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Sample records for low-temperature relaxation processes

  1. Low-temperature relaxation process and memory effect in a nonstoichiometric magnetite of Fe3-δO4 with δ=0.03

    NASA Astrophysics Data System (ADS)

    Xiang, J. Y.; Lv, Y. F.; Wen, F. S.; Hu, W. T.; Lv, W. M.; Liu, Z. Y.

    2014-06-01

    The low-temperature relaxation process has been investigated in a nonstoichiometric magnetite Fe3-δO4 with δ=0.03. Far below the Verwey transition at TV=90 K, the measurements of AC susceptibility χac display a frequency-dependent anomaly of the shoulder in χ' accompanied with the peak in χ″ and their weak thermal hysteresis. These low-temperature anomalies are related to a thermal relaxation process owing to the domain-wall mobility and extra electron exchange inside the walls. Moreover, the low-temperature relaxation process is revealed to exhibit strong memory effect via field-cooling magnetization measurements. Interesting discrete sudden jumps are observed during the logarithmic decay of magnetization in zero field with aging time, indicating the spontaneous magnetization reversals via adjustment of domain configuration.

  2. Low-temperature relaxations in amorphous polyolefins

    NASA Technical Reports Server (NTRS)

    Hiltner, A.; Baer, E.; Martin, J. R.; Gillham, J. K.

    1974-01-01

    The dynamic mechanical relaxation behavior of two series of amorphous polyolefins, was investigated from 4.2 K to the glass transition. Most of the polymers show a damping maximum or plateau in the 40 to 50 K region. Various mechanisms which have been suggested for cryogenic relaxations in amorphous polymers are considered as they might relate to the polyolefins. Two secondary relaxation processes above 80 K are distinguished. A relaxation at about 160 K (beta) in the second and third member of each series is associated with restricted blackbone motion. This process requires a certain degree of chain flexibility since it is not observed in the first member of each series. A lower temperature process (gamma) is observed in each member of the second series and is attributed to motion of the ethyl side group.

  3. Structural origin of low temperature glassy relaxation in magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, Suvra; Regmi, Rajesh; Lawes, Gavin

    2013-03-01

    Magnetic nanoparticles often exhibit glass-like relaxation features at low temperatures. Here we discuss the effects of doping boron, cobalt, gadolinium and lanthanum on the low temperature magnetic properties of Fe3O4 nanoparticles. We investigated the structure of the nanoparticles using both X-ray diffraction and Raman studies, and find evidence for secondary phase formation in certain samples. We acquired Transmission Electron Microscopic images to give direct information on the morphology and microstructure of these doped nanoparticles. We measured the ac out-of-phase susceptibility (χ//) vs temperature (T) to parameterize the low temperature glassy magnetic relaxation. All samples show low temperature magnetic relaxation, but the amplitude of the signal increases dramatically for certain dopants. We attribute these low temperature frequency-dependent magnetic relaxation features to structural defects, which are enhanced in some of the doped Fe3O4 nanoparticles. These studies also confirm that the low temperature relaxation in nanoparticles arises from single particle effects and are not associated with interparticle interactions.

  4. Stretched Exponential Relaxation of Glasses at Low Temperature

    NASA Astrophysics Data System (ADS)

    Yu, Yingtian; Wang, Mengyi; Zhang, Dawei; Wang, Bu; Sant, Gaurav; Bauchy, Mathieu

    2015-10-01

    The question of whether glass continues to relax at low temperature is of fundamental and practical interest. Here, we report a novel atomistic simulation method allowing us to directly access the long-term dynamics of glass relaxation at room temperature. We find that the potential energy relaxation follows a stretched exponential decay, with a stretching exponent β =3 /5 , as predicted by Phillips's diffusion-trap model. Interestingly, volume relaxation is also found. However, it is not correlated to the energy relaxation, but it is rather a manifestation of the mixed alkali effect.

  5. Low temperature dielectric relaxation study of aqueous solutions of diethylsulfoxide

    NASA Astrophysics Data System (ADS)

    Gabrielyan, Liana; Markarian, Shiraz; Lunkenheimer, Peter; Loidl, Alois

    2014-11-01

    In the present work, dielectric spectra of mixtures of diethylsulfoxide (DESO) and water are presented, covering a concentration range of 0.2-0.3 molar fraction of DESO. The measurements were performed at frequencies between 1Hz and 10MHz and for temperatures between 150 and 300K. It is shown that DESO/water mixtures have strong glass-forming abilities. The permittivity spectra in these mixtures reveal a single relaxation process. It can be described by the Havriliak-Negami relaxation function and its relaxation times follow the Vogel-Fulcher-Tammann law, thus showing the typical signatures of glassy dynamics. The concentration dependence of the relaxation parameters, like fragility, broadening, and glass temperature, are discussed in detail.

  6. Picosecond spin relaxation in low-temperature-grown GaAs

    SciTech Connect

    Uemura, M.; Honda, K.; Yasue, Y.; Tackeuchi, A.; Lu, S. L.; Dai, P.

    2014-03-24

    The spin relaxation process of low-temperature-grown GaAs is investigated by spin-dependent pump and probe reflectance measurements with a sub-picosecond time resolution. Two very short carrier lifetimes of 2.0 ps and 28 ps, which can be attributed to nonradiative recombinations related to defects, are observed at 10 K. The observed spin polarization shows double exponential decay with spin relaxation times of 46.2 ps (8.0 ps) and 509 ps (60 ps) at 10 K (200 K). The observed picosecond spin relaxation, which is considerably shorter than that of conventional GaAs, indicates the strong relevance of the Elliott-Yafet process as the spin relaxation mechanism. For the first (second) spin relaxation component, the temperature and carrier density dependences of the spin relaxation time indicate that the Bir-Aronov-Pikus process is also effective at temperatures between 10 K and 77 K, and that the D'yakonov-Perel’ process is effective between 125 K (77 K) and 200 K.

  7. Low temperature waste form process intensification

    SciTech Connect

    Fox, K. M.; Cozzi, A. D.; Hansen, E. K.; Hill, K. A.

    2015-09-30

    This study successfully demonstrated process intensification of low temperature waste form production. Modifications were made to the dry blend composition to enable a 50% increase in waste concentration, thus allowing for a significant reduction in disposal volume and associated costs. Properties measurements showed that the advanced waste form can be produced using existing equipment and processes. Performance of the waste form was equivalent or better than the current baseline, with approximately double the amount of waste incorporation. The results demonstrate the feasibility of significantly accelerating low level waste immobilization missions across the DOE complex and at environmental remediation sites worldwide.

  8. Low temperature alteration processes affecting ultramafic bodies

    USGS Publications Warehouse

    Nesbitt, H.W.; Bricker, O.P.

    1978-01-01

    At low temperatures, in the presence of an aqueous solution, olivine and orthopyroxene are not stable relative to the hydrous phases brucite, serpentine and talc. Alteration of dunite and peridotite to serpentine or steatite bodies must therefore proceed via non-equilibrium processes. The compositions of natural solutions emanating from dunites and peridotites demonstrate that the dissolution of forsterite and/or enstatite is rapid compared with the precipitation of the hydrous phases; consequently, dissolution of anhydrous minerals controls the chemistry of such solutions. In the presence of an aqueous phase, precipitation of hydrous minerals is the rate-controlling step. Brucite-bearing and -deficient serpentinites alter at low temperature by non-equilibrium processes, as evidenced by the composition of natural solutions from these bodies. The solutions approach equilibrium with the least stable hydrous phase and, as a consequence, are supersaturated with other hydrous phases. Dissolution of the least stable phase is rapid compared to precipitation of other phases, so that the dissolving mineral controls the solution chemistry. Non-equilibrium alteration of anhydrous ultramafic bodies continues until at least one anhydrous phase equilibrates with brucite, chrysotile or talc. The lowest temperature (at a given pressure) at which this happens is defined by the reaction: 3H2O + 2Mg2SiO4 ??? Mg3Si2O5(OH)4 + Mg(OH)2 (Johannes, 1968, Contrib. Mineral. Petrol. 19, 309-315) so that non-equilibrium alteration may occur well into greenschist facies metamorphic conditions. ?? 1978.

  9. Vibrational relaxation of diatomic molecules in solids at low temperatures

    NASA Technical Reports Server (NTRS)

    Halcomb, L. L.; Diestler, D. J.

    1984-01-01

    The application of a hemiquantal method to the specific problem of the vibrational relaxation of a diatomic molecule embedded in a one dimensional lattice is presented. The vectorization of a CYBER 205 algorithm which integrates the 1,000 to 10,000 simultaneous hemiquantal differential equations is examined with comments on optimization. Results of the simulations are briefly discussed.

  10. Structural origin for low-temperature relaxation features in magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, S. S.; Regmi, R.; Lawes, G.

    2013-08-01

    In addition to superparamagnetic relaxation associated with coherent spin reversal, magnetic nanoparticles often also exhibit additional relaxation features in the magnetic dissipation at low temperatures. Our studies show that the incorporation of boron, gadolinium and lanthanum into iron oxide (Fe3O4) nanoparticles substantially enhances these low-temperature magnetic relaxation properties. The structural and morphological studies of these nanoparticles were conducted using x-ray diffraction, transmission electron microscopy and Raman spectroscopy. The doped samples have retained the crystal structure of the parent Fe3O4 nanoparticles, although the shape and size of some of the nanoparticle samples have changed. Using ac magnetic susceptibility measurements, we parameterized the low-temperature magnetic features, with the amplitude of the associated magnetic relaxation showing a dramatic increase for certain dopants. The enhanced frequency-dependent magnetic relaxation features can be attributed to structural, rather than magnetic, defects in these doped Fe3O4 nanoparticles. These results strongly suggest that the low-temperature magnetic relaxation typically observed in magnetic nanoparticles is a single-particle effect produced by structural defects and is not significantly influenced by interparticle interactions.

  11. Low-temperature rotational relaxation in gaseous H2 and D2

    NASA Technical Reports Server (NTRS)

    Ramaswamy, R.; Green, S.; Rabitz, H.

    1977-01-01

    Various potentials have been used for generating scattering cross sections for rotational transitions in hydrogen isotope systems. Low-temperature rates were calculated and the relaxation times compared with the results of sound absorption experiments. It is seen that the existing potentials could still be improved since they do not exactly reproduce the experimental results.

  12. Achievement of high nuclear spin polarization using lanthanides as low-temperature NMR relaxation agents.

    PubMed

    Peat, David T; Horsewill, Anthony J; Köckenberger, Walter; Perez Linde, Angel J; Gadian, David G; Owers-Bradley, John R

    2013-05-28

    Many approaches are now available for achieving high levels of nuclear spin polarization. One of these methods is based on the notion that as the temperature is reduced, the equilibrium nuclear polarization will increase, according to the Boltzmann distribution. The main problem with this approach is the length of time it may take to approach thermal equilibrium at low temperatures, since nuclear relaxation times (characterized by the spin-lattice relaxation time T1) can become very long. Here, we show, by means of relaxation time measurements of frozen solutions, that selected lanthanide ions, in the form of their chelates with DTPA, can act as effective relaxation agents at low temperatures. Differential effects are seen with the different lanthanides that were tested, holmium and dysprosium showing highest relaxivity, while gadolinium is ineffective at temperatures of 20 K and below. These observations are consistent with the known electron-spin relaxation time characteristics of these lanthanides. The maximum relaxivity occurs at around 10 K for Ho-DTPA and 20 K for Dy-DTPA. Moreover, these two agents show only modest relaxivity at room temperature, and can thus be regarded as relaxation switches. We conclude that these agents can speed up solid state NMR experiments by reducing the T1 values of the relevant nuclei, and hence increasing the rate at which data can be acquired. They could also be of value in the context of a simple low-cost method of achieving several-hundred-fold improvements in polarization for experiments in which samples are pre-polarized at low temperatures, then rewarmed and dissolved immediately prior to analysis. PMID:23588269

  13. Low temperature glassy relaxation in rare earth doped Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Laha, Suvra; Lawes, Gavin

    2012-10-01

    Magnetic nanoparticles typically exhibit glassy relaxation at low temperature, which can be affected by doping. Gadolinium and Lanthanum doped Fe3O4 nanoparticles were synthesized using a chemical co-precipitation method. The structural and optical properties of these nanoparticles were characterized by using Transmission Electron Microscope (TEM) and the Raman spectroscopy. The TEM images show the formation of nanoparticles of size ranging between 12-14 nm and Raman spectra are consistent with the formation of Fe3O4. AC magnetic measurements were also conducted on these nanoparticles. From the ac out-of-phase susceptibility (χ//) vs temperature (T) graphs, it is observed that the doped nanoparticles show larger amplitude relaxation peaks at low temperature as compared to the undoped particles. These magnetic relaxation features develop roughly between 25K to 35K and show frequency dependence. The increased magnetic relaxation at low temperatures can be attributed to structural defects which may arise due to the doping of lanthanides in Fe3O4 nanoparticles.

  14. Membrane Separation Processes at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde

    2002-01-01

    The primary focus of Kennedy Space Center's gas separation activities has been for carbon dioxide, nitrogen, and argon used in oxygen production technologies for Martian in-situ resource utilization (ISRU) projects. Recently, these studies were expanded to include oxygen for regenerative life support systems. Since commercial membrane systems have been developed for separation of carbon dioxide, nitrogen, and oxygen, initially the studies focused on these membrane systems, but at lower operating temperatures and pressures. Current investigations art examining immobilized liquids and solid sorbents that have the potential for higher selectivity and lower operating temperatures. The gas separation studies reported here use hollow fiber membranes to separate carbon dioxide, nitrogen, and argon in the temperature range from 230 to 300 K. Four commercial membrane materials were used to obtain data at low feed and permeate pressures. These data were used with a commercial solution-diffusion modeling tool to design a system to prepare a buffer gas from the byproduct of a process to capture Martian carbon dioxide. The system was designed to operate, at 230 K with a production rate 0.1 sLpm; Feed composition 30% CO2, 44% N2, and 26% Ar; Feed pressure 104 kPa (780); and Permeate pressure 1 kPa (6 torr); Product concentration 600 ppm CO2. This new system was compared with a similar system designed to operate at ambient temperatures (298 K). The systems described above, along with data, test apparatus, and models are presented.

  15. Relaxation dynamics and exciton energy transfer in the low-temperature phase of MEH-PPV

    SciTech Connect

    Consani, Cristina; Koch, Federico; Panzer, Fabian; Unger, Thomas; Köhler, Anna; Brixner, Tobias

    2015-06-07

    Understanding the effects of aggregation on exciton relaxation and energy transfer is relevant to control photoinduced function in organic electronics and photovoltaics. Here, we explore the photoinduced dynamics in the low-temperature aggregated phase of a conjugated polymer by transient absorption and coherent electronic two-dimensional (2D) spectroscopy. Coherent 2D spectroscopy allows observing couplings among photoexcited states and discriminating band shifts from homogeneous broadening, additionally accessing the ultrafast dynamics at various excitation energies simultaneously with high spectral resolution. By combining the results of the two techniques, we differentiate between an initial exciton relaxation, which is not characterized by significant exciton mobility, and energy transport between different chromophores in the aggregate.

  16. Low temperature dielectric relaxation and charged defects in ferroelectric thin films

    SciTech Connect

    Artemenko, A.; Payan, S.; Rousseau, A.; Arveux, E.; Maglione, M.; Levasseur, D.; Guegan, G.

    2013-04-15

    We report a dielectric relaxation in BaTiO{sub 3}-based ferroelectric thin films of different composition and with several growth modes: sputtering (with and without magnetron) and sol-gel. The relaxation was observed at cryogenic temperatures (T < 100 K) for frequencies from 100 Hz up to 10 MHz. This relaxation activation energy is always lower than 200 meV and is very similar to the relaxation that we reported in the parent bulk perovskites. Based on our Electron Paramagnetic Resonance (EPR) investigation, we ascribe this dielectric relaxation to the hopping of electrons among Ti{sup 3+}-V(O) charged defects. Being dependent on the growth process and on the amount of oxygen vacancies, this relaxation can be a useful probe of defects in actual integrated capacitors with no need for specific shaping.

  17. Low temperature photoluminescence as a tool to measure strain and relaxation effects in multiple quantum wells.

    NASA Astrophysics Data System (ADS)

    Ait-Ouali, Abderrahmane; Yip, Raymond Y.-F.; Brebner, John; Masut, Remo A.

    1997-03-01

    Low temperature photoluminescence studies have been performed on a series of InAs(x)P(1-x)/InP strained-layer multiple quantum wells grown by low pressure metal -organic vapor phase epitaxy. The As content, x, in these samples ranges from 4.426.4at low concentrations and partially-relaxed at the higher end of the range. The temperature and excitation intensity evolution of the spectra and the shape of the transition at low temperature are consistent with the model for the recombination of excitons localized by potential fluctuations [as proposed by Ouadjaout and Marfaing, Phys. Rev. B46, 7908 (1992)]. This has been used to fit precisely the photoluminescence spectra. The evolution of the model parameters allows us to detect the onset of strain relaxation. The results are consistent with detailed structural analyses of these samples performed using X-ray diffraction and transmission electron microscopy [R. Y.-F. Yip et al., J. Appl. Phys. (in press)].

  18. Empirical relaxation function and spectral density for underdamped vibrations at low temperatures

    NASA Astrophysics Data System (ADS)

    Toutounji, Mohamad

    2009-03-01

    A new relaxation function which accounts for electronic dephasing (electronic phase loss and excited state lifetime) is presented, whose applicability for underdamped motion at low temperatures is examined in detail. This new empirical relaxation function φ(t ) yields linear and nonlinear spectral/temporal profiles that render accurate dephasing time in the underdamped regime. The relaxation function φ(t ) is normally expressed in terms of the coupling functions Mj' and Mj″ on which the time evolution of the vibrational modes in question depends. The corresponding spectral density, which is a central quantity in probing dynamics, is derived and compared to that of the multimode Brownian oscillator model. Derivation and discussion of the new position and momentum autocorrelation functions in terms of our new spectral density are presented. While the position autocorrelation function plays a key role in representing solvation structure in polar or nonpolar medium, the momentum correlation function projects out the molecular vibrational motion. The Liouville space generating function (LGF) for harmonic and anharmonic systems is expressed in terms of our new empirical φ(t ) and spectral density, leading to more physical observation. Several statistical quantities are derived from the position and momentum correlation function, which in turn contribute to LGF. Model calculations reflecting the infinite population decay in the low temperature limit in linear and nonlinear spectroscopic signals are presented. The herein quantum dipole moment correlation function is compared to that derived in [M. Toutounji, J. Chem. Phys. 118, 5319 (2003)] using mixed quantum-classical dynamics framework, yielding reasonable results, in fact identical at higher temperatures. The results herein are found to be informative, useful, and consistent with experiments.

  19. Empirical relaxation function and spectral density for underdamped vibrations at low temperatures.

    PubMed

    Toutounji, Mohamad

    2009-03-01

    A new relaxation function which accounts for electronic dephasing (electronic phase loss and excited state lifetime) is presented, whose applicability for underdamped motion at low temperatures is examined in detail. This new empirical relaxation function phi(t) yields linear and nonlinear spectral/temporal profiles that render accurate dephasing time in the underdamped regime. The relaxation function phi(t) is normally expressed in terms of the coupling functions M(j) (') and M(j) (") on which the time evolution of the vibrational modes in question depends. The corresponding spectral density, which is a central quantity in probing dynamics, is derived and compared to that of the multimode Brownian oscillator model. Derivation and discussion of the new position and momentum autocorrelation functions in terms of our new spectral density are presented. While the position autocorrelation function plays a key role in representing solvation structure in polar or nonpolar medium, the momentum correlation function projects out the molecular vibrational motion. The Liouville space generating function (LGF) for harmonic and anharmonic systems is expressed in terms of our new empirical phi(t) and spectral density, leading to more physical observation. Several statistical quantities are derived from the position and momentum correlation function, which in turn contribute to LGF. Model calculations reflecting the infinite population decay in the low temperature limit in linear and nonlinear spectroscopic signals are presented. The herein quantum dipole moment correlation function is compared to that derived in [M. Toutounji, J. Chem. Phys. 118, 5319 (2003)] using mixed quantum-classical dynamics framework, yielding reasonable results, in fact identical at higher temperatures. The results herein are found to be informative, useful, and consistent with experiments. PMID:19275403

  20. Nonphotochemical hole burning and relaxation dynamics of amorphous solids at low temperature

    SciTech Connect

    Shu, Luchuan.

    1991-12-20

    Nonphotochemcial hole burning (NPHB) is applied to cresyl violet perchlorate (CV) in polyvinyl alcohol (PVOH) films. The results of temperature-dependent NPHB, polarization NPHB, spontaneous hole filing (SPHF) and laser induced hole filling (LIHF) are presented. A new mechanism of NPHB is proposed. The relaxation dynamics of amorphous solids at low temperature is extensively studied and a high degree of positive correlation between hole burning and SPHF has been found. Both NPHB and SPHF can be described with dispersive kinetics theory. A more physically reasonable interpretation of SPHF kinetics is described by a new methodology in which absolute hole filling is considered. The data on absolute hole filling together with the observation of a high degree of positive correlation between the rates of burning and filling indicate that the dominant mechanism for filling is not global spectral diffusion but rather anti-hole reversion.

  1. Employing low-temperature barriers to achieve strain-relaxed and high-performance GaN-based LEDs.

    PubMed

    Lin, Zhiting; Wang, Haiyan; Wang, Wenliang; Lin, Yunhao; Yang, Meijuan; Chen, Shuqi; Li, Guoqiang

    2016-05-30

    The epitaxial structure design of low-temperature barriers has been adopted to promote strain relaxation in multiple quantum well (MQWs) and achieve high-efficient GaN-based light-emitting diodes (LEDs). With these barriers, the relaxation value of wells increases from 0 to 4.59%. The strain-relaxed mechanism of low-temperature barriers is also discussed. The LED chip with the barriers grown at the TMIn flow of 75 sccm and the growth temperature of 830 °C has an optimal strain relaxation value of 1.53% in wells, and exhibits the largest light output power of 63.83 mW at the injection current of 65 mA, which is higher than that of conventional LED (51.89 mW) by 23%. In-depth studies reveal that the optimal low-temperature barriers remarkably promote the strain relaxation in wells without forming large density of crystalline defects. This achievement of high-efficiency LEDs sheds light on the future solid-state lighting applications. PMID:27410111

  2. Low-Temperature Solution Processable Electrodes for Piezoelectric Sensors Applications

    NASA Astrophysics Data System (ADS)

    Tuukkanen, Sampo; Julin, Tuomas; Rantanen, Ville; Zakrzewski, Mari; Moilanen, Pasi; Lupo, Donald

    2013-05-01

    Piezoelectric thin-film sensors are suitable for a wide range of applications from physiological measurements to industrial monitoring systems. The use of flexible materials in combination with high-throughput printing technologies enables cost-effective manufacturing of custom-designed, highly integratable piezoelectric sensors. This type of sensor can, for instance, improve industrial process control or enable the embedding of ubiquitous sensors in our living environment to improve quality of life. Here, we discuss the benefits, challenges and potential applications of piezoelectric thin-film sensors. The piezoelectric sensor elements are fabricated by printing electrodes on both sides of unmetallized poly(vinylidene fluoride) film. We show that materials which are solution processable in low temperatures, biocompatible and environmental friendly are suitable for use as electrode materials in piezoelectric sensors.

  3. Low temperature exfoliation process in hydrogen-implanted germanium layers

    NASA Astrophysics Data System (ADS)

    Ferain, I. P.; Byun, K. Y.; Colinge, C. A.; Brightup, S.; Goorsky, M. S.

    2010-03-01

    The feasibility of transferring hydrogen-implanted germanium to silicon with a reduced thermal budget is demonstrated. Germanium samples were implanted with a splitting dose of 5×1016 H2+ cm-2 at 180 keV and a two-step anneal was performed. Surface roughness and x-ray diffraction pattern measurements, combined with cross-sectional TEM analysis of hydrogen-implanted germanium samples were carried out in order to understand the exfoliation mechanism as a function of the thermal budget. It is shown that the first anneal performed at low temperature (≤150 °C for 22 h) enhances the nucleation of hydrogen platelets significantly. The second anneal is performed at 300 °C for 5 min and is shown to complete the exfoliation process by triggering the formation of extended platelets. Two key results are highlighted: (i) in a reduced thermal budget approach, the transfer of hydrogen-implanted germanium is found to follow a mechanism similar to the transfer of hydrogen-implanted InP and GaAs, (ii) such a low thermal budget (<300 °C) is found to be suitable for directly bonded heterogeneous substrates, such as germanium bonded to silicon, where different thermal expansion coefficients are involved.

  4. Conformational relaxation of a low-temperature protein as probed by photochemical hole burning. Horseradish peroxidase.

    PubMed Central

    Zollfrank, J; Friedrich, J; Vanderkooi, J M; Fidy, J

    1991-01-01

    For the first time, conformational relaxation processes have been measured in a small protein, mesoporphyrin-horseradish peroxidase via their influence on spectral diffusion broadening of holes burnt in the fluorescence excitation spectrum of free base mesoporphyrin. Holes were burnt in three 0----0 bands of different tautomeric forms of the chromophore at 1.5 and 4 K, and the spectral diffusion broadening was measured in temperature cycling experiments between 4 and 30 K. The inhomogeneous linewidth for the tautomeric 0----0 bands was estimated to be 60-70 cm-1; the hole width was found narrow, being in the order of 350 MHz (10(-2) cm-1) at 1.5 K what allowed for an extremely sensitive detection of the conformational changes. Though proteins have many features in common with glasses, the spectral diffusion broadening of photochemical holes under temperature cycling conditions in mesoporphyrin horseradish peroxidase has a very different pattern as a function of temperature. Up to 12 K, the linewidth did not significantly change, then around 14 K; a steplike broadening was observed for all three tautomers, although to a different extent. The total magnitude of line broadening up to 30 K was large and also different for the tautomers. We argue that the difference between the behavior of this protein and that of glassy matrices originate from finite size effects; the protein may be characterized by a small number of TLS, and their distribution may bear discrete features. PMID:2009354

  5. Low-temperature oxidation of magnetite - a humidity sensitive process?

    NASA Astrophysics Data System (ADS)

    Appel, Erwin; Fang, Xiaomin; Herb, Christian; Hu, Shouyun

    2015-04-01

    Extensive multi-parameter palaeoclimate records were obtained from two long-term lacustrine archives at the Tibetan Plateau: the Qaidam basin (2.69-0.08 Ma) and Heqing basin (0.90-0.03 Ma). At present the region of the Qaidam site has an arid climate (<100 mm mean annual precipitation) while the Heqing site is located in the sub-tropical region with monsoonal rainfall. Magnetic properties play a prominent role for palaeoclimate interpretation in both records. Several parameters show a 100 kyr eccentricity cyclicity; in the Qaidam record also the Mid-Pleistocene Transition is seen. Both magnetic records are controlled by different absolute and relative contributions of magnetite and its altered (maghemitized) phases as well as hematite. Weathering conditions likely cause a systematic variation of magnetic mineralogy due to low-temperature oxidation (LTO). Maghemitization is well recognized as an alteration process in submarine basalts but about its relevance for climate-induced weathering in continental environments little is known. Various factors i.e., humidity, temperature, seasonality, duration of specific weathering conditions, and bacterial activity could be responsible for maghemitization (LTO) and transformation to hematite (or goethite) when a critical degree of LTO is reached. These factors may lead to a complex interplay, but one has to note that water acts as an electrolyte for Fe(II) to Fe(III) oxidation at the crystal surface and due to maghemitization-induced lattice shrinking a larger internal particle surface area becomes exposed to oxidation. We suggest that humidity is the most crucial driver for the two studied archives - for the following reasons: (1) The overall parameter variations and catchment conditions are well in agreement with an LTO scenario. (2) In the Qaidam record we observe a direct relationship of a humidity sensitive pollen Ratio with magnetic susceptibility (reflecting the degree of alteration by LTO). (3) In the Heqing record

  6. Ultra-low temperature processing of barium tellurate dielectrics

    NASA Astrophysics Data System (ADS)

    Kwon, Do-Kyun

    Ceramics, metals and polymers have unique electrical properties that are combined for electronic devices and systems. It necessitates lower processing temperatures for ceramics to be compatible with metal and polymer systems. In this thesis, the synthesis, crystal structure, and dielectric properties of barium tellurate are studied for temperatures between 500 and 900°C. Barium tellurate dielectric ceramics (BaTe4O9, BaTe 2O5, BaTe2O6, BaTeO3, BaTeO 4, and Ba2TeO5) are extensively investigated as new LTCC (Low-Temperature Cofired Ceramics) dielectric systems integrated with low resistivity metal electrodes such as silver and aluminum for microwave application. Studies on the phase formation and crystal structure through thermal analyses (Differential Scanning Calorimetry and Thermogravimetric Analysis, DSC-TGA) and X-ray diffraction phase analysis attest that barium tellurates are formed in the temperature range of 500 ˜ 900°C, through the sequential phase formations from Te-rich to Ba-rich phases. The oxygen coordination of the tellurium ion progresses from TeO4 to TeO6 via TeO 3+1 and TeO3 with increasing barium content as confirmed by structural analysis using infrared spectroscopy. High density barium tellurate ceramics are achieved at temperatures as low as 550°C, which provides the potential to be co-fired with low-melting aluminum metal electrodes in LTCC processing. Dielectric permittivity, loss, and temperature stability of barium tellurate dielectric ceramics were measured from 100 Hz to 13 GHz. Barium tellurate ceramics exhibit excellent microwave dielectric properties with intermediate dielectric permittivities and high quality factors (Q). The dielectric properties at microwave frequencies are epsilonr = 17.5, Qxf = 54700 GHz, TCf = -90 ppm/°C for BaTe4O9, epsilonr = 21, Qxf = 50300 GHz, TCf = -51 ppm/°C for BaTe2O6, epsilonr = 10, Qxf = 34000 GHz, TCf = -54 ppm/°C for BaTeO3, and epsilonr = 17, Qx f = 49600 GHz, TCf = -124 ppm/°C for Ba 2TeO5

  7. Inert Anode Life in Low Temperature Reduction Process

    SciTech Connect

    Bradford, Donald R.

    2005-06-30

    The production of aluminum metal by low temperature electrolysis utilizing metal non-consumable anodes and ceramic cathodes was extensively investigated. Tests were performed with traditional sodium fluoride--aluminum fluoride composition electrolytes, potassium fluoride-- aluminum fluoride electrolytes, and potassium fluoride--sodium fluoride--aluminum fluoride electrolytes. All of the Essential First-Tier Requirements of the joint DOE-Aluminum Industry Inert Anode Road Map were achieved and those items yet to be resolved for commercialization of this technology were identified. Methods for the fabrication and welding of metal alloy anodes were developed and tested. The potential savings of energy and energy costs were determined and potential environmental benefits verified.

  8. Low temperature barriers for use with in situ processes

    SciTech Connect

    Kim, Dong Sub; Vinegar, Harold J

    2009-06-16

    A method of forming and maintaining a low temperature zone around at least a portion of a subsurface treatment area is described. The method includes reducing a temperature of heat transfer fluid with a refrigeration system. The heat transfer fluid is circulated through freeze well canisters and placed in a formation around at least a portion of the subsurface treatment area. An initial temperature of the heat transfer fluid supplied to a first freeze well canister is in a range from about -35 .degree. C. to about -55 .degree. C. At least one of the well canisters includes carbon steel. The heat transfer fluid is returned to the refrigeration system.

  9. A Low Temperature Analysis of the Boundary Driven Kawasaki Process

    NASA Astrophysics Data System (ADS)

    Maes, Christian; O'Kelly de Galway, Winny

    2013-12-01

    Low temperature analysis of nonequilibrium systems requires finding the states with the longest lifetime and that are most accessible from other states. We determine these dominant states for a one-dimensional diffusive lattice gas subject to exclusion and with nearest neighbor interaction. They do not correspond to lowest energy configurations even though the particle current tends to zero as the temperature reaches zero. That is because the dynamical activity that sets the effective time scale, also goes to zero with temperature. The result is a non-trivial asymptotic phase diagram, which crucially depends on the interaction coupling and the relative chemical potentials of the reservoirs.

  10. In-reactor stress relaxation of selected metals and alloys at low temperatures

    NASA Astrophysics Data System (ADS)

    Causey, A. R.; Carpenter, G. J. C.; MacEwen, S. R.

    1980-05-01

    Sttess relaxation of bent beam specimens under fast neutron irradiation at 340 and 570 K has been studied for a range of materials, as follows: several stainless steels, a maraged steel, AISI4140, Ni, Inconel X-750, Ti, Zircaloy-2, Zr-2.5% Nb and Zr 3 Al. All specimens were in the annealed or solution-treated condition. Where comparisons were possible, the creep coefficients derived from the stress relaxation tests were found to be consistent with other studies of irradiation-induced creep. The steels showed the lowest rates of stress relaxation; the largest rates were observed with Zr-Nb, Ti and Ni. For most materials, the creep coefficient at 340 K was equal to or greater than that at 570 K. Such weak temperature dependence is not easily reconciled with existing models of irradiation creep based on dislocation climb, such as SIPA or climb-induced glide. Rate theory calculations indicate that because the vacancy mobility becomes very low at the lower temperature, recombination should dominate point defect annealing, resulting in a very low creep rate compared to that at the higher temperature. It is shown that the weak temperature dependence observed experimentally cannot be accounted for by the inclusion of more mobile divacancies in the calculation.

  11. Macro and nano scale modelling of water-water interactions at ambient and low temperature: relaxation and residence times.

    PubMed

    Morón, María Carmen; Prada-Gracia, Diego; Falo, Fernando

    2016-04-14

    The decay dynamics of ambient and low temperature liquid water has been investigated through all-atom molecular dynamics simulations, residence times calculations and time correlation functions from 300 K down to 243 K. Those simulations replicate the experimental value of the self-diffusion constant as a function of temperature by tuning the damping factor of the Langevin equation of motion. A stretched exponential function exp[-(t/τ)(β)] has been found to properly describe the relaxation of residence times calculated at different temperatures for solvent molecules in a nanodrop of free water modelled as a sphere of nanometric dimensions. As the temperature goes down the decay time τ increases showing a divergence at Ts = 227 ± 3 K. The temperature independence of the dimensionless stretched exponent β = 0.59 ± 0.01 suggests the presence of, not a characteristic relaxation time (since β≠ 1), but a distribution of decay times that also holds at low temperature. An explanation for such heterogeneity can be found at the nanoscopic level. Moreover it can be concluded that the distribution of times already reported for the dynamics of water surrounding proteins (β≤ 0.5) can not be exclusively due to the presence of the biomolecule itself since isolated water also exhibits such behaviour. The above reported Ts and β values quantitatively reproduce experimental data. PMID:26782269

  12. Low-temperature dipolar echoes in amorphous dielectrics: Significance of relaxation and decoherence free two-level systems

    NASA Astrophysics Data System (ADS)

    Burin, A. L.; Leveritt, J. M., III; Ruyters, G.; Schötz, C.; Bazrafshan, M.; Fassl, P.; von Schickfus, M.; Fleischmann, A.; Enss, C.

    2013-12-01

    The theoretical model for dielectric echoes in amorphous solids at low temperatures has been developed and applied to the recent two- and three-pulse echo experimental data in borosilicate glass BK7 where the amplitude of dipolar echoes has been observed for unprecedentedly long delay times extending the experimental window for studying the decay by several orders of magnitude. We show that at long delay times the echo amplitude is determined by a small subset of two-level systems (TLSs) with negligible relaxation and decoherence because of their weak coupling to phonons. The universal statistics of coupling is obtained by assuming that different TLS elastic tensor components are almost independent. Under this assumption the echo decay can be described approximately by the power law time dependences with different powers at times shorter and longer than the typical TLS relaxation time. These predictions are in a very good agreement with the experimental data and can be used to extract TLS relaxation and decoherence rates from the echo experiments.

  13. Rotational relaxation of fluoromethane molecules in low-temperature collisions with buffer-gas helium

    NASA Astrophysics Data System (ADS)

    Li, Xingjia; Xu, Liang; Yin, Yanning; Xu, Supeng; Xia, Yong; Yin, Jianping

    2016-06-01

    We propose a method to study the rotational relaxation of polar molecules [here taking fluoromethane (CH3F ) as an example] in collisions with 3.5 K buffer-gas helium (He) atoms by using an electrostatic guiding technique. The dependence of the guiding signal of CH3F on the injected He flux and the dependence of the guiding efficiency of CH3F on its rotational temperature are investigated both theoretically and experimentally. By comparing the experimental and simulated results, we find that the translational and rotational temperatures of the buffer-gas cooled CH3F molecules can reach to about 5.48 and 0.60 K, respectively, and the ratio between the translational and average rotational collisional cross sections of CH3F -He is γ =σt/σr=36.49 ±6.15 . In addition, the slowing, cooling, and boosting effects of the molecular beam with different injected He fluxes are also observed and their forming conditions are investigated in some detail. Our study shows that our proposed method can not only be used to measure the translational and rotational temperatures of the buffer-gas cooled molecules, but also to measure the ratio of the translational collisional cross section to the average rotational collisional cross section, and even to measure the average rotational collisional cross section when the translational collisional cross section is measured by fitting the lifetime of molecule signal to get a numerical solution from the diffusion equation of buffer-gas He atoms in the cell.

  14. Process assessment of small scale low temperature methanol synthesis

    NASA Astrophysics Data System (ADS)

    Hendriyana, Susanto, Herri; Subagjo

    2015-12-01

    Biomass is a renewable energy resource and has the potential to make a significant impact on domestic fuel supplies. Biomass can be converted to fuel like methanol via several step process. The process can be split into following main steps: biomass preparation, gasification, gas cooling and cleaning, gas shift and methanol synthesis. Untill now these configuration still has a problem like high production cost, catalyst deactivation, economy of scale and a huge energy requirements. These problems become the leading inhibition for biomass conversion to methanol, which should be resolved to move towards the economical. To address these issues, we developed various process and new configurations for methanol synthesis via methyl formate. This configuration combining two reactors: the one reactor for the carbonylation of methanol and CO to form methyl formate, and the second for the hydrogenolysis of methyl formate and H2 to form two molecule of methanol. Four plant process configurations were compared with the biomass basis is 300 ton/day. The first configuration (A) is equipped with a steam reforming process for converting methane to CO and H2 for increasing H2/CO ratio. CO2 removal is necessary to avoid poisoning the catalyst. COSORB process used for the purpose of increasing the partial pressure of CO in the feed gas. The steam reforming process in B configuration is not used with the aim of reducing the number of process equipment, so expect lower investment costs. For C configuration, the steam reforming process and COSORB are not used with the aim of reducing the number of process equipment, so expect lower investment costs. D configuration is almost similar to the configuration A. This configuration difference is in the synthesis of methanol which was held in a single reactor. Carbonylation and hydrogenolysis reactions carried out in the same reactor one. These processes were analyzed in term of technical process, material and energy balance and economic

  15. Process assessment of small scale low temperature methanol synthesis

    SciTech Connect

    Hendriyana; Susanto, Herri Subagjo

    2015-12-29

    Biomass is a renewable energy resource and has the potential to make a significant impact on domestic fuel supplies. Biomass can be converted to fuel like methanol via several step process. The process can be split into following main steps: biomass preparation, gasification, gas cooling and cleaning, gas shift and methanol synthesis. Untill now these configuration still has a problem like high production cost, catalyst deactivation, economy of scale and a huge energy requirements. These problems become the leading inhibition for biomass conversion to methanol, which should be resolved to move towards the economical. To address these issues, we developed various process and new configurations for methanol synthesis via methyl formate. This configuration combining two reactors: the one reactor for the carbonylation of methanol and CO to form methyl formate, and the second for the hydrogenolysis of methyl formate and H{sub 2} to form two molecule of methanol. Four plant process configurations were compared with the biomass basis is 300 ton/day. The first configuration (A) is equipped with a steam reforming process for converting methane to CO and H{sub 2} for increasing H{sub 2}/CO ratio. CO{sub 2} removal is necessary to avoid poisoning the catalyst. COSORB process used for the purpose of increasing the partial pressure of CO in the feed gas. The steam reforming process in B configuration is not used with the aim of reducing the number of process equipment, so expect lower investment costs. For C configuration, the steam reforming process and COSORB are not used with the aim of reducing the number of process equipment, so expect lower investment costs. D configuration is almost similar to the configuration A. This configuration difference is in the synthesis of methanol which was held in a single reactor. Carbonylation and hydrogenolysis reactions carried out in the same reactor one. These processes were analyzed in term of technical process, material and energy

  16. Low temperature processable binderless silver inks for flexible electronics

    NASA Astrophysics Data System (ADS)

    Nayak, Arun

    2013-01-01

    A new class of screen-printable conductive silver inks that can be transformed into conductive traces at temperatures below 120°C is presented. The low transformation temperature required for processing these inks renders them suitable for printing on flexible substrates, such as polyester films to form conductive patterns/devices. The ink composition includes silver flakes (average particle size of 0.45 μm-8 μm), an organometallic silver salt, a free radical initiator and a novel dispersant. This binder-free silver ink can be thermally converted into pure metallic patterns containing no binder or any other organic moieties. The initiator catalyzes the decomposition of organometallic silver compounds to produce reactive silver at a relatively lower temperature. The silver thus generated chemically welds the silver flakes. Conductive silver traces with conductivities approaching within two orders of magnitude of elemental silver have been fabricated using these inks. In addition, a novel dispersant comprising amine-carbamate based gels was also developed. These gels act as suitable transport agents for the ink and completely decompose and vaporize during the thermal transformation process. The ink was formulated after careful optimization of the particle sizes of the silver flakes, weight percentages of the silver organometallic salt, silver flakes and amine carbamate gel and the relative molar ratio of the silver salt to the catalyst. These factors influence the conductivity and the mechanical integrity of the printed patterns fabricated from the ink. The inks have also been characterized for their rheological properties to assess their suitability for being processed using commercial roll to roll manufacturing processes such as screen, flexographic or gravure printing. The inks show shear thinning behavior with a viscosity in the range of 5-6.6 Pa.s at 1000 s-1, which within commercially acceptable ranges. Applications of these inks range from interconnect for

  17. Modified EVA Encapsulant Formulations for Low Temperature Processing: Preprint

    SciTech Connect

    Mei, Z.; Pern, F. J.; Glick, S. H.

    2001-10-01

    Presented at the 2001 NCPV Program Review Meeting: We have developed several new ethylene-vinyl acetate (EVA) formulations modified on the basis of NREL patented EVA formulations [1]. The new formulations can be cured to a desired gel content of {approx}80% in the ambient at temperatures 20-30 C lower than the typical conditions in vacuum (i.e. {approx}150 C). Glass/glass laminates showed transmittance spectra that are essentially the same as that of EVA 15295P in the visible and NIR regions but higher in the UV region. Results of fluorescence analysis of the ambient-processed new EVA formulations showed the concentrations of the curing-generated {alpha},{beta}-unsaturated carbonyl chromophores, which are responsible for the UV induced EVA discoloration and photodegradation, were considerably lower than that of EVA 15295P, therefore suggesting a better photochemical stability of new EVA formulations.

  18. Generation of low-temperature air plasma for food processing

    NASA Astrophysics Data System (ADS)

    Stepanova, Olga; Demidova, Maria; Astafiev, Alexander; Pinchuk, Mikhail; Balkir, Pinar; Turantas, Fulya

    2015-11-01

    The project is aimed at developing a physical and technical foundation of generating plasma with low gas temperature at atmospheric pressure for food industry needs. As known, plasma has an antimicrobial effect on the numerous types of microorganisms, including those that cause food spoilage. In this work an original experimental setup has been developed for the treatment of different foods. It is based on initiating corona or dielectric-barrier discharge in a chamber filled with ambient air in combination with a certain helium admixture. The experimental setup provides various conditions of discharge generation (including discharge gap geometry, supply voltage, velocity of gas flow, content of helium admixture in air and working pressure) and allows for the measurement of the electrical discharge parameters. Some recommendations on choosing optimal conditions of discharge generation for experiments on plasma food processing are developed.

  19. Low temperature plasma processing for cell growth inspired carbon thin films fabrication.

    PubMed

    Kumar, Manish; Piao, Jin Xiang; Jin, Su Bong; Lee, Jung Heon; Tajima, Satomi; Hori, Masaru; Han, Jeon Geon

    2016-09-01

    The recent bio-applications (i.e. bio-sensing, tissue engineering and cell proliferation etc.) are driving the fundamental research in carbon based materials with functional perspectives. High stability in carbon based coatings usually demands the high density deposition. However, the standard techniques, used for the large area and high throughput deposition of crystalline carbon films, often require very high temperature processing (typically >800 °C in inert atmosphere). Here, we present a low temperature (<150 °C) pulsed-DC plasma sputtering process, which enables sufficient ion flux to deposit dense unhydrogenated carbon thin films without any need of substrate-bias or post-deposition thermal treatments. It is found that the control over plasma power density and pulsed frequency governs the density and kinetic energy of carbon ions participating during the film growth. Subsequently, it controls the contents of sp(3) and sp(2) hybridizations via conversion of sp(2) to sp(3) hybridization by ion's energy relaxation. The role of plasma parameters on the chemical and surface properties are presented and correlated to the bio-activity. Bioactivity tests, carried out in mouse fibroblast L-929 and Sarcoma osteogenic (Saos-2) bone cell lines, demonstrate promising cell-proliferation in these films. PMID:27036854

  20. Defect-related relaxation processes in irradiated rare gas solids

    NASA Astrophysics Data System (ADS)

    Savchenko, E. V.; Grigorashchenko, O. N.; Gumenchuk, G. B.; Ogurtsov, A. N.; Frankowski, M.; Smith-Gicklhorn, A. M.; Bondybey, V. E.

    Electronic and atomic relaxation processes in preirradiated solid Ar doped with N-2 were studied with a focus on the role of radiative electronic transitions in relaxation cascades. Combining methods of activation spectroscopy - thermally stimulated and photon-stimulated exoelectron emission, a new channel of relaxation induced by photon emission from metastable N atoms was detected. It was shown that in insulating materials with a wide conduction band photons of visible range can release electrons from both kinds of traps - shallow (lattice defects) and deep thermally disconnected ones. Correlation in the charge recombination reaction yield and the yield of low temperature desorption - important relaxation channel in a preirradiated solid - clearly demonstrates interconnection between atomic and electronic processes of relaxation.

  1. Hydration of Rhyolitic Glasses: Comparison Between High- and Low-Temperature Processes

    NASA Astrophysics Data System (ADS)

    Anovitz, L.; Fayek, M.; Cole, D. R.; Carter, T.

    2012-12-01

    While a great deal is known about the interaction between water and rhyolitic glasses and melts at temperatures above the glass transition, the nature of this interaction at lower temperatures is more obscure. Comparisons between high- and low-temperature diffusive studies suggest that several factors play an important role under lower-temperatures conditions that are not significant at higher temperatures. Surface concentrations, which equilibrate quickly at high temperature, change far more slowly as temperatures decrease, and may not equilibrate at room temperature for hundreds or thousands of years. Coupled with temperature-dependent diffusion coefficients this complicates calculation of diffusion profiles as a function of time. A key factor in this process appears to be the inability of "self-stress", caused by the in-diffusing species, to relax at lower temperatures, a result expected below the glass transition. Regions of the glass hydrated at low temperatures are strongly optically anisotropic, and preliminary calculations suggest that the magnitude of stress involved may be very high. On the microstuctural scale, extrapolations of high-temperature FTIR data to lower temperatures suggests there should be little or no hydroxyl present in glasses "hydrated" at low temperatures. Analyses of both block and powder samples suggest that this is generally true in the bulk of the hydrated glass, excluding hydroxyl groups that formed during the initial cooling of the melt. However, hydroxyl do groups appear to be present at the glass surface, where both SIMS and neutron reflectometry data suggest hydration levels may be higher than projected from the bulk of the glass. Isotopic exchange experiments also suggest that bonding is relatively weak, as hydration water exchanges readily with the enviroment. All of these observations lead to the conclusion that the observed stress is due to the presence of interstructural, rather than bonded, water. This likely explains the

  2. Low-Temperature Toughening Mechanism in Thermomechanically Processed High-Strength Low-Alloy Steels

    NASA Astrophysics Data System (ADS)

    Hwang, Byoungchul; Lee, Chang Gil; Kim, Sung-Joon

    2011-03-01

    High-strength low-alloy (HSLA) steels were fabricated by varying thermomechanical processing conditions such as rolling and cooling conditions in the intercritical region, and the low-temperature toughening mechanism was investigated in terms of microstructure and the associated grain boundary characteristics. The steels acceleratedly cooled to relatively higher temperature had lower tensile strength than those acceleratedly cooled to room temperature due to the increased volume fraction of granular bainite or polygonal ferrite (PF) irrespective of rolling in the intercritical region, while the yield strength was dependent on intercritical rolling, and start and finish cooling temperatures, which affected the formation of PF and low-temperature transformation phases. The steel rolled in the intercritical region and cooled to 673 K (400 °C) provided the best combination of high yield strength and excellent low-temperature toughness because of the presence of fine PF and appropriate mixture of various low-temperature transformation phases such as granular bainite, degenerate upper bainite (DUB), lower bainite (LB), and lath martensite (LM). Despite the high yield strength, the improvement of low-temperature toughness could be explained by the reduction of overall effective grain size based on the electron backscattered diffraction (EBSD) analysis data, leading to the decrease in ductile-to-brittle transition temperature (DBTT).

  3. Low-temperature α peak of the internal friction in niobium and its relation to the relaxation of kinks in dislocations

    NASA Astrophysics Data System (ADS)

    Natsik, V. D.; Pal'-Val', P. P.; Pal'-Val', L. N.; Semerenko, Yu. A.

    2001-05-01

    The influence of impurities on the parameters of the α peak of the internal friction in single-crystal and polycrystalline niobium is investigated; the internal friction is recorded in the temperature range 200-250 K at a vibrational frequency of ≈80 kHz. It is found that increasing the purity of the samples leads to an increase of the peak location temperature and to an increase of its width and amplitude. The structural sensitivity of this peak was observed previously in a study of the influence on this peak of a preliminary plastic deformation, thermocycling, and low-temperature recovery. A statistical description of the whole set of experimental data is proposed, which takes into account the dependence of the activation energy and attempt period on the impurity concentration and on the characteristic value and statistical scatter of the internal stresses. A new algorithm is developed for analyzing the experimental data to obtain empirical estimates for the values of the activation energy, its variance, the attempt period, and relaxation strength for the different structural states of the samples. It is shown that the α peak is a consequence of the resonant interaction of elastic vibrations with the thermally activated nucleation of kink pairs on dislocation segments lying in the valleys of the Peierls potential relief. Empirical estimates are obtained for the values of the main parameters characterizing this process. It is found that the properties of the α peak in niobium are in qualitative agreement with Engelke's theory of the nucleation and relaxation of dislocation kinks.

  4. Exploring the limits: A low-pressure, low-temperature Haber-Bosch process

    NASA Astrophysics Data System (ADS)

    Vojvodic, Aleksandra; Medford, Andrew James; Studt, Felix; Abild-Pedersen, Frank; Khan, Tuhin Suvra; Bligaard, T.; Nørskov, J. K.

    2014-04-01

    The Haber-Bosch process for ammonia synthesis has been suggested to be the most important invention of the 20th century, and called the ‘Bellwether reaction in heterogeneous catalysis’. We examine the catalyst requirements for a new low-pressure, low-temperature synthesis process. We show that the absence of such a process for conventional transition metal catalysts can be understood as a consequence of a scaling relation between the activation energy for N2 dissociation and N adsorption energy found at the surface of these materials. A better catalyst cannot obey this scaling relation. We define the ideal scaling relation characterizing the most active catalyst possible, and show that it is theoretically possible to have a low pressure, low-temperature Haber-Bosch process. The challenge is to find new classes of catalyst materials with properties approaching the ideal, and we discuss the possibility that transition metal compounds have such properties.

  5. Low-temperature solution-processed p-type vanadium oxide for perovskite solar cells.

    PubMed

    Sun, Haocheng; Hou, Xiaomeng; Wei, Qiulong; Liu, Huawei; Yang, Kecheng; Wang, Wei; An, Qinyou; Rong, Yaoguang

    2016-06-21

    A low-temperature solution-processed inorganic p-type contact material of vanadium oxide (VOx) was developed to fabricate planar-heterojunction perovskite solar cells. Using a solvent-assisted process, high-quality uniform and compact perovskite (CH3NH3PbI3) films were deposited on VOx coated substrates. Due to the high transmittance and quenching efficiency of VOx layers, a power conversion efficiency of over 14% was achieved. PMID:27263631

  6. Joining of Silver Nanomaterials at Low Temperatures: Processes, Properties, and Applications.

    PubMed

    Peng, Peng; Hu, Anming; Gerlich, Adrian P; Zou, Guisheng; Liu, Lei; Zhou, Y Norman

    2015-06-17

    A review is provided, which first considers low-temperature diffusion bonding with silver nanomaterials as filler materials via thermal sintering for microelectronic applications, and then other recent innovations in low-temperature joining are discussed. The theoretical background and transition of applications from micro to nanoparticle (NP) pastes based on joining using silver filler materials and nanojoining mechanisms are elucidated. The mechanical and electrical properties of sintered silver nanomaterial joints at low temperatures are discussed in terms of the key influencing factors, such as porosity and coverage of substrates, parameters for the sintering processes, and the size and shape of nanomaterials. Further, the use of sintered silver nanomaterials for printable electronics and as robust surface-enhanced Raman spectroscopy substrates by exploiting their optical properties is also considered. Other low-temperature nanojoining strategies such as optical welding of silver nanowires (NWs) through a plasmonic heating effect by visible light irradiation, ultrafast laser nanojoining, and ion-activated joining of silver NPs using ionic solvents are also summarized. In addition, pressure-driven joining of silver NWs with large plastic deformation and self-joining of gold or silver NWs via oriented attachment of clean and activated surfaces are summarized. Finally, at the end of this review, the future outlook for joining applications with silver nanomaterials is explored. PMID:26005792

  7. Influence of thermally activated processes on the deformation behavior during low temperature ECAP

    NASA Astrophysics Data System (ADS)

    Fritsch, S.; Scholze, M.; F-X Wagner, M.

    2016-03-01

    High strength aluminum alloys are generally hard to deform. Therefore, the application of conventional severe plastic deformation methods to generate ultrafine-grained microstructures and to further increase strength is considerably limited. In this study, we consider low temperature deformation in a custom-built, cooled equal channel angular pressing (ECAP) tool (internal angle 90°) as an alternative approach to severely plastically deform a 7075 aluminum alloy. To document the maximum improvement of mechanical properties, these alloys are initially deformed from a solid solution heat-treated condition. We characterize the mechanical behavior and the microstructure of the coarse grained initial material at different low temperatures, and we analyze how a tendency for the PLC effect and the strain-hardening rate affect the formability during subsequent severe plastic deformation at low temperatures. We then discuss how the deformation temperature and velocity influence the occurrence of PLC effects and the homogeneity of the deformed ECAP billets. Besides the mechanical properties and these microstructural changes, we discuss technologically relevant processing parameters (such as pressing forces) and practical limitations, as well as changes in fracture behavior of the low temperature deformed materials as a function of deformation temperature.

  8. Low resistivity ohmic contacts to moderately doped n-GaAs with low temperature processing

    SciTech Connect

    Lovejoy, M.L.; Howard, A.J.; Zavadil, K.R.; Rieger, D.J.; Shul, R.J.; Barnes, P.A.

    1994-12-31

    A low-temperature process for forming ohmic contacts to moderately doped GaAs has been optimized using a PdGe metallization scheme. Minimum specific contact resistivity of 1.5 {times} 10{sup {minus}6} {minus}cm{sup 2} has been obtained with a low anneal temperature of 250 C. Results for optimizing both time and temperature are reported and compared to GeAu n-GaAs contacts. Material compositions was analyzed by x-ray photoelectron spectroscopy and circuit metal interconnect contact resisitivity to the low-temperature processed PdGe contacts is reported. For the lowest temperature anneals considered, excess Ge on the ohmic contact layer is suspected of degrading interconnect metal contacts, while higher temperature anneals permitted interconnect metal formation with negligible contact resistivity. Atomic force microscopy measurements showed that the PdGe surface morphology is much more uniform than standard GeAu contacts.

  9. Numerical Simulation of Steady and Filling Process of Low Temperature Liquid Propellants Pipeline

    NASA Astrophysics Data System (ADS)

    Gao, F.; Chen, Y.; Zhang, Z. P.

    Liquid hydrogen and liquid oxygen are widely used in the fields of the national defense, chemical industry and other advanced industries. Especially in the astronautics field, the transportation process of low temperature liquid propellants becomes an important research task. For exmple, if the pre-cooling condition of the low temperature propellants of the engine to start up will not be reached, it will take longer pre-cooling time and more expenses to experiment. Further more after rocket engine startup, the pump of liquid hydrogen will be resulted in shutting down due to overspeed if there is the two phase flow. It is necessary to progress numerical simulation for the steady flow and pre-cooling process of liquid hydrogen/liquid oxygen transportation pipe by using the method of computational fluid dynamics and numerical heat transmission. The main contents of the article includes two aspects. Firstly, considering compressibility of liquid hydrogen/liquid oxygen, the SIMPLE method has been used to calculate 2-D steady state transportation, and finite difference method has been adopted to simulate 1-D heat transmission of the high vacuum multi-layers adiabatic structure. Flow field, temperature field and heat transmission have been calculated and analyzed, in order to optimize existing transportation pipe and reduce the loss of low temperature propellants. Secondly, using fluid dynamics model of 1-D homogeneous balance state and heat transfer model covering main heat transfer work conditions in pre-cooling process, considering compressibility of low temperature propellants, pipe flow formula is calculated by finite volume method and 1-D non-steady state heat conduction formula of internal pipe-wall is calculated by finite difference method. The pre-cooling process of the test-bed system of rocket engine is calculated, simulative and experimental results are analyzed, and the results provide the evidences for the improvement of the engine system, test-bed system

  10. Low-temperature optical processing of semiconductor devices using photon effects

    SciTech Connect

    Sopori, B.L.; Cudzinovic, M.; Symko, M.

    1995-08-01

    In an RTA process the primary purpose of the optical energy incident on the semiconductor sample is to increase its temperature rapidly. The activation of reactions involved in processes such as the formation of junctions, metal contacts, deposition of oxides or nitrides, takes place purely by the temperature effects. We describe the observation of a number of new photonic effects that take place within the bulk and at the interfaces of a semiconductor when a semiconductor device is illuminated with a spectrally broad-band light. Such effects include changes in the diffusion properties of impurities in the semiconductor, increased diffusivity of impurities across interfaces, and generation of electric fields that can alter physical and chemical properties of the interface. These phenomena lead to certain unique effects in an RTA process that do not occur during conventional furnace annealing under the same temperature conditions. Of particular interest are observations of low-temperature alloying of Si-Al interfaces, enhanced activation of phosphorus in Si during drive-in, low-temperature oxidation of Si, and gettering of impurities at low-temperatures under optical illumination. These optically induced effects, in general, diminish with an increase in the temperature, thus allowing thermally activated reaction rates to dominate at higher temperatures.

  11. Low-Temperature Processable Block Copolymers That Preserve the Function of Blended Proteins.

    PubMed

    Iwasaki, Yasuhiko; Takemoto, Kyohei; Tanaka, Shinya; Taniguchi, Ikuo

    2016-07-11

    Low-temperature processable polymers have attracted increasing interest as ecological materials because of their reduced energy consumption during processing and suitability for making composites with heat-sensitive biomolecules at ambient temperature. In the current study, low-temperature processable biodegradable block copolymers were synthesized by ring-opening polymerization of l-lactide (LLA) using polyphosphoester as a macroinitiator. The polymer films could be processed under a hydraulic pressure of 35 MPa. The block copolymer films swelled in water because the polyphosphoester block was partially hydrated. Interestingly, the swelling ratio of the films changed with temperature. The pressure-induced order-to-disorder transition of the block copolymers was characterized by small-angle X-ray scattering; a crystallinity reduction in the block copolymers was observed after application of pressure. The crystallinity of the block copolymers was recovered after removing the applied pressure. The Young's modulus of the block copolymer films increased as the LLA unit content increased. Moreover, the modulus did not change after multiple processing cycles and the recyclability of the block copolymers was also confirmed. Finally, polymer films with embedded proteinase K as a model protein were prepared. The activity of catalase loaded into the polymer films was evaluated after processing at different temperatures. The activity of catalase was preserved when the polymer films were processed at room temperature but was significantly reduced after high-temperature processing. The suitability of low-temperature processable biodegradable polymers for making biofunctional composites without reducing protein activity was clarified. These materials will be useful for biomedical and therapeutic applications. PMID:27280847

  12. Surface-morphology evolution and strain relaxation during heteroepitaxial growth of GaN films without low-temperature nucleation layers

    NASA Astrophysics Data System (ADS)

    Lee, Sanghwa; Choe, Hyeokmin; Oh, Taegeon; Jean, Jai Weon; Shin, Boa; Sohn, Yuri; Kim, Chinkyo; Choi, Jaewan; Moon, Yong-Tae; Lee, Jeong Soo

    2007-04-01

    With no low-temperature nucleation layers, heteroepitaxial GaN films were grown at 1050°C on c-plane sapphire substrates by hydride vapor phase epitaxy. Not like for the films grown on low-temperature buffer layers, upon island merging no immediate smoothing of a surface was observed, but through several intermediate stages the surface morphology evolved from three-dimensional islands to terrace-and-step structures. From synchrotron x-ray diffraction measurements, it was revealed that the density of screw-or mixed-type threading dislocations greatly increased when the islands merged, but that of edge-type dislocations did not (edge-type threading dislocations are known to be dominantly formed in the GaN films grown on low-temperature buffer layers). This implies that the evolution of surface morphology sensitively depends on the type of threading dislocations introduced during island merging. Despite the absence of intentional nucleation layers, the strain was found to be fully relaxed even before the nucleated islands began to merge.

  13. Pilot scale studies on nitritation-anammox process for mainstream wastewater at low temperature.

    PubMed

    Trojanowicz, Karol; Plaza, Elzbieta; Trela, Jozef

    2016-01-01

    Process of partial nitritation-anammox for mainstream wastewater at low temperature was run in a pilot scale moving bed biofilm reactor (MBBR) system for about 300 days. The biofilm history in the reactor was about 3 years of growth at low temperature (down to 10 °C). The goal of the studies presented in this paper was to achieve effective partial nitritation-anammox process. Influence of nitrogen loading rate, hydraulic retention time, aeration strategy (continuous versus intermittent) and sludge recirculation (integrated fixed-film activated sludge (IFAS) mode) on deammonification process' efficiency and microbial activity in the examined system was tested. It was found that the sole intermittent aeration strategy is not a sufficient method for successful suppression of nitrite oxidizing bacteria in MBBR. The best performance of the process was achieved in IFAS mode. The highest recorded capacity of ammonia oxidizing bacteria and anammox bacteria in biofilm was 1.4 gN/m(2)d and 0.5 gN/m(2)d, respectively, reaching 51% in nitrogen removal efficiency. PMID:26901718

  14. Progresses in cMUT device fabrication using low temperature processes

    NASA Astrophysics Data System (ADS)

    Bahette, E.; Michaud, J. F.; Certon, D.; Gross, D.; Alquier, D.

    2014-04-01

    In this paper, we present an original fabrication process of capacitive micromachined ultrasonic transducers (cMUTs) using a low temperature method for high frequency medical imaging applications. The process, which is limited to 400 °C, is based on surface micromachining. The material choices are adapted in order to respect the thermal specifications allowing monolithic integration. Thus, we have found alternative methods to replace the usual high temperature steps in cMUT elaboration. In this way, a nickel silicide layer, presenting good physical and electrical characteristics, is used as a bottom electrode. The membrane, silicon nitride, is deposited using a 200 °C PECVD process. Then, a metallic layer is chosen as a sacrificial layer, in order to achieve the cavity. For that, nickel has been chosen due to its low roughness and its high etching selectivity during the excavation. After their fabrication, the transducers have been tested to verify their functionality and, thus, to validate this low temperature process. Device physical properties have been determined by electrical and optical measurement in air. We evaluated resonance frequency, collapse voltage and electromechanical coupling coefficient in accordance with the simulation. Eventually, low charging effects and low initial deflections can predict good long-term use and ageing of the cMUTs.

  15. Physical and chemical processes of low-temperature plasma decomposition of liquids under ultrasonic treatment

    NASA Astrophysics Data System (ADS)

    Bulychev, N. A.; Kazaryan, M. A.

    2015-12-01

    In this work, a low-temperature plasma initiated in liquid media between electrodes has been shown to be able to decompose hydrogen containing organic molecules leading to obtaining gaseous products with volume part of hydrogen higher than 90% (up to gas chromatography data). Preliminary evaluations of energetic efficiency, calculated from combustion energy of hydrogen and initial liquids and electrical energy consumption have demonstrated the efficiency about 60-70% depending on initial liquids composition. Theoretical calculations of voltage and current values for this process have been done, that is in good agreement with experimental data.

  16. Helium-3 relaxation time measurements at low temperatures for the neutron electric dipole moment (nEDM) experiment

    NASA Astrophysics Data System (ADS)

    Ye, Qiang

    The search for the existence of a nonzero neutron electric dipole moment (nEDM) has the potential to reveal new sources of T and CP violation beyond the Standard Model and may have a significant impact on our understanding of the universe. A new experiment aiming at two orders of magnitude improvement (˜ 10--28 e·cm) over the current experimental upper limit has been proposed in the United States. In the experiment, the measurement cell will be made of dTPB-dPS coated acrylic and filled with superfluid 4He at ˜300-500 mK. The measurement of the neutron precession frequency will rely on the spin-dependence of the cross section of the nuclear reaction between polarized neutrons and 3He atoms: n⃗+H3 ⃗e → p + t + 764 keV. Polarized 3He will also be used as a comagnetometer based on the nuclear magnetic resonance technique. The 3He polarization needs to have sufficiently long relaxation time so that little polarization is lost during the measurement period in order to achieve the proposed sensitivity. Understanding the relaxation mechanism of 3He polarization in the measurement cell under the nEDM experimental conditions and maintaining 3He polarization is crucial for the experiment. With the presence of superfluid 4He, 3He relaxation time measurements in a dTPB-dPS coated cylindrical acrylic cell at the temperature of 1.9 K and ˜400 mK have been performed at the Triangle University Nuclear Laboratory (TUNL) on the campus of Duke University. The extracted depolarization probabilities of polarized 3He on the cell surface are on the order of (1 -- 2) x 10--7 at 1.9 K and ˜ 4.7 x 10--7 at ˜400 mK. The extrapolated relaxation time of polarized 3He in the nEDM cell geometry is ˜ 4870 seconds at ˜400 mK, which is sufficiently long for the nEDM experiment and further improvements are anticipated.

  17. High permittivity Bi24Fe2O39 thin films prepared by a low temperature process

    NASA Astrophysics Data System (ADS)

    Zhu, X. H.; Defaÿ, E.; Lee, Y.; André, B.; Aïd, M.; Zhu, J. L.; Xiao, D. Q.; Zhu, J. G.

    2010-12-01

    High permittivity Bi24Fe2O39 (BFO) thin films have been deposited on platinized silicon substrates by a low temperature process combining rf magnetron sputtering at room temperature and postdeposition annealing at 450 °C. A nearly pure tetragonal crystal structure with highly (201)-preferred orientation, determined by x-ray diffraction, was formed in the BFO thin film. The BFO film not only exhibits high dielectric permittivity (ɛr=113) and relatively low loss tangent (tan δ=0.012), but also shows a fairly small quadratic voltage coefficient of capacitance (α ˜800 ppm/V2) and a small temperature coefficient of capacitance (αT˜790 ppm/°C). Moreover, the leakage current density, obeying the Fowler-Nordheim tunneling mechanism, remains at a reasonably low level with the increase in applied electric field (J ˜10-6-10-4 A/cm2 under E=400 kV/cm). These attractive dielectric and electrical properties make the low temperature processed Bi24Fe2O39 thin film a promising candidate for high-k dielectric applications in silicon-based integrated circuits.

  18. Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3{NIT(C6H4OPh)}]: A μ+ spin relaxation study

    NASA Astrophysics Data System (ADS)

    Arosio, Paolo; Corti, Maurizio; Mariani, Manuel; Orsini, Francesco; Bogani, Lapo; Caneschi, Andrea; Lago, Jorge; Lascialfari, Alessandro

    2015-05-01

    The spin dynamics of the molecular magnetic chain [Dy(hfac)3{NIT(C6H4OPh)}] were investigated by means of the Muon Spin Relaxation (μ+SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac)3{NIT(C6H4OPh)}] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ+SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λinterm(T), associated with the intermediate relaxing component. The experimental λinterm(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ0 exp(Δ/kBT), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state.

  19. Information entropy of activation process: Application for low-temperature fluctuations of a myoglobin molecule

    NASA Astrophysics Data System (ADS)

    Stepanov, A. V.

    2015-11-01

    Activation process for unimolecular reaction has been considered by means of radiation theory. The formulae of information entropy of activation have been derived for the Boltzmann-Arrhenius model and the activation process model (APM). The physical meaning of this entropy has been determined. It is a measure of conversion of thermal radiation energy to mechanical energy that moves atoms in a molecule during elementary activation act. It is also a measure of uncertainty of this energy conversion. The uncertainty is due to unevenness of distribution function representing the activation process. It has been shown that Arrhenius dependence is caused by the entropy change. Efficiency comparison of the two models under consideration for low-temperature fluctuations of a myoglobin molecule structure shows that the APM should be favored over the Boltzmann-Arrhenius one.

  20. Low temperature processing of flexible planar perovskite solar cells with efficiency over 10%

    NASA Astrophysics Data System (ADS)

    Dkhissi, Yasmina; Huang, Fuzhi; Rubanov, Sergey; Xiao, Manda; Bach, Udo; Spiccia, Leone; Caruso, Rachel A.; Cheng, Yi-Bing

    2015-03-01

    A device fabrication method is reported to efficiently produce CH3NH3PbI3-based planar perovskite solar cells on polymer substrates with the entire process conducted at 150 °C or below. The hole blocking layer employed is a solution processed 100 nm thick mesoporous TiO2 layer. A gas-assisted perovskite deposition method is used to produce excellent coverage of the hole blocking layer by a ∼350 nm thick CH3NH3PbI3 film, resulting in high device performance reproducibility. We show that an average efficiency of 10.6 ± 1.2%, and a maximum efficiency of 12.3% are obtained for flexible perovskite solar cells, offering great promise for further improvement of this low-temperature, low-cost processing solar technology.

  1. Thermofluid analysis and design of a low-temperature preforming process

    SciTech Connect

    Pitchumani, R.; Kordon, A.K.; Beris, A.N.; Karbhari, V.M.; Dhurjati, P.S. ); Rossing, B.R.; Johnson, W.B. )

    1994-10-01

    A simplified, one-dimensional analysis is presented for the phenomena related to flow and heat transfer involved in a commercial low-temperature molding process for manufacturing porous ceramic preforms. The process consists of injecting an aqueous slurry of ceramic particles and additives into a mold and freezing the slurry into the shape of the mold cavity. The purpose of this study is to demonstrate the use of reduced-order models in the analysis and design of a complex process. The flow analysis is based on an approximate model using the Bernoulli complex process. The flow analysis is based on an approximate model using the Bernoulli equation accounting for frictional and geometric losses, while the heat-transfer problem of freezing of the slurry inside the mold cavity is solved using an order-of-magnitude analysis of the interface energy balance equation. The thermofluid analysis yields the mold-fill times and freeze times, which are subsequently used in conjunction with practical considerations of ice crystal formation, complete mold fill, and operating limits of the processing equipment, to derive design guidelines for the mold temperatures and injection pressures. Experimental investigations were carried out on the manufacture of silicon carbide preforms used in metal-matrix composites. Good agreement is demonstrated between the theoretical predictions and the experimental observations. The simplified analysis is shown to provide valuable information on the class of molding processes at low temperatures, for simple part geometries, without resorting to tedious numerical computations. For complex geometries, the physical groups and the design approach presented in this article may be used to correlate data from rigorous numerical simulations and experiments.

  2. Low temperature solution process-based defect-induced orange-red light emitting diode

    PubMed Central

    Biswas, Pranab; Baek, Sung-Doo; Hoon Lee, Sang; Park, Ji-Hyeon; Jeong Lee, Su; Il Lee, Tae; Myoung, Jae-Min

    2015-01-01

    We report low-temperature solution-processed p-CuO nanorods (NRs)/n-ZnO NRs heterojunction light emitting diode (LED), exploiting the native point defects of ZnO NRs. ZnO NRs were synthesized at 90 °C by using hydrothermal method while CuO NRs were synthesized at 100 °C by using microwave reaction system. The electrical properties of newly synthesized CuO NRs revealed a promising p-type nature with a hole concentration of 9.64 × 1018 cm−3. The current-voltage characteristic of the heterojunction showed a significantly high rectification ratio of 105 at 4 V with a stable current flow. A broad orange-red emission was obtained from the forward biased LED with a major peak at 610 nm which was attributed to the electron transition from interstitial zinc to interstitial oxygen point defects in ZnO. A minor shoulder peak was also observed at 710 nm, corresponding to red emission which was ascribed to the transition from conduction band of ZnO to oxygen vacancies in ZnO lattice. This study demonstrates a significant progress toward oxide materials based, defect-induced light emitting device with low-cost, low-temperature methods. PMID:26648420

  3. Substrate-dependent thermal conductivity of aluminum nitride thin-films processed at low temperature

    SciTech Connect

    Belkerk, B. E.; Bensalem, S.; Soussou, A.; Carette, M.; Djouadi, M. A.; Scudeller, Y.; Al Brithen, H.

    2014-12-01

    In this paper, we report on investigation concerning the substrate-dependent thermal conductivity (k) of Aluminum Nitride (AlN) thin-films processed at low temperature by reactive magnetron sputtering. The thermal conductivity of AlN films grown at low temperature (<200 °C) on single-crystal silicon (Si) and amorphous silicon nitride (SiN) with thicknesses ranging from 100 nm to 4000 nm was measured with the transient hot-strip technique. The k values for AlN films on SiN were found significantly lower than those on Silicon consistently with their microstructures revealed by X-ray diffraction, high resolution scanning electron microscopy, and transmission electron microscopy. The change in k was due to the thermal boundary resistance found to be equal to 10 × 10{sup −9} Km{sup 2}W{sup −1} on SiN against 3.5 × 10{sup −9} Km{sup 2}W{sup −1} on Si. However, the intrinsic thermal conductivity was determined with a value as high as 200 Wm{sup −1}K{sup −1} whatever the substrate.

  4. Novel Surface Passivation Technique for Low-Temperature Solution-Processed Perovskite PV Cells.

    PubMed

    Tripathi, Neeti; Shirai, Yasuhiro; Yanagida, Masatoshi; Karen, Akiya; Miyano, Kenjiro

    2016-02-24

    Low-temperature solution-processed perovskite solar cells are attracting immense interest due to their ease of fabrication and potential for mass production on flexible substrates. However, the unfavorable surface properties of planar substrates often lead to large variations in perovskite crystal size and weak charge extractions at interfaces, resulting in inferior performance. Here, we report the improved performance, reproducibility, and high stability of "p-i-n" planar heterojunction perovskite solar cells. The key fabrication process is the addition of the amine-polymer poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN-P1) to a simple spin-coating process. The PFN-P1 works as a surfactant and helps promote uniform crystallization. As a result, perovskite films with PFN-P1 have a uniform distribution of grain sizes and improved open circuit voltage. Devices with PFN-P1 showed the best efficiency (13.2%), with a small standard deviation (0.40), out of 60 cells. Moreover, ∼90% of the initial efficiency was retained over more than 6 months. Additionally, devices fabricated from PFN-P1 mixed perovskite films showed higher stability under continuous operation at maximum power point over 150 h. Our results show that this approach is simple and effective for improving device performance, reproducibility, and stability by modifying perovskite properties with PFN-P1. Because of the simplicity of the fabrication process and reliable performance increase, this approach marks important progress in low-temperature solution-processed perovskite solar cells. PMID:26821862

  5. Low temperature processed planar heterojunction perovskite solar cells employing silver nanowires as top electrode

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhua; Li, Fushan; Yang, Kaiyu; Veeramalai, Chandrasekar Perumal; Guo, Tailiang

    2016-04-01

    In this paper, we reported a low temperature processed planar heterojunction perovskite solar cell employing silver nanowires as the top electrode and ZnO nanoparticles as the electron transport layer. The CH3NH3PbI3 perovskite was grown as the light absorber via two-step spin-coating technique. The as-fabricated perovskite solar cell exhibited the highest power conversion efficiency of 9.21% with short circuit current density of 19.75 mA cm-2, open circuit voltage of 1.02, and fill factor value of 0.457. The solar cell's performance showed negligible difference between the forward and reverse bias scan. This work paves a way for realizing low cost solution processable solar cells.

  6. Graphics processing unit accelerated three-dimensional model for the simulation of pulsed low-temperature plasmas

    SciTech Connect

    Fierro, Andrew Dickens, James; Neuber, Andreas

    2014-12-15

    A 3-dimensional particle-in-cell/Monte Carlo collision simulation that is fully implemented on a graphics processing unit (GPU) is described and used to determine low-temperature plasma characteristics at high reduced electric field, E/n, in nitrogen gas. Details of implementation on the GPU using the NVIDIA Compute Unified Device Architecture framework are discussed with respect to efficient code execution. The software is capable of tracking around 10 × 10{sup 6} particles with dynamic weighting and a total mesh size larger than 10{sup 8} cells. Verification of the simulation is performed by comparing the electron energy distribution function and plasma transport parameters to known Boltzmann Equation (BE) solvers. Under the assumption of a uniform electric field and neglecting the build-up of positive ion space charge, the simulation agrees well with the BE solvers. The model is utilized to calculate plasma characteristics of a pulsed, parallel plate discharge. A photoionization model provides the simulation with additional electrons after the initial seeded electron density has drifted towards the anode. Comparison of the performance benefits between the GPU-implementation versus a CPU-implementation is considered, and a speed-up factor of 13 for a 3D relaxation Poisson solver is obtained. Furthermore, a factor 60 speed-up is realized for parallelization of the electron processes.

  7. Highly Crystalline Nanoparticle Suspensions for Low-Temperature Processing of TiO2 Thin Films.

    PubMed

    Watté, Jonathan; Lommens, Petra; Pollefeyt, Glenn; Meire, Mieke; De Buysser, Klaartje; Van Driessche, Isabel

    2016-05-25

    In this work, we present preparation and stabilization methods for highly crystalline TiO2 nanoparticle suspensions for the successful deposition of transparent, photocatalytically active TiO2 thin films toward the degradation of organic pollutants by a low temperature deposition method. A proof-of-concept is provided wherein stable, aqueous TiO2 suspensions are deposited on glass substrates. Even if the processing temperature is lowered to 150-200 °C, the subsequent heat treatment provides transparent and photocatalytically active titania thin layers. Because all precursor solutions are water-based, this method provides an energy-efficient, sustainable, and environmentally friendly synthesis route. The high load in crystalline titania particles obtained after microwave heating opens up the possibility to produce thin coatings by low temperature processing, as a conventional crystallization procedure is in this case superfluous. The impact of the precursor chemistry in Ti(4+)-peroxo solutions, containing imino-diacetic acid as a complexing ligand and different bases to promote complexation was studied as a function of pH, reaction time and temperature. The nanocrystal formation was followed in terms of colloidal stability, crystallinity and particle size. Combined data from Raman and infrared spectroscopy, confirmed that stable titanium precursors could be obtained at pH levels ranging from 2 to 11. A maximum amount of 50.7% crystallinity was achieved, which is one of the highest reported amounts of anatase nanoparticles that are suspendable in stable aqueous titania suspensions. Decoloring of methylene blue solutions by precipitated nanosized powders from the TiO2 suspensions proves their photocatalytic properties toward degradation of organic materials, a key requisite for further processing. This synthesis method proves that the deposition of highly crystalline anatase suspensions is a valid route for the production of photocatalytically active, transparent

  8. Low temperature dielectric and conductivity relaxation studies on magnetoelectric Pb(Fe2/3W1/3)O3

    NASA Astrophysics Data System (ADS)

    Matteppanavar, Shidaling; Shivaraja, I.; Rayaprol, Sudhindra; Angadi, Basavaraj

    2016-05-01

    The single phase perovskite Pb(Fe2/3W1/3)O3 [PFW] was synthesized by modified low - temperature (sintering at 850°C) solid-state reaction. Rietveld refinement ofroom temperature (RT) X-ray diffraction (XRD) and neutron diffraction (ND) patterns of the samples confirm the single phase formation with cubic structure (Pm-3m). Surface morphology of the compounds was studied by Scanning electron microscope (SEM) and average grain size was estimated to be ˜2 µm. The RT dielectric properties of PFW ceramic are studied as a function of frequency from 100 - 1MHz. The temperature dependent (120 - 293K) dielectric properties were studied at few selected frequencies. We found the frequency dependent dielectric constant shows increasing trend with increase in temperature from 120 - 293K, with minimum dielectric loss. The frequency dependence of dielectric loss shows a maximum in between 10 Hz and 1 kHz, confirms the extrinsic phenomena like interfacial polarization due to space charge accumulation at grain boundaries. Impedance spectroscopy is used to study the electrical behaviour of PFW in the frequency range from 100 to 1MHz and in the temperature range from 120 - 293 K. The frequency-dependent electrical data are analysed by impedance formalisms and shows the relaxation (conduction) mechanism in the sample. We suggest this low temperature sintered PFW is a suitable candidate for the multilayer ceramic capacitorsandrelated negative temperature coefficient of resistance type (NTCR) behavior like that of semiconductors.

  9. Low Temperature Solution-Processed Gate Dielectrics for Low-Voltage Organic Field-Effect Transistors.

    PubMed

    Ha, Young-Geun

    2015-09-01

    We report on the design, preparation, and electrical properties of novel solution-processed organic-inorganic hybrid dielectric films for the low-voltage operation of organic field-effect transistors (OFETs). Hybrid dielectric thin films (-20 nm thick) are easily fabricated by spin-coating a zirconium chloride precursor/organic additive reagent mixture, followed by annealing at low temperatures (-150 degrees C). The smooth and transparent hybrid dielectrics exhibit great insulating properties (leakage current densities -10(-7) A/cm2 at 2 MV/cm), high capacitance (170 nF/cm2). OFETs fabricated with hybrid dielectric and pentacene semiconductor function great at relatively low voltage (mobility: 1 cm2/V x s, on/off current ratio: 10(5)). PMID:26716219

  10. Fabrication of multilayer passive electric components using inkjet printing and low temperature laser processing on polymer

    NASA Astrophysics Data System (ADS)

    Ko, Seung Hwan; Chung, Jaewon; Pan, Heng; Grigoropoulos, Costas P.; Poulikakos, Dimos

    2006-02-01

    The low temperature fabrication of passive electrical components (conductor, capacitor) on the flexible polymer substrate is presented in this paper. A drop-on-demand (DOD) ink-jetting system was used to print gold nano-particles suspended in Alpha-Terpineol solvent and PVP in PGMEA solvent to fabricate passive electrical components on flexible polymer substrate. Short pulsed laser ablation enabled finer electrical components to overcome limitation of inkjet process. Continuous Argon ion laser was irradiated locally to evaporate carrier solvent as well as to sinter gold nano-particles. In addition, a self alignment technique for PVP layer was demonstrated taking advantage of the deliberate modification of surface wetting characteristics. Finally, a new selective ablation of multilayered gold nanoparticle film was demonstrated using the ablation threshold difference for sintered and non sintered gold nanoparticles.

  11. Low-temperature baroplastic processing of graphene-based polymer composites by pressure-induced flow

    NASA Astrophysics Data System (ADS)

    Tang, Wei; He, Cheng-en; Wang, Yuanzhen; Yang, Yingkui; Pong Tsui, Chi

    2014-08-01

    Two-stage emulsion polymerization was employed to synthesize nanoparticles consisting of a low glass transition temperature core of poly(n-butyl acrylate) (PBA) and a glassy poly(methyl methylacrylate) (PMMA) shell. Incorporation of graphene oxide (GO) into the PBA-PMMA latex produced GO/PBA-PMMA composites after demulsification and graphene/PBA-PMMA composites after chemical reduction of GO. The as-prepared powdery materials were processed into thin films by compression molding at room temperature as the result of a pressure-induced mixing mechanism of microphase-separated baroplastics. The presence of oxygen-containing groups for GO sheets contributed to better dispersion and stronger interface with the matrix, thereby showing greater reinforcement efficiency toward polymers compared to graphene sheets. In addition, both Young's modulus and yield strength for all materials increased with applied pressure and processing time due to better flowability, processability and cohesion at higher pressure and longer time. Low-temperature processing under pressure is of significance for energy conservation, recyclability and environmental protection during plastic processing.

  12. Full Scale Field Trial of the Low Temperature Mercury Capture Process

    SciTech Connect

    Locke, James; Winschel, Richard

    2012-05-21

    CONSOL Energy Inc., with partial funding from the Department of Energy (DOE) National Energy Technology Laboratory, designed a full-scale installation for a field trial of the Low-Temperature Mercury Control (LTMC) process, which has the ability to reduce mercury emissions from coal-fired power plants by over 90 percent, by cooling flue gas temperatures to approximately 230°F and absorbing the mercury on the native carbon in the fly ash, as was recently demonstrated by CONSOL R&D on a slip-stream pilot plant at the Allegheny Energy Mitchell Station with partial support by DOE. LTMC has the potential to remove over 90 percent of the flue gas mercury at a cost at least an order of magnitude lower (on a $/lb mercury removed basis) than activated carbon injection. The technology is suitable for retrofitting to existing and new plants, and, although it is best suited to bituminous coal-fired plants, it may have some applicability to the full range of coal types. Installation plans were altered and moved from the original project host site, PPL Martins Creek plant, to a second host site at Allegheny Energy's R. Paul Smith plant, before installation actually occurred at the Jamestown (New York) Board of Public Utilities (BPU) Samuel A. Carlson (Carlson) Municipal Generating Station Unit 12, where the LTMC system was operated on a limited basis. At Carlson, over 60% mercury removal was demonstrated by cooling the flue gas to 220-230°F at the ESP inlet via humidification. The host unit ESP operation was unaffected by the humidification and performed satisfactorily at low temperature conditions.

  13. Nitrogen Turnover Processes in Low Temperatures in an Agricultural Peat Soil

    NASA Astrophysics Data System (ADS)

    Silvennoinen, H. M.; Hämäläinen, R.; Koponen, H. T.; Martikainen, P. J.

    2009-12-01

    Nitrogen (N) cycling in agricultural soils has a key impact on the environment. Agricultural ecosystems are the most important sources of nitrous oxide (N2O), an important greenhouse gas, to the atmosphere. Additionally N fertilizers used to improve plant growth lead to enhanced N leaching and thereby to eutrophication of surrounding aquatic ecosystems. Microbial processes are normally enhanced by increase in temperature. Several recent studies have shown that although N2O emissions from agricultural soils are of microbiological origin, produced mainly in microbial reduction of nitrate (NO3-) via nitric oxide (NO) and N2O to molecular nitrogen (N2) (denitrification), the temperature response of N2O emissions is greatly variable and there is a lot of evidence of high emissions during cold periods (Koponen et al. 2006). Denitrification is, however, regulated by availability of inorganic N and therefore dependant not only on N fertilization but also on N turnover processes in soil. These processes include mineralization of organic N to ammonium (NH4+), oxidation of NH4+ to nitrite and NO3- (nitrification). These processes and their regulation especially in low temperatures are yet poorly understood. In this experiment, gross rates of N mineralization and nitrification and carbon dioxide production were studied in various temperatures ranging from -1.5 to 15 °C. Soil samples were taken from grassland on peat soil in Southern Finland (60o49’N, 23o30’E) on September 8th 2008 from depths of 0-10 cm. Temperature responses of N gross mineralization and nitrification and of microbial respiration were measured in a laboratory experiment. The incubation temperatures used for experiments were 15, 5, 2.5, 1.5, 0.5, 0, -0.5 and -1.5 °C. After 7 d temperature-specific incubation, gross rates of N mineralization and nitrification were determined with pool dilution technique in a 24 h incubation experiment. This study showed that N turnover processes in agricultural peat soil

  14. Hydrothermal-Assisted Cold Sintering Process: A New Guidance for Low-Temperature Ceramic Sintering.

    PubMed

    Guo, Hanzheng; Guo, Jing; Baker, Amanda; Randall, Clive A

    2016-08-17

    Sintering is a thermal treatment process that is generally applied to achieve dense bulk solids from particulate materials below the melting temperature. Conventional sintering of polycrystalline ceramics is prevalently performed at quite high temperatures, normally up to 1000 to 1200 °C for most ceramic materials, typically 50% to 75% of the melting temperatures. Here we present a new sintering route to achieve dense ceramics at extraordinarily low temperatures. This method is basically modified from the cold sintering process (CSP) we developed very recently by specifically incorporating the hydrothermal precursor solutions into the particles. BaTiO3 nano polycrystalline ceramics are exemplified for demonstration due to their technological importance and normally high processing temperature under conventional sintering routes. The presented technique could also be extended to a much broader range of material systems than previously demonstrated via a hydrothermal synthesis using water or volatile solutions. Such a methodology is of significant importance, because it provides a chemical roadmap for cost-effective inorganic processing that can enable broad practical applications. PMID:27468626

  15. Structural properties of relaxed thin film germanium layers grown by low temperature RF-PECVD epitaxy on Si and Ge (100) substrates

    SciTech Connect

    Cariou, R.; Ruggeri, R.; Tan, X.; Nassar, J.; Roca i Cabarrocas, P.; Mannino, Giovanni

    2014-07-15

    We report on unusual low temperature (175 °C) heteroepitaxial growth of germanium thin films using a standard radio-frequency plasma process. Spectroscopic ellipsometry and transmission electron microscopy (TEM) reveal a perfect crystalline quality of epitaxial germanium layers on (100) c-Ge wafers. In addition direct germanium crystal growth is achieved on (100) c-Si, despite 4.2% lattice mismatch. Defects rising from Ge/Si interface are mostly located within the first tens of nanometers, and threading dislocation density (TDD) values as low as 10{sup 6} cm{sup −2} are obtained. Misfit stress is released fast: residual strain of −0.4% is calculated from Moiré pattern analysis. Moreover we demonstrate a striking feature of low temperature plasma epitaxy, namely the fact that crystalline quality improves with thickness without epitaxy breakdown, as shown by TEM and depth profiling of surface TDD.

  16. Preliminary operational results of the low-temperature solar industrial process heat field tests

    SciTech Connect

    Kutscher, C.F.; Davenport, R.L.

    1980-06-01

    Six solar industrial process heat field tests have been in operation for a year or more - three are hot water systems and three are hot air systems. All are low-temperature projects (process heat at temperatures below 212/sup 0/F). Performance results gathered by each contractor's data acquisition system are presented and project costs and problems encountered are summarized. Flat-plate, evacuated-tube, and line-focus collectors are all represented in the program, with collector array areas ranging from 2500 to 21,000 ft/sup 2/. Collector array efficiencies ranged from 12% to 36% with net system efficiencies from 8% to 33%. Low efficiencies are attributable in some cases to high thermal losses and, for the two projects using air collectors, are due in part to high parasitic power consumption. Problems have included industrial effluents on collectors, glazing and absorber surface failures, excessive thermal losses, freezing and overheating, control problems, and data acquisition system failure. With design and data acquisition costs excluded costs of the projects ranged from $25/ft/sup 2/ to $87/ft/sup 2/ and $499/(MBtu/yr) to $1537/(MBtu/yr).

  17. Application of Atmospheric-Pressure Microwave Line Plasma for Low Temperature Process

    NASA Astrophysics Data System (ADS)

    Suzuki, Haruka; Nakano, Suguru; Itoh, Hitoshi; Sekine, Makoto; Hori, Masaru; Toyoda, Hirotaka

    2015-09-01

    Atmospheric pressure (AP) plasmas have been given much attention because of its high cost benefit and a variety of possibilities for industrial applications. In various kinds of plasma production technique, pulsed-microwave discharge plasma using slot antenna is attractive due to its ability of high-density and stable plasma production. In this plasma source, however, size of the plasma has been limited up to a few cm in length due to standing wave inside a waveguide. To solve this, we have proposed a newly-developed AP microwave plasma source that utilizes not standing wave but travelling wave. By using this plasma source, spatially-uniform AP line plasma with 40 cm in length was realized by pure helium discharge in 60 cm slot and with nitrogen gas additive of 1%. Furthermore, gas temperature as low as 400 K was realized in this device. In this study, as an example of low temperature processes, hydrophilic treatment of PET films was performed. Processing speed increased with pulse frequency and a water contact angle of ~20° was easily obtained within 5 s with no thermal damage to the substrate. To evaluate treatment-uniformity of long line length, PET films were treated by 90 cm slot-antenna plasma and uniform treatment performance was confirmed.

  18. Low temperature solution processed high-κ ZrO2 gate dielectrics for nanoelectonics

    NASA Astrophysics Data System (ADS)

    Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara

    2016-05-01

    The high-κ gate dielectrics, specifically amorphous films offer salient features such as exceptional mechanical flexibility, smooth surfaces and better uniformity associated with low leakage current density. In this work, ∼35 nm thick amorphous ZrO2 films were deposited on silicon substrate at low temperature (300 °C, 1 h) from facile spin-coating method and characterized by various analytical techniques. The X-ray diffraction and X-ray photoelectron spectroscopy reveal the formation of amorphous phase ZrO2, while ellipsometry analysis together with the Atomic Force Microscope suggest the formation of dense film with surface roughness of 1.5 Å, respectively. The fabricated films were integrated in metal-oxide-semiconductor (MOS) structures to check the electrical capabilities. The oxide capacitance (Cox), flat band capacitance (CFB), flat band voltage (VFB), dielectric constant (κ) and oxide trapped charges (Qot) extracted from high frequency (1 MHz) C-V curve are 186 pF, 104 pF, 0.37 V, 15 and 2 × 10-11 C, respectively. The small flat band voltage 0.37 V, narrow hysteresis and very little frequency dispersion between 10 kHz-1 MHz suggest an excellent a-ZrO2/Si interface with very less trapped charges in the oxide. The films exhibit a low leakage current density 4.7 × 10-9 A/cm2 at 1 V. In addition, the charge transport mechanism across the MOSC is analyzed and found to have a strong bias dependence. The space charge limited conduction mechanism is dominant in the high electric field region (1.3-5 V) due to the presence of traps, while the trap-supported tunneling is prevailed in the intermediate region (0.35-1.3 V). Low temperature solution processed ZrO2 thin films obtained are of high quality and find their importance as a potential dielectric layer on Si and polymer based flexible electronics.

  19. Perovskite Solar Cells Based on Low-Temperature Processed Indium Oxide Electron Selective Layers.

    PubMed

    Qin, Minchao; Ma, Junjie; Ke, Weijun; Qin, Pingli; Lei, Hongwei; Tao, Hong; Zheng, Xiaolu; Xiong, Liangbin; Liu, Qin; Chen, Zhiliang; Lu, Junzheng; Yang, Guang; Fang, Guojia

    2016-04-01

    Indium oxide (In2O3) as a promising n-type semiconductor material has been widely employed in optoelectronic applications. In this work, we applied low-temperature solution-processed In2O3 nanocrystalline film as an electron selective layer (ESL) in perovskite solar cells (PSCs) for the first time. By taking advantages of good optical and electrical properties of In2O3 such as high mobility, wide band gap, and high transmittance, we obtained In2O3-based PSCs with a good efficiency exceeding 13% after optimizing the concentration of the precursor solution and the annealing temperature. Furthermore, to enhance the performance of the In2O3-based PSCs, a phenyl-C61-butyric acid methyl ester (PCBM) layer was introduced to modify the surface of the In2O3 film. The PCBM film could fill up the pinholes or cracks along In2O3 grain boundaries to passivate the defects and make the ESL extremely compact and uniform, which is conducive to suppressing the charge recombination. As a result, the efficiency of the In2O3-based PSC was improved to 14.83% accompanied with VOC, JSC, and FF being 1.08 V, 20.06 mA cm(-2), and 0.685, respectively. PMID:26996215

  20. An Integrated, Low Temperature Process to Capture and Sequester Carbon Dioxide from Industrial Emissions

    NASA Astrophysics Data System (ADS)

    Wendlandt, R. F.; Foremski, J. J.

    2013-12-01

    Laboratory experiments show that it is possible to integrate (1) the chemistry of serpentine dissolution, (2) capture of CO2 gas from the combustion of natural gas and coal-fired power plants using aqueous amine-based solvents, (3) long-term CO2 sequestration via solid phase carbonate precipitation, and (4) capture solvent regeneration with acid recycling in a single, continuous process. In our process, magnesium is released from serpentine at 300°C via heat treatment with ammonium sulfate salts or at temperatures as low as 50°C via reaction with sulfuric acid. We have also demonstrated that various solid carbonate phases can be precipitated directly from aqueous amine-based (NH3, MEA, DMEA) CO2 capture solvent solutions at room temperature. Direct precipitation from the capture solvent enables regenerating CO2 capture solvent without the need for heat and without the need to compress the CO2 off gas. We propose that known low-temperature electrochemical methods can be integrated with this process to regenerate the aqueous amine capture solvent and recycle acid for dissolution of magnesium-bearing mineral feedstocks and magnesium release. Although the direct precipitation of magnesite at ambient conditions remains elusive, experimental results demonstrate that at temperatures ranging from 20°C to 60°C, either nesquehonite Mg(HCO3)(OH)●2H2O or a double salt with the formula [NH4]2Mg(CO3)2●4H2O or an amorphous magnesium carbonate precipitate directly from the capture solvent. These phases are less desirable for CO2 sequestration than magnesite because they potentially remove constituents (water, ammonia) from the reaction system, reducing the overall efficiency of the sequestration process. Accordingly, the integrated process can be accomplished with minimal energy consumption and loss of CO2 capture and acid solvents, and a net generation of 1 to 4 moles of H2O/6 moles of CO2 sequestered (depending on the solid carbonate precipitate and amount of produced H2

  1. PREFACE: Low temperature Plasma in the Processes of Functional Coating Preparation

    NASA Astrophysics Data System (ADS)

    Gali Yunusovich, Dautov; Kashapov Faikovich, Nail; Larionov, Viktor; Gerfanovich Zaripov, Renat; Galyautdinov Tagirovich, Raphael; Ilnaz, Fayrushin; Ramil Nailevich, Kashapov

    2013-12-01

    In November 2013 the V Republican Scientific Technical Conference 'Low-temperature plasma during the deposition of functional coatings' was held in Kazan. The Conference took place from 4-7 November at the Academy of Sciences of the Republic of Tatarstan and Kazan Federal University chaired by a member of the Academy of Sciences of the Republic of Tatarstan Nail Kashapov, Professor, Doctor of Technical Science, and a member of the Scientific and Technical Council of the Ministry of Economy of the Republic of Tatarstan. At the conference, the participants were offered a wide range of issues affecting the theoretical and computational aspects of the research problems in the physics and technology of low-temperature plasma. There was also a whole series of works devoted to the study of thin films, obtained by low-temperature plasma. For the second year at this conference, work dedicated to the related field of pulsation combustion and low- temperature plasma was considered. In addition much interest is devoted to reports on the exploration of gas discharges with liquid electrolytic electron trodes and the study of dusty plasmas. The VI All-Russian Conference 'Low-temperature plasma during the deposition of functional coatings', an extended version with international participation, is scheduled to take place in November 2014. Nail Kashapov Editor

  2. Fractionation of 238U/235U by reduction during low temperature uranium mineralisation processes

    NASA Astrophysics Data System (ADS)

    Murphy, Melissa J.; Stirling, Claudine H.; Kaltenbach, Angela; Turner, Simon P.; Schaefer, Bruce F.

    2014-02-01

    Investigations of ‘stable’ uranium isotope fractionation during low temperature, redox transformations may provide new insights into the usefulness of the 238U/235U isotope system as a tracer of palaeoredox processes. Sandstone-hosted uranium deposits accumulate at an oxidation/reduction interface within an aquifer from the low temperature reduction of soluble U(VI) complexes in groundwaters, forming insoluble U(IV) minerals. This setting provides an ideal environment in which to investigate the effects of redox transformations on 238U/235U fractionation. Here we present the first coupled measurements of 238U/235U isotopic compositions and U concentrations for groundwaters and mineralised sediment samples from the same redox system in the vicinity of the high-grade Pepegoona sandstone-hosted uranium deposit, Australia. The mineralised sediment samples display extremely variable 238U/235U ratios (herein expressed as δUCRM145238, the per-mil deviation from the international NBL standard CRM145). The majority of mineralised sediment samples have δUCRM145238 values between -1.30±0.05 and 0.55±0.12‰, spanning a ca. 2‰ range. However, one sample has an unusually light isotopic composition of -4.13±0.05‰, which suggests a total range of U isotopic variability of up to ca. 5‰, the largest variation found thus far in a single natural redox system. The 238U/235U isotopic signature of the mineralised sediments becomes progressively heavier (enriched in 238U) along the groundwater flow path. The groundwaters show a greater than 2‰ variation in their 238U/235U ratios, ranging from δUCRM145238 values of -2.39±0.07 to -0.71±0.05‰. The majority of the groundwater data exhibit a clear systematic relationship between 238U/235U isotopic composition and U concentration; samples with the lowest U concentrations have the lowest 238U/235U ratios. The preferential incorporation of 238U during reduction of U(VI) to U(IV) and precipitation of uranium minerals leaves

  3. Bottom-up processing and low temperature transport properties of polycrystalline SnSe

    SciTech Connect

    Ge, Zhen-Hua; Wei, Kaya; Lewis, Hutton; Martin, Joshua; Nolas, George S.

    2015-05-15

    A hydrothermal approach was employed to efficiently synthesize SnSe nanorods. The nanorods were consolidated into polycrystalline SnSe by spark plasma sintering for low temperature electrical and thermal properties characterization. The low temperature transport properties indicate semiconducting behavior with a typical dielectric temperature dependence of the thermal conductivity. The transport properties are discussed in light of the recent interest in this material for thermoelectric applications. The nanorod growth mechanism is also discussed in detail. - Graphical abstract: SnSe nanorods were synthesized by a simple hydrothermal method through a bottom-up approach. Micron sized flower-like crystals changed to nanorods with increasing hydrothermal temperature. Low temperature transport properties of polycrystalline SnSe, after SPS densification, were reported for the first time. This bottom-up synthetic approach can be used to produce phase-pure dense polycrystalline materials for thermoelectrics applications. - Highlights: • SnSe nanorods were synthesized by a simple and efficient hydrothermal approach. • The role of temperature, time and NaOH content was investigated. • SPS densification allowed for low temperature transport properties measurements. • Transport measurements indicate semiconducting behavior.

  4. PREFACE: VII Conference on Low Temperature Plasma in the Processes of Functional Coating Preparation

    NASA Astrophysics Data System (ADS)

    Nail, Kashapov

    2016-01-01

    The VII All-Russian (with international participation) Scientific Technical Conference "Low-temperature plasma during the deposition of functional coatings" took place from 4-7 November 2015 at the Academy of Sciences of the Republic of Tatarstan and the Kazan Federal University. The conference was attended by over 150 people from Russia and abroad. The participants proposed a wide range of issues affecting the theoretical and experimental aspects of the problems of the physics of low-temperature plasma. We heard the reports of experts from leading universities and research organizations in the field of plasma physics: Moscow State University, St. Petersburg State University, MEPhI, Tomsk Polytechnic University, Institute of High Current Electronics SB RAS, etc. A series of works were devoted to the study of thin films obtained by low-temperature plasma. This year, work dedicated to the related field of heat mass transfer in multiphase media and low-temperature plasma was also presented. Of special interest were reports on the exploration of gas discharges with liquid electrolytic electrodes and the study of dusty plasmas. Kashapov Nail, D.Sc., professor (Kazan Federal University)

  5. Mainstream partial nitritation and anammox: long-term process stability and effluent quality at low temperatures.

    PubMed

    Laureni, Michele; Falås, Per; Robin, Orlane; Wick, Arne; Weissbrodt, David G; Nielsen, Jeppe Lund; Ternes, Thomas A; Morgenroth, Eberhard; Joss, Adriano

    2016-09-15

    The implementation of autotrophic anaerobic ammonium oxidation processes for the removal of nitrogen from municipal wastewater (known as "mainstream anammox") bears the potential to bring wastewater treatment plants close to energy autarky. The aim of the present work was to assess the long-term stability of partial nitritation/anammox (PN/A) processes operating at low temperatures and their reliability in meeting nitrogen concentrations in the range of typical discharge limits below 2  [Formula: see text] and 10 mgNtot·L(-1). Two main 12-L sequencing batch reactors were operated in parallel for PN/A on aerobically pre-treated municipal wastewater (21 ± 5 [Formula: see text] and residual 69 ± 19 mgCODtot·L(-1)) for more than one year, including over 5 months at 15 °C. The two systems consisted of a moving bed biofilm reactor (MBBR) and a hybrid MBBR (H-MBBR) with flocculent biomass. Operation at limiting oxygen concentrations (0.15-0.18 [Formula: see text] ) allowed stable suppression of the activity of nitrite-oxidizing bacteria at 15 °C with a production of nitrate over ammonium consumed as low as 16% in the MBBR. Promising nitrogen removal rates of 20-40 mgN·L(-1)·d(-1) were maintained at hydraulic retention times of 14 h. Stable ammonium and total nitrogen removal efficiencies over 90% and 70% respectively were achieved. Both reactors reached average concentrations of total nitrogen below 10 mgN·L(-1) in their effluents, even down to 6 mgN·L(-1) for the MBBR, with an ammonium concentration of 2 mgN·L(-1) (set as operational threshold to stop aeration). Furthermore, the two PN/A systems performed almost identically with respect to the biological removal of organic micropollutants and, importantly, to a similar extent as conventional treatments. A sudden temperature drop to 11 °C resulted in significant suppression of anammox activity, although this was rapidly recovered after the temperature was increased back to 15 °C. Analyses of 16S

  6. Dynamic processes of indigenous microorganisms from a low-temperature petroleum reservoir during nutrient stimulation.

    PubMed

    Gao, Pei-Ke; Li, Guo-Qiang; Zhao, Ling-Xia; Dai, Xue-Cheng; Tian, Hui-Mei; Dai, Liu-Bing; Wang, Hong-Bo; Huang, Hai-Dong; Chen, Yue-Hua; Ma, Ting

    2014-02-01

    Compared to medium-high temperature petroleum reservoirs (30°C-73°C), little is known about microbial regulation by nutrients in low-temperature reservoirs. In this study, we report the performance (oil emulsification and biogas production) and community structure of indigenous microorganisms from a low-temperature (22.6°C) petroleum reservoir during nutrient stimulation. Culture-dependent approaches indicated that the number of hydrocarbon-oxidizing bacteria (HOB), nitrate-reducing bacteria (NRB) and methane-producing bacteria (MPB) increased by between 10- and 1000-fold, while sulfate-reducing bacteria (SRB) were observed at low levels during stimulation. Phylogenetic analysis of the 16S rRNA gene indicated that Pseudomonas, Ochrobactrum, Acinetobacter, Halomonas and Marinobacter, which have the capability to produce surfactants, were selectively enriched. Methanoculleus, Methanosaeta, Methanocorpusculum and Methanocalculus showed the largest increase in relative abundance among archaea. Micro-emulsion formed with an average oil droplet diameter of 14.3 μm (ranging between 4.1 μm and 84.2 μm) during stimulation. Gas chromatographic analysis of gas production (186 mL gas/200 mL medium) showed the levels of CO2 and CH4 increased 8.97% and 6.21%, respectively. Similar to medium-high temperature reservoirs, HOB, NRB, SRB and MPB were ubiquitous in the low-temperature reservoir, and oil emulsification and gas production were the main phenomena observed during stimulation. Oil emulsification required a longer duration of time to occur in the low-temperature reservoir. PMID:23968868

  7. Electronic Structure of Low-Temperature Solution-Processed Amorphous Metal Oxide Semiconductors for Thin-Film Transistor Applications

    PubMed Central

    Socratous, Josephine; Banger, Kulbinder K; Vaynzof, Yana; Sadhanala, Aditya; Brown, Adam D; Sepe, Alessandro; Steiner, Ullrich; Sirringhaus, Henning

    2015-01-01

    The electronic structure of low temperature, solution-processed indium–zinc oxide thin-film transistors is complex and remains insufficiently understood. As commonly observed, high device performance with mobility >1 cm2 V−1 s−1 is achievable after annealing in air above typically 250 °C but performance decreases rapidly when annealing temperatures ≤200 °C are used. Here, the electronic structure of low temperature, solution-processed oxide thin films as a function of annealing temperature and environment using a combination of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and photothermal deflection spectroscopy is investigated. The drop-off in performance at temperatures ≤200 °C to incomplete conversion of metal hydroxide species into the fully coordinated oxide is attributed. The effect of an additional vacuum annealing step, which is beneficial if performed for short times at low temperatures, but leads to catastrophic device failure if performed at too high temperatures or for too long is also investigated. Evidence is found that during vacuum annealing, the workfunction increases and a large concentration of sub-bandgap defect states (re)appears. These results demonstrate that good devices can only be achieved in low temperature, solution-processed oxides if a significant concentration of acceptor states below the conduction band minimum is compensated or passivated by shallow hydrogen and oxygen vacancy-induced donor levels. PMID:26190964

  8. Low-temperature process of the formation of tubular and graphene carbon structures

    SciTech Connect

    Dubkov, S. V.; Gavrilov, S. A.; Gromov, D. G. Krasulin, G. A.

    2011-12-15

    The formation of carbon nanostructures by chemical vapor deposition enhanced by glow-discharge plasma is considered. The studies are conducted in the temperature range 300 to 700 Degree-Sign C. Dependences of the structure of the carbon deposit on the thickness of the Ni catalyst film and on the concentration of the carbon-containing component in the vapor phase are analyzed. The reproducible growth of arrays of homogeneous vertical nanotubes or graphene flakes is observed at a low temperature ({approx}350 Degree-Sign C). The electrical properties of the structures are studied.

  9. Radicals and Non-Equilibrium Processes in Low-Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Petrović, Zoran; Mason, Nigel; Hamaguchi, Satoshi; Radmilović-Radjenović, Marija

    2007-06-01

    Serbian Academy of Sciences and Arts and Institute of Physics, Belgrade. Each Symposium has sought to highlight a key topic of plasma research and the 5th EU - Japan symposium explored the role of Radicals and Non-Equilibrium Processes in Low-Temperature Plasmas since these are key elements of plasma processing. Other aspects of technologies for manufacturing integrated circuits were also considered. Unlike bio-medicine and perhaps politics, in plasma processing free radicals are `good radicals' but their kinetics are difficult to understand since there remains little data on their collisions with electrons and ions. One of the goals of the symposium was to facilitate communication between experimentalists and theorists in binary collision physics with plasma modellers and practitioners of plasma processing in order to optimize efforts to provide much needed data for both molecules and radicals of practical importance. The non-equilibrium nature of plasmas is critical in the efficient manufacturing of high resolution structures by anisotropic plasma etching on Si wafers since they allow separate control of the directionality and energy of ions and provide a high level of separation between the mean energies of electrons and ions. As nanotechnologies become practical, plasma processing may play a key role, not only in manufacturing of integrated circuits, but also for self-organization of massively parallel manufacturing of nanostructures. In this Symposium the key issues that are hindering the development of such new, higher resolution technologies were discussed and some possible solutions were proposed. In particular, damage control, fast neutral etching, processes at surface and modeling of profiles were addressed in several of the lectures. A wide range of topics are covered in this book including atomic and molecular collision physics - primarily focused towards formation and analysis of radicals, basic swarm data and breakdown kinetics, basic kinetics of RF and DC

  10. RELAXATION PROCESSES IN SOLAR WIND TURBULENCE

    SciTech Connect

    Servidio, S.; Carbone, V.; Gurgiolo, C.; Goldstein, M. L.

    2014-07-10

    Based on global conservation principles, magnetohydrodynamic (MHD) relaxation theory predicts the existence of several equilibria, such as the Taylor state or global dynamic alignment. These states are generally viewed as very long-time and large-scale equilibria, which emerge only after the termination of the turbulent cascade. As suggested by hydrodynamics and by recent MHD numerical simulations, relaxation processes can occur during the turbulent cascade that will manifest themselves as local patches of equilibrium-like configurations. Using multi-spacecraft analysis techniques in conjunction with Cluster data, we compute the current density and flow vorticity and for the first time demonstrate that these localized relaxation events are observed in the solar wind. Such events have important consequences for the statistics of plasma turbulence.

  11. Low-temperature solution-processed tin oxide as an alternative electron transporting layer for efficient perovskite solar cells.

    PubMed

    Ke, Weijun; Fang, Guojia; Liu, Qin; Xiong, Liangbin; Qin, Pingli; Tao, Hong; Wang, Jing; Lei, Hongwei; Li, Borui; Wan, Jiawei; Yang, Guang; Yan, Yanfa

    2015-06-01

    Lead halide perovskite solar cells with the high efficiencies typically use high-temperature processed TiO2 as the electron transporting layers (ETLs). Here, we demonstrate that low-temperature solution-processed nanocrystalline SnO2 can be an excellent alternative ETL material for efficient perovskite solar cells. Our best-performing planar cell using such a SnO2 ETL has achieved an average efficiency of 16.02%, obtained from efficiencies measured from both reverse and forward voltage scans. The outstanding performance of SnO2 ETLs is attributed to the excellent properties of nanocrystalline SnO2 films, such as good antireflection, suitable band edge positions, and high electron mobility. The simple low-temperature process is compatible with the roll-to-roll manufacturing of low-cost perovskite solar cells on flexible substrates. PMID:25987132

  12. Radicals and Non-Equilibrium Processes in Low-Temperature Plasmas

    NASA Astrophysics Data System (ADS)

    Petrović, Zoran; Mason, Nigel; Hamaguchi, Satoshi; Radmilović-Radjenović, Marija

    2007-06-01

    Serbian Academy of Sciences and Arts and Institute of Physics, Belgrade. Each Symposium has sought to highlight a key topic of plasma research and the 5th EU - Japan symposium explored the role of Radicals and Non-Equilibrium Processes in Low-Temperature Plasmas since these are key elements of plasma processing. Other aspects of technologies for manufacturing integrated circuits were also considered. Unlike bio-medicine and perhaps politics, in plasma processing free radicals are `good radicals' but their kinetics are difficult to understand since there remains little data on their collisions with electrons and ions. One of the goals of the symposium was to facilitate communication between experimentalists and theorists in binary collision physics with plasma modellers and practitioners of plasma processing in order to optimize efforts to provide much needed data for both molecules and radicals of practical importance. The non-equilibrium nature of plasmas is critical in the efficient manufacturing of high resolution structures by anisotropic plasma etching on Si wafers since they allow separate control of the directionality and energy of ions and provide a high level of separation between the mean energies of electrons and ions. As nanotechnologies become practical, plasma processing may play a key role, not only in manufacturing of integrated circuits, but also for self-organization of massively parallel manufacturing of nanostructures. In this Symposium the key issues that are hindering the development of such new, higher resolution technologies were discussed and some possible solutions were proposed. In particular, damage control, fast neutral etching, processes at surface and modeling of profiles were addressed in several of the lectures. A wide range of topics are covered in this book including atomic and molecular collision physics - primarily focused towards formation and analysis of radicals, basic swarm data and breakdown kinetics, basic kinetics of RF and DC

  13. Reducing the interface trap density in Al2O3/InP stacks by low-temperature thermal process

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Kai; Cao, Mingmin; Sun, Bing; Li, Haiou; Liu, Honggang

    2015-09-01

    By applying low-temperature processes below 300 °C, high-performance Al/Al2O3/InP metal-insulator-semiconductor capacitors with low interface trap density and small capacitance frequency dispersion at the accumulation regime are demonstrated. A minimum interface trap density of 1.2 × 1011 cm-2 eV-1 near the midgap is obtained. The impacts of thermal treatment on interface traps, thermal stability, and interfacial bonding configurations are studied and discussed. It is found that interface trap density could be significantly reduced by removing phosphorus and its oxides at low temperature (250-300 °C), while further increasing the thermal treatment temperature is harmful to interface quality.

  14. Low-temperature solution-processed flexible solar cells based on (In,Ga)N nanocubes.

    PubMed

    Qaeed, M A; Ibrahim, K; Saron, K M A; Ahmed, M A; Allam, Nageh K

    2014-07-01

    Indium gallium nitride nanocubes were syntheized via a low-temperature chemical route. Energy-dispersive X-ray spectroscopy and X-ray diffraction analyses confirmed the successful fabrication of (In,Ga)N with various indium mole fractions. The bandgap of the material was tunded as a function of the indium content. The fabricated nanocubes showed a deep level photoluminescence emission at 734 nm as well as in the visible region at 435-520 nm. The Hall effect measurements showed the hole concentration to constantly increase from 6.2 × 10(16) to 2.3 × 10(18) cm(-3), while the hole mobility to decrease from 0.92 to 0.1 cm(2) /(V s) as the doping ratio increases from 0.005 to 0.025 cm(-3). The solar cell device made of nanocubes film containing 0.4 indium on flexible substrates showed a short-circuit current density of 12.47 mA/cm(2) and an open-circuit voltage (Voc) of 0.48 V with 54% fill factor. The relationship between Voc and indium content in the fabricated films was also investigated. PMID:24937197

  15. Low-Temperature Oxidation of Fine UO2 Powders: A Process of Nanosized Domain Development.

    PubMed

    Leinders, Gregory; Pakarinen, Janne; Delville, Rémi; Cardinaels, Thomas; Binnemans, Koen; Verwerft, Marc

    2016-04-18

    The nanostructure and phase evolution in low-temperature oxidized (40-250 °C), fine UO2 powders (<200 nm) have been investigated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The extent of oxidation was also measured via in situ thermogravimetric analysis. The oxidation of fine powders was found to proceed differently as compared to oxidation of coarse-grained UO2. No discrete surface oxide layer was observed and no U3O8 was formed, despite the high degree of oxidation (up to O/U = 2.45). Instead, nanosized (5-15 nm) amorphous nuclei (interpreted as amorphous UO3), unmodulated and modulated U4O9, and a continuous range of U3O7-z phases with varying tetragonal distortion (c/a > 1) were observed. Oxidation involves formation of higher uranium oxides in nanodomains near the grain surface which, initially, have a disordered defect structure ("disordered U4O9"). As oxidation progresses, domain growth increases and the long-period modulated structure of U4O9 develops ("ordered U4O9"). A similar mechanism is understood to happen also in U3O7-z. PMID:27015279

  16. Structural, ferroelectric and piezoelectric properties of chemically processed, low temperature sintered piezoelectric BZT-BCT ceramics

    NASA Astrophysics Data System (ADS)

    Roy, Subir; Maharana, Rajalaxmi; Rangaswamy Reddy, S.; Singh, Sarabjit; Kumar, Pawan; Karthik, T.; Asthana, Saket; Bhanu Prasad, V. V.; Kamat, S. V.

    2016-03-01

    0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3TiO3) nanopowders were synthesized at very low temperature using a soft chemical approach. The synthesized powders and the consolidated disks were structurally characterized thoroughly by XRD, SEM, TEM and EPMA and also by ultraviolet and Raman spectroscopy. The 1350 °C sintered BZT-BCT disk displayed the highest density, underwent diffused phase transition centered at ˜100 °C and showed the highest dielectric constant (8917) and lowest dielectric loss (0.015). The sintered BZT-BCT sample with the highest density showed a maximum polarization (P max) of 13 μC cm-2 and remnant polarization of 6 μC cm-2. The same sample exhibited very high electrostrain of ˜0.12% under a relatively low electrical field of 3.5 kV mm-1.

  17. Low temperature adsorption and site-conversion process of CO on the Ni(111) surface

    NASA Astrophysics Data System (ADS)

    Beniya, Atsushi; Isomura, Noritake; Hirata, Hirohito; Watanabe, Yoshihide

    2012-12-01

    Low-temperature (25 K) adsorption states and the site conversion of adsorbed CO between the ontop and the hollow sites on Ni(111) were studied by means of temperature programmed desorption and infrared reflection absorption spectroscopy. The activation energy and pre-exponential factor of desorption were estimated to be 1.2 eV and 2.6 × 1013 s- 1, respectively, in the limit of zero coverage. At low coverage, CO molecules preferentially adsorbed at the hollow sites below 100 K. With increasing temperature, the ontop sites were also occupied. Using a van't Hoff plot, the enthalpy and the entropy differences between the hollow and ontop CO were estimated to be 36 meV and 0.043 meV K- 1, respectively, and the vibrational entropy difference was estimated to be 0.085 meV K- 1. The positive entropy difference was the result of the low-energy frustrated translational mode of the ontop CO, which was estimated to be 4.6 ± 0.3 meV. With the harmonic approximation, the upper limit of the activation energy of site hopping from ontop sites to hollow sites was estimated to be 61 meV. In addition, it was suggested that the activation energy of hollow-to-hollow site hopping via a bridge site was less than 37 meV.

  18. Sintering process and critical current density of low activation Mg11B2 superconductors from low temperature to high temperature

    NASA Astrophysics Data System (ADS)

    Cheng, Fang; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, Md; Somer, M.

    2016-08-01

    As the "low activation" superconductor, Mg11B2 has a potential application in superconducting coils for fusion reactor. In present work, the sintering process and critical current density of low activation Mg11B2 superconductors were systemically studied from low temperature to high temperature. It was found that the Jc and Hirr values of Mg11B2 bulks in present work are both obviously higher than that of those samples prepared in previous studies. Furthermore, the low-temperature sintered samples exhibit better Jc performance at high fields than the high-temperature sintered samples, due to strong grain boundaries pinning. On the other hand, the high-temperature sintered samples have higher Jc at low fields compared to low-temperature sintered samples, mainly owing to their better crystallinity and grain connectivity. The highest Jc value (2.20 ×105 A cm-2 at 20 K, self-field) is obtained in the Mg11B2 sample sintered at 850 °C for 45 min.

  19. Aluminizing Oil Casing Steel N80 by a Low-Temperature Pack Processing Modified with Zinc Addition

    NASA Astrophysics Data System (ADS)

    Huang, Min; Wang, Yu; Zhang, Xiao Yong

    Different aluminide coatings were prepared on oil casing steel N80 at a relatively lower temperature of 530°C for 2 h by pack powder modified with different content of zinc (Zn). The cross-sectional microstructure, element distribution and properties of as-aluminized oil casing steel N80 were investigated by SEM, EDS, micro-hardness test and electrochemical corrosion measurement. Results show that aluminide coating with around 50 μm in thickness can be successfully achieved by a low-temperature pack aluminizing processing with the addition of Zn. Zn in the pack powder can enhance the uniformity and continuity of the coating layer, while it has little effect on the thickness of as-packed coating with the increasing content of Zn from 38.8 wt.% to 84.4 wt.%. As the content of Zn is over 58.8 wt.%, two layer coating consisting of pure Zn layer and Fe-Al aluminide layer can be formed on oil casing steel N80 substrate. Furthermore, oil casing steel N80 with aluminizing coating shows a higher microhardness than that of original one except in the depth range of pure Zn layer, but the microhardness of oil casing steel substrate does not decrease after aluminizing which can be inferred that low-temperature aluminizing processing reported here will not bring any damages on the mechanical properties of oil casing steel N80. Additionally, a lower self-corrosion current density of oil casing steel N80 with aluminizing coating also indicates that low-temperature aluminizing processing is helpful to the corrosion resistance of oil casing steel N80.

  20. Low temperature process for the reduction of nitrogen oxides in an effluent

    SciTech Connect

    Epperly, W.R.; Sullivan, J.C.; Sprague, B.N.

    1989-10-10

    This patent describes a process for the reduction of the concentration of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel. The process comprising introducing a treatment agent which comprises an ammonium salt selected from the group consisting of triammonium citrate and ammonium formate into the effluent at an effluent temperature below 1300{sup 0}F.

  1. Thin-film copper indium gallium selenide solar cell based on low-temperature all-printing process.

    PubMed

    Singh, Manjeet; Jiu, Jinting; Sugahara, Tohru; Suganuma, Katsuaki

    2014-09-24

    In the solar cell field, development of simple, low-cost, and low-temperature fabrication processes has become an important trend for energy-saving and environmental issues. Copper indium gallium selenide (CIGS) solar cells have attracted much attention due to the high absorption coefficient, tunable band gap energy, and high efficiency. However, vacuum and high-temperature processing in fabrication of solar cells have limited the applications. There is a strong need to develop simple and scalable methods. In this work, a CIGS solar cell based on all printing steps and low-temperature annealing is developed. CIGS absorber thin film is deposited by using dodecylamine-stabilized CIGS nanoparticle ink followed by printing buffer layer. Silver nanowire (AgNW) ink and sol-gel-derived ZnO precursor solution are used to prepare a highly conductive window layer ZnO/[AgNW/ZnO] electrode with a printing method that achieves 16 Ω/sq sheet resistance and 94% transparency. A CIGS solar cell based on all printing processes exhibits efficiency of 1.6% with open circuit voltage of 0.48 V, short circuit current density of 9.7 mA/cm(2), and fill factor of 0.34 for 200 nm thick CIGS film, fabricated under ambient conditions and annealed at 250 °C. PMID:25180569

  2. Efficient polymer solar cells enabled by low temperature processed ternary metal oxide as electron transport interlayer with large stoichiometry window.

    PubMed

    Leong, Wei Lin; Ren, Yi; Seng, Hwee Leng; Huang, Zihao; Chiam, Sing Yang; Dodabalapur, Ananth

    2015-06-01

    Highly efficient organic photovoltaic cells are demonstrated by incorporating low temperature solution processed indium zinc oxide (IZO) as cathode interlayers. The IZOs are synthesized using a combustion synthesis method, which enables low temperature processes (150-250 °C). We investigated the IZO films with different electron mobilities (1.4×10(-3) to 0.23 cm2/(V·s)), hydroxide-oxide content (38% to 47%), and surface roughness (0.19-5.16 nm) by modulating the ternary metal oxide stoichiometry. The photovoltaic performance was found to be relatively insensitive to the composition ratio of In:Zn over the range of 0.8:0.2 to 0.5:0.5 despite the differences in their electrical and surface properties, achieving high power conversion efficiencies of 6.61%-7.04%. Changes in composition ratio of IZO do not lead to obvious differences in energy levels, diode parameters and morphology of the photoactive layer, as revealed by ultraviolet photoelectron spectroscopy (UPS), dark current analysis and time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements, correlating well with the large IZO stoichiometry window that enables efficient photovoltaic devices. Our results demonstrate the robustness of this ETL system and provide a convenient approach to realize a wide range of multicomponent oxides and compatible with processing on flexible plastic substrates. PMID:25978551

  3. Efficient planar Sb2S3 solar cells using a low-temperature solution-processed tin oxide electron conductor.

    PubMed

    Lei, Hongwei; Yang, Guang; Guo, Yaxiong; Xiong, Liangbin; Qin, Pingli; Dai, Xin; Zheng, Xiaolu; Ke, Weijun; Tao, Hong; Chen, Zhao; Li, Borui; Fang, Guojia

    2016-06-28

    Efficient planar antimony sulfide (Sb2S3) heterojunction solar cells have been made using chemical bath deposited (CBD) Sb2S3 as the absorber, low-temperature solution-processed tin oxide (SnO2) as the electron conductor and poly (3-hexylthiophene) (P3HT) as the hole conductor. A solar conversion efficiency of 2.8% was obtained at 1 sun illumination using a planar device consisting of F-doped SnO2 substrate/SnO2/CBD-Sb2S3/P3HT/Au, whereas the solar cells based on a titanium dioxide (TiO2) electron conductor exhibited a power conversion efficiency of 1.9%. Compared with conventional Sb2S3 sensitized solar cells, the high-temperature processed mesoscopic TiO2 scaffold is no longer needed. More importantly, a low-temperature solution-processed SnO2 layer was introduced for electron transportation to substitute the high-temperature sintered dense blocking TiO2 layer. Our planar solar cells not only have simple geometry with fewer steps to fabricate but also show enhanced performance. The higher efficiency of planar Sb2S3 solar cell devices based on a SnO2 electron conductor is attributed to their high transparency, uniform surface, efficient electron transport properties of SnO2, suitable energy band alignment, and reduced recombination at the interface of SnO2/Sb2S3. PMID:27264190

  4. Novel Low Temperature Processing for Enhanced Properties of Ion Implanted Thin Films and Amorphous Mixed Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Vemuri, Rajitha

    This research emphasizes the use of low energy and low temperature post processing to improve the performance and lifetime of thin films and thin film transistors, by applying the fundamentals of interaction of materials with conductive heating and electromagnetic radiation. Single frequency microwave anneal is used to rapidly recrystallize the damage induced during ion implantation in Si substrates. Volumetric heating of the sample in the presence of the microwave field facilitates quick absorption of radiation to promote recrystallization at the amorphous-crystalline interface, apart from electrical activation of the dopants due to relocation to the substitutional sites. Structural and electrical characterization confirm recrystallization of heavily implanted Si within 40 seconds anneal time with minimum dopant diffusion compared to rapid thermal annealed samples. The use of microwave anneal to improve performance of multilayer thin film devices, e.g. thin film transistors (TFTs) requires extensive study of interaction of individual layers with electromagnetic radiation. This issue has been addressed by developing detail understanding of thin films and interfaces in TFTs by studying reliability and failure mechanisms upon extensive stress test. Electrical and ambient stresses such as illumination, thermal, and mechanical stresses are inflicted on the mixed oxide based thin film transistors, which are explored due to high mobilities of the mixed oxide (indium zinc oxide, indium gallium zinc oxide) channel layer material. Semiconductor parameter analyzer is employed to extract transfer characteristics, useful to derive mobility, subthreshold, and threshold voltage parameters of the transistors. Low temperature post processing anneals compatible with polymer substrates are performed in several ambients (oxygen, forming gas and vacuum) at 150 °C as a preliminary step. The analysis of the results pre and post low temperature anneals using device physics fundamentals

  5. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

    PubMed Central

    2013-01-01

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  6. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

    PubMed

    Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

    2014-01-28

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm(2) V(-1) s(-1). We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm(2) V(-1) s(-1)) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  7. New Ultrasonic Controller and Characterization System for Low Temperature Drying Process Intensification

    NASA Astrophysics Data System (ADS)

    Andrés, R. R.; Blanco, A.; Acosta, V. M.; Riera, E.; Martínez, I.; Pinto, A.

    Process intensification constitutes a high interesting and promising industrial area. It aims to modify conventional processes or develop new technologies in order to reduce energy needs, increase yields and improve product quality. It has been demonstrated by this research group (CSIC) that power ultrasound have a great potential in food drying processes. The effects associated with the application of power ultrasound can enhance heat and mass transfer and may constitute a way for process intensification. The objective of this work has been the design and development of a new ultrasonic system for the power characterization of piezoelectric plate-transducers, as excitation, monitoring, analysis, control and characterization of their nonlinear response. For this purpose, the system proposes a new, efficient and economic approach that separates the effect of different parameters of the process like excitation, medium and transducer parameters and variables (voltage, current, frequency, impedance, vibration velocity, acoustic pressure and temperature) by observing the electrical, mechanical, acoustical and thermal behavior, and controlling the vibrational state.

  8. Low-temperature catalytic gasification of food processing wastes. 1995 topical report

    SciTech Connect

    Elliott, D.C.; Hart, T.R.

    1996-08-01

    The catalytic gasification system described in this report has undergone continuing development and refining work at Pacific Northwest National Laboratory (PNNL) for over 16 years. The original experiments, performed for the Gas Research Institute, were aimed at developing kinetics information for steam gasification of biomass in the presence of catalysts. From the fundamental research evolved the concept of a pressurized, catalytic gasification system for converting wet biomass feedstocks to fuel gas. Extensive batch reactor testing and limited continuous stirred-tank reactor tests provided useful design information for evaluating the preliminary economics of the process. This report is a follow-on to previous interim reports which reviewed the results of the studies conducted with batch and continuous-feed reactor systems from 1989 to 1994, including much work with food processing wastes. The discussion here provides details of experiments on food processing waste feedstock materials, exclusively, that were conducted in batch and continuous- flow reactors.

  9. Energy (mass) transfer processes in low-temperature plasma as applied to forming ordered structures

    NASA Astrophysics Data System (ADS)

    Abramenko, T. N.; Laktyushina, T. V.; Laktyushin, A. N.

    2000-03-01

    The methods of irreversible thermodynamics are adopted to analyze the energy (mass) transfer in gases (their mixtures) over a wide temperature range up to 20000 K. An energy transfer process is considered as a path in the state space, and a concept of non-Euclidean state space is postulated. Experimental data on the gas thermal conductivity over a wide temperature range is generalized by the methods of thermodynamic similarity theory. Thermal conductivities of CH4-O2 and CH4-H2O mixtures are calculated for technological applications. The process of forming a space-time structure is analyzed by using the experimental data on the gas thermal conductivity over a wide temperature range. An attempt is made to interpret the mechanism of the thermal diffusion in gases due to the forming of ordered structures. A contribution of the diffusional thermoeffect to the energy transfer processes in a three-component nitrogen plasma is calculated.

  10. Pathogenic psychrotolerant sporeformers: an emerging challenge for low-temperature storage of minimally processed foods.

    PubMed

    Markland, Sarah M; Farkas, Daniel F; Kniel, Kalmia E; Hoover, Dallas G

    2013-05-01

    Sporeforming bacteria are a significant problem in the food industry as they are ubiquitous in nature and capable of resisting inactivation by heat and chemical treatments designed to inactivate them. Beyond spoilage issues, psychrotolerant sporeformers are becoming increasingly recognized as a potential hazard given the ever-expanding demand for refrigerated processed foods with extended shelf-life. In these products, the sporeforming pathogens of concern are Bacillus cereus, Bacillus weihenstephanensis, and Clostridium botulinum type E. This review article examines the foods, conditions, and organisms responsible for the food safety issue caused by the germination and outgrowth of psychrotolerant sporeforming pathogens in minimally processed refrigerated foods. PMID:23536982

  11. Low temperature epoxy-free and flux-less bonding process applied to solid-state microchip laser

    NASA Astrophysics Data System (ADS)

    Kopp, Christophe; Gilbert, Karen

    2005-06-01

    Epoxy free bonding is decisive to improve reliability of optoelectronic devices using active components such as laser diode. Therefore soldering is usually preferred as bonding technology but it often needs components metallizing, heating over 140°C and liquid or gas fluxing which may let some corrosive residues. Thus soldering cannot be widely used on optical microchip components. Working on solid-state microchip laser bonding in a project called NANOPACK supported by the French research ministry, we have developed low temperature epoxy free bonding technology. The microchip laser is bonded onto a submount by thermocompression at low temperature and moderate relative pressure using an indium foil to form the adhesive joint. This technology uses both a unique property of indium to wet and to bond to certain non-metallics such as glass, quartz, and various metallic oxides, and fluxless soldering of indium with gold by solid-state interdiffusion bonding or solid-liquid interdiffusion bonding. This way, mean bond strength about 300g/mm2 has been obtained for 2mg chip with very good resistance to thermal aging. This epoxy free technology offers a real alternative for bonding non-metallic components which cannot stand usual soldering processes. Moreover, as it is a fluxless process, this technology is very attractive to hermetically seal lids under controlled atmosphere.

  12. Rapid low-temperature epitaxial growth using a hot-element assisted chemical vapor deposition process

    DOEpatents

    Iwancizko, Eugene; Jones, Kim M.; Crandall, Richard S.; Nelson, Brent P.; Mahan, Archie Harvin

    2001-01-01

    The invention provides a process for depositing an epitaxial layer on a crystalline substrate, comprising the steps of providing a chamber having an element capable of heating, introducing the substrate into the chamber, heating the element at a temperature sufficient to decompose a source gas, passing the source gas in contact with the element; and forming an epitaxial layer on the substrate.

  13. Modified Phenylethynyl Containing Imides for Secondary Bonding: Non-Autoclave, Low Temperature Processable Adhesives

    NASA Technical Reports Server (NTRS)

    Dezern, James F. (Technical Monitor); Chang, Alice C.

    1999-01-01

    As part of a program to develop structural adhesives for high performance aerospace applications, research continued on the development of modified phenylethynyl containing imides, LaRC(trademark)MPEIs. In previous reports, the polymer properties were controlled by varying the molecular weight, the amount of branching, and the phenylethynyl content and by blending with low molecular weight materials. This research involves changing the flexibility in the copolyimide backbone of the branched, phenylethynyl terminated adhesives. These adhesives exhibit excellent processability at pressures as low as 15 psi and temperatures as low as 288 C. The Ti/Ti lap shear specimens are processable in an autoclave or a temperature programmable oven under a vacuum bag at 288-300 C without external pressure. The cured polymers exhibit high mechanical properties and excellent solvent resistance. The chemistry and properties of these adhesives are presented.

  14. Low Temperature Processed Complementary Metal Oxide Semiconductor (CMOS) Device by Oxidation Effect from Capping Layer

    PubMed Central

    Wang, Zhenwei; Al-Jawhari, Hala A.; Nayak, Pradipta K.; Caraveo-Frescas, J. A.; Wei, Nini; Hedhili, M. N.; Alshareef, H. N.

    2015-01-01

    In this report, both p- and n-type tin oxide thin-film transistors (TFTs) were simultaneously achieved using single-step deposition of the tin oxide channel layer. The tuning of charge carrier polarity in the tin oxide channel is achieved by selectively depositing a copper oxide capping layer on top of tin oxide, which serves as an oxygen source, providing additional oxygen to form an n-type tin dioxide phase. The oxidation process can be realized by annealing at temperature as low as 190°C in air, which is significantly lower than the temperature generally required to form tin dioxide. Based on this approach, CMOS inverters based entirely on tin oxide TFTs were fabricated. Our method provides a solution to lower the process temperature for tin dioxide phase, which facilitates the application of this transparent oxide semiconductor in emerging electronic devices field. PMID:25892711

  15. Low temperature-dependent salmonid alphavirus glycoprotein processing and recombinant virus-like particle formation.

    PubMed

    Metz, Stefan W; Feenstra, Femke; Villoing, Stephane; van Hulten, Marielle C; van Lent, Jan W; Koumans, Joseph; Vlak, Just M; Pijlman, Gorben P

    2011-01-01

    Pancreas disease (PD) and sleeping disease (SD) are important viral scourges in aquaculture of Atlantic salmon and rainbow trout. The etiological agent of PD and SD is salmonid alphavirus (SAV), an unusual member of the Togaviridae (genus Alphavirus). SAV replicates at lower temperatures in fish. Outbreaks of SAV are associated with large economic losses of ~17 to 50 million $/year. Current control strategies rely on vaccination with inactivated virus formulations that are cumbersome to obtain and have intrinsic safety risks. In this research we were able to obtain non-infectious virus-like particles (VLPs) of SAV via expression of recombinant baculoviruses encoding SAV capsid protein and two major immunodominant viral glycoproteins, E1 and E2 in Spodoptera frugiperda Sf9 insect cells. However, this was only achieved when a temperature shift from 27°C to lower temperatures was applied. At 27°C, precursor E2 (PE2) was misfolded and not processed by host furin into mature E2. Hence, E2 was detected neither on the surface of infected cells nor as VLPs in the culture fluid. However, when temperatures during protein expression were lowered, PE2 was processed into mature E2 in a temperature-dependent manner and VLPs were abundantly produced. So, temperature shift-down during synthesis is a prerequisite for correct SAV glycoprotein processing and recombinant VLP production. PMID:21991361

  16. Low Temperature-Dependent Salmonid Alphavirus Glycoprotein Processing and Recombinant Virus-Like Particle Formation

    PubMed Central

    Villoing, Stephane; van Hulten, Marielle C.; van Lent, Jan W.; Koumans, Joseph; Vlak, Just M.; Pijlman, Gorben P.

    2011-01-01

    Pancreas disease (PD) and sleeping disease (SD) are important viral scourges in aquaculture of Atlantic salmon and rainbow trout. The etiological agent of PD and SD is salmonid alphavirus (SAV), an unusual member of the Togaviridae (genus Alphavirus). SAV replicates at lower temperatures in fish. Outbreaks of SAV are associated with large economic losses of ∼17 to 50 million $/year. Current control strategies rely on vaccination with inactivated virus formulations that are cumbersome to obtain and have intrinsic safety risks. In this research we were able to obtain non-infectious virus-like particles (VLPs) of SAV via expression of recombinant baculoviruses encoding SAV capsid protein and two major immunodominant viral glycoproteins, E1 and E2 in Spodoptera frugiperda Sf9 insect cells. However, this was only achieved when a temperature shift from 27°C to lower temperatures was applied. At 27°C, precursor E2 (PE2) was misfolded and not processed by host furin into mature E2. Hence, E2 was detected neither on the surface of infected cells nor as VLPs in the culture fluid. However, when temperatures during protein expression were lowered, PE2 was processed into mature E2 in a temperature-dependent manner and VLPs were abundantly produced. So, temperature shift-down during synthesis is a prerequisite for correct SAV glycoprotein processing and recombinant VLP production. PMID:21991361

  17. Simulation of the Thermal Process of Butt Welding of Polyethylene Pipes at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Starostin, N. P.; Ammosova, O. A.

    2016-06-01

    A theoretical study has been made of the thermal process of welding polyethylene pipes for gas pipelines at low ambient air temperatures. The mathematical model used takes into account the heat of the phase transition in the temperature range, as well as the thermal effect of the fin formed by the slip. Computing experiments have shown that it is possible to control the temperature regime in welding at low ambient air temperatures and provide, in the thermal influence zone, the same change in the temperature field as at permissible air temperatures.

  18. Low temperature removal of inorganic sulfur compounds from mining process waters.

    PubMed

    Liljeqvist, Maria; Sundkvist, Jan-Eric; Saleh, Amang; Dopson, Mark

    2011-06-01

    Process water and effluents from mining operations treating sulfide rich ores often contain considerable concentrations of metastable inorganic sulfur compounds such as thiosulfate and tetrathionate. These species may cause environmental problems if released to downstream recipients due to oxidation to sulfuric acid catalyzed by acidophilic microorganisms. Molecular phylogenic analysis of the tailings pond and recipient streams identified psychrotolerant and mesophilic inorganic sulfur compound oxidizing microorganisms. This suggested year round thiosalt oxidation occurs. Mining process waters may also contain inhibiting substances such as thiocyanate from cyanidation plants. However, toxicity experiments suggested their expected concentrations would not inhibit thiosalt oxidation by Acidithiobacillus ferrivorans SS3. A mixed culture from a permanently cold (4-6 °C) low pH environment was tested for thiosalt removal in a reactor design including a biogenerator and a main reactor containing a biofilm carrier. The biogenerator and main reactors were successively reduced in temperature to 5-6 °C when 43.8% of the chemical oxidation demand was removed. However, it was found that the oxidation of thiosulfate was not fully completed to sulfate since low residual concentrations of tetrathionate and trithionate were found in the discharge. This study has demonstrated the potential of using biotechnological solutions to remove inorganic sulfur compounds at 6°C and thus, reduce the impact of mining on the environment. PMID:21280027

  19. Characterization of low temperature graphene synthesis in inductively coupled plasma chemical vapor deposition process with optical emission spectroscopy.

    PubMed

    Ma, Yifei; Kim, Daekyoung; Jang, Haegyu; Cho, Sung Min; Chae, Heeyeop

    2014-12-01

    Low-temperature graphene was synthesized at 400 degrees C with inductively coupled plasma chemical vapor deposition (PECVD) process. The effects of plasma power and flow rate of various carbon containing precursors and hydrogen on graphene properties were investigated with optical emission spectroscopy (OES). Various radicals monitored by OES were correlated with graphene film properties such as sheet resistance, I(D)/I(G) ratio of Raman spectra and transparency. C2H2 was used as a main precursor and the increase of plasma power enhanced intensity of carbon (C2) radical OES intensity in plasma, reduced sheet resistance and increased transparency of graphene films. The reduced flow rate of C2H2 decreased sheet resistance and increased transparency of graphene films in the range of this study. H2 addition was found to increase sheet resistance, transparency and attributed to reduction of graphene grain and etching graphene layers. OES analysis showed that C2 radicals contribute to graphite networking and sheet resistance reduction. TEM and AFM were applied to provide credible information that graphene had been successfully grown at low temperature. PMID:25971011

  20. Electro-Mechanical Properties of Metal-Insulator-Metal Device Fabricated on Polymer Substrate Using Low-Temperature Process

    NASA Astrophysics Data System (ADS)

    Park, Sung Kyu; Han, Jeong In; Kim, Won Keun; Hong, Sung Jei; Kwak, Min Gi; Lee, Myung Jae; Chung, Kwan Soo

    2002-02-01

    High-performance metal-insulator-metal (MIM) devices on flexible polymer substrates were successfully fabricated without any defects such as cracks, delamination and blistering. This work examines the mechanical and electrical properties of MIM devices constructed using anodic Ta2O5 films. Using newly developed methods including stepped heating process and low-temperature post-annealing below 180°C, we obtained high-performances MIM devices on polymer substrates. Here, we propose the use of stacked bottom electrode and water barrier layer in order to enhance the ductility of the Ta electrode and to prevent blistering problems, respectively. Rutherford backscattering spectroscopy (RBS), auger electron spectroscopy (AES) and transmission electronic microscope (TEM) observations were performed for the structural investigation of the MIM devices on polymer substrates. Electrical measurements were also carried out for as-deposited and thermally treated MIM devices including Al/Ta/Ta2O5/Cr or Ti structures. They exhibit a low leakage current (below 10-7 A/cm2 at 2 MV) and reasonable breakdown voltage (5-7 MV/cm) with a uniformity of 92%. Finally, under low-temperature post-annealing conditions, The Current-Voltage (I-V) behaviors and conduction mechanisms of MIM devices on polymer substrates are discussed based on the results of electrical measurements, structural investigations and conduction band modeling.

  1. Low-Temperature and Solution-Processed Amorphous WO(x) as Electron-Selective Layer for Perovskite Solar Cells.

    PubMed

    Wang, Kai; Shi, Yantao; Dong, Qingshun; Li, Yu; Wang, Shufeng; Yu, Xufeng; Wu, Mengyao; Ma, Tingli

    2015-03-01

    The electron-selective layer (ESL) is an indispensable component of perovskite solar cells (PSCs) and is responsible for the collection of photogenerated electrons. Preparing ESL at a low temperature is significant for future fabrication of flexible PSCs. In this work, solution-processed amorphous WO(x) thin film was prepared facilely at low temperature and used as ESL in PSCs. Results indicated that a large quantity of nanocaves were observed in the WO(x) thin film. In comparison with the conventional TiO2 ESL, the WO(x) ESL exhibited comparable light transmittance but higher electrical conductivity. Compared with the TiO2-based PSCs, PSCs that use WO(x) ESL exhibited comparable photoelectric conversion efficiency, larger short-circuit current density, but lower open-circuit voltage. Electrochemical characterization indicated that the unsatisfied open-circuit voltage and fill factor were caused by the inherent charge recombination. This study demonstrated that this material is an excellent candidate for ESL. PMID:26262648

  2. Experimental determination of barium isotope fractionation during diffusion and adsorption processes at low temperatures

    NASA Astrophysics Data System (ADS)

    van Zuilen, Kirsten; Müller, Thomas; Nägler, Thomas F.; Dietzel, Martin; Küsters, Tim

    2016-08-01

    Variations in barium (Ba) stable isotope abundances measured in low and high temperature environments have recently received increasing attention. The actual processes controlling Ba isotope fractionation, however, remain mostly elusive. In this study, we present the first experimental approach to quantify the contribution of diffusion and adsorption on mass-dependent Ba isotope fractionation during transport of aqueous Ba2+ ions through a porous medium. Experiments have been carried out in which a BaCl2 solution of known isotopic composition diffused through u-shaped glass tubes filled with silica hydrogel at 10 °C and 25 °C for up to 201 days. The diffused Ba was highly fractionated by up to -2.15‰ in δ137/134Ba, despite the low relative difference in atomic mass. The time-dependent isotope fractionation can be successfully reproduced by a diffusive transport model accounting for mass-dependent differences in the effective diffusivities of the Ba isotope species (D137Ba /D134Ba =(m134 /m137) β). Values of β extracted from the transport model were in the range of 0.010-0.011. Independently conducted batch experiments revealed that adsorption of Ba onto the surface of silica hydrogel favoured the heavier Ba isotopes (α = 1.00015 ± 0.00008). The contribution of adsorption on the overall isotope fractionation in the diffusion experiments, however, was found to be small. Our results contribute to the understanding of Ba isotope fractionation processes, which is crucial for interpreting natural isotope variations and the assessment of Ba isotope ratios as geochemical proxies.

  3. Low-temperature and solution-processed indium tin oxide films and their applications in flexible transparent capacitive pressure sensors

    NASA Astrophysics Data System (ADS)

    Yu, Jian; Chen, Sujie; Wang, Nana; Ye, Zhizhen; Qi, Hang; Guo, Xiaojun; Jin, Yizheng

    2016-04-01

    It is of great interest to fabricate indium tin oxide (ITO) films by solution-based techniques at low temperatures. Here, we combined the use of colloidal ITO nanoflowers synthesized by the strategy of limited ligand protection and oxygen plasma treatment which effectively remove the surface ligands of ITO nanocrystals to meet this goal. These efforts led to high-quality ITO films with resistivity as low as 2.33 × 10-2 Ω cm, which is the best result for solution-processed ITO nanocrystal films deposited at temperatures lower than 200 °C. The annealing-free processing allowed us to deposit ITO nanoflower films onto plastic substrates and apply them in flexible capacitive pressure sensors. The single-pixel device showed decent sensitivity and reproducibility, and the arrayed sensors exhibited good spatial resolution.

  4. Zoned chondrules in Semarkona: Evidence for high-and low-temperature processing

    USGS Publications Warehouse

    Grossman, J.N.; Alexander, C.M. O'D.; Wang, Jingyuan; Brearley, A.J.

    2002-01-01

    between altered glass and surrounding matrix and rim material. Calcium was mainly lost during this process, and other nonvolatile elements may have been mobile as well. Some unzoned, low-FeO chondrules appear to have fully altered mesostasis.

  5. Ultra-Slow Dielectric Relaxation Process in Polyols

    NASA Astrophysics Data System (ADS)

    Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

    2004-04-01

    Dielectric relaxation processes with relaxation times larger than that for the structural α process are reported for glycerol, xylitol, sorbitol and their mixtures for the first time. Appearance of this ultra-slow process depends on cooling rate. More rapid cooling gives larger dielectric relaxation strength. However, relaxation time is not affected by cooling rate and shows non-Arrhenius temperature dependence with correlation to the α process. It can be considered that non-equilibrium dynamic structure causes the ultra-slow process. Scale of such structure would be much larger than that of the region for the cooperative molecular orientations for the α process.

  6. Dynamics of the phase formation process upon the low temperature selenization of Cu/In-multilayer stacks

    SciTech Connect

    Oertel, M. Ronning, C.

    2015-03-14

    Phase reactions occurring during a low temperature selenization of thin In/Cu-multilayer stacks were investigated by ex-situ x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). Therefore, dc-sputtered In/Cu-multilayers onto molybdenum coated soda lime glass were selenized in a high vacuum system at temperatures between 260 and 340 °C with different dwell times and selenium supply. The combination of the results of the phase analysis by XRD and the measurements of the in-depth elemental distribution by EDS allowed a conclusion on the occurring reactions within the layer depth. We found two CuInSe{sub 2} formation processes depending on the applied temperature. Already, at a heater temperature of 260 °C, the CuInSe{sub 2} formation can occur by the reaction of Cu{sub 2−x}Se with In{sub 4}Se{sub 3} and Se. At 340 °C, CuInSe{sub 2} is formed by the reaction of Cu{sub 2−x}Se with InSe and Se. Because both reactions need additional selenium, the selenium supply during the selenization can shift the reaction equilibria either to the metal binaries side or to the CuInSe{sub 2} side. Interestingly, a lower selenium supply shifts the equilibrium to the CuInSe{sub 2} side, because the amount of selenium incorporated into the metallic layer is higher for a lower selenium supply. Most likely, a larger number of grain boundaries are the reason for the stronger selenium incorporation. The results of the phase formation studies were used to design a two stage selenization process to get a defined structure of an indium selenide- and a copper selenide-layer at low temperatures as the origin for a controlled interdiffusion to form the CuInSe{sub 2}-absorber-layer at higher temperatures. The approach delivers a CuInSe{sub 2} absorber which reach total area efficiencies of 11.8% (13.0% active area) in a CuInSe{sub 2}-thin-film solar cell. A finished formation of CuInSe{sub 2} at low temperature was not observed in our experiments but is probably

  7. Dynamics of the phase formation process upon the low temperature selenization of Cu/In-multilayer stacks

    NASA Astrophysics Data System (ADS)

    Oertel, M.; Ronning, C.

    2015-03-01

    Phase reactions occurring during a low temperature selenization of thin In/Cu-multilayer stacks were investigated by ex-situ x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS). Therefore, dc-sputtered In/Cu-multilayers onto molybdenum coated soda lime glass were selenized in a high vacuum system at temperatures between 260 and 340 °C with different dwell times and selenium supply. The combination of the results of the phase analysis by XRD and the measurements of the in-depth elemental distribution by EDS allowed a conclusion on the occurring reactions within the layer depth. We found two CuInSe2 formation processes depending on the applied temperature. Already, at a heater temperature of 260 °C, the CuInSe2 formation can occur by the reaction of Cu2-xSe with In4Se3 and Se. At 340 °C, CuInSe2 is formed by the reaction of Cu2-xSe with InSe and Se. Because both reactions need additional selenium, the selenium supply during the selenization can shift the reaction equilibria either to the metal binaries side or to the CuInSe2 side. Interestingly, a lower selenium supply shifts the equilibrium to the CuInSe2 side, because the amount of selenium incorporated into the metallic layer is higher for a lower selenium supply. Most likely, a larger number of grain boundaries are the reason for the stronger selenium incorporation. The results of the phase formation studies were used to design a two stage selenization process to get a defined structure of an indium selenide- and a copper selenide-layer at low temperatures as the origin for a controlled interdiffusion to form the CuInSe2-absorber-layer at higher temperatures. The approach delivers a CuInSe2 absorber which reach total area efficiencies of 11.8% (13.0% active area) in a CuInSe2-thin-film solar cell. A finished formation of CuInSe2 at low temperature was not observed in our experiments but is probably possible for longer dwell times.

  8. Deposition behavior and microstructural development of TiNi powder particles in low temperature-HVOF spraying process

    NASA Astrophysics Data System (ADS)

    Lin, Q. S.; Zhou, K. S.; Deng, C. M.; Liu, M.; Xiao, X. L.; Deng, C. G.

    2013-10-01

    TiNi alloy particles were deposited at high velocity on Q235 steel substrate in thermally softened solid state by the modified high-velocity oxygen fuel spraying process (so called low temperature HVOF). Microstructural developments and deposition behaviors of a deposited single particle were observed by high resolution scanning electron microscopy and transmission electron microscopy. A single TiNi particle sprayed onto the substrate was severely deformed and the jetting-out phenomenon occurred in the margin of the splat. Extremely fine grains were observed along the interfacial boundary of the deposited particles where the most severe deformation had taken place. The grain refinement at the high deformed region of a splat was arisen from dynamic recrystallization of heavily deformed grain during deformation.

  9. Low-temperature processable amorphous In-W-O thin-film transistors with high mobility and stability

    SciTech Connect

    Kizu, Takio; Aikawa, Shinya; Mitoma, Nobuhiko; Shimizu, Maki; Gao, Xu; Lin, Meng-Fang; Tsukagoshi, Kazuhito; Nabatame, Toshihide

    2014-04-14

    Thin-film transistors (TFTs) with a high stability and a high field-effect mobility have been achieved using W-doped indium oxide semiconductors in a low-temperature process (∼150 °C). By incorporating WO{sub 3} into indium oxide, TFTs that were highly stable under a negative bias stress were reproducibly achieved without high-temperature annealing, and the degradation of the field-effect mobility was not pronounced. This may be due to the efficient suppression of the excess oxygen vacancies in the film by the high dissociation energy of the bond between oxygen and W atoms and to the different charge states of W ions.

  10. Preparation of nitrogen doped zinc oxide nanoparticles and thin films by colloidal route and low temperature nitridation process

    NASA Astrophysics Data System (ADS)

    Valour, Arnaud; Cheviré, François; Tessier, Franck; Grasset, Fabien; Dierre, Benjamin; Jiang, Tengfei; Faulques, Eric; Cario, Laurent; Jobic, Stéphane

    2016-04-01

    Nitrogen doped zinc oxide (ZnO) nanoparticles have been synthesized using a colloidal route and low temperature nitridation process. Based on these results, 200 nm thick transparent ZnO thin films have been prepared by dip-coating on SiO2 substrate from a ZnO colloidal solution. Zinc peroxide (ZnO2) thin film was then obtained after the chemical conversion of a ZnO colloidal thin film by H2O2 solution. Finally, a nitrogen doped ZnO nanocrystalline thin film (ZnO:N) was obtained by ammonolysis at 250 °C. All the films have been characterized by scanning electron microscopy, X-ray diffraction, X-Ray photoelectron spectroscopy and UV-Visible transmittance spectroscopy.

  11. [Study on bio-contact oxidation A/O process of Guanting Reservior water under low temperature].

    PubMed

    He, Xing-hai; Wu, Jiang-jin; Chang, Li-chun; Wei, Shu-jun; Ke, Jian-ming

    2004-01-01

    The results of the experiments showed that biological contact A/O process could run steadily under low temperature and had better removal effect for ammonia nitrogen and had some removal effect for COD and TN from water of Guanting Reservoir. When the temperature dropped greatly, removal ratio of ammonia nitrogen dropped evidently, but gradually rose and remained at high removal level at last. Under the conditions of the experiment that the temperature was 0-5 degrees C and influent ammonia nitrogen was about 10 mg/L, ammonia nitrogen removal rate remained more than 95% at last. The change of temperature had no evident influence on removal effect of COD. And the conclusion could be got by microscope that under the temperature at 0-5 degrees C the microorganism in the biofilm still had a good activity. PMID:15330431

  12. Nanocrystalline rutile electron extraction layer enables low-temperature solution processed perovskite photovoltaics with 13.7% efficiency.

    PubMed

    Yella, Aswani; Heiniger, Leo-Philipp; Gao, Peng; Nazeeruddin, Mohammad Khaja; Grätzel, Michael

    2014-05-14

    We demonstrate low-temperature (70 °C) solution processing of TiO2/CH3NH3PbI3 based solar cells, resulting in impressive power conversion efficiency (PCE) of 13.7%. Along with the high efficiency, a strikingly high open circuit potential (VOC) of 1110 mV was realized using this low-temperature chemical bath deposition approach. To the best of our knowledge, this is so far the highest VOC value for solution-processed TiO2/CH3NH3PbI3 solar cells. We deposited a nanocrystalline TiO2 (rutile) hole-blocking layer on a fluorine-doped tin oxide (FTO) conducting glass substrate via hydrolysis of TiCl4 at 70 °C, forming the electron selective contact with the photoactive CH3NH3PbI3 film. We find that the nanocrystalline rutile TiO2 achieves a much better performance than a planar TiO2 (anatase) film prepared by high-temperature spin coating of TiCl4, which produces a much lower PCE of 3.7%. We attribute this to the formation of an intimate junction of large interfacial area between the nanocrystalline rutile TiO2 and the CH3NH3PbI3 layer, which is much more effective in extracting photogenerated electrons than the planar anatase film. Since the complete fabrication of the solar cell is carried out below 100 °C, this method can be easily extended to plastic substrates. PMID:24628563

  13. Low temperature benefits discussed.

    PubMed

    2016-03-01

    At a recent educational workshop event hosted by Advanced Sterilization Products, expert speakers including Authorising Engineers, and delegates, discussed some of their experiences of low temperature sterilisation of 'hi-tech' medical devices, and highlighted the benefits of a process which allows decontamination of instruments and, for example, parts of robotic surgery systems, that cannot be decontaminated using standard methods. Also examined,and reported on here in an article that first appeared in HEJ's sister publication, The Clinical Services Journal, were some of the disadvantages of low temperature sterilisation, the key considerations and options when choosing such a system, and a focus on how the technology's use had benefited a major London-based NHS Trust. PMID:27132304

  14. [Startup, stable operation and process failure of EBPR system under the low temperature and low dissolved oxygen condition].

    PubMed

    Ma, Juan; Li, Lu; Yu, Xiao-Jun; Wei, Xue-Fen; Liu, Juan-Li

    2015-02-01

    A sequencing batch reactor (SBR) was started up and operated with alternating anaerobic/oxic (An/O) to perform enhanced biological phosphorus removal (EBPR) under the condition of 13-16 degrees C. The results showed that under the condition of low temperature, the EBPR system was successfully started up in a short time (<6 d). The reactor achieved a high and stable phosphorus removal performance with an influent phosphate concentration of 20 mg x L(-1) and the dissolved oxygen (DO) concentration of 2 mg x L(-1). The effluent phosphate concentration was lower than 0.5 mg x L(-1). It was found that decreasing DO had an influence on the steady operation of EBPR system. As DO concentration of aerobic phase decreased from 2 mg x L(-1) to 1 mg x L(-1), the system could still perform EBPR and the phosphorus removal efficiency was greater than 97.4%. However, the amount of phosphate released during anaerobic phase was observed to decrease slightly compared with that of 2 mg x L(-1) DO condition. Moreover, the phosphorus removal performance of the system deteriorated immediately and the effluent phosphate concentration couldn't meet the national integrated wastewater discharge standard when DO concentration was further lowered to 0.5 mg x L(-1). The experiments of increasing DO to recover phosphorus removal performance of the EBPR suggested the process failure resulted from low DO was not reversible in the short-term. It was also found that the batch tests of anoxic phosphorus uptake using nitrite and nitrate as electron acceptors had an impact on the stable operation of EBPR system, whereas the resulting negative influence could be recovered within 6 cycles. In addition, the mixed liquid suspended solids (MLSS) of the EBPR system remained stable and the sludge volume index (SVI) decreased to a certain extend in a long run, implying long-term low temperature and low DO condition favored the sludge sedimentation. PMID:26031088

  15. Low-Temperature Solution-Processed Kesterite Solar Cell Based on in Situ Deposition of Ultrathin Absorber Layer.

    PubMed

    Hou, Yi; Azimi, Hamed; Gasparini, Nicola; Salvador, Michael; Chen, Wei; Khanzada, Laraib S; Brandl, Marco; Hock, Rainer; Brabec, Christoph J

    2015-09-30

    The production of high-performance, solution-processed kesterite Cu2ZnSn(Sx,Se1-x)4 (CZTSSe) solar cells typically relies on high-temperature crystallization processes in chalcogen-containing atmosphere and often on the use of environmentally harmful solvents, which could hinder the widespread adoption of this technology. We report a method for processing selenium free Cu2ZnSnS4 (CZTS) solar cells based on a short annealing step at temperatures as low as 350 °C using a molecular based precursor, fully avoiding highly toxic solvents and high-temperature sulfurization. We show that a simple device structure consisting of ITO/CZTS/CdS/Al and comprising an extremely thin absorber layer (∼110 nm) achieves a current density of 8.6 mA/cm(2). Over the course of 400 days under ambient conditions encapsulated devices retain close to 100% of their original efficiency. Using impedance spectroscopy and photoinduced charge carrier extraction by linearly increasing voltage (photo-CELIV), we demonstrate that reduced charge carrier mobility is one limiting parameter of low-temperature CZTS photovoltaics. These results may inform less energy demanding strategies for the production of CZTS optoelectronic layers compatible with large-scale processing techniques. PMID:26353923

  16. Modeling of Two-Phase Flow and Heat Transfer in Low-Temperature Oxygen-Fuel Spray Process

    NASA Astrophysics Data System (ADS)

    Shan, Y. G.; Shen, C. H.; Jia, L. B.; Mostaghimi, J.

    2014-01-01

    The low-temperature oxygen-fuel (LTOF) spray is a modification of high velocity oxygen fuel spray. In this process, the high-temperature gas is accelerated to supersonic speed through a Laval nozzle followed by a straight barrel. By injecting room temperature gas into the mixing chamber, the temperature of the gas can be controlled in a range of about 1000-2500 K, so that some oxygen and temperature-sensitive materials, such as titanium and copper, can avoid oxidation or decomposition during the spraying process. The purpose of this paper is to establish a 2-D mathematical model to simulate the supersonic gas dynamics and particles behavior in LTOF process. The temperature and velocity of the flow fields, and the trajectory and heating of in-flight particles are predicted for different operating parameters. The model is validated by experimental data in the literature. Effects of the mixing gas flow rates, particle sizes, and injection conditions on this process were investigated as well.

  17. Novel Combination of Efficient Perovskite Solar Cells with Low Temperature Processed Compact TiO2 Layer via Anodic Oxidation.

    PubMed

    Du, Yangyang; Cai, Hongkun; Wen, Hongbin; Wu, Yuxiang; Huang, Like; Ni, Jian; Li, Juan; Zhang, Jianjun

    2016-05-25

    In this work, a facile and low temperature processed anodic oxidation approach is proposed for fabricating compact and homogeneous titanium dioxide film (AO-TiO2). In order to realize morphology and thickness control of AO-TiO2, the theory concerning anodic oxidation (AO) is unveiled and the influence of relevant parameters during the process of AO such as electrolyte ingredient and oxidation voltage on AO-TiO2 formation is observed as well. Meanwhile, we demonstrate that the planar perovskite solar cells (p-PSCs) fabricated in ambient air and utilizing optimized AO-TiO2 as electron transport layer (ETL) can deliver repeatable power conversion efficiency (PCE) over 13%, which possess superior open-circuit voltage (Voc) and higher fill factor (FF) compared to its counterpart utilizing conventional high temperature processed compact TiO2 (c-TiO2) as ETL. Through a further comparative study, it is indicated that the improvement of device performance should be attributed to more effective electron collection from perovskite layer to AO-TiO2 and the decrease of device series resistance. Furthermore, hysteresis effect about current density-voltage (J-V) curves in TiO2-based p-PSCs is also unveiled. PMID:27150310

  18. Low-Temperature Solution Processing of Amorphous Metal Oxide Semiconductors for High-Performance Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Hennek, Jonathan W.

    The growing field of large-area flexible electronics presents the need for amorphous materials with electrical performances superior to amorphous hydrogenated silicon (a-Si:H). Metal oxide semiconductors show great promise in thin film transistors (TFTs) due to their high electron mobility (micro, 1--100 cm2V-1s-1), mechanical flexibility, and electrical stability. However, most oxide semiconductor fabrication still relies on expensive, inflexible and energy intensive vacuum deposition methods. To overcome these limitations, my thesis work has focused on developing low-temperature solution processing routes to functional metal oxide materials. In Chapter 2, we demonstrate an optimized "ink" and printing process for inkjet patterning of amorphous indium gallium zinc oxide (a-IGZO) and investigate the effects of device structure on derived electron mobility. Bottom-gate top-contact (BGTC) TFTs are fabricated and shown to exhibit electron mobilities comparable to a-Si:H. Furthermore, a record micro of 2.5 cm 2V-1s-1 is demonstrated for bottom-gate bottom-contact (BGBC) TFTs. The mechanism underlying such impressive performance is investigated using transmission line techniques, and it is shown that the semiconductor-source/drain electrode interface contact resistance is nearly an order of magnitude lower for BGBC transistors versus BGTC devices. In Chapter 3, we report the implementation of amorphous indium yttrium oxide (a-IYO) as a TFT semiconductor for the first time. Amorphous and polycrystalline IYO films are grown via a low-temperature solution process utilizing exothermic "combustion" precursors. Precursor transformation and the IYO films are analyzed by DTA, TGA, XRD, AFM, XPS, and optical transmission, revealing efficient conversion to the metal-oxide lattice, and smooth, transparent films. a-IYO TFTs fabricated with a hybrid nanodielectric exhibit impressive electron mobilities of 7.3 cm2V-1s-1 (Tanneal = 300 °C) and 5.0 cm2V-1s -1 (Tanneal = 250 °C) for 2

  19. Ultraslow dielectric relaxation process in supercooled polyhydric alcohols

    NASA Astrophysics Data System (ADS)

    Yomogida, Yoshiki; Minoguchi, Ayumi; Nozaki, Ryusuke

    2006-04-01

    Complex permittivity was obtained on glycerol, xylitol, sorbitol and sorbitol-xylitol mixtures in the supercooled liquid state in the frequency range between 10μHz and 500MHz at temperatures near and above the glass transition temperature. For all the materials, a dielectric relaxation process was observed in addition to the well-known structural α and Johari-Goldstein β relaxation process [G. P. Johari and M. Goldstein, J. Chem. Phys. 53, 2372 (1970)]. The relaxation time for the new process is always larger than that for the α process. The relaxation time shows non-Arrhenius temperature dependence with correlation to the behavior of the α process and it depends on the molecular size systematically. The dielectric relaxation strength for the new process shows the effect of thermal history and decreases exponentially with time at a constant temperature. It can be considered that a nonequilibrium dynamics causes the new process.

  20. Physical Property Evaluation of ZnO Thin Film Fabricated by Low-Temperature Process for Flexible Transparent TFT.

    PubMed

    Khafe, Adie Bin Mohd; Watanabe, Hiraku; Yamauchi, Hiroshi; Kuniyoshi, Shigekazu; Iizuka, Masaaki; Sakai, Masatoshi; Kudo, Kazuhiro

    2016-04-01

    The usual silicon-based display back planes require fairly high process temperature and thus the development of a low temperature process is needed on flexible plastic substrates. A new type of flexible organic light emitting transistor (OLET) had been proposed and investigated in the previous work. By using ultraviolet/ozone (UV/O3) assisted thermal treatments on wet processed zinc oxide field effect transistor (ZnO-FET), through low-process temperature, ZnO-FETs were fabricated which succeeded to achieve target drain current value and mobility. In this study, physical property evaluation of ZnO was conducted in term of their crystallinity, the increase composition of ZnO formed inside the thin film and the decrease of the carbon impurities originated from aqueous solution of the ZnO itself. The X-ray diffraction (XRD) evaluation showed UV/03 assisted thermal treatment has no obvious effect towards crystallinity of ZnO in the range of low process temperature. Moreover, through X-ray photoelectron spectroscopy (XPS) evaluation and Fourier transform infrared (FT-IR) spectroscopy evaluation, more carbon impurities disappeared from the ZnO thin film and the increase of composition amount of ZnO, when the thin film was subjected to UV/O3 assisted thermal treatment. Therefore, UV/O3 assisted thermal treatment contributed in carbon impurities elimination and accelerate ZnO formation in ZnO thin film, which led to the improvement in the electrical property of ZnO-FET in the low-process temperature. PMID:27451599

  1. Mechanical properties and microstructure of 6061 aluminum alloy severely deformed by ARB process and subsequently aged at low temperatures

    NASA Astrophysics Data System (ADS)

    Terada, Daisuke; Kaneda, Yoma; Horita, Zenji; Matsuda, Kenji; Hirosawa, Shoichi; Tsuji, Nobuhiro

    2014-08-01

    In order to clarify the aging behavior in ultrafine grained (UFG) Al alloys, a commercial Al-Mg-Si alloy was severely deformed by accumulative roll-bonding (ARB) process and subsequently aged at 100°C or 170°C. The age-hardening behavior and microstructure change during aging were investigated. At 170 °C, age-hardening was observed in solution treated (ST) specimens, but solution-treated and ARB-processed specimens were not hardened by aging. On the other hand, the hardness of the both ST specimen and ARB-processed specimen increased by aging at 100°C. From TEM observation, it was found that the ARB- processed specimen had an ultrafine lamellar boundary structure and the structure was kept during aging at 170°C and 100°C. In the ST specimen aged at 170°C, fine precipitates were observed within coarse grains. In the specimen ARB-processed and subsequently aged at 170°C, coarser precipitates were observed within ultrafine grains and on grain boundaries. It was considered that the reason why the hardness of the specimens ARB-processed and subsequently aged did not increase was coarsening of precipitates. In the specimens aged at 100°C, obvious precipitates were not observed, but clusters Mg and Si seemed to form during the aging, leading to the increase in the hardness of the specimen. From the results, it was suggested that aging at low temperatures could improve mechanical properties of Al alloys through combining grain refinement and precipitation hardening.

  2. Low-temperature-processed efficient semi-transparent planar perovskite solar cells for bifacial and tandem applications

    PubMed Central

    Fu, Fan; Feurer, Thomas; Jäger, Timo; Avancini, Enrico; Bissig, Benjamin; Yoon, Songhak; Buecheler, Stephan; Tiwari, Ayodhya N.

    2015-01-01

    Semi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process. Here we report a low-temperature process for efficient semi-transparent planar perovskite solar cells. A hybrid thermal evaporation–spin coating technique is developed to allow the introduction of PCBM in regular device configuration, which facilitates the growth of high-quality absorber, resulting in hysteresis-free devices. We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region. With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration. PMID:26576667

  3. Deposition Mechanisms and Oxidation Behaviors of Ti-Ni Coatings Deposited in Low-Temperature HVOF Spraying Process

    NASA Astrophysics Data System (ADS)

    Lin, Q. S.; Zhou, K. S.; Deng, C. M.; Liu, M.; Xu, L. P.; Deng, C. G.

    2014-08-01

    Three kinds of Ti-Ni powders were deposited on 316L stainless steel by low-temperature high-velocity oxygen fuel (LT-HVOF) spraying process, respectively. Deposition mechanisms and oxidation behaviors of the coatings were researched in this paper. The coating deposited from TiNi intermetallic powder had obvious laminar structure and the oxygen content was the highest among the three kinds of coatings. The oxygen content of the coating deposited from small-sized Ni-clad Ti powder was still high due to the melting of parts of particles. However, most of the coarse Ni-clad Ti powder was deposited in solid states without changes of chemical compositions and phase compositions. The oxygen content of the coating deposited from coarse Ni-clad Ti powder was the lowest among the three kinds of coatings. It indicated that the deposition behavior of the coating could effectively preserve the inner titanium from oxidation. The results of the present research demonstrated that it is entirely feasible to deposit active metal materials such as titanium and titanium alloy through the optimizing selection of powder in the LT-HVOF process.

  4. A fast low-temperature micromolding process for hydrophilic microfluidic devices using UV-curable acrylated hyperbranched polymers

    NASA Astrophysics Data System (ADS)

    Jin, Young-Hyun; Cho, Young-Ho; Schmidt, Lars E.; Leterrier, Yves; Månson, Jan-Anders E.

    2007-06-01

    A novel UV-curable low-stress hyperbranched polymer (HBP) micromolding process is presented for the fast and low-temperature fabrication of hydrophilic microfluidic devices. Process, material and surface properties of the acrylated polyether HBP are also characterized and compared to those of polydimethylsiloxane (PDMS) and cyclic olefin copolymers (COC). The HBP dispensed on a PDMS master was cured at room temperature using a 3 min UV exposure at the intensity of 22.2 mW cm-2. Thermal, mechanical and surface properties of the micromolded HBP structures have been characterized and resulted in a glass transition temperature of 55 °C, Young's modulus of 770 MPa and hydrophilic surface having a water contact angle of 54°. Micromolding of 33 µm thick HBP microstructures has been demonstrated. We achieved 14.5 µm wide vertical walls, 14.7 µm wide fluidic channels, 24.1 µm wide square pillars and 53.4 µm wide square holes. A microfluidic network device, composed of microfluidic channels and reservoirs, was fabricated and its microfluidic performance has been verified by a fluidic test.

  5. Low-temperature-processed efficient semi-transparent planar perovskite solar cells for bifacial and tandem applications

    NASA Astrophysics Data System (ADS)

    Fu, Fan; Feurer, Thomas; Jäger, Timo; Avancini, Enrico; Bissig, Benjamin; Yoon, Songhak; Buecheler, Stephan; Tiwari, Ayodhya N.

    2015-11-01

    Semi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process. Here we report a low-temperature process for efficient semi-transparent planar perovskite solar cells. A hybrid thermal evaporation-spin coating technique is developed to allow the introduction of PCBM in regular device configuration, which facilitates the growth of high-quality absorber, resulting in hysteresis-free devices. We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region. With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration.

  6. Low-temperature-processed efficient semi-transparent planar perovskite solar cells for bifacial and tandem applications.

    PubMed

    Fu, Fan; Feurer, Thomas; Jäger, Timo; Avancini, Enrico; Bissig, Benjamin; Yoon, Songhak; Buecheler, Stephan; Tiwari, Ayodhya N

    2015-01-01

    Semi-transparent perovskite solar cells are highly attractive for a wide range of applications, such as bifacial and tandem solar cells; however, the power conversion efficiency of semi-transparent devices still lags behind due to missing suitable transparent rear electrode or deposition process. Here we report a low-temperature process for efficient semi-transparent planar perovskite solar cells. A hybrid thermal evaporation-spin coating technique is developed to allow the introduction of PCBM in regular device configuration, which facilitates the growth of high-quality absorber, resulting in hysteresis-free devices. We employ high-mobility hydrogenated indium oxide as transparent rear electrode by room-temperature radio-frequency magnetron sputtering, yielding a semi-transparent solar cell with steady-state efficiency of 14.2% along with 72% average transmittance in the near-infrared region. With such semi-transparent devices, we show a substantial power enhancement when operating as bifacial solar cell, and in combination with low-bandgap copper indium gallium diselenide we further demonstrate 20.5% efficiency in four-terminal tandem configuration. PMID:26576667

  7. Indium tin oxide nanowires grown by one-step thermal evaporation-deposition process at low temperature.

    PubMed

    Dong, Haibo; Zhang, Xiaoxian; Niu, Zhiqiang; Zhao, Duan; Li, Jinzhu; Cai, Le; Zhou, Weiya; Xie, Sishen

    2013-02-01

    Indium tin oxide (ITO), as one of the most important transparent conducting oxide, is widely used in electro-optical field. We have developed a simple one-step method to synthesize ITO nanowires at low temperature of 600 degrees C. In detail, mixtures of InN nanowires and SnO powder, with the molar ratio of 10:1, have been used as precursors for the thermal evaporation-deposition of ITO nanowires on silicon/quartz slices. During the growth process, the evaporation temperature is maintained at 600 degrees C, which favors the decomposition of InN and oxidation of In, with a limited incorporation of Sn in the resulting compound (In:Sn approximately 11:1 in atomic ratio). As far as we know, this is the lowest growth temperature reported on the thermal deposition of ITO nanowires. The diameters of the nanowires are about 120 nm and the lengths are up to tens of micrometers. XRD characterization indicates the high crystallization of the nanowires. HRTEM results show the nanowires grow along the [200] direction. The transmittance of the nanowire film on quartz slice is more than 75% in the visible region. Based on photolithography and lift-off techniques, four-terminal measurement was utilized to test the resistivity of individual nanowire (6.11 x 10(-4) omega x cm). The high crystallization quality, good transmittance and low resistivity make as-grown ITO nanowires a promising candidate as transparent electrodes of nanoscale devices. PMID:23646624

  8. Rapid low-temperature processing of metal-oxide thin film transistors with combined far ultraviolet and thermal annealing

    SciTech Connect

    Leppäniemi, J. Ojanperä, K.; Kololuoma, T.; Huttunen, O.-H.; Majumdar, H.; Alastalo, A.; Dahl, J.; Tuominen, M.; Laukkanen, P.

    2014-09-15

    We propose a combined far ultraviolet (FUV) and thermal annealing method of metal-nitrate-based precursor solutions that allows efficient conversion of the precursor to metal-oxide semiconductor (indium zinc oxide, IZO, and indium oxide, In{sub 2}O{sub 3}) both at low-temperature and in short processing time. The combined annealing method enables a reduction of more than 100 °C in annealing temperature when compared to thermally annealed reference thin-film transistor (TFT) devices of similar performance. Amorphous IZO films annealed at 250 °C with FUV for 5 min yield enhancement-mode TFTs with saturation mobility of ∼1 cm{sup 2}/(V·s). Amorphous In{sub 2}O{sub 3} films annealed for 15 min with FUV at temperatures of 180 °C and 200 °C yield TFTs with low-hysteresis and saturation mobility of 3.2 cm{sup 2}/(V·s) and 7.5 cm{sup 2}/(V·s), respectively. The precursor condensation process is clarified with x-ray photoelectron spectroscopy measurements. Introducing the FUV irradiation at 160 nm expedites the condensation process via in situ hydroxyl radical generation that results in the rapid formation of a continuous metal-oxygen-metal structure in the film. The results of this paper are relevant in order to upscale printed electronics fabrication to production-scale roll-to-roll environments.

  9. Relaxation processes in administered-rate pricing

    NASA Astrophysics Data System (ADS)

    Hawkins, Raymond J.; Arnold, Michael R.

    2000-10-01

    We show how the theory of anelasticity unifies the observed dynamics and proposed models of administered-rate products. This theory yields a straightforward approach to rate model construction that we illustrate by simulating the observed relaxation dynamics of two administered rate products. We also demonstrate how the use of this formalism leads to a natural definition of market friction.

  10. Low Temperature Adaptation Is Not the Opposite Process of High Temperature Adaptation in Terms of Changes in Amino Acid Composition

    PubMed Central

    Yang, Ling-Ling; Tang, Shu-Kun; Huang, Ying; Zhi, Xiao-Yang

    2015-01-01

    Previous studies focused on psychrophilic adaptation generally have demonstrated that multiple mechanisms work together to increase protein flexibility and activity, as well as to decrease the thermostability of proteins. However, the relationship between high and low temperature adaptations remains unclear. To investigate this issue, we collected the available predicted whole proteome sequences of species with different optimal growth temperatures, and analyzed amino acid variations and substitutional asymmetry in pairs of homologous proteins from related species. We found that changes in amino acid composition associated with low temperature adaptation did not exhibit a coherent opposite trend when compared with changes in amino acid composition associated with high temperature adaptation. This result indicates that during their evolutionary histories the proteome-scale evolutionary patterns associated with prokaryotes exposed to low temperature environments were distinct from the proteome-scale evolutionary patterns associated with prokaryotes exposed to high temperature environments in terms of changes in amino acid composition of the proteins. PMID:26614525

  11. Structure engineering of hole-conductor free perovskite-based solar cells with low-temperature-processed commercial carbon paste as cathode.

    PubMed

    Zhang, Fuguo; Yang, Xichuan; Wang, Haoxin; Cheng, Ming; Zhao, Jianghua; Sun, Licheng

    2014-09-24

    Low-temperature-processed (100 °C) carbon paste was developed as counter electrode material in hole-conductor free perovskite/TiO2 heterojunction solar cells to substitute noble metallic materials. Under optimized conditions, an impressive PCE value of 8.31% has been achieved with this carbon counter electrode fabricated by doctor-blading technique. Electrochemical impedance spectroscopy demonstrates good charge transport characteristics of low-temperature-processed carbon counter electrode. Moreover, this carbon counter electrode-based perovskite solar cell exhibits good stability over 800 h. PMID:25162717

  12. Controlled Nitrogen Atom Incorporation at Silicon - Dioxide Interfaces by a New, Low-Temperature Remote Plasma Process

    NASA Astrophysics Data System (ADS)

    Lee, David Roger

    1995-01-01

    A new, low-temperature (300^circ C), remote plasma process has been developed for incorporating controlled amounts of N-atoms at Si-SiO _2 interfaces and has been shown to improve the quality and reliability of Metal-Oxide-Semiconductor (MOS) devices. The process involves exposing an ex-situ cleaned wafer to species from a remote N_2 O plasma as a prelude to Remote Plasma Enhanced Chemical Vapor Deposition (Remote PECVD) of gate-quality SiO_2 films. Auger Electron Spectroscopy (AES) studies and Secondary Ion Mass Spectrometry (SIMS) depth profiles have been used to investigate the chemical nature of the Si-SiO_2 interface formed by this new technique. The results indicate that this pre-deposition process (1) removed residual carbon to ~10^{12 } C-atoms/cm^2, (2) resulted in the remote plasma-assisted growth of ~0.5 nm of SiO_2, and (3) incorporated controllably between 10^ {14}-10^{15} N-atoms/cm^2 at the Si-SiO _2 interface. Optical Second Harmonic Generation (SHG) spectroscopy has shown that the N-atoms are bonded to Si-atoms at the Si-SiO_2 interface and relieve chemical strain in adjacent Si-Si bonds relative to the case where only O-atoms are bonded at the interface. This N_2O remote plasma, predeposition oxidation process was used in a cluster tool manufacturing test bed for the fabrication of MOS capacitors and Field-Effect Transistors (FETs). Remote PECVD oxides with and without nitrided interfaces were compared, and N-atom incorporation by this technique was found to improve the drive current and high-field electron mobility of n -MOSFETs while not adversely affecting the threshold voltage, V_{rm t}, or peak channel transconductance, g_{rm m}, of the devices. N-atom incorporation also suppressed hot-carrier damage in the gate dielectric of sub-micron (effective channel length ~ 0.64 μm) n-MOSFETs. In particular, peak g_{rm m}, V _{rm t}, and the slope of the subthreshold current are all degraded less with increasing N-atom concentrations at the Si-SiO _2

  13. High performance perovskite solar cell via multi-cycle low temperature processing of lead acetate precursor solutions.

    PubMed

    Singh, Trilok; Miyasaka, Tsutomu

    2016-04-01

    A lead acetate-based precursor, as a lead source in CH3NH3PbI3 perovskite, showed potential in rapidly (<60 seconds) forming homogeneous films with a very smooth interface and large grain growth at relatively low temperatures via multi-step coating. Cells based on this method exhibited high power conversion efficiency beyond 17% with good reproducibility. PMID:26958661

  14. The influence of the secondary relaxation processes on the structural relaxation in glass-forming materials

    NASA Astrophysics Data System (ADS)

    Khamzin, A. A.; Popov, I. I.; Nigmatullin, R. R.

    2013-06-01

    In the frame of fractional-kinetic approach, the model of the structural α-relaxation in the presence of the secondary β-relaxation processes is suggested. The model is based on the rigorous bond between β-processes with α-process and leads to the generalized and justified expression for the complex dielectric permittivity (CDP). It allows to form a new sight on the problem of the fitting of multi-peak structure of the dielectric loss spectra in glass-forming materials. The consistency of the CDP expressions obtained is based on a good fit of experimental data for binary methanol-water mixtures.

  15. The influence of the secondary relaxation processes on the structural relaxation in glass-forming materials.

    PubMed

    Khamzin, A A; Popov, I I; Nigmatullin, R R

    2013-06-28

    In the frame of fractional-kinetic approach, the model of the structural α-relaxation in the presence of the secondary β-relaxation processes is suggested. The model is based on the rigorous bond between β-processes with α-process and leads to the generalized and justified expression for the complex dielectric permittivity (CDP). It allows to form a new sight on the problem of the fitting of multi-peak structure of the dielectric loss spectra in glass-forming materials. The consistency of the CDP expressions obtained is based on a good fit of experimental data for binary methanol-water mixtures. PMID:23822251

  16. Difference and similarity of dielectric relaxation processes among polyols

    NASA Astrophysics Data System (ADS)

    Minoguchi, Ayumi; Kitai, Kei; Nozaki, Ryusuke

    2003-09-01

    Complex permittivity measurements were performed on sorbitol, xylitol, and sorbitol-xylitol mixture in the supercooled liquid state in an extremely wide frequency range from 10 μHz to 500 MHz at temperatures near and above the glass transition temperature. We determined detailed behavior of the relaxation parameters such as relaxation frequency and broadening against temperature not only for the α process but also for the β process above the glass transition temperature, to the best of our knowledge, for the first time. Since supercooled liquids are in the quasi-equilibrium state, the behavior of all the relaxation parameters for the β process can be compared among the polyols as well as those for the α process. The relaxation frequencies of the α processes follow the Vogel-Fulcher-Tammann manner and the loci in the Arrhenius diagram are different corresponding to the difference of the glass transition temperatures. On the other hand, the relaxation frequencies of the β processes, which are often called as the Johari-Goldstein processes, follow the Arrhenius-type temperature dependence. The relaxation parameters for the β process are quite similar among the polyols at temperatures below the αβ merging temperature, TM. However, they show anomalous behavior near TM, which depends on the molecular size of materials. These results suggest that the origin of the β process is essentially the same among the polyols.

  17. Local spin dynamics at low temperature in the slowly relaxing molecular chain [Dy(hfac)3(NIT(C6H4OPh))]: A μ{sup +} spin relaxation study

    SciTech Connect

    Arosio, Paolo Orsini, Francesco; Corti, Maurizio; Mariani, Manuel; Bogani, Lapo; Caneschi, Andrea; Lago, Jorge; Lascialfari, Alessandro

    2015-05-07

    The spin dynamics of the molecular magnetic chain [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] were investigated by means of the Muon Spin Relaxation (μ{sup +}SR) technique. This system consists of a magnetic lattice of alternating Dy(III) ions and radical spins, and exhibits single-chain-magnet behavior. The magnetic properties of [Dy(hfac){sub 3}(NIT(C{sub 6}H{sub 4}OPh))] have been studied by measuring the magnetization vs. temperature at different applied magnetic fields (H = 5, 3500, and 16500 Oe) and by performing μ{sup +}SR experiments vs. temperature in zero field and in a longitudinal applied magnetic field H = 3500 Oe. The muon asymmetry P(t) was fitted by the sum of three components, two stretched-exponential decays with fast and intermediate relaxation times, and a third slow exponential decay. The temperature dependence of the spin dynamics has been determined by analyzing the muon longitudinal relaxation rate λ{sub interm}(T), associated with the intermediate relaxing component. The experimental λ{sub interm}(T) data were fitted with a corrected phenomenological Bloembergen-Purcell-Pound law by using a distribution of thermally activated correlation times, which average to τ = τ{sub 0} exp(Δ/k{sub B}T), corresponding to a distribution of energy barriers Δ. The correlation times can be associated with the spin freezing that occurs when the system condenses in the ground state.

  18. Reduction of absorption loss in silica-on-silicon channel waveguides fabricated by low-temperature PECVD process

    NASA Astrophysics Data System (ADS)

    Sahu, Jayanta K.; Wosinski, Lech; Fernando, Harendra

    1999-12-01

    This study is focused on the low temperature plasma enhanced chemical vapor deposition technique used for fabrication of silica based optical waveguides on silicon, utilizing nitrous oxide as an oxidant for both silane and dopant. Fabricated channel waveguide shows total insertion loss of 1.2 dB at 1.55 micrometers , and no absorption peaks associated with N-H and Si-H bonds around 1.5 micrometers have been observed in the as deposited material. This fabrication technology adds flexibility to the monolithic integration of electronic and optical components. Using this technology, a n umber of different couplers based on multimode interference technique have been investigated.

  19. Shortening spin-lattice relaxation using a copper-chelated lipid at low-temperatures - A magic angle spinning solid-state NMR study on a membrane-bound protein.

    PubMed

    Yamamoto, Kazutoshi; Caporini, Marc A; Im, Sangchoul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2013-12-01

    Inherent low sensitivity of NMR spectroscopy has been a major disadvantage, especially to study biomolecules like membrane proteins. Recent studies have successfully demonstrated the advantages of performing solid-state NMR experiments at very low and ultralow temperatures to enhance the sensitivity. However, the long spin-lattice relaxation time, T1, at very low temperatures is a major limitation. To overcome this difficulty, we demonstrate the use of a copper-chelated lipid for magic angle spinning solid-state NMR measurements on cytochrome-b5 reconstituted in multilamellar vesicles. Our results on multilamellar vesicles containing as small as 0.5mol% of a copper-chelated lipid can significantly shorten T1 of protons, which can be used to considerably reduce the data collection time or to enhance the signal-to-noise ratio. We also monitored the effect of slow cooling on the resolution and sensitivity of (13)C and (15)N signals from the protein and (13)C signals from lipids. PMID:24246881

  20. Shortening Spin-lattice Relaxation Using a Copper-Chelated lipid at Low-Temperatures – A Magic Angle Spinning Solid-State NMR Study on a Membrane-Bound Protein

    PubMed Central

    Yamamoto, Kazutoshi; Caporini, Marc; Im, Sangchoul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2013-01-01

    Inherent low sensitivity of NMR spectroscopy has been a major disadvantage, especially to study biomolecules like membrane proteins. Recent studies have successfully demonstrated the advantages of performing solid-state NMR experiments at very low and ultralow temperatures to enhance the sensitivity. However, the long spin-lattice relaxation time, T1, at very low temperatures is a major limitation. To overcome this difficulty, we demonstrate the use of a copper-chelated lipid for magic angle spinning solid-state NMR measurements on cytochrome-b5 reconstituted in multilamellar vesicles. Our results on multilamellar vesicles containing as small as 0.5 mole % of a copper-chelated lipid can significantly shorten T1 of protons, which can be used to considerably reduce the data collection time or to enhance the signal-to-noise ratio. We also monitored the effect of slow cooling on the resolution and sensitivity of 13C and 15N signals from the protein and 13C signals from lipids. PMID:24246881

  1. Auger recombination as the dominant recombination process in indium nitride at low temperatures during steady-state photoluminescence

    SciTech Connect

    Seetoh, I. P.; Soh, C. B.; Fitzgerald, E. A.; Chua, S. J.

    2013-03-11

    Auger recombination in InN films grown by metal-organic chemical vapor deposition was studied by steady-state photoluminescence at different laser excitation powers and sample temperatures. It was dominant over radiative recombination and Shockley-Read-Hall recombination at low temperatures, contributing to the sub-linear relationship between the integrated photoluminescence intensity and laser excitation power. Auger recombination rates increased gradually with temperature with an activation energy of 10-17 meV, in good agreement with values from transient photoluminescence reported in literature. As the Auger recombination rates were independent of material quality, they may form an upper limit to the luminous efficiency of InN.

  2. Auger recombination as the dominant recombination process in indium nitride at low temperatures during steady-state photoluminescence

    NASA Astrophysics Data System (ADS)

    Seetoh, I. P.; Soh, C. B.; Fitzgerald, E. A.; Chua, S. J.

    2013-03-01

    Auger recombination in InN films grown by metal-organic chemical vapor deposition was studied by steady-state photoluminescence at different laser excitation powers and sample temperatures. It was dominant over radiative recombination and Shockley-Read-Hall recombination at low temperatures, contributing to the sub-linear relationship between the integrated photoluminescence intensity and laser excitation power. Auger recombination rates increased gradually with temperature with an activation energy of 10-17 meV, in good agreement with values from transient photoluminescence reported in literature. As the Auger recombination rates were independent of material quality, they may form an upper limit to the luminous efficiency of InN.

  3. Low-temperature, solution-processed indium-oxide thin-film transistors fabricated by using an ultraviolet-ozone treatment

    NASA Astrophysics Data System (ADS)

    Kim, Hoon; Kang, Chan-mo; Oh, Yeon-Wha; Ryu, Jin Hwa; Baek, Kyu-Ha; Do, Lee-Mi

    2016-04-01

    For the fabrication of low-temperature solution-processed metal-oxide thin-film transistors (TFTs), alternative annealing processes have recently been studied for reduced fabrication cost and applications to flexible devices. Indium nitrate solution has been proposed as a precursor for the low-temperature solution-processed TFTs. However, due to its high decomposition temperature, achieving a high-performance indium-oxide (In2O3) TFT at temperatures below 200°C is still difficult. In this study, for improved metal-oxide formation in low-temperature solution-processed In2O3 TFT, indium nitrate film was exposed to UV-ozone for 30 min before annealing at 200°C. The smooth scanning electron microscopy (SEM) image of the UV-ozone treated film implies that the indium nitrates are condensed after treatment. In addition, X-ray photoemission spectroscopy (XPS) data suggest that UV-ozone decreases the number of oxygen vacancies and increases the number of metal-oxygen-metal bonds in the indium-oxide films. As a result, high electrical device performance was achieved with an improved Ion/off ratio (˜107) and mobility (1.25 cm2V -1s -1).

  4. Resource Paper: Molecular Excited State Relaxation Processes.

    ERIC Educational Resources Information Center

    Rhodes, William

    1979-01-01

    Develops the concept of oscillatory v dissipative limits as it applies to electronic excited state processes in molecular systems. Main emphasis is placed on the radiative and nonradiative dynamics of the excited state of a molecule prepared by interaction with light or some other excitation source. (BT)

  5. Sedimentologic to metamorphic processes recorded in the high-pressure/low-temperature Mesozoic Rosetta Marble of Anatolia

    NASA Astrophysics Data System (ADS)

    Scheffler, F.; Oberhänsli, R.; Pourteau, A.; Immenhauser, A.; Candan, O.

    2016-01-01

    Anatolia's high-pressure metamorphic belts are characterized in part by a Neotethyan stratigraphic succession that includes a mid-Cretaceous hemi-pelagic marble sequence. This unit contains, towards its stratigraphic top, dm-to-m-long radiating calcitic rods forming rosette-like textures. Here, we refer to these features as "Rosetta Marble". The remarkable textural similarity of non-metamorphic selenite crystals and radiating calcite rods in the Rosetta Marble strongly suggests that these textures represent pseudomorphs after selenites. Metamorphosed hemi-pelagic limestones, dominated by Rosetta selenite pseudomorphs, are alternating with siliceous meta-sediments containing relictic radiolaria tests. This stratigraphic pattern is indicative of transient phases characterized by evaporites precipitated from basinal brines alternating with non-evaporative hemi-pelagic deposition from normal-marine seawater. The regional distribution of Rosetta Marble exposures over 600 km is indicative of basin-scale evaporitic intervals. High-pressure, low-temperature metamorphism of these rocks is witnessed by Sr-rich (up to 3500 ppm), fibrous calcite pseudomorphs after aragonite and isolated aragonite inclusions in quartz. Peak metamorphic conditions of 1.2 GPa and 300-350 °C are attested by high-Si white mica thermobarometry. The Rosetta Marble case example examines the potential to unravel the complete history from deposition to diagenesis and metamorphism of meta-sedimentary rocks.

  6. Low-temperature-processed a-SiOx:H/a-Si:H tandem cells for full spectrum solar cells

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Won; Sichanugrist, Porponth; Miyajima, Shinsuke; Konagai, Makoto

    2015-08-01

    We developed wide-bandgap amorphous silicon (a-Si:H) and amorphous silicon oxide (a-SiOx:H) absorbers by extremely decreasing deposition temperature to as low as 100 °C. By adjusting hydrogen and carbon dioxide gas flow rates, device-quality absorbers and thus suitable single junction cells were obtained. An a-SiOx:H single-junction cell (i = 100 nm) fabricated employing the absorber we developed showed an open circuit voltage (Voc) of 1.007 V and a fill factor of 0.741, which are better than those of a-Si:H cells. This a-SiOx:H cell was introduced in a-SiOx:H/a-Si:H tandem cells as the top cell, which contributed to the achievement of a markedly high Voc of 1.910 V. This tandem cell with an efficiency of 9.25% showed better Voc and current matching property than the a-Si:H/a-Si:H (8.74%) tandem structure. The low-temperature-gradient a-SiOx:H/a-Si:H tandem cells can be a promising configuration for spectrum splitting applications.

  7. Glass transition and relaxation processes of nanocomposite polymer electrolytes.

    PubMed

    Money, Benson K; Hariharan, K; Swenson, Jan

    2012-07-01

    This study focus on the effect of δ-Al(2)O(3) nanofillers on the dc-conductivity, glass transition, and dielectric relaxations in the polymer electrolyte (PEO)(4):LiClO(4). The results show that there are three dielectric relaxation processes, α, β, and γ, in the systems, although the structural α-relaxation is hidden in the strong conductivity contribution and could therefore not be directly observed. However, by comparing an enhanced dc-conductivity, by approximately 2 orders of magnitude with 4 wt % δ-Al(2)O(3) added, with a decrease in calorimetric glass transition temperature, we are able to conclude that the dc-conductivity is directly coupled to the hidden α-relaxation, even in the presence of nanofillers (at least in the case of δ-Al(2)O(3) nanofillers at concentrations up to 4 wt %). This filler induced speeding up of the segmental polymer dynamics, i.e., the α-relaxation, can be explained by the nonattractive nature of the polymer-filler interactions, which enhance the "free volume" and mobility of polymer segments in the vicinity of filler surfaces. PMID:22686254

  8. A low-temperature process for the denitration of Hanford single-shell tank, nitrate-based waste utilizing the nitrate to ammonia and ceramic (NAC) process

    SciTech Connect

    Mattus, A.J.; Lee, D.D.; Dillow, T.A.; Farr, L.L.; Loghry, S.L.; Pitt, W.W.; Gibson, M.R.

    1994-12-01

    Bench-top feasibility studies with Hanford single-shell tank (SST) simulants, using a new, low-temperature (50 to 60C) process for converting nitrate to ammonia and ceramic (NAC), have conclusively shown that between 85 to 99% of the nitrate can be readily converted. In this process, aluminum powders or shot can be used to convert alkaline, nitrate-based supernate to ammonia and an aluminum oxide-sodium aluminate-based solid which might function as its own waste form. The process may actually be able to utilize already contaminated aluminum scrap metal from various DOE sites to effect the conversion. The final, nearly nitrate-free ceramic-like product can be pressed and sintered like other ceramics. Based upon the starting volumes of 6.2 and 3.1 M sodium nitrate solution, volume reductions of 50 to 55% were obtained for the waste form produced, compared to an expected 35 to 50% volume increase if the Hanford supernate were grouted. Engineering data extracted from bench-top studies indicate that the process will be very economical to operate, and data were used to cost a batch, 1,200-kg NO{sub 3}/h plant for working off Hanford SST waste over 20 years. Their total process cost analysis presented in the appendix, indicates that between $2.01 to 2.66 per kilogram of nitrate converted will be required. Additionally, data on the fate of select radioelements present in solution are presented in this report as well as kinetic, operational, and control data for a number of experiments. Additionally, if the ceramic product functions as its own waste form, it too will offer other cost savings associated with having a smaller volume of waste form as well as eliminating other process steps such as grouting.

  9. Attaining Low Temperatures

    ERIC Educational Resources Information Center

    Wheatley, John D.; Van Till, Howard J.

    1970-01-01

    Discusses the definition of temperature and the concept of order in non-mathematical terms. Describes the cooling techniques necessary in low temperature physics research, including magnetic cooling, the use of the Pomeranchuk Effect, and dilution refrigeration. Outlines the types of phenomena observed in matter within various temperature ranges…

  10. Low temperature fluid blender

    NASA Technical Reports Server (NTRS)

    Repas, G. A.

    1971-01-01

    Blender supplies hydrogen at temperatures from 289 deg K to 367 deg K. Hydrogen temperature is controlled by using blender to combine flow from liquid hydrogen tank /276 deg K/ and gaseous hydrogen cylinder /550 deg K/. Blenders are applicable where flow of controlled low-temperature fluid is desired.

  11. Combined modified atmosphere packaging and low temperature storage delay lignification and improve the defense response of minimally processed water bamboo shoot

    PubMed Central

    2013-01-01

    Background Minimally processed water bamboo shoot (WBS) lignifies and deteriorates rapidly at room temperature, which limits greatly its marketability. This study was to investigate the effect of modified atmosphere packaging (MAP) on the sensory quality index, lignin formation, production of radical oxygen species (ROS) and activities of scavenging enzymes, membrane integrity and energy status of minimally processed WBS when packaged with or without the sealed low-density polyethylene (LDPE) bags, and then stored at 20°C for 9 days or 2°C for 60 days. Results The sensory quality of minimally processed WBS decreased quickly after 6 days of storage at 20°C. Low temperature storage maintained a higher sensory quality index within the first 30 days, but exhibited higher contents of lignin and hydrogen peroxide (H2O2) as compared with non-MAP shoots at 20°C. Combined MAP and low temperature storage not only maintained good sensory quality after 30 days, but also reduced significantly the increases in lignin content, superoxide anion (O2.-) production rate, H2O2 content and membrane permeability, maintained high activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), and reduced the increase in activities of lipase, phospholipase D (PLD) and lipoxygenase (LOX). Furthermore, the minimally processed WBS under MAP condition exhibited higher energy charge (EC) and lower adenosine monophosphate (AMP) content by the end of storage (60 days) at 2°C than those without MAP or stored for 9 days at 20°C. Conclusion These results indicated that MAP in combination with low temperature storage reduced lignification of minimally processed WBS, which was closely associated with maintenance of energy status and enhanced activities of antioxidant enzymes, as well as reduced alleviation of membrane damage caused by ROS. PMID:24006941

  12. Low-temperature solution-processable Ni(OH)2 ultrathin nanosheet/N-graphene nanohybrids for high-performance supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Chang, Haixin; Kang, Jianli; Chen, Luyang; Wang, Junqiang; Ohmura, Kazuyo; Chen, Na; Fujita, Takeshi; Wu, Hongkai; Chen, Mingwei

    2014-05-01

    A novel and facile strategy is developed to fabricate highly nitrogen-doped graphene (N-graphene) based layered, quasi-two-dimensional nanohybrids with ultrathin nanosheet nanocrystals using a low-temperature, solution processing method for high-performance supercapacitor electrodes. High N doping can be achieved together with one of the lowest oxygen content in chemically reduced graphene and related nanohybrids at low temperature by large-scale residue defects of chemically reduced graphene. The layered, quasi-two-dimensional nanohybrids or heterostructures of ultrathin Ni(OH)2 nanosheet nanocrystal/N-graphene can be applied in supercapacitor electrodes with ultrahigh capacitances of ~1551 F g-1, excellent rate performance in the scan measurements (from 2 mV s-1 to 100 mV s-1) and in the discharge tests (from 1.5 A g-1 to 30 A g-1) and good cycling stability. Moreover, the capacitance of Ni(OH)2 nanosheet/N-graphene nanohybrids is two and one orders of magnitude higher than that for pure nanocrystals and for the physical mixture of nanocrystal/N-graphene, respectively. Electron transfer in supercapacitor electrodes based on nanohybrids is over 100 times faster than that in electrodes from pure nanocrystals and several tens of times faster than that in electrodes from nanocrystal/N-graphene mixtures. This low-temperature method may provide a low-cost, solution-processable and easily scalable route to high-performance graphene nanohybrid electrodes for energy applications.A novel and facile strategy is developed to fabricate highly nitrogen-doped graphene (N-graphene) based layered, quasi-two-dimensional nanohybrids with ultrathin nanosheet nanocrystals using a low-temperature, solution processing method for high-performance supercapacitor electrodes. High N doping can be achieved together with one of the lowest oxygen content in chemically reduced graphene and related nanohybrids at low temperature by large-scale residue defects of chemically reduced graphene. The

  13. Structural, optical, and electrical properties of ZnO thin films deposited by sol-gel dip-coating process at low temperature

    NASA Astrophysics Data System (ADS)

    Kim, Soaram; Nam, Giwoong; Yoon, Hyunsik; Park, Hyunggil; Choi, Hyonkwang; Kim, Jong Su; Kim, Jin Soo; Kim, Do Yeob; Kim, Sung-O.; Leem, Jae-Young

    2014-07-01

    Sol-gel dip-coating was used to prepare ZnO thin films with relaxed residual stress by lowering the deposition temperature from room temperature (25°C) to -25°C. The effect of deposition temperature on the structural, optical, and electrical properties of the films was characterized using scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL), ultraviolet-visible (UV-Vis) spectroscopy and reflectance accessory, and the van der Pauw method. All the thin films were deposited successfully onto quartz substrates and exhibited fibrous root morphology. At low temperature, the deposition rate was higher than at room temperature (RT) because of enhanced viscosity of the films. Further, lowering the deposition temperature affected the structural, optical, and electrical properties of the ZnO thin films. The surface morphology, residual stress, PL properties, and optical transmittance and reflectance of the films were measured, and this information was used to determine the absorption coefficient, optical band gap, Urbach energy, refractive index, refractive index at infinite wavelength, extinction coefficient, single-oscillator energy, dispersion energy, average oscillator wavelength, moments M -1 and M -3, dielectric constant, optical conductivity, and electrical resistivity of the ZnO thin films.

  14. Genetic algorithm-assisted optimization of nanoporous TiO₂ for low-temperature processable photoanodes of dye-sensitized solar cells.

    PubMed

    Kim, Soyoung; Sohn, Kee-Sun; Pyo, Myoungho

    2011-03-14

    Genetic algorithm (GA), a promising optimization process in Heuristics, has proven to be a powerful tool in controlling the nanostructure of low-temperature processable photoanodes in dye-sensitized solar cells (DSSC). For photoanodes that are composed of various sizes of TiO₂ nanoparticles and multiwalled carbon nanotubes in a double-layer configuration, the best composition was determined based on the objective functions of cell efficiency (η) and its variance. The latter function was chosen since TiO₂ dispersions with no organic binders often aggravated the efficiency of reproducibility. From a total of 64,536 cases, 24 different cases (6 samples prepared for each composition) per generation were selected, and their objective functions were compared. GA was effective in the optimization of photoanodes, and resulted in a cell efficiency of 7.3 ± 0.2% with a short circuit current of 13.8 ± 0.4 mA cm(-2), an open circuit voltage of 0.737 ± 0.006 V, and a fill factor of 71.8 ± 0.6% after 3 generations. The η of 7.3 ± 0.2% is the highest value for low-temperature processable dye-sensitized solar cells prepared without further treatment of TiO₂ films to enhance interparticle connections. PMID:21207976

  15. A Low Temperature, Solution-Processed Poly(4-vinylphenol), YO(x) Nanoparticle Composite/Polysilazane Bi-Layer Gate Insulator for ZnO Thin Film Transistor.

    PubMed

    Shin, Hyeonwoo; Kang, Chan-Mo; Chae, Hyunsik; Kim, Hyun-Gwan; Baek, Kyu-Ha; Choi, Hyoung Jin; Park, Man-Young; Do, Lee-Mi; Lee, Changhee

    2016-03-01

    Low temperature, solution-processed metal oxide thin film transistors (MEOTFTs) have been widely investigated for application in low-cost, transparent, and flexible electronics. To enlarge the application area, solution-processed gate insulators (GI) have been investigated in recent years. We investigated the effects of the organic/inorganic bi-layer GI to ZnO thin film transistors (TFTs). PVP, YO(x) nanoparticle composite, and polysilazane bi-layer showed low leakage current (-10(-8) A/cm2 in 2 MV), which are applicable in low temperature processed MEOTFTs. Polysilazane was used as an interlayer between ZnO and PVP, YO(x) nanoparticle composite as a good charge transport interface with ZnO. By applying the PVP, YO(x), nanoparticle composite/polysilazane bi-layer structure to ZnO TFTs, we successfully suppressed the off current (I(off)) to -10(-11) and fabricated good MEOTFTs in 180 degrees C. PMID:27455680

  16. Green processing of metal oxide core-shell nanoparticles as low-temperature dielectrics in organic thin-film transistors.

    PubMed

    Portilla, Luis; Etschel, Sebastian H; Tykwinski, Rik R; Halik, Marcus

    2015-10-21

    TiO2 , Fe3 O4, AlOx , ITO (indium tin oxide), and CeO2 nanoparticles are tailored to exhibit excellent dispersability in deionized water and alcohols. The latter provides an ecofriendly solution for processing metal oxide nanoparticles at a neutral pH. Water-processed dielectrics from the metal oxide nanoparticles are incorporated into organic thin-film transistors fabricated on rigid and flexible substrates. PMID:26308740

  17. A versatile and flexible low-temperature full-wafer bonding process of monolithic 3D microfluidic structures in SU-8

    NASA Astrophysics Data System (ADS)

    Steigert, J.; Brett, O.; Müller, C.; Strasser, M.; Wangler, N.; Reinecke, H.; Daub, M.; Zengerle, R.

    2008-09-01

    We present a versatile fabrication process for the precise fabrication of embedded three-dimensional microfluidic structures in SU-8 photoresist. The full-wafer bond process based on a polyester (PET) handling layer enhances the previous low-temperature bonding technology. We achieved an extremely high bond strength of 45 MPa while requiring only small anchoring structures. Small channel structures with an aspect ratio >2 as well as wide membranes with an aspect ratio <0.02 were successfully bonded to realize precisely defined channel structures. Furthermore, the developed process features high yields (>80%) and enables the integration of microelectronics. The flexibility of the fabrication process is presented in two contrary applications. A completely freestanding and transparent SU-8 foil with a thickness of 225 µm featuring embedded 3D microchannels was fabricated. Also, high quality ink-jet dispensers were successfully fabricated whereas the dispenser quality mainly depends on the channel quality.

  18. Solution-processed lithium-doped zinc oxide thin-film transistors at low temperatures between 100 and 300 °C

    NASA Astrophysics Data System (ADS)

    Liu, Fangmei; Qian, Chuan; Sun, Jia; Liu, Peng; Huang, Yulan; Gao, Yongli; Yang, Junliang

    2016-04-01

    Lithium-doped zinc oxide (Li-ZnO) thin-film transistors (TFTs) were fabricated by solution process at the low temperatures ranged from 100 to 300 °C. Li-ZnO TFTs fabricated at 300 °C under nitrogen condition showed a mobility of 1.2 cm2/Vs. Most importantly, the mobility of Li-ZnO TFT devices fabricated at 100 °C could be increased significantly from 0.08 to 0.4 cm2/Vs by using double spin-coated and UV irradiation-treated Li-ZnO film, and the on-/off-current ratio is in the order of 106. Notably, the XPS analyses proved that the performance improvement was originated from the chemical composition or stoichiometry evolution, in which the hydroxide was converted into metal oxide and accelerated the formation of the oxygen vacancies. Furthermore, low-voltage operating Li-ZnO TFTs were demonstrated by using a high-capacitance ion gel gate dielectrics. The Li-ZnO TFTs with an operating voltage as low as 2 V exhibited the carrier mobilities of 2.1 and 0.65 cm2/Vs for the devices treated at 300 and 100 °C, respectively. The low-temperature, solution-processed Li-ZnO TFTs showed greatly potential applications in flexible displays, smart label, and sensors.

  19. Low temperature diffusion process using rare earth-Cu eutectic alloys for hot-deformed Nd-Fe-B bulk magnets

    SciTech Connect

    Akiya, T. Sepehri-Amin, H.; Ohkubo, T.; Liu, J.; Hono, K.; Hioki, K.; Hattori, A.

    2014-05-07

    The low temperature grain boundary diffusion process using RE{sub 70}Cu{sub 30} (RE = Pr, Nd) eutectic alloy powders was applied to sintered and hot-deformed Nd-Fe-B bulk magnets. Although only marginal coercivity increase was observed in sintered magnets, a substantial enhancement in coercivity was observed when the process was applied to hot-deformed anisotropic bulk magnets. Using Pr{sub 70}Cu{sub 30} eutectic alloy as a diffusion source, the coercivity was enhanced from 1.65 T to 2.56 T. The hot-deformed sample expanded along c-axis direction only after the diffusion process as RE rich intergranular layers parallel to the broad surface of the Nd{sub 2}Fe{sub 14}B are thickened in the c-axis direction.

  20. A Dry-Etch Process for Low Temperature Superconducting Transition Edge Sensors for Far Infrared Bolometer Arrays

    NASA Technical Reports Server (NTRS)

    Allen, Christine A.; Chervenak, James A.; Hsieh, Wen-Ting; McClanahan, Richard A.; Miller, Timothy M.; Mitchell, Robert; Moseley, S. Harvey; Staguhn, Johannes; Stevenson, Thomas R.

    2003-01-01

    The next generation of ultra-low power bolometer arrays, with applications in far infrared imaging, spectroscopy and polarimetry, utilizes a superconducting bilayer as the sensing element to enable SQUID multiplexed readout. Superconducting transition edge sensors (TES s) are being produced with dual metal systems of superconductinghormal bilayers. The transition temperature (Tc) is tuned by altering the relative thickness of the superconductor with respect to the normal layer. We are currently investigating MoAu and MoCu bilayers. We have developed a dry-etching process for MoAu TES s with integrated molybdenum leads, and are working on adapting the process to MoCu. Dry etching has the advantage over wet etching in the MoAu system in that one can achieve a high degree of selectivity, greater than 10, using argon ME, or argon ion milling, for patterning gold on molybdenum. Molybdenum leads are subsequently patterned using fluorine plasma.. The dry-etch technique results in a smooth, featureless TES with sharp sidewalls, no undercutting of the Mo beneath the normal metal, and Mo leads with high critical current. The effects of individual processing parameters on the characteristics of the transition will be reported.

  1. Energy-transfer and exciton-state relaxation processes in allophycocyanin

    SciTech Connect

    Beck, W.F.; Sauer, K.

    1992-05-28

    The authors have employed picosecond spectroscopic techniques to characterize the photophysics of the phycocyanobilin chromophores in linker-free allophycocyanin isolated from the cyanobactrium Synechococcus PCC 6301 (AN112 mutant). In analogy with the known structure of the related phycobiliprotein C-phycocyanin, allophycocyanin is probably organized as a ringlike homotrimer; the monomeric units are composed of an {alpha} and a {beta} subunit, each of which binds a phycocyanobilin chromophore via a thioether linkage to a cysteine residue at amino acid position 84. The authors observe bidirectional excitation transfer in the {alpha}{beta} monomer between the {alpha}84 and {beta}84 chromophores with a 140-ps time constant. The authors assign an ultrafast (<2-ps time constant) anisotropy and photobleaching transient observed only in ({alpha}{beta}){sub 3} trimers to an interexciton level transition; the transient occurs with a polarization change that is consistent with a transition between the orthogonal upper and lower exciton states. The upper exciton state also relaxes directly to the ground state through a decay process with a 45-ps time constant. They attribute the heterogeneous relaxation of the upper exciton state through these two paths to an inhomogeneous broadening due to site heterogeneity, which was previously observed in C-phycocyanin in hole-burning experiments at low temperature. Excitation transfer among the degenerate lower exciton states is detected in terms of a 70-ps anisotropy decay observed in the photobleaching and stimulated emission. The interexcition level transition rapidly concentrates excitation in the lower exciton state of allophycocyanin ({alpha}{beta}){sub 3} trimers; this kind of spectral relaxation process may be important in facilitating directional excitation transfer in reaction center/light-harvesting protein assemblies. 47 refs., 8 figs.

  2. Energy efficient production of hydrogen and syngas from biomass: development of low-temperature catalytic process for cellulose gasification.

    PubMed

    Asadullah, Mohammad; Ito, Shin-ichi; Kunimori, Kimio; Yamada, Muneyoshi; Tomishige, Keiichi

    2002-10-15

    The Rh/CeO2/M (M = SiO2, Al2O3, and ZrO2) type catalysts with various compositions have been prepared and investigated in the gasification of cellulose, a model compound of biomass, in a fluidized bed reactor at 500-700 degrees C. The conventional nickel and dolomite catalysts have also been investigated. Among the catalysts, Rh/CeO2/SiO2 with 35% CeO2 has been found to be the best catalyst with respect to the carbon conversion to gas and product distribution. The steam addition contributed to the complete conversion of cellulose to gas even at 600 degrees C. Lower steam supply gave the syngas and higher steam supply gave the hydrogen as the major product. Hydrogen and syngas from cellulose or cellulosic biomass gasification are environmentally super clean gaseous fuels for power generation. Moreover, the syngas derived liquid fuels such as methanol, dimethyl ether, and synthetic diesels are also super clean transportation fuels. However, the use of cellulose or cellulosic biomass for energy source through the gasification is challenging because of the formation of tar and char during the gasification process. It is interesting that no tar or char was finally formed in the effluent gas at as low as 500-600 degrees C using Rh/CeO2/SiO2(35) catalyst in this process. PMID:12387426

  3. Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel

    SciTech Connect

    Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K.

    2013-02-14

    This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 {+-} 0.3) Multiplication-Sign 10{sup -6} m{sup 2}/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 {+-} 0.5) Multiplication-Sign 10{sup -6} m{sup 2}/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 Degree-Sign C, the thermal diffusivity increases up to (12.0 {+-} 2) Multiplication-Sign 10{sup -6} m{sup 2}/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

  4. Low-temperature synthesis of soluble and processable organic-capped anatase TiO2 nanorods.

    PubMed

    Cozzoli, P Davide; Kornowski, Andreas; Weller, Horst

    2003-11-26

    We demonstrate the controlled growth of high aspect ratio anatase TiO2 nanorods by hydrolysis of titanium tetraisopropoxide (TTIP) in oleic acid (OLEA) as surfactant at a temperature as low as 80 degrees C. Chemical modification of TTIP by OLEA is proven to be a rational strategy to tune the reactivity of the precursor toward water. The most influential factors in shape control of the nanoparticles are investigated by simply manipulating their growth kinetics. The presence of tertiary amines or quaternary ammonium hydroxides as catalysts is essential to promote fast crystallization under mild conditions. The novelty of the present approach relies on the large-scale production of organic-capped TiO2 nanocrystals to which standard processing of colloidal nanocrystals, such as surface ligand exchange, can be applied for the first time. Concentrated colloidal titania dispersions can be prepared for a number of fundamental studies in homogeneous solutions and represent a new source of easily processable oxide material for many technological applications. PMID:14624603

  5. Plasma nitriding process by direct current glow discharge at low temperature increasing the thermal diffusivity of AISI 304 stainless steel

    NASA Astrophysics Data System (ADS)

    Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K.

    2013-02-01

    This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 ± 0.3) × 10-6 m2/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 ± 0.5) × 10-6 m2/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 °C, the thermal diffusivity increases up to (12.0 ± 2) × 10-6 m2/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.

  6. A low-temperature processed environment-friendly full-organic carrier collection layer for polymer solar cells

    SciTech Connect

    Shi, Ai-Li; Li, Yan-Qing E-mail: zhangdd@suda.edu.cn Jiang, Xiao-Chen; Ma, Zhong-Sheng; Wang, Qian-Kun; Guo, Zhen-Yu; Zhang, Dan-Dan E-mail: zhangdd@suda.edu.cn Lee, Shuit-Tong; Tang, Jian-Xin E-mail: zhangdd@suda.edu.cn

    2014-08-04

    We constructed a concept of the full-organic carrier collection layer (CCL) used for polymer solar cells. The CCL is composed of dipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile as hole collection layer (HCL) and chlorine-free solvents (formic acid (FA)) processed 4,7-Diphenyl-1,10-phenanthroline (Bphen) as electron collection layer, exhibiting good solubility, and environmental protection. The FA based device shows ideal power conversion efficiency (3.75%), which is higher than that of control device (3.6%). Besides, the HCL shows a different mechanism in hole extraction by functioning as a charge recombination zone for electrons injected from anode and holes extracted from the donor materials.

  7. A low-temperature processed environment-friendly full-organic carrier collection layer for polymer solar cells

    NASA Astrophysics Data System (ADS)

    Shi, Ai-Li; Li, Yan-Qing; Jiang, Xiao-Chen; Ma, Zhong-Sheng; Wang, Qian-Kun; Guo, Zhen-Yu; Zhang, Dan-Dan; Lee, Shuit-Tong; Tang, Jian-Xin

    2014-08-01

    We constructed a concept of the full-organic carrier collection layer (CCL) used for polymer solar cells. The CCL is composed of dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile as hole collection layer (HCL) and chlorine-free solvents (formic acid (FA)) processed 4,7-Diphenyl-1,10-phenanthroline (Bphen) as electron collection layer, exhibiting good solubility, and environmental protection. The FA based device shows ideal power conversion efficiency (3.75%), which is higher than that of control device (3.6%). Besides, the HCL shows a different mechanism in hole extraction by functioning as a charge recombination zone for electrons injected from anode and holes extracted from the donor materials.

  8. Low-temperature processed electron collection layers of graphene/TiO2 nanocomposites in thin film perovskite solar cells.

    PubMed

    Wang, Jacob Tse-Wei; Ball, James M; Barea, Eva M; Abate, Antonio; Alexander-Webber, Jack A; Huang, Jian; Saliba, Michael; Mora-Sero, Iván; Bisquert, Juan; Snaith, Henry J; Nicholas, Robin J

    2014-02-12

    The highest efficiencies in solution-processable perovskite-based solar cells have been achieved using an electron collection layer that requires sintering at 500 °C. This is unfavorable for low-cost production, applications on plastic substrates, and multijunction device architectures. Here we report a low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes provide superior charge-collection in the nanocomposites, enabling the entire device to be fabricated at temperatures no higher than 150 °C. These solar cells show remarkable photovoltaic performance with a power conversion efficiency up to 15.6%. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly toward the development of low-cost solar cells. PMID:24341922

  9. Highly Reliable Liquid-Phase-Deposited SiO2 with Nitrous Oxide Plasma Post-Treatment for Low-Temperature-Processed Polysilicon Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Yeh, Ching-Fa; Chen, Darren Chi-Hsiang; Lu, Cheng-Yu; Liu, Chung; Lee, Su-Tseng; Liu, Cheng-Hong; Chen, Tai-Ju

    2002-10-01

    Low-temperature (˜300°C) N2O-plasma post-treatment for liquid-phase-deposited (LPD) gate oxide has been proposed for the first time. This treatment successfully takes the place of conventional furnace annealing in O2 ambient. Results of physicochemical and electrical characteristics show that N2O-plasma post-treated LPD-SiO2 has a high electrical breakdown field and low interface state density. In addition, N2O-plasma treatment also improves the Si-rich phenomenon of LPD-SiO2. From the comparison with pure N2O-plasma oxidation film, LPD-SiO2 with its short re-oxidation time in N2O plasma plays an important role in relieving interfacial stress. Finally, the novel technology is applied to the gate oxide of low-temperature-processed (LTP) polysilicon thin film transistors (poly-Si TFTs). The device performance reveals excellent electrical characteristics, and the reliability shows a satisfactory result, as well as the gate oxide reliability. It is believed that the N2O-plasma post-treatment not only improves the oxide quality, but also effectively passivates the trap states of poly-Si TFTs.

  10. Large Perovskite Grain Growth in Low-Temperature Solution-Processed Planar p-i-n Solar Cells by Sodium Addition.

    PubMed

    Bag, Santanu; Durstock, Michael F

    2016-03-01

    Thin-film p-i-n type planar heterojunction perovskite solar cells have the advantage of full low temperature solution processability and can, therefore, be adopted in roll-to-roll production and flexible devices. One of the main challenges with these devices, however, is the ability to finely control the film morphology during the deposition and crystallization of the perovskite layer. Processes suitable for optimization of the perovskite layer film morphology with large grains are highly desirable for reduced recombination of charge carriers. Here, we show how uniform thin films with micron size perovskite grains can be made through the use of a controlled amount of sodium ions in the precursor solution. Large micrometer-size CH3NH3PbI3 perovskite grains are formed during low-temperature thin-film growth by adding sodium ions to the PbI2 precursor solution in a two-step interdiffusion process. By adjusting additive concentration, film morphologies were optimized and the fabricated p-i-n planar perovskite-PCBM solar cells showed improved power conversion efficiences (an average of 3-4% absolute efficiency enhancement) compared to the nonsodium based devices. Overall, the additive enhanced grain growth process helped to reach a high 14.2% solar cell device efficiency with low hysteresis. This method of grain growth is quite general and provides a facile way to fabricate large-grained CH3NH3PbI3 on any arbitrary surface by an all solution-processed route. PMID:26862869

  11. Copper-Assisted Direct Growth of Vertical Graphene Nanosheets on Glass Substrates by Low-Temperature Plasma-Enhanced Chemical Vapour Deposition Process

    NASA Astrophysics Data System (ADS)

    Ma, Yifei; Jang, Haegyu; Kim, Sun Jung; Pang, Changhyun; Chae, Heeyeop

    2015-08-01

    Vertical graphene (VG) nanosheets are directly grown below 500 °C on glass substrates by a one-step copper-assisted plasma-enhanced chemical vapour deposition (PECVD) process. A piece of copper foil is located around a glass substrate as a catalyst in the process. The effect of the copper catalyst on the vertical graphene is evaluated in terms of film morphology, growth rate, carbon density in the plasma and film resistance. The growth rate of the vertical graphene is enhanced by a factor of 5.6 with the copper catalyst with denser vertical graphene. The analysis of optical emission spectra suggests that the carbon radical density is increased with the copper catalyst. Highly conductive VG films having 800 Ω/□ are grown on glass substrates with Cu catalyst at a relatively low temperature.

  12. Experimental investigation of low temperature garnet-melt partitioning in CMASH, with application to subduction zone processes.

    NASA Astrophysics Data System (ADS)

    Morizet, Y.; Blundy, J.; McDade, P.

    2003-04-01

    During subduction, the slab undergoes several processes such as dehydration and partial melting at pressures of 2-3 GPa and temperatures of 600-900^oC. Under these conditions, there is little or no distinction between melt and fluid phases (Bureau &Keppler, 1999, EPSL 165, 187-196). To investigate the behaviour of trace elements under these conditions we have carried out partitioning experiments in the system CMASH at 2.2 GPa, 700-920^oC. CMAS starting compositions were doped with trace elements, and loaded together with quartz and water into a Pt capsule, which was in turn contained within a Ni-lined Ti capsule. Run durations were 3-7 days. A run at 810^oC produced euhedral calcic garnet, zoisite, quartz, hydrous melt and tiny clinopyroxene interpreted as quench crystals. LA-ICPMS and SIMS were used to quantify trace element concentrations of the phases. Garnet-melt D's for the HREE decrease from ˜300 for Lu to less than 0.2 for La. DSc and D_V are less than 5, consistent with the large X-site dimension in the garnet. DLi DSr and DBa are considerably less than the adjacent REE. There is a very slight negative partitioning anomaly for Zr and Hf relative to Nd and Sm; DHf is slightly greater than DZr. D_U < DTh, due largely to the oxidizing conditions of the experiment (NNO). The most striking result is very high D's for Nb and Ta: 18±10 and 5.4±1.9 (LA-ICPMS), 25.8±11.9 and 6.6±1.3 (SIMS) for Nb and Ta respectively. These are considerably larger than any previously measured (at much higher temperatures). The observed partitioning behaviour is consistent with the large temperature dependence for DREE proposed by Van Westrenen et al. (2001, Contrib Min Pet, 142, 219-234), and an even larger temperature dependence for DNb and DTa. These preliminary results suggest that garnet (rather than rutile) may play the key role in controlling the Nb and Ta budget of arc magmas and the Nb/Ta ratio of residual eclogites. For example, modelling of eclogite melting, using a N

  13. Relaxation Processes within Flux Ropes in Solar Wind

    NASA Astrophysics Data System (ADS)

    Telloni, D.; Carbone, V.; Perri, S.; Bruno, R.; Lepreti, F.; Veltri, P.

    2016-08-01

    Flux ropes are localized structures in space plasma whose tube-like organized magnetic configuration can be well approximated by a force-free field model. Both numerical simulations and simple models suggest that the ideal magnetohydrodynamics (MHD) can relax toward a minimum energy state, where magnetic helicity is conserved, characterized by force-free magnetic fields (Taylor relaxation). In this paper, we evaluate MHD rugged invariants within more than 100 flux ropes identified in the solar wind at 1 AU, showing that the magnetic and cross-helicity content carried out by these structures tend to be “attracted” toward a particular subphase in the parameter plane. The final configuration of the MHD rugged invariants in the parameter plane suggests indeed that flux ropes represent well-organized structures coming from the dynamical evolution of MHD turbulent cascade. These observational results, along with a simple model based on a truncated set of nonlinear ordinary differential equations for both the velocity and magnetic field Fourier coefficients, thus, support a scenario in which the flux ropes naturally come out from the ideal MHD decay to large-scale magnetic field in space plasmas, probably governed by relaxation processes similar to those observed in laboratory plasmas.

  14. Collective relaxation processes in atoms, molecules and clusters

    NASA Astrophysics Data System (ADS)

    Kolorenč, Přemysl; Averbukh, Vitali; Feifel, Raimund; Eland, John

    2016-04-01

    Electron correlation is an essential driver of a variety of relaxation processes in excited atomic and molecular systems. These are phenomena which often lead to autoionization typically involving two-electron transitions, such as the well-known Auger effect. However, electron correlation can give rise also to higher-order processes characterized by multi-electron transitions. Basic examples include simultaneous two-electron emission upon recombination of an inner-shell vacancy (double Auger decay) or collective decay of two holes with emission of a single electron. First reports of this class of processes date back to the 1960s, but their investigation intensified only recently with the advent of free-electron lasers. High fluxes of high-energy photons induce multiple excitation or ionization of a system on the femtosecond timescale and under such conditions the importance of multi-electron processes increases significantly. We present an overview of experimental and theoretical works on selected multi-electron relaxation phenomena in systems of different complexity, going from double Auger decay in atoms and small molecules to collective interatomic autoionization processes in nanoscale samples.

  15. Dual role of boron in improving electrical performance and device stability of low temperature solution processed ZnO thin film transistors

    SciTech Connect

    Gandla, Srinivas; Gollu, Sankara Rao; Sharma, Ramakant; Sarangi, Venkateshwarlu; Gupta, Dipti

    2015-10-12

    In this paper, we have demonstrated the dual role of boron doping in enhancing the device performance parameters as well as the device stability in low temperatures (200 °C) sol-gel processed ZnO thin film transistors (TFTs). Our studies suggest that boron is able to act as a carrier generator and oxygen vacancy suppressor simultaneously. Boron-doped ZnO TFTs with 8 mol. % of boron concentration demonstrated field-effect mobility value of 1.2 cm{sup 2} V{sup −1} s{sup −1} and threshold voltage of 6.2 V, respectively. Further, these devices showed lower shift in threshold voltage during the hysteresis and bias stress measurements as compared to undoped ZnO TFTs.

  16. Synthesis of CuInSe2 nanoparticles by phase transformation of In2Se3 via wet chemical process in low temperature

    NASA Astrophysics Data System (ADS)

    Li, Shi-na; Ma, Rui-xin; Zhu, Hong-min

    2014-07-01

    Chalcopyrite-type CuInSe2 nanoparticles are successfully prepared by using In2Se3 nanoparticles as a precursor reacted with copper chloride (CuCl) solution via a phase transformation process in low temperature. The reaction time is a key parameter. After the reaction time increasing from 0.5 h to 8 h, In2Se3 and CuCl react with each other gradually via phase transformation into CuInSe2 without any intermediate phase. The crystalline structure and morphology of the CuInSe2 nanoparticles are characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The diameter of CuInSe2 nanoparticles with good dispersibility ranges from 10 nm to 20 nm. The band gap of the CuInSe2 nanoparticles is 1.04 eV calculated from the ultraviolet-visible (UV-VIS) spectrum.

  17. Dye removal of activated carbons prepared from NaOH-pretreated rice husks by low-temperature solution-processed carbonization and H3PO4 activation.

    PubMed

    Chen, Yun; Zhai, Shang-Ru; Liu, Na; Song, Yu; An, Qing-Da; Song, Xiao-Wei

    2013-09-01

    A coupling of low-temperature sulfuric acid-assisted carbonization and H3PO4 activation was employed to convert NaOH-pretreated rice husks into activated carbons with extremely high surface area (2028 m(2) g(-1)) and integrated characteristics. The influences of the activation temperature and impregnation ratio on the surface area, pore volume of activated carbons were thoroughly investigated. The morphology and surface chemistry of activated carbons were characterized using N2 sorption, FTIR, XPS, SEM, TEM, etc. The adsorption capacity of resulting carbons obtained under optimum preparation conditions was systematically evaluated using methylene blue under various simulated conditions. The adsorption process can be well described by both Langmuir isotherm model and the pseudo-second order kinetics models; and the maximum monolayer capacity of methylene blue was ca. 578 mg g(-1). PMID:23892148

  18. Spacecraft Charging in Low Temperature Environments

    NASA Technical Reports Server (NTRS)

    Parker, Linda N.

    2007-01-01

    Spacecraft charging in plasma and radiation environments is a temperature dependent phenomenon due to the reduction of electrical conductivity in dielectric materials at low temperatures. Charging time constants are proportional to l/conductivity may become very large (on the order of days to years) at low temperatures and accumulation of charge densities in insulators in charging environments traditionally considered benign at ambient temperatures may be sufficient to produce charge densities and electric fields of concern in insulators at low temperatures. Low temperature charging is of interest because a number of spacecraft-primarily infrared astronomy and microwave cosmology observatories-are currently being design, built, and or operated at very cold temperatures on the order of 40K to 100K. This paper reviews the temperature dependence of spacecraft charging processes and material parameters important to charging as a function of temperature with an emphasis on low temperatures regimes.

  19. Defect formation in Cu(In,Ga)Se{sub 2} thin films due to the presence of potassium during growth by low temperature co-evaporation process

    SciTech Connect

    Pianezzi, F. Reinhard, P.; Chirilă, A.; Nishiwaki, S.; Bissig, B.; Buecheler, S.; Tiwari, A. N.

    2013-11-21

    Doping the Cu(In,Ga)Se{sub 2} (CIGS) absorber layer with alkaline metals is necessary to process high efficiency solar cells. When growth of CIGS solar cells is performed on soda-lime glass (SLG), the alkaline elements naturally diffuse from the substrate into the absorber layer. On the other hand, when CIGS is grown on alkaline free substrates, the alkaline metals have to be added from another source. In the past, Na was believed to be the most important dopant of the alkaline elements, even though K was also observed to diffuse into CIGS from the SLG. Recently, the beneficial effect of a post deposition treatment with KF was pointed out and enabled the production of a 20.4% CIGS solar cell grown at low substrate temperature (<500 °C). However, possible negative effects of the presence or addition of the alkaline impurities during the low temperature growth process were observed for Na, but were not investigated for K so far. In this study, we investigate in detail the role of K on the defect formation in CIGS layers deposited at low temperature on alkaline free polyimide with intentional addition of K during selected time intervals of the CIGS layer growth. By means of admittance spectroscopy and deep level transient spectroscopy, we identify a deep minority carrier trap at around 280 meV below the conduction band E{sub C} in CIGS layers grown with K. Its influence on recombination and minority carrier lifetime in the absorber layer is investigated with external quantum efficiency measurements and time-resolved photoluminescence. Furthermore, to support the experimental findings device simulations were performed using the software SCAPS.

  20. Approaches to label-free flexible DNA biosensors using low-temperature solution-processed InZnO thin-film transistors.

    PubMed

    Jung, Joohye; Kim, Si Joon; Lee, Keun Woo; Yoon, Doo Hyun; Kim, Yeong-Gyu; Kwak, Hee Young; Dugasani, Sreekantha Reddy; Park, Sung Ha; Kim, Hyun Jae

    2014-05-15

    Low-temperature solution-processed In-Zn-O (IZO) thin-film transistors (TFTs) exhibiting a favorable microenvironment for electron transfer by adsorbed artificial deoxyribonucleic acid (DNA) have extraordinary potential for emerging flexible biosensor applications. Superb sensing ability to differentiate even 0.5 μL of 50 nM DNA target solution was achieved through using IZO TFTs fabricated at 280 °C. Our IZO TFT had a turn-on voltage (V(on)) of -0.8 V, on/off ratio of 6.94 × 10(5), and on-current (I(on)) value of 2.32 × 10(-6)A in pristine condition. A dry-wet method was applied to immobilize two dimensional double crossover tile based DNA nanostructures on the IZO surface, after which we observed a negative shift of the transfer curve accompanied by a significant increase in the Ion and degradation of the Von and on/off ratio. As the concentration of DNA target solution increased, variances in these parameters became increasingly apparent. The sensing mechanism based on the current evolution was attributed to the oxidation of DNA, in which the guanine nucleobase plays a key role. The sensing behavior obtained from flexible biosensors on a polymeric substrate fabricated under the identical conditions was exactly analogous. These results compare favorably with the conventional field-effect transistor based DNA sensors by demonstrating remarkable sensitivity and feasibility of flexible devices that arose from a different sensing mechanism and a low-temperature process, respectively. PMID:24368226

  1. Effects of fermentation time and low temperature during the production process of Thai pickled fish (pla-som) on the viability and infectivity of Opisthorchis viverrini metacercariae.

    PubMed

    Onsurathum, Sudarat; Pinlaor, Porntip; Haonon, Ornuma; Chaidee, Apisit; Charoensuk, Lakhanawan; Intuyod, Kitti; Boonmars, Thidarut; Laummaunwai, Porntip; Pinlaor, Somchai

    2016-02-01

    Contamination of a popular fermented fish dish, pla-som, by Opisthorchis viverrini metacercariae (OVMC) is a possible cause of carcinogenic liver fluke infection in Thailand. Affected individuals are at risk of bile duct cancer, which is a major health problem for people in the Greater Mekong Subregion. In order to investigate concerns about food safety, we studied the effects of fermentation time and low temperature on the viability and infectivity of OVMC during the pla-som production process. Pla-som was prepared at room temperature for up to 1 week in duplicate experiments using cyprinid freshwater fish obtained from an O. viverrini-endemic area. OVMC were then isolated and identified under a stereomicroscope. Complete and viable OVMC were found on days 1-4 of fermentation, while their morphology was degenerated thereafter. After OVMC were fed to hamsters, the percentage of the worm recovery after 1 to 2 months of infection was 52%, 44.7%, 11.3% and 1% for days 1, 2, 3 and 4, respectively. In order to measure the effect of low temperature on OVMC, fish were kept in a refrigerator (4 °C) for up to five days and then subsequently fermented for three days. In fish stored in a refrigerator for 1 and 2 days, viable OVMC were clearly observed and were able to infect hamsters, a worm-recovery percentage of 3.3% and 12.7%, respectively. By contrast, in pla-som prepared from fish stored for 3 to 5 days, OVMC were degenerated and could not infect the host. In conclusion, pla-som fermentation for more than four days and refrigerating fish for three days before pla-som processing can prevent O. viverrini infection. This study may increase awareness of fermented-fish dish preparation to prevent liver fluke infection. PMID:26587967

  2. Low-Temperature Supercapacitors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik J.; West, William C.; Smart, Marshall C.

    2008-01-01

    An effort to extend the low-temperature operational limit of supercapacitors is currently underway. At present, commercially available non-aqueous supercapacitors are rated for a minimum operating temperature of -40 C. A capability to operate at lower temperatures would be desirable for delivering power to systems that must operate in outer space or in the Polar Regions on Earth. Supercapacitors (also known as double-layer or electrochemical capacitors) offer a high power density (>1,000 W/kg) and moderate energy density (about 5 to 10 Wh/kg) technology for storing energy and delivering power. This combination of properties enables delivery of large currents for pulsed applications, or alternatively, smaller currents for low duty cycle applications. The mechanism of storage of electric charge in a supercapacitor -- at the electrical double-layer formed at a solid-electrode/liquid-electrolyte interface -- differs from that of a primary or secondary electrochemical cell (i.e., a battery) in such a manner as to impart a long cycle life (typically >10(exp 6) charge/discharge cycles).

  3. Low Temperature Plasma Medicine

    NASA Astrophysics Data System (ADS)

    Graves, David

    2013-10-01

    Ionized gas plasmas near room temperature are used in a remarkable number of technological applications mainly because they are extraordinarily efficient at exploiting electrical power for useful chemical and material transformations near room temperature. In this tutorial address, I will focus on the newest area of low temperature ionized gas plasmas (LTP), in this case operating under atmospheric pressure conditions, in which the temperature-sensitive material is living tissue. LTP research directed towards biomedical applications such as sterilization, surgery, wound healing and anti-cancer therapy has seen remarkable growth in the last 3-5 years, but the mechanisms responsible for the biomedical effects have remained mysterious. It is known that LTP readily create reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS (or RONS), in addition to a suite of other radical and non-radical reactive species, are essential actors in an important sub-field of aerobic biology termed ``redox'' (or oxidation-reduction) biology. I will review the evidence suggesting that RONS generated by plasmas are responsible for their observed therapeutic effects. Other possible bio-active mechanisms include electric fields, charges and photons. It is common in LTP applications that synergies between different mechanisms can play a role and I will review the evidence for synergies in plasma biomedicine. Finally, I will address the challenges and opportunities for plasma physicists to enter this novel, multidisciplinary field.

  4. Electronic Relaxation Processes of Transition Metal Atoms in Helium Nanodroplets

    NASA Astrophysics Data System (ADS)

    Kautsch, Andreas; Lindebner, Friedrich; Koch, Markus; Ernst, Wolfgang E.

    2014-06-01

    Spectroscopy of doped superfluid helium nanodroplets (He_N) gives information about the influence of this cold, chemically inert, and least interacting matrix environment on the excitation and relaxation dynamics of dopant atoms and molecules. We present the results from laser induced fluorescence (LIF), photoionization (PI), and mass spectroscopy of Cr and Cu doped He_N. From these results, we can draw a comprehensive picture of the complex behavior of such transition metal atoms in He_N upon photo-excitation. The strong Cr and Cu ground state transitions show an excitation blueshift and broadening with respect to the bare atom transitions which can be taken as indication for the solvation inside the droplet. From the originally excited states the atoms relax to energetically lower states and are ejected from the He_N. The relaxation processes include bare atom spin-forbidden transitions, which clearly bears the signature of the He_N influence. Two-color resonant two-photon ionization (2CR2PI) also shows the formation of bare atoms and small Cr-He_n and Cu-He_n clusters in their ground and metastable states ^c. Currently, Cr dimer excitation studies are in progress and a brief outlook on the available results will be given. C. Callegari and W. E. Ernst, Helium Droplets as Nanocryostats for Molecular Spectroscopy - from the Vacuum Ultraviolet to the Microwave Regime, in Handbook of High-Resolution Spectroscopy, eds. M. Quack and F. Merkt, John Wiley & Sons, Chichester, 2011. A. Kautsch, M. Koch, and W. E. Ernst, J. Phys. Chem. A, 117 (2013) 9621-9625, DOI: 10.1021/jp312336m F. Lindebner, A. Kautsch, M. Koch, and W. E. Ernst, Int. J. Mass Spectrom. (2014) in press, DOI: 10.1016/j.ijms.2013.12.022 M. Koch, A. Kautsch, F. Lackner, and W. E. Ernst, submitted to J. Phys. Chem. A

  5. Periodically pulsed wet annealing approach for low-temperature processable amorphous InGaZnO thin film transistors with high electrical performance and ultrathin thickness.

    PubMed

    Kim, Ye Kyun; Ahn, Cheol Hyoun; Yun, Myeong Gu; Cho, Sung Woon; Kang, Won Jun; Cho, Hyung Koun

    2016-01-01

    In this paper, a simple and controllable "wet pulse annealing" technique for the fabrication of flexible amorphous InGaZnO thin film transistors (a-IGZO TFTs) processed at low temperature (150 °C) by using scalable vacuum deposition is proposed. This method entailed the quick injection of water vapor for 0.1 s and purge treatment in dry ambient in one cycle; the supply content of water vapor was simply controlled by the number of pulse repetitions. The electrical transport characteristics revealed a remarkable performance of the a-IGZO TFTs prepared at the maximum process temperature of 150 °C (field-effect mobility of 13.3 cm(2) V(-1) s(-1); Ion/Ioff ratio ≈ 10(8); reduced I-V hysteresis), comparable to that of a-IGZO TFTs annealed at 350 °C in dry ambient. Upon analysis of the angle-resolved x-ray photoelectron spectroscopy, the good performance was attributed to the effective suppression of the formation of hydroxide and oxygen-related defects. Finally, by using the wet pulse annealing process, we fabricated, on a plastic substrate, an ultrathin flexible a-IGZO TFT with good electrical and bending performances. PMID:27198067

  6. Periodically pulsed wet annealing approach for low-temperature processable amorphous InGaZnO thin film transistors with high electrical performance and ultrathin thickness

    PubMed Central

    Kim, Ye Kyun; Ahn, Cheol Hyoun; Yun, Myeong Gu; Cho, Sung Woon; Kang, Won Jun; Cho, Hyung Koun

    2016-01-01

    In this paper, a simple and controllable “wet pulse annealing” technique for the fabrication of flexible amorphous InGaZnO thin film transistors (a-IGZO TFTs) processed at low temperature (150 °C) by using scalable vacuum deposition is proposed. This method entailed the quick injection of water vapor for 0.1 s and purge treatment in dry ambient in one cycle; the supply content of water vapor was simply controlled by the number of pulse repetitions. The electrical transport characteristics revealed a remarkable performance of the a-IGZO TFTs prepared at the maximum process temperature of 150 °C (field-effect mobility of 13.3 cm2 V−1 s−1; Ion/Ioff ratio ≈ 108; reduced I-V hysteresis), comparable to that of a-IGZO TFTs annealed at 350 °C in dry ambient. Upon analysis of the angle-resolved x-ray photoelectron spectroscopy, the good performance was attributed to the effective suppression of the formation of hydroxide and oxygen-related defects. Finally, by using the wet pulse annealing process, we fabricated, on a plastic substrate, an ultrathin flexible a-IGZO TFT with good electrical and bending performances. PMID:27198067

  7. A low-temperature growth process of GaAs by electron-cyclotron-resonance plasma-excited molecular-beam-epitaxy (ECR-MBE)

    NASA Astrophysics Data System (ADS)

    Kondo, Naoto; Nanishi, Yasushi

    1988-09-01

    Taking advantage of plasma excitation, surface cleaning and growth process are realized at low temperatures by electron-cyclotron-resonance (ECR) plasma-excited molecular-beam-epitaxy (MBE). Prior to growth, substrates are cleaned by exposure to hydrogen plasma at temperatures ranging from 300 to 550°C. Arsine gas is introduced and cracked in an ECR plasma generation chamber. Gallium is supplied either as trimethylgallium (TMG) or as metallic Ga. Epitaxial films are successfully grown at substrate temperatures low as 430°C for the TMG-arsine system and 350°C for the metallic Ga-arsine system. The growth rate for the TMG-arsine system is found to be governed by a balance between TMG decomposition and surface atom desorption. By contrast, the metallic Ga-arsine system is only governed by the desorption process. Exposure to plasma is found to promote desorption of atoms migrating on the substrate surface. The interface between the substrate and the epitaxial layer produced by the ECR-MBE process is found to be clean without piling up of impurity.

  8. Periodically pulsed wet annealing approach for low-temperature processable amorphous InGaZnO thin film transistors with high electrical performance and ultrathin thickness

    NASA Astrophysics Data System (ADS)

    Kim, Ye Kyun; Ahn, Cheol Hyoun; Yun, Myeong Gu; Cho, Sung Woon; Kang, Won Jun; Cho, Hyung Koun

    2016-05-01

    In this paper, a simple and controllable “wet pulse annealing” technique for the fabrication of flexible amorphous InGaZnO thin film transistors (a-IGZO TFTs) processed at low temperature (150 °C) by using scalable vacuum deposition is proposed. This method entailed the quick injection of water vapor for 0.1 s and purge treatment in dry ambient in one cycle; the supply content of water vapor was simply controlled by the number of pulse repetitions. The electrical transport characteristics revealed a remarkable performance of the a-IGZO TFTs prepared at the maximum process temperature of 150 °C (field-effect mobility of 13.3 cm2 V‑1 s‑1 Ion/Ioff ratio ≈ 108 reduced I-V hysteresis), comparable to that of a-IGZO TFTs annealed at 350 °C in dry ambient. Upon analysis of the angle-resolved x-ray photoelectron spectroscopy, the good performance was attributed to the effective suppression of the formation of hydroxide and oxygen-related defects. Finally, by using the wet pulse annealing process, we fabricated, on a plastic substrate, an ultrathin flexible a-IGZO TFT with good electrical and bending performances.

  9. Electron decoherence at low temperatures

    NASA Astrophysics Data System (ADS)

    Mohanty, Pritiraj

    2001-03-01

    Electron decoherence is fundamental to condensed matter physics. Our understanding of metals and insulators in the Fermi-liquid framework relies entirely on a diverging decoherence rate 1/τ_φ at low temperatures, which is expected to vanish at T=0. However, recent experiments find that 1/τ_φ saturates at low temperatures [1-2]. We review these measurements on a variety of mesoscopic systems (in 0D, 1D, 2D and 3D) as well as the control experiments used to check for various artifacts [1-3]. We emphasize the connection between the temperature-independent decoherence rate and persistent current in normal metals [4]. We briefly discuss decoherence induced by dynamic defects or two-level systems [5,6], including its relevance--or lack thereof---to the experiments on metallic wires [2]. Saturation of decohrence rate is argued to be present in---and relevant to---the following phenomena: metal-insulator transition in 2D [7,8], superconductor-insulator transition in 2D [9], quantum-Hall-insulator transition [10], transport through superconductor/normal-metal hybrid junctions [11], normal-state resistivity of high Tc superconductors [12], persistent current in normal metals [4], and energy relaxation in normal metals [13]. [1] P. Mohanty, Physica B 280, 446 (2000). [2] P. Mohanty, E.M.Q. Jariwala, R. Webb, PRL 78, 3366 (1997); PRB 55, R13542 (1997). [3] P. Mohanty, R. Webb, PRL 84, 4481 (2000). [4] P. Mohanty, Ann. Phys. 8, 549 (1999). [5] P. Mohanty, M.L. Roukes (to be published). [6] K. Ahn, P. Mohanty, cond-mat/ 0011139. [7] S. Kravchenko et al. PRB 50, 8039 (1994). [8] G. Brunthaler, A. Prinz, G. Bauer, V. Pudalov, cond-mat/0007230. [9] A. Kapitulnik, N. Mason, S. Kivelson, S. Chakravarty, cond-mat/0008005. [10] D. Shahar, D. Tsui, M. Shayegan, J. Cunningham, E. Shimsoni, S. Sondhi, SSC. 102, 817 (1997). [11] A. Vaknin, A. Frydman, Z. Ovadyahu, PRB 61, 13037 (2000). [12] P. Fournier et al., PRB 62, R11993 (2000). [13] A. Gougam, F. Pierre, H. Pothier, D. Esteve, N

  10. Performance of partial denitrification (PD)-ANAMMOX process in simultaneously treating nitrate and low C/N domestic wastewater at low temperature.

    PubMed

    Du, Rui; Cao, Shenbin; Wang, Shuying; Niu, Meng; Peng, Yongzhen

    2016-11-01

    The simultaneous treatment of nitrate (NO3(-)-N∼50mgL(-1)) and domestic wastewater (ammonia (NH4(+)-N)∼60.6mgL(-1), COD∼166.3mgL(-1)) via a novel partial denitrification (PD)-ANaerobic AMMonium OXidation (ANAMMOX) process was investigated at low temperature (12.9∼15.1°C). Results showed that desirable performance was achieved with average NO3(-)-N, NH4(+)-N and COD removal efficiencies of 89.5%, 97.6% and 78.7%, respectively. However, deteriorated sludge settleability in PD reactor was observed during operation, which bulked with serious sludge wash-out, leading to excess NO3(-)-N remaining in PD effluent. Fortunately, a satisfactory nitrogen removal was still achieved due to the occurrence of partial denitrification in ANAMMOX reactor. This was demonstrated by high-throughput sequencing, which revealed that the high nitrite (NO2(-)-N) production denitrifying bacteria of Thauera was detected (6.1%). ANAMMOX (above 70%) maintained the dominant pathway for nitrogen removal, and Candidatus Jettenia was identified as the major ANAMMOX species accounted for 2.7%. PMID:27521780

  11. Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process

    PubMed Central

    2012-01-01

    One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods. PMID:22768847

  12. Low temperature and anhydrous electron microscopy techniques to observe the infection process of the bacterial pathogen Xanthomonas fragariae on strawberry leaves.

    PubMed

    Allan-Wojtas, P; Hildebrand, P D; Braun, P G; Smith-King, H L; Carbyn, S; Renderos, W E

    2010-09-01

    Preserving the structural arrangement of the components of a bacterial infection process within a plant for microscopy study is a technical challenge because of the different requirements of each component for optimal preservation and visualization. We used low temperature scanning electron microscopy (cryo-SEM), anhydrous fixation at ambient temperature and freeze-substitution for transmission electron microscopy to examine fractured and sectioned strawberry leaves infected with Xanthomonas fragariae. Cryo-SEM images of fractured samples showed the bacterial colonization of mesophyll air spaces in the leaf, limited by the vascular bundles and the orientation and packing of bacteria in extracellular polysaccharide. Transmission electron microscopy of samples fixed using osmium tetroxide dissolved in FC-72 solvent at ambient temperature showed that the entire plant/bacteria/extracellular polysaccharide system was preserved in situ, and showed plasmolysis of mesophyll cells and disruption of organelles. In freeze-substitution samples, osmium tetroxide in FC-72 solvent gave superior preservation of the extracellular polysaccharide as compared to a conventional cocktail. In addition, strands believed to be xanthan were preferentially contrasted to show their density and orientation around the bacterial cells. We conclude that anhydrous fixation using osmium tetroxide in FC-72 at ambient temperature gave the best preservation of the entire system, and freeze-substitution using this same fixative enhanced the visualization of strands in the biofilm. PMID:20701664

  13. Influence of inelastic Rydberg atom-atom collisional process on kinetic and optical properties of low-temperature laboratory and astrophysical plasmas

    NASA Astrophysics Data System (ADS)

    Klyucharev, A. N.; Bezuglov, N. N.; Mihajlov, A. A.; Ignjatović, Lj M.

    2010-11-01

    Elementary processes in plasma phenomena traditionally attract physicist's attention. The channel of charged-particle formation in Rydberg atom-atom thermal and sub-thermal collisions (the low temperature plasmas conditions) leads to creation of the molecular ions - associative ionization (AI). atomic ions - Penning-like ionization (PI) and the pair of the negative and positive ions. In our universe the chemical composition of the primordial gas consists mainly of Hydrogen and Helium (H, H-, H+, H2, He,He+). Hydrogen-like alkali-metal Lithium (Li, Li+,Li-) and combinations (HeH+, LiH-, LiH+). There is a wide range of plasma parameters in which the Rydberg atoms of the elements mentioned above make the dominant contribution to ionization and that process may be regarded as a prototype of the elementary process of light excitation energy transformation into electric one. The latest stochastic version of chemi-ionisation (AI+PI) on Rydberg atom-atom collisions extends the treatment of the "dipole resonant" model by taking into account redistribution of population over a range of Rydberg states prior to ionization. This redistribution is modelled as diffusion within the frame of stochastic dynamic of the Rydberg electron in the Rydberg energy spectrum. This may lead to anomalies of Rydberg atom spectra. Another result obtained in recent time is understanding that experimental results on chemi-ionization relate to the group of mixed Rydberg atom closed to the primary selected one. The Rydberg atoms ionisation theory today makes a valuable contribution in the deterministic and stochastic approaches correlation in atomic physic.

  14. Up-cycling waste glass to minimal water adsorption/absorption lightweight aggregate by rapid low temperature sintering: optimization by dual process-mixture response surface methodology.

    PubMed

    Velis, Costas A; Franco-Salinas, Claudia; O'Sullivan, Catherine; Najorka, Jens; Boccaccini, Aldo R; Cheeseman, Christopher R

    2014-07-01

    Mixed color waste glass extracted from municipal solid waste is either not recycled, in which case it is an environmental and financial liability, or it is used in relatively low value applications such as normal weight aggregate. Here, we report on converting it into a novel glass-ceramic lightweight aggregate (LWA), potentially suitable for high added value applications in structural concrete (upcycling). The artificial LWA particles were formed by rapidly sintering (<10 min) waste glass powder with clay mixes using sodium silicate as binder and borate salt as flux. Composition and processing were optimized using response surface methodology (RSM) modeling, and specifically (i) a combined process-mixture dual RSM, and (ii) multiobjective optimization functions. The optimization considered raw materials and energy costs. Mineralogical and physical transformations occur during sintering and a cellular vesicular glass-ceramic composite microstructure is formed, with strong correlations existing between bloating/shrinkage during sintering, density and water adsorption/absorption. The diametrical expansion could be effectively modeled via the RSM and controlled to meet a wide range of specifications; here we optimized for LWA structural concrete. The optimally designed LWA is sintered in comparatively low temperatures (825-835 °C), thus potentially saving costs and lowering emissions; it had exceptionally low water adsorption/absorption (6.1-7.2% w/wd; optimization target: 1.5-7.5% w/wd); while remaining substantially lightweight (density: 1.24-1.28 g.cm(-3); target: 0.9-1.3 g.cm(-3)). This is a considerable advancement for designing effective environmentally friendly lightweight concrete constructions, and boosting resource efficiency of waste glass flows. PMID:24871934

  15. Low-temperature, solution-processed ZrO2:B thin film: a bifunctional inorganic/organic interfacial glue for flexible thin-film transistors.

    PubMed

    Park, Jee Ho; Oh, Jin Young; Han, Sun Woong; Lee, Tae Il; Baik, Hong Koo

    2015-03-01

    A solution-processed boron-doped peroxo-zirconium oxide (ZrO2:B) thin film has been found to have multifunctional characteristics, providing both hydrophobic surface modification and a chemical glue layer. Specifically, a ZrO2:B thin film deposited on a hydrophobic layer becomes superhydrophilic following ultraviolet-ozone (UVO) treatment, whereas the same treatment has no effect on the hydrophobicity of the hydrophobic layer alone. Investigation of the ZrO2:B/hydrophobic interface layer using angle-resolved X-ray photoelectron spectroscopy (AR XPS) confirmed it to be chemically bonded like glue. Using the multifunctional nature of the ZrO2:B thin film, flexible amorphous indium oxide (In2O3) thin-film transistors (TFTs) were subsequently fabricated on a polyimide substrate along with a ZrO2:B/poly-4-vinylphenol (PVP) dielectric. An aqueous In2O3 solution was successfully coated onto the ZrO2:B/PVP dielectric, and the surface and chemical properties of the PVP and ZrO2:B thin films were analyzed by contact angle measurement, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The surface-engineered PVP dielectric was found to have a lower leakage current density (Jleak) of 4.38 × 10(-8) A/cm(2) at 1 MV/cm, with no breakdown behavior observed up to a bending radius of 5 mm. In contrast, the electrical characteristics of the flexible amorphous In2O3 TFT such as on/off current ratio (Ion/off) and electron mobility remained similar up to 10 mm of bending without degradation, with the device being nonactivated at a bending radius of 5 mm. These results suggest that ZrO2:B thin films could be used for low-temperature, solution-processed surface-modified flexible devices. PMID:25664940

  16. Protection of signal processing at low temperature in baroreceptive neurons in the nucleus tractus solitarius of Syrian hamsters, a hibernating species

    PubMed Central

    Sekizawa, Shin-Ichi; Horwitz, Barbara A.; Horowitz, John M.

    2013-01-01

    We previously described synaptic currents between baroreceptor fibers and second-order neurons in the nucleus tractus solitarius (NTS) that were larger in Syrian hamsters than in rats. This suggested that although electrical activity throughout the hamster brain decreased as brain temperature declined, the greater synaptic input to its NTS would support continued operation of cardiorespiratory reflexes at low body temperatures. Here, we focused on properties that would protect these neurons against potential damage from the larger synaptic inputs, testing the hypotheses that hamster NTS neurons exhibit: 1) intrinsic N-methyl-d-aspartate receptor (NMDAR) properties that limit Ca2+ influx to a greater degree than do rat NTS neurons and 2) properties that reduce gating signals to NMDARs to a greater degree than in rat NTS neurons. Whole cell patch-clamp recordings on anatomically identified second-order NTS baroreceptive neurons showed that NMDAR-mediated synaptic currents between sensory fibers and second-order NTS neurons were larger in hamsters than in rats at 33°C and 15°C, with no difference in their permeability to Ca2+. However, at 15°C, but not at 33°C, non-NMDAR currents evoked by glutamate released from baroreceptor fibers had significantly shorter durations in hamsters than in rats. Thus, hamster NMDARs did not exhibit lower Ca2+ influx than did rats (negating hypothesis 1), but they did exhibit significant differences in non-NMDAR neuronal properties at low temperature (consistent with hypothesis 2). The latter (shorter duration of non-NMDAR currents) would likely limit NMDAR coincidence gating and may help protect hamster NTS neurons, enabling them to contribute to signal processing at low body temperatures. PMID:24068050

  17. Influence Of Inelastic Ridberg Atom-Atom Collisional Process On Kinetic And Optical Properties Of Low-Temperature Laboratory And Astrophysical Plasmas

    NASA Astrophysics Data System (ADS)

    Klyucharev, A. N.; Bezuglov, N. N.; Mihajlov, A. A.; Ignjatovic, Lj. M.

    2010-07-01

    Elementary processes in plasma phenomena traditionally attract physicist`s attention. The channel of charged-particle formation in Rydberg Atom-Atom thermal and subthermal collisions (the low temperature plasmas conditions) leads to creation of the molecular ions - associative ionization (AI), atomic ions - penning-like ionization (PI) and the pair of the negative and positive ions. In our universe the chemical composition of the primordial gas consists mainly of Hydrogen and Helium (H, H- , H+, H2, He, He+ ), Hydrogen-like alkali-metal Litium (Li, Li+, Li-) and combinations (HeH+ , LiH- , LiH+). There is a wide range of plasma parameters in which the Rydberg Atoms of the elements called above make the dominant construction to ionization and that process may be regarded as a prototype of the elementary process of light excitation energy transformation into electric one. The first series of quantitative measurements of the rate constants for Rydberg Atoms starts in 1978 (Devdariani, Klyucharev et al.). The method of AI and PI calculations, so-called "dipole resonant" mechanism proposed in 1971 (Smirnov, Mihaylov) was used in semiclassical (Mihailov and Janev 1981) and quantum mechanical theories (Duman, Shmatov, 1980). The latest stochastic version of chemi-ionisation (AI+PI) on Rydberg Atom - Atom collisions extends the treatment of the "dipole resonant" model by taking into account redistribution of population over a range of Rydberg states prior to ionization. This redistribution is modeled as diffusion in the frame of stochastic dynamic of the Rydberg electron in the Rydberg energy spectrum (Bezuglov, Borodin, Klyucharev et al. 1997). Such approach makes it possible to operate on efficiently of inelastic collisional processes and sometimes to operate on time of Rydberg Atoms life. This may lead to anomalies of Rydberg Atoms spectra. Another result obtained in recent time is understanding that experimental results on chemi-ionization relate to the group of mixed

  18. Relaxation process of Fe(CuNb)SiB amorphous alloys investigated by dynamical calorimetry

    SciTech Connect

    Zhu, J.; Clavaguera-Mora, M.T.; Clavaguera, N.

    1997-03-01

    Differential scanning calorimetry and dynamic differential scanning calorimetry were used to analyze the relaxation process of Fe(CuNb)SiB amorphous alloys. The Curie temperature (T{sub C}) evolution of the amorphous phase during relaxation as a function of heating rate, time and pre-annealing temperature were measured. Two distinct relaxation processes are observed, consequent with topological and chemical short range order changes. {copyright} {ital 1997 American Institute of Physics.}

  19. Low-temperature coal desulfurization

    NASA Technical Reports Server (NTRS)

    Ganguli, P. S.; Gavalas, G. R.; Hsu, G. C.; Kalfayan, S. H.

    1977-01-01

    Economical, low-temperature chlorinolysis converts sulfur to water-soluble sulfates. Sulfates are removed by washing. Subsequent steps dry coal and remove chlorine. Chlorine and solvents can be reused.

  20. Sensors for low temperature application

    DOEpatents

    Henderson, Timothy M.; Wuttke, Gilbert H.

    1977-01-01

    A method and apparatus for low temperature sensing which uses gas filled micro-size hollow glass spheres that are exposed in a confined observation area to a low temperature range (Kelvin) and observed microscopically to determine change of state, i.e., change from gaseous state of the contained gas to condensed state. By suitable indicia and classification of the spheres in the observation area, the temperature can be determined very accurately.

  1. Low Temperature Research in Microgravity

    NASA Technical Reports Server (NTRS)

    Strayer, D.

    1993-01-01

    The recent flight of the Lambda Point Experiment has demonstrated the potential for performing precise tests of fundamental theories using low temperature techniques in Earth orbit. NASA's Microgravity Science and Applications Division has established a program of successor expermients to investigate other aspects of condensed matter physics using the same low temperature flight facility. This paper describes the new investigations that have been chosen for flight experiments, and those selected for ground-based studies that could lead to flight experiments later.

  2. Final technical report to Department of Energy, Basic Energy Sciences. ''Oxide ceramic alloys and microlaminates'' (1996-1999) and ''Low temperature processing and kinetics of ceramics and ceramic matrix composites with large interfacial areas'' (1999-2000)

    SciTech Connect

    Chen, I-Wei

    2001-03-26

    We have discovered a novel two-step sintering method that opened up a low temperature processing window within which fully dense nanocrystalline yttrium oxide was obtained with no concurrent grain growth during final-stage sintering. We have developed a new method of processing laminate ceramics using deformation processing in the green state. We have lastly developed a colloidal processing technique to encapsulate biomolecules at ambient, neutral-pH, aqueous conditions.

  3. The effect of a novel low temperature-short time (LTST) process to extend the shelf-life of fluid milk.

    PubMed

    Myer, Phillip R; Parker, Kyle R; Kanach, Andrew T; Zhu, Tengliang; Morgan, Mark T; Applegate, Bruce M

    2016-01-01

    Pasteurization has long been the standard method to extend the shelf-life of dairy products, as well as a means to reduce microbial load and the risk of food-borne pathogens. However, the process has limitations, which include cost effectiveness, high energy input, and reduction of product quality/organoleptic characteristics. In an effort to reduce these limitations and extend shelf-life, this study examined a novel low temperature, short time (LTST) method in which dispersed milk in the form of droplets was treated with low heat/pressure variation over a short treatment time, in conjunction with pasteurization. Lactobacillus fermentum and Pseudomonas fluorescens Migula were exposed to conventional pasteurization treatments with and without LTST. Using these organisms, the LTST addition was able to reduce microbial load below detection limits; 1.0 × 10(1) cfu/mL, from approximately 1.2 × 10(8) and 1.0 × 10(7) cfu/mL for L. fermentum and P. fluorescens Migula, respectively. In addition, the shelf-life of the treated, raw, and uninoculated product was prolonged from 14 to 35 days, compared with standard pasteurization, to as long as 63 days with the LTST amendment. Sensory analysis of samples also demonstrated equal or greater preference for LTST + pasteurization treated milk when compared to pasteurization alone (α = 0.05). Conventional pasteurization was effective at reducing the above mentioned microorganisms by as much as 5.0 log10 cfu/mL. However, LTST was able to achieve 7.0-8.0 log10 cfu/mL reduction of the same microorganisms. In addition, BActerial Rapid Detection using Optical scattering Technology detected and identified microorganisms isolated both pre- and post-treatment, of which the only organisms surviving LTST were Bacillus spp. Increased lethality, improved shelf-life, and equal or better organoleptic characteristics without increased energy consumption demonstrate the effectiveness of the incorporation of LTST. The improved

  4. Fast dynamics and relaxation of colloidal drops during the drying process using multispeckle diffusing wave spectroscopy.

    PubMed

    Lee, Jeong Yong; Hwang, Ji Won; Jung, Hyun Wook; Kim, Sung Hyun; Lee, Seong Jae; Yoon, Kisun; Weitz, David A

    2013-01-22

    The fast dynamics generated by the Brownian motion of particles in colloidal drops, and the related relaxation during drying, which play key roles in suspension systems, were investigated incorporating multispeckle diffusing wave spectroscopy (MSDWS). MSDWS equipment was implemented to analyze the relaxation properties of suspensions under a nonergodic and nonstationary drying process, which cannot be elucidated by conventional light scattering methods, such as dynamic light scattering and diffusing wave spectroscopy. Rapid particle movement can be identified by the characteristic relaxation time, which is closely related to the Brownian motion due to thermal fluctuations of the particles. In the compacting stage of the drying process, the characteristic relaxation time increased gradually with the drying time because the particles in the colloidal drop were constrained by themselves. Moreover, variations of the initial concentration and particle size considerably affected the complete drying time and characteristic relaxation time, producing a shorter relaxation time for a low concentrated suspension with small particles. PMID:23281633

  5. Development of an alternative kraft black liquor recovery process based on low-temperature processing in fluidized beds. Final technical report on Annex 9, Task 1

    SciTech Connect

    Kubes, G.J.

    1994-03-24

    The overall objective of this research program was to provide the fundamental knowledge and experimental data from pilot scale operation for an alternative black liquor recovery technology which would have a higher overall energy efficiency, would not suffer from the smelt-water explosion hazard and would be lower in capital cost. In addition, the alternative process would be more flexible and well suited for incremental recovery capacity or for new pulping processes, such as the new sulfide-sulfide-AQ process. The research program consists of number of specific research objectives with the aim to achieve the ultimate objective of developing an alternative recovery process which is shown in Figure 1. The specific objectives are linked to individual unit operations and they represent the following research topics: (1) superheated steam drying of kraft black liquors; (2) fast pyrolysis of black liquor; (3) hydrogen sulfide absorption from flue gas; (4) reduction of sodium sulfate in solid phase with gaseous hydrogen; and (5) verification of the fundamental results in fluidized bed pilot plant. The accomplishments in each of these objectives are described.

  6. Low temperature synthesis of methyl formate

    DOEpatents

    Mahajan, Devinder; Slegeir, William A.; Sapienza, Richard S.; O'Hare, Thomas E.

    1986-01-01

    A gas reaction process for the preferential production of methyl formate over the co-production of methanol wherein the reactant ratio of CO/H.sub.2 is upgraded and this reaction takes place at low temperatures of 50.degree.-150.degree. C. and moderate pressures of .gtoreq.100 psi.

  7. Manufacturing Demonstration Facility: Low Temperature Materials Synthesis

    SciTech Connect

    Graham, David E.; Moon, Ji-Won; Armstrong, Beth L.; Datskos, Panos G.; Duty, Chad E.; Gresback, Ryan; Ivanov, Ilia N.; Jacobs, Christopher B.; Jellison, Gerald Earle; Jang, Gyoung Gug; Joshi, Pooran C.; Jung, Hyunsung; Meyer, III, Harry M.; Phelps, Tommy

    2015-06-30

    The Manufacturing Demonstration Facility (MDF) low temperature materials synthesis project was established to demonstrate a scalable and sustainable process to produce nanoparticles (NPs) for advanced manufacturing. Previous methods to chemically synthesize NPs typically required expensive, high-purity inorganic chemical reagents, organic solvents and high temperatures. These processes were typically applied at small laboratory scales at yields sufficient for NP characterization, but insufficient to support roll-to-roll processing efforts or device fabrication. The new NanoFermentation processes described here operated at a low temperature (~60 C) in low-cost, aqueous media using bacteria that produce extracellular NPs with controlled size and elemental stoichiometry. Up-scaling activities successfully demonstrated high NP yields and quality in a 900-L pilot-scale reactor, establishing this NanoFermentation process as a competitive biomanufacturing strategy to produce NPs for advanced manufacturing of power electronics, solid-state lighting and sensors.

  8. Low Temperature Trapping: from Reactions to Spectroscopy

    NASA Astrophysics Data System (ADS)

    Schlemmer, S.; Asvany, O.; Brunken, S.

    2013-06-01

    The kinetics of ion - molecule reactions are investigated in higher-order multipole traps by observation of the temporal evolution of mass selected parent ions in the presence of a neutral reaction partner. Rate coeffients for fast reactions (proceeding at collision rate) and very slow reactions (taking millions of collisions) are determined over a wide range of temperatures. Endothermic or hindered reactions can be promoted by excitation of the ion via absorption of a photon. Scanning the photon energy while detecting the number of product ions establishes an action spectroscopy method which we developed over the last 10-15 years and termed LIR: laser or light induced reactions. The main advantages of LIR are mass selection of the parent ion and low temperature conditions in the trap. Long storage times in combination with a near unity detection efficiency make LIR one of the most sensitive spectroscopy methods. The status quo of LIR will be discussed on selected examples. Recent measurements are concerned with ro-vibrational spectra of CH_2D^+ and CH_5^+ at highest resolution using cw OPO radiation. In the particular case of CH_5^+, the lines in the mid IR have been measured at a nominal temperature of 10 K and a frequency comb has been used for absolute calibration. Line positions can be determined to an accuracy which shall enable us in the future to obtain rotational spectra in a THz-IR double resonance approach. We tested the feasibility of this two photon method recently on H_2D^+. S. Schlemmer, T. Kuhn, E. Lescop, and D. Gerlich, Laser excited N_2^+ in a 22-Pole Trap: Experimental Studies of Rotational Relaxation Processes, Int. J. Mass Spectrometry and Ion Processes, 185-187, 589-602, (1999), S.D. Ivanov, O. Asvany, A. Witt, E. Hugo, G. Mathias, B. Redlich, D. Marx and S. Schlemmer, Quantum-induced symmetry breaking explains infrared spectra of CH_5^+ isotopologues, Nature Chemistry, 2, 298-302 (2010) S. Gaertner, J. Krieg, A. Klemann, O. Asvany and S

  9. Relaxation processes and glass transition in confined 1,4-polybutadiene films: A Molecular Dynamics study

    NASA Astrophysics Data System (ADS)

    Paul, Wolfgang; Solar, Mathieu

    We will present results from Molecular Dynamics simulations of a chemically realistic model of 1,4-polybutadiene (PB) chains confined by graphite walls. Relaxation processes in this system are heterogeneous and anisotropic. We will present evidence for a slow additional relaxation process related to chain desorption from the walls. We also study the structural relaxation resolved with respect to the distance from the graphite walls and show the influence of structural changes on the relaxation behavior. The temperature dependence of the dielectric relaxation in layers of different thickness near the walls shows no indication of a shift of Tg as a function of thickness when analyzed with a Vogel-Fulcher fit. We explain this by the importance of intramolecular dihedral barriers for the glass transition in PB which dominate over the density changes next to a wall except for a 1 nm thick layer directly at the wall.

  10. Catalysts for low temperature oxidation

    DOEpatents

    Toops, Todd J.; Parks, III, James E.; Bauer, John C.

    2016-03-01

    The invention provides a composite catalyst containing a first component and a second component. The first component contains nanosized gold particles. The second component contains nanosized platinum group metals. The composite catalyst is useful for catalyzing the oxidation of carbon monoxide, hydrocarbons, oxides of nitrogen, and other pollutants at low temperatures.

  11. Low-temperature magnetic refrigerator

    DOEpatents

    Barclay, J.A.

    1983-05-26

    The invention relates to magnetic refrigeration and more particularly to low temperature refrigeration between about 4 and about 20 K, with an apparatus and method utilizing a belt of magnetic material passed in and out of a magnetic field with heat exchangers within and outside the field operably disposed to accomplish refrigeration.

  12. Low-temperature magnetic refrigerator

    DOEpatents

    Barclay, John A.

    1985-01-01

    The disclosure is directed to a low temperature 4 to 20 K. refrigeration apparatus and method utilizing a ring of magnetic material moving through a magnetic field. Heat exchange is accomplished in and out of the magnetic field to appropriately utilize the device to execute Carnot and Stirling cycles.

  13. Development of low temperature battery

    NASA Technical Reports Server (NTRS)

    Armstrong, G. M.

    1967-01-01

    Self-contained low temperature battery system consisting of a magnesium anode, potassium thiocyanate-ammonia electrolyte and a cathode composed of a mixture of sulfur, carbon, and mercuric sulfate operates for at least seventy-two hours within a discharge temperature range of plus 20 degrees C to minus 90 degrees C.

  14. Low-Temperature Synthesis of Nanoparticles in the Process of Evaporation of Femtoliter Droplets of a Solution at a Low Pressure

    NASA Astrophysics Data System (ADS)

    Penyazkov, O. G.; Saverchenko, V. I.; Fisenko, S. P.

    2014-07-01

    Results of an X-ray phase analysis of the products of the low-temperature spray pyrolysis of femtoliter droplets of aqueous nickel-chloride solutions are presented. It is shown that the composition of the nanoparticles accumulated on the electrode-substrate in an aerosol reactor depends on the pressure in it and the initial supersaturation of the solution. It was established that marked chemical transformations of the indicated droplets begin at a pressure lower than 80 Torr. The influence of the evaporation of droplets from a solution and the nucleation in the supersaturated solution formed on the kinetics of the chemical transformations of these droplets, giving rise to the substances obtained in the experiments, is discussed.

  15. Nanocrystalline copper sulfide of varying morphologies and stoichiometries in a low temperature solvothermal process using a new single-source molecular precursor

    NASA Astrophysics Data System (ADS)

    Bera, Pulakesh; Seok, Sang Il

    2012-08-01

    Surfactantless synthesis of copper sulfide nanoparticles (NPs) with varied morphologies such as hexagonal rods, rhombohedral, and spherical, has been carried out via low-temperature thermolysis of a new single-source precursor, [Cu(SMDTC)Cl2], (where SMDTC is S-methyl dithiocarbazate). The reaction parameters e.g., temperature and nature of solvent can be used to control the size and morphology of the nanoparticles. It is observed that the solvents played an important role to control the morphology and stoichiometry of copper sulfide. The anisotropic absorption by the chelating solvent (diamine or ethyleneglycol) at the different facets of the newborn microcrystals results the growth of one-dimensional (1D) copper sulfide NPs. The possible formation mechanism of copper sulfide NPs has also been discussed.

  16. Dynamics of Relaxation Processes of Spontaneous Otoacoustic Emissions

    NASA Astrophysics Data System (ADS)

    Murphy, William James

    The dynamical response of spontaneous otoacoustic emissions (SOAEs) to suppression by ipsilateral pulsed external tones of different frequencies and levels is investigated in nine female subjects under normal conditions and in four female subjects during periods when aspirin is being administered. A simple Van der Pol limit-cycle oscillator driven by an external tone is used as an interpretive model. Typical results for both the onset of, and recovery from suppression yield 1/r_1 (where -r_1 is the negative linear component of the damping function) in the range of 2-25 msec. In accordance with the predictions of the model: (a) the relaxation time for the onset of suppression increases with the amount of suppression induced by the external tone, (b) the values of r _1 and the amplitudes of the unsuppressed emissions exhibit an inverse correlation, (c) the values inferred for r_1 are not significantly dependent on the frequency of the pulsed suppressor tone and (d) the inferred r_1 values are not significantly dependent upon the amount of suppression. In investigations involving subjects under aspirin administration, the changes in the relaxation time constants indicate that the main effect of aspirin administration is to reduce the negative damping parameter r_1. The salicylate is apparently not metabolized in some subjects whose emissions are negligibly affected by aspirin administration. A modification of the single-oscillator model is used to describe pulsed suppression data obtained from a primary SOAE (2545 Hz) which is suppressed by a neighboring secondary emission (2895 Hz). The response of the SOAE amplitude during pulsed suppression is modeled by a pair of Van der Pol limit-cycle oscillators with the primary oscillator linearly coupled to the displacement of the secondary higher-frequency one. The relaxation time constants for the onset of, and recovery from, suppression are 4.5 and 4.8 msec, respectively, for the primary SOAE and 7.5 and 10.5 msec for the

  17. Synthesizing primary molecular relaxation processes in excitable gases using a two-frequency reconstructive algorithm.

    PubMed

    Petculescu, Andi G; Lueptow, Richard M

    2005-06-17

    Identifying molecular relaxation processes in excitable gases remains challenging. An algorithm that reconstructs the primary relaxation processes is presented. Based on measurements of acoustic attenuation and sound speed at two frequencies, it synthesizes the entire frequency dependence of the complex effective specific heat of the gas, which is the macroscopic "footprint" of relaxation effects. The algorithm is based on the fact that for a simple relaxation process, such as occurs in many polyatomic gases at temperatures around 300 K, the effective specific heat traces a semicircle in the complex plane as a function of frequency. Knowing the high-frequency or instantaneous value of the specific heat provides the capability to not only sense the presence, but also infer the nature and, for mixtures of unlike-symmetry molecules, the concentration of foreign molecules leaking in a host gas. PMID:16090508

  18. Intergranular fracture in some precipitation-hardened aluminum alloys at low temperatures

    SciTech Connect

    Kuramoto, S.; Itoh, G.; Kanno, M.

    1996-10-01

    Intergranular fracture at low temperatures from room temperature down to 4.2 K has been studied in some precipitation-hardened aluminum alloys. Microscopic appearance of intergranular facets is revealed to be greatly affected by the microstructure adjacent to the grain boundaries (GBs). When large precipitates on GBs and wide precipitation-free zones (PFZs) are present, coalescence of microvoids initiated at the GB precipitates causes the intergranular fracture with dimples. This fracture process is found to be unaffected by deformation temperature. On the other hand, in the presence of fine precipitates on GBs and narrow PFZs, matrix slip localization exerts significant influence on the fracture behavior. At low temperatures, large stress concentration at GBs leads to intergranular fracture, forming sharp ledges on the fracture surfaces, while at room temperature, the dynamic recovery process is thought to relax such stress concentration, resulting in a transgranular ductile rupture.

  19. Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

    PubMed

    Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

    2016-05-01

    Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere. PMID:27483916

  20. Effect of thermo-mechanical processing on the material properties at low temperature of a large size Al-Ni stabilized Nb-Ti/Cu superconducting cable

    NASA Astrophysics Data System (ADS)

    Langeslag, S. A. E.; Curé, B.; Sgobba, S.; Dudarev, A.; ten Kate, H. H. J.; Neuenschwander, J.; Jerjen, I.

    2014-01-01

    For future high-resolution particle experiments, a prototype for a 60 kA at 5 T, 4.2 K class conductor is realized by co-extrusion of a large, 40-strand Nb-Ti/Cu superconducting cable with a precipitation type Al-0.1wt.%Ni stabilizer. Microalloying with nickel contributes to the strength of the stabilizer, and avoids significant degradation in residual resistivity ratio, owing to its low solid solubility in aluminum. Sections of the conductor are work hardened to increase the mechanical properties of the as-extruded temper. Mechanical and resistivity characteristics are assessed as function of the amount of work hardening, at room temperature as well as at 4.2 K. Thermal treatments, like resin curing after coil winding, can cause partial annealing of the cold-worked material and reverse the strengthening effect. However, targeted thermal treatments, applied at relatively low temperature can result in precipitation hardening. The depletion of nickel in the aluminum-rich matrix around the precipitates results in an increased strength and a decreased effect of nickel on the thermal and electrical resistivity of the material. The present work aims at identifying an optimal work hardening sequence, and an optimal thermal treatment, possibly coinciding with a suitable coil resin curing cycle, for the Al-Ni stabilized superconductor.

  1. Fracturing fluids for low temperature wells

    SciTech Connect

    Montgomery, C.T.; Dollarhide, F.E.

    1980-01-01

    Highly viscous fluids are used to initiate and propagate fractures and to place proppant in the fractures during the hydraulic stimulation process. These fluids can cause damage to the conductivity of the induced fractures if they are not properly cleaned out after the fracturing treatment. The clean-up process is aided by the degradation of the polymers, and in low temperature wells the breakdown of the polymer must be chemically induced. This work presents data on a new fracturing fluid aimed specifically at stimulating low temperature and low pressure reservoirs. The system consists of a CO/sub 2/-energized, cross-linked hydroxypropyl guar fluid. The gel is degraded by a traditional breaker that is activated by a new, low temperature breaker activator. The fluid is effective in wells as cool as 60 F and with bhp as low as 100 psi and should be particularly applicable to the shallow gas wells in the Alberta Medicine Hat and high level Keg River areas.

  2. Direct simulation Monte Carlo modeling of relaxation processes in polyatomic gases

    NASA Astrophysics Data System (ADS)

    Pfeiffer, M.; Nizenkov, P.; Mirza, A.; Fasoulas, S.

    2016-02-01

    Relaxation processes of polyatomic molecules are modeled and implemented in an in-house Direct Simulation Monte Carlo code in order to enable the simulation of atmospheric entry maneuvers at Mars and Saturn's Titan. The description of rotational and vibrational relaxation processes is derived from basic quantum-mechanics using a rigid rotator and a simple harmonic oscillator, respectively. Strategies regarding the vibrational relaxation process are investigated, where good agreement for the relaxation time according to the Landau-Teller expression is found for both methods, the established prohibiting double relaxation method and the new proposed multi-mode relaxation. Differences and applications areas of these two methods are discussed. Consequently, two numerical methods used for sampling of energy values from multi-dimensional distribution functions are compared. The proposed random-walk Metropolis algorithm enables the efficient treatment of multiple vibrational modes within a time step with reasonable computational effort. The implemented model is verified and validated by means of simple reservoir simulations and the comparison to experimental measurements of a hypersonic, carbon-dioxide flow around a flat-faced cylinder.

  3. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    SciTech Connect

    Harlan U. Anderson; Wayne Huebner; Igor Kosacki

    2000-09-30

    This project has three main goals: Thin Films Studies, Preparation of Graded Porous Substrates and Basic Electrical Characterization and testing of Planar Single Cells. During this time period substantial progress has been made in developing low temperature deposition techniques to produce dense, nanocrystalline yttrium-stabilized zirconia films on both dense oxide and polymer substrates. Microstructural changes in unsupported nanocrystalline yttrium stabilized zirconia (ZrO{sub 2}:16%Y, or YSZ) thin films were examined as a function of temperature and annealing time in order to determine the grain growth exponent and the mechanisms of pinhole formation. Grain growth and pinhole formation were measured using high resolution transmission electron microscopy (HRTEM), normal imaging mode transmission electron microscopy (TEM), electron diffraction, and energy dispersive X-ray microanalysis (EDS). Grain growth was found to vary with a time exponent of about one half before pinhole formation and about one third after. Pinhole formation in 70 nm thick films occurred at temperatures near 600 C, corresponding to a grain size of about 15 nm, or a grain size to film thickness ration of approximately 0.25. The deposition of films on porous substrates is hampered by the penetration of the polymer precursor solution into the substrate whose pores as > 0.2 {micro}m, therefore much attention has to be paid to the development of porous colloidal oxide films onto surfaces. Thus during this line period we have been studying these films. Optical properties have proven to be an excellent way to study the quality of these nanoporous films. The influence of porosity and densification on optical properties of films on sapphire substrates that were prepared from water colloidal suspensions of small ({approx}5nm) particles of ceria was investigated. The colloidal ceria films have initially very porous structure (porosity about 50%) and densification starts at about 600 C accompanied by

  4. Probing of structural relaxation times in the glassy state of sucrose and trehalose based on dynamical properties of two secondary relaxation processes

    SciTech Connect

    Kaminski, K.; Adrjanowicz, K.; Paluch, M.; Kaminska, E.

    2011-06-15

    Time-dependent isothermal dielectric measurements were carried out deeply in the glassy state on two very important saccharides: sucrose and trehalose. In both compounds two prominent secondary relaxation processes were identified. The faster one is an inherent feature of the whole family of carbohydrates. The slower one can also be detected in oligo- and polysaccharides. It was shown earlier that the {beta} process is the Johari-Goldstein (JG) relaxation coupled to motions of the glycosidic linkage, while the {gamma} relaxation originates from motions of the exocyclic hydroxymethyl unit. Recently, it was shown that the JG relaxation process can be used to determine structural relaxation times in the glassy state [R. Casalini and C. M. Roland, Phys. Rev. Lett. 102, 035701 (2009)]. In this paper we present the results of an analysis of the data obtained during aging using two independent approaches. The first was proposed by Casalini and Roland, and the second one is based on the variation of the dielectric strength of the secondary relaxation process during aging [J. K. Vij and G. Power, J. Non-Cryst. Solids 357, 783 (2011)]. Surprisingly, we found that the estimated structural relaxation times in the glassy state of both saccharides are almost the same, independent of the type of secondary mode. This finding calls into question the common view that secondary modes of intramolecular origin do not provide information about the dynamics of the glassy state.

  5. Griffith Saponite as an Analog for Clay Minerals at Yellowknife Bay in Gale Crater, Mars: A Marker for Low-temperature Hydrothermal Processes

    NASA Technical Reports Server (NTRS)

    Morris, R.V.; Treiman, A. H.; Agresti, D. G.; Graff, T. G.; Achilles, C. N.; Rampe, E. B.; Bristow, T. F.; Ming, D. W.; Blake, D. F.; Vaniman, D. T.; Bish, D. L.; Chipera, S. J.; Morrison, S. M.; Downs, R. T.

    2014-01-01

    The CheMin X-ray diffraction (XRD) instrument onboard the Mars Science Laboratory rover Curiosity in Gale Crater, Mars, discovered smectite in drill fines of the Sheepbed mudstone at Yellowknife Bay (YNB). The mudstone has a basaltic composition, and the XRD powder diffraction pattern shows smectite 02l diffraction bands peaking at 4.59 A for targets John Klein and Cumberland, consistent with tri-octahedral smectites (saponite). From thermal analysis, the saponite abundance is 20 wt. %. Among terrestrial analogues we have studied, ferrian saponite from Griffith Park (Los Angeles, CA) gives the best match to the position of the 02l diffraction band of YNB saponites. Here we describe iron-rich saponites from a terrestrial perspective, with a focus on Griffith saponite, and discuss their implications for the mineralogy of Sheepbed saponite and its formation pathways. Iron-rich saponite: Iron-rich saponite on the Earth is recognized as a low-temperature (<100 C), authigenic alteration product of basalt [e.g., 4-16]. In the discussion that follows, we reference the position of the 02l band because it is a measure of the unit cell 'b' dimension of the octahedral layer and thus the cations (including Fe redox state) in the octahedral layer. Ordinarily, the 06l band near 1.5 A is used to determine the 'b' dimension of smectite, but this band is not accessible with MSL CheMin instrument. For reference, a ferrosaponite (i.e., Fe2+ saponite) studied by [15] has a 02l spacing of 4.72 A and Fe3+/?Fe = 0.27 [15]. Samples of terrestrial ferrosaponite, however, are reported to oxidize on the timescale of days when removed from their natural environment and not protected from oxidation. The Griffith saponite is Mg-rich ferrian saponite, and sample AMNH 89172 has an 02l spacing of 4.59 A (same as the Sheepbed saponites) and Fe3+/?Fe = 0.64 [3]. This similarity suggests that Sheepbed saponites are ferrian (incompletely oxidized ferrosaponite). More oxidized Griffith saponites (Fe3

  6. Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes.

    PubMed

    Welch, K; Mousavi, S; Lundberg, B; Strømme, M

    2005-09-01

    A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes. PMID:16184321

  7. Viscoelastic characterization of compacted pharmaceutical excipient materials by analysis of frequency-dependent mechanical relaxation processes

    NASA Astrophysics Data System (ADS)

    Welch, K.; Mousavi, S.; Lundberg, B.; Strømme, M.

    2005-09-01

    A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes.

  8. Binary nucleation at low temperatures

    NASA Technical Reports Server (NTRS)

    Zahoransky, R. A.; Peters, F.

    1985-01-01

    The onset of homogeneous condensation of binary vapors in the supersaturated state is studied in ethanol/n-propanol and water/ethanol via their unsteady expansion in a shock tube at temperatures below 273 K. Ethanol/n-propanol forms a nearly ideal solution, whereas water/ethanol is an example of a strongly nonideal mixture. Vapor mixtures of various compositions are diluted in dry air at small mole fractions and expanded in the driver section from room temperature. The onset of homogeneous condensation is detected optically and the corresponding thermodynamic state is evaluated. The experimental results are compared with the binary nucleation theory, and the particular problems of theoretical evaluation at low temperatures are discussed.

  9. Dielectric characterization of collagen, elastin, and aortic valves in the low temperature range.

    PubMed

    Samouillan, V; Lamure, A; Maurel, E; Dandurand, J; Lacabanne, C; Spina, M

    2000-01-01

    The low temperature dielectric relaxation of porcine aortic valves and its main macromolecular proteins. i.e. elastin and collagen, have been investigated in the dry state and at low levels of hydration by thermally stimulated currents spectrometry, with an equivalent frequency of 10(-3) Hz. Two secondary relaxation modes, labeled gamma and beta with increasing temperature, are found for the three materials. Since the gamma-mode is independent upon hydration while the beta-mode is strongly plasticized by water, these relaxation modes have been attributed to localized motions of the polypeptidic chains containing apolar and polar residues, respectively. The deconvolution of the beta-mode by fractional polarization gives the experimental distribution of the dielectric relaxation times of the three materials, and allows us to deduce the activation parameters of each elementary process. These analyses shows the existence of compensation phenomena between the activation parameters, implying cooperative mechanisms. The occurrence of these phenomena with their characteristic parameters are used to specify the origin of the localized relaxation modes in collagen and elastin, and to assign the specific role of each protein in the aortic valves. PMID:10981675

  10. The use of the Wagner function to describe poled-order relaxation processes in electrooptic polymers

    NASA Astrophysics Data System (ADS)

    Verbiest, T.; Burland, D. M.

    1995-04-01

    The Wagner (lognormal) time decay function is used to describe decay of the second harmonic signal due to electric field poled-order relaxation in the guest—host polymer system 20 wt% lophine 1 in Ultem ®. This function can be related to a Gaussian distribution of Arrhenius activation energies. From the temperature dependence of the relaxation process one can determine the average value for the activation energy. In the present case a value of 40 kcal/mol is found consistent with experimental values obtained for a variety of other thermally activated processes in polymers.

  11. Theoretical description of slow non-monotonic relaxation processes in Al-Y melts

    NASA Astrophysics Data System (ADS)

    Vasin, M. G.; Menshikova, S. G.; Ivshin, M. D.

    2016-05-01

    The slow non-monotonic relaxation processes, which have been recently fixed in Al-Y melts, are described theoretically. The theoretical description is based on the Cahn-Hilliard theory and functional methods of non-equilibrium dynamics. In terms of the suggested approach the reasons of this relaxation kinetics are non-linearity of the system near to the liquidus line, which sharply increases with Y concentration, and strong initial heterogeneity of the melt on the concentration of Y atoms. According to our analysis one can conclude that the non-monotonic temporal dependence of viscosity is caused by the Ostwald ripening processes in the rich in yttrium areas.

  12. Ultrafast and low temperature synthesis of highly crystalline and patternable few-layers tungsten diselenide by laser irradiation assisted selenization process.

    PubMed

    Chen, Yu-Ze; Medina, Henry; Su, Teng-Yu; Li, Jian-Guang; Cheng, Kai-Yuan; Chiu, Po-Wen; Chueh, Yu-Lun

    2015-04-28

    Recently, a few attempts to synthesize monolayers of transition metal dichalcogenides (TMDs) using the chemical vapor deposition (CVD) process had been demonstrated. However, the development of alternative processes to synthesize TMDs is an important step because of the time-consuming, required transfer and low thermal efficiency of the CVD process. Here, we demonstrate a method to achieve few-layers WSe2 on an insulator via laser irradiation assisted selenization (LIAS) process directly, for which the amorphous WO3 film undergoes a reduction process in the presence of selenium gaseous vapors to form WSe2, utilizing laser annealing as a heating source. Detailed growth parameters such as laser power and laser irradiation time were investigated. In addition, microstructures, optical and electrical properties were investigated. Furthermore, a patternable WSe2 concept was demonstrated by patterning the WO3 film followed by the laser irradiation. By combining the patternable process, the transfer-free WSe2 back gate field effect transistor (FET) devices are realized on 300 nm-thick SiO2/P(+)Si substrate with extracted field effect mobility of ∼0.2 cm(2) V(-1) s(-1). Similarly, the reduction process by the laser irradiation can be also applied for the synthesis of other TMDs such as MoSe2 from other metal oxides such as MO3 film, suggesting that the process can be further extended to other TMDs. The method ensures one-step process to fabricate patternable TMDs, highlighting the uniqueness of the laser irradiation for the synthesis of different TMDs. PMID:25768931

  13. The Low Temperature Microgravity Physics Facility Project

    NASA Technical Reports Server (NTRS)

    Chui, T.; Holmes, W.; Lai, A.; Croonquist, A.; Eraker, J.; Abbott, R.; Mills, G.; Mohl, J.; Craig, J.; Balachandra, B.; Gannon, J.

    2000-01-01

    We describe the design and development of the Low Temperature Microgravity Physics Facility, which is intended to provide a unique environment of low temperature and microgravity for the scientists to perform breakthrough investigations on board the International Space Station.

  14. The Low Temperature Microgravity Physics Facility

    NASA Technical Reports Server (NTRS)

    Pensinger, J. F.; Chui, T.; Croonquist, A.; Larson, M.; Liu, F.

    2002-01-01

    The Low Temperature Microgravity Physics Facility currently in the design phase is a multiple user and multiple flight facility intended to provide a long duration low temperature environment onboard the International Space Station.

  15. The low temperature microgravity physics facility

    NASA Technical Reports Server (NTRS)

    Pensinger, J. F.; Croonquist, A P.; Liu, F. C.; Larson, M. E.; Chui, T. C.

    2002-01-01

    The Low Temperature Microgravity Physics Facility currently in the design phase is a multiple user and multiple flight facility intended to provide a long duration low temperature environment onboard the International Space Station.

  16. Overview of low temperature sensitization

    SciTech Connect

    Fox, M.J.; McCright, R.D.

    1983-12-01

    A review of the literature on low temperature sensitization (LTS) has been conducted to determine if LTS-related microstructural changes can occur in Type 304L stainless steel within the times and temperatures associated with nuclear waste storage. It was found that Type 304L stainless steel is susceptible to sensitization and LTS, and that cold work plays an important role in determining the rate of LTS. Severely cold worked Type 304L stainless steel would clearly develop LTS-related microstructural changes within the times and temperatures associated with nuclear waste storage. These changes could lead to increased susceptibility to corrosion. Significant improvements in the long-term resistance to sensitization, LTS and corrosion can be achieved by modest changes in alloy composition and fabrication practices. Therefore, Type 304L would not be the preferred alloy of construction for nuclear waste storage canisters. The final qualification of an alternate canister alloy should involve corrosion experiments on actual canisters. Suggestions for alternate canister alloys are 316L, 316LN, 316ELC, 347, and XM-19. 47 references, 4 figures.

  17. General theory of intraband relaxation processes in heavily doped graphene

    NASA Astrophysics Data System (ADS)

    Kupčić, I.

    2015-05-01

    The frequency and wave-vector-dependent memory function in the longitudinal conductivity tensor of weakly interacting electronic systems is calculated by using an approach based on quantum transport equations. In this paper, we show that there is a close relation between the single-electron self-energy, the electron-hole pair self-energy, and the memory function. It is also shown in which way singular long-range Coulomb interactions, together with other q ≈0 scattering processes, drop out of both the memory function and the related transport equations. The theory is illustrated on heavily doped graphene, which is the prototype of weakly interacting single-band electron-phonon systems. A steplike increase of the width of the quasiparticle peak in angle-resolved photoemission spectra at frequencies of the order of the frequency of in-plane optical phonons is shown to be consistent with the behavior of an intraband plasmon peak in the energy loss spectroscopy spectra. Both anomalies can be understood as a direct consequence of weak electron scattering from in-plane optical phonons.

  18. Relaxation processes in a lower disorder order transition diblock copolymer

    SciTech Connect

    Sanz, Alejandro; Ezquerra, Tiberio A.; Nogales, Aurora

    2015-02-14

    The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition T{sub ODT}, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.

  19. Modeling lithosphere hydration processes at slow spreading ridges: What are the parameters controlling the formation of low temperature ultramafic hydrothermal vents?

    NASA Astrophysics Data System (ADS)

    Gouze, P.; Lods, G.; Godard, M.; Andreani, M.

    2008-12-01

    The numerous ultramafic-hosted hydrothermal systems discovered during the last ten years emphasized the importance of peridotite alteration (serpentinization) as means of chemical exchange between the mantle and the ocean at slow- and ultra-slow spreading ridges. Hydration of the cooling ultramafic lithosphere results from the thermal retraction of the poly-mineral mantle assemblage and/or faulting of stretched lithosphere; it induces in return strong changes in the permeability field. A better understanding of this highly complex system is essential for constraining mass and energy transfers at ridge axis. In order to characterize the roles of these various parameters as well as their feedback effects and to explore different hydro-geothermal initial and boundary conditions, we carried out a series of a two-dimensional flow/reaction simulations. In the model, thermal convection flow is coupled with serpentinization, which is described by the thermo- kinetic-controlled reaction of the hydration of olivine and orthopyroxene (assumed to be pure pure forsterite and enstatite respectively). The changes in porosity and permeability associated with (i) thermal retraction of the solid while cooling and (ii) serpentinization processes are computed including energy production and water consumption during reaction. These highly coupled processes generate a non-linear evolution of the flow regimes, inducing (transient) focalized fluid outputs (events) triggered by the thermal convection. The comparison between the results of numerical simulations and field observations (distribution of the events, outlet fluid composition and distribution of the serpentine at depth) is used to discuss the model parameters and determine which ones control the hydrodynamic processes in natural hydrothermal systems.

  20. Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor.

    PubMed

    Nguyen, Manh-Cuong; Jang, Mi; Lee, Dong-Hwi; Bang, Hyun-Jun; Lee, Minjung; Jeong, Jae Kyeong; Yang, Hoichang; Choi, Rino

    2016-01-01

    Lithium (Li)-assisted indium oxide (In2O3) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO2) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO2 dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li(+)]/([In(3+)] + [Li(+)]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In2O3 nanostructures after thermal dehydration and oxidation. Finally, an In2O3 film doped with 13.5 mol% Li(+) and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm(2) V(-1) s(-1) and an on/off current ratio above 10(8) when utilized in a thin film transistor. PMID:27121951

  1. Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor

    PubMed Central

    Nguyen, Manh-Cuong; Jang, Mi; Lee, Dong-Hwi; Bang, Hyun-Jun; Lee, Minjung; Jeong, Jae Kyeong; Yang, Hoichang; Choi, Rino

    2016-01-01

    Lithium (Li)-assisted indium oxide (In2O3) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO2) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO2 dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li+]/([In3+] + [Li+]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In2O3 nanostructures after thermal dehydration and oxidation. Finally, an In2O3 film doped with 13.5 mol% Li+ and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm2 V−1 s−1 and an on/off current ratio above 108 when utilized in a thin film transistor. PMID:27121951

  2. Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions

    PubMed Central

    2014-01-01

    In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

  3. Low-Temperature Crystallization of PbZr0.3Ti0.7O3 Film Induced by High-Oxygen-Pressure Processing

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodong; Meng, Xiangjian; Sun, Jinglan; Lin, Tie; Ma, Jianhua; Chu, Junhao; Dho, Joonghoe

    2008-09-01

    A 300-nm-thick PbZr0.3Ti0.7O3 [PZT(30/70)] film was sputtered onto LaNiO3 (LNO)/Si(100) substrates at a substrate temperature of 200 °C and then annealed under an oxygen pressure of 4 MPa at 400 °C. The amorphous phase of the as-sputtered PZT(30/70) film was transformed to a highly (h00)-oriented perovskite phase by high-oxygen-pressure-processing (HOPP). The results of electrical measurements such as of polarization (P) as functions of applied electric field (E) (P-E hysteresis loops), the capacitance as functions of the applied dc electric field (C-E loops), and the dielectric constant (ɛr) and dissipation factor (tan δ) suggested that ferroelectric properties of PZT(30/70) films were largely improved by HOPP. We consider that HOPP is compatible with currently existing silicon-based technology, which is characterized by incorporating sputtering and a processing temperature limit of ˜450 °C. The P-E hyteresis loops obtained from a prototype of 128 ×128 uncooled infrared detector arrays prepared by HOPP supported the good ferroelectricity with a high pyroelectric coefficient.

  4. New insight into the promoting role of process on the CeO₂-WO₃/TiO₂ catalyst for NO reduction with NH₃ at low-temperature.

    PubMed

    Zhang, Shule; Zhong, Qin; Shen, Yuge; Zhu, Li; Ding, Jie

    2015-06-15

    This study aimed at investigating the reason of high catalytic activity for CeO2-WO3/TiO2 catalyst from the aspects of WO3 interaction with other species and the NO oxidation process. Analysis by X-ray diffractometry, photoluminescence spectra, diffuse reflectance UV-visible, X-ray photoelectron spectroscopy, density functional theory calculations, electron paramagnetic resonance spectroscopy, temperature-programmed-desorption of NO and in situ diffuse reflectance infrared transform spectroscopy showed that WO3 could interact with CeO2 to improve the electron gaining capability of CeO2 species. In addition, WO3 species acted as electron donating groups to transfer the electrons to CeO2 species. The two aspects enhanced the formation of reduced CeO2 species to improve the formation of superoxide ions. Furthermore, the Ce species were the active sites for the NO adsorption and the superoxide ions over the catalyst needed oxidizing the adsorbed NO to improve the NO oxidation. This process was responsible for the high catalytic activity of CeO2-WO3/TiO2 catalyst. PMID:25746195

  5. Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions.

    PubMed

    Chen, Chong; Li, Chunxi; Li, Fumin; Wu, Fan; Tan, Furui; Zhai, Yong; Zhang, Weifeng

    2014-01-01

    In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2(n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%. PMID:25278818

  6. Efficient perovskite solar cells based on low-temperature solution-processed (CH3NH3)PbI3 perovskite/CuInS2 planar heterojunctions

    NASA Astrophysics Data System (ADS)

    Chen, Chong; Li, Chunxi; Li, Fumin; Wu, Fan; Tan, Furui; Zhai, Yong; Zhang, Weifeng

    2014-09-01

    In this work, the solution-processed CH3NH3PbI3 perovskite/copper indium disulfide (CuInS2) planar heterojunction solar cells with Al2O3 as a scaffold were fabricated at a temperature as low as 250°C for the first time, in which the indium tin oxide (ITO)-coated glass instead of the fluorine-doped tin oxide (FTO)-coated glass was used as the light-incidence electrode and the solution-processed CuInS2 layer was prepared to replace the commonly used TiO2 layer in previously reported perovskite-based solar cells. The influence of the thickness of the as-prepared CuInS2 film on the performance of the ITO/CuInS2( n)/Al2O3/(CH3NH3)PbI3/Ag cells was investigated. The ITO/CuInS2(2)/Al2O3/(CH3NH3)PbI3/Ag cell showed the best performance and achieved power conversion efficiency up to 5.30%.

  7. Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor

    NASA Astrophysics Data System (ADS)

    Nguyen, Manh-Cuong; Jang, Mi; Lee, Dong-Hwi; Bang, Hyun-Jun; Lee, Minjung; Jeong, Jae Kyeong; Yang, Hoichang; Choi, Rino

    2016-04-01

    Lithium (Li)-assisted indium oxide (In2O3) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO2) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO2 dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li+]/([In3+] + [Li+]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In2O3 nanostructures after thermal dehydration and oxidation. Finally, an In2O3 film doped with 13.5 mol% Li+ and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm2 V‑1 s‑1 and an on/off current ratio above 108 when utilized in a thin film transistor.

  8. Low Temperature Decomposition Rates for Tetraphenylborate Ion

    SciTech Connect

    Walker, D.D.

    1998-11-18

    Previous studies indicated that palladium is catalyzes rapid decomposition of alkaline tetraphenylborate slurries. Additional evidence suggest that Pd(II) reduces to Pd(0) during catalyst activation. Further use of tetraphenylborate ion in the decontamination of radioactive waste may require removal of the catalyst or cooling to temperatures at which the decomposition reaction proceeds slowly and does not adversely affect processing. Recent tests showed that tetraphenylborate did not react appreciably at 25 degrees Celsius over six months suggesting the potential to avoid the decomposition at low temperatures. The lack of reaction at low temperature could reflect very slow kinetics at the lower temperature, or may indicate a catalyst ''deactivation'' process. Previous tests in the temperature range 35 to 70 degrees Celsius provided a low precision estimate of the activation energy of the reaction with which to predict the rate of reaction at 25 percent Celsius. To understand the observations at 25 degrees Celsius, experiments must separate the catalyst activation step and the subsequent reaction with TPB. Tests described in this report represent an initial attempt to separate the two steps and determine the rate and activation energy of the reaction between active catalyst and TPB. The results of these tests indicate that the absence of reaction at 25 degrees Celsius was caused by failure to activate the catalyst or the presence of a deactivating mechanism. In the presence of activated catalyst, the decomposition reaction rate is significant.

  9. Low Temperature Reflectance Spectra of Titan Tholins

    NASA Technical Reports Server (NTRS)

    Roush, T. L.; Dalton, J. B.; Fonda, Mark (Technical Monitor)

    2001-01-01

    Compositional interpretation of remotely obtained reflectance spectra of outer solar system surfaces is achieved by a variety of methods. These include matching spectral curves, matching spectral features, quantitative spectral interpretation, and theoretical modeling of spectra. All of these approaches rely upon laboratory measurements of one kind or another. The bulk of these laboratory measurements are obtained with the sample of interest at ambient temperatures and pressures. However, surface temperatures of planets, satellites, and asteroids in the outer solar system are significantly cooler than ambient laboratory conditions on Earth. The infrared spectra of many materials change as a function of temperature. As has been recently demonstrated it is important to assess what effects colder temperatures have on spectral properties and hence, compositional interpretations. Titan tholin is a solid residue created by energetic processing of H-, C-, and N-bearing gases. Such residues can also be created by energetic processing if the gases are condensed into ices. Titan tholin has been suggested as a coloring agent for several surfaces in the outer solar system. Here we report laboratory measurements of Titan tholin at a temperature of 100 K and compare these to measurements of the same sample near room temperature. At low temperature the absorption features beyond 1 micrometer narrow slightly. At wavelengths greater than approx. 0.8 micrometer the overall reflectance of the sample decreases slightly making the sample less red at low temperatures. We will discuss the implications of the laboratory measurements for interpretation of cold outer solar system surfaces.

  10. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    SciTech Connect

    Harlan U. Anderson

    2000-03-31

    This project has three main goals: Thin Films Studies, Preparation of Graded Porous Substrates and Basic Electrical Characterization and Testing of Planar Single Cells. During this time period substantial progress has been made in developing low temperature deposition techniques to produce dense, nanocrystalline yttrium-stabilized zirconia films on both dense oxide and polymer substrates. Progress has been made in the preparation and characterization of thin electrolytes and porous LSM substrates. Both of these tasks are essentially on or ahead of schedule. In our proposal, we suggested that the ZrO{sub 2}/Sc system needed to be considered as a candidate as a thin electrolyte. This was because microcrystalline ZrO{sub 2}/Sc has a significantly higher ionic conductivity than YSZ, particularly at the lower temperatures. As a result, some 0.5 micron thick film of ZrO{sub 2}/16% Sc on an alumina substrate (grain size 20nm) was prepared and the electrical conductivity measured as a function of temperature and oxygen activity. The Sc doped ZrO{sub 2} certainly has a higher conductivity that either 20nm or 2400nm YSZ, however, electronic conductivity dominates the conductivity for oxygen activities below 10{sup -15}. Whereas for YSZ, electronic conductivity is not a problem until the oxygen activity decreases below 10{sup -25}. These initial results show that the ionic conductivity of 20nm YSZ and 20nm ZrO{sub 2}/16% Sc are essentially the same and the enhanced conductivity which is observed for Sc doping in microcrystalline specimens is not observed for the same composition when it is nanocrystalline. In addition they show that the electronic conductivity of Sc doped ZrO{sub 2} is at least two orders of magnitude higher than that observed for YSZ. The conclusion one reaches is that for 0.5 to 1 micron thick nanocrystalline films, Sc doping of ZrO{sub 2} has no benefits compared to YSZ. As a result, electrolyte films of ZrO{sub 2}/Sc should not be considered as candidates

  11. Low-temperature spectroscopy of bacteriochlorophyll c aggregates.

    PubMed

    Paleček, David; Dědic, Roman; Alster, Jan; Hála, Jan

    2014-03-01

    Chlorosomes from green photosynthetic bacteria belong to the most effective light-harvesting antennas found in nature. Quinones incorporated in bacterichlorophyll (BChl) c aggregates inside chlorosomes play an important redox-dependent photo-protection role against oxidative damage of bacterial reaction centers. Artificial BChl c aggregates with and without quinones were prepared. We applied hole-burning spectroscopy and steady-state absorption and emission techniques at 1.9 K and two different redox potentials to investigate the role of quinones and redox potential on BChl c aggregates at low temperatures. We show that quinones quench the excitation energy in a similar manner as at room temperature, yet the quenching process is not as efficient as for chlorosomes. Interestingly, our data suggest that excitation quenching partially proceeds from higher excitonic states competing with ultrafast exciton relaxation. Moreover, we obtained structure-related parameters such as reorganization energies and inhomogeneous broadening of the lowest excited state, providing experimental ground for theoretical studies aiming at designing plausible large-scale model for BChl c aggregates including disorder. PMID:24318566

  12. Site-Resolved Two-Step Relaxation Process in an Asymmetric Dy2 Single-Molecule Magnet.

    PubMed

    Zhang, Li; Jung, Julie; Zhang, Peng; Guo, Mei; Zhao, Lang; Tang, Jinkui; Le Guennic, Boris

    2016-01-22

    Elaborate chemical design is of utmost importance in order to slow down the relaxation dynamics in single-molecule magnets (SMMs) and hence improve their potential applications. Much interest was devoted to the study of distinct relaxation processes related to the different crystal fields of crystallographically independent lanthanide ions. However, the assignment of the relaxation processes to specific metal sites remains a challenging task. To address this challenge, a new asymmetric Dy2 SMM displaying a well-separated two-step relaxation process with the anisotropic centers in fine-tuned local environments was elaborately designed. For the first time a one-to-one relationship between the metal sites and the relaxation processes was evidenced. This work sheds light on complex multiple relaxation and may direct the rational design of lanthanide SMMs with enhanced magnetic properties. PMID:26670125

  13. Fast and low-temperature sintering of silver complex using oximes as a potential reducing agent for solution-processible, highly conductive electrodes

    NASA Astrophysics Data System (ADS)

    Yoo, Ji Hoon; Han, Dae Sang; Park, Su Bin; Chae, Jangwoo; Kim, Ji Man; Kwak, Jeonghun

    2014-11-01

    Highly conductive, solution-processed silver thin-films were obtained at a low sintering temperature of 100 °C in a short sintering time of 10 min by introducing oximes as a potential reductant for silver complex. The thermal properties and reducibility of three kinds of oximes, acetone oxime, 2-butanone oxime, and one dimethylglyoxime, were investigated as a reducing agent, and we found that the thermal decomposition product of oximes (ketones) accelerated the conversion of silver complex into highly conductive silver at low sintering temperature in a short time. Using the acetone oxime, the silver thin-film exhibited the lowest surface resistance (0.91 Ω sq-1) compared to those sing other oximes. The silver thin-film also showed a high reflectance of 97.8%, which is comparable to evaporated silver films. We also demonstrated inkjet printed silver patterns with the oxime-added silver complex inks.

  14. Low-temperature preparation of highly (100)-oriented Pb(ZrxTi1-x)O3 thin film by high oxygen-pressure processing

    NASA Astrophysics Data System (ADS)

    Zhang, X. D.; Meng, X. J.; Sun, J. L.; Lin, T.; Chu, J. H.

    2005-06-01

    A method for thin-film fabrication employing high oxygen-pressure processing (HOPP) was developed. With this method, the highly (100) oriented Pb(ZrxTi1-x)O3 (PZT) thin film was fabricated at temperature as low as 400°C. HOPP is compatible to the ferroelectric PZT film integration with a readout integrated circuit. The sol-gel-derived PZT 50/50 thin film showed a well-saturated hysteresis loop at an applied electric field of 367kV /cm with Pr and Ec of 45μC/cm2 and 121kV/cm, respectively. Large electric leakage was attributed to remnant organic components, which was demonstrated by sputtered organic-free PZT films. The optimized Pr and Ec are of 26μC/cm2 and 93kV/cm under an applied electric field of 400kV/cm.

  15. Luminescence processes in (Tb contains bpy x bpy x bpy)/sup 3 +/ cryptate: a low-temperature solid-state study

    SciTech Connect

    Blasse, G.; Dirksen, G.J.; Sabbatini, N.; Perathoner, S.; Lehn, J.M.; Alpha, B.

    1988-05-05

    The luminescence properties of solid (Tb contains bpy x bpy x bpy)/sup 3 +/, (La contains bpy x bpy x bpy)/sup 3 +/, and (Na contains bpy x bpy x bpy)/sup +/ are reported for temperature down to 4.2 K. The 2,2'-bipyridine phosphorescence in the case of the La/sup 3 +/ and Na/sup +/ cryptate is quenched by energy migration to killers. In the case of Tb/sup 3 +/, however, efficient energy transfer from the cryptand to Tb/sup 3 +/ takes place up till 100 K. At that temperature migration competes with energy transfer to Tb/sup 3 +/, reducing the Tb/sup 3 +/ luminescence output. The rates of the processes involved are determined as accurately as possible. A comparison is made with the same cryptate molecules in solution.

  16. Magnetometer probe with low temperature rotation and optical fibers

    NASA Astrophysics Data System (ADS)

    Pajerowski, D. M.; Meisel, M. W.

    2009-02-01

    A new probe has been developed that allows for both optical irradiation and uniaxial rotation, all in the low temperature environment of a commercial superconducting quantum interference device (SQUID) magnetometer. As part of the design process, various materials were investigated and characterized for their low temperature structural and magnetic properties, including nylon, Vespel, Delrin, Spiderwire monofilament, and PowerPro braided microfilament. Using this information, a prototype was built and operated. Characteristics of the probe will be presented along with a summary of the low temperature (T >= 2 K) and high magnetic field (H <= 7 T) properties of the construction materials.

  17. β-NaVOPO4 obtained by a low-temperature synthesis process: A new 3.3 V cathode for sodium-ion batteries

    DOE PAGESBeta

    He, Guang; Huq, Ashfia; Manthiram, Arumugam; Kan, Wang Hay

    2016-02-02

    Vanadyl phosphates (VOPO4) represent a class of attractive cathodes in lithium-ion batteries. However, the exploration of this type of materials in sodium-ion batteries is rare. Here, we report for the first time the synthesis of orthorhombic β-NaVOPO4 by first chemically extracting lithium from beta-LiVOPO4 and then inserting sodium into the obtained β-VOPO4 by a microwave-assisted solvothermal process with NaI, which serves both as a reducing agent and sodium source. Intermediate NaxVOPO4 compositions with x = 0.3, 0.5, and 0.8 have also been obtained by controlling the amount of NaI in the reaction mixture. Joint Rietveld refinement of synchrotron X-ray diffractionmore » (XRD) and neutron diffraction confirms that the fully sodiated β-NaVOPO4 is isostructural with the lithium counterpart β-LiVOPO4. Bond valence sum maps suggest that sodium ions possibly diffuse along the [010] direction in the lattice, similar to the ionic conduction pathway in β-LiVOPO4. Although the initial discharge capacity is low due to the protons in the structure, it steadily increases with cycling with a long plateau at 3.3 V. As a result, ex situ XRD data of cycled β-VOPO4 and β-NaVOPO4 electrodes confirm the reversible reaction in sodium cells involving the V4+/V5+ redox couple.« less

  18. Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by sol-gel process

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1990-01-01

    Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water:TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, x ray diffraction, surface area and pore size distribution measurements.

  19. Low temperature synthesis of CaO-SiO2 glasses having stable liquid-liquid immiscibility by the sol-gel process

    NASA Technical Reports Server (NTRS)

    Bansal, N. P.

    1992-01-01

    Calcium silicate glass compositions lying within the liquid-liquid immiscibility dome of the phase diagram, which could not have been prepared by the conventional melting method, were synthesized by the sol-gel process. Hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS) solutions containing up to 20 mol percent calcium nitrate resulted in the formation of clear and transparent gels. The gel formation time decreased with increase in water: TEOS mole ratio, calcium content, and the reaction temperature. Smaller values of gel times in the presence of calcium nitrate are probably caused by lowering of the ionic charge on the sol particles by the salt present. The gelation activation energy, E(sub gel), was evaluated from temperature dependence of the gel time. Presence of Ca(2+) ions or the water:TEOS mole ratio did not have an appreciable effect on the value of E(sub gel). Presence of glycerol in the solution helped in the formation of crack-free monolithic gel specimens. Chemical and structural changes occurring in the gels, as a function of the heat treatments, have been monitored using DTA, TGA, IR-spectroscopy, X-ray diffraction, surface area and pore size distribution measurements.

  20. Analysis of Schottky Contact Formation in Coplanar Au/ZnO/Al Nanogap Radio Frequency Diodes Processed from Solution at Low Temperature.

    PubMed

    Semple, James; Rossbauer, Stephan; Anthopoulos, Thomas D

    2016-09-01

    Much work has been carried out in recent years in fabricating and studying the Schottky contact formed between various metals and the n-type wide bandgap semiconductor zinc oxide (ZnO). In spite of significant progress, reliable formation of such technologically interesting contacts remains a challenge. Here, we report on solution-processed ZnO Schottky diodes based on a coplanar Al/ZnO/Au nanogap architecture and study the nature of the rectifying contact formed at the ZnO/Au interface. Resultant diodes exhibit excellent operating characteristics, including low-operating voltages (±2.5 V) and exceptionally high current rectification ratios of >10(6) that can be independently tuned via scaling of the nanogap's width. The barrier height for electron injection responsible for the rectifying behavior is studied using current-voltage-temperature and capacitance-voltage measurements (C-V) yielding values in the range of 0.54-0.89 eV. C-V measurements also show that electron traps present at the Au/ZnO interface appear to become less significant at higher frequencies, hence making the diodes particularly attractive for high-frequency applications. Finally, an alternative method for calculating the Richardson constant is presented yielding a value of 38.9 A cm(-2) K(-2), which is close to the theoretically predicted value of 32 A cm(-2) K(-2). The implications of the obtained results for the use of these coplanar Schottky diodes in radio frequency applications is discussed. PMID:27530144

  1. Sorption enhanced reaction process for direct production of fuel-cell grade hydrogen by low temperature catalytic steam-methane reforming

    NASA Astrophysics Data System (ADS)

    Beaver, Michael G.; Caram, Hugo S.; Sircar, Shivaji

    New experimental data are reported to demonstrate that a sorption enhanced reaction (SER) concept can be used to directly produce fuel-cell grade H 2 (<20 ppm CO) by carrying out the catalytic, endothermic, steam-methane reforming (SMR) reaction (CH 4 + 2H 2O ↔ CO 2 + 4H 2) in presence of a CO 2 selective chemisorbent such as K 2CO 3 promoted hydrotalcite at reaction temperatures of 520 and 550 °C, which are substantially lower than the conventional SMR reaction temperatures of 700-800 °C. The H 2 productivity of the sorption enhanced reactor can be large, and the conversion of CH 4 to H 2 can be very high circumventing the thermodynamic limitations of the SMR reaction due to the application of the Le Chetalier's principle in the SER concept. Mathematical simulations of a cyclic two-step SER concept showed that the H 2 productivity of the process (moles of essentially pure H 2 produced per kg of catalyst-chemisorbent admixture in the reactor per cycle) is much higher at a reaction temperature of 590 °C than that at 550 or 520 °C. On the other hand, the conversion of feed CH 4 to high purity H 2 product is relatively high (>99+%) at all three temperatures. The conversion is much higher than that in a conventional catalyst-alone reactor at these temperatures, and it increases only moderately (<1%) as the reaction temperature is increased from 520 to 590 °C. These results are caused by complex interactions of four phenomena. They are (a) favorable thermodynamic equilibrium of the highly endothermic SMR reaction at the higher reaction temperature, (b) faster kinetics of SMR reaction at higher temperatures, (c) favorable removal of CO 2 from the reaction zone at lower temperatures, and (d) higher cyclic working capacity for CO 2 chemisorption at higher temperature.

  2. Ta{sub 2}O{sub 5}-based high-K dielectric thin films from solution processed at low temperatures

    SciTech Connect

    Frunză, Raluca C.; Kmet, Brigita; Jankovec, Marko; Topič, Marko; Malič, Barbara

    2014-02-01

    Highlights: • Ta{sub 2}O{sub 5}–Al{sub 2}O{sub 3}–SiO{sub 2} (Ta:Al:Si = 8:1:1 atomic ratio) and Ta{sub 2}O{sub 5} films were processed from solutions. • The XRD-amorphous films, heated at or below 400 °C, are smooth (RMS < 0.5 nm). • The dielectric permittivity of the single- and mixed-oxide films heated at 400 °C is 27 and 22, respectively. • The current–voltage characteristics of the mixed-oxide films reveal the Poole–Frenkel behaviour. - Abstract: Ta{sub 2}O{sub 5}-based thin films were prepared by chemical solution deposition at temperatures not exceeding 400 °C. The aim of the work was to investigate the properties of high-K dielectric films of the ternary composition Ta{sub 2}O{sub 5}–Al{sub 2}O{sub 3}–SiO{sub 2} with the Ta:Al:Si = 8:1:1 atomic ratio. Pure Ta{sub 2}O{sub 5} samples were also prepared. All thin films were amorphous, and had smooth and flat surfaces with the average roughness of below 0.5 nm. The mixed oxide samples heated between 300 °C and 400 °C showed little difference in the dielectric permittivity with the values ranging from about 19 to 22. The Ta{sub 2}O{sub 5} film heated at 400 °C exhibited the highest permittivity of about 27. The current–voltage measurements revealed considerably improved characteristics of the Ta{sub 2}O{sub 5}–Al{sub 2}O{sub 3}–SiO{sub 2} samples within the investigated heating temperature range, with a significant overall decrease of the leakage currents in contrast to that of the pure Ta{sub 2}O{sub 5} thin films.

  3. Numerical methods for TVD transport and coupled relaxing processes in gases and plasmas

    NASA Technical Reports Server (NTRS)

    Cambier, Jean-Luc

    1990-01-01

    The construction of second-order upwind schemes for nonequilibrium plasmas, for both one- and two-fluid formulations is demonstrated. Coupled relaxation processes, including ionization kinetics and radiative processes and their algorithms for nonequilibrium, multiple temperature conditions are described as well. The paper applies the numerical techniques on some simple test cases, points out critical problems and their solutions, and makes qualitative comparisons with known results, whenever possible.

  4. Coal desulfurization by low-temperature chlorinolysis

    NASA Technical Reports Server (NTRS)

    Hsu, G. C.; Kalvinskas, J. J.; Ganguli, P. S.; Gavalas, G. R.

    1977-01-01

    Among the three principal methods for precombustion desulfurization of coal, which include physical depyriting, chemical desulfurization, and coal conversion to low-sulfur liquid and gaseous fuels, the potential of chemical methods looks promising in terms of both total sulfur removal and processing cost. The principal chemical methods for coal desulfurization involve treatment with either oxidizing agents or basic media at elevated temperature and pressure. A description is given of some recent experimental results which show the feasibility of removing sulfur, particularly organic sulfur, from high-sulfur coals by a simple method of low-temperature chlorinolysis followed by hydrolysis and dechlorination. The chemical feasibility of sulfur removal by chlorinolysis rather than the detailed engineering process is emphasized.

  5. Low Temperature Flow of PVC Chains

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Xue, Gi

    2011-03-01

    PVC is usually processed at temperature above 180& circ; C, however, it starts to degrade at 130& circ; C. If PVC can flow at temperatures below glass transition temperature (Tg), the manufacturing procedure will be energy-conserving and environment-friendly. We find that PVC powders with controlled inter-segment van der Waals attraction can be compressed into a transparent pellet with high modulus at low temperatures. The molecular mechanism underlying this phenomenon involves shear-induced unjamming transition. PVC chains are unjammed by cold-pressing freeze-dried powder with decreased packing density. Because the Tg of freeze-dried PVC is dramatically reduced to the test temperatures under compression, PVC chains are able to flow by applying pressure solely. These results help us better understanding glass transition and can possible to develop a theory for cold processes.

  6. Potato Processing from Low Temperature Storage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Everyone who grows or stores potatoes for chips or fries knows how challenging it is to deliver tubers that consistently produce light-colored fried products that meet processor and consumer expectations. Many factors contribute to dark color formation, including heat and water stress during tuber d...

  7. RECYCLING NICKEL ELECTROPLATING RINSE WATERS BY LOW TEMPERATURE EVAPORATION AND REVERSE OSMOSIS

    EPA Science Inventory

    Low temperature evaporation and reverse osmosis systems were each evaluated (on a pilot scale) on their respective ability to process rinse water collected from a nickel electroplating operation. ach system offered advantages under specific operating conditions. he low temperatur...

  8. Study of relaxation and transport processes by means of AFM based dielectric spectroscopy

    SciTech Connect

    Miccio, Luis A.

    2014-05-15

    Since its birth a few years ago, dielectric spectroscopy studies based on atomic force microscopy (AFM) have gained a growing interest. Not only the frequency and temperature ranges have become broader since then but also the kind of processes that can be studied by means of this approach. In this work we analyze the most adequate experimental setup for the study of several dielectric processes with a spatial resolution of a few nanometers by using force mode AFM based dielectric spectroscopy. Proof of concept experiments were performed on PS/PVAc blends and PMMA homopolymer films, for temperatures ranging from 300 to 400 K. Charge transport processes were also studied by this approach. The obtained results were analyzed in terms of cantilever stray contribution, film thickness and relaxation strength. We found that the method sensitivity is strongly coupled with the film thickness and the relaxation strength, and that it is possible to control it by using an adequate experimental setup.

  9. Relaxation times of the two-phonon processes with spin-flip and spin-conserving in quantum dots

    SciTech Connect

    Wang, Zi-Wu; Liu, Lei; Li, Shu-Shen

    2014-04-07

    We perform a theoretical investigation on the two-phonon processes of the spin-flip and spin-conserving relaxation in quantum dots in the frame of the Huang-Rhys' lattice relaxation model. We find that the relaxation time of the spin-flip is two orders of magnitude longer than that of the spin-conserving, which is in agreement with previous experimental measurements. Moreover, the opposite variational trends of the relaxation time as a function of the energy separation for two-phonon processes are obtained in different temperature regime. The relaxation times display the oscillatory behaviors at the demarcation point with increasing magnetic field, where the energy separation matches the optical phonon energy and results in the optical phonon resonance. These results are useful in understanding the intraband levels' relaxation in quantum dots and could be helpful in designing photoelectric and spin-memory devices.

  10. Low Temperature Detectors: Principles and Applications

    SciTech Connect

    Hilton, G. C.

    2009-12-16

    Despite the added cost and complexity of operating at sub-Kelvin temperatures, there are many measurement applications where the sensitivity and precision provided by low temperature detectors greatly outweigh any disadvantages. As a result, low temperature detectors are now finding wide application for measurements ranging from cosmology to homeland defense. In this tutorial I will introduce the basic operating principles and fundamental performance limits of several types of low temperature detectors.

  11. Final Report: Wetted Cathodes for Low-Temperature Aluminum Smelting

    SciTech Connect

    Brown, Craig W

    2002-09-30

    A low-temperature aluminum smelting process being developed differs from the Hall-Heroult process in several significant ways. The low-temperature process employs a more acidic electrolyte than cryolite, an alumina slurry, oxygen-generating metal anodes, and vertically suspended electrodes. Wetted and drained vertical cathodes are crucial to the new process. Such cathodes represent a significant portion of the capital costs projected for the new technology. Although studies exist of wetted cathode technology with Hall-Heoult cells, the differences make such a study desirable with the new process.

  12. Low temperature CVD growth of ultrathin carbon films

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Wu, Peng; Gan, Wei; Habib, Muhammad; Xu, Weiyu; Fang, Qi; Song, Li

    2016-05-01

    We demonstrate the low temperature, large area growth of ultrathin carbon films by chemical vapor deposition under atmospheric pressure on various substrates. In particularly, uniform and continuous carbon films with the thickness of 2-5 nm were successfully grown at a temperature as low as 500 oC on copper foils, as well as glass substrates coated with a 100 nm thick copper layer. The characterizations revealed that the low-temperature-grown carbon films consist on few short, curved graphene layers and thin amorphous carbon films. Particularly, the low-temperature grown samples exhibited over 90% transmittance at a wavelength range of 400-750 nm and comparable sheet resistance in contrast with the 1000oC-grown one. This low-temperature growth method may offer a facile way to directly prepare visible ultrathin carbon films on various substrate surfaces that are compatible with temperatures (500-600oC) used in several device processing technologies.

  13. Anomalous C-V response correlated to relaxation processes in TiO2 thin film based-metal-insulator-metal capacitor: Effect of titanium and oxygen defects

    NASA Astrophysics Data System (ADS)

    Kahouli, A.; Marichy, C.; Sylvestre, A.; Pinna, N.

    2015-04-01

    Capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements are performed on atomic layer deposited TiO2 thin films with top and bottom Au and Pt electrodes, respectively, over a large temperature and frequency range. A sharp capacitance peak/discontinuity (C-V anomalous) is observed in the C-V characteristics at various temperatures and voltages. It is demonstrated that this phenomenon is directly associated with oxygen vacancies. The C-V peak irreversibility and dissymmetry at the reversal dc voltage are attributed to difference between the Schottky contacts at the metal/TiO2 interfaces. Dielectric analyses reveal two relaxation processes with degeneration of the activation energy. The low trap level of 0.60-0.65 eV is associated with the first ionized oxygen vacancy at low temperature, while the deep trap level of 1.05 eV is associated to the second ionized oxygen vacancy at high temperature. The DC conductivity of the films exhibits a transition temperature at 200 °C, suggesting a transition from a conduction regime governed by ionized oxygen vacancies to one governed by interstitial Ti3+ ions. Both the C-V anomalous and relaxation processes in TiO2 arise from oxygen vacancies, while the conduction mechanism at high temperature is governed by interstitial titanium ions.

  14. Low temperature catalysts for methanol production

    DOEpatents

    Sapienza, R.S.; Slegeir, W.A.; O'Hare, T.E.; Mahajan, D.

    1986-09-30

    A catalyst and process useful at low temperatures (below about 160 C) and preferably in the range 80--120 C used in the production of methanol from carbon monoxide and hydrogen are disclosed. The catalyst is used in slurry form and comprises a complex reducing agent derived from the component structure NaH--RONa-M(OAc)[sub 2] where M is selected from the group consisting of Ni, Pd, and Co and R is a lower alkyl group containing 1--6 carbon atoms. This catalyst is preferably used alone but is also effective in combination with a metal carbonyl of a group VI (Mo, Cr, W) metal. The preferred catalyst precursor is Nic (where M = Ni and R = tertiary amyl). Mo(CO)[sub 6] is the preferred metal carbonyl if such component is used. The catalyst is subjected to a conditioning or activating step under temperature and pressure, similar to the parameters given above, to afford the active catalyst.

  15. Low temperature catalyst system for methanol production

    DOEpatents

    Sapienza, R.S.; Slegeir, W.A.; O'Hare, T.E.

    1984-04-20

    This patent discloses a catalyst and process useful at low temperatures (150/sup 0/C) and preferably in the range 80 to 120/sup 0/C used in the production of methanol from carbon monoxide and hydrogen. The catalyst components are used in slurry form and comprise (1) a complex reducing agent derived from the component structure NaH-ROH-M(OAc)/sub 2/ where M is selected from the group consisting of Ni, Pd, and Co and R is a lower alkyl group containing 1 to 6 carbon atoms and (2) a metal carbonyl of a group VI (Mo, Cr, W) metal. For the first component, Nic is preferred (where M = Ni and R = tertiary amyl). For the second component, Mo(CO)/sub 6/ is preferred. The mixture is subjected to a conditioning or activating step under temperature and pressure, similar to the parameters given above, to afford the active catalyst.

  16. Optically controlled release of DNA based on nonradiative relaxation process of quenchers.

    PubMed

    Ogura, Yusuke; Onishi, Atsushi; Nishimura, Takahiro; Tanida, Jun

    2016-06-01

    Optically controlled release of a DNA strand based on a nonradiative relaxation process of black hole quenchers (BHQs), which are a sort of dark quenchers, is presented. BHQs act as efficient energy sources because they relax completely via a nonradiative process, i.e., without fluorescent emission-based energy losses. A DNA strand is modified with BHQs and the release of its complementary strand is controlled by excitation of the BHQs. Experimental results showed that up to 50% of the target strands were released, and these strands were capable of inducing subsequent reactions. The controlled release was localized on a substrate within an area of no more than 5 micrometers in diameter. PMID:27375933

  17. Molecular mobility and relaxation process of isolated lignin studied by multifrequency calorimetric experiments.

    PubMed

    Guigo, Nathanael; Mija, Alice; Vincent, Luc; Sbirrazzuoli, Nicolas

    2009-02-28

    The glass transition of lignin has been studied by multifrequency calorimetric measurements in order to highlight the morphological changes and the dynamic aspects associated to this relaxation process. Influences of water sorption and thermal annealing on molecular mobility have been considered. Additional investigations by thermogravimetry, infra-red spectroscopy and rheometry have been performed to corroborate the claims. The relaxation process of annealed lignin shows a different behaviour as the consequence of micro-structural modifications of lignin. These are explained by redistribution of secondary bonds as well as formation of new interunit linkages. Concerning the dynamic aspects, apparent activation energy, E, and sizes of cooperatively rearranging region, V(crr), have been evaluated respectively from the frequency dependence and heat capacity measurements of the glass transition. Compared to dried lignin, both E and V(crr) significantly decrease in a water-sorbed matrix indicating that the three-dimensional structure presents a higher mobility and is less confined. PMID:19209367

  18. Optically controlled release of DNA based on nonradiative relaxation process of quenchers

    PubMed Central

    Ogura, Yusuke; Onishi, Atsushi; Nishimura, Takahiro; Tanida, Jun

    2016-01-01

    Optically controlled release of a DNA strand based on a nonradiative relaxation process of black hole quenchers (BHQs), which are a sort of dark quenchers, is presented. BHQs act as efficient energy sources because they relax completely via a nonradiative process, i.e., without fluorescent emission-based energy losses. A DNA strand is modified with BHQs and the release of its complementary strand is controlled by excitation of the BHQs. Experimental results showed that up to 50% of the target strands were released, and these strands were capable of inducing subsequent reactions. The controlled release was localized on a substrate within an area of no more than 5 micrometers in diameter. PMID:27375933

  19. Relaxation processes in a low-order three-dimensional magnetohydrodynamics model

    NASA Technical Reports Server (NTRS)

    Stribling, Troy; Matthaeus, William H.

    1991-01-01

    The time asymptotic behavior of a Galerkin model of 3D magnetohydrodynamics (MHD) has been interpreted using the selective decay and dynamic alignment relaxation theories. A large number of simulations has been performed that scan a parameter space defined by the rugged ideal invariants, including energy, cross helicity, and magnetic helicity. It is concluded that time asymptotic state can be interpreted as a relaxation to minimum energy. A simple decay model, based on absolute equilibrium theory, is found to predict a mapping of initial onto time asymptotic states, and to accurately describe the long time behavior of the runs when magnetic helicity is present. Attention is also given to two processes, operating on time scales shorter than selective decay and dynamic alignment, in which the ratio of kinetic to magnetic energy relaxes to values 0(1). The faster of the two processes takes states initially dominant in magnetic energy to a state of near-equipartition between kinetic and magnetic energy through power law growth of kinetic energy. The other process takes states initially dominant in kinetic energy to the near-equipartitioned state through exponential growth of magnetic energy.

  20. Operation of FPGAs at Extremely Low Temperatures

    NASA Technical Reports Server (NTRS)

    Burke, Gary R.; Cozy, Scott; Lacayo, Veronica; Bakhshi, Alireza; Stern, Ryan; Mojarradi, Mohammad; Johnson, Travis; Kolawa, Elizabeth; Bolotin, Gary; Gregoire, Tim; Ramesham, Rajeshuni

    2004-01-01

    This paper describes the operation of FPGAs at very low temperatures eg -160(deg)C. Both Actel and Xilinx parts are tested It was found that low temperature operations is not a problem with the parts tested, but there is a problem with powering on an FPGA at cold temperatures.

  1. Low Temperature Thermometry Using Inexpensive Silicon Diodes.

    ERIC Educational Resources Information Center

    Waltham, N. R.; And Others

    1981-01-01

    Describes the use of silicon diodes for low temperature thermometry in the teaching laboratory. A simple and inexpensive circuit for display of the diode forward voltage under constant current conditions is described, and its application in the evaluation of low cost silicon diodes as low temperature thermometers is presented. (SK)

  2. Dislocation mechanisms of low-temperature internal friction in nanostructured materials

    NASA Astrophysics Data System (ADS)

    Natsik, V. D.; Semerenko, Yu. A.

    2016-02-01

    A new method of statistically describing the dislocation component of low-temperature internal friction in nanostructured materials. The latter term is applied to ultrafine polycrystals with high density intragranular and grain boundary dislocations, the lines of which are divided into nanometer-scale fragments (dislocation relaxants) with random geometrical and energy parameters. The resonant interaction of elastic vibrations and thermally activated excitations of such relaxators are examined, and the maxima caused by these relaxators along the internal friction temperature dependence are analyzed. It is shown that at low temperatures, the shape of the peaks and the region of their localization along the temperature axis are largely determined by the dispersion of the relaxator activation energy. An algorithm is written in order to analyze the internal friction recorded in the experiment, allowing us to identify the physical model corresponding to the relaxator, and obtain empirical estimates of its parameters.

  3. Uncertainty management by relaxation of conflicting constraints in production process scheduling

    NASA Technical Reports Server (NTRS)

    Dorn, Juergen; Slany, Wolfgang; Stary, Christian

    1992-01-01

    Mathematical-analytical methods as used in Operations Research approaches are often insufficient for scheduling problems. This is due to three reasons: the combinatorial complexity of the search space, conflicting objectives for production optimization, and the uncertainty in the production process. Knowledge-based techniques, especially approximate reasoning and constraint relaxation, are promising ways to overcome these problems. A case study from an industrial CIM environment, namely high-grade steel production, is presented to demonstrate how knowledge-based scheduling with the desired capabilities could work. By using fuzzy set theory, the applied knowledge representation technique covers the uncertainty inherent in the problem domain. Based on this knowledge representation, a classification of jobs according to their importance is defined which is then used for the straightforward generation of a schedule. A control strategy which comprises organizational, spatial, temporal, and chemical constraints is introduced. The strategy supports the dynamic relaxation of conflicting constraints in order to improve tentative schedules.

  4. Low Temperature Aluminum Dissolution Of Sludge Waste

    SciTech Connect

    Keefer, M.T.; Hamm, B.A.; Pike, J.A.

    2008-07-01

    primarily of radioactive wastes containing a very high aluminum concentration. Based on initial laboratory testing and previous sludge characterization, aluminum in this sludge could be dissolved at low temperature (no more than 65 deg. C) in a concentrated caustic solution. The amount of aluminum predicted to dissolve under these conditions ranged from 25% to 80%. An opportunity existed to remove a significant amount of aluminum prior to vitrification in DWPF and increase the level of understanding of the effects of caustic dissolution of aluminum at lower temperatures. This paper presents the results of a real waste laboratory demonstration and full-scale implementation of a low temperature aluminum dissolution process which should be considered as a viable means to reduce radioactive sludge mass and reduce the amount of waste to be vitrified. (authors)

  5. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    SciTech Connect

    Harlan U. Anderson; Wayne Huebner; Igor Kosacki

    2001-09-30

    This project has three main goals: Thin Films Studies, Preparation of Graded Porous Substrates and Basic Electrical Characterization and testing of Planar Single Cells. In this portion of study we have focused on producing YSZ films on porous LSM substrates. When using the polymer precursor there are a number of obstacles to overcome in order to form dense electrolyte layers on porous substrates (cathode or anode). Probably the most difficult problems are: (1) Extreme penetration of the polymer into the substrate must be prevented. (2) Shrinkage cracking must be avoided. (3) Film thickness in the 1 to 5{micro}m range must be achieved. We have demonstrated that cracking due to shrinkage involved during the elimination of solvents and organic matter and densification of the remaining oxide is not a problem as long as the resulting oxide film is < {approx} 0.15 {micro}m in thickness. We have also shown that we can make thicker films by making multiple depositions if the substrate is smooth (roughness {le} 0.1 {micro}m) and contains no surface pores > 0.2 {micro}m. The penetration of the polymer into the porous substrate can be minimized by increasing the viscosity of the polymer and reducing the largest pore at the surface of the substrate to {le} 0.2 {micro}m. We have shown that this can be done, but we have also shown that it is difficult to make dense films that are defect free with areas > 1 cm{sup 2}. This is because of the roughness of the substrate and the difficulty in making a substrate which does not have surface voids > 0.2 {micro}m. Thus the process works well for dense, smooth substrates for films < 1 {micro}m thick, but is difficult to apply to rough, porous surfaces and to make film thickness > 1 {micro}m. As a result of these problems, we have been addressing the issue of how to make dense films in the thickness range of 1 to 5 {micro}m on sintered porous substrates without introducing cracks and holes due to shrinkage and surface voids? These

  6. Photoexcited carrier relaxation dynamics in pentacene probed by ultrafast optical spectroscopy: Influence of morphology on relaxation processes

    NASA Astrophysics Data System (ADS)

    Thorsmølle, V. K.; Averitt, R. D.; Demsar, J.; Smith, D. L.; Tretiak, S.; Martin, R. L.; Chi, X.; Crone, B. K.; Ramirez, A. P.; Taylor, A. J.

    2009-10-01

    We present a comparative study of ultrafast photoexcited state relaxation in pentacene single crystals and in pure and C60-doped pentacene films using optical pump-probe spectroscopy. The photoinduced absorption spectra in pentacene crystals is consistent with a dominant singlet-triplet fission decay channel for above-gap excitation. This decay channel is suppressed in thin films and even further suppressed by electron trapping in C60-doped films. Thus we show that suppression of triplet state production, which is necessary for free carrier formation and thus photovoltaic and photodiode performance, is controllable via sample morphology.

  7. Low-Temperature Power Electronics Program

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Dickman, John E.; Hammoud, Ahmad; Gerber, Scott

    1997-01-01

    Many space and some terrestrial applications would benefit from the availability of low-temperature electronics. Exploration missions to the outer planets, Earth-orbiting and deep-space probes, and communications satellites are examples of space applications which operate in low-temperature environments. Space probes deployed near Pluto must operate in temperatures as low as -229 C. Figure 1 depicts the average temperature of a space probe warmed by the sun for various locations throughout the solar system. Terrestrial applications where components and systems must operate in low-temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation system, and arctic exploration. The development of electrical power systems capable of extremely low-temperature operation represents a key element of some advanced space power systems. The Low-Temperature Power Electronics Program at NASA Lewis Research Center focuses on the design, fabrication, and characterization of low-temperature power systems and the development of supporting technologies for low-temperature operations such as dielectric and insulating materials, power components, optoelectronic components, and packaging and integration of devices, components, and systems.

  8. Efficient indium-tin-oxide free inverted organic solar cells based on aluminum-doped zinc oxide cathode and low-temperature aqueous solution processed zinc oxide electron extraction layer

    SciTech Connect

    Chen, Dazheng; Zhang, Chunfu Wang, Zhizhe; Zhang, Jincheng; Tang, Shi; Wei, Wei; Sun, Li; Hao, Yue

    2014-06-16

    Indium-tin-oxide (ITO) free inverted organic solar cells (IOSCs) based on aluminum-doped zinc oxide (AZO) cathode, low-temperature aqueous solution processed zinc oxide (ZnO) electron extraction layer, and poly(3-hexylthiophene-2, 5-diyl):[6, 6]-phenyl C{sub 61} butyric acid methyl ester blend were realized in this work. The resulted IOSC with ZnO annealed at 150 °C shows the superior power conversion efficiency (PCE) of 3.01%, if decreasing the ZnO annealing temperature to 100 °C, the obtained IOSC also shows a PCE of 2.76%, and no light soaking issue is observed. It is found that this ZnO film not only acts as an effective buffer layer but also slightly improves the optical transmittance of AZO substrates. Further, despite the relatively inferior air-stability, these un-encapsulated AZO/ZnO IOSCs show comparable PCEs to the referenced ITO/ZnO IOSCs, which demonstrates that the AZO cathode is a potential alternative to ITO in IOSCs. Meanwhile, this simple ZnO process is compatible with large area deposition and plastic substrates, and is promising to be widely used in IOSCs and other relative fields.

  9. Efficient indium-tin-oxide free inverted organic solar cells based on aluminum-doped zinc oxide cathode and low-temperature aqueous solution processed zinc oxide electron extraction layer

    NASA Astrophysics Data System (ADS)

    Chen, Dazheng; Zhang, Chunfu; Wang, Zhizhe; Zhang, Jincheng; Tang, Shi; Wei, Wei; Sun, Li; Hao, Yue

    2014-06-01

    Indium-tin-oxide (ITO) free inverted organic solar cells (IOSCs) based on aluminum-doped zinc oxide (AZO) cathode, low-temperature aqueous solution processed zinc oxide (ZnO) electron extraction layer, and poly(3-hexylthiophene-2, 5-diyl):[6, 6]-phenyl C61 butyric acid methyl ester blend were realized in this work. The resulted IOSC with ZnO annealed at 150 °C shows the superior power conversion efficiency (PCE) of 3.01%, if decreasing the ZnO annealing temperature to 100 °C, the obtained IOSC also shows a PCE of 2.76%, and no light soaking issue is observed. It is found that this ZnO film not only acts as an effective buffer layer but also slightly improves the optical transmittance of AZO substrates. Further, despite the relatively inferior air-stability, these un-encapsulated AZO/ZnO IOSCs show comparable PCEs to the referenced ITO/ZnO IOSCs, which demonstrates that the AZO cathode is a potential alternative to ITO in IOSCs. Meanwhile, this simple ZnO process is compatible with large area deposition and plastic substrates, and is promising to be widely used in IOSCs and other relative fields.

  10. Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by scanning tunneling microscopy, reflected high-energy electron diffraction, and high resolution transmission electron microscopy

    SciTech Connect

    Arapkina, L. V.; Krylova, L. A.; Chizh, K. V.; Chapnin, V. A.; Uvarov, O. V.; Yuryev, V. A.

    2012-07-01

    Structural properties of the clean Si(001) surface obtained as a result of low-temperature (470-650 Degree-Sign C) pre-growth annealings of silicon wafers in a molecular-beam epitaxy chamber have been investigated. To decrease the cleaning temperature, a silicon surface was hydrogenated in the process of a preliminary chemical treatment in HF and NH{sub 4}F aqueous solutions. It has been shown that smooth surfaces composed of wide terraces separated by monoatomic steps can be obtained by dehydrogenation at the temperatures Greater-Than-Or-Equivalent-To 600 Degree-Sign C, whereas clean surfaces obtained at the temperatures <600 Degree-Sign C are rough. It has been found that there exists a dependence of structural properties of clean surfaces on the temperature of hydrogen thermal desorption and the process of the preliminary chemical treatment. The frequency of detachment/attachment of Si dimers from/to the steps and effect of the Ehrlich-Schwoebel barrier on ad-dimer migration across steps have been found to be the most probable factors determining a degree of the resultant surface roughness.

  11. Low Temperature Sintering of PZT

    NASA Astrophysics Data System (ADS)

    Medesi, A.; Greiner, T.; Benkler, M.; Megnin, C.; Hanemann, T.

    2014-11-01

    This paper describes the fabrication and characterization of lead zirconate titanate (PZT) films fired in a liquid-phase sintering process at 900 °C in air. In detail the manufacturing of piezoelectric multilayers with internal pure silver (Tm = 961 °C) electrodes are reported. The feasibility of ten sintering aids in two different volume fractions was investigated for a commercial hard PZT powder (PIC 181, PI Ceramics) with respect to density, microstructure, mechanical behaviour, and piezoelectric properties. Li2O, Li2CO3, PbO, MnO2, V2O5, CuO, Bi2O3, the eutectic mixtures Cu2O·PbO and PbO·WO3 and the ternary system Li2CO3·Bi2O3·CuO (LBCu) have been tested as liquid phase sintering aids. The combination of PZT with LBCu showed the best results. With 5 vol.% LBCu an average relative density of 97% and a characteristic breaking strength of 77 MPa was achieved. Composition of PZT with 2 vol.% LBCu exhibits the highest averaged piezoelectrical charge constant (d33) of 181 pC/N.

  12. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    SciTech Connect

    Harlan U. Anderson; Fatih Dogan; Vladimir Petrovsky

    2003-03-31

    This report represents a summary of the work carried out on this project which started October 1999 and ended March 2003. A list of the publications resulting from the work are contained in Appendix A. The most significant achievements are: (1) Dense nanocrystalline zirconia and ceria films were obtained at temperatures < 400 C. (2) Nanocrystalline films of both ceria and zirconia were characterized. (3) We showed that under anodic conditions 0.5 to 1 micron thick nanocrystalline films of Sc doped zirconia have sufficient electronic conductivity to prevent them from being useful as an electrolyte. (4) We have developed a process by which dense 0.5 to 5 micron thick dense films of either YSZ or ceria can be deposited on sintered porous substrates which serve as either the cathode or anode at temperatures as low as 400 C. (5) The program has provided the research to produce two PhD thesis for students, one is now working in the solid oxide fuel cell field. (6) The results of the research have resulted in 69 papers published, 3 papers submitted or being prepared for publication, 50 oral presentations and 3 patent disclosures.

  13. Improved Low Temperature Performance of Supercapacitors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik J.; West, William C.; Smart, Marshall C.; Gnanaraj, Joe

    2013-01-01

    Low temperature double-layer capacitor operation enabled by: - Base acetonitrile / TEATFB salt formulation - Addition of low melting point formates, esters and cyclic ethers center dot Key electrolyte design factors: - Volume of co-solvent - Concentration of salt center dot Capacity increased through higher capacity electrodes: - Zeolite templated carbons - Asymmetric cell designs center dot Continuing efforts - Improve asymmetric cell performance at low temperature - Cycle life testing Motivation center dot Benchmark performance of commercial cells center dot Approaches for designing low temperature systems - Symmetric cells (activated carbon electrodes) - Symmetric cells (zeolite templated carbon electrodes) - Asymmetric cells (lithium titanate/activated carbon electrodes) center dot Experimental results center dot Summary

  14. Rate statistics and thermodynamic analogies for relaxation processes in systems with static disorder: Application to stretched exponential

    NASA Astrophysics Data System (ADS)

    Vlad, Marcel O.; Huber, David L.; Ross, John

    1997-03-01

    The paper deals with the relationships between the total rate of a relaxation process occurring in a system with static disorder and the decay rates attached to the different individual reaction channels. It is proven that the models of relaxation constructed on the basis of these two types of rates are equivalent to each other. From an experimentally observed relaxation curve it is possible to evaluate only the density of channels characterized by different relaxation rates and the overall probability distribution of the total relaxation rate. For evaluating the probability density of the individual relaxation rates attached to different channels an approach based on the maximum information entropy principle is suggested. A statistical thermodynamic formalism is developed for the relaxation time of a given channel, i.e., for the reciprocal value of the individual relaxation rate. The probability density of the relaxation time is proportional to the product of the density of channels to an exponentially decreasing function similar to the Boltzmann's factor in equilibrium statistical mechanics. The theory is applied to the particular case of stretched exponential relaxation for which the density of channels diverges to infinity in the limit of large relaxation times according to a power law. The extremal entropy of the system as well as the moments and the cumulants of the relaxation times and of the relaxation rates are evaluated analytically. The probability of fluctuations can be expressed by a relationship similar to the Greene-Callen generalization of Einstein's fluctuation formula. In the limit of large rates the density of channels and the probability density of individual rates have the same behavior; both functions have long tails of the negative power law type characterized by the same fractal exponent. For small rates, however, their behavior is different; the probability density tends to zero in the limit of very small rates whereas the density of

  15. Unusual eigenvalue spectrum and relaxation in the Lévy-Ornstein-Uhlenbeck process.

    PubMed

    Janakiraman, Deepika; Sebastian, K L

    2014-10-01

    We consider the rates of relaxation of a particle in a harmonic well, subject to Lévy noise characterized by its Lévy index μ. Using the propagator for this Lévy-Ornstein-Uhlenbeck process (LOUP), we show that the eigenvalue spectrum of the associated Fokker-Planck operator has the form (n+mμ)ν where ν is the force constant characterizing the well, and n,m∈N. If μ is irrational, the eigenvalues are all nondegenerate, but rational μ can lead to degeneracy. The maximum degeneracy is shown to be 2. The left eigenfunctions of the fractional Fokker-Planck operator are very simple while the right eigenfunctions may be obtained from the lowest eigenfunction by a combination of two different step-up operators. Further, we find that the acceptable eigenfunctions should have the asymptotic behavior |x|(-n1-n2μ) as |x|→∞, with n1 and n2 being positive integers, though this condition alone is not enough to identify them uniquely. We also assert that the rates of relaxation of LOUP are determined by the eigenvalues of the associated fractional Fokker-Planck operator and do not depend on the initial state if the moments of the initial distribution are all finite. If the initial distribution has fat tails, for which the higher moments diverge, one can have nonspectral relaxation, as pointed out by et al. [Phys. Rev. Lett. 110, 150602 (2013)]. PMID:25375420

  16. Mutual friction in superfluid [sup 3]He. II. Continuous vortices in [sup 3]He-[ital A] at low temperatures

    SciTech Connect

    Kopnin, N.B. )

    1993-06-01

    The mutual-friction parameters for axisymmetric continuous vortices in the [ital A] phase at low temperatures are calculated on the basis of microscopic BCS theory for nonstationary processes. The parameters depend on the ratio of the distance between the energy levels of quasiparticles localized in the vortex, [omega][sub 0], and the relaxation rate of these quasiparticles, 1/[tau]. The transition from viscous to dissipationless flow of vortices occurs when [omega][sub 0][tau][similar to]1, the corresponding temperatures being well below [ital T][sub [ital c

  17. Low-temperature full wafer adhesive bonding

    NASA Astrophysics Data System (ADS)

    Niklaus, Frank; Enoksson, Peter; Kälvesten, Edvard; Stemme, Göran

    2001-03-01

    We have systematically investigated the influence of different bonding parameters on void formation in a low-temperature adhesive bonding process. As a result of these studies we present guidelines for void free adhesive bonding of 10 cm diameter wafers. We have focused on polymer coatings with layer thicknesses between 1 µm and 18 µm. The tested polymer materials were benzocyclobutene (BCB) from Dow Chemical, a negative photoresist (ULTRA-i 300) and a positive photoresist (S1818) from Shipley, a polyimide (HTR3) from Arch Chemical and two different polyimides (PI2555 and PI2610) from DuPont. The polymer material, the bonding pressure and the pre-curing time and temperature for the polymer significantly influence void formation at the bond interface. High bonding pressure and optimum pre-curing times/temperatures counteract void formation. We present the process parameters to achieve void-free bonding with the BCB coating and with the ULTRA-i 300 photoresist coating as adhesive materials. Excellent void-free and strong bonds have been achieved by using BCB as the bonding material which requires a minimum bonding temperature of 180 °C.

  18. Low Temperature Atmospheric Pressure Plasma Sterilization Shower

    NASA Astrophysics Data System (ADS)

    Gandhiraman, R. P.; Beeler, D.; Meyyappan, M.; Khare, B. N.

    2012-10-01

    Low-temperature atmospheric pressure plasma sterilization shower to address both forward and backward biological contamination issues is presented. The molecular effects of plasma exposure required to sterilize microorganisms is also analysed.

  19. Low-Temperature Electronic Components Being Developed

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammond, Ahmad

    1999-01-01

    In many future NASA missions, such as deep space planetary exploration and the Next Generation Space Telescope, electrical components and systems must operate reliably and efficiently in extremely low temperature environments. Most modern electronic components cannot operate below moderately low operating temperatures (-40 to -55 C). The low-temperature electronics program at the NASA Lewis Research Center is focusing on the development and characterization of low-temperature components and the integration of the developed devices into demonstrable very low-temperature (-200 C) power systems such as dc-dc converters. Such low-temperature electronics will not only tolerate hostile environments but also will reduce system size and weight by eliminating radioisotope heating units, thereby reducing launch cost, improving reliability and lifetime, and increasing energy densities. Low-temperature electronic components will also have a great influence on terrestrial applications such as medical instrumentation, magnetic levitation transportation systems, and arctic and antarctic exploration. Lewis researchers are now performing extensive evaluations of commercially available as well as custom-made devices. These include various types of energy storage and signal capacitors, power switching devices, magnetic and superconducting materials, and primary lithium batteries, to name a few.

  20. Fim study on the relaxation and crystallization processes of a Cu-Zr amorphous alloy

    NASA Astrophysics Data System (ADS)

    H, Lu; Lu, Hua; D, S. Tang; Tang, Disheng; Y, Y. Xiong; Xiong, Yanyun

    1987-09-01

    The relaxation of the Cu-50at.%Zr amorphous alloy was revealed by FIM as a process of formation of clusters consisting of 2, 3, or 4 atoms, which afterwards migrate towards some definite centers, predominantly the quenched-in "embryos", to construct ordered structure. This dynamic picture, so far as we know, is observed for the first time. Crystallized regions were determined by atom-probe analysis as Cu10Zr7 phase, and the coexisting phase CuZr2 was not revealed simultaneously.

  1. Slowing hot-carrier relaxation in graphene using a magnetic field

    NASA Astrophysics Data System (ADS)

    Plochocka, P.; Kossacki, P.; Golnik, A.; Kazimierczuk, T.; Berger, C.; de Heer, W. A.; Potemski, M.

    2009-12-01

    A degenerate pump-probe technique is used to investigate the nonequilibrium carrier dynamics in multilayer graphene. Two distinctly different dynamics of the carrier relaxation are observed. A fast relaxation (˜50fs) of the carriers after the initial effect of phase-space filling followed by a slower relaxation (˜4ps) due to thermalization. Both relaxation processes are less efficient when a magnetic field is applied at low temperatures which is attributed to the suppression of the electron-electron Auger scattering due to the nonequidistant Landau-level spacing of the Dirac fermions in graphene.

  2. Dynamical fingerprints for probing individual relaxation processes in biomolecular dynamics with simulations and kinetic experiments

    SciTech Connect

    Noe, F; Diadone, Isabella; Lollmann, Marc; Sauer, Marcus; Chondera, John D; Smith, Jeremy C

    2011-01-01

    There is a gap between kinetic experiment and simulation in their views of the dynamics of complex biomolecular systems. Whereas experiments typically reveal only a few readily discernible exponential relaxations, simulations often indicate complex multistate behavior. Here, a theoretical framework is presented that reconciles these two approaches. The central concept is dynamical fingerprints which contain peaks at the time scales of the dynamical processes involved with amplitudes determined by the experimental observable. Fingerprints can be generated from both experimental and simulation data, and their comparison by matching peaks permits assignment of structural changes present in the simulation to experimentally observed relaxation processes. The approach is applied here to a test case interpreting single molecule fluorescence correlation spectroscopy experiments on a set of fluorescent peptides with molecular dynamics simulations. The peptides exhibit complex kinetics shown to be consistent with the apparent simplicity of the experimental data. Moreover, the fingerprint approach can be used to design new experiments with site-specific labels that optimally probe specific dynamical processes in the molecule under investigation.

  3. Low temperature catalysts for methanol production

    DOEpatents

    Sapienza, Richard S.; Slegeir, William A.; O'Hare, Thomas E.; Mahajan, Devinder

    1986-01-01

    A catalyst and process useful at low temperatures (below about 160.degree. C.) and preferably in the range 80.degree.-120.degree. C. used in the production of methanol from carbon monoxide and hydrogen is disclosed. The catalyst is used in slurry form and comprises a complex reducing agent derived from the component structure NaH--RONa--M(OAc).sub.2 where M is selected from the group consisting of Ni, Pd, and Co and R is a lower alkyl group containing 1-6 carbon atoms. This catalyst is preferably used alone but is also effective in combination with a metal carbonyl of a group VI (Mo, Cr, W) metal. The preferred catalyst precursor is Nic (where M=Ni and R=tertiary amyl). Mo(CO).sub.6 is the preferred metal carbonyl if such component is used. The catalyst is subjected to a conditioning or activating step under temperature and pressure, similar to the parameters given above, to afford the active catalyst.

  4. Low temperature catalysts for methanol production

    DOEpatents

    Sapienza, R.S.; Slegeir, W.A.; O'Hare, T.E.; Mahajan, D.

    1986-10-28

    A catalyst and process useful at low temperatures (below about 160 C) and preferably in the range 80--120 C used in the production of methanol from carbon monoxide and hydrogen are disclosed. The catalyst is used in slurry form and comprises a complex reducing agent derived from the component structure NaH--RONa-M(OAc)[sub 2] where M is selected from the group consisting of Ni, Pd, and Co and R is a lower alkyl group containing 1-6 carbon atoms. This catalyst is preferably used alone but is also effective in combination with a metal carbonyl of a group VI (Mo, Cr, W) metal. The preferred catalyst precursor is NiC (where M = Ni and R = tertiary amyl). Mo(CO)[sub 6] is the preferred metal carbonyl if such component is used. The catalyst is subjected to a conditioning or activating step under temperature and pressure, similar to the parameters given above, to afford the active catalyst.

  5. Low temperature catalysts for methanol production

    DOEpatents

    Sapienza, R.S.; Slegeir, W.A.; O'Hare, T.E.; Mahajan, D.

    1985-03-12

    A catalyst and process useful at low temperatures (below about 160/sup 0/C) and preferably in the range 80 to 120/sup 0/C used in the production of methanol from carbon monoxide and hydrogen is disclosed. The catalyst is used in slurry form and comprises a complex reducing agent derived from the component structure NaH-RONa-M(OAc)/sub 2/ where M is selected from the group consisting of Ni, Pd, and Co and R is a lower alkyl group containing 1 to 6 carbon atoms. This catalyst is preferably used alone but is also effective in combination with a metal carbonyl of a group VI (Mo, Cr, W) metal. The preferred catalyst precursor is Nic (where M = Ni and R = tertiary amyl). Mo(CO)/sub 6/ is the preferred metal carbonyl if such component is used. The catalyst is subjected to a conditioning or activating step under temperature and pressure, similar to the parameters given above, to afford the active catalyst.

  6. Low Temperature Catalyst for NH3 Removal

    NASA Technical Reports Server (NTRS)

    Monje, Oscar; Melendez, Orlando

    2013-01-01

    Air revitalization technologies maintain a safe atmosphere inside spacecraft by the removal of C02, ammonia (NH3), and trace contaminants. NH3 onboard the International Space Station (ISS) is produced by crew metabolism, payloads, or during an accidental release of thermal control refrigerant. Currently, the ISS relies on removing NH3 via humidity condensate and the crew wears hooded respirators during emergencies. A different approach to cabin NH3 removal is to use selective catalytic oxidation (SCO), which builds on thermal catalytic oxidation concepts that could be incorporated into the existing TCCS process equipment architecture on ISS. A low temperature platinum-based catalyst (LTP-Catalyst) developed at KSC was used for converting NH3 to H20 and N2 gas by SCO. The challenge of implementing SCO is to reduce formation of undesirable byproducts like NOx (N20 and NO). Gas mixture analysis was conducted using FTIR spectrometry in the Regenerable VOC Control System (RVCS) Testbed. The RVCS was modified by adding a 66 L semi-sealed chamber, and a custom NH3 generator. The effect of temperature on NH3 removal using the LTP-Catalyst was examined. A suitable temperature was found where NH3 removal did not produce toxic NO, (NO, N02) and N20 formation was reduced.

  7. Low temperature deformation detwinning - a reverse mode of twinning.

    SciTech Connect

    Wang, Y. D.; Liu, W.; Lu, L.; Ren, Y.; Nie, Z. H.; Almer, J.; Cheng, S.; Shen, Y. F.; Zuo, L.; Liaw, P. K.; Lu, K.

    2010-01-01

    The origin of the plasticity in bulk nanocrystalline metals have, to date, been attributed to the grain-boundary-mediated process, stress-induced grain coalescence, dislocation plasticity, and/or twinning. Here we report a different mechanism - detwinning, which operates at low temperatures during the tensile deformation of an electrodeposited Cu with a high density of nanosized growth twins. Both three-dimensional XRD microscopy using the Laue method with a submicron-sized polychromatic beam and high-energy XRD technique with a monochromatic beam provide the direct experimental evidences for low temperature detwinning of nanoscale twins.

  8. Preparation and characterization of low-temperature expandable graphite

    SciTech Connect

    Ying Zongrong Lin Xuemei; Qi Yu; Luo Jie

    2008-10-02

    The low-temperature expandable graphite was successfully prepared with perchloric acid, phosphoric acid and KMnO{sub 4} by chemical process. The optimum weight ratio of perchloric acid to phosphoric acid in mixed acid was 1:0.2, and the weight ratio of the mixed acid, KMnO{sub 4} and natural flake graphite was preferably 1.5:0.1:1. The expanded volume can reach 260 mL/g at a relatively low temperature of 300 deg. C. Meanwhile, the prepared samples were characterized by means of Fourier transform infrared, thermogravimetry-differential scanning calorimetry and X-ray diffraction.

  9. Instrument for Measuring Thermal Conductivity of Materials at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Fesmire, James; Sass, Jared; Johnson, Wesley

    2010-01-01

    With the advance of polymer and other non-metallic material sciences, whole new series of polymeric materials and composites are being created. These materials are being optimized for many different applications including cryogenic and low-temperature industrial processes. Engineers need these data to perform detailed system designs and enable new design possibilities for improved control, reliability, and efficiency in specific applications. One main area of interest is cryogenic structural elements and fluid handling components and other parts, films, and coatings for low-temperature application. An important thermal property of these new materials is the apparent thermal conductivity (k-value).

  10. Electronics Demonstrated for Low- Temperature Operation

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammond, Ahmad; Gerber, Scott S.

    2000-01-01

    The operation of electronic systems at cryogenic temperatures is anticipated for many NASA spacecraft, such as planetary explorers and deep space probes. For example, an unheated interplanetary probe launched to explore the rings of Saturn would experience an average temperature near Saturn of about 183 C. Electronics capable of low-temperature operation in the harsh deep space environment also would help improve circuit performance, increase system efficiency, and reduce payload development and launch costs. An ongoing research and development program on low-temperature electronics at the NASA Glenn Research Center at Lewis Field is focusing on the design of efficient power systems that can survive and exploit the advantages of low-temperature environments. The targeted systems, which are mission driven, include converters, inverters, controls, digital circuits, and special-purpose circuits. Initial development efforts successfully demonstrated the low-temperature operation and cold-restart of several direct-current/direct-current (dc/dc) converters based on different types of circuit design, some with superconducting inductors. The table lists some of these dc/dc converters with their properties, and the photograph shows a high-voltage, high-power dc/dc converter designed for an ion propulsion system for low-temperature operation. The development efforts of advanced electronic systems and the supporting technologies for low-temperature operation are being carried out in-house and through collaboration with other Government agencies, industry, and academia. The Low Temperature Electronics Program supports missions and development programs at NASA s Jet Propulsion Laboratory and Goddard Space Flight Center. The developed technologies will be transferred to commercial end users for applications such as satellite infrared sensors and medical diagnostic equipment.

  11. Room-temperature thermally induced relaxation effect in a two-dimensional cyano-bridged Cu-Mo bimetal assembly and thermodynamic analysis of the relaxation process

    SciTech Connect

    Umeta, Yoshikazu; Ozaki, Noriaki; Tokoro, Hiroko; Ohkoshi, Shin-ichi

    2013-04-15

    We observed a photo-switching effect in [Cu{sup II}(1,4,8,11-tetraazacyclodecane)]{sub 2}[Mo{sup IV}(CN){sub 8}]{center_dot}10H{sub 2}O by irradiation with 410-nm light around room temperature using infrared spectroscopy. This photo-switching is caused by the photo-induced charge transfer from Mo{sup IV} to Cu{sup II}. The photo-induced phase thermally relaxed to the initial phase with a half-life time of 2.7 Multiplication-Sign 10{sup 1}, 6.9 Multiplication-Sign 10{sup 1}, and 1.7 Multiplication-Sign 10{sup 2} s at 293, 283, and 273 K, respectively. The relaxation process was analyzed using Hauser's equation, k=k{sub 0}exp[-(E{sub a}+E{sub a}{sup *}{gamma}) /k{sub B}T], where k is the rate constant of relaxation, k{sub 0} is the frequency factor, E{sub a} is the activation energy, E{sub a}{sup *} is the additional activation energy due to the cooperativity, and {gamma} is the fraction of the photo-induced phase. k{sub 0}, E{sub a}, and E{sub a}{sup *} were evaluated as 1.28 Multiplication-Sign 10{sup 7}{+-} 2.6 s{sup -1}, 4002 {+-} 188 cm{sup -1}, and 546 {+-} 318 cm{sup -1}, respectively. The value of E{sub a} is much larger than that of the relaxation process for the typical light-induced spin crossover effect (E{sub a} Almost-Equal-To 1000 cm{sup -1}). Room-temperature photo-switching is an important issue in the field of optical functional materials. The present system is useful for the demonstration of high-temperature photo-switching material.

  12. Method of measurement of optical cable stiffness at low temperatures

    NASA Astrophysics Data System (ADS)

    Burdin, Vladimir A.; Alekhin, Ivan N.; Nikulina, Tatiana G.

    2014-04-01

    In this article the new method of determination of optical cable stiffness at low temperatures is offered. The method is allows to simplify process of measurements. Thus presence of technicians at climatic chamber in the course of measurements is not required.

  13. Intra-well relaxation process in magnetic fluids subjected to strong polarising fields

    NASA Astrophysics Data System (ADS)

    Marin, C. N.; Fannin, P. C.; Mălăescu, I.; Barvinschi, P.; Ercuţa, A.

    2012-02-01

    We report on the frequency and field dependent complex magnetic susceptibility measurements of a kerosene-based magnetic fluid with iron oxide nanoparticles, stabilized with oleic acid, in the frequency range 0.1-6 GHz and over the polarising field range of 0-168.4 kA/m. By increasing polarising field, H, a subsidiary loss-peak clearly occurs in the vicinity of the ferromagnetic resonance peak, from which it remains distinct even in strong polarising fields of 168.4 kA/m. This is in contrast to other reported cases in which the intra-well relaxation process is manifested only as a shoulder of the resonance peak, which vanishes in polarising fields larger than that of 100 kA/m. The results of the XRD analysis connected to the anisotropy field results confirm that the investigated sample contains particles of magnetite and of the tetragonal phase of maghemite. Taking into account the characteristics of our sample, the theoretical analysis revealed that the intra-well relaxation process of the small particles of the tetragonal phase of maghemite may be responsible for the subsidiary loss peak of the investigated magnetic fluid.

  14. Estimation of magnetic relaxation property for CVD processed YBCO-coated conductors

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Shikimachi, K.; Watanabe, T.; Kashima, N.; Nagaya, S.

    2010-11-01

    Ion Beam Assist Deposition/Chemical Vapor Deposition(IBAD/CVD)-processed YBCO-coated conductors with high critical current density Jc at high magnetic fields are expected to be applied to superconducting equipments such as superconducting magnetic energy storage (SMES). For application to superconducting magnet in SMES one of the most important properties for superconductors is the relaxation property of superconducting current. In this paper, the relaxation property is investigated for IBAD/CVD-processed YBCO-coated conductors of the superconducting layer in the range of 0.18-0.90 μm. This property can be quantitatively characterized by the apparent pinning potential, U0∗. It is found that U0∗ takes a smaller value due to the two-dimensional pinning mechanism at high magnetic fields for conductor with thinner superconducting layer. Although U0∗ decreases with increasing thickness at low magnetic fields at 20 K, it increases at high magnetic fields. The results are theoretically explained by the model of the flux creep and flow based on the dimensionality of flux pinning. Scaling analysis is examined for the dependence of U0∗ on the magnetic field, temperature and the layer thickness.

  15. Separation of elastic and inelastic processes in the relaxation-time approximation for the collision integral

    NASA Astrophysics Data System (ADS)

    Florkowski, Wojciech; Ryblewski, Radoslaw

    2016-06-01

    We introduce a generalized relaxation-time-approximation form of the collision term in the Boltzmann kinetic equation that allows for using different relaxation times for elastic and inelastic collisions. The efficacy of the proposed framework is demonstrated with the numerical calculations that describe systems with different relations between the two relaxation times and the evolution time of the system.

  16. Unusual eigenvalue spectrum and relaxation in the Lévy-Ornstein-Uhlenbeck process

    NASA Astrophysics Data System (ADS)

    Janakiraman, Deepika; Sebastian, K. L.

    2014-10-01

    We consider the rates of relaxation of a particle in a harmonic well, subject to Lévy noise characterized by its Lévy index μ. Using the propagator for this Lévy-Ornstein-Uhlenbeck process (LOUP), we show that the eigenvalue spectrum of the associated Fokker-Planck operator has the form (n+mμ)ν where ν is the force constant characterizing the well, and n ,m∈N. If μ is irrational, the eigenvalues are all nondegenerate, but rational μ can lead to degeneracy. The maximum degeneracy is shown to be 2. The left eigenfunctions of the fractional Fokker-Planck operator are very simple while the right eigenfunctions may be obtained from the lowest eigenfunction by a combination of two different step-up operators. Further, we find that the acceptable eigenfunctions should have the asymptotic behavior |x|-n1-n2μ as |x|→∞, with n1 and n2 being positive integers, though this condition alone is not enough to identify them uniquely. We also assert that the rates of relaxation of LOUP are determined by the eigenvalues of the associated fractional Fokker-Planck operator and do not depend on the initial state if the moments of the initial distribution are all finite. If the initial distribution has fat tails, for which the higher moments diverge, one can have nonspectral relaxation, as pointed out by Toenjes et al. [Phys. Rev. Lett. 110, 150602 (2013), 10.1103/PhysRevLett.110.150602].

  17. Spin relaxation via exchange with donor impurity-bound electrons

    NASA Astrophysics Data System (ADS)

    Qing, Lan; Li, Jing; Appelbaum, Ian; Dery, Hanan

    2015-06-01

    At low temperatures, electrons in semiconductors are bound to shallow donor impurity ions, neutralizing their charge in equilibrium. Inelastic scattering of other externally injected conduction electrons accelerated by electric fields can excite transitions within the manifold of these localized states. Promotion of the bound electron into highly spin-orbit-mixed excited states drives a strong spin relaxation of the conduction electrons via exchange interactions, reminiscent of the Bir-Aronov-Pikus process where exchange occurs with valence band hole states. Through low-temperature experiments with silicon spin transport devices and complementary theory, we reveal the consequences of this spin depolarization mechanism both below and above the impact ionization threshold.

  18. Mechanism of low-temperature-induced pollen failure in rice.

    PubMed

    Al Mamun, Ezaz; Cantrill, Laurence C; Overall, Robyn L; Sutton, Bruce G

    2010-05-01

    Low-temperature stress during microspore development alters cellular organization in rice anthers. The major cellular damage includes unusual starch accumulation in the plastids of the endothecium in postmeiotic anthers, abnormal vacuolation and hypertrophy of the tapetum, premature callose (1,3-beta-glucan) breakdown and lack of normal pollen wall formation. These cellular lesions arise from damage to critical biochemical processes that include sugar metabolism in the anthers and its use by the microspores. Failure of utilization of the callose breakdown product and other microspore wall components like sporopollenin can also be considered as critical. In recent years, considerable progress has been made in the understanding of major biochemical processes including the expression of critical genes that are sensitive to low temperature in rice and cause male sterility. This paper combines a discussion of cellular organization and associated biochemical processes that are sensitive to low temperatures and provides an overview of the potential mechanisms of low-temperature-induced male sterility in rice. PMID:20100170

  19. A low temperature thermal conductivity database

    NASA Astrophysics Data System (ADS)

    Woodcraft, Adam L.; Gray, Adam

    2009-12-01

    Low temperature detectors necessarily require low temperature instruments. Constructing good low temperature instruments requires information on the properties of materials used in their construction, in particular the thermal conductivity. Unfortunately, this is poorly known for many materials. Collections of data in text books tend to be incomplete and in the worst cases are misleading. For most materials, what information is known is scattered through the literature. Searching out this data is time consuming, and in any case often results in conflicting information. We have started a programme to locate, consolidate and critically analyse thermal conductivity measurements from the literature, particularly for the challenging temperature range below 1 K. This has already produced useful results. We present some preliminary results here.

  20. Understanding charge carrier relaxation processes in terbium arsenide nanoparticles using transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Vanderhoef, Laura R.

    Erbium arsenide nanoparticles epitaxially grown within III-V semiconductors have been shown to improve the performance of devices for applications ranging from thermoelectrics to THz pulse generation. The small size of rare-earth nanoparticles suggests that interesting electronic properties might emerge as a result of both spatial confinement and surface states. However, ErAs nanoparticles do not exhibit any signs of quantum confinement or an emergent bandgap, and these experimental observations are understood from theory. The incorporation of other rare-earth monopnictide nanoparticles into III-V hosts is a likely path to engineering carrier excitation, relaxation and transport dynamics for optoelectronic device applications. However, the electronic structure of these other rare-earth monopnictide nanoparticles remains poorly understood. The objective of this research is to explore the electronic structure and optical properties of III-V materials containing novel rare-earth monopnictides. We use ultrafast pump-probe spectroscopy to investigate the electronic structure of TbAs nanoparticles in III-V hosts. We start with TbAs:GaAs, which was expected to be similar to ErAs:GaAs. We study the dynamics of carrier relaxation into the TbAs states using optical pump terahertz probe transient absorption spectroscopy. By analyzing how the carrier relaxation rates depend on pump fluence and sample temperature, we conclude that the TbAs states are saturable. Saturable traps suggest the existence of a bandgap for TbAs nanoparticles, in sharp contrast with previous results for ErAs. We then apply the same experimental technique to two samples of TbAs nanoparticles in InGaAs with different concentrations of TbAs. We observe similar relaxation dynamics associated with trap saturation, though the ability to resolve these processes is contingent upon a high enough TbAs concentration in the sample. We have also constructed an optical pump optical probe transient absorption

  1. Revisiting the low-temperature dielectric properties of ZnO

    NASA Astrophysics Data System (ADS)

    Wang, Chunchang; Liu, Lina; Li, Qiuju; Huang, Shouguo; Zhang, Jian; Zheng, Jun; Cheng, Chao

    2014-09-01

    Electric modulus spectroscopy and impedance analysis were used to investigate the low-temperature (˜100-333 K) dielectric properties of ZnO crystals. Two relaxations were observed. The low-temperature relaxation (R1) features a thermally activated behavior resulting from the bulk response. Our results convincingly demonstrate that this relaxation is a polaronic relaxation. The relaxing species for R1 are localized holes created by zinc vacancies instead of the commonly agreed oxygen vacancies. The high-temperature relaxation (R2) is a Maxwell-Wagner relaxation due to skin-layer effect as it can be eliminated by grinding off the sample surface. The inhomogeneous distribution of zinc interstitials leads to the formation of the skin layer. Interestingly, an abnormal dielectric behavior contrary to the thermally activated behavior was found for the R2 relaxation. This abnormal behavior was confirmed to be related to the positive temperature coefficient of resistance due to the metal-insulator transition occurring within the skin layer.

  2. Influence of relaxation processes on the evaluation of the metastable defect density in Cu(In,Ga)Se2

    NASA Astrophysics Data System (ADS)

    Maciaszek, M.; Zabierowski, P.

    2016-06-01

    In this contribution, we investigated by means of numerical simulations the influence of relaxation processes related to metastable defects on electrical characteristics of Cu(In,Ga)Se2. In particular, we analyzed the relaxation of a metastable state induced by illumination at a fixed temperature as well as the dependence of the hole concentration on the temperature during cooling. The knowledge of these two relaxation processes is crucial in the evaluation of the hole concentration in the relaxed state and after light soaking. We have shown that the distribution of the metastable defects can be considered frozen below 200 K. The hole capture cross section was estimated as ˜3 × 10-15 cm2. It was shown that the usually used cooling rates may lead to relevant changes of the hole concentration. We calculated the lower limit of the hole concentration after cooling, and we presented how it depends on densities of shallow acceptors and metastable defects. Moreover, we proposed a method which allows for the evaluation of shallow acceptor and metastable defect densities from two capacitance-voltage profiles measured in the relaxed and light soaking states. Finally, we indicated experimental conditions in which the influence of relaxation processes on the accuracy of this method is the smallest.

  3. Uncovering Molecular Relaxation Processes with Nonlinear Spectroscopies in the Deep UV

    NASA Astrophysics Data System (ADS)

    West, Brantley Andrew

    Conical intersections mediate internal conversion dynamics that compete with even the fastest nuclear motions in molecular systems. Traditional kinetic models do not apply in this regime of commensurate electronic and nuclear motion because the surroundings do not maintain equilibrium throughout the relaxation process. This dissertation focuses on uncovering the physics associated with vibronic interactions at conical intersections. Of particular interest are coherent nuclear motions driven by steep excited state potential energy gradients. Technical advances have only recently made these dynamics accessible in many systems including DNA nucleobases and cyclic polyene molecules. Optical analogues of multidimensional NMR spectroscopies have recently yielded transformative insight in relaxation processes ranging from energy transfer in photosynthesis to bond making and breaking in liquids. Prior to the start of this research, such experiments had only been conducted at infrared and visible wavelengths. Applications in the ultraviolet were motivated by studies of numerous biological systems (e.g., DNA, proteins), but had been challenged by technical issues. The work presented in this dissertation combines pulse generation techniques developed in the optical physics community with spectroscopic techniques largely pioneered by physical chemists to implement two-dimensional ultraviolet spectroscopy (2DUV). This technique is applied at the shortest wavelengths and with the best signal-to-noise ratios reported to date. Sub-picosecond excited state deactivation processes provide photo stability to the DNA double helix. Vibrational energy transfer from the solute to surrounding solvent enables relaxation of the highly non-equilibrium ground state produced by fast internal conversion. In this dissertation, nonlinear spectroscopies carried out at cryogenic temperatures are used to uncover the particular nuclear modes in the solvent that primarily accept vibrational energy from

  4. Slow processes in viscous liquids: Stress and structural relaxation, chemical reaction freezing, crystal nucleation and microemulsion arrest, in relation to liquid fragility

    NASA Astrophysics Data System (ADS)

    Angell, C. A.; Alba, C.; Arzimanoglou, A.; Fan, J.; Böhmer, R.; Lu, Q.; Sanchez, E.; Senapati, H.; Tatsumisago, M.

    1992-05-01

    We review a variety of measurements on model systems in the medium viscosity range which seem consistent with both thermodynamical (entropy vanishing) and dynamical (mode coupling) origins of glassy behavior and then examine behavior near and below Tg to seek relations between liquid fragility and the non-exponential and non-linear aspects of liquid relaxation processes. We include the model ionic system Ca(NO3)2-KNO3 and analogs, van der Waals systems, and the covalently-bonded system Ge-As-Se in which the relation of liquid properties to the vector percolation concepts of Phillips and Thorpe can be conveniently studied. With some basic phenomenology in the liquid state itself thereby established, we turn attention to longer length-scale processes occurring in viscous liquid media. Among these will be the kinetics of nucleation of crystals, the freezing of microemulsion droplet sizes during continuous cooling of temperature sensitive microemulsions, and the freezing of chemical reactions during continuous cooling or continuous evaporation of solvent. The latter freezings can occur at temperatures which are far above the solvent glass transition temperature depending on solvent fragility, which may be a consideration in the strategies adopted by nature in preservation of plant and insect integrity in cold and arid climates. Finally we consider the slowing down which occurs in liquids with density maxima like water and SiO2 which appear to have, as their low temperature metastable limits, spinodal instabilities (with associated divergences in physical properties) in place of the usual ideal glass transitions. So far little studied for lack of tractable slow systems, these offer a new and challenging arena for relaxation studies.

  5. Relaxation dynamics of the phase transformation process at its ripening stage

    NASA Astrophysics Data System (ADS)

    Alexandrov, D. V.

    2015-06-01

    A complete analytical solution of the integro-differential model describing the transient phase transformation process at the Ostwald ripening stage is constructed. A new theoretical approach developed here is based on the recent theory (Alexandrov 2015 J. Phys. A: Math. Theor. 48 035103), where a new method was developed to account for the initial state (initial distribution function) at the ripening stage. The obtained relaxation solution contains two contributions proportional to {{e}-τ } (classical term) and {{e}-4τ /3} (the term predicted by Slezov), where τ is the dimensionless time. The distribution function obtained is more broad than the Lifshitz-Slyozov solution, lies below it, and has a supplementary tail on the right of the blocking point u=3/2, where u is the dimensionless spatial coordinate. The distribution function relaxes to earlier known solutions and is in good agreement with experimental data. The dynamics of number density and average radius of crystals is studied. The role of ‘diffusion’ term in the kinetic equation is discussed.

  6. Low temperature monitoring system for subsurface barriers

    SciTech Connect

    Vinegar, Harold J.; McKinzie, II. Billy John

    2009-08-18

    A system for monitoring temperature of a subsurface low temperature zone is described. The system includes a plurality of freeze wells configured to form the low temperature zone, one or more lasers, and a fiber optic cable coupled to at least one laser. A portion of the fiber optic cable is positioned in at least one freeze well. At least one laser is configured to transmit light pulses into a first end of the fiber optic cable. An analyzer is coupled to the fiber optic cable. The analyzer is configured to receive return signals from the light pulses.

  7. Two field-induced slow magnetic relaxation processes in a mononuclear Co(ii) complex with a distorted octahedral geometry.

    PubMed

    Li, Jing; Han, Yuan; Cao, Fan; Wei, Rong-Min; Zhang, Yi-Quan; Song, You

    2016-05-31

    A distorted octahedral Co(II) complex is reported with homoscorpionate ligands. This complex comprised a field-induced single-molecule magnet, showing two slow relaxation processes under a low dc field (<800 Oe) and only one process under a high dc field (≥800 Oe), which was an unusually discovery for 3d metal ions. On the basis of the ac magnetic data, we show for the first time that one of the slow relaxation processes in the low dc field originates from intermolecular dipolar interactions. Interestingly, the Raman process is predominant in the spin reversal relaxation process. The origin of the behaviours of the complex was elucidated by ab initio calculations. PMID:27180637

  8. Relaxation Processes in Aqueous Systems upon X-ray Ionization: Entanglement of Electronic and Nuclear Dynamics.

    PubMed

    Slavíček, Petr; Kryzhevoi, Nikolai V; Aziz, Emad F; Winter, Bernd

    2016-01-21

    The knowledge of primary processes following the interaction of high-energy radiation with molecules in liquid phase is rather limited. In the present Perspective, we report on a newly discovered type of relaxation process involving simultaneous autoionization and proton transfer between adjacent molecules, so-called proton transfer mediated charge separation (PTM-CS) process. Within PTM-CS, transients with a half-transferred proton are formed within a few femtoseconds after the core-level ionization event. Subsequent nonradiative decay of the highly nonequilibrium transients leads to a series of reactive species, which have not been considered in any high-energy radiation process in water. Nonlocal electronic decay processes are surprisingly accelerated upon proton dynamics. Such strong coupling of electronic and nuclear dynamics is a general phenomenon for hydrogen-bonded systems, however, its probability correlates strongly with hydration geometry. We suggest that the newly observed processes will impact future high-energy radiation-chemistry-relevant modeling, and we envision application of autoionization spectroscopy for identification of solution structure details. PMID:26712083

  9. The kinetics of the structural relaxation process in PHEMA-silica nanocomposites based on an equation for the configurational entropy

    NASA Astrophysics Data System (ADS)

    Théneau, C.; Salmerón Sánchez, M.; Rodrıguez Hernández, J. C.; Monleón Pradas, M.; Saiter, J. M.; Gómez Ribelles, J. L.

    2007-09-01

    The enthalpy relaxation of polymer-silica nanocomposites prepared by simultaneous polymerization of poly(2-hydroxyethyl methacrylate) (PHEMA) and tetraethyloxysilane, TEOS, a silica precursor, is investigated. Both the glass transition temperature, Tg, and the temperature interval of the glass transition, ΔTg , increase as the silica content in the sample does. Structural relaxation experiments show that the temperature interval in which conformational motions take place broadens as the silica content in the hybrid increases. A phenomenological model based on the evolution of the configurational entropy during the structural relaxation process, the SC model, has been used for determining the temperature dependence of the relaxation times during the process. The results show an increase of the fragility of the polymer as the silica content increases, a feature that can be related to the broadening of the distribution of relaxation times characterized by the β parameter of the stretched exponential distribution. On another hand the silica content increase produces a significant change of the relaxation times in the glassy state.

  10. Cryosurgery: ultrastructural changes in pancreas tissue after low temperature exposure.

    PubMed

    Korpan, N N

    2007-04-01

    A number of theoretical and experimental studies, both in vitro and in vivo, have been performed to explain the action of low temperatures on tissue. It is now evident that the thermal parameters used in the past for freezing during cryosurgery were not precise; this may have resulted in the failure of treatment. For the first time, this report describes the early ultrastructural features of pancreatic parenchyma after low temperature exposure, i.e., cryosurgery, in vivo. We demonstrate the effect of freeze-thawing processes using temperatures of various intensities. The cryosurgical response of pancreas parenchyma, i.e., ultrastructural cellular changes in pancreas tissue, was investigated. The electronic microscopic analysis showed that, after local cryodestruction at temperatures of -80 degrees C and -180 degrees C, similar processes occurred within the pancreas tissue in the early postcryosurgical phase -- immediately and up to 24 hours after low temperature exposure on tissue. The exocrine pancreatic cells in the center of the cryozone changed upon thawing. Ultrastructural changes in the exocrine pancreatic cells, where the first signs of dystrophic processes had been noticed, were increased. These ultrastructural changes in the pancreatic cells provide a platform to better understand the mechanisms of damage and the pathogenesis of frostbite after cryosurgery. The properties of the pancreas parenchyma response after low temperature exposure provide important insights into the mechanisms of damage and the cryogenic lesion immediately after thawing in cryosurgery. Our new insights prove on the cell level that suddenly and progressively damaged pancreatic cells in the postcryosurgical zone lead to aseptic cryonecrosis and then to aseptic cryoapoptosis of vital normal tissue. The vascular capillary changes and circulatory stagnation demonstrate the anti-angiogenesis mechanism, which, together with cryoaponecrosis and cryoapoptosis, are some of the main mechanisms

  11. Fuzzy Logic Controller for Low Temperature Application

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob; Gonzalez, A.; Barmatz, M.

    1996-01-01

    The most common temperature controller used in low temperature experiments is the proportional-integral-derivative (PID) controller due to its simplicity and robustness. However, the performance of temperature regulation using the PID controller depends on initial parameter setup, which often requires operator's expert knowledge on the system. In this paper, we present a computer-assisted temperature controller based on the well known.

  12. CVD growth of graphene at low temperature

    NASA Astrophysics Data System (ADS)

    Zeng, Changgan

    2012-02-01

    Graphene has attracted a lot of research interest owing to its exotic properties and a wide spectrum of potential applications. Chemical vapor deposition (CVD) from gaseous hydrocarbon sources has shown great promises for large-scale graphene growth. However, high growth temperature, typically 1000^oC, is required for such growth. In this talk, I will show a revised CVD route to grow graphene on Cu foils at low temperature, adopting solid and liquid hydrocarbon feedstocks. For solid PMMA and polystyrene precursors, centimeter-scale monolayer graphene films are synthesized at a growth temperature down to 400^oC. When benzene is used as the hydrocarbon source, monolayer graphene flakes with excellent quality are achieved at a growth temperature as low as 300^oC. I will also talk about our recent progress on low-temperature graphene growth using paraterphenyl as precursor. The successful low-temperature growth can be qualitatively understood from the first principles calculations. Our work might pave a way to economical and convenient growth route of graphene, as well as better control of the growth pattern of graphene at low temperature.

  13. Industrial Applications of Low Temperature Plasmas

    SciTech Connect

    Bardsley, J N

    2001-03-15

    The use of low temperature plasmas in industry is illustrated by the discussion of four applications, to lighting, displays, semiconductor manufacturing and pollution control. The type of plasma required for each application is described and typical materials are identified. The need to understand radical formation, ionization and metastable excitation within the discharge and the importance of surface reactions are stressed.

  14. Low temperature thermophysical properties of lunar soil

    NASA Technical Reports Server (NTRS)

    Cremers, C. J.

    1973-01-01

    The thermal conductivity and thermal diffusivity of lunar fines samples from the Apollo 11 and Apollo 12 missions, determined at low temperatures as a function of temperature and various densities, are reviewed. It is shown that the thermal conductivity of lunar soil is nearly the same as that of terrestrial basaltic rock under the same temperature and pressure conditions.

  15. Low-Temperature Seal for Actuator Rod

    NASA Technical Reports Server (NTRS)

    Lindfors, R. J.

    1985-01-01

    Combination bearing and seal used on Space Shuttle functions reliably at temperatures as low as - 160 degrees F and as high as + 130 degrees F. Corrosion-resistant stainless-steel spacer separates secondary and primary seals in both old and new versions of seal assembly. In new version, combination of flexible sealing lip and bridge is less susceptible to cracking at low temperatures.

  16. High and Low Temperature Oceanic Detachment Faults

    NASA Astrophysics Data System (ADS)

    Titarenko, Sofya; McCaig, Andrew

    2013-04-01

    One of the most important discoveries in Plate Tectonics in the last ten years is a "detachment mode" of seafloor spreading. Up to 50% of the Atlantic seafloor has formed by a combination of magmatism and slip on long-lived, convex-up detachment faults, forming oceanic core complexes (OCC). Two end-member types of OCC can be defined: The Atlantis Bank on the Southwest Indian Ridge is a high temperature OCC sampled by ODP Hole 735b. Deformation was dominated by crystal-plastic flow both above and below the solidus at 800-950 °C, over a period of around 200 ka. In contrast, the Atlantis Massif at 30 °N in the Atlantic, sampled by IODP Hole 1309D, is a low temperature OCC in which crystal plastic deformation of gabbro is very rare and greenschist facies deformation was localised onto talc-tremolite-chlorite schists in serpentinite, and breccia zones in gabbro and diabase. The upper 100m of Hole 1309D contains about 43% diabase intruded into hydrated fault breccias. This detachment fault zone can be interpreted as a dyke-gabbro transition, which was originally (before flexural unroofing) a lateral boundary between active hydrothermal circulation in the fault zone and hangingwall, and intrusion of gabbroic magma in the footwall. Thus a major difference between high and low temperature detachment faults may be cooling of the latter by active hydrothermal circulation. 2-D thermal modelling suggests that if a detachment fault is formed in a magmatically robust segment of a slow spreading ridge, high temperature mylonites can be formed for 1-2 ka provided there is no significant hydrothermal cooling of the fault zone. In contrast, if the fault zone is held at temperatures of 400 °C by fluid circulation, cooling of the upper 1 km of the fault footwall occurs far too rapidly for extensive mylonites to form. Our models are consistent with published cooling rate data from geospeedometry and isotopic closure temperatures. The control on this process is likely a combination of

  17. Composite Materials for Low-Temperature Applications

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Composite materials with improved thermal conductivity and good mechanical strength properties should allow for the design and construction of more thermally efficient components (such as pipes and valves) for use in fluid-processing systems. These materials should have wide application in any number of systems, including ground support equipment (GSE), lunar systems, and flight hardware that need reduced heat transfer. Researchers from the Polymer Science and Technology Laboratory and the Cryogenics Laboratory at Kennedy Space Center were able to develop a new series of composite materials that can meet NASA's needs for lightweight materials/composites for use in fluid systems and also expand the plastic-additive markets. With respect to thermal conductivity and physical properties, these materials are excellent alternatives to prior composite materials and can be used in the aerospace, automotive, military, electronics, food-packaging, and textile markets. One specific application of the polymeric composition is for use in tanks, pipes, valves, structural supports, and components for hot or cold fluid-processing systems where heat flow through materials is a problem to be avoided. These materials can also substitute for metals in cryogenic and other low-temperature applications. These organic/inorganic polymeric composite materials were invented with significant reduction in heat transfer properties. Decreases of 20 to 50 percent in thermal conductivity versus that of the unmodified polymer matrix were measured. These novel composite materials also maintain mechanical properties of the unmodified polymer matrix. These composite materials consist of an inorganic additive combined with a thermoplastic polymer material. The intrinsic, low thermal conductivity of the additive is imparted into the thermoplastic, resulting in a significant reduction in heat transfer over that of the base polymer itself, yet maintaining most of the polymer's original properties. Normal

  18. A new application of the nonlinear dielectric method for studying relaxation processes in liquids

    NASA Astrophysics Data System (ADS)

    Górny, M.; Ziolo, J.; Rzoska, S. J.

    1996-12-01

    The measurement setup for studying changes of electric permittivity induced in liquids by a strong electric field nonlinear dielectric effect, (NDE) is presented. The construction is based on the idea of frequency modulation of an LC generator (with an inductance L and a capacitance C in resonant circuit), proposed by Malecki [J. Chem. Soc. Faraday Trans. II 72, 104 (1976)]. The strong electric field is applied in the form of rectangular pulses (typically 1-4 ms). The setup enables measurements in a broad range of frequencies (80 kHz-12 MHz) and contains a new calibrating system, minimizing the influence of systematic error on the measured NDE values. We also indicate menthol as a standard, reference liquid in NDE studies. New applications of the NDE technique for studying relaxation processes in critical solution are also presented. They are based on the time resolved analysis of NDE decay after switching off the strong electric field.

  19. Nonlinear structural response using adaptive dynamic relaxation on a massively-parallel-processing system

    NASA Technical Reports Server (NTRS)

    Oakley, David R.; Knight, Norman F., Jr.

    1994-01-01

    A parallel adaptive dynamic relaxation (ADR) algorithm has been developed for nonlinear structural analysis. This algorithm has minimal memory requirements, is easily parallelizable and scalable to many processors, and is generally very reliable and efficient for highly nonlinear problems. Performance evaluations on single-processor computers have shown that the ADR algorithm is reliable and highly vectorizable, and that it is competitive with direct solution methods for the highly nonlinear problems considered. The present algorithm is implemented on the 512-processor Intel Touchstone DELTA system at Caltech, and it is designed to minimize the extent and frequency of interprocessor communication. The algorithm has been used to solve for the nonlinear static response of two and three dimensional hyperelastic systems involving contact. Impressive relative speedups have been achieved and demonstrate the high scalability of the ADR algorithm. For the class of problems addressed, the ADR algorithm represents a very promising approach for parallel-vector processing.

  20. Low Temperature Surface Carburization of Stainless Steels

    SciTech Connect

    Collins, Sunniva R; Heuer, Arthur H; Sikka, Vinod K

    2007-12-07

    Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility. LTCSS is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface with no risk of delamination or peeling. The treatment retains the austenitic phase and is completely non-magnetic. In addition, because parts are treated at low temperature, they do not distort or change dimensions. During this treatment, carbon diffusion proceeds into the metal at temperatures that constrain substitutional diffusion or mobility between the metal alloy elements. Though immobilized and unable to assemble to form carbides, chromium and similar alloying elements nonetheless draw enormous amounts of carbon into their interstitial spaces. The carbon in the interstitial spaces of the alloy crystals makes the surface harder than ever achieved before by more conventional heat treating or diffusion process. The carbon solid solution manifests a Vickers hardness often exceeding 1000 HV (equivalent to 70 HRC). This project objective was to extend the LTCSS treatment to other austenitic alloys, and to quantify improvements in fatigue, corrosion, and wear resistance. Highlights from the research include the following: • Extension of the applicability of the LTCSS process to a broad range of austenitic and duplex grades of steels • Demonstration of LTCSS ability for a variety of different component shapes and sizes • Detailed microstructural characterization of LTCSS-treated samples of 316L and other alloys

  1. Formation of silicon oxide grains at low temperature

    SciTech Connect

    Krasnokutski, S. A.; Rouillé, G.; Jäger, C.; Huisken, F.; Zhukovska, S.; Henning, Th.

    2014-02-10

    The formation of grains in the interstellar medium, i.e., at low temperature, has been proposed as a possibility to solve the lifetime problem of cosmic dust. This process lacks a firm experimental basis, which is the goal of this study. We have investigated the condensation of SiO molecules at low temperature using neon matrix and helium droplet isolation techniques. The energies of SiO polymerization reactions have been determined experimentally with a calorimetric method and theoretically with calculations based on the density functional theory. The combined experimental and theoretical values have revealed the formation of cyclic (SiO) {sub k} (k = 2-3) clusters inside helium droplets at T = 0.37 K. Therefore, the oligomerization of SiO molecules is found to be barrierless and is expected to be fast in the low-temperature environment of the interstellar medium on the surface of dust grains. The incorporation of numerous SiO molecules in helium droplets leads to the formation of nanoscale amorphous SiO grains. Similarly, the annealing and evaporation of SiO-doped Ne matrices lead to the formation of solid amorphous SiO on the substrate. The structure and composition of the grains were determined by infrared absorption spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Our results support the hypothesis that interstellar silicates can be formed in the low-temperature regions of the interstellar medium by accretion through barrierless reactions.

  2. Low-temperature thermochronology applied to ancient settings

    NASA Astrophysics Data System (ADS)

    Enkelmann, Eva; Garver, John I.

    2016-01-01

    Low-temperature thermochronometric dating techniques are commonly used to reveal and quantify the spatial and temporal pattern of cooling and exhumation in many active mountain belts. These methods illuminate the relationship between rock exhumation, and the processes that bring rock to the surface, including climate-driven surface processes. Thermochronological studies on rocks in ancient settings (Precambrian and Paleozoic) are far more complicated, and in general have largely failed to reveal exhumation processes in orogenic belts, mainly due to imprecision of the technique, complications from radiation damage, and subsequent resetting. However, in a few locations, remnants of the exhumation record of ancient orogens may be studied with low-temperature dating techniques and in these cases we can gather first-order information on tectonics, thermal events, and exhumation processes that have occurred in the deep past. Here we provide an overview of the most common low-temperature thermochronology methods of fission-track and (U-Th)/He dating of apatite and zircon and discuss methodological challenges in their application to old settings. We review several case studies from the Northern Appalachians, central Argentina, the Canadian Shield, central Wyoming, and the European Variscides where thermochronology data have been successful in reconstructing geologic processes in deep-time that have affected the upper crust. With these examples we provide sampling strategies and analytical approaches that partly circumvent issues related to radiation damage in old mineral grains that result in changes in the retention of helium and fission tracks.

  3. Relaxation System

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Environ Corporation's relaxation system is built around a body lounge, a kind of super easy chair that incorporates sensory devices. Computer controlled enclosure provides filtered ionized air to create a feeling of invigoration, enhanced by mood changing aromas. Occupant is also surrounded by multidimensional audio and the lighting is programmed to change colors, patterns, and intensity periodically. These and other sensory stimulators are designed to provide an environment in which the learning process is stimulated, because research has proven that while an individual is in a deep state of relaxation, the mind is more receptive to new information.

  4. Kolmogorov Turbulence in Low-Temperature Superflows

    SciTech Connect

    Nore, C.; Brachet, M.E.; Abid, M.

    1997-05-01

    Low-temperature decaying superfluid turbulence is studied using the nonlinear Schroedinger equation in the geometry of the Taylor-Green (TG) vortex flow with resolutions up to 512{sup 3}. The rate of (irreversible) kinetic energy transfer in the superfluid TG vortex is found to be comparable to that of the viscous TG vortex. At the moment of maximum dissipation, the energy spectrum of the superflow has an inertial range compatible with Kolmogorov`s scaling. Physical-space visualizations show that the vorticity dynamics of the superflow is similar to that of the viscous flow, including vortex reconnection. The implications to experiments in low-temperature helium are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  5. Cyclic and low temperature effects on microcircuits

    NASA Technical Reports Server (NTRS)

    Weissflug, V. A.; Sisul, E. V.

    1977-01-01

    Cyclic temperature and low temperature operating life tests, and pre-/post-life device evaluations were used to determine the degrading effects of thermal environments on microcircuit reliability. Low power transistor-transistor-logic gates and linear devices were included in each test group. Device metallization systems included aluminum metallization/aluminum wire, aluminum metallization/gold wire, and gold metallization/gold wire. Fewer than 2% electrical failures were observed during the cyclic and low temperature life tests and the post-life evaluations revealed approximately 2% bond pull failures. Reconstruction of aluminum die metallization was observed in all devices and the severity of the reconstruction appeared to be directly related to the magnitude of the temperature excursion. All types of bonds except the gold/gold bonds were weakened by exposure to repeated cyclic temperature stress.

  6. Surface-layer effect in MnTiO3 ceramics at low temperatures

    NASA Astrophysics Data System (ADS)

    Li, Teng; Wang, Chunchang; Sun, Xiaohong; Wang, Guojing; Lei, Changmei; Liu, Lina

    2012-12-01

    MnTiO3 ceramics were prepared via the traditional solid-state reaction route. The low-temperature (100-330 K) dielectric properties of MnTiO3 have been systematically investigated in the frequency range from 100 Hz to 5 MHz. Our results showed that MnTiO3 exhibits intrinsic dilectric response in a wide temperature range up to 200 K. A relaxation appears near room temperature. This relaxation can be enhanced by annealing treatment in oxygen and weakened in nitrogen. Reducing the sample thickness gradually leads to the disappearance of the relaxation. Based on these experimental facts, the relaxation was ascribed to be a Maxwell-Wagner relaxation due to surface-layer effect.

  7. Low-Temperature Hydrothermal Resource Potential

    DOE Data Explorer

    Katherine Young

    2016-06-30

    Compilation of data (spreadsheet and shapefiles) for several low-temperature resource types, including isolated springs and wells, delineated area convection systems, sedimentary basins and coastal plains sedimentary systems. For each system, we include estimates of the accessible resource base, mean extractable resource and beneficial heat. Data compiled from USGS and other sources. The paper (submitted to GRC 2016) describing the methodology and analysis is also included.

  8. Low-Temperature Hydrothermal Resource Potential Estimate

    DOE Data Explorer

    Katherine Young

    2016-06-30

    Compilation of data (spreadsheet and shapefiles) for several low-temperature resource types, including isolated springs and wells, delineated area convection systems, sedimentary basins and coastal plains sedimentary systems. For each system, we include estimates of the accessible resource base, mean extractable resource and beneficial heat. Data compiled from USGS and other sources. The paper (submitted to GRC 2016) describing the methodology and analysis is also included.

  9. Thermodynamic power stations at low temperatures

    NASA Astrophysics Data System (ADS)

    Malherbe, J.; Ployart, R.; Alleau, T.; Bandelier, P.; Lauro, F.

    The development of low-temperature thermodynamic power stations using solar energy is considered, with special attention given to the choice of the thermodynamic cycle (Rankine), working fluids (frigorific halogen compounds), and heat exchangers. Thermomechanical conversion machines, such as ac motors and rotating volumetric motors are discussed. A system is recommended for the use of solar energy for irrigation and pumping in remote areas. Other applications include the production of cold of fresh water from brackish waters, and energy recovery from hot springs.

  10. Low-Temperature Spacecraft: Challenges/Opportunities

    NASA Astrophysics Data System (ADS)

    Dickman, J. E.; Patterson, R. L.; Overton, E.; Hammoud, A. N.; Gerber, S. S.

    2001-01-01

    Imagine sending a spacecraft into deep space that operates at the ambient temperature of its environment rather than hundreds of degrees Kelvin warmer. The average temperature of a spacecraft warmed only by the sun drops from 279 K near the Earth's orbit to 90 K near the orbit of Saturn, and to 44 K near Pluto's orbit. At present, deep space probes struggle to maintain an operating temperature near 300 K for the onboard electronics. To warm the electronics without consuming vast amounts of electrical energy, radioisotope heater units (RHUs) are used in vast numbers. Unfortunately, since RHU are always 'on', an active thermal management system is required to reject the excess heat. A spacecraft designed to operate at cryogenic temperatures and shielded from the sun by a large communication dish or solar cell array could be less complex, lighter, and cheaper than current deep space probes. Before a complete low-temperature spacecraft becomes a reality, there are several challenges to be met. Reliable cryogenic power electronics is one of the major challenges. The Low-Temperature Power Electronics Research Group at NASA Glenn Research Center (GRC) has demonstrated the ability of some commercial off the shelf power electronic components to operate at temperatures approaching that of liquid nitrogen (77 K). Below 77 K, there exists an opportunity for the development of reliable semiconductor power switching technologies other than bulk silicon CMOS. This paper will report on the results of NASA GRC's Low-Temperature Power Electronics Program and discuss the challenges to (opportunities for) the creation of a low-temperature spacecraft.

  11. Low-temperature geothermal database for Oregon

    SciTech Connect

    Black, G.

    1994-11-01

    The goals of the low-temperature assessment project, performed by the Oregon Department of Geology and Mineral Industries (DOGAMI) is aimed primarily at updating the inventory of the nation's low and moderate temperature geothermal resources. The study has begun in Oregon, where the areas of Paisley, Lakeview, Burns/Hines, Lagrande, and Vale were identified over 40 sites as having potential for direct heat utilization. Specifics sites are outlined, detailing water temperature, flow, and current uses of the sites.

  12. Relaxation of Isolated Ventricular Cardiomyocytes by a Voltage-Dependent Process

    NASA Astrophysics Data System (ADS)

    Bridge, John H. B.; Spitzer, Kenneth W.; Ershler, Philip R.

    1988-08-01

    Cell contraction and relaxation were measured in single voltage-clamped guinea pig cardiomyocytes to investigate the contribution of sarcolemmal Na+-Ca2+ exchange to mechanical relaxation. Cells clamped from -80 to 0 millivolts displayed initial phasic and subsequent tonic contractions; caffeine reduced or abolished the phasic and enlarged the tonic contraction. The rate of relaxation from tonic contractions was steeply voltage-dependent and was significantly slowed in the absence of a sarcolemmal Na+ gradient. Tonic contractions elicited in the absence of a Na+ gradient promptly relaxed when external Na+ was applied, reflecting activation of Na+-Ca2+ exchange. It appears that a voltage-dependent Na+-Ca2+ exchange can rapidly mechanically relax mammalian heart muscle.

  13. Minimizing material damage using low temperature irradiation

    NASA Astrophysics Data System (ADS)

    Craven, E.; Hasanain, F.; Winters, M.

    2012-08-01

    Scientific advancements in healthcare driven both by technological breakthroughs and an aging and increasingly obese population have lead to a changing medical device market. Complex products and devices are being developed to meet the demands of leading edge medical procedures. Specialized materials in these medical devices, including pharmaceuticals and biologics as well as exotic polymers present a challenge for radiation sterilization as many of these components cannot withstand conventional irradiation methods. The irradiation of materials at dry ice temperatures has emerged as a technique that can be used to decrease the radiation sensitivity of materials. The purpose of this study is to examine the effect of low temperature irradiation on a variety of polymer materials, and over a range of temperatures from 0 °C down to -80 °C. The effectiveness of microbial kill is also investigated under each of these conditions. The results of the study show that the effect of low temperature irradiation is material dependent and can alter the balance between crosslinking and chain scission of the polymer. Low temperatures also increase the dose required to achieve an equivalent microbiological kill, therefore dose setting exercises must be performed under the environmental conditions of use.

  14. Honeycomb artificial spin ice at low temperatures

    NASA Astrophysics Data System (ADS)

    Zeissler, Katharina; Chadha, Megha; Cohen, Lesley; Branford, Will

    2015-03-01

    Artificial spin ice is a macroscopic playground for magnetically frustrated systems. It consists of a geometrically ordered but magnetically frustrated arrangement of ferromagnetic macros spins, e.g. an arrangement of single domain ferromagnetic nanowires on a honeycomb lattice. Permalloy and cobalt which have critical temperature scales far above 290 K, are commonly used in the construction of such systems. Previous measurements have shown unusual features in the magnetotransport signature of cobalt honeycomb artificial spin ice at temperatures below 50 K which are due to changes in the artificial spin ice's magnetic reversal. In that case, the artificial spin ice bars were 1 micron long, 100 nm wide and 20 nm thick. Here we explore the low temperature magnetic behavior of honeycomb artificial spin ice structures with a variety of bar dimensions, indirectly via electrical transport, as well as, directly using low temperature magnetic imaging techniques. We discuss the extent to which this change in the magnetic reversal at low temperatures is generic to the honeycomb artificial spin ice geometry and whether the bar dimensions have an influence on its onset temperature. The EPSRC (Grant No. EP/G004765/1; Grant No. EP/L504786/1) and the Leverhulme Trust (Grant No. RPG 2012-692) funded this scientific work.

  15. Dynamical States of Low Temperature Cirrus

    NASA Technical Reports Server (NTRS)

    Barahona, D.; Nenes, A.

    2011-01-01

    Low ice crystal concentration and sustained in-cloud supersaturation, commonly found in cloud observations at low temperature, challenge our understanding of cirrus formation. Heterogeneous freezing from effloresced ammonium sulfate, glassy aerosol, dust and black carbon are proposed to cause these phenomena; this requires low updrafts for cirrus characteristics to agree with observations and is at odds with the gravity wave spectrum in the upper troposphere. Background temperature fluctuations however can establish a dynamical equilibrium between ice production and sedimentation loss (as opposed to ice crystal formation during the first stages of cloud evolution and subsequent slow cloud decay) that explains low temperature cirrus properties. This newly-discovered state is favored at low temperatures and does not require heterogeneous nucleation to occur (the presence of ice nuclei can however facilitate its onset). Our understanding of cirrus clouds and their role in anthropogenic climate change is reshaped, as the type of dynamical forcing will set these clouds in one of two preferred microphysical regimes with very different susceptibility to aerosol.

  16. Convective heat transfer to low-temperature fluids

    NASA Technical Reports Server (NTRS)

    Graham, R. W.; Hendricks, R. C.; Simoneau, R. J.

    1974-01-01

    Research into forced and natural convection processes in low-temperature (cryogenic) fluids is reviewed with primary emphasis on forced convection. Boundaries of the near-critical region are defined, fluid properties near the critical state are discussed, and heat-transfer processes around the critical point are described. The thermodynamics of the critical point is analyzed together with transport properties of a near-critical fluid, and the quantum states of low-temperature molecular hydrogen (para and ortho) are discussed. Experimental work on heat transfer in free, natural, and forced convection systems is briefly summarized. Graham's (1969) penetration model for near-critical fluids is outlined, near-critical heat transfer is discussed in relation to conventional geometric effects, and the effects of curvature on the properties of near-critical hydrogen are noted. Theoretical considerations in free and forced convection are examined.

  17. Analysis of Low-Temperature Utilization of Geothermal Resources

    SciTech Connect

    Anderson, Brian

    2015-06-30

    Full realization of the potential of what might be considered “low-grade” geothermal resources will require that we examine many more uses for the heat than traditional electricity generation. To demonstrate that geothermal energy truly has the potential to be a national energy source we will be designing, assessing, and evaluating innovative uses for geothermal-produced water such as hybrid biomass-geothermal cogeneration of electricity and district heating and efficiency improvements to the use of cellulosic biomass in addition to utilization of geothermal in district heating for community redevelopment projects. The objectives of this project were: 1) to perform a techno-economic analysis of the integration and utilization potential of low-temperature geothermal sources. Innovative uses of low-enthalpy geothermal water were designed and examined for their ability to offset fossil fuels and decrease CO2 emissions. 2) To perform process optimizations and economic analyses of processes that can utilize low-temperature geothermal fluids. These processes included electricity generation using biomass and district heating systems. 3) To scale up and generalize the results of three case study locations to develop a regionalized model of the utilization of low-temperature geothermal resources. A national-level, GIS-based, low-temperature geothermal resource supply model was developed and used to develop a series of national supply curves. We performed an in-depth analysis of the low-temperature geothermal resources that dominate the eastern half of the United States. The final products of this study include 17 publications, an updated version of the cost estimation software GEOPHIRES, and direct-use supply curves for low-temperature utilization of geothermal resources. The supply curves for direct use geothermal include utilization from known hydrothermal, undiscovered hydrothermal, and near-hydrothermal EGS resources and presented these results at the Stanford

  18. Low-Temperature Synthesis Routes to Intermetallic Superconductors

    SciTech Connect

    Schaak, Raymond E

    2008-01-08

    Over the past few years, our group has gained expertise at developing low-temperature solution-based synthetic pathways to complex nanoscale solids, with particular emphasis on nanocrystalline intermetallic compounds. Our synthetic capabilities are providing tools to reproducibly generate intermetallic nanostructures with simultaneous control over crystal structure, composition, and morphology. This DOE-funded project aims to expand these capabilities to intermetallic superconductors. This could represent an important addition to the tools that are available for the synthesis and processing of intermetallic superconductors, which traditionally utilize high-temperature, high-pressure, thin film, or gas-phase vacuum deposition methods. Our current knowledge of intermetallic superconductors suggests that significant enhancements could result from the inherent benefits of low-temperature solution synthesis, e.g. metastable phase formation, control over nanoscale morphology to facilitate size-dependent property studies, robust and inexpensive processability, low-temperature annealing and consolidation, and impurity incorporation (for doping, stoichiometry control, flux pinning, and improving the critical fields). Our focus is on understanding the superconducting properties as a function of synthetic route, crystal structure, crystallite size, and morphology, and developing the synthetic tools necessary to accomplish this. This research program can currently be divided into two classes of superconducting materials: intermetallics (transition metal/post transition metal) and metal carbides/borides. Both involve the development and exploitation of low-temperature synthesis routes followed by detailed characterization of structures and properties, with the goal of understanding how the synthetic pathways influence key superconducting properties of selected target materials. Because of the low-temperature methods used to synthesize them and the nanocrystalline morphologies

  19. Method and apparatus for low temperature destruction of halogenated hydrocarbons

    DOEpatents

    Reagen, William Kevin; Janikowski, Stuart Kevin

    1999-01-01

    A method and apparatus for decomposing halogenated hydrocarbons are provided. The halogenated hydrocarbon is mixed with solvating agents and maintained in a predetermined atmosphere and at a predetermined temperature. The mixture is contacted with recyclable reactive material for chemically reacting with the recyclable material to create dehalogenated hydrocarbons and halogenated inorganic compounds. A feature of the invention is that the process enables low temperature destruction of halogenated hydrocarbons.

  20. Plasmon-mediated energy relaxation in graphene

    NASA Astrophysics Data System (ADS)

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    2015-12-01

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  1. Plasmon-mediated energy relaxation in graphene

    SciTech Connect

    Ferry, D. K.; Somphonsane, R.; Ramamoorthy, H.; Bird, J. P.

    2015-12-28

    Energy relaxation of hot carriers in graphene is studied at low temperatures, where the loss rate may differ significantly from that predicted for electron-phonon interactions. We show here that plasmons, important in the relaxation of energetic carriers in bulk semiconductors, can also provide a pathway for energy relaxation in transport experiments in graphene. We obtain a total loss rate to plasmons that results in energy relaxation times whose dependence on temperature and density closely matches that found experimentally.

  2. Dynamical and orientational structural crossovers in low-temperature glycerol

    NASA Astrophysics Data System (ADS)

    Seyedi, Salman; Martin, Daniel R.; Matyushov, Dmitry V.

    2016-07-01

    Mean-square displacements of hydrogen atoms in glass-forming materials and proteins, as reported by incoherent elastic neutron scattering, show kinks in their temperature dependence. This crossover, known as the dynamical transition, connects two approximately linear regimes. It is often assigned to the dynamical freezing of subsets of molecular modes at the point of equality between their corresponding relaxation times and the instrumental observation window. The origin of the dynamical transition in glass-forming glycerol is studied here by extensive molecular dynamics simulations. We find the dynamical transition to occur for both the center-of-mass translations and the molecular rotations at the same temperature, insensitive to changes of the observation window. Both the translational and rotational dynamics of glycerol show a dynamic crossover from the structural to a secondary relaxation at the temperature of the dynamical transition. A significant and discontinuous increase in the orientational Kirkwood factor and in the dielectric constant is observed in the same range of temperatures. No indication is found of a true thermodynamic transition to an ordered low-temperature phase. We therefore suggest that all observed crossovers are dynamic in character. The increase in the dielectric constant is related to the dynamic freezing of dipolar domains on the time scale of simulations.

  3. Dynamical and orientational structural crossovers in low-temperature glycerol.

    PubMed

    Seyedi, Salman; Martin, Daniel R; Matyushov, Dmitry V

    2016-07-01

    Mean-square displacements of hydrogen atoms in glass-forming materials and proteins, as reported by incoherent elastic neutron scattering, show kinks in their temperature dependence. This crossover, known as the dynamical transition, connects two approximately linear regimes. It is often assigned to the dynamical freezing of subsets of molecular modes at the point of equality between their corresponding relaxation times and the instrumental observation window. The origin of the dynamical transition in glass-forming glycerol is studied here by extensive molecular dynamics simulations. We find the dynamical transition to occur for both the center-of-mass translations and the molecular rotations at the same temperature, insensitive to changes of the observation window. Both the translational and rotational dynamics of glycerol show a dynamic crossover from the structural to a secondary relaxation at the temperature of the dynamical transition. A significant and discontinuous increase in the orientational Kirkwood factor and in the dielectric constant is observed in the same range of temperatures. No indication is found of a true thermodynamic transition to an ordered low-temperature phase. We therefore suggest that all observed crossovers are dynamic in character. The increase in the dielectric constant is related to the dynamic freezing of dipolar domains on the time scale of simulations. PMID:27575188

  4. Low-Temperature Plasma Functionalization of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Khare, Bishun; Meyyappan, M.

    2004-01-01

    A low-temperature plasma process has been devised for attaching specified molecular groups to carbon nanotubes in order to impart desired chemical and/or physical properties to the nanotubes for specific applications. Unlike carbon-nanotube- functionalization processes reported heretofore, this process does not involve the use of wet chemicals, does not involve exposure of the nanotubes to high temperatures, and generates very little chemical residue. In addition, this process can be carried out in a relatively simple apparatus and can readily be scaled up to mass production.

  5. Ionization yield and absorption spectra reveal superexcited Rydberg state relaxation processes in H2O and D2O

    NASA Astrophysics Data System (ADS)

    Fillion, J.-H.; Dulieu, F.; Baouche, S.; Lemaire, J.-L.; Jochims, H. W.; Leach, S.

    2003-07-01

    The absorption cross section and the ionization quantum yield of H2O have been measured using a synchrotron radiation source between 9 and 22 eV. Comparison between the two curves highlights competition between relaxation processes for Rydberg states converging to the first tilde A 2A 1 and to the second tilde B 2B 2 excited states of H2O+. Comparison with D2O absorption and ionization yields, derived from Katayama et al (1973 J. Chem. Phys. 59 4309), reveals specific energy-dependent deuteration effects on competitive predissociation and autoionization relaxation channels. Direct ionization was found to be only slightly affected by deuteration.

  6. Changes in Osmotic Pressure and Mucilage during Low-Temperature Acclimation of Opuntia ficus-indica 1

    PubMed Central

    Goldstein, Guillermo; Nobel, Park S.

    1991-01-01

    Opuntia ficus-indica, a Crassulacean acid metabolism plant cultivated for its fruits and cladodes, was used to examine chemical and physiological events accompanying low-temperature acclimation. Changes in osmotic pressure, water content, low molecular weight solutes, and extracellular mucilage were monitored in the photosynthetic chlorenchyma and the water-storage parenchyma when plants maintained at day/night air temperatures of 30/20°C were shifted to 10/0°C. An increase in osmotic pressure of 0.13 megapascal occurred after 13 days at 10/0°C. Synthesis of glucose, fructose, and glycerol accounted for most of the observed increase in osmotic pressure during the low-temperature acclimation. Extracellular mucilage and the relative apoplastic water content increased by 24 and 10%, respectively, during exposure to low temperatures. These increases apparently favor the extracellular nucleation of ice closer to the equilibrium freezing temperature for plants at 10/0°C, which could make the cellular dehydration more gradual and less damaging. Nuclear magnetic resonance studies helped elucidate the cellular processes during ice formation, such as those revealed by changes in the relaxation times of two water fractions in the chlorenchyma. The latter results suggested a restricted mobility of intracellular water and an increased mobility of extracellular water for plants at 10/0°C compared with those at 30/20°C. Increased mobility of extracellular water could facilitate extracellular ice growth and thus delay the potentially lethal intracellular freezing during low-temperature acclimation. PMID:16668536

  7. Low-temperature friction-stir welding of 2024 aluminum

    SciTech Connect

    Benavides, S.; Li, Y.; Murr, L.E.; Brown, D.; McClure, J.C.

    1999-09-10

    Solid-state, friction-stir welding (FSW) has been demonstrated to involve dynamic recrystallization producing ultra-fine, equiaxed grain structures to facilitate superplastic deformation as the welding or joining mechanism. Since the recrystallization temperature also decreases with increasing strain rate, the FSW process is somewhat complicated because the ambient temperature, the frictional heating fraction, and the adiabatic heating fraction (proportional to the product of strain and strain-rate) will all influence both the recrystallization and grain growth within the FSW zone. Significantly reducing the ambient temperature of the base metal or work pieces to be welded would be expected to reduce the residual weld-zone grain size. The practical consequences of this temperature reduction would be the achievement of low-temperature welding. This study compares the residual grain sizes and microstructures in 2024 Al friction-stir welded at room temperature ({approximately} 30 C) and low temperature ({minus} 30 C).

  8. Damping by slow relaxing rare earth impurities in Ni80Fe20.

    PubMed

    Woltersdorf, G; Kiessling, M; Meyer, G; Thiele, J-U; Back, C H

    2009-06-26

    Doping Ni80Fe20 by heavy rare earth atoms alters the magnetic relaxation properties of this material drastically. We show that this effect can be well explained by the slow relaxing impurity mechanism. This process is a consequence of the anisotropy of the on site exchange interaction between the 4f magnetic moments and the conduction band. As expected from this model the magnitude of the damping effect scales with the anisotropy of the exchange interaction and increases by an order of magnitude at low temperatures. In addition, our measurements allow us to determine the relaxation time of the 4f electrons as a function of temperature. PMID:19659120

  9. A low-temperature process for the denitration of Hanford single-shell tank, nitrate-based waste utilizing the nitrate to ammonia and ceramic (NAC) or nitrate to ammonia and glass (NAG) process: Phase 2 report

    SciTech Connect

    Mattus, A.J.; Walker, J.F. Jr.; Youngblood, E.L.; Farr, L.L.; Lee, D.D.; Dillow, T.A.; Tiegs, T.N.

    1994-12-01

    Continuing benchtop studies using Hanford single-shell tank (SST) simulants and actual Oak Ridge National Laboratory (ORNL) low-level waste (LLW), employing a new denitration process for converting nitrate to ammonia and ceramic (NAC), have conclusively shown that between 85 and 99% of the nitrate can be readily converted to gaseous ammonia. In this process, aluminum powders can be used to convert alkaline, nitrate-based supernate to ammonia and an aluminum oxide-sodium aluminate-based solid. The process may be able to use contaminated aluminum scrap metal from DOE sites to effect the conversion. The final, nitrate-free ceramic product can be pressed and sintered like other ceramics or silica and/or fluxing agents can be added to form a glassy ceramic or a flowable glass product. Based upon the starting volumes of 6.2 and 3.1 M sodium nitrate solution, volume reductions of 50 to 70% were obtained for the waste form produced. Sintered pellets produced from supernate from Melton Valley Storage Tanks (MVSTs) have been leached in accordance with the 16.1 leach test for the radioelements {sup 85}Sr and {sup 137}Cs. Despite lengthy counting times, {sup 85}Sr could not be detected in the leachates. {sup 137}Cs was only slightly above background and corresponded to a leach index of 12.2 to 13.7 after 8 months of leaching. Leach testing of unsintered and sintered reactor product spiked with hazardous metals proved that both sintered and unsintered product passed the Toxicity Characteristic Leaching Procedure (TCLP) test. Design of the equipment and flowsheet for a pilot demonstration-scale system to prove the nitrate destruction portion of the NAC process and product formation is under way.

  10. Vapor pressures of acetylene at low temperatures

    NASA Technical Reports Server (NTRS)

    Masterson, C. M.; Allen, John E., Jr.; Kraus, G. F.; Khanna, R. K.

    1990-01-01

    The atmospheres of many of the outer planets and their satellites contain a large number of hydrocarbon species. In particular, acetylene (C2H2) has been identified at Jupiter, Saturn and its satellite Titan, Uranus and Neptune. In the lower atmospheres of these planets, where colder temperatures prevail, the condensation and/or freezing of acetylene is probable. In order to obtain accurate models of the acetylene in these atmospheres, it is necessary to have a complete understanding of its vapor pressures at low temperatures. Vapor pressures at low temperatures for acetylene are being determined. The vapor pressures are measured with two different techniques in order to cover a wide range of temperatures and pressures. In the first, the acetylene is placed in a sample tube which is immersed in a low temperature solvent/liquid nitrogen slush bath whose temperature is measured with a thermocouple. The vapor pressure is then measured directly with a capacitance manometer. For lower pressures, a second technique which was called the thin-film infrared method (TFIR) was developed. It involves measuring the disappearance rate of a thin film of acetylene at a particular temperature. The spectra are then analyzed using previously determined extinction coefficient values, to determine the disappearance rate R (where R = delta n/delta t, the number of molecules that disappear per unit time). This can be related to the vapor pressure directly. This technique facilitates measurement of the lower temperatures and pressures. Both techniques have been calibrated using CO2, and have shown good agreement with the existing literature data.

  11. Noise thermometry at ultra-low temperatures.

    PubMed

    Rothfuss, D; Reiser, A; Fleischmann, A; Enss, C

    2016-03-28

    The options for primary thermometry at ultra-low temperatures are rather limited. In practice, most laboratories are using (195)Pt NMR thermometers in the microkelvin range. In recent years, current sensing direct current superconducting quantum interference devices (DC-SQUIDs) have enabled the use of noise thermometry in this temperature range. Such devices have also demonstrated the potential for primary thermometry. One major advantage of noise thermometry is the fact that no driving current is needed to operate the device and thus the heat dissipation within the thermometer can be reduced to a minimum. Ultimately, the intrinsic power dissipation is given by the negligible back action of the readout SQUID. For thermometry in low-temperature experiments, current noise thermometers and magnetic flux fluctuation thermometers have proved to be most suitable. To make use of such thermometers at ultra-low temperatures, we have developed a cross-correlation technique that reduces the amplifier noise contribution to a negligible value. For this, the magnetic flux fluctuations caused by the Brownian motion of the electrons in our noise source are measured inductively by two DC-SQUID magnetometers simultaneously and the signals from these two channels are cross-correlated. Experimentally, we have characterized a thermometer made of a cold-worked high-purity copper cylinder with a diameter of 5 mm and a length of 20 mm for temperatures between 42 μK and 0.8 K. For a given temperature, a measuring time below 1 min is sufficient to reach a precision of better than 1%. The extremely low power dissipation in the thermometer allows continuous operation without heating effects. PMID:26903101

  12. Femtosecond dynamics of fundamental reaction processes in liquids: Proton transfer, geminate recombination, isomerization and vibrational relaxation

    SciTech Connect

    Schwartz, B.J.

    1992-11-01

    The fast excited state intramolecular proton transfer of 3-hydroxyflavone is measured and effects of external hydrogen-bonding interactions on the proton transfer are studied. The proton transfer takes place in {approximately}240 fsec in nonpolar environments, but becomes faster than instrumental resolution of 110 fsec in methanol solution. The dynamics following photodissociation of CH{sub 2}I{sub 2} and other small molecules provide the first direct observations of geminate recombination. The recombination of many different photodissociating species occurs on a {approximately}350 fsec time scale. Results show that recombination yields but not rates depend on the solvent environment and suggest that recombination kinetics are dominated by a single collision with surrounding solvent cage. Studies of sterically locked phenyl-substituted butadienes offer new insights into the electronic structure and isomerization behavior of conjugated polyenes. Data show no simple correlation between hinderance of specific large amplitude motions and signatures of isomerizative behavior such as viscosity dependent excited state lifetimes, implying that the isomerization does not provide a suitable for simple condensed phase reaction rate theories. The spectral dynamics of a photochromic spiropyran indicate that recombination, isomerization and vibrational relaxation all play important roles in photoreactivity of complex molecules. The interplay of these microscopic phenomena and their effect on macroscopic properties such as photochromism are discussed. All the results indicate that the initial steps of the photochromic reaction process occur extremely rapidly. Laser system and computer codes for data analysis are discussed.

  13. Relationship between relaxation processes of light scattering in network of droplets

    NASA Astrophysics Data System (ADS)

    Sharifi, Soheil

    2015-02-01

    This work presents a study of the association behavior of different length scale of tri-block polymers in aqueous solution, in the presence of oil in water microemulsion nano-droplets. We have investigated various types of multiply bridging tri-block polymers and their effect on the structure and dynamics of droplets. A detailed structural form was obtained by X-ray scattering measurements, especially with respect to the effects on the droplet sizes and even more on the interactions in the microemulsion systems induced by the bridging tri-block polymer. The results show that the size of droplets is little affected by the addition of the polymer while the interactions are modified by the presence of the polymer. The dynamic response of the systems becomes much more complex with increasing number of arms and slow relaxation processes become very pronounced due to a much more efficient network formation. The distance between diffusion coefficient of slow and fast motion of droplets is increasing with increase of length scale of bridging tri-block polymer.

  14. Cellular Particle Dynamics simulation of biomechanical relaxation processes of multi-cellular systems

    NASA Astrophysics Data System (ADS)

    McCune, Matthew; Kosztin, Ioan

    2013-03-01

    Cellular Particle Dynamics (CPD) is a theoretical-computational-experimental framework for describing and predicting the time evolution of biomechanical relaxation processes of multi-cellular systems, such as fusion, sorting and compression. In CPD, cells are modeled as an ensemble of cellular particles (CPs) that interact via short range contact interactions, characterized by an attractive (adhesive interaction) and a repulsive (excluded volume interaction) component. The time evolution of the spatial conformation of the multicellular system is determined by following the trajectories of all CPs through numerical integration of their equations of motion. Here we present CPD simulation results for the fusion of both spherical and cylindrical multi-cellular aggregates. First, we calibrate the relevant CPD model parameters for a given cell type by comparing the CPD simulation results for the fusion of two spherical aggregates to the corresponding experimental results. Next, CPD simulations are used to predict the time evolution of the fusion of cylindrical aggregates. The latter is relevant for the formation of tubular multi-cellular structures (i.e., primitive blood vessels) created by the novel bioprinting technology. Work supported by NSF [PHY-0957914]. Computer time provided by the University of Missouri Bioinformatics Consortium.

  15. Superconducting layer thickness dependence of magnetic relaxation property in CVD processed YGdBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Shikimachi, K.; Watanabe, T.; Kashima, N.; Nagaya, S.

    2011-11-01

    One of the most important properties of coated conductors for Superconducting Magnetic Energy Storage (SMES) is the relaxation property of persistent superconducting current. This property can be quantitatively characterized by the apparent pinning potential U0∗. In this paper, the dependence of U0∗ on the thickness of superconducting layer d is investigated in the range of 0.33-1.43 μm at the temperature range of 20-30 K and in magnetic fields up to 6.5 T for Y 0.7Gd 0.3Ba 2Cu 3O 7- δ coated conductors. It was found that the value of critical current density did not appreciably depend on d at 20 K. This indicates that no structural deterioration of superconducting layer occurs during the process of increasing thickness. U0∗ increases and then tends to decrease with an increasing magnetic field. The magnetic field at which U0∗ starts to decrease increases with increasing thickness. This property was analyzed using the flux creep-flow model. Application of scaling law is examined for the dependence of U0∗ on magnetic field and temperature. It was found that the dependence could be expressed using scaling parameters B,U0 peak∗ in the temperature range 20-30 K.

  16. Femtosecond Dynamics of Fundamental Reaction Processes in Liquids: Proton Transfer, Geminate Recombination, Isomerization and Vibrational Relaxation.

    NASA Astrophysics Data System (ADS)

    Schwartz, Benjamin Joel

    Femtosecond and picosecond transient absorption spectroscopy are used to probe several fundamental aspects of chemical reactivity in the condensed phase including proton transfer, germinate recombination, isomerization and vibrational relaxation. The fast excited state intramolecular proton transfer of 3-hydroxyflavone is measured for the first time, and the effects of external hydrogen-bonding interactions on the proton transfer are studied in detail. The proton transfer takes place in ~240 fsec in non-polar environments, but becomes faster than the instrumental resolution of 110 fsec in methanol solutions. A simple model is proposed to explain these results. The dynamics following photodissociation of CH _2I_2 and other small molecules provide the first direct observations of germinate recombination. The recombination of many different photodissociating species occurs on a ~350 fsec time scale. Results also show that recombination yields but not rates depend on the molecular details of the solvent environment and suggest that recombination kinetics are dominated by a single collision with the surrounding solvent cage. Studies of sterically locked phenyl-substituted butadienes offer new insights into the electronic structure and isomerization behavior of conjugated polyenes. The data show no simple correlation between the hinderance of specific large amplitude motions and signatures of isomerizative behavior such as viscosity dependent excited state lifetimes. This strongly implies that the isomerization of these systems does not provide a suitable testing ground for simple condensed phase reaction rate theories. The spectral dynamics of a photochromic spiropyran indicate that recombination, isomerization and vibrational relaxation all play important roles in the photoreactivity of complex molecules. The interplay of these microscopic phenomena and their effect on macroscopic properties such as photochromism are discussed. All the results indicate that the initial

  17. Investigations of Low Temperature Time Dependent Cracking

    SciTech Connect

    Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J

    2002-09-30

    The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.

  18. The development of low temperature curing adhesives

    NASA Technical Reports Server (NTRS)

    Green, H. E.; Sutherland, J. D.; Hom, J. M.; Sheppard, C. H.

    1975-01-01

    An approach for the development of a practical low temperature (293 K-311 K/68 F-100 F) curing adhesive system based on a family of amide/ester resins was studied and demonstrated. The work was conducted on resin optimization and adhesive compounding studies. An improved preparative method was demonstrated which involved the reaction of an amine-alcohol precursor, in a DMF solution with acid chloride. Experimental studies indicated that an adhesive formulation containing aluminum powder provided the best performance when used in conjunction with a commercial primer.

  19. Ionometric determination of fluorides at low temperatures

    SciTech Connect

    Kostyukova, I.S.; Ennan, A.A.; Dzerzhko, E.K.; Leivikova, A.A.

    1995-12-01

    A method for determining fluoride ions in solution at low temperatures using a solid-contact fluorine-selective electrode (FSE) has been developed. The effect of temperature (60 to -15{degrees}C) on the calibration slope, potential equilibrium time, and operational stability is studied; the effect of an organic additive (cryoprotector) on the calibration slope is also studied. The temperature relationships obtained for the solid-contact FSEs allow appropriate corrections to be applied to the operational algorithm of the {open_quotes}Ftoring{close_quotes} hand-held semiautomatic HF gas analyzer for the operational temperature range of -16 to 60{degrees}C.

  20. Low temperature photoresponse of monolayer tungsten disulphide

    SciTech Connect

    Cao, Bingchen; Shen, Xiaonan; Shang, Jingzhi; Cong, Chunxiao; Yang, Weihuang; Eginligil, Mustafa E-mail: meginligil@ntu.edu.sg; Yu, Ting E-mail: meginligil@ntu.edu.sg

    2014-11-01

    High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD) method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup), while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  1. Cryocoolers near their low-temperature limit

    NASA Astrophysics Data System (ADS)

    de Waele, A. T. A. M.

    2015-07-01

    This paper analyses the recently-observed temperature-time dependence in a GM-cooler near its low-temperature limit. The paper mainly focusses on GM-coolers with 4He as the working fluid, but some attention is also paid to pulse-tube refrigerators (PTR's) using 3He and many features of the treatment equally apply to Stirling coolers. Ample attention is paid to the thermodynamics of the cycle by considering the isentropes in the Tp-diagrams of 4He and 3He. The role of the line, where the thermal expansion coefficient is zero, is emphasized. Some fundamental thermodynamic relationships are derived.

  2. Low temperature breakers for gelled fracturing fluids

    SciTech Connect

    Syrinek, A.R.; Lyon, L.B.

    1989-01-03

    A method is described for breaking gelled viscosities of oil-based gelled fracturing fluids containing a gellant comprising aluminum complexes of alkyl phosphate esters and a proppant. The fracturing fluids are used in low-temperature formations having operating temperatures ranging between 60/sup 0/ - 120/sup 0/F. The oil-based gelled fracturing fluids are treated with an effective viscosity breaking amount of a chemical breaker consisting essentially of an admixture of hydrated lime and sodium bicarbonate containing a weight ratio ranging between 100/0 to about 20/80 hydrated lime to sodium bicarbonate.

  3. Low temperature steam and formaldehyde sterilization.

    PubMed

    Robertshaw, R G

    1983-09-01

    A standard low temperature steam/formaldehyde autoclave was tested according to the manufacturer's instructions, using a range of test pieces containing Bacillus stearothermophilus spores as the challenge organism. There were failures in killing the challenge organism and the reasons for these are discussed. A description of modifications made to the autoclave is given together with details of an improved operating cycle. The performance of the modified autoclave was greatly improved and conditions were established for reliable and consistent sterilization of all the test pieces. A commercially produced prototype autoclave similarly modified also showed effective sterilization. PMID:6195245

  4. Transport in Strained Graphene at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Aguilera-Servin, Juan; Nosek, Adrian; Pan, Cheng; Bockrath, Marc

    2015-03-01

    Strain in graphene layers produces synthetic gauge fields that may be used to modify the properties of its electron system. We study single layers of graphene transferred over Ti/Au electrical contacts on oxidized Si wafers with etched triangular holes in the oxide. The layers are strained by applying pressure electrostatically using a gate voltage and hydrostatically using an external inert gas. We investigate electronic transport in this suspended variable-strain graphene system at low temperatures. We will discuss our latest results.

  5. Low-temperature magnetic resonance force microscopy

    NASA Astrophysics Data System (ADS)

    Wago, Koichi

    Magnetic resonance force microscopy (MRFM) is a technique whose goal is to combine the three-dimensional, chemically specific imaging capability of magnetic resonance imaging with the atomic-scale spatial resolution of scanning force microscopy. MRFM relies on the detection of small oscillatory magnetic forces between spins in the sample and a magnetic tip, using a micromechanical cantilever. The force resolution is a key issue for successfully operating MRFM experiments. Operating at low temperature improves the force resolution because of the reduced thermal energy and increased mechanical Q of the cantilever. The spin polarization is also enhanced at low temperature, leading to the improved magnetic resonance sensitivity for ensemble spin samples. A low-temperature magnetic resonance force detection apparatus was built and used to demonstrate a force resolution of 8×10sp{-17}\\ N/sqrt{Hz} at 6 K with a commercial single-crystal silicon cantilever. Both nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) were detected in micron-size samples. Force-detection technique was also applied to a wide range of magnetic resonance measurements, including inversion recovery, nutation, and spin echoes. Force-detected EPR spectra of phosphorus-doped silicon revealed hyperfine splitting, illustrating the possibility of using the MRFM technique for spectroscopic purposes. An improved low-temperature magnetic resonance force microscope was also built, incorporating a magnetic tip mounted directly on the cantilever. This allows a much wider variety of samples to be investigated and greatly improves the convenience of the technique. Using the improved microscope, three-dimensional EPR imaging of diphenylpicrylhydrazil (DPPH) particles was accomplished by scanning the sample in two dimensions while stepping an external field. The EPR force map showed a broad response reflecting the size and shape of the sample, allowing a three-dimensional real

  6. Electronics for Low Temperature Space Exploration Missions

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Hammoud, Ahmad; Elbuluk, Malik

    2007-01-01

    Exploration missions to outer planets and deep space require spacecraft, probes, and on-board data and communication systems to operate reliably and efficiently under severe harsh conditions. On-board electronics, in particular those in direct exposures to the space environment without any shielding or protection, will encounter extreme low temperature and thermal cycling in their service cycle in most of NASA s upcoming exploration missions. For example, Venus atmosphere, Jupiter atmosphere, Moon surface, Pluto orbiter, Mars, comets, Titan, Europa, and James Webb Space Telescope all involve low-temperature surroundings. Therefore, electronics for space exploration missions need to be designed for operation under such environmental conditions. There are ongoing efforts at the NASA Glenn Research Center (GRC) to establish a database on the operation and reliability of electronic devices and circuits under extreme temperature operation for space applications. This work is being performed under the Extreme Temperature Electronics Program with collaboration and support of the NASA Electronic Parts and Packaging (NEPP) Program. The results of these investigations will be used to establish safe operating areas and to identify degradation and failure modes, and the information will be disseminated to mission planners and system designers for use as tools for proper part selection and in risk mitigation. An overview of this program along with experimental data will be presented.

  7. Antimisting kerosene: Low temperature degradation and blending

    NASA Technical Reports Server (NTRS)

    Yavrouian, A.; Parikh, P.; Sarohia, V.

    1988-01-01

    The inline filtration characteristics of freshly blended and degraded antimisting fuels (AMK) at low temperature are examined. A needle valve degrader was modified to include partial recirculation of degraded fuel and heat addition in the bypass loop. A pressure drop across the needle valve of up to 4,000 psi was used. The pressure drop across a 325 mesh filter screen placed inline with the degrader and directly downstream of the needle valve was measured as a function of time for different values of pressure drop across the needle valve. A volume flux of 1 gpm/sq in was employed based on the frontal area of the screen. It was found that, at ambient temperatures, freshly blended AMK fuel could be degraded using a single pass degradation at 4,000 psi pressure drop across the needle valve to give acceptable filterability performance. At fuel temperatures below -20 C, degradation becomes increasingly difficult and a single pass technique results in unacceptable filtration performance. Recirculation of a fraction of the degraded fuel and heat addition in the bypass loop improved low temperature degradation performance. The problem is addressed of blending the AMK additive with Jet A at various base fuel temperatures.

  8. Bone marrow segmentation based on a combined consideration of transverse relaxation processes and Dixon oscillations.

    PubMed

    Balasubramanian, Mukund; Jarrett, Delma Y; Mulkern, Robert V

    2016-05-01

    The aim of this study was to demonstrate that gradient-echo sampling of single spin echoes can be used to isolate the signal from trabecular bone marrow, with high-quality segmentation and surface reconstructions resulting from the application of simple post-processing strategies. Theoretical expressions of the time-domain single-spin-echo signal were used to simulate signals from bone marrow, non-bone fatty deposits and muscle. These simulations were compared with and used to interpret signals obtained by the application of the gradient-echo sampling of a spin-echo sequence to image the knee and surrounding tissues at 1.5 T. Trabecular bone marrow has a much higher reversible transverse relaxation rate than surrounding non-bone fatty deposits and other musculoskeletal tissues. This observation, combined with a choice of gradient-echo spacing that accentuates Dixon-type oscillations from chemical-shift interference effects, enabled the isolation of bone marrow signal from surrounding tissues through the use of simple image subtraction and thresholding. Three-dimensional renderings of the marrow surface were then readily generated with this approach - renderings that may prove useful for bone morphology assessment, e.g. for the measurement of femoral anteversion. In conclusion, understanding the behavior of signals from bone marrow and surrounding tissue as a function of time through a spin echo facilitates the segmentation and reconstruction of bone marrow surfaces using straightforward post-processing strategies that are typically available on modern radiology workstations. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26866627

  9. RNA Silencing Is Resistant to Low-Temperature in Grapevine

    PubMed Central

    Romon, Marjorie; Soustre-Gacougnolle, Isabelle; Schmitt, Carine; Perrin, Mireille; Burdloff, Yannick; Chevalier, Elodie; Mutterer, Jérome; Himber, Christophe; Zervudacki, Jérôme; Montavon, Thomas; Zimmermann, Aude; Elmayan, Taline; Vaucheret, Hervé; Dunoyer, Patrice; Masson, Jean E.

    2013-01-01

    RNA silencing is a natural defence mechanism against viruses in plants, and transgenes expressing viral RNA-derived sequences were previously shown to confer silencing-based enhanced resistance against the cognate virus in several species. However, RNA silencing was shown to dysfunction at low temperatures in several species, questioning the relevance of this strategy in perennial plants such as grapevines, which are often exposed to low temperatures during the winter season. Here, we show that inverted-repeat (IR) constructs trigger a highly efficient silencing reaction in all somatic tissues in grapevines. Similarly to other plant species, IR-derived siRNAs trigger production of secondary transitive siRNAs. However, and in sharp contrast to other species tested to date where RNA silencing is hindered at low temperature, this process remained active in grapevine cultivated at 4°C. Consistently, siRNA levels remained steady in grapevines cultivated between 26°C and 4°C, whereas they are severely decreased in Arabidopsis grown at 15°C and almost undetectable at 4°C. Altogether, these results demonstrate that RNA silencing operates in grapevine in a conserved manner but is resistant to far lower temperatures than ever described in other species. PMID:24376561

  10. A review of the slow relaxation processes in the glass-rubber transition region of amorphous polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; He, Xianru; Huang, Guangsu

    2015-09-01

    This article is a review that introduces several articles about slow relaxation processes, also known as slower segmental dynamics. According to the literature, the coupling effect and free volume holes are two important elements for slower micro-dynamics. In addition, the slower processes of many-body systems (blend and diluted systems) are summarised. A good numerical method for detecting multiple modes in the glass-rubber transition region is introduced.

  11. Crystallization and doping of amorphous silicon on low temperature plastic

    DOEpatents

    Kaschmitter, J.L.; Truher, J.B.; Weiner, K.H.; Sigmon, T.W.

    1994-09-13

    A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate is disclosed. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900 C), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180 C for more than a few microseconds. This method enables use of plastics incapable of withstanding sustained processing temperatures (higher than 180 C) but which are much lower cost, have high tolerance to ultraviolet light, have high strength and good transparency, compared to higher temperature plastics such as polyimide. 5 figs.

  12. Crystallization and doping of amorphous silicon on low temperature plastic

    DOEpatents

    Kaschmitter, James L.; Truher, Joel B.; Weiner, Kurt H.; Sigmon, Thomas W.

    1994-01-01

    A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900.degree. C.), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180.degree. C. for more than a few microseconds. This method enables use of plastics incapable of withstanding sustained processing temperatures (higher than 180.degree. C.) but which are much lower cost, have high tolerance to ultraviolet light, have high strength and good transparency, compared to higher temperature plastics such as polyimide.

  13. Metal stable isotopes in low-temperature systems: A primer

    USGS Publications Warehouse

    Bullen, T.D.; Eisenhauer, A.

    2009-01-01

    Recent advances in mass spectrometry have allowed isotope scientists to precisely determine stable isotope variations in the metallic elements. Biologically infl uenced and truly inorganic isotope fractionation processes have been demonstrated over the mass range of metals. This Elements issue provides an overview of the application of metal stable isotopes to low-temperature systems, which extend across the borders of several science disciplines: geology, hydrology, biology, environmental science, and biomedicine. Information on instrumentation, fractionation processes, data-reporting terminology, and reference materials presented here will help the reader to better understand this rapidly evolving field.

  14. Programming Enhancements for Low Temperature Thermal Decomposition Workstation

    SciTech Connect

    Igou, R.E.

    1998-10-01

    This report describes a new control-and-measurement system design for the Oak Ridge Y-12 Plant's Low Temperature Thermal Decomposition (LTTD) process. The new design addresses problems with system reliability stemming from equipment obsolescence and addresses specific functional improvements that plant production personnel have identified, as required. The new design will also support new measurement techniques, which the Y-12 Development Division has identified for future operations. The new techniques will function in concert with the original technique so that process data consistency is maintained.

  15. The Low Temperature Microgravity Physics Experiments Project

    NASA Technical Reports Server (NTRS)

    Holmes, Warren; Lai, Anthony; Croonquist, Arvid; Chui, Talso; Eraker, J. H.; Abbott, Randy; Mills, Gary; Mohl, James; Craig, James; Balachandra, Balu; Gannon, Jade

    2000-01-01

    The Low Temperature Microgravity Physics Facility (LTMPF) is being developed by NASA to provide long duration low temperature and microgravity environment on the International Space Station (ISS) for performing fundamental physics investigations. Currently, six experiments have been selected for flight definition studies. More will be selected in a two-year cycle, through NASA Research Announcement. This program is managed under the Low Temperature Microgravity Physics Experiments Project Office at the Jet Propulsion Laboratory. The facility is being designed to launch and returned to earth on a variety of vehicles including the HII-A and the space shuttle. On orbit, the facility will be connected to the Exposed Facility on the Japanese Experiment Module, Kibo. Features of the facility include a cryostat capable of maintaining super-fluid helium at a temperature of 1.4 K for 5 months, resistance thermometer bridges, multi-stage thermal isolation system, thermometers capable of pico-Kelvin resolution, DC SQUID magnetometers, passive vibration isolation, and magnetic shields with a shielding factor of 80dB. The electronics and software architecture incorporates two VME buses run using the VxWorks operating system. Technically challenging areas in the design effort include the following: 1) A long cryogen life that survives several launch and test cycles without the need to replace support straps for the helium tank. 2) The minimization of heat generation in the sample stage caused by launch vibration 3) The design of compact and lightweight DC SQUID electronics. 4) The minimization of RF interference for the measurement of heat at pico-Watt level. 5) Light weighting of the magnetic shields. 6) Implementation of a modular and flexible electronics and software architecture. The first launch is scheduled for mid-2003, on an H-IIA Rocket Transfer Vehicle, out of the Tanegashima Space Center of Japan. Two identical facilities will be built. While one facility is onboard

  16. Radically Different Kinetics at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Sims, Ian

    2014-06-01

    The use of the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme, or Reaction Kinetics in Uniform Supersonic Flow) technique coupled with pulsed laser photochemical kinetics methods has shown that reactions involving radicals can be very rapid at temperatures down to 10 K or below. The results have had a major impact in astrochemistry and planetology, as well as proving an exacting test for theory. The technique has also been applied to the formation of transient complexes of interest both in atmospheric chemistry and combustion. Until now, all of the chemical reactions studied in this way have taken place on attractive potential energy surfaces with no overall barrier to reaction. The F + H2 {→} HF + H reaction does possess a substantial energetic barrier ({\\cong} 800 K), and might therefore be expected to slow to a negligible rate at very low temperatures. In fact, this H-atom abstraction reaction does take place efficiently at low temperatures due entirely to tunneling. I will report direct experimental measurements of the rate of this reaction down to a temperature of 11 K, in remarkable agreement with state-of-the-art quantum reactive scattering calculations by François Lique (Université du Havre) and Millard Alexander (University of Maryland). It is thought that long chain cyanopolyyne molecules H(C2)nCN may play an important role in the formation of the orange haze layer in Titan's atmosphere. The longest carbon chain molecule observed in interstellar space, HC11N, is also a member of this series. I will present new results, obtained in collaboration with Jean-Claude Guillemin (Ecole de Chimie de Rennes) and Stephen Klippenstein (Argonne National Labs), on reactions of C2H, CN and C3N radicals (using a new LIF scheme by Hoshina and Endo which contribute to the low temperature formation of (cyano)polyynes. H. Sabbah, L. Biennier, I. R. Sims, Y. Georgievskii, S. J. Klippenstein, I. W. M. Smith, Science 317, 102 (2007). S. D. Le Picard, M

  17. Ultrafast dynamics of liquid water: Energy relaxation and transfer processes of the OH stretch and the HOH bend

    SciTech Connect

    Imoto, Sho; Xantheas, Sotiris S.; Saito, Shinji

    2015-08-27

    The vibrational energy relaxation and transfer processes of the OH stretching and the HOH bending vibrations in liquid water are investigated via the theoretical calculation of the pump-probe spectra obtained from non-equilibrium molecular dynamics simulations with the TTM3-F interaction potential. The excitation of the OH stretch induces an instantaneous response of the high frequency librational motions in the 600-1000 cm-1 range. In addition, the excess energy of the OH stretch of a water molecule quickly transfers to the OH stretches of molecules in its first hydration shell with a time constant of ~50 fs, followed by relaxation to the HOH bends of the surrounding molecules with a time constant of 230 fs. The excitation of the HOH bend also results in the ultrafast excitation of the high frequency librational motions. The energy of the excited HOH bend of a water molecule decays, with a time constant of 200 fs, mainly to the relaxation of the HOH bends of its surrounding molecules. The energies of the HOH bends were found to transfer quickly to the intermolecular motions via the coupling with the high frequency librational motions. The excess energy of the OH stretch or the HOH bend relaxes to the high frequency intermolecular librational motions and eventually to the hot ground state with a time scale of ~1 ps via the coupling with the librational and translational motions. The energy relaxation and transfer processes were found to depend on the local hydrogen bonding network; the relaxations of the excess energy of the OH stretch and the HOH bend of four- and five-coordinated molecules are faster than those of a three-coordinated molecule due to the delocalization of the vibrational motions of the former (four- and five-coordinated molecules) compared to those of the later (three-coordinated molecules). The present results highlight the importance of the high frequency intermolecular librational modes in facilitating the ultrafast energy relaxation process in

  18. Low temperature synthesis of zinc ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Bardhan, A.; Ghosh, C. K.; Mitra, M. K.; Das, G. C.; Mukherjee, S.; Chattopadhyay, K. K.

    2010-05-01

    Zinc ferrite (ZnFe 2O 4) nanocrystalline powder materials with various particle sizes were prepared by a unique solid-state combustion method. Phase purity of ZnFe 2O 4 was confirmed by X-ray diffraction studies. High resolution transmission electron microscopic analysis and selected area diffraction pattern also confirmed the correct crystalline phase formation. Particle size was determined from both the transmission electron microscopic images and also from the XRD peak broadening analysis. Oxidation states of different elements present in ZnFe 2O 4 were determined by X-ray photoelectron spectroscopy. Frequency dependent dielectric constant and a.c. conductivity were measured as a function of particle size and both of them were found to decrease with decreasing particle size. These studies indicated that good quality zinc ferrite nanocrystalline powdered materials can be synthesized at low temperature.

  19. Low Temperature SQUID for NDE Applications

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz (Technical Monitor); Selim, Raouf

    2003-01-01

    We have developed a low temperature SuperConducting Quantum Interference Device - SQUID measurement system for detection of defects deep under the surface of aluminum structures using eddy current techniques. The system uses a two dimensional planar inducer with two different excitation frequencies to induce a current in the sample. We have developed a data analysis software program that enabled us to distinguish between round defects (holes), straight defects (slots) and slots close to holes simulating cracks starting from rivets in aluminum structures. We were able to detect defects that are 8mm below the surface. We have also measured the change in phase of the detected signal as a function of depth of the defect. This relationship can be used to determine the depth of hidden flaws. Using this analysis software with the high temperature SQUID system at NASA Langley we were able to detect slots close to holes in layered aluminum sample.

  20. Magnetic refrigeration for low-temperature applications

    NASA Technical Reports Server (NTRS)

    Barclay, J. A.

    1985-01-01

    The application of refrigeration at low temperatures ranging from production of liquid helium for medical imaging systems to cooling of infrared sensors on surveillance satellites is discussed. Cooling below about 15 K with regenerative refrigerators is difficult because of the decreasing thermal mass of the regenerator compared to that of the working material. In order to overcome this difficulty with helium gas as the working material, a heat exchanger plus a Joule-Thomson or other exponder is used. Regenerative magnetic refrigerators with magnetic solids as the working material have the same regenerator problem as gas refrigerators. This problem provides motivation for the development of nonregenerative magnetic refrigerators that span approximately 1 K to approximately 0 K. Particular emphasis is placed on high reliability and high efficiency. Calculations indicate considerable promise in this area. The principles, the potential, the problems, and the progress towards development of successful 4 to 20 K magnetic refrigerators are discussed.

  1. REFRIGERATION ESPECIALLY FOR VERY LOW TEMPERATURES

    DOEpatents

    Kennedy, P.B.; Smith, H.R. Jr.

    1960-09-13

    A refrigeration system for producing very low temperatures is described. The system of the invention employs a binary mixture refrigerant in a closed constant volume, e.g., Freon and ethylene. Such mixture is compressed in the gaseous state and is then separated in a fractionating column element of the system. Thenceforth, the first liquid to separate is employed stagewise to cool and liq uefy successive portions of the refrigerant at successively lower temperatures by means of heat exchangers coupled between the successive stages. When shut down, all of the volumes of the system are interconnected and a portion of the refrigerant remains liquid at ambient temperatures so that no dangerous overpressures develop. The system is therefore rugged, simple and dependable in operation.

  2. Low Temperature Waste Immobilization Testing Vol. I

    SciTech Connect

    Russell, Renee L.; Schweiger, Michael J.; Westsik, Joseph H.; Hrma, Pavel R.; Smith, D. E.; Gallegos, Autumn B.; Telander, Monty R.; Pitman, Stan G.

    2006-09-14

    The Pacific Northwest National Laboratory (PNNL) is evaluating low-temperature technologies to immobilize mixed radioactive and hazardous waste. Three waste forms—alkali-aluminosilicate hydroceramic cement, “Ceramicrete” phosphate-bonded ceramic, and “DuraLith” alkali-aluminosilicate geopolymer—were selected through a competitive solicitation for fabrication and characterization of waste-form properties. The three contractors prepared their respective waste forms using simulants of a Hanford secondary waste and Idaho sodium bearing waste provided by PNNL and characterized their waste forms with respect to the Toxicity Characteristic Leaching Procedure (TCLP) and compressive strength. The contractors sent specimens to PNNL, and PNNL then conducted durability (American National Standards Institute/American Nuclear Society [ANSI/ANS] 16.1 Leachability Index [LI] and modified Product Consistency Test [PCT]) and compressive strength testing (both irradiated and as-received samples). This report presents the results of these characterization tests.

  3. Evaluation of Low Temperature CO Removal Catalysts

    NASA Technical Reports Server (NTRS)

    Monje, Oscar

    2015-01-01

    CO removal from spacecraft gas streams was evaluated for three commercial, low temperature oxidation catalysts: Carulite 300, Sofnocat 423, and Hamilton Sundstrand Pt1. The catalysts were challenged with CO concentrations (1-100 ppm) under dry and wet (50% humidity) conditions using 2-3 % O2. CO removal and CO2 concentration were measured at constant feed composition using a FTIR. Water vapor affected the CO conversion of each catalyst differently. An initial screening found that Caulite 300 could not operate in humid conditions. The presence of water vapor affected CO conversion of Sofnocat 423 for challenge concentrations below 40 ppm. The conversion of CO by Sofnocat 423 was 80% at CO concentrations greater than 40 ppm under both dry and moist conditions. The HS Pt1 catalyst exhibited CO conversion levels of 100% under both dry and moist conditions.

  4. Low-temperature geothermal resources of Washington

    SciTech Connect

    Schuster, J.E.; Bloomquist, R.G.

    1994-06-01

    This report presents information on the location, physical characteristics, and water chemistry of low-temperature geothermal resources in Washington. The database includes 941 thermal (>20C or 68F) wells, 34 thermal springs, lakes, and fumaroles, and 238 chemical analyses. Most thermal springs occur in the Cascade Range, and many are associated with stratovolcanoes. In contrast, 97 percent of thermal wells are located in the Columbia Basin of southeastern Washington. Some 83.5 percent are located in Adams, Benton, Franklin, Grant, Walla Walla, and Yakima Counties. Yakima County, with 259 thermal wells, has the most. Thermal wells do not seem to owe their origin to local sources of heat, such as cooling magma in the Earth`s upper crust, but to moderate to deep circulation of ground water in extensive aquifers of the Columbia River Basalt Group and interflow sedimentary deposits, under the influence of a moderately elevated (41C/km) average geothermal gradient.

  5. Low-temperature thermodynamics with quantum coherence

    PubMed Central

    Narasimhachar, Varun; Gour, Gilad

    2015-01-01

    Thermal operations are an operational model of non-equilibrium quantum thermodynamics. In the absence of coherence between energy levels, exact state transition conditions under thermal operations are known in terms of a mathematical relation called thermo-majorization. But incorporating coherence has turned out to be challenging, even under the relatively tractable model wherein all Gibbs state-preserving quantum channels are included. Here we find a mathematical generalization of thermal operations at low temperatures, ‘cooling maps', for which we derive the necessary and sufficient state transition condition. Cooling maps that saturate recently discovered bounds on coherence transfer are realizable as thermal operations, motivating us to conjecture that all cooling maps are thermal operations. Cooling maps, though a less-conservative generalization to thermal operations, are more tractable than Gibbs-preserving operations, suggesting that cooling map-like models at general temperatures could be of use in gaining insight about thermal operations. PMID:26138621

  6. Low temperature double-layer capacitors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik J. (Inventor); Smart, Marshall C. (Inventor); West, William C. (Inventor)

    2011-01-01

    Double-layer capacitors capable of operating at extremely low temperatures (e.g., as low as -75.degree. C.) are disclosed. Electrolyte solutions combining a base solvent (e.g., acetonitrile) and a cosolvent are employed to lower the melting point of the base electrolyte. Example cosolvents include methyl formate, ethyl acetate, methyl acetate, propionitrile, butyronitrile, and 1,3-dioxolane. An optimized concentration (e.g., 0.10 M to 0.75 M) of salt, such as tetraethylammonium tetrafluoroborate, is dissolved into the electrolyte solution. In some cases (e.g., 1,3-dioxolane cosolvent) additives, such as 2% by volume triethylamine, may be included in the solvent mixture to prevent polymerization of the solution. Conventional device form factors and structural elements (e.g., porous carbon electrodes and a polyethylene separator) may be employed.

  7. A symmetrical low temperature pressure transducer

    NASA Astrophysics Data System (ADS)

    Helvensteijn, B. P. M.; VanSciver, S. W.

    1990-03-01

    The design and operating characteristics of a fully differential pressure transducer are described. The device is intended for use with He II heat transfer experiments where it operates in vacuum and at low temperatures (T<4.2 K). A movable electrode is attached to two sets of miniature bellows such that the electrode position is determined by the differential pressure across the device. The movable electrode is located between two fixed electrodes, thus forming a pair of variable capacitors. A dedicated charge amplifier is used to convert the pressure induced capacitance change to an ac output voltage. The sensitivity is roughly 5 μV/Pa. For the present application, the capacitor and electronics have acceptable performance, with a mean noise level of ±5 Pa.

  8. Preparation of silver nanoparticles at low temperature

    NASA Astrophysics Data System (ADS)

    Mishra, Mini; Chauhan, Pratima

    2016-04-01

    Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaks of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.

  9. Ultra-low temperature MAS-DNP.

    PubMed

    Lee, Daniel; Bouleau, Eric; Saint-Bonnet, Pierre; Hediger, Sabine; De Paëpe, Gaël

    2016-03-01

    Since the infancy of NMR spectroscopy, sensitivity and resolution have been the limiting factors of the technique. Regular essential developments on this front have led to the widely applicable, versatile, and powerful spectroscopy that we know today. However, the Holy Grail of ultimate sensitivity and resolution is not yet reached, and technical improvements are still ongoing. Hence, high-field dynamic nuclear polarization (DNP) making use of high-frequency, high-power microwave irradiation of electron spins has become very promising in combination with magic angle sample spinning (MAS) solid-state NMR experiments. This is because it leads to a transfer of the much larger polarization of these electron spins under suitable irradiation to surrounding nuclei, greatly increasing NMR sensitivity. Currently, this boom in MAS-DNP is mainly performed at minimum sample temperatures of about 100K, using cold nitrogen gas to pneumatically spin and cool the sample. This Perspective deals with the desire to improve further the sensitivity and resolution by providing "ultra"-low temperatures for MAS-DNP, using cryogenic helium gas. Different designs on how this technological challenge has been overcome are described. It is shown that stable and fast spinning can be attained for sample temperatures down to 30K using a large cryostat developed in our laboratory. Using this cryostat to cool a closed-loop of helium gas brings the additional advantage of sample spinning frequencies that can greatly surpass those achievable with nitrogen gas, due to the differing fluidic properties of these two gases. It is shown that using ultra-low temperatures for MAS-DNP results in substantial experimental sensitivity enhancements and according time-savings. Access to this temperature range is demonstrated to be both viable and highly pertinent. PMID:26920837

  10. Ultra-low temperature MAS-DNP

    NASA Astrophysics Data System (ADS)

    Lee, Daniel; Bouleau, Eric; Saint-Bonnet, Pierre; Hediger, Sabine; De Paëpe, Gaël

    2016-03-01

    Since the infancy of NMR spectroscopy, sensitivity and resolution have been the limiting factors of the technique. Regular essential developments on this front have led to the widely applicable, versatile, and powerful spectroscopy that we know today. However, the Holy Grail of ultimate sensitivity and resolution is not yet reached, and technical improvements are still ongoing. Hence, high-field dynamic nuclear polarization (DNP) making use of high-frequency, high-power microwave irradiation of electron spins has become very promising in combination with magic angle sample spinning (MAS) solid-state NMR experiments. This is because it leads to a transfer of the much larger polarization of these electron spins under suitable irradiation to surrounding nuclei, greatly increasing NMR sensitivity. Currently, this boom in MAS-DNP is mainly performed at minimum sample temperatures of about 100 K, using cold nitrogen gas to pneumatically spin and cool the sample. This Perspective deals with the desire to improve further the sensitivity and resolution by providing "ultra"-low temperatures for MAS-DNP, using cryogenic helium gas. Different designs on how this technological challenge has been overcome are described. It is shown that stable and fast spinning can be attained for sample temperatures down to 30 K using a large cryostat developed in our laboratory. Using this cryostat to cool a closed-loop of helium gas brings the additional advantage of sample spinning frequencies that can greatly surpass those achievable with nitrogen gas, due to the differing fluidic properties of these two gases. It is shown that using ultra-low temperatures for MAS-DNP results in substantial experimental sensitivity enhancements and according time-savings. Access to this temperature range is demonstrated to be both viable and highly pertinent.

  11. Low-temperature gas from marine shales

    PubMed Central

    2009-01-01

    Thermal cracking of kerogens and bitumens is widely accepted as the major source of natural gas (thermal gas). Decomposition is believed to occur at high temperatures, between 100 and 200°C in the subsurface and generally above 300°C in the laboratory. Although there are examples of gas deposits possibly generated at lower temperatures, and reports of gas generation over long periods of time at 100°C, robust gas generation below 100°C under ordinary laboratory conditions is unprecedented. Here we report gas generation under anoxic helium flow at temperatures 300° below thermal cracking temperatures. Gas is generated discontinuously, in distinct aperiodic episodes of near equal intensity. In one three-hour episode at 50°C, six percent of the hydrocarbons (kerogen & bitumen) in a Mississippian marine shale decomposed to gas (C1–C5). The same shale generated 72% less gas with helium flow containing 10 ppm O2 and the two gases were compositionally distinct. In sequential isothermal heating cycles (~1 hour), nearly five times more gas was generated at 50°C (57.4 μg C1–C5/g rock) than at 350°C by thermal cracking (12 μg C1–C5/g rock). The position that natural gas forms only at high temperatures over geologic time is based largely on pyrolysis experiments under oxic conditions and temperatures where low-temperature gas generation could be suppressed. Our results indicate two paths to gas, a high-temperature thermal path, and a low-temperature catalytic path proceeding 300° below the thermal path. It redefines the time-temperature dimensions of gas habitats and opens the possibility of gas generation at subsurface temperatures previously thought impossible. PMID:19236698

  12. Low-temperature gas from marine shales.

    PubMed

    Mango, Frank D; Jarvie, Daniel M

    2009-01-01

    Thermal cracking of kerogens and bitumens is widely accepted as the major source of natural gas (thermal gas). Decomposition is believed to occur at high temperatures, between 100 and 200 degrees C in the subsurface and generally above 300 degrees C in the laboratory. Although there are examples of gas deposits possibly generated at lower temperatures, and reports of gas generation over long periods of time at 100 degrees C, robust gas generation below 100 degrees C under ordinary laboratory conditions is unprecedented. Here we report gas generation under anoxic helium flow at temperatures 300 degrees below thermal cracking temperatures. Gas is generated discontinuously, in distinct aperiodic episodes of near equal intensity. In one three-hour episode at 50 degrees C, six percent of the hydrocarbons (kerogen & bitumen) in a Mississippian marine shale decomposed to gas (C1-C5). The same shale generated 72% less gas with helium flow containing 10 ppm O2 and the two gases were compositionally distinct. In sequential isothermal heating cycles (approximately 1 hour), nearly five times more gas was generated at 50 degrees C (57.4 microg C1-C5/g rock) than at 350 degrees C by thermal cracking (12 microg C1-C5/g rock). The position that natural gas forms only at high temperatures over geologic time is based largely on pyrolysis experiments under oxic conditions and temperatures where low-temperature gas generation could be suppressed. Our results indicate two paths to gas, a high-temperature thermal path, and a low-temperature catalytic path proceeding 300 degrees below the thermal path. It redefines the time-temperature dimensions of gas habitats and opens the possibility of gas generation at subsurface temperatures previously thought impossible. PMID:19236698

  13. Bethe lattice approach and relaxation dynamics study of spin-crossover materials

    NASA Astrophysics Data System (ADS)

    Oke, Toussaint Djidjoho; Hontinfinde, Félix; Boukheddaden, Kamel

    2015-07-01

    Dynamical properties of Prussian blue analogs and spin-crossover materials are investigated in the framework of a Blume-Emery-Griffiths (BEG) spin-1 model, where states ±1 and 0 represent the high-spin (HS) state and the low-spin state, respectively. The quadrupolar interaction depends on the temperature in the form . Magnetic interactions are controlled by a factor such that for (), magnetic ordering is not expected. The model is exactly solved using the Bethe lattice approach for the equilibrium properties. The results are closer to those calculated by numerical simulations with suitable Arrhenius-type transition rates. The study of relaxation processes of non-equilibrium HS states revealed one-step nonlinear sigmoidal relaxation curves of the HS fraction at low temperatures. We found that increasing the magnetic interactions leads to the appearance of a plateau in the thermal hysteresis as well as in the relaxation curves of the HS fraction at low temperature.

  14. Anomalous C-V response correlated to relaxation processes in TiO{sub 2} thin film based-metal-insulator-metal capacitor: Effect of titanium and oxygen defects

    SciTech Connect

    Kahouli, A.; Marichy, C.; Pinna, N.

    2015-04-21

    Capacitance-voltage (C–V) and capacitance-frequency (C–f) measurements are performed on atomic layer deposited TiO{sub 2} thin films with top and bottom Au and Pt electrodes, respectively, over a large temperature and frequency range. A sharp capacitance peak/discontinuity (C–V anomalous) is observed in the C–V characteristics at various temperatures and voltages. It is demonstrated that this phenomenon is directly associated with oxygen vacancies. The C–V peak irreversibility and dissymmetry at the reversal dc voltage are attributed to difference between the Schottky contacts at the metal/TiO{sub 2} interfaces. Dielectric analyses reveal two relaxation processes with degeneration of the activation energy. The low trap level of 0.60–0.65 eV is associated with the first ionized oxygen vacancy at low temperature, while the deep trap level of 1.05 eV is associated to the second ionized oxygen vacancy at high temperature. The DC conductivity of the films exhibits a transition temperature at 200 °C, suggesting a transition from a conduction regime governed by ionized oxygen vacancies to one governed by interstitial Ti{sup 3+} ions. Both the C–V anomalous and relaxation processes in TiO{sub 2} arise from oxygen vacancies, while the conduction mechanism at high temperature is governed by interstitial titanium ions.

  15. Copyrolysis of bitumen and oxygenate containing materials at low temperature

    NASA Astrophysics Data System (ADS)

    Toosi, Elaheh

    Bitumen, as one of the most important unconventional sources of energy, has long been an attractive source for production of liquid fuels. It is important to improve the yield and quality of the useful products resulting from bitumen upgrading processes so that the best outcome can be achieved with the least capital cost. It has been shown in literature that if the thermal upgrading processes are performed at lower temperature (below 400 °C), the obtained liquid yield can be improved. However, the low temperature slows down the rates and in general low temperature processes are less likely to be economical in industry. If this rate-challenge can be overcome, it is more beneficial to operate the bitumen upgrading processes at lower temperature. The working hypothesis was that oxygenate containing compounds, which are more reactive for thermal conversion, can be used to increase the overall reaction rate of bitumen conversion at lower temperature. This thesis studied the effect of co-processing some oxygenate containing materials with bitumen, namely, different coal and biomass derived materials.

  16. Research on the low-temperature decontamination of soil

    SciTech Connect

    Hetland, M.D.; Rindt, J.R.

    1995-10-01

    Decontamination of organically contaminated soil requires at least two processes: (1) separation of the contaminants from the soil and (2) destruction or stabilization and recovery of the organic contaminants. Techniques used to convert the organic contaminants must produce environmentally acceptable products. A process is seen as more favorable if the inorganic portion remaining after destruction of the organic contaminants retains a {open_quotes}natural{close_quotes} state, since ideally the residual should be returned to the original ecological system. Low-temperature plasma (LTP) processing has the potential to offer decontamination equivalent to incineration with decreased production of harmful by-products and without changing the morphology of the inorganic matrix. Low-temperature plasmas are formed by electric discharge (rather than thermal means) at conditions that do not result in thermal equilibrium. It is possible with an LTP system for typical plasma reactions to occur at nearly ambient bulk temperatures. The purpose of this project is to perform the appropriate engineering evaluations needed to scale up an LTP soil decontamination process developed at the Energy & Environmental Research Center (EERC). The LTP process under development uses oxygen plasma, resulting in oxidation of the contaminant species. Previous research at the EERC proved that the technique successfully separates organic contaminants from soil. The success of this previous research indicated that the use of LTP as a decontamination technique should be investigated further, with possible scale up to real-world application.

  17. Modeling Chemical Growth Processes in Titan's Atmosphere: 1. Theoretical Rates for Reactions between Benzene and the Ethynyl (C2H) and Cyano (CN) Radicals at Low Temperature and Pressure

    NASA Technical Reports Server (NTRS)

    Woon, David E.

    2006-01-01

    Density functional theory calculations at the B3LYP/6-31+G** level were employed to characterize the critical points for adducts, isomers, products, and intervening transition states for the reactions between benzene and the ethynyl (C2H) or cyano (CN) radicals. Both addition reactions were found to have no barriers in their entrance channels, making them efficient at the low temperature and pressure conditions that prevail in the haze-forming region of Titan's atmosphere as well as in the dense interstellar medium (ISM). The dominant products are ethynylbenzene (C6H5C2H) and cyanobenzene (C6H5CN). Hydrogen abstraction reactions were also characterized but found to be non-competitive. Trajectory calculations based on potentials fit to about 600 points calculated at the ROMP2/6-31+G** level for each interaction surface were used to determine reaction rates. The rates incorporated any necessary corrections for back reactions as ascertained from a multiwell treatment used to determine outcome distributions over the range of temperatures and pressures pertinent to Titan and the ISM and are in good agreement with the limited available experimental data.

  18. Low-temperature photoluminescence studies of mercuric-iodide photodetectors

    NASA Astrophysics Data System (ADS)

    James, R. B.; Bao, X. J.; Schlesinger, T. E.; Markakis, J. M.; Cheng, A. Y.; Ortale, C.

    1989-09-01

    Mercuric-iodide (HgI2 ) photodetectors with sputtered indium-tin-oxide (ITO) entrance electrodes were studied using low-temperature photoluminescence spectroscopy. The photoluminescence spectrum obtained on each photodetector was found to differ for points beneath the ITO contact and points adjacent to it, indicating that the contact fabrication process introduces new carrier traps and radiative recombination centers within the ITO-HgI2 interfacial region. In particular, a new broad band was observed in the spectra taken from points beneath the ITO electrode. Photocurrent-versus-position measurements showed that the intensity of this broad band was enhanced in regions having relatively poor photoresponse.

  19. Design for ASIC reliability for low-temperature applications

    NASA Technical Reports Server (NTRS)

    Chen, Yuan; Mojaradi, Mohammad; Westergard, Lynett; Billman, Curtis; Cozy, Scott; Burke, Gary; Kolawa, Elizabeth

    2005-01-01

    In this paper, we present a methodology to design for reliability for low temperature applications without requiring process improvement. The developed hot carrier aging lifetime projection model takes into account both the transistor substrate current profile and temperature profile to determine the minimum transistor size needed in order to meet reliability requirements. The methodology is applicable for automotive, military, and space applications, where there can be varying temperature ranges. A case study utilizing this methodology is given to design for reliability into a custom application-specific integrated circuit (ASIC) for a Mars exploration mission.

  20. The science capability of the Low Temperature Microgravity Physics Facility

    NASA Technical Reports Server (NTRS)

    Larson, M.; Croonquist, A.; Dick, G. J.; Liu, Y.

    2002-01-01

    The Low Temperature Microgravity Physics Facility (LTMPF) is a multiple user and multiple-flight NASA facility that will provide a low temperature environment for about 4. 5 months on board the International Space Station (ISS).

  1. Dielectric spectroscopy of amino alcohols at low temperatures

    NASA Astrophysics Data System (ADS)

    Solonina, I. A.; Vasilyeva, M. A.; Greenbaum (Gutina), A.; Gusev, Yu. A.; Lounev, I. V.; Rodnikova, M. N.; Feldman, Yu.

    2016-01-01

    The dielectric properties of three vicinal amino alcohols are studied at temperatures in the range of‒140-70°C and the frequency interval of 0.1 Hz to 1 MHz. The temperature dependences of the observed relaxation processes indicate both glass transition and melting processes. The relatively high conductivity of the samples was considered from the viewpoint of proton conductivity through a network of hydrogen bonds of amino alcohol molecules.

  2. Correlation between low temperature properties and fragility of glasses

    NASA Astrophysics Data System (ADS)

    Zhu, Da-Ming

    1997-03-01

    The nature of glass transition and the nature of low energy excitations that govern the low temperature properties of glasses are the two fundamental problems remain unsolved in the study of glasses. It was recently suggested that several properties governed by the low energy excitations in glasses are correlated to the glass fragility,[1] a parameter used to characterize the temperature variation of relaxation time near glass transitions.[2] A previous examination of the specific heats at T < 1 K and the fragility of a dozen different glasses found a correlation seems to exist.[3] The correlation is also consistent with an interpretation of fragility of glasses in terms of difference in potential energy landscape in configuration space.[2] We recently compared the specific heats and thermal conductivity of several glasses at 1K < T < 20 K and their fragility. We found that a general trend appears to exist that more fragile glasses have lower specific heat bump in the plot of C/T3 versus T or lower step in the plot of C/T versus T. The implication of the correlation and the possible interpretation in terms of potential energy landscape will be discussed. [1] A. P. Sokolov et al, Phys. Rev. Lett. 71, 2062 (1993). [2] C. A. Angell, J. Non-Cryst. Solids 131-133, 13 (1993). [3] Da-Ming Zhu, Phys. Rev. B 54, 6287 (1996).

  3. 46 CFR 57.05-5 - Low temperature application.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Low temperature application. 57.05-5 Section 57.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Performance Qualifications § 57.05-5 Low temperature application. For low temperature application, each...

  4. 46 CFR 57.05-5 - Low temperature application.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Low temperature application. 57.05-5 Section 57.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Performance Qualifications § 57.05-5 Low temperature application. For low temperature application, each...

  5. 46 CFR 57.05-5 - Low temperature application.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Low temperature application. 57.05-5 Section 57.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Performance Qualifications § 57.05-5 Low temperature application. For low temperature application, each...

  6. 46 CFR 57.05-5 - Low temperature application.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Low temperature application. 57.05-5 Section 57.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Performance Qualifications § 57.05-5 Low temperature application. For low temperature application, each...

  7. 46 CFR 57.05-5 - Low temperature application.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Low temperature application. 57.05-5 Section 57.05-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING WELDING AND BRAZING Performance Qualifications § 57.05-5 Low temperature application. For low temperature application, each...

  8. RECYCLING NICKEL ELECTROPLATING RINSE WATERS BY LOW TEMPERATURE EVAPORATION AND REVERSE OSMOSIS

    EPA Science Inventory

    Low temperature evaporation and reverse osmosis systems were each evaluated (on a pilot scale) on their respective ability to process rinse water collected from a nickel electroplating operation. Each system offered advantages under specific operating conditions. The low temperat...

  9. Low temperature engineering applied to lunar in-situ resource utilization

    NASA Technical Reports Server (NTRS)

    Zhang, Burt; Chui, Talso; Croonquist, Arvid

    2005-01-01

    In support of NASA's Exploration Mission low-temperature scientists and engineers have investigated the process of extracting volatile materials from the lunar regolith, their purification/liquefaction, and storage.

  10. Low temperature growth of conformal, transparent conducting oxides

    NASA Astrophysics Data System (ADS)

    Gordon, Roy

    2013-03-01

    Transparent conductors (TC) are essential components of many widely-used technologies, including energy conserving low-E windows, electronic displays and solar cells. Currently, TC films are made by chemical vapor deposition (CVD) or by sputtering or evaporation (PVD). CVD has generally required high temperatures (greater than 500 C), so that is not applicable to plastic substrates and some solar cells. PVD makes films with low step coverage, so textured substrates, such as those with narrow holes, cannot be coated uniformly. The most effective PVD films are based on indium, a rare and expensive element. Recently, atomic layer deposition (ALD) processes have been developed that overcome all of these limitations, allowing highly uniform and conformal coating of substrates with very narrow holes even at substrate temperatures below 100 C. The metals used in these ALD TCs are tin and/or zinc, which are abundant and inexpensive elements. In this talk, we will review these ALD processes, along with the optical, structural and electrical properties of the TCs that they produce. Applications of these low-temperature, conformal TCs will also be discussed. Record-breaking solar cells made entirely from Earth-abundant elements were enabled by these ALD processes. Transparent transistors with excellent characteristics can now be made at low temperature even on rough or textured plastic surfaces. Micro-channel plate array detectors are being produced for use in highly sensitive imaging applications.

  11. Surface modification of superaustenitic and maraging stainless steels by low-temperature gas-phase carburization

    NASA Astrophysics Data System (ADS)

    Gentil, Johannes

    Low-temperature gas-phase carburization of 316L austenitic stainless steel was developed in recent years by the Swagelok company. This process generates great mechanical and electrochemical surface properties. Hardness, wear resistance, fatigue behavior, and corrosion resistance are dramatically improved, while the formation of carbides is effectively suppressed. This new technique is of technical, economical, but especially of scientific interest because the surface properties of common stainless steel can be enhanced to a level of more sophisticated and more expensive superalloys. The consequential continuation of previous research is the application of the carburization process to other steel grades. Differences in chemical composition, microstructure, and passivity between the various alloys may cause technical problems and it is expected that the initial process needs to be optimized for every specific material. This study presents results of low-temperature carburization of AL-6XN (superaustenitic stainless steel) and PH13-8Mo (precipitation-hardened martensitic stainless steel). Both alloys have been treated successfully in terms of creating a hardened surface by introducing high amounts of interstitially dissolved carbon. The surface hardness of AL-6XN was increased to 12GPa and is correlated with a colossal carbon supersaturation at the surface of up to 20 at.%. The hardened case develops a carburization time-dependent thickness between 10mum after one carburization cycle and up to 35mum after four treatments and remains highly ductile. Substantial broadening of X-ray diffraction peaks in low-temperature carburized superaustenitic stainless steels are attributed to the generation of very large compressive biaxial residual stresses. Those large stresses presumably cause relaxations of the surface, so-called undulations. Heavily expanded regions of carburized AL-6XN turn ferromagnetic. Non-carburized AL-6XN is known for its outstanding corrosion resistance

  12. Silicon Vibrating Wires at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Collin, Eddy; Filleau, Laure; Fournier, Thierry; Bunkov, Yuriy M.; Godfrin, Henri

    2008-03-01

    Nowadays microfabrication techniques originating from micro-electro nics enable to create mechanical objects of micron-size. The field of Micro-Electro-Mechanical devices (MEMs) is continuously expanding, with an amazingly broad range of applications at room temperature. Vibrating objects (torsional oscillators, vibrating wires) widely used at low temperatures to study quantum fluids, can be replaced advantageously by Silicon MEMs. In this letter we report on the study of Silicon vibrating wire devices. A goal-post structure covered with a metal layer is driven at resonance by the Laplace force acting on a current in a magnetic field, while the induced voltage arising from the cut magnetic flux allows to detect the motion. The characteristics of the resonance have been studied from 10 mK to 30 K, in vacuum and in 4He gas. In this article, we focus on the results obtained above 1.5 K, in vacuum and gas, and introduce some features observed at lower temperatures. The resonant properties can be quantitatively understood by means of simple models, from the linear regime to a highly non-linear response at strong drives. We demonstrate that the non-linearity is mostly due to the geometry of the vibrators. We also show that in our device the friction mechanisms originate in the metallic layers, and can be fully characterized. The interaction with 4He gas is fit to theory without adjustable parameters.

  13. A Low Temperature, Reverse Brayton Cryocooler

    NASA Technical Reports Server (NTRS)

    Swift, Walter L.

    2001-01-01

    This status report covers the fifty-second month of a project to develop a low temperature, reverse-Brayton cryocooler using turbomachines. This program consists of a Basic Phase and four Option Phases. Each of the Phases is directed to a particular load/temperature combination. The technology and fundamental design features of the components used in these systems are related but differ somewhat in size, speed, and some details in physical geometry. Each of the Phases can be carried out independently of the others, except that all of the Phases rely on the technology developed and demonstrated during the Basic Phase. The Basic Phase includes the demonstration of a critical component and the production of a prototype model cryocooler. The critical technology demonstration will be the test of a small turboalternator over a range of conditions at temperatures down to 6 K. These tests will provide design verification data useful for the further design of the other coolers. The prototype model cooler will be designed to provide at least 5 mW of cooling at 6 K. The heat rejection temperature for this requirement is 220 K or greater. The input power to the system at these conditions is to be less than 60 W.

  14. Low temperature operation of a boost converter

    SciTech Connect

    Moss, B.S.; Boudreaux, R.R.; Nelms, R.M.

    1996-12-31

    The development of satellite power systems capable of operating at low temperatures on the order of 77K would reduce the heating system required on deep space vehicles. The power supplies in the satellite power system must be capable of operating at these temperatures. This paper presents the results of a study into the operation of a boost converter at temperatures close to 77K. The boost converter is designed to supply an output voltage and power of 42 V and 50 W from a 28 V input source. The entire system, except the 28 V source, is placed in the environmental chamber. This is important because the system does not require any manual adjustments to maintain a constant output voltage with a high efficiency. The constant 42 V output of this converter is a benefit of the application of a CMOS microcontroller in the feedback path. The switch duty cycle is adjusted by the microcontroller to maintain a constant output voltage. The efficiency of the system varied less than 1% over the temperature range of 22 C to {minus}184 C and was approximately 94.2% when the temperature was {minus}184 C.

  15. Extreme low temperature tolerance in woody plants

    PubMed Central

    Strimbeck, G. Richard; Schaberg, Paul G.; Fossdal, Carl G.; Schröder, Wolfgang P.; Kjellsen, Trygve D.

    2015-01-01

    Woody plants in boreal to arctic environments and high mountains survive prolonged exposure to temperatures below -40°C and minimum temperatures below -60°C, and laboratory tests show that many of these species can also survive immersion in liquid nitrogen at -196°C. Studies of biochemical changes that occur during acclimation, including recent proteomic and metabolomic studies, have identified changes in carbohydrate and compatible solute concentrations, membrane lipid composition, and proteins, notably dehydrins, that may have important roles in survival at extreme low temperature (ELT). Consideration of the biophysical mechanisms of membrane stress and strain lead to the following hypotheses for cellular and molecular mechanisms of survival at ELT: (1) Changes in lipid composition stabilize membranes at temperatures above the lipid phase transition temperature (-20 to -30°C), preventing phase changes that result in irreversible injury. (2) High concentrations of oligosaccharides promote vitrification or high viscosity in the cytoplasm in freeze-dehydrated cells, which would prevent deleterious interactions between membranes. (3) Dehydrins bind membranes and further promote vitrification or act stearically to prevent membrane–membrane interactions. PMID:26539202

  16. Low Temperature Detectors for Neutrino Physics

    NASA Astrophysics Data System (ADS)

    Nucciotti, A.

    2014-09-01

    Recent years have witnessed many exciting breakthroughs in neutrino physics. The detection of neutrino oscillations has proved that neutrinos are massive particles but the assessment of their absolute mass scale is still an outstanding challenge in today particle physics and cosmology. Due to their abundance as big-bang relics, massive neutrinos strongly affect the large-scale structure and dynamics of the universe. In addition, the knowledge of the scale of neutrino masses, together with their hierarchy pattern, is invaluable to clarify the origin of fermion masses beyond the Higgs mechanism. The mass hierarchy is not the only missing piece in the puzzle. Theories of neutrino mass generation call into play Majorana neutrinos and there are experimental observations pointing to the existence of sterile neutrinos in addition to the three ones weakly interacting. Since low temperature detectors were first proposed for neutrino physics experiments in 1984, there have been impressive technical progresses: today this technique offers the high energy resolution and scalability required for leading edges and competitive experiments addressing the still open questions.

  17. Effect of relaxation processes on fluorescence lifetime and polarization characteristics of rhodamine 6G in glycerol

    SciTech Connect

    Levshin, L.V.; Struganova, I.A.; Tolevtaev, B.N.

    1986-11-01

    Some new phenomena which can be attributed to the relaxation kinetics of the distribution halfwidth over the 0-0 frequencies for organic dye solutions have been discovered in the present work. The kinetic and polarization characteristics of flourescence from the viscous dipolar solutions of the dyes exhibiting dynamic inhomogeneous broadening upon excitation near the absorption band center have been studied. The objects of the study are rhodamine 6G solutions in glycerol and ethanol at the concentration 10/sup -//sub 6/ mole/liter. It was concluded that the presence of the dip in the flourescence lifetime and the hump in the fluorescence polarization dependences on emission wavelength in the viscous dipolar solution of rhodamine 6G has been detected. The phenomena have been explained by the formation of the excited-state nonequilibrium distribution of the flourescence centers over the 0-0 transition frequencies upon monochromatic excitation and by the subsequent relaxation of the nonequilibrium distribution into the equilibrium one.

  18. Spin relaxation via exchange with donor impurity-bound electrons

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian

    In the Bir-Aronov-Pikus depolarization process affecting conduction electrons in p-type cubic semiconductors, spin relaxation is driven by exchange with short-lived valence band hole states. We have identified an analogous spin relaxation mechanism in nominally undoped silicon at low temperatures, when many electrons are bound to dilute dopant ion potentials. Inelastic scattering with externally injected conduction electrons accelerated by electric fields can excite transitions into highly spin-orbit-mixed bound excited states, driving strong spin relaxation of the conduction electrons via exchange interaction. We reveal the consequences of this spin depolarization mechanism both below and above the impact ionization threshold, where conventional charge and spin transport are restored. Based upon: Lan Qing, Jing Li, Ian Appelbaum, and Hanan Dery, Phys Rev. B 91, 241405(R) (2015). We acknowledge support from NSF, DTRA, and ONR.

  19. Low temperature viscosity in elongated ferrofluids

    NASA Astrophysics Data System (ADS)

    Alarcón, T.; Pérez-Madrid, A.; Rubí, J. M.

    1997-12-01

    We have studied the relaxation and transport properties of a ferrofluid in an elongational flow. These properties are influenced by the bistable nature of the potential energy. Bistability comes from the irrotational character of the flow together with the symmetry of the dipoles. Additionally, the presence of a constant magnetic field destroys the symmetry of the potential energy magnetizing the system. We have shown that at a moderate temperature, compared to the height of the energy barrier, the viscosity decreases with respect to the value it would have if the potential were stable. This phenomenon is known as the "negative viscosity" effect. Thermal motion induces jumps of the magnetic moment between the two stable states of the system leading to the aforementioned lowered dissipation effect.

  20. Influence of the turbulence on the processes formation and relaxation of periodical artificial irregularities in the lower ionosphere

    NASA Astrophysics Data System (ADS)

    Terina, Galina

    2016-07-01

    The periodic artificial irregularities (PAI) are formed in the standing wave field of powerful radio emission. The study the scattering of probing radio pulses on PAI allowed to create a method diagnostics of the ionospheric plasma parameters - the resonance scattering method (RSM) of radio waves on the periodic artificial irregularities. The different mechanisms of PAI formation in D and E ranges of the lower ionosphere were investigated (G.I. Terina, J.Atm.Terr.Phys., 1996, 58, 645). However the height range 75-90 km where there is turbulent diffusion, remained unstudied. In present paper the study results the processes formation and relaxation of periodic artificial irregularities in this height range are considered. For the analysis the processes of the formation and the relaxation of PAI one can use quasi-hydrodynamic equation for the homogeneous isotropic ionospheric plasma. Under the small disturbances, quasi-neutral plasma and some assumptions can to obtain the differential equations for regular and fluctuation PAI parts, which take account: the ambipolar diffusion, the temperature dependence of the coefficient of electrons recombination, the temperature dependence of the coefficient of the electrons attachment to the neutral molecules and also the turbulent diffusion and caused by it small-scale irregularities of the electron density. The solutions of the inhomogeneous and homogeneous equations present the processes of the formation and relaxation of PAI accordingly. The numerical estimations of obtained solutions showed that the main reasons of PAI formation in considered range of heights are the small-scale irregularities of the electron concentration and the turbulence diffusion. The obtained results qualitatively agree with results of experimental investigations. The experiments were carried out at the heating facilities "Zimenki" and "Sura". The heater transmitter periodically was switched on for several seconds and off for the same duration. The

  1. Improved Thermal-Insulation Systems for Low Temperatures

    NASA Technical Reports Server (NTRS)

    Fesmire, James E.; Augustynowicz, Stanislaw D.

    2003-01-01

    Improved thermal-insulation materials and structures and the techniques for manufacturing them are undergoing development for use in low-temperature applications. Examples of low-temperature equipment for which these thermal insulation systems could provide improved energy efficiency include storage tanks for cryogens, superconducting electric-power-transmission equipment, containers for transport of food and other perishable commodities, and cold boxes for low-temperature industrial processes. These systems could also be used to insulate piping used to transfer cryogens and other fluids, such as liquefied natural gas, refrigerants, chilled water, crude oil, or low-pressure steam. The present thermal-insulation systems are layer composites based partly on the older class of thermal-insulation systems denoted generally as multilayer insulation (MLI). A typical MLI structure includes an evacuated jacket, within which many layers of radiation shields are stacked or wrapped close together. Low-thermal-conductivity spacers are typically placed between the reflection layers to keep them from touching. MLI can work very well when a high vacuum level (less than 10(exp-4) torr) is maintained and utmost care is taken during installation, but its thermal performance deteriorates sharply as the pressure in the evacuated space rises into the soft vacuum range [pressures greater than 0.1 torr (greater than 13 Pa)]. In addition, the thermal performance of MLI is extremely sensitive to mechanical compression and edge effects and can easily decrease from one to two orders of magnitude from its ideal value even when the MLI is kept under high vacuum condition. The present thermal-insulation systems are designed to perform well under soft vacuum level, in particular the range of 1 to 10 torr. They are also designed with larger interlayer spacings to reduce vulnerability to compression (and consequent heat leak) caused by installation and use. The superiority of these systems is the

  2. Metabolic responses to low temperature in fish muscle.

    PubMed

    Guderley, Helga

    2004-05-01

    For most fish, body temperature is very close to that of the habitat. The diversity of thermal habitats exploited by fish as well as their capacity to adapt to thermal change makes them excellent organisms in which to examine the evolutionary and phenotypic responses to temperature. An extensive literature links cold temperatures with enhanced oxidative capacities in fish tissues, particularly skeletal muscle. Closer examination of inter-species comparisons (i.e. the evolutionary perspective) indicates that the proportion of muscle fibres occupied by mitochondria increases at low temperatures, most clearly in moderately active demersal species. Isolated muscle mitochondria show no compensation of protein-specific rates of substrate oxidation during evolutionary adaptation to cold temperatures. During phenotypic cold acclimation, mitochondrial volume density increases in oxidative muscle of some species (striped bass Morone saxatilis, crucian carp Carassius carassius), but remains stable in others (rainbow trout Oncorhynchus mykiss). A role for the mitochondrial reticulum in distributing oxygen through the complex architecture of skeletal muscle fibres may explain mitochondrial proliferation. In rainbow trout, compensatory increases in the protein-specific rates of mitochondrial substrate oxidation maintain constant capacities except at winter extremes. Changes in mitochondrial properties (membrane phospholipids, enzymatic complement and cristae densities) can enhance the oxidative capacity of muscle in the absence of changes in mitochondrial volume density. Changes in the unsaturation of membrane phospholipids are a direct response to temperature and occur in isolated cells. This fundamental response maintains the dynamic phase behaviour of the membrane and adjusts the rates of membrane processes. However, these adjustments may have deleterious consequences. For fish living at low temperatures, the increased polyunsaturation of mitochondrial membranes should raise

  3. Low-temperature indium-bonded alkali vapor cell for chip-scale atomic clocks

    NASA Astrophysics Data System (ADS)

    Straessle, R.; Pellaton, M.; Affolderbach, C.; Pétremand, Y.; Briand, D.; Mileti, G.; de Rooij, N. F.

    2013-02-01

    A low-temperature sealing technique for micro-fabricated alkali vapor cells for chip-scale atomic clock applications is developed and evaluated. A thin-film indium bonding technique was used for sealing the cells at temperatures of ≤140 °C. These sealing temperatures are much lower than those reported for other approaches, and make the technique highly interesting for future micro-fabricated cells, using anti-relaxation wall coatings. Optical and microwave spectroscopy performed on first indium-bonded cells without wall coatings are used to evaluate the cleanliness of the process as well as a potential leak rate of the cells. Both measurements confirm a stable pressure inside the cell and therefore an excellent hermeticity of the indium bonding. The double-resonance measurements performed over several months show an upper limit for the leak rate of 1.5 × 10-13 mbar.l/s. This is in agreement with additional leak-rate measurements using a membrane deflection method on indium-bonded test structures.

  4. The low temperature formation of octacalcium phosphate

    NASA Astrophysics Data System (ADS)

    Graham, Stephan; Brown, Paul W.

    1993-09-01

    The low temperature formation of octacalcium phosphate (Ca 8(HPO 4) 2(PO 4) 4·5H 2O) was investigated. Octacalcium phosphate (OCP) was formed by the hydrolysis of α-tricalcium phosphate (α-TCP), and by reaction between monocalcium phosphate monohydrate (MCPM) and tetracalcium phosphate (TetCP). Relationships between phase formation, microstructural evolution, and variations in solution chemistry were examined. Hydrolysis of α-TCP to form OCP occurs more rapidly at elevated temperatures. At the highest temperature studied, 70°C, initial precipitation of OCP occurs in about one hour, but its inevitable hydrolysis to the more stable HAp phase takes place over several days. At room temperature, nearly three days are required to initiate OCP formation, yet remains a final product phase for well over a period of months. When the initial solution pH is less than 7, pure phase OCP is the final product, while HAp forms when initial pH values are higher than this. Furthermore, OCP precipitates faster at the highest initial pH values where its formation is observed. OCP formation by reaction between MCPM and TetCP is also dependent on temperature and time of reaction. For temperatures between 40 and 55°C and at reasonable times (less than four days) the product is phase pure OCP. After that time, inevitable hydrolysis of the OCP product to HAp occurs. Between 30 and 40°C, DCPD (CaHPO 4·2H 2O) is simultaneously present with OCP, and below 30°C, HAp and DCPD coexist within this aforementioned time span. Conversely, between 55 and 60°C, DCP (CaHPO 4) and OCP are the product phases (in the allowed time of reaction, before the eventual degradation of OCP), and above 60°C HAp and DCP are the final products.

  5. The Low-temperature Ion Sulfurizing Technology and its Applications

    NASA Astrophysics Data System (ADS)

    Ma, G. Z.; Xu, B. S.; Wang, H. D.; Li, G. L.; Zhang, S.

    A solid lubrication film mainly consists of FeS, which has excellent tribology properties, can be formed on the sulfurized iron or steel surface. The sulfurizing technology has aroused intense attention from the day it appeared. However, the widespread industrial application of sulfurizing technology was promoted by the low-temperature ion sulfurizing (LTIS) process. This paper summarized the phylogeny and sorts of sulfurizing technology firstly; then, the process flow of LTIS technology, the forming mechanism, microstructure and tribological properties of ion sulfurized layer were introduced detailedly; and then, the technological, economic and environmental merits of LTIS technology were generalized; finally, the industrial applications of LTIS technology in various typical rolling, sliding and heavy duty parts were reviewed briefly. LTIS technology, with the advantages of high sulfurizing speed, good performance of sulfurized layer and without sideeffect, has played an important role in the tribology modification of ferrous parts, and the LTIS process will become more green, simple and efficient in the future.

  6. Low Temperature Growth of Nanostructured Diamond Films on Metals

    NASA Technical Reports Server (NTRS)

    Baker, Paul A.; Catledge, Shane A.; Vohra, Yogesh K.

    2001-01-01

    The field of nanocrystalline diamond and tetrahedral amorphous carbon films has been the focus of intense experimental activity in the last few years for applications in field emission display devices, optical windows, and tribological coatings, The choice of substrate used in most studies has typically been silicon. For metals, however, the thermal expansion mismatch between the diamond film and substrate gives rise to thermal stress that often results in delamination of the film. To avoid this problem in conventional CVD deposition low substrate temperatures (less than 700 C) have been used, often with the incorporation of oxygen or carbon monoxide to the feedgas mixture. Conventionally grown CVD diamond films are also rough and would require post-deposition polishing for most applications. Therefore, there is an obvious need to develop techniques for deposition of well-adhered, smooth nano-structured diamond films on metals for various tribological applications. In our work, nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 C) for 30 minutes using a H2/CH4/N2 gas mixture in order to grow a thin (approx. 600 nm) nanostructured diamond layer and improve film adhesion. The remainder of the deposition involves growth at low temperature (less than 600 C) in a H2/CH4/O2 gas mixture. Laser reflectance Interferometry (LRI) pattern during growth of a nanostructured diamond film on Ti-6Al-4V alloy. The first 30 minutes are at a high temperature of 820 C and the rest of the film is grown at a low temperature of 580 T. The fringe pattern is observed till the very end due to extremely low surface roughness of 40 nm. The continuation of the smooth nanostructured diamond film growth during low temperature deposition is confirmed by in-situ laser reflectance interferometry and by post-deposition micro-Raman spectroscopy and surface profilometry. Similar experiments

  7. Anomalous diffusion and non-monotonic relaxation processes in Ge-Se liquids

    NASA Astrophysics Data System (ADS)

    Yildirim, Can; Raty, Jean-Yves; Micoulaut, Matthieu

    2016-06-01

    We investigate the dynamical properties of liquid GexSe100-x as a function of Ge content by first-principles molecular dynamic simulations for a certain number of temperatures in the liquid state. The focus is set on ten compositions (where x ≤ 33%) encompassing the reported flexible to rigid and rigid to stressed-rigid transitions. We examine diffusion coefficients, diffusion activation energies, glassy relaxation behavior, and viscosity of these liquids from Van Hove correlation and intermediate scattering functions. At fixed temperature, all properties/functions exhibit an anomalous behavior with Ge content in the region 18%-22%, and provide a direct and quantitative link to the network rigidity.

  8. A dipole model of generating electric pulses in relaxation processes in the Earth's crust

    NASA Astrophysics Data System (ADS)

    Loseva, T. V.; Spivak, A. A.; Kuz'micheva, M. Yu.

    2012-01-01

    A new numerical model of generating electric pulses in the Earth's crust with use of a system of electric dipoles that are located uniformly over an active surface of the structural block relaxing after its constrained turn is developed. Electric moments of dipoles change with time according to the amplitude of differential movements. It is shown that the amplitude of electric pulses and the degree of their attenuation with distance to the source are in agreement with the data of results of instrumental observations.

  9. Homochiral mononuclear Dy-Schiff base complexes showing field-induced double magnetic relaxation processes.

    PubMed

    Ren, Min; Xu, Zhong-Li; Wang, Ting-Ting; Bao, Song-Song; Zheng, Ze-Hua; Zhang, Zai-Chao; Zheng, Li-Min

    2016-01-14

    A pair of enantiopure mononuclear dysprosium/salen-type complexes (Et3NH)[Dy((R,R)/(S,S)-3-NO2salcy)2] (/), where 3-NO2salcyH2 represents N,N'-(1,2-cyclohexanediylethylene)bis(3-nitrosalicylideneiminato), are reported. The enantiomer contains two crystallographically independent dysprosium(iii) ions, each chelated by two enantiopure 3-NO2salcy(2-) ligands forming a [DyN4O4] core. Detailed magnetic studies on compound reveal a field-induced dual magnetic relaxation behavior, originating from single ion anisotropy and intermolecular interactions, respectively. PMID:26621766

  10. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich; Shiryaev, Vasili Nikolaevich

    2010-03-02

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron:3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  11. Material for electrodes of low temperature plasma generators

    DOEpatents

    Caplan, Malcolm; Vinogradov, Sergel Evge'evich; Ribin, Valeri Vasil'evich; Shekalov, Valentin Ivanovich; Rutberg, Philip Grigor'evich; Safronov, Alexi Anatol'evich

    2008-12-09

    Material for electrodes of low temperature plasma generators. The material contains a porous metal matrix impregnated with a material emitting electrons. The material uses a mixture of copper and iron powders as a porous metal matrix and a Group IIIB metal component such as Y.sub.2O.sub.3 is used as a material emitting electrons at, for example, the proportion of the components, mass %: iron: 3-30; Y.sub.2O.sub.3:0.05-1; copper: the remainder. Copper provides a high level of heat conduction and electric conductance, iron decreases intensity of copper evaporation in the process of plasma creation providing increased strength and lifetime, Y.sub.2O.sub.3 provides decreasing of electronic work function and stability of arc burning. The material can be used for producing the electrodes of low temperature AC plasma generators used for destruction of liquid organic wastes, medical wastes, and municipal wastes as well as for decontamination of low level radioactive waste, the destruction of chemical weapons, warfare toxic agents, etc.

  12. Low-temperature multi-OSL-thermochronometry of feldspar

    NASA Astrophysics Data System (ADS)

    King, Georgina; Herman, Frederic; Lambert, Renske; Valla, Pierre; Guralnik, Benny

    2016-04-01

    Constraining exhumation rates and landscape histories over Quaternary timescales represents a major challenge for understanding the interaction between changing climate and erosion processes. Facilitated by closure temperatures of as low as ~30 C, OSL-thermochronometry is able to constrain cooling rates from the top few km of the earth's crust, and offers the potential for recent changes in erosion to be determined. Based on the well-established Quaternary dating technique of optically stimulated luminescence dating, OSL-thermochronometry benefits from a strong methodological and theoretical foundation. A further advantage of OSL-thermochronometry is that it is possible to measure multiple luminescence signals from a single mineral, such as feldspar. Therefore OSL-thermochronometry can be used as a multi-thermochronometer whereby different signals from the same mineral have closure temperatures in the range of 30-70 C, enabling the derivation of very precise cooling histories. However, in contrast to other low-temperature methods, OSL-thermochronometry is limited by signal saturation, restricting its application to either elevated temperature settings (e.g. bore holes, tunnels) or rapidly exhuming terranes. Here we outline the principles of multi-OSL-thermochronometry of feldspar and its potential as a low-temperature thermochronometry system.

  13. Challenges in Characterizing Low-Temperature Regolith Properties

    NASA Technical Reports Server (NTRS)

    Swanger, Adam Michael; Mantovani, James G.

    2014-01-01

    The success or failure of in-situ resource utilization for planetary surface exploration--be it for scientific, colonization or commercialization purposes--relies heavily on the ability to design and implement systems which effectively process the associated regolith and exploit its benefits. In most cases this challenge necessarily includes the characterization of low-temperature (cryogenic) properties; as many celestial destinations of interest, such as the moon, Mars and asteroids, have little or no atmosphere to help sustain the consistently "high" surface temperatures seen on planets such as Earth, and therefore can experience permanent cryogenic temperatures or dramatic cyclical changes. Characterization of physical properties (such as specific heat, thermal and electrical conductivity, etc.) over the entire temperature profile is undoubtedly an important piece of the puzzle; however, the impact on mechanical properties due to the introduction of icy deposit must also be explored in order to devise effective and robust excavation technologies. Currently the Granular Mechanics and Regolith Operations Lab and the Cryogenics Test Lab at NASA Kennedy Space Center are developing technologies and experimental methods to address these challenges and aid in the characterization of physical and mechanical properties of regolith at cryogenic temperatures. This presentation will review the current state of knowledge concerning lunar regolith at low temperature including that of icy regolith.

  14. Relaxation processes in liquids: Variations on a theme by Stokes and Einstein

    NASA Astrophysics Data System (ADS)

    Shi, Zane; Debenedetti, Pablo G.; Stillinger, Frank H.

    2013-03-01

    We investigate numerically the temperature and density dependence of the Stokes-Einstein ratio, Dη/T, and of two commonly-used variants thereof, Dτ and Dτ/T, where D is a diffusivity, η the shear viscosity, and τ a structural relaxation time. We consider a family of atomic binary mixtures with systematically-softened repulsive interactions, and the Lewis-Wahnström model of ortho-terphenyl (OTP). The three quantities grow significantly as the temperature decreases in the supercooled regime, a well-known phenomenon. At higher temperatures, Dτ exhibits negative violations of Stokes-Einstein behavior, i.e., decrease upon cooling, for the atomic systems, though not for OTP. We consider two choices for the relaxation time, one based on the decay of the self-intermediate scattering function, and the other on the integral of the stress autocorrelation function. The instantaneous shear modulus exhibits appreciable temperature dependence for the two classes of systems investigated here. Our results suggest that commonly-invoked assumptions, such as τ ˜ η and τ ˜ η/T, should be critically evaluated across a wide spectrum of systems and thermodynamic conditions. We find the Stokes-Einstein ratio, Dη/T, to be constant across a broad range of temperatures and densities for the two classes of systems investigated here.

  15. Low temperature conversion of plastic waste into light hydrocarbons.

    PubMed

    Shah, Sajid Hussain; Khan, Zahid Mahmood; Raja, Iftikhar Ahmad; Mahmood, Qaisar; Bhatti, Zulfiqar Ahmad; Khan, Jamil; Farooq, Ather; Rashid, Naim; Wu, Donglei

    2010-07-15

    Advance recycling through pyrolytic technology has the potential of being applied to the management of plastic waste (PW). For this purpose 1 l volume, energy efficient batch reactor was manufactured locally and tested for pyrolysis of waste plastic. The feedstock for reactor was 50 g waste polyethylene. The average yield of the pyrolytic oil, wax, pyrogas and char from pyrolysis of PW were 48.6, 40.7, 10.1 and 0.6%, respectively, at 275 degrees C with non-catalytic process. Using catalyst the average yields of pyrolytic oil, pyrogas, wax and residue (char) of 50 g of PW was 47.98, 35.43, 16.09 and 0.50%, respectively, at operating temperature of 250 degrees C. The designed reactor could work at low temperature in the absence of a catalyst to obtain similar products as for a catalytic process. PMID:20172649

  16. Identification of ultrafast relaxation processes as a major reason for inefficient exciton diffusion in perylene-based organic semiconductors.

    PubMed

    Settels, Volker; Schubert, Alexander; Tafipolski, Maxim; Liu, Wenlan; Stehr, Vera; Topczak, Anna K; Pflaum, Jens; Deibel, Carsten; Fink, Reinhold F; Engel, Volker; Engels, Bernd

    2014-07-01

    The exciton diffusion length (LD) is a key parameter for the efficiency of organic optoelectronic devices. Its limitation to the nm length scale causes the need of complex bulk-heterojunction solar cells incorporating difficulties in long-term stability and reproducibility. A comprehensive model providing an atomistic understanding of processes that limit exciton trasport is therefore highly desirable and will be proposed here for perylene-based materials. Our model is based on simulations with a hybrid approach which combines high-level ab initio computations for the part of the system directly involved in the described processes with a force field to include environmental effects. The adequacy of the model is shown by detailed comparison with available experimental results. The model indicates that the short exciton diffusion lengths of α-perylene tetracarboxylicdianhydride (PTCDA) are due to ultrafast relaxation processes of the optical excitation via intermolecular motions leading to a state from which further exciton diffusion is hampered. As the efficiency of this mechanism depends strongly on molecular arrangement and environment, the model explains the strong dependence of LD on the morphology of the materials, for example, the differences between α-PTCDA and diindenoperylene. Our findings indicate how relaxation processes can be diminished in perylene-based materials. This model can be generalized to other organic compounds. PMID:24909402

  17. Relative permittivity measurement during the thrombus formation process using the dielectric relaxation method for various hematocrit values.

    PubMed

    Asakura, Yuta; Sapkota, Achyut; Maruyama, Osamu; Kosaka, Ryo; Yamane, Takashi; Takei, Masahiro

    2015-12-01

    The relative permittivity ε' and the dielectric loss ε″ for various hematocrit values H for static bovine blood condition have been measured using the dielectric relaxation method to detect thrombosis in real time. The suitable measurement frequency f m ranged within 60 kHz to 1 MHz, and the relaxation frequency of red blood cells (RBCs) f rc was observed to be 2 MHz. In the f m, the temporal change of normalized ε' exhibited a minimum (called as bottom point). The bottom point was observed to be exponentially shortened as H increased. This characteristic of the ε'* minimum is discussed from three viewpoints: during fibrin formation, direct thrombus formation, and rouleaux formation processes. ε'* during the fibrin formation process decreased over time, irrespective of f. However, ε'* in f m during the direct thrombus formation process and during the aggregation formation process increased immediately and rapidly over time. Therefore, the ε'* bottom point in f m might be the indication of micrometer-scale thrombus formation by RBC aggregation due to fibrin formation. PMID:26058831

  18. Advanced Low Temperature Geothermal Power Cycles (The ENTIV Organic Project) Final Report

    SciTech Connect

    Mugerwa, Michael

    2015-11-18

    Feasibility study of advanced low temperature thermal power cycles for the Entiv Organic Project. Study evaluates amonia-water mixed working fluid energy conversion processes developed and licensed under Kalex in comparison with Kalina cycles. Both cycles are developed using low temperature thermal resource from the Lower Klamath Lake Geothermal Area. An economic feasibility evaluation was conducted for a pilot plant which was deemed unfeasible by the Project Sponsor (Entiv).

  19. Impact of the localized wetting layer states on carrier relaxation processes in GaAs-based quantum dash structures

    SciTech Connect

    Syperek, M.; Musial, A.; Seek, G.; Podemski, P.; Misiewicz, J.; Loeffler, A.; Hoefling, S.; Worschech, L.; Forchel, A.

    2011-12-23

    The exciton kinetics in the low strain InGaAs/GaAs structures with quantum dashes on a wetting layer has been examined by means of time-resolved photoluminescence and micro-photoluminescence. There has been proven a multistage relaxation process with a key role of the exciton localization within the wetting layer revealing also short radiative lifetime of excitons in the dashes as a consequence of a weak carrier confinement. The peculiar properties of the system can be responsible for the observation of pronounced biexciton sideband, which can be related to QDash biexciton interaction with excitons confined in the wetting layer potential fluctuations.

  20. Mechanism of the typical relaxation process at low frequency based on dielectric measurements of water absorbed in porous titanium dioxide

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Wang, Qiang; Sun, Gang; Li, Chenxi; Hu, Lin

    2016-02-01

    Dielectric spectroscopy is a valuable tool in physics, chemistry, biophysics, and materials science. However, there is still an argument about the typical relaxation process at low frequency, which is always masked by electrode polarization. Low-frequency dielectric measurements of water absorbed in porous titanium dioxide have been performed. The experimental results show that typical polarization at low frequency is caused by space-charge polarization. A model is proposed to explain the experimental results, which indicates that the electric field in the sample is close to 0. An effective circuit is given, and the calculation gives similar dielectric spectra to those measured in experiments, which confirms the physical model.

  1. Low temperature environmental degradation of zirconia ceramics

    NASA Astrophysics Data System (ADS)

    Zhao, Zhenbo

    2005-11-01

    The low temperature environmental degradation (LTED) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has been prevented, or at least retarded, by using both bulk doping and surface doping methods with either cation, or anion, stabilizers. The introduction of both mullite and alumina into 3Y-TZP by a bulk-doping method was found to be effective in suppressing the tetragonal-->monoclinic transformation induced by water during hydrothermal treatment thus giving rise to better mechanical properties. The beneficial effects of alumina on the phase stability of the 3Y-TZP ceramic are considered to be due to the increase in the elastic modulus of the constraining matrix, as well as to the segregation of A12O3 at grain boundaries. The LTED transformation kinetics as determined by x-ray diffraction (XRD) and White Light Interferometer (WLI) analysis showed that the isothermal tetragonal-to-monoclinic transformation starts from the surface and has an incubation-nucleation-growth mechanism which can be described by the Johnson-Mehl-Avrami equation. The degradation of Y-TZP ceramic after hydrothermal treatment can be effectively overcome by surface doping by a solid diffusion method with tetravalent dopants: CeO2 and GeO2; with trivalent dopants: La2O 3 and Fe2O3; and with divalent dopants: CuO and MgO. For surface CeO2-, GeO2- and Fe2O 3-doping, this degradation inhibition behaviour is attributed to a localized increase in cation stabilizer content which satisfies the requirements for stabilization of the tetragonal phase. However, in each case, the stability mechanisms are different. For surface La2O3doping, surface doping overcomes the formation of La2O3 and La 2Zr2O7 since the extra La2O3 can further diffuse to the center of the 3Y-TZP ceramic. For CuO-doping, small amounts of CuO form a liquid that can act as a conduit for the re-distribution of yttria. In the case of surface MgO modification, the stabilization results from the isolated nature of the

  2. Li-Ion Cell Development for Low Temperature Applications

    NASA Technical Reports Server (NTRS)

    Huang, C.-K.; Sakamoto, J. S.; Surampudi, S.; Wolfenstine, J.

    2000-01-01

    JPL is involved in the development of rechargeable Li-ion cells for future Mars Exploration Missions. The specific objectives are to improve the Li-ion cell cycle life performance and rate capability at low temperature (<<-20 C) in order to enhance survivability of the Mars lander and rover batteries. Poor Li-ion rate capability at low temperature has been attributed to: (1) the electrolytes becoming viscous or freezing and/or (2) reduced electrode capacity that results from decreased Li diffusivity. Our efforts focus on increasing the rate capability at low temperature for Li-ion cells. In order to improve the rate capability we evaluated the following: (1) cathode performance at low temperatures, (2) electrode active material particle size on low temperature performance and (3) Li diffusivity at room temperature and low temperatures. In this paper, we will discuss the results of our study.

  3. Modeling and simulation of the deposition/relaxation processes of polycrystalline diatomic structures of metallic nitride films

    NASA Astrophysics Data System (ADS)

    García, M. F.; Restrepo-Parra, E.; Riaño-Rojas, J. C.

    2015-05-01

    This work develops a model that mimics the growth of diatomic, polycrystalline thin films by artificially splitting the growth into deposition and relaxation processes including two stages: (1) a grain-based stochastic method (grains orientation randomly chosen) is considered and by means of the Kinetic Monte Carlo method employing a non-standard version, known as Constant Time Stepping, the deposition is simulated. The adsorption of adatoms is accepted or rejected depending on the neighborhood conditions; furthermore, the desorption process is not included in the simulation and (2) the Monte Carlo method combined with the metropolis algorithm is used to simulate the diffusion. The model was developed by accounting for parameters that determine the morphology of the film, such as the growth temperature, the interacting atomic species, the binding energy and the material crystal structure. The modeled samples exhibited an FCC structure with grain formation with orientations in the family planes of < 111 >, < 200 > and < 220 >. The grain size and film roughness were analyzed. By construction, the grain size decreased, and the roughness increased, as the growth temperature increased. Although, during the growth process of real materials, the deposition and relaxation occurs simultaneously, this method may perhaps be valid to build realistic polycrystalline samples.

  4. Performance Characteristics of Lithium Ion Cells for Low Temperature Applications

    NASA Technical Reports Server (NTRS)

    Smart, M. C.; Ratnakumar, B. V.; Huang, C. K.; Surampudi, S.

    1998-01-01

    Several of NASA's future Planetary Exploration (specifically Mars) missions will require rechargeable batteries of high specific energy and energy density and more importantly of good low temperature performance.

  5. Low-temperature catalytic gasification of wet industrial wastes

    SciTech Connect

    Elliott, D C; Neuenschwander, G G; Baker, E G; Sealock, Jr, L J; Butner, R S

    1991-04-01

    Bench-scale reactor tests are in progress at Pacific Northwest Laboratory to develop a low-temperature, catalytic gasification system. The system, licensed under the trade name Thermochemical Environmental Energy System (TEES{reg sign}), is designed for treating a wide variety of feedstocks ranging from dilute organics in water to waste sludges from food processing. This report describes a test program which used a continuous-feed tubular reactor. This test program is an intermediate stage in the process development. The reactor is a laboratory-scale version of the commercial concept as currently envisioned by the process developers. An energy benefit and economic analysis was also completed on the process. Four conceptual commercial installations of the TEES process were evaluated for three food processing applications and one organic chemical manufacturing application. Net energy production (medium-Btu gas) was achieved in all four cases. The organic chemical application was found to be economically attractive in the present situation. Based on sensitivity studies included in the analysis, the three food processing cases will likely become attractive in the near future as waste disposal regulations tighten and disposal costs increase. 21 refs., 2 figs., 9 tabs.

  6. Low-temperature formation of magnetic iron oxides

    NASA Technical Reports Server (NTRS)

    Koch, Chr. Bender; Madsen, M. B.

    1992-01-01

    Elemental analysis and magnetic measurements of the surface of Mars have indicated the presence of an iron oxide with a considerable magnetic moment. Identification of the oxide phase(s) is an important subject as this may be used to identify the process of weathering on the martian surface as well as the composition of the Mars regolith itself. Consequently, interest was in evidence of new formation of strongly magnetic phases (e.g., magnetite, maghemite, feroxyhyte) in terrestrially derived Mars sample analogs. Within the group of Mars sample analogs derived from low-temperature weathering of basalts in Arctic regions, evidence of magnetic oxides formed at the outermost weathering rind was never observed. However, in one instance where the weathering products accumulating in a crack of a basaltic stone were investigated, evidence of magnetite was found. The experimental details are presented.

  7. Low-temperature radiation copolymerization of tetrafluoroethylene with perfluorovinyl ethers

    SciTech Connect

    Kim, I.P.; Pirozhnaya, L.N.; Loginova, N.N.; Barkalov, I.M.

    1986-12-01

    The copolymerization of perfluorovinyl ethers with tetrafluoroethylene at low temperature was studied and compared with the process conducted with chemical initiation in bulk or aqueous medium. A calorimetric method was used for studying the kinetics of copolymerization, the phase state of the system, and the phase transition dynamics. Ampules containing the samples of monomers and mixtures were irradiated at 77/sup 0/K with /sup 60/Co ..gamma.. rays with a dose rate of 25 kGy/h. Radiolysis in the solid phase at 77/sup 0/K with a 130 kGy dose resulted in the formation of 0.5-1.0 wt.% of a polymer, and this polymer was soluble in the monomer.

  8. Evaluation of a low-temperature steam and formaldehyde sterilizer.

    PubMed

    Kanemitsu, K; Kunishima, H; Imasaka, T; Ishikawa, S; Harigae, H; Yamato, S; Hirayama, Y; Kaku, M

    2003-09-01

    We evaluated a low-temperature steam and formaldehyde (LTSF) sterilizer based on the draft European Standard prEN 14180. Microbiological tests were conducted on small and full loads using process challenge devices in five programs (P1-P5). With small loads all tests showed no growth of Bacillus stearothermophilus (ATCC7953) spores. However, positive cultures were observed with full-load tests using P5 (sterilization temperature, 50 degrees C). Our data indicated that the load influenced the efficacy of the LTSF sterilizer. Desorption tests were conducted to determine residual formaldehyde in indicator strips. The mean concentrations of formaldehyde in P1-P5 were 31.9, 56.3, 54.9, 82.2 and 180.6 microg, respectively, which are below the limits allowed by the draft Standard. Our results indicate that the LTSF sterilizer is useful for sterilization because of its excellent efficacy, short handling time, and safety. PMID:14505609

  9. Gasoline Ultra Efficient Fuel Vehicle with Advanced Low Temperature Combustion

    SciTech Connect

    Confer, Keith

    2014-09-30

    The objective of this program was to develop, implement and demonstrate fuel consumption reduction technologies which are focused on reduction of friction and parasitic losses and on the improvement of thermal efficiency from in-cylinder combustion. The program was executed in two phases. The conclusion of each phase was marked by an on-vehicle technology demonstration. Phase I concentrated on short term goals to achieve technologies to reduce friction and parasitic losses. The duration of Phase I was approximately two years and the target fuel economy improvement over the baseline was 20% for the Phase I demonstration. Phase II was focused on the development and demonstration of a breakthrough low temperature combustion process called Gasoline Direct- Injection Compression Ignition (GDCI). The duration of Phase II was approximately four years and the targeted fuel economy improvement was 35% over the baseline for the Phase II demonstration vehicle. The targeted tailpipe emissions for this demonstration were Tier 2 Bin 2 emissions standards.

  10. Industrial applications of low-temperature plasma physics

    SciTech Connect

    Chen, F.F.

    1995-06-01

    The application of plasma physics to the manufacturing and processing of materials may be the new frontier of our discipline. Already partially ionized discharges are used in industry, and the performance of plasmas has a large commercial and technological impact. However, the science of low-temperature plasmas is not as well developed as that of high-temperature, collisionless plasmas. In this paper several major areas of application are described and examples of forefront problems in each are given. The underlying thesis is that gas discharges have evolved beyond a black art, and that intellectually challenging problems with elegant solutions can be found. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  11. Formation of GeSn alloy on Si(100) by low-temperature molecular beam epitaxy

    SciTech Connect

    Talochkin, A. B.; Mashanov, V. I.

    2014-12-29

    GeSn alloys grown on Si(100) by the low-temperature (100 °C) molecular beam epitaxy are studied using scanning tunneling microscopy and Raman spectroscopy. It is found that the effect of Sn as a surfactant modifies substantially the low-temperature growth mechanism of Ge on Si. Instead of the formation of small Ge islands surrounded by amorphous Ge, in the presence of Sn, the growth of pure Ge islands appears via the Stranski-Krastanov growth mode, and a partially relaxed Ge{sub 1−x}Sn{sub x} alloy layer with the high Sn-fraction up to 40 at. % is formed in the area between them. It is shown that the observed growth mode induced by high surface mobility of Sn and the large strain of the pseudomorphic state of Ge to Si ensures the minimum elastic-strain energy of the structure.

  12. Formation of GeSn alloy on Si(100) by low-temperature molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Talochkin, A. B.; Mashanov, V. I.

    2014-12-01

    GeSn alloys grown on Si(100) by the low-temperature (100 °C) molecular beam epitaxy are studied using scanning tunneling microscopy and Raman spectroscopy. It is found that the effect of Sn as a surfactant modifies substantially the low-temperature growth mechanism of Ge on Si. Instead of the formation of small Ge islands surrounded by amorphous Ge, in the presence of Sn, the growth of pure Ge islands appears via the Stranski-Krastanov growth mode, and a partially relaxed Ge1-xSnx alloy layer with the high Sn-fraction up to 40 at. % is formed in the area between them. It is shown that the observed growth mode induced by high surface mobility of Sn and the large strain of the pseudomorphic state of Ge to Si ensures the minimum elastic-strain energy of the structure.

  13. Low Temperature Magnetic Ordering of the Magnetic Ionic Plastic Crystal, Choline[FeCl4

    NASA Astrophysics Data System (ADS)

    de Pedro, I.; García-Saiz, A.; Andreica, D.; Fernández Barquín, L.; Fernández-Díaz, M. T.; Blanco, J. A.; Amato, A.; Rodríguez Fernández, J.

    2015-11-01

    We report on the nature of the low temperature magnetic ordering of a magnetic ionic plastic crystal, Choline[FeCl4]. This investigation was carried out using heat capacity measurements, neutron diffraction experiments and muon spin relaxation (μSR) spectroscopy. The calorimetric measurements show the onset of an unusual magnetic ordering below 4 K with a possible second magnetic phase transition below 2 K. Low temperature neutron diffraction data reveal a three dimensional antiferromagnetic ordering at 2 K compatible with the previous magnetometry results. The analysis of μSR spectra indicates a magnetic phase transition below 2.2 K. At 1.6 K, the analysis of the shape of the μSR spectra suggests the existence of an additional magnetic phase with features of a possible incommensurate magnetic structure.

  14. Investigating Low Temperature Properties of Rubber Seals - 13020

    SciTech Connect

    Jaunich, M.; Wolff, D.; Stark, W.

    2013-07-01

    To achieve the required tightness levels of containers for low and intermediate level radioactive wastes rubbers are widely applied as main sealing materials. The save encapsulation of the radioactive container contents has to be guaranteed according to legislation and appropriate guidelines for long storage periods as well as down to temperatures of -40 deg. C during transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly influenced by temperature. At low temperatures this is caused by the rubber-glass transition (abbr. glass transition). During continuous cooling the material changes from rubber-like entropy-elastic to stiff energy-elastic behaviour, that allows nearly no strain or retraction. Therefore, rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely, what can cause problems during application. The temperature range where full functionality is possible is strongly dependent on the application conditions and the material. For this investigation mainly ethylene propylene diene (EPDM) and fluorocarbon rubbers (FKM) were selected as they are often used for radioactive waste containers. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) are typically used for the determination of the temperature range of the glass transition process. The standardized compression set measurement according to ISO 815 is common for investigation of rubber sealing materials as the test simulates the seal behaviour after release. To reduce the test time of the standard tests a faster technique giving the same information was developed. Additionally, the breakdown temperature of the sealing function of complete O-ring seals is measured in a component test setup to compare it with the results of the other tests. The experimental setup is capable of

  15. Low temperature induced changes in gene expression in low temperature-sensitive and -tolerant tomatoes

    SciTech Connect

    Vallejos, C.E.; Camp, S.F. )

    1989-04-01

    The objective of this project is to identify genes that control low temperature (LT) tolerance/acclimation in a high altitude ecotype of the wild tomato L. hirsutum. LT induced changes in gene expression were monitored via 2-D gel electrophoresis and fluorography of radiolabeled in vitro translation products. Two types of changes were detected when both LT-sensitive (L. esculentum, L. hirsutum 100m) and LT-tolerant (L. hirsutum 3100m) genotypes were exposed to 6{degrees}C for 12 h in the dark: (a) specific LT induction or up-regulation or up-regulation of some genes; and (b) changes in the turnover rate of day specific mRNA's. Increased exposure lead to the disappearance of some mRNA's. These comparisons will lead to the identification of mRNA's involved in acclimation, and those involved in stress response.

  16. Dipole Model of Electric Pulse Generation Caused by the Relaxation Processes in the Earth's Crust

    NASA Astrophysics Data System (ADS)

    Losseva, T. V.; Spivak, A.; Kuzmicheva, M. Y.

    2011-12-01

    Study of electric and magnetic (EM) signals in the Earth's crust is of interest from a viewpoint of both establishing mechanisms and conditions for generation of geophysical fields and interpreting physical and mechanical characteristics of a hierarchically structured medium. In a previously developed model [1] it was proposed that generation of electromagnetic impulses in the Earth's crust with low water content was a result of a quasi independent displacement of a structural block being relaxed in constrained conditions. A transient electric current system generated on an active side of the structural block due to electric polarization of an inter-block gap content was considered as a source of EM radiation. In a new numerical model we use a set of Hertz's dipoles distributed over the active surface. Time dependence of the dipole moments was defined by displacement of the structural unit. To estimate EM signals the full system of Maxwell equations in a conductive medium was solved. The results of numerical simulations were compared with electric field records in a surface layer of the Earth's crust in the area of influence of the tectonically active Kurai structure (Gornyi Altai) [2]. The amplitudes of electric fields at a distance of 50-100 linear block sizes obtained in numerical simulations are in good agreement with the instrumental observations, which proves the validity of our model for the estimation of electric effects in the low moisture rock medium.

  17. [On Atomic Nuclear Fusion Processes at Low-Temperatures. An Enhancement of the Probability of Transition through a Potential Barrier Due to the So-Called Barrier Anti-Zeno Effect].

    PubMed

    Namiot, V A

    2016-01-01

    It is known that in quantum mechanics the act of observing the experiment can affect the experimental findings in some cases. In particular, it happens under the so-called Zeno effect. In this work it is shown that in contrast to the "standard" Zeno-effect where the act of observing a process reduces the probability of its reality, an inverse situation when a particle transmits through a potential barrier (a so-called barrier anti-Zeno effect) can be observed, the observation of the particle essentially increases the probability of its transmission through the barrier. The possibility of using the barrier anti-Zeno effect is discussed to explain paradoxical results of experiments on "cold nuclear fusion" observed in various systems including biological ones. (According to the observers who performed the observations, the energy generation, which could not be explained by any chemical processes, as well as the change in the isotope and even element composition of the studied object may occur in these systems. PMID:27192844

  18. Low temperatures shear viscosity of a two-component dipolar Fermi gas with unequal population

    NASA Astrophysics Data System (ADS)

    Darsheshdar, E.; Yavari, H.; Zangeneh, Z.

    2016-07-01

    By using the Green's functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose-Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer-atom, dimer-dimer, and atom-atom take into account to the viscous relaxation time (τη) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer-atom (τDA) , dimer-dimer (τcDD ,τdDD) , and atom-atom (τAA) interactions. We will show that relaxation rates due to these interactions τDA-1 ,τcDD-1, τdDD-1, and τAA-1 have T2, T4, e - E /kB T (E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit (T → 0) and consequently, the atom-atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization (τDA ,τAA ≫τcDD ,τdDD), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T-5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium.

  19. Low temperature barrier wellbores formed using water flushing

    DOEpatents

    McKinzie, II; John, Billy [Houston, TX; Keltner, Thomas Joseph [Spring, TX

    2009-03-10

    A method of forming an opening for a low temperature well is described. The method includes drilling an opening in a formation. Water is introduced into the opening to displace drilling fluid or indigenous gas in the formation adjacent to a portion of the opening. Water is produced from the opening. A low temperature fluid is applied to the opening.

  20. Low temperature magnetic force microscopy on ferromagnetic and superconducting oxides

    NASA Astrophysics Data System (ADS)

    Sirohi, Anshu; Sheet, Goutam

    2016-05-01

    We report the observation of complex ferromagnetic domain structures on thin films of SrRuO3 and superconducting vortices in high temperature superconductors through low temperature magnetic force microscopy. Here we summarize the experimental details and results of magnetic imaging at low temperatures and high magnetic fields. We discuss these data in the light of existing theoretical concepts.