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Sample records for al au bi

  1. Al-Au-La (010)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Au-La (010)' with the content:

  2. Crystalline metallic Au nanoparticle-loaded α-Bi2O3 microrods for improved photocatalysis.

    PubMed

    Jiang, Hai-Ying; Cheng, Kun; Lin, Jun

    2012-09-21

    Crystalline metallic Au nanoparticles were loaded on α-Bi(2)O(3) microrods (Au/α-Bi(2)O(3)) using an Au deposition-precipitation method. The prepared samples were characterized by scanning electron and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectroscopy. Upon visible light irradiation, the Au/α-Bi(2)O(3) exhibits much higher photocatalytic activities than the pure α-Bi(2)O(3) for the degradation of Rhodamine B and 2,4-dichlorophenol in aqueous solution. The role of the Au and the paths of electron transport in the photocatalysis of the Au/α-Bi(2)O(3) were investigated and discussed in detail based on the analysis of the photo-generated hydroxyl radicals (˙OH) and hydrogen peroxide (H(2)O(2)) in the visible light irradiated suspension of pure α-Bi(2)O(3) and Au/α-Bi(2)O(3). The result reveals that the Au loaded on α-Bi(2)O(3) plays a critical role in the separation of the electron and hole pairs by accumulating the electrons from the excited α-Bi(2)O(3), which is responsible for the enhanced photocatalytic activity.

  3. Investigation of Terahertz Emission from BiVO4/Au Thin Film Interface

    NASA Astrophysics Data System (ADS)

    Kumar, Nishant; Abdi, Fatwa F.; Trzesniewski, Bartek; Smith, Wilson A.; Planken, Paul C. M.; Adam, Aurèle J. L.

    2015-11-01

    We demonstrate emission of terahertz pulses from a BiVO4/Au thin film interface, illuminated with femtosecond laser pulses. Based on the experimental observations, we propose that the most likely cause of the THz emission is the Photo-Dember effect caused by the standing wave intensity distribution formed at the BiVO4/Au interfaces.

  4. In situ investigation of spinodal decomposition in hypermonotectic Al Bi and Al Bi Zn alloys

    NASA Astrophysics Data System (ADS)

    Schaffer, P. L.; Mathiesen, R. H.; Arnberg, L.; Di Sabatino, M.; Snigirev, A.

    2008-05-01

    Spinodal decomposition of hypermonotectic Al-6 wt.%Bi, Al-8 wt.%Bi and Al-6 wt.%Bi-8 wt.%Zn alloys has been investigated using synchrotron radiography. In the case of the 6 and 8 wt.%Bi binary alloys undercoolings of 70 and 110 K, respectively, were required to initiate the L→L1+L2 reaction, which appeared to occur very close to the monotectic reaction temperature. The nucleated L2 droplets were set in collective size-dependent motion by forces coupled to external fields (gravity and imposed temperature gradient) as well as forces arising due to internal fluctuations of the system. With experimental conditions similar to those realized during strip casting of the same materials, it was found that the size-dependant droplet velocity field combined with Stokes drag at the L1-L2 interfaces as well as attractive and repulsive diffusion-coupling between adjacent L2 droplets, yield complex meso- to microscale hydrodynamics. The hydrodynamics are the dominating mechanisms for L2 droplet coagulation, and are accordingly decisive for the final size distribution and geometrical dispersion of the soft Bi-rich component in the cast material. A different decomposition mode was observed in the Al-6 wt.%Bi-8 wt.%Zn ternary alloy, with the L2 droplets undergoing an immiscible-miscible-immiscible transition. In contrast to what was found for the binaries, L2 domains formed at relatively small undercoolings, and very little droplet motion was observed, as all L2 domains nucleated and remained on the crucible walls until they encroached on the monotectic front. At small distances from the monotectic front a Zn-rich solute boundary layer preceding the α-Al, caused the L2 domains to dissolve as Bi-Zn-Al regains complete miscibility upon reaching a critical Zn-concentration. In the shallow mush region behind the monotectic reaction, a high Zn solid solubility and a relatively fast diffusion of Zn in α-Al combine to cause a rapid diminishing Zn concentration in the mush liquid

  5. Ultranarrow AuPd and Al wires

    SciTech Connect

    Altomare, Fabio; Chang, Albert M.; Melloch, Michael R.; Hong Yuguang; Tu, Charles W.

    2005-04-25

    In this letter, we discuss a versatile template technique aimed to the fabrication of sub-10 nm wide wires. Using this technique, we have measured AuPd wires, 12 nm wide and as long as 20 {mu}m. Even materials that form a strong superficial oxide, and thus not suited to be used in combination with other techniques, can be employed. In particular, we have measured Al wires, with lateral width smaller or comparable to 10 nm, and length exceeding 10 {mu}m.

  6. Photoelectrochemical sensing of 4-chlorophenol based on Au/BiOCl nanocomposites.

    PubMed

    Yan, Pengcheng; Xu, Li; Xia, Jiexiang; Huang, Yan; Qiu, Jingxia; Xu, Qian; Zhang, Qi; Li, Huaming

    2016-08-15

    The Au/BiOCl composites have been prepared by a facile one-pot ethylene glycol (EG) assisted solvothermal reaction in the presence of ionic liquid 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl). During the synthesis procedure, the [C16mim]Cl has been used as Cl source, solvent of this system, and dispersing agent to effectively disperse Au on the surface of BiOCl. The as-prepared samples have been systematically characterized by multiple instruments to investigate the structure, morphology, and photoelectrochemical properties. According to the photoelectrochemical data, the Au/BiOCl composites exhibit better photoelectrochemical performance toward the detection of 4-chlorophenol than that of the pure BiOCl. The photocurrent response of Au/BiOCl modified electrode is high and stable under light irradiation. The proposed Au/BiOCl modified electrode shows a wide linear response ranging from 0.16 to 20mgL(-1) with detection limit of 0.05mgL(-1). It indicates a dramatically promising application of bismuth oxyhalides in photoelectrochemical detection. It will be expected that the present study may be lightly extended to the monitor of other organic pollutants by photoelectrochemical detection of the Au/BiOCl composites.

  7. Preparation of Au-BiVO4 heterogeneous nanostructures as highly efficient visible-light photocatalysts.

    PubMed

    Cao, Shao-Wen; Yin, Zhen; Barber, James; Boey, Freddy Y C; Loo, Say Chye Joachim; Xue, Can

    2012-01-01

    Au-BiVO(4) heterogeneous nanostructures have been successfully prepared through in situ growth of gold nanoparticles on BiVO(4) microtubes and nanosheets via a cysteine-linking strategy. The experimental results reveal that these Au-BiVO(4) heterogeneous nanostructures exhibit much higher visible-light photocatalytic activities than the individual BiVO(4) microtubes and nanosheets for both dye degradation and water oxidation. The enhanced photocatalytic efficiencies are attributed to the charge transfer from BiVO(4) to the attached gold nanoparticles as well as their surface plasmon resonance (SPR) absorption. These new heteronanostructures are expected to show considerable potential applications in solar-driven wastewater treatment and water splitting.

  8. Structural and dynamical properties of liquid Al-Au alloys

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Voigtmann, Th.; Kolland, G.; Kobatake, H.; Brillo, J.

    2015-11-01

    We investigate temperature- and composition-dependent structural and dynamical properties of Al-Au melts. Experiments are performed to obtain accurate density and viscosity data. The system shows a strong negative excess volume, similar to other Al-based binary alloys. We develop a molecular-dynamics (MD) model of the melt based on the embedded-atom method (EAM), gauged against the available experimental liquid-state data. A rescaling of previous EAM potentials for solid-state Au and Al improves the quantitative agreement with experimental data in the melt. In the MD simulation, the admixture of Au to Al can be interpreted as causing a local compression of the less dense Al system, driven by less soft Au-Au interactions. This local compression provides a microscopic mechanism explaining the strong negative excess volume of the melt. We further discuss the concentration dependence of self- and interdiffusion and viscosity in the MD model. Al atoms are more mobile than Au, and their increased mobility is linked to a lower viscosity of the melt.

  9. Magnetic properties of nearly stoichiometric CeAuBi{sub 2} heavy fermion compound

    SciTech Connect

    Adriano, C.; Jesus, C. B. R.; Pagliuso, P. G.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Garcia, D. J.

    2015-05-07

    Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX{sub 2} (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu{sub 1−x}Bi{sub 2−y} by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu{sub 1−x}Bi{sub 2−y} (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at T{sub N} = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (H{sub c} ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu{sub 0.92}Bi{sub 1.6} exhibits a weak heavy fermion behavior with strongly localized Ce{sup 3+} 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J{sub RKKY} exchange parameters between the Ce{sup 3+} ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu{sub 1−x}Bi{sub 2−y} compounds, and we compare our results with the isostructural compound CeCuBi{sub 2}.

  10. Theoretical prediction of thermodynamic activities of liquid Au-Sn-X (X=Bi, Sb, Zn) solder systems

    NASA Astrophysics Data System (ADS)

    Awe, O. E.; Oshakuade, O. M.

    2017-02-01

    Molecular interaction volume model has been theoretically used to predict the thermodynamic activities of tin in Au-Sn-Bi and Au-Sn-Sb and the thermodynamic activity of zinc in Au-Sn-Zn at experimental temperatures 800 K, 873 K and 973 K, respectively. On the premise of agreement between the predicted and experimental values, we predicted the activities of the remaining two components in each of the three systems. This prediction was extended from three cross-sections to five cross-sections, and to temperature range 400-600 K, relevant for applications. Iso-activities were plotted. Results show that addition of tin reduces the tendency for chemical short range order in both Au-Sb and Au-Zn systems, while addition of gold and bismuth, respectively, reduce the tendency for chemical short range order in Sn-Sb and Au-Sn systems. Also, we found that, in the desired high-temperature region for applications, while a combination of chemical order and miscibility of components exist in both Au-Sn-Bi and Au-Sn-Zn systems, only chemical order exist in the Au-Sn-Sb system. Results, further show that increase in temperature reduces the phase separation tendency in Au-Sn-Bi system.

  11. Microstructural characteristics of Au/Al bonded interfaces

    SciTech Connect

    Li Junhui . E-mail: lijunhui@mail.csu.edu.cn; Han Lei; Duan Jian; Zhong Jue

    2007-02-15

    Fracture characteristics at the interface of ultrasonic bonds between Au and Al were characterized by SEM following pull-testing to effect separation of the bonded joints. Vertical sections at the bonding point were produced by ion-sputter thinning, and were examined by TEM. Results show that the thickness of the Au/Al atomic diffusion interface was about 500 nm due to combined effects of ultrasonic and thermal energy. Ultrasonic vibration activates dislocations in the crystalline lattice and increases atomic diffusion. The fracture morphology on the lift-off interface was dimpled rupture. Tensile fracture occurred during the pull-test not at the bonded interface but in the base material; the bond strength at the interface was enhanced by the diffusion reactions that occurred across the interface due to the combined ultrasonic and thermal energy.

  12. Colorimetric Biosensor for Detection of Cancer Biomarker by Au Nanoparticle-Decorated Bi2Se3 Nanosheets.

    PubMed

    Xiao, Liangping; Zhu, Aimei; Xu, Qingchi; Chen, Ying; Xu, Jun; Weng, Jian

    2017-03-01

    The colorimetric biosensors have attracted intensive interest; however, their relatively low sensitivity limits their applications in clinic detection. Herein, we develop an effective colorimetric biosensor based on highly catalytic active Au nanoparticle-decorated Bi2Se3 (Au/Bi2Se3) nanosheets. Au/Bi2Se3 nanosheets are facilely synthesized by simply sonicating Au precursor with the as-synthesized Bi2Se3 nanosheets in aqueous solution. Because of the low redox potential and typical topological insulating properties, Bi2Se3 nanosheets is capable of providing and accumulating electrons on its surface. Such unique properties of Bi2Se3 nanosheets contribute to strong synergistic catalytic effects with Au nanoparticles, particularly when Au/Bi2Se3 nanosheets are utilized for catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH4 (K = 386.67 s(-1)g(-1)). The excellent catalytic activity of Au/Bi2Se3 nanosheets can be "switched off" upon treatment of antibody of cancer biomarker such as anticarcinoembryonic antibody (anti-CEA). Addition of the corresponding antigen such as cancer biomarker carcinoembryonic antibody (CEA) can successively help "switch on" the catalytic activity of Au/Bi2Se3 nanosheets, where the resuming degree however depends on the antigen concentration. This cancer biomarker depended catalytic behavior therefore allows Au/Bi2Se3 nanosheets to be employed as a colorimetric sensor for detection of a particular cancer biomarker, for the reduction of 4-nitrophenol (4-NP) by NaBH4 itself involves apparent color change. The sensor shows high sensitivity and selectivity for the cancer biomarker, even for a concentration as low as 160 pg/mL for CEA, which fully satisfies the requirement for real clinical applications. The developed colorimetric sensor shows good generality for detection of different types of cancer biomarkers, such as α-fetoprotein (AFP) and prostate-specific antigen (PSA). Furthermore, real clinic sample analyzing result shows that the

  13. In-situ growth of Au and β-Bi2O3 nanoparticles on flower-like Bi2O2CO3: A multi-heterojunction photocatalyst with enhanced visible light responsive photocatalytic activity.

    PubMed

    Wang, Peifang; Xu, Liya; Ao, Yanhui; Wang, Chao

    2017-06-01

    In this work, flower-like Au/Bi2O2CO3/Bi2O3 multi-heterojunction photocatalysts were prepared by a in-situ growth method. The as-prepared samples were characterized by different techniques including Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectrometry (DRS), X-ray photoelectron spectroscopy (XPS), Photoluminescence (PL) and photo-induced current. The photocatalytic performance of the as prepared samples was evaluated by degradation of rhodamine B (RhB) under visible light (λ>400nm). Au/Bi2O2CO3/Bi2O3 exhibited much higher activity than pure Bi2O2CO3 or Bi2O2CO3/Bi2O3. The rate constant of best one Au/Bi2O2CO3/Bi2O3 sample is 100 and 14 times as that of pure Bi2O2CO3 and β-Bi2O3/Bi2O2CO3, respectively. The enhanced photocatalytic activity of Au/Bi2O2CO3/Bi2O3 can be ascribed to the surface plasmon resonance (SPR) effects of Au nanoparticles and the formed multi-heterojunctions, which enhanced the absorbance of visible light and facilitated the transferring and separation of photogenerated electron-hole pairs, respectively.

  14. Bi-functional Au/FeS (Au/Co3O4) composite for in situ SERS monitoring and degradation of organic pollutants

    NASA Astrophysics Data System (ADS)

    Ma, Shuzhen; Cai, Qian; Lu, Kailing; Liao, Fan; Shao, Mingwang

    2016-01-01

    The bi-functional Au/FeS (Au/Co3O4) composite was fabricated by in situ reducing Au nanoparticles onto the surface of FeS (Co3O4). The as-prepared FeS possessed a multi-structure composed of plenty of nanoplates, which were coated by Au nanoparticles with an average size of 47.5 nm. While the Co3O4 showed a thin hexagonal sheet containing Au nanoparticles on its surface with an average size of 79.0 nm. Both the as-prepared Au/FeS and Au/Co3O4 composites exhibited excellent SERS performance, capable of enhancing the Raman signals of R6G molecules with the enhancement factor up to 1.81 × 106 and 7.60 × 104, respectively. Moreover, Au/FeS (Au/Co3O4) composite also has been verified to have intrinsic peroxidase-like activity, which could decompose H2O2 into hydroxyl radicals and then degrade organic pollutants into small molecules. Therefore, SERS can be used to real-time and in situ monitoring the degradation process of R6G molecules, employing the Au/FeS (Au/Co3O4) composite both as SERS substrate and catalyst.

  15. High-pressure synthesis of BiFeO3-BiAlO3 and BiFeO3-MnTiO3 solid solution

    NASA Astrophysics Data System (ADS)

    Shimura, Gen; Kusaba, Keiji; Miyawaki, Tetsuya; Niwa, Ken; Asano, Hidefumi; Hasegawa, Masashi

    2013-06-01

    There have been so many investigations for high-pressure synthesis of perovskite-type oxides in the material science field. Multiferroic material is particularly attracted in the field of electronic device materials. BiFeO3 (ferroelectric antiferromagnet) is known as the only Bi-contained perovskite which can be synthesized at ambient pressure. We investigated solid solution systems of BiFeO3-BiAlO3 and BiFeO3-MnTiO3 under high pressure and high temperature to synthesize a new multiferroic compound in the present study. Chemical reagents of simple oxides were mixed with a mortar as a starting material. The mixture was rapped with a gold foil, and it encased in a cubic pressure-medium with a graphite furnace. High pressure experiments were carried out using two DIA-type high pressure apparatuses installed in Nagoya University. X-ray powder diffraction patterns of all recovered specimens were collected using Cu-K α radiation and magnetic susceptibilities for some of the recovered specimens were measured using a vibrating sample magnetometer. In the system of BiFeO3-BiAlO3, the BiFeO3-type solid solution was only obtained in the both Fe- and Al-rich composition. While in the system of BiFeO3-MnTiO3, no solid solutions were observed.

  16. Structural and electrical properties of AuPd/Mo bi-layer films for transition edge sensors

    NASA Astrophysics Data System (ADS)

    Boucher, R.; May, T.; Wagner, Th; Zakosarenko, V.; Anders, S.; Mayer, H. G.

    2006-01-01

    We have tuned the transition temperature of the AuPd/Mo bi-layer in the temperature range 100-800 mK and used models derived from the Usadel theory to predict and fit the behaviour of the transition temperature. As expected, the influence of the AuPd on the transition temperature is stronger than that found by others from pure Au, but weaker than that of pure Pd. The extracted coherence length of the Cooper pairs in the metal alloy points to the greatest influence coming from the Pd part of the AuPd. X-ray measurements show the films to be textured, with the Mo(110) and AuPd(111) peaks being dominant in the out-of-plane direction. The transition width is seen to increase with the spread of the orientation of the z direction of the individual grains.

  17. Formation of dislocations and hardening of LiF crystals irradiated with energetic Au, Bi, Pb, and S ions

    NASA Astrophysics Data System (ADS)

    Maniks, J.; Manika, Ilze; Schwartz, K.; Toulemonde, M.; Trautmann, C.

    2003-08-01

    The irradiation of LiF crystals with Au, Pb, Bi, and S ions in the range of 400 - 2200 MeV leads to a remarkable increase of the hardness. The effect appears for Bi and Pb ions at fluences above 109 ions/cm2 and for S ions above 1010 ions/cm2. The increase of hardness follows the energy loss and is related to the formation of defects along the ion path. Defect complexes, clusters and aggregates with nanoscale dimensions serve as strong obstacles for dislocations and cause dispersion strengthening. Structural investigations reveal the generation of long-range stress in the adjacent non-irradiated part of the crystal. Close to the implantation zone, the stress exceeds the yield strength, causing microplastic deformation and work hardening. Compared to light S ions, heavy ions (Au, Pb, Bi) cause more severe structural damage, larger hardening effects, and higher internal and long-range stress.

  18. Au/BiOCl heterojunction within mesoporous silica shell as stable plasmonic photocatalyst for efficient organic pollutants decomposition under visible light.

    PubMed

    Yan, Xiaoqing; Zhu, Xiaohui; Li, Renhong; Chen, Wenxing

    2016-02-13

    A new mesoporous silica protected plasmonic photocatalyst, Au/BiOCl@mSiO2, was prepared by a modified AcHE method and a subsequent UV light induced photodeposition process. The surfactant-free heterojunction allows the electrons spontaneously flow from Au to nearby BiOCl surface, leading to the accumulation of positive charges on Au surface, and negative charges on Bi species under visible light. Au/BiOCl@mSiO2 exhibits high visible light photocatalytic efficiency in complete oxidation of aqueous formaldehyde and Rhodamin B. We showed that a positive relationship exists between the LSPR effect and rate enhancements, and leads to a hypothesis that the metallic Au LSPR enhances the photocatalytic rates on nearby semiconductors by transferring energetic electrons to BiOCl and increasing the steady-state concentration of active OH species by a multi-electron reduction of molecular oxygen. The OH species is the main oxidant in photocatalytic transformations, whose intensity is greatly enhanced in the dye-involving systems due to the synergetic effect between LSPR and dye sensitization processes. In addition, the mesoporous SiO2 shell not only inhibits the over growth of BiOCl nanocrystals within the silica frameworks, but also protects the dissolution of chloride or Au species into aqueous solution, which ultimately makes the Au/BiOCl@mSiO2 catalysts rather stable during photocatalysis.

  19. Structural and mechanical properties of magnetron-sputtered Al-Au thin films

    NASA Astrophysics Data System (ADS)

    Azadmanjiri, Jalal; Wang, James; Berndt, Christopher C.; Wen, Cuie; Srivastava, Vijay K.; Kapoor, Ajay

    2017-01-01

    There is global interest in improving the mechanical properties of light metals such as aluminum (Al)-based alloys by tailoring their microstructures at the nanometer scale. On the other hand, gold (Au) has been widely applied as a wire bonding material due to its prominent ductility and conductivity. In this study, the microstructure, hardness and elastic modulus of DC magnetron-sputtered aluminum/gold (Al/Au) composite thin films of different thicknesses were investigated. It is shown that in addition to the formation of AlAu2 phase, additional Al and Au nanosegregated phases also formed. The Al/Au thin films of 600 and 800 nm thickness exhibit the maximum hardness ( 5.40 GPa) and elastic modulus ( 97.00 GPa). However, film thicknesses of 1000 and 1200 nm demonstrate a reduction in hardness and elastic modulus due to different growth mechanisms and the formation of voids that can be attributed to the Kirkendall phenomenon.

  20. Highly efficient and stable Au/Bi2MoO6/Bi2WO6 heterostructure with enhanced photocatalytic activity for NO gas removal under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Jia, Jia; Du, Xiao; Liu, Enzhou; Wan, Jun; Pan, Chao; Ma, Yongning; Hu, Xiaoyun; Fan, Jun

    2017-04-01

    The ternary composite photocatalyst Au/Bi2MoO6/Bi2WO6 has been successfully synthesized by a facile hydrothermal process and microwave-assisted chemical reduction method for the first time. A series of characterization results reveal that Au nanoparticles are uniformly dispersed on the surface of Bi2MoO6/Bi2WO6 microspheres. The unique photocatalytic performance of the novel composite material is evaluated by the photocatalytic removal of NO gas at ppb levels under visible light irradiation. The photocatalytic removal rate of NO gas in the presence of Au/Bi2MoO6/Bi2WO6 sample is the highest, which directly attributes to the effective separation of photoinduced charge carriers through the formation of the heterojunction and the Schottky junction at the interface between Au nanoparticles and Bi2MoO6 or Bi2WO6. Additionally, it is indicated that the h + and \\centerdot \\text{O}2- play indispensable role in photocatalytic process by free radicals trapping experiments and the oxidation products of NO gas on the surface of the catalysts are nitrate by drawing the standard curve of total N content in nitrate. Meanwhile, a possible mechanism for the photocatalytic activity enhancement of the Au/Bi2MoO6/Bi2WO6 composites is proposed. These results demonstrate that the Au/Bi2MoO6/Bi2WO6 photocatalyst is a promising candidate for indoor air purification under solar light irradiation.

  1. Gold enrichment and the Bi-Au association in pyrrhotite-rich massive sulfide deposits, Escanaba trough, Southern Gorda Ridge

    USGS Publications Warehouse

    Tormanen, T.O.; Koski, R.A.

    2005-01-01

    High gold contents (to 10.1 ppm, avg 1.4 ppm, n = 34) occur in pyrrhotite-rich massive sulfide samples from the sediment-covered floor of the Escanaba trough, the slow-spreading, southernmost segment of Gorda Ridge. These concentrations reflect the presence of primary gold, formed during high-temperature hydrothermal activity in mounds and chimneys, and secondary gold deposited during sea-floor weathering of massive sulfide. Primary gold occurs as fine-grained (2 ??m) secondary gold grains have a porous, flaky morphology and occur in samples in which pyrrhotite is oxidized and replaced by Fe oxyhydroxides, Fe sulfate, and sulfur. Mounds and chimneys dominated by pyrrhotite and containing lesser amounts of isocubanite, chalcopyrite, and Fe-rich sphalerite were formed by high-temperature (estimated range 325??-275??C), reduced, low-sulfur vent fluids. The mineral and fluid compositions during this main stage of hydrothermal venting reflect subsurface interaction between circulating hydrothermal fluids and turbiditic sediment containing as much as 1.1 percent organic carbon. As the deposition of pyrrhotite, Cu-Fe sulfides, and sphalerite waned, a volumetrically minor suite of sulfarsenide, arsenide, Bi, and Au minerals was deposited from highly reduced, late main-stage fluids diffusing through mounds and chimneys. The low solubility of Au as a bisulfide complex and the absence of fluid mixing during this stage of hydrothermal activity apparently inhibited the precipitation of gold directly from solution. Instead, gold precipitation is thought to be linked to elevated concentrations of Bi in the late main-stage fluids. The textural relationships of Au and Bi minerals in pyrrhotite-rich samples, low melting point of native bismuth (271.4??C), and recent experimental results on Au and Bi in hydrothermal fluids contribute to the hypothesis that gold was effectively scavenged from the Escanaba trough vent fluids by coexisting droplets of liquid bismuth. Additional phase

  2. Josephson effect in Al/Bi2Se3/Al coplanar hybrid devices

    NASA Astrophysics Data System (ADS)

    Galletti, L.; Charpentier, S.; Lucignano, P.; Massarotti, D.; Arpaia, R.; Tafuri, F.; Bauch, T.; Suzuki, Y.; Tagliacozzo, A.; Kadowaki, K.; Lombardi, F.

    2014-08-01

    The edge states of Topological Insulators (TI) are protected against backscattering, thanks to the topological properties arising from their band structure. Coupling a TI to a superconductor (S) can induce unconventional effects, including the creation of Majorana bound states (MBS). The fabrication of coplanar hybrid devices is a fundamental step to pave the way to the understanding of proximity effects in topologically non-trivial systems, and to a large variety of experiments aimed at the possible detection of MBS. We discuss the feasibility and some relevant properties of Al-Bi2Se3-Al coplanar proximity devices. Special attention is devoted to the design of the junction, aimed at enhancing the coupling between the electrodes and the TI.

  3. Determination of Te, Bi, Ni, Sb and Au by X-ray fluorescence spectrometry following electroenrichment on a copper cathode

    NASA Astrophysics Data System (ADS)

    Zawisza, Beata; Sitko, Rafał

    2007-10-01

    The electrodepositons of Te, Bi, Ni, Sb and Au from aqueous solution of pH = 1 on the cathode surface have been studied for X-ray fluorescence analysis (XRF). A special holder for a copper electrode has been constructed to perform the electrodeposition process on only one side of the electrode. After electrolysis, the copper electrode can be easily removed from the holder; after rinsing it with water and drying it can be analyzed by XRF. The proposed method of sample preparation and preconcentration of Te, Bi, Ni, Sb, Au provides suitable samples which are devoid of the negative and undesirable effects of XRF analysis, such as particle size and matrix effects. The influence of time on the deposition yield has been examined. The method of preconcentration is efficient. The inhomogeneity of the prepared specimens has been studied using internal standard method. The calibration is based on using synthetic standards, certified reference materials and standard addition method. The best results are achieved by the standard addition method. The agreement between results obtained with XRF analysis and certified values is satisfactory and indicates the usefulness of the proposed method for determination of Te, Bi, Ni, Sb and Au in anode slime.

  4. Electronic properties and topological phases of ThXY (X = Pb, Au, Pt and Y = Sb, Bi, Sn) compounds

    NASA Astrophysics Data System (ADS)

    Zahra, Nourbakhsh; Aminollah, Vaez

    2016-03-01

    The electronic properties and topological phases of ThXY (X = Pb, Au, Pt, Pd and Y = Sb, Bi, Sn) compounds in the presence of spin-orbit coupling, using density functional theory are investigated. The ThPtSn compound is stable in the ferromagnetic phase and the other ThXY compounds are stable in nonmagnetic phases. Band structures of these compounds in topological phases (insulator or metal) and normal phases within generalized gradient approximation (GGA) and Engel-Vosko generalized gradient approximation (GGA_EV) are compared. The ThPtSn, ThPtBi, ThPtSb, ThPdBi, and ThAuBi compounds have topological phases and the other ThXY compounds have normal phases. Band inversion strengths and topological phases of these compounds at different pressure are studied. It is seen that the band inversion strengths of these compounds are sensitive to pressure and for each compound a second-order polynomial fitted on the band inversion strengths-pressure curves.

  5. Interaction of Au, Ag, and Bi ions with Ba2YCu3O(7-y) - Implications for superconductor applications

    NASA Technical Reports Server (NTRS)

    Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Hambourger, P. D.

    1988-01-01

    Results are presented on the reactions of Au, Ag, and Bi ions with Ba2YCu3O(7-y) oxides and on the properties of the resultant materials. The results indicate that Au(3+) structural chemistry makes gold an excellent candidate for multiphase structures of the Ba2Y(Cu/1-x/Au/x/)3O(7-y)-type substituted superconductors. Silver is structurally and chemically compatible with the perovskite structure, but when it forms a second phase, it does so without the destruction of the superconducting phase, making silver a useful metal for metal/ceramic applications. On the other hand, bismuth was shown to degrade Tc phase or to form other phases, indicating that it may not be useful in applications with rare-earth-based superconductors.

  6. Evolution of local atomic structure during solidification of Al2Au liquid: An ab initio study

    SciTech Connect

    Xiong, L H; Lou, H B; Wang, X D; Debela, T T; Cao, Q P; Zhang, D X; Wang, S Y; Wang, C Z; Jiang, J Z

    2014-04-01

    The local atomic structure evolution in Al2Au alloy during solidification from 2000 K to 400 K was studied by ab initio molecular dynamics simulations and analyzed using the structure factor, pair correlation functions, bond angle distributions, the Honeycutt-Anderson (HA) index and Voronoi tessellation methods. It was found that the icosahedral-like clusters are negligible in the Al2Au stable liquid and supercooled liquid states, and the most abundant clusters are those having HA indices of 131 and 120 or Voronoi indices of < 0,4,4,0 >, < 0,3, 6,0 > and < 0,4,4,2 > with coordination numbers of 8, 9 and 10, respectively. These clusters are similar to the local atomic structures in the CaF2-type Al2Au crystal, revealing the existence of structure heredity between liquid and crystalline phase in Al2Au alloy. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  7. Prediction of AU, AL, and AE indices using solar wind parameters

    NASA Astrophysics Data System (ADS)

    Luo, B.; Li, X.; Temerin, M. A.; Liu, S.

    2013-12-01

    An empirical model that predicts the AU index, a measure of the Earth's east electrojet, derived from magnetometers in the Northern hemisphere, is introduced. In addition, we have improved the previous AL model (Li et al., 2007) and have combined it with the AU model to produce an AE model. All models are based on upstream solar wind and interplanetary magnetic field parameters that have been propagated to the magnetopause by a simple ballistic propagation scheme for the years 1995 to 2001. The AU model predicts the 10-min averaged AU index for the seven years 1995-2001 with a prediction efficiency (PE) of 0.716, a linear correlation coefficient (LC) between the AU index and the model of 0.846, and a root mean square (RMS) error of 39.3 nT. We have updated the AL model introduced in Li et al. [2007] using the same prediction functions used to predict AU but with different parameters. The new AL model predicts the seven year AL index with a PE of 0.715, an LC of 0.846, and an RMS error of 81.6 nT. Using AE = AU-AL, the AE index is predicted with a PE of 0.788, an LC of 0.888, and an RMS error of 95.7 nT. The better PE and LC of the AE model over AU and AL models is because AU and AL are better correlated then their prediction errors. It is also found that: (1) The F10.7 index modulates the growth of auroral electrojet indices; (2) AU and AL behave differently during geomagnetic storm main phases. AU can drop to a low level while the magnitude of AL does not drop as much; (3) the longer-averaged auroral electrojets indices can be predicted very well but shorter timescale variations are much less predictable; (4) auroral electrojet activity is strongly dependent on the upstream solar wind velocity and the interplanetary magnetic field but is only weakly dependent on the solar wind density.

  8. Petrogenetic significance of Au-Bi-Te-S associations: The example of Maldon, Central Victorian gold province, Australia

    NASA Astrophysics Data System (ADS)

    Ciobanu, Cristiana L.; Birch, William D.; Cook, Nigel J.; Pring, Allan; Grundler, Pascal V.

    2010-04-01

    Mineralization at Maldon, Victorian goldfields, Australia, is part of the Western Lachlan Foldbelt and is hosted by deformed Lower Ordovician metasediments intruded by the Late Devonian Harcourt Granite. Gold-Bi-Te-S associations in the deposit include four gold-bearing minerals (maldonite, native gold, jonassonite, and aurostibite) and a range of sulphotellurides from the tetradymite group, all of which are paragenetically tied to native bismuth. The simpler phase associations, involving bismuth, maldonite and one or the other Bi-(sulpho)tellurides, resemble the equivalents of eutectics in the system Au-Bi-Te and hint at crystallisation from melts. The complex associations include symplectites of gold and bismuth resulting from replacement of maldonite and are dominated by co-existing, sulphur-bearing species (joséite-A, joséite-B, an unnamed phase with bulk composition approximating to Bi 3(Te,S) 2 and jonassonite). The complexity of such assemblages is also underpinned by chemical-structural inhomogeneity within the unnamed phase, i.e. nanoscale domains of Bi 14(Te,S) 9 and Bi 5(Te,S) 3, as documented from electron diffractions obtained from a FIB-TEM foil. Although such lattice-scale intergrowths reveal polysomatic disorder that can be associated with replacement of one telluride by another, the structural modules in the overall stacking sequence indicate formation under local equilibrium conditions. The mineralogical complexity of all Au-Bi-Te-S associations can be modelled in terms of interaction between simpler assemblages and sulphur-bearing fluids. Three stages—all involving gold minerals—are recognised: (1) bismuth + maldonite ± hedleyite; (2) Bi-sulphotellurides + jonassonite, and decomposition of maldonite (gold + bismuth); and (3) bismuthinite + gold from decomposition of maldonite or jonassonite. The last stage is coincident with chloritisation and occurs during or following granite emplacement. Thermodynamic modelling of maldonite replacement

  9. Nano features of Al/Au ultrasonic bond interface observed by high resolution transmission electron microscopy

    SciTech Connect

    Ji Hongjun; Li Mingyu Kim, Jong-Myung; Kim, Dae-Won; Wang Chunqing

    2008-10-15

    Nano-scale interfacial details of ultrasonic AlSi1 wire wedge bonding to a Au/Ni/Cu pad were investigated using high resolution transmission electron microscopy (HRTEM). The intermetallic phase Au{sub 8}Al{sub 3} formed locally due to diffusion and reaction activated by ultrasound at the Al/Au bond interface. Multilayer sub-interfaces roughly parallel to the wire/pad interface were observed among this phase, and interdiffusional features near the Au pad resembled interference patterns, alternately dark and bright bars. Solid-state diffusion theory cannot be used to explain why such a thick compound formed within milliseconds at room temperature. The major formation of metallurgical bonds was attributed to ultrasonic cyclic vibration.

  10. Preparation, characterization and dye adsorption of Au nanoparticles/ZnAl layered double oxides nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Yu Xin; Hao, Xiao Dong; Kuang, Min; Zhao, Han; Wen, Zhong Quan

    2013-10-01

    In this work, Au/ZnAl-layer double oxides (LDO) nanocomposties were prepared through a facile calcination process of AuCl4- intercalated ZnAl-layered double hydroxides (LDHs) nanocomposites. The morphology and crystal structure of these nanocomposites were characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and N2 sorption analysis. By tailoring the process parameter, such as calcination temperature, heating time and the component composition, the adsorption properties of methyl orange (MO) on the Au/ZnAl-LDO nanocomposites were investigated in this work. In a typical adsorption process, it was found that 0.985 mg of MO (0.01 g L-1, 100 mL, 1 mg of MO in total) can be removed in 60 min by utilizing only 2.5 mg of Au/ZnAl-LDO (Au content, 1%) as adsorbents. Our adsorption data obtained from the Langmuir model also gave good values of the determination coefficient, and the saturated adsorption capacity of Au/ZnAl-LDO nanocomposites for MO was found to be 627.51 mg/g under ambient condition (e.g., room temperature, 1 atm). In principle, these hybrid nanostructures with higher adsorption abilities could be very promising adsorbents for wastewater treatment.

  11. Corrosion Protection of Al/Au/ZnO Anode for Hybrid Cell Application

    PubMed Central

    Slaughter, Gymama; Stevens, Brian

    2015-01-01

    Effective protection of power sources from corrosion is critical in the development of abiotic fuel cells, biofuel cells, hybrid cells and biobateries for implantable bioelectronics. Corrosion of these bioelectronic devices result in device inability to generate bioelectricity. In this paper Al/Au/ZnO was considered as a possible anodic substrate for the development of a hybrid cell. The protective abilities of corrosive resistant aluminum hydroxide and zinc phosphite composite films formed on the surface of Al/Au/ZnO anode in various electrolyte environments were examined by electrochemical methods. The presence of phosphate buffer and physiological saline (NaCl) buffer allows for the formation of aluminum hyrdroxide and zinc phosphite composite films on the surface of the Al/Au/ZnO anode that prevent further corrosion of the anode. The highly protective films formed on the Al/Au/ZnO anode during energy harvesting in a physiological saline environment resulted in 98.5% corrosion protective efficiency, thereby demonstrating that the formation of aluminum hydroxide and zinc phosphite composite films are effective in the prevention of anode corrosion during energy harvesting. A cell assembly consisting of the Al/Au/ZnO anode and platinum cathode resulted in an open circuit voltage of 1.03 V. A maximum power density of 955.3 μW/ cm2 in physiological saline buffer at a cell voltage and current density of 345 mV and 2.89 mA/ cm2, respectively. PMID:26580661

  12. Electronic diffuse reflectance spectra of Bi-V-Sb-Al catalysts for oxidative ammonolysis

    SciTech Connect

    Rizaev, R.G.; Akhverdiev, R.B.; Alieva, T.C.; Efendiev, M.R.; Krylov, O.V.; Magerranova, Z.Y.

    1986-10-01

    Diffuse reflectance spectra of monocomponent, binary, and tricomponent Bi-VSb-Al catalysts for the oxidative ammonolysis of aromatic compounds were taken in the 200- to 850-nm region and interpreted. It was established that vanadium ions in two valence states, V/sup 4 +/ and V/sup 5 +/, exist on the surface of ..gamma..-Al/sub 2/O/sub 3/. On treatment of V-Sb-Al with a reaction mixture of C/sub 7/H/sub 6/Cl/sub 2/ + O/sub 2/ + NH/sub 3/, V/sup 5 +/ ions are reduced to V/sup 4 +/ and Sb/sup 3 +/ ions are oxidized to Sb/sup 5 +/. This is also characteristic of the V-Al and Sb-Al oxide systems. In the case of V-Bi-Al, treatment with the reaction mixture does not lead to the reduction of V/sup 5 +/ ions. After treatment of Sb-Bi-Al with the reaction mixture, the presence of three phases, Sb/sub 2/O/sub 3/, Sb/sub 2/O/sub 5/, and Bi/sub 2/O/sub 3/ was detected spectroscopically. After treatment of the Bi-V-Sb-Al with the reaction mixture, the formation of a chemical compound of the bismuth vanadate type in which the V/sup 5 +/ ions are tightly held and resistant to oxidation was observed. The phases Sb/sub 2/O/sub 3/ and Sb/sub 2/O/sub 5/ were also found.

  13. Degradation mechanisms of Ti/Al/Ni/Au-based Ohmic contacts on AlGaN/GaN HEMTs

    DOE PAGES

    Hwang, Ya-Hsi; Ahn, Shihyun; Dong, Chen; ...

    2015-04-27

    We investigated the degradation mechanism of Ti/Al/Ni/Au-based Ohmic metallization on AlGaN/GaN high electron mobility transistors upon exposure to buffer oxide etchant (BOE). The major effect of BOE on the Ohmic metal was an increase of sheet resistance from 2.89 to 3.69 Ω/ₜafter 3 min BOE treatment. The alloyed Ohmic metallization consisted 3–5 μm Ni-Al alloy islands surrounded by Au-Al alloy-rings. The morphology of both the islands and ring areas became flatter after BOE etching. Lastly, we used energy dispersive x-ray analysis and Auger electron microscopy to analyze the compositions and metal distributions in the metal alloys prior to and aftermore » BOE exposure.« less

  14. Degradation mechanisms of Ti/Al/Ni/Au-based Ohmic contacts on AlGaN/GaN HEMTs

    SciTech Connect

    Hwang, Ya-Hsi; Ahn, Shihyun; Dong, Chen; Zhu, Weidi; Kim, Byung-Jae; Le, Lingcong; Ren, Fan; Lind, Aaron G.; Dahl, James; Jones, Kevin S.; Pearton, Stephen J.; Kravchenko, Ivan I.; Zhang, Ming-Lan

    2015-04-27

    We investigated the degradation mechanism of Ti/Al/Ni/Au-based Ohmic metallization on AlGaN/GaN high electron mobility transistors upon exposure to buffer oxide etchant (BOE). The major effect of BOE on the Ohmic metal was an increase of sheet resistance from 2.89 to 3.69 Ω/ₜafter 3 min BOE treatment. The alloyed Ohmic metallization consisted 3–5 μm Ni-Al alloy islands surrounded by Au-Al alloy-rings. The morphology of both the islands and ring areas became flatter after BOE etching. Lastly, we used energy dispersive x-ray analysis and Auger electron microscopy to analyze the compositions and metal distributions in the metal alloys prior to and after BOE exposure.

  15. Ag/Au bi-metallic film based color surface plasmon resonance biosensor with enhanced sensitivity, color contrast and great linearity.

    PubMed

    Li, Chung-Tien; Lo, Kun-Chi; Chang, Hsin-Yun; Wu, Hsieh-Ting; Ho, Jennifer H; Yen, Ta-Jen

    2012-01-01

    In wavelength surface plasmon resonance (SPR) biosensor, the manipulation of SPR dispersion relation by Ag/Au bi-metallic film was first time implemented. Due to the enhanced resonant wavelength shift and the sharper SPR slope of using Ag/Au bi-metallic film, the illuminated color of reflection shows one order of magnitude greater contrast than conventional SPR biosensors. Such an Ag/Au bi-metallic film based color SPR biosensor (CSPRB) allows the detail bio-interactions, for example 100 nM streptavidin, to be distinguished by directly observing the color change of reflection through naked eyes rather than the analysis of spectrometer. In addition to the enhanced sensitivity and color contrast, this CSPRB also possesses a great linear detection range up to 0.0254 RIU, which leading to the application of point-of-care tests.

  16. Effects of V2O5/Au bi-layer electrodes on the top contact Pentacene-based organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Borthakur, Tribeni; Sarma, Ranjit

    2017-01-01

    Top-contact Pentacene-based organic thin film transistors (OTFTs) with a thin layer of Vanadium Pent-oxide between Pentacene and Au layer are fabricated. Here we have found that the devices with V2O5/Au bi-layer source-drain electrode exhibit better field-effect mobility, high on-off ratio, low threshold voltage and low sub-threshold slope than the devices with Au only. The field-effect mobility, current on-off ratio, threshold voltage and sub-threshold slope of V2O5/Au bi-layer OTFT estimated from the device with 15 nm thick V2O5 layer is .77 cm2 v-1 s-1, 7.5×105, -2.9 V and .36 V/decade respectively.

  17. Probing the electronic and vibrational structure of Au{sub 2}Al{sub 2}{sup −} and Au{sub 2}Al{sub 2} using photoelectron spectroscopy and high resolution photoelectron imaging

    SciTech Connect

    Lopez, Gary V.; Czekner, Joseph; Jian, Tian; Li, Wei-Li; Yang, Zheng; Wang, Lai-Sheng

    2014-12-14

    The electronic and vibrational structures of Au{sub 2}Al{sub 2}{sup −} and Au{sub 2}Al{sub 2} have been investigated using photoelectron spectroscopy (PES), high-resolution photoelectron imaging, and theoretical calculations. Photoelectron spectra taken at high photon energies with a magnetic-bottle apparatus reveal numerous detachment transitions and a large energy gap for the neutral Au{sub 2}Al{sub 2}. Vibrationally resolved PE spectra are obtained using high-resolution photoelectron imaging for the ground state detachment transition of Au{sub 2}Al{sub 2}{sup −} at various photon energies (670.55−843.03 nm). An accurate electron affinity of 1.4438(8) eV is obtained for the Au{sub 2}Al{sub 2} neutral cluster, as well as two vibrational frequencies at 57 ± 8 and 305 ± 13 cm{sup −1}. Hot bands transitions yield two vibrational frequencies for Au{sub 2}Al{sub 2}{sup −} at 57 ± 10 and 144 ± 12 cm{sup −1}. The obtained vibrational and electronic structure information is compared with density functional calculations, unequivocally confirming that both Au{sub 2}Al{sub 2}{sup −} and Au{sub 2}Al{sub 2} possess C{sub 2v} tetrahedral structures.

  18. Fabrication of Bi Nanowire Array into Nanoporous Film Made from Phase-Separated Al-Si Film

    NASA Astrophysics Data System (ADS)

    Fukutani, Kazuhiko; Den, Tohru

    2008-04-01

    Ultrahigh-pore-density nanoporous films with a pore diameter less than 10 nm and a pore density exceeding 1016 pores/m2 have been fabricated by the phase separation of an Al-Si system and the subsequent removal of Al cylinders, for use in the template-assisted growth of Bi nanowire arrays. Bi was used to fill the pores of template films by electrodeposition. The temperature dependence of the resistance of the obtained Bi nanowires with a diameter of 9 nm, parallel to the Bi nanowire growth direction, exhibits a semimetal-to-semiconductor transition due to the quantum confinement effect.

  19. Structural and Magnetic Properties of Fe and Au Ion-Implanted Al2O3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Kinoshita, Ryosuke; Sakamoto, Isao; Hayashi, Nobuyuki; Nomura, Kiyoshi; Honda, Shigeo; Ishida, Tomoya; Iio, Satoshi; Tashiro, Hiroyuki; Toriyama, Tamotsu

    2011-01-01

    Au ion implantation in Fe ion-implanted Al2O3 (Fe/Al2O3) has been performed in order to tailor the structural, magnetic and optical properties of Fe granules in Al2O3 matrix. After Au ion implantation, Rutherford backscattering (RBS) measurements indicate the decrease and the redistribution of retained Fe atoms with the inclusion of Au atoms, and the patterns of X-ray diffraction (XRD) show the formation of Au granules in the Fe/Al2O3. Besides, the magnetization curves of the Fe/Al2O3 after Au ion implantation show still the superparamagnetic characteristics and the decrease of saturation magnetization, and the optical absorption measurements indicate the formation of Au granules in the Fe/Al2O3 in accordance with the XRD result. In addition, we investigated a behavior of Fe granules in Al2O3 matrix by conversion electron Mössbauer spectroscopy (CEMS), which indicates the decrease of superparamagnetic state as a function of Au ion dose. As a result, it is suggested that Au ion implantation has potentialities to tailor the physical properties of Fe granules in Al2O3 matrix.

  20. Reconnaissance geology of the Bi'r Al Badriyah quadrangle, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Overstreet, William C.; Whitlow, J.W.; Kahr, V.P.; Ankary, A.O.

    1972-01-01

    The Bi'r al Badriyah quadrangle covers an area of 2843 sq km in the extreme eastern part of the Precambrian Shield in central Saudi Arabia. The Precambrian rocks in the southeastern part of the area are unconformably overlain by limestone of Permian age, which occupies only a small part of the quadrangle. Three great sequences of Precambrian rocks are recognized and called, from oldest to youngest, the Halaban Group, the Bi'r Khountina Group, and the Murdama Group. From evidence within the quadrangle itself the three groups are seen to be separated by erosional unconformities, and the Halaban and Bi'r Khountina Groups are intruded by granitic and gabbroic plutonic rocks and a wide variety of dikes. Exposures north of the quadrangle show that the Murdama Group is also intruded by granitic rocks. The Halaban Group, consists of three formations called, from oldest to youngest, the Umm Mushraha Formation, the Jebal al Egfool Formation, and the Wadi al Jifr Formation. These rocks are variably metamorphosed, but characteristically they are at the epidote-albite amphibolite facies of regional metamorphism, are polymetamorphic, and rest unconformably on ancient granite gneiss. The Umm Mushraha Formation consists of amphibolite, schistose andesite, and greenstone associated with minor meta-agglomerate, meta-graywacke, and marble. The Jebal al Egfool Formation consists of sheared and metamorphosed volcanic rocks of intermediate composition, and the Wadi al Jifr Formation is made up of metamorphosed felsic volcanic rocks. Rocks of the Bi'r Khountina Group are rather similar to the Halaban Group in original composition, but they are separated from the Halaban by an angular unconformity and have distinctive formations of conglomerate (the Idsas Formation), marble (the Fawara Formation), and graywacke (the Abu Sawarir Formation) at the base. Most of the Bi'r Khountina Group consists of andesitic volcanic rocks in the Badriyah Formation. Mostly, the Bi'r Khountina Group is

  1. Effect of poling process on resistive switching in Au/BiFeO3/SrRuO3 structures

    NASA Astrophysics Data System (ADS)

    Zhu, Hui; Zhang, Yingqiao; Jiang, Anquan; Bai, Zilong; Feng, Shiwei; Wang, Pengfei; Meng, Xiao; Qi, Qiong

    2016-12-01

    We studied the resistive switching of Au/BiFeO3/SrRuO3 structures. Their current-voltage characteristics complied with space-charge-limited (SCL) conduction. A full cycle of the poling process enlarged the I-V hysteresis and increased the transition voltage from Ohmic to SCL for an I-V sweeping bias less than the coercive voltage. A cycle of poling could increase the resistance switching ratio under low bias by 20 times over that of a virgin sample without poling. Measurements of thermally stimulated current showed a difference between the sample in the pristine state and that under the polarization state, indicating a relationship between the trap filling status and the resistive switching behavior.

  2. Network Formation by Condensed Tetrahedral [Au3Al] Units in Na2Au3Al: Crystal and Electronic Structure, Spectroscopic Investigations, and Physical Properties of an Ordered Ternary Auride.

    PubMed

    Stegemann, Frank; Benndorf, Christopher; Zhang, Yuemei; Bartsch, Manfred; Zacharias, Helmut; Fokwa, Boniface P T; Eckert, Hellmut; Janka, Oliver

    2017-02-20

    Na2Au3Al, the first experimentally prepared compound in the ternary Na-Au-Al system, crystallizes in the cubic crystal system with space group P4132 (a = 771.42(2) pm). It can be described as a P-centered ternary ordered variant of the F-centered Laves phase MgCu2 and is isostructural to Mo3Al2C. A phase width was found for the series Na2Au4-xAlx allowing a successive substitution of Au by Al. The primitive structure forms for x ≥ 0.5. Na2Au3Al is diamagnetic at room temperature but metallic in nature, as seen from susceptibility and electrical resistivity measurements. Band structure calculations and X-ray photoelectron spectroscopy confirm the metallic nature of the title compound as states are found at the Fermi level of the DOS, along with its "auride" character. (23)Na and (27)Al solid-state-NMR investigations show the existence of both a disordered (x = 0.5 and 0.75) and a fully ordered (x = 1.0) representative within this series. Both COHP and Bader charge analyses suggest the presence of strong Au-Al interactions forming an anionic [Au3Al](δ-) network, with the Na cations occupying the cavities.

  3. The ultraviolet and visible luminescence of Bi3+ in the orthorhombic perovskite, GdAlO3

    NASA Astrophysics Data System (ADS)

    Srivastava, A. M.; Comanzo, H. A.

    2017-01-01

    The spectroscopic properties of the Bi3+ ion as a function of its concentration is examined to clarify the nature of optical transitions that are responsible for the ultraviolet (333 nm) and visible emission of GdAlO3:Bi3+. The UV band which is characterized by small Stokes shift (0.52 eV) is ascribed to emission from isolated Bi3+ ions (3P0,1 → 1S0 transition). The peak emission wavelength and the width of the visible band depend on the Bi3+ concentration. This emission is ascribed to pairs or cluster of Bi3+ ions in the perovskite lattice. The spectroscopic properties of the pair emission in GdAlO3 are contrasted with the impurity trapped excitonic emission in CaSnO3. A comparative study of the behavior of Bi3+ luminescence in a series of materials with the orthorhombic perovskite structure is presented.

  4. Study on the contact resistance of various metals (Au, Ti, and Sb) on Bi-Te and Sb-Te thermoelectric films

    NASA Astrophysics Data System (ADS)

    Yong, Ho; Na, Sekwon; Gang, Jun-Gu; Shin, HaeSun; Jeon, Seong-Jae; Hyun, SeungMin; Lee, Hoo-Jeong

    2016-06-01

    In this study, we explore various electrode materials (Au, Ti, and Sb) for use as contact materials on Bi2Te3 and Sb2Te3 thermoelectric films. Using the transmission line method (TLM), we measured the specific resistivity of the contacts, which showed that Au has the lowest contact resistivity for both the thermoelectric films (after annealing): 2.7 × 10-10 Ω m2 for Bi2Te3 and 2.9 × 10-11 Ω m2 for Sb2Te3. The specific contact resistivity data suggest that the dominant factor for the contact properties is interface states. After annealing, the contact resistivity does not change much for the Bi2Te3 contacts while it drops greatly for the Sb2Te3 ones. Analysis of the carrier transport mechanism across the contacts discloses that changes in the carrier concentration in the thermoelectric films after annealing are responsible for the different behaviors.

  5. Atomic structure and electronic properties of the two-dimensional (Au ,Al )/Si (111 )2 ×2 compound

    NASA Astrophysics Data System (ADS)

    Gruznev, D. V.; Bondarenko, L. V.; Matetskiy, A. V.; Tupchaya, A. Y.; Chukurov, E. N.; Hsing, C. R.; Wei, C. M.; Eremeev, S. V.; Zotov, A. V.; Saranin, A. A.

    2015-12-01

    A combination of scanning tunneling microscopy, angle-resolved photoelectron spectroscopy, ab initio random structure searching, and density functional theory electronic structure calculations was applied to elucidate the atomic arrangement and electron band structure of the (Au ,Al )/Si (111 )2 ×2 two-dimensional compound formed upon Al deposition onto the mixed 5 ×2 /√{3 }×√{3 } Au/Si(111) surface. It was found that the most stable 2 ×2 -(Au, Al) compound incorporates four Au atoms, three Al atoms, and two Si atoms per 2 ×2 unit cell. Its atomic arrangement can be visualized as an array of meandering Au atomic chains with two-thirds of the Al atoms incorporated into the chains and one-third of the Al atoms interconnecting the chains. The compound is metallic and its electronic properties can be controlled by appropriate Al dosing since energetic location of the bands varies by ˜0.5 eV during increasing of Al contents. The 2 ×2 -(Au, Al) structure appears to be lacking the C3 v symmetry typical for the hexagonal lattices. The consequence of the peculiar atomic structure of the two-dimensional alloy is spin splitting of the metallic states, which should lead to anisotropy of the current-induced in-plane spin polarization.

  6. Bulk Properties of Ni3Al(gamma') With Cu and Au Additions

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1995-01-01

    The BFS method for alloys is applied to the study of 200 alloys obtained from adding Cu and Au impurities to a Ni3Al matrix. We analyze the trends in the bulk properties of these alloys (heat of formation, lattice parameter, and bulk modulus) and detect specific alloy compositions for which these quantities have particular values. A detailed analysis of the atomic interactions that lead to the preferred ordering patterns is presented.

  7. Comparison of laser ablation and sputter desorption of clusters from Au7Cu5Al4

    NASA Astrophysics Data System (ADS)

    King, B. V.; Moore, J. F.; Cui, Y.; Veryovkin, I. V.; Tripa, C. E.

    2014-12-01

    Ionized and neutral clusters were desorbed from spangold, a polycrystalline ternary alloy with composition Au7Cu5Al4, using both a femtosecond laser beam and an energetic ion beam and the resulting time of flight mass spectra compared. Neutral clusters containing up to 7 atoms were ejected by the 15 keV Ar+ beam whereas only smaller positively and negatively charged clusters were observed from the laser ablated spangold surface. Laser ionization mass spectrometry (LIMS) positive ion spectra were dominated by Al containing cluster ions whereas Au containing ions dominated the negative LIMS spectrum. An odd-even variation in LIMS cluster yield was observed, consistent with previous results and due to fragmentation of photoionized clusters. The laser sputtered neutral mass spectrometry (laser SNMS) spectrum showed that larger desorbed clusters were gold rich. The cluster signals also followed a power law dependence with cluster size with the exponent value of 6-7.6 for sputtered mixed clusters being greater than that found from sputtering of pure elements, similar to the result found previously in the Cu-Au system.

  8. The effects of Bi4Ti3O12 interfacial ferroelectric layer on the dielectric properties of Au/n-Si structures

    NASA Astrophysics Data System (ADS)

    Gökçen, Muharrem; Yıldırım, Mert

    2015-06-01

    Au/n-Si metal-semiconductor (MS) and Au/Bi4Ti3O12/n-Si metal-ferroelectric-semiconductor (MFS) structures were fabricated and admittance measurements were held between 5 kHz and 1 MHz at room temperature so that dielectric properties of these structures could be investigated. The ferroelectric interfacial layer Bi4Ti3O12 decreased the polarization voltage by providing permanent dipoles at metal/semiconductor interface. Depending on different mechanisms, dispersion behavior was observed in dielectric constant, dielectric loss and loss tangent versus bias voltage plots of both MS and MFS structures. The real and imaginary parts of complex modulus of MFS structure take smaller values than those of MS structure, because permanent dipoles in ferroelectric layer cause a large spontaneous polarization mechanism. While the dispersion in AC conductivity versus frequency plots of MS structure was observed at high frequencies, for MFS structure it was observed at lower frequencies.

  9. Experimental Investigation on Thermoresistance between AlN, Bi-2223 and OFHC in High Tc- Direct Cooling Technology

    NASA Astrophysics Data System (ADS)

    Wang, H. L.; Rao, R. S.; Wang, J.

    2014-12-01

    In the development of high temperature superconducting (HTS) direct cooling technology, the high electric insulation high heat conducting AlN has become one of the important components. The thermal contact resistance between AlN, Bi-2223 and OFHC is investigated by experiment with a G-M cryocooler as the source of cooling. The heat conductivity of AlN is measured between 29 and 160 K temperatures. When the temperature on the interface layer side of Bi-2223 is 55 K, under the action of the contact pressure of 0.5469 MPa, the thermal contact resistance between AlN and Bi-2223 is 38.86 times to the thermal conduction resistance of a 10 mm thick AlN pad. Baced on micro-nanocryogenics, it is proposed that the thermal contact resistance is one of the crucial techniques to be attacked in HTS direct cooling technology.

  10. Au, Bi, Co and Nb cross-section measured by quasimonoenergetic neutrons from p + 7Li reaction in the energy range of 18-36 MeV

    NASA Astrophysics Data System (ADS)

    Majerle, M.; Bém, P.; Novák, J.; Šimečková, E.; Štefánik, M.

    2016-09-01

    Au, Bi, Co and Nb samples were irradiated several times with quasi-monoenergetic neutrons from p + 7Li reaction in the energy range of 18-36 MeV. The activities of the samples were measured with the HPGe detector and the reaction rates were calculated. The cross-sections were extracted using the SAND-II method with the reference cross-sections from the EAF-2010 database. The uncertainties of the final results are discussed.

  11. Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites.

    PubMed

    Boona, Stephen R; Vandaele, Koen; Boona, Isabel N; McComb, David W; Heremans, Joseph P

    2016-12-12

    Transverse thermoelectric devices produce electric fields perpendicular to an incident heat flux. Classically, this process is driven by the Nernst effect in bulk solids, wherein a magnetic field generates a Lorentz force on thermally excited electrons. The spin Seebeck effect also produces magnetization-dependent transverse electric fields. It is traditionally observed in thin metallic films deposited on electrically insulating ferromagnets, but the films' high resistance limits thermoelectric conversion efficiency. Combining Nernst and spin Seebeck effect in bulk materials would enable devices with simultaneously large transverse thermopower and low electrical resistance. Here we demonstrate experimentally that this is possible in composites of conducting ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong spin-orbit interactions (Pt or Au). These materials display positive shifts in transverse thermopower attributable to inverse spin Hall electric fields in the nanoparticles. This more than doubles the power output of the Ni-Pt materials, establishing proof of principle that the spin Seebeck effect persists in bulk nanocomposites.

  12. Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites

    NASA Astrophysics Data System (ADS)

    Boona, Stephen R.; Vandaele, Koen; Boona, Isabel N.; McComb, David W.; Heremans, Joseph P.

    2016-12-01

    Transverse thermoelectric devices produce electric fields perpendicular to an incident heat flux. Classically, this process is driven by the Nernst effect in bulk solids, wherein a magnetic field generates a Lorentz force on thermally excited electrons. The spin Seebeck effect also produces magnetization-dependent transverse electric fields. It is traditionally observed in thin metallic films deposited on electrically insulating ferromagnets, but the films' high resistance limits thermoelectric conversion efficiency. Combining Nernst and spin Seebeck effect in bulk materials would enable devices with simultaneously large transverse thermopower and low electrical resistance. Here we demonstrate experimentally that this is possible in composites of conducting ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong spin-orbit interactions (Pt or Au). These materials display positive shifts in transverse thermopower attributable to inverse spin Hall electric fields in the nanoparticles. This more than doubles the power output of the Ni-Pt materials, establishing proof of principle that the spin Seebeck effect persists in bulk nanocomposites.

  13. Synthesis of bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles

    PubMed Central

    Li, Xue-Mei; Liu, Hong-Ling; Liu, Xiao; Fang, Ning; Wang, Xian-Hong; Wu, Jun-Hua

    2015-01-01

    Bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The morphology and crystal structure of the nanoparticles were studied by TEM/HRTEM and XRD. The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ~19 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the nanoparticles. The UV-vis and PL results reveal the well-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures. PMID:26548369

  14. Observation of spin Seebeck contribution to the transverse thermopower in Ni-Pt and MnBi-Au bulk nanocomposites

    PubMed Central

    Boona, Stephen R.; Vandaele, Koen; Boona, Isabel N.; McComb, David W.; Heremans, Joseph P.

    2016-01-01

    Transverse thermoelectric devices produce electric fields perpendicular to an incident heat flux. Classically, this process is driven by the Nernst effect in bulk solids, wherein a magnetic field generates a Lorentz force on thermally excited electrons. The spin Seebeck effect also produces magnetization-dependent transverse electric fields. It is traditionally observed in thin metallic films deposited on electrically insulating ferromagnets, but the films' high resistance limits thermoelectric conversion efficiency. Combining Nernst and spin Seebeck effect in bulk materials would enable devices with simultaneously large transverse thermopower and low electrical resistance. Here we demonstrate experimentally that this is possible in composites of conducting ferromagnets (Ni or MnBi) containing metallic nanoparticles with strong spin–orbit interactions (Pt or Au). These materials display positive shifts in transverse thermopower attributable to inverse spin Hall electric fields in the nanoparticles. This more than doubles the power output of the Ni-Pt materials, establishing proof of principle that the spin Seebeck effect persists in bulk nanocomposites. PMID:27941927

  15. Synthesis of bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Xue-Mei; Liu, Hong-Ling; Liu, Xiao; Fang, Ning; Wang, Xian-Hong; Wu, Jun-Hua

    2015-11-01

    Bi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO) as the surfactant. The morphology and crystal structure of the nanoparticles were studied by TEM/HRTEM and XRD. The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ~19 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. The FTIR study confirms the PEO-PPO-PEO molecules on the surface of the nanoparticles. The UV-vis and PL results reveal the well-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures.

  16. Two-dimensional Mineral [Pb2BiS3 ][AuTe2 ]: High mobility Charge Carriers in Single-atom-thick Layers

    NASA Astrophysics Data System (ADS)

    Fang, Lei; Im, J.; Stoumpos, C.; Shi, F.; Dravid, V.; Leroux, M.; Freeman, A.; Kwok, W.-K.,; Chung, D.-Y.; Kanatzidis, M.

    2015-03-01

    We report that [Pb2BiS3][AuTe2], known as a naturally occurring mineral buckhornite, hosts 2D carriers in single-atom-thick layers. The structure is composed of stacking layers of weakly coupled [Pb2BiS3] and [AuTe2] sheets. The insulating [Pb2BiS3] sheet inhibits interlayer charge hopping and confines the carriers in the basal plane of the single-atom-thick [AuTe2] layer. Magneto-transport measurements and theoretical calculations show a property of multiband semimetal with compensated density of electrons and holes, which exhibit high hole carrier mobility of 1360 cm2/Vs. This material possesses an extremely large anisotropy 104, comparable to benchmark materials graphite. The electronic structure features linear band dispersion at the Fermi level and ultrahigh Fermi velocities of 106 m/s which are virtually identical to that of graphene. The weak interlayer coupling gives rise to the highly cleavable property of single crystal specimens, indicating a prospect for monolayer system. This research was supported by the DoE, BES, under Contract No. DE-AC02-06CH11357, and NUANCE Center at the Northwestern Univeristy.

  17. Origin of Quantum Criticality in Yb-Al-Au Approximant Crystal and Quasicrystal

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinji; Miyake, Kazumasa

    2016-06-01

    To get insight into the mechanism of emergence of unconventional quantum criticality observed in quasicrystal Yb15Al34Au51, the approximant crystal Yb14Al35Au51 is analyzed theoretically. By constructing a minimal model for the approximant crystal, the heavy quasiparticle band is shown to emerge near the Fermi level because of strong correlation of 4f electrons at Yb. We find that charge-transfer mode between 4f electron at Yb on the 3rd shell and 3p electron at Al on the 4th shell in Tsai-type cluster is considerably enhanced with almost flat momentum dependence. The mode-coupling theory shows that magnetic as well as valence susceptibility exhibits χ ˜ T-0.5 for zero-field limit and is expressed as a single scaling function of the ratio of temperature to magnetic field T/B over four decades even in the approximant crystal when some condition is satisfied by varying parameters, e.g., by applying pressure. The key origin is clarified to be due to strong locality of the critical Yb-valence fluctuation and small Brillouin zone reflecting the large unit cell, giving rise to the extremely-small characteristic energy scale. This also gives a natural explanation for the quantum criticality in the quasicrystal corresponding to the infinite limit of the unit-cell size.

  18. Probing of the pseudogap via thermoelectric properties in the Au-Al-Gd quasicrystal approximant

    NASA Astrophysics Data System (ADS)

    Ishikawa, Asuka; Takagiwa, Yoshiki; Kimura, Kaoru; Tamura, Ryuji

    2017-03-01

    The pseudogap of the recently discovered Au-Al-Gd quasicrystal approximant crystal (AC) is investigated over a wide electron-per-atom (e /a ) ratio of ˜0.5 using thermoelectric properties as an experimental probe. This Au-Al-Gd AC provides an ideal platform for fine probing of the pseudogap among a number of known ACs because the Au-Al-Gd AC possesses an extraordinarily wide single-phase region with respect to the variation in the electron concentration [A. Ishikawa, T. Hiroto, K. Tokiwa, T. Fujii, and R. Tamura, Phys. Rev. B 93, 024416 (2016), 10.1103/PhysRevB.93.024416], in striking contrast to, for instance, binary stoichiometric C d6R ACs. As a result, a salient peak structure is observed in the Seebeck coefficient, S , with the composition as well as that of the power factor S2σ , in addition to a gradual variation in the conductivity, σ , and S . These two features are directly associated with rapid and slow variations, respectively, of spectral conductivity σ (E ) , and hence the fine structure inside the pseudogap, in the vicinity of the Fermi level EF. Based on the observed continuous variation of the Fermi wave vector reported in the previous experimental work, fine tuning of EF toward an optimal position was attempted, which led to the successful observation of a sharp peak in S2σ with a value of ˜270 μ W /m .K2 at 873 K. This is the highest value ever reported among both Tsai-type and Bergman-type compounds. The dimensionless figure of merit was determined as 0.026 at 873 K, which is also the highest reported among both Tsai-type and Bergman-type compounds.

  19. Synthesis of bi-metallic Au-Ag nanoparticles loaded on functionalized MCM-41 for immobilization of alkaline protease and study of its biocatalytic activity

    NASA Astrophysics Data System (ADS)

    Sadjadi, M. S.; Farhadyar, N.; Zare, K.

    2009-10-01

    In this work, Au-Ag nanoparticles (Au-Ag-bi-MNPs) have been prepared on amine functionalized Si-MCM-41 (NH 2-Si-MCM-41) particles through a reduction of AgNO 3 and HAuCl 4 by NaBH 4 at ambient conditions. Au-Ag-bi-MNPs loaded on the NH2-Si-MCM-41, provide a good biocompatible surface for immobilization of the enzyme alkaline protease. This immobilization, presumably due to bonding between core shell nanoparticles and OH in serine 183 in alkaline protease seems to be of an ionic exchange nature. We found that the alkaline protease immobilized on the Au-Ag-bi-MNPs/Si-MCM-41 is an active biocatalyst, stable at different pH and temperature. The bio catalytic activity of free alkaline protease in solution was 64 U/mg (Units per milligram), whereas that of the alkaline protease immobilized on Au-Ag-bi-MNPs/Si-MCM-41 was 75 U/mg. This improvement of the biocatalytic activity may be due to a really increased activity per molecule of immobilized enzyme or to a purification of the enzyme. The alkaline protease molecules immobilized on the (Au-Ag)/ NH 2-MCM-41 surface retained as much as 80% of the catalytic activity recorded at pH=8, and showed significant catalytic activity of alkaline protease in the bioconjugate material. The biocatalytic materials were easily separated from the reaction medium by mild centrifugation and exhibits excellent reuse and stability characteristics over four successive cycles. The optimum temperature ranged from 35 ∘C-55 ∘C and pH=8 for bioactivity of the alkaline protease in the assembly system was observed to be higher than that of the free enzyme in solution. The enzyme biocatalytic activity was monitored by UV-visible spectroscopy. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and dispersive analysis of X-RAY (EDAX) were used to characterize the size and morphology of the prepared materials.

  20. Liquid-liquid phase equilibrium and core-shell structure formation in immiscible Al-Bi-Sn alloys

    NASA Astrophysics Data System (ADS)

    Li, Mingyang; Jia, Peng; Sun, Xiaofei; Geng, Haoran; Zuo, Min; Zhao, Degang

    2016-04-01

    In this paper, the liquid-phase separation of ternary immiscible Al45Bi19.8Sn35.2 and Al60Bi14.4Sn25.6 melts was studied with resistivity and thermal analysis methods at different temperature. The resistivity-temperature curves appear abrupt and anomalously change with rising temperature, corresponding to the anomalous and low peak of melting process in DSC curves, indicative of the occurrence of the liquid-phase separation. The anomalous behavior of the resistivity temperature dependence is attributable to concentration-concentration fluctuations. The effect of composition and melt temperature on the liquid-phase separation and core-shell structure formation in immiscible Al-Bi-Sn alloys was studied. The liquid-phase separation and formation of the core-shell structure in immiscible Al-Bi-Sn alloys are readily acquired when the alloy compositions fall into liquid miscibility gap. What's more, the cross-sectional structure changes from irregular, dispersed to core-type shapes under the actions of Marangoni motion with increasing melt temperature. This study provides some clues for the preparation of core-shell microspheres of immiscible Al-Bi-Sn alloys via liquid-phase separation.

  1. Mechanical, electrical, and thermal properties of the directionally solidified Bi-Zn-Al ternary eutectic alloy

    NASA Astrophysics Data System (ADS)

    Şahin, M.; Çadırlı, E.

    2014-10-01

    A Bi-2.0Zn-0.2Al (wt%) ternary eutectic alloy was prepared using a vacuum melting furnace and a casting furnace. The samples were directionally solidified upwards at a constant growth rate ( V = 18.4 μm/s) under different temperature gradients ( G = 1.15-3.44 K/mm) and at a constant temperature gradient ( G = 2.66 K/mm) under different growth rates ( V = 8.3-500 μm/s) in a Bridgman-type directional solidification furnace. The dependence of microstructure parameter ( λ) on the solidification parameters ( G and V) and that of the microhardness (Hv) on the microstructure and solidification parameters were investigated. The resistivity ( ρ) measurements of the studied alloy were performed using the standard four-point-probe method, and the temperature coefficient of resistivity ( α) was calculated from the ρ- T curve. The enthalpy (Δ H) and the specific heat ( C p ) values were determined by differential scanning calorimetry analysis. In addition, the thermal conductivities of samples, obtained using the Wiedemann-Franz and Smith-Palmer equations, were compared with the experimental results. The results revealed that, the thermal conductivity values obtained using the Wiedemann-Franz and Smith-Palmer equations for the Bi-2.0Zn-0.2Al (wt%) alloy are in the range of 5.2-6.5 W/Km and 15.2-16.4 W/Km, respectively.

  2. Ballistic Electron Emission Microscopy (BEEM) of Au/Al/GaAs Schottky barriers under Ultra High Vacuum conditions

    NASA Astrophysics Data System (ADS)

    Mani, R. G.; Narayanamurti, V.

    2000-03-01

    BEEM investigations of the Au/GaAs system have reported substantial redirection of the ballistic current into the L-valley of GaAs, based on a study of the I-V spectroscopic measurement. The result has been attributed to the absence of conservation of interface parallel wave-vector in the non-epitaxial Au/GaAs system. Theory has modeled the effect and it suggests an interesting scenario based on a progressive redistribution of the ballistic current between the relevant bands as a function of scattering strength at the interface. Experiments reported here attempt to investigate this regime by examining BEEM in Au/Al/GaAs Schottky barrier devices that preserve the topographic image of Au at the metal surface, while changing the metal semiconductor interface by placing Al between the surface Au surface layer and the GaAs substrate. As aluminum has been reported to grow epitaxially on GaAs, this approach has been pursued here in the hopes of realizing a metal-semiconductor device with varying degree of interfacial order depending upon growth conditions. Thus, we have fabricated Au/Al/GaAs Schottky barrier devices in a three chamber UHV system and subsequently carried out BEEM measurements between 90 K and 300 K. Collector current images and spectroscopic results obtained in such specimens will be compared with expectations based on relevant theory in order to obtain possible new insight into interface scattering in metal semiconductor structures.

  3. RE(AuAl2)nAl2(AuxSi1-x)2: a new homologous series of quaternary intermetallics grown from aluminum flux.

    PubMed

    Latturner, Susan E; Kanatzidis, Mercouri G

    2008-03-17

    The combination of early rare earth metals (La- to Gd and Yb), gold, and silicon in molten aluminum results in the formation of intermetallic compounds with four related structures, forming a new homologous series: RE[AuAl2]nAl2(AuxSi(1-x))2, with x approximately 0.5 for most of the compound and n = 0, 1, 2, and 3. Because of the highly reducing nature of the Al flux, rare earth oxides instead of metals can also be used in these reactions. These compounds grow as large plate-like crystals and have tetragonal structure types that can be viewed as intergrowths of the BaAl4 structure and antifluorite-type AuAl2 layers. REAuAl2Si materials form with the BaAl4 structure type in space group I4/mmm (cell parameters for the La analogue are a = 4.322(2) A, c = 10.750(4) A, and Z = 2). REAu2Al4Si forms in a new ordered superstructure of the KCu4S3 structure type, with space group P4/nmm and cell parameters of the La analogue of a = 6.0973(6) A, c = 8.206(1) A, and Z = 2. REAu3Al6Si forms in a new I4/mmm symmetry structure type with cell parameters of a = 4.2733(7) A, c = 22.582(5) A, and Z = 2 for RE = Eu. The end member of the series, REAu4Al8Si, forms in space group P4/mmm with cell parameters for the Yb analogue of a = 4.2294(4) A, c = 14.422(2) A, and Z = 1. New intergrowth structures containing two different kinds of AuAl2 layers were also observed. The magnetic behavior of all these compounds is derived from the RE ions. Comparison of the susceptibility data for the europium compounds indicates a switch from 3-D magnetic interactions to 2-D interactions as the size of the AuAl2 layer increases. The Yb ions in YbAu(2.91)Al(6)Si(1.09) and YbAu(3.86)Al(8)Si(1.14) are divalent at high temperatures.

  4. Boat-like Au nanoparticles embedded mesoporous γ-Al2O3 films: an efficient SERS substrate

    NASA Astrophysics Data System (ADS)

    Dandapat, Anirban; Pramanik, Sourav; Bysakh, Sandip; De, Goutam

    2013-07-01

    Boat-like Au nanoparticles (NPs) have been synthesized within the mesoporous γ-Al2O3 films. First, mesoporous γ-Al2O3 film was prepared using aluminum alkoxide derived boehmite sol in the presence of CTAB as structure directing agent. The film was heat-treated at 500 °C to obtain γ-Al2O3 film with an average pore diameter of 4.3 nm. HAuCl4 solution was then soaked into the porous film followed by heat-treatment at 500 °C to generate Au NPs. The blue-colored films so obtained were characterized by UV-visible spectroscopy, grazing incidence X-ray diffraction, FESEM, and TEM studies. FESEM and TEM studies reveal the formation boat-like Au NPs in γ-Al2O3 film matrix. Cross-sectional FESEM shows the thickness of the films to be 2.2 μm. These nanocomposite films were used as a unique surface-enhanced Raman scattering (SERS) substrate for easy detection of low concentration (10-8 M) analyte (methylene blue) molecule. Boat-like shape of Au NPs have several edges and junctions that contain high density of hotspots to exhibit very high SERS signals. Due to such shape of Au NPs, the films also show strong absorption in the visible-NIR region that would extend the use of the films in heat-absorbing and biomedical applications.

  5. Improved optical storage properties of NaAlSiO4: Tb3+ induced by Bi3+

    NASA Astrophysics Data System (ADS)

    Zhou, Junhe; Yu, Xue; Wang, Ting; Zhou, Dacheng; Qiu, Jianbei

    2016-07-01

    NaAlSiO4: Tb3+, Bi3+ phosphor was synthesized with green long persistent luminescence (LPL) and photo-stimulated luminescence (PSL) observed. The influence of metal ion Bi3+ on the optical storage properties of NaAlSiO4: Tb3+ was investigated in detail. The emitter Tb3+ introduced two kinds of traps located at 350 K (TA) and 440 K (TB) in the thermoluminescence (TL) glow curve. Bi3+ as a codopant ion introduced a new trap peaking at 390 K (TC), which contributed to the improved LPL properties. Besides, owing to the existence of deep and stable trap TB, green PSL can still be observed after 72 h since the excitation was stopped. Accordingly, the mechanism of LPL and PSL process was discussed briefly.

  6. A bi-overlayer type plasmonic photocatalyst consisting of mesoporous Au/TiO2 and CuO/SnO2 films separately coated on FTO.

    PubMed

    Naya, Shin-ichi; Kume, Takahiro; Okumura, Nozomi; Tada, Hiroaki

    2015-07-21

    The principal purpose of this study is to present a new design for preparing highly active immobilized gold nanoparticle-based plasmonic photocatalysts. Gold nanoparticles were loaded on rutile TiO2 particles with a mean size of 80 nm (Au/TiO2) by the deposition precipitation method. The surface of SnO2 particles with a mean size of 100 nm was modified by copper(ii) oxide clusters (CuO/SnO2) with the loading amount (Γ/Cu ions nm(-2)) precisely controlled by the chemisorption-calcination cycle technique. Two mesoporous overlayers of Au/TiO2 and CuO/SnO2 were coated side by side on glass substrates with a fluorine-doped tin oxide film (FTO) using the doctor blade method (Au/mp-TiO2|FTO|CuO/mp-SnO2). As test reactions for assessing the visible-light activity, we carried out gas-phase decomposition of acetaldehyde and liquid-phase oxidation of alcohol. In each reaction, this bi-overlayer type catalyst shows a high level of visible-light activity much exceeding those of Au/TiO2 particles and a Au/mp-TiO2|FTO mono-overlayer type catalyst [J. Phys. Chem. C, 2014, 118, 26887]. To confirm the origin of the striking visible-light activity, we studied the electrocatalytic activity of CuO/mp-SnO2|FTO electrodes for the oxygen reduction reaction (ORR). Both the visible-light activity of Au/mp-TiO2|FTO|CuO/mp-SnO2 and the electrocatalytic activity of CuO/mp-SnO2|FTO for ORR strongly depend on the Γ value. A good positive correlation has been found between the visible-light activities and the electrocatalytic activity for ORR. The striking activity of the present bi-overlayer type catalyst can be attributed to the efficient and long-range charge separation by the vectorial electron transport (Au(oxidation sites) → TiO2→ FTO, SnO2→ CuO(reduction sites)) and the excellent electrocatalytic activity of the CuO clusters.

  7. Self-field ac losses of a twisted multifilamentary (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape

    NASA Astrophysics Data System (ADS)

    Friend, C. M.; Huang, Y. B.

    2000-06-01

    Self-field loss measurements at 77 K on a superconducting (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape with twisted filaments are presented. Using the first- and third-harmonic components of the electric field, the hysteretic losses are separated from the total loss. At peak transport currents less than half the critical current, the hysteretic losses are considerably reduced. However, sizable nonhysteretic losses are also observed. At higher currents, the hysteretic loss increases, dominating the total loss, and is similar to that for an untwisted tape.

  8. Laser-produced spectra and QED effects for Fe-, Co-, Cu-, and Zn-like ions of Au, Pb, Bi, Th, and U

    NASA Technical Reports Server (NTRS)

    Seely, J. F.; Ekberg, J. O.; Brown, C. M.; Feldman, U.; Behring, W. E.

    1986-01-01

    Spectra of very highly charged ions of Au, Pb, Bi, Th, and U have been observed in laser-produced plasmas generated by the OMEGA laser. Line identifications in the region 9-110 A were made for ions in the Fe, Co, Cu, and Zn isoelectronic sequences. Comparison of the measured wavelengths of the Cu-like ions with values calculated with and without QED corrections shows that the inclusion of QED corrections greatly improves the accuracy of the calculated 4s-4p wavelengths. However, significant differences between the observed and calculated values remain.

  9. Structural, dielectric, and ferroelectric properties of the (1-x)PbTiO₃-xBiAlO₃ solid solution.

    PubMed

    Yu, Huichun; Ren, Wei; Ye, Zuo-Guang

    2010-10-01

    Ferroelectric ceramics derived from the solid solution of (1-x)PbTiO₃-xBiAlO₃ (x = 0, 0.05, 0.10, 0.15, and 0.18) have been synthesized by solid-state reactions. A pure perovskite phase is formed for 0 ≤ x ≤ 0.15. The tetragonality (c/a) of the solid solution decreases with the increasing amount of BiAlO₃. Scanning electron microscopic images reveal a microstructure with a fine grain size of less than 1 μm for the solid solution ceramics (x ≥ 0.05). Compared with pure PbTiOPbTiO₃ ceramics whose high conductivity and poor densification were harmful to their dielectric performance, the ceramics of (1-x)PbTiO₃-xBiAlO₃ are well-densified (with a relative density of up to 93%) and their dielectric and ferroelectric properties are significantly improved with the addition of BiAlO₃, exhibiting reduced dielectric losses, well-developed P-E hysteresis loops (for x = 0.05, 0.10, and 0.15) and a high remnant polarization (P(r)) of 64 μC/cm² (for x = 0.15).

  10. Valence Change Driven by Constituent Element Substitution in the Mixed-Valence Quasicrystal and Approximant Au-Al-Yb

    NASA Astrophysics Data System (ADS)

    Matsukawa, Shuya; Tanaka, Katsumasa; Nakayama, Mika; Deguchi, Kazuhiko; Imura, Keiichiro; Takakura, Hiroyuki; Kashimoto, Shiro; Ishimasa, Tsutomu; Sato, Noriaki K.

    2014-03-01

    Quantum criticality has been considered to be specific to crystalline materials such as heavy fermions. Very recently, however, the Tsai-type quasicrystal Au51Al34Yb15 has been reported to show unusual quantum critical behavior. To obtain a deeper understanding of this new material, we have searched for other Tsai-type cluster materials. Here, we report that the metal alloys Au44Ga41Yb15 and Ag47Ga38Yb15 are members of the 1/1 approximant to the Tsai-type quasicrystal and that both possess no localized magnetic moment. We suggest that the Au-Al-Yb system is located near the border of the divalent and trivalent states of the Yb ion; we also discuss a possible origin of the disappearance of magnetism, associated with the valence change, by the substitution of the constituent elements.

  11. La-doped Al2O3 supported Au nanoparticles: highly active and selective catalysts for PROX under PEMFC operation conditions.

    PubMed

    Lin, Qingquan; Qiao, Botao; Huang, Yanqiang; Li, Lin; Lin, Jian; Liu, Xiao Yan; Wang, Aiqin; Li, Wen-Cui; Zhang, Tao

    2014-03-14

    La-doped γ-Al2O3 supported Au catalysts show high activity and selectivity for the PROX reaction under PEMFC operation conditions. The superior performance is attributed to the formation of LaAlO3, which suppresses H2 oxidation and strengthens CO adsorption on Au sites, thereby improving competitive oxidation of CO at elevated temperature.

  12. Au on MgAl2O4 spinels: The effect of support surface properties in glycerol oxidation

    SciTech Connect

    Villa, Alberto; Gaiassi, Aureliano; Rossetti, Ilenia; Bianchi, Claudia; van Benthem, Klaus; Veith, Gabriel M; Prati, Laura

    2010-01-01

    Here we investigated the properties of Au nanoparticles, prepared via three different techniques and supported on three different MgAl2O4 spinels. The surface composition and area of the spinel plays an important role in determining the selectivity of the catalyst in the selective oxidation of glycerol. it was found that aluminum rich surfaces enhance the C-C bond cleavage reaction for large gold particles which is opposite of what is normally observed for large clusters which typically show no C-C cleavage. We also report that similarly sized AuNPs on the different MgAl2O4 spinels with the same surface Al/Mg ratio, show a similar selectivity; however activity depends on surface area.

  13. Radiation effects in multilayer ohmic contacts Au-Ti-Al-Ti-n-GaN

    SciTech Connect

    Belyaev, A. E.; Boltovets, N. S.; Ivanov, V. N.; Kapitanchuk, L. M.; Konakova, R. V. Kudryk, Ya. Ya.; Lytvyn, O. S.; Milenin, V. V.; Sheremet, V. N.; Sveshnikov, Yu. N.

    2009-07-15

    Radiation effects in the Au-Ti-Al-Ti-n-GaN multilayer metallization subjected to irradiation with {sup 60}Co {gamma}-ray photons in the dose range 4 x 10{sup 6}-2 x 10{sup 7} Gy are considered, and the effect of radiation on the initial contact structures and the structures subjected to a rapid thermal annealing (RTA) at high-temperature in the nitrogen atmosphere is studied. Irradiation does not significantly affect the properties of structures that were not subjected to the heat treatment. An RTA at 700 deg. C brings about a deterioration of the contact-layer morphology. The morphological and structural transformations in the contact metallization due to the RTA are enhanced by irradiation with {gamma}-ray photons. The combined radiation-thermal treatment is conducive to the mass transfer between contacting layers. In addition, after {gamma}-ray irradiation with the dose of 2 x 10{sup 7} Gy, the oxygen-impurity atoms appear over the entire contact's structure and are observed in a large amount in the near-contact GaN region.

  14. Nanoporous Gold Nanoparticles and Au/Al2O3 Hybrid Nanoparticles with Large Tunability of Plasmonic Properties.

    PubMed

    Rao, Wenye; Wang, Dong; Kups, Thomas; Baradács, Eszter; Parditka, Bence; Erdélyi, Zoltán; Schaaf, Peter

    2017-02-22

    Nanoporous gold nanoparticles (NPG-NPs) with controlled particle size and pore size are fabricated via a combination of solid-state dewetting and a subsequent dealloying process. Because of the combined effects of size and porosity, the NPG-NPs exhibit greater plasmonic tunability and significantly higher local field enhancement as compared to solid NPs. The effects of the nanoscale porosity and pore size on the optical extinction are investigated for the NPG-NPs with different particle sizes experimentally and theoretically. The influences of both porosity and pore size on the plasmonic properties are very complicated and clearly different for small particles with dominated dipole mode and large particles with dominated quadrupole mode. Au/Al2O3 hybrid porous NPs with controlled porosity and composition ratio are fabricated through plasma-enhanced atomic layer deposition of Al2O3 into the porous structure. In the Au/Al2O3 hybrid porous NPs, both Au and Al2O3 components are bicontinuously percolated over the entire structure. A further red shift of the plasmon peak is observed in the hybrid NPs due to the change of the environmental refractive index. The high tunability of the plasmonic resonances in the NPG-NPs and the hybrid porous NPs can be very useful for many applications in sensing biological and organic molecules.

  15. Electrical and photoresponse properties of vacuum deposited Si/Al:ZnSe and Bi:ZnTe/Al:ZnSe photodiodes

    NASA Astrophysics Data System (ADS)

    Rao, Gowrish K.

    2017-04-01

    The paper reports fabrication and characterization of Bi:ZnTe/Al:ZnSe and Si/Al:ZnSe thin film photodiodes. The characteristics of the devices were studied under dark and illuminated conditions. The normalized spectral response, speed of photoresponse and variation of photocurrent with power density were studied in detail. Many vital parameters, such as diode ideality factor, barrier height, the thickness of the depletion region, trap depth, rise and decay times of photocurrent, were determined. Conduction mechanism in the photodiodes is discussed with the help of widely accepted theoretical models.

  16. Au/n-InP Schottky diodes using an Al2O3 interfacial layer grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Kim, Hogyoung; Kim, Min Soo; Yoon, Seung Yu; Choi, Byung Joon

    2017-02-01

    We investigated the effect of an Al2O3 interfacial layer grown by atomic layer deposition on the electrical properties of Au Schottky contacts to n-type InP. Considering barrier inhomogeneity, modified Richardson plots yielded a Richardson constant of 8.4 and 7.5 Acm-2K-2, respectively, for the sample with and without the Al2O3 interlayer (theoretical value of 9.4 Acm-2K-2 for n-type InP). The dominant reverse current flow for the sample with an Al2O3 interlayer was found to be Poole-Frenkel emission. From capacitance-voltage measurements, it was observed that the capacitance for the sample without the Al2O3 interlayer was frequency dependent. Sputter-induced defects as well as structural defects were passivated effectively with an Al2O3 interlayer.

  17. Bi-directional streaming of halo electrons in interplanetary plasma clouds observed between 0.3 and 1 AU

    NASA Technical Reports Server (NTRS)

    Ivory, K.; Schwenn, R.

    1995-01-01

    The solar wind data obtained from the two Helios solar probes in the years 1974 to 1986 were systematically searched for the occurrence of bi-directional electron events. Most often these events are found in conjunction with shock associated magnetic clouds. The implications of these observations for the topology of interplanetary plasma clouds are discussed.

  18. A Thermally Stable NiZn/Ta/Ni Scheme to Replace AuBe/Au Contacts in High-Efficiency AlGaInP-Based Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyun; Park, Jae-Seong; Kang, Daesung; Seong, Tae-Yeon

    2017-03-01

    We developed NiZn/(Ta/)Ni ohmic contacts to replace expensive AuBe/Au contacts commonly used in high-efficiency AlGaInP-based light-emitting diodes (LEDs), and compared the electrical properties of the two contact types. Unlike the AuBe/Au (130 nm/100 nm) contact, the NiZn/Ta/Ni (130 nm/20 nm/100 nm) contact shows improved electrical properties after being annealed at 500°C, with a contact resistivity of 5.2 × 10-6 Ω cm2. LEDs with the NiZn/Ta/Ni contact exhibited a 4.4% higher output power (at 250 mW) than LEDs with the AuBe/Au contact. In contrast to the trend for the AuBe/Au contact, the Ga 2p core level for the NiZn/Ta/Ni contact shifted toward lower binding energies after being annealed at 500°C. Auger electron spectroscopy (AES) depth profiles showed that annealing the AuBe/Au samples caused the outdiffusion of both Be and P atoms into the metal contact, whereas in the NiZn/Ta/Ni samples, Zn atoms indiffused into the GaP layer. The annealing-induced electrical degradation and ohmic contact formation mechanisms are described and discussed on the basis of the results of x-ray photoemission spectroscopy and AES.

  19. A Kinetic Monte Carlo model for material aging: Simulations of second phase formation at Au/Bi{sub 2}Te{sub 3} junction in oxygen environments

    SciTech Connect

    Zhou, X. W.; Yang, N. Y. C.

    2014-03-14

    Electronic properties of semiconductor devices are sensitive to defects such as second phase precipitates, grain sizes, and voids. These defects can evolve over time especially under oxidation environments and it is therefore important to understand the resulting aging behavior in order for the reliable applications of devices. In this paper, we propose a kinetic Monte Carlo framework capable of simultaneous simulation of the evolution of second phases, precipitates, grain sizes, and voids in complicated systems involving many species including oxygen. This kinetic Monte Carlo model calculates the energy barriers of various events based directly on the experimental data. As a first step of our model implementation, we incorporate the second phase formation module in the parallel kinetic Monte Carlo codes SPPARKS. Selected aging simulations are performed to examine the formation of second phase precipitates at the eletroplated Au/Bi{sub 2}Te{sub 3} interface under oxygen and oxygen-free environments, and the results are compared with the corresponding experiments.

  20. Large spin-orbit coupling and helical spin textures in 2D heterostructure [Pb2BiS3][AuTe2

    PubMed Central

    Fang, L.; Im, J.; DeGottardi, W.; Jia, Y.; Glatz, A.; Matveev, K. A.; Kwok, W.-K.; Crabtree, G. W.; Kanatzidis, M. G.

    2016-01-01

    Two-dimensional heterostructures with strong spin-orbit coupling have direct relevance to topological quantum materials and potential applications in spin-orbitronics. In this work, we report on novel quantum phenomena in [Pb2BiS3][AuTe2], a new 2D strong spin-orbit coupling heterostructure system. Transport measurements reveal the spin-related carrier scattering is at odds with the Abrikosov-Gorkov model due to strong spin-orbit coupling. This is consistent with our band structure calculations which reveal a large spin-orbit coupling gap of εso = 0.21 eV. The band structure is also characterized by helical-like spin textures which are mainly induced by strong spin-orbit coupling and the inversion symmetry breaking in the heterostructure system. PMID:27731394

  1. Effects of substitutional impurity Au and Si atoms on antiphase boundary energies in Ti3Al: A first principles study

    NASA Astrophysics Data System (ADS)

    Koizumi, Yuichiro; Mizuno, Masataka; Sugihara, Atsushi; Minamino, Yoritoshi; Shirai, Yasuharu

    2010-10-01

    Effects of substitutional impurity atoms Au and Si on the energies of antiphase boundaries (APBs) on {1overline 1 00} and (0001) planes in a Ti3Al intermetallic compound were examined using first principles calculations. Au additions reduce the energies of APBs on both {1overline 1 00} and (0001) planes by up to more than 40%. The reduction tends to be more remarkable especially when the added Au atom has larger number of Al atoms on its second-nearest neighbor sites rather than on first-nearest neighbor ones. In addition, in the case of Si addition, a significant energy reduction was found only for APBs on (0001) planes, and no remarkable dependence of APB energies on the coordinating atoms was found even for APBs on (0001) planes. These results are crucial to both understanding of the effect of APBs on the impurity diffusivity and predicting the ability of impurity atoms to stabilize antiphase domain structure that increases the strength of Ti3Al dramatically.

  2. Electrochemistry in ultrahigh vacuum: underpotential deposition of Al on polycrystalline W and Au from room temperature AlCl(3)/1-ethyl-3-methylimidazolium chloride melts.

    PubMed

    Johnston, Matthew; Lee, Jae-Joon; Chottiner, Gary S; Miller, Barry; Tsuda, Tetsuya; Hussey, Charles L; Scherson, Daniel A

    2005-06-09

    The voltammetric characteristics of polycrystalline Au and W electrodes cleaned (thermal annealing at 1100 K) and characterized (Auger electron spectroscopy) in ultrahigh vacuum (UHV) have been examined in ultrapure AlCl(3)/1-ethyl-3-methylimidazolium chloride (EtMeImCl) melts in UHV. These experiments were performed using a custom-designed transfer system that allows for the all-Al electrochemical cell to be filled with EtMeImCl in an auxiliary UHV chamber and later transferred under UHV to the main UHV chamber that houses the Auger electron spectrometer. The results obtained for the underpotential (UPD) and bulk deposition of Al on Au were found to be very similar to those reported in the literature for measurements carried out under 1 atm of an inert gas in a glovebox. For the far more reactive W surfaces, voltammetric features ascribed to the stripping of underpotential-deposited Al could be observed following a single scan from 1.0 V vs Al(3+)/Al to a potential negative enough for bulk deposition of Al to ensue. This behavior is unlike that reported in the literature for experiments performed in a glovebox, which required either extensive potential cycling in the Al bulk deposition and stripping region or excursions to potentials positive enough for chlorine evolution to ensue for Al UPD features to be clearly discerned. These observations open new prospects for fundamental electrochemical studies of well-characterized, highly reactive metals, including single crystals, in a variety of low vapor pressure ionic liquids.

  3. Vertically arrays of Si-LaNiO3/BiFeO3/Au core-shell nano-capacitors for prominent coupled electro-optic effect

    NASA Astrophysics Data System (ADS)

    Singh, Kirandeep; Kaur, Davinder

    2017-03-01

    The current study delivers the first assessment of well-separated cone shaped n-type epitaxial BiFe0.9Mn0.1O3 (n-BFMO) shells integrated on LaNiO3 (LNO) buffered vertical arrays of p-type nanoporous Si nanowire cores as an absorber for high efficiency and sustainable all- oxide photovoltaic devices. The photovoltaic effect of the LNO/n-BFMO/Au radial heterojunction is investigated by registering the current-voltage curves under AM 1.5 (100 mW cm-2) illumination conditions at various ferroelectric polarization states of BFMO. The as-deposited LNO/BFMO/Au nanowire arrays fabricated by scalable Pulsed Laser deposition are completely self-polarized and produced a remarkably large open circuit photovoltage up to 0.53 V under zero poling condition. The direction of photocurrent and photovoltage is reversibly switchable in response to ferroelectric polarization switching. The short circuit photocurrent "ISC" and open circuit voltage "VOC" depict a hysteresis loop which is more or less identical to that of ferroelectric polarization and thus can be utilized as a nondestructive optical readout of the ferroelectric nonvolatile memories. By introducing special architecture for the BFO based photovoltaic device, a photoconversion efficiency ˜0.3% and External Quantum Efficiency ˜11% are achieved at zero polarization state, which can further be enhanced and modulated to ˜0.6% and 14%, respectively, at the negative poling state of BFMO.

  4. Influence of Au nanoparticles on the photoluminescent and electrical properties of Bi{sub 3.6}Eu{sub 0.4}Ti{sub 3}O{sub 12} ferroelectric thin films

    SciTech Connect

    Su, Li; Qin, Ni E-mail: stsbdh@mail.sysu.edu.cn; Xie, Wei; Fu, Jianhui; Bao, Dinghua E-mail: stsbdh@mail.sysu.edu.cn

    2014-07-21

    Au-doped Bi{sub 3.6}Eu{sub 0.4}Ti{sub 3}O{sub 12} (BET) thin films were prepared on fused silica and Pt/Ti/SiO{sub 2}/Si substrates by a chemical solution deposition method. The existence of Au nanoparticles (NPs) has been confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscope analysis. Enhanced photoluminescence (PL) of Eu{sup 3+} ions was obtained in a wide range of Au doping level. Role of the Au NPs in the PL enhancement was investigated by means of optical absorption, excitation, and emission spectra, as well as decay lifetime measurements. The results indicated that the intra-4f transition of Eu{sup 3+} ions can be intensively activated by the coupling of the charge transfer band of BET with the {sup 5}D{sub 0} state of Eu{sup 3+} ions. The influence of Au NPs on the PL properties of Eu{sup 3+} ions in the present thin films was attributed to the band bending at Au/BET interface and the localized surface plasma resonance absorption of Au NPs in the visible light region. The dielectric and ferroelectric properties of Au-doped BET thin films were investigated as well.

  5. Screening on binary Zr-1X (X = Ti, Nb, Mo, Cu, Au, Pd, Ag, Ru, Hf and Bi) alloys with good in vitro cytocompatibility and magnetic resonance imaging compatibility.

    PubMed

    Zhou, F Y; Qiu, K J; Li, H F; Huang, T; Wang, B L; Li, L; Zheng, Y F

    2013-12-01

    In this study, the microstructures, mechanical properties, corrosion behaviors, in vitro cytocompatibility and magnetic susceptibility of Zr-1X alloys with various alloying elements, including Ti, Nb, Mo, Cu, Au, Pd, Ag, Ru, Hf and Bi, were systematically investigated to explore their potential use in biomedical applications. The experimental results indicated that annealed Zr-1X alloys consisted entirely or primarily of α phase. The alloying elements significantly increased the strength and hardness of pure Zr and had a relatively slight influence on elastic modulus. Ru was the most effective enhancing element and Zr-1Ru alloy had the largest elongation. The results of electrochemical corrosion indicated that adding various elements to Zr improved its corrosion resistance, as indicated by the reduced corrosion current density. The extracts of the studied Zr-1X alloys produced no significant deleterious effects on osteoblast-like cells (MG 63), indicating good in vitro cytocompatibility. All except for Zr-1Ag alloy showed decreased magnetic susceptibility compared to pure Zr, and Zr-1Ru alloy had the lowest magnetic susceptibility value, being comparable to that of α' phase Zr-Mo alloy and Zr-Nb alloy and far lower than that of Co-Cr alloy and Ti-6Al-4V alloy. Among the experimental Zr-1X alloys, Zr-1Ru alloy possessing high strength coupled with good ductility, good in vitro cytocompatibility and low magnetic susceptibility may be a good candidate alloy for medical devices within a magnetic resonance imaging environment.

  6. Nanoindentation Mechanical Properties of a Bi-phase Cu29Zr32Ti15Al5Ni19 Alloy

    NASA Astrophysics Data System (ADS)

    Pi, JinHong; Wang, ZhangZhong; He, XianCong; Bai, YunQiang

    2016-01-01

    Mechanical properties of cylindrical bi-phasic high-entropy alloy Cu29Zr32Ti15Al5Ni19 (3 mm in diameter) were characterized by nanoindentation test in each phase. The results show that the constituent FCC phase is of low nanohardness (2.35 GPa) and modulus (60.9 GPa), while another constituent phase in the alloy, the HCP phase, shows much higher nanohardness (6.5 GPa) and modulus (115.3 GPa). Creep occurs in both phases during the indentation.

  7. White luminescence and energy transfer process in Bi3+,Sm3+ co-doped Ca3Al2O6 phosphors

    NASA Astrophysics Data System (ADS)

    Wang, LongJun; Guo, Hai; Wei, YunLe; Noh, Hyeon Mi; Jeong, Jung Hyun

    2015-04-01

    Ca3Al2O6:Bi3+,Sm3+ phosphors were synthesized by conventional solid state reaction method and their luminescent properties were systemically investigated by excitation, emission spectra and decay curves measurement. Through an efficient energy transfer process from Bi3+ to Sm3+, the obtained phosphors exhibit emission from Bi3+ and Sm3+ with considerable intensity under near-ultraviolet excitation (300 nm). Tuning the content of Sm3+ can generate the varied hues from blue green to white. Our research will extend the understanding of interactions between Bi3+ and rare earth ions and show the potential application of Bi3+,Sm3+ co-doped phosphors in W-LEDs field.

  8. Leakage current limiting mechanisms and ferroelectric properties of BiAlO3/La0.67Sr0.33MnO3 heterostructure

    NASA Astrophysics Data System (ADS)

    Zhao, Yanan; Luo, Bingcheng; Chen, Changle; Xing, Hui; Wang, Jianyuan; Jin, Kexin

    2017-03-01

    The BiAlO3/La0.67Sr0.33MnO3 heterostructure was deposited on LaAlO3 (111) substrate by pulse laser deposition technology. X-ray diffraction measurement indicates that BiAlO3 thin films belong to tetragonal phase. Two different leakage current mechanisms, i.e., Space Charge Limited Current and Schottky emission models are observed in J-E characteristics of BiAlO3/La0.67Sr0.33MnO3 heterostructure in different temperature regions, respectively. The ferroelectric hysteresis loops measured by positive-up negative-down method show intrinsic remnant polarization (2Pr = 2.4 μC/cm2) at the applied electric field of 750 kV/cm, with the 80 nm thickness of BiAlO3 thin films at room temperature. The domain imagines and local piezoelectric hysteresis loops obtained by Piezoresponse Force Microscopy technique further reveal the intrinsic ferroelectricity of. BiAlO3 thin films at room temperature.

  9. Bose-Einstein correlations in Si + Al and Si + Au collisions at 14.6A GeV/c

    NASA Technical Reports Server (NTRS)

    Abbott, T.; Akiba, Y.; Beavis, D.; Bloomer, M. A.; Bond, P. D.; Chasman, C.; Chen, Z.; Chu, Y. Y.; Cole, B. A.; Costales, J. B.

    1992-01-01

    The E802 Spectrometer at the Brookhaven Alternating Gradient Synchrotron has been used to measure the correlation in relative momentum between like-sign pions emitted in central Si + Al and Si + Au collisions at 14.6A GeV/c. Data are presented in terms of the correlation function for both identified pi(-) and pi(+) pairs near the nucleon-nucleon center-of-mass rapidity. All parametrizations of the correlation function are consistent with a spherically symmetric source of rms radius 3.5 +/- 0.4 fm and lifetime fm/c.

  10. Site preference of ternary alloying additions to NiTi: Fe, Pt, Pd, Au, Al, Cu, Zr and Hf

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Mosca, Hugo O.

    2004-01-01

    Atomistic modeling of the site substitution behavior of Pd in NiTi (J. Alloys and Comp. (2004), in press) has been extended to examine the behavior of several other alloying additions, namely, Fe, Pt, Au, Al, Cu, Zr and Hf in this important shape memory alloy. It was found that all elements, to a varying degree, displayed absolute preference for available sites in the deficient sublattice. How- ever, the energetics of the different substitutional schemes, coupled with large scale simulations indicate that the general trend in all cases is for the ternary addition to want to form stronger ordered structures with Ti.

  11. Effect of annealing temperature on the structural reorganization of Eu3+ optical centers in Al2O3-Eu2O3-BiOF gel films

    NASA Astrophysics Data System (ADS)

    Malashkevich, G. E.; Kornienko, A. A.; Dunina, E. B.; Prusova, I. V.; Shevchenko, G. P.; Bokshits, Yu. V.

    2007-06-01

    The dependence of the structural reorganization of Eu3+ optical centers in Al2O3-Eu2O3-BiOF films on the annealing temperature has been investigated. It is shown by the methods of crystal field theory and computer simulation that the increase in the annealing temperature from 700 to 1100 °C leads to removal of bismuth from Eu-O-Bi complex centers with the C 3V symmetry in the Al2O3 structure and the change in symmetry from D 3 to O h for a large fraction of EuAlO3 centers.

  12. Au-free ohmic Ti/Al/TiN contacts to UID n-GaN fabricated by sputter deposition

    NASA Astrophysics Data System (ADS)

    Garbe, V.; Weise, J.; Motylenko, M.; Münchgesang, W.; Schmid, A.; Rafaja, D.; Abendroth, B.; Meyer, D. C.

    2017-02-01

    The fabrication and characterization of an Au-free Ti/Al/TiN (20/100/100 nm) contact stack to unintentionally doped n-GaN with TiN serving as the diffusion barrier is presented. Sputter deposition and lift-off in combination with post deposition annealing at 850 °C are used for contact formation. After annealing, contact shows ohmic behavior to n-GaN and a specific contact resistivity of 1.60 × 10-3 Ω cm2. To understand the contact formation on the microscopic scale, the contact was characterized by current-voltage measurements, linear transmission line method, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show the formation of Ti-N bonds at the GaN/Ti interface in the as-deposited stack. Annealing leads to diffusion of Ti, Al, Ga, and N, and the remaining metallic Ti is fully consumed by the formation of the intermetallic tetragonal Al3Ti phase. Native oxide from the GaN surface is trapped during annealing and accumulated in the Al interlayer. The TiN capping layer, however, was chemically stable during annealing. It prevented oxidation of the Ti/Al contact bilayer successfully and thus proved to be a well suitable diffusion barrier with ideal compatibility to the Ti/Al contact metallization.

  13. Theoretical Predictions of Structural, Electronic, and Optical Properties of Dilute Bismide AlN1- x Bi x in Zinc-Blend Structures

    NASA Astrophysics Data System (ADS)

    Alaya, R.; Slama, S.; Hashassi, M.; Mbarki, M.; Rebey, A.; Alaya, S.

    2017-04-01

    We report the results of first-principles calculations based on the full-potential linearized augmented plane wave (FP-LAPW + lo) method to explore the effects of alloying under the non-conventional AlN III-V compound with bismuth. We have calculated the structural and electronic properties of the binary compounds AlN and AlBi in the zinc blend structure. We have found a good agreement between our results and the experimental and theoretical results available for that binary compounds which may be a support for the results of the ternary alloys. For the AlNBi ternary alloys, we have found a rapid reduction of the energy gap by 1.31 eV/%Bi accompanied by a strong increase in the spin-orbit splitting energy (Δso) with increasing Bi composition. We have also shown that the Δso becomes greater than the energy gap for composition of Bi about 4.2% (Δso > E g). This result is significant due to the possibility of suppressing Auger recombination, which is expected to improve the high temperature performance and thermal stability of light emitting devices. Finally, we have calculated the variation of the optical properties of AlNBi compounds, such as dielectric function and refractive index versus Bi composition.

  14. Correlation between microstructure and temperature dependent electrical behavior of annealed Ti/Al/Ni/Au Ohmic contacts to AlGaN/GaN heterostructures

    SciTech Connect

    Iucolano, Ferdinando; Greco, Giuseppe; Roccaforte, Fabrizio

    2013-11-11

    This letter reports on the temperature behavior of the structural and electrical properties of Ti/Al/Ni/Au contacts to AlGaN/GaN heterostructures. While Ohmic contacts formed at 750 °C showed a decreasing temperature behavior of the specific contact resistance ρ{sub C}, which was explained by a thermionic field emission mechanism, an increasing trend is observed in the contacts formed at 850 °C. In this case, ρ{sub C} exhibits a “metal-like” behavior, i.e., describable by a T{sup 1.8} dependence. The microstructural analysis of the interfacial region allowed to explain the results with the formation of metallic intrusions contacting directly the two dimensional electron gas.

  15. Experimental study of loss mechanisms of AgAu/PbBi-2223 tapes with twisted filaments under perpendicular AC magnetic fields at power frequencies

    NASA Astrophysics Data System (ADS)

    Martínez, E.; Yang, Y.; Beduz, C.; Huang, Y. B.

    2000-05-01

    AC losses under perpendicular AC fields have been measured at 77 K and power frequencies for multifilamentary AgAu (10 wt.%)/Bi-2223 tapes with filaments twisted at different pitches. Using simultaneous measurements of the first and higher harmonics of the voltage induced in the pick-up coil, the main loss contributions (superconductor and coupling current losses) have been obtained separately. At power frequencies, twisting produces the desired uncoupling of the filaments at fields lower than the coupling field, which has also been determined experimentally. In the uncoupled-filament regime, the superconductor losses are reduced strongly with respect to the untwisted tapes. The reduction of the total loss with twisting is also observed. However, due to the important contribution of the coupling current losses for this field orientation, a very small pitch (<5 mm) is necessary for a considerably lower loss than that of untwisted tapes. The dependence of the coupling field and coupling current losses on the twist pitch has been analysed and compared with the theoretical predictions.

  16. Cation-Poor Complex Metallic Alloys in Ba(Eu)-Au-Al(Ga) Systems: Identifying the Keys that Control Structural Arrangements and Atom Distributions at the Atomic Level.

    PubMed

    Smetana, Volodymyr; Steinberg, Simon; Mudryk, Yaroslav; Pecharsky, Vitalij; Miller, Gordon J; Mudring, Anja-Verena

    2015-11-02

    Four complex intermetallic compounds BaAu(6±x)Ga(6±y) (x = 1, y = 0.9) (I), BaAu(6±x)Al(6±y) (x = 0.9, y = 0.6) (II), EuAu6.2Ga5.8 (III), and EuAu6.1Al5.9 (IV) have been synthesized, and their structures and homogeneity ranges have been determined by single crystal and powder X-ray diffraction. Whereas I and II originate from the NaZn13-type structure (cF104-112, Fm3̅c), III (tP52, P4/nbm) is derived from the tetragonal Ce2Ni17Si9-type, and IV (oP104, Pbcm) crystallizes in a new orthorhombic structure type. Both I and II feature formally anionic networks with completely mixed site occupation by Au and triel (Tr = Al, Ga) atoms, while a successive decrease of local symmetry from the parental structures of I and II to III and, ultimately, to IV correlates with increasing separation of Au and Tr on individual crystallographic sites. Density functional theory-based calculations were employed to determine the crystallographic site preferences of Au and the respective triel element to elucidate reasons for the atom distribution ("coloring scheme"). Chemical bonding analyses for two different "EuAu6Tr6" models reveal maximization of the number of heteroatomic Au-Tr bonds as the driving force for atom organization. The Fermi levels fall in broad pseudogaps for both models allowing some electronic flexibility. Spin-polarized band structure calculations on the "EuAu6Tr6" models hint to singlet ground states for europium and long-range magnetic coupling for both EuAu6.2Ga5.8 (III) and EuAu6.1Al5.9 (IV). This is substantiated by experimental evidence because both compounds show nearly identical magnetic behavior with ferromagnetic transitions at TC = 6 K and net magnetic moments of 7.35 μB/f.u. at 2 K. The effective moments of 8.3 μB/f.u., determined from Curie-Weiss fits, point to divalent oxidation states for europium in both III and IV.

  17. InAlN high electron mobility transistor Ti/Al/Ni/Au Ohmic contact optimisation assisted by in-situ high temperature transmission electron microscopy

    SciTech Connect

    Smith, M. D.; Parbrook, P. J.; O'Mahony, D.; Conroy, M.; Schmidt, M.

    2015-09-14

    This paper correlates the micro-structural and electrical characteristics associated with annealing of metallic multi-layers typically used in the formation of Ohmic contacts to InAlN high electron mobility transistors. The multi-layers comprised Ti/Al/Ni/Au and were annealed via rapid thermal processing at temperatures up to 925 °C with electrical current-voltage analysis establishing the onset of Ohmic (linear IV) behaviour at 750–800 °C. In-situ temperature dependent transmission electron microscopy established that metallic diffusion and inter-mixing were initiated near a temperature of 500 °C. Around 800 °C, inter-diffusion of the metal and semiconductor (nitride) was observed, correlating with the onset of Ohmic electrical behaviour. The sheet resistance associated with the InAlN/AlN/GaN interface is highly sensitive to the anneal temperature, with the range depending on the Ti layer thickness. The relationship between contact resistivity and measurement temperature follow that predicted by thermionic field emission for contacts annealed below 850 °C, but deviated above this due to excessive metal-semiconductor inter-diffusion.

  18. Wide quantum critical region of valence fluctuations: Origin of robust quantum criticality in quasicrystal Yb15Al34Au51 under pressure

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinji; Miyake, Kazumasa

    2015-03-01

    The mechanism of the emergence of robust quantum criticality in the heavy- electron quasicrystal YR15Al34Au51 is analyzed theoretically. By constructing a minimal model for the quasicrystal and its crystalline approximant, which contain concentric shell structures with Yb and Al-Au clusters, we show that a set of quantum critical points of the first-order valence transition of Yb appears as spots in the ground-state phase diagram. Their critical regions overlap each other, giving rise to a wide quantum critical region. This well explains the robust criticality observed in YR15Al34Au51 under pressure, and predicts the emergence of the common criticality in the crystalline approximant under pressure. The wider critical region in the quasicrystal than that in the crystalline approximant in the T-P phase diagram and the field-induced valence-crossover "region" in the T-H phase diagram are predicted to appear.

  19. Fluid sources and metallogenesis in the Blackbird Co-Cu-Au-Bi-Y-REE district, Idaho, U.S.A.: Insights from major-element and boron isotopic compositions of tourmaline

    USGS Publications Warehouse

    Trumbull, R.B.; Slack, J.F.; Krienitz, M.-S.; Belkin, H.E.; Wiedenbeck, M.

    2011-01-01

    Tourmaline is a widespread mineral in the Mesoproterozoic Blackbird Co-Cu-Au-Bi-Y-REE district, Idaho, where it occurs in both mineralized zones and wallrocks. We report here major-element and B-isotope compositions of tourmaline from stratabound sulfide deposits and their metasedimentary wallrocks, from mineralized and barren pipes of tourmaline breccia, from late barren quartz veins, and from Mesoproterozoic granite. The tourmalines are aluminous, intermediate in the schorl-dravite series, with Fe/(Fe + Mg) values of 0.30 to 0.85, and 10 to 50% X-site vacancies. Compositional zoning is prominent only in tourmaline from breccias and quartz veins; crystal rims are enriched in Mg, Ca and Ti, and depleted in Fe and Al relative to cores. The chemical composition of tourmaline does not correlate with the presence or absence of mineralization. The ??11B values fall into two groups. Isotopically light tourmaline (-21.7 to-7.6%o) occurs in unmineralized samples from wallrocks, late quartz veins and Mesoproterozoic granite, whereas heavy tourmaline (-6.9 to +3.2%o) is spatially associated with mineralization (stratabound and breccia-hosted), and is also found in barren breccia. At an inferred temperature of 300??C, boron in the hydrothermal fluid associated with mineralization had ??11B values of-3 to +7%o. The high end of this range indicates a marine source of the boron. A likely scenario involves leaching of boron principally from marine carbonate beds or B-bearing evaporites in Mesoproterozoic strata of the region. The ??11B values of the isotopically light tourmaline in the sulfide deposits are attributed to recrystallization during Cretaceous metamorphism, superimposed on a light boron component derived from footwall siliciclastic sediments (e.g., marine clays) during Mesoproterozoic mineralization, and possibly a minor component of light boron from a magmatic-hydrothermal fluid. The metal association of Bi-Be-Y-REE in the Blackbird ores suggests some magmatic input

  20. Pronounced matrix effect in YbMo{sub 2}Al{sub 4}-type Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} (x=0.09–0.89)

    SciTech Connect

    Mishra, Trinath; Lin, Qisheng; Corbett, John D.

    2014-10-15

    Electron-poor polar intermetallics Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} have been synthesized through fusion of stoichiometric metals in sealed tantalum tubes at 800 °C and annealing at 400 °C for one week. Single crystal X-ray diffraction analyses reveal that this phase belongs to the YbMo{sub 2}Al{sub 4}-type structure (I4/mmm, Pearson symbol tI14), a≈6.943–7.017 Å, c≈5.278–5.286 Å, Z=2, with homogeneous composition range of x=0.09(1)–0.89(1). The structure exhibits a three-dimensional framework of (Au{sub 8}){sub 1/2} featuring square and octagonal channels extending in c, in which Ca and the infinite linear chains of [(Au,Zn){sub 2}]{sub 1/2} are located, respectively. Mulliken population analyses demonstrate that Zn prefers to form the linear chains in the whole homogeneous composition range, consistent with experimental observations. Crystal orbital Hamilton population (COHP) analyses reveal that the channel-to-chain Au–Zn contact has strong bonding interactions regardless of its large interatomic distance (∼2.85 Å), a signature of pronounced matrix effect. The last mentioned effect in YbMo{sub 2}Al{sub 4}-type structures is expected in case the linear chains are defined by small size atoms. - Graphical abstract: Pronounced matrix effect incurred by Au–Au bonding within the gold substructure in Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} results in an elongation of the channel-to-chain Au–Zn interatomic distance without weakening bonding interactions. - Highlights: • The complete solid solution of Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} was accomplished. • Site preference was explained by “coloring” analyses. • Abnormally large Au–Zn distance but with strong bonding was observed. • Pronounced matrix effect incurred by Au–Au bonding in gold substructure was found.

  1. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    SciTech Connect

    Ren, Jian; Yan, Dawei Yang, Guofeng; Wang, Fuxue; Xiao, Shaoqing; Gu, Xiaofeng

    2015-04-21

    Lattice-matched Pt/Au-In{sub 0.17}Al{sub 0.83}N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

  2. Spin Polarization of Mg-23 in Mg-24 + Au, Cu and Al Collisions at 91 A MeV

    NASA Technical Reports Server (NTRS)

    Matsuta, K.; Fukuda, S.; Izumikawa, T.; Tanigaki, M.; Fukuda, M.; Nakazato, M.; Mihara, M.; Onishi, T.; Yamaguchi, T.; Miyake, T.

    1994-01-01

    Spin polarization of beta-emitting fragment Mg-23(I(sup pi) = 3/2(sup +), T(sub 1/2 = l1.3 s) produced through the projectile fragmentation process in Mg-24 + Au, Cu and Al collisions has been observed at 91 AMeV. General trend in the observed momentum dependence of polarization is reproduced well qualitatively by a simple fragmentation model based on the participant-spectator picture, for heavy and light targets. However the polarization behavior differs from this model in tern of zero crossing momentum, which become prominent in the case of Cu target, where the polarization is not monotone function of the fragment momentum.

  3. Pressure-Driven Quantum Criticality and T/H Scaling in the Icosahedral Au-Al-Yb Approximant

    NASA Astrophysics Data System (ADS)

    Matsukawa, Shuya; Deguchi, Kazuhiko; Imura, Keiichiro; Ishimasa, Tsutomu; Sato, Noriaki K.

    2016-06-01

    We report on ac magnetic susceptibility measurements under pressure of the Au-Al-Yb alloy, a crystalline approximant to the icosahedral quasicrystal that shows unconventional quantum criticality. In describing the susceptibility as χ(T)-1 - χ(0)-1 ∝ Tγ, we find that χ(0)-1 decreases with increasing pressure and vanishes to zero at the critical pressure Pc ≃ 2 GPa, with γ ( ≃ 0.5) unchanged. We suggest that this quantum criticality emerges owing to critical valence fluctuations. Above Pc, the approximant undergoes a magnetic transition at T ≃ 100 mK. These results are contrasted with the fact that, in the quasicrystal, the quantum criticality is robust against the application of pressure. The applicability of the so-called T/H scaling to the approximant is also discussed.

  4. In situ synchrotron study of liquid phase separation process in Al-10 wt.% Bi immiscible alloys by radiography and small angle X-ray scattering

    NASA Astrophysics Data System (ADS)

    Lu, W. Q.; Zhang, S. G.; Li, J. G.

    2016-03-01

    Liquid phase separation process of immiscible alloys has been repeatedly tuned to create special structure for developing materials with unique properties. However, the fundamental understanding of the liquid phase separation process is still under debate due to the characteristics of immiscible alloys in opacity and high temperature environment of alloy melt. Here, the liquid phase separation process in solidifying Al-Bi immiscible alloys was investigated by synchrotron radiography and small angle X-ray scattering. We provide the first direct evidence of surface segregation prior to liquid decomposition and present that the time dependence on the number of Bi droplets follows Logistic curve. The liquid decomposition results from a nucleation and growth process rather than spinodal decomposition mechanism because of the positive deviation from Porod's law. We also found that the nanometer-sized Bi-rich droplets in Al matrix melt present mass fractal characteristics.

  5. Friction-Stir Welding - Heavy Inclusions in Bi-metallic welds of Al 2219/2195

    NASA Technical Reports Server (NTRS)

    Rietz, Ward W., Jr.

    2008-01-01

    Heavy Inclusions (HI) were detected for the first time by radiographic examination in aluminum alloy 2219forging/2195plate (advancing/retreating side) Friction Sir Welds (FSW) for the Space Shuttle External Tank (ET) Program. Radiographic HI indications appear as either small (approx.0.005"-0.025") individual particles or clusters of small particles. Initial work was performed to verify that the HI was not foreign material or caused by FSW pin tool debris. That and subsequent elemental analysis determined that the HI were large agglomerations of Al2Cu (theta phase), which is the strengthening precipitate in Al2219. A literature search on that subject determined that the agglomeration of phase has also been found in Al2219 bead on plate FSW [Ref. 1]. Since this was detected in ET space flight hardware, an investigative study of the effect of agglomerated theta phase particles in FSW Al2219f/2195p was performed. Numerous panels of various lengths were welded per ET weld procedures and radiographically inspected to determine if any HI was detected. Areas that had HI were sampled for room temperature and cyclic cryogenic (-423F) tensile testing and determined no significant adverse affect on mechanical properties when compared to test specimens without HI and historical data. Fracture surface examination using the Scanning Electron Microscope (SEM) revealed smaller phase agglomerations undetectable by radiographic inspection dispersed throughout the Al2219f/2195p FSW. This indicates that phase agglomeration is inherent to the Al2219f/2195p FSW process and only rarely creates agglomerations large enough to be detected by radiography. HI has not been observed in FSW of plate to plate material for either Al2219 or AL2195.

  6. Development of high volume fraction SiCP/Al composite-bismuthate glass metal plus dielectric films optics Au-mirror

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Qu, Shengguan; Li, Xiang-Long

    2017-01-01

    This paper reports the development of high volume fraction SiCP/Al composite-bismuthate glass multilayer films optics Au-mirror with high reflectivity in a wavelength range of 760 to 1000 nm. Multilayer films were fabricated using an radio frequency-magnetron sputtering deposition system. The measured reflectivity of Ta2O5/SiO2/Au/Cr metal plus dielectric films optics Au-mirror could reach up to ≥97%. Then, on the basis of experiments, a Φ75-mm high volume fraction SiCP/Al composite-bismuthate glass multilayer optical Au-mirror for a wavelength range of 760 to 1000 nm was manufactured. The tested results indicate that a peak-to-valley value of 0.854λ (λ=632.8 nm) was achieved on the Au-mirror surface, and the slope deviation error for the flat surface was lower than 0.153λ root mean square. The surface roughness of Ta2O5/SiO2/Au/Cr multilayer thin films was 1.30 nm (Ra).

  7. Mise au point dans le ternaire TlBiTe. Existence de deux phases nonstoechiometriques de type TlBiTe 2

    NASA Astrophysics Data System (ADS)

    Pradel, A.; Tedenac, J. C.; Brun, G.; Maurin, M.

    1982-11-01

    The cross section BiTeTlTe of the phase diagram TlBiTe was constructed by X-ray, microstructure, and DTA methods. Two phases were emphasized: Tl 1- xBi 1+ xTe 2 with x = 0.06, and Tl 1- yBi 1+ yTe 2 with y = 0.2. The first one is a nonstoichiometric representation of what so many authors studied as TlBiTe 2. The latter is a high-temperature phase which decomposes in eutectoïd reaction (415°C): 1.18{ Tl0.8Bi1.2Te2} ⇄ Tl0.94Bi1.06Te2 + 0.36 { BiTe} . The high-temperature form undergoes a phase transformation by quenching, giving a metastable low-temperature form. The discussion includes electrical resistivity and thermoelectric measurements of each of them.

  8. RE2MAl6Si4 (RE = Gd, Tb, Dy; M = Au, Pt): layered quaternary intermetallics featuring CaAl2Si2-type and YNiAl4Ge2-type slabs grown from aluminum flux.

    PubMed

    Latturner, Susan E; Bilc, Daniel; Mahanti, S D; Kanatzidis, Mercouri G

    2003-12-01

    Six new intermetallic aluminum silicides--Gd(2)PtAl(6)Si(4), Gd(2)AuAl(6)Si(4), Tb(2)PtAl(6)Si(4), Tb(2)AuAl(6)Si(4), Dy(2)PtAl(6)Si(4), and Dy(2)AuAl(6)Si(4)--have been obtained from reactions carried out in aluminum flux. The structure of these compounds was determined by single-crystal X-ray diffraction. They form in space group Rthremacr;m with cell constants of a = 4.1623(3) A and c = 51.048(5) A for the Gd(2)PtAl(6)Si(4) compound. The crystal structure is comprised of hexagonal nets of rare earth atoms alternating with two kinds of layers that have been observed in other multinary aluminide intermetallic compounds (CaAl(2)Si(2) and YNiAl(4)Ge(2)). All six RE(2)MAl(6)Si(4) compounds show antiferromagnetic transitions at low temperatures (T(N) < 20 K); magnetization studies of the Dy compounds show metamagnetic behavior with reorientation of spins at 6000 G. Band structure calculations indicate that the AlSi puckered hexagonal sheets in this structure are electronically distinct from the other surrounding structural motifs.

  9. Phase characteristics of 0.92Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.08BiAlO{sub 3} ceramics

    SciTech Connect

    Peng, Wei; Mao, Chaoliang; Liu, Zhen; Dong, Xianlin; Cao, Fei; Wang, Genshui

    2015-03-02

    The phase characteristics of 0.92Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.08BiAlO{sub 3} lead-free ceramics were investigated systematically. The loss tangent of poled sample shows a broad peak when heating to about 80 °C, i.e., depolarization temperature T{sub d}. The polarization-electric field hysteresis loops at different temperature exhibit the feature of ferroelectric (FE)- antiferroelectric (AFE) phase transition and the co-existence of FE and AFE phase. The pyroelectric coefficients curve confirms its diffusion behaviors. The initial hysteresis loop and switching current curves under T{sub d} indicate the co-existence of FE and AFE phase. The domain morphology of transmission electron microscopy supports the co-existence of FE and AFE phase. Our work not only exhibit that the FE and AFE phase characteristics of 0.92Bi{sub 0.5}Na{sub 0.5}TiO{sub 3}-0.08BiAlO{sub 3} ceramics but also they may be helpful for further investigation on lead-free ceramics.

  10. Enhancing the Photocatalytic Activity of Sr4 Al14 O25 :Eu(2+) ,Dy(3+) Persistent Phosphors by Codoping with Bi(3+) ions.

    PubMed

    García, Carlos R; Oliva, Jorge; Romero, Maria Teresa; Diaz-Torres, Luis A

    2016-01-20

    The photocatalytic activity of Bismuth codoped Sr4 Al14 O25 : Eu(2+) ,Dy(3+) persistent phosphors is studied by monitoring the degradation of the blue methylene dye UV light irradiation. Powder phosphors are obtained by a combustion synthesis method and a post-annealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase of Sr4 Al14 O25 : Eu(2+) ,Dy(3+) ,Bi(3+) phosphors even at high Bismuth dopant concentrations of 12 mol%, suggesting that Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micro grains with sizes in the range of 0.5-20 μm. The samples present an intense greenish-blue fluorescence and persistent emissions at 495 nm, attributed to the 5d-4f allowed transitions of Eu(2+) . The fluorescence decreases as Bi concentration increases; that suggest bismuth induced traps formation that in turn quench the luminescence. The photocatalytic evaluation of the powders was studied under both 365 nm UV and solar irradiations. Sample with 12 mol% of Bi presented the best MB degradation activity; 310 min of solar irradiation allow 100% MB degradation whereas only 62.49% MB degradation is achieved under UV irradiation. Our Results suggest that codoping the persistent phosphors with Bi(3+) can be an alternative to enhance their photocatalytic activity. This article is protected by copyright. All rights reserved.

  11. Investigation of Low Temperature Non-Linear Magnetization Behavior in Al and Ga - Substituted La0.4Bi0.6Mno3 Manganites

    NASA Astrophysics Data System (ADS)

    Dayal, Vijaylakshmi; v, Punith Kumar; Hadimani, Ravi; Jiles, David; David C Jiles Team; Vijaylakshmi Dayal Collaboration

    Low temperature magnetization measurements have been carried out for the samples containing Al and Ga at B-site in La0.4Bi0.6MnO3 manganites. The magnetization (M) vs. T(K) data shows strong ferromagnetic behavior with highest magnetization of 6.45 emu/g for La0.4Bi0.6Mn0.95Al0.05O3 and 5.40 emu/g for La0.4Bi0.6Mn0.90Al0.1O3 samples respectively for an applied magnetic field of H =100 Oe at T =20 K. Similarly at T =20 K for La0.4Bi0.6Mn0.95Ga0.05O3 the highest magnetization (MS) was found to be 5.44 emu/g and for La0.4Bi0.6Mn0.90Ga0.1O3 the MS is 5.05 emu/g. The decrease in magnetization with both Al and Ga substitution produces magnetic dilution with increasing concentrations. Both Al and Ga substituted samples exhibit non-linear behavior in their magnetization (MNL) curves around 40 -120 K due to the frustrations arising from mismatch in their magnetic spin arrangements. The quantity non linear susceptibility, χNL = - MNL/H, diverges as the temperature approaches the frustrated region Tf from above (i.e.TC) . Further from dχNL/dT vs. T(K) plots and critical analysis with unusual critical exponent's γ and β gives an experimental evidence for the observed non linearity and magnetic frustration.

  12. Distribution of Be, Al, Se and Bi in the surface waters of the western North Atlantic and Caribbean

    NASA Astrophysics Data System (ADS)

    Measures, C. I.; Grant, B.; Khadem, M.; Lee, D. S.; Edmond, J. M.

    1984-11-01

    The mixed layer distributions of several trace elements have been determined along a detailed transect from Rhode Island to the Panama Canal. When taken together with a new and existing profile data from the North Atlantic and North Pacific, some general inferences emerge as to the processes controlling their concentrations in the surface waters. The large enrichments in Be observed in the upper waters of the North Atlantic relative to the North Pacific appear to be sustained mainly by fluvial inputs. Those of Se are derived from atmospheric transport. Aluminium and Bi also appear to have an aeolian source in the Sargasso Sea. However, in the tropical eastern Pacific, the Al input may be fluvial On this cruise, Be, Al and the Se species were analyzed on board ship within a few hours of collection. The demonstration that this is feasible opens up the prospect of the application of large-scale chemical hydrography to the study of the processes controlling the distribution and water column variability of trace elements in the oceans.

  13. Temperature-Dependent Electrical Properties and Carrier Transport Mechanisms of TMAH-Treated Ni/Au/Al2O3/GaN MIS Diode

    NASA Astrophysics Data System (ADS)

    Reddy, M. Siva Pratap; Puneetha, Peddathimula; Reddy, V. Rajagopal; Lee, Jung-Hee; Jeong, Seong-Hoon; Park, Chinho

    2016-11-01

    The temperature-dependent electrical properties and carrier transport mechanisms of tetramethylammonium hydroxide (TMAH)-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes have been investigated by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements. The experimental results reveal that the barrier height ( I- V) increases whereas the ideality factor decreases with increasing temperature. The TMAH-treated Ni/Au/Al2O3/GaN MIS diode showed nonideal behaviors which indicate the presence of a nonuniform distribution of interface states ( N SS) and effect of series resistance ( R S). The obtained R S and N SS were found to decrease with increasing temperature. Furthermore, it was found that different transport mechanisms dominated in the TMAH-treated Ni/Au/Al2O3/GaN MIS diode. At 150 K to 250 K, Poole-Frenkel emission (PFE) was found to be responsible for the reverse leakage, while Schottky emission (SE) was the dominant mechanism at high electric fields in the temperature range from 300 K to 400 K. Feasible energy band diagrams and possible carrier transport mechanisms for the TMAH-treated Ni/Au/Al2O3/GaN MIS diode are discussed based on PFE and SE.

  14. On the origin of near-IR luminescence in Bi-doped materials (II). Subvalent monocation Bi⁺ and cluster Bi₅³⁺ luminescence in AlCl₃/ZnCl₂/BiCl₃ chloride glass.

    PubMed

    Romanov, Alexey N; Fattakhova, Zukhra T; Veber, Alexander A; Usovich, Olga V; Haula, Elena V; Korchak, Vladimir N; Tsvetkov, Vladimir B; Trusov, Lev A; Kazin, Pavel E; Sulimov, Vladimir B

    2012-03-26

    Broadband NIR photoluminescence (from 1000 to 2500 nm) was observed from partially reduced AlCl₃/ZnCl₂/BiCl₃ glass, containing subvalent bismuth species. The luminescence consists of three bands, assigned to Bi⁺ , Bi₂⁴⁺, and Bi₅³⁺ ions. The physical and optical characteristics of these centers and possible contribution to NIR luminescence from bismuth-doped oxide glasses are discussed.

  15. Thermoelectric properties of n-type Bi2Te2.7Se0.3 with addition of nano-ZnO:Al particles

    NASA Astrophysics Data System (ADS)

    Song, Shaowei; Wang, Jueling; Xu, Bo; Lei, Xiaobo; Jiang, Hongchuan; Jin, Yingrong; Zhang, Qinyong; Ren, Zhifeng

    2014-09-01

    Nano Al-doped ZnO (AZO) particles were added into n-type Bi2Te2.7Se0.3 alloys by ball milling and hot pressing method. The power factor was improved by ˜22% with addition of nano-AZO particles, accompanied with a ˜40% decrease of lattice thermal conductivity, leading to peak ZT of ˜0.85 at 323 K for Bi2Te2.7Se0.3(AZO)0.005 sample. The effects of the addition of AZO nanoparticles on the microstructure and thermoelectric transport properties are discussed.

  16. Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing

    SciTech Connect

    Zhang, Jinhan; Zhou, Qi; Chen, Wanjun; Zhang, Bo; Huang, Sen Bao, Qilong; Wang, Xinhua; Wei, Ke; Zheng, Yingkui; Li, Yankui; Zhao, Chao; Liu, Xinyu

    2015-12-28

    The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN heterostructures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 °C, pre-ohmic recess etching of the AlGaN barrier down to several nanometers is demonstrated to be an effective method to reduce the contact resistance between Ti/Al/Ti/W ohmic metals and AlGaN/GaN heterostructures. However, further over recess of the AlGaN barrier leads to only sidewall contact to 2D electron gas channel and thus degraded contact performance. It is verified by temperature-dependent contact resistivity measurements that field emission (tunneling) dominates the current transport mechanism in Au-free ohmic contacts with AlGaN barrier partially and over recessed, while both field emission and thermionic emission contribute to traditional Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructures that annealed at high temperature (850 °C)

  17. Origin of interface magnetism in BiMnO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures.

    PubMed

    Salluzzo, M; Gariglio, S; Stornaiuolo, D; Sessi, V; Rusponi, S; Piamonteze, C; De Luca, G M; Minola, M; Marré, D; Gadaleta, A; Brune, H; Nolting, F; Brookes, N B; Ghiringhelli, G

    2013-08-23

    Possible ferromagnetism induced in otherwise nonmagnetic materials has been motivating intense research in complex oxide heterostructures. Here we show that a confined magnetism is realized at the interface between SrTiO3 and two insulating polar oxides, BiMnO3 and LaAlO3. By using polarization dependent x-ray absorption spectroscopy, we find that in both cases the magnetism can be stabilized by a negative exchange interaction between the electrons transferred to the interface and local magnetic moments. These local magnetic moments are associated with magnetic Ti3+ ions at the interface itself for LaAlO3/SrTiO3 and to Mn3+ ions in the overlayer for BiMnO3/SrTiO3. In LaAlO3/SrTiO3 the induced magnetism is quenched by annealing in oxygen, suggesting a decisive role of oxygen vacancies in this phenomenon.

  18. Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

    SciTech Connect

    Hu, J. Groeseneken, G.; Stoffels, S.; Lenci, S.; Venegas, R.; Decoutere, S.; Bakeroot, B.

    2015-02-23

    This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕ{sub B} increase) together with R{sub ON} degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

  19. Effects of temperature, silicate melt composition, and oxygen fugacity on the partitioning of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide phases and silicate melt

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Audétat, Andreas

    2015-08-01

    In order to assess the role of sulfide in controlling the ore metal budgets and fractionation during magmatic genesis and differentiation, the partition coefficients (D) of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide liquid (SL), monosulfide solid solution (MSS), and basaltic to rhyolitic melts (SM) were determined at 900-1200 °C, 0.5-1.5 GPa, and oxygen fugacity (fO2) ranging from ∼FMQ-2 to FMQ+3, in a piston-cylinder apparatus. The DSL/SM values range from 0.4 to 2 for V, 0.5 to 3 for Mn, 80 to 580 for Co, 2300 to 18,000 for Ni, 800 to 4600 for Cu, 1 to 11 for Zn, 20 to 180 for As, 4 to 230 for Mo, 450 to 1600 for Ag, 5 to 24 for Sn, 10 to 80 for Sb, 0.03 to 0.16 for W, 2000 to 29,000 for Au, 24 to 170 for Pb, and 830 to 11,000 for Bi; whereas the DMSS/SM values range from 0.04 to 10 for V, 0.5 to 10 for Mn, 70 to 2500 for Co, 650 to 18,000 for Ni, 280 to 42,000 for Cu, 0.1 to 80 for Zn, 0.2 to 30 for As, 1 to 820 for Mo, 20 to 500 for Ag, 0.2 to 220 for Sn, 0.1 to 40 for Sb, 0.01 to 24 for W, 10 to 2000 for Au, 0.03 to 6 for Pb, and 1 to 350 for Bi. Both DMSS/SM and DSL/SM values generally increase with decreasing temperature or decreasing FeOtot content in silicate melt, except for Mo, DMSS/SM and DSL/SM of which show a clear decrease with decreasing temperature. At given temperature and FeOtot content, high oxygen fugacity appears to lead to a significant decrease in DMSS/SM of Au, Bi, Mo, and potentially As. The partitioning data obtained experimentally in this study and previous studies were fitted to an empirical equation that expresses the DMSS/SM and/or DSL/SM of a given element as a function of temperature, oxygen fugacity, and FeOtot content of the silicate melt: log (DSL/SMorDMSS/SM = d + a · 10, 000 / T + b · (ΔFMQ) + c · log (FeOmelt) in which T is temperature in K, FeOmelt denotes wt% FeOtot in silicate melt, and ΔFMQ denotes log fO2 relative to the fayalite-magnetite-quartz (FMQ) oxygen buffer. The

  20. The impact of ultrathin Al2O3 films on the electrical response of p-Ge/Al2O3/HfO2/Au MOS structures

    NASA Astrophysics Data System (ADS)

    Botzakaki, M. A.; Skoulatakis, G.; Kennou, S.; Ladas, S.; Tsamis, C.; Georga, S. N.; Krontiras, C. A.

    2016-09-01

    It is well known that the most critical issue in Ge CMOS technology is the successful growth of high-k gate dielectrics on Ge substrates. The high interface quality of Ge/high-k dielectric is connected with advanced electrical responses of Ge based MOS devices. Following this trend, atomic layer deposition deposited ultrathin Al2O3 and HfO2 films were grown on p-Ge. Al2O3 acts as a passivation layer between p-Ge and high-k HfO2 films. An extensive set of p-Ge/Al2O3/HfO2 structures were fabricated with Al2O3 thickness ranging from 0.5 nm to 1.5 nm and HfO2 thickness varying from 2.0 nm to 3.0 nm. All structures were characterized by x-ray photoelectron spectroscopy (XPS) and AFM. XPS analysis revealed the stoichiometric growth of both films in the absence of Ge sub-oxides between p-Ge and Al2O3 films. AFM analysis revealed the growth of smooth and cohesive films, which exhibited minimal roughness (~0.2 nm) comparable to that of clean bare p-Ge surfaces. The electrical response of all structures was analyzed by C-V, G-V, C-f, G-f and J-V characteristics, from 80 K to 300 K. It is found that the incorporation of ultrathin Al2O3 passivation layers between p-Ge and HfO2 films leads to superior electrical responses of the structures. All structures exhibit well defined C-V curves with parasitic effects, gradually diminishing and becoming absent below 170 K. D it values were calculated at each temperature, using both Hill-Coleman and Conductance methods. Structures of p-Ge/0.5 nm Al2O3/2.0 nm HfO2/Au, with an equivalent oxide thickness (EOT) equal to 1.3 nm, exhibit D it values as low as ~7.4  ×  1010 eV-1 cm-2. To our knowledge, these values are among the lowest reported. J-V measurements reveal leakage currents in the order of 10-1 A cm-2, which are comparable to previously published results for structures with the same EOT. A complete mapping of the energy distribution of D its into the energy bandgap of p-Ge, from the valence band

  1. Thermodynamic properties and equations of state for Ag, Al, Au, Cu and MgO using a lattice vibrational method

    NASA Astrophysics Data System (ADS)

    Jacobs, M.; Schmid-Fetzer, R.

    2012-04-01

    A prerequisite for the determination of pressure in static high pressure measurements, such as in diamond anvil cells is the availability of accurate equations of state for reference materials. These materials serve as luminescence gauges or as X-ray gauges and equations of state for these materials serve as secondary pressure scales. Recently, successful progress has been made in the development of consistency between static, dynamic shock-wave and ultrasonic measurements of equations of state (e.g. Dewaele et al. Phys. Rev. B70, 094112, 2004, Dorogokupets and Oganov, Doklady Earth Sciences, 410, 1091-1095, 2006, Holzapfel, High Pressure Research 30, 372-394, 2010) allowing testing models to arrive at consistent thermodynamic descriptions for X-ray gauges. Apart from applications of metallic elements in high-pressure work, thermodynamic properties of metallic elements are also of mandatory interest in the field of metallurgy for studying phase equilibria of alloys, kinetics of phase transformation and diffusion related problems, requiring accurate thermodynamic properties in the low pressure regime. Our aim is to develop a thermodynamic data base for metallic alloy systems containing Ag, Al, Au, Cu, Fe, Ni, Pt, from which volume properties in P-T space can be predicted when it is coupled to vibrational models. This mandates the description of metallic elements as a first step aiming not only at consistency in the pressure scales for the elements, but also at accurate representations of thermodynamic properties in the low pressure regime commonly addressed in metallurgical applications. In previous works (e.g. Jacobs and de Jong, Geochim. Cosmochim. Acta, 71, 3630-3655, 2007, Jacobs and van den Berg, Phys. Earth Planet. Inter., 186, 36-48, 2011) it was demonstrated that a lattice vibrational framework based on Kieffer's model for the vibrational density of states, is suitable to construct a thermodynamic database for Earth mantle materials. Such a database aims at

  2. Superconductivity up to 114 K in the Bi-Al-Ca-Sr-Cu-O compound system without rare-earth elements

    NASA Technical Reports Server (NTRS)

    Chu, C. W.; Bechtold, J.; Gao, L.; Hor, P. H.; Huang, Z. J.

    1988-01-01

    Stable superconductivity up to 114 K has been reproducibly detected in Bi-Al-Ca-Sr-Cu-O multiphase systems without any rare-earth elements. Pressure has only a slight positive effect on T(c). These observations provide an extra material base for the study of the mechanism of high-temperature superconductivity and also the prospect of reduced material cost for future applications of superconductivity.

  3. Peculiarities of excited state structure and photoluminescence in Bi(3+)-doped Lu(3)Al(5)O(12) single-crystalline films.

    PubMed

    Babin, V; Gorbenko, V; Krasnikov, A; Makhov, A; Nikl, M; Polak, K; Zazubovich, S; Zorenko, Yu

    2009-10-14

    Single-crystalline films of Lu(3)Al(5)O(12):Bi, prepared by the liquid phase epitaxy method from the melt-solution based on Bi(2)O(3) flux, have been studied at 4.2-400 K by time-resolved luminescence spectroscopy methods. Their emission spectra consist of two types of bands with strongly different characteristics. The ultraviolet emission band consists of two components, arising from the electronic transitions which correspond to the [Formula: see text] and [Formula: see text] transitions in a free Bi(3+) ion. At low temperatures, mainly the lower-energy component of this emission is observed, having the decay time∼10(-3) s at T<100 K and arising from the metastable (3)P(0) level. At T>100 K, the higher-energy emission component appears, arising from the thermally populated emitting (3)P(1) level. The visible emission spectrum consists of two dominant strongly overlapped broad bands with large Stokes shifts. At 4.2 K, their decay times are ∼10(-5) s and decrease with increasing temperature. Both of the visible emission bands are assumed to have an exciton origin. The lower-energy band is ascribed to an exciton, localized near a single Bi(3+) ion. The higher-energy band shows a stronger intensity dependence on the Bi(3+) content and is assumed to arise from an exciton localized near a dimer Bi(3+) center. The origin and structure of the corresponding excited states is considered and the processes, taking place in the excited states, are discussed.

  4. Conduction phenomenon of Al3+ modified lead free (Na0.5Bi0.5)0.92Ba0.08TiO3 electroceramics

    NASA Astrophysics Data System (ADS)

    Borkar, Hitesh; Kumar, Ashok

    2016-05-01

    Choice of proper dopants at A or B-site of ABO3 perovskite structure can modify the morphotropic phase boundary (MPB), and hence functional properties of polar systems. The chemical nature of donor or acceptor will significantly influence the fundamental properties. Lead-free ferroelectrics have vast potential to replace the lead-based ceramics. The (Na0.5Bi0.5)1-xBaxTiO3 (NBT-BT) (at x=0.08) near MPB with small substitution of trivalent cations (Al3+) has been synthesized by solid state reaction route. The aim to choose the trivalent cations (Al3+) was its relatively smaller radii than that of Bi3+ cations to develop the antipolar phases in the ferroelectric ceramic. Structural, morphological and elemental compositional analyses were studied by X-ray diffraction (XRD), Secondary electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDAX), respectively. Ferroelectric studies were carried out on various compositions of (Na0.46Bi0.46-xAlxBa0.08)TiO3 (NBAT-BT) (x=0, 0.05, 0.07, 0.10) electroceramics. It was observed that with increase in concentration of Al the ferroelectricity state changes from soft to hard. Temperature dependent dielectric spectroscopy shows broad dielectric dispersion. The Al doping diminishes the relaxor behavior of NBT-BT ceramics. Impedance spectroscopy shows that electrical resistivity and relaxation frequency decreases with increase in Al-concentration. Modulus spectra indicate that Al significantly change the bulk capacitance of NBT-BT.

  5. Thermally stable AuBe-based ohmic contacts to p-type GaP for AlGaInP-based light-emitting diode by using a tungsten barrier layer

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyun; Kang, Daesung; Park, Jae-Seong; Seong, Tae-Yeon

    2016-01-01

    We investigated how a tungsten diffusion barrier layer affected the electrical properties of AuBe/Au contacts to a p-GaP window layer (na = 5 × 1019 cm-3) for an AlGaInP-based light emitting diode. All of the as-deposited samples were ohmic. After annealing at 500 °C, the AuBe/Au contacts were electrically degraded with a specific contact resistivity of 1.0 × 10-4 Ωcm2. However, the electrical properties of the W-based contacts were improved, having a contact resistivity of 5.0 × 10-6 Ωcm2. The X-ray photoemission spectroscopy (XPS) results showed that the Ga 2 p core level for the annealed AuBe/Au contacts shifted to the high binding-energy side. On the other hand, that for the AuBe/W/Au contacts shifted toward the lower binding-energy side. For the AuBe/Au contacts, both Be and P atoms were shown to be outdiffused into the metal contact after annealing. However, for the AuBe/W/Au contacts, the outdiffusion of Be atoms was prevented by the W barrier layer, and the Be atoms were indiffused into GaP. Based on the X-ray photoemission spectroscopy (XPS), Auger electron spectroscopy (AES), and electrical results, the annealing-induced electrical degradation and improvement are described and discussed.

  6. Bi-layer channel structure-based oxide thin-film transistors consisting of ZnO and Al-doped ZnO with different Al compositions and stacking sequences

    NASA Astrophysics Data System (ADS)

    Cho, Sung Woon; Yun, Myeong Gu; Ahn, Cheol Hyoun; Kim, So Hee; Cho, Hyung Koun

    2015-03-01

    Zinc oxide (ZnO)-based bi-layers, consisting of ZnO and Al-doped ZnO (AZO) layers grown by atomic layer deposition, were utilized as the channels of oxide thin-film transistors (TFTs). Thin AZO layers (5 nm) with different Al compositions (5 and 14 at. %) were deposited on top of and beneath the ZnO layers in a bi-layer channel structure. All of the bi-layer channel TFTs that included the AZO layers showed enhanced stability (Δ V Th ≤ 3.2 V) under a positive bias stress compared to the ZnO single-layer channel TFT (Δ V Th = 4.0 V). However, the AZO/ZnO bi-layer channel TFTs with an AZO interlayer between the gate dielectric and the ZnO showed a degraded field effect mobility (0.3 cm2/V·s for 5 at. % and 1.8 cm2/V·s for 14 at. %) compared to the ZnO single-layer channel TFT (5.5 cm2/V·s) due to increased scattering caused by Al-related impurities near the gate dielectric/channel interface. In contrast, the ZnO/AZO bi-layer channel TFTs with an AZO layer on top of the ZnO layer exhibited an improved field effect mobility (7.8 cm2/V·s for 14 at. %) and better stability. [Figure not available: see fulltext.

  7. @AuAg nanostructures

    NASA Astrophysics Data System (ADS)

    Singh, Rina; Soni, R. K.

    2014-09-01

    Bimetallic and trimetallic nanoparticles have attracted significant attention in recent times due to their enhanced electrochemical and catalytic properties compared to monometallic nanoparticles. The numerical calculations using Mie theory has been carried out for three-layered metal nanoshell dielectric-metal-metal (DMM) system consisting of a particle with a dielectric core (Al@Al2O3), a middle metal Ag (Au) layer and an outer metal Au (Ag) shell. The results have been interpreted using plasmon hybridization theory. We have also prepared Al@Al2O3@Ag@Au and Al@Al2O3@AgAu triple-layered core-shell or alloy nanostructure by two-step laser ablation method and compared with calculated results. The synthesis involves temporal separations of Al, Ag, and Au deposition for step-by-step formation of triple-layered core-shell structure. To form Al@Ag nanoparticles, we ablated silver for 40 min in aluminium nanoparticle colloidal solution. As aluminium oxidizes easily in water to form alumina, the resulting structure is core-shell Al@Al2O3. The Al@Al2O3 particle acts as a seed for the incoming energetic silver particles for multilayered Al@Al2O3@Ag nanoparticles is formed. The silver target was then replaced by gold target and ablation was carried out for different ablation time using different laser energy for generation of Al@Al2O3@Ag@Au core-shell or Al@Al2O3@AgAu alloy. The formation of core-shell and alloy nanostructure was confirmed by UV-visible spectroscopy. The absorption spectra show shift in plasmon resonance peak of silver to gold in the range 400-520 nm with increasing ablation time suggesting formation of Ag-Au alloy in the presence of alumina particles in the solution.

  8. Atomic structure and bonding of the interfacial bilayer between Au nanoparticles and epitaxially regrown MgAl{sub 2}O{sub 4} substrates

    SciTech Connect

    Zhu, Guo-zhen; Majdi, Tahereh; Preston, John S.; Shao, Yang; Bugnet, Matthieu; Botton, Gianluigi A.

    2014-12-08

    A unique metal/oxide interfacial bilayer formed between Au nanoparticles and MgAl{sub 2}O{sub 4} substrates following thermal treatment is reported. Associated with the formation of the bilayer was the onset of an abnormal epitaxial growth of the substrate under the nanoparticle. According to the redistribution of atoms and the changes of their electronic structure probed across the interface by a transmission electron microscopy, we suggest two possible atomic models of the interfacial bilayer.

  9. Plasma versus thermal annealing for the Au-catalyst growth of ZnO nanocones and nanowires on Al-doped ZnO buffer layers

    NASA Astrophysics Data System (ADS)

    Güell, Frank; Martínez-Alanis, Paulina R.; Roso, Sergio; Salas-Pérez, Carlos I.; García-Sánchez, Mario F.; Santana, Guillermo; Marel Monroy, B.

    2016-06-01

    We successfully synthesized ZnO nanocones and nanowires over polycrystalline Al-doped ZnO (AZO) buffer layers on fused silica substrates by a vapor-transport process using Au-catalyst thin films. Different Au film thicknesses were thermal or plasma annealed in order to analyze their influence on the ZnO nanostructure growth morphology. Striking differences have been observed. Thermal annealing generates a distribution of Au nanoclusters and plasma annealing induces a fragmentation of the Au thin films. While ZnO nanowires are found in the thermal-annealed samples, ZnO nanocones and nanowires have been obtained on the plasma-annealed samples. Enhancement of the preferred c-axis (0001) growth orientation was demonstrated by x-ray diffraction when the ZnO nanocones and nanowires have been grown over the AZO buffer layer. The transmittance spectra of the ZnO nanocones and nanowires show a gradual increase from 375 to 900 nm, and photoluminescence characterization pointed out high concentration of defects leading to observation of a broad emission band in the visible range from 420 to 800 nm. The maximum emission intensity peak position of the broad visible band is related to the thickness of the Au-catalyst for the thermal-annealed samples and to the plasma power for the plasma-annealed samples. Finally, we proposed a model for the plasma versus thermal annealing of the Au-catalyst for the growth of the ZnO nanocones and nanowires. These results are promising for renewable energy applications, in particular for its potential application in solar cells.

  10. Effect of the Molar Ratio of B2O3 to Bi2O3 in Al Paste with Bi2O3-B2O3-ZnO Glass on Screen Printed Contact Formation and Si Solar Cell Performance

    NASA Astrophysics Data System (ADS)

    Kim, Bit-Na; Kim, Hyeong Jun; Chang, Hyo Sik; Hong, Hyun Seon; Ryu, Sung-Soo; Lee, Heon

    2013-10-01

    In this study, eco-friendly Pb-free Bi2O3-B2O3-ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3 to B2O3 in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3 to B2O3 increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3 to B2O3 increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.

  11. Mechanochemical-thermal preparation and structural studies of mullite-type Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} solid solutions

    SciTech Connect

    Da Silva, K.L.; Sepelak, V.; Duevel, A.; Paesano, A.; Hahn, H.; Litterst, F.J.; Heitjans, P.; Becker, K.D.

    2011-05-15

    A series of Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} solid solutions (0{<=}x{<=}1), prepared by mechanochemical processing of Bi{sub 2}O{sub 3}/Ga{sub 2}O{sub 3}/Al{sub 2}O{sub 3} mixtures and subsequent annealing, was investigated by XRD, EDX, and {sup 27}Al MAS NMR. The structure of the Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} solid solutions is found to be orthorhombic, space group Pbam (No. 55). The lattice parameters of the Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} series increase linearly with increasing gallium content. Rietveld refinement of the XRD data as well as the analysis of the {sup 27}Al MAS NMR spectra show a preference of gallium cations for the tetrahedral sites in Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9}. As a consequence, this leads to a far from random distribution of Al and Ga cations across the whole series of solid solutions. -- Graphical Abstract: Mullite-type Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} mixed crystals (0{<=}x{<=}1) prepared by a combined mechanochemical-thermal route possess a non-random distribution of Ga{sup 3+} and Al{sup 3+} cations over the sites of tetrahedral (T) and octahedral [O] coordination, characterized by the preference of Ga{sup 3+} (Al{sup 3+}) for tetrahedral (octahedral) sites. Display Omitted Highlights: {yields} Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} (0{<=}x{<=}1) were synthesized via mechanochemical-thermal route. {yields} The lattice parameters of Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} increase linearly with gallium content. {yields} Quantitative information on the cation distribution in Bi{sub 2}(Ga{sub x}Al{sub 1-x}){sub 4}O{sub 9} is derived. {yields} Ga{sup 3+} and Al{sup 3+} show the preference for tetrahedral and octahedral sites, respectively.

  12. Synthesis, thermal and electrical properties of Al-doped Bi4V1.8Cu0.2O10.7

    NASA Astrophysics Data System (ADS)

    Essalim, R.; Ammar, A.; Tanouti, B.; Mauvy, F.

    2016-08-01

    Partial substitution of copper with aluminum in Bi4V1.8Cu0.2O10.7 has led to the Bi4V1.8Cu0.2-xAlxO10.7+x/2 solid solution. X-ray diffraction and thermal analysis have shown that the compounds with x=0.05 and x=0.10 are tetragonal with γ‧ form of Bi4V2O11, while the compound with x=0.15 is of β polymorph. The effect of Al3+ doping on electrical conductivity has been studied using Electrochemical Impedance Spectroscopy. The electrical conductivity of doped samples along with the amount of Al3+ has been studied by electrochemical impedance spectroscopy in the temperature range 250-700 °C. The slope changes observed in the Arrhenius plots agree with the microstructural transitions occurring in these compounds. The highest ionic conductivity values are obtained for the sample with x=0.05.

  13. Molecular beam epitaxy and characterization of thin Bi{sub 2}Se{sub 3} films on Al{sub 2}O{sub 3} (110)

    SciTech Connect

    Tabor, Phillip; Keenan, Cameron; Urazdhin, Sergei; Lederman, David

    2011-07-04

    The structural and electronic properties of thin Bi{sub 2}Se{sub 3} films grown on Al{sub 2}O{sub 3} (110) by molecular beam epitaxy are investigated. The epitaxial films grow in the Frank-van der Merwe mode and are c-axis oriented. They exhibit the highest crystallinity, the lowest carrier concentration, and optimal stoichiometry at a substrate temperature of 200 deg. C determined by the balance between surface kinetics and desorption of Se. The crystallinity of the films improves with increasing Se/Bi flux ratio. Our results enable studies of thin topological insulator films on inert, non-conducting substrates that allow optical access to both film surfaces.

  14. Enhancement of photoinduced electrical properties of Al-doped ZnO/BiFeO3 layered thin films prepared by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Katayama, Takeshi; Sakamoto, Wataru; Yuitoo, Isamu; Takeuchi, Teruaki; Hayashi, Koichiro; Yogo, Toshinobu

    2015-10-01

    Polycrystalline BiFeO3 and Al-doped ZnO/BiFeO3 bilayered thin films were prepared on Pt/TiOx/SiO2/Si substrates by chemical solution deposition. Their photoinduced electrical properties under blue light irradiation were characterized. The rapid on/off response of the photocurrent to light in unpoled BiFeO3 (BFO) and Al-doped ZnO/BiFeO3 (AZO/BFO) thin films was demonstrated. The AZO/BFO layered film exhibited an approximately triple-digit larger photocurrent in comparison with a BFO single-layer film. This is attributable to the photoexcited carrier generation effect at the interface between AZO (n-type) and BFO (p-type) films. Furthermore, in the AZO/BFO layered structure, the direction of the internal bias electric field caused by the space charge distribution in the unpoled BFO film is the same as that of the built-in electric field by forming a p-n junction of AZO and BFO layers. Photovoltaic properties were also improved by fabricating such a layered film. On the other hand, when the placement of BFO to AZO was reversed, the photoelectric current decreased to approximately one-tenth of that of the BFO single-layer film. In the BFO/AZO film, the internal electric field at the p-n junction between BFO and AZO is considered to have an orientation opposite to the self-bias field formed in the BFO film.

  15. Microstructure of Co/X (X=Cu,Ag,Au) epitaxial thin films grown on Al{sub 2}O{sub 3}(0001) substrates

    SciTech Connect

    Ohtake, Mitsuru; Akita, Yuta; Futamoto, Masaaki; Kirino, Fumiyoshi

    2007-05-01

    Epitaxial thin films of Co/X (X=Cu,Ag,Au) were prepared on Al{sub 2}O{sub 3}(0001) substrates at substrate temperatures of 100 and 300 degree sign C by UHV molecular beam epitaxy. A complicated microstructure was realized for the epitaxial thin films. In-situ reflection high-energy electron diffraction observation has shown that X atoms of the buffer layer segregated to the surface during Co layer deposition, and it yielded a unique epitaxial granular structure. The structure consists of small Co grains buried in the X buffer layer, where both the magnetic small Co grains and the nonmagnetic X layer are epitaxially grown on the single crystal substrate. The structure varied depending on the X element and the substrate temperature. The crystal structure of Co grains is influenced by the buffer layer material and determined to be hcp and fcc structures for the buffer layer materials of Au and Cu, respectively.

  16. Electroreduction of Peroxide on Au(100) Surface Modified with Underpotentially Deposited Bismuth

    NASA Astrophysics Data System (ADS)

    Hara, Masanori; Nagahara, Yoshiki; Yoshimoto, Soichiro; Inukai, Junji; Itaya, Kingo

    2004-10-01

    The adlayer structure of Bi underpotentially deposited on Au(100) was investigated in a HClO4 solution using in-situ scanning tunneling microscopy. The underpotential deposition of Bi was found to occur in three steps. The electrochemical reduction rate of H2O2 on the Bi-modified Au(100) surface was the highest for an intermediate coverage of Bi.

  17. XAFS study of a Au/Al 2O 3 catalytic nanosystem doped by Ce and Ce-Zr oxides

    NASA Astrophysics Data System (ADS)

    Kriventsov, V. V.; Simakova, I. L.; Simakov, A.; Smolentseva, E.; Castillon, F.; Estrada, M.; Vargas, E.; Yakimchuk, E. P.; Ivanov, D. P.; Aksenov, D. G.; Andreev, D. V.; Novgorodov, B. N.; Kochubey, D. I.; Fuentes, S.

    2009-05-01

    This work is devoted to a structural study of the finely dispersed nanosized gold species supported on nanosized mixed oxides prepared by the sol-gel method. An analysis of the XANES (Au-L 3) spectra has revealed mainly Au 3+ cations located on the oxide matrix surface in distorted octahedral coordination for the catalysts reduced at 150 °C. For the catalysts reduced at 300 °C, a highly distorted metallic gold species has been mainly found, within the method limitation. The synthesized catalysts have also been characterized by transmission electron microscopy (TEM), BET, X-ray diffraction (XRD) and XPS.

  18. Temperature-induced changes in optical properties of thin film TiO2-Al2O3 bi-layer structures grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Ali, Rizwan; Saleem, Muhammad Rizwan; Honkanen, Seppo

    2016-02-01

    We investigate the optical properties and corresponding temperature-induced changes in highly uniform thin amorphous films and their bi-layer stacks grown by Atomic Layer Deposition (ALD). The environmentally driven conditions such as temperature, humidity and pressure have a significant influence on optical properties of homogeneous and heterogeneous bi-layer stacked structures of TiO2-Al2O3 and subsequently affect the specific sensitive nature of optical signals from nano-optical devices. Owing to the super hydrophilic behavior and inhibited surface defects in the form of hydrogenated species, the thermo-optic coefficient (TOC) of ~ 100 nm thick ALD-TiO2 films vary significantly with temperature, which can be used for sensing applications. On the other hand, the TOC of ~ 100 nm thick ALD-Al2O3 amorphous films show a differing behavior with temperature. In this work, we report on reduction of surface defects in ALD-TiO2 films by depositing a number of ultra-thin ALD-Al2O3 films to act as impermeable barrier layers. The designed and fabricated heterostructures of ALD-TiO2/Al2O3 films with varying ALD-Al2O3 thicknesses are exploited to stabilize the central resonance peak of Resonant Waveguide Gratings (RWGs) in thermal environments. The temperature-dependent optical constants of ALD-TiO2/Al2O3 bi-layer films are measured by a variable angle spectroscopic ellipsometer (VASE), covering a wide spectral range 380 <= λ <= 1800 nm at a temperature range from 25 to 105 °C. The Cauchy model is used to design and retrieve refractive indices at these temperatures, measured with three angles of incidence (59°, 67°, and 75°). The optical constants of 100 nm thick ALD-TiO2 and various combinational thicknesses of ALD-Al2O3 films are used to predict TOCs using a polynomial fitting algorithm.

  19. Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

    NASA Astrophysics Data System (ADS)

    Othmani, Cherif; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

    2016-09-01

    The propagation of Rayleigh-Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh-Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

  20. Operation of ohmic Ti/Al/Pt/Au multilayer contacts to GaN at 600 °C in air

    SciTech Connect

    Hou, Minmin; Senesky, Debbie G.

    2014-08-25

    The high-temperature characteristics (at 600 °C) of Ti/Al/Pt/Au multilayer contacts to gallium nitride (GaN) in air are reported. Microfabricated circular-transfer-line-method test structures were subject to 10 h of thermal storage at 600 °C. Intermittent electrical characterization during thermal storage showed minimal variation in the contact resistance after 2 h and that the specific contact resistivity remained on the order of 10{sup −5} Ω-cm{sup 2}. In addition, the thermally stored multilayer contacts to GaN showed ohmic I-V characteristics when electrically probed at 600 °C. The microstructural analysis with atomic force microscopy showed minimal changes in surface roughness after thermal storage. Observations of the thermochemical reactions after thermal storage using Auger electron spectroscopy chemical depth profiling showed diffusion of Pt and minimal additional Al oxidation. The results support the use of Ti/Al/Pt/Au multilayer metallization for GaN-based sensors and electronic devices that will operate within a high-temperature and oxidizing ambient.

  1. Reversible transition between coherently strained BiFeO3 and the metastable pseudotetragonal phase on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001)

    NASA Astrophysics Data System (ADS)

    Fu, Z.; Yin, Z. G.; Zhang, X. W.; Chen, N. F.; Zhao, Y. J.; Bai, Y. M.; Zhao, D. Y.; Zhang, H. F.; Yuan, Y. D.; Chen, Y. N.; Wu, J. L.; You, J. B.

    2017-02-01

    Coherently strained BiFeO3 epitaxial films deposited on (001)-oriented (LaAlO3)0.3(Sr2AlTaO6)0.7 have a tetragonal crystal form, a stress-distorted version of the rhombohedral phase. A conversion from coherent BiFeO3 to a new, tilted pseudotetragonal phase with the c/a ratio exceeding 1.2 is observed beyond the critical thickness of 60 nm. X-ray reciprocal space maps display that this highly elongated metastable structure is monoclinically distorted by ˜0.2° and exhibits an out-of-plane tilt of ˜3°. These observations are at odds with traditional understandings that a coherent epilayer should turn into its parent structure upon increasing the thickness, providing a new insight into the strain relaxation mechanism of epitaxial films. We show that in the heating and cooling cycles, the transition between these two phases is completely reversible and is associated with the alleviation of thermal stress. Our results reveal that the coherent BiFeO3 epilayer with tetragonal symmetry stabilized by moderate compressive strain behaves as a structural bridge that links the thermally stable rhombohedral phase and the metastable tetragonal-like phase with a giant axial ratio. Moreover, the finding of a BiFeO3 phase mixture in our study extends the threshold in-plane strain of the stress-driven morphotropic phase boundary to a value as low as -2.3%.

  2. Enhancement in the excitonic spontaneous emission rates for Si nanocrystal multi-layers covered with thin films of Au, Ag, and Al

    NASA Astrophysics Data System (ADS)

    Estrin, Y.; Rich, D. H.; Rozenfeld, N.; Arad-Vosk, N.; Ron, A.; Sa'ar, A.

    2015-10-01

    The enhancement in the spontaneous emission rate (SER) for Ag, Au, and Al films on multilayer Si nanocrystals (SiNCs) was probed with time-resolved cathodoluminescence (CL). The SiNCs were grown on Si(100) using plasma enhanced chemical vapor deposition. Electron-hole pairs were generated in the metal-covered SiNCs by injecting a pulsed high-energy electron beam through the thin metal films, which is found to be an ideal method of excitation for plasmonic quantum heterostructures and nanostructures that are opaque to laser or light excitation. Spatially, spectrally, and temporally resolved CL was used to measure the excitonic lifetime of the SiNCs in metal-covered and bare regions of the same samples. The observed enhancement in the SER for the metal-covered SiNCs, relative to the SER for the bare sample, is attributed to a coupling of the SiNC excitons with surface plasmon polaritons (SPPs) of the thin metal films. A maximum SER enhancement of ˜2.0, 1.4 and 1.2 was observed for the Ag, Au, and Al films, respectively, at a temperature of 55 K. The three chosen plasmonic metals of Ag, Au, and Al facilitate an interesting comparison of the exciton-SPP coupling for metal films that exhibit varying differences between the surface plasmon energy, ωsp, and the SiNC excitonic emission energy. A modeling of the temperature dependence of the Purcell enhancement factor, Fp, was performed and included the temperature dependence of the dielectric properties of the metals.

  3. Structure and magnetic properties of the REAuBi{sub 2} (RE=La–Nd, Sm) phases

    SciTech Connect

    Seibel, Elizabeth M. Xie, Weiwei; Gibson, Quinn D.; Cava, R.J.

    2015-10-15

    We present the crystal structures and basic magnetic properties of the REAuBi{sub 2} (RE=La–Nd, Sm) compounds. This isostructural family crystallizes in the tetragonal P4/nmm (no. 129) HfCuSi{sub 2}-type, as determined by single crystal X-ray diffraction. Three distinct substructures are present: an RE layer, a tetrahedral AuBi layer, and a Bi square net layer. Electronic structure calculations indicate that these compounds display bands which cross the Fermi level, derived from both the Bi square net and the covalent AuBi layer. The small size of LaAuBi{sub 2} crystals precluded detailed physical property measurements, whereas large single crystals could be grown for all other phases investigated here. Single crystal measurements of CeAuBi{sub 2}, PrAuBi{sub 2}, and NdAuBi{sub 2} show overall antiferromagnetic ordering and decreasing magnetic anisotropy with decreasing rare earth size. SmAuBi{sub 2} also shows signatures of magnetic ordering. - Graphical abstract: The crystal structures and basic electronic and magnetic properties of the five REAuBi{sub 2} (RE=La–Nd, Sm) phases are presented. These tetragonal structures have alternating layers of AuBi{sub 4} tetrahedra and a Bi square net balanced by RE cations. Measurements performed on single crystals show strong magnetic anisotropy for CeAuBi{sub 2} and PrAuBi{sub 2} and weak anisotropy for NdAuBi{sub 2}. SmAuBi{sub 2} is weakly magnetic. - Highlights: • We present the structures and basic properties of single crystals of the new, tetragonal REAuBi{sub 2} (RE=La–Nd, Sm) phases. • CeAuBi{sub 2}, PrAuBi{sub 2}, NdAuBi{sub 2}, and SmAuBi{sub 2} order magnetically. • CeAuBi{sub 2} and PrAuBi{sub 2} display magnetic anisotropy. • CeAuBi{sub 2} appears analogous to CeAuSb{sub 2} and may be worthy of further study as a potential system for quantum criticality.

  4. He and Au ion radiation damage in sodalite, Na4Al3Si3O12Cl

    NASA Astrophysics Data System (ADS)

    Vance, Eric R.; Gregg, Daniel J.; Karatchevtseva, Inna; Davis, Joel; Ionescu, Mihail

    2014-10-01

    Sodalite, a candidate ceramic for the immobilisation of pyroprocessing nuclear waste, showed no observable lattice dilatation in grazing incidence X-ray diffraction when irradiated with up to 1017 5 MeV He ions/cm2. However micro-Raman scattering showed considerable spectral broadening characteristic of radiation damage near the end of the ∼22 μm He range. Partial amorphism plus nepheline formation was observed in grazing incidence X-ray diffraction when sodalite was irradiated by 1016 12 MeV Au ions/cm2. Nepheline appeared less susceptible to 12 MeV Au ion damage than sodalite, with ∼25% less amorphous fraction at 1016 ions/cm2.

  5. Photoresponse and photocapacitor properties of Au/AZO/p-Si/Al diode with AZO film prepared by pulsed laser deposition (PLD) method

    NASA Astrophysics Data System (ADS)

    Alyamani, A.; Tataroğlu, A.; El Mir, L.; Al-Ghamdi, Ahmed A.; Dahman, H.; Farooq, W. A.; Yakuphanoğlu, F.

    2016-04-01

    The electrical and photoresponse properties of Au/nanostructure AZO/p-Si/Al diode were investigated. Al-doped ZnO (AZO) thin films were deposited via pulsed laser deposition method on silicon substrate. Structural properties of the films were performed by using transmission electron microscopy and X-ray powder diffraction (XRD). The XRD patterns showed that the AZO films are polycrystalline with hexagonal wurtzite structure preferentially oriented in (002) direction. Electrical and photoresponse properties of the diode were analyzed under in a wide range of frequencies and illumination intensities. It is observed that the reverse current of the diode increases with increasing illumination intensity. This result confirms that the diode exhibits both photoconducting and photovoltaic behavior. Also, the transient photocurrent, photocapacitance and photoconductance measured as a function of time highly depend on transient illumination. In addition, the frequency dependence of capacitance and conductance is attributed to the presence of interface states.

  6. Wetting and spontaneous infiltration: the case study of TaC/(Au, Al and Cu) compared to TiC/Cu

    NASA Astrophysics Data System (ADS)

    Aizenshtein, M.; Froumin, N.; Nafman, O.; Frage, N.

    2016-06-01

    Spontaneous infiltration of molten metals in to ceramic skeletons, in the course MMCs' production, is related to improved wetting of the ceramic by metals. TiC is considered a "metal-like" carbide and is supposed to be wetted well by metals through metallic bonding mechanism. Nevertheless, TiC/Cu exhibit an unusual behavior since spontaneous infiltration of molten Cu takes place, while TiC is partially wetted by Cu (θ=90°).In this work we studied the relation between wetting and spontaneous infiltration in the TaC/Au, Al and Cu systems. TaC is also considered a "metal-like" carbide and indeed no chemical interaction was observed at the interfaces of the studied systems.Sessile drop experiments showed almost perfect wetting in the three system but spontaneous infiltration occurred only in the first two (e.g. TaC/Au or Al). Thermodynamic calculation shows the difference between the systems which also has its' influence on the mechanical properties of the MMCs'. Further calculation clarifies the difference between TaC/Cu and TiC/Cu infiltration behavior, but is unable to explain the wetting results differences.Correlation between wetting and spontaneous infiltration in some cases is not straight forward and more studies and calculations on the atomistic level should be done in order to clarify this matter.

  7. Formation of multinary intermetallics from reduction of perovskites by aluminum flux: M(3)Au(6+)(x)()Al(26)Ti (M = Ca, Sr, Yb), a stuffed variant of the BaHg(11) type.

    PubMed

    Latturner, Susan E; Kanatzidis, Mercouri G

    2004-01-12

    New intermetallic phases were synthesized by reacting oxidic perovskites and gold metal in aluminum flux. The combination of MTiO(3) (M = Ca, Sr, Ba) and Au metal in excess molten aluminum produces quaternary compounds M(3)Au(6+)(x)()Al(26)Ti with a stuffed BaHg(11) structure type. An analogue with M = Yb was also synthesized; it shows mixed valent behavior.

  8. UV sensing using film bulk acoustic resonators based on Au/n-ZnO/piezoelectric-ZnO/Al structure

    PubMed Central

    Bian, Xiaolei; Jin, Hao; Wang, Xiaozhi; Dong, Shurong; Chen, Guohao; Luo, J. K.; Deen, M. Jamal; Qi, Bensheng

    2015-01-01

    A new type of ultraviolet (UV) light sensor based on film bulk acoustic wave resonator (FBAR) is proposed. The new sensor uses gold and a thin n-type ZnO layer deposited on the top of piezoelectric layer of FBAR to form a Schottky barrier. The Schottky barrier's capacitance can be changed with UV light, resulting in an enhanced shift in the entire FBAR's resonant frequency. The fabricated UV sensor has a 50 nm thick n-ZnO semiconductor layer with a carrier concentration of ~ 1017 cm−3. A large frequency downshift is observed when UV light irradiates the FBAR. With 365 nm UV light of intensity 1.7 mW/cm2, the FBAR with n-ZnO/Au Schottky diode has 250 kHz frequency downshift, much larger than the 60 kHz frequency downshift in a conventional FBAR without the n-ZnO layer. The shift in the new FBAR's resonant frequency is due to the junction formed between Au and n-ZnO semiconductor and its properties changes with UV light. The experimental results are in agreement with the theoretical analysis using an equivalent circuit model of the new FBAR structure. PMID:25773146

  9. Na-Au intermetallic compounds formed under high pressure at room temperature

    NASA Astrophysics Data System (ADS)

    Takemura, K.; Fujihisa, H.

    2011-07-01

    High-pressure powder x-ray diffraction experiments have revealed that sodium and gold react at room temperature and form Na-Au intermetallic compounds under high pressure. We have identified four intermetallic phases up to 60 GPa. The first phase (phase I) is the known Na2Au with the tetragonal CuAl2-type structure. It changed to the second phase (phase II) at ˜0.8 GPa, which has the composition Na3Au with the trigonal Cu3As-type or hexagonal Cu3P-type structure. Phase II further transformed to phase III at 3.6 GPa. Phase III has the same composition, Na3Au, with the cubic BiF3-type structure. Finally, phase III changed to phase IV at ˜54 GPa. Phase IV gives broad diffraction peaks, indicating large structural disorder.

  10. Photoluminescence properties of Y0.75-xGdxAl0.10BO3:Eu3+0.10, 0.05R3+ (R = Sc, Bi) (0.00 <= x <= 0.45)

    NASA Astrophysics Data System (ADS)

    Li, Jie; Wang, Yu-Hua; Dong, Qi-Zheng; Liu, Ji-Di

    2010-06-01

    Y0.75-xGdxAl0.10BO3:Eu3+0.10, 0.05R3+ (R = Sc, Bi) (0.00 <= x <= 0.45) powder samples are prepared by solid-state reaction and their luminescence properties are investigated. With the replacement of Y3+ ions by Sc3+ (or Bi3+) and Gd3+ ions in (Y,Al)BO3:Eu, the intensities of emission at 254 and 147 nm are remarkably improved, because Sc3+ ions can absorb UV light and transfer the energy to Eu3+ ions efficiently. Moreover, Gd3+ and Bi3+ ions act as an intermediate “bridge" between the sensitizer and the activator (Eu3+) in energy transfer to produce light in the (Y, Gd)BO3:Bi3+, Eu3+ system more effectively. After doping an appropriate concentration of Gd3+ into Y0.50Gd0.25Al0.10BO3:Eu3+0.01, Bi3+0.05, the emission intensity reaches its maximum, which is nearly 110% compared with the red commercial phosphor (Y,Gd)BO3:Eu and better chromaticity coordinates (0.650, 0.350) are obtained.

  11. Determination of the complex refractivity of Au, Cu and Al in terahertz and far-infrared regions from reflection spectra measurements

    NASA Astrophysics Data System (ADS)

    Mou, Yuan; Wu, Zhen-sen; Gao, Yan-qing; Yang, Zhi-qiang; Yang, Qiu-jie; Zhang, Geng

    2017-01-01

    A scheme to determine the complex refractivity of gold (Au), Copper (Cu) and Aluminum (Al) from measurements of ellipsometer and spectrometer are proposed in this paper. The reflection spectra of the metals from 4 THz to 40 THz are measured with spectrometer. The determined refractivity by Kramers-Kronig (KK) algorithm coincides with the measured results from ellipsometer in far infrared region. Drude model is invited to make the wing correction on the terahertz reflection spectra, which helps to eliminate the effects of the noises from spectrometer on KK algorithm. The calculated refractive indexes from measured spectra in terahertz region are in consistent with those from corrected reflection spectra. The advantage of the scheme is to obtain terahertz dispersion properties based on limited information in infrared region.

  12. Temperature dependent forward current-voltage characteristics of Ni/Au Schottky contacts on AlGaN/GaN heterostructures described by a two diodes model

    NASA Astrophysics Data System (ADS)

    Greco, Giuseppe; Giannazzo, Filippo; Roccaforte, Fabrizio

    2017-01-01

    This paper reports on the temperature dependence of Ni/Au Schottky contacts on AlGaN/GaN heterostructures. The electrical properties of the Schottky barrier were monitored by means of forward current-voltage (I-V) measurements, while capacitance-voltage measurements were used to determine the properties of the two dimensional electron gas. The forward I-V characteristics of Schottky diodes revealed a strong deviation from the ideal behavior, which could not be explained by a standard thermionic emission model. Thus, the Ni/AlGaN/GaN system has been described by a "two diode model," considering the presence of a second barrier height at the AlGaN/GaN heterojunction. Following this approach, the anomalous I-V curves could be explained and the value of the flat-band barrier height (at zero-electric field) could be correctly determined, thus resulting in good agreement with literature data based on photoemission measurements.

  13. Origin of REE mineralization in the Bastnäs-type Fe-REE-(Cu-Mo-Bi-Au) deposits, Bergslagen, Sweden

    NASA Astrophysics Data System (ADS)

    Holtstam, Dan; Andersson, Ulf B.; Broman, Curt; Mansfeld, Joakim

    2014-12-01

    The Bastnäs-type deposits, with mineral assemblages of Fe oxides, Ca-Mg silicates, rare earth element (REE) silicates, REE fluorocarbonates, and Cu-Fe-Mo-Bi sulfides, are associated with marble horizons in a strongly Na, K, and/or Mg altered, metavolcanic succession, over a distance of at least 80 km in a SW-NE trending zone in western Bergslagen. Two subtypes occur: (1) enriched (relative to the other type) in light REE (LREE) and Fe, exemplified by the Bastnäs and Rödbergsgruvan deposits, and (2) enriched in heavy REE (HREE), Y, Mg, Ca, and F, represented by deposits in the Norberg district. Bastnäsite hosts primary fluid H2O-CO2 inclusions with salinities of 6-29 eq. wt% CaCl2 and with total homogenization temperatures ( Th tot) of ca. 300-400 °C. Subtype 2 has late-stage fluorite with fluid inclusions that show 1-16 eq. wt% NaCl and Th tot of ca. 90-150 °C. Molybdenite Re-Os ages obtained from three deposits are 1,904 ± 6, 1,863 ± 4, and 1,842 ± 4 Ma. Nd isotopic data from five different REE minerals yielded no defined isochron, but a range in ɛNd (1.88 Ga) of +0.2 to +1.6. The oxygen isotope values (δ18OSMOW) of dolomite and calcite from the associated REE-mineralized skarn and recrystallized carbonate assemblages lie in the range 6.1-8.6 ‰, overlapping with those of the host marbles. Carbon isotope values (δ13CPDB) show typical magmatic signatures of -6.7 to -4.4 ‰, while the host marbles group around ca. -2.4 ‰. The sulfur isotope (δ34SCDT) values of associated sulfides range between -10.8 and +0.2 ‰. The combined evidence suggests REE mineralization, beginning at 1.9 Ga, from mainly Svecofennian, juvenile magmatic (>400 °C) fluids carrying Si, F, Cl, S, CO2, and the REE in addition to other metals; mineralization occurred through reactions with dolomitic layers in the supracrustal units coevally with regional metasomatic alteration associated with fluid circulation through an extensive active volcano-plutonic complex.

  14. Plasma-assisted atomic layer deposition of Al2O3 and parylene C bi-layer encapsulation for chronic implantable electronics

    NASA Astrophysics Data System (ADS)

    Xie, Xianzong; Rieth, Loren; Merugu, Srinivas; Tathireddy, Prashant; Solzbacher, Florian

    2012-08-01

    Encapsulation of biomedical implants with complex three dimensional geometries is one of the greatest challenges achieving long-term functionality and stability. This report presents an encapsulation scheme that combines Al2O3 by atomic layer deposition with parylene C for implantable electronic systems. The Al2O3-parylene C bi-layer was used to encapsulate interdigitated electrodes, which were tested invitro by soak testing in phosphate buffered saline solution at body temperature (37 °C) and elevated temperatures (57 °C and 67 °C) for accelerated lifetime testing up to 5 months. Leakage current and electrochemical impedance spectroscopy were measured for evaluating the integrity and insulation performance of the coating. Leakage current was stably about 15 pA at 5 V dc, and impedance was constantly about 3.5 MΩ at 1 kHz by using electrochemical impedance spectroscopy for samples under 67 °C about 5 months (approximately equivalent to 40 months at 37 °C). Alumina and parylene coating lasted at least 3 times longer than parylene coated samples tested at 80 °C. The excellent insulation performance of the encapsulation shows its potential usefulness for chronic implants.

  15. Analyses of temperature-dependent interface states, series resistances, and AC electrical conductivities of Al/p—Si and Al/Bi4Ti3O12/p—Si structures by using the admittance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Mert, Yıldırım; Perihan, Durmuş; Şemsettin, Altındal

    2013-10-01

    In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interface states (Nss), the values of series resistance (Rs), and AC electrical conductivity (σac) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance—voltage (C—V) and conductance—voltage (G—V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of Nss and Rs are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that Nss and Rs, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of Nss and the reordering and restructuring of Nss under the effect of temperature. The values of activation energy (Ea), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the Ea of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal—semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (NA), built-in potential (Vbi), Fermi energy (EF), image force barrier lowering (Δ Φb), and barrier height (Φb), are extracted using reverse bias C-2—V characteristics as a function of temperature.

  16. Proton-helium correlation in 94 MeV/nucleon sup 16 O-induced reactions on Al, Ni, and Au targets

    SciTech Connect

    Badala, A.; Barbera, R.; Palmeri, A.; Pappalardo, G.S. ); Riggi, F. ); Bizard, G.; Durand, D.; Laville, J.L. )

    1992-04-01

    Azimuthal distributions of helium ions have been measured in coincidence with high-energy protons in reactions induced by {sup 16}O at 94 MeV/nucleon on {sup 27}Al, {sup 58}Ni, and {sup 197}Au. Helium ions have been detected in a large area multidetector. Protons have been observed at 90{degree}. Mean multiplicities of light charged particles (H and He) are found slightly dependent on the target mass. Strong azimuthal asymmetries whose intensity is larger for the Al target and vanishes with the increasing of the target mass are observed in the He distributions. Experimental data are discussed in the framework of the participant-spectator picture of a modified fireball model, taking into account intermediate energy corrections. In this framework the behavior of the azimuthal asymmetries, as a function of the target mass, indicates a strong final-state interaction between participant and spectator fragments. Such a result is found in agreement with interaction time predictions of a microscopical calculation based on the Boltzmann-Nordheim-Vlasov equation.

  17. The behavior of the I-V-T characteristics of inhomogeneous (Ni /Au)-Al0.3Ga0.7N/AlN/GaN heterostructures at high temperatures

    NASA Astrophysics Data System (ADS)

    Tekeli, Z.; Altındal, Ş.; ćakmak, M.; Özçelik, S.; ćalışkan, D.; Özbay, E.

    2007-09-01

    We investigated the behavior of the forward bias current-voltage-temperature (I-V-T) characteristics of inhomogeneous (Ni/Au)-Al0.3Ga0.7N/AlN/GaN heterostructures in the temperature range of 295-415K. The experimental results show that all forward bias semilogarithmic I-V curves for the different temperatures have a nearly common cross point at a certain bias voltage, even with finite series resistance. At this cross point, the sample current is temperature independent. We also found that the values of series resistance (Rs) that were obtained from Cheung's method are strongly dependent on temperature and the values abnormally increased with increasing temperature. Moreover, the ideality factor (n ), zero-bias barrier height (ΦB0) obtained from I-V curves, and Rs were found to be strongly temperature dependent and while ΦB0 increases, n decreases with increasing temperature. Such behavior of ΦB0 and n is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution (GD) of the barrier heights (BHs) at the metal/semiconductor interface. We attempted to draw a ΦB0 versus q /2kT plot in order to obtain evidence of the GD of BHs, and the values of Φ¯B0=1.63eV and σ0=0.217V for the mean barrier height and standard deviation at a zero bias, respectively, were obtained from this plot. Therefore, a modified ln(I0/T2)-q2σ02/2(kT)2 versus q /kT plot gives ΦB0 and Richardson constant A* as 1.64eV and 34.25A/cm2K2, respectively, without using the temperature coefficient of the barrier height. The Richardson constant value of 34.25A/cm2K2 is very close to the theoretical value of 33.74A/cm2K2 for undoped Al0,3Ga0,7N. Therefore, it has been concluded that the temperature dependence of the forward I-V characteristics of the (Ni /Au)-Al0.3Ga0.7/AlN/GaN heterostructures can be successfully explained based on the thermionic emission mechanism with the GD of BHs.

  18. Chromium substitution in mullite type bismuth aluminate: Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with 0≤x≤2.0

    SciTech Connect

    Debnath, Tapas; Ullah, Ahamed; Rüscher, Claus H.; Hussain, Altaf

    2014-12-15

    Nominal compositions Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with 0.0≤x≤2.0 (Δx=0.2) were prepared using appropriate amounts of nitrates dissolved in glycerine and heated at 800 °C for 24 h as we previously used for the preparation of solid solution series Bi{sub 2}M{sub x}/M′{sub 4−x}O{sub 9} (M/M′=Fe/Al, Ga/Al and Fe/Ga). The samples were characterized using XRD, FTIR and optical microscopic techniques. Analyses of XRD data show mullite type single phase can be prepared up to x=1.2. The lattice parameters (a, b and c) increases with increasing Cr content. Further increase in x (i.e., x≥1.4) show the presence of some additional phases indicating a limiting value for Cr doping is in the range of 1.2≤x<1.4. The effect of Cr incorporation could also be observed in the infrared absorption spectra via systematic hard mode shifts of certain lattice modes, e.g. the Bi–O related vibration changes from 96 cm{sup −1} to 93 cm{sup −1} with increasing x up to 1.2 and certain intensity changes together with shift in peak positions. Interestingly, the absence of any splitting and shift of the high energy IR absorption peak at 821 cm{sup −1} as assigned to the characteristic tetrahedral type dimer, Al{sub 2}O{sub 7}, indicate that the Cr thus partially substitutes only the octahedrally coordinated Al. This is confirmed by Rietveld structure refinements, too. - Graphical abstract: Structural model of Cr doped bismuth aluminate, Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9}. - Highlights: • Chromium doped bismuth aluminate, Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with mullite type structure are synthesized. • The samples are characterized by XRD and FTIR techniques. • Cr can replace only certain amount of octahedrally coordinated Al in Bi{sub 2}Al{sub 4}O{sub 9} under present experimental conditions.

  19. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  20. Texture Evaluation of a Bi-Modal Structure During Static Recrystallization of Hot-Deformed Mg-Al-Sn Alloy

    NASA Astrophysics Data System (ADS)

    Kabir, Abu Syed Humaun; Su, Jing; Yue, Stephen

    2016-12-01

    In this study, Mg-Al-Sn alloy was hot compressed at 523 K (250 °C) and annealed at 623 K (350 °C) for various times. The initial as-deformed microstructure was partially dynamic recrystallized with strain-induced precipitates on the recrystallized grain boundaries. After annealing at 623 K (350 °C), static recrystallization (SRX) of the bimodal microstructure took place where, at this temperature, no static precipitates formed. The goal of this work was to study the effect of dynamic precipitation on the texture evolution during the SRX process. Progressive texture evolution was studied during annealing by electron backscattered diffraction technique through a microstructure-tracking process. It was found that the grain-coarsening mechanism during the early stage of annealing is not totally controlled by the basal-oriented grains. Also, it was found that the dynamic precipitates may have significant influence in the early texture weakening during annealing of a bimodal structure.

  1. Thickness-dependent optical properties in compressively strained BiFeO{sub 3}/LaAlO{sub 3} films grown by pulsed laser deposition

    SciTech Connect

    Duan, Zhihua; Jiang, Kai; Wu, Jiada; Sun, Jian; Hu, Zhigao; Chu, Junhao

    2014-03-01

    Graphical abstract: - Highlights: • BFO with various thicknesses was grown on LAO substrates by pulsed laser deposition. • The structure and compressive strains were clarified via Raman scattering. • The charge transfer excitation was blue shifted with increasing compressive strain. • The compressive strain affects the distortion of Fe{sup 3+} local environment and O 2p states. - Abstract: Bismuth ferrite (BiFeO{sub 3}) films with various thicknesses were epitaxially grown on LaAlO{sub 3} substrates by pulsed laser deposition. The X-ray diffraction and Raman scattering spectra reveal that the films were highly (11{sup ¯}1) oriented with the single phase. With increasing the thickness, the compressive strain decreases and the strain ratios between the film and bulk crystal are evaluated to be 1.75, 1.57, and 1. Moreover, the compressive strain induces band gap shrinkage from 2.7 to 2.65 eV, while the charge transfer transition energy increases from 3.5 to 4.1 eV. It could be due to the shift of O 2p states and the variation of local Fe{sup 3+} crystal field.

  2. Structural and electronic properties of AB- and AA-stacking bilayer-graphene intercalated by Li, Na, Ca, B, Al, Si, Ge, Ag, and Au atoms

    NASA Astrophysics Data System (ADS)

    Tayran, Ceren; Aydin, Sezgin; Çakmak, Mehmet; Ellialtıoğlu, Şinasi

    2016-04-01

    The structural and electronic properties of X (=Li, Na, Ca, B, Al, Si, Ge, Ag, and Au)-intercalated AB- and AA-stacking bilayer-graphene have been investigated by using ab initio density functional theory. It is shown that Boron (Lithium)-intercalated system is energetically more stable than the others for the AB (AA) stacking bilayer-graphene systems. The structural parameters, electronic band structures, and orbital nature of actual interactions are studied for the relaxed stable geometries. It is seen that the higher the binding energy, the smaller is the distance between the layers, in these systems. The electronic band structures for these systems show that different intercalated atoms can change the properties of bilayer-graphene differently. For qualitative description of the electronic properties, the metallicities of the systems are also calculated and compared with each other. The Mulliken analysis and electron density maps clearly indicate that the interactions inside a single layer (intralayer interactions) are strong and highly covalent, while the interactions between the two layers (interlayer interactions) are much weaker.

  3. Study of the A(e,e'$\\pi^+$) Reaction on $^1$H, $^2$H, $^{12}$C, $^{27}$Al, $^{63}$Cu and $^{197}$Au

    SciTech Connect

    Qian, X; Clasie, B; Arrington, J; Asaturyan, R; Benmokhtar, F; Boeglin, W; Bosted, P; Bruell, A; Christy, M E; Chudakov, E; Dalton, M M; Daniel, A; Day, D; Dutta, D; El Fassi, L; Ent, R; Fenker, H C; Ferrer, J; Fomin, N; Gao, H; Garrow, K; Gaskell, D; Gray, C; Huber, G M; Jones, M K; Kalantarians, N; Keppel, C E; Kramer, K; Li, Y; Liang, Y; Lung, A F; Malace, S; Markowitz, P; Matsumura, A; Meekins, D G; Mertens, T; Miyoshi, T; Mkrtchyan, H; Monson, R; Navasardyan, T; Niculescu, G; Niculescu, I; Okayasu, Y; Opper, A K; Perdrisat, C; Punjabi, V; Rauf, A W; Rodriquez, V M; Rohe, D; Seely, J; Segbefia, E; Smith, G R; Sumihama, M; Tadevosyan, V; Tang, L; Villano, A; Vulcan, W F; Wesselmann, F R; Wood, S A; Yuan, L; Zheng, X

    2010-05-01

    Cross sections for the p($e,e'\\pi^{+}$)n process on $^1$H, $^2$H, $^{12}$C, $^{27}$Al, $^{63}$Cu and $^{197}$Au targets were measured at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in order to extract the nuclear transparencies. Data were taken for four-momentum transfers ranging from $Q^2$=1.1 to 4.8 GeV$^2$ for a fixed center of mass energy of $W$=2.14 GeV. The ratio of $\\sigma_L$ and $\\sigma_T$ was extracted from the measured cross sections for $^1$H, $^2$H, $^{12}$C and $^{63}$Cu targets at $Q^2$ = 2.15 and 4.0 GeV$^2$ allowing for additional studies of the reaction mechanism. The experimental setup and the analysis of the data are described in detail including systematic studies needed to obtain the results. The results for the nuclear transparency and the differential cross sections as a function of the pion momentum at the different values of $Q^2$ are presented. Global features of the data are discussed and the data are compared with the results of model calculations for the p($e,e'\\pi^{+}$)n reaction from nuclear targets.

  4. Thermal expansion of mullite-type Bi{sub 2}Al{sub 4}O{sub 9}: A study by X-ray diffraction, vibrational spectroscopy and density functional theory

    SciTech Connect

    Mangir Murshed, M.; Mendive, Cecilia B.; Curti, Mariano; Šehović, Malik; Friedrich, Alexandra; Fischer, Michael; Gesing, Thorsten M.

    2015-09-15

    Polycrystalline Bi{sub 2}Al{sub 4}O{sub 9} powder samples were synthesized using the glycerine method. Single crystals were produced from the powder product in a Bi{sub 2}O{sub 3} melt. The lattice thermal expansion of the mullite-type compound was studied using X-ray diffraction, Raman spectroscopy and density functional theory (DFT). The metric parameters were modeled using Grüneisen approximation for the zero pressure equation of state, where the temperature-dependent vibrational internal energy was calculated from the Debye characteristic frequency. Both the first-order and second-order Grüneisen approximations were applied for modeling the volumetric expansion, and the second-order approach provided physically meaningful axial parameters. The phonon density of states as well as phonon dispersion guided to set the characteristic frequency for simulation. The experimental infrared and Raman phonon bands were compared with those calculate from the DFT calculations. Selective Raman modes were analyzed for the thermal anharmonic behaviors using simplified Klemens model. The respective mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. - Graphical abstract: Crystal structure of mullite-type Bi{sub 2}Al{sub 4}O{sub 9} showing the edge-sharing AlO{sub 6} octahedra running parallel to the c-axis. - Highlights: • Thermal expansion of Bi{sub 2}Al{sub 4}O{sub 9} was studied using XRD, FTIR, Raman and DFT. • Metric parameters were modeled using Grüneisen approximation. • Phonon DOS and phonon dispersion helped to set the Debye frequency. • Mode Grüneisen parameters were calculated from the pressure-dependent Raman spectra. • Anharmonicity was analyzed for some selective Raman modes.

  5. Elution behavior of metal ions with mixed glycine-nitric acid eluents in Dowex 50W-X8 column: separation of Th(IV), Ce(IV), Bi(III), Fe(III), and Al(III)

    SciTech Connect

    Eusebius, L.; Ghose, A.; Dey, A.

    1982-01-01

    Distribution coefficients (K) determined by the batch technique in acidic glycine media using Dowex 50W-X8 cation exchanger (H/sup +/-form, 100-200 mesh size) revealed that this medium can effectively be employed to separate a number of tetravalent and trivalent metal ions from bivalent metal ions. In fixed glycine (0.40 M) and varying concentration of nitric acid (0.10 to 1.0 M), a number of mixtures containing two or three metal ions were resolved on columns using about 8 g of exchanger. In 0.40 M glycine-1.0 M HNO/sub 3/ medium, Th(IV)/Ce(IV) were separated from Al(III)/Fe(III)/Bi(III)/Co(II)/Ni(II)/Cu(II)/Zn(II)/Cd(II)/Hg(II)/Pb(II)/Ag(I) and also Al(III)/Bi(III) from a number of divalent metal ions. In 0.40 M glycine-0.50 M HNO/sub 3/ medium, the resolution of following ternary mixtures were also achieved: Th(IV)/Ce(IV)-Al(III)/Bi(III)-Fe(III)/Co(II)/Ni(II)/Cu(II)/Zn(II)/Cd(II)/Hg(II)/Pb(II)/Ag(I). Th(IV)/Al(III)/Fe(III)/Bi(III) were also separated from other divalent metal ions in 1.60 M glycine-0.50 M HNO/sub 3/ medium. The values of K, elution characteristics of metal ions, elution curves, and the results of the resolution of a number of mixtures of metal ions along with standard deviations are reported.

  6. High-quality, large-area MoSe2 and MoSe2/Bi2Se3 heterostructures on AlN(0001)/Si(111) substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xenogiannopoulou, E.; Tsipas, P.; Aretouli, K. E.; Tsoutsou, D.; Giamini, S. A.; Bazioti, C.; Dimitrakopulos, G. P.; Komninou, Ph.; Brems, S.; Huyghebaert, C.; Radu, I. P.; Dimoulas, A.

    2015-04-01

    Atomically-thin, inherently 2D semiconductors offer thickness scaling of nanoelectronic devices and excellent response to light for low-power versatile applications. Using small exfoliated flakes, advanced devices and integrated circuits have already been realized, showing great potential to impact nanoelectronics. Here, high-quality single-crystal MoSe2 is grown by molecular beam epitaxy on AlN(0001)/Si(111), showing the potential for scaling up growth to low-cost, large-area substrates for mass production. The MoSe2 layers are epitaxially aligned with the aluminum nitride (AlN) lattice, showing a uniform, smooth surface and interfaces with no reaction or intermixing, and with sufficiently high band offsets. High-quality single-layer MoSe2 is obtained, with a direct gap evidenced by angle-resolved photoemission spectroscopy and further confirmed by Raman and intense room temperature photoluminescence. The successful growth of high-quality MoSe2/Bi2Se3 multilayers on AlN shows promise for novel devices exploiting the non-trivial topological properties of Bi2Se3.Atomically-thin, inherently 2D semiconductors offer thickness scaling of nanoelectronic devices and excellent response to light for low-power versatile applications. Using small exfoliated flakes, advanced devices and integrated circuits have already been realized, showing great potential to impact nanoelectronics. Here, high-quality single-crystal MoSe2 is grown by molecular beam epitaxy on AlN(0001)/Si(111), showing the potential for scaling up growth to low-cost, large-area substrates for mass production. The MoSe2 layers are epitaxially aligned with the aluminum nitride (AlN) lattice, showing a uniform, smooth surface and interfaces with no reaction or intermixing, and with sufficiently high band offsets. High-quality single-layer MoSe2 is obtained, with a direct gap evidenced by angle-resolved photoemission spectroscopy and further confirmed by Raman and intense room temperature photoluminescence. The

  7. Al{sub 15}Ge{sub 4}Ni{sub 3}: A new intergrowth structure with Cu{sub 3}Au- and CaF{sub 2}-type building blocks

    SciTech Connect

    Reichmann, Thomas L.; Jandl, Isabella; Effenberger, Herta S.; Herzig, Peter; Richter, Klaus W.

    2015-05-15

    The new ternary compound Al{sub 15}Ge{sub 4}Ni{sub 3} (τ{sub 2} in the system Al–Ge–Ni) was synthesized in single crystalline form by a special annealing procedure from samples located in the three phase fields [L+Al+τ{sub 2}] and [L+Ge+τ{sub 2}]. The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} was determined by single-crystal X-ray diffraction. The compound crystallizes in a new structure type in space group I4-bar3m, Pearson Symbol cI88, cubic lattice parameter a=11.405(1) Å. Phase diagram investigations indicate stoichiometric composition without considerable homogeneity range; τ{sub 2} melts peritectically at T=444 °C. The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} shows a unique combination of simple Cu{sub 3}Au- and CaF{sub 2}-type building blocks: a three dimensional network of CaF{sub 2}-type units, formed by Ni and Al atoms, is interspaced by clusters (Al{sub 6}Ge{sub 8}) resembling unit cells of the Cu{sub 3}Au-type. Both structural motifs are connected by Al–Ge bonds. The ground state energy of the compound was obtained by DFT calculations and the densities of states were analyzed in detail. In addition, electron density maps were calculated in four different sections through the unit cell using the full potential linearized augmented plane-wave (FLAPW) method. The bonding situation in Al{sub 15}Ge{sub 4}Ni{sub 3} was discussed combining results from electronic calculations with the analysis of the coordination of atoms. - Graphical abstract: The new compound Al{sub 15}Ge{sub 4}Ni{sub 3} shows a unique combination of simple Cu{sub 3}Au- and CaF{sub 2}-type building blocks. - Highlights: • The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} (space group I4-bar3m) was determined. • It shows a unique combination of CaF{sub 2}- and Cu{sub 3}Au-type building blocks. • Electronic (DFT) calculations were performed to gain insight to chemical bonding.

  8. Contact interaction of the Bi12GeO20, Bi12SiO20, and Bi4Ge3O12 melts with noble metals

    NASA Astrophysics Data System (ADS)

    Denisov, V. M.; Podkopaev, O. I.; Denisova, L. T.; Kuchumova, O. V.; Istomin, S. A.; Pastukhov, E. A.

    2014-02-01

    The sessile drop method is used to study the contact interaction of Ag, Au, Pd, Pt, and Ir with the Bi2O3-GeO2 and Bi2O3-SiO2 melts. These melts spread over Ag and Pd and, in some cases, over Au and Pt at a rather high speed and form equilibrium contact angles on Ir.

  9. Correlation between CO surface coverage and selectivity/kinetics for the preferential CO oxidation over Pt/γ-Al 2O 3 and Au/α-Fe 2O 3: an in-situ DRIFTS study

    NASA Astrophysics Data System (ADS)

    Schubert, M. M.; Kahlich, M. J.; Gasteiger, H. A.; Behm, R. J.

    We present in-situ IR (DRIFTS) measurements on CO adsorption and preferential CO oxidation (PROX) in H 2-rich gas on Pt/γ-Al 2O 3 and Au/α-Fe 2O 3 catalysts at their envisaged operating temperatures of 200°C and 80°C, respectively, which in combination with kinetic data show that the underlying reason for the very different PROX reaction kinetics on these two catalysts is the difference in steady-state CO coverage. Whereas on the platinum catalyst this is always near saturation under reaction conditions, causing a negative reaction order (-0.4) and a pCO-independent selectivity, the amount of adsorbed CO on the gold particles (indicated by an IR band at ˜2110 cm -1) strongly depends on the CO partial pressure. From the position of the IR band of CO adsorbed on Au/α-Fe 2O 3, the steady-state coverages on the Au surface are shown to be significantly below saturation, with an upper limit of approximately θCO=0.2. Low reactant surface concentrations on Au explain the positive reaction order with respect to pCO (+0.55 at 80°C) as well as the observed decoupling of the CO and H 2 oxidation rates, which results in a loss of selectivity with decreasing pCO.

  10. R3Au(6+x)Al26T (R = Ca, Sr, Eu, Yb; T = early transition metal): a large family of compounds with a stuffed BaHg11 structure type grown from aluminum flux.

    PubMed

    Latturner, Susan E; Bilc, Daniel; Mahanti, S D; Kanatzidis, Mercouri G

    2009-02-16

    A collection of new quaternary intermetallic compounds with a cubic, stuffed BaHg(11) structure type has been synthesized by the combination of a divalent rare earth or alkaline earth metal R, an early transition metal T, and gold in an excess of molten aluminum. Structural characterization of these R(3)Au(6+x)Al(26)T compounds by powder and single crystal X-ray diffraction indicates that the unit cell varies with the radii of the early transition metal T and the rare earth/alkaline earth R as expected. The element T (where T = group 4, 5, 6, and 7 element) appears to be responsible for the stabilization of up to 43 different members of the R(3)Au(6+x)Al(26)T family of compounds. Varying amounts of disorder and trends in partial occupancies of the Au stuffed site--the site that is vacant in the parent compound BaHg(11)--are also indicated by the diffraction studies of this family of compounds. Magnetic susceptibility data reveals that the transition metal atoms in these materials do not possess local magnetic moments. For the magnetic rare earth containing materials, the europium compounds undergo a ferromagnetic transition at 10 K, and the ytterbium analogues show mixed valent behavior. Band structure calculations also support a mixed valent state for Yb in these compounds.

  11. Temperature dependence of exciton-surface plasmon polariton coupling in Ag, Au, and Al films on In{sub x}Ga{sub 1−x}N/GaN quantum wells studied with time-resolved cathodoluminescence

    SciTech Connect

    Estrin, Y.; Rich, D. H.; Keller, S.; DenBaars, S. P.

    2015-01-28

    The optical properties and coupling of excitons to surface plasmon polaritons (SPPs) in Ag, Au, and Al-coated In{sub x}Ga{sub 1−x}N/GaN multiple and single quantum wells (SQWs) were probed with time-resolved cathodoluminescence. Excitons were generated in the metal coated SQWs by injecting a pulsed high-energy electron beam through the thin metal films. The Purcell enhancement factor (F{sub p}) was obtained by direct measurement of changes in the temperature-dependent radiative lifetime caused by the SQW exciton-SPP coupling. Three chosen plasmonic metals of Al, Ag, and Au facilitate an interesting comparison of the exciton-SPP coupling for energy ranges in which the SP energy is greater than, approximately equal to, and less than the excitonic transition energy for the InGaN/GaN QW emitter. A modeling of the temperature dependence of the Purcell enhancement factor, F{sub p}, included the effects of ohmic losses of the metals and changes in the dielectric properties due to the temperature dependence of (i) the intraband behavior in the Drude model and (ii) the interband critical point transition energies which involve the d-bands of Au and Ag. We show that an inclusion of both intraband and interband effects is essential when calculating the ω vs k SPP dispersion relation, plasmon density of states (DOS), and the dependence of F{sub p} on frequency and temperature. Moreover, the “back bending” in the SPP dispersion relation when including ohmic losses can cause a finite DOS above ω{sub sp} and lead to a measurable F{sub p} in a limited energy range above ω{sub sp}, which can potentially be exploited in plasmonic devices utilizing Ag and Au.

  12. High-quality, large-area MoSe2 and MoSe2/Bi2Se3 heterostructures on AlN(0001)/Si(111) substrates by molecular beam epitaxy.

    PubMed

    Xenogiannopoulou, E; Tsipas, P; Aretouli, K E; Tsoutsou, D; Giamini, S A; Bazioti, C; Dimitrakopulos, G P; Komninou, Ph; Brems, S; Huyghebaert, C; Radu, I P; Dimoulas, A

    2015-05-07

    Atomically-thin, inherently 2D semiconductors offer thickness scaling of nanoelectronic devices and excellent response to light for low-power versatile applications. Using small exfoliated flakes, advanced devices and integrated circuits have already been realized, showing great potential to impact nanoelectronics. Here, high-quality single-crystal MoSe2 is grown by molecular beam epitaxy on AlN(0001)/Si(111), showing the potential for scaling up growth to low-cost, large-area substrates for mass production. The MoSe2 layers are epitaxially aligned with the aluminum nitride (AlN) lattice, showing a uniform, smooth surface and interfaces with no reaction or intermixing, and with sufficiently high band offsets. High-quality single-layer MoSe2 is obtained, with a direct gap evidenced by angle-resolved photoemission spectroscopy and further confirmed by Raman and intense room temperature photoluminescence. The successful growth of high-quality MoSe2/Bi2Se3 multilayers on AlN shows promise for novel devices exploiting the non-trivial topological properties of Bi2Se3.

  13. Optical properties and electronic structures of d- and f-electron metals and alloys, Ag-In, Ni-Cu, AuGa sub 2 , PtGa sub 2 ,. beta. prime -NiAl,. beta. prime -CoAl, CeSn sub 3 , and LaSn sub 3

    SciTech Connect

    Kim, Kwang Joo.

    1990-10-17

    Optical properties and electronic structures of disordered Ag{sub 1- x}In{sub x}(x = 0.0, 0.04, 0.08, 0.12) and Ni{sub 1-x}Cu{sub x} (x = 0.0, 0.1, 0.3, 0.4) alloys and ordered AuGa{sub 2}, PtGa{sub 2}, {beta}{prime}-NiAl, {beta}{prime}-CoAl, CeSn{sub 3}, and LaSn{sub 3} have been studied. The complex dielectric functions have been determined for Ag{sub 1-x}In{sub x}, Ni{sub 1-x}Cu{sub x}, AuGa{sub 2}, and PtGa{sub 2} in the 1.2--5.5 eV region and for CeSn{sub 3} and LaSn{sub 3} in the 1.5--4.5 eV region using spectroscopic ellipsometry. Self-consistent relativistic band calculations using the linearized-augmented-plane-wave method have been performed for AuGa{sub 2}, PtGa{sub 2}, {beta}{prime}-NiAl, {beta}{prime}-CoAl, CeSn{sub 3}, and LaSn{sub 3} to interpret the experimental optical spectra.

  14. Ab initio study of deformed As, Sb, and Bi with an application to thin films

    NASA Astrophysics Data System (ADS)

    Zouhar, M.; Šob, M.

    2016-11-01

    We present a comprehensive density-functional theory study of total energy and structural properties of As, Sb, and Bi in their A7 ground-state structure and in the bcc, fcc, and simple cubic (sc) modifications. We also investigate continuous structural transitions between these structures. The electronic structures and total energies are calculated both within the generalized gradient approximation (GGA) and local-density approximation (LDA) to the exchange-correlation energy as well as with and without inclusion of the spin-orbit coupling (SOC). The total energies of deformed structures are displayed in contour plots as functions of selected structural parameters and/or atomic volume; these plots are then used for understanding and interpreting structural parameters of As, Sb and Bi thin films on various substrates. Our calculated values of lattice parameters for (0001) thin films of Bi on Si(111) and Ge(111) substrates agree very well with available experimental data. In analogy with that, we suggest to investigate (0001) thin films of As on Ti(0001), Co(0001), Zn(0001) and Rh(111) substrates, of Sb on C(0001), Zn(0001), Al(111), Ag(111) and Au(111) substrates and of Bi on Co(0001), Al(111), Rh(111), Ba(111) and Pb(111) substrates. For these cases, we also predict the lattice parameters of the films. A large part of our results are theoretical predictions which may motivate experimentalists for a deeper study of these systems.

  15. Molecular Beam Epitaxy Growth of GaBi, InBi and InGaBi

    NASA Astrophysics Data System (ADS)

    Keen, B.; Makin, R.; Stampe, P. A.; Kennedy, R. J.; Piper, L. F. J.; McCombe, B.; McConville, C. F.; Durbin, S. M.

    2014-03-01

    Recent interest in bismuth alloys of III-V semiconductors for infrared and far-infrared device applications, specifically GaAsBi and InAsBi, has indicated that further study of the III-Bi family of binary compounds would be of great help in improving the quality of these material systems. While immiscibility issues have so far frustrated the growth of GaBi and AlBi, InBi is less problematic, and we have grown it by molecular beam epitaxy on (001) GaAs substrates. However, regions of varying composition exist across the substrate due to poor wetting of the surface. In an effort to improve film quality we have continued to refine the growth parameters by adjusting substrate temperature, beam flux ratio, and deposition rate. Characterization of these films has been performed by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Additionally, we have explored growth of GaBi and In1-xGaxBi at low Ga mole fractions, and modeled this using molecular dynamics simulations. This work is supported by the Research Foundation of the State University of New York Collaborations Fund.

  16. Several Microstrip-Based Conductor/Thin Film Ferroelectric Phase Shifter Designs Using (YBa2Cu3O(7 - Delta), Au)/SrTiO3/LaAlO3 Structures

    NASA Technical Reports Server (NTRS)

    VanKeuls, F. W.; Romanofsky, R. R.; Miranda, F. A.

    1998-01-01

    We have designed, fabricated, and tested several novel microstrip-base YBa2Cu3O7-delta/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3ALO3 (Au/STO/LAO) phase shifters. The first design consists of eight coupled microstrip phase shifters (CMPS) in series. This design using YBCO achieved a relative insertion phase shift (Delta f) of 484 degrees with a figure of merit of 80 degrees/dB at Vdc = 375 V, 16 GHz, and 40 K. A Delta f of 290 degrees was observed while maintaining the insertion loss below 4.5 dB. At 77 K, a Delta of 420 degrees was obtained for this phase shifter at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. A second compact design, consisting of an Au meander line and a CMPS section was also tested. Of the two samples tested, the best showed a figure of merit of 43 degrees/dB with Delta f = 290 degrees and 6.8 dB loss, at 40 K, 10 GHz and 400 V. Experimental and modeling results on these circuits will be discussed in the context of potential applications.

  17. A heterotrimetallic Ir(III), Au(III) and Pt(II) complex incorporating cyclometallating bi- and tridentate ligands: simultaneous emission from different luminescent metal centres leads to broad-band light emission.

    PubMed

    Muñoz-Rodríguez, Rebeca; Buñuel, Elena; Fuentes, Noelia; Williams, J A Gareth; Cárdenas, Diego J

    2015-05-14

    Di- and tri-nuclear metal complexes incorporating gold(III), iridium(III) and platinum(II) units linked via a 1,3,5-triethynylbenzene core are reported, together with the corresponding mononuclear complexes as models. The gold(III) and platinum(II) units comprise tridentate, cyclometallating, C^N^C and N^N^C-coordinating ligands, respectively, with the Ar-C≡C- directly bound to the metal at the fourth coordination site. The iridium moiety is an Ir(ppy)2(acac) unit bound to the triethynylbenzene through a phenyl substituent at the 3-position of the acac ligand. The multinuclear compounds are prepared, using a modular synthetic strategy, from the monometallic complexes. All of the compounds are luminescent in solution at room temperature, and their photophysical properties were studied. The triplet excited state energies of the mononuclear complexes lie in the order Au > Ir > Pt. Consistent with this order, energy transfer from Au to Ir and from Au to Pt is observed, leading to quenching of the Au emission in the gold-containing multinuclear complexes. Energy transfer from Ir to Pt occurs at a rate that only partially quenches the Ir-based emission. As a result, the dinuclear Ir-Pt and trinuclear Au-Ir-Pt complexes display broad emission across most of the visible region of the spectrum.

  18. DFT study of Hg adsorption on M-substituted Pd(1 1 1) and PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Jiancheng; Yu, Huafeng; Geng, Lu; Liu, Jianwen; Han, Lina; Chang, Liping; Feng, Gang; Ling, Lixia

    2015-11-01

    The adsorption of Hgn (n = 1-3) on the Au-, Ag-, Cu-substituted Pd(1 1 1) surfaces as well as the PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces has been investigated using spin-polarized density functional theory calculations. It is found that M-substituted Pd(1 1 1) surfaces show as good Hg adsorption capacity as the perfect Pd(1 1 1) at low Hg coverage, while the Hg adsorption capacity is only slightly weakened at high Hg coverage. On the basis of stepwise adsorption energies analysis, it is concluded that M-substituted Pd(1 1 1) surfaces can contribute to the binding of Hg atom on the surfaces at high Hg coverage. The electronic properties of the second metal atoms are the main factor contributes to the Hg adsorption capacity. Gas phase Pd2 shows better Hg adsorption capacity than Pd2/γ-Al2O3, while PdM/γ-Al2O3 can adsorb Hg more efficiently than bare PdM clusters. It suggests that the γ-Al2O3 support can enhance the activity of PdM for Hg adsorption and reduces the activity of Pd2. It is also found that Pd is the main active composition responsible for the interaction of mercury with the surface for PdM/γ-Al2O3 sorbent. Taking Hg adsorption capacity and economic costs into account, Cu addition is a comparatively good candidate for Hg capture.

  19. Controlling the growth of Bi(110) and Bi(111) films on an insulating substrate.

    PubMed

    Jankowski, Maciej; Kamiński, Daniel; Vergeer, Kurt; Mirolo, Marta; Carla, Francesco; Rijnders, Guus; Bollmann, Tjeerd R J

    2017-04-18

    We demonstrate the controlled growth of Bi(110) and Bi(111) films on an α-Al2O3(0001) substrate by surface x-ray diffraction and x-ray reflectivity using synchrotron radiation. At temperatures as low as 40 K, unanticipated pseudo-cubic Bi(110) films are grown with thicknesses ranging from a few to tens of nanometers. The roughness at the film-vacuum as well as the film-substrate interface, can be reduced by mild heating, where a crystallographic orientation transition of Bi(110) towards Bi(111) is observed at 400 K. From 450 K onwards high quality ultrasmooth Bi(111) films form. Growth around the transition temperature results in the growth of competing Bi(110) and Bi(111) domains.

  20. Controlling the growth of Bi(110) and Bi(111) films on an insulating substrate

    NASA Astrophysics Data System (ADS)

    Jankowski, Maciej; Kamiński, Daniel; Vergeer, Kurt; Mirolo, Marta; Carla, Francesco; Rijnders, Guus; Bollmann, Tjeerd R. J.

    2017-04-01

    We demonstrate the controlled growth of Bi(110) and Bi(111) films on an α-Al2O3(0001) substrate by surface x-ray diffraction and x-ray reflectivity using synchrotron radiation. At temperatures as low as 40 K, unanticipated pseudo-cubic Bi(110) films are grown with thicknesses ranging from a few to tens of nanometers. The roughness at the film–vacuum as well as the film–substrate interface, can be reduced by mild heating, where a crystallographic orientation transition of Bi(110) towards Bi(111) is observed at 400 K. From 450 K onwards high quality ultrasmooth Bi(111) films form. Growth around the transition temperature results in the growth of competing Bi(110) and Bi(111) domains.

  1. Molecular beam epitaxy-grown Bi4Te3 nanowires

    NASA Astrophysics Data System (ADS)

    Wang, G.; Lok, S. K.; Wong, G. K. L.; Sou, I. K.

    2009-12-01

    With Au nanoparticles as the catalyst, the formation of Bi4Te3 nanowires was achieved at an optimized substrate temperature of around 330 °C. We found two growth mechanisms for the nanowires: a self-assembled growth mode through islands as the seed and a vapor-solid-solid growth mode through the assistance of Au catalyst nanoparticles, the decisive factor for which was identified as the density of the Au nanoparticles.

  2. Growth of Bi2Te3 films and other phases of Bi-Te system by MOVPE

    NASA Astrophysics Data System (ADS)

    Kuznetsov, P. I.; Yapaskurt, V. O.; Shchamkhalova, B. S.; Shcherbakov, V. D.; Yakushcheva, G. G.; Luzanov, V. A.; Jitov, V. A.

    2016-12-01

    We have deposited films of Bi-Te system by atmospheric pressure MOVPE on (0001) Al2O3 substrates with thin ZnTe or thick GaN buffer layers at different temperatures and Te/Bi ratio in the vapor phase. As-grown films were studied by X-ray diffractometry, SEM microscopy and Raman spectroscopy. To determine the elemental composition of the films, an energy dispersive spectrometer was used. Single-phase films of Bi2Te3, Bi4Te5, BiTe, Bi10Te9, Bi4Te3, Bi3Te2 have been grown and growth parameter ranges for obtaining different phases were defined. It was found that under the same growth condition different phases of the Bi-Te system realize depending on the film's thickness. Thus, when growing of Bi2Te3 films by MOCVD method the careful control of the phase composition is required.

  3. Structural and electrical properties of metal ferroelectric insulator semiconductor structure of Al/SrBi2Ta2O9/HfO2/Si using HfO2 as buffer layer

    NASA Astrophysics Data System (ADS)

    Roy, A.; Dhar, A.; Bhattacharya, D.; Ray, S. K.

    2008-05-01

    Ferroelectric SrBi2Ta2O9 (SBT) thin films have been deposited by the radio-frequency magnetron sputtering technique on bare p-Si as well as on HfO2 insulating buffer p-Si. XRD patterns revealed the formation of a well-crystallized SBT perovskite thin film on the HfO2 buffer layer. The electrical properties of the metal-ferroelectric-insulator-semiconductor (MFIS) structure were characterized by varying thicknesses of the HfO2 layer. The MFIS structure exhibits a maximum clockwise C-V memory window of 1.60 V when the thickness of the HfO2 layer was 12 nm with a lower leakage current density of 6.20 × 10-7 A cm-2 at a positive applied voltage of 7 V. However, the memory window reaches a maximum value of 0.7 V at a bias voltage of ±5 and then decreases due to charge injection in the case of the insulating buffer layer thickness of 3 nm. The density of oxide trapped charges at/near the buffer layer-ferroelectric interface is studied by the voltage stress method. Capacitance-voltage (C-V) and leakage current density (J-V) characteristics of the Al/SBT/HfO2/Si(1 0 0) capacitor indicate that the introduction of the HfO2 buffer layer prevents interfacial diffusion between the SBT thin film and the Si substrate effectively and improves the interface quality. Furthermore, the Al/SBT/HfO2/Si structures exhibit excellent retention characteristics, the high and low capacitance values clearly distinguishable for over 1 h and 30 min. This shows that the proposed Al/SrBi2Ta2O9/HfO2/Si structure is ideally suitable for high performance ferroelectric memories.

  4. Visible-Light-Driven BiOI-Based Janus Micromotor in Pure Water.

    PubMed

    Dong, Renfeng; Hu, Yan; Wu, Yefei; Gao, Wei; Ren, Biye; Wang, Qinglong; Cai, Yuepeng

    2017-02-08

    Light-driven synthetic micro-/nanomotors have attracted considerable attention due to their potential applications and unique performances such as remote motion control and adjustable velocity. Utilizing harmless and renewable visible light to supply energy for micro-/nanomotors in water represents a great challenge. In view of the outstanding photocatalytic performance of bismuth oxyiodide (BiOI), visible-light-driven BiOI-based Janus micromotors have been developed, which can be activated by a broad spectrum of light, including blue and green light. Such BiOI-based Janus micromotors can be propelled by photocatalytic reactions in pure water under environmentally friendly visible light without the addition of any other chemical fuels. The remote control of photocatalytic propulsion by modulating the power of visible light is characterized by velocity and mean-square displacement analysis of optical video recordings. In addition, the self-electrophoresis mechanism has been confirmed for such visible-light-driven BiOI-based Janus micromotors by demonstrating the effects of various coated layers (e.g., Al2O3, Pt, and Au) on the velocity of motors. The successful demonstration of visible-light-driven Janus micromotors holds a great promise for future biomedical and environmental applications.

  5. BiFeO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} heterostructures deposited on spark plasma sintered LaAlO{sub 3} substrates

    SciTech Connect

    Pravarthana, D.; Lacotte, M.; David, A.; Prellier, W.; Trassin, M.; Haw Chu, Jiun; Ramesh, R.; Salvador, P. A.

    2014-02-24

    Multiferroic BiFeO{sub 3} (BFO)/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} heterostructured thin films were grown by pulsed laser deposition on polished spark plasma sintered LaAlO{sub 3} (LAO) polycrystalline substrates. Both polycrystalline LAO substrates and BFO films were locally characterized using electron backscattering diffraction, which confirmed the high-quality local epitaxial growth on each substrate grain. Piezoforce microscopy was used to image and switch the piezo-domains, and the results are consistent with the relative orientation of the ferroelectric variants with the surface normal. This high-throughput synthesis process opens the routes towards wide survey of electronic properties as a function of crystalline orientation in complex oxide thin film synthesis.

  6. Measurement of the relative yields of ψ (2 S ) to ψ (1 S ) mesons produced at forward and backward rapidity in p +p , p +Al , p +Au , and 3He+Au collisions at √{sNN}=200 GeV

    NASA Astrophysics Data System (ADS)

    Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Alfred, M.; Andrieux, V.; Aoki, K.; Apadula, N.; Asano, H.; Ayuso, C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Bathe, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Blau, D. S.; Boer, M.; Bok, J. S.; Bownes, E. K.; Boyle, K.; Brooks, M. L.; Bryslawskyj, J.; Bumazhnov, V.; Butler, C.; Campbell, S.; Canoa Roman, V.; Cervantes, R.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Chujo, T.; Citron, Z.; Connors, M.; Cronin, N.; Csanád, M.; Csörgő, T.; Danley, T. W.; Datta, A.; Daugherity, M. S.; David, G.; Deblasio, K.; Dehmelt, K.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Dion, A.; Diss, P. B.; Dixit, D.; Do, J. H.; Drees, A.; Drees, K. A.; Dumancic, M.; Durham, J. M.; Durum, A.; Dusing, J. P.; Elder, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Fadem, B.; Fan, W.; Feege, N.; Fields, D. E.; Finger, M.; Finger, M.; Fokin, S. L.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fukuda, Y.; Gal, C.; Gallus, P.; Garg, P.; Ge, H.; Giordano, F.; Glenn, A.; Goto, Y.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Guragain, H.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamilton, H. F.; Han, S. Y.; Hanks, J.; Hasegawa, S.; Haseler, T. O. S.; Hashimoto, K.; He, X.; Hemmick, T. K.; Hill, J. C.; Hill, K.; Hollis, R. S.; Homma, K.; Hong, B.; Hoshino, T.; Hotvedt, N.; Huang, J.; Huang, S.; Imai, K.; Imrek, J.; Inaba, M.; Iordanova, A.; Isenhower, D.; Ito, Y.; Ivanishchev, D.; Jacak, B. V.; Jezghani, M.; Ji, Z.; Jia, J.; Jiang, X.; Johnson, B. M.; Jorjadze, V.; Jouan, D.; Jumper, D. S.; Kanda, S.; Kang, J. H.; Kapukchyan, D.; Karthas, S.; Kawall, D.; Kazantsev, A. V.; Key, J. A.; Khachatryan, V.; Khanzadeev, A.; Kim, C.; Kim, D. J.; Kim, E.-J.; Kim, G. W.; Kim, M.; Kimball, M. L.; Kimelman, B.; Kincses, D.; Kistenev, E.; Kitamura, R.; Klatsky, J.; Kleinjan, D.; Kline, P.; Koblesky, T.; Komkov, B.; Kotler, J. R.; Kotov, D.; Kudo, S.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Lacey, R.; Lajoie, J. G.; Lallow, E. O.; Lebedev, A.; Lee, S.; Lee, S. H.; Leitch, M. J.; Leung, Y. H.; Lewis, N. A.; Li, X.; Li, X.; Lim, S. H.; Liu, L. D.; Liu, M. X.; Loggins, V.-R.; Loggins, V.-R.; Lovasz, K.; Lynch, D.; Majoros, T.; Makdisi, Y. I.; Makek, M.; Malaev, M.; Manion, A.; Manko, V. I.; Mannel, E.; Masuda, H.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Meles, A.; Mendez, A. R.; Mendoza, M.; Mignerey, A. C.; Mihalik, D. E.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Mitsuka, G.; Miyasaka, S.; Mizuno, S.; Mohanty, A. K.; Montuenga, P.; Moon, T.; Morrison, D. P.; Morrow, S. I. M.; Moukhanova, T. V.; Murakami, T.; Murata, J.; Mwai, A.; Nagai, K.; Nagashima, K.; Nagashima, T.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakano, K.; Nattrass, C.; Netrakanti, P. K.; Niida, T.; Nishimura, S.; Nouicer, R.; Novák, T.; Novitzky, N.; Novotny, R.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Orjuela Koop, J. D.; Osborn, J. D.; Oskarsson, A.; Ottino, G. J.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, J. S.; Park, S.; Pate, S. F.; Patel, M.; Peng, J.-C.; Peng, W.; Perepelitsa, D. V.; Perera, G. D. N.; Peressounko, D. Yu.; Perezlara, C. E.; Perry, J.; Petti, R.; Phipps, M.; Pinkenburg, C.; Pinson, R.; Pisani, R. P.; Press, C. J.; Pun, A.; Purschke, M. L.; Rak, J.; Ramson, B. J.; Ravinovich, I.; Read, K. F.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richford, D.; Rinn, T.; Rolnick, S. D.; Rosati, M.; Rowan, Z.; Rubin, J. G.; Runchey, J.; Safonov, A. S.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sako, H.; Samsonov, V.; Sarsour, M.; Sato, K.; Sato, S.; Schaefer, B.; Schmoll, B. K.; Sedgwick, K.; Seidl, R.; Sen, A.; Seto, R.; Sett, P.; Sexton, A.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shioya, T.; Shukla, P.; Sickles, A.; Silva, C. L.; Silva, J. A.; Silvermyr, D.; Singh, B. K.; Singh, C. P.; Singh, V.; Slunečka, M.; Smith, K. L.; Snowball, M.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Stankus, P. W.; Stepanov, M.; Stien, H.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sumita, T.; Sun, J.; Syed, S.; Sziklai, J.; Takeda, A.; Taketani, A.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarnai, G.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Tomášek, M.; Towell, C. L.; Towell, R.; Towell, R. S.; Tserruya, I.; Ueda, Y.; Ujvari, B.; van Hecke, H. W.; Vazquez-Carson, S.; Velkovska, J.; Virius, M.; Vrba, V.; Vukman, N.; Wang, X. R.; Wang, Z.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; White, A. S.; Wong, C. P.; Woody, C. L.; Wysocki, M.; Xia, B.; Xu, C.; Xu, Q.; Xue, L.; Yalcin, S.; Yamaguchi, Y. L.; Yamamoto, H.; Yanovich, A.; Yin, P.; Yoo, J. H.; Yoon, I.; Yu, H.; Yushmanov, I. E.; Zajc, W. A.; Zelenski, A.; Zharko, S.; Zhou, S.; Zou, L.; Phenix Collaboration

    2017-03-01

    The PHENIX Collaboration has measured the ratio of the yields of ψ (2 S ) to ψ (1 S ) mesons produced in p +p , p +Al , p +Au , and 3He+Au collisions at √{s NN}=200 GeV over the forward and backward rapidity intervals 1.2 <|y |<2.2 . We find that the ratio in p +p collisions is consistent with measurements at other collision energies. In collisions with nuclei, we find that in the forward (p -going or 3He-going) direction, the relative yield of ψ (2 S ) mesons to ψ (1 S ) mesons is consistent with the value measured in p +p collisions. However, in the backward (nucleus-going) direction, the ψ (2 S ) meson is preferentially suppressed by a factor of ˜2 . This suppression is attributed in some models to the breakup of the weakly bound ψ (2 S ) meson through final-state interactions with comoving particles, which have a higher density in the nucleus-going direction. These breakup effects may compete with color screening in a deconfined quark-gluon plasma to produce sequential suppression of excited quarkonia states.

  7. Depth profile of production yields of natPb(p, xn) 206,205,204,203,202,201Bi nuclear reactions

    NASA Astrophysics Data System (ADS)

    Mokhtari Oranj, Leila; Jung, Nam-Suk; Kim, Dong-Hyun; Lee, Arim; Bae, Oryun; Lee, Hee-Seock

    2016-11-01

    Experimental and simulation studies on the depth profiles of production yields of natPb(p, xn) 206,205,204,203,202,201Bi nuclear reactions were carried out. Irradiation experiments were performed at the high-intensity proton linac facility (KOMAC) in Korea. The targets, irradiated by 100-MeV protons, were arranged in a stack consisting of natural Pb, Al, Au foils and Pb plates. The proton beam intensity was determined by activation analysis method using 27Al(p, 3p1n)24Na, 197Au(p, p1n)196Au, and 197Au(p, p3n)194Au monitor reactions and also by Gafchromic film dosimetry method. The yields of produced radio-nuclei in the natPb activation foils and monitor foils were measured by HPGe spectroscopy system. Monte Carlo simulations were performed by FLUKA, PHITS/DCHAIN-SP, and MCNPX/FISPACT codes and the calculated data were compared with the experimental results. A satisfactory agreement was observed between the present experimental data and the simulations.

  8. Investigation of constant voltage off-state stress on Au-free AlGaN/GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Hu, Jie; Stoffels, Steve; Lenci, Silvia; Wu, Tian-Li; Ronchi, Nicolò; You, Shuzhen; Bakeroot, Benoit; Groeseneken, Guido; Decoutere, Stefaan

    2015-04-01

    In this work, we perform an in-depth analysis of electron-trapping in AlGaN/GaN Schottky barrier diodes under constant voltage (VAC = -100 V) off-state stress conditions. The current-voltage (I-V) characteristics of the diode after stressing show a leakage reduction and on-state degradation due to electron-trapping occurring in the vicinity of the Schottky contact. Capacitance-voltage (C-V) measurements confirm an increase of the barrier height and the on-resistance of the stressed device. Furthermore, the on-resistance increase has been studied with different temperatures and stressing times. By TCAD simulations, a lateral extension of the “trapped region” at the AlGaN/Si3N4 interface has been visualized and can qualitatively explain the phenomenon of higher on-resistance increase at higher temperatures.

  9. Growth and Characterization of Bi2Te3/Bi2Se3 Bilayers

    NASA Astrophysics Data System (ADS)

    Henderson, Rachel; Babakiray, Sercan; Johnson, Trent; Borisov, Pavel; Lederman, David; West Virginia University Team

    2014-03-01

    Bi2Te3/Bi2Se3 bilayers were grown on Al2O3 (0001) substrates using molecular beam epitaxy. Bi2Te3 was grown at a stoichiometric ratio (Te/Bi) of 3:2 and Bi2Se3 was grown at stoichiometric ratio (Se/Bi) of 15:1. Reflection high energy electron diffraction and x-ray diffraction were used to confirm the epitaxial growth of these films. X-ray reflectivity was used to determine the thickness and roughness of these bilayers. The magnetotransport of these heterostructures was used to determine whether charge compensation can be achieved within the bulk of the material in order to enhance the properties of surface topological states. This work was supported by a Research Challenge Grant from the West Virginia Higher Education Policy Commission (HEPC.dsr.12.29) and the West Virginia University Shared Research Facilities.

  10. Hadron Production and Freeze-Out Dynamics at square root of sNN = 3.0 GeV Au+Al and square root of sNN = 19.6 GeV Au+Au Collisions as Measured at STAR

    NASA Astrophysics Data System (ADS)

    Brovko, Samantha Gail

    The Beam Energy Scan program at RHIC was commissioned to search for the critical point and the turn-off of QGP signatures. The program has completed collisions of Au+Au at energies from 7.7 to 62.4 GeV per nucleon pair in 2010 and 2011. The addition of a full-coverage Time-of-Flight detector at STAR extended the momentum range for clean particle identification. Mid-rapidity (|y| < 0.5) hadron spectra will be used to determine the freeze-out dynamics of the system. Particle spectra for pi, K, p and p¯ as a function of mT -- m0 will be presented and these will be used to discuss in particular the source's Coulombic effect on soft pions, as well as three of the four signs of the onset of deconfinement: the "Kink," the "Horn," and the "Step." Comparisons will be made to √s NN) = 7.7 GeV, 11.5 GeV, 19.6 GeV (from 2001), 27 GeV, 39 GeV Au+Au data from STAR, and (sqrt of sNN = 17.3 GeV Pb+Pb data from the SPS heavy ion program. Collisions between gold ions in the RHIC beam with aluminum nuclei in the beam pipe allow us to analyze fixed-target interactions with the STAR detector at RHIC. These lower-energy fixed-target collisions may allow us to extend the low-energy reach of the RHIC beam energy scan and possibly improve the chance of finding the critical point of the hadronic to quark matter phase boundary. In this thesis, we will present preliminary results of spectra analyses for a fixed target collision system at √sNN)= 3.0 GeV and colliding beam system at √sNN = 19.6 GeV . Also, the viability of doing fixed-target experiments with a collider detector will be discussed. Comparisons to simulation, using UrQMD, will also be made. The analysis provides a good reference to study excitation functions of strangeness production, net baryon number, and collective flow in heavy-ion collisions.

  11. Influence of the Biasing Scheme on the Performance of Au/SrTiO3/LaAlO3 Thin Film Conductor/Ferroelectric Tunable Ring Resonators

    NASA Technical Reports Server (NTRS)

    VanKeuls, F. W.; Romanofsky, R. R.; Bohman, D. Y.; Miranda, F. A.

    1998-01-01

    The performance of gold/SrTio3 /LaAlO3 conductor/ferroelectric/dielectric side-coupled, tunable ring resonators at K-band frequencies is presented. The tunability of these rings arises from the sensitivity of the relative dielectric constant (Er) of SrTiO 3 to changes in temperature and dc electric fields (E). We observed that the change in F-, which takes place by biasing the ring up to 450 V alters the effective dielectric constant (e-eff) of the circuit resulting in a 3k resonant frequency shift of nearly 12 % at 77 K. By applying a separate dc bias between the microstrip line and the ring, one can optimize their coupling to obtain bandstop resonators with unloaded quality factors (Q(sub o)) as high as 12,000. The 31 resonance was tuned from 15.75 to 17.41 GHz while keeping Q. above 768 over this range. The relevance of these results for practical microwave components will be discussed.

  12. Size control of Au nanoparticles on TiO2 and Al2O3 by DP Urea: optical absorption and electron microscopy as control probes.

    PubMed

    Reyes-Esqueda, Jorge Alejandro; Salvador, Amado Bautista; Zanella, Rodolfo

    2008-08-01

    Gold nanoparticles supported on TiO2 and Al2O3 were prepared by using the deposition-precipitation with urea (DP Urea) method. The control of the particle size was achieved by varying both, the stirring time during the deposition-precipitation (DP) procedure and the conditions of thermal treatment. We focused mainly on the stirring time and the treatment temperature, although gas flow and type of atmosphere also influence importantly the particle's size and shape, as we shall show. The optical response of metallic nanoparticles is given by its surface plasmon resonance and its position and shape depends strongly on the size and the shape of the nanoparticle, as well as on its surrounding. Then, we followed the control of the nanoparticles size by using mainly optical absorption measurements, which gave us account of the size and the shape of the nanoparticles and the effect of the support on their optical response. These optical results were compared to, and supported with, TEM micrographs of our samples.

  13. Strain evolution of epitaxial tetragonal-like BiFeO3 thin films on LaAlO3(001) substrates prepared by sputtering and their bulk photovoltaic effect

    NASA Astrophysics Data System (ADS)

    Nakashima, Seiji; Uchida, Tomohisa; Doi, Kentaro; Saitoh, Koh; Fujisawa, Hironori; Sakata, Osami; Katsuya, Yoshio; Tanaka, Nobuo; Shimizu, Masaru

    2016-10-01

    The structural evolution of high-quality 3.3-73.2-nm-thick tetragonal-like BiFeO3 (T-BFO) thin films grown on LaAlO3(001) substrates and the bulk photovoltaic effect of the films were investigated. The T-BFO films were grown by rf magnetron sputtering, showing the Peudellösung fringes around the T-BFO (001) diffraction peak in X-ray diffraction θ-2θ patterns. These indicate the structural coherence between the surface and the interface in the surface normal direction of the films. High-resolution synchrotron X-ray diffraction analysis and transmission electron microscopy reveal that the lattice relaxation behavior from the MA monoclinic to MC monoclinic structure occurs as the film thickness increases. The domain structure was partly controlled by using a vicinal LAO (001) substrate along [100]. Regarding the current-voltage characteristics of the Pt/T-BFO/Pt coplanar capacitor under violet laser illumination, T-BFO films show an anomalous photovoltaic effect with an open-circuit voltage of 6.1 V and a short-circuit current of -290 pA along the [100]T-BFO direction.

  14. Investigation of luminescence and laser transition of Dy3+ ion in P2O5sbnd PbOsbnd Bi2O3sbnd R2O3 (R = Al, Ga, In) glasses

    NASA Astrophysics Data System (ADS)

    Ram, G. Chinna; Narendrudu, T.; Suresh, S.; Kumar, A. Suneel; Rao, M. V. Sambasiva; Kumar, V. Ravi; Rao, D. Krishna

    2017-04-01

    P2O5sbnd PbOsbnd Bi2O3sbnd R2O3 (R = Al, Ga, In) glasses doped with Dy2O3 were prepared by melt quenching technique. The prepared glasses were characterized by XRD, optical absorption, FTIR, luminescence studies. Judd-Ofelt parameters have been evaluated for three glass systems from optical absorption spectra and in turn radiative parameters for excited luminescent levels of Dy3+ ion are also calculated. Emission cross section and branching ratio values are observed to high for 6H13/2 level for Dy3+ ion. The yellow to blue intensity ratios and CIE chromaticity coordinates were calculated. Decay curves exhibit non exponential behavior. Quantum efficiency of prepared glasses was measured by using radiative and calculated life times. IR studies, J-O parameters and Y/B ratio values indicate that more asymmetry around Dy3+ ions in Ga2O3 mixed glass was observed. Chromaticity coordinates lie near ideal white light region. These coordinates and CCT values have revealed that all the prepared glasses emit quality white light especially the glasses mixed with Ga2O3 are suitable for development of white LEDs.

  15. Ferroelectric properties of Bi2VO5.5 thin films on LaAlO3 and SiO2/Si substrates with LaNiO3 base electrode

    NASA Astrophysics Data System (ADS)

    Satyalakshmi, K. M.; Varma, K. B. R.; Hegde, M. S.

    1995-07-01

    Ferroelectric bismuth vanadate Bi2VO5.5 (BVO) thin films have been grown on LaAlO3 (LAO) and SiO2/Si substrates with LaNiO3 (LNO) base electrodes by the pulsed laser deposition technique. The effect of substrate temperature on the ferroelectric properties of BVO thin films, has been studied by depositing the thin films at different temperatures. The BVO thin films grown on LNO/LAO were textured whereas the thin films grown on LNO/SiO2/Si were polycrystalline. The BVO thin films grown at 450 °C exhibited good ferroelectric properties indicating that LNO acts as a good electrode material. The remanent polarization Pr and coercive field Ec obtained for the BVO thin films grown at 450 °C on LNO/LAO and LNO/SiO2/Si were 2.5 μC/cm2, 37 kV/cm and 4.6μC/cm2, 93 kV/cm, respectively.

  16. Fabrication and Characterization of ZnO:Al/Sr0.8Bi2.2Ta2O9/Y2O3:Eu Structures for Ferroelectric-Electroluminescent Devices

    NASA Astrophysics Data System (ADS)

    Aizawa, Koji; Inagaki, Hiroyuki; Takatsuka, Yushi; Hoko, Koichi; Otani, Yusuke; Tokunaga, Yoshiaki

    2009-09-01

    ZnO:Al (AZO)/Sr0.8Bi2.2Ta2O9 (SBT)/Pt and AZO/SBT/Y2O3:Eu/Pt structures were fabricated, and their crystallinity, ferroelectric, and electroluminescent (EL) properties were investigated for the first time. The AZO/SBT/Pt structures showed a typical hysteresis loop, in which their double remnant polarization was approximately 5.3 µC/cm2. The polycrystalline SBT/Y2O3:Eu structures were grown on a Pt-coated substrate, in which ferroelectric phases were formed on an Y2O3:Eu film with cubic crystals. The electrical and EL properties of the AZO/SBT/Y2O3:Eu/Pt structures were measured, and then EL emission peaks associated with the 5D0-7F1 (λ=601 nm) and 5D0-7F2 (λ=617 nm) transitions of Eu3+ were observed. The EL emission pattern of the AZO/SBT/Y2O3:Eu/Pt structure was different from the PL emission pattern of the Y2O3:Eu film. Furthermore, polarization-voltage characteristics with counterclockwise hysteresis loops and an asymmetric behavior of current-voltage characteristics were observed in the fabricated AZO/SBT/Y2O3/Pt:Eu structures.

  17. Resonant Levels, Vacancies, and Doping in Bi2Te3, Bi2Te2Se, and Bi2Se3 Tetradymites

    NASA Astrophysics Data System (ADS)

    Wiendlocha, Bartlomiej

    2016-07-01

    The electronic structure of the tetradymites, Bi_2Te_3, Bi_2Te_2Se, and Bi_2Se_3, containing various dopants and vacancies, has been studied using first-principles calculations. We focus on the possibility of formation of resonant levels (RL), confirming the formation of RL by Sn in Bi_2Te_3 and predicting similar behavior of Sn in Bi_2Te_2Se and Bi_2Se_3. Vacancies, which are likely present on chalcogen atom sites in real samples of Bi_2Te_2Se and Bi_2Se_3, are also studied and their charged donor and resonant behavior discussed. Doping of vacancy-containing materials with regular acceptors, such as Ca or Mg, is shown to compensate the donor effect of vacancies, and n-p crossover, while increasing the dopant concentration, is observed. We verify that the RL on Sn is not disturbed by chalcogen vacancies in Bi_2Te_2Se or Bi_2Se_3, and for the Sn-doped materials with Se or Te vacancies, double doping, instead of heavy doping with Sn, is suggested as an effective way of obtaining the resonant level. This should help to avoid smearing of the RL, a possible reason for earlier unsuccessful experimental observation of the influence of the RL on the thermoelectric properties of Sn-doped Bi_2Te_2Se. Finally, we show that Al and Ga are possible new resonant impurities in tetradymites, hoping that this will stimulate further experimental studies.

  18. Exclusive studies of 130-270 MeV {sup 3}He- and 200-MeV proton-induced reactions on {sup 27}Al, {sup nat}Ag, and {sup 197}Au

    SciTech Connect

    Ginger, D. S.; Kwiatkowski, K.; Wang, G.; Hsi, W.-C.; Hudan, S.; Cornell, E.; Souza, R. T. de; Viola, V. E.; Korteling, R. G.

    2008-09-15

    Exclusive light-charged-particle and IMF spectra have been measured with the ISiS detector array for bombardments of {sup 27}Al, {sup nat}Ag, and {sup 197}Au nuclei with 130-270-MeV {sup 3}He and 200-MeV protons. The results are consistent with previous interpretations based on inclusive data that describe the global yield of complex fragments in terms of a time-dependent process. The emission mechanism for energetic nonequilibrium fragments observed at forward angles with momenta up to twice the beam momentum is also investigated. This poorly understood mechanism, for which the angular distributions indicate formation on a time scale comparable to the nuclear transit time, are accompanied primarily by thermal-like emissions. The data are most consistent with a schematic picture in which nonequilibrium fragments are formed in a localized region of the target nucleus at an early stage in the energy-dissipation process, where the combined effects of high energy density and Fermi motion produce the observed suprathermal spectra.

  19. Synthesis of GdAlO3:Mn(4+),Ge(4+)@Au Core-Shell Nanoprobes with Plasmon-Enhanced Near-Infrared Persistent Luminescence for in Vivo Trimodality Bioimaging.

    PubMed

    Liu, Jing-Min; Liu, Yao-Yao; Zhang, Dong-Dong; Fang, Guo-Zhen; Wang, Shuo

    2016-11-09

    The rise of multimodal nanoprobes has promoted the development of new methods to explore multiple molecular targets simultaneously or to combine various bioimaging tools in one assay to more clearly delineate localization and expression of biomarkers. Persistent luminescence nanophosphors (PLNPs) have been qualified as a promising contrast agent for in vivo imaging. The easy surface modification and proper nanostructure design strategy would favor the fabrication of PLNP-based multifunctional nanoprobes for biological application. In this paper, we have proposed novel multifunctional core-shell nanomaterials, applying the Mn(4+) and Ge(4+) co-doped gadolinium aluminate (GdAlO3:Mn(4+),Ge(4+)) PLNPs as the near-infrared persistent luminescence emission center and introducing the gold nanoshell coated on the PLNPs to enhance the luminescence efficiency via plasmon resonance. Our developed core-shell nanoprobes have demonstrated the excellent features of ultrabrightness, superlong afterglow, good monodispersity, low toxicity, and excellent biocompatibility. The well-characterized nanoprobes have been utilized for trimodality in vivo imaging, with near-infrared persistent luminescence for optical imaging, Gd element for magnetic resonance imaging, and Au element for computed tomography imaging.

  20. LaMgX and CeMgX (X = Ga, In, Tl, Pd, Ag, Pt, Au) with ZrNiAl type structure - A systematic view on electronic structure and chemical bonding

    NASA Astrophysics Data System (ADS)

    Matar, Samir F.; Etourneau, Jean; Pöttgen, Rainer

    2015-05-01

    The intermetallic magnesium compounds LaMgX and CeMgX (X = Ga, In, Tl, Pd, Ag, Pt, Au) crystallize with the hexagonal ZrNiAl type structure, space group P 6 bar 2 m , with full Mg-X ordering. From density functional theory calculations carried out exemplarily on four representative compounds: LaMgX and CeMgX with X = Ga, Pd, significant differences were traced out as to the magnetism arising only for the Ce series leading to identify CeMgGa as an antiferromagnet in its ground state, in agreement with experiment. The bulk module magnitudes show the trend of harder transition metal based ternaries and the cohesive energies favor the X = Pd compounds versus X = Ga ones. Such features were clarified by examining the properties of chemical bonding which exhibit more directional bonds thanks to the Pd d states. Rationalizing the trends of charge transfers, negatively charged triel and transition element atoms are observed. The resulting chemical pictures assign these compounds as gallides and palladides.

  1. Breakup of the projectile in [sup 16]O-induced reactions on [sup 27]Al, [sup 58]Ni, and [sup 197]Au targets around 100 MeV/nucleon

    SciTech Connect

    Badala, A.; Barbera, R.; Palmeri, A.; Pappalardo, G.S. ); Riggi, F. Dipartimento di Fisica dell'Universita di Catania, Corso Italia 57, 95129 Catania )

    1993-08-01

    The spatial correlation among the four He ions coming from the disassembly of the [sup 16]O projectile on [sup 27]Al, [sup 58]Ni, and [sup 197]Au targets has been studied at 94 MeV/nucleon. Charged particles have been detected by a multielement array of plastic scintillators covering the angular domain between 3[degree] and 150[degree]. Standard relativistic kinematics has been used to reconstruct the excitation energy of the primary projectilelike nucleus ([ital E][sub PLN][sup *]). Mean values of this quantity are found independent of the target mass and the comparison with existing similar data taken at lower bombarding energies shows a saturation of [ital E][sub PLN][sup *] around 3 MeV/nucleon. An event-by-event analysis has been performed in order to study the distributions of some global variables such as coplanarity, sphericity, and relative angle, helpful in the understanding of the topological characteristics of the process and in the evaluation of its time scale. Experimental data have also been compared with the results of Monte Carlo simulations based on different reaction mechanisms and it is possible to conclude that sequential emission of the fragments is preferred.

  2. Interfacial charge-induced polarization switching in Al{sub 2}O{sub 3}/Pb(Zr,Ti)O{sub 3} bi-layer

    SciTech Connect

    Kim, Yu Jin; Park, Min Hyuk; Jeon, Woojin; Kim, Han Joon; Moon, Taehwan; Lee, Young Hwan; Kim, Keum Do; Hyun, Seung Dam; Hwang, Cheol Seong

    2015-12-14

    Detailed polarization switching behavior of an Al{sub 2}O{sub 3}/Pb(Zr,Ti)O{sub 3} (AO/PZT) structure is examined by comparing the phenomenological thermodynamic model to the experimental polarization–voltage (P-V) results. Amorphous AO films with various thicknesses (2–10 nm) were deposited on the polycrystalline 150-nm-thick PZT film. The thermodynamic calculation showed that the transition from the ferroelectric-like state to the paraelectric-like state with increasing AO thickness occurs at ∼3 nm thickness. This paraelectric-like state should have exhibited a negative capacitance effect without permanent polarization switching if no other adverse effects are involved. However, experiments showed typical ferroelectric-like hysteresis loops where the coercive voltage increased with the increasing AO thickness, which could be explained by the carrier injection through the thin AO layer and trapping of the carriers at the AO/PZT interface. The fitting of the experimental P-V loops using the thermodynamic model considering the depolarization energy effect showed that trapped charge density was ∼±0.1 Cm{sup −2} and critical electric field at the Pt electrode/AO interface, at which the carrier transport occurs, was ∼±10 MV/cm irrespective of the AO thickness. Energy band model at each electrostatic state along the P-V loop was provided to elucidate correlation between macroscopic polarization and internal charge state of the stacked films.

  3. Genesis of the Au-Bi-Cu-As, Cu-Mo ± W, and base-metal Au-Ag mineralization at the Mountain Freegold (Yukon, Canada): constraints from Ar-Ar and Re-Os geochronology and Pb and stable isotope compositions

    NASA Astrophysics Data System (ADS)

    Bineli Betsi, Thierry; Lentz, David; Chiaradia, Massimo; Kyser, Kurt; Creaser, Robert A.

    2013-12-01

    The genesis of mineralized systems across the Mountain Freegold area, in the Dawson Range Cu-Au ± Mo Belt of the Tintina Au province was constrained using Pb and stable isotope compositions and Ar-Ar and Re-Os geochronology. Pb isotope compositions of sulfides span a wide compositional range (206Pb/204Pb, 18.669-19.861; 208Pb/204Pb, 38.400-39.238) that overlaps the compositions of the spatially associated igneous rocks, thus indicating a magmatic origin for Pb and probably the other metals. Sulfur isotopic compositions of sulfide minerals are broadly similar and their δ34S (Vienna-Canyon Diablo Troilite (V-CDT)) values range from -1.4 to 3.6 ‰ consistent with the magmatic range, with the exception of stibnite from a Au-Sb-quartz vein, which has δ34S values between -8.1 and -3.1 ‰. The δ34S values of sulfates coexisting with sulfide are between 11.2 and 14.2 ‰; whereas, those from the weathering zone range from 3.7 to 4.3 ‰, indicating supergene sulfates derived from oxidation of hypogene sulfides. The δ13C (Vienna Peedee Belemnite (VPDB)) values of carbonate range from -4.9 to 1.1 ‰ and are higher than magmatic values. The δ18O (V-SMOW) values of magmatic quartz phenocrysts and magmatic least-altered rocks vary between 6.2 and 10.1 ‰ and between 5.0 and 10.1 ‰, respectively, whereas altered magmatic rocks and hydrothermal minerals (quartz and magnetite) are relatively 18O-depleted (4.2 to 7.9 ‰ and -6.3 to 1.5 ‰, respectively). Hydrogen isotope compositions of both least-altered and altered igneous rock samples are D-depleted (from -133 to -161 ‰ Vienna-Standard Mean Ocean Water (V-SMOW)), consistent with differential magma degassing and/or post-crystallization exchange between the rocks and meteoric ground water. Zircon from a chlorite-altered dike has a U-Pb crystallization age of 108.7 ± 0.4 Ma; whereas, the same sample yielded a whole-rock Ar-Ar plateau age of 76.25 ± 0.53 Ma. Likewise, molybdenite Re-Os model ages range from 75.8 to

  4. In situ stress and nanogravimetric measurements during underpotential deposition of bismuth on (111)-textured Au.

    PubMed

    Stafford, G R; Bertocci, U

    2006-08-10

    The surface stress associated with the underpotential deposition (upd) of bismuth on (111)-textured Au is examined, using the wafer curvature method, in acidic perchlorate and nitrate supporting electrolyte. The surface stress is correlated to Bi coverage by independent nanogravimetric measurements using an electrochemical quartz crystal nanobalance. The mass increase measured in the presence of perchlorate is consistent with the (2 x 2) and (p x square root 3)-2Bi adlayers reported in the literature. ClO(4)(-) does not play a significant role in the upd process. The complete Bi monolayer causes an overall surface stress change of about -1.4 N m(-1). We attribute this compressive stress to the formation of Bi-Au bonds which partially satisfy the bonding requirements of the Au surface atoms, thereby reducing the tensile surface stress inherent to the clean Au surface. At higher Bi coverage, an additional contribution to the compressive stress is due to the electrocompression of the (p x square root 3)-2Bi adlayer. In nitric acid electrolyte, NO(3)(-) coadsorbs with Bi over the entire upd region but has little fundamental impact on adlayer structure and stress.

  5. Topological Insulators as Substrates for CO Oxidation Catalysis by Ultrathin Au Films

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Zhu, Wenguang; Xiao, Di; Zhang, Zhenyu

    2011-03-01

    We propose a novel application of three dimensional topological insulators (3DTIs) in heterogeneous catalysis based on first- principles calculations within density functional theory. We use a Bi 2 Se 3 substrate as the support of an ultrathin Au film, and show that the Au adatoms are strongly bound to and able to wet the surface of Bi 2 Se 3 . More importantly, we find the topological surface states of Bi 2 Se 3 are robust against Au deposition, and it can enhance the interaction between Au and CO, O2 molecules by acting as an electron bath . The present study may broaden the potential technological applications of 3DTIs, and shine some new light on the understanding of the role of surface states in heterogeneous catalysis. Supported by DMSE/BES of USDOE, USNSF, and NNSFC.

  6. Au Fixed Point Development at NRC

    NASA Astrophysics Data System (ADS)

    Dedyulin, S. N.; Gotoh, M.; Todd, A. D. W.

    2017-04-01

    Two Au fixed points filled using metal of different nominal purities in carbon crucibles have been developed at the National Research Council Canada (NRC). The primary motivation behind this project was to provide the means for direct thermocouple calibrations at the Au freezing point (1064.18°C). Using a Au fixed point filled with the metal of maximum available purity [99.9997 % pure according to glow discharge mass spectroscopy (GDMS)], multiple freezing plateaus were measured in a commercial high-temperature furnace. Four Pt/Pd thermocouples constructed and calibrated in-house were used to measure the freezing plateaus. From the calibration at Sn, Zn, Al and Ag fixed points, the linear deviation function from the NIST-IMGC reference function (IEC 62460:2008 Standard) was determined and extrapolated to the freezing temperature of Au. For all the Pt/Pd thermocouples used in this study, the measured EMF values agree with the extrapolated values within expanded uncertainty, thus substantiating the use of 99.9997 % pure Au fixed point cell for thermocouple calibrations at NRC. Using the Au fixed point filled with metal of lower purity (99.99 % pure according to GDMS), the effect of impurities on the Au freezing temperature measured with Pt/Pd thermocouple was further investigated.

  7. PHENIX results on jets in d + Au

    NASA Astrophysics Data System (ADS)

    Hanks, J. Ali

    2016-12-01

    We present recently published results [A. Adare, et al., arxiv:arXiv:1509.04657] on fully reconstructed R=0.3 anti-kt jets measured in p+p and d+Au collisions at 200 GeV center-of-mass energy. The jet yields for four centrality classes along with the p+p reference are presented, as well as both the minimum bias RdAu and centrality dependent RdAu and RCP. We find that while the minimum bias RdA is consistent with unity, providing a strong constraint on models including cold-nuclear-matter effects or energy loss in small systems, the centrality dependent RdAu show a striking variation which presents a challenge to models attempting to describe the interplay between soft and hard processes in these systems.

  8. Size Dependent Plasmonic Effect on BiVO4 Photoanodes for Solar Water Splitting

    PubMed Central

    Zhang, Liwu; Herrmann, Lars O.; Baumberg, Jeremy J.

    2015-01-01

    Plasmonic nanostructures show great promise in enhancing the solar water splitting efficiency due to their ability to confine light to extremely small volumes inside semiconductors. While size plays a critical role in the plasmonic performance of Au nanoparticles (AuNPs), its influence on plasmon-assisted water splitting is still not fully understood. This holds especially true for low band gap semiconductors, for which interband excitations occur in wavelength regions that overlap with plasmonic resonances. Here, BiVO4 films are modified with AuNPs of diameters varying from 10 to 80 nm to study the size dependence of the plasmonic effect. Plasmon resonance energy transfer (PRET) is found to be the dominant effect in enhancing the water splitting efficiency of BiVO4. “Hot electron” injection effect is weak in the case of BiVO4/AuNP. This is attributed to the interband excitation of BiVO4, which is unfavourable for the hot electrons accumulation in BiVO4 conduction band. The resonant scattering effect also contributes to the enhanced water splitting efficiency for the larger diameter AuNPs. It is also for the first time found that higher PRET effect can be achieved at larger off-normal irradiation angle. PMID:26581942

  9. First-principles electronic structure of the delafossites ABO 2 (A=Cu, Ag, Au; B=Al, Ga, Sc, In, Y): evolution of d 10-d 10 interactions

    NASA Astrophysics Data System (ADS)

    Kandpal, Hem Chandra; Seshadri, Ram

    2002-08-01

    While bonding between d 10 atoms and ions in molecular systems has been well studied, less attention has been paid to interactions between such seemingly closed shell species in extended inorganic solids. In this contribution, we present visualizations of the electronic structures of the delafossites ABO 2 (A = Cu, Ag, Au) with particular emphasis on the nature of d 10-d 10 interactions in the close packed plane of the coinage metal ion. We find that on going from Cu to Ag to Au, the extent of bonding between A and A increases. However, the structures (in terms of distances) of these compounds are largely determined by the strongly ionic B IIIO interaction and for the larger B ions Sc, In and Y, the A atoms are sufficiently well-separated that AA bonding is almost negligible. We also analyze some interesting differences between Ag and Au, including the larger AO covalency of the Au. The trends in electronic structure suggest that the Ag and Au compounds are not good candidate transparent conducting oxides.

  10. Pt, Au and Ag Electrodes on BiCuVOx

    DTIC Science & Technology

    2007-11-02

    the stabilized zirconia’s or t.%_*O ceria’s. In its behaviour many smilarities are found with the ,Electrolyte 0 doped-bismuth oxide /gold electrode...Aircraft Subsystem, Chemistry, Materials, oxygen pump, porous electrode, oxygen ion conductivity, 16. PRICE CODE oxide electrode N/A 17. SECURITY...electrodes is characterised by considerable hysteresis in the I-V curves. The observed behaviour can well be explained by the occurrance of a change

  11. From the ternary Eu(Au/In)2 and EuAu4(Au/In)2 with remarkable Au/In distributions to a new structure type: The gold-rich Eu5Au16(Au/In)6 structure

    DOE PAGES

    Steinberg, Simon; Card, Nathan; Mudring, Anja -Verena

    2015-08-13

    The ternary Eu(Au/In)2 (EuAu0.46In1.54(2)) (I), EuAu4(Au/In)2 (EuAu4+xIn2–x with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squaredmore » Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2–“EuAu4In2”. The site preferences of the disordered Au/In positions in II were investigated for different hypothetical “EuAu4(Au/In)2” models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au–In contacts. Furthermore, a chemical bonding analysis on two “EuAu5In” and “EuAu4In2” models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems.« less

  12. Strategic BI for All

    ERIC Educational Resources Information Center

    Raths, David

    2008-01-01

    Implementing a complex business intelligence (BI) system at a small school or one with limited resources can seem daunting. For small to midsize schools and community colleges, a strategic BI initiative may still be an elusive goal. This article discusses how schools with limited resources are making the dream a reality.

  13. Caractérisation au-dessous du seuil de doubles hétérostructures lasers GaInAsSb/GaAlAsSb émettant vers 2,37 μm

    NASA Astrophysics Data System (ADS)

    Leclercq, J. L.; Grunberg, P.; Boissier, G.; Fouillant, C.; Sadik, S.; Martin, P.; Lazzari, J. L.; Joullié, A. M.; Joullié, A.

    1993-10-01

    Planar stripe gain-guided laser diodes have been prepared from Ga{0.77}In{0.23}As{0.20}Sb{0.80}/Ga{0.53}Al{0.47}As{0.04}Sb{0.96} double-heterostructures grown by liquid phase epitaxy on GaSb (100) oriented. The emission wavelength is 2.1 μm at 80 K (in continuous mode) and 2.37 μm at 292 K (in pulsed mode) with threshold current ≈265 mA at 80 K and 4 A at room temperature. The analysis of the spontaneous emitted power versus the injection current allowed us at 292 K to determine, in the case of low injection, the non radiative lifetime that accounts for non radiative recombination via levels in the bulk of the active region and at the interfaces tau_nr≈ 4{-}5 ns, and for higher injection the Auger recombination coefficient C ≈ 1.1 × 10^{-28} cm^6/s. A study of the optical gain from the emitted wavelength spectra gave us the linewidth enhancement factor of the laser diode α = 3.8 ± 1.3 at the lasing wavelength at 80 K. Des diodes lasers planars à ruban à guidage par le gain ont été préparées à partir de la double hétérostructure Ga{0,77}In{0,23}As{0,20}Sb{0,80}/Ga{0,53}Al{0,47}As{0,04}Sb{0,96} obtenue par épitaxie en phase liquide sur substrat GaSb orienté (100). Ces diodes émettent vers 2,1 μm à 80 K en régime continu et vers 2,37 μm à 292 K en régime pulsé avec des courants de seuil proches de 265 mA à 80 K et de 4 A à température ambiante. L'analyse de la puissance spontanée émise en fonction du courant d'injection a permis à 292 K de déterminer, à faible injection, la durée de vie non radiative de recombinaison sur centres profonds tau_nr≈ 4{-}5 ns et à plus forte injection le coefficient de recombinaison Auger C ≈ 1,1 × 10^{-28} cm^6/s. Une étude du gain optique à partir des spectres d'émission a permis de déterminer le paramètre d'élargissement de raie au seuil α = 3,8 ± 1,3 à 80 K.

  14. Structural stability of ternary C22–Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds

    SciTech Connect

    Colinet, Catherine; Crivello, Jean-Claude; Tedenac, Jean-Claude

    2013-09-15

    The crystal and electronic structures, and the thermodynamic properties of Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe{sub 2}P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr{sub 6}Sb{sub 2}Co compound. Display Omitted - Highlights: • Structural stability of Zr{sub 6}X{sub 2}T′ compounds (X: p element, T′: late transition metal) in the Fe{sub 2}P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

  15. The characteristics of solar wind magnetic field during the negative-AU and large-AU (>1200nT) events

    NASA Astrophysics Data System (ADS)

    Lyu, L. H.; Kao, W.

    2014-12-01

    The negative-AU events are relatively unusual, which have caught our attention. To understand the cause of negative AU, we first eliminate the ring-current effect by considering only the events with AUAU has strong negative Bz and By components during these negative-AU events. We also found that one of the negative AU events has been reported by Feldstein et al. (2006). They associated the enhancement of westward electric jet by the negative IMF-By component based on previous models obtained independently by Friis-Christensen et al. (1972) and Sumaruk & Feldstein (1973). Enhancement of electric jet in opposite direction is expected to be found when the IMF-By is positive. To verify their models we also examine the strong AU events with AU > 1200nT. We found that these large-AU events are associated with IMF-Bz<0 and IMF-By >0. Both negative-AU and large-AU events tend to occur during the beginning of the main phase of a strong magnetic storm with Kp= 7~9. The enhancement of Cowling electrojet has been proposed by Kan et al. (2011) for the triggering of substorm onset. We will discuss the possibility that a similar enhancement process might take place in the dayside auroral oval during these extreme AU events.

  16. Overlayer effects on perpendicular magnetic anisotropy in Co/Au/Cu films

    NASA Astrophysics Data System (ADS)

    Lee, Sukmock; Park, Sungkyun; Falco, Charles M.

    2001-03-01

    We have performed Brillouin light scattering measurements to investigate the effect on the perpendicular magnetic anisotropy (PMA) of overlayers on ultra--thin Co films prepared by Molecular Beam Epitaxy. The overlayer materials used for these studies were Al and Au. We observed a systematic decrease in PMA when using Al instead of Au overlayers, and will present results of the uniaxial anisotropies of the films as a function of Au underlayer thickness. In addition, we found the unexpected result that the PMA is significantly reduced when an Au overlayer of 3.5 nm is covered by an extra Al capping layer. The amount of this reduction depends on the thickness of the Al layer. We speculate that misfit strain at the interface between the Al and the Au can be propagated through the Au layer to affect the magnetic properties of Co.

  17. Interfacial Microstructure Evolution and Shear Behavior of Au-Sn/Ni- xCu Joints at 350°C

    NASA Astrophysics Data System (ADS)

    Peng, J.; Wang, R. C.; Wang, M.; Liu, H. S.

    2017-04-01

    Interfacial reaction and shear behavior of the joints between Au-29Sn (at.%) solder and Ni- xCu ( x = 20 at.%, 40 at.%, 60 at.%, and 80 at.%) substrate alloys soldered at 350°C for various durations were investigated in this study. The results show that α(Au) is the common reaction product at the solder/substrate interfaces after a short-time reaction regardless of Cu content. As soldering goes on, another new Ni3Sn2 layer forms at the interface company with ordering of the α(Au) phase, AuCu I/Ni3Sn2 bi-layers formed at the Au-Sn/Ni-20Cu interface, or with AuCu III/Ni3Sn2 bi-layers at the Au-Sn/Ni-40Cu interface. If the content of Cu in the substrate is higher than 40 at.%, periodic layered structure and discontinuous Ni3Sn2 layers appear. In the couple of Au-Sn/Ni-60Cu, AuCu I + AuCu III/Ni3Sn2/α(Au) can be observed while AuCu3/Ni3Sn2/α(Au) forms in the couple of Au-Sn/Ni-80Cu. Shear fracture always occurs in the region near the Ni-20Cu substrate in Au-Sn/Ni-20Cu joints, whereas it appears in the reaction layer for the joint of higher Cu content. The shear strength of Au-Sn/Ni-60Cu and Au-Sn/Ni-80Cu joints achieves about 55 MPa as α(Au) phase forms but decreases remarkably due to pore formation after soldering for a long duration. Whereas, the shear strength of Au-Sn/Ni-40Cu joints can reach 62 MPa as the α(Au) phase forms at an early stage, and maintains above 52 MPa even soldered for a long duration because of the adequate thick α(Au) and AuCu III layer adjacent to substrate provides good bonding. The reason why the soldering joint of Au-Sn/Ni-40Cu possesses higher strength and a better stability exists is that high Ni concentration in α(Au) and the continuous Ni3Sn2 layer inhibit formation of Kirkendall pores.

  18. Spin transport in Au films: An investigation by spin pumping

    NASA Astrophysics Data System (ADS)

    Montoya, Eric; Kardasz, Bartek; Burrowes, Capucine; Huttema, Wendell; Girt, Erol; Heinrich, Bret

    2012-04-01

    The thickness and temperature dependence of spin transport in Au has been investigated in multilayer films via the spin pumping effect. To study spin transport in Au, single layer GaAs/16Fe/(d)Au(001) and double layer GaAs/16Fe/(d)Au/12Fe/20Au(001) were investigated using ferromagnetic resonance (FMR), where d = 20, 300, and the numerals preceding Fe and Au indicate the layer thickness in atomic layers (AL). FMR measurements were performed at frequencies ranging from 27.3 to 40.6 GHz and at temperatures ranging from 88 to 295 K. By measuring the total Gilbert damping in the 16Fe layer as a function of d and temperature for both single and double magnetic layer structures and by utilizing the spin diffusion equation, one is able to determine the spin mixing conductance, g↑↓, at the Fe/Au interface, and the spin flip relaxation time, τsf, in Au as a function of temperature. The temperature dependence of the momentum relaxation time, τm, in Au was measured independently by means of electron transport measurements in a van der Pauw configuration. It has been found that the spin flip relaxation time, τsf, in Au is dominated by phonon interactions.

  19. Exploratory Bi-Factor Analysis

    ERIC Educational Resources Information Center

    Jennrich, Robert I.; Bentler, Peter M.

    2011-01-01

    Bi-factor analysis is a form of confirmatory factor analysis originally introduced by Holzinger. The bi-factor model has a general factor and a number of group factors. The purpose of this article is to introduce an exploratory form of bi-factor analysis. An advantage of using exploratory bi-factor analysis is that one need not provide a specific…

  20. Discovery of FeBi2

    PubMed Central

    2016-01-01

    Recent advances in high-pressure techniques offer chemists access to vast regions of uncharted synthetic phase space, expanding our experimental reach to pressures comparable to the core of the Earth. These newfound capabilities enable us to revisit simple binary systems in search of compounds that for decades have remained elusive. The most tantalizing of these targets are systems in which the two elements in question do not interact even as molten liquids—so-called immiscible systems. As a prominent example, immiscibility between iron and bismuth is so severe that no material containing Fe–Bi bonds is known to exist. The elusiveness of Fe–Bi bonds has a myriad of consequences; crucially, it precludes completing the iron pnictide superconductor series. Herein we report the first iron–bismuth binary compound, FeBi2, featuring the first Fe–Bi bond in the solid state. We employed geologically relevant pressures, similar to the core of Mars, to access FeBi2, which we synthesized at 30 GPa and 1500 K. The compound crystallizes in the Al2Cu structure type (space group I4/mcm) with a = 6.3121(3) Å and c = 5.4211(4) Å. The new binary intermetallic phase persists from its formation pressure of 30 GPa down to 3 GPa. The existence of this phase at low pressures suggests that it might be quenchable to ambient pressure at low temperatures. These results offer a pathway toward the realization of new exotic materials. PMID:27924316

  1. Double exponential I-V characteristics and double Gaussian distribution of barrier heights in (Au/Ti)/Al2O3/ n-GaAs (MIS)-type Schottky barrier diodes in wide temperature range

    NASA Astrophysics Data System (ADS)

    Güçlü, Çiğdem Ş.; Özdemir, Ahmet Faruk; Altindal, Şemsettin

    2016-12-01

    In this study, current conduction mechanisms of the sample (Au/Ti)/Al2O3/ n-GaAs were investigated in detail using current-voltage (I-V) measurements in the temperature range of 80-380 K. The semilogarithmic I-V plots reveal two distinct linear regions with different slopes between 0.07-0.30 and 0.30-0.69 V which are called as Region I (RI) and Region II (RII), respectively. The ideality factor ( n) and zero-bias barrier height (Φ_{{bo}}) were found to be strong functions of temperature and voltage. In both regions, as the temperature increases, Φ_{{bo}} increases, whereas the value of n decreases. The high value of n at low temperatures is an evidence of deviation from thermionic emission, and it cannot be explained solely by tunneling mechanism, the existence of surface states and interfacial layer. Therefore, the Φ_{{bo}} versus q/kT plots were drawn for two linear regions of lnI-V plots, and these plots also revealed two distinct linear regions with different slopes between two temperature regions of 80-170 and 200-380 K which are called as low- and high-temperature range (LTR and HTR), respectively. Such behavior of these plots confirmed the existence of double Gaussian distribution (DGD) in the samples which in turn has mean barrier heights bar{Φ}_{{bo}} and standard deviations ( σ s). These values were obtained from the intercept and slope of these plots as 0.38 eV and 0.061 V for LTR and as 0.88 eV and 0.142 V for HTR (in RI), whereas they were obtained as 0.37 eV and 0.061 V for LTR and as 0.92 eV and 0.148 V for HTR (in RII), respectively. Thus, the modified ln( I s/ T 2)- q 2 σ s 2 /2 k 2 T 2 versus q/ kT plots were drawn, and the values of (bar{Φ}_{{bo}}) and effective Richardson constant ( A *) were extracted from the intercept and slope of these plots as 0.39 eV and 7.07 A/cm2 K2 for LTR and as 0.92 eV and 8.158 A/cm2 K2 for HTR (in RI), whereas they were extracted as 0.38 eV and 7.92 A/cm2 K2 for LTR and as 0.94 eV and 4.66 A/cm2 K2 for HTR

  2. Stability of crystalline solids—II: Application to temperature-induced martensitic phase transformations in a bi-atomic crystal

    NASA Astrophysics Data System (ADS)

    Elliott, Ryan S.; Shaw, John A.; Triantafyllidis, Nicolas

    2006-01-01

    This paper applies the stability theory of crystalline solids presented in the companion paper (Part I) to the study of martensitic transformations found in shape memory alloys (SMA's). The focus here is on temperature-induced martensitic transformations of bi-atomic crystals under stress-free loading conditions. A set of temperature-dependent atomic potentials and a multilattice description are employed to derive the energy density of a prototypical SMA ( B2 cubic austenite crystal). The bifurcation and stability behavior are then investigated with respect to two stability criteria (Cauchy-Born (CB) and phonon). Using a 4-lattice description five different equilibrium crystal structures are predicted: B2 cubic, L10 tetragonal, B19 orthorhombic, Cmmm orthorhombic, and B19' monoclinic. For our chosen model only the B2 and B19 equilibrium paths have stable segments which satisfy both the CB- and phonon-stability criteria. These stable segments overlap in temperature indicating the possibility of a hysteretic temperature-induced proper martensitic transformation. The B2 and B19 crystal structures are common in SMA's and therefore the simulated jump in the deformation gradient at a temperature for which both crystals are stable is compared to experimental values for NiTi, AuCd, and CuAlNi. Good agreement is found for the two SMA's which have cubic to orthorhombic transformations (AuCd and CuAlNi).

  3. High energy, low temperature gelled bi-propellant formulation

    NASA Technical Reports Server (NTRS)

    Di Salvo, Roberto (Inventor)

    2011-01-01

    The present invention is a bi-propellant system comprising a gelled liquid propane (GLP) fuel and a gelled MON-30 (70% N.sub.2O.sub.4+30% NO) oxidizer. The bi-propellant system is particularly well-suited for outer planet missions greater than 3 AU from the sun and also functions in earth and near earth environments. Additives such as powders of boron, carbon, lithium, and/or aluminum can be added to the fuel component to improve performance or enhance hypergolicity. The gelling agent can be silicon dioxide, clay, carbon, or organic or inorganic polymers. The bi-propellant system may be, but need not be, hypergolic.

  4. Plasmonic Bi metal as cocatalyst and photocatalyst: The case of Bi/(BiO)2CO3 and Bi particles.

    PubMed

    Sun, Yanjuan; Zhao, Zaiwang; Zhang, Wendong; Gao, Chunfeng; Zhang, Yuxin; Dong, Fan

    2017-01-01

    Semimetal bismuth with plasmonic properties has triggered increased interests. In this work, a facile strategy was developed to synthesize the Bi/(BiO)2CO3 (Bi-BOC) nanocomposites and Bi elemental photocatalysts. The Bi nanoparticles were produced via the insitu reduction of (BiO)2CO3 by NaBH4. The catalysts were utilized for the photocatalytic NO removal under visible light and UV illumination. Significantly, the photocatalytic capability of the Bi-BOC was highly enhanced with an unprecedented NO removal of 63.6%. The Bi metal demonstrated a direct plasmonic photocatalytic NO removal ratio of 53.6% under UV irradiation. The significantly enhanced photocatalytic capability of Bi-BOC can be ascribed to the synergistic effects of the SPR effect, enhanced visible-light-harvesting and the efficient electron-hole separation induced by Bi nanoparticles. The Bi nanoparticles can perform as a non-noble metal-based plasmonic cocatalyst for advancing photocatalytic ability. The mechanism of photocatalytic NO oxidation was proposed and compared under both visible light and UV illumination. Furthermore, the Bi-BOC photocatalysts showed good photochemical stability under repeated tests. This work could not only offer new insights into in-situ fine-tune reduction strategy for Bi-based photocatalysts, but also proves the potentials of utilizing low cost Bi cocatalysts as a substitute for noble metals to improve other photocatalysts.

  5. Kinetics and thermodynamics associated with Bi adsorption transitions at Cu and Ni grain boundaries

    SciTech Connect

    Tai, Kaiping; Feng, Lin; Dillon, Shen J.

    2013-05-21

    The grain boundary diffusivity of Au in Cu and Cu-Bi, and Cu in Ni and Ni-Bi are characterized by secondary ion mass spectroscopy depth profiling. Samples are equilibrated in a Bi containing atmosphere at temperatures above and below the onset of grain boundary adsorption transitions, sometimes called complexion transitions. A simple thermo-kinetic model is used to estimate the relative entropic contributions to the grain boundary energies. The results indicate that the entropy term plays a major role in promoting thermally and chemically induced grain boundary complexion transition.

  6. Enhancement of photocatalytic activity over Bi2O3/black-BiOCl heterojunction

    NASA Astrophysics Data System (ADS)

    Kim, Dahye; Jung, Dongwoon

    2017-04-01

    Several Bi2O3/BiOCl heterojunction compounds with different Bi2O3/BiOCl ratios were prepared by treating Bi2O3 with HCl. Within the Bi2O3/BiOCl heterojunction, white BiOCl was turned into black by thermal treatment. Upon the result, Bi2O3/black-BiOCl heterojunction could be prepared. The photocatalytic activities of samples were tested depending upon the Bi2O3/BiOCl ratio. Basically, Bi2O3/black-BiOCl samples showed advanced photocatalytic activity compared with the original Bi2O3/white-BiOCl. The highest photocatalytic efficiency was found in the Bi2O3/black-BiOCl when Bi2O3/BiOCl ratio was 15/85.

  7. Formation and stability of dense arrays of Au nanoclusters on hexagonal boron nitride/Rh(111)

    NASA Astrophysics Data System (ADS)

    Patterson, Matthew C.; Habenicht, Bradley F.; Kurtz, Richard L.; Liu, Li; Xu, Ye; Sprunger, Phillip T.

    2014-05-01

    We have studied the nucleation and growth of Au clusters at submonolayer and greater coverages on the h-BN nanomesh grown on Rh(111) by means of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). STM reveals that submonolayer Au deposited at 115 K nucleates within the nanomesh pores and remains confined to the pores even after warming to room temperature. Whereas there is a propensity of monoatomic high islands at low temperature, upon annealing, bi- and multilayer Au clusters emerge. Deposition of higher coverages of Au similarly results in Au clusters primarily confined to the nanomesh pores at room temperature. XPS analysis of core-level electronic states in the deposited Au shows strong final-state effects induced by restricted particle size dominating for low Au coverage, with indications that larger Au clusters are negatively charged by interaction through the h-BN monolayer. DFT calculations suggest that the structure of the Au clusters transitions from monolayer to bilayer at a size between 30 and 37 atoms per cluster, in line with our experiment. Bader charge analysis supports the negative charge state of deposited Au.

  8. Fabrication of Bi-doped In2O3-ITO nanocomposites and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Gil Na, Han; Jung, Taek-Kyun; Lee, Ji-Woon; Hyun, Soong-Keun; Kwon, Yong Jung; Mirzaei, Ali; Kim, Tae-Bum; Shin, Young-Chul; Choi, Ho-Joon; Kim, Hyoun Woo; Jin, Changhyun

    2016-09-01

    For the first time, Bi-doped In2O3-indium tin oxide (ITO) nanocomposites were prepared on Si substrates with the assistance of a Au catalyst through the simple gas-phase transport of a mixture of Bi, In, and Sn powders. The square-shaped Bi-doped In2O3-ITO nanostructures were straight, a few hundreds of nanometres in width, and below a few tens of micrometres in length. Electron microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy analyses indicated that the Bi-doped In2O3-ITO nanorods were single crystals with a basis of cubic In2O3 structures. The photoluminescence spectra revealed that the Bi-doped In2O3-ITO nanorods had a strong orange emission band centred at approximately 626 nm without any shoulder bands. The enhancement of orange emission might be due to the oxygen deficiencies of structural defects in the nanorods.

  9. Gold Apes Hydrogen. The Structure and Bonding in the Planar B7Au2- and B7Au2 Clusters

    SciTech Connect

    Zhai, Hua JIN.; Wang, Lai S.; Zubarev, Dmitry Y.; Boldyrev, Alexander I.

    2006-02-09

    We produced the B7Au2- mixed cluster and studied its electronic structure and chemical bonding using photoelectron spectroscopy and ab initio calculations. The photoelectron spectra of B7Au2- were observed to be relatively simple with vibrational resolution, in contrast to the complicated spectra observed for pure B7-, which had contributions from three isomers (Alexandrova et al., J. Phys. Chem. A, 2004, 108, 3509). Theoretical calculations show that B7Au2- possesses an extremely stable planar structure, identical to that of B7H2-, demonstrating that Au mimics H in its bonding to boron, analogous to the Au-Si bonding. The ground state structure of B7Au2- (B7H2-) can be viewed as adding two Au (H) atoms to the terminal B atoms of a higher-lying planar isomer of B7-. The bonding and stability in the planar B7Au2- (B7H2-) clusters are elucidated on the basis of the strong covalent B-Au (H) bonding and the concepts of aromaticity/antiaromaticity in these systems.

  10. Ag-Al-Ca

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Ag-Al-Ca' with the content:

  11. Epitaxial integration of tetragonal BiFeO3 with silicon for nonvolatile memory applications

    NASA Astrophysics Data System (ADS)

    Zhu, Jingbin; Yin, Zhigang; Fu, Zhen; Zhao, Yajuan; Zhang, Xingwang; Liu, Xin; You, Jingbi; Li, Xingxing; Meng, Junhua; Liu, Heng; Wu, Jinliang

    2017-02-01

    Ferroelectric field-effect transistor has long been considered as a promising nonvolatile memory technology, but its application is limited by the poor scalability. Here we show that this problem can be solved by epitaxially integrating tetragonal BiFeO3, a stress-induced metastable phase which exhibits remarkably low dielectric permittivity and high coercive field, on the silicon platform. Tetragonal BiFeO3 was stabilized on (001)-oriented silicon by using Bi2SiO5, which is chemically and structurally compatible with both silicon and tetragonal BiFeO3, as the buffer layer. Unlike the commonly observed MC structure, the obtained BiFeO3 layer exhibits a true tetragonal symmetry. An unprecedented high memory window of 6.5 V was observed for the Au/BiFeO3/Bi2SiO5/Si capacitor with BiFeO3 thickness of 135 nm. The epitaxial integration of tetragonal BiFeO3 with silicon may pave a possible avenue for nanosized, power-efficient ferroelectric nonvolatile memories.

  12. Partial Melt Processing of Solid-Solution Bi2Sr2CaCu2O8+delta Thick-Film Conductors with Nanophase Al2O3 Additions

    DTIC Science & Technology

    2006-04-01

    range of partial-melt temperatures. Results were compared to Al2O3-free films with compositions lying within the single-phase solid - solution 2212 region...Nanophase Al2O3 reacted with 2212-type precursors to form a composite of micron size or smaller particles of solid - solution (Sr,Ca)3Al2O6 in a solid ... solution 2212 superconducting matrix. The Ca content of the (Sr,Ca)3Al2O6 in a solid - solution 2212 superconducting matrix. The Ca content of the (Sr,Ca

  13. Interfacing 2D and 3D Topological Insulators: Bi(111) Bilayer on Bi2Te3

    NASA Astrophysics Data System (ADS)

    Hirahara, Toru; Bihlmayer, Gustav; Sakamoto, Yusuke; Yamada, Manabu; Miyazaki, Hidetoshi; Kimura, Shin-Ichi; Blügel, Stefan; Hasegawa, Shuji

    2012-02-01

    Topological insulators (TI) are insulating materials but have metallic edge states that carry spin currents and are robust against nonmagnetic impurities [1]. While there have been a large number of reports on three-dimensional (3D) TI, only few works have been done in terms of two-dimensional (2D) TI. In the present paper, we report the successful formation of bilayer Bi, which was theoretically predicted to be a 2D TI [2]. We deposited bilayer Bi on a 3D TI Bi2Te3, which the lattice mismatch is very small. From angle-resolved photoemission spectroscopy measurements and ab initio calculations, the electronic structure of the system can be understood as an overlap of the band dispersions of bilayer Bi and Bi2Te3. Our results show that the Dirac cone is actually robust against nonmagnetic perturbations and imply a unique situation where the topologically protected one- and two-dimensional edge states are coexisting at the surface [3]. [0pt] [1] M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010).[0pt] [2] S. Murakami, Phys. Rev. Lett. 97, 236805 (2006).[0pt] [3] T. Hirahara et al., Phys. Rev. Lett. 107, 166801 (2011).

  14. Relativistic multireference many-body perturbation theory calculations on Au64+ - Au69+ ions

    SciTech Connect

    Vilkas, M J; Ishikawa, Y; Trabert, E

    2006-03-31

    Many-body perturbation theory (MBPT) calculations are an adequate tool for the description of the structure of highly charged multi-electron ions and for the analysis of their spectra. They demonstrate this by way of a re-investigation of n=3, {Delta}n=0 transitions in the EUV spectra of Na-, Mg-, Al-like, and Si-like ions of Au that have been obtained previously by heavy-ion accelerator based beam-foil spectroscopy. They discuss the evidence and propose several revisions on the basis of the multi-reference many-body perturbation theory calculations of Ne- through P-like ions of Au.

  15. Spin resonance transport properties of a single Au atom in S-Au-S junction and Au-Au-Au junction

    NASA Astrophysics Data System (ADS)

    Fangyuan, Wang; Guiqin, Li

    2016-07-01

    The spin transport properties of S-Au-S junction and Au-Au-Au junction between Au nanowires are investigated with density functional theory and the non-equilibrium Green's function. We mainly focus on the spin resonance transport properties of the center Au atom. The breaking of chemical bonds between anchor atoms and center Au atom significantly influences their spin transmission characteristics. We find the 0.8 eV orbital energy shift between anchor S atoms and the center Au atom can well protect the spin state stored in the S-Au-S junction and efficiently extract its spin state to the current by spin resonance mechanism, while the spin interaction of itinerant electrons and the valence electron of the center Au atom in the Au-Au-Au junction can extract the current spin information into the center Au atom. Fermi energy drift and bias-dependent spin filtering properties of the Au-Au-Au junction may transform information between distance, bias, and electron spin. Those unique properties make them potential candidates for a logical nanocircuit. Project supported by the National Basic Research Program of China (Grants No. 2011CB921602) and the National Natural Science Foundation of China (Grants No. 20121318158).

  16. Crystal structure and electronic properties of a thiolate-protected Au24 nanocluster

    NASA Astrophysics Data System (ADS)

    Das, Anindita; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Rosi, Nathaniel L.; Jin, Rongchao

    2014-05-01

    Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''.Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''. Electronic supplementary information (ESI) available: Experimental and supporting Fig. S1-S3. CCDC NUMBER(1000102). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr01350f

  17. Suitability of Au- and self-assisted GaAs nanowires for optoelectronic applications.

    PubMed

    Breuer, Steffen; Pfüller, Carsten; Flissikowski, Timur; Brandt, Oliver; Grahn, Holger T; Geelhaar, Lutz; Riechert, Henning

    2011-03-09

    The incorporation of Au during vapor-liquid-solid nanowire growth might inherently limit the performance of nanowire-based devices. Here, we assess the material quality of Au-assisted and Au-free grown GaAs/(Al,Ga)As core-shell nanowires using photoluminescence spectroscopy. We show that at room temperature, the internal quantum efficiency is systematically much lower for the Au-assisted nanowires than for the Au-free ones. In contrast, the optoelectronic material quality of the latter is comparable to that of state-of-the-art planar double heterostructures.

  18. BI Project Success

    ERIC Educational Resources Information Center

    Tracey, Graham; Riha, James

    2009-01-01

    Managing business intelligence (BI) projects in higher education is a formidable responsibility that challenges even the most experienced technical project managers. Data source dependencies, uncertain data quality, changing information requirements, and urgency for actionable information are but a few examples among the multitude of challenges.…

  19. The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits

    NASA Astrophysics Data System (ADS)

    Deditius, Artur P.; Reich, Martin; Kesler, Stephen E.; Utsunomiya, Satoshi; Chryssoulis, Stephen L.; Walshe, John; Ewing, Rodney C.

    2014-09-01

    The ubiquity of Au-bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of Au and As in this sulfide occurs under a wide range of physico-chemical conditions. Despite significant advances in the last 20 years, fundamental factors controlling Au and As ratios in pyrite from ore deposits remain poorly known. Here we explore these constraints using new and previously published EMPA, LA-ICP-MS, SIMS, and μ-PIXE analyses of As and Au in pyrite from Carlin-type Au, epithermal Au, porphyry Cu, Cu-Au, and orogenic Au deposits, volcanogenic massive sulfide (VHMS), Witwatersrand Au, iron oxide copper gold (IOCG), and coal deposits. Pyrite included in the data compilation formed under temperatures from ∼30 to ∼600 °C and in a wide variety of geological environments. The pyrite Au-As data form a wedge-shaped zone in compositional space, and the fact that most data points plot below the solid solubility limit defined by Reich et al. (2005) indicate that Au1+ is the dominant form of Au in arsenian pyrite and that Au-bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native Au. The analytical data also show that the solid solubility limit of Au in arsenian pyrite defined by an Au/As ratio of 0.02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal-chemical properties of pyrite and post-depositional alteration. Compilation of Au-As concentrations and formation temperatures for pyrite indicates that Au and As solubility in pyrite is retrograde; Au and As contents decrease as a function of increasing temperature from ∼200 to ∼500 °C. Based on these results, two major Au-As trends for Au-bearing arsenian pyrite from ore deposits are defined. One trend is formed by pyrites from Carlin-type and orogenic Au deposits where compositions are largely controlled by fluid-rock interactions and/or can be highly perturbed by changes in temperature and

  20. Solid-Phase Equilibria in the Au-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries.

    DTIC Science & Technology

    1986-02-28

    AD6i5 469 SOLID- PHASE EQUILIBRIA IN THE Ru-As AU-GA-SB AU-IN-AS- 1/17 AND AU-IN-SB TERNAR (U) CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY AND...REPORT & PERIOD COVERED SOLID- PHASE EQUILIBRIA IN THE Au-Ga-As, Au-Ga-Sb Thchnical Report Au-In-As, and Au-In-Sb TEARIEIS S. PERFORMING ORG. REPORT NUMBER...CLASSIFICATION OF THIS PAGEMI*n Does Entepd) 4./ lie- . .- - - - - -- -- Solid Phase Equilibria in the Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries C

  1. Fahrzeug-Außengeräusch

    NASA Astrophysics Data System (ADS)

    Genuit, Klaus

    Wirtschaftliches Wachstum ist mit steigenden Anforderungen an Mobilität und Transport verknüpft. Zukunftsorientierter Fortschritt muss hierbei die Wirkungen von Verkehrsgeräuschen auf Mensch und Umwelt berücksichtigen, um eine hohe Lebensqualität sicherstellen zu können. Mehr als die Hälfte der Bevölkerung in der EU fühlt sich durch Verkehrslärm belästigt oder befürchtet direkte Auswirkungen auf Gesundheit und Wohlbefinden. Nach einer repräsentativen Umfrage des Umweltbundesamtes fühlen sich durch Straßenverkehrslärm 20 % der Bevölkerung stark oder wesentlich belästigt (UBA 2008). Daher ist das "Fahrzeug-Außengeräusch“ Gegenstand zahlreicher Forschungsprojekte zu Themen wie Identifikation wesentlicher Geräuschquellen, Zusammenhang zwischen Verkehrsgeräusch und Belästigung, medizinische Folgen aufgrund chronischer Lärmexposition, Geräuschqualität, Entwicklung neuer Methoden und Technologien zur Fahrzeug-Außengeräuschmessung und das Fahrzeug-Außengeräusch als wesentliches Produktattribut, das aktiver Gestaltung bedarf.

  2. Non-linear Electrical Characteristics of ZnO Modified by Trioxides Sb2O3, Bi2O3, Fe2O3, Al2O3 and La2O3

    NASA Astrophysics Data System (ADS)

    Mekap, Anita; Das, Piyush R.; Choudhary, R. N. P.

    2016-08-01

    The non-linear behavior of polycrystalline-ZnO-based voltage-dependent resistors is considered in the present study. A high-temperature solid-state reaction route was used to synthesize polycrystalline samples of ZnO modified by small amounts of the trioxides Sb2O3, Bi2O3, Fe2O3, etc. in various proportions. X-ray diffraction and scanning electron microscopy techniques were used to study the structural and microstructural characteristics of modified ZnO. Detailed studies of non-linear phenomena of the I-V characteristics, dielectric permittivity ( ɛ r), impedance ( Z), etc. of the samples have provided many interesting results. All the samples exhibited dielectric anomaly. Non-linear variation in polarization with electric field for all the samples was observed. Moreover, significant non-linearity in the I-V characteristics was observed in the breakdown region of all the samples at room temperature. The non-linear coefficient ( α) in different cases, i.e. for I- V, ɛ r- f, ɛ r- T, and ɛ r- Z, was calculated and found to be appreciable. The frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law.

  3. Magnetoresistance of Au films

    DOE PAGES

    Zhang, D. L.; Song, X. H.; Zhang, X.; ...

    2014-12-10

    Measurement of the magnetoresistance (MR) of Au films as a function of temperature and film thickness reveals a strong dependence on grain size distribution and clear violation of the Kohler s rule. Using a model of random resistor network, we show that this result can be explained if the MR arises entirely from inhomogeneity due to grain boundary scattering and thermal activation of grain boundary atoms.

  4. From the ternary Eu(Au/In)2 and EuAu4(Au/In)2 with remarkable Au/In distributions to a new structure type: The gold-rich Eu5Au16(Au/In)6 structure

    SciTech Connect

    Steinberg, Simon; Card, Nathan; Mudring, Anja -Verena

    2015-08-13

    The ternary Eu(Au/In)2 (EuAu0.46In1.54(2)) (I), EuAu4(Au/In)2 (EuAu4+xIn2–x with x = 0.75(2) (II), 0.93(2), and 1.03(2)), and Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (III) have been synthesized, and their structures were characterized by single-crystal X-ray diffraction. I and II crystallize with the CeCu2-type (Pearson Symbol oI12; Imma; Z = 4; a = 4.9018(4) Å; b = 7.8237(5) Å; c = 8.4457(5) Å) and the YbAl4Mo2-type (tI14; I4/mmm; Z = 2; a = 7.1612(7) Å; c = 5.5268(7) Å) and exhibit significant Au/In disorder. I is composed of an Au/In-mixed diamond-related host lattice encapsulating Eu atoms, while the structure of II features ribbons of distorted, squared Au8 prisms enclosing Eu, Au, and In atoms. Combination of these structural motifs leads to a new structure type as observed for Eu5Au16(Au/In)6 (Eu5Au17.29In4.71(3)) (oS108; Cmcm; Z = 4; a = 7.2283(4) Å; b = 9.0499(6) Å; c = 34.619(2) Å), which formally represents a one-dimensional intergrowth of the series EuAu2–“EuAu4In2”. The site preferences of the disordered Au/In positions in II were investigated for different hypothetical “EuAu4(Au/In)2” models using the projector-augmented wave method and indicate that these structures attempt to optimize the frequencies of the heteroatomic Au–In contacts. Furthermore, a chemical bonding analysis on two “EuAu5In” and “EuAu4In2” models employed the TB-LMTO-ASA method and reveals that the subtle interplay between the local atomic environments and the bond energies determines the structural and site preferences for these systems.

  5. Polar and nonpolar phases of BiMO{sub 3}: A review

    SciTech Connect

    Belik, Alexei A.

    2012-11-15

    Simple Bi-based compounds, BiMO{sub 3}, are quite interesting materials. They offer large variations in crystal symmetries, polarity, and properties. Their chemical simplicity makes them ideal systems for materials fabrications, theoretical understanding, and thin-film growths. They can only be prepared at high-pressure high-temperature conditions (except for BiFeO{sub 3}) in a bulk form. Some of them can be stabilized in thin films (M=Al, Sc, Cr, Mn, and Fe). In this review, we collect and analyze the recent experimental and theoretical results on BiMO{sub 3} with M=Al, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Ga, In, and Rh. In addition, unresolved problems and desirable future experiments are emphasized especially for the highly controversial compound BiMnO{sub 3}. - Graphical abstract: Crystal symmetries in which BiMO{sub 3} compounds crystallize. Highlights: Black-Right-Pointing-Pointer BiMO{sub 3} compounds offer large variations in crystal symmetries, polarity, and properties. Black-Right-Pointing-Pointer Experimental and theoretical results on BiMO{sub 3} were reviewed. Black-Right-Pointing-Pointer Unresolved problems and desirable future experiments are emphasized. Black-Right-Pointing-Pointer Special attention is paid on the highly controversial compound BiMnO{sub 3}.

  6. Bi-phase transition diagrams of metallic thin multilayers

    SciTech Connect

    Li, J.C.; Liu, W.; Jiang, Q. . E-mail: jiangq@jlu.edu.cn

    2005-02-01

    Phase transitions of metallic multilayers induced by differences in interface energy are considered thermodynamically, based on a thermodynamic model for interface energy and the Goldschmidt premise for lattice contraction. Bi-phase transition diagrams of Co/Cr, Zr/Nb, Ti/Nb and Ti/Al multilayers are constructed, which are in agreement with experimental results.

  7. meson production in Au+Au collisions at in STAR

    NASA Astrophysics Data System (ADS)

    Zhou, Long; STAR collaboration

    2017-01-01

    In this article, we report the measurements of the nuclear modification factor (R AA) and elliptic flow (v 2) for in Au+Au collisions at from the STAR experiment. These results are compared with the results of other open charm mesons to study the hadronization mechanism of the charm quarks and disentangle the transport properties of quark-gluon plasma and hadronic phase [1]. We found that the nuclear modification factor for D s are systematically higher than unity and D 0 R AA. The ratio of D s /D 0 for 10-40% central Au+Au collisions is also higher than that in p+p collisions as predicted by PYTHIA. The D s /D 0 ratio is also compared to that in Pb+Pb collisions at measured by the ALICE experiment. Our results indicate an enhancement of D s meson production in Au+Au collisions.

  8. Growth of Single- and Bilayer ZnO on Au(111) and Interaction with Copper

    SciTech Connect

    Deng, Xingyi; Yao, Kun; Sun, Keju; Li, Wei-Xue; Lee, Junseok; Matranga, Christopher

    2013-05-02

    The stoichiometric single- and bi-layer ZnO(0001) have been prepared by reactive deposition of Zn on Au(111) and studied in detail with X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations. Both single- and bi-layer ZnO(0001) adopt a planar, graphite-like structure similar to freestanding ZnO(0001) due to the weak van der Waals interactions dominating their adhesion with the Au(111) substrate. At higher temperature, the single-layer ZnO(0001) converts gradually to bi-layer ZnO(0001) due to the twice stronger interaction between two ZnO layers than the interfacial adhesion of ZnO with Au substrate. It is found that Cu atoms on the surface of bi-layer ZnO(0001) are mobile with a diffusion barrier of 0.31 eV, and likely to agglomerate and form nanosized particles at low coverages; while Cu atoms tend to penetrate a single layer of ZnO(0001) with a barrier of 0.10 eV, resulting in a Cu free surface.

  9. The New Superconductor tP-SrPd2Bi2: Structural Polymorphism and Superconductivity in Intermetallics.

    PubMed

    Xie, Weiwei; Seibel, Elizabeth M; Cava, Robert J

    2016-04-04

    We consider a system where structural polymorphism suggests the possible existence of superconductivity through the implied structural instability. SrPd2Bi2 has two polymorphs, which can be controlled by the synthesis temperature: a tetragonal form (CaBe2Ge2-type) and a monoclinic form (BaAu2Sb2-type). Although the crystallographic difference between the two forms may, at first, seem trivial, we show that tetragonal SrPd2Bi2 is superconducting at 2.0 K, whereas monoclinic SrPd2Bi2 is not. We rationalize this finding and place it in context with other 1-2-2 phases.

  10. Bismuth as a modifier of Au Pd catalyst: Enhancing selectivity in alcohol oxidation by suppressing parallel reaction

    SciTech Connect

    Villa, Alberto; Wang, Di; Veith, Gabriel M; Prati, Laura

    2012-01-01

    Bi has been widely employed as a modifier for Pd and Pt based catalyst mainly in order to improve selectivity. We found that when Bi was added to the bimetallic system AuPd, the effect on activity in alcohol oxidation mainly depends on the amount of Bi regardless its position, being negligible when Bi was 0.1 wt% and detectably negative when the amount was increased to 3 wt%. However, the selectivity of the reactions notably varied only when Bi was deposited on the surface of metal nanoparticles suppressing parallel reaction in both benzyl alcohol and glycerol oxidation. After a careful characterization of all the catalysts and additional catalytic tests, we concluded that the Bi influence on the activity of the catalysts could be ascribed to electronic effect whereas the one on selectivity mainly to a geometric modification. Moreover, the Bi-modified AuPd/AC catalyst showed possible application in the production of tartronic acid, a useful intermediate, from glycerol.

  11. Liquidus Projections of Bi-Se-Ga and Bi-Se-Te Ternary Systems

    NASA Astrophysics Data System (ADS)

    Lin, Po-han; Chen, Sinn-wen; Hwang, Jenn-dong; Chu, Hsu-shen

    2016-12-01

    This study determines the liquidus projections of both Bi-Se-Ga and Bi-Se-Te ternary systems which are constituent ternary systems of promising Bi-Se-Te-Ga thermoelectric materials. Ternary Bi-Se-Ga and Bi-Se-Te alloys are prepared. Their primary solidification phases are experimentally determined, and thermal analysis experiments are carried out. The liquidus projections are determined based on the ternary experimental results and phase diagrams of constituent binary systems. The Bi-Se-Ga system includes seven primary solidification phases, Bi, Ga, GaSe, Ga2Se3, Se, Bi2Se3, and (Bi2)n(Bi2Se3)m. In the Bi-Se-Te system, there are five primary solidification phases, Bi, (Bi2)n(Bi2Te3)m, Bi2(Se,Te)3, (Se,Te), and (Bi2)n(Bi2Se3)m. Both the (Bi2)n(Bi2Te3)m and (Bi2)n(Bi2Se3)m phases are not a single phase, but a collection of series undetermined phases. Large miscibility gaps are observed in the Bi-Se-Ga system. The temperatures of the invariant reactions, Liquid + Bi + GaSe = Ga and Liquid + Ga2Se3 = Bi + GaSe, are at 495 K (222 °C) and 533 K (260 °C), respectively.

  12. Crystal structures and magnetic properties of CeAu 4Si 2 and CeAu 2Si 2

    NASA Astrophysics Data System (ADS)

    Sefat, Athena S.; Palasyuk, Andriy M.; Bud'ko, Sergey L.; Corbett, John D.; Canfield, Paul C.

    2008-02-01

    Single crystals of CeAu 4Si 2 and CeAu 2Si 2 have been grown out of ternary fluxes rich in Au, and the former, also by sintering the stoichiometric composition at 750 °C. The single-crystal X-ray refinement result for CeAu 4Si 2 is orthorhombic, Cmmm (No. 65, Z=2), different from a tetragonal result found from an X-ray powder diffraction refinement [H. Nakashima, et al., J. Alloys Compds. 424 (2006) 7]. For CeAu 2Si 2, this is the first report of the stoichiometric crystalline phase, in the known tetragonal I4/ mmm structure. The anisotropic field- and temperature-dependent magnetizations, as well as specific heat and resistivity data are compared. Although both compounds have related structural packing, they present unique magnetic features. CeAu 2Si 2 is a typical antiferromagnet with TN=8.8(1) K and CeAu 4Si 2 features a ferromagnetic component below Tc=3.3(1) K. Both phases have effective moments close in value to that of free Ce 3+.

  13. Crystal structures and magnetic properties of CsAu4Si2 and CeAu2Si2

    SciTech Connect

    Sefat, A.; Palasyuk, A.; Bud'ko, S.; Corbett, J.; Canfield, P.

    2007-12-03

    Single crystals of CeAu{sub 4}Si{sub 2} and CeAu{sub 2}Si{sub 2} have been grown out of ternary fluxes rich in Au, and the former, also by sintering the stoichiometric composition at 750 C. The single-crystal X-ray refinement result for CeAu{sub 4}Si{sub 2} is orthorhombic, Cmmm (No. 65, Z=2), different from a tetragonal result found from an X-ray powder diffraction refinement [H. Nakashima, et al., J. Alloys Compds. 424 (2006) 7]. For CeAu{sub 2}Si{sub 2}, this is the first report of the stoichiometric crystalline phase, in the known tetragonal I4/mmm structure. The anisotropic field- and temperature-dependent magnetizations, as well as specific heat and resistivity data are compared. Although both compounds have related structural packing, they present unique magnetic features. CeAu{sub 2}Si{sub 2} is a typical antiferromagnet with T{sub N} = 8.8(1) K and CeAu{sub 4}Si{sub 2} features a ferromagnetic component below T{sub c}=3.3(1) K. Both phases have effective moments close in value to that of free Ce{sup 3+}.

  14. Spin Hall effect in 5d Au: W transition metal alloys (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Laczkowski, Piotr; Rojas-Sánchez, Juan Carlos; Savero-Torres, Williams; Reyren, Nicolas; Deranlot, Cyrile; George, Jean-Marie; Jaffrès, Henri; Fu, Yu; Marty, Alain; Warin, Patrick; Attané, Jean-Philippe; Vila, Laurent; Fert, Albert

    2016-10-01

    The spin Hall effect (SHE) [1] allows for a reciprocal conversion between charge and spin currents using the spin orbit coupling which can be at the core of several promising spintronics devices. The spin orbit interaction is used to produce a transverse flow of spin or charge in response to a longitudinal excitation, these are the direct or inverse SHE. The spin Hall angle (SHA), the ratio of longitudinal and transverse electronic conductivities, is the characterising parameter of this conversion. So far, large SHA have been reported in transition metals like Pt, Pd, W, Beta-Ta and in a few alloys with large spin orbit coupling impurities: CuIr, CuBi or CuPb [2]. In this presentation we will report on our study of the SHA in Au based alloys [3] which exhibits a non-monotonic relation with the impurity concentration. In the regime of diluted alloys this behaviour suggests the dominent side-jump contribution to the spin Hall resistivity, thus allowing precise tuning of the SHA as a function of impurities concentration. We will present our analyses results by using the Lateral Spin Valves, with newly introduced spin-absorption model adapted to the case of the strong spin-orbit interactions and by using complementary Ferromagnetic-Resonance/Spin-Pumping technique thus demonstrating very large SHA of the order of 15 % or even larger. [1] J.E. Hirsch, PRL 83, 1834 (1999). [2] Y. Niimi et al., PRL 106, 126601 (2011), PRL 109, 156602 (2012), PRB 89, 054401 (2014). [3] P. Laczkowski et al., APL 104, 142403 (2014) [4] E. Saitoh, et al., APL 88, 182509 (2006).

  15. Charge-to-Spin Conversion and Spin Diffusion in Bi/Ag Bilayers Observed by Spin-Polarized Positron Beam

    NASA Astrophysics Data System (ADS)

    Zhang, H. J.; Yamamoto, S.; Gu, B.; Li, H.; Maekawa, M.; Fukaya, Y.; Kawasuso, A.

    2015-04-01

    Charge-to-spin conversion induced by the Rashba-Edelstein effect was directly observed for the first time in samples with no magnetic layer. A spin-polarized positron beam was used to probe the spin polarization of the outermost surface electrons of Bi /Ag /Al2O3 and Ag /Bi /Al2O3 when charge currents were only associated with the Ag layers. An opposite surface spin polarization was found between Bi /Ag /Al2O3 and Ag /Bi /Al2O3 samples with the application of a charge current in the same direction. The surface spin polarizations of both systems decreased exponentially with the outermost layer thickness, suggesting the occurrence of spin diffusion from the Bi/Ag interface to the outermost surfaces. This work provides a new technique to measure spin diffusion length.

  16. Plasmon-enhanced nanoporous BiVO4 photoanodes for efficient photoelectrochemical water oxidation

    NASA Astrophysics Data System (ADS)

    Gan, Jiayong; Bangalore Rajeeva, Bharath; Wu, Zilong; Penley, Daniel; Liang, Chaolun; Tong, Yexiang; Zheng, Yuebing

    2016-06-01

    Conversion of solar irradiation into chemical fuels such as hydrogen with the use of a photoelectrochemical (PEC) cell is an attractive strategy for green energy. The promising technique of incorporating metal nanoparticles (NPs) in the photoelectrodes is being explored to enhance the performance of the photoelectrodes. In this work, we developed Au-NPs-functionalized nanoporous BiVO4 photoanodes, and utilized the plasmonic effects of Au NPs to enhance the photoresponse. The plasmonic enhancement leads to an AM 1.5 photocurrent of 5.1 ± 0.1 mA cm-2 at 1.23 V versus a reverse hydrogen electrode. We observed an enhancement of five times with respect to pristine BiVO4 in the photocurrent with long-term stability and high energy-conversion efficiency. The overall performance enhancement is attributed to the synergy between the nanoporous architecture of BiVO4 and the plasmonic effects of Au NPs. Our further study reveals that the commendable photoactivity arises from the different plasmonic effects and co-catalyst effects of Au NPs.

  17. Antibacterial Au nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Wu, Songmei; Zuber, Flavia; Brugger, Juergen; Maniura-Weber, Katharina; Ren, Qun

    2016-01-01

    We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It was found that all the Au nanostructures, regardless their shapes, exhibited similar excellent antibacterial properties. A comparison of live cells attached to nanotopographic surfaces showed that the number of live S. aureus cells was <1% of that from flat and rough reference surfaces. Our micro/nanofabrication process is a scalable approach based on cost-efficient self-organization and provides potential for further developing functional surfaces to study the behavior of microbes on nanoscale topographies.We present here a technological platform for engineering Au nanotopographies by templated electrodeposition on antibacterial surfaces. Three different types of nanostructures were fabricated: nanopillars, nanorings and nanonuggets. The nanopillars are the basic structures and are 50 nm in diameter and 100 nm in height. Particular arrangement of the nanopillars in various geometries formed nanorings and nanonuggets. Flat surfaces, rough substrate surfaces, and various nanostructured surfaces were compared for their abilities to attach and kill bacterial cells. Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterial strain responsible for many infections in health care system, was used as the model bacterial strain. It

  18. Surface morphology and optical properties of porphyrin/Au and Au/porphyrin/Au systems

    PubMed Central

    2013-01-01

    Porphyrin/Au and Au/porphyrin/Au systems were prepared by vacuum evaporation and vacuum sputtering onto glass substrate. The surface morphology of as-prepared systems and those subjected to annealing at 160°C was studied by optical microscopy, atomic force microscopy, and scanning electron microscopy techniques. Absorption and luminescence spectra of as-prepared and annealed samples were measured. Annealing leads to disintegration of the initially continuous gold layer and formation of gold nanoclusters. An amplification of Soret band magnitude was observed on the Au/meso-tetraphenyl porphyrin (TPP) system in comparison with mere TPP. Additional enhancement of luminescence was observed after the sample annealing. In the case of sandwich Au/porphyrin/Au structure, suppression of one of the two porphyrins’ luminescence maxima and sufficient enhancement of the second one were observed. PMID:24373347

  19. Comment on 'Bi nanolines on Si(001): registry with substrate'.

    PubMed

    Bowler, D R; Owen, J H G; Miki, K

    2006-03-28

    A recent article (Miwa et al 2005 Nanotechnology 16 2427) casts doubt on the four-dimer-wide Haiku model for the Bi nanoline on Si(001), suggesting instead that the three-dimer-wide Miki model (which had been ruled out) is a better fit in particular to x-ray data. The reasons why the Haiku model provides the best fit to all published data among currently proposed structures are discussed, concentrating on the width and registry of the Bi nanoline, and mentioning new data which shows that under appropriate conditions the two structures coexist in the same surface.

  20. Bi-stem gripping apparatus

    NASA Technical Reports Server (NTRS)

    Sanders, Fred G. (Inventor)

    1988-01-01

    This invention relates to devices which grip cylindrical structures and more particularly to a device which has three arcuate gripping members having frictional surfaces for gripping and compressing a bi-stem. The bi-stem gripping apparatus is constructed having a pair of side gripping members, and an intermediate gripping member disposed between them. Sheets of a gum stock silicone rubber with frictional gripping surfaces are bonded to the inner region of the gripping members and provide frictional engagement between the bi-stem and the apparatus. A latch secures the gripping apparatus to a bi-stem, and removable handles are attached, allowing an astronaut to pull the bi-stem from its cassette. A tethering ring on the outside of the gripping apparatus provides a convenient point to which a lanyard may be attached.

  1. High Energy, Low Temperature Gelled Bi-propellant Formulation Preparation Method

    NASA Technical Reports Server (NTRS)

    DiSalvo, Roberto (Inventor)

    2013-01-01

    A method for preparing a gelled liquid propane (GLP) composition comprises the introduction of liquid propane into an evacuated mixing vessel containing a gellant and mixing the liquid propane with the gellant. A bi-propellant system comprising GLP is particularly well-suited for outer planet missions greater than 3 AU from the sun and also functions in earth and near earth environments. Additives such as powders of boron, carbon, lithium, and/or aluminum can be added improve performance or enhance hypergolicity. The gelling agent can be silicon dioxide, clay, carbon, or organic or inorganic polymers. The bi-propellant system may be, but need not be, hypergolic.

  2. Swift heavy ion induced nano-dimensional phase separation in liquid immiscible binary Mn-Bi

    NASA Astrophysics Data System (ADS)

    Srivastava, S. K.; Khan, S. A.; Sudheer Babu, P.; Avasthi, D. K.

    2014-08-01

    Pulsed laser deposited 60 nm thin film of homogeneous Mn0.82Bi0.18 composite has been irradiated by 100 MeV Au ions at fluence 1 × 1013 ions/cm2, and investigated by field emission scanning electron microscopy, X-ray diffraction, magnetic hysteresis, X-ray photoelectron spectroscopy, and nanoindentation measurements. Dispersed nanostructures of soft Bi-rich phase of about 20 nm diameter emerged in a hard Mn-rich matrix on irradiation. Such structures, as synthesized by the present novel swift heavy ion irradiation approach, are usable as self-lubricating thin films.

  3. (Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents)

    SciTech Connect

    Not Available

    1991-01-01

    Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

  4. [Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents

    SciTech Connect

    Not Available

    1991-12-31

    Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

  5. Magnetoresistance of Au films

    SciTech Connect

    Zhang, D. L. Song, X. H.; Zhang, X.; Zhang, X.-G.

    2014-12-14

    Classical magnetoresistance (MR) in nonmagnetic metals are conventionally understood in terms of the Kohler rule, with violation usually viewed as anomalous electron transport, in particular, as evidence of non-Fermi liquid behavior. Measurement of the MR of Au films as a function of temperature and film thickness reveals a strong dependence on grain size distribution and clear violation of the Kohler rule. Using a model of random resistor network, we show that this result can be explained if the MR arises entirely from inhomogeneity due to grain boundary scattering and thermal activation of grain boundary atoms. Consequently, the Kohler rule should not be used to distinguish normal and anomalous electron transport in solids.

  6. Isothermal melt processing of Bi-2212 thick films

    NASA Astrophysics Data System (ADS)

    Holesinger, T. G.; Phillips, D. S.; Coulter, J. Y.; Willis, J. O.; Peterson, D. E.

    1995-02-01

    An alternative melt-processing technique has been developed for the fabrication of Bi 2Sr 2CaCu 2O y (Bi-2212) thick films at temperatures over 100°C lower than those employed in conventional Bi-2212 melt processing. Isothermal melt processing combines the melting and solidification steps at the same temperature [T.G. Holesinger et al., Appl. Phys. Lett. 63 (1993) 982]. This technique is possible due to the large drop in the solidus temperature with decreasing oxygen partial pressure. High-quality thick films were processed at temperatures as low as 770°C. Such films were found to be well-textured, contain relatively few secondary phases, and possess critical current densities over 1 × 10 5 A/cm 2 at 4 K in self-field.

  7. Ion induced dewetting of Au-Si on a SiO2 surface: composite nanodot evolution and wettability transition.

    PubMed

    Datta, D P; Siva, V; Varma, S; Kanjilal, D; Sahoo, P K

    2016-11-21

    A nanodot array morphology gradually develops on SiO2 surface when a thin bi-layer of Au and Si undergoes ion irradiation. An increasing amount of gold silicide is detected as islands on the insulator surface evolve into nanodots as a function of increasing ion fluence. Different stages of evolution from islands to nanodots are found to be driven by the localized melting of Au along the ion-track and dewetting of the metal film. Dewetting is accompanied by sputter-erosion and mixing of Au and Si at the bi-layer interface due to ion energy deposition. Interestingly, a gradual transition in wettability of the surface from the hydrophilic to the hydrophobic one is observed with the growth of nanodots, which is correlated with the compositional variation. The experimental results indicate a route towards the controlled growth of composite nanodots on an insulator surface having hydrophobic properties using ion irradiation.

  8. Cu-Ag sulfides as indicators of pre-porphyritic epithermal Au-Ag deposits in Northeastern Russia

    NASA Astrophysics Data System (ADS)

    Savva, N. E.; Sidorov, A. A.; Volkov, A. V.

    2016-08-01

    Au-Ag mineralization of the Olcha and Teploe epithermal deposits underwent thermal metamorphism due to porphyritic intrusions. The presence of Bi-bearing galena and matildite in the ores (Teploe), Cu-Te-bearing naumannite (Olcha), the occurrence of middle- and high-temperature facies of metasomatic rocks (epidote and actinolite), and temperature formation conditions are related, firstly, to the influence of granitoids on the ore process, which supplied not only Cu and Mo, but also Bi, Te, and, secondly, to the heating of host rocks containing pre-porphyritic epithermal Au-Ag mineralization. The abundance of Cu-Ag sulfides and Cu-acanthite resulted from the enrichment of later mineral phases in Cu and Ag under the substance redistribution with the formation of Ag-acanthite ores. The data considered in the paper are of practical importance for regional forecasting of metallogenic constructions, exploration, and evaluation of the epithermal Au-Ag deposits.

  9. On the electron affinity of Au3

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.

    1989-01-01

    The EA of Au3 is estimated to be 3.93 eV. The calculations also show that the feature in the photodetachment spectrum at about 2 eV electron binding energy is due to a two-photon process involving fragmentation of Au3(-) to Au and Au2(-) and subsequent photodetachment of Au2(-). Au3 is found to have a 2B2 ground state that is only slightly distorted from an equilateral triangle.

  10. Al-Co-Fe (030)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Co-Fe (030)' with the content:

  11. Al-La-Nb (068)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-La-Nb (068)' with the content:

  12. Al-Cu-Zr (050)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Cu-Zr (050)' with the content:

  13. Al-La-Ni (069)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-La-Ni (069)' with the content:

  14. Al-Ce-V (029)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Ce-V (029)' with the content:

  15. Spectroscopic constants and potential energy curves of Bi2 and Bi - 2

    NASA Astrophysics Data System (ADS)

    Balasubramanian, K.; Liao, Dai-Wei

    1991-09-01

    We compute the spectroscopic constants of 26 electronic states of Bi2 and six electronic states of Bi-2. In addition, the potential energy curves of electronic states of Bi2 dissociating into Bi(4S)+Bi(4S), Bi(4S)+Bi(2D), Bi(4S)+Bi(2P), Bi(2D)+Bi(2D), and Bi(4S)+Bi(4P) limits are computed. We use a complete active space multiconfiguration self-consistent field (CAS-MCSCF) followed by first-order configuration interaction (FOCI) and second-order configuration interaction (SOCI) methods. In addition, the spin-orbit effects are included through the relativistic configuration interaction (RCI) method. Our computed spectroscopic properties facilitate the assignment of recently observed negative ion photodetachment spectra as well as the electronic spectra accumulated up to now. The observed lifetime and transition moment dependence on internuclear distance are also explained based on computed potential energy curves.

  16. Bi-Cell Unit for Fuel Cell.

    DTIC Science & Technology

    The patent concerns a bi-cell unit for a fuel cell . The bi-cell unit is comprised of two electrode packs. Each of the electrode packs includes an...invention relates in general to a bi-cell unit for a fuel cell and in particular, to a bi-cell unit for a hydrazine-air fuel cell .

  17. Discovery of FeBi 2

    SciTech Connect

    Walsh, James P. S.; Clarke, Samantha M.; Meng, Yue; Jacobsen, Steven D.; Freedman, Danna E.

    2016-10-26

    Recent advances in high-pressure techniques offer chemists access to vast regions of uncharted synthetic phase space, expanding our experimental reach to pressures comparable to the core of the Earth. These newfound capabilities enable us to revisit simple binary systems in search of compounds that for decades have remained elusive. The most tantalizing of these targets are systems in which the two elements in question do not interact even as molten liquids—so-called immiscible systems. As a prominent example, immiscibility between iron and bismuth is so severe that no material containing Fe–Bi bonds is known to exist. The elusiveness of Fe–Bi bonds has a myriad of consequences; crucially, it precludes completing the iron pnictide superconductor series. Herein we report the first iron–bismuth binary compound, FeBi2, featuring the first Fe–Bi bond in the solid state. We employed geologically relevant pressures, similar to the core of Mars, to access FeBi2, which we synthesized at 30 GPa and 1500 K. The compound crystallizes in the Al2Cu structure type (space group I4/mcm) with a = 6.3121(3) Å and c = 5.4211(4) Å. The new binary intermetallic phase persists from its formation pressure of 30 GPa down to 3 GPa. The existence of this phase at low pressures suggests that it might be quenchable to ambient pressure at low temperatures. These results offer a pathway toward the realization of new exotic materials.

  18. Determination of relative sensitivity factors during secondary ion sputtering of silicate glasses by Au+, Au2+ and Au3+ ions.

    PubMed

    King, Ashley; Henkel, Torsten; Rost, Detlef; Lyon, Ian C

    2010-01-01

    In recent years, Au-cluster ions have been successfully used for organic analysis in secondary ion mass spectrometry. Cluster ions, such as Au(2)(+) and Au(3)(+), can produce secondary ion yield enhancements of up to a factor of 300 for high mass organic molecules with minimal sample damage. In this study, the potential for using Au(+), Au(2)(+) and Au(3)(+) primary ions for the analysis of inorganic samples is investigated by analyzing a range of silicate glass standards. Practical secondary ion yields for both Au(2)(+) and Au(3)(+) ions are enhanced relative to those for Au(+), consistent with their increased sputter rates. No elevation in ionization efficiency was found for the cluster primary ions. Relative sensitivity factors for major and trace elements in the standards showed no improvement in quantification with Au(2)(+) and Au(3)(+) ions over the use of Au(+) ions. Higher achievable primary ion currents for Au(+) ions than for Au(2)(+) and Au(3)(+) allow for more precise analyses of elemental abundances within inorganic samples, making them the preferred choice, in contrast to the choice of Au(2)(+) and Au(3)(+) for the analysis of organic samples. The use of delayed secondary ion extraction can also boost secondary ion signals, although there is a loss of overall sensitivity.

  19. The microstructure of MnBi/Bi eutectic alloys

    NASA Technical Reports Server (NTRS)

    Ravishankar, P. S.; Wilcox, W. R.; Larson, D. J.

    1980-01-01

    Directionally solidified eutectic alloys of the system MnBi/Bi have been investigated with reference to the dependence of the fiber spacing on the growth rate and the interfacial temperature gradient. It is found that the fiber spacing varies as the inverse square root of the growth rate and does not depend on the temperature gradient in contrast to the claims that all faceted/non-faceted eutectics should show a temperature gradient influence.

  20. Mapping Photoelectrochemical Current Distribution at Nanoscale Dimensions on Morphologically Controlled BiVO4.

    PubMed

    Chakthranont, Pongkarn; Seitz, Linsey C; Jaramillo, Thomas F

    2015-09-17

    We develop a method that can be used to qualitatively map photocurrent on photoelectrode surfaces, and show its utility for morphologically controlled W-doped BiVO4. The method is based on the deliberate photoinduced sintering of Au NPs, a photon-driven process that indicates oxidation with nanoscale-resolution. This strategy allows us to identify the active regions on W-doped BiVO4 photoelectrodes, and we observe a strong dependence of photoactivity on the electrode morphology, controlled by varying the relative humidity during the sol-gel fabrication process. We find that photoelectrode morphologies that exhibit the most evenly distributed Au sintering are those that yield the highest photoelectrochemical (PEC) activity. Understanding the correlation between electrode morphology and PEC activity is essential for designing structured semiconductors for PEC water splitting.

  1. Sulfur poisoning of CeO[subscript 2]-Al[subscript 2]O[subscript 3]-supported mono- and bi-metallic Ni and Rh catalysts in steam reforming of liquid hydrocarbons at low and high temperatures

    SciTech Connect

    Xie, Chao; Chen, Yongsheng; Li, Yan; Wang, Xiaoxing; Song, Chunshan

    2010-12-01

    In order to develop a better understanding on sulfur poisoning of reforming catalysts in fuel processing for hydrogen production, steam reforming of liquid hydrocarbons was performed over CeO{sub 2}-Al{sub 2}O{sub 3} supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 C. XANES was used to identify the sulfur species in the used catalysts and to study their impacts on the metal surface properties probed by XPS. It was found that both monometallic catalysts rapidly deactivated at 550 C, and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 C dramatically improved the sulfur tolerance of the Rh catalyst. XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The presence of sulfur induced severe carbon deposition on the Ni catalyst at 800 C. The superior sulfur tolerance of the Rh catalyst at 800 C may be associated with its capability in sulfur oxidation. It is likely that the formation of the oxygen-shielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh by inhibiting direct rhodium-sulfur interaction. Moreover, XPS indicated that the metal surface properties of the Rh catalysts after the reaction without and with sulfur at 800 C are similar, suggesting that sulfur poisoning on Rh was mitigated under the high-temperature condition. Although the Rh-Ni catalyst exhibited better sulfur tolerance than the monometallic catalysts at 550 C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800 C probably due to the severe carbon deposition on the bimetallic catalyst.

  2. Fabrication and characterization of Au/p-ZnO Schottky contacts

    NASA Astrophysics Data System (ADS)

    Singh, Brijesh Kumar; Tripathi, Shweta

    2015-09-01

    This paper reports the electrical characteristics of gold contacts on p-type ZnO thin films synthesized by spin coating the sol containing zinc acetate and bismuth nitrate as main precursors. The structural, morphological and optical properties of the deposited thin film have been investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and Ellipsometry, respectively. Further, hot probe measurement has been used to ascertain the type of deposited film and it was observed that films doped with the concentration of 10 mol% Bi shows p-type nature that was found to be stable over the period of five months. Moreover, reflectance of the Bi doped ZnO with varying Bi concentrations, have also been calculated over the wavelength range of 300-800 nm. The optical band gap of Bi doped ZnO films have also been determined for different concentrations of Bi using the data taken by ellipsometer. The gold (Au) contacts have been deposited on the p-ZnO thin films using low cost thermal evaporation method. Electrical parameters such as the reverse saturation current, barrier height and ideality factor have also been determined for Au/p-ZnO thin film based Schottky contact using conventional thermionic emission model and Cheung's method. The conventional thermionic emission model yields barrier height ∼0.681 eV and ideality factor ∼2.3 however Cheung method gives barrier height ∼0.556 eV, ideality factor ∼2.186 and series resistance ∼923 Ω. The present study establishes the fact that Cheung's method can be the best and most realistic method for approximating the diode parameters including the effect of series resistance of the Au/p-ZnO Schottky diode under consideration.

  3. BiHom-Associative Algebras, BiHom-Lie Algebras and BiHom-Bialgebras

    NASA Astrophysics Data System (ADS)

    Graziani, Giacomo; Makhlouf, Abdenacer; Menini, Claudia; Panaite, Florin

    2015-10-01

    A BiHom-associative algebra is a (nonassociative) algebra A endowed with two commuting multiplicative linear maps α,β\\colon A→ A such that α (a)(bc)=(ab)β (c), for all a, b, cin A. This concept arose in the study of algebras in so-called group Hom-categories. In this paper, we introduce as well BiHom-Lie algebras (also by using the categorical approach) and BiHom-bialgebras. We discuss these new structures by presenting some basic properties and constructions (representations, twisted tensor products, smash products etc).

  4. Spatial profile of thermoelectric effects during Peltier pulsing in Bi and Bi/MnBi eutectic

    NASA Technical Reports Server (NTRS)

    Silberstein, R. P.; Larson, D. J., Jr.

    1987-01-01

    The spatial profile of the thermal transients that occur during and following the current pulsing associated with Peltier Interface Demarcation during directional solidification is studied. Results for pure Bi are presented in detail and compared with corresponding results for the Bi/MnBi eutectic. Significant thermal transients occur throughout the sample that can be accounted for by the Peltier effect, the Thomson effect, and Joule heating. These effects are separated and their behavior is studied as a function of time, current density, and position with respect to the solid/liquid interface.

  5. Pion Interferometry in AU+AU Collisions at the AGS

    SciTech Connect

    Lee, J. H.

    1999-01-09

    Two-pion Bose-Einstein correlations have been studied using the BNL-E866 Forward Spectrometer in 11.6 A {center_dot} GeV/c Au + Au collisions. The data were analyzed using three-dimensional correlation parameterizations to study transverse momentum-dependent source parameters. The freeze-out time and the duration of emission were derived from the source radii parameters.

  6. Optical nonlinearities of Au nanoparticles and Au/Ag coreshells.

    PubMed

    Seo, Jae Tae; Yang, Qiguang; Kim, Wan-Joong; Heo, Jinhwa; Ma, Seong-Min; Austin, Jasmine; Yun, Wan Soo; Jung, Sung Soo; Han, Sang Woo; Tabibi, Bagher; Temple, Doyle

    2009-02-01

    Au nanoparticles exhibited both negative and positive nonlinear absorptions with ground-state plasmon bleaching and free-carrier absorption that could be origins of the saturable and reverse-saturable optical properties. Au/Ag coreshells displayed only positive nonlinear absorption and reverse-saturable optical properties as a function of excitation intensity at the edge of surface-plasmon resonance, which implies no ground-state plasmon bleaching and the existence of two-photon absorption.

  7. SN 2014bc, SN2014bi and SN 1981K not detected in radio

    NASA Astrophysics Data System (ADS)

    Bietenholz, Michael; Bartel, Norbert

    2014-08-01

    We report on 10 GHz Jansky Very Large Array radio observations of SN 2014bc (Psn J12185771+4718113; Smartt et al CBET #3877) and SN 2014bi (PSN J12060299+4729335; Kumar et al, CBET #3892), as well as SN 1981K.

  8. Influence of preparation conditions on the depth-dependent composition of AuPd nanoparticles grown on planar oxide surfaces

    NASA Astrophysics Data System (ADS)

    Haire, Andrew R.; Gustafson, Johan; Trant, Aoife G.; Jones, Timothy E.; Noakes, Timothy C. Q.; Bailey, Paul; Baddeley, Christopher J.

    2011-01-01

    The high resolution depth profiling capabilities of medium energy ion scattering are employed to determine the depth dependent composition of Au/Pd nanoparticles grown on thin silica films on Si(100) as functions of Au/Pd composition, total metal loading and annealing temperature. We show that, despite the fact that Au is deposited prior to Pd, the surface of the particles is generally enriched in Au compared to the bulk composition. The extent of this Au enrichment decreases with annealing temperature. In addition, we examine the influence of the adsorption of acetic acid on the surface composition of Au/Pd particles grown on thin alumina films on NiAl(110). We find that acetic acid causes limited segregation of Pd to the bimetallic surface of relatively Au-rich particles.

  9. Diagnosing ALS

    MedlinePlus

    ... that a person diagnosed with ALS seek a second opinion from an ALS "expert" - someone who diagnoses and treats many ALS patients and has training in this medical specialty. The ALS Association maintains a list of recognized experts in the field of ALS. See ALS Association Certified Centers of ...

  10. One-dimensional edge state of Bi thin film grown on Si(111)

    SciTech Connect

    Kawakami, Naoya; Lin, Chun-Liang; Kawai, Maki; Takagi, Noriaki; Arafune, Ryuichi

    2015-07-20

    The geometric and electronic structures of the Bi thin film grown on Si(111) were investigated by using scanning tunneling microscopy and spectroscopy. We have found two types of edges, one of which hosts an electronic state localized one-dimensionally. We also revealed the energy dispersion of the localized edge state from the evolution of quasiparticle interference patterns as a function of energy. These spectroscopic findings well reproduce those acquired for the cleaved surface of the bulk Bi crystal [I. K. Drozdov et al., Nat. Phys. 10, 664 (2014)]. The present results indicate that the deposited Bi film provides a tractable stage for further scrutiny of the one-dimensional edge state.

  11. The Effect of Bi on the Selective Oxide Formation on CMnSi TRIP Steel

    NASA Astrophysics Data System (ADS)

    Oh, Jonghan; Cho, Lawrence; Kim, Myungsoo; Kang, Kichul; De Cooman, Bruno C.

    2016-11-01

    The effect of Bi addition on the selective oxidation and the galvanizability of CMnSi transformation-induced plasticity (TRIP) steels was studied by hot dip galvanizing laboratory simulations. Bi-added TRIP steels were intercritically annealed at 1093 K (820 °C) and galvanized in a 0.22 wt pct Al-containing Zn bath. The oxide morphology was investigated by scanning electron microscopy, transmission electron microscopy, and 3D atom probe tomography. Bi formed a Bi-enriched surface layer during the intercritical annealing. A decrease of the oxygen permeability was observed with increasing Bi addition. The internal oxidation was suppressed in Bi-added CMnSi TRIP steel. The surface oxide morphology was changed from a continuous layer morphology to a more lens-shaped morphology. The galvanizability of the Bi-added TRIP steel was improved by the combination of the change of the oxide morphology and the dissolution of the Bi-enriched surface layer during immersion of the strip in the Zn bath.

  12. Growth Parameters for Thin Film InBi Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Keen, B.; Makin, R.; Stampe, P. A.; Kennedy, R. J.; Sallis, S.; Piper, L. J.; McCombe, B.; Durbin, S. M.

    2014-04-01

    The alloying of bismuth with III-V semiconductors, in particular GaAs and InAs thin films grown by molecular beam epitaxy (MBE), has attracted considerable interest due to the accompanying changes in band structure and lattice constant. Specifically, bismuth incorporation in these compounds results in both a reduction in band gap (through shifting of the valence band) and an increase in the lattice constant of the alloy. To fully understand the composition of these alloys, a better understanding of the binary endpoints is needed. At present, a limited amount of literature exists on the III-Bi family of materials, most of which is theoretical work based on density functional theory calculations. The only III-Bi material known to exist (in bulk crystal form) is InBi, but its electrical properties have not been sufficiently studied and, to date, the material has not been fabricated as a thin film. We have successfully deposited crystalline InBi on (100) GaAs substrates using MBE. Wetting of the substrate is poor, and regions of varying composition exist across the substrate. To obtain InBi, the growth temperature had to be below 100 °C. It was found that film crystallinity improved with reduced Bi flux, into an In-rich regime. Additionally, attempts were made to grow AlBi and GaBi.

  13. Atomic and electronic structures of Si(1 1 1)-\\left(\\sqrt{\\mathbf{3}}\\times\\sqrt{\\mathbf{3}}\\right)\\text{R}\\mathbf{3}{{\\mathbf{0}}^{\\circ}} -Au and (6 × 6)-Au surfaces

    NASA Astrophysics Data System (ADS)

    Patterson, C. H.

    2015-12-01

    Si(1 1 1)-Au surfaces with around one monolayer of Au exhibit many ordered structures and structures containing disordered domain walls. Hybrid density functional theory (DFT) calculations presented here reveal the origin of these complex structures and tendency to form domain walls. The conjugate honeycomb chain trimer (CHCT) structure of the \\sqrt{3} -Au phase contains Si atoms with non-bonding surface states which can bind Au atoms in pairs in interstices of the CHCT structure and make this surface metallic. Si adatoms adsorbed on the \\sqrt{3} -Au surface induce a gapped surface through interaction with the non-bonding states. Adsorption of extra Au atoms in interstitial sites of the \\sqrt{3} -Au surface is stabilized by interaction with the non-bonding orbitals and leads to higher coverage ordered structures including the ≤ft(6× 6\\right) -Au phase. Extra Au atoms bound in interstitial sites of the \\sqrt{3} -Au surface result in top layer Si atoms with an SiAu4 butterfly wing configuration. The structure of a ≤ft(6× 6\\right) -Au phase, whose in-plane top atomic layer positions were previously determined by an electron holography technique (Grozea et al 1998 Surf. Sci. 418 32), is calculated using total energy minimization. The Patterson function for this structure is calculated and is in good agreement with data from an in-plane x-ray diffraction study (Dornisch et al 1991 Phys. Rev. B 44 11221). Filled and empty state scanning tunneling microscopy (STM) images are calculated for domain walls and the ≤ft(6× 6\\right) -Au structure. The ≤ft(6× 6\\right) -Au phase is 2D chiral and this is evident in computed and actual STM images. ≤ft(6× 6\\right) -Au and domain wall structures contain the SiAu4 motif with a butterfly wing shape. Chemical bonding within the Si-Au top layers of the \\sqrt{3} -Au and ≤ft(6× 6\\right) -Au surfaces is analyzed and an explanation for the SiAu4 motif structure is given.

  14. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    PubMed Central

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-01-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size. PMID:27476577

  15. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters.

    PubMed

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-08-01

    Understanding of the "structure-activity" relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au(3+) ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

  16. Preparation and Catalytic Activity for Aerobic Glucose Oxidation of Crown Jewel Structured Pt/Au Bimetallic Nanoclusters

    NASA Astrophysics Data System (ADS)

    Zhang, Haijun; Wang, Liqiong; Lu, Lilin; Toshima, Naoki

    2016-08-01

    Understanding of the “structure-activity” relations for catalysts at an atomic level has been regarded as one of the most important objectives in catalysis studies. Bimetallic nanoclusters (NCs) in its many types, such as core/shell, random alloy, cluster-in-cluster, bi-hemisphere, and crown jewel (one kind of atom locating at the top position of another kind of NC), attract significant attention owing to their excellent optical, electronic, and catalytic properties. PVP-protected crown jewel-structured Pt/Au (CJ-Pt/Au) bimetallic nanoclusters (BNCs) with Au atoms located at active top sites were synthesized via a replacement reaction using 1.4-nm Pt NCs as mother clusters even considering the fact that the replacement reaction between Pt and Au3+ ions is difficult to be occurred. The prepared CJ-Pt/Au colloidal catalysts characterized by UV-Vis, TEM, HR-TEM and HAADF-STEM-EELS showed a high catalytic activity for aerobic glucose oxidation, and the top Au atoms decorating the Pt NCs were about 15 times more active than the Au atoms of Au NCs with similar particle size.

  17. Local variation in Bi crystal sites of epitaxial GaAsBi studied by photoelectron spectroscopy and first-principles calculations

    NASA Astrophysics Data System (ADS)

    Laukkanen, P.; Punkkinen, M. P. J.; Lahti, A.; Puustinen, J.; Tuominen, M.; Hilska, J.; Mäkelä, J.; Dahl, J.; Yasir, M.; Kuzmin, M.; Osiecki, J. R.; Schulte, K.; Guina, M.; Kokko, K.

    2017-02-01

    Epitaxial Bi-containing III-V crystals (III-V1-xBix) have attracted increasing interest due to their potential in infrared applications. Atomic-scale characterization and engineering of bulk-like III-V1-xBix properties (e.g., Bi incorporation and defect formation) are challenging but relevant to develop applications. Toward that target, we report here that the traditional surface-science measurement of photoelectron spectroscopy (PES) is a potential, non-destructive method to be combined in the studies of bulk-like properties, when surface effects are properly removed. We have investigated epitaxial GaAs1-xBix films, capped by epitaxial AlAs layers, with high-resolution photoelectron spectroscopy. The Bi5d core-level spectra of GaAs1-xBix together with ab-initio calculations give direct evidence of variation of Bi bonding environment in the lattice sites. The result agrees with photoluminescence (PL) measurement which shows that the studied GaAs1-xBix films include local areas with higher Bi content, which contribute to PL but do not readily appear in x-ray diffraction (XRD). The measured and calculated Bi core-level shifts show also that Ga vacancies and Bi clusters are dominant defects.

  18. A Grand Avenue to Au Nanocluster Electrochemiluminescence.

    PubMed

    Hesari, Mahdi; Ding, Zhifeng

    2017-02-21

    In most cases of semiconductor quantum dot nanocrystals, the inherent optical and electrochemical properties of these interesting nanomaterials do not translate into expected efficient electrochemiluminescence or electrogenerated chemiluminescence (ECL) because of the surface-state induction effect. Thus, their low ECL efficiencies, while very interesting to explore, limit their applications. As their electrochemistry is not well-defined, insight into their ECL mechanistic details is also limited. Alternatively, gold nanoclusters possess monodispersed sizes with atomic precision, low and well defined HOMO-LUMO energy gaps, and stable optical and electrochemical properties that make them suitable for potential ECL applications. In this Account, we demonstrate strong and sustainable ECL of gold nanoclusters Au25(z) (i.e., Au25(SR)18(z), z = 1-, 0, 1+), Au38(SR)24, and Au144(SR)60, where the ligand SR is 2-phenylethanethiol. By correlation of the optical and electrochemical features of Au25 nanoclusters, a Latimer-type diagram can be constructed to reveal thermodynamic relationships of five oxidation states (Au25(2+), Au25(+), Au25(0), Au25(-), and Au25(2-)) and three excited states (Au25(-)*, Au25(0)*, and Au25(+)*). We describe ECL mechanisms and reaction kinetics by means of conventional ECL-voltage curves and novel spooling ECL spectroscopy. Notably, their ECL in the presence of tri-n-propylamine (TPrA), as a coreactant, is attributed to emissions from Au25(-)* (950 nm, strong), Au25(0)* (890 nm, very strong), and Au25(+)* (890 nm, very strong), as confirmed by the photoluminescence (PL) spectra of the three Au25 clusters electrogenerated in situ. The ECL emissions are controllable by adjustment of the concentrations of TPrA· and Au25(-), Au25(0), and Au25(+) species in the vicinity of the working electrode and ultimately the applied potential. It was determined that the Au25(-)/TPrA coreactant system should have an ECL efficiency of >50% relative to the Ru(bpy)3

  19. Facile synthesis and optical properties of polymer-laced ZnO-Au hybrid nanoparticles

    PubMed Central

    2014-01-01

    Bi-phase dispersible ZnO-Au hybrid nanoparticles were synthesized via one-pot non-aqueous nanoemulsion using the triblock copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) as the surfactant. The characterization shows that the polymer-laced ZnO-Au nanoparticles are monosized and of high crystallinity and demonstrate excellent dispersibility and optical performance in both organic and aqueous medium, revealing the effects of quantum confinement and medium. The findings show two well-behaved absorption bands locating at approximately 360 nm from ZnO and between 520 and 550 nm from the surface plasmon resonance of the nanosized Au and multiple visible fingerprint photoluminescent emissions. Consequently, the wide optical absorbance and fluorescent activity in different solvents could be promising for biosensing, photocatalysis, photodegradation, and optoelectronic devices. PMID:24606946

  20. Facile synthesis and optical properties of polymer-laced ZnO-Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, XianHong; Zhang, XiaoYan; Cheng, WenZheng; Shao, HongQin; Liu, Xiao; Li, XueMei; Liu, HongLing; Wu, JunHua

    2014-03-01

    Bi-phase dispersible ZnO-Au hybrid nanoparticles were synthesized via one-pot non-aqueous nanoemulsion using the triblock copolymer poly(ethylene glycol)- block-poly(propylene glycol)- block-poly(ethylene glycol) as the surfactant. The characterization shows that the polymer-laced ZnO-Au nanoparticles are monosized and of high crystallinity and demonstrate excellent dispersibility and optical performance in both organic and aqueous medium, revealing the effects of quantum confinement and medium. The findings show two well-behaved absorption bands locating at approximately 360 nm from ZnO and between 520 and 550 nm from the surface plasmon resonance of the nanosized Au and multiple visible fingerprint photoluminescent emissions. Consequently, the wide optical absorbance and fluorescent activity in different solvents could be promising for biosensing, photocatalysis, photodegradation, and optoelectronic devices.

  1. Crystal structures and magnetic properties of CeAu{sub 4}Si{sub 2} and CeAu{sub 2}Si{sub 2}

    SciTech Connect

    Sefat, Athena S. Palasyuk, Andriy M.; Bud'ko, Sergey L.; Corbett, John D.; Canfield, Paul C.

    2008-02-15

    Single crystals of CeAu{sub 4}Si{sub 2} and CeAu{sub 2}Si{sub 2} have been grown out of ternary fluxes rich in Au, and the former, also by sintering the stoichiometric composition at 750 deg. C. The single-crystal X-ray refinement result for CeAu{sub 4}Si{sub 2} is orthorhombic, Cmmm (No. 65, Z=2), different from a tetragonal result found from an X-ray powder diffraction refinement [H. Nakashima, et al., J. Alloys Compds. 424 (2006) 7]. For CeAu{sub 2}Si{sub 2}, this is the first report of the stoichiometric crystalline phase, in the known tetragonal I4/mmm structure. The anisotropic field- and temperature-dependent magnetizations, as well as specific heat and resistivity data are compared. Although both compounds have related structural packing, they present unique magnetic features. CeAu{sub 2}Si{sub 2} is a typical antiferromagnet with T{sub N}=8.8(1) K and CeAu{sub 4}Si{sub 2} features a ferromagnetic component below T{sub c}=3.3(1) K. Both phases have effective moments close in value to that of free Ce{sup 3+}. - Graphical abstract: The magnetization versus applied field for CeAu{sub 2}Si{sub 2} along two crystallographic directions.

  2. A study of the electronic properties of Au nanowires and Au nanoislands on Au(111) surfaces.

    PubMed

    Schouteden, K; Lijnen, E; Muzychenko, D A; Ceulemans, A; Chibotaru, Liviu F; Lievens, P; Van Haesendonck, C

    2009-09-30

    By means of ion bombardment of clean Au(111) films, atomically flat nanoparticles of various shapes and sizes were created, ranging from several tens of nm(2) down to only a few nm(2). Both two-dimensional Au islands as well as one-dimensional Au nanowire-like structures have been investigated by means of low-temperature scanning tunneling microscopy and spectroscopy. We were able to probe their local electronic structure in a broad energy range, which was found to be dominated by pronounced size-dependent confinement effects. Mapping of the local density of states revealed complex standing wave patterns that arise due to interference of scattered Au surface state electrons at the edges of the Au nanoparticles. The observed phenomena could be modeled with high accuracy by theoretical particle-in-a-box calculations based on a variational method that can be applied to '2D boxes' of arbitrary polygonal shape and that we have previously successfully applied to explain the electronic wave patterns on Co islands on Au(111). Our findings support the general validity of this particle-in-a-box model.

  3. n vivo retention of ingested Au NPs by Daphnia magna: No evidence for trans-epithelial alimentary uptake

    USGS Publications Warehouse

    Khan, Farhan R.; Kennaway, Gabrielle M.; Croteau, Marie-Noële; Dybowska, Agnieszka; Smith, Brian D.; Nogueira, António J.A.; Rainbow, Philip S.; Luoma, Samuel N.; Valsami-Jones, Eugenia

    2014-01-01

    In vivo studies with Daphnia magna remain inconclusive as to whether engineered nanoparticles (NPs) are internalized into tissues after ingestion. Here we used a three-pronged approach to study the in vivo retention and efflux kinetics of 20 nm citrate stabilized Au NPs ingested by this key aquatic species. Daphnids were exposed to suspended particles (600 μg L−1) for 5 h after which they were depurated for 24 h in clean water containing algae. Light microscopy was used to follow the passage of Au NPs through the gastrointestinal tract, Au body burdens were determined by ICP-MS (inductively coupled plasma mass spectrometry), and transmission electron microscopy (TEM) was used to examine the presence and distribution of Au NPs in tissues. Results revealed that the elimination of Au NPs was bi-phasic. The fast elimination phase lasted −1 (±SE) which accounted for ∼75% of the ingested Au. The remaining ∼25% of the ingested Au NPs was eliminated at a 100-fold slower rate. TEM analysis revealed that Au NPs in the midgut were in close proximity to the peritrophic membrane after 1 and 24 h of depuration. There were no observations of Au NP uptake at the microvilli. Thus, although Au NPs were retained in the gut lumen, there was no observable internalization into the gut epithelial cells. Similar to carbon nanotubes and CuO NPs, our findings indicate that in daphnids the in vivo retention of Au NPs does not necessarily result in their internalization.

  4. A reagentless electrochemiluminescent immunosensor for apurinic/apyrimidinic endonuclease 1 detection based on the new Ru(bpy)3(2+)/bi-arginine system.

    PubMed

    Zhao, Min; Chai, Xi Deng Ya-Qin; Han, Jing; Gui, Guo-Feng; Yuan, Ruo; Zhuo, Ying

    2014-10-10

    Apurinic/apyrimidinic endonuclease 1 (APE-1), a kind of multifunctional protein widely-distributed in the body, plays an essential role in the DNA base excision repair and serves as multiple possible roles in the response of human cancer to radiotherapy and chemotherapy. In this work, an ultrasensitive solid-state electrochemiluminescence (ECL) immunosensor is designed to determine APE-1 based on the new Ru(bpy)3(2+)/bi-arginine system. The bi-arginine (bi-Arg) is decorated on the Au nanoparticles functionalized magnetic Fe3O4/reduced graphene oxide (bi-Arg/Au@Fe3O4-rGO) according to the self-assembling and covalent cross-linking interaction to obtain the functionalized nanocomposite of bi-Arg/Au@Fe3O4-rGO. Herein, the bi-Arg/Au@Fe3O4-rGO plays not only an amplification label to enhance the ECL signal of Ru(bpy)3(2+) due to the coreactant of bi-Arg but also an ideal nanocarrier to load numerous secondary antibody. Based on sandwich-type immunoassay format, this proposed method offers a linear range of 1.0fgmL(-1)-5.0pgmL(-1) and an estimated detection limit of 0.3fgmL(-1) for the APE-1. Moreover, the reagentless ECL immunosensor also exhibits high sensitivity, excellent selectivity and good stability, which has greatly potential development and application in clinical diagnostics, immunology and biomedical research.

  5. ALS Association

    MedlinePlus

    ... toward a world without ALS! Walk to Defeat ALS® Walk to Defeat ALS® draws people of all ... We need your help. I Will Advocate National ALS Registry The National ALS Registry is a congressionally ...

  6. Absence of ferroelectricity in BiMnO3 ceramics

    NASA Astrophysics Data System (ADS)

    Goian, V.; Kamba, S.; Savinov, M.; Nuzhnyy, D.; Borodavka, F.; Vaněk, P.; Belik, A. A.

    2012-10-01

    We performed factor-group analysis of all phonons in possible monoclinic C2/c and C2 structures of BiMnO3 and compared it with our experimental infrared and Raman spectra. We conclude that the crystal structure is centrosymmetric C2/c in the whole investigated temperature range from 10 to 550 K, therefore BiMnO3 cannot be ferroelectric. We revealed a dielectric relaxation in THz spectra above the structural phase transition taking place at TC1 = 475 K giving evidence in strong lattice anharmonicity and a large dynamical disorder of Bi cations above TC1. Step-like dielectric anomaly observed at TC1 in THz permittivity reminds antiferroelectric phase transition. Nevertheless, the low-temperature dielectric studies did not reveal any antiferroelectric or ferroelectric hysteresis loop. Our experimental results support theoretical paper of Baettig et al. (J. Am. Chem. Soc. 129, 9854 (2007)) claiming that BiMnO3 is not multiferroic but only antipolar ferromagnet.

  7. Electronic band structure and material gain of III-V-Bi quantum wells grown on GaSb substrate and dedicated for mid-infrared spectral range

    NASA Astrophysics Data System (ADS)

    Gladysiewicz, M.; Kudrawiec, R.; Wartak, M. S.

    2016-02-01

    The 8-band kp Hamiltonian is applied to calculate electronic band structure and material gain in III-V-Bi quantum wells (QWs) grown on GaSb substrates. We analyzed three Bi-containing QWs (GaSbBi, GaInSbBi, and GaInAsSbBi) and different Bi-free barriers (GaSb and AlGaInAsSb), lattice matched to GaSb. Bi-related changes in the electronic band structure of III-V host incorporated into our formalism are based on recent ab-initio calculations for ternary alloys (III-Ga-Bi and III-In-Bi) [Polak et al., Semicond. Sci. Technol. 30, 094001 (2015)]. When compared to Bi-free QWs, the analyzed Bi-containing structures show much better quantum confinement in the valence band and also larger redshift of material gain peak per percent of compressive strain. For 8 nm thick GaInSb/GaSb QWs, material gain of the transverse electric (TE) mode is predicted at 2.1 μm for the compressive strain of ɛ = 2% (32% In). The gain peak of the TE mode in 8 nm thick GaSbBi/GaSb QW reaches this wavelength for compressive strain of 0.15% that corresponds to about 5% Bi. It has also been shown that replacing In atoms by Bi atoms in GaInSbBi/GaSb QWs while keeping the same compressive strain (ɛ = 2%) in QW region enhances and shifts gain peak significantly to the longer wavelengths. For 8 nm wide GaInSbBi/GaSb QW with 5% Bi, the gain peak is predicted at around 2.6 μm, i.e., is redshifted by about 400 nm compared to Bi-free QW. For 8 nm wide GaInAsSbSb QWs (80% In, 5% Bi, and ɛ = 2%) with proper AlGaInAsSb barriers, it is possible to achieve large material gain even at 4.0 μm.

  8. Pt-Bi decorated nanoporous gold for high performance direct glucose fuel cell

    NASA Astrophysics Data System (ADS)

    Guo, Hong; Yin, Huiming; Yan, Xiuling; Shi, Shuai; Yu, Qingyang; Cao, Zhen; Li, Jian

    2016-12-01

    Binary PtBi decorated nanoporous gold (NPG-PtBi) electrocatalyst is specially designed and prepared for the anode in direct glucose fuel cells (DGFCs). By using electroless and electrochemical plating methods, a dense Pt layer and scattered Bi particles are sequentially coated on NPG. A simple DGFC with NPG-PtBi as anode and commercial Pt/C as cathode is constructed and operated to study the effect of operating temperatures and concentrations of glucose and NaOH. With an anode noble metal loading of only 0.45 mg cm‑2 (Au 0.3 mg and Pt 0.15 mg), an open circuit voltage (OCV) of 0.9 V is obtained with a maximum power density of 8 mW cm‑2. Furthermore, the maximum gravimetric power density of NPG-PtBi is 18 mW mg‑1, about 4.5 times higher than that of commercial Pt/C.

  9. Ternary CuBiS2 nanoparticles as a sensitizer for quantum dot solar cells.

    PubMed

    Suriyawong, Nipapon; Aragaw, Belete; Shi, Jen-Bin; Lee, Ming-Way

    2016-07-01

    This work investigates the synthesis and application in solar cells of a novel solar absorber material CuBiS2. Ternary copper chalcogenide CuBiS2 nanoparticles were grown on a mesoporous TiO2 electrode by the chemical bath deposition (CBD) method. The synthesized CuBiS2 nanoparticles, size 5-10nm, have an energy gap Eg of 2.1eV. Liquid-junction quantum dot-sensitized solar cells were fabricated from the CuBiS2-sensitized electrode using a polysulfide electrolyte. Three types of counter electrodes (CEs) - Pt, Au and Cu2S - were tested. The photovoltaic performance depends on the CBD reaction time and the CE. The best cell, obtained with the Cu2S CE, exhibited the photovoltaic performance of a short-circuit current density Jsc of 6.87mA/cm(2), an open-circuit voltage Voc of 0.25V, a fill factor FF of 36% and a power conversion efficiency η of 0.62%. The present work demonstrates the feasibility of CuBiS2 as a solar energy material.

  10. Pt-Bi decorated nanoporous gold for high performance direct glucose fuel cell

    PubMed Central

    Guo, Hong; Yin, Huiming; Yan, Xiuling; Shi, Shuai; Yu, Qingyang; Cao, Zhen; Li, Jian

    2016-01-01

    Binary PtBi decorated nanoporous gold (NPG-PtBi) electrocatalyst is specially designed and prepared for the anode in direct glucose fuel cells (DGFCs). By using electroless and electrochemical plating methods, a dense Pt layer and scattered Bi particles are sequentially coated on NPG. A simple DGFC with NPG-PtBi as anode and commercial Pt/C as cathode is constructed and operated to study the effect of operating temperatures and concentrations of glucose and NaOH. With an anode noble metal loading of only 0.45 mg cm−2 (Au 0.3 mg and Pt 0.15 mg), an open circuit voltage (OCV) of 0.9 V is obtained with a maximum power density of 8 mW cm−2. Furthermore, the maximum gravimetric power density of NPG-PtBi is 18 mW mg−1, about 4.5 times higher than that of commercial Pt/C. PMID:27966629

  11. Pt-Bi decorated nanoporous gold for high performance direct glucose fuel cell.

    PubMed

    Guo, Hong; Yin, Huiming; Yan, Xiuling; Shi, Shuai; Yu, Qingyang; Cao, Zhen; Li, Jian

    2016-12-14

    Binary PtBi decorated nanoporous gold (NPG-PtBi) electrocatalyst is specially designed and prepared for the anode in direct glucose fuel cells (DGFCs). By using electroless and electrochemical plating methods, a dense Pt layer and scattered Bi particles are sequentially coated on NPG. A simple DGFC with NPG-PtBi as anode and commercial Pt/C as cathode is constructed and operated to study the effect of operating temperatures and concentrations of glucose and NaOH. With an anode noble metal loading of only 0.45 mg cm(-2) (Au 0.3 mg and Pt 0.15 mg), an open circuit voltage (OCV) of 0.9 V is obtained with a maximum power density of 8 mW cm(-2). Furthermore, the maximum gravimetric power density of NPG-PtBi is 18 mW mg(-1), about 4.5 times higher than that of commercial Pt/C.

  12. Combined fast reversible liquidlike elastic deformation with topological phase transition in Na3Bi

    NASA Astrophysics Data System (ADS)

    Cheng, Xiyue; Li, Ronghan; Li, Dianzhong; Li, Yiyi; Chen, Xing-Qiu

    2015-10-01

    By means of first-principles calculations, we identified the structural phase transition of Na3Bi from the hexagonal ground state to the cubic c F 16 phase above 0.8 GPa, in agreement with the experimental findings. Upon the releasing of pressure, the cF 16 phase of Na3Bi is mechanically stable at ambient condition. The calculations revealed that the c F 16 phase is topological semimetal (TS), similar to well-known HgTe, and it even exhibits an unusually low C' modulus (only about 1.9 GPa) and a huge anisotropy Au of as high as 11, which is the third-highest value among all known cubic crystals in their elastic behaviors. These facts render cF 16 -type Na3Bi very soft with a liquidlike elastic deformation in the (110)<1 1 ¯0 > slip system. Importantly, accompanying this deformation, Na3Bi shows a topological phase transition from a TS state at its strain-free cubic phase to a topological insulator (TI) at its distorted phase. Because the C' elastic deformation has almost no energy cost in a reversible and liquidlike soft manner, cF 16 -type Na3Bi would potentially provide a fast on/off switching method between TS and TI, which would be beneficial to quantum electronic devices for practical applications.

  13. On interplanetary coronal mass ejection identification at 1 AU

    NASA Astrophysics Data System (ADS)

    Mulligan, T.; Russell, C. T.; Gosling, J. T.

    1999-06-01

    Coronal mass ejections are believed to be produced in the corona from closed magnetic regions not previously participating in the solar wind expansion. At 1 AU their interplanetary counterparts (ICMEs) generally have a number of distinct plasma and field signatures that distinguish them from the ambient solar wind. These include heat flux dropouts, bi-directional streaming, enhanced alpha particle events, times of depressed proton temperatures, intervals of distorted or enhanced magnetic field, and times of large magnetic field rotations characteristic of magnetic clouds. The first three of these signatures are phenomena that occur at some point within the ICME, but do not necessarily persist throughout the entire ICME. The large scale magnetic field rotations, distortions and enhancements, and the proton temperature depressions tend to mark more accurately the beginning and end of the ICME proper. We examine herein the reliability with which each of these markers identifies ICMEs utilizing ISEE-3 data from 1978-1980.

  14. Disassembly of hot nuclear matter formed in Au-induced reactions near the Fermi energy

    SciTech Connect

    Delis, D.N.

    1993-09-01

    Complex fragment emission has been studied in the 60 MeV/A {sup 197}Au + {sup 12}C, {sup 27}Al, {sup 51}V, {sup nat}Cu, and {sup 197}Au reactions. Velocity spectra, angular distributions and cross sections have been constructed for each target from the inclusive data. Coincidence data including 2-, 3-, 4-, and 5-fold events have also been examined. Furthermore neutron multiplicity distributions have been obtained for the above reactions by utilizing a novel neutron calorimetric approach.

  15. Bi-stable optical actuator

    DOEpatents

    Holdener, Fred R.; Boyd, Robert D.

    2000-01-01

    The present invention is a bi-stable optical actuator device that is depowered in both stable positions. A bearing is used to transfer motion and smoothly transition from one state to another. The optical actuator device may be maintained in a stable position either by gravity or a restraining device.

  16. Bi-isotropic constitutive relations

    NASA Astrophysics Data System (ADS)

    Sihvola, A. H.; Lindell, I. V.

    1991-03-01

    The constitutive relations of general bi-isotropic media, requiring four material parameters, can be written in different ways to describe their electromagnetic behavior. This communication contains a two-way 'dictionary' between a proposed formulation of the constitutive relations with three other sets of relations, generalized from relations used for chiral materials.

  17. Bi-substituted LPE garnet films with FMR linewidth as small as YIG

    SciTech Connect

    Tamada, H.; Kaneko, K.; Okamoto, T. . Research Lab.)

    1988-02-01

    This paper reports highly Bi-substituted LPE garnet films, Bi{sub 0.85}Lu{sub 2.15}FE{sub 5}O{sub 12} and Fi{sub 1.4}Y{sub 1.6}Fe{sub 5}O{sub 12}, with FMR linewidths as small as that of YIG, grown using only Bi{sub 2}O{sub 3} as a flux. Substitution of Al for FE causes a sharp increase in {Delta}H. The minimum values of {Delta}H obtained were 1.5 Oe for Bi{sub 0.85}Lu{sub 2.15}Fe{sub 5}O{sub 12} films and 0.73 Oe for Bi{sub 1.45}Y{sub 1.6}Fe{sub 5}O{sub 12} films, which are the smallest values reported to date for such heavily Bi-substituted garnet films. This may be ascribed to the fact that no Pb was included in the films. It was experimentally verified that MSSW propagation is possible for Bi{sub 0.85}Lu{sub 2.15}Fe{sub 5}O{sub 12} films. These films are very promising for MSW-based optical waveguide devices, since they have a specific Faraday rotation ten times larger than that of YIG, as well as a very small optical absorption coefficient at a wavelength of 1.3 {mu}m.

  18. Correlation effects and phonon modes softening with doping in Ba₁-xKxBiO₃.

    PubMed

    Korotin, Dm M; Novoselov, D; Anisimov, V I

    2014-05-14

    The monoclinic crystal structure of the undoped BaBiO₃ can be described as a cubic perovskite which is distorted by the frozen breathing and tilting phonon modes of the BiO₆ octahedra. The phonon mode softening is experimentally observed (Braden et al 1996 Europhys. Lett. 34 531) in Ba₁-xKxBiO₃ through potassium doping followed by a transition into an ideal cubic perovskite structure at x = 0.37, close to the emergence of superconductivity. In our previous paper (Korotin et al 2012 J. Phys.: Condens. Matter 24 415603) we demonstrated that it is necessary to take into account correlation effects using the DFT+U method in Wannier functions as a basis to obtain a good agreement between the calculated and experimental values of crystal structure distortion and the energy gap in BaBiO₃. In the present work, using the same method, we calculated the breathing mode phonon frequencies as a function of the potassium doping level in Ba₁-xKxBiO₃. The obtained frequencies are in good agreement with experimental values and the breathing mode softening with doping is reproduced, contrary to calculations made without consideration of correlation effects. We show that the cubic crystal structure becomes stable at x = 0.30 in agreement with the experimental transition to cubic perovskite at x = 0.37. The possible connections between the correlation effects, phonon mode softening and superconductivity in Ba₁-xKxBiO₃ are discussed.

  19. New real ternary and pseudoternary phases in the Li-Au-In system

    NASA Astrophysics Data System (ADS)

    Dmytriv, G. S.; Pavlyuk, V. V.; Pauly, H.; Eckert, J.; Ehrenberg, H.

    2011-05-01

    Two real ternary lithium gold indides LiAu 2In and Li 280Au 22In 130 (Li 0.65Au 0.05In 0.30) were found in the Li-Au-In system. They are isostructural to the respective Ag-alloys. LiAu 2In crystallizes in the MnCu 2Al-type structure ( Fm-3 m, Heusler phase, a=6.4982(8) Å, based on single crystal XRD-data) and Li 280Au 22In 130 in the Li 278Ag 40In 114-type structure ( F-43 m, a=19.9970(2) Å, based on powder XRD-data). The analogy of the two ternary systems Li-Au-In and Li-Ag-In is additionally reaffirmed by the wide homogeneity range of the pseudoternary solid solution with NaTl-type structure (Zintl phase),which expands not only in the direction of the quasibinary cut Li(Au xIn 1- x) with 0≤ x≤0.5, but also into the directions of both higher and lower Li-concentrations.

  20. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    SciTech Connect

    Herz, A. E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D. E-mail: dong.wang@tu-ilmenau.de; Schaaf, P.; Friák, M.; Holec, D.; Šob, M.; Schneeweiss, O.

    2015-08-17

    Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observed phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.

  1. Photoneutron cross sections for Au

    SciTech Connect

    Itoh, O.; Utsunomiya, H.; Akimune, H.; Yamagata, T.; Kondo, T.; Kamata, M.; Toyokawa, H.; Harada, H.; Kitatani, F.; Goko, S.; Nair, C.; Lui, Y.-W.

    2011-10-28

    Photoneutron cross sections were measured for Au in the entire energy range of the ({gamma},n) channel based on a direct neutron-counting technique with quasimonochromatic {gamma} rays produced in inverse Compton-scattering of laser photons with relativistic electrons. We present results of the measurement in comparison with the past data.

  2. Crystal structure of TiBi2

    PubMed Central

    Watanabe, Kei; Yamane, Hisanori

    2016-01-01

    Black granular single crystals of monotitanium dibismuth, TiBi2, were synthesized by slow cooling of a mixture of Bi and Ti from 693 K. The title compound is isostructural with CuMg2 (ortho­rhom­bic Fddd symmetry). Ti atoms are located in square anti­prisms of Bi atoms. The network of one type of Bi atom spirals along the a-axis direction while honeycomb layers of the other type of Bi atom spreading in the ab plane inter­lace one another. PMID:27920910

  3. Metastable β-Bi2O3 nanoparticles with high photocatalytic activity from polynuclear bismuth oxido clusters.

    PubMed

    Schlesinger, Maik; Schulze, Steffen; Hietschold, Michael; Mehring, Michael

    2013-01-28

    The synthesis of nanoscaled β-Bi(2)O(3) starting from the bismuth oxido clusters [Bi(6)O(4)(OH)(4)](NO(3))(6)·H(2)O, [Bi(22)O(26)(OSiMe(2)(t)Bu)(14)], [Bi(38)O(45)(NO(3))(20)(DMSO)(28)](NO(3))(4)·4DMSO and [Bi(38)O(45)(OMc)(24)(DMSO)(9)]·2DMSO·7H(2)O (OMc = O(2)CC(3)H(5)) under ambient conditions is reported. The metal oxido clusters are regarded as ideal precursors for β-Bi(2)O(3) due to their structural relationship with the latter. Nevertheless, different bismuth oxide polymorphs are accessible dependent on the hydrolysis protocol. Hydrolysis over a period of 18 h gave stable α-Bi(2)O(3) whereas after 3 min an amorphous material is observed. Annealing of the amorphous material at 370 °C gave nanoscaled β-Bi(2)O(3). An unusual high reactivity of the β-Bi(2)O(3) particles with SiO(2) and Al(2)O(3) is observed at temperatures above 400 °C. Powder X-ray diffraction studies, transmission electron microscopy, diffuse reflectance UV/Vis spectroscopy and nitrogen adsorption measurements are used for characterization of the as-prepared β-Bi(2)O(3) nanoparticles. The properties of the β-Bi(2)O(3) nanoparticles depend on the starting bismuth oxido clusters with regard to particle size and optical band gap. The β-Bi(2)O(3) nanoparticles show excellent photocatalytic activity as demonstrated by dye decomposition (rhodamine B, methyl orange, methylene blue and orange G) under visible light.

  4. Global transverse and forward energy measurements for Si+A and Au+A at the AGS

    SciTech Connect

    Moskowitz, B.; E802 /866 Collaboration

    1993-04-01

    The global transverse and forward energy from Si+Al,Au at 14.6A GeV/c and Au+Al,Au, at 11.6A GeV/c have been measured using the E802 lead-glass and ZCAL. Preliminary d{sigma}/dE{sub T}, dE{sub T}/d{eta} and d{sigma}dT{sub ZCAL} spectra are presented, and the shapes of the spectra from different systems are compared. The transverse and forward energies in Au+Au are observed to be anticorrelated in a manner that is reproduced by the cascade model ARC but not by the essentially geometric model Fritiof.

  5. Global transverse and forward energy measurements for Si+A and Au+A at the AGS

    SciTech Connect

    Moskowitz, B.

    1993-01-01

    The global transverse and forward energy from Si+Al,Au at 14.6A GeV/c and Au+Al,Au, at 11.6A GeV/c have been measured using the E802 lead-glass and ZCAL. Preliminary d[sigma]/dE[sub T], dE[sub T]/d[eta] and d[sigma]dT[sub ZCAL] spectra are presented, and the shapes of the spectra from different systems are compared. The transverse and forward energies in Au+Au are observed to be anticorrelated in a manner that is reproduced by the cascade model ARC but not by the essentially geometric model Fritiof.

  6. Spiral Patterning of Au Nanoparticles on Au Nanorod Surface to Form Chiral AuNR@AuNP Helical Superstructures Templated by DNA Origami.

    PubMed

    Shen, Chenqi; Lan, Xiang; Zhu, Chenggan; Zhang, Wei; Wang, Leyu; Wang, Qiangbin

    2017-02-20

    Plasmonic motifs with precise surface recognition sites are crucial for assembling defined nanostructures with novel functionalities and properties. In this work, a unique and effective strategy is successfully developed to pattern DNA recognition sites in a helical arrangement around a gold nanorod (AuNR), and a new set of heterogeneous AuNR@AuNP plasmonic helices is fabricated by attaching complementary-DNA-modified gold nanoparticles (AuNPs) to the predesigned sites on the AuNR surface. AuNR is first assembled to one side of a bifacial rectangular DNA origami, where eight groups of capture strands are selectively patterned on the other side. The subsequently added link strands make the rectangular DNA origami roll up around the AuNR into a tubular shape, therefore giving birth to a chiral patterning of DNA recognition sites on the surface of AuNR. Following the hybridization with the AuNPs capped with the complementary strands to the capture strands on the DNA origami, left-handed and right-handed AuNR@AuNP helical superstructures are precisely formed by tuning the pattern of the recognition sites on the AuNR surface. Our strategy of nanoparticle surface patterning innovatively realizes hierarchical self-assembly of plasmonic superstructures with tunable chiroptical responses, and will certainly broaden the horizon of bottom-up construction of other functional nanoarchitectures with growing complexity.

  7. New ideally absorbing Au plasmonic nanostructures for biomedical applications

    NASA Astrophysics Data System (ADS)

    Zakomirnyi, Vadim I.; Rasskazov, Ilia L.; Karpov, Sergey V.; Polyutov, Sergey P.

    2017-01-01

    In this paper a new set of plasmonic nanostructures operating at the conditions of an ideal absorption (Grigoriev et al., 2015 [1]) was proposed for novel biomedical applications. We consider spherical x/Au nanoshells and Au/x/Au nanomatryoshkas, where 'x' changes from conventional Si and SiO2 to alternative plasmonic materials (Naik and Shalaev, 2013 [2]), such as zinc oxide doped with aluminum, gallium and indium tin oxide. The absorption peak of proposed nanostructures lies within 700-1100 nm wavelength region and corresponds to the maximal optical transparency of hemoglobin and melanin as well as to the radiation frequency of available pulsed medical lasers. It was shown that the ideal absorption takes place in a given wavelength region for Au coatings with thickness less than 12 nm. In this case finite quantum size effects for metallic nanoshells play a significant role. The mathematical model for the search of the ideal absorption conditions was modified by taking into account the finite quantum size effects.

  8. Interface behavior of Al2O3/Ti joints produced by liquid state bonding.

    PubMed

    Lemus-Ruiz, J; Guevara-Laureano, A O; Zarate-Medina, J; Arellano-Lara, A; Ceja-Cárdenas, L

    2015-04-01

    In this work we study brazing of Al2O3 to Ti with biocompatibility properties, using a Au-foil as joining element. Al2O3 was produced by sintering of powder at 1550°C. Al2O3 samples were coated with a 2 and 4μm thick of Mo layer and then stacked with Ti. Al2O3-Mo/Au/Ti combinations were joined at 1100°C in vacuum. Successful joining of Mo-Al2O3 to Ti was observed. Interface shows the formation of a homogeneous diffusion zone. Mo diffused inside Au forming a concentration line. Ti3Au and TiAu phases were observed.

  9. New Structure Model of Au22(SR)18: Bitetrahederon Golden Kernel Enclosed by [Au6(SR)6] Au(I) Complex.

    PubMed

    Pei, Yong; Tang, Jian; Tang, Xianqiong; Huang, Yunqing; Zeng, Xiao Cheng

    2015-04-16

    The study of atomic structure of thiolate-protected gold with decreased core size is important to explore the structural evolution from Au(I) complex to Au nanoclusters. In this work, we theoretically predicted the structure of recently synthesized four valence electron (4e) Au22(SR)18 cluster. The Au22(SR)18 cluster is proposed to possess a bitetrahedron Au7 kernel that is surrounded by a unique [Au6(SR)6] Au(I) complex and three Au3(SR)4 staple motifs. More interestingly, the Au22(SR)18 exhibits structural connections with Au24(SR)20 and Au20(SR)16. The stability of Au22(SR)18 can be understood from the superatom electronic configuration of the Au kernel as well as the formation of superatomic network. The present study can offer new insight into the structural evolution as well as electronic structure of thiolate-protected Au nanoclusters.

  10. Onset of nuclear matter expansion in Au+Au collisions

    NASA Astrophysics Data System (ADS)

    Crochet, P.; Rami, F.; Gobbi, A.; Dona, R.; Coffin, J. P.; Fintz, P.; Guillaume, G.; Jundt, F.; Kuhn, C.; Roy, C.; de Schauenburg, B.; Tizniti, L.; Wagner, P.; Alard, J. P.; Amouroux, V.; Andronic, A.; Basrak, Z.; Bastid, N.; Belyaev, I.; Best, D.; Biegansky, J.; Buta, A.; Čaplar, R.; Cindro, N.; Dupieux, P.; Dželalija, M.; Fan, Z. G.; Fodor, Z.; Fraysse, L.; Freifelder, R. P.; Berrmann, N.; Hildenbrand, K. D.; Hong, B.; Jeong, S. C.; Kecskemeti, J.; Kirejczyk, M.; Koncz, P.; Korolija, M.; Kotte, R.; Lebedev, A.; Leifels, Y.; Manko, V.; Moisa, D.; Mösner, J.; Neubert, W.; Pelte, D.; Petrovici, M.; Pinkenburg, C.; Pras, P.; Ramillien, V.; Reisdorf, W.; Ritman, J. L.; Sadchikov, A. G.; Schüll, D.; Seres, Z.; Sikora, B.; Simion, V.; Siwek-Wilczyńska, K.; Sodan, U.; Teh, K. M.; Trzaska, M.; Vasiliev, M.; Wang, G. S.; Wessels, J. P.; Wienold, T.; Wisniewski, K.; Wohlfarth, D.; Zhilin, A.; FOPI Collaboration

    1997-02-01

    Using the FOPI detector at GSI Darmstadt, excitation functions of collective flow components were measured for the Au+Au system, in the reaction plane and out of this plane, at seven incident energies ranging from 100 A MeV to 800 A MeV. The threshold energies, corresponding to the onset of sideward-flow (balance energy) and squeeze-out effect (transition energy), are extracted from extrapolations of these excitation functions toward lower beam energies for charged products with Z ⩾ 2. The transition energy is found to be larger than the balance energy. The impact parameter dependence of both balance and transition energies, when extrapolated to central collisions, suggests comparable although slightly higher values than the threshold energy for the radial flow. The relevant parameter seems to be the energy deposited into the system in order to overcome the attractive nuclear forces.

  11. Universality in fragment inclusive yields from Au+Au collisions

    NASA Astrophysics Data System (ADS)

    Insolia, A.; Tuvè, C.; Albergo, S.; Bieser, F.; Brady, F. P.; Caccia, Z.; Cebra, D.; Chacon, A. D.; Chance, J. L.; Choi, Y.; Costa, S.; Elliott, J. B.; Gilkes, M.; Hauger, J. A.; Hirsch, A. S.; Hjort, E. L.; Justice, M.; Keane, D.; Kintner, J.; Lisa, M.; Matis, H. S.; McMahan, M.; McParland, C.; Olson, D. L.; Partlan, M. D.; Porile, N. T.; Potenza, R.; Rai, G.; Rasmussen, J.; Ritter, H. G.; Romero, J. L.; Russo, G. V.; Scharenberg, R.; Scott, A.; Shao, Y.; Srivastava, B. K.; Symons, T. J. M.; Tincknell, M. L.; Wang, S.; Warren, P. G.; Wieman, H. H.; Wolf, K. L.

    2001-11-01

    The inclusive light fragment (Z⩽7) yield data in Au+Au reactions, measured by the EOS Collaboration at the LBNL Bevalac, are presented and discussed. For peripheral collisions the measured charge distributions develop progressively according to a power law which can be fitted by a single τ exponent independently of the bombarding energy in the range 250-1200 A MeV. In addition to this universal feature, we observe that the location of the maximum in the individual yields of different charged fragments shift towards lower multiplicity as the fragment charge increases from Z=3 to Z=7. This trend is common to all six measured beam energies. Moments of charge distributions and correlations among different moments are reported. Finally, the THe,DT thermometer has been constructed for central and peripheral collisions using the double yield ratios of He and D, T projectile fragments. The measured nuclear temperatures are in agreement with experimental findings in other fragmentation reactions.

  12. Evolutionary Dynamics on Protein Bi-stability Landscapes can Potentially Resolve Adaptive Conflicts

    PubMed Central

    Sikosek, Tobias; Bornberg-Bauer, Erich; Chan, Hue Sun

    2012-01-01

    Experimental studies have shown that some proteins exist in two alternative native-state conformations. It has been proposed that such bi-stable proteins can potentially function as evolutionary bridges at the interface between two neutral networks of protein sequences that fold uniquely into the two different native conformations. Under adaptive conflict scenarios, bi-stable proteins may be of particular advantage if they simultaneously provide two beneficial biological functions. However, computational models that simulate protein structure evolution do not yet recognize the importance of bi-stability. Here we use a biophysical model to analyze sequence space to identify bi-stable or multi-stable proteins with two or more equally stable native-state structures. The inclusion of such proteins enhances phenotype connectivity between neutral networks in sequence space. Consideration of the sequence space neighborhood of bridge proteins revealed that bi-stability decreases gradually with each mutation that takes the sequence further away from an exactly bi-stable protein. With relaxed selection pressures, we found that bi-stable proteins in our model are highly successful under simulated adaptive conflict. Inspired by these model predictions, we developed a method to identify real proteins in the PDB with bridge-like properties, and have verified a clear bi-stability gradient for a series of mutants studied by Alexander et al. (Proc Nat Acad Sci USA 2009, 106:21149–21154) that connect two sequences that fold uniquely into two different native structures via a bridge-like intermediate mutant sequence. Based on these findings, new testable predictions for future studies on protein bi-stability and evolution are discussed. PMID:23028272

  13. Successful synthesis and thermal stability of immiscible metal Au-Rh, Au-Ir and Au-Ir-Rh nanoalloys.

    PubMed

    Shubin, Yury; Plusnin, Pavel; Sharafutdinov, Marat; Makotchenko, Evgenia; Korenev, Sergey

    2017-04-06

    We successfully prepared face-centred cubic nanoalloys in systems of Au-Ir, Au-Rh and Au-Ir-Rh, with large bulk miscibility gaps, in one-run reactions under thermal decomposition of specially synthesised single-source precursors, namely, [AuEn2][Ir(NO2)6], [AuEn2][Ir(NO2)6]х[Rh(NO2)6]1-х and [AuEn2][Rh(NO2)6]. The precursors employed contain all desired metals "mixed" at the molecular level, thus providing significant advantages for obtaining alloys. The observations using HR TEM show that the nanoalloy structures are composed of well-dispersed aggregates of crystalline domains with a mean size of 5±3 nm. EDX and XRD measurements confirm the formation of AuIr, AuRh, AuIr0.75Rh0.25, AuIr0.50Rh0.50 and AuIr0.25Rh0.75 metastable solid solutions. In-situ real-time synchrotron XRD was used to study the formation mechanism of nanoalloys. The observed transformations are described by the "conversion chemistry" mechanism characterised by the primary development of particles comprising atoms of only one type, followed by a chemical reaction resulting in the final formation of a nanoalloy. The obtained metastable nanoalloys exhibit essential thermal stability. Exposure to 180 ºC for 30 h does not cause any dealloying process.

  14. Genetic Pd, Pt, Au, Ag, and Rh mineralogy in Noril'sk sulfide ores

    NASA Astrophysics Data System (ADS)

    Spiridonov, E. M.; Kulagov, E. A.; Serova, A. A.; Kulikova, I. M.; Korotaeva, N. N.; Sereda, E. V.; Tushentsova, I. N.; Belyakov, S. N.; Zhukov, N. N.

    2015-09-01

    The undeformed ore-bearing intrusions of the Noril'sk ore field (NOF) cut through volcanic rocks of the Late Permian-Early Triassic trap association folded in brachysynclines. Due to the nonuniform load on the roof of intrusive bodies, most sulfide melts were squeezed, up to the tops of ore-bearing intrusions; readily fusible Ni-Fe-Cu sulfide melts were almost completely squeezed. In our opinion, not only one but two stages of mineralization developed at the Noril'sk deposits: (i) syntrap magmatic and (ii) epigenetic post-trap metamorphic-hydrothermal. All platinum-group minerals (PGM) and minerals of gold are metasomatic in the Noril'sk ores. They replaced sulfide solid solutions and exsolution structures. All types of PGM and Au minerals occur in the ores, varying in composition from pyrrhotite to chalcopyrite, talnakhite, mooihoekite, and rich in galena; they are localized in the inner and outer contact zones and differ only in the quantitative proportions of ore minerals. The aureoles of PGM and Au-Ag minerals are wider than the contours of sulfide bodies and coincide with halos of fluid impact on orebodies and adjacent host rocks. The pneumatolytic PGM and Au-Ag minerals are correlated in abundance with the dimensions of sulfide bodies. Their amounts are maximal in veins of late fusible ore composed of eutectic PbS ss and iss intergrowths, as well as at their contacts. The Pd and Pt contents in eutectic sulfide ores of NOF are the world's highest. In the process of noble-metal mineral formation, the fluids supply Pd, Pt, Au, As, Sb, Sn, Bi, and a part of Te, whereas Fe, Ni, Cu, Pb, Ag, Rh, a part of Te and Pd are leached from the replaced sulfide minerals. The pneumatolytic PGM of the early stage comprises Pd and Pt intermetallic compounds enriched in Au along with Pd-Pt-Fe-Ni-Cu-Sn-Pb(As) and (Pd,Pt,Au)(Sn,Sb,Bi,Te,As) solid solutions. Pneumatolytic PGM and Au minerals of the middle stage are products of solid-phase transformation and recrystallization of

  15. Atomic-level structural and chemical analysis of Cr-doped Bi2Se3 thin films

    NASA Astrophysics Data System (ADS)

    Ghasemi, A.; Kepaptsoglou, D.; Collins-McIntyre, L. J.; Ramasse, Q.; Hesjedal, T.; Lazarov, V. K.

    2016-05-01

    We present a study of the structure and chemical composition of the Cr-doped 3D topological insulator Bi2Se3. Single-crystalline thin films were grown by molecular beam epitaxy on Al2O3 (0001), and their structural and chemical properties determined on an atomic level by aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy. A regular quintuple layer stacking of the Bi2Se3 film is found, with the exception of the first several atomic layers in the initial growth. The spectroscopy data gives direct evidence that Cr is preferentially substituting for Bi in the Bi2Se3 host. We also show that Cr has a tendency to segregate at internal grain boundaries of the Bi2Se3 film.

  16. New real ternary and pseudoternary phases in the Li-Au-In system

    SciTech Connect

    Dmytriv, G.S.; Pavlyuk, V.V.; Pauly, H.; Eckert, J.; Ehrenberg, H.

    2011-05-15

    Two real ternary lithium gold indides LiAu{sub 2}In and Li{sub 280}Au{sub 22}In{sub 130} (Li{sub 0.65}Au{sub 0.05}In{sub 0.30}) were found in the Li-Au-In system. They are isostructural to the respective Ag-alloys. LiAu{sub 2}In crystallizes in the MnCu{sub 2}Al-type structure (Fm-3m, Heusler phase, a=6.4982(8) A, based on single crystal XRD-data) and Li{sub 280}Au{sub 22}In{sub 130} in the Li{sub 278}Ag{sub 40}In{sub 114}-type structure (F-43m, a=19.9970(2) A, based on powder XRD-data). The analogy of the two ternary systems Li-Au-In and Li-Ag-In is additionally reaffirmed by the wide homogeneity range of the pseudoternary solid solution with NaTl-type structure (Zintl phase),which expands not only in the direction of the quasibinary cut Li(Au{sub x}In{sub 1-x}) with 0{<=}x{<=}0.5, but also into the directions of both higher and lower Li-concentrations. -- Graphical abstract: Two real ternary compounds (1: Heusler phase, 2: n=6 variant of a cubic nxnxn W-type superstructure) together with one pseudoternary compound (3: Zintl phase with its broad homogeneity range). Display Omitted Highlights: {yields} 'Real' ternary phases were found in the Li-Au-In systems: LiAu{sub 2}In and Li{sub 280}Au{sub 22}In{sub 130}. {yields} The homogeneity range of 'pseudoternary' Li(Au{sub x}In{sub 1-x}) extends to the binary phase x=0. {yields} The three-element sets, both Li, Au, In and Li, Ag, In, are compound formers*. (*in the definition of Villars et al., J. Alloys Compd. 317-318, 2001, 26).

  17. Superconductivity in textured Bi clusters/Bi{sub 2}Te{sub 3} films

    SciTech Connect

    Le, Phuoc Huu; Tzeng, Wen-Yen; Chen, Hsueh-Ju; Luo, Chih Wei; Lin, Jiunn-Yuan; Leu, Jihperng

    2014-09-01

    We report superconductivity at an onset critical temperature below 3.1 K in topological insulator ∼200-nm-thick Bi{sub 2}Te{sub 3} thin films grown by pulsed laser deposition. Using energy-dispersive X-ray spectroscopy elemental mapping and Auger electron spectroscopy elemental depth profiling, we clearly identified bismuth (Bi) precipitation and Bi cluster signatures. Superconductivity in the Bi{sub 2}Te{sub 3} films was attributed to the proximity effect of Bi clusters precipitated on the surface of the Bi{sub 2}Te{sub 3} films.

  18. On the elastic, elastic-plastic properties of Au nanowires in the range of diameter 1-200 nm

    NASA Astrophysics Data System (ADS)

    Deb Nath, S. K.; Kim, Sung-Gaun

    2012-12-01

    In the present study, we obtain Young's modulus and yield strength of <100> Au nanowire in the range of diameters 1-30 nm by tension and bending tests using molecular dynamics simulations. Double clamped Au nanowire is bended applying a point load at its middle span using cylindrical indenter by the atomistic approach. The superiority of the present bending technique is highlighted by analyzing the distribution of Von Misses stress of the present bending Au nanowire by 3D finite element modeling. First, Young's modulus and yield strength of Au nanowires are determined using classical theory of continuum mechanics. Then the obtained Young's modulus and yield strength of Au nanowires are corrected using 3D finite element modeling based on inverse technique [Deb Nath et al. Appl. Phys. A 103(2), 493 (2011) and Tohmyoh et al. Appl. Phys. A 103(2), 285 (2011)]. Effects of anisotropy on the tension and bending stiffness, tension and bending strength of Au nanowires are also discussed with graphs. Effects of temperature on the tension and bending stiffness, tension and bending strength of Au nanowires are discussed. Effects of vertical displacement of the indenter on the mid span of double clamped Au nanowires on the bending stiffness and strength during molecular dynamics simulation are discussed. Besides, the obtained Young's modulus and yield strength of Au nanowires by Wu et al. [Nature Mater. 4, 525 (2005)] in the range of diameters 40 to 200 nm using the theory of classical continuum mechanics are corrected using the 3D finite element modeling based on inverse technique [Deb Nath et al. Appl. Phys. A 103(2), 493 (2011) and Tohmyoh et al. Appl. Phys. A 103(2), 285 (2011)].

  19. MODELING THE ACCRETION STRUCTURE OF AU Mon

    SciTech Connect

    Atwood-Stone, Corwin; Miller, Brendan P.; Richards, Mercedes T.; Budaj, Jan; Peters, Geraldine J. E-mail: mbrendan@umich.edu E-mail: budaj@ta3.sk

    2012-12-01

    AU Mon is a long-period (11.113 days) Algol-type binary system with a persistent accretion disk that is apparent as double-peaked H{alpha} emission. We present previously unpublished optical spectra of AU Mon which were obtained over 20 years from 1991-2011 with dense orbital phase coverage. We utilize these data, along with archival UV spectra, to model the temperature and structure of the accretion disk and the gas stream. Synthetic spectral profiles for lines including H{alpha}, H{beta}, and the Al III and Si IV doublets were computed with the Shellspec program. The best match between the model spectra and the observations is obtained for an accretion disk of inner/outer radius 5.1/23 R {sub Sun }, thickness of 5.2 R {sub Sun }, density of 1.0 Multiplication-Sign 10{sup -13} g cm{sup -3}, and maximum temperature of 14,000 K, along with a gas stream at a temperature of {approx}8000 K transferring {approx}2.4 Multiplication-Sign 10{sup -9} M {sub Sun} yr{sup -1}. We show H{alpha} Doppler tomograms of the velocity structure of the gas, constructed from difference profiles calculated through sequentially subtracting contributions from the stars and accretion structures. The tomograms provide independent support for the Shellspec modeling, while also illustrating that residual emission at sub-Keplerian velocities persists even after subtracting the disk and stream emission. Spectral variability in the H{alpha} profile beyond that expected from either the orbital or the long-period cycle is present on both multi-week and multi-year timescales, and may reflect quasi-random changes in the mass transfer rate or the disk structure. Finally, a transient UV spectral absorption feature may be modeled as an occasional outflow launched from the vicinity of the disk-stream interaction region.

  20. d + Au hadron correlation measurements at PHENIX

    SciTech Connect

    Anne M. Sickles

    2014-05-13

    In these proceedings, we discuss recent results from d + Au collisions in PHENIX ridge related measurements and their possible hydrodynamic origin. We present the v2 at midrapidity and measurements of the pseudorapidity dependence of the ridge, distinguishing between the d-going and Au-going directions. We investigate the possible geometrical origin by comparing v2 in d + Au to that in p + Pb, Au + Au and Pb + Pb collisions. Future plans to clarify the role of geometry in small collision systems at RHIC are discussed.

  1. Tribal Militias: An Effective Tool to Counter Al-Qaida and Its Affiliates?

    DTIC Science & Technology

    2014-11-01

    Notable Serious Tension between Al-Qaida and the Tribes”), Akhbar Aden, December 2, 2011, avail- able from www.aden-news.net/nprint.php? lng =arabic...available from www.akhbaralyom.net/nprint. php? lng =arabic&sid=63050. 106. “Fi-ma tazhahurat ihtijajiyat li’l-lijan al-shabiya bi- ahwar li’l...www.akhbaralyom.net/ print.php? lng =arabic&sid=63741; and “Fi ijtima damm mudara’ al-mudiriyat wa-qiyadat al-lijan al-shabiya bi-Lahij Al-Majidi yu’akkid tashkil

  2. ALS - resources

    MedlinePlus

    Resources - ALS ... The following organizations are good resources for information on amyotrophic lateral sclerosis : Muscular Dystrophy Association -- www.mda.org/disease/amyotrophic-lateral-sclerosis National Amyotrophic Lateral Sclerosis (ALS) ...

  3. Reply to Gopalswamy et al.

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Richardson, I. G.

    2003-01-01

    The comment of Gopalswamy et al. (thereafter GMY) relates to a letter discussing coronal mass ejections (CMEs), interplanetary ejecta and geomagnetic storms. GMY contend that Cane et al. incorrectly identified ejecta (interplanetary CMEs) and hypothesize that this is because Cane et al. fail to understand how to separate ejecta from "shock sheaths" when interpreting solar wind and energetic particle data sets. They (GMY) are wrong be cause the relevant section of the paper was concerned with the propagation time to 1 AU of any potentially geoeffective structures caused by CMEs, i.e. upstream compression regions with or without shocks, or ejecta. In other words, the travel times used by Cane et al. were purposefully and deliberately distinct from ejecta travel times (except for those slow ejecta, approx. 30% of their events, which generated no upstream features), and no error in identification was involved. The confusion of GMY stems from the description did not characterize the observations sufficiently clearly.

  4. Optical properties and electronic structure of BiTeCl and BiTeBr compounds

    NASA Astrophysics Data System (ADS)

    Makhnev, A. A.; Nomerovannaya, L. V.; Kuznetsova, T. V.; Tereshchenko, O. E.; Kokh, K. A.

    2016-09-01

    Optical properties of BiTeCl and BiTeBr compounds with a strong Rashba spin-orbit coupling are studied in the 0.08-5.0 eV range using the optical ellipsometry method. Fundamental characteristics of the electronic structure are obtained. Similarly to BiTeI, spectra of the imaginary part of dielectric permittivity constant ɛ2( E) in the energy interval between the plasma edge and the threshold of an intense interband absorption (0.7 eV in BiTeCl and 0.6 eV in BiTeBr) display a fine structure of electronic transitions at 0.25 and 0.55 eV in BiTeCl and 0.20 and 0.50 eV in BiTeBr. These features are assigned to electronic transitions between the bulk conduction zones split by the Rashba spin-orbit interaction. The parameters of the electronic structure of BiTeCl and BiTeBr are compared with the BiTeI compound that was studied earlier. In the BiTeCl-BiTeBr-BiTeI row, the absorption edge and main features of the fundamental absorption exhibit a shift to low energies.

  5. In-situ synthesis of nanofibers with various ratios of BiOClx/BiOBry/BiOIz for effective trichloroethylene photocatalytic degradation

    NASA Astrophysics Data System (ADS)

    Zhang, Yifan; Park, Mira; Kim, Hak Yong; Ding, Bin; Park, Soo-Jin

    2016-10-01

    In this work, BiOClx/BiOBry/BiOIz (x + y + z = 1) composite nanofibers were prepared through electrospinning and the sol-gel methods. Photocatalytic degradation of trichloroethylene (TCE) by BiOClx/BiOBry/BiOIz/PAN nanofibers was systematically investigated via gas chromatography (GC). Optimum photocatalytic activity was achieved with BiOCl0.3/BiOBr0.3/BiOI0.4 fibers under solar light irradiation. X-ray photoelectron spectroscopy (XPS) peaks due to Csbnd O and Cdbnd O were observed at 286.0 and 288.3 eV, respectively, it indicated that the BiOClx/BiOBry/BiOIz mixture had been successfully doped on the polyacrylonitrile (PAN) fibers. Furthermore, X-ray diffraction (XRD) results also confirmed that we had synthesized the as-prepared composite nanofibers successfully. Photocatalytic activities of BiOCl0.3/BiOBr0.3/BiOI0.4 were up to 3 times higher than the pure BiOCl, BiOBr and BiOI samples, respectively.

  6. Magnetic interactions in BiFe₀.₅Mn₀.₅O₃ films and BiFeO₃/BiMnO₃ superlattices.

    PubMed

    Xu, Qingyu; Sheng, Yan; Khalid, M; Cao, Yanqiang; Wang, Yutian; Qiu, Xiangbiao; Zhang, Wen; He, Maocheng; Wang, Shuangbao; Zhou, Shengqiang; Li, Qi; Wu, Di; Zhai, Ya; Liu, Wenqing; Wang, Peng; Xu, Y B; Du, Jun

    2015-03-13

    The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces.

  7. Stable excited Au= and Pt= negative ions: A Regge-pole prediction

    NASA Astrophysics Data System (ADS)

    Felfli, Z.; Msezane, A. Z.; Sokolovski, D.

    2010-03-01

    Electron elastic scattering from Au and Pt atoms is investigated in the energy region E < 4.0 eV in search of the possibility of forming and observing stable excited Au= and Pt= negative ions as Regge resonances. Total elastic cross sections (TCSs) and differential cross sections (DCSs) in both impact energy and scattering angle for the excited Au and Pt atoms are calculated. The investigation uses the recent Regge-pole methodology [1] wherein is embedded the vital electron-electron correlations together with a Thomas-Fermi type potential that incorporates the crucial core-polarization interaction, essential for the existence and stability of most negative ions. From the characteristic dramatically sharp resonances in the elastic total and Mulholland partial cross sections we identify excited Au= and Pt= anions and extract their binding energies (BEs). Ramsauer-Townsend minima and shape resonances are also determined. The DCSs also yield the BEs of the Au= and Pt= anions [2]. The TCSs for the excited and ground Au= and Pt= anions are contrasted as well; they provide a clue to the significant catalytic properties of their nanoparticles. [1] D. Sokolovski et al, Phys. Rev. A 76, 012705 (2007); [2] Z. Felfli et al, NIMB, At Press (2010). Supported by U.S. DOE, AFOSR and CAU CFNM, NSF-CREST Program

  8. Near-infrared to mid-infrared photoluminescence of Bi2O3-GeO2 binary glasses.

    PubMed

    Jiang, Xiantao; Su, Liangbi; Guo, Xin; Tang, Huili; Fan, Xiao; Zhan, Yaoyu; Wang, Qingguo; Zheng, Lihe; Li, Hongjun; Xu, Jun

    2012-10-15

    Near-infrared and mid-infrared (MIR) ultrabroad emission bands were observed in as-grown and annealed Bi(2)O(3)-GeO(2) binary glasses, in the wavelength ranges of 1000-1800 nm and 1800-3020 nm, respectively. The MIR emission band could appear through high doping ratio of Bi(2)O(3) or annealing process in air atmosphere. The structure of these glasses, the transformation of emission centers, and the effect of Al ions doping have been discussed, with the conclusion that the Bi(2)O(3)-GeO(2) binary glasses could be a promising laser material.

  9. Development and Manufacture of Bi-2223 Wires

    NASA Astrophysics Data System (ADS)

    Kobayashi, Shin-Ichi

    This chapter reviews Ag-sheathed (Bi, Pb)2Sr2Ca2Cu3Ox (Bi-2223) wire made by the powder-in-tube technique (PIT). The currently leading high-temperature superconductors (HTS) wire technology for practical use is Bi-2223 wire, made by the controlled over-pressure (CT-OP) sintering process. The CT-OP process uses pressures up to 30MPa during heat treatment. The technique densifies the Bi-2223 filaments and enhances the uniformity of the electrical and mechanical performance in the Bi-2223 wire. Today, Bi-2223 wires are used in most HTS applications, such as power cables, many kinds of magnets, and motors for ship propulsion and electric vehicles.

  10. Efficient Charge Separation between Bi and Bi2 MoO6 for Photoelectrochemical Properties.

    PubMed

    Ma, Ying; Jia, Yulong; Wang, Lina; Yang, Min; Bi, Yingpu; Qi, Yanxing

    2016-04-18

    Herein, porous Bi/Bi2 MoO6 nanoparticles have been prepared by a facile in-situ reduction approach. Moreover, the morphology and Bi content of product could be controlled by varying the reaction time. By controlled fabrication, the desired porous Bi2 MoO6 nanostructure with incorporation of Bi was obtained and exhibited high photoelectric and photocatalytic activity. In particular, the samples yield a photocurrent density of 320 μA cm(-2) , which is 3.2 times that of the pure Bi2 MoO6 nanosheet (100 μA cm(-2) ) under the same conditions. UV/Vis diffuse reflectance spectroscopy analysis confirmed the surface plasmon resonance in the as-prepared porous nanoparticles. The improved photoelectric properties could be the synergistic effect of the porous structure with large surface area and effective electron-hole separations between Bi and Bi2 MoO6 .

  11. Energy levels, wavelengths, and transition rates of multipole transitions (E1, E2, M1, M2) in Au{sup 67+} and Au{sup 66+} ions

    SciTech Connect

    Hamasha, Safeia

    2013-11-15

    The fully relativistic configuration interaction method of the FAC code is used to calculate atomic data for multipole transitions in Mg-like Au (Au{sup 67+}) and Al-like Au (Au{sup 66+}) ions. Generated atomic data are important in the modeling of M-shell spectra for heavy Au ions and Au plasma diagnostics. Energy levels, oscillator strengths and transition rates are calculated for electric-dipole (E1), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) for transitions between excited and ground states 3l−nl{sup ′}, such that n=4,5,6,7. The local central potential is derived using the Dirac–Fock–Slater method. Correlation effects to all orders are considered by the configuration interaction expansion. All relativistic effects are included in the calculations. Calculated energy levels are compared against published values that were calculated using the multi-reference many body perturbation theory, which includes higher order QED effects. Favorable agreement was observed, with less than 0.15% difference.

  12. Detection of current induced spin polarization in epitaxial Bi2Te3 thin film

    NASA Astrophysics Data System (ADS)

    Dey, Rik; Roy, Anupam; Pramanik, Tanmoy; Rai, Amritesh; Heon Shin, Seung; Majumder, Sarmita; Register, Leonard F.; Banerjee, Sanjay K.

    2017-03-01

    We electrically detect charge current induced spin polarization on the surface of a molecular beam epitaxy grown Bi2Te3 thin film in a two-terminal device with a ferromagnetic MgO/Fe contact and a nonmagnetic Ti/Au contact. The two-point resistance, measured in an applied magnetic field, shows a hysteresis tracking the magnetization of Fe. A theoretical estimate is obtained for the change in resistance on reversing the magnetization direction of Fe from coupled spin-charge transport equations based on the quantum kinetic theory. The order of magnitude and the sign of the hysteresis are consistent with the spin-polarized surface state of Bi2Te3.

  13. Transport properties of Ar+ irradiated resistive switching BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    Jin, L.; Shuai, Y.; Ou, X.; Luo, W. B.; Wu, C. G.; Zhang, W. L.; Bürger, D.; Skorupa, I.; You, T.; Du, N.; Schmidt, O. G.; Schmidt, H.

    2015-05-01

    BiFeO3 thin films were irradiated by Ar+ ions with different fluences. The rectifying and resistive switching behaviour were retained on the Au/BiFeO3/Pt stack, and the ON/OFF ratio clearly depends on the Ar+ fluence. It was observed that the transport in high resistance state changes from Poole-Frenkel conduction to space-charge-limited conduction after irradiation. While the conduction of the low resistance state is dominated by both the interface and the bulk thin film in the pristine devices, however, it is only dominated by the interface in the irradiated devices. The observed change of conduction mechanism was explained by additionally created oxygen vacancies (OVs) during irradiation, which also improves the stability of resistive switching.

  14. Unique activity of Pd monomers: hydrogen evolution at AuPd(111) surface alloys.

    PubMed

    Pluntke, Y; Kibler, L A; Kolb, D M

    2008-07-07

    Well-defined Au/Pd(111) alloy films have been prepared on a Ru(0001) substrate by electrochemical metal deposition and subsequent heating up to 700 degrees C. The electrochemical behaviour of the 20 monolayers thick epitaxially-grown films is in excellent agreement with both equilibrium surface composition and distribution for Au/Pd alloys on Mo(110) as previously reported (D. W. Goodman et al., J. Phys. Chem., 2005, B109, 18535). The electrocatalytic activity of the AuPd(111) surface alloys was studied for the hydrogen evolution in 0.1 M H(2)SO(4) as a function of surface composition. Maximum activities were found for Pd fractions of 0.2 +/- 0.1, where the population of Pd atoms surrounded by Au has its maximum. These Pd monomers are found to be about 20 times more active than Pd atoms in the Pd overlayer.

  15. Nanostructure, Excitations, and Thermoelectric Properties of Bi2Te3-Based Nanomaterials

    NASA Astrophysics Data System (ADS)

    Aabdin, Z.; Peranio, N.; Eibl, O.; Töllner, W.; Nielsch, K.; Bessas, D.; Hermann, R. P.; Winkler, M.; König, J.; Böttner, H.; Pacheco, V.; Schmidt, J.; Hashibon, A.; Elsässer, C.

    2012-06-01

    The effect of dimensionality and nanostructure on thermoelectric properties in Bi2Te3-based nanomaterials is summarized. Stoichiometric, single-crystalline Bi2Te3 nanowires were prepared by potential-pulsed electrochemical deposition in a nanostructured Al2O3 matrix, yielding transport in the basal plane. Polycrystalline, textured Sb2Te3 and Bi2Te3 thin films were grown at room temperature using molecular beam epitaxy and subsequently annealed at 250°C. Sb2Te3 films revealed low charge carrier density of 2.6 × 1019 cm-3, large thermopower of 130 μV K-1, and large charge carrier mobility of 402 cm2 V-1 s-1. Bi2(Te0.91Se0.09)3 and (Bi0.26Sb0.74)2Te3 nanostructured bulk samples were prepared from as-cast materials by ball milling and subsequent spark plasma sintering, yielding grain sizes of 50 nm and thermal diffusivities reduced by 60%. Structure, chemical composition, as well as electronic and phononic excitations were investigated by x-ray and electron diffraction, nuclear resonance scattering, and analytical energy-filtered transmission electron microscopy. Ab initio calculations yielded point defect energies, excitation spectra, and band structure. Mechanisms limiting the thermoelectric figure of merit ZT for Bi2Te3 nanomaterials are discussed.

  16. Electrodeposition of Bi-Te alloy films

    SciTech Connect

    Takahashi, Makoto; Oda, Youichi; Ogino, Takayuki; Furuta, Shinsaku . Dept. of Industrial Chemistry)

    1993-09-01

    Electrochemical deposition of Bi-Te alloy films from acidic solutions containing Bi(NO[sub 3])[sub 3] and TeO[sub 2] has been investigated. The thickness, compound, and composition of the Bi-Te alloy films have been examined using stylus-type surface profiling techniques, X-ray diffraction peak measurement, and inductively coupled plasma/Auger electron spectroscopy measurements. At potentials where limiting current was observed, the compositions of films were controlled by the mole ratio [Bi[sup 3+

  17. Photocatalytic activity of Bi2WO6/Bi2S3 heterojunctions: the facilitation of exposed facets of Bi2WO6 substrate

    NASA Astrophysics Data System (ADS)

    Yan, Long; Wang, Yufei; Shen, Huidong; Zhang, Yu; Li, Jian; Wang, Danjun

    2017-01-01

    Bi2S3/Bi2WO6 hybrid architectures with exposed (020) Bi2WO6 facets have been synthesized via a controlled anion exchange approach. X-ray photoelectron spectroscopy (XPS) reveals that a small amount of Bi2S3 was formed on the surface of Bi2WO6 during the anion exchange process, thus leading to the transformation from the Bi2WO6 to Bi2S3/Bi2WO6. A rhodamine B (RhB) aqueous solution was chosen as model organic pollutants to evaluate the photocatalytic activities of the Bi2S3/Bi2WO6 catalysts. Under visible light irradiation, the Bi2S3/Bi2WO6-TAA displayed the excellent visible light photoactivities compared with pure Bi2S3, Bi2WO6 and other composite photocatalysts. The efficient photocatalytic activity of the Bi2S3/Bi2WO6-TAA composite microspheres was ascribed to the constructed heterojunctions and the inner electric field caused by the exposed (020) Bi2WO6 facets. Active species trapping experiments revealed that h+ and O2rad - are the main active species in the photocatalytic process. Furthermore, the as-obtained photocatalysts showed good photocatalytic activity after four recycles. The results presented in this study provide a new concept for the rational design and development of highly efficient photocatalysts.

  18. Chiral exciton in the topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Kung, Hsiang-Hsi; Salehi, Maryam; Wang, Xueyun; Koirala, Nikesh; Brahlek, Matthew; Lee, Alexander; Cheong, Sang-Wook; Oh, Seongshik; Blumberg, Girsh

    Materials with novel band structures can host ``chiral excitons'', where the exciton emission preserves the helicity of the excitation photon, as recently demonstrated in transition metal dichalcogenide monolayers. Here, we report the observation of a highly polarized photoluminescence peak, which is due to chiral exciton emission in the topological insulator Bi2Se3. Surprisingly, the energy of the emission is centered at 2.26 eV, much higher than the 0.3 eV bulk band gap of Bi2Se3. The excitation profile shows maximum polarization around 2.60 eV excitation, suggesting the chiral exciton is due to interband transition between the topological surface states and a bulk band. We demonstrate that the polarization of the exciton emission is insensitive to temperature and Bi2Se3 film thickness, providing a convenient and robust platform for optoelectronic applications. Gb, HHK and AL acknowledge support from NSF Award DMR-1104884. MS, NK, MB and SO are funded by Gordon and Betty Moore Foundation's EPiQS initiative (GBMF4418) and NSF(DMR-1308142). XYW and SWC acknowledge support from NSF Award DMREF-1233349.

  19. The role of Te(IV) and Bi(III) chloride complexes in hydrothermal mass transfer: An X-ray absorption spectroscopic study

    SciTech Connect

    Etschmann, Barbara E.; Liu, Weihua; Pring, Allan; Grundler, Pascal V.; Tooth, Blake; Borg, Stacey; Testemale, Denis; Brewe, Dale; Brugger, Joël

    2016-05-01

    Tellurium (Te) and bismuth (Bi) are two metal(loid)s often enriched together with gold (Au) in hydrothermal deposits; however the speciation and transport properties for these two metals in hydrothermal systems are poorly understood. We investigated the effect of chloride on the speciation of Te(IV) and Bi(III) in hydrothermal solutions using in-situ XAS spectroscopy. At ambient temperature, oxy-hydroxide complexes containing the [TeO3] moiety (e.g., H3TeO3+ under highly acidic conditions) predominate in salty solutions over a wide range in pH and salt concentrations. Te(IV)-Cl complexes only appear at pH(25 degrees C) <= 2 and high Cl- activity (>= 10). The highest order Te(IV) chloride complex detected is TeCl4(aq), and contains the [TeCl4] moiety. Upon heating to 199 degrees C, the Te(IV)-Cl complexes become more stable; however they still required highly acidic conditions which are likely to exist only in very limited environments in nature. At ambient temperature, Bi(III) is coordinated to 5.5(5) Cl atoms in high salinity, acidic (HCl >= 0.5 m) chloride solutions. This, combined with large EXAFS-derived structural disorder parameters, suggests that the Bi(III) complex is most likely present as both BiCl52- and BiCl63-. The number of Cl atoms coordinated to Bi(III) decreases with increasing temperature; at around 200 degrees C and above, Bi(III) is coordinated to three Cl atoms. Overall the data show that Te(IV) chloride complexes can be ignored in predicting Te mobility under oxidizing conditions in most geological environments, but that Bi(III) chloride complexes are expected to account for Bi mobility in acidic brines. New thermodynamic properties for Bi(III) chloride complexes are provided to improve reactive transport modeling of Bi up to 500 degrees C. Although higher order complexes such as BiCl52- and BiCl63- exist at ambient temperature, the BiCl3(aq) complex becomes the predominant chloride complex in saline solutions at T >= 200 degrees C.

  20. EDTA assisted highly selective detection of As(3+) on Au nanoparticle modified glassy carbon electrodes: facile in situ electrochemical characterization of Au nanoparticles.

    PubMed

    Chen, Hsiao-Hua; Huang, Jing-Fang

    2014-12-16

    A facile electrochemical characterization technique of Au nanoparticles (AuNPs) developed by Wang et al. ( Wang, Y.; Laborda, E.; Salter, C.; Crossley, A.; Compton, R. G. Analyst 2012 , 137 , 4693 - 4697 ) was used to track the variation in the particle size and density of AuNPs in situ and to assist in optimizing the conditions of analysis and catalysis. In this method, the combination of total surface area determined by Pb underpotential deposition (UPD) and the amount of Au obtained by anodic stripping of Au in HCl solution was used to evaluate the average diameter of AuNPs and the number of particles on the electrode. The detection of As(3+) in aqueous solution by a AuNP modified glassy carbon electrode (Aunano@GCE) using the electrochemical characterization technique was examined. The AuNPs with a uniform shape and size, deposited onto the GCEs using multiple-scan cyclic voltammetry (MSCV), were suitable for the electrochemical evaluation. The calibration curve for the detection of As(3+) had a dynamic range of 0.1-15.0 μg L(-1) (from 1.30 to 200 nM, y = 0.21x (in μA L μg(-1)) + 0.01 (R(2) = 0.999)) and showed a sensitivity of 0.21 μA L μg(-1) (16.15 μA μM(-1)). A detection limit as low as 0.0025 μg L(-1) (32.5 pM) was achieved. The chelating agent ethylenediaminetetraacetate (EDTA) selectively chelated with the interfering metal ions and effectively inhibited the interfering ions from competing with the ion of interest (As(3+)), in the preconcentration process. The presence of EDTA effectively eliminated interference from several metal ions, especially Cu(2+) and Hg(2+). This method was validated by analyzing the As(3+) content in real water samples.

  1. The equilibrium geometry and electronic structure of Bi nanolines on clean and hydrogenated Si(001) surfaces.

    PubMed

    Miwa, R H; Macleod, J M; McLean, A B; Srivastava, G P

    2005-10-01

    The equilibrium geometry, electronic structure and energetic stability of Bi nanolines on clean and hydrogenated Si(001) surfaces have been examined by means of ab initio total energy calculations and scanning tunnelling microscopy. For the Bi nanolines on a clean Si surface the two most plausible structural models, the Miki or M model (Miki et al 1999 Phys. Rev. B 59 14868) and the Haiku or H model (Owen et al 2002 Phys. Rev. Lett. 88 226104), have been examined in detail. The results of the total energy calculations support the stability of the H model over the M model, in agreement with previous theoretical results. For Bi nanolines on the hydrogenated Si(001) surface, we find that an atomic configuration derived from the H model is also more stable than an atomic configuration derived from the M model. However, the energetically less stable (M) model exhibits better agreement with experimental measurements for equilibrium geometry. The electronic structures of the H and M models are very similar. Both models exhibit a semiconducting character, with the highest occupied Bi-derived bands lying at approximately 0.5 eV below the valence band maximum. Simulated and experimental STM images confirm that at a low negative bias the Bi lines exhibit an 'antiwire' property for both structural models.

  2. The equilibrium geometry and electronic structure of Bi nanolines on clean and hydrogenated Si(001) surfaces

    NASA Astrophysics Data System (ADS)

    Miwa, R. H.; MacLeod, J. M.; McLean, A. B.; Srivastava, G. P.

    2005-10-01

    The equilibrium geometry, electronic structure and energetic stability of Bi nanolines on clean and hydrogenated Si(001) surfaces have been examined by means of ab initio total energy calculations and scanning tunnelling microscopy. For the Bi nanolines on a clean Si surface the two most plausible structural models, the Miki or M model (Miki et al 1999 Phys. Rev. B 59 14868) and the Haiku or H model (Owen et al 2002 Phys. Rev. Lett. 88 226104), have been examined in detail. The results of the total energy calculations support the stability of the H model over the M model, in agreement with previous theoretical results. For Bi nanolines on the hydrogenated Si(001) surface, we find that an atomic configuration derived from the H model is also more stable than an atomic configuration derived from the M model. However, the energetically less stable (M) model exhibits better agreement with experimental measurements for equilibrium geometry. The electronic structures of the H and M models are very similar. Both models exhibit a semiconducting character, with the highest occupied Bi-derived bands lying at ~0.5 eV below the valence band maximum. Simulated and experimental STM images confirm that at a low negative bias the Bi lines exhibit an 'antiwire' property for both structural models.

  3. An Icosahedral Quasicrystal and Its 1/0 Crystalline Approximant in the Ca–Au–Al System

    SciTech Connect

    Pham, Joyce; Kreyssig, Andreas; Goldman, Alan I.; Miller, Gordon J.

    2016-10-17

    A new icosahedral quasicrystalline phase, CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.40(6); CaAu4.4Al1.6, aQC = 5.383(4) Å, and Pm35], and its lowest-order 1/0 cubic crystalline approximant phase, CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1); a = 9.0766(5)–9.1261(8) Å, Pa3(No. 205), and Pearson symbol cP40], have been discovered in the Ca-poor region of the Ca–Au–Al system. In the crystalline approximant, eight [Au3–xAl1+x] tetrahedra fill the unit cell, and each tetrahedron is surrounded by four Ca atoms, thus forming a three-dimensional network of {Ca4/4[Au3–xAl1+x]} tetrahedral stars. A computational study of Au and Al site preferences concurs with the experimental results, which indicate a preference for near-neighbor Au–Al interactions over Au–Au and Al–Al interactions. Analysis of the electronic density of states and the associated crystal orbital Hamilton population curves was used to rationalize the descriptions of CaAu4.5–xAl1.5+x [0.11 ≤ x ≤ 0.46(6)] and CaAu3+xAl1–x [0 ≤ x ≤ 0.31(1)] as polar intermetallic species, whereby Ca atoms engage in polar covalent bonding with the electronegative, electron-deficient [Au3–xAl1+x] tetrahedral clusters and the observed phase width of the crystalline approximant.

  4. Methanobactin-Mediated Synthesis of Gold Nanoparticles Supported over Al2O3 toward an Efficient Catalyst for Glucose Oxidation

    PubMed Central

    Xin, Jia-Ying; Lin, Kai; Wang, Yan; Xia, Chun-Gu

    2014-01-01

    Methanobactin (Mb) is a copper-binding peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and reduce Au(III) to Au(0). In this paper, Au/Al2O3 catalysts prepared by a novel incipient wetness-Mb-mediated bioreduction method were used for glucose oxidation. The catalysts were characterized, and the analysis revealed that very small gold nanoparticles with a particle size <4 nm were prepared by the incipient wetness-Mb-mediated bioreduction method, even at 1.0% Au loading (w/w). The influence of Au loading, calcination temperature and calcination time on the specific activity of Au/Al2O3 catalysts was systematically investigated. Experimental results showed that decomposing the Mb molecules properly by calcinations can enhance the specific activity of Au/Al2O3 catalysts, though they acted as reductant and protective agents during the catalyst preparation. Au/Al2O3 catalysts synthesized by the method exhibited optimum specific activity under operational synthesis conditions of Au loading of 1.0 wt % and calcined at 450 °C for 2 h. The catalysts were reused eight times, without a significant decrease in specific activity. To our knowledge, this is the first attempt at the preparation of Au/Al2O3 catalysts by Mb-mediated in situ synthesis of gold nanoparticles. PMID:25429424

  5. Materials Data on Li2BiAu (SG:216) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-02-10

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. Materials Data on AcBiAu2 (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-08-27

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  7. Materials Data on Ba2BiAu (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-07-31

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  8. Materials Data on Yb2BiAu (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-08-05

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  9. Materials Data on LaBiAu2 (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-08-21

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  10. Materials Data on Sr2BiAu (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-08-21

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  11. Materials Data on PrBiAu2 (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-08-21

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  12. Materials Data on Pu2BiAu (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-07-31

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  13. Materials Data on NdBiAu2 (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-08-31

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  14. Materials Data on Tb5BiAu2 (SG:140) by Materials Project

    SciTech Connect

    Kristin Persson

    2016-05-23

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  15. THZ Phonon Spectroscopy of Bi-2223 and Bi-2212: Evidence for Phonon Pairing

    NASA Astrophysics Data System (ADS)

    Ponomarev, Ya. G.; Van, Hoang Hoai

    Facts are presented evidencing the strong electron-phonon interaction and the scaling of a superconducting gap and a critical temperature in doped Bi-2212 single crystals. A sharp extra structure in the current-voltage characteristics (CVC's) of Bi-2212 contacts is attributed to the presence of the extended van Hove singularity (EVHS) close to the Fermi level in slightly overdoped and slightly underdoped samples. THZ phonon spectroscopy studies of Bi-2223 and Bi-2212 are overviewed. An observed giant instability in I(V) - characteristics of Bi-2223 nanosteps is probably caused by a resonant emission of 2Δ - optical phonons in a process of recombination of nonequilibrium quasiparticles (Krasnov model).

  16. Screen printed Y and Bi-based superconductors

    NASA Technical Reports Server (NTRS)

    Haertling, Gene H.; Hsi, Chi-Shiung

    1992-01-01

    High T(sub c) superconducting thick film was prepared by screen printing process. Y-based (YBa2Cu3O(7 - x)) superconducting thick films were printed on 211/Al2O3, SNT/Al2O3, and YSZ substrates. Because of poor adhesion of the superconducting thick films to 211/Al2O3 and SNT/Al2O3 substrates, relatively low T(sub c) and J(sub c) values were obtained from the films printed on these substrates. Critical temperatures of YBa2Cu3O(7 - x) thick films deposited on 211/Al2O3 and SNT/Al2O3 substrates were about 80 K. The critical current densities of these films were less than 2 A/cm(exp 2). Higher T(sub c) and J(sub c) films were printed on the YSZ substrates; T(sub c) = 86.4 K and J(sub c) = 50.4 A/cm(exp 2). Multiple lead samples were also prepared on the YSZ substrates. These showed lower T(sub c) and J(sub c) values than plain samples. The heat treatment conditions of the multiple lead samples are still under investigation. Bi-based superconductor thick films have been obtained so far. Improving the superconducting properties of the BSCCO screen printed thick films will be emphasized in future work.

  17. Nanoporous bimetallic Pt-Au alloy nanocomposites with superior catalytic activity towards electro-oxidation of methanol and formic acid

    NASA Astrophysics Data System (ADS)

    Zhang, Zhonghua; Wang, Yan; Wang, Xiaoguang

    2011-04-01

    We present a facile route to fabricate novel nanoporous bimetallic Pt-Au alloy nanocomposites by dealloying a rapidly solidified Al75Pt15Au10 precursor under free corrosion conditions. The microstructure of the precursor and the as-dealloyed sample was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray (EDX) analysis. The Al75Pt15Au10 precursor is composed of a single-phase Al2(Au,Pt) intermetallic compound, and can be fully dealloyed in a 20 wt.% NaOH or 5 wt.% HCl aqueous solution. The dealloying leads to the formation of the nanoporous Pt60Au40 nanocomposites (np-Pt60Au40 NCs) with an fcc structure. The morphology, size and crystal orientation of grains in the precursor can be conserved in the resultant nanoporous alloy. The np-Pt60Au40 NCs consist of two zones with distinct ligament/channel sizes and compositions. The formation mechanism of these np-Pt60Au40 NCs can be rationalized based upon surface diffusion of more noble elements and spinodal decomposition during dealloying. Electrochemical measurements demonstrate that the np-Pt60Au40 NCs show superior catalytic activity towards the electro-oxidation of methanol and formic acid in the acid media compared to the commercial JM-Pt/C catalyst. This material can find potential applications in catalysis related areas, such as direct methanol or formic acidfuelcells. Our findings demonstrate that dealloying is an effective and simple strategy to realize the alloying of immiscible systems under mild conditions, and to fabricate novel nanostructures with superior performance.We present a facile route to fabricate novel nanoporous bimetallic Pt-Au alloy nanocomposites by dealloying a rapidly solidified Al75Pt15Au10 precursor under free corrosion conditions. The microstructure of the precursor and the as-dealloyed sample was characterized using X-ray diffraction, scanning electron

  18. Influence of the initial Bi2223 phase content on microstructure development in Bi2223/Ag tapes

    NASA Astrophysics Data System (ADS)

    J-C, Grivel; P, Yang X.; B, Abrahamsen A.; Z, Han; H, Andersen N.; Zimmermann M, von

    2010-06-01

    (Bi,Pb)2Sr2Ca2Cu3O10 (Bi2223) Ag-sheathed tapes were produced from precursors containing various amounts of pre-reacted Bi2223 phase obtained by means of controlled calcinations of the starting powder mixture. The evolution of the critical current density during the first 20h of the first heat treatment follows closely that of the Bi2223 phase content. A maximum rate of increase is observed for precursor powders initially containing a small amount of Bi2223. The crystallinity of the Bi2223 phase along its c-axis improves with sintering time and is better in the tapes manufactured with precursor powders containing the largest amount of prereacted Bi2223. While the degree of preferential orientation of the Bi2223 phase at the Ag/ceramic core interface is not influenced by the initial Bi2223 phase content, the average texture in the ceramic core worsens with the increase of initial Bi2223 phase content. This effect is likely to play a role in the limited performance of Bi2223-rich precursors.

  19. Site Preference of Ternary Alloying Additions to AuTi

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Mosca, Hugo O.; Noebe, Ronald D.

    2006-01-01

    Atomistic modeling of the site substitution behavior of several alloying additions, namely. Na, Mg, Al, Si. Sc, V, Cr, Mn. Fe, Co, Ni, Cu, Zn, Y, Zr. Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, and Pt in B2 TiAu is reported. The 30 elements can be grouped according to their absolute preference for a specific site, regardless of concentration, or preference for available sites in the deficient sublattice. Results of large scale simulations are also presented, distinguishing between additions that remain in solution from those that precipitate a second phase.

  20. Bi- or multifunctional peptide drugs

    PubMed Central

    Schiller, Peter W.

    2009-01-01

    Strategies for the design of bi- or multifunctional drugs are reviewed. A distinction is made between bifunctional drugs interacting in a monovalent fashion with two targets and ligands containing two distinct pharmacophores binding in a bivalent mode to the two binding sites in a receptor heterodimer. Arguments are presented to indicate that some of the so-called “bivalent” ligands reported in the literature are unlikely to simultaneously interact with two binding sites. Aspects related to the development of bi- or multifunctional drugs are illustrated with examples from the field of opioid analgesics. The drug-like properties of the tetrapeptide Dmt1[DALDA] with triple action as a μ opioid agonist, norepinephrine uptake inhibitor and releaser of endogenous opioid peptides to produce potent spinal analgesia are reviewed. Rationales for the development of opioid peptides with mixed agonist/antagonist profiles as analgesics with reduced side effects are presented. Progress in the development of mixed μ opioid agonist/δ opioid antagonists with low propensity to produce tolerance and physical dependence is reviewed. Efforts to develop bifunctional peptides containing a μ opioid agonist and a cholecystokinin antagonist or an NK1 receptor antagonist as analgesics expected to produce less tolerance and dependence are also reviewed. A strategy to improve the drug-like properties of bifunctional opioid peptide analgesics is presented. PMID:19285088

  1. COMMENT: Comment on 'Bi nanolines on Si(001): registry with substrate'

    NASA Astrophysics Data System (ADS)

    Bowler, D. R.; Owen, J. H. G.; Miki, K.

    2006-03-01

    A recent article (Miwa et al 2005 Nanotechnology 16 2427) casts doubt on the four-dimer-wide Haiku model for the Bi nanoline on Si(001), suggesting instead that the three-dimer-wide Miki model (which had been ruled out) is a better fit in particular to x-ray data. The reasons why the Haiku model provides the best fit to all published data among currently proposed structures are discussed, concentrating on the width and registry of the Bi nanoline, and mentioning new data which shows that under appropriate conditions the two structures coexist in the same surface.

  2. In-vitro and in-vivo evaluation of a new Ti-15Mo-1Bi alloy.

    PubMed

    Lee, Jing-Wei; Lin, Dan-Jae; Ju, Chien-Ping; Yin, Hsiang-Shu; Chuang, Cheng-Chung; Lin, Jiin-Huey Chern

    2009-11-01

    The newly developed Ti-15Mo-1Bi alloy not only possesses all the desirable mechanical properties inherent to beta-Ti Mo alloys, but may even enjoy better clinical applicability with the addition of bismuth element, which has long been administered as antibacterial and antitumor medicines. A significantly higher viability of 3T3 cells was demonstrated when they were grown on Ti-15Mo-1Bi alloy than on Ti-15Mo and Ti-6Al-4V. Cells incubated in the medium conditioned by Bi powder at 37 degrees C for 96 h exhibited viability similar to that in the blank group and higher than that in the Ni conditioned group. In vivo experiments using 6 mm x 2 mm metal pin implanted into the epicondyle of rabbit femur revealed superior potential of new bone growth and better persistence of the deposited bony tissue with the Ti-15Mo-1Bi alloy in contrast to that with Ti-6Al-4V. The difference is evident at 12th week and become even more prominent after 26 weeks, with the new bone area measuring 249% of that around Ti-6Al-4V alloy. In summary, Ti-15Mo-1Bi alloys show no cytotoxicity in the in-vitro test and demonstrates superior ability to retain bone in the in-vivo implantation experiment as compared with Ti-6Al-4V alloys.

  3. The Electronic Properties and L3 XANES of Au and Nano-Au

    SciTech Connect

    Yiu, Y.M.; Zhang, P.; Sham, T.K.

    2004-04-20

    The electronic properties of Au crystal and nano Au have been investigated by theory and experiment. Molecularly capped nano-Au was synthesized using the two-phase method. Au nano-particles have been characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). They retain the fcc crystal structure. Their sizes have been determined to be in a range from 5.5 nm to 1.7 nm. The L3 X-ray Absorption Near Edge Structure (XANES) of nano-Au and Au foil have been recorded using synchrotron radiation, and examined by theoretical calculation based on the first principles. Both theory and experiment show that the nano-Au particles have essentially all the Au L3 XANES features of bulk Au in the near edge region with less pronounced resonance peaks. It is also shown that nano Au exhibits lower 4f binding energy than bulk Au in good agreement with quantum confined Au systems reported previously.

  4. Anisotropic Terahertz Emission from Bi2Se3 Thin Films with Inclined Crystal Planes.

    PubMed

    Hamh, Sun Young; Park, Soon-Hee; Han, Jeongwoo; Jeon, Jeong Heum; Kahng, Se-Jong; Kim, Sung; Choi, Suk-Ho; Bansal, Namrata; Oh, Seongshik; Park, Joonbum; Kim, Jun Sung; Kim, Jae Myung; Noh, Do Young; Lee, Jong Seok

    2015-12-01

    We investigate the surface states of topological insulator (TI) Bi2Se3 thin films grown on Si nanocrystals and Al2O3 substrates by using terahertz (THz) emission spectroscopy. Compared to bulk crystalline Bi2Te2Se, film TIs exhibit distinct behaviors in the phase and amplitude of emitted THz radiation. In particular, Bi2Se3 grown on Al2O3 shows an anisotropic response with a strong modulation of the THz signal in its phase. From x-ray diffraction, we find that the crystal plane of the Bi2Se3 films is inclined with respect to the plane of the Al2O3 substrate by about 0.27°. This structural anisotropy affects the dynamics of photocarriers and hence leads to the observed anisotropic response in the THz emission. Such relevance demonstrates that THz emission spectroscopy can be a sensitive tool to investigate the fine details of the surface crystallography and electrostatics of thin film TIs.

  5. Nanoporous bimetallic Pt-Au alloy nanocomposites with superior catalytic activity towards electro-oxidation of methanol and formic acid.

    PubMed

    Zhang, Zhonghua; Wang, Yan; Wang, Xiaoguang

    2011-04-01

    We present a facile route to fabricate novel nanoporous bimetallic Pt-Au alloy nanocomposites by dealloying a rapidly solidified Al(75)Pt(15)Au(10) precursor under free corrosion conditions. The microstructure of the precursor and the as-dealloyed sample was characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray (EDX) analysis. The Al(75)Pt(15)Au(10) precursor is composed of a single-phase Al(2)(Au,Pt) intermetallic compound, and can be fully dealloyed in a 20 wt.% NaOH or 5 wt.% HCl aqueous solution. The dealloying leads to the formation of the nanoporous Pt(60)Au(40) nanocomposites (np-Pt(60)Au(40) NCs) with an fcc structure. The morphology, size and crystal orientation of grains in the precursor can be conserved in the resultant nanoporous alloy. The np-Pt(60)Au(40) NCs consist of two zones with distinct ligament/channel sizes and compositions. The formation mechanism of these np-Pt(60)Au(40) NCs can be rationalized based upon surface diffusion of more noble elements and spinodal decomposition during dealloying. Electrochemical measurements demonstrate that the np-Pt(60)Au(40) NCs show superior catalytic activity towards the electro-oxidation of methanol and formic acid in the acid media compared to the commercial JM-Pt/C catalyst. This material can find potential applications in catalysis related areas, such as direct methanol or formic acid fuel cells. Our findings demonstrate that dealloying is an effective and simple strategy to realize the alloying of immiscible systems under mild conditions, and to fabricate novel nanostructures with superior performance.

  6. Bi-substituted iron garnet films for one-dimensional magneto-photonic crystals: Synthesis and properties

    SciTech Connect

    Shaposhnikov, A.N.; Karavainikov, A.V.; Prokopov, A.R.; Berzhansky, V.N.; Salyuk, O.Y.

    2012-06-15

    Graphical abstract: Faraday hysteresis loops for Bi{sub 1.0}Y{sub 0.5}Gd{sub 1.5}Fe{sub 4.2}Al{sub 0.8}O{sub 12} film on glass-ceramic substrate (a), Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} film on gallium–gadolinium garnet (b) and for glass-ceramic/SiO{sub 2}/Bi{sub 1.0}Y{sub 0.5}Gd{sub 1.5}Fe{sub 4.2}Al{sub 0.8}O{sub 12}/Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} structure (c). Highlights: ► Bismuth-substituted iron garnet films as magneto-optical layers in magneto-photonic crystals. ► It is impossible to crystallize the films with high Bi content on amorphous substrates. ► The crystallization of the films can be achieved by their deposition on buffer layer with low bismuth content. -- Abstract: The crystallization processes in Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12}, Bi{sub 2.5}Gd{sub 0.5}Fe{sub 3.8}Al{sub 1.2}O{sub 12}, Bi{sub 1.5}Gd{sub 1.5}Fe{sub 4.5}Al{sub 0.5}O{sub 12} and Bi{sub 1.0}Y{sub 0.5}Gd{sub 1.5}Fe{sub 4.2}Al{sub 0.8}O{sub 12} garnet films deposited by reactive ion beam sputtering on (1 1 1) gadolinium–gallium garnet substrates, optical glass-ceramic and SiO{sub 2} films have been studied. Films were annealed at low pressure in oxygen atmosphere and in the air. The possibility of preparation of crystalline garnet films with high concentration of bismuth on the SiO{sub 2} films using a buffer layer with low concentration of Bi has been shown. This allows to produce one-dimensional magneto-photonic crystals with high effective Faraday rotation (several tens of°/μm for the visible optical spectrum).

  7. M-Au/TiO2 (M = Ag, Pd, and Pt) nanophotocatalyst for overall solar water splitting: role of interfaces

    NASA Astrophysics Data System (ADS)

    Melvin, Ambrose A.; Illath, Kavya; Das, Tanmay; Raja, Thirumalaiswamy; Bhattacharyya, Somnath; Gopinath, Chinnakonda S.

    2015-08-01

    M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2 generation activity by forming a bi-metallic system. Degussa P25 was used as a TiO2 substrate to photodeposit Au followed by Au + M (M = Ag/Pd/Pt). The SWS activity of the M-Au/TiO2 was determined through photocatalytic H2 production in the presence of methanol as a sacrificial agent under one sun conditions with an AM1.5 filter. The highest H2 yield was observed for Pt0.5-Au1/TiO2 and was around 1.3 +/- 0.07 mmol h-1 g-1, with an apparent quantum yield (AQY) of 6.4%. Pt0.5-Au1/TiO2 also demonstrated the same activity for 25 cycles of five hours each for 125 h. Critically, the same Pt0.5-Au1/TiO2 catalyst was active in overall SWS (OSWS) without any sacrificial agent, with an AQY = 0.8%. The amount of Au and/or Pt was varied to obtain the optimum composition and it was found that the Pt0.5-Au1/TiO2 composition exhibits the best activity. Detailed characterization by physico-chemical, spectral and microscopy measurements was carried out to obtain an in-depth understanding of the origin of the photocatalytic activity of Pt0.5-Au1/TiO2. These in-depth studies show that gold interacts predominantly with oxygen vacancies present on titania surfaces, and Pt preferentially interacts with gold for an effective electron-hole pair separation at Pt-Au interfaces and electron storage in metal particles. The Pt in Pt0.5-Au1/TiO2 is electronically and catalytically different from the Pt in Pt/TiO2 and it is predicted that the former suppresses the oxygen reduction reaction.M-Au/TiO2 (M = Ag, Pd, Pt) composites were prepared through a facile one-pot photodeposition synthesis and evaluated for solar water splitting (SWS) with and without a sacrificial agent. The M-Au combination exhibits a dominant role in augmenting the H2

  8. Neutron diffraction study of the BiFeO₃ spin cycloid at low temperature.

    PubMed

    Herrero-Albillos, Julia; Catalan, Gustau; Rodriguez-Velamazan, José Alberto; Viret, Michel; Colson, Dorothée; Scott, James F

    2010-06-30

    The reported observation of two anomalies in the intensity of the magnon Raman peaks of BiFeO₃ at 140 and 200 K (Singh et al 2008 J. Phys.: Condens. Mater 20 252203; Cazayous et al 2008 Phys. Rev. Lett. 101 037601) led to the hypothesis that such anomalies might originate from a spin reorientation transition. In order to test this hypothesis, we have used temperature-dependent neutron diffraction to track the evolution of the magnetic configuration in single crystals of BiFeO₃. Our results indicate that there is no average reorientation of the spins. This suggests that the magnon anomalies may instead be related to the freezing of modes that do not alter the average projection of the spins over the plane of the cycloid, as also reported for multiferroic TbMnO₃ (Senff et al 2006 J. Phys.: Condens. Mater 18 2069).

  9. Neutron diffraction study of the BiFeO3 spin cycloid at low temperature

    NASA Astrophysics Data System (ADS)

    Herrero-Albillos, Julia; Catalan, Gustau; Rodriguez-Velamazan, José Alberto; Viret, Michel; Colson, Dorothée; Scott, James F.

    2010-06-01

    The reported observation of two anomalies in the intensity of the magnon Raman peaks of BiFeO3 at 140 and 200 K (Singh et al 2008 J. Phys.: Condens. Mater 20 252203; Cazayous et al 2008 Phys. Rev. Lett. 101 037601) led to the hypothesis that such anomalies might originate from a spin reorientation transition. In order to test this hypothesis, we have used temperature-dependent neutron diffraction to track the evolution of the magnetic configuration in single crystals of BiFeO3. Our results indicate that there is no average reorientation of the spins. This suggests that the magnon anomalies may instead be related to the freezing of modes that do not alter the average projection of the spins over the plane of the cycloid, as also reported for multiferroic TbMnO3 (Senff et al 2006 J. Phys.: Condens. Mater 18 2069).

  10. Synthesis and electrocatalytic properties of PtBi nanoplatelets and PdBi nanowires

    NASA Astrophysics Data System (ADS)

    Liao, Hanbin; Zhu, Jinghan; Hou, Yanglong

    2013-12-01

    We have demonstrated a one-pot, facile and rapid strategy to synthesize novel PtBi nanoplatelets (NPLs) and PdBi nanowires (NWs) with controlled shape, size, and composition in the presence of oleylamine (OAm) and NH4Br. In contrast to the conventional face centered cubic (fcc) structure of Pt-based NPs, PtBi possesses a chemically ordered intermetallic hexagonal close packed (hcp) structure. Using this uniaxial crystal structural character of PtBi, we succeed in synthesizing two-dimensional (2-D) PtBi NPLs. Significantly, the electrochemical studies indicate that the as-prepared 2-D PtBi NPLs exhibit enhanced electrocatalytic activity toward formic acid and methanol oxidation with larger oxidation current density, higher tolerance to CO poisoning, and more negative onset potential in comparison with the commercial Pt/C catalyst. This is attributed to the addition of second metal Bi. In addition, to the best of our knowledge, this is the first time that synthesis of one-dimensional (1-D) PdBi alloy NWs has been reported. The as-synthesized 1-D PdBi bimetallic NWs may find promising potential applications in various fields, such as fuel cells, electrochemical sensors, and organocatalysis.We have demonstrated a one-pot, facile and rapid strategy to synthesize novel PtBi nanoplatelets (NPLs) and PdBi nanowires (NWs) with controlled shape, size, and composition in the presence of oleylamine (OAm) and NH4Br. In contrast to the conventional face centered cubic (fcc) structure of Pt-based NPs, PtBi possesses a chemically ordered intermetallic hexagonal close packed (hcp) structure. Using this uniaxial crystal structural character of PtBi, we succeed in synthesizing two-dimensional (2-D) PtBi NPLs. Significantly, the electrochemical studies indicate that the as-prepared 2-D PtBi NPLs exhibit enhanced electrocatalytic activity toward formic acid and methanol oxidation with larger oxidation current density, higher tolerance to CO poisoning, and more negative onset potential

  11. Adsorption-controlled growth of BiFeO3 by MBE and integration with wide band gap semiconductors.

    SciTech Connect

    Ramesh, Ramamoorthy; Uecker, Reinhard , Germany); Doolittle, W. Alan; Reiche, P. , Germany); Liu, Zi-Kui; Bernhagen, Margitta , Germany); Tian, Wei; Ihlefeld, Jon F.; Schlom, Darrell G.

    2008-08-01

    BiFeO3 thin films have been deposited on (101) DyScO3, (0001) AlGaN/GaN, and (0001) SiC single crystal substrates by reactive molecular-beam epitaxy in an adsorption-controlled growth regime. This is achieved by supplying a bismuth over-pressure and utilizing the differential vapor pressures between bismuth oxides and BiFeO3 to control stoichiometry. Four-circle x-ray diffraction reveals phase-pure, epitaxial films with rocking curve full width at half maximum values as narrow as 7.2 arc seconds. Epitaxial growth of (0001)-oriented BiFeO3 thin films on (0001) GaN, including AlGaN HEMT structures, and (0001) SiC has been realized utilizing intervening epitaxial (111) SrTiO3/(100) TiO2 buffer layers. The epitaxial BiFeO3 thin films have two in-plane orientations: [1120] BiFeO3 [1120] GaN (SiC) plus a twin variant related by a 180{sup o} in-plane rotation. This epitaxial integration of the ferroelectric with the highest known polarization, BiFeO3, with wide band gap semiconductors is an important step toward novel field-effect devices.

  12. Au-induced deep groove nanowire structure on the Ge(001) surface: DFT calculations

    NASA Astrophysics Data System (ADS)

    Tsay, Shiow-Fon

    2016-09-01

    The atomic geometry, stability, and electronic properties of self-organized Au induced nanowires on the Ge(001) surface are investigated based on the density-functional theory in GGA and the stoichiometry of Au. A giant Ge zigzag chain structure is suggested for 0.75 ML Au coverage, which displays c(8 × 2) deep groove zigzag nanowire structure simulated STM images. The top layer Ge and Au atomic disorder introduces the chevron units into the zigzag nanowire structure STM image as per the experimental observations. The zigzag Ge nanowire exhibits a semi-metallic characteristic, and the electric transport occurs in between the Ge zigzag nanowire and the subsurface. The system exhibits obvious electronic correlations among the Ge nanowire, the nano-facet Au trimers and the deeper layer Ge atoms, that play an important role in the electronic structure. At surface Brillouin zone boundaries, an anisotropic two-dimensional upward parabolic surface-state band is consistent with the ARPES spectra reported by Nakatsuji et al. [Phys. Rev. B 80, 081406(R) (2009); Phys. Rev. B 84, 115411 (2011)]; this electronic structure is different from the quasi-one-dimensional energy trough reported by Schäfer et al. [Phys. Rev. Lett. 101, 236802 (2008); Phys. Rev. B 83, 121411(R) (2011)].

  13. Enhanced spin Hall effect by electron correlations in CuBi alloys

    SciTech Connect

    Gu, Bo Xu, Zhuo; Mori, Michiyasu; Maekawa, Sadamichi; Ziman, Timothy

    2015-05-07

    A recent experiment in CuBi alloys obtained a large spin Hall angle (SHA) of −0.24 (Niimi et al., Phys. Rev. Lett. 109, 156602 (2012)). We find that the SHA can be dramatically enhanced by Bi impurities close to the Cu surface. The mechanisms of this enhancement are two-fold. One is that the localized impurity state on surface has a decreased hybridization and combined with Coulomb correlation effect. The other comes from the low-dimensional state of conduction electrons on surface, which results in a further enhancement of skew scattering by impurities. Furthermore, we note that a discrepancy in sign of SHA between the experiment and previous theories is simply caused by different definitions of SHA. This re-establishes skew scattering as the essential mechanism underlying the spin Hall effect in CuBi alloys.

  14. Stabilization of Au at edges of bimetallic PdAu nanocrystallites.

    PubMed

    Yudanov, Ilya V; Neyman, Konstantin M

    2010-05-21

    Density functional calculations were performed to study the distribution of Au atoms in bimetallic PdAu nanoparticles. A series of Pd(79-n)Au(n) clusters of truncated octahedral shape with different content of Au ranging from n = 1 to 60 was used to model such bimetallic nanosystems. Segregation of Au to the particle surface is found to be thermodynamically favorable. The most stable sites for Au substitution are located at the edges of the PdAu nanoclusters. The stabilization at the edges is rationalized by their higher flexibility for surface relaxation which minimizes the strain induced by larger atomic radius of Au as compared to Pd. This stabilization of Au at the edges indicates the possibility to synthesize PdAu particles with Pd atoms located mainly on the facets, and edges "decorated" by Au atoms. Such nanocrystallites are expected to exhibit peculiar catalytic properties and, being thermodynamically stable, should be prone to retaining their initial shape under catalytic conditions.

  15. RVB states in doped band insulators from Coulomb forces: theory and a case study of superconductivity in BiS2 layers

    NASA Astrophysics Data System (ADS)

    Baskaran, G.

    2016-12-01

    Doped band insulators, HfNCl, WO3, diamond, Bi2Se3, BiS2 families, STO/LAO interface, gate doped SrTiO3, MoS2 and so on are unusual superconductors. With an aim to build a general theory for superconductivity in doped band insulators, we focus on the BiS2 family which was discovered by Mizuguchi et al in 2012. While maximum Tc is only ˜11 K in {{LaO}}1-{{x}}{{{F}}}{{x}}{{BiS}}2, a number of experimental results are puzzling and anomalous in the sense that they resemble high T c and unconventional superconductors. Using a two orbital model of Usui, Suzuki and Kuroki, we show that the uniform low density free Fermi sea in {{LaO}}{0,5}{{{F}}}0.5{{BiS}}2 is unstable towards formation of the next nearest neighbor Bi-S-Bi diagonal valence bond (charged -2e Cooper pair) and their Wigner crystallization. Instability to this novel state of matter is caused by unscreened nearest neighbor coulomb repulsions (V ˜ 1 eV) and a hopping pattern with sulfur mediated diagonal next nearest neighbor Bi-S-Bi hopping t’ ˜ 0.88 eV, as well as larger than nearest neighbor Bi-Bi hopping, t ˜ 0.16 eV. Wigner crystals of Cooper pairs quantum melt for doping around x = 0.5 and stabilize certain resonating valence bond states and superconductivity. We study a few variational RVB states and suggest that BiS2 family members are latent high Tc superconductors, but challenged by competing orders and the fragile nature of many body states sustained by unscreened Coulomb forces. One of our superconducting states has d XY symmetry and a gap. We also predict a 2d Bose metal or vortex liquid normal state, as charged -2e valence bonds survive in the normal state.

  16. Synthesis and Characterization of SrBi

    SciTech Connect

    Wang, Ying C.; Hoffmann, Roald; DiSalvo, Francis J.

    2001-01-01

    SrBi{sub 2}Se{sub 4} was synthesized at 945 C and its structure was determined using single-crystal X-ray diffraction data obtained at 165 K. SrBi{sub 2}Se{sub 4}is isotypic to 12-Ba Bi{sub 2}Se{sub 4} and Eu1.1 Bi{sub 2}Se{sub 4}. The compound crystallizes in P6{sub 3}/m (Z=12) with a=25.970(2) {angstrom} and c=4.2437(3) {angstrom}. Final R{sub 1}=0.0630 and w R{sub 2}=0.1246 (I > 2{sigma}(I)). The coordination environments of Bi are distorted Se octahedra. These octahedra build up a uniaxial three-dimensional network with tunnels along the z direction, which are filled by Sr{sup 2+}. There is also a second tunnel along the z direction which is partially occupied by Bi atoms. The coordination spheres of Sr are bicapped trigonal prisms of Se. Transport measurements indicate that SrBi{sub 2}Se{sub 4}is semiconducting. This work adds one high-symmetry compound to the family of complex chalcogenides, in which low-symmetry compounds are common.

  17. An α-Bi2O3/BiOBr core-shell heterojunction with high photocatalytic activity.

    PubMed

    Shan, Lianwei; Liu, Yuteng; Chen, Hongtao; Wu, Ze; Han, Zhidong

    2017-02-14

    We prepared an α-Bi2O3/BiOBr core-shell heterojunction via a facile in situ chemical transformation method. Ultrathin BiOBr nanosheets were observed and these were found to be evenly distributed on the surface of α-Bi2O3/BiOBr by SEM and TEM. The results revealed that the prepared α-Bi2O3/BiOBr photocatalysts were porous, and their specific surface areas were found to be raised on comparing with α-Bi2O3 and BiOBr. In our experiments, the photocatalytic activity of α-Bi2O3 was obviously enhanced when assembling with ultrathin BiOBr compared with α-Bi2O3/BiOBr and the individual phase. It is considered that the surface porous structure increases the specific surface areas, which improved the adsorption characteristics of α-Bi2O3/BiOBr. The suitable band alignment (between α-Bi2O3 and BiOBr) and oxygen vacancy effect can be attributed to the increased photocatalytic activity under visible irradiation.

  18. PHENIX results on fluctuations and Bose-Einstein correlations in Au + Au collisions from the RHIC Beam Energy Scan

    NASA Astrophysics Data System (ADS)

    Garg, Prakhar

    2016-12-01

    The RHIC Beam Energy Scan focuses on mapping the QCD phase diagram and pinpointing the location of a possible critical end point. Bose-Einstein correlations and event-by-event fluctuations of conserved quantities, measured as a function of centrality and collision energy, are promising tools in these studies. Recent lattice QCD and statistical thermal model calculations predict that higher-order cumulants of the fluctuations are sensitive indicators of the phase transition. Products of these cumulants can be used to extract the freeze-out parameters [A. Bazavov et al., Phys. Rev. Lett. 109, 192302 (2012)] and to locate the critical point [M. A. Stephanov, K. Rajagopal and E. V. Shuryak, Phys. Rev. D 60, 114028 (1999)]. Two-pion interferometry measurements are predicted to be sensitive to potential softening of the equation of state and prolonged emission duration close to the critical point [S. Pratt, Phys. Rev. Lett. 53, 1219 (1984)]. We present recent PHENIX results on fluctuations of net-charge using high-order cumulants and their products in Au+Au collisions at √{sNN} = 7.7- 200 GeV, and measurement of two-pion correlation functions and emission-source radii in Cu+Cu and Au+Au collisions at several beam energies. The extracted source radii are compared to previous measurements at RHIC and LHC in order to study energy dependence of the specific quantities sensitive to expansion velocity and emission duration. Implications for the search of a critical point and baryon chemical potentials at various collision energies are discussed.

  19. Reflectance anisotropy spectroscopy of the Si (111 )-(5 ×2 )Au surface

    NASA Astrophysics Data System (ADS)

    Patterson, C. H.; Banerjee, S.; McGilp, J. F.

    2016-10-01

    Hybrid DFT calculations of atomic structure, electronic band structure, and reflectance anisotropy (RA) are used to correlate atomic and electronic structures and optical transitions of eight structures for the Si (111 )-(5 ×2 )Au phase with Au coverage and Si adatom site occupancy. The structure recently proposed by Kwon and Kang (KK) [S. G. Kwon and M. H. Kang, Phys. Rev. Lett. 113, 086101 (2014), 10.1103/PhysRevLett.113.086101] and strongly supported by surface x-ray diffraction [T. Shirasawa et al., Phys. Rev. Lett. 113, 165501 (2014), 10.1103/PhysRevLett.113.165501] is found to be the most stable in the Au coverage range from 0.6 to 0.8 ML. The band structure of the Si adatom covered (5 ×4 ) surface has a surface state whose dispersion and position agree very well with the prominent S1 surface state observed in angle-resolved photoemission experiment. Reflectance anisotropy spectra in the energy range 0.5 to 5 eV for the eight surface structures show variations with Au and Si adatom coverage which can be explained in terms of filling of this surface state. The best agreement between predicted and measured RA spectra, which are sensitive to both Au atom and Si adatom coverage, is found for coverages from 0.7 to 0.75 ML Au, when the surface has regions where Si adatoms are absent and where there are sufficient adatoms to cause surface-state band filling, in equal parts. Surface formation energy calculations favor a coverage of 0.7-ML Au. The structures of the (5 ×2 ) KK and (6 ×6 )Au phases on the Si(111) surface are compared and it is shown that the repeat unit of the KK phase also occurs in the (6 ×6 ) structure.

  20. A comparative study of the Au + H{sub 2}, Au{sup +} + H{sub 2}, and Au{sup −} + H{sub 2} systems: Potential energy surfaces and dynamics of reactive collisions

    SciTech Connect

    Dorta-Urra, Anaís; Zanchet, Alexandre; Roncero, Octavio; Aguado, Alfredo

    2015-04-21

    In order to study the Au{sup −} + H{sub 2} collision, a new global potential energy surface (PES) describing the ground electronic state of AuH{sub 2}{sup −} system is developed and compared with the PESs of the neutral [Zanchet et al., J. Chem. Phys. 132, 034301 (2010)] and cationic systems [Anaís et al., J. Chem. Phys. 135, 091102 (2011)]. We found that Au{sup −} − H{sub 2} presents a H-Au-H insertion minimum attributed to the stabilization of the LUMO 3b{sub 2} orbital, which can be considered as the preamble of the chemisorption well appearing in larger gold clusters. While the LUMO orbital is stabilized, the HOMO 6a{sub 1} is destabilized, creating a barrier at the geometry where the energy orbitals’ curves are crossing. In the anion, this HOMO is doubly occupied, while in the neutral system is half-filled and completely empty in the cation, explaining the gradual disappearance of the well and the barrier as the number of electrons decreases. The cation presents a well in the entrance channel partially explained by electrostatic interactions. The three systems’ reactions are highly endothermic, by 1.66, 2.79, and 3.23 eV for AuH, AuH{sup +}, and AuH{sup −} products, respectively. The reaction dynamics is studied using quasi-classical trajectory method for the three systems. The one corresponding to the anionic system is new in this work. Collision energies between 1.00 and 8.00 eV, measured for the cation, are in good agreement with the simulated cross section for the AuH{sup +}. It was also found that the total fragmentation, in three atoms, competes becoming dominant at sufficiently high energy. Here, we study the competition between the two different reaction pathways for the anionic, cationic, and neutral species, explaining the differences using a simple model based on the topology of the potential energy surfaces.

  1. Impact of Ni/Ge/Au/Ti/Au and Ti/Pt/Au collector metal on GaInP/GaAs HBT characteristics

    NASA Astrophysics Data System (ADS)

    Park, Jae-Woo; Mohammadi, Saeed; Pavlidis, Dimitris

    2000-10-01

    The collector-emitter offset voltage of GaInP/GaAs HBTs grown by chemical-beam epitaxy with reduced toxicity precursors is investigated for Ni/Ge/Au/Ti/Au and Ti/Pt/Au collector contact metals. The offset voltage for HBTs with Ti/Pt/Au collector metal is increased by 0.26 V compared to Ni/Ge/Au/Ti/Au due to the 0.26 eV barrier existing between the n-GaAs subcollector and the Ti/Pt/Au contact metal. Other parameters affected by the collector contact barrier and impacting transistor performance include DC gain, microwave and power performance.

  2. BiHermitian supersymmetric quantum mechanics

    NASA Astrophysics Data System (ADS)

    Zucchini, Roberto

    2007-04-01

    BiHermitian geometry, discovered long ago by Gates, Hull and Rocek, is the most general sigma model target space geometry allowing for (2, 2) world sheet supersymmetry. In this paper, we work out supersymmetric quantum mechanics for a biHermitian target space. We display the full supersymmetry of the model and illustrate in detail its quantization procedure. Finally, we show that the quantized model reproduces the Hodge theory for compact twisted generalized Kähler manifolds recently developed by Gualtieri in [33]. This allows us to recover and put in a broader context the results on the biHermitian topological sigma models obtained by Kapustin and Li in [9].

  3. TOOL ASSEMBLY WITH BI-DIRECTIONAL BEARING

    DOEpatents

    Longhurst, G.E.

    1961-07-11

    A two-direction motion bearing which is incorporated in a refueling nuclear fuel element trsnsfer tool assembly is described. A plurality of bi- directional bearing assembliesare fixed equi-distantly about the circumference of the transfer tool assembly to provide the tool assembly with a bearing surface- for both axial and rotational motion. Each bi-directional bearing assembly contains a plurality of circumferentially bulged rollers mounted in a unique arrangement which will provide a bearing surface for rotational movement of the tool assembly within a bore. The bi-direc tional bearing assembly itself is capable of rational motion and thus provides for longitudinal movement of the tool assembly.

  4. Heterostructured CIGS-Au nanoparticles: from Au-CIGS side-by-side structure to Au-core/CIGS-shell configuration.

    PubMed

    Xu, Yeming; Li, Quan

    2011-08-01

    Heterostructured Au-Copper Indium Gallium Selenide (CIGS) nanoparticles (nps) with Au-CIGS side-by-side and Au-core/CIGS-shell configurations have been synthesized in a controllable manner using seed mediated growth. Detailed microstructure analysis reveals that (112) planes in the tetragonal chalcopyrite CIGS serve as the predominant termination surfaces during single phase CIGS nanoparticle growth. Preferential nucleation of Au on such planes determines the Au-CIGS side-by-side configuration when the pre-synthesized CIGS nps are used as the seeds for further Au growth. Reversing the growth sequence by employing Au nano-seeds results in Au-core/CIGS-shell configuration, as determined by the non-preferential nucleation of CIGS on the spherical Au nanoparticle surface. The different morphological configurations of the heterostructures are found to modify the surface plasmon resonance of Au in the corresponding samples.

  5. Growth mode, magnetic and magneto-optical properties of pulsed-laser-deposited Au/Co/Au(1 1 1) trilayers

    NASA Astrophysics Data System (ADS)

    Clavero, C.; Cebollada, A.; Armelles, G.; Fruchart, O.

    2010-03-01

    The growth mode, magnetic and magneto-optical properties of epitaxial Au/Co/Au(1 1 1) ultrathin trilayers grown by pulsed-laser deposition (PLD) under ultra-high vacuum are presented. Sapphire wafers buffered with a single-crystalline Mo(1 1 0) buffer layer were used as substrates. Owing to PLD-induced interfacial intermixing at the lower Co/Au(1 1 1) interface, a close-to layer-by-layer growth mode is promoted. Surprisingly, despite this intermixing, ferromagnetic behavior is found at room temperature for coverings starting at 1 atomic layer (AL). The films display perpendicular magnetization with anisotropy constants reduced by 50% compared to TD-grown or electrodeposited films, and with a coercivity more than one order of magnitude lower (≲5 mT). The magneto-optical (MO) response in the low Co thickness range is dominated by Au/Co interface contributions. For thicknesses starting at 3 AL Co, the MO response has a linear dependence with the Co thickness, indicative of a continuous-film-like MO behavior.

  6. Exploratory Bi-Factor Analysis: The Oblique Case

    ERIC Educational Resources Information Center

    Jennrich, Robert I.; Bentler, Peter M.

    2012-01-01

    Bi-factor analysis is a form of confirmatory factor analysis originally introduced by Holzinger and Swineford ("Psychometrika" 47:41-54, 1937). The bi-factor model has a general factor, a number of group factors, and an explicit bi-factor structure. Jennrich and Bentler ("Psychometrika" 76:537-549, 2011) introduced an exploratory form of bi-factor…

  7. Tuning the electronic properties at the surface of BaBiO3 thin films

    NASA Astrophysics Data System (ADS)

    Ferreyra, C.; Guller, F.; Marchini, F.; Lüders, U.; Albornoz, C.; Leyva, A. G.; Williams, F. J.; Llois, A. M.; Vildosola, V.; Rubi, D.

    2016-06-01

    The presence of 2D electron gases at surfaces or interfaces in oxide thin films remains a hot topic in condensed matter physics. In particular, BaBiO3 appears as a very interesting system as it was theoretically proposed that its (001) surface should become metallic if a Bi-termination is achieved (Vildosola et al., PRL 110, 206805 (2013)). Here we report on the preparation by pulsed laser deposition and characterization of BaBiO3 thin films on silicon. We show that the texture of the films can be tuned by controlling the growth conditions, being possible to stabilize strongly (100)-textured films. We find significant differences on the spectroscopic and transport properties between (100)-textured and non-textured films. We rationalize these experimental results by performing first principles calculations, which indicate the existence of electron doping at the (100) surface. This stabilizes Bi ions in a 3+ state, shortens Bi-O bonds and reduces the electronic band gap, increasing the surface conductivity. Our results emphasize the importance of surface effects on the electronic properties of perovskites, and provide strategies to design novel oxide heterostructures with potential interface-related 2D electron gases.

  8. Large enhancement of superconducting transition temperature of SrBi3 induced by Na substitution for Sr

    PubMed Central

    Iyo, Akira; Yanagi, Yousuke; Kinjo, Tatsuya; Nishio, Taichiro; Hase, Izumi; Yanagisawa, Takashi; Ishida, Shigeyuki; Kito, Hijiri; Takeshita, Nao; Oka, Kunihiko; Yoshida, Yoshiyuki; Eisaki, Hiroshi

    2015-01-01

    The Matthias rule, which is an empirical correlation between the superconducting transition temperature (Tc) and the average number of valence electrons per atom (n) in alloys and intermetallic compounds, has been used in the past as a guiding principle to search for new superconductors with higher Tc. The intermetallic compound SrBi3 (AuCu3 structure) exhibits a Tc of 5.6 K. An ab-initio electronic band structure calculation for SrBi3 predicted that Tc increases on decreasing the Fermi energy, i.e., on decreasing n, because of a steep increase in the density of states. In this study, we demonstrated that high-pressure (~ 3 GPa) and low-temperature ( < 350 °C) synthesis conditions enables the substitution of Na for about 40 at.% of Sr. With a consequent decrease in n, the Tc of (Sr,Na)Bi3 increases to 9.0 K. A new high-Tc peak is observed in the oscillatory dependence of Tc on n in compounds with the AuCu3 structure. We have shown that the oscillatory dependence of Tc is in good agreement with the band structure calculation. Our experiments reaffirm the importance of controlling the number of electrons in intermetallic compounds. PMID:25965162

  9. New Reaction Pathway Induced by Plasmon for Selective Benzyl Alcohol Oxidation on BiOCl Possessing Oxygen Vacancies.

    PubMed

    Li, Hao; Qin, Feng; Yang, Zhiping; Cui, Ximin; Wang, Jianfang; Zhang, Lizhi

    2017-03-08

    Selective organic transformation under mild conditions constitutes a challenge in green chemistry, especially for alcohol oxidation, which typically requires environmentally unfriendly oxidants. Here, we report a new plasmonic catalyst of Au supported on BiOCl containing oxygen vacancies. It photocatalyzes selective benzyl alcohol oxidation with O2 under visible light through synergistic action of plasmonic hot electrons and holes. Oxygen vacancies on BiOCl facilitate the trapping and transfer of plasmonic hot electrons to adsorbed O2, producing •O2(-) radicals, while plasmonic hot holes remaining on the Au surface mildly oxidize benzyl alcohol to corresponding carbon-centered radicals. The hypothesized concerted ring addition between these two radical species on the BiOCl surface highly favors the production of benzaldehyde along with an unexpected oxygen atom transfer from O2 to the product. The results and understanding acquired in this study, based on the full utilization of hot charge carriers in a plasmonic metal deposited on a rationally designed support, will contribute to the development of more active and/or selective plasmonic catalysts for a wide variety of organic transformations.

  10. Influence of freezing rate changes of MnBi-Bi eutectic microstructure. [effects of space processing

    NASA Technical Reports Server (NTRS)

    Wilcox, W. R.; Doddi, K.; Nair, M.; Larson, D. J.

    1983-01-01

    In an attempt to explain the influence of space processing on the microstructure of MnBi-Bi, eutectic mixtures were directionally solidified with a sudden change of translation rate. The MnBi fiber spacing was able to adapt to the changing freezing rate as predicted by heat transfer computations. Thus the microstructure adapts more rapidly than the freezing rate could be changed in the present experiments.

  11. Metalorganic vapor phase epitaxy of ternary rhombohedral (Bi1-xSbx) 2 Se3 solid solutions

    NASA Astrophysics Data System (ADS)

    Kuznetsov, P. I.; Yakushcheva, G. G.; Shchamkhalova, B. S.; Luzanov, V. A.; Temiryazev, A. G.; Jitov, V. A.

    2016-01-01

    We studied the metalorganic vapor phase epitaxy (MOVPE) of (Bi1-xSbx) 2Se3 solid solution films with a different Sb content on (001) Al2O3 substrates with thin ZnSe buffer layer in the range of temperatures 250-480 °C. As-grown films were studied by atom force and scanning electron microscopy (AFM and SEM), Raman spectroscopy and X-ray diffractometry (XRD) techniques. To determine the elemental composition of the grown films, we used an energy dispersive spectrometer (EDS). The dependencies of the crystal structure of films on the growth temperature and Sb content (0 ≤ x ≤ 1) were explored. At different growth temperatures we obtained the following bismuth compounds: the films grown at the temperature of 370 °C or lower consist of the pure Bi phase, whereas we got the Bi4Se3 phase at 380 °C, the phase BiSe at 430 °C and Bi2Se3 at the temperature of 460 °C or above. We found out that at the temperature of 480 °C the single-phase films of (Bi1-xSbx) 2Se3 with rhombohedral and orthorhombic lattices are realized when x is less than 0.25 and greater than 0.935, respectively. For 0.25 < x < 0.935 the grown films are composites of rhombohedral and orthorhombic phases. At the temperature of 440 °C we obtained films consisting of three rhombohedral phases (Bi1-xSbx) 4Se3, (Bi1-xSbx) Se and Bi. The room temperature transport properties of rhombohedral samples were characterized using the Van der Pauw technique.

  12. Superconducting Bi2Te: Pressure-induced universality in the (Bi2)m(Bi2Te3)n series

    DOE PAGES

    Stillwell, Ryan L.; Jeffries, Jason R.; Jenei, Zsolt; ...

    2016-03-09

    Using high-pressure magnetotransport techniques we have discovered superconductivity in Bi2Te, a member of the infinitely adaptive (Bi2)m(Bi2Te3)n series, whose end members, Bi and Bi2Te3, can be tuned to display topological surface states or superconductivity. Bi2Te has a maximum Tc = 8.6 K at P = 14.5 GPa and goes through multiple high pressure phase transitions, ultimately collapsing into a bcc structure that suggests a universal behavior across the series. High-pressure magnetoresistance and Hall measurements suggest a semi-metal to metal transition near 5.4 GPa, which accompanies the hexagonal to intermediate phase transition seen via x-ray diffraction measurements. In addition, the linearitymore » of Hc2 (T) exceeds the Werthamer-Helfand-Hohenberg limit, even in the extreme spin-orbit scattering limit, yet is consistent with other strong spin-orbit materials. Furthermore, considering these results in combination with similar reports on strong spin-orbit scattering materials seen in the literature, we suggest the need for a new theory that can address the unconventional nature of their superconducting states.« less

  13. Three-Dimensional BiOI/BiOX (X = Cl or Br) Nanohybrids for Enhanced Visible-Light Photocatalytic Activity.

    PubMed

    Liu, Yazi; Xu, Jian; Wang, Liqiong; Zhang, Huayang; Xu, Ping; Duan, Xiaoguang; Sun, Hongqi; Wang, Shaobin

    2017-03-14

    Three-dimensional flower-like BiOI/BiOX (X = Br or Cl) hybrids were synthesized via a facile one-pot solvothermal approach. With systematic characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), the Brunauer-Emmett-Teller (BET)specific surface area, X-ray photoelectron spectroscopy (XPS), and the UV-Vis diffuse reflectance spectra (DRS), the BiOI/BiOCl composites showed a fluffy and porous 3-D architecture with a large specific surface area (SSA) and high capability for light absorption. Among all the BiOX (X = Cl, Br, I) and BiOI/BiOX (X = Cl or Br) composites, BiOI/BiOCl stands out as the most efficient photocatalyst under both visible and UV light irradiations for methyl orange (MO) oxidation. The reaction rate of MO degradation on BiOI/BiOCl was 2.1 times higher than that on pure BiOI under visible light. Moreover, BiOI/BiOCl exhibited enhanced water oxidation efficiency for O₂ evolution which was 1.5 times higher than BiOI. The enhancement of photocatalytic activity could be attributed to the formation of a heterojunction between BiOI and BiOCl, with a nanoporous structure, a larger SSA, and a stronger light absorbance capacity especially in the visible-light region. The in situ electron paramagnetic resonance (EPR) revealed that BiOI/BiOCl composites could effectively evolve superoxide radicals and hydroxyl radicals for photodegradation, and the superoxide radicals are the dominant reactive species. The superb photocatalytic activity of BiOI/BiOCl could be utilized for the degradation of various industrial dyes under natural sunlight irradiation which is of high significance for the remediation of industrial wastewater in the future.

  14. Three-Dimensional BiOI/BiOX (X = Cl or Br) Nanohybrids for Enhanced Visible-Light Photocatalytic Activity

    PubMed Central

    Liu, Yazi; Xu, Jian; Wang, Liqiong; Zhang, Huayang; Xu, Ping; Duan, Xiaoguang; Sun, Hongqi; Wang, Shaobin

    2017-01-01

    Three-dimensional flower-like BiOI/BiOX (X = Br or Cl) hybrids were synthesized via a facile one-pot solvothermal approach. With systematic characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), the Brunauer-Emmett-Teller (BET)specific surface area, X-ray photoelectron spectroscopy (XPS), and the UV-Vis diffuse reflectance spectra (DRS), the BiOI/BiOCl composites showed a fluffy and porous 3-D architecture with a large specific surface area (SSA) and high capability for light absorption. Among all the BiOX (X = Cl, Br, I) and BiOI/BiOX (X = Cl or Br) composites, BiOI/BiOCl stands out as the most efficient photocatalyst under both visible and UV light irradiations for methyl orange (MO) oxidation. The reaction rate of MO degradation on BiOI/BiOCl was 2.1 times higher than that on pure BiOI under visible light. Moreover, BiOI/BiOCl exhibited enhanced water oxidation efficiency for O2 evolution which was 1.5 times higher than BiOI. The enhancement of photocatalytic activity could be attributed to the formation of a heterojunction between BiOI and BiOCl, with a nanoporous structure, a larger SSA, and a stronger light absorbance capacity especially in the visible-light region. The in situ electron paramagnetic resonance (EPR) revealed that BiOI/BiOCl composites could effectively evolve superoxide radicals and hydroxyl radicals for photodegradation, and the superoxide radicals are the dominant reactive species. The superb photocatalytic activity of BiOI/BiOCl could be utilized for the degradation of various industrial dyes under natural sunlight irradiation which is of high significance for the remediation of industrial wastewater in the future. PMID:28336897

  15. Synthesis of Au microwires by selective oxidation of Au-W thin-film composition spreads.

    PubMed

    Hamann, Sven; Brunken, Hayo; Salomon, Steffen; Meyer, Robert; Savan, Alan; Ludwig, Alfred

    2013-02-01

    We report on the stress-induced growth of Au microwires out of a surrounding Au-W matrix by selective oxidation, in view of a possible application as 'micro-Velcro'. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au-W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au48W52 composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au48W52 composition are suitable for micro-Velcro applications.

  16. Au/Au@polythiophene core/shell nanospheres for heterogeneous catalysis of nitroarenes.

    PubMed

    Shin, Hye-Seon; Huh, Seong

    2012-11-01

    Monodisperse Au/Au@polythiophene core/shell nanospheres were facilely prepared through the reduction of gold precursor, AuCl₄⁻, by 2-thiopheneacetonitrile in an aqueous solution. Concomitantly, 2-thiopheneacetonitrile polymerized during this redox process. As a result, Au nanoparticle was encapsulated by conductive polymer shell to afford novel core/shell nanospheres. Interestingly, the shell was composed of very tiny Au nanoparticles surrounded with thiophene polymers. Thus, the new material is best described as Au/Au@polythiophene core/shell nanospheres. FT-IR spectroscopy revealed that the Au nanoparticles were coordinated by the C≡N groups of the polythiophene shell. Some of the C≡N groups were partially hydrolyzed into COOH groups during the redox process because of the acidic reaction condition. The shell was conductive based on the typical ohmic behavior found in electrical measurement. The Au/Au@polythiophene core/shell nanospheres were found to be very active catalysts for the hydrogenation of various nitroarene compounds into corresponding aminoarene compounds in the presence of NaBH₄. Both hydrophilic and hydrophobic nitroarenes were efficiently hydrogenated under mild conditions.

  17. Photoreduction of non-noble metal Bi on the surface of Bi2WO6 for enhanced visible light photocatalysis

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojing; Yu, Shan; Liu, Yang; Zhang, Qian; Zhou, Ying

    2017-02-01

    In this report, Bi2WO6-Bi composite was prepared through an in situ photoreduction method and was characterized systematically by X-Ray diffraction, transmission electron microscopy, X-Ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The as-prepared Bi2WO6-Bi maintains the same crystal structure with the pristine Bi2WO6 regardless of some surface defects. Nevertheless, these surface defects result in the change of surface oxygen adsorption mode from hydroxyl to molecular oxygen on Bi2WO6. Photocatalytic activity over Bi2WO6-Bi is 2.4 times higher than that of Bi2WO6 towards the degradation of organic dye Rhodamine B (RhB) under visible light irradiation (λ > 420 nm). A deep study shows that cleavage of benzene ring is the main pathway for RhB degradation over Bi2WO6, but both the benzene cleavage and de-ethylation pathway coexist for RhB decomposition in the presence of Bi2WO6-Bi as the photocatalyst. Photoelectrochemical study including transient photocurrent tests and electrochemical impedance spectroscopy measurements shows that Bi2WO6-Bi could facilitate the charge transfer process compared to Bi2WO6. These data above has indicated a new insight into the promotion mechanism based on Bi related heterostructures.

  18. The stability and the electronic structure of ultrathin Bi/Bi2Se3 heterostructure

    NASA Astrophysics Data System (ADS)

    Liu, X.; Du, X.; Huang, G. Q.

    2016-12-01

    The stability and the electronic structure of ultrathin Bi/Bi2Se3 heterostructure are studied from density-functional theory by including spin-orbit coupling. Our calculations show that the thinnest and dynamically stable heterostructure is one bilayer Bi deposited on Bi2Se3 with the thickness of two quintuple layers. Due to charge transfer and the strong hybridize effect at the interface, the band structure of ultrathin heterostructure make a large change, but the Dirac-like surface states persist. Our findings propose the possibility to engineer heterostructure to obtain ultrathin topological materials.

  19. Synthesis and electrocatalytic properties of PtBi nanoplatelets and PdBi nanowires.

    PubMed

    Liao, Hanbin; Zhu, Jinghan; Hou, Yanglong

    2014-01-21

    We have demonstrated a one-pot, facile and rapid strategy to synthesize novel PtBi nanoplatelets (NPLs) and PdBi nanowires (NWs) with controlled shape, size, and composition in the presence of oleylamine (OAm) and NH4Br. In contrast to the conventional face centered cubic (fcc) structure of Pt-based NPs, PtBi possesses a chemically ordered intermetallic hexagonal close packed (hcp) structure. Using this uniaxial crystal structural character of PtBi, we succeed in synthesizing two-dimensional (2-D) PtBi NPLs. Significantly, the electrochemical studies indicate that the as-prepared 2-D PtBi NPLs exhibit enhanced electrocatalytic activity toward formic acid and methanol oxidation with larger oxidation current density, higher tolerance to CO poisoning, and more negative onset potential in comparison with the commercial Pt/C catalyst. This is attributed to the addition of second metal Bi. In addition, to the best of our knowledge, this is the first time that synthesis of one-dimensional (1-D) PdBi alloy NWs has been reported. The as-synthesized 1-D PdBi bimetallic NWs may find promising potential applications in various fields, such as fuel cells, electrochemical sensors, and organocatalysis.

  20. Bi nanobelts, nanocubes and their thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Wang, Wenzhong; Chen, Shuo; Huang, Jianyu; Ren, Zhifeng; Harris, T.; Chen, Gang; Dresselhaus, M.

    2006-03-01

    Highly crystallized Bi nanobelts and monodispersed nanocubes have been synthesized via a low-temperature organic solution approach, in which sodium bismuthate was reduced by ethylene glycol in the presence of poly(vinylpyrrolidone) (PVP). By changing some experimental conditions, Bi nanobelts and nanocubes have been prepared successfully. The as-prepared Bi nanobelts are single crystal with high crystallinity. The width of the nanobelts is in the range of 50-500 nanometers and the length is up to of several tens of micrometers. The as-synthesized Bi nanocubes are highly crystallized and monodispersed with edge length of 50-60 nm. The electrical, thermal, and Seebeck properties of the as-grown nanobelts were studied by a TEM-STM probe inside a high resolution TEM. The same studies were also carried out on bulk samples made by hot-press using the nanocubes.

  1. Surface superconductivity in thin cylindrical Bi nanowire.

    PubMed

    Tian, Mingliang; Wang, Jian; Ning, Wei; Mallouk, Thomas E; Chan, Moses H W

    2015-03-11

    The physical origin and the nature of superconductivity in nanostructured Bi remains puzzling. Here, we report transport measurements of individual cylindrical single-crystal Bi nanowires, 20 and 32 nm in diameter. In contrast to nonsuperconducting Bi nanoribbons with two flat surfaces, cylindrical Bi nanowires show superconductivity below 1.3 K. However, their superconducting critical magnetic fields decrease with their diameter, which is the opposite of the expected behavior for thin superconducting wires. Quasiperiodic oscillations of magnetoresistance were observed in perpendicular fields but were not seen in the parallel orientation. These results can be understood by a model of surface superconductivity with an enhanced surface-to-bulk volume in small diameter wires, where the superconductivity originates from the strained surface states of the nanowires due to the surface curvature-induced stress.

  2. Bi-directional electrothermal electromagnetic actuators

    NASA Astrophysics Data System (ADS)

    Cao, Andrew; Kim, Jongbaeg; Lin, Liwei

    2007-05-01

    A new breed of in-plane bi-directional MEMS actuators based on controlled electrothermal buckling and electromagnetic Lorentz force has been demonstrated under both dc and ac operations. Experimentally, bi-directional actuators made by the standard surface-micromachining process have a lateral actuation range of several microns and can exert forces over 100 µN, while those made by SOI and MetalMUMPs processes have an operation range up to several tens of microns and can exert more than 20 mN of force. Reliability tests show that SOI/MetalMUMPs and surface-micromachined actuators can operate for more than 1 and 100 million cycles, respectively, with no signs of degradation. As such, these micro-actuators could be used for MEMS devices that require a bi-directional movement with a large force output such as bi-directional micro-relays.

  3. Study of the radiation line width and shape from the Bi2212 mesa structure

    NASA Astrophysics Data System (ADS)

    Kashiwagi, Takanari; Yamamoto, Takashi; Ishida, Kazuya; Tsujimoto, Manabu; Delfanazari, Kaveh; Nakayama, Ryo; Kitamura, Takeo; Sawamura, Masashi; Asai, Hidehiro; Minami, Hidetoshi; Kadowaki, Kazuo

    2012-02-01

    Continuous electromagnetic waves in terahertz (THz) range have been observed from mesa structures of Bi2Sr2CaCu2O8+δ(Bi2212) single crystals^1) It has been established that the radiation frequency is determined by both the ac Josephson frequency and the resonance condition of the geometrical cavity^2). In order to understand the mechanism of the radiation from the intrinsic Josephson junctions (IJJs) in Bi2212, we studied the radiation line width and shape. These might depend upon the physical parameters of the Bi2212 single crystal such as the number of IJJs the fluctuations of the quasiparticles and pairs, the non-linearity and non-equilibrium conditions, and the stability of the electrical circuit including the IJJs. However, technical difficulties have been delayed the line width measurements in the THz range. Recently, we succeeded in measuring the radiation line width using a frequency mixer. These results will be compared to those from a single junction 1) L. Ozyuzer et al., Science 318 (2007) 1291., 2) K. Kadowaki et al., J. Phys. Soc. Jpn. 79 (2010) 023703

  4. Au40: A Large Tetrahedral Magic Cluster

    SciTech Connect

    Jiang, Deen; Walter, Michael

    2011-01-01

    40 is a magic number for tetrahedral symmetry predicted in both nuclear physics and the electronic jellium model. We show that Au{sub 40} could be such a magic cluster from density functional theory-based basin hopping for global minimization. The putative global minimum found for Au{sub 40} has a twisted pyramid structure, reminiscent of the famous tetrahedral Au{sub 20}, and a sizable HOMO-LUMO gap of 0.69 eV, indicating its molecular nature. Analysis of the electronic states reveals that the gap is related to shell closings of the metallic electrons in a tetrahedrally distorted effective potential.

  5. Pegasus Airwave and Bi-Wave Plus.

    PubMed

    Lowthian, P

    The Pegasus Airwave and the Bi-Wave Plus are examples of alternating-pressure air mattress (APAM) systems that are more reliable than the older generation of APAMs. The Pegasus Airwave is useful for managing severe pressure sores, as well as for preventing sores in 'high-risk' patients. The Bi-Wave Plus is more suitable for patients with a 'fairly high risk' of developing sores and some patients may find it more comfortable than the Pegasus Airwave.

  6. Optical and electrical properties of bi-layers organic devices

    NASA Astrophysics Data System (ADS)

    Trad, Hager; Rouis, Ahlem; Davenas, Jöel; Majdoub, Mustapha

    2014-10-01

    The influence of interfacial charges on the device characteristics of bi-layers structure LEDs with poly[5-methoxy-2-octyloxy-1,4-phenylenevinylene] (MO-PPV) as active polymer layer is investigated. The concept to improve device performance is presented using: a diacetate cellulose (DAC) and a new synthetized 5-{2-(2-chloroethoxy)ethoxy}-2-{(E)-(2-pyridyl)azo}phenol (PDEG) components. The DAC and mixed (DAC+PDEG) layers were inserted between indium tin oxide (ITO) and MO-PPV polymer. The optical properties (UV-Vis) of MO-PPV, PDEG and mixed (DAC+PDEG) in solutions were studied and compared to those on thin films. Detailed current-voltage measurements of the bi-layers devices showed improvements of the threshold voltage (Vth) of the ITO/(DAC+PDEG)/MO-PPV/Al device attributed to the enhancement of carriers injection and transport resulted from the modified electrode structures. Conduction mechanisms of structure LEDs were matched with space-charge-limited current (SCLC) one. The impedance spectra for all devices can be discussed in terms of an equivalent circuit model designed as a parallel resistor Rp and capacitor Cp network in series with resistor Rs. The ITO/(DAC+PDEG)/MO-PPV/Al device showed the lowest impedance attributed to the removal of contaminants and to changes in the work function of ITO. The frequency-dependent electrical properties of the ITO/(DAC+PDEG)/MO-PPV/Al structure is analyzed by impedance spectroscopy as function of bias. We have extracted numerical values of the equivalent circuit model parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution.

  7. Dynamical Scenarios for Chromosome Bi-orientation

    PubMed Central

    Zhang, Tongli; Oliveira, Raquel A.; Schmierer, Bernhard; Novák, Béla

    2013-01-01

    Chromosome bi-orientation at the metaphase spindle is essential for precise segregation of the genetic material. The process is error-prone, and error-correction mechanisms exist to switch misaligned chromosomes to the correct, bi-oriented configuration. Here, we analyze several possible dynamical scenarios to explore how cells might achieve correct bi-orientation in an efficient and robust manner. We first illustrate that tension-mediated feedback between the sister kinetochores can give rise to a bistable switch, which allows robust distinction between a loose attachment with low tension and a strong attachment with high tension. However, this mechanism has difficulties in explaining how bi-orientation is initiated starting from unattached kinetochores. We propose four possible mechanisms to overcome this problem (exploiting molecular noise; allowing an efficient attachment of kinetochores already in the absence of tension; a trial-and-error oscillation; and a stochastic bistable switch), and assess their impact on the bi-orientation process. Based on our results and supported by experimental data, we put forward a trial-and-error oscillation and a stochastic bistable switch as two elegant mechanisms with the potential to promote bi-orientation both efficiently and robustly. PMID:23790367

  8. BiP negatively affects ricin transport.

    PubMed

    Gregers, Tone F; Skånland, Sigrid S; Wälchli, Sébastien; Bakke, Oddmund; Sandvig, Kirsten

    2013-05-10

    The AB plant toxin ricin binds both glycoproteins and glycolipids at the cell surface via its B subunit. After binding, ricin is endocytosed and then transported retrogradely through the Golgi to the endoplasmic reticulum (ER). In the ER, the A subunit is retrotranslocated to the cytosol in a chaperone-dependent process, which is not fully explored. Recently two separate siRNA screens have demonstrated that ER chaperones have implications for ricin toxicity. ER associated degradation (ERAD) involves translocation of misfolded proteins from ER to cytosol and it is conceivable that protein toxins exploit this pathway. The ER chaperone BiP is an important ER regulator and has been implicated in toxicity mediated by cholera and Shiga toxin. In this study, we have investigated the role of BiP in ricin translocation to the cytosol. We first show that overexpression of BiP inhibited ricin translocation and protected cells against the toxin. Furthermore, shRNA-mediated depletion of BiP enhanced toxin translocation resulting in increased cytotoxicity. BiP-dependent inhibition of ricin toxicity was independent of ER stress. Our findings suggest that in contrast to what was shown with the Shiga toxin, the presence of BiP does not facilitate, but rather inhibits the entry of ricin into the cytosol.

  9. Comment on ''Coincidence studies of He ionized by C{sup 6+}, Au{sup 24+}, and Au{sup 53+}''

    SciTech Connect

    Schulz, M.; Moshammer, R.; Fischer, D.; Ullrich, J.

    2010-06-15

    In a recent article, McGovern et al. [Phys. Rev. A 81, 042704 (2010)] suggested that the normalization of our measured fully differential cross section for ionization of helium by Au{sup 53+} needs to be checked. In this comment we confirm that the normalization of the published data is correct. Furthermore, we point out that, for a conclusive comparison between experiment and theory, an accurate inclusion of the experimental resolution using correct experimental parameters in the calculation is important.

  10. Surface patterning of GaAs under irradiation with very heavy polyatomic Au ions

    NASA Astrophysics Data System (ADS)

    Bischoff, L.; Böttger, R.; Heinig, K.-H.; Facsko, S.; Pilz, W.

    2014-08-01

    Self-organization of surface patterns on GaAs under irradiation with heavy polyatomic Au ions has been observed. The patterns depend on the ion mass, and the substrate temperature as well as the incidence angle of the ions. At room temperature, under normal incidence the surface remains flat, whereas above 200 °C nanodroplets of Ga appear after irradiation with monatomic, biatomic as well as triatomic Au ions of kinetic energies in the range of 10-30 keV per atom. In the intermediate temperature range of 100-200 °C meander- and dot-like patterns form, which are not related to Ga excess. Under oblique ion incidence up to 45° from the surface normal, at room temperature the surface remains flat for mon- and polyatomic Au ions. For bi- and triatomic ions in the range of 60° ≤ α ≤ 70° ripple patterns have been found, which become shingle-like for α ≥ 80°, whereas the surface remains flat for monatomic ions.

  11. Ir-induced activation of Au towards CO adsorption: Ir films deposited on Au{111}

    NASA Astrophysics Data System (ADS)

    Zhang, Tianfu; Driver, Stephen M.; Pratt, Stephanie J.; Jenkins, Stephen J.; King, David A.

    2016-06-01

    We have investigated the interaction of CO with Ir/Au{111} bimetallic surfaces, and the influence of morphology changes as Ir moves sub-surface into the Au bulk, using reflection-absorption infrared spectroscopy (RAIRS). The presence of Ir stabilises CO on exposed regions of the Au surface at temperatures up to around 200 K: we attribute this to low-coordinated Au sites, probably associated with lifting of the clean-surface 'herringbone' reconstruction by Ir deposition. The highest density of active Au sites is obtained after annealing the bimetallic surface to 500-600 K: we attribute this to morphology changes associated with the movement of Ir into bulk Au.

  12. Regulating the surface plasmon resonance coupling between Au-nanoparticle and Au-film

    NASA Astrophysics Data System (ADS)

    Wang, Shuang; Li, Kewu; Zhang, Rui; Jing, Ning; Chen, Youhua; Chen, Yuanyuan; Wang, Zhibin

    2017-01-01

    In this paper, we report the coupling between the localized surface plasmon resonance (LSPR) of Au-nanoparticles and surface plasmon resonance (SPR) of the Au-film. According to the conditions for SPR excitation of the classical Kretschmann-Raether structure with 50nm Au thin film, the commonly used classes of spherical Au-nanoparticle is studied and optimized. We used the finite element analysis (COMSOL Multiphysics 5.0), to simulate the coupling. The results from calculation and simulation indicate that the resonant plasmonic coupling between Au-nanoparticles and Au-film could lead to a large field enhancement and thus improve SPR. We demonstrate that the resonant plasmonic coupling could be regulated by the size of nanoparticles, the distance between nanoparticles .

  13. Bi-Dust Solitary Waves

    NASA Astrophysics Data System (ADS)

    Puerta, Julio; Martin, Pablo

    2010-11-01

    Propagations of non-linear solitary waves in bi-dust plasma system is analyzed. In the present treatment one of the dust particles is assumed to be much smaller than other one, in such a way that there are enough time for these particles to reach quasi thermal equilibrium. Maxwell-Boltzmann factors are therefore applied for the density distribution of electrons, ions and light dust grains. The treatment of the problem can now be made by the method of the pseudo-potential taking in to account temperature effects in function of the density of the first grains. A density threshold can be found. In the limit where the light grain density tends to zero recovering the effects found by other authors are founded, where one kind of grains is only present [1,2]. Several numerical calculations for different values of the characteristic parameters will be shown. [4pt] [1] Rao N. N., Shukla P. K. and Tu M. Y. (1990), Planet Space Science 38, 543 [0pt] [2] Mendoza-Briceño C. A., Russel S. M. and Mamun A. A., (2000) Planet Space Science 48, 599

  14. Main Group Metal-Actinide Magnetic Coupling and Structural Response Upon U(4+) Inclusion Into Bi, Tl/Bi, or Pb/Bi Cages.

    PubMed

    Lichtenberger, Niels; Wilson, Robert J; Eulenstein, Armin R; Massa, Werner; Clérac, Rodolphe; Weigend, Florian; Dehnen, Stefanie

    2016-07-27

    The encapsulation of actinide ions in intermetalloid clusters has long been proposed but was never realized synthetically. We report the isolation and experimental, as well as quantum chemical, characterization of the uranium-centered clusters [U@Bi12](3-), [U@Tl2Bi11](3-), [U@Pb7Bi7](3-), and [U@Pb4Bi9](3-), upon reaction of (EE'Bi2)(2-) (E = Ga, Tl, E' = Bi; E = E' = Pb) and [U(C5Me4H)3] or [U(C5Me4H)3Cl] in 1,2-diaminoethane. For [U@Bi12](3-), magnetic susceptibility measurements rationalize an unprecedented antiferromagnetic coupling between a magnetic U(4+) site and a unique radical Bi12(7-) shell.

  15. Directional light scattering from individual Au nanocup

    NASA Astrophysics Data System (ADS)

    Bai, Jinjun; Li, Yong; Zhao, Bo

    2017-03-01

    We investigate the optical scattering properties of gold nanocup with different orientation and fractional height by full vector finite element method. All of the scattering cross section, the distribution of electric field intensity, and the ability of directional light scattering are simulated, respectively. It is demonstrated that the scattering cross section of Au nanocup is a superposition of scattering spectrum of a transverse mode and an axial mode. The wavelength and the intensity of the maximum value of the scattering cross section increase initially then reduce with the fractional height increasing for transverse mode, while they increase monotonously with the fractional height increasing for axial mode. Furthermore, the calculation results show that the ability of redirecting incident light of Au nanocup mainly depends on the transverse mode. And the deflected angle of scattering increases with the fractional height of Au nanocup decreasing. These results indicate that Au nanocup has a promising application in the planar plasmon devices.

  16. RHIC Au beam in Run 2014

    SciTech Connect

    Zhang, S. Y.

    2014-09-15

    Au beam at the RHIC ramp in run 2014 is reviewed together with the run 2011 and run 2012. Observed bunch length and longitudinal emittance are compared with the IBS simulations. The IBS growth rate of the longitudinal emittance in run 2014 is similar to run 2011, and both are larger than run 2012. This is explained by the large transverse emittance at high intensity observed in run 2012, but not in run 2014. The big improvement of the AGS ramping in run 2014 might be related to this change. The importance of the injector intensity improvement in run 2014 is emphasized, which gives rise to the initial luminosity improvement of 50% in run 2014, compared with the previous Au-Au run 2011. In addition, a modified IBS model, which is calibrated using the RHIC Au runs from 9.8 GeV/n to 100 GeV/n, is presented and used in the study.

  17. Thermal Expansion of AuIn2

    SciTech Connect

    Saw, C K; Siekhaus, W J

    2004-07-12

    The thermal expansion of AuIn{sub 2} gold is of great interest in soldering technology. Indium containing solders have been used to make gold wire interconnects at low soldering temperature and over time, AuIn{sub 2} is formed between the gold wire and the solder due to the high heat of formation and the high inter-metallic diffusion of indium. Hence, the thermal expansion of AuIn{sub 2} alloy in comparison with that of the gold wire and the indium-containing solder is critical in determining the integrity of the connection. We present the results of x-ray diffraction measurement of the coefficient of linear expansion of AuIn{sub 2} as well as the bulk expansion and density changes over the temperature range of 30 to 500 C.

  18. The giant Pebble Cu-Au-Mo deposit and surrounding region, southwest Alaska: introduction

    USGS Publications Warehouse

    Kelley, Karen D.; Lang, James R.; Eppinger, Robert G.

    2013-01-01

    The Pebble deposit is located about 320 km southwest of and 27 km northwest of the village of Iliamna in Alaska (Fig. 1A). It is one of the largest porphyry deposits in terms of contained Cu (Fig. 2A) and it has the largest Au endowment of any porphyry deposit in the world (Fig. 2B). The deposit comprises the Pebble West and Pebble East zones that represent two coeval hydrothermal centers within a single system (Lang et al., 2013). Together the measured and indicated resources total 5,942 million metric tons (Mt) at 0.42% Cu, 0.35 g/t Au, and 250 ppm Mo with an inferred resource of 4,835 Mt at 0.24% Cu, 0.26 g/t Au, and 215 ppm Mo. In addition, the deposit contains significant concentrations of Ag, Pd, and Re (Northern Dynasty Minerals, 2011).

  19. Growth of Au on Ni(110): A Semiempirical Modeling of Surface Alloy Phases

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ibanez-Meier, Rodrigo; Ferrante, John

    1995-01-01

    Recent experiments using scanning tunneling microscopy show evidence for the formation of surface alloys of otherwise immiscible metals. Such is the case for Au deposited in Ni(110), where experiments by Pleth Nielsen el al.indicate that at low Au coverage (less than 0. 5 ML), Au atoms replace Ni atoms in the surface layer forming a surface alloy while the Ni atoms form islands on the surface. In this paper, we present results of a theoretical modeling of this phenomenon using the recently developed Bozzolo-Ferrante-Smith method for alloys. We provide results of an extensive analysis of the growth process that strongly support the conclusions drawn from the experiment: at very low coverages, there is a tendency for dimer formation on the overlayer, which later exchange positions with Ni atoms in the surface layer, thus accounting for the large number of substituted dimers. Ni island formation as well as other alternative short-range-order patterns are discussed.

  20. Growth of Au on Ni(110): a BFS Modelling of Surface Alloy Phases

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ibanez-Meier, Rodrigo; Ferrante, John

    1994-01-01

    Recent experiments using scanning tunneling microscopy show evidence for the formation of surface alloys of otherwise immiscible metals. Such is the case for Au deposited in Ni(11), where experiments by Pleth Nielsen et al. indicate that at low Au coverage (less than 0.5 ML), Au atoms replace Ni atoms in the surface layer forming a surface alloy while the Ni atoms form islands on the surface. In this work, we present results of a theoretical modeling of this phenomenon using the recently developed BFS method for alloys. We provide results of an extensive analysis of the growth process which strongly support the conclusions drawn from the experiment; at very low coverages, there is tendency for dimer formation on the overlayer, which later exchange positions with Ni atoms in the surface layer, thus accounting for the large number of substituted dimers. Ni island formations as well as other alternative short range order patterns are discussed.

  1. [Sensitive determination of Bi3+ by spectrofluorimetry based on graphene oxide-methylene blue system].

    PubMed

    Zhai, Qiu-ge; Guo, Peng; Zhou, Lin; Liu, Yan-ming

    2014-08-01

    Graphene oxide was prepared by the modified Hummers method and characterized by field emission scanning electron microscopy. The interaction of graphene with methylene blue was studied by UV absorption, the intensity of two main absorption peaks of methylene blue decreased significantly after the fluorescence was quenched, and the energy transfer didn't occur because the overlap of the absorption spectrum of GO and the emission spectrum of MB is too small. Therefore, the fluorescence quenching of MB and GO was static. When adding a certain amount of Bi3+ in the graphene-methylene blue system, Bi3+ replaces the methylene blue from the graphene-methylene blue complexes because Bi3+ has the smaller volume and is more positively charged. The methylene blue therefore dissociates from the GO-MB complexes, resulting in the recovery of fluorescence of the system. Furthermore, the fluorescence of the system increases with the increase in the amount of Bi3+ due to the enhanced amount of MB in the system. A novel spectrofluorimetric method was therefore developed for the sensitive determination of Bi3+. Some parameters including the concentration of methylene blue, the amount of graphene oxide, the amount of nitric acid and the sequence of reagent adding were optimized to obtain higher sensitivity. The fluorescence of the system was detected at an emission wavelength of 667 nm with excitation at 690 nm. Under the optimized conditions, the concentration of Bi3+ showed good linear relationships with the fluorescence intensity in the range of 0.5-100 micromol x L(-1), with correlation coefficients of r = 0.9955. The limits of detection for Bi3+ was 1.0 x 10(-8) mol x L(-1) (S/N=3). The selectivity of the proposed method was evaluated and the results showed that 1000-fold K+, Ca+, Na+, Mg2+, Cu2+; 100-fold Fe3+, Be2+, SiO2- Al3+, Ni2+, Sb3+, NO3-, Cl-, F-, and 20-fold Pb2+, Hg2+, Cd2+ had negligible interference with the determination of Bi3+. The method has advantages of

  2. Counterion-Mediated Assembly of Spherical Nucleic Acid-Au Nanoparticle Conjugates (SNA-AuNPs)

    NASA Astrophysics Data System (ADS)

    Kewalramani, Sumit; Moreau, Liane; Guerrero-García, Guillermo; Mirkin, Chad; Olvera de La Cruz, Monica; Bedzyk, Michael; Afosr Muri Team

    2015-03-01

    Controlled crystallization of colloids from solution has been a goal of material scientists for decades. Recently, nucleic acid functionalized spherical Au nanoparticles (SNA-AuNPs) have been programmed to assemble in a wide variety of crystal structures. In this approach, the assembly is driven by Watson-Crick hybridization between DNAs coating the AuNPs. Here, we show that counterions can induce ordered assembly of SNA-AuNPs in bulk solutions, even in the absence of base pairing interactions. The electrostatics-driven assembly of spherical nucleic acid-Au nanoparticle conjugates (SNA-AuNPs) is probed as a function of counterion concentration and counterion valency [ +1 (Na+) or +2 (Ca2+) ] by in situ solution X-ray scattering. Assemblies of AuNPs capped with single-stranded (ss-) or double-stranded (ds-) DNA are examined. SAXS reveals disordered (gas-like) --> face-centered-cubic (FCC) --> glass-like phase transitions with increasing solution ionic strength. These studies demonstrate how non-base-pairing interactions can be tuned to create crystalline assemblies of SNA-AuNPs. The dependence of the inter-SNA-AuNP interactions on counterion valency and stiffness of the DNA corona will be discussed.

  3. DFT study on cysteine adsorption mechanism on Au(111) and Au(110)

    SciTech Connect

    Buimaga-Iarinca, Luiza; Floare, Calin G.; Calborean, Adrian; Turcu, Ioan

    2013-11-13

    Periodic density functional theory calculations were used to investigate relevant aspects of adsorption mechanisms of cysteine dimers in protonated form on Au(111) and Au(110) surfaces. The projected densities of states are explicitly discussed for all main chemical groups of cysteine, i.e. the amino group (NH2), the thiol group (SH) and the carboxylic group (COOH) to identify differences in adsorption mechanism. Special emphasis is put on the analysis of changes in the electronic structure of molecules adsorbed on Au(111) and Au(110) surfaces as well as the accompanying charge transfer mechanisms at molecule-substrate interaction.

  4. Reactions of saturated hydrocarbons with hydrogen and deuterium on epitaxially oriented (111) Pd and Pd-Au alloy films

    SciTech Connect

    Karpinski, Z.

    1982-09-01

    The reactions of neopentane, n-butane, propane, and n-pentane in the presence of an excess of hydrogen have been studied on evaporated Pd/Au-on-mica films. The characterization of films showed that they were predominantly (111) oriented. The selectivity in hydrogenolysis of all hydrocarbons decreased markedly with an increase in the content in Au. The catalytic activity for isomerization of neopentane and n-butane was higher for ca. 10 at. % Au alloys than for pure Pd. This finding appears to support the mechanism involving 1,2-bond shift isomerization at one metal site proposed by McKervey et al. Additional experiments with CH/sub 4//D/sub 2/ and neopentane/D/sub 2/ exchange over Pd-Au(111) alloys at higher temperatures showed considerable difficulties in forming carbene adspecies which could be responsible for another isomerization route. The isotopic exchange between cyclopentane and deuterium over (111) oriented Pd-Au alloys showed that the rate of multiple exchange goes through a gentle maximum for ca. 10 at. % Au. At the same time no special catalytic role of the surface sites of a low coordination number is seen. It is speculated that the rollover process may involve similar intermediate species as in alkene hydrogenation. The relative importance of ensemble size vs electronic effects in the Pd-Au alloys for various reactions is discussed.

  5. The study on the extraction and recovery of Au from scrap of the used computer using chloride solvent

    NASA Astrophysics Data System (ADS)

    Oh, Su-ji; Choi, Eunju; Choi, Nagchoul; Park, Cheonyoung

    2013-04-01

    Recently, due to the realization of environmental problems of cyanide, it is a worldwide quest to find viable alternatives. One of the alternatives is a chloride solvent(chlorine-hypochlorite acid) with an appropriate oxidizing agent. The rate of dissolution of Au by chloride solvent is much faster than that by cyanide. Also, due to presence of chloride ions, there is no passivation of gold surfaces during chlorination. The objective of this work was to investigate the effect of Au extraction efficiency under various experimental conditions(pulp density, chlorine-hypochlorite ratio and concentration of NaCl) from scrap of the used computer by chloride solvent. In addition, the recovery experiment was conducted to examine of the precipitation efficiency of Au under various metabisulfite concentration from extracted solution. In an EDS analysis, valuable metals such as Cu, Sn, Sb, Al, Ni, Pb and Au were observed in scrap of the used computer. The result of extraction experiment showed that the highest extraction rate was obtained under 1% of pulp density with a chlorine-hypochlorite ratio of 2:1, and a concentration of NaCl at 2M. The highest Au recovery(precipitation) rate was observed the addition of sodium metabisulfite at 2M concentration. Under these conditions, chlorine-hypochlorite could effectively Au extraction from scrap of the used computer sections and the additive reagent using sodium metabisulfite could easily precipitate the Au from the chlorine-hypochlorite solution.

  6. Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR

    SciTech Connect

    STAR Coll

    2009-04-11

    Identified charged particle spectra of {pi}{sup {+-}}, K{sup {+-}}, p and {bar p} at mid-rapidity (|y| < 0.1) measured by the dE/dx method in the STAR-TPC are reported for pp and d + Au collisions at {radical}s{sub NN} = 200 GeV and for Au + Au collisions at 62.4 GeV, 130 GeV, and 200 GeV. Average transverse momenta, total particle production, particle yield ratios, strangeness and baryon production rates are investigated as a function of the collision system and centrality. The transverse momentum spectra are found to be flatter for heavy particles than for light particles in all collision systems; the effect is more prominent for more central collisions. The extracted average transverse momentum of each particle species follows a trend determined by the total charged particle multiplicity density. The Bjorken energy density estimate is at least several GeV/fm{sub 3} for a formation time less than 1 fm/c. A significantly larger net-baryon density and a stronger increase of the net-baryon density with centrality are found in Au + Au collisions at 62.4 GeV than at the two higher energies. Antibaryon production relative to total particle multiplicity is found to be constant over centrality, but increases with the collision energy. Strangeness production relative to total particle multiplicity is similar at the three measured RHIC energies. Relative strangeness production increases quickly with centrality in peripheral Au + Au collisions, to a value about 50% above the pp value, and remains rather constant in more central collisions. Bulk freeze-out properties are extracted from thermal equilibrium model and hydrodynamics-motivated blast-wave model fits to the data. Resonance decays are found to have little effect on the extracted kinetic freeze-out parameters due to the transverse momentum range of our measurements. The extracted chemical freeze-out temperature is constant, independent of collision system or centrality; its value is close to the predicted phase

  7. Tri-icosahedral Gold Nanocluster [Au37(PPh3)10(SC2H4Ph)10X2](+): Linear Assembly of Icosahedral Building Blocks.

    PubMed

    Jin, Renxi; Liu, Chong; Zhao, Shuo; Das, Anindita; Xing, Hongzhu; Gayathri, Chakicherla; Xing, Yan; Rosi, Nathaniel L; Gil, Roberto R; Jin, Rongchao

    2015-08-25

    The [Au37(PPh3)10(SR)10X2](+) nanocluster (where SR = thiolate and X = Cl/Br) was theoretically predicted in 2007, but since then, there has been no experimental success in the synthesis and structure determination. Herein, we report a kinetically controlled, selective synthesis of [Au37(PPh3)10(SC2H4Ph)10X2](+) (counterion: Cl(-) or Br(-)) with its crystal structure characterized by X-ray crystallography. This nanocluster shows a rod-like structure assembled from three icosahedral Au13 units in a linear fashion, consistent with the earlier prediction. The optical absorption and the electrochemical and catalytic properties are investigated. The successful synthesis of this new nanocluster allows us to gain insight into the size, structure, and property evolution of gold nanoclusters that are based upon the assembly of icosahedral units (i.e., cluster of clusters). Some interesting trends are identified in the evolution from the monoicosahedral [Au13(PPh3)10X2](3+) to the bi-icosahedral [Au25(PPh3)10(SC2H4Ph)5X2](2+) and to the tri-icosahedral [Au37(PPh3)10(SC2H4Ph)10X2](+) nanocluster, which also points to the possibility of achieving even longer rod nanoclusters based upon assembly of icosahedral building blocks.

  8. Composition and source of salinity of ore-bearing fluids in Cu-Au systems of the Carajás Mineral Province, Brazil

    USGS Publications Warehouse

    Xavier, Roberto; Rusk, Brian; Emsbo, Poul; Monteiro, Lena

    2009-01-01

    The composition and Cl/Br – NaCl ratios of highly saline aqueous inclusions from large tonnage (> 100 t) IOCG deposits (Sossego, Alvo 118, and Igarapé Bahia) and a Paleoproterozoic intrusion-related Cu-Au-(Mo-W-Bi-Sn) deposit (Breves; < 50 Mt)) in the Carajás Mineral Province have been analysed by LA-ICP-MS and ion chromatography. In both Cu-Au systems, brine inclusions are Ca-dominated (5 to 10 times more than in porphyry Cu-Au fluids), and contain percent level concentrations of Na and K. IOCG inclusion fluids, however, contain higher Sr, Ba, Pb, and Zn concentrations, but significantly less Bi, than the intrusion-related Breves inclusion fluids. Cu is consistently below detection limits in brine inclusions from the IOCG and intrusion-related systems and Fe was not detected in the latter. Cl/Br and Na/Cl ratios of the IOCG inclusion fluids range from entirely evaporative brines (bittern fluids; e.g. Igarapé Bahia and Alvo 118) to values that indicate mixing with magma-derived brines. Cl/Br and Na/Cl ratios of the Breves inclusion fluids strongly suggest the involvement of magmatic brines, but that possibly also incorporated bittern fluids. Collectively, these data demonstrate that residual evaporative and magmatic brines were important components of the fluid regime involved in the formation of Cu-Au systems in the Carajás Mineral Province.

  9. High photocatalytic performance of BiOI/Bi2WO6 toward toluene and Reactive Brilliant Red

    NASA Astrophysics Data System (ADS)

    Li, Huiquan; Cui, Yumin; Hong, Wenshan

    2013-01-01

    BiOI sensitized nano-Bi2WO6 photocatalysts with different BiOI contents were successfully synthesized by a facile deposition method at room temperature, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) spectra, UV-vis diffuse reflection spectroscopy (UV-vis DRS) and Brunauer-Emmett-Teller (BET) surface area measurements. The photocatalytic activity of BiOI/Bi2WO6 was evaluated by the photo-degradation of Reactive Brilliant Red (X-3B) in suspended solution and toluene in gas phase. It has been shown that the BiOI/Bi2WO6 catalysts exhibit a coexistence of both tetragonal BiOI and orthorhombic Bi2WO6 phases. With increasing BiOI content, the absorption intensity of BiOI/Bi2WO6 catalysts increases in the 380-600 nm region and the absorption edge shifts significantly to longer wavelengths as compared to pure Bi2WO6. The 13.2% BiOI/Bi2WO6 catalyst exhibits obviously higher UV and visible light photocatalytic activities than commercial P25, pure Bi2WO6 and BiOI, for the photodegradation of toluene and X-3B. The remarkably enhanced photocatalytic activities can be attributed to the fact that the proper BiOI sensitized nano-Bi2WO6 increase its BET surface area, decrease band-gap energy, enhance absorption in the 380-600 nm region and inhibit the recombination of photo-induced carriers.

  10. 78 FR 64327 - Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Bi-State...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-28

    ... sage-grouse movements both within and among populations. These variations are related to the spatial... of annual movements among populations of greater sage-grouse within the Bi-State area, and the degree...). Migratory movements (defined in Connelly et al. (2000a, p. 969) as moving more than 10 kilometers (km)...

  11. Ca- and Sc-based ternary AlB2-like crystals: a first-principles study

    NASA Astrophysics Data System (ADS)

    Tsetseris, Leonidas

    2017-02-01

    The aluminum diboride (AlB2) crystal structure comprises intercalated metal atoms between honeycomb sheets. In addition to metal diborides, which represent the most common family of AlB2-like structures, many more materials are known to crystallize in this geometry. Here we use first-principles calculations to probe the structural and electronic properties of several such systems. Specifically, we investigate the stability of various polymorphs of CaAuAs, CaAuP, CaCuP, ScAuGe, ScAuSi, Ca2AgSi3 and Ca2AuGe3 and find lattice parameters in excellent agreement with available experimental data. The analysis of densities of states and band structure diagrams show that all materials are metallic. However, the details of band dispersion vary significantly, from typical metals such as CaAuP, to almost semi-metallic behaviour in CaCuP.

  12. BiTeCl and BiTeBr: A comparative high-pressure optical study

    NASA Astrophysics Data System (ADS)

    Crassee, I.; Borondics, F.; Tran, M. K.; Autès, G.; Magrez, A.; Bugnon, P.; Berger, H.; Teyssier, J.; Yazyev, O. V.; Orlita, M.; Akrap, A.

    2017-01-01

    We here report a detailed high-pressure infrared transmission study of BiTeCl and BiTeBr. We follow the evolution of two band transitions: the optical excitation β between two Rashba-split conduction bands, and the absorption γ across the band gap. In the low-pressure range, p <4 GPa, for both compounds β is approximately constant with pressure and γ decreases, in agreement with band structure calculations. In BiTeCl, a clear pressure-induced phase transition at 6 GPa leads to a different ground state. For BiTeBr, the pressure evolution is more subtle, and we discuss the possibility of closing and reopening of the band gap. Our data is consistent with a potential Weyl phase in BiTeBr at 5 -6 GPa, followed by the onset of a structural phase transition above 7 GPa.

  13. Influence of gravity on the microstructure of the MnBi/Bi eutectic

    NASA Technical Reports Server (NTRS)

    Rydzewski, J. H.; Wilcox, W. R.

    1991-01-01

    Directional solidification of MnBiBi eutectic in space produced MnBi fibers that were significantly finer and closer together than when solidification was carried out on earth under otherwise identical conditions. Use of a strong magnetic field during solidification on earth gave about the same results as solidification in space, indicating that convection is the cause of the difference in microstructure. However, 15 years of theoretical and experimental research have failed to reveal the mechanism for this phenomenon. It has been found that temperature gradient has no effect; the concentration field in front of the freezing interface is not altered sufficiently by buoyancy-driven convection to explain it, even if the MnBi fibers project out in front of the Bi matrix; and the Soret effect is not sufficiently large. On the other hand, vigorous forced convection caused a change in microstructure in agreement with theory.

  14. Development of MnBi permanent magnet: neutron diffraction of MnBi powder

    SciTech Connect

    Cui, Jun; Choi, Jung-Pyung; Li, Guosheng; Polikarpov, Evgueni; Darsell, Jens T.; Kramer, Matthew J.; Zarkevich, Nikolai; Wang, L. L.; Johnson, D. D.; Marinescu, Melania; Huang, Qingzhen; Wu, Hui; Vuong, Nguyen V.; Liu, J.Ping

    2014-03-05

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained power. The result shows that the purity of the obtained powder is about 91wt.% at 300K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μB at 50 K and 300 K respectively.

  15. Absence of low-temperature dependence of the decay of {sup 7}Be and {sup 198}Au in metallic hosts

    SciTech Connect

    Kumar, V.; Hass, M.; Nir-El, Y.; Haquin, G.; Yungreiss, Z.

    2008-05-15

    The electron-capture (EC) decay rate of {sup 7}Be in metallic Cu host and the {beta}{sup -}-decay rate of {sup 198}Au in the host alloy Al-Au have been measured simultaneously at several temperatures, ranging from 0.350 K to 293 K. No difference of the half-life of {sup 198}Au between 12.5 K and 293 K is observed to a precision of 0.1%. By utilizing the special characteristics of our double-source assembly, possible geometrical effects that influence the individual rates could be eliminated. The ratio of {sup 7}Be to {sup 198}Au activity thus obtained also remains constant for this temperatures range to the experimental precision of 0.15{+-}0.16%. The resulting null temperature dependence is discussed in terms of the inadequacy of the often-used Debye-Hueckel model for such measurements.

  16. Fully Cationized Gold Clusters: Synthesis of Au25(SR(+))18.

    PubMed

    Ishida, Yohei; Narita, Kunihiro; Yonezawa, Tetsu; Whetten, Robert L

    2016-10-06

    Although many thiolate-protected Au clusters with different numbers of Au atoms and a variety of thiolate ligands have been synthesized, to date there has been no report of a fully cationized Au cluster protected with cationic thiolates. Herein, we report the synthesis of the first member of a new series of thiolate-protected Au cluster molecules: a fully cationized Au25(SR(+))18 cluster.

  17. AL Amyloidosis

    PubMed Central

    2012-01-01

    Definition of the disease AL amyloidosis results from extra-cellular deposition of fibril-forming monoclonal immunoglobulin (Ig) light chains (LC) (most commonly of lambda isotype) usually secreted by a small plasma cell clone. Most patients have evidence of isolated monoclonal gammopathy or smoldering myeloma, and the occurrence of AL amyloidosis in patients with symptomatic multiple myeloma or other B-cell lymphoproliferative disorders is unusual. The key event in the development of AL amyloidosis is the change in the secondary or tertiary structure of an abnormal monoclonal LC, which results in instable conformation. This conformational change is responsible for abnormal folding of the LC, rich in β leaves, which assemble into monomers that stack together to form amyloid fibrils. Epidemiology AL amyloidosis is the most common type of systemic amyloidois in developed countries with an estimated incidence of 9 cases/million inhabitant/year. The average age of diagnosed patients is 65 years and less than 10% of patients are under 50. Clinical description The clinical presentation is protean, because of the wide number of tissues or organs that may be affected. The most common presenting symptoms are asthenia and dyspnoea, which are poorly specific and may account for delayed diagnosis. Renal manifestations are the most frequent, affecting two thirds of patients at presentation. They are characterized by heavy proteinuria, with nephrotic syndrome and impaired renal function in half of the patients. Heart involvement, which is present at diagnosis in more than 50% of patients, leading to restrictive cardiopathy, is the most serious complication and engages prognosis. Diagnostic methods The diagnosis relies on pathological examination of an involved site showing Congo red-positive amyloid deposits, with typical apple-green birefringence under polarized light, that stain positive with an anti-LC antibody by immunohistochemistry and/or immunofluorescence. Due to the

  18. Pt based nanocomposites (mono/bi/tri-metallic) decorated using different carbon supports for methanol electro-oxidation in acidic and basic media.

    PubMed

    Singh, Baljit; Murad, Lukaa; Laffir, Fathima; Dickinson, Calum; Dempsey, Eithne

    2011-08-01

    Pt based mono/bi/tri-metallic nanocomposites on different carbon based supports (activated carbon (AC), carbon nanotubes (CNTs) and carbon nanofibers (CNFs)) were synthesised and Pt surface enrichment achieved. The overall theoretical metallic content (Pt + Au + Sn) was 20% (w/w) in all mono/bi/tri-metallic nanocomposites and was found to be uniformly distributed in the supporting matrix (80%). The surface morphology and composition of the synthesised materials was characterised using scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while cyclic voltammetry was employed in order to confirm their typical metallic electrochemical characteristics. Electrochemical measurements indicated that Pt(2)Au(1)Sn(1) trimetallic catalysts demonstrated a significantly higher electrochemically active surface area relative to activated carbon supported PtAu based bimetallic counterparts. The results show that the CNT based trimetallic catalyst (Pt(2)Au(1)Sn(1)/CNT) showed greatest electroactive surface area (49.3 m(2)/g) and current density for methanol oxidation in acidic (490 mA mg(-1) Pt) as well as basic (1700 mA mg(-1) Pt) conditions. Results demonstrated that in comparison to Au/C and Sn/C (no/negligible response), the presence of a small amount of Pt in the Au and Sn based nanocomposites, significantly modified the catalytic properties. The activated carbon supported bimetallic (Pt(1)Au(3)/C) catalyst showed reasonably good response (260 mA mg(-1) Pt) among all bimetallic nanomaterials examined. The current response achieved for Pt(2)Au(1)Sn(1)/CNT was 1.9 times (in acidic media) and 2.1 times (in basic media) that for synthesised Pt/C in terms of per mg Pt activity. Overall the methanol oxidation studies demonstrated that the presence of Au and Sn in Pt

  19. Luminescence and charge carrier trapping in YPO4:Bi

    NASA Astrophysics Data System (ADS)

    Awater, Roy H. P.; Niemeijer-Berghuijs, Louise C.; Dorenbos, Pieter

    2017-04-01

    YPO4 doped with Bi3+ and/or Tb3+ samples were prepared in air. X-ray excited luminescence measurements showed emission from isolated Bi3+ and Bi-pairs, and also emission from Bi2+ was observed. Based on the obtained spectroscopic data, the electron binding energies in the ground and excited states of Bi3+ and Bi2+ were placed inside the vacuum referred binding energy (VRBE) scheme, and this was used to explain the luminescence of bismuth doped YPO4. The VRBE scheme and additional thermoluminescence glow curves show that bismuth can act both as electron and as hole trap in YPO4.

  20. Influence of photoinduced Bi-related self-doping on the photocatalytic activity of BiOBr nanosheets

    NASA Astrophysics Data System (ADS)

    Wu, Dan; Yue, Songtao; Wang, Wei; An, Tiacheng; Li, Guiying; Ye, Liqun; Yip, Ho Yin; Wong, Po Keung

    2017-01-01

    Under UV irradiation, self-doped Bi5+ is evidenced to be generated on the surface of BiOBr nanosheets, but with well-preserved crystal structure and morphology compared with pure counterpart. Bi5+ self-doping BiOBr (BiOBr-4) exhibits distinct photocatalytic mode for dyes degradation, as compared with pure BiOBr nanosheets. These photodegradation distinctions are mainly due to the simultaneous occurrence of two photoinduced hole (h+) mediated oxidation processes on the BiOBr surfaces: (1) a portion of photoexcited h+ participates in the photocatalytic oxidation of dyes, and (2) partial h+ involves the oxidation of Bi3+ to Bi5+. Notably, BiOBr-4 nanosheets comparatively show superior photocatalytic activity for the phenol decomposition as well as the bacterial inactivation. Besides Bi5+ induced narrowed bandgap and enhanced light adsorption capacity, significantly, the oxidative Bi5+ acts as electron traps to promote the photoexcited electron-hole separation and accelerate h+ migration, resulting in the considerable photocatalytic enhancement of BiOBr-4 nanosheets. These novel findings will not only give new insights into the photocatalytic mechanism but also explore new route to enhance photocatalytic performance of Bi-based materials.

  1. Determination of environmental dependence of the &-circ; decay half-life of ^198Au

    NASA Astrophysics Data System (ADS)

    Dibidad, A.; Goodwin, J.; Hardy, J.

    2009-10-01

    A series of articles by the C. Rolfs group [1] claimed changes in the half-lives of isotopes undergoing α, β^-, β^+, and electron-capture decays as the temperature reduced to 12 K from room temperature. These isotopes were contained in metallic, conductive environments, such as Au, Cu, and Pd, but it was also suggested that the half-life is different in an insulator. One publication [1] reported the half-life of ^198Au in a gold metal environment to change by 3.6 ±1.0% between room temperature and 12 K. Until then, radioactive half-lives were considered independent of environmental factors. We repeated the measurements of the ^198Au half-life in a gold metal environment under similar conditions as ref. [1] and demonstrated [2] that the half-life is the same at both temperatures within 0.04%, two orders of magnitude below the original claims. In the experiment reported here, we measured the half-life of ^198Au in an insulated environment -- gold (III) oxide -- at room temperature. Preliminary results indicate there is no difference in the measured half-life in an insulator as compared in a conductor. [4pt] [1] T. Spillane et al, Eur. Phys. J. A 31, 203 (2007) [0pt] [2] J.R. Goodwin et al, Eur. Phys. J. A 34, 271 (2007)

  2. Amplification of Collective Magnetic Fluctuations in Magnetized Bi-Maxwellian Plasmas for Parallel Wave Vectors. I. Electron-Proton Plasma

    NASA Astrophysics Data System (ADS)

    Vafin, S.; Schlickeiser, R.; Yoon, P. H.

    2016-09-01

    The general electromagnetic fluctuation theory is a powerful tool to analyze the magnetic fluctuation spectrum of a plasma. Recent works utilizing this theory for a magnetized non-relativistic isotropic Maxwellian electron-proton plasma have demonstrated that the equilibrium ratio of | δ B| /{B}0 can be as high as 10-12. This value results from the balance between spontaneous emission of fluctuations and their damping, and it is considerably smaller than the observed value | δ B| /{B}0 in the solar wind at 1 au, where {10}-3≲ | δ B| /{B}0≲ {10}-1. In the present manuscript, we consider an anisotropic bi-Maxwellian distribution function to investigate the effect of plasma instabilities on the magnetic field fluctuations. We demonstrate that these instabilities strongly amplify the magnetic field fluctuations and provide a sufficient mechanism to explain the observed value of | δ B| /{B}0 in the solar wind at 1 au.

  3. Magnetism of MnBi-Based Nanomaterials

    SciTech Connect

    Kharel, P; Shah, VR; Skomski, R; Shield, JE; Sellmyer, DJ

    2013-07-01

    Nanostructured MnBi ribbons doped with impurity elements including B, C, Fe, Hf, Sm and Tb were prepared using the arc melting and melt-spinning techniques. The melt-spun ribbons were annealed in vacuum furnace at 350 degrees C to obtain the intended hexagonal structure. The external impurity doping made a significant change in the magnetic properties of the nanostructured MnBi ribbons including a decrease in saturation magnetization (M-s) and anisotropy energy (K) and an increase in coercivity H-c. However, Hf and C co-doping showed the opposite effect with a small increase in both M-s and K. Interestingly, the anisotropy energy of the boron doped sample increased by about 15% irrespective of the small decrease in magnetization. A significant increase in H-c of MnBi ribbons was found due to Hf, Tb and Sm doping. H-c as high as 13 kOe was achieved in Hf-doped sample after the sample was aligned in a magnetic field. A thermal hysteresis was observed at the structural phase transition of MnBi, which shifts by about 5 K towards higher temperatures due to impurity doping. The observed magnetic properties of the impurity doped MnBi ribbons are explained as the consequences of the disorder and the competing ferromagnetic and antiferromagnetic interactions.

  4. Optimization of excess Bi doping to enhance ferroic orders of spin casted BiFeO{sub 3} thin film

    SciTech Connect

    Gupta, Surbhi; Gupta, Vinay; Tomar, Monika; James, A. R.; Pal, Madhuparna; Guo, Ruyan; Bhalla, Amar

    2014-06-21

    Multiferroic Bismuth Ferrite (BiFeO{sub 3}) thin films with varying excess bismuth (Bi) concentration were grown by chemical solution deposition technique. Room temperature multiferroic properties (ferromagnetism, ferroelectricity, and piezoelectricity) of the deposited BiFeO{sub 3} thin films have been studied. High resolution X-ray diffraction and Raman spectroscopy studies reveal that the dominant phases formed in the prepared samples change continuously from a mixture of BiFeO{sub 3} and Fe{sub 2}O{sub 3} to pure BiFeO{sub 3} phase and, subsequently, to a mixture of BiFeO{sub 3} and Bi{sub 2}O{sub 3} with increase in the concentration of excess Bi from 0% to 15%. BiFeO{sub 3} thin films having low content (0% and 2%) of excess Bi showed the traces of ferromagnetic phase (γ-Fe{sub 2}O{sub 3}). Deterioration in ferroic properties of BiFeO{sub 3} thin films is also observed when prepared with higher content (15%) of excess Bi. Single-phased BiFeO{sub 3} thin film prepared with 5% excess Bi concentration exhibited the soft ferromagnetic hysteresis loops and ferroelectric characteristics with remnant polarization 4.2 μC/cm{sup 2} and saturation magnetization 11.66 emu/g. The switching of fine spontaneous domains with applied dc bias has been observed using piezoresponse force microscopy in BiFeO{sub 3} thin films having 5% excess Bi. The results are important to identify optimum excess Bi concentration needed for the formation of single phase BiFeO{sub 3} thin films exhibiting the improved multiferroic properties.

  5. SN 2012au: A Golden Link between Superluminous Supernovae and Their Lower-luminosity Counterparts

    NASA Astrophysics Data System (ADS)

    Milisavljevic, Dan; Soderberg, Alicia M.; Margutti, Raffaella; Drout, Maria R.; Howie Marion, G.; Sanders, Nathan E.; Hsiao, Eric Y.; Lunnan, Ragnhild; Chornock, Ryan; Fesen, Robert A.; Parrent, Jerod T.; Levesque, Emily M.; Berger, Edo; Foley, Ryan J.; Challis, Pete; Kirshner, Robert P.; Dittmann, Jason; Bieryla, Allyson; Kamble, Atish; Chakraborti, Sayan; De Rosa, Gisella; Fausnaugh, Michael; Hainline, Kevin N.; Chen, Chien-Ting; Hickox, Ryan C.; Morrell, Nidia; Phillips, Mark M.; Stritzinger, Maximilian

    2013-06-01

    We present optical and near-infrared observations of SN 2012au, a slow-evolving supernova (SN) with properties that suggest a link between subsets of energetic and H-poor SNe and superluminous SNe. SN 2012au exhibited conspicuous Type-Ib-like He I lines and other absorption features at velocities reaching ≈2 × 104 km s-1 in its early spectra, and a broad light curve that peaked at MB = -18.1 mag. Models of these data indicate a large explosion kinetic energy of ~1052 erg and 56Ni mass ejection of M Ni ≈ 0.3 M ⊙ on par with SN 1998bw. SN 2012au's spectra almost one year after explosion show a blend of persistent Fe II P-Cyg absorptions and nebular emissions originating from two distinct velocity regions. These late-time emissions include strong [Fe II], [Ca II], [O I], Mg I], and Na I lines at velocities >~ 4500 km s-1, as well as O I and Mg I lines at noticeably smaller velocities <~ 2000 km s-1. Many of the late-time properties of SN 2012au are similar to the slow-evolving hypernovae SN 1997dq and SN 1997ef, and the superluminous SN 2007bi. Our observations suggest that a single explosion mechanism may unify all of these events that span -21 <~ MB <~ -17 mag. The aspherical and possibly jetted explosion was most likely initiated by the core collapse of a massive progenitor star and created substantial high-density, low-velocity Ni-rich material.

  6. Using supported Au nanoparticles as starting material for preparing uniform Au/Pd bimetallic catalysts.

    PubMed

    Villa, Alberto; Wang, Di; Su, Dangsheng; Veith, Gabriel M; Prati, Laura

    2010-03-07

    One of the best methods for producing bulk homogeneous (composition) supported bimetallic AuPd clusters involves the immobilization of a protected Au seed followed by the addition of Pd. This paper investigates the importance of this gold seed in controlling the resulting bimetallic AuPd clusters structures, sizes and catalytic activities by investigating three different gold seeds. Uniform Au-Pd alloy were obtained when a steric/electrostatic protecting group, poly(vinyl alcohol) (PVA), was used to form the gold clusters on activated carbon (AC). In contrast Au/AC precursors prepared using Au nanoparticles with only electrostatic stabilization (tetrakis(hydroxypropyl)phosphonium chloride (THPC)), or no stabilization (magnetron sputtering) produced inhomogeneous alloys and segregation of the gold and palladium. The uniform alloyed catalyst (Pd@Au(PVA)/AC) is the most active and selective catalyst, while the inhomogenous catalysts are less active and selective. Further study of the PVA protected Au clusters revealed that the amount of PVA used is also critical for the preparation of uniform alloyed catalyst, their stability, and their catalytic activity.

  7. Using supported Au nanoparticles as starting material for preparing uniform Au/Pd bimetallic catalysts

    SciTech Connect

    Villa, Alberto; Prati, Laura; Su, Dangshen; Wang, Di; Veith, Gabriel M

    2010-01-01

    One of the best methods for producing bulk homogeneous (composition) supported bimetallic AuPd clusters involves the immobilization of a protected Au seed followed by the addition of Pd. This paper investigates the importance of this gold seed in controlling the resulting bimetallic AuPd clusters structures, sizes and catalytic activities by investigating three different gold seeds. Uniform Au-Pd alloy were obtained when a steric/electrostatic protecting group, poly(vinyl alcohol) (PVA), was used to form the gold clusters on activated carbon (AC). In contrast Au/AC precursors prepared using Au nanoparticles with only electrostatic stabilization (tetrakis(hydroxypropyl)phosphonium chloride (THPC)), or no stabilization (magnetron sputtering) produced inhomogeneous alloys and segregation of the gold and palladium. The uniform alloyed catalyst (Pd{at}Au{sub PVA}/AC) is the most active and selective catalyst, while the inhomogenous catalysts are less active and selective. Further study of the PVA protected Au clusters revealed that the amount of PVA used is also critical for the preparation of uniform alloyed catalyst, their stability, and their catalytic activity.

  8. LaAu2 and CeAu2 surface intermetallic compounds grown by high-temperature deposition on Au(111)

    NASA Astrophysics Data System (ADS)

    Ormaza, M.; Fernández, L.; Lafuente, S.; Corso, M.; Schiller, F.; Xu, B.; Diakhate, M.; Verstraete, M. J.; Ortega, J. E.

    2013-09-01

    We report on the crystal structure and electronic bands of LaAu2 and CeAu2 surface intermetallic compounds grown by high-temperature deposition on Au(111). By scanning-tunneling microscopy we study the formation of different alloy phases as a function of growth temperature and lanthanide coverage. We determine the specific growth conditions to achieve monolayers and bilayers of LaAu2 and CeAu2 with high crystalline quality. Due to lattice mismatch with the underlying Au substrate, both LaAu2 and CeAu2 exhibit long-range moiré patterns, which can serve as templates for further nanostructure growth. By angle-resolved photoemission we map the two-dimensional band structure of these surface alloys, discussing the nature of the different spectral features in the light of first-principles calculations.

  9. Enhancement of Rashba interaction in GaAs/AlGaAs quantum wells due to the incorporation of bismuth

    SciTech Connect

    Simmons, R. A.; Jin, S. R.; Sweeney, S. J.; Clowes, S. K.

    2015-10-05

    This paper reports on the predicted increase in the Rashba interaction due to the incorporation of Bi in GaAs/AlGaAs heterostructures. Band structure parameters obtained from the band anti-crossing theory have been used in combination with self-consistent Schrödinger-Poisson calculations and k.p models to determine the electron spin-splitting caused by structural inversion asymmetry and increased spin-orbit interaction. A near linear seven fold increase in the strength of the Rashba interaction is predicted for a 10% concentration of Bi in a GaAsBi/AlGaAs quantum well heterostructure.

  10. Reduction in thermal conductivity of BiSbTe lump

    NASA Astrophysics Data System (ADS)

    Ahmad, Kaleem; Wan, C.; Al-Eshaikh, M. A.; Kadachi, A. N.

    2017-03-01

    In this work, systematic investigations on the thermal conductivities of BiSbTe lump, microstructured pristine BiSbTe bulk and single wall carbon nanotubes (SWCNTs)/BiSbTe bulk nanocomposites were performed. BiSbTe lumps were crushed to form a coarse powder (200 µm) and effect of particle size reduction on the effective thermal conductivity of BiSbTe (200 µm) bulk were analyzed. For further reduction in the conductivity, a two pronged strategy has been employed. First, additional refinement of BiSbTe (200 µm) were performed through ball milling in an inert environment. Second, SWCNTs in 0.75, and 1.0 vol% were distributed uniformly in the fine BiSbTe ball milled powder. The results showed that the effective thermal conductivities decrease with the reduction in the particle size from lump to BiSbTe (200 µm) bulk as well as with the addition of SWCNTs accompanied by further refinement of BiSbTe particles. The significant reduction in thermal conductivities of the lump was achieved for pure BiSbTe (200 µm) bulk and 0.75 vol% of SWCNTs/BiSbTe composite. This can be ascribed to the enhanced phonon scattering by the grain boundaries between the nanostructured BiSbTe particles as well as the interfaces between BiSbTe and the low dimensional carbon nanotubes.

  11. A tantalum diffusion barrier layer for improving the output performance of AlGaInP-based light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyun; Park, Jae-Seong; Kang, Daesung; Seong, Tae-Yeon

    2016-03-01

    We have investigated the effect of a Ta diffusion barrier layer on the electrical characteristics of AuBe/Au contacts on a p-GaP window layer for AlGaInP-based light-emitting diodes (LEDs). It was shown that after annealing at 500 °C, the AuBe/Ta/Au contacts exhibited nearly 2 orders of magnitude lower specific contact resistance (2.8 × 10-6 Ω·cm2) than the AuBe/Au contacts (1.0 × 10-4 Ω·cm2). The LEDs with and without the Ta diffusion barrier layer showed an external quantum efficiency of 14.03 and 13.5% at 50 mA, respectively. After annealing at 500 °C, the AuBe/Ta/Au contacts showed a higher reflectance (92.8% at 617 nm) than that of the AuBe/Au contacts (87.7%). X-ray photoemission spectroscopy (XPS) results showed that the Ga 2p core level for the annealed AuBe/Au samples shifted to higher binding energies, while this level shifted towards lower binding energies for the AuBe/Ta/Au samples. Depth profiles using Auger electron spectroscopy (AES) showed that annealing of the AuBe/Au samples caused the outdiffusion of both Be and P atoms into the metal contact, while for the AuBe/Ta/Au samples, the outdiffusion of Be atoms was blocked by the Ta barrier layer and more Be atoms were indiffused into GaP. The annealing-induced electrical degradation and ohmic contact formation are described and discussed based on the XPS and electrical results.

  12. Adsorbate-modified Electron Relaxation in Au-Au_2S Nanoshells

    NASA Astrophysics Data System (ADS)

    Westcott, Sarah; Averitt, Richard; Wolfgang, John; Nordlander, Peter; Halas, Naomi

    2001-03-01

    Au-Au_2S nanoshells are 50 nm nanoparticles consisting of an Au_2S core encapsulated by a thin (<5 nm) Au shell. Their optical properties are determined by the metallic shell layer, whose inner and outer radii control plasmon frequency and whose thickness determines plasmon linewidth[1]. We studied the time-resolved relaxation of hot electrons in the Au shell, using degenerate pump-probe spectroscopy. The electron relaxation for nanoshells in solution was appreciably slower than relaxation for bulk gold, moreover, adsorbed molecules on the nanoshell surface strongly modify this relaxation. Density functional theory calculations indicate that the molecules providing the strongest modification of relaxation possess the largest induced dipole moments above a metal surface, indicating that the adsorbate-induced perturbation of the nanoshell electron dynamics appears to be primarily electronic in nature. [1] R. D. Averitt, D. Sarkar and N. J. Halas, Phys. Rev. Lett. 78, 4217 (1997).

  13. Microwave-assisted synthesis and photocatalytic properties of flower-like Bi2WO6 and Bi2O3-Bi2WO6 composite.

    PubMed

    Li, Zhao-Qian; Chen, Xue-Tai; Xue, Zi-Ling

    2013-03-15

    Flower-like Bi(2)WO(6) and Bi(2)O(3)-Bi(2)WO(6) composite microstructures have been synthesized via a facile and rapid microwave-assisted hydrothermal method through controlling the experimental parameters. The phases and morphologies of the products are characterized by powder X-ray diffraction (XRD), energy dispersion X-ray analysis (EDX), high resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM). Photocatalytic experiments indicate that such Bi(2)O(3)-Bi(2)WO(6) composite possesses higher photocatalytic activity for RhB degradation under visible-light irradiation in comparison with pure Bi(2)O(3) and Bi(2)WO(6). On the basis of the calculated energy band positions, the enhanced photocatalytic activity is attributed to the effective separation of electron-hole pairs between the two semiconductors. The present study provides a new strategy to design composite materials with enhanced photocatalytic activity.

  14. Exfoliation of Layered Topological Insulators Bi2Se3 and Bi2Te3 via Electrochemistry.

    PubMed

    Ambrosi, Adriano; Sofer, Zdeněk; Luxa, Jan; Pumera, Martin

    2016-12-27

    Among layered materials, topological insulators such as Bi2Se3 and Bi2Te3 are lately attracting much attention due to particular electronic properties and, especially with Bi2Te3, excellent thermoelectric properties. Methods of preparation of few-layered nanosheets of Bi2Se3 and Bi2Te3 range from the bottom-up chemical vapor deposition or hydrothermal synthesis from oxide precursors to the top-down mechanical exfoliation and liquid-based exfoliation supported by sonication from the natural bulk crystals. Here, we propose a simple and rapid electrochemical approach to exfoliate natural Bi2Se3 and Bi2Te3 crystals in aqueous media to single/few-layer sheets. The exfoliated materials have been characterized by scanning transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and Raman spectroscopy in addition to evaluation of their electrochemical properties. This electrochemical procedure represents a simple, reagent-free, and scalable method for the fabrication of single/few-layer sheets of these materials.

  15. Jets and dijets in Au+Au and p+p collisions at RHIC

    SciTech Connect

    Hardtke, D.; STAR Collaboration

    2002-12-09

    Recent data from RHIC suggest novel nuclear effects in the production of high p{sub T} hadrons. We present results from the STAR detector on high p{sub T} angular correlations in Au+Au and p+p collisions at {radical}S = 200 GeV/c. These two-particle angular correlation measurements verify the presence of a partonic hard scattering and fragmentation component at high p{sub T} in both central and peripheral Au+Au collisions. When triggering on a leading hadron with p{sub T}>4 GeV, we observe a quantitative agreement between the jet cone properties in p+p and all centralities of Au+Au collisions. This quantitative agreement indicates that nearly all hadrons with p{sub T}>4 GeV/c come from jet fragmentation and that jet fragmentation properties are not substantially modified in Au+Au collisions. STAR has also measured the strength of back-to-back high p{sub T} charged hadron correlations, and observes a small suppression of the back-to-back correlation strength in peripheral collisions, and a nearly complete disappearance o f back-to-back correlations in central Au+Au events. These phenomena, together with the observed strong suppression of inclusive yields and large value of elliptic flow at high p{sub T}, are consistent with a model where high p{sub T} hadrons come from partons created near the surface of the collision region, and where partons that originate or propagate towards the center of the collision region are substantially slowed or completely absorbed.

  16. Intraoperative BiPAP in OSA Patients

    PubMed Central

    Singh, Bhavna P

    2015-01-01

    Obstructive sleep apnea syndrome (OSA) is characterized by recurrent episodes of partial or complete upper airway obstructions during sleep. Severe OSA presents with a number of challenges to the anesthesiologist, the most life threatening being loss of the airway. We are reporting a case where we successfully used intraoperative bi level positive pressure ventilation (BiPAP) with moderate sedation and a regional technique in a patient with severe OSA posted for total knee replacement (TKR). A 55-year-old lady with osteoarthritis of right knee joint was posted for total knee replacement. She had severe OSA with an apnea-hypopnea index of 35. She also had moderate pulmonary hypertension due to her long standing OSA. We successfully used in her a combined spinal epidural technique with intraoperative BiPAP and sedation. She had no complications intraoperatively or post operatively and was discharged on day 5. Patients with OSA are vulnerable to sedatives, anaesthesia and analgesia which even in small doses can cause complete airway collapse. The problem, with regional techniques is that it requires excellent patient cooperation. We decided to put our patient on intraoperative BiPAP hoping that this would allow us to sedate her adequately for the surgery. As it happened we were able to successfully sedate her with slightly lesser doses of the commonly used sedatives without any episodes of desaturation, snoring or exacerbation of pulmonary hypertension. Many more trials are required before we can conclusively say that intraoperative BiPAP allows us to safely sedate OSA patients but we hope that our case report draws light on this possibility. Planning ahead and having a BiPAP machine available inside the operating may allow us to use sedatives in these patients to keep them comfortable under regional anaesthesia. PMID:26023625

  17. Microarray analysis of Arabidopsis under gold exposure to identify putative genes involved in the synthesis of gold nanoparticles (AuNPs).

    PubMed

    Shukla, Devesh; Krishnamurthy, Sneha; Sahi, Shivendra V

    2015-03-01

    Very little is known about the genes responsible for Au uptake, reduction and detoxification in plants, which indeed essential to understand the complex trait of AuNP biosynthesis. We designed a targeted experiment to elucidate the response of plant at transcriptional level under Au exposure, and a microarray was performed on root tissue treated with AuCl4 (-) in the absence of nutrient media to record specific gene expression signature. Here, we describe the experimental procedures and data analysis in detail to reproduce the results (available at GEO database under GSE55436) published by Shukla et al. (2014) [1] in the Frontiers in Plant Sciences. The data produced from this study provide significant information of genes which may be used to enhance the AuNP biosynthesis.

  18. Au13-nAgn clusters: a remarkably simple trend.

    PubMed

    Munoz, Francisco; Varas, Alejandro; Rogan, José; Valdivia, Juan Alejandro; Kiwi, Miguel

    2015-11-11

    The planar to three dimensional transition of Au13-nAgn clusters is investigated. To do so the low lying energy configurations for all possible concentrations (n values) are evaluated. Many thousands of possible conformations are examined. They are generated using the procedure developed by Rogan et al. in combination with the semi-empirical Gupta potential. A large fraction of these (the low lying energy ones) are minimized by means of Density Functional Theory (DFT) calculations. We employ the Tao, Perdew, Staroverov, and Scuseria (TPSS) meta-GGA functional and the Perdew, Burke and Ernzerhof (PBE) GGA functional, and compare their results. The effect of spin-orbit coupling is studied as well as the s-d hybridization. As usual in this context the results are functional-dependent. However, both functionals lead to agreement as far as trends are concerned, yielding just two relevant motifs, but their results differ quantitatively.

  19. Healthcare BI: a tool for meaningful analysis.

    PubMed

    Rohloff, Rose

    2011-05-01

    Implementing an effective business intelligence (BI) system requires organizationwide preparation and education to allow for meaningful analysis of information. Hospital executives should take steps to ensure that: Staff entering data are proficient in how the data are to be used for decision making, and integration is based on clean data from primary sources of entry. Managers have the business acumen required for effective data analysis. Decision makers understand how multidimensional BI offers new ways of analysis that represent significant improvements over historical approaches using static reporting.

  20. The biHermitian topological sigma model

    NASA Astrophysics Data System (ADS)

    Zucchini, Roberto

    2006-12-01

    BiHermitian geometry, discovered long ago by Gates, Hull and Rocek, is the most general sigma model target space geometry allowing for (2,2) world sheet supersymmetry. By using the twisting procedure proposed by Kapustin and Li, we work out the type A and B topological sigma models for a general biHermtian target space, we write down the explicit expression of the sigma model's action and BRST transformations and present a computation of the topological gauge fermion and the topological action.

  1. The influences of convection on directional solidification of eutectic Bi/MnBi

    NASA Technical Reports Server (NTRS)

    Larson, David J., Jr.

    1988-01-01

    Eutectic alloys of Bi-Mn were directionally solidified using the Bridgman-Stockbarger technique to determine the influences of gravitationally-driven thermo-solutal convection on the Bi-MnBi rod eutectic. Experiments were conducted that varied the level of convection by varying the growth parameters and growth orientation, by microgravity damping, by applied magnetic field damping, and by imposing forced convection. Peltier interface demarcation and in situ thermocouple measurements were used to monitor interface velocity and thermal gradient and to evaluate interface planarity.

  2. Superconducting, surface and interface properties of Ho(123) and Bi(2212) films on sapphire with cerium oxide buffer layers

    NASA Astrophysics Data System (ADS)

    Castro, L. F.; Suryanarayanan, R.; Das, A.; Bacca, E.; Gómez, M. E.; Lopera, W.; Prieto, P.; Kreisler, A.; Martin, J. C.

    1995-09-01

    We report on the X-ray diffraction, secondary ion mass spectrometry, and atomic force microscopy on Ho(123) and Bi(2212) films dc sputtered in pure oxygen atmosphere onto heated sapphire substrates with CeO 2 buffer layers. The films were c-axis oriented. The Ho(123) films had a T c of 88 K but had a relatively high room temperature resistivity of 400 μΩcm. The Bi(2212) films showed a broad transition and a low T c of 46 K. The data may be explained by a certain amount of Al diffusion and inhomogenous grain growth.

  3. Electron transfer at the contact between Al electrode and gold nanoparticles of polymer: Nanoparticle resistive switching devices studied by alternating current impedance spectroscopy

    SciTech Connect

    Ouyang, Jianyong

    2013-12-02

    Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO{sub 3}/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles.

  4. Phase diagram for Bi1-xCaxMnO3 (x < 0.4)

    NASA Astrophysics Data System (ADS)

    Qin, Yuhai; Tyson, Trevor; Cheong, Sang-Wook; Xu, Xiao-Nong

    2008-03-01

    The multiferroic BiMnO3 system, in which ferroelectronic and ferromagnetic orders can coexist, has attracted much research work in the past years for its potential technological applications. For the more general system Bi1-xCaxMnO3, the phase diagram for the Ca rich region (x > 0.4) has been established[1]. In order to understand the multiferroic behavior near the x=0 system, the hole-doped region (0Bi1-xCaxMnO3, by performing detailed structural (XRD and XAFS), magnetization (ZFC/FC) and electrical measurements on Bi1-xCaxMnO3 (0al, Phys. Rev. B: Condensed Matter and Materials Physics 63, 134412/1 (2001).

  5. High-precision electronic structure studies of thermoelectrics: Bi_2Te_3

    NASA Astrophysics Data System (ADS)

    Kim, Miyoung; Freeman, A. J.; Geller, C. B.

    2004-03-01

    The heavy-atom, narrow-bandgap semiconductor Bi_2Te3 is of centralcommercial importance for thermoelectric cooling. Detailed ab initio screened exchange(R. Asahi, W. Mannstadt, A.J. Freeman, Phys. Rev. B, 59), 7486 (1999) (sX-LDA) electronic structure calculations have been performed for Bi_2Te3 within the full-potential linearized augmented plane wave (FLAPW)footnote Wimmer, Krakauer, Weinert, Freeman, Phys. Rev. B 24, 864(1981) method, accounting for spin-orbit coupling self-consistently. An indirect bandgap of 0.155 eV is found for a conduction band (CB) minimum on the mirror plane containing the trigonal and bisectric axes, thus confirming the experimental(H. Köhler, Phys. Status. Solidi, 73), 95 (1976); 74, 591 (1976) and earlier theoretical(S. Youn, A.J. Freeman, Phys. Rev. B, 63), 085112 (2001) observations of sixfold-degenerate CB and VB extrema in doped Bi_2Te_3. The predicted sX-LDA bandgap value is <5% of the zero temperature-extrapolated experimental value(B.M. Golts'man, et.al., Thermoelectric Semiconductor Materials Based on Bi_2Te_3, English trans., US Nat. Tech. Info Center (1973).) (0.162 eV). These values compare with a predicted LDA bandgap^3 (on the mirror plane) of 0.045 eV. The carrier density dependence of the effective mass tensor and the Seebeck coefficient are explored using our accurate quasiparticle band structure.

  6. Au nanoparticles films used in biological sensing

    NASA Astrophysics Data System (ADS)

    Rosales Pérez, M.; Delgado Macuil, R.; Rojas López, M.; Gayou, V. L.; Sánchez Ramírez, J. F.

    2009-05-01

    Lactobacillus para paracasei are used commonly as functional food and probiotic substances. In this work Au nanoparticles self-assembled films were used for Lactobacillus para paracasei determination at five different concentrations. Functionalized substrates were immersed in a colloidal solution for one and a half hour at room temperature and dried at room temperature during four hours. After that, drops of Lactobacillus para paracasei in aqueous solution were put into the Au nanoparticles film and let dry at room temperature for another two hours. Infrared spectroscopy in attenuated total reflectance sampling mode was used to observe generation peaks due to substrate silanization, enhancement of Si-O band intensity due to the Au colloids added to silanized substrate and also to observe the enhancement of Lactobacillus para paracasei infrared intensity of the characteristic frequencies at 1650, 1534 and 1450 cm-1 due to surface enhancement infrared absorption.

  7. Engineering interface-type resistive switching in BiFeO3 thin film switches by Ti implantation of bottom electrodes.

    PubMed

    You, Tiangui; Ou, Xin; Niu, Gang; Bärwolf, Florian; Li, Guodong; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Jia, Qi; Yu, Wenjie; Wang, Xi; Schmidt, Oliver G; Schmidt, Heidemarie

    2015-12-22

    BiFeO3 based MIM structures with Ti-implanted Pt bottom electrodes and Au top electrodes have been fabricated on Sapphire substrates. The resulting metal-insulator-metal (MIM) structures show bipolar resistive switching without an electroforming process. It is evidenced that during the BiFeO3 thin film growth Ti diffuses into the BiFeO3 layer. The diffused Ti effectively traps and releases oxygen vacancies and consequently stabilizes the resistive switching in BiFeO3 MIM structures. Therefore, using Ti implantation of the bottom electrode, the retention performance can be greatly improved with increasing Ti fluence. For the used raster-scanned Ti implantation the lateral Ti distribution is not homogeneous enough and endurance slightly degrades with Ti fluence. The local resistive switching investigated by current sensing atomic force microscopy suggests the capability of down-scaling the resistive switching cell to one BiFeO3 grain size by local Ti implantation of the bottom electrode.

  8. Engineering interface-type resistive switching in BiFeO3 thin film switches by Ti implantation of bottom electrodes

    PubMed Central

    You, Tiangui; Ou, Xin; Niu, Gang; Bärwolf, Florian; Li, Guodong; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Jia, Qi; Yu, Wenjie; Wang, Xi; Schmidt, Oliver G.; Schmidt, Heidemarie

    2015-01-01

    BiFeO3 based MIM structures with Ti-implanted Pt bottom electrodes and Au top electrodes have been fabricated on Sapphire substrates. The resulting metal-insulator-metal (MIM) structures show bipolar resistive switching without an electroforming process. It is evidenced that during the BiFeO3 thin film growth Ti diffuses into the BiFeO3 layer. The diffused Ti effectively traps and releases oxygen vacancies and consequently stabilizes the resistive switching in BiFeO3 MIM structures. Therefore, using Ti implantation of the bottom electrode, the retention performance can be greatly improved with increasing Ti fluence. For the used raster-scanned Ti implantation the lateral Ti distribution is not homogeneous enough and endurance slightly degrades with Ti fluence. The local resistive switching investigated by current sensing atomic force microscopy suggests the capability of down-scaling the resistive switching cell to one BiFeO3 grain size by local Ti implantation of the bottom electrode. PMID:26692104

  9. Characterization of a Novel Apoptosis Regulator BI-1

    DTIC Science & Technology

    2000-07-01

    BI-l is an important cell death regulator that protects cells against Bax-induced cell death . It is expressed in all four prostate cancer lines and... cell death . I have also mapped important BI-l domains essential for its function. These provide the basis for understanding the mechanism through which BI-l regulates apoptosis.

  10. Factors Influencing BI Data Collection Strategies: An Empirical Investigation

    ERIC Educational Resources Information Center

    Ramakrishnan, Thiagarajan

    2010-01-01

    The purpose of this dissertation is to examine the external factors that influence an organizations' business intelligence (BI) data collection strategy when mediated by BI attributes. In this dissertation, data warehousing strategies are used as the basis on which to frame the exploration of BI data collection strategies. The attributes include…

  11. Au-Ag@Au Hollow Nanostructure with Enhanced Chemical Stability and Improved Photothermal Transduction Efficiency for Cancer Treatment.

    PubMed

    Jiang, Tongtong; Song, Jiangluqi; Zhang, Wenting; Wang, Hao; Li, Xiaodong; Xia, Ruixiang; Zhu, Lixin; Xu, Xiaoliang

    2015-10-07

    Despite the fact that Au-Ag hollow nanoparticles (HNPs) have gained much attention as ablation agents for photothermal therapy, the instability of the Ag element limits their applications. Herein, excess Au atoms were deposited on the surface of a Au-Ag HNP by improving the reduction power of l-ascorbic acid (AA) and thereby preventing the reaction between HAuCl4 and the Ag element in the Au-Ag alloy nanostructure. Significantly, the obtained Au-Ag@Au HNPs show excellent chemical stability in an oxidative environment, together with remarkable increase in extinction peak intensity and obvious narrowing in peak width. Moreover, finite-difference time-domain (FDTD) was used to simulate the optical properties and electric field distribution of HNPs. The calculated results show that the proportion of absorption cross section in total extinction cross section increases with the improvement of Au content in HNP. As predicted by the theoretical calculation results, Au-Ag@Au nanocages (NCs) exhibit a photothermal transduction efficiency (η) as high as 36.5% at 808 nm, which is higher than that of Au-Ag NCs (31.2%). Irradiated by 808 nm laser at power densities of 1 W/cm(2), MCF-7 breast cancer cells incubated with PEGylated Au-Ag@Au NCs were seriously destroyed. Combined together, Au-Ag@Au HNPs with enhanced chemical stability and improved photothermal transduction efficiency show superior competitiveness as photothermal agents.

  12. The role of interfaces in the magnetoresistance of Au/Fe/Au/Fe/GaAs(001)

    SciTech Connect

    Enders, A.; Monchesky, T. L.; Myrtle, K.; Urban, R.; Heinrich, B.; Kirschner, J.; Zhang, X.-G.; Butler, W. H.

    2001-06-01

    The electron transport and magnetoresistance (MR) were investigated in high quality crystalline epitaxial Fe(001) and Au(001) films and exchange coupled Au/Fe/Au/Fe/GaAs(001) trilayer structures. Fits to the experimental data were based on the semiclassical Boltzmann equation, which incorporates the electronic properties obtained from first-principles local density functional calculations. The fits require a surprisingly high asymmetry for the spin dependent electron lifetimes in Fe, {tau}{sup {down_arrow}}/{tau}{sup {up_arrow}}=10 at room temperature. Despite the large atomic terraces at the Au/vacuum and Fe/GaAs interfaces the scattering at the outer interfaces was found to be diffuse. The origin of MR in Au/Fe/Au/Fe/GaAs(001) structures is due to electron channeling in the Au spacer layer. The measured MR is consistent with the diffusivity parameters s{sup {up_arrow}}=0.55, s{sup {down_arrow}}=0.77 at the metal{endash}metal interfaces. {copyright} 2001 American Institute of Physics.

  13. Development of bi-metallic Fe-Bi nanocomposites: synthesis and characterization.

    PubMed

    Mattei, J G; Pelletier, F; Ciuculescu, D; Lecante, P; Amiens, C; Casanove, M J

    2012-11-01

    We investigate the formation of bi-metallic particles in the Fe-Bi system, well known as totally immiscible in the bulk, using a large combination of structural and element-sensitive techniques, well-adapted to the nanoscale. The synthesis approach makes use of the kinetics of decomposition of the different precursors to achieve a controlled sequential growth of the different elements. Different ligands have also been used in order to limit the size and ensure dispersion of the synthesized particles. Our results give evidence for the presence of body-centered cubic ferromagnetic iron nanograins together with larger bismuth crystallites. Interestingly, while the iron particles remain very small, the resistance to oxidation of the Fe-Bi nanocomposites highly depends on the stabilizing ligand used in the synthesis. The presence of both metals, Fe and Bi, in a single cluster has been clearly revealed in the oxidation resistant composite synthesized using the HMDS ligand.

  14. Synthesis of ultrathin face-centered-cubic au@pt and au@pd core-shell nanoplates from hexagonal-close-packed au square sheets.

    PubMed

    Fan, Zhanxi; Zhu, Yihan; Huang, Xiao; Han, Yu; Wang, Qingxiao; Liu, Qing; Huang, Ying; Gan, Chee Lip; Zhang, Hua

    2015-05-04

    The synthesis of ultrathin face-centered-cubic (fcc) Au@Pt rhombic nanoplates is reported through the epitaxial growth of Pt on hexagonal-close-packed (hcp) Au square sheets (AuSSs). The Pt-layer growth results in a hcp-to-fcc phase transformation of the AuSSs under ambient conditions. Interestingly, the obtained fcc Au@Pt rhombic nanoplates demonstrate a unique (101)f orientation with the same atomic arrangement extending from the Au core to the Pt shell. Importantly, this method can be extended to the epitaxial growth of Pd on hcp AuSSs, resulting in the unprecedented formation of fcc Au@Pd rhombic nanoplates with (101)f orientation. Additionally, a small amount of fcc (100)f -oriented Au@Pt and Au@Pd square nanoplates are obtained with the Au@Pt and Au@Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures.

  15. Calendar of Selected Aeronautical and Space Meetings July 1991 Onwards (Calendrier des Manifestations et Spatiales (Selection) Juillet 1991 et au-dela)

    DTIC Science & Technology

    1991-07-01

    informations relatives i de futures manifestations a~rospatiales destin6es tre incluses dans la prochaine 6dition, condition que cet envoi soit fait au...Wind Tunnels 04-25 119 Part 4 Chapitre 4 Country Codes Codes des Pays AR Argentina LU Luxembourg AU Austria ME Mexico BA Bermuda MO Monaco BE Belgium NL...Microelectronics: PO Box 3255, Montgomery, AL 36109. Tel 2(5-272-3191 US ISNP Institution of Space Nuclear Power: University of New Mexico , Chemical

  16. Synthesis of chemically bonded BiOCl@Bi2WO6 microspheres with exposed (0 2 0) Bi2WO6 facets and their enhanced photocatalytic activities under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Ma, Yongchao; Chen, Zhiwei; Qu, Dan; Shi, Jinsheng

    2016-01-01

    Bi2WO6 photocatalysts has been extensively studied for its photocatalytic activity. However, few works have been conducted on hierarchical Bi2WO6 composite photocatalysts with specifically exposed facets. In this work, we report a facile method to synthesize BiOCl@Bi2WO6 hierarchical composite microspheres. Bi2WO6 nanosheets with specifically exposed (0 2 0) facet were directly formed on the surface of BiOCl precursor microspheres via a controlled anion exchange route between BiOCl and Na2WO4. The visible-light photocatalytic activity of the BiOCl@Bi2WO6 heterojunction with exposed (0 2 0) facets (denoted as BiOCl@Bi2WO6) was investigated by degradation of Rhodamine B (RhB) and ciprofloxacin (CIP) aqueous solution under visible light irradiation. The experimental results indicated that the BiOCl@Bi2WO6 composite microsphere with intimate interfacial contacts exhibited improved efficiency for RhB photodegradation in comparison with pure BiOCl and Bi2WO6. The BiOCl@Bi2WO6 composite microsphere also shows high photocatalytic activity for degradation of CIP under visible light irradiation. The enhanced photocatalytic performance of BiOCl@Bi2WO6-020 hierarchical microspheres can be ascribed to the improved visible light harvesting ability, high charge separation and transfer. This work will make significant contributions toward the exploration of novel heterostructures with high potential in photocatalytic applications.

  17. Nanoporous Au structures by dealloying Au/Ag thermal- or laser-dewetted bilayers on surfaces

    NASA Astrophysics Data System (ADS)

    Ruffino, F.; Torrisi, V.; Grillo, R.; Cacciato, G.; Zimbone, M.; Piccitto, G.; Grimaldi, M. G.

    2017-03-01

    Nanoporous Au attracts great technological interest and it is a promising candidate for optical and electrochemical sensors. In addition to nanoporous Au leafs and films, recently, interest was focused on nanoporous Au micro- and nano-structures on surfaces. In this work we report on the study of the characteristics of nanoporous Au structures produced on surfaces. We developed the following procedures to fabricate the nanoporous Au structures: we deposited thin Au/Ag bilayers on SiO2 or FTO (fluorine-doped tin oxide) substrates with thickness xAu and xAg of the Au and Ag layers; we induced the alloying and dewetting processes of the bilayers by furnace annealing processes of the bilayers deposited on SiO2 and by laser irradiations of the bilayers deposited on FTO; the alloying and dewetting processes result in the formation of AuxAgy alloy sub-micron particles being x and y tunable by xAu and xAg. These particles are dealloyed in HNO3 solution to remove the Ag atoms. We obtain, so, nanoporous sub-micron Au particles on the substrates. Analyzing the characteristics of these particles we find that: a) the size and shape of the particles depend on the nature of the dewetting process (solid-state dewetting on SiO2, molten-state dewetting on FTO); b) the porosity fraction of the particles depends on how the alloying process is reached: about 32% of porosity for the particles fabricated by the furnace annealing at 900 °C, about 45% of porosity for the particles fabricated by the laser irradiation at 0.5 J/cm2, in both cases independently on the Ag concentration in the alloy; c) After the dealloying process the mean volume of the Au particles shrinks of about 39%; d) After an annealing at 400 °C the nanoporous Au particles reprise their initial volume while the porosity fraction is reduced. Arguments to justify these behaviors are presented.

  18. SHG anisotropy in Au/Co/Au/Cu/vicinal Si(1 1 1)

    NASA Astrophysics Data System (ADS)

    Cheikh-Rouhou, W.; Sampaio, L. C.; Bartenlian, B.; Beauvillain, P.; Brun, A.; Ferré, J.; Georges, P.; Jamet, J.-P.; Mathet, V.; Stupakewicz, Andrei

    2002-02-01

    The second harmonic generation (SHG) reflectivity on magnetic multilayers is a very sensitive technique to reveal the crystallography of buried interfaces. We have used the azimuthal anisotropy of SHG to demonstrate that the vicinal character of Si(1 1 1) substrate is duplicated in the metallic multilayer Au/Co/Au/Cu. The magnetic properties of these multilayers as anisotropy and magneto-optic polar Kerr rotation were studied by linear magneto-optic effects in correlation with SHG experiments, by varying the Co and Au buffer thicknesses as well as the Cu buffer deposition condition.

  19. Time Dependent Universal Conductance Fluctuations In AuPd, Ag, And Au Wires

    NASA Astrophysics Data System (ADS)

    Trionfi, A.; Lee, S.; Natelson, D.

    2006-09-01

    Quantum transport phenomena allow experimental determinations of the phase coherence information in metals. We report quantitative comparisons of inferred coherence lengths from independent measurements of the weak localization magnetoresistance and time-dependent universal conductance fluctuations' magnetic field dependence. Strong agreement is observed in both quasi-2D and quasi-1D AuPd samples. However, quantitative agreement is not seen in quasi-1D Ag wires below 10 K and quasi-1D Au wires below 14 K. A possible explanation for this disagreement will be discussed. Attempts to produce changes in the coherence length in Au by annealing have also been made and results will be reported.

  20. Cluster observations on linear magnetic decreases in the solar wind at 1 AU

    NASA Astrophysics Data System (ADS)

    Xiao, T.; Shi, Q.; Tian, A.; Fu, S.; Pu, Z.; Zong, Q.; Sun, W.; Lucek, E. A.; Reme, H.

    2013-12-01

    Magnetic decreases (MDs) are structures observed in interplanetary space with significant decreases in the magnetic field magnitude, of which the events with no or little change in the field direction are linear magnetic decreases (LMDs). Xiao et al., (2010) have reported that the geometrical shape of LMDs observed in the solar wind at 1 AU was consistent with rotational ellipsoid, and the occurrence rate was about 3.7 LMDs/d. It was found that not only the occurrence rate but also the geometrical shape of LMDs had no significant change from 0.72 AU to 1 AU in comparison with Zhang et al., (2008)'s results, which may infer that most of LMDs observed at 1 AU were formed and fully developed before 0.72 AU. Recently, we have focused on the magnetic field and plasma (e.g. ion density and velocity) characteristics of those LMD structures observed during the period of 2001 to 2009. Compared with the average solar wind condition, it is shown that the LMDs prefer to be observed in the region with relatively lower magnetic field magnitude, higher ion density, larger plasma β (ratio of the thermal pressure to the magnetic pressure) and slower solar wind velocity. We also investigated the LMDs which located in the interplanetary coronal mass ejections (ICME) or the sheath of the ICME. It is found that the events related to ICMEs could account for more than 20% of LMDs during solar maximum. Therefore, the ICME should be an important source of the LMDs during the solar maximum. However, other mechanisms during the solar minimum may be more important, because the occurrence rate of LMDs during the solar minimum is higher than that of the solar maximum. We also calculate the propagation speed of the structures in the solar wind frame to infer the generation mechanism of these structures.