WorldWideScience

Sample records for crystal forehead temperature

  1. 21 CFR 880.2200 - Liquid crystal forehead temperature strip.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Liquid crystal forehead temperature strip. 880.2200 Section 880.2200 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... the presence or absence of fever, or to monitor body temperature changes. The device displays...

  2. Forehead lift - slideshow

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/presentations/100020.htm Forehead lift - series—Indications To use the sharing features on ... to slide 3 out of 3 Overview Forehead lifts are most commonly done for people in their ...

  3. Forehead tissue expander.

    Science.gov (United States)

    Kisner, W H

    1991-02-01

    The use of the forehead flap for nasal reconstruction has long been used by reconstructive surgeons. A case is presented in which comprised forehead skin is utilized following expansion by a tissue expander.

  4. Reliability of an infrared forehead skin thermometer for core temperature measurements

    NARCIS (Netherlands)

    Kistemaker, J.A.; Hartog, E.A. den; Daanen, H.A.M.

    2006-01-01

    The SensorTouch thermometer performs an infrared measurement of the skin temperature above the Superficial Temporal Artery (STA). This study evaluates the validity and the accuracy of the SensorTouch thermometer. Two experiments were performed in which the body temperature was measured with a rectal

  5. Temperature stabilization of optofluidic photonic crystal cavities

    DEFF Research Database (Denmark)

    Kamutsch, Christian; Smith, Cameron L.C.; Graham, Alexandra;

    2009-01-01

    We present a principle for the temperature stabilization of photonic crystal (PhC) cavities based on optofluidics. We introduce an analytic method enabling a specific mode of a cavity to be made wavelength insensitive to changes in ambient temperature. Using this analysis, we experimentally demon...

  6. An Update on the Anatomy of the Forehead Compartments.

    Science.gov (United States)

    Cotofana, Sebastian; Mian, Asima; Sykes, Jonathan M; Redka-Swoboda, Wolfgang; Ladinger, Andrea; Pavicic, Tatjana; Schenck, Thilo L; Benslimane, Fahd; Ingallina, Fabio; Schlattau, Alexander

    2017-04-01

    The forehead is one of the most frequent locations for neuromodulator and soft tissue filler applications; however, the underlying anatomy is still poorly understood. Thus far, the presence of deep forehead compartments has not been confirmed. Twenty Caucasian cephalic specimens, 15 fresh frozen (six female and nine male) and five with formalin-phenol embalmment (three female and two male) were investigated using contrast-enhanced computed tomographic scans, dye injections, and anatomical dissections. Three superficial (one central and two lateral) and three deep (one central and two lateral) forehead compartments were identified. The superficial fat compartments were found within the subcutaneous fat tissue (layer 2) and measured 2.1 × 4.6 mm for the superficial central forehead compartments and the right superficial lateral forehead compartments and 2.6 × 3.2 cm for the left superficial lateral forehead compartments, with a mean volume of 2.5, 3.1, and 3.4 cc, respectively. The deep fat compartments were identified deep to the frontalis muscle but superficial to the periosteum with an extent of 6.4 × 5.9 cm for the deep central forehead compartments, 2.6 × 5.8 cm for the right deep lateral forehead compartments, and 2.7 × 5.8 cm for the left deep lateral forehead compartments, and a mean volume of 9.1, 1.6, and 1.4 cc, respectively. The results presented in this study increase the understanding of the forehead anatomy. Understanding the presence of the superficial and the deep forehead compartments allows one to change the signs of frontal aging. The deep forehead compartments are in general avascular planes and permit blunt dissection for access to the supraorbital region.

  7. Temperature fields in a growing solar silicon crystal

    Directory of Open Access Journals (Sweden)

    Kondrik A. I.

    2012-06-01

    Full Text Available The optimal thermal terms for growing by Czochralski method Si single-crystals, suitable for making photoelectric energy converters, has been defined by the computer simulation method. Dependences of temperature fields character and crystallization front form on the diameter of the crystal, stage and speed of growing, and also on correlation between diameter and height of the crystal has been studied.

  8. An ignored variable: solution preparation temperature in protein crystallization.

    Science.gov (United States)

    Chen, Rui-Qing; Lu, Qin-Qin; Cheng, Qing-Di; Ao, Liang-Bo; Zhang, Chen-Yan; Hou, Hai; Liu, Yong-Ming; Li, Da-Wei; Yin, Da-Chuan

    2015-01-19

    Protein crystallization is affected by many parameters, among which certain parameters have not been well controlled. The temperature at which the protein and precipitant solutions are mixed (i.e., the ambient temperature during mixing) is such a parameter that is typically not well controlled and is often ignored. In this paper, we show that this temperature can influence protein crystallization. The experimental results showed that both higher and lower mixing temperatures can enhance the success of crystallization, which follows a parabolic curve with an increasing ambient temperature. This work illustrates that the crystallization solution preparation temperature is also an important parameter for protein crystallization. Uncontrolled or poorly controlled room temperature may yield poor reproducibility in protein crystallization.

  9. Temperature dependent spin structures in Hexaferrite crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chao, Y.C. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan (China); Lin, J.G., E-mail: jglin@ntu.edu.tw [Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan (China); Chun, S.H.; Kim, K.H. [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2016-01-01

    In this work, the Hexaferrite Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} (BSZFO) is studied due to its interesting characteristics of long-wavelength spin structure. Ferromagnetic resonance (FMR) is used to probe the magnetic states of BSZFO single crystal and its temperature dependence behavior is analyzed by decomposing the multiple lines of FMR spectra into various phases. Distinguished phase transition is observed at 110 K for one line, which is assigned to the ferro(ferri)-magnetic transition from non-collinear to collinear spin state. - Highlights: • For the first time Ferromagnetic Resonance is used to probe the local magnetic structure of Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22.} • The multiphases in the single crystal is identified, which provides important information toward its future application for the magnetoelectric devices.

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

    KAUST Repository

    Saidaminov, Makhsud I.

    2015-07-06

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

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

    Science.gov (United States)

    Saidaminov, Makhsud I.; Abdelhady, Ahmed L.; Murali, Banavoth; Alarousu, Erkki; Burlakov, Victor M.; Peng, Wei; Dursun, Ibrahim; Wang, Lingfei; He, Yao; Maculan, Giacomo; Goriely, Alain; Wu, Tom; Mohammed, Omar F.; Bakr, Osman M.

    2015-07-01

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

  12. Paramedian forehead flap thinning using a flexible razor blade.

    Science.gov (United States)

    Justiniano, Hilda; Edwards, Julia; Eisen, Daniel B

    2009-03-15

    Paramedian forehead flaps are sometimes required to resurface large or deep nasal defects. The flap often needs to be thinned to match the contour of the surrounding skin at the recipient site. We describe a technique to thin the distal potion of the paramedian forehead flap using a flexible razor blade, the Dermablade. Once familiar with it, this same technique may be applied to thin other interpolation flaps.

  13. Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Joanna Ptasinski

    2014-03-01

    Full Text Available In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths.

  14. High-Temperature Piezoelectric Crystals for Acoustic Wave Sensor Applications.

    Science.gov (United States)

    Zu, Hongfei; Wu, Huiyan; Wang, Qing-Ming

    2016-03-01

    In this review paper, nine different types of high-temperature piezoelectric crystals and their sensor applications are overviewed. The important materials' properties of these piezoelectric crystals including dielectric constant, elastic coefficients, piezoelectric coefficients, electromechanical coupling coefficients, and mechanical quality factor are discussed in detail. The determination methods of these physical properties are also presented. Moreover, the growth methods, structures, and properties of these piezoelectric crystals are summarized and compared. Of particular interest are langasite and oxyborate crystals, which exhibit no phase transitions prior to their melting points ∼ 1500 °C and possess high electrical resistivity, piezoelectric coefficients, and mechanical quality factor at ultrahigh temperature ( ∼ 1000 °C). Finally, some research results on surface acoustic wave (SAW) and bulk acoustic wave (BAW) sensors developed using this high-temperature piezoelectric crystals are discussed.

  15. Temperature dependence of crystal structure and digestibility of roasted diaspore

    Institute of Scientific and Technical Information of China (English)

    周秋生; 李小斌; 彭志宏; 刘桂华

    2004-01-01

    Through X-ray diffraction patterns and scanning electronic micrographs, temperature dependence of the crystal structure of roasted diasporic bauxite at different temperatures and the digestibility of roasting production were investigated systematically. The lattice parameters of unit cell for chemically purified diaspore and unequilibrium alumina-contained oxide obtained from the diaspore roasted at different temperatures were determined. It is found that, with roasting temperature increasing, the roasting production changes from the original dense and perfect diaspore crystal into imperfect corundum with many microcracks and small pores on its surface and then into perfect corundum with low digestibility. The optimum roasting temperature with best digestibility is approximately 525 ℃ when residence time is about 25 min. It is thought that the change of crystal structure, formation of microcracks and small pores in the temperature field are the main essential reasons for improving digestibility of diasporic bauxite and its roasting production.

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

    Science.gov (United States)

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

    2017-01-01

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

  17. Solid state crystal physics at very low temperatures

    Science.gov (United States)

    Davis, W.; Krack, K.; Richard, J. P.; Weber, J.

    1980-01-01

    The mechanical dissipation (Q) and resonant frequency of a 15 kg silicon crystal were measured at cryogenic temperatures. In the experiment described, temperature control was incorporated to reduce the time derivative of the temperature. The results of the Q measurements with and without this temperature control are quite different. Measurements of the resonant frequency of the fundamental longitudinal mode of the silicon crystal from 6 to 300 Kelvin are presented and discussed with respect to temperature, df/dT. It is observed that frequency increases as temperature decreases down to about 16 Kelvin, i.e. dt/dT is negative. However, below this temperature the frequency decreases as temperature decreases, i.e. dt/dT is positive. It is suggested that this behavior is related to the coefficient of thermal contraction of silicon, which changes sign at 18 Kelvin. Continuation of these experiments to 20 mK is discussed.

  18. Extended temperature dependence of elastic constants in cubic crystals.

    Science.gov (United States)

    Telichko, A V; Sorokin, B P

    2015-08-01

    To extend the theory of the temperature dependence of the elastic constants in cubic crystals beyond the second- and third-order elastic constants, the fourth-order elastic constants, as well as the non-linearity in the thermal expansion temperature dependence, have been taken into account. Theoretical results were represented as temperature functions of the effective elastic constants and compared with experimental data for a number of cubic crystals, such as alkali metal halides, and elements gold and silver. The relations obtained give a more accurate description of the experimental temperature dependences of second-order elastic constants for a number of cubic crystals, including deviations from linear behavior. A good agreement between theoretical estimates and experimental data has been observed.

  19. Temperature-mediated polymorphism in molecular crystals: The impact on crystal packing and charge transport

    KAUST Repository

    Stevens, Loah A.

    2015-01-13

    We report a novel synthesis to ultra high purity 7,14-bis((trimethylsilyl)ethynyl)dibenzo[b,def]-chrysene (TMS-DBC) and the use of this material in the growth of single crystals by solution and vapor deposition techniques. We observe that the substrate temperature has a dramatic impact on the crystal growth, producing two distinct polymorphs of TMS-DBC; low temperature (LT) fine red needles and high temperature (HT) large yellow platelets. Single crystal X-ray crystallography confirms packing structures where the LT crystals form a 1D slipped-stack structure, while the HT crystals adopt a 2D brickwork motif. These polymorphs also represent a rare example where both are extremely stable and do not interconvert to the other crystal structure upon solvent or thermal annealing. Single crystal organic field-effect transistors of the LT and HT crystals show that the HT 2D brickwork motif produces hole mobilities as high as 2.1 cm2 V-1 s-1, while the mobility of the 1D structure is significantly lower, at 0.028 cm2 V-1 s-1. Electronic-structure calculations indicate that the superior charge transport in the brickwork polymorph in comparison to the slipped-stack polymorph is due to the presence of an increased dimensionality of the charge migration pathways.

  20. Calorimetric Measurements at Low Temperatures in Toluene Glass and Crystal

    Science.gov (United States)

    Alvarez-Ney, C.; Labarga, J.; Moratalla, M.; Castilla, J. M.; Ramos, M. A.

    2017-04-01

    The specific heat of toluene in glass and crystal states has been measured both at low temperatures down to 1.8 K (using the thermal relaxation method) and in a wide temperature range up to the liquid state (using a quasiadiabatic continuous method). Our measurements therefore extend earlier published data to much lower temperatures, thereby allowing to explore the low-temperature "glassy anomalies" in the case of toluene. Surprisingly, no indication of the existence of tunneling states is found, at least within the temperature range studied. At moderate temperatures, our data either for the glass or for the crystal show good agreement with those found in the literature. Also, we have been able to prepare bulk samples of toluene glass by only doping with 2% mol ethanol instead of with higher impurity doses used by other authors.

  1. Unusual case of frontal mucocele presenting with forehead ulcer.

    Science.gov (United States)

    Altıntaş Kakşi, S; Kakşi, M; Balevi, A; Özdemir, M; Çakır, A

    2014-11-15

    Paranasal mucoceles are benign slow-growing paranasal sinus lesions, which usually develop following the obstruction of the sinus ostiu. They most frequently occur in the frontal sinus. Frontal mucoceles are expansive lesions usually causing visual clinical signs and symptoms such as diminution of vision, visual field defects, diplopia, orbital swelling, retroorbital pain, displacement of eye globe, ptosis, and proptosis. When the frontal mucocele extends intracranially, it can manifest with meningitis, meningoencephalitis, intracranial abscess, seizures, or cerebrospinal fluid fistula. Very rarely it can cause forehead swelling. We report an 80-year-old woman presenting with a forehead skin ulcer and painless subcutaneous forehead induration. Histopathologic examination revealed mucin deposition and inflammation. Computerized tomography (CT) and magnetic resonance imaging (MRI) scans showed a mass originating from the frontal sinus with frontal bony defect and frontocutaneous fistula. Surgical excision of the mass confirmed the mucocele diagnosis. In this article, we present a case of frontocutaneous fistula and skin ulcer, which is an unexpected complication of frontal mucocele. We propose that in the case of a localized non-healing ulcerated forehead skin lesions, mucocele should be considered in the differential diagnosis.

  2. Controlling protein crystal growth rate by means of temperature

    Energy Technology Data Exchange (ETDEWEB)

    SantamarIa-Holek, I; Gadomski, A [Institute of Mathematics and Physics, University of Technology and Life Sciences, PL-85796 Bydgoszcz (Poland); RubI, J M, E-mail: isholek.fc@gmail.com, E-mail: agad@utp.edu.pl, E-mail: mrubi@ub.edu [Departament de Fisica Fonamental, University of Barcelona, Av. Diagonal 647, E-08028 Barcelona (Spain)

    2011-06-15

    We have proposed a model to analyze the growth kinetics of lysozyme crystals/aggregates under non-isothermal conditions. The model was formulated through an analysis of the entropy production of the growth process which was obtained by taking into account the explicit dependence of the free energy on the temperature. We found that the growth process is coupled with temperature variations, resulting in a novel Soret-type effect. We identified the surface entropy of the crystal/aggregate as a decisive ingredient controlling the behavior of the average growth rate as a function of temperature. The behavior of the Gibbs free energy as a function of temperature is also analyzed. The agreement between theory and experiments is very good in the range of temperatures considered.

  3. Controlling protein crystal growth rate by means of temperature.

    Science.gov (United States)

    Sanamaría-Holek, I; Gadomski, A; Rubí, J M

    2011-06-15

    We have proposed a model to analyze the growth kinetics of lysozyme crystals/aggregates under non-isothermal conditions. The model was formulated through an analysis of the entropy production of the growth process which was obtained by taking into account the explicit dependence of the free energy on the temperature. We found that the growth process is coupled with temperature variations, resulting in a novel Soret-type effect. We identified the surface entropy of the crystal/aggregate as a decisive ingredient controlling the behavior of the average growth rate as a function of temperature. The behavior of the Gibbs free energy as a function of temperature is also analyzed. The agreement between theory and experiments is very good in the range of temperatures considered.

  4. Transitions through critical temperatures in nematic liquid crystals

    KAUST Repository

    Majumdar, Apala

    2013-08-06

    We obtain estimates for critical nematic liquid crystal (LC) temperatures under the action of a slowly varying temperature-dependent control variable. We show that biaxiality has a negligible effect within our model and that these delay estimates are well described by a purely uniaxial model. The static theory predicts two critical temperatures: the supercooling temperature below which the isotropic phase loses stability and the superheating temperature above which the ordered nematic states do not exist. In contrast to the static problem, the isotropic phase exhibits a memory effect below the supercooling temperature in the dynamic framework. This delayed loss of stability is independent of the rate of change of temperature and depends purely on the initial value of the temperature. We also show how our results can be used to improve estimates for LC material constants. © 2013 American Physical Society.

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

    Science.gov (United States)

    Barrientos, Alfonso

    1997-01-01

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

  6. Low-temperature Raman spectra of L-histidine crystal

    CERN Document Server

    De Sousa, G P; Filho, J Mendes; Melo, F E A; Lima, C L

    2013-01-01

    We present a Raman spectroscopy investigation of the vibrational properties of L-histidine crystals at low temperatures. The temperature dependence of the spectra show discontinuities at 165 K, which we identify with modifications in the bonds associated to both the NH3+ and CO2- motifs indicative of a conformational phase transition that changes the intermolecular bonds. Additional evidence of such a phase transition was provided by differential scanning calorimetry measurements, which identified an enthalpic anomaly at ~165 K.

  7. Crystal structures at high pressures and temperatures

    Science.gov (United States)

    Caldwell, Wendel Alexander

    2000-10-01

    The diamond anvil cell (DAC) is a unique instrument that can generate pressures equivalent to those inside planetary interiors (pressures on the order of 1 million atmospheres) under sustained conditions. When combined with a bright source of collimated x-rays, the DAC can be used to probe the structure of materials in-situ at ultra-high pressures. An understanding of the high-pressure structure of materials is important in determining what types of processes may take place in the Earth at great depths. Motivated by previous studies showing that xenon becomes metallic at pressures above ˜1 megabar (100 GPa), we examined the stable structures and reactivity of xenon at pressures approaching that of the core-mantle boundary in the Earth. Our findings indicate the transformation of xenon from face-centered cubic (fcc) to hexagonal close-packed (hcp) structures is kinetically hindered at room temperature, with the equilibrium fcc--hcp phase boundary at 21 (+/-3) gigapascals, a pressure lower than was previously thought. Additionally, we find no tendency on the part of xenon to form a metal alloy with iron or platinum to at least 100 to 150 gigapascals, making it unlikely that the Earth's core serves as a reservoir for primordial xenon. Measurements of the compressibility of natural (Mg.75,Fe .25)2SiO4 gamma-spinel at pressures of the Earth's transition zone yield a pressure derivative of the bulk modulus K0 ' = 6.3 (+/-0.3). As gamma-spinel is considered to be a dominant mineral phase of the transition-zone of the Earth's mantle (400--670 km depth), the relatively high value of K0' for gamma-spinel may help explain the rapid increase with depth of seismic velocities through the transition zone. The thermodynamics, mechanisms and kinetics of pressure-induced amorphization are not well understood. We report here new studies indicating little or no entropy difference between the crystalline and glassy states of Ca(OH) 2 (portlandite). Additional work on the pressure

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

    Science.gov (United States)

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

    1966-01-01

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

  9. Unusual Forehead Tremor in Four Patients with Essential Tremor

    Directory of Open Access Journals (Sweden)

    Jordi Gascón-Bayarri

    2012-01-01

    Full Text Available Forehead tremor has only been reported in two patients with essential tremor, one with rhythmic tremor and the other with dystonic tremor. We report 4 new patients with essential tremor who present a 4–6 Hz frontal tremor registered by electromyography and unusual features like frontal tremor preceding limb tremor or unilateral involvement. Frontal tremor is present in some patients with essential tremor, sometimes preceding limb tremor. Treatment with botulinum toxin may be useful.

  10. Comparison of High Temperature Crystal Lattice and Bulk Thermal Expansion Measurements of LGT Single Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Beaucage, Timothy R [University of Maine; Beenfeldt, Eric P [University of Maine; Speakman, Scott A [ORNL; Porter, Wallace D [ORNL; Payzant, E Andrew [ORNL; Pereira da Cunha, Mauricio [University of Maine

    2006-01-01

    Among the langasite family of crystals (LGX), the three most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their melting point above 1400degC. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25degC) to 1200degC. Two methods of extracting the thermal expansion coefficients have been used and compared: (a) dual push-rod dilatometry, which provides the bulk expansion; and (b) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from <001> Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25degC to 400degC, 400degC to 900degC, 900degC to 1200degC. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The

  11. Growth of EuO single crystals at reduced temperatures

    Science.gov (United States)

    Ramirez, Daniel C.; Besara, Tiglet; Whalen, Jeffrey B.; Siegrist, Theo

    2017-01-01

    Single crystals of (E u1 -xB ax)O have been grown in a molten barium-magnesium metal flux at temperatures up to 1000 °C, producing single crystals of (E u1 -xB ax)O with barium doping levels ranging from x =0.03 to x =0.25 . Magnetic measurements show that the ferromagnetic Curie temperature TC correlates with the Ba doping levels, and a modified Heisenberg model was used to describe the stoichiometry dependence of TC. Extrapolation of the results indicates that a sample with Ba concentration of x =0.72 should have a TC of 0 K, potentially producing a quantum phase transition in this material.

  12. Treating temperature effect on bandgap in polymer opal photonic crystals

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The optical reflective spectra and microstruc- tures of polystyrene opal photonic crystals treated with dif- ferent temperatures have been investigated. With tempera- ture increasing, the polystyrene spheres in opal structure transform to dodecahedrons, and the peak of reflective spec- trum moves to shorter wavelength. The experiment result testifies the effect of the effective refractive index and the filling ratio to the bandgap position, and it corresponds to the theoretical simulative result.

  13. Efficient low-temperature thermophotovoltaic emitters from metallic photonic crystals.

    Science.gov (United States)

    Nagpal, Prashant; Han, Sang Eon; Stein, Andreas; Norris, David J

    2008-10-01

    We examine the use of metallic photonic crystals as thermophotovoltaic emitters. We coat silica woodpile structures, created using direct laser writing, with tungsten or molybdenum. Optical reflectivity and thermal emission measurements near 650 degrees C demonstrate that the resulting structures should provide efficient emitters at relatively low temperatures. When matched to InGaAsSb photocells, our structures should generate over ten times more power than solid emitters while having an optical-to-electrical conversion efficiency above 32%. At such low temperatures, these emitters have promise not only in solar energy but also in harnessing geothermal and industrial waste heat.

  14. Yawning as a Brain Cooling Mechanism: Nasal Breathing and Forehead Cooling Diminish the Incidence of Contagious Yawning

    Directory of Open Access Journals (Sweden)

    Andrew C. Gallup

    2007-01-01

    Full Text Available We conducted two experiments that implicate yawning as a thermoregulatory mechanism. The first experiment demonstrates that different patterns of breathing influence susceptibility to contagious yawning. When participants were not directed how to breathe or were instructed to breathe orally (inhaling and exhaling through their mouth, the incidence of contagious yawning in response to seeing videotapes of people yawning was about 48%. When instructed to breathe nasally (inhaling and exhaling through their nose, no participants exhibited contagious yawning. In a second experiment, applying temperature packs to the forehead also influenced the incidence of contagious yawning. When participants held a warm pack (460C or a pack at room temperature to their forehead while watching people yawn, contagious yawning occurred 41% of the time. When participants held a cold pack (40C to their forehead, contagious yawning dropped to 9%. These findings suggest that yawning has an adaptive/functional component that it is not merely the derivative of selection for other forms of behavior.

  15. Low-Temperature Kinetics and Dynamics with Coulomb Crystals

    Science.gov (United States)

    Heazlewood, Brianna R.; Softley, Timothy P.

    2015-04-01

    Coulomb crystals-as a source of translationally cold, highly localized ions-are being increasingly utilized in the investigation of ion-molecule reaction dynamics in the cold regime. To develop a fundamental understanding of ion-molecule reactions, and to challenge existing models that describe the rates, product branching ratios, and temperature dependence of such processes, investigators need to exercise full control over the experimental reaction parameters. This requires not only state selection of the reactants, but also control over the collision process (e.g., the collisional energy and angular momentum) and state-selective product detection. The combination of Coulomb crystals in ion traps with cold neutral-molecule sources is enabling the measurement of state-selective reaction rates in a diverse range of systems. With the development of appropriate product detection techniques, we are moving toward the ultimate goal of examining low-energy, state-to-state ion-molecule reaction dynamics.

  16. Low temperature properties of pnictide CrAs single crystal

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    High quality single crystal CrAs was grown by Sn flux method.The results of magnetic susceptibility and electrical resistivity are reported in a temperature range of 2 to 800 K.At low temperatures,a T2 dependence of resistivity is observed showing a Fermi-liquid behavior.The Kadowaki-Woods ratio is found to be 1×10-5 μΩ cm mol2 K2 mJ-2,which fits well to the universal value for many correlated electron systems.At about 270 K,a clear magnetic transition is observed with sharp changes of resistivity and susceptibility.Above 270 K,a linear-temperature dependence of the magnetic susceptibility is observed up to 700 K,which resembles the T-dependent magnetic susceptibility of parents of iron-pnictides superconductors.

  17. Temperature dependence of pulse-induced mechanoluminescence excitation in coloured alkali halide crystals

    Indian Academy of Sciences (India)

    Namita Rajput; S Tiwari; B P Chandra

    2004-12-01

    In practice, the relative efficiencies of different crystals are often determined under identical conditions of temperature and excitation. If the temperature of a crystal is increased or decreased with respect to room temperature, luminescence efficiency may get increased or decreased according to the composition of the crystal. When coloured crystals of NaCl, NaBr, KCl and KBr are excited by pulse-induced excitation at different temperatures, the mechanoluminescence (ML) intensity increases with temperature. The ML intensity of first peak, ml, second peak, _m2 and the total ML intensity, T, initially increase with temperature and then tend to attain an optimum value for a particular temperature of crystals. The ratio, m2/ml, is found to increase with increasing temperature of the crystals. The expression derived on the basis of rate equations, are able to explain the temperature dependence of ML intensity on several parameters.

  18. Vibrational relaxation and vibrational cooling in low temperature molecular crystals

    Science.gov (United States)

    Hill, Jeffrey R.; Chronister, Eric L.; Chang, Ta-Chau; Kim, Hackjin; Postlewaite, Jay C.; Dlott, Dana D.

    1988-01-01

    The processes of vibrational relaxation (VR) and vibrational cooling (VC) are investigated in low temperature crystals of complex molecules, specifically benzene, naphthalene, anthracene, and durene. In the VR process, a vibration is deexcited, while VC consists of many sequential and parallel VR steps which return the crystal to thermal equilibrium. A theoretical model is developed which relates the VR rate to the excess vibrational energy, the molecular structure, and the crystal structure. Specific relations are derived for the vibrational lifetime T1 in each of three regimes of excess vibrational energy. The regimes are the following: Low frequency regime I where VR occurs by emission of two phonons, intermediate frequency regime II where VR occurs by emission of one phonon and one vibration, and high frequency regime III where VR occurs by evolution into a dense bath of vibrational combinations. The VR rate in each regime depends on a particular multiphonon density of states and a few averaged anharmonic coefficients. The appropriate densities of states are calculated from spectroscopic data, and together with available VR data and new infrared and ps Raman data, the values of the anharmonic coefficients are determined for each material. The relationship between these parameters and the material properties is discussed. We then describe VC in a master equation formalism. The transition rate matrix for naphthalene is found using the empirically determined parameters of the above model, and the time dependent redistribution in each mode is calculated.

  19. Crystallization in Earth's Core after High-Temperature Core Formation

    Science.gov (United States)

    Hirose, K.; Morard, G.; Hernlund, J. W.; Helffrich, G. R.; Ozawa, H.

    2015-12-01

    Recent core formation models based on the metal-silicate partitioning of siderophile elements suggest that the Earth's core was formed by metal segregation at high pressure and high temperature in a deep magma ocean. It is also thought that the simultaneous solubility of silicon and oxygen in liquid iron are strongly enhanced at high pressure and high temperature, such that at the end of accretion the core was rich in both silicon and oxygen. Here we performed crystallization experiments on the Fe-Si binary and Fe-Si-O ternary systems up to core pressure in a laser-heated diamond-anvil cell. The starting material for the latter was a homogeneous mixture of fine-grain Fe-Si and SiO2 (sustain without extreme degrees of secular cooling. However, even for modest degrees of joint Si-O incorporation into the early core, the buoyancy released by crystallization of SiO2 is sufficient to overcome thermal stratification and sustain the geodynamo.

  20. Er:YAG crystal temperature influence on laser output characteristics

    Science.gov (United States)

    Němec, Michal; Å ulc, Jan; Hubka, Zbyněk.; Hlinomaz, Kryštof; Jelínková, Helena

    2017-02-01

    The main goal of this work was to investigate the influence of the temperature of the Er:YAG active medium on laser properties in eye-safe spectral region for three various pump wavelengths. The tested Er:YAG sample doped by 0.5% of Er3+ ions had a cylindrical shape with 25mm in length and 5mm in diameter. The absorption spectrum of the Er:YAG active medium in the range from 1400nm up to 1700nm for temperatures 80K and 300K was measured. The crystal was placed inside the vacuum chamber of a liquid nitrogen cooled cryostat. The temperature was controlled within the 80 - 340K temperature range. Three pump sources generating at 1535, 1452, and 1467nm were applied. The first one was flash lamp pumped Er:glass laser (repetition rate 0.5 Hz, pulse duration 1 ms, pulse energy 148 mJ). The further two sources were fiber coupled laser diodes (repetition rate 10 Hz, pulse duration 10 ms, maximum pulse energies 106mJ and 195 mJ). The semi-hemispherical laser resonator consisted of a pump curved mirror and output plan coupler with a reflectivity of 90% @ 1645 nm. The laser output characteristics were investigated in dependence on temperature of active medium for three laser pumping systems. The output energy has an optimum in dependence on active medium temperature and pump wavelengths. The maximal generated laser energies were 16.2mJ (90 K), 28.7mJ (120 K), and 33.2mJ (220 K), for pump wavelengths 1452 nm, 1467 nm, and 1535 nm, respectively.

  1. Nocardia nova mycetoma over forehead in a lepromatous leprosy patient.

    Science.gov (United States)

    Dhingra, M; Kaistha, N; Bansal, N; Solanki, L S; Chander, J; Thami, G P; van de Sande, W W

    2012-07-15

    We present a case of a 31-year-old male, a known patient with lepromatous leprosy with a type 2 lepra reaction, who presented with a slowly growing asymptomatic swelling with multiple discharging sinuses over the forehead that developed over 6 months. Smears of the serosanguinous discharge on Gram staining showed Gram-positive branching filamentous bacilli, which on culture on blood agar showed chalky-white colonies. Histology of the lesion showed suppurative granulomas with polymorphs surrounding characteristic grains. The isolate was identified as Nocardia nova by gene sequencing and the patient was started on combined antibiotic therapy that resulted in complete resolution of the infection in six months. To the best of our knowledge, this is the first report of mycetoma related to Nocardia nova in association with leprosy.

  2. Dural arteriovenous fistulae after forehead knife-cut injury

    Institute of Scientific and Technical Information of China (English)

    朱刚; 陈志; 冯华

    2004-01-01

    @@ Dural arteriovenous fistulae (DAVF) is a rare intracranial vascular disease. It is pathologically characterized by direct shunting of the intracranial artery and vein, which results in cerebral ischemia, intracranial hemorrhage, neural deficit and intracranial murmur. The etiological mechanism of DAVF is not well known, but most researchers think it is associated with congenital abnormal development, especially abnormal development of dural blood vessels at the stage of embryogenesis. Recently, some researchers have found that DAVF is also associated with some acquired factors. This article reports a case who developed DAVF within 2 years after debridement of frontal bone fragmentation, depressed fracture, left frontal lobe contusion and superior sagittal sinus injury due to forehead knife-cut injury. The pathogenic mechanism was explored through a review of the related literatures.

  3. Mucormycosis of the Forehead and Sinuses in a Trauma Patient

    Science.gov (United States)

    Lee, Nathan; Kimbrough, Mary K.

    2016-01-01

    Summary: Mucormycosis is a rare fungal infection in immunocompetent patients. It is not commonly seen in trauma patients who sustain multisystem injuries and are often exposed to numerous infectious sources. A multidisciplinary approach between medical and surgical specialties is crucial to ensuring timely diagnosis and treatment as morbidity and mortality can be high once acquired. In addition to antifungal therapy, radical debridement and reconstruction by plastic surgery is often necessary. Review of the literature shows that there is no definitive reconstructive technique for mucormycosis of the forehead and sinuses because the amount of tissue destruction may be varied in location and depth, therefore requiring varying extents of debridement. However, other reconstructive techniques commonly used for oncologic and trauma reconstructions can be used to achieve functionality and a satisfactory cosmetic result. Few facial reconstructions after infection with mucormycosis have been documented in the literature. PMID:27536497

  4. Mucormycosis of the Forehead and Sinuses in a Trauma Patient.

    Science.gov (United States)

    Kumbla, Pallavi A; Lee, Nathan; Kimbrough, Mary K

    2016-07-01

    Mucormycosis is a rare fungal infection in immunocompetent patients. It is not commonly seen in trauma patients who sustain multisystem injuries and are often exposed to numerous infectious sources. A multidisciplinary approach between medical and surgical specialties is crucial to ensuring timely diagnosis and treatment as morbidity and mortality can be high once acquired. In addition to antifungal therapy, radical debridement and reconstruction by plastic surgery is often necessary. Review of the literature shows that there is no definitive reconstructive technique for mucormycosis of the forehead and sinuses because the amount of tissue destruction may be varied in location and depth, therefore requiring varying extents of debridement. However, other reconstructive techniques commonly used for oncologic and trauma reconstructions can be used to achieve functionality and a satisfactory cosmetic result. Few facial reconstructions after infection with mucormycosis have been documented in the literature.

  5. Molecular Weight and Crystallization Temperature Effects on Poly(ethylene terephthalate (PET Homopolymers, an Isothermal Crystallization Analysis

    Directory of Open Access Journals (Sweden)

    Leonardo A. Baldenegro-Perez

    2014-02-01

    Full Text Available The isothermal crystallization of poly(ethylene terephthalate (PET homopolymers with different molecular weight was studied in a wide temperature range (140–230 °C using different experimental techniques. Three different morphological regions, labeled r1, r2 and r3, were distinguished as a function of crystallization temperature (Tc. In r1 (low Tc crystallized samples were characterized by a low crystalline degree with a small spherulite texture containing thin crystals. In r2 (intermediate Tc samples showed medium size spherulites composed of two distinct crystalline families (thin and thick crystals. In this temperature range, the crystallization exhibited a maximum value and it was associated with a high content of secondary crystals. In r3 (high Tc, samples presented considerable amorphous zones and regions consisting of oversized spherulites containing only thick crystals. Time-resolved wide-angle X-ray diffraction measurements, using synchrotron radiation, indicated a rapid evolution of the crystalline degree within the second region, in contrast with the quite slow evolution observed in the third region. On the other hand, by small-angle X-ray scattering (SAXS and time-resolved SAXS experiment, it was found that the long period (L as well as the lamellar thickness (lc increase as a function of Tc, corroborating the formation of the thickest crystals in the third region. From all these observations, a morphological model was proposed for each region.

  6. Simulation of the temperature distribution in crystals grown by Czochralski method

    Science.gov (United States)

    Dudokovic, M. P.; Ramachandran, P. A.

    1985-01-01

    Production of perfect crystals, free of residual strain and dislocations and with prescribed dopant concentration, by the Czochralski method is possible only if the complex, interacting phenomena that affect crystal growth in a Cz-puller are fully understood and quantified. Natural and forced convection in the melt, thermocapillary effect and heat transfer in and around the crystal affect its growth rate, the shape of the crystal-melt interface and the temperature gradients in the crystal. The heat transfer problem in the crystal and between the crystal and all other surfaces present in the crystal pulling apparatus are discussed at length. A simulation and computer algorithm are used, based on the following assumptions: (1) only conduction occurs in the crystal (experimentally determined conductivity as a function of temperature is used), (2) melt temperature and the melt-crystal heat transfer coefficient are available (either as constant values or functions of radial position), (3) pseudo-steady state is achieved with respect to temperature gradients, (4) crystal radius is fixed, and (5) both direct and reflected radiation exchange occurs among all surfaces at various temperatures in the crystal puller enclosure.

  7. In situ co-crystallisation as a tool for low-temperature crystal engineering

    DEFF Research Database (Denmark)

    Bond, Andrew D

    2003-01-01

    Synthesis and single-crystal X-ray diffraction of a series of low-melting co-crystals of pyrazine and n-alkyl carboxylic acids demonstrates in situ co-crystallisation as a versatile tool for low-temperature crystal engineering....

  8. Room Temperature Operation of a Buried Heterostructure Photonic Crystal Quantum Cascade Laser

    CERN Document Server

    Peretti, R; Wolf, J M; Bonzon, C; Süess, M J; Lourdudoss, S; Metaferia, W; Beck, M; Faist, J

    2015-01-01

    We demonstrated room temperature operation of deep etched photonic crystal quantum cascade laser emitting around 8.5 micron. We fabricated buried heterostructure photonic crystals, resulting in single mode laser emission on a high order slow Bloch modes of the photonic crystal, between high symmetry points of the Brillouin.

  9. Architecture of the sperm whale forehead facilitates ramming combat

    Directory of Open Access Journals (Sweden)

    Olga Panagiotopoulou

    2016-04-01

    Full Text Available Herman Melville’s novel Moby Dick was inspired by historical instances in which large sperm whales (Physeter macrocephalus L. sank 19th century whaling ships by ramming them with their foreheads. The immense forehead of sperm whales is possibly the largest, and one of the strangest, anatomical structures in the animal kingdom. It contains two large oil-filled compartments, known as the “spermaceti organ” and “junk,” that constitute up to one-quarter of body mass and extend one-third of the total length of the whale. Recognized as playing an important role in echolocation, previous studies have also attributed the complex structural configuration of the spermaceti organ and junk to acoustic sexual selection, acoustic prey debilitation, buoyancy control, and aggressive ramming. Of these additional suggested functions, ramming remains the most controversial, and the potential mechanical roles of the structural components of the spermaceti organ and junk in ramming remain untested. Here we explore the aggressive ramming hypothesis using a novel combination of structural engineering principles and probabilistic simulation to determine if the unique structure of the junk significantly reduces stress in the skull during quasi-static impact. Our analyses indicate that the connective tissue partitions in the junk reduce von Mises stresses across the skull and that the load-redistribution functionality of the former is insensitive to moderate variation in tissue material parameters, the thickness of the partitions, and variations in the location and angle of the applied load. Absence of the connective tissue partitions increases skull stresses, particularly in the rostral aspect of the upper jaw, further hinting of the important role the architecture of the junk may play in ramming events. Our study also found that impact loads on the spermaceti organ generate lower skull stresses than an impact on the junk. Nevertheless, whilst an impact on the

  10. Paramedian forehead flap combined with hinge flap for nasal tip reconstruction*

    Science.gov (United States)

    Cerci, Felipe Bochnia; Dellatorre, Gerson

    2016-01-01

    The paramedian forehead flap is a great option for restoration of complex nasal defects. For full-thickness defects, it may be used alone or in combination with other methods. We present a patient with a basal cell carcinoma on the distal nose treated by Mohs micrographic surgery, and a resulting full-thickness defect repaired with paramedian forehead flap combined with a hinge flap. For optimal results with the paramedian forehead flap, adequate surgical planning, patient orientation and meticulous surgical technique are imperative.

  11. Stimulated Globular Scattering of Laser Radiation in Photonic Crystals: Temperature Dependences

    CERN Document Server

    Gorelik, V S; Tcherniega, N V; Vodchits, A I

    2007-01-01

    Stimulated globular scattering (SGS) characteristics (frequency shifts, threshold, conversion efficiency) have been studied in photonic crystals (synthetic opal matrices and opal nanocomposites) at different temperatures. Results have been compared with stimulated Raman scattering investigations in calcite single crystals. In both cases temperature lowering from +20 C to -196 C resulted in the stimulated scattering energy increase and its redistribution to the higher order components.

  12. Physicochemical principles of high-temperature crystallization and single crystal growth methods

    Science.gov (United States)

    Bagdasarov, Kh. S.

    The mechanisms of crystal growth are reviewed, with attention given to the physicochemical reactions taking place in the melt near the phase boundary; phenomena determining physical and chemical kinetics directly at the growth front; solid-phase processes occurring within the crystal. Methods for growing refractory single crystals are discussed with particular reference to the Verneuil method, zone melting, Czhochralskii growth, horizontal directional solidification, and the Stockbarger method. Methods for growing crystals of complex geometrical shapes are also discussed.

  13. Usage of a rotational flap for coverage of a large central forehead defect

    Science.gov (United States)

    El-Sabbagh, Ahmed Hassan

    2017-01-01

    Background: The forehead is a donor site for facial reconstruction but has no generous donor site for its coverage. All options of the reconstructive ladder can be used. A large rotation flap was used to reconstruct a big central forehead defect following failed previous repair in an elderly diabetic patient after a motor car accident. Case presentation: A 64-year-old diabetic man presented with an extensive central forehead defect after failed previous repair following a motor car accident. Coverage of the defect was performed using a flap based around the ear on one side in a rotation movement. An accepted functional and esthetic result was achieved after 3 months of follow-up. Conclusion: A rotation flap based on arteries around the ear can be used for coverage of a difficult lesion in the central forehead. Level of evidence: Level V, therapeutic study PMID:28194323

  14. Usage of a rotational flap for coverage of a large central forehead defect

    Directory of Open Access Journals (Sweden)

    El-Sabbagh, Ahmed Hassan

    2017-02-01

    Full Text Available Background: The forehead is a donor site for facial reconstruction but has no generous donor site for its coverage. All options of the reconstructive ladder can be used. A large rotation flap was used to reconstruct a big central forehead defect following failed previous repair in an elderly diabetic patient after a motor car accident. Case presentation: A 64-year-old diabetic man presented with an extensive central forehead defect after failed previous repair following a motor car accident. Coverage of the defect was performed using a flap based around the ear on one side in a rotation movement. An accepted functional and esthetic result was achieved after 3 months of Conclusion: A rotation flap based on arteries around the ear can be used for coverage of a difficult lesion in the central forehead. Level of evidence: Level V, therapeutic study

  15. Time lapse microscopy of temperature control during self-assembly of 3D DNA crystals

    Science.gov (United States)

    Conn, Fiona W.; Jong, Michael Alexander; Tan, Andre; Tseng, Robert; Park, Eunice; Ohayon, Yoel P.; Sha, Ruojie; Mao, Chengde; Seeman, Nadrian C.

    2017-10-01

    DNA nanostructures are created by exploiting the high fidelity base-pairing interactions of double-stranded branched DNA molecules. These structures present a convenient medium for the self-assembly of macroscopic 3D crystals. In some self-assemblies in this system, crystals can be formed by lowering the temperature, and they can be dissolved by raising it. The ability to monitor the formation and melting of these crystals yields information that can be used to monitor crystal formation and growth. Here, we describe the development of an inexpensive tool that enables direct observation of the crystal growth process as a function of both time and temperature. Using the hanging-drop crystallization of the well-characterized 2-turn DNA tensegrity triangle motif for our model system, its response to temperature has been characterized visually.

  16. Liquid crystal thermography. A method for monitoring temperature gradients in microtitration plates.

    Science.gov (United States)

    Oliver, D G; Sanders, A H; Jang, L; Poy, D; Van Heuvelen, A

    1983-03-11

    Precise quantitative heat transfer information in microtitration plates can be obtained by filling the wells of a microtitration plate with cholesteric liquid crystals and incubating the plates at the desired temperature in different incubators. The liquid crystals indicate temperature by changes in discrete reproducible colors over various temperature ranges. With these instrumented plates, interwell thermal gradients may be documented visually and are in close agreement with results obtained by using wire thermocouple measuring techniques.

  17. High-temperature vesuvianite: crystal chemistry and surface considerations

    Science.gov (United States)

    Elmi, Chiara; Brigatti, Maria Franca; Pasquali, Luca; Montecchi, Monica; Laurora, Angela; Malferrari, Daniele; Nannarone, Stefano

    2011-06-01

    A multi-methodical approach has been applied for characterizing the bulk and surface crystal chemical features of a high-temperature vesuvianite crystal from skarns of Mount Somma-Vesuvius Volcano (Naples, Italy). Vesuvianite belongs to the space group P4/ nnc with unit cell parameters a = 15.633(1) Å, c = 11.834(1) Å and chemical formula (Ca18.858 Na0.028 Ba0.004 K0.006 Sr0.005 □0.098)19.000 (Al8.813 Ti0.037 Mg2.954 Mn0.008 Fe{0.114/2+} Fe{1.375/3+} Cr0.008 B0.202)13.511 Si18.000(O0.261 F0.940 OH7.799)9.000. Structure refinement, which converges at R = 0.0328, demonstrates a strong positional disorder down the fourfold axes, indicating that the Y1 site is split into two positions (Y1A and Y1B) alternatively occupied. However, because of X4 proximity to Y1B and Y1A, X4 cannot be occupied if Y1B or Y1A are. Overall Y1 occupancy (Y1A + Y1B) reaches approximately 0.5, as common in vesuvianite and occupancy of Y1B site is extremely limited. Moreover, T1 position, limitedly occupied, accommodates the excess of cations generally related to Y position. A small quantity (0.202 apfu) of boron is sited at the T2 site that, like T1, is poorly occupied. The determination of the amount of each element on the (100) vesuvianite surface, obtained through X-ray photoelectron spectroscopy high-resolution spectra in the region of the Si2p, Al2p, Mg1s, and Ca2p core levels, evidences that a greater amount of aluminum and a smaller amount of calcium characterize the surface with respect to the bulk. Although both of these features require further investigation, we may consider the Al increase can be related to preferential orientation of Al-rich sites on the (100) plane. Furthermore, the surface structure of vesuvianite suggests that Al, Ca, and Mg cations maintain coordination features at the surface similar to the bulk. Silica, however, while presenting fourfold coordination, shows also a [1]-fold small coordinated component at binding energy 99.85 eV, due to broken Si-O bonds at

  18. Local Refractive Index Measurements at Low Temperatures using Photonic Crystal Cavities

    CERN Document Server

    Wolters, Janik; Schoengen, Max; Schell, Andreas W; Probst, Jürgen; Löchel, Bernd; Benson, Oliver

    2012-01-01

    Photonic crystal cavities have a wide range of applications in physics today. Here we demonstrate a method to use the narrow resonances of photonic crystal cavities to measure the temperature dependence of the refractive index of gallium phosphide in a temperature range between 5 K and near room temperature at a wavelength of about 605 nm. On one hand, this is an essential step for the design of GaP photonic crystal structures for quantum technology applications. On the other hand, this demonstrates how photonic structures can be utilized to locally determine the optical properties of semiconductor materials in attoliter volumina.

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

    Science.gov (United States)

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

    1995-12-01

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

  20. Large single crystal growth of MnWO4-type materials from high-temperature solutions

    Science.gov (United States)

    Gattermann, U.; Röska, B.; Paulmann, C.; Park, S.-H.

    2016-11-01

    A simple high-temperature growth apparatus was constructed to obtain large crystals of chemically gradient (In, Na)-doped MnWO4solid-solutions. This paper presents the crystal growth and characterisation of both MnWO4and epitaxially grown (In, Na): MnWO4crystals on MnWO4. These large monolithic crystals were made in two steps: A MnWO4 crystal was grown in the crystallographic main direction [001] applying the Czochralski method, followed by the top seeded growth of (In, Na): MnWO4 solid-solutions with an oriented seed crystal of MnWO4. Such a monolithic crystal will serve to fundamental investigation of coupling properties at boundaries between various multiferroic MnWO4-typesolid-solutions.

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

    OpenAIRE

    Saidaminov, Makhsud I.; Abdelhady, Ahmed L.; Murali, Banavoth; Alarousu, Erkki; Burlakov, Victor M.; Peng, Wei; Dursun, Ibrahim; Wang, Lingfei; He, Yao; Maculan, Giacomo; Goriely, Alain; Wu, Tom; Mohammed, Omar F.; Bakr, Osman M.

    2015-01-01

    Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3 +, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at e...

  2. Boron Arsenide and Boron Phosphide for High Temperature and Luminescent Devices. [semiconductor devices - crystal growth/crystal structure

    Science.gov (United States)

    Chu, T. L.

    1975-01-01

    The crystal growth of boron arsenide and boron phosphide in the form of bulk crystals and epitaxial layers on suitable substrates is discussed. The physical, chemical, and electrical properties of the crystals and epitaxial layers are examined. Bulk crystals of boron arsenide were prepared by the chemical transport technique, and their carrier concentration and Hall mobility were measured. The growth of boron arsenide crystals from high temperature solutions was attempted without success. Bulk crystals of boron phosphide were also prepared by chemical transport and solution growth techniques. Techniques required for the fabrication of boron phosphide devices such as junction shaping, diffusion, and contact formation were investigated. Alloying techniques were developed for the formation of low-resistance ohmic contacts to boron phosphide. Four types of boron phosphide devices were fabricated: (1) metal-insulator-boron phosphide structures, (2) Schottky barriers; (3) boron phosphide-silicon carbide heterojunctions; and (4) p-n homojunctions. Easily visible red electroluminescence was observed from both epitaxial and solution grown p-n junctions.

  3. Temperature and thermal stress evolutions in sapphire crystal during the cooling process by heat exchanger method

    Science.gov (United States)

    Ma, Wencheng; Zhao, Wenhan; Wu, Ming; Ding, Guoqiang; Liu, Lijun

    2017-09-01

    Transient numerical calculations were carried out to predict the evolutions of temperature and thermal stress in sapphire single crystal during the cooling process by heat exchanger method (HEM). Internal radiation in the semitransparent sapphire crystal was taken into account using the finite volume method (FVM) in the global heat transfer model. The numerical results seem to indicate that the narrow bottom region of the sapphire crystal is subjected to high thermal stress during the cooling process, which could be responsible for the seed cracking of the as-grown crystal, while the thermal stress is relatively small in the central main body of the crystal, and is less than 10 MPa during the whole cooling process. The fast decrease of the thermal stress in the bottom region of the crystal during the initial stage of cooling process is dominated by the reduction of the cooling helium gas in the heat exchanger shaft, and is not significantly affected by the heating power reduction rate.

  4. Thermodynamic Analysis Of Pure And Impurity Doped Pentaerythritol Tetranitrate Crystals Grown At Room Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Pitchimani, R; Zheng, W; Simon, S; Hope-Weeks, L; Burnham, A K; Weeks, B L

    2006-05-25

    Pentaerythritol tetranitrate (PETN) powders are used to initiate other explosives. During long-term storage, changes in powder properties can cause changes in the initiation performance. Changes in the morphology and surface area of aging powders are observed due to sublimation and growth of PETN crystals through coarsening mechanisms, (e.g. Ostwald ripening, sintering, etc.). In order to alleviate the sublimation of PETN crystals under service conditions, stabilization methods such as thermal cycling and doping with certain impurities during or after the crystallization of PETN have been proposed. In this report we present our work on the effect of impurities on the morphology and activation energy of the PETN crystals. The pure and impurity doped crystals of PETN were grown from supersaturated acetone solution by solvent evaporation technique at room temperature. The difference in the morphology of the impurity-doped PETN crystal compared to pure crystal was examined by optical microscopy. The changes in the activation energies and the evaporation rates are determined by thermogravimetric (TGA) analyses. Our activation energies of evaporation agree with earlier reported enthalpies of vaporization. The morphology and activation energy of PETN crystals doped with Ca, Na, and Fe cations are similar to that for pure PETN crystal, whereas the Zn-ion-doped PETN crystals have different morphology and decreased activation energy.

  5. Influence of dissolved CO2 on crystallization of epsomite - variation of temperature

    Science.gov (United States)

    Huang, J.; Yin, Q.; Ulrich, J.

    2017-07-01

    Despite the minor amounts of gases dissolved in solutions, they can bring effects on many crystallization systems, which should be regarded as one type of ;invisible; impurity. The evidence of the effect of different dissolved gases on crystallization was provided in previous work. The variation of temperature was taken into consideration in this study. CO2 saturated solutions were prepared and air saturated solutions were used as a comparison. The results indicate that the influence of dissolved CO2 on crystallization of epsomite is altered with the variation of temperature. At low temperature, dissolved CO2 tends to suppress the thermodynamics and kinetic aspects of the solutions. With the increase of temperature the trend is reversed, i.e. at high temperature (>30 °C), dissolved CO2 enhances the relating properties of the solutions. At low temperature, the decrease of the pH value could be the dominating factor. Whereas at high temperature when the dissolved CO2 is in a supersaturated state, it starts to nucleate and grow, and partially changes into nano- or microbubbles, which can attach on crystal surfaces and disturb the crystallization process just as impurities do.

  6. Limit growth of ice crystals under different temperature oscillations levels in nile Tilapia

    Directory of Open Access Journals (Sweden)

    Mirko Salomon Chávez GUTIÉRREZ

    Full Text Available Abstract The degenerative effect of temperature fluctuations during storage time is a critical condition that needs to be quantitatively characterized in products where drip losses are appreciable. In this work, real storage conditions were reproduced using freezers modified to cause 3 levels of temperature fluctuation (± 0, ± 3, ± 5; ± 7 during storage of Tilapia (Oreochromis sp, at temperature of –18 °C. The fast frozen tilapia muscle (freezing cabinet was chosen to quantify the growth of ice crystals according to temperature fluctuations. The identification of crystals in the optical microscope as well as histological treatments and measurements using specific software has shown that the growth of ice crystals in the first days of storage follows an asymptote, whose final value is conditioned only by the level of temperature fluctuations regardless of initial diameter, which begins storage. It has also been found that the growth of crystals formed during rapid freezing rapidly develops according to temperature fluctuations to which the product has been subjected. This work also identified statistically significant differences in the equivalent diameter of crystals formed at the four proposed levels of temperature fluctuation with significance level of p < 0.05.

  7. Extracting the temperature distribution on a phase-change memory cell during crystallization

    Science.gov (United States)

    Bakan, Gokhan; Gerislioglu, Burak; Dirisaglik, Faruk; Jurado, Zoila; Sullivan, Lindsay; Dana, Aykutlu; Lam, Chung; Gokirmak, Ali; Silva, Helena

    2016-10-01

    Phase-change memory (PCM) devices are enabled by amorphization- and crystallization-induced changes in the devices' electrical resistances. Amorphization is achieved by melting and quenching the active volume using short duration electrical pulses (˜ns). The crystallization (set) pulse duration, however, is much longer and depends on the cell temperature reached during the pulse. Hence, the temperature-dependent crystallization process of the phase-change materials at the device level has to be well characterized to achieve fast PCM operations. A main challenge is determining the cell temperature during crystallization. Here, we report extraction of the temperature distribution on a lateral PCM cell during a set pulse using measured voltage-current characteristics and thermal modelling. The effect of the thermal properties of materials on the extracted cell temperature is also studied, and a better cell design is proposed for more accurate temperature extraction. The demonstrated study provides promising results for characterization of the temperature-dependent crystallization process within a cell.

  8. Three-dimensional self-assembled photonic crystals with high temperature stability for thermal emission modification

    Science.gov (United States)

    Arpin, Kevin A.; Losego, Mark D.; Cloud, Andrew N.; Ning, Hailong; Mallek, Justin; Sergeant, Nicholas P.; Zhu, Linxiao; Yu, Zongfu; Kalanyan, Berç; Parsons, Gregory N.; Girolami, Gregory S.; Abelson, John R.; Fan, Shanhui; Braun, Paul V.

    2013-10-01

    Selective thermal emission in a useful range of energies from a material operating at high temperatures is required for effective solar thermophotovoltaic energy conversion. Three-dimensional metallic photonic crystals can exhibit spectral emissivity that is modified compared with the emissivity of unstructured metals, resulting in an emission spectrum useful for solar thermophotovoltaics. However, retention of the three-dimensional mesostructure at high temperatures remains a significant challenge. Here we utilize self-assembled templates to fabricate high-quality tungsten photonic crystals that demonstrate unprecedented thermal stability up to at least 1,400 °C and modified thermal emission at solar thermophotovoltaic operating temperatures. We also obtain comparable thermal and optical results using a photonic crystal comprising a previously unstudied material, hafnium diboride, suggesting that refractory metallic ceramic materials are viable candidates for photonic crystal-based solar thermophotovoltaic devices and should be more extensively studied.

  9. Estimating the Position, Number and Length of Forehead Wrinkles Using Neural Network

    Directory of Open Access Journals (Sweden)

    Ayman AbuBaker

    2012-08-01

    Full Text Available A novel approach towards 2D Facial Aging (FA techniques using Neural Network (NN is proposed in this study. This approach is proposed to automatically predicate the position, number and length of wrinkles on the forehead area. The method is divided into three main stages; the first stage is the preprocessing stage, where the forehead area is manually cropped then filtered to gain sharpness. After that, the wrinkles segmentation process is carried out using row-by-row threshold, morphological erosion and connected component labeling to accurately extract the wrinkles form the image. Finally, the NN is used to convert the detected wrinkle lengths from 2D to 3D curvature shape. The proposed method is objectively compared with other techniques and can accurately predict the position, number and length of the forehead wrinkles in different ages.

  10. Predicting High Temperature Dislocation Physics in HCP Crystal Structures

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, Abigail [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carpenter, John S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez Saez, Enrique [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-09

    This report applies models and experiments to answer key questions about the way materials deform; specifics regarding phase field dislocations dynamics; as well as high temperature rolling experiments.

  11. Forehead Augmentation with a Methyl Methacrylate Onlay Implant Using an Injection-Molding Technique

    Directory of Open Access Journals (Sweden)

    Dong Kwon Park

    2013-09-01

    Full Text Available BackgroundThe forehead, which occupies about one third of the face, is one of the major determinants of a feminine or masculine look. Various methods have been used for the augmentation of the forehead using autologous fat grafts or alloplastic materials. Methylmethacrylate (MMA is the most appropriate material for augmentation of the forehead, and we have used an injection-molding technique with MMA to achieve satisfactory results.MethodsUnder local anesthesia with intravenous (IV sedation, an incision was made on the scalp and a meticulous and delicate subperiosteal dissection was then performed. MMA monomers and polymers were mixed, the dough was injected into the space created, and manual molding was performed along with direct inspection. This surgery was indicated for patients who wanted to correct an unattractive appearance by forehead augmentation. Every patient in this study visited our clinics 3 months after surgery to evaluate the results. We judged the postoperative results in terms of re-operation rates caused by the dissatisfaction of the patients and complications.ResultsDuring a 13-year period, 516 patients underwent forehead augmentation with MMA. With the injection-molding technique, the inner surface of the MMA implant is positioned close to the underlying frontal bone, which minimizes the gap between the implant and bone. The borders of the implant should be tapered sufficiently until no longer palpable or visible. Only 28 patients (5.4% underwent a re-operation due to an undesirable postoperative appearance.ConclusionsThe injection-molding technique using MMA is a simple, safe, and ideal method for the augmentation of the forehead.

  12. Forehead Augmentation with a Methyl Methacrylate Onlay Implant Using an Injection-Molding Technique

    Directory of Open Access Journals (Sweden)

    Dong Kwon Park

    2013-09-01

    Full Text Available Background The forehead, which occupies about one third of the face, is one of the majordeterminants of a feminine or masculine look. Various methods have been used for the augmentationof the forehead using autologous fat grafts or alloplastic materials. Methylmethacrylate(MMA is the most appropriate material for augmentation of the forehead, and we have usedan injection-molding technique with MMA to achieve satisfactory results.Methods Under local anesthesia with intravenous (IV sedation, an incision was made onthe scalp and a meticulous and delicate subperiosteal dissection was then performed. MMAmonomers and polymers were mixed, the dough was injected into the space created, andmanual molding was performed along with direct inspection. This surgery was indicated forpatients who wanted to correct an unattractive appearance by forehead augmentation. Everypatient in this study visited our clinics 3 months after surgery to evaluate the results. Wejudged the postoperative results in terms of re-operation rates caused by the dissatisfactionof the patients and complications.Results During a 13-year period, 516 patients underwent forehead augmentation with MMA.With the injection-molding technique, the inner surface of the MMA implant is positionedclose to the underlying frontal bone, which minimizes the gap between the implant and bone.The borders of the implant should be tapered sufficiently until no longer palpable or visible.Only 28 patients (5.4% underwent a re-operation due to an undesirable postoperative appearance.Conclusions The injection-molding technique using MMA is a simple, safe, and ideal methodfor the augmentation of the forehead.

  13. The temperature gradient on section of casting in process of primary crystallization of chromium cast iron

    OpenAIRE

    2008-01-01

    The methodology of defining in article was introduced the temperature gradient in process of primary crystallization during cooling the casting from chromium cast iron on basis of measurements of thermal field in test DTA-K3. Insert also the preliminary results of investigations of influence temperature gradient on structure of studied wear resistance chromium cast iron.

  14. Temperature influence on electrically controlled liquid crystal filled photonic bandgap fiber devices

    DEFF Research Database (Denmark)

    Wei, Lei; Alkeskjold, Thomas Tanggaard; Bjarklev, Anders Overgaard

    2009-01-01

    We experimentally investigate the temperature influence on electrically controlled liquid crystal filled photonic bandgap fiber device. The phase shift in the wavelength range 1520nm-1600nm for realizing quarter and half wave plates at different temperatures by applying a certain voltage...

  15. The temperature gradient on section of casting in process of primary crystallization of chromium cast iron

    Directory of Open Access Journals (Sweden)

    A. Studnicki

    2008-08-01

    Full Text Available The methodology of defining in article was introduced the temperature gradient in process of primary crystallization during cooling the casting from chromium cast iron on basis of measurements of thermal field in test DTA-K3. Insert also the preliminary results of investigations of influence temperature gradient on structure of studied wear resistance chromium cast iron.

  16. Relation between the concentration of defects and the temperature on a crystal

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, A.T.V.; Cilense, M. (UNESP, Araraquara (Brazil). Inst. de Quimica); Garlipp, W. (Sao Paulo Univ., Sao Carlos (Brazil). Escola de Engenharia)

    1982-01-01

    Following the basic thermodynamics principles, the relation between the concentration of defects and the temperature on a crystal was established. In the case of vacancies, the relation between the changes in the resistivity and the absolute quench temperature was also obtained.

  17. Molecular relaxation behavior and isothermal crystallization above glass transition temperature of amorphous hesperetin.

    Science.gov (United States)

    Shete, Ganesh; Khomane, Kailas S; Bansal, Arvind Kumar

    2014-01-01

    The purpose of this paper was to investigate the relaxation behavior of amorphous hesperetin (HRN), using dielectric spectroscopy, and assessment of its crystallization kinetics above glass transition temperature (Tg ). Amorphous HRN exhibited both local (β-) and global (α-) relaxations. β-Relaxation was observed below Tg , whereas α-relaxation prominently emerged above Tg . β-Relaxation was found to be of Johari-Goldstein type and was correlated with α-process by coupling model. Secondly, isothermal crystallization experiments were performed at 363 K (Tg + 16.5 K), 373 K (Tg + 26.5 K), and 383 K (Tg + 36.5 K). The kinetics of crystallization, obtained from the normalized dielectric strength, was modeled using the Avrami model. Havriliak-Negami (HN) shape parameters, αHN and αHN .βHN , were analyzed during the course of crystallization to understand the dynamics of amorphous phase during the emergence of crystallites. HN shape parameters indicated that long range (α-like) were motions affected to a greater extent than short range (β-like) motions during isothermal crystallization studies at all temperature conditions. The variable behavior of α-like motions at different isothermal crystallization temperatures was attributed to evolving crystallites with time and increase in electrical conductivity with temperature.

  18. The facile and low temperature synthesis of nanophase hydroxyapatite crystals using wet chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Dhand, Vivek [Department of Mechanical Engineering, College of Engineering, Kyung Hee University, 446–701 Yongin (Korea, Republic of); Rhee, K.Y., E-mail: rheeky@khu.ac.kr [Department of Mechanical Engineering, College of Engineering, Kyung Hee University, 446–701 Yongin (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, Incheon (Korea, Republic of)

    2014-03-01

    A simple and facile wet chemistry route was used to synthesize nanophase hydroxyapatite (HaP) crystals at low temperature. The synthesis was carried out at a pH of 11.0 and at a temperature of 37 °C. The resulting samples were washed several times and subjected to further analysis. XRD studies revealed that the HaP crystals were polycrystalline in nature with a crystallite size of ∼ 15–60 ± 5 nm. SEM-EDXA images confirmed the presence of calcium (Ca), phosphorous (P), and oxygen (O) peaks. Likewise, FTIR confirmed the presence of characteristic phosphate and hydroxyl peaks in samples. Lastly, HRTEM images clearly showed distinctive lattice fringes positioned in the 100 and 002 planes. TGA analysis shows that HaP crystals can withstand higher calcination temperatures and are thermally stable. - Highlights: • Facile and low temperature nanophase HaP crystals synthesized at pH 11 and 37 °C • Electron microscopy image of HaP shows characteristic rice grain like morphology. • FTIR results show the characteristic and fingerprint functional groups of HaP. • Thermal stability of HaP crystals up to 500 °C • Growth of Hap crystals occur parallel to c-axis and a possible mechanism proposed.

  19. Interface Instability of Diamond Crystals at High Temperature and High Pressure

    Institute of Scientific and Technical Information of China (English)

    尹龙卫; 李木森; 许斌; 崔建军; 郝兆印

    2002-01-01

    Diamond growth instability at high temperature and high pressure (HPHT) has been elucidated by observing the cellular interface in diamond crystals. The HPHIT diamond crystals grow layer by layer from solution of carbon in the molten catalyst. In the growth of any other crystals from solution, the growth interface is not stable and should be of the greatest significance to understand further the diamond growth mechanism. During the diamond growth, the carbon atoms are delivered to the growing diamond crystal by diffusion through a diamond crystal-solution boundary layer. In front of the boundary layer, there is a narrow constitutional supercooling zone related to the solubility difference between diamond and graphite in the molten catalyst. The diamond growth stability is broken, and the flat or planar growth interface transforms into a cellular interface due to the light supercooling. The phenomenon of solute trails in the diamonds was observed, the formation of solute trails was closely associated with the cellular interface.

  20. Temperature distribution in growing semi-transparent crystals. 3. Conical liquid/solid interface

    Energy Technology Data Exchange (ETDEWEB)

    Kvapil, J.; Kubelka, J.; Kvapil, J.; Perner, B. (Monokrystaly, Turnov (Czechoslovakia))

    1983-05-01

    Temperature distribution in Al/sub 2/O/sub 3/ and YAG crystals grown by Czochralski method and in the melt layer adjacent to the liquid/solid interface of the conical shape was computed. The results were compared with the quality of the crystals. Using a highly absorbing material, temperature difference near the deeply submerged sharp interface decreases from the edge to the centre of a crystal and it is relatively great and unalterable in the case of a shallowly submerged blunt interface. Sharp interface show the crystals grown from the melt of the same composition (Al/sub 2/O/sub 3/ or accurately ''stoichiometric'' YAG), whereas the blunt one is typical of YAG grown from the melt of the ''non-stoichiometric'' composition, because its solidifying point is below the melting point of YAG phase.

  1. Nanostructure characterization of beta-sheet crystals in silk under various temperatures

    Directory of Open Access Journals (Sweden)

    Zhang Yan

    2014-01-01

    Full Text Available This paper studies the nanostructure characterizations of β-sheet in silk fiber with different reaction temperatures. A molecular dynamic model is developed and simulated by Gromacs software packages. The results reveal the change rules of the number of hydrogen bonds in β-sheet under different temperatures. The best reaction temperature for the β-sheet crystals is also found. This work provides theoretical basis for the designing of materials based on silk.

  2. The effect of impurity on temperature variations in the refractive indices and thickness of TGS crystals

    Science.gov (United States)

    Stadnyk, V. Yo.; Andriyevsky, B. V.; Gaba, V. M.; Kogut, Z. A.

    2016-06-01

    Temperature dependences of optical path difference δΔi and the relative changes in thickness δ l i/ l of TGS crystals doped with L-valine are studied. Temperature dependences of the relative changes in refractive indices δ n i/( n-1) are calculated. The anisotropy coefficients of refractive indices An-1(T) and linear expansion Aα(T) are calculated, and a characteristic minimum of these dependences is found near the phase transition temperature.

  3. Oxide films: low-temperature deposition and crystallization

    Science.gov (United States)

    Park, Sangmoon; Herman, Gregory S.; Keszler, Douglas A.

    2003-10-01

    Thin films of CeO 2 and (Ce,Sm)O 2 have been prepared by using the SILAR method of deposition in conjunction with hydrothermal and high-temperature annealing. Low-temperature, low-pressure hydrothermal annealing of amorphous Mn:Zn 2GeO 4 films has lead to the growth of grains having edge lengths near 1 μm. Thick films of crystalline Zn 2SiO 4 exhibiting limited cracking have been prepared by a doctor-blade method also in conjunction with hydrothermal dehydration and annealing.

  4. Electromechanical characterization of [Formula: see text] crystals as a function of crystallographic orientation and temperature.

    Science.gov (United States)

    Zhang, Shujun; Luo, Jun; Hackenberger, Wesley; Sherlock, Nevin P; Meyer, Richard J; Shrout, Thomas R

    2009-05-15

    Relaxor based [Formula: see text] ternary single crystals (PIN-PMN-PT) were reported to have broader temperature usage range [Formula: see text] and comparable piezoelectric properties to [Formula: see text] (PMNT) crystals. In this work, the orientation dependent dielectric, piezoelectric and electromechanical properties for PIN-PMN-PT crystals were investigated along [Formula: see text] and [Formula: see text] directions. The electromechanical couplings [Formula: see text] and [Formula: see text] for [Formula: see text] poled crystals were found to be 0.91 and 0.91, respectively, with piezoelectric coefficients [Formula: see text] and [Formula: see text] on the order of 925 and -1420 pC/N. Of particular significance was the mechanical quality factor [Formula: see text] for [Formula: see text] oriented crystals, which was found to be [Formula: see text], much higher than the [Formula: see text] values of [Formula: see text] oriented relaxor-PT crystals [Formula: see text]. The temperature dependence of the piezoelectric properties exhibited good temperature stability up to their ferroelectric phase transition [Formula: see text], indicating [Formula: see text] and [Formula: see text] oriented PIN-PMN-PT are promising materials for transducer applications, with the latter for high power resonant devices where low loss (high [Formula: see text]) was required.

  5. Study on temperature property of band structures in onedimensional photonic crystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Using transfer matrix method, the optical transmission properties in one-dimensional (1-D) photonic crystal is analyzed.When the temperature varies, not only the refractive index of the optical medium is changed because of the thermo-optical effect, but also the thickness of the optical medium is changed due to the thermal-expansion effect. Thus, the structure of 1/4 wave-plate stack in original photonic crystal is destroyed and the band structure varies. In this work, the effects of the temperature variation on the first and second band gap in a 1-D photonic crystal are analyzed in detail. It is found that the changes of the starting wavelength, the cut-off wavelength and the forbidden band width depend linearly on the temperature.

  6. Technique for anisotropic extension of organic crystals: Application to temperature dependence of electrical resistance

    Science.gov (United States)

    Yamamoto, Takashi; Kato, Reizo; Yamamoto, Hiroshi M.; Fukaya, Atsuko; Yamasawa, Kenji; Takahashi, Ichiro; Akutsu, Hiroki; Akutsu-Sato, Akane; Day, Peter

    2007-08-01

    We have developed a technique for the anisotropic extension of fragile molecular crystals. The pressure medium and the instrument, which extends the pressure medium, are both made from epoxy resin. Since the thermal contraction of our instrument is identical to that of the pressure medium, the strain applied to the pressure medium has no temperature dependence down to 2K. Therefore, the degree of extension applied to the single crystal at low temperatures is uniquely determined from the degree of extension in the pressure medium and thermal contractions of the epoxy resin and the single crystal at ambient pressure. Using this novel instrument, we have measured the temperature dependence of the electrical resistance of metallic, superconducting, and insulating materials. The experimental results are discussed from the viewpoint of the extension (compression) of the lattice constants along the parallel (perpendicular) direction.

  7. Characterization of Anodic Aluminum Oxide Membrane with Variation of Crystallizing Temperature for pH Sensor.

    Science.gov (United States)

    Yeo, Jin-Ho; Lee, Sung-Gap; Jo, Ye-Won; Jung, Hye-Rin

    2015-11-01

    We fabricated electrolyte-dielectric-metal (EDM) device incorporating a high-k Al2O3 sensing membrane from a porous anodic aluminum oxide (AAO) using a two step anodizing process for pH sensors. In order to change the properties of the AAO template, the crystallizing temperature was varied from 400 degrees C to 700 degrees C over 2 hours. The structural properties were observed by field emission scanning electron microscopy (FE-SEM). The pH sensitivity increased with an increase in the crystallizing temperature from 400 degrees C to 600 degrees C. However at 700 degrees C, deformation occurred. The porous AAO sensor with a crystallizing temperature of 600 degrees C displayed the good sensitivity and long-term stability and the values were 55.7 mV/pH and 0.16 mV/h, respectively.

  8. The facile and low temperature synthesis of nanophase hydroxyapatite crystals using wet chemistry.

    Science.gov (United States)

    Dhand, Vivek; Rhee, K Y; Park, Soo-Jin

    2014-03-01

    A simple and facile wet chemistry route was used to synthesize nanophase hydroxyapatite (HaP) crystals at low temperature. The synthesis was carried out at a pH of 11.0 and at a temperature of 37°C. The resulting samples were washed several times and subjected to further analysis. XRD studies revealed that the HaP crystals were polycrystalline in nature with a crystallite size of ~15-60 ± 5 nm. SEM-EDXA images confirmed the presence of calcium (Ca), phosphorous (P), and oxygen (O) peaks. Likewise, FTIR confirmed the presence of characteristic phosphate and hydroxyl peaks in samples. Lastly, HRTEM images clearly showed distinctive lattice fringes positioned in the 100 and 002 planes. TGA analysis shows that HaP crystals can withstand higher calcination temperatures and are thermally stable.

  9. Forward to cryogenic temperature: laser cooling of Yb: LuLiF crystal

    Science.gov (United States)

    Zhong, Biao; Luo, Hao; Lei, Yongqing; Shi, Yanling; Yin, Jianping

    2017-06-01

    The high quality Yb-doped fluoride crystals have broad prospects for optical refrigeration. We have laser cooled the Yb:LuLiF crystal to a temperature below the limit of current thermoelectric coolers ( 180 K). The 5% Yb:LuLiF crystal sample has a geometry of 2 mm×2 mm×5 mm and was supported by two fibers of 200 μm in diameter. They were placed in a 2×10-4 Pa vacuum chamber with an environment temperature of 294.5 K. The 1019 nm CW laser of power 38.7 W was adopted to irradiate the sample. The temperature of the sample was measured utilizing the DLT methods. After 20 minutes of laser irradiation, the 5% Yb:LuLiF crystal sample was cooled down to 182.4 K. By further optimizing experimental conditions and increasing the doped Yb concentration, the Yb:LuLiF crystal might be optically cooled below the cryogenic temperature of 123K in the near future.

  10. Development of a CE-QUAL-W2 temperature model for Crystal Springs Lake, Portland, Oregon

    Science.gov (United States)

    Buccola, Norman L.; Stonewall, Adam J.

    2016-05-19

    During summer 2014, lake level, streamflow, and water temperature in and around Crystal Springs Lake in Portland, Oregon, were measured by the U.S. Geological Survey and the City of Portland Bureau of Environmental Services to better understand the effect of the lake on Crystal Springs Creek and Johnson Creek downstream. Johnson Creek is listed as an impaired water body for temperature by the Oregon Department of Environmental Quality (ODEQ), as required by section 303(d) of the Clean Water Act. A temperature total maximum daily load applies to all streams in the Johnson Creek watershed, including Crystal Springs Creek. Summer water temperatures downstream of Crystal Springs Lake and the Golf Pond regularly exceed the ODEQ numeric criterion of 64.4 °F (18.0 °C) for salmonid rearing and migration. To better understand temperature contributions of this system, the U.S. Geological Survey developed two-dimensional hydrodynamic water temperature models of Crystal Springs Lake and the Golf Pond. Model grids were developed to closely resemble the bathymetry of the lake and pond using data from a 2014 survey. The calibrated models simulated surface water elevations to within 0.06 foot (0.02 meter) and outflow water temperature to within 1.08 °F (0.60 °C). Streamflow, water temperature, and lake elevation data collected during summer 2014 supplied the boundary and reference conditions for the model. Measured discrepancies between outflow and inflow from the lake, assumed to be mostly from unknown and diffuse springs under the lake, accounted for about 46 percent of the total inflow to the lake.

  11. A temperature-dependent surface free energy model for solid single crystals

    Science.gov (United States)

    Cheng, Tianbao; Fang, Daining; Yang, Yazheng

    2017-01-01

    A temperature-dependent theoretical model for the surface free energy of the solid single crystals is established. This model relates the surface free energy at the elevated temperatures to that at the reference temperature, the temperature-dependent specific heat at constant pressure and coefficient of the linear thermal expansion, the heat of phase transition, the melting heat, and the vapor heat. As examples, the surface free energies of Fe, Cu, Al, Ni, and Pb from 0 K to melting points are calculated and are in reasonable agreement with these from Tyson's theories and the experimental results. This model has obvious advantages compared to Tyson's semi-empirical equations from the aspect of physical meaning, applicable condition, and accuracy. The study shows that the surface free energy of the solid single crystals firstly remains approximately constant and then decreases linearly as temperature increases from 0 K to melting point.

  12. Dynamic yield and tensile strength of aluminum single crystals at temperatures up to the melting point

    Energy Technology Data Exchange (ETDEWEB)

    Kanel, G. I.; Razorenov, S. V.; Baumung, K.; Singer, J.

    2001-07-01

    This article presents experimental results of the dynamic yield strength and dynamic tensile strength ({open_quotes}spall strength{close_quotes}) of aluminum single crystals at shock-wave loading as a function of temperature. The load duration was {similar_to}40 and {similar_to}200 ns. The temperature varied from 20 to 650{degree}C which is only by 10{degree}C below the melting temperature. A linear growth of the dynamic yield strength by more than a factor of 4 was observed within this temperature range. This is attributed to the phonon drag effect on the dislocation motion. High dynamic tensile strength was maintained over the whole temperature range, including the conditions at which melting should start in a material under tension. This could be an indication of the existence of superheated states in solid crystals. {copyright} 2001 American Institute of Physics.

  13. Nasal reconstruction with the paramedian forehead flap using the aesthetic subunits principle.

    Science.gov (United States)

    de Pochat, Victor Diniz; Alonso, Nivaldo; Ribeiro, Emilie Barreto; Figueiredo, Bruno Suffredini; de Magaldi, Eduarda Nilo; Cunha, Marcelo Sacramento; Meneses, José Valber Lima

    2014-11-01

    Reconstruction of nasal defects is challenging because it requires covering skin, supporting framework, and lining. Traditionally, the forehead flaps are transferred in 2 stages; however, it can be accomplished in a single stage or in 3 stages. Few published studies are available about the paramedian forehead flap using the intermediate stage (3-stage) and the aesthetic subunits principle. The purpose of this study is to evaluate the use of the paramedian forehead flap in 2 and 3 stages for nasal reconstructions, highlighting the indications, complications, and technical details and evaluating the patient's satisfaction through a questionnaire about the quality of life (Derriford Appearance Scale 24). A retrospective review was performed between 2011 and 2013 for a consecutive series of 11 patients who underwent nasal reconstructions using the paramedian forehead flap in 2 or 3 stages. All preoperative and postoperative data were collected, and outcomes were also assessed through a questionnaire about the patients' postoperative quality of life. The causes of nasal lesions varied among skin cancer, trauma, and infection. Two-stage paramedian forehead flap reconstruction was performed upon 4 patients, whereas the 3-stage reconstruction was performed for 7 patients. Of the 10 survey respondents, 6 were highly satisfied (score of 11-27), and 4 were moderately satisfied (score of 28-44), whereas no one was dissatisfied after his/her surgical nasal reconstruction procedure. Whether the approach is accomplished in 2 or 3 stages, all areas of the reconstructed nose must be firmly supported. Applying the nasal subunits principle seems to contribute to an overall satisfied population in our study, according to the score obtained by the questionnaire about quality of life.

  14. Knowledge-based Identification of Sleep Stages based on Two Forehead Electroencephalogram Channels

    Directory of Open Access Journals (Sweden)

    Chih-Sheng eHuang

    2014-09-01

    Full Text Available Sleep quality is important, especially given the considerable number of sleep-related pathologies. The distribution of sleep stages is a highly effective and objective way of quantifying sleep quality. As a standard multi-channel recording used in the study of sleep, polysomnography (PSG is a widely used diagnostic scheme in sleep medicine. However, the standard process of sleep clinical test, including PSG recording and manual scoring, is complex, uncomfortable, and time-consuming. This process is difficult to implement when taking the whole PSG measurements at home for general healthcare purposes. This work presents a novel sleep stage classification system, based on features from the two forehead EEG channels FP1 and FP2. By recording EEG from forehead, where there is no hair, the proposed system can monitor physiological changes during sleep in a more practical way than previous systems. Through a headband or self-adhesive technology, the necessary sensors can be applied easily by users at home. Analysis results demonstrate that classification performance of the proposed system overcomes the individual differences between different participants in terms of automatically classifying sleep stages. Additionally, the proposed sleep stage classification system can identify kernel sleep features extracted from forehead EEG, which are closely related with sleep clinician’s expert knowledge. Moreover, forehead EEG features are classified into five sleep stages by using the relevance vector machine. In a leave-one-subject-out cross validation analysis, we found our system to correctly classify five sleep stages at an average accuracy of 76.7 ± 4.0 (SD % (average kappa 0.68 ± 0.06 (SD. Importantly, the proposed sleep stage classification system using forehead EEG features is a viable alternative for measuring EEG signals at home easily and conveniently to evaluate sleep quality reliably, ultimately improving public healthcare.

  15. Knowledge-based identification of sleep stages based on two forehead electroencephalogram channels.

    Science.gov (United States)

    Huang, Chih-Sheng; Lin, Chun-Ling; Ko, Li-Wei; Liu, Shen-Yi; Su, Tung-Ping; Lin, Chin-Teng

    2014-01-01

    Sleep quality is important, especially given the considerable number of sleep-related pathologies. The distribution of sleep stages is a highly effective and objective way of quantifying sleep quality. As a standard multi-channel recording used in the study of sleep, polysomnography (PSG) is a widely used diagnostic scheme in sleep medicine. However, the standard process of sleep clinical test, including PSG recording and manual scoring, is complex, uncomfortable, and time-consuming. This process is difficult to implement when taking the whole PSG measurements at home for general healthcare purposes. This work presents a novel sleep stage classification system, based on features from the two forehead EEG channels FP1 and FP2. By recording EEG from forehead, where there is no hair, the proposed system can monitor physiological changes during sleep in a more practical way than previous systems. Through a headband or self-adhesive technology, the necessary sensors can be applied easily by users at home. Analysis results demonstrate that classification performance of the proposed system overcomes the individual differences between different participants in terms of automatically classifying sleep stages. Additionally, the proposed sleep stage classification system can identify kernel sleep features extracted from forehead EEG, which are closely related with sleep clinician's expert knowledge. Moreover, forehead EEG features are classified into five sleep stages by using the relevance vector machine. In a leave-one-subject-out cross validation analysis, we found our system to correctly classify five sleep stages at an average accuracy of 76.7 ± 4.0 (SD) % [average kappa 0.68 ± 0.06 (SD)]. Importantly, the proposed sleep stage classification system using forehead EEG features is a viable alternative for measuring EEG signals at home easily and conveniently to evaluate sleep quality reliably, ultimately improving public healthcare.

  16. Superfluid density and superconducting transition temperature in Bi-based cuprate single crystals.

    Science.gov (United States)

    Gasparov, L.; Tanner, D.; Berger, H.; Forro, L.; Margaritondo, G.

    2000-03-01

    We present temperature-dependent reflectance measurements for Bi-based cuprate single crystals in the frequency range from 100 to 40,000 cm-1 (0.012--5 eV). The optical conductivity is obtained by Kramers-Kronig analysis. We compare differently doped Bi-2212 (particularly in the underdoped regime) as well as Pr-doped Bi-2212 crystals by analyzing optical conductivity in the framework of a two-fluid approach. This approach allows us to study correlations between superfluid density and superconducting transition temperature of these materials.

  17. Temperature dependences of piezoelectric, elastic and dielectric constants of L-alanine crystal

    Science.gov (United States)

    Tylczyński, Z.; Sterczyńska, A.; Wiesner, M.

    2011-09-01

    Temperature changes in the components of piezoelectric, elastic and dielectric tensors were studied in L-alanine crystals in the range 100-300 K. A jumpwise increase in the c55 component of the elastic stiffness accompanied by maxima in damping of all face-shear modes observed at 199 K in L-alanine crystal were interpreted as a result of changes in the NH3+ vibrations occurring through electron-phonon coupling. All components of the piezoelectric tensor show small anomalies in this temperature range. The components of the electromechanical coupling coefficient determined indicate that L-alanine is a weak piezoelectric.

  18. The clinical value of infrared forehead thermometer dancing%红外线额温计的临床应用价值

    Institute of Scientific and Technical Information of China (English)

    秦梅; 马燕舞; 刘宁

    2016-01-01

    目的:探讨红外线额式体温计(额温计)测量体温临床应用价值。方法:随机抽取住院患者40例,采用自身对照的方法比较红外线额温计和水银体温计测量的腋温之间的差异。评价:红外线额式体温计的测温价值。结果:40例患者同时应用红外线额式体温计与水银体温计测量体温,其中水银体温计测出的温度为(36.42±0.38)℃,红外线额式体温计测出的温度为(36.47±0.4)℃,两者差异无统计学意义(P>0.05)。结论:红外线额式体温计与水银体温计都能准确反映人体的体表温度。%Objective:To study the infrared forehead thermometer (thermometer).Methods:40 cases of patients hospitalized were randomly selected by self contrast method comparison of infrared thermometer and mercury temperature gauge differences between measured axillary temperature.The value of the infrared thermometer was evaluated.Results:40 patients were applied infrared thermometer and the mercurial thermometer simultaneously. Mercurial thermometer read (36.42±0.38) C,infrared forehead thermometer read (36.47±0.4 DEG C,the difference between the two groups is not significant (P>0.05).Conclusion:infrared forehead thermometer and mercurial thermometer can both accurately reflect body's temperature.

  19. Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Michael J. Mills

    2009-03-05

    Cast nickel-based superalloys are used for blades in land-based, energy conversion and powerplant applications, as well as in aircraft gas turbines operating at temperatures up to 1100 C, where creep is one of the life-limiting factors. Creep of superalloy single crystals has been extensively studied over the last several decades. Surprisingly, only recently has work focused specifically on the dislocation mechanisms that govern high temperature and low stress creep. Nevertheless, the perpetual goal of better engine efficiency demands that the creep mechanisms operative in this regime be fully understood in order to develop alloys and microstructures with improved high temperature capability. At present, the micro-mechanisms controlling creep before and after rafting (the microstructure evolution typical of high temperature creep) has occurred have yet to be identified and modeled, particularly for [001] oriented single crystals. This crystal orientation is most interesting technologically since it exhibits the highest creep strength. The major goal of the program entitled ''Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals'' (DOE Grant DE-FG02-04ER46137) has been to elucidate these creep mechanisms in cast nickel-based superalloys. We have utilized a combination of detailed microstructure and dislocation substructure analysis combined with the development of a novel phase-field model for microstructure evolution.

  20. Temperature stable operation of YCOB crystal for giant-pulse green microlaser.

    Science.gov (United States)

    Kausas, Arvydas; Loiseau, Pascal; Aka, Gerard; Zheng, Yanqing; Zheng, Lihe; Taira, Takunori

    2017-03-20

    In this work the performance of two yttrium calcium oxyborate (YCOB) crystals made by Czochralski and Bridgman growth process was measured. By using high peak power, passively Q-switched Nd3+:YAG/Cr4+:YAG microlaser, high conversion second harmonic generation efficiency were obtained. Laser pulses at 532 nm with 1.14 mJ energy and 223 ps duration were obtained with a 15-mm long YCOB crystal that was grown by Bridgman method. The conversion efficiency was 70.2%, comparable with the conversion efficiency of 72.8% that was achieved with 10-mm long lithium triborate (LBO) nonlinear crystal. Also, for the first time, experimental data on temperature tuning in type I YCOB crystal was measured with linear slope in 200°C temperature range equal to -0.057%/°C and -0.064%/°C for the Czochralski and Bridgman grown crystals, respectively. Such YCOB nonlinear crystal can become a serious option for developing laser sources with high-peak power at high repetition rate that can operate in harsh environment.

  1. Continuous-wave mid-infrared photonic crystal light emitters at room temperature

    Science.gov (United States)

    Weng, Binbin; Qiu, Jijun; Shi, Zhisheng

    2017-01-01

    Mid-infrared photonic crystal enhanced lead-salt light emitters operating under continuous-wave mode at room temperature were investigated in this work. For the device, an active region consisting of 9 pairs of PbSe/Pb0.96Sr0.04Se quantum wells was grown by molecular beam epitaxy method on top of a Si(111) substrate which was initially dry-etched with a two-dimensional photonic crystal structure in a pattern of hexagonal holes. Because of the photonic crystal structure, an optical band gap between 3.49 and 3.58 µm was formed, which matched with the light emission spectrum of the quantum wells at room temperature. As a result, under optical pumping, using a near-infrared continuous-wave semiconductor laser, the device exhibited strong photonic crystal band-edge mode emissions and delivered over 26.5 times higher emission efficiency compared to the one without photonic crystal structure. The output power obtained was up to 7.68 mW (the corresponding power density was 363 mW/cm2), and a maximum quantum efficiency reached to 1.2%. Such photonic crystal emitters can be used as promising light sources for novel miniaturized gas-sensing systems.

  2. Effect of annealing temperatures on the secondary re-crystallization of extruded PM2000 steel bar.

    Science.gov (United States)

    Chen, C-L; Tatlock, G J; Jones, A R

    2009-03-01

    The ferritic oxide dispersion-strengthened alloy PM2000 is an ideal candidate for high-temperature applications as it contains uniform nano-oxide dispersoids, which act as pinning points to obstruct dislocation and grain boundary motion and therefore impart excellent creep resistance. The development of the microstructure during re-crystallization of oxide dispersion-strengthened alloys has been discussed by a number of authors, but the precise mechanism of secondary re-crystallization still remains uncertain. Hence, this work is aimed at investigating the re-crystallization behaviour of extruded PM2000 bar for different annealing temperatures, using electron backscatter diffraction, in particular, to determine grain orientations, grain boundary misorientation angles, etc. The results show that the as-extruded bar microstructure comprises both low-angle grain boundaries pinned by oxide particles and high-angle boundaries that will have inherent boundary mobility to allow boundary migration. In addition, dynamical re-crystallization was found in the outer region of the non-heat-treated PM2000 bar, which suggested that deformation heterogeneities can be introduced during thermo-mechanical processing that enhance the nucleation of re-crystallization. Subsequent heat treatments promote and stimulate secondary re-crystallization, giving rise to large grains with few sub-grain boundaries.

  3. Dielectric and electromechanical properties of rare earth calcium oxyborate piezoelectric crystals at high temperatures.

    Science.gov (United States)

    Yu, Fapeng; Zhang, Shujun; Zhao, Xian; Yuan, Duorong; Qin, Lifeng; Wang, Qing-Ming; Shrout, Thomas R

    2011-04-01

    The electrical resistivity, dielectric, and electromechanical properties of ReCa(4)O(BO(3))(3) (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000 °C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p > 3 × 10(7) ω.cm at 1000 °C. The property variation in ReCOB crystals is discussed with respect to their disordered structure. The highest electromechanical coupling factor κ(26) and piezoelectric coefficient d(26) at 1000°C, were achieved in PrCOB crystals, with values being on the order of 24.7% and 13.1 pC/N, respectively. The high thermal stability of the electromechanical properties, with variation less than 25%, together with the low dielectric loss (factor (>1500) at elevated temperatures of 1000 °C, make ErCOB, YCOB, and GdCOB crystals promising for ultrahigh temperature electromechanical applications.

  4. Nucleation and crystallization kinetics of hydrated amorphous lactose above the glass transition temperature.

    Science.gov (United States)

    Schmitt, E A; Law, D; Zhang, G G

    1999-03-01

    The crystallization kinetics of amorphous lactose in the presence and absence of seed crystals were investigated at 57.5% relative humidity. Isothermal crystallization studies were conducted gravimetrically in an automated vacuum moisture balance at several temperatures between 18 and 32 degrees C. The crystallization rate constants were then determined from Johnson-Mehl-Avrami (JMA) treatment and isothermal activation energies were obtained from Arrhenius plots. Based on microscopic observations, a reaction order of 3 was used for JMA analysis. The nonisothermal activation energies were determined by differential scanning calorimetry using Kissinger's analysis. Isothermal activation energies for amorphous lactose with and without seed crystals were 89.5 (+/-5.6) kJ/mol and 186.5 (+/-17.6) kJ/mol, respectively. Nonisothermal activation energies with and without seed crystals were 71 (+/-7.5) kJ/mol and 80.9 (+/-8.9) kJ/mol, respectively. The similarity of the isothermal and nonisothermal activation energies for the sample with seeds suggested that crystallization was occurring by growth from a fixed number of preexisting nuclei. Markedly different isothermal and nonisothermal activation energies in the absence of seeds suggested a site-saturated nucleation mechanism, and therefore allowed calculation of an activation energy for nucleation of 317 kJ/mol.

  5. Effect of the Cu and Ni content on the crystallization temperature and crystallization mechanism of La-Al-Cu(Ni) metallic glasses

    Science.gov (United States)

    Li, Peiyou

    2016-02-01

    The effect of the Cu and Ni content on the crystallization mechanism and the crystallization temperatures of La-Al-Cu(Ni) metallic glasses (MGs) was studied by differential scanning calorimetry (DSC). The experimental results have shown that the DSC curves obtained for the La-Al-Cu and La-Al-Ni MGs exhibit two and three crystallization temperatures, respectively. The crystallization temperatures of the La-Al-Cu and La-Al-Ni MGs result from the merging and splitting of thermal events related to the corresponding eutectic atomic pairs in the La72Cu28 and La81.6Al18.4 MGs, and La72Ni28 and La81.6Al18.4 MGs, respectively. In addition, Al- and Ni-containing clusters with weak or strong atomic interaction in the Al-Ni atomic pairs strongly affect the crystallization mechanism and thus the crystallization temperature of La-Al-Ni MGs. This study provides a novel understanding of the relation between the crystallization temperature and the underlying crystallization mechanisms in La-Al-Cu(Ni) MGs.

  6. Temperature-Dependent Raman Spectra and Microstructure of Barium Metaborate Crystals and Its Melts

    Institute of Scientific and Technical Information of China (English)

    尤静林; 蒋国昌; 侯怀宇; 吴永全; 陈辉; 徐匡迪

    2002-01-01

    We have measured the Raman spectra of β- and α-barium metaborate in crystal and liquid states from room temperature to 1873K, with a semiconductor laser as the laser source, coupled with a time-resolved detection system to eliminate the dense thermal emission background when temperature was considerably high.Temperature-dependent Raman spectra can clearly indicate that the phase transformation from β- to α-barium metaborate has been completed during 1273 - 1300 K. Variations of different kinds of microstructure units with temperature are identified and discussed.

  7. Exponential temperature dependence of the penetration depth in single crystal MgB2.

    Science.gov (United States)

    Manzano, F; Carrington, A; Hussey, N E; Lee, S; Yamamoto, A; Tajima, S

    2002-01-28

    The temperature dependence of the London penetration depth, lambda(T), was measured in both single crystal and polycrystalline MgB2 samples by a high-resolution, radio frequency technique. A clear exponential temperature dependence of lambda(T) was observed at low temperature, indicating s-wave pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap Delta of 30+/-2 K (2Delta/T(c) = 1.5+/-0.1), which is significantly smaller than the standard BCS weak coupling value of 3.5. We find that the data are best described by a two-gap model.

  8. Low-Temperature Scintillation Properties of CaWO4 Crystals for Rare-Event Searches

    CERN Document Server

    Sivers, M v; Di Stefano, P C F; Erb, A; Gütlein, A; Lanfranchi, J -C; Münster, A; Nadeau, P; Piquemal, M; Potzel, W; Roth, S; Schreiner, K; Strauss, R; Wawoczny, S; Willers, M; Zöller, A

    2015-01-01

    In prospect of its application in cryogenic rare-event searches, we have investigated the low-temperature scintillation properties of CaWO4 crystals down to 3.4 K under {\\alpha} and {\\gamma} excitation. Concerning the scintillation decay times, we observe a long component in the ms range which significantly contributes to the light yield below 40K. For the first time we have measured the temperature dependence of the {\\alpha}/{\\gamma}- ratio of the light yield. This parameter which can be used to discriminate {\\alpha} and {\\gamma} events in scintillating bolometers is found to be about 8-15% smaller at low temperatures compared to room temperature.

  9. Transition Temperatures of Thermotropic Liquid Crystals from the Local Binary Gray Level Cooccurrence Matrix

    Directory of Open Access Journals (Sweden)

    S. Sreehari Sastry

    2012-01-01

    Full Text Available This paper presents a method which combines the statistical analysis with texture structural analysis called Local Binary Gray Level Cooccurrence Matrix (LBGLCM to investigate the phase transition temperatures of thermotropic p,n-alkyloxy benzoic acid (nOBA, n=4,6,8,10 and 12 liquid crystals. Textures of the homeotropically aligned liquid crystal compounds are recorded as a function of temperature using polarizing optical microscope attached to the hot stage and high resolution camera. In this method, second-order statistical parameters (contrast, energy, homogeneity, and correlation are extracted from the LBGLCM of the textures. The changes associatedwiththe values of extracted parameters as a function of temperature are a helpful process to identify the phases and phase transition temperatures of the samples. Results obtained from this method have validity and are in good agreement with the literature.

  10. Temperature sensitivity of Cu K(alpha) imaging efficiency using a spherical Bragg reflecting crystal

    Energy Technology Data Exchange (ETDEWEB)

    Akli, K U; Key, M H; Chung, H K; Hansen, S B; Freeman, R R; Chen, M H; Gregori, G; Hatchett, S; Hey, D; Izumi, N; King, J A; Kuba, J; Norreys, P; Mackinnon, A J; Murphy, C D; Snavely, R; Stepehens, R; Stoeckel, C; Theobald, W; Zhang, B

    2006-08-07

    The Vulcan laser facility at the Rutherford Appleton Laboratory was used to study the interaction of a 75 J 10 ps, high intensity laser beam with low-mass solid, Cu targets. Two instruments were fielded as diagnostics of the Cu K-shell emission from the targets: A single photon counting CCD spectrometer provided the absolute K{sub {alpha}} yield and a spherically bent Bragg crystal recorded 2D monochromatic images with a spatial resolution of 10 {micro}m. Due to the shifting and broadening of the K{sub {alpha}} spectral lines with increasing temperature, there is a temperature dependence of the crystal collection efficiency. This provides a temperature diagnostic when cross calibrated against a single hit CCD spectrometer, and it affects measurements of the spatial pattern of electron transport. The experimental data showing changing collection efficiency are presented. The results are discussed in light of modeling of the temperature-dependent spectrum of Cu K-shell emission.

  11. Temperature dependence of luminescence spectra of δ-KIO3-HIO3 crystal

    Science.gov (United States)

    Gavrilko, T.; Melnik, V.; Puchkovska, Galina A.

    2002-12-01

    In the present, photoluminescence of δ-KIO3 HIO3 crystals has been studied for the first time in the temperature range of 4.2-77K. It was shown experimentally that at T=4.2 K the edge of self-absorption band is located near 295 nm. In the luminescence spectra of the title crystal, two bands are found which differ in their spectral position and lifetime. The short-wave luminescence band centered at 367.5 nm. This band appears only in the csae of the crystal excitation by the light with the wavelength that does not fall in the region of self-absorption of the crystal, eg λexc = 340 nm. When the temperature increases from 4.2 to 34 K, the intensity of this band falls down almost to the background value, whereas the position of its maximum remains practically unchanged. The long-wave luminscence band of the δ-KIO3 HIO3 crystal with peak position at 410-420 nm and the lifetime of about 1 s is attributed to phosphorescence. This spectrum appears only in the case of excitation within the region of self-absorption of the crystal, eg λ3xc = 275 nm. On the basis of experimental data analysis, the assumption has been made that the short-wave band originates from the emission of excitons located at the defects of the crystal structure, and the long-wave band is related to radiation decay of autolocated bihalide excitons. Possible photoprocesses in the title crystal caused by light absorption of different wavelength are discussed.

  12. Effects of Temperature Raising Speed on the Growth of BN Crystals in Hydrothermal Solutions

    Institute of Scientific and Technical Information of China (English)

    YU,Mei-Yan(于美燕); LI,Kai(李凯); CUI,De-Liang(崔得良); DONG,Shou-Yi(董守义); WANG,Qi-Long(王琪珑); JIANG,Min-Hua(蒋民华)

    2004-01-01

    Cubic boron nitride (cBN) and orthorhombic boron nitride (oBN) crystals have been prepared in hydrothermal solutions by reacting H3BO3+NaN3+P and H3BO3+NaN3+N2H4 respectively. The experimental results indicated that, if the temperature was increased rapidly, both the yield and perfectness of BN crystals became poor. On the contrast, the yield and perfectness of BN crystals can be improved very much by slowly increasing the temperature of the reaction mixture. The results of X-ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR)and high resolution transmission electron microscopy (HRTEM) proved that the samples were composed of oBN and cBN.

  13. Surface induces different crystal structures in a room temperature switchable spin crossover compound.

    Science.gov (United States)

    Gentili, Denis; Liscio, Fabiola; Demitri, Nicola; Schäfer, Bernhard; Borgatti, Francesco; Torelli, Piero; Gobaut, Benoit; Panaccione, Giancarlo; Rossi, Giorgio; Degli Esposti, Alessandra; Gazzano, Massimo; Milita, Silvia; Bergenti, Ilaria; Ruani, Giampiero; Šalitroš, Ivan; Ruben, Mario; Cavallini, Massimiliano

    2016-01-01

    We investigated the influence of surfaces in the formation of different crystal structures of a spin crossover compound, namely [Fe(L)2] (LH: (2-(pyrazol-1-yl)-6-(1H-tetrazol-5-yl)pyridine), which is a neutral compound thermally switchable around room temperature. We observed that the surface induces the formation of two different crystal structures, which exhibit opposite spin transitions, i.e. on heating them up to the transition temperature, one polymorph switches from high spin to low spin and the second polymorph switches irreversibly from low spin to high spin. We attributed this inversion to the presence of water molecules H-bonded to the complex tetrazolyl moieties in the crystals. Thin deposits were investigated by means of polarized optical microscopy, atomic force microscopy, X-ray diffraction, X-ray absorption spectroscopy and micro Raman spectroscopy; moreover the analysis of the Raman spectra and the interpretation of spin inversion were supported by DFT calculations.

  14. Frequency and Temperature Dependence of Fabrication Parameters in Polymer Dispersed Liquid Crystal Devices

    Directory of Open Access Journals (Sweden)

    Juan C. Torres

    2014-05-01

    Full Text Available A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed.

  15. Single-Crystal Elastic Constants of Yttria (Y2O3) Measured to High Temperatures

    Science.gov (United States)

    Sayir, Ali; Palko, James W.; Kriven, Waltraud M.; Sinogeikin, Sergey V.; Bass, Jay D.

    2001-01-01

    Yttria, or yttrium sesquioxide (Y2O3), has been considered for use in nuclear applications and has gained interest relatively recently for use in infrared optics. Single crystals of yttria have been grown successfully at the NASA Glenn Research Center using a laser-heated float zone technique in a fiber and rod. Such samples allow measurement of the single-crystal elastic properties, and these measurements provide useful property data for the design of components using single crystals. They also yield information as to what degree the elastic properties of yttria ceramics are a result of the intrinsic properties of the yttria crystal in comparison to characteristics that may depend on processing, such as microstructure and intergranular phases, which are common in sintered yttria. The single-crystal elastic moduli are valuable for designing such optical components. In particular, the temperature derivatives of elastic moduli allow the dimensional changes due to heating under physical constraints, as well as acoustic excitation, to be determined. The single-crystal elastic moduli of yttria were measured by Brillouin spectroscopy up to 1200 C. The room-temperature values obtained were C(sub 11) = 223.6 + 0.6 GPa, C(sub 44) = 74.6 + 0.5 GPa, and C(sub 12) = 112.4 + 1.0 GPa. The resulting bulk and (Voigt-Reuss-Hill) shear moduli were K = 149.5 + 1.0 GPa and G(sub VRH) = 66.3 + 0.8 GPa, respectively. Linear least-squares regressions to the variation of bulk and shear moduli with temperature resulted in derivatives of dK/dT = -17 + 2 MPa/C and dG(sub VRH)/dT = -8 + 2 MPa/ C. Elastic anisotropy was found to remain essentially constant over the temperature range studied.

  16. Variation of low temperature internal friction of microplastic deformation of high purity molybdenum single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Pal-Val, P.P. (AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst. Nizkikh Temperatur); Kaufmann, H.J. (Akademie der Wissenschaften der DDR, Berlin)

    1984-08-01

    Amplitude and temperature spectra of ultrasound absorption in weakly deformed high purity molybdenum single crystals of different orientations were measured. The results were discussed in terms of parameter changes related to quasiparticle or dislocation oscillations, respectively, dislocation point defect interactions as well as defect generation at microplastic deformation.

  17. Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index, strain, and temperature sensing

    DEFF Research Database (Denmark)

    Rindorf, Lars Henning; Bang, Ole

    2008-01-01

    We study the sensitivity of fiber grating sensors in the applications of strain, temperature, internal label-free biosensing, and internal refractive index sensing. New analytical expressions for the sensitivities, valid for photonic crystal fibers are rigorously derived. These are generally valid...

  18. Low-temperature, template-free synthesis of single-crystal bismuth telluride nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Purkayastha, A. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180 (United States); Lupo, F. [Max Planck Institut fuer Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart (Germany); Kim, S.; Borca-Tasciuc, T. [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180 (United States); Ramanath, G. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180 (United States); Max Planck Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)

    2006-02-17

    Synthesis of single-crystal bismuth telluride nanorods is reported by using a low-temperature, template-free approach. Films of thioglycolic acid functionalized nanorods doped with sulfur exhibit n-type behavior with a high Seebeck coefficient, holding promise for thermoelectric device applications. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  19. Dielectric relaxation processes in smoky quartz crystals at very low temperatures

    NARCIS (Netherlands)

    Vos, W.J. de; Volger, J.

    1967-01-01

    The relaxation time governing the dielectric loss of smoky quartz crystals appears to level off as a function of temperature below 12°K, approaching a value of about 1 msec. The relaxational behaviour of the colour centres is discussed in terms of tunneling processes.

  20. Dielectric relaxation processes in smoky quartz crystals at very low temperatures

    NARCIS (Netherlands)

    Vos, W.J. de; Volger, J.

    1967-01-01

    The relaxation time governing the dielectric loss of smoky quartz crystals appears to level off as a function of temperature below 12°K, approaching a value of about 1 msec. The relaxational behaviour of the colour centres is discussed in terms of tunneling processes.

  1. Low-temperature photoluminescence analysis of CdTeSe crystals for radiation-detector applications

    Energy Technology Data Exchange (ETDEWEB)

    YANG G.; Roy, U. N.; Bolotnikov, A. E.; Cui, Y.; Camarda, G.S.; Hossain, A.; and James, R. B.

    2015-10-05

    Goal: Understanding the changes of material defects in CdTeSe following annealing. Experimental results and discussions: Infrared (IR) transmission microscopy; current-voltage measurements (Highlight: Improvement of resistivity of un-doped crystals after annealing); low-temperature photoluminescence (PL) spectrum of as-grown and annealed samples.

  2. Crystallization speed of salbutamol as a function of relative humidity and temperature.

    Science.gov (United States)

    Zellnitz, Sarah; Narygina, Olga; Resch, Christian; Schroettner, Hartmuth; Urbanetz, Nora Anne

    2015-07-15

    Spray dried salbutamol sulphate and salbutamol base particles are amorphous as a result of spray drying. As there is always the risk of recrystallization of amorphous material, the aim of this work is the evaluation of the temperature and humidity dependent recrystallization of spray dried salbutamol sulphate and base. Therefore in-situ Powder X-ray Diffraction (PXRD) studies of the crystallization process at various temperature (25 and 35 °C) and humidity (60%, 70%, 80%, 90% relative humidity) conditions were performed. It was shown that the crystallization speed of salbutamol sulphate and base is a non-linear function of both temperature and relative humidity. The higher the relative humidity the higher is the crystallization speed. At 60% relative humidity salbutamol base as well as salbutamol sulphate were found to be amorphous even after 12 h, however samples changed optically. At 70% and 90% RH recrystallization of salbutamol base is completed after 3 h and 30 min and recrystallization of salbutamol sulphate after 4h and 1h, respectively. Higher temperature (35 °C) also leads to increased crystallization speeds at all tested values of relative humidity.

  3. Calcium aluminate silicate Ca2Al2SiO7 single crystal applicable to piezoelectric sensors at high temperature

    Science.gov (United States)

    Takeda, Hiroaki; Hagiwara, Manabu; Noguchi, Hiroaki; Hoshina, Takuya; Takahashi, Tomoko; Kodama, Nobuhiro; Tsurumi, Takaaki

    2013-06-01

    Ca2Al2SiO7 (CAS) bulk single crystals were grown by the Czochralski method. Material constants of the crystal were determined over the driving temperature range of a typical combustion pressure sensor. The electrical resistivity at 800 °C was found to be of the order of 108 Ωcm. We constructed a measurement system for the direct piezoelectric effect at high temperature, and characterized the crystals in a simulated engine cylinder combustion environment. Output charge signal against applied stress was detected at 700 °C. These observations suggest that CAS crystals are superior candidate materials for high temperature for stress sensing.

  4. Recent Developments on High Curie Temperature PIN-PMN-PT Ferroelectric Crystals.

    Science.gov (United States)

    Zhang, Shujun; Li, Fei; Sherlock, Nevin P; Luo, Jun; Lee, Hyeong Jae; Xia, Ru; Meyer, Richard J; Hackenberger, Wesley; Shrout, Thomas R

    2011-03-01

    Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) ferroelectric crystals attracted extensive attentions in last couple years, due to their higher usage temperatures range (> 30°C) and coercive fields (~5kV/cm), meanwhile maintaining similar electromechanical couplings (k(33)> 90%) and piezoelectric coefficients (d(33)~1500pC/N), when compared to their binary counterpart Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3). In this article, we reviewed recent developments on the PIN-PMN-PT single crystals, including the Bridgman crystal growth, dielectric, electromechanical, piezoelectric and ferroelectric behaviors as function of temperature and dc bias. Mechanical quality factor Q was studied as function of orientation and phase. Of particular interest is the dynamic strain, which related to the Q and d(33), was found to be improved when compared to binary system, exhibiting the potential usage of PIN-PMN-PT in high power application. Furthermore, PIN-PMN-PT crystals exhibit improved thickness dependent properties, due to their small domain size, being on the order of 1μm. Finally, the manganese acceptor dopant in the ternary crystals was investigated and discussed briefly in this paper.

  5. Effect of crystallization temperature and propylene sequence length on the crystalline structure of propylene-ethylene random copolymers

    Institute of Scientific and Technical Information of China (English)

    GOU QingQiang; LI HuiHui; YU ZhenQiang; CHEN ErQiang; ZHANG YuDong; YAN ShouKe

    2008-01-01

    Crystallization behavior and resultant crystalline structure of a series of temperature-rising elu-tion-fractionated specimen of a Ziegler-Natta catalyst-synthesized propylene-ethylene random co-polymer were studied by DSC, WAXD and AFM. The experimental results indicate that both crystalliza-tion temperature and propylene sequence length exhibit great influence on the crystallization behavior and crystalline structure of the copolymer. It was found that the ethylene co-monomers acting as point defects inserted into the polypropylene chains play an important role in the formation of γ-iPP. As the co-monomer content increases, the crystallizable sequence length of iPP decreases, which produces an appropriate condition for its γ crystallization. At the same time, the existence of chain defects leads to a lower crystallinity of the copolymer and imperfection of the resultant crystals. For each individual sample with certain propylene sequence length or ethylene content, the increment of γ-iPP crystal content with increasing crystallization temperature demonstrates that higher crystallization tempera-ture is in favor of the γ-iPP crystallization. Pure γ-iPP crystals have been got in samples with propylene sequence length lower than 21 under suitable crystallization conditions.

  6. EFFECTS OF CONVECTIVE FLUID MOTION UPON OXIDE CRYSTAL GROWTH IN HIGH TEMPERATURE SOLUTION

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ For understanding of the influence of convective flow on crystal growth, space high temperature in situ observation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystals in high temperature up to 1000°C. Model experiments using transparent liquids such as KNbO3 and a mix ture of Li2B4O7+KNbO3 were chosen to investigate effects on ground and in space.On the earth, an investigation of growth kinetics of KNbO3 crystal related to two different states of convection: diffusive-advective flow and diffusive-convective flow,has been performed. The per unit length of a step e is calculated from the exper imental data for two different states of convection. Analyses of these data show the effect of buoyancy convection is to enhance the sharpness of the interface. The growth of KNbO3 crystals from solution of KNbO3+Li2B4O7 was investigated in space. The streamlines of the steady thermocapillary convection in Li2B4O7 solvent was observed. Due to thermocapillary convection, KNbO3 crystal grains grew and filled the whole solution homogeneously. Earth-based quenching experiments are de signed in order to study polyhedral instability of KNbO3 crystal, which is controlled by diffusion mechanism limitation. In all cases, when the crystal was nucleated near air/solution surface, it lost its polyhedral stability and varied from polyhedrons to dedrites. The thickness of diffusion mechanism limitation layer is about 60μm.

  7. Differential Phononic Crystal Sensor: Towards a Temperature Compensation Mechanism for Field Applications Development.

    Science.gov (United States)

    Villa-Arango, Simón; Betancur Sánchez, David; Torres, Róbinson; Kyriacou, Panayiotis; Lucklum, Ralf

    2017-08-25

    Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be used as measures to quantify changes in the speed of sound of liquid samples that could be related to the concentration of analytes or the presence of pathogens among other interesting applications. In order to be able to implement this new technology in more challenging applications, such as biomedical applications, it is necessary to have a very precise and accurate measurement. Changes in temperature greatly affect the speed of sound of the liquid samples, causing errors in the measurements. This article presents a phononic crystal sensor that, by introducing additional defect modes, can carry out differential measurements as a temperature compensation mechanism. Theoretical studies using the transmission line model and analytes at various temperatures show that the proposed temperature compensation mechanism enhances the performance of the sensor in a significant way. This temperature compensation strategy could also be implemented in crystals with different topologies.

  8. Cu-Al-Ni Shape Memory Single Crystal Wires with High Transformation Temperature

    Science.gov (United States)

    Hautcoeur, Alain; Fouché, Florian; Sicre, Jacques

    2016-01-01

    CN-250X is a new material with higher performance than Nickel-Titanium Shape Memory Alloy (SMA). For space mechanisms, the main disadvantage of Nickel-Titanium Shape Memory Alloy is the limited transformation temperature. The new CN-250X Nimesis alloy is a Cu-Al-Ni single crystal wire available in large quantity because of a new industrial process. The triggering of actuators made with this Cu-Al-Ni single crystal wire can range from ambient temperature to 200 C in cycling and even to 250 C in one-shot mode. Another advantage of CN-250X is a better shape recovery (8 to 10%) than Ni-Ti (6 to 7%). Nimesis is the first company able to produce this type of material with its new special industrial process. A characterization study is presented in this work, including the two main solicitation modes for this material: tensile and torsion. Different tests measure the shape recovery of Cu-Al-Ni single crystals wires during heating from room temperature to a temperature higher than temperature of end of martensitic transformation.

  9. Temperature-Dependent Sellmeier Equations of IR Nonlinear Optical Crystal BaGa4Se7

    Directory of Open Access Journals (Sweden)

    Naixia Zhai

    2017-02-01

    Full Text Available The thermal dependent principal refractive indices of a new promising IR nonlinear optical crystal BaGa4Se7 at wavelengths of 0.546, 0.5806, 0.644, 0.7065, 1.530, 1.970, and 2.325μm were measured by using the vertical incidence method within the temperature range from 25 to 150 °C. We derived equations of thermal refractive index coefficients as a function of wavelength that could be used to calculate the principal thermal refractive indices at different wavelengths. The temperature-dependent Sellmeier equations were also obtained and used to calculate the phase matching angles for the optical parametric process of BaGa4Se7 crystal at different temperatures.

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

    Science.gov (United States)

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

    1999-01-01

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

  11. Experimental setup for investigating silicon solid phase crystallization at high temperatures.

    Science.gov (United States)

    Schmidt, Thomas; Gawlik, Annett; Schneidewind, Henrik; Ihring, Andreas; Andrä, Gudrun; Falk, Fritz

    2013-07-15

    An experimental setup is presented to measure and interpret the solid phase crystallization of amorphous silicon thin films on glass at very high temperatures of about 800 °C. Molybdenum-SiO(2)-silicon film stacks were irradiated by a diode laser with a well-shaped top hat profile. From the relevant thermal and optical parameters of the system the temperature evolution can be calculated accurately. A time evolution of the laser power was applied which leads to a temperature constant in time in the center of the sample. Such a process will allow the observation and interpretation of solid phase crystallization in terms of nucleation and growth in further work.

  12. Influence of temperature and humidity on the detection of benzene vapor by piezoelectric crystal sensor

    CERN Document Server

    Han, Chan-Hyon; Yun, Jong-Ho; Sin, Kye-Ryong

    2016-01-01

    The effects of temperature and humidity on the estimation of air pollution by benzene by using the piezoelectric crystal gas sensor were studied. Polyvinylchloride films were used as substrate for the immobilization of polymethylphenylsiloxane onto the electrode surface of the piezoelectric crystal. The sensing layer consisting of polymethylphenylsiloxane and polyvinylchloride was used for real-time monitoring of benzene, one of the atmospheric pollutants. According to the humidity from 35% to 75%, the upper limit of detection by this sensor was decreased and the response time and frequency recovery time for detecting benzene were long. On the other hand, as increasing the temperature, the response time and the frequency recovery time of the sensor were short, but its sensitivity got worse. The models for the correlation between the benzene concentration and temperature (or humidity) were presented.

  13. Dermofat Graft in Severe Wrinkles on the Forehead and Glabellar Region

    Institute of Scientific and Technical Information of China (English)

    马群; 吴海龙; 张丛

    2012-01-01

      Background] leather high fat transplantation has been used many surgeons in the patient's facial recontouring aesthetic, has the good long-term results. Methods:leather fat transplantation yield from the left bottom, then leather fat transplantation into tunnel beneath the wrinkle. All patients were followed up for 3 years, the absorption of interest rate, the activity, the satisfaction of the patients is used as outcome measures and careful analysis. Results:the seriousness of the improved obviously, wrinkles forehead and glabllar area is obvious, most patients leather fat amount after transplantation. Conclusion:dermal high fat transplantation can be a good treatment choice of patients with the severity of the forehead wrinkles and glabllar area.

  14. Crystal growth and electronic structure of low-temperature phase SrMgF{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Atuchin, Victor V. [Laboratory of Optical Materials and Structures, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Functional Electronics Laboratory, Tomsk State University, Tomsk 634050 (Russian Federation); Laboratory of Semiconductor and Dielectric Materials, Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Goloshumova, Alina A. [Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Isaenko, Ludmila I. [Laboratory of Semiconductor and Dielectric Materials, Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Jiang, Xingxing [BCCRD, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lobanov, Sergey I. [Laboratory of Crystal Growth, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090 (Russian Federation); Zhang, Zhaoming [Australian Nuclear Science & Technology Organisation, Lucas Heights, NSW 2234 (Australia); Lin, Zheshuai, E-mail: zslin@mail.ipc.ac.cn [BCCRD, Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-04-15

    Using the vertical Bridgman method, the single crystal of low temperature phase SrMgF{sub 4} is obtained. The crystal is in a very good optical quality with the size of 10×7×5 mm{sup 3}. Detailed photoemission spectra of the element core levels are determined by a monochromatic AlKa (1486.6 eV) X-ray source. Moreover, the first-principles calculations are performed to investigate the electronic structure of SrMgF{sub 4}. A good agreement between experimental and calculated results is achieved. It is demonstrated that almost all the electronic orbitals are strongly localized and the hybridization with the others is very small, but the Mg–F bonds covalency is relatively stronger than that of Sr–F bonds. - Graphical abstract: Large size of low-temperature phase SrMgF{sub 4} crystal was obtained (right) and its electronic structure was investigated by X-ray photoelectron spectroscopy and first-principles calculation (left). - Highlights: • Large size single crystal of low-temperature phase SrMgF{sub 4} is obtained. • Electronic structure of SrMgF{sub 4} is measured by X-ray photoelectron spectroscopy. • Partial densities of states are determined by first-principles calculation. • Good agreement between experimental and calculated results is achieved. • Strong ionic characteristics of chemical bonds are exhibited in SrMgF{sub 4}.

  15. Integrated optic current transducers incorporating photonic crystal fiber for reduced temperature dependence.

    Science.gov (United States)

    Chu, Woo-Sung; Kim, Sung-Moon; Oh, Min-Cheol

    2015-08-24

    Optical current transducers (OCT) are indispensable for accurate monitoring of large electrical currents in an environment suffering from severe electromagnetic interference. Temperature dependence of OCTs caused by its components, such as wave plates and optical fibers, should be reduced to allow temperature-independent operation. A photonic crystal fiber with a structural optical birefringence was incorporated instead of a PM fiber, and a spun PM fiber was introduced to overcome the temperature-dependent linear birefringence of sensing fiber coil. Moreover, an integrated optic device that provides higher stability than fiber-optics was employed to control the polarization and detect the phase of the sensed optical signal. The proposed OCT exhibited much lower temperature dependence than that from a previous study. The OCT satisfied the 0.5 accuracy class (IIEC 60044-8) and had a temperature dependence less than ± 1% for a temperature range of 25 to 78 °C.

  16. Analysis of the temperature dependence of the thermal conductivity of insulating single crystal oxides

    Directory of Open Access Journals (Sweden)

    E. Langenberg

    2016-10-01

    Full Text Available The temperature dependence of the thermal conductivity of 27 different single crystal oxides is reported from ≈20 K to 350 K. These crystals have been selected among the most common substrates for growing epitaxial thin-film oxides, spanning over a range of lattice parameters from ≈3.7 Å to ≈12.5 Å. Different contributions to the phonon relaxation time are discussed on the basis of the Debye model. This work provides a database for the selection of appropriate substrates for thin-film growth according to their desired thermal properties, for applications in which heat management is important.

  17. Room Temperature Ferromagnetism in InTe Layered Semiconductor Crystals Intercalated by Cobalt

    Directory of Open Access Journals (Sweden)

    V.B. Boledzyuk

    2015-03-01

    Full Text Available The magnetic properties of CoxInTe layered crystals electrochemically intercalated with cobalt in constant gradient magnetic field and the morphology of the van der Waals surfaces of layers of these crystals were studied. It was established that impurity clusters consisting of cobalt nanoparticles are formed in the intercalates under investigation on the van der Waals planes in the interlayer space. It was revealed that at room temperature the investigated CoxInTe intercalates exhibit magnetic properties characteristic for magnetically hard ferromagnetic materials.

  18. A note on temperature-dependent band narrowing in oligo-acene crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hannewald, K; Stojanovic, V M; Bobbert, P A [Group Polymer Physics, Eindhoven Polymer Laboratories, Technische Universiteit Eindhoven, PO Box 513, 5600 MB Eindhoven (Netherlands)

    2004-03-31

    We present a theoretical description of polaron band narrowing in oligo-acene crystals due to electron-lattice interaction. The analysis is based on a model which takes both local and nonlocal contributions to the electron-phonon coupling into account. Different approximation schemes are discussed and compared. The theory is supplemented by quantitative ab initio calculations of the temperature dependence of polaron bandwidths in oligo-acene crystals which show the important role of in-plane nonlocal electron-phonon coupling.

  19. A note on temperature-dependent band narrowing in oligo-acene crystals

    Science.gov (United States)

    Hannewald, K.; Stojanovic, V. M.; Bobbert, P. A.

    2004-03-01

    We present a theoretical description of polaron band narrowing in oligo-acene crystals due to electron-lattice interaction. The analysis is based on a model which takes both local and nonlocal contributions to the electron-phonon coupling into account. Different approximation schemes are discussed and compared. The theory is supplemented by quantitative ab initio calculations of the temperature dependence of polaron bandwidths in oligo-acene crystals which show the important role of in-plane nonlocal electron-phonon coupling.

  20. Temperature dependence of ratio between dielectric anisotropy and order parameter in fluorinated nematic liquid crystals

    Institute of Scientific and Technical Information of China (English)

    Ma Heng; Sun Rui-Zhi; Li Zhen-Xin; Liu Yu-Fang

    2008-01-01

    Temperature dependence of ratio between dielectric anisotropy and order parameter of fluorinated nematic liquid crystal is investigated by using a semi-empirical molecular orbital package that can accurately calculate an angle between molecular dipole moment and long axis.We optimize the molecular conformations with three semi-empirical Hamiltonians AM1,PM3 and PM5,and then make a comparison between computational results and experimental measurements.It is shown that the results obtained from AM1 method are in good agreement with the measurements.The present study offers an applicable method to predict the dielectric properties of liquid crystal material.

  1. Phase sensitivity to temperature of the guiding mode in polarization-maintaining photonic crystal fiber.

    Science.gov (United States)

    Song, Jingming; Sun, Kang; Li, Shuai; Cai, Wei

    2015-08-20

    The propagating phase changing of a polarization-maintaining photonic crystal fiber (PM-PCF) caused by temperature variation is theoretically studied, as well as compared with conventional PANDA fiber. As to verifying numerical analysis, a platform based on a Michelson interferometer for phase versus temperature measurement was built for both kinds of fiber. Experiments show that PM-PCF has similar temperature sensitivity with conventional polarization-maintaining fiber. With optimized PM-PCF design (thinner coating layer and coating material with smaller thermal expansion coefficient), the sensitivity could be further reduced to about 80% of the present level.

  2. A multimodal approach to estimating vigilance using EEG and forehead EOG

    Science.gov (United States)

    Zheng, Wei-Long; Lu, Bao-Liang

    2017-04-01

    Objective. Covert aspects of ongoing user mental states provide key context information for user-aware human computer interactions. In this paper, we focus on the problem of estimating the vigilance of users using EEG and EOG signals. Approach. The PERCLOS index as vigilance annotation is obtained from eye tracking glasses. To improve the feasibility and wearability of vigilance estimation devices for real-world applications, we adopt a novel electrode placement for forehead EOG and extract various eye movement features, which contain the principal information of traditional EOG. We explore the effects of EEG from different brain areas and combine EEG and forehead EOG to leverage their complementary characteristics for vigilance estimation. Considering that the vigilance of users is a dynamic changing process because the intrinsic mental states of users involve temporal evolution, we introduce continuous conditional neural field and continuous conditional random field models to capture dynamic temporal dependency. Main results. We propose a multimodal approach to estimating vigilance by combining EEG and forehead EOG and incorporating the temporal dependency of vigilance into model training. The experimental results demonstrate that modality fusion can improve the performance compared with a single modality, EOG and EEG contain complementary information for vigilance estimation, and the temporal dependency-based models can enhance the performance of vigilance estimation. From the experimental results, we observe that theta and alpha frequency activities are increased, while gamma frequency activities are decreased in drowsy states in contrast to awake states. Significance. The forehead setup allows for the simultaneous collection of EEG and EOG and achieves comparative performance using only four shared electrodes in comparison with the temporal and posterior sites.

  3. Preliminary stages before nasal reconstruction using forehead flap: restoring perinasal subunits and nostril patency

    Directory of Open Access Journals (Sweden)

    Victor Diniz de Pochat

    2015-03-01

    Full Text Available Due to the complex three-dimensional structure of the nose, the repair of the nasal defect requires reconstruction of three different layers: skin envelope, osteocartilaginous framework and nasal lining. Before nasal reconstruction can be accomplished, the nose must rest on a stable platform to avoid late nasal obstructions, and septal deviations resulting from scar contraction. We present three cases of nasal reconstruction using a forehead flap in which we performed a preliminary stage to increase reliability of outcomes.

  4. Eyelid-associated complications after autogenous fat injection for cosmetic forehead augmentation

    Science.gov (United States)

    2013-01-01

    Background We report two cases of unilateral upper eyelid swelling with multiple small lumps as an unusual complication of autogenous fat injection for cosmetic forehead augmentation. Case presentation Two female patients were referred to our clinic for unusual unilateral eyelid swelling, with multiple small lumps. The duration of symptoms differed in each case, but both patients had a history of autogenous fat injection for cosmetic forehead augmentation at a local plastic surgery clinic. The lumps were small (diameter 5 mm~10 mm), palpable, hard, and nonmobile, and were evaluated by magnetic resonance imaging (MRI). Lumps from the eyelids of two patients were excised under general anesthesia. All of the masses were located deeply and found near the superior orbital rim or lateral orbital rim. The lumps exhibited chronic inflammation with fibrosis. Some of the lumps showed foamy histiocytic aggregation and foreign body lipogranuloma, resulting from iatrogenic fat injection. After excision, all masses and swelling disappeared, and moderate ptotic eyelid or lagophthalmos of affected eyes also improved. Conclusions To our knowledge, eyelid swelling with multiple lumps in the eyelid is a very rare complication of autogenous fat injection for cosmetic forehead augmentation. This report should be helpful for ophthalmic clinicians who encounter these unusual symptoms. PMID:23841959

  5. Acoustic property reconstruction of a pygmy sperm whale (Kogia breviceps) forehead based on computed tomography imaging.

    Science.gov (United States)

    Song, Zhongchang; Xu, Xiao; Dong, Jianchen; Xing, Luru; Zhang, Meng; Liu, Xuecheng; Zhang, Yu; Li, Songhai; Berggren, Per

    2015-11-01

    Computed tomography (CT) imaging and sound experimental measurements were used to reconstruct the acoustic properties (density, velocity, and impedance) of the forehead tissues of a deceased pygmy sperm whale (Kogia breviceps). The forehead was segmented along the body axis and sectioned into cross section slices, which were further cut into sample pieces for measurements. Hounsfield units (HUs) of the corresponding measured pieces were obtained from CT scans, and regression analyses were conducted to investigate the linear relationships between the tissues' HUs and velocity, and HUs and density. The distributions of the acoustic properties of the head at axial, coronal, and sagittal cross sections were reconstructed, revealing that the nasal passage system was asymmetric and the cornucopia-shaped spermaceti organ was in the right nasal passage, surrounded by tissues and airsacs. A distinct dense theca was discovered in the posterior-dorsal area of the melon, which was characterized by low velocity in the inner core and high velocity in the outer region. Statistical analyses revealed significant differences in density, velocity, and acoustic impedance between all four structures, melon, spermaceti organ, muscle, and connective tissue (p acoustic properties of the forehead tissues provide important information for understanding the species' bioacoustic characteristics.

  6. Half forehead reconstruction with a single rotational scalp flap for dermatofibrosarcoma protuberans treatment

    Directory of Open Access Journals (Sweden)

    Mori Stefano

    2012-05-01

    Full Text Available Abstract Background Dermatofibrosarcoma protuberans (DFSP is a soft tissue neoplasm of intermediate to low-grade malignancy. Although metastasis rarely occurs, DFSP has a locally aggressive behavior with a high recurrence rate. In the head and neck area, resection involving a wide margin of healthy tissue can be difficult because of functional and cosmetic considerations. We describe a novel reconstructive method for half forehead defects with an innovative single local wide scalp flap following excision of DFSP with a 3 cm margin of healthy tissue. Methods Two patients underwent wide resection of forehead DFSP and reconstruction with a single rotational scalp flap. The scalp flap blood supply was provided from three main vessels: the superficial temporal artery, occipital artery and posterior auricular artery. Results No early or late complications were observed in either patient with no local recurrence after 18 months of follow-up. The donor area could be closed primarily in both cases and the flaps survived completely. Conclusion This innovative technique allowed a radical excision of forehead DFSP with sufficient healthy margins, thus potentially decreasing tumor recurrence rate. Reconstruction was achieved avoiding microsurgery, skin expanders and large skin grafts. Moreover, all main reconstructive criteria, such as functional and cosmetic tissue characteristics, were completely fulfilled.

  7. High-Pressure High-Temperature Phase Diagram of the Organic Crystal Paracetamol

    Science.gov (United States)

    Smith, Spencer; Montgomery, Jeffrey; Vohra, Yogesh

    High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped diamond as heating anvil. The HPHT data obtained from boron-doped diamond heater is cross-checked with data obtained using a standard block heater diamond anvil cell. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in a number of different experiments. Solid state phase transitions from monoclinic Form I --> orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II --> unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. Our previous angle dispersive x-ray diffraction studies at the Advanced Photon Source has confirmed the existence of two unknown crystal structures Form IV and Form V of paracetamol at high pressure and ambient temperature. The phase transformation from Form II to Form IV occurs at ~8.5 GPa and from Form IV to Form V occurs at ~11 GPa at ambient temperature. Our new data is combined with the previous ambient temperature high-pressure Raman and X- ray diffraction data to create the first HPHT phase diagram of paracetamol. Doe-NNSA Carnegie DOE Alliance Center (CDAC) under Grant Number DE-NA0002006.

  8. Crystal Structure of D-Valine at the Temperature of 293, 270, 223 and 173K

    Institute of Scientific and Technical Information of China (English)

    WANG Wen-Qing; GONG Yan; WANG Zhe-Ming; YAN Chun-Hua

    2003-01-01

    The crystal structure of D-valine has been determined by Mo-Kα (λ = 0.71073 A) X-ray diffraction method for the first time. It crystallizes in monoclinic, space group P21 (Z = 4) with a = 9.6728(5), b = 5.2722(3), c = 12.0425(8) A, β = 90.750(2)° at 293 K. The asymmetric unit contains two crystallographically independent molecules — A (trans form) and B (gauche I form). They are rotational isomers with two kinds of conformations about the Cα -Cβ bond. The results of measurements of crystal structure at 293, 270, 223 and 173 K show a little change in bond lengths and geometries as a function of temperature. No evidence was obtained for the existence of configuration transformation from D- to L-valine.

  9. Room-temperature effects of UV radiation in KBr:Eu{sup 2+} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Salas, R.; Melendrez, R. [Centro de Investigacion Cientifica y de Educacion Superior de Ensenada - IFUNAM, Ensenada, Apartado Postal 2732 Ensenada, BC, 22800 (Mexico); Aceves, R.; Rodriguez, R.; Barboza-Flores, M. [Centro de Investigacion en Fisica, Universidad de Sonora, Apartado Postal 5-088 Hermosillo, Sonora, 83190 (Mexico)

    1996-07-01

    Thermoluminescence and optical absorption measurements have been carried out in KBr:Eu{sup 2+} crystals irradiated with monochromatic UV light (200-300 nm) and x-rays at room temperature. For UV- and x-irradiated crystals strong similarities between the thermoluminescence glow curves have been found, suggesting that the low-energy UV radiation produces the same defects as produced by x-irradiation in this material. The thermoluminescence glow curves are composed of six glow peaks located at 337, 383, 403, 435, 475 and 509 K. Thermal annealing experiments in previously irradiated crystals show clearly a correlation between the glow peak located at 383 K and the F-centre thermal bleaching process. Also, the excitation spectrum for each thermoluminescence glow peak has been investigated, showing that the low-energy radiation induces the formation of F centres. (author)

  10. Electronic liquid crystal state in a strongly underdoped high-temperature superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Hinkov, V.; Haug, D.; Lin, C.T.; Keimer, B. [MPI-FKF, Stuttgart (Germany); Fauque, B.; Sidis, Y.; Bourges, P. [LLB, Saclay (France); Ivanov, A. [ILL, Grenoble (France); Bernhard, C. [Univ. of Fribourg (Switzerland)

    2008-07-01

    Liquid crystals are states of matter without static crystalline order that break the rotational symmetry of free space while at least partially preserving its translational symmetry. Highly correlated electronic phases with symmetry properties analogous to those of conventional liquid crystals have been theoretically predicted (Kivelson et al., Nature 393, 550) and recently discovered in the layered bulk transition metal oxide Sr{sub 3}Ru{sub 2}O{sub 7} (Borzi et al., Science 315, 214). In both cases, however, these phases are stable only at milli-Kelvin temperatures and in high magnetic fields, and have thus far only been probed by transport measurements. After briefly summarizing our work on YBCO{sub 6.6} (Hinkov et al., Nature Physics 3, 780), we report the spontaneous onset of a strong one-dimensional, incommensurate modulation of the spin system in the underdoped high-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 6.45} upon cooling below 150 K, while muon-spin-relaxation experiments on the same sample demonstrate that static magnetic order is absent down to temperatures of at least 2 K. The symmetry properties of the spin system thus match those of a nematic liquid crystal over a wide temperature range. Soft spin fluctuations are thus a microscopic route towards the formation of electronic nematic phases, which can coexist with high-T{sub c} superconductivity.

  11. Temperature-Induced Lattice Relaxation of Perovskite Crystal Enhances Optoelectronic Properties and Solar Cell Performance

    KAUST Repository

    Banavoth, Murali

    2016-12-14

    Hybrid organic-inorganic perovskite crystals have recently become one of the most important classes of photoactive materials in the solar cell and optoelectronic communities. Albeit improvements have focused on state-of-the-art technology including various fabrication methods, device architectures, and surface passivation, progress is yet to be made in understanding the actual operational temperature on the electronic properties and the device performances. Therefore, the substantial effect of temperature on the optoelectronic properties, charge separation, charge recombination dynamics, and photoconversion efficiency are explored. The results clearly demonstrated a significant enhancement in the carrier mobility, photocurrent, charge carrier lifetime, and solar cell performance in the 60 ± 5 °C temperature range. In this temperature range, perovskite crystal exhibits a highly symmetrical relaxed cubic structure with well-aligned domains that are perpendicular to a principal axis, thereby remarkably improving the device operation. This finding provides a new key variable component and paves the way toward using perovskite crystals in highly efficient photovoltaic cells.

  12. Wide Range Temperature Sensors Based on One-Dimensional Photonic Crystal with a Single Defect

    Directory of Open Access Journals (Sweden)

    Arun Kumar

    2012-01-01

    Full Text Available Transmission characteristics of one-dimensional photonic crystal structure with a defect have been studied. Transfer matrix method has been employed to find the transmission spectra of the proposed structure. We consider a Si/air multilayer system and refractive index of Si layer has been taken as temperature dependent. As the refractive index of Si layer is a function of temperature of medium, so the central wavelength of the defect mode is a function of temperature. Variation in temperature causes the shifting of defect modes. It is found that the average change or shift in central wavelength of defect modes is 0.064 nm/K. This property can be exploited in the design of a temperature sensor.

  13. High-pressure high-temperature phase diagram of organic crystal paracetamol

    Science.gov (United States)

    Smith, Spencer J.; Montgomery, Jeffrey M.; Vohra, Yogesh K.

    2016-01-01

    High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped heating diamond anvil. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in five different experiments. Solid state phase transitions from monoclinic Form I  →  orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II  →  unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. This new data is combined with previous ambient temperature high-pressure Raman and x-ray diffraction data to create the first HPHT phase diagram of paracetamol.

  14. Highly sensitive temperature sensor based on an isopropanol-filled photonic crystal fiber long period grating

    Science.gov (United States)

    Du, Chao; Wang, Qi; Zhao, Yong; Li, Jin

    2017-03-01

    A high sensitivity measurement method for temperature has been proposed and investigated based on an isopropanol-filled photonic crystal fiber long period grating (PCF-LPG). Due to the high thermo-optic coefficient (TOC) of isopropanol, the sensitivity of the proposed temperature sensor could be effectively improved by filling isopropanol in the air waveguides of PCF. It can be found that the resonant dip will be split in two dips after filling isopropanol and the two dips have different sensitivities to surrounding temperature. Because of PCF-LPG is sensitive to the refractive index (RI) of internal filled liquid, the isopropanol-filled PCF-LPG temperature sensor has a high sensitivities of 1.356 nm/°C in the range of 20-50 °C. The simplicity and the excellent performance of our proposed device make it potential for the applications of high-precision temperature measurement is required.

  15. The effect of temperature on one-dimensional nanometallic photonic crystals with coupled defects

    Indian Academy of Sciences (India)

    ABDOLRASOUL GHARAATI; ZEINAB ZARE

    2017-05-01

    Using the transfer matrix method, the effect of temperature on one-dimensional (1D) nanostructure photonic crystal with coupled defects has been investigated. One of the layers of this structure is silver. The complex refractive index of silver is dependent on temperature and wavelength. This structure is tunable with temperature and incident angle. It is found that the number of defect modes is equal to the number of coupled defects in all incident angles for both polarizations. Also by increasing the temperature, due to dissipation, the wavelength of the defect modes increases and the height of the defect modes decreases. The wavelengths of defect modes depend linearly on temperature for both polarizations in all incident angles.

  16. Temperature-dependent far-infrared properties of Bi_(12) GeO_(20) single crystal

    Institute of Scientific and Technical Information of China (English)

    Muhammad Kamran; Dai Yao-Min; Ma Ji-Yun; Li Bo-Hong; He Shi-Kun; Zhang Wei-Jun; Zheng Xiao-Rui; Qiu Xiang-Gang

    2009-01-01

    Far-infrared reflectivity spectra of bismuth germanium oxide(Bi_(12)GeO_(20))single crystals are measured from room temperature down to 10 K. All the reflectivity spectra are fitted to a complex dielectric function ε(w) in the factorised form. Phonon modes at low frequency are found to develop upon decreasing temperature and gain considerable spectrum weight below 150 K. The temperature dependent static dielectric constants are obtained from the Lyddane-Sachs-Teller relation based on the obtained oscillator parameters. The dielectric constants are found to increase upon decreasing temperature. which is attributed to the charge transfer among the ions in the unit cell with the temperature varying.

  17. Forehead and scalp sensation after brow-lift: a comparison between open and endoscopic techniques.

    Science.gov (United States)

    Guillot, Jason M; Rousso, Daniel E; Replogle, William

    2011-01-01

    To compare postoperative forehead and scalp sensation for the "open" brow-lift (OBL) (coronal and trichophytic) with that of the endoscopic brow-lift (EBL). A controlled outcome evaluation study was designed to objectively (mechanoceptive and thermoceptive) and subjectively (visual analog scale) test forehead and scalp sensation in a group of patients having undergone or scheduled to undergo either OBL or EBL in a single, private facial plastic surgery clinic. Prospectively enrolled participants were tested at defined intervals (A, preoperation; B,1-2 weeks after; C, 4-6 weeks after; D, 12-14 weeks after; and E, 24-26 weeks after). To provide extended follow-up data (≥6 months), patients returning for scheduled follow-up examination who had already undergone either OBL or EBL were subjected to the same test battery. For statistical analysis of the extended follow-up data, the participants were divided into 2 groups (F, 6-18 months; and G, >18 months). The null hypothesis was that there would be no measurable difference between the OBL and the EBL groups related to postoperative forehead and scalp sensation. Twenty-one individuals (EBL, n = 11; OBL, n = 10) were enrolled prospectively. All showed normal objective and subjective values preoperatively. While both groups objectively and subjectively demonstrated decreased sensation over follow-up, the OBL group showed statistically significant decrement in objective scalp sensitivity at times B, C, and D vs the EBL group. Subjectively, the OBL group felt less sensitive than the EBL group at times C and D. Those relationships disappeared at time E. Fifty-eight individuals were retrospectively enrolled. At time F (EBL, n = 16; OBL, n = 10), an objective and subjective difference was again observed with the OBL group demonstrating less scalp sensitivity vs the EBL group. At time G (EBL, n = 20; OBL, n = 12), this difference was no longer observed. We reject the null hypothesis and state that there is a measurable

  18. Temperature-tunable lasing in negative dielectric chiral nematic liquid crystal

    Science.gov (United States)

    Wu, Ri-Na; Wu, Jie; Wu, Xiao-Jiao; Dai, Qin

    2015-05-01

    In this work, negative dielectric nematic liquid crystal SLC12V620-400, chiral dopant S811, and laser dye DCM are used to prepare dye-doped chiral nematic liquid crystal laser sample. In order to investigate temperature-tunable lasing in negative dielectric chiral nematic liquid crystal, we measure the transmission and lasing spectrum of this sample. The photonic band gap (PBG) is observed to red shift with its width reducing from 71.2 nm to 40.2 nm, and its short-wavelength band edge moves 55.3 nm while the long-wavelength band edge only moves 24.9 nm. The wavelength of output laser is found to red shift from 614.4 nm at 20 °C to 662.8 nm at 67 °C, which is very different from the previous experimental phenomena. The refractive indices, parallel and perpendicular to the director in chiral nematic liquid crystal have different dependencies on temperature. The experiment shows that the pitch of this chiral nematic liquid crystal increases with the increase of temperature. The decrease in the PBG width, different shifts of band edges, and the red shift of laser wavelength are the results of refractive indices change and pitch thermal elongation. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Outstanding Young Scholars Growth Plans of Colleges and Universities in Liaoning Province, China (Grant No. LJQ2013022), the Science and Technology Research of Liaoning Province, China (Grant No. L2010465), the Open Funds of Liaoning Province Key Laboratory of Laser and Optical Information of Shenyang Ligong University, China.

  19. Characterization and inhibitive study of gel-grown hydroxyapatite crystals at physiological temperature

    Science.gov (United States)

    Parekh, Bharat; Joshi, Mihir; Vaidya, Ashok

    2008-04-01

    Hydroxyapatite is very useful for various biomedical applications, due to its chemical similarity with mineralized bone of human. Hydroxyapatite is also responsible for arthropathy (joint disease). In the present study, the growth of hydroxyapatite crystals was carried out by using single-diffusion gel growth technique in silica hydro gel media, at physiological temperature. The growth of hydroxyapatite crystals under slow and controlled environment in gel medium can be simulated in a simple manner to the growth in human body. The crystals, formed in the Liesegang rings, were characterized by powder XRD, FTIR and dielectric study. The diffusion study is also carried out for the hydroxyapatite crystals using the moving boundary model. The inhibitive influence of various Ayurvedic medicinal plant extracts such as Boswellia serrata gum resin , Tribulus terrestris fruits, Rotula aquatica roots, Boerhaavia diffusa roots and Commiphora wightii, on the growth of hydroxyapatite was studied. Roots of R. aquatica and B. diffusa show some inhibition of the hydroxyapatite crystals in vitro. This preclinical study will be helpful to design the therapy for prevention of hydroxyapatite-based ailments.

  20. Scintillation properties of the silver doped lithium iodide single crystals at room and low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Sajid [Department of Physics, Kyungpook National University, Daegu 41566 (Korea, Republic of); Department of Physics, Kohat University of Science and Technology, Kohat 26000 (Pakistan); Kim, H.J. [Department of Physics, Kyungpook National University, Daegu 41566 (Korea, Republic of); Lee, M.H., E-mail: mhlee@ibs.re.kr [Center for Underground Physics, Institute for Basic Science (IBS), Daejon 34047 (Korea, Republic of)

    2016-06-11

    This study presents luminescence and scintillation properties of Silver doped LiI crystals. Single crystals of LiI: x% Ag (x=0.02, 0.05, 0.1 and 0.5) were grown by using the Bridgman technique. X-ray induced luminescence spectra show emission bands spanning from 275 nm to 675 nm, dominated by Ag{sup +} band having a peak at 300 nm. Under UV-luminescence, a similar emission band was observed with the peak excitation wavelength of 265 nm. Energy resolution, light yield and decay time profiles of the samples were measured under a {sup 137}Cs γ-ray irradiation. The LiI(0.1%Ag) showed the highest light yield and the best energy resolution among the samples. The light yield of LiI(0.1%Ag) is higher than commercially available LiI(Eu) crystal (15,000±1500 ph/MeV). The LiI(Ag) samples exhibit three exponential decay time components except the LiI(0.02%Ag), where the fitting found two decay time components. Temperature dependences of emission spectra, light yield and decay time were studied from 300 K to 10 K. The LiI(0.1%Ag) crystal showed an increase in the light yield and a shortening of decay time with a decrease in temperature..

  1. Investigations of Cadmium Manganese Telluride Crystals for Room-Temperature Radiation Detection

    Energy Technology Data Exchange (ETDEWEB)

    Yang, G.; Bolotnikov, A.; Camarda, G.; Cui, Y.; Hossain, A.; Kim, K.; Carcelen, V.; Gul, R.; James, R.

    2009-10-06

    Cadmium manganese telluride (CMT) has high potential as a material for room-temperature nuclear-radiation detectors. We investigated indium-doped CMT crystals taken from the stable growth region of the ingot, and compared its characteristics with that from the last-to-freeze region. We employed different techniques, including synchrotron white-beam X-ray topography (SWBXT), current-voltage (I-V) measurements, and low-temperature photoluminescence spectra, and we also assessed their responses as detectors to irradiation exposure. The crystal from the stable growth region proved superior to that from the last-to-freeze region; it is a single-grain crystal, free of twins, and displayed a resistivity higher by two orders-of-magnitude. The segregation of indium dopant in the ingot might be responsible for its better resistivity. Furthermore, we recorded a good response in the detector fabricated from the crystal taken from the stable growth region; its ({mu}{tau}){sub e} value was 2.6 x 10{sup -3} cm{sup 2}/V, which is acceptable for thin detectors, including for applications in medicine.

  2. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.; Yang, Mengjin; Kovarik, Libor; Holesinger, Terry; Al-Jassim, Mowafak M.; Zhu, Kai; Zhou, Weilie; Berry, J. J.

    2016-07-08

    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapor results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 °C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 °C in ±25 °C steps (150-200 °C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.

  3. Effect of Water Vapor, Temperature, and Rapid Annealing on Formamidinium Lead Triiodide Perovskite Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Wozny, Sarah; Alkurd, Nooraldeen R.; Yang, Mengjin; Kovarik, Libor; Holesinger, Terry G.; Al-Jassim, Mowafak; Zhu, Kai; Zhou, Weilie; Berry, Joseph J.

    2016-07-08

    Perovskite-based solar cells are one of the emerging candidates for radically lower cost photovoltaics. Herein, we report on the synthesis and crystallization of organic-inorganic formamidinium lead triiodide perovskite films under controlled atmospheric and environmental conditions. Using in situ (scanning) transmission electron microscopy, we make observations of the crystallization process of these materials in nitrogen and oxygen gas with and without the presence of water vapor. Complementary planar samples were also fabricated in the presence of water vapor and characterized by in situ X-ray diffraction. Direct observations of the material structure and final morphology indicate that the exposure to water vapor results in a porous film that is metastable, regardless of the presence of argon, nitrogen, or oxygen. However, the optimal crystallization temperature of 175 degrees C is unperturbed across conditions. Rapid modulation about the annealing temperature of 175 degrees C in +/-25 degrees C steps (150-200 degrees C) promotes crystallization and significantly improves the film morphology by overcoming the presence of impregnated water trapped in the material. Following this processing protocol, we demonstrate substantial growth to micron-size grains via observation inside of an environmentally controlled transmission electron microscope. Adapting this insight from our in situ microscopy, we are able to provide an informed materials protocol to control the structure and morphology of these organic-inorganic semiconductors, which is readily applicable to benchtop device growth strategies.

  4. Low Temperature Rhombohedral Single Crystal SiGe Epitaxy on c-plane Sapphire

    Science.gov (United States)

    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.

  5. Preparation of room temperature terahertz detector with lithium tantalate crystal and thin film

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun, E-mail: ueoewj@gmail.com; Gou, Jun; Li, Weizhi [State Key Lab of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2014-02-15

    Research on room temperature terahertz (THz) detector is essential for promoting the application of THz science and technology. Both lithium tantalate crystal (LiTaO{sub 3}) and lithium tantalate thin film were used to fabricate the THz detector in this paper. Polishing process were used to reduce the thickness of LiTaO{sub 3} crystal slice by chemical mechanical polishing techniques and an improved sol-gel process was used to obtain high concentration LiTaO{sub 3} precursor solution to fabricate LiTaO{sub 3} thin film. Three dimension models of two THz detectors were set up and the temperature increasing map of two devices were simulated using finite element method. The lowest noise equivalent power value for terahertz detector using pyroelectric material reaches 6.8 × 10{sup −9} W at 30 Hz operating frequency, which is suitable for THz imaging application.

  6. Preparation of room temperature terahertz detector with lithium tantalate crystal and thin film

    Directory of Open Access Journals (Sweden)

    Jun Wang

    2014-02-01

    Full Text Available Research on room temperature terahertz (THz detector is essential for promoting the application of THz science and technology. Both lithium tantalate crystal (LiTaO3 and lithium tantalate thin film were used to fabricate the THz detector in this paper. Polishing process were used to reduce the thickness of LiTaO3 crystal slice by chemical mechanical polishing techniques and an improved sol-gel process was used to obtain high concentration LiTaO3 precursor solution to fabricate LiTaO3 thin film. Three dimension models of two THz detectors were set up and the temperature increasing map of two devices were simulated using finite element method. The lowest noise equivalent power value for terahertz detector using pyroelectric material reaches 6.8 × 10−9 W at 30 Hz operating frequency, which is suitable for THz imaging application.

  7. Co-doped sodium chloride crystals exposed to different irradiation temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-Morales, A. [Unidad Profesional Interdisciplinaria de Ingenieria y Tecnologias Avanzadas, IPN, Av. Instituto Politecnico Nacional 2580, Col. La Laguna Ticoman, 07340 Mexico D.F., Mexico and Unidad de Irradiacion y Segurid (Mexico); Cruz-Zaragoza, E.; Furetta, C. [Unidad de Irradiacion y Seguridad Radiologica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, A.P. 70-543, 04510 Mexico D.F (Mexico); Kitis, G. [Nuclear Physics Laboratory, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Flores J, C.; Hernandez A, J.; Murrieta S, H. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, AP. 20-364, 01000 Mexico D.F (Mexico)

    2013-07-03

    Monocrystals of NaCl:XCl{sub 2}:MnCl{sub 2}(X = Ca,Cd) at four different concentrations have been analyzed. The crystals were exposed to different irradiation temperature, such as at room temperature (RT), solid water (SW), dry ice (DI) and liquid nitrogen (LN). The samples were irradiated with photon from {sup 60}Co irradiators. The co-doped sodium chloride crystals show a complex structure of glow curves that can be related to different distribution of traps. The linearity response was analyzed with the F(D) index. The F(D) value was less than unity indicating a sub-linear response was obtained from the TL response on the function of the dose. The glow curves were deconvoluted by using the CGCD program based on the first, second and general order kinetics.

  8. Low Temperature Synthesis of Metal Oxides by a Supercritical Seed Enhanced Crystallization (SSEC) Process

    DEFF Research Database (Denmark)

    Jensen, Henrik; Brummerstedt Iversen, Steen; Joensen, Karsten Dan

    2006-01-01

    A novel method for producing crystalline nanosized metal oxides by a Supercritical Seed Enhanced Crystallization (SSEC) Process has been developed. The process is a modified sol-gel process taking place at temperatures as low as 95 ºC with supercritical CO2 as solvent and polypropylene as seeding....... The crystallinity can be controlled by changing the heating rate of the initial formation of the nanoparticles and the morphology can be altered by changing the process time....

  9. Demonstration of coherent emission from high-$\\beta$ photonic crystal nanolasers at room temperature

    CERN Document Server

    Hostein, Richard; Gratiet, Luc Le; Talneau, Anne; Beaudoin, Gregoire; Robert-Philip, Isabelle; Sagnes, Isabelle; Beveratos, Alexios

    2010-01-01

    We report on lasing at room temperature and at telecommunications wavelength from photonic crystal nanocavities based on InAsP/InP quantum dots. Such laser cavities with a small modal volume and high quality factor display a high spontaneous emission coupling factor beta. Lasing is confirmed by measuring the second order autocorrelation function. A smooth transition from chaotic to coherent emission is observed, and coherent emission is obtained at 8 times the threshold power.

  10. Demonstration of coherent emission from high-beta photonic crystal nanolasers at room temperature.

    Science.gov (United States)

    Hostein, R; Braive, R; Le Gratiet, L; Talneau, A; Beaudoin, G; Robert-Philip, I; Sagnes, I; Beveratos, A

    2010-04-15

    We report on lasing at room temperature and at telecommunications wavelength from photonic crystal nanocavities based on InAsP/InP quantum dots. Such laser cavities with a small modal volume and high quality factor display a high spontaneous emission coupling factor (beta). Lasing is confirmed by measuring the second-order autocorrelation function. A smooth transition from chaotic to coherent emission is observed, and coherent emission is obtained at eight times the threshold power.

  11. Low-temperature Growth of Single-crystal SrCO3 Nanoneedles

    Institute of Scientific and Technical Information of China (English)

    Guang Sheng GUO; Fu Bo GU; Zhi Hua WANG; Hong You GUO

    2005-01-01

    Single-crystal SrCO3 nanoneedles were synthesized in reverse micelles at low temperature. The products were characterized by X-ray diffraction, X-ray energy dispersive spectrometer, transmission electron microscopy and selected area electronic diffraction. The influences of experimental conditions on the morphologies of the products were discussed. The growth mechanism of SrCO3 nanoneedles in reverse micelles were proposed.

  12. Growth and characterization of crystals for room temperature I.R. detectors and second harmonic generation devices

    Science.gov (United States)

    Lal, R. B.

    1995-01-01

    One of the major objectives of this program was to modify the triglycine sulfate (TGS) crystals with suitable dopants and variants to achieve better pyroelectric properties and improved infrared detectivities (D(sup *)), and higher Curie transition temperature compared to undoped TGS crystals. Towards these objectives, many promising dopants, both inorganic and organic, were investigated in the last few years. These dopants gave significant improvement in the D(sup *) value of the infrared detectors fabricated from the grown crystals with no significant increase in the Curie temperature (49 C). The IR detectors were fabricated at EDO/Barnes Engineering Division, Shelton, CT. In the last one year many TGS crystals doped with urea were grown using the low temperature solution crystal growth facility. It is found that doping with urea, the normalized growth yield increased significantly compared to pure TGS crystals and there is an improvement in the pyroelectric and dielectric constant values of doped crystals. This gave a significant increase in the materials figure of merits. The Vicker's hardness of 10 wt percent urea doped crystals is found to be about three times higher in the (010) direction compared to undoped crystals. This report describes in detail the results of urea doped TGS crystals.

  13. Advances in crystal growth, device fabrication and characterization of thallium bromide detectors for room temperature applications

    Science.gov (United States)

    Datta, Amlan; Moed, Demi; Becla, Piotr; Overholt, Matthew; Motakef, Shariar

    2016-10-01

    Thallium bromide (TlBr) is a promising room-temperature radiation detector candidate with excellent charge transport properties. However, several critical issues need to be addressed before deployment of this material for long-term field applications can be realized. In this paper, progress made towards solving some of these challenges is discussed. The most significant factors for achieving long-term performance stability for TlBr devices include residual stress as generated during crystal growth and fabrication processes, surface conditions, and the choice of contact metal. Modifications to the commonly used traveling molten zone growth technique for TlBr crystals can significantly minimize the stresses generated by large temperature gradients near the melt-solid interface of the growing crystal. Plasma processing techniques were introduced for the first time to modify the Br-etched TlBr surfaces, which resulted in improvements to the surface conditions, and consequently the spectroscopic response of the detectors. Palladium electrodes resulted a 20-fold improvement in the room-temperature device lifetime when compared to its Br-etched Pt counterpart.

  14. Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Guo J.

    2015-06-01

    Full Text Available Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

  15. Temperature effect on lactose crystallization, maillard reactions, and lipid oxidation in whole milk powder.

    Science.gov (United States)

    Thomsen, Marianne K; Lauridsen, Lene; Skibsted, Leif H; Risbo, Jens

    2005-09-07

    Whole milk powder with an initial water content of 4.4% (w/w) and a water activity of 0.23 stored in hermetically sealed vials for up to 147 days below (37 and 45 degrees C) and above (55 degrees C) the glass transition temperature (T(g) determined to have the value 48 degrees C) showed a strong temperature dependence for quality deterioration corresponding to energies of activation close to 200 kJ/mol for most deteriorative processes. The glass transition was found not to cause any deviation from Arrhenius temperature dependence. Lactose crystallization, which occurred as a gradual process as monitored by isothermal calorimetry, is concluded to liberate bound water (a(w) increase to 0.46) with a modest time delay (approximately 2 days at 55 degrees C) and with concomitant surface browning as evidenced by an increasing Hunter b-value. Browning and formation of bound hydroxymethyl-furfural determined by HPLC seem to be coupled, while formation of another Maillard reaction product, furosine, occurred gradually and was initiated prior to crystallization. Initiation of lipid oxidation, as detected by lipid-derived radicals (high g-value ESR spectra), and progression of lipid oxidation, as detected by headspace GC, seem not to be affected by lactose crystallization and browning, and no indication of browning products acting as antioxidants could be determined.

  16. Temperature dependent phonon modes and ionicity of LiGaO2 single crystal

    Institute of Scientific and Technical Information of China (English)

    Ma Ji-Yun; Fang Xu; M.Kamran; Zhao Hua-Ying; Bi Cong-Zhi; Zhao Bai-Ru; Qiu Xiang-Gang

    2008-01-01

    This paper reports that polarized far-infrared reflectivity measurements have been done on LiGaO2 single crystal along two crystalline axes at different temperatures.The temperature dependent frequencies of the longitudinal and transverse optical phonon have been obtained from the real part of optical conductivity and the loss function respectively.A small Drude component is observed at frequency below 300 cm-1 which could arise from Li ions or oxygen deficiencies.The ionicity of LiGaO2 has been studied from the analysis of the Born effective charge of different ions.

  17. Laser beam propagation in nematic liquid crystals at the temperature close to the nematicisotropic critical point.

    Science.gov (United States)

    Chen, Yu-Jen; Lin, Yu-Sung; Jiang, I-Min; Tsai, Ming-Shan

    2008-03-17

    This study investigates the optical nonlinearity of beam propagation in homogeneously aligned nematic liquid crystal (NLC) cells at a temperature close to the nematic-isotropic temperature (TNI). The undulate propagation mode with convergent and divergent loops appearing alternately is reported and the thermally enhanced optical reorientation nonlinearity at the focus is described. The optically induced phase transition exists along the pump beam direction. With the application of the conscopic technique, the arrangements of LC at the focus are proposed in this study. Results of this study demonstrate that the evolution of the LC configuration was affected by the pump beam based on the analysis of conoscopic patterns.

  18. Thermal stimulated current response in cupric oxide single crystal thin films over a wide temperature range

    Science.gov (United States)

    Yang, Kungan; Wu, Shuxiang; Yu, Fengmei; Zhou, Wenqi; Wang, Yunjia; Meng, Meng; Wang, Gaili; Zhang, Yueli; Li, Shuwei

    2017-01-01

    Cupric oxide single crystal thin films (~26 nm) were grown by plasma-assisted molecular beam epitaxy. X-ray diffraction, Raman spectra and in situ reflection high-energy electron diffraction show that the thin films are 2  ×  2 reconstructed with an in-plane compression and out-of-plane stretching. A thermal stimulated current measurement indicates that the electric polarization response is shown in the special 2D cupric oxide single crystal thin film over a wide temperature range from 130 K to near-room temperature. We infer that the abnormal electric response involves the changing of phase transition temperature induced by structure distortion, the spin frustration and the magnetic fluctuation effect of a short-range magnetic order, or the combined action of both of the two factors mentioned above. This work suggests a promising clue for finding new room temperature single phase multiferroics or tuning phase transition temperatures.

  19. Formation of Polymer Networks for Fast In-Plane Switching of Liquid Crystals at Low Temperatures

    Science.gov (United States)

    Yu, Byeong-Hun; Song, Dong Han; Kim, Ki-Han; Wok Park, Byung; Choi, Sun-Wook; Park, Sung Il; Kang, Sung Gu; Yoon, Jeong Hwan; Kim, Byeong Koo; Yoon, Tae-Hoon

    2013-09-01

    We formed a polymer structure to enable fast in-plane switching of liquid crystals at low temperatures. The problem of the inevitable slow response at low temperatures was reduced by the formation of in-cell polymer networks in in-plane switching (IPS) cells. The electro-optic characteristics of polymer-networked IPS cells were measured at temperatures ranging from -10 to 20 °C. The turn-on and turn-off times of an IPS cell were reduced by 44.5 and 47.2% at -10 °C by the formation of polymer networks. We believe that the proposed technology can be applied to emerging display devices such as mobile phones and automotive displays that may be used at low temperatures.

  20. High temperature defect equilibrium in ZnS:Cu single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lott, K.; Shinkarenko, S.; Tuern, L.; Nirk, T.; Oepik, A. [Department of Materials Science, Tallinn University of Technology, Tallinn (Estonia); Kallavus, U. [Centre for Materials Research, Tallinn University of Technology, Tallinn (Estonia); Gorokhova, E. [Scientific Research and Technological Institute of Optical Material Science, S. I. Vavilov State Optical Institute, All-Russia Science Center, St. Petersburg (Russian Federation); Grebennik, A.; Vishnjakov, A. [Department of Physical Chemistry, D. Mendelejev University of Chemical Technology of Russia, Moscow (Russian Federation)

    2010-07-15

    High temperature investigations in ZnS:Cu crystals were performed under defined conditions. High temperature electrical conductivity and copper solubility data were obtained under different component vapour pressures and under different sample temperatures. The experimental data at sulphur vapour pressure can be explained by the inclusion of abnormal site occupation i.e. by antistructural disorder. Compensating association of copper with this antistructure defect may occur. Antistructure disorder disappears with increasing of zinc vapour pressure and with increasing role of holes in bipolar conductivity. The method for solving the system of quasichemical reactions without approximation was used to model high temperature defect equilibrium. This model contains antistructure disorder and copper solubility limitation. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  1. Alignment and temperature effects in liquid-crystal-based active polarimetry.

    Science.gov (United States)

    Gladish, James C; Duncan, Donald D

    2014-06-20

    It is well known that in liquid crystal (LC)-based active polarimetry, alignment and temperature effects impact polarimeter performance. Practically speaking, when constructing a polarimetric measurement system from LC variable retarders (LCVRs), unavoidable alignment and temperature uncertainties will occur, leading to systematic error that propagates to the Mueller matrix. Typical calibration methods use only a single metric to assess polarimeter performance (the condition number) and often ignore the relationship between systematic error and specific Mueller matrix elements. Here we explore alignment and temperature effects in a Stokes generator and polarimeter, each consisting of two LCVRs, through a series of simulations to calibrate the polarimeter and measure the Mueller matrix of air. We achieve this by modifying an existing LCVR model to incorporate alignment and temperature effects. This new approach offers insight into employing LCVRs individually and associating particular Mueller matrix element error with specific LCVR effects.

  2. New Crystal-Growth Methods for Producing Lattice-Matched Substrates for High-Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, L.A.

    2008-06-24

    This effort addressed the technical problem of identifying and growing, on a commercial scale, suitable single-crystal substrates for the subsequent deposition of epitaxial thin films of high temperature semiconductors such as GaN/AlN. The lack of suitable lattice-matched substrate materials was one of the major problem areas in the development of semiconducting devices for use at elevated temperatures as well as practical opto-electronic devices based on Al- and GaN technology. Such lattice-matched substrates are necessary in order to reduce or eliminate high concentrations of defects and dislocations in GaN/AlN and related epitaxial thin films. This effort concentrated, in particular, on the growth of single crystals of ZnO for substrate applications and it built on previous ORNL experience in the chemical vapor transport growth of large single crystals of zinc oxide. This combined expertise in the substrate growth area was further complemented by the ability of G. Eres and his collaborators to deposit thin films of GaN on the subject substrates and the overall ORNL capability for characterizing the quality of such films. The research effort consisted of research on the growth of two candidate substrate materials in conjunction with concurrent research on the growth and characterization of GaN films, i.e. the effort combined bulk crystal growth capabilities in the area of substrate production at both ORNL and the industrial partner, Commercial Crystal Growth Laboratories (CCL), Naples, Florida, with the novel thin-film deposition techniques previously developed in the ORNL SSD.

  3. Forehead lift

    Science.gov (United States)

    ... Elsevier Saunders; 2013:chap 1. McLain L. Facial cosmetic surgery. In: Hupp JR, Ellis E, Tucker MR, eds. ... Editorial team. Related MedlinePlus Health Topics Plastic and Cosmetic Surgery Skin Aging Browse the Encyclopedia A.D.A. ...

  4. Temperature dependence of birefringence in olarization-maintaining photonic crystal fibres

    Institute of Scientific and Technical Information of China (English)

    Zhao Hong; Chen Meng; Li Gang

    2012-01-01

    In this paper,the temperature dependence of birefringence in polarization maintaining photonic crystal fibres (PMPCFs) is investigated theoretically and experimentally.Utilizing the structural parameters of the PM-PCF samples in the experiment,two effects leading to the birefringence variation under different temperatures are analysed,which are the thermal expansion of silica material and the refractive index variation due to the temperature variation.The actual birefringence variation of the PM-PCF is the combination of the two effects,which is in the order of 10-9 K-1 for both fibre samples.Calculation results also show that the influence of refractive index variation is the dominant contribution,which determines the tendency of the fibre birefringence variation with varying temperature.Then,the birefringence beat lengths of the two fibre samples are measured under the temperature,which varies from -40 ℃ to 80 ℃.A traditional PANDA-type polarization maintaining fibre (PMF) is also measured in the same way for comparison.The experimental results indicate that the birefringence variation of the PM-PCF due to temperature variation is far smaller than that of the traditional PMF,which agrees with the theoretical analysis.The ultra-low temperature dependence of the birefringence in the PM-PCF has great potential applications in temperature-insensitive fibre interferometers,fibre sensors,and fibre gyroscopes.

  5. Low temperature amorphization and superconductivity in FeSe single crystals at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Stemshorn, Andrew K.; Tsoi, Georgiy; Vohra, Yogesh K.; Sinogeiken, Stanislav; Wu, Phillip M.; Huang, Yilin; Rao, Sistla M.; Wu, Maw-Kuen; Yeh, Kuo W.; Weir, Samuel T. (IP-Taiwan); (UAB); (Duke); (LLNL)

    2010-08-04

    In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 {+-} 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

  6. High-temperature crystallization of nanocrystals into three-dimensional superlattices

    Science.gov (United States)

    Wu, Liheng; Willis, Joshua J.; McKay, Ian Salmon; Diroll, Benjamin T.; Qin, Jian; Cargnello, Matteo; Tassone, Christopher J.

    2017-08-01

    Crystallization of colloidal nanocrystals into superlattices represents a practical bottom-up process with which to create ordered metamaterials with emergent functionalities. With precise control over the size, shape and composition of individual nanocrystals, various single- and multi-component nanocrystal superlattices have been produced, the lattice structures and chemical compositions of which can be accurately engineered. Nanocrystal superlattices are typically prepared by carefully controlling the assembly process through solvent evaporation or destabilization or through DNA-guided crystallization. Slow solvent evaporation or cooling of nanocrystal solutions (over hours or days) is the key element for successful crystallization processes. Here we report the rapid growth (seconds) of micrometre-sized, face-centred-cubic, three-dimensional nanocrystal superlattices during colloidal synthesis at high temperatures (more than 230 degrees Celsius). Using in situ small-angle X-ray scattering, we observe continuous growth of individual nanocrystals within the lattices, which results in simultaneous lattice expansion and fine nanocrystal size control due to the superlattice templates. Thermodynamic models demonstrate that balanced attractive and repulsive interparticle interactions dictated by the ligand coverage on nanocrystal surfaces and nanocrystal core size are responsible for the crystallization process. The interparticle interactions can also be controlled to form different superlattice structures, such as hexagonal close-packed lattices. The rational assembly of various nanocrystal systems into novel materials is thus facilitated for both fundamental research and for practical applications in the fields of magnetics, electronics and catalysis.

  7. The role of temperature on dielectric relaxation and conductivity mechanism of dark conglomerate liquid crystal phase

    Energy Technology Data Exchange (ETDEWEB)

    Yildiz, Alptekin [Istanbul Technical University, Department of Physics Engineering, 34469 Maslak, Istanbul (Turkey); Yildiz Technical University, Department of Physics, 34210 Esenler, Istanbul (Turkey); Canli, Nimet Yilmaz, E-mail: niyilmaz@yahoo.com [Yildiz Technical University, Department of Physics, 34210 Esenler, Istanbul (Turkey); Özdemir, Zeynep Güven [Yildiz Technical University, Department of Physics, 34210 Esenler, Istanbul (Turkey); Ocak, Hale; Eran, Belkız Bilgin [Yildiz Technical University, Department of Chemistry, 34210 Esenler, Istanbul (Turkey); Okutan, Mustafa [Yildiz Technical University, Department of Physics, 34210 Esenler, Istanbul (Turkey)

    2016-03-15

    In this study, dielectric properties and ac conductivity mechanism of the bent-core liquid crystal 3′-{4-[4-(3,7-Dimethyloctyloxy)benzoyloxy]benzoyloxy}-4-{4- [4-[6-(1,1,3,3,5,5,5-heptamethyltrisiloxan-1yl)hex-1-yloxy]benzoyloxy] benzoyloxy}biphenyl (DBB) have been analyzed by impedance spectroscopy measurements at different temperatures. According to the polarizing microscopy results, DBB liquid crystal compound exhibits a dark conglomerate mesophase (DC{sup [*]} phase) which can be identified by the occurrence of a conglomerate of domains with opposite chirality. The chiral domains of this low-birefringent mesophase become more visible by rotating the polarizer. The variation of the real (ε′) and imaginary (ε″) parts of dielectric constant with angular frequency and Cole–Cole curves of DBB have been analyzed. The fitting results for dispersion curves at different temperatures revealed that DBB system exhibits nearly Debye-type relaxation except for 125 °C. Moreover, it has been determined that while the relaxation frequencies shift to higher frequencies as the temperature increases from 25 °C to 125 °C, the peak intensities remarkably decrease with increasing temperature. According to Cole–Cole plot and phase angle versus frequency curve, it has been determined that DBB LC may have a possibility of utilizing as a super-capacitor at room temperature. Furthermore, it has been found that the conductivity mechanism of the DBB alters from Correlated Barrier Hoping (CBH) model to Quantum Tunneling Model (QMT) with in increasing temperature at high frequency region. In terms of CBH model, optical band gaps at 25 °C and 75 °C temperatures have also been calculated. Finally, activation energies for some selected angular frequencies have also been calculated.

  8. The role of temperature on dielectric relaxation and conductivity mechanism of dark conglomerate liquid crystal phase

    Science.gov (United States)

    Yildiz, Alptekin; Canli, Nimet Yilmaz; Özdemir, Zeynep Güven; Ocak, Hale; Eran, Belkız Bilgin; Okutan, Mustafa

    2016-03-01

    In this study, dielectric properties and ac conductivity mechanism of the bent-core liquid crystal 3‧-{4-[4-(3,7-Dimethyloctyloxy)benzoyloxy]benzoyloxy}-4-{4-[4-[6-(1,1,3,3,5,5,5-heptamethyltrisiloxan-1yl)hex-1-yloxy]benzoyloxy]benzoyloxy}biphenyl (DBB) have been analyzed by impedance spectroscopy measurements at different temperatures. According to the polarizing microscopy results, DBB liquid crystal compound exhibits a dark conglomerate mesophase (DC[*] phase) which can be identified by the occurrence of a conglomerate of domains with opposite chirality. The chiral domains of this low-birefringent mesophase become more visible by rotating the polarizer. The variation of the real (ε‧) and imaginary (ε″) parts of dielectric constant with angular frequency and Cole-Cole curves of DBB have been analyzed. The fitting results for dispersion curves at different temperatures revealed that DBB system exhibits nearly Debye-type relaxation except for 125 °C. Moreover, it has been determined that while the relaxation frequencies shift to higher frequencies as the temperature increases from 25 °C to 125 °C, the peak intensities remarkably decrease with increasing temperature. According to Cole-Cole plot and phase angle versus frequency curve, it has been determined that DBB LC may have a possibility of utilizing as a super-capacitor at room temperature. Furthermore, it has been found that the conductivity mechanism of the DBB alters from Correlated Barrier Hoping (CBH) model to Quantum Tunneling Model (QMT) with in increasing temperature at high frequency region. In terms of CBH model, optical band gaps at 25 °C and 75 °C temperatures have also been calculated. Finally, activation energies for some selected angular frequencies have also been calculated.

  9. Method of determination of temperature and heat resistance of the points on the integrated circuit crystal surface

    Directory of Open Access Journals (Sweden)

    Popov V. M.

    2011-12-01

    Full Text Available Method for visualization of integrated circuit (IC surface temperature by means of the liquid crystal film deposited from solution on its surface is proposed. The boundaries of local regions represent isotherms with corresponding phase transitions. On the base of isotherms positions and consumed by IC power thermal resistances between crystal and environment are determined.

  10. Effects of catalyst height on diamond crystal morphology under high pressure and high temperature

    Science.gov (United States)

    Ya-Dong, Li; Xiao-Peng, Jia; Bing-Min, Yan; Ning, Chen; Chao, Fang; Yong, Li; Hong-An, Ma

    2016-04-01

    The effect of the catalyst height on the morphology of diamond crystal is investigated by means of temperature gradient growth (TGG) under high pressure and high temperature (HPHT) conditions with using a Ni-based catalyst in this article. The experimental results show that the morphology of diamond changes from an octahedral shape to a cub-octahedral shape as the catalyst height rises. Moreover, the finite element method (FEM) is used to simulate the temperature field of the melted catalyst/solvent. The results show that the temperature at the location of the seed diamond continues to decrease with the increase of catalyst height, which is conducive to changing the morphology of diamond. This work provides a new way to change the diamond crystal morphology. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Program for New Century Excellent Talents in University, the Natural Science Foundation of Guizhou Provincial Education Department (Grant No. KY[2013]183), and the Collaborative Fund of Science and Technology Office of Guizhou Province, China (Grant No. LH[2015]7232).

  11. Structure determination of an integral membrane protein at room temperature from crystals in situ

    Energy Technology Data Exchange (ETDEWEB)

    Axford, Danny [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Foadi, James [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Hu, Nien-Jen; Choudhury, Hassanul Ghani [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Iwata, So [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Kyoto University, Kyoto 606-8501 (Japan); Beis, Konstantinos [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Alguel, Yilmaz, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom)

    2015-05-14

    The X-ray structure determination of an integral membrane protein using synchrotron diffraction data measured in situ at room temperature is demonstrated. The structure determination of an integral membrane protein using synchrotron X-ray diffraction data collected at room temperature directly in vapour-diffusion crystallization plates (in situ) is demonstrated. Exposing the crystals in situ eliminates manual sample handling and, since it is performed at room temperature, removes the complication of cryoprotection and potential structural anomalies induced by sample cryocooling. Essential to the method is the ability to limit radiation damage by recording a small amount of data per sample from many samples and subsequently assembling the resulting data sets using specialized software. The validity of this procedure is established by the structure determination of Haemophilus influenza TehA at 2.3 Å resolution. The method presented offers an effective protocol for the fast and efficient determination of membrane-protein structures at room temperature using third-generation synchrotron beamlines.

  12. Single-Crystal Tungsten Carbide in High-Temperature In-Situ Additive Manufacturing Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kolopus, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Boatner, Lynn A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-18

    Nanoindenters are commonly used for measuring the mechanical properties of a wide variety of materials with both industrial and scientific applications. Typically, these instruments employ an indenter made of a material of suitable hardness bonded to an appropriate shaft or holder to create an indentation on the material being tested. While a variety of materials may be employed for the indenter, diamond and boron carbide are by far the most common materials used due to their hardness and other desirable properties. However, as the increasing complexity of new materials demands a broader range of testing capabilities, conventional indenter materials exhibit significant performance limitations. Among these are the inability of diamond indenters to perform in-situ measurements at temperatures above 600oC in air due to oxidation of the diamond material and subsequent degradation of the indenters mechanical properties. Similarly, boron carbide also fails at high temperature due to fracture. [1] Transition metal carbides possess a combination of hardness and mechanical properties at high temperatures that offer an attractive alternative to conventional indenter materials. Here we describe the technical aspects for the growth of single-crystal tungsten carbide (WC) for use as a high-temperature indenter material, and we examine a possible approach to brazing these crystals to a suitable mount for grinding and attachment to the indenter instrument. The use of a by-product of the recovery process is also suggested as possibly having commercial value.

  13. Laser parameters of a Fe : ZnSe crystal in the 85-255-K temperature range

    NARCIS (Netherlands)

    Voronov, AA; Kozlovskii, [No Value; Korostelin, YV; Podmar'kov, YP; Frolov, MP

    The temperature dependence of the efficiency of a laser based on a Fe:ZnSe crystal grown from the vapour phase by the free-growth method is studied in the 85-255-K temperature range. As the temperature was increased, the slope efficiency of the laser with respect to absorbed energy decreased from

  14. Low Temperature heat capacity of Uranium-Plutonium MOX single crystals

    Science.gov (United States)

    Griveau, Jean-Christophe; Colineau, Eric; Eloirdi, Rachel; Caciuffo, Roberto

    2015-03-01

    The establishment of the basic properties of actinides based materials is crucial for the understanding of conventional and advanced nuclear fuels. Accessing ground state properties at very low temperature for these systems gives a direct overview of their fundamental features. Moreover, when these materials can be produced as single crystals, side effects due to the presence of grains and impurities phases are drastically reduced, giving a very powerful add-in for theoretical and industrial oriented studies. This clearly ensures the reliability of the parameters determined while existing models of these strategic materials can be probed especially in the purpose of applications/developments and safety concerns. Here we report on heat capacity measurements performed on U-Pu MOX in single crystal form. Tiny crystals with mass of 2 to 15 mg have been produced by solid-solid chemical vapour transport technique with several different compositions ranging from pure UO2 to PuO2. Compositions close to UO2 (U rich) present a persistent signature similarly to the magnetic transition reported for the pure phase TN ~ 31 K while plutonium rich concentrations do not show any hint of the magnetic transition down to the minimum temperature achieved.

  15. Control of polythiophene film microstructure and charge carrier dynamics through crystallization temperature

    KAUST Repository

    Marsh, Hilary S.

    2014-03-22

    The microstructure of neat conjugated polymers is crucial in determining the ultimate morphology and photovoltaic performance of polymer/fullerene blends, yet until recently, little work has focused on controlling the former. Here, we demonstrate that both the long-range order along the (100)-direction and the lamellar crystal thickness along the (001)-direction in neat poly(3-hexylthiophene) (P3HT) and poly[(3,3″-didecyl[2,2′:5′, 2″-terthiophene]-5,5″-diyl)] (PTTT-10) thin films can be manipulated by varying crystallization temperature. Changes in crystalline domain size impact the yield and dynamics of photogenerated charge carriers. Time-resolved microwave conductivity measurements show that neat polymer films composed of larger crystalline domains have longer photoconductance lifetimes and charge carrier yield decreases with increasing crystallite size for P3HT. Our results suggest that the classical polymer science description of temperature-dependent crystallization of polymers from solution can be used to understand thin-film formation in neat conjugated polymers, and hence, should be considered when discussing the structural evolution of organic bulk heterojunctions. © 2014 Wiley Periodicals, Inc.

  16. [Temperature-dependent optical activity and birefringence study of D-alanine single crystal].

    Science.gov (United States)

    Li, Zong-Sheng; Gong, Yan; Wang, Wen-Qing; Du, Wei-Min

    2006-02-01

    The measurement of the anisotropy of optical acitivity and birefringence is one of the most important clues to studying physical properties of a biaxial crystal of D-alanine. In order to investigate a second-order phase transition predicted by A. Salam between two states of D-alanine, the behavior of birefringence and optical activity is useful for the phenomenological approach to the transition mechanism. The optical activity as a peculiar quantity can respond to the modulation of the crystal lattice and to the change in the bonding nature of constituent atoms. In the present paper, the authors use the PEM-90 photoelastic modulator to study the conformation change of D-alanine at the temperature ranging from 220 to 290 K. The temperature dependence of I(2f)/I(dc) showed that the conformation of D-alanine molecule in single crystal changed around 250 K. The obtained results provide an obvious evidence of optical rotation phase transition predicted by Salam.

  17. Temperature-induced valence instability in the charge-transfer crystal TMB-TCNQ

    Science.gov (United States)

    Castagnetti, Nicola; Kociok-Köhn, Gabriele; Da Como, Enrico; Girlando, Alberto

    2017-01-01

    The occurrence of so-called temperature-induced neutral-ionic transitions (TINIT) in mixed-stack charge-transfer crystals is quite rare. Here we reinvestigate one of the crystals which has been claimed to undergo such a transition, 3 ,3',5 ,5' -tetramethylbenzidine-tetracyanoquinodimethane (TMB-TCNQ). Extensive optical data allow us to conclude that the transition should be classified as a valence instability, and not as a "true" TINIT, as the ˜0.5 neutral-ionic borderline is not crossed. The ionicity ϱ , or average charge at the molecular sites, indeed changes very little at the transition, from about 0.3 to about 0.4, and is accompanied by stack dimerization. The transition is first order with large hysteresis, and the crystal may crack or break. For this reason we have been unable to collect x-ray structural data on the low-temperature phase, but with the help of semiempirical calculations we are able to assess a plausible scenario for this peculiar phase transition and its mechanism.

  18. Constitutive modeling of creep behavior in single crystal superalloys: Effects of rafting at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Ya-Nan, E-mail: fanyn12@mails.tsinghua.edu.cn; Shi, Hui-Ji, E-mail: shihj@mail.tsinghua.edu.cn; Qiu, Wen-Hui

    2015-09-17

    Rafting and creep modeling of single crystal superalloys at high temperatures are important for the safety assessment and life prediction in practice. In this research, a new model has been developed to describe the rafting evolution and incorporated into the Cailletaud single crystal plasticity model to simulate the creep behavior. The driving force of rafting is assumed to be the relaxation of the strain energy, and it is calculated with the local stress state, a superposition of the external and misfit stress tensors. In addition, the isotropic coarsening is introduced by the cube root dependence of the microstructure periodicity on creep time based on Ostwal ripening. Then the influence of rafting on creep deformation is taken into account as the Orowan stress in the single crystal plasticity model. The capability of the proposed model is validated with creep experiments of CMSX-4 at 950 °C and 1050 °C. It is able to predict the rafting direction at complex loading conditions and evaluate the channel width during rafting. For [001] tensile creep tests, good agreement has been shown between the model predictions and experimental results at different temperatures and stress levels. The creep acceleration can be captured with this model and is attributed to the microstructure degradation caused by the precipitate coarsening.

  19. Optokinetic stimulation increases limb pain and forehead hyperalgesia in complex regional pain syndrome

    DEFF Research Database (Denmark)

    Knudsen, Lone F.; Drummond, Peter D.

    2015-01-01

    to investigate the mechanisms underlying the link between sensory conflicts and pain in CRPS using optokinetic stimulation (OKS) - a method known to induce motion sickness. METHODS: Twenty-one CRPS patients underwent OKS and rated symptoms of motion sickness. Patients also rated limb pain and pain....... In a subgroup of nauseated patients who withdrew early from OKS, hyperalgesia to pressure in the ipsilateral forehead persisted longer than in the remaining participants. Sharpness sensations remained constant at all sites. CONCLUSIONS: Sensory conflicts may facilitate pain in CRPS by activating the mechanisms...

  20. Neutron diffraction in a quartz single crystal under the action of acoustic oscillations or a temperature gradient

    CERN Document Server

    Mkrtchyan, A R; Hunanyan, H A; Beglaryan, A G

    1986-01-01

    The paper deals with the problem of neutron diffraction in a quartz single crystal under the action of acoustic oscillations or a temperature gradient in the Laue geometry. Theoretical conclusions were compared with experimental results.

  1. Thermal radiation and low-temperature-vapour growth of HgI 2 crystal in production furnace

    Science.gov (United States)

    Roux, A.; Fedoseyev, A.; Roux, B.

    1993-06-01

    Heat exchanges in a sealed ampoule in the LTVG (low temperature vapour growth) furnace have been modelled in order to compute temperature fields and control the growth of HgI 2 crystals from vapour phase at low temperatures. We use a coupled conductive-radiative model to determine the shapes of the source and the crystal at different equilibrium states (i.e. without growth rate). The model involves conductivity anisotropy in the crystal and radiative exchanges between grey and diffuse surfaces (source and crystal interfaces, Pyrex walls), which are considered as opaque. Internal buoyancy effect is not taken into account as the pressure inside the ampoule is very small. The source temperature is fixed. For different undercoolings, i.e. for different cold finger temperatures, the "equilibrium" isotherm between the source/gas and crystal/gas interface has been numerically obtained. This "equilibrium" isotherm, which is associated with the stop of the growing process, gives a crystal shape. This shape is compared with experimental results given by the ETH-Zürich group. The model would permit a better understanding and control of the future HgI 2 crystal growth experiment. The computations are performed using a finite element package (FIDAP).

  2. Fiber Sagnac interferometer based on a liquid-filled photonic crystal fiber for temperature sensing

    Science.gov (United States)

    Liu, Qiang; Li, Shu-Guang; Shi, Min

    2016-12-01

    A fiber Sagnac interferometer based on the square-lattice photonic crystal fiber (PCF) for temperature sensing is designed. All the air holes are assumed to be filled with temperature sensitive liquid. The temperature sensing characteristics are analyzed by finite element method (FEM). The phase birefringence B, the group birefringence Bg, and the sensitivity dependence on the operable wavelength λ are studied, and the temperature varies from 25 °C to 85 °C. The birefringence sensitive coefficient of ∂ B / ∂ T is -10-7 / ° C. The sensitivity could reach to -11.9 nm/°C (-29 750 nm/RIU) at 1.8 μm as the temperature is 25 °C. The sensitivity is also studied by the transmission spectrum, and the wavelength spacing between the resonance wavelengths at 85 °C can reach to 492 nm. The average sensitivity could reach to -7.54 nm/°C (-18 850 nm/RIU). The diameter d1 on the sensing characteristics of the temperature sensor is also analyzed. The temperature sensor shows high sensitivity and broad detecting window.

  3. Predicting Molecular Crystal Properties from First Principles: Finite-Temperature Thermochemistry to NMR Crystallography.

    Science.gov (United States)

    Beran, Gregory J O; Hartman, Joshua D; Heit, Yonaton N

    2016-11-15

    Molecular crystals occur widely in pharmaceuticals, foods, explosives, organic semiconductors, and many other applications. Thanks to substantial progress in electronic structure modeling of molecular crystals, attention is now shifting from basic crystal structure prediction and lattice energy modeling toward the accurate prediction of experimentally observable properties at finite temperatures and pressures. This Account discusses how fragment-based electronic structure methods can be used to model a variety of experimentally relevant molecular crystal properties. First, it describes the coupling of fragment electronic structure models with quasi-harmonic techniques for modeling the thermal expansion of molecular crystals, and what effects this expansion has on thermochemical and mechanical properties. Excellent agreement with experiment is demonstrated for the molar volume, sublimation enthalpy, entropy, and free energy, and the bulk modulus of phase I carbon dioxide when large basis second-order Møller-Plesset perturbation theory (MP2) or coupled cluster theories (CCSD(T)) are used. In addition, physical insight is offered into how neglect of thermal expansion affects these properties. Zero-point vibrational motion leads to an appreciable expansion in the molar volume; in carbon dioxide, it accounts for around 30% of the overall volume expansion between the electronic structure energy minimum and the molar volume at the sublimation point. In addition, because thermal expansion typically weakens the intermolecular interactions, neglecting thermal expansion artificially stabilizes the solid and causes the sublimation enthalpy to be too large at higher temperatures. Thermal expansion also frequently weakens the lower-frequency lattice phonon modes; neglecting thermal expansion causes the entropy of sublimation to be overestimated. Interestingly, the sublimation free energy is less significantly affected by neglecting thermal expansion because the systematic

  4. Low-temperature photoluminescence in CuIn$_5$S$_8$ single crystals

    Indian Academy of Sciences (India)

    GASANLY N M

    2016-06-01

    Photoluminescence (PL) spectra of CuIn$_5$S$_8$ single crystals grown by Bridgman method have been studied in the wavelength region of 720–1020 nm and in the temperature range of 10–34 K. A broad PL band centred at 861 nm (1.44 eV) was observed at $T$ = 10 K. Variations of emission band has been studied as a function of excitation laser intensity in the 0.5–60.2 mW cm$^{−2}$ range. Radiative transitions from shallow donor level located at 17 meV below thebottom of the conduction band to the acceptor level located at 193 meV above the top of the valence band were suggested to be responsible for the observed PL band. An energy level diagram showing transitions in the band gap of the crystal has been presented.

  5. Rheological, optical, and thermal characterization of temperature-induced transitions in liquid crystal ferrosuspensions

    Science.gov (United States)

    Diestra-Cruz, Heberth; Rinaldi, Carlos; Acevedo, Aldo

    2012-04-01

    Liquid crystal ferrosuspensions (LCFs) were obtained by inclusion of magnetic microparticles in a nematic liquid crystal (NLC) at mass fractions of up to 20%. The phase transition of the NLC promotes the formation of a space filling particle network and an enhancement of the mechanical properties. Polarized optical microscopy (POM) and differential scanning calorimetry were used to study microparticle network formation. POM images show that an anisotropic particle structure formed when an external magnetic field was applied, whereas a quasihomogeneous cellular network is obtained in the absence of the field. A jump in the viscoelastic moduli at the isotropic-nematic transition temperature of the NLC was observed for all particle concentrations and applied magnetic fields. Experimental results also showed that the rheological response of the LCFs increased with magnetic field and tend to saturate at high fields. A linear relation between the particle mass fraction and the saturation value of the storage modulus was found.

  6. Temperature-Dependent Defect-Induced New Emission in ZnSe Crystal

    Institute of Scientific and Technical Information of China (English)

    SHU Shi-Wei; MA Guo-Hong

    2009-01-01

    @@ The temperature-dependent photoluminescence behaviour of chemical vapour transport (CVT)-grown ZnSe crys-tal is investigated. A new emission band appears when temperature is reduced to 155K. It is shown that the new emission band is strongly related to defect emission peaked at around 2.1 eV. The emergence of the new emission band is accompanied by decreasing emission intensity of free exciton, as well as redshift of defect emis-sion with temperature decreases. The activated energy of the defect state is estimated to be 60.6meV, which is approximately equal to the energy difference between the new emission and the Tree exciton emission at 155 K.

  7. Two-Dimensional Spatial Imaging of Charge Transport in Germanium Crystals at Cryogenic Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Moffatt, Robert [Stanford U.

    2016-01-01

    In this dissertation, I describe a novel apparatus for studying the transport of charge in semiconductors at cryogenic temperatures. The motivation to conduct this experiment originated from an asymmetry observed between the behavior of electrons and holes in the germanium detector crystals used by the Cryogenic Dark Matter Search (CDMS). This asymmetry is a consequence of the anisotropic propagation of electrons in germanium at cryogenic temperatures. To better model our detectors, we incorporated this effect into our Monte Carlo simulations of charge transport. The purpose of the experiment described in this dissertation is to test those models in detail. Our measurements have allowed us to discover a shortcoming in our most recent Monte Carlo simulations of electrons in germanium. This discovery would not have been possible without the measurement of the full, two-dimensional charge distribution, which our experimental apparatus has allowed for the first time at cryogenic temperatures.

  8. Fluorescein filled photonic crystal fiber sensor for simultaneous ultraviolet light and temperature monitoring

    Science.gov (United States)

    Tatar, Peter; Kacik, Daniel; Tarjanyi, Norbert

    2016-07-01

    We present a novel structure composed of a photonic crystal fiber filled with fluorescein dissolved in water spliced between two conventional multimode fibers. Based on unique features of the fluorescein luminescence it is possible to adjust its emission spectrum to required spectral region. With increasing value of the fluorescein solvent pH factor, the peak wavelength of the emission spectrum is shifting to longer wavelength values. Since the excitation spectrum of fluorescein is relatively wide, this optical fiber sensor could be used for an efficient ultraviolet light monitoring. The detection limit at the level 0.24 mW with 490 nm excitation wavelength is presented. Moreover the emission spectrum is temperature sensitive what provides possibility of simultaneous ultraviolet light and temperature monitoring. Also the temperature sensitivity of the structure based on intermodal interference investigation for a compensation purposes and structure usage as spectrum enlarger are outlined.

  9. Temperature dependence of hardness in yttria-stabilized zirconia single crystals

    Science.gov (United States)

    Morscher, Gregory N.; Pirouz, Pirouz; Heuer, Arthur H.

    1991-01-01

    The temperature dependence of hardness and microcracking in single-crystal 9.5-mol pct-Y2O3-fully-stabilized cubic-ZrO2 was studied as a function of orientation. Crack lengths increased with increased temperature up to 500 C; above 800 C, no cracks were found, indicating an indentation brittle-to-ductile transition of about 800 C. The temperature dependence of hardness was reduced around 500 C. Etching studies to delineate the plastic zone around and below indents identified the operative slip systems. The role of dislocations and their interactions within the plastic zone on the hardness and indentation fracture behavior of cubic-ZrO2 are discussed.

  10. The measurement of temperature with using of birefringence crystals as detectors

    Directory of Open Access Journals (Sweden)

    Gaba V. M.

    2009-02-01

    Full Text Available The carried out researches allowed to motivate and put into practice the polarizatoin-optical method of temperature measurement based on the phenomenon of temperature alteration in value of birefringence of the optically anisotropic crystals. The practical realization of the method with the use of Al2O3 and LiNbO3 plates as active elements of thermometers has shown, that the application of Al2O3 is more preferable due to a wide temperature interval of employment of material, its mechanical and chemical stability, absence of phase transitions. LiNbO3 has such lacks as nonlinearity of graduate dependence and presence of a phase transition point. Nevertheless, its use allows to raise the sensitivity of the thermometer and to increase the accuracy of measurements.

  11. Single-crystal Sapphire Based Optical Polarimetric Sensor for High Temperature Measurement

    Directory of Open Access Journals (Sweden)

    Anbo Wang

    2006-08-01

    Full Text Available Optical sensors have been investigated and widely deployed in industrial andscientific measurement and control processes, mainly due to their accuracy, high sensitivityand immunity to electromagnetic interference and other unique characteristics. They areespecially suited for harsh environments applications, where no commercial electricalsensors are available for long-term stable operations. This paper reports a novel contactoptical high temperature sensor targeting at harsh environments. Utilizing birefringentsingle crystal sapphire as the sensing element and white light interferometric signalprocessing techniques, an optical birefringence based temperature sensor was developed.With a simple mechanically structured sensing probe, and an optical spectrum-codedinterferometric signal processor, it has been tested to measure temperature up to 1600 °Cwith high accuracy, high resolution, and long-term measurement stability.

  12. Fiber-optic temperature sensor using a liquid crystal film for laser-induced interstitial thermotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bong-Soo; Tack, Gye-Rae; Chung, Soon-Cheol; Yi, Jeong-Han [Konkuk University, Chungju (Korea, Republic of); Kim, Sin [Cheju National University, Cheju (Korea, Republic of); Cho, Hyo-Sung [Yonsei University, Wonju (Korea, Republic of)

    2005-06-15

    In this paper, we describe the feasibility of developing a new fiber-optic temperature sensor using a thermo-sensitive liquid crystal (LC) film for laser-induced interstitial thermotherapy (LITT). The temperature change in the tissue or the tumor causes the color of the LC film in contacted with the tissue to change, and that change alters the reflectivity of the LC film. The light with a selected wavelength that is transmitted to the LC film and the optical power of the reflected light are measured using transmitting and receiving optical fibers, respectively. Also, the relationship between the temperature and the optical power of reflected light is determined using the characteristics of the LC films.

  13. Sensitive temperature measurements based on Lorentzian and Fano resonance lineshapes of a silicon photonic crystal cavity

    Science.gov (United States)

    Zhao, Chenyang; Fang, Liang; Yuan, Qinchen; Gan, Xuetao; Zhao, Jianlin

    2016-10-01

    We report a high-performance photonic temperature sensor by exploiting a silicon photonic crystal (PC) cavity. Since the PC cavity's spectra are very sensitive to the refractive index change, we observe remarkable variations of its resonant wavelength and output power under varying temperature levels. In a PC cavity with Lorentzian resonance lineshape, the sensor exhibits a linear spectrum-sensitivity of 70 pm/°, and the power-variation presents a high sensitivity as 1.28 dB/°. In addition, the Fano resonance lineshape generated by the PC cavity has also been employed to measure the temperature, which shows improved power sensitivity as 2.94 dB/ °. The demonstrated PC cavity-based sensor offers great potentials for low-cost, high sensitivity homogeneous sensing in chip-integrated devices.

  14. Room-temperature switching of magnetic hysteresis by reversible single-crystal-to-single-crystal solvent exchange in imidazole-inspired Fe(ii) complexes.

    Science.gov (United States)

    Huang, Wei; Shen, Fuxing; Zhang, Ming; Wu, Dayu; Pan, Feifei; Sato, Osamu

    2016-10-14

    The recent upsurge in molecular magnetism reflects its application in the areas of sensors and molecular switches. Thermal hysteresis is crucial to the molecular bistability and information storage, a wide hysteresis near room temperature is expected to be of practical sense for the molecular compound. In this work, spin crossover iron(ii) complexes [Fe(Liq)2](BF4)2·(CH3CH2)2O (1-Et2O) and [Fe(Liq)2](BF4)2·3H2O (1-3H2O) were prepared and structurally and magnetically analysed. The single-crystal-to-single-crystal (SCSC) solvation transformation and the influence on the crystal structures and magnetic hysteresis were investigated in an etherification-hydration cycle. At room temperature, X-ray diffraction experiments indicated a transformation from one crystal (1-Et2O, P21212) to another crystal (1-3H2O, P212121) upon humidity exposure and reversible recovery of its crystallinity upon exposure to ether vapor. The etherified phase 1-Et2O exhibits room temperature spin crossover (T1/2 = 305 K) but negligible thermal hysteresis, however the hydrated phase 1-3H2O exhibits the apparent hysteresis loop (T1/2↑ = 346 K, T1/2↓ = 326 K) which expands to room temperature. This effect is associated with the change of intermolecular cooperativity in the etherification-hydration recyclability.

  15. Room temperature terahertz wave imaging at 60 fps by frequency up-conversion in DAST crystal

    Science.gov (United States)

    Fan, Shuzhen; Qi, Feng; Notake, Takashi; Nawata, Kouji; Matsukawa, Takeshi; Takida, Yuma; Minamide, Hiroaki

    2014-02-01

    Terahertz imaging has attracted a lot of interests for more than 10 years. But real time, high sensitive, low cost THz imaging in room temperature, which is widely needed by fields such as biology, biomedicine and homeland security, has not been fully developed yet. A lot of approaches have been reported on electro-optic (E-O) imaging and THz focal plane arrays with photoconductive antenna or micro-bolometer integrated. In this paper, we report high sensitive realtime THz image at 60 frames per second (fps) employing a commercial infrared camera, using nonlinear optical frequency up-conversion technology. In this system, a flash-lamp pumped nanosecond pulse green laser is used to pump two optical parametric oscillator systems with potassium titanyl phosphate crystals (KTP-OPO). One system with dual KTP crystals is used to generate infrared laser for the pumping of THz difference frequency generation (DFG) in a 4- Dimethylamino-N-Methyl-4-Stilbazolium Tosylate (DAST) crystal. The other one is for generation of pumping laser for THz frequency up-conversion in a second DAST crystal. The THz frequency can be tuned continuously from a few THz to less than 30 THz by controlling the angle of KTP crystals. The frequency up-converted image in infrared region is recorded by a commercial infrared camera working at 60 Hz. Images and videos are presented to show the feasibility of this technique and the real-time ability. Comparison with a general micro-bolometer THz camera shows the high sensitivity of this technique.

  16. Temperature dependence of protein solubility-determination, application to crystallization, and growth kinetics studies

    Science.gov (United States)

    Rosenberger, Franz

    1993-01-01

    A scintillation method was developed for determinations of the temperature dependence of the solubility, and of nucleation induction times of proteins, in 50-100 mu(l) volumes of solution. Solubility data for lysozyme and horse serum albumin were obtained for various combinations of pH and precipitant concentrations. These data and the nucleation induction information were used for dynamic crystallization control, that is, for the controlled separation of nucleation and growth stages. Individual lysozyme and horse serum albumin crystals were grown in 15-20 mu(l) solution volumes contained in x-ray capillaries. The morphology and kinetics of the growth and dissolution of lysozyme in aqueous solutions with 2.5 percent NaCl and at pH = 4.5 was studied in situ with a depth resolution of 300 A (4 unit cells) by high resolution optical microscopy and digital image processing. The bulk super- or under saturation, sigma, of the solution inside a closed growth cell was controlled by temperature. The growth habit was bound by (110) and (101) faces that grew through layer spreading, although with different growth rate dependencies on supersaturation/temperature. At sigma less than 10 (obtained at higher temperatures) growth was purely kinetic ally controlled, with impurity effects (macrostep formation and kinetic hindrance) becoming significant for sigma less than 2. At sigma greater than 10 (lower temperatures), anisotropies in the interfacial kinetics were more pronounced, with interfacial kinetics and bulk transport becoming equally important to the growth morphology. Growth rates were growth history dependent. The formation of striations (layers of irregularly incorporated solution) was unambiguously correlated with growth temperature variations. Etching exposed dislocations and various high-index faces whose growth morphologies were studied during return to the steady state growth form. Growth steps were observed to originate from two-dimensional nuclei or from outcrops

  17. Effect of temperature on the luminescence of Sm{sup 3+} ions in YAM crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kaczkan, M. [Institute of Microelectronics and Optoelectronics PW, ul. Koszykowa 75, 00-662 Warsaw (Poland); Boruc, Z., E-mail: z.boruc@stud.elka.pw.edu.pl [Institute of Microelectronics and Optoelectronics PW, ul. Koszykowa 75, 00-662 Warsaw (Poland); Turczyński, S. [Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warsaw (Poland); Malinowski, M. [Institute of Microelectronics and Optoelectronics PW, ul. Koszykowa 75, 00-662 Warsaw (Poland)

    2014-11-05

    Highlights: • Different concentration Sm{sup 3+}-doped Y{sub 4}Al{sub 2}O{sub 9} crystals are fabricated by μ-pulling down method. • Thermally activated {sup 4}F{sub 3/2} → {sup 6}H{sub 5/2} emission of Sm{sup 3+} in YAM is studied. • Temperature dependent quenching mechanism of the {sup 4}G{sub 5/2} luminescence is proposed. - Abstract: The spectroscopic features of samarium Sm{sup 3+} activated Y{sub 4}Al{sub 2}O{sub 9} (YAM) crystals are presented and discussed. Temperature sensing properties of Sm{sup 3+}:YAM phosphor was demonstrated over the 300–1200 K range. Temperature dependent luminescence spectra and decay curves for the {sup 4}G{sub 5/2} level of Sm{sup 3+} in YAM were measured. Ratio of the fluorescence intensities arising from the two close lying {sup 4}F{sub 3/2} and {sup 4}G{sub 5/2} levels (with energy separation of ΔE ∼ 1000 cm{sup −1}) followed a straight line pattern, which confirms the Boltzmann distribution of the population, and can be used to measure temperature. The lifetime for the {sup 4}G{sub 5/2} level in 1% Sm doped sample decreases from 1.65 to 0.08 ms with heating from room temperature to 1200 K. This behavior of decays is discussed in terms of radiative and multiphonon decays as well as cross-relaxation dependence on temperature.

  18. Laser on single-crystal ZnSe:Fe2+ with high pulse radiation energy at room temperature

    Science.gov (United States)

    Firsov, K. N.; Frolov, M. P.; Gavrishchuk, E. M.; Kazantsev, S. Yu; Kononov, I. G.; Korostelin, Yu V.; Maneshkin, A. A.; Velikanov, S. D.; Yutkin, I. M.; Zaretsky, N. A.; Zotov, E. A.

    2016-01-01

    A laser on single-crystal ZnSe:Fe2+ was investigated at room temperature. Pumping of the laser was performed by a pulsed electrodischarge HF laser. In experiments, the spot diameter of HF laser radiation incident to the surface of the crystal varied from 5.6 to 17 mm. Generation energy of ~1.2 J was obtained and the efficiency with respect to the energy arriving at the crystal was η in  ≈  25%. The slope efficiency with respect to the energy absorbed in the crystal at large spot dimensions was η slope  =  45%.

  19. Full-Thickness Entire Nasal Alar Reconstruction Using a Forehead Flap in Asians: No Cartilaginous Infrastructural Lining Is Necessary.

    Science.gov (United States)

    Funayama, Emi; Yamamoto, Yuhei; Furukawa, Hiroshi; Murao, Naoki; Shichinohe, Ryuji; Yamao, Takeshi; Hayashi, Toshihiko; Oyama, Akihiko

    2017-05-01

    Full-thickness defects of the entire nasal ala, including the rim, can be challenging to reconstruct. A forehead flap may provide a more imperceptible and natural-appearing reconstructed nasal ala. Previously, many authors have insisted adding cartilaginous infrastructural support for an entire, full-thickness defect to keep the postoperative alar structure symmetrical. They finally use a forehead flap after thinning of the distal covering portion subcutaneously, possibly for a Caucasian-type nasal ala. However, Asian skin has a thicker and more compact dermis than that of Caucasian skin, and the Asian ala is rounder and thicker. There may be another approach for an Asian-type nasal ala. The authors propose the possibility of nasal alar reconstruction for an entire, full-thickness defect in Asians using a forehead flap without structural support. Six patients with entire full-thickness nasal alar defects treated with full-thickness forehead flaps above the periosteum without structural support were reviewed. Five patients demonstrated esthetically good to excellent outcomes in color, texture, and symmetry. Their nasal linings were reconstructed using mucoperiosteal flaps or mucosal grafts. One patient treated with a nasal lining using a local flap showed a fair result esthetically. Asians forehead above the periosteum has adequate thickness and supportability to reconstruct the entire full-thickness nasal ala in Asians. No cartilage support is necessary.

  20. Temperature dependent tunneling study of CaFe1.96Ni0.04As2 single crystals

    Science.gov (United States)

    Dutta, Anirban; Thamizhavel, A.; Gupta, Anjan K.

    2014-04-01

    We report on temperature dependent scanning tunneling microscopy and spectroscopy studies on CaFe1.96Ni0.04As2 single crystals in 5.4 - 19.7 K temperature range across the normal metal - superconductor transition temperature, TC = 14K. The in-situ cleaved crystals show reasonably flat surface with signatures of atomic resolution. The tunnel spectra show significant spatial inhomogeneity below TC, which reduces significantly as the temperature goes above the TC. We discuss these results in terms of an inhomogeneous electronic phase that may exist due to the vicinity of this composition to the quantum critical point.

  1. How important is thermal expansion for predicting molecular crystal structures and thermochemistry at finite temperatures?

    Science.gov (United States)

    Heit, Yonaton N; Beran, Gregory J O

    2016-08-01

    Molecular crystals expand appreciably upon heating due to both zero-point and thermal vibrational motion, yet this expansion is often neglected in molecular crystal modeling studies. Here, a quasi-harmonic approximation is coupled with fragment-based hybrid many-body interaction calculations to predict thermal expansion and finite-temperature thermochemical properties in crystalline carbon dioxide, ice Ih, acetic acid and imidazole. Fragment-based second-order Möller-Plesset perturbation theory (MP2) and coupled cluster theory with singles, doubles and perturbative triples [CCSD(T)] predict the thermal expansion and the temperature dependence of the enthalpies, entropies and Gibbs free energies of sublimation in good agreement with experiment. The errors introduced by neglecting thermal expansion in the enthalpy and entropy cancel somewhat in the Gibbs free energy. The resulting ∼ 1-2 kJ mol(-1) errors in the free energy near room temperature are comparable to or smaller than the errors expected from the electronic structure treatment, but they may be sufficiently large to affect free-energy rankings among energetically close polymorphs.

  2. High-Precision Temperature Control of a Crystal Growth Furnace at 1,500 C

    Science.gov (United States)

    Stenzel, Ch.; Hess, A.; Croell, A.; Breuer, D.; Sauermann, H.

    2012-01-01

    For crystal growth of semiconductor materials a short-term temperature stability of 0.1 C at 1500 C is one of the essential parameters to be addressed for achieving high-quality crystals. Hence, for temperature monitoring and control with high precision in a floating zone furnace two sets of thermo-sensors, type B thermocouples and optical fibre thermometers, have been implemented and successfully operated in the furnace for more than 2000 h. The optical fibre thermometers consist of an optical system made of sapphire (two fibres plus a prism in between for deflection) and transmit the infra-red radiation of the heater to the outside of the hot core of the furnace for pyrometric temperature measurement. A dedicated control algorithm has been set up which controlled the power settings to the individual heaters. Both sensor types showed no degradation after this period and yielded a short-term stability at 1200 C of 0.05 C (optical fibre thermometers), respectively 0.08 C (thermocouples).

  3. Large field-induced-strain at high temperature in ternary ferroelectric crystals

    Science.gov (United States)

    Wang, Yaojin; Chen, Lijun; Yuan, Guoliang; Luo, Haosu; Li, Jiefang; Viehland, D.

    2016-10-01

    The new generation of ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals have potential applications in high power devices due to their surperior operational stability relative to the binary system. In this work, a reversible, large electric field induced strain of over 0.9% at room temperature, and in particular over 0.6% above 380 K was obtained. The polarization rotation path and the phase transition sequence of different compositions in these ternary systems have been determined with increasing electric field applied along [001] direction based on x-ray diffraction data. Thereafter, composition dependence of field-temperature phase diagrams were constructed, which provide compositional and thermal prospectus for the electromechanical properties. It was found the structural origin of the large stain, especially at higher temperature is the lattice parameters modulated by dual independent variables in composition of these ternary solid solution crystals.

  4. Cooking skyrmions: modeling temperature dependence of defect textures in cholesteric liquid crystals

    Science.gov (United States)

    Afghah, Sajedeh; Konya, Andrew; Selinger, Jonathan; Selinger, Robin

    Using 3-d simulations and analytical calculations, we study temperature dependence of defect structures in liquid crystals in confined geometries. We model a cholesteric liquid crystal confined in a microchannel with homeotropic anchoring, and investigate resulting defect structures--skyrmions, alone or in periodic arrays (bubble domains), and striped textures --as a function of microchannel dimensions, cholesteric pitch, and surface anchoring strength. We model temperature dependence by varying Frank constants and pitch using functions fit to experimental values. Experiments by the Qihuo Wei group show that skyrmion arrays in a microchannel appear to ``pop'' at a threshold temperature, transforming into elongated defects that span the microchannel's width. We explore this behavior using simulation and show that skyrmions elongate when their spacing is below a critical distance. Implementation of the simulation code in CUDA for a GPU-equipped computer produces highly efficient performance. We also carry out analytical calculations of free energy to determine optimal/stable structures for skyrmions and other defect textures in thin cells. Both simulation and analytical results are compared to recent experiments by the Qihuo Wei group. Supported by NSF CMMI-1436565. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research.

  5. Effects of temperature and solvent concentration on the solvent crystallization of palm-based dihydroxystearic acid with isopropyl alcohol

    Institute of Scientific and Technical Information of China (English)

    Gregory F.L.Koay; Teong-Guan Chuah; Sumaiya Zainal-Abidin; Salmiah Ahmad; Thomas S.Y.Choong

    2012-01-01

    Palm-based dihydroxystearic acid of 69.55% purity was produced in a 500-kg-per-batch operation pilot plant and purified through solvent crystallization in a custom fabricated simultaneous batch crystallizer unit.The effects of temperature and solvent concentration on yield,particle size distribution and purity were studied.The purity was higher,while the yield and particle size were lower and smaller,respectively,at higher temperature and solvent concentration.The solvent crystallization process efficiency was rated at 66-69% when carried out with 70-80% isopropyl alcohol at 20 ℃.

  6. High-temperature Raman study of L-alanine, L-threonine and taurine crystals related to thermal decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Cavaignac, A.L.O. [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão, Imperatriz, MA 65900-410 (Brazil); Lima, R.J.C., E-mail: ricardo.lima.ufma@gmail.com [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão, Imperatriz, MA 65900-410 (Brazil); Façanha Filho, P.F. [Centro de Ciências Sociais, Saúde e Tecnologia, Universidade Federal do Maranhão, Imperatriz, MA 65900-410 (Brazil); Moreno, A.J.D. [Coordenação de Ciências Naturais, Universidade Federal do Maranhão, Bacabal, MA 65700-000 (Brazil); Freire, P.T.C. [Departamento de Física, Universidade Federal do Ceará, Fortaleza, CE 60455-760 (Brazil)

    2016-03-01

    In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.

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

    KAUST Repository

    Maculan, Giacomo

    2015-09-02

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

  8. Experimental evidence for thermal generation of interstitials in a metallic crystal near the melting temperature

    Science.gov (United States)

    Safonova, E. V.; Mitrofanov, Yu P.; Konchakov, R. A.; Vinogradov, A. Yu; Kobelev, N. P.; Khonik, V. A.

    2016-06-01

    The only intrinsic point defects of simple crystalline metals known from solid state physics are vacancies and interstitials. It is widely believed that while vacancies play a major role in crystal properties and their concentration reaches relatively big values near the melting temperature T m, interstitials essentially do not occur in thermodynamic equilibrium and their influence on properties is minor. Here, taking aluminum single crystals as an example, we present compelling experimental evidence for rapid thermoactivated growth of interstitial concentration upon approaching T m. Using high precision measurements of the shear modulus we found a diaelastic effect of up to -1.5% near T m. It is argued that this effect is mostly due to the generation of dumbbell (split) interstitials. The interstitial concentration c i rapidly increases upon approaching T m and becomes only 2-3 times smaller than that of vacancies just below T m. The reason for this c i -increase is conditioned by a decrease of the Gibbs free energy with temperature, which in turn originates from the high formation entropy of dumbbell interstitials and a decrease of their formation enthalpy at high c i . Special molecular dynamic simulation confirmed all basic aspects of the proposed interpretation. The results obtained (i) demonstrate the significance of interstitial concentration near T m that could lead to the revaluation of vacancy concentration at high temperatures, (ii) suggest that dumbbell interstitials play a major role in the melting mechanism of monatomic metallic crystals and (iii) support a new avenue for in-depth understanding of glassy metals.

  9. Low-temperature properties of neutron irradiated CuGeO3 single crystals

    Science.gov (United States)

    Gladczuk, L.; Mosiniewicz-Szablewska, E.; Dabkowska, H.; Baran, M.; Pytel, B.; Szymczak, R.; Szymczak, H.

    2000-07-01

    The effect of neutron irradiation on the magnetic properties of CuGeO3 single crystal which shows the spin-Peierls transition below T sp=14 K was investigated by means of electron paramagnetic resonance (EPR) and susceptibility measurements. It was found that the irradiation led to a decrease of the spin-Peierls transition temperature and induced appreciable changes in the EPR signal intensity, resonance linewidth, g-factor and magnetic susceptibility of this material. These changes may be associated with a partial suppression of both the energy gap and the dimerization within the Cu chains.

  10. Observation of ultraslow light propagation in a ruby crystal at room temperature.

    Science.gov (United States)

    Bigelow, Matthew S; Lepeshkin, Nick N; Boyd, Robert W

    2003-03-21

    We have observed slow light propagation with a group velocity as low as 57.5+/-0.5 m/s at room temperature in a ruby crystal. A quantum coherence effect, coherent population oscillations, produces a very narrow spectral "hole" in the homogeneously broadened absorption profile of ruby. The resulting rapid spectral variation of the refractive index leads to a large value of the group index. We observe slow light propagation both for Gaussian-shaped light pulses and for amplitude modulated optical beams in a system that is much simpler than those previously used for generating slow light.

  11. Nematic liquid crystals on spherical surfaces: Control of defect configurations by temperature, density, and rod shape

    Science.gov (United States)

    Dhakal, Subas; Solis, Francisco J.; Olvera de la Cruz, Monica

    2012-07-01

    Recent experiments have shown that defect conformations in spherical nematic liquid crystals can be controlled through variations of temperature, shell thickness, and other environmental parameters. These modifications can be understood as a result of the induced changes in the effective elastic constants of the system. To characterize the relation between defect conformations and elastic anisotropy, we carry out Monte Carlo simulations of a nematic on a spherical surface. As the anisotropy is increased, the defects flow from a tetrahedral arrangement to two coalescing pairs and then to a great circle configuration. We also analyze this flow using a variational method based on harmonic configurations.

  12. A 3D MOF showing unprecedented solvent-induced single-crystal-to-single-crystal transformation and excellent CO2 adsorption selectivity at room temperature.

    Science.gov (United States)

    Qin, Tao; Gong, Jun; Ma, Junhan; Wang, Xin; Wang, Yonghua; Xu, Yan; Shen, Xuan; Zhu, Dunru

    2014-12-28

    A water stable porous 3D metal-organic framework, [Cu3L2(μ3-OH)2(μ2-H2O)]·2DMA (1, mother crystal, H2L = 2,2'-dinitrobiphenyl-4,4'-dicarboxylic acid, DMA = N,N-dimethylacetamide), shows unprecedented irreversible solvent-induced substitutions of bridging aqua ligands and guest-exchanges in single-crystal-to-single-crystal (SCSC) transformations at room temperature (RT), producing quantitatively three daughter crystals, [Cu3L2(μ3-OH)2]·2S (2: 2A, S = acetone; 2B, S = 2-propanol; 2C, S = 2-butanol), which exhibit reversible interconversion by guest-exchanges at RT in SCSC transformations. MOF 1 shows excellent separation selectivity (128) of CO2/N2 at RT and is a better sorbent of micro-solid-phase extraction (μ-SPE) than currently known benchmark ZIF-8.

  13. Three-dimensional analysis of dislocation multiplication in single-crystal silicon under accurate control of cooling history of temperature

    Science.gov (United States)

    Gao, B.; Kakimoto, K.

    2014-06-01

    Dislocation multiplication in single-crystal silicon during heating and cooling processes was studied by three-dimensional simulation under accurate control of the temperature history. Three different cooling temperature histories were designed. The results showed that the cooling rate in the high-temperature region has a large effect on the final dislocations and residual stress. The most effective method to reduce dislocations is to use a slow cooling rate in the high-temperature region.

  14. Strength of orthoenstatite single crystals at mantle pressure and temperature and comparison with olivine

    Science.gov (United States)

    Raterron, Paul; Fraysse, Guillaume; Girard, Jennifer; Holyoke, Caleb W.

    2016-09-01

    Oriented single crystals of orthopyroxenes (OPx) were deformed in axisymmetric compression in the D-DIA at pressure and temperature in excess of 3 GPa and 1040 °C. Two crystal orientations were tested with the compression axis parallel to either [101]c crystallographic direction, to investigate [001](100) dislocation slip-system strength, or [011]c direction to investigate [001](010) slip-system strength. These slip systems are the most active in orthopyroxenes. Applied differential stresses and specimen strain rates were measured in situ by synchrotron X-ray diffraction and radiography. We used these data and comparison with previously reported low-pressure flow laws for protoenstatite and orthoenstatite to determine the power law parameters for the deformation of orthoenstatite crystals, which characterize OPx dislocation slip-system strengths. Applying these laws at reasonable mantle stresses along oceanic and continental geotherms indicates that OPx [001](100) slip system is weaker than OPx [001](010) slip system to ∼260 km depth where the strengths converge. It also indicates that both OPx slip systems are significantly stronger than olivine slip systems throughout the upper mantle, except in the upper most mantle, in the lithosphere, were OPx [001](100) slip system may be as weak or even weaker than olivine [100](010) easy slip system.

  15. Magnetism and variable temperature and pressure crystal structures of a linear oligonuclear cobalt bis-semiquinonate.

    Science.gov (United States)

    Overgaard, Jacob; Møller, Louise H; Borup, Mette A; Tricoire, Maxime; Walsh, James P S; Diehl, Marcel; Rentschler, Eva

    2016-08-09

    The crystal structure of the first oligomeric cobalt dioxolene complex, Co3(3,5-DBSQ)2((t)BuCOO)4(NEt3)2, 1, where DBSQ is 3,5-di-tert-butyl-semiquinonate, has been studied at various temperatures between 20 and 200 K. Despite cobalt-dioxolene complexes being generally known for their extensive ability to exhibit valence tautomerism (VT), we show here that the molecular geometry of compound 1 is essentially unchanged over the full temperature range, indicating the complete absence of electron transfer between ligand and metal. Magnetic susceptibility measurements clearly support the lack of VT between 8 and 300 K. The crystal structure is also determined at elevated pressures in the range from 0 to 2.5 GPa. The response of the crystal structure is surprisingly dependent on the dynamics of pressurisation: following rapid pressurization to 2 GPa, a structural phase transition occurs; yet, this is absent when the pressure is increased incrementally to 2.6 GPa. In the new high pressure phase, Z' is 2 and one of the two molecules displays changes in the coordination of one bridging carboxylate from μ2:κO:κO' to μ2:κ(2)O,O':κO', while the other molecule remains unchanged. Despite the significant changes to the molecular connectivity, analysis of the crystal structures shows that the phase transition leaves the spin and oxidation states of the molecules unaltered. Intermolecular interactions in the high pressure crystal structures have been analysed using Hirshfeld surfaces but they cannot explain the origin of the phase transition. The lack of VT in this first oligomeric Co-dioxolene complex is speculated to be due to the coordination geometry of the terminal Co-atoms, which are trigonal bipyramidally coordinated, different from the more common octahedral coordination. The energy that is gained by a hs-to-ls change in Oh is equal to Δ, while in the case of the trigonal bipyramidal (C3v), the energy gain is equal to the splitting between d(z(2)) and degenerate d

  16. Low-temperature embrittlement and fracture of metals with different crystal lattices – Dislocation mechanisms

    Directory of Open Access Journals (Sweden)

    V.M. Chernov

    2016-12-01

    Full Text Available The state of a low-temperature embrittlement (cold brittleness and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals with various crystal lattices (BCC, FCC, HCP are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation and after a low-temperature damaging (neutron irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.

  17. Investigation on cubic boron nitride crystals doped with Si by high temperature thermal diffusion

    Science.gov (United States)

    Li, Xinlu; Feng, Shuang; Liu, Xiuhuan; Hou, Lixin; Gao, Yanjun; Wang, Qi; Liu, Nian; Zhang, Hai; Chen, Zhanguo; Zheng, Jie; Jia, Gang

    2014-07-01

    The method of high temperature thermal diffusion was successfully applied for doping Si impurities into cubic boron nitride (cBN) crystals. X-ray photoelectron spectra (XPS) and the current-voltage (I-V) characteristics at different temperatures were respectively used for analyzing the chemical states and the activation energy of Si impurity in cBN. According to the XPS results, Si impurities mainly replace B atoms bonding with the adjacent N atoms and become donors in cBN. Without surface cleaning, there are a lot of C and O contaminations on the surface of cBN, so a small quantity of C-Si and Si-N-O bonds also exist at the surface of cBN. Most Si impurities distribute in the shallow layer underneath the surface of cBN. Based on the electric measurement, Si impurities in cBN usually have the activation energy beyond 0.4 eV, and they can only be slightly ionized at room temperature, therefore the resistivity of Si-doped cBN is still high, and the space charge limited current becomes the main conductive mechanism in cBN. However, the conductivity of Si-doped cBN can rapidly increase with the temperature. In addition, the activation energy and the concentration of Si impurity in cBN can be affected by the temperature and the time of thermal diffusion, which needs to be verified further.

  18. Surface Plasmon Resonance Temperature Sensor Based on Photonic Crystal Fibers Randomly Filled with Silver Nanowires

    Directory of Open Access Journals (Sweden)

    Nannan Luan

    2014-08-01

    Full Text Available We propose a temperature sensor design based on surface plasmon resonances (SPRs supported by filling the holes of a six-hole photonic crystal fiber (PCF with a silver nanowire. A liquid mixture (ethanol and chloroform with a large thermo-optic coefficient is filled into the PCF holes as sensing medium. The filled silver nanowires can support resonance peaks and the peak will shift when temperature variations induce changes in the refractive indices of the mixture. By measuring the peak shift, the temperature change can be detected. The resonance peak is extremely sensitive to temperature because the refractive index of the filled mixture is close to that of the PCF material. Our numerical results indicate that a temperature sensitivity as high as 4 nm/K can be achieved and that the most sensitive range of the sensor can be tuned by changing the volume ratios of ethanol and chloroform. Moreover, the maximal sensitivity is relatively stable with random filled nanowires, which will be very convenient for the sensor fabrication.

  19. Investigation into the temperature dependence of isotropic- nematic phase transition of Gay- Berne liquid crystals

    Directory of Open Access Journals (Sweden)

    A Avazpour

    2014-12-01

    Full Text Available Density functional approach was used to study the isotropic- nematic (I-N transition and calculate the values of freezing parameters of the Gay- Berne liquid crystal model. New direct and pair correlation functions of a molecular fluid with Gay- Berne pair potential were used. These new functions were used in density functional theory as input to calculate the isotropic- nematic transition densities for elongation at various reduced temperatures. It was observed that the isotropic- nematic transition densities increase as the temperature increases. It was found that the new direct correlation function is suitable to study the isotropic- nematic transition of Gay- Berne liquids. Comparison to other works showed qualitative agreement

  20. Pressure effect on crystallization temperature in Zr70Pd30 metallic glass

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Jeppesen, S; Saida, J.

    2004-01-01

    -to-icosahedral quasicrystalline and (2) icosahedral quasicrystalline-to-intermetallic Zr2 + xPd alloy. The intermetallic alloy has a tetragonal structure with lattice parameters, a = 3.310(1) Å and c = 10.974(1) Å, and a space group of I4/mmm. External pressure enhances the onset temperatures for the formation......The pressure effect on amorphous-to-quasicrystalline-to-intermetallic phase transformations in a Zr70Pd30 metallic glass has been investigated by in situ x-ray diffraction measurements using synchrotron radiation. It is found that the glass crystallizes in two steps: (1) amorphous...... of quasicrystalline phase and intermetallic compound with rates of 11±3 and 9±4 K/GPa, respectively, while the temperature interval for the stability of quasicrystals remains almost unchanged in the pressure range of 0–3 GPa. External pressure does not affect the phase-selection sequence. The enhancement of the onset...

  1. Na2TiGeO5: Crystal structure stability at low temperature and high pressure

    DEFF Research Database (Denmark)

    Waskowska, A.; Gerward, Leif; Olsen, J.S.

    2008-01-01

    and GeO4 tetrahedra, alternating with layers of Na+ cations. Antiparallel alignment of the short apical titanyl bond in adjacent rows of the polyhedral layer gives rise to spontaneous strain, when a distortion of the TiO5 groups occurs. Single-crystal structures determined at room temperature and 120 K......-axis. The structure distortion, however, is too small to allow any unambiguous determination of the symmetry-breaking effects. The bulk modulus and its pressure derivative have been determined as B-0 = 89(2) GPa and B'(0) = 4.0. A pressure-induced phase transformation takes place at P-c approximate to 12.5 GPa......, presumably to an orthorhombic structure. The pressure effect on the transition temperature is given by Delta T-c/Delta P approximate to 1.76 K/GPa....

  2. Electrical Conductivity of Synthetic Quartz Crystals at High Temperature and Pressure from Complex Impedance Measurements

    Institute of Scientific and Technical Information of China (English)

    王多君; 李和平; 刘丛强; 易丽; 丁东业; 苏根利; 张卫刚

    2002-01-01

    An electrical conductivity measurement system under high-pressure conditions with a multi-anvil high-pressure apparatus by an ac complex impedance method was set up. With this system, we have successfully measured the electrical conductivity of synthetic quartz under pressure up to approximately 1.0 GPa in the temperature range 661-987K. The values of electrical conductivity decrease with the increasing pressure and increase with the increasing temperature. The activation enthalpies for the α-quartz crystals are 1.10-1.28eV. The electrical conductivity of α-quartz is ionic, with Na ions moving in channels parallel to the c-axis being the predominant current carrier.

  3. Crystallization and structure of cast A390.0 alloy with melt overheating temperature

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2012-07-01

    Full Text Available The paper presents the research on the influence of melt overheating temperature on crystallization parameters and primary structure of cast AlSi17Cu5Mg (A390.0 alloy overheated to temperature: 820 °C, 880 °C, 940 °C and 1 000 °C. It was found that the degree of overheating influences the change of microstructure significantly and morphologies of primary silicon of the castings from Al-Si alloys. Research has shown that the overheating of the liquid metal bath is one of the methods of finding more applications of hypereutectic Al-Si system alloys without the addition of modifiers.

  4. Biocompatible Single-Crystal Selenium Nanobelt Based Nanodevice as a Temperature-Tunable Photosensor

    Directory of Open Access Journals (Sweden)

    Yongshan Niu

    2012-01-01

    Full Text Available Selenium materials are widely used in photoelectrical devices, owing to their unique semiconductive properties. Single-crystal selenium nanobelts with large specific surface area, fine photoconductivity, and biocompatibility provide potential applications in biomedical nanodevices, such as implantable artificial retina and rapid photon detector/stimulator for optogenetics. Here, we present a selenium nanobelt based nanodevice, which is fabricated with single Se nanobelt. This device shows a rapid photo response, different sensitivities to visible light of variable wave length, and temperature-tunable property. The biocompatibility of the Se nanobelts was proved by MTT test using two cell lines. Our investigation introduced a photosensor that will be important for multiple potential applications in human visual system, photocells in energy or MEMS, and temperature-tunable photoelectrical device for optogenetics research.

  5. Molecular Dynamics Simulation of the Crystal Orientation and Temperature Influences in the Hardness on Monocrystalline Silicon

    Directory of Open Access Journals (Sweden)

    Hongwei Zhao

    2014-01-01

    Full Text Available A nanoindentation simulation using molecular dynamic (MD method was carried out to investigate the hardness behavior of monocrystalline silicon with a spherical diamond indenter. In this study, Tersoff potential was used to model the interaction of silicon atoms in the specimen, and Morse potential was used to model the interaction between silicon atoms in the specimen and carbon atoms in the indenter. Simulation results indicate that the silicon in the indentation zone undergoes phase transformation from diamond cubic structure to body-centred tetragonal and amorphous structure upon loading of the diamond indenter. After the unloading of the indenter, the crystal lattice reconstructs, and the indented surface with a residual dimple forms due to unrecoverable plastic deformation. Comparison of the hardness of three different crystal surfaces of monocrystalline silicon shows that the (0 0 1 surface behaves the hardest, and the (1 1 1 surface behaves the softest. As for the influence of the indentation temperature, simulation results show that the silicon material softens and adhesiveness of silicon increases at higher indentation temperatures.

  6. Temperature- and excitation intensity-dependent photoluminescence in TlInSeS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Gasanly, N M [Physics Department, Middle East Technical University, 06531 Ankara (Turkey); Aydinli, A [Physics Department, Bilkent University, 06533 Ankara (Turkey); Yuksek, N S [Physics Department, Middle East Technical University, 06531 Ankara (Turkey)

    2002-12-16

    Photoluminescence (PL) spectra of TlInSeS layered single crystals were investigated in the wavelength region 460-800 nm and in the temperature range 10-65 K. We observed one wide PL band centred at 584 nm (2.122 eV) at T=10 K and an excitation intensity of 7.5 W cm{sup -2}. We have also studied the variation of the PL intensity versus excitation laser intensity in the range from 0.023 to 7.5 W cm{sup -2}. The red shift of this band with increasing temperature and blue shift with increasing laser excitation intensity was observed. The PL was found to be due to radiative transitions from the moderately deep donor level located at 0.243 eV below the bottom of the conduction band to the shallow acceptor level at 0.023 eV located above the top of the valence band. The proposed energy-level diagram permits us to interpret the recombination processes in TlInSeS layered single crystals.

  7. Temperature- and excitation intensity-dependent photoluminescence in TlInSeS single crystals

    Science.gov (United States)

    Gasanly, N. M.; Aydinli, A.; Yuksek, N. S.

    2002-12-01

    Photoluminescence (PL) spectra of TlInSeS layered single crystals were investigated in the wavelength region 460-800 nm and in the temperature range 10-65 K. We observed one wide PL band centred at 584 nm (2.122 eV) at T = 10 K and an excitation intensity of 7.5 W cm-2. We have also studied the variation of the PL intensity versus excitation laser intensity in the range from 0.023 to 7.5 W cm-2. The red shift of this band with increasing temperature and blue shift with increasing laser excitation intensity was observed. The PL was found to be due to radiative transitions from the moderately deep donor level located at 0.243 eV below the bottom of the conduction band to the shallow acceptor level at 0.023 eV located above the top of the valence band. The proposed energy-level diagram permits us to interpret the recombination processes in TlInSeS layered single crystals.

  8. Temperature- and excitation intensity-dependent photoluminescence in TlInSeS single crystals

    CERN Document Server

    Gasanly, N M; Yuksek, N S

    2002-01-01

    Photoluminescence (PL) spectra of TlInSeS layered single crystals were investigated in the wavelength region 460-800 nm and in the temperature range 10-65 K. We observed one wide PL band centred at 584 nm (2.122 eV) at T=10 K and an excitation intensity of 7.5 W cm sup - sup 2. We have also studied the variation of the PL intensity versus excitation laser intensity in the range from 0.023 to 7.5 W cm sup - sup 2. The red shift of this band with increasing temperature and blue shift with increasing laser excitation intensity was observed. The PL was found to be due to radiative transitions from the moderately deep donor level located at 0.243 eV below the bottom of the conduction band to the shallow acceptor level at 0.023 eV located above the top of the valence band. The proposed energy-level diagram permits us to interpret the recombination processes in TlInSeS layered single crystals.

  9. Giant magnetocaloric effect and temperature induced magnetization jump in GdCrO3 single crystal

    Science.gov (United States)

    Yin, L. H.; Yang, J.; Kan, X. C.; Song, W. H.; Dai, J. M.; Sun, Y. P.

    2015-04-01

    We report on a systematic study of the single-crystal GdCrO3, which shows various novel magnetic features, such as temperature-induced magnetization reversal (TMR), temperature-induced magnetization jump (TMJ), spin reorientation, and giant magnetocaloric effect (MCE). In the field-cooled cooling process with modest magnetic field along the c axis, GdCrO3 first shows a TMR at T c o m p ˜ 120 - 130 K and then an abrupt TMJ with a sign change of magnetization at T j u m p ˜ 52 - 120 K , and finally a spin reorientation at T S R ˜ 4 - 7 K . Interestingly, the remarkable TMJ behavior, which was not reported ever before, persists at higher fields up to 10 kOe even when TMR disappears. In addition, giant MCE with the maximum value of magnetic entropy change reaching ˜31.6 J/kg K for a field change of 44 kOe was also observed in GdCrO3 single crystal, suggesting it could be a potential material for low-T magnetic refrigeration. A possible mechanism for these peculiar magnetic behaviors is discussed based on the various competing magnetic interactions between the 3d electrons of Cr3+ ions and 4f electrons of Gd3+ ions.

  10. Optical properties of CsI single crystals irradiated with neutrons at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Okada, M. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Nakagawa, M. [Faculty of Education, Kagawa Univ., Takamatsu, Kagawa (Japan); Atobe, K. [Faculty of Science, Naruto Univ. of Education, Naruto, Tokushima (Japan); Itatani, N.; Ozawa, K. [Horiba Ltd., Minamiku, Kyoto (Japan)

    1998-05-01

    Optical properties of the irradiation-induced-defects in neutron-irradiated CsI single crystals have been investigated. The nominally pure CsI crystals are irradiated by reactor fast neutrons (E>0.1 MeV) with a fluence of 1.4 x 10{sup 15} n/cm{sup 2} at 20 K and by {gamma}-rays from {sup 60}Co source to a dose of 1.5 x 10{sup 4} Gy at liquid nitrogen temperature (LNT). After the irradiations, isochronal annealings are performed to investigate the thermal behavior of the defects. The glow peaks of the thermoluminescence (TL) in each sample irradiated with neutrons at 20 K and with {gamma}-rays at LNT are observed at about 100, 160 and 220 K. In the neutron-irradiated samples at 20 K, the emission band at 338 nm is observed at LNT. It is supposed that this emission band occurs by an excitation of {gamma}-rays from {sup 134}Cs, which is radioactivated by thermal neutrons among the reactor radiations. It is confirmed that the temperature dependence of the 338 nm band is similar with that of the emission band due to the self-trapped exciton which is introduced into the non-irradiated samples illuminated by higher energy photons. (orig.) 13 refs.

  11. The room temperature crystal structure of a bacterial phytochrome determined by serial femtosecond crystallography

    Science.gov (United States)

    Edlund, Petra; Takala, Heikki; Claesson, Elin; Henry, Léocadie; Dods, Robert; Lehtivuori, Heli; Panman, Matthijs; Pande, Kanupriya; White, Thomas; Nakane, Takanori; Berntsson, Oskar; Gustavsson, Emil; Båth, Petra; Modi, Vaibhav; Roy-Chowdhury, Shatabdi; Zook, James; Berntsen, Peter; Pandey, Suraj; Poudyal, Ishwor; Tenboer, Jason; Kupitz, Christopher; Barty, Anton; Fromme, Petra; Koralek, Jake D.; Tanaka, Tomoyuki; Spence, John; Liang, Mengning; Hunter, Mark S.; Boutet, Sebastien; Nango, Eriko; Moffat, Keith; Groenhof, Gerrit; Ihalainen, Janne; Stojković, Emina A.; Schmidt, Marius; Westenhoff, Sebastian

    2016-01-01

    Phytochromes are a family of photoreceptors that control light responses of plants, fungi and bacteria. A sequence of structural changes, which is not yet fully understood, leads to activation of an output domain. Time-resolved serial femtosecond crystallography (SFX) can potentially shine light on these conformational changes. Here we report the room temperature crystal structure of the chromophore-binding domains of the Deinococcus radiodurans phytochrome at 2.1 Å resolution. The structure was obtained by serial femtosecond X-ray crystallography from microcrystals at an X-ray free electron laser. We find overall good agreement compared to a crystal structure at 1.35 Å resolution derived from conventional crystallography at cryogenic temperatures, which we also report here. The thioether linkage between chromophore and protein is subject to positional ambiguity at the synchrotron, but is fully resolved with SFX. The study paves the way for time-resolved structural investigations of the phytochrome photocycle with time-resolved SFX. PMID:27756898

  12. Using a titanium-in-quartz geothermometer for crystallization temperature estimation of the Palaeoproterozoic Suursaari quartz porphyry

    Directory of Open Access Journals (Sweden)

    Kairi Ehrlich

    2012-11-01

    Full Text Available The Suursaari volcanic sequence represents volcanic activity related to Wiborg Batholith rapakivi intrusions in the southern part of the Fennoscandian Shield. The estimated pressure conditions for batholith granitic rocks are 1–5 kbar and crystallization temperatures range from 670 to 890 °C. To describe the temperature regime of the Suursaari volcanic system, a rock sample was taken from the Mäkiinpäällys Mountain outcrop and analysed with laser ablation inductively coupled plasma mass spectrometry. Sample spots were selected from quartz phenocrysts and groundmass. Quartz crystallization temperatures were calculated by the Ti-in-quartz method that takes into account rutile equilibrium and Ti activity in each phase. The calculated crystallization temperatures of the Suursaari quartz porphyry are in the range of 647–738 °C. The results show that the Suursaari quartz porphyry contains two generations of quartz which can be distinguished on the basis of crystallization temperatures: phenocrysts crystallized at higher and groundmass quartz at lower temperature.

  13. Optical investigations on Tb3+ doped L-Histidine hydrochloride mono hydrate single crystals grown by low temperature solution techniques

    Science.gov (United States)

    Rajyalakshmi, S.; Ramachandra Rao, K.; Brahmaji, B.; Samatha, K.; Visweswara Rao, T. K.; Bhagavannarayana, G.

    2016-04-01

    The potential nonlinear optical material of Terbium (Tb3+) ion doped L-Histidine hydrochloride monohydrate (LHHC) single crystals were successfully grown. Tb3+:LHHC crystals of 7 mm × 5 mm × 3 mm and 59 mm length and 15 mm diameter have been grown by the slow solvent evaporation and Sankaranarayanan-Ramasamy (SR) techniques respectively. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystalline structure and morphology. High resolution X-ray diffraction (HRXRD) studies revealed that the SR grown sample shows relatively good crystalline nature with 9″ full-width at half-maximum (FWHM) for the diffraction curve. Functional groups were identified by Fourier transform infra-red spectroscopy (FTIR). The optical transparency and band gaps of grown crystals were measured by UV-Vis spectroscopy. Thermogravimetric and differential thermal analysis (TG/DTA) studies reveal that the crystal was thermally stable up to 155 °C in SR grown crystal. Surface morphology of the growth plane was observed using scanning electron microscopy (SEM). The incorporation of Tb ion was estimated by EDAX. The frequency-dependent dielectric properties of the crystals were carried out for different temperatures. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the SR method grown crystal. Second harmonic generation efficiency of SEST and SR grown crystals are 3.2 and 3.5 times greater than that of pure KDP. The Photoluminescence (PL) studies of Tb3+ ions result from the radiative intra-configurational f-f transitions that occur from the 5D4 excited state to the 7Fj (j = 6, 5, 4, 3) ground states. The decay curve of the 5D4 level of emission was observed with a long life time of 319.2041 μs for the SR grown Tb3+:LHHC crystal.

  14. Temperature dependent lattice instability in single crystals of ferromagnetic CdCr2Se4 diluted with In and Sb

    DEFF Research Database (Denmark)

    Waskowska, A.; Gerward, Leif; Olsen, J.S.

    2008-01-01

    to occur at the same temperature as the magnetic transition, T-c = 130 K, which also is the same T-c as for the parent crystal CdCr2Se4. The low temperature phase has been described in orthorhombic space group Fddd. For In admixture, a structural transition occurs in the paramagnetic state at about T...

  15. The mechanisms and temperature dependence of superlattice stacking fault formation in the single-crystal superalloy PWA 1480

    Science.gov (United States)

    Milligan, Walter W.; Antolovich, Stephen D.

    1991-01-01

    The mechanism of the formation of superlattice staking faults in the single-crystal nickel-base superalloy PWA 1480 was investigated by observing deformation microstructures in the superalloy single crystals in the temperature range 20-1100 C. Results showed that, in addition to superlattice stacking faults observed after slow strain rate deformation at temperatures from 700 to 950 C, a high-density of superlattice staking faults formed after deformation at 200 C and below. The mechanisms of fault formation, which are different in the high- and the low-temperature regimes, are discussed.

  16. In-Situ Alignment of MnBi Crystals Induced by High Magnetic Field above Curie Temperature

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-Sheng; ZHANG Jin-Cang; REN Zhong-Ming; CAO Shi-Xun

    2007-01-01

    @@ Above Curie temperature, MnBi crystals are aligned in situ along the c-axis in a Bi matrix by a high fabrication magnetic field Hf of 10 T. Magnetic testing shows a pronounced anisotropy in magnetization in directions normal and parallel to the fabrication field, resulting from the alignment. The successful alignment may result from the fact that the easy magnetization direction is along the c-axis of MnBi and the high fabrication field of 10 T is large enough to rotate the MnBi crystal to this direction even though the temperature is above the Curie temperature.

  17. Novel Design Integrating a Microwave Applicator into a Crystallizer for Rapid Temperature Cycling. A Direct Nucleation Control Study

    Science.gov (United States)

    2017-01-01

    The control of nucleation in crystallization processes is a challenging task due to the often lacking knowledge on the process kinetics. Inflexible (predetermined) control strategies fail to grow the nucleated crystals to the desired quality because of the variability in the process conditions, disturbances, and the stochastic nature of crystal nucleation. Previously, the concept of microwave assisted direct nucleation control (DNC) was demonstrated in a laboratory setup to control the crystal size distribution in a batch crystallization process by manipulating the number of particles in the system. Rapid temperature cycling was used to manipulate the super(under)saturation and hence the number of crystals. The rapid heating response achieved with the microwave heating improved the DNC control efficiency, resulting in halving of the batch time. As an extension, this work presents a novel design in which the microwave applicator is integrated in the crystallizer, hence avoiding the external loop though the microwaves oven. DNC implemented in the 4 L unseeded crystallizer, at various count set points, resulted in strong efficiency enhancement of DNC, when compared to the performance with a slow responding system. The demonstrated crystallizer design is a basis for extending the enhanced process control opportunity to other applications. PMID:28729813

  18. Efficacy of two ethanol-based skin antiseptics on the forehead at shorter application times

    Directory of Open Access Journals (Sweden)

    Pitten Frank-Albert

    2007-09-01

    Full Text Available Abstract Background Recent research suggests that alcohol-based skin antiseptics exhibit their efficacy on the resident skin flora of the forehead in less than 10 minutes. That is why we have looked at the efficacy of two ethanol-based skin antiseptics applied for 10, 2.5 and 2 minutes on skin with a high density of sebaceous glands. Each experiment was performed in a reference-controlled cross-over design with at least 20 participants. Application of isopropanol (70%, v/v for 10 minutes to the forehead served as the reference treatment. The clear (skin antiseptic A and coloured preparations (skin antiseptic B contain 85% ethanol (w/w. Pre-values and post-values (immediately after the application and after 30 min were obtained by swabbing a marked area of 5 cm2 for about 10 s. Swabs were vortexed in tryptic soy broth containing valid neutralizing agents. After serial dilution aliquots were spread on tryptic soy agar. Colonies were counted after incubation of plates at 36°C for 48 h. The mean log10 reduction of bacteria was calculated. The Wilcoxon matched-pairs signed-ranks test was used for a comparison of treatments. Results Skin antiseptic A applied for 10 min was significantly more effective than the reference treatment. When applied for 2.5 min (three experiments it was significantly more effective than the reference treatment immediately after application (2.7 versus 2.2 log10 reduction; p 10 reduction; p = 0.053. Skin antiseptic B applied for 2.5 min (three experiments was significantly more effective than the reference treatment both immediately after application (2.3 versus 1.9 log10 reduction; p 10 reduction; p = 0.002. Conclusion The clear and coloured skin antiseptics applied for 2.5 min on the skin of the forehead fulfilled the efficacy requirements for skin antisepsis. The shorter application time on skin with a high density of sebaceous glands will allow to act more efficiently in clinical practice.

  19. Single crystal elasticity of majoritic garnet at high pressure and temperature

    Science.gov (United States)

    Pamato, M. G.; Kurnosov, A.; Boffa Ballaran, T.; Frost, D. J.; Ziberna, L.; Giannini, M.; Trots, D. M.; Tkachev, S. N.; Zhuravlev, K. K.; Prakapenka, V.

    2013-12-01

    Seismological observations are fundamental for understanding the chemistry and structure of the Earth's interior, providing a tangible method for tracing the chemical anomalies caused by the subduction of oceanic lithosphere. The mineral garnet is a dominant component of subducted mid ocean ridge basalts (MORB) in the upper mantle and transition zone and as such can influence its physical-chemical properties. Among garnet minerals, the high pressure structured majoritic garnet, is stable throughout the entire transition zone, being volumetrically the most abundant mineral phase in this region. In order to constrain the seismic appearance and buoyancy of subducting slabs into the Earth's transition zone, the knowledge of the elastic properties and density of majoritic garnet at high pressures and temperatures is of crucial importance. Here, we report for the first time the P-V-T equation of state and Vs and Vp sound velocities of single crystals of majoritic garnet (Mg3.24Al1.53Si3.23O12) simultaneously determined by means of Brillouin spectroscopy and X ray diffraction, up to 30 GPa and 880 K. Measurements were performed on single-crystals synthesized in a multianvil apparatus at 17 GPa and 1900 °C and loaded in a diamond anvil cell with Ne as a pressure transmitting medium. A single crystal of Sm:YAG, whose fluorescence has been calibrated against an absolute pressure determination, was used as a pressure calibrant. In addition, ruby chips were used to accurately derive the temperature inside the cell. A specially designed internal resistive heater was placed around the diamonds for achieving high temperatures. An accurate pressure scale is a major issue in the investigation of physical properties of mantle minerals at the depth and temperature required to understand the Earth's interior. In this study, simultaneous measurements of density and sound velocities at the same conditions, allowed accurate determinations of the absolute pressure. We combine our

  20. Study of crystal structure at high temperature phase in KIO sub 3 crystal by synchrotron powder X-ray diffraction

    CERN Document Server

    Kasatani, H; Kuroiwa, Y; Yagi, K; Katayama, R; Terauchi, H

    2003-01-01

    The accurate crystal structure of the I-phase in KIO sub 3 crystal has been obtained at 530 K, for the first time, by the MEM/Rietveld analysis from high-energy X-ray powder-diffraction data. The crystal structure of the I-phase is the rhombohedral perovskite structure (space group R3m; Z=1). The MEM charge-density distributions reveal that the shorter I-O bond exhibits a covalent bonding character and others (I-K, K-O and longer I-O bonds) an ionic.

  1. Crystal induced phosphorescence from Benz(a)anthracene microcrystals at room temperature

    Science.gov (United States)

    Maity, Samir; Mazumdar, Prativa; Shyamal, Milan; Sahoo, Gobinda Prasad; Misra, Ajay

    2016-03-01

    Pure organic compounds that are also phosphorescent at room temperature are very rare in literature. Here, we report efficient phosphorescence emission from aggregated hydrosol of Benz(a)anthracene (BaA) at room temperature. Aggregated hydrosol of BaA has been synthesized by re-precipitation method and SDS is used as morphology directing agent. Morphology of the particles is characterized using optical and scanning electronic microcopy (SEM). Photophysical properties of the aggregated hydrosol are carried out using UV-vis, steady state and time resolved fluorescence study. The large stoke shifted structured emission from aggregated hydrosol of BaA has been explained due to phosphorescence emission of BaA at room temperature. In the crystalline state, the restricted intermolecular motions (RIM) such as rotations and vibrations are activated by crystal lattice. This rigidification effect makes the chromophore phosphorescent at room temperature. The possible stacking arrangement of the neighboring BaA within the aggregates has been substantiated by computing second order Fukui parameter as local reactivity descriptors. Computational study also reveals that the neighboring BaA molecules are present in parallel slipped conformation in its aggregated crystalline form.

  2. Reversible room-temperature ferromagnetism in Nb-doped SrTiO3 single crystals

    Science.gov (United States)

    Liu, Z. Q.; Lü, W. M.; Lim, S. L.; Qiu, X. P.; Bao, N. N.; Motapothula, M.; Yi, J. B.; Yang, M.; Dhar, S.; Venkatesan, T.; Ariando

    2013-06-01

    The search for oxide-based room-temperature ferromagnetism has been one of the holy grails in condensed matter physics. Room-temperature ferromagnetism observed in Nb-doped SrTiO3 single crystals is reported in this Rapid Communication. The ferromagnetism can be eliminated by air annealing (making the samples predominantly diamagnetic) and can be recovered by subsequent vacuum annealing. The temperature dependence of magnetic moment resembles the temperature dependence of carrier density, indicating that the magnetism is closely related to the free carriers. Our results suggest that the ferromagnetism is induced by oxygen vacancies. In addition, hysteretic magnetoresistance was observed for magnetic field parallel to the current, indicating that the magnetic moments are in the plane of the samples. The x-ray photoemission spectroscopy, the static time-of-flight and the dynamic secondary ion mass spectroscopy and proton induced x-ray emission measurements were performed to examine the magnetic impurities, showing that the observed ferromagnetism is unlikely due to any magnetic contaminant.

  3. Effect of high temperature annealing on defects and optical properties of ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, M.; Wang, D.D.; Zou, B.; Chen, Z.Q. [Hubei Nuclear Solid Physics Key Laboratory, Department of Physics, Wuhan University, Wuhan 430072 (China); Kawasuso, A. [Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Sekiguchi, T. [Advanced Electronic Materials Center, National Institute for Materials Science, Tsukuba 305-0044 (Japan)

    2012-11-15

    Hydrothermal grown ZnO single crystals were annealed in N{sub 2} or O{sub 2} between 900 and 1300 C. Positron lifetime measurements reveal a single lifetime in all the ZnO samples before and after annealing. The positron lifetime is about 181 ps after annealing at 900 C in either N{sub 2} or O{sub 2} atmosphere. However, increase of the positron lifetime is observed after further annealing the sample at higher temperatures up to 1300 C, and it has a faster increase in O{sub 2} ambient. Temperature dependence measurements show that the positron lifetime has very slight increase with temperature for the 900 C annealed sample, while it shows notable variation for the sample annealed at 1300 C. This implied that annealing at high temperature introduces additional defects. These defects are supposed to be Zn vacancy-related defects. Cathodoluminescence (CL) measurements indicates enhancement of both UV and green emission after annealing, and the enhancement of green emission is much stronger for the samples annealed in O{sub 2} ambient. The possible origin of green emission is tentatively discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Crystal Structure of Pure and Aluminous Calcium Silicate Perovskites at Mantle Related Pressure and Temperature

    Science.gov (United States)

    Chen, H.; Shim, S. H.; Leinenweber, K. D.; Meng, Y.; Prakapenka, V.

    2015-12-01

    CaSiO3-perovskite (CaPv) is believed to be the third most abundant mineral (5 wt%) in the Earth's lower mantle (LM). Subducted slabs contain 23 wt% CaPv at the LM related pressure (P) and temperature (T), where Al2O3 could be incorporated into the crystal structure of CaPv (AlCaPv). However, there remains important discrepancy between computations and experiments on the crystal structure of CaPv at high P and low T. Some computations have predicted a tetragonal I4/mcm structure with a pseudo-cubic axial ratio (cp/ap) greater than 1, while X-ray diffraction (XRD) studies have suggested a tetragonal P4/mmm structure with cp/ap ~ 0.995. Using Ne as a pressure medium, we conducted in-situ XRD of CaSiO3 and 5 wt% Al-bearing CaSiO3 in the laser heated diamond anvil cell at the GSECARS and HPCAT sectors of the Advanced Photon Source. Rietveld refinements are performed on the diffraction patterns of CaPv at 300 K and 20-60 GPa. Similar to previous studies, we observed splitting of the 200 and 211 peaks after T-quench in pure CaPv. However, unlike previous experiments, diffraction patterns were more consistent with a tetragonal I4/mcm structure with cp/ap ~ 1.005 than P4/mmm. All the previous diffraction patterns have been measured with an Ar or MgO medium, or even without a medium, while we used more hydrostatic Ne medium. Considering the small free energy differences among different perovskite structures, the crystal structure of CaPv may be very sensitive to non-hydrostatic stresses. In runs with AlCaPv, asymmetrical 200 peaks are found up to 60 GPa and 2200 K, showing that non-cubic could be still stable at mantle geotherm temperatures in AlCaPv. The extreme sensitivity of CaPv on deviatoric stresses may have important implications for the elastic properties of the mantle regions with strong deformations, because the elastic anisotropy can change with the crystal structure of CaPv.

  5. Spatial distributions of hemoglobin signals from superficial layers in the forehead during a verbal-fluency task

    Science.gov (United States)

    Kohno, Satoru; Hoshi, Yoko

    2016-06-01

    Functional near-infrared spectroscopy (fNIRS) signals originate in hemoglobin changes in both the superficial layer of the head and the brain. Under the assumption that the changes in the blood flow in the scalp are spatially homogeneous in the region of interest, a variety of methods for reducing the superficial signals has been proposed. To clarify the spatial distributions of the superficial signals, the superficial signals from the forehead during a verbal-fluency task were investigated by using ten source-detector pairs separated by 5 mm, whereas fNIRS signals were also detected from two source-detector pairs separated by 30 mm. The fNIRS signals strongly correlated with the superficial signals at some channels on the forehead. Hierarchical cluster analysis was performed on the temporal cross-correlation coefficients for two channels of both the NIRS signals, and the analysis results demonstrate spatially heterogeneous distributions and network structures of the superficial signals from within the forehead. The results also show that the assumption stated above is invalid for homogeneous superficial signals from any region of interest of 15-mm diameter or larger on the forehead. They also suggest that the spatially heterogeneous distributions may be attributable to vascular networks, including supraorbital, supratrochlear, and superficial temporal vessels.

  6. Gull Wing Midforehead Lift When a Poor Man's Forehead Lift Becomes the Treatment of Choice for Brow Ptosis

    NARCIS (Netherlands)

    Huijing, Marijn A.; van der Lei, Berend

    In case of both medial and lateral brow ptosis in a balding candidate with a furrowed forehead, one may consider a midforehead lift, a technique that has not gained much popularity because of concerns regarding clearly visible scarring. We have applied this technique in a selected group of patients

  7. Room temperature X- and gamma-ray detectors using thallium bromide crystals

    CERN Document Server

    Hitomi, K; Shoji, T; Suehiro, T; Hiratate, Y

    1999-01-01

    Thallium bromide (TlBr) is a compound semiconductor with wide band gap (2.68 eV) and high X- and gamma-ray stopping power. The TlBr crystals were grown by the horizontal travelling molten zone (TMZ) method using purified material. Two types of room temperature X- and gamma-ray detectors were fabricated from the TlBr crystals: TlBr detectors with high detection efficiency for positron annihilation gamma-ray (511 keV) detection and TlBr detectors with high-energy resolution for low-energy X-ray detection. The detector of the former type demonstrated energy resolution of 56 keV FWHM (11%) for 511 keV gamma-rays. Energy resolution of 1.81 keV FWHM for 5.9 keV was obtained from the detector of the latter type. In order to analyze noise characteristics of the detector-preamplifier assembly, the equivalent noise charge (ENC) was measured as a function of the amplifier shaping time for the high-resolution detector. This analysis shows that parallel white noise and 1/f noise were dominant noise sources in the detector...

  8. Imaging the oblique propagation of electrons in germanium crystals at low temperature and low electric field

    Energy Technology Data Exchange (ETDEWEB)

    Moffatt, R. A., E-mail: rmoffatt@stanford.edu; Cabrera, B.; Corcoran, B. M.; Kreikebaum, J. M.; Redl, P.; Shank, B.; Yen, J. J. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Young, B. A. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Department of Physics, Santa Clara University, Santa Clara, California 95053 (United States); Brink, P. L.; Cherry, M.; Tomada, A. [SLAC National Accelerator Facility, Menlo Park, California 94025 (United States); Phipps, A.; Sadoulet, B.; Sundqvist, K. M. [Department of Physics, University of California, Berkeley, California 94720 (United States)

    2016-01-11

    Excited electrons in the conduction band of germanium collect into four energy minima, or valleys, in momentum space. These local minima have highly anisotropic mass tensors which cause the electrons to travel in directions which are oblique to an applied electric field at sub-Kelvin temperatures and low electric fields, in contrast to the more isotropic behavior of the holes. This experiment produces a full two-dimensional image of the oblique electron and hole propagation and the quantum transitions of electrons between valleys for electric fields oriented along the [0,0,1] direction. Charge carriers are excited with a focused laser pulse on one face of a germanium crystal and then drifted through the crystal by a uniform electric field of strength between 0.5 and 6 V/cm. The pattern of charge density arriving on the opposite face is used to reconstruct the trajectories of the carriers. Measurements of the two-dimensional pattern of charge density are compared in detail with Monte Carlo simulations developed for the Cryogenic Dark Matter Search (SuperCDMS) to model the transport of charge carriers in high-purity germanium detectors.

  9. Precision Measurements of Light Quenching in CaWO$_4$ Crystals at mK Temperatures

    CERN Document Server

    Strauss, R; Bento, A; Bucci, C; Canonica, L; Carli, W; Ciemniak, C; Erb, A; Feilitzsch, F v; Gorla, P; Gütlein, A; Hagn, H; Hauff, D; Hellgartner, D; Jochum, J; Kraus, H; Lanfranchi, J -C; Loebell, J; Münster, A; Petricca, F; Potzel, W; Pröbst, F; Reindl, F; Roth, S; Rottler, K; Sailer, C; Schäffner, K; Schieck, J; Scholl, S; Schönert, S; Seidel, W; Sivers, M v; Stodolsky, L; Strandhagen, C; Tanzke, A; Uffinger, M; Ulrich, A; Usherov, I; Wawoczny, S; Willers, M; Wüstrich, M; Zöller, A

    2014-01-01

    Scintillating CaWO$_4$ single crystals are a promising multi-element target for rare-event searches and are currently used in the direct Dark Matter experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers). The relative light output of different particle interactions in CaWO$_4$ is quantified by Quenching Factors (QFs). These are essential for an active background discrimination and the identification of a possible signal induced by weakly interacting massive particles (WIMPs). We present the first precise measurements of the QFs of O, Ca and W at mK temperatures by irradiating a cryogenic detector with a fast neutron beam. A clear energy dependence of the QFs and a variation between different CaWO$_4$ single crystals were observed for the first time. For typical CRESST detectors the QFs in the region-of-interest (10-40$\\,$keV) are $QF_O^{ROI}=(11.2\\pm0.5)\\,$%, $QF_{Ca}^{ROI}=(5.94\\pm0.49)\\,$% and $QF_W^{ROI}=(1.72\\pm0.21)\\,$%. The latest CRESST data (run32) is reanalyzed using these ...

  10. Single-Crystal Elasticity of MgO at High Pressure and Temperature

    Science.gov (United States)

    Fan, D.; Mao, Z.; Lin, J. F.; Yang, J.; Prakapenka, V.

    2014-12-01

    Periclase (MgO) is a material of key importance to Earth sciences: it is one of the most abundant minerals in Earth's lower mantle. It has the simple NaCl structure with no phase transition at least up to 200 GPa and also has very high melting temperatures above 3000 K. These wide stability ranges of MgO cover high-pressure and high-temperature conditions corresponding to the Earth's lower mantle. Therefore, precise knowledge of the thermal elastic properties of MgO, major end-members of constituent mineral phases of the lower mantle, under high pressure and high temperature condition is crucial for constructing the accurate mineralogical model of the Earth's lower mantle. Here we have measured the single-crystal elasticity of MgO using in situ Brillouin spectroscopy and X-ray diffraction at simultaneous high pressure-temperature conditions up to 33 GPa and 900 K in an externally-heated diamond anvil cell. Using the third-order Eulerian finite-strain equations to model the elasticity data, we have derived the aggregate adiabatic bulk, KS0, and shear moduli, G0, at ambient conditions: KS0=162.9 (6) GPa (the value in parentheses represents propagated uncertainties) and G0=130.7 (8) GPa, respectively, consistent with literature results. The pressure derivatives of the bulk and shear moduli at 300K are (∂KS/∂P)T=4.06 (22) and (∂G/∂P)T=2.75(±0.18), respectively, which are also consistent with previous literature results. We also derived the temperature derivatives of these moduli at constant pressure. Our results here provide accurate insights into seismic profiles and mineralogical models of the lower mantle region.

  11. Elevated Temperature Creep Deformation in Solid Solution NiAL-3.6Ti Single Crystals

    Science.gov (United States)

    Whittenberger, J. Daniel; Noebe, Ronald D.; Darolia, Ram

    2003-01-01

    The 1100 to 1500 K slow plastic strain rate compressive properties of oriented NiAl-3.6Ti single crystals have been measured, and the results suggests that two deformation processes exist. While the intermediate temperature/faster strain rate mechanism is uncertain, plastic flow at elevated temperature/slower strain rates in NiAl-3.6Ti appears to be controlled by solute drag as described by the Cottrell-Jaswon solute drag model for gliding b = a(sub 0) dislocations. While the calculated activation energy of deformation is much higher (approximately 480 kJ/mol) than the activation energy for diffusion (approximately 290 kJ/mol) used in the Cottrell-Jaswon creep model, a forced temperature compensated - power law fit using the activation energy for diffusion was able to adequately (greater than 90%) predict the observed creep properties. Thus we conclude that the rejection of a diffusion controlled mechanism can not be simply based on a large numerical difference between the activation energies for deformation and diffusion.

  12. Quantized Hamiltonian dynamics captures the low-temperature regime of charge transport in molecular crystals.

    Science.gov (United States)

    Wang, Linjun; Akimov, Alexey V; Chen, Liping; Prezhdo, Oleg V

    2013-11-07

    The quantized Hamiltonian dynamics (QHD) theory provides a hierarchy of approximations to quantum dynamics in the Heisenberg representation. We apply the first-order QHD to study charge transport in molecular crystals and find that the obtained equations of motion coincide with the Ehrenfest theory, which is the most widely used mixed quantum-classical approach. Quantum initial conditions required for the QHD variables make the dynamics surpass Ehrenfest. Most importantly, the first-order QHD already captures the low-temperature regime of charge transport, as observed experimentally. We expect that simple extensions to higher-order QHDs can efficiently represent other quantum effects, such as phonon zero-point energy and loss of coherence in the electronic subsystem caused by phonons.

  13. Room temperature synthesis of single-crystal Te nanorods from Na2TeO4

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Single-crystalline tellurium nanorods were synthesized through the reduction of Na2TeO4 by hydrazine monohydrate,in the absence of surfactants,in an aqueous ammonia solution at room temperature.X-ray diffraction (XRD),transmission electron microscopy (TEM),and selected area electron diffraction (SAED) were used to characterize the composition and morphology of the products.The concentration of the OH- ion has a significant influence on the morphology of the products and is found to be responsible for tailoring the crystal growth dynamically:the concentration of Te blocking in the solution is reduced via increasing the concentration of the OH- ion,and subsequently the nucleation rate of Te is suppressed and Te nanorods gradually grow because of the inherently anisotropic structure of Te.New generation tellurium atoms add to the surface of the particles during the long period of reaction.

  14. Temperature-induced tuning of emission spectra of liquid-crystal optical microcavities

    Science.gov (United States)

    Zemánek, Pavel; Pilát, Zdeněk.; Ježek, Jan; Bernatová, Silvie; Aas, Mehdi; Kiraz, Alper; Jonáš, Alexandr

    2016-12-01

    Emulsion droplets of liquid crystals (LC) suspended in water and labeled with a suitable fluorescent dye can serve as active optofluidic microcavities, since the contrast of refractive index between the LC droplets and the surrounding aqueous medium allows excitation of whispering gallery modes (WGMs) in the droplets. In addition, such emulsion droplets can be also stably trapped in three-dimensions using optical tweezers which stabilizes the droplets while investigating their spectral characteristics. We explore various combinations of fluorescently dyed LC droplets and host liquid - surfactant systems and show that the WGM emission spectrum of an optically trapped LC droplet-based cavity can be largely and (almost) reversibly tuned by controlled changes of the ambient temperature that induce phase transitions in the LC droplets. Our results indicate feasibility of this approach for creating miniature tunable sources of coherent light.

  15. Complete Stokes polarimetry of magneto-optical Faraday effect in a terbium gallium garnet crystal at cryogenic temperatures.

    Science.gov (United States)

    Majeed, Hassaan; Shaheen, Amrozia; Anwar, Muhammad Sabieh

    2013-10-21

    We report the complete determination of the polarization changes caused in linearly polarized incident light due to propagation in a magneto-optically active terbium gallium garnet (TGG) single crystal, at temperatures ranging from 6.3 to 300 K. A 28-fold increase in the Verdet constant of the TGG crystal is seen as its temperature decreases to 6.3 K. In contrast with polarimetry of light emerging from a Faraday material at room temperature, polarimetry at cryogenic temperatures cannot be carried out using the conventional fixed polarizer-analyzer technique because the assumption that ellipticity is negligible becomes increasingly invalid as temperature is lowered. It is shown that complete determination of light polarization in such a case requires the determination of its Stokes parameters, otherwise inaccurate measurements will result with negative implications for practical devices.

  16. Room temperature synthesis of crystallized luminescent SrWO 4 films by an adjustable galvanic cell method

    Science.gov (United States)

    Cui, Chunhua; Bi, Jian; Gao, Daojiang

    2008-09-01

    Highly crystallized luminescent SrWO 4 films were prepared directly on tungsten substrate in strontium hydroxide aqueous solution by a galvanic cell method without impressed current at room temperature. It is noteworthy that the driving force of galvanic cell method is adjustable by adding different concentrations of oxidant. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results reveal that the crystallized films have a scheelite-type tetragonal structure and homogeneous surface. The film showed single blue emissions at 447 nm with excitation lights of 220, 230, 250, 260 and 270 nm at room temperature, respectively.

  17. Strain and temperature characterization of LPGs written by CO2 laser in pure silica LMA photonic crystal fibers

    Science.gov (United States)

    Chaves, Roberta Cardoso; Pohl, Alexandre de Almeida Prado; Abe, Ilda; Sebem, Renan; Paterno, Aleksander

    2015-09-01

    This paper reports on the writing of long period gratings (LPGs) in a six-ring pure silica solid core, and large mode area photonic crystal fiber (fiber core diameter ρ = 10.1 μm) using a CO2 laser system, and the characterization of their strain and temperature sensitivities. Temperature and strain sensitivities in the order of -19.6 pm/°C and -88 pm/μɛ, respectively, were obtained, which were comparable or surpassed values of the similar photonic crystal fiber (PCF)-based LPG or sensor configurations found in the literature.

  18. Effects of B2O3 content and sintering temperature on crystallization and microstructure of CBS glass-ceramic coatings

    Science.gov (United States)

    Li, Pengyang; Wang, Shubin; Liu, Jianggao; Feng, Mengjie; Yang, Xinwang

    2015-11-01

    Borosilicate glass-ceramics precursors with varying compositional ratios in the CaO-SiO2-B2O3 (CBS) system were synthesized by sol-gel method. The precursors were calcined at 1200 °C for 2 h to form glass powders. The glass-ceramics were prepared by overlaying glass slurries on the substrates before sintering at different temperatures. The as-prepared glasses and glass-ceramics were characterized by differential scanning calorimetry and X-ray diffraction. The crystallization activation energies (Ec) were calculated using the Kissinger method from DSC results. The morphology and crystallization behavior of the glass-ceramics were monitored by scanning electron microscopy. Both glass transition and crystallization temperatures decreased, however, the metastable zone increased. The Ec values of CBS glasses and glass-ceramics were 254.1, 173.2 and 164.4 kJ/mol with increasing B2O3 content, whereas that of the calcined G3 glass was 104.9 kJ/mol. Finally, the coatings were prepared at a low temperature (700 °C). The crystals that grew on the surface of multilayer coatings demonstrated heterogeneous surface nucleation and crystallization after heat-treatment from 700 °C to 850 °C for 4 h.

  19. Effect of deposition temperature on electron-beam evaporated polycrystalline silicon thin-film and crystallized by diode laser

    Energy Technology Data Exchange (ETDEWEB)

    Yun, J., E-mail: j.yun@unsw.edu.au; Varalmov, S.; Huang, J.; Green, M. A. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); Kim, K. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); Suntech R and D Australia, Botany, New South Wales 2019 (Australia)

    2014-06-16

    The effects of the deposition temperature on the microstructure, crystallographic orientation, and electrical properties of a 10-μm thick evaporated Si thin-film deposited on glass and crystallized using a diode laser, are investigated. The crystallization of the Si thin-film is initiated at a deposition temperature between 450 and 550 °C, and the predominant (110) orientation in the normal direction is found. Pole figure maps confirm that all films have a fiber texture and that it becomes stronger with increasing deposition temperature. Diode laser crystallization is performed, resulting in the formation of lateral grains along the laser scan direction. The laser power required to form lateral grains is higher in case of films deposited below 450 °C for all scan speeds. Pole figure maps show 75% occupancies of the (110) orientation in the normal direction when the laser crystallized film is deposited above 550 °C. A higher density of grain boundaries is obtained when the laser crystallized film is deposited below 450 °C, which limits the solar cell performance by n = 2 recombination, and a performance degradation is expected due to severe shunting.

  20. High-temperature relaxations in CaF{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J. [Laboratory of Dielectric Functional Materials, School of Physics and Material Science, Anhui University, Hefei 230601 (China); Wang, C.C., E-mail: ccwang@ahu.edu.cn [Laboratory of Dielectric Functional Materials, School of Physics and Material Science, Anhui University, Hefei 230601 (China); Li, Q.J.; Yu, Y. [Laboratory of Dielectric Functional Materials, School of Physics and Material Science, Anhui University, Hefei 230601 (China); Zhang, J. [School of Electronics Science and Applied Physics, Hefei University of Technology, Hefei 230009 (China); Zheng, J.; Cheng, C. [Center of Modern Experimental Technology, Anhui University, Hefei 230039 (China); Li, Y.D.; Wang, H.; Huang, S.G. [Laboratory of Dielectric Functional Materials, School of Physics and Material Science, Anhui University, Hefei 230601 (China)

    2014-10-15

    Highlights: • Both Debye-like relaxation and relaxor-like anomaly were observed in CaF{sub 2}. • Raman and DSC results revealed that the defects in CaF{sub 2} are V{sub F}{sup ·}, F{sup ′}{sub i}, and oxygen ions. • The Debye-like behavior was ascribed to the mobility of the fluorine vacancies. • The anomaly stems from the relaxation associated with the dipolar complex of O{sup ″}−V{sub F}{sup ·}. - Abstract: The dielectric properties of CaF{sub 2} single crystals were investigated in the temperature range from room temperature to 773 K and the frequency range of 50 Hz–10 MHz. A Debey-like relaxation and a relaxor-like dielectric anomaly were observed. Raman spectrum and the differential scanning calorimeter measurement revealed the coexistence of native defects of fluorine vacancies (V{sub F}{sup ·}) and interstitial fluorine ions (F{sup ′}{sub i}) and external defect of oxygen ions. Impedance analysis showed that the Debey-like relaxation results from the mobility of V{sub F}{sup ·}, while the relaxor-like behavior is associated with the relaxation caused by complexes of O{sup ″}−V{sub F}{sup ·}.

  1. Influence of maleic acid copolymers on calcium orthophosphates crystallization at low temperature

    Science.gov (United States)

    Pelin, Irina M.; Popescu, Irina; Suflet, Dana M.; Aflori, Magdalena; Bulacovschi, Victor

    2013-08-01

    The goal of this study was to investigate the maleic acid copolymers role on calcium orthophosphates crystallization at low temperature. In this respect, two maleic acid copolymers with different structures [poly(sodium maleate-co-vinyl acetate) and poly(sodium maleate-co-methyl methacrylate)] were used. The syntheses of the calcium orthophosphates in the absence and in the presence of the copolymers were performed through the wet chemical method using calcium nitrate, ammonium dihydrogen phosphate and ammonium hydroxide as reactants. The syntheses were monitored in situ by potentiometric and conductometric measurements. To ensure the transformation of less thermodynamically stable calcium orthophosphates into more stable forms, the samples were aged 30 days in mother solutions, at room temperature. The presence of the copolymers in the final products was evidenced by FTIR spectroscopy and thermogravimetric analysis. Scanning and transmission electron microscopy and laser light scattering measurements gave information about the composites morphology and the size of the formed structures. X-ray diffraction evidenced that, as a function of comonomer structure and of copolymer concentration, the products could contain hydroxyapatite with low crystallinity, calcium-deficient or carbonated hydroxyapatite. At high concentration of poly(sodium maleate-co-methyl methacrylate) the transformation of brushite into apatitic structures was inhibited.

  2. Room temperature all-silicon photonic crystal nanocavity light emitting diode at sub-bandgap wavelengths

    CERN Document Server

    Shakoor, A; Cardile, P; Portalupi, S L; Gerace, D; Welna, K; Boninelli, S; Franzo, G; Priolo, F; Krauss, T F; Galli, M; Faolain, L O

    2013-01-01

    Silicon is now firmly established as a high performance photonic material. Its only weakness is the lack of a native electrically driven light emitter that operates CW at room temperature, exhibits a narrow linewidth in the technologically important 1300- 1600 nm wavelength window, is small and operates with low power consumption. Here, an electrically pumped all-silicon nano light source around 1300-1600 nm range is demonstrated at room temperature. Using hydrogen plasma treatment, nano-scale optically active defects are introduced into silicon, which then feed the photonic crystal nanocavity to enahnce the electrically driven emission in a device via Purcell effect. A narrow ({\\Delta}{\\lambda} = 0.5 nm) emission line at 1515 nm wavelength with a power density of 0.4 mW/cm2 is observed, which represents the highest spectral power density ever reported from any silicon emitter. A number of possible improvements are also discussed, that make this scheme a very promising light source for optical interconnects a...

  3. Crystal structure and chemical bonding of the high-temperature phase of AgN3.

    Science.gov (United States)

    Schmidt, Carsten L; Dinnebier, Robert; Wedig, Ulrich; Jansen, Martin

    2007-02-05

    The crystal structure of silver azide (AgN3) in its high-temperature (HT) modification was determined from X-ray powder diffraction data, recorded at T = 170 degrees C and was further refined by the Rietveld method. The structure is monoclinic (P21/c (No. 14), a = 6.0756(2) A, b = 6.1663(2) A, c = 6.5729(2) A, beta = 114.19(0) degrees, V = 224.62(14) A3, Z = 4) and consists of two-dimensional Ag and N containing layers in which the silver atoms are coordinated by four nitrogen atoms exhibiting a distorted square coordination environment. These sheets are linked together by weaker perpendicular Ag-N contacts, thus forming a 4 + 2 coordination geometry around the silver atoms. The phase transition has been characterized by DTA, DSC, and measurement of the density, as well as of the ionic conductivity. Both, the room-temperature and the HT phase are electrically insulating. This fact is getting support by DFT band structure calculations within the generalized gradient approximation, using the PBE functional. On the basis of the DFT band structure, the bonding characteristics of both phases are essentially the same. Finally, the implication of the existence of a low-symmetry HT-phase in a crystalline explosive concerning decomposition mechanisms is discussed.

  4. Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN3

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt,C.; Dinnebier, R.; Wedig, U.; Jansen, M.

    2007-01-01

    The crystal structure of silver azide (AgN{sub 3}) in its high-temperature (HT) modification was determined from X-ray powder diffraction data, recorded at T = 170 {sup o}C and was further refined by the Rietveld method. The structure is monoclinic (P2{sub 1}lc (No. 14), a = 6.0756(2) {angstrom}, b = 6.1663(2) {angstrom}, c = 6.5729(2) {angstrom}, {beta} = 114.19(0){sup o}, V = 224.62(14) {angstrom}{sup 3}, Z = 4) and consists of two-dimensional Ag and N containing layers in which the silver atoms are coordinated by four nitrogen atoms exhibiting a distorted square coordination environment. These sheets are linked together by weaker perpendicular Ag-N contacts, thus forming a 4 + 2 coordination geometry around the silver atoms. The phase transition has been characterized by DTA, DSC, and measurement of the density, as well as of the ionic conductivity. Both, the room-temperature and the HT phase are electrically insulating. This fact is getting support by DFT band structure calculations within the generalized gradient approximation, using the PBE functional. On the basis of the DFT band structure, the bonding characteristics of both phases are essentially the same. Finally, the implication of the existence of a low-symmetry HT-phase in a crystalline explosive concerning decomposition mechanisms is discussed.

  5. Thermal expansion behavior of A- and B-type amylose crystals in the low-temperature region.

    Science.gov (United States)

    Kobayashi, Kayoko; Kimura, Satoshi; Naito, Philip-Kunio; Togawa, Eiji; Wada, Masahisa

    2015-10-20

    The thermal expansion behaviors of A-type and B-type amylose crystals, which were prepared by recrystallization of short amylose chains synthesized by phosphorylase, were investigated using synchrotron X-ray powder diffraction between 100 and 300K. For both types of crystals, the room-temperature phase (RT phase), which is the usually observed phase, transitioned to a low-temperature phase (LT phase), on cooling. The phase transitions took place reversibly with rapid changes in the unit-cell parameters around 200-270K. The differences between the RT and LT phase were investigated using solid-state (13)C NMR spectroscopy, which revealed there were changes in molecular chain conformations. These results suggest that the phase transition of water molecules on the crystalline surfaces affects the thermal behavior and structure of polysaccharide crystals.

  6. Room-Temperature Tensile Behavior of Oriented Tungsten Single Crystals with Rhenium in Dilute Solid Solution

    Science.gov (United States)

    1966-01-01

    SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION Sby M. Garfinkle Lewis Research Center Cleveland, Ohio 20060516196 NATIONAL AERONAUTICS AND...WITH RHENIUM IN DILUTE SOLID SOLUTION By M. Garfinkle Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by...ORIENTED TUNGSTEN SINGLE CRYSTALS WITH RHENIUM IN DILUTE SOLID SOLUTION * by M. Garfinkle Lewis Research Center SUMMARY Tungsten single crystals

  7. Low-temperature change of lattice parameters in LiKB{sub 4}O{sub 7} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Adamiv, Volodymyr; Burak, Yaroslav; Teslyuk, Ihor [Institute of Physical Optics, Lviv (Ukraine)

    2009-02-15

    Structural investigations of LiKB{sub 4}O{sub 7} crystals in the 13-290 K temperature range have been carried out by means of the high-resolution powder diffraction technique applying synchrotron radiation. It is shown that the structural phase transitions are absent and all the linear thermal expansion coefficients {alpha}{sub ij} are positive in the investigated temperature range. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Temperature and wavevector dependence of overdoped Bi_2Sr_2CaCu_2O_8+x single crystal samples

    Science.gov (United States)

    Rast, S.; Klohs, A.; Frazer, B. H.; Hirai, Y.; Schmauder, T.; Gatt, R.; Abrecht, M.; Pavuna, D.; Margaritondo, G.; Onellion, M.

    2000-03-01

    We report on measuring the temperature and wavevector change of angle-resolved photoemission spectra for overdoped Bi_2Sr_2CaCu_2O_8+x single crystal samples. Spectra taken from close to to close to were analyzed. The changes of spectral lineshape with temperature and wave vector indicate qualitatively different behavior in different parts of the Brillouin zone and will be analyzed and presented.

  9. Organic semiconducting single crystals as next generation of low-cost, room-temperature electrical X-ray detectors.

    Science.gov (United States)

    Fraboni, Beatrice; Ciavatti, Andrea; Merlo, Francesco; Pasquini, Luca; Cavallini, Anna; Quaranta, Alberto; Bonfiglio, Annalisa; Fraleoni-Morgera, Alessandro

    2012-05-02

    Direct, solid-state X-ray detectors based on organic single crystals are shown to operate at room temperature, in air, and at voltages as low as a few volts, delivering a stable and reproducible linear response to increasing X-ray dose rates, with notable radiation hardness and resistance to aging. All-organic and optically transparent devices are reported.

  10. The Insulator to Superconductor Transition in Ga-Doped Semiconductor Ge Single Crystal Induced by the Annealing Temperature

    Directory of Open Access Journals (Sweden)

    Y. B. Sun

    2015-01-01

    Full Text Available We have fabricated the heavily Ga-doped layer in Ge single crystal by the implantation and rapid thermal annealing method. The samples show a crossover from the insulating to the superconducting behavior as the annealing temperature increases. Transport measurements suggest that the superconductivity is from the heavily Ga-doped layer in Ge.

  11. The effects of temperature and strain rate on the yielding behavior of the single crystal superalloy PWA 1480

    Science.gov (United States)

    Milligan, Walter W.; Antolovich, Stephen D.

    1988-01-01

    Interrupted tensile tests were conducted on (001) oriented single crystals at temperatures from 20 to 1093 C. Two strain rates were used, 0.5 and 50 percent/min. After the tests, the deformation substructures were characterized by transmission electron microscopy. Results of these tests are given.

  12. Impurity microsegregation due to periodic changes in the temperature and pulling rate of crystal grown by the Stepanov method

    Energy Technology Data Exchange (ETDEWEB)

    Zhdanov, A.V.; Nikolaeva, L.P.; Red`kin, B.S. [Institute of Solid-State Physics, Chernogolovka (Russian Federation)

    1995-12-01

    A mathematical model is proposed to describe the behavior of a doping impurity concentration in a crystal grown by the Stepanov method from a melt and subjected to periodic changes in its pulling rate and temperature of the thermal node. Various modes of these effects are discussed. The results obtained are given by graphs that characterize their influence on concentration distribution.

  13. High-temperature piezoelectric single crystal ReCa(4)O(BO(3))(3) for sensor applications.

    Science.gov (United States)

    Zhang, Shujun; Fei, Yiting; Frantz, Eric; Snyder, David W; Chai, Bruce H T; Shrout, Thomas R

    2008-12-01

    Large-size and high-quality ReCa(4)O(BO(3))(3) (ReCOB, Re = rare earth) single crystals were grown by the Czochralski pulling method. In this work, the electrical properties were investigated at room temperature and elevated temperature for YCa(4)O(BO(3))(3) (YCOB). The dielectric permittivity, piezoelectric strain coefficient, and electromechanical coupling were found to be on the order of 11, 6.5 pC/N, and 12.5%, respectively, with a high piezoelectric voltage coefficient around 0.067 Vm/N. The electrical resistivity of YCOB was found to be 2 x 10(8) Ohm.m at 800 degrees C, with Q values of 4,500 at 950 degrees C. The frequency/temperature coefficient of YCOB was found to be -75 to -85ppm/K in the temperature range of 30 to 950 degrees C, depending on the crystal orientations. Together with their temperature-independent properties, ReCOB crystals are promising candidates for sensing applications at elevated temperatures.

  14. How Sensitive Is the Elasticity of Hydroxyapatite-Nanoparticle-Reinforced Chitosan Composite to Changes in Particle Concentration and Crystallization Temperature?

    Directory of Open Access Journals (Sweden)

    Kean Wang

    2015-10-01

    Full Text Available Hydroxyapatite (HA nanoparticle-reinforced chitosan composites are biocompatible and biodegradable structural materials that are used as biomaterials in tissue engineering. However, in order for these materials to function effectively as intended, e.g., to provide adequate structural support for repairing damaged tissues, it is necessary to analyse and optimise the material processing parameters that affect the relevant mechanical properties. Here we are concerned with the strength, stiffness and toughness of wet-spun HA-reinforced chitosan fibres. Unlike previous studies which have addressed each of these parameters as singly applied treatments, we have carried out an experiment designed using a two-factor analysis of variance to study the main effects of two key material processing parameters, namely HA concentration and crystallization temperature, and their interactions on the respective mechanical properties of the composite fibres. The analysis reveals that significant interaction occurs between the crystallization temperature and HA concentration. Starting at a low HA concentration level, the magnitude of the respective mechanical properties decreases significantly with increasing HA concentration until a critical HA concentration is reached, at around 0.20–0.30 (HA mass fraction, beyond which the magnitude of the mechanical properties increases significantly with HA concentration. The sensitivity of the mechanical properties to crystallization temperature is masked by the interaction between the two parameters—further analysis reveals that the dependence on crystallization temperature is significant in at least some levels of HA concentration. The magnitude of the mechanical properties of the chitosan composite fibre corresponding to 40 °C is higher than that at 100 °C at low HA concentration; the reverse applies at high HA concentration. In conclusion, the elasticity of the HA nanoparticle-reinforced chitosan composite fibre is

  15. Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature

    Institute of Scientific and Technical Information of China (English)

    Li Yong; Jia Xiao-Peng; Hu Mei-Hua; Liu Xiao-Bing; Yan Bing-Min; Zhou Zhen-Xiang; Zhang Zhuang-Fei; Ma Hong-An

    2012-01-01

    A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 ℃ to 1350 ℃.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp3-CH2-symmetric(2850 cm-1)and sp3 CH2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the spa C-H bond is rather stable in diamond crystals.

  16. The effects of glass doping, temperature and time on the morphology, composition, and iron redox of spinel crystals

    Energy Technology Data Exchange (ETDEWEB)

    Matyas, Josef [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amonette, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kukkadapu, Ravi K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Schreiber, Daniel K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kruger, Albert A. [Office of River Protection, Richland, WA (United States)

    2014-10-31

    Precipitation of large crystals/agglomerates of spinel and their accumulation in the pour spout riser of a Joule-heated ceramic melter during idling can plug the melter and prevent pouring of molten glass into canisters. Thus, there is a need to understand the effects of spinel-forming components, temperature, and time on the growth of crystals in connection with an accumulation rate. In our study, crystals of spinel [Fe, Ni, Mn, Zn, Sn][Fe, Cr]₂O₄ were precipitated from simulated high-level waste borosilicate glasses containing different concentrations of Ni, Fe, and Cr by heat treating at 850 and 900°C for different times. These crystals were extracted from the glasses and analyzed with scanning electron microscopy and image analysis for size and shape, with inductively coupled plasma-atomic emission spectroscopy and atom probe tomography for concentration of spinel-forming components, and with wet colorimetry and Mössbauer spectroscopy for Fe²⁺/Fetotal ratio. High concentrations of Ni, Fe, and Cr in glasses resulted in the precipitation of crystals larger than 100 µm in just two days. Crystals were a solid solution of NiFe₂O₄, NiCr₂O₄, and -Fe₂O₃ (identified only in the high-Ni-Fe glass) and also contained small concentrations of less than 1 at% of Li, Mg, Mn, and Al.

  17. Synthesis, crystal structure and high-temperature transport properties of the new cluster compound Rb2Mo15Se19

    Science.gov (United States)

    Daigre, Gilles; Gougeon, Patrick; Gall, Philippe; Gautier, Régis; Guillou, Olivier; Vaney, Jean-Baptiste; Candolfi, Christophe; Dauscher, Anne; Lenoir, Bertrand

    2016-05-01

    We report on the synthesis, crystal structure and high-temperature transport properties of Rb2Mo15Se19, a new member of the large family of M2Mo15Se19 (M=In, Tl, K, Ba) cluster compounds. Polycrystalline samples and single crystals of the ternary selenide Rb2Mo15Se19 were obtained by solid-state reactions. The trigonal crystal structure, successfully refined in space group R 3 bar c (No. 167) with unit-cell parameters a=9.7618(1) Å, c=58.254(1) Å and Z=6, was determined by single-crystal X-ray diffraction. The crystal structure contains Mo6 Se8i Se6a and Mo9Se11iSe6a cluster units in equal proportion and separated from each other by large voids, which are filled up by Rb atoms. Measurements of the electrical resistivity, thermopower and thermal conductivity revealed that Rb2Mo15Se19 behaves as a p-type metal with relatively low electrical resistivity and thermopower. Despite its complex crystal structure, the lattice thermal conductivity that amounts to 1.3 W m-1 K-1 at 300 K is significantly higher than in Ag-filled analogues, which provides possible guidelines to enhance its thermoelectric properties.

  18. Synthesis of zeolite from Italian coal fly ash: differences in crystallization temperature using seawater instead of distilled water.

    Science.gov (United States)

    Belviso, Claudia; Cavalcante, Francesco; Fiore, Saverio

    2010-05-01

    In this study Italian coal fly ash was converted into several types of zeolite in laboratory experiments with temperatures of crystallization ranging from 35 up to 90 degrees C. Distilled and seawater were used during the hydrothermal synthesis process in separate experiments, after a pre-treatment fusion with NaOH. The results indicate that zeolites could be formed from different kind of Italian coal fly ash at low temperature of crystallization using both distilled and seawater. SEM data and the powder patterns of X-ray diffraction analysis show that faujasite, zeolite ZK-5 and sodalite were synthesized when using both distilled and seawater; zeolite A crystallized only using distilled water. In particular the experiments indicate that the synthesis of zeolite X and zeolite ZK-5 takes place at lower temperatures when using seawater (35 and 45 degrees C, respectively). The formation of sodalite is always competitive with zeolite X which shows a metastable behaviour at higher temperatures (70-90 degrees C). The chemical composition of the fly ash source could be responsible of the differences on the starting time of synthesized zeolite with distilled water, in any case our data show that the formation of specific zeolites takes place always at lower temperatures when using seawater.

  19. Temperature Distribution and Thermal Deformation of the Crystallization Roller Based on the Direct Thermal-Structural Coupling Method

    Science.gov (United States)

    Pan, Liping; He, Zhu; Li, Baokuan; Zhou, Kun; Sun, Ke

    2017-03-01

    The temperature distribution and the thermal deformation of the crystallization roller have a significant effect on the forming process of the thin steel strip. Finite element analysis has been used to simulate the temperature distribution and the thermal deformation in a crystallization roller through the direct thermal-structural coupling analysis method. Various parameters, such as different rotational velocities, diverse locations of cooling water pipes, and typical velocities of cooling water have been systematically investigated. It is found that the temperature and the equivalent stress of the outer surface reach the steady state after 30 s of rotations, and they are influenced remarkably by the factors of rotational velocity and cooling water pipe depth. Meanwhile, the radial displacement approaches the steady state after 300 s of revolutions and is significantly affected by the cooling water velocity.

  20. Temperature dependence of Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal

    Science.gov (United States)

    Lu, Qieni; Han, Jinxin; Dai, Haitao; Ge, Baozhen; Zhao, Shuang

    2015-08-01

    We measure temperature dependence on Kerr coefficient and quadratic polarized optical coefficient of a paraelectric Mn:Fe:KTN crystal simultaneously in this work, based on digital holographic interferometry (DHI). And the spatial distribution of the field-induced refractive index change can also be visualized and estimated by numerically retrieving sequential phase maps of Mn:Fe:KTN crystal from recording digital holograms in different states. The refractive indices decrease with increasing temperature and quadratic polarized optical coefficient is insensitive to temperature. The experimental results suggest that the DHI method presented here is highly applicable in both visualizing the temporal and spatial behavior of the internal electric field and accurately measuring electro-optic coefficient for electrooptical media.

  1. Temperature Distribution and Thermal Deformation of the Crystallization Roller Based on the Direct Thermal-Structural Coupling Method

    Science.gov (United States)

    Pan, Liping; He, Zhu; Li, Baokuan; Zhou, Kun; Sun, Ke

    2016-12-01

    The temperature distribution and the thermal deformation of the crystallization roller have a significant effect on the forming process of the thin steel strip. Finite element analysis has been used to simulate the temperature distribution and the thermal deformation in a crystallization roller through the direct thermal-structural coupling analysis method. Various parameters, such as different rotational velocities, diverse locations of cooling water pipes, and typical velocities of cooling water have been systematically investigated. It is found that the temperature and the equivalent stress of the outer surface reach the steady state after 30 s of rotations, and they are influenced remarkably by the factors of rotational velocity and cooling water pipe depth. Meanwhile, the radial displacement approaches the steady state after 300 s of revolutions and is significantly affected by the cooling water velocity.

  2. Elasticity of single-crystal superhydrous phase B at simultaneous high pressure-temperature conditions

    Science.gov (United States)

    Li, Xinyang; Mao, Zhu; Sun, Ningyu; Liao, Yifan; Zhai, Shuangmeng; Wang, Yi; Ni, Huaiwei; Wang, Jingyun; Tkachev, Sergey N.; Lin, Jung-Fu

    2016-08-01

    We investigated the combined effect of pressure and temperature on the elasticity of single-crystal superhydrous phase B (Shy-B) using Brillouin scattering and X-ray diffraction up to 12 GPa and 700 K. Using the obtained elasticity, we modeled the anisotropy of Shy-B along slab geotherms, showing that Shy-B has a low anisotropy and cannot be the major cause of the observed anisotropy in the region. Modeled velocities of Shy-B show that Shy-B will be shown as positive velocity anomalies at the bottom transition zone. Once Shy-B is transported to the topmost lower mantle, it will exhibit a seismic signature of lower velocities than topmost lower mantle. We speculate that an accumulation of hydrous phases, such as Shy-B, at the topmost lower mantle with a weight percentage of ~17-26% in the peridotite layer as subduction progresses could help explain the observed 2-3% low shear velocity anomalies in the region.

  3. Phase relations study on the melting and crystallization regions of the Bi-2223 high temperature superconductor

    Directory of Open Access Journals (Sweden)

    Polasek Alexander

    2004-01-01

    Full Text Available The melting and solidification behavior of Bi2Sr2Ca2Cu3 O10 (Bi-2223 precursors has been studied. Nominal compositions corresponding to excess of liquid, Ca2CuO3 and CuO have been investigated. Each sample was made by packing a precursor powder into a silver crucible, in order to approximately simulate the situation found in 2223 silver-sheathed tapes. The samples were partially melted and then slow-cooled, being quenched from different temperatures and analyzed through X-ray diffraction (XRD and scanning electron microscopy (SEM/EDS. The precursors decomposed peritectically during melting, forming liquid and solid phases. Very long plates with compositions falling in the vicinity of the 2223 primary phase field formed upon slow-cooling. The 2223 phase may have been formed and the results suggest that long grains of this phase might be obtained by melting and crystallization if the exact peritectic region and the optimum processing conditions are found.

  4. Peculiarities of diffuse synchrotron radiation scattering in the SBN-60 single crystal at room temperature

    Directory of Open Access Journals (Sweden)

    Alexey А. Bosak

    2015-10-01

    Full Text Available The study of Sr0.6Ba0.4Nb2O6 (SBN-60 crystal structure at room temperature and at the zero applied electric field has been carried out by synchrotron radiation scattering. The wavelength of incident X-rays was λ = 0.7749 Å, the Δλ/λ value was ≈2 × 10−4. The two-dimensional distributions of diffuse and elastic intensities were obtained and analyzed in the several cross-sections: (H K 0, (H K 1/2, (H K 1, (H K 2, (H 0 L and (H H L. As a result, it was shown the coexistence of two different types of ordering with different correlation lengths and various correlation functions: the first type is described by squared Lorentzian and the second one – by Lorentzian. The first component is characterized by the correlation lengths ξ(1ab ≈ 10 nm and ξ(1c ≈ 15 nm, the second one is with ξ(2ab ≈ 3 nm and ξ(2c ≈ 25 nm.

  5. Forehead galeal pericranial flap for single-staged total upper eyelid reconstruction in sebaceous gland carcinoma excision

    Directory of Open Access Journals (Sweden)

    Chang HH

    2017-09-01

    Full Text Available Hui-hsiu Chang,1,2 Edward Suh,3 Blake H Fortes,3 Franklin Zheng,3 Anny MS Cheng3,4 1Division of Plastic and Reconstructive Surgery, Department of Surgery, National Taiwan University Hosiptal Yunlin Branch, Yunlin, Taiwan; 2Department of Industrial Engineering and Management, National Yunlin University of Science and Technology, Yunlin, Taiwan; 3Department of Ophthalmology, Florida International University, Herbert Wertheim College of Medicine, Miami, FL, USA; 4Ocular Surface Center, Miami, FL, USA Purpose: To present a successful case of single-staged total upper eyelid reconstruction after sebaceous gland carcinoma excision by using forehead galeal pericranial flap.Observations: An 80-year-old female with a progressively enlarged left upper eyelid mass presented with ocular irritation, blurred vision, and gritty sensation despite topical antibiotics treatment. This multinodular mass involved the left total upper eyelid, compromised corneal surface integrity, and caused complete ptosis. Excisional biopsy confirmed advanced sebaceous gland carcinoma, which was followed by extensive excision. The resultant total upper eyelid defect was reconstructed by a forehead galeal pericranial flap accompanied by anterior and posterior lamellar grafts. For the 34-month follow-up period, patient remained symptom-free without tumor recurrence and achieved acceptable cosmetic outcome.Conclusion: The forehead galeal pericranial flap appears to be effective as single-staged total upper lid reconstruction following extensive sebaceous gland carcinoma excision to restore eyelid function, avoid corneal exposure, and achieve acceptable cosmesis. Keywords: forehead, galeal pericranial flap, reconstruction, sebaceous gland carcinoma, single-staged, total upper eyelid reconstruction

  6. Temperature evolution of the crystal structure of Bi1 - xPrxFeO3 solid solutions

    Science.gov (United States)

    Karpinsky, D. V.; Troyanchuk, I. O.; Sikolenko, V. V.; Efimov, V.; Efimova, E.; Silibin, M. V.; Chobot, G. M.; Willinger, E.

    2014-11-01

    The crystal structure of solid solutions in the Bi1 - xPrxFeO3 system near the structural transition between the rhombohedral and orthorhombic phases (0.125 ≤ x ≤ 0.15) has been studied. The structural phase transitions induced by changes in the concentration of praseodymium ions and in the temperature have been investigated using X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. It has been established that the sequence of phase transformations in the crystal structure of Bi1 - xPrxFeO3 solid solutions with variations in the temperature differs significantly from the evolution of the crystal structure of the BiFeO3 compounds with the substitution of other rare-earth elements for bismuth ions. The regions of the existence of the single-phase structural state and regions of the coexistence of the structural phases have been determined in the investigation of the crystal structure of the Bi1 - xPrxFeO3 solid solutions. A three-phase structural state has been revealed for the solid solution with x = 0.125 at temperatures near 400°C. The specific features of the structural phase transitions of the compounds in the vicinity of the morphotropic phase boundary have been determined by analyzing the obtained results. It has been found that the solid solutions based on bismuth ferrite demonstrate a significant improvement in their physical properties.

  7. Temperature dependence of Raman-active modes of TlGaS{sub 2} layered crystals: an anharmonicity study

    Energy Technology Data Exchange (ETDEWEB)

    Yuksek, N. S.; Gasanly, N. M.; Ozkan, H. [Middle East Technical University, Ankara (Turkmenistan); Aydinli, A. [Bilkent University, Ankara (Turkmenistan)

    2004-08-15

    The temperature dependence (16 - 300 K) of unpolarized Raman spectra from TlGaS{sub 2} layered crystals was measured in the frequency range of 10 - 400 cm{sup -1}. The analysis of the experimental data showed that the temperature dependencies of the phonon frequencies and linewidths were well described by considering the contributions from thermal expansion and lattice anharmonicity. The anharmonic contribution (phonon-phonon coupling) was found to be due to three-phonon processes. The present work demonstrates that the interlayer Raman mode at 42.6 cm{sup -1} shifts toward high frequency as the temperature is raised from 16 to 300 K.

  8. Measurement of the electron and ion temperatures by the x-ray imaging crystal spectrometer on joint Texas experimental tokamak

    Science.gov (United States)

    Yan, W.; Chen, Z. Y.; Jin, W.; Lee, S. G.; Shi, Y. J.; Huang, D. W.; Tong, R. H.; Wang, S. Y.; Wei, Y. N.; Ma, T. K.; Zhuang, G.

    2016-11-01

    An x-ray imaging crystal spectrometer has been developed on joint Texas experimental tokamak for the measurement of electron and ion temperatures from the Kα spectra of helium-like argon and its satellite lines. A two-dimensional multi-wire proportional counter has been applied to detect the spectra. The electron and ion temperatures have been obtained from the Voigt fitting with the spectra of helium-like argon ions. The profiles of electron and ion temperatures show the dependence on electron density in ohmic plasmas.

  9. Reconstruction of the columella and the tip of the nose with an island-shaped forehead flap

    Directory of Open Access Journals (Sweden)

    Vulović Dejan

    2011-01-01

    Full Text Available Background. Posttraumatic and postoperative defects of columella and the tip of the nose are difficult to reconstruct. There are several operative methods described in the literature, and many of them are step-by-step procedures with long duration. The aim of this study was to present one-step procedure for reconstruction of the columella and the tip of the nose with island-shaped arterial forehead flap. Case report. A 45-year old man was submitted to surgical excision of basocellular skin cancer. After the excision, a defect of the columella and tip of the nose the remained, 3 × 2.5 cm in dimensions, with exposed alar cartilages. During the same operation, the defect was covered with an island-shaped arterial forehead flap. Postoperative one-year course was uneventful, without signs of tumor recurrence after one year, and further surgical corrections were unnecessary. Conclusion. Considering the results of our operative technique, we believe that middle island-shaped forehead flap is suitable for reconstruction of the columella and the tip of the nose, due to the following reasons: safe vascularization of flap, similarity of the transferred tissue with the excised one, the procedure is completed in one step, simple surgical technique and uncomplicated healing of a flap-harvesting site.

  10. Ferroelectric InMnO{sub 3}: Growth of single crystals, structure and high-temperature phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Bekheet, Maged F., E-mail: maged.bekheet@ceramics.tu-berlin.de [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany); Svoboda, Ingrid; Liu, Na [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Bayarjargal, Lkhamsuren [Institut für Geowissenschaften, Goethe-Universität, Altenhöferallee 1, d-60438 Frankfurt a.M. (Germany); Irran, Elisabeth [Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin (Germany); Dietz, Christian; Stark, Robert W.; Riedel, Ralf [Fachbereich Material‐ und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany); Gurlo, Aleksander [Fachgebiet Keramische Werkstoffe / Chair of Advanced Ceramic Materials, Institut für Werkstoffwissenschaften und -technologien, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin (Germany)

    2016-09-15

    To understand the origin of the ferroelectricity in InMnO{sub 3}, single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. The results of single crystal X-ray diffraction, second harmonic generation and piezoresponse force microscopy studies of high-quality InMnO{sub 3} single crystals reveal that the room-temperature state in this material is ferroelectric with P6{sub 3}cm symmetry. The polar InMnO{sub 3} specimen undergoes a reversible phase transition from non-centrosymmetric P6{sub 3}cm structure to a centrosymmetric P6{sub 3}/mmc structure at 700 °C as confirmed by the in situ high-temperature Raman spectroscopic and synchrotron X-ray diffraction experiments. - Graphical abstract: Piezoresponse fore microscopy (PFM) studies of high quality InMnO{sub 3} single crystal revealed that the room-temperature state of this material is ferroelectric with a clear cloverleaf pattern corresponding to six antiphase ferroelectric domains with alternating polarization ±P{sub z}. Display Omitted - Highlights: • InMnO{sub 3} single crystals with average size of 1 mm were grown in PbF{sub 2} flux at 950 °C. • The room-temperature state of InMnO{sub 3} is ferroelectric with polar P6{sub 3}cm structure. • PolarInMnO{sub 3} reversibly transforms to a centrosymmetric P6{sub 3}/mmc structure above 700 °C.

  11. Effects on Humans Elicited by Inhaling the Fragrance of Essential Oils: Sensory Test, Multi-Channel Thermometric Study and Forehead Surface Potential Wave Measurement on Basil and Peppermint

    National Research Council Canada - National Science Library

    SATOH, Tomoko; SUGAWARA, Yoshiaki

    2003-01-01

    The effects on humans inhaling the fragrance of essential oils were examined in terms of a sensory test, a multi-channel skin thermometer study and a portable forehead surface electroencephalographic (IBVA-EEG) measurement...

  12. δ-KIO 3·HIO 3: crystal structure, proton disorder and low temperature phase transition

    Science.gov (United States)

    Engelen, B.; Gavrilko, T.; Panthöfer, M.; Puchkovskaya, G.; Sekirin, I.

    2000-05-01

    δ-KIO 3·HIO 3, obtained by slowly cooling a concentrated solution of KIO 3 and HIO 3, has been investigated by means of single crystal X-ray diffraction measurements at ambient temperature and temperature dependent powder X-ray diffraction, dielectric, calorimetric and FT-IR and FT-Raman measurements. From the single crystal X-ray measurements, the I-O bonding scheme of the iodine atoms and the hydrogen bond system were determined. The crystal structure of δ-KIO 3·HIO 3 was found to consist of [I 3O 9H 3/2] 3/2- ions possibly originating from occupationally disordered [I 3O 9H 2] - and [I 3O 9H] 2- anions. These ions are connected via hydrogen bonds to form plane grids parallel (100) with the K + ions placed between them. Thus δ-KIO 3·HIO 3 should be formulated as K 3/2[I 3O 9H 3/2]. The temperature dependent FT-IR data give an evidence for a dynamic proton disorder at room temperature and for a proton ordering below 220 K, which may be regarded as a structural phase transition in the proton sublattice.

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

    Science.gov (United States)

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

    1999-01-01

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

  14. Growth of KH/sub 2/PO/sub 4/ crystals at constant temperature and supersaturation. Final report, October 20, 1980-October 20, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Loiacono, G.M.; Zola, J.; Kostecky, G.

    1982-02-01

    A large three-zone crystallizer system was constructed and successfully operated for growing KH/sub 2/PO/sub 4/ single crystals. Under conditions of constant crystallization temperature and supersaturation, growth rates exceding 5 mm per day were demonstrated for KH/sub 2/PO/sub 4/ crystals of 5 x 5 cm cross section. The optical quality of these crystals was equivalent to that of crystals grown at rates presently considered as state-of-the-art (approx. 1 mm/day). Sample crystals were supplied for comparison testing. The three-zone system appears to be ideally suitable for growth of large-diameter KH/sub 2/PO/sub 4/ crystals for the Laser Fusion Program.

  15. Photocurrent response of B12As2 crystals to blue light, and its temperature- dependent electrical characterizations

    Directory of Open Access Journals (Sweden)

    R. Gul

    2016-02-01

    Full Text Available With the global shortage of 3He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B12As2 for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B12As2 bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W−1 and 2.47 mA ⋅ cm−2, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B12As2 bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm−2 and 7.6x105-7.7x103 Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B12As2 is a potential candidate for thermal-neutron detectors.

  16. Validity of diagnostic computer-based air and forehead bone conduction audiometry.

    Science.gov (United States)

    Swanepoel, De Wet; Biagio, Leigh

    2011-04-01

    Computer-based audiometry allows for novel applications, including remote testing and automation, that may improve the accessibility and efficiency of hearing assessment in various clinical and occupational health settings. This study describes the validity of computer-based, diagnostic air and forehead bone conduction audiometry when compared wtih conventional industry standard audiometry in a sound booth environment. A sample of 30 subjects (19 to 77 years of age) was assessed with computer-based (KUDUwave 5000) and industry standard conventional audiometers (GSI 61) to compare air and bone conduction thresholds and test-retest reliability. Air conduction thresholds for the two audiometers corresponded within 5 dB or less in more than 90% of instances, with an average absolute difference of 3.5 dB (3.8 SD) and a 95% confidence interval of 2.6 to 4.5 dB. Bone conduction thresholds for the two audiometers corresponded within 10 dB or less in 92% of instances, with an average absolute difference of 4.9 dB (4.9 SD) and a 95% confidence interval of 3.6 to 6.1 dB. The average absolute test-retest threshold difference for bone conduction on the industry standard audiometer was 5.1 dB (5.3 SD) and for the computer-based audiometer 7.1 dB (6.4 SD). Computer-based audiometry provided air and bone conduction thresholds within the test-retest reliability limits of industry standard audiometry.

  17. Spatially Resolved Spectra from a new X-ray Imaging Crystal Spectrometer for Measurements of Ion and Electron Temperature Profiles

    Energy Technology Data Exchange (ETDEWEB)

    Bitter, M; Stratton, B; Roquemore, A; Mastrovito, D; Lee, S; Bak, J; Moon, M; Nam, U; Smith, G; Rice, J; Beiersdorfer, P; Fraenkel, B

    2004-08-10

    A new type of high-resolution X-ray imaging crystal spectrometer is being developed to measure ion and electron temperature profiles in tokamak plasmas. The instrument is particularly valuable for diagnosing plasmas with purely Ohmic heating and rf heating, since it does not require the injection of a neutral beam - although it can also be used for the diagnosis of neutral-beam heated plasmas. The spectrometer consists of a spherically bent quartz crystal and a two-dimensional position-sensitive detector. It records spectra of helium-like argon (or krypton) from multiple sightlines through the plasma and projects a de-magnified image of a large plasma cross-section onto the detector. The spatial resolution in the plasma is solely determined by the height of the crystal, its radius of curvature, and the Bragg angle. This new X-ray imaging crystal spectrometer may also be of interest for the diagnosis of ion temperature profiles in future large tokamaks, such as KSTAR and ITER, where the application of the presently used charge-exchange spectroscopy will be difficult, if the neutral beams do not penetrate to the plasma center. The paper presents the results from proof-of-principle experiments performed with a prototype instrument at Alcator C-Mod.

  18. The effect of substrate temperature and growth rate on the doping efficiency of single crystal boron doped diamond

    Energy Technology Data Exchange (ETDEWEB)

    Demlow, SN; Rechenberg, R; Grotjohn, T

    2014-10-01

    The substrate growth temperature dependence of the plasma gas-phase to solid-phase doping efficiency in single crystal, boron doped diamond (BDD) deposition is investigated. Single crystal diamond (SCD) is grown by microwave plasma assisted chemical vapor deposition (MPACVD) on high pressure, high temperature (HPHT) type Ib substrates. Samples are grown at substrate temperatures of 850-950 degrees C for each of five doping concentration levels, to determine the effect of the growth temperature on the doping efficiency and defect morphology. The substrate temperature during growth is shown to have a significant effect on the grown sample defect morphology, and a temperature dependence of the doping efficiency is also shown. The effect of the growth rate on the doping efficiency is discussed, and the ratio of the boron concentration in the gas phase to the flux of carbon incorporated into the solid diamond phase is shown to be a more predictive measure of the resulting boron concentration than the gas phase boron to carbon ratio that is more commonly reported. (C) 2014 Elsevier B.V. All rights reserved.

  19. Analysis of the temperature dependence of the spectral characteristics for the hollow-core photonic-crystal fibers

    Science.gov (United States)

    Bzheumikhov, K. A.; Margushev, Z. Ch.; Savoiskii, Yu. V.

    2013-07-01

    The temperature dependence of the spectral characteristics of monocapillaries made of S87-2 glass and filled with air and ethanol is experimentally and theoretically studied in temperature intervals 23-90°C and 23-40°C, respectively. The same measurements are performed using the photonic-crystal fibers made of AR-Glass (Schott). The transmission spectra of the air-filled fibers are slightly transformed when the temperature is varied in the above interval. It is demonstrated that the transmission peak is red-shifted and the shift is proportional to the temperature when the cavities are filled with ethanol. It is also demonstrated that the temperature dependence of the shape of the transmission spectra is predominantly determined by the parameters of the medium that fills the hollow channel rather than the fiber material. The temperature sensitivities of the photonic-crystal fiber filled with ethanol and a monocapillary are 1.25 and 0.40 nm/°C, respectively.

  20. Equation of state calculations for two-dimensional dust coulomb crystal at near zero temperature by molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Djouder, M., E-mail: djouder-madjid@ummto.dz; Kermoun, F.; Mitiche, M. D.; Lamrous, O. [Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri Tizi-Ouzou, BP 17 RP, 15000 Tizi-Ouzou (Algeria)

    2016-01-15

    Dust particles observed in universe as well as in laboratory and technological plasma devices are still under investigation. At low temperature, these particles are strongly negatively charged and are able to form a 2D or 3D coulomb crystal. In this work, our aim was to check the ideal gas law validity for a 2D single-layer dust crystal recently reported in the literature. For this purpose, we have simulated, using the molecular dynamics method, its thermodynamic properties for different values of dust particles number and confinement parameters. The obtained results have allowed us to invalidate the ideal gas behaviour and to propose an effective equation of state which assumes a near zero dust temperature. Furthermore, the value of the calculated sound velocity was found to be in a good agreement with experimental data published elsewhere.

  1. Low-temperature crystal structure evolution of (Na,Ca)(Cr,Mg)Si2O6 pyroxene

    DEFF Research Database (Denmark)

    Nestola, F.; Madsen, Anders Østergaard; Tribaudino, M.;

    2008-01-01

    The crystal structure of a clinopyroxene with composition (Na0.75Ca0.25)(Cr0.75Mg0.25)Si2O6 was refined at 100, 150, 200, 250 and 298 K. The work was performed in the context of an investigation on the low-temperature behaviour of A+M3+Si2O6 (with A dominant in Na and M = transition elements...

  2. Temperature- and moisture-induced crystallization of amorphous lactose in composite particles with sodium alginate prepared by spray-drying.

    Science.gov (United States)

    Takeuchi, H; Yasuji, T; Yamamoto, H; Kawashima, Y

    2000-01-01

    The purpose of this study was to investigate the temperature- and moisture-induced crystallization of amorphous lactose in the composite particles prepared by spray-drying an aqueous solution of crystalline lactose and sodium alginate. The temperature-induced crystallization of amorphous lactose in the composite particles was suppressed by increasing the amount of sodium alginate in the particles. The stabilizing effect of sodium alginate on amorphous lactose in the composite particles was greater than that in physical mixtures having the same formulating ratios. The improved stability of amorphous lactose in the composite particles was attributed to an increase in the glass transition temperature (Tg) of the mixture. Moisture-induced crystallization of amorphous lactose was also retarded by increasing the amount of sodium alginate in composite particles. Although the Tg of the mixture was reduced by increasing the water content of the particles, the values were higher than that of 100% amorphous lactose when particles of the same water content were compared. The change in the Tg of the composite particles with increasing water content was interpreted as involving three components of the Gordon-Taylor equation. In the amorphous lactose-sodium alginate systems, the Tg values of the composite particles containing sodium alginate were higher than the theoretical line predicted by two components of the Gordon-Taylor equation. These results suggested that there was a specific interaction between the sodium alginate and lactose molecules. This specific interaction was suggested by the fact that only very little amorphous lactose was measured in the spray-dried composite particles stored under humid conditions using differential scanning calorimetry. This molecular interaction may also be partly responsible for the suppression of both the temperature- and moisture-induced crystallization of amorphous lactose in the composite particles.

  3. Room-Temperature Photonic Crystal Laser in H3 Cavity on InGaAsP/InP Slab

    Institute of Scientific and Technical Information of China (English)

    REN Gang; ZHENG Wan-Hua; ZHANG Ye-Jin; XING Ming-Xin; WANG Ke; DU Xiao-Yu; CHEN Liang-Hui

    2008-01-01

    @@ We fabricate and investigate two-dimensional photonic crystal H3 microcavities in an InGaAsP slab.The lasing action at room temperature is observed.The lasering threshold is 7mW under the pulsed pump of 0.75% duty cycle.The Q factor and the lasing mode characteristics are simulated by three-dimensional finite difference time domain method.The simulation result matches well with the experiment.

  4. Construction of a low-temperature thermodynamic measurement system for single crystal of molecular compounds under pressures.

    Science.gov (United States)

    Kubota, Osamu; Nakazawa, Yasuhiro

    2008-05-01

    An apparatus to obtain low-temperature thermodynamic information under high pressures for a tiny single crystal of molecular compounds was developed based on the ac technique. To detect small temperature oscillation of a sample inside the cramp-type pressure cell, we have used a small ruthenium oxide chip sensor as a thermometer. The adoption of the four-terminal method by the ac resistance bridge has made high-resolution detection of thermal anomaly possible in the low-temperature region. The constructed high-pressure thermodynamic system was mounted on a 3He refrigerator and we have succeeded to detect the thermal anomaly in relevant to magnetic order of single crystal sample of Mn4-cluster complex up to 1.05 GPa. A distinct peak of the heat capacity and its upward shift with increasing pressures was observed using a tiny crystal of about 100 microg. The high-pressure behavior of the discontinuity of heat capacity at the superconductive transition of 6 mg of metal indium has also been detected by this apparatus. The details and performance of the technique are reported.

  5. High stable, high efficient ultraviolet laser with angle-phase-mismatching compensation by adjusting temperature of the nonlinear crystals

    Science.gov (United States)

    Yang, Houwen; Wang, Bo; Wang, Junhua; Li, Xiaofang; Liu, Zhaojun; Cheng, Wenyong

    2017-03-01

    We demonstrated an ultraviolet laser at 355 nm using a type-I and a type-II phase-matching nonlinear optical crystal of LiB3O5 (LBO). A method of adjusting temperature for compensation is presented. The crystal temperature is controlled by proportional integral derivative (PID) thermal controllers with a  ±0.01 °C resolution. The value of wave vector mismatch, distance of light propagation in nonlinear crystals, effective nonlinear coefficient, theoretical analysis and calculation of conversion efficiency versus temperature are discussed. The experimental results show that the average output power of the 355 nm laser is 1.24 W with the pump power of 13.33 W, when the repetition frequency is 15 kHz. The pulse duration is 9.8 ns, and the beam quality factors are of Mx2   =  1.8, My2   =  1.7. The conversion efficiency from 808 nm to 355 nm laser is 9.3%, which nearly reaches the optimum value reported so far and is limited by the wavelength mismatch between the pumping and absorbing lasers. The 355 nm output power instability of the laser device is 0.45% in 2 h. A compact no-water-cooling ultraviolet laser with high stability and high efficiency is obtained.

  6. Surface recrystallization of a Ni_3Al based single crystal superalloy at different annealing temperatures and blasting pressure

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The effects of annealing temperature and grit blasting pressure on the recrystallization behavior of a Ni3Al based single crystal superalloy were studied in this work. The results show that the precipitation of the Y-NiMo phase occurs at 900 and 1000 °C, which precedes recrystallization. The initial recrystallization temperature was between 1000 and 1100 °C. Cellular recrystallization was formed at 1100 and 1200 °C, which consisted of large columnar γ′ and fine γ + γ′. The dendrite arm closed to the interde...

  7. Highly sensitive optical temperature sensor based on a SiN micro-ring resonator with liquid crystal cladding.

    Science.gov (United States)

    Wang, Chun-Ta; Wang, Cheng-Yu; Yu, Jui-Hao; Kuo, I-Tun; Tseng, Chih-Wei; Jau, Hung-Chang; Chen, Yung-Jui; Lin, Tsung-Hsien

    2016-01-25

    This work develops a sensitivity-enhanced optical temperature sensor that is based on a silicon nitride (SiN) micro-ring resonator that incorporates nematic liquid crystal (NLC) cladding. As the ambient temperature changes, the refractive index of the NLCs, which have a large thermal-optical coefficient, dramatically varies. The change in the refractive index of the NLC cladding that is caused by the temperature shift can alter the effective refractive index of the micro-ring resonator and make the resonance wavelength very sensitive to the ambient temperature. The temperature-sensitivity of the device with 5CB cladding for TM-polarized light was measured to be as high as 1nm/°C between 25 and 33 °C and over 2nm/°C at temperatures close to clearing temperature of the 5CB cladding. The temperature-sensitivity of the proposed device is at least 55 times that of the micro-ring resonator with air cladding, whose temperature-dependent wavelength shift for TM-polarized light is 18pm/ °C.

  8. The transport phenomena during the growth of ZnTe crystal by the temperature gradient solution growth technique

    Science.gov (United States)

    Yin, Liying; Jie, Wanqi; Wang, Tao; Zhou, Boru; Yang, Fan

    2017-03-01

    A numerical model is developed to simulate the temperature field, the thermosolutal convection, the solute segregation and the growth interface morphology during the growth of ZnTe crystal from Te rich solution by the temperature gradient solution growth (TGSG) technique. Effects of the temperature gradient on the transport phenomena, the growth interface morphology and the growth rate are examined. The influences of the latent heat and the thermal conductivity of ZnTe crystal on the transport phenomena and the growth interface are also discussed. We find that the mass transfer of ZnTe in the solution is very slow because of the low diffusion coefficient and the lack of mixing in the lower part of the solution. During the growth, dilute solution with high density and low growth temperature accumulates in the central region of the growth interface, making the growth interface change into two distinct parts. The inner part is very concave, while the outer part is relatively flat. Growth conditions in front of the two parts of the growth interface are different. The crystalline quality of the inner part of the ingot is predicted to be worse than that of the outer part. High temperature gradient can significantly increase the growth rate, and avoid the diffusion controlled growth to some extent.

  9. First principle study on the elastic and thermodynamic properties of TiB2 crystal under high temperature

    Institute of Scientific and Technical Information of China (English)

    Wang Chun-Lei; Yu Ben-Hai; Huo Hai-Liang; Chen Dong; Sun Hai-Bin

    2009-01-01

    This paper predicts the elastic and thermodynamic characteristics of T1B2 crystal through the method of density functional theory within the generalized gradient approximation (GGA). The five independent elastic constants (Cij), the bulk modulus (Bo), the dependence of bulk modulus (Bo) on temperature T and pressure P and the coefficient of thermal expansion (αL) at various temperatures have been evaluated and discussed. According to calculation, the bulk modulus will increase with increasing pressure while decrease with the increasing temperature. The coefficient of thermal expansion is consistent with the famous Griineisen's law when the temperature is not too high. The obtained results agree well with the experimental and other theoretical results.

  10. Growth of KH/sub 2/PO/sub 4/ crystals at constant temperature and supersaturation. Final report, 20 October 1980-20 October 1981

    Energy Technology Data Exchange (ETDEWEB)

    Loiacono, G.M.; Zola, J.; Kostecky, G.

    1982-02-01

    A large three-zone cyrstallizer system was constructed and successfully operated for growing KH/sub 2/PO/sub 4/ single crystals. Under conditions of constant crystallization temperature and supersaturation, growth rates exceeding 5 mm per day were demonstrated for KH/sub 2/PO/sub 4/ crystals of 5 x 5 cm cross section. The optical quality of these crystals was equivalent to that of crystals grown at rates presently considered as state-of-the-art (approx. 1 mm/day). Sample crystals were supplied for comparison testing. The three-zone system appears to be ideally suitable for growth of large-diameter KH/sub 2/PO/sub 4/ crystals for the Laser Fusion Program.

  11. Growth temperature-dependent metal–insulator transition of vanadium dioxide epitaxial films on perovskite strontium titanate (111) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liangxin; Zhao, Jiangtao; Hong, Bin; Hu, Kai; Luo, Zhenlin [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, Anhui 230029 (China); Yang, Yuanjun, E-mail: yangyuanjun@ustc.edu.cn, E-mail: cgao@ustc.edu.cn; Gao, Chen, E-mail: yangyuanjun@ustc.edu.cn, E-mail: cgao@ustc.edu.cn [National Synchrotron Radiation Laboratory and Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, Anhui 230029 (China); Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Peng, Jinlan; Zhang, Haibin; Wen, Xiaolei; Li, Xiaoguang [Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230027 (China)

    2016-04-14

    Vanadium dioxide (VO{sub 2}) epitaxial films were grown on perovskite single-crystal strontium titanate (SrTiO{sub 3}) substrates by reactive radio-frequency magnetron sputtering. The growth temperature-dependent metal–insulator transition (MIT) behavior of the VO{sub 2} epitaxial films was then investigated. We found that the order of magnitude of resistance change across the MIT increased from 10{sup 2} to 10{sup 4} with increasing growth temperature. In contrast, the temperature of the MIT does not strongly depend on the growth temperature and is fairly stable at about 345 K. On one hand, the increasing magnitude of the MIT is attributed to the better crystallinity and thus larger grain size in the (010)-VO{sub 2}/(111)-SrTiO{sub 3} epitaxial films at elevated temperature. On the other hand, the strain states do not change in the VO{sub 2} films deposited at various temperatures, resulting in stable V-V chains and V-O bonds in the VO{sub 2} epitaxial films. The accompanied orbital occupancy near the Fermi level is also constant and thus the MIT temperatures of VO{sub 2} films deposited at various temperatures are nearly the same. This work demonstrates that high-quality VO{sub 2} can be grown on perovskite substrates, showing potential for integration into oxide heterostructures and superlattices.

  12. Electrolyte effects on the chiral induction and on its temperature dependence in a chiral nematic lyotropic liquid crystal.

    Science.gov (United States)

    Dawin, Ute C; Osipov, Mikhail A; Giesselmann, Frank

    2010-08-19

    We present a study on the effect of added CsCl and of temperature variation on the chiral induction in a chiral nematic lyotropic liquid crystal (LC) composed of the surfactant cesium perfluorooctanoate (CsPFO), water, and the chiral dopant d-Leucine (d-Leu). The chiral induction was measured as the helical pitch P. The role of the additives CsCl and d-Leu on the phase behavior is investigated and discussed. The thermal stabilization effect of CsCl is shown to lead to an apparent salt effect on the pitch when the pitch is compared at a constant temperature. This apparent effect is removed by comparing the pitch measured for different salt concentrations at a temperature relative to the phase-transition temperatures; thus, the real salt effect on the pitch is described. High salt concentrations are shown to increase the pitch, that is, hinder the chiral induction. The effect is discussed in terms of a decreased solubilization of the amphiphilic chiral solute d-Leu in the micelles due to the salt-induced screening of the surfactant head groups and the consequential denser packing of the surfactants. The temperature variation of the pitch is investigated for all CsCl concentrations and is found to be essentially independent of the salt concentration. The temperature variation is analyzed and discussed in the context of a theoretical model taking into account specific properties of lyotropic liquid crystals. A hyperbolic decrease of the pitch is found with increasing temperature, which is known, from thermotropic liquid crystals, to stem from pretransitional critical fluctuations close to the lamellar phase. However, the experimental data confirmed the theoretical prediction that, at high temperature, that is, far away from the transition into the lamellar phase, the pitch is characterized by a linear temperature dependence which is determined by a combination of steric and dispersion chiral interactions. The parameters of the theoretical expression for the pitch have

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Collecting, shipping, storing, and imaging snow crystals and ice grains with low-temperature scanning electron microscopy

    Science.gov (United States)

    Erbe, E.F.; Rango, A.; Foster, J.; Josberger, E.G.; Pooley, C.; Wergin, W.P.

    2003-01-01

    Methods to collect, transport, and store samples of snow and ice have been developed that enable detailed observations of these samples with a technique known as low-temperature scanning electron microscopy (LTSEM). This technique increases the resolution and ease with which samples of snow and ice can be observed, studied, and photographed. Samples are easily collected in the field and have been shipped to the electron microscopy laboratory by common air carrier from distances as far as 5,000 miles. Delicate specimens of snow crystals and ice grains survive the shipment procedures and have been stored for as long as 3 years without undergoing any structural changes. The samples are not subjected to the melting or sublimation artifacts. LTSEM allows individual crystals to be observed for several hours with no detectable changes. Furthermore, the instrument permits recording of photographs containing the parallax information necessary for three-dimensional imaging of the true shapes of snowflakes, snow crystals, snow clusters, ice grains, and interspersed air spaces. This study presents detailed descriptions of the procedures that have been used successfully in the field and the laboratory to collect, ship, store, and image snow crystals and ice grains. Published 2003 Wiley-Liss, Inc.

  15. Effects of Temperature and Humidity History on Brittleness of α-Sulfonated Fatty Acid Methyl Ester Salt Crystals.

    Science.gov (United States)

    Watanabe, Hideaki; Morigaki, Atsunori; Kaneko, Yukihiro; Tobori, Norio; Aramaki, Kenji

    2016-01-01

    α-Sulfonated fatty acid methyl ester salts (MES), which were made from vegetable sources, are attractive candidates for eco-friendly washing detergents because they have various special features like excellent detergency, favorable biodegradability, and high stability against enzymes. To overcome some disadvantages of powder-type detergents like caking, sorting, and dusting, we studied how temperature and humidity history, as a model for long-term storage conditions, can affect crystalline structures and reduce the brittleness of MES powder. We characterized the crystalline structure of MES grains using small-angle X-ray scattering, wide-angle X-ray scattering, differential scanning calorimetry, and Fourier transform infrared spectroscopy measurements and determined the yield values, which measure the brittleness of MES grains, in shear stress using dynamic viscoelasticity measurements. This study confirmed that MES crystals form three pseudo-polymorphs via thermal or humidity conditioning: metastable crystals (αsubcell), anhydrous crystals (β subcell), and dihydrate crystals (β' subcell). Further, we found that the yield value increases upon phase transition from the β subcell to the β' subcell and from the β' subcell to the αsubcell. Therefore, controlling the thermal and humidity conditioning of MES grains is an effective way to decrease the brittleness of MES powders and can be used to overcome the above mentioned disadvantages of powder-type detergents in the absence of co-surfactants.

  16. Determination of saturation, heart rate, and respiratory rate at forearm using a Nellcor™ forehead SpO2-saturation sensor.

    Science.gov (United States)

    Harju, Jarkko; Vehkaoja, Antti; Lindroos, Ville; Kumpulainen, Pekka; Liuhanen, Sasu; Yli-Hankala, Arvi; Oksala, Niku

    2016-10-17

    Alterations in arterial blood oxygen saturation, heart rate (HR), and respiratory rate (RR) are strongly associated with intra-hospital cardiac arrests and resuscitations. A wireless, easy-to-use, and comfortable method for monitoring these important clinical signs would be highly useful. We investigated whether the Nellcor™ OxiMask MAX-FAST forehead sensor could provide data for vital sign measurements when located at the distal forearm instead of its intended location at the forehead to provide improved comfortability and easy placement. In a prospective setting, we recruited 30 patients undergoing surgery requiring postoperative care. At the postoperative care unit, patients were monitored for two hours using a standard patient monitor and with a study device equipped with a Nellcor™ Forehead SpO2 sensor. The readings were electronically recorded and compared in post hoc analysis using Bland-Altman plots, Spearman's correlation, and root-mean-square error (RMSE). Bland-Altman plot showed that saturation (SpO2) differed by a mean of -0.2 % points (SD, 4.6), with a patient-weighted Spearman's correlation (r) of 0.142, and an RMSE of 4.2 points. For HR measurements, the mean difference was 0.6 bpm (SD, 2.5), r = 0.997, and RMSE = 1.8. For RR, the mean difference was -0.5 1/min (4.1), r = 0.586, and RMSE = 4.0. The SpO2 readings showed a low mean difference, but also a low correlation and high RMSE, indicating that the Nellcor™ saturation sensor cannot reliably assess oxygen saturation at the forearm when compared to finger PPG measurements.

  17. The high temperature photoluminescence and optical absorption of undoped ZnO single crystals and thin films

    Energy Technology Data Exchange (ETDEWEB)

    Margueron, Samuel [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Laboratoire Matériaux Optiques, Photonique et Systèmes, Université de Lorraine, F-57070 Metz Cedex (France); Clarke, David R. [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

    2014-11-21

    The photoluminescence of undoped ZnO single crystals up to 1350 °C and the optical absorption of stress-relaxed, epitaxial ZnO thin films up to 1100 °C are reported. The photoluminescence intensity and power dependence with illumination flux are related to the crystal growth methods and stabilize after high temperature annealing. The observation of excitonic recombination at very high temperatures requires high illumination flux. It is found that the zero phonon line model reproduces the shift and the band gap narrowing as well as the free excitonic transition up to the cross-over with a defect level at 2.83 eV that occurs at 800 °C. A phenomenological model of the excitonic recombination band shape, taking account exciton-phonon losses and defect levels provides an excellent fit up to 2.2–2.4 eV (1100 °C). At these cross-over temperatures, an energy transfer is observed between the free exciton transition and defect transitions. However, at temperature above 1100 °C, the decrease of the band gap and the increase of thermal radiation, as well as the restrictions of our experimental set-up and particularly the illumination flux of the exciting laser, limit the analysis of the photoluminescence spectra measurements.

  18. Temperature dependence of full set tensor properties of KTiOPO4 single crystal measured from one sample

    Science.gov (United States)

    Zhang, Yang; Tang, Liguo; Ji, Nianjing; Liu, Gang; Wang, Jiyang; Jiang, Huaidong; Cao, Wenwu

    2016-03-01

    The temperature dependence of the complete set of elastic, dielectric, and piezoelectric constants of KTiOPO4 single crystal has been measured from 20 °C to 150 °C. All 17 independent constants for the mm2 symmetry piezoelectric crystal were measured from one sample using extended resonance ultrasound spectroscopy (RUS), which guaranteed the self-consistency of the matrix data. The unique characteristics of the RUS method allowed the accomplishment of such a challenging task, which could not be done by any other existing methods. It was found that the elastic constants ( c11 E , c13 E , c22 E , and c33 E ) and piezoelectric constants ( d 15 , d 24 , and d 32 ) strongly depend on temperature, while other constants are only weakly temperature dependent in this temperature range. These as-grown single domain data allowed us to calculate the orientation dependence of elastic, dielectric, and piezoelectric properties of KTiOPO4, which are useful for finding the optimum cut for particular applications.

  19. BiI{sub 3} single crystal for room-temperature gamma ray detectors

    Energy Technology Data Exchange (ETDEWEB)

    Saito, T., E-mail: saito.tatsuya125@canon.co.jp [Frontier Research Center, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo 146-8501 (Japan); Iwasaki, T. [Frontier Research Center, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo 146-8501 (Japan); Kurosawa, S.; Yoshikawa, A. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Den, T. [Frontier Research Center, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo 146-8501 (Japan)

    2016-01-11

    BiI{sub 3} single crystals were grown by the physical vapor transport method. The repeated sublimation of the starting material reduced impurities in the BiI{sub 3} single crystal to sub-ppm levels. The detector was fabricated by depositing Au electrodes on both surfaces of the 100-μm-thick BiI{sub 3} single crystal platelet. The resistivity of the BiI{sub 3} single crystal was increased by post-annealing in an iodine atmosphere (ρ=1.6×10{sup 11} Ω cm). Pulse height spectroscopy measurements showed clear peaks in the energy spectrum of alpha particles or gamma rays. It was estimated that the mobility-lifetime product was μ{sub e}τ{sub e}=3.4–8.5×10{sup −6} cm{sup 2}/V and the electron–hole pair creation energy was 5.8 eV. Our results show that BiI{sub 3} single crystals are promising candidates for detectors used in radiographic imaging or gamma ray spectroscopy.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Twin Diamond Crystals Grown at High Temperature and High Pressure from the Fe-Ni-C System

    Institute of Scientific and Technical Information of China (English)

    尹龙卫; 袁泉; 李木森; 刘玉先; 许斌; 郝兆印

    2002-01-01

    Twin diamond crystals grown at high temperature and high pressure (HPHT) in the presence of FeNi catalyst have been examined by transmission electron microscopy (TEM). Direct observation by TEM shows that there are a large amount of twins which lie on the {111} planes in the HPHT-grown diamonds. The twins in the diamond may be formed and may extend into the inner crystal from the twin nucleus formed in the nucleation process.The twins can be formed due to the carbon atoms falling mistakenly into positions where a twin crystal can form during diamond growth, or condensation of supersaturated vacancies on the {111} plane. Some hexagonal dislocation loops related to supersaturated vacancies are found on the twins. The Moiré fringe image reveals that stacking faults terminate on the intersecting twin boundary. This suggests that, at the temperature that the HPHT diamond is grown, the bordering partial has propagated by gliding up to the twin interface, which can be described by the reaction of a Shockley partial dislocation with a twin on the {111} plane.

  2. The Surface-to-volume Ratio of the Synthesis Reactor Vessel Governing the Low Temperature Crystallization of ZSM-5

    Directory of Open Access Journals (Sweden)

    Ana Hidayati Mukaromah

    2016-12-01

    Full Text Available Zeolite ZSM-5 is one of major catalysts in petroleum and fine-chemical industries. The synthesis of zeolite ZSM-5 is usually carried out at high temperature above 100 °C using the immense amount of organic structure-directing agents (OSDA. It is interesting to note that fine-tuning the initial gel mixture can be used to enhance the typical slow crystallization rate of ZSM-5. Herein, we report the effect of the surface-to-volume ratio of the reactor vessel to the crystallization of ZSM-5 at low temperature. The surface-to-volume ratio of the reactor vessel could influence the heat-transfer during the synthesis which further governed the crystallization of ZSM-5. It was found that the higher the surface-to-volume of the reactor, the more crystalline of the resulting products. The product with the highest crystallinity exhibited a nearly-spherical morphology composed of smaller ZSM-5 crystallites. This phenomenon allowed the presence of inter-crystallite mesopores which is an advantage for the catalytic reaction using bulky molecules.

  3. Nucleation and evaporation of domains due to electric field at room temperature in BaTiO3 single crystals

    Indian Academy of Sciences (India)

    C M Dudhe; P R Arjunwadkar

    2015-09-01

    A study of nucleation and evaporation of 90° and 180° domains by external direct current (dc) electric field at room temperature in barium titanate single crystals has been carried out using reflecting microscope. It was observed that both the 90° and 180° domains were nucleated at some sites, while evaporated at some other sites of the crystal surface. The 90° domain follows the mechanism of micro-domain wall nucleation as well as the evaporation based on impurity dipoles, like reported for KNbO3. The mechanism of the 180° domain nucleation is not established yet. However, in both cases, nucleation and evaporation are operative simultaneously by the same electric field, which seems to be quite interesting and which can be attributed to the different critical lengths of the domains.

  4. Raman spectroscopic evidence of low temperature stability of D,L-glycolic and L-(+)-lactic acid crystals.

    Science.gov (United States)

    Mohaček-Grošev, Vlasta; Šoštarić, Vladimir; Maksimović, Aleksandar

    2015-04-01

    Raman and infrared spectra of polycrystalline D,L-glycolic and L-(+) lactic acid are presented and assigned both by an ab initio calculation of normal modes of free conformers and by self-consistent-charge density-functional-theory computational program DFTB+. Temperature dependent Raman spectra from 295 K to 10 K reveal great stability of crystal lattices, since no soft modes and no band splittings that could be attributed to changes of the number of molecules per unit cell were observed. A semiempirical calculation with GULP program was used to estimate the strength of hydrogen bonds in crystals: in glycolic acid they have energies of -0.337 eV/mol, -0.329 eV/mol, -0.262 eV/mol and -0.242 eV/mol, while in lactic acid two hydrogen bonds have energies of -0.283 eV/mol and -0.202 eV/mol.

  5. Oblique propagation of electrons in crystals of germanium and silicon at sub-Kelvin temperature in low electric fields

    CERN Document Server

    Cabrera, B; Moffatt, R; Sundqvist, K; Sadoulet, B

    2010-01-01

    We show that oblique propagation of electrons in crystals of Ge and Si, where the electron velocity does not follow the electric field even on average, can be explained using standard anisotropic theory for indirect gap semiconductors. These effects are pronounced at temperatures below ~1K and for electric fields below ~5V/cm because inter-valley transitions are energetically suppressed forcing electrons to remain in the same band valley throughout their motion and the valleys to separate in position space. To model, we start with an isotropic approximation which incorporates the average properties of the crystals with one phonon mode, and include the ellipsoidal electron valleys by transforming into a momentum space where constant energy surfaces are spheres. We include comparisons of simulated versus measured drift velocities for holes and electrons, and explain the large discrepancy between electrons and holes for shared events in adjacent electrodes.

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

    Science.gov (United States)

    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.

  7. Low temperature specific heat in BaFe1.9Ni0.1As2 single crystals

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Low-temperature specific heat was measured on the BaFe1.9Ni0.1As2 single crystals with critical transition temperature Tc = 20.1 K.A clear specific heat jump with the value ΔC/T|Tc ≈ 23 mJ/mol K2 was observed.In addition,a roughly linear magnetic field dependence of the electronic specific heat coefficient Δγ(H) was found in the zero-temperature limit,suggesting that at least one Fermi pocket,probably the hole derivative one,was fully gapped with a small anisotropy in the present sample.A slight curvature of the curve Δγ(H) may suggest a complex gap structure(anisotropic gap or nodes) at other Fermi surfaces.

  8. Low-Temperature Specific Heat of the Underdoped La2-xSrxCuO4 Single Crystals

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi-Yong; YANG Hai-Peng; LU Xi-Feng; ZHOU Fang; WEN Hai-Hu

    2004-01-01

    @@ We report the low-temperature specific heat of La2-xSrxCuO4 (x = 0.063) single crystals before and after annealing in the temperature region of 2-10 K and magnetic fields up to 12 T. The data confirm the √H dependence of the linear term coefficient γpredicted for d-wave paring in the Volovik theory at T = 0 K. However, the data do not satisfy the proposed Simon-Lee scaling law at finite temperatures, i.e. CDOs/ (T2) = f(T/ √H), where f is an unknown scaling function and CDos is the extra specific heat contributed by the nodal quasiparticles due to the Doppler effect. Possible reasons for this failure are presented.

  9. The temperature-dependent single-crystal Raman spectroscopy of a model dipeptide: L-Alanyl-L-alanine

    Science.gov (United States)

    Silva, J. G.; Arruda, L. M.; Pinheiro, G. S.; Lima, C. L.; Melo, F. E. A.; Ayala, A. P.; Filho, J. Mendes; Freire, P. T. C.

    2015-09-01

    A single-crystal of peptide L-alanyl-L-alanine (C6H12N2O3) was studied by Raman spectroscopy at low-temperature, and a tentative assignment of the normal modes was given. Evidence of a second order structural phase transition was found through Raman spectroscopy between the temperatures of 80 K and 60 K. Group theory considerations suggest that the transition leads the sample from the tetragonal to a monoclinic structure. Additionally, our study suggests that the mechanism for the structural phase transition is governed by the occupation of non-equivalent C1 local symmetry sites by the CH3 molecular groups. Analysis based on group theory suggests L-alanyl-L-alanine presents C2 symmetry at low temperatures.

  10. Influence of oxygen partial pressure on crystallization behaviour and high-temperature stability of stone wool fibres

    Energy Technology Data Exchange (ETDEWEB)

    Kaasgaard, M.; Jacobsen, P.A.L.; Yue Yuanzheng [Aalborg Univ. (Denmark). Section of Chemistry

    2005-04-01

    The influence of oxygen partial pressure on the redox state of the iron in stone wool is studied using thermogravimetry (TG). The thermal response of the stone wool is measured using differential scanning calorimetry (DSC). The high-temperature stability of stone wool depending on the oxygen partial pressure is observed using scanning electron microscopy (SEM). It is confirmed that the oxidation of Fe{sup 2+} to Fe{sup 3+} is responsible for the high-temperature stability of stone wool. Even a minor increase in oxygen partial pressure can considerably alter the crystallization behaviour and enhance the high-temperature stability of the stone wool. The origin for that is discussed. (orig.)

  11. Liquid phase growth of GaSe1-xTex mixed crystals by temperature difference method under controlled vapor pressure

    Science.gov (United States)

    Zhao, S.; Sato, Y.; Maeda, K.; Tanabe, T.; Ohtani, H.; Oyama, Y.

    2017-06-01

    GaSe crystal is one of a group of nonlinear optical (NLO) crystals expected to be utilized as a highly efficient generators of terahertz waves. However, GaSe has some drawbacks that limit it from further application. Firstly, it has poor crystallinity and, secondly, the layers are prone to exfoliation. In this work, crystal growth was carried out at a constant low temperature under a controlled Se vapor pressure to improve the crystallinity. In addition, Te was added in order to grow mixed crystals to improve the bonding forces between the layers. X-ray fluorescence was used to measure the Te composition in the grown crystals. Red shifts of the excitation peaks were found from photoluminescence with increasing Te composition, indicating that mixed crystals were successfully grown. The lattice constant, c, was calculated from the results of X-ray diffraction and was shown to have an almost linear dependence on Te composition.

  12. Synthesis of High Surface Area and Well Crystallized Mesoporous WC at Low Temperature with a Pore Structure Collapsed Replication Route

    Institute of Scientific and Technical Information of China (English)

    LI Hua; SHI Jianlin; CHEN Hangrong; ZHANG Lingxia; LI Lei

    2011-01-01

    An approach named "pore structure collapsed replication route" has been developed to prepare mesoporous WC materials with a high surface area (105 m2/g) and crystallized framework at a temperature as low as 700 ℃. The XRD, TEM, EDS, and BET characterizations were conducted to analyze the effects of the synthesis parameters and the template types on the structure of mesoporous WC. The compaction on the templates is the key to form mesoporous structure of WC while the templates help to control the size of crystalline. At a content of 7 wt% for the precursor of WC, the mesoporous WC could be formed with well ordered structure.

  13. Simultaneous measurements of anisotropic thermal diffusivity and thermal effusivity of liquid crystals using temperature wave analysis method

    Science.gov (United States)

    Ryu, Meguya; Morikawa, Junko

    2016-11-01

    Simultaneous measurements of anisotropic thermal diffusivity and thermal effusivity in the phase transition of the liquid crystal 4‧-(pentyloxy)-4-biphenyl carbonitrile (5OCB), Cry-53-N-68-Iso, are demonstrated using the temperature wave analysis method. A detailed calibration procedure for determining thermal diffusivity (α), thermal effusivity (e), thermal conductivity (λ), and heat capacity per unit volume (Cp ρ) is proposed utilizing hexaethylene glycol monododecyl ether (C12E6) as a calibration material, the heat capacity of which is precisely determined using a calorimetric method.

  14. Crystal Structure of Calcium Silicate Perovskite Synthesized under Water Saturated Conditions at Mantle Related Pressure-Temperature

    Science.gov (United States)

    Chen, H.; Shim, S. H. D.; Leinenweber, K. D.; Meng, Y.; Prakapenka, V.

    2014-12-01

    Perovskite-structured CaSiO3 (Ca-Pv) is the third most abundant mineral in the lower mantle. However, its crystal structure is still under debate and the solubility of H2O in Ca-Pv is not well constrained. We have conducted in situ X-ray diffraction measurements on Ca-Pv under H2O saturated conditions in the laser-heated diamond-anvil cell at the GSECARS and HPCAT sectors of the Advanced Photon Source. Glass starting materials were mixed with platinum powder (10 wt%) for laser coupling and internal pressure scale. Cold compressed foils of the mixtures were loaded in the diamond-anvil cell together with Ne or water. The X-ray diffraction patterns of the Ca-Pv sample synthesized in a Ne medium are consistent with a cubic perovskite structure at both 300 K and high temperatures up to 2,400 K at 50 GPa. No clear peak splittings were observed within the resolution of the angle-dispersive powder diffraction technique. However, in the experiments with water, clear splitting of the 200 diffraction line appears during heating to temperatures over 2000 K and remain after temperature quench at 32 GPa. The peak splittings were clearly observed at high temperatures to 2400 K, which is close to the melting point of water at the pressure. The different structural behaviors of Ca-Pv depending on media (Ne and water) may suggest that OH might enter into the crystal structure of nominally anhydrous Ca-Pv phase at high pressure and high temperature.

  15. Growth and fluorescence characteristics of Cr3+ : YAG crystal fiber for temperature sensor from -10°C to 500°C

    Science.gov (United States)

    Ye, Linhua; Qiu, Yanqing; He, Jinlei; Shen, Yonghang; He, Sailing

    2005-01-01

    The temperature-dependent characteristics of fluorescence of transient-metal doped and/or rare-earth-doped YAG has made these materials the focus of fluorescence thermometer. This article reports growth and fluorescence characteristics of Cr3+: YAG crystal fiber used for thermometer based on fluorescence decay time. Using a long pure YAG crystal fiber as the seed and a 0.1 at. % Cr2O3-doped Y3Al5O12 sintered powder rod as the source rod, a YAG fiber thermal probe with Cr3+-ions doped end was grown by laser heated pedestal growth method. The crystal fiber shows good optical properties and mechanical strength and offers advantages of compact construct, high performance and ability to withstand high temperature. The fluorescence decay characteristics of the crystal fiber, including the temperature dependence of both fluorescence decay time and intensity, were comprehensively investigated. The experimental results indicated the Cr3+:YAG crystal fiber showed a monotonic relationship between the fluorescence lifetime and temperature over a wide temperature range from cryogenic to high temperature(>500°C). The fiber was found to be an excellent candidate material to be used as a fiber thermometer based on fluorescence lifetime. This thermometer may be used as temperature monitor in microwave treatment and Medium Voltage substations.

  16. CdTe and CdZnTe crystals for room temperature gamma-ray detectors

    CERN Document Server

    Franc, J; Belas, E; Grill, R; Hlidek, P; Moravec, P; Bok, J B

    1999-01-01

    CdTe(Cl) detectors from CdTe single crystals, grown by the Bridgman method from Te-rich melt, were fabricated. The quality of the detectors was tested with sup 5 sup 7 Co and sup 2 sup 4 sup 1 Am sources. In the sup 5 sup 7 Co spectrum low noise is demonstrated by the presence of a 14 keV peak and good resolution approx 7 keV (FWHM) evident from the separation of 122 and 136 keV peaks. A review is given of the state-of-the-art properties of (CdZn)Te single crystals prepared for substrates in the Institute of Physics of Charles University. The quality of samples is tested by measurements of the diffusion length of minority carriers, from which the mobility-lifetime product is evaluated. (author)

  17. Low Temperature Quartz Crystal Oscillator Fast Warm-Up Saw Oscillator.

    Science.gov (United States)

    1981-07-01

    and given at I Hz from the carrier. From these experimental data the dependance between 1/F noise and Q-fact : is determined by using a regression...for the thermal phonons. The anharmonicities are introduced by means of a strain dependance of the phono frequencies. A detailed description of the...study shown for the first time a correlation between 1/F noise and Q-factor in quartz crystal resonators. This dependance was confirmed on the one

  18. The Crystal Structure at Room Temperature of Six Cast Heat-Resisting Alloys

    Science.gov (United States)

    Rosenbaum, Burt M.

    1947-01-01

    The crystal structures of alloys 61, X-40,X-50, 422-19, 6059, and Vitallium, derived from x-ray diffraction, are discussed. The alloys have been, or are being considered for use in gas turbine applications. The predominant phase was a solid solution of the face centered cubic type of the principal constituent elements.The lattice parameters were found to be between 3.5525 and 3.5662.

  19. Effects on humans elicited by inhaling the fragrance of essential oils: sensory test, multi-channel thermometric study and forehead surface potential wave measurement on basil and peppermint.

    Science.gov (United States)

    Satoh, Tomoko; Sugawara, Yoshiaki

    2003-01-01

    The effects on humans inhaling the fragrance of essential oils were examined in terms of a sensory test, a multi-channel skin thermometer study and a portable forehead surface electroencephalographic (IBVA-EEG) measurement. The essential oils examined in this study were those of basil and peppermint, because our previous sensory test had indicated an opposite effect of these essential oils when mental work was undertaken; the inhalation of basil produced a more favorable impression after work than before work, whereas peppermint produced an unfavorable impression under these circumstances. For subjects administered basil or peppermint before and after mental work using an inhalator, a series of multi-channel skin thermometer studies and IBVA-EEG measurements were conducted. Using such paired odorants, our results showed that when compared between before and after mental work assigned to subjects: (1) the inhalation of basil, in which a favorable impression was predominant on the whole in terms of the sensory evaluation spectrum, was shown to be associated upward tendency in finger-tip skin temperature; (2) whereas these situations were opposite in the case of peppermint, in which the reversed (unfavorable) feature in sensory profiling was accompanied by a decrease in the magnitude of beta waves and a decrease in the finger-tip skin temperature both based on Welch's method, even at p < 0.01, implying a decreasing propensity of the aroused state and of the arousal response. The elucidation of such sensory and physiological endpoints of paired odorants would be of primary importance for human chemoreception science, because these are only rarely recorded during the same experiments, and this paradigm is highly informative about non-verbal responses to odorants.

  20. Study of the temperature evolution of defect agglomerates in neutron irradiated molybdenum single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lambri, O.A. [Instituto de Fisica Rosario. Member of the CONICET' s Research Staff, Avda. Pellegrini 250, (2000) Rosario, Santa Fe (Argentina); Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Laboratorio de Materiales, Escuela de Ingenieria Electrica, Avda. Pellegrini 250, (2000) Rosario, Santa Fe (Argentina)], E-mail: olambri@fceia.unr.edu.ar; Zelada-Lambri, G.I. [Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Laboratorio de Materiales, Escuela de Ingenieria Electrica, Avda. Pellegrini 250, (2000) Rosario, Santa Fe (Argentina); Cuello, G.J. [Institut Laue Langevin, 6, rue Jules Horowitz, BP 156, 38042 Grenoble (France); Departamento de Fisica Aplicada II, Facultad de Ciencias y Tecnologia, Universidad del Pais Vasco, Apdo. 644, 48080 Bilbao, Pais Vasco (Spain); Bozzano, P.B. [Laboratorio de Microscopia Electronica. Unidad de Actividad Materiales, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Avda. Gral. Paz 1499, (1650) San Martin (Argentina); Garcia, J.A. [Departamento de Fisica Aplicada II, Facultad de Ciencias y Tecnologia, Universidad del Pais Vasco, Apdo. 644, 48080 Bilbao, Pais Vasco (Spain)

    2009-04-15

    Small angle neutron scattering as a function of temperature, differential thermal analysis, electrical resistivity and transmission electron microscopy studies have been performed in low rate neutron irradiated single crystalline molybdenum, at room temperature, for checking the evolution of the defects agglomerates in the temperature interval between room temperature and 1200 K. The onset of vacancies mobility was found to happen in temperatures within the stage III of recovery. At around 550 K, the agglomerates of vacancies achieve the largest size, as determined from the Guinier approximation for spherical particles. In addition, the decrease of the vacancy concentration together with the dissolution of the agglomerates at temperatures higher than around 920 K was observed, which produce the release of internal stresses in the structure.

  1. Temperature effects of Mach-Zehnder interferometer using a liquid crystal-filled fiber

    DEFF Research Database (Denmark)

    Ho, Bo-Yan; Su, Hsien-Pin; Tseng, Yu-Pei;

    2015-01-01

    with a maximum interferometric contrast over 35dB. The temperature-induced resonant wavelength blue-shifts 70.4 nm for the MZI with an LC length of 9.79 mm and the wavelength temperature sensitivity of -1.55 nm/degrees C is easily achieved as the temperature increases from 25 degrees C to 77 degrees C. (C)2015...

  2. Hydrogen related crystallization in intrinsic hydrogenated amorphous silicon films prepared by reactive radiofrequency magnetron sputtering at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Senouci, D. [Laboratoire de Genie Physique, Universite Ibn-Khaldoun, 14000 Tiaret (Algeria); LPCMME, Departement de Physique, Universite d' Oran Es-senia, 3100, Oran (Algeria); Baghdad, R., E-mail: r_baghdad@mail.univ-tiaret.dz [Laboratoire de Genie Physique, Universite Ibn-Khaldoun, 14000 Tiaret (Algeria); Belfedal, A.; Chahed, L. [LPCMME, Departement de Physique, Universite d' Oran Es-senia, 3100, Oran (Algeria); Portier, X. [CIMAP, CEA, CNRS UMR 6252-ENSICAEN, UCBN, 6 Bvd Marechal Juin, 14050 Caen Cedex (France); Charvet, S. [LPMC, UFR des Sciences, Universite de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens (France); Kim, K.H. [LPICM, Laboratoire de Physique des Interfaces et Couches Minces, CNRS UMR 7647, Ecole Polytechnique, 91128 Palaiseau (France); TOTAL S.A., Gas and Power, R and D Division, Courbevoie (France); Roca i Cabarrocas, P. [LPICM, Laboratoire de Physique des Interfaces et Couches Minces, CNRS UMR 7647, Ecole Polytechnique, 91128 Palaiseau (France); Zellama, K. [LPMC, UFR des Sciences, Universite de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens (France)

    2012-11-01

    We present an investigation on the transition from amorphous to nanocrystalline silicon and associated hydrogen changes during the first steps of hydrogenated nanocrystalline silicon growth for films elaborated by reactive radiofrequency magnetron sputtering at a substrate temperature as low as room temperature and for deposition times varying from 3 to 60 min. Complementary experimental techniques have been used to characterize the films in their as-deposited state. They are completed by thermal hydrogen effusion experiments conducted in the temperature range, from room temperature to 800 Degree-Sign C. The results show that, during the initial stages of growth, the presence of a hydrogen-rich layer is necessary to initiate the crystallization process. - Highlights: Black-Right-Pointing-Pointer Nanocrystalline silicon growth at room temperature. Black-Right-Pointing-Pointer Transition from amorphous to nanocrystalline silicon. Black-Right-Pointing-Pointer Chemical reactions of H atoms with strained Si-Si bonds. Black-Right-Pointing-Pointer H selective etching and chemical transport caused the silicon nucleation.

  3. A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

    Science.gov (United States)

    Burnell, E. Elliott; Weber, Adrian C. J.; Dong, Ronald Y.; Meerts, W. Leo; de Lange, Cornelis A.

    2015-01-01

    The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche+ gauche+, pp, and gauche+ gauche-, pm), the isotropic trans-gauche energy difference Etg and its temperature coefficient Etg ' are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche+ gauche- conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase.

  4. A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Burnell, E. Elliott, E-mail: elliott.burnell@ubc.ca [Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1 (Canada); Weber, Adrian C. J., E-mail: webera@brandonu.ca [Chemistry Department, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9 (Canada); Dong, Ronald Y., E-mail: rondong@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1 (Canada); Meerts, W. Leo, E-mail: leo.meerts@science.ru.nl [Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, NL-6525 AJ Nijmegen (Netherlands); Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Lange, Cornelis A. de, E-mail: c.a.de.lange@vu.nl [Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands)

    2015-01-14

    The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche{sub +} gauche{sub +}, pp, and gauche{sub +} gauche{sub −}, pm), the isotropic trans-gauche energy difference E{sub tg} and its temperature coefficient E{sub tg}{sup ′} are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche{sub +} gauche{sub −} conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase.

  5. High-birefringence photonic crystal fiber Michelson interferometer with cascaded fiber Bragg grating for pressure and temperature discrimination

    Science.gov (United States)

    Tan, Xiaoling; Geng, Youfu; Li, Xuejin

    2016-09-01

    A simple and compact interferometer for temperature and pressure discrimination is proposed and demonstrated experimentally. It consists of a short section of high-birefringence photonic crystal fiber (Hi-Bi PCF) and a cascaded fiber Bragg grating (FBG). In the Hi-Bi PCF, two orthogonal polarized modes are employed as optical arms to construct, such as a Michelson interferometer. Combined with a cascaded FBG, pressure and temperature measurements are discriminated by a matrix method, and the pressure sensitivity of Hi-Bi PCF is determined to be around 3.65 nm/MPa. The proposed Michelson interferometer is easy-to-fabricate, flexible, and low-cost, which shows great potential in future applications of remote sensing.

  6. Multibeam Interferometer Using a Photonic Crystal Fiber with Two Asymmetric Cores for Torsion, Strain and Temperature Sensing

    Science.gov (United States)

    Naeem, Khurram; Kwon, Il-Bum; Chung, Youngjoo

    2017-01-01

    We present a fiber-optic multibeam Mach-Zehnder interferometer (m-MZI) for simultaneous multi-parameter measurement. The m-MZI is comprised of a section of photonic crystal fiber integrated with two independent cores of distinct construction and birefringence properties characterized for torsion, strain and temperature sensing. Due to the presence of small core geometry and use of a short fiber length, the sensing device demonstrates inter-modal interference in the small core alongside the dominant inter-core interference between the cores for each of the orthogonal polarizations. The output spectrum of the device is characterized by the three-beam interference model and is polarization-dependent. The two types of interferometers present in the fiber m-MZI exhibit distinct sensitivities to torsion, strain and temperature for different polarizations, and matrix coefficients allowing simultaneous measurement of the three sensing parameters are proposed in experiment. PMID:28085046

  7. Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

    Science.gov (United States)

    Pal, Rumpa; Reddy, M B Madhusudana; Dinesh, Bhimareddy; Balaram, Padmanabhan; Guru Row, Tayur N

    2014-10-01

    Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components. The thermal behavior of the dipeptide crystals was characterized by differential scanning calorimetry experiments. Visual changes in birefringence of the sample during heating and cooling cycles on a hot-stage microscope with polarized light supported the phase transition. Variable-temperature unit cell check measurements from 300 to 100 K showed discontinuity in the volume and cell parameters near the transition temperature, supporting the first-order behavior. A detailed comparison of the room-temperature orthorhombic form with the low-temperature (100 K) monoclinic form revealed that the strong hydrogen-bonding motif is retained in both crystal systems, whereas the non-covalent interactions involving side chains of the dipeptide differ significantly, leading to a small change in molecular conformation in the monoclinic form as well as a small reorientation of the molecules along the ac plane. A rigid-body thermal motion analysis (translation, libration, screw; correlation of translation and libration) was performed to study the crystal entropy. The reversible nature of the phase transition is probably the result of an interplay between enthalpy and entropy: the low-temperature monoclinic form is enthalpically favored, whereas the room-temperature orthorhombic form is entropically favored.

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

    Science.gov (United States)

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

    1999-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Low coherence technique to interrogate optical sensors based on selectively filled double-core photonic crystal fiber for temperature measurement

    Science.gov (United States)

    Li, Kun; Jiang, Meng; Zhao, Zhongze; Wang, Zeming

    2017-04-01

    In this paper, an optical fiber sensing system based on low coherence interferometry (LCI) is proposed and demonstrated to interrogate sensors comprised of selectively filled double-core photonic crystal fiber (SFDC-PCF). The sensor used here is made by selectively filling about 1/3 area of air holes in the cladding of photonic crystal fiber with distilled water. So the dual-core in the sensor has different effective refractive indices, resulting in a phase delay between two lights transmitting in the fiber. The phase delay of the sensor can be compensated by a Mach-Zehnder interferometer with a scanning optical tunable delay line in one arm of the interferometer, namely temporal interrogation. By tracking the value of phase delay, the change of the measurand can be detected. Temperature measurement is carried out to testify the system performance. An average sensitivity of 0.9 μm/°C is achieved within the temperature range of 29-92 °C. This work provides a new thinking for fiber sensing technology based on LCI. The proposed all-fiber sensing system, with the merits of cost-effective, stability, and flexibility, can demodulate the SFDC-PCF sensor signals well. Further improvements such as better sensitivity, larger measurement range and multiplexing efficiency can be realized by tailoring the PCF sensor's structure.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Synthesis of indium oxide cubic crystals by modified hydrothermal route for application in room temperature flexible ethanol sensors

    Energy Technology Data Exchange (ETDEWEB)

    Seetha, M., E-mail: seetha.phy@gmail.com [Department of Physics, SRM University, Kattankulathur, Kancheepuram Dt 603 203 (India); Meena, P. [Department of Physics, PSGR Krishnammal College for Women, Coimbatore 641 046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.com [DRDO-BU Centre for Life Sciences, Bharathiar University Campus, Coimbatore (India); Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 014 (India); Masuda, Yoshitake [National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Senthil, K. [School of Advanced Materials Science and Engineering, Sungkyunkwan University (Suwon Campus), Cheoncheon-dong 300, Jangan-gu, Suwon 440-746 (Korea, Republic of)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer For the first time HMT is used in the preparation of indium oxide. Black-Right-Pointing-Pointer HMT itself acts as base for the precursor and results in cubic indium hydroxide. Black-Right-Pointing-Pointer Modified hydrothermal route used for the preparation of cubic indium oxide crystals. Black-Right-Pointing-Pointer As a new approach a composite film synthesized with prepared indium oxide. Black-Right-Pointing-Pointer Film showed good response to ethanol vapours with quick response and recovery times. - Abstract: Indium oxide cubic crystals were prepared by using hexamethylenetetramine and indium chloride without the addition of any structure directing agents. The chemical route followed in the present work was a modified hydrothermal synthesis. The average crystallite size of the prepared cubes was found to be 40 nm. A blue emission at 418 nm was observed at room temperature when the sample was excited with a 380 nm Xenon lamp. This emission due to oxygen vacancies made the material suitable for gas sensing applications. The synthesized material was made as a composite film with polyvinyl alcohol which was more flexible than the films prepared on glass substrates. This flexible film was used as a sensing element and tested with ethanol vapours at room temperature. The film showed fast response as well as recovery to ethanol vapours with a sensor response of about 1.4 for 100 ppm of the gas.

  15. Jamin-interferometer-setup for the determination of concentration and temperature dependent face-specific crystal growth rates from a single experiment

    Science.gov (United States)

    Eder, Cornelia; Choscz, Carsten; Müller, Vesna; Briesen, Heiko

    2015-09-01

    An interference technique that permits the investigation of the crystal growth from a temperature controlled solution is presented. Contrary to Mach-Zehnder- or Michelson-type interferometers, the Jamin-interferometer applied in this work is characterized by improved thermal and long-time stability. In consequence a single experiment may comprise several temperature steps leading to significant changes in the bulk concentration. A procedure for the automated analysis of the acquired sequence of interference patterns is presented. Within this evaluation procedure the position of the selected crystal face, the bulk concentration and the vertical concentration distribution above the crystal are determined simultaneously. Long-term single crystal growth experiments in the range from 20 to 60 °C with sucrose and lactose crystals are used to test the method. The exact bulk concentration is determined by the interferometer. The obtained results for the growth rate of sucrose are consistent with values given in the literature. The vertical concentration distribution above the two saccharide crystals differs clearly indicating that the diffusion strongly limits the sucrose growth but not the growth of the lactose crystal. The major benefit of the described setup is that the data of a single experiment are sufficient to deduce the parameters of the model equation for the growth rate as a function of temperature and supersaturation.

  16. Scenario of temperature-related variation of phosphorescence spectra of ortho-bromobenzophenone crystal

    Science.gov (United States)

    Strzhemechny, M. A.; Stepanian, S. G.; Zloba, D. I.; Buravtseva, L. M.; Pyshkin, O. S.; Piryatinski, Yu. P.; Melnik, V. I.; Klishevich, G. V.; Adamowicz, L.

    2015-12-01

    Luminescence and other properties of solid 2-bromobenzophenone demonstrate features, which require special attention. We present results, which include DFT calculations, integrated and time-resolved phosphorescence spectra, and excitation spectra. The energies of the title molecule were calculated for the S0 , S1 , and T1 states. Nanosecond time-resolved phosphorescence spectra were measured at three temperature points at which the spectra undergo substantial changes. Joint analysis of energy surfaces and experimental evidence allowed reconstruction of the emission scenario that determines temperature-related variations of spectra. Upon excitation to state S1 the molecule converges very fast to T1 , emission from which can occur from the minima at 60° or at 180°. At low temperatures the molecule emits from the former, whereas at higher temperatures the molecule can overcome the barrier to emit from the lower minimum. The probability of excimer formation increases with increasing temperature.

  17. Temperature effects on the atomic structure and kinetics in single crystal electrochemistry

    Science.gov (United States)

    Gründer, Yvonne; Markovic, Nenad M.; Thompson, Paul; Lucas, Christopher A.

    2015-01-01

    The influence of temperature on the atomic structure at the electrochemical interface has been studied using in-situ surface x-ray scattering (SXS) during the formation of metal monolayers on a Au(111) electrode. For the surface reconstruction of Au(111), higher temperatures increase the mobility of surface atoms in the unreconstructed phase which then determines the surface ordering during the formation of the reconstruction. For the underpotential deposition (UPD) systems, the surface diffusion of the depositing metal adatoms is significantly reduced at low temperatures which results in the frustration of ordered structures in the case of Cu UPD, occurring on a Br-modified surface, and in the formation of a disordered Ag monolayer during Ag UPD. The results indicate that temperature changes affect the mass transport and diffusion of metal adatoms on the electrode surface. This demonstrates the importance of including temperature as a variable in studying surface structure and reactions at the electrochemical interface.

  18. Low Temperature Synthesis of Single-crystal Alpha Alumina Platelets by Calcining Bayerite and Potassium Sulfate

    Institute of Scientific and Technical Information of China (English)

    Xinghua Su; Jiangong Li

    2011-01-01

    Single-crystal alpha alumina (α-Al2O3) platelets were synthesized by calcining a powder mixture of bayerite (α-AI(OH)3) and potassium sulfate (K2SO4) at 900℃. The crystalline phase evolutions and morphologies of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized samples mainly consisted of single-crystal α-Al2O3 platelets with a diameter of 0.5-1.5 μm and a thickness of 50-150 nm. Moreover, with 3, 5, and 8 wt% (referred to the obtained alumina) α-Al2O3 seeds adding into the powder mixture of bayerite and potassium sulfate, the average diameter of α-Al2O3 platelets can be reduced to 450, 240, and 220 nm, respectively. It is found that the sequence of the phase transformation is the bayerite (α-Al(OH)3) → boehmite (γ-AIOOH) →γ-Al2O3 → α-Al2O3. Further analysis indicated that K2SO4 can promote the phase transformation from α-Al2O3 to α-Al2O3 and the formation of single-crystal α-Al2O3 platelets might be attributed to the liquid phase K3AI(SO4)3.

  19. Influence of skin blood flow on near-infrared spectroscopy signals measured on the forehead during a verbal fluency task.

    Science.gov (United States)

    Takahashi, Toshimitsu; Takikawa, Yoriko; Kawagoe, Reiko; Shibuya, Satoshi; Iwano, Takayuki; Kitazawa, Shigeru

    2011-08-01

    Brain activity during a verbal fluency task (VFT) has been the target of many functional imaging studies. Most studies using near-infrared spectroscopy (NIRS) have reported major activation in the frontal pole, but those using PET or fMRI have not. This led us to hypothesize that changes in the NIRS signals measured in the forehead during VFT were due to changes in skin blood flow. To test this hypothesis, we measured NIRS signals and the Doppler tissue blood flow signals in the foreheads of 50 participants. The measurements were performed while each participant produced words during two 60-s periods with an interval of 100 s. In addition to a conventional optode separation distance of 30 mm (FAR channels), we used a short distance--5mm (NEAR channels)--to measure NIRS signals that originated exclusively from surface tissues. The oxygenated hemoglobin (oxyHb) concentration in the FAR and NEAR channels, as well as the Doppler blood flow signal, increased in a similar manner during the two periods of word production; the signal increase in the first period was twice as high as that in the second period. Accordingly, the mean changes in oxyHb concentration in the FAR channels were correlated closely with the changes in the NEAR channels (R(2) = 0.91) and with the integrated Doppler skin blood flow signal (R(2) = 0.94). Furthermore, task-related NIRS responses disappeared when we blocked skin blood flows by pressing a small area that covered a pair of optodes. Additionally, changes in the FAR channel signals were correlated closely with the magnitude of pulsatile waves in the Doppler signal (R(2) = 0.92), but these signals were not highly correlated with the pulse rate (R(2) = 0.43). These results suggest that a major part of the task-related changes in the oxyHb concentration in the forehead is due to task-related changes in the skin blood flow, which is under different autonomic control than heart rate.

  20. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    Science.gov (United States)

    Ponomarev, V. I.; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.

    2015-09-01

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide В15- х С х , (1.5 ≤ x ≤ 3) and its magnesium derivative C4B25Mg1.42. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from В12.9С2.1 to В12.4С2.6.

  1. Experimental observations on the crystalline structures of YAlO{sub 3} single crystal at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Takahiro; Morimoto, Takaaki [Waseda University, Department of Electrical Engineering and Bioscience, Tokyo (Japan); Ohki, Yoshimichi [Waseda University, Department of Electrical Engineering and Bioscience, Tokyo (Japan); Waseda University, Research Institute for Materials Science and Technology, Tokyo (Japan)

    2015-06-15

    To understand the effects of thermal annealing on a high-permittivity gate insulating material YAlO{sub 3}, its single crystal was annealed at various high temperatures ranging from 900 to 1300 C and was examined by various instrumental analyses such as X-ray diffraction, infrared absorption spectroscopy, laser confocal microscopy, and atomic force microscopy. As a result, it was clarified that the crystalline YAlO{sub 3} takes at least three structures in a temperature range up to 1300 C. Namely, it is perovskite below 1160 C, at which the garnet structure starts to appear, while an unknown structure appears at 1250 C. On the other hand, the sample surface also shows drastic changes if the temperature exceeds 1160 C. Furthermore, many elliptical spots are induced after the annealing at 1200 or 1250 C. Moreover, hydroxyl groups are generated at 1300 C. It is desirable to take these structural changes into account in determining the annealing temperature of YAlO{sub 3} for various industrial purposes such as the manufacture of semiconductor devices. (orig.)

  2. Cyclic deformation of NI/sub 3/(Al,Nb) single crystals at ambient and elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bonda, N.R.

    1985-01-01

    Cyclic tests were performed on Ni/sub 3/(Al,Nb) (..gamma..' phase) single crystals by using a servo-hydraulic machine under fully reversed plastic strain control at a frequency of 0.1-0.2 Hz at room temperature, 400/sup 0/C and 700/sup 0/C. Since the monotonic behavior is orientation dependent, three orientations were studied. Asymmetry in tensile and compressive stresses was observed in the cyclic hardening curves of specimens tested at these temperatures and they were discussed with regard to the model suggested by Paider et al for monotonic behavior. The stress levels in the cyclic stress-strain curves (CSSC) at room temperature depended on orientation and cyclic history. No CSSCs were established at 400/sup 0/C and 700/sup 0/C. The deformation in cyclic tests at small plastic strain amplitudes was found to be different from that in monotonic tests in the microplastic regions in which the deformation is believed to be carried by a small density of edge dislocations. But in cyclic deformation, to and from motion of dislocations trap the edge dislocations into dipoles and therefore screw dislocations will be forced to participate in the deformation. Cracks on the surfaces of specimens tested at room temperature and 400/sup 0/C were found to be of stage I type, whereas at 700/sup 0/C, they were of stage II type.

  3. Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    At 1.0-4.0 GPa and 1123-1473 K and under oxygen fugacity-controlled conditions (Ni + NiO, Fe + Fe3O4, Fe +FeO and Mo + MoO2 buffers), a YJ-3000t Model six-anvil solid high-pressure apparatus and a Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (103-106 Hz), the electrical conductivity of the sample is of great dependence on the frequency; (2) with the rise of temperature (T), the electrical conductivity (σ) will increase, and the Arrenhius linear relationship is established between lgσ and 1/T; (3) under the control of oxygen buffer Fe + Fe3O4, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase,with the activation energy and activation volume of the sample estimated at ( 1.25 ± 0.08) eV and (0. 105 ± 0. 025) cm3/mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and (5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.

  4. Phase transition, phase transition temperature and crystal structure of a new compound----Ca2PdWO6

    Institute of Scientific and Technical Information of China (English)

    傅正民; 李文秀

    1996-01-01

    A new compound Ca2PdWO6 has been synthesized by solid state sintering. The phase transition of this compound was investigated by means of differential thermal analysis (DTA), X-ray phase analysis, precise measurement of lattice parameters and other methods. It is discovered that the compound has a displacive phase transition of the first order at (806+5)C. The low temperature phase, a-Ca2PdWO6, belongs to orthorhombic system, with space group Pmm2. Its lattice parameters at room temperature are: a=0.79946nm, b=0.55404nm and c=0.58008nm. The measured density is Dm=6.26g/cm3, and each unit cell contains two formula weights. The high temperature phase, Ca2PdWO6, belongs to the cubic system, with space group fm3m and the lattice parameter is a = 0.810 3 nm at 860C; Z = 4. The calculated density is Dx=5.821g/cm3. The crystal structure of Ca2PdWO6 and Ca,PdWO6 was also determined by means of the X-ray polycrystal diffraction method. The factors influencing phase transition temperature are discussed in detail.

  5. Minimization of temperature for laser cooling of Yb-ion-doped crystals.

    Science.gov (United States)

    Ivanov, Andrei; Rozhdestvensky, Yuriy; Perlin, Evgeniy

    2016-10-01

    In this paper, quantum mechanical calculations of cooling characteristics for the Yb3+:  YLF system with use of the vibronic model of laser cooling are presented. Dynamics of the laser cooling process for the seven-level system of an Yb ion is described by the density-matrix formalism. Dependences of the cooling characteristics on the pump intensity are obtained for various temperatures and absorption coefficients of impurity ions. It is shown that the pump intensity, at which the net cooling power has a maximum, depends on temperature. Thus, choosing the intensities, which correspond to the net cooling power maximum over the entire temperature range, we achieve a lower sample temperature at a shorter time than in the case of using a constant intensity throughout the cooling process. Calculations are performed for the parameters of the Yb3+:YLF system.

  6. P-type poly-Si prepared by low-temperature aluminum-induced crystallization and doping for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Yasuhiro; Yu, Zhenrui; Morales-Acevedo, Arturo [CINVESTAV-IPN, Mexico, D.F. (Mexico)

    2000-07-01

    P-type poly-Si thin films prepared by low temperature aluminum-induced crystallization and doping are reported. The starting material was boron-doped a-Si:H prepared by PECVD on glass substrates. Aluminum layers with different thickness were evaporated on a-Si:H surface and conventional thermal annealing was performed at temperatures ranging from 300 to 550 Celsius degrees. XRD, SIMS, and Hall effect measurements were carried out to characterize the annealed Al could be crystallized at temperature as low as 300 Celsius degrees in 60 minutes. This material has high carrier concentration as well as high Hall mobility and can be used as a p-layer of seed layer for thin film poly-Si solar cells. The technique reported here is compatible with PECVD process. [Spanish] Se informa sobre la preparacion de peliculas delgadas tipo P y Poli-Si mediante la cristalizacion inducida de aluminio a baja temperatura y el dopado. El material inicial era de boro dopado y a-Si:H preparado PECVD sobre substratos de vidrio. Se evaporaron capas de aluminio de diferente espesor sobre una superficie de a-Si:H y se llevo a cabo un destemplado termico convencional a temperaturas que varian entre 300 y 500 grados Celsius. Se llevaron a cabo mediciones de XRB, SIMS y del efecto Hall para caracterizar el aluminio destemplado para que pudiera ser cristalizado a temperaturas tan bajas como 300 grados Celsius en 60 minutos. Este material tiene una alta concentracion portadora asi como una alta movilidad Hall y puede usarse como una capa de semilla para celdas solares de pelicula delgada Poli-Si. La tecnica reportada aqui es compatible con el proceso PECVD.

  7. Room-temperature serial crystallography using a kinetically optimized microfluidic device for protein crystallization and on-chip X-ray diffraction

    Directory of Open Access Journals (Sweden)

    Michael Heymann

    2014-09-01

    Full Text Available An emulsion-based serial crystallographic technology has been developed, in which nanolitre-sized droplets of protein solution are encapsulated in oil and stabilized by surfactant. Once the first crystal in a drop is nucleated, the small volume generates a negative feedback mechanism that lowers the supersaturation. This mechanism is exploited to produce one crystal per drop. Diffraction data are measured, one crystal at a time, from a series of room-temperature crystals stored on an X-ray semi-transparent microfluidic chip, and a 93% complete data set is obtained by merging single diffraction frames taken from different unoriented crystals. As proof of concept, the structure of glucose isomerase was solved to 2.1 Å, demonstrating the feasibility of high-throughput serial X-ray crystallography using synchrotron radiation.

  8. EFFECT OF FINAL HEATING TEMPERATURE ON CRYSTALLIZATION OF ISOTACTIC POLYPROPYLENE NUCLEATED WITH AN ARYL AMIDE DERIVATIVE AS β-FORM NUCLEATING AGENT

    Institute of Scientific and Technical Information of China (English)

    Mu Dong; Ming-yin Jia; Zhao-xia Guo; Jian Yu

    2011-01-01

    An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene (iPP). Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed with melting conditions. Effects of final heating temperature (Tf) on heterogeneous nucleation of iPP/TMB-5 were investigated. It was discovered that the crystallization temperature increased with decreasing Tf value. The optical microscopic images indicated that when TMB-5 partially dissolved in iPP melt, the remaining (non-dissolved) TMB-5 facilitated the recrystallization of dissolved nucleating agent from the melt, which promoted crystallization. Complete solubility of nucleating agent caused the decreasing efficiency. TMB-5 recrystallized in the form of tiny needles, whose aggregates induced dendritic iPP crystals.

  9. The Naso-labial and lateral forehead flaps as a single stage: A case report and review of literature

    Directory of Open Access Journals (Sweden)

    Adigun I

    2008-01-01

    Full Text Available We present here the case of a patient with a major traumatic nasal loses who had a near-total nasal reconstruction as a single-stage procedure. A 35 year-old civil servant who was involved in a road traffic injury about two years before presentation. He sustained extensive and multiple facial injuries with complete loss of nasal cover and lining. Reconstruction was performed by using superiorly based, bilateral, nasolabial flaps to line the floor and the nasal septum, and a paramedian forehead flap for skin cover. The patient did well postoperatively and was discharged home on the 7 th postoperative day. If the principles concerning cover, support, and lining are adhered to, excellent functional and aesthetic results can be achieved as we have obtained in our patient.

  10. Utilidad del colgajo frontal en la reconstrucción nasal Usefulness of the forehead flap in the nasal reconstruction

    Directory of Open Access Journals (Sweden)

    Julio César Gálvez Chávez

    2009-03-01

    Full Text Available INTRODUCCIÓN. La nariz constituye el centro estético de la cara y cualquier deformidad en ella afecta de modo importante a la armonía facial. Este estudio tuvo como objetivo caracterizar las experiencias en reconstrucción nasal con colgajo frontal en pacientes con defectos anatómicos de la nariz, como consecuencia fundamentalmente de una cirugía oncológica. MÉTODOS. Se realizó un estudio descriptivo, prospectivo, para caracterizar la experiencia de la reconstrucción nasal con colgajo frontal en pacientes con defectos nasales, atendidos en el Hospital «Hermanos Ameijeiras» y en el Instituto Nacional de Oncología y Radiobiología, entre junio de 1999 y mayo de 2007. RESULTADOS. Destacó que el motivo más frecuente de reconstrucción fue la lesión neoplásica, con igual número de pacientes afectados por carcinoma basocelular y epidermoide. El ala nasal fue la zona más afectada y se presentó recidiva tumoral en 5 pacientes. En todos los casos se pudo crear una cubierta externa al defecto y el diseño oblicuo fue el más utilizado. Se reconstruyó la cubierta interna nasal fundamentalmente con injerto de piel total y el soporte nasal, mayormente con injertos cartilaginosos de la concha auricular. Todos los colgajos frontales se mantuvieron vitales después de su desconexión en el segundo tiempo quirúrgico. El cierre directo de la zona donante fue el más utilizado y en algunos casos se logró con la utilización de expansión tisular. Se realizó un tercer tiempo de remodelación en los pacientes que lo necesitaron. Las complicaciones no afectaron al resultado final de la reconstrucción. CONCLUSIONES. Se demostró la utilidad y vigencia del colgajo frontal en la reconstrucción nasal.ABSTRACT INTRODUCTION. The nose is the aesthetic center of the face and any deformity in it significantly affects facial harmony. This study was aimed at characterizing the experiences in nasal reconstruction with forehead flap in patients with

  11. Temperature-dependent adsorption of surfactant molecules and associated crystallization kinetics of noncentrosymmetric Fe(IO{sub 3}){sub 3} nanorods in microemulsions

    Energy Technology Data Exchange (ETDEWEB)

    El-Kass, Moustafa [Université de Savoie, Laboratoire SYMME, BP 80439, 74944 Annecy Le Vieux Cedex (France); Ladj, Rachid [Université de Savoie, Laboratoire SYMME, BP 80439, 74944 Annecy Le Vieux Cedex (France); Université Lyon1, CNRS, UMR 5007, LAGEP, CPE, 43 bd 11 Novembre 1918, F-69622 Villeurbanne (France); Mugnier, Yannick, E-mail: Yannick.Mugnier@univ-savoie.fr [Université de Savoie, Laboratoire SYMME, BP 80439, 74944 Annecy Le Vieux Cedex (France); Le Dantec, Ronan [Université de Savoie, Laboratoire SYMME, BP 80439, 74944 Annecy Le Vieux Cedex (France); Hadji, Rachid [Institut Jean Lamour, UMR CNRS n°7198, Université de Lorraine, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Marty, Jean-Christophe [Université de Savoie, Laboratoire SYMME, BP 80439, 74944 Annecy Le Vieux Cedex (France); Rouxel, Didier [Institut Jean Lamour, UMR CNRS n°7198, Université de Lorraine, Nancy 1, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex (France); Durand, Christiane [Université de Savoie, Laboratoire SYMME, BP 80439, 74944 Annecy Le Vieux Cedex (France); Fontvieille, Dominique [UMR CARRTEL (INRA/Université de Savoie), Laboratoire de Microbiologie Aquatique, BP 511, 74203 Thonon Cedex (France); Rogalska, Ewa [Structure et Réactivité des Systèmes Moléculaires Complexes, UMR 7565, Nancy Université, BP 70239, 54506 Vandoeuvre-lès-Nancy cedex (France); and others

    2013-11-15

    Graphical abstract: - Highlights: • Crystallization of Fe(IO{sub 3}){sub 3} in microemulsions probed by hyper-Rayleigh scattering. • A faster growth and a better shape control of nanorods are obtained at 80 °C. • Different persistent cell deformations are related to the crystallization kinetics. • A temperature-dependent adsorption of surfactants on nanorods is suggested. - Abstract: Aggregation-induced crystallization of iron iodate nanorods within organic–inorganic aggregates of primary amorphous precursors is probed by time-dependent hyper-Rayleigh scattering measurements in Triton X-100 based-microemulsions. In the context of a growing interest of noncentrosymmetric oxide nanomaterials in multi-photon bioimaging, we demonstrate by a combination of X-ray diffraction and electron microscopy that an increase in the synthesis of temperature results in faster crystallization kinetics and in a better shape-control of the final Fe(IO{sub 3}){sub 3} nanorods. For initial microemulsions of fixed composition, room-temperature synthesis leads to bundles of 1–3 μm long nanorods, whereas shorter individual nanorods are obtained when the temperature is increased. Results are interpreted in terms of kinetically unfavorable mesoscale transformations due to the strong binding interactions with Triton molecules. The interplay between the nanorod crystallization kinetics and their corresponding unit cell deformation, evidenced by lattice parameter refinements, is attributed to a temperature-dependent adsorption of surfactants molecules at the organic–inorganic interface.

  12. Fabrication of La2Ti2O7 crystals using an alkali-metal molybdate flux growth method and their nitridability to form LaTiO2N crystals under a high-temperature NH3 atmosphere.

    Science.gov (United States)

    Hojamberdiev, Mirabbos; Yamaguchi, Akiko; Yubuta, Kunio; Oishi, Shuji; Teshima, Katsuya

    2015-04-06

    Flux growth is a promising method that allows one to control over the crystalline phase, crystal shape, crystal size, and crystal surface through the selection of a suitable flux. In this work, lanthanum titanate (La2Ti2O7) crystals with different morphologies were grown using the Na2MoO4, K2MoO4, NaCl, and mixed NaCl + K2MoO4 (molar ratio = 3:7) fluxes, and their nitridability to form LaTiO2N crystals under a high-temperature NH3 atmosphere was also investigated. The effects of the solute concentration and cooling rate on the growth of the La2Ti2O7 crystals were also studied. The X-ray diffraction results revealed that the {100} plane was dominant in the La2Ti2O7 platelet crystals grown using the alkali-metal molybdate fluxes. When the solute concentration was increased from 1 to 20 mol %, the average size of the crystals decreased without considerable alteration of the overall crystal morphology. The La2Ti2O7 crystals with the preferred ⟨010⟩ and ⟨001⟩ growth directions along the b and c axes were grown using the Na2MoO4 and K2MoO4 fluxes, respectively. Compared to the Na2MoO4 flux, the K2MoO4 flux did not show a cooling-rate-dependent effect on the growth of the La2Ti2O7 crystals. It was found that conversion of the La2Ti2O7 crystals to the LaTiO2N crystals was strongly dependent on the flux used to grow the precursor La2Ti2O7 crystals. That is, the La2Ti2O7 crystals grown using the K2MoO4 and NaCl fluxes were nearly completely converted into the LaTiO2N crystals, while conversion of the La2Ti2O7 crystals grown using the Na2MoO4 and mixed NaCl + K2MoO4 fluxes to the LaTiO2N crystals seemed to be not completed yet even after nitridation at 950 °C for 15 h using NH3 because of the larger crystal size and the presence of unintentional impurities (sodium and molybdenum from the flux) in the La2Ti2O7 crystal lattice. Nevertheless, the LaTiO2N crystals fabricated by nitriding the La2Ti2O7 crystals grown using the K2MoO4 and NaCl fluxes should be suitable for

  13. Temperature-driven massless Kane fermions in HgCdTe crystals

    Science.gov (United States)

    Teppe, F.; Marcinkiewicz, M.; Krishtopenko, S. S.; Ruffenach, S.; Consejo, C.; Kadykov, A. M.; Desrat, W.; But, D.; Knap, W.; Ludwig, J.; Moon, S.; Smirnov, D.; Orlita, M.; Jiang, Z.; Morozov, S. V.; Gavrilenko, V. I.; Mikhailov, N. N.; Dvoretskii, S. A.

    2016-08-01

    It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07+/-0.05) × 106 m s-1 remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe.

  14. Zero temperature magnetic phase diagram of Wigner crystal in anisotropic two-dimensional electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Chenggang [Department of Electrical Engineering, Princeton University, Princeton, NJ 08544 (United States)], E-mail: zcf@ornl.gov; Bhatt, Ravin N. [Department of Electrical Engineering, Princeton Center for Theoretical Physics, and Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, NJ 08544 (United States)

    2008-04-01

    We study the effect of mass anisotropy on the magnetic ordering of the Wigner crystal phase of low density electron systems in two dimensions at T=0. We apply the instanton approximation to various ring exchange processes, which includes the lowest order Gaussian fluctuations beyond the WKB approximation. The multi-particle exchange frequencies are calculated with effective mass anisotropy, both with and without ensuing lattice distortions. We find that when sufficient mass anisotropy is present, the two-spin exchange process between the nearest neighbors becomes more frequent than the three particle processes. Therefore, its corresponding antiferromagnetic exchange exceeds the ferromagnetic exchange from the three-spin process and becomes dominant. Numerical diagonalization of small clusters with two, three, and four-spin exchange terms shows a transition from a ferromagnetic to an antiferromagnetic ground state with increasing mass anisotropy.

  15. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, V. I., E-mail: ksv17@ism.ac.ru; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I. [Russian Academy of Sciences, Institute of Structural Macrokinetics and Materials Science (Russian Federation)

    2015-09-15

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide B{sub 15–x}C{sub x}, (1.5 ≤ x ≤ 3) and its magnesium derivative C{sub 4}B{sub 25}Mg{sub 1.42}. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from B{sub 12.9}C{sub 2.1} to B{sub 12.4}C{sub 2.6}.

  16. Crystal structure of pseudo-six-fold carbon dioxide phase II at high pressures and temperatures

    Science.gov (United States)

    Yoo, C. S.; Kohlmann, H.; Cynn, H.; Nicol, M. F.; Iota, V.; Lebihan, T.

    2002-03-01

    The crystal structure of CO2-II is determined to be tetragonal P42/mnm with z=2, with evidence of some tetragonal-to-orthorhombic (Pnnm) disorder in the ab plane. In this structure, carbon atoms are pseudo-sixfold-coordinated by oxygens; two oxygens are at an elongated intramolecular C=O bond distance, 1.331(3) Å, and four are at a collapsed intermolecular distance, 2.377(2) Å, at the apices of highly distorted octahedral. Strong intermolecular association results in a large splitting of the symmetric stretching ν1 mode and in a high bulk modulus 131.5 GPa. At 11 GPa, CO2-II is about 6.8% denser than CO2-III (Cmca).

  17. THE OPTION OF USING THE PARAMEDIAN FOREHEAD FLAP TO ELIMINATE DEFORMATIONS OF THE EXTERNAL NOSE AFTER TREATMENT OF CANCER (CLINICAL OBSERVATION

    Directory of Open Access Journals (Sweden)

    T. V. Ostrinskaya

    2014-01-01

    Full Text Available The article tells about the possibilities of recovering of cicatricial deformities and extensive defects of external nose with the using of paramedian forehead flap and free rib cartilage. Despite its antiquity, this method is still relevant, providing a good cosmetic and functional results.

  18. One-Step Synthesis of Hybrid Liquid-Crystal ZnO Nanoparticles: Existence of a Critical Temperature Associated with the Anisotropy of the Nanoparticles.

    Science.gov (United States)

    Zheng, Zhiqin; Butynska, Rémy; Serrano, Clara Valverde; Marty, Jean-Daniel; Mingotaud, Christophe; Kahn, Myrtil L

    2016-10-24

    Zinc oxide nanoparticles were obtained from the hydrolysis of an organometallic precursor in pure hexadecylamine. Interestingly, we demonstrate that the final (anisotropic or isotropic) shape of the nanoparticles is strongly correlated to the existence of a critical temperature. This suggests that the organization of the fatty amines is a paramount parameter in this synthesis. Moreover, the final hybrid ZnO materials systematically exhibit a liquid-crystal smectic phase, whereas no liquid-crystal phase was observed in the pristine reaction media. This simple process is, therefore, a direct and straightforward method to synthesize liquid-crystal hybrid materials.

  19. MORPHOLOGY EVOLUTION IN PTFE AS A FUNCTION OF MELT TIME AND TEMPERATURE Ⅰ. HIGH MOLECULAR WEIGHT SINGLE- AND MULTI-MOLECULE FOLDED CHAIN SINGLE CRYSTALS AND BAND STRUCTURES

    Institute of Scientific and Technical Information of China (English)

    J.Yang; K.L.Petersen; R.A.Williams; P.H.Geil; T.C.Long; P.Xu

    2005-01-01

    The effect of sintering dispersed dispersion and nano-emulsion particles of high molecular weight polytetrafluoroethylene (PTFE) on a substrate as a function of "melt" time and temperature is described. Folded chain single crystals parallel to the substrate and as ribbons on-edge (with double striations), as well as bands, are produced for longer sintering times; particle merger and diffusion of individual molecules, crystallizing as folded chain, single (or few) molecule,single crystals when "trapped" on the substrate by cooling occur for shorter sintering times. It is suggested the observed structures develop with sintering time, in a mesomorphic melt. The structure of the nascent particles is also discussed.

  20. Crystal structure of polymeric carbon nitride and the determination of its process-temperature-induced modifications

    Science.gov (United States)

    Tyborski, T.; Merschjann, C.; Orthmann, S.; Yang, F.; Lux-Steiner, M.-Ch; Schedel-Niedrig, Th

    2013-10-01

    Based on the arrangement of two-dimensional ‘melon’, we construct a unit cell for polymeric carbon nitride (PCN) synthesized via thermal polycondensation, whose theoretical diffraction powder pattern includes all major features measured in x-ray diffraction. With the help of this unit cell, we describe the process-temperature-induced crystallographic changes in PCN that occur within a temperature interval between 510 and 610 °C. We also discuss further potential modifications of the unit cell for PCN. It is found that both triazine- and heptazine-based g-C3N4 can only account for minor phases within the investigated synthesis products.

  1. Mapping the body surface temperature of cattle by infrared thermography.

    Science.gov (United States)

    Salles, Marcia Saladini Vieira; da Silva, Suelen Corrêa; Salles, Fernando André; Roma, Luiz Carlos; El Faro, Lenira; Bustos Mac Lean, Priscilla Ayleen; Lins de Oliveira, Celso Eduardo; Martello, Luciane Silva

    2016-12-01

    Infrared thermography (IRT) is an alternative non-invasive method that has been studied as a tool for identifying many physiological and pathological processes related to changes in body temperature. The objective of the present study was to evaluate the body surface temperature of Jersey dairy cattle in a thermoneutral environment in order to contribute to the determination of a body surface temperature pattern for animals of this breed in a situation of thermal comfort. Twenty-four Jersey heifers were used over a period of 35 days at APTA Brazil. Measurements were performed on all animals, starting with the physiological parameters. Body surface temperature was measured by IRT collecting images in different body regions: left and right eye area, right and left eye, caudal left foreleg, cranial left foreleg, right and left flank, and forehead. High correlations were observed between temperature and humidity index (THI) and right flank, left flank and forehead temperatures (0.85, 0.81, and 0.81, respectively). The IRT variables that exhibited the five highest correlation coefficients in principal component 1 were, in decreasing order: forehead (0.90), right flank (0.87), left flank (0.84), marker 1 caudal left foreleg (0.83), marker 2 caudal left foreleg (0.74). The THI showed a high correlation coefficient (0.88) and moderate to low correlations were observed for the physiological variables rectal temperature (0.43), and respiratory frequency (0.42). The thermal profile obtained indicates a surface temperature pattern for each region studied in a situation of thermal comfort and may contribute to studies investigating body surface temperature. Among the body regions studied, IRT forehead temperature showed the highest association with rectal temperature, and forehead and right and left flank temperatures are strongly associated with THI and may be adopted in future studies on thermoregulation and body heat production.

  2. How the Molecular Packing Affects the Room Temperature Phosphorescence in Pure Organic Compounds: Ingenious Molecular Design, Detailed Crystal Analysis, and Rational Theoretical Calculations.

    Science.gov (United States)

    Xie, Yujun; Ge, Yuwei; Peng, Qian; Li, Conggang; Li, Qianqian; Li, Zhen

    2017-02-21

    Long-lived phosphorescence at room temperature (RTP) from pure organic molecules is rare. Recent research reveals various crystalline organic molecules can realize RTP with lifetimes extending to the magnitude of second. There is little research on how molecular packing affecting RTP. Three compounds are designed with similar optical properties in solution, but tremendously different solid emission characteristics. By investigating the molecular packing arrangement in single crystals, it is found that the packing style of the compact face to face favors of long phosphorescence lifetime and high photoluminescence efficiency, with the lifetime up to 748 ms observed in the crystal of CPM ((9H-carbazol-9-yl)(phenyl)methanone). Theoretical calculation analysis also reveals this kind of packing style can remarkably reduce the singlet excited energy level and prompt electron communication between dimers. Surprisingly, CPM has two very similar single crystals, labeled as CPM and CPM-A, with almost identical crystal data, and the only difference is that molecules in CPM-A crystal take a little looser packing arrangement. X-ray diffraction and cross-polarization under magic spinning (13) C NMR spectra double confirm that they are different crystals. Interestingly, CPM-A crystal shows negligible RTP compared to the CPM crystal, once again proving that the packing style is critical to the RTP property.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Spin Dephasing as a Probe of Mode Temperature, Motional State Distributions, and Heating Rates in a 2D Ion Crystal

    CERN Document Server

    Sawyer, Brian C; Bollinger, John J

    2014-01-01

    We employ spin-dependent optical dipole forces to characterize the transverse center-of-mass (COM) motional mode of a two-dimensional Wigner crystal of hundreds of $^9$Be$^+$. By comparing the measured spin dephasing produced by the spin-dependent force with the predictions of a semiclassical dephasing model, we obtain absolute mode temperatures in excellent agreement with both the Doppler laser cooling limit and measurements obtained from a previously published technique (B. C. Sawyer et al. Phys. Rev. Lett. \\textbf{108}, 213003 (2012)). Furthermore, the structure of the dephasing histograms allows for discrimination between initial thermal and coherent states of motion. We also apply the techniques discussed here to measure, for the first time, the ambient heating rate of the COM mode of a 2D Coulomb crystal in a Penning trap. This measurement places an upper limit on the anomalous single-ion heating rate due to electric field noise from the trap electrode surfaces of $\\frac{d\\bar{n}}{dt}\\sim 5$ s$^{-1}$ fo...

  5. Uniaxial anisotropy and low-temperature antiferromagnetism of Mn{sub 2}BO{sub 4} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Kazak, N.V., E-mail: nat@iph.krasn.ru [L.V. Kirensky Institute of Physics, SB of RAS, Academgorodok 50/38, 660036 Krasnoyarsk (Russian Federation); Platunov, M.S. [L.V. Kirensky Institute of Physics, SB of RAS, Academgorodok 50/38, 660036 Krasnoyarsk (Russian Federation); Knyazev, Yu.V.; Ivanova, N.B. [Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Bayukov, O.A. [L.V. Kirensky Institute of Physics, SB of RAS, Academgorodok 50/38, 660036 Krasnoyarsk (Russian Federation); Vasiliev, A.D. [L.V. Kirensky Institute of Physics, SB of RAS, Academgorodok 50/38, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Bezmaternykh, L.N. [L.V. Kirensky Institute of Physics, SB of RAS, Academgorodok 50/38, 660036 Krasnoyarsk (Russian Federation); Nizhankovskii, V.I. [International Laboratory of High Magnetic Fields and Low Temperatures, PL-53421 Wroclaw (Poland); Gavrilkin, S.Yu. [P.N. Lebedev Physical Institute of RAS, 119991 Moscow (Russian Federation); Lamonova, K.V. [O.O. Galkin Donetsk Institute for Physics and Engineering, National Academy of Sciences of Ukraine, 83114 Donetsk (Ukraine); Ovchinnikov, S.G. [L.V. Kirensky Institute of Physics, SB of RAS, Academgorodok 50/38, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660074 Krasnoyarsk (Russian Federation); Siberian State Aerospace University, 660014 Krasnoyarsk (Russian Federation)

    2015-11-01

    The Mn{sub 2}BO{sub 4} single crystals have been grown by the flux technique. A careful study of the crystal structure and magnetic properties have been carried out. The antiferromagnetic transition at T{sub N}=26 K has been traced through the dc magnetization and specific heat temperature dependences. Magnetic uniaxial anisotropy has been found with easy axis magnetization lying in the ab-plane. The obtained value of effective magnetic moment is assigned to the non-quenched orbital moment of Jahn–Teller Mn{sup 3+} ions. The discussion of magnetic properties is based on the superexchange interaction calculations. - Highlights: • Single-crystalline samples of Mn{sub 2}BO{sub 4} of high quality were grown. The charge ordering oftype Mn{sup 2+}(1)-Mn{sup 3+}(2) was found. • The intrinsic antiferromagnetic transition at T{sub N}=26 K was observed through the magnetization and specific heat measurements. • An uniaxial magnetic anisotropy with easy axis of magnetization lying in ab-plane was found. • The superexchange interactions were calculated and the magnetic frustration was found.

  6. Spherulites and lithophysae—200 years of investigation on high-temperature crystallization domains in silica-rich volcanic rocks

    Science.gov (United States)

    Breitkreuz, Christoph

    2013-04-01

    High-temperature crystallization domains (HTCDs) including spherulites and lithophysae form during cooling of silica-rich lava and welded ignimbrites. Spherulites grow in silicate melts or hot glass and they display a radiating or microcrystalline texture, typically consisting of cristobalite, tridymite, and sanidine. Lithophysae are HTCDs comprising one or more cavities. This contribution reviews the research and discussions on HTCDs carried out over the last 200 years. The emphasis, here, is on lithophysae and summarizes current knowledge of their formation. A number of parameters influence the initiation and growth of lithophysae, as well as, their shapes and internal textures. The most likely cause of cavity formation is transient tensional stress that produces a mechanical opening and widening at the interface between the crystallization front and the host melt (e.g., where T > T g ). Cavity growth and expansion forced by rising vapor pressure is considered less important. In some cases, further growth of HTCD cavities results from vapor phase corrosion and brecciation.

  7. The influence of cobalt, tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys

    Science.gov (United States)

    Nathal, M. V.; Ebert, L. J.

    1985-10-01

    The influence of composition on the tensile and creep strength of [001] oriented nickel-base superalloy single crystals at temperatures near 1000 °C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247.* For alloys with the baseline refractory metal level of 3 wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta plus W totals, strength was independent of Co level. The effects of composition on properties were related to the microstructural features of the alloys. In general, high creep strength was associated with high levels of γ' volume fraction, γ-γ' lattice mismatch, and solid solution hardening.

  8. Compositional and temperature evolution of crystal structure of new thermoelectric compound LaOBiS2-xSex

    Science.gov (United States)

    Mizuguchi, Y.; Miura, A.; Nishida, A.; Miura, O.; Tadanaga, K.; Kumada, N.; Lee, C. H.; Magome, E.; Moriyoshi, C.; Kuroiwa, Y.

    2016-04-01

    We examined the crystal structure of the new thermoelectric material LaOBiS2-xSex, whose thermoelectric performance is enhanced by Se substitution, by using powder synchrotron X-ray diffraction and Rietveld refinement. The emergence of metallic conductivity and enhancement of the thermoelectric power factor of LaOBiS2-xSex can be explained with the higher in-plane chemical pressure caused by the increase of Se concentration at the in-plane Ch1 site (Ch = S, Se). High-temperature X-ray diffraction measurements for optimally substituted LaOBiSSe revealed anomalously large atomic displacement parameters (Uiso) for Bi and Ch atoms in the BiCh2 conduction layers. The anisotropic analysis of the atomic displacement parameters (U11 and U33) for the in-plane Bi and Ch1 sites suggested that Bi atoms exhibit large atomic displacement along the c-axis direction above 300 K, which could be the origin of the low thermal conductivity in LaOBiSSe. The large Bi vibration along the c-axis direction could be related to in-plane rattling, which is a new strategy for attaining low thermal conductivity and phonon-glass-electron-crystal states.

  9. Carbon monoxide oxidation on Pt single crystal electrodes: understanding the catalysis for low temperature fuel cells.

    Science.gov (United States)

    García, Gonzalo; Koper, Marc T M

    2011-08-01

    Herein the general concepts of fuel cells are discussed, with special attention to low temperature fuel cells working in alkaline media. Alkaline low temperature fuel cells could well be one of the energy sources in the next future. This technology has the potential to provide power to portable devices, transportation and stationary sectors. With the aim to solve the principal catalytic problems at the anode of low temperature fuel cells, a fundamental study of the mechanism and kinetics of carbon monoxide as well as water dissociation on stepped platinum surfaces in alkaline medium is discussed and compared with those in acidic media. Furthermore, cations involved as promoters for catalytic surface reactions are also considered. Therefore, the aim of the present work is not only to provide the new fundamental advances in the electrocatalysis field, but also to understand the reactions occurring at fuel cell catalysts, which may help to improve the fabrication of novel electrodes in order to enhance the performance and to decrease the cost of low temperature fuel cells.

  10. Giant volume magnetostriction in the Y{sub 2}Fe{sub 17} single crystal at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, S. A., E-mail: nikitin@phys.msu.ru; Pankratov, N. Yu.; Smarzhevskaya, A. I.; Politova, G. A. [Physics Faculty, Lomonosov Moscow State University, Moscow 119992 (Russian Federation); Pastushenkov, Yu. G., E-mail: yupast@mail.ru; Skokov, K. P. [Physics Faculty, Tver State University, 170100 Tver (Russian Federation); Moral, A. del [Laboratorio de Magnetismo de Slidos, Departamento de Fisica de Materia Condensada and Instituto de Ciencia de Materiales de Aragn, Facultad de Ciencias, Universidad de Zaragoza-C.S.I.C, E-50009 Zaragoza (Spain)

    2015-05-21

    An investigation of the Y{sub 2}Fe{sub 17} compound belonging to the class of intermetallic alloys of rare-earth and 3d-transition metals is presented. The magnetization, magnetostriction, and thermal expansion of the Y{sub 2}Fe{sub 17} single crystal were studied. The forced magnetostriction and magnetostriction constants were investigated in the temperature range of the magnetic ordering close to the room temperature. The giant field induced volume magnetostriction was discovered in the room temperature region in the magnetic field up to 1.2 T. The contributions of both anisotropic single-ion and isotropic pair exchange interactions to the volume magnetostriction and magnetostriction constants were determined. The experimental results were interpreted within the framework of the Standard Theory of Magnetostriction and the Landau thermodynamic theory. It was found out that the giant values of the volume magnetostriction were caused by the strong dependence of the 3d-electron Coulomb charge repulsion on the deformations and width of the 3d-electron energy band.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ravindra, A. V.; Behera, B. C.; Padhan, P. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Lebedev, O. I.; Prellier, W. [Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd du Marechal Juin, F-14050 Caen Cedex (France)

    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.

  12. Fabry-Perot based strain insensitive photonic crystal fiber modal interferometer for inline sensing of refractive index and temperature.

    Science.gov (United States)

    Dash, Jitendra Narayan; Jha, Rajan

    2015-12-10

    We report a highly stable, compact, strain insensitive inline microcavity-based solid-core photonic crystal fiber (SCPCF) modal interferometer for the determination of the refractive index (RI) of an analyte and its temperature. The interferometer is fabricated by splicing one end of SCPCF with single-mode fiber (SMF) and the other end with hollow-core PCF. This is followed by cleaving the part of the solid glass portion possibly present after the microcavity. The formation of the cavities at the end faces of the SCPCF results in reduction of the period of the interference pattern that helps in achieving distinctiveness in the measurement. Three sensor heads have been fabricated, and each has a different length of the collapsed region formed by splicing SMF with SCPCF. The response of the sensors is found to be sensitive to the length of this collapsed region between SMF and SCPCF with a sensitivity of 53 nm/RI unit (RIU) and resolution of 1.8×10(-4) RIU. The temperature response of the sensor is found to be linear, having a temperature sensitivity of 12 pm/°C. In addition to these findings, the effect of strain on the proposed structure is analyzed in both wavelength and intensity interrogation.

  13. Crystallization in Zr60Al15Ni25 bulk metallic glass subjected to rolling at room temperature

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The microstructure evolution of Zr60Al15Ni25 bulk metallic glass during rolling at room temperature is investigated by differential scanning calorimetry(DSC),high-resolution transmission electron microscopy(HRTEM) and selected area electronic diffraction(SAED).The HRTEM images show that shear bands are produced in the rolled specimens,indicating the essence of inhomogeneous deformation due to rolling,and that there exist nanocrystals with size of about 5-10 nm in the transition regions between the shear bands and the undeformed matrix in the rolled specimens with deformation degrees of 80% and 95%.Based on the polyhedral structure model and the shear transformation zone(STZ) theory,the influence of viscous flow,free volume,viscosity and the stress situation on the crystallization behaviors in the metallic glass during rolling is discussed.

  14. Elastic properties of the degenerate f.c.c. crystal of polydisperse soft dimers at zero temperature

    CERN Document Server

    Narojczyk, J W

    2015-01-01

    Elastic properties of soft, three-dimensional dimers, interacting through site-site n-inverse-power potential, are determined by computer simulations at zero temperature. The degenerate crystal of dimers exhibiting (Gaussian) size distribution of atomic diameters - i.e. size polydispersity - is studied at the molecular number density $1/\\sqrt{2}$; the distance between centers of atoms forming dimers is considered as a length unit. It is shown that, at the fixed number density of the dimers, increasing polydispersity causes, typically, an increase of pressure, elastic constants and Poisson's ratio; the latter is positive in most direction. A direction is found, however, in which the size polydispersity causes substantial decrease of Poisson's ratio, down to negative values for large $n$. Thus, the system is partially auxetic for large polydispersity and large n.

  15. Detection of antihydrogen with a Si- mu -strip and CsI-crystal detector at cryogenic temperature

    CERN Document Server

    Regenfus, C

    2001-01-01

    ATHENA, one of 3 experiments at the new low energy antiproton facility at CERN (AD), is designed for testing fundamental physic principles (CPT, Gravitation) to a high degree of precision by comparing cold antihydrogen to hydrogen. To monitor the production of the antihydrogen atoms and their spectroscopic response, a new detector dedicated for the endproducts of antihydrogen annihilations was developed. To meet the requirements of low temperature operation (77 K) in a high magnetic field, compact size, low power consumption and high granularity, a combination of two layers of each 16 double sided Si- mu -strip modules (16 cm long) was chosen, surrounded by 192 pure-CsI crystals (each approximately= 4 cm/sup 3/), which are read by UV sensitive photo diodes. The frontend electronics (working point 77 K), realised in VLSI CMOS technique, features a self triggering capability of independent sub modules.

  16. Spontaneous emission of semiconductor quantum dots in inverse opal SiO2 photonic crystals at different temperatures.

    Science.gov (United States)

    Yang, Peng; Yang, Yingshu; Wang, Yinghui; Gao, Jiechao; Sui, Ning; Chi, Xiaochun; Zou, Lu; Zhang, Han-Zhuang

    2016-02-01

    The photoluminescence (PL) characteristics of CdSe quantum dots (QDs) infiltrated into inverse opal SiO2 photonic crystals (PCs) are systemically studied. The special porous structure of inverse opal PCs enhanced the thermal exchange rate between the CdSe QDs and their surrounding environment. Finally, inverse opal SiO2 PCs suppressed the nonlinear PL enhancement of CdSe QDs in PCs excited by a continuum laser and effectively modulated the PL characteristics of CdSe QDs in PCs at high temperatures in comparison with that of CdSe QDs out of PCs. The final results are of benefit in further understanding the role of inverse opal PCs on the PL characteristics of QDs.

  17. Effect of irradiation temperature on crystallization of {alpha}-Fe induced by He irradiations in Fe{sub 80}B{sub 20} amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    San-noo, Toshimasa; Toriyama, Tamotsu; Wakabayashi, Hidehiko; Iijima, Hiroshi [Musashi Inst. of Tech., Tokyo (Japan); Hayashi, Nobuyuki; Sakamoto, Isao

    1997-03-01

    Since amorphous alloys are generally highly resistant to irradiation and their critical radiation dose is an order of magnitude higher for Fe-B amorphous alloy than Mo-methods, these alloys are expected to become applicable as for fusion reactor materials. The authors investigated {alpha}-Fe crystallization in an amorphous alloy, Fe{sub 80}B{sub 20} using internal conversion electron Moessbauer spectroscopy. The amount of {alpha}-Fe component was found to increase by raising the He-irradiation dose. The target part was modified to enable He ion radiation at a lower temperature (below 400 K) by cooling with Peltier element. Fe{sub 80}B{sub 20} amorphous alloy was cooled to keep the temperature at 300 K and exposed to 40 keV He ion at 1-3 x 10{sup 8} ions/cm{sup 2}. The amount of {alpha}-Fe crystal in each sample was determined. The crystal formation was not observed for He ion radiation below 2 x 10{sup 18} ions/cm{sup 2}, but that at 3 x 10{sup 8} ions/ cm{sup 2} produced a new phase ({delta} +0.40 mm/sec, {Delta} = 0.89 mm/sec). The decrease in the radiation temperature from 430 to 300 K resulted to extremely repress the production of {alpha}-Fe crystal, suggesting that the crystallization induced by He-radiation cascade is highly depending on the radiation temperature. (M.N.)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  19. Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Tang-Qing, E-mail: tangqing.yu@nyu.edu; Vanden-Eijnden, Eric, E-mail: eve2@cims.nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Chen, Pei-Yang; Chen, Ming [Department of Chemistry, New York University, New York, New York 10003 (United States); Samanta, Amit [Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA and Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Tuckerman, Mark, E-mail: mark.tuckerman@nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States); Department of Chemistry, New York University, New York, New York 10003 (United States); NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062 (China)

    2014-06-07

    The problem of predicting polymorphism in atomic and molecular crystals constitutes a significant challenge both experimentally and theoretically. From the theoretical viewpoint, polymorphism prediction falls into the general class of problems characterized by an underlying rough energy landscape, and consequently, free energy based enhanced sampling approaches can be brought to bear on the problem. In this paper, we build on a scheme previously introduced by two of the authors in which the lengths and angles of the supercell are targeted for enhanced sampling via temperature accelerated adiabatic free energy dynamics [T. Q. Yu and M. E. Tuckerman, Phys. Rev. Lett. 107, 015701 (2011)]. Here, that framework is expanded to include general order parameters that distinguish different crystalline arrangements as target collective variables for enhanced sampling. The resulting free energy surface, being of quite high dimension, is nontrivial to reconstruct, and we discuss one particular strategy for performing the free energy analysis. The method is applied to the study of polymorphism in xenon crystals at high pressure and temperature using the Steinhardt order parameters without and with the supercell included in the set of collective variables. The expected fcc and bcc structures are obtained, and when the supercell parameters are included as collective variables, we also find several new structures, including fcc states with hcp stacking faults. We also apply the new method to the solid-liquid phase transition in copper at 1300 K using the same Steinhardt order parameters. Our method is able to melt and refreeze the system repeatedly, and the free energy profile can be obtained with high efficiency.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Electronic liquid crystal state in the high-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 6.45}

    Energy Technology Data Exchange (ETDEWEB)

    Hinkov, V.; Haug, D.; Lin, C.T.; Keimer, B. [Max Planck Inst Festkorperforsch, D-70569 Stuttgart, (Germany); Fauque, B.; Bourges, P.; Sidis, Y. [CEA Saclay, CNRS, Lab Leon Brillouin, F-91191 Gif Sur Yvette, (France); Ivanov, A. [Inst Max Von Laue Paul Langevin, F-38042 Grenoble, (France); Bernhard, C. [Univ Fribourg, Dept Phys, CH-1700 Fribourg, (Switzerland); Bernhard, C. [Univ Fribourg, FriMat Ctr Nanomat, CH-1700 Fribourg, (Switzerland)

    2008-07-01

    Electronic phases with symmetry properties matching those of conventional liquid crystals have recently been discovered in transport experiments on semiconductor heterostructures and metal oxides at milli-kelvin temperatures. We report the spontaneous onset of a one- dimensional, incommensurate modulation of the spin system in the high-transition-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 6.45} upon cooling below similar to 150 kelvin, whereas static magnetic order is absent above 2 kelvin. The evolution of this modulation with temperature and doping parallels that of the in-plane anisotropy of the resistivity, indicating an electronic nematic phase that is stable over a wide temperature range. The results suggest that soft spin fluctuations are a microscopic route toward electronic liquid crystals and that nematic order can coexist with high-temperature superconductivity in under-doped cuprates. (authors)

  2. Low temperature crystallization of a stable phase of microspherical MoO 2

    Science.gov (United States)

    Naouel, R.; Touati, F.; Gharbi, N.

    2010-07-01

    MoO 2 microspheres were synthesized by a facile wet chemical method using the molybdenum trioxide as an inorganic precursor and paraphenylendiamine as a reducing agent and also a template, via a hydrothermal way. The as prepared product was characterized by XRD, SEM, TEM, DTA-TG, and IR. It was found that this product was composed by MoO 2 nanoparticles encapsulated into the organic shell microspheres with diameters of 1-3 μm. The influence of the temperature on the crystallinity of the products was investigated. Optimal conditions founded were: reaction temperature: 220 °C, reaction time: 72 h and cooling time remains unchanged. The possible formation mechanism of MoO 2 microspheres was also discussed.

  3. Polymorphism and the crystal structures of InSb at elevated temperature and pressure

    Science.gov (United States)

    Yu, S.-C.; Spain, I. L.; Skelton, E. F.

    1978-01-01

    The paper presents polycrystalline X-ray diffraction data for three high-pressure phases of InSb. The study employed two types of diamond-anvil pressure cells. The X-ray diffraction parameters were recorded at different fixed pressures and temperatures on flat film. The experiment utilized Zr-filtered Mo radiation. The intensities were estimated from the X-ray photographs using a semiautomated microdensitometer.

  4. Intermolecular hydrogen bonds: From temperature-driven proton transfer in molecular crystals to denaturation of DNA

    Indian Academy of Sciences (India)

    Mark Johnson

    2008-11-01

    We have combined neutron scattering and a range of numerical simulations to study hydrogen bonds in condensed matter. Two examples from a recent thesis will be presented. The first concerns proton transfer with increasing temperature in short inter-molecular hydrogen bonds [1,2]. These bonds have unique physical and chemical properties and are thought to play a fundamental role in processes like enzymatic catalysis. By combining elastic and inelastic neutron scattering results with ab initio, lattice dynamics and molecular dynamics simulations, low frequency lattice modes are identified which modulate the potential energy surface of the hydrogen bond proton and drive proton transfer. The second example concerns base-pair opening in DNA which is the fundamental physical process underlying biological processes like denaturation and transcription. We have used an emprical force field and a large scale, all-atom phonon calculation to gain insight into the base-pair opening modes and the apparent `energy gap' between the accepted frequencies for these modes (∼ 100 cm-1 or ∼ 140 K) and the temperature of the biological processes (room temperature to 100° C) [3]. Inelastic neutron scattering spectra on aligned, highly crystalline DNA samples, produced at the ILL, provide the reference data for evaluating the precision of these simulation results.

  5. XPS analysis for cubic boron nitride crystal synthesized under high pressure and high temperature using Li{sub 3}N as catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiaofei [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China); School of Materials Science and Engineering, Shandong University, Ji’nan 250061 (China); Xu, Bin, E-mail: xubin@sdjzu.edu.cn [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China); Zhang, Wen [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China); Cai, Zhichao [School of Materials Science and Engineering, Shandong University, Ji’nan 250061 (China); Wen, Zhenxing [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China)

    2014-12-01

    Highlights: • The cBN was synthesized by Li{sub 3}N as catalyst under high pressure and high temperature (HPHT). • The film coated on the as-grown cBN crystals was studied by XPS. • The electronic structure variation in the film was investigated. • The growth mechanism of cubic boron nitride crystal was analyzed briefly. - Abstract: Cubic boron nitride (cBN) single crystals are synthesized with lithium nitride (Li3N) as catalyst under high pressure and high temperature. The variation of electronic structures from boron nitride of different layers in coating film on the cBN single crystal has been investigated by X-ray photoelectron spectroscopy. Combining the atomic concentration analysis, it was shown that from the film/cBN crystal interface to the inner, the sp{sup 2} fractions are decreasing, and the sp{sup 3} fractions are increasing in the film at the same time. Moreover, by transmission electron microscopy, a lot of cBN microparticles are found in the interface. For there is no Li{sub 3}N in the film, it is possible that Li{sub 3}N first reacts with hexagonal boron nitride to produce Li{sub 3}BN{sub 2} during cBN crystals synthesis under high pressure and high temperature (HPHT). Boron and nitrogen atoms, required for cBN crystals growth, could come from the direct conversion from hexagonal boron nitride with the catalysis of Li{sub 3}BN{sub 2} under high pressure and high temperature, but not directly from the decomposition of Li{sub 3}BN{sub 2}.

  6. The effects of initial welding temperature and welding parameters on the crystallization behaviors of laser spot welded Zr-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huei-Sen, E-mail: huei@mail.isu.edu.tw [Department of Materials Science and Engineering, I-Shou University, Kaohsiung County 84001, Taiwan (China); Chiou, Mau-Sheng; Chen, Hou-Guang [Department of Materials Science and Engineering, I-Shou University, Kaohsiung County 84001, Taiwan (China); Jang, Jason Shian-Ching [Department of Mechanical Engineering, National Central University, Taoyuan County 32001, Taiwan (China)

    2011-09-15

    This study investigated the effects of the initial welding temperature (IWT) and welding parameters on the crystallization behaviors of laser spot welded (Zr{sub 53}Cu{sub 30}Ni{sub 9}Al{sub 8})Si{sub 0.5} bulk metallic glass (BMG). After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's micro-hardness test. The results showed that the heat-affected zone (HAZ) crystallization seemed avoidable under the room temperature welding process. However, with a combination of a lower energy input (welding Condition C) and a lower IWT (at 0 deg. C), a crystallization-free HAZ was finally obtained. Using the above welding condition into the refined heat flow equation, a critical retention time of 79 ms for the crystallization temperature interval was estimated. Moreover, as the laser welded samples came to crystallization in the HAZ, it was observed that a higher content of spherical-type crystalline precipitates tended to result in a higher value of glass transition temperature, T{sub g}. Therefore, the GFA indices, {Delta}T{sub x}, {gamma} and {gamma}{sub m}, were reduced. Furthermore, it was found that the micro-hardness value in the HAZ crystallization area was decreased due to the massive cracks formed in most parts of the crystalline precipitates. For a crystallization-free HAZ, the hardness seemed unaffected.

  7. Low temperature phase transition and crystal structure of CsMgPO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, Maria, E-mail: maria.p.orlova@gmail.com [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Khainakov, Sergey [Departamento de Química Física y Analítica, Universidad de Oviedo—CINN, 33006 Oviedo (Spain); Servicios Científico Técnicos, Universidad de Oviedo, 33006 Oviedo (Spain); Michailov, Dmitriy [Department of Chemistry, University of Nizhny Novgorod, 23 Gagarin av., Nizhny Novgorod 603950 (Russian Federation); Perfler, Lukas [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Langes, Christoph [Institute of Pharmacy, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Kahlenberg, Volker [Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, Innsbruck 6020 (Austria); Orlova, Albina [Department of Chemistry, University of Nizhny Novgorod, 23 Gagarin av., Nizhny Novgorod 603950 (Russian Federation)

    2015-01-15

    CsMgPO{sub 4} doped with radioisotopes is a promising compound for usage as a radioactive medical source. However, a low temperature phase transition at temperatures close to ambient conditions (∼−40 °C) was observed. Information about such kind of structural changes is important in order to understand whether it can cause any problem for medical use of this compound. The phase transition has been investigated in detail using synchrotron powder diffraction, Raman spectroscopy and DFT calculations. The structure undergoes a transformation from an orthorhombic modification, space group Pnma (RT phase) to a monoclinic polymorph, space group P2{sub 1}/n (LT phase). New LT modification adopts similar to RT but slightly distorted unit cell: a=9.58199(2) Å, b=8.95501(1) Å, c=5.50344(2) Å, β=90.68583(1)°, V=472.198(3) Å{sup 3}. CsMgPO{sub 4} belongs to the group of framework compounds and is made up of strictly alternating MgO{sub 4}- and PO{sub 4}-tetrahedra sharing vertices. The cesium counter cations are located in the resulting channel-like cavities. Upon the transformation a combined tilting of the tetrahedra is observed. A comparison with other phase transitions in ABW-type framework compounds is given. - Graphical abstract: Structural behavior of β-tridymite-type phosphate CsMgPO{sub 4}, considered as potential chemical form for radioactive Cs-source has been studied at near ambient temperatures. A phase transition at (∼−40 °C) has been found and investigated. It has been established that the known orthorhombic RT modification, space group Pnma, adopts a monoclinic cell with space group P2{sub 1}/n at low temperatures. In this paper, we present results of structural analysis of changes accompanying this phase transition and discuss its possible impact on the application properties. - Highlights: • β-Tridymite type phosphate CsMgPO{sub 4} undergoes so called translationengleiche phase transition of index 2 at −40 °C. • The structure

  8. Design, crystal growth, and physical properties of low-temperature thermoelectric materials

    Science.gov (United States)

    Fuccillo, Michael K.

    Thermoelectric materials serve as the foundation for two important modern technologies, namely 1) solid-state cooling, which enables small-area refrigeration without vibrations or moving parts, and 2) thermoelectric power generation, which has important implications for waste heat recovery and improved sources of alternative energy. Although the overall field of thermoelectrics research has been active for decades, and several consumer and industrial products have already been commercialized, the design and synthesis of new thermoelectrics that outperform long-standing state of the art materials has proven extremely challenging. This is particularly true for low-temperature refrigeration applications, which is the focus of this work; however, scientific advances in this area generally support power generation as well. In order to achieve more efficient materials for virtually all thermoelectric applications, improved materials design principles must be developed and synthetic procedures must be better understood. We aim to contribute to these goals by studying two classes of materials, namely 1) the tetradymites Bi2TeSe 2 and Bi2Te2Se, which are close relatives of state of the art thermoelectric cooling materials, and 2) Kondo insulating (-like) FeSb2 and FeSi, which possess anomalously enhanced low-temperature thermoelectric properties that arise from exotic electronic and magnetic properties. The organization of this dissertation is as follows: Chapter 1 is a brief perspective on solid-state chemistry. Chapter 2 presents experimental methods for synthesizing and characterizing thermoelectric materials. In Chapter 3, two original research projects are discussed: first, work on the tetradymite Bi2TeSe2 doped with Sb to achieve an n- to p-type transition, and second, the tetradymite Bi2Te2Se with chemical defects through two different methods. Chapter 4 gives the magnetic and transport properties of FeSb 2--RuSb2 alloys, a family of compounds exemplifying what we

  9. Low temperature phase transition and crystal structure of CsMgPO4

    Science.gov (United States)

    Orlova, Maria; Khainakov, Sergey; Michailov, Dmitriy; Perfler, Lukas; Langes, Christoph; Kahlenberg, Volker; Orlova, Albina

    2015-01-01

    CsMgPO4 doped with radioisotopes is a promising compound for usage as a radioactive medical source. However, a low temperature phase transition at temperatures close to ambient conditions (~-40 °C) was observed. Information about such kind of structural changes is important in order to understand whether it can cause any problem for medical use of this compound. The phase transition has been investigated in detail using synchrotron powder diffraction, Raman spectroscopy and DFT calculations. The structure undergoes a transformation from an orthorhombic modification, space group Pnma (RT phase) to a monoclinic polymorph, space group P21/n (LT phase). New LT modification adopts similar to RT but slightly distorted unit cell: a=9.58199(2) Å, b=8.95501(1) Å, c=5.50344(2) Å, β=90.68583(1)°, V=472.198(3) Å3. CsMgPO4 belongs to the group of framework compounds and is made up of strictly alternating MgO4- and PO4-tetrahedra sharing vertices. The cesium counter cations are located in the resulting channel-like cavities. Upon the transformation a combined tilting of the tetrahedra is observed. A comparison with other phase transitions in ABW-type framework compounds is given.

  10. The use of quasi-isothermal modulated temperature differential scanning calorimetry for the characterization of slow crystallization processes in lipid-based solid self-emulsifying systems.

    Science.gov (United States)

    Otun, Sarah O; Meehan, Elizabeth; Qi, Sheng; Craig, Duncan Q M

    2015-04-01

    Slow or incomplete crystallization may be a significant manufacturing issue for solid lipid-based dosage forms, yet little information is available on this phenomenon. In this investigation we suggest a novel means by which slow solidification may be monitored in Gelucire 44/14 using quasi-isothermal modulated temperature DSC (QiMTDSC). Conventional linear heating and cooling DSC methods were employed, along with hot stage microscopy (HSM), for basic thermal profiling of Gelucire 44/14. QiMTDSC experiments were performed on cooling from the melt, using a range of incremental decreases in temperature and isothermal measurement periods. DSC and HSM highlighted the main (primary) crystallization transition; solid fat content analysis and kinetic analysis were used to profile the solidification process. The heat capacity profile from QiMTDSC indicated that after an initial energetic primary crystallisation, the lipid underwent a slower period of crystallization which continued to manifest at much lower temperatures than indicated by standard DSC. We present evidence that Gelucire 44/14 undergoes an initial crystallization followed by a secondary, slower process. QIMTDSC appears to be a promising tool in the investigation of this secondary crystallization process.

  11. Discovery of room-temperature spin-glass behaviors in two-dimensional oriented attached single crystals

    Science.gov (United States)

    Ma, Ji; Chen, Kezheng

    2016-05-01

    In this study, room-temperature spin-glass behaviors were observed in flake-like oriented attached hematite (α-Fe2O3) and iron phosphate hydroxide hydrate (Fe5(PO4)4(OH)3·2H2O) single crystals. Remarkably, their coercivity (HC) values were found to be almost invariable at various given temperatures from 5 to 300 K. The spin topographic map in these flakes was assumed as superparamagnetic (SPM) "islands" isolated by spin glass (SG)-like "bridges". A spin-glass model was then proposed to demonstrate the spin frustration within these "bridges", which were formed by the staggered atomic planes in the uneven surfaces belonging to different attached nanoparticles. Under the spatial limitation and coupling shield of these "bridges", the SPM "islands" were found to be collectively frozen to form a superspin glass (SSG) state below 80 K in weak applied magnetic fields; whereas, when strong magnetic fields were applied, the magnetic coupling of these "islands" would become superferromagnetic (SFM) through tunneling superexchange, so that, these SFM spins could antiferromagnetically couple with the SG-like "bridges" to yield pronounced exchange bias (EB) effect.

  12. Temperature dependences of the Hall and magnetoresistance coefficients of vanadium and tantalum single crystals: Anisotropy of electron-phonon scattering

    Energy Technology Data Exchange (ETDEWEB)

    Volkenshtein, N.V.; Veprev, A.G.; Startsev, V.E.; Cherepanov, A.N.; Cherepanov, V.I.

    1985-07-01

    The Hall coefficient R/sub H/(T), transverse magnetoresistance rho/sub c/(T), and the temperature-dependent component rho/sub c/(T) of the impurity electrical resistance are measured as functions of temperature T = 4.2--300 K for vanadium and tantalum single crystals with rho/sub 273.2//rho/sub 4.2/ = 1350 and 500, respectively. The curves R/sub H/(T) have minima at T0 = 33 and 24 K for vanadium and tantalum, respectively, which indicates that the electron-phonon scattering is anisotropic. The anisotropy is caused by ''intersheet'' electron-phonon processes in which the charge carriers are scattered between the open hole surface GAMMAH3h and the closed hole ellipsoids N3h. The curves r/sub H/(T) and rho/sub c/(T) have maxima for T close to T0. The observed extrema have a common physical origin and can be explained by the Kagan-Zhernov-Flerov theory, which postulates that the nonequilibrium part of the electron distribution function is anisotropic. The observed dependence R/sub H/(T) for T>T0 agrees with calculations of R/sub H/(T) for vanadium based on realistic models for the electron and phonon spectra, including the anisotropy for the electron-phonon interaction matrix element.

  13. Practical approach for measuring heat capacity of pharmaceutical crystals/glasses by modulated-temperature differential scanning calorimetry.

    Science.gov (United States)

    Harada, Takuji; Kawakami, Kohsaku; Yoshihashi, Yasuo; Yonemochi, Etsuo; Terada, Katsuhide; Moriyama, Hiroshi

    2013-01-01

    A practical protocol to obtain accurate heat capacity values of pharmaceutical compounds using modulated-temperature differential scanning calorimetry was established. Three pharmaceutical compounds, acetaminophen, indomethacin, and tri-O-methyl-β-cyclodextrin were used as model compounds. Powder samples did not produce reproducible results, presumably due to inclusion of gas in gap of powders that influenced the measured heat capacity and thermal homogeneity in the sample. Thus, the amorphous characteristics were evaluated using quench-cooled samples. Crystalline samples were obtained by partially melting the sample to allow recrystallization using the residual crystal as a template. Optimum sample mass was about 10 mg. Use of too small sample size resulted in poor reproducibility due to localization of the sample in the pan, while too large size resulted in low heat capacity values probably because of heterogeneity of the sample temperature. The optimum modulation period was in the range of 60 s and 90 s, to which the ramp rates of 2°C/min and 1°C/min, respectively, were applied. The ramp amplitude was less significant in the evaluation. This information should help in comprehending basic characteristics of pharmaceutical compounds.

  14. Coupling of temperature with pressure induced initial decomposition mechanisms of two molecular crystals: An ab initio molecular dynamics study

    Indian Academy of Sciences (India)

    QIONG WU; DONG XIANG; GUOLIN XIONG; WEIHUA ZHU; HEMING XIAO

    2016-05-01

    Ab initio molecular dynamics simulations were performed to study the initiation of decompositionand formation of first products of two molecular crystals pentaerythritol tetranitrate (PETN) and 5-nitro-2,4-dihydro-1,2,4-triazole-3-one (NTO) under thermal decomposition temperature (475 K for PETN and 531 Kfor NTO) coupled with different pressures (1-5 GPa). The pressure effects on the initial decomposition stepsand initially generated products on PETN and NTO were very different. PETN was triggered by C-H... O intermolecular hydrogen transfer. The initial decomposition mechanism was independent of the pressure. ForNTO, two different initial decomposition mechanisms were found. At 1, 2, and 3 GPa, it was triggered by NH....O intermolecular hydrogen transfer, while at 4 and 5 GPa, it was triggered by N-H.....N intermolecularhydrogen transfer. This indicates that the initial decomposition mechanism was dependent on the pressure.Our study may provide new insights into initial mechanisms and decomposition reactions of molecular crystalexplosives under thermal decomposition temperature coupled with different pressures with details at atomiclevel.

  15. Crystal structure, hydrogen bonding, and {sup 81}Br NQR of low-temperature phase of 4-aminopyridinium tetrabromoantimonate (3)

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Masao [Kobe Univ., Faculty of Science, Dept. of Chemistry, Kobe, Hyogo (Japan); Terao, Hiromitsu [Tokushima Univ., Faculty of Integrated Arts and Sciences, Dept. of Chemistry, Tokushima (Japan); Fuess, Hartmut; Svoboda, Ingrid; Ehrenberg, Helmut [Darmstadt Univ. of Technology, Inst. for Materials Science, Darmstadt (Germany)

    2003-04-01

    The crystal structure of the low-temperature phase (LTP) of the title compound was determined at 220 K (monoclinic, P2{sub 1/c}). The 4-aminopyridinium cations (4-NH{sub 2}C{sub 5}H{sub 4}NH{sup +}) were found to be ordered in LTP, while being severely disordered in the room-temperature phase (monoclinic, C2/c). The tetrabromoantimonate anions (SbBr{sub 4}{sup -}) were incorporated into the infinite polyanion chains of irregular SbBr{sub 6} octahedra with two-edges sharing. The trans-Br-Sb-Br moiety in the SbBr{sub 4}{sup -} anion was approximately symmetric differing from the asymmetric Br-Sb{center_dot}{center_dot}{center_dot}Br moiety found in LTP of pyridinium tetrabromoantimonate (3). The N-H moieties in both of the pyridine ring and the amino (-NH{sub 2}) group participate in the formation of N-H{center_dot}{center_dot}{center_dot}Br hydrogen bonds. It was shown that the {sup 81}Br NQR spectrum of LTP is closely related to the anion structure and the hydrogen bonds. The distinctive anion structures, as well as the different types of phase transitions, exhibited by the PyH and 4-APyH salts, seemed to be attributable to the difference in the hydrogen bond scheme between them. (author)

  16. Cr-MCM-41 Molecular Sieves Crystallized at Room Temperature for Reaction of Ethane with CO2

    Institute of Scientific and Technical Information of China (English)

    Yanan Li; Xin He; Shujie Wu; Ke Zhang; Guangdong Zhou; Jie Liu; Kaiji Zhen; Tonghao Wu; Tiexin Cheng

    2005-01-01

    A series of Cr-containing MCM-41 molecular sieves crystallized at room temperature with a hexagonal and well-ordered structure were synthesized. XRD, FT-IR and DRS UV-Vis techniques were used to characterize the samples. The results indicate incorporation of Cr into the MCM-41 framework,and dispersion of some Cr2O3 on the surface or/and in the bulk of the MCM-41. Test of catalytic properties of the series of samples for the topic reaction was carried out using a continuous-flow fixed-bed quartz reactor. Factors influencing the catalytic performance for this title reaction, such as Cr/Si ratio in MCM-41 and reaction temperature were investigated. The experimental results indicate that over the 5%CrMCM-41 a 43.27% conversion of ethane and a 86.70% selectivity for ethylene were achieved in the ethane dehydrogenation with CO2 to ethylene at 973 K. It is suggested that both Cr6+ and Cr3+ are the catalytic activity center.

  17. Stress-induced melting of crystals in natural rubber: a new way to tailor the transition temperature of shape memory polymers.

    Science.gov (United States)

    Heuwers, Benjamin; Quitmann, Dominik; Katzenberg, Frank; Tiller, Joerg C

    2012-09-26

    Lightly cross-linked natural rubber (NR, cis-1,4-polyisoprene) was found to be an exceptional cold programmable shape memory polymer (SMP) with strain storage of up to 1000%. These networks are stabilized by strain-induced crystals. Here, we explore the influence of mechanical stress applied perpendicular to the elongation direction of the network on the stability of these crystals. We found that the material recovers its original shape at a critical transverse stress. It could be shown that this is due to a disruption of the strain-stabilizing crystals, which represents a completely new trigger for SMPs. The variation of transverse stress allows tuning of the trigger temperature T(trig) (σ) in a range of 45 to 0 °C, which is the first example of manipulating the transition of a crystal-stabilized SMP after programming.

  18. Monte Carlo simulations of temperature-programmed and isothermal desorption from single-crystal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lombardo, S.J. (California Inst. of Tech., Pasadena, CA (USA). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (USA))

    1990-08-01

    The kinetics of temperature-programmed and isothermal desorption have been simulated with a Monte Carlo model. Included in the model are the elementary steps of adsorption, surface diffusion, and desorption. Interactions between adsorbates and the metal as well as interactions between the adsorbates are taken into account with the Bond-Order-Conservation-Morse-Potential method. The shape, number, and location of the TPD peaks predicted by the simulations is shown to be sensitive to the binding energy, coverage, and coordination of the adsorbates. In addition, the occurrence of lateral interactions between adsorbates is seen to strongly effect the distribution of adsorbates is seen to strongly effect the distribution of adsorbates on the surface. Temperature-programmed desorption spectra of a single type of adsorbate have been simulated for the following adsorbate-metal systems: CO on Pd(100); H{sub 2} on Mo(100); and H{sub 2} on Ni(111). The model predictions are in good agreement with experimental observation. TPD spectra have also been simulated for two species coadsorbed on a surface; the model predictions are in qualitative agreement with the experimental results for H{sub 2} coadsorbed with strongly bound atomic species on Mo(100) and Fe(100) surfaces as well as for CO and H{sub 2} coadsorbed on Ni(100) and Rh(100) surfaces. Finally, the desorption kinetics of CO from Pd(100) and Ni(100) in the presence of gas-phase CO have been examined. The effect of pressure is seen to lead to an increase in the rate of desorption relative to the rate observed in the absence of gas-phase CO. This increase arises as a consequence of higher coverages and therefore stronger lateral interactions between the adsorbed CO molecules.

  19. Giant room-temperature barocaloric effect and pressure-mediated electrocaloric effect in BaTiO{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry Cedex 92295 (France); Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Wei, Jie [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry Cedex 92295 (France); Electronic Materials Research Laboratory, Key Laboratory of Ministry of Education, Xi' an Jiaotong University, Xi' an 710049 (China); Janolin, Pierre-Eymeric; Infante, Ingrid C.; Dkhil, Brahim, E-mail: brahim.dkhil@ecp.fr, E-mail: xlou03@mail.xjtu.edu.cn [Laboratoire Structures, Propriétés et Modélisation des Solides, UMR 8580 CNRS-Ecole Centrale Paris, Grande Voie des Vignes, Châtenay-Malabry Cedex 92295 (France); Lou, Xiaojie, E-mail: brahim.dkhil@ecp.fr, E-mail: xlou03@mail.xjtu.edu.cn [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2014-04-21

    Barocaloric effect in BaTiO{sub 3} single crystal is studied by a thermodynamic phenomenological model. It is demonstrated that a giant barocaloric effect can be achieved near room temperature with an adiabatic temperature change of more than 3 K and a temperature span about 50 K. As expected, the electrocaloric peak can be shifted towards room temperature by pressure. However, a slight reduction of the electrocaloric peak is found in contrast to relaxor ferroelectrics and LiNbO{sub 3}. We believe that our findings could open a potential route by combining the barocaloric effect and pressure-mediated electrocaloric effect in BaTiO{sub 3} single crystal for cooling devices.

  20. Temperature dependence of dielectric and electromechanical properties of (K,Na)(Nb,Ta)O3 single crystal and corresponding domain structure evolution.

    Science.gov (United States)

    Zheng, Limei; Wang, Junjun; Huo, Xiaoqing; Wang, Rui; Sang, Shijing; Li, Shiyang; Zheng, Peng; Cao, Wenwu

    2014-07-28

    Domain structures and their evolution with temperature in the [001] C oriented (K,Na)(Nb,Ta)O3 (KNNT) single crystal have been studied before and after poling by polarizing light microscopy. The results indicate that the KNNT crystal is difficult to be completely poled by the room temperature poling process. The domain structure is rather stable in the orthorhombic phase, but exhibits substantial changes near the phase transition temperatures TO-T and TC. Narrower stripe domains are formed during both the orthorhombic-tetragonal and tetragonal-cubic phase transition processes, no intermediate phases were found during the phase transitions. The temperature dependence of the dielectric and piezoelectric properties were measured, and the influence of domain structures on the dielectric and electromechanical properties were quantified.

  1. Energy-dependent light quenching in CaWO{sub 4} crystals at mK temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Strauss, R. [Technische Universitaet Muenchen, Physik-Department, Garching (Germany); Max-Planck-Institut fuer Physik, Munich (Germany); Angloher, G.; Hauff, D.; Petricca, F.; Proebst, F.; Reindl, F.; Seidel, W.; Stodolsky, L.; Tanzke, A.; Wuestrich, M. [Max-Planck-Institut fuer Physik, Munich (Germany); Bento, A. [Universidade de Coimbra, CIUC, Departamento de Fisica, Coimbra (Portugal); Bucci, C.; Canonica, L.; Gorla, P.; Schaeffner, K. [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Carli, W. [Ludwig-Maximilians-Universitaet Muenchen, Maier-Leibnitz-Laboratorium, Garching (Germany); Erb, A. [Technische Universitaet Muenchen, Physik-Department, Garching (Germany); Walther-Meissner-Institut fuer Tieftemperaturforschung, Garching (Germany); Feilitzsch, F. von; Guetlein, A.; Hellgartner, D.; Lanfranchi, J.C.; Muenster, A.; Potzel, W.; Roth, S.; Schoenert, S.; Sivers, M. von; Ulrich, A.; Wawoczny, S.; Willers, M.; Zoeller, A. [Technische Universitaet Muenchen, Physik-Department, Garching (Germany); Jochum, J.; Loebell, J.; Rottler, K.; Sailer, C.; Scholl, S.; Strandhagen, C.; Uffinger, M.; Usherov, I. [Eberhard-Karls-Universitaet Tuebingen, Physikalisches Institut, Tuebingen (Germany); Kraus, H. [University of Oxford, Department of Physics, Oxford (United Kingdom); Schieck, J. [Institut fuer Hochenergiephysik der Oesterreichischen Akademie der Wissenschaften, Vienna (Austria)

    2014-07-15

    Scintillating CaWO{sub 4} single crystals are a promising multi-element target for rare-event searches and are currently used in the direct dark matter experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers). The relative light output of different particle interactions in CaWO{sub 4} is quantified by quenching factors (QFs). These are essential for an active background discrimination and the identification of a possible signal induced by weakly interacting massive particles (WIMPs). We present the first precise measurements of the QFs of O, Ca and W at mK temperatures by irradiating a cryogenic detector with a fast neutron beam. A clear energy dependence of the QF of O and, less pronounced, of Ca was observed for the first time. Furthermore, in CRESST neutron-calibration data a variation of the QFs among different CaWO{sub 4} single crystals was found. For typical CRESST detectors the QFs in the region-of-interest (10-40 keV) are QF{sub O}{sup ROI} = (11.2 ± 0.5) %, QF{sub Ca}{sup ROI} = (5.94 ± 0.49)%and QF{sub W}{sup ROI} = (1.72 ± 0.21) %. The latest CRESST data (run32) is reanalyzed using these fundamentally new results on light quenching in CaWO{sub 4} having moderate influence on the WIMP analysis. Their relevance for future CRESST runs and for the clarification of previously published results of direct dark matter experiments is emphasised. (orig.)

  2. Low-temperature phases of rubidium silver iodide: crystal structures and dynamics of the mobile silver ions.

    Science.gov (United States)

    Funke, Klaus; Banhatti, Radha D; Wilmer, Dirk; Dinnebier, Robert; Fitch, Andrew; Jansen, Martin

    2006-03-09

    Recently, broad-band conductivity spectra have been taken in the low-temperature gamma-phase of the archetypal fast ion conductor RbAg4I5. Attempts to reproduce the experimental data in a simple model calculation have led to the conclusion that strictly localized displacive movements of interacting ionic charge carriers should play an important role in the low-temperature phase. However, with no detailed structural study of gamma-RbAg4I5 available, the relevant processes could not be identified within the crystal structure. This state of affairs has triggered the present investigation of the structures of all three phases of rubidium silver iodide. Powder diffraction data of RbAg4I5 have been collected at the high-resolution powder diffractometer at ID31 at the European Synchrotron Radiation Facility (ESRF). The structure of the gamma-phase has been solved by successive Rietveld refinements in combination with difference Fourier analyses. The same structural principle is found to prevail in all three phases, interconnected distorted RbI6 octahedra forming a three-dimensional framework, which undergoes only displacive structural changes during the alpha-beta and beta-gamma phase transitions. With decreasing temperature, the disorder in the silver sublattice is found to decrease, and a clustering of the disordered silver ions is found to develop. In the gamma-phase, "pockets" containing partially occupied silver sites have been identified, and it is suggested that the localized displacive motion detected by conductivity spectroscopy is performed by the silver ions located within these pockets.

  3. Time temperature transformation diagram for secondary crystal products of Co-based Co-Fe-B-Si-Nb-Mn soft magnetic nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    DeGeorge, V., E-mail: vdegeorge@cmu.edu; Zoghlin, E.; Keylin, V.; McHenry, M. [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2015-05-07

    Secondary crystallization is the subject of much investigation in magnetic amorphous and nanocomposites (MANCs) as it limits the long term and thermal stability of their operation in device applications, including power electronics, sensors, and electric motors. Secondary crystal products [Blazquez et al., Philos. Mag. Lett. 82(7), 409–417 (2002); Ohodnicki et al., Phys. Rev. B 78, 144414 (2008); Willard et al., Metall. Mater. Trans. A 38, 725 (2007)], nanostructure and crystallization kinetics [Hsiao et al., IEEE Trans. Magn. 38(5), 3039 (2002); McHenry et al., Scr. Mater. 48(7), 881 (2003)], and onset temperatures and activation energies [Ohodnicki et al., Acta. Mater. 57, 87 (2009); Long et al., J. Appl. Phys. 101, 09N114 (2007)] at constant heating have been reported for similar alloys. However, a time-temperature-transformation (TTT) diagram for isothermal crystallization, more typical of application environments, has not been reported in literature. Here, a TTT diagram for the Co based, Co-Fe-Si-Nb-B-Mn MANC system is presented, along with a method for determining such. The method accounts for the presence of primary crystal phases and yields crystal fraction of secondary phase(s) by using a novel four stage heating profile. The diagram, affirmed by Kissinger activation energy analysis, reports thermal stability of the MANC for millennia at conventional device operating temperatures, and stability limits less than a minute at elevated temperatures. Both extremes are necessary to be able to avoid secondary crystalline products and establish operating limits for this mechanically attractive, high induction soft magnetic nanocomposite.

  4. Temperature- and Pressure-Induced Changes in the Crystal Structure of Sr(NHsub>3sub>)>8sub>Cl>2sub>

    DEFF Research Database (Denmark)

    Johnsen, Rune; Jensen, Peter Bjerre; Norby, Poul

    2014-01-01

    ABSTRACT: The structural transformations occurring in the crystal structure of strontium chloride octamine, Sr(NH3)8Cl2, as a function of temperature and pressure of ammonia gas were studied by detailed in situ X-ray powder diffraction (XRPD) and supported by density functional theory (DFT) calcu...

  5. Core temperature in super-Gaussian pumped air-clad photonic crystal fiber lasers compared with double-clad fiber lasers

    Indian Academy of Sciences (India)

    P Elahi; H Nadgaran; F Kalantarifard

    2007-03-01

    In this paper we investigate the core temperature of air-clad photonic crystal fiber (PCF) lasers pumped by a super-Gaussian (SG) source of order four. The results are compared with conventional double-clad fiber (DCF) lasers pumped by the same super-Gaussian and by top-hat pump profiles.

  6. influence of the molecular structures on the high-pressure and low-temperature phase transitions of plastic crystals.

    Science.gov (United States)

    Wunschel, Markus; Dinnebier, Robert E; Carlson, Stefan; Bernatowicz, Piotr; van Smaalen, Sander

    2003-02-01

    The crystal structures of tert-butyl-tris(trimethylsilyl)silane, Si[C(CH(3))(3)](1)[Si(CH(3))(3)](3) (Bu1), and di-tert-butyl-bis(trimethylsilyl)silane, Si[C(CH(3))(3)](2)[Si(CH(3))(3)](2) (Bu2), at room temperature and at 105 K have been determined by X-ray powder diffraction; the high-pressure behavior for pressures between 0 and 5 GPa is reported. The room-temperature structures have cubic Fm3m symmetry (Z = 4) with a = 13.2645 (2) A, V = 2333.87 (4) A(3) for Bu1 and a = 12.9673 (1) A, V = 2180.46 (3) A(3) for Bu2. The molecules are arranged in a cubic close packing (c.c.p.) and exhibit at least 48-fold orientational disorder. Upon cooling both compounds undergo a first-order phase transition at temperatures T(c) = 230 (5) K (Bu1) and T(c) = 250 (5) K (Bu2) into monoclinic structures with space group P2(1)/n. The structures at 105 K have a = 17.317 (1), b = 15.598 (1), c = 16.385 (1) A, gamma = 109.477 (4) degrees, V = 4172.7 (8) A(3) and Z = 8 for Bu1and a = 17.0089 (9), b = 15.3159 (8), c = 15.9325 (8) A, gamma = 110.343 (3) degrees, V = 3891.7 (5) A(3) and Z = 8 for Bu2. The severe disorder of the room-temperature phase is significantly decreased and only a two- or threefold rotational disorder of the molecules remains at 105 K. First-order phase transitions have been observed at pressures of 0.13-0.28 GPa for Bu1 and 0.20-0.24 GPa for Bu2. The high-pressure structures are isostructural to the low-temperature structures. The pressure dependencies of the unit-cell Volumes were fitted with Vinet equations of state and the bulk moduli were obtained. At still higher pressures further anomalies in the pressure dependencies of the lattice parameters were observed. These anomalies are explained as additional disorder-order phase transitions.

  7. Effects of temperature gradient in the growth of Si0.5Ge0.5 crystals by the traveling liquidus-zone method on board the International Space Station

    Science.gov (United States)

    Kinoshita, K.; Arai, Y.; Inatomi, Y.; Tsukada, T.; Miyata, H.; Tanaka, R.

    2016-12-01

    Si0.5Ge0.5 crystals were grown at two different temperature gradients on board the International Space Station (ISS) using the traveling liquidus-zone (TLZ) method and effects of temperature gradient on crystal quality were investigated. Although average axial Ge concentration profile was not affected by the temperature gradient, crystal quality was affected greatly. Single crystal length was shortened and constitutional supercooling (CS) is shown to occur more easily at higher temperature gradient. The calculated degree of CS based on the solute concentration profile in the melt and phase diagram data is about 4 times larger when the temperature gradient is twice, which supports the experimental results. Instability at high temperature gradient is unique to the TLZ method and is not common to other crystal growth methods such as the directional solidification method and Czochralski method.

  8. Effects of B{sub 2}O{sub 3} content and sintering temperature on crystallization and microstructure of CBS glass–ceramic coatings

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pengyang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Wang, Shubin, E-mail: shubinwang@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials and Engneering, Beihang University, Beijing 100191 (China); Liu, Jianggao; Feng, Mengjie; Yang, Xinwang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-11-30

    Graphical abstract: (a) TEM photogram of CG3 sintered at 800 °C, crystals are obvious; (b) the XRD patterns of CG3 glass samples sintered at various temperatures; (c) SEM photogram of CG3 sintered at 800 °C; (d) Kissinger, Augis–Bennett and Ozawa kinetics plots of CG3 glass samples. - Highlights: • Combining sol–gel method with direct sintering method to reduce the temperature of coatings formation. • Characterizing CaO–SiO{sub 2}–B{sub 2}O{sub 3} glass–ceramic coatings on porous substrates. • Surface crystallization of CBS glass–ceramic coatings: nucleation and kinetics. • Activation energies for crystal growth in CBS glass–ceramics with different contents of B{sub 2}O{sub 3}. - Abstract: Borosilicate glass–ceramics precursors with varying compositional ratios in the CaO–SiO{sub 2}–B{sub 2}O{sub 3} (CBS) system were synthesized by sol–gel method. The precursors were calcined at 1200 °C for 2 h to form glass powders. The glass–ceramics were prepared by overlaying glass slurries on the substrates before sintering at different temperatures. The as-prepared glasses and glass–ceramics were characterized by differential scanning calorimetry and X-ray diffraction. The crystallization activation energies (E{sub c}) were calculated using the Kissinger method from DSC results. The morphology and crystallization behavior of the glass–ceramics were monitored by scanning electron microscopy. Both glass transition and crystallization temperatures decreased, however, the metastable zone increased. The E{sub c} values of CBS glasses and glass–ceramics were 254.1, 173.2 and 164.4 kJ/mol with increasing B{sub 2}O{sub 3} content, whereas that of the calcined G3 glass was 104.9 kJ/mol. Finally, the coatings were prepared at a low temperature (700 °C). The crystals that grew on the surface of multilayer coatings demonstrated heterogeneous surface nucleation and crystallization after heat-treatment from 700 °C to 850 °C for 4 h.

  9. Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5.

    Science.gov (United States)

    Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

    2016-08-25

    We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

  10. Investigation on crystalline perfection, optical transmittance, birefringence, temperature-dependent refractive index, laser damage threshold and pyroelectric characteristics of inversely soluble lithium sulfate monohydrate single crystals

    Science.gov (United States)

    Silambarasan, A.; Rajesh, P.; Bhatt, Rajeev; Bhaumik, Indranil; Karnal, A. K.; Ramasamy, P.; Gupta, P. K.

    2016-08-01

    Bulk prismatic lithium sulfate monohydrate (LSMH) single crystals were grown by seed rotation with slow heating method from aqueous solution. Small FWHM obtained from high-resolution X-ray diffraction spectrum shows that the crystals grown by this method have less defects and absence of low-angle grain boundaries. The high transmittance and low reflectance nature of the grown crystal was observed using UV-Vis-NIR spectrometer. The principal refractive indices of a LSMH crystal have been measured by a prism coupling method for the wavelengths of 0.407, 0.532, 0.828, 1.064 and 1.551 µm at room temperature, and Sellmeier equations are determined from the fitting of the data point. The refractive index data confirm that LSMH crystal is negative biaxial and the optic axis lies in YZ plane with an angle (2 V y ) of 51.74° with respect to y axis at 532 nm wavelength. The thermo-optic coefficients were determined from the temperature-dependent refractive indices measured in the range of 30-125 °C for the wavelengths of 532 and 1064 nm. The surface laser damage threshold studies reveal the higher optical radiation stability against 532-nm laser. The pyroelectric coefficients and pyroelectric figure of merit were determined from the pyroelectric current measurement by the Byer and Roundy method.

  11. Low-temperature (˜180 °C) position-controlled lateral solid-phase crystallization of GeSn with laser-anneal seeding

    Science.gov (United States)

    Matsumura, Ryo; Chikita, Hironori; Kai, Yuki; Sadoh, Taizoh; Ikenoue, Hiroshi; Miyao, Masanobu

    2015-12-01

    To realize next-generation flexible thin-film devices, solid-phase crystallization (SPC) of amorphous germanium tin (GeSn) films on insulating substrates combined with seeds formed by laser annealing (LA) has been investigated. This technique enables the crystallization of GeSn at controlled positions at low temperature (˜180 °C) due to the determination of the starting points of crystallization by LA seeding and Sn-induced SPC enhancement. The GeSn crystals grown by SPC from LA seeds showed abnormal lateral profiles of substitutional Sn concentration. These lateral profiles are caused by the annealing time after crystallization being a function of distance from the LA seeds. This observation of a post-annealing effect also indicates that GeSn with a substitutional Sn concentration of up to ˜10% possesses high thermal stability. These results will facilitate the fabrication of next-generation thin-film devices on flexible plastic substrates with low softening temperatures (˜250 °C).

  12. Bindi tattoo on forehead: Success with modified R-20 technique using low fluence Q-switched Nd YAG laser: A case report

    Directory of Open Access Journals (Sweden)

    Vijay Zawar

    2014-01-01

    Full Text Available Bindi tattoo on the forehead, is one of the cultural practice in Indian women from rural areas. Many patients are not pleased with the appearance of their tattoo and thus seek removal. The development of quality-switched lasers has revolutionized the removal of unwanted tattoos. However, despite multiple treatment sessions, the efficacy is often found to be limited. We herein report a case of green-blue bindi tattoo which failed to clear after 8 sessions of Q-switched Nd YAG laser. The tattoo significantly cleared with R-20 method using low fluence Q-switched Nd YAG Laser. R-20 technique seems to be an effective method of tattoo removal and might be a boon for patients who are reluctant to pursue laser treatment because of fear of expenditure, side effects and uncertainty of result. We report efficacy of R-20 technique for a bindi tattoo on forehead.

  13. H/D isotopic recognition and temperature effects in IR spectra of hydrogen-bonded cyclic dimers in crystals: 3-Methylcinnamic acid and 4-phenylbutyric acid

    Science.gov (United States)

    Hachuła, Barbara; Jabłońska-Czapla, Magdalena; Flakus, Henryk T.; Nowak, Maria; Kusz, Joachim

    2015-01-01

    In the present work, the experimental and theoretical study of the nature of the inter-hydrogen bond interactions in two different carboxylic acids, 3-methylcinnamic acid (3MCA) and 4-phenylbutyric acid (4PBA), were reported. The polarized IR spectra of 3MCA and 4PBA crystals were recorded at the frequency ranges of the νOsbnd H and νOsbnd D bands. The spectral properties of 3MCA and 4PBA interpreted with the aid of the calculations based on the "strong-coupling" model. The differences in the spectral properties of the two different dimeric systems in the crystals provide a valuable information about the existence of a direct relationship between the crystal spectral properties in IR and the electronic structure of the molecular systems. In 3MCA crystals strong vibrational exciton interactions favor a "tail-to-head" (TH)-type Davydov coupling widespread via the π-electrons, whereas in 4PBA crystals a weak "through-space" (SS) exciton coupling is responsible for a "side-to-side"-type coupling. The relative contribution of each individual exciton coupling mechanism in IR spectra generation strongly depends on temperature and molecular electronic structure. The H/D isotopic recognition effect, depending on a non-random distribution of protons and deuterons in the crystal hydrogen bridges, was also analyzed.

  14. Low-temperature scanning tunneling microscopy/ultraviolet photoelectron spectroscopy investigation of two-dimensional crystallization of C60: pentacence binary system on Ag(111)

    Science.gov (United States)

    Lin Zhang, Jia; Hong Liang Zhang, Kelvin; Qiang Zhong, Jian; Chao Niu, Tian; Chen, Wei

    2012-02-01

    Atomic scale investigation of temperature-dependent two-dimensional (2 D) crystallization processes of fullerene-C60 on pentacene-covered Ag(111) surface has been carried out by in situ low-temperature scanning tunneling microscopy (LT-STM) experiments. To evaluate the effect of molecule-substrate interfacial interactions on the 2 D crystallization of C60: pentacene binary system, we also carried out the same self-assembly experiments of C60 on monolayer pentacene covered graphite substrate. It is revealed that temperature-dependent structural transition of various ordered C60 nanoassemblies is strongly influenced by the molecule-Ag(111) interfacial interactions, and further mediated by the weak C60-pentacene intermolecular interactions. In situ ultraviolet photoelectron spectroscopy (UPS) has been used to evaluate the nature of the intermolecular interactions between C60 and pentacene films.

  15. Influence of stress, temperature and crystal morphology on isothermal densification and specific surface area decrease of new snow

    Directory of Open Access Journals (Sweden)

    S. Schleef

    2014-10-01

    Full Text Available Laboratory-based, experimental data for the microstructural evolution of new snow are scarce, though applications would benefit from a quantitative characterization of the main influences. To this end, we have analyzed the metamorphism and concurrent densification of new snow under isothermal conditions by means of X-ray microtomography and compiled a comprehensive data set of 45 time series. In contrast to previous measurements on isothermal metamorphism on time scales of weeks to months, we analyzed the initial 24–48 h of snow evolution at a high temporal resolution of 3 hours. The data set comprised natural and laboratory-grown snow, and experimental conditions included systematic variations of overburden stress, temperature and crystal habit to address the main influences on specific surface area (SSA decrease rate and densification rate in a snowpack. For all conditions, we found a linear relation between density and SSA, indicating that metamorphism has an immediate influence for the densification of new snow. The slope of the linear relation, however, depends on the other parameters which were analyzed individually to derive a best-fit parameterization for the SSA decrease rate and densification rate. In the investigated parameter range, we found that the initial value of the SSA constituted the main morphological influence on the SSA decrease rate. In turn, the SSA decrease rate constituted the main influence on the densification rate.

  16. Investigations on nucleation thermodynamical parameters of NdBa2Cu3O7– (Nd123) crystallization by high temperature solution growth

    Indian Academy of Sciences (India)

    D P Paul; R Jayavel; C Subramanian; P Ramasamy

    2000-04-01

    Investigations on nucleation thermodynamical parameters are very essential for the successful growth of good quality single crystals from high temperature solution. A theoretical estimation of the nucleation thermodynamical parameters like interfacial energy between the solid Nd123 and its flux BaO–CuO, metastable zone-width, Gibbs free energy, critical energy barrier for nucleation and critical nucleation radius have been calculated from the knowledge of solubility data and by applying the classical nucleation theory. Results are discussed to understand the growth kinetics of Nd123 crystals.

  17. Influence of the laser-diode temperature on crystal absorption and output power in an end-pumped Nd:YVO4 laser

    Indian Academy of Sciences (India)

    Ebrahim Safari

    2011-01-01

    In this work, we studied the influence of heat loaded into the laser crystal in an endpumped solid-state Nd:YVO4 high power laser. We have shown experimentally that the optimum value of the laser-diode temperature for the maximum pump power absorption by the Nd:YVO4 crystal and the maximum Nd:YVO4 laser output power are approximately similar to that of a system of the low power type, but by increasing the pump power, different values can be obtained.

  18. The Influence of the Hot Wire Temperature on the Crystallization of μc-Si:H Films Prepared by Hot Wire-Assisted-ECR-CVD

    OpenAIRE

    Li, Ying; Li, Zhi Zhong; Chen, Guang hua; Kumeda, Minoru

    2007-01-01

    We have constructed a hot-wire-assisted ECR-CVD system to prepare a-Si:H and μc-Si:H films. The effect of hot wire (HW) temperature on crystallization of a-Si:H films is studied in the films prepared by this system. At low HW temperature, about 20 at.% hydrogen is included in the film. With increasing the HW temperature, the contents of the total hydrogen, SiH2 and SiH decrease, and the microcrystalline phase appears. It is found from the area of the TO peak of the Raman scattering spectra th...

  19. Influence of precipitate morphology on intermediate temperature creep properties of a nickel-base superalloy single crystal

    Science.gov (United States)

    Nathal, M. V.; Mackay, R. A.; Miner, R. V.

    1989-01-01

    The relative creep behavior of cuboidal (as-heat treated) and rafted (precrept at 1000 C) gamma-prime microstructures in the single-crystal Ni-based superalloy NASAIR 100 at 760 C was investigated using SEM and TEM examinations of materials at various stages of creep. It was found that, at high applied stresses, the crystals with cuboidal gamma-prime structure had both lower minimum creep rates and longer rupture lives than the crystals with lamellar gamma-prime. At lower stress levels, the initially cuboidal gamma-prime microstructure maintained a lower creep rate, but exhibited a similar rupture life compared to the prerafted crystals.

  20. Schottky barrier diode based on β-Ga2O3 (100) single crystal substrate and its temperature-dependent electrical characteristics

    Science.gov (United States)

    He, Qiming; Mu, Wenxiang; Dong, Hang; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tang, Minghua; Tao, Xutang; Liu, Ming

    2017-02-01

    The Pt/β-Ga2O3 Schottky barrier diode and its temperature-dependent current-voltage characteristics were investigated for power device application. The edge-defined film-fed growth (EFG) technique was utilized to grow the (100)-oriented β-Ga2O3 single crystal substrate that shows good crystal quality characterized by X-ray diffraction and high resolution transmission electron microscope. Ohmic and Schottky electrodes were fabricated by depositing Ti and Pt metals on the two surfaces, respectively. Through the current-voltage (I-V) measurement under different temperature and the thermionic emission modeling, the fabricated Pt/β-Ga2O3 Schottky diode was found to show good performances at room temperature, including rectification ratio of 1010, ideality factor (n) of 1.1, Schottky barrier height (ΦB) of 1.39 eV, threshold voltage (Vbi) of 1.07 V, ON-resistance (RON) of 12.5 mΩ.cm2, forward current density at 2 V (J@2V) of 56 A/cm2, and saturation current density (J0) of 2 × 10-16 A/cm2. The effective donor concentration Nd - Na was calculated to be about 2.3 × 1014 cm3. Good temperature dependent performance was also found in the device. The Schottky barrier height was estimated to be about 1.3 eV-1.39 eV at temperatures ranging from room temperature to 150 °C. With increasing temperature, parameters such as RON and J@2V become better, proving that the diode can work well at high temperature. The EFG grown β-Ga2O3 single crystal is a promising material to be used in the power devices.

  1. Semiclassical treatments for small-molecule dynamics in low-temperature crystals using fixed and adiabatic vibrational bases

    Science.gov (United States)

    Chapman, Craig T.; Cina, Jeffrey A.

    2007-09-01

    Time-resolved coherent nonlinear optical experiments on small molecules in low-temperature host crystals are exposing valuable information on quantum mechanical dynamics in condensed media. We make use of generic features of these systems to frame two simple, comprehensive theories that will enable the efficient calculations of their ultrafast spectroscopic signals and support their interpretation in terms of the underlying chemical dynamics. Without resorting to a simple harmonic analysis, both treatments rely on the identification of normal coordinates to unambiguously partition the well-structured guest-host complex into a system and a bath. Both approaches expand the overall wave function as a sum of product states between fully anharmonic vibrational basis states for the system and approximate Gaussian wave packets for the bath degrees of freedom. The theories exploit the fact that ultrafast experiments typically drive large-amplitude motion in a few intermolecular degrees of freedom of higher frequency than the crystal phonons, while these intramolecular vibrations indirectly induce smaller-amplitude—but still perhaps coherent—motion among the lattice modes. The equations of motion for the time-dependent parameters of the bath wave packets are fairly compact in a fixed vibrational basis/Gaussian bath (FVB/GB) approach. An alternative adiabatic vibrational basis/Gaussian bath (AVB/GB) treatment leads to more complicated equations of motion involving adiabatic and nonadiabatic vector potentials. Computational demands for propagation of the parameter equations of motion appear quite manageable for tens or hundreds of atoms and scale similarly with system size in the two cases. Because of the time-scale separation between intermolecular and lattice vibrations, the AVB/GB theory may in some instances require fewer vibrational basis states than the FVB/GB approach. Either framework should enable practical first-principles calculations of nonlinear optical

  2. Thermal expansion behavior of empressite, AgTe: A structural study by means of in situ high-temperature single-crystal X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Bindi, Luca [Museo di Storia Naturale, sez. di Mineralogia, Universita di Firenze, Via La Pira 4, I-50121 Firenze (Italy)], E-mail: luca.bindi@unifi.it

    2009-04-03

    The crystal structure of empressite, AgTe, a rare silver telluride, has been investigated by in situ X-ray single-crystal diffraction methods within the temperature range 298-463 K. AgTe remains orthorhombic, space group Pmnb (Pnma as standard), and shows only normal thermal expansion over the entire temperature range. The unit-cell parameters show a gradual increase with the increase of temperature. Slight adjustments in the geometry of Ag-tetrahedra and in the crystal-chemical environment of tellurium atoms occur in a continuous way without abrupt structural changes. The coefficients of thermal expansion along various axes are: {alpha}{sub a} = 1.5 x 10{sup -5} K{sup -1}, {alpha}{sub b} = 3.0 x 10{sup -5} K{sup -1}, {alpha}{sub c} = 2.2 x 10{sup -5} K{sup -1}, and the bulk thermal expansion coefficient {alpha}{sub V} is 5.4 x 10{sup -5} K{sup -1} for the temperature range 298-463 K.

  3. Determination of temperature-dependent thermal conductivity of a BaSnO{sub 3−δ} single crystal by using the 3ω method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyung Joon; Kim, Tai Hoon; Lee, Woong-Jhae; Chai, Yisheng; Kim, Jae Wook; Jwa, Yeon Jae; Chung, Sukhwan; Kim, Seon Joong; Sohn, Egon [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Lee, Seung Min [Hanbeam Corporation Ltd, Iui-dong 906-5, Yeongtong-gu, Suwon-si, Gyeonggi-do (Korea, Republic of); Choi, Ki-Young [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Kim, Kee Hoon, E-mail: khkim@phya.snu.ac.kr [Center for Novel States of Complex Materials Research, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2014-06-01

    Highlights: • This is the first report about thermal conductivity of BaSnO{sub 3−δ} single crystals. • We report the successful κ measurement of the crystals by employing the 3ω method. • The BaSnO{sub 3−δ} single crystal can be a good perovskite substrate with high κ. • We found that phonons mainly contribute to the heat transport in BaSnO{sub 3−δ}. - Abstract: The single crystal of the electron doped BaSnO{sub 3−δ} system has been recently found to have high electrical mobility (up to 320 cm{sup 2} V{sup −1} s{sup −1}) at room temperature and excellent oxygen stability. Although thermal conductivity (κ) of the BaSnO{sub 3−δ} single crystal is an important physical quantity, the κ measurement by the conventional DC method has been difficult due to the limited crystal size. Herein, we report the first measurement of κ by using the 3ω method from ∼20 to 300 K in the oxygen deficient BaSnO{sub 3−δ} single crystal with carrier concentration of ∼10{sup 18} cm{sup −3}. We found that κ is proportional to T{sup −1} above 50 K, indicating that phonons mainly contribute to the heat transport. Moreover, the electronic contribution is determined as ∼4% of the measured κ from the Wiedemann–Franz law. The κ value is 0.132 W cm{sup −1} K{sup −1} at room temperature and is increased progressively at lower temperatures, becoming overall larger than that of the SrTiO{sub 3} single crystal. Our results thus point out that BaSnO{sub 3−δ} can be a good substrate for growing transparent electronic thin films with the perovskite structure.

  4. Determination of elastic constants of a single-crystal topaz and their temperature dependence via sphere resonance method

    Science.gov (United States)

    Sema, Fumie; Watanabe, Tohru

    2017-10-01

    Water and halogens in ocean floor sediments transported by a descending slab might play important roles in geodynamic processes. Imaging subducted sediments through seismological observations requires a thorough understanding of elastic properties of sediment origin hydrous minerals. Topaz is a sediment origin hydrous mineral, which is formed at the depth of 250-350 km on a cold subducting slab. We determined elastic constants and their temperature derivatives of a natural single-crystal of topaz (Al1.97SiO4(F1.56, OH0.42)) at the temperature from 271.5 to 312.7 °K by using the sphere-resonance method. Elastic constants at an ambient temperature (T = 291.9 °K) are C11 = 281.21(1) GPa, C22 = 346.23(9) GPa, C33 = 294.99(9) GPa, C44 = 108.49(1) GPa, C55 = 132.47(1) GPa, C66 = 130.32(1) GPa, C12 = 121.48(3) GPa, C13 = 80.94(3) GPa and C23 = 81.77(2) GPa. Since our sample [Al2SiO4(F1.56,OH0.42)] was relatively rich in fluorine, only small differences in elastic constants can be seen between our sample and fluorine end member. Elastic constants of OH-rich topaz should be experimentally investigated to understand the influence of F-OH substitution on elasticity of topaz. All the elastic constants decrease linearly with increasing temperature. The temperature derivatives are dC11/dT = -0.014(3) GPa/°K, dC22/dT = -0.010(7) GPa/°K, dC33/dT = -0.021(5) GPa/°K, dC44/dT = -0.011(1) GPa/°K, dC55/dT = -0.016(2) GPa/°K, dC66/dT = -0.0101(2) GPa/°K, dC12/dT = -0.0041(6) GPa/°K, dC13/dT = -0.001(2) GPa/°K and dC23/dT = -0.002(1) GPa/°K. The isotropic seismic velocities in topaz are distinctly higher than those in olivine at 10 GPa and 300-1400 °K. There should be a strong velocity contrast between the overlying mantle and the thin sediment-origin layer at the depth around 300 km. A seismological technique like the receiver function technique should be applied to detect a thin layer of topaz in a cold subduction zone.

  5. Temperature dependence of lattice disorder in Ar-irradiated (1 0 0), (1 1 0) and (1 1 1) MgO single crystals

    Science.gov (United States)

    Usov, I. O.; Valdez, J. A.; Sickafus, K. E.

    2011-02-01

    To better appreciate dynamic annealing processes in ion irradiated MgO single crystals of three low-index crystallographic orientations, lattice damage variation with irradiation temperature was investigated. Irradiations were performed with 100 keV Ar ions to a fluence of 1 × 10 15 Ar/cm 2 in a temperature interval from -150 to 1100 °C. Rutherford backscattering spectroscopy combined with ion channeling was used to analyze lattice damage. Damage recovery with increasing irradiation temperature proceeded via two characteristic stages separated by 200 °C. Strong radiation damage anisotropy was observed at temperatures below 200 °C, with (1 1 0) MgO being the most radiation damage tolerant. Above 200 °C damage recovery was isotropic and almost complete recovery was reached at 1100 °C. We attributed this orientation dependence to a variation of dynamic annealing mechanisms with irradiation temperature.

  6. Low-temperature phase transition in glycine-glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry.

    Science.gov (United States)

    Zakharov, Boris A; Losev, Evgeniy A; Kolesov, Boris A; Drebushchak, Valeri A; Boldyreva, Elena V

    2012-06-01

    The occurrence of a first-order reversible phase transition in glycine-glutaric acid co-crystals at 220-230 K has been confirmed by three different techniques - single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P2(1)/c to P1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

  7. Photocurrent response of B{sub 12}As{sub 2} crystals to blue light, and its temperature- dependent electrical characterizations

    Energy Technology Data Exchange (ETDEWEB)

    Gul, R., E-mail: rubi786@yahoo.com [Brookhaven National Laboratory, Upton, NY, 11973 (United States); Alabama A& M University, Normal AL, 35762 (United States); Cui, Y.; Bolotnikov, A. E.; Camarda, G. S.; Hossain, A.; Roy, U. N.; Yang, G.; James, R. B. [Brookhaven National Laboratory, Upton, NY, 11973 (United States); Egarievwe, S. U. [Alabama A& M University, Normal AL, 35762 (United States); Edgar, J. H.; Nwagwu, U. [Kansas State University, Manhattan, KS, 66506 (United States)

    2016-02-15

    With the global shortage of {sup 3}He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B{sub 12}As{sub 2}) for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B{sub 12}As{sub 2} bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W{sup −1} and 2.47 mA ⋅ cm{sup −2}, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K) were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B{sub 12}As{sub 2} bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm{sup −2} and 7.6x10{sup 5}-7.7x10{sup 3} Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B{sub 12}As{sub 2} is a potential candidate for thermal-neutron detectors.

  8. 低温液相合成Engel复盐晶体研究%Low Temperature Liquid Synthesis of Engel Double Salt Crystal

    Institute of Scientific and Technical Information of China (English)

    张文辉; 张茜; 谷守玉; 万亚珍

    2013-01-01

    It was of great importance in plotting the phase diagram of the Engel double salt crystal for the aim to control the production process.The best conditions of synthesis Engel double salt by low temperature liquid synthesis method were studied.The results shown the basic magnesium carbonate was putting the saturated solution of potassium bicarbonate according to the ratio as following; potassium bicarbonate; basic magnesium carbonate ( wt.) = 39.0: 0.2 and then reacted under the hydrothermal condition as 40 ℃ for 10 min, the mixture solution was crystallized rapidly cooling down to 25℃ and water-bathed for 7 h for the crystal growth process , the Engel double salt crystal were synthesized.The crystal was tested by X-ray powder diffraction ( XRD), which proved that it was in agreeing with the standard spectra.The result showed that the crystal's morphology was of good crystallization.%Engel复盐晶体合成对于准确绘制Engel复盐相图及指导实际生产有重要意义.论文研究了低温条件下液相合成Engel复盐晶体的适宜条件,即碳酸氢钾饱和溶液中加入碱式碳酸镁,其重量比39.0 g/0.2 g,在40℃下水热反应10 min;然后反应溶液从40℃冷却降温到25℃进行析晶,析晶过程持续约7.0h,制备出Engel复盐晶体;对产物进行了XRD及晶体形貌分析,其衍射峰与标准图谱一致,晶体形貌规则,结晶良好.

  9. In Situ Observation of Skeletal Shape Transition during BaB2O4 Crystal Growth in High-Temperature Solution

    Institute of Scientific and Technical Information of China (English)

    PAN Xiu-Hong; JIN Wei-Qing; HONG Yong; AI Fei

    2006-01-01

    @@ The transition from a flat solid-liquid interface to a skeletal shape during BaB2O4(BBO) single crystal growth in Li2B4O7 flux is observed in real time by an optical high-temperature in-situ observation system. The movement of crystal step is also investigated. The obserwation results demonstrate that the steps propagate along and parallel to the flat interface when the crystal size is small.Nevertheless, they will ‘bend’ close to the face centre if the crystal size becomes greater. Atomic force microscopy reveals that more deposition places near the face centre give rise to the bending of advancing steps and thus the formation of a vicinal interface structure. Measurements of step velocity show that the velocity keeps nearly constant at different moments for one specific step, whereas the step on a newly formed layer advanced faster than that on a previously formed one when the crystal size is larger than 210μm or so. Thus interfacial morphological instability occurs and a skeletal interface is obtained.

  10. Confined-space synthesis of single crystal TiO2 nanowires in atmospheric vessel at low temperature: a generalized approach

    Science.gov (United States)

    Wang, Xiaoyue; Wang, Hai; Zhou, Yu; Liu, Yong; Li, Baojun; Zhou, Xiang; Shen, Hui

    2015-01-01

    Extensive efforts have been devoted to develop innovative synthesis strategies for nanomaterials in order to exploit the true potential of nanotechnology. However, most approaches require high temperature or high pressure to favor crystallization. Here we highlight an unconventional approach for the confined-space synthesis of the single crystal TiO2 nanowires in the atmospheric vessel at low temperature by cleverly manipulating the unique physical properties of straight-chain saturated fatty acids. Our method also applys to icosane due to its straight-chain saturated hydrocarbon structure and similar physical properties to the saturated fatty acids. Interestingly, we also found that the unsaturated fatty acids can facilitate the crystal growth, but their bent chains lead to the formation of TiO2 particle aggregates. In addition, we demonstrate the growth of TiO2 nanowires on arbitrary substrates, which are of great importance for their wider applications. We thus anticipate our presented method to be a possible starting point for non-classical crystallization strategies and be easily adapted for the fabrication of all other inorganic materials.

  11. Large single crystal diamond grown in FeNiMnCo-S-C system under high pressure and high temperature conditions

    Science.gov (United States)

    Zhang, He; Li, Shangsheng; Su, Taichao; Hu, Meihua; Li, Guanghui; Ma, Hongan; Jia, Xiaopeng

    2016-11-01

    Large diamonds have successfully been synthesized from FeNiMnCo-S-C system at temperatures of 1255-1393 °C and pressures of 5.3-5.5 GPa. Because of the presence of sulfur additive, the morphology and color of the large diamond crystals change obviously. The content and shape of inclusions change with increasing sulfur additive. It is found that the pressure and temperature conditions required for the synthesis decrease to some extent with the increase of S additive, which results in left down of the V-shape region. The Raman spectra show that the introduction of additive sulfur reduces the quality of the large diamond crystals. The x-ray photoelectron spectroscopy (XPS) spectra show the presence of S in the diamonds. Furthermore, the electrical properties of the large diamond crystals are tested by a four-point probe and the Hall effect method. When sulfur in the cell of diamond is up to 4.0 wt.%, the resistance of the diamond is 9.628×105 Ω·cm. It is shown that the large single crystal samples are n type semiconductors. This work is helpful for the further research and application of sulfur-doped semiconductor large diamond. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Education Department of Henan Province, China (Grant No. 12A430010), and the Fundamental Research Funds for the Universities of Henan Province, China (Grant No. NSFRF140110).

  12. Synthesis,Crystal Structural and Electrical Conductivity Properties of Fe-Doped Zinc Oxide Powders at High Temperatures

    Institute of Scientific and Technical Information of China (English)

    Hakan Colak; Orhan Trkoglu

    2012-01-01

    The synthesis,crystal structure and electrical conductivity properties of Fe-doped ZnO powders(in the range of 0.25-15 mol%) were reported in this paper.I-phase samples,which were indexed as single phase with a hexagonal(wurtzite) structure in the Fe-doped ZnO binary system,were determined by X-ray diffraction(XRD).The solubility limit of Fe in the ZnO lattice is 3 mol% at 950℃.The above mixed phase was observed.And the impurity phase was determined as the cubic-ZnFe 2 O 4 phase when compared with standard XRD data using the PDF program.This study focused on single I-phase ZnO samples which were synthesized at 950℃ because the limit of the solubility range is the widest at this temperature.The lattice parameters a and c of the I-phase decreased with Fe-doping concentration.The morphology of the I-phase samples was analyzed with a scanning electron microscope.The grain size of the I-phase samples increased with heat treatment and doping concentration.The electrical conductivity of the pure ZnO and single I-phase samples was investigated using the four-probe dc method at 100-950℃ in air atmosphere.The electrical conductivity values of pure ZnO,0.25 and 3 mol% Fe-doped ZnO samples at 100℃ were 2×10-6,1.7×10-3 and 6.3×10-4 S.cm-1,and at 950℃ they were 3.4,8.5 and 4 S.cm-1,respectively.

  13. Modified low temperature Czochralski growth of xylenol orange doped benzopheone single crystal for fabricating dual band patch antenna

    Science.gov (United States)

    Yadav, Harsh; Sinha, Nidhi; Kumar, Binay

    2016-09-01

    Organic non-linear optical pure and xylenol orange (XO) doped benzophenone (BP) single crystals have been grown by a modified Czochralski technique. A low cost CZ system was designed and fabricated that is suitable for the growth of single crystals of low melting point organic materials. Structural analysis was performed by powder and single crystal XRD. LC-HRMS spectra reveal that the dye molecules are present in the doped crystal. The linear optical characterization was carried out by UV-vis spectroscopy. In the case of the XO doped BP crystal, two absorption peaks were found at 504 nm and 620 nm. The enhancement of photoluminescence intensity of blue emission was observed in the dye doped crystal. Dielectric studies reveal that the XO doped BP has shown improved a dielectric constant with low dielectric loss. A dual band compact circular patch antenna was simulated and fabricated using the XO doped crystal. Resonant frequencies of the dual bands at 4.80 GHz and 9.22 GHz were achieved by introducing a defect ground state in the circular patch antenna. The piezoelectric coefficient (d33) value was increased from 1 to 4 pC/N by XO dye doping, which opens up the possibilities of simultaneous transducer applications.

  14. Influence of High Temperature Creep upon the Structure of ß-NiAl and ß-NiAl(Fe) Single Crystals

    OpenAIRE

    Zhang, Hui

    2002-01-01

    The principal aim of this thesis is to characterise quantitatively the influence of high temperature creep upon the structure of ß-NiAl and ß-NiAl(Fe) single crystals. A non-destructive procedure is established following the classic line of X-ray structure analysis, namely controlling the chemical composition with the electron probe microanalysis, determining the unit cell contents from the combined lattice parameter and mass density measurements, and refining the structure parameters accordi...

  15. Tunable (0. 86--1. mu. ) cw room-temperature laser utilizing F/sup +//sub 2/ color centers in an LiF crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gusev, Y.L.; Kirpichnikov, A.V.; Kruglov, S.N.; Marennikov, S.I.

    1980-05-01

    The development of a cw room-temperature laser tunable in the 0.86--1 ..mu.. range, utilizing F/sup +//sub 2/ color centers in an LiF crystal, is reported. When pumped by a krypton laser (lambda=0.647 mm), its lasing threshold was 400 mW. A method of regenerating centers using excimer laser radiation (lambda=310 nm) was tried.

  16. Inorganic Lead Halide Perovskite Single Crystals: Phase-Selective Low-Temperature Growth, Carrier Transport Properties, and Self-Powered Photodetection

    KAUST Repository

    Saidaminov, Makhsud I.

    2016-12-06

    A rapid, low-temperature, and solution-based route is developed for growing large-sized cesium lead halide perovskite single crystals under ambient conditions. An ultralow minority carrier concentration was measured in CsPbBr3 (≈108 holes per cm3, much lower than in any other lead halide perovskite and crystalline silicon), which enables to realize self-powered photodetectors with a high ON/OFF ratio (105).

  17. Investigation on defects in the high temperature inorganic scintillation single crystals of Ce:YAlO sub 3

    CERN Document Server

    Zhao Guang Jun; He Xiao Ming; Xu Jun; Tian Yu Lian; Huang Wan Xia

    2002-01-01

    The defects in Ce:YAlO sub 3 single crystals grown by Czochralski method were investigated by transmission white beam synchrotron radiation topography method. It was shown in experiments that the growth striations, inclusions precipitations, twins, core and dislocation group were the main growth defects in Ce:YAP single crystals. The mechanism of the defects formation was also discussed. The results showed that the doped concentration, purity of starting materials and growth conditions are the main causes for defects formation in Ce:YAP single crystals

  18. Effects of heat treatment temperature on crystallization and thermal expansion coefficient of Li2 O-Al2 O3-SiO2

    Institute of Scientific and Technical Information of China (English)

    卢安贤; 贾明; 刘树江

    2004-01-01

    The basic glass of Li2 O-Al2 O3-SiO2 system using P2O5 as nucleator was prepared by means of conventional melt quenching technology, and the heat-treatment process was determined by using differential thermal analysis. The crystalline phases and the microstructure of the glass-ceramics were investigated by using X-ray diffraction and scanning electron microscopy. The results show that the glass based on Li2 O-Al2 O3-SiO2 oxides using P2 O5 as nucleator can be prepared at lower melt temperature of 1 450 ℃ and the glass-ceramics with lower thermal expansion coefficient of 21.6 × 10-7 ℃ 1 can also be obtained at 750 ℃. The glass-ceramics contain a few crystal phases in which the main crystal phase is β-quartz solid solution and the second crystal phase is β-spodumene solid solution. When the heat treatment temperature is not higher than 650 ℃, the transparent glass-ceramics containing β-quartzsolid solution can be prepared. β-quartz solid solution changes into β-spodumene solid solution at about 750 ℃. And the appearance of the glass-ceramics changes from translucent, part opaque to complete opaque with increasing temperature.

  19. Conductivity of single-crystal Y1-yPryBa2Cu3O7-δ over a wide range of temperatures and Pr concentrations

    Science.gov (United States)

    Khadzhai, G. Ya.; Vovk, N. R.; Vovk, R. V.

    2014-06-01

    The in-plane electrical resistance of Y1-yPryBa2Cu3O7-δ single crystals with a high degree of perfection is studied for temperatures in the range TC-300 K, where TC ranges from 92 to 52 K, with varying praseodymium content. The experimental data are approximated by an expression that takes electron scattering on phonons and defects into account, as well as fluctuation conductivity in a 3D Aslamazov-Larkin model. According to the approximation data the Debye temperature ranges from 350-370 K, depending on the praseodymium content. The transverse coherence length is ˜1 Å.

  20. Compositional effects on the low-temperature transport properties of non-stoichiometric Bi2Te x Se y -based crystals

    Science.gov (United States)

    Ramachandran, B.; Wu, K. K.; Kuo, Y. K.; Guo, L. S.; Wang, L. M.

    2017-01-01

    We grew a series of non-stoichiometric crystals of the ternary alloy Bi2Te x Se y via a direct solidification route. The temperature-dependent electrical and thermal transport properties, such as electrical resistivity (ρ), Seebeck coefficient (S), Hall coefficient (R H), and thermal conductivity (κ), of six selected crystals of Bi2Te x Se y with x  +  y ~ 3 were studied. We found that the physical properties of the Bi2Te x Se y -based crystals varied significantly with the Te/Se (x/y) content. This is essentially due to the modification of the electronic band structure of the crystals with the change in sample composition, which ultimately leads to the formation of a p-type material (Bi2Te2.10Se0.66) from an n-type Bi2Te1.89Se0.98. Most importantly, the feature associated with surface-state conduction at low temperatures was also observed in some of these crystals, including Bi2Te1.89Se0.98, Bi2Te2.16Se0.71, and Bi2Te2.10Se0.66. In particular, two highly resistive compounds, Bi2Te2.16Se0.71 and Bi2Te2.10Se0.66 with low carrier densities were identified as potential materials for topological applications. The observed complex transport behavior was realized in connection with the formation of impurity bands (multiband effects) in the Bi2Te x Se y -based systems. Analysis of the lattice thermal conductivity of the Bi2Te x Se y -based crystals indicates that the sample composition has a major effect on low-temperature heat conduction via phonon-boundary and phonon-point-defect scattering. Finally, the highest room temperature thermoelectric figure of merit, a ZT of about 0.46, was achieved for n-type Bi2Te1.63Se1.23.

  1. Calc-alkali rocks derived from tholeiite magma in Hakone volcano; pyroxene crystallization trends and pyroxene geothermometry to estimate the magma temperature

    Science.gov (United States)

    Ishii, T.

    2012-12-01

    Calc-alkali rocks are widely distributed in the island arcs. The several models of their magma-genesis were proposed by many geoscientists (e.g. Kuno 1950, Osborn 1959, Sakuyama 1981, Tatsumi 2011) on the bases of precise petrological investigations. Crystallization trends of rock forming minerals (pyroxene, feldspar etc.) in the individual lava flow of the hydrous tholeiitic magma are represented by chemical zoning from phenocryst through microphenocryst to the groundmass in each lava. Those trends indicate degassing (or dehydrating) trends of erupted lava (Ishii 1991). Crystallization trend of minerals of hydrous magma in the subvolcanic magma reservoir is represented by core of phenocrysts throughout lava-flow strata in each volcano. Those trends indicate water-enrichment (or hydrating) trend in the magma reservoir. On the bases of the detailed analyses of the pyroxene crystallization sequences as well as estimated magmatic temperatures using pyroxene geothermometer, for calc-alkali rocks from the Central Cone (CC) in the Hakone volcano, the following working hypothesis is suggested, i.e. those calc-alkali rocks are induced by magma mixing between high temperature (about 1120 Degree Centigrade) tholeiite magma and low temperature (about 970 Degree Centigrade) magma, the latter is originated from fractional crystallization of the primitive high temperature hydras island-arc tholeiite magma within magma reservoir under closed environment for water. Reference Ishii, T., 1991. Lava-flow and subvolcanic magma reservoir composition trends in the Ca-poor pyroxenes of Hakone Volcano, Japan. Jour. Petrol., 32, 429-450 Kuno, H., 1950. Petrology of Hakone volcano and the adjacent areas, Japan. Bull. Geol. Soc. Am., 61, 957-1019. Sakuyama, M., 1981. Petrological study of the Myoko and Kurohime volcanoes, Japan: crystallization sequence and evidence for magma mixing. Jour. Petrol., 22, 553-583. Osborn, E. F., 1959. Role of oxygen pressure in the crystallization and

  2. Optical pressure and temperature sensor based on the luminescence properties of Nd3+ ion in a gadolinium scandium gallium garnet crystal.

    Science.gov (United States)

    León-Luis, S F; Muñoz-Santiuste, J E; Lavín, V; Rodríguez-Mendoza, U R

    2012-04-23

    Hypersensitivity to pressure and temperature is observed in the near-infrared emission lines of the Nd(3+) ion in a Cr(3+),Nd(3+):Gd(3)Sc(2)Ga(3)O(12) crystal, associated to the R(1,2)((4)F(3/2))→Z(5)((4)I(9/2)) and R(1,2)((4)F(3/2))→Z(1)((4)I(9/2)) transitions. The former emissions show large linear pressure coefficients of -11.3 cm(-1)/GPa and -8.8 cm(-1)/GPa, while the latter show high thermal sensitivity in the low temperature range. Thus this garnet crystal can be considered a potential optical pressure and/or temperature sensor in high pressure and temperature experiments up to 12 GPa and below room temperature, used in diamond anvil cells and excited with different UV and visible commercial laser due to the multiple Cr(3+) and Nd(3+) absorption bands.

  3. A Compact, Radiation Hardened, Stable, Low Power, Programmable Crystal Oscillator for Extreme Temperature and High Reliability Space Application Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a feasibility study of a fully intgrated radiation hardened (>1Mrad/si), programmable crystal oscilator (RPXO) in a miniature package that will deliver...

  4. Effect of the ion-beam bombardment and annealing temperature on sol-gel derived yttrium aluminum oxide film as liquid crystal alignment layer

    Science.gov (United States)

    Jeong, Hae-Chang; Heo, Gi-Seok; Kim, Eun-Mi; Lee, Ju Hwan; Han, Jeong-Min; Seo, Dae-Shik

    2017-02-01

    We demonstrated a homogeneous liquid-crystal (LC) alignment state on yttrium aluminum oxide (YAlO) films, where the alignment was induced by ion-beam (IB) irradiation. Topographical analysis was performed by atomic force microscopy as a function of annealing temperature. Higher annealing temperatures yielded a smoother surface, accompanied by reduced light scattering. Transparency in the visible region increased on the surface fabricated at higher annealing temperatures. LC alignment mechanism was determined by X-ray diffraction (XRD) analysis. Moreover, IB-irradiated YAlO films annealed at temperatures greater than 200 °C exhibited good thermal stability and low capacitance-voltage hysteresis. The IB-irradiated YAlO films are suitable as alternative alignment layers in advanced LC display applications.

  5. Temperature and concentration quenching of Tb{sup 3+} emissions in Y{sub 4}Al{sub 2}O{sub 9} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Boruc, Z., E-mail: z.boruc@stud.elka.pw.edu.pl [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw (Poland); Fetlinski, B.; Kaczkan, M. [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw (Poland); Turczynski, S.; Pawlak, D. [Institute of Electronic Materials Technology, ul. Wolczynska 133, 01-919 Warsaw (Poland); Malinowski, M. [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw (Poland)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Spectroscopic properties of Tb{sup 3+}:Y{sub 4}Al{sub 2}O{sub 9} crystals are studied. Black-Right-Pointing-Pointer Concentration and temperature dependencies of fluorescence are investigated. Black-Right-Pointing-Pointer The cross-relaxation transfer rates are experimentally determined. Black-Right-Pointing-Pointer Strong influence of cross relaxation process on {sup 5}D{sub 3} emission quenching is observed. Black-Right-Pointing-Pointer Decays are modelled using Inokuti-Hirayama approach. - Abstract: Spectroscopic properties of trivalent terbium (Tb{sup 3+}) activated Y{sub 4}Al{sub 2}O{sub 9} (abbreviated YAM) crystals were studied. Concentration and temperature dependent emission spectra and fluorescence dynamics profiles have been investigated in YAM:Tb{sup 3+} in order to understand better processes responsible for quenching of the terbium {sup 5}D{sub 3} and {sup 5}D{sub 4} emissions. Decays were modelled using Inokuti-Hirayama approach to obtain information on the energy transfer mechanism. The cross-relaxation transfer rates were experimentally determined as a function of temperature and Tb{sup 3+} concentration. The investigation revealed strong influence of cross-relaxation process on {sup 5}D{sub 3} emission quenching. The two different processes responsible for the increase of fluorescence quenching with growing temperature were observed, both related to thermal activation energy. For temperatures above 700 K, the temperature dependence of the emission intensity ratio ({sup 5}D{sub 3}/{sup 5}D{sub 4}) becomes linear and the decay times are rapidly decreasing monotonously with increasing temperature, what is confirming the potential of Y{sub 4}Al{sub 2}O{sub 9}:Tb{sup 3+} material in high temperature luminescence thermometry.

  6. Anomalies in thermal expansion and heat capacity of TmB50 at low temperatures: magnetic phase transition and crystal electric field effect.

    Science.gov (United States)

    Novikov, V V; Zhemoedov, N A; Mitroshenkov, N V; Matovnikov, A V

    2016-11-01

    We experimentally study the heat capacity and thermal expansion of thulium boride (TmB50) at temperatures of 2-300 K. The wide temperature range (2-180 K) of boride negative expansion was revealed. We found the anomalies in C(T) heat capacity temperature dependence, attributed to the Schottky contribution (i.e. the influence of the crystal electric field: CEF), as well as the magnetic phase transition. CEF-splitting of the f-levels of the Tm(3+) ion was described by the Schottky function of heat capacity with a quasi-quartet in the ground state. Excited multiplets are separated from the ground state by energy gaps δ1 = 100 K, and δ2 ≈ 350 K. The heat capacity maximum at Tmax ≈ 2.4 K may be attributed to the possible magnetic transition in TmB50. Other possible causes of the low-temperature maximum of C(T) dependence are the nonspherical surroundings of rare earth atoms due to the boron atoms in the crystal lattice of the boride and the emergence of two-level systems, as well as the splitting of the ground multiplet due to local magnetic fields of the neighboring ions of thulium. Anomalies in heat capacity are mapped with the thermal expansion features of boride. It is found that the TmB50 thermal expansion characteristic features are due to the influence of the CEF, as well as the asymmetry of the spatial arrangement of boron atoms around the rare earth atoms in the crystal lattice of RB50. The Grüneisen parameters, corresponding to the excitation of different multiplets of CEF-splitting, were determined. A satisfactory accordance between the experimental and estimated temperature dependencies of the boride thermal expansion coefficient was achieved.

  7. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    Energy Technology Data Exchange (ETDEWEB)

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  8. Electrochemical oxidation of carbon monoxide: from platinum single crystals to low temperature fuel cells catalysts. Part I: Carbon monoxide oxidation onto low index platinum single crystals

    Directory of Open Access Journals (Sweden)

    PHILIP N. ROSS JR

    2001-12-01

    Full Text Available The electrochemical oxidation of carbon monoxide and the interfacial structure of the CO adlayer (COads on platinum low index single crystals, Pt(111, Pt(100 and two reconstruction of Pt(110, were examined using the rotation disk electrode method in combination with the in situ surface X-ray diffraction scattering technique. The mechanism of CO oxidation is discussed on the basis of the findings that, depending on the potential, two energetic states of COads exist on the platinum surfaces. Thus, at lower potentials, weakly bonded states (COads,w and at higher potentials strongly bonded states (COads,s are formed. The mechanism of the oxidation of hydrogen-carbon monoxide mixtures is also proposed.

  9. Upgrades of poloidal and tangential x-ray imaging crystal spectrometers for temperature and rotation measurements on EAST

    Science.gov (United States)

    Wang, Fudi; Chen, Jun; Hu, Ruiji; Lyu, Bo; Colledani, Gilles; Fu, Jia; Li, Yingying; Bitter, Manfred; Hill, Kenneth; Lee, Sangon; Ye, Minyou; Shi, Yuejiang; Wan, Baonian

    2016-11-01

    During the past two years, key parts of poloidal and tangential x-ray imaging crystal spectrometers (PXCSs and TXCSs) have been upgraded. For poloidal XCSs, double-crystals of ArXVII and FeXXV were deployed. For fulfilling in situ alignment of a poloidal XCS, the beryllium window must be flexibly removed. By utilizing a design, where the beryllium window was installed in the vacuum chamber of the double-crystal, and between the double-crystal and wall of this chamber, an in situ alignment for the two spectrometers was fulfilled. Also, a new holder for the double-crystal was installed to allow for precise adjustments of azimuth angle and vertical height of the double-crystal. In order to facilitate these adjustments of double-crystal and installation of beryllium window, the chamber of the double-crystal for PXCS was upgraded from a cylinder to a cuboid. The distance between double-crystal and magnetic axis was extended from 8936 mm to 9850 mm in order to improve spatial resolution for PXCS, which is currently in the range from 1.237 mm to 4.80 mm at magnetic axis. Furthermore, a new pixelated detector (PILATUS 900K), which has a large sensitive area of 83.8 × 325.3 mm2 and which is vacuum compatible, is being implemented on the PXCS. This detector is mounted on a rail, so that its position can be changed by 50 mm to effectively record spectra of He-like argon and He-like iron (ArXVII and FeXXV). Similarly, a rail, which allows detector movement by 50 mm, was also installed in TXCS to alternatively record spectra of ArXVII and ArXVIII. Presently, the operation duration of PXCS and TXCS has been upgraded to hundreds of seconds in one shot. Ti- and uϕ-profiles measured by TXCS and charge exchange recombination spectroscopy (CXRS) were compared and found to be in good agreement.

  10. Precise Magnetic Structures of Hard Ferromagnets of ND2FE14B Type as Determined at Low Temperature from Single Crystal Neutron Diffraction

    Science.gov (United States)

    Wolfers, P.; Bacmann, M.; Fruchart, D.

    2000-09-01

    The main constituent of the hard magnet materials Nd-Fe-B is the prototype of a new ferromagnet series, the Nd2Fe14B type (Space Group P42/nmm). Such compounds are characterised by high magnetocrystalline anisotropy parameters, those of rare earth origin being several times higher than the contribution of the iron subblattices. In many cases, these two contributions exhibit markedly different thermal behaviours, resulting in spin rotation phenomena or (and) lowering of the crystalline and the magnetic symmetry from the tetragonal high temperature state. Low temperature very precise studies on selected compounds of the series R2Fe14B with R = Nd, Ho, Er and Y, were undertaken by using neutron four circle diffractometry on single crystals. When temperature is lowered, the two first compounds exhibit a continuous spin reorientation within the [110] plane from the c-axis at high temperature towards an intermediate direction. The Er compound presents a first order transition around 350K where the resulting magnetisation first order rotates from the c-axis a high temperature to the a basal plane direction at low temperature. The last one compound remains c-easy axis in the whole temperature range. From our neutron diffraction experiments, lowering of the crystal symmetry to monoclinic (orthorhombic) space groups was precisely measured for the two first (third) samples. Besides marked deviations to collinearity affect the different sublattice magnetisations. Yet, these well marked phenomena have not been accounted for in the hundert experimental and theoretical analysis dedicated to the series. However, our results are in good agreement with a detailed 57Fe Mössbauer spectroscopy analysis of the Ho ternary hydrides.

  11. Characterization of PMN-PT piezoelectric single crystal and PMN-PT 1-3 composite at elevated temperatures by electrical impedance resonance analysis.

    Science.gov (United States)

    Wu, Zhengbin; Xi, Kui

    2014-07-01

    In this paper, lead magnesium niobate-lead titanate (PMN-PT) piezoelectric single crystal and its 1-3 composite counterpart were characterized and analyzed under different stable temperatures using both a Simulated Annealing (SA) optimization algorithm and the commercial software PRAP (Piezoelectric Resonance Analysis Program). Electrical impedance resonance characteristics of the two material samples over the range 25-125 °C were measured. The correlation between experimental data and numerical fits derived from both SA and PRAP is considered. Calculation of the determination coefficient (R1(2)) between numerically fitted and measured results is above 95% for both methods. Furthermore, variations in the number of data values used for the fit introduced no more than 3.1% uncertainty on the calculated material parameters. It is found that the complex material parameters of PMN-PT composite are more dependent on temperature than the single crystal. The phase transition of the PMN-PT, which is close to 90 °C, has an effect on the high temperature material characteristics of both piezoelectric materials. These calculated complex material parameters can be used for the design of ultrasonic transducers for elevated temperature applications.

  12. Estimation of low-temperature spectra behavior in Nd-doped Sc2SiO5 single crystal.

    Science.gov (United States)

    Zheng, Lihe; Xu, Jun; Su, Liangbi; Li, Hongjun; Wang, Qingguo; Ryba-Romanowski, Witold; Lisiecki, Radosław; Wu, Feng

    2009-11-15

    High optical quality Nd-doped Sc(2)SiO(5) crystal with size of diameter 27 mm x 60 mm was obtained by Czochralski method. An x-ray diffraction pattern of Nd:SSO crystal confirmed that the as-grown crystal was isostructual with the SSO crystal. Absorption and emission spectra were recorded at 10 K. The Judd-Ofelt theory was applied to obtain standard parameters Omega t(t=2,4,6) and the fitting result of experimental absorption line strengths, which provided the F3/24 radiative lifetime (tau(rad)) of 219 micros and the luminescence branching ratio beta of 0.57 for the (4)F(3/2)-(4)I(9/2) laser transition. The stimulated emission cross section of 1.04 x 10(-19) cm(2) at 1074 nm was calculated using the Füchtbauer-Ladenburg equation. The (4)F(3/2) luminescence lifetimes with 215 micros at 10 K and 198 micros at 300 K were determined from luminescence decay curves, indicating high quantum efficiency in the Nd:SSO crystal. All these results showed that Nd:SSO would be a promising gain media in solid-state lasers.

  13. Microstructural investigation of Si-ion-irradiated single crystal 3C-SiC and SA-Tyrannohex SiC fiber-bonded composite at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Chun-Yu [Institute of Nuclear Engineering and Science, National Tsing-Hua University, Hsinchu 30013, Taiwan (China); Tsai, Shuo-Cheng [Department of Engineering and System Science, National Tsing-Hua University, Hsinchu 30013, Taiwan (China); Lin, Hua-Tay [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Chen, Fu-Rong [Department of Engineering and System Science, National Tsing-Hua University, Hsinchu 30013, Taiwan (China); Kai, Ji-Jung, E-mail: ceer0001@gmail.com [Institute of Nuclear Engineering and Science, National Tsing-Hua University, Hsinchu 30013, Taiwan (China); Department of Engineering and System Science, National Tsing-Hua University, Hsinchu 30013, Taiwan (China)

    2013-11-15

    Silicon carbides (SiCs) are considered as one of the promising candidates for structural and core materials used in fusion reactor and high temperature gas-cooled reactor (HTGR) due to its high thermal stability, and good resistance to irradiation and chemical attack. Single crystal 3C-SiC with less intrinsic defects was used to precisely characterize the radiation-induced defects in 3C-SiC. In addition, there are limited discussions related to radiation effect of SA-Tyrannohex fiber-bonded composite at high temperatures. Therefore, in this study, single crystal 3C-SiC thin film and SA-Tyrannohex SiC fiber-bonded composite were irradiated at 1000–1350 °C with 7 MeV Si{sup 3+} ion to simulate the neutron irradiation in reactors. The microstructure of the irradiated SiC was examined by using high resolution transmission electron microscope (HRTEM). In irradiated single crystal 3C-SiC, high resolution images showed that the planar defects were extrinsic stacking faulted loop with changing atomic sequences and intrinsic stacking faulted loop, i.e. vacancy loop. In addition, dislocation loops, voids, and edge dislocations in SA-Tyrannohex SiC fiber-bonded composite after irradiation were investigated. Besides, larger voids (with diameter 10–40 nm) formed in alumina with preferred orientation after irradiation perhaps resulting in degradation of strength of the SA-Tyrannohex SiC fiber-bonded composite.

  14. Temperature Dependence of Electrical Properties and Crystal Structure of 0.29Pb(In1/2Nb1/2O3–0.44Pb(Mg1/3Nb2/3O3–0.27PbTiO3 Single Crystals

    Directory of Open Access Journals (Sweden)

    Qian Li

    2013-01-01

    Full Text Available We characterized the temperature dependent (~25–200°C electromechanical properties and crystal structure of Pb(In1/2Nb1/2O3-Pb(Mg1/3Nb2/3O3-PbTiO3 single crystals using in situ electrical measurement and neutron diffraction techniques. The results show that the poled crystal experiences an addition phase transition around 120°C whereas such a transition is absent in the unpoled crystal. It is also found that the polar order persists above the maximum dielectric permittivity temperature at which the crystal shows a well-defined antiferroelectric behavior. The changes in the electrical properties and underlying crystal structure are discussed in the paper.

  15. Final Report - Crystal Settling, Redox, and High Temperature Properties of ORP HLW and LAW Glasses, VSL-09R1510-1, Rev. 0, dated 6/18/09

    Energy Technology Data Exchange (ETDEWEB)

    Kruger, Albert A.; Wang, C.; Gan, H.; Pegg, I. L.; Chaudhuri, M.; Kot, W.; Feng, Z.; Viragh, C.; McKeown, D. A.; Joseph, I.; Muller, I. S.; Cecil, R.; Zhao, W.

    2013-11-13

    The radioactive tank waste treatment programs at the U. S. Department of Energy (DOE) have featured joule heated ceramic melter technology for the vitrification of high level waste (HLW). The Hanford Tank Waste Treatment and Immobilization Plant (WTP) employs this same basic technology not only for the vitrification of HLW streams but also for the vitrification of Low Activity Waste (LAW) streams. Because of the much greater throughput rates required of the WTP as compared to the vitrification facilities at the West Valley Demonstration Project (WVDP) or the Defense Waste Processing Facility (DWPF), the WTP employs advanced joule heated melters with forced mixing of the glass pool (bubblers) to improve heat and mass transport and increase melting rates. However, for both HLW and LAW treatment, the ability to increase waste loadings offers the potential to significantly reduce the amount of glass that must be produced and disposed and, therefore, the overall project costs. This report presents the results from a study to investigate several glass property issues related to WTP HLW and LAW vitrification: crystal formation and settling in selected HLW glasses; redox behavior of vanadium and chromium in selected LAW glasses; and key high temperature thermal properties of representative HLW and LAW glasses. The work was conducted according to Test Plans that were prepared for the HLW and LAW scope, respectively. One part of this work thus addresses some of the possible detrimental effects due to considerably higher crystal content in waste glass melts and, in particular, the impact of high crystal contents on the flow property of the glass melt and the settling rate of representative crystalline phases in an environment similar to that of an idling glass melter. Characterization of vanadium redox shifts in representative WTP LAW glasses is the second focal point of this work. The third part of this work focused on key high temperature thermal properties of

  16. Effect of crystal structure of manganese dioxide on response for electrolyte of ahydrogen sensor operative at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Koyanaka, Hideki [Forward Science Laboratory Ltd, Oita, Japan; Ueda, Yoshikatsu [Kyoto University, Japan; Takeuchi, K [Tokyo University of Science, Oshamanbe Hokkaido, Japan; Kolesnikov, Alexander I [ORNL

    2013-01-01

    Sensoring properties of a hydrogen sensor that used electrolytes made of different crystal type manganese dioxides were compared. An electrolyte made of a manganese dioxide, which has a high purity of ramsdellite-type crystal structure, provided the best characteristics for the hydrogen sensor. To explain the sensor property, network model of oxygen-pairs to store protons with a weak covalent bond and to conduct protons along the network in the ideal crystal structure of ramsdellite manganese dioxide was proposed. The inter-atomic distance of those oxygen-pairs in the high purity of ramsdellite manganese dioxide was estimated between 2.57 and 2.60 A using inelastic neutron scattering measurements. The property of the hydrogen sensor supported the unique proton conduction based on the network model.

  17. Low-temperature Raman scattering spectra of GaSe{sub x}S{sub 1-x} layered mixed crystals

    Energy Technology Data Exchange (ETDEWEB)

    Gasanly, N.M. [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey); Aydinli, A. [Department of Physics, Bilkent University, 06533 Ankara (Turkey)

    2002-07-01

    Raman scattering has been used to study the vibrational spectra of GaSe{sub x}S{sub 1-x} layered mixed crystals at 10 K. We report the frequency dependencies of different modes on composition x, with particular emphasis on A'{sub 1}{sup (2)} (A{sub 1g}{sup 1}) and A'{sub 1}{sup (4)} (A{sub 1g}{sup 2}) intralayer compressional modes having low dispersion in the Brillouin zone. The appearance of additional bands is attributed to multimode behavior typically exhibited by mixed crystals of anisotropic compounds. (Abstract Copyright[2002], Wiley Periodicals, Inc.)

  18. Room-temperature InAs/InP Quantum Dots laser operation based on heterogeneous "2.5 D" Photonic Crystal.

    Science.gov (United States)

    Ben Bakir, Badhise; Seassal, Christian; Letartre, Xavier; Regreny, Philippe; Gendry, Michel; Viktorovitch, Pierre; Zussy, Marc; Di Cioccio, Léa; Fedeli, Jean-Marc

    2006-10-02

    The authors report on the design, fabrication and operation of heterogeneous and compact "2.5 D" Photonic Crystal microlaser with a single plane of InAs quantum dots as gain medium. The high quality factor photonic structures are tailored for vertical emission. The devices consist of a top two-dimensional InP Photonic Crystal Slab, a SiO(2) bonding layer, and a bottom high index contrast Si/SiO(2) Bragg mirror deposited on a Si wafer. Despite the fact that no more than about 5% of the quantum dots distribution effectively contribute to the modal gain, room-temperature lasing operation, around 1.5 microm, was achieved by photopumping. A low effective threshold, on the order of 350 microW, and a spontaneous emission factor, over 0.13, could be deduced from experiments.

  19. Freeform Fabrication of Magnetophotonic Crystals with Diamond Lattices of Oxide and Metallic Glasses for Terahertz Wave Control by Micro Patterning Stereolithography and Low Temperature Sintering

    Directory of Open Access Journals (Sweden)

    Maasa Nakano

    2013-04-01

    Full Text Available Micrometer order magnetophotonic crystals with periodic arranged metallic glass and oxide glass composite materials were fabricated by stereolithographic method to reflect electromagnetic waves in terahertz frequency ranges through Bragg diffraction. In the fabrication process, the photo sensitive acrylic resin paste mixed with micrometer sized metallic glass of Fe72B14.4Si9.6Nb4 and oxide glass of B2O3·Bi2O3 particles was spread on a metal substrate, and cross sectional images of ultra violet ray were exposed. Through the layer by layer stacking, micro lattice structures with a diamond type periodic arrangement were successfully formed. The composite structures could be obtained through the dewaxing and sintering process with the lower temperature under the transition point of metallic glass. Transmission spectra of the terahertz waves through the magnetophotonic crystals were measured by using a terahertz time domain spectroscopy.

  20. Simultaneous three-dimensional temperature and velocity field measurements using astigmatic imaging of non-encapsulated thermo-liquid crystal (TLC) particles.

    Science.gov (United States)

    Segura, Rodrigo; Rossi, Massimiliano; Cierpka, Christian; Kähler, Christian J

    2015-02-07

    A combination of cutting edge developments is presented to characterize three-dimensional (3D) temperature and velocity fields in microscopic flows. An emulsion of non-encapsulated thermo-liquid crystal (TLC) micro spheres, with a narrow size distribution is used to track the flow's motion and temperature distribution. A state-of-the-art light engine, which combines the spectrum of six light pipes, provides a balanced illumination which allows for strong and detectable color patterns across the TLC's temperature response range. Lastly, the ability of the TLC material to reflect select wavelength bands with an unchanging and independent circular polarization chirality is exploited by a filter that blocks background noise, while exclusively transmitting the color signal of the TLC particles. This approach takes advantage of the peculiar physical properties of TLCs to allow the estimation of individual TLC particle's 3D position, for the first time, using Astigmatism Particle Tracking Velocimetry (APTV).