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Sample records for highly conductive undoped

  1. Normal and anti Meyer-Neldel rule in conductivity of highly crystallized undoped microcrystalline silicon films

    OpenAIRE

    Ram, Sanjay K.; Kumar, Satyendra; Cabarrocas, P. Roca i

    2007-01-01

    We have studied the electrical conductivity behavior of highly crystallized undoped hydrogenated microcrystalline silicon films having different microstructures. The dark conductivity is seen to follow Meyer Neldel rule (MNR) in some films and anti MNR in others, which has been explained on the basis of variation in the film microstructure and the corresponding changes in the effective density of states distributions. A band tail transport and statistical shift of Fermi level are used to expl...

  2. Easy growth of undoped and doped tungsten oxide nanowires with high purity and orientation

    Science.gov (United States)

    Liu, Kun; Foord, David T.; Scipioni, Lawrence

    2005-01-01

    An economic method is presented to grow undoped/doped tungsten oxide nanowires with high purity and erect orientation, simply by heating a tungsten filament in a vacuum chamber with some room air leakage. Tungsten oxide nanowires were studied using scanning electron microscopy (SEM), energy dispersion x-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Wires are found standing straight and clean on the filament, {\\sim }30 nm in diameter and up to a few tens of micrometres long. The composition along the wire is uniform for all elements including dopants.

  3. Control of conductivity type in undoped ZnO thin films grown by metalorganic vapor phase epitaxy

    Science.gov (United States)

    Ma, Y.; Du, G. T.; Yang, S. R.; Li, Z. T.; Zhao, B. J.; Yang, X. T.; Yang, T. P.; Zhang, Y. T.; Liu, D. L.

    2004-06-01

    The properties of the ZnO thin films prepared by metalorganic vapor phase epitaxy under various oxygen partial pressures were thoroughly studied. It was found that the conduction type in undoped ZnO epilayers could be controlled by adjusting the family VI precursor, oxygen partial pressure during growth. The films were characteristic of n-type conductivity under oxygen partial pressure lower than 45 Pa. With the increase of oxygen content, the crystallinity of the ZnO thin films was degraded to polycrystalline with additional (10-12) orientation and the intrinsic p-type ZnO was produced as the oxygen partial pressure was larger than 55 Pa. The hole concentration and mobility could reach to 1.59×1016 cm-3 and 9.23 cm2 V-1 s-1, and the resistivity was 42.7 Ω cm. The near-band-edge emission and the deep level emission in photoluminescence (PL) spectra at room temperature were influenced strongly by the oxygen partial pressure. Temperature-dependent PL spectra in n-type ZnO films showed a dominant neutral-donor bound exciton emission, while p-ZnO was dominated by neutral-acceptor bound exciton emission. Both peaks increased in intensity with the decrease of the temperature and shifted to the short-wavelength side. The band that originated from zinc vacancies emerged at a temperature lower than 155 K only in the p-type films. The origin of intrinsic p-type conductivity in ZnO thin films might be related to zinc vacancy.

  4. Conductive tracks of 30-MeV C{sub 60} clusters in doped and undoped tetrahedral amorphous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Krauser, J., E-mail: jkrauser@hs-harz.de [Harz University of Applied Sciences, 38855 Wernigerode (Germany); Gehrke, H.-G.; Hofsäss, H. [II. Institute of Physics, University of Göttingen, 37077 Göttingen (Germany); Trautmann, C. [Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt (Germany); Technische Universität Darmstadt, 64287 Darmstadt (Germany); Weidinger, A. [Helmholtz-Zentrum Berlin GmbH, 14109 Berlin (Germany)

    2013-07-15

    In insulating tetrahedral amorphous carbon (ta-C), the irradiation with 30-MeV C{sub 60} cluster ions leads to the formation of well conducting tracks. While electrical currents through individual tracks produced with monoatomic projectiles (e.g. Au or U) often exhibit rather large track to track fluctuations, C{sub 60} clusters are shown to generate highly conducting tracks with very narrow current distributions. Additionally, all recorded current–voltage curves show linear characteristics. These findings are attributed to the large specific energy loss dE/dx of the 30-MeV C{sub 60} clusters. We also investigated C{sub 60} tracks in ta-C films which were slightly doped with B, N or Fe during film growth. Doping apparently increases the ion track conductivity. However, at the same time the insulating characteristics of the pristine ta-C film can be reduced. The present C{sub 60} results are compared with data from earlier experiments with monoatomic heavy ion beams. The investigations were performed by means of atomic force microscopy including temperature dependent conductivity measurements of single ion tracks.

  5. Deep levels induced by high fluence proton irradiation in undoped GaAs diodes

    Energy Technology Data Exchange (ETDEWEB)

    Castaldini, A.; Cavallini, A.; Polenta, L. [Univ. of Bologna (Italy); Canali, C.; Nava, F. [Univ. of Modena (Italy); Ferrini, R.; Galli, M. [Univ. of Pavia (Italy). Dipt. di Fisica

    1998-12-31

    Semi-insulating liquid encapsulated Czochralski grown GaAs has been investigated after irradiation at high fluences of high-energy protons. Electron beam induced current observations of scanning electron microscopy evidenced a radiation stimulated ordering. An analysis has been carried out of the deep levels associated with defects as a function of the irradiation fluence, using complementary current transient spectroscopies. By increasing the irradiation fluence, the concentration of the native traps at 0.37 eV together with that of the EL2 defect significantly increases and, at the same time, two new electron traps at 0.15 eV and 0.18 eV arise and quickly increase in density.

  6. Highly Thermal Conductive Nanocomposites

    Science.gov (United States)

    Sun, Ya-Ping (Inventor); Connell, John W. (Inventor); Veca, Lucia Monica (Inventor)

    2017-01-01

    Disclosed are methods for forming carbon-based fillers as may be utilized in forming highly thermal conductive nanocomposite materials. Formation methods include treatment of an expanded graphite with an alcohol/water mixture followed by further exfoliation of the graphite to form extremely thin carbon nanosheets that are on the order of between about 2 and about 10 nanometers in thickness. Disclosed carbon nanosheets can be functionalized and/or can be incorporated in nanocomposites with extremely high thermal conductivities. Disclosed methods and materials can prove highly valuable in many technological applications including, for instance, in formation of heat management materials for protective clothing and as may be useful in space exploration or in others that require efficient yet light-weight and flexible thermal management solutions.

  7. High Thermal Conductivity Materials

    CERN Document Server

    Shinde, Subhash L

    2006-01-01

    Thermal management has become a ‘hot’ field in recent years due to a need to obtain high performance levels in many devices used in such diverse areas as space science, mainframe and desktop computers, optoelectronics and even Formula One racing cars! Thermal solutions require not just taking care of very high thermal flux, but also ‘hot spots’, where the flux densities can exceed 200 W/cm2. High thermal conductivity materials play an important role in addressing thermal management issues. This volume provides readers a basic understanding of the thermal conduction mechanisms in these materials and discusses how the thermal conductivity may be related to their crystal structures as well as microstructures developed as a result of their processing history. The techniques for accurate measurement of these properties on large as well as small scales have been reviewed. Detailed information on the thermal conductivity of diverse materials including aluminum nitride (AlN), silicon carbide (SiC), diamond, a...

  8. Post-irradiation examinations and high-temperature tests on undoped large-grain UO{sub 2} discs

    Energy Technology Data Exchange (ETDEWEB)

    Noirot, J., E-mail: jean.noirot@cea.fr [CEA, DEN, DEC, Cadarache, F-13108 St. Paul Lez Durance (France); Pontillon, Y. [CEA, DEN, DEC, Cadarache, F-13108 St. Paul Lez Durance (France); Yagnik, S. [EPRI, P.O. Box 10412, Palo Alto, CA 94303-0813 (United States); Turnbull, J.A. [Independent Consultant (United Kingdom)

    2015-07-15

    Within the Nuclear Fuel Industry Research (NFIR) programme, several fuel variants –in the form of thin circular discs – were irradiated in the Halden Boiling Water Reactor (HBWR) at burn-ups up to ∼100 GWd/t{sub HM}. The design of the fuel assembly was similar to that used in other HBWR programmes: the assembly contained several rods with fuel discs sandwiched between Mo discs, which limited temperature differences within each fuel disc. One such variant was made of large-grain UO{sub 2} discs (3D grain size = ∼45 μm) which were subjected to three burn-ups: 42, 72 and 96 GWd/t{sub HM}. Detailed characterizations of some of these irradiated large-grain UO{sub 2} discs were performed in the CEA Cadarache LECA-STAR hot laboratory. The techniques used included electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). Comparisons were then carried out with more standard grain size UO{sub 2} discs irradiated under the same conditions. Examination of the high burn-up large-grain UO{sub 2} discs revealed the limited formation of a high burn-up structure (HBS) when compared with the standard-grain UO{sub 2} discs at similar burn-up. High burn-up discs were submitted to temperature transients up to 1200 °C in the heating test device called Merarg at a relatively low temperature ramp rate (0.2 °C/s). In addition to the total gas release during these tests, the release peaks throughout the temperature ramp were monitored. Tests at 1600 °C were also conducted on the 42 GWd/t{sub HM} discs. The fuels were then characterized with the same microanalysis techniques as those used before the tests, to investigate the effects of these tests on the fuel’s microstructure and on the fission gas behaviour. This paper outlines the high resistance of this fuel to gas precipitation at high temperature and to HBS formation at high burn-up. It also shows the similarity of the positions, within the grains, where HBS forms

  9. Effect of the undoped BaSnO3 space layer on the high mobility LaInO3/Ba1-xLaxSnO3 polar interface

    Science.gov (United States)

    Shin, Juyeon; Park, Chulkwon; Kim, Young Mo; Kim, Youjung; Char, Kookrin

    We have recently reported on the sheet conductance enhancement at the interface between two band insulators: LaInO3 (LIO) and BaSnO3 (BSO). The advantages of the two-dimensional electron gas-like (2DEG) state at the LIO/Ba1-xLaxSnO3 (BLSO) polar interface are its stability, the controllability of the local carrier concentration, and the high electron mobility of BLSO. The origin of enhanced conductance at the interface is still under investigation, but the doping level of BSO is a critical parameter for the polar charge contribution. We have investigated a new structure using an undoped BSO space layer at the LIO/BLSO interface. On one hand, this new structure will improve the mobility of the LIO/BLSO structure by reducing La impurity scattering. On the other hand, through this new structure we can answer the issues related with La diffusion at the LIO/BLSO polar interface and trace the origin of the 2DEG-like charge. This new modified structure of the LIO/BSO polar interface looks promising for higher electron mobility devices.

  10. High frequency conductivity of hot electrons in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Amekpewu, M., E-mail: mamek219@gmail.com [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, S.Y. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Musah, R. [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, N.G. [Department of Mathematics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Abukari, S.S.; Dompreh, K.A. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana)

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac–dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons’ source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  11. High-Thermal-Conductivity Fabrics

    Science.gov (United States)

    Chibante, L. P. Felipe

    2012-01-01

    Heat management with common textiles such as nylon and spandex is hindered by the poor thermal conductivity from the skin surface to cooling surfaces. This innovation showed marked improvement in thermal conductivity of the individual fibers and tubing, as well as components assembled from them. The problem is centered on improving the heat removal of the liquid-cooled ventilation garments (LCVGs) used by astronauts. The current design uses an extensive network of water-cooling tubes that introduces bulkiness and discomfort, and increases fatigue. Range of motion and ease of movement are affected as well. The current technology is the same as developed during the Apollo program of the 1960s. Tubing material is hand-threaded through a spandex/nylon mesh layer, in a series of loops throughout the torso and limbs such that there is close, form-fitting contact with the user. Usually, there is a nylon liner layer to improve comfort. Circulating water is chilled by an external heat exchanger (sublimator). The purpose of this innovation is to produce new LCVG components with improved thermal conductivity. This was addressed using nanocomposite engineering incorporating high-thermalconductivity nanoscale fillers in the fabric and tubing components. Specifically, carbon nanotubes were added using normal processing methods such as thermoplastic melt mixing (compounding twin screw extruder) and downstream processing (fiber spinning, tubing extrusion). Fibers were produced as yarns and woven into fabric cloths. The application of isotropic nanofillers can be modeled using a modified Nielsen Model for conductive fillers in a matrix based on Einstein s viscosity model. This is a drop-in technology with no additional equipment needed. The loading is limited by the ability to maintain adequate dispersion. Undispersed materials will plug filtering screens in processing equipment. Generally, the viscosity increases were acceptable, and allowed the filled polymers to still be

  12. Optical transmission damage of undoped and Ce doped Y{sub 3}Al{sub 5}O{sub 12} scintillation crystals under 24 GeV protons high fluence

    Energy Technology Data Exchange (ETDEWEB)

    Auffray, E. [CERN, Geneva (Switzerland); Fedorov, A. [Research Institute for Nuclear Problems, Minsk (Belarus); Dormenev, V. [Justus Liebig University, Giessen (Germany); Houžvička, J. [CRYTUR, spol. s r.o., Palackého 175, 51101 Turnov (Czech Republic); Korjik, M., E-mail: Mikhail.Korjik@cern.ch [Research Institute for Nuclear Problems, Minsk (Belarus); Lucchini, M.T. [CERN, Geneva (Switzerland); Mechinsky, V. [Research Institute for Nuclear Problems, Minsk (Belarus); Ochesanu, S. [CRYTUR, spol. s r.o., Palackého 175, 51101 Turnov (Czech Republic)

    2017-06-01

    This report presents results on the optical transmission damage of undoped and Ce doped Y{sub 3}Al{sub 5}O{sub 12} scintillation crystals under high fluence of 24 GeV protons. We observed that, similarly to other middle heavy scintillators, it possesses the unique radiation hardness at fluence values as high as 5×10{sup 14} p/cm{sup 2} and it is thus promising for the application in the detectors at High Luminosity LHC. The crystalline structure of the garnet scintillator allows to control and further optimize its scintillation parameters, such as scintillation decay time and emission wavelength, and shows a limited set of the radioisotopes after the irradiation with protons.

  13. Calibration-free electrical conductivity measurements for highly conductive slags

    Energy Technology Data Exchange (ETDEWEB)

    MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

    2000-05-01

    This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

  14. High frequency conductivity in carbon nanotubes

    Directory of Open Access Journals (Sweden)

    S. S. Abukari

    2012-12-01

    Full Text Available We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.

  15. Performance analysis of undoped cylindrical gate all around (GAA) MOSFET at subthreshold regime

    Science.gov (United States)

    Jena, B.; Pradhan, K. P.; Dash, S.; Mishra, G. P.; Sahu, P. K.; Mohapatra, S. K.

    2015-09-01

    In this work the sensitivity of process parameters like channel length (L), channel thickness (tSi), and gate work function (φM) on various performance metrics of an undoped cylindrical gate all around (GAA) metal-oxide-semiconductor field effect transistor (MOSFET) are systematically analyzed. Undoped GAA MOSFET is a radical invention as it introduces a new direction for transistor scaling. In conventional MOSFET, generally the channel doping concentration is very high to provide high on-state current, but in contrary it causes random dopant fluctuation and threshold voltage variation. So, the undoped nature of GAA MOSFET solves the above complications. Hence, we have analyzed the electrical characteristics as well as the analog/RF performances of undoped GAA MOSFET through Sentaurus device simulator.

  16. Characterization and Conduction Mechanism of Highly Conductive Vanadate Glass

    Directory of Open Access Journals (Sweden)

    Tetsuaki Nishida

    2015-12-01

    Full Text Available This paper reviews recent studies of highly conductive barium iron vanadate glass with a composition of 20 BaO ∙ 10 Fe2O3 ∙ 70 V2O5 (in mol %. Isothermal annealing of the vanadate glass for several ten minutes at a given temperature, higher than glass transition temperature or crystallization temperature, caused an increase in σ. Substitution of CuI (3d10, ZnII (3d10 and CuII (3d9 for FeIII (3d5 was investigated to elucidate the effect of electron configuration on the conductivity (σ. A marked decrease in the activation energy of conduction (Ea was also observed after the annealing. Values of Ea were correlated to the energy gap between the donor level and the conduction band (CB in the n-type semiconductor model. Isothermal annealing of ZnII-substituted vanadate glass (20 BaO ∙ 5 ZnO ∙ 5 Fe2O3 ∙ 70 V2O5 at 450 °C for 30 min showed an increase in σ from 2.5 × 10–6 to 2.1 × 10–1 S cm–1, which was one order of magnitude larger than that of non-substituted vanadate glass (3.4 × 10–2 S cm–1. Under the same annealing condition, σ’s of 2.0 × 10–1 and 3.2 × 10–1 S cm–1 were observed for 20 BaO ∙ 5 Cu2O ∙ 5 Fe2O3 ∙ 70 V2O5 and 20 BaO ∙ 5 CuO ∙ 5 Fe2O3 ∙ 70 V2O5 glasses, respectively. These results demonstrate an increase in the carrier (electron density in the CB, primarily composed of anti-bonding 4s-orbitals.

  17. Nanostructuring of Undoped ZnSb by Cryo-Milling

    Science.gov (United States)

    Song, X.; Valset, K.; Graff, J. S.; Thøgersen, A.; Gunnæs, A. E.; Luxsacumar, S.; Løvvik, O. M.; Snyder, G. J.; Finstad, T. G.

    2015-08-01

    We report the preparation of nanosized ZnSb powder by cryo-milling. The effect of cryo-milling then hot-pressing of undoped ZnSb was investigated and compared with that of room temperature ball-milling and hot-pressing under different temperature conditions. ZnSb is a semiconductor with favorable thermoelectric properties when doped. We used undoped ZnSb to study the effect of nanostructuring on lattice thermal conductivity, and with little contribution at room temperature from electronic thermal conductivity. Grain growth was observed to occur during hot-pressing, as observed by transmission electron microscopy and x-ray diffraction. The thermal conductivity was lower for cryo-milled samples than for room-temperature ball-milled samples. The thermal conductivity also depended on hot-pressing conditions. The thermal conductivity could be varied by a factor of two by adjusting the process conditions and could be less than a third that of single-crystal ZnSb.

  18. Thermal conductivity of iron at high pressures

    Science.gov (United States)

    Suehiro, S.; Ohta, K.; Yagi, T.; Hirose, K.

    2016-12-01

    Earth generates and preserves a dipole magnetic field by self-sustained dynamo action in its liquid outer core for geologic timescale. Secular cooling of the core induces growth of the solid inner core that contributes additional buoyant source for the core convection. The electrical and thermal conductivities of core are fundamental physical parameters for knowing the dynamics inside the Earth. Direct measurements of the electrical and thermal conductivities of iron (Fe) at the Earth's core conditions have been recently reported (Konôpková et al., 2016; Ohta et al., 2016). Measurements of Fe thermal conductivity at the core conditions suggested thermal conductivity of the outer core was 18-32 W/m/K (Konôpková et al., 2016). On the other hand, Ohta et al. (2016) experimentally determined electrical conductivity of Fe at the core conditions, and estimated the core conductivity to be 75-117 W/m/K from obtained electrical conductivity and Wiedemann-Franz relation (κ = σLT; κ: thermal conductivity, σ: electrical conductivity, L: Lorenz number, T: absolute temperature) with ideal Lorenz number. Such large discrepancy in the estimated core thermal conductivity throw doubt on the validity of the Wiedemann-Franz relation at extremely high P-T conditions. In this study, we performed thermal conductivity measurements on Fe up to 130 GPa at room temperature in a diamond anvil cell using the pulsed light heating thermoreflectance technique (Ohta et al., 2012). The obtained thermal conductivity of Fe is in good agreement with calculated thermal conductivity via high-P/room-T Fe electrical conductivity and the Wiedemann-Franz law with constant Lorenz number up to around 50 GPa. However, the obtained thermal conductivity deviated downward from the calculated thermal conductivity profile above 50 GPa. Our results suggest pressure-dependent Lorenz number of Fe,which could be due to pressure- induced electronic topological transition in hcp Fe (Glazyrin et al., 2013). Kon

  19. Electrical Conductivity of Micas at High Temperatures

    Science.gov (United States)

    Watanabe, T.

    2008-12-01

    Electrical conductivity, along with seismic velocity, gives us clues to infer constituent materials and temperatures in the Earth's interior. Dry rocks have been considered to be electrically insulating at crustal temperatures. Observed high conductivity has been ascribed to the existence of fluids. However, Fuji-ta et al. (2007) recently reported that a dry gneiss shows relatively high conductivity (10-4-10-3 S/m) at the temperature of 300-400°C, and that it is strongly anisotropic in conductivity. They suggested that the alignment of biotite grains governs conductivity of the gneiss sample. Electrical properties of rock forming minerals are still poorly understood. We thus have measured electrical properties of biotite single crystals up to 700°C. In order to get a good understanding of conduction mechanisms, measurements have been also made on phlogopite and muscovite, which are common micas with similar crystallographic structures. Thin plates parallel to cleavages (thickness~0.1mm) were prepared from mica single crystals. Electrical impedance was measured by 2-electrode method. The specimen was kept in nitrogen or argon atmosphere. The conductivity measured parallel to cleavages is higher than that measured perpendicular to cleavages by 3-4 orders of magnitude. However, no significant difference in the activation energy of conductivity was observed between two directions. The activation energy of conductivity is ~50 kJ/mol for biotite and ~100 kJ/mol for phlogopite and muscovite. The conductivity of biotite is higher than those of phlogopite and muscovite by several orders of magnitude at the same temperature. The conductivity of biotite parallel to cleavages is ~10-1 S/m at 400°C. The conductivity of biotite increases irreversibly by heating. The irreversible change was not significant below 450°C. Remarkable increase is observed at the temperature of 450-550°C. No significant change was observed in the second heating. Such an increase in conductivity

  20. Undoped strained germanium quantum wells towards spin qubits

    Science.gov (United States)

    Scappucci, Giordano; Sammak, Amir; Yeoh, Lareine; Sabbagh, Diego; Conesa-Boj, Sonia; Kolling, Sebastian; Zaumseil, Peter; Capellini, Giovanni

    Germanium is emerging as a promising material to implement spin qubits because of the key properties of high carrier mobility, strong spin-orbit coupling, long spin coherence times and compatibility with silicon technology. We report the deposition of undoped strained Ge/SiGe quantum wells of high structural quality in a reduced pressure chemical vapor deposition tool. Structural analysis of the Ge/SiGe heterostructures confirm sharp interfaces, full relaxation of the virtual substrate, and coherent deposition of the strained quantum well. Furthermore, we will discuss architectures towards the development of CMOS compatible spin qubits in laterally defined Ge quantum dots. .

  1. Ion transport in Au doped/undoped KDP crystals with KI/NaI as ...

    Indian Academy of Sciences (India)

    Unknown

    meter (Hewlett–Packard) was used to measure capaci- tance (C) of the sample as a function of frequency. 2.2 Conductivity measurement. Both undoped and Au+ doped crystals were subjected to γ-irradiation using 60Co source to a dosage 5 Mrads. The conductivity measurements were carried out for both irradiated and ...

  2. Measuring nanowire thermal conductivity at high temperatures

    Science.gov (United States)

    Wang, Xiaomeng; Yang, Juekuan; Xiong, Yucheng; Huang, Baoling; Xu, Terry T.; Li, Deyu; Xu, Dongyan

    2018-02-01

    This work extends the micro-thermal-bridge method for thermal conductivity measurements of nanowires to high temperatures. The thermal-bridge method, based on a microfabricated device with two side-by-side suspended membranes with integrated platinum resistance heaters/thermometers, has been used to determine thermal conductivity of various nanowires/nanotubes/nanoribbons at relatively low temperatures. However, to date, thermal conductivity characterization of nanowires at temperatures above 600 K has seldom been reported presumably due to several technical difficulties including the instability of the microfabricated thermometers, radiation heat loss, and the effect of the background conductance on the measurement. Here we report on our attempt to address the aforementioned challenges and demonstrate thermal conductivity measurement of boron nanoribbons up to 740 K. To eliminate high temperature resistance instability, the device is first annealed at 1023 K for 5 min in an argon atmosphere. Two radiation shields are installed in the measurement chamber to minimize radiation heat loss from the measurement device to the surroundings; and the temperature of the device at each set point is calibrated by an additional thermocouple directly mounted on the chip carrier. The effect of the background conductance is eliminated by adopting a differential measurement scheme. With all these modifications, we successfully measured the thermal conductivity of boron nanoribbons over a wide temperature range from 27 K to 740 K. The measured thermal conductivity increases monotonically with temperature and reaches a plateau of ~2.5 W m‑1 K‑1 at approximately 400 K, with no clear signature of Umklapp scattering observed in the whole measurement temperature range.

  3. High Conductive CFRP Sandwich Technologies for Platforms

    Science.gov (United States)

    Ihle, Alexander; Hartmann, D.; Wurfl, T.; Reichmann, O.; Liedtke, V.; Tschepe, C.; Berrill, M.

    2014-06-01

    A general trend in the design of Satellites structures is to use more and more extensively CFRP materials. These materials are lighter, stiffer and have a better dimensional stability than their metallic counterparts. However, the usually used CFRP materials have a low thermal conductivity, which makes the use of these materials difficult if not impossible for all parts that must conduct and distribute heat.For such applications, aluminium skin/core panels are often used for e.g. radiative structure panels. The goal of the study was to design, manufacture and test a CFRP spacecraft sandwich panel structure (based on a shear web supporting dissipative equipments) using high conductive CFRP in order to substitute common aluminium panels.

  4. Highly stretchable electrospun conducting polymer nanofibers

    Science.gov (United States)

    Boubée de Gramont, Fanny; Zhang, Shiming; Tomasello, Gaia; Kumar, Prajwal; Sarkissian, Andranik; Cicoira, Fabio

    2017-08-01

    Biomedical electronics research targets both wearable and biocompatible electronic devices easily adaptable to specific functions. To achieve such goals, stretchable organic electronic materials are some of the most intriguing candidates. Herein, we develop highly stretchable poly-(3,4-ethylenedioxythiphene) (PEDOT) doped with tosylate (PEDOT:Tos) nanofibers. A two-step process involving electrospinning of a carrier polymer (with oxidant) and vapor phase polymerization was used to produce fibers on a polydimethylsiloxane substrate. The fibers can be stretched up to 140% of the initial length maintaining high conductivity.

  5. Highly conductive, printable pastes from capillary suspensions

    Science.gov (United States)

    Schneider, Monica; Koos, Erin; Willenbacher, Norbert

    2016-08-01

    We have used the capillary suspension phenomenon to design conductive pastes for printed electronic applications, such as front side metallization of solar cells, without non-volatile, organic additives that often deteriorate electrical properties. Adding a small amount of a second, immiscible fluid to a suspension creates a network of liquid bridges between the particles. This capillary force-controlled microstructure allows for tuning the flow behavior in a wide range. Yield stress and low-shear viscosity can be adjusted such that long-term stability is provided by inhibiting sedimentation, and, even more importantly, narrow line widths and high aspect ratios are accessible. These ternary mixtures, called capillary suspensions, exhibit a strong degree of shear thinning that allows for conventional coating or printing equipment to be used. Finally, the secondary fluid, beneficial for stability and processing of the wet paste, completely evaporates during drying and sintering. Thus, we obtained high purity silver and nickel layers with a conductivity two times greater than could be obtained with state-of-the-art, commercial materials. This revolutionary concept can be easily applied to other systems using inorganic or even organic conductive particles and represents a fundamental paradigm change to the formulation of pastes for printed electronics.

  6. Highly Conductive Multifunctional Graphene Polycarbonate Nanocomposites

    Science.gov (United States)

    Yoonessi, Mitra; Gaier, James R.

    2010-01-01

    Graphene nanosheet bisphenol A polycarbonate nanocomposites (0.027 2.2 vol %) prepared by both emulsion mixing and solution blending methods, followed by compression molding at 287 C, exhibited dc electrical percolation threshold of approx.0.14 and approx.0.38 vol %, respectively. The conductivities of 2.2 vol % graphene nanocomposites were 0.512 and 0.226 S/cm for emulsion and solution mixing. The 1.1 and 2.2 vol % graphene nanocomposites exhibited frequency-independent behavior. Inherent conductivity, extremely high aspect ratio, and nanostructure directed assembly of the graphene using PC nanospheres are the main factors for excellent electrical properties of the nanocomposites. Dynamic tensile moduli of nanocomposites increased with increasing graphene in the nanocomposite. The glass transition temperatures were decreased with increasing graphene for the emulsion series. High-resolution electron microscopy (HR-TEM) and small-angle neutron scattering (SANS) showed isolated graphene with no connectivity path for insulating nanocomposites and connected nanoparticles for the conductive nanocomposites. A stacked disk model was used to obtain the average particle radius, average number of graphene layers per stack, and stack spacing by simulation of the experimental SANS data. Morphology studies indicated the presence of well-dispersed graphene and small graphene stacking with infusion of polycarbonate within the stacks.

  7. Laser patterning of highly conductive flexible circuits

    Science.gov (United States)

    Ji, Seok Young; Muhammed Ajmal, C.; Kim, Taehun; Chang, Won Seok; Baik, Seunghyun

    2017-04-01

    There has been considerable attention paid to highly conductive flexible adhesive (CFA) materials as electrodes and interconnectors for future flexible electronic devices. However, the patterning technology still needs to be developed to construct micro-scale electrodes and circuits. Here we developed the selective laser sintering technology where the pattering and curing were accomplished simultaneously without making additional masks. The CFA was composed of micro-scale Ag flakes, multiwalled carbon nanotubes decorated with Ag nanoparticles, and a nitrile-butadiene-rubber matrix. The Teflon-coated polyethylene terephthalate film was used as a flexible substrate. The width of lines (50-500 μm) and circuit patterns were controlled by the programmable scanning of a focused laser beam (power = 50 mW, scanning speed = 1 mm s-1). The laser irradiation removed solvent and induced effective coalescence among fillers providing a conductivity as high as 25 012 S cm-1. The conductivity stability was excellent under the ambient air and humid environments. The normalized resistance change of the pattern was smaller than 1.2 at the bending radius of 5 mm. The cyclability and adhesion of the laser-sintered line pattern on the substrate was excellent. A flexible circuit was fabricated sequentially for operating light emitting diodes during the bending motion, demonstrating excellent feasibility for practical applications in flexible electronics.

  8. Solvothermal synthesis and thermoelectric property of undoped and indium doped lead telluride nanoparticles

    Science.gov (United States)

    Kadel, Kamal; Li, Wenzhi

    2013-03-01

    Undoped and indium (In) doped lead telluride (PbTe) nanostructures were synthesized via solvothermal/hydrothermal route. The crystallinity of the as-prepared un-doped and In-doped PbTe sample were examined by X-ray diffraction (XRD) which indicated the formation of face centered single phase cubic PbTe. Lattice constant calculation from XRD pattern revealed the formation of un-doped and In-doped PbTe crystals with almost similar size. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) examinations indicated that undoped and In-doped PbTe nanostructures were mostly cubically shaped and highly crystalline. The effect of the synthesis temperature on the structure and morphology of undoped PbTe was also investigated; it was found that the particle size increased with the synthesis temperature. Thermoelectric property of as-synthesized lead telluride sample was also investigated. This work is supported by the National Science Foundation under the grant DMR- 0548061.

  9. Generic R&D on undoped cesium iodide and lead fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Kierstead, J.A.; Levy, P.W.; Stoll, S.; Woody, C.L. [Brookhaven National Lab., Upton, NY (United States); Goldberg, M.; Horwitz, N.; Skwarnicki, T.; Sobolewski, Z.; Anderson, D.F.; Ramberg, E.J.; Zimmerman, J.

    1991-12-31

    A summary is given on the recent progress on generic R&D on undoped CsI and PbF{sub 2}. Both of these materials are being investigated for use as a high resolution electromagnetic calorimeter for RHIC, as well as for other potential applications. Results are given on the development of a low gain readout system for use with undoped CsI crystals. A study has also been made of radiation damage in both undoped and thallium doped CsI. The progress on the growth of large, high quality PbF{sub 2} crystals, which would be suitable for calorimeter applications, is discussed, and some first test beam results with a prototype PbF{sub 2} calorimeter are given. Finally, results are presented on the improved radiation resistance of the new PbF{sub 2} material.

  10. Highly anisotropic conductivity in organosiloxane liquid crystals

    Science.gov (United States)

    Gardiner, D. J.; Coles, H. J.

    2006-12-01

    In this paper, we present the conductivity and dielectric characterization of three homologous series of smectic A siloxane containing liquid crystals. The materials studied include one monomesogenic series, which consists of a 4-(ω-alkyloxy)-4'-cyanobiphenyl unit terminated by pentamethyldisiloxane, and two bimesogenic series, which consist of twin 4-(ω-alkyloxy)-4'-cyanobiphenyls joined via tetramethyldisiloxane or decamethylpentasiloxane. All of the compounds exhibit wide temperature range enantiotropic smectic A phases; the effect of the siloxane moiety is to suppress nematic morphology even in the short chain homologs. We find that these compounds exhibit a highly anisotropic conductivity: the value perpendicular to the director is to up to 200 times that parallel to the director. For the nonsiloxane analog 4-(ω-octyl)-4'-cyanobiphenyl (8CB), this value is approximately 2. It is also found that the dielectric anisotropy is reduced significantly; a typical value is ˜1 compared to 8.4 for 8CB. We propose that the origin of these unusual properties is in the smectic structure; the microphase separation of the bulky, globular siloxane moieties into liquidlike regions severely inhibits the mobility parallel to the director and across the smectic layers. Further, the inclusion of this unit acts to increase the antiparallel correlations of molecular dipoles in the aromatic and alkyloxy sublayers, reducing the dielectric anisotropy significantly compared to nonsiloxane analogs. The highly anisotropic conductivity suggests that these materials are particularly suitable for application in electro-optic effects which exploit this property, e.g., the bistable electro-optic effect in smectic A liquid crystals.

  11. Highly Conducting Graphite Epoxy Composite Demonstrated

    Science.gov (United States)

    Gaier, James R.

    1999-01-01

    Weight savings as high as 80 percent could be achieved if graphite polymer composites could replace aluminum in structures such as electromagnetic interference shielding covers and grounding planes. This could result in significant cost savings, especially for the mobile electronics found in spacecraft, aircraft, automobiles, and hand-held consumer electronics. However, such composites had not yet been fabricated with conductivity sufficient to enable these applications. To address this lack, a partnership of the NASA Lewis Research Center, Manchester College, and Applied Sciences, Inc., fabricated nonmetallic composites with unprecedented electrical conductivity. For these composites, heat-treated, vapor-grown graphite fibers were selected which have a resistivity of about 80 mW-cm, more than 20 times more conductive than typical carbon fibers. These fibers were then intercalated with iodine bromide (IBr). Intercalation is the insertion of guest atoms or molecules between the carbon planes of the graphite fibers. Since the carbon planes are not highly distorted in the process, intercalation has little effect on mechanical and thermal properties. Intercalation does, however, lower the carbon fiber resistivity to less than 10 mW-cm, which is comparable to that of metal fibers. Scaleup of the reaction was required since the initial intercalation experiments would be carried out on 20-mg quantities of fibers, and tens of grams of intercalated fibers would be needed to fabricate even small demonstration composites. The reaction was first optimized through a time and temperature study that yielded fibers with a resistivity of 8.7 2 mW-cm when exposed to IBr vapor at 114 C for 24 hours. Stability studies indicated that the intercalated fibers rapidly lost their conductivity when exposed to temperatures as low as 40 C in air. They were not, however, susceptible to degradation by water vapor in the manner of most graphite intercalation compounds. The 1000-fold scaleup

  12. Optical-loss suppressed InGaN laser diodes using undoped thick waveguide structure

    Science.gov (United States)

    Kawaguchi, Masao; Imafuji, Osamu; Nozaki, Shinichiro; Hagino, Hiroyuki; Takigawa, Shinichi; Katayama, Takuma; Tanaka, Tsuyoshi

    2016-02-01

    We propose optical-loss suppressed thick-optical-waveguide (TOW) InGaN laser diodes (LDs) without operatingvoltage increase. A record high continuous-wave (CW) output of 7.2W for a single-emitting InGaN LD is achieved without thermal peak-out in the light-current curve. The TOW enables to confine major part of the propagating light into a transparent undoped region, and thus significantly reduces the optical-loss. An electron-overflow-suppression (EOS) layer placed between the waveguide layer and a p-cladding layer plays an important role to reduce the operating voltage after introduction of the undoped TOW layer. We executed a self-consisted calculation of voltage-current characteristics taking into account Schrödinger and Poisson equations in conjunction with a carrier continuity equation. The calculation result indicates possible presence of conductivity-modulation in the waveguide filled with electrons reflected backward by the EOS layer and holes injected from the p-type cladding layer. We successfully demonstrated the optical-loss suppressed operation resulting in the slope efficiency (SE) increase from 2.0W/A to 2.5W/A. It is noted that the operating voltage of the TOW LD is nearly identical to the conventional LD thanks to the above conductivitymodulation phenomenon. The presented result suggests that our TOW structure can overcome the optical-loss drawback of the InGaN LDs, and hence will lead them to the applications requiring high wattage light sources.

  13. Highly conducting one-dimensional solids

    CERN Document Server

    Evrard, Roger; Doren, Victor

    1979-01-01

    Although the problem of a metal in one dimension has long been known to solid-state physicists, it was not until the synthesis of real one-dimensional or quasi-one-dimensional systems that this subject began to attract considerable attention. This has been due in part to the search for high­ temperature superconductivity and the possibility of reaching this goal with quasi-one-dimensional substances. A period of intense activity began in 1973 with the report of a measurement of an apparently divergent conduc­ tivity peak in TfF-TCNQ. Since then a great deal has been learned about quasi-one-dimensional conductors. The emphasis now has shifted from trying to find materials of very high conductivity to the many interesting problems of physics and chemistry involved. But many questions remain open and are still under active investigation. This book gives a review of the experimental as well as theoretical progress made in this field over the last years. All the chapters have been written by scientists who have ...

  14. Structural, optical and morphological studies of undoped and Zn ...

    Indian Academy of Sciences (India)

    Undoped and Zn-doped CdSe quantum dots (QDs) were successfully synthesized by the chemical precipitation method. The structural, optical and morphological properties of the synthesized undoped and Zn-dopedCdSe QDs were studied by X-ray diffraction (XRD), UV–visible absorption spectroscopy, ...

  15. Current emitted by highly conducting Taylor cones

    Science.gov (United States)

    Delamora, J. Fernandez; Loscertales, I. G.

    1994-02-01

    When a liquid meniscus held at the exit of a metallic capillary tube is charged to a high voltage V, the free surface often takes the form of a cone whose apex emits a steady microjet, and thus injects a certain charge I and liquid volume Q per unit time into the surrounding gas. This work deals with liquids with relatively large conductivities K, for which the jet diameter d(j) is much smaller than the diameter d(n) of the capillary tube. In the limit d(j)/d(n) to O, the structure of the jet (d(j) and I, in particular) becomes independent of electrostatic parameters such as V or the electrode configuration, being governed mostly by the liquid properties and flow rate Q. Furthermore, the measured current is given approximately by I = f(epsilon)(gamma QK/epsilon)(exp 1/2) for a wide variety of liquids and conditions (epsilon, and gamma are, respectively, the dielectric constant of the liquid and the coefficient of interfacial tension, f(epsilon) is shown). A proposed explanation for this behavior is presented.

  16. Thermal conductivity measurements of high and low thermal conductivity films using a scanning hot probe method in the 3ω mode and novel calibration strategies.

    Science.gov (United States)

    Wilson, Adam A; Muñoz Rojo, Miguel; Abad, Begoña; Perez, Jaime Andrés; Maiz, Jon; Schomacker, Jason; Martín-Gonzalez, Marisol; Borca-Tasciuc, Diana-Andra; Borca-Tasciuc, Theodorian

    2015-10-07

    This work discusses measurement of thermal conductivity (k) of films using a scanning hot probe method in the 3ω mode and investigates the calibration of thermal contact parameters, specifically the thermal contact resistance (R(th)C) and thermal exchange radius (b) using reference samples with different thermal conductivities. R(th)C and b were found to have constant values (with b = 2.8 ± 0.3 μm and R(th)C = 44,927 ± 7820 K W(-1)) for samples with thermal conductivity values ranging from 0.36 W K(-1) m(-1) to 1.1 W K(-1) m(-1). An independent strategy for the calibration of contact parameters was developed and validated for samples in this range of thermal conductivity, using a reference sample with a previously measured Seebeck coefficient and thermal conductivity. The results were found to agree with the calibration performed using multiple samples of known thermal conductivity between 0.36 and 1.1 W K(-1) m(-1). However, for samples in the range between 16.2 W K(-1) m(-1) and 53.7 W K(-1) m(-1), calibration experiments showed the contact parameters to have considerably different values: R(th)C = 40,191 ± 1532 K W(-1) and b = 428 ± 24 nm. Finally, this work demonstrates that using these calibration procedures, measurements of both highly conductive and thermally insulating films on substrates can be performed, as the measured values obtained were within 1-20% (for low k) and 5-31% (for high k) of independent measurements and/or literature reports. Thermal conductivity results are presented for a SiGe film on a glass substrate, Te film on a glass substrate, polymer films (doped with Fe nano-particles and undoped) on a glass substrate, and Au film on a Si substrate.

  17. A study of transport suppression in an undoped AlGaAs/GaAs quantum dot single-electron transistor

    DEFF Research Database (Denmark)

    See, A. M.; Klochan, O.; Micolich, P.

    2013-01-01

    We report a study of transport blockade features in a quantum dot single-electron transistor, based on an undoped AlGaAs/GaAs heterostructure. We observe suppression of transport through the ground state of the dot, as well as negative differential conductance at finite source-drain bias. The tem......We report a study of transport blockade features in a quantum dot single-electron transistor, based on an undoped AlGaAs/GaAs heterostructure. We observe suppression of transport through the ground state of the dot, as well as negative differential conductance at finite source-drain bias...

  18. Growth and characterization of undoped and Mn doped lead-free piezoelectric NBT–KBT single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Babu, G. Anandha, E-mail: anandcgc@gmail.com [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Subramaniyan, Raja R. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Bhaumik, Indranil [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Ganesamoorthy, S. [X-ray Scattering and Crystal Growth Section, Condensed Matter Physics Division, Materials Science Group, IGCAR, Kalpakkam 603102 (India); Ramasamy, P. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603 110 (India); Gupta, P.K. [Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

    2014-05-01

    Highlights: • Single crystals of undoped and Mn doped NKBT crystals are grown by spontaneous nucleation. • Temperature and frequency dependent dielectric constant and loss are measured. • Dielectric constant has increased and the loss has reduced on Mn doped NKBT. • Concentration of oxygen vacancies has been reduced in Mn doped NKBT. • The activation energy for undoped and Mn doped NKBT are calculated. - Abstract: Lead-free piezoelectric single crystals of undoped and 1 wt% Mn doped 0.80 Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}–0.20 K{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NKBT) was grown using self-flux. Powder X-ray diffraction analysis revealed that the grown crystals belong to tetragonal system at room temperature. The lattice strain was calculated from Williamson Hall relation for undoped and Mn doped NKBT crystals. A significant change is observed in dielectric behavior of Mn doped NKBT when compared to undoped sample. The diffuseness increased substantially on Mn doped NKBT which masked the ferroelectric to antiferroelectric transition in the dielectric constant plot. The AC impedance study revealed that the conduction is governed by the singly ionized oxygen vacancy. Further, the decrease in the conductivity on Mn doping suggests that Mn replaces the Bi vacancy, which reduces the oxygen vacancy.

  19. Modelling and measurement of high switching frequency conducted EMI

    CSIR Research Space (South Africa)

    Grobler, Inus

    2013-11-01

    Full Text Available High density high switching frequency power converter conducted EMC had been analysed, modelling the noise source and noise path, while providing accurate conducted EMC noise levels comparable to accredited noise measurements up to 100 MHz...

  20. Geometry dependent transport properties of undoped InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Guenel, H. Yusuf; Bloemers, Christian; Sladek, Kamil; Penz, Andreas; Hardtdegen, Hilde; Lenk, Steffi; Schubert, Juergen; Schaepers, Thomas; Gruetzmacher, Detlev [Institute of Bio- and Nanosystems (IBN-1) and JARA-Fundamentals of Future Information Technology, Research Centre Juelich GmbH, 52425 Juelich (Germany); Luysberg, Martina [Institute of Solid State Research and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forchungszentrum Juelich, 52425 Juelich (Germany)

    2010-07-01

    In recent time nanowire (NW) structures attracted much attention, for electronics, optoelectronics and fundamental quantum properties. On account of different application purposes basic transport properties are crucially important at room temperature as well as low temperatures. In this respect InAs NWs are particularly important due to the low band gap and high carrier concentration. We characterized the basic transport parameters of undoped InAs NWs at room temperature, which were grown on GaAs(001) substrate by MOVPE without catalyst. The NWs that we used in this work had diameters ranging from 25 nm to 200 nm and lengths up to 3.5 {mu}m. Basic transport parameters, such as carrier concentration and mobility, were determined by using two- and four-terminal measurement configuration. The carrier concentration could be controlled by a SiO{sub 2} -isolated back-gate structure. By analyzing the transfer characteristics of the NW FET, we observed very good gate controllability.

  1. DEVELOPMENT OF HIGH THERMAL CONDUCTIVITY ELECTRICAL EMBEDDING COMPOUNDS.

    Science.gov (United States)

    This report describes the development of high thermal conductivity electrical embedding compounds utilizing a technique wherein the mold is first...Contained herein, are the pertinent results of a previously reported study which led to the development of three high thermal conductivity compounds...and the further development of several additional compounds with still higher conductivities. (Author)

  2. Enhancing The Extremely High Thermal Conduction of Graphene Nanoribbons

    Directory of Open Access Journals (Sweden)

    Xiuqiang eLi

    2013-10-01

    Full Text Available Graphene and Graphene nanoribbons (GNRs are found to have superior high thermal conductivity favorable for high-performance heat dissipation. In this letter, by using molecular dynamics simulations, we show that constructing specific structure can further enhance high thermal conduction of GNRs. By introducing a small gap at the center, the average heat flux (thermal conductivity can be enhanced by up to 23%, the corresponding increase in total heat current is 16%. This unusual thermal conduction enhancement is achieved by an intriguing physical mechanism of suppress phonon-phonon scattering. Our findings uncover new mechanism to increase thermal conduction of GNRs.

  3. Magnetic properties of undoped and Al doped layered α-Co(OH)2

    Science.gov (United States)

    Gupta, Anu; Tiwari, S. D.

    2017-11-01

    Undoped, 10% and 20% Al doped samples of layered hexagonal α-Co(OH)2 are synthesized. X-ray diffraction patterns show that the samples are nanocrystalline with average crystallite size 15 nm. Fourier transform infrared spectroscopy and thermogravimetric analysis are performed to establish molecular formula of samples. Analysis of susceptibility χ as a function of temperature T (5-300 K) data indicates for ferromagnetic transitions in the system at lower temperatures. Curie transition temperature TC for undoped, 10% and 20% Al doped α-Co(OH)2 are found to be 9, 7.5 and 6.0 K respectively. Fitting of χ vs. T data for T >TC to the high temperature series yields strength of intralayer and interlayer exchange interactions among Co2+ ions. For undoped sample values of these interactions are estimated to be 1.070 and 0.240 K respectively. Strength of these interactions decrease with increasing concentration of Al3+ ions in the lattice. Magnetization as a function of applied magnetic field (up to ± 50 kG) data confirm ferromagnetic nature of the samples at 5 K.

  4. Structural, optical and morphological studies of undoped and Zn ...

    Indian Academy of Sciences (India)

    From the UV–visible absorption spectral analysis, the absorption wavelengths of both undoped and Zn-doped ... TEM analysis shows that the prepared QDs are spherical in shape. Keywords. CdSe QDs; cubic crystalline phase; quantum ... tuned according to the particle size. Scientists have taken many efforts to control the ...

  5. Undoped InSb radiation detector for radiation measurement

    CERN Document Server

    Hishiki, S; Sugiura, O; Murase, Y; Nakamura, T; Katagiri, M

    2003-01-01

    A Schottky type detector was fabricated with undoped InSb wafer. We could measure the energy of sup 2 sup 4 sup 1 Am alpha particles with this InSb detector at the operating temperature from 2 K to 65 K.

  6. Extremely High Thermal Conductivity of Graphene: Experimental Study

    OpenAIRE

    Balandin, A. A.; Ghosh, S.; Bao, W.; Calizo, I.; Teweldebrhan, D.; Miao, F.; Lau, C. N.

    2008-01-01

    We report on the first measurement of the thermal conductivity of a suspended single layer graphene. The measurements were performed using a non-contact optical technique. The near room-temperature values of the thermal conductivity in the range ~ 4840 to 5300 W/mK were extracted for a single-layer graphene. The extremely high value of the thermal conductivity suggests that graphene can outperform carbon nanotubes in heat conduction.

  7. Heat conductivity of high-temperature thermal insulators

    Science.gov (United States)

    Kharlamov, A. G.

    The book deals essentially with the mechanisms of heat transfer by conduction, convection, and thermal radiation in absorbing and transmitting media. Particular attention is given to materials for gas-cooled reactor systems, the temperature dependent conductivities of high-temperature insulations in vacuum, and the thermal conductivities of MgO, Al2O3, ZrO2, and other powders at temperatures up to 2000 C. The thermal conductivity of pyrolitic graphite and graphite foam are studied.

  8. Continuous Processing of High Thermal Conductivity Polyethylene Fibers and Sheets

    Energy Technology Data Exchange (ETDEWEB)

    None

    2016-12-01

    This factsheet describes a project that developed a new, continuous manufacturing process to make high molecular weight, high thermal conductivity polyethylene fibers and sheets to replace metals and ceramics in heat transfer applications.

  9. Nanostructure design for drastic reduction of thermal conductivity while preserving high electrical conductivity.

    Science.gov (United States)

    Nakamura, Yoshiaki

    2018-01-01

    The design and fabrication of nanostructured materials to control both thermal and electrical properties are demonstrated for high-performance thermoelectric conversion. We have focused on silicon (Si) because it is an environmentally friendly and ubiquitous element. High bulk thermal conductivity of Si limits its potential as a thermoelectric material. The thermal conductivity of Si has been reduced by introducing grains, or wires, yet a further reduction is required while retaining a high electrical conductivity. We have designed two different nanostructures for this purpose. One structure is connected Si nanodots (NDs) with the same crystal orientation. The phonons scattering at the interfaces of these NDs occurred and it depended on the ND size. As a result of phonon scattering, the thermal conductivity of this nanostructured material was below/close to the amorphous limit. The other structure is Si films containing epitaxially grown Ge NDs. The Si layer imparted high electrical conductivity, while the Ge NDs served as phonon scattering bodies reducing thermal conductivity drastically. This work gives a methodology for the independent control of electron and phonon transport using nanostructured materials. This can bring the realization of thermoelectric Si-based materials that are compatible with large scale integrated circuit processing technologies.

  10. Improving electrical conductivity in polycarbonate nanocomposites using highly conductive PEDOT/PSS coated MWCNTs

    KAUST Repository

    Zhou, Jian

    2013-07-10

    We describe a strategy to design highly electrically conductive polycarbonate nanocomposites by using multiwalled carbon nanotubes (MWCNTs) coated with a thin layer of poly(3,4-ethylenedioxythiophene)/ poly(styrenesulfonate), a conductive polymer. We found that this coating method improves the electrical properties of the nanocomposites in two ways. First, the coating becomes the main electrical conductive path. Second, the coating promotes the formation of a percolation network at a low filler concentration (0.3 wt %). To tailor the electrical properties of the conductive polymer coating, we used a polar solvent ethylene glycol, and we can tune the final properties of the nanocomposite by controlling the concentrations of the elementary constituents or the intrinsic properties of the conductive polymer coating. This very flexible technique allows for tailoring the properties of the final product. © 2013 American Chemical Society.

  11. Heavily doped silicon electrode for dielectrophoresis in high conductivity media

    Science.gov (United States)

    Zhu, Xiongfeng; Tung, Kuan-Wen; Chiou, Pei-Yu

    2017-10-01

    A hemispherically shaped, heavily doped (N++) silicon electrode is proposed to overcome the challenges of dielectrophoretic (DEP) manipulation using a conventional metal electrode operating in high conductivity media. An N++ electrode decouples the strong electric field region from the electrode interface and provides a large interface capacitance to prevent surface charging in high conductivity media, thereby effectively suppressing electrochemical reactions. Compared to a conventional metal electrode, an N++ electrode can provide 3 times higher threshold voltage and a corresponding 9-fold enhancement of maximum DEP force in 1× phosphate-buffered saline buffer with an electrical conductivity of 1 S/m. Furthermore, an N++ silicon electrode has excellent thermal conductivity and low electrical impedance, ideal for powering massively parallel DEP manipulation in high conductivity media across a large area.

  12. High conductivity Be-Cu alloys for fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Lilley, E.A. [NGK Metals Corp., Reading, PA (United States); Adachi, Takao; Ishibashi, Yoshiki [NGK Insulators, Ltd., Aichi-ken (Japan)

    1995-09-01

    The optimum material has not yet been identified. This will result in heat from plasma to the first wall and divertor. That is, because of cracks and melting by thermal power and shock. Today, it is considered to be some kinds of copper, alloys, however, for using, it must have high conductivity. And it is also needed another property, for example, high strength and so on. We have developed some new beryllium copper alloys with high conductivity, high strength, and high endurance. Therefore, we are introducing these new alloys as suitable materials for the heat sink in fusion reactors.

  13. Development of high-thermal-conductivity silicon nitride ceramics

    Directory of Open Access Journals (Sweden)

    You Zhou

    2015-09-01

    Full Text Available Silicon nitride (Si3N4 with high thermal conductivity has emerged as one of the most promising substrate materials for the next-generation power devices. This paper gives an overview on recent developments in preparing high-thermal-conductivity Si3N4 by a sintering of reaction-bonded silicon nitride (SRBSN method. Due to the reduction of lattice oxygen content, the SRBSN ceramics could attain substantially higher thermal conductivities than the Si3N4 ceramics prepared by the conventional gas-pressure sintering of silicon nitride (SSN method. Thermal conductivity could further be improved through increasing the β/α phase ratio during nitridation and enhancing grain growth during post-sintering. Studies on fracture resistance behaviors of the SRBSN ceramics revealed that they possessed high fracture toughness and exhibited obvious R-curve behaviors. Using the SRBSN method, a Si3N4 with a record-high thermal conductivity of 177 Wm−1K−1 and a fracture toughness of 11.2 MPa m1/2 was developed. Studies on the influences of two typical metallic impurity elements, Fe and Al, on thermal conductivities of the SRBSN ceramics revealed that the tolerable content limits for the two impurities were different. While 1 wt% of impurity Fe hardly degraded thermal conductivity, only 0.01 wt% of Al caused large decrease in thermal conductivity.

  14. Free-Standing Undoped ZnO Microtubes with Rich and Stable Shallow Acceptors

    OpenAIRE

    Qiang Wang; Yinzhou Yan; Yong Zeng; Yue Lu; Liang Chen; Yijian Jiang

    2016-01-01

    Fabrication of reliable large-sized p-ZnO is a major challenge to realise ZnO-based electronic device applications. Here we report a novel technique to grow high-quality free-standing undoped acceptor-rich ZnO (A-ZnO) microtubes with dimensions of ~100??m (in diameter)???5?mm (in length) by optical vapour supersaturated precipitation. The A-ZnO exhibits long lifetimes (>1 year) against compensation/lattice-relaxation and the stable shallow acceptors with binding energy of ~127?meV are confirm...

  15. Highly Conductive Wire: Cu Carbon Nanotube Composite Ampacity and Metallic CNT Buckypaper Conductivity

    Science.gov (United States)

    de Groh, Henry C.

    2017-01-01

    NASA is currently working on developing motors for hybrid electric propulsion applications in aviation. To make electric power more feasible in airplanes higher power to weight ratios are sought for electric motors. One facet to these efforts is to improve (increase) the conductivity and (lower) density of the magnet wire used in motors. Carbon nanotubes (CNT) and composites containing CNT are being explored as a possible way to increase wire conductivity and lower density. Presented here are measurements of the current carrying capacity (ampacity) of a composite made from CNT and copper. The ability of CNT to improve the conductivity of such composites is hindered by the presence of semiconductive CNT (s-CNT) that exist in CNT supplies naturally, and currently, unavoidably. To solve this problem, and avoid s-CNT, various preferential growth and sorting methods are being explored. A supply of sorted 95 metallic CNT (m-CNT) was acquired in the form of thick film Buckypaper (BP) as part of this work and characterized using Raman spectroscopy, resistivity, and density measurements. The ampacity (Acm2) of the Cu-5volCNT composite was 3.8 lower than the same gauge pure Cu wire similarly tested. The lower ampacity in the composite wire is believed to be due to the presence of s-CNT in the composite and the relatively low (proper) level of longitudinal cooling employed in the test method. Although Raman spectroscopy can be used to characterize CNT, a strong relation between the ratios of the primary peaks GGand the relative amounts of m-CNT and s-CNT was not observed. The average effective conductivity of the CNT in the sorted, 95 m-CNT BP was 2.5 times higher than the CNT in the similar but un-sorted BP. This is an indication that improvements in the conductivity of CNT composites can be made by the use of sorted, highly conductive m-CNT.

  16. Survey of Processing Methods for High Strength High Conductivity Wires for High Field Magnet Applications

    Energy Technology Data Exchange (ETDEWEB)

    Han, K.; Embury, J.D.

    1998-10-01

    This paper will deal with the basic concepts of attaining combination of high strength and high conductivity in pure materials, in-situ composites and macrocomposites. It will survey current attainments, and outline where some future developments may lie in developing wire products that are close to the theoretical strength of future magnet applications.

  17. Silicon-graphene conductive photodetector with ultra-high responsivity

    Science.gov (United States)

    Liu, Jingjing; Yin, Yanlong; Yu, Longhai; Shi, Yaocheng; Liang, Di; Dai, Daoxin

    2017-01-01

    Graphene is attractive for realizing optoelectronic devices, including photodetectors because of the unique advantages. It can easily co-work with other semiconductors to form a Schottky junction, in which the photo-carrier generated by light absorption in the semiconductor might be transported to the graphene layer efficiently by the build-in field. It changes the graphene conduction greatly and provides the possibility of realizing a graphene-based conductive-mode photodetector. Here we design and demonstrate a silicon-graphene conductive photodetector with improved responsivity and response speed. An electrical-circuit model is established and the graphene-sheet pattern is designed optimally for maximizing the responsivity. The fabricated silicon-graphene conductive photodetector shows a responsivity of up to ~105 A/W at room temperature (27 °C) and the response time is as short as ~30 μs. The temperature dependence of the silicon-graphene conductive photodetector is studied for the first time. It is shown that the silicon-graphene conductive photodetector has ultra-high responsivity when operating at low temperature, which provides the possibility to detect extremely weak optical power. For example, the device can detect an input optical power as low as 6.2 pW with the responsivity as high as 2.4 × 107 A/W when operating at -25 °C in our experiment.

  18. Hybrid electrokinetic manipulation in high-conductivity media†

    Science.gov (United States)

    Gao, Jian; Sin, Mandy L. Y.; Liu, Tingting; Gau, Vincent; Liao, Joseph C.

    2014-01-01

    This study reports a hybrid electrokinetic technique for label-free manipulation of pathogenic bacteria in biological samples toward medical diagnostic applications. While most electrokinetic techniques only function in low-conductivity buffers, hybrid electrokinetics enables effective operation in high-conductivity samples, such as physiological fluids (~1 S m−1). The hybrid electrokinetic technique combines short-range electrophoresis and dielectrophoresis, and long-range AC electrothermal flow to improve its effectiveness. The major technical hurdle of electrode instability for manipulating high conductivity samples is tackled by using a Ti–Au–Ti sandwich electrode and a 3-parallel-electrode configuration is designed for continuous isolation of bacteria. The device operates directly with biological samples including urine and buffy coats. We show that pathogenic bacteria and biowarfare agents can be concentrated for over 3 orders of magnitude using hybrid electrokinetics. PMID:21487576

  19. Highly Confined Electronic and Ionic Conduction in Oxide Heterostructures

    DEFF Research Database (Denmark)

    Pryds, Nini

    2015-01-01

    The conductance confined at the interface of complex oxide heterostructures provides new opportunities to explore nanoelectronic as well as nanoionic devices. In this talk I will present our recent results both on ionic and electronic conductivity at different heterostructures systems. In the first...... unattainable for Bi2O3-based materials, is achieved[1]. These confined heterostructures provide a playground not only for new high ionic conductivity phenomena that are sufficiently stable but also uncover a large variety of possible technological perspectives. At the second part, I will discuss and show our...... recent results of high mobile samples realized by, interface confined redox reactions[2], strain induced polarization[3]and modulation doping at complex oxide interfaces. This collection of samples offers unique opportunities for a wide range of rich world of mesoscopic physics. [1] S. Sanne et al...

  20. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...... of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk....

  1. Strength of VGCF/Al Composites for High Thermal Conductivity

    Science.gov (United States)

    Fukuchi, Kohei; Sasaki, Katsuhiko; Imanishi, Terumitsu; Katagiri, Kazuaki; Kakitsuji, Atsushi; Shimizu, Akiyuki

    In this paper, the evaluation of the strength of the VGCF/Aluminum composites which have high thermal conductivity is reported. VGCF (Vapor Growth Carbon Fiber) is a kind of the Carbon nanotube (CNT) which has very high thermal conductivity as well as CNT. The composites are made by spark plasma sintering. The stress-strain curves of the composites are obtained by the tensile tests and show that the composites have brittle behavior. The brittleness of the composites increases with increase in the volume fraction of VGCF. A numerical simulation based on the micromechanics is conducted to estimate nonlinear behavior in the elastic deformation and plastic deformation of the stress-strain relations of the composites. The theories of Eshelby, Mori-Tanaka, Weibull, and Ramberg-Osgood are employed for the numerical simulation. The simulations give some information of the microstructural change in the composite related to the volume fraction of VGCF.

  2. Novel Highly Conductive and Transparent Graphene-Based Conductors

    OpenAIRE

    Khrapach, Ivan; Withers, Freddie; Bointon, Thomas H.; Polyushkin, Dmitry K.; Barnes, William L.; Russo, Saverio; Craciun, Monica F.

    2012-01-01

    Future wearable electronics, displays and photovoltaic devices rely on highly conductive, transparent and yet mechanically flexible materials. Nowadays indium tin oxide (ITO) is the most wide spread transparent conductor in optoelectronic applications, however the mechanical rigidity of this material limits its use for future flexible devices. Here we report novel transparent conductors based on few layer graphene (FLG) intercalated with ferric chloride (FeCl3) with an outstandingly high elec...

  3. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...

  4. Chemical and electronic interface structure of spray pyrolysis deposited undoped and Al-doped ZnO thin films on a commercial Cz-Si solar cell substrate

    Energy Technology Data Exchange (ETDEWEB)

    Gabas, M.; Ramos-Barrado, J.R. [Dpto. de Fisica Aplicada I, Lab. de Materiales y Superficies, Universidad de Malaga 29071 Malaga (Spain); Barrett, N.T. [CEA DSM/IRAMIS/SPCSI, CEA Saclay, 91191 Gif sur Yvette (France); Gota, S. [Laboratoire Leon Brillouin, UMR 012 CEA-CNRS CEA Saclay, 91191 Gif sur Yvette (France); Rojas, T.C. [Instituto de Ciencia de Materiales de Sevilla, CSIC, Americo Vespucio 49, 41092 Sevilla (Spain); Lopez-Escalante, M.C. [Isofoton S.A., Parque Tecnologico de Andalucia, Severo Ochoa, 50, 29590 Malaga (Spain)

    2009-08-15

    We have studied differences in the interface between undoped and Al-doped ZnO thin films deposited on commercial Si solar cell substrates. The undoped ZnO film is significantly thicker than the Al-doped film for the same deposition time. An extended silicate-like interface is present in both samples. Transmission electron microscopy (TEM) and photoelectron spectroscopy (PES) probe the presence of a zinc silicate and several Si oxides in both cases. Although Al doping improves the conductivity of ZnO, we present evidence for Al segregation at the interface during deposition on the Si substrate and suggest the presence of considerable fixed charge near the oxidized Si interface layer. The induced distortion in the valence band, compared to that of undoped ZnO, could be responsible for considerable reduction in the solar cell performance. (author)

  5. High ion conducting polymer nanocomposite electrolytes using hybrid nanofillers.

    Science.gov (United States)

    Tang, Changyu; Hackenberg, Ken; Fu, Qiang; Ajayan, Pulickel M; Ardebili, Haleh

    2012-03-14

    There is a growing shift from liquid electrolytes toward solid polymer electrolytes, in energy storage devices, due to the many advantages of the latter such as enhanced safety, flexibility, and manufacturability. The main issue with polymer electrolytes is their lower ionic conductivity compared to that of liquid electrolytes. Nanoscale fillers such as silica and alumina nanoparticles are known to enhance the ionic conductivity of polymer electrolytes. Although carbon nanotubes have been used as fillers for polymers in various applications, they have not yet been used in polymer electrolytes as they are conductive and can pose the risk of electrical shorting. In this study, we show that nanotubes can be packaged within insulating clay layers to form effective 3D nanofillers. We show that such hybrid nanofillers increase the lithium ion conductivity of PEO electrolyte by almost 2 orders of magnitude. Furthermore, significant improvement in mechanical properties were observed where only 5 wt % addition of the filler led to 160% increase in the tensile strength of the polymer. This new approach of embedding conducting-insulating hybrid nanofillers could lead to the development of a new generation of polymer nanocomposite electrolytes with high ion conductivity and improved mechanical properties. © 2012 American Chemical Society

  6. Highly thermally conductive and mechanically strong graphene fibers.

    Science.gov (United States)

    Xin, Guoqing; Yao, Tiankai; Sun, Hongtao; Scott, Spencer Michael; Shao, Dali; Wang, Gongkai; Lian, Jie

    2015-09-04

    Graphene, a single layer of carbon atoms bonded in a hexagonal lattice, is the thinnest, strongest, and stiffest known material and an excellent conductor of heat and electricity. However, these superior properties have yet to be realized for graphene-derived macroscopic structures such as graphene fibers. We report the fabrication of graphene fibers with high thermal and electrical conductivity and enhanced mechanical strength. The inner fiber structure consists of large-sized graphene sheets forming a highly ordered arrangement intercalated with small-sized graphene sheets filling the space and microvoids. The graphene fibers exhibit a submicrometer crystallite domain size through high-temperature treatment, achieving an enhanced thermal conductivity up to 1290 watts per meter per kelvin. The tensile strength of the graphene fiber reaches 1080 megapascals. Copyright © 2015, American Association for the Advancement of Science.

  7. Highly conductive paper for energy-storage devices

    KAUST Repository

    Hu, L.

    2009-12-07

    Paper, invented more than 2,000 years ago and widely used today in our everyday lives, is explored in this study as a platform for energy-storage devices by integration with 1D nanomaterials. Here, we show that commercially available paper can be made highly conductive with a sheet resistance as low as 1 ohm per square (Omega/sq) by using simple solution processes to achieve conformal coating of single-walled carbon nanotube (CNT) and silver nanowire films. Compared with plastics, paper substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance. When only CNT mass is considered, a specific capacitance of 200 F/g, a specific energy of 30-47 Watt-hour/kilogram (Wh/kg), a specific power of 200,000 W/kg, and a stable cycling life over 40,000 cycles are achieved. These values are much better than those of devices on other flat substrates, such as plastics. Even in a case in which the weight of all of the dead components is considered, a specific energy of 7.5 Wh/kg is achieved. In addition, this conductive paper can be used as an excellent lightweight current collector in lithium-ion batteries to replace the existing metallic counterparts. This work suggests that our conductive paper can be a highly scalable and low-cost solution for high-performance energy storage devices.

  8. Simulation Basics: How to Conduct a High-Fidelity Simulation.

    Science.gov (United States)

    Willhaus, Janet

    2016-02-01

    Well-planned and conducted health care simulation scenarios provide opportunities for staff development in areas such as communication, patient care, and teamwork. Consideration of resources, the location for the training, preparation of learners, and use of either a high-fidelity mannequin or a trained actor (eg, a standardized patient) are all part of the operational attentions needed to conduct a simulation training scenario. In order for participants to meet training objectives, the execution of the simulation session must be both planned and purposeful.

  9. Electric conductivity of high explosives with carbon nanotubes

    Science.gov (United States)

    Rubtsov, I. A.; Pruuel, E. R.; Ten, K. A.; Kashkarov, A. O.; Kremenko, S. I.

    2017-09-01

    The paper presents a technique for introducing carbon nanotubes into high explosives (HEs). For a number of explosives (trinitrotoluene, pentaerythritol tetranitrate, benzotrifuroxan), it was possible to achieve the appearance of conductivity by adding a small amount (up to 1% by mass) of single-walled carbon nanotubes TUBALL COATE H2O (CNTs) produced by OCSiAl. Thus it is possible to reduce the sensitivity of explosives to static electricity by adding an insignificant part of conductive nanotubes. This will increase safety of HEs during production and application and will reduce the number of accidents.

  10. Conducting high quality writing intervention research: Twelve recommendations

    Directory of Open Access Journals (Sweden)

    Steve Graham

    2014-10-01

    Full Text Available Writing intervention research can enhance our knowledge about writing, its development, and how to teach it effectively. Despite the importance of such research, many of the writing intervention studies conducted previously were of poor quality, as documented by Graham and colleagues in a series of meta-analyses (Graham, McKeown, Kiuhara, & Harris, 2012; Graham & Perin, 2007; Rogers & Graham, 2008. In this article, we offer 12 recommendations for conducting high quality intervention research, recommendations that draw on those meta-analyses as well as previous work on improving the quality of intervention research (Pressley & Harris, 1994a, 1994b and our experiences as writing intervention researchers and editors of journals that publish intervention research (including the Journal of Writing Research . The recommendations address issues and actions involved in designing, conducting, and reporting such research.

  11. Highly Conductive Polypropylene-Graphene Nonwoven Composite via Interface Engineering.

    Science.gov (United States)

    Pan, Qin; Shim, Eunkyoung; Pourdeyhimi, Behnam; Gao, Wei

    2017-08-01

    Here we report a highly conductive polypropylene-graphene nonwoven composite via direct coating of melt blown polypropylene (PP) nonwoven fabrics with graphene oxide (GO) dispersions in N,N-dimethylformamide (DMF), followed by the chemical reduction of GO with hydroiodic acid (HI). GO as an amphiphilic macromolecule can be dispersed in DMF homogeneously at a concentration of 5 mg/mL, which has much lower surface tension (37.5 mN/m) than that of GO in water (72.9 mN/m, at 5 mg/mL). The hydrophobic PP nonwoven has a surface energy of 30.1 mN/m, close to the surface tension of GO in DMF. Therefore, the PP nonwoven can be easily wetted by the GO/DMF dispersion without any pretreatment. Soaking PP nonwoven in a GO/DMF dispersion leads to uniform coatings of GO on PP-fiber surfaces. After chemical reduction of GO to graphene, the resulting PP/graphene nonwoven composite offers an electrical conductivity of 35.6 S m -1 at graphene loading of 5.2 wt %, the highest among the existing conductive PP systems reported, indicating that surface tension of coating baths has significant impact on the coating uniformity and affinity. The conductivity of our PP/graphene nonwoven is also stable against stirring washing test. In addition, here we demonstrate a monolithic supercapacitor derived from the PP-GO nonwoven composite by using a direct laser-patterning process. The resulted sandwich supercapacitor shows a high areal capacitance of 4.18 mF/cm 2 in PVA-H 2 SO 4 gel electrolyte. The resulting highly conductive or capacitive PP/graphene nonwoven carries great promise to be used as electronic textiles.

  12. Analysis of Slug Tests in Formations of High Hydraulic Conductivity

    Science.gov (United States)

    Butler, J.J.; Garnett, E.J.; Healey, J.M.

    2003-01-01

    A new procedure is presented for the analysis of slug tests performed in partially penetrating wells in formations of high hydraulic conductivity. This approach is a simple, spreadsheet-based implementation of existing models that can be used for analysis of tests from confined or unconfined aquifers. Field examples of tests exhibiting oscillatory and nonoscillatory behavior are used to illustrate the procedure and to compare results with estimates obtained using alternative approaches. The procedure is considerably simpler than recently proposed methods for this hydrogeologic setting. Although the simplifications required by the approach can introduce error into hydraulic-conductivity estimates, this additional error becomes negligible when appropriate measures are taken in the field. These measures are summarized in a set of practical field guidelines for slug tests in highly permeable aquifers.

  13. Switch on the high thermal conductivity of graphene paper.

    Science.gov (United States)

    Xie, Yangsu; Yuan, Pengyu; Wang, Tianyu; Hashemi, Nastaran; Wang, Xinwei

    2016-10-14

    This work reports on the discovery of a high thermal conductivity (κ) switch-on phenomenon in high purity graphene paper (GP) when its temperature is reduced from room temperature down to 10 K. The κ after switch-on (1732 to 3013 W m(-1) K(-1)) is 4-8 times that before switch-on. The triggering temperature is 245-260 K. The switch-on behavior is attributed to the thermal expansion mismatch between pure graphene flakes and impurity-embedded flakes. This is confirmed by the switch behavior of the temperature coefficient of resistance. Before switch-on, the interactions between pure graphene flakes and surrounding impurity-embedded flakes efficiently suppress phonon transport in GP. After switch-on, the structure separation frees the pure graphene flakes from the impurity-embedded neighbors, leading to a several-fold κ increase. The measured κ before and after switch-on is consistent with the literature reported κ values of supported and suspended graphene. By conducting comparison studies with pyrolytic graphite, graphene oxide paper and partly reduced graphene paper, the whole physical picture is illustrated clearly. The thermal expansion induced switch-on is feasible only for high purity GP materials. This finding points out a novel way to switch on/off the thermal conductivity of graphene paper based on substrate-phonon scattering.

  14. HIGH-CONDUCTIVE NANOSTRUCTURES IN BIOCHEMICAL STUDIES: FLUORESCENCE ENHANCING

    Directory of Open Access Journals (Sweden)

    V. I. Chegel

    2015-10-01

    Full Text Available This paper presents the results of experimental and theoretical studies of quenching and enhancement of fluorescence by colloidal solutions of nanoparticles and arrays of nanostructures on solid substrates — nanochips. The literature data and the results of authors’ own studies on the possibility of fluorescence signal manipulation in the presence of gold and silver nanostructures were shown. Mathematical modeling and comparative investigation of the samples with high-conductive metal nanostructures as active elements for the regulation of fluorescence signal were also performed. Nanochips samples were fabricated by thermal annealing of highly conductive gold and silver island films. Using developed novel laser-based fluorometer FluorotestNano it was shown that fluorescence intensity of Rhodamine 6G dye can be enhanced up to 23 times near gold nanostructures by spacing the dye from the nanoparticle at the distance of 20 nm using SiO2 coating. Using high-conductive metal nanostructures to adjust the fluorescence signal opens promising new directions in biochemical studies, such as increasing the sensitivity of fluorescence methods, development of new biosensors, fluorescence microscopy techniques and medical diagnostics.

  15. High pressure electrical conductivity in naturally occurring silicate liquids

    Science.gov (United States)

    Tyburczy, James A.; Waff, Harve S.

    Electrical conductivities of molten Hawaiian rhyodacite and Yellowstone rhyolite obsidian were measured between 1200° C and 1400° C and at pressures up to 25 kilobars. The two melts exhibit similar trends. Arrhenius behavior is observed at all pressures studied. Isobaric activation enthalpies increase from about 0.5 eV at atmospheric pressure to about 0.9 eV at 25 kbars, and the magnitude of the conductivity decreases by about a factor of 4 between 0 and 25 kbar. At pressures between about 10 and 15 kbar an abrupt decrease in the slopes of isothermal log a versus pressure plots is observed. In each pressure range an equation of the form σ = σ'0 exp [- (E'σ + PΔV'σ)/kT], where σ'0, E'σ, and ΔV'σ, are constants, describes the polybaric, polythermal data. Comparison of these data with high pressure electrical conductivities of molten basalt and andesite reveals that relatively silica-rich melts, from andesitic to rhyolitic in composition, display similar trends, while the basaltic melt has analogous, but quantitatively different trends. Comparison of zero-pressure electrical conductivity and sodium diffusivity by means of the Nernst-Einstein relation indicates that sodium ion transport is the dominant mechanism of charge transport in the obsidian melt at zero pressure. The tholeiitic melt, on the other hand, displays only order of magnitude agreement between the electrical conductivity and sodium diffusivity, indicating that either ions other than sodium play a significant role in electrical transport or that the motions of the sodium ions are strongly correlated, or both. Comparison of the isobaric and isochoric activation enthalpies indicates that electrical conduction is energy restrained, as opposed to volume restrained. Conductivities in the andesitic, rhyodacitic, and rhyolitic melts conform to a single compensation law line, with no indication of the change in activation volume. The tholeiitic melt has a slightly different compensation line. In light

  16. Electrical properties of undoped zinc oxide nanostructures at different annealing temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, M. F., E-mail: babaibaik2002@yahoo.com; Zainol, M. N., E-mail: nizarzainol@yahoo.com; Hannas, M., E-mail: mhannas@gmail.com [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Mamat, M. H., E-mail: mhmamat@salam.uitm.edu.my; Rusop, Mohamad, E-mail: rusop@salam.uitm.edu.my [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia); Rahman, S. A., E-mail: saadah@um.edu.my [NANO-ElecTronic Centre (NET), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Low Dimensional Materials Research Centre, Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2016-07-06

    This project has been focused on the electrical and optical properties respectively on the effect of Undoped zinc oxide (ZnO) thin films at different annealing temperature which is varied 400 °C, 450 °C, 500 °C, and 550 °C.Undoped ZnO solutions were deposited onto the glass substrates using sol-gel spin coating method. This project was involved with three phases, which are thin films preparation, deposition and characterization. The thin films were characterized using Current Voltage (I-V) measurement and UV-vis-NIR spectrophotometer for electrical properties and optical properties. The electrical properties show that the resistivity is the lowest at 500 °C which its resistivity is 5.36 × 10{sup 4} Ωcm{sup −1}. The absorption coefficient spectrum obtained from UV-Vis-NIR spectrophotometer measurement shows all films exhibit very low absorption in the visible (400-800 nm) and near infrared (NIR) (>800 nm) range but exhibit high absorption in the UV range.

  17. Visible sub-band gap photoelectron emission from nitrogen doped and undoped polycrystalline diamond films

    Science.gov (United States)

    Elfimchev, S.; Chandran, M.; Akhvlediani, R.; Hoffman, A.

    2017-07-01

    In this study the origin of visible sub-band gap photoelectron emission (PEE) from polycrystalline diamond films is investigated. The PEE yields as a function of temperature were studied in the wavelengths range of 360-520 nm. Based on the comparison of electron emission yields from diamond films deposited on silicon and molybdenum substrates, with different thicknesses and nitrogen doping levels, we suggested that photoelectrons are generated from nitrogen related centers in diamond. Our results show that diamond film thickness and substrate material have no significant influence on the PEE yield. We found that nanocrystalline diamond films have low electron emission yields, compared to microcrystalline diamond, due to the presence of high amount of defects in the former, which trap excited electrons before escaping into the vacuum. However, the low PEE yield of nanocrystalline diamond films was found to increase with temperature. The phenomenon was explained by the trap assisted photon enhanced thermionic emission (ta-PETE) model. According to the ta-PETE model, photoelectrons are trapped by shallow traps, followed by thermal excitation at elevated temperatures and escape into the vacuum. Activation energies of trap levels were estimated for undoped nanocrystalline, undoped microcrystalline and N-doped diamond films using the Richardson-Dushman equation, which gives 0.13, 0.39 and 0.04 eV, respectively. Such low activation energy of trap levels makes the ta-PETE process very effective at elevated temperatures.

  18. Synthesis of Rare-Earth Doped and Undoped GaN Nano-Crystallites

    Science.gov (United States)

    El Nadi, Lotfia; Ahmed, Samah; Awaad, M.; Omar, Magdy; Badr, Yehia

    2013-03-01

    Semiconductor nanostructures doped with rare earth ions is a possible way to overcome the limitation of low luminescence efficiency of rare earth ions, providing that the strong confinement of carriers in dots will enhance their recombination in the vicinity of RE ions. Undoped and Eu3+-doped GaN crystallites have been synthesized by the co-precipitation method followed by nitridation reaction at 1100 °C for 2 h, under a continuous flow of NH3 gas. X-ray diffraction patterns (XRD) revealed that the synthesized undoped and Eu3+-doped GaN crystallites are of a single-phase wurtzite structure. The morphology of the samples was examined by field emission scanning electron microscope (FE-SEM) and high resolution transmission electron microscope (HR-TEM), and it was shown that the micron-sized particles are composed of agglomerated nano-crystallites. Under the above band gap excitation, all samples exhibited room-temperature photoluminescence with the characteristic GaN band-edge emission peak centered at 363 nm (˜3.4 eV, FWHM ˜ 10 nm) as well as broad defect-related emission peak centered at about 405 nm. The Eu-doped GaN sample, under below bandgap excitation, exhibited red emission peaks centered at 593 nm and 616 nm corresponding to the 5D0 → 7F1 and 5D0 → 7F2 transitions, respectively, within the 4f shell of Eu3+ ions.

  19. Radio-frequency reflectometry on an undoped AlGaAs/GaAs single electron transistor

    DEFF Research Database (Denmark)

    MacLeod, S. J.; See, A. M.; Keane, Z. K.

    2014-01-01

    Radio frequency reflectometry is demonstrated in a sub-micron undoped AlGaAs/GaAs device. Undoped single electron transistors (SETs) are attractive candidates to study single electron phenomena, due to their charge stability and robust electronic properties after thermal cycling. However, these d......Radio frequency reflectometry is demonstrated in a sub-micron undoped AlGaAs/GaAs device. Undoped single electron transistors (SETs) are attractive candidates to study single electron phenomena, due to their charge stability and robust electronic properties after thermal cycling. However...

  20. Conductive MOF electrodes for stable supercapacitors with high areal capacitance

    Science.gov (United States)

    Sheberla, Dennis; Bachman, John C.; Elias, Joseph S.; Sun, Cheng-Jun; Shao-Horn, Yang; Dincă, Mircea

    2017-02-01

    Owing to their high power density and superior cyclability relative to batteries, electrochemical double layer capacitors (EDLCs) have emerged as an important electrical energy storage technology that will play a critical role in the large-scale deployment of intermittent renewable energy sources, smart power grids, and electrical vehicles. Because the capacitance and charge-discharge rates of EDLCs scale with surface area and electrical conductivity, respectively, porous carbons such as activated carbon, carbon nanotubes and crosslinked or holey graphenes are used exclusively as the active electrode materials in EDLCs. One class of materials whose surface area far exceeds that of activated carbons, potentially allowing them to challenge the dominance of carbon electrodes in EDLCs, is metal-organic frameworks (MOFs). The high porosity of MOFs, however, is conventionally coupled to very poor electrical conductivity, which has thus far prevented the use of these materials as active electrodes in EDLCs. Here, we show that Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2), a MOF with high electrical conductivity, can serve as the sole electrode material in an EDLC. This is the first example of a supercapacitor made entirely from neat MOFs as active materials, without conductive additives or other binders. The MOF-based device shows an areal capacitance that exceeds those of most carbon-based materials and capacity retention greater than 90% over 10,000 cycles, in line with commercial devices. Given the established structural and compositional tunability of MOFs, these results herald the advent of a new generation of supercapacitors whose active electrode materials can be tuned rationally, at the molecular level.

  1. Transient Response of Different Highly Conductive PCM Composites

    Science.gov (United States)

    Mahmoud Alhamdo, Mohammed H.; Bdaiwi, Bashar A.; Hasan, Ali H.

    In this work, the thermal conductivity of paraffin wax has been enhanced by employing four different high conductivity additives infiltrated within the PCM. These include the use of Graphite Powder (GP), Copper Particles (CP), Aluminum oxide Particles (AP), and Copper Network (CN). Four different types of pure waxes were selected, tested and compared. Twelve samples of wax/additives composites were prepared by adding different mass ratios of 3, 6 and 9 % of additives by weight in each type of wax. The storage system contains spherical capsules filled with composite PCMs that are packed in an insulated cylindrical storage. Transient temperature based governing equations have been developed and solved numerically by both ANSYS FLUENT 14 code and by numerical implicit time marching model. With progress of time, results showed that the numerical predictions of ANSYS software start to deviate from the experimental observations. The grade-B paraffin was found to be the best one. Results indicate that all the enhancement methods have significant effect on the thermal response of the system. However, the utilization of 6 % additives by weight has been found to provide the best enhancement effect. The developed new-sort CN composite is found to produce the best thermal response due to its good homogeneity with wax and its high conductivity. Results showed that for CN composite with 6 % additives, the charging and discharging time decreased by 26.4 and 30.3 % respectively than that of pure wax and the thermal conductivity enhanced by 2.57 times that of pure wax.

  2. High-throughput search for improved transparent conducting oxides

    Science.gov (United States)

    Miglio, Anna

    High-throughput methodologies are a very useful computational tool to explore the space of binary and ternary oxides. We use these methods to search for new and improved transparent conducting oxides (TCOs). TCOs exhibit both visible transparency and good carrier mobility and underpin many energy and electronic applications (e.g. photovoltaics, transparent transistors). We find several potential new n-type and p-type TCOs with a low effective mass. Combining different ab initio approaches, we characterize candidate oxides by their effective mass (mobility), band gap (transparency) and dopability. We present several compounds, not considered previously as TCOs, and discuss the chemical rationale for their promising properties. This analysis is useful to formulate design strategies for future high mobility oxides and has led to follow-up studies including preliminary experimental characterization of a p-type TCO candidate with unexpected chemistry. G. Hautier, A. Miglio, D. Waroquiers, G.-M. Rignanese, and X. Gonze, ``How Does Chemistry Influence Electron Effective Mass in Oxides? A High-Throughput Computational Analysis'', Chem. Mater. 26, 5447 (2014). G. Hautier, A. Miglio, G. Ceder, G.-M. Rignanese, and X. Gonze, ``Identification and design principles of low hole effective mass p-type transparent conducting oxides'', Nature Commun. 4, 2292 (2013).

  3. Development of a high capacity variable conductance heat pipe.

    Science.gov (United States)

    Kosson, R.; Hembach, R.; Edelstein, F.; Loose, J.

    1973-01-01

    The high-capacity, pressure-primed, tunnel-artery wick concept was used in a gas-controlled variable conductance heat pipe. A variety of techniques were employed to control the size of gas/vapor bubbles trapped within the artery. Successful operation was attained with a nominal 6-foot long, 1-inch diameter cold reservoir VCHP using ammonia working fluid and nitrogen control gas. The pipe contained a heat exchanger to subcool the liquid in the artery. Maximum transport capacity with a 46-inch effective length was 1200 watts level (more than 50,000 watt-inches) and 800 watts at 0.5-inch adverse tilt.

  4. Electro-flow focusing. The high conductivity, low viscosity limit

    Science.gov (United States)

    Ganan-Calvo, Alfonso M.; Lopez-Herrera, José M.

    2006-11-01

    Electro-flow focusing, a technique combining the features of electrospray (ES) and flow focusing (FF), provides a reliable tool to reach parametrical micro-jetting ranges not attainable by ES or FF alone under specific operational regimes (liquid properties and flow rate). In this work, we provide not only a closed theoretical model predicting the diameter of a high electrical conductivity electro-flow focused liquid micro-jet, but also its convective/absolute instability, linked to the jetting/dripping transition and the minimum liquid flow rate that can be issued in steady jetting regime. Our predictions are compared to experiments with good accord.

  5. High-Temperature Proton-Conducting Ceramics Developed

    Science.gov (United States)

    Sayir, Ali; Dynys, Frederick W.; Berger, M. H.

    2005-01-01

    High-temperature protonic conductors (HTPC) are needed for hydrogen separation, hydrogen sensors, fuel cells, and hydrogen production from fossil fuels. The HTPC materials for hydrogen separation at high temperatures are foreseen to be metal oxides with the perovskite structure A(sup 2+)B(sup 4+)C(sup 2-, sub 3) and with the trivalent cation (M(sup 3+)) substitution at the B(sup 4+)-site to introduce oxygen vacancies. The high affinity for hydrogen ions (H(sup +)) is advantageous for protonic transport, but it increases the reactivity toward water (H2O) and carbon dioxide (CO2), which can lead to premature membrane failure. In addition, there are considerable technological challenges related to the processing of HTPC materials. The high melting point and multi-cation chemistry of HTPC materials creates difficulties in in achieving high-density, single-phase membranes by solid-state sintering. The presence of secondary phases and grain-boundary interfaces are detrimental to the protonic conduction and environmental stability of polycrystalline HTPC materials.

  6. OPTICAL AND DYNAMIC PROPERTIES OF UNDOPED AND DOPED SEMICONDUCTOR NANOSTRUCTURES

    Energy Technology Data Exchange (ETDEWEB)

    Grant, C D; Zhang, J Z

    2007-09-28

    This chapter provides an overview of some recent research activities on the study of optical and dynamic properties of semiconductor nanomaterials. The emphasis is on unique aspects of these properties in nanostructures as compared to bulk materials. Linear, including absorption and luminescence, and nonlinear optical as well as dynamic properties of semiconductor nanoparticles are discussed with focus on their dependence on particle size, shape, and surface characteristics. Both doped and undoped semiconductor nanomaterials are highlighted and contrasted to illustrate the use of doping to effectively alter and probe nanomaterial properties. Some emerging applications of optical nanomaterials are discussed towards the end of the chapter, including solar energy conversion, optical sensing of chemicals and biochemicals, solid state lighting, photocatalysis, and photoelectrochemistry.

  7. Swift heavy ion irradiation induced phase transformation in undoped and niobium doped titanium dioxide composite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gautam, Subodh K., E-mail: subodhkgtm@gmail.com [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India); Chettah, Abdelhak [LGMM Laboratory, Université 20 Août 1955-Skikda, BP 26, 21000 Skikda (Algeria); Singh, R.G. [Department of Physics, Bhagini Nivedita College, Delhi University, Delhi 110043 (India); Ojha, Sunil; Singh, Fouran [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067 (India)

    2016-07-15

    Study reports the effect of swift heavy ion (SHI) irradiation induced phase transformation in undoped and Niobium doped anatase TiO{sub 2} composite thin films. Investigations were carried out at different densities of electronic excitations (EEs) using 120 MeV Ag and 130 MeV Ni ions irradiations. Films were initially annealed at 900 °C and results revealed that undoped films were highly stable in anatase phase, while the Nb doped films showed the composite nature with the weak presence of Niobium penta-oxide (Nb{sub 2}O{sub 5}) phase. The effect at low density of EEs in undoped film show partial anatase to rutile phase transformation; however doped film shows only further growth of Nb{sub 2}O{sub 5} phase beside the anatase to rutile phase transformation. At higher density of EEs induced by Ag ions, registered continuous ion track of ∼3 nm in lattice which leads to nano-crystallization followed by decomposition/amorphization of rutile TiO{sub 2} and Nb{sub 2}O{sub 5} phases in undoped and doped films, respectively. However, Ni ions are only induced discontinuous sequence of ion tracks with creation of damage and disorder and do not show amorphization in the lattice. The in-elastic thermal spike calculations were carried out for anatase TiO{sub 2} phase to understand the effect of EEs on anatase to rutile phase transformation followed by amorphization in NTO films in terms of continuous and discontinuous track formation by SHI irradiation.

  8. Physical processes in high field insulating liquid conduction

    Science.gov (United States)

    Mazarakis, Michael; Kiefer, Mark; Leckbee, Joshua; Anderson, Delmar; Wilkins, Frank; Obregon, Robert

    2017-10-01

    In the power grid transmission where a large amount of energy is transmitted to long distances, High Voltage DC (HVDC) transmission of up to 1MV becomes more attractive since is more efficient than the counterpart AC. However, two of the most difficult problems to solve are the cable connections to the high voltage power sources and their insulation from the ground. The insulating systems are usually composed of transformer oil and solid insulators. The oil behavior under HVDC is similar to that of a weak electrolyte. Its behavior under HVDC is dominated more by conductivity than dielectric constant. Space charge effects in the oil bulk near high voltage electrodes and impeded plastic insulators affect the voltage oil hold-off. We have constructed an experimental facility where we study the oil and plastic insulator behavior in an actual HVDC System. Experimental results will be presented and compared with the present understanding of the physics governing the oil behavior under very high electrical stresses. Sandia National Laboratories managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. D.O.E., NNSA under contract DE-NA-0003525.

  9. Evaluation of undoped ZnS single crystal materials for x-ray imaging applications

    Science.gov (United States)

    Saleh, Muad; Lynn, Kelvin G.; McCloy, John S.

    2017-05-01

    ZnS-based materials have a long history of use as x-ray luminescent materials. ZnS was one of the first discovered scintillators and is reported to have one of the highest scintillator efficiencies. The use of ZnS for high energy luminescence has been thus far limited to thin powder screens, such as ZnS:Ag which is used for detecting alpha radiation, due to opacity to its scintillation light, primarily due to scattering. ZnS in bulk form (chemical vapor deposited, powder processed, and single crystal) has high transmission and low scattering compared to powder screens. In this paper, the performance of single crystalline ZnS is evaluated for low energy x-ray (PLE) of several undoped ZnS single crystals is compared to their Radioluminescence (RL) spectra. It was found that the ZnS emission wavelength varies on the excitation source energy.

  10. Avoiding vacuum arcs in high gradient normal conducting RF structures

    CERN Document Server

    Sjøbæk, Kyrre Ness; Adli, Erik; Grudiev, Alexej; Wuensch, Walter

    In order to build the Compact LInear Collider (CLIC), accelerating structures reaching extremely high accelerating gradients are needed. Such structures have been built and tested using normal-conducting copper, powered by X-band RF power and reaching gradients of 100 MV/m and above. One phenomenon that must be avoided in order to reliably reach such gradients, is vacuum arcs or “breakdowns”. This can be accomplished by carefully designing the structure geometry such that high surface fields and large local power flows are avoided. The research presented in this thesis presents a method for optimizing the geometry of accelerating structures so that these breakdowns are made less likely, allowing the structure to operate reliably at high gradients. This was done primarily based on a phenomenological scaling model, which predicted the maximum gradient as a function of the break down rate, pulse length, and field distribution in the structure. The model is written in such a way that it allows direct comparis...

  11. Conduction cooled high temperature superconducting dipole magnet for accelerator applications

    DEFF Research Database (Denmark)

    Zangenberg, N.; Nielsen, G.; Hauge, N.

    2012-01-01

    A 3T proof-of-principle dipole magnet for accelerator applications, based on 2nd generation high temperature superconducting tape was designed, built, and tested by a consortium under the lead of Danfysik. The magnet was designed to have a straight, circular bore with a good field region of radius...... = 25 mm, and a magnetic length of 250 mm. A total length of 2.5 km YBCO-based copper stabilized conductor supplied by SuperPower Inc., NY, USA, was isolated with 0.025 mm of epoxy and subsequently wound into 14 saddle coils and 4 racetrack coils with a cosine theta like configuration. The coils were......-liquid free operation of an HTS accelerator magnet was demonstrated. The cold mass support design permits magnet orientation under arbitrary angles. Careful choice of materials in terms of magnetic, heat conducting and mechanical properties resulted in a robust and compact solution which opens up...

  12. Flexible and conductive MXene films and nanocomposites with high capacitance.

    Science.gov (United States)

    Ling, Zheng; Ren, Chang E; Zhao, Meng-Qiang; Yang, Jian; Giammarco, James M; Qiu, Jieshan; Barsoum, Michel W; Gogotsi, Yury

    2014-11-25

    MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti3C2T(x) MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti3C2T(x)/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10(4) S/m in the case of the Ti3C2T(x)/PVA composite film and 2.4 × 10(5) S/m for pure Ti3C2T(x) films. The tensile strength of the Ti3C2T(x)/PVA composites was significantly enhanced compared with pure Ti3C2T(x) or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm(3) for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.

  13. Visible sub-band gap photoelectron emission from nitrogen doped and undoped polycrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Elfimchev, S., E-mail: sergeyel@tx.technion.ac.il; Chandran, M.; Akhvlediani, R.; Hoffman, A.

    2017-07-15

    Highlights: • Nitrogen related centers in diamond film are mainly responsible for visible sub-band-gap photoelectron emission. • The influence of film thickness and substrate on the measured photoelectron emission yields was not found. • Nanocrystalline diamonds have low electron emission yields most likely because of high amount of defects. • Visible sub-band gap photoelectron emission may increase with temperature due to electron trapping/detrapping processes. - Abstract: In this study the origin of visible sub-band gap photoelectron emission (PEE) from polycrystalline diamond films is investigated. The PEE yields as a function of temperature were studied in the wavelengths range of 360–520 nm. Based on the comparison of electron emission yields from diamond films deposited on silicon and molybdenum substrates, with different thicknesses and nitrogen doping levels, we suggested that photoelectrons are generated from nitrogen related centers in diamond. Our results show that diamond film thickness and substrate material have no significant influence on the PEE yield. We found that nanocrystalline diamond films have low electron emission yields, compared to microcrystalline diamond, due to the presence of high amount of defects in the former, which trap excited electrons before escaping into the vacuum. However, the low PEE yield of nanocrystalline diamond films was found to increase with temperature. The phenomenon was explained by the trap assisted photon enhanced thermionic emission (ta-PETE) model. According to the ta-PETE model, photoelectrons are trapped by shallow traps, followed by thermal excitation at elevated temperatures and escape into the vacuum. Activation energies of trap levels were estimated for undoped nanocrystalline, undoped microcrystalline and N-doped diamond films using the Richardson-Dushman equation, which gives 0.13, 0.39 and 0.04 eV, respectively. Such low activation energy of trap levels makes the ta-PETE process very

  14. Preparation of Highly Conductive Yarns by an Optimized Impregnation Process

    Science.gov (United States)

    Amba Sankar, K. N.; Mohanta, Kallol

    2018-03-01

    We report the development of the electrical conductivity in textile yarns through impregnation and post-treatment of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The conductive polymer is deposited on fibers, which fills the gap space within the hierarchical structure of the yarns. Organic nonpolar solvents act as reducing agent to increase the density of PEDOT moieties on the yarns, galvanizing increment in conductivity values. Post-treatment by ethylene glycol transforms the resonance configuration of the conductive moieties of conjugated polymer, which helps in further enhancement of electrical conductivity of the yarns. We have optimized the method in terms of loading and conformal change of the polymer to have a lesser resistance of the coated conductive yarns. The minimum resistance achieved has a value of 77 Ωcm-1. This technique of developing conductivity in conventional yarns enables retaining the flexibility of yarns and feeling of softness which would find suitable␣applications for wearable electronics.

  15. Preparation of Highly Conductive Yarns by an Optimized Impregnation Process

    Science.gov (United States)

    Amba Sankar, K. N.; Mohanta, Kallol

    2017-12-01

    We report the development of the electrical conductivity in textile yarns through impregnation and post-treatment of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The conductive polymer is deposited on fibers, which fills the gap space within the hierarchical structure of the yarns. Organic nonpolar solvents act as reducing agent to increase the density of PEDOT moieties on the yarns, galvanizing increment in conductivity values. Post-treatment by ethylene glycol transforms the resonance configuration of the conductive moieties of conjugated polymer, which helps in further enhancement of electrical conductivity of the yarns. We have optimized the method in terms of loading and conformal change of the polymer to have a lesser resistance of the coated conductive yarns. The minimum resistance achieved has a value of 77 Ωcm-1. This technique of developing conductivity in conventional yarns enables retaining the flexibility of yarns and feeling of softness which would find suitable applications for wearable electronics.

  16. Undoped and doped poly(tetraphenylbenzidine) as sensitive material for an impedimetric nitrogen dioxide gas dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Marr, I.; Moos, R., E-mail: functional.materials@uni-bayreuth.de [Department of Functional Materials, University of Bayreuth, Bayreuth 95440 (Germany); Neumann, K.; Thelakkat, M. [Department of Macromolecular Chemistry I, Applied Functional Polymers, University of Bayreuth, Bayreuth 95440 (Germany)

    2014-09-29

    This article presents a nitrogen dioxide (NO{sub 2}) detecting gas dosimeter based on poly(tetraphenylbenzidine) poly(TPD) as nitrogen oxide (NO{sub x}) sensitive layer. Gas dosimeters are suitable devices to determine reliably low levels of analytes over a long period of time. During NO{sub x} exposure, the analyte molecules are accumulated irreversibly in the sensing layer of the dosimeter enhancing the conductivity of the hole conducting poly(TPD), which can be measured by impedance spectroscopy. Due to their possibility for low cost production by simple printing techniques and very good physical, photochemical, and electrochemical properties, poly(TPD)s are suitable for application in gas dosimeters operated at room temperature. We studied the effect of doping with a Co(III)-complex in combination with a conducting salt on the dosimeter behavior. Compared to the undoped material, a strong influence of the doping can be observed: the conductivity of the sensing material increases significantly, the noise of the signal decreases and an unwanted recovery of the sensor signal can be prevented, leading to a NO{sub x} detection limit <10 ppm.

  17. High conducting oxide--sulfide composite lithium superionic conductor

    Science.gov (United States)

    Liang, Chengdu; Rangasamy, Ezhiylmurugan; Dudney, Nancy J.; Keum, Jong Kahk; Rondinone, Adam Justin

    2017-01-17

    A solid electrolyte for a lithium-sulfur battery includes particles of a lithium ion conducting oxide composition embedded within a lithium ion conducting sulfide composition. The lithium ion conducting oxide composition can be Li.sub.7La.sub.3Zr.sub.2O.sub.12 (LLZO). The lithium ion conducting sulfide composition can be .beta.-Li.sub.3PS.sub.4 (LPS). A lithium ion battery and a method of making a solid electrolyte for a lithium ion battery are also disclosed.

  18. Tuning of undoped ZnO thin film via plasma enhanced atomic layer deposition and its application for an inverted polymer solar cell

    Directory of Open Access Journals (Sweden)

    Mi-jin Jin

    2013-10-01

    Full Text Available We studied the tuning of structural and optical properties of ZnO thin film and its correlation to the efficiency of inverted solar cell using plasma-enhanced atomic layer deposition (PEALD. The sequential injection of DEZn and O2 plasma was employed for the plasma-enhanced atomic layer deposition of ZnO thin film. As the growth temperature of ZnO film was increased from 100 °C to 300 °C, the crystallinity of ZnO film was improved from amorphous to highly ordered (002 direction ploy-crystal due to self crystallization. Increasing oxygen plasma time in PEALD process also introduces growing of hexagonal wurtzite phase of ZnO nanocrystal. Excess of oxygen plasma time induces enhanced deep level emission band (500 ∼ 700 nm in photoluminescence due to Zn vacancies and other defects. The evolution of structural and optical properties of PEALD ZnO films also involves in change of electrical conductivity by 3 orders of magnitude. The highly tunable PEALD ZnO thin films were employed as the electron conductive layers in inverted polymer solar cells. Our study indicates that both structural and optical properties rather than electrical conductivities of ZnO films play more important role for the effective charge collection in photovoltaic device operation. The ability to tune the materials properties of undoped ZnO films via PEALD should extend their functionality over the wide range of advanced electronic applications.

  19. High Thermal Conductivity Functionally Graded Heat Sinks for High Power Packaging Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This NASA SBIR Phase I program proposes the development of a high thermal conductivity (400 W/mK), low coefficient of thermal expansion (7-10 ppm/?K), and light...

  20. Disruption of the Electrical Conductivity of Highly Conductive Poly(3,4-ethylenedioxythiophene) : Poly(styrene sulfonate) by Hypochlorite

    NARCIS (Netherlands)

    Oostra, A. Jolt; Bos, Karel H.W. van den; Blom, Paul W.M.; Michels, Jasper J.

    2013-01-01

    The effect of hypochlorite treatment on the layer thickness and conductivity of a state-of-the-art high conducting poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is investigated as a function of exposure time and hypochlorite concentration. Because of overoxidation by the

  1. Defect induced ferromagnetism in undoped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rainey, K.; Chess, J.; Eixenberger, J.; Tenne, D. A.; Hanna, C. B.; Punnoose, A., E-mail: apunnoos@boisestate.edu [Department of Physics, Boise State University, Boise, Idaho 83725 (United States)

    2014-05-07

    Undoped ZnO nanoparticles (NPs) with size ∼12 nm were produced using forced hydrolysis methods using diethylene glycol (DEG) [called ZnO-I] or denatured ethanol [called ZnO-II] as the reaction solvent; both using Zn acetate dehydrate as precursor. Both samples showed weak ferromagnetic behavior at 300 K with saturation magnetization M{sub s} = 0.077 ± 0.002 memu/g and 0.088 ± 0.013 memu/g for ZnO-I and ZnO-II samples, respectively. Fourier transform infrared (FTIR) spectra showed that ZnO-I nanocrystals had DEG fragments linked to their surface. Photoluminescence (PL) data showed a broad emission near 500 nm for ZnO-II which is absent in the ZnO-I samples, presumably due to the blocking of surface traps by the capping molecules. Intentional oxygen vacancies created in the ZnO-I NPs by annealing at 450 °C in flowing Ar gas gradually increased M{sub s} up to 90 min and x-ray photoelectron spectra (XPS) suggested that oxygen vacancies may have a key role in the observed changes in M{sub s}. Finally, PL spectra of ZnO showed the appearance of a blue/violet emission, attributed to Zn interstitials, whose intensity changes with annealing time, similar to the trend seen for M{sub s}. The observed variation in the magnetization of ZnO NP with increasing Ar annealing time seems to depend on the changes in the number of Zn interstitials and oxygen vacancies.

  2. Evidence for high ionic conductivity in lithium–lanthanum titanate,

    Indian Academy of Sciences (India)

    ion migration and the number of defects at the Li sites. Recent investigations have been shown that tilting of TiO6 octahedra changes the bottle-neck size, which is directly related to the Li. + conductivity (Latie et al. ∗. Author for correspondence (swamydts@yahoo.co.in). 1984; Inaguma et al 1993, 2002; Fourquet et al 1996; ...

  3. Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure

    Directory of Open Access Journals (Sweden)

    Taizoh Sadoh

    2011-03-01

    Full Text Available The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications.

  4. Highly anisotropic electric conductivity in PAN-based carbon nanofibers

    Science.gov (United States)

    Aprojanz, J.; Dreyer, B.; Wehr, M.; Wiegand, J.; Baringhaus, J.; Koch, J.; Renz, F.; Sindelar, R.; Tegenkamp, C.

    2017-12-01

    In addition to the chemical and physical properties of nanostructures their successful utilization for applications is strongly triggered by economic aspects. Electrospinning of nanowires from solution followed by subsequent annealing steps is a comparably cheap technique to fabricate conductive carbon nanofibers (CNF) made from polyacrylonitrile (PAN) molecules in large quantities. In this work, we investigated the microscopic properties of the CNFs with diameters of 100–300 nm by means of Raman and x-ray photoelectron spectroscopy and correlated these results with transport measurements done with a 4-tip STM. In particular, we investigated the effect of fiber alignment and knot densities, which can be controlled by applying constant creep due to stress during the stabilization process. The comparison of the conductivity obtained from single CNFs revealed further that the fiber crossings within the ensemble structure act as scattering centers and proofs that the transport is along the surfaces of the CNFs.

  5. Lattice thermal conductivity of silicate glasses at high pressures

    Science.gov (United States)

    Chang, Y. Y.; Hsieh, W. P.

    2016-12-01

    Knowledge of the thermodynamic and transport properties of magma holds the key to understanding the thermal evolution and chemical differentiation of Earth. The discovery of the remnant of a deep magma ocean above the core mantle boundary (CMB) from seismic observations suggest that the CMB heat flux would strongly depend on the thermal conductivity, including lattice (klat) and radiative (krad) components, of dense silicate melts and major constituent minerals around the region. Recent measurements on the krad of dense silicate glasses and lower-mantle minerals show that krad of dense silicate glasses could be significantly smaller than krad of the surrounding solid mantle phases, and therefore the dense silicate melts would act as a thermal insulator in deep lower mantle. This conclusion, however, remains uncertain due to the lack of direct measurements on the lattice thermal conductivity of silicate melts under relevant pressure-temperature conditions. Besides the CMB, magmas exist in different circumstances beneath the surface of the Earth. Chemical compositions of silicate melts vary with geological and geodynamic settings of the melts and have strong influences on their thermal properties. In order to have a better view of heat transport within the Earth, it is important to study compositional and pressure dependences of thermal properties of silicate melts. Here we report experimental results on lattice thermal conductivities of silicate glasses with basaltic and rhyolitic compositions up to Earth's lower mantle pressures using time-domain thermoreflectance coupled with diamond-anvil cell techniques. This study not only provides new data for the thermal conductivity of silicate melts in the Earth's deep interior, but is crucial for further understanding of the evolution of Earth's complex internal structure.

  6. High Thermal Conductivity of Copper Matrix Composite Coatings with Highly-Aligned Graphite Nanoplatelets.

    Science.gov (United States)

    Simoncini, Alessandro; Tagliaferri, Vincenzo; Ucciardello, Nadia

    2017-10-25

    Nanocomposite coatings with highly-aligned graphite nanoplatelets in a copper matrix were successfully fabricated by electrodeposition. For the first time, the disposition and thermal conductivity of the nanofiller has been evaluated. The degree of alignment and inclination of the filling materials has been quantitatively evaluated by polarized micro-Raman spectroscopy. The room temperature values of the thermal conductivity were extracted for the graphite nanoplatelets by the dependence of the Raman G-peak frequency on the laser power excitation. Temperature dependency of the G-peak shift has been also measured. Most remarkable is the global thermal conductivity of 640 ± 20 W·m -1 ·K -1 (+57% of copper) obtained for the composite coating by the flash method. Our experimental results are accounted for by an effective medium approximation (EMA) model that considers the influence of filler geometry, orientation, and thermal conductivity inside a copper matrix.

  7. High Thermal Conductivity of Copper Matrix Composite Coatings with Highly-Aligned Graphite Nanoplatelets

    Directory of Open Access Journals (Sweden)

    Alessandro Simoncini

    2017-10-01

    Full Text Available Nanocomposite coatings with highly-aligned graphite nanoplatelets in a copper matrix were successfully fabricated by electrodeposition. For the first time, the disposition and thermal conductivity of the nanofiller has been evaluated. The degree of alignment and inclination of the filling materials has been quantitatively evaluated by polarized micro-Raman spectroscopy. The room temperature values of the thermal conductivity were extracted for the graphite nanoplatelets by the dependence of the Raman G-peak frequency on the laser power excitation. Temperature dependency of the G-peak shift has been also measured. Most remarkable is the global thermal conductivity of 640 ± 20 W·m−1·K−1 (+57% of copper obtained for the composite coating by the flash method. Our experimental results are accounted for by an effective medium approximation (EMA model that considers the influence of filler geometry, orientation, and thermal conductivity inside a copper matrix.

  8. High-Conductance Thermal Interfaces Based on Carbon Nanotubes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a novel thermal interface material (TIM) that is based on an array of vertical carbon nanotubes (CNTs) for high heat flux applications. For...

  9. High throughput thermal conductivity of high temperature solid phases: The case of oxide and fluoride perovskites

    CERN Document Server

    van Roekeghem, Ambroise; Oses, Corey; Curtarolo, Stefano; Mingo, Natalio

    2016-01-01

    Using finite-temperature phonon calculations and machine-learning methods, we calculate the mechanical stability of about 400 semiconducting oxides and fluorides with cubic perovskite structures at 0 K, 300 K and 1000 K. We find 92 mechanically stable compounds at high temperatures -- including 36 not mentioned in the literature so far -- for which we calculate the thermal conductivity. We demonstrate that the thermal conductivity is generally smaller in fluorides than in oxides, largely due to a lower ionic charge, and describe simple structural descriptors that are correlated with its magnitude. Furthermore, we show that the thermal conductivities of most cubic perovskites decrease more slowly than the usual $T^{-1}$ behavior. Within this set, we also screen for materials exhibiting negative thermal expansion. Finally, we describe a strategy to accelerate the discovery of mechanically stable compounds at high temperatures.

  10. Highly conductive interwoven carbon nanotube and silver nanowire transparent electrodes

    Directory of Open Access Journals (Sweden)

    Andrew J Stapleton, Rakesh A Afre, Amanda V Ellis, Joe G Shapter, Gunther G Andersson, Jamie S Quinton and David A Lewis

    2013-01-01

    Full Text Available Electrodes fabricated using commercially available silver nanowires (AgNWs and single walled carbon nanotubes (SWCNTs produced sheet resistances in the range 4–24 Ω squ−1 with specular transparencies up to 82 %. Increasing the aqueous dispersibility of SWCNTs decreased the bundle size present in the film resulting in improved SWCNT surface dispersion in the films without compromising transparency or sheet resistance. In addition to providing conduction pathways between the AgNW network, the SWCNTs also provide structural support, creating stable self-supporting films. Entanglement of the AgNWs and SWCNTs was demonstrated to occur in solution prior to deposition by monitoring the transverse plasmon resonance mode of the AgNWs during processing. The interwoven AgNW/SWCNT structures show potential for use in optoelectronic applications as transparent electrodes and as an ITO replacement.

  11. Development of high performance proton-conducting solid electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Linkous, C.A.; Kopitzke, R.W. [Florida Solar Energy Center, Cocoa, FL (United States)

    1998-08-01

    This work seeks to improve the efficiency of fuel cell and electrolyzer operation by developing solid electrolytes that will function at higher temperatures. Two objectives were pursued: (1) determine the mechanism of hydrolytic decomposition of aromatic sulfonic acid ionomers, with the intent of identifying structural weaknesses that can be avoided in future materials; and (2) identify new directions in solid electrolyte development. After evaluating a number of aromatic sulfonates, it became apparent that no common mechanism was going to be found; instead, each polymer had its own sequence of degradation steps, involving some combination of desulfonation and/or chain scission. For electrochemical cell operation at temperatures > 200 C, it will be necessary to develop solid electrolytes that do not require sulfonic acids and do not require water to maintain its conductivity mechanism.

  12. Evidence for high ionic conductivity in lithium–lanthanum titanate

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 36; Issue 6. Evidence ... The analysis of FTIR and Raman spectra of the sample supported tetragonal structure inferred from XRD data. The impedance spectrum of the sample is separated into bulk and grain boundary parts by analysing the impedance data. The high ...

  13. Highly conductive anion exchange membrane for high power density fuel-cell performance.

    Science.gov (United States)

    Ren, Xiaoming; Price, Samuel C; Jackson, Aaron C; Pomerantz, Natalie; Beyer, Frederick L

    2014-08-27

    Anion exchange membrane fuel cells (AEMFCs) are regarded as a new generation of fuel cell technology that has the potential to overcome many obstacles of the mainstream proton exchange membrane fuel cells (PEMFCs) in cost, catalyst stability, efficiency, and system size. However, the low ionic conductivity and poor thermal stability of current anion exchange membranes (AEMs) have been the key factors limiting the performance of AEMFCs. In this study, an AEM made of styrenic diblock copolymer with a quaternary ammonium-functionalized hydrophilic block and a cross-linkable hydrophobic block and possessing bicontinuous phases of a hydrophobic network and hydrophilic conduction paths was found to have high ionic conductivity at 98 mS cm(-1) and controlled membrane swelling with water uptake at 117 wt % at 22 °C. Membrane characterizations and fuel cell tests of the new AEM were carried out together with a commercial AEM, Tokuyama A201, for comparison. The high ionic conductivity and water permeability of the new membrane reported in this study is attributed to the reduced torturosity of the ionic conduction paths, while the hydrophobic network maintains the membrane mechanical integrity, preventing excessive water uptake.

  14. Highly conductive side chain block copolymer anion exchange membranes.

    Science.gov (United States)

    Wang, Lizhu; Hickner, Michael A

    2016-06-28

    Block copolymers based on poly(styrene) having pendent trimethyl styrenylbutyl ammonium (with four carbon ring-ionic group alkyl linkers) or benzyltrimethyl ammonium groups with a methylene bridge between the ring and ionic group were synthesized by reversible addition-fragmentation radical (RAFT) polymerization as anion exchange membranes (AEMs). The C4 side chain polymer showed a 17% increase in Cl(-) conductivity of 33.7 mS cm(-1) compared to the benzyltrimethyl ammonium sample (28.9 mS cm(-1)) under the same conditions (IEC = 3.20 meq. g(-1), hydration number, λ = ∼7.0, cast from DMF/1-propanol (v/v = 3 : 1), relative humidity = 95%). As confirmed by small angle X-ray scattering (SAXS), the side chain block copolymers with tethered ammonium cations showed well-defined lamellar morphologies and a significant reduction in interdomain spacing compared to benzyltrimethyl ammonium containing block copolymers. The chemical stabilities of the block copolymers were evaluated under severe, accelerated conditions, and degradation was observed by (1)H NMR. The block copolymer with C4 side chain trimethyl styrenylbutyl ammonium motifs displayed slightly improved stability compared to that of a benzyltrimethyl ammonium-based AEM at 80 °C in 1 M NaOD aqueous solution for 30 days.

  15. Electrochemical Properties for Co-Doped Pyrite with High Conductivity

    Directory of Open Access Journals (Sweden)

    Yongchao Liu

    2015-09-01

    Full Text Available In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS2. The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. Co in the crystal lattice of FeS2 could change the growth rate of different crystal planes of the crystal particles, which resulted in various polyhedrons with clear faces and sharp outlines. In addition, the electrochemical performance of the doping pyrite in Li/FeS2 batteries was evaluated using the galvanostatic discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the discharge capacity of the doped material (801.8 mAh·g−1 with a doping ratio of 7% was significantly higher than that of the original FeS2 (574.6 mAh·g−1 because of the enhanced conductivity. Therefore, the doping method is potentially effective for improving the electrochemical performance of FeS2.

  16. Thermal Conductivity of Foam Glasses Prepared using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    The increasing focus on better building insulation is important to lower energy consumption. Development of new and improved insulation materials can contribute to solving this problem. Foam glass has a good insulating effect due to its large gas volume (porosity >90 %). It can be produced...... with open or closed pores. If only open pores exist, air is the dominating medium for the insulating effect. However, closed pores make it possible to trap gases inside the foam. The gas can be introduced either chemically, through foaming agents, or physically, by gas compression-decompression at high...... temperatures. By introducing the gas physically it is possible to control composition of both the gas phase and the solid phase of the foam glass. In this work we have prepared foam glasses by physical foaming. Panel glass powder from obsolete televisions was first sintered under a gas pressure of 5-25 MPa...

  17. Metal-insulator transition properties of sputtered silicon-doped and un-doped vanadium dioxide films at terahertz range

    Science.gov (United States)

    Zhang, Huafu; Wu, Zhiming; Niu, Ruihua; Wu, Xuefei; he, Qiong; Jiang, Yadong

    2015-03-01

    Silicon-doped and un-doped vanadium dioxide (VO2) films were synthesized on high-purity single-crystal silicon substrates by means of reactive direct current magnetron sputtering followed by thermal annealing. The structure, morphology and metal-insulator transition properties of silicon-doped VO2 films at terahertz range were measured and compared to those of un-doped VO2 films. X-ray diffraction and scanning electron microscopy indicated that doping the films with silicon significantly affects the preferred crystallographic orientation and surface morphologies (grain size, pores and characteristics of grain boundaries). The temperature dependence of terahertz transmission shows that the transition temperature, hysteresis width and transition sharpness greatly depend on the silicon contents while the transition amplitude was relatively insensitive to the silicon contents. Interestingly, the VO2 film doped with a silicon content of 4.6 at.% shows excellent terahertz switching characteristics, namely a small hysteresis width of 4.5 °C, a giant transmission modulation ratio of about 82% and a relatively low transition temperature of 56.1 °C upon heating. This work experimentally indicates that silicon doping can effectively control not only the surface morphology but also the metal-insulator transition characteristics of VO2 films at terahertz range.

  18. Graphite-high density polyethylene laminated composites with high thermal conductivity made by filament winding

    Directory of Open Access Journals (Sweden)

    W. Lv

    2018-03-01

    Full Text Available The low thermal conductivity of polymers limits their use in numerous applications, where heat transfer is important. The two primary approaches to overcome this limitation, are to mix in other materials with high thermal conductivity, or mechanically stretch the polymers to increase their intrinsic thermal conductivity. Progress along both of these pathways has been stifled by issues associated with thermal interface resistance and manufacturing scalability respectively. Here, we report a novel polymer composite architecture that is enabled by employing typical composites manufacturing method such as filament winding with the twist that the polymer is in fiber form and the filler in form of sheets. The resulting novel architecture enables accession of the idealized effective medium composite behavior as it minimizes the interfacial resistance. The process results in neat polymer and 50 vol% graphite/polymer plates with thermal conductivity of 42 W·m–1·K–1 (similar to steel and 130 W·m–1·K–1 respectively.

  19. Optical and electrical properties of undoped and boron doped zinc oxide synthesized by chemical route

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Snigdha; Basu, Moumita; Roy, Asim, E-mail: 28.asim@gmail.com [Department of Physics, National Institute Technology Silchar, Silchar-788010, Assam (India)

    2015-08-28

    We have synthesized and studied the boron doped ZnO nanostructure thin films. The crystallinity of undoped and boron (B) doped ZnO (BZO) has been studied from XRD results. Using the Debye-Scherrer Formula, the grain size has been evaluated, which was found to decrease with increased doping concentration. The optical and electrical properties of (1, 3, 5 wt%) B-doped ZnO (BZO) has been investigated with reference to the undoped counterpart. The UV-VIS spectroscopic analysis revealed that the transmittance for undoped ZnO is maximum and it decreases with doping up to 3% but increases for 5% BZO. The dark as well as photo current–voltage (I–V) characteristics have been investigated in details and the changes occurred in the I-V characteristics with doping concentration as well as under illumination are also quite significant.

  20. Synthesis and structure of undoped and indium-doped thermoelectric lead telluride nanoparticles

    Science.gov (United States)

    Kadel, Kamal; Kumari, Latha; Wang, Xuewen; Li, Wenzhi; Huang, Jian Yu; Provencio, Paula Polyak

    2014-05-01

    Undoped and indium (In)-doped lead telluride (PbTe) nanostructures were synthesized via solvothermal/hydrothermal route. The crystalline structure of the as-prepared undoped and In-doped PbTe samples was examined by X-ray diffraction (XRD) which indicated the formation of face-centered single-phase cubic crystal. A first principle calculation on indium doping shows that the indium atoms are more likely to replace lead (Pb) rather than to take the interstitial sites. Laser-induced breakdown spectroscopy (LIBS) analysis confirms that indium is incorporated into the PbTe matrix of the indium-doped PbTe samples. The effects of surfactant and synthesis temperature on the structure and morphology of the undoped PbTe were also investigated; it was found that PbTe nanostructures synthesized with the addition of surfactants exhibited uniform shapes and their size increased with the synthesis temperature.

  1. Highly conductive ionic liquids toward high-performance space-lubricating greases.

    Science.gov (United States)

    Fan, Xiaoqiang; Wang, Liping

    2014-08-27

    Although ionic liquids (ILs) as a class of promising materials have a wide range of applications due to the excellent properties, their potential as space lubricants has been not systematically explored. Here two kinds of conductive alkyl imidazolium ILs greases were prepared using 1-hexyl-3-methylimidazolium tetrafluoroborate (LB106) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide (L-F106) as base oil and the polytetrafluoroethylene (PTFE) as thickener, with multiple-alkylated cyclopentane grease (MACs) as a comparison. Their chemical composition and tribological properties were investigated in detail under simulated space environment which is composed of high vacuum, high temperature and irradiation. Results show that the high conductive ILs greases not only possess good adaptive abilities to space environment and thermal stability but also provide excellent friction reducing and antiwear behaviors as well as high load carrying capacities. The unique physicochemical properties are attributed to a combination of special anions and cations, the excellent tribological properties are strongly dependent on a boundary protective film on the rubbing surfaces.

  2. Study on possible correlation of superconductivity with defects and superparamagnetism in undoped AFe2As2 with A =Ca, Sr and Ba

    Science.gov (United States)

    Zhao, Kui; Lv, Bing; Deng, Liangzi; Xue, Yuyi; Chu, Paul; High pressure low temperature lab Team

    2014-03-01

    Extensive studies have been carried out on the induction of bulk superconductivity in the Fe-pnictide 122 system with a Tc up to 38 K through doping and/or pressure. However, non-bulk superconductivity has also been detected unexpectedly in undoped AFe2As2 where A = Ca, Sr, and Ba with Tc = ~12K, ~22K and ~23K, respectively. The reason for the observation remains unknown. Recently, systematic investigation shows that highly anisotropic superconductivity with a Tc up to 49 K and superparamagnetism occur in rare-earth doped Ca122. Further examination reveals slight deviation from the 1:2:2 stoichiometry which correlates closely with the occurrence of non-bulk superconductivity and superparamagnetism in these samples. We have therefore decided to investigate systematically the stoichiometry, defects, magnetism and superconductivity in undoped AFe2As2 single crystals under different synthesis conditions where A = Ca, Sr, and Ba. Results will be presented and discussed.

  3. Synthesis and structure of undoped and indium-doped thermoelectric lead telluride nanoparticles

    OpenAIRE

    Kadel, Kamal; Kumari, Latha; Wang, Xuewen; Li, Wenzhi; Huang, Jian Yu; Provencio, Paula Polyak

    2014-01-01

    Undoped and indium (In)-doped lead telluride (PbTe) nanostructures were synthesized via solvothermal/hydrothermal route. The crystalline structure of the as-prepared undoped and In-doped PbTe samples was examined by X-ray diffraction (XRD) which indicated the formation of face-centered single-phase cubic crystal. A first principle calculation on indium doping shows that the indium atoms are more likely to replace lead (Pb) rather than to take the interstitial sites. Laser-induced breakdown sp...

  4. Increase of the photosensitivity of undoped poly(methylmethacrylate) under UV radiation at 325 nm

    DEFF Research Database (Denmark)

    Sáez-Rodríguez, D.; Nielsen, Kristian; Bang, Ole

    2014-01-01

    In this paper we report, for the first time to our knowledge, an increase of the photosensitivity of a microstructured polymer optical fibre (mPOF) made of undoped PMMA due to applied strain during the fabrication of the gratings. In the work, fibre Bragg gratings (FBGs) have been fabricated...... in undoped PMMA mPOFs with a hexagonal structure of three rings in the inner cladding. Two sets of FBGs were inscribed at two different resonant wavelengths (827 nm and 1562 nm) at different strains using an UV He-Cd laser at 325 nm focused by a lens and scanned over the fibre. We observed an increase...

  5. Novel high refractive index, thermally conductive additives for high brightness white LEDs

    Science.gov (United States)

    Hutchison, Richard Stephen

    In prior works the inclusion of nanoparticle fillers has typically been shown to increase the thermal conductivity or refractive index of polymer nanocomposites separately. High refractive index zirconia nanoparticles have already proved their merit in increasing the optical efficiency of encapsulated light emitting diodes. However, the thermal properties of zirconia-silicone nanocomposites have yet to be investigated. While phosphor-converted light emitting diodes are at the forefront of solid-state lighting technologies for producing white light, they are plagued by efficiency losses due to excessive heating at the semiconductor die and in and around the phosphor particles, as well as photon scattering losses in the phosphor layer. It would then be of great interest if the high refractive index nanoparticles were found to both be capable of increasing the refractive index, thus reducing the optical scattering, and also the thermal conductivity, channeling more heat away from the LED die and phosphors, mitigating efficiency losses from heat. Thermal conductance measurements on unfilled and nanoparticle loaded silicone samples were conducted to quantify the effect of the zirconia nanoparticle loading on silicone nanocomposite thermal conductivity. An increase in thermal conductivity from 0.27 W/mK to 0.49 W/mK from base silicone to silicone with 33.5 wt% zirconia nanoparticles was observed. This trend closely mirrored a basic rule of mixtures prediction, implying a further enhancement in thermal conductivity could be achieved at higher nanoparticle loadings. The optical properties of transparency and light extraction efficiency of these composites were also investigated. While overall the zirconia nanocomposite showed good transparency, there was a slight decrease at the shorter wavelengths with increasing zirconia content. For longer wavelength LEDs, such as green or red, this might not matter, but phosphor-converted white LEDs use a blue LED as the photon source

  6. Extremely high thermal conductivity anisotropy of double-walled carbon nanotubes

    Science.gov (United States)

    Ma, Zhaoji; Guo, Zhengrong; Zhang, Hongwei; Chang, Tienchong

    2017-06-01

    Based on molecular dynamics simulations, we reveal that double-walled carbon nanotubes can possess an extremely high anisotropy ratio of radial to axial thermal conductivities. The mechanism is basically the same as that for the high thermal conductivity anisotropy of graphene layers - the in-plane strong sp2 bonds lead to a very high intralayer thermal conductivity while the weak van der Waals interactions to a very low interlayer thermal conductivity. However, different from flat graphene layers, the tubular structures of carbon nanotubes result in a diameter dependent thermal conductivity. The smaller the diameter, the larger the axial thermal conductivity but the smaller the radial thermal conductivity. As a result, a DWCNT with a small diameter may have an anisotropy ratio of thermal conductivity significantly higher than that for graphene layers. The extremely high thermal conductivity anisotropy allows DWCNTs to be a promising candidate for thermal management materials.

  7. Extremely high thermal conductivity anisotropy of double-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Zhaoji Ma

    2017-06-01

    Full Text Available Based on molecular dynamics simulations, we reveal that double-walled carbon nanotubes can possess an extremely high anisotropy ratio of radial to axial thermal conductivities. The mechanism is basically the same as that for the high thermal conductivity anisotropy of graphene layers - the in-plane strong sp2 bonds lead to a very high intralayer thermal conductivity while the weak van der Waals interactions to a very low interlayer thermal conductivity. However, different from flat graphene layers, the tubular structures of carbon nanotubes result in a diameter dependent thermal conductivity. The smaller the diameter, the larger the axial thermal conductivity but the smaller the radial thermal conductivity. As a result, a DWCNT with a small diameter may have an anisotropy ratio of thermal conductivity significantly higher than that for graphene layers. The extremely high thermal conductivity anisotropy allows DWCNTs to be a promising candidate for thermal management materials.

  8. Combining Proximal and Penetrating Soil Electrical Conductivity Sensors for High Resolution Digital Soil Mapping

    Science.gov (United States)

    Proximal ground conductivity sensors produce high spatial resolution maps that integrate the bulk electrical conductivity (ECa) of the soil profile. Variability in conductivity maps must either be inverted to profile conductivity, or be directly calibrated to profile properties for meaningful interp...

  9. COMBINING PROXIMAL AND PENETRATING CONDUCTIVITY SENSORS FOR HIGH RESOLUTION SOIL MAPPING

    Science.gov (United States)

    Proximal ground conductivity sensors produce a high spatial resolution map that integrates the bulk electrical conductivity (ECa) of the soil profile. Variability in the conductivity map must either be inverted to estimate profile conductivity, or be directly calibrated to soil profile properties fo...

  10. High Thermal Conductivity and High Wear Resistance Tool Steels for cost-effective Hot Stamping Tools

    Science.gov (United States)

    Valls, I.; Hamasaiid, A.; Padré, A.

    2017-09-01

    In hot stamping/press hardening, in addition to its shaping function, the tool controls the cycle time, the quality of the stamped components through determining the cooling rate of the stamped blank, the production costs and the feasibility frontier for stamping a given component. During the stamping, heat is extracted from the stamped blank and transported through the tool to the cooling medium in the cooling lines. Hence, the tools’ thermal properties determine the cooling rate of the blank, the heat transport mechanism, stamping times and temperature distribution. The tool’s surface resistance to adhesive and abrasive wear is also an important cost factor, as it determines the tool durability and maintenance costs. Wear is influenced by many tool material parameters, such as the microstructure, composition, hardness level and distribution of strengthening phases, as well as the tool’s working temperature. A decade ago, Rovalma developed a hot work tool steel for hot stamping that features a thermal conductivity of more than double that of any conventional hot work tool steel. Since that time, many complimentary grades have been developed in order to provide tailored material solutions as a function of the production volume, degree of blank cooling and wear resistance requirements, tool geometries, tool manufacturing method, type and thickness of the blank material, etc. Recently, Rovalma has developed a new generation of high thermal conductivity, high wear resistance tool steel grades that enable the manufacture of cost effective tools for hot stamping to increase process productivity and reduce tool manufacturing costs and lead times. Both of these novel grades feature high wear resistance and high thermal conductivity to enhance tool durability and cut cycle times in the production process of hot stamped components. Furthermore, one of these new grades reduces tool manufacturing costs through low tool material cost and hardening through readily

  11. Tensile and electrical properties of high-strength high-conductivity copper alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J.; Eatherly, W.S. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    Electrical conductivity and tensile properties have been measured on an extruded and annealed CuCrNb dispersion strengthened copper alloy which has been developed for demanding aerospace high heat flux applications. The properties of this alloy are somewhat inferior to GlidCop dispersion strengthened copper and prime-aged CuCrZr over the temperature range of 20--500 C. However, if the property degradation in CuCrZr due to joining operations and the anisotropic properties of GlidCop in the short transverse direction are taken into consideration, CuCrNb may be a suitable alternative material for high heat flux structural applications in fusion energy devices. The electrical conductivity and tensile properties of CuCrZr that was solution annealed and then simultaneously aged and diffusion bonded are also summarized. A severe reduction in tensile elongation is observed in the diffusion bonded joint, particularly if a thin copper shim is not placed in the diffusion bondline.

  12. Origin of donor and acceptor species in undoped ZnSe grown by low-pressure metalorganic chemical vapor deposition

    Science.gov (United States)

    Morimoto, Keizo

    1988-11-01

    Effects of the [H2 Se]/[Dimethylzinc] source ratio on the electrical properties in the temperature range of 15-300 K and on the cathodoluminescence properties at 77 K have been investigated for undoped ZnSe films grown in one deposition run on (100)GaAs substrates at 350 °C by metalorganic chemical vapor deposition. The properties correlated with each other and depended on the degrees of deviation from stoichiometry. The dominant donor is identified with selenium vacancy from the dependence of donor concentration on the ratio and on the film thickness. Two kinds of acceptors were introduced according to the deviation from stoichiometry. They are tentatively associated with NSe and NaZn . Extended lattice defects which reduce the electron mobility are favored at the high ratios and they seem a principal factor of the high-resistive property of this material.

  13. Ion-Irradiation-Induced Ferromagnetism in Undoped ZnO Thin Films

    Science.gov (United States)

    2013-01-01

    suggestions for reducing this burden, to Washington Headquarters Services , Directorate for Information Operations and Reports, 1215 Jefferson Davis...ments extensively on doped and undoped ZnO thin films using both (i) a vibrating sample magnetometer ( VSM ) in conjunction with a physical property

  14. Dielectric properties of solution-grown-undoped and acrylic-acid ...

    Indian Academy of Sciences (India)

    Dielectric capacities and losses were measured, in the temperature (50–170°C) and frequency (01–100 kHz range), for undoped and acrylic acid (AA) doped ethyl cellulose (EC) films (thickness about 20 m) with progressive increase in the concentration of dopant in the polymer matrix. The variation of capacity with ...

  15. Highly conductive ultrathin Co films by high-power impulse magnetron sputtering

    Science.gov (United States)

    Jablonka, L.; Riekehr, L.; Zhang, Z.; Zhang, S.-L.; Kubart, T.

    2018-01-01

    Ultrathin Co films deposited on SiO2 with conductivities exceeding that of Cu are demonstrated. Ionized deposition implemented by high-power impulse magnetron sputtering (HiPIMS) is shown to result in smooth films with large grains and low resistivities, namely, 14 µΩ cm at a thickness of 40 nm, which is close to the bulk value of Co. Even at a thickness of only 6 nm, a resistivity of 35 µΩ cm is obtained. The improved film quality is attributed to a higher nucleation density in the Co-ion dominated plasma in HiPIMS. In particular, the pulsed nature of the Co flux as well as shallow ion implantation of Co into SiO2 can increase the nucleation density. Adatom diffusion is further enhanced in the ionized process, resulting in a dense microstructure. These results are in contrast to Co deposited by conventional direct current magnetron sputtering where the conductivity is reduced due to smaller grains, voids, rougher interfaces, and Ar incorporation. The resistivity of the HiPIMS films is shown to be in accordance with models by Mayadas-Shatzkes and Sondheimer which consider grain-boundary and surface-scattering.

  16. New perspectives for undoped CaF2 scintillator as a threshold activation neutron detector

    Directory of Open Access Journals (Sweden)

    Sibczynski Pawel

    2018-01-01

    Full Text Available In this paper we present the prompt photofission neutron detection performance of undoped CaF2 scintillator using Threshold Activation Detection (TAD. The study is carried out in the frame of C-BORD Horizon 2020 project, during which an efficient toolbox for high volume freight non-intrusive inspection (NII is under development. Technologies for radiation monitoring are the part of the project. Particularly, detection of various radiological threats on country borders plays an important significant role in Homeland Security applications. Detection of illegal transfer of Special Nuclear Material (SNM - 235U, 233U and 239Pu - is particular due to the potential use for production of nuclear weapon as well as radiological dispersal device (RDD V known also as a “dirty bomb”. This technique relies on activation of 19F nuclei in the scintillator medium by fast neutrons and registration of high-energy β particles and γ-rays from the decay of reaction products. The radiation from SNM is detected after irradiation in order to avoid detector blinding. Despite the low 19F(n,α16N or 19F(n,p19O reaction cross-section, the method could be a good solution for detection of shielded nuclear material. Results obtained with the CaF2 detector were compared with the previous study done for BaF2 and 3He detector. These experimental results were obtained using 252Cf source and 9 MeV Varian Linatron M9 linear accelerator (LINAC. Finally, performance of the prompt neutron detection system based on CaF2 will be validated at Rotterdam Seaport during field trails in 2018.

  17. Free-Standing Undoped ZnO Microtubes with Rich and Stable Shallow Acceptors.

    Science.gov (United States)

    Wang, Qiang; Yan, Yinzhou; Zeng, Yong; Lu, Yue; Chen, Liang; Jiang, Yijian

    2016-06-06

    Fabrication of reliable large-sized p-ZnO is a major challenge to realise ZnO-based electronic device applications. Here we report a novel technique to grow high-quality free-standing undoped acceptor-rich ZnO (A-ZnO) microtubes with dimensions of ~100 μm (in diameter) × 5 mm (in length) by optical vapour supersaturated precipitation. The A-ZnO exhibits long lifetimes (>1 year) against compensation/lattice-relaxation and the stable shallow acceptors with binding energy of ~127 meV are confirmed from Zn vacancies. The A-ZnO provides a possibility for a mimetic p-n homojunction diode with n(+)-ZnO:Sn. The high concentrations of holes in A-ZnO and electrons in n(+)-ZnO make the dual diffusion possible to form a depletion layer. The diode threshold voltage, turn-on voltage, reverse saturated current and reverse breakdown voltage are 0.72 V, 1.90 V, 15 V, respectively. The A-ZnO also demonstrates quenching-free donor-acceptor-pairs (DAP) emission located in 390-414 nm with temperature of 270-470 K. Combining the temperature-dependent DAP violet emission with native green emission, the visible luminescence of A-ZnO microtube can be modulated in a wide region of colour space across white light. The present work opens up new opportunities to achieve ZnO with rich and stable acceptors instead of p-ZnO for a variety of potential applications.

  18. New perspectives for undoped CaF2 scintillator as a threshold activation neutron detector

    Science.gov (United States)

    Sibczynski, Pawel; Dziedzic, Andrzej; Grodzicki, Krystian; Iwanowska-Hanke, Joanna; Moszyński, Marek; Swiderski, Lukasz; Syntfeld-Każuch, Agnieszka; Wolski, Dariusz; Carrel, Frédérick; Grabowski, Amélie; Hamel, Matthieu; Laine, Frederic; Sari, Adrien; Iovene, Alessandro; Tintori, Carlo; Fontana, Cristiano; Pino, Felix

    2018-01-01

    In this paper we present the prompt photofission neutron detection performance of undoped CaF2 scintillator using Threshold Activation Detection (TAD). The study is carried out in the frame of C-BORD Horizon 2020 project, during which an efficient toolbox for high volume freight non-intrusive inspection (NII) is under development. Technologies for radiation monitoring are the part of the project. Particularly, detection of various radiological threats on country borders plays an important significant role in Homeland Security applications. Detection of illegal transfer of Special Nuclear Material (SNM) - 235U, 233U and 239Pu - is particular due to the potential use for production of nuclear weapon as well as radiological dispersal device (RDD) V known also as a "dirty bomb". This technique relies on activation of 19F nuclei in the scintillator medium by fast neutrons and registration of high-energy β particles and γ-rays from the decay of reaction products. The radiation from SNM is detected after irradiation in order to avoid detector blinding. Despite the low 19F(n,α)16N or 19F(n,p)19O reaction cross-section, the method could be a good solution for detection of shielded nuclear material. Results obtained with the CaF2 detector were compared with the previous study done for BaF2 and 3He detector. These experimental results were obtained using 252Cf source and 9 MeV Varian Linatron M9 linear accelerator (LINAC). Finally, performance of the prompt neutron detection system based on CaF2 will be validated at Rotterdam Seaport during field trails in 2018.

  19. Highly Conductive Aromatic Functionalized Multi-Walled Carbon Nanotube for Inkjet Printable High Performance Supercapacitor Electrodes.

    Directory of Open Access Journals (Sweden)

    Sanjeev K Ujjain

    Full Text Available We report the functionalization of multiwalled carbon nanotubes (MWCNT via the 1,3-dipolar [3+2] cycloaddition of aromatic azides, which resulted in a detangled CNT as shown by transmission electron microscopy (TEM. Carboxylic moieties (-COOH on aromatic azide result in highly stable aqueous dispersion (max. conc. ~ 10 mg/mL H2O, making the suitable for inkjet printing. Printed patterns on polyethylene terephthalate (PET flexible substrate exhibit low sheet resistivity ~65 Ω. cm, which is attributed to enhanced conductivity. Fabricated Supercapacitors (SC assembled using these printed substrates exhibit good electrochemical performance in organic as well as aqueous electrolytes. High energy and power density (57.8 Wh/kg and 0.85 kW/kg in 1M H2SO4 aqueous electrolyte demonstrate the excellent performance of the proposed supercapacitor. Capacitive retention varies from ~85-94% with columbic efficiency ~95% after 1000 charge/discharge cycles in different electrolytes, demonstrating the excellent potential of the device for futuristic power applications.

  20. Design of instantaneous liquid film thickness measurement system for conductive or non-conductive fluid with high viscosity

    Directory of Open Access Journals (Sweden)

    Yongxin Yu

    2017-06-01

    Full Text Available In the paper, a new capacitive sensor with a dielectric film coating was designed to measure the thickness of the liquid film on a flat surface. The measured medium can be conductive or non-conductive fluid with high viscosity such as silicone oil, syrup, CMC solution and melt. With the dielectric film coating, the defects caused by the humidity in a capacitor can be avoided completely. With a excitation frequency 0-20kHz, the static permittivity of capacitive sensor is obtained and stable when small thicknesses are monitored within the frequency of 0-3kHz. Based on the measurement principle, an experimental system was designed and verified including calibration and actual measurement for different liquid film thickness. Experimental results showed that the sensitivity, the resolution, repeatability and linear range of the capacitive sensor are satisfied to the liquid film thickness measurement. Finally, the capacitive measuring system was successfully applied to the water, silicone oil and syrup film thickness measurement.

  1. High Transparent Conductive Aluminum-Doped Zinc Oxide Thin Films by Reactive Co-Sputtering (Postprint)

    Science.gov (United States)

    2016-03-30

    AFRL-RX-WP-JA-2017-0144 HIGH TRANSPARENT CONDUCTIVE ALUMINUM- DOPED ZINC OXIDE THIN FILMS BY REACTIVE CO- SPUTTERING (POSTPRINT...TRANSPARENT CONDUCTIVE ALUMINUM-DOPED ZINC OXIDE THIN FILMS BY REACTIVE CO-SPUTTERING (POSTPRINT) 5a. CONTRACT NUMBER FA8650-16-D-5402-0001 5b. GRANT...ANSI Std. Z39-18 TD.11.pdf Optical Interference Coatings (OIC) 2016 © OSA 2016 1 High Transparent Conductive Aluminum-doped Zinc Oxide Thin

  2. Directly patternable, highly conducting polymers for broad applications in organic electronics.

    Science.gov (United States)

    Yoo, Joung Eun; Lee, Kwang Seok; Garcia, Andres; Tarver, Jacob; Gomez, Enrique D; Baldwin, Kimberly; Sun, Yangming; Meng, Hong; Nguyen, Thuc-Quyen; Loo, Yueh-Lin

    2010-03-30

    Postdeposition solvent annealing of water-dispersible conducting polymers induces dramatic structural rearrangement and improves electrical conductivities by more than two orders of magnitude. We attain electrical conductivities in excess of 50 S/cm when polyaniline films are exposed to dichloroacetic acid. Subjecting commercially available poly(ethylene dioxythiophene) to the same treatment yields a conductivity as high as 250 S/cm. This process has enabled the wide incorporation of conducting polymers in organic electronics; conducting polymers that are not typically processable can now be deposited from solution and their conductivities subsequently enhanced to practical levels via a simple and straightforward solvent annealing process. The treated conducting polymers are thus promising alternatives for metals as source and drain electrodes in organic thin-film transistors as well as for transparent metal oxide conductors as anodes in organic solar cells and light-emitting diodes.

  3. Sintering and annealing effects on undoped yttria transparent ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Letue, Laetitia; Petit, Johan, E-mail: johan.petit@onera.fr; Ritti, Marie-Hélène; Lalanne, Sylvie; Landais, Stéphane

    2017-06-15

    Transparent yttrium oxide (Y{sub 2}O{sub 3}) ceramics were processed by several densifications steps without any doping species. The green bodies were obtained by the aqueous way and sintered at high temperature under vacuum and then under high pressure. We studied the effects of different sintering cycles and air annealing at different steps of the process on the density and the grain growth. We also focused on the reaction between yttria ceramics and BN-coated graphite crucible which occurs during HIP. We noted that a low heating rate and two annealing steps are necessary to improve our samples’ transparency. - Highlights: • The quality of transparent ceramics is compared with the tested process parameters. • Air annealing is critical when using a carbon environment in the process. • Intra-granular pores, and so the final transparency, are directly linked to the sintering heating rates.

  4. An overview of high thermal conductive hot press forming die material development

    Directory of Open Access Journals (Sweden)

    A.R. Zulhishamuddin

    2015-12-01

    Full Text Available Most of the automotive industries are using high strength steel components, which are produced via hot press forming process. This process requires die material with high thermal conductivity that increases cooling rate during simultaneous quenching and forming stage. Due to the benefit of high quenching rate, thermal conductive die materials were produced by adding carbide former elements. This paper presents an overview of the modification of alloying elements in tool steel for high thermal conductivity properties by transition metal elements addition. Different types of manufacturing processes involved in producing high thermal conductive materials were discussed. Methods reported were powder metallurgy hot press, direct metal deposition, selective laser melting, direct metal laser sintering and spray forming. Elements likes manganese, nickel, molybdenum, tungsten and chromium were proven to increase thermal conductivity properties. Thermal conductivity properties resulted from carbide network presence in the steel microstructure. To develop feasible and low cost hot press forming die material, casting of Fe-based alloy with carbide former composition can be an option. Current thermal conductivity properties of hot press forming die material range between 25 and 66 W/m.K. The wide range of thermal conductivity varies the mechanical properties of the resulting components and lifetime of HPF dies.

  5. Liquid Phase Synthesis of CoP Nanoparticles with High Electrical Conductivity for Advanced Energy Storage

    Directory of Open Access Journals (Sweden)

    Guo-Qun Zhang

    2017-01-01

    Full Text Available Transition metal phosphide alloys possess the metalloid characteristics and superior electrical conductivity and are a kind of high electrical conductive pseudocapacitive materials. Herein, high electrical conductive cobalt phosphide alloys are fabricated through a liquid phase process and a nanoparticles structure with high surface area is obtained. The highest specific capacitance of 286 F g−1 is reached at a current density of 0.5 A g−1. 63.4% of the specific capacitance is retained when the current density increased 16 times and 98.5% of the specific capacitance is maintained after 5000 cycles. The AC//CoP asymmetric supercapacitor also shows a high energy density (21.3 Wh kg−1 and excellent stability (97.8% of the specific capacitance is retained after 5000 cycles. The study provides a new strategy for the construction of high-performance energy storage materials by enhancing their intrinsic electrical conductivity.

  6. Spectroscopic studies of undoped and Mn2+-doped calcium borophosphate phosphor (CaBP) nanopowders

    Science.gov (United States)

    Yadav, M. R.; Raja, B. J.; Manjari, V. P.; Avinash, M.; Krishna, C. R.; Ravikumar, R. V. S. S. N.

    2016-02-01

    Undoped and Mn2+-doped Ca6BP5O20 nanopowders (CaBP) have been prepared by modified solid-state synthesis and characterized by spectroscopic investigations like X-ray diffraction (XRD), field emission scanning electron microscope with EDX, optical absorption, electron paramagnetic resonance, photoluminescence and Fourier transform infrared spectroscopy. From powder XRD patterns, the crystal structure is confirmed to be triclinic. Unit cell parameters, average crystal size, strain and dislocation densities have been calculated by using powder XRD data. Field emission scanning electron micrograph with EDX images, taken at different magnifications, shows that the prepared samples contain Ca, B, P, O, Mn species and micrographs exhibit irregular shaped spheres with agglomeration. By using optical absorption and electron paramagnetic resonance data, crystal field, inter-electronic repulsion and spin-Hamiltonian parameters have been evaluated. The site symmetry of Mn2+ ions is ascribed as octahedral sites with ligands. Fourier transform infrared spectra show the specific vibrations of phosphate and inorganic molecules. Photoluminescence spectra of undoped and Mn2+-doped CaBP nanopowders exhibit pale yellow to white emission under the excitation wavelength of 325 nm. The CIE chromaticity coordinates have been also calculated from emission spectrum for undoped and Mn2+-doped CaBP nanopowders.

  7. Oxidant-Dependent Thermoelectric Properties of Undoped ZnO Films by Atomic Layer Deposition

    KAUST Repository

    Kim, Hyunho

    2017-02-27

    Extraordinary oxidant-dependent changes in the thermoelectric properties of undoped ZnO thin films deposited by atomic layer deposition (ALD) have been observed. Specifically, deionized water and ozone oxidants are used in the growth of ZnO by ALD using diethylzinc as a zinc precursor. No substitutional atoms have been added to the ZnO films. By using ozone as an oxidant instead of water, a thermoelectric power factor (σS) of 5.76 × 10 W m K is obtained at 705 K for undoped ZnO films. In contrast, the maximum power factor for the water-based ZnO film is only 2.89 × 10 W m K at 746 K. Materials analysis results indicate that the oxygen vacancy levels in the water- and ozone-grown ZnO films are essentially the same, but the difference comes from Zn-related defects present in the ZnO films. The data suggest that the strong oxidant effect on thermoelectric performance can be explained by a mechanism involving point defect-induced differences in carrier concentration between these two oxides and a self-compensation effect in water-based ZnO due to the competitive formations of both oxygen and zinc vacancies. This strong oxidant effect on the thermoelectric properties of undoped ZnO films provides a pathway to improve the thermoelectric performance of this important material.

  8. Interactions of gamma rays with undoped and Mn-doped sodium phosphate glasses

    Science.gov (United States)

    ElBatal, Fatma H.; Ouis, Mona A.; Morsi, Reham M.; Marzouk, Samir Y.

    2010-07-01

    Ultraviolet and visible spectroscopic measurements were used to investigate prepared undoped and Mn-doped sodium phosphate glasses before and after successive gamma irradiation. The effects of both glass composition and MnO2 content on the generation of radiation-induced defects were investigated. Undoped sodium phosphate glass shows strong UV absorption, which is attributed to the presence of trace iron impurities present in the raw materials. Mn-doped glasses reveal an additional visible broad band centered at about 500 nm due to Mn3+, which has recently been related to the 5Eg →5T2g transition. The radiation-induced bands are correlated with the generation of liberated electron-hole pairs during the process of gamma irradiation and the possibility of photochemical reactions especially with trace iron impurities and manganese ions. The intensity and the position of the induced bands are observed to depend on the type and composition of glass, concentration of the dopant and also on the irradiation dose. Manganese ions when present in relatively higher content have been found to show a shielding behavior towards the effects of progressive gamma irradiation causing a retardation of the growth of the induced defects. Infrared and Raman spectra of the undoped and Mn-doped glasses were measured to investigate the structural phosphate groups present and the effect of MnO2 on the network structure. An ESR investigation was carried out to confirm the state of manganese ions in the prepared sodium phosphate glasses.

  9. Electrical conductivity of molten SnCl{sub 2} at temperature as high as 1314 K

    Energy Technology Data Exchange (ETDEWEB)

    Salyulev, Alexander B.; Potapov, Alexei M. [Ural Branch of RAS, Ekaterinburg (Russian Federation). Inst. of High-Temperature Electrochemistry

    2015-07-01

    The electrical conductivity of molten SnCl{sub 2} was measured in a wide temperature range (ΔT=763 K), from 551 K to temperature as high as 1314 K, that is, 391 above the boiling point of the salt. The specific electrical conductance was found to reach its maximum at 1143 K, after that it decreases with the temperature rising.

  10. A Simplified Method for Upscaling Composite Materials with High Contrast of the Conductivity

    KAUST Repository

    Ewing, R.

    2009-01-01

    A large class of industrial composite materials, such as metal foams, fibrous glass materials, mineral wools, and the like, are widely used in insulation and advanced heat exchangers. These materials are characterized by a substantial difference between the thermal properties of the highly conductive materials (glass or metal) and the insulator (air) as well as low volume fractions and complex network-like structures of the highly conductive components. In this paper we address the important issue for the engineering practice of developing fast, reliable, and accurate methods for computing the macroscopic (upscaled) thermal conductivities of such materials. We assume that the materials have constant macroscopic thermal conductivity tensors, which can be obtained by upscaling techniques based on the postprocessing of a number of linearly independent solutions of the steady-state heat equation on representative elementary volumes (REVs). We propose, theoretically justify, and computationally study a numerical method for computing the effective conductivities of materials for which the ratio δ of low and high conductivities satisfies δ ≪ 1. We show that in this case one needs to solve the heat equation in the region occupied by the highly conductive media only. Further, we prove that under certain conditions on the microscale geometry the proposed method gives an approximation that is O(δ)-close to the upscaled conductivity. Finally, we illustrate the accuracy and the limitations of the method on a number of numerical examples. © 2009 Society for Industrial and Applied Mathematics.

  11. First-principles calculation of thermal conductivity of silicate perovskite at high pressures and high temperatures

    Science.gov (United States)

    Dong, Jianjun; Tang, Xiaoli; Kavner, Abby; Ntam, Moses

    2011-03-01

    The lattice thermal conductivity of silicate perovskite, the most abundant mineral in the Earth's lower mantle, is calculated by combining the first-principles electronic structure theory and Peierls-Boltzmann transport theory. The phonon scattering rate due to lattice anharmonicity and Mg/Fe mass disorder is evaluated for each mode at the extreme P-T conditions of the lower mantle. The predicted thermal conductivity of single crystal MgSiO3 perovskite at ambient condition, about 5.7 W/m/K, is in excellent agreement with experiment. Adding about 6% Fe will lower the thermal conductivity by nearly 40%. Our calculation also reveals an unique pressure dependence for the thermal conductivity of perovskite, and the calculated thermal conductivity of iron bearing perovskite is almost an order of magnitude lower than the previously estimates based on long extrapolation of single crystal data. Including a re-evaluation of radiative contribution, we discuss the implications of our results for the heat flow in deep Earth. Funded by NSF (EAR-0757847).

  12. CTE-Matched, Liquid-Cooled, High Thermal Conductivity Heat Sink Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose the development of a CTE-matched, liquid-cooled, high thermal conductivity heat sink for use in spacecraft thermal management applications. The material...

  13. Irregular Firing and High-Conductance States in Spinal Motoneurons during Scratching and Swimming

    DEFF Research Database (Denmark)

    Guzulaitis, Robertas; Hounsgaard, Jorn; Alaburda, Aidas

    2016-01-01

    in general. Here we compare conductance and firing patterns in spinal motoneurons during network activity for scratching and swimming in an ex vivo carapace-spinal cord preparation from adult turtles (Trachemys scripta elegans). The pattern and relative engagement of motoneurons are distinctly different...... of spinal motor network activity. SIGNIFICANCE STATEMENT: Neurons embedded in active neural networks can enter high-conductance states with irregular firing. This was previously shown for spinal motoneurons during scratching. Because scratching is highly specialized rhythmic behavior, it is not known...... whether high-conductance states and irregular firing are a peculiarity for motoneurons during scratching. Here, using intracellular recordings from motoneurons in an ex vivo carapace-spinal cord preparation from adult turtles, we demonstrate that irregular firing and high-conductance states are present...

  14. Highly conductive graphene by low-temperature thermal reduction and in situ preparation of conductive polymer nanocomposites.

    Science.gov (United States)

    Yang, Liping; Kong, Junhua; Yee, Wu Aik; Liu, Wanshuang; Phua, Si Lei; Toh, Cher Ling; Huang, Shu; Lu, Xuehong

    2012-08-21

    Polydopamine-coated graphene oxide (DGO) films exhibit electrical conductivities of 11,000 S m(-1) and 30,000 S m(-1) upon vacuum annealing at 130 °C and 180 °C, respectively. Conductive poly(vinyl alcohol)/graphene and epoxy/graphene nanocomposites show low percolation thresholds due to the excellent dispersibility of the DGO sheets and their effective in situ reduction.

  15. NanoCapillary Network Proton Conducting Membranes for High Temperature Hydrogen/Air Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Pintauro, Peter [Vanderbilt Univ., Nashville, TN (United States)

    2012-07-09

    The objective of this proposal is to fabricate and characterize a new class of NanoCapillary Network (NCN) proton conducting membranes for hydrogen/air fuel cells that operate under high temperature, low humidity conditions. The membranes will be intelligently designed, where a high density interconnecting 3-D network of nm-diameter electrospun proton conducting polymer fibers is embedded in an inert (uncharged) water/gas impermeable polymer matrix. The high density of fibers in the resulting mat and the high ion-exchange capacity of the fiber polymer will ensure high proton conductivity. To further enhance water retention, molecular silica will be added to the sulfonated polymer fibers. The uncharged matrix material will control water swelling of the high ion-exchange capacity proton conducting polymer fibers and will impart toughness to the final nanocapillary composite membrane. Thus, unlike other fuel cell membranes, the role of the polymer support matrix will be decoupled from that of the proton-conducting channels. The expected final outcome of this 5-year project is the fabrication of fuel cell membranes with properties that exceed the DOE’s technical targets, in particular a proton conductivity of 0.1 S/cm at a temperature less than or equal to120°C and 25-50% relative humidity.

  16. Conductivity of SrTiO3 based oxides in the reducing atmosphere at high temperature

    DEFF Research Database (Denmark)

    Hashimoto, Shin-Ichi; Poulsen, Finn Willy; Mogensen, Mogens Bjerg

    2007-01-01

    The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 degrees C in 9% H-2/N-2, even after 100 h. Nb-doped SrTiO3 showed relatively...... at 500-800 degrees C, while that of La-doped SrTiO3 dropped immediately on exposure to air. The conduction behavior of Nb-doped SrTiO3 was explained by reduction of Ti4+ and/or Nb5+ and the relatively slow oxygen diffusibility. (c) 2006 Elsevier B.V. All rights reserved.......The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 degrees C in 9% H-2/N-2, even after 100 h. Nb-doped SrTiO3 showed relatively...... fast reduction and high conductivity compared with the other SrTiO3 based oxides. The conductivity of Nb-doped SrTiO3 was ca. 50 S cm(-1) at 500 degrees C after reduction at 1200 degrees C. After strong reduction, the conductivity of Nb-doped SrTiO3 was almost independent of the oxygen partial pressure...

  17. Surprisingly High Conductivity and Efficient Exciton Blocking in Fullerene/Wide-Energy-Gap Small Molecule Mixtures.

    Science.gov (United States)

    Bergemann, Kevin J; Amonoo, Jojo A; Song, Byeongseop; Green, Peter F; Forrest, Stephen R

    2015-06-10

    We find that mixtures of C60 with the wide energy gap, small molecular weight semiconductor bathophenanthroline (BPhen) exhibit a combination of surprisingly high electron conductivity and efficient exciton blocking when employed as buffer layers in organic photovoltaic cells. Photoluminescence quenching measurements show that a 1:1 BPhen/C60 mixed layer has an exciton blocking efficiency of 84 ± 5% compared to that of 100% for a neat BPhen layer. This high blocking efficiency is accompanied by a 100-fold increase in electron conductivity compared with neat BPhen. Transient photocurrent measurements show that charge transport through a neat BPhen buffer is dispersive, in contrast to nondispersive transport in the compound buffer. Interestingly, although the conductivity is high, there is no clearly defined insulating-to-conducting phase transition with increased insulating BPhen fraction. Thus, we infer that C60 undergoes nanoscale (80%) BPhen fractions.

  18. Protection of Conductive and Non-conductive Advanced Polymer-based Paints from Highly Aggressive Oxidative Environments

    Science.gov (United States)

    Gudimenko, Y.; Ng, R.; Iskanderova, Z.; Kleiman, J.; Grigorevsky, A.; Kiseleva, L.; Finckenor, M.; Edwards, D.

    2005-01-01

    Research has been continued to further improve the space durability of conductive and non-conductive polymer-based paints and of conductive thermal control paints for space applications. Efforts have been made to enhance the space durability and stability of functional Characteristics in ground-based space environment imitating conditions, using specially developed surface modification treatment. The results of surface modification of new conductive paints, including the ground-based testing in aggressive oxidative environments, such as atomic oxygen/UV and oxygen plasma, and performance evaluation are presented. Functional properties and performance characteristics, such as thermal optical properties (differential solar absorptance and thermal emittance representing the thermal optical performance of thermal control paints) and surface resistivity characteristics of pristine, surface modified, and tested materials were verified. Extensive surface analysis studies have been performed using complementary surface analyses including SEM/EDS and XPS. Test results revealed that the successfully treated materials exhibit reduced mass loss and no surface morphology change, thus indicating good protection from the severe oxidative environment. It was demonstrated that the developed surface modification treatment could be applied successfully to charge dissipative and conductive paints.

  19. Thermal Properties and Phonon Spectral Characterization of Synthetic Boron Phosphide for High Thermal Conductivity Applications.

    Science.gov (United States)

    Kang, Joon Sang; Wu, Huan; Hu, Yongjie

    2017-12-13

    Heat dissipation is an increasingly critical technological challenge in modern electronics and photonics as devices continue to shrink to the nanoscale. To address this challenge, high thermal conductivity materials that can efficiently dissipate heat from hot spots and improve device performance are urgently needed. Boron phosphide is a unique high thermal conductivity and refractory material with exceptional chemical inertness, hardness, and high thermal stability, which holds high promises for many practical applications. So far, however, challenges with boron phosphide synthesis and characterization have hampered the understanding of its fundamental properties and potential applications. Here, we describe a systematic thermal transport study based on a synergistic synthesis-experimental-modeling approach: we have chemically synthesized high-quality boron phosphide single crystals and measured their thermal conductivity as a record-high 460 W/mK at room temperature. Through nanoscale ballistic transport, we have, for the first time, mapped the phonon spectra of boron phosphide and experimentally measured its phonon mean free-path spectra with consideration of both natural and isotope-pure abundances. We have also measured the temperature- and size-dependent thermal conductivity and performed corresponding calculations by solving the three-dimensional and spectral-dependent phonon Boltzmann transport equation using the variance-reduced Monte Carlo method. The experimental results are in good agreement with that predicted by multiscale simulations and density functional theory, which together quantify the heat conduction through the phonon mode dependent scattering process. Our finding underscores the promise of boron phosphide as a high thermal conductivity material for a wide range of applications, including thermal management and energy regulation, and provides a detailed, microscopic-level understanding of the phonon spectra and thermal transport mechanisms of

  20. Development of high pressure-high vacuum-high conductance piston valve for gas-filled radiation detectors

    Science.gov (United States)

    Prasad, D. N.; Ayyappan, R.; Kamble, L. P.; Singh, J. P.; Muralikrishna, L. V.; Alex, M.; Balagi, V.; Mukhopadhyay, P. K.

    2008-05-01

    Gas-filled radiation detectors need gas filling at pressures that range from few cms of mercury to as high as 25kg/cm2 at room temperature. Before gas-filling these detectors require evacuation to a vacuum of the order of ~1 × 10-5 mbar. For these operations of evacuation and gas filling a system consisting of a vacuum pump with a high vacuum gauge, gas cylinder with a pressure gauge and a valve is used. The valve has to meet the three requirements of compatibility with high-pressure and high vacuum and high conductance. A piston valve suitable for the evacuation and gas filling of radiation detectors has been designed and fabricated to meet the above requirements. The stainless steel body (80mm×160mm overall dimensions) valve with a piston arrangement has a 1/2 inch inlet/outlet opening, neoprene/viton O-ring at piston face & diameter for sealing and a knob for opening and closing the valve. The piston movement mechanism is designed to have minimum wear of sealing O-rings. The valve has been hydrostatic pressure tested up to 75bars and has Helium leak rate of less than 9.6×10-9 m bar ltr/sec in vacuum mode and 2×10-7 mbar ltr/sec in pressure mode. As compared to a commercial diaphragm valve, which needed 3 hours to evacuate a 7 litre chamber to 2.5×10-5 mbar, the new valve achieved vacuum 7.4×10-6mbar in the same time under the same conditions.

  1. Fabrication of Aligned-Carbon-Nanotube-Composite Paper with High and Anisotropic Conductivity

    Directory of Open Access Journals (Sweden)

    Yuki Fujitsuka

    2012-01-01

    Full Text Available A functional carbon-nanotube (CNT-composite paper is described in which the CNTs are aligned. This “aligned-CNT composite paper” is a flexible composite material that has CNT functionality (e.g., electrical conductivity despite being a paper. An advanced fabrication method was developed to overcome the problem of previous CNT-composite papers, that is, reduced conductivity due to random CNT alignment. Aligning the CNTs by using an alternating current (AC field was hypothesized to increase the electrical conductivity and give the paper an anisotropic characteristic. Experimental results showed that a nonionic surfactant was not suitable as a CNT dispersant for fabricating aligned-CNT composite paper and that catechin with its six-membered rings and hydrophilic groups was suitable. Observation by scanning electron microscopy of samples prepared using catechin showed that the CNTs were aligned in the direction of the AC field on the paper fibers. Measurement of the electric conductivity showed that the surface resistance was different between the direction of the aligned CNTs (high conductivity and that of verticality (low. The conductivity of the aligned-CNT-composite paper samples was higher than that of nonaligned samples. This unique and functional paper, which has high and anisotropic conductivity, is applicable to a conductive material to control the direction of current.

  2. Optimizing amorphous indium zinc oxide film growth for low residual stress and high electrical conductivity

    Science.gov (United States)

    Kumar, Mukesh; Sigdel, A. K.; Gennett, T.; Berry, J. J.; Perkins, J. D.; Ginley, D. S.; Packard, C. E.

    2013-10-01

    With recent advances in flexible electronics, there is a growing need for transparent conductors with optimum conductivity tailored to the application and nearly zero residual stress to ensure mechanical reliability. Within amorphous transparent conducting oxide (TCO) systems, a variety of sputter growth parameters have been shown to separately impact film stress and optoelectronic properties due to the complex nature of the deposition process. We apply a statistical design of experiments (DOE) approach to identify growth parameter-material property relationships in amorphous indium zinc oxide (a-IZO) thin films and observed large, compressive residual stresses in films grown under conditions typically used for the deposition of highly conductive samples. Power, growth pressure, oxygen partial pressure, and RF power ratio (RF/(RF + DC)) were varied according to a full-factorial test matrix and each film was characterized. The resulting regression model and analysis of variance (ANOVA) revealed significant contributions to the residual stress from individual growth parameters as well as interactions of different growth parameters, but no conditions were found within the initial growth space that simultaneously produced low residual stress and high electrical conductivity. Extrapolation of the model results to lower oxygen partial pressures, combined with prior knowledge of conductivity-growth parameter relationships in the IZO system, allowed the selection of two promising growth conditions that were both empirically verified to achieve nearly zero residual stress and electrical conductivities >1480 S/cm. This work shows that a-IZO can be simultaneously optimized for high conductivity and low residual stress.

  3. A robust, highly stretchable supramolecular polymer conductive hydrogel with self-healability and thermo-processability

    Science.gov (United States)

    Wu, Qian; Wei, Junjie; Xu, Bing; Liu, Xinhua; Wang, Hongbo; Wang, Wei; Wang, Qigang; Liu, Wenguang

    2017-01-01

    Dual amide hydrogen bond crosslinked and strengthened high strength supramolecular polymer conductive hydrogels were fabricated by simply in situ doping poly (N-acryloyl glycinamide-co-2-acrylamide-2-methylpropanesulfonic) (PNAGA-PAMPS) hydrogels with PEDOT/PSS. The nonswellable conductive hydrogels in PBS demonstrated high mechanical performances—0.22-0.58 MPa tensile strength, 1.02-7.62 MPa compressive strength, and 817-1709% breaking strain. The doping of PEDOT/PSS could significantly improve the specific conductivities of the hydrogels. Cyclic heating and cooling could lead to reversible sol-gel transition and self-healability due to the dynamic breakup and reconstruction of hydrogen bonds. The mending hydrogels recovered not only the mechanical properties, but also conductivities very well. These supramolecular conductive hydrogels could be designed into arbitrary shapes with 3D printing technique, and further, printable electrode can be obtained by blending activated charcoal powder with PNAGA-PAMPS/PEDOT/PSS hydrogel under melting state. The fabricated supercapacitor via the conducting hydrogel electrodes possessed high capacitive performances. These cytocompatible conductive hydrogels have a great potential to be used as electro-active and electrical biomaterials.

  4. High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

    Science.gov (United States)

    Bhat, Biliyar N.; Ellis, David; Singh, Jogender

    2014-01-01

    Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion

  5. Dehydration of chlorite explains anomalously high electrical conductivity in the mantle wedges.

    Science.gov (United States)

    Manthilake, Geeth; Bolfan-Casanova, Nathalie; Novella, Davide; Mookherjee, Mainak; Andrault, Denis

    2016-05-01

    Mantle wedge regions in subduction zone settings show anomalously high electrical conductivity (~1 S/m) that has often been attributed to the presence of aqueous fluids released by slab dehydration. Laboratory-based measurements of the electrical conductivity of hydrous phases and aqueous fluids are significantly lower and cannot readily explain the geophysically observed anomalously high electrical conductivity. The released aqueous fluid also rehydrates the mantle wedge and stabilizes a suite of hydrous phases, including serpentine and chlorite. In this present study, we have measured the electrical conductivity of a natural chlorite at pressures and temperatures relevant for the subduction zone setting. In our experiment, we observe two distinct conductivity enhancements when chlorite is heated to temperatures beyond its thermodynamic stability field. The initial increase in electrical conductivity to ~3 × 10(-3) S/m can be attributed to chlorite dehydration and the release of aqueous fluids. This is followed by a unique, subsequent enhancement of electrical conductivity of up to 7 × 10(-1) S/m. This is related to the growth of an interconnected network of a highly conductive and chemically impure magnetite mineral phase. Thus, the dehydration of chlorite and associated processes are likely to be crucial in explaining the anomalously high electrical conductivity observed in mantle wedges. Chlorite dehydration in the mantle wedge provides an additional source of aqueous fluid above the slab and could also be responsible for the fixed depth (120 ± 40 km) of melting at the top of the subducting slab beneath the subduction-related volcanic arc front.

  6. Prevalence of conduct disorder and associated factors among the high school students in Sanandaj, 2013

    Directory of Open Access Journals (Sweden)

    Fayegh Yousefi

    2015-04-01

    Full Text Available Background: This study was performed to assess the prevalence of conduct disorder and its associated factors among the high school students of Sanandaj in 2013. Methods: The study sample included 375 high school students selected from the high school students in Sanandaj through multistage stratified random sampling. The instruments for data collection comprised of Child Symptom Inventory and Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-1. The results were evaluated by SPSS (version 21 using chi-square test. Results: The results showed the prevalence of conduct disorder among the high school students was 8.8%. Also, the prevalence of conduct disorder among students with separated parents was higher than other students. The prevalence of conduct disorder in the male students was significantly more than that of the female students. Moreover, there was a significant correlation between students’ conduct disorder and their parents’ separation and divorce. However, no significant difference was obtained between conduct disorder and other associated factors, including parents’ death rate, parents’ history of psychological disorder and academic level of students (P<0.05. Conclusion: Based on the results of this study, running counseling centers at schools and holding family training programs for parents by psychologists are recommended.

  7. Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Matthew (DOE/NNSA Kansas City Plant (United States)); Weyant, J.; Garner, S. (Advanced Cooling Technologies, Inc. (Lancaster, PA (United States)); Occhionero, M. (CPS Technologies Corporation, Norton, MA (United States))

    2010-01-07

    Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 50,000 and 200,000 W/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plate’s effective thermal conductivity. AlSiC plates alone have a thermal conductivity of roughly 200 W/m-K and a CTE ranging from 7-12 ppm/ deg C, similar to that of silicon. An equivalent sized heat pipe embedded AlSiC plate has effective thermal conductivity ranging from 400 to 500 W/m-K and retains the CTE of AlSiC.

  8. Fabrication of Al2O3/glass/Cf Composite Substrate with High Thermal Conductivity

    Science.gov (United States)

    Wang, S. X.; Liu, G. S.; Ouyang, X. Q.; Wang, Y. D.; Zhang, D.

    2016-02-01

    In this paper, carbon fiber with high thermal conductivity was introduced into the alumina-based composites. To avoid oriented alignment of carbon fibers (Cf) and carbothermal reactions during the sintering process, the Al2O3/glass/Cf substrate was hot-pressed under a segmental-pressure procedure at 1123 K. Experimental results show that carbon fibers randomly distribute and form a bridging structure in the matrix. The three-dimensional network of Cf in Al2O3/glass/Cf substrate brings excellent heat conducting performance due to the heat conduction by electrons. The thermal conductivity of Al2O3/30%glass/30%Cf is as high as 28.98 W mK-1, which is 4.56 times larger than that of Al2O3/30%glass.

  9. Ink-jet printing of cu-ag-based highly conductive tracks on a transparent substrate.

    Science.gov (United States)

    Woo, Kyoohee; Kim, Dongjo; Kim, Jang Sub; Lim, Soonkwon; Moon, Jooho

    2009-01-06

    We have developed a Cu-Ag-based mixed metal conductive ink from which highly conductive tracks form on a flexible substrate after annealing at low temperature. Addition of small Ag particles significantly improves the particle packing density by filling the interstices formed between the larger Cu particles, which in turn facilitates better conductivity compared to pure Cu metal film. The particle size and volume ratio of the Ag particles added should be carefully controlled to achieve maximum packing density in the bimodal particle system, which is consistent with the theoretical considerations of the Furnas model. In addition, we demonstrate direct writing of complex patterns that exhibit high conductivity upon annealing at sufficiently low temperature (175-210 degrees C) to not damage the transparent plastic substrate such as polyethersulphone (PES).

  10. 3D Printing of Highly Conductive Nanocomposites for the Functional Optimization of Liquid Sensors.

    Science.gov (United States)

    Chizari, Kambiz; Daoud, Mohamed Amine; Ravindran, Anil Raj; Therriault, Daniel

    2016-11-01

    The utilization of 3D printing of highly conductive (σ ≈ 2350 S m-1 ) polymer composite structures for the functional optimization of scaffold-shaped liquid sensors is demonstrated. This study can open the pathway of the application of 3D printing of conductive composites for optimization of structures useful for various applications such as smart sensors in textile or in the field of electronics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The Whitehill Formation - a high conductivity marker horizon in the Karoo Basin

    OpenAIRE

    T. Branch; Oliver Ritter; Ute Weckmann; R. F. Sachsenhofer; Frank R. Schilling;  

    2007-01-01

    Within the Inkaba yeAfrica project, magnetotelluric (MT) data were acquired along three profiles across the Karoo Basin in South Africa. The entire Karoo Basin and its sedimentary sequences are intersected by a number of deep boreholes, which were drilled during exploration for coal, oil and uranium. One of the most consistent and prominent features in the electrical conductivity images is a shoallow, regionally continuous, sub-horizontal band of high conductivity that seems to correlate with...

  12. Tunable architecture for flexible and highly conductive graphene-polymer composites

    OpenAIRE

    Noël, Amélie; Faucheu, Jenny; Rieu, Mathilde; Viricelle, Jean-Paul; Bourgeat-Lami, Elodie

    2014-01-01

    International audience; Printed electronics, particularly on flexible and textile substrates, raised a strong interest during the past decades. This work presents a good candidate for conductive inks based on a graphene/polymer nanocomposite material that gathers three main benefits that are 1 - neither clogging nor flocculation, 2 - spontaneous film formation around room temperature, 3 - high conductivity. Nanosized Multilayered Graphene (NMG) is produced through a solvent-free procedure, us...

  13. Electrical conductivity of molten CdCl{sub 2} at temperatures as high as 1474 K

    Energy Technology Data Exchange (ETDEWEB)

    Salyulev, Alexander B.; Potapov, Alexei M. [Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of High-Temperature Electrochemistry

    2016-11-01

    The electrical conductivity of molten CdCl{sub 2} was measured across a wide temperature range (ΔT=628 K), from 846 K to as high as 1474 K, i.e. 241 above the normal boiling point of the salt. In previous studies, a maximum temperature of 1201 K was reached, this being 273 lower than in the present work. The activation energy of electrical conductivity was calculated.

  14. Method for producing high carrier concentration p-Type transparent conducting oxides

    Science.gov (United States)

    Li, Xiaonan; Yan, Yanfa; Coutts, Timothy J.; Gessert, Timothy A.; Dehart, Clay M.

    2009-04-14

    A method for producing transparent p-type conducting oxide films without co-doping plasma enhancement or high temperature comprising: a) introducing a dialkyl metal at ambient temperature and a saturated pressure in a carrier gas into a low pressure deposition chamber, and b) introducing NO alone or with an oxidizer into the chamber under an environment sufficient to produce a metal-rich condition to enable NO decomposition and atomic nitrogen incorporation into the formed transparent metal conducting oxide.

  15. A facile approach to a silver conductive ink with high performance for macroelectronics

    OpenAIRE

    Tao, Yu; Tao, Yuxiao; Wang, Biaobing; Wang, Liuyang; Tai, Yanlong

    2013-01-01

    An unusual kind of transparent and high-efficiency organic silver conductive ink (OSC ink) was synthesized with silver acetate as silver carrier, ethanolamine as additive, and different kinds of aldehyde-based materials as reduction agents and was characterized by using a thermogravimetric analyzer, X-ray diffraction, a scanning electron microscope, and a four-point probe. The results show that different reduction agents all have an important influence on the conductive properties of the ink ...

  16. Stochastic inference with spiking neurons in the high-conductance state

    Science.gov (United States)

    Petrovici, Mihai A.; Bill, Johannes; Bytschok, Ilja; Schemmel, Johannes; Meier, Karlheinz

    2016-10-01

    The highly variable dynamics of neocortical circuits observed in vivo have been hypothesized to represent a signature of ongoing stochastic inference but stand in apparent contrast to the deterministic response of neurons measured in vitro. Based on a propagation of the membrane autocorrelation across spike bursts, we provide an analytical derivation of the neural activation function that holds for a large parameter space, including the high-conductance state. On this basis, we show how an ensemble of leaky integrate-and-fire neurons with conductance-based synapses embedded in a spiking environment can attain the correct firing statistics for sampling from a well-defined target distribution. For recurrent networks, we examine convergence toward stationarity in computer simulations and demonstrate sample-based Bayesian inference in a mixed graphical model. This points to a new computational role of high-conductance states and establishes a rigorous link between deterministic neuron models and functional stochastic dynamics on the network level.

  17. Structural, optical and electrical study of undoped GaN layers obtained by metalorganic chemical vapor deposition on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Rangel-Kuoppa, Victor-Tapio, E-mail: tapio.rangel@gmail.co [Institute of Semiconductor and Solid State Physics, Johannes Kepler Universitaet, A-4040 Linz (Austria); Aguilar, Cesia Guarneros [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico); Sanchez-Resendiz, Victor, E-mail: victors@sees.cinvestav.m [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico)

    2011-01-31

    We investigate optical, structural and electrical properties of undoped GaN grown on sapphire. The layers were prepared in a horizontal reactor by low pressure metal organic chemical vapor deposition at temperatures of 900 {sup o}C and 950 {sup o}C on a low temperature grown (520 {sup o}C) GaN buffer layer on (0001) sapphire substrate. The growth pressure was kept at 10,132 Pa. The photoluminescence study of such layers revealed a band-to-band emission around 366 nm and a yellow band around 550 nm. The yellow band intensity decreases with increasing deposition temperature. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies show the formation of hexagonal GaN layers with a thickness of around 1 {mu}m. The electrical study was performed using temperature dependent Hall measurements between 35 and 373 K. Two activation energies are obtained from the temperature dependent conductivity, one smaller than 1 meV and the other one around 20 meV. For the samples grown at 900 {sup o}C the mobilities are constant around 10 and 20 cm{sup 2} V{sup -1} s{sup -1}, while for the sample grown at 950 {sup o}C the mobility shows a thermally activated behavior with an activation energy of 2.15 meV.

  18. Electrokinetic device design and constraints for use in high conductance solutions.

    Science.gov (United States)

    Heineck, D P; Lewis, J M; Heller, M J

    2017-06-01

    The quest for new cell-free DNA and exosome biomarker-based molecular diagnostics require fast and efficient sample preparation techniques. Conventional methods for isolating these biomarkers from blood are both time-consuming and laborious. New electrokinetic microarray devices using dielectrophoresis (DEP) to isolate cell-free DNA and exosome biomarkers have now greatly improved the sample preparation process. Nevertheless, these devices still have some limitations when used with high conductance biological fluids, e.g. blood, plasma, and serum. This study demonstrates that electrochemical damage may occur on the platinum electrodes of DEP microarray devices. It further examines two model device designs that include a parallel wire arrangement and a planar array. Effective isolation of fluorescent beads with parallel wires is shown under low-conductance conditions (10-4  S/m), but electrothermal flow overcomes DEP forces under high conductance conditions (>0.1 S/m). Planar devices are shown to be effective under high conductance conditions (∼1 S/m) without the deleterious effects of electrothermal flow. This study provides new insights into design compromises and limitations for producing future electrokinetic devices for better performance with high conductance solutions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Low temperature platinum atomic layer deposition on nylon-6 for highly conductive and catalytic fiber mats

    Energy Technology Data Exchange (ETDEWEB)

    Mundy, J. Zachary; Shafiefarhood, Arya; Li, Fanxing; Khan, Saad A.; Parsons, Gregory N., E-mail: gnp@ncsu.edu [Department of Chemical and Biomolecular Engineering, North Carolina State University, Engineering Building I, 911 Partners Way, Raleigh, North Carolina 27695-7905 (United States)

    2016-01-15

    Low temperature platinum atomic layer deposition (Pt-ALD) via (methylcyclopentadienyl)trimethyl platinum and ozone (O{sub 3}) is used to produce highly conductive nonwoven nylon-6 (polyamide-6, PA-6) fiber mats, having effective conductivities as high as ∼5500–6000 S/cm with only a 6% fractional increase in mass. The authors show that an alumina ALD nucleation layer deposited at high temperature is required to promote Pt film nucleation and growth on the polymeric substrate. Fractional mass gain scales linearly with Pt-ALD cycle number while effective conductivity exhibits a nonlinear trend with cycle number, corresponding to film coalescence. Field-emission scanning electron microscopy reveals island growth mode of the Pt film at low cycle number with a coalesced film observed after 200 cycles. The metallic coating also exhibits exceptional resistance to mechanical flexing, maintaining up to 93% of unstressed conductivity after bending around cylinders with radii as small as 0.3 cm. Catalytic activity of the as-deposited Pt film is demonstrated via carbon monoxide oxidation to carbon dioxide. This novel low temperature processing allows for the inclusion of highly conductive catalytic material on a number of temperature-sensitive substrates with minimal mass gain for use in such areas as smart textiles and flexible electronics.

  20. Optical properties and toxicity of undoped and Mn-doped ZnS semiconductor nanoparticles synthesized through the aqueous route

    Science.gov (United States)

    Labiadh, Houcine; Sellami, Badreddine; Khazri, Abdelhafidh; Saidani, Wiem; Khemais, Said

    2017-02-01

    Undoped and Mn-doped ZnS nanoparticles were synthesized at 95 °C in basic aqueous solution using the nucleation-doping strategy. Various samples of the Mn:ZnS NPs with 5, 10 and 20% of Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive X-ray analysis, high resolution electron microscopy and photoluminescence (PL) measurements. When increasing the concentration of manganese Mn, the photoluminescence intensity gradually decreases. The PL spectra of the Mn-doped ZnS nanoparticles at room temperature exhibit both, the 450 nm blue defect-related emission and the 592 nm orange Mn2+ emission. It is vital to obtain NPs that meet the application requirements, however their environmental toxicity needs to be investigated. In this study, the induction of oxidative stress within the digestive gland of the Ruditapes decussatus organism (clam) is described. Antioxidant enzyme activities (superoxide dismutase (SOD) and catalase (CAT)) as well as malondialdehyde (MDA) levels have been determined in the digestive gland after exposure to 100 μg/L of ZnS, ZnS:Mn (5%), ZnS:Mn (10%) and ZnS:Mn (20%). The nanomaterials studied exhibit different responses in the digestive gland. Undoped Mn-ZnS has no effect on the markers considered, showing the limited interaction between this nanoparticle and the cells of the test organisms. In contrast, Mn-doped ZnS increases the activities of SOD and CAT and the level of MDA species, although this toxicity is highly dependent on the chemical properties of the material. These findings provide ideas for future considerations of ZnS nanoparticles, as well as information on the interaction between these materials and an aquatic environment. These data are the first evidence available of the formation of ZnS NPs using aqueous method and are an indication of the importance of knowing the biological target of the NPs when testing their potential impact on environmental model organisms.

  1. Process for introducing electrical conductivity into high-temperature polymeric materials

    Science.gov (United States)

    Liepins, R.; Jorgensen, B.S.; Liepins, L.Z.

    1987-08-27

    High-temperature electrically conducting polymers. The in situ reactions: AgNO/sub 3/ + RCHO ..-->.. Ag/sup 0/ + RCOOH and R/sub 3/M ..-->.. M/sup 0/ + 3R, where M = Au or Pt have been found to introduce either substantial bulk or surface conductivity in high- temperature polymers. The reactions involving the R/sub 3/M were caused to proceed thermally suggesting the possibility of using laser means for initiating such reactions in selected areas or volumes of the polymeric materials. The polymers successfully investigated to date are polyphenylquinoxaline, polytolylquinoxaline, polyquinoline, polythiazole, and pyrrone. 3 tabs.

  2. Strain dependent defect mediated ferromagnetism in Mn-doped and undoped ZnO thin films

    Science.gov (United States)

    Schoofs, Frank; Fix, Thomas; Hakimi, Ali M. H. R.; Dhesi, Sarnjeet S.; van der Laan, Gerrit; Cavill, Stuart A.; Langridge, Sean; MacManus-Driscoll, Judith L.; Blamire, Mark G.

    2010-09-01

    The structural and magnetic properties of pulsed laser deposited zinc oxide thin films have been investigated. Room temperature ferromagnetism is present in undoped as well as Mn-doped films. The saturation magnetization of the thin films reveals a dependence on both the composition and the out of plane lattice parameter. X-ray magnetic circular dichroism down to 2 K reveals a purely paramagnetic contribution from the Mn in Mn:ZnO films. We conclude that the observed ferromagnetism arises entirely from intrinsic defects in the ZnO which can be varied by manipulation of the lattice parameter.

  3. Study of cerium diffusion in undoped lithium-6 enriched glass with Rutherford backscattering spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaodong, E-mail: xzhang39@utk.edu [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D. [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Hayward, Jason P. [Department of Nuclear Engineering, University of Tennessee, TN 37996 (United States); Oak Ridge National Lab, Oak Ridge, TN 37831 (United States)

    2016-07-01

    Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick’s second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.

  4. The thermal conductivity of high modulus Zylon fibers between 400 mK and 4 K

    Science.gov (United States)

    Wikus, Patrick; Figueroa-Feliciano, Enectalí; Hertel, Scott A.; Leman, Steven W.; McCarthy, Kevin A.; Rutherford, John M.

    2008-11-01

    Zylon is a synthetic polyurethane polymer fiber featuring very high mechanical strength. Measurements of the thermal conductivity λZ(T) of high modulus Zylon fibers at temperatures between 400 mK and 4 K were performed to assess if they can be successfully employed in the design of high performance suspension systems for cold stages of adiabatic demagnetization refrigerators. The linear mass density of the yarn used in these measurements amounts to 3270 dtex, which is also a measure for the yarn's cross section. The experimental data for the thermal conductivity was fitted to a function of the form λZ=(1010±30)·TpWmmdtexK. This result was normalized to the breaking strength of the fibers and compared with Kevlar. It shows that Kevlar outperforms Zylon in the investigated temperature range. At 1.5 K, the thermal conductivity integral of Zylon yarn is twice as high as the thermal conductivity integral of Kevlar yarn with the same breaking strength. A linear mass density of 1 tex is equivalent to a yarn mass of 1 g/km. High modulus Zylon has a density of 1.56 g/cm 3.

  5. Exfoliation approach for preparing high conductive reduced graphite oxide and its application in natural rubber composites

    Energy Technology Data Exchange (ETDEWEB)

    Wipatkrut, Pattharaporn [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Poompradub, Sirilux, E-mail: sirilux.p@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Center for Petroleum, Petrochemical and Advanced Material, Chulalongkorn University, Bangkok 10330 (Thailand)

    2017-04-15

    Highlights: • Graphite waste was exfoliated by oxidation and chemical and thermal reduction. • The obtained graphene-T was a single layer sheet with a high electrical conductivity. • Graphene-T incorporation at 5 phr improved the electrical conductivity of NR. • Graphene-T incorporation at 5–25 phr improved the mechanical properties of NR. - Abstract: High conductivity reduced graphite oxide (RGO) was prepared by exfoliation of graphite waste from the metal smelting industry. To improve the surface properties of the RGO, the graphite oxide obtained based on Hummers’ method was reduced by L-ascorbic acid to give RGOV, which was then subjected to thermal reduction to obtain RGOT. The residual oxygen-containing groups in RGOV were almost completely removed by the thermal reduction and the conjugated graphene networks were restored in RGOT. The effect of the RGOT content in natural rubber (NR) on the cure, electrical and mechanical properties of the NR-RGOT (NG) composites was evaluated. The electrical conductivity of NR was increased by the inclusion of RGOT at a percolation threshold of 5 phr, with an electrical conductivity of 8.71 × 10{sup −6} S/m. The mechanical properties, i.e., the modulus, tensile strength and hardness, of NG were comparable with those of conductive carbon black filled NR ones.

  6. Atomistic simulations of highly conductive molecular transport junctions under realistic conditions

    KAUST Repository

    French, William R.

    2013-01-01

    We report state-of-the-art atomistic simulations combined with high-fidelity conductance calculations to probe structure-conductance relationships in Au-benzenedithiolate (BDT)-Au junctions under elongation. Our results demonstrate that large increases in conductance are associated with the formation of monatomic chains (MACs) of Au atoms directly connected to BDT. An analysis of the electronic structure of the simulated junctions reveals that enhancement in the s-like states in Au MACs causes the increases in conductance. Other structures also result in increased conductance but are too short-lived to be detected in experiment, while MACs remain stable for long simulation times. Examinations of thermally evolved junctions with and without MACs show negligible overlap between conductance histograms, indicating that the increase in conductance is related to this unique structural change and not thermal fluctuation. These results, which provide an excellent explanation for a recently observed anomalous experimental result [Bruot et al., Nat. Nanotechnol., 2012, 7, 35-40], should aid in the development of mechanically responsive molecular electronic devices. © 2013 The Royal Society of Chemistry.

  7. Geochemical and isotopic characteristics associated with high electrical conductivities in a shallow hydrocarbon-contaminated aquifer

    Science.gov (United States)

    Legall, F.; Atekwana, E.; Atekwana, E.; Krishnamurthy, R.; Sauck, W.

    2003-04-01

    Data collected from a network of in-situ vertical resistivity probes (VRPs) deployed within a hydrocarbon contaminated aquifer showed high soil conductivities associated with zones where residual and dissolved phase hydrocarbons (RDH) occur and zones where these phases coexist with free phase hydrocarbons (RDFH). Bulk soil conductivities were highest (12 to 30 mS/m) in the RDFH zone compared to the RDH zone (10 to 25 mS/m). Groundwater from closely spaced multi-level piezometers (MLPs) installed in the aquifer was analyzed to investigate the role of mineral weathering as the source of ions responsible for the high soil conductivity. Evidence for mineral weathering in the aquifer was assessed using major inorganic ions, dissolved inorganic carbon (DIC), stable carbon isotope ratio of DIC (δ13CDIC), and bulk soil conductivity. The link between bulk soil conductivity and δ13CDIC in contaminant plumes has never been reported in the literature. The results show higher Na, Ca, and Mg in the contaminated zone compared to background. The higher TDS in the contaminated zones is consistent with the weathering of carbonates and Na and Ca feldspars, the dominant minerals in the aquifer. Higher TDS at the contaminated locations was also coincident with higher DIC. The δ13CDIC values of 16.9 to 9.5 ppm suggest that DIC evolution within this zone is controlled by carbonate dissolution through enhanced CO_2 production related to microbial hydrocarbon degradation. Within the range of δ13CDIC values reported for groundwater at the RDH locations, the more positive δ13CDIC values were observed in zones where reduction of NO_3, Mn(IV), Fe(III), and SO_4 was occurring and was coincident with higher bulk soil conductivity. Within the portion of the aquifer with RDFH, δ13CDIC ranged from +6.5 to 4.4 ppm, suggesting that methanogenesis is the dominant redox process at this location. High DIC within the methanogenic zone is also coincident with higher bulk soil conductivity. Thus the

  8. Highly Thermally Conductive Composite Papers Prepared Based on the Thought of Bioinspired Engineering.

    Science.gov (United States)

    Yao, Yimin; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2016-06-22

    The rapid development of modern electronics and three-dimensional integration sets stringent requirements for efficient heat removal of thermal-management materials to ensure the long lifetime of the electronics. However, conventional polymer composites that have been used widely as thermal-management materials suffer from undesired thermal conductivity lower than 10 W m(-1) K(-1). In this work, we report a novel thermally conductive composite paper based on the thought of bioinspired engineering. The advantage of the bioinspired papers over conventional composites lies in that they possess a very high in-plane thermal conductivity up to 21.7 W m(-1) K(-1) along with good mechanical properties and high electrical insulation. We attribute the high thermal conductivity to the improved interfacial interaction between assembled components through the introduction of silver nanoparticles and the oriented structure based on boron nitride nanosheets and silicon carbide nanowires. This thought based on bioinspired engineering provides a creative opportunity for design and fabrication of novel thermally conductive materials, and this kind of composite paper has potential applications in powerful integrated microelectronics.

  9. Highly conductive and flexible nylon-6 nonwoven fiber mats formed using tungsten atomic layer deposition.

    Science.gov (United States)

    Kalanyan, Berç; Oldham, Christopher J; Sweet, William J; Parsons, Gregory N

    2013-06-12

    Low-temperature vapor-phase tungsten atomic layer deposition (ALD) using WF6 and dilute silane (SiH4, 2% in Ar) can yield highly conductive coatings on nylon-6 microfiber mats, producing flexible and supple nonwovens with conductivity of ∼1000 S/cm. We find that an alumina nucleation layer, reactant exposure, and deposition temperature all influence the rate of W mass uptake on 3D fibers, and film growth rate is calibrated using high surface area anodic aluminum oxide. Transmission electron microscopy (TEM) reveals highly conformal tungsten coatings on nylon fibers with complex "winged" cross-section. Using reactant gas "hold" sequences during the ALD process, we conclude that reactant species can transport readily to reactive sites throughout the fiber mat, consistent with conformal uniform coverage observed by TEM. The conductivity of 1000 S/cm for the W-coated nylon is much larger than found in other conductive nonwovens. We also find that the nylon mats maintain 90% of their conductivity after being flexed around cylinders with radii as small as 0.3 cm. Metal ALD coatings on nonwovens make possible the solvent-free functionalization of textiles for electronic applications.

  10. High frequency characterization of conductive inks embedded within a structural composite

    Science.gov (United States)

    Pa, Peter; McCauley, Raymond; Larimore, Zachary; Mills, Matthew; Yarlaggada, Shridhar; Mirotznik, Mark S.

    2015-06-01

    Woven fabric composites provide an attractive platform for integrating electromagnetic functionality—such as conformal load-bearing antennas and frequency selective surfaces—into a structural platform. One practical fabrication method for integrating conductive elements within a woven fabric composite system involves using additive manufacturing systems such as screen printing. While screen printing is an inherently scalable, flexible and cost effective method, little is known about the high frequency electrical properties of its conductive inks when they are embedded within the woven fabric composite. Thus, we have completed numerical and experimental studies to determine the electrical conductivity of screen printable conductive inks that are embedded within this composite. We have also performed mechanical studies to evaluate how printing affects the structural performance of the composite.

  11. The physics of high-conductivity transparent materials based on wide-band zinc oxide

    Science.gov (United States)

    Lashkarev, G. V.; Karpyna, V. A.; Ovsiannikova, L. I.; Kartuzov, V. V.; Dranchuk, M. V.; Godlewski, M.; Pietruszka, R.; Khomyak, V. V.; Petrosyan, L. I.

    2017-04-01

    The properties of transparent conductive materials based on wide-gap zinc oxide semiconductors are considered, which are promising in their application to photovoltaics and liquid crystal displays. The impact of aluminum doping on the conductivity of thin ZnO films is examined. Temperature studies of the concentration, mobility, and resistivity in the temperature range of 77-300 K are conducted, revealing the metal conductivity of highly doped films. The electroactivity of aluminum as a donor impurity in the ZnO lattice is studied for thin films grown using atomic layer deposition on glass and silicone, containing 1-7 at. % aluminum. The reasons behind the low electroactivity of Al in ZnO are discussed, as are the methods for its enhancement.

  12. Thermal Conductivity of High Performance Concrete in Wide Temperature and Moisture Ranges

    Directory of Open Access Journals (Sweden)

    J. Toman

    2001-01-01

    Full Text Available The thermal conductivity of two types of high performance concrete was measured in the temperature range from 100 °C to 800 °C and in the moisture range from dry material to saturation water content. A transient measuring method based on analysis of the measured temperature fields was chosen for the high temperature measurements, and a commercial hot wire device was employed in room temperature measurements of the effect of moisture on thermal conductivity. The measured results reveal that both temperature and moisture exhibit significant effects on the values of thermal conductivity, and these effects are quite comparable from the point of view of the magnitude of the observed variations.

  13. Anatomy of a Nanoscale Conduction Channel Reveals the Mechanism of a High-Performance Memristor

    Science.gov (United States)

    Miao, Feng; Strachan, John Paul; Yang, J. Joshua; Yi, Wei; Goldfarb, Ilan; Zhang, M.-X.; Torrezan, Antonio C.; Eschbach, Peter; Kelley, Ronald D.; Medeiros-Ribeiro, Gilberto; Williams, R. Stanley

    2012-02-01

    Two major challenges for resistance memory devices (memristors) based on conductivity changes in oxide materials are better performance and understanding of the microscopic picture of the switching. After researchers' relentless pursuit for years, tantalum oxide-based memristors have rapidly risen to be the top candidate, showing fast speed, high endurance and excellent scalability. While the microscopic picture of these devices remains obscure, by employing a precise method for locating and directly visualizing the conduction channel, here we observed a nanoscale channel consisting of an amorphous Ta(O) solid solution surrounded by crystalline Ta2O5. Structural and chemical analyses of the channel combined with temperature dependent transport measurements revealed a unique resistance switching mechanism: the modulation of the channel elemental composition, and thus the conductivity, by the cooperative influence of drift, diffusion and thermophoresis, which seem to enable the high switching performance observed. (Miao*, Strachan*, Yang* et al., Advanced Materials. DOI: 10.1002/adma201103379 (2011))

  14. Highly conductive and flexible paper of 1D silver-nanowire-doped graphene.

    Science.gov (United States)

    Chen, Jian; Bi, Hui; Sun, Shengrui; Tang, Yufeng; Zhao, Wei; Lin, Tianquan; Wan, Dongyun; Huang, Fuqiang; Zhou, Xiaodong; Xie, Xiaoming; Jiang, Mianheng

    2013-02-01

    A novel architecture of graphene paper is proposed to consist of "1D metallic nanowires/defect-free graphene sheets". Highly conductive and flexible papers of 1D silver nanowires (Ag NWs) and chemical vapor deposition (CVD) graphene sheets as an example were fabricated by a simple filtration method. CVD graphene paper possesses much higher electrical conductivity of 1097 S/cm, compared with other reported carbon-related papers (graphene, carbon nanotube, etc.). With the addition of Ag NWs to form Ag NWs/graphene paper, the electrical conductivity is further improved up to 3189 S/cm, even higher than ∼2000 S/cm of bulk graphite. Ag NWs/graphene papers have very good flexibility with the only papers have potential in high-performance, flexible energy conversion and storage devices.

  15. Statistical properties of Joule heating rate, electric field and conductances at high latitudes

    Directory of Open Access Journals (Sweden)

    A. T. Aikio

    2009-07-01

    Full Text Available Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox and from similar sunspot conditions (about 1.5 years before the sunspot minimum providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03–05 MLT for Kp≥3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp≥3. In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcs as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004 In

  16. Statistical properties of Joule heating rate, electric field and conductances at high latitudes

    Directory of Open Access Journals (Sweden)

    A. T. Aikio

    2009-07-01

    Full Text Available Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox and from similar sunspot conditions (about 1.5 years before the sunspot minimum providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution.

    All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03–05 MLT for Kp≥3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity.

    An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp≥3. In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to

  17. Conductive 3D sponges for affordable and highly-efficient water purification.

    Science.gov (United States)

    Liu, Yanbiao; Li, Fang; Xia, Qin; Wu, Jiawei; Liu, Jianshe; Huang, Mingzhi; Xie, Jianping

    2018-02-22

    Effective, affordable and low energy water purification technologies are highly desirable to address the current environmental issues. In this study, we developed a low-cost method to achieve efficient organic pollutants degradation by incorporating conductive nanomaterials (i.e., carbon nanotubes, CNTs) to assist electro-oxidation, leading to an efficient conductive nano-sponge filtration device. The integration of electrochemistry has significantly improved the performance of the sponge-based device to adsorb and oxidize organic compounds in aqueous solution. In particular, CNT materials could serve as both high-performance electro-catalysts for pollutant degradation and conductive additives that make polyurethane sponges highly conductive. On the other hand, the polyurethane sponge could work as a low-cost and highly porous matrix that could effectively host these CNT conductors. The conductive sponge can be easily fabricated by a simple dying based approach. The as-fabricated gravity fed device could effectively oxidize two model organic compounds (i.e., >92% antibiotic tetracycline and >94% methyl orange) via a single pass through the conductive sponge under the optimized experimental conditions (e.g., [Na 2 SO 4 ] = 10 mmol L -1 , [CNT] = 0.3 mg mL -1 , and [SDBS] = 2.0 mg mL -1 ). We have achieved >88% degradation efficiency for the antibiotic tetracycline within 6 h of continuous operation with an average electro-oxidation flux of 0.82 ± 0.05 mol h -1 m -2 and an energy requirement of 1.0 kW h kg -1 COD or <0.02 kW h m -3 . These promising data make our CNT-sponge filtration device attractive for affordable and effective water purification.

  18. Cross-correlations in high-conductance states of a model cortical network

    DEFF Research Database (Denmark)

    Hertz, John

    2010-01-01

    (dansk abstrakt findes ikke) Neuronal firing correlations are studied using simulations of a simple network model for a cortical column in a high-conductance state with dynamically balanced excitation and inhibition.  Although correlations between individual pairs of neurons exhibit considerable ...

  19. Nanoscale Soldering of Positioned Carbon Nanotubes using Highly Conductive Electron Beam Induced Gold Deposition

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina

    2003-01-01

    We have developed an in-situ method for controlled positioning of carbon nanotubes followed by highly conductive contacting of the nanotubes, using electron beam assisted deposition of gold. The positioning and soldering process takes place inside an Environmental Scanning Electron Microscope (E...

  20. High electrical conductivity of individual epitaxially grown MoO2 nanorods

    Science.gov (United States)

    Xie, Qiliang; Zheng, Xiaoming; Wu, Di; Chen, Xiaoliu; Shi, Jiao; Han, Xintong; Zhang, Xueao; Peng, Gang; Gao, Yongli; Huang, Han

    2017-08-01

    Molybdenum dioxides (MoO2) have potential applications in batteries owing to their good electrical conductivity. Here, we report the electrical properties of high-quality MoO2 nanorods grown using chemical vapor deposition which are partially wrapped in MoS2 on c-sapphire [α-Al2O3(0001)] substrates and subsequently transferred onto Si wafers for device fabrication. The as-fabricated devices with the individual MoO2 nanorods showed a high electrical conductivity of 6.04 × 103 S/cm and a low contact resistance of 33 Ω, thus demonstrating a superior electrical performance than in any other previous reports on MoO2-based devices. The MoS2 wrapping around the rods had a negligible effect on the conductivity. The electrical conductivity of the MoO2 nanorods was observed to decline in air when a high voltage was applied; this could be mitigated by packaging the nanorods using SiO2 or holding them under high vacuum. Our results provide the foundation for understanding the properties and potential applications of MoO2 nanorods in nanoscale electronic devices.

  1. Methodological Lessons Learned from Conducting Civic Education Research in High Schools

    Science.gov (United States)

    Matto, Elizabeth C.; Vercellotti, Timothy

    2012-01-01

    With the growing size of the "Millennial Generation" and its potential impact on American democracy, the civic education of this cohort deserves study. Using news media and discussion of politics at home and in the classroom at four public high schools in New Jersey, we conducted an experiment to measure changes in media use, political…

  2. Erythrocyte orientation and lung conductivity analysis with a high temporal resolution FEM model for bioimpedance measurements

    NARCIS (Netherlands)

    Ulbrich, M.; Paluchowski, P.; Muehlsteff, J.; Leonhardt, S.

    2012-01-01

    Impedance cardiography (ICG) is a simple and cheap method to acquirehemodynamic parameters. In this work, the influence of three dynamic physiological sources has been analyzed using a model of the humanthorax with a high temporal resolution. Therefore, simulations havebeen conducted using the

  3. Highly electrically conductive Ag-doped graphene fibers as stretchable conductors.

    Science.gov (United States)

    Xu, Zhen; Liu, Zheng; Sun, Haiyan; Gao, Chao

    2013-06-18

    Ag-doped graphene fibers show remarkable electrical conductivity, high current capacity, good mechanical strength and fine flexibility. The integration of these merits promises Ag-doped graphene fibers expanding applications as stretchable conductors, wearable electronics, and actual microcables. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Electrical conductivity of molten ZnCl{sub 2} at temperature as high as 1421 K

    Energy Technology Data Exchange (ETDEWEB)

    Salyulev, Alexander B.; Potapov, Alexei M. [RAS Ural Branch, Ekaterinburg. (Russian Federation) Institute of High-Temperature Electrochemistry

    2015-07-01

    The electrical conductivity of molten ZnCl{sub 2} was measured in a wide temperature range (ΔT=863 K) to a temperature as high as 1421 K that is 417 degrees above the boiling point of the salt. At the temperature maximum of the own vapor pressure of the salt reached several megapascals.

  5. High Biofilm Conductivity Maintained Despite Anode Potential Changes in a Geobacter-Enriched Biofilm

    Science.gov (United States)

    This study systematically assessed intracellular electron transfer (IET) and extracellular electron transfer (EET) kinetics with respect to anode potential (Eanode) in a mixed-culture biofilm anode enriched with Geobacter spp. High biofilm conductivity (0.96–1.24 mScm^-1) was mai...

  6. "Saturday Night Live" Goes to High School: Conducting and Advising a Political Science Fair Project

    Science.gov (United States)

    Allen, Meg; Brewer, Paul R.

    2010-01-01

    This article uses a case study to illustrate how science fair projects--which traditionally focus on "hard science" topics--can contribute to political science education. One of the authors, a high school student, conducted an experimental study of politics for her science fair project. The other author, a faculty member, was asked to advise the…

  7. A polyoxometalate-organic supramolecular nanotube with high chemical stability and proton-conducting properties.

    Science.gov (United States)

    Cao, Gao-Juan; Liu, Jing-Dong; Zhuang, Ting-Ting; Cai, Xiu-Hong; Zheng, Shou-Tian

    2015-02-07

    The use of 1H-1,2,4-triazole-3-thiol (H2trzS) has led to a rare inorganic-organic hybrid supramolecular nanotube built from novel Ni5-substituted polyoxotungstates, which presents interesting structural characteristics, high chemical stability, and proton-conducting properties.

  8. A Simple Demonstration of the High-Temperature Electrical Conductivity of Glass

    Science.gov (United States)

    Chiaverina, Chris

    2014-01-01

    We usually think of glass as a good electrical insulator; this, however, is not always the case. There are several ways to show that glass becomes conducting at high temperatures, but the following approach, devised by Brown University demonstration manager Gerald Zani, may be one of the simplest to perform.

  9. Preparation, characterization and photocatalytic properties of doped and undoped Bi2O3

    Directory of Open Access Journals (Sweden)

    Sh. Labib

    2017-09-01

    Full Text Available CuO-doped Bi2O3 and undoped Bi2O3 were prepared using tartaric acid assisted co-precipitation to be applied as nano-photocatalysts for shape controlling Al2O3 ceramics. The prepared powders annealed at 300 °C were characterized using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, scanning electron microscopy (SEM, ultraviolet–visible absorbance spectroscopy (UV–vis and photoluminescence (PL spectrophotometry. According to the XRD results the undoped sample consisted of pure β-Bi2O3 while the doped one consisted of β-Bi2O3–CuBi2O4. The prepared Bi2O3 powders were characterized by band gap energy values ranging from 3.0 to 2.3 eV. The developed CuBi2O4 was characterized by band gap energy of 1.3 eV. Al2O3 ceramics were prepared using a modified polyol method. A marked variation in the microstructure of Al2O3 ceramics treated with the different prepared nano-photocatalysts was observed. This variation was referred to the free motions of photocarriers that were the backbone in varying the size, composition and morphology of the particles.

  10. Experimental Preparation and Numerical Simulation of High Thermal Conductive Cu/CNTs Nanocomposites

    Directory of Open Access Journals (Sweden)

    Muhsan Ali Samer

    2014-07-01

    Full Text Available Due to the rapid growth of high performance electronics devices accompanied by overheating problem, heat dissipater nanocomposites material having ultra-high thermal conductivity and low coefficient of thermal expansion was proposed. In this work, a nanocomposite material made of copper (Cu reinforced by multi-walled carbon nanotubes (CNTs up to 10 vol. % was prepared and their thermal behaviour was measured experimentally and evaluated using numerical simulation. In order to numerically predict the thermal behaviour of Cu/CNTs composites, three different prediction methods were performed. The results showed that rules of mixture method records the highest thermal conductivity for all predicted composites. In contrast, the prediction model which takes into account the influence of the interface thermal resistance between CNTs and copper particles, has shown the lowest thermal conductivity which considered as the closest results to the experimental measurement. The experimentally measured thermal conductivities showed remarkable increase after adding 5 vol.% CNTs and higher than the thermal conductivities predicted via Nan models, indicating that the improved fabrication technique of powder injection molding that has been used to produced Cu/CNTs nanocomposites has overcome the challenges assumed in the mathematical models.

  11. Two-dimensional quantum transport in highly conductive carbon nanotube fibers

    Science.gov (United States)

    Piraux, L.; Abreu Araujo, F.; Bui, T. N.; Otto, M. J.; Issi, J.-P.

    2015-08-01

    Measurements of the electrical resistivity, from 1.5 to 300 K, and of the low temperature magnetoresistance of highly conductive carbon nanotube (CNT) fibers, obtained by wet-spinning from liquid crystalline phase (LCP), are reported. At high temperature the results obtained on the raw CNT fibers show a typical metallic behavior and the resistivity levels without postdoping process were found to be only one order of magnitude higher than the best electrical conductors, with the specific conductivity (conductivity per unit weight) comparable to that of pure copper. At low temperature a logarithmic dependence of the resistivity and the temperature dependence of the negative magnetoresistance are consistent with a two-dimensional quantum charge transport—weak localization and Coulomb interaction—in the few-walled CNT fibers. The temperature dependence of the phase-breaking scattering rate has also been determined from magnetoresistance measurements. In the temperature range T conductive CNT fibers. While quantum effects demonstrate the two-dimensional aspect of conduction in the fibers, the fact that it was found that their resistance is mainly determined by the intrinsic resistivity of the CNTs—and not by intertube resistances—suggests that better practical conductors could be obtained by improving the quality of the CNTs and the fiber morphology.

  12. High thermal conductivity in soft elastomers with elongated liquid metal inclusions.

    Science.gov (United States)

    Kazem, Navid; Bartlett, Michael D.; Powell-Palm, Matthew J.; Huang, Xiaonan; Sun, Wenhuan; Malen, Jonathan A.; Majidi, Carmel

    Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrains thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (E) . This is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with a dielectric composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (E 600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a 25x increase in thermal conductivity (4.7 +/-0.2 W/mK) over the base polymer (0.20 +/-0.01 W/mK) under stress-free conditions and a 50x increase (9.8 +/-0.8 W/mK) when strained. This exceptional combination of thermal and mechanical properties is through the deformation of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer new possibilities for passive heat exchange in stretchable electronics and bio-inspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high power LED lamp and a swimming soft robot. AFOSR Young Investigator Program (Mechanics of Multifunctional Materials and Microsystems; Dr. Les Lee; FA9550-13-1-0123), NASA Early Career Faculty Award (NNX14AO49G), Army Research Office Grant W911NF-14-0350.

  13. Highly Water-Stable Lanthanide-Oxalate MOFs with Remarkable Proton Conductivity and Tunable Luminescence.

    Science.gov (United States)

    Zhang, Kun; Xie, Xiaoji; Li, Hongyu; Gao, Jiaxin; Nie, Li; Pan, Yue; Xie, Juan; Tian, Dan; Liu, Wenlong; Fan, Quli; Su, Haiquan; Huang, Ling; Huang, Wei

    2017-09-01

    Although proton conductors derived from metal-organic frameworks (MOFs) are highly anticipated for various applications including solid-state electrolytes, H2 sensors, and ammonia synthesis, they are facing serious challenges such as poor water stability, fastidious working conditions, and low proton conductivity. Herein, we report two lanthanide-oxalate MOFs that are highly water stable, with so far the highest room-temperature proton conductivity (3.42 × 10-3 S cm-1 ) under 100% relative humidity (RH) among lanthanide-based MOFs and, most importantly, luminescent. Moreover, the simultaneous response of both the proton conductivity and luminescence intensity to RH allows the linkage of proton conductivity with luminescence intensity. This way, the electric signal of proton conductivity variation versus RH will be readily translated to optical signal of luminescence intensity, which can be directly visualized by the naked eye. If proper lanthanide ions or even transition-metal ions are used, the working wavelengths of luminescence emissions can be further extended from visible to near infrared light for even wider-range applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Protic Salt Polymer Membranes: High-Temperature Water-Free Proton-Conducting Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Gervasio, Dominic Francis [Univ. of Arizona, Tucson, AZ (United States)

    2010-09-30

    This research on proton-containing (protic) salts directly addresses proton conduction at high and low temperatures. This research is unique, because no water is used for proton ionization nor conduction, so the properties of water do not limit proton fuel cells. A protic salt is all that is needed to give rise to ionized proton and to support proton mobility. A protic salt forms when proton transfers from an acid to a base. Protic salts were found to have proton conductivities that are as high as or higher than the best aqueous electrolytes at ambient pressures and comparable temperatures without or with water present. Proton conductivity of the protic salts occurs providing two conditions exist: i) the energy difference is about 0.8 eV between the protic-salt state versus the state in which the acid and base are separated and 2) the chemical constituents rotate freely. The physical state of these proton-conducting salts can be liquid, plastic crystal as well as solid organic and inorganic polymer membranes and their mixtures. Many acids and bases can be used to make a protic salt which allows tailoring of proton conductivity, as well as other properties that affect their use as electrolytes in fuel cells, such as, stability, adsorption on catalysts, environmental impact, etc. During this project, highly proton conducting (~ 0.1S/cm) protic salts were made that are stable under fuel-cell operating conditions and that gave highly efficient fuel cells. The high efficiency is attributed to an improved oxygen electroreduction process on Pt which was found to be virtually reversible in a number of liquid protic salts with low water activity (< 1% water). Solid flexible non-porous composite membranes, made from inorganic polymer (e.g., 10%indium 90%tin pyrophosphate, ITP) and organic polymer (e.g., polyvinyl pyridinium phosphate, PVPP), were found that give conductivity and fuel cell performances similar to phosphoric acid electrolyte with no need for hydration at

  15. Die attach dimension and material on thermal conductivity study for high power COB LED

    Science.gov (United States)

    Sarukunaselan, K.; Ong, N. R.; Sauli, Z.; Mahmed, N.; Kirtsaeng, S.; Sakuntasathien, S.; Suppiah, S.; Alcain, J. B.; Retnasamy, V.

    2017-09-01

    High power LED began to gain popularity in the semiconductor market due to its efficiency and luminance. Nonetheless, along with the increased in efficiency, there was an increased in the junction temperature too. The alleviating junction temperature is undesirable since the performances and lifetime will be degraded over time. Therefore, it is crucial to solve this thermal problem by maximizing the heat dissipation to the ambience. Improvising the die attach (DA) layer would be the best option because this layer is sandwiched between the chip (heat source) and the substrate (channel to the ambient). In this paper, the impact of thickness and thermal conductivity onto the junction temperature and Von Mises stress is analyzed. Results obtained showed that the junction temperature is directly proportional to the thickness but the stress was inversely proportional to the thickness of the DA. The thermal conductivity of the materials did affect the junction temperature as there was not much changes once the thermal conductivity reached 20W/mK. However, no significant changes were observed on the Von Mises stress caused by the thermal conductivity. Material with the second highest thermal conductivity had the lowest stress, whereas the highest conductivity material had the highest stress value at 20 µm. Overall, silver sinter provided the best thermal dissipation compared to the other materials.

  16. A highly conductive, non-flammable polymer–nanoparticle hybrid electrolyte

    KAUST Repository

    Agrawal, Akanksha

    2015-01-01

    © 2015 The Royal Society of Chemistry. We report on the physical properties of lithium-ion conducting nanoparticle-polymer hybrid electrolytes created by dispersing bidisperse mixtures of polyethylene glycol (PEG)-functionalized silica nanoparticles in an aprotic liquid host. At high particle contents, we find that the ionic conductivity is a non-monotonic function of the fraction of larger particles xL in the mixtures, and that for the nearly symmetric case xL ≈ 0.5 (i.e. equal volume fraction of small and large particles), the room temperature ionic conductivity is nearly ten-times larger than in similar nanoparticle hybrid electrolytes comprised of the pure small (xL ≈ 0) or large (xL ≈ 1) particle components. Complementary trends are seen in the activation energy for ion migration and effective tortuosity of the electrolytes, which both exhibit minima near xL ≈ 0.5. Characterization of the electrolytes by dynamic rheology reveals that the maximum conductivity coincides with a distinct transition in soft glassy properties from a jammed to partially jammed and back to jammed state, as the fraction of large particles is increased from 0 to 1. This finding implies that the conductivity enhancement arises from purely entropic loss of correlation between nanoparticle centers arising from particle size dispersity. As a consequence of these physics, it is now possible to create hybrid electrolytes with MPa elastic moduli and mS cm-1 ionic conductivity levels at room temperature using common aprotic liquid media as the electrolyte solvent. Remarkably, we also find that even in highly flammable liquid media, the bidisperse nanoparticle hybrid electrolytes can be formulated to exhibit low or no flammability without compromising their favorable room temperature ionic conductivity and mechanical properties.

  17. Highly Conductive Graphene/Ag Hybrid Fibers for Flexible Fiber-Type Transistors

    Science.gov (United States)

    Yoon, Sang Su; Lee, Kang Eun; Cha, Hwa-Jin; Seong, Dong Gi; Um, Moon-Kwang; Byun, Joon-Hyung; Oh, Youngseok; Oh, Joon Hak; Lee, Wonoh; Lee, Jea Uk

    2015-11-01

    Mechanically robust, flexible, and electrically conductive textiles are highly suitable for use in wearable electronic applications. In this study, highly conductive and flexible graphene/Ag hybrid fibers were prepared and used as electrodes for planar and fiber-type transistors. The graphene/Ag hybrid fibers were fabricated by the wet-spinning/drawing of giant graphene oxide and subsequent functionalization with Ag nanoparticles. The graphene/Ag hybrid fibers exhibited record-high electrical conductivity of up to 15,800 S cm-1. As the graphene/Ag hybrid fibers can be easily cut and placed onto flexible substrates by simply gluing or stitching, ion gel-gated planar transistors were fabricated by using the hybrid fibers as source, drain, and gate electrodes. Finally, fiber-type transistors were constructed by embedding the graphene/Ag hybrid fiber electrodes onto conventional polyurethane monofilaments, which exhibited excellent flexibility (highly bendable and rollable properties), high electrical performance (μh = 15.6 cm2 V-1 s-1, Ion/Ioff > 104), and outstanding device performance stability (stable after 1,000 cycles of bending tests and being exposed for 30 days to ambient conditions). We believe that our simple methods for the fabrication of graphene/Ag hybrid fiber electrodes for use in fiber-type transistors can potentially be applied to the development all-organic wearable devices.

  18. Conductive Microporous Covalent Triazine-Based Framework for High-Performance Electrochemical Capacitive Energy Storage.

    Science.gov (United States)

    Li, Yajuan; Zheng, Shuanghao; Liu, Xue; Li, Pan; Sun, Lei; Yang, Ruixia; Wang, Sen; Wu, Zhong-Shuai; Bao, Xinhe; Deng, Wei-Qiao

    2017-11-14

    Nitrogen-enriched porous nanocarbon, graphene, and conductive polymers attract increasing attention for application in supercapacitors. However, electrode materials with a large specific surface area (SSA) and a high nitrogen doping concentration, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane-derived conductive microporous covalent triazine-based frameworks (TCNQ-CTFs) with both high nitrogen content (>8 %) and large SSA (>3600 m2  g-1 ). These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F g-1 , considerable energy density of 42.8 Wh kg-1 , and remarkable cycling stability without any capacitance degradation after 10 000 cycles. This class of CTFs should hold a great potential as high-performance electrode material for electrochemical energy-storage systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Design of conduction cooling system for a high current HTS DC reactor

    Science.gov (United States)

    Dao, Van Quan; Kim, Taekue; Le Tat, Thang; Sung, Haejin; Choi, Jongho; Kim, Kwangmin; Hwang, Chul-Sang; Park, Minwon; Yu, In-Keun

    2017-07-01

    A DC reactor using a high temperature superconducting (HTS) magnet reduces the reactor’s size, weight, flux leakage, and electrical losses. An HTS magnet needs cryogenic cooling to achieve and maintain its superconducting state. There are two methods for doing this: one is pool boiling and the other is conduction cooling. The conduction cooling method is more effective than the pool boiling method in terms of smaller size and lighter weight. This paper discusses a design of conduction cooling system for a high current, high temperature superconducting DC reactor. Dimensions of the conduction cooling system parts including HTS magnets, bobbin structures, current leads, support bars, and thermal exchangers were calculated and drawn using a 3D CAD program. A finite element method model was built for determining the optimal design parameters and analyzing the thermo-mechanical characteristics. The operating current and inductance of the reactor magnet were 1,500 A, 400 mH, respectively. The thermal load of the HTS DC reactor was analyzed for determining the cooling capacity of the cryo-cooler. The study results can be effectively utilized for the design and fabrication of a commercial HTS DC reactor.

  20. 3D printable highly conductive and mechanically strong thermoplastic-based nanocomposites

    Science.gov (United States)

    Tabiai, Ilyass; Therriault, Daniel

    Highly conductive 3D printable inks can be used to design electrical devices with various functionalities and geometries. We use the solvent evaporation assisted 3D-printing method to create high resolution structures made of poly(lactid) acid (PLA) reinforced with multi-walled carbon nanotube (MWCNTs). We characterize fibers with diameters ranging between 100 μm to 330 μm and reinforced with MWCNTs from 0.5 up to 40wt% here. Tensile test, shrinkage ratio, density and electrical conductivity measurements of the printed nanocomposite are presented. The material's electrical conductivity is strongly improved by adding MWCNTs (up to 3000S/m), this value was found to be higher than any 3D-printable carbon based material available in the literature. It is observed that MWCNTs significantly increase the material's strength and stiffness while reducing its ductility. The ink's density was also higher while still being in the range of polymers' densities. The presented nanocomposite is light weight, highly conductive, has good mechanical properties and can be printed in a freeform fashion at the micro scale. A myriad of low power consumption with less resistive heating sensors and devices can potentially be designed using it and integrated into other 3D printable products.

  1. Conductance fluctuations in high mobility monolayer graphene: Nonergodicity, lack of determinism and chaotic behavior.

    Science.gov (United States)

    da Cunha, C R; Mineharu, M; Matsunaga, M; Matsumoto, N; Chuang, C; Ochiai, Y; Kim, G-H; Watanabe, K; Taniguchi, T; Ferry, D K; Aoki, N

    2016-09-09

    We have fabricated a high mobility device, composed of a monolayer graphene flake sandwiched between two sheets of hexagonal boron nitride. Conductance fluctuations as functions of a back gate voltage and magnetic field were obtained to check for ergodicity. Non-linear dynamics concepts were used to study the nature of these fluctuations. The distribution of eigenvalues was estimated from the conductance fluctuations with Gaussian kernels and it indicates that the carrier motion is chaotic at low temperatures. We argue that a two-phase dynamical fluid model best describes the transport in this system and can be used to explain the violation of the so-called ergodic hypothesis found in graphene.

  2. Proton conducting membranes for high temperature fuel cells with solid state water free membranes

    Science.gov (United States)

    Narayanan, Sekharipuram R. (Inventor); Yen, Shiao-Pin S. (Inventor)

    2006-01-01

    A water free, proton conducting membrane for use in a fuel cell is fabricated as a highly conducting sheet of converted solid state organic amine salt, such as converted acid salt of triethylenediamine with two quaternized tertiary nitrogen atoms, combined with a nanoparticulate oxide and a stable binder combined with the converted solid state organic amine salt to form a polymeric electrolyte membrane. In one embodiment the membrane is derived from triethylenediamine sulfate, hydrogen phosphate or trifiate, an oxoanion with at least one ionizable hydrogen, organic tertiary amine bisulfate, polymeric quaternized amine bisulfate or phosphate, or polymeric organic compounds with quaternizable nitrogen combined with Nafion to form an intimate network with ionic interactions.

  3. High-conductance states in a mean-field cortical network model

    CERN Document Server

    Lerchner, A; Hertz, J

    2004-01-01

    Measured responses from visual cortical neurons show that spike times tend to be correlated rather than exactly Poisson distributed. Fano factors vary and are usually greater than 1 due to the tendency of spikes being clustered into bursts. We show that this behavior emerges naturally in a balanced cortical network model with random connectivity and conductance-based synapses. We employ mean field theory with correctly colored noise to describe temporal correlations in the neuronal activity. Our results illuminate the connection between two independent experimental findings: high conductance states of cortical neurons in their natural environment, and variable non-Poissonian spike statistics with Fano factors greater than 1.

  4. Fast prototyping of conducting polymer microelectrodes using resistance-controlled high precision drilling

    DEFF Research Database (Denmark)

    Kafka, Jan Robert; Geschke, Oliver; Skaarup, Steen

    2011-01-01

    We present a straightforward method for fast prototyping of microelectrode arrays in the highly conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT). Microelectrode arrays were produced by electrical resistance-controlled microdrilling through an insulating polymer layer (TOPAS® 5013...... of 130μm and 300μm, respectively, were fabricated. Their functionality was verified by chronoamperometry on potassium ferro-/ferricyanide. Comparison of the experimentally obtained results to finite element modeling of the respective electrode configurations shows that the conducting polymer electrodes...

  5. Geochemical and isotopic characteristics associated with high soil conductivities in a shallow hydrocarbon-contaminated aquifer

    Science.gov (United States)

    Legall, Franklyn David

    Data collected from a network of in-situ vertical resistivity probes (VRPs) deployed at a hydrocarbon-contaminated site in SW Michigan showed high conductivities associated with the zone of contamination. Within the contaminated portion of the aquifer, different phases of hydrocarbon impact are recognized, namely, zones with residual and dissolved phase hydrocarbons (RDH) and zones where these phases coexist with free product (RDFH). Bulk soil conductivities were highest (12 to 30 mS/m) in the RDFH zone compared to the RDH zone (10 to 25 mS/m). Geochemical and isotopic data from closely spaced vertical samples within the high conductive zones were used to provide geochemical evidence for biodegradation and to investigate redox processes occurring within the conductive zones. Depth distribution of TEAs and educts showed evidence of reduction of nitrate, iron, manganese, and sulfate across steep vertical gradients. Within the portion of the plume characterized by RDH, SO4 reduction has supplanted denitrification via dissimilatory nitrate reduction, and the reduction of Fe (III) and Mn(IV) as the major observed redox process. This zone was also characterized by the highest DIC. The delta 13CDIC values of -16.9 to -9.5‰ suggest that DIC evolution within this zone is controlled by carbonate dissolution through enhanced CO2 production related to microbial hydrocarbon degradation. Within the portion of the aquifer with RDFH, DIC was lower compared to the RDH location with an associated delta13CDIC in the range of +6.5 to -4.4‰. Both the DIC and delta 13CDIC suggest that methanogenesis is the dominant redox process. With respect to mineral weathering as a possible source of ions contributing to high conductivities, the results show higher concentrations of Na, Ca, and Mg in the contaminated portion of the aquifer compared to uncontaminated parts. This is consistent with the weathering of carbonate and Na and Ca feldspars, the dominant minerals in the aquifer. Higher

  6. Highly conductive quasi-coaxial electrospun quaternized polyvinyl alcohol nanofibers and composite as high-performance solid electrolytes

    Science.gov (United States)

    Liao, Guan-Ming; Li, Pin-Chieh; Lin, Jia-Shiun; Ma, Wei-Ting; Yu, Bor-Chern; Li, Hsieh-Yu; Liu, Ying-Ling; Yang, Chun-Chen; Shih, Chao-Ming; Lue, Shingjiang Jessie

    2016-02-01

    Electrospun quaternized polyvinyl alcohol (Q-PVA) nanofibers are prepared, and a potassium hydroxide (KOH)-doped nanofiber mat demonstrates enhanced ionic conductivity compared with a dense Q-PVA film with KOH doping. The Q-PVA composite containing 5.98% electrospun Q-PVA nanofibers exhibits suppressed methanol permeability. Both the high conductivity and suppressed methanol permeability are attributed to the quasi-coaxial structure of the electrospun nanofibers. The core of the fibers exhibits a more amorphous region that forms highly conductive paths, while the outer shell of the nanofibers contains more polymer crystals that serve as a hard sheath surrounding the soft core. This shell induces mass transfer resistance and creates a tortuous fuel pathway that suppresses methanol permeation. Such a Q-PVA composite is an effective solid electrolyte that makes the use of alkaline fuel cells viable. In a direct methanol alkaline fuel cell operated at 60 °C, a peak power density of 54 mW cm-2 is obtained using the electrospun Q-PVA composite, a 36.4% increase compared with a cell employing a pristine Q-PVA film. These results demonstrate that highly conductive coaxial electrospun nanofibers can be prepared through a single-opening spinneret and provide a possible approach for high-performance electrolyte fabrication.

  7. Thermal conductivity changes across a structural phase transition: The case of high-pressure silica

    Science.gov (United States)

    Aramberri, Hugo; Rurali, Riccardo; Íñiguez, Jorge

    2017-11-01

    By means of first-principles calculations, we investigate the thermal properties of silica as it evolves, under hydrostatic compression, from a stishovite phase into a CaCl2-type structure. We compute the thermal conductivity tensor by solving the linearized Boltzmann transport equation iteratively in a wide temperature range, using for this the pressure-dependent harmonic and anharmonic interatomic couplings obtained from first principles. Most remarkably, we find that, at low temperatures, SiO2 displays a large peak in the in-plane thermal conductivity and a highly anisotropic behavior close to the structural transformation. We trace back the origin of these features by analyzing the phonon contributions to the conductivity. We discuss the implications of our results in the general context of continuous structural transformations in solids, as well as the potential geological interest of our results for silica.

  8. Chemical synthesis and characterization of highly soluble conducting polyaniline in the mixtures of common solvents

    Directory of Open Access Journals (Sweden)

    Zeghioud Hichem

    2015-01-01

    Full Text Available This work presents the synthesis and characterization of soluble and conducting polyaniline PANI-PIA according to chemical polymerization route. This polymerization pathway leads to the formation of poly(itaconic acid doped polyaniline salts, which are highly soluble in a number of mixtures between organic common polar solvents and water, the solubility reaches 4 mg mL-1. The effect of synthesis parameters such as doping level on the conductivity and the study of solubility and other properties of the resulting PANI salts were also undertaken. The maximum of conductivity was found equal to 2.48×10-4 S cm-1 for fully protonated PANI-EB. In addition, various characterizations of the synthesized materials were also done with the help of viscosity measurements, UV-vis spectroscopy, XRD, FTIR and finally TGA for the thermal properties behaviour.

  9. A facile approach to a silver conductive ink with high performance for macroelectronics.

    Science.gov (United States)

    Tao, Yu; Tao, Yuxiao; Wang, Biaobing; Wang, Liuyang; Tai, Yanlong

    2013-06-25

    An unusual kind of transparent and high-efficiency organic silver conductive ink (OSC ink) was synthesized with silver acetate as silver carrier, ethanolamine as additive, and different kinds of aldehyde-based materials as reduction agents and was characterized by using a thermogravimetric analyzer, X-ray diffraction, a scanning electron microscope, and a four-point probe. The results show that different reduction agents all have an important influence on the conductive properties of the ink through a series of complex chemical reactions, and especially when formic acid or dimethylformamide was used as the reduction agent and sintered at 120°C for 30 s, the resistivity can be lowered to 6 to 9 μΩ·cm. Furthermore, formula mechanism, conductive properties, temperature, and dynamic fatigue properties were investigated systematically, and the feasibility of the OSC ink was also verified through the preparation of an antenna pattern.

  10. Portable conduction velocity experiments using earthworms for the college and high school neuroscience teaching laboratory.

    Science.gov (United States)

    Shannon, Kyle M; Gage, Gregory J; Jankovic, Aleksandra; Wilson, W Jeffrey; Marzullo, Timothy C

    2014-03-01

    The earthworm is ideal for studying action potential conduction velocity in a classroom setting, as its simple linear anatomy allows easy axon length measurements and the worm's sparse coding allows single action potentials to be easily identified. The earthworm has two giant fiber systems (lateral and medial) with different conduction velocities that can be easily measured by manipulating electrode placement and the tactile stimulus. Here, we present a portable and robust experimental setup that allows students to perform conduction velocity measurements within a 30-min to 1-h laboratory session. Our improvement over this well-known preparation is the combination of behaviorally relevant tactile stimuli (avoiding electrical stimulation) with the invention of minimal, low-cost, and portable equipment. We tested these experiments during workshops in both a high school and college classroom environment and found positive learning outcomes when we compared pre- and posttests taken by the students.

  11. Enhanced high temperature thermoelectric response of sulphuric acid treated conducting polymer thin films

    KAUST Repository

    Sarath Kumar, S. R.

    2015-11-24

    We report the high temperature thermoelectric properties of solution processed pristine and sulphuric acid treated poly(3, 4-ethylenedioxythiophene):poly(4-styrenesulfonate) (or PEDOT:PSS) films. The acid treatment is shown to simultaneously enhance the electrical conductivity and Seebeck coefficient of the metal-like films, resulting in a five-fold increase in thermoelectric power factor (0.052 W/m. K ) at 460 K, compared to the pristine film. By using atomic force micrographs, Raman and impedance spectra and using a series heterogeneous model for electrical conductivity, we demonstrate that acid treatment results in the removal of PSS from the films, leading to the quenching of accumulated charge-induced energy barriers that prevent hopping conduction. The continuous removal of PSS with duration of acid treatment also alters the local band structure of PEDOT:PSS, resulting in simultaneous enhancement in Seebeck coefficient.

  12. Preparation of solid silver nanoparticles for inkjet printed flexible electronics with high conductivity

    Science.gov (United States)

    Shen, Wenfeng; Zhang, Xianpeng; Huang, Qijin; Xu, Qingsong; Song, Weijie

    2014-01-01

    Silver nanoparticles (NPs) which could be kept in solid form and were easily stored without degeneration or oxidation at room temperature for a long period of time were synthesized by a simple and environmentally friendly wet chemistry method in an aqueous phase. Highly stable dispersions of aqueous silver NP inks, sintered at room temperature, for printing highly conductive tracks (~8.0 μΩ cm) were prepared simply by dispersing the synthesized silver NP powder in water. These inks are stable, fairly homogeneous and suitable for a wide range of patterning techniques. The inks were successfully printed on paper and polyethylene terephthalate (PET) substrates using a common color printer. Upon annealing at 180 °C, the resistivity of the printed silver patterns decreased to 3.7 μΩ cm, which is close to twice that of bulk silver. Various factors affecting the resistivity of the printed silver patterns, such as annealing temperature and the number of printing cycles, were investigated. The resulting high conductivity of the printed silver patterns reached over 20% of the bulk silver value under ambient conditions, which enabled the fabrication of flexible electronic devices, as demonstrated by the inkjet printing of conductive circuits of LED devices.Silver nanoparticles (NPs) which could be kept in solid form and were easily stored without degeneration or oxidation at room temperature for a long period of time were synthesized by a simple and environmentally friendly wet chemistry method in an aqueous phase. Highly stable dispersions of aqueous silver NP inks, sintered at room temperature, for printing highly conductive tracks (~8.0 μΩ cm) were prepared simply by dispersing the synthesized silver NP powder in water. These inks are stable, fairly homogeneous and suitable for a wide range of patterning techniques. The inks were successfully printed on paper and polyethylene terephthalate (PET) substrates using a common color printer. Upon annealing at 180 °C, the

  13. Flexible Lithium-Ion Batteries with High Areal Capacity Enabled by Smart Conductive Textiles.

    Science.gov (United States)

    Ha, Sung Hoon; Shin, Kyu Hang; Park, Hae Won; Lee, Yun Jung

    2018-02-05

    Increasing demand for flexible devices in various applications, such as smart watches, healthcare, and military applications, requires the development of flexible energy-storage devices, such as lithium-ion batteries (LIBs) with high flexibility and capacity. However, it is difficult to ensure high capacity and high flexibility simultaneously through conventional electrode preparation processes. Herein, smart conductive textiles are employed as current collectors for flexible LIBs owing to their inherent flexibility, fibrous network, rough surface for better adhesion, and electrical conductivity. Conductivity and flexibility are further enhanced by nanosizing lithium titanate oxide (LTO) and lithium iron phosphate (LFP) active materials, and hybridizing them with a flexible 2D graphene template. The resulting LTO/LFP full cells demonstrate high areal capacity and flexibility with tolerance to mechanical fatigue. The battery achieves a capacity of 1.2 mA h cm-2 while showing excellent flexibility. The cells demonstrate stable open circuit voltage retention under repeated flexing for 1000 times at a bending radius of 10 mm. The discharge capacity of the unflexed battery is retained in cells subjected to bending for 100 times at bending radii of 30, 20, and 10 mm, respectively, confirming that the suggested electrode configuration successfully prevents structural damage (delamination or cracking) upon repeated deformation. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. High-Thermal-Conductivity Densified Graphitic Foams as Novel Bearing Materials

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Jun [ORNL; Blau, Peter Julian [ORNL; Klett, James William [ORNL; Jolly, Brian C [ORNL

    2006-01-01

    The high-thermal-conductivity graphitic foams (foam-reinforced carbon-carbon composites) developed at ORNL have been mainly used for thermal management, as in heat sinks for electronic circuit boards and highly-efficient automotive radiators. However, recent studies in our laboratory have rather unexpectedly revealed their potential as novel bearing materials. In addition to their low density and potential for weight savings, there are three primary tribological advantages of the graphitic foam materials: (1) their graphitic structures provide self-lubricating qualities, (2) their extraordinarily high thermal conductivity aids in the efficient removal of frictionally-generated heat, and (3) the pores in the foam serve both as wear debris traps and lubricant reservoirs. Previous studies on the densified graphitic foam (DGF) sliding against steel and alumina at relatively low speed (1 m/s) and low load (10 N), revealed their encouraging self-lubricating behavior, comparable to solid graphite while much better than bronze and polytetrafluoroethylene (Teflon{trademark}). In this study, pin-on-disk tests with higher speeds (2, 6, and 10 m/s) and higher loads (322 N) were conducted on DGF and graphite disks sliding against a DGF pin. The surface temperature on the graphite disk increased rapidly due to frictional heating and the friction coefficient increased proportionally with surface temperature when it was higher than 40 C. The DGF disk, however, ran much cooler due to the higher thermal conductivity, and more impressively, the friction coefficient remained low and constant even at elevated disk temperatures. This suggests high potential for the graphitic foam material in weight-sensitive, high-speed, and elevated temperature bearing applications.

  15. Impaired neural conduction in the auditory brainstem of high-risk very preterm infants.

    Science.gov (United States)

    Jiang, Ze D; Chen, Chao

    2014-06-01

    To test the hypothesis that neural conduction in the auditory brainstem is impaired in high-risk very preterm infants. Eighty-two very preterm infants (gestation 28-32 weeks) with various perinatal problems or complications were studied at term using maximum length sequence (MLS) brainstem auditory evoked response (BAER) with click rates 91-910/s. The data were compared with those in 31 age-matched low-risk very preterm infants and 44 normal gestation (term) infants. High-risk very preterm infants showed a general increase in MLS BAER wave latencies and interpeak intervals. Wave V latency, and III-V and I-V intervals in high-risk very preterm infants were significantly longer than in normal term infants at all click rates, particularly higher rates. I-III interval was significantly longer, and III-V/I-III interval ratio was significantly greater at higher rates. These latency and intervals in high-risk very preterm infants were also longer, though relatively less significantly, than in low-risk very preterm infants. Click rate-related changes in major MLS BAER variables in high-risk infants were more significant than in the two groups of controls. There were major abnormalities in MLS BAER variables that mainly reflect central neural conduction in high-risk very preterm infants. The abnormalities were relatively less significant when compared with low-risk very preterm infants than with normal term infants. Neural conduction in the auditory brainstem, mainly the more central regions, is impaired in high-risk very preterm infants. The impairment is largely attributed to the associated perinatal problems, and partially related to very preterm birth. Copyright © 2013. Published by Elsevier Ireland Ltd.

  16. Thermal conductivity and diffusivity of climax stock quartz monzonite at high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Durham, W.B.; Abey, A.E.

    1981-11-01

    Measurements of thermal conductivity and thermal diffusivity have been made on two samples of Climax Stock quartz monzonite at pressures between 3 and 50 MPa and temperatures between 300 and 523{sup 0}K. Following those measurements the apparatus was calibrated with respect to the thermal conductivity measurement using a reference standard of fused silica. Corrected thermal conductivity of the rock indicates a value at room temperature of 2.60 +- 0.25 W/mK at 3 MPa increasing linearly to 2.75 +- 0.25 W/mK at 50 MPa. These values are unchanged (+- 0.07 W/mK) by heating under 50-MPa pressure to as high as 473{sup 0}K. The conductivity under 50-MPa confining pressure falls smoothly from 2.75 +- 0.25 W/mK at 313{sup 0}K to 2.15 +- 0.25 W/mK at 473{sup 0}K. Thermal diffusivity at 300{sup 0}K was found to be 1.2 +- 0.4 X 10{sup -6} m{sup 2}/s and shows approximately the same pressure and temperature dependencies as the thermal conductivity.

  17. The design of high-temperature thermal conductivity measurements apparatus for thin sample size

    Directory of Open Access Journals (Sweden)

    Hadi Syamsul

    2017-01-01

    Full Text Available This study presents the designing, constructing and validating processes of thermal conductivity apparatus using steady-state heat-transfer techniques with the capability of testing a material at high temperatures. This design is an improvement from ASTM D5470 standard where meter-bars with the equal cross-sectional area were used to extrapolate surface temperature and measure heat transfer across a sample. There were two meter-bars in apparatus where each was placed three thermocouples. This Apparatus using a heater with a power of 1,000 watts, and cooling water to stable condition. The pressure applied was 3.4 MPa at the cross-sectional area of 113.09 mm2 meter-bar and thermal grease to minimized interfacial thermal contact resistance. To determine the performance, the validating process proceeded by comparing the results with thermal conductivity obtained by THB 500 made by LINSEIS. The tests showed the thermal conductivity of the stainless steel and bronze are 15.28 Wm-1K-1 and 38.01 Wm-1K-1 with a difference of test apparatus THB 500 are −2.55% and 2.49%. Furthermore, this apparatus has the capability to measure the thermal conductivity of the material to a temperature of 400°C where the results for the thermal conductivity of stainless steel is 19.21 Wm-1K-1 and the difference was 7.93%.

  18. Effects of high-frequency alternating current on axonal conduction through the vagus nerve

    Science.gov (United States)

    Waataja, Jonathan J.; Tweden, Katherine S.; Honda, Christopher N.

    2011-10-01

    High-frequency alternating current (HFAC) is known to disrupt axonal conduction in peripheral nerves, and HFAC has much potential as a therapeutic approach for a number of pathological conditions. Many previous studies have utilized motor output as a bioassay of effects of HFAC on conduction through medium- to large-diameter motor axons. However, little is known about the effectiveness of HFAC on smaller, more slowly conducting nerve fibres. The present study tested whether HFAC influences axonal conduction through sub-diaphragmatic levels of the rat vagus nerve, which consists almost entirely of small calibre axons. Using an isolated nerve preparation, we tested the effects of HFAC on electrically evoked compound action potentials (CAPs). We found that delivery of charge-balanced HFAC at 5000 Hz for 1 min was effective in producing reversible blockade of axonal conduction. Both Aδ and C components of the vagus CAP were attenuated, and the degree of blockade as well as time to recovery was proportional to the amount of HFAC current delivered. The Aδ waves were more sensitive than C waves to HFAC blockade, but they required more time to recover.

  19. Highly Sulfonated Diamine Synthesized Polyimides and Protic Ionic Liquid Composite Membranes Improve PEM Conductivity

    Directory of Open Access Journals (Sweden)

    Bor-Kuan Chen

    2015-06-01

    Full Text Available A novel sulfonated diamine was synthesized from 1,4-bis(4-aminophenoxy benzene [pBAB]. Sulfonated polyimides (SPIs were synthesized from sulfonated pBAB, 1,4-bis(4-aminophenoxy-2-sulfonic acid benzenesulfonic acid [pBABTS], various diamines and aromatic dianhydrides. Composite proton exchange membranes (PEMs made of novel SPIs and a protic ionic liquid (PIL 1-vinyl-3-H-imidazolium trifluoromethanesulfonate [VIm][OTf] showed substantially increased conductivity. We prepared an SPI/PIL composite PEM using pBABTS, 4,4′-(9-fluorenylidene dianiline (9FDA as diamine, 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA as dianhydride and 40 wt % [VIm][OTf] with a high conductivity of 16 mS/cm at 120 °C and anhydrous condition. pBABTS offered better conductivity, since the chemical structure had more sulfonated groups that provide increased conductivity. The new composite membrane could be a promising anhydrous or low-humidity PEM for intermediate or high-temperature fuel cells.

  20. Temperature-Dependent Thermal Conductivity of High Strength Lightweight Raw Perlite Aggregate Concrete

    Science.gov (United States)

    Tandiroglu, Ahmet

    2010-06-01

    Twenty-four types of high strength lightweight concrete have been designed with raw perlite aggregate (PA) from the Erzincan Mollaköy region as new low-temperature insulation material. The effects of the water/cement ratio, the amount of raw PA, and the temperature on high strength lightweight raw perlite aggregate concrete (HSLWPAC) have been investigated. Three empirical equations were derived to correlate the thermal conductivity of HSLWPAC as a function of PA percentage and temperature depending on the water/cement ratio. Experimentally observed thermal conductivities of concrete samples were predicted 92 % of the time for each set of concrete matrices within 97 % accuracy and over the range from 1.457 W · m-1 · K-1 to 1.777 W · m-1 · K-1. The experimental investigation revealed that the usage of raw PA from the Erzincan Mollaköy region in concrete production reduces the concrete unit mass, increases the concrete strength, and furthermore, the thermal conductivity of the concrete has been improved. The proposed empirical correlations of thermal conductivity were considered to be applicable within the range of temperatures 203.15 K ≤ T ≤ 303.15 K in the form of λ = a( PAP b ) + c( T d ).

  1. Single-layer nanosheets with exceptionally high and anisotropic hydroxyl ion conductivity.

    Science.gov (United States)

    Sun, Pengzhan; Ma, Renzhi; Bai, Xueyin; Wang, Kunlin; Zhu, Hongwei; Sasaki, Takayoshi

    2017-04-01

    When the dimensionality of layered materials is reduced to the physical limit, an ultimate two-dimensional (2D) anisotropy and/or confinement effect may bring about extraordinary physical and chemical properties. Layered double hydroxides (LDHs), bearing abundant hydroxyl groups covalently bonded within 2D host layers, have been proposed as inorganic anion conductors. However, typical hydroxyl ion conductivities for bulk or lamellar LDHs, generally up to 10 -3 S cm -1 , are considered not high enough for practical applications. We show that single-layer LDH nanosheets exhibited exceptionally high in-plane conductivities approaching 10 -1 S cm -1 , which were the highest among anion conductors and comparable to proton conductivities in commercial proton exchange membranes (for example, Nafion). The in-plane conductivities were four to five orders of magnitude higher than the cross-plane or cross-membrane values of restacked LDH nanosheets. This 2D superionic transport characteristic might have great promises in a variety of applications including alkaline fuel cells and water electrolysis.

  2. Construction of 3D Skeleton for Polymer Composites Achieving a High Thermal Conductivity.

    Science.gov (United States)

    Yao, Yimin; Sun, Jiajia; Zeng, Xiaoliang; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2018-02-02

    Owing to the growing heat removal issue in modern electronic devices, electrically insulating polymer composites with high thermal conductivity have drawn much attention during the past decade. However, the conventional method to improve through-plane thermal conductivity of these polymer composites usually yields an undesired value (below 3.0 Wm -1 K -1 ). Here, construction of a 3D phonon skeleton is reported composed of stacked boron nitride (BN) platelets reinforced with reduced graphene oxide (rGO) for epoxy composites by the combination of ice-templated and infiltrating methods. At a low filler loading of 13.16 vol%, the resulting 3D BN-rGO/epoxy composites exhibit an ultrahigh through-plane thermal conductivity of 5.05 Wm -1 K -1 as the best thermal-conduction performance reported so far for BN sheet-based composites. Theoretical models qualitatively demonstrate that this enhancement results from the formation of phonon-matching 3D BN-rGO networks, leading to high rates of phonon transport. The strong potential application for thermal management has been demonstrated by the surface temperature variations of the composites with time during heating and cooling. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Highly Conductive Anion-Exchange Membranes from Microporous Tröger's Base Polymers.

    Science.gov (United States)

    Yang, Zhengjin; Guo, Rui; Malpass-Evans, Richard; Carta, Mariolino; McKeown, Neil B; Guiver, Michael D; Wu, Liang; Xu, Tongwen

    2016-09-12

    The development of polymeric anion-exchange membranes (AEMs) combining high ion conductivity and long-term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V-shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion-exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm(-1) is obtained at a relatively a low ion-exchange capacity of 0.82 mmol g(-1) under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Nano silver diffusion behaviour on conductive polymer during doping process for high voltage application

    Science.gov (United States)

    Mohammad, A.; Mahmood, A.; Chin, K. T.; Danquah, M. K.; van Stratan, S.

    2017-06-01

    Conductive polymer had opened a new era of engineering for microelectronics and semiconductor applications. However, it is still a challenge for high voltage applications due to lower electrical conductivity compare to metals. This results tremendous energy losses during transmission and restricts its usage. In order to address such problem a novel method was investigated using nano silver particle doped iodothiophene since silver is the highest electrical conductive material. The experiments were carried out to study the organometallic diffusion behaviour of nanosilver doped iodothiophene with different concentration of iodothiophene. Five different mixing ratio between nanosilver and the solution of iodothiophene dissolved in diethyl ether were used which are 1:1.25, 1:1.5, 1:2.5, 1:3 and l:5. It was revealed that there is an effective threshold concentration of which the nano silver evenly distributed and there was no coagulation observed. These parameters laid the foundation of better doping process between the nano silver and the polymer significantly which would contribute developing conductive polymer towards high voltage application for industries that are vulnerable to corrosive environment.

  5. Aqueous dispersed conducting polyaniline nanofibers: Promising high specific capacity electrode materials for supercapacitor

    Science.gov (United States)

    Zhang, Hongming; Zhao, Qiang; Zhou, Shuiping; Liu, Nianjiang; Wang, Xianhong; Li, Ji; Wang, Fosong

    Aqueous dispersed conducting polyaniline nanofiber, new electrode material for supercapacitor, is prepared employing acidic phosphate ester as dopant for nanofibrous polyaniline emeraldine base, which is synthesized by polymerization of aniline using ferric nitrate as oxidant through pseudo-high dilution technique. Highly crystalline and uniform polyaniline fibers with thin diameter of 17-26 nm are obtained, the film from which shows electrical conductivity of 32 S cm -1. The thin nanofibrous polyaniline is used as electrode material for supercapacitor and its performance is evaluated in non-protonic solvent system. It shows a specific capacitance as high as 160 F g -1 at discharge rate of 0.4 A g -1 from -1 V to 1 V in 1 mol L -1 tetraethylammonium tetrafluoroborate/propylene carbonate solution, and the discharge/charge efficiency reaches 92%, indicating that it possesses good electrochemical reversibility. The high capacitance can be attributed to its relatively high surface area of 70 m 2 g -1, which is 3-5 times higher than spherical polyaniline or thick fiberous polyaniline, leading to high utilization of the electroactive materials.

  6. The Origin of High Thermal Conductivity and Ultralow Thermal Expansion in Copper-Graphite Composites.

    Science.gov (United States)

    Firkowska, Izabela; Boden, André; Boerner, Benji; Reich, Stephanie

    2015-07-08

    We developed a nanocomposite with highly aligned graphite platelets in a copper matrix. Spark plasma sintering ensured an excellent copper-graphite interface for transmitting heat and stress. The resulting composite has superior thermal conductivity (500 W m(-1) K(-1), 140% of copper), which is in excellent agreement with modeling based on the effective medium approximation. The thermal expansion perpendicular to the graphite platelets drops dramatically from ∼20 ppm K(-1) for graphite and copper separately to 2 ppm K(-1) for the combined structure. We show that this originates from the layered, highly anisotropic structure of graphite combined with residual stress under ambient conditions, that is, strain-engineering of the thermal expansion. Combining excellent thermal conductivity with ultralow thermal expansion results in ideal materials for heat sinks and other devices for thermal management.

  7. Highly conductive Cu2-xS nanoparticle films through room-temperature processing and an order of magnitude enhancement of conductivity via electrophoretic deposition.

    Science.gov (United States)

    Otelaja, Obafemi O; Ha, Don-Hyung; Ly, Tiffany; Zhang, Haitao; Robinson, Richard D

    2014-11-12

    A facile room-temperature method for assembling colloidal copper sulfide (Cu2-xS) nanoparticles into highly electrically conducting films is presented. Ammonium sulfide is utilized for connecting the nanoparticles via ligand removal, which transforms the as-deposited insulating films into highly conducting films. Electronic properties of the treated films are characterized with a combination of Hall effect measurements, field-effect transistor measurements, temperature-dependent conductivity measurements, and capacitance-voltage measurements, revealing their highly doped p-type semiconducting nature. The spin-cast nanoparticle films have carrier concentration of ∼ 10(19) cm(-3), Hall mobilities of ∼ 3 to 4 cm(2) V(-1) s(-1), and electrical conductivities of ∼ 5 to 6 S · cm(-1). Our films have hole mobilities that are 1-4 orders of magnitude higher than hole mobilities previously reported for heat-treated nanoparticle films of HgTe, InSb, PbS, PbTe, and PbSe. We show that electrophoretic deposition (EPD) as a method for nanoparticle film assembly leads to an order of magnitude enhancement in film conductivity (∼ 75 S · cm(-1)) over conventional spin-casting, creating copper sulfide nanoparticle films with conductivities comparable to bulk films formed through physical deposition methods. The X-ray diffraction patterns of the Cu2-xS films, with and without ligand removal, match the Djurleite phase (Cu(1.94)S) of copper sulfide and show that the nanoparticles maintain finite size after the ammonium sulfide processing. The high conductivities reported are attributed to better interparticle coupling through the ammonium sulfide treatment. This approach presents a scalable room-temperature route for fabricating highly conducting nanoparticle assemblies for large-area electronic and optoelectronic applications.

  8. Highly Conductive Cu 2– x S Nanoparticle Films through Room-Temperature Processing and an Order of Magnitude Enhancement of Conductivity via Electrophoretic Deposition

    KAUST Repository

    Otelaja, Obafemi O.

    2014-11-12

    © 2014 American Chemical Society. A facile room-temperature method for assembling colloidal copper sulfide (Cu2-xS) nanoparticles into highly electrically conducting films is presented. Ammonium sulfide is utilized for connecting the nanoparticles via ligand removal, which transforms the as-deposited insulating films into highly conducting films. Electronic properties of the treated films are characterized with a combination of Hall effect measurements, field-effect transistor measurements, temperature-dependent conductivity measurements, and capacitance-voltage measurements, revealing their highly doped p-type semiconducting nature. The spin-cast nanoparticle films have carrier concentration of ∼1019 cm-3, Hall mobilities of ∼3 to 4 cm2 V-1 s-1, and electrical conductivities of ∼5 to 6 S·cm-1. Our films have hole mobilities that are 1-4 orders of magnitude higher than hole mobilities previously reported for heat-treated nanoparticle films of HgTe, InSb, PbS, PbTe, and PbSe. We show that electrophoretic deposition (EPD) as a method for nanoparticle film assembly leads to an order of magnitude enhancement in film conductivity (∼75 S·cm-1) over conventional spin-casting, creating copper sulfide nanoparticle films with conductivities comparable to bulk films formed through physical deposition methods. The X-ray diffraction patterns of the Cu2-xS films, with and without ligand removal, match the Djurleite phase (Cu1.94S) of copper sulfide and show that the nanoparticles maintain finite size after the ammonium sulfide processing. The high conductivities reported are attributed to better interparticle coupling through the ammonium sulfide treatment. This approach presents a scalable room-temperature route for fabricating highly conducting nanoparticle assemblies for large-area electronic and optoelectronic applications.

  9. Hydralazine-induced vasodilation involves opening of high conductance Ca2+-activated K+ channels

    DEFF Research Database (Denmark)

    Bang, Lone; Nielsen-Kudsk, J E; Gruhn, N

    1998-01-01

    The purpose of this study was to investigate whether high conductance Ca2+-activated K+ channels (BK(Ca)) are mediating the vasodilator action of hydralazine. In isolated porcine coronary arteries, hydralazine (1-300 microM), like the K+ channel opener levcromakalim, preferentially relaxed......M) suppressed this response by 82% (P opening of BK(Ca) takes part in the mechanism whereby...

  10. High temperature color conductivity at next-to-leading log order

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, Peter; Yaffe, Laurence G.

    2000-12-15

    The non-Abelian analogue of electrical conductivity at high temperature has previously been known only at leading logarithmic order -- that is, neglecting effects suppressed only by an inverse logarithm of the gauge coupling. We calculate the first sub-leading correction. This has immediate application to improving, to next-to-leading log order, both effective theories of non-perturbative color dynamics, and calculations of the hot electroweak baryon number violation rate.

  11. High-Throughput Synthesis, Screening, and Scale-Up of Optimized Conducting Indium Tin Oxides

    OpenAIRE

    Marchand, P; Makwana, N. M.; Tighe, C. J.; Gruar, R. I.; Parkin, I. P.; Carmalt, C. J.; Darr, J. A.

    2016-01-01

    A high-throughput optimization and subsequent scale-up methodology has been used for the synthesis of conductive tin-doped indium oxide (known as ITO) nanoparticles. ITO nanoparticles with up to 12 at % Sn were synthesized using a laboratory scale (15 g/hour by dry mass) continuous hydrothermal synthesis process, and the as-synthesized powders were characterized by powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscop...

  12. High electrical conductivity in out of plane direction of electrodeposited Bi2Te3 films

    Directory of Open Access Journals (Sweden)

    Miguel Muñoz Rojo

    2015-08-01

    Full Text Available The out of plane electrical conductivity of highly anisotropic Bi2Te3 films grown via electro-deposition process was determined using four probe current-voltage measurements performed on 4.6 - 7.2 μm thickness Bi2Te3 mesa structures with 80 - 120 μm diameters sandwiched between metallic film electrodes. A three-dimensional finite element model was used to predict the electric field distribution in the measured structures and take into account the non-uniform distribution of the current in the electrodes in the vicinity of the probes. The finite-element modeling shows that significant errors could arise in the measured film electrical conductivity if simpler one-dimensional models are employed. A high electrical conductivity of (3.2 ± 0.4 ⋅ 105 S/m is reported along the out of plane direction for Bi2Te3 films highly oriented in the [1 1 0] direction.

  13. From industrially weavable and knittable highly conductive yarns to large wearable energy storage textiles.

    Science.gov (United States)

    Huang, Yan; Hu, Hong; Huang, Yang; Zhu, Minshen; Meng, Wenjun; Liu, Chang; Pei, Zengxia; Hao, Chonglei; Wang, Zuankai; Zhi, Chunyi

    2015-05-26

    Wearable electronic textiles that store capacitive energy are a next frontier in personalized electronics. However, the lack of industrially weavable and knittable conductive yarns in conjunction with high capacitance, limits the wide-scale application of such textiles. Here pristine soft conductive yarns are continuously produced by a scalable method with the use of twist-bundle-drawing technique, and are mechanically robust enough to be knitted to a cloth by a commercial cloth knitting machine. Subsequently, the reduced-graphene-oxide-modified conductive yarns covered with a hierarchical structure of MnO2 nanosheets and a polypyrrole thin film were used to fabricate weavable, knittable and wearable yarn supercapacitors. The resultant modified yarns exhibit specific capacitances as high as 36.6 mF cm(-1) and 486 mF cm(-2) in aqueous electrolyte (three-electrode cell) or 31 mF cm(-1) and 411 mF cm(-2) in all solid-state two-electrode cell. The symmetric solid-state supercapacitor has high energy densities of 0.0092 mWh cm(-2) and 1.1 mWh cm(-3) (both normalized to the whole device) with a long cycle life. Large energy storage textiles are fabricated by weaving our flexible all-solid-state supercapacitor yarns to a 15 cm × 10 cm cloth on a loom and knitting in a woollen wrist band to form a pattern, enabling dual functionalities of energy storage capability and wearability.

  14. Facile synthesis of highly conductive sulfur-doped reduced graphene oxide sheets.

    Science.gov (United States)

    Tian, Zhengshan; Li, Jitao; Zhu, Gangyi; Lu, Junfeng; Wang, Yueyue; Shi, Zengliang; Xu, Chunxiang

    2016-01-14

    A facile hydrothermal strategy to synthesize sulfur-doped reduced graphene oxide (S-RGO) sheets with good conductivity is proposed by using only graphene oxide (GO) sheets and sodium sulphide (Na2S) as precursors through a hydrothermal reaction process at 200 °C in one pot. The introduced Na2S can act as not only a sulfur dopant, but also as a highly efficient reducing agent in the formation of S-RGO sheets, which dramatically improves the electrical conductivities of the resulting S-RGO sheets compared with previous reports. The current reaches about 50.0 mA at an applied bias of 2.0 V for the optimized sample with 2.22 at% sulfur doping. This current value is much higher than that of RGO sheets (∼1.2 mA) annealed at 200 °C, and very close to that of single-layer graphene sheets (∼68.0 mA) prepared using chemical vapor deposition under the same test conditions. The resulting highly conductive S-RGO sheets offer many promising technological applications such as efficient metal-free electrocatalysts in oxygen reduction reactions in fuel cells and as supercapacitor electrode materials for high-performance Li-ion batteries.

  15. Metastable defects are the origin of high conductivity in gallium doped zinc oxide

    Science.gov (United States)

    Zakutayev, Andriy; Perry, Nicola; Mason, Thomas; Ginley, David; Lany, Stephan

    2014-03-01

    Doping in wide-bandgap materials is often counteracted by formation of intrinsic compensating defects of opposite charge. One prototypical exception to this general rule is gallium doped zinc oxide (ZnO:Ga) used as transparent conductor in numerous applications. High conductivities (1,000-10,000 S/cm) in ZnO:Ga are typically achieved during the growth at 250 - 350C around 10⌃-8 atm. The corresponding electron concentration exceed by a factor of 100,000 the values expected in equilibrium from first principles calculations. In contrast at high temperature and high oxygen partial pressure conductivity of ZnO:Ga measured in-situ shows good agreement with the ab initio theoretical thermodynamic model. The results of this study indicate that degenerate levels of doping in ZnO:Ga transparent conductive oxide used in practical applications are enabled by non-equilibrium concentration of both extrinsic donors and compensating acceptors. This work was supported by U.S. Department of Energy.

  16. Electrical properties of highly conducting Sno2:Sb nanocrystals synthesized using a nonaqueous sol gel method

    OpenAIRE

    Conti, Tiago Góes; Chiquito, A. J.; Silva, Rafael Oliveira da; Longo, Elson [UNESP; Leite, Edson Roberto

    2010-01-01

    This work describes the synthesis of highly conducting antimony-doped tin oxide (ATO) nanocrystals prepared via a nonaqueous sol–gel route in the size range of 4–6 nm and provides insights into its electrical properties. The antimony composition was varied from 1 to 18 mol% and the lowest resistivity (4.0 × 10−4Ω·cm) was observed at room temperature in the SnO2:8.8 mol% Sb composition. The samples were evaluated by X-ray diffraction, high-resolution transmission electron microscopy, energy-di...

  17. Theory of electrical conductivity and dielectric permittivity of highly aligned graphene-based nanocomposites.

    Science.gov (United States)

    Xia, Xiaodong; Hao, Jia; Wang, Yang; Zhong, Zheng; Weng, George J

    2017-05-24

    Highly aligned graphene-based nanocomposites are of great interest due to their excellent electrical properties along the aligned direction. Graphene fillers in these composites are not necessarily perfectly aligned, but their orientations are highly confined to a certain angle, [Formula: see text] with 90° giving rise to the randomly oriented state and 0° to the perfectly aligned one. Recent experiments have shown that electrical conductivity and dielectric permittivity of highly aligned graphene-polymer nanocomposites are strongly dependent on this distribution angle, but at present no theory seems to exist to address this issue. In this work we present a new effective-medium theory that is derived from the underlying physical process including the effects of graphene orientation, filler loading, aspect ratio, percolation threshold, interfacial tunneling, and Maxwell-Wagner-Sillars polarization, to determine these two properties. The theory is formulated in the context of preferred orientational average. We highlight this new theory with an application to rGO/epoxy nanocomposites, and demonstrate that the calculated in-plane and out-of-plane conductivity and permittivity are in agreement with the experimental data as the range of graphene orientations changes from the randomly oriented to the highly aligned state. We also show that the percolation thresholds of highly aligned graphene nanocomposites are in general different along the planar and the normal directions, but they converge into a single one when the statistical distribution of graphene fillers is spherically symmetric.

  18. The Whitehill Formation - a high conductivity marker horizon in the Karoo Basin

    Energy Technology Data Exchange (ETDEWEB)

    Branch, T.; Ritter, O.; Weckmann, U.; Sachsenhofer, R.F.; Schilling, F. [Geoforschungszentrum Potsdam, Potsdam (Germany)

    2007-09-15

    Within the Inkaba yeAfrica project, magnetotelluric (MT) data were acquired along three profiles across the Karoo Basin in South Africa. The Whitehill Formation is known to be regionally persistent in composition and thickness and can be traced throughout the entire Karoo Basin. In the region of our experiments, the Whitehill Formation varies in thickness between 50 to 70 m and consists of pyritic black shales with up to 14 weight % carbonaceous matter. Rocks can exhibit high electrical conductivity if electronically conducting minerals, such as graphite, are interconnected. To study physical properties and the maturity of the carbon present in the Whitehill Formation, impedance spectroscopy and vitrinite reflectance were applied to core samples from the SA1/66 borehole, taken from this formation at a depth range between 2750 m and 2800 m. Vitrinite reflectance analysis of the pseudo-coal and oil shale rocks indicates that most of the carbon is in the meta-anthracite maturity field, approaching, in one sample, the 'graphite window'. Impedance spectroscopy reveals that the highest electrical conductivities are associated with the pyrite rich portion of one sample, showing conductivities well above 1 S/m. Recordings on pyrite-poor samples are less conclusive, with observed conductivities varying in the range of a few S/m to mS/m. Measurements on samples from the Whilehill Formation, on the other hand, show consistently low resistivities in the range between 4 to 6 {Omega} m. This result suggests strongly that the sub-horizontal conductivity anomaly in the MT models is linked with the carbon-rich sequences of the Whitehill Formation.

  19. Three-Dimensional Printing of Highly Conductive Carbon Nanotube Microarchitectures with Fluid Ink.

    Science.gov (United States)

    Kim, Jung Hyun; Lee, Sanghyeon; Wajahat, Muhammad; Jeong, Hwakyung; Chang, Won Suk; Jeong, Hee Jin; Yang, Jong-Ryul; Kim, Ji Tae; Seol, Seung Kwon

    2016-09-27

    Moving printed electronics to three dimensions essentially requires advanced additive manufacturing techniques yielding multifunctionality materials and high spatial resolution. Here, we report the meniscus-guided 3D printing of highly conductive multiwall carbon nanotube (MWNT) microarchitectures that exploit rapid solidification of a fluid ink meniscus formed by pulling a micronozzle. To achieve high-quality printing with continuous ink flow through a confined nozzle geometry, that is, without agglomeration and nozzle clogging, we design a polyvinylpyrrolidone-wrapped MWNT ink with uniform dispersion and appropriate rheological properties. The developed technique can produce various desired 3D microstructures, with a high MWNT concentration of up to 75 wt % being obtained via post-thermal treatment. Successful demonstrations of electronic components such as sensing transducers, emitters, and radio frequency inductors are also described herein. We expect that the technique presented in this study will facilitate selection of diverse materials in 3D printing and enhance the freedom of integration for advanced conceptual devices.

  20. Study of electrical conductivity response upon formation of ice and gas hydrates from salt solutions by a second generation high pressure electrical conductivity probe.

    Science.gov (United States)

    Sowa, Barbara; Zhang, Xue Hua; Kozielski, Karen A; Dunstan, Dave E; Hartley, Patrick G; Maeda, Nobuo

    2014-11-01

    We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane-propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an "electrical conductivity response phase diagrams" that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.

  1. High performance diamond-like carbon layers obtained by pulsed laser deposition for conductive electrode applications

    Science.gov (United States)

    Stock, F.; Antoni, F.; Le Normand, F.; Muller, D.; Abdesselam, M.; Boubiche, N.; Komissarov, I.

    2017-09-01

    For the future, one of the biggest challenge faced to the technologies of flat panel display and various optoelectronic and photovoltaic devices is to find an alternative to the use of transparent conducting oxides like ITO. In this new approach, the objective is to grow high conductive thin-layer graphene (TLG) on the top of diamond-like carbon (DLC) layers presenting high performance. DLC prepared by pulsed laser deposition (PLD) have attracted special interest due to a unique combination of their properties, close to those of monocrystalline diamond, like its transparency, hardness and chemical inertia, very low roughness, hydrogen-free and thus high thermal stability up to 1000 K. In our future work, we plane to explore the synthesis of conductive TLG on top of insulating DLC thin films. The feasibility and obtained performances of the multi-layered structure will be explored in great details in the short future to develop an alternative to ITO with comparable performance (conductivity of transparency). To select the best DLC candidate for this purpose, we focus this work on the physicochemical properties of the DLC thin films deposited by PLD from a pure graphite target at two wavelengths (193 and 248 nm) at various laser fluences. A surface graphenization process, as well as the required efficiency of the complete structure (TLG/DLC) will clearly be related to the DLC properties, especially to the initial sp3/sp2 hybridization ratio. Thus, an exhaustive description of the physicochemical properties of the DLC layers is a fundamental step in the research of comparable performance to ITO.

  2. Experimental investigation of the reliability issue of RRAM based on high resistance state conduction.

    Science.gov (United States)

    Zhang, Lijie; Hsu, Yen-Ya; Chen, Frederick T; Lee, Heng-Yuan; Chen, Yu-Sheng; Chen, Wei-Su; Gu, Pei-Yi; Liu, Wen-Hsing; Wang, Shun-Min; Tsai, Chen-Han; Huang, Ru; Tsai, Ming-Jinn

    2011-06-24

    In this paper, reliability issues of robust HfO(x)-based RRAM are experimentally investigated in terms of cycling ageing, temperature impact and voltage acceleration. All reliability issues can be estimated by the conduction of the high resistance state (HRS). The conduction current of the HRS exponentially increases as the square root of the applied voltage, which is well explained by 'quasi-Poole-Frenkel-type' trap assistant tunneling. Further experiments on HRS conduction at different temperatures show that the depth of the potential well of the trap in HfO(x) film is about 0.31 eV. The degradation induced by the cycling ageing is possibly ascribed to the increase of the amount of oxygen ions in the TiO(x) layer of the TiN/TiO(x)/HfO(x)/TiN device. The retention times with various stress voltages at different temperatures also exhibit an exponential relationship to the square root of the applied voltage, indicating that stress current plays a dominant role for the degradation of the HRS. An oxygen-release model is proposed to explain the relationship of retention time to HRS conduction current.

  3. Tailoring highly conductive graphene nanoribbons from small polycyclic aromatic hydrocarbons: a computational study

    KAUST Repository

    Bilić, A

    2013-06-14

    Pyrene, the smallest two-dimensional mesh of aromatic rings, with various terminal thiol substitutions, has been considered as a potential molecular interconnect. Charge transport through two terminal devices has been modeled using density functional theory (with and without self interaction correction) and the non-equilibrium Green\\'s function method. A tetra-substituted pyrene, with dual thiol terminal groups at opposite ends, has been identified as an excellent candidate, owing to its high conductance, virtually independent of bias voltage. The two possible extensions of its motif generate two series of graphene nanoribbons, with zigzag and armchair edges and with semimetallic and semiconducting electron band structure, respectively. The effects related to the wire length and the bias voltage on the charge transport have been investigated for both sets. The conductance of the nanoribbons with a zigzag edge does not show either length or voltage dependence, owing to an almost perfect electron transmission with a continuum of conducting channels. In contrast, for the armchair nanoribbons a slow exponential attenuation of the conductance with the length has been found, due to their semiconducting nature. © 2013 IOP Publishing Ltd.

  4. Experimental investigation of the reliability issue of RRAM based on high resistance state conduction

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Lijie; Huang Ru [Institute of Microelectronics, Peking University, Beijing 100871 (China); Hsu, Yen-Ya; Chen, Frederick T; Lee, Heng-Yuan; Chen Yusheng; Chen Weisu; Gu Peiyi; Liu, Wen-Hsing; Wang, Shun-Min; Tsai, Chen-Han; Tsai, Ming-Jinn, E-mail: zhanglijie@ime.pku.edu.cn [Nanoelectronic Technology Division, Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute (ITRI), Chutung, Hsinchu 31040, Taiwan (China)

    2011-06-24

    In this paper, reliability issues of robust HfO{sub x}-based RRAM are experimentally investigated in terms of cycling ageing, temperature impact and voltage acceleration. All reliability issues can be estimated by the conduction of the high resistance state (HRS). The conduction current of the HRS exponentially increases as the square root of the applied voltage, which is well explained by 'quasi-Poole-Frenkel-type' trap assistant tunneling. Further experiments on HRS conduction at different temperatures show that the depth of the potential well of the trap in HfO{sub x} film is about 0.31 eV. The degradation induced by the cycling ageing is possibly ascribed to the increase of the amount of oxygen ions in the TiO{sub x} layer of the TiN/TiO{sub x}/HfO{sub x}/TiN device. The retention times with various stress voltages at different temperatures also exhibit an exponential relationship to the square root of the applied voltage, indicating that stress current plays a dominant role for the degradation of the HRS. An oxygen-release model is proposed to explain the relationship of retention time to HRS conduction current.

  5. Highly anisotropic conductivity of tablets pressed from polyaniline-montmorillonite nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Tokarský, Jonáš, E-mail: jonas.tokarsky@vsb.cz [Nanotechnology centre, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); IT4Innovations Centre of Excellence, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Kulhánková, Lenka [Faculty of Metallurgy and Materials Engineering, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Neuwirthová, Lucie; Mamulová Kutláková, Kateřina [Nanotechnology centre, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Vallová, Silvie [Faculty of Metallurgy and Materials Engineering, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Stýskala, Vítězslav [Faculty of Electrical Engineering and Computer Science, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Čapková, Pavla [Faculty of Science, University of J.E. Purkyně, České mládeže 8, 400 96 Ústí nad Labem (Czech Republic)

    2016-03-15

    Highlights: • Montmorillonite (MMT) can be intercalated with polyaniline (PANI) chains. • Tablets pressed from PANI/MMT exhibit high anisotropy in electrical conductivity. • Pressure 28MPa is sufficient to reach the anisotropy. • Tablets pressed from pure PANI also exhibit anisotropy in electrical conductivity. - Abstract: Polyaniline-montmorillonite nanocomposite was prepared from anilinium sulfate (precursor) and ammonium peroxodisulfate (oxidizing agent) using simple one-step method. The resulting nanocomposite obtained in powder form has been pressed into tablets using various compression pressures (28–400 MPa). Electrical conductivities of tablets in two perpendicular directions, i.e. direction parallel with the main surface of tablet (σ=) and in orthogonal direction (σ⊥), and corresponding anisotropy factors (i.e., the ratio σ=/σ⊥) have been studied in dependence on compression pressure used during the preparation. Polyaniline-montmorillonite nanocomposite was characterized using X-ray diffraction analysis, raman spectroscopy, transmission electron microscopy, thermogravimetric analysis and molecular modeling which led to the understanding of the internal structure. Measurement of hardness performed on pressed tablets has been also involved. Taking into account the highest value of anisotropy factor reached (σ=/σ⊥ = 490), present study shows a chance to design conductors with nearly two-dimensional conductivity.

  6. A highly sensitive, low-cost, wearable pressure sensor based on conductive hydrogel spheres

    KAUST Repository

    Tai, Yanlong

    2015-01-01

    Wearable pressure sensing solutions have promising future for practical applications in health monitoring and human/machine interfaces. Here, a highly sensitive, low-cost, wearable pressure sensor based on conductive single-walled carbon nanotube (SWCNT)/alginate hydrogel spheres is reported. Conductive and piezoresistive spheres are embedded between conductive electrodes (indium tin oxide-coated polyethylene terephthalate films) and subjected to environmental pressure. The detection mechanism is based on the piezoresistivity of the SWCNT/alginate conductive spheres and on the sphere-electrode contact. Step-by-step, we optimized the design parameters to maximize the sensitivity of the sensor. The optimized hydrogel sensor exhibited a satisfactory sensitivity (0.176 ΔR/R0/kPa-1) and a low detectable limit (10 Pa). Moreover, a brief response time (a few milliseconds) and successful repeatability were also demonstrated. Finally, the efficiency of this strategy was verified through a series of practical tests such as monitoring human wrist pulse, detecting throat muscle motion or identifying the location and the distribution of an external pressure using an array sensor (4 × 4). © 2015 The Royal Society of Chemistry.

  7. Is Geometric Frustration-Induced Disorder a Recipe for High Ionic Conductivity?

    Science.gov (United States)

    Düvel, Andre; Heitjans, Paul; Fedorov, Pavel; Scholz, Gudrun; Cibin, Giannantonio; Chadwick, Alan V; Pickup, David M; Ramos, Silvia; Sayle, Lewis W L; Sayle, Emma K L; Sayle, Thi X T; Sayle, Dean C

    2017-04-26

    Ionic conductivity is ubiquitous to many industrially important applications such as fuel cells, batteries, sensors, and catalysis. Tunable conductivity in these systems is therefore key to their commercial viability. Here, we show that geometric frustration can be exploited as a vehicle for conductivity tuning. In particular, we imposed geometric frustration upon a prototypical system, CaF2, by ball milling it with BaF2, to create nanostructured Ba1-xCaxF2 solid solutions and increased its ionic conductivity by over 5 orders of magnitude. By mirroring each experiment with MD simulation, including "simulating synthesis", we reveal that geometric frustration confers, on a system at ambient temperature, structural and dynamical attributes that are typically associated with heating a material above its superionic transition temperature. These include structural disorder, excess volume, pseudovacancy arrays, and collective transport mechanisms; we show that the excess volume correlates with ionic conductivity for the Ba1-xCaxF2 system. We also present evidence that geometric frustration-induced conductivity is a general phenomenon, which may help explain the high ionic conductivity in doped fluorite-structured oxides such as ceria and zirconia, with application for solid oxide fuel cells. A review on geometric frustration [ Nature 2015 , 521 , 303 ] remarks that classical crystallography is inadequate to describe systems with correlated disorder, but that correlated disorder has clear crystallographic signatures. Here, we identify two possible crystallographic signatures of geometric frustration: excess volume and correlated "snake-like" ionic transport; the latter infers correlated disorder. In particular, as one ion in the chain moves, all the other (correlated) ions in the chain move simultaneously. Critically, our simulations reveal snake-like chains, over 40 Å in length, which indicates long-range correlation in our disordered systems. Similarly, collective

  8. A new assessment of the crystalline structure of undoped and doped aniline oligomers and polymers

    Energy Technology Data Exchange (ETDEWEB)

    Lux, F. [School of Chemistry, University of Bristol, Cantock`s Close, Bristol BS8 1TS (United Kingdom); Samuelsen, E.J. [Department of Physics and Mathematics, University of Trondheim, Norwegian Institute of Technology, 7034 Trondheim (Norway); Kang, E.T. [Department of Chemical Engineering, National University of Singapore, Kent Ridge, 0511 Singapore (Singapore)

    1995-03-01

    We describe here the crystalline structure of aniline oligomers and polymers, derived from the aniline dimer, p-aminodiphenylamine, and aniline. It is shown that while the crystalline structure of the undoped samples is generally in reasonable accord with the findings of Pouget et al. for their EBII-structure, especially the crystalline arrangement of the doped materials does not fit the picture, given by these authors for the ESII-salt. The latter fact might be rationalized by the simple exchange of the two main peaks of the ESII arrangement, thus giving the P2{sub 1}22{sub 1} arrangement, proposed by Pouget et al. but not found in their experimental studies. (orig.)

  9. Intrinsic oxygen vacancies mediated multi-mechano-responsive piezoluminescence in undoped zinc calcium oxysulfide

    Science.gov (United States)

    Pan, Cong; Zhang, Jun-Cheng; Zhang, Min; Yan, Xu; Long, Yun-Ze; Wang, Xusheng

    2017-06-01

    Piezoluminescence has achieved enormous advancement in the field of stress sensors, and mechano-driven lightings and displays; however the existing piezoluminescent materials universally need the external dopants of lanthanide or transition metal ions to create efficient luminescence. Herein, we report a bright piezoluminescence in undoped piezoelectric semiconductor CaZnOS, which is multi-mechano-sensitive to ultrasonic vibration, friction, impact and compression. Our experimental and density functional theory computational investigations indicate that the intrinsic oxygen vacancies of VO 2 +, VO + and VO 0 act as luminescent centers and trap states in multi-colored components of luminescence. In addition to saving resources and protecting environment, our research is expected to open a door for design and development of self-piezoluminescent materials, thereby largely expanding our understanding of piezoluminescent mechanism and promoting further utilization of piezoluminescence.

  10. Magnetoresistance in a nominally undoped InGaN thin film

    Energy Technology Data Exchange (ETDEWEB)

    Ding, K. [Chinese Academy of Sciences, Key Laboratory of Semiconductor Materials Science, P.O. Box 912, Beijing (China); Chinese Academy of Sciences, Novel Material Center, Institute of Semiconductors, P.O. Box 912, Beijing (China); Zeng, Y.P. [Chinese Academy of Sciences, Key Laboratory of Semiconductor Materials Science, P.O. Box 912, Beijing (China); Chinese Academy of Sciences, Novel Material Center, Institute of Semiconductors, P.O. Box 912, Beijing (China); Chinese Academy of Sciences, Research and Development Center for Semiconductor Lighting, P.O. Box 912, Beijing (China); Li, Y.Y.; Cui, L.J. [Chinese Academy of Sciences, Novel Material Center, Institute of Semiconductors, P.O. Box 912, Beijing (China); Wang, J.X.; Lu, H.X.; Cong, P.P. [Chinese Academy of Sciences, Research and Development Center for Semiconductor Lighting, P.O. Box 912, Beijing (China)

    2010-04-15

    The magnetotransport properties of a nominally undoped InGaN thin film grown by metal-organic chemical vapor deposition were investigated. Resistivity was measured under a magnetic field up to 5 T over the temperature range of 3 to 298 K. The film exhibits a negative magnetoresistance at low temperatures. Its magnitude decreases with increasing temperature, and turns to be positive for temperatures above 100 K. The negative component was described by a model proposed by Khosla and Fischer for spin scattering of carriers in an impurity band. The positive part was attributed to the effect of Lorentz force on the carrier motion. Agreement between the model and the data is presented. (orig.)

  11. Liquid Crystalline Epoxies with Lateral Substituents Showing a Low Dielectric Constant and High Thermal Conductivity

    Science.gov (United States)

    Guo, Huilong; Lu, Mangeng; Liang, Liyan; Wu, Kun; Ma, Dong; Xue, Wei

    2017-02-01

    In this work, liquid crystalline epoxies with lateral substituents were synthesized and cured with aromatic amines or anhydride. The liquid crystalline phase structure of liquid crystalline epoxies with lateral substituents was determined by polarized optical microscopy. The relationship between thermal conductivity and dielectric properties and liquid crystalline domain structure was discussed in the paper. The samples show high thermal conductivity up to 0.29 W/(m × K), due to the orientation of mesogenic units in epoxies. The sample's low dielectric constant of 2.29 is associated with the oriented mesogenic units and long nonpolar lateral substituents. This indicates a new way to obtain materials with high thermal conductivity and a low dielectric constant by introducing oriented mesogenic units into cross-linked epoxy systems. The water repellency is reflected in the contact angles of 92-98°, which are apparently higher than that of conventional epoxy systems. It was also found that the better toughness of liquid crystalline epoxies with lateral substituents was attributed to the existence of long flexible alkyl lateral substituents.

  12. Hierarchically-structured silver nanoflowers for highly conductive metallic inks with dramatically reduced filler concentration

    Science.gov (United States)

    Muhammed Ajmal, C.; K. P., Faseela; Singh, Swati; Baik, Seunghyun

    2016-10-01

    Silver has long been employed as an electrically conductive component, and morphology-dependent properties have been actively investigated. Here we present a novel scalable synthesis method of flower-shaped silver nanoparticles (silver nanoflowers, Ag NFs). The preferential affinity of citrate molecules on (111) surface of silver enabled spontaneous anisotropic growth of Ag NFs (bud size: 250~580 nm, single crystalline petal thickness: 9~22 nm) with high reproducibility and a high yield of >99.5%. The unique hierarchical structure resulted in coalescence of petals over 80~120 °C which was practically employed in conductive inks to construct percolation pathways among Ag NFs. The ink with only 3 wt% of Ag NFs provided two orders of magnitude greater conductivity (1.008 × 105 Scm-1), at a low curing temperature of 120 °C, compared with the silver nanoparticle ink with a much higher silver concentration (50 wt%). This extraordinary property may provide an excellent opportunity for Ag NFs for practical applications in printable and flexible electronics.

  13. Record-high specific conductance and water temperature in San Francisco Bay during water year 2015

    Science.gov (United States)

    Work, Paul; Downing-Kunz, Maureen; Livsey, Daniel

    2017-02-22

    The San Francisco estuary is commonly defined to include San Francisco Bay (bay) and the adjacent Sacramento–San Joaquin River Delta (delta). The U.S. Geological Survey (USGS) has operated a high-frequency (15-minute sampling interval) water-quality monitoring network in San Francisco Bay since the late 1980s (Buchanan and others, 2014). This network includes 19 stations at which sustained measurements have been made in the bay; currently, 8 stations are in operation (fig. 1). All eight stations are equipped with specific conductance (which can be related to salinity) and water-temperature sensors. Water quality in the bay constantly changes as ocean tides force seawater in and out of the bay, and river inflows—the most significant coming from the delta—vary on time scales ranging from those associated with storms to multiyear droughts. This monitoring network was designed to observe and characterize some of these changes in the bay across space and over time. The data demonstrate a high degree of variability in both specific conductance and temperature at time scales from tidal to annual and also reveal longer-term changes that are likely to influence overall environmental health in the bay.In water year (WY) 2015 (October 1, 2014, through September 30, 2015), as in the preceding water year (Downing-Kunz and others, 2015), the high-frequency measurements revealed record-high values of specific conductance and water temperature at several stations during a period of reduced freshwater inflow from the delta and other tributaries because of persistent, severe drought conditions in California. This report briefly summarizes observations for WY 2015 and compares them to previous years that had different levels of freshwater inflow.

  14. Magnetic amphiphilic hybrid carbon nanotubes containing N-doped and undoped sections: powerful tensioactive nanostructures

    Science.gov (United States)

    Purceno, Aluir D.; Machado, Bruno F.; Teixeira, Ana Paula C.; Medeiros, Tayline V.; Benyounes, Anas; Beausoleil, Julien; Menezes, Helvecio C.; Cardeal, Zenilda L.; Lago, Rochel M.; Serp, Philippe

    2014-11-01

    In this work, unique amphiphilic magnetic hybrid carbon nanotubes (CNTs) are synthesized and used as tensioactive nanostructures in different applications. These CNTs interact very well with aqueous media due to the hydrophilic N-doped section, whereas the undoped hydrophobic one has strong affinity for organic molecules. The amphiphilic character combined with the magnetic properties of these CNTs opens the door to completely new and exciting applications in adsorption science and catalysis. These amphiphilic N-doped CNTs can also be used as powerful tensioactive emulsification structures. They can emulsify water/organic mixtures and by a simple magnetic separation the emulsion can be easily broken. We demonstrate the application of these CNTs in the efficient adsorption of various molecules, in addition to promoting biphasic processes in three different reactions, i.e. transesterification of soybean oil, quinoline extractive oxidation with H2O2 and a metal-catalyzed aqueous oxidation of heptanol with molecular oxygen.In this work, unique amphiphilic magnetic hybrid carbon nanotubes (CNTs) are synthesized and used as tensioactive nanostructures in different applications. These CNTs interact very well with aqueous media due to the hydrophilic N-doped section, whereas the undoped hydrophobic one has strong affinity for organic molecules. The amphiphilic character combined with the magnetic properties of these CNTs opens the door to completely new and exciting applications in adsorption science and catalysis. These amphiphilic N-doped CNTs can also be used as powerful tensioactive emulsification structures. They can emulsify water/organic mixtures and by a simple magnetic separation the emulsion can be easily broken. We demonstrate the application of these CNTs in the efficient adsorption of various molecules, in addition to promoting biphasic processes in three different reactions, i.e. transesterification of soybean oil, quinoline extractive oxidation with H2O2 and

  15. Calculation of the high-frequency conductivity and the Hall constant of a thin semiconductor film

    Science.gov (United States)

    Savenko, O. V.; Romanov, D. N.; Kuznetsova, I. A.

    2016-12-01

    The task about calculation of high-frequency conductivity and Hall constant of a thin semiconductor film is solved by the kinetic method. This film is placed in transverse stationary magnetic field and longitudinal alternative electric field. The ratio between film thickness and mean free path of charge carriers is assumed to be arbitrary. Skin effect is negligible. The diffuse-specular mechanism of charge carriers scattering from film surfaces is considered in the view of equal mirrority coefficients of the upper and lower film surfaces. The dependences of non-dimensional conductivity and Hall constant on non-dimensional parameters: electric field frequency, magnetic field induction and film thickness are investigated. The comparative analysis of obtained results with the calculations for the case of a metal film are made.

  16. Free-Standing Reduced Graphene Oxide Paper with High Electrical Conductivity

    Science.gov (United States)

    Gao, Jie; Liu, Chengyan; Miao, Lei; Wang, Xiaoyang; Chen, Yu

    2016-03-01

    With high carrier mobility and low cost, reduced graphene oxide (RGO) shows bright prospects for use in the field of thermoelectric materials. To investigate the intrinsic thermoelectric properties of RGO sheets, we prepared RGO papers which were reduced by HBr solution for 5 min, 20 min, and 60 min, respectively. Thermogravimetry analysis (TGA) and Raman analysis showed that the conjugated carbon network of graphene oxide (GO) was restored during the reduction process and the thermal stability of the RGO papers was much better than that of GO paper. The RGO paper that was reduced for 60 min and then annealed in Ar/H2 atmosphere exhibited the highest electrical conductivity of 3.22 × 105 S/m at 160°C. As the reduction degree of the RGO paper deepens, the Seebeck coefficient gradually transforms from positive to negative, indicating that the conduction type of RGO paper can be controlled by regulating the reduction degree.

  17. Bone conduction errors at high frequencies: implications for clinical and medico-legal practice.

    Science.gov (United States)

    Lightfoot, G R; Hughes, J B

    1993-04-01

    The magnitude and origin of audiometric air-bone gaps in the range 3 kHz to 8 kHz was investigated in 20 normal subjects. The average gap ranged from a minimum of about 3 dB at 3 kHz to a maximum of about 19 dB at 6 kHz. Approximately 5 dB of the gap at high frequencies is caused by excess air-radiated sound from the bone vibrator. A larger error appears to result from discrepancies between the air and bone conduction standards to which audiometers are calibrated. These errors may influence diagnosis and we recommend that bone conduction tests at frequencies greater than 4 kHz are avoided. These findings have implications for medico-legal work where small air-bone gaps have diagnostic significance.

  18. High-conductance states in a mean-field cortical network model

    DEFF Research Database (Denmark)

    Lerchner, Alexander; Ahmadi, Mandana; Hertz, John

    2004-01-01

    Measured responses from visual cortical neurons show that spike times tend to be correlated rather than exactly Poisson distributed. Fano factors vary and are usually greater than 1, indicating a tendency toward spikes being clustered. We show that this behavior emerges naturally in a balanced...... cortical network model with random connectivity and conductance-based synapses. We employ mean-field theory with correctly colored noise to describe temporal correlations in the neuronal activity. Our results illuminate the connection between two independent experimental findings: high-conductance states...... of cortical neurons in their natural environment, and variable non-Poissonian spike statistics with Fano factors greater than 1. (C) 2004 Elsevier B.V. All rights reserved....

  19. A Tunable 3D Nanostructured Conductive Gel Framework Electrode for High-Performance Lithium Ion Batteries.

    Science.gov (United States)

    Shi, Ye; Zhang, Jun; Bruck, Andrea M; Zhang, Yiman; Li, Jing; Stach, Eric A; Takeuchi, Kenneth J; Marschilok, Amy C; Takeuchi, Esther S; Yu, Guihua

    2017-06-01

    This study develops a tunable 3D nanostructured conductive gel framework as both binder and conductive framework for lithium ion batteries. A 3D nanostructured gel framework with continuous electron pathways can provide hierarchical pores for ion transport and form uniform coatings on each active particle against aggregation. The hybrid gel electrodes based on a polypyrrole gel framework and Fe3 O4 nanoparticles as a model system in this study demonstrate the best rate performance, the highest achieved mass ratio of active materials, and the highest achieved specific capacities when considering total electrode mass, compared to current literature. This 3D nanostructured gel-based framework represents a powerful platform for various electrochemically active materials to enable the next-generation high-energy batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Filme autosuportado de polianilina desdopada para aplicações anticorrosivas Characterization of self-standing films of undoped polyanilina

    Directory of Open Access Journals (Sweden)

    Rodrigo S. Silva

    2012-01-01

    Full Text Available Os polímeros intrinsecamente condutores (PIC, como a polianilina (PAni, têm sido estudados com alternativa em filmes protetores de metais oxidáveis contra a corrosão. Dada a dificuldade de fusão ou dissolução da PAni para a produção de filmes, investigou-se a possibilidade de obter filmes pela mistura de PAni no estado oxidado e desdopado, conhecida como base esmeraldina, com plastificante não dopante 4-cloro-3-metilfenol (CMF e solvente conveniente. Filmes produzidos desta forma foram caracterizados por espectroscopia FTIR e RAMAN, por TGA e ensaio de voltametria cíclica. A caracterização mostrou filmes termicamente estáveis até a temperatura de 200 ºC com indícios de interação da PAni com o CMF, com a PAni se mantendo no estado oxidado no filme produzido, condição necessária para futura aplicação como filme anticorrosivo de proteção anódica.The intrinsically conductive polymers (PCI, such as polyaniline (PAni, have been studied as an alternative in the development of protective films of oxidizable metals against corrosion. Given the difficulty of mixing and dissolving PAni for the production of films, here we investigated the possibility of obtaining a mixture of PAni films in the oxidized, undoped state, referred to as emeraldine base, with the non-doping plasticizer 4-chloro-3-methylphenol (CMF and a convenient solvent. Films produced in this way were characterized by FTIR and Raman spectroscopy, TGA and cyclic voltammetry. The characterization showed films thermally stable up to 200 ºC with evidence of interaction between PAni and CMF, with PAni remaining in the oxidized state in the film produced, which a necessary condition for application as anodic protection in anticorrosion films.

  1. Honeycomb supports with high thermal conductivity for the Tischer-Tropsch synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Visconti, C.G.; Rronconi, E.; Groppi, G.; Lietti, L. [Politecnico di Milano (Italy). Dipt. di Energia; Iovane, M.; Rossini, S.; Zennaro, R. [Eni S.p.A., San Donato Milanese (Italy). Div. Exploration and Production

    2011-07-01

    The potential of multitubular reactors loaded with washcoated structured catalysts having highly conductive honeycomb supports is investigated herein in the low temperature Fischer- Tropsch synthesis by means of a theoretical investigation. Simulation results indicate that extruded aluminum honeycomb monoliths, washcoated with a Co-based catalyst, are promising for the application at the industrial scale, in particular when adopting supports with high cell densities and catalysts with high activity. Limited temperature gradients within the reactor are in fact possible even at extreme process conditions, thus leading to interesting volumetric reactor yields with negligible pressure drop. This result is achieved without the need of cofeeding to the reactor large amounts of liquid hydrocarbons to remove the reaction heat, as opposite to existing industrial Fischer-Tropsch packed-bed reactors. (orig.)

  2. Preparation of water-soluble graphene nanoplatelets and highly conductive films

    KAUST Repository

    Xu, Xuezhu

    2017-08-11

    This paper tackles the challenge of preparation stable, highly concentrated aqueous graphene dispersions. Despite tremendous recent interest, there has been limited success in developing a method that ensures the total dispersion of non-oxidized, defect-free graphene nanosheets in water. This study successfully demonstrates that few-layer graphene nanoplatelets (GNPs) can form highly concentrated aqueous colloidal solutions after they have been pretreated in a low-concentration inorganic sodium-hypochlorite and sodium-bromide salted aqueous solvent. This method retains the graphitic structure as evidenced by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Vacuum-filtrated freestanding films demonstrate an electrical conductivity as high as 3000 S m−1. This dispersion technique is believed to be applicable not only for GNPs, but also for dispersing other types of graphitic materials, including fullerenes, single/double/multi-walled carbon nanotubes, graphene nanoribbons and etc.

  3. High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte.

    Science.gov (United States)

    Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

    2016-02-22

    Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known "polysulfide shuttle" effect. Here, we report a novel cell design by sandwiching a sp(3) boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates.

  4. Highly conductive metal interconnects on three-dimensional objects fabricated with omnidirectional ink jet printing technology

    Science.gov (United States)

    Yoshida, Yasunori; Wada, Hikaru; Izumi, Konami; Tokito, Shizuo

    2017-05-01

    In this work, we demonstrate that highly conductive metal interconnects can be fabricated on the surface of three-dimensional objects using “omnidirectional ink jet” (OIJ) printing technology. OIJ printing technology makes it possible to perform ink jet printing in all directions by combining the motion of a 6-axis vertically articulated robot with precise positioning and a thermal drying process, which allows for the printing of stacked layers. By using OIJ technology, we were the first to successfully fabricate printed interconnect layers having a very low electrical resistance of 12 mΩ over a 10 mm length. Moreover, the results of the high-current test demonstrated that the printed interconnects can withstand high-current-flow of 5 A for 30 min or more.

  5. High Speed Scanning Ion Conductance Microscopy for Quantitative Analysis of Nanoscale Dynamics of Microvilli.

    Science.gov (United States)

    Ida, Hiroki; Takahashi, Yasufumi; Kumatani, Akichika; Shiku, Hitoshi; Matsue, Tomokazu

    2017-06-06

    Observation of nanoscale structure dynamics on cell surfaces is essential to understanding cell functions. Hopping-mode scanning ion conductance microscopy (SICM) was used to visualize the topography of fragile convoluted nanoscale structures on cell surfaces under noninvasive conditions. However, conventional hopping mode SICM does not have sufficient temporal resolution to observe cell-surface dynamics in situ because of the additional time required for performing vertical probe movements of the nanopipette. Here, we introduce a new scanning algorithm for high speed SICM measurements using low capacitance and high-resonance-frequency piezo stages. As a result, a topographic image is taken within 18 s with a 64 × 64 pixel resolution at 10 × 10 μm. The high speed SICM is applied to the characterization of microvilli dynamics on surfaces, which shows clear structural changes after the epidermal growth factor stimulation.

  6. High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte

    Science.gov (United States)

    Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

    2016-01-01

    Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known “polysulfide shuttle” effect. Here, we report a novel cell design by sandwiching a sp3 boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates. PMID:26898772

  7. Thermal Conductivity and Elastic Modulus Evolution of Thermal Barrier Coatings under High Heat Flux Conditions

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.

    1999-01-01

    Laser high heat flux test approaches have been established to obtain critical properties of ceramic thermal barrier coatings (TBCs) under near-realistic temperature and thermal gradients that may he encountered in advanced engine systems. Thermal conductivity change kinetics of a thin ceramic coating were continuously monitored in real time at various test temperatures. A significant thermal conductivity increase was observed during the laser simulated engine heat flux tests. For a 0.25 mm thick ZrO2-8%Y2O3 coating system, the overall thermal conductivity increased from the initial value of 1.0 W/m-K to 1. 15 W/m-K, 1. 19 W/m-K and 1.5 W/m-K after 30 hour testing at surface temperatures of 990C, 1100C, and 1320C. respectively. Hardness and modulus gradients across a 1.5 mm thick TBC system were also determined as a function of laser testing time using the laser sintering/creep and micro-indentation techniques. The coating Knoop hardness values increased from the initial hardness value of 4 GPa to 5 GPa near the ceramic/bond coat interface, and to 7.5 GPa at the ceramic coating surface after 120 hour testing. The ceramic surface modulus increased from an initial value of about 70 GPa to a final value of 125 GPa. The increase in thermal conductivity and the evolution of significant hardness and modulus gradients in the TBC systems are attributed to sintering-induced micro-porosity gradients under the laser-imposed high thermal gradient conditions. The test techniques provide a viable means for obtaining coating data for use in design, development, stress modeling, and life prediction for various thermal barrier coating applications.

  8. Nerve conduction block in diabetic rats using high-intensity focused ultrasound for analgesic applications.

    Science.gov (United States)

    Lee, Y-F; Lin, C-C; Cheng, J-S; Chen, G-S

    2015-05-01

    Nerve conduction block using high-intensity focused ultrasound (HIFU) has been conducted with nerves of mixed fibres in normal animal models. This study tested the feasibility and safety of HIFU for sensory nerve conduction block in diabetic neuropathic nerves to determine its potential for pain relief. Diabetes was induced in Sprague-Dawley rats using streptozotocin, and HIFU at 2.68 MHz was used for the block. This study consisted of two sections, in vitro and in vivo. For the in vitro experiments, the entire contiguous sciatic-sural nerves were obtained. Compound action potentials and sensory action potentials were recorded in the sciatic and sural nerves, respectively. For the in vivo experiments, compound muscle action potentials (CMAPs) were recorded from the gastrocnemius muscles. All data were expressed as median (range). The in vitro results showed that HIFU temporarily inhibited sensory action potentials of the control and diabetic rat nerves to 33.9 (8.2) and 14.0 (10.7)% of the baseline values, respectively, whereas the compound action potentials were suppressed to 53.6 (8.4) and 76.2 (7.5)% of baseline, respectively. The in vivo results showed that HIFU acutely blocked CMAPs to 32.9 (12.6) and 19.9 (10.9)% of baseline in control and diabetic rat nerves, respectively. Measurements of CMAPs and histological exanmination were used for indirect assessment of the safety of the HIFU technique. High-intensity focused ultrasound safely and reversibly suppressed nerve conduction in diabetic rat nerves when the stimulation parameters were appropriate. The results suggest that HIFU may have potential to block sensory nerves reversibly and provide peripheral pain relief. © The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Ultrathin MoO2 nanosheets with good thermal stability and high conductivity

    Directory of Open Access Journals (Sweden)

    Enqiang Pu

    2017-02-01

    Full Text Available Exploration and development of new two-dimensional (2D materials with good stability and remarkable physical properties have become the research hotspots. We report for the first time the monodispersity of ultrathin MoO2 nanosheets have been synthesized through an improved chemical vapor deposition (CVD method using only molybdenum trioxide as precursor. The grown MoO2 nanosheets have an average thickness of ∼ 5 to 10 nm and exhibit good crystal-quality. Temperature-dependent Raman spectra show that the ultrathin MoO2 nanosheets have high thermal stability up to 503 K. In addition, the first order temperature coefficients of the MoO2 characteristic Raman modes O1–Mo and O2–Mo were firstly found to be -1.91×10-2 and -3.94×10-2 cm−1/K, respectively. Two-probe electrical measurements show that the as-fabricated ultrathin MoO2 nanosheets devices preserve a high electrical conductivity in ambient conditions, reaching up to 200 - 475 S/cm. The exceptionally high conductivity of individual MoO2 nanosheet is ascribed to the unique crystal structure. Our results demonstrate that the ultrathin MoO2 nanosheets show great potential applications in constructing new integrated electronic devices and systems.

  10. Homogeneous vertical ZnO nanorod arrays with high conductivity on an in situ Gd nanolayer

    KAUST Repository

    Flemban, Tahani H.

    2015-10-30

    We demonstrate a novel, one-step, catalyst-free method for the production of size-controlled vertical highly conductive ZnO nanorod (NR) arrays with highly desirable characteristics by pulsed laser deposition using a Gd-doped ZnO target. Our study shows that an in situ transparent and conductive Gd nanolayer (with a uniform thickness of ∼1 nm) at the interface between a lattice-matched (11-20) a-sapphire substrate and ZnO is formed during the deposition. This nanolayer significantly induces a relaxation mechanism that controls the dislocation distribution along the growth direction; which consequently improves the formation of homogeneous vertically aligned ZnO NRs. We demonstrate that both the lattice orientation of the substrate and the Gd characteristics are important in enhancing the NR synthesis, and we report precise control of the NR density by changing the oxygen partial pressure. We show that these NRs possess high optical and electrical quality, with a mobility of 177 cm2 (V s)-1, which is comparable to the best-reported mobility of ZnO NRs. Therefore, this new and simple method has significant potential for improving the performance of materials used in a wide range of electronic and optoelectronic applications.

  11. High-ampacity conductive polymer microfibers as fast response wearable heaters and electromechanical actuators

    KAUST Repository

    Zhou, Jian

    2016-01-04

    Conductive fibers with enhanced physical properties and functionalities are needed for a diversity of electronic devices. Here, we report very high performance in the thermal and mechanical response of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) microfibers when subjected to an electrical current. These fibers were made by combining the hot-drawing assisted wetspinning process with ethylene glycol doping/de-doping that can work at a current density as high as 1.8 × 104 A cm−2, which is comparable to that of carbon nanotube fibers. Their electrothermal response was investigated using optical sensors and verified to be as fast as 63 °C s−1 and is comparable with that of metallic heating elements (20–50 °C s−1). We investigated the electromechanical actuation resulted from the reversible sorption/desorption of moisture controlled by electro-induced heating. The results revealed an improvement of several orders of magnitudes compared to other linear conductive polymer-based actuators in air. Specifically, the fibers we designed here have a rapid stress generation rate (>40 MPa s−1) and a wide operating frequency range (up to 40 Hz). These fibers have several characteristics including fast response, low-driven voltage, good repeatability, long cycle life and high energy efficiency, favoring their use as heating elements on wearable textiles and as artificial muscles for robotics.

  12. High-frequency magneto-conductivity studies of low-dimensional organic conductors

    CERN Document Server

    Schrama, J M

    2000-01-01

    Chapter 5 I report two studies of the angle dependence of FTRs in the high-frequency magneto-conductivity. The FTRs in kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 and alpha-(BEDT- TTF) sub 2 KHg(SCN) sub 4 show two previously unknown corrugations in the Q1D Fermi-surface sections of the two materials. The FTRs in alpha-(BEDT-TTF) sub 2 KHg(SCN) sub 4 are investigated both in the density-wave state and near its collapse into a high-temperature, high-field state. In Chapter 6 a study of the millimetre-wave properties of (TMTSF) sub 2 ClO sub 4 at low temperatures is described. Finally, in Chapter 7 I present a study of the angle dependence of the superconductor order parameter in kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 with a new millimetre-wave technique. In this thesis I present experimental studies of the millimetre-wave magneto-conductivity of the organic charge-transfer salts kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 , alpha-(BEDT-TTF sub 2 KHg(SCN) sub 4 and (TMTSF) sub 2 ClO sub 4. A rotating resonant cavity insert was...

  13. Highly stable supercapacitors with conducting polymer core-shell electrodes for energy storage applications

    KAUST Repository

    Xia, Chuan

    2015-01-14

    Conducting polymers such as polyaniline (PAni) show a great potential as pseudocapacitor materials for electrochemical energy storage applications. Yet, the cycling instability of PAni resulting from structural alteration is a major hurdle to its commercial application. Here, the development of nanostructured PAni-RuO2 core-shell arrays as electrodes for highly stable pseudocapacitors with excellent energy storage performance is reported. A thin layer of RuO2 grown by atomic layer deposition (ALD) on PAni nanofibers plays a crucial role in stabilizing the PAni pseudocapacitors and improving their energy density. The pseudocapacitors, which are based on optimized PAni-RuO2 core-shell nanostructured electrodes, exhibit very high specific capacitance (710 F g-1 at 5 mV s-1) and power density (42.2 kW kg-1) at an energy density of 10 Wh kg-1. Furthermore, they exhibit remarkable capacitance retention of ≈88% after 10 000 cycles at very high current density of 20 A g-1, superior to that of pristine PAni-based pseudocapacitors. This prominently enhanced electrochemical stability successfully demonstrates the buffering effect of ALD coating on PAni, which provides a new approach for the preparation of metal-oxide/conducting polymer hybrid electrodes with excellent electrochemical performance.

  14. Defect-induced magnetism in undoped and Mn-doped wide band gapzinc oxide grown by aerosol spray pyrolysis

    CSIR Research Space (South Africa)

    Motaung, DE

    2014-08-01

    Full Text Available We present a systemic study on the structural, optical and magnetic properties of the un-doped and Mn doped ZnO thin films grown by aerosol spray pyrolysis at different deposition times. XRD profilinghas shown that the structures of the prepared...

  15. Thermo-oxidation of laboratory-produced undoped and W-doped carbon films: A reaction product analysis

    Directory of Open Access Journals (Sweden)

    B.W.N. Fitzpatrick

    2017-08-01

    A glow discharge was used to produce sets of undoped and W-doped films on stainless steel (SS foil substrates. X-ray photoelectron spectroscopy (XPS found the W-doped films to contain an average 0.1 at.% W/(W+C. Laser thermal desorption spectroscopy (LTDS was used to measure the areal D-concentration. Reaction products during oxidation were measured using a quadrupole mass spectrometer (QMS. Both the undoped and W-doped specimens were oxidized in 2Torr O2, at 350 °C for 4h, total. LTDS was then used to determine how much D had been removed during oxidation (93% and 32% of the D was removed after oxidation for the undoped and W-doped cases respectively. The reduced D loss for the W-doped specimens is attributed to a change in film structure due to the incorporation of W in the film. Oxidation reaction products for both undoped and W-doped films include CO, CO2, and D2O, with no finding of D2 or CD4 within experimental uncertainty. Particle accounting was performed for oxygen, deuterium and carbon atoms.

  16. Highly Conductive, Mechanically Robust, and Electrochemically Inactive TiC/C Nanofiber Scaffold for High-Performance Silicon Anode Batteries

    KAUST Repository

    Yao, Yan

    2011-10-25

    Silicon has a high specific capacity of 4200 mAh/g as lithium-ion battery anodes, but its rapid capacity fading due to >300% volume expansion and pulverization presents a significant challenge for practical applications. Here we report a core-shell TiC/C/Si inactive/active nanocomposite for Si anodes demonstrating high specific capacity and excellent electrochemical cycling. The amorphous silicon layer serves as the active material to store Li+, while the inactive TiC/C nanofibers act as a conductive and mechanically robust scaffold for electron transport during the Li-Si alloying process. The core-shell TiC/C/Si nanocomposite anode shows ∼3000 mAh g-1 discharge capacity and 92% capacity retention after 100 charge/discharge cycles. The excellent cycling stability and high rate performance could be attributed to the tapering of the nanofibers and the open structure that allows facile Li ion transport and the high conductivity and mechanical stability of the TiC/C scaffold. © 2011 American Chemical Society.

  17. High Conductivity, High Strength Solid Electrolytes Formed by in Situ Encapsulation of Ionic Liquids in Nanofibrillar Methyl Cellulose Networks.

    Science.gov (United States)

    Mantravadi, Ramya; Chinnam, Parameswara Rao; Dikin, Dmitriy A; Wunder, Stephanie L

    2016-06-01

    Strong, solid polymer electrolyte ion gels, with moduli in the MPa range, a capacitance of 2 μF/cm(2), and high ambient ionic conductivities (>1 × 10(-3) S/cm), all at room temperature, have been prepared from butyl-N-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide (PYR14TFSI) and methyl cellulose (MC). These properties are particularly attractive for supercapacitor applications. The ion gels are prepared by codissolution of PYR14TFSI and MC in N,N-dimethylformamide (DMF), which after heating and subsequent cooling form a gel. Evaporation of DMF leave thin, flexible, self-standing ion gels with up to 97 wt % PYR14TFSI, which have the highest combined moduli and ionic conductivity of ion gels to date, with an excellent electrochemical stability window (5.6 V). These favorable properties are attributed to the immiscibility of PYR14TFSI in MC, which permits the ionic conductivity to be independent of the MC at low MC content, and the in situ formation of a volume spanning network of semicrystalline MC nanofibers, which have a high glass transition temperature (Tg = 190 °C) and remain crystalline until they degrade at 300 °C.

  18. Peculiarities of high electric field conduction in p-type diamond

    Science.gov (United States)

    Mortet, V.; Trémouilles, D.; Bulíř, J.; Hubík, P.; Heller, L.; Bedel-Pereira, E.; Soltani, A.

    2016-04-01

    The electrical properties of chemical vapour deposited p-type epitaxial diamond layers are studied in high electric field conditions. The quasi-static current-voltage characteristics have been measured using transmission-line pulse method with 100 ns pulses. Reproducible impurity impact ionization avalanche breakdown occurs at a critical electrical field in the range of 100-200 kV cm-1 depending on the acceptor concentration and temperature, leading to complete ionisation of neutral impurities. The current-voltage characteristics exhibit an S-shape with the bi-stable conduction characteristic of impurity impact ionisation.

  19. Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing

    OpenAIRE

    Oscar Galao; Luis Bañón; Francisco Javier Baeza; Jesús Carmona; Pedro Garcés

    2016-01-01

    This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at −15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., −15 °C, for cur...

  20. Use of high-thermal conductive aluminum nitride based ceramics in vacuum UHF electronic devices

    Directory of Open Access Journals (Sweden)

    Chasnyk V. I.

    2013-06-01

    Full Text Available Analysis of properties and characteristics of the alumina, beryllium oxide and aluminum nitride based ceramic materials used in UHF electronic devices has been made. It was shown that the complex of parameters including structural and functional characteristics of the high-thermal conductive aluminum nitride ceramics prevail over all types of alumina ceramics and is not lower than the same characteristics of the beryllium oxide ceramics especially at the temperatures higher than 450 °C. The examples of the prevailing use of the aluminum nitride ceramics inside vacuum UHF-region devices: TWT’s and klystrons.

  1. Highly Conductive Semitransparent Graphene Circuits Screen-Printed from Water-Based Graphene Oxide Ink

    DEFF Research Database (Denmark)

    Overgaard, Marc H.; Kuhnel, Martin; Hvidsten, Rasmus

    2017-01-01

    The use of graphene materials as conductive inks for flexible and transparent electronics is promising, but challenged by the need for stabilizers, specialized organic solvents, and/or high temperature annealing, severely limiting performance or compatibility with substrates and printing techniques....... Here, the development of a scalable water-based graphene oxide ink is reported that can be screen-printed on flexible plastic substrates and subsequently reduced using a 1: 1 mixture of trifluoroacetic acid and hydroiodic acid, thereby creating an electric circuit. The reduced prints exhibit low sheet...

  2. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    Science.gov (United States)

    Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

    2010-07-27

    Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

  3. High temperature electrical conductivity due to small polaron hopping motion in DNA molecules

    Energy Technology Data Exchange (ETDEWEB)

    Triberis, G P [University of Athens, Physics Department, Solid State Section, Panepistimiopolis, 15784 Zografos, Athens (Greece); Karavolas, V C [University of Athens, Physics Department, Solid State Section, Panepistimiopolis, 15784 Zografos, Athens (Greece); Simserides, C D [University of Athens, Physics Department, Solid State Section, Panepistimiopolis, 15784 Zografos, Athens (Greece); Leibniz Institute for Neurobiology, Special Lab for Non-Invasing Brain Imaging, Brenneckestr. 6, D-39118 Magdeburg (Germany)

    2005-01-01

    We present a small polaron hopping model to interpret the high-temperature electrical conductivity measured along the DNA molecules. The model takes into account the one-dimensional character of the system and the presence of disorder in the DNA double helix. The experimental data for the lambda phage DNA ({lambda}-DNA) and the poly(dA)-poly(dT) DNA follow nicely the theoretically predicted behavior leading to realistic values of the maximum hopping distances supporting the idea of multiphonon-assisted hopping of small polarons between next nearest neighbors of the DNA molecular 'wire'.

  4. Reflecting and Polarizing Properties of Conductive Fabrics in Ultra-High Frequency Range

    Directory of Open Access Journals (Sweden)

    Oleg Kiprijanovič

    2015-09-01

    Full Text Available The system based on ultra-wide band (UWB signals was employed for qualitative estimation of attenuating, reflecting and polarizing properties of conductive fabrics, capable to prevent local static charge accumulation. Pulsed excitation of triangle monopole antenna of 6.5 cm height by rectangular electric pulses induced radiation of UWB signals with spectral density of power having maximum in ultra-high frequency (UHF range. The same antenna was used for the radiated signal receiving. Filters and amplifiers of different passband were employed to divide UHF range into subranges of 0.3-0.55 GHz, 0.55-1 GHz, 1-2 GHz and 2-4 GHz bands. The free space method, when conductive fabric samples of 50x50 cm2 were placed between transmitting and receiving antennas, was used to imitate a practical application. Received wideband signals corresponding to the defined range were detected by unbiased detectors. The fabrics made of two types of warps, containing different threads with conductive yarns, were investigated. It was estimated attenuation and reflective properties of the fabrics when electric field is collinear or perpendicular to thread direction. In the UHF range it was revealed good reflecting properties of the fabrics containing metallic component in the threads. The system has advantages but not without a certain shortcoming. Adapting it for specific tasks should lead to more effective usage, including yet unused properties of the UWB signals.

  5. Highly Conductive 3D Segregated Graphene Architecture in Polypropylene Composite with Efficient EMI Shielding

    Directory of Open Access Journals (Sweden)

    Fakhr E. Alam

    2017-12-01

    Full Text Available The extensive use of electronic equipment in modern life causes potential electromagnetic pollution harmful to human health. Therefore, it is of great significance to enhance the electrical conductivity of polymers, which are widely used in electronic components, to screen out electromagnetic waves. The fabrication of graphene/polymer composites has attracted much attention in recent years due to the excellent electrical properties of graphene. However, the uniform distribution of graphene nanoplatelets (GNPs in a non-polar polymer matrix like polypropylene (PP still remains a challenge, resulting in the limited improvement of electrical conductivity of PP-based composites achieved to date. Here, we propose a single-step approach to prepare GNPs/PP composites embedded with a segregated architecture of GNPs by coating PP particles with GNPs, followed by hot-pressing. As a result, the electrical conductivity of 10 wt % GNPs-loaded composites reaches 10.86 S·cm−1, which is ≈7 times higher than that of the composites made by the melt-blending process. Accordingly, a high electromagnetic interference shielding effectiveness (EMI SE of 19.3 dB can be achieved. Our method is green, low-cost, and scalable to develop 3D GNPs architecture in a polymer matrix, providing a versatile composite material suitable for use in electronics, aerospace, and automotive industries.

  6. Hybrid local piezoelectric and conductive functions for high performance airborne sound absorption

    Science.gov (United States)

    Rahimabady, Mojtaba; Statharas, Eleftherios Christos; Yao, Kui; Sharifzadeh Mirshekarloo, Meysam; Chen, Shuting; Tay, Francis Eng Hock

    2017-12-01

    A concept of hybrid local piezoelectric and electrical conductive functions for improving airborne sound absorption is proposed and demonstrated in composite foam made of porous polar polyvinylidene fluoride (PVDF) mixed with conductive single-walled carbon nanotube (SWCNT). According to our hybrid material function design, the local piezoelectric effect in the PVDF matrix with the polar structure and the electrical resistive loss of SWCNT enhanced sound energy conversion to electrical energy and subsequently to thermal energy, respectively, in addition to the other known sound absorption mechanisms in a porous material. It is found that the overall energy conversion and hence the sound absorption performance are maximized when the concentration of the SWCNT is around the conductivity percolation threshold. For the optimal composition of PVDF/5 wt. % SWCNT, a sound reduction coefficient of larger than 0.58 has been obtained, with a high sound absorption coefficient higher than 50% at 600 Hz, showing their great values for passive noise mitigation even at a low frequency.

  7. A high performance cathode for proton conducting solid oxide fuel cells

    KAUST Repository

    Wang, Zhiquan

    2015-01-01

    Intermediate temperature solid-oxide fuel cells (IT-SOFCs)), as one of the energy conversion devices, have attracted worldwide interest for their great fuel efficiency, low air pollution, much reduced cost and excellent longtime stability. In the intermediate temperature range (500-700°C), SOFCs based on proton conducting electrolytes (PSOFCs) display unique advantages over those based on oxygen ion conducting electrolytes. A key obstacle to the practical operation of past P-SOFCs is the poor stability of the traditionally used composite cathode materials in the steam-containing atmosphere and their low contribution to proton conduction. Here we report the identification of a new Ruddlesden-Popper-type oxide Sr3Fe2O7-δ that meets the requirements for much improved long-term stability and shows a superior single-cell performance. With a Sr3Fe2O7-δ-5 wt% BaZr0.3Ce0.5Y0.2O3-δ cathode, the P-SOFC exhibits high power densities (683 and 583 mW cm-2 at 700°C and 650°C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. More importantly, no decay in discharging was observed within a 100 hour test. © The Royal Society of Chemistry 2015.

  8. High conductive and scalable Ag nanowires flexible transparent electrode by nanowelding with physical methods

    Science.gov (United States)

    He, W. W.; Yan, X. H.; Long, Y. F.; Liang, Y. M.; Pan, C.; Zhao, J. L.; Liu, Q. X.

    2017-09-01

    Transparent electrodes (TEs) are very important for electronic devices. At present, ITO is gaining the largest market share but will be reduced. Ag nanowires (AgNWs) TEs is acknowledged as one of the most potential alternative to ITO. However, AgNWs TEs still have electrical problems because of the low contact between the AgNWs. In this paper, we report three physics methods to increase the conductivity of AgNWs TEs by nanowelding the contact of nanowires. For heat-resistant materials, 200 °C heat-nanowelding can help to reduce the sheet resistance by 96.7%. For pressure resistant materials, 20MPa pressure-nanowelding can help to increase the conductivity by 98.7%. And the transmittance (>90%) remains constant during the above process. Yet, both of these methods cannot improve the adhesion between nanowires and the substrates. Luckily, tight adhesion can be obtained by overcoating a PEDOT: PSS lalyer on AgNWs film which can reduce the sheet resistance by 87.8%. This means that things are usually not perfect, and they have their own advantages and lay the foundation for the popularization and application of AgNWs TEs. In a word, these three nano-welding methods are all suit for manufacture on a large scale for high conductive AgNWs TEs.

  9. Synthesis and characterization of low temperature Sn nanoparticles for the fabrication of highly conductive ink.

    Science.gov (United States)

    Jo, Yun Hwan; Jung, Inyu; Choi, Chung Seok; Kim, Inyoung; Lee, Hyuck Mo

    2011-06-03

    To fabricate a low cost, highly conductive ink for inkjet printing, we synthesized a gram scale of uniformly sized Sn nanoparticles by using a modified polyol process and observed a significant size-dependent melting temperature depression from 234.1 °C for bulk Sn to 177.3 °C for 11.3 nm Sn nanoparticles. A 20 wt% of Sn nanoparticles was dispersed in the 50% ethylene glycol: 50% isopropyl alcohol mixed solvent for the appropriate viscosity (11.6 cP) and surface tension (32 dyn cm(-1)). To improve the electrical property, we applied the surface treatments of hydrogen reduction and plasma ashing. The two treatments had the effect of diminishing the sheet resistance from 1 kΩ/sq to 50 Ω/sq. In addition, conductive patterns (1 cm × 1 cm) were successfully drawn on the Si wafer using an inkjet printing instrument with conductive Sn ink. The maximum resistivity for an hour of sintering at 250 °C was 64.27 µΩ cm, which is six times higher than the bulk Sn resistivity (10.1 µΩ cm).

  10. Binder-free highly conductive graphene laminate for low cost printed radio frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xianjun; Leng, Ting; Zhang, Xiao; Hu, Zhirun, E-mail: Z.Hu@manchester.ac.uk [School of Electrical and Electronic Engineering, University of Manchester, Manchester (United Kingdom); Chen, Jia Cing; Chang, Kuo Hsin [BGT Materials Limited, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom); Geim, Andre K. [Manchester Centre for Mesoscience and Nanotechnology, University of Manchester, Manchester (United Kingdom); Novoselov, Kostya S. [School of Physics and Astronomy, University of Manchester, Manchester (United Kingdom)

    2015-05-18

    In this paper, we demonstrate realization of printable radio frequency identification (RFID) antenna by low temperature processing of graphene ink. The required ultra-low resistance is achieved by rolling compression of binder-free graphene laminate. With compression, the conductivity of graphene laminate is increased by more than 50 times compared to that of as-deposited one. Graphene laminate with conductivity of 4.3 × 10{sup 4 }S/m and sheet resistance of 3.8 Ω/sq (with thickness of 6 μm) is presented. Moreover, the formation of graphene laminate from graphene ink reported here is simple and can be carried out in low temperature (100 °C), significantly reducing the fabrication costs. A dipole antenna based on the highly conductive graphene laminate is further patterned and printed on a normal paper to investigate its RF properties. The performance of the graphene laminate antenna is experimentally measured. The measurement results reveal that graphene laminate antenna can provide practically acceptable return loss, gain, bandwidth, and radiation patterns, making it ideal for low cost printed RF applications, such as RFID tags and wearable wireless sensor networks.

  11. Final Report for Project titled High Thermal Conductivity Polymer Composites for Low-Cost Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Thibaud-Erkey, Catherine [United Technologies reserach Center, East Hartford, CT (United States); Alahyari, Abbas [United Technologies reserach Center, East Hartford, CT (United States)

    2016-12-28

    Heat exchangers (HXs) are critical components in a wide range of heat transfer applications, from HVAC (Heating Ventilation and Cooling) to automobiles to manufacturing plants. They require materials capable of transferring heat at high rates while also minimizing thermal expansion over the usage temperature range. Conventionally, metals are used for applications where effective and efficient heat exchange is required, since many metals exhibit thermal conductivity over 100 W/m K. While metal HXs are constantly being improved, they still have some inherent drawbacks due to their metal construction, in particular corrosion. Polymeric material can offer solution to such durability issues and allow designs that cannot be afforded by metal construction either due to complexity or cost. A major drawback of polymeric material is their low thermal conductivity (0.1-0.5? W/mK) that would lead to large system size. Recent improvements in the area of filled polymers have highlighted the possibility to greatly improve the thermal conductivity of polymeric materials while retaining their inherent manufacturing advantage, and have been applied to heat sink applications. Therefore, the objective of this project was to develop a robust review of materials for the manufacturing of industrial and commercial non-metallic heat exchangers. This review consisted of material identification, literature evaluation, as well as empirical and model characterization, resulting in a database of relevant material properties and characteristics to provide guidance for future heat exchanger development.

  12. High-Performance Electrochemical Catalysts Based on Three-Dimensional Porous Architecture with Conductive Interconnected Networks.

    Science.gov (United States)

    Wang, Dong; Wang, Jie; Liu, Zi-En; Yang, Xiangdong; Hu, Xiaoxia; Deng, Jinqi; Yang, Nianjun; Wan, Qijin; Yuan, Quan

    2016-10-26

    The electrochemical applications of traditional carbon nanomaterials such as carbon nanotubes (CNTs) and graphene (G) powders are significantly impeded by their poor three-dimensional (3D) conductivity and lack of hierarchical porous structure. Here, we have constructed a 3D highly conductive CNTs networks and further combined it with mesoporous carbon (mC) for the creation of a core-shell structured (CNT@mC) composite sponge that featured 3D conductivity and hierarchical porous structure. In the composite sponge, interconnected CNTs efficiently eliminates the contact resistance and the hierarchical pores significantly facilitate the mass transport. The electron transfer rates, electroactive surface area and catalytic activity of the CNT@mC composite sponge based catalysts were tested in the direct methanol fuel cells (DMFCs) and electrochemical sensors. In DMFCs, the Pd nanoparticles deposited CNT@mC showed significantly improved catalytic activity and methanol oxidization current. As for amperometric sensing of endocrine disrupting compounds (EDCs), CNT@mC-based catalyst gave a liner range from 10 nM to 1 mM for bisphenol A (BPA) detection and showed great promise for simultaneous detection of multiple EDCs. BPA recovery from environmental water further indicated the potential practical applications of the sensor for BPA detection. Finally, the electrochemical performance of CNT@mC were also investigated in impedimetric sensors. Good selectivity was obtained in impedimetric sensing of BPA and the detection limit was measured to be 0.3 nM. This study highlighted the exceptional electrochemical properties of the CNT@mC composite sponge enabled by its 3D conductivity and hierarchical porous structure. The strategy described may further pave a way for the creation of novel functional materials through integrating multiple superior properties into a single nanostructure for future clean energy technologies and environmental monitoring systems.

  13. High-performance Bi-stage process in reduction of graphene oxide for transparent conductive electrodes

    Science.gov (United States)

    Alahbakhshi, Masoud; Fallahi, Afsoon; Mohajerani, Ezeddin; Fathollahi, Mohammad-Reza; Taromi, Faramarz Afshar; Shahinpoor, Mohsen

    2017-02-01

    A novel and innovative approach to develop reduction of graphene oxide (GO) solution for fabrication of highly and truly transparent conductive electrode (TCE) has been presented. Thanks to outstanding mechanical and electronic properties of graphene which offer practical applications in synthesizing composites as well as fabricating various optoelectronic devices, in this study, conductive reduced graphene oxide (r-GO) thin films were prepared through sequential chemical and thermal reduction process of homogeneously dispersed GO solutions. The conductivity and transparency of r-GO thin film is regulated using hydroiodic acid (HI) as reducing agent following by vacuum thermal annealing. The prepared r-GO is characterized by XRD, AFM, UV-vis and Raman spectroscopy. the AFM topographic images reveal surface roughness almost ∼11 nm which became less than 2 nm for the 4 mg/mL solution. Moreover, XRD analysis and Raman spectra substantiate the interlayer spacing between rGO layers has been reduced dramatically and also electronic conjugation has been ameliorated after using HI chemical agent and 700 °C thermal annealing sequentially. Subsequently providing r-GO transparent electrode with decent and satisfactory transparency, acceptable conductivity and suitable work function, it has been exploited as the anode in organic light emitting diode (OLED). The maximum luminance efficiency and maximum power efficiency reached 4.2 cd/A and 0.83 lm/W, respectively. We believe that by optimizing the hole density, sheet resistance, transparency and surface morphology of the r-GO anodes, the device efficiencies can be remarkably increased further.

  14. High Thermal Conductivity NARloy-Z-Diamond Composite Liner for Advanced Rocket Engines

    Science.gov (United States)

    Bhat, Biliyar; Greene, Sandra

    2015-01-01

    NARloy-Z (Cu-3Ag-0.5Zr) alloy is state-of-the-art combustion chamber liner material used in liquid propulsion engines such as the RS-68 and RS-25. The performance of future liquid propulsion systems can be improved significantly by increasing the heat transfer through the combustion chamber liner. Prior work1 done at NASA Marshall Space Flight Center (MSFC) has shown that the thermal conductivity of NARloy-Z alloy can be improved significantly by embedding high thermal conductivity diamond particles in the alloy matrix to form NARloy-Z-diamond composite (fig. 1). NARloy-Z-diamond composite containing 40vol% diamond showed 69% higher thermal conductivity than NARloy-Z. It is 24% lighter than NARloy-Z and hence the density normalized thermal conductivity is 120% better. These attributes will improve the performance and life of the advanced rocket engines significantly. The research work consists of (a) developing design properties (thermal and mechanical) of NARloy-Z-D composite, (b) fabrication of net shape subscale combustion chamber liner, and (c) hot-fire testing of the liner to test performance. Initially, NARloy-Z-D composite slabs were made using the Field Assisted Sintering Technology (FAST) for the purpose of determining design properties. In the next step, a cylindrical shape was fabricated to demonstrate feasibility (fig. 3). The liner consists of six cylinders which are sintered separately and then stacked and diffusion bonded to make the liner (fig. 4). The liner will be heat treated, finish-machined, and assembled into a combustion chamber and hot-fire tested in the MSFC test facility (TF 115) to determine perform.

  15. Studies on high electronic energy deposition in transparent conducting indium tin oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, N G [Thin Film and Nanotechnology Laboratory, Department of Physics, Dr Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (MS) (India); Gudage, Y G [Thin Film and Nanotechnology Laboratory, Department of Physics, Dr Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (MS) (India); Ghosh, A [Thin Film and Nanotechnology Laboratory, Department of Physics, Dr Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (MS) (India); Vyas, J C [Technical and Prototype Engineering Division, Bhabha Atomic Research Center, Trombay, Mumbai (MS) (India); Singh, F [Inter-University Accelerator Center, Aruna Asaf Ali Marg, Post Box 10502, New Delhi 110067 (India); Tripathi, A [Inter-University Accelerator Center, Aruna Asaf Ali Marg, Post Box 10502, New Delhi 110067 (India); Sharma, Ramphal [Thin Film and Nanotechnology Laboratory, Department of Physics, Dr Babasaheb Ambedkar Marathwada University, Aurangabad-431004 (MS) (India)

    2008-02-07

    We have examined the effect of swift heavy ions using 100 MeV Au{sup 8+} ions on the electrical properties of transparent, conducting indium tin oxide polycrystalline films with resistivity of 0.58 x 10{sup -4} {omega} cm and optical transmission greater than 78% (pristine). We report on the modifications occurring after high electronic energy deposition. With the increase in fluency, x-ray line intensity of the peaks corresponding to the planes (1 1 0), (4 0 0), (4 4 1) increased, while (3 3 1) remained constant. Surface morphological studies showed a pomegranate structure of pristine samples, which was highly disturbed with a high dose of irradiation. For the high dose, there was a formation of small spherical domes uniformly distributed over the entire surface. The transmittance was seen to be decreasing with the increase in ion fluency. At higher doses, the resistivity and photoluminescence intensity was seen to be decreased. In addition, the carrier concentration was seen to be increased, which was in accordance with the decrease in resistivity. The observed modifications after high electronic energy deposition in these films may lead to fruitful device applications.

  16. Laser-Assisted Reduction of Highly Conductive Circuits Based on Copper Nitrate for Flexible Printed Sensors

    Science.gov (United States)

    Bai, Shi; Zhang, Shigang; Zhou, Weiping; Ma, Delong; Ma, Ying; Joshi, Pooran; Hu, Anming

    2017-10-01

    Stretchable electronic sensing devices are defining the path toward wearable electronics. High-performance flexible strain sensors attached on clothing or human skin are required for potential applications in the entertainment, health monitoring, and medical care sectors. In this work, conducting copper electrodes were fabricated on polydimethylsiloxane as sensitive stretchable microsensors by integrating laser direct writing and transfer printing approaches. The copper electrode was reduced from copper salt using laser writing rather than the general approach of printing with pre-synthesized copper or copper oxide nanoparticles. An electrical resistivity of 96 μΩ cm was achieved on 40-μm-thick Cu electrodes on flexible substrates. The motion sensing functionality successfully demonstrated a high sensitivity and mechanical robustness. This in situ fabrication method leads to a path toward electronic devices on flexible substrates.[Figure not available: see fulltext.

  17. Highly Flexible and Conductive Printed Graphene for Wireless Wearable Communications Applications.

    Science.gov (United States)

    Huang, Xianjun; Leng, Ting; Zhu, Mengjian; Zhang, Xiao; Chen, JiaCing; Chang, KuoHsin; Aqeeli, Mohammed; Geim, Andre K; Novoselov, Kostya S; Hu, Zhirun

    2015-12-17

    In this paper, we report highly conductive, highly flexible, light weight and low cost printed graphene for wireless wearable communications applications. As a proof of concept, printed graphene enabled transmission lines and antennas on paper substrates were designed, fabricated and characterized. To explore its potentials in wearable communications applications, mechanically flexible transmission lines and antennas under various bended cases were experimentally studied. The measurement results demonstrate that the printed graphene can be used for RF signal transmitting, radiating and receiving, which represents some of the essential functionalities of RF signal processing in wireless wearable communications systems. Furthermore, the printed graphene can be processed at low temperature so that it is compatible with heat-sensitive flexible materials like papers and textiles. This work brings a step closer to the prospect to implement graphene enabled low cost and environmentally friendly wireless wearable communications systems in the near future.

  18. Highly transparent and conductive ZnO:Al thin films prepared by vacuum arc plasma evaporation

    Science.gov (United States)

    Miyata, Toshihiro; Minamino, Youhei; Ida, Satoshi; Minami, Tadatsugu

    2004-07-01

    A vacuum arc plasma evaporation (VAPE) method using both oxide fragments and gas sources as the source materials is demonstrated to be very effective for the preparation of multicomponent oxide thin films. Highly transparent and conductive Al-doped ZnO (AZO) thin films were prepared by the VAPE method using a ZnO fragment target and a gas source Al dopant, aluminum acethylacetonate (Al(C5H7O2)3) contained in a stainless steel vessel. The Al content in the AZO films was altered by controlling the partial pressure (or flow rate) of the Al dopant gas. High deposition rates as well as uniform distributions of resistivity and thickness on the substrate surface were obtained on large area glass substrates. A low resistivity on the order of 10-4 Ω cm and an average transmittance above 80% in the visible range were obtained in AZO thin films deposited on glass substrates. .

  19. A high sensitivity ultralow temperature RF conductance and noise measurement setup

    Science.gov (United States)

    Parmentier, F. D.; Mahé, A.; Denis, A.; Berroir, J.-M.; Glattli, D. C.; Plaçais, B.; Fève, G.

    2011-01-01

    We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.

  20. High-temperature supercapacitor with a proton-conducting metal pyrophosphate electrolyte

    Science.gov (United States)

    Hibino, Takashi; Kobayashi, Kazuyo; Nagao, Masahiro; Kawasaki, Shinji

    2015-01-01

    Expanding the range of supercapacitor operation to temperatures above 100°C is important because this would enable capacitors to operate under the severe conditions required for next-generation energy storage devices. In this study, we address this challenge by the fabrication of a solid-state supercapacitor with a proton-conducting Sn0.95Al0.05H0.05P2O7 (SAPO)-polytetrafluoroethylene (PTFE) composite electrolyte and a highly condensed H3PO4 electrode ionomer. At a temperature of 200°C, the SAPO-PTFE electrolyte exhibits a high proton conductivity of 0.02 S cm−1 and a wide withstanding voltage range of ±2 V. The H3PO4 ionomer also has good wettability with micropore-rich activated carbon, which realizes a capacitance of 210 F g−1 at 200°C. The resulting supercapacitor exhibits an energy density of 32 Wh kg−1 at 3 A g−1 and stable cyclability after 7000 cycles from room temperature to 150°C. PMID:25600936

  1. Highly conductive carbon black supported amorphous molybdenum disulfide for efficient hydrogen evolution reaction

    Science.gov (United States)

    Cao, Pengfei; Peng, Jing; Li, Jiuqiang; Zhai, Maolin

    2017-04-01

    Molybdenum disulfide (MoS2) is a promising electrocatalyst for hydrogen evolution reaction (HER), however, the catalytic activity of reported MoS2-based materials towards HER still can't satisfy the requirement of practical application. Herein, highly conductive carbon black (CB) supported amorphous MoS2 nanocomposite is synthesized by a facile one-pot hydrothermal process. XRD and TEM analysis proves the amorphous morphology of MoS2. XPS further confirms both hexagonal and orthorhombic S ligands exist in the amorphous MoS2. Compared with crystalline MoS2, amorphous MoS2/CB shows an onset overpotential of 78 mV and current density of 470 mA cm-2 at the overpotential of 200 mV, which is even 50% higher than that of the commercial 20% Pt/C catalyst. Furthermore, a fairly stable performance can be achieved even after 5000 CV cycles. The outstanding HER activity and stability of the amorphous MoS2/CB nanocomposite can be attributed to these advantages: (1) amorphous structure offers more active sites in MoS2; (2) highly conductive CB reduces the charge transfer resistance (RCT); (3) relative hydrophilic CB can largely reduce the resistance between catalyst/electrolyte interface and allows rapid mass transport; (4) electron penetration effect between amorphous MoS2 and CB increases the intrinsic activity of amorphous MoS2 by two orders of magnitude.

  2. Highly Conductive Solvent-Free Polymer Electrolytes for Lithium Rechargeable Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Robert Filler, Zhong Shi and Braja Mandal

    2004-10-21

    In order to obviate the deficiencies of currently used electrolytes in lithium rechargeable batteries, there is a compelling need for the development of solvent-free, highly conducting solid polymer electrolytes (SPEs). The problem will be addressed by synthesizing a new class of block copolymers and plasticizers, which will be used in the formulation of highly conducting electrolytes for lithium-ion batteries. The main objective of this Phase-I effort is to determine the efficacy and commercial prospects of new specifically designed SPEs for use in electric and hybrid electric vehicle (EV/HEV) batteries. This goal will be achieved by preparing the SPEs on a small scale with thorough analyses of their physical, chemical, thermal, mechanical and electrochemical properties. SPEs will play a key role in the formulation of next generation lithium-ion batteries and will have a major impact on the future development of EVs/HEVs and a broad range of consumer products, e.g., computers, camcorders, cell phones, cameras, and power tools.

  3. How to conduct a high-quality original study on a diagnostic research topic.

    Science.gov (United States)

    Yao, Xiaomei; Vella, Emily

    2017-09-01

    As health research methodologists and journal reviewers, we noticed that the methodological rigor of many publications on diagnostic or prognostic topics in the medical literature could be improved. We present a concise and clear series of reviews to help clinicians and health researchers to master the basic key components of how to conduct a high-quality original study or systematic review on a diagnostic or prognostic research topic from a methodological perspective. This is the first review of the series, which focuses on how to conduct a high-quality diagnostic study. We are introducing four aspects: clarifying the objectives; generating an appropriate research question; planning the study design; and reporting and analyzing data. This review highlights that diagnostic test accuracy outcomes are surrogates for patient outcomes, a diagnostic test has three roles, the "PIRO" components should be included in a diagnostic research question, a new study should be registered, multiple index tests can be compared in one study, and prevalence affects test accuracy outcomes. This review also emphasizes reporting any thresholds, calculating sample size, and performing a two-by-three table to calculate diagnostic outcomes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Low Thermal Conductivity, High Durability Thermal Barrier Coatings for IGCC Environments

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, Eric [Univ. of Connecticut, Storrs, CT (United States); Gell, Maurice [Univ. of Connecticut, Storrs, CT (United States)

    2015-01-15

    Advanced thermal barrier coatings (TBC) are crucial to improved energy efficiency in next generation gas turbine engines. The use of traditional topcoat materials, e.g. yttria-stabilized zirconia (YSZ), is limited at elevated temperatures due to (1) the accelerated undesirable phase transformations and (2) corrosive attacks by calcium-magnesium-aluminum-silicate (CMAS) deposits and moisture. The first goal of this project is to use the Solution Precursor Plasma Spray (SPPS) process to further reduce the thermal conductivity of YSZ TBCs by introducing a unique microstructural feature of layered porosity, called inter-pass boundaries (IPBs). Extensive process optimization accompanied with hundreds of spray trials as well as associated SEM cross-section and laser-flash measurements, yielded a thermal conductivity as low as 0.62 Wm⁻¹K⁻¹ in SPPS YSZ TBCs, approximately 50% reduction of APS TBCs; while other engine critical properties, such as cyclic durability, erosion resistance and sintering resistance, were characterized to be equivalent or better than APS baselines. In addition, modifications were introduced to SPPS TBCs so as to enhance their resistance to CMAS under harsh IGCC environments. Several mitigation approaches were explored, including doping the coatings with Al₂O₃ and TiO₂, applying a CMAS infiltration-inhibiting surface layer, and filling topcoat cracks with blocking substances. The efficacy of all these modifications was assessed with a set of novel CMAS-TBC interaction tests, and the moisture resistance was tested in a custom-built high-temperature moisture rig. In the end, the optimal low thermal conductivity TBC system was selected based on all evaluation tests and its processing conditions were documented. The optimal coating consisted on a thick inner layer of YSZ coating made by the SPPS process having a thermal conductivity 50% lower than standard YSZ coatings topped with a high temperature tolerant CMAS resistant gadolinium

  5. Spin-sprayed ferrite films with high resistivity and high-frequency magnetic loss for GHz conducted noise suppressors

    Energy Technology Data Exchange (ETDEWEB)

    Subramani, A.K. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama (Japan)], E-mail: subramani.aa@m.titech.ac.jp; Matsushita, N. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama (Japan)], E-mail: matsushita@msl.titech.ac.jp; Watanabe, T. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama (Japan); Tada, M.; Abe, M. [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8552 (Japan); Kondo, K. [NEC Tokin Corporation, 6-7-1 Koriyama, Taihaku-ku, Sendai, Miyagi 982-8510 (Japan); Yoshimura, M. [Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama (Japan)

    2008-02-25

    In the present study, crystallized ferrite (an intermediate between Fe{sub 3}O{sub 4} and {gamma}-Fe{sub 2}O{sub 3}) films prepared by spin-spray technique exhibited strong magnetic losses at high frequencies and are applicable as GHz conducted noise suppressors. The reaction (metal ions) and oxidizing (pH buffers and oxidizing agent) solutions were separately sprayed onto the substrates (90 deg. C) mounted on a rotating disc. Two types of films were prepared on the basis of the different oxidizing solutions; CH{sub 3}COONa + NaNO{sub 2} in the case of film-A and CH{sub 3}COONa + (NH{sub 4}){sub 2}CO{sub 3} + NaNO{sub 2} + NaOH for film-B. The as-prepared films were heat-treated under a condition similar to that of the reflow soldering process (265 deg. C). The effects of the preparation conditions and film morphology on the electrical and magnetic properties before and after the heat treatment were studied. The results revealed that film-B had a relatively smaller initial permeability ({mu}') compared to film-A. However, it had a high-imaginary permeability ({mu}''), resonance frequency (f{sub r}) and surface resistivity ({rho}{sub s}) even after heat treatment. Also, the noise suppressing properties of film-B were relatively good, hence ideal for use as conducted noise suppressors.

  6. High-Throughput Synthesis, Screening, and Scale-Up of Optimized Conducting Indium Tin Oxides.

    Science.gov (United States)

    Marchand, Peter; Makwana, Neel M; Tighe, Christopher J; Gruar, Robert I; Parkin, Ivan P; Carmalt, Claire J; Darr, Jawwad A

    2016-02-08

    A high-throughput optimization and subsequent scale-up methodology has been used for the synthesis of conductive tin-doped indium oxide (known as ITO) nanoparticles. ITO nanoparticles with up to 12 at % Sn were synthesized using a laboratory scale (15 g/hour by dry mass) continuous hydrothermal synthesis process, and the as-synthesized powders were characterized by powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. Under standard synthetic conditions, either the cubic In2O3 phase, or a mixture of InO(OH) and In2O3 phases were observed in the as-synthesized materials. These materials were pressed into compacts and heat-treated in an inert atmosphere, and their electrical resistivities were then measured using the Van der Pauw method. Sn doping yielded resistivities of ∼ 10(-2) Ω cm for most samples with the lowest resistivity of 6.0 × 10(-3) Ω cm (exceptionally conductive for such pressed nanopowders) at a Sn concentration of 10 at %. Thereafter, the optimized lab-scale composition was scaled-up using a pilot-scale continuous hydrothermal synthesis process (at a rate of 100 g/hour by dry mass), and a comparable resistivity of 9.4 × 10(-3) Ω cm was obtained. The use of the synthesized TCO nanomaterials for thin film fabrication was finally demonstrated by deposition of a transparent, conductive film using a simple spin-coating process.

  7. Defibrillation success with high frequency electric fields is related to degree and location of conduction block.

    Science.gov (United States)

    Weinberg, Seth H; Chang, Kelly C; Zhu, Renjun; Tandri, Harikrishna; Berger, Ronald D; Trayanova, Natalia A; Tung, Leslie

    2013-05-01

    We recently demonstrated that high frequency alternating current (HFAC) electric fields can reversibly block propagation in the heart by inducing an oscillating, elevated transmembrane potential (Vm) that maintains myocytes in a refractory state for the field duration and can terminate arrhythmias, including ventricular fibrillation (VF). To quantify and characterize conduction block (CB) induced by HFAC fields and to determine whether the degree of CB can be used to predict defibrillation success. Optical mapping was performed in adult guinea pig hearts (n = 14), and simulations were performed in an anatomically accurate rabbit ventricular model. HFAC fields (50-500 Hz) were applied to the ventricles. A novel power spectrum metric of CB-the loss of spectral power in the 1-30 Hz range, termed loss of conduction power (LCP)-was assessed during the HFAC field and compared with defibrillation success and VF vulnerability. LCP increased with field strength and decreased with frequency. Optical mapping experiments conducted on the epicardial surface showed that LCP and the size of CB regions were significantly correlated with VF initiation and termination. In simulations, subsurface myocardial LCP and CB sizes were more closely correlated with VF termination than surface values. Multilinear regression analysis of simulation results revealed that while CB on both the surface and the subsurface myocardium was predictive, subsurface myocardial CB was the better predictor of defibrillation success. HFAC fields induce a field-dependent state of CB, and defibrillation success is related to the degree and location of the CB. Copyright © 2013. Published by Elsevier Inc.

  8. Handbook for Planning and Conducting Charrettes for High-Performance Projects

    Energy Technology Data Exchange (ETDEWEB)

    Lindsey, G.; Todd, J. A.; Hayter, S. J.

    2003-08-01

    The purpose of this handbook is to furnish guidance for planning and conducting a"high-performance building" charrette, sometimes called a"greening charrette." The handbook answers typical questions that will arise, such as"What is a charrette?""Why conduct a charrette?""What topics should we cover during the charrette?" and"Whom should we invite?" It also contains samples of agendas, invitation letters, and other commonly used charrette materials. This handbook also outlines the characteristics of a good charrette facilitator. It gives suggestions for the types of experts to invite to the event to motivate participants and answer their questions. The handbook includes sample presentations that can be used by these experts to ensure they address the required technical content. It suggests the types of participants, including technical, political, and community representatives, to invite to the charrette. It offers advice for forming effective breakout groups to ensure that a broad range of complementary expertise is represented in each group. We have also included guidance on how best to include key decision makers and stakeholders who are able to attend only portions of the event.

  9. Experimental Investigation of Surface Layer Properties of High Thermal Conductivity Tool Steel after Electrical Discharge Machining

    Directory of Open Access Journals (Sweden)

    Rafał Świercz

    2017-12-01

    Full Text Available New materials require the use of advanced technology in manufacturing complex shape parts. One of the modern materials widely used in the tool industry for injection molds or hot stamping dies is high conductivity tool steel (HTCS 150. Due to its hardness (55 HRC and thermal conductivity at 66 W/mK, this material is difficult to machine by conventional treatment and is being increasingly manufactured by nonconventional technology such as electrical discharge machining (EDM. In the EDM process, material is removed from the workpiece by a series of electrical discharges that cause changes to the surface layers properties. The final state of the surface layer directly influences the durability of the produced elements. This paper presents the influence of EDM process parameters: discharge current Ic and the pulse time ton on surface layer properties. The experimental investigation was carried out with an experimental methodology design. Surface layers properties including roughness 3D parameters, the thickness of the white layer, heat affected zone, tempered layer and occurring micro cracks were investigated and described. The influence of the response surface methodology (RSM of discharge current Ic and the pulse time ton on the thickness of the white layer and roughness parameters Sa, Sds and Ssc were described and established.

  10. A charge transfer complex nematic liquid crystalline gel with high electrical conductivity

    Science.gov (United States)

    Bhargavi, R.; Nair, Geetha G.; Krishna Prasad, S.; Majumdar, R.; Bag, Braja G.

    2014-10-01

    We describe the rheological, dielectric and elastic properties of a nematic liquid crystal gel created using an anthrylidene derivative of arjunolic acid, a chiral triterpenoid, obtained from the extracts of the wood of Terminalia arjuna. In this novel gel, having the electron-donor and acceptor components as minority constituents, the gelation and strengthening of charge-transfer complex (CTC) formation are seen to be occurring concomitantly. In addition to being mechanically strong with a large storage modulus, the gel with the maximized CTC exhibits Frank bend elastic constant values that approach nanonewton levels. The highlight of the study is the observation of 4-5 orders of magnitude increase in electrical conductivity for this gel, a value that is higher than even in the CT complexes of 2-d ordered columnar structures. A further important advantage of the present system over the columnar complex is that the high conductivity is seen for ac probing also, and owing to the nematic nature can be switched between its anisotropic limits. Some of these features are ascribed to a specific molecular packing architecture, which reduces the trapping of the charge carriers.

  11. A charge transfer complex nematic liquid crystalline gel with high electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Bhargavi, R.; Nair, Geetha G., E-mail: geeraj88@gmail.com, E-mail: skpras@gmail.com; Krishna Prasad, S., E-mail: geeraj88@gmail.com, E-mail: skpras@gmail.com [Centre for Nano and Soft Matter Sciences, Jalahalli, Bangalore 560013 (India); Majumdar, R.; Bag, Braja G. [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore (W) 721 102 (India)

    2014-10-21

    We describe the rheological, dielectric and elastic properties of a nematic liquid crystal gel created using an anthrylidene derivative of arjunolic acid, a chiral triterpenoid, obtained from the extracts of the wood of Terminalia arjuna. In this novel gel, having the electron-donor and acceptor components as minority constituents, the gelation and strengthening of charge-transfer complex (CTC) formation are seen to be occurring concomitantly. In addition to being mechanically strong with a large storage modulus, the gel with the maximized CTC exhibits Frank bend elastic constant values that approach nanonewton levels. The highlight of the study is the observation of 4–5 orders of magnitude increase in electrical conductivity for this gel, a value that is higher than even in the CT complexes of 2-d ordered columnar structures. A further important advantage of the present system over the columnar complex is that the high conductivity is seen for ac probing also, and owing to the nematic nature can be switched between its anisotropic limits. Some of these features are ascribed to a specific molecular packing architecture, which reduces the trapping of the charge carriers.

  12. Theory of quantum metal to superconductor transitions in highly conducting systems

    Energy Technology Data Exchange (ETDEWEB)

    Spivak, B.

    2010-04-06

    We derive the theory of the quantum (zero temperature) superconductor to metal transition in disordered materials when the resistance of the normal metal near criticality is small compared to the quantum of resistivity. This can occur most readily in situations in which 'Anderson's theorem' does not apply. We explicitly study the transition in superconductor-metal composites, in an swave superconducting film in the presence of a magnetic field, and in a low temperature disordered d-wave superconductor. Near the point of the transition, the distribution of the superconducting order parameter is highly inhomogeneous. To describe this situation we employ a procedure which is similar to that introduced by Mott for description of the temperature dependence of the variable range hopping conduction. As the system approaches the point of the transition from the metal to the superconductor, the conductivity of the system diverges, and the Wiedemann-Franz law is violated. In the case of d-wave (or other exotic) superconductors we predict the existence of (at least) two sequential transitions as a function of increasing disorder: a d-wave to s-wave, and then an s-wave to metal transition.

  13. Three-Dimensional Highly Stretchable Conductors from Elastic Fiber Mat with Conductive Polymer Coating.

    Science.gov (United States)

    Duan, Shasha; Wang, Zhihui; Zhang, Ling; Liu, Jin; Li, Chunzhong

    2017-09-13

    The manufacture of stretchable conductors with well-reserved electrical performance under large-degree deformations via scalable processes remains of great importance. In this work, a highly stretchable 3D conductive framework consisting of a polyurethane fiber mat (PUF) and poly(3,4-ethylenedioxythiophene) (PEDOT) is reported through facile approaches, electrospinning, and in situ interfacial polymerization, which was then backfilled with poly(dimethylsiloxane) to obtain 3D conductors. The excellent stretchability of the 3D conductive network imparted the as-prepared electrode a superior mechanical durability. Moreover, the applied strains can be effectively accommodated by the arrangement and orientation of the fibers resulting in a relatively stable electrical performance with only a 20% increased resistance at 100% stretching. Meanwhile, the resistance of the conductor could remain constant during 2000 bending cycles and showed a slight increase during 100 cycles of 50% stretching. The potential in the applications of large-area stretchable electrodes was demonstrated by the construction of LED arrays with the PUF-based conductors as electrical connections.

  14. Welded-Ag-nanowires/FTO conducting film with high transmittance and its application in transparent supercapacitors

    Science.gov (United States)

    Qiao, Zhensong; Yang, Xiaopeng; Liu, Feng; Duan, Guangbin; Cao, Bingqiang

    2017-03-01

    Silver nanowires (AgNW) with a small diameter were synthesized by a facile and novel polyol reduction method. Ag nanowires ink was then spun on the surface of F-doped SnO2 (FTO) to form the AgNW/FTO conducting film. Welding treatment of the AgNW/FTO conducting film not only increased the optical transmittance from 71.9 % to 79.3 % at 550 nm and decreased the sheet resistance from 11.4 ohm sq-1 to 9.8 ohm sq-1, but also improved the adhesivity of AgNW network on FTO substrate. Furthermore, MnO2 nanosheets were directly deposited on welded-AgNW/FTO (wAF) substrate to prepare a transparent MnO2/weled-AgNW/FTO (MwAF) composite electrode. The MwAF electrode displayed excellent electrochemical performance, including high specific capacitance (375 F g-1 at 5 mV s-1) and superior cycle stability (173.3 % of the initial capacitance after 20000 GCD cycles).

  15. High-speed imaging and evolution dynamics of laser induced deposition of conductive inks (Conference Presentation)

    Science.gov (United States)

    Makrygianni, Marina; Papazoglou, Symeon; Zacharatos, Filimonas; Chatzandroulis, Stavros; Zergioti, Ioanna

    2017-02-01

    During the last decade there is an ever-increasing interest for the study of laser processes dynamics and specifically of the Laser Induced Forward Transfer (LIFT) technique, since the evolution of the phenomena under investigation may provide real time metrology in terms of jet velocity, adjacent jet interaction and impact pressure. The study of such effects leads to a more thorough understanding of the deposition process, hence to an improved printing outcome and in these frames, this work presents a study on the dynamics of LIFT for conductive nanoparticles inks using high-speed imaging approaches. Moreover, in this study, we investigated the printing regimes and the printing quality during the transfer of copper (Cu) nanoink, which is a metallic nanoink usually employed in interconnect formation as well as the printing of silver nanowires, which provide transparency and may be used in applications where transparent electrodes are needed as in photovoltaics, batteries, etc. Furthermore, we demonstrate the fabrication of an all laser printed resistive chemical sensor device that combines Ag nanoparticles ink and graphene oxide, for the detection of humidity fabricated on a flexible polyimide substrate. The sensor device architecture was able to host multiple pairs of electrodes, where Ag nanoink or nanopaste were laser printed, to form the electrodes as well as the electrical interconnections between the operating device and the printed circuit board. Performance evaluation was conducted upon flow of different concentrations of humidity vapors to the sensor, and good response (500 ppm limit of detection) with reproducible operation was observed.

  16. High School Sports Involvement Diminishes the Association Between Childhood Conduct Disorder and Adult Antisocial Behavior.

    Science.gov (United States)

    Samek, Diana R; Elkins, Irene J; Keyes, Margaret A; Iacono, William G; McGue, Matt

    2015-07-01

    Life course-persistent antisocial behavior manifests as a display of aggressive and antisocial behavior beginning in childhood (conduct disorder [CD]) and lasting through adulthood (adult antisocial personality disorder). This study aimed to build on prior research by evaluating whether involvement in high school sports helped attenuate the association between CD and subsequent adult antisocial behavior (AAB). A prospective sample of 967 male and female adolescents (56% adopted) was used. Structured interviews were used to assess CD (symptoms before the age of 15 years), involvement in sports during high school, and past-year adult antisocial personality disorder symptoms in young adulthood (M age = 22.4 years). As expected, the association between CD and AAB was significantly less for those involved in sports (β = .28; p sports (β = .49; p behavior in the model (age, gender, adoption status), and results were consistent across males and females. Involvement in other extracurricular activities (e.g., student government, plays, clubs) did not significantly moderate the relationship between CD and AAB. Although selection effects were evident (those with more CD symptoms were less likely to be involved in sports), findings nevertheless suggest high school sports involvement may be a notable factor related to disrupting persistent antisocial behavior beginning in childhood and adolescence and lasting through young adulthood. Implications are discussed. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  17. A priori Considerations When Conducting High-Throughput Amplicon-Based Sequence Analysis

    Directory of Open Access Journals (Sweden)

    Aditi Sengupta

    2016-03-01

    Full Text Available Amplicon-based sequencing strategies that include 16S rRNA and functional genes, alongside “meta-omics” analyses of communities of microorganisms, have allowed researchers to pose questions and find answers to “who” is present in the environment and “what” they are doing. Next-generation sequencing approaches that aid microbial ecology studies of agricultural systems are fast gaining popularity among agronomy, crop, soil, and environmental science researchers. Given the rapid development of these high-throughput sequencing techniques, researchers with no prior experience will desire information about the best practices that can be used before actually starting high-throughput amplicon-based sequence analyses. We have outlined items that need to be carefully considered in experimental design, sampling, basic bioinformatics, sequencing of mock communities and negative controls, acquisition of metadata, and in standardization of reaction conditions as per experimental requirements. Not all considerations mentioned here may pertain to a particular study. The overall goal is to inform researchers about considerations that must be taken into account when conducting high-throughput microbial DNA sequencing and sequences analysis.

  18. Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing

    Directory of Open Access Journals (Sweden)

    Oscar Galao

    2016-04-01

    Full Text Available This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at −15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., −15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention and deicing (curing, which could turn into an environmentally friendly and cost-effective deicing method.

  19. Conductivity of the PGT Synthesized by the High Energy Ball Milling (HEBM

    Directory of Open Access Journals (Sweden)

    S. K. S. Parashar

    2013-01-01

    Full Text Available Nanocrystalline Pb1−3x/2GdxTiO3 (where x=0.01 abbreviated as PGT has been synthesised by high energy ball milling at room temperature. Milling was continuous and X-ray analysis shows that single phase tetragonal structure of nanocrystalline PGT was formed after 15 h milling. The average crystallite size was found to be 17 nm. The frequency dependent ac conductivity of the PGT ceramic was studied in the range 100–525°C. Complex impedance analysis suggested the dielectric relaxation to be of non-Debye type. The activation energy was found to be 1.04 ev. The mechanism of charge transport in nanocrystalline PGT was successfully explained by correlated hopping model.

  20. High conductivity, shallow doping in silicon by ion implantation and furnace annealing

    Energy Technology Data Exchange (ETDEWEB)

    Wu, S.; Hodel, M.W.; Samadpour, F. (Motorola, Inc., Phoenix, AZ (USA). Solar Energy Research and Development Dept.; Motorola, Inc., Phoenix, AZ (USA). Semiconductor Group)

    1985-01-01

    High dose, shallow implants (proportional 0.2 ..mu..m) were furnace annealed. As expected, As/sup +/ and P/sup +/ implants showed the same annealing characteristics. Both can be activated to their maximum levels at 550/sup 0/C; but P/sup +/ implant gave higher conductivity than As/sup +/ implant. BF/sup +//sub 2/ implant gave better activation than B/sup +/ implant at anneal temperatures below 900/sup 0/C; but both require additional moderate dose Si/sup +/ implant with proper energy and implant sequence to achieve maximum activation at these low temperatures. Maximum activation with minimum diffusion and acceptable junction leakage for VLSIC applications can be achieved by conventional furnace annealing technology.

  1. Nanogap based graphene coated AFM tips with high spatial resolution, conductivity and durability.

    Science.gov (United States)

    Lanza, Mario; Gao, Teng; Yin, Zixuan; Zhang, Yanfeng; Liu, Zhongfan; Tong, Yuzhen; Shen, Ziyong; Duan, Huiling

    2013-11-21

    After one decade of analyzing the intrinsic properties of graphene, interest into the development of graphene-based devices and micro electromechanical systems is increasing. Here, we fabricate graphene-coated atomic force microscope tips by growing the graphene on copper foil and transferring it onto the apex of a commercially available AFM tip. The resulting tip exhibits surprising enhanced resolution in nanoscale electrical measurements. By means of topographic AFM maps and statistical analyses we determine that this superior performance may be related to the presence of a nanogap between the graphene and the tip apex, which reduces the tip radius and tip-sample contact area. In addition, the graphene-coated tips show a low tip-sample interaction, high conductivity and long life times. The novel fabrication-friendly tip could improve the quality and reliability of AFM experiments, while reducing the cost of AFM-based research.

  2. Hydrogen separation by nanocrystalline titanium nitride membranes with high hydride ion conductivity

    Science.gov (United States)

    Kura, Chiharu; Kunisada, Yuji; Tsuji, Etsushi; Zhu, Chunyu; Habazaki, Hiroki; Nagata, Shinji; Müller, Michael P.; De Souza, Roger A.; Aoki, Yoshitaka

    2017-10-01

    The production of pure hydrogen for use in energy applications and related industries often relies on the permeation of hydrogen through palladium-based membranes. However, the scarcity of Pd reserves necessitates the development of affordable alternatives with high hydrogen permeability. Here we report room-temperature hydrogen permeability of titanium nitrides (widely used as tough and inert coating materials) enabled by mixed hydride ion-electron conductivity. Combined spectroscopic, permeability and microgravimetric measurements reveal that nanocrystalline TiNx membranes feature enhanced grain-boundary diffusion of hydride anions associated with interfacial Ti cations on nanograins. Since the corresponding activation energies are very low (kJ mol-1), these membranes yield a considerably higher room-temperature hydrogen flux than Pd membranes of equivalent thickness. Overall, the current study establishes general guidelines for developing hydride ion transport membranes based on a simple transition metal nitride for hydrogen purification, membrane reactors and other applications.

  3. Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing.

    Science.gov (United States)

    Galao, Oscar; Bañón, Luis; Baeza, Francisco Javier; Carmona, Jesús; Garcés, Pedro

    2016-04-12

    This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at -15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., -15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention) and deicing (curing), which could turn into an environmentally friendly and cost-effective deicing method.

  4. Polymer and Composite Membranes for Proton-Conducting, High-Temperature Fuel Cells: A Critical Review

    Science.gov (United States)

    Quartarone, Eliana; Angioni, Simone; Mustarelli, Piercarlo

    2017-01-01

    Polymer fuel cells operating above 100 °C (High Temperature Polymer Electrolyte Membrane Fuel Cells, HT-PEMFCs) have gained large interest for their application to automobiles. The HT-PEMFC devices are typically made of membranes with poly(benzimidazoles), although other polymers, such as sulphonated poly(ether ether ketones) and pyridine-based materials have been reported. In this critical review, we address the state-of-the-art of membrane fabrication and their properties. A large number of papers of uneven quality has appeared in the literature during the last few years, so this review is limited to works that are judged as significant. Emphasis is put on proton transport and the physico-chemical mechanisms of proton conductivity. PMID:28773045

  5. Highly conductive copper nano/microparticles ink via flash light sintering for printed electronics.

    Science.gov (United States)

    Joo, Sung-Jun; Hwang, Hyun-Jun; Kim, Hak-Sung

    2014-07-04

    In this study, the size effect of copper particles on the flash light sintering of copper (Cu) ink was investigated using Cu nanoparticles (20-50 nm diameter) and microparticles (2 μm diameter). Also, the mixed Cu nano-/micro-inks were fabricated, and the synergetic effects between the Cu nano-ink and micro-ink on flash light sintering were assessed. The ratio of nanoparticles to microparticles in Cu ink and the several flash light irradiation conditions (irradiation energy density, pulse number, on-time, and off-time) were optimized to obtain high conductivity of Cu films. In order to precisely monitor the milliseconds-long flash light sintering process, in situ monitoring of electrical resistance and temperature changes of Cu films was conducted during the flash light irradiation using a real-time Wheatstone bridge electrical circuit, thermocouple-based circuit, and a high-rate data acquisition system. Also, several microscopic and spectroscopic characterization techniques such as scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the flash light sintered Cu nano-/micro-films. In addition, the sheet resistance of Cu film was measured using a four-point probe method. This work revealed that the optimal ratio of nanoparticles to microparticles is 50:50 wt%, and the optimally fabricated and flash light sintered Cu nano-/micro-ink films have the lowest resistivity (80 μΩ cm) among nano-ink, micro-ink, or nano-micro mixed films.

  6. Spectroscopic XPEEM of highly conductive SI-doped GaN wires

    Energy Technology Data Exchange (ETDEWEB)

    Renault, O., E-mail: olivier.renault@cea.fr [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Morin, J. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Tchoulfian, P. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France); Chevalier, N. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Feyer, V. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich (Germany); Pernot, J. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France); Institut Universitaire de France, F-75005 Paris (France); Schneider, C.M. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, D-52425 Jülich (Germany)

    2015-12-15

    Using soft X-ray photoelectron emission microscopy (XPEEM), complemented by scanning Auger microscopy (SAM) and scanning capacitance microscopy, we have quantitatively studied the incorporation of silicon and band bending at the surface (m-facet) of an individual, highly conductive Si-doped GaN micro-wires (Tchoulfian et al., Applied Physics Letters 102 (12), 2013). Electrically active n-dopants Si atoms in Ga interstitial sites are detected as nitride bonding states in the high-resolution Si2p core level spectra, and represent only a small fraction (<10%) of the overall Si surface concentration measured by SAM. The derived carrier concentration of 2×10{sup 21} at cm{sup −3} is in reasonable agreement with electrical measurements. A consistent surface band bending of ~1 eV is directly evidenced by surface photo-voltage measurements. Such an approach combining different surface-sensitive microscopies is of interest for studying other heavily doped semiconducting wires. - Highlights: • XPEEM analysis of state-of-the-art, heavily doped GaN wires with insights on the issue of the origin of the increased conductivity. • Combined microscopic approach with Scanning Auger microscopy and X-ray Photoeletron Emission Microscopy, to quantity the electrically active Si-dopants in GaN. • The determined concentration is found in reasonable agreement with the one derived from bulk electrical measurements. • The proposed method is of interest for studying the electronics and chemistry of doping in other heavily doped semiconducting wires.

  7. Study of high-anionic conducting sulfonated microporous membranes for zinc-air electrochemical cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, G.M. [Institute of Electro-Optical Engineering, Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan 333, Taiwan (China)], E-mail: wu@mail.cgu.edu.tw; Lin, S.J.; You, J.H. [Institute of Electro-Optical Engineering, Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan 333, Taiwan (China); Yang, C.C. [Ming Chi University of Technology, Taipei 243, Taiwan (China)

    2008-12-20

    High-performance electrochemical membranes have been in great demand due to the rapid market growth in the portable power source devices. The electrochemical characteristics of high-anionic conducting membrane separators were studied in this report using microporous membranes with different sulfonation degrees obtained by changing the sulfonation reaction time. The degree of sulfonation treatment and the effects on the membrane separators were carefully investigated. The room temperature anionic conductivity of the membranes was improved by 132% to 3.52 x 10{sup -2} S cm{sup -1} when the sulfonation treatment time was 128 h. It was about 1.52 x 10{sup -2} S cm{sup -1} for the unsulfonated membranes. The anionic transport number in 1 M KOH aqueous solution was also improved to 0.89 from 0.79. The characteristic properties of these membrane separators were studied by infrared spectroscopy (IR), elemental analysis (EA), X-ray diffraction (XRD), scanning electron microscopy (SEM), AC impedance, contact angle measuring system and stress-strain tests. In addition, the solid-state zinc-air cells assembled from the sulfonated membrane separators showed enhanced battery power density of 38 mW cm{sup -2} while the discharge current density was higher at 45 mA cm{sup -2}. The battery power density was around 20 mW cm{sup -2} and the discharge current density was 25 mA cm{sup -2} for the unsulfonated samples. Therefore, the sulfonated microporous membranes could be tailored for the different electrochemical cell applications.

  8. Cu ion ink for a flexible substrate and highly conductive patterning by intensive pulsed light sintering.

    Science.gov (United States)

    Wang, Byung-Yong; Yoo, Tae-Hee; Song, Yong-Won; Lim, Dae-Soon; Oh, Young-Jei

    2013-05-22

    Direct printing techniques that utilize nanoparticles to mitigate environmental pollution and reduce the processing time of the routing and formation of electrodes have received much attention lately. In particular, copper (Cu) nanoink using Cu nanoparticles offers high conductivity and can be prepared at low cost. However, it is difficult to produce homogeneous nanoparticles and ensure good dispersion within the ink. Moreover, Cu particles require a sintering process over an extended time at a high temperature due to high melting temperature of Cu. During this process, the nanoparticles oxidize quickly in air. To address these problems, the authors developed a Cu ion ink that is free of Cu particles or any other impurities. It consequently does not require separate dispersion stability. In addition, the developed ink is environmentally friendly and can be sintered even at low temperatures. The Cu ion ink was sintered on a flexible substrate using intense pulsed light (IPL), which facilitates large-area, high-speed calcination at room temperature and at atmospheric pressures. As the applied light energy increases, the Cu2O phase diminishes, leaving only the Cu phase. This is attributed to the influence of formic acid (HCOOH) on the Cu ion ink. Only the Cu phase was observed above 40 J cm(-2). The Cu-patterned film after sintering showed outstanding electrical resistivity in a range of 3.21-5.27 μΩ·cm at an IPL energy of 40-60 J cm(-2). A spiral-type micropattern with a line width of 160 μm on a PI substrate was formed without line bulges or coffee ring effects. The electrical resistivity was 5.27 μΩ·cm at an energy level of 40.6 J cm(-2).

  9. [High-resolution patch-clamp technique based on feedback control of scanning ion conductance microscopy].

    Science.gov (United States)

    Yang, Xi; Liu, Xiao; Zhang, Xiao-Fan; Lu, Hu-Jie; Zhang, Yan-Jun

    2010-06-25

    The ion channels located on the cell fine structures play an important role in the physiological functions of cell membrane. However, it is impossible to achieve precise positioning on the nanometer scale cellular microstructures by conventional patch-clamp technique, due to the 200 nm resolution limit of optical microscope. To solve this problem, we have established a high-resolution patch-clamp technique, which combined commercial scanning ion conductance microscopy (SICM) and patch-clamp recording through a nanopipette probe, based on SICM feedback control. MDCK cells were used as observation object to test the capability of the technique. Firstly, a feedback controlled SICM nanopipette (approximately 150 MOmega) non-contactly scanned over a selected area of living MDCK cells monolayer to obtain high-resolution topographic images of microvilli and tight-junction microstructures on the MDCK cells monolayer. Secondly, the same nanopipette was non-contactly moved and precisely positioned over the microvilli or tight-junction microstructure under SICM feedback control. Finally, the SICM feedback control was switched off, the nanopipette slowly contacted with the cell membrane to get a patch-clamp giga-ohm sealing in the cell-attached patch-clamp configuration, and then performed ion channel recording as a normal patch-clamp electrode. The ion channel recordings showed that ion channels of microvilli microstructure opened at pipette holding potential of -100, -60, -40, 0, +40, +60, +100 mV (n=11). However, the opening of ion channels of tight-junction microstructure was not detected at pipette holding potential of -100, -40, 0, +40, +100 mV (n=9). These results suggest that our high-resolution patch-clamp technique can achieve accurate nanopipette positioning and nanometer scale high-resolution patch-clamp recording, which may provide a powerful tool to study the spatial distribution and functions of ion channel in the nanometer scale microstructures of living

  10. Combined astigmatic keratotomy and conductive keratoplasty to correct high corneal astigmatism.

    Science.gov (United States)

    Sy, Mary Ellen; Kovoor, Timmy A; Tannan, Anjali; Choi, Daniel; Deng, Sophie X; Danesh, Jennifer; Hamilton, D Rex

    2015-05-01

    To determine the safety, efficacy, and predictability of combined astigmatic keratotomy (AK) and conductive keratoplasty (CK) for treating high corneal astigmatism. University of California-Los Angeles, Los Angeles, California, USA. Retrospective case series. From January 1, 2004, to December 31, 2009, AK and CK were performed in eyes with corneal astigmatism of 5.0 diopters (D) or more after keratoplasty or trauma. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), defocus equivalent, mean astigmatism, efficacy index, and complications were evaluated. In 11 eyes of 11 patients, the mean UDVA improved from 1.54 logMAR ± 0.50 (SD) preoperatively to 0.69 ± 0.62 logMAR 3 months postoperatively (P astigmatism decreased from 10.25 ± 4.71 D to 4.31 ± 2.34 D (P astigmatism showed a statistically significant decrease. The efficacy index was 0.82. One case of wound gape after AK required suturing. No infectious keratitis, corneal perforation, or graft rejection occurred. Results indicate that combined AK and CK is safe and effective for correcting high corneal astigmatism after surgery or trauma. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  11. Optoelectrochemical biorecognition by optically transparent highly conductive graphene-modified fluorine-doped tin oxide substrates.

    Science.gov (United States)

    Lamberti, F; Brigo, L; Favaro, M; Luni, C; Zoso, A; Cattelan, M; Agnoli, S; Brusatin, G; Granozzi, G; Giomo, M; Elvassore, N

    2014-12-24

    Both optical and electrochemical graphene-based sensors have gone through rapid development, reaching high sensitivity at low cost and with fast response time. However, the complex validating biochemical operations, needed for their consistent use, currently limits their effective application. We propose an integration strategy for optoelectrochemical detection that overcomes previous limitations of these sensors used separately. We develop an optoelectrochemical sensor for aptamer-mediated protein detection based on few-layer graphene immobilization on selectively modified fluorine-doped tin oxide (FTO) substrates. Our results show that the electrochemical properties of graphene-modified FTO samples are suitable for complex biological detection due to the stability and inertness of the engineered electrodic interface. In addition, few-layer immobilization of graphene sheets through electrostatic linkage with an electrochemically grafted FTO surface allows obtaining an optically accessible and highly conductive platform. As a proof of concept, we used insulin as the target molecule to reveal in solution. Because of its transparency and low sampling volume (a few microliters), our sensing unit can be easily integrated in lab-on-a-chip cell culture systems for effectively monitoring subnanomolar concentrations of proteins relevant for biomedical applications.

  12. Knitted Strain Sensor Textiles of Highly Conductive All-Polymeric Fibers.

    Science.gov (United States)

    Seyedin, Shayan; Razal, Joselito M; Innis, Peter C; Jeiranikhameneh, Ali; Beirne, Stephen; Wallace, Gordon G

    2015-09-30

    A scaled-up fiber wet-spinning production of electrically conductive and highly stretchable PU/PEDOT:PSS fibers is demonstrated for the first time. The PU/PEDOT:PSS fibers possess the mechanical properties appropriate for knitting various textile structures. The knitted textiles exhibit strain sensing properties that were dependent upon the number of PU/PEDOT:PSS fibers used in knitting. The knitted textiles show sensitivity (as measured by the gauge factor) that increases with the number of PU/PEDOT:PSS fibers deployed. A highly stable sensor response was observed when four PU/PEDOT:PSS fibers were co-knitted with a commercial Spandex yarn. The knitted textile sensor can distinguish different magnitudes of applied strain with cyclically repeatable sensor responses at applied strains of up to 160%. When used in conjunction with a commercial wireless transmitter, the knitted textile responded well to the magnitude of bending deformations, demonstrating potential for remote strain sensing applications. The feasibility of an all-polymeric knitted textile wearable strain sensor was demonstrated in a knee sleeve prototype with application in personal training and rehabilitation following injury.

  13. Highly conductive templated-graphene fabrics for lightweight, flexible and foldable supercapacitors

    Science.gov (United States)

    Zhang, Ping; Zhang, Hanzhi; Yan, Casey; Zheng, Zijian; Yu, You

    2017-07-01

    The templated-rGO fabric, featuring high conductivity (<1.0 Ω □-1) and low density (160 mg cm-2), is prepared by a simple dip-coating technique with sequentially coating nickel via polymer-assisted metal deposition (PAMD) and reduced-graphene oxide (rGO) on textile fabric templates at very mild conditions and is used in the fabrication of energy storage devices. As a proof of concept, both the layered and planar supercapacitors (SCs) are successfully fabricated using the rGO fabrics as templates, and both exhibit excellent electrochemical performance, ultrahigh stability with 2000 charge-discharge cycles and mechanical flexibility at bending (r  =  3 mm) and even folding states. It is found that the material of textile fabric used has a profound effect on the electrochemical property of SCs. The comparison result reveals that loose natural cotton fabrics are more suitable than tight man-made nylon fabrics for preparing high-performance SCs. In addition, such supercapacitor can be sewed into commercial textiles and powers a LED light, indicating promising applications in wearable electronics.

  14. Spectroscopic XPEEM of highly conductive SI-doped GaN wires.

    Science.gov (United States)

    Renault, O; Morin, J; Tchoulfian, P; Chevalier, N; Feyer, V; Pernot, J; Schneider, C M

    2015-12-01

    Using soft X-ray photoelectron emission microscopy (XPEEM), complemented by scanning Auger microscopy (SAM) and scanning capacitance microscopy, we have quantitatively studied the incorporation of silicon and band bending at the surface (m-facet) of an individual, highly conductive Si-doped GaN micro-wires (Tchoulfian et al., Applied Physics Letters 102 (12), 2013). Electrically active n-dopants Si atoms in Ga interstitial sites are detected as nitride bonding states in the high-resolution Si2p core level spectra, and represent only a small fraction (<10%) of the overall Si surface concentration measured by SAM. The derived carrier concentration of 2×10(21) at cm(-3) is in reasonable agreement with electrical measurements. A consistent surface band bending of ~1 eV is directly evidenced by surface photo-voltage measurements. Such an approach combining different surface-sensitive microscopies is of interest for studying other heavily doped semiconducting wires. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. High-concentration copper nanoparticles synthesis process for screen-printing conductive paste on flexible substrate

    Energy Technology Data Exchange (ETDEWEB)

    Tam, Sze Kee; Ng, Ka Ming, E-mail: kekmng@ust.hk [The Hong Kong University of Science and Technology, Department of Chemical and Biomolecular Engineering (Hong Kong)

    2015-12-15

    This study presents a method for the synthesis of copper nanoparticles, which are poised to replace silver nanoparticles in some application areas of printed electronics. This method offers three advantages. Firstly, copper loading in the synthesis reaction can be as high as 1 M, offering high productivity in large-scale production. Secondly, the size of the copper nanoparticles can be controlled from 12 to 99 nm. Thirdly, the surface polarity of the particles can be modified. Thus, a tailor-made product can be synthesized. The synthesis of copper nanoparticles coated with various capping agents, including dodecanethiol, lauric acid, nonanoic acid, polyacrylic acid, and polyvinyl pyrrolidone, was demonstrated. The nonanoic acid-coated copper nanoparticles were formulated as a screen-printing conductive paste. The particles were readily dispersed in terpineol, and the paste could be screen printed onto flexible polyester. The electrical resistivity of patterns after a low-temperature (120 °C) sintering treatment was around 5.8 × 10{sup −5} Ω cm.Graphical Abstract.

  16. Ultra-high aspect ratio copper nanowires as transparent conductive electrodes for dye sensitized solar cells

    Science.gov (United States)

    Zhu, Zhaozhao; Mankowski, Trent; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

    2016-09-01

    We report the synthesis of ultra-high aspect ratio copper nanowires (CuNW) and fabrication of CuNW-based transparent conductive electrodes (TCE) with high optical transmittance (>80%) and excellent sheet resistance (Rs AZO) thin-film coatings, or platinum thin film coatings, or nickel thin-film coatings. Our hybrid transparent electrodes can replace indium tin oxide (ITO) films in dye-sensitized solar cells (DSSCs) as either anodes or cathodes. We highlight the challenges of integrating bare CuNWs into DSSCs, and demonstrate that hybridization renders the solar cell integrations feasible. The CuNW/AZO-based DSSCs have reasonably good open-circuit voltage (Voc = 720 mV) and short-circuit current-density (Jsc = 0.96 mA/cm2), which are comparable to what is obtained with an ITO-based DSSC fabricated with a similar process. Our CuNW-Ni based DSSCs exhibit a good open-circuit voltage (Voc = 782 mV) and a decent short-circuit current (Jsc = 3.96 mA/cm2), with roughly 1.5% optical-to-electrical conversion efficiency.

  17. Investigation of high thermal contact conductance at low contact pressure for high-heat-load optical elements of synchrotron radiation

    Science.gov (United States)

    Takeuchi, T.; Tanaka, M.; Ohashi, H.; Goto, S.

    2013-09-01

    We measured the thermal-contact-conductance (TCC) of indirect cooling components in synchrotron radiation beamlines. To reduce the strain on the optical element, we explored conditions for insertion materials with a high TCC in region with low contact pressures of 0.1-1.0 MPa. We examined the TCC at the interface between oxygen-free copper (OFC) and insertion materials such as indium, graphite, and gold foil. The TCC depended on the hardness and thickness of the insertion material. Thin indium (20 μm thick) showed the highest TCC. Nickel and gold passivation on the OFC surface reduced the TCC to 30% of that for the bare OFC. Future work will involve exploring the passivation conditions of OFC for higher TCC is and measuring the TCC under cryogenic-cooling conditions.

  18. Bulk- and electrode-limited conduction mechanisms in different phases of Mn{sup 2+}-doped potassium tetrachlorozincate crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gaffar, M A [Physics Department, School of Science and Engineering, American University in Cairo, Cairo 11511 (Egypt); Abousehly, A M [Physics Department, Faculty of Science, Al-Azhar University, 71524 Assiut (Egypt); El-Fadl, A Abu [Physics Department, Faculty of Science, Assiut University, 71516 Assiut (Egypt); Mostafa, M M [Physics Department, Faculty of Science, Al-Azhar University, 71524 Assiut (Egypt)

    2005-02-21

    The current density-electric field intensity relationship of pre-heated potassium tetrachlorozincate (KZC) crystals (undoped and doped with Mn{sup 2+} in different concentrations) has been measured along the polar a-axis. The dependence was studied at selected temperatures covering the three high-temperature phases of KZC in order to investigate the type of conduction mechanism dominating in each phase. The original Richardson-Schottky (R-S) equation shows disagreement between calculated and experimental values of the Richardson and optical dielectric constants. The modified R-S equation fits the data well and facilitated the calculation of the barrier height, electronic mobility and high-frequency dielectric constant of KZC. The calculated parameters are in good agreement with the corresponding experimental values. The results indicated that the bulk- and electrode-limited mechanisms contribute to conduction in different phases of KZC. The temperature dependence of the dc conductivity along the polar axis of undoped and Mn{sup 2+}-doped KZC shows anomalous behaviour in the region of the phase transitions. The dc conductivity and the activation energy of conduction (w) changed significantly due to doping. As indicated by the extremely high w values, superionic conduction is the dominating mechanism in the high-temperature part of the incommensurate (IC) and normal phases of KZC. Suppression of the superionic conduction by Mn{sup 2+}-doping is observed. The effect of discommensurate pinning by Mn{sup 2+} ions and the possibility of dislocation formation on the dc conduction in the IC phase is also discussed.

  19. Processing, characterization, and bactericidal activity of undoped and silver-doped vanadium oxides

    Energy Technology Data Exchange (ETDEWEB)

    Tousley, M.E.; Wren, A.W.; Towler, M.R. [Inamori School of Engineering, Alfred University, Alfred, NY 14803 (United States); Mellott, N.P., E-mail: mellott@alfred.edu [Inamori School of Engineering, Alfred University, Alfred, NY 14803 (United States)

    2012-12-14

    Vanadium oxide (V) and silver-doped vanadium oxide (Ag-V) powders were prepared via sol-gel processing. Structural evolution and bactericidal activity was examined as a function of temperature ranging from 250, 350, 450 and 550 Degree-Sign C. Powders were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy. Results from all techniques showed vanadium pentoxide (V{sub 2}O{sub 5}) is the predominant phase regardless of heat treatment temperature or the addition of silver (Ag). XRD analysis suggests Ag is present as AgCl in samples heat treated to 250, 350, and 450 Degree-Sign C and as AgV{sub 6}O{sub 15} at 550 Degree-Sign C. Bactericidal activity was evaluated against Escherichia coli using the agar disk diffusion method considering both Ag-V and undoped, V powders. While the addition of Ag significantly increased bactericidal properties, the specific Ag valency, or crystal structure and morphology formed at higher temperatures, had little effect on functionality. -- Highlights: Black-Right-Pointing-Pointer Vanadium and silver-doped vanadium oxide powders were prepared via sol-gel. Black-Right-Pointing-Pointer Powders were characterized using advanced, complementary structural techniques. Black-Right-Pointing-Pointer Bactericidal activity was evaluated against E. coli. Black-Right-Pointing-Pointer Both vanadium and silver doped vanadium oxide show bactericidal activity.

  20. Electrical current at micro-/macro-scale of undoped and nitrogen-doped MWPECVD diamond films

    Science.gov (United States)

    Cicala, G.; Velardi, L.; Senesi, G. S.; Picca, R. A.; Cioffi, N.

    2017-12-01

    Chemical, structural, morphological and micro-/macro-electrical properties of undoped and nitrogen-(N-)doped diamond films are determined by X-ray photoelectron spectroscopy, Raman and photoluminescence spectroscopies, field emission scanning electron microscopy, atomic force microscopy, scanning capacitance microscopy (SCM) and two points technique for I-V characteristics, respectively. The characterization results are very useful to examine and understand the relationship among these properties. The effect of the nitrogen incorporation in diamond films is investigated through the evolution of the chemical, structural, morphological and topographical features and of the electrical behavior. The distribution of the electrical current is first assessed at millimeter scale on the surface of diamond films and then at micrometer scale on small regions in order to establish the sites where the carriers preferentially move. Specifically, the SCM images indicate a non-uniform distribution of carriers on the morphological structures mainly located along the grain boundaries. A good agreement is found by comparing the electrical currents at the micro- and macro-scale. This work aims to highlight phenomena such as photo- and thermionic emission from N-doped diamond useful for microelectronic engineering.

  1. Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

    Science.gov (United States)

    An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.

    2015-01-01

    Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects. PMID:26391053

  2. Effects of free electrons and quantum confinement in ultrathin ZnO films: a comparison between undoped and Al-doped ZnO.

    Science.gov (United States)

    Li, X D; Chen, T P; Liu, P; Liu, Y; Leong, K C

    2013-06-17

    Band gaps and exciton binding energies of undoped and Al-doped ZnO thin films were determined from optical absorption measurement based on the Elliott's exciton absorption theory. As compared to the undoped films, the doped films exhibit a band gap expansion and a reduction in the exciton binding energies due to the free electron screening effect, which suppresses the excitonic absorption and results in a blue shift of the absorption edge. The undoped and doped films show the same quantum size dependence, i.e. both the exciton binding energies and band gap energies increase with decreasing grain size of the oxides.

  3. Use of high-power diode lasers for hardening and thermal conduction welding of metals

    Science.gov (United States)

    Klocke, Fritz; Demmer, Axel; Zaboklicki, A.

    1997-08-01

    CO2 and Nd:YAG high power lasers have become established as machining tools in industrial manufacturing over the last few years. The most important advantages compared to conventional processing techniques lie in the absence of forces introduced by the laser into the workpiece and in the simple arid highly accurate control in terms ofpositioning and timing making the laser a universally applicable, wear-free and extremely flexible tool /1,2/. The laser can be utilised costeffectively in numerous manufacturing processes but there are also further applications for the laser which produce excellent results from a technical point of view, but are not justified in terms of cost. The extensive use of lasers, particularly in small companies and workshops, is hindered by two main reasons: the complexity and size ofthe laser source and plant and the high investment costs /3/. A new generation of lasers, the high power diode lasers (HDL), combines high performance with a compact design, making the laser a cheap and easy to use tool with many applications /3,4,5,6/. In the diode laser, the laser beam is generated by a microelectronic diode which transforms electrical energy directly into laser energy. Diode lasers with low power outputs have, for some time, been making their mark in our everyday lives: they are used in CD players, laser printers and scanners at cash tills. Modern telecommunications would be impossible without these lasers which enable information to be transmitted in the form oflight impulses through optical fibres. They can also be found in compact precision measurement instrumentation - range fmders, interferometers and pollutant analysis devices /3,6/. In the field of material processing, the first applications ofthe laser, such as for soldering, inscribing, surface hardening and plastic or heat conduction welding, will exceed the limits ofthe relatively low performance output currently available. The diode laser has a shorter wavelength than the CO2 and

  4. Blue, green, and red emission from undoped and doped ZnGa2O4 colloidal nanocrystals

    Science.gov (United States)

    Byun, Ho-June; Kim, Jong-Uk; Yang, Heesun

    2009-12-01

    Undoped, Tb3+- and Eu3+-doped ZnGa2O4 colloidal nanocrystals were synthesized by a nonhydrolytic hot solution chemistry. Undoped nanocrystals exhibited an intrinsic blue emission peaking at 437 nm by self-activated transition. The emissions of Tb3+-and Eu3+-doped ZnGa2O4 nanocrystals consisted of their own characteristic green and red line peaks (5D4-7Fj transitions), respectively. Synthetic parameters such as activator concentration and reaction time were varied to investigate their effects on luminescent properties. Tb3+-doped colloidal nanocrystals synthesized for a short reaction time showed an unprecedented, exclusively green luminescence with the host blue emission effectively suppressed. On the other hand, the emission of Eu3+-doped ones was weak with the host emission persistently present regardless of reaction time.

  5. Effect of doped and undoped POMA on the morphology and miscibility of blends with Poly(vinylidene fluoride (PVDF

    Directory of Open Access Journals (Sweden)

    I.S. Rocha

    1999-04-01

    Full Text Available The effect of the addition of small amounts of doped and undoped poly(o-methoxyaniline (POMA on the morphology of melt crystallized PVDF was investigated by means of polarized light optical microscopy. Undoped POMA (POMA-EB inhibits nucleation and growth of non ringed spherulites, partially formed by the polar gphase, whereas POMA doped with toluene sulfonic acid (POMA-TSA favors this process. Moreover, the doping of POMA increases the miscibility between the components of the PVDF/POMA blends, resulting in more homogeneous films. A possible cause of this miscibility increase and for the favoring of the polar gphase, is the higher polarity of the POMA chains as a result of the doping.

  6. K⁺ conduction and Mg²⁺ blockade in a shaker Kv-channel single point mutant with an unusually high conductance.

    Science.gov (United States)

    Moscoso, Cristian; Vergara-Jaque, Ariela; Márquez-Miranda, Valeria; Sepúlveda, Romina V; Valencia, Ignacio; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

    2012-09-19

    Potassium channels exhibit a large diversity of single-channel conductances. Shaker is a low-conductance K-channel in which Pro475→Asp, a single-point mutation near the internal pore entrance, promotes 6- to 8-fold higher unitary current. To assess the mechanism for this higher conductance, we measured Shaker-P475D single-channel current in a wide range of symmetrical K(+) concentrations and voltages. Below 300 mM K(+), the current-to-voltage relations (i-V) showed inward rectification that disappeared at 1000 mM K(+). Single-channel conductance reached a maximum of ∼190 pS at saturating [K(+)], a value 4- to 5-fold larger than that estimated for the native channel. Intracellular Mg(2+) blocked this variant with ∼100-fold higher affinity. Near zero voltage, blockade was competitively antagonized by K(+); however, at voltages >100 mV, it was enhanced by K(+). This result is consistent with a lock-in effect in a single-file diffusion regime of Mg(2+) and K(+) along the pore. Molecular-dynamics simulations revealed higher K(+) density in the pore, especially near the Asp-475 side chains, as in the high-conductance MthK bacterial channel. The molecular dynamics also showed that K(+) ions bound distally can coexist with other K(+) or Mg(2+) in the cavity, supporting a lock-in mechanism. The maximal K(+) transport rate and higher occupancy could be due to a decrease in the electrostatic energy profile for K(+) throughout the pore, reducing the energy wells and barriers differentially by ∼0.7 and ∼2 kT, respectively. Copyright © 2012 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  7. High capacity and high density functional conductive polymer and SiO anode for high-energy lithium-ion batteries.

    Science.gov (United States)

    Zhao, Hui; Yuca, Neslihan; Zheng, Ziyan; Fu, Yanbao; Battaglia, Vincent S; Abdelbast, Guerfi; Zaghib, Karim; Liu, Gao

    2015-01-14

    High capacity and high density functional conductive polymer binder/SiO electrodes are fabricated and calendered to various porosities. The effect of calendering is investigated in the reduction of thickness and porosity, as well as the increase of density. SiO particle size remains unchanged after calendering. When compressed to an appropriate density, an improved cycling performance and increased energy density are shown compared to the uncalendered electrode and overcalendered electrode. The calendered electrode has a high-density of ∼1.2 g/cm(3). A high loading electrode with an areal capacity of ∼3.5 mAh/cm(2) at a C/10 rate is achieved using functional conductive polymer binder and simple and effective calendering method.

  8. Is high-resolution inverse characterization of heterogeneous river bed hydraulic conductivities needed and possible?

    Directory of Open Access Journals (Sweden)

    W. Kurtz

    2013-10-01

    Full Text Available River–aquifer exchange fluxes influence local and regional water balances and affect groundwater and river water quality and quantity. Unfortunately, river–aquifer exchange fluxes tend to be strongly spatially variable, and it is an open research question to which degree river bed heterogeneity has to be represented in a model in order to achieve reliable estimates of river–aquifer exchange fluxes. This research question is addressed in this paper with the help of synthetic simulation experiments, which mimic the Limmat aquifer in Zurich (Switzerland, where river–aquifer exchange fluxes and groundwater management activities play an important role. The solution of the unsaturated–saturated subsurface hydrological flow problem including river–aquifer interaction is calculated for ten different synthetic realities where the strongly heterogeneous river bed hydraulic conductivities (L are perfectly known. Hydraulic head data (100 in the default scenario are sampled from the synthetic realities. In subsequent data assimilation experiments, where L is unknown now, the hydraulic head data are used as conditioning information, with the help of the ensemble Kalman filter (EnKF. For each of the ten synthetic realities, four different ensembles of L are tested in the experiments with EnKF; one ensemble estimates high-resolution L fields with different L values for each element, and the other three ensembles estimate effective L values for 5, 3 or 2 zones. The calibration of higher-resolution L fields (i.e. fully heterogeneous or 5 zones gives better results than the calibration of L for only 3 or 2 zones in terms of reproduction of states, stream–aquifer exchange fluxes and parameters. Effective L for a limited number of zones cannot always reproduce the true states and fluxes well and results in biased estimates of net exchange fluxes between aquifer and stream. Also in case only 10 head data are used for conditioning, the high

  9. Positron annihilation spectroscopy study of lattice defects in non-irradiated doped and un-doped fuels

    Directory of Open Access Journals (Sweden)

    Chollet Mélanie

    2017-01-01

    Full Text Available Fission gas behavior within the fuel structure plays a major role for the safety of nuclear fuels during operation in the nuclear power plant. Fission gas distribution and retention is determined by both, micro- and lattice-structure of the fuel matrix. The ADOPT (Advanced Doped Pellet Technology fuel, containing chromium and aluminum additives, shows larger grain sizes than standard (undoped UO2 fuel, enhancing the fission gas retention properties of the matrix. However, the additions of such trivalent cations shall also induce defects in the lattice. In this study, we investigated the microstructure of such doped fuels as well as a reference standard UO2 by positron annihilation spectroscopy (PAS. Although this technique is particularly sensitive to lattice point defects in materials, a wider application in the UO2 research is still missing. The PAS-lifetime components were measured in the hotlab facility of PSI using a 22Na source sandwiched between two 500-μm-thin sample discs. The values of lifetime at the center and the rim of both samples, examined to check at the radial homogeneity of the pellets, are not significantly different. The mean lifetimes were found to be longer in the ADOPT material, 220 ps, than in standard UO2, 190 ps, which indicates a larger presence of additional defects, presumably generated by the dopants. While two-component decomposition (bulk + one defect component could be performed for the standard material, only one lifetime component was found in the doped material. The absence of the bulk component in the ADOPT sample refers to a saturated positron trapping (i.e., all positrons are trapped at defects. In order to associate a type of lattice defect to each PAS component, interpretation of the PAS experimental observations was conducted with respect to existing experimental and modeling studies. This work has shown the efficiency of PAS to detect lattice point defects in UO2 produced by Cr and Al oxides

  10. High conductivity composite flip-chip joints and silver-indium bonding to bismuth telluride for high temperature applications

    Science.gov (United States)

    Lin, Wen P.

    Two projects are reported. First, the barrier layer and silver (Ag)-indium (In) transient liquid phase (TLP) bonding for thermoelectric (TE) modules at high temperature were studied, and followed with a survey of Ag microstructure and grain growth kinetics. Second, the high electrical conductivity joint materials bonded by both Ag-AgIn TLP and solid-state bonding processes for small size flip-chip applications were designed. In the first project, barrier and Ag-In TLP bonding layer for TE module at high temperature application were studied. Bismuth telluride (Bi2 Te3) and its alloys are used as materials for a TE module. A barrier/bonding composite was developed to satisfy the TE module for high temperature operation. Titanium (Ti)/ gold (Au) was chosen as the barrier layers and an Ag-rich Ag-In joint was chosen as the bonding layer. An electron-beam evaporated Ti layer was selected as the barrier layer. An Ag-In fluxless TLP bonding process was developed to bond the Bi 2Te3 chips to the alumina substrates for high temperature applications. To prepare for bonding, the Bi2Te3 chips were coated with a Ti/Au barrier layer followed by a Ag layer. The alumina substrates with titanium-tungsten (TiW)/Au were then electroplated with the Ag/In/Ag structure. These Bi2Te3 chips were bonded to alumina substrates at a bonding temperature of 180ºC with a static pressure as low as 100psi. The resulting void-free joint consists of five regions: Ag, (Ag), Ag2In, (Ag), and Ag, where (Ag) is Ag-rich solid solution with In atoms in it and Ag is pure Ag. This joint has a melting temperature higher than 660ºC, and it manages the coefficient of thermal expansion (CTE) mismatch between the Bi2Te3 and alumina substrate. The whole Ti/Au barrier layer and Ag-In bonding composite between Bi 2Te3 and alumina survived after an aging test at 250°C for 200 hours. The Ag-In joint transformed from Ag/(Ag)/Ag2In/(Ag)/Ag to a more reliable (Ag) rich layer after the aging test. Ag thin films were

  11. High glucose attenuates shear-induced changes in endothelial hydraulic conductivity by degrading the glycocalyx.

    Science.gov (United States)

    Lopez-Quintero, Sandra V; Cancel, Limary M; Pierides, Alexis; Antonetti, David; Spray, David C; Tarbell, John M

    2013-01-01

    Diabetes mellitus is a risk factor for cardiovascular disease; however, the mechanisms through which diabetes impairs homeostasis of the vasculature have not been completely elucidated. The endothelium interacts with circulating blood through the surface glycocalyx layer, which serves as a mechanosensor/transducer of fluid shear forces leading to biomolecular responses. Atherosclerosis localizes typically in regions of low or disturbed shear stress, but in diabetics, the distribution is more diffuse, suggesting that there is a fundamental difference in the way cells sense shear forces. In the present study, we examined the effect of hyperglycemia on mechanotranduction in bovine aortic endothelial cells (BAEC). After six days in high glucose media, we observed a decrease in heparan sulfate content coincident with a significant attenuation of the shear-induced hydraulic conductivity response, lower activation of eNOS after exposure to shear, and reduced cell alignment with shear stress. These studies are consistent with a diabetes-induced change to the glycocalyx altering endothelial response to shear stress that could affect the distribution of atherosclerotic plaques.

  12. Microscopic observation of highly mobile charge carriers in organic transistors of semicrystalline conducting polymers

    Science.gov (United States)

    Kawamura, Shinya; Wakamatsu, Ayato; Kuroda, Shin-ichi; Takenobu, Taishi; Tanaka, Hisaaki

    2018-02-01

    Charge carrier dynamics in organic field-effect transistors (OFETs) of semicrystalline conducting polymers poly(2,5-bis(3-hexadecylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) and poly(3-hexylthiophene) (P3HT) have been investigated down to 4 K by field-induced electron spin resonance (FI-ESR) spectroscopy. The highly mobile nature of charge carriers within the ordered regions of the polymers has been clarified from the observation of the motional narrowing effect of the ESR spectra even below 30 K, where device operation cannot be observed presumably owing to the effect of domain boundaries. The activation energy of carrier motion observed by ESR has been determined as 17 meV for PBTTT and 13 meV for P3HT, which are an order of magnitude smaller than that of FET mobility (>110 meV) obtained for the same devices. These results demonstrate that the intrinsic carrier mobility within the ordered region is much higher than that expected from the macroscopic transport measurements in the semicrystalline polymers.

  13. High-speed XYZ-nanopositioner for scanning ion conductance microscopy

    Science.gov (United States)

    Watanabe, Shinji; Ando, Toshio

    2017-09-01

    We describe a tip-scan-type high-speed XYZ-nanopositioner designed for scanning ion conductance microscopy (SICM), with a special care being devoted to the way of nanopipette holding. The nanopipette probe is mounted in the center of a hollow piezoactuator, both ends of which are attached to identical diaphragm flexures, for Z-positioning. This design minimizes the generation of undesirable mechanical vibrations. Mechanical amplification is used to increase the XY-travel range of the nanopositioner. The first resonance frequencies of the nanopositioner are measured as ˜100 kHz and ˜2.3 kHz for the Z- and XY-displacements, respectively. The travel ranges are ˜6 μm and ˜34 μm for Z and XY, respectively. When this nanopositioner is used for hopping mode imaging of SICM with a ˜10-nm radius tip, the vertical tip velocity can be increased to 400 nm/ms; hence, the one-pixel acquisition time can be minimized to ˜1 ms.

  14. High-conductivity silicon based spectrally selective plasmonic surfaces for sensing in the infrared region

    Science.gov (United States)

    Gorgulu, K.; Gok, A.; Yilmaz, M.; Topalli, K.; Okyay, A. K.

    2017-02-01

    Plasmonic perfect absorbers have found a wide range of applications in imaging, sensing, and light harvesting and emitting devices. Traditionally, metals are used to implement plasmonic structures. For sensing applications, it is desirable to integrate nanophotonic active surfaces with biasing and amplification circuitry to achieve monolithic low cost solutions. Commonly used plasmonic metals such as Au and Ag are not compatible with standard silicon complementary metal-oxide-semiconductor (CMOS) technology. Here we demonstrate plasmonic perfect absorbers based on high conductivity silicon. Standard optical lithography and reactive ion etching techniques were used for the patterning of the samples. We present computational and experimental results of surface plasmon resonances excited on a silicon surface at normal and oblique incidences. We experimentally demonstrate our absorbers as ultra-low cost, CMOS-compatible and efficient refractive index sensing surfaces. The experimental results reveal that the structure exhibits a sensitivity of around 11 000 nm/RIU and a figure of merit of up to 2.5. We also show that the sensing performance of the structure can be improved by increasing doping density.

  15. High and Stable Ionic Conductivity in 2D Nanofluidic Ion Channels between Boron Nitride Layers.

    Science.gov (United States)

    Qin, Si; Liu, Dan; Wang, Guang; Portehault, David; Garvey, Christopher J; Gogotsi, Yury; Lei, Weiwei; Chen, Ying

    2017-05-10

    Achieving a high rate of ionic transport through porous membranes and ionic channels is important in numerous applications ranging from energy storage to water desalination, but it still remains a challenge. Herein we show that ions can quickly pass through interlayer spaces in hydrated boron nitride (BN) membranes. Measurements of surface-charge governed ionic currents between BN nanosheets in a variety of salt solutions (KCl, NaCl and CaCl2) at low salt concentrations (<10-4 M) showed several orders of magnitude higher ionic conductivity compared to that of the bulk solution. Moreover, due to the outstanding chemical and thermal stability of BN, the ionic conduits remain fully functional at temperatures up to 90 °C. The BN conduits can operate in acidic and basic environments and do not degrade after immersing in solutions with extreme pH (pH ∼ 0 or 14) for 1 week. Those excellent properties make the BN ionic conduits attractive for applications in nanofluidic devices and membrane separation.

  16. High rate deposition of transparent conducting oxide thin films by vacuum arc plasma evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Minami, Tadatsugu; Ida, Satoshi; Miyata, Toshihiro

    2002-09-02

    Transparent conducting oxide (TCO) thin films have been deposited at a high rate above 370 nm/min by vacuum arc plasma evaporation (VAPE) using sintered oxide fragments as the source material. It was found that the deposition rate of TCO films was strongly dependent on the deposition pressure, whereas the obtained electrical properties were relatively independent of the pressure. Resistivities of 5.6x10{sup -4} and 2.3x10{sup -4} {omega}{center_dot}cm and an average transmittance above 80% (with substrate included) in the visible range were obtained in Ga-doped ZnO (GZO) thin films deposited at 100 and 350 deg. C, respectively. In addition, a resistivity as low as 1.4x10{sup -4} {omega}{center_dot}cm and an average transmittance above 80% were also obtained in indium-tin-oxide (ITO) films deposited at 300 deg. C. The deposited TCO films exhibited uniform distributions of resistivity and thickness on large area substrates.

  17. Enhanced p-type conduction of B-doped nanocrystalline diamond films by high temperature annealing

    Energy Technology Data Exchange (ETDEWEB)

    Gu, S. S.; Hu, X. J. [College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014 (China)

    2013-07-14

    We report the enhanced p-type conduction with Hall mobility of 53.3 cm{sup 2} V{sup -1} s{sup -1} in B-doped nanocrystalline diamond (NCD) films by 1000 Degree-Sign C annealing. High resolution transmission electronic microscopy, uv, and visible Raman spectroscopy measurements show that a part of amorphous carbon grain boundaries (GBs) transforms to diamond phase, which increases the opportunity of boron atoms located at the GBs to enter into the nano-diamond grains. This phase transition doping is confirmed by the secondary ion mass spectrum depth profile results that the concentration of B atoms in nano-diamond grains increases after 1000 Degree-Sign C annealing. It is also observed that 1000 Degree-Sign C annealing improves the lattice perfection, reduces the internal stress, decreases the amount of trans-polyacetylene, and increases the number or size of aromatic rings in the sp{sup 2}-bonded carbon cluster in B-doped NCD films. These give the contributions to improve the electrical properties of 1000 Degree-Sign C annealed B-doped NCD films.

  18. Simultaneous Conduction and Valence Band Quantization in Ultrashallow High-Density Doping Profiles in Semiconductors

    Science.gov (United States)

    Mazzola, F.; Wells, J. W.; Pakpour-Tabrizi, A. C.; Jackman, R. B.; Thiagarajan, B.; Hofmann, Ph.; Miwa, J. A.

    2018-01-01

    We demonstrate simultaneous quantization of conduction band (CB) and valence band (VB) states in silicon using ultrashallow, high-density, phosphorus doping profiles (so-called Si:P δ layers). We show that, in addition to the well-known quantization of CB states within the dopant plane, the confinement of VB-derived states between the subsurface P dopant layer and the Si surface gives rise to a simultaneous quantization of VB states in this narrow region. We also show that the VB quantization can be explained using a simple particle-in-a-box model, and that the number and energy separation of the quantized VB states depend on the depth of the P dopant layer beneath the Si surface. Since the quantized CB states do not show a strong dependence on the dopant depth (but rather on the dopant density), it is straightforward to exhibit control over the properties of the quantized CB and VB states independently of each other by choosing the dopant density and depth accordingly, thus offering new possibilities for engineering quantum matter.

  19. High glucose attenuates shear-induced changes in endothelial hydraulic conductivity by degrading the glycocalyx.

    Directory of Open Access Journals (Sweden)

    Sandra V Lopez-Quintero

    Full Text Available Diabetes mellitus is a risk factor for cardiovascular disease; however, the mechanisms through which diabetes impairs homeostasis of the vasculature have not been completely elucidated. The endothelium interacts with circulating blood through the surface glycocalyx layer, which serves as a mechanosensor/transducer of fluid shear forces leading to biomolecular responses. Atherosclerosis localizes typically in regions of low or disturbed shear stress, but in diabetics, the distribution is more diffuse, suggesting that there is a fundamental difference in the way cells sense shear forces. In the present study, we examined the effect of hyperglycemia on mechanotranduction in bovine aortic endothelial cells (BAEC. After six days in high glucose media, we observed a decrease in heparan sulfate content coincident with a significant attenuation of the shear-induced hydraulic conductivity response, lower activation of eNOS after exposure to shear, and reduced cell alignment with shear stress. These studies are consistent with a diabetes-induced change to the glycocalyx altering endothelial response to shear stress that could affect the distribution of atherosclerotic plaques.

  20. Laser-patterned functionalized CVD-graphene as highly transparent conductive electrodes for polymer solar cells.

    Science.gov (United States)

    La Notte, Luca; Villari, Enrica; Palma, Alessandro Lorenzo; Sacchetti, Alberto; Michela Giangregorio, Maria; Bruno, Giovanni; Di Carlo, Aldo; Bianco, Giuseppe Valerio; Reale, Andrea

    2017-01-07

    A five-layer (5L) graphene on a glass substrate has been demonstrated as a transparent conductive electrode to replace indium tin oxide (ITO) in organic photovoltaic devices. The required low sheet resistance, while maintaining high transparency, and the need of a wettable surface are the main issues. To overcome these, two strategies have been applied: (i) the p-doping of the multilayer graphene, thus reaching 25 Ω□-1 or (ii) the O2-plasma oxidation of the last layer of the 5L graphene that results in a contact angle of 58° and a sheet resistance of 134 Ω□-1. A Nd:YVO4 laser patterning has been implemented to realize the desired layout of graphene through an easy and scalable way. Inverted Polymer Solar Cells (PSCs) have been fabricated onto the patterned and modified graphene. The use of PEDOT:PSS has facilitated the deposition of the electron transport layer and a non-chlorinated solvent (ortho-xylene) has been used in the processing of the active layer. It has been found that the two distinct functionalization strategies of graphene have beneficial effects on the overall performance of the devices, leading to an efficiency of 4.2%. Notably, this performance has been achieved with an active area of 10 mm2, the largest area reported in the literature for graphene-based inverted PSCs.

  1. Highly Elastic, Transparent, and Conductive 3D-Printed Ionic Composite Hydrogels

    KAUST Repository

    Odent, Jérémy

    2017-07-17

    Despite extensive progress to engineer hydrogels for a broad range of technologies, practical applications have remained elusive due to their (until recently) poor mechanical properties and lack of fabrication approaches, which constrain active structures to simple geometries. This study demonstrates a family of ionic composite hydrogels with excellent mechanical properties that can be rapidly 3D-printed at high resolution using commercial stereolithography technology. The new material design leverages the dynamic and reversible nature of ionic interactions present in the system with the reinforcement ability of nanoparticles. The composite hydrogels combine within a single platform tunable stiffness, toughness, extensibility, and resiliency behavior not reported previously in other engineered hydrogels. In addition to their excellent mechanical performance, the ionic composites exhibit fast gelling under near-UV exposure, remarkable conductivity, and fast osmotically driven actuation. The design of such ionic composites, which combine a range of tunable properties and can be readily 3D-printed into complex architectures, provides opportunities for a variety of practical applications such as artificial tissue, soft actuators, compliant conductors, and sensors for soft robotics.

  2. Depletion of parallel conducting layers in high mobility In0.53Ga0.47As/In0.52Al0.48As modulation doped field effect transistors

    Science.gov (United States)

    Skuras, E.; Gavalas, A.; Spathara, D.; Makris, Th.; Anagnostopoulos, D.; Stanley, C. R.; Long, A. R.

    2013-12-01

    Self-consistent calculations for solving the Poisson and Schrödinger equations were performed in order to study parallel conduction in the In0.52Al0.48As barrier layer in In0.53Ga0.47As/In0.52Al0.48As Modulation Doped Field Effect Transistors. It is shown that the parallel conducting layer occupied sub-bands can be entirely depleted by wet chemical etching of the upper part of the un-doped In0.52Al0.48As Schottky layer without affecting the total carrier concentration at the In0.53Ga0.47As quantum well.

  3. Depletion of parallel conducting layers in high mobility In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As modulation doped field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Skuras, E., E-mail: eskuras@cc.uoi.gr; Gavalas, A., E-mail: eskuras@cc.uoi.gr; Spathara, D., E-mail: eskuras@cc.uoi.gr; Makris, Th., E-mail: eskuras@cc.uoi.gr; Anagnostopoulos, D., E-mail: eskuras@cc.uoi.gr [Department of Material, Engineering, University of Ioannina, Ioannina 45110 (Greece); Stanley, C. R. [School of Engineering, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Long, A. R. [School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2013-12-04

    Self-consistent calculations for solving the Poisson and Schrödinger equations were performed in order to study parallel conduction in the In{sub 0.52}Al{sub 0.48}As barrier layer in In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As Modulation Doped Field Effect Transistors. It is shown that the parallel conducting layer occupied sub-bands can be entirely depleted by wet chemical etching of the upper part of the un-doped In{sub 0.52}Al{sub 0.48}As Schottky layer without affecting the total carrier concentration at the In{sub 0.53}Ga{sub 0.47}As quantum well.

  4. Defect-induced magnetism in undoped and Mn-doped wide band gap zinc oxide grown by aerosol spray pyrolysis

    Science.gov (United States)

    Motaung, D. E.; Kortidis, I.; Papadaki, D.; Nkosi, S. S.; Mhlongo, G. H.; Wesley-Smith, J.; Malgas, G. F.; Mwakikunga, B. W.; Coetsee, E.; Swart, H. C.; Kiriakidis, G.; Ray, S. S.

    2014-08-01

    We present a systemic study on the structural, optical and magnetic properties of the un-doped and Mn doped ZnO thin films grown by aerosol spray pyrolysis at different deposition times. XRD profiling has shown that the structures of the prepared products are wurtzite without any evidence of second phases. Surface morphology analysis revealed that incorporation of Mn in the ZnO matrix results in the formation of "doughnut-like" structures while the corresponding un-doped ZnO showed permeable structures only at long deposition time. Optical results demonstrated that Mn-doped ZnO nanostructures exhibited both the characteristic orange Mn2+ ion-related emission at 595 nm and a shoulder around 667 nm, denoting that the Mn ions have successfully occupied lattice positions of Zn ions. The chemical composition and charge states of the Mn ions in the doped ZnO nanostructures analysed by the EDX and XPS, also confirmed that Mn2+ ions were successfully incorporated onto zinc sites in the ZnO host crystal. With the combination of defect analysis based on PL and XPS, the effect of defects on the nature and origin of ferromagnetism through EPR was investigated. These findings suggested that zinc and oxygen defects, especially zinc interstitials and singly ionized oxygen vacancies, play a crucial role in mediating ferromagnetism in the undoped ZnO.

  5. Structural, electrical and magnetic behaviour of undoped and nickel doped nanocrystalline bismuth ferrite by solution combustion route

    Directory of Open Access Journals (Sweden)

    Kakali Sarkar

    2015-03-01

    Full Text Available Multiferroic bismuth ferrite (BFO and Ni-doped bismuth ferrites, with perovskite structure, were synthesized by chemical route at the temperatures ranging from 500 to 600 °C in controlled atmosphere. The structural phase analysis of materials was identified by XRD and crystallite size was calculated from the half width measurement of the well defined major XRD diffraction peak. Average crystallite size was calculated by applying Scherrer’s formula and found to have values in the range from 14 to 35 nm. FESEM was used to evaluate the morphology and structural formation of nanocrystallite grains, while EDX confirmed elemental composition including the presence of dopant in the matrix. Dielectric properties and effect of electric field on polarization behaviour were studied for both undoped and Ni-doped BFO. Doping shows a clear change in ferroelectric behaviour. Antiferromagnetic nature of bulk bismuth ferrite transforms to superparamagnetic strong ferroelectric nature for both undoped and nickel doped nanocrystalline bismuth ferrite due to its close dimension of crystallite size with magnetic domains leading to break-down of frustrated spin cycloidal moment. The superparamagnetism behaviour is more pronounced for the nickel doped BFO though magnetic saturation is slightly higher for the undoped nanocrystalline bismuth ferrite.

  6. Modification of the Poly(bisdodecylquaterthiophene) Structure for High and Predominantly Nonionic Conductivity with Matched Dopants.

    Science.gov (United States)

    Li, Hui; DeCoster, Mallory E; Ireland, Robert M; Song, Jian; Hopkins, Patrick E; Katz, Howard E

    2017-08-16

    Four p-type polymers were synthesized by modifying poly(bisdodecylquaterthiophene) (PQT12) to increase oxidizability by p-dopants. A sulfur atom is inserted between the thiophene rings and dodecyl chains, and/or 3,4-ethylenedioxy groups are appended to thiophene rings of PQT12. Doped with NOBF4, PQTS12 (with sulfur in side chains) shows a conductivity of 350 S cm-1, the highest reported nonionic conductivity among films made from dopant-polymer solutions. Doped with tetrafluorotetracyanoquinodimethane (F4TCNQ), PDTDE12 (with 3,4-ethylenedioxy groups on thiophene rings) shows a conductivity of 140 S cm-1. The converse combinations of polymer and dopant and formulations using a polymer with both the sulfur and ethylenedioxy modifications showed lower conductivities. The conductivities are stable in air without extrinsic ion contributions associated with PEDOT:PSS that cannot support sustained current or thermoelectric voltage. Efficient charge transfer, tighter π-π stacking, and strong intermolecular coupling are responsible for the conductivity. Values of nontransient Seebeck coefficient and conductivity agree with empirical modeling for materials with these levels of pure hole conductivity; the power factor compares favorably with prior p-type polymers made by the alternative process of immersion of polymer films into dopant solutions. Models and conductivities point to significant mobility increases induced by dopants on the order of 1-5 cm2 V-1 s-1, supported by field-effect transistor studies of slightly doped samples. The thermal conductivities were in the range of 0.2-0.5 W m-1 K-1, typical for conductive polymers. The results point to further enhancements that could be obtained by increasing doped polymer mobilities.

  7. Ultrabroadband terahertz conductivity of highly doped ZnO and ITO

    DEFF Research Database (Denmark)

    Wang, Tianwu; Zalkovskij, Maksim; Iwaszczuk, Krzysztof

    2015-01-01

    The broadband complex conductivities of transparent conducting oxides (TCO), namely aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by terahertz time domain spectroscopy (THz-TDS) in the frequency range from 0.5 to 18 THz using a...

  8. On the Conductive Loss of High-Q Frequency Reconfigurable Antennas for LTE Frequencies

    DEFF Research Database (Denmark)

    Barrio, Samantha Caporal Del

    2018-01-01

    , the soldering tin and the conductivity of the antenna material. It shows that conductive loss from the non-perfect electric conductor becomes the main source of loss for certain Q values. This loss is intrinsic to the antenna manufacturing and cannot be mitigated even with the best conductor, i.e. silver...

  9. Preparation and characterization of highly electrically and thermally conductive polymeric nanocomposites

    OpenAIRE

    I. Tavman; V. Çeçen; Özdemir, I.; A. Turgut; I. Krupa; Omastova, M.; Novak, I

    2009-01-01

    Purpose: The conducting polymers and polymeric composites have attracted considerable attention in recent years because of their potential applications in advanced technologies, for example, in antistatic coatings, electromagnetic shielding.Design/methodology/approach: In this study the conductive fillers were expanded graphite (EG) and untreated graphite (UG), the base material was ethylene- vinyl acetate copolymer (EVA). Nanocomposites containi...

  10. The effect of low-temperature conditions on the electrochemical polymerization of polypyrrole films with high density, high electrical conductivity and high stability

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, C.O.; Sung, H.K.; Kim, J.H.; Barsoukov, E.; Kim, J.H.; Lee, H. [Korea Kumho Petrochem. Co. Ltd., Yuseong, Taejeon (Korea, Republic of). Kumho Chem. Labs.

    1999-02-26

    High-quality polypyrrole-hexafluorophosphate (PPy-PF{sub 6}) films with high density ({proportional_to}1.4 g/cm{sup 3}), high conductivity (>300 S/cm for unstretched film) and high electrochemical stability are obtained reproducibly by galvanostatic polymerization at low-temperature conditions. The optimal polymerization current density of J{sub p}=0.02-0.05 mA/cm{sup 2} was obtained at the polymerization temperature of T{sub p}=-40 C. The surface morphology of the film sensitively varies depending upon the properties of electrode and its surface conditions. The transport measurements characterize the high-density PPy-PF{sub 6} film as a disordered metal close to the boundary of disorder induced metal-insulator (M-I) transition. The X-ray diffraction measurements suggest that partially crystalline structure of PPy-PF{sub 6} film is related to the transport properties. The uniaxial stretching induces an increase of the conductivity up to {proportional_to}930 S/cm in a direction parallel to stretching as well as the anisotropy of conductivity. The comparative studies of thermogravimetric analysis (TGA), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) for PPy-PF{sub 6} films prepared at room-temperature and low-temperature conditions show that the latter exhibit better thermal stability as well as electrochemical stability under long oxidative polarization. (orig.) 33 refs.

  11. Highly conductive composites for fuel cell flow field plates and bipolar plates

    Science.gov (United States)

    Jang, Bor Z; Zhamu, Aruna; Song, Lulu

    2014-10-21

    This invention provides a fuel cell flow field plate or bipolar plate having flow channels on faces of the plate, comprising an electrically conductive polymer composite. The composite is composed of (A) at least 50% by weight of a conductive filler, comprising at least 5% by weight reinforcement fibers, expanded graphite platelets, graphitic nano-fibers, and/or carbon nano-tubes; (B) polymer matrix material at 1 to 49.9% by weight; and (C) a polymer binder at 0.1 to 10% by weight; wherein the sum of the conductive filler weight %, polymer matrix weight % and polymer binder weight % equals 100% and the bulk electrical conductivity of the flow field or bipolar plate is at least 100 S/cm. The invention also provides a continuous process for cost-effective mass production of the conductive composite-based flow field or bipolar plate.

  12. Study on synthesis of ultrafine Cu-Ag core-shell powders with high electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Peng Yuhsien [Department of Environmental Engineering, Dayeh University, 168 University Rd., Dacun, Changhua 515, Taiwan (China); Department of Research and Development, Oriental Happy Enterprise Co., No. 27, Xin' ai Rd., South Dist., Tainan 702, Taiwan (China); Center for General Education, Kun Shan University, No. 949, Dawan Rd., Yongkang Dist., Tainan 710, Taiwan (China); Yang Chihhao [Department of Research and Development, Oriental Happy Enterprise Co., No. 27, Xin' ai Rd., South Dist., Tainan 702, Taiwan (China); Chen Kuanting, E-mail: pengyuhsien@hotmail.com [Department of Resources Engineering, National Cheng Kung University, No.1, Da-Hsueh Road, Tainan 701, Taiwan (China); Popuri, Srinivasa R. [Department of Biological and Chemical Sciences, The University of the West Indies, Cave Hill Campus 11000 (Barbados); Lee, Ching-Hwa [Department of Environmental Engineering, Dayeh University, 168 University Rd., Dacun, Changhua 515, Taiwan (China); Tang, Bo-Shin [Department of Research and Development, Oriental Happy Enterprise Co., No. 27, Xin' ai Rd., South Dist., Tainan 702, Taiwan (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer This synthesis method is relatively facile, novel and eco-friendly. Black-Right-Pointing-Pointer Toxic agents were not used for chelating agent, reductant or dispersant in our method. Black-Right-Pointing-Pointer The reaction can under room temperature for energy saving purpose. Black-Right-Pointing-Pointer Cu-Ag core-shell powders with homogeneous cover-silver layer. Black-Right-Pointing-Pointer The resistivity of Cu-Ag core-shell powders has the same value as the pure silver. - Abstract: Cu-Ag composite powders with high electrical conductivity were synthesized by electroless plating of silver sulfate, copper powders with eco-friendly sodium citrate as reducing agent, dispersant and chelating agent in an aqueous system. The influences of sodium citrate/Ag ratio on Ag coatings of Cu powders were investigated. Ag was formed a dense coating on the surface of Cu powders at a molar ratio of sodium citrate/Ag = 0.07/1. SEM showed an uniformity of Ag coatings on Cu powders. SEM-EDX also revealed that Cu cores were covered by Ag shells on the whole. The surface composition analysis by XPS indicated that without Cu or Ag atoms in the surface were oxidized. The resistivity measurements of Cu-Ag paste shows that they have closer resistivity as the pure silver paste's after 250 Degree-Sign C for 30 min heat-treatment (2.55 Multiplication-Sign 10{sup -4} {Omega} cm) and 350 Degree-Sign C for 30 min heat-treatment (1.425 Multiplication-Sign 10{sup -4} {Omega} cm).

  13. Conductive two-dimensional titanium carbide `clay' with high volumetric capacitance

    Science.gov (United States)

    Ghidiu, Michael; Lukatskaya, Maria R.; Zhao, Meng-Qiang; Gogotsi, Yury; Barsoum, Michel W.

    2014-12-01

    Safe and powerful energy storage devices are becoming increasingly important. Charging times of seconds to minutes, with power densities exceeding those of batteries, can in principle be provided by electrochemical capacitors--in particular, pseudocapacitors. Recent research has focused mainly on improving the gravimetric performance of the electrodes of such systems, but for portable electronics and vehicles volume is at a premium. The best volumetric capacitances of carbon-based electrodes are around 300 farads per cubic centimetre; hydrated ruthenium oxide can reach capacitances of 1,000 to 1,500 farads per cubic centimetre with great cyclability, but only in thin films. Recently, electrodes made of two-dimensional titanium carbide (Ti3C2, a member of the `MXene' family), produced by etching aluminium from titanium aluminium carbide (Ti3AlC2, a `MAX' phase) in concentrated hydrofluoric acid, have been shown to have volumetric capacitances of over 300 farads per cubic centimetre. Here we report a method of producing this material using a solution of lithium fluoride and hydrochloric acid. The resulting hydrophilic material swells in volume when hydrated, and can be shaped like clay and dried into a highly conductive solid or rolled into films tens of micrometres thick. Additive-free films of this titanium carbide `clay' have volumetric capacitances of up to 900 farads per cubic centimetre, with excellent cyclability and rate performances. This capacitance is almost twice that of our previous report, and our synthetic method also offers a much faster route to film production as well as the avoidance of handling hazardous concentrated hydrofluoric acid.

  14. Thickness dependence of structural, electrical and optical behaviour of undoped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bouderbala, M.; Hamzaoui, S. [Laboratoire de Microscopie Electronique et des Sciences des Materiaux, Departement de Physique, USTO, B.P. 1505, El-Mnaouer, 31000 Oran (Algeria); Amrani, B. [Department of Physics, Centre Universitaire de Mascara, Mascara 29000 (Algeria)], E-mail: abouhalouane@yahoo.fr; Reshak, Ali H. [Institute of Physical Biology-South Bohemia University, Institute of System Biology and Ecology-Academy of Sciences, Nove Hrady 37333 (Czech Republic); Adnane, M.; Sahraoui, T.; Zerdali, M. [Laboratoire de Microscopie Electronique et des Sciences des Materiaux, Departement de Physique, USTO, B.P. 1505, El-Mnaouer, 31000 Oran (Algeria)

    2008-09-01

    Undoped ZnO thin films of different thicknesses were prepared by r.f. sputtering in order to study the thickness effect upon their structural, morphological, electrical and optical properties. The results suggest that the film thickness seems to have no clear effect upon the orientation of the grains growth. Indeed, the analysis with X-ray diffraction show that the grains were always oriented according to the c(0 0 2)-axis perpendicular to substrate surface whatever the thickness is. However, the grain size was influenced enough by this parameter. An increase in the grain size versus the thickness was noted. For the electrical properties, measurements revealed behaviour very dependent upon thickness. The resistivity decreased from 25 to 1.5x10{sup -3} {omega} cm and the mobility increased from 2 to 37 cm{sup 2} V{sup -1} s{sup -1} when the thickness increased from 70 to 1800 nm while the carrier concentration seems to be less affected by the film thickness and varied slightly remaining around 10{sup 20} cm{sup -3}. Nevertheless, a tendency to a decrease was noticed. This behaviour in electrical properties was explained by the crystallinity and the grain size evolution. The optical measurements showed that all the samples have a strong transmission higher than 80% in the visible range. A slight shift of the absorption edge towards the large wavelengths was observed as the thickness increased. This result shows that the band gap is slightly decreases from 3.37 to 3.32 eV with the film thickness vary from 0.32 to 0.88 {mu}m.

  15. The Role of Alloy Composition and T7 Heat Treatment in Enhancing Thermal Conductivity of Aluminum High Pressure Diecastings

    Science.gov (United States)

    Lumley, Roger N.; Deeva, Natalia; Larsen, Robert; Gembarovic, Jozef; Freeman, Joe

    2013-02-01

    The thermal conductivity of some common and experimental high pressure diecasting (HPDC) Al-Si-Cu alloys is evaluated. It is shown that the thermal conductivity of some compositions may be increased by more than 60 pct by utilizing T7 heat treatments. This may have substantial performance and cost benefits for applications where thermal management is a key design parameter.

  16. Undoped and boron doped diamond nanoparticles as platinum and platinum-ruthenium catalyst support for direct methanol fuel cell application

    Science.gov (United States)

    La Torre Riveros, Lyda

    Nanoparticular diamond is a promising material that can be used as a robust and chemically stable catalytic support. It has been studied and characterized physically and electrochemically, in its powder and thin film forms. This thesis work intends to demonstrate that undoped diamond nanoparticles (DNPs) and boron-doped diamond nanoparticles (BDDNPs) can be used as an electrode and a catalytic support material for platinum and ruthenium catalysts. The electrochemical properties of diamond nanoparticle electrodes, fabricated using the ink paste method, were investigated. As an initial step, we carried out chemical purification of commercially available undoped DNPs by refluxing in aqueous HNO3 as well as of BDDNPs which were doped through a collaborative work with the University of Missouri. The purified material was characterized by spectroscopic and surface science techniques. The reversibility of reactions such as ferricyanide/ferrocyanide (Fe(CN) 63-/Fe(CN)64-) and hexaamineruthenium (III) chloride complexes as redox probes were evaluated by cyclic voltammetry at the undoped DNPs and BDDNPs surface. These redox probes showed limited peak currents and presented linear relationships between current (i) and the square root of the potential scan rate (v1/2). However, compared to conventional electrodes, the peak currents were smaller. BDDNPs show an improvement in charge transfer currents when compared to undoped DNPs. Platinum and ruthenium nanoparticles were chemically deposited on undoped DNPs and BDDNPs through the use of the excess of a mild reducing agent such NaBH4. In order to improve the nanoparticle dispersion sodium dodecyl benzene sulfonate (SDBS), a surfactant agent, was used. Percentages of platinum and ruthenium metals were varied as well as the stoichiometric amount of the reducing agent to determine adequate parameters for optimum performance in methanol oxidation. Both before and after the reducing process the samples were characterized by scanning

  17. Highly efficient conductivity modulation of cinnamate-based light-responsive ionic liquids in aqueous solutions.

    Science.gov (United States)

    Yang, Jie; Wang, Huiyong; Wang, Jianji; Zhang, Yue; Guo, Zhongjia

    2014-12-11

    A new class of cinnamate-based light-responsive ionic liquids was synthesized and characterized, and these ionic liquids with longer alkyl chains showed a remarkable increase in ionic conductivity under UV light irradiation in aqueous solutions.

  18. Physical conditions for conducting radiobiological experiments in beams of accelerated particles with high linear energy transfer

    Science.gov (United States)

    Kudryashov, Y. I.; Marennyy, A. M.; Popov, V. I.; Aykhorn, K.; Ertsgreber, G.

    1974-01-01

    The design and construction of an accelerator to conduct radiobiological experiments is reported that uses aluminum filters to control the accelerated ion beam while preserving its stability, and a vacuum chamber to conduct the ion beam with the help of a collector through a lavsan exit port to the target. Depth distribution of the absorbed dose from a monodirectional ion beam is practically completely represented by the change in the energy spectrum of the biological object.

  19. A flexible metal-organic framework with a high density of sulfonic acid sites for proton conduction

    Science.gov (United States)

    Yang, Fan; Xu, Gang; Dou, Yibo; Wang, Bin; Zhang, Heng; Wu, Hui; Zhou, Wei; Li, Jian-Rong; Chen, Banglin

    2017-11-01

    The design of stable electrolyte materials with high proton conductivity for use in proton exchange membrane fuel cells remains a challenge. Most of the materials explored have good conductivity at high relative humidity (RH), but significantly decreased conductivity at reduced RH. Here we report a chemically stable and structurally flexible metal-organic framework (MOF), BUT-8(Cr)A, possessing a three-dimensional framework structure with one-dimensional channels, in which high-density sulfonic acid (-SO3H) sites arrange on channel surfaces for proton conduction. We propose that its flexible nature, together with its -SO3H sites, could allow BUT-8(Cr)A to self-adapt its framework under different humid environments to ensure smooth proton conduction pathways mediated by water molecules. Relative to other MOFs, BUT-8(Cr)A not only has a high proton conductivity of 1.27 × 10-1 S cm-1 at 100% RH and 80 °C but also maintains moderately high proton conductivity at a wide range of RH and temperature.

  20. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    NARCIS (Netherlands)

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to

  1. Effects of CO2 on stomatal conductance: do stomata open at very high CO2 concentrations?

    Science.gov (United States)

    Wheeler, R. M.; Mackowiak, C. L.; Yorio, N. C.; Sager, J. C.

    1999-01-01

    Potato and wheat plants were grown for 50 d at 400, 1000 and 10000 micromoles mol-1 carbon dioxide (CO2). and sweetpotato and soybean were grown at 1000 micromoles mol-1 CO2 in controlled environment chambers to study stomatal conductance and plant water use. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 300 micromoles m-2 s-1 PAR. Mid-day stomatal conductances for potato were greatest at 400 and 10000 micromoles mol-1 and least at 1000 micromoles mol-1 CO2. Mid-day conductances for wheat were greatest at 400 micromoles mol-1 and least at 1000 and 10000 micromoles mol-1 CO2. Mid-dark period conductances for potato were significantly greater at 10000 micromoles mol-1 than at 400 or 1000 micromoles mol-1, whereas dark conductance for wheat was similar in all CO2 treatments. Temporarily changing the CO2 concentration from the native 1000 micromoles mol-1 to 400 micromoles mol-1 increased mid-day conductance for all species, while temporarily changing from 1000 to 10000 micromoles mol-1 also increased conductance for potato and sweetpotato. Temporarily changing the dark period CO2 from 1000 to 10000 micromoles mol-1 increased conductance for potato, soybean and sweetpotato. In all cases, the stomatal responses were reversible, i.e. conductances returned to original rates following temporary changes in CO2 concentration. Canopy water use for potato was greatest at 10000, intermediate at 400, and least at 1000 micromoles mol-1 CO2, whereas canopy water use for wheat was greatest at 400 and similar at 1000 and 10000 micromoles mol-1 CO2. Elevated CO2 treatments (i.e. 1000 and 10000 micromoles mol-1) resulted in increased plant biomass for both wheat and potato relative to 400 micromoles mol-1, and no injurious effects were apparent from the 10000 micromoles mol-1 treatment. Results indicate that super-elevated CO2 (i.e. 10000 micromoles mol-1) can increase stomatal conductance in some species, particularly during the dark period, resulting in

  2. Influence of La/W ratio on electrical conductivity of lanthanum tungstate with high La/W ratio

    Energy Technology Data Exchange (ETDEWEB)

    Kojo, Gen; Shono, Yohei [Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwa, Chiba 277-8563 (Japan); Ushiyama, Hiroshi [Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Oshima, Yoshito [Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwa, Chiba 277-8563 (Japan); Otomo, Junichiro, E-mail: otomo@k.u-tokyo.ac.jp [Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwa, Chiba 277-8563 (Japan)

    2017-04-15

    The proton-conducting properties of lanthanum tungstates (LWOs) with high La/W ratios were investigated using electrochemical measurements and quantum chemical calculations. Single phases of LWOs with high La/W ratios (6.3≤La/W≤6.7) were synthesized by high-temperature sintering at around 1700 °C. The electrical conductivity of LWO increased with increasing La/W ratio in the single-phase region. The LWO synthesized at the optimum sintering temperature and time, and with the optimum La/W ratio gave the maximum conductivity, i.e., 2.7×10{sup −3} S cm{sup −1} with La/W=6.7 at 500 °C. Density functional theory calculations, using the nudged elastic band method, were performed to investigate the proton diffusion barrier. The results suggest that the proton diffusion paths around La sites have the lowest proton diffusion barrier. These findings improve our understanding of LWO synthesis and the proton-conducting mechanism and provide a strategy for improving proton conduction in LWOs. - Graphical abstract: The LWOs with high La/W ratios were synthesized for the first time. The optimum La/W ratio gave the maximum conductivity with La/W=6.7 at 500 °C. The proton diffusion paths were also considered with density functional theory calculations. - Highlights: • The proton-conducting properties of lanthanum tungstates (LWOs) were investigated. • Single phase LWOs with high La/W ratios (6.3≤La/W≤6.7) were synthesized successfully. • LWOs with the high La/W ratios showed high proton conductivity. • The DFT calculation suggested the lowest proton diffusion barrier in the path around La sites.

  3. A Combination of Boron Nitride Nanotubes and Cellulose Nanofibers for the Preparation of a Nanocomposite with High Thermal Conductivity.

    Science.gov (United States)

    Zeng, Xiaoliang; Sun, Jiajia; Yao, Yimin; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2017-05-23

    With the current development of modern electronics toward miniaturization, high-degree integration and multifunctionalization, considerable heat is accumulated, which results in the thermal failure or even explosion of modern electronics. The thermal conductivity of materials has thus attracted much attention in modern electronics. Although polymer composites with enhanced thermal conductivity are expected to address this issue, achieving higher thermal conductivity (above 10 W m-1 K-1) at filler loadings below 50.0 wt % remains challenging. Here, we report a nanocomposite consisting of boron nitride nanotubes and cellulose nanofibers that exhibits high thermal conductivity (21.39 W m-1 K-1) at 25.0 wt % boron nitride nanotubes. Such high thermal conductivity is attributed to the high intrinsic thermal conductivity of boron nitride nanotubes and cellulose nanofibers, the one-dimensional structure of boron nitride nanotubes, and the reduced interfacial thermal resistance due to the strong interaction between the boron nitride nanotubes and cellulose nanofibers. Using the as-prepared nanocomposite as a flexible printed circuit board, we demonstrate its potential usefulness in electronic device-cooling applications. This thermally conductive nanocomposite has promising applications in thermal interface materials, printed circuit boards or organic substrates in electronics and could supplement conventional polymer-based materials.

  4. Inkjet printing of flexible high-performance carbon nanotube transparent conductive films by ``coffee ring effect''

    Science.gov (United States)

    Shimoni, Allon; Azoubel, Suzanna; Magdassi, Shlomo

    2014-09-01

    Transparent and flexible conductors are a major component in many modern optoelectronic devices, such as touch screens for smart phones, displays, and solar cells. Carbon nanotubes (CNTs) offer a good alternative to commonly used conductive materials, such as metal oxides (e.g. ITO) for flexible electronics. The production of transparent conductive patterns, and arrays composed of connected CNT ``coffee rings'' on a flexible substrate poly(ethylene terephthalate), has been reported. Direct patterning is achieved by inkjet printing of an aqueous dispersion of CNTs, which self-assemble at the rim of evaporating droplets. After post-printing treatment with hot nitric acid, the obtained TCFs are characterized by a sheet resistance of 156 Ω sq-1 and transparency of 81% (at 600 nm), which are the best reported values obtained by inkjet printing of conductive CNTs. This makes such films very promising as transparent conductors for various electronic devices, as demonstrated by using an electroluminescent device.

  5. Electron transport and defect structure in highly conducting reactively sputtered ultrathin tin oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Bansal, Shikha; Pandya, Dinesh K., E-mail: dkpandya@physics.iitd.ac.in; Kashyap, Subhash C. [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

    2014-02-24

    Electrical conduction behavior of ultrathin (5–110 nm) SnO{sub 2} films reactively sputtered at 150–400 °C substrate temperatures is presented. The surface roughness studies revealed that the films with lower thickness were smoother (≤0.6 nm). Stoichiometry/defect structure of the films obtained from X-ray photoelectron spectroscopy data and electron mobility are found to be dependent on film thickness and substrate temperature. The observed increase in conductivity of semi-metallic films with decrease in film thickness is attributed to changes in defect structure and surface roughness. Highest value of conductivity of about 715 Ω{sup −1} cm{sup −1} is obtained for 5 nm thick films deposited at 300 °C.

  6. Experimental Study on Electromagnetic Shielding Characteristics of Conductive O-rings at High Frequencies

    Science.gov (United States)

    Yamamoto, Shinnichiro; Hatakeyama, Kennichi; Yamada, Takeshi

    The O-rings have been usually applied to mechanically moving parts for sealing oil and air and preventing dust so far. In order to measure the electromagnetic shielding effectiveness of the conductive O-rings, we proposed a electromagnetic shielding evaluation setup for the O-ring. There are two ways to apply O-rings in narrow gaps, cylinder-fixing and plane-fixing. By the use of this setup, the electromagnetic shielding effectiveness of conductive O-rings can be evaluated from 10kHz to 1GHz for both fixing types. The reflection and transmission characteristics of this setup and measured results of electromagnetic shielding effects are described. Anisotropic conductivity of the ring material and an equivalent circuit of the O-rings are discussed.

  7. High-density carbon nanotube wet-laid buckypapers with enhanced strength and conductivity using a high-pressure homogenization process

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jun; Jang, Si Hoon; Park, No Hyung; Jeong, Won Young; Lim, Dae Young [Human and Culture Convergence Technology Group, Korea Institute of Industrial Technology (KITECH), Ansan (Korea, Republic of); Oh, Jun Young; Yang, Seung Jae [Dept. of Applied Organic Materials Engineering, Inha University, Incheon (Korea, Republic of)

    2017-04-15

    In this work, we prepared homogeneously dispersed carbon nanotubes in water using a high-pressure homogenizer, while high-density carbon nanotube buckypapers were prepared by wet-laid process. The strength and conductivity of the buckypaper were increased dramatically after the high-pressure homogenization because of the increased density and uniformity of the paper. In addition, the buckypapers containing various additives and treated with SOCl{sub 2} exhibited further increase of strength and conductivity resulting from the binding and the p-type doping effect. The buckypapers with high electrical conductivity exhibited superior electromagnetic interference shielding effectiveness that could be applied for structural shielding materials.

  8. Experimental study of electrical conduction across high-Tc superconductor-graphene interfaces

    Science.gov (United States)

    Perconte, David; Cuellar, Fabian; Martin, Marie-Blandine; Dlubak, Bruno; Piquemal-Banci, Maelis; Bernard, Rozenn; Trastoy, Juan; Moreau-Luchaire, Constance; Seneor, Pierre; Villegas, Javier; Kidambi, Piran; Robertson, John; Hofmann, Stephan

    Proximity-induced superconductivity presents unusual features in graphene (i.e. specular Andreev reflection) due to its particular electronic structure. It has been theoretically discussed that, if a d-wave superconductor is put contact with graphene, the latter will sustain d-wave superconductivity, and further unusual features (such as oscillatory behavior) should be observed in the superconductor-graphene junction conductance. Motivated by these prospects, we experimentally investigate YBCO-graphene junctions. We will show differential conductance measurements as a function of temperature, magnetic field, and graphene doping. The observed behavior will be discussed in the frame of the theory developed in. Work supported by Labex Nanosaclay.

  9. Aligned Graphene Oxide Nanofillers: An Approach to Prepare Highly Thermally Conductive and Electrically Insulative Transparent Polymer Composites

    Directory of Open Access Journals (Sweden)

    Genlian Lin

    2015-01-01

    Full Text Available Graphene oxide (GO/polyvinyl alcohol composites with extremely high in-plane thermal conductivities are prepared by a simple tape casting process using water as process solvent. The in-plane thermal conductivity of the composite can reach 17.61 W/mK at only 0.1 wt% GO loading, which is close to that of fully dense alumina. The excellent thermal conducting ability, the unique two-dimensional morphology, and the all-wet handling of the GO fillers as well as the high orientation of the fillers in the polymer matrix all contribute to the high thermal conductivities achieved. Meanwhile, the composites show good electrical insulation property and decent transparency.

  10. Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity

    Science.gov (United States)

    Wieg, A. T.; Kodera, Y.; Wang, Z.; Imai, T.; Dames, C.; Garay, J. E.

    2012-09-01

    Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb3+, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.

  11. Emotional Communication in Families of Conduct Problem Children with High versus Low Callous-Unemotional Traits

    Science.gov (United States)

    Pasalich, Dave S.; Dadds, Mark R.; Vincent, Lucy C.; Cooper, Francesca A.; Hawes, David J.; Brennan, John

    2012-01-01

    This study examined relationships between parent-child emotional communication and callous-unemotional (CU) traits and conduct problems. References to negative and positive emotions made by clinic-referred boys (3-9 years) and their parents were coded from direct observations of family interactions involving the discussion of shared emotional…

  12. Current Spreading Layer with High Transparency and Conductivity for near-ultraviolet light emitting diodes

    DEFF Research Database (Denmark)

    Lin, Li; Jensen, Flemming; Herstrøm, Berit

    Transparent conductive aluminum-doped zinc oxide (AZO) layer was deposited on GaN-based near-ultraviolet (NUV) light emitting epitaxial wafers as current spreading layer by a sputtering process. Efforts were made to improve the electrical properties of AZO in order to produce ohmic contact....

  13. Optimization routes for high electrical conductivity of polypyrrole nanotubes prepared in presence of methyl orange

    Czech Academy of Sciences Publication Activity Database

    Kopecký, D.; Varga, M.; Prokeš, J.; Vrňata, M.; Trchová, Miroslava; Kopecká, J.; Václavík, M.

    2017-01-01

    Roč. 230, August (2017), s. 89-96 ISSN 0379-6779 R&D Projects: GA ČR(CZ) GA16-02787S; GA ČR(CZ) GA17-04109S Institutional support: RVO:61389013 Keywords : polypyrrole * electrical conductivity * nanotube Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 2.435, year: 2016

  14. High proton conductivity in cyanide-bridged metal-organic frameworks: understanding the role of water

    NARCIS (Netherlands)

    Gao, Y.; Broersen, R.; Hageman, W.; Yan, N.; Mittelmeijer-Hazeleger, M.; Rothenberg, G.; Tanase, S.

    2015-01-01

    We investigate and discuss the proton conductivity properties of the cyanide-bridged metal–organic framework (MOF) [Nd(mpca)2Nd(H2O)6Mo(CN)8]·nH2O (where mpca is 5-methyl-2-pyrazinecarboxylate). This MOF is one of an exciting class of cyanide-bridged materials that can combine porosity with

  15. A highly conductive carbon-sulfur film with interconnected mesopores as an advanced cathode for lithium-sulfur batteries.

    Science.gov (United States)

    Liu, Mingkai; Liu, Yuqing; Yan, Yan; Wang, Fengsheng; Liu, Jiahui; Liu, Tianxi

    2017-08-10

    A highly conductive graphene sheet-mesoporous carbon (MC) sphere/active sulfur (GMC-S) film, with MC-sulfur spheres as "active islands" and graphene sheets as "trapping nets", exhibits good cycling stability (500 cycles, with a capacity retention of 85%) with a high specific capacity of 1322 mA h g-1 at 0.1C.

  16. High adhesion transparent conducting films using graphene oxide hybrid carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Da, Shi-Xun; Wang, Jie; Geng, Hong-Zhang, E-mail: genghz@tjpu.edu.cn; Jia, Song-Lin; Xu, Chun-Xia; Li, Lin-Ge; Shi, Pei-Pei; Li, Guangfen

    2017-01-15

    Graphical abstract: The GO hybrid CNTs to fabricate TCFs could dramatically enhance the conductivity, adhesion, flatness, and wettability of the films, all these improvements are advantageous for optoelectronic applications. - Highlights: • TCFs were fabricated using GO/CNT hybrid inks by a simple spray method. • Conductivity of TCFs was improved through the hybrid of GO/CNT, sheet resistance of TCFs was 146 Ω/sq at the transmittance of 86.0% when the ratio of GO/CNT got 1.5:1.0. • The flatness and wettability of TCFs were improved dramatically, which is advantageous for the solution-based processing of organic electronics for spraying and printing. • The adhesion of the TCFs increased dramatically with the raise of the ratio GO/CNT hybrid. - Abstract: Flexible transparent conducting films (TCFs) with carbon nanotubes (CNTs) have attracted more and more attention for their wide range of potential applications. While, there are still some problems to be solved on several aspects. In this study, a graphene oxide/carbon nanotube (GO/CNT) hybrid TCF was fabricated through the simple spray coating method. GO sheets were introduced to form new electron transporting channels. It was found that the best optoelectronic property films were fabricated when the ratio of GO/CNT is 1.5:1.0, which the sheet resistance of the film was found to be 146 Ω/sq at the transmittance of 86.0%. Due to the two-dimensional structure and the oxidation groups of GO sheets, flatness and wettability of the electrode surface was improved obviously. Adhesion factor of the TCFs was calculated by the change of transparent and sheet resistance after trial test, the addition of GO sheets enhanced the adhesion dramatically and the mechanism was analyzed. Improvements of conductivity, flatness, wettability and adhesion above are all advantageous for the solution-based processing of organic electronics for spraying and printing.

  17. A C++ Framework for Conducting High-Speed, Long-Term Particle Tracking Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kabel, A.C.; /SLAC

    2006-02-06

    For the purpose of conducting parallel, long-term tracking studies of storage rings such as the ones described in [3], [4], maximum execution speed is essential. We describe an approach involving metaprogramming techniques in C++ which results in execution speeds rivaling hand-optimized assembler code for a particular tracking lattice while retaining the generality and flexibility of an all-purpose tracking code.

  18. Determination of photo-catalytic activity of un-doped and Mn-doped TiO{sub 2} anatase powders on acetaldehyde under UV and visible light

    Energy Technology Data Exchange (ETDEWEB)

    Papadimitriou, Vassileios C., E-mail: bpapadim@chemistry.uoc.gr [Laboratory of Photochemistry and Kinetics, Department of Chemistry, University of Crete, 71003 Heraklion, Crete (Greece); Stefanopoulos, Vassileios G.; Romanias, Manolis N. [Laboratory of Photochemistry and Kinetics, Department of Chemistry, University of Crete, 71003 Heraklion, Crete (Greece); Papagiannakopoulos, Panos, E-mail: panosp@chemistry.uoc.gr [Laboratory of Photochemistry and Kinetics, Department of Chemistry, University of Crete, 71003 Heraklion, Crete (Greece); Sambani, Kyriaki; Tudose, Valentin; Kiriakidis, George [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, PO Box 1527,Vasilika Vouton, 71110 Heraklion, Crete (Greece)

    2011-12-01

    .1%) doping of TiO{sub 2} with Mn results in a significant increase of their photocatalytic activity in the visible range, compared to un-doped TiO{sub 2}. This elevated activity is lost at high doping levels (1-33%). Finally, the photocatalytic degradation mechanism of CH{sub 3}CHO on 0.1% Mn-TiO{sub 2} surfaces under visible irradiation leading to low CO{sub 2} yields is different than that under UV irradiation resulting to high CO{sub 2} yields.

  19. VOx effectively doping CVD-graphene for transparent conductive films

    Science.gov (United States)

    Ji, Qinghua; Shi, Liangjing; Zhang, Qinghong; Wang, Weiqi; Zheng, Huifeng; Zhang, Yuzhi; Liu, Yangqiao; Sun, Jing

    2016-11-01

    Chemical vapor deposition(CVD)-synthesized graphene is potentially an alternative for tin-doped indium oxide (ITO) transparent conductive films (TCFs), however its sheet resistance is still too high to meet many demands. Vanadium oxide has been widely applied as smart window materials, however, no study has been reported to use it as dopant to improve the conductivity of graphene TCFs. In this study, we firstly reported that VOx doping can effectively lower the sheet resistance of CVD-graphene films while keeping its good optical properties, whose transmittance is as high as 86-90%. The optimized VOx-doped graphene exhibits a sheet resistance as low as 176 Ω/□, which decreases by 56% compared to the undoped graphene films. The doping process is convenient, stable, economical and easy to operate. What is more, VOx can effectively increase the work function(WF) of the film, making it more appropriate for use in solar cells. The evolution of the VOx species annealed at different temperatures below 400 °C has been detailed studied for the first time, based on which the doping mechanism is proposed. The prepared VOx doped graphene is expected to be a promising candidate for transparent conductive film purposes.

  20. Stable aqueous based Cu nanoparticle ink for printing well-defined highly conductive features on a plastic substrate.

    Science.gov (United States)

    Jeong, Sunho; Song, Hae Chun; Lee, Won Woo; Lee, Sun Sook; Choi, Youngmin; Son, Wonil; Kim, Eui Duk; Paik, Choon Hoon; Oh, Seok Heon; Ryu, Beyong-Hwan

    2011-03-15

    With the aim of inkjet printing highly conductive and well-defined Cu features on plastic substrates, aqueous based Cu ink is prepared for the first time using water-soluble Cu nanoparticles with a very thin surface oxide layer. Owing to the specific properties, high surface tension and low boiling point, of water, the aqueous based Cu ink endows a variety of advantages over conventional Cu inks based on organic solvents in printing narrow conductive patterns without irregular morphologies. It is demonstrated how the design of aqueous based ink affects the basic properties of printed conductive features such as surface morphology, microstructure, conductivity, and line width. The long-term stability of aqueous based Cu ink against oxidation is analyzed through an X-ray photoelectron spectroscopy (XPS) based investigation on the evolution of the surface oxide layer in the aqueous based ink.

  1. Studies of deep level centers determining the diffusion length in epitaxial layers and crystals of undoped n-GaN

    Energy Technology Data Exchange (ETDEWEB)

    Lee, In-Hwan [School of Advanced Materials Engineering and Research Center of Advanced Materials Development, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Polyakov, A. Y.; Turutin, A. V.; Shemerov, I. V. [National University of Science and Technology MISiS, Leninskiy pr. 4, Moscow 119049 (Russian Federation); Smirnov, N. B. [National University of Science and Technology MISiS, Leninskiy pr. 4, Moscow 119049 (Russian Federation); Institute of Rare Metals, B. Tolmachevsky, 5, Moscow 119017 (Russian Federation); Yakimov, E. B. [National University of Science and Technology MISiS, Leninskiy pr. 4, Moscow 119049 (Russian Federation); Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Science, 6, Academician Ossipyan str., Chernogolovka, Moscow Region 142432 (Russian Federation); Tarelkin, S. A. [National University of Science and Technology MISiS, Leninskiy pr. 4, Moscow 119049 (Russian Federation); Technological Institute for Superhard and Novel Carbon Materials, 7 Centralnaya St., Troitsk, Moscow 142190 (Russian Federation); Pearton, S. J., E-mail: spear@mse.ufl.edu [University of Florida, Gainesville, Florida 32611 (United States)

    2016-05-28

    A wide variety of parameters were measured for undoped n-GaN grown by hydride vapor phase epitaxy and compared to n-GaN films grown by conventional and lateral overgrowth metalorganic chemical vapor deposition. The parameters included deep level electron and hole trap spectra, microcathodoluminescence, electron beam induced current, diffusion length, and electron capture cross section from the dependence of the low temperature persistent photocapacitance on forward bias injection pulse duration. The results show a prominent role of electron traps with levels near E{sub c}-0.56 eV in limiting the lifetime and diffusion length values in all these materials.

  2. Photosensitivity mechanism of undoped poly(methyl methacrylate) under UV radiation at 325 nm and its spatial resolution limit

    DEFF Research Database (Denmark)

    Sáez-Rodríguez, D.; Nielsen, Kristian; Bang, Ole

    2014-01-01

    In this Letter, we provide evidence suggesting that the main photosensitive mechanism of an undoped poly(methyl methacrylate)-based microstructured optical fiber under UV radiation at 325 nm is a competitive process of both photodegradation and polymerization. We found experimentally...... that increasing strain during photo-inscription leads to an increased photosensitivity, which is evidence of photodegradation. Likewise, refractive index change in the fiber was measured to be positive, which provides evidence for further polymerization of the material. Finally, we relate the data obtained...

  3. Light yield of an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin

    OpenAIRE

    Liu, Jing; Yamashita, Masaki; Soma, Arun Kumar

    2016-01-01

    A light yield of 20.4 $\\pm$ 0.8 photoelectrons/keV was achieved with an undoped CsI crystal coupled directly to a photomultiplier tube at 77 Kelvin. This is by far the largest yield in the world achieved with CsI crystals. An energy threshold that is several times lower than the current dark matter experiments utilizing CsI(Tl) crystals may be achievable using this technique. Together with novel CsI crystal purification methods, the technique may be used to improve the sensitivities of dark m...

  4. Effective-medium method, percolation theory and conductivity data applied to study polymorphic transformations in solids under high pressure

    CERN Document Server

    Daunov, M I; Arslanov, R C; Daunova, D M; Gabibov, S F

    2003-01-01

    An approximate model is proposed for calculating the relative volume phase fractions in the critical region of polymorphic transformations in solids. The threshold values of the effective conductivity and the corresponding pressure P sub c , at which an infinite domain of the high-conductivity phase is formed, are determined. It is proposed to define the pressure P sub c as the phase transition pressure.

  5. Densification-induced conductivity percolation in high-porosity pharmaceutical microcrystalline cellulose compacts

    Science.gov (United States)

    Strømme, M.; Niklasson, G. A.; Ek, R.

    2003-01-01

    The percolation theory is established as a useful tool in the field of pharmaceutical materials science. It is shown that percolation theory, developed for analyzing insulator-conductor transitions, can be applied to describe imperfect dc conduction in pharmaceutical microcrystalline cellulose during densification. The system, in fact, exactly reproduces the values of the percolation threshold and exponent estimated for a three-dimensional random continuum. Our data clearly show a crossover from a power-law percolation theory region to a linear effective medium theory region at a cellulose porosity of ˜0.7.

  6. Preparation and Property Study of Graphene Oxide Reinforced Epoxy Resin Insulation Nanocomposites with High Heat Conductivity

    Science.gov (United States)

    Shan, Xinran; Liu, Yongchang; Wu, Zhixiong; Liu, Huiming; Zhang, Zhong; Huang, Rongjin; Huang, Chuanjun; Liu, Zheng; Li, Laifeng

    2017-02-01

    In this paper, graphene oxide reinforced epoxy resin nanocomposites were successfully prepared. Compared with unmodified epoxy resin, the heat conductivity of the graphene oxide reinforced epoxy resin nanocomposites had been improved while keeping the insulation performance. The tensile strength was investigated at both room temperature (300 K) and liquid nitrogen temperature (77 K). And the fracture surfaces were examined by scanning electron microscopy (SEM). Results showed that the materials had excellent mechanical properties, which could be advantages for the applications as insulating layer in low temperature superconducting magnets.

  7. Microwave metamaterials made by fused deposition 3D printing of a highly conductive copper-based filament

    Science.gov (United States)

    Xie, Yangbo; Ye, Shengrong; Reyes, Christopher; Sithikong, Pariya; Popa, Bogdan-Ioan; Wiley, Benjamin J.; Cummer, Steven A.

    2017-05-01

    This work reports a method for fabricating three-dimensional microwave metamaterials by fused deposition modeling 3D printing of a highly conductive polymer composite filament. The conductivity of such a filament is shown to be nearly equivalent to that of a perfect conductor for microwave metamaterial applications. The expanded degrees-of-freedom made available by 3D metamaterial designs are demonstrated by designing, fabricating, and testing a 3D-printed unit cell with a broadband permittivity as high as 14.4. The measured and simulated S-parameters agree well with a mean squared error smaller than 0.1. The presented method not only allows reliable and convenient fabrication of microwave metamaterials with high conductivity but also opens the door to exploiting the third dimension of the unit cell design space to achieve enhanced electromagnetic properties.

  8. Conducted Interference Immunity Characteristics to High-speed Power Line Communication System

    Science.gov (United States)

    Tokuda, Masamitsu; Hosoya, Satoshi; Yamagata, Toru; Matsuo, Takashi

    In this paper, we measured the immunity characteristics to the conducted interference wave, from the aspect of PHY rate (physical layer data rate) of PLC (Power Line Communication) system, and compared with simulation results by MATLAB/ Simulink. When the interference signal is impressed to the OFDM (Orthogonal Frequency Division Multiplexing) signal, the PHY rate decrease rapidly below C/I (Carrier / Interference) = 25dB and become nearly zero around C/I = -35dB, and so it turns out that the PLC System with OFDM signal has a good narrowband interference immunity characteristic. In addition, it is revealed that the PHY rate of PLC modem can be calculated by MATLAB/Simulink even when the narrowband interference signal is impressed through the power line. Furthermore, we examined the improving effect of the notch band for the immunity characteristics to the conducted interference wave. As a result, it is revealed that the PHY rate normalized by the maximum value increases by 15∼25% by inserting the notch when impressing the interference signal in the notch band and C/I is improved by 10∼15dB by inserting the notch.

  9. Controlling the conduction band offset for highly efficient ZnO nanorods based perovskite solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Juan; Shi, Jiangjian; Li, Dongmei; Luo, Yanhong; Meng, Qingbo, E-mail: qbmeng@iphy.ac.cn [Key Laboratory for Renewable Energy, Chinese Academy of Sciences, Beijing 100190 (China); Beijing Key Laboratory for New Energy Materials and Devices, Beijing 100190 (China); Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-08-17

    The mechanism of charge recombination at the interface of n-type electron transport layer (n-ETL) and perovskite absorber on the carrier properties in the perovskite solar cell is theoretically studied. By solving the one dimensional diffusion equation with different boundary conditions, it reveals that the interface charge recombination in the perovskite solar cell can be suppressed by adjusting the conduction band offset (ΔE{sub C}) at ZnO ETL/perovskite absorber interface, thus leading to improvements in cell performance. Furthermore, Mg doped ZnO nanorods ETL has been designed to control the energy band levels. By optimizing the doping amount of Mg, the conduction band minimum of the Mg doped ZnO ETL has been raised up by 0.29 eV and a positive ΔE{sub C} of about 0.1 eV is obtained. The photovoltage of the cell is thus significantly increased due to the relatively low charge recombination.

  10. High performance low cost interconnections for flip chip attachment with electrically conductive adhesive. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-05-01

    This final report is a compilation of final reports from each of the groups participating in the program. The main three groups involved in this effort are the Thomas J. Watson Research Center of IBM Corporation in Yorktown Heights, New York, Assembly Process Design of IBM Corporation in Endicott, New York, and SMT Laboratory of Universal Instruments Corporation in Binghamton, New York. The group at the research center focused on the conductive adhesive materials development and characterization. The group in process development focused on processing of the Polymer-Metal-Solvent Paste (PMSP) to form conductive adhesive bumps, formation of the Polymer-Metal Composite (PMC) on semiconductor devices and study of the bonding process to circuitized organic carriers, and the long term durability and reliability of joints formed using the process. The group at Universal Instruments focused on development of an equipment set and bonding parameters for the equipment to produce bond assembly tooling. Reports of each of these individual groups are presented here reviewing their technical efforts and achievements.

  11. Conducting π Columns of Highly Symmetric Coronene, The Smallest Fragment of Graphene.

    Science.gov (United States)

    Yoshida, Yukihiro; Isomura, Kazuhide; Kishida, Hideo; Kumagai, Yoshihide; Mizuno, Motohiro; Sakata, Masafumi; Koretsune, Takashi; Nakano, Yoshiaki; Yamochi, Hideki; Maesato, Mitsuhiko; Saito, Gunzi

    2016-04-18

    Coronene, which is the smallest D6h -symmetric polycyclic aromatic hydrocarbon, attracts particular attention as a basic component of electronic materials because it is the smallest fragment of graphene. However, carrier generation by physical methods, such as photo- or electric field-effect, has barely been studied, primarily because of the poor π-conduction pathway in pristine coronene solid. In this work we have developed unprecedented π-stacking columns of cationic coronene molecules by electrochemical hole-doping with polyoxometallate dianions. The face-to-face π-π interactions as well as the partially charged state lead to electrical conductivity at room temperature of up to 3 S cm(-1) , which is more than 10 orders of magnitude higher than that of pristine coronene solid. Additionally, the robust π-π interactions strongly suppress the in-plane rotation of the coronene molecules, which has allowed the first direct observation of the static Jahn-Teller distortion of cationic coronene molecules. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Characterization of the interface between highly conductive Ga:ZnO films and the silicon substrate

    Science.gov (United States)

    Gabás, M.; Ochoa-Martínez, E.; Navarrete-Astorga, E.; Landa-Cánovas, A. R.; Herrero, P.; Agulló-Rueda, F.; Palanco, S.; Martínez-Serrano, J. J.; Ramos-Barrado, J. R.

    2017-10-01

    Gallium-doped zinc oxide films are an interesting alternative for transparent conductive materials. To improve their performance, the interface between the grown layer and the substrate must be fully understood. Accordingly, ZnO and Ga:ZnO films have been deposited onto p-type doped Si (111) substrates by magnetron sputtering for 1, 2, 3 and 20 min and their interfaces characterized by transmission electron microscopy, photoelectron spectroscopy, spectroscopic ellipsometry and impedance spectroscopy. The combination of transmission electron microscopy techniques suggested a more complex interface chemistry in the Ga:ZnO/Si case, a point confirmed by x-ray photoelectron spectroscopy measurements on very thin films. While the ZnO/Si interface consists mostly of silicon oxides, zinc silicates and some Zn0, the Ga:ZnO/Si interface, besides these constituents, has a noticeable amount of Ga:ZnO and small quantities of Ga0. The band alignment deduced from the photoelectron spectroscopy measurements, together with the layers and Si band gap values, evidences a higher work function for the doped film and a smaller conduction band barrier for the Ga:ZnO/Si interface. Concerning the optical and electrical characteristics, spectroscopic ellipsometry revealed no significant differences between the two interfaces, while impedance spectroscopy measurements demonstrated that the Ga:ZnO/Si interface is less resistive than the ZnO/Si one.

  13. Silver nanowire-graphene hybrid transparent conductive electrodes for highly efficient inverted organic solar cells

    Science.gov (United States)

    Ye, Neng; Yan, Jielin; Xie, Shuang; Kong, Yuhan; Liang, Tao; Chen, Hongzheng; Xu, Mingsheng

    2017-07-01

    Silver nanowires (AgNWs) and graphene are both promising candidates as a transparent conductive electrode (TCE) to replace expensive and fragile indium tin oxide (ITO) TCE. A synergistically optimized performance is expected when the advantages of AgNWs and graphene are combined. In this paper, the AgNW-graphene hybrid electrode is constructed by depositing a graphene layer on top of the network of AgNWs. Compared with the pristine AgNWs electrode, the AgNW-graphene TCE exhibits reduced sheet resistance, lower surface roughness, excellent long-term stability, and corrosion resistance in corrosive liquids. The graphene layer covering the AgNWs provides additional conduction pathways for electron transport and collection by the electrode. Benefiting from these advantages of the hybrid electrodes, we achieve a power conversion efficiency of 8.12% of inverted organic solar cells using PTB7:PC71BM as the active layer, which is compared to that of the solar cells based on standard ITO TCE but about 10% higher than that based on AgNWs TCE.

  14. Experimental Evaluation and Comparison of Thermal Conductivity of High-Voltage Insulation Materials for Vacuum Electronic Devices

    Science.gov (United States)

    Suresh, C.; Srikrishna, P.

    2017-07-01

    Vacuum electronic devices operate with very high voltage differences between their sub-assemblies which are separated by very small distances. These devices also emit large amounts of heat that needs to be dissipated. Hence, there exists a requirement for high-voltage insulators with good thermal conductivity for voltage isolation and efficient heat dissipation. However, these voltage insulators are generally poor conductors of heat. In the present work, an effort has been made to obtain good high-voltage insulation materials with substantial improvement in their thermal conductivity. New mixtures of composites were formed by blending varying percentages (by volumes) of aluminum nitride powders with that of neat room-temperature vulcanizing (RTV) silicone elastomer compound. In this work, a thermal conductivity test setup has been devised for the quantification of the thermal conductivity of the insulators. The thermal conductivities and high-voltage isolation capabilities of various blended composites were quantified and were compared with that of neat RTV to evaluate the relative improvement.

  15. Composite Conducting Polymer Cathodes For High Energy Density Lithium-Ion Batteries Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future NASA planetary exploration missions require secondary (rechargeable) batteries that can operate at extreme temperatures (-60oC to 60oC) yet deliver high...

  16. Electrically stimulated high-frequency replicas of a resonant current in GaAs/AlAs resonant-tunneling double-barrier THz nanostructures

    Science.gov (United States)

    Aleksanyan, A. A.; Karuzskii, A. L.; Kazakov, I. P.; Mityagin, Yu. A.; Murzin, V. N.; Perestoronin, A. V.; Shmelev, S. S.; Tskhovrebov, A. M.

    2016-12-01

    The periodical-in-voltage features of the negative differential conductance (NDC) region in the current-voltage characteristics of a high-quality GaAs/AlAs terahertz resonant-tunneling diode have been detected. The found oscillations are considered taking account of the LO-phonon excitation stimulated by tunneling of electrons through the quantum active region in the resonance nanostructure where an undoped quantum well layer is sandwiched between two undoped barrier layers. Rearrangements in the I-V characteristics of the resonant-tunneling diode as a consequence of the topological transformation of a measurement circuit from the circuit with the series resistance Rs to the circuit with the shunt Rp have been experimentally studied and analyzed. The revealed substantial changes in the current-voltage characteristics of the resonant-tunneling diode are discussed schematically using Kirchhoff's voltage law.

  17. Solution-processed, undoped, deep-blue organic light-emitting diodes based on starburst oligofluorenes with a planar triphenylamine core.

    Science.gov (United States)

    Liu, Cui; Li, Yanhu; Zhang, Yingyue; Yang, Chuluo; Wu, Hongbin; Qin, Jingui; Cao, Yong

    2012-05-29

    A series of starburst oligomers (T1-T3) that contained a fully diarylmethene-bridged triphenylamine core and oligofluorene arms were designed and synthesized through Suzuki cross-coupling reactions. Their thermal, photophysical, and electrochemical properties were also investigated. These materials showed high glass transition, in the range of 123-129 °C, and good film-forming abilities. They displayed deep-blue emission both in solution and as thin films. Solution-processed devices based on these oligomers exhibited highly efficient deep-blue electroluminescence and the device performances were significantly enhanced with the extension of the oligofluorene arms. The double-layered device that contained T3 as an emitter showed a maximum current efficiency of 3.83 cd A(-1) and a maximum external quantum efficiency of 4.19% with CIE coordinates of (0.16, 0.09), which are among the highest values for undoped deep-blue OLEDs that are based on solution-processable starburst oligomers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Influence of the solar flares in March 2012 on the conductivity profile of the high-latitude lower ionosphere

    Directory of Open Access Journals (Sweden)

    Lebed O. M.

    2016-03-01

    Full Text Available The ionospheric D-layer affects the electromagnetic waves propagated in the Earth – ionosphere waveguide. It is known that the propagation velocity of atmospherics – electromagnetic pulses from lightning discharge depends on the conductivity profile of the lower ionosphere. In this paper the authors have considered the influence of solar flares in March 2012 on the propagation velocity of atmospherics and thus the state of the high-latitude lower ionosphere. The possibility to estimate the conductivity profiles of the daytime ionosphere under disturbed and undisturbed geomagnetic conditions using the measurements of the propagation velocity of atmospherics along the high-latitude path has been demonstrated

  19. Elastomeric thermal interface materials with high through-plane thermal conductivity from carbon fiber fillers vertically aligned by electrostatic flocking.

    Science.gov (United States)

    Uetani, Kojiro; Ata, Seisuke; Tomonoh, Shigeki; Yamada, Takeo; Yumura, Motoo; Hata, Kenji

    2014-09-03

    Electrostatic flocking is applied to create an array of aligned carbon fibers from which an elastomeric thermal interface material (TIM) can be fabricated with a high through-plane thermal conductivity of 23.3 W/mK. A high thermal conductivity can be achieved with a significantly low filler level (13.2 wt%). As a result, this material retains the intrinsic properties of the matrix, i.e., elastomeric behavior. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Highly efficient conductance control in a topological insulator based magnetoelectric transistor

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Xiaopeng; Li, Xi-Lai; Li, Xiaodong; Semenov, Yuriy G. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Kim, Ki Wook, E-mail: kwk@ncsu.edu [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-12-14

    The spin-momentum interlocked properties of the topological insulator (TI) surface states are exploited in a transistor-like structure for efficient conductance control in the TI-magnet system. Combined with the electrically induced magnetization rotation as part of the gate function, the proposed structure takes advantage of the magnetically modulated TI electronic band dispersion in addition to the conventional electrostatic barrier. The transport analysis coupled with the magnetic simulation predicts super-steep current-voltage characteristics near the threshold along with the GHz operating frequencies. Potential implementation to a complementary logic is also examined. The predicted characteristics are most suitable for applications requiring low power or those with small signals.

  1. Heating of heat-conducting targets by laser pulses with a high-intensity leading spike

    Science.gov (United States)

    Ageev, V. P.; Burdin, S. G.; Konov, V. I.; Uglov, S. A.; Chapliev, N. I.

    1983-04-01

    The results of an analysis of the solution of a one-dimensional heat conduction equation are used to study the specific features of the thermal effects of laser pulses with a leading spike on a target. Simple criteria are obtained for establishing the ability of a pulse to cause a given increase in the target surface temperature during the leading edge of a spike and also during the tail of the laser pulse. A study is made of the influence of the inhomogeneity of the distribution of surface heat sources on the realization of processes characterized by a threshold in respect of the temperature of the irradiated surface. The results obtained are compared with the experimental delay time in the process of initiation of an air breakdown plasma by interaction of CO2 laser pulses with a metal target.

  2. A Green Plastic Constructed from Cellulose and Functionalized Graphene with High Thermal Conductivity.

    Science.gov (United States)

    Song, Na; Hou, Xingshuang; Chen, Li; Cui, Siqi; Shi, Liyi; Ding, Peng

    2017-05-31

    It is urgent to fabricate a class of green plastics to substitute synthetic plastics with increasing awareness of sustainable development of an ecological environment and economy. In this work, a novel green plastic constructed from cellulose and functionalized graphene has been explored. The mechanical properties and thermal stability of the resultant cellulose/functionalized graphene composite plastics (CGPs) equal or even exceed those of synthetic plastics. Moreover, the in-plane thermal conductivity of CGPs can reach 9.0 W·m -1 ·K -1 with only 6 wt % functionalized graphene loading. These superior properties are attributed to the strong hydrogen-bonding interaction between cellulose and functionalized graphene, the uniform dispersion of functionalized graphene, and the alignment structure of CGPs. Given the promising synergistic performances and ecofriendly features of CGPs, we envisage that CGPs as novel green plastics could play important roles in thermal management devices.

  3. Highly conductive and flexible polymer composites with improved mechanical and electromagnetic interference shielding performances.

    Science.gov (United States)

    Chen, Mengting; Zhang, Ling; Duan, Shasha; Jing, Shilong; Jiang, Hao; Luo, Meifang; Li, Chunzhong

    2014-04-07

    New flexible and conductive materials (FCMs) comprising a quartz fiber cloth (QFC) reinforced multi-walled carbon nanotubes (MWCNTs)-carbon aerogel (QMCA) and poly(dimethylsiloxane) (PDMS) have been successfully prepared. The QMCA-PDMS composite with a very low loading of MWCNTs (∼1.6 wt%) demonstrates enhanced performance in tensile strength (129.6 MPa), modulus (3.41 GPa) and electromagnetic interference (EMI) shielding efficiency (SE) (∼16 dB in X-band (8.2-12.4 GHz) region). Compared to the QC (where MWCNTs were simply deposited on the QFCs without forming aerogel networks) based PDMS composite, a ∼120%, 330% and 178% increase of tensile strength, modulus, and EMI SE was obtained, respectively. Moreover, the EMI SE of the QMCA-PDMS composite can further reach 20 dB (a SE level needed for commercial applications) with only 2 wt% MWCNTs. Furthermore, the conductivity of the QMCA-PDMS laminate can reach 1.67 S cm(-1) even with very low MWCNTs (1.6 wt%), which still remains constant even after 5000 times bending and exhibits an increase of ∼170% than that of MWCNT-carbon aerogel (MCA)-PDMS at 20% strain. Such intriguing performances are mainly attributed to their unique networks in QMCA-PDMS composites. In addition, these features can also protect electronics against harm from external forces and EMI, giving the brand-new FCMs huge potential in next-generation devices, like E-skin, robot joints and so on.

  4. Three-dimensional highly conductive graphene-silver nanowire hybrid foams for flexible and stretchable conductors.

    Science.gov (United States)

    Wu, Chao; Fang, Lijun; Huang, Xingyi; Jiang, Pingkai

    2014-12-10

    Graphene foams have showed huge application potentials owing to their unique 3D structure and superior properties. Thus, it is highly desired to develop a simple and effective pathway to fabricate high performance graphene-based foams. Here, we present a polymer template-assisted assembly strategy for fabricating a novel class of graphene/AgNW hybrid foams. The hybrid foams show 3D ordered microstructures, high thermal stability, and excellent electrical and mechanical properties, and demonstrate huge application potential in the fields of flexible and stretchable conductors. Importantly, the polymer-template assisted assembly technique is simple, scalable, and low-cost, providing a new synthesis protocol for various multifunctional graphene hybrid foam-based composites.

  5. Highly Anisotropic Thermal Conductivity of Layer-by-Layer Assembled Nanofibrillated Cellulose/Graphene Nanosheets Hybrid Films for Thermal Management.

    Science.gov (United States)

    Song, Na; Jiao, Dejin; Cui, Siqi; Hou, Xingshuang; Ding, Peng; Shi, Liyi

    2017-01-25

    An anisotropic thermally conductive film with tailorable microstructures and macroproperties is fabricated using a layer-by-layer (LbL) assembly of graphene oxide (GO) and nanofibrillated cellulose (NFC) on a flexible NFC substrate driven by hydrogen bonding interactions, followed by chemical reduction process. The resulting NFC/reduced graphene oxide (RGO) hybrid film reveals an orderly hierarchical structure in which the RGO nanosheets exhibit a high degree of orientation along the in-plane direction. The assembly cycles dramatically increase the in-plane thermal conductivity (λX) of the hybrid film to 12.6 W·m(-1)·K(-1), while the cross-plane thermal conductivity (λZ) shows a lower value of 0.042 W·m(-1)·K(-1) in the hybrid film with 40 assembly cycles. The thermal conductivity anisotropy reaches up to λX/λZ = 279, which is substantially larger than that of similar polymeric nanocomposites, indicating that the LbL assembly on a flexible NFC substrate is an efficient technique for the preparation of polymeric nanocomposites with improved heat conducting property. Moreover, the layered hybrid film composed of 1D NFC and 2D RGO exhibits synergetic mechnical properties with outstanding flexibility and a high tensile strength (107 MPa). The combination of anisotropic thermal conductivity and superior mechanical performance may facilitate the applications in thermal management.

  6. Highly doped carbon nanotubes with gold nanoparticles and their influence on electrical conductivity and thermopower of nanocomposites.

    Directory of Open Access Journals (Sweden)

    Kyungwho Choi

    Full Text Available Carbon nanotubes (CNTs are often used as conductive fillers in composite materials, but electrical conductivity is limited by the maximum filler concentration that is necessary to maintain composite structures. This paper presents further improvement in electrical conductivity by precipitating gold nanoparticles onto CNTs. In our composites, the concentrations of CNTs and poly (vinyl acetate were respectively 60 and 10 vol%. Four different gold concentrations, 0, 10, 15, or 20 vol% were used to compare the influence of the gold precipitation on electrical conductivity and thermopower of the composites. The remaining portion was occupied by poly(3,4-ethylenedioxythiophene poly(styrenesulfonate, which de-bundled and stabilized CNTs in water during synthesis processes. The concentrations of gold nanoparticles are below the percolation threshold of similar composites. However, with 15-vol% gold, the electrical conductivity of our composites was as high as ∼6×10(5 S/m, which is at least ∼500% higher than those of similar composites as well as orders of magnitude higher than those of other polymer composites containing CNTs and gold particles. According to our analysis with a variable range hopping model, the high conductivity can be attributed to gold doping on CNT networks. Additionally, the electrical properties of composites made of different types of CNTs were also compared.

  7. Highly sensitive antenna using inkjet overprinting with particle-free conductive inks.

    Science.gov (United States)

    Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Otsuka, Kanji

    2012-11-01

    Printed antennas with low signal losses and fast response in high-frequency bands have been required. Here we reported on highly sensitive antennas using additive patterning of particle-free metallo-organic decomposition silver inks. Inkjet overprinting of metallo-organic decomposition inks onto copper foil and silver nanowire line produced antenna with mirror surfaces. As a result, the overprinted antennas decreased their return losses at 0.5-4.0 GHz and increased the speed of data communication in WiFi network.

  8. Unlocking the full potential of conducting polymers for high-efficiency organic light-emitting devices.

    Science.gov (United States)

    Huang, Yi-Hsiang; Tsai, Wei-Lung; Lee, Wei-Kai; Jiao, Min; Lu, Chun-Yang; Lin, Chun-Yu; Chen, Chien-Yu; Wu, Chung-Chih

    2015-02-04

    By carefully tuning the thicknesses of low-optical index PEDOT:PSS and high-index ITO layers in organic light-emitting devices (OLEDs), very high optical coupling efficiencies can be obtained through the generation of appropriate microcavity effects. These experiments result in an external quantum efficiency (EQE) of 33.7% for green phosphorescent OLEDs and even higher EQEs of 54.3% can be obtained by adopting an external out-coupling lens. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Influence of La/W ratio on electrical conductivity of lanthanum tungstate with high La/W ratio

    Science.gov (United States)

    Kojo, Gen; Shono, Yohei; Ushiyama, Hiroshi; Oshima, Yoshito; Otomo, Junichiro

    2017-04-01

    The proton-conducting properties of lanthanum tungstates (LWOs) with high La/W ratios were investigated using electrochemical measurements and quantum chemical calculations. Single phases of LWOs with high La/W ratios (6.3≤La/W≤6.7) were synthesized by high-temperature sintering at around 1700 °C. The electrical conductivity of LWO increased with increasing La/W ratio in the single-phase region. The LWO synthesized at the optimum sintering temperature and time, and with the optimum La/W ratio gave the maximum conductivity, i.e., 2.7×10-3 S cm-1 with La/W=6.7 at 500 °C. Density functional theory calculations, using the nudged elastic band method, were performed to investigate the proton diffusion barrier. The results suggest that the proton diffusion paths around La sites have the lowest proton diffusion barrier. These findings improve our understanding of LWO synthesis and the proton-conducting mechanism and provide a strategy for improving proton conduction in LWOs.

  10. A Study of Personality Change Associated with the Conducting of a High School Unit on Homosexuality.

    Science.gov (United States)

    Greenberg, Jerrold S.

    In this study of homosexuality the following variables were tested: (1) acceptance of others, (2) faith in others, and (3) levels of masculinity and femininity (M-F). The subjects were 11th and 12th graders enrolled in a suburban high school (n=68). Three standardized measurement instruments, each designed to measure one of the above-mentioned…

  11. Determining Studies Conducted upon Individuals with Autism Spectrum Disorder Using High-Tech Devices

    Science.gov (United States)

    Eliçin, Özge; Kaya, Ali

    2017-01-01

    This study explores 67 experimental research articles written about children with Autism Spectrum Disorder using high-tech devices. The studies in this research were accessed through EBSCO, Academic Search Complete, ERIC, and Uludag University online search engines using keywords such as "autism and technology", "autism and…

  12. Highly conductive ion tracks in tetrahedral amorphous carbon by irradiation with 30 MeV C{sub 60} projectiles

    Energy Technology Data Exchange (ETDEWEB)

    Krauser, J [Hochschule Harz, University of Applied Sciences, 38855 Wernigerode (Germany); Nix, A-K; Gehrke, H-G; Hofsaess, H [II Institute of Physics, University of Goettingen, 37077 Goettingen (Germany); Trautmann, C [Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Weidinger, A, E-mail: jkrauser@hs-harz.de [Helmholtz-Zentrum Berlin fuer Materialien und Energie, 14109 Berlin (Germany)

    2011-08-15

    Electrically conducting ion tracks are produced when high-energy heavy ions pass through a layer of tetrahedral amorphous carbon (ta-C). The tracks are embedded in the insulating ta-C matrix and have a diameter of about 8 nm. Earlier studies showed that the electrical currents through individual tracks produced with Au and U projectiles exhibit rather large track-to-track fluctuations. In striking contrast, 30 MeV C{sub 60} cluster ions are shown to generate conducting tracks of very narrow conductivity distributions. Their current-versus-voltage curves are linear at room temperature. We also investigated ta-C films doped with B, N, Cu and Fe at a concentration of 1 or 2 at.%. In particular, Cu- and Fe-doped samples show increased ion track conductivity.

  13. Noise Analysis of Second-Harmonic Generation in Undoped and MgO-Doped Periodically Poled Lithium Niobate

    Directory of Open Access Journals (Sweden)

    Yong Wang

    2008-01-01

    Full Text Available Noise characteristics of second-harmonic generation (SHG in periodically poled lithium niobate (PPLN using the quasiphase matching (QPM technique are analyzed experimentally. In the experiment, a0.78 μm second-harmonic (SH wave was generated when a 1.56 μm fundamental wave passed through a PPLN crystal (bulk or waveguide. The time-domain and frequency-domain noise characteristics of the fundamental and SH waves were analyzed. By using the pump-probe method, the noise characteristics of SHG were further analyzed when a visible light (532 nm and an infrared light (1090 nm copropagated with the fundamental light, respectively. The noise characterizations were also investigated at different temperatures. It is found that for the bulk and waveguide PPLN crystals, the SH wave has a higher relative noise level than the corresponding fundamental wave. For the same fundamental wave, the SH wave has lower noise in a bulk crystal than in a waveguide, and in MgO-doped PPLN than in undoped PPLN. The 532 nm irradiation can lead to higher noise in PPLN than the 1090 nm irradiation. In addition, increasing temperature of device can alleviate the problem of noise in conjunction with the photorefractive effect incurred by the irradiation light. This is more significant in undoped PPLN than in MgO-doped one.

  14. Optical properties of in situ doped and undoped titania nanocatalysts and doped titania sol-gel nanofilms

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira da Silva, A. [Instituto de Fisica, Universidade Federal da Bahia, Campus Ondina, 40 210-340 Salvador, BA (Brazil)]. E-mail: ferreira@venus.fis.ufba.br; Pepe, I. [Instituto de Fisica, Universidade Federal da Bahia, Campus Ondina, 40 210-340 Salvador, BA (Brazil); Gole, James L. [Schools of Physics and Mechanical Engineering, Georgia Institute of Technology Atlanta, GA 30332-0430 (United States); Tomas, S.A. [Departamento de Fisica, CINVESTAV-IPN, AP 14-740, Mexico D.F. 07300 (Mexico); Palomino, R. [Facultad de Ciencias Fisico-Matematicas, BUAP, AP 1152, Puebla (Mexico); Azevedo, W.M. de [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, Cidade Universitaria, 50670-901 Recife, PE (Brazil); Silva, E.F. da [Departamento de Fisica, Universidade Federal de Pernambuco, Cidade Universitaria, 50670-901 Recife, PE (Brazil); Ahuja, R. [Department of Physics, Uppsala University, SE-751 21 Uppsala (Sweden); Persson, C. [Department of Materials Science and Engineering, Royal Institute of Technology SE-100 44 Stockholm (Sweden)

    2006-05-30

    In this paper we present spectroscopic properties of doped and undoped titanium dioxide (TiO{sub 2}) as nanofilms prepared by the sol-gel process with rhodamine 6G doping and studied by photoacoustic absorption, excitation and emission spectroscopy. The absorption spectra of TiO{sub 2} thin films doped with rhodamine 6G at very low concentration during their preparation show two absorption bands, one at 2.3 eV attributed to molecular dimmer formation, which is responsible for the fluorescence quenching of the sample and the other at 3.0 eV attributed to TiO{sub 2} absorption, which subsequently yields a strong emission band at 600 nm. The electronic band structure and optical properties of the rutile phase of TiO{sub 2} are calculated employing a fully relativistic, full-potential, linearized, augmented plane-wave (FPLAPW) method within the local density approximation (LDA). Comparison of this calculation with experimental data for TiO{sub 2} films prepared for undoped sol-gels and by sputtering is performed.

  15. Conductive-probe atomic force microscopy characterization of silicon nanowire

    Directory of Open Access Journals (Sweden)

    Yu Linwei

    2011-01-01

    Full Text Available Abstract The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs were investigated using a conductive-probe atomic force microscopy (AFM. Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V. Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated.

  16. A High-Performance Adaptive Incremental Conductance MPPT Algorithm for Photovoltaic Systems

    Directory of Open Access Journals (Sweden)

    Chendi Li

    2016-04-01

    Full Text Available The output characteristics of photovoltaic (PV arrays vary with the change of environment, and maximum power point (MPP tracking (MPPT techniques are thus employed to extract the peak power from PV arrays. Based on the analysis of existing MPPT methods, a novel incremental conductance (INC MPPT algorithm is proposed with an adaptive variable step size. The proposed algorithm automatically regulates the step size to track the MPP through a step size adjustment coefficient, and a user predefined constant is unnecessary for the convergence of the MPPT method, thus simplifying the design of the PV system. A tuning method of initial step sizes is also presented, which is derived from the approximate linear relationship between the open-circuit voltage and MPP voltage. Compared with the conventional INC method, the proposed method can achieve faster dynamic response and better steady state performance simultaneously under the conditions of extreme irradiance changes. A Matlab/Simulink model and a 5 kW PV system prototype controlled by a digital signal controller (TMS320F28035 were established. Simulations and experimental results further validate the effectiveness of the proposed method.

  17. Hole injection energetics at highly conducting polymer anode: small molecule interfaces studied with photoemission spectroscopy

    Science.gov (United States)

    Maekinen, Antti J.; Kim, W. H.; Hill, Ian G.; Shashidhar, Ranganathan; Nikolov, Nikolay; Kafafi, Zakya H.

    2002-02-01

    We report a photoemission study of the interfaces between spin-cast films of a new variation of a polymer blend consisting of poly(3,4-ethylenedioxy-thiophene) (PEDOT) and poly(4-styrenesulfonate) (PSS) and glycerol as an additive, and vacuum-evaporated hole transport layers (HTL) of 4,4'-bis(carbazol-9-yl)biphenyl (CBP),N,N'-diphenyl-N,N'-bis(1-naphthyl)-1-1'biphenyl-4,4'di amine (NPD) and N,N'-diphenyl-N,N'-bis(3methylphenyl)-1,1'-biphenyl-4,4'-dia mine (TPD). The hole injection barrier, as deduced from photoemission spectroscopy, is 0.5 - 0.9 eV at the PEDOT-PSS / HTL interface, which compares very well with the previously reported barrier heights for oxygen plasma -treated indium-tin oxide (ITO)/NPD and ITO/TPD interfaces, and which is, most notably, a factor of two smaller than barriers measured for a PEDOT-PSS/hole-transporting luminescent polymer, e.g. poly(bis-(2-dimethyloctylsilyl)-1,4-phenylvinylene, interface. The measured energy barriers imply a sufficiently efficient charge injection at the studied PEDOT-PSS/HTL interface, which is very encouraging for further development of anode structures based on similar conducting polymer blends and chemically modified structures to be utilized in molecular organic light-emitting device applications.

  18. Highly stretchable strain sensor based on SWCNTs/CB synergistic conductive network for wearable human-activity monitoring and recognition

    Science.gov (United States)

    Guo, Xiaohui; Huang, Ying; Zhao, Yunong; Mao, Leidong; Gao, Le; Pan, Weidong; Zhang, Yugang; Liu, Ping

    2017-09-01

    Flexible, stretchable, and wearable strain sensors have attracted significant attention for their potential applications in human movement detection and recognition. Here, we report a highly stretchable and flexible strain sensor based on a single-walled carbon nanotube (SWCNTs)/carbon black (CB) synergistic conductive network. The fabrication, synergistic conductive mechanism, and characterization of the sandwich-structured strain sensor were investigated. The experimental results show that the device exhibits high stretchability (120%), excellent flexibility, fast response (∼60 ms), temperature independence, and superior stability and reproducibility during ∼1100 stretching/releasing cycles. Furthermore, human activities such as the bending of a finger or elbow and gestures were monitored and recognized based on the strain sensor, indicating that the stretchable strain sensor based on the SWCNTs/CB synergistic conductive network could have promising applications in flexible and wearable devices for human motion monitoring.

  19. Advice to the high school teacher in the conduct of its work teachers

    Directory of Open Access Journals (Sweden)

    Carlos Rosales López

    2011-09-01

    Full Text Available This paper analyzes the characteristics of advice to high school teacher for the realization of their basic teaching duties. We beging to identify current features of this stage as openness to multiple choice and the consequent need of guidance, the increase in enrollment in it, the decline in academic performance, diversification of its students, the increase in disruptive and violent behavior and the introduction of new technologies. It is emphasized that the high school teacher needs advice on a variety of tasks such as planning ac- cording to various perspectives, diverse and cooperative teaching and learning assessment. This advice can be external or internal to the school, can be performed by different professionals and according to different modalities. It is a task of the support and help to optimize your professional intervention and in this sense is con- sidered to constitute a component of teacher training. advice; secondary education; teaching duties; planning; methodology; evaluation. 

  20. Highly conductive and stretchable Ag nanowire/carbon nanotube hybrid conductors.

    Science.gov (United States)

    Woo, Ju Yeon; Kim, Kyun Kyu; Lee, Jongsoo; Kim, Ju Tae; Han, Chang-Soo

    2014-07-18

    Fabricating stretchable conductors through simple, cost-effective and scalable methods is a challenge. Here, we report on an approach used to develop nanowelded Ag nanowire/single-walled carbon nanotube (AgNW/SWCNT) hybrid films to be used as high-performance stretchable conductors. Plasmonic welding, which was done at the junctions of AgNWs in order to form hybrid AgNW/SWCNT conductors on an Ecoflex substrate, enabled excellent electrical and mechanical stability under large tensile strains of over 480% without the need to pre-strain. Furthermore, we demonstrate highly stretchable circuits that are used to power LED arrays. The LED arrays are formed using the plasmonic-welded AgNW/SWCNT/Ecoflex hybrid material, which demonstrates suitability for interconnector applications in flexible electronics.

  1. High performance electrochemical pseudocapacitors from ionic liquid assisted electrochemically synthesized p-type conductive polymer.

    Science.gov (United States)

    Ehsani, A; Mohammad Shiri, H; Kowsari, E; Safari, R; Torabian, J; Hajghani, S

    2017-03-15

    In this paper firstly, 1-methyl-3-methylimidazolium bromide (MB) as a new high efficient ionic liquid was synthesized using chemical approach and then fabricated POAP/MB films by electro-polymerization of POAP in the presence of MB to serve as the active electrode for electrochemical supercapacitor. Theoretical study (AIM) and electrochemical analysis have been used for characterization of ionic liquid and POAP/MB composite film. Different electrochemical methods including galvanostatic charge-discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new most efficient materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area and stability in an aqueous electrolyte. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Self-constructed tree-shape high thermal conductivity nanosilver networks in epoxy

    Science.gov (United States)

    Pashayi, Kamyar; Fard, Hafez Raeisi; Lai, Fengyuan; Iruvanti, Sushumna; Plawsky, Joel; Borca-Tasciuc, Theodorian

    2014-03-01

    We report the formation of high aspect ratio nanoscale tree-shape silver networks in epoxy, at low temperatures (polyvinylpyrrolidone (PVP) coated nanoparticles, removal of PVP coating from the surface, and sintering of silver nanoparticles in high aspect ratio networked structures. Controlling self-assembly and sintering by carefully designed multistep temperature and time processing leads to κ of our silver nanocomposites that are up to 300% of the present state of the art polymer nanocomposites at similar volume fractions. Our investigation of the κ enhancements enabled by tree-shaped network nanocomposites provides a basis for the development of new polymer nanocomposites for thermal transport and storage applications.We report the formation of high aspect ratio nanoscale tree-shape silver networks in epoxy, at low temperatures (polyvinylpyrrolidone (PVP) coated nanoparticles, removal of PVP coating from the surface, and sintering of silver nanoparticles in high aspect ratio networked structures. Controlling self-assembly and sintering by carefully designed multistep temperature and time processing leads to κ of our silver nanocomposites that are up to 300% of the present state of the art polymer nanocomposites at similar volume fractions. Our investigation of the κ enhancements enabled by tree-shaped network nanocomposites provides a basis for the development of new polymer nanocomposites for thermal transport and storage applications. Electronic supplementary information (ESI) available: Raman spectroscopy of particles with and without PVP coating, the morphology of uncoated particles, the curing time of samples presented in Fig. 2, optical microscopy images studying the effect of processing time and temperature on nanocomposite agglomeration, measurement results of viscosity versus time for pure epoxy and the 20 vol% silver-epoxy nanocomposite, theoretical determination of the agglomeration time, and the DSC curve of pure bulk PVP are presented in the

  3. Lab-on-a-Chip device with laser-patterned polymer electrodes for high voltage application and contactless conductivity detection.

    Science.gov (United States)

    Henderson, Rowan D; Guijt, Rosanne M; Andrewartha, Lee; Lewis, Trevor W; Rodemann, Thomas; Henderson, Alan; Hilder, Emily F; Haddad, Paul R; Breadmore, Michael C

    2012-09-25

    A laser-patterned microchip electrophoresis device with integrated polymer electrodes for DC high voltages and AC capacitively-coupled contactless conductivity detection was developed. Electrophoresis separations comparable to devices with metal electrodes were obtained, at approximately 20 times lower cost.

  4. Exploring the Use of Suspension in High School Codes of Conduct for Mild, Moderate, and Severe Behaviors

    Science.gov (United States)

    Horwitz, Amy Beth

    2010-01-01

    The purpose of this investigation is to describe the outcomes of a multi-state study of written discipline policies in a high school setting. This study examines discipline codes of conduct and analyzes the content for behaviors ranging in severity (mild, moderate, and severe) while specifically examining the use of suspension as a punitive…

  5. Associations between high callous-unemotional traits and quality of life across youths with non-conduct disorder diagnoses

    NARCIS (Netherlands)

    Herpers, P.C.; Klip, H.; Rommelse, N.N.J.; Greven, C.U.; Buitelaar, J.K.

    2016-01-01

    Research regarding callous-unemotional (CU) traits in non-conduct disorder (CD) diagnoses is sparse. We investigated the presence of high CU traits and their associations with quality of life (QoL) in a clinically referred sample of youths with non-CD diagnoses. Parents of 1018 children referred to

  6. Highly Conductive Transparent and Flexible Electrodes Including Double-Stacked Thin Metal Films for Transparent Flexible Electronics.

    Science.gov (United States)

    Han, Jun Hee; Kim, Do-Hong; Jeong, Eun Gyo; Lee, Tae-Woo; Lee, Myung Keun; Park, Jeong Woo; Lee, Hoseung; Choi, Kyung Cheol

    2017-05-17

    To keep pace with the era of transparent and deformable electronics, electrode functions should be improved. In this paper, an innovative structure is suggested to overcome the trade-off between optical and electrical properties that commonly arises with transparent electrodes. The structure of double-stacked metal films showed high conductivity (electronics are expected.

  7. Weavable, Conductive Yarn-Based NiCo//Zn Textile Battery with High Energy Density and Rate Capability.

    Science.gov (United States)

    Huang, Yan; Ip, Wing Shan; Lau, Yuen Ying; Sun, Jinfeng; Zeng, Jie; Yeung, Nga Sze Sea; Ng, Wing Sum; Li, Hongfei; Pei, Zengxia; Xue, Qi; Wang, Yukun; Yu, Jie; Hu, Hong; Zhi, Chunyi

    2017-09-26

    With intrinsic safety and much higher energy densities than supercapacitors, rechargeable nickel/cobalt-zinc-based textile batteries are promising power sources for next generation personalized wearable electronics. However, high-performance wearable nickel/cobalt-zinc-based batteries are rarely reported because there is a lack of industrially weavable and knittable highly conductive yarns. Here, we use scalably produced highly conductive yarns uniformly covered with zinc (as anode) and nickel cobalt hydroxide nanosheets (as cathode) to fabricate rechargeable yarn batteries. They possess a battery level capacity and energy density, as well as a supercapacitor level power density. They deliver high specific capacity of 5 mAh cm -3 and energy densities of 0.12 mWh cm -2 and 8 mWh cm -3 (based on the whole solid battery). They exhibit ultrahigh rate capabilities of 232 C (liquid electrolyte) and 116 C (solid electrolyte), which endows the batteries excellent power densities of 32.8 mW cm -2 and 2.2 W cm -3 (based on the whole solid battery). These are among the highest values reported so far. A wrist band battery is further constructed by using a large conductive cloth woven from the conductive yarns by a commercial weaving machine. It powers various electronic devices successfully, enabling dual functions of wearability and energy storage.

  8. High oxygen ion conduction in sintered oxides of the $Bi_2O_3-Er_2O_3$ system

    NARCIS (Netherlands)

    Verkerk, M.J.; Keizer, Klaas; Burggraaf, A.J.

    1980-01-01

    The phase diagram of the Bi2O3-Er2O3 system was investigated. A monophasic f c c structure was stabilized for samples containing 17.5–45.5 mol% Er2O3. Above and below this concentration range polyphasic regions appear. The f c c phase showed high oxygen ion conduction. The ionic transference number

  9. One-step fabrication of a highly conductive and durable copper paste and its flexible dipole tag-antenna application.

    Science.gov (United States)

    Shin, Keun-Young; Lee, James S; Hong, Jin-Yong; Jang, Jyongsik

    2014-03-21

    A highly conductive and durable copper (Cu) paste was successfully fabricated via acid treatment and mechanical blending with corrosion inhibitors. A screen-printed Cu pattern was evaluated as a dipole tag-antenna with long term and thermal stability, and structural flexibility.

  10. : Signal Decomposition of High Resolution Time Series River data to Separate Local and Regional Components of Conductivity

    Science.gov (United States)

    Signal processing techniques were applied to high-resolution time series data obtained from conductivity loggers placed upstream and downstream of a wastewater treatment facility along a river. Data was collected over 14-60 days, and several seasons. The power spectral densit...

  11. Signal Decomposition of High Resolution Time Series River Data to Separate Local and Regional Components of Conductivity

    Science.gov (United States)

    Signal processing techniques were applied to high-resolution time series data obtained from conductivity loggers placed upstream and downstream of an oil and gas wastewater treatment facility along a river. Data was collected over 14-60 days. The power spectral density was us...

  12. Large scale, highly conductive and patterned transparent films of silver nanowires on arbitrary substrates and their application in touch screens

    Energy Technology Data Exchange (ETDEWEB)

    Madaria, Anuj R; Kumar, Akshay; Zhou Chongwu, E-mail: chongwuz@usc.edu [Ming-Hsieh Department of Electrical Engineering and Center for Energy and Nanoscience Research and Technology, University of Southern California, Los Angeles, CA 90089 (United States)

    2011-06-17

    The application of silver nanowire films as transparent conductive electrodes has shown promising results recently. In this paper, we demonstrate the application of a simple spray coating technique to obtain large scale, highly uniform and conductive silver nanowire films on arbitrary substrates. We also integrated a polydimethylsiloxane (PDMS)-assisted contact transfer technique with spray coating, which allowed us to obtain large scale high quality patterned films of silver nanowires. The transparency and conductivity of the films was controlled by the volume of the dispersion used in spraying and the substrate area. We note that the optoelectrical property, {sigma}{sub DC}/{sigma}{sub Op}, for various films fabricated was in the range 75-350, which is extremely high for transparent thin film compared to other candidate alternatives to doped metal oxide film. Using this method, we obtain silver nanowire films on a flexible polyethylene terephthalate (PET) substrate with a transparency of 85% and sheet resistance of 33 {Omega}/sq, which is comparable to that of tin-doped indium oxide (ITO) on flexible substrates. In-depth analysis of the film shows a high performance using another commonly used figure-of-merit, {Phi}{sub TE}. Also, Ag nanowire film/PET shows good mechanical flexibility and the application of such a conductive silver nanowire film as an electrode in a touch panel has been demonstrated.

  13. First-principles study of high-conductance DNA sequencing with carbon nanotube electrodes

    KAUST Repository

    Chen, X.

    2012-03-26

    Rapid and cost-effective DNA sequencing at the single nucleotide level might be achieved by measuring a transverse electronic current as single-stranded DNA is pulled through a nanometer-sized pore. In order to enhance the electronic coupling between the nucleotides and the electrodes and hence the current signals, we employ a pair of single-walled close-ended (6,6) carbon nanotubes (CNTs) as electrodes. We then investigate the electron transport properties of nucleotides sandwiched between such electrodes by using first-principles quantum transport theory. In particular, we consider the extreme case where the separation between the electrodes is the smallest possible that still allows the DNA translocation. The benzene-like ring at the end cap of the CNT can strongly couple with the nucleobases and therefore it can both reduce conformational fluctuations and significantly improve the conductance. As such, when the electrodes are closely spaced, the nucleobases can pass through only with their base plane parallel to the plane of CNT end caps. The optimal molecular configurations, at which the nucleotides strongly couple to the CNTs, and which yield the largest transmission, are first identified. These correspond approximately to the lowest energy configurations. Then the electronic structures and the electron transport of these optimal configurations are analyzed. The typical tunneling currents are of the order of 50 nA for voltages up to 1 V. At higher bias, where resonant transport through the molecular states is possible, the current is of the order of several μA. Below 1 V, the currents associated to the different nucleotides are consistently distinguishable, with adenine having the largest current, guanine the second largest, cytosine the third and, finally, thymine the smallest. We further calculate the transmission coefficient profiles as the nucleotides are dragged along the DNA translocation path and investigate the effects of configurational variations

  14. Diagnostic criteria of carpal tunnel syndrome using high-resolution ultrasonography: correlation with nerve conduction studies.

    Science.gov (United States)

    Ooi, Chin Chin; Wong, Siew Kune; Tan, Agnes B H; Chin, Andrew Y H; Abu Bakar, Rafidah; Goh, Shy Yunn; Mohan, P Chandra; Yap, Robert T J; Png, Meng Ai

    2014-10-01

    The aim of this work was to evaluate the diagnostic performance of grey-scale, color Doppler, and dynamic ultrasound (US) for diagnosing carpal tunnel syndrome (CTS) using the medical diagnostic test called nerve conduction study (NCS) as the reference standard, and to correlate the increase in median nerve (MN) cross-sectional area (CSA) with severity of CTS. Fifty-one patients (95 wrists) with clinical symptoms of idiopathic CTS were recruited. The CSA and flattening ratio of the MN were measured at the distal radio-ulnar joint, pisiform, and hamate levels; bowing of the flexor retinaculum was determined at the hamate level. The hypervascularity of the MN was evaluated. The transverse sliding of the MN was observed dynamically and recorded as being either normal or restricted/absent. Another 15 healthy volunteers (30 wrists) were recruited as controls. Interoperator reliability was established for all criteria. CTS was confirmed in 75 wrists (75/95: 79%; 14 minimal, 21 mild, 23 moderate, 17 severe). CSA at the pisiform level was found to be the most reliable and accurate grey-scale criterion to diagnose CTS (optimum threshold: 9.8 mm(2)). There was a good correlation between the severity of NCS and CSA (r = 0.78, p < 0.001). The sensitivity and specificity of color-Doppler and dynamic US in detecting CTS was 69, 95, 58, and 86%, respectively. Combination of these subjective criteria with CSA increases the sensitivity to 98.3%. US measurement of CSA provides additional information about the severity of MN involvement. Color-Doppler and dynamic US are useful supporting criteria that may expand the utility of US as a screening tool for CTS.

  15. High-capacity conductive nanocellulose paper sheets for electrochemically controlled extraction of DNA oligomers.

    Directory of Open Access Journals (Sweden)

    Aamir Razaq

    Full Text Available Highly porous polypyrrole (PPy-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg(-1, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30-50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m(2 g(-1 of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT(6, (dT(20, and (dT(40 DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules.

  16. SOCIAL PERCEPTION OF THE EDUCATION SYSTEM REFORM. SURVEY CONDUCTED IN UPPER HIGH SCHOOLS OF BIHOR COUNTY

    Directory of Open Access Journals (Sweden)

    Sabau Remus Mircea

    2011-12-01

    Full Text Available Between the elements which mark the global processes, we can include educational issues, the management of processes in pre-university education. Therefore, the synthetic approach to educational problems in Romania, studied in terms of the processes and the phenomena of social development, but also due to the need for submiting the pre-university Romanian educational process to the European Union requirements, appears to be current and important. This analysis focuses on the decentralization of education. This theme is a true significant of the stage and of the the changing potential of the management practice in the public area. Its actuality is also hard to contest under the conditions in which changes in this area have been slow compared to those of the other countries that joined the European Union (Hungary, Czech Republic, Poland, contradictory and inconsistent (Herczynski and Levitas, 2001: 1-2. The legislative changes, training facilities, as well as the constant institutional reorganization of pre-university education show the presence of an active interest in this matter. However, the real reform of university education still requires essential improvements. This study analyzes the social perception of performers in pre-university system, establishes positive and negative aspects of the reform in pre-university education, all from the perspective of teachers. The research was conducted between March 1st, 2011 and April 1st, 2011. During this time the questionnaire was applied and the data interpreted. The data obtained from the questionnaire interpretation were introduced into the SPSS program. For the analysis and interpretation of data we used SPSS 15.0. under Windows license. My investigation efforts were directed towards the impact of decentralization on the performers in pre-university education system and on their perception. The main purpose of the experimental study was to determine the essential perceptions of the performers

  17. Monitoring gradient profile on-line in micro- and nano-high performance liquid chromatography using conductivity detection.

    Science.gov (United States)

    Zhang, Min; Chen, Apeng; Lu, Joann J; Cao, Chengxi; Liu, Shaorong

    2016-08-19

    In micro- or nano-flow high performance liquid chromatography (HPLC), flow-splitters and gradient elutions are commonly used for reverse phase HPLC separations. When a flow splitter was used at a high split-ratio (e.g., 1000:1 or higher), the actual gradient may deviate away from the programmed gradient. Sometimes, mobile phase concentrations can deviate by as much as 5%. In this work, we noticed that the conductivity (σ) of a gradient decreased with the increasing organic-solvent fraction (φ). Based on the relationship between σ and φ, a method was developed for monitoring gradient profile on-line to record any deviations in these HPLC systems. The conductivity could be measured by a traditional conductivity detector or a capacitively coupled contactless conductivity detector (C(4)D). The method was applied for assessing the performance of an electroosmotic pump (EOP) based nano-HPLC. We also observed that σ value of the gradient changed with system pressure; a=0.0175ΔP (R(2)=0.964), where a is the percentage of the conductivity increase and ΔP is the system pressure in bar. This effect was also investigated. Copyright © 2016. Published by Elsevier B.V.

  18. High accuracy thermal conductivity measurement of aqueous cryoprotective agents and semi-rigid biological tissues using a microfabricated thermal sensor.

    Science.gov (United States)

    Liang, Xin M; Sekar, Praveen K; Zhao, Gang; Zhou, Xiaoming; Shu, Zhiquan; Huang, Zhongping; Ding, Weiping; Zhang, Qingchuan; Gao, Dayong

    2015-05-20

    An improved thermal-needle approach for accurate and fast measurement of thermal conductivity of aqueous and soft biomaterials was developed using microfabricated thermal conductivity sensors. This microscopic measuring device was comprehensively characterized at temperatures from 0 °C to 40 °C. Despite the previous belief, system calibration constant was observed to be highly temperature-dependent. Dynamic thermal conductivity response during cooling (40 °C to -40 °C) was observed using the miniaturized single tip sensor for various concentrations of CPAs, i.e., glycerol, ethylene glycol and dimethyl sulfoxide. Chicken breast, chicken skin, porcine limb, and bovine liver were assayed to investigate the effect of anatomical heterogeneity on thermal conductivity using the arrayed multi-tip sensor at 20 °C. Experimental results revealed distinctive differences in localized thermal conductivity, which suggests the use of approximated or constant property values is expected to bring about results with largely inflated uncertainties when investigating bio-heat transfer mechanisms and/or performing sophisticated thermal modeling with complex biological tissues. Overall, the presented micro thermal sensor with automated data analysis algorithm is a promising approach for direct thermal conductivity measurement of aqueous solutions and soft biomaterials and is of great value to cryopreservation of tissues, hyperthermia or cryogenic, and other thermal-based clinical diagnostics and treatments.

  19. High accuracy thermal conductivity measurement of aqueous cryoprotective agents and semi-rigid biological tissues using a microfabricated thermal sensor

    Science.gov (United States)

    Liang, Xin M.; Sekar, Praveen K.; Zhao, Gang; Zhou, Xiaoming; Shu, Zhiquan; Huang, Zhongping; Ding, Weiping; Zhang, Qingchuan; Gao, Dayong

    2015-01-01

    An improved thermal-needle approach for accurate and fast measurement of thermal conductivity of aqueous and soft biomaterials was developed using microfabricated thermal conductivity sensors. This microscopic measuring device was comprehensively characterized at temperatures from 0 °C to 40 °C. Despite the previous belief, system calibration constant was observed to be highly temperature-dependent. Dynamic thermal conductivity response during cooling (40 °C to –40 °C) was observed using the miniaturized single tip sensor for various concentrations of CPAs, i.e., glycerol, ethylene glycol and dimethyl sulfoxide. Chicken breast, chicken skin, porcine limb, and bovine liver were assayed to investigate the effect of anatomical heterogeneity on thermal conductivity using the arrayed multi-tip sensor at 20 °C. Experimental results revealed distinctive differences in localized thermal conductivity, which suggests the use of approximated or constant property values is expected to bring about results with largely inflated uncertainties when investigating bio-heat transfer mechanisms and/or performing sophisticated thermal modeling with complex biological tissues. Overall, the presented micro thermal sensor with automated data analysis algorithm is a promising approach for direct thermal conductivity measurement of aqueous solutions and soft biomaterials and is of great value to cryopreservation of tissues, hyperthermia or cryogenic, and other thermal-based clinical diagnostics and treatments. PMID:25993037

  20. Faradic redox active material of Cu7S4 nanowires with a high conductance for flexible solid state supercapacitors

    Science.gov (United States)

    Javed, Muhammad Sufyan; Dai, Shuge; Wang, Mingjun; Xi, Yi; Lang, Qiang; Guo, Donglin; Hu, Chenguo

    2015-08-01

    The exploration of high Faradic redox active materials with the advantages of low cost and low toxicity has been attracting great attention for producing high energy storage supercapacitors. Here, the high Faradic redox active material of Cu7S4-NWs coated on a carbon fiber fabric (CFF) is directly used as a binder-free electrode for a high performance flexible solid state supercapacitor. The Cu7S4-NW-CFF supercapacitor exhibits excellent electrochemical performance such as a high specific capacitance of 400 F g-1 at the scan rate of 10 mV s-1 and a high energy density of 35 Wh kg-1 at a power density of 200 W kg-1, with the advantages of a light weight, high flexibility and long term cycling stability by retaining 95% after 5000 charge-discharge cycles at a constant current of 10 mA. The high Faradic redox activity and high conductance behavior of the Cu7S4-NWs result in a high pseudocapacitive performance with a relatively high specific energy and specific power. Such a new type of pseudocapacitive material of Cu7S4-NWs with its low cost is very promising for actual application in supercapacitors.The exploration of high Faradic redox active materials with the advantages of low cost and low toxicity has been attracting great attention for producing high energy storage supercapacitors. Here, the high Faradic redox active material of Cu7S4-NWs coated on a carbon fiber fabric (CFF) is directly used as a binder-free electrode for a high performance flexible solid state supercapacitor. The Cu7S4-NW-CFF supercapacitor exhibits excellent electrochemical performance such as a high specific capacitance of 400 F g-1 at the scan rate of 10 mV s-1 and a high energy density of 35 Wh kg-1 at a power density of 200 W kg-1, with the advantages of a light weight, high flexibility and long term cycling stability by retaining 95% after 5000 charge-discharge cycles at a constant current of 10 mA. The high Faradic redox activity and high conductance behavior of the Cu7S4-NWs result in

  1. Highly conductive transparent organic electrodes with multilayer structures for rigid and flexible optoelectronics.

    Science.gov (United States)

    Guo, Xiaoyang; Liu, Xingyuan; Lin, Fengyuan; Li, Hailing; Fan, Yi; Zhang, Nan

    2015-05-27

    Transparent electrodes are essential components for optoelectronic devices, such as touch panels, organic light-emitting diodes, and solar cells. Indium tin oxide (ITO) is widely used as transparent electrode in optoelectronic devices. ITO has high transparency and low resistance but contains expensive rare elements, and ITO-based devices have poor mechanical flexibility. Therefore, alternative transparent electrodes with excellent opto-electrical performance and mechanical flexibility will be greatly demanded. Here, organics are introduced into dielectric-metal-dielectric structures to construct the transparent electrodes on rigid and flexible substrates. We show that organic-metal-organic (OMO) electrodes have excellent opto-electrical properties (sheet resistance of below 10 Ω sq(-1) at 85% transmission), mechanical flexibility, thermal and environmental stabilities. The OMO-based polymer photovoltaic cells show performance comparable to that of devices based on ITO electrodes. This OMO multilayer structure can therefore be used to produce transparent electrodes suitable for use in a wide range of optoelectronic devices.

  2. Method and apparatus for conducting structural health monitoring in a cryogenic, high vibration environment

    Science.gov (United States)

    Qing, Xinlin (Inventor); Beard, Shawn J. (Inventor); Li, Irene (Inventor)

    2013-01-01

    Sensors affixed to various such structures, where the sensors can withstand, remain affixed, and operate while undergoing both cryogenic temperatures and high vibrations. In particular, piezoelectric single crystal transducers are utilized, and these sensors are coupled to the structure via a low temperature, heat cured epoxy. This allows the transducers to monitor the structure while the engine is operating, even despite the harsh operating conditions. Aspects of the invention thus allow for real time monitoring and analysis of structures that operate in conditions that previously did not permit such analysis. A further aspect of the invention relates to use of piezoelectric single crystal transducers. In particular, use of such transducers allows the same elements to be used as both sensors and actuators.

  3. Highly transparent conductive ITO/Ag/ITO trilayer films deposited by RF sputtering at room temperature

    Directory of Open Access Journals (Sweden)

    Ningyu Ren

    2017-05-01

    Full Text Available ITO/Ag/ITO (IAI trilayer films were deposited on glass substrate by radio frequency magnetron sputtering at room temperature. A high optical transmittance over 94.25% at the wavelength of 550 nm and an average transmittance over the visual region of 88.04% were achieved. The calculated value of figure of merit (FOM reaches 80.9 10-3 Ω-1 for IAI films with 15-nm-thick Ag interlayer. From the morphology and structural characterization, IAI films could show an excellent correlated electric and optical performance if Ag grains interconnect with each other on the bottom ITO layer. These results indicate that IAI trilayer films, which also exhibit low surface roughness, will be well used in optoelectronic devices.

  4. High-resolution XPS studies of electrochemically synthesized conducting polyaniline films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S.N. (Dept. de Chimie Appliquee et Genie Chimique, Univ. Claude Bernard, 69 - Villeurbanne (France) Lab. de Physique de la Matiere, Inst. National des Sciences Appliquees de Lyon, 69 - Villeurbanne (France)); Gaillard, F.; Bouyssoux, G. (Dept. de Chimie Appliquee et Genie Chimique, Univ. Claude Bernard, 69 - Villeurbanne (France)); Sartre, A. (Science et Surface S.A., 69 - Charbonnieres (France))

    1990-05-01

    The electronic structure of electrochemically synthesized acceptor-doped, KOH-treated and electrochemically reduced polyaniline films has been examined by a high-resolution XPS technique. The deconvoluted core level C 1s and N 1s XPS lines show clear evidence of the existence of imine, amine and multiple charged states of N, which can be conveniently explained by assuming protonated and bipolaron states in the polymer. The shake-up satellites observed in the N 1s and C 1s spectra are interpreted in terms of a {pi} {yields} {pi}{sup *} transition accompanying core ionization. The trend of evolution of shake-up intensity for these films agree with the principle of {pi}-electron-donating power of the nitrogen functionality. (orig.).

  5. [Efficiency of two motivational interventions for adolescent smokers (brief and intensive) conducted in high schools].

    Science.gov (United States)

    Pérez-Milena, Alejandro; Navarreteguillén, Ana Belén; Mesa-Gallardo, María Inmaculada; Martínez Pérez, Rocío; Leal-Helmling, Francisco Javier; Pérez-Fuentes, Carlos

    2012-01-01

    We set out to determine the efficiency of two motivational interventions (brief and intensive) in adolescent smokers, based on obtaining cognitive dissonance and seeking to help them stop smoking. A multicenter randomized experimental study was carried out at five high schools. Individual anti-smoking interventions were applied at the schools, the participants being adolescent smokers (≤ 20 years) who wished to quit smoking. Exclusion criteria were use of anti-smoking drugs, severe psychiatric illness and pregnancy. Informed consent was obtained and a questionnaire recorded demographic variables and alcohol/tobacco/other drug use. Two motivational interventions were carried out at each school by GP, in accordance with a stratified randomization procedure: intensive (four sessions, progressive reduction of smoking) and brief (single session, immediate cessation of smoking). Smoking abstinence was confirmed by co-oximetry at 1, 6 and 12 months after the intervention, with analysis by intention to treat. A total of 92 adolescents participated, with a mean age of 15.4 ± 1.0 years; no differences at the beginning of the interventions: daily smokers accounted for 82% of the sample, with low dependence (62%) and moderate-high motivation to quit smoking (88%). Seventy-eight per cent used alcohol and 21% other drugs. Family functioning and social support were normal in the majority. 47% received the intensive intervention. Abstinence was achieved by 64% ± 5.0 by the first month (20% better in intensive intervention), 42% ± 5.2 by the sixth month and 27% ± 4.6 by the twelfth month (without differences). The brief intervention appears to be more efficient, while more research is needed to determine the profile of those adolescents who would benefit from intensive intervention.

  6. Facile Preparation of Highly Conductive Metal Oxides by Self-Combustion for Solution-Processed Thermoelectric Generators.

    Science.gov (United States)

    Kang, Young Hun; Jang, Kwang-Suk; Lee, Changjin; Cho, Song Yun

    2016-03-02

    Highly conductive indium zinc oxide (IZO) thin films were successfully fabricated via a self-combustion reaction for application in solution-processed thermoelectric devices. Self-combustion efficiently facilitates the conversion of soluble precursors into metal oxides by lowering the required annealing temperature of oxide films, which leads to considerable enhancement of the electrical conductivity of IZO thin films. Such enhanced electrical conductivity induced by exothermic heat from a combustion reaction consequently yields high performance IZO thermoelectric films. In addition, the effect of the composition ratio of In to Zn precursors on the electrical and thermoelectric properties of the IZO thin films was investigated. IZO thin films with a composition ratio of In:Zn = 6:2 at the low annealing temperature of 350 °C showed an enhanced electrical conductivity, Seebeck coefficient, and power factor of 327 S cm(-1), 50.6 μV K(-1), and 83.8 μW m(-1) K(-2), respectively. Moreover, the IZO thin film prepared at an even lower temperature of 300 °C retained a large power factor of 78.7 μW m(-1) K(-2) with an electrical conductivity of 168 S cm(-1). Using the combustive IZO precursor, a thermoelectric generator consisting of 15 legs was fabricated by a printing process. The thermoelectric array generated a thermoelectric voltage of 4.95 mV at a low temperature difference (5 °C). We suggest that the highly conductive IZO thin films by self-combustion may be utilized for fabricating n-type flexible printed thermoelectric devices.

  7. Coexistence of high-T(c) ferromagnetism and n-type electrical conductivity in FeBi2Se4.

    Science.gov (United States)

    Ranmohotti, Kulugammana G S; Djieutedjeu, Honore; Lopez, Juan; Page, Alexander; Haldolaarachchige, Neel; Chi, Hang; Sahoo, Pranati; Uher, Ctirad; Young, David; Poudeu, Pierre F P

    2015-01-21

    The discovery of n-type ferromagnetic semiconductors (n-FMSs) exhibiting high electrical conductivity and Curie temperature (Tc) above 300 K would dramatically improve semiconductor spintronics and pave the way for the fabrication of spin-based semiconducting devices. However, the realization of high-Tc n-FMSs and p-FMSs in conventional high-symmetry semiconductors has proven extremely difficult due to the strongly coupled and interacting magnetic and semiconducting sublattices. Here we show that decoupling the two functional sublattices in the low-symmetry semiconductor FeBi2Se4 enables unprecedented coexistence of high n-type electrical conduction and ferromagnetism with Tc ≈ 450 K. The structure of FeBi2Se4 consists of well-ordered magnetic sublattices built of [FenSe4n+2]∞ single-chain edge-sharing octahedra, coherently embedded within the three-dimensional Bi-rich semiconducting framework. Magnetotransport data reveal a negative magnetoresistance, indicating spin-polarization of itinerant conducting electrons. These findings demonstrate that decoupling magnetic and semiconducting sublattices allows access to high-Tc n- and p-FMSs as well as helps unveil the mechanism of carrier-mediated ferromagnetism in spintronic materials.

  8. Post stimulus effects of high frequency biphasic electrical current on a fibre's conductibility in isolated frog nerves

    Science.gov (United States)

    Liu, Hailong; Zhu, Linlin; Sheng, Shulei; Sun, Lifei; Zhou, Hongmin; Tang, Hong; Qiu, Tianshuang

    2013-06-01

    Objective. High frequency biphasic (HFB) electrical currents are widely used in nerve blocking studies. Their safety margins largely remain unknown and need to be investigated. Approach. This study, exploring the post stimulus effects of HFB electrical currents on a nerve's conductibility, was performed on bullfrog sciatic nerves. Both compound action potentials (CAPs) and differential CAPs (DCAPs, i.e. control CAPs subtracted by CAPs following HFB currents) were obtained, and N1 and N2 components, which were the first and second upward components of DCAPs, were used for analyses of the effects introduced by HFB electrical stimulation. Main results. First, HFB currents of 10 kHz at a completely blocking threshold were applied for 5 s. The maximum amplitudes and conducting velocities of the CAPs were significantly (P conductibility and the appearances of new delayed conductions. Decreases of N1 amplitudes along time, regarded as the recovery of the nerve's conductibility, exhibited two distinct phases: a fast one lasting several seconds and a slow one lasting longer than 5 min. Further tests showed a linear relationship between the HFB stimulation durations and recovering periods of N1 amplitudes. Supra-threshold blocking did not cause higher N1 amplitudes. Significance. This study indicates that HFB electrical currents lead to long lasting post stimulus reduction of a nerve's conductibility, which might relate to potential nerve injuries. A possible mechanism, focusing on changes in intracellular and periaxonal ionic concentrations, was proposed to underlie the reduction of the nerve's conductibility and potential nerve injuries. Greater caution and stimulation protocols with greater safety margins should be explored when utilizing HFB electrical current to block nerve conductions.

  9. High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library

    Science.gov (United States)

    d'Acremont, Quentin; Pernot, Gilles; Rampnoux, Jean-Michel; Furlan, Andrej; Lacroix, David; Ludwig, Alfred; Dilhaire, Stefan

    2017-07-01

    A High-Throughput Time-Domain ThermoReflectance (HT-TDTR) technique was developed to perform fast thermal conductivity measurements with minimum user actions required. This new setup is based on a heterodyne picosecond thermoreflectance system. The use of two different laser oscillators has been proven to reduce the acquisition time by two orders of magnitude and avoid the experimental artefacts usually induced by moving the elements present in TDTR systems. An amplitude modulation associated to a lock-in detection scheme is included to maintain a high sensitivity to thermal properties. We demonstrate the capabilities of the HT-TDTR setup to perform high-throughput thermal analysis by mapping thermal conductivity and interface resistances of a ternary thin film silicide library FexSiyGe100-x-y (20 analysis areas of different ternary alloy compositions.

  10. Conductive Polymer Binder-Enabled SiO-SnxCoyCz Anode for High-Energy Lithium-Ion Batteries.

    Science.gov (United States)

    Zhao, Hui; Fu, Yanbao; Ling, Min; Jia, Zhe; Song, Xiangyun; Chen, Zonghai; Lu, Jun; Amine, Khalil; Liu, Gao

    2016-06-01

    A SiOSnCoC composite anode is assembled using a conductive polymer binder for the application in next-generation high energy density lithium-ion batteries. A specific capacity of 700 mAh/g is achieved at a 1C (900 mA/g) rate. A high active material loading anode with an areal capacity of 3.5 mAh/cm(2) is demonstrated by mixing SiOSnCoC with graphite. To compensate for the lithium loss in the first cycle, stabilized lithium metal powder (SLMP) is used for prelithiation; when paired with a commercial cathode, a stable full cell cycling performance with a 86% first cycle efficiency is realized. By achieving these important metrics toward a practical application, this conductive polymer binder/SiOSnCoC anode system presents great promise to enable the next generation of high-energy lithium-ion batteries.

  11. Self-assembly of highly charged polyelectrolyte complexes with superior proton conductivity and methanol barrier properties for fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaztuerk, Serpil; Deligoez, Hueseyin; Yilmazoglu, Mesut; Damyan, Hakan; Oeksuezoemer, Faruk; Koc, S. Naci; Durmus, Ali; Ali Guerkaynak, M. [Istanbul University, Engineering Faculty, Chemical Engineering Dept., 34320 Avcilar-Istanbul (Turkey)

    2010-02-01

    The paper is concerned with the formation of Layer-by-Layer (LbL) self-assembly of highly charged polyvinyl sulfate potassium salt (PVS) and polyallylamine hydrochloride (PAH) on Nafion membrane to obtain the multilayered composite membranes with both high proton conductivity and methanol blocking properties. Also, the influences of the salt addition to the polyelectrolyte solutions on membrane selectivity (proton conductivity/methanol permeability) are discussed in terms of controlled layer thickness and charge density. The deposition of the self-assembly of PAH/PVS is confirmed by SEM analysis and it is observed that the polyelectrolyte layers growth on each side of Nafion membrane regularly. (PAH/PVS){sub 10}-Na{sup +} and (PAH/PVS){sub 10}-H{sup +} with 1.0 M NaCl provide 55.1 and 43.0% reduction in lower methanol permittivity in comparison to pristine Nafion, respectively, while the proton conductivities are 12.4 and 78.3 mS cm{sup -1}. Promisingly, it is found that the membrane selectivity values ({phi}) of all multilayered composite membranes in H{sup +} form are much higher than those of Na{sup +} form and perfluorosulfonated ionomers reported in the literature. These encouraging results indicate that composite membranes having both superior proton conductivity and improved methanol barrier properties can be prepared from highly charged polyelectrolytes including salt for fuel cell applications. (author)

  12. Highly conductive bridges between graphite spheres to improve the cycle performance of a graphite anode in lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, Yoga-machi 1341, Saga 840-0047 (Japan); Umeno, Tatsuo; Mizuma, Koutarou [Research Center, Mitsui Mining Co. Ltd., Hibiki-machi 1-3, Wakamatsu-ku, Kitakyushu 808-0021 (Japan); Yoshio, Masaki [Advanced Research Center, Saga University, Yoga-machi 1341, Saga 840-0047 (Japan)

    2008-01-10

    Spherical carbon-coated natural graphite (SCCNG) is a promising anode material for lithium-ion batteries, but the smooth surface of graphite spheres is difficult to wet with an aqueous binder solution, and lacks electrical contacts. As a result, the cycle performance of such a graphite anode material is not satisfactory. An effective method has been introduced to tightly connect adjacent SCCNG particles by a highly conductive binder, viz. acetylene black bridges. The effect of the conductive bridges on the cyclability of SCCNG electrode has been investigated. (author)

  13. Printable highly conductive conjugated polymer sensitized ZnO NCs as cathode interfacial layer for efficient polymer solar cells.

    Science.gov (United States)

    Liu, Jian; Wu, Jiang; Shao, Shuyan; Deng, Yunfeng; Meng, Bin; Xie, Zhiyuan; Geng, Yanhou; Wang, Lixiang; Zhang, Fengling

    2014-06-11

    We report a facile way to produce printable highly conductive cathode interfacial layer (CIL) for efficient polymer solar cells (PSCs) by sensitizing ZnO nanocrystals (NCs) with a blue fluorescent conjugated polymer, poly(9, 9-bis-(6'-diethoxylphosphorylhexyl) fluorene) (PFEP). Herein, PFEP plays dual distinctive roles in the composite. Firstly, PFEP chains can effectively block the aggregation of ZnO NCs, leading to uniform and smooth film during solution processing via assembly on ZnO NC surfaces through their pending phosphonate groups. Secondly, PFEP can greatly improve the conductivity of ZnO NCs by charge transfer doping, that is the charge transfer from the sensitizer driven by electron-chemical potential equilibrium, which could be even more pronounced under light illumination because of light excitation of PFEP sensitizer. The increased conductivity in ZnO-PFEP layer renders more efficient electron transport and extraction compared to pristine ZnO layer. This ZnO-PFEP CIL was successfully applied to PSCs based on three polymer donor systems with different band-gaps, and efficiency enhancements from 44 to 70% were observed compared to those PSCs with pristine ZnO CIL. The highest efficiency of 7.56% was achieved in P(IID-DTC):PC70BM-based PSCs by using ZnO-PFEP film as CIL. Moreover, the enhanced conductivity due to the charge-transfer doping effect allows thick ZnO-PFEP film to be used as CIL in high-performance PSCs. Both the high conductivity and good film-forming properties of ZnO-PFEP CIL are favorable for large-scale printable PSCs, which is also verified by high-efficiency PSCs with ZnO-PFEP CIL fabricated using doctor-blading, a large-scale processing technique. The work provides an efficient printable cathode interfacial material for efficient PSCs.

  14. Minor-alloyed Cu-Ni-Si alloys with high hardness and electric conductivity designed by a cluster formula approach

    Directory of Open Access Journals (Sweden)

    Dongmei Li

    2017-08-01

    Full Text Available Cu-Ni-Si alloys are widely used due to their good electrical conductivities in combination with high strength and hardness. In the present work, minor-alloying with M = (Cr, Fe, Mo, Zr was conducted for the objective of further improving their hardness while maintaining their conductivity level. A cluster-plus-glue-atom model was introduced to design the compositions of M-alloyed Cu-Ni-Si alloys, in which an ideal composition formula [(Ni,Si,M-Cu12]Cu3 (molar proportion was proposed. To guarantee the complete precipitation of solute elements in fine δ-Ni2Si precipitates, the atomic ratio of (Ni,M/Si was set as 2/1. Thus the designed alloy series of Cu93.75(Ni/Zr3.75Si2.08(Cr/Fe/Mo0.42 (at% were arc-melted into ingots under argon atmosphere, and solid-solutioned at 950 °C for 1 h plus water quenching and then aged at 450 °C for different hours. The experimental results showed that these designed alloys exhibit high hardness (HV > 1.7 GPa and good electrical conductivities (≥ 35% IACS. Specifically, the quinary Cu93.75Ni3.54Si2.08(Cr/Fe0.42Zr0.21 alloys (Cu-3.32Ni-0.93Si-0.37(Cr/Fe−0.30Zr wt% possess both a high hardness with HV = 2.5–2.7 GPa, comparable to the high-strength KLFA85 alloy (Cu-3.2Ni-0.7Si-1.1Zn wt%, HV = 2.548 GPa, and a good electrical conductivity (35–36% IACS.

  15. Distribution of high-conductance calcium-activated potassium channels in rat vestibular epithelia.

    Science.gov (United States)

    Schweizer, Felix E; Savin, David; Luu, Cindy; Sultemeier, David R; Hoffman, Larry F

    2009-11-10

    Voltage- and calcium-activated potassium channels (BK) are important regulators of neuronal excitability. BK channels seem to be crucial for frequency tuning in nonmammalian vestibular and auditory hair cells. However, there are a paucity of data concerning BK expression in mammalian vestibular hair cells. We therefore investigated the localization of BK channels in mammalian vestibular hair cells, specifically in rat vestibular neuroepithelia. We find that only a subset of hair cells in the utricle and the crista ampullaris express BK channels. BK-positive hair cells are located mainly in the medial striolar region of the utricle, where they constitute at most 12% of hair cells, and in the central zone of the horizontal crista. A majority of BK-positive hair cells are encapsulated by a calretinin-positive calyx defining them as type I cells. The remainder are either type I cells encapsulated by a calretinin-negative calyx or type II hair cells. Surprisingly, the number of BK-positive hair cells in the utricle peaks in juvenile rats and declines in early adulthood. BK channels were not found in vestibular afferent dendrites or somata. Our data indicate that BK channel expression in the mammalian vestibular system differs from the expression pattern in the mammalian auditory and the nonmammalian vestibular system. The molecular diversity of vestibular hair cells indicates a functional diversity that has not yet been fully characterized. The predominance of BK-positive hair cells within the medial striola of juvenile animals suggests that they contribute to a scheme of highly lateralized coding of linear head movements during late development.

  16. Highly-wrinkled reduced graphene oxide-conductive polymer fibers for flexible fiber-shaped and interdigital-designed supercapacitors

    Science.gov (United States)

    Li, Bo; Cheng, Jianli; Wang, Zhuanpei; Li, Yinchuan; Ni, Wei; Wang, Bin

    2018-02-01

    Flexible supercapacitors have attracted great interest due to outstanding flexibility and light weight. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fibers have the great potential in using as electrodes for flexible supercapacitors due to the good flexibility. However, the reported conductivity and specific capacitance of these PEDOT: PSS fibers are not very high, which limit their electrochemical performances. In this work, composite fibers of reduced graphene oxide(rGO)-PEDOT: PSS with a highly-wrinkled structure on the surface and pores inside are prepared by wet spinning. The fibers with different ratios of graphene to PEDOT:PSS show a distinctly enhanced conductivity up to ca. 590 S·cm-1 and high strength up to ca. 18.4 MPa. Meanwhile, the composite fibers show an improved electrochemical performances, including a high specific areal capacitance of 131 mF cm-2 and high specific areal energy density of 4.55 μWh·cm-2. The flexible supercapacitors including fiber-shaped supercapacitors and interdigital designed supercapacitors not only could work in different bending states without obvious capacitance decay, but also have small leakage current. The interdigital design can further improve the performances of composite fibers with high capacitance and high utilization compared with traditional parallel connected structure.

  17. Highly Conductive Cu-Cu Joint Formation by Low-Temperature Sintering of Formic Acid-Treated Cu Nanoparticles.

    Science.gov (United States)

    Liu, Jingdong; Chen, Hongtao; Ji, Hongjun; Li, Mingyu

    2016-12-07

    Highly conductive Cu-Cu interconnections of SiC die with Ti/Ni/Cu metallization and direct bonded copper substrate for high-power semiconductor devices are achieved by the low-temperature sintering of Cu nanoparticles with a formic acid treatment. The Cu-Cu joints formed via a long-range sintering process exhibited good electrical conductivity and high strength. When sintered at 260 °C, the Cu nanoparticle layer exhibited a low resistivity of 5.65 μΩ·cm and the joints displayed a high shear strength of 43.4 MPa. When sintered at 320 °C, the resistivity decreased to 3.16 μΩ·cm and the shear strength increased to 51.7 MPa. The microstructure analysis demonstrated that the formation of Cu-Cu joints was realized by metallurgical bonding at the contact interface between the Cu pad and the sintered Cu nanoparticle layer, and the densely sintered layer was composed of polycrystals with a size of hundreds of nanometers. In addition, high-density twins were found in the interior of the sintered layer, which contributed to the improvement of the performance of the Cu-Cu joints. This bonding technology is suitable for high-power devices operating under high temperatures.

  18. Characterization of Copper Coatings Deposited by High-Velocity Oxy-Fuel Spray for Thermal and Electrical Conductivity Applications

    Science.gov (United States)

    Salimijazi, H. R.; Aghaee, M.; Salehi, M.; Garcia, E.

    2017-11-01

    Copper coatings were deposited on steel substrates by high-velocity oxy-fuel spraying. The microstructure of the feedstock copper powders and free-standing coatings were evaluated by optical and scanning electron microscopy. The x-ray diffraction pattern was utilized to determine phase compositions of powders and coatings. Oxygen content was determined by a LECO-T300 oxygen determiner. The thermal conductivity of the coatings was measured in two directions, through-thickness and in-plane by laser flash apparatus. The electrical resistivity of the coatings was measured by the four-point probe method. Oxygen content of the coatings was two times higher than that of the initial powders (0.35-0.37%). The thermal and electrical conductivities of the coatings were different depending on the direction of the measurement. The thermal and electrical conductivity of the coatings improved after annealing for 6 h at a temperature of 600°C.

  19. Toward practical application of functional conductive polymer binder for a high-energy lithium-ion battery design.

    Science.gov (United States)

    Zhao, Hui; Wang, Zhihui; Lu, Peng; Jiang, Meng; Shi, Feifei; Song, Xiangyun; Zheng, Ziyan; Zhou, Xin; Fu, Yanbao; Abdelbast, Guerfi; Xiao, Xingcheng; Liu, Zhi; Battaglia, Vincent S; Zaghib, Karim; Liu, Gao

    2014-11-12

    Silicon alloys have the highest specific capacity when used as anode material for lithium-ion batteries; however, the drastic volume change inherent in their use causes formidable challenges toward achieving stable cycling performance. Large quantities of binders and conductive additives are typically necessary to maintain good cell performance. In this report, only 2% (by weight) functional conductive polymer binder without any conductive additives was successfully used with a micron-size silicon monoxide (SiO) anode material, demonstrating stable and high gravimetric capacity (>1000 mAh/g) for ∼500 cycles and more than 90% capacity retention. Prelithiation of this anode using stabilized lithium metal powder (SLMP) improves the first cycle Coulombic efficiency of a SiO/NMC full cell from ∼48% to ∼90%. The combination enables good capacity retention of more than 80% after 100 cycles at C/3 in a lithium-ion full cell.

  20. A novel conductivity mechanism of highly disordered carbon systems based on an investigation of graph zeta function

    Science.gov (United States)

    Matsutani, Shigeki; Sato, Iwao

    2017-09-01

    In the previous report (Matsutani and Suzuki, 2000 [21]), by proposing the mechanism under which electric conductivity is caused by the activational hopping conduction with the Wigner surmise of the level statistics, the temperature-dependent of electronic conductivity of a highly disordered carbon system was evaluated including apparent metal-insulator transition. Since the system consists of small pieces of graphite, it was assumed that the reason why the level statistics appears is due to the behavior of the quantum chaos in each granular graphite. In this article, we revise the assumption and show another origin of the Wigner surmise, which is more natural for the carbon system based on a recent investigation of graph zeta function in graph theory. Our method can be applied to the statistical treatment of the electronic properties of the randomized molecular system in general.