser film.

  10. Titanium-doped sapphire laser research and design study

    NASA Technical Reports Server (NTRS)

    Moulton, Peter F.

    1987-01-01

    Three main topics were considered in this study: the fundamental laser parameters of titanium-doped sapphire, characterization of commercially grown material, and design of a tunable, narrow-linewidth laser. Fundamental parameters investigated included the gain cross section, upper-state lifetime as a function of temperature and the surface-damage threshold. Commercial material was found to vary widely in the level of absorption of the laser wavelength with the highest absorption in Czochralski-grown crystals. Several Yi:sapphire lasers were constructed, including a multimode laser with greater than 50mJ of output energy and a single-transverse-mode ring laser, whose spectral and temporal characteristics were completely characterized. A design for a narrow-linewidth (single-frequency) Ti:sapphire laser was developed, based on the results of the experimental work. The design involves the use of a single-frequency, quasi-cw master oscillator, employed as an injection source for a pulsed ring laser.

  11. A comparison of the abilities of natural rubber (NR) and synthetic polyisoprene cis-1,4 rubber (IR) to crystallize under strain at high strain rates.

    PubMed

    Candau, Nicolas; Chazeau, Laurent; Chenal, Jean-Marc; Gauthier, Catherine; Munch, Etienne

    2016-02-01

    Strain induced crystallization (SIC) of a natural rubber (NR) and a synthetic rubber (IR) with a high amount of cis-1,4 units (98.6%) is studied, thanks to in situ wide angle X-ray (WAXS) experiments at room temperature performed in a large range of strain rates. During stretching at a low strain rate (4.2 × 10(-3) s(-1)), SIC in IR occurs at a larger stretching ratio than in NR. As a result, the crystallinity index at a given stretching ratio is lower in IR than in NR, in spite of the similar crosslink densities of the chains involved in the crystallization in both materials. This lower ability for crystallization in IR is attributed to the presence of branching along its backbone and its lower stereoregularity. Conversely, dynamic experiments performed at high strain rates (10(1)/10(2) s(-1)) show for both materials a similar ability to crystallize. This unexpected result is confirmed by monotonic tensile tests performed in a large range of strain rates. The reason is thermodynamic: the chain extension plays a predominant role compared to the role of the microstructure defects when the strain rate is high, i.e. when the kinetics of the crystallite nucleation forces the crystallization to occur at a large stretching ratio. A thermodynamic model enables qualitative reproduction of the experimental results. PMID:26750589

  12. Chemical mechanical polishing (CMP) of sapphire

    NASA Astrophysics Data System (ADS)

    Zhu, Honglin

    The concept of chemical mechanical polishing (CMP) was examined for finishing sapphire. In this study sapphire was used as a model system for oxide ceramics. The removal rates were determined by weight loss. Surface quality and structure were characterized with surface probe microscopy (SPM). Polishing experiments were designed to test the chemically modified surface layer. A series of abrasives with various hardnesses including mono-crystalline and polycrystalline diamond, alpha and gamma alumina, zirconia, ceria and silica were used. Diaspore was also evaluated. The results indicated that, with similar particle size and shape, harder abrasives do not necessarily cause faster material removal and better surface finish, and abrasives with hardness equal to or less than sapphire such as alpha alumina and gamma alumina achieved the best surface finish and efficient material removal. A hypothesis was proposed that the sapphire surface was modified by water to form a thin hydration laver with structure and hardness close to diaspore. Abrasives with a hardness between diaspore and sapphire polished the c-plane of sapphire with good surface finish and efficient removal. SPM indicated the hydration layer on the c-plane surface was about 1 nm thick. Removal rate and surface finish as a function of pH were also examined on c-plane sapphire with nano-alumina abrasives. The removal rate as a function of pH was compared to the solubility behavior of alumina. The results showed the deviation of pH from the lowest solubility pH for alumina (pH = 5) was a driving force for the surface reaction to form a hydration layer. The anisotropy of sapphire strongly affects removal rate and surface quality in CMP. The relationships among orientation. pH and abrasive were studied for sapphire with c (0001), a (11-20), and m (10-10) planes. Based on the results, the CMP process for sapphire includes chemical reaction of the surface to form a thin reaction layer that is softer than sapphire

  13. Residual stresses in sapphire rods grown by the Stepanov method

    NASA Astrophysics Data System (ADS)

    Krymov, V. M.; Nosov, Yu. G.; Bakholdin, S. I.; Galaktionov, E. V.; Maslov, V. N.; Tropp, E. A.

    2015-04-01

    The residual stresses in cylindrical [0001] sapphire crystals have been studied using the polarization-optical method. The angle between the optical axes 2 V and the difference in the normal components of the tensor of elastic residual stresses (σφ - σ r ) have been determined from the isogyre divergence. It has been found that a tangential tensile stress of no more than 20 MPa acts on the ingot surface. The residual stresses have been compared with the calculated thermoelastic stresses generated during the crystal growth in a given heating zone. It has been shown that the determined pattern of residual stresses can be caused by thermoelastic stresses developing in the immediate vicinity of the crystallization front.

  14. Sapphire reinforced alumina matrix composites

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Setlock, John A.

    1994-01-01

    Unidirectionally reinforced A1203 matrix composites have been fabricated by hot pressing. Approximately 30 volume % of either coated or uncoated sapphire fiber was used as reinforcement. Unstabilized ZrO2 was applied as the fiber coating. Composite mechanical behavior was analyzed both after fabrication and after additional heat treatment. The results of composite tensile tests were correlated with fiber-matrix interfacial shear strengths determined from fiber push-out tests. Substantially higher strength and greater fiber pull-out were observed for the coated fiber composites for all processing conditions studied. The coated fiber composites retained up to 95% and 87% of their as-fabricated strength when heat treated at 14000C for 8 or 24 hours, respectively. Electron microscopy analysis of the fracture surfaces revealed extensive fiber pull-out both before and after heat treatment.

  15. LASE Ti:Sapphire Laser

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In the photo, Dr. Larry B. Petway (Science Applications International Corp.) is making final adjustments to the Ti:Sapphire Laser in preparing the Lidar Atmospheric Sensing Experiment (LASE) Instrument for intergration into a NASA/ER-2 aircraft. LASE is the first fully- engineered, autonomous differential Absorption Lidar (DIAL) System for the measurement of water vapor, aerosol and cloud in the troposphere. LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150mJ/pulse. The laser beam is seeded to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere with accuracy having less than 6% of error. No other instrument can provide the spatial coverage and accuracy of LASE.Water vapor is the most radiative active gas in the troposphere, and the lack of understanding about its distribution provides one of the largest uncertainties in modeling climate change. LASE has demonstrated the necessary potential in providing high resolution water vapor measurements that can advance the studies of tropospheric water vapor distributions. LASE has flown 19 times during the development of the instrument and the validation of the science data. A joint international field mission was completed in the summer of 1996; adding 9 more successful flights. The LASE Instument is being adapted to other aircraft platforms to support planned missions and to increase its utility.

  16. Towards rhombohedral SiGe epitaxy on 150mm c-plane sapphire substrates

    NASA Astrophysics Data System (ADS)

    Duzik, Adam J.; Park, Yeonjoon; Choi, Sang H.

    2015-04-01

    Previous work demonstrated for the first time the ability to epitaxially grow uniform single crystal diamond cubic SiGe (111) films on trigonal sapphire (0001) substrates. While SiGe (111) forms two possible crystallographic twins on sapphire (0001), films consisting primarily of one twin were produced on up to 99.95% of the total wafer area. This permits new bandgap engineering possibilities and improved group IV based devices that can exploit the higher carrier mobility in Ge compared to Si. Models are proposed on the epitaxy of such dissimilar crystal structures based on the energetic favorability of crystallographic twins and surface reconstructions. This new method permits Ge (111) on sapphire (0001) epitaxy, rendering Ge an economically feasible replacement for Si in some applications, including higher efficiency Si/Ge/Si quantum well solar cells. Epitaxial SiGe films on sapphire showed a 280% increase in electron mobility and a 500% increase in hole mobility over single crystal Si. Moreover, Ge possesses a wider bandgap for solar spectrum conversion than Si, while the transparent sapphire substrate permits an inverted device structure, increasing the total efficiency to an estimated 30-40%, much higher than traditional Si solar cells. Hall Effect mobility measurements of the Ge layer in the Si/Ge/Si quantum well structure were performed to demonstrate the advantage in carrier mobility over a pure Si solar cell. Another application comes in the use of microelectromechanical devices technology, where high-resistivity Si is currently used as a substrate. Sapphire is a more resistive substrate and offers better performance via lower parasitic capacitance and higher film carrier mobility over the current Si-based technology.

  17. Temperature dependence of sapphire fiber Raman scattering

    DOE PAGESBeta

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

    2015-04-27

    Anti-Stokes Raman scattering in sapphire fiber has been observed for the first time. Temperature dependence of Raman peaks’ intensity, frequency shift, and linewidth were also measured. Three anti-Stokes Raman peaks were observed at temperatures higher than 300°C in a 0.72-m-long sapphire fiber excited by a second-harmonic Nd YAG laser. The intensity of anti-Stokes peaks are comparable to that of Stokes peaks when the temperature increases to 1033°C. We foresee the combination of sapphire fiber Stokes and anti-Stokes measurement in use as a mechanism for ultrahigh temperature sensing.

  18. Ti:Sapphire micro-structures by femtosecond laser inscription: Guiding and luminescence properties

    NASA Astrophysics Data System (ADS)

    Ren, Yingying; Jiao, Yang; Vázquez de Aldana, Javier R.; Chen, Feng

    2016-08-01

    We report on the fabrication of buried cladding waveguides with different diameters in a Ti:Sapphire crystal by femtosecond laser inscription. The propagation properties are studied, showing that the cladding waveguides could support near- to mid-infrared waveguiding at both TE and TM polarizations. Confocal micro-photoluminescence experiments reveal that the original fluorescence properties in the waveguide region are very well preserved, while it suffers from a strong quenching at the centers of laser induced filaments. Broadband waveguide fluorescence emissions with high efficiency are realized, indicating the application of the cladding waveguides in Ti:Sapphire as compact broadband luminescence sources in biomedical fields.

  19. The morphology of an epitaxial Mg Al spinel layer on a sapphire surface

    NASA Astrophysics Data System (ADS)

    Liu, Che-Ming; Chen, Jyh-Chen; Chen, Chun-Jen

    2006-07-01

    In this work an epitaxial Mg-Al spinel layer was successfully grown on a C- and A-plane sapphire single crystal surface by solid-state reactions. When observed by a scanning electron microscope, it can be seen that the morphology of an epitaxial spinel layer surface has a three-fold symmetrical structure. The results of X-ray diffraction analysis indicate that the surface morphology of the epitaxial spinel layer has particular crystallographic directions and the crystallographic directions will be influenced by the orientation of the sapphire substrates.

  20. Detection of beryllium treatment of natural sapphires by NRA

    NASA Astrophysics Data System (ADS)

    Gutiérrez, P. C.; Ynsa, M.-D.; Climent-Font, A.; Calligaro, T.

    2010-06-01

    Since the 1990's, artificial treatment of natural sapphires (Al 2O 3 crystals coloured by impurities) by diffusion of beryllium at high temperature has become a growing practice. This process permits to enhance the colour of these gemstones, and thus to increase their value. Detection of such a treatment - diffusion of tens of μg/g of beryllium in Al 2O 3 crystals - is usually achieved using high sensitivity techniques like laser-ablation inductively coupled plasma mass spectrometry (LA-ICP/MS) or laser-induced breakdown spectrometry (LIBS) which are unfortunately micro-destructive (leaving 50-100-μm diameter craters on the gems). The simple and non-destructive alternative method proposed in this work is based on the nuclear reaction 9Be(α, nγ) 12C with an external helium ion beam impinging on the gem directly placed in air. The 4439 keV prompt γ-ray tagging Be atoms are detected with a high efficiency bismuth germanate scintillator. Beam dose is monitored using the 2235 keV prompt γ-ray produced during irradiation by the aluminium of the sapphire matrix through the 27Al(α, pγ) 30Si nuclear reaction. The method is tested on a series of Be-treated sapphires previously analyzed by LA-ICP/MS to determine the optimal conditions to obtain a peak to background appropriate to reach the required μg/g sensitivity. Using a 2.8-MeV external He beam and a beam dose of 200 μC, beryllium concentrations from 5 to 16 μg/g have been measured in the samples, with a detection limit of 1 μg/g.

  1. Thermal and optical behavior of sapphire fiber tips for laser angioplasty

    NASA Astrophysics Data System (ADS)

    Ashley, Simon; Brooks, Stephen G.; Gehani, Abdurrazak A.; Kester, Ralph C.; Rees, Michael R.

    1990-07-01

    Atraumatic rounded contact probes made from artificial sapphire crystal were developed for general laser surgery and are currently being evaluated for use in percutaneous laser angioplasty utilising continuous wave (cw) Nd-YAG energy (1064nm). The thermal and optical characteristics of five different types of rounded sapphire probe [Surgical Laser Technologies (SLT) - SMTR (1.8mm), MTh (2.2mm), MTRL (3.0mm); Living Technology - LT (2.2mm), OS (2.2mm)] were investigated and related to efficiency of contact ablation of arterial wall in vitro. The sapphire probes were mounted on catheters containing a 0.6 mm quartz optical fiber, coupled to a cw Nd-YAG laser. All probes produced a similar beam profile but there was some variation in their forward transmission of energy (54-85%).Probe heating occurs due to energy absorption within the sapphire and was measured in air by infrared thermography. There was a high temperature gradient from the front surface of the sapphires to the probe rim. But, at energy settings used clinically (10 J pulses, 10 Watts for 1 second) the SMTR, MTR, and MTRL probes exhibited a higher mean temperature rise (63-74 C) than the OS and LT probes (20 C) [3-way ANOVA psapphire temperature rise recorded after 5 seconds exposure at 20 Watts was 340 C, but at all energy settings sapphire temperatures were much lower than attained by metal probes. Furthermore, there was relatively little heating of the metal jacket behind the sapphires (maximum 35 C) reducing the risk of thermal injury to surrounding vessel. These properties enhanced contact ablation by the MTR probe relative to the other 2.2mm probes when applied with a downward force of 80 g, perpendicular to fresh porcine aortic segments immersed in whole blood. Penetration efficiencies at energy levels producing the most efficient ablation by each probe were as follows [mean (SD) microns/JI:- MTR 50 (7), LT 9 (5), 05 4 (2), (p

  2. Extended depth-of-field 3D endoscopy with synthetic aperture integral imaging using an electrically tunable focal-length liquid-crystal lens.

    PubMed

    Wang, Yu-Jen; Shen, Xin; Lin, Yi-Hsin; Javidi, Bahram

    2015-08-01

    Conventional synthetic-aperture integral imaging uses a lens array to sense the three-dimensional (3D) object or scene that can then be reconstructed digitally or optically. However, integral imaging generally suffers from a fixed and limited range of depth of field (DOF). In this Letter, we experimentally demonstrate a 3D integral-imaging endoscopy with tunable DOF by using a single large-aperture focal-length-tunable liquid crystal (LC) lens. The proposed system can provide high spatial resolution and an extended DOF in synthetic-aperture integral imaging 3D endoscope. In our experiments, the image plane in the integral imaging pickup process can be tuned from 18 to 38 mm continuously using a large-aperture LC lens, and the total DOF is extended from 12 to 51 mm. To the best of our knowledge, this is the first report on synthetic aperture integral imaging 3D endoscopy with a large-aperture LC lens that can provide high spatial resolution 3D imaging with an extend DOF. PMID:26258358

  3. Variable Synthetic Capacitance

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L.

    1986-01-01

    Feedback amplifier circuit synthesizes electronically variable capacitance. Variable Synthetic Capacitor is amplifier circuit with follower/feedback configuration. Effective input capacitance depends on input set current. If synthetic capacitor is connected across resonant element of oscillator, oscillator frequency controlled via input set current. Circuit especially suitable for fine frequency adjustments of piezoelectric-crystal or inductor/capacitor resonant oscillators.

  4. High Q Miniature Sapphire Acoustic Resonator

    NASA Technical Reports Server (NTRS)

    Wang, Rabi T.; Tjoelker, R. L.

    2010-01-01

    We have demonstrated high Q measurements in a room temperature Miniature Sapphire Acoustic Resonator (MSAR). Initial measurements of bulk acoustic modes in room temperature sapphire at 39 MHz have demonstrated a Q of 8.8 x 10(exp 6). The long term goal of this work is to integrate such a high Q resonator with small, low noise quartz oscillator electronics, providing a fractional frequency stability better than 1 x 10(exp -14) @ 1s.

  5. Distinct crystallinity and orientations of hydroxyapatite thin films deposited on C- and A-plane sapphire substrates

    NASA Astrophysics Data System (ADS)

    Akazawa, Housei; Ueno, Yuko

    2014-10-01

    We report how the crystallinity and orientation of hydroxyapatite (HAp) films deposited on sapphire substrates depend on the crystallographic planes. Both solid-phase crystallization of amorphous HAp films and crystallization during sputter deposition at elevated temperatures were examined. The low-temperature epitaxial phase on C-plane sapphire substrates has c-axis orientated HAp crystals regardless of the crystallization route, whereas the preferred orientation switches to the (310) direction at higher temperatures. Only the symmetric stretching mode (ν1) of PO43- units appears in the Raman scattering spectra, confirming well-ordered crystalline domains. In contrast, HAp crystals grown on A-plane sapphire substrates are always oriented toward random orientations. Exhibiting all vibrational modes (ν1, ν3, and ν4) of PO43- units in the Raman scattering spectra reflects random orientation, violating the Raman selection rule. If we assume that Raman intensities of PO43- units represent the crystallinity of HAp films, crystallization terminating the surface with the C-plane is hindered by the presence of excess H2O and OH species in the film, whereas crystallization at random orientations on the A-plane sapphire is rather promoted by these species. Such contrasting behaviors between C-plane and A-plane substrates will reflect surface-plane dependent creation of crystalline seeds and eventually determine the orientation of resulting HAp films.

  6. Cyclic fatigue-crack propagation in sapphire in air and simulated physiological environments.

    PubMed

    Asoo, B; McNaney, J M; Mitamura, Y; Ritchie, R O

    2000-12-01

    Single-crystal aluminas are being considered for use in the manufacture of prosthetic heart valves. To characterize such materials for biomedical application, subcritical crack growth by stress corrosion (static fatigue) and by cyclic fatigue has been examined in sapphire along (1100) planes in 24 degrees C humid air and 37 degrees C Ringer's solution (the latter as a simulated physiological environment). The relationships between crack-propagation rates and the linear-elastic stress intensity have been determined for the first time in sapphire for both modes of subcritical cracking. It was found that growth rates were significantly faster at a given stress intensity in the Ringer's solution compared to the humid air environment. Mechanistically, a true cyclic fatigue effect was not found in sapphire as experimentally measured cyclic fatigue-crack growth rates could be closely predicted simply by integrating the static fatigue-crack growth data over the cyclic loading cycle. PMID:11007616

  7. Development of an efficient Ti:sapphire laser transmitter for atmospheric ozone lidar measurements

    NASA Astrophysics Data System (ADS)

    Elsayed, Khaled Abdelsabour

    The impetus of this work was to develop an all solid-state Ti:sapphire laser transmitter to replace the current dye lasers that could provide a potentially compact, robust, and highly reliable laser transmitter for differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 nm and 900 nm, with M2 of 1.3, have been experimentally demonstrated and compared to model results. The Ti:sapphire lasers have shown the required output beam quality at maximum output pulse energy, 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively, to achieve 30 mJ of ultraviolet laser output at 289 run and 300 nm with two LBO nonlinear crystals.

  8. Fabrication of Monolithic Sapphire Membranes for High T(sub c) Bolometer Array Development

    NASA Technical Reports Server (NTRS)

    Pugel, D. E.; Lakew, B.; Aslam, S.; Wang, L.

    2004-01-01

    This paper examines the effectiveness of Pt/Cr thin film masks for the architecture of monolithic membrane structures in r-plane single crystal sapphire. The development of a pinhole-free Pt/Cr composite mask that is resistant to boiling H2SO4:H3PO4 etchant will lead to the fabrication of smooth sapphire membranes whose surfaces are well-suited for the growth of low-noise high Tc films. In particular, the relationship of thermal annealing conditions on the Pt/Cr composite mask system to: (1) changes in the surface morphology (2) elemental concentration of the Pt/Cr thin film layers and (3) etch pit formation on the sapphire surface will be presented.

  9. Interfacial Shear Strength of Cast and Directionally Solidified Nial-Sapphire Fiber Composites

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Asthana, R.; Noebe, R. D.

    1993-01-01

    The feasibility of fabricating intermetallic NiAl-sapphire fiber composites by casting and zone directional solidification has been examined. The fiber-matrix interfacial shear strengths measured using a fiber push-out technique in both cast and directionally solidified composites are greater than the strengths reported for composites fabricated by powder cloth process using organic binders. Microscopic examination of fibers extracted from cast, directionally solidified (DS), and thermally cycled composites, and the high values of interfacial shear strengths suggest that the fiber-matrix interface does not degrade due to casting and directional solidification. Sapphire fibers do not pin grain boundaries during directional solidification, suggesting that this technique can be used to fabricate sapphire fiber reinforced NiAl composites with single crystal matrices.

  10. Rate of F center formation in sapphire under low-energy low-fluence Ar+ irradiation

    NASA Astrophysics Data System (ADS)

    Epie, E. N.; Wijesundera, D. N.; Tilakaratne, B. P.; Chen, Q. Y.; Chu, W. K.

    2016-03-01

    Ionoluminescence, optical absorption spectroscopy and Rutherford backscattering spectrometry channelling (RBS-C) have been used to study the rate of F center formation with fluence in 170 keV Ar+ irradiated single crystals of α-Al2O3 (sapphire) at room temperature. Implantation fluences range between 1013 cm-2 and 5 ×1014 cm-2. F center density (NF) has been found to display an initial rapid linear increase with Ar+ fluence followed by saturation to a maximum value of 1.74 ×1015 cm-2. Experimental results show a 1-1 correlation between radiation damage in the oxygen sublattice and F center density. This suggest F center kinetics in sapphire under low-energy low-fluence Ar irradiation is a direct consequence of dynamic competition between oxygen defect creation and recombination. An attempt has also been made to extend this discussion to F center kinetics in sapphire under swift heavy ion irradiation.

  11. Synthetic Hemozoin (β-Hematin) Crystals Nucleate at the Surface of Neutral Lipid Droplets that Control Their Sizes

    PubMed Central

    Ambele, Melvin A.; Sewell, B. Trevor; Cummings, Franscious R.; Smith, Peter J.; Egan, Timothy J.

    2013-01-01

    Emulsions of monopalmitoylglycerol (MPG) and of a neutral lipid blend (NLB), consisting of MPG, monostearoylglycerol, dipalmitoylglycerol, dioleoylglycerol and dilineoylglycerol (4:2:1:1:1), the composition associated with hemozoin from the malaria parasite Plasmodium falciparum, have been used to mediate the formation of β-hematin microcrystals. Transmission electron microscopy (TEM), electron diffraction and electron spectroscopic imaging/electron energy loss spectroscopy (ESI/EELS) have been used to characterize both the lipid emulsion and β-hematin crystals. The latter have been compared with β-hematin formed at a pentanol/aqueous interface and with hemozoin both within P. falciparum parasites and extracted from the parasites. When lipid and ferriprotoporphyrin IX solutions in 1:9 v/v acetone/methanol were thoroughly pre-mixed either using an extruder or ultrasound, β-hematin crystals were found formed in intimate association with the lipid droplets. These crystals resembled hemozoin crystals, with prominent {100} faces. Lattice fringes in TEM indicated that these faces made contact with the lipid surface. The average length of these crystals was 0.62 times the average diameter of NLB droplets and their size distributions were statistically equivalent after 10 min incubation, suggesting that the lipid droplets also controlled the sizes of the crystals. This most closely resembles hemozoin formation in the helminth worm Schistosoma mansoni, while in P. falciparum, crystal formation appears to be associated with the much more gently curved digestive vacuole membrane which apparently leads to formation of much larger hemozoin crystals, similar to those formed at the flat pentanol-water interface. PMID:24244110

  12. Temperature Compensated Sapphire Resonator for Ultrastable Oscillator Operating at Temperatures Near 77 Deg Kelvin

    NASA Technical Reports Server (NTRS)

    Dick, G. John (Inventor); Santiago, David G. (Inventor)

    1999-01-01

    A sapphire resonator for an ultrastable oscillator capable of substantial performance improvements over the best available crystal quartz oscillators in a compact cryogenic package is based on a compensation mechanism enabled by the difference between copper and sapphire thermal expansion coefficients for so tuning the resonator as to cancel the temperature variation of the sapphire's dielectric constant. The sapphire resonator consists of a sapphire ring separated into two parts with webs on the outer end of each to form two re-entrant parts which are separated by a copper post. The re-entrant parts are bonded to the post by indium solder for good thermal conductivity between parts of that subassembly which is supported on the base plate of a closed copper cylinder (rf shielding casing) by a thin stainless steel cylinder. A unit for temperature control is placed in the stainless steel cylinder and is connected to the subassembly of re-entrant parts and copper post by a layer of indium for good thermal conduction. In normal use, the rf shielding casing is placed in a vacuum tank which is in turn placed in a thermos flask of liquid nitrogen. The temperature regulator is controlled from outside the thermos flask to a temperature in a range of about 40K to 150K, such as 87K for the WGH-811, mode of resonance in response to microwave energy inserted into the rf shielding casing through a port from an outside source.

  13. Measurement of optical extinction coefficients in sapphire as a function of the shock pressure

    NASA Astrophysics Data System (ADS)

    Zhou, Xianming; Li, Jun; Li, Jiabo

    2009-06-01

    Sapphire has been extensively used as a window material for both optical and thermal property measurements of shocked materials. Its optical extinction characteristic under dynamic compression is crucial in understanding the measured physical behaviors. Here we demonstrated a quantitative study of the dynamic optical extinction of sapphire in the shock pressure range from 72 to 183 GPa. Along its <1000> orientation, the optical extinction coefficient (α) of sapphire crystal has been in-situ measured at several discrete wavelengths with an optical pyrometer incorporated with a shock-generated bright light source. The significant findings indicated that: (i) the α coefficient increases with the shock pressure but decreases with the wavelength, showing a quite different behavior from that observed in the low-pressure compression in the literature; (ii) the obtained linear relationship between the square-root of α coefficient and the photon energy can be well described by a Mie scattering calculation assuming a particle radii of ˜140nm, which suggests that the optical extinction of sapphire is attributed to a light scattering mechanism related with the shock-induced crack-net distribution in this strong brittle material. These quantitative extinction data have provided new insight into the decay nature of thermal radiance histories previously concerned at a metal/sapphire interface, which is crucial for inferring an interfacial equilibrium temperature.

  14. BBO sapphire compound for high-power frequency conversion

    NASA Astrophysics Data System (ADS)

    Rothhardt, Carolin; Rothhardt, Jan; Klenke, Arno; Peschel, Thomas; Eberhardt, Ramona; Limpert, Jens; Tünnermann, Andreas

    2015-02-01

    Lasers used for diverse applications from industry to fundamental science tend to increasing output powers. Some applications require frequency conversion via nonlinear optical crystals, which suffer from the formation of temperature gradients at high power operation which causes thermal lensing or destruction of the crystal due to tensile stresses. To avoid these unwanted effects we joined a beta barium borate (BBO) crystal with sapphire disks serving as effective heat spreaders due to their high thermal conductivity (thermal conductivity κ = 42 W/Km). Therefore, smooth and flat crystal surfaces were joined by plasma-activated bonding. The joining relies on covalent bonds, which are formed via a condensation reaction of the surfaces which are first connected by Van der Waals forces. The cleaned surfaces are activated by plasma and brought into contact, pressed together and heat treated at a temperature of about 100°C. Special attention has been paid to the cleaning of the surfaces. Therefor the surfaces have been evaluated before and after treatment by means of atomic force microscopy. A stable connection has been formed successfully, which has been tested in a proof of principle experiment and demonstrated efficient second harmonic generation at up to 253 W of input power. Compared to a bare single BBO crystal it could be shown that the temperature within the crystal compound is significantly reduced. Such hybrid structures pave the way for frequency conversion at kilowatts of average power for future high power lasers.

  15. X-ray structure of snow flea antifreeze protein determined by racemic crystallization of synthetic protein enantiomers.

    PubMed

    Pentelute, Brad L; Gates, Zachary P; Tereshko, Valentina; Dashnau, Jennifer L; Vanderkooi, Jane M; Kossiakoff, Anthony A; Kent, Stephen B H

    2008-07-30

    Chemical protein synthesis and racemic protein crystallization were used to determine the X-ray structure of the snow flea antifreeze protein (sfAFP). Crystal formation from a racemic solution containing equal amounts of the chemically synthesized proteins d-sfAFP and l-sfAFP occurred much more readily than for l-sfAFP alone. More facile crystal formation also occurred from a quasi-racemic mixture of d-sfAFP and l-Se-sfAFP, a chemical protein analogue that contains an additional -SeCH2- moiety at one residue and thus differs slightly from the true enantiomer. Multiple wavelength anomalous dispersion (MAD) phasing from quasi-racemate crystals was then used to determine the X-ray structure of the sfAFP protein molecule. The resulting model was used to solve by molecular replacement the X-ray structure of l-sfAFP to a resolution of 0.98 A. The l-sfAFP molecule is made up of six antiparallel left-handed PPII helixes, stacked in two sets of three, to form a compact brick-like structure with one hydrophilic face and one hydrophobic face. This is a novel experimental protein structure and closely resembles a structural model proposed for sfAFP. These results illustrate the utility of total chemical synthesis combined with racemic crystallization and X-ray crystallography for determining the unknown structure of a protein. PMID:18598029

  16. X-ray Structure of Snow Flea Antifreeze Protein Determined by Racemic Crystallization of Synthetic Protein Enantiomers

    SciTech Connect

    Pentelute, Brad L.; Gates, Zachary P.; Tereshko, Valentina; Dashnau, Jennifer L.; Vanderkooi, Jane M.; Kossiakoff, Anthony A.; Kent, Stephen B.H.

    2008-08-20

    Chemical protein synthesis and racemic protein crystallization were used to determine the X-ray structure of the snow flea antifreeze protein (sfAFP). Crystal formation from a racemic solution containing equal amounts of the chemically synthesized proteins d-sfAFP and l-sfAFP occurred much more readily than for l-sfAFP alone. More facile crystal formation also occurred from a quasi-racemic mixture of d-sfAFP and l-Se-sfAFP, a chemical protein analogue that contains an additional -SeCH2- moiety at one residue and thus differs slightly from the true enantiomer. Multiple wavelength anomalous dispersion (MAD) phasing from quasi-racemate crystals was then used to determine the X-ray structure of the sfAFP protein molecule. The resulting model was used to solve by molecular replacement the X-ray structure of l-sfAFP to a resolution of 0.98 {angstrom}. The l-sfAFP molecule is made up of six antiparallel left-handed PPII helixes, stacked in two sets of three, to form a compact brick-like structure with one hydrophilic face and one hydrophobic face. This is a novel experimental protein structure and closely resembles a structural model proposed for sfAFP. These results illustrate the utility of total chemical synthesis combined with racemic crystallization and X-ray crystallography for determining the unknown structure of a protein.

  17. Heteroepitaxial growth of Cu{sub 2}ZnSnS{sub 4} thin film on sapphire substrate by radio frequency magnetron sputtering

    SciTech Connect

    Song, Ning E-mail: n.song@student.unsw.edu.au; Huang, Yidan; Li, Wei; Huang, Shujuan; Hao, Xiaojing E-mail: n.song@student.unsw.edu.au; Wang, Yu; Hu, Yicong

    2014-03-03

    The heteroepitaxy of tetragonal Cu2ZnSnS4 (CZTS) thin films on hexagonal sapphire (0001) single crystal substrates is successfully obtained by radio frequency magnetron sputtering. The sputtered CZTS film has a mirror-like smooth surface with a root mean square roughness of about 5.44 nm. X-ray θ-2θ scans confirm that CZTS film is (112) oriented on sapphire with an out of plane arrangement of CZTS (112) ‖ sapphire (0001). X-ray Phi scan further illustrates an in plane ordering of CZTS [201{sup ¯}] ‖ sapphire [21{sup ¯}1{sup ¯}0]. The high resolution transmission electron microscopy image of the interface region clearly shows that the CZTS thin film epitaxially grows on the sapphire (0001) substrate. The band gap of the film is found to be approximately 1.51 eV.

  18. Acoustic and NMR investigations of melting and crystallization of indium-gallium alloys in pores of synthetic opal matrices

    NASA Astrophysics Data System (ADS)

    Pirozerskii, A. L.; Charnaya, E. V.; Lee, M. K.; Chang, L. J.; Nedbai, A. I.; Kumzerov, Yu. A.; Fokin, A. V.; Samoilovich, M. I.; Lebedeva, E. L.; Bugaev, A. S.

    2016-05-01

    The paper presents the results of studying the crystallization and melting processes of Ga-In eutectic alloys, which are embedded in opal matrices, using acoustic and NMR methods. The indium concentrations in the alloys were 4, 6, 9, and 15 at %. Measurements were performed upon cooling from room temperature to complete crystallization of the alloys and subsequent heating. It is revealed how the size effects and alloy composition influence the formation of phases with α- and β-Ga structures and on changes in the melting-temperature ranges. A difference was observed between the results obtained using acoustic and NMR methods, which was attributed to different temperature measurement conditions.

  19. The crystal structure analysis of d(CGCGAASSCGCG)2, a synthetic DNA dodecamer duplex containing four 4'-thio-2'-deoxythymidine nucleotides.

    PubMed Central

    Boggon, T J; Hancox, E L; McAuley-Hecht, K E; Connolly, B A; Hunter, W N; Brown, T; Walker, R T; Leonard, G A

    1996-01-01

    The crystal structure refinement of the synthetic dodecamer d(CGCGAASSCGCG), where S = 4'-thio-2'-deoxythymidine, has converged at R=0.201 for 2605 reflections with F > 2sigma(F) in the resolution range 8.0-2.4 A for a model consisting of the dodecamer duplex and 66 water molecules. A comparison of its structure with that of the native dodecamer d(CGCGAATTCGCG) has revealed that the major differences between the two structures is a change in the conformation of the sugar-phosphate backbone in the regions at and adjacent to the positions of the modified nucleosides. Examination of the fine structural parameters for each of the structures reveals that the thiosugars adopt a C3'-exo conformation in d(CGCGAASSCGCG), rather than the approximate C1'-exo conformation found for the analogous sugars in the structure of d(CGCGAATTCGCG). The observed differences in structure between the two duplexes may help to explain the enhanced resistance to nuclease digestion of synthetic oligonucleotides containing 4'-thio-2'-deoxynucleotides. PMID:8600465

  20. Anisotropic Transverse Stress in Calcite and Sapphire Measured Using Birefringence

    NASA Astrophysics Data System (ADS)

    Tear, Gareth R.; Chapman, David J.; Eakins, Daniel E.; Proud, William G.

    2015-06-01

    Many significant geological minerals have anisotropic crystal structures leading to material properties that are anisotropic, including compressive elastic behaviour. A non-invasive approach to investigate the directional dependence of transverse stress in these materials during shock compression would supplement current understanding. As many geological minerals are transparent and hence optically anisotropic, measuring the change in birefringence induced by transverse stress in the material offers the possibility of a fast, non-invasive approach to probe transverse behaviour. Shock compression experiments have been performed on a-cut calcite and a-cut sapphire for strain rates of order 105 s-1 and up to longitudinal stresses of 2 GPa for calcite and 12 GPa for sapphire. We present measured changes in birefringence for these materials under shock compression, comparing with current and past literature as well as an in house optical model. The authors would like to thank Mr Steve Johnson and Mr David Pittman for technical support. The Institute of Shock Physics acknowledges the continued support of AWE and Imperial College London.

  1. Temperature behavior of damage in sapphire implanted with light ions

    NASA Astrophysics Data System (ADS)

    Alves, E.; Marques, C.; Sáfrán, G.; McHargue, Carl J.

    2009-05-01

    In this study, we compare and discuss the defect behavior of sapphire single crystals implanted with different fluences (1 × 1016-1 × 1017 cm-2) of carbon and nitrogen with 150 keV. The implantation temperatures were RT, 500 °C and 1000 °C to study the influence of temperature on the defect structures. For all the ions the Rutherford backscattering-channeling (RBS-C) results indicate a surface region with low residual disorder in the Al-sublattice. Near the end of range the channeled spectrum almost reaches the random indicating a high damage level for fluences of 1 × 1017 cm-2. The transmission electron microscopy (TEM) photographs show a layered contrast feature for the C implanted sample where a buried amorphous region is present. For the N implanted sample the Electron Energy Loss Spectroscopy (EELS) elemental mapping give evidence for the presence of a buried damage layer decorated with bubbles. Samples implanted at high temperatures (500 °C and 1000 °C) show a strong contrast fluctuation indicating a defective crystalline structure of sapphire.

  2. Generation of continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling of a Ti:sapphire laser.

    PubMed

    Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

    2010-03-20

    We have generated continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling a high-power Ti:sapphire laser in an external enhancement cavity. An LBO crystal that is Brewster-cut and antireflection coated on both ends is used for a long-term stable frequency doubling. By optimizing the input coupler's reflectivity, we could generate 1.5 W 378 nm radiation from a 5 W 756 nm Ti:sapphire laser. According to our knowledge, this is the highest CW frequency-doubled power of a Ti:sapphire laser. PMID:20300165

  3. Improved crystal quality of GaN film with the in-plane lattice-matched In0.17Al0.83N interlayer grown on sapphire substrate using pulsed metal—organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Li, Liang; Yang, Lin-An; Xue, Jun-Shuai; Cao, Rong-Tao; Xu, Sheng-Rui; Zhang, Jin-Cheng; Hao, Yue

    2014-06-01

    We report on an improvement in the crystal quality of GaN film with an In0.17Al0.83N interlayer grown by pulsed metal—organic chemical vapor deposition, which is in-plane lattice-matched to GaN films. The indium composition of about 17% and the reductions of both screw and edge threading dislocations (TDs) in GaN film with the InAlN interlayer are estimated by high resolution X-ray diffraction. Transmission electron microscopy (TEM) measurements are employed to understand the mechanism of reduction in TD density. Raman and photoluminescence measurements indicate that the InAlN interlayer can improve the crystal quality of GaN film, and verify that there is no additional residual stress induced into the GaN film with InAlN interlayer. Atomic force microscopy measurement shows that the InAlN interlayer brings in a smooth surface morphology of GaN film. All the results show that the insertion of the InAlN interlayer is a convenient method to achieve excellent crystal quality in GaN epitaxy.

  4. Bonding of sapphire to sapphire by eutectic mixture of aluminum oxide and zirconium oxide

    NASA Technical Reports Server (NTRS)

    Deluca, J. J. (Inventor)

    1979-01-01

    An element comprising sapphire, ruby or blue sapphire can be bonded to another element of such material with a eutectic mixture of aluminum oxide and zirconium oxide. The bonding mixture may be applied in the form of a distilled water slurry or by electron beam vapor deposition. In one embodiment the eutectic is formed in situ by applying a layer of zirconium oxide and then heating the assembly to a temperature above the eutectic temperature and below the melting point of the material from which the elements are formed. The formation of a sapphire rubidium maser cell utilizing eutectic bonding is shown.

  5. Bonding of sapphire to sapphire by eutectic mixture of aluminum oxide and zirconium oxide

    NASA Technical Reports Server (NTRS)

    Deluca, J. J. (Inventor)

    1975-01-01

    Bonding of an element comprising sapphire, ruby or blue sapphire to another element of such material with a eutectic mixture of aluminum oxide and zirconium oxide is discussed. The bonding mixture may be applied in the form of a distilled water slurry or by electron beam vapor deposition. In one embodiment the eutectic is formed in situ by applying a layer of zirconium oxide and then heating the assembly to a temperature above the eutectic temperature and below the melting point of the material from which the elements are formed. The formation of a sapphire rubidium maser cell utilizing eutectic bonding is shown.

  6. Enhanced performances of diode-pumped sapphire/Er³⁺:Yb³⁺:LuAl₃(BO₃)₄/sapphire micro-laser at 1.5-1.6 μm.

    PubMed

    Chen, Yujin; Lin, Yanfu; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

    2015-05-01

    A sandwich-type sapphire/Er3+:Yb3+:LuAl3(BO3)4/sapphire micro-laser was fabricated by tightly pressing two sapphire crystals and a Er3+:Yb3+:LuAl3(BO3)4 microchip together, and directly depositing cavity mirrors onto the outside surfaces of the sapphire crystals. Pumped by a continuous-wave 976 nm diode laser, a 1543 nm laser with maximum output power of 1.17 W and slope efficiency of 33% with respect to incident pump power was realized in the sandwich-type micro-laser, whereas a laser with maximum output power of 0.46 W and slope efficiency of 17% was obtained in a monolithic Er3+:Yb3+:LuAl3(BO3)4 micro-laser. Furthermore, efficient 1521 nm continuous-wave and passively Q-switched pulse lasers were also demonstrated in the sandwich-type micro-laser. PMID:25969325

  7. Final EDP Ti: sapphire amplifiers for ELI project

    NASA Astrophysics Data System (ADS)

    Chvykov, Vladimir; Kalashnikov, Mikhail; Osvay, Károly

    2015-05-01

    Recently several ultrahigh intensity Chirped Pulse Amplification (CPA) laser systems have reached petawatt output powers [1, 2] setting the next milestone at tens or even hundreds petawatts for the next three to ten years [3, 4]. These remarkable results were reached when laser amplifiers (opposite to Optical Parametric Amplification (OPA) [5]) were used as final ones and from them Ti:Sapphire crystals supposed to be the working horses as well in the future design of these laser systems. Nevertheless, the main limitation that arises on the path toward ultrahigh output power and intensity is the restriction on the pumping and extraction energy imposed by Transverse Amplified Spontaneous Emission (TASE) [6] and/or transverse parasitic generation (TPG) [7] within the large aperture of the disc-shape amplifier volume.

  8. Growth of sapphire and oxide eutectic fibers by the EFG technique

    NASA Astrophysics Data System (ADS)

    Kurlov, V. N.; Stryukov, D. O.; Shikunova, I. A.

    2016-01-01

    Single-crystal sapphire and oxide binary (Al2O3-Y3Al5O12, Al2O3-Er3Al5O12, Al2O3- GdAlO3) and ternary (Al2O3-ZrO2(Y2O3)) eutectic fibers of 150-300 µm in diameters were grown by the edge-defined film-fed growth (EFG) technique. Microstructure and some properties of fibers were investigated.

  9. Silicon on sapphire for ion implantation studies

    NASA Technical Reports Server (NTRS)

    Pisciotta, B. P.

    1974-01-01

    Van der Pauw or bridge samples are ultrasonically cut from silicon on sapphire wafers. Contact pad regions are implanted with moderately heavy dose of ions. Ion of interest is implanted into sample; and, before being annealed in vacuum, sample is sealed with sputtered layer of silicon dioxide. Nickel or aluminum is sputtered onto contact pad areas and is sintered in nitrogen atmosphere.

  10. Temperature-Compensated Sapphire Microwave Resonator

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Santiago, David G.

    1996-01-01

    Sapphire-dielectric-ring microwave resonator operating in "whispering-gallery" electromagnetic mode features differential-thermal-expansion design providing temperature compensation for ultrahigh frequency stability. Designed to minimize frequency fluctuations caused by temperature fluctuations at normal temperature equal to or even somewhat greater than temperature of liquid nitrogen. Ancillary equipment needed for operation smaller and less expensive, and liquid nitrogen used as coolant.

  11. Tailoring of crystal phase and Néel temperature of cobalt monoxides nanocrystals with synthetic approach conditions

    NASA Astrophysics Data System (ADS)

    Ravindra, A. V.; Behera, B. C.; Padhan, P.; Lebedev, O. I.; Prellier, W.

    2014-07-01

    Cobalt monoxide (CoO) nanocrystals were synthesized by thermal decomposition of cobalt oleate precursor in a high boiling point organic solvent 1-octadecene. The X-ray diffraction pattern and transmission electron microscopy studies suggest that pure face-centered-cubic (fcc) phase of CoO can be synthesized in the temperature range of 569-575 K. Thermolysis product at higher synthesis temperature 585 K is a mixture of fcc and hexagonal-closed-packed (hcp) phases. These nanocrystals are single crystals of CoO and exhibit mixture of two types of morphologies; one is nearly spherical with 5-25 nm diameter, and other one is 5-10 nm thick flake. The pure fcc-CoO nanocrystals show enhanced, and mixture of fcc- and hcp-CoO nanocrystals show reduced antiferromagnetic ordering temperature. Such results provide new opportunities for optimizing and enhancing the properties and performance of cobalt oxide nanomaterials.

  12. Vanadium-rich ruby and sapphire within Mogok Gemfield, Myanmar: implications for gem color and genesis

    NASA Astrophysics Data System (ADS)

    Zaw, Khin; Sutherland, Lin; Yui, Tzen-Fu; Meffre, Sebastien; Thu, Kyaw

    2015-01-01

    Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr3+ yields red in ruby and Fe2+, Fe3+, and Ti4+ ionic interactions color sapphires. A minor ion, V3+ induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry.

  13. Neutron reflectivity study of substrate surface chemistry effects on supported phospholipid bilayer formation on (1120) sapphire.

    SciTech Connect

    Oleson, Timothy A.; Sahai, Nita; Wesolowski, David J; Dura, Joseph A; Majkrzak, Charles F; Giuffre, Anthony J.

    2012-01-01

    Oxide-supported phospholipid bilayers (SPBs) used as biomimetric membranes are significant for a broad range of applications including improvement of biomedical devices and biosensors, and in understanding biomineralization processes and the possible role of mineral surfaces in the evolution of pre-biotic membranes. Continuous-coverage and/or stacjed SPBs retain properties (e.,g. fluidity) more similar to native biological membranes, which is desirable for most applications. Using neutron reflectivity, we examined face coverage and potential stacking of dipalmitoylphosphatidylcholine (DPPC) bilayers on the (1120) face of sapphire (a-Al2O3). Nearly full bilayers were formed at low to neutral pH, when the sapphire surface is positively charged, and at low ionic strength (l=15 mM NaCl). Coverage decreased at higher pH, close to the isoelectric point of sapphire, and also at high I>210mM, or with addition of 2mM Ca2+. The latter two effects are additive, suggesting that Ca2+ mitigates the effect of higher I. These trends agree with previous results for phospholipid adsorption on a-Al2O3 particles determined by adsorption isotherms and on single-crystal (1010) sapphire by atomic force microscopy, suggesting consistency of oxide surface chemistry-dependent effects across experimental techniques.

  14. Formation of Hematite fine crystals by hydrothermal alteration of synthetic Martian basalt, static and fluid flow experiments

    NASA Astrophysics Data System (ADS)

    Kobayashi, K.; Isobe, H.

    2011-12-01

    Exploration made by Martian rovers and probes provided enormous information on the composition of the Martian surface materials. Origin and formation processes of the Martian surface materials should be various depending on topography and history of the Martian crust. Especially, iron minerals in the Martian soil should have essential role to characterize surface environment of the "red planet". In the present study, experimental reproduction of the Martian soil was carried out by hydrothermal alteration of the synthetic iron-rich basaltic rock. Experimental conditions for temperature and fluid composition followed Isobe and Yoshizawa (2010). Static alteration experiments are carried out at 100 °C and 150 °C, and mass ratio of the starting material to the pH1.0 sulfuric acid solution is 1:50. Run durations are 1, 2, 4 or 8 weeks. Appropriate mass of dry ice was sealed in the experimental vessels to expel atmospheric oxygen with CO2. For the static experiments, powdered starting materials were charged in PFA vial to keep textures of the run products. For the fluid flow experiments, we constructed closed loop with Teflon tube inclined approximately 45°. One of the vertical tube is charged with crushed synthetic basalt and heated approximately 150°C by aluminum block with ribbon heater. Surlfuric acid solution flows through the tube from bottom to top and cooled at the end of the aluminum block. Cooled solution returns to the bottom of the heated tube through another vertical tube without heating block. In the static condition run products, characteristic iron mineral particles are formed for 100°C and 150°C concordant with Isobe and Yoshizawa (2010). These iron minerals distributed not only inside the starting material powder but also on the surface of the reaction vessel and the PFA vial in the reactive solution. The surface of the reaction vessel shows orange and reddish color on 100°C and 150°C run products, respectively. By SEM observation, dissolution of

  15. Tailoring of crystal phase and Néel temperature of cobalt monoxides nanocrystals with synthetic approach conditions

    SciTech Connect

    Ravindra, A. V.; Behera, B. C.; Padhan, P.; Lebedev, O. I.; Prellier, W.

    2014-07-21

    Cobalt monoxide (CoO) nanocrystals were synthesized by thermal decomposition of cobalt oleate precursor in a high boiling point organic solvent 1-octadecene. The X-ray diffraction pattern and transmission electron microscopy studies suggest that pure face-centered-cubic (fcc) phase of CoO can be synthesized in the temperature range of 569–575 K. Thermolysis product at higher synthesis temperature 585 K is a mixture of fcc and hexagonal-closed-packed (hcp) phases. These nanocrystals are single crystals of CoO and exhibit mixture of two types of morphologies; one is nearly spherical with 5–25 nm diameter, and other one is 5–10 nm thick flake. The pure fcc-CoO nanocrystals show enhanced, and mixture of fcc- and hcp-CoO nanocrystals show reduced antiferromagnetic ordering temperature. Such results provide new opportunities for optimizing and enhancing the properties and performance of cobalt oxide nanomaterials.

  16. External-cavity frequency doubling of a 5-W 756-nm injection-locked Ti:sapphire laser.

    PubMed

    Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

    2008-03-31

    We have developed a 5-W 756-nm injection-locked Ti:sapphire laser and frequency-doubled it in an external enhancement cavity for the generation of watt-level 378-nm single-frequency radiation, which is essential for isotope-selective optical pumping of thallium atoms. With a lithium triborate (LBO) crystal in the enhancement cavity, 1.1 W at 378 nm was coupled out from the cavity. Such results are to our knowledge the highest powers of continuous-wave single-frequency radiation generated from a Ti:sapphire laser and its frequency doubling. PMID:18542585

  17. Radiation tolerance of a high quality synthetic single crystal chemical vapor deposition diamond detector irradiated by 14.8 MeV neutrons

    SciTech Connect

    Pillon, M.; Angelone, M.; Aielli, G.; Almaviva, S.; Marinelli, Marco; Milani, E.; Prestopino, G.; Tucciarone, A.; Verona, C.; Verona-Rinati, G.

    2008-09-01

    Diamond exhibits many properties such as an outstanding radiation hardness and fast response time both important to design detectors working in extremely radioactive environments. Among the many applications these devices can be used for, there is the development of a fast and radiation hard neutron detector for the next generation of fusion reactors, such as the International Thermonuclear Experimental Reactor project, under construction at Cadarache in France. A technology to routinely produce electronic grade synthetic single crystal diamond detectors was recently developed by our group. One of such detectors, with an energy resolution of 0.9% as measured using an {sup 241}Am{alpha} particle source, has been heavily irradiated with 14.8 MeV neutrons produced by the Frascati Neutron Generator. The modifications of its spectroscopic properties have been studied as a function of the neutron fluence up to 2.0x10{sup 14} n/cm{sup 2}. In the early stage of the irradiation procedure an improvement in the spectroscopic performance of the detector was observed. Subsequently the detection performance remains stable for all the given neutron fluence up to the final one thus assessing a remarkable radiation hardness of the device. The neutron damage in materials has been calculated and compared with the experimental results. This comparison is discussed within the nonionizing energy loss (NIEL) hypothesis, which states that performance degradation is proportional to NIEL.

  18. Thermodynamic effects of calcium and iron oxides on crystal phase formation in synthetic gasifier slags containing from 0 to 27wt.% V2O3

    DOE PAGESBeta

    Nakano, Jinichiro; Duchesne, Marc; Bennett, James; Kwong, Kyei -Sing; Nakano, Anna; Hughes, Robin

    2014-11-15

    Thermodynamic phase equilibria in synthetic slags (Al2O3–CaO–FeO–SiO2–V2O3) were investigated with 0–27 wt.% vanadium oxide corresponding to industrial coal–petroleum coke (petcoke) feedstock blends in a simulated gasifier environment. Samples encompassing coal–petcoke mixed slag compositions were equilibrated at 1500 °C in a 64 vol.% CO/36 vol.% CO2 atmosphere (Po2 ≈ 10–8 atm at 1500 °C) for 72 h, followed by rapid water quench, then analyzed by inductively coupled plasma optical emission spectrometry, X-ray diffractometry, and scanning electron microscopy with wavelength dispersive spectroscopy. With increasing CaO content, FeO content, or both; the slag homogeneity region expanded and a composition range exhibiting crystals wasmore » reduced. The mullite (Al6Si2O13) crystalline phase was not present in the slags above 9 wt.% FeO while the karelianite (V2O3) crystalline phase was always present in compositions studied if a sufficient amount of vanadium existed in the slag. Furthermore, based on the present experimental equilibrium evaluation, a set of isothermal phase diagrams showing effects of CaO and FeO on thermodynamic phase stabilities in the vanadium-bearing slags is proposed. Some uses of the diagrams for potential industrial practice are discussed.« less

  19. Radiation tolerance of a high quality synthetic single crystal chemical vapor deposition diamond detector irradiated by 14.8 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Pillon, M.; Angelone, M.; Aielli, G.; Almaviva, S.; Marinelli, Marco; Milani, E.; Prestopino, G.; Tucciarone, A.; Verona, C.; Verona-Rinati, G.

    2008-09-01

    Diamond exhibits many properties such as an outstanding radiation hardness and fast response time both important to design detectors working in extremely radioactive environments. Among the many applications these devices can be used for, there is the development of a fast and radiation hard neutron detector for the next generation of fusion reactors, such as the International Thermonuclear Experimental Reactor project, under construction at Cadarache in France. A technology to routinely produce electronic grade synthetic single crystal diamond detectors was recently developed by our group. One of such detectors, with an energy resolution of 0.9% as measured using an A241m α particle source, has been heavily irradiated with 14.8 MeV neutrons produced by the Frascati Neutron Generator. The modifications of its spectroscopic properties have been studied as a function of the neutron fluence up to 2.0×1014 n/cm2. In the early stage of the irradiation procedure an improvement in the spectroscopic performance of the detector was observed. Subsequently the detection performance remains stable for all the given neutron fluence up to the final one thus assessing a remarkable radiation hardness of the device. The neutron damage in materials has been calculated and compared with the experimental results. This comparison is discussed within the nonionizing energy loss (NIEL) hypothesis, which states that performance degradation is proportional to NIEL.

  20. Crystal violet: Study of the photo-fading of an early synthetic dye in aqueous solution and on paper with HPLC-PDA, LC-MS and FORS

    NASA Astrophysics Data System (ADS)

    Confortin, Daria; Neevel, Han; Brustolon, Marina; Franco, Lorenzo; Kettelarij, Albert J.; Williams, Renè M.; van Bommel, Maarten R.

    2010-06-01

    The photo-fading of crystal violet (CV), one of the earliest synthetic dyes and an ink component, is examined both in solution and on paper. Aqueous solutions of CV were exposed to UV light (365nm) and samples were taken at constant time intervals and analysed with a High Performance Liquid Chromatography-Photo Diode Array (HPLC-PDA) and Liquid Chromatography-Mass Spectroscopy (LC-MS). Demethylation products were positively identified. Also, deamination probably occurred. The oxidation at the central carbon likely generates Michler's ketone (MK) or its derivatives, but still needs confirmation. To study CV on paper, Whatman paper was immersed in CV and exposed to UV light. Before and after different irradiation periods, reflectance spectra were recorded with Fibre Optic Reflectance Spectrophotometry (FORS). A decrease in CV concentration and a change in aggregation type for CV molecules upon irradiation was observed. Colorimetric L*a*b* values before and during irradiation were also measured. Also, CV was extracted from paper before and after different irradiation periods and analysed with HPLC-PDA. Photo-fading of CV on paper produced the same products as in solution, at least within the first 100 hours of irradiation. Finally, a photo-fading of CV in the presence of MK on Whatman paper was performed. It was demonstrated that MK both accelerates CV degradation and is consumed during the reaction. The degradation pathway identified in this work is suitable for explaining the photo/fading of other dyes belonging to the triarylmethane group.

  1. Crystal-structure and FTIR spectroscopy of synthetic Na(NaMg)Mg5Si8O22(OH)2, a P21/m amphibole

    NASA Astrophysics Data System (ADS)

    Iezzi, G.; Camara, F.; della Ventura, G.; Oberti, R.; Holtz, F.

    2003-04-01

    Na(NaMg)Mg_5Si_8O22(OH)_2 is an interesting amphibole composition never found in nature, which has been the object of much experimental work (Maresch and Langer, 1976; Raudsepp et al., 1991). It typically gives very high-yield run-products, consisting of extremely acicular and well formed crystals, generally less than 1 or 2 μm wide. X-ray powder analysis suggested various symmetries and space groups. The IR spectrum in the OH region consists of two major absorbances: a single well-resolved and rather sharp band at 3714 cm-1, and a broader band, possibly consisting of three overlapping components, centred at 3743 cm-1. No clear explanations for such a pattern have been provided so far. We prepared four samples, using hydrothermal techniques, at the following T and P conditions: 750, 800 and 850^oC and 0.4 GPa and 900^oC and 0.5 GPa. Runs at 800^oC and 900^oC yielded crystals suitable for single-crystal X-ray data collection. All samples have P2_1/m symmetry, similarly to what found by Oberti et al. (2002) for a similar composition with excess water synthesised by W. Maresch. This symmetry implies non equivalence of the two double-chains of tetrahedra facing base-to-base, which is mainly expressed by different degrees of stretching and kinking. There are also two independent anion sites (O3A and O3B) which may be occupied by OH. This feature explains the IR pattern. The band at 3743 cm-1 is assigned to the shorter O3B-H2 bond, whereas the 3715 cm-1 is assigned to the longer O3A-H1 bond. In addition, the broader shape of the higher-frequency, 3743 cm-1 band, suggests a stronger interaction of the O3B-H2 dipole with ^ANa, which is confirmed by structure refinement. Increasing T of syntheses implies progressive departure from the ideal stoichiometry via the ^BMg^ANa-1 exchange, which has been characterised by EMPA, structure refinement and FTIR spectroscopy. The latter in particular can now be used to detect unusual symmetries in X-ray powder patterns of synthetic

  2. Measurement of the dielectric properties of high-purity sapphire at 1.865 GHZ from 2-10 Kelvin

    SciTech Connect

    N. Pogue, P. McIntyre, Akhdiyor Sattarov, Charles Reece

    2012-06-01

    A dielectric test cavity was designed and tested to measure the microwave dielectric properties of ultrapure sapphire at cryogenic temperatures. Measurements were performed by placing a large cylindrical crystal of sapphire in a Nb superconducting cavity operating in the TE01 mode at 1.865 GHz. The dielectric constant, heat capacity, and loss tangent were all calculated using experimental data and RF modeling software. The motivation for these measurements was to determine if such a sapphire could be used as a dielectric lens to focus the magnetic field onto a sample wafer in a high field wafer test cavity. The measured properties have been used to finalize the design of the wafer test cavity.

  3. Sapphire Viewports for a Venus Probe

    NASA Technical Reports Server (NTRS)

    Bates, Stephen

    2012-01-01

    A document discusses the creation of a viewport suitable for use on the surface of Venus. These viewports are rated for 500 C and 100 atm pressure with appropriate safety factors and reliability required for incorporation into a Venus Lander. Sapphire windows should easily withstand the chemical, pressure, and temperatures of the Venus surface. Novel fixture designs and seals appropriate to the environment are incorporated, as are materials compatible with exploration vessels. A test cell was fabricated, tested, and leak rate measured. The window features polish specification of the sides and corners, soft metal padding of the sapphire, and a metal C-ring seal. The system safety factor is greater than 2, and standard mechanical design theory was used to size the window, flange, and attachment bolts using available material property data. Maintenance involves simple cleaning of the window aperture surfaces. The only weakness of the system is its moderate rather than low leak rate for vacuum applications.

  4. Surface modification of sapphire by ion implantation

    SciTech Connect

    McHargue, C.J.

    1998-11-01

    The range of microstructures and properties of sapphire (single crystalline Al{sub 2}O{sub 3}) that are produced by ion implantation are discussed with respect to the implantation parameters of ion species, fluence, irradiation temperature and the orientation of the ion beam relative to crystallographic axes. The microstructure of implanted sapphire may be crystalline with varying concentrations of defects or it may be amorphous perhaps with short-range order. At moderate to high fluences, implanted metallic ions often coalesce into pure metallic colloids and gas ions form bubbles. Many of the implanted microstructural features have been identified from studies using transmission electron microscopy (TEM), optical spectroscopy, Moessbauer spectroscopy, and Rutherford backscattering-channeling. The chemical, mechanical, and physical properties reflect the microstructures.

  5. Failure Analysis of Sapphire Refractive Secondary Concentrators

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Quinn, George D.

    2009-01-01

    Failure analysis was performed on two sapphire, refractive secondary concentrators (RSC) that failed during elevated temperature testing. Both concentrators failed from machining/handling damage on the lens face. The first concentrator, which failed during testing to 1300 C, exhibited a large r-plane twin extending from the lens through much of the cone. The second concentrator, which was an attempt to reduce temperature gradients and failed during testing to 649 C, exhibited a few small twins on the lens face. The twins were not located at the origin, but represent another mode of failure that needs to be considered in the design of sapphire components. In order to estimate the fracture stress from fractographic evidence, branching constants were measured on sapphire strength specimens. The fractographic analysis indicated radial tensile stresses of 44 to 65 MPa on the lens faces near the origins. Finite element analysis indicated similar stresses for the first RSC, but lower stresses for the second RSC. Better machining and handling might have prevented the fractures, however, temperature gradients and resultant thermal stresses need to be reduced to prevent twinning.

  6. Shear strength of metal-sapphire contacts

    NASA Technical Reports Server (NTRS)

    Pepper, S. V.

    1976-01-01

    The shear strength of polycrystalline Ag, Cu, Ni, and Fe contacts on clean (0001) sapphire has been studied in ultrahigh vacuum. Both clean metal surfaces and surfaces exposed to O2, Cl2, and C2H4 were used. The results indicate that there are two sources of strength of Al2O3-metal contacts: an intrinsic one that depends on the particular clean metal in contact with Al2O3 and an additional one due to intermediate films. The shear strength of the clean metal contacts correlated directly with the free energy of oxide formation for the lowest metal oxide, in accord with the hypothesis that a chemical bond is formed between metal cations and oxygen anions in the sapphire surface. Contacts formed by metals exposed to chlorine exhibited uniformly low shear strength indicative of van der Waals bonding between chlorinated metal surfaces and sapphire. Contacts formed by metals exposed to oxygen exhibited enhanced shear strength, in accord with the hypothesis that an intermediate oxide layer increases interfacial strength.

  7. Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence

    SciTech Connect

    Yerci, S.; Serincan, U.; Dogan, I.; Tokay, S.; Genisel, M.; Aydinli, A.; Turan, R.

    2006-10-01

    Silicon nanocrystals, average sizes ranging between 3 and 7 nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800 deg. C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.

  8. High-Temperature Mechanical Properties of Cr(3+) Doped Sapphire Fibers

    NASA Technical Reports Server (NTRS)

    Sayir, A.; QuispeCancapa, J. J.; deArellanoLopez, A. R.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    High-temperature slow-crack growth of single crystal 10 wt% Cr2O3 - Al2O3 (nominal composition) fibers has been studied by tensile rupture experiments at 1400 C, under different stressing rates (0.5 to 41.5 MPa/s). Slow-crack growth (SCG) is less pronounced with increasing Cr2O3. Rupture stresses increased with the stressing rate from 397 MPa to 515 MPa, resulting in a SCG exponent, N=19. The Cr2O3 composition was analyzed by Energy Dispersed X-Ray Spectra (EDS) and fracture surfaces were studied by scanning electron microscopy (SEM). Results are compared with previous studies on 100-300 ppm Cr3(+) doped sapphire fibers and on commercial sapphire fibers.

  9. Modified porous silica antireflective coatings with laser damage resistance for Ti:sapphire

    NASA Astrophysics Data System (ADS)

    Jia, Qiaoying; Li, Haiyuan; Liu, Ruijun; Tang, Yongxing; Jiang, Zhonghong

    2005-04-01

    Porous SiO2 antireflective (AR) coatings are prepared from the colloidal silica solution modified with methyltriethoxysilane (MTES) based on the sol-gel route. The viscosity of modified silica suspensions changes but their stability keeps when MTES is introduced. The refractive indices of modified coatings vary little after bake treatment from 100 to 150 Celsius. The modified silica coatings on Ti:sapphire crystal, owning good homogeneity, display prominent antireflective effect within the laser output waveband (750-850 nm) of Ti:sapphire lasers, with average transmission above 98.6%, and own laser induced damage thresholds (LIDTs) of more than 2.2 J/cm2 at 800 nm with the pulse duration of 300 ps.

  10. High-energy large-aperture Ti:sapphire amplifier for 5 PW laser pulses.

    PubMed

    Chu, Yuxi; Gan, Zebiao; Liang, Xiaoyan; Yu, Lianghong; Lu, Xiaoming; Wang, Cheng; Wang, Xinliang; Xu, Lu; Lu, Haihe; Yin, Dingjun; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

    2015-11-01

    We report on the generation of 192.3 J centered at 800 nm wavelength from a chirped-pulse amplification (CPA) Ti:sapphire laser system. The experimental results demonstrate that parasitic lasing can be suppressed successfully in the final amplifier based on a Ti:sapphire crystal of 150 mm in diameter. An over 50% pump-to-signal conversion efficiency was measured for the final amplifier by optimizing the time delay of two pump pulses and enhancing the injected seed energy. With 72% compressor throughput efficiency and 27 fs long compressed pulse duration obtained at a lower energy level, this laser could potentially support a compressed laser pulse of 5.13 PW peak power. The experimental results represent notable progress regarding the CPA laser. PMID:26512506